JP2009120096A - Speed reducer and electric power steering system equipped with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a speed reducer provided with a holder easy to mount on a housing for suppressing gearing noise of a gearing part, and also to provide an electric power steering system equipped with the speed reducer. <P>SOLUTION: The holder 19 and an energizing member 20 are arranged on the bottom at the bag-like end of the housing 11, and a coil spring 21 is wound around the energizing member 20 and the outer periphery of the holder 19. The holder 19 and the outer ring of a ball bearing 15 are mounted on the step part 11a of the housing 11. A corrugated washer 17 and a retainer 16 are arranged on the outside of the ball bearing 15 and pressed and fixed thereto in the axial direction. A worm can be elastically deformed by the elastic deformation of the coil spring 21 and a bush 18 and the corrugated washer 17, thus imparting preload to the worm gearing part and suppressing the generation of the gearing noises of the gearing part. The retainer 16 is provided with a notched part 16d having a plurality of end edges of an arcuate shape. Elastic deformation is allowed when pressing and inserting the retainer 16 into the step part 11a, so that the strength is not reduced by stress concentration. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a reduction gear and an electric power steering apparatus including the same.

  As a vehicle steering apparatus, a power steering apparatus for reducing a driver's steering load is known. Conventionally, hydraulic power steering devices have been widely used as power steering devices. However, with the recent trend toward higher efficiency of automobiles, there is an increasing number of cases where a hydraulic power steering apparatus is replaced with an efficient electric power steering apparatus (EPS).

  FIG. 6 is a diagram for explaining an outline of an example of the basic configuration of such an EPS. A steering shaft 102 having a steering wheel 101 is coupled to an input shaft of a reduction gear 104, and an output shaft of the reduction gear 104 is a universal joint. 107, the intermediate shaft 108, and the universal joint 109 are connected to the worm shaft 110. A worm 111 formed on the worm shaft 110 meshes with a rack 112 and is configured to operate the direction of the steering wheel 114 via a tie rod 113 connected to an end of the rack 112.

  The steering shaft 102 is provided with a torque sensor 103 that detects a steering torque generated in the shaft. The control device 106 determines the auxiliary steering force to be supplied to the steering mechanism based on the torque signal detected by the torque sensor 103 and the vehicle speed signal input from the vehicle speed sensor (not shown), that is, the magnitude of the current supplied to the motor 105. The current command value to be determined is calculated, and the motor 105 is driven by the calculated current command value.

  FIG. 7 is a front view for explaining an example of the configuration of the reduction gear 104, and a part thereof is shown as a cross section. The speed reducer 104 is a worm speed reducer. A worm 121 splined to the rotation shaft 105 a of the motor 105 is rotatably held by the housing 120 by a ball bearing 122 and a ball bearing 123 held by a holder 125 described later, and is formed in a part of the worm 121. The worm teeth 121a thus engaged mesh with worm wheel teeth 124a formed on a worm wheel 124 rotatably held in the housing 120.

  8A and 8B are diagrams for explaining the details of the configuration of the holder 125 and the ball bearing 123 described above. FIG. 8A is a front view of the worm 121 viewed from the axial end surface, and FIG. It is sectional drawing along the axial direction.

  The holder 125 is attached to the inner surface of a hole 120c (see FIG. 7) formed in the bottom surface of the housing 120. As apparent from FIG. 8B, an outer ring of a ball bearing 123 is fitted to the holder 125, and an annular bush 126 made of a resin material is fitted to the inner ring of the ball bearing 123. The shaft end of the worm 121 is supported via the bush 126.

  An urging member 127 having a hole 127a that fits into the shaft end 121c of the worm 121 is arranged on the outer side in the axial direction of the bush 126 (on the opposite side to the worm 121), and the step portion 125b of the holder 125 and the urging member 127 are arranged. A coil spring 128 is wound between the outer surface and the end of the coil spring 128 is locked to a locking portion 127 d formed on the left and right side surfaces of the biasing member 127.

  With this configuration, when the shaft end 121c of the worm 121 is fitted in the hole 127a of the biasing member 127, the worm teeth 121a of the worm 121 are moved in the direction of the worm wheel teeth 124a of the worm wheel 124 by elastic deformation of the coil spring 128. Since the preload is applied to the meshing portion between the worm tooth 121a and the worm wheel tooth 124a, generation of rattling noise at the meshing portion can be suppressed (see Patent Document 1).

In the above configuration, the holder 125 that holds the ball bearing 123 is fitted in the housing 120 and is held by frictional contact between the outer peripheral surface of the holder 125 and the inner peripheral surface of the housing 120, but is held on the inner peripheral surface of the housing. As a means to fix the axial movement of the fixed holder, etc., a flat retaining ring provided with a number of radial notches (slits) from the center to the outer periphery is mounted on the inner surface of the housing, and the axial direction of the holder Some have been proposed to fix the movement (see Patent Document 2).
JP 2005-042913 A JP 2002-130234 A

  The holder with the above configuration is effective in suppressing the rattling noise of the meshing portion of the worm speed reducer, but the workability is poor because the holder is attached to the bag-like hole on the bottom of the housing. The assembly process is complicated by tightening and fixing the outer ring of the ball bearing, and the manufacturing cost is increased.

  Further, the flat retaining ring for fixing the holder having the above-described configuration to the inner surface of the housing cannot fix the axial movement of the bearing outer ring even if the axial movement of the bearing is fixed. Furthermore, depending on the shape of many radial notches from the center of the retaining ring toward the outer periphery, when the retaining ring is press-fitted into the inner surface of the housing, stress concentrates on the notch and deforms or the strength decreases. Has a disadvantage that it cannot be sufficiently fixed and held on the inner surface of the housing.

  An object of the present invention is to provide a speed reducer that solves the above-described problems and an electric power steering apparatus including the same.

  The present invention solves the above-mentioned problems, and the invention according to claim 1 is characterized in that the biasing member having a fitting portion fitted to the shaft end portion of the worm shaft disposed inside the housing and the spring is attached. And a holder for supporting the urging member so as to be movable in the meshing direction of the worm and the worm wheel. A ball bearing arranged in parallel with the holder supports the worm shaft in the holding hole inside the housing, and the worm shaft is engaged in the meshing direction. In a reduction gear including a worm and a worm wheel that elastically preloads, one end of the holder and the outer ring of the ball bearing in the axial direction is positioned at a step formed in a holding hole inside the housing, and the axial direction The other end is fixed by an annular fixing member having a notch having a plurality of arc-shaped end edges that are pressed and inserted into a holding hole inside the housing via an elastic member. A reduction gear, wherein the door.

  The annular fixing member includes a disc-shaped flange portion having an opening at the center portion and an outer edge portion that rises substantially perpendicularly from the outer edge thereof. The flange portion approaches the outer edge portion. A notch portion having a plurality of arc-shaped end edges is formed, and when the fixing member is pressed and inserted into the holding hole inside the housing, the outer edge portion is allowed to be elastically deformed in the radial direction.

  In addition, it is preferable to provide at least three or more cutout portions having a plurality of arc-shaped end edges formed in the flange portion of the annular fixing member.

  Further, the notch portion having a plurality of arc-shaped end edges formed in the flange portion of the annular fixing member may be a notch portion having a size for partially separating the flange portion.

  The holder includes a convex portion extending in the axial direction, the holding hole inside the housing has a concave portion into which the convex portion is fitted, and the convex portion of the holder is fitted into the concave portion of the holding hole inside the housing. Thus, the phase around the axial direction of the worm shaft is determined, and the rotation of the holder is restricted.

  The elastic member interposed between the end of the outer ring of the holder and the ball bearing and the annular fixing member that fixes the end of the outer ring of the holder and the ball bearing is an annular corrugated washer.

  A seventh aspect of the invention is an electric power steering device for a vehicle, the electric power steering device including the speed reduction device according to any one of the first to sixth aspects.

  In the speed reducer provided with a worm and a worm wheel that elastically preloads the worm shaft in the meshing direction according to the present invention, one end in the axial direction of the outer ring of the holder and the ball bearing is formed in a holding hole inside the housing. The other end in the axial direction of the outer ring of the holder and the ball bearing is annularly provided with a notch portion having a plurality of arc-shaped end edges that are pressed into a holding hole inside the housing via an elastic member. It is fixed by the fixing member.

  The annular fixing member is composed of a disc-shaped flange portion having an opening in the center portion and an outer edge portion that rises substantially perpendicularly from the outer edge, and the flange portion approaches the outer edge portion and has a radius. Notch portions having a plurality of arc-shaped end edges extending outward in the direction are formed, and when the fixing member is pressed and inserted into the holding hole inside the housing, elastic deformation in the radial direction of the outer edge portion is allowed.

  As a result, the fixing member is allowed to be elastically deformed in the radial direction, so that the fixing member can be easily mounted, and the notch portion formed in the flange portion has an arc-shaped edge, so that the stress is partially concentrated. The holder and the ball bearing can be fixed to the inner surface of the housing with sufficient strength without being deformed or reduced in strength.

  With this configuration, the holder and the ball bearing can be easily mounted in the bag-like hole on the bottom surface of the housing, the assembly process is simplified, and the biting sound of the meshing portion of the reduction gear can be generated without increasing the manufacturing cost. Can be suppressed.

  Hereinafter, a reduction gear according to an embodiment of the present invention and an electric power steering device provided with the reduction gear will be described. The entire configuration of the electric power steering device is the conventional electric motor described above with reference to FIG. The configuration is similar to the power steering device, and the configuration of the reduction gear of the electric power steering device is also similar to the configuration of the prior art described above with reference to FIG. 7, and the worm shaft end portion of the reduction gear is supported. Since only the structure is different, the description of the overall configuration of the electric power steering device and the overall configuration of the reduction gear will be omitted here, and the support of the worm shaft end portion of the reduction gear which is the configuration of the characteristic part of the present invention. The structure will be described.

  FIG. 1 is a cross-sectional view for explaining the details of the support structure of the worm shaft end portion of the speed reducer, and corresponds to the support structure of the worm shaft end portion of the speed reducer described above with reference to FIG.

  2A and 2B are diagrams for explaining constituent members of the support structure of the worm shaft end portion shown in FIG. 1, FIG. 2A is a sectional view of the retainer 16 as a fixing member, and FIG. 2B is an elastic member. 2C is a cross-sectional view of the ball bearing 15 that is a bearing with the bush 18 mounted on the inner diameter portion, and FIG. 2D is a cross-sectional view of the holder 19 and the biasing member 20. It is. 3 is a front view of the holder 19 and the urging member 20 shown in FIG. 2D as seen from the axial end direction, FIG. 4 is an external view of the holder 19, and FIG. 5 is a configuration of the retainer 16 that is an annular fixing member. FIG.

  The support structure for the worm shaft end will be described with reference to FIGS. In FIG. 1, 11 is a housing, 12 is a worm shaft, and the shaft end is shown here. The end portion of the housing 11 is closed in a bag shape, and a holder 19 and a biasing member 20 described later are disposed on the bottom portion thereof. Further, a step portion 11a which is a holding hole is formed inside the end portion of the housing 11, and the outer peripheral surface of the outer ring of the ball bearing 15 and the outer peripheral surface of the holder 19 are fitted to the step portion 11a. The side surface of the axial end of the outer ring of the ball bearing 15 contacts the holder 19.

  An annular bush 18 made of a resin material and elastically deformable is fitted to the inner ring of the ball bearing 15, and the small diameter portion 12 b of the worm shaft 12 is supported via the bush 18.

  Further, a substantially annular holder 19 is arranged on the outer side in the axial direction of the ball bearing 15 (on the side opposite to the worm shaft 12), and the side surface of the outer edge of the holder 19 is in contact with the side surface of the outer ring of the ball bearing 15. . An annular groove 19b is formed on the outer side of the holder 19 in the axial direction (opposite to the worm shaft 12), and a hole 20a for fitting the shaft end 12c of the worm shaft 12 is provided inside the groove 19b. A biasing member 20 is disposed, and a coil spring 21 as a spring member is wound between the outer periphery of the biasing member 20 and the outer periphery of the holder 19, and ends of the coil spring 21 are formed on the left and right side surfaces of the holder 19. It is latched by the latching part 19d.

  5A and 5B are views for explaining the configuration of the retainer 16 that is an annular fixing member. FIG. 5A is a plan view of the retainer 16 and FIG. 5B is a side view of the retainer 16.

  As shown in FIG. 5, the retainer 16 includes a flange portion 16 a and an outer edge portion 16 b that rises substantially vertically from the outer edge of the flange portion 16 a.

  The flange portion 16a constitutes a surface that abuts against the outer ring side surface of the ball bearing 15, and a hole 16c through which the worm shaft 12 and the annular bush 18 pass is formed in the center portion of the flange portion 16a. In addition, the outer edge portion 16 b that rises substantially perpendicularly from the outer edge of the flange portion 16 a constitutes a surface that contacts the step portion 11 a of the inner surface of the housing 11.

  The flange portion 16a is formed with a notch portion 16d having a plurality of arc-shaped end edges close to the outer edge portion 16b. A portion 16e which is a part of the flange portion 16a remains between the adjacent notch portions 16d, but the arc-shaped end edge of the notch portion 16d is extended to the outer edge portion 16b, and the flange portion 16a is left leaving the outer edge portion 16b. It is good also as a notch part of the magnitude | size isolate | separated partially.

  When the retainer 16 is pressed and inserted into the holding hole 11a inside the housing, the cutout portion 16d can allow the elastic deformation of the outer edge portion 16b in the radial direction.

  The plurality of notches 16d formed in the flange portion 16a may be provided at least three locations (four locations in FIG. 5) close to the outer edge portion 16b.

  The size and number of the notches 16d formed in the flange portion 16a are determined by the tightening allowance that the outer edge portion 16b is frictionally held by the step portion 11a that is the holding hole when the retainer 16 is pressed into the holding hole 11a inside the housing. It is determined by how much it is made, and it is good to determine the optimum size by experiment.

  By providing the retainer 16 with a plurality of cutout portions 16d having arc-shaped edges, when the retainer 16 is pressed and inserted into the stepped portion 11a that is the holding hole of the housing 11, stress is concentrated on a part of the cutout portion 16d. Accordingly, the elastic deformation to reduce the diameter in the radial direction is allowed, the strength of the retainer 16 is not lowered, and a slight movement of the ball bearing 15 in the axial direction is allowed.

  Next, the assembly of the above members will be described. First, as a preparatory work, the coil spring 21 is wound between the outer periphery of the biasing member 20 and the outer periphery of the holder 19. Next, the holder 19 and the biasing member 20 around which the coil spring 21 is wound are disposed on the bottom portion of the housing 11 which is closed in a bag shape, and the holder 19 and the urging member 20 are disposed on the step portion 11a of the housing 11. The outer ring of the ball bearing 15 to which the bush 18 is attached is attached.

  Further, an annular wave washer 17 is arranged on the outer side (worm side) of the outer ring of the ball bearing 15, a retainer 16 is arranged on the outer side thereof, and the outer edge portion 16 b of the retainer 16 is inserted into the step of the housing 11. It fixes in the state pressed against the part 11a.

  Next, the worm shaft 12 is inserted. First, the shaft end 12 c of the worm shaft 12 is inserted into the hole 20 a of the urging member 20, and the small diameter portion 12 b of the worm shaft 12 is inserted into and supported by the bush 18 attached to the inner ring of the ball bearing 15.

  With this configuration, in a state where the shaft end 12c of the worm shaft 12 is fitted in the hole 20a of the biasing member 20, the worm teeth of the worm 12 are caused by the elastic deformation of the coil spring 21 and the elastic deformation of the bush 18. The wheel bearings 17 are arranged so as to be displaced elastically in the worm wheel teeth direction of the wheel, and since the wave washer 17 is disposed, the ball bearings 15 and the holder 19 are not pressed in the axial direction to generate backlash. A preload is applied to the meshing portion between the worm wheel and the worm wheel teeth, and generation of rattling noise at the meshing portion can be suppressed.

  According to the above configuration, even if the end portion of the housing 11 is formed in a bag shape, the holder 19, the urging member 20, and the ball bearing 15 are easily mounted inside the housing 11, and the worm shaft 12 is mounted on the ball bearing. 15 can be rotatably supported.

  Further, by providing the retainer 16 with a plurality of cutout portions 16d having arc-shaped end edges, when the outer edge portion 16b of the retainer 16 is pressed and inserted into the stepped portion 11a which is the holding hole of the housing 11, the cutout portion 16d Elastic deformation that shrinks in the radial direction without allowing stress to concentrate in part is allowed, and stress is not concentrated in the notch portion 16d to be deformed or the strength is not reduced. Movement is allowed.

  Furthermore, since the wave washer 17 can be visually confirmed from the notch 16d in the assembly work of the retainer 16, it is possible to prevent the wave washer 17 from being forgotten to be assembled.

  The holder 19 is formed with a convex portion 19c extending parallel to the axial direction. On the other hand, the bottom surface of the housing 11 is formed with a concave portion 11c corresponding to the convex portion 19c. 11, the projection 19 c of the holder 19 is engaged with the recess 11 c of the housing 11, the phase (rotation angle) around the axial direction of the holder 19 is determined, and the holder 19 is rotated. Regulated and easy to assemble.

  The convex portion 19 c of the holder 19 can also be used as one of the locking portions 19 d that locks the end portion of the coil spring 21. In this case, one locking portion 19d is extended in parallel to the axial direction to form a convex portion 19c (see FIG. 4). The coil spring 21 has an arm position in the axial direction (end position of the coil spring) determined by the winding direction, and is locked to the convex portion 19c. Since the convex portion 19c of the holder 19 engages with the concave portion 11c of the housing 11 and is buried in the housing 11, the coil spring 21 is regulated by the housing 11 and does not fall off.

  In addition, although the phase of the convex part 19c shown by FIG. 1, FIG. 2 and the phase of the latching | locking part 19d which latches the edge part of the coil spring 21 shown by FIG. In FIG. 1, in order to explain the state in which the convex portion 19 c of the holder is engaged with the concave portion 11 c of the housing, the phase is shifted and illustrated.

  The holder material described above may be a synthetic resin or a sintered metal. The wave washer 17 that is an elastic member is not limited to the wave washer 17, and rubber or a disc spring may be used.

  The speed reducer according to the present invention and the electric power steering apparatus including the speed reducer have been described above. Needless to say, the speed reducer according to the present invention can be applied to a speed reducer for general machines in addition to the electric power steering apparatus.

  A reduction gear having a holder at the shaft end of the worm shaft, and an electric power steering device having the reduction gear, wherein the holder is effective in suppressing rattling noise of the meshing portion of the worm reduction gear, Provide a configuration that allows easy mounting of the holder.

Sectional drawing explaining the detail of the support structure of the worm shaft end part of a reduction gear. The figure explaining the structural member of the support structure of the worm shaft end part shown in FIG. The front view which looked at the holder and the urging | biasing member from the axial end part direction. External view of the holder. The figure explaining the structure of a retainer (annular fixing member). The figure explaining the outline of an example of the basic composition of conventional EPS. The front view explaining an example of the composition of the conventional reduction gear. The figure explaining the detail of a structure of the holder and ball bearing part of the conventional speed reducer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Housing 11a Step part 11c Recessed part 12 Worm shaft 12b Thin diameter part 12c Shaft end 15 Ball bearing 16 Fixing member (annular fixing member, retainer)
16a Flange (Retainer flange)
16b Outer edge (outer edge of retainer)
16c hole 16d notch (notch having a plurality of arc-shaped edges)
16e portion (a part of the flange portion 16a remaining between the adjacent cutout portions 16d)
17 Wave washer (elastic member)
18 Bush 19 Holder 19b Groove 19c Protruding portion 19d Engaging portion 20 Biasing member 20a Hole 21 Coil spring

Claims (7)

A biasing member having a fitting portion fitted to a shaft end portion of a worm shaft arranged inside the housing, and a holder for supporting the biasing member by a spring so as to be movable in a meshing direction of the worm and the worm wheel. A reduction gear having a worm and a worm wheel that elastically preloads the worm shaft in a meshing direction by supporting the worm shaft in a holding hole inside the housing by a ball bearing arranged in parallel with the holder,
One end in the axial direction of the outer ring of the holder and ball bearing is positioned in a step formed in a holding hole inside the housing, and the other end in the axial direction is placed in a holding hole inside the housing via an elastic member. A speed reducer fixed by an annular fixing member having a cutout portion having a plurality of arc-shaped edges to be pressed and inserted. The annular fixing member is composed of a disc-shaped flange portion having an opening at a center portion and an outer edge portion that rises substantially perpendicularly from the outer edge thereof. The cutout portion having an arcuate edge is formed, and when the fixing member is pressed and inserted into the holding hole inside the housing, elastic deformation in the radial direction of the outer edge portion is allowed. Speed reducer. The speed reducer according to claim 2, wherein at least three cutout portions having a plurality of arc-shaped end edges formed in the flange portion of the annular fixing member are provided. The cutout portion having a plurality of arc-shaped end edges formed in the flange portion of the annular fixing member is a cutout portion having a size for partially separating the flange portion. Speed reducer. The holder has a convex portion extending in the axial direction, the holding hole inside the housing has a concave portion into which the convex portion is fitted, and the convex portion of the holder fits into the concave portion of the holding hole inside the housing. The speed reducer according to any one of claims 1 to 4, wherein a phase around the axial direction of the worm shaft is determined and rotation of the holder is restricted. The elastic member interposed between the end of the outer ring of the holder and the ball bearing and the annular fixing member that fixes the end of the outer ring of the holder and the ball bearing is an annular corrugated washer. Item 4. The reduction gear according to item 1. An electric power steering apparatus for a vehicle, comprising the speed reducer according to any one of claims 1 to 6.

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