JP7275837B2 - worm reducer - Google Patents

Description

The present invention relates to a worm reduction gear having a worm shaft biased toward a worm wheel.

Conventionally, there is a worm speed reducer that urges a worm shaft toward a worm wheel with the spring force of a coil spring in order to prevent backlash (see Patent Document 1). Such a worm speed reducer can suppress the generation of collision noise (slamming sound) even when torque is suddenly input.

JP 2015-187461 A

However, the present inventors have found that some worm speed reducers with coil springs generate an abnormal sound different from the hammering sound depending on the number of years of use. Through further experiments and research, the inventors of the present invention have found that the abnormal noise is stick-slip noise between the spring and the bearing, and that the occurrence of the stick-slip noise can be suppressed without increasing the number of parts. I have found a structure that works.

The present invention has been made based on the findings of the inventors described above, and provides a worm speed reducer capable of suppressing the occurrence of stick-slip noise.

To achieve the above object, a worm reduction gear according to one aspect of the present invention is a worm reduction gear comprising a worm shaft, a worm wheel, and a housing for housing the worm shaft and the worm wheel, a bearing that holds the worm shaft inside the housing; a coil spring that abuts against the outer peripheral surface of the bearing and applies a biasing force in the direction of the worm wheel; and determining means for determining the position of the bearing-side tip, which is the bearing-side tip of the wire forming the .

According to the worm speed reducer of the present invention, the position of the bearing-side tip of the coil spring relative to the bearing can be determined, and stick-slip noise generated between the coil spring and the bearing can be suppressed.

1 is a diagram showing the overall configuration of a steering system; FIG. FIG. 2 is a cross-sectional view showing the internal structure of the worm speed reducer according to the embodiment; FIG. 2 is a perspective view showing a coil spring according to the present embodiment and the vicinity of a bearing with which the coil spring abuts; 3 is a cross-sectional view showing the relationship between the coil spring, the determining means, and the bearing-side tip according to the present embodiment, taken along the line II shown in FIG. 2. FIG. FIG. 5 is a cross-sectional view similar to that in FIG. 4 showing the relationship between the left-handed coil spring, the determining means, and the bearing-side tip; 3 is a cross-sectional view showing the internal structure of the worm speed reducer according to Example 1. FIG. 2 is a plan view showing the preload member according to example 1 from the outside; FIG. FIG. 10 is a plan view showing the preload member according to Example 2 from the outside; FIG. 11 is a cross-sectional view showing a bent protrusion according to Example 3;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. It should be noted that all of the embodiments described below represent comprehensive or specific examples of the present invention. Numerical values, shapes, materials, components, arrangement positions and connection forms of components, steps, order of steps, and the like shown in the following embodiments are examples and are not intended to limit the present invention. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in independent claims representing the highest concept will be described as optional constituent elements.

In addition, the drawings are schematic diagrams in which emphasis, omissions, and ratios are appropriately adjusted in order to illustrate the present invention, and may differ from actual shapes, positional relationships, and ratios.

First, the overall configuration of a steering system 100 to which a structural member according to an embodiment of the invention is attached will be described. FIG. 1 is a diagram schematically showing the overall configuration of a steering system.

As shown in FIG. 1, the steering system 100 is a power steering device that assists a driver's force to rotate a steering wheel 110 for steering. , a rack and pinion device 140 that converts the rotation of the steering shaft 130 into a reciprocating motion of the steering shaft 141; a sensor device 120 that detects the steering torque of the steering wheel 110; A worm reducer 150 is provided to provide steering assist force to 130 .

The worm speed reducer 150 is a device that is connected to a motor 152 and applies an assist force to the steering shaft 130 for assisting steering using the motor 152 as a drive source. Motor 152 is controlled by an ECU (Electronic Control Unit) (not shown) to appropriately adjust the assist force applied to steering shaft 130 .

The steering shaft 130 is composed of three shafts, a column shaft 131, an intermediate shaft 132, and a pinion shaft 133 from the steering wheel 110 side. In the power steering apparatus, the position where the worm speed reducer 150 is attached is not particularly limited, but in the case of the present embodiment, it is connected to the pinion shaft 133 .

FIG. 2 is a cross-sectional view showing the internal structure of the worm speed reducer. As shown in the figure, the worm speed reducer 150 includes a worm shaft 164, a worm wheel 163, a housing 153, a bearing 161, a coil spring 170, and determining means 168.

The housing 153 is a box-shaped structural member that accommodates the worm shaft 164 and the worm wheel 163, and is provided with a hole 154 passing through the housing 153 and an engaging portion 156 arranged outside the hole 154. ing. A coil spring 170 is arranged in the hole 154 . A preload member 155 that pressurizes the coil spring 170 is attached to the engaging portion 156 . In the case of this embodiment, a housing portion 165 (see FIG. 4), which is a constituent element of the determining means, is provided on the peripheral surface of the hole portion 154 . Note that the determining means 168 will be described later.

The hole portion 154 is a through hole penetrating from the outside to the inside of the housing 153 in the radial direction of the bearing 161 . The shape of the hole portion 154 is not particularly limited, but in the case of the present embodiment, it has a cylindrical shape.

The engaging portion 156 is a cylindrical portion that is provided coaxially with the hole portion 154, and has a female thread on its inner peripheral surface.

The preload member 155 is a member that engages with the engaging portion 156 of the housing 153 to pressurize the coil spring 170 . In the case of this embodiment, the preload member 155 is a bolt-shaped (locking nut-shaped) member that is screwed into the engaging portion 156 to seal the hole portion 154 and pressurize the coil spring 170 .

The worm shaft 164 is rotatably held by the bearing 161 and the other end side bearing 162 in the worm shaft accommodating portion. The worm shaft 164 is held so as to be tiltable about the other end side bearing 162 , and is pressed against the worm wheel 163 by the biasing force of the coil spring 170 . In this embodiment, the worm shaft 164 is connected to the motor 152 and rotates about its axis at high speed.

The worm wheel 163 is rotatably held in the worm wheel housing. In the case of this embodiment, the worm wheel 163 is connected to the pinion shaft 133 and amplifies the torque input to the worm shaft 164 to apply assist torque to the pinion shaft 133 .

A bearing 161 holds one end of a worm shaft 164 inside the housing 153 . The bearing 161 is held by the housing 153 so as to be able to reciprocate in the direction toward the worm wheel 163 (the Z-axis direction in the drawing). 164 can be tilted.

FIG. 3 is a perspective view showing a coil spring and the vicinity of a bearing with which the coil spring abuts. As shown in the figure, the coil spring 170 is a member that abuts against the outer peripheral surface of the bearing 161 and applies an urging force that presses the worm shaft 164 toward the worm wheel 163 with the housing 153 as a reference. In the case of the present embodiment, the coil spring 170 protrudes outward from a main body portion 172 which is a portion formed by winding a wire rod into a cylindrical shape, and a cylindrical outer peripheral surface formed by the main body portion 172 which is formed of a wire rod. and a projecting portion 173 . A bearing-side tip 171 , which is the tip of the wire on the bearing 161 side, is included in the body portion 172 . That is, the bearing-side tip 171 is included in the cylinder formed by the wire. On the other hand, the bearing-side tip 171 and the opposite-side tip 174 on the opposite side are included in the projecting portion 173 .

The coil spring 170 is arranged such that the winding axis of the body portion 172 passes through the ridgeline 169 of the outer peripheral surface of the outer ring of the bearing 161 and the axis of the worm shaft 164 . The ridge line 169 of the bearing 161 is a line of contact when a plane perpendicular to the winding axis of the main body 172 is in line contact with the outer peripheral surface of the cylindrical bearing 161 .

The coil spring 170 is a member whose one end is supported by a preload member 155 press-fitted into the hole 154 of the housing 153 and pressurizes the bearing 161 arranged inside the housing 153 with an urging force. In this embodiment, the coil spring 170 is a metal compression spring, is in a compressed state between the preload member 155 and the bearing 161 , and pressurizes the bearing 161 with the restoring force of the preload member 155 .

The determination means 168 is a structural part that regulates the circumferential rotation of the coil spring 170 with respect to the housing 153 and determines the position of the bearing-side tip 171 . The position of the bearing-side tip 171 is determined at a position where the bearing-side tip 171 cannot come into contact with the outer peripheral surface of the bearing 161 . The structure of the determination means 168 is not particularly limited, but in the case of the present embodiment, as shown in FIG. A determining means 168 is formed by the containing portion 165 .

Specifically, for example, the coil spring 170 is inserted into the hole 154 of the housing 153 with the bearing-side tip 171 leading. The coil spring 170 is rotated around its axis to a position where the protruding portion 173 of the coil spring 170 can be accommodated in the accommodation portion 165 which is open at the outer end of the hole portion 154 and also opens toward the outside of the housing 153 , and the preload member 155 is moved. It is attached to the engaging portion 156 . As described above, the bearing-side tip 171 can be arranged at a predetermined position. Further, since the determining means 168 restricts the rotation of the coil spring 170 around the winding axis, it is possible to maintain the bearing-side tip 171 at a predetermined position. Therefore, the bearing-side tip 171 can be arranged at a position where it does not come into contact with the outer circumference of the bearing 161, and can be maintained at this position even while the worm reduction gear 150 is in use.

The positional relationship of the bearing-side tip 171 with respect to the bearing 161 determined by the determining means 168 is preferably within the range shown below. That is, on a plane perpendicular to the biasing direction of the coil spring 170 (the XY plane in the drawing), the point at which the winding axis of the coil spring 170 and the plane intersect is defined as the vertex O, and the ridgeline 169 of the outer peripheral surface of the bearing 161 (the right side in the drawing) is 0° and the other (the left side in the drawing) is 180°, and the angle increases clockwise. In the case of clockwise rotation, the angle range in which the bearing-side tip 171 is arranged is preferably 0°<θ≦135° (θ1 in the figure) or 180°<θ≦315° (θ2 in the figure). More preferably, 0°<θ≦120° or 180°≦θ≦300°.

Further, as shown in FIG. 5, when the winding direction of the coil spring 170 is counterclockwise toward the bearing 161, the angular range in which the bearing-side tip 171 is arranged is 45°≦θ<180° (θ3 in the drawing), Alternatively, 225°≦θ<360° (θ4 in the figure) is desirable, and 60°≦θ<180° or 240°≦θ<360° is desirable.

As described above, with the protruding portion 173 accommodated in the accommodating portion 165, the coil spring 170 is preloaded, and the position of the bearing-side tip 171 with respect to the ridge line 169 of the bearing 161 is determined.

A coil spring 170 supported by the preload member 155 urges the worm shaft 164 toward the worm wheel via the bearing 161 . The worm shaft 164 is tilted with respect to the other end side bearing 162 due to the movement of the pressurized bearing 161, and meshes with the worm wheel 163 while maintaining an inter-axial distance that can suppress backlash. That is, the so-called anti-backlash system (ABLS) of this embodiment is constructed.

Specifically, the worm shaft 164 and the output shaft of the motor 152 are connected via a rubber spring made of an elastic material, and the worm shaft 164 is allowed to tilt with respect to the output shaft of the motor 152. there is The other end side bearing 162 supporting the motor 152 side of the worm shaft 164 is a rolling bearing, the outer ring of which is fixed to the housing 153, and the inner ring to which the worm shaft 164 is connected is allowed to tilt with respect to the outer ring. It is On the other hand, the bearing 161 that supports the opposite side of the worm shaft 164 is provided movably in the direction (the Z-axis direction in the drawing) toward and away from the worm wheel 163 within the housing 153 . The outer ring of the bearing 161, which is a rolling bearing, is biased toward the worm wheel 163 by the elastic force of the coil spring 170. As shown in FIG.

According to the worm speed reducer 150 configured as described above, even when the coil spring 170 is vibrated or the coil spring 170 is repeatedly elongated, the position of the bearing-side tip 171 can be maintained, and the coil spring 170 and the bearing 161 can maintain their position. It is possible to continue suppressing the stick-slip sound that occurs between In addition, since the worm shaft 164 tilts about the other end side bearing 162 and the center distance between the worm shaft 164 and the worm wheel 163 is optimally maintained, even if a sudden torque is generated in the worm shaft 164, collision is avoided. Sound can be suppressed.

It should be noted that the present invention is not limited to the above embodiments. For example, another embodiment realized by arbitrarily combining the constituent elements described in this specification or omitting some of the constituent elements may be an embodiment of the present invention. The present invention also includes modifications obtained by making various modifications to the above-described embodiment within the scope of the gist of the present invention, that is, the meaning of the words described in the claims, which a person skilled in the art can think of. be

For example, the preload member 155 may be fixed to the coil spring 170 at least in the circumferential direction, and may be provided with a mark 177 at a position visible from the outside of the housing 153 for identifying the circumferential position of the bearing-side tip 171 . Specifically, for example, as shown in FIGS. 6 and 7, the preload member 155 is a rod-shaped member that is press-fitted into the housing 153, and a projection 158 protrudes radially outward from its outer end. is provided as follows. A through-hole 160 into which a preload member 155 is press-fitted is provided in the housing 153 coaxially with the hole portion 154 , and a groove portion 157 is provided at the outer end portion of the through-hole 160 so as to fit with the protrusion 158 . The protrusion 158 and the groove 157 constitute a mark 177. As shown in FIG. That is, by press-fitting the preload member 155 to which the coil spring 170 is fixed so that the projection 158 fits into the groove 157, the bearing-side tip 171 of the coil spring 170 can be arranged at a predetermined position. Further, since the preload member 155 is fixed to the housing 153, the position of the bearing-side tip 171 can be maintained.

In this case, the coil spring 170 may not have the protrusion 173 and the opposite tip 174 may be located within the cylindrical region formed by the body portion 172 . Further, in order to fix the coil spring 170 to the preload member 155 by welding or the like, the tip 174 on the opposite side may be arranged in an arbitrary direction.

Moreover, the mark 177 is not limited to the one that is mechanically fitted as described above, and as shown in FIG. The mark 177 may be configured with the mark 182 . In this case, since the preload member 155 is not restricted in the circumferential direction with respect to the housing 153 by the marks 177, the preload member 155 may be fixed to the housing 153 not only by press fitting but also by screwing.

Moreover, as shown in FIG. 9, the projecting portion 173 of the coil spring 170 may be formed by bending an arbitrary position of the wire forming the coil spring 170 .

Alternatively, the portion of the wire forming the coil spring 170 near the bearing-side tip 171 may be bent so that the bearing-side tip 171 does not come into contact with the outer peripheral surface of the bearing 161 .

INDUSTRIAL APPLICABILITY The present invention is applicable to worm reduction gears having coil springs as components of the anti-backlash system.

REFERENCE SIGNS LIST 100 Steering system 110 Steering wheel 120 Sensor device 130 Steering shaft 131 Column shaft 132 Intermediate shaft 133 Pinion shaft 140 Rack and pinion device 141 Steering shaft 150 Worm reduction gear 152 Motor 153 Housing 154 Hole 155 Preload member 156 Engaging portion 157 Groove 158 Protrusion 160 Through hole 161 Bearing 162 Others End side bearing 163 Worm wheel 164 Worm shaft 165 Accommodating portion 168 Determining means 169 Ridge line 170 Coil spring 171 Bearing side tip 172 Body portion 173 Protruding portion 174 Opposite tip, 177...Mark, 181...First mark, 182...Second mark

Claims (4)

A worm reduction gear comprising a worm shaft, a worm wheel, and a housing accommodating the worm shaft and the worm wheel,
a bearing that holds the worm shaft inside the housing;
a coil spring that contacts the outer peripheral surface of the bearing and applies a biasing force in the worm wheel direction;
determining means for restricting the rotation of the coil spring in the circumferential direction with respect to the housing and determining the position of a bearing-side tip, which is the bearing-side tip of a wire forming the coil spring;
Worm reducer with The coil spring is
a body portion which is a cylindrically wound portion;
a protruding portion that is formed of the wire and protrudes outward from the cylindrical shape formed by the main body,
The housing is
An accommodating portion that accommodates the projecting portion,
2. A worm reduction gear according to claim 1, wherein said protrusion and said accommodating portion form said determining means. A preload member fixed to the housing and pressurizing the coil spring,
The preload member is
fixed at least in the circumferential direction with the coil spring;
A worm reduction gear according to claim 1 or 2, wherein a mark is provided at a position visible from the outside of said housing so that the circumferential position of said bearing-side tip can be determined. The point at which the winding axis of the coil spring and the plane intersect with the plane perpendicular to the urging direction of the coil spring is defined as the vertex, and one side of the ridgeline of the outer peripheral surface of the bearing with respect to the vertex is set at 0°, and the other side is set at 180°. in the case of
When the winding direction of the coil spring is clockwise toward the bearing,
an angle range of 0°<θ≦135° or 180°<θ≦315°;
When the winding direction of the coil spring is counterclockwise toward the bearing,
In the angle range of 45°≦θ<180° or 225°≦θ<360°,
A worm reducer according to any one of claims 1 to 3, wherein said determining means locates said bearing-side tip.

Images