JP5050901B2 - Bearing support structure for worm reducer - Google Patents

Description

The present invention relates to an electric power steering apparatus, and more particularly to a bearing support structure for the worm reduction gear.

  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, in accordance 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.

  FIG. 6 is a front view for explaining an example of the configuration of the speed reducer 100 of the electric power steering apparatus, and a part thereof is shown as a cross section. The speed reducer 100 is a worm speed reducer, and a worm 121 splined to the rotating shaft 105 a of the motor 105 is rotatably held by a housing 120 with a ball bearing 122 and a ball bearing 123 held by a holder 125. The worm teeth 121 a formed on a part of the worm 121 mesh with the worm wheel teeth 124 a formed on the worm wheel 124 rotatably held by the housing 120.

In the speed reducer having the above-described configuration, the worm teeth 121a of the worm 121 are elastically displaced toward the meshing direction of the worm wheel teeth 124a of the worm wheel 124, and a preload is applied to the meshing surface to form the meshing. A configuration that suppresses generation of rattling noise generated on a surface is known (see Patent Document 1). In this case, an annular retainer is used in order to press and hold the holder and the ball bearing for holding the member for suppressing the generation of rattling noise in the worm shaft direction inside the housing.
JP 2005-042913 A

  The annular retainer described above is fixed by bringing the annular edge of the retainer into frictional contact with the inner diameter portion of the housing, and the frictional force between the retainer and the outer diameter of the retainer is larger than the inner diameter of the housing. It is determined by the tightening allowance when set. Accordingly, the tightening margin is increased in order to increase the fixing force of the retainer to the housing. However, if the tightening margin is too large, the retainer is deformed or broken. The present invention aims to solve the above problems.

The present invention is intended to solve the above problems, a biasing member having a fitted portion to be fitted to the axial end portion of the worm shaft arranged inside the housing, a worm and a worm of the urging member by the spring And a worm wheel for supporting the worm shaft elastically in the meshing direction by supporting the worm shaft inside the housing by a bearing arranged in parallel with the holder. In the bearing support structure of the worm speed reducer provided, the holder and the bearing arranged in parallel with the holder are pressed and held toward an end portion inside the housing by a retainer mounted inside the housing, and the housing includes the retainer annular groove along the annular edge of the retainer inner diameter portion to be mounted is formed, the housing bore The annular groove formed on the retainer is formed in a direction in which the retainer is removed from the mounting position of the annular edge of the retainer, and the retainer is a dish-shaped member composed of a plane portion and an annular edge. Thus, the bearing support structure for the worm speed reducer is characterized in that the annular edge is pressed against the inner diameter of the housing and is held by frictional contact .

  As described above, the bearing support structure of the worm reduction device according to the present invention is such that the holder and the bearing arranged in parallel with the holder are pressed and held by the retainer toward the end inside the housing, An annular groove along the annular edge of the retainer is formed in the inner diameter where the retainer is mounted, and even if the retainer is displaced in the pulling direction due to vibration, aging or other reasons, the edge of the retainer remains in the housing The annular groove portion cannot be easily passed through, and the retainer can be prevented from coming out with a simple configuration.

  Hereinafter, the bearing support structure in the worm speed reduction device of the electric power steering apparatus according to the embodiment of the present invention, that is, the retainer mounting structure for holding the holder and the ball bearing inside the housing will be described. The overall configuration of the worm speed reduction device of the electric power steering apparatus according to the embodiment is similar to the configuration described above with reference to FIG. A support structure for a certain worm shaft end will be described.

  FIG. 1 is a cross-sectional view illustrating a bearing support structure of a worm shaft end portion of a reduction gear, FIG. 1 (a) is a cross-sectional view of a worm shaft end portion, and FIG. 1 (b) is an enlarged view of a contact portion between a housing and a retainer. The cross-sectional view shows a state where the retainer is displaced in the removal direction and is caught on the annular edge.

  2 is a view for explaining various members constituting the bearing support structure of the worm shaft end, FIG. 2 (a) is a sectional view of the retainer 16 as a fixing member, and FIG. 2 (b) is an elastic member. 2C is a cross-sectional view of the ball bearing 15 with the bush mounted on the inner diameter portion, and FIG. 2D is a cross-sectional view of the holder 19 and the urging member 20.

  3 is a front view of the holder 19 and the urging member 20 shown in FIG. 2D viewed from the axial end direction, FIG. 4 is an external view of the holder 19, and FIG. 5 is a front view of the retainer.

  The bearing support structure at the end of the worm shaft will be described with reference to FIGS. In FIG. 1A, 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. A side surface of the ball bearing 15 on the end side in the axial direction of the outer ring contacts the holder 19.

  Furthermore, the retainer 16 of the housing 11 is fitted into the inner diameter portion where the retainer 16 is press-fitted, and the retainer 16 is removed from the mounting position of the annular edge 16b, that is, the direction opposite to the end of the housing 11 in FIG. An annular groove 11v is formed at the position (see FIGS. 1A and 1B).

  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.

  As shown in FIG. 2A, the retainer 16 is a dish-shaped member composed of a flat surface portion 16a and an annular edge portion 16b. The outer diameter of the annular edge portion 16b is a portion where the retainer 16 is mounted. The inner diameter of the housing 11 is made larger by an appropriate tightening allowance. Further, as shown in FIG. 5, the planar portion 16 a of the retainer 16 is provided with a plurality of cuts 16 c along the circumferential direction.

  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 disposed on the outer side (worm side) of the outer ring of the ball bearing 15, and a retainer 16 is disposed on the outer side thereof. An annular edge portion 16b of the retainer 16 is press-fitted into the inner diameter portion of the housing 11, pressed toward the bag-like bottom portion, and fixed by frictional contact.

  As shown in FIG. 5, the retainer 16 is provided with a plurality of cuts along the circumferential direction on the bottom surface 16a to form an elastic piece 16c, so that a slight movement of the ball bearing 15 in the axial direction is allowed. The

  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.

  Then, when the retainer 16 that is press-fitted into the housing 11 and brought into frictional contact is loosened due to vibration, aging or other causes, and is displaced in the pulling direction, that is, in the direction opposite to the bag-like bottom of the housing 11 in FIG. An annular edge 16 b of the retainer 16 interferes with an annular groove 11 v formed in the housing 11. That is, the outer diameter of the annular edge portion 16b of the retainer 16 is slightly increased due to elastic deformation and is caught in the annular groove portion 11v of the housing 11 (see FIG. 1B), so that the retainer 16 is an annular groove portion of the housing 11. If it is going to pass 11v, it will not come out unless a force larger than the press fit of the retainer 16 is applied, and the retainer 16 can be prevented from coming out.

  According to the above configuration, the annular groove portion 11v formed in the housing 11 allows the retainer 16 to come out even if loosening occurs due to vibration, aging, or other causes between the retainer 16 that is brought into frictional contact with the housing 11. Can be suppressed.

  Even if the end portion of the housing 11 is formed in a bag shape, the holder 19, the biasing member 20 and the ball bearing 15 can be easily mounted inside the housing 11, and the worm shaft 12 can be rotated by the ball bearing 15. Can be supported.

  Further, the holder 19 is formed with a convex portion 19 c extending in parallel with the axial direction, while the housing 11 is formed with a concave portion 11 c corresponding to the convex portion 19 c on the bottom surface of the end portion of the housing 11. 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 becomes 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 axial arm position (coil spring end position) determined by the winding direction and is locked to the locking portion 19d. 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.

  As described above, the bearing support structure of the worm reduction device according to the embodiment of the present invention has been described as an example applied to the electric power steering device. However, the bearing support structure of the worm reduction device of the present invention is not limited to the electric power steering device, but the general machine. Needless to say, the present invention can also be applied to other worm speed reducers.

  A bearing support structure for a worm reduction device that is provided with a holder at the shaft end of the worm shaft and is effective in suppressing the rattling noise of the meshing portion of the worm reduction device, and an annular groove formed in the housing is a holder and bias Provided is a bearing support structure for a worm reduction device that prevents the retainer that holds a member and a ball bearing from coming out, and makes it easy to attach the holder to the housing.

Sectional drawing explaining the bearing support structure of the worm shaft end part of a reduction gear. The figure explaining the structural member of the bearing 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 external view of a retainer. The front view explaining an example of the composition of the conventional worm reduction gear.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Housing 11a Step part 11c Recessed part 11v Annular groove part 12 Worm shaft 12b Thin diameter part 12c Shaft end 15 Ball bearing 16 Retainer 16a Plane part (flat part of retainer)
16b Annular edge (annular edge of retainer)
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 (1)

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. In the bearing support structure of the worm reduction device, the worm shaft is supported in the housing by the bearing arranged in parallel with the holder, and the worm shaft is elastically preloaded in the meshing direction.
The holder and the bearing arranged in parallel with the holder are pressed and held toward the end inside the housing by a retainer mounted inside the housing,
The housing is formed with an annular groove portion along an annular edge of the retainer at an inner diameter portion where the retainer is mounted ,
The annular groove formed in the inner diameter portion of the housing is formed in the direction in which the retainer is removed from the mounting position of the annular edge portion of the retainer,
The retainer is a dish-shaped member composed of a flat portion and an annular edge, and the annular edge is pressed against the inner diameter of the housing and held by frictional contact . Bearing support structure.

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