Rack and pinion type steering gear unit

Abstract

To achieve a structure of a rack pinion type steering gear unit which can suppress axial direction backlash of a rack bush without deteriorating assembly workability.SOLUTION: A rack stopper 20 is internally fitted into a middle diameter hole section 29 provided in a rack storage section 23, and a side face on an axial direction one side is abutted on a step face 31. A rack bush 19 is internally fitted into a small diameter hole section 30 arranged on a depth side of the middle diameter hole section 29, and an engaging flange section 40 provided on an outer peripheral surface is engaged with an engaging recess 32 provided in an axial direction part of an inner peripheral surface of the small diameter hole section 30. A preload applying member 21 made of an elastic material is arranged between the rack bush 19 and the rack stopper 20 so as to apply axial direction preload to the rack bush 19.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a rack and pinion type steering gear unit. [Background technology]

[0002] Rack and pinion steering devices are widely used in automobile steering devices because they can be configured to be small and lightweight, and have high rigidity and provide a good steering feeling, etc. Figures 20 and 21 show a steering gear unit 100 of a conventional structure incorporated in a rack and pinion steering device, which is described in JP 2016-155443 A (Patent Document 1).

[0003] The rack and pinion type steering gear unit 100 converts the rotational motion of the steering wheel into linear motion in the width direction of the vehicle, thereby applying a steering angle to the left and right steered wheels.

[0004] The steering gear unit 100 includes a housing 101, a pinion shaft 102 to which the rotational motion of the steering wheel is transmitted, a rack shaft 103 that converts the rotational motion of the pinion shaft 102 into linear motion, and a pair of rack bushes 104.

[0005] The housing 101 includes a rack accommodating portion 101a that accommodates an axial middle portion of the rack shaft 103, and a pinion accommodating portion 101b that accommodates a tip half portion of the pinion shaft 102. The housing 101 is fixed to the vehicle body with the longitudinal direction (axial direction) of the rack accommodating portion 101a facing the width direction of the vehicle.

[0006] The pinion shaft 102 has pinion teeth on the tip half of its outer circumferential surface. The pinion shaft 102 is rotatably supported inside the pinion accommodating portion 101b via a plurality of bearings. The pinion shaft 102 is connected to the steering wheel via a steering shaft and an intermediate shaft (not shown), and rotates in response to the steering operation of the steering wheel.

[0007] The rack shaft 103 has rack teeth on a portion of its outer circumferential surface in the axial direction that mesh with the pinion teeth of the pinion shaft 102. The rack shaft 103 is disposed inside the rack housing portion 101a so as to be capable of reciprocating in the axial direction. Both axial ends of the rack shaft 103 protrude from both axial ends of the rack housing portion 101a and are connected to a tie rod 106 via a spherical joint 105.

[0008] The pair of rack bushes 104 are fitted into openings on both axial sides of the rack accommodating portion 101a, respectively. The rack bushes 104 function as slide bearings and support the rack shaft 103 so that it can be displaced in the axial direction relative to the rack accommodating portion 101a without rattle.

[0009] As shown in FIG. 21, the rack bush 104 includes a bush body 107 and a pair of elastic rings 108. The bush body 107 has a cylindrical shape. The bush body 107 has slits (not shown) extending in the axial direction at multiple locations in the circumferential direction, and can expand and contract in the radial direction. The bush body 107 has an engagement flange 107a protruding radially outward at one end in the axial direction of the outer circumferential surface. The bush body 107 also has an engagement groove 107b extending in the circumferential direction at an axially intermediate portion of the outer circumferential surface.

[0010] The rack bush 104 is fitted into the rack accommodating part 101a with an engagement flange 107a provided on the outer circumferential surface of the bush body 107 engaged with an engagement recess 109 provided on the inner circumferential surface of the rack accommodating part 101a. This prevents the rack bush 104 from being displaced in the axial direction relative to the rack accommodating part 101a.

[0011] With the rack bushing 104 fitted inside the rack accommodating portion 101a, each of the pair of elastic rings 108 is elastically sandwiched between the groove bottom surface of the locking recessed groove 107b and the inner circumferential surface of the rack accommodating portion 101a. This causes the inner circumferential surface of the bushing body 107 to be elastically pressed against the outer circumferential surface of the rack shaft 103, suppressing the occurrence of rattling in the radial direction of the rack shaft 103. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] JP 2016-155443 A Summary of the Invention [Problem to be solved by the invention]

[0013] When adopting a configuration in which the engagement flange 107a is engaged with the engagement recess 109 to prevent the axial displacement of the rack bush 104, as in the steering gear unit 100 of the conventional structure described in JP 2016-155443 A, the axial dimension of the engagement flange 107a is usually set slightly smaller than the axial dimension of the engagement recess 109 to ensure ease of assembly of the steering gear unit 100. However, when the axial dimension of the engagement flange 107a is set smaller than the axial dimension of the engagement recess 109, the rack bush 104 is likely to rattle in the axial direction relative to the rack accommodating portion 101a. As a result, when the rack shaft 103 is displaced in the axial direction, the rack bush 104 and the rack accommodating portion 101a may collide with each other, generating a hitting sound.

[0014] The present invention has been made to solve the above-mentioned problems, and has been invented to realize a rack and pinion type steering gear unit structure that can suppress axial wobble of the rack bush without reducing assembly workability. [Means for solving the problem]

[0015] A rack and pinion steering gear unit according to one aspect of the present invention includes a rack shaft, a pinion shaft, a housing, a rack bush, a rack stopper, and a preload applying member. The pinion shaft meshes with the rack shaft. The housing has a rack accommodating portion that accommodates the rack shaft, and a pinion accommodating portion that accommodates the pinion shaft. The rack bush supports the rack shaft relative to the rack housing portion so as to allow the rack shaft to move in the axial direction. The rack stopper is formed in an annular shape and is fitted into the rack accommodating portion to restrict axial displacement of the rack shaft. The preload applying member is disposed between the rack bush and the rack stopper, and applies an axial preload to the rack bush. The rack accommodating portion has a first hole portion, a second hole portion that is positioned further back than the first hole portion and has an engagement recess in part of the axial direction, and a step surface that is positioned between the first hole portion and the second hole portion. The rack bush is fitted into the second hole portion with an engagement flange portion, which is provided on a portion of an outer circumferential surface in the axial direction, engaged with the engagement recess portion. The rack stopper is fitted into the first hole portion with an abutment portion provided on a side surface in the axial direction abutting against the step surface.

[0017] In a rack and pinion steering gear unit according to one embodiment of the present invention, the preload applying member is configured separately from the rack stopper, and has a main body made of an elastic material, and a core to which the main body is fixed and has a higher rigidity than the main body, and the core is press-fitted into a portion of the inner surface of the second hole portion that is located closer to the opening of the rack accommodating portion than the engagement recess. The means for fixing the main body portion to the core portion is not particularly limited, but for example, chemical joining means such as adhesion (including vulcanization adhesion) or bonding can be used, or mechanical joining means such as pressing or crimping can be used.

[0018] In a rack and pinion steering gear unit according to one embodiment of the present invention, the core portion has a fixed cylindrical portion that is approximately L-shaped in cross section and is press-fitted into the second hole portion, and a core abutment portion against which the axial side surface of the rack stopper abuts, and the main body portion can be adhesively fixed to the core portion.

[0019] In the rack and pinion steering gear unit according to one aspect of the present invention, the generatrix shape of the inner circumferential surface of the preload applying member can be made non-parallel to the central axis of the preload applying member. In this case, the generatrix shape of the inner peripheral surface of the preload applying member may be a tapered surface inclined with respect to the central axis of the preload applying member. Effect of the Invention

[0020] According to the present invention, it is possible to realize a rack and pinion type steering gear unit structure that can suppress axial wobble of the rack bush without reducing the ease of assembly. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a partial cutaway side view showing a steering device equipped with a rack and pinion type steering gear unit according to a first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Diagram 3] FIG. 3 is a plan view showing the rack and pinion type steering gear unit according to the first embodiment with some members omitted. [Figure 4] FIG. 4 is a rear view of the rack and pinion steering gear unit according to the first embodiment with some members omitted. [Diagram 5] FIG. 5 is a cross-sectional view of a rack and pinion type steering gear unit according to a first example of an embodiment with some members omitted. [Figure 6] FIG. 6 is a partially enlarged view of FIG. [Figure 7] FIG. 7 is a partially enlarged view of FIG. [Figure 8] 8A, 8B, and 8C are diagrams showing a rack bush taken out from a rack and pinion type steering gear unit according to a first example of an embodiment, in which (A) is a plan view, (B) is a right side view, and (C) is a left side view. [Figure 9] FIG. 9 is a cross-sectional view showing a rack bush taken out from a rack and pinion type steering gear unit according to a first example of the embodiment. [Figure 10] 10A and 10B are perspective views showing a rack bush taken out from a rack and pinion type steering gear unit according to a first example of an embodiment, in which (A) is a perspective view seen from the other axial side and the radial outside, and (B) is a perspective view seen from one axial side and the radial outside. [Figure 11] FIG. 11 is a diagram showing a rack stopper with an elastic material taken out from a rack and pinion type steering gear unit according to a first example of an embodiment, where (A) is a plan view, (B) is a right side view, and (C) is a left side view. [Figure 12] FIG. 12 is a cross-sectional view showing a rack stopper with an elastic material taken out from a rack and pinion type steering gear unit according to a first example of the embodiment. [Figure 13] FIG. 13 is a perspective view showing a rack stopper with elastic material taken out from a rack and pinion type steering gear unit according to a first example of an embodiment, where (A) is a perspective view seen from the other axial side and the radial outside, and (B) is a perspective view seen from one axial side and the radial outside. [Figure 14] FIG. 14 is a diagram showing a second example of the embodiment, and corresponds to FIG. [Figure 15] FIG. 15 is a diagram showing a second example of the embodiment, and corresponds to FIG. [Figure 16]16A and 16B are perspective views showing a rack stopper taken out from a rack and pinion type steering gear unit according to a second example of the embodiment, where (A) is a perspective view seen from the other axial side and the radial outside, and (B) is a perspective view seen from one axial side and the radial outside. [Figure 17] 17A, 17B, and 17C are views showing a preload applying member taken out from a rack and pinion type steering gear unit according to a second example of an embodiment, in which (A) is a plan view, (B) is a right side view, and (C) is a left side view. [Figure 18] FIG. 18 is a cross-sectional view showing a preload applying member taken out from a rack and pinion type steering gear unit according to a second example of the embodiment. [Figure 19] 19A and 19B are perspective views showing a preload applying member taken out from a rack and pinion type steering gear unit according to a second example of the embodiment, where (A) is a perspective view seen from the other axial side and the radial outside, and (B) is a perspective view seen from one axial side and the radial outside. [Figure 20] FIG. 20 is a partial cross-sectional view showing a rack and pinion steering gear unit of a conventional structure. [Figure 21] FIG. 21 is a partially enlarged view of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] [First Example of Implementation] A first embodiment will be described with reference to Figs. 1 to 13. In the following description, the front-rear direction means the front-rear direction of the vehicle, the up-down direction means the up-down direction of the vehicle, and the left-right direction means the width direction of the vehicle. The left-right direction coincides with the axial direction of the rack shaft 18 and the rack housing unit 23 described below. One side with respect to the axial direction of the rack shaft 18 and the rack housing unit 23 refers to the left side in Figs. 3 and 5 to 7 and the right side in Fig. 4, and the other side with respect to the axial direction of the rack shaft 18 and the rack housing unit 23 refers to the right side in Figs. 3 and 5 to 7 and the left side in Fig. 4.

[0023] [Overall configuration of steering device] The rack and pinion steering device 1 of this embodiment is a column assist type electric power steering device, the overall configuration of which is shown in FIG.

[0024] The steering device 1 includes a steering wheel 2, a steering shaft 3, a steering column 4, a pair of universal joints 5a, 5b, an intermediate shaft 6, a steering gear unit 7, a pair of tie rods 8, and an electric assist device 9.

[0025] The steering wheel 2 is fixed to the rear end of a steering shaft 3 that is rotatably supported inside a steering column 4. As shown in Fig. 2, the front end of the steering shaft 3 is inserted inside a gear housing 10 that is fixed to the front end of the steering column 4, and is connected to an output shaft 12 via a torsion bar 11.

[0026] The rotation of the output shaft 12 is transmitted to a pinion shaft 17 (described later) constituting a steering gear unit 7 via a pair of universal joints 5a, 5b and the intermediate shaft 6. The rotation of the pinion shaft 17 is converted into linear motion of a rack shaft 18 (described later) constituting the steering gear unit 7, thereby pushing and pulling a pair of tie rods 8 and applying a steering angle to steered wheels (not shown).

[0027] The electric assist device 9 aims to reduce the force required by the driver to operate the steering wheel 2, and is equipped with a torque sensor 13, an ECU (not shown), an electric motor 14, and a worm reduction gear 15 which is a reduction device.

[0028] The torque sensor 13 is disposed around the output shaft 12 and detects the relative twist direction and amount of twist of the output shaft 12 with respect to the steering shaft 3. The ECU determines the assist torque based on the detection signal of the torque sensor 13, a vehicle speed signal measured by a vehicle speed sensor (not shown), and the like. The electric motor 14 is fixed to the gear housing 10, and the direction and amount of current flow are controlled by the ECU. The worm reduction gear 15 reduces the rotational force of the electric motor 14 and transmits it to the output shaft 12. As a result, an assist torque can be applied to the output shaft 12, so that the steering force required for the driver to operate the steering wheel 2 can be reduced.

[0029] Hereinafter, a specific structure of the steering gear unit 7 of this embodiment will be described with reference to FIGS.

[0030] [Steering gear unit] The steering gear unit 7 has a housing 16, a pinion shaft 17 (see FIG. 1), a rack shaft 18, a rack guide (not shown), a rack bush 19, and a rack stopper 22 with an elastic material consisting of a rack stopper 20 and a preload applying member 21, and converts the rotational motion of the steering wheel 2 into linear motion in the axial direction of the rack shaft 18.

[0031] <housing> The housing 16 is fixed to the vehicle body and is a casting integrally made by die-casting a light alloy such as an aluminum alloy. As shown in Figs. 3 to 5, the housing 16 includes a rack accommodating portion 23, a pinion accommodating portion 24, a rack guide accommodating portion 25, and a plurality of mounting portions 26a, 26b.

[0032] <Rack storage section> The rack accommodating section 23 is a cylindrical member extending in the left-right direction and has, at its radial center, an insertion hole 27 penetrating in the axial direction, through which the rack shaft 18 is inserted. Therefore, the rack accommodating section 23 has open ends on both axial sides. The axial middle portion of the rack shaft 18 is accommodated inside the rack accommodating section 23. The rack accommodating section 23 is disposed approximately horizontally.

[0033] 5, the insertion hole 27 has a main body hole portion 27a in the axial middle portion, whose inner diameter does not change along the axial direction, and has stepped hole portions 27b, 27c at both axial ends, whose inner diameter increases in stages as they move away from the main body hole portion 27a (toward the opening side). The main body hole portion 27a has an inner diameter slightly larger than the outer diameter of the rack shaft 18.

[0034] In the steering gear unit 7 of this example, the rack bushing 19 and the elastic rack stopper 22 are attached to the stepped hole portion 27c arranged on the other axial side of the insertion hole 27 of the rack accommodating portion 23. In this example, the stepped hole portion 27c is configured to include a large diameter hole portion 28, a medium diameter hole portion 29, a small diameter hole portion 30, and a step surface 31, as shown in FIG.

[0035] The large diameter hole portion 28 is disposed in the opening side portion (the other axial side portion) of the stepped hole portion 27c. In the illustrated example, the large diameter hole portion 28 is formed by axially alternatingly arranging two cylindrical hole portions and two conical hole portions. The large diameter hole portion 28 has an inner diameter larger than the outer diameter of a spherical joint 36 (described below) that is fixed to the axial end portion of the rack shaft 18. The spherical joint 36 is disposed inside the large diameter hole portion 28 when the steering wheel 2 is rotated to the stroke end of the rack shaft 18.

[0036] The medium diameter hole portion 29 corresponds to a first hole portion recited in the claims, and is disposed in an axial middle portion of the stepped hole portion 27c adjacent to the deep side (one axial side) of the large diameter hole portion 28. The medium diameter hole portion 29 has a cylindrical inner peripheral surface, and has a smaller inner diameter than the large diameter hole portion 28. Therefore, a step facing the other axial side is provided between the medium diameter hole portion 29 and the large diameter hole portion 28. The medium diameter hole portion 29 has an axial dimension smaller than the axial dimension of the rack stopper 20.

[0037] The small diameter hole portion 30 corresponds to the second hole portion described in the claims, and is disposed in the rear portion (one axial side portion) of the stepped hole portion 27c adjacent to the rear side (one axial side) of the medium diameter hole portion 29. The small diameter hole portion 30 has an engagement recess 32 recessed radially outward in an axial middle portion. The engagement recess 32 has a rectangular cross-sectional shape, and is provided around the entire circumference of the small diameter hole portion 30. The engagement recess 32 is a portion that engages with an engagement flange portion 40 (described later) provided on the rack bush 19, and has axial and radial dimensions slightly larger than the axial and radial dimensions of the engagement flange portion 40.

[0038] Small diameter hole portion 30 has a cylindrical inner circumferential surface except for the portion where engagement recess 32 is provided. Small diameter hole portion 30 has an inner diameter smaller than medium diameter hole portion 29 and larger than main body hole portion 27a. In the illustrated example, the inner diameter of the bottom of engagement recess 32 is also smaller than the inner diameter of medium diameter hole portion 29.

[0039] The step surface 31 is a circular flat surface facing the other axial direction on an imaginary plane perpendicular to the central axis of the rack housing section 23, and is disposed between the medium diameter hole section 29 and the small diameter hole section 30. In other words, the step surface 31 connects the medium diameter hole section 29 and the small diameter hole section 30.

[0040] In this example, a second step surface 33, which is a circular flat surface facing the other axial direction side and exists on an imaginary plane perpendicular to the central axis of the rack accommodating section 23, is provided between the main body hole section 27a and the stepped hole section 27c (small diameter hole section 30) that configure the insertion hole 27. In other words, the second step surface 33 connects the main body hole section 27a and the small diameter hole section 30.

[0041] Pinion housing The pinion accommodating section 24 has a cylindrical shape with a bottom, and only the upper end is open. The tip half of the pinion shaft 17 is disposed inside the pinion accommodating section 24. The pinion accommodating section 24 is disposed in front of the rack accommodating section 23 (the lower side in Figs. 3 and 5, the rear side in Fig. 4) and on one axial side of the rack accommodating section 23 (the left side in Figs. 3 and 5, the right side in Fig. 4). The pinion accommodating section 24 is disposed in a twisted positional relationship with respect to the rack accommodating section 23. That is, the central axis of the pinion accommodating section 24 and the central axis of the rack accommodating section 23 are in a twisted positional relationship. Also, when viewed from the front-rear direction, the central axis of the pinion accommodating section 24 is not disposed in a direction perpendicular to the central axis of the rack accommodating section 23, but is inclined with respect to the perpendicular direction. The internal space of the pinion accommodating section 24 is in communication with the internal space of the rack accommodating section 23.

[0042] <Rack guide storage section> The rack guide accommodating portion 25 has a cylindrical shape and extends in the front-rear direction. A rack guide (not shown) is accommodated inside the rack guide accommodating portion 25. The rack guide accommodating portion 25 is disposed on the rear side of the rack accommodating portion 23 and on one axial side of the rack accommodating portion 23. Specifically, the rack guide accommodating portion 25 is disposed at the same position as the pinion accommodating portion 24 in the axial direction of the rack accommodating portion 23. The internal space of the rack guide accommodating portion 25 also communicates with the internal space of the rack accommodating portion 23.

[0043] Mounting Part Of the multiple (three in the illustrated example) mounting portions 26a, 26b, the one mounting portion 26a arranged on the front side of the rack accommodating portion 23 is arranged at one axial end of the rack accommodating portion 23. In contrast, the pair of mounting portions 26b arranged on the rear side of the rack accommodating portion 23 are arranged at both axial end portions of the rack accommodating portion 23. The housing 16 is fixed to the vehicle body using fixing members such as bolts or studs inserted through each of the multiple mounting portions 26a, 26b.

[0044] <Pinion shaft> The pinion shaft 17 has pinion teeth on the tip half of its outer circumferential surface. The pinion shaft 17 is rotatably supported inside the pinion accommodating portion 24 by a plurality of bearings (for example, two bearings) not shown. The central axis of the pinion shaft 17 is arranged coaxially with the central axis of the pinion accommodating portion 24. The pinion shaft 17 is connected to the steering wheel 2 via universal joints 5a, 5b and an intermediate shaft 6, and rotates in response to the steering operation of the steering wheel 2. The rotation of the pinion shaft 17 is converted into linear motion of the rack shaft 18, which pushes and pulls the tie rods 8 connected to the ends of the rack shaft 18 on both axial sides. This imparts a steering angle to the left and right steered wheels.

[0045] <Rack shaft> The rack shaft 18 is a solid rod-shaped member made of metal such as carbon steel. As shown in Fig. 5, the rack shaft 18 has rack teeth 34 on part of the outer circumferential surface of one axial side portion, which mesh with pinion teeth provided on the outer circumferential surface of the pinion shaft 17. The rack shaft 18 has a pair of screw holes 35 opening on both axial end faces.

[0046] The rack shaft 18 is supported inside the rack accommodating section 23 so as to be capable of reciprocating movement in the axial direction, with its axial direction (longitudinal direction) facing the left-right direction and both axial ends protruding from both left-right openings of the rack accommodating section 23. Both axial ends of the rack shaft 18 are connected to the tie rod 8 via a spherical joint 36. Specifically, male threads provided on a shaft portion 36a of the spherical joint 36 are screwed into each of a pair of screw holes 35 of the rack shaft 18, and a spherical portion 8a provided on a base end of the tie rod 8 is supported so as to be able to swing in a cylindrical holder portion 36b of the spherical joint 36.

[0047] <Rack guide> A rack guide (not shown) presses the rack shaft 18 toward the pinion shaft 17, and is disposed inside the rack guide housing portion 25. By pressing the rack shaft 18 toward the pinion shaft 17, the rack guide reduces backlash at the meshing portion between the pinion teeth and the rack teeth 34. This also prevents abnormal noise from being generated at the meshing portion between the pinion teeth and the rack teeth 34. As the rack guide, a conventionally known sliding type rack guide or roller type rack guide can be used.

[0048] In the following description of the rack bush 19, rack stopper 20, and preload applying member 21 that constitute the steering gear unit 7 of this example, unless otherwise specified, the axial direction, radial direction, and circumferential direction refer to the axial direction, radial direction, and circumferential direction with respect to the rack bush 19, rack stopper 20, and preload applying member 21. Furthermore, the axial direction of each of the rack bush 19, rack stopper 20, and preload applying member 21 coincides with the axial direction of the rack shaft 18.

[0049] <Rack bush> The rack bush 19 functions as a sliding bearing and supports the rack shaft 18 so that it can be displaced in the axial direction relative to the rack accommodating portion 23 without rattling.

[0050] 5 and 6, the rack bushing 19 is attached to the stepped hole portion 27c located on the other axial side of the rack accommodating portion 23. In this example, no rack bushing is attached to the stepped hole portion 27b located on one axial side of the rack accommodating portion 23 closer to the pinion shaft 17. The reason for this is that a rack guide (not shown) is arranged on one axial side of the rack accommodating portion 23, which can suppress rattling of the rack shaft 18. However, when implementing the present invention, rack bushings can also be provided on both axial sides of the rack accommodating portion.

[0051] As shown in FIGS. 8 to 10, the rack bush 19 is composed of a bush body 37 and a plurality of elastic rings 38 (two in the illustrated example).

[0052] The bushing body 37 is made of a thermoplastic synthetic resin such as polyacetal resin, polyamide resin, polyethylene resin, or tetrafluoroethylene resin, and has a cylindrical shape.

[0053] The bush body 37 has a plurality of slits 39a extending in the axial direction, which are formed from an end on one axial side to an axial middle part, and a plurality of slits 39b extending in the axial direction, which are formed from an end on the other axial side to an axial middle part, which are alternately arranged in the circumferential direction. The slits 39a open on the end face on one axial side of the bush body 37 and on both the inner and outer peripheral surfaces of the bush body 37, and the slits 39b open on the end face on the other axial side of the bush body 37 and on both the inner and outer peripheral surfaces of the bush body 37. This allows the bush body 37 to expand and contract in the radial direction. In the illustrated example, the bush body 37 has four slits 39a and four slits 39b, but the number of slits can be changed as appropriate when implementing the present invention.

[0054] The bushing body 37 has an engagement flange 40 that protrudes radially outward at the other axial end of the outer circumferential surface. The engagement flange 40 is provided around the entire circumference of the bushing body 37 except for the portion where the slit 39b is formed. In other words, the engagement flange 40 is discontinuous in the portion where the slit 39b is formed.

[0055] 9, the engagement flange 40 has a rectangular cross-sectional shape. The engagement flange 40 has axial and radial dimensions that are slightly smaller than the axial and radial dimensions of the engagement recess 32 provided on the inner circumferential surface of the small diameter hole 30 of the rack accommodating section 23.

[0056] The bushing body 37 has locking grooves 41 at multiple locations (two locations in the illustrated example) on its outer circumferential surface, extending in the circumferential direction so as to cross the slits 39a, 39b. The locking grooves 41 are formed in an axially intermediate portion of the outer circumferential surface of the bushing body 37 that is axially offset from the engagement flange 40, and have a rectangular cross-sectional shape. The elastic ring 38 is locked in the locking grooves 41.

[0057] The bushing body 37 has a cylindrical surface portion 37a at an axially intermediate portion of its inner circumferential surface, whose inner diameter does not change along the axial direction, and tapered surface portions 37b, 37c at both axial ends of its inner circumferential surface, whose inner diameter increases the farther away from the cylindrical surface portion. The tapered surface portions 37b, 37c are provided to improve ventilation inside the bushing body 37 and the ease of insertion of the rack shaft 18. Note that recesses 37d are provided at multiple locations in the circumferential direction on the end surface on the other axial side of the bushing body 37, into which injector pins are inserted for use when removing the bushing body 37 from the injection mold.

[0058] The elastic ring 38 is made of an elastic material such as rubber or thermoplastic synthetic resin, and is configured in an annular shape as a whole. The elastic ring 38 is a so-called O-ring having a circular cross-sectional shape. In a free state, the elastic ring 38 has an outer diameter larger than the inner diameter of the small diameter hole portion 30 of the rack accommodating portion 23, and an inner diameter smaller than the outer diameter of the groove bottom of the locking groove 41 of the bush body 37. The diameter (wire diameter) of the cross-sectional shape of the elastic ring 38 is slightly smaller than the axial width of the locking groove 41, and slightly larger than the radial depth of the locking groove 41. Therefore, when the elastic ring 38 is locked in the locking groove 41 of the bush body 37, the radial outer portion of the elastic ring 38 protrudes radially outward from the outer circumferential surface of the bush body 37.

[0059] The rack bush 19 of this example is fitted into the small diameter hole 30 of the rack accommodating section 23 with an elastic ring 38 attached to an engagement groove 41 provided on the outer circumferential surface of the bush body 37. Therefore, the bush body 37 is pressed radially inward by the elastic ring 38 and is in a reduced diameter state. Therefore, the inner circumferential surface (cylindrical surface portion 37a) of the bush body 37 slidably holds the outer circumferential surface of the rack shaft 18, making it possible to suppress the occurrence of rattling in the radial direction of the rack shaft 18.

[0060] In addition, with the rack bush 19 fitted inside the small diameter hole portion 30, an engagement flange portion 40 provided on the outer circumferential surface of the bush body 37 is engaged with an engagement recess portion 32 provided on the inner circumferential surface of the small diameter hole portion 30. This prevents the rack bush 19 from being displaced in the axial direction relative to the rack accommodating portion 23. Since the axial dimension of the engagement flange portion 40 is set slightly smaller than the axial dimension of the engagement recess portion 32, the engagement flange portion 40 can be easily engaged with the engagement recess portion 32 during the assembly work of the rack bush 19. Furthermore, one end face of the bush body 37 on one axial side is closely opposed to the second step surface 33.

[0061] <Rack stopper with elastic material> As shown in Figs. 11 to 13, the rack stopper with elastic material 22 is a single part in which a preload applying member 21 made of an elastic material is fixed to the rack stopper 20. In other words, the rack stopper 20 and the preload applying member 21 are joined to each other to form a single part. The rack stopper with elastic material 22 has an annular shape and functions as both the rack stopper 20 and the preload applying member 21. The rack stopper with elastic material 22 is provided with the preload applying member 21 on one axial side, and the rack stopper 20 on the other axial side. Below, the rack stopper 20 and the preload applying member 21 constituting the rack stopper with elastic material 22 will each be described in detail.

[0062] <Rack stopper> The rack stopper 20 has the function of restricting the axial displacement (stroke) of the rack shaft 18 by abutting against the spherical joint 36 fixed to the axial end of the rack shaft 18 when the rack shaft 18 is displaced in the axial direction, and the function of preventing the spherical joint 36 from directly colliding with the rack bush 19 made of synthetic resin.

[0063] The rack stopper 20 has an annular shape and is made of a material stronger than the synthetic resin that constitutes the rack bush 19. Specifically, the rack stopper 20 is made of a metal that is rust-resistant and has sufficient strength and rigidity. The rack stopper 20 has an L-shaped cross section and includes a cylindrical fitting tube portion 42 and an inward flange portion 43 that extends radially inward from the inner circumferential surface of one axial end of the fitting tube portion 42.

[0064] The fitting cylindrical portion 42 has an outer diameter slightly larger than the inner diameter of the medium diameter hole portion 29. The fitting cylindrical portion 42 has an inner diameter larger than the outer diameter of the base end portion connected to the shaft portion 36a of the holder portion 36b that constitutes the spherical joint 36. Therefore, the base end portion of the holder portion 36b can be inserted into the radial inside of the fitting cylindrical portion 42. The fitting cylindrical portion 42 has an abutment portion 44 on one axial side surface that abuts against the step surface 31 of the rack accommodating portion 23.

[0065] The inward flange portion 43 is configured in the shape of an annular plate and has an inner diameter larger than the outer diameter of the rack shaft 18. The preload applying member 21 is fixed to one axial side surface of the inward flange portion 43. The inward flange portion 43 has a stopper portion 45 on the other axial side surface against which an end face on one axial side of the holder portion 36b constituting the spherical joint 36 abuts. The abutment portion 44 and the stopper portion 45 exist on an imaginary plane perpendicular to the central axis of the rack stopper 20 and are arranged parallel to each other.

[0066] In the rack stopper 20 of this example, when the fitting tube portion 42 is fitted (pressed) into the medium diameter hole portion 29 by interference fit, the abutting portion 44 provided on one axial side of the fitting tube portion 42 abuts against the step surface 31 over the entire circumference. This regulates the axial position of the stopper portion 45 provided on the other axial side of the inward flange portion 43 to an appropriate position. In addition, since the rack stopper 20 can be axially positioned relative to the rack accommodating portion 23, the amount of elastic deformation of the preload applying member 21 fixed to the rack stopper 20 can be regulated to an appropriate amount. Note that, when carrying out the present invention, the fixing structure of the rack stopper is not limited to interference fit, and a structure in which a male thread portion formed on the outer peripheral surface of the fitting tube portion is screwed into a female thread portion formed on the inner peripheral surface of the medium diameter hole portion, or a fixing structure using an adhesive or the like can also be adopted.

[0067] <Preload applying member> The preload applying member 21 is made of an elastic material such as rubber or synthetic resin, and has a circular ring shape. The other axial side of the preload applying member 21 is fixed over the entire circumference to the axial side of the inward flange portion 43. In this example, the preload applying member 21 is bonded and fixed to the axial side of the inward flange portion 43 by vulcanization bonding (insert molding). That is, the process of molding the preload applying member 21 and the process of bonding the preload applying member 21 to the rack stopper 20 are performed simultaneously. For example, a phenol resin-based or epoxy resin-based adhesive can be used as the adhesive. When carrying out the present invention, the means for fixing the preload applying member to the rack stopper is not limited to vulcanization bonding, and in addition to so-called post-bonding in which the preload applying member after molding is bonded using an adhesive, chemical bonding means such as pasting using a double-sided adhesive tape can also be used, and mechanical bonding means such as press-fitting or crimping can also be used.

[0068] The preload applying member 21 has a generally triangular or generally trapezoidal cross-sectional shape in a free state. The preload applying member 21 also has a tapered cross-sectional shape in which the radial dimension decreases as the preload applying member 21 moves away from the rack stopper 20 in the axial direction.

[0069] The preload applying member 21 has a tapered outer peripheral surface in a free state. Therefore, the generatrix shape of the outer peripheral surface of the preload applying member 21 is non-parallel to the central axis of the preload applying member 21. The outer peripheral surface of the preload applying member 21 is inclined in a direction in which the outer diameter becomes smaller toward the tip side in the axial direction (away from the rack stopper 20). The outer diameter of the preload applying member 21 is smaller than the inner diameter of the small diameter hole portion 30 even at the portion where the outer diameter is largest.

[0070] The preload applying member 21 has a tapered inner circumferential surface in a free state. Therefore, the generatrix shape of the inner circumferential surface of the preload applying member 21 is non-parallel to the central axis of the preload applying member 21. The inner circumferential surface of the preload applying member 21 is inclined in a direction such that the inner diameter increases toward the tip side in the axial direction (away from the rack stopper 20). The inner diameter of the preload applying member 21 at its smallest portion is approximately the same as the inner diameter of the inward flange portion 43 and is sufficiently larger than the outer diameter of the rack shaft 18.

[0071] With the rack stopper 20 fixedly fitted into the medium diameter hole portion 29 by interference fit, the preload applying member 21 is elastically sandwiched between a side surface on one axial direction side of the inward flange portion 43 and a side surface on the other axial direction side of the rack bush 19 (bush body 37). As a result, the preload applying member 21 elastically presses the rack bush 19 toward one axial direction side. In other words, the preload applying member 21 applies a preload to the rack bush 19 facing one axial direction side. Then, the side surface on one axial direction side of the engagement flange portion 40 provided on the rack bush 19 is pressed (butted) against an inner side surface on one axial direction side of the engagement recess 32.

[0072] According to the steering device 1 of this embodiment having the above-mentioned configuration, it is possible to suppress rattling of the rack bush 19 in the axial direction without deteriorating the ease of assembly. That is, in this example, the preload applying member 21 constituting the elastic rack stopper 22 applies a preload to the rack bush 19 in one axial direction, and the side surface on one axial direction of the engagement flange 40 provided on the rack bush 19 can be pressed against the inner surface on one axial direction of the engagement recess 32. Therefore, even if the axial dimension of the engagement flange 40 is set slightly smaller than the axial dimension of the engagement recess 32 in order to ensure ease of assembly of the steering gear unit 7, it is possible to suppress axial wobbling of the rack bush 19. As a result, even when the rack shaft 18 is displaced in the axial direction, it is possible to effectively prevent the occurrence of hitting sounds caused by collision between the rack bush 19 and the rack accommodating portion 23.

[0073] Moreover, in this example, the preload applying member 21 for suppressing axial rattle of the rack bush 19 is fixed in advance to the rack stopper 20 for regulating the stroke of the rack shaft 18, so that the work of fitting the preload applying member 21 between the rack bush 19 and the rack stopper 20 does not need to be performed separately from the work of attaching (pressing) the rack stopper 20. Therefore, compared to a structure not including the preload applying member 21, the number of assembly steps does not increase. Therefore, in this example, the ease of assembly of the steering gear unit 7 is not reduced, and the steering gear unit 7 of This helps prevent increases in manufacturing costs.

[0074] In this example, the preload applying member 21 made of an elastic material is fixed to the rack stopper 20, so that the preload applying member 21 can be prevented from being displaced radially relative to the rack shaft 18. Therefore, it is possible to prevent the inner circumferential surface of the preload applying member 21 from coming into contact with the outer circumferential surface of the rack shaft 18, thereby preventing the generation of abnormal noise.

[0075] Furthermore, since the outer and inner peripheral surfaces of the preload applying member 21 are each tapered in a free state, even when the preload applying member 21 is elastically deformed, the outer peripheral surface of the preload applying member 21 can be prevented from abutting against the inner peripheral surface of the small diameter hole portion 30, and the inner peripheral surface of the preload applying member 21 can be prevented from abutting against the outer peripheral surface of the rack shaft 18.

[0076] In addition, because the preload applying member 21 is made of an elastic material, it is possible to prevent the preload applied to the rack bush 19 from becoming excessive due to dimensional variations, etc., and therefore damage to the rack bush 19 can be prevented. Furthermore, because the cross-sectional shape of the preload applying member 21 in a free state is tapered, it is possible to gently increase the rise of the elastic force when the preload applying member 21 is elastically deformed in the axial direction between the rack bush 19 and the rack stopper 20. This makes it easy to adjust the magnitude of the preload applied to the rack bush 19.

[0077] With the rack stopper 20 fitted into the medium diameter hole portion 29, the abutment portion 44 provided on the fitting cylindrical portion 42 abuts against the step surface 31, so that the rack stopper 20 can be prevented from moving to one side in the axial direction even if the spherical joint 36 repeatedly collides with the stopper portion 45 provided on the inward flange portion 43. This prevents the stroke end of the rack shaft 18 from changing.

[0078] As a modification of this example, the preload applying member may be configured not from one annular member that is continuous in the circumferential direction, but from a plurality of members each made of an elastic material.

[0079] [Second Example of the Implementation Form] The second embodiment will be described with reference to FIGS.

[0080] In this example, the preload applying member 21 a is not fixed to the rack stopper 20 , but is a separate part from the rack stopper 20 .

[0081] As shown in FIGS. 17 to 19, the preload applying member 21a is composed of a main body portion 46 made of an elastic material and a core portion 47 having higher rigidity than the main body portion 46.

[0082] The core 47 is formed by bending a metal plate having sufficient strength and rigidity, such as a steel plate. The core 47 has an L-shaped cross section, and includes a cylindrical fixed tube portion 48 and a bent portion 49 that is bent at a substantially right angle from the other axial end of the fixed tube portion 48 toward the inside in the radial direction. When implementing the present invention, the material of the core may be any material having a higher rigidity than the main body portion, and is not limited to metal, and hard resin, hard rubber, etc. may also be used.

[0083] The fixed cylinder portion 48 has an outer diameter slightly larger than the inner diameter of the small diameter hole portion 30, and is press-fitted into a portion of the inner circumferential surface of the small diameter hole portion 30 that is located closer to the opening (the other axial direction side) than the engagement recess 32. The axial dimension of the fixed cylinder portion 48 is smaller than the axial dimension of the portion of the small diameter hole portion 30 that is away from the engagement recess 32 on the other axial direction side.

[0084] The bent portion 49 is configured in a circular plate shape and has an inner diameter approximately the same as that of the inward flange portion 43 constituting the rack stopper 20. Both axial side surfaces of the bent portion 49 exist on an imaginary plane perpendicular to the central axis of the preload applying member 21a and are arranged parallel to each other. The bent portion 49 has a core abutment portion 50 on its side surface on the other axial side that abuts against the side surface of the inward flange portion 43 on one axial side over the entire circumference.

[0085] The main body 46 is made of an elastic material such as rubber or synthetic resin, has a circular ring shape, and is fixed to the core 47. In this example, the main body 46 is vulcanized and bonded (insert molded) to the core 47. That is, the process of molding the main body 46 and the process of bonding the main body 46 to the core 47 are performed simultaneously. The outer peripheral surface of the main body 46 is bonded and fixed to the inner peripheral surface of the fixed cylinder 48 over the entire circumference, and the side surface of the other axial side of the main body 46 is bonded and fixed to the side surface of one axial side of the bent portion 49 over the entire circumference. In this way, in this example, the main body 46 made of an elastic material is bonded and fixed to the core 47 having an L-shaped cross section, so that the bonding area can be secured and sufficient adhesive force can be secured. For example, a phenol resin-based adhesive or an epoxy resin-based adhesive can be used as the adhesive. When implementing the present invention, the means for fixing the main body to the core is not limited to vulcanization adhesion, but may also include so-called post-adhesion, in which the main body is adhered after molding using an adhesive, as well as chemical joining means such as pasting using double-sided adhesive tape, or mechanical joining means such as pressing or crimping.

[0086] The main body 46 has a generally trapezoidal cross-sectional shape in a free state. The main body 46 also has a tapered cross-sectional shape in which the radial dimension decreases as the main body 46 moves away from the rack stopper 20 in the axial direction.

[0087] The main body 46 has a tapered inner peripheral surface in a free state. Therefore, the generatrix shape of the inner peripheral surface of the main body 46 is not parallel to the central axis of the preload applying member 21a. The inner peripheral surface of the main body 46 is inclined in a direction such that the inner diameter increases toward the tip side in the axial direction (away from the rack stopper 20). The inner diameter of the main body 46 at its smallest portion is approximately the same as the inner diameter of the bent portion 49 and the inward flange portion 43, and is sufficiently larger than the outer diameter of the rack shaft 18.

[0088] The preload applying member 21a of this example is attached by press-fitting the fixed cylinder portion 48 into a portion of the inner circumferential surface of the small diameter hole portion 30 that is located closer to the opening side (the other axial side) than the engagement recess 32, and by abutting a side surface on one axial side of the inward flange portion 43 constituting the rack stopper 20 against a core abutment portion 50 provided on a side surface on the other axial side of the bent portion 49. As a result, the main body portion 46 elastically deforms in the axial direction, and applies a preload to the rack bush 19 facing one axial side. Then, the side surface on one axial side of the engagement flange portion 40 provided on the rack bush 19 is pressed against an inner side surface on one axial side of the engagement recess 32.

[0089] Even in the case of this example having the above-described configuration, the main body portion 46 constituting the preload applying member 21a can apply a preload to the rack bush 19 toward one axial side, thereby suppressing axial wobble of the rack bush 19.

[0090] In this example, since the preload applying member 21a is configured separately from the rack stopper 20, the installation work (press-in work) of the preload applying member 21a needs to be performed separately from the installation work (press-in work) of the rack stopper 20. However, since the preload applying member 21a is configured not only from the main body portion 46 made of an elastic material but by fixing the main body portion 46 made of an elastic material to the core portion 47, the installation work of the preload applying member 21a can be easily performed by pressing the core portion abutting portion 50 provided on the highly rigid core portion 47 with the tip of a tool (not shown). Therefore, even in the case of this example, the assembly workability of the steering gear unit 7 does not decrease. In addition, since the highly rigid core portion 47 is pressed with a tool (not shown), the press-in load can be easily detected, and abnormality can also be easily detected.

[0091] Furthermore, when the rack stopper 20 is fitted into the medium diameter hole portion 29, the axial position of the preload applying member 21a can be regulated to an appropriate position by abutting one axial side surface of the inward flange portion 43 against the core abutment portion 50 of the bent portion 49. Therefore, the magnitude of the preload applied to the rack bush 19 can be easily regulated to an appropriate value.

[0092] Since the main body 46 made of an elastic material is fixed to the core 47 having high rigidity and the core 47 is press-fitted into the small diameter hole 30, it is possible to prevent the preload applying member 21a from being displaced radially relative to the rack shaft 18. Therefore, it is possible to prevent the generation of abnormal noise caused by the inner circumferential surface of the main body 46 coming into contact with the outer circumferential surface of the rack shaft 18.

[0093] Furthermore, since the inner circumferential surface of the main body portion 46 is tapered in a free state, the inner circumferential surface of the main body portion 46 can be prevented from contacting the outer circumferential surface of the rack shaft 18 even when the main body portion 46 is elastically deformed. The other configurations and effects are the same as those of the first embodiment.

[0094] Although the embodiment of the present invention has been described above, the present invention is not limited to this, and can be modified as appropriate without departing from the technical concept of the invention. Furthermore, the structures of the examples of the embodiment can be combined as appropriate as long as no contradiction occurs.

[0095] When carrying out the present invention, the structures of the rack bush, rack stopper, and preload applying member are not limited to those described in the respective embodiments, and can be modified as appropriate. Specifically, in the first embodiment, the structure in which the preload applying member is fixed to the axial side surface of the rack stopper is shown, but the fixing position of the preload applying member is not particularly limited, and can be modified as appropriate according to the shape of the rack stopper.

[0096] In each of the examples of the above-mentioned embodiments, the present invention is described as being applied to the opening of the rack accommodating section that is farther from the pinion shaft, but the present invention can also be applied to the opening on the closer side to the pinion shaft, or to the openings on both sides of the rack accommodating section.

[0097] In each of the above-described embodiments, the present invention has been described as being applied to a column-assist type electric power steering device, but the present invention is not limited to column-assist type electric power steering devices, and can be applied to various types of electric power steering devices such as rack-assist type, pinion-assist type, and dual pinion type electric power steering devices. The present invention is also not limited to electric power steering devices, and can be applied to hydraulic power steering devices and manual steering devices. Furthermore, the present invention can be applied to a steer-by-wire type steering device. [Explanation of symbols]

[0098] 1 Steering device 2 Steering wheel 3 Steering shaft 4. Steering column 5a, 5b Universal joint 6 Intermediate shaft 7 Steering gear unit 8 Tie Rod 8a Spherical part 9 Electrically assisted devices 10 Gear housing 11 Torsion bar 12 Output shaft 13 Torque Sensor 14 Electric motor 15 Worm reducer 16 Housing 17 Pinion shaft 18 Rack shaft 19 Luck Bush 20 Rack stopper 21, 21a Preloading member 22 Rack stopper with elastic material 23 Rack storage section 24 Pinion housing 25 Rack guide housing 26a, 26b Mounting part 27 Insertion hole 27a Body hole 27b Stepped hole 27c Stepped hole 28 Large diameter hole 29 Medium diameter hole 30 Small diameter hole 31 Step surface 32 Engagement recess 33 Second step surface 34 rack teeth 35 Screw hole 36 Spherical joint 36a Shaft 36b Holder part 37 Bush body 37a Cylindrical surface part 37b, 37c Tapered surface part 37d Recess 38 Elastic Ring 39a, 39b slit 40 Engagement flange 41 Locking groove 42 Fitting cylinder part 43 Inward flange 44 Stopping part 45 Stopper part 46 Main body 47 Core 48 Fixed cylinder part 49 Bend section 50 Core butt section 100 Steering gear unit 101 Housing 101a Rack storage section 101b Pinion housing 102 Pinion shaft 103 Rack shaft 104 Rack Bush 105 Spherical joint 106 Tie rod 107 Bush body 107a Engagement flange 107b Locking groove 108 Elastic Ring 109 Engagement recess

Claims

1. A rack shaft; a pinion shaft meshing with the rack shaft; a housing having a rack accommodating portion that accommodates the rack shaft and a pinion accommodating portion that accommodates the pinion shaft; a rack bushing for supporting the rack shaft relative to the rack housing portion so as to allow the rack shaft to move in an axial direction; a rack stopper that is fitted into the rack accommodating portion and that restricts axial displacement of the rack shaft; a preload applying member that is disposed between the rack bush and the rack stopper and applies a preload in an axial direction to the rack bush, The rack accommodating portion has a first hole portion, a second hole portion that is disposed on the inner side of the first hole portion and has an engagement recess in a part in the axial direction, and a step surface that is disposed between the first hole portion and the second hole portion, The rack bush is fitted into the second hole portion with an engagement flange provided on an axial portion of an outer circumferential surface of the rack bush engaged with the engagement recess, The rack stopper is fitted into the first hole portion with an abutment portion provided on a side surface in an axial direction abutting against the step surface, The preload applying member has a main body made of an elastic material and a core to which the main body is fixed and has higher rigidity than the main body, and the core is press-fitted into a portion of an inner circumferential surface of the second hole portion that is located closer to the opening of the rack accommodating portion than the engagement recess. Rack and pinion type steering gear unit.

2. the core portion has a substantially L-shaped cross section, and includes a fixed cylindrical portion that is press-fitted into the second hole portion, and a core portion abutting portion against which an axial side surface of the rack stopper abuts, The main body is adhesively fixed to the core.

2. A rack and pinion type steering gear unit according to claim 1.

3. 3. The rack and pinion type steering gear unit according to claim 1, wherein the preload applying member has an inner peripheral surface having a generatrix shape that is non-parallel to the central axis.

Images