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WO2018180281A1 - Rack shaft and electric power steering device - Google Patents

Rack shaft and electric power steering device Download PDF

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Publication number
WO2018180281A1
WO2018180281A1 PCT/JP2018/008566 JP2018008566W WO2018180281A1 WO 2018180281 A1 WO2018180281 A1 WO 2018180281A1 JP 2018008566 W JP2018008566 W JP 2018008566W WO 2018180281 A1 WO2018180281 A1 WO 2018180281A1
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WO
WIPO (PCT)
Prior art keywords
shaft
rack
axis
outer diameter
pinion
Prior art date
Application number
PCT/JP2018/008566
Other languages
French (fr)
Japanese (ja)
Inventor
真楽 吉川
前原　秀雄
勝海 下田
Original Assignee
Ｋｙｂ株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ｋｙｂ株式会社 filed Critical Ｋｙｂ株式会社
Publication of WO2018180281A1 publication Critical patent/WO2018180281A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D3/00—Steering gears
    • B62D3/02—Steering gears mechanical
    • B62D3/12—Steering gears mechanical of rack-and-pinion type
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D5/00—Power-assisted or power-driven steering
    • B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H19/00—Gearings comprising essentially only toothed gears or friction members and not capable of conveying indefinitely-continuing rotary motion
    • F16H19/02—Gearings comprising essentially only toothed gears or friction members and not capable of conveying indefinitely-continuing rotary motion for interconverting rotary or oscillating motion and reciprocating motion
    • F16H19/04—Gearings comprising essentially only toothed gears or friction members and not capable of conveying indefinitely-continuing rotary motion for interconverting rotary or oscillating motion and reciprocating motion comprising a rack

Definitions

  • the present invention relates to a rack shaft and an electric power steering device.
  • JP2015-205581A describes a rack shaft used in a dual pinion type electric power steering apparatus.
  • the rack shaft includes a hollow first shaft on which a first rack for manual steering force transmission is formed, and a solid second shaft on which a second rack for steering assist force transmission is formed. .
  • the first axis and the second axis have the same diameter, so that one of the first axis and the second axis on which a relatively high load acts is used as a reference.
  • the diameter is determined, the diameter of the other shaft to which a relatively low load acts becomes unnecessarily large, and the mass increases accordingly.
  • An object of the present invention is to reduce the weight of a rack shaft and an electric power steering device.
  • a rack shaft that is engaged with a second pinion that is rotated by an electric motor and a first shaft that is formed with a first rack that meshes with a first pinion that rotates as the steering wheel is steered.
  • a second rack is formed, and includes a second shaft coupled to the first shaft, and the outer diameter of the first shaft and the outer diameter of the second shaft are different from each other.
  • FIG. 1 is a configuration diagram of a steering device according to a first embodiment of the present invention.
  • FIG. 2A is a longitudinal cross-sectional view showing a coupling portion of the rack shaft according to the first embodiment of the present invention, and shows a state before the first shaft and the second shaft are coupled.
  • FIG. 2B is a longitudinal cross-sectional view showing a coupling portion of the rack shaft according to the first embodiment of the present invention, and shows a state where the first shaft and the second shaft are coupled.
  • FIG. 3A is a cross-sectional view of the rack shaft along the line III-III in FIG. 1, and shows the dimensions of each part of the rack shaft.
  • 3B is a cross-sectional view of the rack shaft along the line III-III in FIG.
  • FIG. 4A is a longitudinal sectional view showing a coupling portion of a rack shaft according to the second embodiment of the present invention.
  • FIG. 4B is a longitudinal cross-sectional view showing a coupling portion of rack shafts according to a modification of the second embodiment of the present invention.
  • FIG. 5A is a plan view showing a rack shaft according to a third embodiment of the present invention.
  • FIG. 5B is a plan view showing a rack shaft according to a modification of the third embodiment of the present invention.
  • FIG. 6A is a longitudinal sectional view showing a rack shaft according to a fourth embodiment of the present invention.
  • FIG. 6B is a longitudinal sectional view showing a rack shaft according to the second modification of the fourth embodiment of the present invention.
  • FIG. 6C is a longitudinal sectional view showing a rack shaft according to a third modification of the fourth embodiment of the present invention.
  • FIG. 7 is a cross-sectional view showing a rack shaft according to a fifth embodiment of the present invention.
  • FIG. 8 is a side view showing a rack shaft support structure according to a fifth embodiment of the present invention.
  • FIG. 9 is a cross-sectional view showing a rack shaft according to the first modification of the embodiment of the present invention.
  • FIG. 10 is a cross-sectional view showing a rack shaft according to the second modification of the embodiment of the present invention.
  • FIG. 1 is a configuration diagram of a steering device 100 according to the first embodiment of the present invention.
  • the steering device 100 is a dual pinion type electric power steering device in which a steering force by a driver and an assist driving force by the electric motor 21 are independently input to the rack shaft 12A.
  • the steering device 100 includes a steering mechanism 10 that steers the vehicle wheel 2 in response to rotation of the steering wheel 1 to which a steering force is input by the driver, an assist mechanism 20 that assists the driver's steering force, and steering. And a control device 30 for controlling the force assist amount.
  • the steering mechanism 10 includes a steering shaft 11 that is connected to the steering wheel 1 and rotates according to the rotation of the steering wheel 1, and a rack shaft 12 ⁇ / b> A that steers the vehicle wheel 2 according to the rotation of the steering shaft 11. .
  • the steering shaft 11 includes an input shaft 13 connected to the steering wheel 1, an output shaft 15 connected to the input shaft 13 via a torsion bar 14, and a first pinion 16 formed on the output shaft 15 and meshing with the rack shaft 12A. And having.
  • the assist mechanism 20 includes an electric motor 21 that is a power source of assist force, a pinion shaft 22 as a rotating shaft to which the driving force of the electric motor 21 is transmitted via the speed reduction mechanism 3, and a rack shaft formed on the pinion shaft 22. And a second pinion 23 that meshes with 12A.
  • the speed reduction mechanism 3 includes a worm shaft 3 a connected to the output shaft of the electric motor 21, and a worm wheel 3 b that meshes with the worm shaft 3 a and is connected to the pinion shaft 22.
  • the control device 30 includes a torque sensor 31 that detects the steering torque applied to the torsion bar 14 based on the relative rotation between the input shaft 13 and the output shaft 15, and a rotation angle sensor 32 that detects the rotation angle of the pinion shaft 22.
  • the steering angle sensor 34 that detects the steering angle that is the rotation angle of the steering wheel 1, the motor rotation angle sensor 35 that is configured by a resolver and detects the rotation angle of the electric motor 21, and the controller 33 that controls the operation of the electric motor 21. And having.
  • the controller 33 controls the driving of the electric motor 21 based on the steering torque detected by the torque sensor 31 and the rotation angle of the electric motor 21 detected by the motor rotation angle sensor 35.
  • the controller 33 may control the driving of the electric motor 21 in consideration of the steering angle detected by the steering angle sensor 34 in addition to the steering torque and the rotation angle of the electric motor 21. Further, the controller 33 may control the driving of the electric motor 21 in consideration of the rotation angle of the pinion shaft 22 detected by the rotation angle sensor 32.
  • the detection result of the rotation angle sensor 32 is used also in control of VDC (Vehicle Dynamics Control) etc. which suppress the side slip etc. of a vehicle.
  • VDC Vehicle Dynamics Control
  • the rack shaft 12A is a round bar-like member that extends linearly along the left-right direction of the vehicle, and is formed by coupling the first shaft 110 and the second shaft 120 together.
  • shaft 120 are each formed from the same material (for example, carbon steel).
  • the rack shaft 12A is formed such that the axial length of the first shaft 110 and the axial length of the second shaft 120 are the same.
  • the rack shaft 12A is housed in a housing (not shown) fastened to the vehicle body. Both end portions of the rack shaft 12 ⁇ / b> A pass through an end portion in the axial direction of a housing (not shown) and are connected to the tie rod 25. That is, both end portions of the rack shaft 12 ⁇ / b> A are connected to the left and right wheels 2 via the tie rods 25.
  • the first shaft 110 is formed with a first rack 115 that meshes with the first pinion 16 that rotates as the steering wheel 1 is steered.
  • the rotational force from the steering wheel 1 is transmitted to the output shaft 15 via the input shaft 13 and the torsion bar 14.
  • the rotational force of the output shaft 15 is transmitted to the first rack 115 via the first pinion 16.
  • the rotational force of the first pinion 16 is converted into a force in the axial direction of the rack shaft 12A (the left-right direction of the vehicle). Therefore, when the steering wheel 1 is steered, the driver's steering force is transmitted to the rack shaft 12A via the first rack 115, and the vehicle wheel 2 is steered in accordance with the movement of the rack shaft 12A.
  • a second rack 125 that meshes with a second pinion 23 that is rotated by the electric motor 21 is formed on the second shaft 120.
  • the rotational force from the electric motor 21 is transmitted to the pinion shaft 22 via the speed reduction mechanism 3.
  • the rotational force of the pinion shaft 22 is transmitted to the second rack 125 via the second pinion 23.
  • the rotational force of the second pinion 23 is converted into a force in the axial direction of the rack shaft 12A (the left-right direction of the vehicle). Therefore, when the electric motor 21 is driven to rotate, the rotational force of the electric motor 21 is transmitted to the rack shaft 12A via the second rack 125, and the vehicle wheel 2 is steered in accordance with the movement of the rack shaft 12A.
  • the rack shaft 12A is formed by joining two members of a first shaft 110 that is a solid columnar member and a second shaft 120 that is a solid columnar member.
  • Various methods such as friction welding, welding, and screw fitting can be employed as the coupling method, but it is preferable to employ friction welding with relatively high joint strength.
  • the rack shaft 12A is reduced in weight by making the outer diameter of the first shaft 110 and the outer diameter of the second shaft 120 different.
  • FIG. 2A and FIG. 2B are longitudinal sectional views showing a coupling portion of the rack shaft 12A according to the first embodiment of the present invention.
  • 2A shows a state before the first shaft 110 and the second shaft 120 are coupled
  • FIG. 2B shows a state where the first shaft 110 and the second shaft 120 are coupled.
  • the axial end of the first shaft 110 and the axial end of the second shaft 120 are coupled by friction welding.
  • the first shaft 110 includes a main body portion 111 and a cylindrical connecting tube portion 112 provided at an end portion of the main body portion 111 in the axial direction.
  • the connecting tube portion 112 is a portion in which the outer peripheral portion at the axial end of the main body portion 111 extends in the axial direction, and the outer diameter of the connecting tube portion 112 is the same as the outer diameter of the main body portion 111.
  • the center of the connecting cylinder part 112 is concentric with the center of the main body part 111.
  • the second shaft 120 includes a main body 121 and a cylindrical connecting cylinder 122 provided at an axial end of the main body 121.
  • the connecting cylinder portion 122 protrudes in the axial direction from the axial end portion of the main body portion 121.
  • the center of the connecting cylinder part 122 is concentric with the center of the main body part 121.
  • the outer diameter D1 of the main body 111 of the first shaft 110 is smaller than the outer diameter D2 of the main body 121 of the second shaft 120 (D1 ⁇ D2).
  • the connecting tube portion 122 of the second shaft 120 is formed so that the outer diameter D3 thereof is the same as the outer diameter D1 of the connecting tube portion 112 of the first shaft 110.
  • the connection cylinder part 112 and the connection cylinder part 122 are formed so that each thickness may become the same.
  • the manufacturing method of the rack shaft 12A includes a friction welding process, a first rack forming process, and a second rack forming process.
  • the friction welding process as shown in FIG. 2A, the first shaft 110 and the first shaft 110 are arranged so that the end surface 112a of the connecting tube portion 112 of the first shaft 110 and the end surface 122a of the connecting tube portion 122 of the second shaft 120 face each other.
  • Two axes 120 are arranged coaxially.
  • the first shaft 110 and the second shaft 120 are pressurized in the axial direction in a state where the end surface 112a and the end surface 122a are in contact with each other.
  • first shaft 110 and the second shaft 120 are pressurized, the first shaft 110 and the second shaft 120 are relatively rotated in the circumferential direction to generate frictional heat on the contact surface.
  • mutual diffusion between the first shaft 110 and the second shaft 120 is promoted, The second shaft 120 is joined.
  • the first rack 110 is formed on the first shaft 110 by performing a cutting process in which a part of the outer peripheral surface in the axial direction and the circumferential direction of the first shaft 110 is scraped by a broaching machine or the like.
  • the second rack 125 is formed on the second shaft 120 by performing a cutting process in which a part of the outer peripheral surface in the axial direction and the circumferential direction of the second shaft 120 is scraped with a broaching machine or the like.
  • the first rack 115 has a CGR (Constant Gear Ratio) specification in which the rack teeth have a uniform pitch
  • the second rack 125 has a VGR (Variable Gear) Ratio) specification in which the rack teeth have a variable pitch.
  • the module, the twist angle, and the number of teeth are set so that the stroke amount, the stroke ratio, the axis crossing angle (intersection angle between the output shaft 15 and the rack shaft 12A), the strength requirements, and the like are satisfied.
  • the module, the torsion angle, the outer diameter, and the phase angle are set so that the assist thrust by the electric motor 21, the durability, the mounting property on the vehicle, the requirements for the steering follow-up characteristic, and the like are satisfied.
  • the first rack forming step and the second rack forming step may be performed before the friction welding step or after the friction welding step.
  • the friction welding process is performed, and the other rack is formed so as to correspond to the circumferential position of the already formed rack.
  • a rack forming step may be performed. In this case, the positioning accuracy in the circumferential direction between the first rack 115 and the second rack 125 is not affected by the friction welding, which is preferable.
  • the rack teeth of the first rack 115 and the second rack 125 are formed so that the reference pitch line P1 of the first rack 115 and the reference pitch line P2 of the second rack 125 are parallel to each other ( (See FIG. 3A).
  • the reference pitch line P1 of the first rack 115 and the reference pitch line P2 of the second rack 125 are not limited to being parallel to each other, and may be inclined with respect to each other.
  • FIG. 3A and 3B are cross-sectional views of the rack shaft along the line III-III in FIG. 3A shows the dimensions of each part of the rack shaft 12A, and FIG. 3B shows the positional relationship between the rack shaft 12A, the output shaft 15, and the pinion shaft 22.
  • FIG. 3B only the center axes CL1 and CL2 of the output shaft 15 and the pinion shaft 22 are shown, and the first pinion 16 and the second pinion 23 are not shown.
  • the portion of the main body 111 of the first shaft 110 where the first rack 115 is formed is referred to as a first rack forming portion 116
  • the second rack 125 is formed of the main body 121 of the second shaft 120.
  • the portion in which is formed is referred to as a second rack forming portion 126.
  • the axial lengths of the first rack forming portion 116 and the second rack forming portion 126 correspond to a length that allows the rack shaft 12A to be slid in order to steer the wheel 2 left and right to the maximum turning angle.
  • the shape of the cross section of the first rack forming portion 116 of the first shaft 110 is indicated by a solid line
  • the shape of the cross section of the second rack forming portion 126 of the second shaft 120 is indicated by a two-dot chain line. ing.
  • each part of the first shaft 110 and the dimensions of each part of the second shaft 120 are compared.
  • an axis that is orthogonal to the reference pitch line P1 of the first rack 115 and the center axis O of the rack shaft 12A and that passes through the center axis O of the rack shaft 12A will be described as a Z axis.
  • each part of the first rack forming part 116 are smaller than the dimensions of each part of the second rack forming part 126 corresponding to each part of the first rack forming part 116. This will be described in detail below.
  • the tooth width W1 of the first rack 115 is smaller than the tooth width W2 of the second rack 125 (W1 ⁇ W2).
  • the tooth width W1 of the first rack 115 is smaller than the outer diameter D1 of the first rack forming portion 116
  • the tooth width W2 of the second rack 125 is smaller than the outer diameter D2 of the second rack forming portion 126 (W1 ⁇ D1, W2 ⁇ D2).
  • the wall thickness T1 of the first rack forming section 116 is smaller than the wall thickness T2 of the second rack forming section 126 (T1 ⁇ T2).
  • the wall thickness T1 is the Z-axis dimension from the tooth tip of the first rack 115 on the Z-axis to the back surface of the first rack forming portion 116
  • the wall thickness T2 is from the tooth tip of the second rack 125 on the Z-axis. This is the Z-axis dimension up to the back surface of the second rack forming portion 126.
  • the Z-axis dimension Z1 from the center axis O of the rack shaft 12A to the reference pitch line P1 of the first rack 115 is smaller than the Z-axis dimension Z2 from the center axis O to the reference pitch line P2 of the second rack 125 (Z1 ⁇ Z2).
  • the center axis CL1 of the output shaft 15 can be brought closer to the center axis O of the rack shaft 12A than the center axis CL2 of the pinion shaft 22.
  • the pinion shaft 22 and the output so that the inter-axis distance ZL1 between the rack shaft 12A and the output shaft 15 is smaller than the inter-axis distance ZL2 between the rack shaft 12A and the pinion shaft 22.
  • the inter-axis distance ZL1 is the Z-axis dimension from the central axis O of the rack shaft 12A to the central axis CL1 of the output shaft 15, and the inter-axis distance ZL2 is the central axis CL2 of the pinion shaft 22 from the central axis O of the rack shaft 12A. Z-axis dimensions up to.
  • the rack shaft 12A includes a first shaft 110 on which a first rack 115 to which a steering force is transmitted and a second rack 125 to which a driving force of the electric motor 21 is transmitted. And a second shaft 120 coupled to the second shaft 120.
  • the outer diameter D1 of the first shaft 110 and the outer diameter D2 of the second shaft 120 are different diameters. Since the diameter of one of the first shaft 110 and the second shaft 120 is smaller than the diameter of the other shaft, the mass of one shaft is smaller than that of the other shaft. Can be reduced. Therefore, the rack shaft 12A and the steering device 100 can be reduced in weight.
  • the materials of the first shaft 110 and the second shaft 120 are the same.
  • Each of the first shaft 110 and the second shaft 120 is a solid columnar member.
  • the load acting on the first shaft 110 to which the steering force is transmitted is smaller than that of the second shaft 120 to which the driving force of the electric motor 21 is transmitted.
  • the outer diameter D1 of the first rack forming portion 116 of the first shaft 110 is smaller than the outer diameter D2 of the second rack forming portion 126 of the second shaft 120 (D1 ⁇ D2). .
  • shaft 110 can be made smaller than the mass of the 2nd axis
  • the rack shaft 12 ⁇ / b> A having excellent durability against a high load from the electric motor 21 can be obtained.
  • the rack shaft 12A can be reduced in weight while satisfying the strength required for each of the first shaft 110 and the second shaft 120.
  • the Z-axis dimension Z1 from the center axis O of the rack shaft 12A to the reference pitch line P1 is smaller than the Z-axis dimension Z2 from the center axis O to the reference pitch line P2. Therefore, as shown in FIG. 3B, the center axis CL1 of the output shaft 15 can be brought closer to the center axis O of the rack shaft 12A than the center axis CL2 of the pinion shaft 22 (ZL1 ⁇ ZL2).
  • the output shaft 15 is brought close to the rack shaft 12A so that the distance between the output shaft 15 and the rack shaft 12A is shortened, and this portion is made compact.
  • the degree of freedom of attachment of the steering device 100 to the vehicle can be improved, that is, the mountability can be improved.
  • the outer diameters of the first shaft 110 and the second shaft 120 can be set individually. For this reason, for example, by making the outer diameter D2 of the second shaft 120 larger than the outer diameter D1 of the first shaft 110, the contact area of the rack teeth of the second shaft 120 with the second pinion 23 can be increased. Thereby, the freedom degree of the axis crossing angle which is the crossing angle of the pinion shaft 22 and the rack shaft 12A can be improved. As a result, the degree of freedom of mounting the steering device 100 on the vehicle can be improved, that is, the mountability can be improved.
  • connection cylinder part 112,122 was formed so that the outer diameter D1 of the connection cylinder part 112 and the outer diameter D3 of the connection cylinder part 122 may become the same (FIG. 2A
  • the present invention is not limited to this.
  • Either one of the connecting tube portions 112 and 122 may be formed larger.
  • the outer diameter D3 of the connecting cylinder part 122 may be formed larger than the outer diameter D1 of the connecting cylinder part 112 (D3> D1). What is necessary is just to form the connection cylinder parts 112 and 122 so that the contact area of the grade which can obtain sufficient joint strength at least can be obtained.
  • the example in which the size of each part of the first rack forming unit 116 is smaller than the size of each part of the second rack forming unit 126 corresponding to each part of the first rack forming unit 116 has been described.
  • the invention is not limited to this.
  • the Z-axis dimension Z1 from the central axis O of the rack shaft 12A to the reference pitch lines P1, P2 , Z2 may be such that Z1> Z2.
  • the magnitude relationship between the thicknesses T1 and T2 may satisfy T1> T2.
  • FIG. 4A is a longitudinal sectional view showing a coupling portion of the rack shaft 12B1.
  • each of the first shaft 110 and the second shaft 120 is a solid columnar member.
  • the first shaft 210 is a hollow cylindrical member. This is different from the first embodiment. This will be specifically described below.
  • the first shaft 210 is a cylindrical member.
  • the connecting tube portion 122 of the second shaft 120 is formed so that the thickness of the connecting tube portion 122 is the same as the thickness of the first shaft 210.
  • An axial end portion of the first shaft 210 is joined to the connecting tube portion 122 of the second shaft 120 by friction welding.
  • the first rack forming process before the friction welding process.
  • a cylindrical mandrel is reciprocated in the hollow portion of the first shaft 210 while the first shaft 210 is held by a rack forming mold. Thereby, the first shaft 210 is gradually plastically deformed.
  • the first rack 115 can be formed on the first rack forming portion 116 of the first shaft 210 by reciprocating the mandrel having a large diameter little by little in the axial direction.
  • the outer diameter D1 of the first shaft 210 in the first rack forming portion 116 is smaller than the outer diameter D2 of the second shaft 120 in the second rack forming portion 126 (D1 ⁇ D2).
  • the rack shaft 12B1 and the steering device 100 can be further reduced in weight compared to the first embodiment.
  • FIG. 4B is a longitudinal sectional view showing a coupling portion of the rack shaft 12B2 according to a modification of the second embodiment of the present invention.
  • a connecting tube portion 222 having an outer diameter D2 is formed at the axial end portion of the second shaft 220, and the outer diameter D2 is applied to the axial end portion of the first shaft 210.
  • the connecting tube portion 212 may be formed.
  • the outer diameter D1 of the first rack forming portion 116 can be made smaller than the outer diameter D2 of the second rack forming portion 126, so that the rack shaft 12B2 and the steering device 100 can be reduced in weight.
  • the outer diameters of the connecting tube portions 212 and 222 are larger than those in the above embodiment, so that the relative rotational speed of the first shaft 210 and the second shaft 220 is kept low in the friction welding process. Also, the peripheral speed necessary for friction welding can be obtained.
  • FIG. 5A is a plan view showing a rack shaft 12C1 according to a third embodiment of the present invention.
  • the first shaft 310A and the second shaft 320A are solid cylindrical members formed from the same material. For this reason, the mass per unit length in the first rack forming portion 116 of the small-diameter first shaft 310A is smaller than the mass per unit length in the second rack forming portion 126 of the large-diameter second shaft 320A.
  • the length of the first shaft 310A having a small mass per unit length is made longer than the length of the second shaft 320A having a large mass per unit length, thereby realizing weight reduction.
  • the shaft length of the first shaft 110 is the same as the shaft length of the second shaft 120, but in the third embodiment, the shaft length L1 of the first shaft 310A is the second shaft 320A. This is different from the first embodiment in that it is longer than the axial length L2.
  • the total length of the rack shaft 12C1 is the same as the total length of the rack shaft 12A of the first embodiment.
  • one axis having a small mass per unit length is formed longer than the other axis having a large mass per unit length.
  • the rack shaft 12C1 and the steering device 100 can further be reduced in weight.
  • FIG. 5B is a plan view showing a rack shaft 12C2 according to a modification of the third embodiment of the present invention.
  • the first shaft 310B is a hollow cylindrical member, and the outer diameter of the first shaft 310B is larger than the outer diameter of the second shaft 320B.
  • the first shaft 310B is a hollow cylindrical member, and the first rack 115 is formed by forging.
  • the second shaft 320B is a solid cylindrical member, and the second rack 125 is formed by cutting. Since the rack teeth can be formed more accurately in the cutting process than in the forging process, the meshing accuracy between the second rack 125 and the second pinion 23 is higher than the meshing accuracy between the first rack 115 and the first pinion 16. Is also expensive.
  • the durability of the second rack 125 can be ensured by increasing the meshing accuracy between the rack teeth of the second shaft 320B on which a relatively high load acts and the pinion.
  • the mass per unit length in the first rack forming portion 116 is smaller than the mass per unit length in the second rack forming portion 126. For this reason, by forming the axial length L1 of the first shaft 310B longer than the axial length L2 of the second shaft 320B, the rack shaft 12C2 and the steering device 100 can be reduced in weight compared to the case where the axial length is the same. .
  • a rack shaft 12D1 according to a fourth embodiment of the present invention will be described with reference to FIG. 6A.
  • the following description will focus on differences from the first embodiment, and in the figure, the same or corresponding components as those described in the first embodiment will be denoted by the same reference numerals and description thereof will be omitted. .
  • FIG. 6A is a longitudinal sectional view showing a rack shaft 12D1 according to a fourth embodiment of the present invention.
  • the end surface 112a of the first shaft 110 and the end surface 122a of the second shaft 120 are joined by friction welding (see FIGS. 2A and 2B).
  • the second shaft 420A is a cylindrical member, and the first shaft 410A is press-fitted into the hollow portion of the second shaft 420A and welded, whereby the first shaft 410A and the second shaft 420A are welded.
  • the shaft 420A is coupled.
  • FIG. 6B is a longitudinal sectional view showing a rack shaft 12D2 according to the second modification of the fourth embodiment of the present invention.
  • a fastening member 490 such as a bolt or nut.
  • the first shaft 410B and the second shaft 420B are coupled.
  • FIG. 6C is a longitudinal sectional view showing a rack shaft 12D3 according to Modification 3 of the fourth embodiment of the present invention.
  • the first shaft 410C and the second shaft 420C are sandwiched between the socket 493 of the ball joint 491 and the step 418 provided on the first shaft 410C.
  • the second shaft 420C is coupled.
  • the first shaft 410 ⁇ / b> C is provided with a columnar fitting portion 417 that protrudes in the axial direction from the axial end portion of the main body portion 111.
  • the fitting portion 417 is a portion that is fitted into the hollow portion of the second shaft 420 ⁇ / b> C and has an outer diameter smaller than that of the main body portion 111. Since the fitting portion 417 is formed to have a smaller diameter than the main body portion 111, the axial end surface of the main body portion 111 facing the axial end surface of the second shaft 420 ⁇ / b> C is a stepped portion 418.
  • a ball joint 491 which is a universal joint connected to the end of the rack shaft 12D3 is provided at the end of the tie rod 25.
  • the ball joint 491 includes a socket 493 fixed to the end portion of the first shaft 410C and a ball 492 fixed to the end portion of the shaft portion of the tie rod 25.
  • the socket 493 includes a ball accommodating portion 493a that accommodates the ball 492, and a bolt 493b that is integrally provided on the proximal end side of the ball accommodating portion 493a.
  • the male screw provided on the bolt 493b is screwed into the female screw provided in the hole 449 extending in the axial direction from the distal end surface of the fitting portion 417 of the first shaft 410C, whereby the socket 493 is engaged with the first shaft 410C. It is fixed to.
  • FIG. 6C illustrates an example in which an annular member 499 is interposed between the socket 493 and the rack shaft 12D3, the annular member 499 may be omitted.
  • the outer peripheral portion of the fitting portion 417 of the first shaft 410C and the inner peripheral portion of the second shaft 420C are respectively keyed. It is preferable that a groove is provided and a key is fitted into the key groove to prevent the first shaft 410C and the second shaft 420C from rotating.
  • FIG. 7 is a cross-sectional view showing a rack shaft 12E according to a fifth embodiment of the present invention
  • FIG. 8 is a side view showing a support structure for the rack shaft 12E according to the fifth embodiment of the present invention.
  • the pinion and the rack guide are indicated by a two-dot chain line.
  • the first axis 110 and the second axis 120 are coupled so that the central axis of the first axis 110 and the central axis of the second axis 120 are the same (see FIG. 3A).
  • the central axis O1 of the first shaft 110 and the central axis O2 of the second shaft 120 are eccentric.
  • the steering device 100 includes a first rack guide 561 that presses the first rack forming portion 116 from the back side (back side) toward the first pinion 16, and the second rack forming portion 126 on the back side. And a second rack guide 562 for pressing toward the second pinion 23.
  • the first rack guide 561 includes a guide part 561a having an arc surface corresponding to the shape of the back surface side of the first rack forming part 116, and a coil spring 561b that biases the guide part 561a toward the first pinion 16. I have.
  • the second rack guide 562 includes a guide portion 562a having an arc surface corresponding to the shape of the back surface side of the second rack forming portion 126, and a coil spring 562b that biases the guide portion 562a toward the second pinion 23. And.
  • the first rack forming portion 116 is sandwiched between the first pinion 16 and the first rack guide 561, and the second rack forming portion 126 is sandwiched between the second pinion 23 and the second rack guide 562.
  • FIG. 9 is a cross-sectional view of a rack shaft 12G according to the first modification of the embodiment of the present invention.
  • the shape of the cross section of the first rack forming portion 116 of the first shaft 710 is indicated by a solid line
  • the shape of the cross section of the second rack forming portion 126 of the second shaft 720 is indicated by a two-dot chain line.
  • each part of the first rack forming part 116 are smaller than the dimensions of each part of the second rack forming part 126.
  • the dimensions of the above-mentioned parts include the rack tooth widths W1 and W2, the lengths of the long axes (long diameters a1 and a2) and the short axes (short diameters b1 and b2) in the rack forming part, and the thickness of the rack forming part. T1 and T2, and Z axis dimensions Z1 and Z2 from the center axis O of the rack shaft to the reference pitch lines P1 and P2 are included.
  • the rack shaft 12G according to the modification 1 is not limited to changing all the dimensions of each part in the cross-sectional shape orthogonal to the central axis O, and at least the major axis a1 and a2 has the first axis 710. And the second axis 720 may be different.
  • the rack teeth may be formed so that the tooth width W ⁇ b> 1 of the first rack 115 is the same as the outer diameter D ⁇ b> 1 of the first rack forming portion 116.
  • the rack teeth may be formed such that the rack tooth widths W1 and W2 are larger than the outer diameters D1 and D2 of the shaft (W1> D1, W2> D2).
  • shaft demonstrated the example formed from the same material
  • this invention is not limited to this.
  • the first axis and the second axis may be formed from different materials.
  • the second shaft is made stronger than the first shaft by using a material having a higher strength than the material of the first shaft (ie, a material having a high tensile strength). Also good.
  • the outer diameter of the second shaft can be made smaller than the outer diameter of the first shaft.
  • the materials of the first shaft and the second shaft can be made different.
  • the diameter of the first axis or the second axis, the axis crossing angle, the inter-axis distance between the center axis of the rack shaft and the center axis of the pinion, and the like can be adjusted to improve the mountability to the vehicle.
  • the present invention is not limited to the case where the outer diameter of the connecting cylinder portion of one shaft is the same as the outer diameter of the main body portion of the other shaft.
  • the outer diameter of the connecting cylinder portion of the first shaft and the outer diameter of the connecting cylinder portion of the second shaft may be different from the outer diameters of the main body portion of the first shaft and the main body portion of the second shaft.
  • a rack shaft can be reduced in weight by making the connecting cylinder part of a 1st axis
  • the strength of the rack shaft can be improved by making the connecting cylinder portion of the first shaft and the second shaft larger in diameter than the main body portion of the first shaft and the main body portion of the second shaft.
  • the rack shafts 12A, 12B1, 12B2, 12C1, 12C2, 12D1, 12D2, 12D3, 12E, and 12G have first shafts 110, 210, 310A, 310B, 410A on which a first rack 115 to which a steering force is transmitted is formed.
  • 410B, 410C, 710 and a second rack 125 to which the driving force of the electric motor 21 is transmitted are formed, and the second shaft is coupled to the first shaft 110, 210, 310A, 310B, 410A, 410B, 410C, 710.
  • the mass can be reduced compared to the case where the outer diameter of one shaft is the same as the outer diameter of the other shaft.
  • the rack shafts 12A, 12B1, 12B2, 12C1, 12C2, 12D1, 12D2, 12D3, 12E, and 12G can be reduced in weight.
  • the rack shafts 12A, 12B1, 12B2, 12C1, 12D1, 12D2, 12D3, 12E, and 12G have the first shafts 110, 210, 310A, 410A, 410B, 410C, and 710 having the outer diameter D1 of the second shafts 120, 220, and 320A.
  • 420A, 420B, 420C, 720 is smaller than the outer diameter D2.
  • the outer diameter D1 of the first shaft 110, 210, 310A, 410A, 410B, 410C, 710 having a smaller load acting than the second shaft 120, 220, 320A, 420A, 420B, 420C, 720 is reduced. Accordingly, the outer diameters D1 and D2 of the first shafts 110, 210, 310A, 410A, 410B, 410C, and 710 and the second shafts 120, 220, 320A, 420A, 420B, 420C, and 720 are required for the respective shafts. It is possible to reduce the weight while satisfying the required strength.
  • the central axis O2 of the second shaft 120 is eccentric with respect to the central axis O1 of the first shaft 110.
  • the rack shafts 12C1 and 12C2 are configured such that one of the first shafts 310A and 310B and the second shafts 320A and 320B has a smaller mass per unit length and a larger mass per unit length. It is formed long.
  • the rack shafts 12C1 and 12C2 can be reduced in weight.
  • the steering device 100 includes rack shafts 12A, 12B1, 12B2, 12C1, 12C2, 12D1, 12D2, 12D3, 12E, and 12G, and an electric motor 21, and the rotational force of the electric motor 21 is passed through the second rack 125.
  • This is an electric power steering device for transmitting to rack shafts 12A, 12B1, 12B2, 12C1, 12C2, 12D1, 12D2, 12D3, 12E, and 12G.
  • the steering device 100 can be reduced in weight.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Transportation (AREA)
  • Power Steering Mechanism (AREA)
  • Transmission Devices (AREA)

Abstract

This rack shaft 12A is provided with: a first shaft 110 having formed thereon a first rack 115 meshing with a first pinion 16 which rotates as a steering wheel 1 is turned; and a second shaft 120 which has formed thereon a second rack 125 meshing with a second pinion 23 rotated by an electric motor 21 and which is joined to the first shaft 110. The first shaft 110 and the second shaft 120 have different outer diameters.

Description

ラックシャフト及び電動パワーステアリング装置Rack shaft and electric power steering device
　本発明は、ラックシャフト及び電動パワーステアリング装置に関する。 The present invention relates to a rack shaft and an electric power steering device.
　ＪＰ２０１５－２０５５８１Ａには、デュアルピニオン式の電動パワーステアリング装置に用いるラックシャフトが記載されている。このラックシャフトは、マニュアル操舵力伝達用の第１ラックが形成された中空の第１軸と、操舵補助力伝達用の第２ラックが形成された中実の第２軸と、を備えている。 JP2015-205581A describes a rack shaft used in a dual pinion type electric power steering apparatus. The rack shaft includes a hollow first shaft on which a first rack for manual steering force transmission is formed, and a solid second shaft on which a second rack for steering assist force transmission is formed. .
　しかしながら、ＪＰ２０１５－２０５５８１Ａに記載のラックシャフトでは、第１軸と第２軸が同径であるため、第１軸及び第２軸のうち、相対的に高い負荷が作用する一方の軸を基準に径が定められると、相対的に低い負荷が作用する他方の軸の径が無駄に大きくなってしまい、その分、質量が大きくなってしまう。 However, in the rack shaft described in JP2015-205581A, the first axis and the second axis have the same diameter, so that one of the first axis and the second axis on which a relatively high load acts is used as a reference. When the diameter is determined, the diameter of the other shaft to which a relatively low load acts becomes unnecessarily large, and the mass increases accordingly.
　本発明は、ラックシャフト及び電動パワーステアリング装置の軽量化を図ることを目的とする。 An object of the present invention is to reduce the weight of a rack shaft and an electric power steering device.
　本発明のある態様によれば、ラックシャフトであって、ステアリングホイールの操舵に伴い回転する第１ピニオンと噛み合う第１ラックが形成された第１軸と、電動モータにより回転する第２ピニオンと噛み合う第２ラックが形成され、第１軸に結合された第２軸と、を備え、第１軸の外径と第２軸の外径とは異径である。 According to an aspect of the present invention, a rack shaft that is engaged with a second pinion that is rotated by an electric motor and a first shaft that is formed with a first rack that meshes with a first pinion that rotates as the steering wheel is steered. A second rack is formed, and includes a second shaft coupled to the first shaft, and the outer diameter of the first shaft and the outer diameter of the second shaft are different from each other.
図１は、本発明の第１実施形態に係るステアリング装置の構成図である。FIG. 1 is a configuration diagram of a steering device according to a first embodiment of the present invention. 図２Ａは、本発明の第１実施形態に係るラックシャフトの結合部分を示す縦断面図であり、第１軸と第２軸とが結合される前の状態を示す。FIG. 2A is a longitudinal cross-sectional view showing a coupling portion of the rack shaft according to the first embodiment of the present invention, and shows a state before the first shaft and the second shaft are coupled. 図２Ｂは、本発明の第１実施形態に係るラックシャフトの結合部分を示す縦断面図であり、第１軸と第２軸とが結合された状態を示す。FIG. 2B is a longitudinal cross-sectional view showing a coupling portion of the rack shaft according to the first embodiment of the present invention, and shows a state where the first shaft and the second shaft are coupled. 図３Ａは、図１のＩＩＩ－ＩＩＩ線に沿うラックシャフトの横断面図であり、ラックシャフトの各部寸法を示す。FIG. 3A is a cross-sectional view of the rack shaft along the line III-III in FIG. 1, and shows the dimensions of each part of the rack shaft. 図３Ｂは、図１のＩＩＩ－ＩＩＩ線に沿うラックシャフトの横断面図であり、ラックシャフトと出力軸及びピニオン軸との位置関係を示す。3B is a cross-sectional view of the rack shaft along the line III-III in FIG. 1, and shows the positional relationship between the rack shaft, the output shaft, and the pinion shaft. 図４Ａは、本発明の第２実施形態に係るラックシャフトの結合部分を示す縦断面図である。FIG. 4A is a longitudinal sectional view showing a coupling portion of a rack shaft according to the second embodiment of the present invention. 図４Ｂは、本発明の第２実施形態の変形例に係るラックシャフトの結合部分を示す縦断面図である。FIG. 4B is a longitudinal cross-sectional view showing a coupling portion of rack shafts according to a modification of the second embodiment of the present invention. 図５Ａは、本発明の第３実施形態に係るラックシャフトを示す平面図である。FIG. 5A is a plan view showing a rack shaft according to a third embodiment of the present invention. 図５Ｂは、本発明の第３実施形態の変形例に係るラックシャフトを示す平面図である。FIG. 5B is a plan view showing a rack shaft according to a modification of the third embodiment of the present invention. 図６Ａは、本発明の第４実施形態に係るラックシャフトを示す縦断面図である。FIG. 6A is a longitudinal sectional view showing a rack shaft according to a fourth embodiment of the present invention. 図６Ｂは、本発明の第４実施形態の変形例２に係るラックシャフトを示す縦断面図である。FIG. 6B is a longitudinal sectional view showing a rack shaft according to the second modification of the fourth embodiment of the present invention. 図６Ｃは、本発明の第４実施形態の変形例３に係るラックシャフトを示す縦断面図である。FIG. 6C is a longitudinal sectional view showing a rack shaft according to a third modification of the fourth embodiment of the present invention. 図７は、本発明の第５実施形態に係るラックシャフトを示す横断面図である。FIG. 7 is a cross-sectional view showing a rack shaft according to a fifth embodiment of the present invention. 図８は、本発明の第５実施形態に係るラックシャフトの支持構造を示す側面図である。FIG. 8 is a side view showing a rack shaft support structure according to a fifth embodiment of the present invention. 図９は、本発明の実施形態の変形例１に係るラックシャフトを示す横断面図である。FIG. 9 is a cross-sectional view showing a rack shaft according to the first modification of the embodiment of the present invention. 図１０は、本発明の実施形態の変形例２に係るラックシャフトを示す横断面図である。FIG. 10 is a cross-sectional view showing a rack shaft according to the second modification of the embodiment of the present invention.
　図面を参照して、本発明の実施形態について説明する。 Embodiments of the present invention will be described with reference to the drawings.
　＜第１実施形態＞
　図１は、本発明の第１実施形態に係るステアリング装置１００の構成図である。ステアリング装置１００は、運転者による操舵力と電動モータ２１によるアシスト駆動力とがそれぞれ独立してラックシャフト１２Ａに入力されるデュアルピニオン式の電動パワーステアリング装置である。 <First Embodiment>
FIG. 1 is a configuration diagram of a steering device 100 according to the first embodiment of the present invention. The steering device 100 is a dual pinion type electric power steering device in which a steering force by a driver and an assist driving force by the electric motor 21 are independently input to the rack shaft 12A.
　ステアリング装置１００は、運転者によって操舵力が入力されるステアリングホイール１の回転に応じて車両の車輪２を転舵させる転舵機構１０と、運転者の操舵力をアシストするアシスト機構２０と、操舵力のアシスト量を制御する制御装置３０と、を備える。 The steering device 100 includes a steering mechanism 10 that steers the vehicle wheel 2 in response to rotation of the steering wheel 1 to which a steering force is input by the driver, an assist mechanism 20 that assists the driver's steering force, and steering. And a control device 30 for controlling the force assist amount.
　転舵機構１０は、ステアリングホイール１に連結されステアリングホイール１の回転に応じて回転するステアリングシャフト１１と、ステアリングシャフト１１の回転に応じて車両の車輪２を転舵させるラックシャフト１２Ａと、を有する。 The steering mechanism 10 includes a steering shaft 11 that is connected to the steering wheel 1 and rotates according to the rotation of the steering wheel 1, and a rack shaft 12 </ b> A that steers the vehicle wheel 2 according to the rotation of the steering shaft 11. .
　ステアリングシャフト１１は、ステアリングホイール１に連結された入力軸１３と、入力軸１３にトーションバー１４を介して連結された出力軸１５と、出力軸１５に形成されラックシャフト１２Ａと噛み合う第１ピニオン１６と、を有する。 The steering shaft 11 includes an input shaft 13 connected to the steering wheel 1, an output shaft 15 connected to the input shaft 13 via a torsion bar 14, and a first pinion 16 formed on the output shaft 15 and meshing with the rack shaft 12A. And having.
　アシスト機構２０は、アシスト力の動力源である電動モータ２１と、減速機構３を介して電動モータ２１の駆動力が伝達される回転軸としてのピニオン軸２２と、ピニオン軸２２に形成されラックシャフト１２Ａと噛み合う第２ピニオン２３と、を有する。減速機構３は、電動モータ２１の出力軸に連結されたウォームシャフト３ａと、ウォームシャフト３ａと噛み合うとともにピニオン軸２２に連結されたウォームホイール３ｂと、を有する。 The assist mechanism 20 includes an electric motor 21 that is a power source of assist force, a pinion shaft 22 as a rotating shaft to which the driving force of the electric motor 21 is transmitted via the speed reduction mechanism 3, and a rack shaft formed on the pinion shaft 22. And a second pinion 23 that meshes with 12A. The speed reduction mechanism 3 includes a worm shaft 3 a connected to the output shaft of the electric motor 21, and a worm wheel 3 b that meshes with the worm shaft 3 a and is connected to the pinion shaft 22.
　制御装置３０は、入力軸１３と出力軸１５との相対回転に基づいてトーションバー１４に付与される操舵トルクを検出するトルクセンサ３１と、ピニオン軸２２の回転角度を検出する回転角度センサ３２と、ステアリングホイール１の回転角度である操舵角度を検出する操舵角度センサ３４と、レゾルバによって構成され電動モータ２１の回転角度を検出するモータ回転角度センサ３５と、電動モータ２１の作動を制御するコントローラ３３と、を有する。 The control device 30 includes a torque sensor 31 that detects the steering torque applied to the torsion bar 14 based on the relative rotation between the input shaft 13 and the output shaft 15, and a rotation angle sensor 32 that detects the rotation angle of the pinion shaft 22. The steering angle sensor 34 that detects the steering angle that is the rotation angle of the steering wheel 1, the motor rotation angle sensor 35 that is configured by a resolver and detects the rotation angle of the electric motor 21, and the controller 33 that controls the operation of the electric motor 21. And having.
　コントローラ３３は、トルクセンサ３１によって検出される操舵トルクと、モータ回転角度センサ３５によって検出される電動モータ２１の回転角度と、に基づいて電動モータ２１の駆動を制御する。なお、コントローラ３３は、操舵トルク及び電動モータ２１の回転角度に加えて、操舵角度センサ３４によって検出される操舵角度を考慮して、電動モータ２１の駆動を制御してもよい。さらに、コントローラ３３は、回転角度センサ３２によって検出されるピニオン軸２２の回転角度を考慮して電動モータ２１の駆動を制御してもよい。 The controller 33 controls the driving of the electric motor 21 based on the steering torque detected by the torque sensor 31 and the rotation angle of the electric motor 21 detected by the motor rotation angle sensor 35. The controller 33 may control the driving of the electric motor 21 in consideration of the steering angle detected by the steering angle sensor 34 in addition to the steering torque and the rotation angle of the electric motor 21. Further, the controller 33 may control the driving of the electric motor 21 in consideration of the rotation angle of the pinion shaft 22 detected by the rotation angle sensor 32.
　回転角度センサ３２によって検出されるピニオン軸２２の回転角度を用いれば、車輪２の転舵角を正確に把握することができる。このため、回転角度センサ３２の検出結果は、車両の横滑り等を抑制するＶＤＣ（Ｖｅｈｉｃｌｅ　Ｄｙｎａｍｉｃｓ　Ｃｏｎｔｒｏｌ）等の制御においても用いられる。 If the rotation angle of the pinion shaft 22 detected by the rotation angle sensor 32 is used, the turning angle of the wheel 2 can be accurately grasped. For this reason, the detection result of the rotation angle sensor 32 is used also in control of VDC (Vehicle Dynamics Control) etc. which suppress the side slip etc. of a vehicle.
　ラックシャフト１２Ａは、車両の左右方向に沿って直線状に延在する丸棒状部材であり、第１軸１１０と第２軸１２０とを結合することにより形成される。第１軸１１０及び第２軸１２０は、それぞれ同じ材料（たとえば炭素鋼）から形成される。本実施形態では、ラックシャフト１２Ａは、第１軸１１０の軸長と第２軸１２０の軸長とが同じになるように形成されている。 The rack shaft 12A is a round bar-like member that extends linearly along the left-right direction of the vehicle, and is formed by coupling the first shaft 110 and the second shaft 120 together. The 1st axis | shaft 110 and the 2nd axis | shaft 120 are each formed from the same material (for example, carbon steel). In the present embodiment, the rack shaft 12A is formed such that the axial length of the first shaft 110 and the axial length of the second shaft 120 are the same.
　ラックシャフト１２Ａは、車体に締結されるハウジング（不図示）内に収容されている。ラックシャフト１２Ａの両端部は、ハウジング（不図示）の軸方向端部を貫通して、タイロッド２５に接続されている。つまり、ラックシャフト１２Ａの両端部のそれぞれは、タイロッド２５を介して左右の車輪２に連結されている。 The rack shaft 12A is housed in a housing (not shown) fastened to the vehicle body. Both end portions of the rack shaft 12 </ b> A pass through an end portion in the axial direction of a housing (not shown) and are connected to the tie rod 25. That is, both end portions of the rack shaft 12 </ b> A are connected to the left and right wheels 2 via the tie rods 25.
　第１軸１１０には、ステアリングホイール１の操舵に伴い回転する第１ピニオン１６と噛み合う第１ラック１１５が形成されている。ステアリングホイール１からの回転力は、入力軸１３及びトーションバー１４を介して出力軸１５に伝達される。出力軸１５の回転力は、第１ピニオン１６を介して第１ラック１１５に伝達される。第１ピニオン１６の回転力は、ラックシャフト１２Ａの軸方向（車両の左右方向）の力に変換される。このため、ステアリングホイール１が操舵されると、運転者の操舵力が第１ラック１１５を介してラックシャフト１２Ａに伝達され、車両の車輪２がラックシャフト１２Ａの移動に応じて転舵される。 The first shaft 110 is formed with a first rack 115 that meshes with the first pinion 16 that rotates as the steering wheel 1 is steered. The rotational force from the steering wheel 1 is transmitted to the output shaft 15 via the input shaft 13 and the torsion bar 14. The rotational force of the output shaft 15 is transmitted to the first rack 115 via the first pinion 16. The rotational force of the first pinion 16 is converted into a force in the axial direction of the rack shaft 12A (the left-right direction of the vehicle). Therefore, when the steering wheel 1 is steered, the driver's steering force is transmitted to the rack shaft 12A via the first rack 115, and the vehicle wheel 2 is steered in accordance with the movement of the rack shaft 12A.
　第２軸１２０には、電動モータ２１により回転する第２ピニオン２３と噛み合う第２ラック１２５が形成されている。電動モータ２１からの回転力は、減速機構３を介してピニオン軸２２に伝達される。ピニオン軸２２の回転力は、第２ピニオン２３を介して第２ラック１２５に伝達される。第２ピニオン２３の回転力は、ラックシャフト１２Ａの軸方向（車両の左右方向）の力に変換される。このため、電動モータ２１が回転駆動されると、電動モータ２１の回転力が第２ラック１２５を介してラックシャフト１２Ａに伝達され、車両の車輪２がラックシャフト１２Ａの移動に応じて転舵される。 A second rack 125 that meshes with a second pinion 23 that is rotated by the electric motor 21 is formed on the second shaft 120. The rotational force from the electric motor 21 is transmitted to the pinion shaft 22 via the speed reduction mechanism 3. The rotational force of the pinion shaft 22 is transmitted to the second rack 125 via the second pinion 23. The rotational force of the second pinion 23 is converted into a force in the axial direction of the rack shaft 12A (the left-right direction of the vehicle). Therefore, when the electric motor 21 is driven to rotate, the rotational force of the electric motor 21 is transmitted to the rack shaft 12A via the second rack 125, and the vehicle wheel 2 is steered in accordance with the movement of the rack shaft 12A. The
　ラックシャフト１２Ａは、中実の円柱状部材である第１軸１１０と、中実の円柱状部材である第２軸１２０の２部材を結合することによって形成される。結合方法には、摩擦圧接、溶接、ねじ嵌合など、種々の方法を採用することができるが、比較的、接合強度が高い摩擦圧接を採用することが好ましい。 The rack shaft 12A is formed by joining two members of a first shaft 110 that is a solid columnar member and a second shaft 120 that is a solid columnar member. Various methods such as friction welding, welding, and screw fitting can be employed as the coupling method, but it is preferable to employ friction welding with relatively high joint strength.
　第１軸と第２軸からなるラックシャフトにおいて、第１軸と第２軸が同径である場合には、第１軸及び第２軸のうち、相対的に高い負荷が作用する一方の軸を基準に径を定める必要がある。このため、相対的に低い負荷が作用する他方の軸の径が無駄に大きくなってしまい、その分、質量が大きくなってしまう。 In the rack shaft composed of the first axis and the second axis, when the first axis and the second axis have the same diameter, one of the first axis and the second axis on which a relatively high load acts. It is necessary to determine the diameter based on the above. For this reason, the diameter of the other shaft on which a relatively low load acts becomes unnecessarily large, and the mass increases accordingly.
　そこで、本実施形態では、第１軸１１０の外径と第２軸１２０の外径を異径とすることで、ラックシャフト１２Ａの軽量化を実現している。 Therefore, in the present embodiment, the rack shaft 12A is reduced in weight by making the outer diameter of the first shaft 110 and the outer diameter of the second shaft 120 different.
　図２Ａ及び図２Ｂは、本発明の第１実施形態に係るラックシャフト１２Ａの結合部分を示す縦断面図である。図２Ａでは、第１軸１１０と第２軸１２０とが結合される前の状態を示し、図２Ｂでは、第１軸１１０と第２軸１２０とが結合された状態を示している。図２Ａ及び図２Ｂに示すように、第１軸１１０の軸方向端部と第２軸１２０の軸方向端部とは摩擦圧接により結合される。 FIG. 2A and FIG. 2B are longitudinal sectional views showing a coupling portion of the rack shaft 12A according to the first embodiment of the present invention. 2A shows a state before the first shaft 110 and the second shaft 120 are coupled, and FIG. 2B shows a state where the first shaft 110 and the second shaft 120 are coupled. As shown in FIGS. 2A and 2B, the axial end of the first shaft 110 and the axial end of the second shaft 120 are coupled by friction welding.
　第１軸１１０は、本体部１１１と、本体部１１１の軸方向端部に設けられた円筒状の連結筒部１１２と、を備えている。連結筒部１１２は、本体部１１１の軸方向端部における外周部が軸方向に延在する部分であり、連結筒部１１２の外径は本体部１１１の外径と同径である。連結筒部１１２の中心は、本体部１１１の中心と同心である。第２軸１２０は、本体部１２１と、本体部１２１の軸方向端部に設けられた円筒状の連結筒部１２２と、を備えている。連結筒部１２２は、本体部１２１の軸方向端部から軸方向に突出している。連結筒部１２２の中心は、本体部１２１の中心と同心である。 The first shaft 110 includes a main body portion 111 and a cylindrical connecting tube portion 112 provided at an end portion of the main body portion 111 in the axial direction. The connecting tube portion 112 is a portion in which the outer peripheral portion at the axial end of the main body portion 111 extends in the axial direction, and the outer diameter of the connecting tube portion 112 is the same as the outer diameter of the main body portion 111. The center of the connecting cylinder part 112 is concentric with the center of the main body part 111. The second shaft 120 includes a main body 121 and a cylindrical connecting cylinder 122 provided at an axial end of the main body 121. The connecting cylinder portion 122 protrudes in the axial direction from the axial end portion of the main body portion 121. The center of the connecting cylinder part 122 is concentric with the center of the main body part 121.
　第１軸１１０の本体部１１１の外径Ｄ１は、第２軸１２０の本体部１２１の外径Ｄ２よりも小さい（Ｄ１＜Ｄ２）。本実施形態では、第２軸１２０の連結筒部１２２は、その外径Ｄ３が第１軸１１０の連結筒部１１２の外径Ｄ１と同一となるように形成されている。なお、連結筒部１１２及び連結筒部１２２は、それぞれの肉厚が同一となるように形成されている。 The outer diameter D1 of the main body 111 of the first shaft 110 is smaller than the outer diameter D2 of the main body 121 of the second shaft 120 (D1 <D2). In the present embodiment, the connecting tube portion 122 of the second shaft 120 is formed so that the outer diameter D3 thereof is the same as the outer diameter D1 of the connecting tube portion 112 of the first shaft 110. In addition, the connection cylinder part 112 and the connection cylinder part 122 are formed so that each thickness may become the same.
　ラックシャフト１２Ａの製造方法の一例を説明する。ラックシャフト１２Ａの製造方法は、摩擦圧接工程と、第１ラック形成工程と、第２ラック形成工程と、を含む。摩擦圧接工程では、図２Ａに示すように、第１軸１１０の連結筒部１１２の端面１１２ａと第２軸１２０の連結筒部１２２の端面１２２ａとが対向するように、第１軸１１０と第２軸１２０を同軸に配置する。図２Ｂに示すように、端面１１２ａと端面１２２ａとを当接させた状態で第１軸１１０と第２軸１２０を軸方向に加圧する。 An example of a method for manufacturing the rack shaft 12A will be described. The manufacturing method of the rack shaft 12A includes a friction welding process, a first rack forming process, and a second rack forming process. In the friction welding process, as shown in FIG. 2A, the first shaft 110 and the first shaft 110 are arranged so that the end surface 112a of the connecting tube portion 112 of the first shaft 110 and the end surface 122a of the connecting tube portion 122 of the second shaft 120 face each other. Two axes 120 are arranged coaxially. As shown in FIG. 2B, the first shaft 110 and the second shaft 120 are pressurized in the axial direction in a state where the end surface 112a and the end surface 122a are in contact with each other.
　第１軸１１０及び第２軸１２０を加圧した状態で、第１軸１１０と第２軸１２０とを周方向に相対回転させて、当接面にて摩擦熱を発生させる。相対回転を停止し、第１軸１１０と第２軸１２０との加圧状態を所定時間保持することによって、第１軸１１０と第２軸１２０との相互拡散を促進させ、第１軸１１０と第２軸１２０とを接合する。 In a state where the first shaft 110 and the second shaft 120 are pressurized, the first shaft 110 and the second shaft 120 are relatively rotated in the circumferential direction to generate frictional heat on the contact surface. By stopping the relative rotation and maintaining the pressurized state of the first shaft 110 and the second shaft 120 for a predetermined time, mutual diffusion between the first shaft 110 and the second shaft 120 is promoted, The second shaft 120 is joined.
　第１ラック形成工程では、第１軸１１０の軸方向及び周方向における外周面の一部をブローチ盤などによって削り取る切削加工を施し、第１軸１１０に第１ラック１１５を形成する。第２ラック形成工程では、第２軸１２０の軸方向及び周方向における外周面の一部をブローチ盤などによって削り取る切削加工を施し、第２軸１２０に第２ラック１２５を形成する。第１ラック１１５は、ラック歯が均等ピッチであるＣＧＲ（Ｃｏｎｓｔａｎｔ　Ｇｅａｒ　Ｒａｔｉｏ）仕様とされ、第２ラック１２５は、ラック歯が可変ピッチであるＶＧＲ（Ｖａｒｉａｂｌｅ　Ｇｅａｒ Ｒａｔｉｏ）仕様とされている。 In the first rack forming step, the first rack 110 is formed on the first shaft 110 by performing a cutting process in which a part of the outer peripheral surface in the axial direction and the circumferential direction of the first shaft 110 is scraped by a broaching machine or the like. In the second rack forming step, the second rack 125 is formed on the second shaft 120 by performing a cutting process in which a part of the outer peripheral surface in the axial direction and the circumferential direction of the second shaft 120 is scraped with a broaching machine or the like. The first rack 115 has a CGR (Constant Gear Ratio) specification in which the rack teeth have a uniform pitch, and the second rack 125 has a VGR (Variable Gear） Ratio) specification in which the rack teeth have a variable pitch.
　第１軸１１０側においては、モジュール、ねじれ角及び歯数が、ストローク量、ストロークレシオ、軸交角（出力軸１５とラックシャフト１２Ａの交差角度）、強度の要件等が満たされるように設定される。第２軸１２０側においては、モジュール、ねじれ角、外径及び位相角が、電動モータ２１によるアシスト推力、耐久強度及び車両への搭載性、転舵追従特性の要件等が満たされるように設定される。 On the first shaft 110 side, the module, the twist angle, and the number of teeth are set so that the stroke amount, the stroke ratio, the axis crossing angle (intersection angle between the output shaft 15 and the rack shaft 12A), the strength requirements, and the like are satisfied. . On the second shaft 120 side, the module, the torsion angle, the outer diameter, and the phase angle are set so that the assist thrust by the electric motor 21, the durability, the mounting property on the vehicle, the requirements for the steering follow-up characteristic, and the like are satisfied. The
　なお、第１ラック形成工程及び第２ラック形成工程は、摩擦圧接工程の前に行ってもよいし、摩擦圧接工程の後に行ってもよい。第１ラック１１５及び第２ラック１２５のいずれか一方を形成するラック形成工程を行ってから摩擦圧接工程を行い、既に形成されたラックの周方向位置に対応するように、他方のラックを形成するラック形成工程を行ってもよい。この場合、第１ラック１１５と第２ラック１２５との周方向の位置決め精度が、摩擦圧接の影響を受けることがないので好適である。本実施形態では、第１ラック１１５の基準ピッチ線Ｐ１と第２ラック１２５の基準ピッチ線Ｐ２とが平行となるように、第１ラック１１５及び第２ラック１２５のラック歯が形成されている（図３Ａ参照）。なお、第１ラック１１５の基準ピッチ線Ｐ１と第２ラック１２５の基準ピッチ線Ｐ２は、平行となる場合に限定されず、互いに傾いていてもよい。 The first rack forming step and the second rack forming step may be performed before the friction welding step or after the friction welding step. After performing the rack forming process for forming one of the first rack 115 and the second rack 125, the friction welding process is performed, and the other rack is formed so as to correspond to the circumferential position of the already formed rack. A rack forming step may be performed. In this case, the positioning accuracy in the circumferential direction between the first rack 115 and the second rack 125 is not affected by the friction welding, which is preferable. In the present embodiment, the rack teeth of the first rack 115 and the second rack 125 are formed so that the reference pitch line P1 of the first rack 115 and the reference pitch line P2 of the second rack 125 are parallel to each other ( (See FIG. 3A). The reference pitch line P1 of the first rack 115 and the reference pitch line P2 of the second rack 125 are not limited to being parallel to each other, and may be inclined with respect to each other.
　図３Ａ及び図３Ｂは、図１のＩＩＩ－ＩＩＩ線に沿うラックシャフトの横断面図である。図３Ａでは、ラックシャフト１２Ａの各部寸法を示し、図３Ｂでは、ラックシャフト１２Ａと出力軸１５及びピニオン軸２２との位置関係を示している。なお、図３Ｂでは、出力軸１５及びピニオン軸２２の中心軸ＣＬ１，ＣＬ２のみを示し、第１ピニオン１６、第２ピニオン２３の図示は省略している。 3A and 3B are cross-sectional views of the rack shaft along the line III-III in FIG. 3A shows the dimensions of each part of the rack shaft 12A, and FIG. 3B shows the positional relationship between the rack shaft 12A, the output shaft 15, and the pinion shaft 22. In FIG. 3B, only the center axes CL1 and CL2 of the output shaft 15 and the pinion shaft 22 are shown, and the first pinion 16 and the second pinion 23 are not shown.
　図１に示すように、第１軸１１０の本体部１１１において、第１ラック１１５が形成された部分を第１ラック形成部１１６と称し、第２軸１２０の本体部１２１において、第２ラック１２５が形成された部分を第２ラック形成部１２６と称する。第１ラック形成部１１６及び第２ラック形成部１２６の軸方向長さは、車輪２を左右に最大転舵角度まで転舵するためにラックシャフト１２Ａをスライド可能な長さに相当する。 As shown in FIG. 1, the portion of the main body 111 of the first shaft 110 where the first rack 115 is formed is referred to as a first rack forming portion 116, and the second rack 125 is formed of the main body 121 of the second shaft 120. The portion in which is formed is referred to as a second rack forming portion 126. The axial lengths of the first rack forming portion 116 and the second rack forming portion 126 correspond to a length that allows the rack shaft 12A to be slid in order to steer the wheel 2 left and right to the maximum turning angle.
　図３Ａ及び図３Ｂでは、第１軸１１０の第１ラック形成部１１６における横断面の形状を実線で示し、第２軸１２０の第２ラック形成部１２６における横断面の形状を二点鎖線で示している。 3A and 3B, the shape of the cross section of the first rack forming portion 116 of the first shaft 110 is indicated by a solid line, and the shape of the cross section of the second rack forming portion 126 of the second shaft 120 is indicated by a two-dot chain line. ing.
　図３Ａを参照して、第１軸１１０の各部寸法と、第２軸１２０の各部寸法とを比較する。なお、第１ラック１１５の基準ピッチ線Ｐ１及びラックシャフト１２Ａの中心軸Ｏのそれぞれに直交し、かつ、ラックシャフト１２Ａの中心軸Ｏを通る軸をＺ軸として説明する。 Referring to FIG. 3A, the dimensions of each part of the first shaft 110 and the dimensions of each part of the second shaft 120 are compared. Note that an axis that is orthogonal to the reference pitch line P1 of the first rack 115 and the center axis O of the rack shaft 12A and that passes through the center axis O of the rack shaft 12A will be described as a Z axis.
　図３Ａに示すように、本実施形態では、第１ラック形成部１１６の各部の寸法は、第１ラック形成部１１６の各部に対応する第２ラック形成部１２６の各部の寸法よりも小さい。以下、詳しく説明する。 As shown in FIG. 3A, in this embodiment, the dimensions of each part of the first rack forming part 116 are smaller than the dimensions of each part of the second rack forming part 126 corresponding to each part of the first rack forming part 116. This will be described in detail below.
　第１ラック１１５の歯幅Ｗ１は、第２ラック１２５の歯幅Ｗ２よりも小さい（Ｗ１＜Ｗ２）。第１ラック１１５の歯幅Ｗ１は、第１ラック形成部１１６の外径Ｄ１よりも小さく、第２ラック１２５の歯幅Ｗ２は、第２ラック形成部１２６の外径Ｄ２よりも小さい（Ｗ１＜Ｄ１，Ｗ２＜Ｄ２）。第１ラック形成部１１６の半径Ｒ１（＝（１／２）×Ｄ１）は、第２ラック形成部１２６の半径Ｒ２（＝（１／２）×Ｄ２）よりも小さい（Ｒ１＜Ｒ２）。 The tooth width W1 of the first rack 115 is smaller than the tooth width W2 of the second rack 125 (W1 <W2). The tooth width W1 of the first rack 115 is smaller than the outer diameter D1 of the first rack forming portion 116, and the tooth width W2 of the second rack 125 is smaller than the outer diameter D2 of the second rack forming portion 126 (W1 < D1, W2 <D2). The radius R1 (= (1/2) × D1) of the first rack forming portion 116 is smaller than the radius R2 (= (1/2) × D2) of the second rack forming portion 126 (R1 <R2).
　第１ラック形成部１１６の肉厚Ｔ１は、第２ラック形成部１２６の肉厚Ｔ２よりも小さい（Ｔ１＜Ｔ２）。肉厚Ｔ１は、Ｚ軸上における第１ラック１１５の歯先から第１ラック形成部１１６の背面までのＺ軸寸法であり、肉厚Ｔ２は、Ｚ軸上における第２ラック１２５の歯先から第２ラック形成部１２６の背面までのＺ軸寸法である。 The wall thickness T1 of the first rack forming section 116 is smaller than the wall thickness T2 of the second rack forming section 126 (T1 <T2). The wall thickness T1 is the Z-axis dimension from the tooth tip of the first rack 115 on the Z-axis to the back surface of the first rack forming portion 116, and the wall thickness T2 is from the tooth tip of the second rack 125 on the Z-axis. This is the Z-axis dimension up to the back surface of the second rack forming portion 126.
　ラックシャフト１２Ａの中心軸Ｏから第１ラック１１５の基準ピッチ線Ｐ１までのＺ軸寸法Ｚ１は、中心軸Ｏから第２ラック１２５の基準ピッチ線Ｐ２までのＺ軸寸法Ｚ２よりも小さい（Ｚ１＜Ｚ２）。このため、出力軸１５の中心軸ＣＬ１をピニオン軸２２の中心軸ＣＬ２に比べて、ラックシャフト１２Ａの中心軸Ｏに近づけることができる。本実施形態では、図３Ｂに示すように、ラックシャフト１２Ａと出力軸１５の軸間距離ＺＬ１が、ラックシャフト１２Ａとピニオン軸２２の軸間距離ＺＬ２よりも小さくなるように、ピニオン軸２２及び出力軸１５が配置されている。軸間距離ＺＬ１は、ラックシャフト１２Ａの中心軸Ｏから出力軸１５の中心軸ＣＬ１までのＺ軸寸法であり、軸間距離ＺＬ２は、ラックシャフト１２Ａの中心軸Ｏからピニオン軸２２の中心軸ＣＬ２までのＺ軸寸法である。 The Z-axis dimension Z1 from the center axis O of the rack shaft 12A to the reference pitch line P1 of the first rack 115 is smaller than the Z-axis dimension Z2 from the center axis O to the reference pitch line P2 of the second rack 125 (Z1 < Z2). For this reason, the center axis CL1 of the output shaft 15 can be brought closer to the center axis O of the rack shaft 12A than the center axis CL2 of the pinion shaft 22. In the present embodiment, as shown in FIG. 3B, the pinion shaft 22 and the output so that the inter-axis distance ZL1 between the rack shaft 12A and the output shaft 15 is smaller than the inter-axis distance ZL2 between the rack shaft 12A and the pinion shaft 22. A shaft 15 is arranged. The inter-axis distance ZL1 is the Z-axis dimension from the central axis O of the rack shaft 12A to the central axis CL1 of the output shaft 15, and the inter-axis distance ZL2 is the central axis CL2 of the pinion shaft 22 from the central axis O of the rack shaft 12A. Z-axis dimensions up to.
　以上の第１実施形態によれば、以下に示す作用効果を奏する。 According to the above 1st Embodiment, there exists the effect shown below.
　（１）ラックシャフト１２Ａは、操舵力が伝達される第１ラック１１５が形成された第１軸１１０と、電動モータ２１の駆動力が伝達される第２ラック１２５が形成され、第１軸１１０に結合された第２軸１２０と、を備えている。第１軸１１０の外径Ｄ１と第２軸１２０の外径Ｄ２とは異径である。第１軸１１０及び第２軸１２０のうち、一方の軸の径が他方の軸の径に比べて小さいので、一方の軸の外径が他方の軸の外径と同じ場合に比べて、質量を軽減できる。したがって、ラックシャフト１２Ａ及びステアリング装置１００を軽量化できる。 (1) The rack shaft 12A includes a first shaft 110 on which a first rack 115 to which a steering force is transmitted and a second rack 125 to which a driving force of the electric motor 21 is transmitted. And a second shaft 120 coupled to the second shaft 120. The outer diameter D1 of the first shaft 110 and the outer diameter D2 of the second shaft 120 are different diameters. Since the diameter of one of the first shaft 110 and the second shaft 120 is smaller than the diameter of the other shaft, the mass of one shaft is smaller than that of the other shaft. Can be reduced. Therefore, the rack shaft 12A and the steering device 100 can be reduced in weight.
　（２）本実施形態では、第１軸１１０及び第２軸１２０の材料は同じである。第１軸１１０及び第２軸１２０は、それぞれ中実の円柱状部材である。電動モータ２１の駆動力が伝達される第２軸１２０に比べて、操舵力が伝達される第１軸１１０に作用する負荷は小さい。このため、本実施形態では、第１軸１１０の第１ラック形成部１１６における外径Ｄ１を第２軸１２０における第２ラック形成部１２６における外径Ｄ２よりも小さくしている（Ｄ１＜Ｄ２）。これにより、第１軸１１０の質量を第２軸１２０の質量よりも小さくしてラックシャフト１２Ａを軽量化できる。さらに、第２軸１２０の強度は、第１軸１１０の強度よりも大きくできるので、電動モータ２１からの高い負荷にも優れた耐久性を有するラックシャフト１２Ａとすることができる。このように、本実施形態によれば、第１軸１１０及び第２軸１２０のそれぞれに必要な強度を満足しつつ、ラックシャフト１２Ａの軽量化を図ることができる。 (2) In the present embodiment, the materials of the first shaft 110 and the second shaft 120 are the same. Each of the first shaft 110 and the second shaft 120 is a solid columnar member. The load acting on the first shaft 110 to which the steering force is transmitted is smaller than that of the second shaft 120 to which the driving force of the electric motor 21 is transmitted. For this reason, in this embodiment, the outer diameter D1 of the first rack forming portion 116 of the first shaft 110 is smaller than the outer diameter D2 of the second rack forming portion 126 of the second shaft 120 (D1 <D2). . Thereby, the mass of the 1st axis | shaft 110 can be made smaller than the mass of the 2nd axis | shaft 120, and the rack shaft 12A can be reduced in weight. Furthermore, since the strength of the second shaft 120 can be greater than the strength of the first shaft 110, the rack shaft 12 </ b> A having excellent durability against a high load from the electric motor 21 can be obtained. Thus, according to the present embodiment, the rack shaft 12A can be reduced in weight while satisfying the strength required for each of the first shaft 110 and the second shaft 120.
　（３）ラックシャフト１２Ａの中心軸Ｏから基準ピッチ線Ｐ１までのＺ軸寸法Ｚ１が、中心軸Ｏから基準ピッチ線Ｐ２までのＺ軸寸法Ｚ２よりも小さい。このため、図３Ｂに示すように、出力軸１５の中心軸ＣＬ１をピニオン軸２２の中心軸ＣＬ２に比べて、ラックシャフト１２Ａの中心軸Ｏに近づけることができる（ＺＬ１＜ＺＬ２）。本実施形態では、出力軸１５とラックシャフト１２Ａの軸間距離が短くなるように、出力軸１５をラックシャフト１２Ａに近接させ、この部分をコンパクトにした。この結果、ステアリング装置１００の車両への取付自由度を向上、すなわち搭載性を向上できる。 (3) The Z-axis dimension Z1 from the center axis O of the rack shaft 12A to the reference pitch line P1 is smaller than the Z-axis dimension Z2 from the center axis O to the reference pitch line P2. Therefore, as shown in FIG. 3B, the center axis CL1 of the output shaft 15 can be brought closer to the center axis O of the rack shaft 12A than the center axis CL2 of the pinion shaft 22 (ZL1 <ZL2). In the present embodiment, the output shaft 15 is brought close to the rack shaft 12A so that the distance between the output shaft 15 and the rack shaft 12A is shortened, and this portion is made compact. As a result, the degree of freedom of attachment of the steering device 100 to the vehicle can be improved, that is, the mountability can be improved.
　（４）本実施形態では、第１軸１１０及び第２軸１２０の外径を個別に設定できる。このため、たとえば、第１軸１１０の外径Ｄ１に比べて第２軸１２０の外径Ｄ２を大きくすることにより、第２ピニオン２３に対する第２軸１２０のラック歯の接触面積を大きくできる。これにより、ピニオン軸２２とラックシャフト１２Ａの交差角度である軸交角の自由度を向上できる。その結果、ステアリング装置１００の車両への取付自由度を向上、すなわち搭載性を向上できる。 (4) In the present embodiment, the outer diameters of the first shaft 110 and the second shaft 120 can be set individually. For this reason, for example, by making the outer diameter D2 of the second shaft 120 larger than the outer diameter D1 of the first shaft 110, the contact area of the rack teeth of the second shaft 120 with the second pinion 23 can be increased. Thereby, the freedom degree of the axis crossing angle which is the crossing angle of the pinion shaft 22 and the rack shaft 12A can be improved. As a result, the degree of freedom of mounting the steering device 100 on the vehicle can be improved, that is, the mountability can be improved.
　＜第１実施形態の変形例１＞
　上記第１実施形態では、連結筒部１１２の外径Ｄ１と連結筒部１２２の外径Ｄ３とが同じになるように連結筒部１１２，１２２が形成される例について説明したが（図２Ａ、図２Ｂ参照）、本発明はこれに限定されない。連結筒部１１２，１２２のいずれか一方を大きく形成してもよい。たとえば、連結筒部１１２の外径Ｄ１に対して、連結筒部１２２の外径Ｄ３を大きく形成してもよい（Ｄ３＞Ｄ１）。少なくとも、十分な接合強度を得ることができる程度の接触面積を得ることができるように連結筒部１１２，１２２を形成すればよい。 <Variation 1 of the first embodiment>
Although the said 1st Embodiment demonstrated the example in which the connection cylinder part 112,122 was formed so that the outer diameter D1 of the connection cylinder part 112 and the outer diameter D3 of the connection cylinder part 122 may become the same (FIG. 2A, The present invention is not limited to this. Either one of the connecting tube portions 112 and 122 may be formed larger. For example, the outer diameter D3 of the connecting cylinder part 122 may be formed larger than the outer diameter D1 of the connecting cylinder part 112 (D3> D1). What is necessary is just to form the connection cylinder parts 112 and 122 so that the contact area of the grade which can obtain sufficient joint strength at least can be obtained.
　＜第１実施形態の変形例２＞
　上記第１実施形態では、第１ラック形成部１１６の各部の寸法が、第１ラック形成部１１６の各部に対応する第２ラック形成部１２６の各部の寸法よりも小さい例について説明したが、本発明はこれに限定されない。たとえば、第１ラック形成部１１６の外径Ｄ１と第２ラック形成部１２６の外径Ｄ２との差が小さい場合、ラックシャフト１２Ａの中心軸Ｏから基準ピッチ線Ｐ１，Ｐ２までのＺ軸寸法Ｚ１，Ｚ２の大小関係が、Ｚ１＞Ｚ２となる場合もある。また、肉厚Ｔ１，Ｔ２の大小関係が、Ｔ１＞Ｔ２となる場合もある。 <Modification 2 of the first embodiment>
In the first embodiment, the example in which the size of each part of the first rack forming unit 116 is smaller than the size of each part of the second rack forming unit 126 corresponding to each part of the first rack forming unit 116 has been described. The invention is not limited to this. For example, when the difference between the outer diameter D1 of the first rack forming portion 116 and the outer diameter D2 of the second rack forming portion 126 is small, the Z-axis dimension Z1 from the central axis O of the rack shaft 12A to the reference pitch lines P1, P2 , Z2 may be such that Z1> Z2. Further, the magnitude relationship between the thicknesses T1 and T2 may satisfy T1> T2.
　＜第２実施形態＞
　図４Ａを参照して、本発明の第２実施形態に係るラックシャフト１２Ｂ１について説明する。以下では、上記第１実施形態と異なる点を中心に説明し、図中、上記第１実施形態で説明した構成と同一の構成または相当する構成には同一の符号を付して説明を省略する。 Second Embodiment
With reference to FIG. 4A, a rack shaft 12B1 according to a second embodiment of the present invention will be described. The following description will focus on differences from the first embodiment, and in the figure, the same or corresponding components as those described in the first embodiment will be denoted by the same reference numerals and description thereof will be omitted. .
　図４Ａは、ラックシャフト１２Ｂ１の結合部分を示す縦断面図である。上記第１実施形態では、第１軸１１０及び第２軸１２０のそれぞれが中実の円柱状部材であったが、第２実施形態では、第１軸２１０が中空の円筒状部材である点で、上記第１実施形態と相違する。以下、具体的に説明する。 FIG. 4A is a longitudinal sectional view showing a coupling portion of the rack shaft 12B1. In the first embodiment, each of the first shaft 110 and the second shaft 120 is a solid columnar member. However, in the second embodiment, the first shaft 210 is a hollow cylindrical member. This is different from the first embodiment. This will be specifically described below.
　図４Ａに示すように、第１軸２１０は、円筒状部材とされている。第２軸１２０の連結筒部１２２は、連結筒部１２２の肉厚が第１軸２１０の肉厚と同一となるように形成されている。第１軸２１０の軸方向端部は、摩擦圧接により、第２軸１２０の連結筒部１２２に接合される。 As shown in FIG. 4A, the first shaft 210 is a cylindrical member. The connecting tube portion 122 of the second shaft 120 is formed so that the thickness of the connecting tube portion 122 is the same as the thickness of the first shaft 210. An axial end portion of the first shaft 210 is joined to the connecting tube portion 122 of the second shaft 120 by friction welding.
　なお、本実施形態では、第１ラック形成工程を摩擦圧接工程前に行うことが好ましい。第１ラック形成工程では、第１軸２１０をラック形成用の金型で保持した状態で、第１軸２１０の中空部に円柱状のマンドレルを往復動作させる。これにより、第１軸２１０を徐々に塑性変形させる。少しずつ径の大きなマンドレルを軸方向に往復動作させることで、第１軸２１０の第１ラック形成部１１６に第１ラック１１５を形成することができる。 In the present embodiment, it is preferable to perform the first rack forming process before the friction welding process. In the first rack forming step, a cylindrical mandrel is reciprocated in the hollow portion of the first shaft 210 while the first shaft 210 is held by a rack forming mold. Thereby, the first shaft 210 is gradually plastically deformed. The first rack 115 can be formed on the first rack forming portion 116 of the first shaft 210 by reciprocating the mandrel having a large diameter little by little in the axial direction.
　第２実施形態では、第１実施形態と同様、第１ラック形成部１１６における第１軸２１０の外径Ｄ１が、第２ラック形成部１２６における第２軸１２０の外径Ｄ２よりも小さい（Ｄ１＜Ｄ２）。 In the second embodiment, as in the first embodiment, the outer diameter D1 of the first shaft 210 in the first rack forming portion 116 is smaller than the outer diameter D2 of the second shaft 120 in the second rack forming portion 126 (D1 <D2).
　このような第２実施形態によれば、第１実施形態と同様の作用効果に加え、次の作用効果を奏する。 According to such a second embodiment, in addition to the same functions and effects as those of the first embodiment, the following functions and effects are achieved.
　（５）第１軸２１０を円筒状部材とすることで、第１実施形態に比べて、さらにラックシャフト１２Ｂ１及びステアリング装置１００を軽量化できる。 (5) By using the first shaft 210 as a cylindrical member, the rack shaft 12B1 and the steering device 100 can be further reduced in weight compared to the first embodiment.
　＜第２実施形態の変形例＞
　上記第２実施形態では、第２軸１２０の外径Ｄ２に比べて小さい外径Ｄ３（＝Ｄ１）の連結筒部１２２を設ける例（Ｄ２＞Ｄ３＝Ｄ１）について説明したが、本発明はこれに限定されない。図４Ｂは、本発明の第２実施形態の変形例に係るラックシャフト１２Ｂ２の結合部分を示す縦断面図である。 <Modification of Second Embodiment>
In the second embodiment, the example (D2> D3 = D1) in which the connecting cylinder portion 122 having the outer diameter D3 (= D1) smaller than the outer diameter D2 of the second shaft 120 is described. It is not limited to. FIG. 4B is a longitudinal sectional view showing a coupling portion of the rack shaft 12B2 according to a modification of the second embodiment of the present invention.
　図４Ｂに示すように、第２軸２２０の軸方向端部に外径Ｄ２の連結筒部２２２を形成し、第１軸２１０の軸方向端部に、拡径加工を施して、外径Ｄ２の連結筒部２１２を形成してもよい。このような変形例であっても、第１ラック形成部１１６における外径Ｄ１を第２ラック形成部１２６における外径Ｄ２よりも小さくできるので、ラックシャフト１２Ｂ２及びステアリング装置１００を軽量化できる。さらに、本変形例によれば、連結筒部２１２，２２２の外径が上記実施形態に比べて大きいため、摩擦圧接工程において、第１軸２１０と第２軸２２０の相対回転速度を低く抑えても摩擦圧接に必要な周速度を得ることができる。 As shown in FIG. 4B, a connecting tube portion 222 having an outer diameter D2 is formed at the axial end portion of the second shaft 220, and the outer diameter D2 is applied to the axial end portion of the first shaft 210. The connecting tube portion 212 may be formed. Even in such a modification, the outer diameter D1 of the first rack forming portion 116 can be made smaller than the outer diameter D2 of the second rack forming portion 126, so that the rack shaft 12B2 and the steering device 100 can be reduced in weight. Furthermore, according to this modification, the outer diameters of the connecting tube portions 212 and 222 are larger than those in the above embodiment, so that the relative rotational speed of the first shaft 210 and the second shaft 220 is kept low in the friction welding process. Also, the peripheral speed necessary for friction welding can be obtained.
　＜第３実施形態＞
　図５Ａを参照して、本発明の第３実施形態に係るラックシャフト１２Ｃ１について説明する。以下では、上記第１実施形態と異なる点を中心に説明し、図中、上記第１実施形態で説明した構成と同一の構成または相当する構成には同一の符号を付して説明を省略する。図５Ａは、本発明の第３実施形態に係るラックシャフト１２Ｃ１を示す平面図である。 <Third Embodiment>
A rack shaft 12C1 according to a third embodiment of the present invention will be described with reference to FIG. 5A. The following description will focus on differences from the first embodiment, and in the figure, the same or corresponding components as those described in the first embodiment will be denoted by the same reference numerals and description thereof will be omitted. . FIG. 5A is a plan view showing a rack shaft 12C1 according to a third embodiment of the present invention.
　第１軸３１０Ａ及び第２軸３２０Ａは、それぞれ同じ材料から形成された中実の円柱状部材である。このため、小径の第１軸３１０Ａの第１ラック形成部１１６における単位長さ当たりの質量は、大径の第２軸３２０Ａの第２ラック形成部１２６における単位長さ当たりの質量よりも小さい。 The first shaft 310A and the second shaft 320A are solid cylindrical members formed from the same material. For this reason, the mass per unit length in the first rack forming portion 116 of the small-diameter first shaft 310A is smaller than the mass per unit length in the second rack forming portion 126 of the large-diameter second shaft 320A.
　そこで、第３実施形態では、単位長さ当たりの質量が小さい第１軸３１０Ａの長さを、単位長さ当たりの質量が大きい第２軸３２０Ａの長さよりも長くして軽量化を実現している。つまり、上記第１実施形態では、第１軸１１０の軸長と第２軸１２０の軸長とが同じであるが、第３実施形態では、第１軸３１０Ａの軸長Ｌ１が第２軸３２０Ａの軸長Ｌ２よりも長い点で、上記第１実施形態と相違する。なお、ラックシャフト１２Ｃ１の全長は第１実施形態のラックシャフト１２Ａの全長と同じである。 Therefore, in the third embodiment, the length of the first shaft 310A having a small mass per unit length is made longer than the length of the second shaft 320A having a large mass per unit length, thereby realizing weight reduction. Yes. That is, in the first embodiment, the shaft length of the first shaft 110 is the same as the shaft length of the second shaft 120, but in the third embodiment, the shaft length L1 of the first shaft 310A is the second shaft 320A. This is different from the first embodiment in that it is longer than the axial length L2. The total length of the rack shaft 12C1 is the same as the total length of the rack shaft 12A of the first embodiment.
　このような第３実施形態によれば、第１実施形態と同様の作用効果に加え、次の作用効果を奏する。 According to the third embodiment as described above, in addition to the same functions and effects as those of the first embodiment, the following functions and effects are achieved.
　（６）第１軸３１０Ａ及び第２軸３２０Ａのうち、単位長さ当たりの質量が小さい一方の軸が、単位長さ当たりの質量が大きい他方の軸に比べて長く形成されている。これにより、第１実施形態に比べて、さらにラックシャフト１２Ｃ１及びステアリング装置１００を軽量化できる。 (6) Of the first axis 310A and the second axis 320A, one axis having a small mass per unit length is formed longer than the other axis having a large mass per unit length. Thereby, compared with 1st Embodiment, the rack shaft 12C1 and the steering device 100 can further be reduced in weight.
　＜第３実施形態の変形例＞
　上記第３実施形態では、第１軸３１０Ａと第２軸３２０Ａとが中実の円柱状部材である例について説明したが、本発明はこれに限定されない。図５Ｂは、本発明の第３実施形態の変形例に係るラックシャフト１２Ｃ２を示す平面図である。 <Modification of Third Embodiment>
In the third embodiment, the example in which the first shaft 310A and the second shaft 320A are solid cylindrical members has been described, but the present invention is not limited to this. FIG. 5B is a plan view showing a rack shaft 12C2 according to a modification of the third embodiment of the present invention.
　図５Ｂに示すように、本変形例では、第１軸３１０Ｂが中空の円筒状部材であって、第１軸３１０Ｂの外径が第２軸３２０Ｂの外径よりも大きい。第１軸３１０Ｂは、中空の円筒状部材であり、鍛造加工により第１ラック１１５が形成される。第２軸３２０Ｂは、中実の円柱状部材であり、切削加工により第２ラック１２５が形成される。鍛造加工よりも切削加工の方が精度良くラック歯を成形することができるため、第２ラック１２５と第２ピニオン２３との噛み合い精度は、第１ラック１１５と第１ピニオン１６との噛み合い精度よりも高い。比較的高い負荷が作用する第２軸３２０Ｂのラック歯とピニオンとの噛み合い精度を高めることにより、第２ラック１２５の耐久性を確保することができる。 As shown in FIG. 5B, in this modification, the first shaft 310B is a hollow cylindrical member, and the outer diameter of the first shaft 310B is larger than the outer diameter of the second shaft 320B. The first shaft 310B is a hollow cylindrical member, and the first rack 115 is formed by forging. The second shaft 320B is a solid cylindrical member, and the second rack 125 is formed by cutting. Since the rack teeth can be formed more accurately in the cutting process than in the forging process, the meshing accuracy between the second rack 125 and the second pinion 23 is higher than the meshing accuracy between the first rack 115 and the first pinion 16. Is also expensive. The durability of the second rack 125 can be ensured by increasing the meshing accuracy between the rack teeth of the second shaft 320B on which a relatively high load acts and the pinion.
　本変形例においても第１ラック形成部１１６における単位長さ当たりの質量は、第２ラック形成部１２６における単位長さ当たりの質量に比べて小さい。このため、第１軸３１０Ｂの軸長Ｌ１を第２軸３２０Ｂの軸長Ｌ２よりも長く形成することで、軸長を同じにする場合に比べて、ラックシャフト１２Ｃ２及びステアリング装置１００を軽量化できる。 Also in this modification, the mass per unit length in the first rack forming portion 116 is smaller than the mass per unit length in the second rack forming portion 126. For this reason, by forming the axial length L1 of the first shaft 310B longer than the axial length L2 of the second shaft 320B, the rack shaft 12C2 and the steering device 100 can be reduced in weight compared to the case where the axial length is the same. .
　＜第４実施形態＞
　図６Ａを参照して、本発明の第４実施形態に係るラックシャフト１２Ｄ１について説明する。以下では、上記第１実施形態と異なる点を中心に説明し、図中、上記第１実施形態で説明した構成と同一の構成または相当する構成には同一の符号を付して説明を省略する。 <Fourth embodiment>
A rack shaft 12D1 according to a fourth embodiment of the present invention will be described with reference to FIG. 6A. The following description will focus on differences from the first embodiment, and in the figure, the same or corresponding components as those described in the first embodiment will be denoted by the same reference numerals and description thereof will be omitted. .
　図６Ａは、本発明の第４実施形態に係るラックシャフト１２Ｄ１を示す縦断面図である。上記第１実施形態では、第１軸１１０の端面１１２ａと第２軸１２０の端面１２２ａとが摩擦圧接により接合される（図２Ａ、図２Ｂ参照）。これに対して、第４実施形態では、第２軸４２０Ａが円筒状部材であり、第１軸４１０Ａが第２軸４２０Ａの中空部に圧入され、溶接されることにより第１軸４１０Ａと第２軸４２０Ａとが結合される。 FIG. 6A is a longitudinal sectional view showing a rack shaft 12D1 according to a fourth embodiment of the present invention. In the first embodiment, the end surface 112a of the first shaft 110 and the end surface 122a of the second shaft 120 are joined by friction welding (see FIGS. 2A and 2B). On the other hand, in the fourth embodiment, the second shaft 420A is a cylindrical member, and the first shaft 410A is press-fitted into the hollow portion of the second shaft 420A and welded, whereby the first shaft 410A and the second shaft 420A are welded. The shaft 420A is coupled.
　このような第４実施形態によれば、第１実施形態と同様の作用効果を奏する。 According to such 4th Embodiment, there exists an effect similar to 1st Embodiment.
　＜第４実施形態の変形例１＞
　上記第４実施形態では、第１軸４１０Ａを第２軸４２０Ａの中空部に圧入した後、溶接により第１軸４１０Ａと第２軸４２０Ａとを結合する例について説明したが、本発明はこれに限定されない。たとえば、焼き嵌めにより両者を結合してもよいし、第１軸４１０Ａに形成した雄ねじを第２軸４２０Ａの中空部に形成した雌ねじに螺合させることにより結合してもよい。 <Modification 1 of 4th Embodiment>
In the fourth embodiment, the example in which the first shaft 410A and the second shaft 420A are joined by welding after the first shaft 410A is press-fitted into the hollow portion of the second shaft 420A has been described. It is not limited. For example, both may be coupled by shrink fitting, or may be coupled by screwing a male screw formed on the first shaft 410A with a female screw formed on the hollow portion of the second shaft 420A.
　＜第４実施形態の変形例２＞
　図６Ｂは、本発明の第４実施形態の変形例２に係るラックシャフト１２Ｄ２を示す縦断面図である。図６Ｂに示すように、本変形例では、ボルト、ナットなどの締結部材４９０により第１軸４１０Ｂの軸方向端部のフランジ４１９と第２軸４２０Ｂの軸方向端部のフランジ４２９とが締結され、第１軸４１０Ｂと第２軸４２０Ｂとが結合される。 <Modification 2 of 4th Embodiment>
FIG. 6B is a longitudinal sectional view showing a rack shaft 12D2 according to the second modification of the fourth embodiment of the present invention. As shown in FIG. 6B, in this modification, the flange 419 at the axial end of the first shaft 410B and the flange 429 at the axial end of the second shaft 420B are fastened by a fastening member 490 such as a bolt or nut. The first shaft 410B and the second shaft 420B are coupled.
　＜第４実施形態の変形例３＞
　図６Ｃは、本発明の第４実施形態の変形例３に係るラックシャフト１２Ｄ３を示す縦断面図である。図６Ｃに示すように、本変形例では、ボールジョイント４９１のソケット４９３と第１軸４１０Ｃに設けられた段部４１８との間に第２軸４２０Ｃが挟まれた状態で、第１軸４１０Ｃと第２軸４２０Ｃとが結合される。第１軸４１０Ｃには、本体部１１１の軸方向端部から軸方向に突出する円柱状の嵌入部４１７が設けられる。嵌入部４１７は、第２軸４２０Ｃの中空部に嵌入される部分であって、本体部１１１よりも外径が小さい。嵌入部４１７が本体部１１１よりも小径に形成されるので、第２軸４２０Ｃの軸方向端面に対向する本体部１１１の軸方向端面が段部４１８とされる。 <Modification 3 of 4th Embodiment>
FIG. 6C is a longitudinal sectional view showing a rack shaft 12D3 according to Modification 3 of the fourth embodiment of the present invention. As shown in FIG. 6C, in this modification, the first shaft 410C and the second shaft 420C are sandwiched between the socket 493 of the ball joint 491 and the step 418 provided on the first shaft 410C. The second shaft 420C is coupled. The first shaft 410 </ b> C is provided with a columnar fitting portion 417 that protrudes in the axial direction from the axial end portion of the main body portion 111. The fitting portion 417 is a portion that is fitted into the hollow portion of the second shaft 420 </ b> C and has an outer diameter smaller than that of the main body portion 111. Since the fitting portion 417 is formed to have a smaller diameter than the main body portion 111, the axial end surface of the main body portion 111 facing the axial end surface of the second shaft 420 </ b> C is a stepped portion 418.
　タイロッド２５の端部には、ラックシャフト１２Ｄ３の端部に接続される自在継手であるボールジョイント４９１が設けられる。ボールジョイント４９１は、第１軸４１０Ｃの端部に固着されるソケット４９３と、タイロッド２５の軸部の端部に固着されるボール４９２と、を有する。ソケット４９３は、ボール４９２を収容するボール収容部４９３ａと、ボール収容部４９３ａの基端側に一体的に設けられたボルト４９３ｂと、を有する。ボルト４９３ｂに設けられた雄ねじが、第１軸４１０Ｃの嵌入部４１７の先端面から軸方向に延在する孔部４４９に設けられた雌ねじに螺合されることにより、ソケット４９３が第１軸４１０Ｃに固着される。 A ball joint 491 which is a universal joint connected to the end of the rack shaft 12D3 is provided at the end of the tie rod 25. The ball joint 491 includes a socket 493 fixed to the end portion of the first shaft 410C and a ball 492 fixed to the end portion of the shaft portion of the tie rod 25. The socket 493 includes a ball accommodating portion 493a that accommodates the ball 492, and a bolt 493b that is integrally provided on the proximal end side of the ball accommodating portion 493a. The male screw provided on the bolt 493b is screwed into the female screw provided in the hole 449 extending in the axial direction from the distal end surface of the fitting portion 417 of the first shaft 410C, whereby the socket 493 is engaged with the first shaft 410C. It is fixed to.
　本変形例では、第１軸４１０Ｃの嵌入部４１７が、第２軸４２０Ｃの中空部に嵌入された後、ソケット４９３のボルト４９３ｂが嵌入部４１７の先端部に螺合される。これにより、ソケット４９３と第１軸４１０Ｃの段部４１８との間で第２軸４２０Ｃが挟持され、第１軸４１０Ｃと第２軸４２０Ｃとが結合される。図６Ｃでは、ソケット４９３とラックシャフト１２Ｄ３との間に円環状の環状部材４９９を介在させる例について図示しているが、環状部材４９９は省略してもよい。このように、ソケット４９３と第１軸４１０Ｃの段部４１８とで第２軸４２０Ｃを挟持する場合、第１軸４１０Ｃの嵌入部４１７の外周部と第２軸４２０Ｃの内周部のそれぞれにキー溝を設け、このキー溝にキーを嵌合させ、第１軸４１０Ｃと第２軸４２０Ｃの回り止めを行うことが好ましい。 In this modification, after the fitting portion 417 of the first shaft 410C is fitted into the hollow portion of the second shaft 420C, the bolt 493b of the socket 493 is screwed into the tip portion of the fitting portion 417. Thereby, the second shaft 420C is sandwiched between the socket 493 and the step portion 418 of the first shaft 410C, and the first shaft 410C and the second shaft 420C are coupled. Although FIG. 6C illustrates an example in which an annular member 499 is interposed between the socket 493 and the rack shaft 12D3, the annular member 499 may be omitted. As described above, when the second shaft 420C is sandwiched between the socket 493 and the step portion 418 of the first shaft 410C, the outer peripheral portion of the fitting portion 417 of the first shaft 410C and the inner peripheral portion of the second shaft 420C are respectively keyed. It is preferable that a groove is provided and a key is fitted into the key groove to prevent the first shaft 410C and the second shaft 420C from rotating.
　＜第５実施形態＞
　図７及び図８を参照して、本発明の第５実施形態に係るラックシャフト１２Ｅについて説明する。以下では、上記第１実施形態と異なる点を中心に説明し、図中、上記第１実施形態で説明した構成と同一の構成または相当する構成には同一の符号を付して説明を省略する。 <Fifth Embodiment>
With reference to FIG.7 and FIG.8, the rack shaft 12E which concerns on 5th Embodiment of this invention is demonstrated. The following description will focus on differences from the first embodiment, and in the figure, the same or corresponding components as those described in the first embodiment will be denoted by the same reference numerals and description thereof will be omitted. .
　図７は、本発明の第５実施形態に係るラックシャフト１２Ｅを示す横断面図であり、図８は、本発明の第５実施形態に係るラックシャフト１２Ｅの支持構造を示す側面図である。なお、図８では、ピニオン及びラックガイドを二点鎖線で示している。 FIG. 7 is a cross-sectional view showing a rack shaft 12E according to a fifth embodiment of the present invention, and FIG. 8 is a side view showing a support structure for the rack shaft 12E according to the fifth embodiment of the present invention. In FIG. 8, the pinion and the rack guide are indicated by a two-dot chain line.
　上記第１実施形態では、第１軸１１０の中心軸と第２軸１２０の中心軸とが同一となるように、第１軸１１０と第２軸１２０とが結合される（図３Ａ参照）。これに対して、第５実施形態では、図７及び図８に示すように、第１軸１１０の中心軸Ｏ１と第２軸１２０の中心軸Ｏ２とが偏心している。 In the first embodiment, the first axis 110 and the second axis 120 are coupled so that the central axis of the first axis 110 and the central axis of the second axis 120 are the same (see FIG. 3A). On the other hand, in the fifth embodiment, as shown in FIGS. 7 and 8, the central axis O1 of the first shaft 110 and the central axis O2 of the second shaft 120 are eccentric.
　図８に示すように、ステアリング装置１００は、第１ラック形成部１１６を背面側（歯裏側）から第１ピニオン１６に向けて押し付ける第１ラックガイド５６１と、第２ラック形成部１２６を背面側から第２ピニオン２３に向けて押し付ける第２ラックガイド５６２と、を備えている。 As shown in FIG. 8, the steering device 100 includes a first rack guide 561 that presses the first rack forming portion 116 from the back side (back side) toward the first pinion 16, and the second rack forming portion 126 on the back side. And a second rack guide 562 for pressing toward the second pinion 23.
　第１ラックガイド５６１は、第１ラック形成部１１６の背面側の形状に対応した円弧面を有するガイド部５６１ａと、ガイド部５６１ａを第１ピニオン１６に向けて付勢するコイルばね５６１ｂと、を備えている。 The first rack guide 561 includes a guide part 561a having an arc surface corresponding to the shape of the back surface side of the first rack forming part 116, and a coil spring 561b that biases the guide part 561a toward the first pinion 16. I have.
　同様に、第２ラックガイド５６２は、第２ラック形成部１２６の背面側の形状に対応した円弧面を有するガイド部５６２ａと、ガイド部５６２ａを第２ピニオン２３に向けて付勢するコイルばね５６２ｂと、を備えている。 Similarly, the second rack guide 562 includes a guide portion 562a having an arc surface corresponding to the shape of the back surface side of the second rack forming portion 126, and a coil spring 562b that biases the guide portion 562a toward the second pinion 23. And.
　第１ラック形成部１１６が第１ピニオン１６と第１ラックガイド５６１とにより挟持され、第２ラック形成部１２６が第２ピニオン２３と第２ラックガイド５６２とにより挟持されている。 The first rack forming portion 116 is sandwiched between the first pinion 16 and the first rack guide 561, and the second rack forming portion 126 is sandwiched between the second pinion 23 and the second rack guide 562.
　ピニオンからラック歯へ回転トルクが作用すると、ラック歯の歯すじに沿ってラックシャフトを回転させるように分力が発生する。しかしながら、本実施形態では、第１軸１１０と第２軸１２０が偏心して配置されているため、一方の軸をその軸の中心軸回りに回転させようとする力が作用したときに、他方の軸のピニオンとラックガイドにより、その回転が阻止される。たとえば、第１軸１１０に対して、第１ピニオン１６から中心軸Ｏ１回りの回転力が作用した場合、第２軸１２０の第２ピニオン２３と第２ラックガイド５６２により、ラックシャフト１２Ｅが中心軸Ｏ１回りに回転することが阻止される。 ∙ When rotational torque acts from the pinion to the rack teeth, a component force is generated to rotate the rack shaft along the rack teeth. However, in the present embodiment, since the first shaft 110 and the second shaft 120 are arranged eccentrically, when a force is applied to rotate one shaft around the central axis of the shaft, The shaft pinion and rack guide prevent its rotation. For example, when a rotational force around the central axis O1 is applied from the first pinion 16 to the first shaft 110, the rack shaft 12E is centered by the second pinion 23 of the second shaft 120 and the second rack guide 562. Rotation around O1 is prevented.
　このような第６実施形態によれば、第１実施形態と同様の作用効果に加え、次の作用効果を奏する。 According to the sixth embodiment, in addition to the same functions and effects as those of the first embodiment, the following functions and effects are achieved.
　（７）第１軸１１０の中心軸Ｏ１に対して、第２軸１２０の中心軸Ｏ２を偏心させたので、ラックシャフト１２Ｅが円形断面であってもラックシャフト１２Ｅの回り止めを行うことができる。 (7) Since the center axis O2 of the second shaft 120 is decentered with respect to the center axis O1 of the first axis 110, the rack shaft 12E can be prevented from rotating even if the rack shaft 12E has a circular cross section. .
　なお、図７では、第１軸１１０の中心軸Ｏ１と第２軸１２０の中心軸Ｏ２とがＺ軸方向に偏心している例について説明したが、偏心の方向は上述した場合に限定されない。また、ラックシャフト１２Ｅの回り止めは、ラックシャフト１２Ｅの両端部を支持する軸受によって行ってもよい。 In FIG. 7, the example in which the central axis O1 of the first shaft 110 and the central axis O2 of the second shaft 120 are eccentric in the Z-axis direction has been described, but the direction of eccentricity is not limited to the case described above. Further, the rotation prevention of the rack shaft 12E may be performed by bearings that support both ends of the rack shaft 12E.
　以下のような変形例も本発明の範囲内であり、変形例に示す構成と上述の実施形態で説明した構成を組み合わせたり、上述の異なる実施形態で説明した構成同士を組み合わせたり、以下の異なる変形例で説明する構成同士を組み合わせることも可能である。 The following modified examples are also within the scope of the present invention, and the configuration shown in the modified example and the configuration described in the above-described embodiment are combined, the configurations described in the above-described different embodiments are combined, or the following different It is also possible to combine the configurations described in the modification.
　（変形例１）
　上記実施形態では、第１軸１１０及び第２軸１２０を円形断面の部材とした例について説明したが、本発明はこれに限定されない。たとえば、第１軸及び第２軸の一方または双方を楕円形状としてもよい。図９は、本発明の実施形態の変形例１に係るラックシャフト１２Ｇの横断面図である。図９では、第１軸７１０の第１ラック形成部１１６の横断面の形状を実線で示し、第２軸７２０の第２ラック形成部１２６の横断面の形状を二点鎖線で示している。変形例１では、第１ラック形成部１１６の各部の寸法が、第２ラック形成部１２６の各部の寸法よりも小さい。上記各部の寸法には、ラックの歯幅Ｗ１，Ｗ２、ラック形成部における長軸の長さ（長径ａ１，ａ２）及び短軸の長さ（短径ｂ１，ｂ２）、ラック形成部の肉厚Ｔ１，Ｔ２、並びに、ラックシャフトの中心軸Ｏから基準ピッチ線Ｐ１，Ｐ２までのＺ軸寸法Ｚ１，Ｚ２が含まれる。 (Modification 1)
Although the said embodiment demonstrated the example which used the 1st axis | shaft 110 and the 2nd axis | shaft 120 as the member of a circular cross section, this invention is not limited to this. For example, one or both of the first axis and the second axis may be elliptical. FIG. 9 is a cross-sectional view of a rack shaft 12G according to the first modification of the embodiment of the present invention. In FIG. 9, the shape of the cross section of the first rack forming portion 116 of the first shaft 710 is indicated by a solid line, and the shape of the cross section of the second rack forming portion 126 of the second shaft 720 is indicated by a two-dot chain line. In the first modification, the dimensions of each part of the first rack forming part 116 are smaller than the dimensions of each part of the second rack forming part 126. The dimensions of the above-mentioned parts include the rack tooth widths W1 and W2, the lengths of the long axes (long diameters a1 and a2) and the short axes (short diameters b1 and b2) in the rack forming part, and the thickness of the rack forming part. T1 and T2, and Z axis dimensions Z1 and Z2 from the center axis O of the rack shaft to the reference pitch lines P1 and P2 are included.
　なお、変形例１に係るラックシャフト１２Ｇは、中心軸Ｏに直交する横断面形状における各部の寸法の全てを異ならせることに限定されることもなく、少なくとも長径ａ１，ａ２が、第１軸７１０と第２軸７２０とで異なっていればよい。 The rack shaft 12G according to the modification 1 is not limited to changing all the dimensions of each part in the cross-sectional shape orthogonal to the central axis O, and at least the major axis a1 and a2 has the first axis 710. And the second axis 720 may be different.
　（変形例２）
　上記実施形態では、ラックの歯幅Ｗ１，Ｗ２が軸の外径Ｄ１，Ｄ２よりも小さい例（Ｗ１＜Ｄ１，Ｗ２＜Ｄ２）について説明したが、本発明はこれに限定されない。たとえば、図１０に示すように、第１ラック１１５の歯幅Ｗ１は、第１ラック形成部１１６の外径Ｄ１と同じ寸法になるようにラック歯を成形してもよい。また、ラックの歯幅Ｗ１，Ｗ２が軸の外径Ｄ１，Ｄ２よりも大きくなるように、ラック歯を成形してもよい（Ｗ１＞Ｄ１，Ｗ２＞Ｄ２）。 (Modification 2)
In the above embodiment, the example in which the rack tooth widths W1 and W2 are smaller than the outer diameters D1 and D2 of the shaft (W1 <D1, W2 <D2) has been described, but the present invention is not limited to this. For example, as shown in FIG. 10, the rack teeth may be formed so that the tooth width W <b> 1 of the first rack 115 is the same as the outer diameter D <b> 1 of the first rack forming portion 116. The rack teeth may be formed such that the rack tooth widths W1 and W2 are larger than the outer diameters D1 and D2 of the shaft (W1> D1, W2> D2).
　（変形例３）
　上記実施形態では、第１軸と第２軸とが同一の材料から形成される例について説明したが、本発明はこれに限定されない。第１軸と第２軸をそれぞれ異なる材料から形成してもよい。たとえば、第２軸には、第１軸の材料に比べて強度の高い材料（すなわち、引張強度の大きい材料）を用いるなどして、第２軸の強度を第１軸に比べて大きくしてもよい。この場合、第２軸の外径を第１軸の外径よりも小さくすることができる。このように、第１軸と第２軸とを結合してラックシャフトを形成する場合、第１軸と第２軸の材料を異ならせることができる。これにより、第１軸や第２軸の径、軸交角、ラックシャフトの中心軸とピニオンの中心軸との軸間距離等を調整して、車両への搭載性を向上できる。 (Modification 3)
In the said embodiment, although the 1st axis | shaft and the 2nd axis | shaft demonstrated the example formed from the same material, this invention is not limited to this. The first axis and the second axis may be formed from different materials. For example, the second shaft is made stronger than the first shaft by using a material having a higher strength than the material of the first shaft (ie, a material having a high tensile strength). Also good. In this case, the outer diameter of the second shaft can be made smaller than the outer diameter of the first shaft. As described above, when the rack shaft is formed by combining the first shaft and the second shaft, the materials of the first shaft and the second shaft can be made different. Thereby, the diameter of the first axis or the second axis, the axis crossing angle, the inter-axis distance between the center axis of the rack shaft and the center axis of the pinion, and the like can be adjusted to improve the mountability to the vehicle.
　（変形例４）
　第１実施形態及び第２実施形態では、第２軸１２０の連結筒部１２２の外径Ｄ３と第１軸１１０，２１０の本体部１１１，２１１の外径Ｄ１とが同じである例について説明した（図２Ａ、図２Ｂ、図４Ａ参照）。第２実施形態の変形例では、第１軸２１０の連結筒部２１２の外径と第２軸２２０の本体部１２１の外径Ｄ２とが同じである例について説明した（図４Ｂ参照）。しかしながら、本発明は、一方の軸の連結筒部の外径を他方の軸の本体部の外径と同一とする場合に限定されない。第１軸の連結筒部の外径及び第２軸の連結筒部の外径は、第１軸の本体部及び第２軸の本体部の外径と異なるようにしてもよい。第１軸及び第２軸の連結筒部を第１軸の本体部及び第２軸の本体部よりも小径とすることで、ラックシャフトを軽量化できる。第１軸及び第２軸の連結筒部を第１軸の本体部及び第２軸の本体部よりも大径とすることで、ラックシャフトの強度を向上できる。 (Modification 4)
In 1st Embodiment and 2nd Embodiment, the outer diameter D3 of the connection cylinder part 122 of the 2nd axis | shaft 120 and the outer diameter D1 of the main-body parts 111,211 of the 1st axis | shafts 110 and 210 were demonstrated. (See FIGS. 2A, 2B, and 4A). In the modification of the second embodiment, the example in which the outer diameter of the connecting cylinder portion 212 of the first shaft 210 is the same as the outer diameter D2 of the main body portion 121 of the second shaft 220 has been described (see FIG. 4B). However, the present invention is not limited to the case where the outer diameter of the connecting cylinder portion of one shaft is the same as the outer diameter of the main body portion of the other shaft. The outer diameter of the connecting cylinder portion of the first shaft and the outer diameter of the connecting cylinder portion of the second shaft may be different from the outer diameters of the main body portion of the first shaft and the main body portion of the second shaft. A rack shaft can be reduced in weight by making the connecting cylinder part of a 1st axis | shaft and a 2nd axis | shaft smaller than the main-body part of a 1st axis | shaft, and the main-body part of a 2nd axis | shaft. The strength of the rack shaft can be improved by making the connecting cylinder portion of the first shaft and the second shaft larger in diameter than the main body portion of the first shaft and the main body portion of the second shaft.
　（変形例５）
　上記実施形態では、第１ラックがＣＧＲ仕様とされ、第２ラックがＶＧＲ仕様とされている例について説明したが、本発明はこれに限定されない。第１ラック及び第２ラックの双方をＣＧＲ仕様としてもよいし、第１ラック及び第２ラックの双方をＶＧＲ仕様としてもよい。第１ラックをＶＧＲ仕様とし、第２ラックをＣＧＲ仕様としてもよい。 (Modification 5)
In the above-described embodiment, the example in which the first rack has the CGR specification and the second rack has the VGR specification has been described, but the present invention is not limited to this. Both the first rack and the second rack may be CGR specifications, and both the first rack and the second rack may be VGR specifications. The first rack may be VGR specification and the second rack may be CGR specification.
　（変形例６）
　第１実施形態では、第１軸１１０を中実の円柱状部材とし、第２軸１２０を中実の円柱状部材とする例を説明し（図２Ａ、図２Ｂ参照）、第２実施形態及び第２実施形態の変形例では、第１軸２１０を中空の円筒状部材とし、第２軸１２０を中実の円柱状部材とする例について説明した（図４Ａ、図４Ｂ参照）。第４実施形態では、第１軸４１０Ａ，４１０Ｂ，４１０Ｃを中実の円柱状部材とし、第２軸４２０を中空の円筒状部材とする例について説明したが（図６Ａ，図６Ｂ，図６Ｃ参照）、本発明はこれらに限定されない。たとえば、第１軸及び第２軸をそれぞれ中空の円筒状部材としてもよい。 (Modification 6)
In the first embodiment, an example in which the first shaft 110 is a solid columnar member and the second shaft 120 is a solid columnar member (see FIGS. 2A and 2B) will be described. In the modification of the second embodiment, the example in which the first shaft 210 is a hollow cylindrical member and the second shaft 120 is a solid columnar member has been described (see FIGS. 4A and 4B). In the fourth embodiment, an example in which the first shafts 410A, 410B, and 410C are solid columnar members and the second shaft 420 is a hollow cylindrical member has been described (see FIGS. 6A, 6B, and 6C). ), The present invention is not limited to these. For example, the first shaft and the second shaft may each be a hollow cylindrical member.
　以下、本発明の実施形態の構成、作用、及び効果をまとめて説明する。 Hereinafter, the configuration, operation, and effect of the embodiment of the present invention will be described together.
　ラックシャフト１２Ａ，１２Ｂ１，１２Ｂ２，１２Ｃ１，１２Ｃ２，１２Ｄ１，１２Ｄ２，１２Ｄ３，１２Ｅ，１２Ｇは、操舵力が伝達される第１ラック１１５が形成された第１軸１１０，２１０，３１０Ａ，３１０Ｂ，４１０Ａ，４１０Ｂ，４１０Ｃ，７１０と、電動モータ２１の駆動力が伝達される第２ラック１２５が形成され、第１軸１１０，２１０，３１０Ａ，３１０Ｂ，４１０Ａ，４１０Ｂ，４１０Ｃ，７１０に結合された第２軸１２０，２２０，３２０Ａ，３２０Ｂ，４２０Ａ，４２０Ｂ，４２０Ｃ，７２０と、を備え、第１軸１１０，２１０，３１０Ａ，３１０Ｂ，４１０Ａ，４１０Ｂ，４１０Ｃ，７１０の外径Ｄ１と第２軸１２０，２２０，３２０Ａ，３２０Ｂ，４２０Ａ，４２０Ｂ，４２０Ｃ，７２０の外径Ｄ２とは異径である。 The rack shafts 12A, 12B1, 12B2, 12C1, 12C2, 12D1, 12D2, 12D3, 12E, and 12G have first shafts 110, 210, 310A, 310B, 410A on which a first rack 115 to which a steering force is transmitted is formed. 410B, 410C, 710 and a second rack 125 to which the driving force of the electric motor 21 is transmitted are formed, and the second shaft is coupled to the first shaft 110, 210, 310A, 310B, 410A, 410B, 410C, 710. 120, 220, 320A, 320B, 420A, 420B, 420C, 720, the outer diameter D1 of the first shaft 110, 210, 310A, 310B, 410A, 410B, 410C, 710 and the second shaft 120, 220, Different from the outer diameter D2 of 320A, 320B, 420A, 420B, 420C, 720 It is.
　この構成では、第１軸１１０，２１０，３１０Ａ，３１０Ｂ，４１０Ａ，４１０Ｂ，４１０Ｃ，７１０及び第２軸１２０，２２０，３２０Ａ，３２０Ｂ，４２０Ａ，４２０Ｂ，４２０Ｃ，７２０のうち、一方の軸の外径が他方の軸の外径に比べて小さいので、一方の軸の外径が他方の軸の外径と同じ場合に比べて、質量を軽減できる。これにより、ラックシャフト１２Ａ，１２Ｂ１，１２Ｂ２，１２Ｃ１，１２Ｃ２，１２Ｄ１，１２Ｄ２，１２Ｄ３，１２Ｅ，１２Ｇを軽量化できる。 In this configuration, the outer diameter of one of the first shafts 110, 210, 310A, 310B, 410A, 410B, 410C, 710 and the second shafts 120, 220, 320A, 320B, 420A, 420B, 420C, 720. Is smaller than the outer diameter of the other shaft, the mass can be reduced compared to the case where the outer diameter of one shaft is the same as the outer diameter of the other shaft. Thereby, the rack shafts 12A, 12B1, 12B2, 12C1, 12C2, 12D1, 12D2, 12D3, 12E, and 12G can be reduced in weight.
　ラックシャフト１２Ａ，１２Ｂ１，１２Ｂ２，１２Ｃ１，１２Ｄ１，１２Ｄ２，１２Ｄ３，１２Ｅ，１２Ｇは、第１軸１１０，２１０，３１０Ａ，４１０Ａ，４１０Ｂ，４１０Ｃ，７１０の外径Ｄ１が第２軸１２０，２２０，３２０Ａ，４２０Ａ，４２０Ｂ，４２０Ｃ，７２０の外径Ｄ２よりも小さい。 The rack shafts 12A, 12B1, 12B2, 12C1, 12D1, 12D2, 12D3, 12E, and 12G have the first shafts 110, 210, 310A, 410A, 410B, 410C, and 710 having the outer diameter D1 of the second shafts 120, 220, and 320A. , 420A, 420B, 420C, 720 is smaller than the outer diameter D2.
　この構成では、第２軸１２０，２２０，３２０Ａ，４２０Ａ，４２０Ｂ，４２０Ｃ，７２０に比べて作用する負荷が小さい第１軸１１０，２１０，３１０Ａ，４１０Ａ，４１０Ｂ，４１０Ｃ，７１０の外径Ｄ１を小さくすることで、第１軸１１０，２１０，３１０Ａ，４１０Ａ，４１０Ｂ，４１０Ｃ，７１０及び第２軸１２０，２２０，３２０Ａ，４２０Ａ，４２０Ｂ，４２０Ｃ，７２０の外径Ｄ１，Ｄ２を、それぞれの軸に必要な強度を満足しつつ、軽量化を図ることができる。 In this configuration, the outer diameter D1 of the first shaft 110, 210, 310A, 410A, 410B, 410C, 710 having a smaller load acting than the second shaft 120, 220, 320A, 420A, 420B, 420C, 720 is reduced. Accordingly, the outer diameters D1 and D2 of the first shafts 110, 210, 310A, 410A, 410B, 410C, and 710 and the second shafts 120, 220, 320A, 420A, 420B, 420C, and 720 are required for the respective shafts. It is possible to reduce the weight while satisfying the required strength.
　ラックシャフト１２Ｅは、第２軸１２０の中心軸Ｏ２が、第１軸１１０の中心軸Ｏ１に対して偏心している。 In the rack shaft 12E, the central axis O2 of the second shaft 120 is eccentric with respect to the central axis O1 of the first shaft 110.
　この構成では、ラックシャフト１２Ｅの回転を防止できる。 In this configuration, rotation of the rack shaft 12E can be prevented.
　ラックシャフト１２Ｃ１，１２Ｃ２は、第１軸３１０Ａ，３１０Ｂ及び第２軸３２０Ａ，３２０Ｂのうち、単位長さ当たりの質量が小さい一方の軸が、単位長さ当たりの質量が大きい他方の軸に比べて長く形成されている。 The rack shafts 12C1 and 12C2 are configured such that one of the first shafts 310A and 310B and the second shafts 320A and 320B has a smaller mass per unit length and a larger mass per unit length. It is formed long.
　この構成では、ラックシャフト１２Ｃ１，１２Ｃ２をより軽量化できる。 In this configuration, the rack shafts 12C1 and 12C2 can be reduced in weight.
　ステアリング装置１００は、ラックシャフト１２Ａ，１２Ｂ１，１２Ｂ２，１２Ｃ１，１２Ｃ２，１２Ｄ１，１２Ｄ２，１２Ｄ３，１２Ｅ，１２Ｇと、電動モータ２１と、を備え、電動モータ２１の回転力を第２ラック１２５を介してラックシャフト１２Ａ，１２Ｂ１，１２Ｂ２，１２Ｃ１，１２Ｃ２，１２Ｄ１，１２Ｄ２，１２Ｄ３，１２Ｅ，１２Ｇに伝達する電動パワーステアリング装置である。 The steering device 100 includes rack shafts 12A, 12B1, 12B2, 12C1, 12C2, 12D1, 12D2, 12D3, 12E, and 12G, and an electric motor 21, and the rotational force of the electric motor 21 is passed through the second rack 125. This is an electric power steering device for transmitting to rack shafts 12A, 12B1, 12B2, 12C1, 12C2, 12D1, 12D2, 12D3, 12E, and 12G.
　この構成では、軽量化が実現されたラックシャフト１２Ａ，１２Ｂ１，１２Ｂ２，１２Ｃ１，１２Ｃ２，１２Ｄ１，１２Ｄ２，１２Ｄ３，１２Ｅ，１２Ｇを有しているので、ステアリング装置１００を軽量化できる。 In this configuration, since the rack shafts 12A, 12B1, 12B2, 12C1, 12C2, 12D1, 12D2, 12D3, 12E, and 12G that have been reduced in weight are provided, the steering device 100 can be reduced in weight.
　以上、本発明の実施形態について説明したが、上記実施形態は本発明の適用例の一部を示したに過ぎず、本発明の技術的範囲を上記実施形態の具体的構成に限定する趣旨ではない。 The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.
　本願は２０１７年３月３０日に日本国特許庁に出願された特願２０１７－０６８４１３に基づく優先権を主張し、この出願の全ての内容は参照により本明細書に組み込まれる。 This application claims priority based on Japanese Patent Application No. 2017-068413 filed with the Japan Patent Office on March 30, 2017, the entire contents of which are incorporated herein by reference.

Claims (5)

  1. 　ステアリングホイールの操舵に伴い回転する第１ピニオンと噛み合う第１ラックが形成された第１軸と、
    　電動モータにより回転する第２ピニオンと噛み合う第２ラックが形成され、前記第１軸に結合された第２軸と、を備え、
    　前記第１軸の外径と前記第２軸の外径とは異径であるラックシャフト。     A first shaft formed with a first rack that meshes with a first pinion that rotates as the steering wheel is steered;
    A second rack that meshes with a second pinion that is rotated by an electric motor, and a second shaft that is coupled to the first shaft; and
    A rack shaft, wherein an outer diameter of the first shaft and an outer diameter of the second shaft are different from each other.
  2. 　請求項１に記載のラックシャフトにおいて、
    　前記第１軸の外径は、前記第２軸の外径よりも小さいラックシャフト。     The rack shaft according to claim 1, wherein
    A rack shaft having an outer diameter of the first shaft smaller than an outer diameter of the second shaft.
  3. 　請求項１に記載のラックシャフトにおいて、
    　前記第２軸の中心軸は、前記第１軸の中心軸に対して偏心しているラックシャフト。     The rack shaft according to claim 1, wherein
    The rack shaft is eccentric with respect to the central axis of the first axis.
  4. 　請求項１に記載のラックシャフトにおいて、
    　前記第１軸及び前記第２軸のうち、単位長さ当たりの質量が小さい一方の軸が、単位長さ当たりの質量が大きい他方の軸に比べて長く形成されているラックシャフト。     The rack shaft according to claim 1, wherein
    A rack shaft in which one of the first shaft and the second shaft having a smaller mass per unit length is formed longer than the other shaft having a larger mass per unit length.
  5. 　請求項１に記載のラックシャフトと、
    　電動モータと、を備え、
    　前記電動モータの回転力を前記第２ラックを介して前記ラックシャフトに伝達する電動パワーステアリング装置。     A rack shaft according to claim 1;
    An electric motor,
    An electric power steering device for transmitting a rotational force of the electric motor to the rack shaft via the second rack.
PCT/JP2018/008566 2017-03-30 2018-03-06 Rack shaft and electric power steering device WO2018180281A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2017068413A JP2018167780A (en) 2017-03-30 2017-03-30 Rack shaft and electric power steering device
JP2017-068413 2017-03-30

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Publication number Priority date Publication date Assignee Title
CN113302007A (en) * 2018-12-27 2021-08-24 日本精工株式会社 Linear drive shaft for steering device, and methods for manufacturing linear drive shaft and steering device
JP2022099680A (en) * 2020-12-23 2022-07-05 日本精工株式会社 Dual pinion type electric power steering device
JP2022111600A (en) * 2021-01-20 2022-08-01 日本精工株式会社 Rack shaft for dual pinion type electric power steering device, manufacturing method thereof, and dual pinion type electric power steering device

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001151132A (en) * 1999-11-26 2001-06-05 Honda Motor Co Ltd Electric power steering device
JP2014046803A (en) * 2012-08-31 2014-03-17 Hitachi Automotive Systems Steering Ltd Method for manufacturing rack bar, rack bar and electric power steering device
JP2014151833A (en) * 2013-02-12 2014-08-25 Nsk Ltd Rack shaft of dual pinion type electric power steering device and method for manufacturing the same
JP2014234882A (en) * 2013-06-03 2014-12-15 高周波熱錬株式会社 Rack manufacturing method and hollow rack bar

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001151132A (en) * 1999-11-26 2001-06-05 Honda Motor Co Ltd Electric power steering device
JP2014046803A (en) * 2012-08-31 2014-03-17 Hitachi Automotive Systems Steering Ltd Method for manufacturing rack bar, rack bar and electric power steering device
JP2014151833A (en) * 2013-02-12 2014-08-25 Nsk Ltd Rack shaft of dual pinion type electric power steering device and method for manufacturing the same
JP2014234882A (en) * 2013-06-03 2014-12-15 高周波熱錬株式会社 Rack manufacturing method and hollow rack bar

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