JP2006151043A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain the reduction of amount of backlash of a meshing part and the reduction of rattling in the axial length direction of a worm due to a rolling bearing supporting the output shaft side and the opposite side of the output shaft of the worm by one elastic annular body and one side rolling bearing. <P>SOLUTION: The outer peripheral surface of a first rolling bearing 7 supporting the output shaft 1a side of the worm 3 interlockingly connected to the output shaft 1a of an electric motor 1 on a housing 5 is made to be an arc-shaped projection surface 7b in the axial length direction, and an arc-shaped recessed surface 53 where the projection surface 7b is internally fitted is provided on the housing 5. The electric power steering device is provided with an elastic annular body 20 having a second pressing part 20b pressing an outer race 8b of a second rolling bearing 8 which supports a first pressing part 20a pressing the worm 3 toward a worm wheel 4, and the opposite side to the output shaft 3a of the worm 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electric power steering apparatus using an electric motor as a generation source of a steering assist force.

  The electric power steering apparatus for a vehicle includes an electric motor for assisting steering and a reduction gear mechanism that transmits a rotational force of the electric motor to the steering means, and the operation of the steering means according to the rotation of the steering means is described above. It is configured to assist by the rotation of the electric motor and reduce the labor burden on the driver for steering.

  The reduction gear mechanism includes a worm as a small gear coupled to the output shaft of the electric motor, and a worm wheel as a large gear meshing with the worm, and the worm rotates into the housing via a rolling bearing. It is supported freely.

  In the electric power steering apparatus using the reduction gear mechanism as described above, backlash occurs at the meshing portion of the worm and the worm wheel, and the worm is rattled in the axial length direction due to the axial clearance of the rolling bearing. become.

Therefore, for backlash, the worm output shaft side is supported by a rolling bearing having a spherical support surface on the outer peripheral surface, and the distance between the rotation center of the worm and worm wheel is long and short on the opposite side of the worm output shaft. By providing an urging means for urging the worm in the direction to become, it is configured to reduce the backlash amount of the meshing portion and eliminate the rattling noise due to backlash at the time of turning, To prevent the worm from rattling in the axial direction, a screw ring that contacts one side of the outer ring of the rolling bearing on the output shaft side is screwed to the housing, and the screw ring presses the outer ring in the axial length direction. There is known an electric power steering apparatus configured to reduce the axial clearance of the rolling bearing and reduce the backlash in the axial direction of the worm (for example, , Patent Document 1.).
JP 2002-211141 A

  However, in the electric power steering apparatus provided with the urging means and the screw ring as in Patent Document 1, the screw ring and the screw ring are screwed to reduce backlash in the shaft length direction of the worm. Therefore, the number of processing steps and assembly steps increases, resulting in high costs, and improvement measures have been demanded. In addition, since the screw ring reduces backlash due to the rolling bearing on the output shaft side, when the worm output shaft is supported by the rolling bearing to increase the worm rotation, In addition to the screw ring, a means for reducing the axial clearance of the rolling bearing opposite to the output shaft is required, and an improvement measure has been demanded in this respect as well.

  The present invention has been made in view of such circumstances, and a main object thereof is to reduce the backlash amount of the meshing portion and to reduce the small gear by a rolling bearing that supports the output shaft side and the output shaft side of the small gear. An object of the present invention is to provide an electric power steering apparatus that can achieve a reduction in backlash in the axial length direction by using one elastic ring body and one rolling bearing.

  An electric power steering apparatus according to a first aspect of the present invention is a small gear coupled to an output shaft of an electric motor, and an output shaft side of the small gear and a side opposite to the output shaft are rotatably supported by a support member. In an electric power steering apparatus comprising first and second rolling bearings and a large gear meshed with the small gear and connected to a steering means, the electric power steering device is configured to assist steering by rotation of the electric motor. The outer peripheral surface of the first rolling bearing has a convex surface that is arcuate in the axial direction, the support member has an arcuate concave surface into which the convex surface is fitted, and the small gear faces the large gear. And an elastic ring body having a second pressing portion that presses an outer ring of the first pressing portion and the second rolling bearing against the first rolling bearing side.

  The electric power steering apparatus according to a second aspect is characterized in that the convex surface and the arc-shaped concave surface form an arc concentric with the center of the first rolling bearing.

  According to the first invention, since the convex surface of the first rolling bearing is fitted in the arc-shaped concave surface of the support member and the movement of the outer ring in the axial length direction is stopped, the first position maintaining member is not provided. Since the position of the rolling bearing can be maintained and the small gear can be pressed against the large gear by the first pressing portion of the elastic ring body and preload can be applied to the meshing portion, the backlash of the meshing portion can be achieved. Further, the elastic ring body has a second pressing portion in addition to the first pressing portion, and the second pressing portion applies a preload in the axial direction to the first and second rolling bearings. Since it can be added, the axial clearance of the first and second rolling bearings can be reduced, and the noise caused by the axial clearance can be reduced. Further, the convex and arcuate concave surfaces can cause the worm to swing at a swing angle that is equal to or greater than the angular clearance of the rolling bearing, thereby increasing the amount of backlash adjustment.

  According to the second aspect of the invention, it is possible to reduce the rocking resistance of the small gear caused by the first rolling bearing, and it is possible to improve the stability of the first rolling bearing within the arc-shaped concave surface.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof. 1 is an enlarged cross-sectional view showing the configuration of a reduction gear mechanism portion of an electric power steering apparatus according to the present invention, FIG. 2 is a cross-sectional view showing the entire structure of the electric power steering apparatus, and FIG. 3 is a sectional view taken along line III-III in FIG. It is an expanded sectional view.

  The electric power steering device includes an electric motor 1 for assisting steering, a worm 3 as a small gear interlocked and connected to an output shaft 1 a of the electric motor 1 via a shaft coupling 2, and a large gear meshing with the worm 3. A reduction gear mechanism A having a worm wheel 4, a housing 5 as a support member that accommodates and supports the reduction gear mechanism A, and steering means 6 connected to the reduction gear mechanism A.

  The steering means 6 is connected to a first steering shaft 61 whose one end is connected to the steering wheel B for steering and the other end of the steering shaft 61, and is twisted by the action of steering torque applied to the steering wheel B. And a second steering shaft 63 connected to the other end portion of the torsion bar 62 and connected to the reduction gear mechanism A. The second steering shaft 63 is, for example, a rack and pinion via a universal joint. This leads to a steering mechanism (not shown).

  The housing 5 accommodates a worm 3 having shaft portions 3b and 3c at both ends of the gear body 3a. The shaft portions 3b and 3c of the worm 3 are rotatably supported by first and second rolling bearings 7 and 8. The first and second storage parts 5a and 4 are accommodated, and the worm wheel 4 is fitted to the second steering shaft 63 and the second steering shaft 63. It is made of aluminum and has a second housing portion 5b supported through the shape.

  The first accommodating portion 5 a is elongated in the axial direction of the worm 3, a support hole 51 for fitting and supporting the first rolling bearing 7 at one end in the longitudinal direction, and a motor mounting portion connected to the support hole 51. 52 is provided, and an arcuate concave surface 53 that forms an arc concentric with the center of the first rolling bearing 7 in the support hole 51, and the support hole 51 from the bisected position of the arcuate concave surface 53 to the motor mounting portion 52 side. Two guide grooves 51 a, 51 a that are notched in parallel with the central axis of the first rolling bearing 7 and are wider than the width of the first rolling bearing 7 are provided. The distance between the bottom surfaces of the guide grooves 51a and 51a is equal to or greater than the diameter of the first rolling bearing 7. Further, the second rolling bearing 8 is supported on the other end of the first accommodating portion 5a via the elastic ring body 20, and a support hole 54 that is tapered with respect to the central axis thereof, and an annular shape that is continuous with the support hole 54. A groove 55 is provided. The electric motor 1 is attached to the motor attachment portion 52.

  The outer peripheral surface of the outer ring 7 a of the first rolling bearing 7 is provided with a convex surface 7 b that is arcuate in the axial length direction and fitted into the arc-shaped concave surface 53, and the convex surface 7 b is fitted into the arc-shaped concave surface 53. Thus, the movement of the outer ring 7a in the axial length direction is stopped, and the position of the first rolling bearing 7 can be maintained. The convex surface 7 b forms an arc concentric with the center of the first rolling bearing 7. The diameter at the apex of the convex surface 7 b is larger than the inner diameter at the edge of the arc-shaped concave surface 53, in other words, larger than the inner diameter of the support hole 51, but at two locations in the circumferential direction of the support hole 51, the guide grooves 51 a facing the arc-shaped concave surface 53. 51a is provided, so that when the outer ring 7a is fitted into the arc-shaped concave surface 53, the outer ring 7a is guided from the motor mounting portion 52 side so that the radial direction of the outer ring 7a is parallel to the central axis of the support hole 51. The convex surface 7b can be fitted into the arc-shaped concave surface 53 by inserting it into the arc-shaped concave surface 53 by inserting it into 51a, 51a and rotating the rolling bearing 90 degrees with the apex of the convex surface 7b of the outer ring 7a positioned in the arc-shaped concave surface 53. It can be done.

  The worm 3 of the reduction gear mechanism A has first and second shaft portions 3b and 3c at both ends of a gear body 3a having a plurality of teeth. The first shaft portion 3 b is fitted into the inner ring 7 c of the first rolling bearing 7 and is rotatably supported by the arc-shaped concave surface 53 by the first rolling bearing 7. The second shaft portion 3 c is press-fitted into the inner ring 8 a of the second rolling bearing 8, and can freely rotate into the support hole 54 via the second rolling bearing 8 and the elastic ring body 20 that is externally fitted to the rolling bearing 8. It is supported. The first shaft portion 3b is provided with a retaining ring 12 that stops relative movement in the axial direction with respect to the first rolling bearing 7.

  The worm wheel 4 is fitted and fixed in the middle of the second steering shaft 63, and the second steering shaft 63 is freely rotatable to the second housing portion 5 b via the third and fourth rolling bearings 9 and 10. It is supported by.

4 is an enlarged cross-sectional view showing the configuration of the elastic ring body, and FIG. 5 is a cross-sectional view taken along the line VV of FIG.
The elastic ring body 20 includes a first pressing portion 20a for pressing the worm 3 toward the worm wheel 4 and an outer ring 8b of the second rolling bearing 8 on the first shaft portion 3b side of the worm 3, in other words, on the output shaft 1a side. The outer ring 8b of the second rolling bearing 8 is press-fitted inside, the outer peripheral surface is tapered with respect to the central axis, and is tapered. It is fitted in the support hole 54.

  The elastic ring body 20 is composed of a rubber ring in which an inner ring member 21 is fitted inside and an outer ring member 22 is fitted outside. The elastic ring body 20 is fitted in a support hole 54 and bent in the axial direction. By fitting the retaining ring 11 in the annular groove 55, an elastic restoring force in the axial length direction is generated, and this elastic restoring force is applied to the second shaft portion 3c via the second rolling bearing 8, and further the gear body. 3a is applied to the inner ring 7c of the first rolling bearing 7 through the first shaft portion 3b, and a preload in the axial length direction is applied to the first and second rolling bearings 7,8. Further, a flange portion 21a that abuts against one side surface of the outer ring 8b protrudes from one end of the inner ring member 21. The inner ring member 21 and the outer ring member 22 are made of a material harder than a rubber material such as a synthetic resin material or a metal material.

  The first pressing portion 20a can be bent in the radial direction, and the worm 3 is pressed against the worm wheel 4 by the elastic restoring force of the first pressing portion 20a. The deflection of the first pressing portion 20a is, for example, the distance L between the centers of the support holes 54 and the support holes 56 and 57 for fitting and supporting the rolling bearings 9 and 10 to φd / 2 of the pitch circle diameter φd of the worm 3. The worm wheel 4 is set to be smaller than the sum of the pitch circle diameters φD and φD / 2 of the worm wheel 4, and the first and second shaft portions 3 b and 3 c of the worm 3 are connected to the first and second rolling bearings 7. , 8, the elastic ring body 20 is bent in the direction in which the distance H between the rotation centers of the worm 3 and the worm wheel 4 becomes longer.

  The output shaft 1a of the electric motor 1 and the first shaft portion 3b of the worm 3 are coupled via a shaft coupling 2 having flexibility so as to be capable of relative movement in the axial direction. The shaft coupling 2 includes a rubber cylindrical member 2a and two transmission cylinder members 2b and 2b fitted in the cylindrical member 2a. The transmission cylinder members 2b and 2b, the output shaft 1a and the first shaft A serration is provided in the portion 3b.

  A torque sensor 13 for detecting the steering torque applied to the steered wheels B by the relative rotational displacement amounts of the first steering shaft 61 and the second steering shaft 63 according to the twist of the torsion bar 62 is provided inside the housing 5. The electric motor 1 is driven and controlled based on the torque detected by the torque sensor 13 and the like.

  In the electric power steering apparatus configured as described above, when the worm 3 is assembled, for example, the first rolling bearing 7 is inserted into the arc-shaped concave surface 53 through the guide grooves 51a and 51a from the motor mounting portion 52 side, and the first rolling bearing 7 is inserted. In a state where the convex surface 7b of the rolling bearing 7 is fitted in the arc-shaped concave surface 53, the worm 3 in which the inner ring 8a of the second rolling bearing 8 is press-fitted into the second shaft portion 3c is inserted into the first housing portion 5a from the support hole 54 side. And the first shaft portion 3 b is fitted into the inner ring 7 c of the first rolling bearing 7. Then, the elastic ring body 20 is inserted into the support hole 54, and the elastic ring body 20 is fitted on the outer ring 8 b of the second rolling bearing 8 to support the second rolling bearing 8 via the elastic ring body 20. The retaining ring 12 is attached to the first shaft portion 3b from the motor mounting portion 52 side while being supported by the hole 54.

  In this case, the elastic ring body 20 can be fixed by pressing the elastic ring body 20 in the axial length direction and fitting the retaining ring 11 into the annular groove 55 in a state where the elastic ring body 20 is bent in the axial length direction. The first pressing portion 20a of the ring body 20 bends in the direction in which the rotation center ring distance H becomes longer (see FIG. 3), and the second pressing portion 20b bends in the axial length direction due to the elastic restoring force of the first pressing portion 20a. The worm 3 can be pressed toward the worm wheel 4 to apply a preload to the meshing portion, and the second rolling bearing 8, the worm 3 and the first rolling bearing 7 are axially lengthened by the elastic restoring force of the second pressing portion 20b. It is possible to apply a preload in the axial direction to the first and second rolling bearings 7 and 8 by pressing in the direction. As a result, the amount of backlash at the meshing portion can be reduced, and the axial gap between the first and second rolling bearings 7 and 8 can be reduced.

  In addition, the worm 3 pressed against the worm wheel 4 by the first pressing portion 20 a swings around the support portion for the first rolling bearing 7, but the outer ring 7 a of the first rolling bearing 7. Since the convex surface 7b forming an arc provided on the inner surface is fitted into the arc-shaped concave surface 53 forming the circular arc provided on the housing 5, the first rolling bearing 7 and the worm 3 are swung around the arc-shaped concave surface 53. Therefore, the allowable swing amount of the worm 3 can be increased.

  Further, since the teeth of the worm 3 and the worm wheel 4 are twisted in the rotational direction with respect to the rotation center line, when a rotational torque is applied to the worm 3 and the worm wheel 4, the worm 3 has a pressing force in the axial direction. Will join. In this case, since the arcuate convex surface 7b provided on the outer ring 7a of the first rolling bearing 7 is fitted into the arcuate concave surface 53 provided on the housing 5, the axial length direction applied to the worm 3 is increased. The pressing force is applied to the arcuate concave surface 53 from the first rolling bearing 7 through the convex surface 7b, and the movement of the worm 3 in the axial length direction can be restricted. Therefore, the amount of bending of the elastic ring body 20 can be limited, and damage due to excessive bending of the elastic ring body 20 can be prevented.

  In the embodiment described above, the convex surface 7b of the first rolling bearing 7 is fitted into the arc-shaped concave surface 53 of the housing so that the axial movement of the outer ring is stopped. 7 may be configured as shown in FIG. 6 and 7 are cross-sectional views showing other embodiments of the main part. In the electric power steering apparatus of FIG. 6, the inner peripheral surface of the fitting ring 14 that is fitted and held in the support hole 51 has an arc-shaped concave surface 53, and the guide groove that faces two places in the circumferential direction of the arc-shaped concave surface 53. The configuration includes 51a and 51a (not shown in FIG. 6). In the electric power steering apparatus of FIG. 7, the inner peripheral surface of the fitting ring 15 that is internally fitted and held in the support hole 51 and has a flange 15 a at its end has an arcuate concave surface 53. Guide grooves 51a and 51a (not shown in FIG. 7) facing two circumferential directions are provided, and after the fitting ring 15 is fitted into the support hole 51, the through holes provided in the flange 15a are provided. The fitting ring 15 is firmly fixed by tightening the male screw 16 in the screw hole 58 provided in the housing 5.

  Further, in the embodiment described above, by setting the center distance L between the support hole 54 and the support holes 56 and 57 to be smaller than the dimension obtained by adding φd / 2 and φD / 2, Although the first pressing portion 20a is configured to bend, for example, the fitting hole of the elastic ring body 20 to the outer ring 8b, in other words, the inner ring member 21 is eccentric in the direction in which the distance H between the rotation centers is shortened. When the second shaft portion 3c of the worm 3 is supported by the second rolling bearing 8, the elastic ring body 20 may be bent in the direction in which the distance H between the rotation centers becomes longer.

In the embodiment described above, the support hole 54 itself of the housing 5 is configured to be tapered. However, the inner peripheral surface of a fitting ring (not shown) fitted in the housing 5 is tapered. You may make it comprise the support hole 54 made | formed.
The reduction gear mechanism A according to the embodiment described above may be a bevel gear or a hypoid gear in addition to a worm gear provided with a small gear that is a worm 3 and a large gear that is a worm wheel 4.

It is an expanded sectional view which shows the structure of the reduction gear mechanism part of the electric power steering apparatus which concerns on this invention. It is sectional drawing which shows the whole structure of the electric power steering apparatus which concerns on this invention. It is an expanded sectional view of the III-III line of FIG. It is an expanded sectional view showing the composition of the elastic ring of the electric power steering device concerning the present invention. It is sectional drawing of the VV line of FIG. It is sectional drawing which shows other embodiment of the principal part of the electric power steering apparatus which concerns on this invention. It is sectional drawing which shows other embodiment of the principal part of the electric power steering apparatus which concerns on this invention.

Explanation of symbols

1 Electric motor 1a Output shaft 3 Worm (small gear)
4 Worm wheel (large gear)
5 Housing (support member)
53 Arc-shaped concave surface 6 Steering means 7 First rolling bearing (bearing)
7b Convex surface 8 Second rolling bearing 20 Elastic ring body 20a First pressing portion 20b Second pressing portion

Claims (2)

  A small gear coupled to the output shaft of the electric motor, first and second rolling bearings rotatably supporting the output shaft side and the opposite side of the output shaft on a support member; In the electric power steering apparatus that includes a large gear that meshes with the gear and that is connected to the steering means, the outer peripheral surface of the first rolling bearing on the output shaft side has an axial length. The support member has an arcuate concave surface into which the convex surface is fitted, and the first pressing portion and the second pressing portion press the small gear toward the large gear. An electric power steering apparatus comprising: an elastic ring body having a second pressing portion that presses an outer ring of the rolling bearing toward the first rolling bearing. The electric power steering apparatus according to claim 1, wherein the convex surface and the arc-shaped concave surface form an arc concentric with the center of the first rolling bearing.

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