JP2016182888A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power steering device capable of improving steering feeling while adjusting backlash of a gear.SOLUTION: A power steering device includes: a worm shaft which is provided to be engaged with a worm wheel in an inclined state of a rotary shaft of the worm shaft to an orthogonal plane with respect to the rotary shaft of the worm wheel; and a holder member formed into a circular shape so that an outer shape in an orthogonal cross section with respect to the rotary shaft of the worm shaft substantially coincides with an inner shape of a holder storage section. The holder member is provided so that the direction of energizing force of a coil spring is located between the direction of reaction force received from the worm wheel when a worm shaft is rotated to a rotation direction one side and the direction of reaction force received from the worm wheel when the worm shaft is rotated to a rotation direction other side.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a power steering apparatus.

  Conventionally, an elastic member is installed on a bearing of a worm shaft that meshes with a worm wheel provided on a steering shaft of a power steering device, and the bearing is urged toward the worm wheel by the elastic member, whereby the worm shaft and the worm shaft are urged. A technique for adjusting a gap (gear backlash) in the engagement of the teeth of the wheel is known.

JP 2013-208933 A

However, the technique described in Patent Document 1 does not consider the direction in which the urging force is applied to the worm shaft by the elastic member, and anisotropy occurs in the meshing force between the worm shaft and the worm wheel depending on the steering direction. There was a problem that the feeling could not be improved.
An object of the present invention is to provide a power steering device capable of improving the steering feeling while adjusting the gear backlash.

  In order to achieve the above object, a power steering device according to the present invention is provided such that a worm shaft meshes with a worm wheel in a state where the rotation axis of the worm shaft is inclined with respect to a plane orthogonal to the rotation axis of the worm wheel. The holder member is formed in a circular shape so that the outer shape in a cross section orthogonal to the rotation axis of the shaft substantially coincides with the inner shape of the holder housing portion. The holder member has a direction of the urging force of the coil spring, and the worm shaft rotates It is provided so as to be positioned between the direction of the reaction force received from the worm wheel when it rotates to one side and the direction of the reaction force received from the worm wheel when the worm shaft rotates to the other side of the rotation direction.

  Therefore, the anisotropy of the urging force accompanying the steering direction can be suppressed, and a stable assist torque can be applied.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram illustrating a vehicle power steering apparatus according to a first embodiment. 1 is an external view of a vehicle power steering apparatus according to a first embodiment. FIG. 3 is a partial perspective view of the vicinity of the worm gear according to the first embodiment. FIG. 3 is a partial cross-sectional view in the vicinity of the pinion shaft according to the first embodiment. 3 is an enlarged cross-sectional view of a backlash adjusting mechanism of Embodiment 1. FIG. FIG. 6 is a six-side view of the elastic member and the holder member according to the first embodiment. It is a semi-transparent perspective view of the backlash adjustment mechanism of Example 1. FIG. 3 is an enlarged schematic view of a bearing housing portion of Example 1. In the holder member of Example 1, it is the schematic showing the installation direction of the bearing accommodating part which has a long hole shape.

  FIG. 1 is a schematic diagram illustrating a vehicle power steering apparatus according to a first embodiment. The power steering device EPS according to the first embodiment includes a steering mechanism, a reduction gear mechanism, an electric motor 3, and a backlash adjusting mechanism 30. The steering mechanism includes a steering shaft S1 connected to the steering wheel SW, an intermediate shaft S2 connected via a universal joint, and a pinion shaft PS connected via a universal joint. A rack and pinion mechanism is configured in which a pinion gear PG formed at the tip of the pinion shaft PS meshes with a rack gear RG formed on the rack bar RB. When the pinion gear PG rotates according to the rotation of the steering wheel SW, the rack bar RB moves left and right. By this movement of the rack bar RB, the steered wheels FR and FL are steered through the link mechanism TR.

  A power steering device EPS is mounted on the pinion shaft PS. The power steering device EPS supplies power to the torque sensor TS that detects the steering torque of the driver, the electric motor 3 that applies assist torque, the controller ECU that controls the operation of the electric motor 3, and the electric motor 3. A battery BATT. The torque sensor TS is arranged on the outer periphery of the pinion shaft PS and closer to the steering wheel SW than the rack bar RB. The electric motor 3 is arranged on the side opposite to the steering wheel SW side of the pinion shaft PS (hereinafter referred to as the tip side of the pinion shaft PS).

  2 is an external view of the vehicle power steering apparatus according to the first embodiment, FIG. 3 is a partial perspective view of the vicinity of the worm gear of the first embodiment, and FIG. 4 is a partial cross-sectional view of the vicinity of the pinion shaft of the first embodiment. 2A is a front view seen from the front front side of the vehicle, and FIG. 2B is a bottom view seen from the bottom side of the vehicle. The power steering device EPS includes a torque sensor housing THS that houses the torque sensor TS, a gear housing HS that houses the reduction gear mechanism, a motor housing MHS that houses the electric motor 3, and a motor cover MC that closes the motor housing MHS. And a rack housing RHS for accommodating the rack bar RB. The gear housing HS has a wheel housing portion HS1 for housing the worm wheel WW and a shaft housing portion HS2 for housing the worm shaft WS.

  A resin worm wheel WW is attached to the pinion shaft PS. The worm wheel WW meshes with a metal worm shaft WS connected to the electric motor 3 to form a reduction gear mechanism by the worm gear WG. When the rotation axis of the worm wheel WW is defined as the wheel axis OWW and the rotation axis of the worm shaft WS is defined as the shaft axis OWS, the shaft axis OWS is inclined with respect to a plane orthogonal to the wheel axis OWW. Intersect. Torque output from the electric motor 3 is transmitted from the worm shaft WS to the worm wheel WW, and assist torque is applied to the pinion shaft PS. The worm wheel WW transmits torque and rotation from the pinion shaft PS to the worm shaft WS. The worm shaft WS transmits torque and rotation from the worm wheel WW to the electric motor 3.

  A first bearing 10 is provided at the end of the worm shaft WS farther from the electric motor 3. The first bearing 10 is a tip side bearing that rotatably holds the tip side of the worm shaft WS. The first bearing 10 is a ball bearing having a ball as a rolling element between a cylindrical inner ring and an outer ring, and is a radial bearing mainly receiving a radial load. The inner ring is fixed to the tip of the worm shaft WS. A backlash adjusting mechanism 30 is provided between the first bearing 10 and the gear housing HS. Details of the backlash adjusting mechanism 30 will be described later. A second bearing 20 is provided on the side of the worm shaft WS close to the electric motor 3. The second bearing 20 is a ball bearing that rotatably holds the electric motor 3 side of the worm shaft WS. The inner ring of the second bearing 20 is in contact with the step portion of the worm shaft WS, and the outer ring is fastened and fixed between the gear housing HS by a lock nut 21. As a result, the worm shaft WS is rotatably supported and the movement in the axial direction is restricted.

(Backlash adjustment mechanism)
Next, the backlash adjustment mechanism will be described. The shaft housing portion HS2 is a space provided on the opposite side to the side where the electric motor 3 is provided in both longitudinal ends of the shaft housing portion HS2, and the inner shape in a cross section orthogonal to the shaft axis OWS is formed in a circle The cylindrical holder accommodating portion HS10 is provided. The backlash adjusting mechanism 30 is fixedly installed in the holder accommodating portion HS10 by press fitting. The holder housing portion HS10 is a simple circular recess without forming a step or the like on the circumferential surface, and does not require a complicated shape. Hereinafter, the direction to be inserted into the holder housing portion HS10 shown in FIG. 4 is referred to as the back side, and the direction on the electric motor 3 side is referred to as the near side. 5 is an enlarged cross-sectional view of the backlash adjusting mechanism of the first embodiment, FIG. 6 is a six-face view of the elastic member and the holder member of the first embodiment, and FIG. 7 is a translucent perspective view of the backlash adjusting mechanism of the first embodiment. is there. 5 and 6 both show a state in which the first bearing 10 is most biased (a state in which the elastic member 32 has the largest diameter), and FIG. 7 is a perspective view of the metal cap 33.
The backlash adjusting mechanism 30 includes a holder member 31, an elastic member 32, and a metal cap 33. The holder member 31 is a member that holds the first bearing 10, and the first bearing 10 is installed on the inner peripheral side thereof so as to be slidable in a certain direction. The elastic member 32 is installed with a part of the elastic member 32 engaged with the holder member 31, and the other part is installed in contact with the first bearing 10, and biases the first bearing 10 in one direction, The tip of the worm shaft WS held by the first bearing 10 is constantly pressed toward the worm wheel WW side (hereinafter referred to as pressing force F). The metal cap 33 is provided so as to cover the outer periphery of the holder member 31, and is a lid member that covers the first bearing 10, the holder member 31, and the elastic member 32. The metal cap 33 is press-fitted into the holder housing part HS10 of the shaft housing part HS2. That is, the backlash adjusting mechanism 30 is press-fitted and fixed in the holder housing portion HS10 of the shaft housing portion HS2 via the metal cap 33.

(Holder member)
The holder member 31 is integrally formed of a resin material. Here, in the description based on FIG. 6, the side approaching the worm wheel WW is defined as the lower side, the direction away from the worm wheel WW is defined as the upper side, and the right side and the left side are defined based on the plan view. The holder member 31 has a bearing accommodating portion 315 that accommodates the first bearing 10. FIG. 8 is an enlarged schematic view of the bearing housing portion of the first embodiment. As shown in FIG. 8, the bearing housing portion 315 has a long hole shape for sliding the first bearing 10 in a certain radial direction (vertical direction shown in FIG. 6), and changes in the center O of the first bearing 10. As seen, the first bearing 10 slides in the range from the center Omin of the first bearing 10 at the initial position to the center Omax of the first bearing 10 at the maximum displacement position. The arc shape of the inner peripheral surface 315a opposite to the worm wheel WW is a combination of an arc having a radius smaller than the radius of the outer peripheral surface 10b of the first bearing 10 and an arc having a radius larger than the radius of the outer peripheral surface 10b. It is configured. As a result, the first bearing 10 is restrained from fitting into the arc of the bearing housing portion 315, and a stable slide is ensured. Note that the arc shape of the inner peripheral surface 315b on the worm wheel WW side is not so much loaded, so it is formed in the same arc as the radius of the first bearing 10, but may be formed in the same manner as the upper arc.

The periphery of the elongated hole-shaped bearing housing portion 315 is surrounded by an outer peripheral wall 310. A ring groove 311 is formed on the outer peripheral surface of the outer peripheral wall 310, and an O-ring 34 is attached to the ring groove 311. And it functions as a buffer member between the metal cap 33 mentioned later.
On the upper side of the outer peripheral wall 310, an upper guide portion 314 having a side end surface 318 facing downward is erected along the outer peripheral wall 310. The inner peripheral side of the upper guide portion 314 is formed in the same shape as the upper inner peripheral surface 315a of the bearing accommodating portion 315. Further, a holding groove 314c for holding the elastic member 32 is formed on the inner periphery of the upper guide portion 314. The holding groove 314c is formed at a position overlapping the first bearing 10 in the radial direction when the first bearing 10 is mounted. Further, a locking portion 314a extending toward the inner diameter side is provided on the front side of the holding groove 314c. The locking portion 314a restricts the movement of the elastic member 32 and the first bearing 10 described later in the axial direction. Further, the upper guide portion 314 is formed with a through hole 314b that penetrates the holding groove 314c and the outer peripheral surface of the holder member 31 in the radial direction. The through hole 314b becomes a hole for forming the holding groove 314c when the holder member 31 is molded, and improves the moldability of the holder member 31.

Further, a lower guide portion 313 having a side end face 319 facing the left and right sides is formed upright along the outer peripheral wall 310 below the outer peripheral wall 310. The inner peripheral side of the lower guide portion 313 is formed in the same shape as the bearing housing portion 315. Further, a holding groove 313 a for holding the elastic member 32 is formed on the outer periphery of the lower guide portion 313. The holding groove 313a is formed at a position overlapping the first bearing 10 in the radial direction when the first bearing 10 is mounted. Further, an engaging convex portion 313b standing on the near side is formed at the approximate center of the lower guide portion 313. This engagement convex part 313b restrict | limits the relative rotation with the holder member 31 between the metal caps 33 mentioned later.
The upper surface 310a of the outer peripheral wall 310 where the upper guide part 314 and the lower guide part 313 are not erected is formed so as to be at the same position as the rear end of the holding grooves 313a and 314a, and holds a part of the elastic member 32 doing. Further, on the right side of the upper surface 310a, a part thereof is cut out toward the back side, and a movable range portion 312 that movably accommodates the other end portion 321 of the elastic member 32 to be described later, and movement in an excessive rotational direction. A rotation restricting portion 312a for restricting is formed.

In the above configuration, the elastic member housing portion in which the elastic member 32 is installed includes the holding groove 313a formed on the outer periphery of the lower guide portion, the upper surface 310a of the outer peripheral wall 310, and the holding groove formed on the inner periphery of the upper guide portion. 314c, the movable part 312 and the rotation restricting part 312a are configured to be substantially circumferential. The elastic member accommodating portion is provided offset from the bearing accommodating portion 315 in the axial direction. In other words, the elastic member housing portion is provided on the front side, and the bearing housing portion 315 is provided on the back side.
Further, the thickness (diameter cross-sectional dimension) of the outer peripheral wall 310 surrounding the bearing housing part 315 is formed larger than the thickness (radial cross-sectional dimension) of each part constituting the elastic member housing part. That is, when the first bearing 10 slides upon receiving a load from the worm shaft WS, the first bearing 10 abuts on the inner periphery of the outer peripheral wall 310 and the load acts. At this time, by forming the outer peripheral wall 310 thick, the radial dimension is effectively used to ensure the strength.
An opening 317 having a larger diameter than the inner peripheral surface 10 a of the first bearing 10 and a smaller diameter than the outer peripheral surface 10 b of the first bearing 10 is formed on the bottom surface 316 of the holder member 31. Even if the tips of the worm shafts WS attached to the first bearing 10 protrude slightly, they do not interfere with each other through the opening 317.

(Elastic member)
The elastic member 32 includes a main body 320, and one end 322 (see FIG. 5) and the other end 321 provided at both ends of the main body 320. The main body 320 is formed of an elastic material in a circular arc shape, and specifically, is constituted by a coil spring formed by processing a wire spring formed of spring steel into a wound shape. The one end 322 is formed at a position where the end of the coil spring is covered with the locking portion 314a with the free end. The position of the one end 322 may be another position that is not covered by the locking portion 314a. The one end portion 322 is provided such that the relative position with respect to the other end portion 321 can be displaced when the main body portion 320 undergoes a diameter expansion deformation. The inner periphery of the main body 320 is provided so as to directly contact the outer periphery 10b of the first bearing 10. The other end 321 is formed by bending the terminal end of the coil spring, and is formed to extend from the main body 320 in parallel with the axial direction of the worm shaft WS. The other end portion 321 is disposed so as to be accommodated in the movable range portion 312 of the holder member 31. The other end portion 312 moves freely within the movable range portion 312 while the rotation restricting portion 312a of the holder member 31 restricts relative movement in the rotation direction relative to the holder member 31 around the rotation axis of the worm shaft WS. Yes.

  The elastic member 32 is disposed so as to be positioned on the inner periphery of the upper guide portion 314 through the outer periphery of the lower guide portion 313 with respect to the elastic member housing portion of the holder member 31, and the inner peripheral surface of the lower guide portion 313. The first bearing 10 is elastically held between 315b and the inner periphery of the main body 320. That is, the initial position is a state in which the inner peripheral surface 315b of the lower guide portion 313 and the outer peripheral surface of the first bearing 10 are in contact with each other. When an upper force is applied from the worm shaft WS in this state, the first bearing 10 slides upward against the elastic force of the elastic member 32. At this time, the elastic member 32 is stretched toward the upper guide portion 314 in a state where movement in the radial direction is restricted by the lower guide portion 313. Since both the one end portion 322 and the other end portion 321 are basically free ends, the main body portion 320 undergoes a diameter expansion deformation, and an elastic force accompanying this deformation is utilized. Thus, by utilizing the diameter expansion deformation, the wire length of the elastic member 32 can be used in a wide range, and as a result, the spring constant can be set small. Therefore, the load change with respect to the slide amount can be set gently.

(Metal cap)
The metal cap 33 is provided between the holder housing portion HS10 of the shaft housing portion HS2 and the holder member 31. The metal cap 33 includes a cylindrical annular portion 330, an axial stopper portion 331 that is reduced in diameter so as to close the opening on the front side of the annular portion 330, and a through hole that opens at the center of the axial stopper portion 331. The mouth 332 is formed of a metal material. Further, in the portion where the lower guide portion 313 of the through-hole 332 of the axial stopper portion 331 is located, a notch 334 through which the engaging convex portion 313b can penetrate and a part on the back side on both sides of the notch 334 are provided. A bent leaf spring portion 333 is formed. Accordingly, relative rotation between the holder member 31 and the metal cap 33 is restricted (a detent portion of the holder member), and the first bearing 10 is urged in the axial direction by the leaf spring portion 333, whereby the axial direction is reduced. Suppresses rattling. Further, the metal cap 33 has a plurality of drop-off restricting portions 335 in the circumferential direction on the back side of the annular portion 330. Thereby, the moldability of the holder accommodating portion HS10 is improved by preventing the holder member 31 from falling off without performing the processing for the dropping restriction on the shaft accommodating portion side. The inner peripheral diameter of the annular portion 330 of the metal cap 33 is formed slightly larger than the outer peripheral diameter of the outer peripheral wall 310 of the holder member 31, and has a size having a radial clearance. Thereby, the difference in linear expansion coefficient is absorbed.

(Assembly)
In the backlash adjusting mechanism 30, the elastic member 32 is assembled to the holder member 31, and the first bearing 10 is attached to the bearing housing portion 315. Further, after attaching the O-ring 34 to the ring groove 311, the metal cap 33 is covered, the drop-off restricting portion 335 is bent, and the holder member 31 is fixed. The assembly parts are press-fitted into the holder housing portion HS10, and the worm shaft WS is inserted into the first bearing 10 in this state, whereby the apparatus is assembled. In the assembled state, there is a gap between the outer peripheral surface 10b of the first bearing 10 and the inner peripheral surfaces 315a and 315b of the holder member 31 in both the separating direction and the contracting direction of the worm shaft WS and the worm wheel WW. Thus, the first bearing 10 is movable in the direction between the worm shafts WS.

The main body 320 is provided so as to undergo a diameter expansion deformation when the first bearing 10 moves in a direction away from the worm wheel WW while holding the worm shaft WS. The main body 320 urges the first bearing 10 in one direction (the lower side shown in FIG. 6) in a state where the first bearing 10 holds the worm shaft WS and constantly presses the first bearing 10 toward the worm wheel side.
As the temperature rises, the worm wheel WW having resin teeth expands, and the worm shaft WS (and the first bearing 10) that meshes with the worm wheel WW increases the distance between the worm shaft WS and the worm wheel WW. Force in the direction to act. At this time, the first bearing 10 of the backlash adjusting mechanism 30 moves in a direction away from the worm wheel WW against the urging force of the elastic member 32. The movement is possible until the outer peripheral surface 10b of the first bearing 10 comes into contact with the inner peripheral surface 315a that is the inner wall of the holder member 31 in the above direction. Therefore, it is possible to adjust the backlash while avoiding a sudden increase in friction caused by the temperature rise.

When the temperature decreases, the worm wheel WW contracts. At this time, the first bearing 10 of the backlash adjusting mechanism 30 is moved in the direction toward the worm wheel WW by the urging force of the elastic member 32, whereby the distance between the worm shaft WS and the worm wheel WW is reduced. Decrease by WW shrinkage. The movement is possible until the outer peripheral surface 10b of the first bearing 10 comes into contact with the inner peripheral surface 315b which is the inner wall in the direction of the holder member 31. Therefore, the backlash can be adjusted regardless of the temperature drop.
Even when the worm gear (worm shaft or worm wheel) is worn by use, the backlash can be adjusted by reducing the distance between the axes by the urging force of the elastic member 32 as in the case of the temperature drop.
When the meshing force of the worm gear WG is generated, a radial force acts on the worm shaft WS in a direction away from the worm wheel WW, and the outer periphery of the first bearing 10 is applied to the inner peripheral surface 315a which is the inner wall of the holder member 31 in the above direction. Move until the surface 10b touches. However, since the amount of backlash to be adjusted is very small, it does not affect the meshing, and the gears mesh smoothly.

  FIG. 9 is a schematic view showing the installation direction of the bearing housing portion having a long hole shape in the holder member of the first embodiment. When the driver steers the steering wheel SW, the worm wheel WW rotates together with the pinion shaft PS. Then, necessary assist torque is transmitted from the electric motor 3 to the worm wheel WW via the worm gear WG according to the steering torque. At this time, the direction of the force acting between the worm shaft WS and the worm wheel WW changes according to the steering direction of the steering wheel SW. In other words, the direction of the urging force applied by the elastic member 32 changes according to the steering angle.

  Temporarily, the bearing moving direction (direction in which the urging force is applied) from the shaft axis OWS toward the inner peripheral surface 315a opposite to the worm wheel WW is a longitudinal direction of the bearing housing portion 315, and the worm shaft WS and the worm. A case is assumed in which the setting is made out of the region where the force acting between the wheels WW is applied. In this case, in one steering direction, the reaction force received from the first bearing 10 decreases as the steering is performed, and in the other steering direction, the reaction force received from the first bearing 10 increases as the steering is performed. In this case, the transmission torque of the worm gear WG varies depending on the steering direction, which may give the driver a feeling of strangeness. Therefore, in the first embodiment, the direction of the urging force of the elastic member 32 is the direction of the reaction force received from the worm wheel WW when the worm shaft WS rotates in one direction of rotation, and the direction of the worm shaft WS in the other direction of rotation. The holder member 31 is set so as to be positioned between the direction of the reaction force received from the worm wheel WW when rotated.

FIG. 9A is a diagram illustrating a case where the longitudinal direction of the bearing accommodating portion 315 is set in an action region of a force acting between the worm shaft WS and the worm wheel WW. By installing the holder member 31 in this manner, the anisotropy of the urging force accompanying the steering direction can be suppressed, and a stable assist torque can be applied.
FIG. 9B shows a case where the longitudinal direction of the bearing accommodating portion 315 is in the action region of the force acting between the worm shaft WS and the worm wheel WW, and the longitudinal direction is set near the center of the action region. FIG. Thus, the anisotropy accompanying the steering direction can be further suppressed by setting the longitudinal direction to approximately the center of the action region.

[Effect of Example 1]
The effects of the present invention ascertained from Example 1 are listed below.

(1) A steering mechanism that transmits the steering operation of the steering wheel SW to the steered wheels, an electric motor 3 that applies a steering force to the steering mechanism, and a rotational force of the electric motor 3 provided between the steering mechanism and the electric motor 3 A speed reducer that transmits to the steering mechanism, and includes a worm shaft WS provided on the electric motor 3 side and a worm wheel WW provided on the steering mechanism side. The worm shaft WS is a rotational axis OWW of the worm wheel WW. The worm gear WG provided so as to mesh with the worm wheel WW in a state where the rotation axis OWS of the worm shaft WS is inclined with respect to the plane orthogonal to the wheel, the wheel housing portion HS1 for housing the worm wheel WW, and the shaft for housing the worm shaft WS Installed on the opposite side of the gear housing HS having the housing portion HS2 and the side where the electric motor 3 is provided from both ends in the longitudinal direction of the shaft housing portion HS2. A holder housing portion HS10 having a circular inner diameter in a cross section orthogonal to the rotation axis of the worm shaft WS, and a bearing housing portion 315 provided in the holder housing portion HS10. The worm shaft WS The holder member 31 is formed in a circular shape so that the outer shape in a cross section orthogonal to the rotation axis OWS substantially matches the inner shape of the holder housing portion HS10, and the bearing member 315 of the holder member 31 is provided in the bearing housing portion 315. The first bearing 10 that rotatably holds the worm shaft WS on the side opposite to the side on which the electric motor 3 is provided, and the elastic member 32 provided on the gear housing HS, are formed in an arc shape. Main body 320 and one end 322 and the other end 321 provided at both ends of main body 320, and main body 320 is formed from worm wheel WW with first bearing 10 holding worm shaft WS. The first bearing 10 is biased by expanding and deforming when moving in the separating direction, and the one end 322 of the elastic member 32 is configured as a free end that is not fixed. A coil spring formed so that the main body portion expands and deforms when the position is displaced, and the holder member 31 has a biasing force direction of the coil spring when the worm shaft WS rotates in one direction of rotation. The direction of the reaction force received from the worm wheel WW and the direction of the reaction force received from the worm wheel WW when the worm shaft WS rotates to the other side in the rotation direction are provided.
Therefore, the anisotropy of the urging force accompanying the steering direction can be suppressed, and a stable assist torque can be applied.

(2) In the holder member 31, the direction of the urging force of the coil spring is such that the direction of the reaction force received from the worm wheel WW when the worm shaft WS rotates in one direction of rotation and the worm shaft WS rotates in the other direction of rotation. Is provided so as to be positioned approximately in the middle of the direction of the reaction force received from the worm wheel WW.
Therefore, the anisotropy of the urging force accompanying the steering direction can be further suppressed, and a stable assist torque can be applied.

[Other embodiments]
As mentioned above, although the form for implement | achieving this invention has been demonstrated based on the Example, the concrete structure of this invention is not limited to an Example, The design change of the range which does not deviate from the summary of invention Are included in the present invention.
In order to prevent the holder member from rattling in the metal cap of the backlash adjusting mechanism, the O-ring is installed in the first embodiment. However, the O-ring may be eliminated and a claw may be provided on the metal cap. Further, for example, in Example 1, a protrusion protruding from the outer peripheral surface is provided on the outer wall of the holder member without providing an O-ring (and an O-ring installation groove), and this protrusion contacts the inner peripheral surface of the metal cap. It is good also as preventing backlash by contacting.
In the embodiment, a coil spring wound twice in the holding groove is used as the elastic member, but the number of turns can be selected as appropriate. For example, it is good also as winding only a half circumference. Further, the shape of the coil spring is not particularly limited, and both ends of a small-diameter coil spring (diameter is large enough to fit into the holding groove) are connected to form a ring shape, and the ring-shaped spring is wound around the holding groove. It is good to do. Further, as the elastic member, for example, an O-ring (made of rubber) may be used instead of the coil spring.

3 Electric motor 10 1st bearing (bearing)
30 Backlash adjusting mechanism 31 Holder member 32 Elastic member 33 Metal cap 34 O-ring 41 First holder member 42 Second holder member 51 Holder member 52 Elastic member
315 Bearing housing
320 Body
321 other end
321a Rotation restriction part
322 one end
335 drop-off regulation department
413a Holding groove
414b Through hole
414c Holding groove
415 Base housing (bearing housing)
421 pedestal
520 Main unit
521 other end
522 one end
EPS power steering system
HS1 wheel housing
HS10 recess
HS2 Shaft housing PS Pinion shaft SW Steering wheel WS Worm shaft WW Worm wheel

Claims (2)

A steering mechanism that transmits the steering operation of the steering wheel to the steered wheels;
An electric motor for applying a steering force to the steering mechanism;
A reduction gear provided between the steering mechanism and the electric motor to transmit the rotational force of the electric motor to the steering mechanism, provided on a worm shaft provided on the electric motor side and on the steering mechanism side A worm gear, wherein the worm shaft is provided so as to mesh with the worm wheel in a state where the rotation axis of the worm shaft is inclined with respect to a plane orthogonal to the rotation axis of the worm wheel;
A gear housing having a wheel housing portion for housing the worm wheel and a shaft housing portion for housing the worm shaft;
A holder provided on the opposite side to the side on which the electric motor is provided in both longitudinal ends of the shaft housing portion, the holder having a circular inner shape in a cross section orthogonal to the rotation axis of the worm shaft A containment section;
A holder member provided in the holder housing portion, having a bearing housing portion, and formed in a circular shape so that an outer shape in a cross section perpendicular to the rotation axis of the worm shaft substantially matches an inner shape of the holder housing portion;
A bearing provided in the bearing housing portion of the holder member and rotatably holding the worm shaft on the opposite side of the both ends of the worm shaft from the side on which the electric motor is provided;
An elastic member provided in the gear housing, comprising a main body portion formed in an arc shape and one end portion and the other end portion provided at both ends of the main body portion, the main body portion including the bearing When the worm shaft is held and moved in a direction away from the worm wheel, the bearing is biased by expanding its diameter, and the one end of the elastic member is configured as a free end that is not fixed, A coil spring formed so that the relative position of the one end portion relative to the other end portion is displaced and the main body portion is deformed to expand in diameter;
When the urging force of the coil spring rotates in one direction of rotation, the direction of the reaction force received from the worm wheel and when the worm shaft rotates in the other direction of rotation. The power steering device is provided so as to be positioned between the direction of the reaction force received from the worm wheel. The power steering apparatus according to claim 1, wherein
When the urging force of the coil spring rotates in one direction of rotation, the direction of the reaction force received from the worm wheel and when the worm shaft rotates in the other direction of rotation. The power steering device is provided so as to be positioned approximately in the middle of the direction of the reaction force received from the worm wheel.

Images