JP2014149053A - Rotation support device - Google Patents

Abstract

To achieve a structure capable of sufficiently ensuring the durability of the radial bearing by making the contact state between the radial bearing and the rotating shaft uniform in the axial direction.
A shell-type outer ring is press-fitted and fixed inside a cylindrical holding portion, and a rotating shaft is rotatably supported inside the outer ring via a plurality of needles. The inner diameter of the holding portion 19 shown in (A) in the free state is made smaller on the opening side where rigidity is lower than on the bottom side. In the state where the outer ring 10 is fitted and fixed to the holding portion 19 shown in (B), the inner diameter of the holding portion 19 is made constant from one axial end to the other axial end.
[Selection] Figure 1

Description

  The present invention relates to an improvement of a rotation support device for rotatably supporting a rotating shaft of an electric motor, for example, on a part of a motor case by a radial bearing. More specifically, the contact state between the radial bearing and the rotary shaft is made uniform in the axial direction, thereby realizing a structure capable of sufficiently ensuring the durability of the radial bearing.

  For example, Patent Document 1 describes the structure of an electric motor as shown in FIGS. In this structure, the base end portion of the rotating shaft 2 with the rotor 1 fixed to the intermediate portion is a bottomed cylindrical holding portion 4 provided in a part of the motor case 3, and is a sliding bearing. It is rotatably supported by a radial bearing 5 corresponding to the described bearing component. In the case of such a structure, since the rigidity in the radial direction of the holding portion 4 is not uniform in the axial direction, it becomes difficult to ensure the durability of the radial bearing 5 if the use conditions become severe. Specifically, the rigidity in the radial direction of the holding portion 4 is large on the right side of FIGS. 4 to 5 closed by the bottom plate portion 6 in the axial direction, and is small on the left side of FIGS. Therefore, when the radial bearing 5 is fitted and fixed to the holding portion 4 by interference fitting, the inner diameter of the holding portion 4 becomes larger on the left side than the right side in FIGS. The shape of the peripheral surface is also elastically deformed following this. As a result, the contact state between the inner peripheral surface of the radial bearing 5 and the outer peripheral surface of the rotary shaft 2 becomes uneven in the axial direction, and the durability of the radial bearing 5 is impaired.

  In the case of the conventional structure shown in FIGS. 4 to 5 described above, the end plate portion 7 exists around the opening of the holding portion 4, and the radial rigidity of the opening of the holding portion 4 is also certain. The degree can be obtained, and since the radial bearing 5 is a sliding bearing, the above-described decrease in durability is not so remarkable. In contrast, for example, in an electric motor as shown in FIG. 6, a bottomed surface as shown in FIGS. 6 and 7A is formed on a part of the inner surface of a light alloy motor case 3a such as an aluminum alloy. In the case where a cylindrical holding portion 8 is projected and the end portion of the rotating shaft 2a with the rotor 1a fixed to the intermediate portion is rotatably supported by the radial needle bearing 9 on the radially inner side of the holding portion 8 The durability of the radial needle bearing 9 is significantly reduced. The reason for this is as follows.

  The inner peripheral surface of the holding portion 8 provided integrally with the motor case 3a in a part of the light alloy motor case 3a cannot be used as the outer ring raceway of the radial needle bearing 9 as it is. In order to obtain the required hardness for the outer ring raceway, a shell-type radial needle bearing 9 having an outer ring (shell) 10 made of hard metal such as case-hardened steel, corresponding to the bearing parts described in the claims. As shown in FIG. 7B, it is necessary to fix (press-fit) the outer ring 10 to the holding portion 8 with an interference fit. Along with the press-fitting of the outer ring 10, a force directed radially outward is applied to the holding portion 8, and the holding portion 8 is elastically deformed radially outward. The amount of elastic deformation of the holding portion 8 generated in this way is large on the opening side (left side in FIGS. 6 to 7) with low radial rigidity, and small on the bottom side (right side in FIGS. 6 to 7) with high rigidity. Become.

  Accordingly, as shown exaggeratedly in FIG. 7B, the holding portion 8 is elastically deformed in a direction in which the inner diameter on the opening side is larger and the inner diameter on the bottom side is smaller, and the outer ring 10 is Follow the elastic deformation. In this state, the distance (radial distance) between the outer ring track, which is the inner peripheral surface of the outer ring 10, and the inner ring track, which is the outer peripheral surface of the end portion of the rotary shaft 2a, is not uniform over the axial direction. Specifically, this interval is narrow on the bottom side of the holding portion 8 and wide on the opening side. For this reason, the surface pressure of the rolling contact portion between the outer ring raceway and the inner ring raceway and the rolling surfaces of a plurality of needles provided between the two raceways is extremely high on the bottom side, Alternatively, a so-called one-sided contact that becomes extremely low on the opening side occurs. As a result, the rolling fatigue life of the outer ring raceway and the inner ring raceway and the rolling surface of each needle is partially shortened, and the durability of the radial needle bearing 9 as a whole is also significantly shortened.

  FIG. 8 shows a structure in which the throttle valve 12 is supported in a swingable manner inside the intake pipe 11 of the internal combustion engine. In this structure, an intermediate portion and a tip portion of the swing shaft 13 provided at the center portion of the throttle valve 12 can be freely displaced by the radial needle bearings 9a and 9b on the inner diameter side of the holding portions 14a and 14b, respectively. I support it. In the case of such a structure, the rigidity in the radial direction of the holding portion 14a for supporting the intermediate portion of the swing shaft 13 among the holding portions 14a and 14b is continuous with the main body portion of the intake pipe 11. It is large at the base end (right end in FIG. 8) and small at the tip end (left end in FIG. 8). On the other hand, the rigidity in the radial direction of the holding portion 14b for supporting the end portion of the swing shaft 13 is large on the closed bottom side (right side in FIG. 8), and on the opening side (in FIG. 8). Smaller on the left). Therefore, in the case of such a structure of FIG. 8 as well, if a shell-type outer ring is fitted and fixed to the holding portions 14a and 14b by an interference fit, the same problem occurs.

  Such a problem is not limited to the structure shown in FIGS. 6 to 8 described above, but also occurs in the case of a rotation support device having holding parts 15a and 15b as shown in FIGS. Among these, the holding portion 15a shown in FIG. 9 is for supporting, for example, a portion near the front end of the intermediate portion of the steering shaft at the front end of the steering column so as to be rotatable and capable of axial displacement. The inner diameter of the end portion of the thick hollow rotating shaft 16 is made larger than that of the intermediate portion. Further, the holding portion 15b shown in FIG. 10 is provided on the inner surface of the housing 18 so as to surround the opening portion of the insertion hole 17 through which the rotation shaft is inserted. For any of the holding portions 15a and 15b, the rigidity of the distal end portion (left end portion in FIGS. 9 to 10) is lower than the rigidity of the base end portion (right end portion in FIGS. 9 to 10). When press-fitted, it is elastically deformed as shown exaggeratedly in FIGS.

  Patent Document 2 describes that the outer peripheral surface of a housing constituting the hydrodynamic bearing device has a shape that allows for the amount of deformation caused by press-fitting a thrust member into the housing. Patent Document 3 describes a structure in which the outer diameter of the outer ring is gradually changed in the axial direction in order to prevent the shell-type outer ring from coming off from the housing. However, the structures described in Patent Documents 2 and 3 cannot be used for reducing the durability of radial bearings such as needle bearings having a shell-type outer ring, which occur as described above, or even if they can be used temporarily. The effect is not expected.

JP 2007-239777 A JP 2004-176778 A JP 2007-155053 A

  In view of the circumstances as described above, the present invention has been invented to realize a structure capable of sufficiently ensuring the durability of the radial bearing by making the contact state between the radial bearing and the rotating shaft uniform in the axial direction. It is.

  A rotation support device according to the present invention includes a cylindrical holding portion, a shaft member disposed inside the holding portion, and a radial bearing provided between the inner peripheral surface of the holding portion and the outer peripheral surface of the shaft member. With. Further, the rigidity of the holding portion in the radial direction is smaller at one axial end than at the other axial end. Of the radial bearings, at least the bearing part that is present at the outermost radial direction is press-fitted from the one end side in the axial direction to the inner side in the radial direction of the holding portion, and is fitted and fixed with an interference fit.

In particular, in the rotation support device of the present invention, the inner diameter of the holding portion in the free state is made smaller at one axial end than at the other axial end.
Preferably, as in the invention described in claim 2, the inner diameter of the holding portion is constant from one end in the axial direction to the other end in the axial direction in a state in which the bearing part is fitted and fixed to the holding portion.
In order to implement such a rotation support device of the present invention, preferably, as in the invention described in claim 3, the thickness in the radial direction of the holding portion is increased at one end side in the axial direction. Decrease gradually toward the other end in the direction.
Furthermore, in order to implement such a rotation support device of the present invention, specifically, as in the invention described in claim 4, a plurality of the radial bearings are arranged radially inward of the shell type outer ring. It is set as the shell type radial needle bearing which has arrange | positioned the needle, and the said bearing component is set as the said outer ring | wheel.

  According to the rotary support device of the present invention configured as described above, the radial bearings for holding the radial bearing have different radial stiffnesses with respect to the axial direction. The contact state with the shaft disposed radially inward of the radial bearing can be made uniform or substantially uniform over the axial direction, and sufficient durability of the radial bearing can be ensured.

Sectional view (A) showing the shape of the holding portion in the free state, exaggerating the inclination angle in the axial direction, showing a first example of the embodiment of the present invention, and a shell-type outer ring pressed into the holding portion Sectional drawing (B) which shows a state. The figure similar to FIG. 1 which shows the 2nd example. The figure similar to FIG. 1 which shows the 3rd example. Sectional drawing which shows the conventional structure of the electric motor provided with the rotation support part. The right end part enlarged view of FIG. Sectional drawing which shows another example of the structure of the electric motor provided with the rotation support part. The same figure as FIG. 1 for demonstrating the problem which arises in the case of the structure shown in this FIG. Sectional drawing which shows an example of the throttle valve apparatus provided with the rocking | fluctuation support part. The same figure as FIG. 2 for demonstrating the problem which arises in the case of the conventional structure. The same figure as FIG.

[First example of embodiment]
FIG. 1 shows a first example of an embodiment of the present invention. In the structure of this example, a bottomed cylindrical holding portion as shown in FIG. 1A is formed on a part of the inner surface of a motor case 3a made of a light alloy such as an aluminum alloy (see FIG. 6 for the entire shape). 19 is provided, and the rotating shaft is rotatably supported by a radial needle bearing provided with a shell-type outer ring 10 on the radially inner side of the holding portion 19. This is the same as the case of the structure shown in FIG.

  In particular, in the case of the structure of this example, the inner peripheral surface 20 of the holding portion 19 is slightly inclined with respect to the axial direction. Specifically, the bus bar of the inner peripheral surface 20 is slightly inclined (for example, about 0.1 to 1 degree) with respect to the axial direction of the holding portion 19 to make the shape of the inner peripheral surface 20 pure. It is not a cylindrical surface, but is a partially conical concave surface that is slightly inclined. The inclination direction is a direction in which the inner diameter of the holding portion 19 in the free state decreases toward the opening of the holding portion 19. On the other hand, the outer diameter of the holding portion 19 is substantially the same except for a chamfered portion or the like existing at the end edge portion. Therefore, the thickness in the radial direction of the holding portion 19 is large on the opening side (left side in FIG. 1) corresponding to the one axial end side described in the claims, and also the bottom corresponding to the other axial end side. It gradually becomes smaller toward the side (the right side in FIG. 1).

  The inclination angle θ of the generatrix of the inner peripheral surface 20 is appropriately regulated by calculation or experiment based on the rigidity of the holding portion 19, the rigidity of the shell-type outer ring 10 press-fitted into the holding portion 19, and the tightening allowance. . In any case, the inclination angle θ is a small value of about 0.1 to 1 degree. In the state where the outer ring 10 is fitted and fixed to the holding portion 19 with an interference fit, the inner diameter of the holding portion 19 is the same from one axial end to the other axial end as shown in FIG. It is trying to become.

  According to the rotation support device of the present example including the holding portion 19 and the outer ring 10 as described above, the rigidity of the holding portion 19 for holding the shell-type outer ring 10 constituting the radial needle bearing is in the axial direction. Despite being different from each other, the inner diameter of the outer ring 10 in the assembled state can be made constant over the axial direction. That is, as the outer ring 10 is press-fitted into the holding portion 19, a force directed radially outward is applied to the holding portion 19, and the holding portion 19 is elastically deformed radially outward. The amount of elastic deformation of the holding portion 19 generated in this way is large on the opening side (left side in FIG. 1) where the rigidity in the radial direction is low and decreases on the bottom side (right side in FIG. 1) where the rigidity is high.

  As shown in FIG. 1A, the inner diameter of the holding portion 19 in the free state is small on the opening side and large on the bottom side, so that the holding portion 19 is pressed with the outer ring 10 being press-fitted. Is elastically deformed in a direction to eliminate the inclination angle θ. In the case of this example, the inclination angle θ is appropriately regulated based on the rigidity of the holding portion 19, the rigidity of the outer ring 10, and the tightening allowance, so that the outer ring 10 is press-fitted into the holding portion 19. In this state, the inner diameter of the holding portion 19 is substantially constant over the entire length in the axial direction (to the extent that the inner diameter is completely the same or does not adversely affect the durability of the radial needle bearing. The difference between the two is small). The diameter of the portion of the outer ring 10 in which the outer ring raceway is formed on the inner peripheral surface of the outer ring 10 that is internally fitted and fixed to the holding portion 19 is substantially constant in the axial direction.

  In this state, the distance between the outer ring raceway and the inner ring raceway which is the outer peripheral surface of the rotating shaft supported by the radial needle bearing is uniform over the axial direction. In other words, the inner ring track and the outer ring track are parallel to the entire axial length. As a result, the outer ring raceway and the inner ring raceway and the rolling surfaces of a plurality of needles provided between the two raceways are in uniform rolling contact over the entire length in the axial direction. As a result, the surface pressure of the rolling contact portion between the rolling surface of each needle and the both raceways does not partially become excessive, and the rolling fatigue life between the rolling surface of each needle and the both raceways is increased. It is possible to ensure the durability of the radial needle bearing as a whole.

  In the case of this example, of the inner and outer peripheral surfaces of the holding portion 19 in the free state, the outer peripheral surface is a simple cylindrical surface having a constant outer diameter in the axial direction, and the inner peripheral surface is the opening. The conical concave surface is inclined in a direction in which the inner diameter becomes smaller as it goes to. Therefore, the thickness in the radial direction of the holding portion 19 increases (thickens) toward the opening, and the thickness decreases in the axial direction to such an extent that the rigidity in the radial direction of the holding portion 19 decreases toward the opening. Is more relaxed than if it is constant. Accordingly, the inclination angle θ may be a small value, but the extent to which the inner diameter of the opening of the holding portion 19 is smaller than the outer diameter of the outer ring 10 is equal to a normal tightening allowance (diameter for interference fit). Larger than the dimension difference). However, the degree is sufficiently smaller than the radial width of the curved surface portion of the outer ring 10 in the outer peripheral edge of the axial end portion of the outer ring 10 whose cross-sectional shape is a quarter arc. Therefore, the operation of press-fitting the outer ring 10 into the holding portion 19 can be easily performed while the opening portion of the holding portion 19 is expanded by the curved surface portion.

[Second Example of Embodiment]
FIG. 2 shows a second example of the embodiment of the present invention. In this example, the rotation support device shown in FIG. 9 described above, for example, supports the portion near the front end of the intermediate portion of the steering shaft at the front end of the steering column so as to be rotatable and displaceable in the axial direction. The case where the present invention is applied is shown.
In the case of this example, the inner diameter of the end portion of the thick hollow rotating shaft 16a is made larger than that of the intermediate portion, and the holding portion 19a is provided at this end portion. The shape of the holding portion 19a, the properties of the outer ring 10 in a state in which the shell-type outer ring 10 is fitted and fixed to the holding portion 19a by interference fit, and the like are the same as in the first example of the above-described embodiment. Therefore, the overlapping description is omitted.

[Third example of embodiment]
FIG. 3 shows a third example of the embodiment of the present invention. In this example, the present invention is applied to the structure shown in FIG. The holding portion 19b of this example is provided on the inner surface of the housing 18 so as to surround the opening portion of the insertion hole 17 through which the rotation shaft is inserted. Regarding the shape of the holding portion 19b and the properties of the outer ring 10 in a state in which the shell-type outer ring 10 is fitted and fixed to the holding portion 19b by interference fitting, the first example of the above-described embodiment and the above-described implementation are described. Since it is the same as that of the 2nd example of this form, the overlapping description is abbreviate | omitted.

In the case of carrying out this example, the thickness of the holding portion does not necessarily need to be increased (thickened) toward the opening. Instead of making the thickness in the radial direction constant over the axial direction, the inclination angle of the inner peripheral surface in the free state may be set larger.
Further, the radial bearing that is press-fitted and fixed to the inner diameter side of the holding portion is not limited to the needle bearing having the shell-type outer ring, and may be a sliding bearing as shown in FIGS.
Furthermore, the present invention can be applied to the holding portions 14a and 14b as shown in FIG. 8, and the present invention can be implemented with a structure in which a rotating member is provided around a fixed support shaft. You can also.

DESCRIPTION OF SYMBOLS 1, 1a Rotor 2, 2a Rotating shaft 3, 3a Motor case 4 Holding part 5 Radial bearing 6 Bottom plate part 7 End plate part 8 Holding part 9, 9a, 9b Radial needle bearing 10 Outer ring (shell)
DESCRIPTION OF SYMBOLS 11 Intake pipe 12 Slot valve 13 Oscillating shaft 14a, 14b Holding part 15a, 15b Holding part 16 Hollow rotating shaft 17 Insertion hole 18 Housing 19, 19a, 19b Holding part 20 Inner peripheral surface

Claims (4)

  A cylindrical holding portion; a shaft member disposed inside the holding portion; and a radial bearing provided between an inner peripheral surface of the holding portion and an outer peripheral surface of the shaft member. The rigidity in the radial direction is smaller at one axial end than at the other axial end, and at least one of the radial bearings that is present at the outermost radial side is axially located on the radial inner side of the holding portion. In the rotary support device that is fitted and fixed with an interference fit, the inner diameter of the holding portion in the free state is made smaller at one end in the axial direction than at the other end in the axial direction. Rotating support device.   The rotation support device according to claim 1, wherein an inner diameter of the holding portion is constant from one axial end to the other axial end in a state in which the bearing part is fitted and fixed to the holding portion.   3. The rotation support device according to claim 1, wherein a thickness of the holding portion in a radial direction is large on one end side in the axial direction and gradually decreases toward the other end side in the axial direction. .   The radial bearing is a shell-type radial needle bearing in which a plurality of needles are arranged radially inside a shell-type outer ring, and the bearing component is the outer ring. The rotation support apparatus described in the item.

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