WO2021241135A1

WO2021241135A1 - Worm speed reducer and electric power assist device

Info

Publication number: WO2021241135A1
Application number: PCT/JP2021/017115
Authority: WO
Inventors: 亮大澤; 隆宏泉; 聡石栗; 徹石井; 良太村田; 茂雄篠原; 貴之石井; 知幸金井
Original assignee: 日本精工株式会社
Priority date: 2020-05-27
Filing date: 2021-04-28
Publication date: 2021-12-02
Also published as: JPWO2021241135A1

Abstract

This worm speed reducer comprises a support bearing with an inner ring fitted onto a distal end portion of a worm and an outer ring disposed around the inner ring so as to be coaxial to the inner ring, a first elastic member for elastically biasing the support bearing towards a worm wheel side, a second elastic member with a pair of clamping pieces that are elastically clamping the support bearing from both sides in a second direction perpendicular to a first direction, which is the direction of biasing by the first elastic member, and to the central axis of a worm accommodating section, and a third elastic member provided around said outer ring and having an elastically deformable section for undergoing elastic deformation on the basis of meshing reaction force exerted to said worm from the meshing site between the teeth of said wheel and the teeth of said worm.

Description

Worm reducer and electric assist device

The present invention relates to a worm reducer including a worm and a worm wheel, and an electric assist device including the worm reducer.

In a steering device for an automobile, when the driver operates (rotates) the steering wheel, the rotation of the steering wheel is transmitted to the input shaft of the steering gear unit by the steering shaft and the intermediate shaft. When the rack shaft of the steering gear unit is displaced in the width direction of the vehicle due to the rotation of the input shaft, the pair of tie rods is pushed and pulled to give the steering wheel a steering angle.

Japanese Patent Application Laid-Open No. 2005-42913 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2004-306988 (Patent Document 2) use an electric motor as an auxiliary power source to provide a steering angle to the steering wheel. An electric power steering device that reduces the force required for the driver to operate the steering wheel is disclosed. In the electric power steering device, the torque of the electric motor is increased by the worm reducer, and then the rotating shaft, such as the steering shaft or the input shaft of the steering gear unit, rotates with the rotation of the steering wheel, or the steering gear unit. It is applied to linear motion shafts such as rack shafts and screw shafts.

FIG. 38 shows the structure of the worm reducer described in Japanese Patent Application Laid-Open No. 2004-306988. The worm reducer 200 includes a housing 201, a worm wheel 202, and a worm 203.

The housing 201 has a wheel accommodating portion 204 and a worm accommodating portion 205 having its own central axis at a twisted position with respect to the central axis of the wheel accommodating portion 204 and an axial middle portion opened in the wheel accommodating portion 204. And have.

The worm wheel 202 has wheel teeth 206 on the outer peripheral surface. The worm wheel 202 is supported and fixed coaxially with the rotating shaft 207 around the rotating shaft 207 rotatably supported inside the wheel accommodating portion 204.

The worm 203 has worm teeth 208 that mesh with the wheel teeth 206 on the outer peripheral surface of the intermediate portion in the axial direction. The worm 203 is rotatably supported inside the worm accommodating portion 205 by a pair of

ball bearings

209a and 209b at two axial positions sandwiching the worm tooth 208. Of the pair of

ball bearings

209a and 209b, the outer ring of the ball bearing 209a on the tip side (right side in FIG. 38) of the worm 203 is fitted and fixed to the holder 210 inside the inner end side portion of the worm accommodating portion 205. It is press-fitted. The inner ring of the ball bearing 209a is externally fitted to the large diameter portion 211 provided in the portion of the worm 203 located on the tip side of the worm tooth 208 by gap fitting via a bush 212 made of synthetic resin. .. That is, the inner ring of the ball bearing 209a is externally fitted to the bush 212 that is fitted to the large diameter portion 211 of the worm 203 by gap fitting without rattling. The outer ring of the ball bearing 209b on the base end side (left side of FIG. 38) of the worm 203 is press-fitted into the opening of the worm accommodating portion 205. The inner ring of the ball bearing 209b is externally fitted to the base end portion of the worm 203. The output shaft of the electric motor 213 is connected to the base end portion of the worm 203 so as to be able to transmit torque. That is, the worm 203 can be rotationally driven by the electric motor 213.

In the worm reducer 200, there is an unavoidable backlash in the meshing portion between the wheel teeth 206 and the worm teeth 208 based on the dimensional error and the assembly error of the parts constituting the worm reducer 200. Based on the presence of this backlash, when the rotation direction of the steering wheel is changed, a jarring rattling noise may be generated at the meshing portion. In the illustrated example, the tip of the worm 203 is elastically urged toward the side of the worm wheel 202 in order to suppress the generation of such a rattling noise.

That is, the base end portion of the worm 203 is supported with respect to the worm accommodating portion 205 by a ball bearing 209b having a radial gap so as to allow a slight swing displacement. An annular gap exists over the entire circumference between the outer peripheral surface of the large diameter portion 211 of the worm 203 and the inner peripheral surface of the bush 212. A pad 214 is fitted tightly to the tip of the worm 203, and a torsion coil spring 215 is installed between the pad 214 and the holder 210. The torsion coil spring 215 makes the pad 214 in the first direction (vertical direction in FIG. 38) orthogonal to the central axis of the electric motor 213 (horizontal direction in FIG. 36) and the central axis of the worm wheel 202 (front and back directions in FIG. 36). ), By elastically pressing toward the side of the worm wheel 202, the tip of the worm 203 is elastically pressed toward the side of the worm wheel 202 with respect to the first direction. As a result, backlash between the wheel teeth 206 and the worm teeth 208 is suppressed, and the generation of rattling noise is suppressed.

Japanese Patent Application Laid-Open No. 2005-42913 Japanese Patent Application Laid-Open No. 2004-306988

By the way, in order to secure a large range (dimensional tolerance) that allows each dimensional error and assembly error of the parts constituting the worm reducer 200, the amount that the tip portion of the worm 203 can be displaced in the first direction is large. It is necessary to secure it.

In addition, in order to reduce the rattling noise generated at the meshing part between the worm teeth and the wheel teeth and to reduce the weight, the worm wheel is made of a metal inner wheel element and a synthetic resin having wheel teeth on the outer peripheral surface. An outer wheel element and a combination thereof can be used. However, when such a worm wheel is used, the outer wheel element made of synthetic resin may expand due to water absorption, heat, or the like, and the friction between the worm tooth and the meshing portion of the wheel tooth may increase. In order to prevent an increase in friction between the worm teeth and the meshing portion due to the expansion of the outer wheel element, it is necessary to secure a large amount of displacement of the tip portion of the worm 203 with respect to the first direction.

In the structure described in Japanese Patent Application Laid-Open No. 2004-306988, a gap exists over the entire circumference between the outer peripheral surface of the large diameter portion 211 of the worm 203 and the inner peripheral surface of the bush 212. Therefore, in order to secure a large amount of displacement of the tip of the worm 203 with respect to the first direction, if the distance between the gaps with respect to the first direction is increased, the first direction and the central axis of the worm accommodating portion 205 are set. The interval with respect to the orthogonal second direction (front and back directions in FIG. 38) also becomes large. Therefore, when the rotation direction of the steering wheel is changed, the tip portion of the worm 203 may be displaced in the second direction (front and back directions in FIG. 38).

In view of the above circumstances, the present invention is in a worm reducer provided with a means for imparting elasticity to the tip of the worm in a direction approaching the worm wheel, the tip of the worm is in the direction of the elasticity (first direction). ) And the central axis of the worm accommodating portion () and the direction orthogonal to the central axis (second direction), the purpose of which is to realize a structure capable of suppressing the generation of abnormal noise due to displacement.

The worm reducer of the present invention includes a housing, a worm wheel, a worm, a support bearing, a first elastic member, a second elastic member, and a third elastic member.
The housing has a wheel accommodating portion and a worm accommodating portion that is arranged in a twisted position with respect to the wheel accommodating portion and has an axial middle portion open to the wheel accommodating portion.
The worm wheel has wheel teeth on the outer peripheral surface and is rotatably supported inside the wheel accommodating portion.
The worm has worm teeth that mesh with the wheel teeth on the outer peripheral surface, and is rotatably supported inside the worm accommodating portion.
The support bearing has an inner ring fitted to the tip of the worm and an outer ring arranged coaxially with the inner ring around the inner ring.
The first elastic member elastically urges the support bearing toward the side of the worm wheel. The second elastic member elastically sandwiches the support bearing from both sides in a second direction orthogonal to the first direction, which is the urging direction of the first elastic member, and the central axis of the worm accommodating portion. Has a holding piece.
The third elastic member is provided around the outer ring and has an elastically deformed portion that elastically deforms based on the meshing reaction force applied to the worm from the meshing portion between the wheel teeth and the worm teeth.

The outer ring has a bearing holding portion that is internally fitted to the worm wheel so as to be able to move in perspective, and can further include a guide member that is internally fitted inside the worm accommodating portion. In this case, the first elastic member is arranged between the outer ring and the guide member, the second elastic member is arranged between the outer ring and the guide member, and the third elastic member is arranged. Is arranged between the outer ring and the guide member.

The guide member is located in the bearing holding portion so that the phase in the circumferential direction coincides with the elastically deformed portion and is radially outside the tip portion (diameterally inner end portion) of the elastically deformed portion. A pair of reaction force bearing surface portions can be provided in the portion to be supported.

The guide member can have a pair of facing surface portions of the bearing holding portion, which are provided on both sides in the second direction and are located radially outside the holding piece.

In the worm reducer of the present invention, the third elastic member can be elastically sandwiched between the worm accommodating portion and the guide member in the axial direction.
In this case, the third elastic member may have a protrusion protruding toward one side in the axial direction on one side surface in the axial direction.

The worm reducer of the present invention can further include an elastic ring elastically sandwiched between the inner peripheral surface of the worm accommodating portion and the outer peripheral surface of the guide member.

The first elastic member includes a locking plate portion locked to the guide member, a pressing plate portion that elastically presses the outer peripheral surface of the outer ring toward the worm wheel side, and substantially U when viewed from the axial direction. A connection plate portion that is curved in a shape and connects the locking plate portion and the pressing plate portion can be provided.

Alternatively, the first elastic member includes a substrate portion, a first pressing plate portion provided on the radial outer side of the substrate portion and elastically pressed against the guide member, the substrate portion, and the first pressing. A first connecting plate portion connecting the plate portions, a second pressing plate portion provided inside the substrate portion in the radial direction and elastically pressed against the outer peripheral surface of the outer ring, the substrate portion and the first It can have a second connecting plate portion that connects the two pressing plate portions.

The second elastic member may have a base that connects the ends of the pair of holding pieces on both sides in the circumferential direction that are closer to the worm wheel.

In the worm reducer of the present invention, the elastically deformed portion can be provided in the half portion of the third elastic member on the side far from the worm wheel in the first direction.

In the worm reducer of the present invention, the elastically deformed portion can be composed of a pair of elastically deformed portions provided at two positions in the circumferential direction of the third elastic member.

The electric assist device of the present invention includes an electric motor and a worm reducer that increases the torque of the electric motor and applies it to a rotary shaft that rotates with the rotation of the steering wheel or a linear motion shaft that constitutes a steering gear unit. To prepare for.
In particular, in the electric assist device of the present invention, the worm reducer is the worm reducer of the present invention.

According to the worm reducer and the electric assist device of the present invention as described above, when the rotation direction of the worm wheel is changed, the tip portion of the worm is urged by the first elastic member (first direction) and the worm is accommodated. It is possible to suppress the displacement in the direction orthogonal to the central axis of the portion (second direction).

FIG. 1 is a partially cut side view showing a column assist type electric power steering device incorporating the electric assist device according to the first example of the embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line AA of FIG. FIG. 3A is a perspective view showing the guide assembly taken out, and FIG. 3B is a perspective view seen from the opposite side of FIG. 3A. 4 (A) is a side view showing the guide assembly taken out, FIG. 4 (B) is a front view seen from the left side of FIG. 4 (A), and FIG. 4 (C) is FIG. 4 (A) is a rear view seen from the right side, FIG. 4 (D) is a plan view seen from the upper side of FIG. 4 (C), and FIG. 4 (E) is a lower side of FIG. 4 (C). It is a bottom view seen from. FIG. 5 is a sectional view taken along the line BB of FIG. 4 (C). FIG. 6 is a sectional view taken along the line CC of FIG. 4 (C). FIG. 7 is a cross-sectional view taken along the line DD of FIG. 4 (A). FIG. 8 is a cross-sectional view taken along the line EE of FIG. 4 (A). FIG. 9 is a perspective view showing the support bearing removed from the guide assembly. FIG. 10 is an exploded perspective view of the guide assembly. 11 (A) is a perspective view showing the guide member taken out, and FIG. 11 (B) is a perspective view seen from the opposite side of FIG. 11 (A). 12 (A) is a side view showing the guide member taken out, FIG. 12 (B) is a front view seen from the left side of FIG. 12 (A), and FIG. 12 (C) is FIG. 12 (C). A) is a rear view seen from the right side, FIG. 12 (D) is a plan view seen from the upper side of FIG. 12 (C), and FIG. 12 (E) is a plan view seen from the lower side of FIG. 12 (C). It is a bottom view as seen. FIG. 13 is a cross-sectional view taken along the line FF of FIG. 12 (C). 14 (A) is a perspective view showing the first elastic member taken out, FIG. 14 (B) is a plan view showing the first elastic member taken out, and FIG. 14 (C) is FIG. 14 (C). B) is a front view seen from the lower side, FIG. 14 (D) is a rear view seen from the upper side of FIG. 14 (B), and FIG. 14 (E) is from the left side of FIG. 14 (B). It is a side view as seen, and FIG. 14 (F) is a side view seen from the right side of FIG. 14 (B). 15 (A) is a perspective view showing the second elastic member taken out, FIG. 15 (B) is a front view showing the second elastic member taken out, and FIG. 15 (C) is FIG. 15 (C). B) is a side view seen from the right side, and FIG. 15 (D) is a bottom view seen from the lower side of FIG. 15 (B). 16 (A) is a perspective view showing the third elastic member taken out, FIG. 16 (B) is a front view showing the third elastic member taken out, and FIG. 16 (C) is FIG. 16 (C). B) is a side view seen from the left side, FIG. 16 (D) is a side view seen from the right side of FIG. 16 (B), and FIG. 16 (E) is a side view seen from the lower side of FIG. 16 (B). It is a bottom view as seen, and FIG. 16 (F) is a rear view seen from the right side of FIG. 16 (D). FIG. 17 is a cross-sectional view of the guide assembly according to the modified example. FIG. 18A is a perspective view showing the second elastic member according to the modified example taken out, and FIG. 18B is a front view showing the second elastic member taken out according to the modified example. (C) is a side view seen from the right side of FIG. 18 (B), and FIG. 18 (D) is a bottom view seen from the lower side of FIG. 18 (B). FIG. 19 is a diagram corresponding to the upper part of FIG. 2, showing the electric assist device according to the second example of the embodiment of the present invention. FIG. 20 is a cross-sectional view taken along the line GG of FIG. 21 is a sectional view taken along the line HH of FIG. FIG. 22 is a perspective view showing the guide assembly taken out. FIG. 23 is a rear view showing the guide assembly taken out. FIG. 24 is an exploded perspective view of the guide assembly. FIG. 25 is a front view showing the first elastic member and the second elastic member taken out. FIG. 26 is a rear view showing the third elastic member taken out. FIG. 27 is a perspective view showing the guide assembly taken out for the third example of the embodiment of the present invention. FIG. 28 is a rear view showing the guide assembly taken out. FIG. 29 is a side view showing the guide assembly taken out. FIG. 30 is a cross-sectional view taken along the line II of FIG. 29. FIG. 31 is a cross-sectional view taken along the line JJ of FIG. 29. FIG. 32 is an exploded perspective view of the guide assembly. 33 (A) is a perspective view showing the first elastic member taken out with respect to the fourth example of the embodiment of the present invention, and FIG. 33 (B) is seen from the side opposite to FIG. 33 (A). It is a perspective view. FIG. 34 (A) is a perspective view showing a state before the guide member and the first elastic member are taken out and combined with respect to the fourth example of the embodiment of the present invention, and FIG. 34 (B) is a perspective view showing a state before the guide member and the first elastic member are taken out and combined. It is a perspective view which shows the state which combined with the 1st elastic member. FIG. 35 (A) is a perspective view showing the fifth example of the embodiment of the present invention by taking out the first elastic member, and FIG. 35 (B) is viewed from the opposite side to FIG. 35 (A). It is a perspective view. FIG. 36 (A) is a perspective view showing a state before the guide member and the first elastic member are taken out and combined with respect to the fifth example of the embodiment of the present invention, and FIG. 36 (B) is a perspective view showing a state before the guide member and the first elastic member are taken out and combined. It is a perspective view which shows the state which combined with the 1st elastic member. FIG. 37 is a diagram corresponding to FIG. 30, showing a fifth example of the embodiment of the present invention. FIG. 38 is a cross-sectional view showing an example of a conventional structure of a worm reducer.

[First example of the embodiment]
1 to 16 (F) show a first example of an embodiment of the present invention. This example is an example in which the electric assist device of the present invention is applied to a column assist type electric power steering device. As shown in FIG. 1, in the electric power steering device 1, the rotation of the steering wheel 2 is transmitted to the input shaft 4 of the steering gear unit 3, and the pair of tie rods 5 is pushed by the rotation of the input shaft 4. When pulled, the steering wheel is given a steering angle. The steering wheel 2 is supported and fixed to the rear end portion of the steering shaft 6, and the steering shaft 6 is rotatably supported inside the steering column 7. The front end of the steering shaft 6 is connected to the rear end of the intermediate shaft 9 via a universal joint 8a, and the front end of the intermediate shaft 9 is connected to the input shaft 4 via another universal joint 8b. ..

The electric power steering device 1 includes an electric assist device 10 that applies auxiliary power to the steering shaft 6 in order to reduce the force required for the driver to operate the steering wheel 2. The electric assist device 10 is a worm reducer that increases the torque of the electric motor 11 and the electric motor 11 and applies it to a rotary shaft that rotates with the rotation of the steering wheel 2 or a linear motion shaft that constitutes the steering gear unit 3. 12 is provided. That is, the electric assist device 10 applies the rotational torque of the output shaft 13 of the electric motor 11 to the steering shaft 6 while being increased by the worm reducer 12.

The worm reducer 12 includes a housing 14, a worm wheel 15, a worm 16, a support bearing 17, and an urging mechanism 18.

The housing 14 is a cast iron-based alloy, a die-cast molded product of a light alloy such as aluminum, an injection-molded product of synthetic resin, or the like. The housing 14 includes a wheel accommodating portion 19 and a worm accommodating portion 20 arranged at a twisted position with respect to the wheel accommodating portion 19 and having an axial intermediate portion opened in the wheel accommodating portion 19.

The wheel accommodating portion 19 is supported and fixed to the front end portion of the steering column 7 so that its own central axis and the central axis of the steering column 7 are coaxial with each other.

The worm accommodating portion 20 is formed in a cylindrical shape and has openings at both ends in the axial direction. The opening on one side (right side in FIG. 2) of the worm accommodating portion 20 in the axial direction is closed by the electric motor 11 coupled and fixed to the housing 14. The opening on the other side (left side in FIG. 2) of the worm accommodating portion 20 in the axial direction is closed by the guide member 45 constituting the urging mechanism 18.

Regarding the worm 16, the worm 16 rotatably supported inside the worm accommodating portion 20, and the members arranged around the worm 16, the axial direction, the radial direction, and the circumferential direction are not specified unless otherwise specified. , Refers to the axial direction, the radial direction, and the circumferential direction of the support bearing 17. Further, with respect to the worm accommodating portion 20, the worm 16 rotatably supported inside the worm accommodating portion 20, and the members arranged around the worm 16, one side in the axial direction is the proximal end side of the worm 16. The right side of FIG. 2 is referred to, and the other side in the axial direction is the tip end side of the worm and refers to the left side of FIG.

The worm accommodating portion 20 has a cylindrical surface portion 21 having a cylindrical surface shape on the inner peripheral surface of one side portion in the axial direction, and a step portion facing one side in the axial direction at the end portion of the cylindrical surface portion 21 on the other side in the axial direction. Has 22. The worm accommodating portion 20 has a cylindrical guide holding portion 23 on the inner peripheral surface of the other side portion in the axial direction. Further, the worm accommodating portion 20 has an inward flange portion 24 protruding inward in the radial direction at a portion adjacent to one side in the axial direction of the guide holding portion 23. Further, the worm accommodating portion 20 is concave outward in the radial direction at the end portion of the inner peripheral surface of the portion adjacent to the other side in the axial direction of the guide holding portion 23 on the side farther from the wheel accommodating portion 19 in the circumferential direction. Moreover, it has an engaging recess 25 opened on the other end surface of the worm accommodating portion 20 in the axial direction.

The worm wheel 15 has wheel teeth 26, which are helical gears, on the outer peripheral surface. The worm wheel 15 is rotatably supported inside the wheel accommodating portion 19. In this example, the worm wheel 15 is supported and fixed so as to rotate integrally with the steering shaft 6 around the front end portion of the steering shaft 6 rotatably supported inside the wheel accommodating portion 19. The worm wheel 15 of this example is formed by coupling and fixing an outer wheel element 28 made of synthetic resin having wheel teeth 26 on the outer peripheral surface around an inner wheel element 27 made of metal and having a circular plate shape.

The worm 16 has a screw-shaped worm tooth 29 that meshes with the wheel tooth 26 of the worm wheel 15 on the outer peripheral surface of the intermediate portion in the axial direction. The worm 16 is rotatably supported inside the worm accommodating portion 20. The base end portion of the worm 16 is connected to the output shaft 13 of the electric motor 11 via a torque transmission joint 30 so as to be able to transmit torque.

The torque transmission joint 30 is driven by a drive-side transmission member 31 that is externally fitted and fixed to the tip end portion (left end portion of FIG. 2) of the output shaft 13 of the electric motor 11 and a driven side transmission member 31 that is externally fitted and fixed to the base end portion of the worm 16. A side transmission member 32 and an elastic member, each of which is made of an elastic material such as an elastomer such as rubber, are provided.

When the torque transmitted between the output shaft 13 of the electric motor 11 and the worm 16 is relatively small, the torque transmission joint 30 transfers the rotational torque of the output shaft 13 from the drive side transmission member 31 via the elastic member. It is transmitted to the driven side transmission member 32. On the other hand, when the torque transmitted between the output shaft 13 of the electric motor 11 and the worm 16 is large, the elastic member is elastically crushed in the circumferential direction, so that the torque transmission joint 30 is the output shaft 13. The rotational torque is directly transmitted from the drive side transmission member 31 to the driven side transmission member 32.

As the specific structure of the torque transmission joint 30, various conventionally known structures can be adopted. In any case, in this example, by connecting the tip end portion of the output shaft 13 of the electric motor 11 and the base end portion of the worm 16 so as to be able to transmit torque via the torque transmission joint 30, the electric motor It prevents the generation of rattling noise in the torque transmission unit between the output shaft 13 of 11 and the worm 16 and enables the worm 16 to swing with respect to the output shaft 13. However, as long as torque can be transmitted between the output shaft 13 of the electric motor 11 and the worm 16 and the worm 16 can swing with respect to the output shaft 13, the tip of the output shaft 13 of the electric motor 11 and the worm The connection method with the base end portion of 16 is not particularly limited, and the base end portion can be connected by spline engagement or the like.

The worm 16 is located between the proximal end portion to which the driven side transmission member 32 is externally fitted and fixed and the axial intermediate portion provided with the worm teeth 29, in order from the proximal end side (one side in the axial direction). A fitting cylinder portion 33 and a flange portion 34 protruding outward in the radial direction are provided. The fitting cylinder portion 33 is rotatably supported by a ball bearing 35 with respect to the cylindrical surface portion 21 of the worm accommodating portion 20. The ball bearing 35 includes an outer ring 36, an inner ring 37, and a plurality of balls 38.

The outer ring 36 is internally fitted into the cylindrical surface portion 21 of the worm accommodating portion 20 by gap fitting, and is sandwiched between the step portion 22 and the retaining ring 39 locked to the cylindrical surface portion 21 from both sides in the axial direction. There is. In other words, the outer ring 36 abuts the other side surface in the axial direction against the step portion 22, and the one side surface in the axial direction abuts against the retaining ring 39. However, the outer ring 36 can be internally fitted to the cylindrical surface portion 21 of the worm accommodating portion 20 by tightening.

The inner ring 37 is externally fitted to the fitting cylinder portion 33 of the worm 16 without rattling, and is externally fitted and fixed to one side surface of the flange portion 34 in the axial direction and the base end portion of the worm 16. It is sandwiched from both sides in the axial direction via a pair of elastic members 40 between the other side surfaces in the axial direction of 32. In other words, the inner ring 37 abuts one side surface in the axial direction against the other side surface in the axial direction of the driven side transmission member 32 via the elastic member 40 on one side in the axial direction, and the other side surface in the axial direction is axially oriented. It abuts against one side surface of the flange portion 34 in the axial direction via the elastic member 40 on the other side.

The plurality of balls 38 are rotatably arranged between the outer ring track provided on the inner peripheral surface of the outer ring 36 and the inner ring track provided on the outer peripheral surface of the inner ring 37.

The ball bearing 35 has a radial gap between the outer ring 36, the inner ring 37, and the ball 38. Therefore, the fitting cylinder portion 33 of the worm 16 is supported so as to be able to rotate and swing with respect to the cylindrical surface portion 21 of the worm accommodating portion 20.

Further, the worm 16 has a small diameter tubular portion 41 having a smaller outer diameter than a portion adjacent to the proximal end side (one side in the axial direction) at the tip end portion (the other end portion in the axial direction). The small-diameter tubular portion 41 is supported by the support bearing 17 and the urging mechanism 18 with respect to the guide holding portion 23 of the worm accommodating portion 20 so as to be able to rotate freely and to move in perspective with respect to the worm wheel 15.

The support bearing 17 includes an inner ring 42 fitted and fixed to the small diameter tubular portion 41, an outer ring 43 arranged coaxially with the inner ring 42 around the inner ring 42, and an inner ring track and an outer ring provided on the outer peripheral surface of the inner ring 42. A plurality of rolling elements 44, which are rotatably arranged between the outer ring track and the outer ring track provided on the inner peripheral surface of the 43, are provided. In this example, a ball bearing in which the rolling element 44 is a ball is used as the support bearing 17, but a radial roller bearing or a radial needle bearing can also be used.

The urging mechanism 18 imparts elasticity to the support bearing 17 to approach the worm wheel 15, and the direction of the elasticity (first direction) and the direction orthogonal to the central axis of the worm accommodating portion 20 (second direction). ), By elastically sandwiching the worm 16 from both sides, it has a function of suppressing the generation of abnormal noise such as a rattling noise due to the displacement of the tip of the worm 16. The urging mechanism 18 of this example includes a guide member 45, an elastic ring 46, a first elastic member 47, a second elastic member 48, and a third elastic member 49.

The guide member 45 has a bearing holding portion 50 on the inner peripheral surface in which the support bearing 17 is internally fitted so as to be able to move in perspective with respect to the worm wheel 15. The guide member 45 is internally fitted to the guide holding portion 23 of the worm accommodating portion 20 without rattling. The guide member 45 of this example includes a stepped cylindrical guide main body 51 and a lid 52 that closes an opening on the other side in the axial direction of the guide main body 51.

The guide main body 51 has a large-diameter cylinder portion 53 on one side in the axial direction, a small-diameter cylinder portion 54 on the other side in the axial direction, an end portion on the other side in the axial direction of the large-diameter cylinder portion 53, and one side in the axial direction of the small-diameter cylinder portion 54. A side wall portion 55 that connects to the end portion is provided. The guide body 51 is made of synthetic resin or metal having sufficient strength and rigidity.

The large-diameter tubular portion 53 has a bearing holding portion 50 on the inner peripheral surface of the other side portion in the axial direction. In this example, the inner diameter of the bearing holding portion 50 is larger than the outer diameter of the outer ring 43 of the support bearing 17, and the axial dimension of the bearing holding portion 50 is larger than the axial dimension of the outer ring 43 of the support bearing 17. Is also short. That is, the bearing holding portion 50 internally fits the other side portion of the outer ring 43 of the support bearing 17 in the axial direction so as to be able to move in perspective with respect to the worm wheel 15. More specifically, the bearing holding portion 50 internally fits the other side portion of the outer ring 43 in the axial direction by gap fitting. In other words, with the outer ring 43 fitted and held inside the bearing holding portion 50, the axial one-sided portion of the outer ring 43 is arranged inside the third elastic member holding portion 66, which will be described later.

The bearing holding portion 50 has distal side partial cylindrical surface portions 56 at two locations (half portion) far from the worm wheel 15 in the circumferential direction, and is located between the distal side partial cylindrical surface portions 56. It has a first elastic member holding recess 57 recessed outward in the radial direction. In other words, the bearing holding portion 50 has the first elastic member holding recess 57 at the end on the side farther from the worm wheel 15 in the circumferential direction, and the first elastic member holding recess 57 in the circumferential direction. The distal side partial cylindrical surface portion 56 is provided on both sides of the sandwich. Further, the bearing holding portion 50 has a second elastic member holding recess 58 recessed outward in the radial direction in a portion (half portion) closer to the worm wheel 15 in the circumferential direction.

Each of the distal partial cylindrical surface portions 56 has a radius of curvature equal to or slightly larger than the radius of curvature of the outer peripheral surface of the outer ring 43 of the support bearing 17.

The first elastic member holding recess 57 has a flat pedestal surface portion 59 on the bottom surface facing inward in the radial direction. The guide main body 51 is shafted from the surface of the first elastic member holding recess 57 facing one side in the axial direction (the end of one side surface of the side wall portion 55 in the axial direction far from the worm wheel 15 in the circumferential direction). It has a rectangular columnar distal projecting portion 60 projecting toward one side in the direction. Then, the flat surface-shaped holding surface portion 61 provided on the radial outer surface of the distal side protruding portion 60 is opposed to the pedestal surface portion 59.

The second elastic member holding recess 58 has convex portions 62 protruding inward in the radial direction at two positions in the circumferential direction of the bottom surface facing inward in the radial direction. The guide main body 51 is shafted from the surface of the second elastic member holding recess 58 facing one side in the axial direction (the end of one side surface of the side wall portion 55 in the axial direction closer to the worm wheel 15 in the circumferential direction). It has a proximal side protrusion 63 having a substantially bow-shaped (substantially arcuate) end face shape protruding toward one side in the direction. The proximal side protrusion 63 has a proximal side partial cylindrical surface portion 64 on the radial inner side surface and a partially cylindrical surface-shaped holding surface portion 65 on the radial outer surface.

The proximal side partial cylindrical surface portion 64 has a radius of curvature equal to or slightly larger than the radius of curvature of the outer peripheral surface of the outer ring 43 of the support bearing 17. Specifically, for example, the distal partial cylindrical surface portion 56 and the proximal partial cylindrical surface portion 64 can be present on the same virtual cylindrical surface.

The holding surface portion 65 is located slightly inward in the radial direction from the tip portion (inner end in the radial direction) of the convex portion 62.

The large-diameter tubular portion 53 has a cylindrical third elastic member holding portion 66 on the inner peripheral surface of the end portion on one side in the axial direction.

Further, the large-diameter tubular portion 53 has an engaging convex portion 67 projecting outward in the radial direction at the end portion of the outer peripheral surface of the end portion on the other side in the axial direction, which is far from the worm wheel 15 in the circumferential direction. Have. Further, the large-diameter tubular portion 53 has a locking groove 68 over the entire circumference on the outer peripheral surface of the intermediate portion in the axial direction, and is radially inward toward the one side in the axial direction on the outer peripheral surface of the end portion on one side in the axial direction. It has an inclined surface portion 69 inclined in the direction toward the direction. In this example, the central axis of the locking groove 68 coincides with the central axis of the large diameter tubular portion 53. However, the central axis of the locking groove 68 may be offset to a side farther from the worm wheel 15 than the central axis of the large diameter tubular portion 53.

Further, the large-diameter tubular portion 53 has a first engaging notch 70 at the end of the end on one side in the axial direction, which is closer to the worm wheel 15 in the circumferential direction, and has one side in the axial direction. The second engaging notch 71 is provided at two positions of the ends of the wheel, which are 90 degrees out of phase with the first engaging notch 70 in the circumferential direction.

The small diameter cylinder portion 54 has an inward flange portion 72 protruding inward in the radial direction at an end portion on the other side in the axial direction.

The lid 52 includes a small diameter portion 73 on one side in the axial direction and a large diameter portion 74 on the other side in the axial direction, and is made of an elastic material such as an elastomer such as synthetic resin or rubber. The small diameter portion 73 has a concave groove 75 over the entire circumference on the outer peripheral surface of the end portion on the other side in the axial direction. The lid 52 is attached to the guide body 51 by inserting the small diameter portion 73 inside the small diameter cylinder portion 54 of the guide body 51 and engaging the concave groove 75 with the inward flange portion 72 to guide the guide body 52. The opening on the other side in the axial direction of the main body 51 is closed. However, the lid 52 may be omitted. In this case, the opening on the other side in the axial direction of the guide body can be left open or can be closed by the circular plate-shaped bottom plate.

The guide member 45 is fitted inside the guide holding portion 23 in a state where the engaging convex portion 67 is engaged with the engaging concave portion 25 of the worm accommodating portion 20 and the elastic ring 46 is locked in the locking groove 68. Has been done. That is, by engaging the engaging convex portion 67 with the engaging concave portion 25, the guide member 45 is positioned in the circumferential direction, and the guide member 45 is prevented from rotating inside the guide holding portion 23. There is. Further, the elastic ring 46 is elastically sandwiched between the guide holding portion 23 and the bottom surface of the locking groove 68 to prevent the grease sealed in the housing 14 from leaking to the outside. Further, in this example, with the guide member 45 fitted in the guide holding portion 23, the retaining ring 88 is attached to the portion of the inner peripheral surface of the worm accommodating portion 20 adjacent to the other side in the axial direction of the guide holding portion 23. It is locked. This prevents the guide member 45 from being displaced to the other side in the axial direction.

In this example, the elastic ring 46 has a circular cross section and is composed of an O-ring made of an elastic material such as an elastomer such as rubber. However, the cross-sectional shape of the elastic ring 46 is not limited to a circle, and various shapes such as a rectangle and an ellipse can be adopted.

Further, in this example, the central axis of the locking groove 68 is aligned with the central axis of the large diameter tubular portion 53, but the central axis of the locking groove 68 is warmer than the central axis of the large diameter tubular portion 53. It can also be offset to the side farther from the wheel 15. As a result, the elastic compression amount of the elastic ring 46 on the side portion far from the worm wheel 15 is made larger than the elastic compression amount of the elastic ring 46 on the side portion close to the worm wheel 15, so that the guide member 45 becomes the worm wheel 15. It is also possible to elastically urge toward the near side and press the side portion of the outer peripheral surface of the large-diameter tubular portion 53 closer to the worm wheel 15 against the guide holding portion 23.

The first elastic member 47 elastically directs the support bearing 17 toward the side of the worm wheel 15 (the lower side of FIGS. 2, 4 (A) to 4 (C), 5, 7, and 8). Is urging. In this example, the first elastic member 47 is composed of a leaf spring formed by bending and molding an elastic metal plate. The first elastic member 47 is arranged between the outer ring 43 of the support bearing 17 and the guide member 45. The first elastic member 47 includes a locking plate portion 76, a pressing plate portion 77, a connecting plate portion 78, and a bent plate portion 79. In addition, in FIGS. 5 and 8, the shape of the first elastic member 47 (particularly the position of the pressing plate portion 77) is shown in the free state of the first elastic member 47. That is, as shown in FIGS. 5 and 8, in the free state of the first elastic member 47, the inner diameter of the first elastic member 47 is smaller than the outer diameter of the outer ring 43 of the support bearing 17. Therefore, when the support bearing 17 is incorporated inside the first elastic member 47, the support bearing 17 is elastically pressed by the first elastic member 47.

The locking plate portion 76 is configured in a flat plate shape.

The pressing plate portion 77 is formed in a flat plate shape and is provided substantially parallel to the locking plate portion 76.

The connecting plate portion 78 is curved in a substantially U shape when viewed from the axial direction, and one end portion (diameter outer end portion) in the circumferential direction is located at the circumferential end portion of the locking plate portion 76. The other end in the circumferential direction (the inner end in the radial direction) is connected to the circumferential end of the pressing plate portion 77.

The bent plate portion 79 is bent outward in the radial direction from one end of the pressing plate portion 77 in the axial direction. As shown in FIGS. 3 (A), 5 (9), and 14 (A) and (F), the bent plate portion 79 of this example is inclined to one side in the axial direction toward the outside in the radial direction. It has a tapered shape. As a result, when the support bearing 17 is inserted into the urging mechanism 18 from one side in the axial direction, the support bearing 17 is guided by the bent plate portion 79.

The first elastic member 47 is arranged inside the first elastic member holding recess 57 of the guide member 45, and is sandwiched between the outer ring 43 of the support bearing 17 and the guide member 45 in an elastically compressed state. ing. Specifically, the locking plate portion 76 of the first elastic member 47 is sandwiched between the pedestal surface portion 59 and the holding surface portion 61. Then, the radial inner surface of the pressing plate portion 77 and the radial inner surface of the radial inner surface of the connecting plate portion 78 are elastically pressed against the end portion of the outer peripheral surface of the outer ring 43 on the side far from the worm wheel 15. Has been done. As a result, the support bearing 17 is elastically urged toward the side of the worm wheel 15.

In the second elastic member 48, the outer ring 43 of the support bearing 17 is urged by the first elastic member 47 in the first direction (FIGS. 2, 4 (A) to 4 (C), 5 and 7). And the vertical direction of FIG. 8) and the second direction (the horizontal direction of FIGS. 4 (B) to 4 (E), FIGS. 6, 7 and 8) orthogonal to the central axis of the worm accommodating portion 20 on both sides. It has a pair of holding pieces 80 that are elastically held from. In this example, the second elastic member 48 is composed of a leaf spring formed by bending and molding an elastic metal plate. The second elastic member 48 is arranged between the outer ring 43 of the support bearing 17 and the guide member 45. The second elastic member 48 is the first engagement between the partial cylindrical portion 81 having a semi-circular end face shape and the end portion on one side of the partial cylindrical portion 81 in the axial direction, which is bent radially outward from the middle portion in the circumferential direction. A piece 82 and a pair of second engaging pieces 83 bent radially outward from the ends on both sides in the circumferential direction among the ends on one side in the axial direction of the partial cylindrical portion 81. In this example, a pair of holding pieces 80 are formed by both sides of the partial cylindrical portion 81 in the circumferential direction.

The second elastic member 48 is supported inside the second elastic member holding recess 58 of the guide member 45. Specifically, the circumferential middle portion of the partial cylindrical portion 81 of the second elastic member 48 is formed between the tip end portion of the convex portion 62 provided inside the second elastic member holding recess 58 and the holding surface portion 65. The second elastic member 48 is supported by the guide member 45 by being sandwiched in the radial direction. In this state, the pair of holding pieces 80 are elastically pressed against the ends on both sides of the outer peripheral surface of the outer ring 43 of the support bearing 17 in the second direction. In other words, the outer ring 43 is sandwiched from both sides in the second direction by the pair of sandwiching pieces 80. In short, in this example, each of the pair of holding pieces 80 holding the outer ring 43 of the support bearing 17 from both sides in the second direction has the circumferential intermediate portion of the partial cylindrical portion 81 as the tip portion of the convex portion 62 and the holding surface portion. It is cantilevered with respect to the guide member 45 by sandwiching it in the radial direction with the guide member 45.

Further, with the second elastic member 48 supported by the guide member 45, the first engaging piece 82 is engaged with the first engaging notch 70 (arranged inside the first engaging notch 70). Moreover, the radial outer portion of the second engaging piece 83 is engaged with the second engaging notch portion 71. As a result, the second elastic member 48 is positioned in the circumferential direction with respect to the guide member 45.

The third elastic member 49 is a portion of the circumference of the outer ring 43 of the support bearing 17 that is far from the worm wheel 15 in the circumferential direction, and is a half portion on the side far from the worm wheel 15 in the first direction. It is provided at a position and has a pair of elastically deformed portions 84 that are elastically deformed based on the meshing reaction force Fr applied to the worm 16 from the meshing portion between the wheel teeth 26 and the worm teeth 29. In this example, the third elastic member 49 is made of an elastomer such as rubber. The third elastic member 49 has a held portion 85 having a partially arcuate (approximately 3/4 arcuate) end face shape in which a portion far from the worm wheel 15 in the circumferential direction is a discontinuous portion, and a held portion 85. Of the portions 85, a convex portion 86 that protrudes radially outward from the end portion on the side closer to the worm wheel 15 is provided. Further, the held portion 85 has recesses 87 opened in the inner peripheral surface and the outer peripheral surface at two positions on one side surface in the axial direction, which are 90 degrees out of phase with the convex portion 86 in the circumferential direction. Further, the held portion 85 has a pair of elastically deformed portions 84 protruding inward in the radial direction at two positions on the inner peripheral surface on the side portion far from the worm wheel 15 in the circumferential direction. Specifically, each of the elastically deformed portions 84 is provided in the direction of the meshing reaction force Fr in the periphery of the outer ring 43 of the support bearing 17. In this example, of the held portion 85, the elastically deformed portion 84 provided on one side portion in the circumferential direction (the left portion in FIG. 7) is composed of one elastic protrusion 91, whereas the covered portion is covered. Of the holding portions 85, the elastically deformed portion 84 provided on the other side portion in the circumferential direction (the right portion in FIG. 7) is composed of three elastic protrusions 91 separated in the circumferential direction. Each of the elastic protrusions 91 has a substantially triangular end face shape when viewed from the axial direction. However, the structure of the elastically deformed portion may be any structure as long as it can be elastically deformed based on the meshing reaction force Fr and absorb the meshing reaction force Fr.

The third elastic member 49 is supported by the guide member 45 by elastically fitting the held portion 85 into the third elastic member holding portion 66 of the guide member 45. With the third elastic member 49 supported by the guide member 45, the convex portion 86 engages with the first engaging notch 70, and the other side surface of the convex portion 86 in the axial direction is the second elastic member 48. Is pressed against one side surface of the first engaging piece 82 in the axial direction. Further, with the third elastic member 49 supported by the guide member 45, the axially other side surface of the radial inner portion of the second engaging piece 83 of the second elastic member 48 is pressed against the recess 87. Further, with the third elastic member 49 supported by the guide member 45, the elastically deformed portion 84 elastically abuts or faces the outer peripheral surface of the outer ring 43.

Further, with the guide member 45 assembled to the guide holding portion 23, the third elastic member 49 is elastically compressed in the axial direction between the guide member 45 and the inward flange portion 24. That is, the guide member 45 is positioned in the axial direction by being sandwiched in the axial direction between the third elastic member 49 and the retaining ring 88.

When assembling the worm reducer 12, the guide member 45, the elastic ring 46, the first elastic member 47, the second elastic member 48, and the third elastic member 49 are combined and as shown in FIG. , Consists of the urging mechanism 18 (referred to as a sub-assembly).

Specifically, first, the elastic ring 46 is locked in the locking groove 68 of the guide main body 51, and the locking plate portion 76 of the first elastic member 47 is placed between the pedestal surface portion 59 and the holding surface portion 61. By sandwiching it, the first elastic member 47 is supported with respect to the guide main body 51. Next, the pair of second engagement pieces 83 of the second elastic member 48 are engaged with the recess 87 of the third elastic member 49, and one side surface of the first engagement piece 82 of the second elastic member 48 in the axial direction. And the other side surface in the axial direction of the convex portion 86 of the third elastic member 49 are brought into contact with each other. In other words, by sandwiching the third elastic member 49 between the first engagement piece 82 of the second elastic member 48 and the pair of second engagement pieces 83 in the axial direction, the second elastic member 48 and the second elastic member 48 Combine with the third elastic member 49. In a state where the second elastic member 48 and the third elastic member 49 are combined, the partial cylindrical portion 81 of the second elastic member 48 is sandwiched between the tip portion of the convex portion 62 and the holding surface portion 65, and the second elastic member 48 is held. The held portion 85 of the 3 elastic member 49 is elastically fitted into the third elastic member holding portion 66. As a result, the second elastic member 48 and the third elastic member 49 are supported by the guide main body 51. Then, by attaching the lid 52 to the small diameter cylinder portion 54 of the guide main body 51, the opening on the other side in the axial direction of the guide main body 51 is closed.

Next, the support bearing 17 is inserted inside the urging mechanism 18 from one side in the axial direction. That is, the outer ring 43 of the support bearing 17 is internally fitted into the bearing holding portion 50 of the guide member 45.

Here, in the free state of the first elastic member 47, the inner diameter of the portion of the first elastic member 47 in which the support bearing 17 is incorporated is smaller than the outer diameter of the outer ring 43 of the support bearing 17 (see FIGS. 5 and 8). ), It may be difficult to incorporate the support bearing 17 inside the first elastic member 47 in the radial direction. However, since the first elastic member 47 of this example has a bent plate portion 79 having a tapered shape that is inclined to one side in the axial direction toward the outside in the radial direction (FIGS. 3 (A), 5 and 9), and 14 (A) and 14 (F)), when the support bearing 17 is inserted into the urging mechanism 18, the support bearing 17 (outer ring 43) is moved inward in the radial direction of the first elastic member 47 by the bent plate portion 79. You will be guided. Therefore, the support bearing 17 can be easily incorporated into the first elastic member 47. The tapered shape of the bent plate portion 79 can also be applied to the second to fifth examples of the embodiments described later.

Similar to the first elastic member 47, even in the free state of the second elastic member 48, the inner diameter of the portion of the second elastic member 48 in which the support bearing 17 is incorporated is smaller than the outer diameter of the outer ring 43 of the support bearing 17. It may be difficult to incorporate the support bearing 17 inside the second elastic member 48 in the radial direction. Therefore, as shown in FIGS. 17 and 18, the pair of second engagement pieces 83 of the second elastic member 48 may have a tapered shape that is inclined to one side in the axial direction toward the outside in the radial direction. According to such a configuration, when the support bearing 17 is inserted into the urging mechanism 18, the support bearing 17 (outer ring 43) is radially inside the second elastic member 48 by the pair of second engaging pieces 83. You will be guided. Therefore, the support bearing 17 can be easily incorporated into the second elastic member 48. The tapered shape of the second engaging piece 83 can also be applied to the second to fifth examples of the embodiments described later.

Then, the radial inner side surface of the pressing plate portion 77 of the first elastic member 47 and the radial inner side surface of the radial inner surface of the connecting plate portion 78 are the ends of the outer peripheral surface of the outer ring 43 on the side far from the worm wheel 15. The outer ring 43 is elastically held from both sides in the second direction by the pair of holding pieces 80 of the second elastic member 48, which are elastically pressed against the portion. Further, the pair of elastically deformed portions 84 of the third elastic member 49 are elastically abutted or brought into close contact with the portion of the outer peripheral surface of the outer ring 43 that is far from the worm wheel 15.

Next, the urging mechanism 18 and the support bearing 17 are inserted into the worm accommodating portion 20 from the opening on the other side in the axial direction of the worm accommodating portion 20. As a result, the guide member 45 is internally fitted into the guide holding portion 23, and the inner ring 42 of the support bearing 17 is externally fitted into the small diameter tubular portion 41 of the worm 16. Then, in a state where one side surface of the third elastic member 49 in the axial direction is elastically pressed against the inward flange portion 24, the inner peripheral surface of the worm accommodating portion 20 is adjacent to the other side in the axial direction of the guide holding portion 23. The retaining ring 88 is locked to the portion. As a result, the guide member 45 is prevented from being displaced to the other side in the axial direction, and the opening on the other side in the axial direction of the worm accommodating portion 20 is closed. The order of the assembly procedure of the worm reducer 12, including the assembly procedure of the urging mechanism 18, can be changed as appropriate as long as there is no contradiction.

In the electric assist device 10 of this example, the small-diameter tubular portion 41 provided at the tip of the worm 16 is provided with a support bearing 17, a guide member 45, and an elastic ring 46 with respect to the guide holding portion 23 of the worm accommodating portion 20. It is rotatable and supports the perspective movement with respect to the worm wheel 15. Further, the support bearing 17 is elastically urged toward the worm wheel 15 side by the first elastic member 47 arranged between the support bearing 17 and the guide member 45. Therefore, backlash between the wheel teeth 26 and the worm teeth 29 can be suppressed.

In particular, in this example, in the first elastic member 47, not only the radial inner surface of the pressing plate portion 77 but also the radial inner surface of the radial inner portion of the connecting plate portion 78 is formed on the outer peripheral surface of the outer ring 43. It is elastically pressed against the end far from the worm wheel 15. Therefore, it is possible to sufficiently secure the contact area of the first elastic member 47 with respect to the outer peripheral surface of the outer ring 43, and it is possible to suppress the surface pressure of the contact portion between the outer peripheral surface of the outer ring 43 and the first elastic member 47 to be small. Therefore, it is possible to suppress the wear of the first elastic member 47.

Further, in the first elastic member 47, the locking plate portion 76 locked to the guide member 45 and the pressing plate portion 77 pressing the outer peripheral surface of the outer ring 43 are curved in a substantially U shape when viewed from the axial direction. It is configured by connecting with a connection plate portion 78. Therefore, as the first elastic member, the locking plate portion supported by the guide member and the pressing plate portion that presses the outer peripheral surface of the outer ring are curved in a substantially U shape when viewed from the circumferential direction (second direction). The axial dimension can be kept short compared to the case where the structure is connected by the connecting plate portion.

Further, in the electric assist device 10 of this example, the support bearing 17 is sandwiched from both sides in the second direction by the pair of sandwiching pieces 80 of the second elastic member 48. Therefore, even if the rotation direction of the worm wheel 15 supported and fixed to the steering shaft 6 changes based on the driver operating the steering wheel 2, the tip portion of the worm 16 vigorously moves in the second direction. Displacement can be suppressed.

As the rotation direction of the worm wheel 15 changes, the force applied to the tip of the worm 16 in the second direction becomes larger than the elasticity of the holding piece 80, and the holding piece 80 is elastically deformed while the worm 16 is deformed. The tip is displaced in the second direction. Then, the outer peripheral surface of the outer ring 43 of the support bearing 17 comes into contact with the end portion of the distal side partial cylindrical surface portion 56 provided on the inner peripheral surface of the guide main body 51 in the second direction, and the guide main body 51 (large diameter) The outer peripheral surface of the tubular portion 53) is pressed against the guide holding portion 23 of the housing 14. As a result, the force based on the change in the rotation direction of the worm wheel 15 is supported by the housing 14. In other words, in the electric assist device 10 of this example, the force based on the change in the rotation direction of the worm wheel 15 is absorbed by the elastic deformation of the holding piece 80, and the housing 14 is absorbed via the guide main body 51. It is divided into two stages, one is the stage of payment and the other is the stage of payment. In this example, the facing surface portion is formed by the end portion of each of the distal side partial cylindrical surface portions 56 in the second direction.

Further, in the electric assist device 10 of this example, when torque is transmitted from the worm 16 to the worm wheel 15 by energizing the electric motor 11, as shown in FIGS. 7 and 8, the wheel teeth 26 and the worm teeth 29 A reaction force Fr is applied to the worm 16 from the meshing portion of the worm 16. The meshing reaction force Fr includes not only a component related to the first direction but also a component related to the second direction perpendicular to the first direction. Of the meshing reaction force Fr, the directions of the components in the second direction are opposite to each other depending on whether the worm 16 rotates in one direction or in the other direction. That is, when torque is transmitted between the worm 16 and the worm wheel 15, the meshing reaction force Fr in the direction inclined with respect to the first direction is applied to the tip of the worm 16 according to the rotation direction of the worm 16. Join.

In this example, elastically deformed portions 84 are provided around the outer ring 43 of the support bearing 17 in the direction of the meshing reaction force Fr. Therefore, even when the electric motor 11 is energized and the torque is transmitted from the worm 16 to the worm wheel 15 and the worm 16 is engaged with the worm 16 from the meshing portion between the wheel teeth 26 and the worm teeth 29, the reaction force Fr is applied. It is possible to prevent the tip portion of the worm 16 from being vigorously displaced in the direction of the meshing reaction force Fr.

The meshing reaction force Fr becomes larger than the elasticity of the elastically deformed portion 84, and the tip portion of the worm 16 is displaced in the direction of the meshing reaction force Fr while the elastically deformed portion 84 is crushed outward in the radial direction. As a result, the outer peripheral surface of the outer ring 43 of the support bearing 17 comes into contact with the circumferential middle portion of the distal side partial cylindrical surface portion 56 provided on the inner peripheral surface of the guide main body 51, and the guide main body 51 (large diameter cylinder portion). The outer peripheral surface of 53) is pressed against the guide holding portion 23 of the housing 14, so that the meshing reaction force Fr is supported. In other words, in the electric assist device 10 of this example, a step of absorbing the meshing reaction force Fr applied to the worm 16 by elastic deformation of the elastic deformation portion 84 and a step of supporting the meshing reaction force Fr by the housing 14 via the guide main body 51. It is divided into two stages.

The distal side partial cylindrical surface portion 56 is provided at two positions on the inner peripheral surface of the guide main body 51, which is far from the worm wheel 15 and is separated in the circumferential direction. Therefore, regardless of the rotation direction of the worm 16, the contact portion between the outer peripheral surface of the outer ring 43 and the distal partial cylindrical surface portion 56 can be positioned in the direction of the meshing reaction force Fr, and the meshing reaction force Fr can be positioned. Can be efficiently supported by the housing 14. In this example, the reaction force bearing surface portion is formed by the circumferential intermediate portions of the distal side partial cylindrical surface portions 56.

The electric assist device of the present invention is not limited to the column assist type electric power steering device, and can be incorporated into an electric power steering device having various structures.

Further, the worm reducer of the present invention can be incorporated not only in an electric assist device but also in various mechanical devices.

[Second example of the embodiment]
19 to 26 show a second example of the embodiment of the present invention. In the urging mechanism 18a of this example, the shapes of the first elastic member 47a and the second elastic member 48a are mainly changed to the first elastic member 47 and the second elastic member 47 of the urging mechanism 18 according to the first example of the embodiment. The shape of the bearing holding portion 50a provided on the inner peripheral surface of the guide member 45a is changed from the bearing holding portion 50 of the guide member 45 according to the first example of the embodiment. doing.

The guide member 45a has a distal side partial cylindrical surface portion 56 at two positions of the bearing holding portion 50a provided on the inner peripheral surface, which is far from the worm wheel 15 in the circumferential direction, and is on the distal side. A first elastic member holding recess 57a recessed outward in the radial direction is provided between the partial cylindrical surface portions 56. Further, the guide member 45a has a second elastic member holding recess 58a recessed outward in the radial direction in a portion of the bearing holding portion 50a on the side closer to the worm wheel 15 in the circumferential direction.

The first elastic member holding recess 57a has a substantially arcuate opening shape when viewed from the axial direction (axial direction of the support bearing 17). Further, the first elastic member holding recess 57a has a flat surface-shaped pedestal surface portion 59a on the bottom surface facing inward in the radial direction. In this example, the guide main body 51a constituting the guide member 45a does not have the distal side protrusion 60 provided with the guide main body 51 of the guide member 45 according to the first example of the embodiment.

The second elastic member holding recess 58a has a pair of recesses 92 that are arranged apart from each other at two points in the circumferential direction and are recessed outward in the radial direction. In other words, the second elastic member holding recess 58a has a convex portion 93 protruding inward in the radial direction at the center position in the circumferential direction.

The first elastic member 47a is composed of a leaf spring formed by bending and molding an elastic metal plate, and has a substantially S-shaped end face shape when viewed from the axial direction. The first elastic member 47a includes a substrate portion 94, a first pressing plate portion 95, a first connecting plate portion 96, a first bent plate portion 97, a second pressing plate portion 98, and a second connecting plate portion 99. And a second bent plate portion 100. In addition, in FIGS. 20 and 21, the shape of the first elastic member 47a (particularly the position of the second pressing plate portion 98) is shown in the free state of the first elastic member 47a.

The substrate portion 94 is configured in a flat plate shape.

The first pressing plate portion 95 is formed in a flat plate shape, and is provided on the radial outer side of the substrate portion 94 substantially parallel to the substrate portion 94.

The first connecting plate portion 96 is curved in a substantially U shape when viewed from the axial direction, and the end portion relating to the radial outer side is connected to the circumferential end portion of the first pressing plate portion 95 and is radially. The inner end is connected to the circumferential end of the substrate 94.

The first bent plate portion 97 is bent inward in the radial direction from the end portion on the other side in the axial direction of the first pressing plate portion 95.

The second pressing plate portion 98 is formed in a flat plate shape, and is provided on the inside of the substrate portion 94 in the radial direction substantially in parallel with the substrate portion 94.

The second connection plate portion 99 is curved in a substantially U shape when viewed from the axial direction, and the end portion related to the radial outer side is connected to the circumferential end portion of the substrate portion 94, and the end portion related to the radial inner side is connected. The portion is connected to the circumferential end portion of the second pressing plate portion 98.

The second bent plate portion 100 is bent outward in the radial direction from one end of the second pressing plate portion 98 in the axial direction.

The first elastic member 47a is arranged inside the first elastic member holding recess 57a of the guide member 45a, and is sandwiched between the outer ring 43 of the support bearing 17 and the guide member 45a in an elastically compressed state. ing. That is, the radial outer surface of the first pressing plate portion 95 (the radial outer surface of the support bearing 17) is elastically pressed against the pedestal surface portion 59a of the first elastic member holding recess 57a, and the second pressing plate portion The radial inner surface of 98 (the radial inner surface of the support bearing 17) is elastically pressed against the end of the outer peripheral surface of the outer ring 43 on the side farther from the worm wheel 15. As a result, the support bearing 17 is elastically urged toward the worm wheel 15.

The second elastic member 48a includes a pair of holding pieces 80a, a base 101, a pair of second engaging pieces 83a, and a pair of bent pieces 102.

The pair of holding pieces 80a have a partially cylindrical shape, and accommodate the worm in the first direction (vertical direction of FIGS. 19 to 21, 23, 25 and 26) which is the urging direction by the first elastic member 47a. It is provided apart with respect to a second direction (the left-right directions of FIGS. 19 to 21, 23, 25 and 26) orthogonal to the central axis of the portion 20.

The base portion 101 has a substantially M-shaped end face shape when viewed from the axial direction, and connects the ends of the pair of holding pieces 80a on both sides in the circumferential direction, which are closer to the worm wheel 15. .. Specifically, the base 101 has a pair of side plate portions 103 arranged in parallel with each other by connecting the inner end portions in each radial direction to the circumferential end portions of the holding pieces 80a, and viewed from the axial direction. A substantially V-shaped bent plate portion 104, and a partially cylindrical connecting plate portion 105 connecting the outer ends of the side plate portions 103 in the radial direction and the end portions on both sides of the bent plate portion 104 in the circumferential direction. , Equipped with.

Each of the pair of second engaging pieces 83a is bent at a right angle from one position in the circumferential direction of one end of the holding piece 80a in the axial direction toward the outside in the radial direction. Specifically, each of the pair of second engaging pieces 83a relates to the circumferential center position (with respect to the second direction of the outer peripheral surface of the outer ring 43 of the support bearing 17) among the ends on one side in the axial direction of the holding piece 80a. It is bent at a right angle toward the outside in the radial direction from a position slightly off the side closer to the worm wheel 15 than the portion that abuts on both ends).

The pair of bent pieces 102 are bent at an obtuse angle from the end of the holding piece 80a on both sides in the circumferential direction, which is far from the worm wheel 15, toward the outside in the radial direction.

The second elastic member 48a is arranged between the outer ring 43 of the support bearing 17 and the guide member 45a, and the outer ring 43 is elastically sandwiched from both sides in the second direction by a pair of sandwiching pieces 80a. Specifically, the base portion 101 is engaged with the second elastic member holding recess 58a of the guide member 45a, that is, both outer surfaces of the base portion 101 with respect to the second direction (relative to each second direction of the pair of side plate portions 103). The outer side surface) is elastically brought into contact with both inner side surfaces of the second elastic member holding recess 58a, and each of the outer surfaces of the pair of bent pieces 102 in the second direction is formed with the first elastic member holding recess 57a. It is elastically brought into contact with both inner surfaces of the. As a result, the second elastic member 48a is supported with respect to the guide member 45a. In this state, the pair of holding pieces 80a are elastically pressed against the ends on both sides of the outer peripheral surface of the outer ring 43 of the support bearing 17 in the second direction. In short, in this example, each of the pair of holding pieces 80a holding the outer ring 43 of the support bearing 17 from both sides in the second direction has a base 101 engaged with the second elastic member holding recess 58a and the first elastic member. The bent piece 102 elastically abuts on the inner surface of the holding recess 57a is supported by both sides of the guide member 45a. Therefore, it is easy to secure the elastic modulus of the pair of holding pieces 80a.

Further, with the second elastic member 48a supported by the guide member 45a, the radial outer portion of the pair of second engaging pieces 83a is provided at the end portion of the guide member 45a on one side in the axial direction. It is engaged with the joint notch 71a. As a result, the second elastic member 48a is positioned in the circumferential direction with respect to the guide member 45a.

The third elastic member 49a includes a held portion 85a having a partially arcuate (approximately 3/4 arcuate) end face shape in which a portion far from the worm wheel 15 in the circumferential direction is a discontinuous portion. In this example, the held portion 85a has elastic protrusions 91a protruding inward in the radial direction at a plurality of locations on both sides of the inner peripheral surface in the second direction. In this example, among the plurality of elastic protrusions 91a, the elastic protrusions 91a located in the direction of the meshing reaction force Fr applied to the worm 16 from the meshing portion between the wheel teeth 26 and the worm teeth 29 are based on the meshing reaction force Fr. An elastically deformed portion 84a that elastically deforms is configured. It is sufficient that the elastic protrusion 91a is provided at least in the portion where the meshing reaction force Fr is applied, and the formation position can be appropriately changed according to the manufacturing cost and the like.

The third elastic member 49a is supported by the guide member 45a by elastically fitting the held portion 85a into the third elastic member holding portion 66 of the guide member 45a. With the third elastic member 49a supported by the guide member 45a, the ends of the held portion 85a on both sides in the second direction are the axes of the radial inner portions of the second engagement piece 83a of the second elastic member 48a. It is pressed by the other side in the direction.

In this example, the second elastic member 48a is supported with respect to the guide member 45a by engaging the base 101 of the second elastic member 48a with the second elastic member holding recess 58a of the guide member 45a. Therefore, the second elastic member 48a can be supported without rattling against the guide member 45a regardless of the dimensional tolerances of the guide member 45a and the second elastic member 48a.

Further, in this example, the base portion 101 of the second elastic member 48a has a substantially M-shaped end face shape when viewed from the axial direction. Therefore, with the base 101 engaged with the second elastic member holding recess 58a, the force that the bent plate portion 104 tries to elastically restore causes the outer surfaces of the pair of side plate portions 103 in each second direction to be elastically restored. , Is pressed against both inner side surfaces of the second elastic member holding recess 58a. Therefore, as the rotation direction of the worm wheel 15 changes, the force applied to the tip of the worm wheel 15 in the second direction increases. Therefore, for example, of the pair of holding pieces 80a, even if the holding piece 80a on one side with respect to the second direction is elastically deformed so as to have a large curvature, the holding piece 80a on one side with respect to the second direction is related to the second direction. It is possible to prevent the side surface from being separated from the inner side surface of the second elastic member holding recess 58a.

In this example, of the ends on both sides of the pair of holding pieces 80a in the circumferential direction, the ends far from the worm wheel 15 are not connected to each other. As a result, the installation space for the first elastic member 47a is secured, and the dimensional tolerance is allowed.

Further, in this example, each of the pair of second engaging pieces 83a is slightly displaced from the end portion on one side in the axial direction of the holding piece 80a to the side closer to the worm wheel 15 than the central position in the circumferential direction. It is provided in. This prevents the portion of the pair of holding pieces 80a that elastically abuts on the outer peripheral surface of the outer ring 43 of the support bearing 17 from becoming a flat surface. If the portion of the pair of second engaging pieces 83a that elastically abuts on the outer peripheral surface of the outer ring 43 of the support bearing 17 can be prevented from becoming a flat surface, the end portion of the holding piece 80a on one side in the axial direction. Of these, it may be provided at a position slightly off the worm wheel 15 from the center position in the circumferential direction. From the surface that stably presses the third elastic member 49a, it is desirable that the pair of second engaging pieces 83a are arranged at a position as close to the center position in the circumferential direction as possible.

Further, in this example, the first elastic member 47a is composed of a leaf spring formed by bending and molding an elastic metal plate into a substantially S shape when viewed from the axial direction. Therefore, it is easy to secure the distance between the fulcrum and the point of action of the first elastic member 47a as compared with the first elastic member 47 according to the first example of the embodiment. The composition and action of other parts are the same as those of the first embodiment.

[Third example of the embodiment]
27 to 32 show a third example of the embodiment of the present invention. The urging mechanism 18b of this example is configured to prevent the first elastic member 47b from being displaced toward one side in the axial direction with respect to the guide member 45b.

The guide member 45b has a partially cylindrical eaves 106 that protrudes toward one side in the axial direction at the end of the end surface on one side in the axial direction that is far from the worm wheel 15 in the first direction. Further, the guide member 45b has a locking hole 107 that radially penetrates the end portion on one side in the axial direction, which is farther from the worm wheel 15 in the first direction.

The first elastic member 47b is composed of a leaf spring formed by bending and molding an elastic metal plate, and has a substantially S-shaped end face shape when viewed from the axial direction (axial direction of the support bearing 17). The first elastic member 47b includes a substrate portion 94, a first pressing plate portion 95, a first connecting plate portion 96, a first bent plate portion 97, a second pressing plate portion 98, and a second connecting plate portion 99. A second bent plate portion 100 and a locking piece 108 are provided. The locking piece 108 is bent radially outward from the axially outer end of the first pressing plate portion 95. In addition, in FIGS. 30 and 31, the shape of the first elastic member 47b (particularly the position of the second pressing plate portion 98) is shown in the free state of the first elastic member 47b.

By inserting the locking piece 108 into the locking hole 107 of the guide member 45b, the first elastic member 47b prevents the first elastic member 47b from being displaced to one side in the axial direction with respect to the guide member 45b and falling off. Moreover, the relative rotation of the first elastic member 47b with respect to the guide member 45b is prevented.

The third elastic member 49b includes a held portion 85b having a partially arcuate (approximately 3/4 arcuate) end face shape in which a portion far from the worm wheel 15 in the circumferential direction is a discontinuous portion. In this example, the held portion 85b has elastic protrusions 91b protruding inward in the radial direction at a plurality of locations on both sides of the inner peripheral surface in the second direction. In this example, among the plurality of elastic protrusions 91b, the elastic protrusions 91b located in the direction of the meshing reaction force Fr applied to the worm 16 from the meshing portion between the wheel teeth 26 and the worm teeth 29 are based on the meshing reaction force Fr. An elastically deformed portion 84b that elastically deforms is configured.

In this example, the center of the inscribed circle of the held portion 85b (the circle inscribed in the tip of the elastic projection 91b) is located from the worm wheel 15 in the second direction from the center of the outer peripheral surface of the held portion 85b. It is offset to the near side. In line with this, the width dimension of the elastic protrusion 91b in the axial direction is reduced from the side closer to the worm wheel 15 to the side farther from the worm wheel 15 in the circumferential direction to adjust the rigidity of the elastic protrusion 91b. However, the width dimension of the elastic protrusion 91b in the axial direction can be fixed.

Further, the third elastic member 49b has

protrusions

115a and 115b protruding toward one side in the axial direction at a plurality of locations in the circumferential direction on one side surface in the axial direction of the held portion 85b. In this example, among the axially one side surfaces of the held portion 85b, circular protrusions 115a viewed from the axial direction are provided at a plurality of positions at equal intervals in the circumferential direction on both sides of the second direction, and the held portion 85b is provided with circular protrusions 115a. An oval protrusion 115b is provided at the end of one side surface in the axial direction on the side closer to the worm wheel 15 in the first direction.

In this example, with the urging mechanism 18b assembled to the guide holding portion 23 (see FIG. 2 and the like), the tips of the

protrusions

115a and 115b of the third elastic member 49b are placed on the other side surfaces of the inward flange portion 24 in the axial direction. It is elastically pressed. Thereby, regardless of the manufacturing error of the urging mechanism 18b and the housing 14, it is possible to prevent the urging mechanism 18b and the housing 14 from rattling in the axial direction. Further, it is possible to prevent the held portion 85b of the third elastic member 49b from being excessively crushed in the axial direction and engaging with the worm 16 to adversely affect the absorption characteristics of the reaction force Fr.

In this example, of the one side surface of the held portion 85b in the axial direction, the protrusion 115b provided on the end portion on the side closer to the worm wheel 15 in the first direction has an oval end face shape when viewed from the axial direction. Have. Therefore, it is possible to effectively prevent the second elastic member 48a sandwiched between the third elastic member 49b and the guide member 45b from rattling in the axial direction. However, the shape of the end face of the protrusion provided on one side surface in the axial direction of the third elastic member is not limited to the circular shape and the oval shape as in this example, and may be any shape. The composition and action of other parts are the same as those of the first and second embodiments of the embodiment.

[Fourth Example of Embodiment]
33 (A) to 34 (B) show a fourth example of the embodiment of the present invention. Also in the case of this example, the first elastic member 47c is configured to be prevented from being displaced toward one side in the axial direction with respect to the guide member 45c.

The guide member 45c has a locking recess 111 recessed outward in the radial direction on the bottom surface (the surface facing inward in the radial direction) of the first elastic member holding recess 57a.

The first elastic member 47c is composed of a leaf spring formed by bending and molding an elastic metal plate, and has a substantially S-shaped end face shape when viewed from the axial direction (axial direction of the support bearing 17). The first elastic member 47c includes a substrate portion 94, a first pressing plate portion 95, a first connecting plate portion 96, a first bent plate portion 97, a second pressing plate portion 98, and a second connecting plate portion 99. A second bent plate portion 100 and a locking piece 108a are provided.

The locking piece 108a is from the base portion 112 protruding toward one side in the axial direction from the center position of the axially outer end portion of the first pressing plate portion 95 with respect to the second direction, and from the end portions on both sides of the second direction of the base portion 112. It has a pair of arm portions 113 that are bent at an obtuse angle toward the outside in the radial direction.

The first elastic member 47c is displaced to one side in the axial direction with respect to the guide member 45c and falls off by inserting the tip portions of the pair of arm portions 113 into the inside of the locking recess 111. And prevent the relative rotation of the first elastic member 47c with respect to the guide member 45c.

Further, in the case of this example, the eaves portion 106 is provided with a structure capable of preventing the first elastic member 47c from being displaced to one side in the axial direction with respect to the guide member 45c, as in the structure according to the third example of the embodiment. It can be realized without providing it. That is, the axial dimension of the urging mechanism can be suppressed to be smaller than that of the urging mechanism 18b according to the third example of the embodiment. The composition and action of other parts are the same as those of the first and third embodiments of the embodiment.

[Fifth Example of Embodiment]
35 (A) to 37 show a fifth example of the embodiment of the present invention. Also in the case of this example, the first elastic member 47d is configured to be prevented from being displaced to one side in the axial direction with respect to the guide member 45c.

The first elastic member 47d is composed of a leaf spring formed by bending and molding an elastic metal plate, and has a substantially S-shaped end face shape when viewed from the axial direction (axial direction of the support bearing 17). The first elastic member 47c includes a substrate portion 94, a first pressing plate portion 95, a first connecting plate portion 96, a first bent plate portion 97, a second pressing plate portion 98, and a second connecting plate portion 99. A second bent plate portion 100 and a locking convex portion 114 are provided. In addition, in FIGS. 30 and 31, the shape of the first elastic member 47d (particularly the position of the second pressing plate portion 98) is shown in the free state of the first elastic member 47d.

The locking convex portion 114 protrudes radially outward from the center position of the axially outer end of the first pressing plate portion 95 with respect to the second direction. The locking convex portion 114 forms a slit extending in the second direction at the center position of the axially outer portion of the first pressing plate portion 95 with respect to the second direction, and a portion located on one side in the axial direction with respect to the slit. It is formed by plastically deforming it so as to lift it outward in the radial direction.

By locking the locking convex portion 114 to the locking concave portion 111, the first elastic member 47d prevents the first elastic member 47d from being displaced to one side in the axial direction with respect to the guide member 45c and falling off. Moreover, the relative rotation of the first elastic member 47d with respect to the guide member 45c is prevented.

Further, in the case of this example, the eaves portion 106 is provided with a structure capable of preventing the first elastic member 47d from being displaced to one side in the axial direction with respect to the guide member 45c, as in the structure according to the third example of the embodiment. It can be realized without providing it. That is, the axial dimension of the urging mechanism can be suppressed to be smaller than that of the urging mechanism 18b according to the third example of the embodiment. The composition and action of other parts are the same as those of the first, third and fourth examples of the embodiment.

The first to fifth examples of the above-described embodiments can be appropriately combined and carried out as long as there is no contradiction.

This application is based on Japanese Patent Application No. 2020-91950 filed on May 27, 2020 and Japanese Patent Application No. 2021-4760 filed on January 15, 2021, the contents of which are referred to herein. It is captured.

1 Electric power steering device 2 Steering wheel 3 Steering gear unit 4 Input shaft 5 Tie rod 6 Steering shaft 7

Steering column

8a, 8b Universal joint 9 Intermediate shaft 10 Electric assist device 11 Electric motor 12 Warm reducer 13 Output shaft 14 Housing 15 Warm wheel 16 Warm 17

Support bearing

18, 18a, 18b Biasing mechanism 19 Wheel accommodating part 20 Warm accommodating part 21 Cylindrical surface part 22 Step part 23 Guide holding part 24 Inward flange part 25 Engagement recess 26 Wheel tooth 27 Inner wheel element 28 Outer wheel element 29 Warm teeth 30 Torque transmission joint 31 Driven side transmission member 32 Driven side transmission member 33 Fitting cylinder part 34 Collar part 35 Ball bearing 36 Outer ring 37 Inner ring 38 Ball 39 Stop ring 40 Elastic member 41 Small diameter cylinder part 42 Inner ring 43 Outer ring 44

Rolling element

45, 45a, 45b, 45c Guide member 46

Elastic ring

47, 47a, 47b, 47c, 47d First

elastic member

48, 48a Second

elastic member

49, 49a, 49b Third

elastic member

50, 50a Bearing holding part 51 Guide body 52 Lid
53 Large-diameter tube 54 Small-diameter tube 55 Side wall 56 Distal part Cylindrical surface 57, 57a First elastic member holding recess 58, 58a Second elastic member holding recess 59, 59a Pedestal surface 60 Distal protruding part 61 Suppressing Surface part 62 Convex part 63 Proximal side protruding part 64 Proximal side part Cylindrical surface part 65 Holding surface part 66 Third elastic member holding part 67 Engaging convex part 68 Locking groove 69 Inclined surface part 70 First engaging notch part 71 Second Engagement notch 72 Inward flange 73 Small diameter 74 Large diameter 75 Concave groove 76 Locking plate 77 Pressing plate 78 Connection plate 79 Bending plate 80, 80a Holding piece 81 Part Cylindrical part 82 First engagement Pieces 83, 83a Second engaging piece 84, 84a, 84b Elastic deformation part 85, 85a, 85b Held part 86 Convex part 87 Concave part 88 Stop ring 91, 91a, 91b Elastic protrusion 92 Concave part 93 Convex part 94 Board part 95 1 Pressing plate part 96 1st connecting plate part 97 1st bent plate part 98 2nd pressing plate part 99 2nd connecting plate part 100 2nd bent plate part 101 base 102 bent piece 103 side plate part 104 bent plate part 105 connection plate part 106 Eaves 107 Locking holes 108, 108a Locking pieces 111 Locking recess 112 Base 113 Arms 114 Locking protrusions 115a, 115b Protrusions 200 Worm reducer 201 Housing 202 Worm wheel 203 Warm 204 Wheel housing 205 Warm housing 206 Wheel teeth 207 Rotating shaft 208 Warm teeth 209a, 209b Ball bearing 210 Holder 211 Large diameter 212 Bush 213 Electric motor 214 Pad 215 Torsion coil spring

Claims

It is arranged in a twisted position with respect to the wheel accommodating portion and the wheel accommodating portion, and
A housing having a worm accommodating portion whose axial middle portion is open to the wheel accommodating portion,
A worm wheel having wheel teeth on the outer peripheral surface and being rotatably supported inside the wheel accommodating portion.
A worm having worm teeth that mesh with the wheel teeth on the outer peripheral surface and being rotatably supported inside the worm accommodating portion.
A support bearing having an inner ring fitted to the tip of the worm and an outer ring coaxially arranged with the inner ring around the inner ring.
A first elastic member that elastically urges the support bearing toward the side of the worm wheel.
A first holding piece having a pair of holding pieces that elastically hold the support bearing from both sides with respect to a first direction which is an urging direction by the first elastic member and a second direction orthogonal to the central axis of the worm accommodating portion. 2 elastic members and
A third elastic member provided around the outer ring and having an elastically deforming portion that elastically deforms based on the meshing reaction force applied to the worm from the meshing portion between the wheel teeth and the worm teeth.
A worm reducer equipped with.
The outer ring has a bearing holding portion that is internally fitted to the worm wheel so as to be able to move in perspective, and further includes a guide member that is internally fitted inside the worm accommodating portion.
The first elastic member is arranged between the outer ring and the guide member.
The second elastic member is arranged between the outer ring and the guide member.
The third elastic member is arranged between the outer ring and the guide member.
The worm reducer according to claim 1.
The guide member has a reaction force bearing surface portion in the bearing holding portion whose phase in the circumferential direction coincides with the elastically deformed portion and is located radially outside the tip portion of the elastically deformed portion. Have,
The worm reducer according to claim 2.
The guide member has a pair of facing surface portions of the bearing holding portion, which are provided on both sides in the second direction and are located radially outside the holding piece.
The worm reducer according to claim 2 or 3.
The third elastic member is elastically sandwiched in the axial direction between the worm accommodating portion and the guide member.
The worm reducer according to any one of claims 2 to 4.
The third elastic member has a protrusion protruding toward one side in the axial direction on one side surface in the axial direction.
The worm reducer according to claim 5.
An elastic ring elastically sandwiched between the inner peripheral surface of the worm accommodating portion and the outer peripheral surface of the guide member is further provided.
The worm reducer according to any one of claims 2 to 6.
The first elastic member includes a locking plate portion locked to the guide member, a pressing plate portion that elastically presses the outer peripheral surface of the outer ring toward the worm wheel side, and an axial direction. It is curved in a substantially U shape and includes a connecting plate portion that connects the locking plate portion and the pressing plate portion.
The worm reducer according to any one of claims 2 to 7.
The first elastic member includes a substrate portion, a first pressing plate portion provided on the radial outer side of the substrate portion and elastically pressed against the guide member, the substrate portion, and the first pressing plate portion. A first connection plate portion that connects the two, a second pressing plate portion that is provided inside the substrate portion in the radial direction and is elastically pressed against the outer peripheral surface of the outer ring, and the substrate portion and the second pressing. It has a second connection plate portion that connects to the plate portion,
The worm reducer according to any one of claims 2 to 7.
The second elastic member has a base that connects the ends of the pair of holding pieces on both sides in the circumferential direction that are closer to the worm wheel.
The worm reducer according to any one of claims 1 to 9.
The elastically deformed portion is provided on a half portion of the third elastic member on the side far from the worm wheel in the first direction.
The worm reducer according to any one of claims 1 to 10.
The elastically deformed portion is composed of a pair of elastically deformed portions provided at two positions in the circumferential direction of the third elastic member.
The worm reducer according to any one of claims 1 to 11.
With an electric motor
A worm reducer that increases the torque of the electric motor and applies it to a rotary shaft that rotates with the rotation of the steering wheel or a linear motion shaft that constitutes the steering gear unit.
Equipped with
The electric assist device, wherein the worm reducer is the worm reducer according to any one of claims 1 to 12.