JP2010007810A - Speed reducer and electric power steering device equipped therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a speed reducer with a holder easy to mount on a housing for suppressing the gearing noises of a meshing portion, and to provide an electric power steering device equipped the speed reducer. <P>SOLUTION: The holder 19 and an energizing member 20 are arranged on the bottom at the bagged end of the housing 11, and a coil spring 21 is coiled between 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 a stepped portion 11a of the housing 11. A corrugated washer 17 and an integrally connected cage 16 are arranged on the outside of the ball bearing 15 and thrust and fixed thereto in the axial direction. A shaft end 12c of the worm shaft is inserted and supported into a hole 20a of the energizing member, and a small diameter portion 12b are inserted and supported into a bush 18 of the inner ring of the ball bearing 15, respectively. A worm can be elastically deformed with the elastic deformation of the coil spring 21 and the bush 18 and the corrugated washer 17, thus preload is imparted to the meshing portion of the worm and the teeth hitting noises of the meshing portion can be suppressed and mounting of the corrugated washer 17 is not forgot. <P>COPYRIGHT: (C)2010,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. 8 is a diagram for explaining an outline of an example of the basic configuration of such an EPS. A steering shaft 102 including 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. The worm 111 formed on the worm shaft 110 is configured to mesh with the rack 112 and operate the direction of the steering wheel 114 via the tie rod 113 connected to the 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. 9 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.

  10A and 10B are diagrams for explaining the details of the configuration of the holder 125 and the ball bearing 123 described above. FIG. 10A is a front view seen from the end surface in the axial direction of the worm 121, 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. 9) formed in the bottom surface of the housing 120. As apparent from FIG. 10B, 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.

  On the axially outer side of the bush 126 (opposite to the worm 121), an urging member 127 having a hole 127a that fits into the shaft end 121c of the worm 121 is disposed. 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).

  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.

As a countermeasure against this, an elastic member (for example, a wave washer) is used to urge the holder and bearing in the axial direction to be fixed to the bottom surface of the housing, and an annular member is used to compress and hold the elastic member inside the housing. A configuration in which a fixing member is disposed behind the elastic member has been proposed by the present applicant (see Patent Document 2).
JP 2005-042913 A JP 2007-321846 A

  In the configuration in which the holder and the bearing are urged in the axial direction by the elastic member and the annular fixing member to be fixed to the bottom surface of the housing, the holder and the bearing are urged and held in the axial direction by the elastic member and are held inside the housing. Positioning can be performed on the stepped portion, and mounting of the holder and the bearing can be easily performed.

  However, in the above-described fixing configuration, the elastic member is hidden behind the annular fixing member in the assembled state, so it cannot be confirmed whether or not the elastic member is mounted, and forget to mount the elastic member. there is a possibility. Further, in the assembled state, a hitting sound may be generated at the contact portion between the elastic member and the annular fixing member.

  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. A holder that supports the urging member so as to be movable in the meshing direction of the worm and the worm wheel, and the worm shaft is supported in the housing by the holder and a bearing arranged in parallel with the holder so that the worm shaft is elastic in the meshing direction. In the speed reducer including the worm and the worm wheel for preloading, the holder and the bearing arranged in parallel with the holder are urged in an axial direction by an elastic member and an annular fixing member integrally coupled to each other inside the housing. It is a speed reducer characterized by being positioned on a formed step portion.

  The integrally coupled elastic member and the annular fixing member are integrally coupled by rivet coupling means.

  Further, the integrally coupled elastic member and the annular fixing member may be integrally coupled by caulking coupling means.

  Further, the integrally coupled elastic member and the annular fixing member may be integrally coupled by welding coupling means.

  The elastic member is an annular wave washer.

  The annular fixing member includes a fixing portion that is pressed against and fixed to the periphery of the housing, and a flat portion that extends from the fixing portion and is perpendicular to the axial direction of the housing, and the flat portion is attached to the elastic member. It shall be the mounting surface to be joined.

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

  As described above, in the reduction gear device according to the first aspect of the present invention, the holder and the bearing arranged in parallel with the holder are urged in the axial direction by the elastic member and the annular fixing member that are integrally coupled to each other inside the housing. Since it is positioned on the formed step portion, there is no possibility of forgetting to attach the elastic member in the assembling work. Further, since the elastic member and the annular fixing member are integrally coupled, there is no possibility that a hitting sound is generated at the contact portion between the elastic member and the annular fixing member.

  Moreover, since the electric power steering device according to the invention of claim 7 includes the speed reduction device according to the invention of claim 1, the same effect as that of the invention of claim 1 is obtained.

  Hereinafter, a reduction gear according to an embodiment of the present invention and an electric power steering device including 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. 9, 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 for the worm shaft end portion of the speed reducer, and corresponds to the support structure for the worm shaft end portion of the speed reducer described above with reference to FIG.

  FIG. 2 is a view for explaining the outline and arrangement order of the constituent members of the support structure of the worm shaft end portion shown in FIG. 1, FIG. 2 (a) is a sectional view of the retainer 16 (single unit) which is a fixing member, and FIG. 2B is a side view of an annular wave washer 17 (single unit) that is an elastic member, FIG. 2C is a cross-sectional view of a ball bearing 15 that is a bearing having a bush 18 mounted on the inner diameter portion, and FIG. These are sectional views of the holder 19 and the biasing member 20.

  FIG. 3 is a front view of the holder 19 and the urging member 20 shown in FIG. 2D as viewed from the axial end direction, and FIG. 4 is an external view of the holder 19.

  5A and 5B are views for explaining the retainer 16 that is an annular fixing member. FIG. 5A is a side view thereof, and FIG. 5B is a plan view thereof. The retainer 16 includes a fixed portion 16a that is fixed to the periphery of the housing by being pressed against the inside of the housing, and a flat portion 16b that extends from the fixed portion and is perpendicular to the axial direction of the housing. The whole is formed in a dish shape having an opening 16d at the center. An annular wave washer 17 is integrally coupled onto the wave washer mounting surface 16 c of the retainer 16.

  6A and 6B are views for explaining an annular wave washer 17 that is an elastic member. FIG. 6A is a side view thereof, and FIG. 6B is a plan view thereof. A corrugated portion 17a of the wave washer 17 indicates a highly corrugated portion of the wave washer 17, and is separated from the wave washer mounting surface 16c of the retainer 16 as a pressurizing portion. Further, between the two striking portions 17a adjacent to each other, there is a coupling portion 17b coupled to the wave washer mounting surface 16c of the retainer 16, and the known rivet coupling and caulking to the wave washer mounting surface 16c of the retainer 16 It couple | bonds integrally by the coupling means C, such as coupling | bonding and welding coupling | bonding.

  7A and 7B are views for explaining a combined state in which the annular wave washer 17 and the retainer 16 that is an annular fixing member are integrally coupled. FIG. 7A is a side view illustrating the coupled state, and FIG. These are top views explaining a combined state.

  A connecting portion 17b of the annular wave washer 17 is disposed on the wave washer mounting surface 16c of the retainer 16, and a known rivet connection, caulking connection, The wave washer mounting surface 16c of the retainer 16 and the coupling portion 17b of the wave washer 17 are integrally coupled by a coupling means C such as welding coupling.

  Since the waved portion 17a of the wave washer 17 which is a pressurizing portion is in a position shifted from the phase different from the wave washer mounting surface 16c of the retainer 16, elastic deformation of the waved portion 17a of the wave washer 17 is allowed. Generation of pressure is possible.

  A support structure for the end portion of the worm shaft 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 11 a is formed inside the end portion of the housing 11, and the outer peripheral surface of the outer ring of the ball bearing 15 is fitted to the step portion 11 a. The side surface of the outer ring of the ball bearing 15 on the end side in the axial direction is in contact with a holder 19 described later.

  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.

  An annular wave washer 17 as an elastic member and a retainer 16 as an annular fixing member are disposed outside the outer ring of the ball bearing 15, and the outer ring of the ball bearing 15 is axially directed toward the bag-like end of the housing 11. It is pressed and fixed to.

  Next, the assembly order of the above members will be described.

  First, before the assembly work is started, as a first preparation work, the annular wave washer 17 that is an elastic member and the retainer 16 that is an annular fixing member are integrally coupled by the appropriate coupling means C described above. Next, as a second preparatory work, the coil spring 21 is wound between the outer periphery of the urging member 20 and the outer periphery of the holder 19.

  Move to assembly work. First, the holder 19 and the urging member 20 around which the coil spring 21 is wound are disposed on the bottom portion of the end portion of the housing 11 that is closed like a bag, and the holder 19 and the bushing are disposed on the step portion 11a of the housing 11. The outer ring of the ball bearing 15 to which 18 is mounted is mounted.

  An annular wave washer 17, which is an elastic member, and an retainer 16, which is an annular fixing member, are integrally attached to the outer side (worm side) of the outer ring of the ball bearing 15 so that the wave washer 17 contacts the outer ring of the ball bearing 15. To place. The retainer 16 is pressed in the axial direction toward the bag-like end portion of the housing 11, and the outer peripheral surface 16 a of the retainer 16 is pressed against and fixed to the inner surface of the housing 11. A slight movement of the ball bearing 15 in the axial direction is allowed by the elastic deformation of the wave washer 17.

  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. Preload is applied to the meshing portion between the worm wheel and the worm wheel teeth, and the occurrence of rattling noise at the meshing portion can be suppressed.

  Since the wave washer 17 is integrally coupled to the retainer 16, the wave washer 17 is also mounted at the same time as the retainer 16 is mounted. There is no fear of forgetting to install the wave washer 17.

  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.

  The holder 19 is formed with a convex portion 19c extending in parallel with the axial direction. On the other hand, the bottom surface of the end of the housing 11 is formed with a concave portion 11c corresponding to the convex portion 19c. Is disposed on the bottom surface of the end portion of the housing 11, the convex portion 19 c of the holder 19 is engaged with the concave portion 11 c of the housing 11, and the phase (rotation angle) around the axial direction of the holder 19 is determined. Rotation is restricted and assembly is easy.

  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 a state in which the convex portion 19 c of the holder is engaged with the concave portion 11 c of the housing 11, 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 outline and arrangement | positioning order of 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 retainer which is a cyclic | annular fixing member. The figure explaining the cyclic | annular wave washer which is an elastic member. The figure explaining the combined state which united the retainer which is a cyclic | annular wave washer and the cyclic | 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 Concave part 12 Worm shaft 12b Thin diameter part 12c Shaft end 15 Ball bearing 16 Retainer 16a Fixing part (fixing part of the periphery of a retainer)
16b Flat surface (the flat surface of the retainer perpendicular to the axial direction of the housing)
16c Wave washer mounting surface 16d Open hole 17 Wave washer (elastic member)
17a Wave portion 17b Coupling portion 18 Bush 19 Holder 19b Groove 19c Protruding portion 19d Engaging portion 20 Energizing 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 disposed inside the housing, and a holder that supports 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 including a worm and a worm wheel that elastically preloads the worm shaft in a meshing direction by supporting the worm shaft inside the housing by the holder and a bearing arranged in parallel with the holder,
The holder and a bearing arranged in parallel with the holder are urged in an axial direction by an elastic member and an annular fixing member that are integrally coupled, and are positioned at a step portion formed inside the housing. apparatus. The speed reducer according to claim 1, wherein the integrally coupled elastic member and the annular fixing member are integrally coupled by a rivet coupling means. The speed reducer according to claim 1, wherein the integrally coupled elastic member and the annular fixing member are integrally coupled by caulking coupling means. The speed reducer according to claim 1, wherein the integrally coupled elastic member and the annular fixing member are integrally coupled by a welding coupling means. The speed reducer according to claim 1, wherein the elastic member is an annular wave washer. The annular fixing member includes a fixing portion that presses and fixes the inside of the housing to the periphery, and a flat portion that extends from the fixing portion and is perpendicular to the axial direction of the housing, and connects the flat portion to the elastic member. The reduction device according to claim 1, wherein the reduction device is a mounting surface. An electric power steering apparatus comprising the reduction gear according to any one of claims 1 to 6.

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