Worm reducer

Abstract

The pad (20) is provided at a plurality of locations in the circumferential direction, and has pad-holding oil recesses (80) for holding grease, the pad-holding oil recesses (80) being open on the inner circumferential surface of an end portion on one side in the second direction of a pad fitting hole portion (61) externally fitted to the tip portion of the worm (18), and on the surface of the pad (20) on one side in the second direction.

Description

Technical Field

[0001] The present disclosure relates to a worm speed reducer assembled in, for example, an electric power steering device and an assembling method thereof. Background Art

[0002] When applying a steering angle to the steering wheels of a vehicle, an electric power steering system using an electric motor as an auxiliary power source is widely used as a device for reducing the force required to operate the steering wheel.

[0003] Electric power steering systems are broadly classified into different structures depending on the installation position of the electric motor. Specifically, various configurations have been proposed, including a column-assisted type in which auxiliary power is applied to a steering shaft rotatably supported inside the steering column; a pinion-assisted type in which auxiliary power is applied to a pinion shaft serving as the input shaft of the steering gear unit; and a dual-pinion type in which the steering gear unit includes a pinion shaft separate from the pinion shaft serving as the input shaft and auxiliary power is applied to this pinion shaft.

[0004] In either configuration, the auxiliary power from the electric motor is applied via a speed reducer to a shaft component that rotates or moves linearly in response to steering wheel operation. Worm speed reducers are widely used as such speed reducers. The worm speed reducer that constitutes an electric power steering system includes a worm that is rotationally driven by the electric motor and a worm wheel that meshes with the worm.

[0005] Figure 23 An example of a conventional structure of a worm speed reducer is described in Japanese Patent No. 4381024 as Patent Document 1. A worm speed reducer 100 includes a housing 101 , a worm wheel 102 , and a worm 103 .

[0006] The housing 101 includes a worm wheel housing portion 104 and a worm housing portion 105 . The worm housing portion 105 has its own central axis twisted relative to the central axis of the worm wheel housing portion 104 and an axially intermediate portion opening into the worm wheel housing portion 104 .

[0007] The worm wheel 102 has gear teeth 106 on its outer peripheral surface, and is supported and fixed around a rotation shaft 107 rotatably supported inside the worm wheel housing portion 104 so as to be coaxial with the rotation shaft 107 .

[0008] The worm 103 has worm teeth 108 on the outer peripheral surface of the axial middle portion that mesh with the gear teeth 106. The worm 103 is rotatably supported inside the worm housing 105 by two ball bearings 109a and 109b at two locations in the axial direction across the worm teeth 108. Figure 23The outer ring of the ball bearing 109a (on the right side) is press-fitted into the retainer 110 fixed to the inner side of the inner end side of the worm housing 105. The inner ring of the ball bearing 109a is fitted onto the large diameter portion 111 of the worm 103 located closer to the end side than the worm teeth 108 through a bushing 112 made of synthetic resin through a clearance fit. That is, the inner ring of the ball bearing 109a is fitted onto the bushing 112 that is fitted onto the large diameter portion 111 of the worm 103 through a clearance fit without any looseness. The base end side ( Figure 23 The outer ring of ball bearing 109b (on the left side of the worm) is loosely fitted into the opening of worm housing 105, while the inner ring of ball bearing 109b is externally fitted into the base end of worm 103. The output shaft of electric motor 113 is connected to the base end of worm 103 in a torque-transmittable manner. In other words, worm 103 can be rotationally driven by electric motor 113.

[0009] In worm reducer 100, backlash inevitably occurs at the meshing point between gear teeth 106 and worm teeth 108 due to dimensional and assembly errors among the components that comprise worm reducer 100. This backlash sometimes produces a harsh rattling sound at the meshing point when the steering wheel's rotational direction is changed. In the illustrated example, to suppress this rattling sound, the distal end of worm 103 is elastically biased toward worm wheel 102.

[0010] That is, the base end of the worm 103 is supported by a ball bearing 109b having a radial clearance so as to be able to slightly swing relative to the worm housing 105. An annular gap exists throughout the entire circumference between the outer peripheral surface of the large diameter portion 111 of the worm 103 and the inner peripheral surface of the bushing 112. A pad 114 is embedded in the distal end of the worm 103, and a torsion coil spring 115 is provided between the pad 114 and the retaining frame 110. The torsion coil spring 115 controls the worm 103 to move in the first direction (the direction in which the worm 103 moves relative to the worm wheel 102) in the direction of the movement. Figure 23 In the vertical direction), the pad 114 is elastically pressed toward the worm wheel 102 side, thereby, the side ( Figure 23 The upper side of the worm 103 is elastically biased. This suppresses the backlash between the gear teeth 106 and the worm teeth 108, thereby suppressing the generation of the gear rattling sound.

[0011] Prior art literature

[0012] Patent Literature

[0013] Patent Document 1: Japanese Patent No. 4381024 Summary of the Invention

[0014] Technical problem to be solved by the invention

[0015] In the structure described in Japanese Patent Gazette No. 4381024, in order to be able to press the distal end of the worm 103 in a direction close to the worm wheel 102, an annular gap exists throughout the entire circumference between the outer peripheral surface of the large diameter portion 111 of the worm 103 and the inner peripheral surface of the bushing 112. In addition, although smaller than the annular gap existing between the outer peripheral surface of the large diameter portion 111 of the worm 103 and the inner peripheral surface of the bushing 112, an annular gap also exists throughout the entire circumference between the distal end of the worm 103 and the through hole of the pad 114. Therefore, when the rotation direction of the steering wheel is changed, that is, when the rotation direction of the worm 103 is changed, the reaction force applied from the gear teeth 106 to the worm teeth 108 is equal to the first direction and the axial direction of the worm housing 105, that is, the second direction ( Figure 23 The third direction ( Figure 23 The direction of the component in the front-back direction (in the front-back direction) changes, and the distal end of the worm 103 may be displaced violently in the third direction. Therefore, there is room for improvement in suppressing abnormal noises such as gear rattling.

[0016] The purpose of the present disclosure is to provide a worm reducer which, when the rotation direction of the worm changes, can make the tip of the worm difficult to displace in a third direction which is orthogonal to both the first direction, the force direction of the tip, and the second direction, the axial direction of the worm housing, and can easily ensure durability.

[0017] Technical means to solve the problem

[0018] The worm speed reducers according to the first and second aspects of the present disclosure each include a housing, a worm wheel, a worm, a cage, a washer, and an elastic member.

[0019] The housing includes a worm wheel accommodation portion and a worm accommodation portion. The worm accommodation portion is arranged at a position twisted relative to the worm wheel accommodation portion, and an axially intermediate portion of the worm accommodation portion opens to the worm wheel accommodation portion.

[0020] The worm wheel has gear teeth on its outer peripheral surface and is rotatably supported inside the worm wheel housing portion.

[0021] The worm has worm teeth meshing with the gear teeth on an outer peripheral surface, and is rotatably supported inside the worm housing portion.

[0022] The retainer is disposed between a distal end portion of the worm and the worm housing portion.

[0023] The pad is externally fitted on the distal end of the worm.

[0024] The elastic member is assembled to the retainer and elastically urges the distal end portion of the worm toward the worm wheel via the washer.

[0025] The retainer has two retainer engagement portions at positions sandwiching the pad from both sides in a third direction. The third direction is orthogonal to both the first direction, the urging direction of the elastic member, and the second direction, the axial direction of the worm housing.

[0026] In particular, in the worm reducer of the first embodiment of the present invention, the above-mentioned gasket has: two gasket clamping parts, which are arranged on both sides of the above-mentioned gasket in the above-mentioned third direction and are in contact with the two above-mentioned retainer clamping parts; a gasket elastic pressing part, which elastically presses a part of the above-mentioned retainer toward the above-mentioned second direction, thereby applying pre-pressure to the contact part between the above-mentioned retainer clamping part and the above-mentioned gasket clamping part; and a gasket oil-retaining recess, which is arranged at multiple circumferential positions and opens on the inner circumferential surface of the above-mentioned gasket interlocking hole part and the surface of the above-mentioned gasket facing the above-mentioned second direction.

[0027] In the worm reducer of the first aspect of the present disclosure, each of the pad oil retaining recesses may open at an inner peripheral surface of an end portion of the pad fitting hole in the second direction and a surface of the pad facing the second direction.

[0028] The worm speed reducer according to the second aspect of the present disclosure further includes a bushing and a support bearing.

[0029] The bushing includes a bushing fitting hole portion that is externally fitted into a portion of the worm gear that is offset in the second direction from a portion in which the washer fitting hole portion is externally fitted.

[0030] The support bearing is arranged between the worm housing portion or the retainer and the bushing.

[0031] In particular, in the worm reducer according to the second aspect of the present disclosure, the bushing has bushing oil retaining recesses at a plurality of locations in the circumferential direction, the recesses being open on the inner circumferential surface of the bushing fitting hole and on the surface of the bushing facing the second direction.

[0032] In the worm reducer according to the second aspect of the present disclosure, each of the bushing oil retaining recesses may open at an inner peripheral surface of an end portion of the bushing fitting hole in the second direction and a surface of the pad facing the second direction.

[0033] In the worm reducers of the first and second aspects of the present disclosure, the two retainer engaging portions can be formed by two retainer inclined surfaces that are inclined in directions approaching each other as they move toward one side of the second direction, and the two pad engaging portions can be formed by two pad inclined surfaces that are in surface contact with the two retainer inclined surfaces.

[0034] In the worm reducers of the first and second modes disclosed in the present invention, the above-mentioned pad elastic pressing portion can be constituted by two pad elastic pressing plates, which are located at a position closer to the second direction than the two above-mentioned pad engaging portions, and respectively extend from the central portion of the above-mentioned pad in the above-mentioned third direction toward the side away from each other in the above-mentioned third direction, and a part of the above-mentioned retaining frame elastically pressed toward the above-mentioned second direction by the two above-mentioned pad elastic pressing plates can be constituted by the pressed surface of the retaining frame on the side facing the above-mentioned second direction.

[0035] In this case, the two pad elastic pressing plates can each include a protrusion extending in the first direction on the side surface on the other side in the second direction, and can elastically press the pressed surface of the retainer toward the other side in the second direction through the terminal end of the protrusion.

[0036] And / or, the two pad elastic pressing plates may each have a slit penetrating in the second direction and extending in the first direction at an end portion on a center side of the pad in the third direction.

[0037] In the worm speed reducers according to the first and second aspects of the present disclosure, the elastic member can be formed of a leaf spring.

[0038] For example, the structure of the bushing (bushing oil retaining recess) and the support bearing in the worm reducer of the second aspect of the present disclosure can be added to the worm reducer of the first aspect of the present disclosure.

[0039] The worm speed reducers according to the first and second aspects of the present disclosure can be implemented by appropriately combining the above-described structures within a range where no contradiction occurs.

[0040] Effects of the Invention

[0041] According to the first and second modes of the worm reducer disclosed in the present invention, the following structure can be achieved: when the rotation direction of the worm changes, the tip of the worm is not easily displaced in a third direction that is orthogonal to both the force application direction of the tip, i.e., the first direction, and the axial direction of the worm housing, i.e., the second direction, and durability is easily ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a diagram showing an electric power steering system incorporating a worm speed reducer according to a first example of an embodiment of the present disclosure.

[0043] Figure 2 This is a diagram showing a portion of an electric power steering system incorporating a worm speed reducer according to a first example of an embodiment of the present disclosure.

[0044] Figure 3 yes Figure 2 AA cross-sectional view.

[0045] Figure 4 The housing is omitted and shown Figure 3 Magnified image of the upper right part.

[0046] Figure 5 It is a perspective view showing the distal end portion of the worm and components arranged around it.

[0047] Figure 6 This is a perspective view showing the distal end portion of the worm and components arranged around it in an exploded manner.

[0048] Figure 7 It is from Figure 4 The right side of the diagram.

[0049] Figure 8 It is from Figure 7 The left side of the diagram.

[0050] Figure 9 It is from Figure 7 Figure viewed from the upper side.

[0051] Figure 10 yes Figure 7 BB cross-sectional view.

[0052] Figure 11 yes Figure 10 A partial enlarged view of .

[0053] Figure 12 (a) is a perspective view showing the holder removed. Figure 12 (b) is from Figure 12 (a) Stereoscopic images observed from different directions.

[0054] Figure 13 (a) is to remove the cage and Figure 4 The right side of the diagram, Figure 13 (b) is from Figure 13 (a) is a diagram of the retainer viewed from the left side. Figure 13 (c) is from Figure 13 (a) is a diagram of the retainer viewed from above. Figure 13 (d) is from Figure 13 (a) the back side ( Figure 4 Observe the diagram of the retainer on the left side).

[0055] Figure 14 (a) is a perspective view showing the pad removed. Figure 14 (b) is from Figure 14 (a) Stereoscopic images observed from different directions.

[0056] Figure 15 (a) is to remove the pad and Figure 4 The right side of the diagram, Figure 15 (b) is from Figure 15 The pad is viewed from the left side of (a). Figure 15 (c) is from Figure 15 (a) is a diagram of the pad viewed from above. Figure 15 (d) is from Figure 15 (a) the back side ( Figure 4 Observe the diagram of the pad on the left side.

[0057] Figure 16 (a) is a perspective view showing the bushing removed. Figure 16 (b) is from Figure 16 (a) Views from different directions.

[0058] Figure 17 (a) is to remove the bushing and Figure 4 The right side of the diagram, Figure 17 (b) is from Figure 17 (a) is a diagram of the bushing viewed from the right side. Figure 17 (c) is from Figure 17 (a) the back side ( Figure 4 Observe the bushing on the left side. Figure 17 (d) is Figure 17 (a) CC cross-sectional view.

[0059] Figure 18 is to remove the elastic component and Figure 4 The right side of the diagram.

[0060] Figure 19 (a) to (d) are figures showing the elastic component taken out of the second example of the embodiment of the present disclosure, (a) is a figure observed from one side of the third direction, (b) is a figure observed from the second direction, (c) is a figure observed from the other side of the third direction, and (d) is a figure observed from the first direction.

[0061] Figure 20 (a) to (c) are diagrams showing a state where elastic members are laminated, (a) is a perspective view, (b) is a view viewed from a first direction, and (c) is a view viewed from one side in a third direction.

[0062] Figure 21 (a) to (d) are about the comparative example with respect to the second example. Figure 19 The same figures (a) to (d).

[0063] Figure 22 (a) to (c) are about the comparative example with respect to the second example. Figure 20 The same figures (a) to (c) are shown in the figure.

[0064] Figure 23 This is a cross-sectional view showing an example of a conventional structure of a worm speed reducer. DETAILED DESCRIPTION

[0065] [First example]

[0066] use Figures 1 to 18 The first example of an embodiment of the present disclosure is described. Furthermore, in this example, the worm reducers of the first and second embodiments of the present disclosure are applied to a pinion-assisted electric power steering system. However, the worm reducers of the first and second embodiments of the present disclosure can be widely applied to column-assisted and double-pinion electric power steering systems, as well as worm reducers incorporated into various mechanical devices other than electric power steering systems.

[0067] Figure 1 The pinion-assisted electric power steering system 1 is shown, incorporating a worm reducer 14 of this embodiment. The electric power steering system 1 includes a steering wheel 2, a steering shaft 3, a steering column 4, a pair of universal joints 5a and 5b, an intermediate shaft 6, a steering gear unit 7, and an electric assist device 8.

[0068] The steering wheel 2 is fixedly supported on the rear end of the steering shaft 3. The steering shaft 3 is rotatably supported inside a steering column 4 supported by the vehicle body. The front end of the steering shaft 3 is connected to the pinion shaft 9 of the steering gear unit 7 via a rear universal joint 5a, an intermediate shaft 6, and a front universal joint 5b. Therefore, when the driver turns the steering wheel 2, the rotation of the steering wheel 2 is transmitted to the pinion shaft 9 via the steering shaft 3, a pair of universal joints 5a and 5b, and the intermediate shaft 6. The rotation of the pinion shaft 9 is converted into linear motion of the rack shaft 10 of the steering gear unit 7, which meshes with the pinion shaft 9. As a result, a steering angle corresponding to the amount of rotation of the steering wheel 2 is applied to the pair of steering wheels. The electric assist device 8 applies auxiliary power generated by the electric motor 15 to the pinion shaft 9. This reduces the force required by the driver to turn the steering wheel 2.

[0069] The steering gear unit 7 includes a housing 11 supported and fixed to the vehicle body, a rack shaft 10, and a pinion shaft 9. The housing 11 includes a rack housing portion 12 extending in the vehicle width direction and an axial side portion ( Figure 1The center axis of the pinion housing portion 13 is in a twisted position relative to the center axis of the rack housing portion 12. The internal space of the pinion housing portion 13 is connected to the internal space of the rack housing portion 12. The rack shaft 10 is supported on the inner side of the rack housing portion 12 in a manner that can only move in the axial direction (vehicle width direction). The pinion shaft 9 is supported on the inner side of the pinion housing portion 13 in a manner that can only rotate. The pinion shaft 9 is arranged in the front half (not shown) on the inner side of the pinion housing portion 13. Figure 2 The outer peripheral surface of the pinion shaft 9 (the lower half) has pinion teeth. Figure 2 The rack shaft 10 is located on the inner side of the rack housing 12 and is connected to the front universal joint 5b. Figure 1 A circumferential portion of the outer peripheral surface (the right side in the middle) has rack teeth that mesh with the pinion teeth of the pinion shaft 9.

[0070] The electric assist device 8 includes a worm speed reducer 14 and an electric motor 15 . The electric assist device 8 is configured such that the rotation of the electric motor 15 is reduced in speed by the worm speed reducer 14 and the rotation is transmitted to the pinion shaft 9 .

[0071] The worm speed reducer 14 includes a housing 16 , a worm wheel 17 , a worm 18 , a retainer 19 , a washer 20 , and an elastic member 21 .

[0072] The housing 16 includes a worm wheel housing portion 22 and a worm housing portion 23 . The worm housing portion 23 is arranged at a position twisted relative to the worm wheel housing portion 22 , and an axially intermediate portion of the worm housing portion 23 opens to the worm wheel housing portion 22 .

[0073] That is, the central axis of the worm wheel housing portion 22 and the central axis of the worm housing portion 23 are arranged in a position twisted with each other. In addition, the axial middle portion of the worm housing portion 23 is integrally connected to a circumferential point of the radial outer end portion of the worm wheel housing portion 22, and the internal space of the worm housing portion 23 is connected to the internal space of the worm wheel housing portion 22 through the connected portion. In this example, the worm housing portion 23 is configured as a bottomed cylindrical shape. Specifically, the axial end ( Figure 3 The right end in the middle) is closed, and the axial base end ( Figure 3 (left end) opening in the middle.

[0074] In this example, the worm gear housing 22 is coaxially and integrally connected to the axially intermediate portion of the pinion gear housing 13 of the housing 11 constituting the steering gear unit 7. The interior space of the worm gear housing 22 communicates with the interior space of the pinion gear housing 13.

[0075] The worm wheel 17 has gear teeth 24 on its outer peripheral surface and is rotatably supported inside the worm wheel housing portion 22. In this example, the worm wheel 17 is externally fitted and fixed to the axially intermediate portion of the pinion shaft 9.

[0076] The worm 18 has worm teeth 25 meshing with the gear teeth 24 at an axially intermediate portion of its outer peripheral surface, and is rotatably supported inside the worm housing portion 23 .

[0077] In this example, the base end portion ( Figure 3 The left end portion in the middle is supported so as to be slightly swingable relative to the worm housing portion 23 and is connected to the output shaft 27 of the electric motor 15 in a torque-transmittable manner.

[0078] Therefore, in this example, the worm 18 has an internal spline portion 26 on the inner circumferential surface of the base end portion. The electric motor 15 is fixed to the axial base end portion of the worm housing portion 23 by screw fastening, with the output shaft 27 and the worm housing portion 23 arranged coaxially. The internal spline portion 26 of the worm 18 is spline-engaged with the external spline portion 28 provided on the outer circumferential surface of the output shaft 27 of the electric motor 15. As a result, the base end portion of the worm 18 and the output shaft 27 of the electric motor 15 are connected in a manner that allows torque transmission and allows the worm 18 to be slightly swung and displaced. In addition, the base end portion of the worm 18 is supported by a ball bearing 29 having a radial clearance so that it can be slightly swung and displaced relative to the worm housing portion 23.

[0079] In this example, the outer peripheral surface of the distal end of the worm 18 is formed of a stepped cylindrical surface. Specifically, the distal end of the worm 18 includes a small-diameter cylindrical surface portion 30 and a base end portion having a larger diameter cylindrical surface portion 31.

[0080] In this example, a support bearing 32 is positioned between the large-diameter cylindrical surface 31 of the worm 18 and the inner circumferential surface of the worm housing 23. In the illustrated example, the support bearing 32 is a ball bearing. Specifically, the support bearing 32 comprises an inner ring 33 with an inner raceway on its outer circumference, an outer ring 34 with an outer raceway on its inner circumference, and a plurality of balls 35, each serving as a rolling element, positioned between the inner and outer raceways. However, the support bearing 32 may also be a rolling bearing, such as a cylindrical roller bearing with cylindrical rollers or a tapered roller bearing with tapered rollers, or a sliding bearing.

[0081] The outer ring 34 is fitted inside the worm housing 23 with a loose fit. This prevents changes in the preload of the support bearing 32 even when the housing 16 thermally expands during use. However, if thermal expansion of the housing is not a significant problem, the outer ring can be press-fitted into the housing.

[0082] As will be described later, the outer ring 34 is axially held between the retainer 19 disposed inside the worm housing portion 23 and a retainer 37 fitted and fixed inside the worm housing portion 23. The retainer 37 includes a fitting cylindrical portion 38 fitted and fixed to the inner circumferential surface of the worm housing portion 23 in an interference fit manner, and an inward flange portion 39 extending from one axial side ( Figure 3 and Figure 4 In this example, the outer ring 34 is bent radially inward at its end face on one axial side and aligned with the annular portion 42 of the retainer 19 on the other axial side ( Figure 3 and Figure 4 The outer ring 34 and the retainer 19 are connected to each other in the radial direction. ...

[0083] The inner ring 33 is externally fitted to the large-diameter cylindrical surface 31 of the worm 18 with a radial gap therebetween. In this example, a cylindrical bushing 36 is disposed between the inner circumferential surface of the inner ring 33 and the large-diameter cylindrical surface 31. Specifically, the inner ring 33 is externally fitted to the outer circumferential surface of the bushing 36 with an interference fit, while the bushing 36 is externally fitted to the large-diameter cylindrical surface 31 of the worm 18 with a clearance fit. The area between the large-diameter cylindrical surface 31 and the inner circumferential surface of the bushing 36 is lubricated with grease. In other words, the area between the large-diameter cylindrical surface 31 and the inner circumferential surface of the bushing 36 is filled with grease.

[0084] The bushing 36 is a component for ensuring slidability and / or cushioning relative to the outer peripheral surface of the distal end of the worm 18. It is made of a material having a low coefficient of friction relative to the metal material constituting the worm 18, such as a light alloy such as aluminum alloy or a synthetic resin. The bushing 36 has a bushing fitting hole 74 that is externally fitted into the large-diameter cylindrical surface portion 31 of the worm 18.

[0085] In this example, the bushing 36 has a stepped cylindrical shape. Specifically, the bushing 36 includes a small-diameter cylindrical portion 75; a side plate portion 76 bent radially outward from the end of the small-diameter cylindrical portion 75 on the other side in the second direction; a large-diameter cylindrical portion 77 bent radially outward from the end of the side plate portion 76 on the radially outer side in the second direction; and an outward flange portion 78 bent radially outward from the end of the large-diameter cylindrical portion 77 on the other side in the second direction. The bushing fitting hole 74 is provided so as to penetrate the center of the small-diameter cylindrical portion 75 in the second direction.

[0086] In this example, the bushing 36 has multiple locations around the circumference of the bushing fitting hole 74, each of which is open on the inner circumferential surface of the end portion on the second side of the bushing fitting hole 74 and on the radially inner end portion of the side surface on the second side of the side plate 76. These bushing oil-retaining recesses 82 function as grease reservoirs for retaining grease. In this example, the bushing oil-retaining recesses 82 are provided at multiple locations spaced evenly around the circumference. In other words, the bushing 36 has a gear-like pattern of concave and convex portions alternately arranged around the entire circumference at the junction between the inner circumferential surface of the bushing fitting hole 74 and the side surface on the second side of the side plate 76.

[0087] In this example, the distal end of the worm 18 is able to move in the direction of distal movement relative to the worm wheel 17 and in the direction of the force applied by the elastic member 21, that is, the first direction ( Figure 3 as well as Figure 4 displacement in the up and down directions).

[0088] In this example, the support bearing 32 is axially clamped between the retainer 19 and the retainer 37. However, when implementing the worm reducers of the first and second aspects of the present disclosure, the arrangement of the support bearing is not particularly limited as long as it enables the distal end of the worm to rotate relative to the worm housing and to move forward or backward relative to the worm wheel. For example, a retainer may be embedded and fixed inside the worm housing, and the support bearing may be embedded and retained inside the retainer.

[0089] In addition, in the worm speed reducer 14 of this embodiment, the central axis O of the worm wheel 17 is 17 The central axis of the worm 18 (the central axis of the output shaft 27 of the electric motor 15) 18 However, the present disclosure can also be applied to the central axis O of the worm wheel 17 when viewed from the first direction. 17 The central axis of the worm 18 (the central axis of the output shaft 27 of the electric motor 15) 18 Oblique, that is, acute-angled worm reducer.

[0090] In the worm reducer 14 of this example, Figures 3 to 10As shown, a retainer 19, a pad 20, and an elastic component 21 are arranged between the small-diameter cylindrical surface portion 30 of the worm 18 and the inner circumferential surface of the terminal portion of the worm housing portion 23. The retainer 19 is arranged between the terminal portion of the worm 18 and the worm housing portion 23. In this example, the retainer 19 is arranged on the inner side of the worm housing portion 23 around the terminal portion of the worm 18 in a state where rotation is prevented. The pad 20 is externally embedded in the terminal portion of the worm 18. In this example, the pad 20 has a pad fitting hole portion 61 externally embedded in the terminal portion of the worm 18. The elastic component 21 is assembled to the retainer 19, and the terminal portion of the worm 18 is directed toward the worm wheel 17 side ( Figure 3 as well as Figure 4 As a result, backlash at the meshing portion between the gear teeth 24 and the worm teeth 25 is suppressed.

[0091] The retainer 19 is in the first direction and the axial direction of the worm housing portion 23, that is, the second direction ( Figure 3 as well as Figure 4 The third direction ( Figure 3 as well as Figure 4 In the front-back direction of the embodiment, two retainer engaging portions, namely, two retainer inclined surfaces 41, are provided at positions sandwiching the pad 20 from both sides. The two retainer inclined surfaces 41 are respectively extended in the first direction and are inclined as they move toward one side of the second direction (in this example, Figure 3 and Figure 4 Furthermore, the retainer 19 is preferably made of a material having sufficient strength and rigidity, such as a metal material, a high-performance resin material such as polyphenylene sulfide (PPS) mixed with glass fiber, or the like.

[0092] More specifically, in this case, Figure 12 (a)~ Figure 13 As shown in (d), the retaining frame 19 includes: an annular portion 42; a substantially annular side plate portion 43, which extends radially inward from an end portion on one side in the second direction of the annular portion 42; and a protrusion 44, which extends from the radial inner end portion of the side plate portion 43 toward one side in the second direction and has a substantially U-shaped end face shape when viewed from one side in the second direction.

[0093] When viewed from one side in the second direction, the annular portion 42 has a non-circular end surface consisting of a straight portion and an arcuate portion. Specifically, the annular portion 42 has a flat portion 45 on the end of its outer circumference that is closest to the worm wheel 17 in the first direction. In this example, the non-circular shape of the annular portion 42 fits inside the worm housing 23, thereby retaining the retainer 19 inside the worm housing 23 in a rotationally prevented state.

[0094] In this example, if Figure 13As shown in (d), the inner circumferential surface 46 of the side plate portion 43 has recesses 47 on both sides in the third direction. The bottom surface of the recess 47 is formed by a plane perpendicular to the third direction. The portion of the inner circumferential surface 46 of the side plate portion 43 that is offset from the two recesses 47, that is, the two side portions in the first direction, is formed by a cylindrical surface centered on the central axis of the retainer 19.

[0095] In this example, the side surface of the radially outer end portion of the side plate portion 43 on one side in the second direction is aligned with the step portion 48 (see FIG. Figure 3 ) abuts against the retaining frame 19, thereby preventing the retaining frame 19 from being displaced to one side in the second direction.

[0096] In this example, the protrusion 44 protrudes toward one side in the second direction from the radial inner end portion of the side plate portion 43, excluding the end portion on the side away from the worm wheel 17 in the first direction. That is, the end portion of the protrusion 44 on the side away from the worm wheel 17 in the first direction is open. The protrusion 44 includes two guide portions 49 and a connecting portion 50. The two guide portions 49 constitute the ends of the protrusion 44 on both sides in the third direction. That is, as Figure 6 、 Figure 12 (a) Figure 13 (a) and Figure 13 As shown in (d), the two guide portions 49 extend from two locations in the radial inner end portion of the side plate portion 43 that are separated in the third direction, specifically, from the same circumferential location as the two recessed portions 47 toward one side in the second direction. The two guide portions 49 have a shape extending in the first direction. The connecting portion 50 constitutes the end portion of the protrusion 44 on the side closer to the worm wheel 17 in the first direction. That is, the connecting portion 50 extends from the end portion of the radial inner end portion of the side plate portion 43 on the side closer to the worm wheel 17 in the first direction toward one side in the second direction, and connects the ends of the two guide portions 49 on the side closer to the worm wheel 17 in the first direction. The connecting portion 50 has a partial cylindrical shape centered on the central axis of the retaining frame 19. In addition, if the retaining frame has sufficient strength to prevent deformation of the two guide portions, the connecting portion can also be omitted.

[0097] The two retainer inclined surfaces 41 constituting the retainer 19 are provided on the inner side surfaces 51 of the two guide portions 49, which are opposite to each other in the third direction. Figure 13As shown in (c), the inner side surfaces 51 of the two guide portions 49 each have a crank shape with a stepped surface (retainer inclined surface 41) in the middle portion in the second direction. That is, the two retainer inclined surfaces 41 are provided in the middle portion of the inner side surfaces 51 of the two guide portions 49 in the second direction, more specifically, in a portion on one side of the middle portion in the second direction. The two retainer inclined surfaces 41 are inclined toward each other as they move toward one side in the second direction. The portion of the inner side surfaces 51 of the two guide portions 49 located on the side closer to the retainer inclined surfaces 41 in the second direction and the portion located on the other side of the retainer inclined surfaces 41 in the second direction are each formed by a plane orthogonal to the third direction. Therefore, the spacing between the inner side surfaces 51 of the two guide portions 49 is narrower in the portion located on the side closer to the retainer inclined surfaces 41 in the second direction than in the portion located on the other side of the retainer inclined surfaces 41 in the second direction.

[0098] In the case of implementing the worm reducers of the first and second aspects of the present disclosure, the inclination angle φ of the retainer inclined surface 41 relative to the second direction can be set to any value within the range of 0°<φ<90°, but is preferably greater than 20° and less than 80°, and more preferably greater than 30° and less than 70°. In this example, the inclination angle φ is set to 30°.

[0099] Furthermore, the retainer 19 has two retainer pressed surfaces 52 on the end surfaces (i.e., distal end surfaces) of the two guide portions 49 in the second direction. Each of the two retainer pressed surfaces 52 is formed by a flat surface perpendicular to the second direction. In this example, the two retainer pressed surfaces 52 and the distal end surface (i.e., the end surface) of the connecting portion 50 in the second direction are continuous with each other and exist in the same imaginary plane perpendicular to the second direction.

[0100] like Figure 6 、 Figure 10 、 Figure 11 as well as Figure 14 (a)~ Figure 15 As shown in (d), the pad 20 has: two pad inclined surfaces 53, which are arranged on both sides in the third direction and are two pad locking parts that contact the two retaining frame inclined surfaces 41; and a pad elastic pressing part 79, which elastically presses a part of the retaining frame 19 toward the other side of the second direction, thereby applying pre-pressure to the contact part between the two retaining frame inclined surfaces 41 and the two pad inclined surfaces 53.

[0101] In this example, the two pad inclined surfaces 53 are in surface contact with the two retainer inclined surfaces 41. Specifically, they are inclined in the same direction and at the same angle as the two retainer inclined surfaces 41 (see FIG. Figure 13 (a)~(d)).

[0102] Furthermore, the pad elastic pressing portion 79 is formed of two pad elastic pressing plates 54. The two pad elastic pressing plates 54 are located on the second direction side relative to the two pad inclined surfaces 53 and extend from the center of the pad 20 in the third direction toward sides separated from each other in the third direction. The two pad elastic pressing plates 54 elastically press the two retainer pressed surfaces 52 constituting the retainer 19 toward the other side in the second direction.

[0103] However, when implementing the present disclosure, such a portion of the retainer can be arbitrarily selected. For example, the end surface of one side of the retainer's side plate portion in the second direction can be used as a portion of the retainer (the retainer pressed surface), and the pad's elastic pressing portion provided at the base of the pad can be used to elastically press this portion of the retainer toward the other side in the second direction. Furthermore, the pad 20 is preferably made of a material with a low coefficient of friction relative to the metal material constituting the worm 18, such as a synthetic resin or a light alloy such as an aluminum alloy.

[0104] Furthermore, in this example, the gasket 20 has gasket oil-retaining recesses 80 disposed at multiple locations along the circumference. These recesses open on the inner circumferential surface of the end portion of the gasket fitting hole 61 on one side in the second direction and on the surface of the gasket 20 facing the second direction. The gasket oil-retaining recesses 80 function as grease reservoirs for retaining grease. It should be noted that, in the case of a worm reducer according to one embodiment of the present disclosure, the gasket oil-retaining recesses may additionally or alternatively be formed to open on the inner circumferential surface of the end portion of the gasket fitting hole on the other side in the second direction and on the surface of the gasket facing the other side in the second direction.

[0105] More specifically, in this example, the pad 20 includes a pad base portion 55 arranged between the two guide portions 49 and a through hole 56 that penetrates the pad base portion 55 along the second direction and for the distal end portion of the worm 18 to be inserted therethrough, and has two pad inclined surfaces 53 on both sides of the pad base portion 55 in the third direction, and a flat plate portion 57 including two pad elastic pressing plates 54 is connected to a portion of the pad base portion 55 that protrudes from between the two guide portions 49 to one side in the second direction.

[0106] The pad base 55 includes a base main body 58 and two base extensions 59 .

[0107] The base body 58 extends in the first direction and has a generally rectangular end face shape. The through hole 56 penetrates the base body 58 in the second direction through the half on the side closer to the worm wheel 17 in the first direction. In this example, the through hole 56 is formed by a stepped hole having an oblong hole portion 60 on one side in the second direction and a gasket fitting hole portion 61 on the other side in the second direction. The gasket fitting hole portion 61 has an inner diameter slightly larger than the outer diameter of the small-diameter cylindrical surface portion 30 of the worm 18. The inner circumferential surface of the oblong hole portion 60 and the inner circumferential surface of the gasket fitting hole portion 61 are connected by a gasket step surface 81 on the side facing the second direction.

[0108] In this example, the gasket oil-retaining recesses 80 are provided so as to open onto the inner circumferential surface of the end portion of the gasket fitting hole 61 on one side in the second direction and the gasket step surface 81. In this example, the gasket oil-retaining recesses 80 are provided at multiple locations spaced evenly apart in the circumferential direction. In other words, the gasket 20 has a gear-like concave-convex structure formed by alternating concave and convex portions along the entire circumference at the junction of the inner circumferential surface of the gasket fitting hole 61 and the gasket step surface 81.

[0109] The base body 58 has two pressed portions 62 at its end in the first direction, distal from the worm wheel 17, and at its ends in the third direction, on the other side of the second direction. Each of the two pressed portions 62 is formed of a partial cylindrical surface centered on the central axis of the through-hole 56. The base body 58 has a base surface portion 63 formed of a flat surface perpendicular to the first direction, at its end in the first direction, distal from the worm wheel 17, and at a portion between the two pressed portions 62 in the third direction.

[0110] The two base extensions 59 protrude from a portion of the other half of the base body 58 in the second direction that is closer to the worm wheel 17 in the first direction toward a side separated from each other in the third direction. The two base extensions 59 are respectively extended in the first direction.

[0111] The two pad inclined surfaces 53 are provided on the side surfaces of the two base extensions 59 on one side in the second direction. The two pad inclined surfaces 53 are inclined toward each other as they move toward one side in the second direction. The inclination angle φ of the pad inclined surfaces 53 with respect to the second direction is the same as the inclination angle φ of the retainer inclined surface 41 with respect to the second direction.

[0112] The flat plate portion 57 is integrally connected to the end portion on one side of the base body 58 in the second direction, and has a circular outer peripheral shape when viewed from the side in the second direction. The through hole 56 penetrates the radial center portion of the flat plate portion 57 in the second direction. Therefore, the flat plate portion 57 is configured as an annular flat plate centered on the central axis of the through hole 56. The outer diameter of the flat plate portion 57 is larger than the width of the base body 58 in the third direction. The ends on both sides of the flat plate portion 57 in the third direction extend further than the base body 58 to both sides in the third direction. The end portion of the flat plate portion 57 on the side closer to the worm wheel 17 in the first direction extends further than the base body 58 to the side closer to the worm wheel 17 in the first direction. The end portion of the base body 58 on the side farther from the worm wheel 17 in the first direction extends further than the flat plate portion 57 to the side farther from the worm wheel 17 in the first direction.

[0113] In this example, the two pad elastic pressing plates 54 constituting the pad 20 are connected to a portion of the pad base 55 that protrudes from between the two guide portions 49 toward one side in the second direction. Specifically, the two pad elastic pressing plates 54 are formed by both end portions of the flat plate portion 57 in the third direction.

[0114] In this example, if Figure 10 、 Figure 11 、 Figure 14 (b) and Figure 15 (b)~ Figure 15 As shown in (d), the two pad elastic pressing plates 54 each have protrusions 64a and 64b extending in the first direction on the side surface on the other side in the second direction. In this example, each of the two pad elastic pressing plates 54 has two protrusions 64a and 64b. In the free state before the two pad elastic pressing plates 54 are elastically deformed, in other words, before the pad 20 is assembled to the protrusion 44 of the retainer 19, the height of at least one of the protrusions 64a and 64b in the second direction increases continuously or stepwise as it moves away from the worm 18 in the third direction.

[0115] In this example, the at least one protrusion 64a, 64b is composed of two protrusions 64a, 64b spaced apart in the third direction. In the free state, the height of the protrusion 64a on the side farther from the worm 18 in the third direction is higher in the second direction than the height of the protrusion 64b on the side closer to the worm 18 in the third direction.

[0116] In this example, the two pad elastic pressing plates 54 each have a slit 65 extending in the first direction and extending through the second direction at the base end portion, i.e., the end portion located at the center of the pad 20 in the third direction. In this example, the flexural rigidity in the second direction of the base end portion of the pad elastic pressing plate 54 adjacent to both sides of the slit 65 in the longitudinal direction is adjusted by appropriately controlling the width and length of the slit 65 and the thickness of the pad elastic pressing plate 54. However, the slit can be omitted when implementing the worm reducer according to the first and second embodiments of the present disclosure.

[0117] like Figures 3 to 5 as well as Figures 7 to 10 As shown, the washer 20 is assembled to the protruding portion 44 of the retainer 19 and is externally fitted to the distal end of the worm 18 .

[0118] Specifically, with the portion of the pad base 55 of the pad 20 located closer to the worm wheel 17 in the first direction positioned between the two guide portions 49 forming the protrusion 44 of the retainer 19, the two pad inclined surfaces 53 come into surface contact with the two retainer inclined surfaces 41. Furthermore, the distal ends of the protrusions 64a and 64b of the two pad elastic pressing plates 54 elastically press the two retainer pressed surfaces 52 toward the other side in the second direction. This applies preload to the contact areas between the two retainer inclined surfaces 41 and the two pad inclined surfaces 53.

[0119] Furthermore, the small-diameter cylindrical surface portion 30 at the distal end of the worm 18 is fitted within the pad fitting hole portion 61 of the through-hole 56 of the pad 20, preventing radial play and allowing relative rotation. The portion between the small-diameter cylindrical surface portion 30 and the inner circumferential surface of the pad fitting hole portion 61 is lubricated with grease. In other words, the space between the small-diameter cylindrical surface portion 30 and the inner circumferential surface of the pad fitting hole portion 61 is filled with grease.

[0120] In this state, a gap in the first direction exists between a side surface of the pad base portion 55 of the pad 20 that is closer to the worm wheel 17 in the first direction and a side surface of the connecting portion 50 that constitutes the protrusion 44 of the retainer 19 that is farther from the worm wheel 17 in the first direction. In this example, the pad 20 is displaceable in the first direction relative to the retainer 19 due to this gap in the first direction.

[0121] In addition, in this state, Figure 10 and Figure 11 As shown, gaps in the third direction exist between the inner side surfaces 51 of the two guide portions 49 located on the second direction side relative to the two retainer inclined surfaces 41 and the inner side surfaces 51 of the two guide portions 49 located on the other second direction side relative to the two retainer inclined surfaces 41 and the pad base 55 of the pad 20. In this example, the pad 20 can be displaced in the third direction relative to the retainer 19 based on these gaps in the third direction.

[0122] In this example, the elastic member 21 is composed of a leaf spring. More specifically, in this example, Figure 6 as well as Figure 18 As shown, the elastic member 21 is composed of a cylindrical leaf spring having a discontinuous portion 66 at one circumferential position. Specifically, the elastic member 21 includes a base portion 67 located farther from the worm 18 in the first direction, and two arms 68 extending circumferentially from both circumferential ends of the base portion 67.

[0123] In this example, the base portion 67 is formed of a flat plate perpendicular to the first direction.

[0124] The two arm portions 68 are each configured in a partial cylindrical shape and each have a bent portion 69 bent radially outward from a distal end portion.

[0125] However, when implementing the worm reducers of the first and second aspects of the present disclosure, the elastic member may have any configuration as long as it can elastically bias the pad toward the worm wheel 17 in the first direction. For example, when the elastic member is formed of a leaf spring, it may have a shape other than a cylindrical shape. Alternatively, the elastic member may be formed of a torsion coil spring.

[0126] The elastic member 21 is assembled to the retainer 19 by being externally fitted over the pad base 55 and two guide portions 49 of the pad 20. In this example, with the pad base 55 of the pad 20 and the protrusion 44 of the retainer 19 inserted radially inward of the elastic member 21, the base 67 of the elastic member 21 abuts against the base surface portion 63 of the pad 20. The inner circumferential surfaces of the base end portions of the two arm portions 68 are elastically pressed against the two pressed portions 62, while the inner circumferential surfaces of the distal end portions of the two arm portions 68 are elastically pressed against the side surface of the connecting portion 50 constituting the protrusion 44 of the retainer 19, which is closer to the worm wheel 17 in the first direction. This elastically biases the distal end of the worm 18 toward the worm wheel 17, that is, toward the side closer to the worm wheel 17 in the first direction, via the pad 20. This reduces backlash at the meshing portion between the gear teeth 24 and the worm teeth 25.

[0127] In the worm reducer 14 of this example, the two pad inclined surfaces 53 constituting the pad 20 are in surface contact with the two retainer inclined surfaces 41 constituting the retainer 19. Furthermore, the distal ends of the protrusions 64a and 64b of the two pad elastic pressing plates 54 constituting the pad 20 elastically press the two retainer pressed surfaces 52 constituting the retainer 19 toward the other side in the second direction. This applies a preload to the contact portion between the two retainer inclined surfaces 41 and the two pad inclined surfaces 53. Therefore, based on the contact between the two retainer inclined surfaces 41 and the two pad inclined surfaces 53, displacement of the pad 20 relative to the retainer 19 in the third direction is restricted, thereby preventing the pad 20 from shaking unimpeded in the third direction relative to the retainer 19.

[0128] Specifically, in this case, Figure 10 and Figure 11 As shown, the distal ends of the protrusions 64a and 64b of the pad elastic pressing plate 54 elastically press the retainer pressed surface 52 toward the other side in the second direction. This results in an elastic force (preload) Fp acting toward one side in the second direction from the pad inclined surface 53 on the retainer inclined surface 41. This elastic force Fp is then converted into an elastic force (preload) Fx acting outward in the third direction from the pad inclined surface 53 on the retainer inclined surface 41. In this example, this elastic force Fx prevents the pad 20 from unresisted rocking relative to the retainer 19 in the third direction.

[0129] Therefore, even if the direction of rotation of the worm 18 changes, and the direction of the component of the reaction force applied from the gear teeth 24 to the worm teeth 25 related to the third direction changes, the tip of the worm 18 is less likely to shift in the third direction. As a result, it is possible to prevent abnormal noises such as rattling sounds from occurring at the meshing portion between the gear teeth 24 and the worm teeth 25, or abnormal noises such as clashing sounds from occurring between the pad 20 and the retainer 19.

[0130] When implementing the worm reducers of the first and second aspects of the present disclosure, the bending rigidity in the second direction of the portion of the base end of the elastic pad pressing plate 54 adjacent to both sides of the longitudinal direction of the slit 65 can be varied by changing the width and length of the slit 65, the thickness of the elastic pad pressing plate 54, the height of the protrusions 64a and 64b in the second direction, and so on. This allows the magnitude of the force with which the distal ends of the protrusions 64a and 64b of the elastic pad pressing plate 54 elastically press the retainer pressed surface 52 toward the other side in the second direction to be varied. Consequently, the magnitude of the elastic force Fp can be arbitrarily varied.

[0131] The pad elastic pressing plate 54 partially presses the retainer pressed surface 52 with the distal ends of the protrusions 64a and 64b. Therefore, the pressing force can be stabilized compared to a case where the pad elastic pressing plate presses the retainer pressed surface over a wider area.

[0132] Between the elastic force Fx and the elastic force Fp, the relationship "Fx = Fp / tanφ" holds. In this example, since the inclination angle φ = 30°, Fx = Fp / tan30° = 1.7Fp. That is, the elastic force Fx is greater than the elastic force Fp. In the case of implementing the worm reducer of the first and second embodiments of the present disclosure, the size of the elastic force Fx can be arbitrarily changed not only by changing the size of Fp, but also by changing the size of the inclination angle φ. For example, if φ = 45°, it can be set to Fx = Fp, if 45° < φ < 90°, it can be set to Fx < Fp, and if 0° < φ < 45°, it can be set to Fx > Fp. In addition, by changing the inclination angle φ without changing the material of the pad 20 (based on the elastic force of the material), the size of the elastic force Fx can be adjusted. Therefore, the size of the elastic force Fx can be easily adjusted in the design stage.

[0133] Furthermore, in the case of implementing the worm reducer of the first and second embodiments of the present disclosure, the inclination angle of the retainer inclined surface 41 relative to the second direction and the inclination angle of the pad inclined surface 53 relative to the second direction do not need to be strictly the same, and may be different within the range of manufacturing error. In addition, the inclination angle of the retainer inclined surface 41 relative to the second direction may be slightly smaller (for example, about 0.5°) than the inclination angle of the pad inclined surface 53 relative to the second direction. In this way, in the contact portion between the retainer inclined surface 41 and the pad inclined surface 53, the end portion of the pad inclined surface 53 ( Figure 11 The right end of the third direction, Figure 11 The end portion on the other side of the second direction in FIG. 4 is in particularly strong contact with the retainer inclined surface 41. As a result, the posture of the pad 20 relative to the retainer 19 is stabilized.

[0134] In addition, when viewed from the first direction, Figure 10 and Figure 11 As shown, considering the state in which the center axis of the retainer 19 and the center axis of the pad 20 coincide with each other, that is, the neutral state, the pad 20 is moved to either side in the third direction relative to the retainer 19, for example Figure 10 and Figure 11 In this case, as the right side pad inclined surface 53 slides and displaces along the right side retaining frame inclined surface 41, the pad base 55 of the pad 20 displaces toward the other side in the second direction, and at the same time, the right side pad elastic pressing plate 54 elastically deforms in the second direction in a manner of tilting to one side. Moreover, the elastic pressing force from the right side pad elastic pressing plate 54 on the right side retaining frame pressed surface 52 increases by an amount corresponding to the amount of the elastic deformation, and accordingly, the elastic forces Fp and Fx increase. As a result, it is difficult for the pad 20 to displace further toward the right side. The pad 20 moves from a neutral state relative to the retaining frame 19 to Figure 10and Figure 11 The same is true for the left displacement in .

[0135] The inner circumferential surface of the elastic member 21's circumferential center portion elastically presses against two pressed portions 62 provided at the ends of the base body 58 of the pad 20 in the third direction. Consequently, the two pressed portions 62 are subjected to a force having a component in the first direction approaching the worm wheel 17, as well as a force having a component in the third direction opposite to the first direction. This prevents the distal end of the worm 18 from displacing in the third direction when the rotational direction of the worm 18 changes.

[0136] In particular, in the worm reducer 14 of this example, the gasket 20 has gasket oil-retaining recesses 80, which are provided at multiple locations along the circumference and open on the inner circumferential surface of the end portion of the gasket fitting hole 61 on one side in the second direction and the gasket step surface 81. Therefore, grease can be retained at the connection between the inner circumferential surface of the gasket fitting hole 61 and the gasket step surface 81. This allows the lubrication of the portion between the small-diameter cylindrical surface portion 30 at the distal end of the worm 18 and the inner circumferential surface of the gasket fitting hole 61 to be maintained for a long period of time, thereby preventing damage such as wear in this portion of the gasket fitting hole 61. As a result, the durability of the worm reducer 14 can be well ensured.

[0137] Furthermore, in this example, each gasket oil-retaining recess 80 opens only at one end portion of the inner circumferential surface of the gasket fitting hole 61 in the second direction. Therefore, according to the worm reducer 14 of this example, compared to a configuration in which each gasket oil-retaining recess extends along the entire length of the inner circumferential surface of the gasket fitting hole in the second direction, the surface pressure at the sliding contact portion between the inner circumferential surface of the gasket fitting hole 61 and the small-diameter cylindrical surface portion 30 can be kept low. This also helps prevent damage, such as wear, from occurring in the portion between the inner circumferential surface of the gasket fitting hole 61 and the small-diameter cylindrical surface portion 30.

[0138] However, when implementing the worm speed reducer according to the first aspect of the present disclosure, each pad oil-retaining recess can be formed over the entire length in the second direction of the inner peripheral surface of the pad fitting hole.

[0139] In this example, the bushing 36 has bushing oil-retaining recesses 82 at multiple locations along its circumference, opening on the inner circumferential surface of the end portion on the other side in the second direction of the bushing fitting hole 74 and the radially inner end portion of the side surface on the other side in the second direction of the side plate portion 76. This allows grease to be retained at the junction between the inner circumferential surface of the bushing fitting hole 74 and the side surface on the other side in the second direction of the side plate portion 76. This maintains good lubrication over a long period of time between the large-diameter cylindrical surface portion 31 at the distal end of the worm 18 and the inner circumferential surface of the bushing fitting hole 74, preventing damage such as wear in this area over a long period of time. This also ensures the durability of the worm reducer 14.

[0140] In addition, in this example, each bushing oil-retaining recess 82 is open only at the end portion on the other side of the second direction of the bushing fitting hole portion 74. Therefore, according to the worm reducer 14 of this example, compared with a structure in which each bushing oil-retaining recess is formed throughout the entire length of the inner circumferential surface of the bushing fitting hole portion in the second direction, the surface pressure of the sliding contact portion between the inner circumferential surface of the bushing fitting hole portion 74 and the large-diameter cylindrical surface portion 31 can be suppressed to a lower level. In this respect, it is also possible to suppress damage such as wear from occurring in the portion between the inner circumferential surface of the bushing fitting hole portion 74 and the large-diameter cylindrical surface portion 31. It should be noted that in the case of implementing a worm reducer of one embodiment of the present disclosure, a bushing oil-retaining recess may be formed in addition to or instead of being open at the inner circumferential surface of the end portion on one side in the second direction of the bushing fitting hole portion and at the surface of the bushing facing the second direction.

[0141] However, when implementing the worm speed reducer according to the second aspect of the present disclosure, each bushing oil retaining recess can be formed over the entire length in the second direction of the inner peripheral surface of the bushing fitting hole.

[0142] Furthermore, in this example, in the free state before the two elastic pad pressing plates 54 are elastically deformed, the height of the at least one protrusion 64a, 64b, respectively, in the second direction, increases continuously or in stages as the protrusion 64a, 64b, moves away from the worm 18 in the third direction. Specifically, the height of the protrusion 64a, 64b, on the side farther from the worm 18 in the third direction, in the second direction, is higher than the height of the protrusion 64b, on the side closer to the worm 18 in the third direction. This stably prevents the distal end of the worm 18 from displacing in the third direction when the rotational direction of the worm 18 changes.

[0143] By assembling the pad 20 to the protrusion 44 of the retaining frame 19, if the terminal ends of the protrusions 64a and 64b of the two pad elastic pressing plates 54 are elastically abutted against the two retaining frame pressed surfaces 52 of the retaining frame 19, the two pad elastic pressing plates 54 are elastically deformed with their respective base ends as the center, in a manner such that they tilt toward the side of the second direction as they move away from the worm gear 18 in the third direction.

[0144] If the heights of the two protrusions in the second direction on each of the two pad elastic pressure plates are equal, when the pad is assembled to the protrusion of the retainer, it is possible that only the distal end of the protrusion on the side closer to the worm in the third direction will contact the retainer's pressed surface, while the distal end of the protrusion on the side farther from the worm in the third direction will not contact the retainer's pressed surface. Consequently, the elastic deformation of the pad elastic pressure plate may not be stabilized, or the surface pressure at the contact area between the distal end of the protrusion on the side closer to the worm in the third direction and the retainer's pressed surface may be excessive, causing wear at this contact area. Consequently, the elastic forces Fx and Fp generated by the distal end of the protrusion elastically pressing the retainer's pressed surface toward the other side of the second direction may not be stabilized.

[0145] In contrast, in this example, the height of the protrusion 64a on the side farther from the worm 18 in the third direction in the second direction is greater than the height of the protrusion 64b on the side closer to the worm 18 in the third direction in the second direction. Therefore, when the pad 20 is assembled to the protrusion 44 of the retainer 19, the distal ends of the two protrusions 64a and 64b can reliably abut the retainer pressed surface 52. This stabilizes the elastic deformation of the pad elastic pressing plate 54, prevents excessive surface pressure at the contact area between the distal ends of the protrusions 64a and 64b and the retainer pressed surface 52, and prevents wear at this contact area. As a result, the elastic forces Fx and Fp generated by the distal ends of the protrusions 64a and 64b elastically pressing the retainer pressed surface 52 toward the other side in the second direction are stabilized, stably preventing the distal end of the worm 18 from displacing in the third direction when the rotational direction of the worm 18 changes.

[0146] Furthermore, according to the worm reducer 14 of this example, grease for lubricating the contact areas between the distal ends of the protrusions 64a and 64b and the retainer pressed surface 52 can be retained between the two protrusions 64a and 64b, respectively, provided on the two pad elastic pressing plates 54. Consequently, the lubrication of the contact areas between the distal ends of the protrusions 64a and 64b and the retainer pressed surface 52 can be maintained well over a long period of time. This also prevents wear of the contact areas between the distal ends of the protrusions 64a and 64b and the retainer pressed surface 52.

[0147] Furthermore, in this example, the number of protrusions 64a and 64b on each of the two pad elastic pressing plates 54 is set to two. However, when implementing the worm reducers of the first and second embodiments of the present disclosure, the number of protrusions on each of the two pad elastic pressing plates can be set to three or more, or even one. When the number of protrusions on each of the two pad elastic pressing plates is set to one, the distal end of the protrusion is formed by an inclined surface that tilts increasingly toward the other side of the second direction as it moves away from the worm in the third direction. This increases the contact area between the distal end of the protrusion and the pressed surface of the retainer, thereby preventing the elastic deformation of the pad elastic pressing plates from becoming unstable or the distal end of the protrusion from wearing out.

[0148] When implementing the worm reducer according to the first embodiment of the present disclosure, a structure having only the washer oil-retaining recess can also be employed. In this case, the bushing 36 can be omitted, or a bushing fitted externally to the outer ring 34 with an interference fit can be internally fitted inside the worm housing 23 with a radial gap therebetween. Furthermore, when implementing the worm reducer according to the second embodiment of the present disclosure, a structure having only the bushing oil-retaining recess can also be employed.

[0149] [Second example]

[0150] use Figure 19 (a)~ Figure 20 (c) The second example of the embodiment of the present disclosure is described. The structure of the elastic member 21a of the worm reducer of this example is different from that of the worm reducer 14 of the first example. The structure and effects of other parts are the same as those of the worm reducer 14 of the first example, so the description is omitted.

[0151] like Figure 19 (a)~ Figure 19 As shown in (d), the elastic member 21a is formed of a leaf spring having a cylindrical shape (roughly C-shaped) and a discontinuous portion 66 at one point in the circumferential direction. In this example, the elastic member 21a includes a base portion 67a located farther from the worm 18 in the first direction, and two arm portions 68a extending circumferentially from both circumferential ends of the base portion 67a.

[0152] In this example, the base 67a is formed of a flat plate perpendicular to the first direction. The base 67a has a constricted portion 70 in the middle portion in the third direction. The constricted portion 70 has a smaller width in the second direction than the width of the two side portions in the third direction. However, the constricted portion 70 may be omitted.

[0153] The two arms 68a are each partially cylindrical. In this example, each arm 68a includes, in order from the side closest to the base 67a in the circumferential direction, a base-side wide width portion 71, a narrow width portion 72, and a terminal-side wide width portion 73. In this example, the width W71 of the base-side wide width portion 71 in the second direction and the width W73 of the terminal-side wide width portion 73 in the second direction are identical, and the width W72 of the narrow width portion 72 in the second direction is smaller than the width W71 of the base-side wide width portion 71 and the width W73 of the terminal-side wide width portion 73 in the second direction (W72 < W71 = W73).

[0154] In this example, each of the two arm portions 68a includes a bent portion 69 that bends radially outward from the distal end of the distal wide portion 73. The width of the bent portion 69 in the second direction is the same as the width W73 of the distal wide portion 73 in the second direction. However, the bent portion 69 may be omitted.

[0155] The elastic force of the elastic member 21a can be adjusted by adjusting the width dimension W68 in the second direction of the narrow portion 72 of the two arm portions 68a. Specifically, in the worm reducer of this example, by adjusting the width dimension W72 in the second direction of the narrow portion 72, the force with which the elastic member 21a elastically urges the distal end of the worm 18 toward the worm wheel 17 via the washer 20 can be appropriately adjusted. As a result, the generation of backlash at the meshing portion between the gear teeth 24 and the worm teeth 25 can be suppressed, suppressing the generation of abnormal noise and preventing unnecessary increases in friction at this meshing portion.

[0156] In addition, according to this embodiment, the operability of the elastic member 21a can be improved. Figure 19 (a)~ Figure 20 In addition to (c), refer to Figure 21 (a)~ Figure 22 (c) is described below.

[0157] Figure 21 (a)~ Figure 22 (c) shows a comparative example relative to the second example. In this comparative example, the two arms 68z constituting the elastic member 21z each have only a base-side wide portion 71 and a narrow portion 72z, sequentially arranged in the circumferential direction from the side closest to the base 67a, and lack the distal-side wide portion 73. The elastic member 21z of this comparative example can also adjust the elastic force by adjusting the width of the narrow portion 72z in the second direction.

[0158] The width dimension of the narrow width portion 72z of the elastic member 21z of the comparative example in the second direction is smaller than the width dimension of the base side wide width portion 71 in the second direction. Therefore, if a plurality of elastic members 21z are to be stacked in the axial direction, Figure 22(a)~ Figure 22 As shown in (c), it will tilt toward the discontinuous portion 66, so the operation is troublesome.

[0159] On the other hand, in this example, the two arms 68a constituting the elastic member 21a have a base-side wide portion 71 and a terminal-side wide portion 73 with the same width dimensions W71 and W72 in the second direction at portions adjacent to the narrow portion 72 on both sides in the circumferential direction. Figure 20 (a)~ Figure 20 As shown in (c), even when multiple elastic members 21a are overlapped in the axial direction, tilting can be prevented, thereby ensuring good handling of the elastic members 21a. This facilitates, for example, so-called strip wrapping, where multiple elastic members 21a are wrapped in an axially overlapping state. Furthermore, it is easy to place them in a fixed placement device in an axially overlapping state.

[0160] In this example, the elastic member 21a has a flat base portion 67a, and the base 67a has a constricted portion 70 in the middle portion in the third direction. This facilitates circumferential phase alignment of the elastic member 21a with respect to the protrusion 44 of the retainer 19. However, phase alignment of the elastic member with respect to the retainer can be performed by any other method, such as by displaying markings. In this case, the base portion can be configured as a partial cylinder and / or the constricted portion can be omitted.

[0161] While various embodiments have been described above, the present disclosure is not limited to these examples. It is obvious that a person skilled in the art would be able to devise various variations or modifications within the scope of the claims, and these variations or modifications are also understood to fall within the technical scope of the present disclosure. Furthermore, the various components of the above embodiments may be arbitrarily combined without departing from the spirit of the invention.

[0162] In addition, this application is based on the Japanese patent application (Japanese Patent Application No. 2022-209400) filed on December 27, 2022, the contents of which are incorporated herein by reference.

[0163] Description of Reference Signs

[0164] 1 Electric power steering

[0165] 2 Steering wheel

[0166] 3 Steering axles

[0167] 4 Steering column

[0168] 5a, 5b universal joints

[0169] 6 Intermediate shaft

[0170] 7 Steering gear unit

[0171] 8 Electric assist device

[0172] 9 Pinion shaft

[0173] 10 Rack shaft

[0174] 11 Housing

[0175] 12 Rack housing

[0176] 13 Pinion housing

[0177] 14 Worm reducer

[0178] 15 Electric Motor

[0179] 16 Housing

[0180] 17 Worm gear

[0181] 18 Worm

[0182] 19 Cage

[0183] 20, 20z pad

[0184] 21, 21a, 21z elastic components

[0185] 22 Worm gear housing

[0186] 23 Worm housing

[0187] 24 teeth

[0188] 25 worm teeth

[0189] 26 Internal spline

[0190] 27 Output shaft

[0191] 28 External spline

[0192] 29 ball bearings

[0193] 30 Small diameter cylindrical face

[0194] 31 Large diameter cylindrical surface

[0195] 32 Support bearings

[0196] 33 inner circle

[0197] 34 outer ring

[0198] 35 Ball

[0199] 36 Bushing

[0200] 37 retainer

[0201] 38 fitting cylinder

[0202] 39 Inward flange

[0203] 40 Wave Washer

[0204] 41 Retainer inclined surface (retainer engagement portion)

[0205] 42 annular part

[0206] 43 side panel

[0207] 44 protrusion

[0208] 45 flat part

[0209] 46 inner circumference

[0210] 47 recess

[0211] 48 Steps

[0212] 49 Guidance Department

[0213] 50 connection

[0214] 51 inner side

[0215] 52 Cage pressed surface

[0216] 53 pad inclined surface (pad engaging portion)

[0217] 54 pad elastic pressing plate

[0218] 55 pad base

[0219] 56 through holes

[0220] 57 Flat Plate

[0221] 58 base body

[0222] 59 base extension

[0223] 60 oblong hole

[0224] 61 Pad fitting hole

[0225] 62 pressed part

[0226] 63 Base Face

[0227] 64a, 64b protrusions

[0228] 65 Slit

[0229] 66 Discontinuity

[0230] Base of 67 and 67a

[0231] 68, 68a, 68z arms

[0232] 69 bending part

[0233] 70 contraction

[0234] 71 Base side wide part

[0235] 72, 72z narrow section

[0236] 73 End side wide part

[0237] 74 Bushing fitting hole

[0238] 75 small diameter cylinder

[0239] 76 side panel

[0240] 77 Large diameter barrel

[0241] 78 outward flange

[0242] 79 pad elastic pressing part

[0243] 80 pad to protect the oil recess

[0244] 81 step surface

[0245] 82 Bushing oil retaining recess

[0246] 100 Worm reducer

[0247] 101 housing

[0248] 102 Worm Gear

[0249] 103 Worm

[0250] 104 Worm gear housing

[0251] 105 worm housing

[0252] 106 gear teeth

[0253] 107 Rotation Axis

[0254] 108 worm teeth

[0255] 109a, 109b ball bearings

[0256] 110 cage

[0257] 111 Large diameter part

[0258] 112 Bushing

[0259] 113 Electric Motor

[0260] 114 pad

[0261] 115 Torsion coil spring

Claims

1. A worm reducer, characterized in that: have: a housing having a worm wheel housing portion and a worm housing portion, wherein the worm housing portion is arranged in a twisted position relative to the worm wheel housing portion, and an axial middle portion of the worm housing portion opens to the worm wheel housing portion; a worm wheel having gear teeth on an outer peripheral surface and rotatably supported inside the worm wheel housing; a worm having worm teeth on an outer peripheral surface thereof that mesh with the gear teeth and being rotatably supported inside the worm housing; a retainer disposed between a distal end of the worm and the worm receiving portion; a pad having a pad fitting hole portion externally fitted into a distal end portion of the worm; as well as an elastic member assembled to the retainer and elastically urging the distal end of the worm toward the worm wheel via the washer; The retainer has two retainer engaging portions at positions sandwiching the pad from both sides in a third direction, wherein the third direction is orthogonal to both the first direction in which the elastic member applies force and the second direction in which the worm housing portion is axially disposed. The gasket comprises: two gasket clamping parts, which are arranged on both sides of the gasket in the third direction and are in contact with the two retainer clamping parts; a gasket elastic pressing part, which applies pre-pressure to the contact part between the retainer clamping part and the gasket clamping part by elastically pressing a part of the retainer; and a gasket oil-retaining recess, which is arranged at multiple circumferential positions and opens on the inner circumferential surface of the gasket interlocking hole and the surface of the gasket facing the second direction.

2. The worm reducer according to claim 1, characterized in that: Each of the pad oil-retaining recesses opens on an inner peripheral surface of an end portion of the pad fitting hole in the second direction and a surface of the pad facing the second direction.

3. A worm reducer, characterized in that: have: a housing having a worm wheel housing portion and a worm housing portion, wherein the worm housing portion is arranged in a twisted position relative to the worm wheel housing portion, and an axial middle portion of the worm housing portion opens to the worm wheel housing portion; a worm wheel having gear teeth on an outer peripheral surface and rotatably supported inside the worm wheel housing; a worm having worm teeth meshing with the gear teeth on an outer peripheral surface thereof and being rotatably supported inside the worm housing portion; and a retainer disposed between a distal end of the worm and the worm receiving portion; a pad having a pad fitting hole portion externally fitted into a distal end portion of the worm; as well as an elastic member assembled to the retainer and elastically urging the distal end of the worm toward the worm wheel via the washer; The retainer has two retainer engaging portions at positions sandwiching the pad from both sides in a third direction, wherein the third direction is orthogonal to both the first direction in which the elastic member applies force and the second direction in which the worm housing portion is axially disposed. The pad comprises: two pad engaging parts, the two pad engaging parts being arranged on both sides of the pad in the third direction and in contact with the two retainer engaging parts; and a pad elastic pressing part, the pad elastic pressing part applying pre-pressure to the contact part between the retainer engaging part and the pad engaging part by elastically pressing a part of the retainer in the second direction. Also features: a bushing having a bushing fitting hole portion, the bushing fitting hole portion being externally fitted in a portion of the worm gear that is offset in the second direction from a portion in which the washer fitting hole portion is externally fitted; and a support bearing, the support bearing being arranged between the worm housing portion or the retainer and the bushing, The bushing includes bushing oil-retaining recesses at a plurality of locations in the circumferential direction, the recesses being open on the inner circumferential surface of the bushing fitting hole and on a surface of the bushing facing the second direction.

4. The worm reducer according to claim 3, characterized in that Each of the bushing oil-retaining recesses opens on an inner peripheral surface of an end portion of the bushing fitting hole in the second direction and a surface of the pad facing the second direction.

5. The worm reducer according to any one of claims 1 to 4, characterized in that: The two retainer engaging portions are composed of two retainer inclined surfaces that are inclined in directions approaching each other as they go toward one side in the second direction. The two pad engagement portions are composed of two pad inclined surfaces that are in surface contact with the two retainer inclined surfaces.

6. The worm reducer according to any one of claims 1 to 4, characterized in that: The pad elastic pressing portion is composed of two pad elastic pressing plates, which are located on one side of the second direction relative to the two pad engaging portions and extend from the center of the pad in the third direction toward the sides separated from each other in the third direction. The portion of the holder elastically pressed toward the second direction by the two pad elastic pressing plates is constituted by a holder pressed surface facing one side in the second direction.

7. The worm reducer according to claim 6, characterized in that The two pad elastic pressing plates each have a protrusion extending in the first direction on the side surface on the other side in the second direction, and elastically press the pressed surface of the retainer toward the other side in the second direction through the distal end of the protrusion.

8. The worm reducer according to claim 6, characterized in that The two pad elastic pressing plates each have a slit extending in the second direction and extending in the first direction at an end portion on a center side of the pad in the third direction.

9. The worm reducer according to any one of claims 1 to 4, characterized in that: The elastic member is composed of a leaf spring.

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