JP2017222257A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power steering device which can accurately adjust a backlash between a worm shaft and a worm wheel by a wire spring.SOLUTION: A power steering device comprises: a steering mechanism 1; an electric motor 11 for applying a steering force to the steering mechanism; a worm gear 13 which has a worm shaft 14 and a worm wheel 15, and transmits a drive force of the electric motor to the steering mechanism; a second ball bearing 24 for pivotally supporting the worm shaft; a holder member 26 for storing a bearing therein; a wire spring 27 having an arc-shaped part 35 provided on an outer peripheral side of the bearing, and extends in a circumferential direction of the worm shaft, and first and second straight line parts 37a, 37b formed by reducing a diameter of a part of the arc-shaped part, and energizing the bearing in an engagement direction D1 via each straight line part; and a rotation regulation part 36 which is provided on only one end part 35a side of the arc-shaped part, and regulates relative rotation by a prescribed angle θ3 or more of the wire spring to the holder member.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a power steering device that applies a driving force of an electric motor to a steering mechanism via a worm gear.

  As a conventional power steering device, for example, one described in Patent Document 1 below is known.

  Briefly, this power steering apparatus includes a worm shaft having one end connected to an electric motor and the other end pivotally supported by a bearing, and a worm wheel provided so as to mesh with the worm shaft. A worm gear, a holder member that accommodates the bearing, and a coil spring that is provided between the holder member and the bearing so as to extend in a radial direction of the worm shaft. The worm shaft is urged through the bearing to reduce backlash of the worm gear.

JP 2013-208933 A

  By the way, in recent years, a wire spring formed in an arc shape along the circumferential direction of the worm shaft between the bearing and the holder member instead of the conventional coil spring from the viewpoint of miniaturization of the power steering device or the like. A technique has been devised in which the wire shaft is used to urge the worm shaft in the meshing direction with the worm wheel.

  The wire spring used in such a technique usually has an urging portion that makes point contact with the outer peripheral surface of the bearing at a predetermined position in the circumferential direction, and provides a restoring force in the reduced diameter direction via the urging portion. By acting on the bearing, the worm shaft is biased in the meshing direction.

  In this case, it is conceivable that the wire spring suppresses displacement of the contact point between the urging portion and the outer peripheral surface of the bearing in the circumferential direction by fixing one end portion to the holder member as a fixed end.

  However, if the one end is completely fixed to the holder member in this way, the contact point is biased toward the one end when the wire spring undergoes a diameter expansion deformation due to a reaction force from the worm wheel. As a result, the worm shaft cannot be properly biased in the meshing direction, and there is a concern that the accuracy required for adjusting the backlash may be reduced.

  The present invention has been devised in view of such technical problems, and an object of the present invention is to provide a power steering device that can accurately adjust backlash between a worm shaft and a worm wheel by a wire spring. .

  The present invention relates to a steering mechanism that transmits a steering operation of a steering wheel to steered wheels, an electric motor that applies a steering force to the steering mechanism, a worm shaft that is linked to the electric motor, and a worm wheel that is linked to the steering mechanism. And a gear housing having a worm gear that decelerates and transmits the rotational force of the electric motor to the steering mechanism, a wheel housing portion that houses the worm wheel, and a shaft housing portion that houses the worm shaft. A bearing that is provided on the end side opposite to the electric motor in the axial direction with respect to the worm shaft, rotatably supports the worm shaft, a holder member having a bearing housing portion that houses the bearing, An arc-shaped portion provided on an outer peripheral side of the bearing and extending in a circumferential direction of the rotation axis of the worm shaft; and the arc A biasing force applying portion formed by reducing a part of the circumferential direction of the portion in a reduced diameter, and biasing force in a direction to reduce backlash of the worm gear on the bearing via the biasing force applying portion And a rotation restricting portion that is provided only on one end side of the arc-shaped portion and restricts relative rotation of the wire spring by a predetermined angle or more with respect to the holder member in the circumferential direction. It is a feature.

  According to the present invention, it is possible to accurately adjust the backlash between the worm shaft and the worm wheel by the wire spring.

1 is a schematic diagram showing a power steering device according to a first embodiment of the present invention. It is the perspective view which permeate | transmitted and displayed the worm gear which concerns on 1st Embodiment through a gear housing. It is the sectional view on the AA line of FIG. It is a perspective view which removes a case member and shows the backlash adjustment mechanism concerning a 1st embodiment. It is the B section enlarged view of FIG. It is a perspective view which shows the holder member which concerns on 1st Embodiment. It is a top view of the holder member. It is a perspective view which shows the wire spring which concerns on 1st Embodiment. It is a figure which shows the backlash adjustment operation | movement by a backlash adjustment mechanism. FIG. 10 is a view corresponding to FIG. 9 when one end of the wire spring is completely fixed. It is a side view which shows the wire spring which concerns on the example of a change of 1st Embodiment. It is a side view which shows the wire spring which concerns on 2nd Embodiment of this invention. It is a side view which shows the wire spring which concerns on 3rd Embodiment of this invention.

Hereinafter, embodiments of a power steering apparatus according to the present invention will be described with reference to the drawings.
[First Embodiment]
As shown in FIGS. 1 to 3, the power steering apparatus according to the present embodiment transmits a steering force input to the steering wheel 3 to the steered wheels 4 a and 4 b, and the steering mechanism 1 performs the steering operation. And a steering assist mechanism 2 that applies a steering assist force according to the force.

  As shown in FIG. 1, the steering mechanism 1 is a so-called rack-and-pinion type steering mechanism, in which one end side is connected to a steering shaft 5 and a rack tooth 6a formed on the outer periphery is a steering shaft. And a rack bar 6 that moves in the axial direction by meshing with pinion teeth 5 a formed on the outer periphery of 5. Steering wheels 4 a and 4 b are linked to both ends of the rack bar 6 via tie rods 7 and knuckle arms 8, respectively, and each knuckle arm 8 is pulled as the rack bar 6 moves in the axial direction. Thereby, the direction of each steered wheel 4a, 4b is changed.

  The steering shaft 5 and the rack bar 6 are respectively housed in a steering gear housing 9 supported and fixed to a vehicle body (not shown), and the pinion of the steering shaft 5 of the steering gear housing 9 is accommodated. A torque sensor 10 for detecting the steering torque input to the steering shaft 5 is provided in the steering shaft accommodating portion 9a that accommodates the tooth 5a side.

  As shown in FIGS. 1 to 3, the steering assist mechanism 2 is generated by an electric motor 11 that generates the steering assist force, a control device 12 that is used for drive control of the electric motor 11, and the electric motor 11. The worm gear 13 transmits the steering assist force to the steering shaft 5 while decelerating the steering assist force.

  The control device 12 is electrically connected to various sensors such as the torque sensor 10 via a sensor harness (not shown), and the electric motor 11 is based on various driving information including a steering torque signal output from the various sensors. Is controlled.

  As shown in FIG. 3, one end of the worm gear 13 is connected to an output shaft 11a of the electric motor 11 through an Oldham coupling 16 so as to be integrally rotatable, and a tooth portion 14a is provided at a substantially central position in the axial direction of the outer periphery. A formed worm shaft 14 and a worm wheel 15 fixed to the lower end portion of the steering shaft so as to be integrally rotatable, and formed with a tooth portion 15a meshing with a tooth portion 14a of the worm shaft 14 on the outer periphery, These are all housed in the gear housing 17.

  The gear housing 17 extends in a cylindrical shape with a bottom on the rotation axis of the output shaft 11 a of the electric motor 11, and includes a shaft housing portion 18 in which the worm shaft 14 is housed, and a circumferential direction in the shaft housing portion 18. And a flat cylindrical wheel accommodating portion 19 for accommodating the worm wheel 15 therein. The gear housing 17 is connected and fixed to the motor housing 21 constituting the electric motor 11 by a plurality of bolts 20 at the end portion on the shaft housing portion 18 side, while the end portion on the wheel housing portion 19 side is a plurality of bolts. 22 is connected and fixed to the steering gear housing 9.

  Two first and second ball bearings 23 and 24 that rotatably support the worm shaft 14 are interposed between the shaft housing portion 18 and the worm shaft 14. The first ball bearing 23 provided at one end 14 b of the worm shaft 14 on the electric motor 11 side is accommodated in a relatively large-diameter annular groove 18 a formed on the opening side of the shaft accommodating portion 18.

  On the other hand, the second ball bearing 24 that pivotally supports the other end portion 14c of the worm shaft 14 constitutes a bearing according to the present invention, and an inner race 24a press-fitted into the outer periphery of the other end portion 14c, An outer race 24b provided on the outer peripheral side of the inner race 24a, and a plurality of balls 24c interposed between the inner race 24a and the outer race 24b are provided. Further, on the outer peripheral side of the second ball bearing 24, the other end portion 14c of the worm shaft 14 is pressed toward the worm wheel 15 via the second ball bearing 24, and both the tooth portions 14a and 15a of the worm gear 13 are pressed. A backlash adjusting mechanism 25 is provided for reducing backlash in the meantime.

  As shown in FIGS. 4 to 9, the backlash adjusting mechanism 25 includes a holder member 26 that accommodates and holds the second ball bearing 24 therein, and an elastic steel wire that is curved in an arc shape. 26 is press-fitted and fixed to a wire spring 27 that is a biasing member that biases the second ball bearing 24 housed in the direction in which the backlash is reduced, and an inner peripheral surface of the shaft housing portion 18 on the bottom 18b side, A case member 28 that accommodates the holder member 26 and the wire spring 27 therein is mainly configured.

  In the following description, the direction in which the backlash is reduced is referred to as “meshing direction D1”, the direction opposite to the meshing direction D1 is referred to as “separating direction D2”, and the worm shaft 14 (second ball bearing 24). ) And the imaginary line parallel to the meshing direction D1 is referred to as “meshing direction axis L”.

  As shown in FIGS. 4 to 7, the holder member 26 is integrally formed of a resin material in a substantially bottomed cylindrical shape, is formed in a substantially disk shape, and is a worm shaft along the internal axial direction. A bottom wall 29 through which an insertion hole 29a through which the other end 14c of 14 is inserted, and a substantially cylindrical peripheral wall 30 standing from the outer peripheral edge of the bottom wall 29 toward the electric motor 11 side, In addition, the bottom wall 29 and the peripheral wall 30 form a bearing housing chamber 31 that is a bearing housing portion that houses the second ball bearing 24.

  The peripheral wall 30 has an inner peripheral surface 30a set to an inner diameter slightly larger than the diameter of the second ball bearing 24 (outer race 24b), and is opposed to the inner peripheral surface 30a across the meshing direction axis L. The first and second bearing guide surfaces 30b and 30c having a two-surface width are formed in the portion to be extended and guide the radial movement of the second ball bearing 24 so as to protrude toward the inner peripheral side. As shown in FIG. 7, both the bearing guide surfaces 30 b and 30 c are formed substantially parallel to the meshing direction axis L with an interval corresponding to the outer diameter of the second ball bearing 24. Thereby, the movement of the second ball bearing 24 in the direction orthogonal to the meshing direction D1 is restricted, while the movement along the meshing direction D1 is allowed.

  The peripheral wall 30 is formed such that its height (axial length) is about half of the axial width of the second ball bearing 24. Thereby, as shown in FIG. 4, a part of the second ball bearing 24 projects forward from the front end surface 30 d of the peripheral wall 30 in the state of being accommodated in the bearing accommodating chamber 31.

  Here, an arc-shaped convex portion 32 having a substantially arc shape in plan view is extended along the axial direction of the worm shaft 14 at a portion of the peripheral wall 30 on the meshing direction D1 side. A concave groove 32a having a rectangular cross section is formed along the circumferential direction on the outer peripheral side of the base end portion of the arc-shaped convex portion 32, and a part of the wire spring 27 is wound around the concave groove 32a. . Further, a rectangular protrusion 32b having a substantially rectangular shape in a plan view is provided on the tip surface of the arc-shaped convex portion 32 and further protrudes along the axial direction of the worm shaft 14 from the tip surface.

  Further, two trapezoidal convex portions 33 and 34 having a substantially trapezoidal shape in a plan view are provided on the portion of the peripheral wall 30 on the side in the separation direction D2 with the meshing direction axis L interposed therebetween, and these trapezoidal convex portions. 33 and 34 and the arcuate convex portion 32 are formed so that the protruding amounts from the tip surface 30d are substantially the same.

  As shown in FIG. 8 in particular, the wire spring 27 is formed in a substantially arc shape along the circumferential direction of the worm shaft 14, and an arc-shaped portion 35 provided on the outer peripheral side of the second ball bearing 24. A rotation restricting portion 36 that is provided only on the one end portion 35a side of the portion 35 and restricts relative rotation between the holder member 26 and the wire spring 27.

  In the arc-shaped part 35, a part of the circumferential direction is formed in a straight line so that the outer diameter becomes small at a part on the side of the separation direction D2 in a state where the relative rotation is restricted by the rotation restricting part 36. The 1st, 2nd linear part 37a, 37b as the urging | biasing force provision part which becomes is provided. As shown in FIG. 9, these first and second straight portions 37 a and 37 b are arranged in the circumferential direction of the arc-shaped portion 35 from the intersection point P 1 on the separation direction D 2 side among the intersection points of the meshing direction axis L and the arc-shaped portion 35. They are arranged at positions offset by predetermined angles θ1 and θ2, respectively. In this embodiment, the predetermined angles θ1 and θ2 are set to 60 degrees, respectively.

  Further, when the arc-shaped portion 35 is disposed on the holder member 26, the portion on the meshing direction D1 side is wound around the groove 32a of the arc-shaped convex portion 32, while the portion on the separating direction D2 side is the second ball. The outer circumferential surface 24d exposed from the bearing accommodating chamber 31 of the bearing 24 is wound around, and the first and second straight portions 37a and 37b are in elastic contact with the outer circumferential surface 24d.

  Further, the arc-shaped portion 35 is formed over a range larger than one round (360 degrees) in the circumferential direction of the worm shaft 14, and both end sides are superposed vertically. That is, the arc-shaped portion 35 has an overlap in the circumferential direction between the one end portion 35a located on the side close to the tip surface 30d of the peripheral wall 30 and the other end portion 35b located on the side far from the tip surface 30d (in the axial direction). It has a region R that faces each other.

  At this time, at the place where the one end 35a and the other end 35b overlap, the restoring force of the arcuate portion 35 is caused by the twist of the one end 35a and the other end 35b accompanying the overlap. It acts in the direction of pressing each other along the axial direction. That is, the arc-shaped portion 35 has a contact portion 35c in which the one end portion 35a and the other end portion 35b elastically contact within the range of the region R.

  The rotation restricting portion 36 is configured as a bent portion 38 that is bent so as to extend from one end portion 35 a of the arc-shaped portion 35 along the axial direction of the worm shaft 14.

  As shown in FIG. 8, the bent portion 38 is bent in an arc shape in which a boundary portion 38 a with the arc-shaped portion 35 is substantially perpendicular to the arc-shaped portion 35, which is another area of the wire spring 27. Is formed so as not to contact. Further, as shown in FIG. 4, the bending portion 38 is engaged with an engagement groove 39 provided in the peripheral wall 30 at the tip end portion 38 b, thereby restricting relative rotation between the holder member 26 and the wire spring 27. It has become so.

  Here, as shown in FIG. 7 in particular, the engagement groove 39 is formed on the outer peripheral side of the bearing guide surface 30c so as to extend in the axial direction of the worm shaft 14. Further, the engagement groove 39 has a U-shape opening toward the outer peripheral side of the peripheral wall 30, and a pair of planar opposing surfaces 40, 41 facing each other in the circumferential direction of the worm shaft 14, and both opposing surfaces A flat bottom surface 42 for connecting 40 and 41, and the opposing surfaces 40 and 41 are disposed with a predetermined circumferential gap larger than the wire diameter of the bent portion 38.

  That is, in the engaging groove 39, the bent portion 38 is engaged in a loose fit, so that a constant movement in the circumferential direction between the opposing surfaces 40, 41 is allowed, while the opposing surfaces 40, 41 Further movement in the circumferential direction is restricted by the contact with 41.

  More specifically, based on the engagement relationship between the bent portion 38 and the engagement groove 39, the holder member 26 and the wire spring 27 are arranged so that the bent portion 38 is shown in FIG. Relative rotation of less than a predetermined angle θ3 is permitted until the transition from the state of contact with the first facing surface 40 of the joint groove 39 to the state of contact with the second facing surface 41 (see the one-dot chain line in FIG. 9). The relative rotation of the angle θ3 or more is restricted.

  In addition, by providing the engagement groove 39, a pair of first and second surfaces facing each other in the circumferential direction of the worm shaft 14 are provided at the boundary portion between the distal end surface 30d of the peripheral wall 30 and the opposing surfaces 40 and 41. Corner portions 43a and 43b are formed. As shown in FIG. 6, the first and second corner portions 43a and 43b are chamfered so that the cross-sectional shape thereof is substantially an arc shape.

  As shown in FIG. 5, the case member 28 is integrally formed of a metal material, and is provided at a cylindrical portion 44 in which the holder member 26 is fitted, and at one end portion of the cylindrical portion 44 on the worm shaft 14 side. The disc-shaped end wall 45 and the other end of the cylindrical portion 44 are provided at predetermined positions in the circumferential direction, and are protruded inward in the radial direction to prevent the holder member 26 accommodated in the cylindrical portion 44 from falling off. And a suppression unit 46.

  The end wall 45 has an insertion hole 45a having a rectangular cross section corresponding to the rectangular protrusion 32b of the holder member 26 at a predetermined position in the circumferential direction, and the rectangular protrusion 32b is inserted into the insertion hole 45a to be locked. Accordingly, the relative rotation of the holder member 26 and the case member 28 is restricted.

  Also, a plate spring portion 45b bent toward the second ball bearing 24 is provided at a portion of the end wall 45 facing the second ball bearing 24 in the axial direction. By urging the second ball bearing 24 toward the bottom wall 29 by elastic force, the backlash in the axial direction of the second ball bearing 24 is suppressed.

Further, the cylindrical portion 44 of the case member 28 and the holder member 26 are made of an elastic material such as synthetic rubber so as to be accommodated in an annular ring groove 47 formed on the outer periphery of the holder member 26. An O-ring 48 is mounted. The O-ring 48 suppresses vibration generated in the gear housing 17 from being transmitted to the worm shaft 14 via the case member 28, the holder member 26 and the second ball bearing 24.
[Effects of First Embodiment]
In the power steering device configured as described above, when the driving force of the electric motor 11 is transmitted from the worm shaft 14 to the worm wheel 15, the worm shaft 14 is provided with the worm shaft 14 as shown in FIG. The reaction force Rr acts from the worm wheel 15 at the time of forward rotation, for example, at the time of rotation in the direction in which both the steered wheels 4a and 4b are steered to the right, and the reaction force Rl acts at the time of reverse rotation.

  Then, the first and second urging forces F1 and F2 which are the restoring forces of the wire spring 27 generated by the worm shaft 14 being pushed out in the separating direction D2 by the reaction force and deformed by expanding the diameter are the first and second straight lines. By acting on the second ball bearing 24 via the portions 37a and 37b, the second ball bearing 24 is urged in the meshing direction D1 with the resultant force F3 of the first and second urging forces F1 and F2, and the backlash Will be reduced.

  At this time, in order to adjust the backlash with high accuracy, the contact point between the first and second straight portions 37a and 37b and the outer peripheral surface 24d of the second ball bearing 24 accompanying the expansion or contraction deformation of the wire spring 27. It is necessary to suppress the deviation of P2 and P3 and to keep the biasing directions of the first and second biasing forces F1 and F2 from shifting.

  That is, when the wire spring 27 is disposed on the outer peripheral side of the second ball bearing 24, a bent portion 38 as a rotation restricting portion 36 is usually provided on the one end portion 35a side of the wire spring 27, and this bent portion 38 is provided as a holder. By engaging with the engaging groove 39 formed in the member 26, relative rotation of the wire spring 27 with respect to the holder member 26 is suppressed, and the first and second biasing forces F1 based on the deviation of the contact points P2 and P3 and the deviation. , F2 can be prevented from shifting in the biasing direction.

  However, at this time, as shown in FIG. 10, the circumferential clearance of the engagement groove 39 is formed to be substantially the same as the wire diameter of the bent portion 38, and the bent portion 38 extends along the circumferential direction of the worm shaft 14. When the movement is completely restricted, the first and second straight portions 37a and 37b are pulled toward the bent portion 38 when the wire spring 27 is deformed to expand, and the contact points P2 and P3. Is biased to the positions of the contact points P2 'and P3' shown in the figure. That is, a deviation occurs in the urging direction of the first and second urging forces F1 and F2 with the deviation of the contact points P2 and P3 (see the first and second urging forces F2 ′ and F3 ′ in FIG. 10). There is a risk that the accuracy required for the adjustment of the backlash may be impaired.

  On the other hand, in this embodiment, as shown in FIG. 9, the engagement groove 39 is set to be larger than the wire diameter of the bent portion 38 and is formed so as to ensure a predetermined circumferential clearance. The bending portion 38 having an angle of less than θ3 is allowed to move in the circumferential direction. As a result, even if the wire spring 27 undergoes a diameter expansion deformation, the bent portion moves in the circumferential direction by the amount of the deformation, so that the first and second straight portions 37a and 37b are restrained from being pulled toward the bent portion 38. The contact points P2 and P3 can be held at appropriate positions.

  Thus, in this embodiment, since it was set as the structure which accept | permits the fixed circumferential direction movement of the bending part 38, the bias of contact point P2, P3 is suppressed, and urging | biasing of 1st, 2nd urging | biasing force F1, F2 is carried out. Directional deviation can be suppressed. As a result, the backlash can be reduced with high accuracy.

  In addition, in the present embodiment, the holder member 26 and the wire spring 27 are formed by the bent portion 38 formed by bending the one end portion 35a side of the arc-shaped portion 35 and the engagement groove 39 formed in the holder member 26 in a notch shape. Since the relative rotation is regulated, no new parts are required for regulating the relative rotation. Thereby, the increase in a number of parts can be suppressed and the increase in the manufacturing cost accompanying the increase in the number of parts can be suppressed.

  Further, in the present embodiment, since the engaging groove 39 is formed so as to extend in the axial direction of the worm shaft 14, for example, the holder member 26 is formed by a split mold that separates in the axial direction with respect to the tip surface 30d of the peripheral wall 30. In this case, the engagement groove 39 is not undercut, and the engagement groove 39 can be formed simultaneously with die cutting. Thereby, in the case where the holder member 26 is formed by the split mold, it is possible to reduce the work process for forming the engagement groove 39 separately, thereby suppressing an increase in manufacturing cost accompanying an increase in the work process. Can do.

  By the way, the engagement groove 39 is formed in advance in a circumferential width (a circumferential gap between the opposing surfaces 40 and 41) that allows relative rotation of the wire spring 27 less than a predetermined angle θ3. If the bent portion 38 is engaged with the engaging groove 39 in an inclined state, the relative rotation angle of the wire spring 27 with respect to the holder member 26 is less than the predetermined angle θ3, and the bent portion 38 The relative rotation is restricted by the contact of the opposing surfaces 40 and 41, and the contact points P2 and P3 may be biased.

  On the other hand, in the present embodiment, since the bent portion 38 is bent along the axial direction of the worm shaft 14, a sufficient amount of relative movement with respect to the circumferential width of the engaging groove 39 is secured, and the wire spring A relative rotation of less than 27 predetermined angles θ3 can be allowed. Thereby, the deviation of the contact points P2 and P3 can be accurately suppressed, and the accuracy related to the adjustment of the backlash can be improved.

  Further, for the convenience of forming the bent portion 38 by bending the wire spring 27, the boundary portion 38a with the arc-shaped portion 35 has an arc shape. In other words, when the first corner 43a facing the boundary portion 38a of the pair of first and second corners 43a and 43b constituting the engagement groove 39 has a shape having an edge, The boundary portion 38a of the bent portion 38 interferes with the corner portion 43a. That is, the relative movement amount of the engagement groove 39 with respect to the circumferential width is reduced based on the interference, so that the relative rotation of the wire spring 27 is achieved despite the circumferential movement amount of the wire spring 27 being less than the predetermined angle θ3. May be restricted, and deviation of the contact points P2 and P3 may be caused.

  In contrast, in the present embodiment, since the first corner 43a is also formed in an arc shape in accordance with the shape of the boundary portion 38a of the bent portion 38, the interference between the boundary portion 38a and the first corner 43a is prevented. The relative rotation of the wire spring 27 less than the predetermined angle θ3 can be appropriately and sufficiently allowed. Thereby, the deviation of the contact points P2 and P3 is more accurately suppressed, and the accuracy related to the adjustment of the backlash can be further improved.

  The wire springs 27 are generally stored in a state where a plurality of wire springs 27 are accommodated in a supply box (not shown) before the assembly to the backlash adjusting mechanism 25. For this reason, for example, when an arc-shaped portion such as a C-shape is less than one round and the both ends are not superposed in the circumferential direction, the other wire springs 27 are opened through the opening due to this non-polymerization. There is a possibility that a part of the wire spring 27 enters and the wire springs 27 are entangled with each other. That is, useless work of removing the entangled urging member increases, which may cause a reduction in the assembly work efficiency of the power steering device.

  In contrast, in the present embodiment, the arc-shaped portion 35 of the wire spring 27 is formed over a range larger than one turn in the circumferential direction of the worm shaft 14. With such a superposed structure, a gap in the circumferential direction of the wire spring 27 can be eliminated, and the entanglement between the wire springs 27 inside the supply box can be suppressed. As a result, the work of removing the entangled wire springs 27 is reduced as much as possible, and a reduction in the assembly work efficiency of the power steering device can be suppressed.

  Moreover, in the present embodiment, the contact portion where the one end portion 35a and the other end portion 35b are elastically contacted within the region R where the one end portion 35a and the other end portion 35b of the arcuate portion 35 overlap in the circumferential direction. 35c was provided. As a result, the other wire springs 27 are prevented from entering into the minute gap between the one end portion 35a and the other end portion 35b, and the entanglement between the wire springs 27 is further suppressed. As a result, the assembly efficiency of the power steering device is increased. Can be further suppressed.

  In the present embodiment, as described above, the one end portion 35a and the other end portion 35b of the arc-shaped portion 35 are intentionally brought into contact with each other from the viewpoint of suppressing the entanglement of the wire spring 27. If the contacted part slides, hysteresis may occur in the part and the spring constant or the like may change. Therefore, it is desirable that the contact part 35c is as small as possible.

  In view of this, in the present embodiment, the bent portion 38 is formed so as not to contact the arcuate portion 35 which is another region of the wire spring 27. Thereby, since the influence of the hysteresis based on the sliding of the bending part 38 and the circular arc-shaped part 35 can be suppressed at least, changes in the spring constant and the like of the wire spring 27 can be suppressed.

FIG. 11 shows a modification of the first embodiment, in which the winding direction of the wire spring 27 is changed. The wire spring 27 has the other end 35b of the arcuate portion 35 at the distal end surface of the peripheral wall 30. The one end 35a is formed on the side closer to 30d, while the one end 35a is on the side far from the distal end surface 30d. Even in such a configuration, it is possible to obtain the same effects as those of the first embodiment.
[Second Embodiment]
The basic configuration of the second embodiment of the present invention shown in FIG. 12 is substantially the same as that of the first embodiment, but the minor angle θ4 of the bending angles θ4 and θ5 of the bending portion 38 with respect to the arc-shaped portion 35 is an acute angle. It is bent and formed.

From this configuration, according to the present embodiment, it is possible to obtain substantially the same operational effects as those of the first embodiment, and as shown by the one-dot chain line in FIG. The other wire springs 27 are easily guided between the one end portion 35a and the other end portion 35b through the bent portion 38, and the wire springs 27 are easily entangled with each other. Therefore, it is possible to effectively suppress the other wire spring 27 from being guided between the one end portion 35a and the other end portion 35b. Thereby, the entanglement between the wire springs 27 is further suppressed, and the reduction in the assembly work efficiency of the power steering device can be further suppressed.
[Third Embodiment]
The basic configuration of the third embodiment of the present invention shown in FIG. 13 is substantially the same as that of the first embodiment, but the shape of the wire spring 27 is partially changed.

  That is, the wire spring 27 according to the present embodiment is formed so as to have a symmetrical shape in the axial direction of the worm shaft 14, and the arcuate portion 35 has bent portions 38, both at one end portion 35a side and the other end portion 35b side. 38 and one of the bent portions 38 functions as the rotation restricting portion 36.

  With this configuration, according to the present embodiment, the wire spring 27 is formed so as to have a symmetrical shape in the axial direction of the worm shaft 14 as well as substantially the same operational effects as the first embodiment. . Thereby, it becomes possible to assemble to the holder member 26 regardless of the front and back of the wire spring 27, and it is possible to improve the working efficiency when assembling.

  The present invention is not limited to the configuration of each of the embodiments described above, and the configuration can be changed without departing from the spirit of the invention.

  For example, in the present embodiment, the engagement groove 39 has been described as being formed in a U-shape that opens toward the outer peripheral side of the peripheral wall 30, but the wire spring 27 is less than a predetermined angle θ3 with respect to the holder member 26. The shape is not limited to this as long as the relative rotation is allowed and the relative rotation of the predetermined angle θ3 or more can be regulated.

  As a power steering apparatus based on each embodiment described above, the thing of the aspect described below can be considered, for example.

  In one aspect thereof, the power steering device includes a steering mechanism that transmits a steering operation of a steering wheel to a steered wheel, an electric motor that applies a steering force to the steering mechanism, a worm shaft that is linked to the electric motor, A worm wheel linked to a steering mechanism is meshed with the worm gear for decelerating and transmitting the rotational force of the electric motor to the steering mechanism, a wheel accommodating portion for accommodating the worm wheel, and the worm shaft. A gear housing having a shaft housing portion, a bearing provided on the end portion opposite to the electric motor in the axial direction with respect to the worm shaft, and a bearing housing portion for housing the bearing, which rotatably supports the worm shaft. A holder member having a rotation of the worm shaft provided on the outer peripheral side of the bearing An arcuate portion extending in the circumferential direction, and an urging force imparting portion formed by reducing a portion of the arcuate portion in the circumferential direction to a reduced diameter, and through the urging force imparting portion A wire spring that applies a biasing force to the bearing in a direction that reduces backlash of the worm gear, and a circular spring that is provided only on one end side of the arcuate portion, and is greater than a predetermined angle of the wire spring with respect to the holder member in the circumferential direction A rotation restricting portion for restricting relative rotation of the rotation.

  In a preferred aspect of the power steering apparatus, the rotation restricting portion is a bent portion provided on the one end side of the arc-shaped portion, and the holder member has an engagement groove into which the bent portion is inserted. .

  In another preferred aspect, in any one of the aspects of the power steering apparatus, the engagement groove is formed to extend in the axial direction.

  In still another preferred aspect, in any one of the aspects of the power steering apparatus, the bent portion is bent in the axial direction.

  In still another preferred aspect, in any one of the aspects of the power steering device, the bent portion is bent in an arc shape at a boundary portion with the arc-shaped portion, and the engagement groove is formed by the holder member. The holder member is provided with a pair of corner portions that constitute the engaging groove by facing each other, and of the pair of corner portions, faces the boundary portion. The corner portion on the side to be formed is formed in an arc shape.

  In still another preferred aspect, in any one of the aspects of the power steering apparatus, the bent portion is bent so that a minor angle of the bent angles is an acute angle.

  In still another preferred aspect, in any one of the aspects of the power steering apparatus, the arc-shaped portion extends over a range larger than one circumference in the circumferential direction, and the one end side and the other end side are the It overlaps in the circumferential direction.

  In still another preferred aspect, in any one of the aspects of the power steering apparatus, the wire spring is formed to have a symmetrical shape in the axial direction.

  In still another preferred aspect, in any one of the aspects of the power steering apparatus, the arc-shaped portion is a predetermined portion on the one end side in a region overlapping in the circumferential direction on the one end side and the other end side. And a predetermined portion on the other end side have a contact portion that comes into contact with each other.

  In still another preferred aspect, in any one of the aspects of the power steering apparatus, the rotation restricting portion is a bent portion provided on the one end side of the arc-shaped portion, and the bent portion is the arc-shaped portion. It is formed so as not to contact the part.

DESCRIPTION OF SYMBOLS 1 ... Steering mechanism 3 ... Steering wheel 11 ... Electric motor 13 ... Worm gear 14 ... Worm shaft 15 ... Worm wheel 17 ... Gear housing 18 ... Shaft accommodating part 19 ... Wheel accommodating part 24 ... 2nd ball bearing (bearing)
26 ... Holder member 27 ... Wire spring 31 ... Bearing housing chamber (bearing housing portion)
35 ... Arc-shaped part 36 ... Rotation restricting part

Claims (10)

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 that meshes with a worm shaft linked to the electric motor and a worm wheel linked to the steering mechanism, and transmits the rotational force of the electric motor to the steering mechanism at a reduced speed,
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 that is provided on the end side opposite to the electric motor in the axial direction with respect to the worm shaft, and rotatably supports the worm shaft;
A holder member having a bearing accommodating portion for accommodating the bearing;
An arcuate portion provided on the outer peripheral side of the bearing and extending in the circumferential direction of the rotating shaft of the worm shaft, and a biasing force applied by forming a portion of the arcuate portion in the circumferential direction in a reduced diameter A wire spring that applies a biasing force in a direction that reduces backlash of the worm gear to the bearing via the biasing force applying unit,
A rotation restricting portion that is provided only on one end side of the arcuate portion and restricts relative rotation of the wire spring with respect to the holder member at a predetermined angle or more in the circumferential direction;
A power steering apparatus comprising: The power steering apparatus according to claim 1, wherein
The rotation restricting portion is a bent portion provided on the one end side of the arc-shaped portion,
The power steering device, wherein the holder member has an engaging groove into which the bent portion is inserted. The power steering apparatus according to claim 2,
The power steering apparatus according to claim 1, wherein the engagement groove is formed to extend in the axial direction. In the power steering device according to claim 3,
The power steering apparatus, wherein the bent portion is bent in the axial direction. The power steering apparatus according to claim 4, wherein
The bent portion has a boundary portion with the arc-shaped portion bent in an arc shape,
The engagement groove is formed so as to open in the axial end surface of the holder member,
The holder member includes a pair of corner portions that constitute the engaging groove by facing each other,
The power steering device according to claim 1, wherein the corner portion on the side facing the boundary portion of the pair of corner portions is formed in an arc shape. In the power steering device according to claim 3,
The power steering device according to claim 1, wherein the bent portion is bent such that an inferior angle is an acute angle. The power steering apparatus according to claim 1, wherein
The arcuate portion extends over a range larger than one turn in the circumferential direction, and the one end side and the other end side overlap in the circumferential direction. The power steering apparatus according to claim 7, wherein
The power steering device according to claim 1, wherein the wire spring is formed to have a symmetrical shape in the axial direction. The power steering apparatus according to claim 7, wherein
The arcuate portion is a contact portion that contacts a predetermined portion on the one end side and a predetermined portion on the other end side in a circumferentially overlapping region on the one end side and the other end side. A power steering apparatus comprising: The power steering apparatus according to claim 7, wherein
The rotation restricting portion is a bent portion provided on the one end side of the arc-shaped portion,
The power steering apparatus according to claim 1, wherein the bent portion is formed so as not to contact the arcuate portion.

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