WO2017090327A1

WO2017090327A1 - Power steering system

Info

Publication number: WO2017090327A1
Application number: PCT/JP2016/079896
Authority: WO
Inventors: 雄介福田
Original assignee: 日立オートモティブシステムズ株式会社
Priority date: 2015-11-24
Filing date: 2016-10-07
Publication date: 2017-06-01
Also published as: JP2017094884A

Abstract

The purpose of the present invention is to provide a power steering system such that the support stability of a worm shaft and the steering feeling can be improved. This power steering system is equipped with: a bearing which is provided at the end on the opposite side of a worm shaft from an electric motor in the direction of the rotational axis of the worm shaft, and rotatably supports the worm shaft; and an elastic member which is provided on the peripheral side of the bearing, and applies biasing force to the bearing at a plurality of points in the direction about the rotational axis of the worm shaft so as to reduce the backlash between a worm wheel and the worm shaft.

Description

Power steering device

The present invention relates to a power steering device.

In this type of device, an elastic member is installed on a worm shaft bearing that meshes with a worm wheel provided on a steering shaft of a power steering device, and the elastic member biases the bearing toward the worm wheel side. The clearance (gear backlash) in the meshing between the teeth of the worm shaft and the worm wheel is adjusted.

JP 2013-208933 A

However, in the technique described in Patent Document 1, the urging force to the worm shaft by the elastic member is applied from one point, and if anisotropy occurs in the meshing force between the worm shaft and the worm wheel depending on the steering direction, the worm There was a problem that the support stability of the shaft could not be obtained and the steering feeling could not be improved.
An object of the present invention is to provide a power steering device capable of improving the support stability and steering feeling of a worm shaft.

A power steering device according to an embodiment of the present invention is provided on the end side of a worm shaft on the opposite side of the electric motor in the direction of the rotation axis of the worm shaft, and on the outer peripheral side of a bearing that rotatably supports the worm shaft. In addition, an elastic member is provided that applies a biasing force to the bearing at a plurality of power points in a direction around the rotation axis of the worm shaft so as to reduce backlash between the worm wheel and the worm shaft.

Therefore, according to the power steering device according to an embodiment of the present invention, the elastic member applies a biasing force to the bearing at a plurality of power points, so that the support stability of the worm shaft is higher than that when the power point is only one point. Can be improved.

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 a worm shaft according to the first embodiment. 3 is an enlarged cross-sectional view of a backlash adjusting mechanism of Embodiment 1. FIG. It is the front surface of the elastic member of Example 1, and a holder member, a plane, a right side surface, and a perspective view. FIG. 3 is an enlarged schematic view of a bearing housing portion of Example 1. It is the schematic showing the relationship between the backlash adjustment mechanism of Example 1, a worm shaft, and a worm wheel. FIG. 10 is a schematic diagram illustrating an operation of a backlash adjusting mechanism according to the second embodiment.

FIG. 1 is a schematic diagram showing 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.

The 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).

FIG. 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 worm 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. 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.

The resin worm wheel WW is attached to the pinion shaft PS. The worm wheel WW meshes with a worm shaft WS formed with a metal worm connected to the electric motor 3, and constitutes 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.

The 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. FIG. 5 is an enlarged sectional view of the backlash adjusting mechanism of the first embodiment, and FIG. 6 is a front view, a plane surface, a right side surface, and a perspective view of the elastic member and the holder member of the first embodiment. 5 and 6 show the state in which the first bearing 10 is most biased (the state in which the elastic member 32 has the largest diameter).

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. A part of the elastic member 32 is installed in engagement with the holder member 31, and the other part is installed in contact with the first bearing 10. FIG. 8 is a schematic diagram illustrating a relationship between the backlash adjusting mechanism, the worm shaft, and the worm wheel according to the first embodiment. A hatched area P in FIG. 8 is an engagement area between the worm shaft WS and the worm wheel WW. The elastic member 32 urges the first bearing 10 to the hatched area P in FIG. 8 and constantly presses the tip of the worm shaft WS held by the first bearing 10 toward the worm wheel WW side (hereinafter referred to as “the worm wheel WW”). Pressing force F: Refer to the arrow in FIG.

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. 7 is an enlarged schematic view of the bearing housing portion of the first embodiment. As shown in FIG. 7, 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. In FIG. 7, the amount of displacement accompanying the slide movement is indicated by α. 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 a cylindrical 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 described later.
Two upper guide portions 314 are erected along the outer peripheral wall 310 on both sides of a lower guide portion 313, which will be described later, above 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 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 is doing. Further, on the right side of the upper surface 310a, a rotation restriction portion 312a that is partially cut away toward the back side, accommodates the other end portion 321 of the elastic member 32 described later, and restricts movement in the rotation direction is formed. Yes.

In the above-described configuration, the elastic member accommodating portion in which the elastic member 32 is installed is substantially circumferential from 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 rotation restricting portion 312a. It is configured. 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 and the other end 321 (see FIG. 8) provided at both ends of the main body 320. The main body 320 is formed of an elastic material in an arc shape, and specifically, a wire spring formed of spring steel is curved so as to cover the lower guide portion 313 from the other end portion 312 from the outer periphery. Unlike the formed first spring part 320a and the curved shape of the first spring part 320a, the second spring part 320b formed linearly through the inner periphery of the upper guide part 314 located on the right side of FIG. A fourth spring portion 320d formed linearly on the inner circumference of the upper guide portion 314 located on the left side of FIG. 8, and a third curved shape connecting the second spring portion 320b and the fourth spring portion 320d. And a spring portion 320c.

That is, the main body 320 has a shape surrounding the first bearing 10 in the direction around the rotation axis of the worm shaft WS. Thereby, compared with the case where an elastic member is individually arrange | positioned to several power points, the apparatus is reduced in size. In addition, since the one end 322 and the other end 321 are provided so as to be separated from each other, stick-slip caused by a frictional force change due to contact between the wire spring ends is prevented. Further, a plane PX in which the two force points of the elastic member 32 are virtual planes orthogonal to the rotation axis of the worm wheel WW and overlap with virtual lines orthogonal to both the rotation axis of the worm wheel WW and the rotation axis of the worm shaft WS. It is provided to straddle. As a result, the outer peripheral surface 10b of the first bearing 10 and the main body 320 have a point A on the inner peripheral side of the second spring part 320b formed linearly and a point B on the inner peripheral side of the third spring part 320c. And the curved first spring portion 320a and the third spring portion 320c are not in contact with each other. In addition, in order to apply a biasing force to the first bearing 10 in the second spring part 320b and the third spring part 320c formed in a straight line, the position of the force point changes as the diameter of the elastic member 32 increases. Also suppresses the change in the direction of action of the biasing force. However, the portion where the outer peripheral surface 10b of the first bearing 10 contacts the main body 320 may be a line contact or a surface contact having a predetermined area regardless of only the point contact. .

The one end portion 322 is formed so that the end of the coil spring is a free end and is located on the lower guide portion 313 side than the rotation restricting portion 312a. Note that the position of the one end portion 322 may be located closer to the upper guide portion 314 than the rotation restricting portion 312a. 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 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 321 is arranged so as to be accommodated in the rotation restricting portion 312a of the holder member 31. The other end portion 312 functions as a starting point of the elastic force of the elastic member 32 while restricting relative movement in the rotational direction relative to the holder member 31 around the rotation axis of the worm shaft WS by the rotation restricting portion 312a of the holder member 31. To do.

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 the one end portion 322 is a free end, the main body portion 320 is deformed to expand its diameter, and a force F is generated downward using the elastic force accompanying the deformation (see FIG. 8). 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. The lower guide portion 313 is provided so as to be offset in the worm wheel side of the holder member 31, that is, in the direction of the resultant force F of the reaction force F1 and the reaction force F2. Therefore, the power points A and B can be easily laid out at positions facing the resultant force F, and the first bearing 10 can be stably held.

(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 stopper 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 axial shaking of the first bearing 10 is suppressed by the stopper portion 333. 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.

(Operation of backlash adjustment mechanism)
FIG. 8 is a schematic diagram illustrating the operation of the backlash adjusting mechanism 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 F, which is the resultant force of the urging forces FA and FB from the two points of the elastic member 32, is received from the worm wheel WW when the worm shaft WS rotates in one direction of rotation. The holder member 31 is installed so as to face the reaction force F1 and the resultant force F12 of the reaction force F2 received from the worm wheel WW when the worm shaft WS rotates in the other direction of rotation. In other words, the holder member 31 is installed so that the longitudinal direction of the bearing accommodating portion 315 and the direction of the resultant force F12 coincide. The anisotropy of the urging force accompanying the steering direction can be suppressed in the direction of the resultant force vector of the resultant force F12, and a stable assist torque can be applied.

Further, the lower guide portion 313 is arranged offset in the direction of the resultant force vector F of the force FA and FB urged by the elastic member 32. Accordingly, the force points A and B and the lower guide portion 313 are positioned so as to face each other with the rotation axis of the worm shaft WS interposed therebetween, and the force points A and B can be easily laid out at positions facing the urging force F.

[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 for applying a steering force to the steering mechanism;
There is a worm gear WG provided between the steering mechanism and the electric motor 3 for transmitting the rotational force of the electric motor 3 to the steering mechanism, provided on the worm shaft WS provided on the electric motor 3 side and the steering mechanism side. A worm gear WG having a worm wheel WW provided to mesh with the worm;
A gear housing HS having a wheel housing portion HS1 for housing the worm wheel WW and a shaft housing portion HS2 for housing the worm shaft WS;
A first bearing 10 (bearing) provided on the end side of the worm shaft WS opposite to the electric motor 3 in the direction of the rotation axis of the worm shaft WS and rotatably supporting the worm shaft WS;
Provided on the outer periphery of the first bearing 10 and attached to the first bearing 10 at a plurality of power points in the direction around the rotation axis of the worm shaft WS so as to reduce backlash between the worm wheel WW and the worm shaft WS. An elastic member 32 for applying a force;
Have
Therefore, since the elastic member 32 applies urging force to the first bearing 10 at a plurality of power points, the support stability of the worm shaft WS can be improved as compared with the case where the power point is only one point.

(2) In the power steering device according to (1) above,
The elastic member 32 applies an urging force to the first bearing 10 at two power points.
That is, the support point of the worm shaft WS in the direction around the rotation axis of the worm shaft WS is three points including the mesh point with the worm wheel WW, and the support stability is the best.
(3) In the power steering device according to (2),
The elastic member 32 is a virtual plane in which the two force points of the elastic member 32 are orthogonal to the rotation axis of the worm wheel WW and are orthogonal to both the rotation axis of the worm wheel WW and the rotation axis of the worm shaft WS. It is provided so as to straddle the overlapping plane PX.
Therefore, the balance between the two power points and the reaction force from the worm wheel is improved, and the support stability can be further improved.

(4) In the power steering apparatus described in (1) above,
The elastic member 32 has a direction of the resultant force vector of a plurality of force points when the worm shaft WS rotates to one side of the rotation direction and the reaction force received from the worm wheel WW and when the worm shaft WS rotates to the other side of the rotation direction. It is provided so as to be positioned between the direction of the reaction force received from the worm wheel WW.
Therefore, it is possible to appropriately apply an urging force to reaction forces from the worm wheels WW that are different in the left and right steering directions of the steering wheel SW.
(5) In the power steering device according to (4),
The elastic member 32 has a worm when all of a plurality of power points are applied when the worm shaft WS rotates in one direction of rotation and the reaction force received from the worm wheel WW and when the worm shaft WS rotates in the other direction of rotation. It is provided so as to be located outside the range sandwiched between the direction of the reaction force received from the wheel WW.
Therefore, the support stability can be further improved by widening the support span of a plurality of power points.

(6) In the power steering device according to (4),
The elastic member 32 is configured such that the direction of the resultant force vector of the plurality of force points is the reaction force received from the worm wheel WW when the worm shaft WS rotates in one direction of rotation and the worm shaft when the worm shaft WS rotates in the other direction. It is provided so as to substantially coincide with the direction of the resultant force vector of the reaction force received from the wheel WW.
Therefore, it is possible to more appropriately apply the urging force to the reaction force from the worm wheel WW that is different in the left and right steering directions of the steering wheel SW.
(7) In the power steering device according to (1),
The elastic member 32 has a shape surrounding the outer periphery of the first bearing 10 in the direction around the rotation axis of the worm shaft WS.
That is, since the elastic member 32 has a shape surrounding the first bearing 10, it is possible to reduce the size of the device as compared with the case where the coil spring is provided at each of the plurality of power points.
(8) In the power steering device according to (7),
The elastic member 32 is a wire spring, and both ends of the wire spring are provided so as to be separated from each other.
Therefore, it is possible to prevent stick slip caused by a change in frictional force due to contact between the ends of the wire springs.

(9) In the power steering device according to (7), the outer peripheral wall 310 (cylindrical portion) that surrounds the outer peripheral side of the first bearing 10, the holding groove 313 a that holds the elastic member 32, and the upper surfaces of the outer peripheral wall 310 310a (elastic member holding part) is provided, and it has the holder member 31 provided in the shaft accommodating part HS2.
That is, by providing the elastic member 32 in the gear housing HS while being held by the holder member 31, the assembling workability is better than when the elastic member 32 is directly assembled to the gear housing HS.
(10) In the power steering device according to (9) above,
The holder member 31 is opposed to the outer peripheral surface 10b of the first bearing 10 in the radial direction of the rotation axis of the worm shaft WS, and is provided on the worm wheel WW side in the direction around the rotation axis of the worm shaft WS. A lower guide portion 313 (elastic member locking portion) is provided,
The elastic member 32 is a wire spring, and the other end 321 that is a part of the elastic member 32 in the direction around the rotation axis of the worm shaft WS is on the outer peripheral side of the lower guide portion 313 (elastic member locking portion). The elastic member 32 is locked, and one of both end portions of the elastic member 32 is locked to a rotation restricting portion 312a (spring end locking portion) provided on the holder member 31.
That is, the other end portion 321 that is the end portion on the rotation restricting portion 312a side in the circumferential range of the elastic member 32 is locked to the holder member 31, so that the holder member 31 accompanying the expansion and contraction of the spring diameter. The relative movement amount with respect to is small. Accordingly, the frictional sliding accompanying the relative movement between the elastic member 32 and the lower guide portion 313 is reduced, the occurrence of hysteresis accompanying this is suppressed, and the urging force can be stabilized.

(11) In the power steering device according to (9) above,
The holder member 31 is opposed to the outer peripheral surface of the first bearing 10 in the radial direction of the rotational axis of the worm shaft WS and is provided on the worm wheel WW side in the direction around the rotational axis of the worm shaft WS. Side guide portion 313 (elastic member locking portion),
The elastic member 32 is formed so as to apply a biasing force to the first bearing 10 at two power points, and these two power points are applied to the lower guide portion 313 in the direction around the rotation axis of the worm shaft WS. It is provided at a symmetrical position.
Therefore, the support stability of the elastic member can be improved.
(12) In the power steering device according to (9) above,
The holder member 31 is opposed to the outer peripheral surface 10b of the first bearing 10 in the radial direction of the rotation axis of the worm shaft WS, and is provided on the worm wheel WW side in the direction around the rotation axis of the worm shaft WS. It has a lower guide part 313,
In the lower guide portion 313, the worm shaft WS is rotated to one side in the rotation direction in the direction around the rotation axis of the worm shaft WS with respect to a virtual line orthogonal to the rotation axis of the worm wheel WW and the rotation axis of the worm shaft WS. The reaction force F1 sometimes received from the worm wheel WW and the reaction force F2 received from the worm wheel WW when the worm shaft WS rotates to the other side in the rotation direction are offset in the vector direction.
Therefore, when a plurality of force points A and B are arranged at a position opposite to the resultant force F, the force points A and B and the lower guide portion 313 are opposed to each other across the rotation axis of the worm shaft WS. It is easy to lay out A and B at positions facing the resultant force.

(13) In the power steering device according to (9),
The holder member 31 is opposed to the outer peripheral surface 10b of the first bearing 10 in the radial direction of the rotation axis of the worm shaft WS, and is provided on the opposite side of the worm wheel WW in the direction around the rotation axis of the worm shaft WS. Provided with an inner peripheral surface 315a (stopper portion) that restricts movement of the first bearing 10 beyond a predetermined amount,
The inner peripheral surface 315a has a direction of reaction force received from the worm wheel WW when the worm shaft WS rotates in one direction of rotation in the direction around the rotation axis of the worm shaft WS and the worm shaft WS rotates in the other direction of rotation. It is provided so as to be positioned between the direction of the reaction force received from the worm wheel WW.
Therefore, even when the direction of the force received by the steering wheel SW is changed by switching the steering wheel SW, the stopper function can be exhibited.

(14) In the power steering device according to (7),
The elastic member 32 has a second spring part 320b and a fourth spring part 320d (straight line part) in which a part of the elastic member 32 is linearly formed in the direction around the rotation axis of the worm shaft WS. A biasing force is applied to the first bearing 10 at the spring portion 320b and the fourth spring portion 320d.
That is, by using the straight line portion as the power point, even if the position of the power point changes with the diameter expansion of the elastic member 32, it is possible to suppress a change in the direction of application of the urging force.

[Example 2]
Next, Example 2 will be described. Since the basic configuration is the same as that of the first embodiment, different points will be described. FIG. 9 is a schematic diagram illustrating the operation of the backlash adjusting mechanism of the second embodiment. In the first embodiment, the direction of the biasing force F, which is the resultant force of the forces FA and FB biased from the two points of the elastic member 32, is the reaction force received from the worm wheel WW when the worm shaft WS rotates in one direction of rotation. The holder member 31 is installed so as to face F1 and the resultant force F12 of the reaction force F2 received from the worm wheel WW when the worm shaft WS rotates in the other direction of rotation. In contrast, in the second embodiment, the worm wheel WW and the worm shaft WS are installed so as to coincide with the direction PM intersecting the plane PX including a virtual line orthogonal to the rotation axis of the worm shaft WS at a predetermined angle θ. Different.

Specifically, the direction of the biasing force F, which is the resultant force of the forces FA and FB biased from two points of the elastic member 32, is the same as the component force component of the reaction force F1 and the component force component of the reaction force F2. The holder member 31 is set to face the direction PM. That is, it is one elastic member that applies the urging force to the first bearing 10, and it is necessary to urge the first bearing 10 with the same urging force in a balanced manner. In the triangle formed by the reaction force F1 and the reaction force F2, the perpendicular direction dropped from the apex that is the center of the first bearing 10 is the direction PM in which the component components of the reaction forces F1 and F2 have the same magnitude. Therefore, by installing the holder member 31 so that the first bearing 10 can move along the perpendicular direction (direction PM) intersecting with the angle θ formed with the plane PX, the holder member 31 is attached to the first bearing 10 in a balanced manner. Can give power.

As described above, the following operational effects are obtained in the second embodiment.
(15) In the power steering device according to (9) above,
The holder member 31 is opposed to the outer peripheral surface 10b of the first bearing 10 in the radial direction of the rotation axis of the worm shaft WS, and is provided on the worm wheel WW side in the direction around the rotation axis of the worm shaft WS. A lower guide portion 313 (elastic member locking portion) is provided,
In the lower guide portion 313, the worm shaft WS is rotated to one side in the rotation direction in the direction around the rotation axis of the worm shaft WS with respect to a virtual line orthogonal to the rotation axis of the worm wheel WW and the rotation axis of the worm shaft WS. The reaction force F1 sometimes received from the worm wheel WW and the component component of the reaction force F2 received from the worm wheel WW when the worm shaft WS rotates to the other side in the rotation direction are offset so as to have the same magnitude.
That is, it is one elastic member that applies the urging force to the first bearing 10, and it is necessary to urge the first bearing 10 with the same urging force in a balanced manner. Therefore, by installing the holder member 31 so that the first bearing 10 can move along the direction PM in which the component components of the reaction forces F1 and F2 have the same magnitude, the holder member 31 is balanced with respect to the first bearing 10. Energizing force can be given.

[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. For example, the O-ring is installed in the first embodiment in order to prevent the holder member from rattling in the metal cap of the backlash adjusting mechanism. 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.

Although only a few embodiments of the present invention have been described above, various modifications or improvements can be made to the illustrated embodiments without substantially departing from the novel teachings and advantages of the present invention. Will be easily understood by those skilled in the art. Therefore, it is intended that the embodiment added with such changes or improvements is also included in the technical scope of the present invention. You may combine the said embodiment arbitrarily.

This application claims priority based on Japanese Patent Application No. 2015-228338 filed on Nov. 24, 2015. The entire disclosure of Japanese Patent Application No. 2015-228338, filed November 24, 2015, including the specification, claims, drawings, and abstract, is incorporated herein by reference in its entirety.

3 Electric motor 10, bearing 10b, outer peripheral surface 30, backlash adjustment mechanism 31, holder member 32, elastic member 33, metal cap 34, ring 310, outer peripheral wall 312, other end 312a, rotation restricting portion 313, lower guide portion 313a, retaining groove 313b, engaging convex portion 314, upper portion Guide section 315 Bearing housing section 320 Main body section 321 Other end section 322 One end ECU Controller EPS Power steering device FR, FL Steering wheel HS Gear housing HS1 Wheel housing section HS10 Holder housing section HS2 Shaft housing section MC Motor cover MHS Motor housing PG Pinion gear PS Pinion shaft SW Steering wheel TS Torque sensor WG Worm gear WS Worm shaft WW Worm wheel

Claims

A power steering device, wherein the power steering device
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 worm gear provided between the steering mechanism and the electric motor for transmitting the rotational force of the electric motor to the steering mechanism, wherein the worm shaft is provided on the electric motor side and formed with a worm, and on the steering mechanism side. A worm gear having a worm wheel provided to mesh with the worm;
A gear housing having a wheel housing portion for housing the worm wheel and a shaft housing portion for housing the worm shaft;
A bearing provided on the end side of the worm shaft opposite to the electric motor in the direction of the rotation axis of the worm shaft, and rotatably supporting the worm shaft;
A biasing force is applied to the bearing at a plurality of power points in a direction around the rotation axis of the worm shaft so as to reduce backlash between the worm wheel and the worm shaft. An elastic member;
A power steering apparatus comprising:
The power steering apparatus according to claim 1, wherein
The power steering device according to claim 1, wherein the elastic member applies a biasing force to the bearing at two power points.
The power steering apparatus according to claim 2,
The elastic member is an imaginary line in which the two force points of the elastic member are virtual planes orthogonal to the rotation axis of the worm wheel and are orthogonal to both the rotation axis of the worm wheel and the rotation axis of the worm shaft. A power steering device that is provided so as to straddle a plane that overlaps with the power steering device.
The power steering apparatus according to claim 1, wherein
In the elastic member, the direction of the resultant force vector of the plurality of force points is the direction of the reaction force received from the worm wheel when the worm shaft rotates in one direction of rotation and the worm shaft rotates in the other direction of rotation. A power steering device characterized in that 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 4, wherein
The elastic member includes a direction of a reaction force received from the worm wheel when the worm shaft rotates in one direction of rotation and a direction of the reaction force received from the worm wheel when the worm shaft rotates in the other direction of rotation. A power steering device, wherein the power steering device is provided so as to be located outside a range sandwiched by a direction of a reaction force received from a worm wheel.
The power steering apparatus according to claim 4, wherein
When the direction of the resultant force vector of the plurality of force points is the reaction force received from the worm wheel when the worm shaft rotates in one direction of rotation and the worm shaft rotates in the other direction of rotation. A power steering device, wherein the power steering device is provided so as to substantially coincide with a direction of a resultant force vector of a reaction force received from the worm wheel.
The power steering apparatus according to claim 1, wherein
The power steering device according to claim 1, wherein the elastic member has a shape surrounding an outer periphery of the bearing in a direction around a rotation axis of the worm shaft.
The power steering apparatus according to claim 7, wherein
The elastic member is a wire spring, and both ends of the wire spring are provided so as to be separated from each other.
The power steering device according to claim 7 includes a cylindrical member that surrounds the outer peripheral side of the bearing and an elastic member holding portion that holds the elastic member, and has a holder member provided in the shaft housing portion. A featured power steering device.
The power steering apparatus according to claim 9, wherein
The holder member is opposed to the outer peripheral surface of the bearing in a radial direction of the rotation axis of the worm shaft and is disposed on the worm wheel side in a direction around the rotation axis of the worm shaft. With a stop,
The elastic member is a wire spring, and a part of the elastic member is locked to the outer peripheral side of the elastic member locking portion in a direction around the rotation axis of the worm shaft, and is out of both ends of the elastic member. One of these is locked by a spring end locking portion provided on the holder member.
The power steering apparatus according to claim 9, wherein
The holder member is opposed to the outer peripheral surface of the bearing in a radial direction of the rotation axis of the worm shaft and is disposed on the worm wheel side in a direction around the rotation axis of the worm shaft. With a stop,
The elastic member is formed so as to apply an urging force to the bearing at two force points, and the two force points are symmetrical with respect to the elastic member locking portion in a direction around the rotation axis of the worm shaft. A power steering device characterized by being provided at a different position.
The power steering apparatus according to claim 9, wherein
The holder member is opposed to the outer peripheral surface of the bearing in a radial direction of the rotation axis of the worm shaft and is disposed on the worm wheel side in a direction around the rotation axis of the worm shaft. With a stop,
The elastic member locking portion rotates the worm shaft to one side in the rotation direction in a direction around the rotation axis of the worm shaft with respect to a virtual line orthogonal to the rotation axis of the worm wheel and the rotation axis of the worm shaft. The power steering is provided so as to be offset in the direction of the resultant vector of the reaction force received from the worm wheel and the reaction force received from the worm wheel when the worm shaft rotates to the other side in the rotation direction. apparatus.
The power steering apparatus according to claim 9, wherein
The holder member is opposed to the outer peripheral surface of the bearing in a radial direction of the rotation axis of the worm shaft, and is provided on the opposite side of the worm wheel in a direction around the rotation axis of the worm shaft, Provided with a stopper that restricts the movement of the bearing beyond a predetermined level,
In the direction around the rotation axis of the worm shaft, the stopper portion rotates in the direction of the reaction force received from the worm wheel when the worm shaft rotates in one direction of rotation and the worm shaft rotates in the other direction of rotation. A power steering device characterized in that 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 7, wherein
The elastic member has a straight portion in which a part of the elastic member is formed in a straight line in a direction around the rotation axis of the worm shaft, and applies a biasing force to the bearing in the straight portion. A featured power steering device.
The power steering apparatus according to claim 9, wherein
The holder member is opposed to the outer peripheral surface of the bearing in a radial direction of the rotation axis of the worm shaft and is disposed on the worm wheel side in a direction around the rotation axis of the worm shaft. With a stop,
The elastic member locking portion rotates the worm shaft to one side in the rotation direction in a direction around the rotation axis of the worm shaft with respect to a virtual line orthogonal to the rotation axis of the worm wheel and the rotation axis of the worm shaft. The reaction force received from the worm wheel and the component component of the reaction force received from the worm wheel when the worm shaft rotates to the other side in the rotation direction are offset so as to have the same magnitude. A featured power steering device.