Steering device and method for manufacturing steering device

Abstract

This steering device (PS1) is configured in such a manner that a preload applying mechanism (6) applies rotational torque to one side in the rotational direction of a ball nut (4) on the basis of a reaction force generated by elastic contact between a plunger (61) and the tip of a first sector tooth (321) of a sector gear (32). Therefore, in the steering device (PS1), it is not necessary to provide a pressed portion pressed by the plunger (61) separately from the sector gear (32) as in the conventional steering device. As a result, it is possible to suppress an increase in size of the sector shaft (3) accompanying the formation of the pressed portion.

Description

Technical Field

[0001] The present invention relates to a steering device and a method for manufacturing the steering device. Background Art

[0002] As an existing steering device, for example, the steering device described in the following Patent Document 1 is known.

[0003] That is, the steering device of Patent Document 1 described below is configured such that a steering shaft connected to a steering wheel and a sector shaft connected to a steering wheel are arranged in a crossed manner, and a rack tooth formed at a ball nut screwed to the steering shaft and a sector gear provided on the sector shaft are engaged with each other.

[0004] Moreover, a preloading mechanism for adjusting a backlash between the rack tooth at the neutral position of the sector shaft and the teeth of the sector gear is provided between the ball nut and the sector shaft. The preloading mechanism includes: a plunger that is buried together with a biasing member at a position facing an axial end portion of the sector gear inside the ball nut and biases the sector gear side via the biasing member; and a plunger sliding contact portion that is provided on the sector shaft and is constituted by a cam profile that can elastically contact the plunger within a predetermined rotation range centered on the neutral position of the sector shaft. That is, the preloading mechanism biases the ball nut toward the rotation direction side within a predetermined range centered on the neutral position of the sector shaft based on a reaction force from the plunger sliding contact portion generated by the elastic contact between the plunger and the plunger sliding contact portion. Thereby, the preloading mechanism can reduce the backlash between the rack tooth and the sector gear near the neutral position of the sector shaft.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Laid-Open No. 5-319285 Summary of the Invention

[0008] Technical Problem to be Solved by the Invention

[0009] However, in the existing steering device, it is necessary to separately provide a plunger sliding contact portion from the sector gear. Therefore, there is still room for improvement in terms of the increase in the axial size of the sector shaft corresponding to the plunger sliding contact portion.

[0010] The present invention has been made in view of the above technical problems, and an object thereof is to provide a steering device and a method for manufacturing the steering device that can suppress the increase in size of the sector shaft.

[0011] Technical Solution for Solving the Technical Problem

[0012] As one aspect of the present invention, a steering device is characterized by comprising: rack teeth formed on the outer side of a ball nut that is screwed onto a steering shaft connected to a steering wheel; a sector gear provided on a sector shaft connected to a steering wheel, including a central tooth that meshes most deeply with the rack teeth at a neutral position of the sector shaft corresponding to a forward steering state, and a plurality of sector teeth provided in the circumferential direction of the sector shaft that mesh with the rack teeth; and a preload applying mechanism that adjusts the engagement between the rack teeth near the neutral position of the sector shaft and the sector gear. The preload applying mechanism has: a plunger receiving hole provided in a region near the neutral position of the sector shaft that is offset toward one end side in the tooth width direction of a specific tooth root of the rack teeth facing the tooth tip of the central tooth and opening at the specific tooth root; a plunger that is received in the plunger receiving hole so as to be able to advance and retreat, and is provided such that the front end side can protrude from an opening portion of the plunger receiving hole facing the sector gear; a sliding ring that is press-fitted onto the outer peripheral side of the plunger and can move integrally with the plunger, and slides relative to the inner peripheral surface of the plunger receiving hole as the plunger advances and retreats; and a biasing member that exists between the bottom of the plunger receiving hole and the sliding ring, and biases the plunger toward the central tooth via the sliding ring. Based on a reaction force generated by elastic contact between the plunger and the tooth tip of the central tooth, a force is applied to the ball nut toward one side in the rotation direction of the ball nut.

[0013] Thus, in the present invention, the plunger biased by the biasing member elastically contacts the tooth tip of the central tooth of the sector gear, thereby applying a rotational torque that becomes a preload to the ball nut. Thus, in the present invention, there is no need to separately provide a pressed portion pressed by the preload applying mechanism as in the prior art, and therefore it is possible to suppress the enlargement of the sector shaft accompanying the formation of the pressed portion.

[0014] Further, as another aspect of the steering device, it is preferable that the engagement between the press-fitted sliding ring and the plunger restricts relative movement between the sliding ring and the plunger in relation to the acting force of the biasing member, while allowing relative movement between the sliding ring and the plunger in relation to the meshing force between the sector gear and the rack teeth.

[0015] When the sliding ring and the plunger are integrally formed, for example, depending on the machining accuracy (machining error) of the plunger that abuts against the central tooth of the sector gear and the plunger receiving hole that houses the plunger, there is a concern that the length of the plunger on the side closer to the sector gear than the sliding ring becomes too long. As a result, when the sector gear meshes with the rack teeth, the plunger is overly pressed in, and as a result, the biasing member is overly compressed, which may lead to breakage or reduced lifespan of the biasing member.

[0016] In contrast, in the present invention, the sliding ring is pressed into the plunger by fitting that restricts the relative movement between the sliding ring and the plunger with respect to the acting force of the biasing member and allows the relative movement between the sliding ring and the plunger to a certain extent with respect to the meshing force between the sector gear and the rack teeth. Thus, by the acting force of the biasing member, the sliding ring and the plunger move integrally. On the other hand, when the sector gear meshes with the rack teeth, the plunger is pressed into the opposite side of the entering direction by the sector gear, and thus the plunger relatively moves with respect to the sliding ring, and the positional relationship between the plunger and the sliding ring can be changed to an appropriate relative position. As a result, the plunger can be biased with respect to the sector gear with an appropriate acting force regardless of the machining errors of the axial dimensions of the plunger housing hole, the plunger, and the sliding ring, and an appropriate preload can be applied to the ball nut.

[0017] In addition, by allowing the relative movement between the sliding ring and the plunger with respect to the meshing force between the sector gear and the rack teeth, the risk that the biasing member is overcompressed due to the meshing between the sector gear and the rack teeth is eliminated. Thereby, it is used to suppress the breakage of the biasing member and improve the durability of the biasing member.

[0018] In addition, as another aspect of the steering device, it is preferable that the plunger housing hole has a recess at the bottom on the side opposite to the opening portion, and the recess can accommodate the end portion of the plunger opposite to the front end portion that abuts against the tip of the central tooth.

[0019] Depending on the length of the end portion of the plunger closer to the biasing member than the sliding ring, there is a concern that when the plunger is pressed into by the central tooth, the end portion of the plunger abuts against the bottom of the plunger housing hole, and the pressing (retreating movement) of the plunger is hindered.

[0020] In contrast, in the present invention, a recess is provided at the bottom of the plunger housing hole on the side opposite to the opening portion, and the recess can accommodate the end portion of the plunger opposite to the front end portion that abuts against the central tooth of the sector gear. Therefore, when the plunger is pressed into by the central tooth, the end portion of the plunger is accommodated in the recess, and thus the risk that the end portion of the plunger abuts against the bottom of the plunger housing hole and hinders the pressing (retreating movement) of the plunger is eliminated. Thereby, the relative position between the plunger and the sliding ring can be adjusted to an appropriate state regardless of the length of the end portion of the plunger closer to the biasing member than the sliding ring.

[0021] Further, as another mode of the steering device, preferably, the plunger receiving hole is reduced in diameter such that the opening portion has an inner diameter smaller than the outer diameter of the sliding ring, and has a stopper for restricting the protruding amount of the plunger by abutting against the sliding ring. In a state where the rotational phase of the sector shaft is near the neutral position, the sliding ring does not abut against the stopper, and the abutment of the plunger against the central tooth is allowed. On the other hand, in a state where the rotational phase of the sector shaft exceeds the vicinity of the neutral position, the sliding ring abuts against the stopper, restricting the abutment of the plunger against the central tooth.

[0022] Thus, the present invention is configured such that the abutment of the plunger against the central tooth is allowed when the rotational phase of the sector shaft is near the neutral position, and the abutment of the plunger against the central tooth is restricted by the stopper when the rotational phase of the sector shaft exceeds the vicinity of the neutral position. In this way, by restricting the protruding amount of the plunger using the stopper, it is possible to adjust the meshing of the rack teeth and the sector gear only near the steering neutral position where a sense of rigidity is required. In other words, outside the vicinity of the steering neutral position where a sense of rigidity is not particularly required, by restricting the abutment of the plunger against the central tooth, it is possible to suppress the deterioration of the steering feeling such as the so-called stiffness (stiffness) feeling caused by the sliding contact between the plunger and the central tooth.

[0023] Further, in the present invention, the stopper is formed only by reducing the opening portion of the plunger receiving hole. Therefore, unlike the prior art where a complex cam profile is formed, the protruding amount of the plunger can be restricted with a relatively simple configuration, which helps to reduce the manufacturing cost of the steering device.

[0024] And, as another alternative of the steering device, preferably, the root of the teeth of the sector gear is a flat surface parallel to the axis of the sector shaft.

[0025] In this way, in the present invention, the tip of the central tooth in contact with the plunger has a linear shape parallel to the axis of the sector shaft. That is, the present invention is configured such that, unlike the prior art where the rack teeth and the sector gear are formed as bevel gear shapes, and no mechanism for adjusting the meshing of the rack teeth and the sector gear is provided other than the preload applying mechanism, and the meshing of the rack teeth and the sector gear is adjusted only by the preload applying mechanism. Therefore, the structure of the steering device can be simplified, which helps to improve the productivity of the steering device and reduce the manufacturing cost.

[0026] Further, as another mode of the steering device, preferably, the root of the teeth of the sector gear has a conical surface where the tooth height of the sector gear gradually increases toward one end side in the axial direction of the sector shaft, and the sector shaft is configured to be movable toward one end side in the axial direction of the sector shaft by an adjustment screw that is screwed in from the other end portion in the axial direction of the sector shaft through an internal threaded hole formed in the end wall of the housing that houses the sector shaft.

[0027] Thus, in the present invention, the rack teeth and the sector gear have a bevel gear shape, and the meshing of the rack teeth and the sector gear can be adjusted by moving the sector shaft along one end side in the axial direction using an adjusting screw. Thus, the proper meshing of the rack teeth and the sector gear can be ensured not only near the neutral position of the sector shaft but also in the entire area of ​​the rotation range of the sector shaft.

[0028] In addition, as another embodiment of the steering device, it is preferred that the axial end side of the fan shaft connected to the steering arm across the fan gear is formed with a larger diameter, and the other axial end side across the fan gear is formed with a smaller diameter than the one axial end side, and the plunger accommodating hole is open at the end portion of the specific tooth root in the tooth width direction, corresponding to the other axial end side of the fan shaft.

[0029] Thus, in the present invention, the plunger receiving hole constituting the preload applying mechanism is arranged on the side where the sector shaft has a smaller diameter, and the preload applying mechanism can be arranged at a position farther from the rotation center of the ball nut. Thus, a larger rotation torque can be applied to the ball nut, and the meshing between the rack teeth and the sector gear can be adjusted more effectively.

[0030] In addition, as a method for manufacturing the steering device, it is preferred that the method includes: a force-applying component assembly step of accommodating the force-applying component in the plunger receiving hole; a sliding ring assembly step of assembling the sliding ring to the plunger; a plunger assembly step of assembling the plunger assembled with the sliding ring in the plunger receiving hole; and a plunger adjustment step of, after the plunger assembly step, meshing the sector gear with the rack teeth to adjust the relative position of the plunger and the sliding ring, the plunger adjustment step comprising: a first step of rotating the sector gear in one direction relative to the rack teeth assembled with the preload applying mechanism, and rotating the sector gear in a non-neutral position. The fan-shaped gear is meshed; a second step, after the first step, the fan-shaped gear is rotated toward the neutral position in the direction in which the distance between the central tooth and the specific tooth root becomes smaller, and the central tooth overcomes the force of the force-applying member and presses the plunger to the side opposite to the force-applying direction of the force-applying member, thereby compressing the force-applying member to the maximum contraction via the sliding ring that moves integrally with the plunger; and a third step, after the second step, when the force-applying member is in the maximum contracted state, the central tooth further presses the plunger to the side opposite to the force-applying direction of the force-applying member, thereby causing the plunger to move relative to the sliding ring to the side opposite to the force-applying direction of the force-applying member.

[0031] Thus, in the present invention, in the plunger adjustment process, when the central tooth further presses the plunger at the maximum contraction of the biasing member, the plunger can move relative to the sliding ring, and the positional relationship between the plunger and the sliding ring can be changed to an appropriate relative position. Thereby, an appropriate biasing force can be applied to the plunger relative to the sector gear regardless of the machining errors of the axial dimensions of the plunger receiving hole, the plunger, and the sliding ring, so as to apply an appropriate preload to the ball nut.

[0032] In addition, in the plunger adjustment process, when the central tooth further presses the plunger in the state where the biasing member is compressed to the maximum, relative movement of the plunger with respect to the sliding ring is allowed. Thus, even when the protruding amount of the plunger is larger than the specified dimension due to machining errors of the axial dimensions of the plunger receiving hole, the plunger, and the sliding ring, etc., the biasing member will not be overcompressed. Thereby, breakage of the biasing member is suppressed, and the durability of the biasing member is improved.

[0033] In addition, as another aspect of the manufacturing method of the steering device, preferably, the plunger receiving hole has a recess at the bottom on the side opposite to the opening portion, and the recess can accommodate the end portion on the opposite side of the front end portion of the plunger that abuts against the tooth top of the central tooth. In the third process, when the plunger moves relative to the sliding ring in the direction opposite to the biasing direction of the biasing member, the end portion of the plunger is accommodated in the recess.

[0034] In the third process, depending on the length of the end portion of the plunger on the side closer to the biasing member than the sliding ring, there is a concern that when the plunger is pressed in by the central tooth, the end portion of the plunger abuts against the bottom of the plunger receiving hole, which may prevent the plunger from being pressed in (retreating movement).

[0035] In contrast, in the present invention, a recess is provided at the bottom of the plunger receiving hole on the side opposite to the opening portion, and the recess can accommodate the end portion on the opposite side of the front end portion of the plunger that abuts against the central tooth of the sector gear. Therefore, in the third process of the plunger adjustment process, when the plunger is pressed in by the central tooth, the end portion of the plunger is accommodated in the recess, thereby eliminating the risk that the end portion of the plunger abuts against the bottom of the plunger receiving hole and prevents the plunger from being pressed in (retreating movement). Thereby, the relative position between the plunger and the sliding ring can be adjusted to an appropriate state regardless of the length of the end portion of the plunger on the side closer to the biasing member than the sliding ring.

[0036] Advantages of the Invention

[0037] According to the present invention, the preload applying mechanism elastically contacts the tooth top of the central tooth of the sector gear, thereby being configured to apply a rotational torque to the ball nut. Therefore, there is no need to separately provide a pressed portion pressed by the preload applying mechanism from the sector gear, and the enlargement of the sector shaft accompanying the formation of the pressed portion can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a longitudinal sectional view of the steering device according to the first embodiment of the present invention.

[0039] Figure 2 is Figure 1 a sectional view taken along line A-A of

[0040] Figure 3 is Figure 1 an enlarged view of the main part of

[0041] Figure 4 is a diagram showing the change in the protruding amount of the plunger corresponding to the steering state. (a) shows the neutral state with a steering angle of 0 degrees, (b) shows the steering state with a steering angle of 12 degrees, and (c) shows the steering state with a steering angle of 25 degrees.

[0042] Figure 5 is a diagram showing the plunger adjustment process of the manufacturing method of the steering device of the present invention. (a) shows the first process, (b) shows the second process, (c) shows the third process, and (d) shows the maximum entry state of the plunger after adjustment.

[0043] Figure 6 represents the second embodiment of the steering device of the present invention, and is a transverse sectional view of the steering device corresponding to the sectional view taken along line A-A of Figure 1 DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] Hereinafter, embodiments of the steering device and the manufacturing method of the steering device of the present invention will be described based on the drawings. In addition, in the following embodiments, an example is shown in which the steering device and the manufacturing method of the steering device are applied to a so-called integral power steering device for large-sized vehicles such as trucks.

[0045] [First Embodiment]

[0046] (Configuration of the Steering Device)

[0047] Figure 1 Represents the first embodiment of the steering device of the present invention, and is a longitudinal sectional view of the steering device PS1 cut along the rotation center of the steering shaft 2. Figure 2 Represents along Figure 1 a transverse sectional view of the steering device PS1 cut along line A-A of Figure 1 In addition, hereinafter, in the rotation axis X direction of the steering shaft 2 in Figure 2In the direction of the rotation axis Y of the sector shaft 3, the side connected to the steering wheel (not shown) is referred to as the "one end side", and the side connected to the ball nut 4 is referred to as the "other end side" for explanation.

[0048] As Figure 1 , Figure 2 As shown, the steering device PS1 is a well-known ball nut type steering device, which has a steering shaft 2 connected to a steering wheel (not shown) and a sector shaft 3 connected to a steering wheel (not shown). The steering shaft 2 and the sector shaft 3 are housed inside the housing 1. And, there is a ball nut 4 between the steering shaft 2 and the sector shaft 3, and the rotation of the steering shaft 2 is converted into the rotation of the sector shaft 3 via the ball nut 4.

[0049] The housing 1 has a first housing 11, a second housing 12, and a third housing 13. The first housing 11 functions as a housing main body that houses the steering shaft 2, the sector shaft 3, and the ball nut 4 inside. That is, the first housing 11 has: a substantially cylindrical steering shaft housing portion 111 that extends in the direction of the rotation axis X and houses the steering shaft 2 and the ball nut 4; and a substantially cylindrical sector shaft housing portion 112 that extends in the direction of the rotation axis Y orthogonal to the rotation axis X and houses the sector shaft 3.

[0050] As Figure 1 As shown, the steering shaft housing portion 111 has a bottomed cylindrical shape, and one end side in the direction of the rotation axis X of the bottomed cylindrical shape opens to the outside through a first opening portion 111a, and the other end side is closed by an end wall 111b. The first opening portion 111a is closed by the second housing 12 that fits with the first opening portion 111a.

[0051] The second housing 12 has a cylindrical shape with an outer diameter that is stepped down toward the other end side, and has: a second housing main body portion 121 that abuts against the end face of the first opening portion 111a; and a second housing fitting portion 122 that is stepped down in diameter with respect to the second housing main body portion 121 and fits with the first opening portion 111a. Moreover, a first sealing member S1 that can elastically abut against the inner peripheral surface of the first opening portion 111a is installed on the outer peripheral side of the second housing fitting portion 122, and by elastically abutting the first sealing member S1 against the inner peripheral surface of the first opening portion 111a, the inside of the steering shaft housing portion 111 is kept liquid-tight.

[0052] Further, the second housing 12 has a steering shaft insertion hole 123 penetrating the central portion. Through the steering shaft insertion hole 123, the steering shaft 2 is inserted into the steering shaft housing portion 111 from the outside. The steering shaft insertion hole 123 is configured such that the inner diameter gradually decreases in a stepped manner from one end side toward the other end side. The large-diameter hole portion 123a having a relatively large diameter is provided at one end side, and the small-diameter hole portion 123b having a relatively small diameter is provided at the other end side. Further, a steering bearing 113 formed of a ball bearing is accommodated in the large-diameter hole portion 123a of the steering shaft insertion hole 123. Through the steering bearing 113, the steering shaft 2 is supported so as to be rotatable.

[0053] In addition, the steering bearing 113 includes an inner ring 113a integrally formed with the second steering shaft 22, an outer ring 113b inserted into the large-diameter hole portion 123a, and a plurality of ball members 113c provided between the inner ring 113a and the outer ring 113b. The outer ring 113b is held in a state of being restricted from axial movement by a lock nut 114 screwed into the large-diameter hole portion 123a.

[0054] As Figure 2 shown, the sector shaft housing portion 112 is disposed substantially tangentially with respect to the steering shaft housing portion 111 and is configured to communicate with the steering shaft housing portion 111 by sharing a part of the circumferential direction therewith. One end side in the direction of the rotation axis Y of the sector shaft housing portion 112 opens to the outside through the second opening portion 112a, and the other end side opens to the outside through the third opening portion 112b.

[0055] That is, in the sector shaft housing portion 112, one end portion of the sector shaft 3 inserted into the sector shaft housing portion 112 through the third opening portion 112b faces the outside through the second opening portion 112a and is connected to the steering arm (not shown) outside the housing 1. On the other hand, after the sector shaft 3 is inserted into the sector shaft housing portion 112 through the third opening portion 112b, the third opening portion 112b is closed by a third housing 13 fitted to the third opening portion 112b.

[0056] The third housing 13 has a cylindrical shape in which the outer diameter gradually decreases toward one end side and includes a third housing main body portion 131 that abuts against the end face of the third opening portion 112b and a third housing fitting portion 132 that is reduced in diameter in a stepped manner with respect to the third housing main body portion 131 and is fitted to the third opening portion 112b. Further, a second seal member S2 capable of elastically abutting against the inner peripheral surface of the third opening portion 112b is mounted on the outer peripheral side of the third housing fitting portion 132. By the elastic abutment of the second seal member S2 against the inner peripheral surface of the third opening portion 112b, the inside of the sector shaft housing portion 112 is kept liquid-tight.

[0057] Further, on the inner circumferential side of the third housing fitting portion 132, there is a bottomed cylindrical shaft support portion 133 for supporting the rotation of the other end portion of the sector shaft 3. The shaft support portion 133 has: a third housing cylindrical portion 134 that opens to one end side; and a third housing end wall 135 that closes the other end side of the third housing cylindrical portion 134.

[0058] As Figure 1 shown, the steering shaft 2 has: a first steering shaft 21, one end side of which is connected to a steering wheel (not shown); and a second steering shaft 22, a part of which is connected to the other end side of the first steering shaft 21 via a torsion bar 23 so as to overlap the first steering shaft 21 in the radial direction and be relatively rotatable. The first steering shaft 21 is connected to the torsion bar 23 via a first pin member 241 that penetrates in the radial direction at the other end portion of the first steering shaft 21. Similarly, the second steering shaft 22 is connected to the torsion bar 23 via a second pin member 242 that penetrates in the radial direction at the other end portion of the second steering shaft 22.

[0059] In addition, although not shown in the present embodiment, the steering shaft 2 may be mechanically connected to the steering wheel (not shown), and may also be electrically connected to the steering wheel (not shown) as in known steer-by-wire. In addition, the steering shaft 2 can be applied not only to the case of being connected to the steering wheel (not shown) and inputting a steering torque via the steering wheel in manual driving, but also to the case of being connected to a motor (not shown) and inputting a steering torque via the motor in autonomous driving. And, in the case of the manual driving method, it includes a method of inputting a steering torque from the steering wheel (not shown) and inputting a steering assist torque from the motor (not shown).

[0060] As Figure 2 shown, the sector shaft 3 has: a sector shaft portion 31 that extends along a direction of a rotation axis Y that intersects the rotation axis X of the steering shaft 2 at a substantially right angle; and a sector gear 32 that is disposed opposite to the ball nut 4 at the other end portion of the sector shaft portion 31. The sector shaft portion 31 and the sector gear 32 are integrally formed, and when the sector gear 32 rotates, the sector shaft portion 31 rotates integrally with the sector gear 32.

[0061] As Figure 2 shown, the sector shaft portion 31 has a first shaft portion 311 provided on the one end side of the sector gear 32 and a second shaft portion 312 provided on the other end side of the sector gear 32. Here, in the present embodiment, the first shaft portion 311 and the second shaft portion 312 are set to have substantially the same outer diameter.

[0062] One end side of the first shaft portion 311 is connected to the steering arm (not shown), and the other end side is supported by a first bearing 331 on the inner peripheral side of the second opening portion 112a so as to be rotatable. In addition, a first sealing member 341 is disposed on one end side of the first bearing 331 to liquid-tightly seal between the outer peripheral surface of the first shaft portion 311 and the inner peripheral surface of the second opening portion 112a. Thereby, the working fluid filled inside the housing 1 (sector shaft housing portion 112) is suppressed from flowing out to the outside through the second opening portion 112a.

[0063] On the other hand, the second shaft portion 312 is supported by a second bearing 332 on the inner peripheral side of the third housing cylindrical portion 134 so as to be rotatable. In addition, a second sealing member 342 is provided on the other end side of the second bearing 332 to liquid-tightly seal between the outer peripheral surface of the second shaft portion 312 and the inner peripheral surface of the third housing cylindrical portion 134. Thereby, the working fluid filled inside the housing 1 (sector shaft housing portion 112) is suppressed from flowing out to the outside through an internal thread hole 136 described later.

[0064] As Figure 1 , Figure 2 shown, the sector gear 32 is provided between the first shaft portion 311 and the second shaft portion 312, and has a connection base portion 320 connected to the first shaft portion 311 and the second shaft portion 312, and a first sector tooth 321, a second sector tooth 322, and a third sector tooth 323 provided on the side portion of the connection base portion 320 so as to face the rack teeth 42 of the ball nut 4. The first sector tooth 321 protrudes along a meshing direction line Z orthogonal to the rotation axis X and the rotation axis Y in the neutral state of the sector gear 32. The second sector tooth 322 protrudes obliquely to the right of the first sector tooth 321 toward one end side of the rotation axis X. The third sector tooth 323 protrudes obliquely to the left of the first sector tooth 321 toward the other end side of the rotation axis X.

[0065] In addition, in the present embodiment, as Figure 2 shown, the tooth root of the sector gear 32 becomes a flat surface parallel to the rotation axis Y so that the tooth height T of the sector gear 32 is constant in the tooth width direction. In other words, in the present embodiment, the tooth root of the sector gear 32 is configured in a linear shape parallel to the rotation axis Y.

[0066] As Figure 1 , Figure 2 shown, the ball nut 4 has a cylindrical shape, and a shaft hole 41 is formed along the direction of the rotation axis X. That is, the ball nut 4 is provided so as to be able to move forward and backward in the direction of the rotation axis X via a plurality of balls 43 existing between the shaft side ball groove 401 and the nut side ball groove 402, where the shaft side ball groove 401 is provided on the outer peripheral side of the second steering shaft 22 housed in the steering shaft housing portion 111, and the nut side ball groove 402 is provided on the inner peripheral side (shaft hole 41) of the ball nut 4.

[0067] In addition, on the outer peripheral portion of the ball nut 4, rack teeth 42 (first rack teeth 421, second rack teeth 422, third rack teeth 423, and fourth rack teeth 424, which will be described later) that mesh with the sector gear 32 are formed in a specified range facing the sector gear 32. On the other hand, on the back side of the rack teeth 42 in the outer peripheral portion of the ball nut 4, that is, on the side opposite to the rack teeth 42 across the rotation axis X, a cylindrical tube member 44 is disposed. The tube member 44 connects one end portion and the other end portion of the nut-side ball groove 402 and is used for the circulation of the plurality of balls 43.

[0068] As Figure 1 shown, the rack teeth 42 have the first rack teeth 421, the second rack teeth 422, the third rack teeth 423, and the fourth rack teeth 424 arranged side by side in the direction along the rotation axis X on the side portion of the ball nut 4 facing the sector gear 32. A central tooth, that is, a specific tooth root, the first rack tooth root 425, which faces the first sector tooth 321, is formed between the second rack teeth 422 and the third rack teeth 423. A second rack tooth root 426 that faces the second sector tooth 322 is formed between the first rack teeth 421 and the second rack teeth 422. A third rack tooth root 427 that faces the third sector tooth 323 is formed between the third rack teeth 423 and the fourth rack teeth 424.

[0069] Moreover, the ball nut 4 functions as a piston of a power cylinder that operates by the hydraulic pressure of the working fluid filled in the steering shaft housing portion 111, and the ball nut 4 is provided so as to be slidable within the steering shaft housing portion 111. That is, by the ball nut 4, two hydraulic chambers, namely, a first hydraulic chamber P1 and a second hydraulic chamber P2, that face each other in the direction of the rotation axis X are partitioned inside the steering shaft housing portion 111 with the ball nut 4 interposed therebetween. In addition, the second hydraulic chamber P2 is configured to be able to communicate with the sector shaft housing portion 112 via a communication hole 115 provided in the first housing 11. By guiding the working fluid in the second hydraulic chamber P2 into the sector shaft housing portion 112, lubrication between the sector gear 32 and the rack teeth 42 can be performed.

[0070] And, a known rotary valve RV as a control valve is formed inside the second housing 12. The rotary valve RV can selectively supply the working fluid supplied from a hydraulic source (for example, a pump) not shown to the first hydraulic chamber P1 or the second hydraulic chamber P2 of the power cylinder according to the relative rotation of the first steering shaft 21 and the second steering shaft 22. The rotary valve RV has: a rotor 210 that is integrally formed at the other end portion of the first steering shaft 21; and a sleeve 220 that is disposed on the outer peripheral side of the rotor 210 and is integrally provided at one end portion of the second steering shaft 22.

[0071] On the inner circumferential side of the second housing 12, there are circumferential grooves, i.e., an inlet 124a, a supply port 124b, and a discharge port 124c, which are arranged side by side in the direction of the rotation axis X and extend in the circumferential direction of the rotation axis X. And, an inlet passage 124d that connects an unillustrated inlet pipe to the inlet 124a and a discharge passage 124e that connects the discharge port 124c to an unillustrated discharge pipe are provided inside the second housing 12. And, inside the first housing 11 and the second housing 12, a supply passage L that connects the supply port 124b to the first hydraulic chamber P1 is provided across the first housing 11 and the second housing 12. Specifically, the supply passage L is composed of a first housing supply passage 116 provided inside the first housing 11 and a second housing supply passage 126 provided inside the second housing 12 and connecting the supply port 124b to the first housing supply passage 116. The inlet 124a is connected to the unillustrated hydraulic source via the inlet passage 124d and the unillustrated inlet pipe. The supply port 124b is connected to the first hydraulic chamber P1 via the supply passage L. The discharge port 124c is connected to an unillustrated liquid storage tank via the discharge passage 124e and the unillustrated discharge pipe.

[0072] On the outer circumferential side of the rotor 210, supply recesses 210a and discharge recesses (not illustrated) that extend in a longitudinal groove shape in the direction of the rotation axis X are alternately arranged side by side in the circumferential direction. Similarly, on the inner circumferential side of the sleeve 220, a right steering recess 220a and a left steering recess (not illustrated) that extend in a longitudinal groove shape in the direction of the rotation axis X are alternately arranged side by side in the circumferential direction. And, a first communication path 221, a second communication path 222, a supply communication path 223, and a discharge communication path 224 are provided in the sleeve 220 so as to communicate the inner circumference and the outer circumference of the sleeve 220. The first communication path 221 opens in the right steering recess 220a, and the second communication path 222 opens in the unillustrated left steering recess. And, in the circumferential direction, a supply communication path 223 or a discharge communication path 224 opens in an unillustrated convex portion sandwiched between the right steering recess 220a and the unillustrated left steering recess, and the supply communication path 223 and the discharge communication path 224 are alternately arranged in the circumferential direction.

[0073] And, as Figure 1 、 Figure 2 shown, a preload applying mechanism 6 is provided between the sector gear 32 and the rack teeth 42, and the preload applying mechanism 6 adjusts the meshing of the sector gear 32 and the rack teeth 42 near the neutral position of the sector shaft 3 corresponding to the forward steering state ( Figure 1 the position shown). In particular, as Figure 2As shown, the preloading mechanism 6 is disposed at the other end side in the tooth width direction of a specific tooth root, i.e., the first rack tooth root 425, that meshes with the central tooth, i.e., the first sector tooth 321, and at a position close to the side of the second shaft portion 312 that faces the other end side of the first sector tooth 321.

[0074] (Configuration of the preloading mechanism)

[0075] Figure 3 Indicates Figure 1 a magnified view of the vicinity of the main part of Figure 1 the preloading mechanism 6,

[0076] As Figure 3 shown, the preloading mechanism 6 includes: a plunger receiving hole 60 formed in the first rack tooth root 425; a plunger 61 received in the plunger receiving hole 60 so as to be able to move forward and backward; and a biasing member 62 present between the bottom of the plunger receiving hole 60 and the bottom of the plunger 61 and biasing the plunger 61 toward the first sector tooth 321.

[0077] The cross-section of the plunger receiving hole 60 is substantially circular, one end opens to the first rack tooth root 425, and the other end is closed by a bottom wall 600. In addition, the plunger receiving hole 60 is a circular hole having a constant inner diameter in the axial direction and is formed into a stepped diameter shape with a tapered tip by press-fitting an annular member 63 from the opening side. That is, the plunger receiving hole 60 has a large-diameter hole portion 601 with a larger diameter provided on the bottom wall 600 side and a small-diameter hole portion 602 with a smaller diameter formed on the inner peripheral side of the annular member 63 provided on the opening side. In addition, a stepped stopper 630 is formed between the large-diameter hole portion 601 and the small-diameter hole portion 602, and the stopper 630 can limit the amount of entry of the plunger 61, i.e., the protruding amount of the plunger 61 protruding from the small-diameter hole portion 602, by abutting against a sliding ring 64 described later provided on the outer peripheral side of the plunger 61.

[0078] The stopper 630 does not abut against the sliding ring 64 in a state where the rotational phase of the sector shaft 3 is near the neutral position, and allows the plunger 61 to abut against the first sector tooth 321 (see Figure 4 (a)). On the other hand, the stopper 630 abuts against the sliding ring 64 in a state where the rotational phase of the sector shaft 3 exceeds the vicinity of the neutral position, and restricts the abutment of the plunger 61 against the first sector tooth 321 (see Figure 4 (c)).

[0079] In addition, the bottom wall 600 of the plunger receiving hole 60 has a concave recess 603 at its central position that can accommodate the end portion 612 on the opposite side of the front end portion 611 of the plunger 61 that faces the first sector gear 321. The recess 603 is formed in a stepped concave shape with a circular cross-section and is provided opposite to the end portion 612 of the plunger 61. In addition, the recess 603 has a specified inner diameter that is larger than the outer diameter of the end portion 612 of the plunger 61 and smaller than the inner diameter of the biasing member 62. Moreover, the recess 603 has a depth that is larger than the machining errors generated in the plunger receiving hole 60, the plunger 61, and the sliding ring 64. In the plunger adjustment process described later, the end portion 612 of the plunger 61 pushed by the sector gear 32 (first sector gear 321) is accommodated. In other words, in the plunger adjustment process described later, when the plunger 61 is pushed by the first sector gear 321, the recess 603 accommodates the end portion 612 of the plunger 61, thereby avoiding collision with the bottom wall 600 of the plunger 61 and ensuring the retraction amount of the plunger 61.

[0080] Furthermore, the recess 603 functions corresponding to the extension amount (the overlapping amount with the biasing member 62) of the end portion 612 of the plunger 61 that extends more toward the bottom wall 600 side than the sliding ring 64. Therefore, when the relative positional relationship between the plunger 61 and the sliding ring 64 is such that the end portion 612 of the plunger 61 does not abut against the bottom wall 600 when the plunger 61 is pressed by the sector gear 32 (first sector gear 321) in the plunger adjustment process described later, the recess 603 is not an essential component in the preload applying mechanism 6.

[0081] The plunger 61 is formed of a resin material into a cylindrical shape with a constant outer diameter, and is formed into a stepped diameter shape by press-fitting an annular sliding ring 64 on the outer peripheral side. That is, the plunger 61 is configured to be able to move integrally with the sliding ring 64 and is slidably housed in the plunger receiving hole 60 via the sliding ring 64. In addition, the plunger 61 has an outer diameter that is slightly smaller than the inner diameter of the annular member 63, and the front end portion 611 that protrudes toward the front end side from the sliding ring 64 protrudes from the small-diameter hole portion 602 of the plunger receiving hole 60 and faces the outside, facing the first sector gear 321. In addition, in the plunger 61, the front end portion 611 has a gentle curved surface shape and can smoothly slide in contact with the tooth surface of the first sector gear 321 when the sector shaft 3 rotates.

[0082] Here, the plunger 61 is preferably set to have an outer diameter that is slightly larger than the inner diameters of the biasing member 62 and the annular member 63. That is, by reducing the gaps between the outer peripheral surface of the plunger 61 and the inner peripheral surfaces of the biasing member 62 and the annular member 63, the forward and backward movement of the plunger 61 can be guided by the inner peripheral surfaces of the biasing member 62 and the annular member 63, and the smoothness of the forward and backward movement of the plunger 61 can be achieved.

[0083] In addition, the plunger 61 is preferably set to have an axial length capable of passing through the inner peripheral side of the biasing member 62 and is such that in the neutral position (for example, refer to Figure 1 , Figure 4 (a)), it is located near the bottom wall 600 of the plunger receiving hole 60 when the biasing member 62 is maximally contracted. That is, it is preferable that the plunger 61 is configured to overlap with the biasing member 62 in a relatively long region on the inner peripheral side of the biasing member 62 when viewed radially from the plunger 61. Thereby, the outer peripheral side of the end portion 612 of the plunger 61 can be supported by the inner peripheral side of the biasing member 62, facilitating the forward and backward movement of the plunger 61.

[0084] The sliding ring 64 is substantially annular, has an inner diameter capable of being press-fitted onto the outer peripheral surface of the plunger 61, and has an outer diameter capable of slidingly contacting the plunger receiving hole 60. Also, the sliding ring 64 is provided so as to face the bottom wall 600 of the plunger receiving hole 60 on one side in the biasing direction of the biasing member 62 and functions as a seating surface for the biasing member 62 interposed between the bottom wall 600 of the plunger receiving hole 60 and the sliding ring 64. Further, the sliding ring 64 is provided so as to face the annular member 63 on the other side in the biasing direction of the biasing member 62 and functions as a contact surface for contacting the annular member 63, and restricts the amount of entry of the plunger 61 by contacting the annular member 63.

[0085] Moreover, the sliding ring 64 is press-fitted onto the plunger 61 with a degree of fitting that restricts the relative movement between the sliding ring 64 and the plunger 61 with respect to the acting force of the biasing member 62 and allows the relative movement between the sliding ring 64 and the plunger 61 with respect to the meshing force between the sector gear 32 and the rack tooth 42. That is, the sliding ring 64 is configured to maintain a fixed state with the plunger 61 in a state where the acting force of the biasing member 62 acts and can move forward and backward integrally with the plunger 61. On the other hand, the sliding ring 64 is configured such that in the plunger adjustment process described later, the plunger 61 can move relative to the sliding ring 64 in a state where the meshing force between the sector gear 32 and the rack tooth 42 acts.

[0086] The biasing member 62 is in the form of a ring or a cylinder that penetrates along the biasing direction on the inner peripheral side. One end of the biasing member 62 is seated on the bottom wall 600 of the plunger receiving hole 60, and the other end is seated on the sliding ring 64. The biasing member 62 is received between the bottom wall 600 of the plunger receiving hole 60 and the sliding ring 64 with a prescribed preload. More specifically, the biasing member 62 is applied with the prescribed preload in such a manner that the biasing force of the biasing member 62 acts on the plunger 61 even when the sliding ring 64 is in contact with the stopper 630, and the biasing force always acts on the plunger 61. In the present embodiment, the biasing member 62 is formed by serially overlapping a plurality of known disc springs. In addition, the biasing member 62 is not limited to a member formed by overlapping a plurality of disc springs as in the present embodiment. As long as it is a member such as a helical spring that is formed in a hollow shape and can continuously apply a biasing force to the plunger 61, the material and shape can be arbitrarily changed.

[0087] (Description of the operation of the preload applying mechanism)

[0088] Figure 4 This is a diagram showing the change in the protruding amount of the plunger 61 corresponding to the steering state. (a) shows the neutral state where the steering angle is 0 degrees, (b) shows the steering state where the steering angle is 12 degrees, and (c) shows the steering state where the steering angle is 25 degrees.

[0089] As Figure 4 As shown in (a) of [], in the neutral state where the steering angle is 0 degrees, the plunger 61 is in the most retracted state, and the sliding ring 64 is in a state of being separated from the stopper 630. Based on the biasing force of the biasing member 62, the front end portion 611 of the plunger 61 is in a state of elastically contacting the tooth top of the first sector gear 321. In this state, due to the reaction force generated by the contact between the front end portion 611 of the plunger 61 and the tooth top of the first sector gear 321, the ball nut 4 is biased toward one side in the rotational direction. As a result, on the other end side of the sector gear 32, the gap C between the first sector gear 321 and the root of the first rack tooth 425 becomes smaller. Thereby, the meshing between the first sector gear 321 and the second rack tooth 422 and the third rack tooth 423 becomes deeper, and the backlash between the first sector gear 321 and the second rack tooth 422 and the third rack tooth 423 decreases.

[0090] As Figure 4As shown in (b), in the steering state with a steering angle of 12 degrees, the plunger 61 is in the forward state, which is the state before the sliding ring 64 is about to contact the stopper 630, and becomes the state where the front end 611 of the plunger 61 elastically contacts the tooth top of the first sector gear 321 due to the acting force of the biasing member 62. In this state, corresponding to the elongation of the biasing member 62 due to the entry of the plunger 61, a relatively small acting force acts on the plunger 61 compared to the neutral state. That is, based on an acting force smaller than the neutral state, a reaction force generated by the contact between the front end 611 of the plunger 61 and the tooth top of the first sector gear 321 biases the ball nut 4 toward one side in the rotational direction. As a result, on the other end side of the sector gear 32, the clearance C between the first sector gear 321 and the root of the first rack tooth 425 decreases, and the backlash between the first sector gear 321 and the second rack tooth 422 and the third rack tooth 423 decreases.

[0091] As Figure 4 As shown in (c), in the steering state with a steering angle of 25 degrees, the plunger 61 is in the maximum forward state, which is the state where the sliding ring 64 contacts the stopper 630 and the entry movement of the plunger 61 is restricted, and becomes the state where the front end 611 of the plunger 61 separates from the tooth top of the first sector gear 321. In this state, since no acting force acts on the ball nut 4, the clearance C between the first sector gear 321 and the root of the first rack tooth 425 does not change, and the backlash between the first sector gear 321 and the second rack tooth 422 and the third rack tooth 423 is not adjusted.

[0092] (Manufacturing method of the steering device)

[0093] Figure 5 This is a diagram showing the plunger adjustment process for adjusting the protruding amount of the plunger 61 in the manufacturing method of the steering device PS1. (a) shows the first process, (b) shows the second process, (c) shows the third process, and (d) shows the maximum entry state of the plunger after the plunger adjustment.

[0094] Hereinafter, the manufacturing method of the steering device PS1 will be described. In addition, in the following description, the preloading mechanism assembly process for assembling the preloading mechanism 6, which is a characteristic configuration of the steering device PS1, in the manufacturing method of the steering device PS1 will be described.

[0095] That is, in the manufacturing method of the steering device PS1, as the preloading mechanism assembly process, it includes a biasing member assembly process for assembling the biasing member 62, a sliding ring assembly process for assembling the sliding ring 64, a plunger assembly process for assembling the plunger 61, and a plunger adjustment process for adjusting the relative position between the plunger 61 and the sliding ring 64.

[0096] In the force-applying member assembling process, the force-applying member 62 is received from the opening side inside the plunger receiving hole 60. In the sliding ring assembling process, the sliding ring 64 is assembled on the outer peripheral side of the plunger 61. In addition, regarding the force-applying member assembling process and the plunger assembling process, regardless of the order of implementation, either process can be implemented first. In the plunger assembling process, after the force-applying member assembling process, the plunger assembly body 610 formed by integrating the plunger 61 and the sliding ring 64 is received from the opening side inside the plunger receiving hole 60. The plunger adjustment process is carried out after the plunger assembling process, and the relative positions of the plunger 61 and the sliding ring 64 are adjusted by engaging the sector gear 32 with the rack teeth 42.

[0097] Here, the plunger adjustment process mainly includes the first process, the second process, and the third process detailed below.

[0098] In the first process, as shown in (a) of Figure 5 , the sector gear 32 is rotated in one direction relative to the rack teeth 42 of the preload applying mechanism 6, and the sector gear 32 is engaged in a state of being in a non-neutral position. At this moment, the plunger assembly body 610 is in a state of being maximally inserted by abutting against the stopper 630 through the sliding ring 64. On the other hand, the first sector tooth 321 is not in contact with the plunger 61 and is in a state just before contacting the plunger 61.

[0099] In the second process, after the first process, the sector gear 32 is rotated toward the neutral position in the direction in which the distance C between the first sector tooth 321 and the first rack tooth root 425 becomes smaller (the arrow R direction in the figure). Then, as the sector gear 32 rotates, the first sector tooth 321 presses the plunger 61 in the direction opposite to the force-applying direction of the force-applying member 62 against the acting force of the force-applying member 62. As shown in (b) of Figure 5 , the force-applying member 62 is compressed to the maximum contraction via the sliding ring 64 that moves integrally with the plunger 61.

[0100] In the third process, after the second process, in the state where the force-applying member 62 is maximally contracted (refer to (b) of Figure 5 ), the first sector tooth 321 further presses the plunger 61 in the direction opposite to the force-applying direction of the force-applying member 62. Thus, as shown in Figure 5As shown in (c), the plunger 61 moves relatively (recedes) in the direction opposite to the biasing direction of the biasing member 62 with respect to the sliding ring 64. At this time, since the end portion 612 of the plunger 61 pressed back by the first sector gear 321 is received by the recessed portion 603, the backward movement of the plunger 61 is not obstructed by the bottom wall 600. Thus, by the relative movement (recession) of the plunger 61 with respect to the sliding ring 64, the relative position of the plunger 61 and the sliding ring 64 is automatically adjusted to an appropriate position such that, in the neutral position, with the biasing member 62 in a maximally compressed state, the front end portion 611 of the plunger 61 abuts against the tooth crest of the first sector gear 321.

[0101] After that, if the sector gear 32 is further rotated in one direction, then as Figure 5 shown in (d), the plunger 61 and the sliding ring 64 move again toward the first sector gear 321 side while maintaining the relative position adjusted in the third process.

[0102] (Function and Effect of the Present Embodiment)

[0103] In the conventional steering device, the preload applying mechanism biases the ball nut toward one side in the rotational direction based on the reaction force from the plunger sliding contact portion, thereby reducing the backlash between the rack teeth and the sector gear near the neutral position of the sector shaft. This reaction force is generated by the elastic abutment of a plunger arranged to be able to bias toward the sector gear inside the ball nut and a plunger sliding contact portion adjacent to the sector gear and having a prescribed cam profile. However, in the conventional steering device, it is necessary to separately provide the plunger sliding contact portion from the sector gear. Therefore, there is room for improvement in terms of the increase in the axial size of the sector shaft solely caused by the corresponding plunger sliding contact portion.

[0104] In contrast, the steering device PS1 of the present embodiment includes: a rack tooth 42 formed on the outer side of a ball nut 4 that is screwed with a steering shaft 2 (second steering shaft 22) connected to a steering wheel (not shown); a sector gear 32 provided on a sector shaft 3 connected to a steering wheel (not shown), including a central tooth (first sector tooth 321) that meshes most deeply with the rack tooth 42 at the neutral position of the sector shaft 3 corresponding to the forward steering state, and a plurality of sector teeth (first sector tooth 321, second sector tooth 322, and third sector tooth 323) provided in the circumferential direction of the sector shaft 3 mesh with the rack tooth 42; a preload applying mechanism 6 that adjusts the meshing between the rack tooth 42 near the neutral position of the sector shaft 3 and the sector gear 32, and the preload applying mechanism 6 has: a plunger receiving hole 60 provided in a region offset to one end side in the tooth width direction of a specific tooth root (first rack tooth root 425) of the rack tooth 42 facing the tooth tip of the central tooth (first sector tooth 321) near the neutral position of the sector shaft 3 and opening at the specific tooth root (first rack tooth root 425); a plunger 61 that is retractably housed in the plunger receiving hole 60 and is provided such that the front end side can protrude from the opening portion of the plunger receiving hole 60 facing the sector gear 32; a sliding ring 64 that is press-fitted to the outer peripheral side of the plunger 61 and is provided so as to be able to move integrally with the plunger 61 and slide relative to the inner peripheral surface of the plunger receiving hole 60 as the plunger 61 moves forward and backward; and a biasing member 62 that exists between the bottom (bottom wall 600) of the plunger receiving hole 60 and the sliding ring 64 and biases the plunger 61 toward the central tooth (first sector tooth 321), and based on the reaction force generated by the elastic contact between the plunger 61 and the tooth tip of the central tooth (first sector tooth 321), biases the ball nut 4 toward one side in the rotation direction of the ball nut 4.

[0105] Thus, in the present embodiment, there is a configuration in which: based on the reaction force generated by the elastic contact between the plunger 61 biased by the biasing member 62 and the tooth tip of the first sector tooth 321 of the sector gear 32, a rotational torque that becomes preload is applied to the ball nut 4 toward one side in the rotation direction of the ball nut 4. Therefore, in the present embodiment, there is no need to separately provide a pressed portion pressed by the plunger 61 as in the existing steering device described above. As a result, it is possible to suppress the enlargement of the sector shaft 3 accompanying the formation of the pressed portion.

[0106] In addition, in the present embodiment, the relative movement between the sliding ring 64 and the plunger 61 is restricted in relation to the acting force of the biasing member 62 due to the combination of the press-fitted sliding ring 64 and the plunger 61, while the relative movement between the sliding ring 64 and the plunger 61 is allowed in relation to the meshing force between the sector gear 32 and the rack tooth 42.

[0107] In the case where the sliding ring 64 is integrally formed with the plunger 61, due to the machining accuracy (machining error) of the plunger receiving hole 60, the plunger 61, the sliding ring 64, etc., there is a concern that the length of the front end portion 611 of the plunger 61, which is more toward the sector gear 32 (first sector tooth 321) side than the sliding ring 64, becomes too long. Then, when the sector gear 32 meshes with the rack tooth 42, the plunger 61 is pressed in excessively, and as a result, the biasing member 62 is compressed excessively, which may cause breakage or reduced lifespan of the biasing member 62.

[0108] In contrast, in the present embodiment, the relative movement of the sliding ring 64 and the plunger 61 is restricted with respect to the acting force of the biasing member 62, and the sliding ring 64 is press-fitted into the plunger 61 by fitting that allows the relative movement of the sliding ring 64 and the plunger 61 to the extent of the meshing force between the sector gear 32 and the rack tooth 42. Thus, by the acting force of the biasing member 62, the sliding ring 64 and the plunger 61 move integrally. On the other hand, when the sector gear 32 meshes with the rack tooth 42, the plunger 61 is pressed by the sector gear 32 (first sector tooth 321) toward the opposite side of the entering direction, so that the plunger 61 moves relative to the sliding ring 64, and the relative position between the plunger 61 and the sliding ring 64 can be changed to an appropriate positional relationship. As a result, it is possible to apply an appropriate acting force to the plunger 61 with respect to the sector gear 32 regardless of the machining error of the respective dimensions (axial dimensions) of the plunger receiving hole 60, the plunger 61, and the sliding ring 64 in the biasing direction of the biasing member 62, and to apply an appropriate preload (rotational torque) to the ball nut 4.

[0109] In addition, with respect to the meshing force between the sector gear 32 and the rack tooth 42, the relative movement of the sliding ring 64 and the plunger 61 is allowed, thereby eliminating the risk that the biasing member 62 is compressed excessively due to the meshing of the sector gear 32 and the rack tooth 42. Thereby, breakage of the biasing member 62 is suppressed, and the durability of the biasing member 62 is improved.

[0110] In addition, in the present embodiment, the plunger receiving hole 60 has a recessed portion 603 at the bottom (bottom wall 600) on the side opposite to the opening portion, and the recessed portion 603 can accommodate the end portion 612 of the plunger 61 on the side opposite to the front end portion 611 that abuts against the tooth tip of the central tooth (first sector tooth 321).

[0111] Depending on the length of the end portion 612 of the plunger 61, which is more toward the biasing member 62 side than the sliding ring 64, there is a concern that when the plunger 61 is pressed by the central tooth (first sector tooth 321), the end portion 612 of the plunger 61 abuts against the bottom (bottom wall 600) of the plunger receiving hole 60, and the pressing-in (retreating movement) of the plunger 61 is obstructed.

[0112] In contrast, in the present embodiment, a recessed portion 603 is provided at the bottom (bottom wall 600) of the plunger receiving hole 60 on the side opposite to the opening portion, and the recessed portion 603 can receive the end portion 612 of the plunger 61 on the side opposite to the front end portion 611 that abuts against the central tooth (first sector gear tooth 321) of the sector gear 32. Therefore, when the plunger 61 is pressed in by the central tooth (first sector gear tooth 321), the end portion 612 of the plunger 61 is received in the recessed portion 603, thereby eliminating the risk that the end portion 612 of the plunger 61 abuts against the bottom (bottom wall 600) of the plunger receiving hole 60 and hinders the pressing-in (retreating movement) of the plunger 61. Thus, the relative position of the plunger 61 and the sliding ring 64 can be adjusted to an appropriate state regardless of the length of the end portion 612 of the plunger 61 that is more toward the biasing member 62 side than the sliding ring 64.

[0113] In addition, in the present embodiment, the plunger receiving hole 60 is reduced in diameter such that the opening portion has an inner diameter smaller than the outer diameter of the sliding ring 64, and has a stopper 630 that restricts the protruding amount of the plunger 61 by abutting against the sliding ring 64. In a state where the rotational phase of the sector shaft 3 is near the neutral position, the sliding ring 64 does not abut against the stopper 630, and the abutment of the plunger 61 against the central tooth (first sector gear tooth 321) is allowed. On the other hand, in a state where the rotational phase of the sector shaft 3 exceeds the vicinity of the neutral position, the sliding ring 64 abuts against the stopper 630, restricting the abutment of the plunger 61 against the central tooth (first sector gear tooth 321).

[0114] That is, the present embodiment is configured such that when the rotational phase of the sector shaft 3 is near the neutral position of the steering, the abutment of the plunger 61 against the first sector gear tooth 321 is allowed. On the other hand, when the rotational phase of the sector shaft 3 exceeds the vicinity of the neutral position, the abutment of the plunger 61 against the first sector gear tooth 321 is restricted by the stopper 630.

[0115] In this way, in the present embodiment, by restricting the protruding amount of the plunger 61 with the stopper 630, it is possible to adjust the meshing of the rack tooth 42 and the sector gear 32 only near the neutral position of the sector shaft 3 where a rigid feeling is required. In other words, outside the vicinity of the neutral position where a rigid feeling is not particularly required, by restricting the abutment of the plunger 61 against the first sector gear tooth 321, it is possible to suppress the deterioration of the steering experience feeling such as a so-called uncomfortable feeling caused by the sliding contact between the plunger 61 and the first sector gear tooth 321.

[0116] In addition, in the present embodiment, the stopper 630 is constituted by disposing an annular member 63 at the opening portion of the plunger receiving hole 60. Therefore, in the present embodiment, for example, unlike the existing steering device, a complex cam profile is not formed, and the protruding amount of the plunger 61 can be restricted with a relatively simple configuration. Thereby, it is possible to contribute to a reduction in the manufacturing cost of the steering device PS1.

[0117] Further, in the present embodiment, the tooth root of the sector gear 32 has a linear shape substantially parallel to the rotation axis Y of the sector shaft 3. In other words, in the present embodiment, it is configured such that the tooth root of the sector gear 32 is not a tapered shape, and no mechanism (backlash adjusting mechanism) for adjusting the engagement between the rack tooth 42 and the sector gear 32 is provided except for the preload applying mechanism 6. The engagement between the rack tooth 42 and the sector gear 32 can be adjusted only by the preload applying mechanism 6. Therefore, the structure of the steering device PS1 can be simplified, which contributes to the improvement of the productivity of the steering device PS1 and the reduction of the manufacturing cost.

[0118] Further, the manufacturing method of the steering device PS1 according to the present embodiment includes: a biasing member assembling step of housing the biasing member 62 in the plunger receiving hole 60; a sliding ring assembling step of assembling the sliding ring 64 to the plunger 61; a plunger assembling step of assembling the plunger 61 with the sliding ring 64 assembled thereto in the plunger receiving hole 60; and a plunger adjusting step of, after the plunger assembling step, engaging the sector gear 32 with the rack tooth 42 and adjusting the relative positions of the plunger 61 and the sliding ring 64. The plunger adjusting step includes: a first step of rotating the sector gear 32 in one direction with respect to the rack tooth 42 having the preload applying mechanism 6 assembled thereto and engaging the sector gear 32 in a non-neutral position state; a second step of, after the first step, rotating the sector gear 32 toward the neutral position in a direction in which the distance C between the central tooth (first sector tooth 321) and the specific tooth root (first rack tooth root 425) becomes smaller. The central tooth (first sector tooth 321) presses the plunger 61 in a direction opposite to the biasing direction of the biasing member 62 against the acting force of the biasing member 62, thereby compressing the biasing member 62 to the maximum contraction via the sliding ring 64 that moves integrally with the plunger 61; and a third step of, after the second step, further pressing the plunger 61 in a direction opposite to the biasing direction of the biasing member 62 in a state where the biasing member 62 is maximally contracted, thereby causing the plunger 61 to relatively move in a direction opposite to the biasing direction of the biasing member 62 with respect to the sliding ring 64.

[0119] Thus, in the present embodiment, in the plunger adjusting step, by further pressing the plunger 61 when the biasing member 62 is maximally contracted, the plunger 61 can be relatively moved with respect to the sliding ring 64, and the relative positions of the plunger 61 and the sliding ring 64 can be changed to an appropriate positional relationship. Thereby, regardless of the machining errors of the respective axial dimensions of the plunger receiving hole 60, the plunger 61, the sliding ring 64, etc., the plunger 61 can be biased with an appropriate acting force with respect to the sector gear 32, and an appropriate preload can be applied to the ball nut 4.

[0120] In addition, in the plunger adjustment process, when the central tooth (the first sector tooth 321) further presses the plunger 61 with the biasing member 62 compressed to the maximum state, relative movement of the plunger 61 with respect to the sliding ring 64 is allowed. Thus, for example, even when the protruding amount of the plunger 61 is greater than the specified dimension in relation to the bottom wall 600 of the plunger receiving hole 60 due to machining errors in the respective axial dimensions of the plunger receiving hole 60, the plunger 61, the sliding ring 64, etc., there is no risk of the biasing member 62 being over-compressed. Thereby, breakage of the biasing member 62 is suppressed and the durability of the biasing member 62 is improved.

[0121] Moreover, according to the manufacturing method of the steering device PS1, the plunger receiving hole 60 has a recess 603 at the bottom (bottom wall 600) on the side opposite to the opening portion. The recess 603 can accommodate the end portion 612 of the plunger 61 on the side opposite to the front end portion 611 that abuts against the tooth tip of the central tooth (the first sector tooth 321). In the third process, when the plunger 61 moves relative to the sliding ring 64 in the direction opposite to the biasing direction of the biasing member 62, the end portion 612 of the plunger 61 is received in the recess 603.

[0122] In the third process, depending on the length of the end portion 612 of the plunger 61 on the side closer to the biasing member 62 than the sliding ring 64, when the plunger 61 is pressed in by the central tooth (the first sector tooth 321), there is a concern that the end portion 612 of the plunger 61 may abut against the bottom (bottom wall 600) of the plunger receiving hole 60, preventing the plunger 61 from being pressed in (retreating movement).

[0123] In contrast, in the present embodiment, a recess 603 is provided at the bottom (bottom wall 600) of the plunger receiving hole 60 on the side opposite to the opening portion. The recess 603 can accommodate the end portion 612 of the plunger 61 on the side opposite to the front end portion 611 that abuts against the central tooth (the first sector tooth 321) of the sector gear 32. Therefore, in the third process of the plunger adjustment process, when the plunger 61 is pressed in by the central tooth (the first sector tooth 321), the end portion 612 of the plunger 61 is received in the recess 603. Thereby, the risk that the end portion 612 of the plunger 61 abuts against the bottom (bottom wall 600) of the plunger receiving hole 60 and prevents the plunger 61 from being pressed in (retreating movement) is eliminated. Thereby, the relative position of the plunger 61 and the sliding ring 64 can be adjusted to an appropriate state regardless of the length of the end portion 612 of the plunger 61 on the side closer to the biasing member 62 than the sliding ring 64.

[0124] [Second Embodiment]

[0125] Figure 6This represents the second embodiment of the steering device of the present invention. In addition, in this embodiment, the configuration of the sector shaft 3 is mainly changed, and a backlash adjustment mechanism for adjusting the backlash between the sector gear 32 and the rack teeth 42 is provided separately from the preload applying mechanism 6. Other configurations are the same as those of the first embodiment. Therefore, the same reference numerals are assigned to the same configurations as those of the first embodiment, and detailed descriptions thereof are omitted.

[0126] Figure 6 This represents the steering device PS2 of the second embodiment of the present invention, and represents a transverse cross-sectional view of the steering device PS2 corresponding to the cross-sectional view taken along line A-A shown in Figure 1 ...

[0127] As Figure 6 shown, in the steering device PS2 of this embodiment, the portion of the sector shaft portion 31 on the end side closer to the sector gear 32 is configured as a large-diameter shaft portion 313 with a relatively large diameter, and the portion of the sector shaft portion 31 on the other end side closer to the sector gear 32 is configured as a small-diameter shaft portion 314 with a relatively small diameter. One end side of the large-diameter shaft portion 313 is connected to a steering arm (not shown), and the other end side is supported by a large-diameter bearing 333 on the inner peripheral side of the second opening 112a so as to be rotatable. That is, in relation to applying a large torque to the steering wheel (not shown) via the steering arm (not shown) connected to one end portion of the large-diameter shaft portion 313, the large-diameter shaft portion 313 is formed with a relatively large diameter in order to ensure the rigidity to withstand the large torque.

[0128] And, a large-diameter seal member 343 capable of liquid-tightly sealing between the outer peripheral surface of the large-diameter shaft portion 313 and the inner peripheral surface of the second opening 112a is provided on one end side of the large-diameter bearing 333. Thereby, the working fluid filled inside the housing 1 (sector shaft housing portion 112) is suppressed from flowing out to the outside through the second opening 112a.

[0129] On the other hand, the small-diameter shaft portion 314 is supported by a small-diameter bearing 334 on the inner peripheral side of the third housing cylindrical portion 134 so as to be rotatable. That is, the small-diameter shaft portion 314 is used to support the rotation of the other end side of the sector shaft 3. In relation to not acting with a large torque like the large-diameter shaft portion 313, high rigidity capable of withstanding the applied large torque is not required, and thus it is formed with a relatively small diameter.

[0130] In addition, a small-diameter seal member 344 capable of liquid-tightly sealing between the outer peripheral surface of the small-diameter shaft portion 314 and the inner peripheral surface of the third housing cylindrical portion 134 is provided on the other end side of the small-diameter bearing 334. Thereby, the working fluid filled inside the housing 1 (sector shaft housing portion 112) is suppressed from flowing out to the outside through the internal thread hole 136 described later.

[0131] The sector gear 32 is configured as a so-called bevel gear. That is, asFigure 6 As shown, the first sector tooth root 325 of the sector gear 32 between the first sector tooth 321 and the second sector tooth 322 and the second sector tooth root 326 between the first sector tooth 321 and the third sector tooth 323 are constituted by conical surfaces whose heights T of the first sector tooth 321, the second sector tooth 322, and the third sector tooth 323 gradually increase toward one end side of the sector shaft 3.

[0132] Moreover, along with the constitution of the above bevel gear, an internally threaded hole 136 penetrating along the rotation axis Y is formed in the third housing end wall 135. Through this internally threaded hole 136, the adjusting screw 5 is screwed in from the other end side (outside) of the third housing 13. The adjusting screw 5 is screwed in while being in contact with the other end portion (small-diameter shaft portion 314) of the sector shaft 3, and thus enters toward one end side to apply a force to the sector shaft 3 toward one end side. That is, by screwing in the adjusting screw 5, the sector shaft 3 moves toward one end side, and the gaps between the first sector tooth root 325, the second sector tooth root 326 and the second rack tooth 422, the third rack tooth 423 are reduced, and the backlash of the sector gear 32 with respect to the rack teeth 42 can be reduced.

[0133] In this way, in the present embodiment, a backlash adjusting mechanism is provided. The backlash adjusting mechanism is constituted by the sector gear 32 constituted by the bevel gear and the adjusting screw 5 that applies a force to the sector shaft 3, and the backlash between the sector gear 32 and the rack teeth 42 can be adjusted by a manual operation of rotating (screwing in) the adjusting screw 5. Thereby, when repairing a vehicle, the backlash between the sector gear 32 and the rack teeth 42 increased due to wear of the sector gear 32 and the rack teeth 42 or the like can be adjusted.

[0134] As described above, in the steering device PS2 of the present embodiment, the tooth roots (the first sector tooth root 325 and the second sector tooth root 326) of the sector gear 32 have conical surfaces whose heights T of the sector gear 32 gradually increase toward one end side in the axial direction of the sector shaft 3, and the sector shaft 3 is configured to be movable toward one end side in the axial direction of the sector shaft 3 by the adjusting screw 5 screwed in from the other end portion in the axial direction of the sector shaft 3 through the internally threaded hole 136 formed in the end wall (the third housing 13) of the housing 1 (the first housing 11) that houses the sector shaft 3.

[0135] In this way, in the present embodiment, the first sector tooth root 325 and the second sector tooth root 326 of the sector gear 32 have a bevel gear shape that is a conical surface, and by moving the sector shaft 3 toward one end side in the axial direction by using the adjusting screw 5, the engagement between the rack teeth 42 and the sector gear 32 can be adjusted. Thereby, not only near the neutral position of the sector shaft 3, but also in the entire region of the rotation range of the sector shaft 3, an appropriate engagement between the rack teeth 42 and the sector gear 32 can be ensured.

[0136] Further, in the present embodiment, the axial one end side of the sector shaft 3, which is connected to a steering arm (not shown) and is separated by the sector gear 32, is formed with a larger diameter, and the axial other end side separated by the sector gear 32 is formed with a smaller diameter than the axial one end side. The plunger accommodation hole 60 is provided at the end in the tooth width direction of a specific tooth root (the first rack tooth root 425), which corresponds to the axial other end side of the sector shaft 3.

[0137] Thus, in the present embodiment, the plunger accommodation hole 60 constituting the preload applying mechanism 6 is arranged on the small-diameter shaft portion 314 side where the sector shaft 3 has a smaller diameter. Therefore, corresponding to the reduction in the diameter of the sector shaft portion 31 such as the small-diameter shaft portion 314, the space where the preload applying mechanism 6 can be arranged is enlarged, and the preload applying mechanism 6 can be arranged at a position farther from the rotation center of the ball nut 4. As a result, a larger rotational torque can be applied to the ball nut 4, and the meshing between the first sector tooth 321 and the second rack tooth 422 and the third rack tooth 423 can be adjusted more effectively.

[0138] The present invention is not limited to the configurations exemplified in the above-described embodiments. The configurations of the detailed parts of the steering device, such as the configuration of the steering shaft 2, the input method with respect to the steering shaft 2, the shapes of the sector gear 32 and the rack teeth 42, etc., needless to say the configurations of the detailed parts that have no direct relation to the configuration of the present invention. Even for parts directly related to the configuration of the present invention, such as the preload applying mechanism 6, for example, the specific forms of the plunger 61 and the biasing member 62, the presence or absence of the recessed portion 603, the respective dimensions of the plunger 61 and the sliding ring 64, etc., can be freely changed within the scope not departing from the gist of the present invention according to the specifications of the steering device and the vehicle as the application object.

Claims

1. A steering device, characterized in that, Comprising: A rack tooth formed on the outer side of a ball nut that is screwed onto a steering shaft connected to a steering wheel; A sector gear provided on a sector shaft connected to a steering wheel, including a central tooth that meshes deepest with the rack tooth at a neutral position of the sector shaft corresponding to a forward steering state, and a plurality of sector teeth provided in the circumferential direction of the sector shaft mesh with the rack tooth; And A preload applying mechanism that adjusts the meshing of the rack tooth near the neutral position of the sector shaft with the sector gear, The preload applying mechanism has: A plunger receiving hole provided in a region offset to one end side in the tooth width direction of a specific tooth root of the rack tooth facing the tooth tip of the central tooth near the neutral position of the sector shaft, and opening at the specific tooth root; A plunger housed in the plunger receiving hole in a manner capable of advancing and retreating, and provided such that the front end side can protrude from an opening portion of the plunger receiving hole facing the sector gear; A sliding ring press-fitted on the outer peripheral side of the plunger and capable of moving integrally with the plunger, and sliding relative to the inner peripheral surface of the plunger receiving hole as the plunger advances and retreats; And A biasing member present between the bottom of the plunger receiving hole and the sliding ring, and biasing the plunger toward the central tooth via the sliding ring, Based on the reaction force generated by the elastic contact between the plunger and the tooth tip of the central tooth, the ball nut is biased toward one side in the rotation direction of the ball nut.

2. The steering device according to claim 1, wherein Based on the press-fit of the sliding ring and the plunger, the relative movement of the sliding ring and the plunger is restricted in relation to the acting force of the biasing member, and on the other hand, the relative movement of the sliding ring and the plunger is allowed in relation to the meshing force of the sector gear with the rack tooth.

3. The steering device according to claim 2, wherein The plunger receiving hole has a recessed portion at the bottom on the side opposite to the opening portion, and the recessed portion can accommodate the end portion of the plunger opposite to the front end portion that abuts against the tooth tip of the central tooth.

4. The steering device according to claim 2, wherein The plunger receiving hole is reduced in diameter such that the opening portion has an inner diameter smaller than the outer diameter of the sliding ring, and has a stopper that restricts the protruding amount of the plunger by abutting against the sliding ring, In a state where the rotation phase of the sector shaft is near the neutral position, the sliding ring does not abut against the stopper, and the abutment of the plunger with the central tooth is allowed, and on the other hand, In a state where the rotation phase of the sector shaft exceeds the vicinity of the neutral position, the sliding ring abuts against the stopper, restricting the abutment of the plunger with the central tooth.

5. The steering device according to claim 1, wherein The tooth root of the sector gear becomes a flat surface parallel to the axis of the sector shaft.

6. The steering device according to claim 1, wherein The root of the sector gear has a conical surface whose tooth height gradually increases toward one end side in the axial direction of the sector shaft. The sector shaft is configured to be movable toward one end side in the axial direction of the sector shaft by an adjusting screw screwed into the other end portion in the axial direction of the sector shaft through an internal threaded hole formed in an end wall of a housing that houses the sector shaft.

7. The steering device according to claim 1, wherein the portion of the sector shaft connected to the steering arm is formed with a larger diameter on one end side in the axial direction of the sector gear, and is formed with a smaller diameter on the other end side in the axial direction of the sector gear than the one end side. The plunger receiving hole opens at an end corresponding to the other end side in the axial direction of the sector shaft among the end portions in the tooth width direction of the specific tooth root.

8. A method of manufacturing a steering device, which is a method of manufacturing the steering device according to claim 1, comprising: a biasing member assembling step of housing the biasing member in the plunger receiving hole; a sliding ring assembling step of assembling the sliding ring to the plunger; a plunger assembling step of assembling the plunger having the sliding ring assembled thereto to the plunger receiving hole; and a plunger adjusting step of, after the plunger assembling step, bringing the sector gear into meshing engagement with the rack teeth and adjusting the relative positions of the plunger and the sliding ring. The plunger adjusting step includes: a first step of rotating the sector gear in one direction relative to the rack teeth having the preload applying mechanism assembled thereto and bringing the sector gear into meshing engagement in a non-neutral position state; a second step of, after the first step, rotating the sector gear toward the neutral position in a direction in which the distance between the central tooth and the specific tooth root becomes smaller, and the central tooth presses the plunger in a direction opposite to the biasing direction of the biasing member against the acting force of the biasing member, whereby the biasing member is compressed to the maximum contraction via the sliding ring that moves integrally with the plunger; and a third step of, after the second step, further pressing the plunger in a direction opposite to the biasing direction of the biasing member by the central tooth in a state where the biasing member is maximally contracted, whereby the plunger relatively moves in a direction opposite to the biasing direction of the biasing member with respect to the sliding ring.

9. The method of manufacturing a steering device according to claim 8, wherein the plunger receiving hole has a recess at a bottom portion on the side opposite to the opening portion, and the recess is capable of housing an end portion on the opposite side of the front end portion of the plunger that abuts against the tooth top of the central tooth. In the third step, when the plunger relatively moves in a direction opposite to the biasing direction of the biasing member with respect to the sliding ring, the end portion of the plunger is housed in the recess.

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