Steering device

Abstract

To provide a steering device that is able to secure the stable cushioning characteristics of a cushioning member.SOLUTION: In a steering device according to the present invention, a recessed part 33 has a first inclined surface 831 and a second inclined surface 832 which are asymmetrical in an axial direction of a rack bar 3, and the second inclined surface 832 is inclined more gently than the first inclined surface 831. Therefore, when a cushioning member 8 is sandwiched between a ball joint 40 and a housing 1 (a rack bar housing portion 13) at a stroke end of the rack bar 3, the cushioning member 8 can be guided toward the second inclined surface 832. As a result, because a part of a thick portion 81 that has radially bulged and deformed due to the axial compressive deformation of the cushioning member 8 is sandwiched between a rack-bar insertion hole 130 of the housing 1 and the rack bar 3 at the stroke end of the rack bar 3, a change in cushioning characteristics can be prevented, making it possible to secure the stable cushioning characteristics of the cushioning member 8.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a steering device. [Background technology]

[0002] As a conventional steering device, for example, the device described in the following patent document is known.

[0003] That is, in the steering device disclosed in this patent document, a rubber buffer member is attached to the outer periphery of the axial end of the rack bar. This buffer member is sandwiched between the ball joint connected to the axial end of the rack bar and the housing (rack housing) and is compressed and deformed, thereby buffering collision between the housing (rack housing) and the ball joint. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-049798 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the conventional steering device, when the buffer member is sandwiched between the ball joint and the housing (rack housing), there is a risk that the buffer member may be sandwiched between the housing and the rack bar, which makes it difficult to ensure stable buffering characteristics of the buffer member, and there is still room for improvement.

[0006] The present invention has been devised in view of the above technical problems, and provides a steering device that can ensure stable buffering characteristics of a buffer member. [Means for solving the problem]

[0007] In one aspect of the present invention, a recess for attaching a buffer member to a rack shaft has a first inclined surface and a second inclined surface that are asymmetric in the axial direction of the rack shaft, and the first inclined surface has a gentler slope than the second inclined surface. [Effects of the Invention]

[0008] According to the present invention, stable cushioning characteristics of the cushioning member can be ensured. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of a steering device according to the present invention; [Figure 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 3] FIG. 2 is a cross-sectional view taken along line BB in FIG. [Figure 4] 2 is an enlarged view of the vicinity of an axial end of the rack bar shown in FIG. 1. [Figure 5] 4 is an enlarged view of a main part of FIG. 3, showing a state before deformation of the buffer member. FIG. [Figure 6] 4 is an enlarged view of a main part of FIG. 3, illustrating a state after deformation of the buffer member in a locked end state. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A steering device according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings. In the following embodiments, the steering device is applied to a steering device for an automobile, as in the prior art.

[0011] (Steering system configuration) FIG. 1 is a schematic diagram of a steering device according to this embodiment, showing a partial cross section of the vicinity of an end of a rack bar 3 along the axial direction of the rack bar 3. As shown in FIG.

[0012] 1, the steering device includes a steering mechanism SM that transmits the steering force of the driver, and a steering assist mechanism AM that assists the driver's steering operation. The steering device is suspended from the body of the automobile (not shown) via a pair of brackets BKT attached to a rack housing 1 that houses the steering mechanism SM.

[0013] The steering mechanism SM has a steering shaft 2 which is a pinion shaft having one end connected to a steering wheel (not shown) and the other end formed with pinion teeth (not shown), and a rack bar 3 which is a rack shaft connected to a steered wheel (not shown) and formed with rack teeth (not shown) that mesh with the pinion teeth (not shown). The steering shaft 2 and rack bar 3 are connected via a conversion mechanism (not shown). The conversion mechanism is a so-called rack and pinion mechanism made up of the pinion teeth (not shown) formed on the other end of the steering shaft 2 (output shaft 22 described below) and the rack teeth (not shown) formed on the rack bar 3.

[0014] The housing 1 is formed from a metal material, such as an aluminum alloy material, and mainly integrally includes a steering shaft accommodating portion 11, a retainer accommodating portion 12, a rack bar accommodating portion 13, and a transmission mechanism accommodating portion 14. The steering shaft accommodating portion 11 extends along the direction of the rotation axis Z of the steering shaft 2 and is formed into a generally cylindrical shape capable of accommodating the steering shaft 2 therein. The retainer accommodating portion 12 is formed on the rear side of the rack bar 3, intersecting the steering shaft accommodating portion 11 and perpendicular to the rack bar accommodating portion 13, and accommodates a rack retainer (not shown) that supports the rear side of the rack bar 3 therein. The rack bar accommodating portion 12 extends along the direction of the central axis X of the rack bar 3, intersecting the steering shaft accommodating portion 11, and is formed into a generally cylindrical shape capable of accommodating the rack bar 3 therein.

[0015] The steering shaft 2 is configured by connecting an input shaft 21 that rotates integrally with a steering wheel (not shown) and an output shaft 22 that is linked to a rack bar 3 by a torsion bar (not shown). One end of the input shaft 21 in the direction of the rotation axis Z of the steering shaft 2 (the upper end side in FIG. 1) is connected to a steering wheel (not shown), and the other end is connected to a torsion bar (not shown). One end of the output shaft 22 in the direction of the rotation axis Z of the steering shaft 2 (the upper end side in FIG. 1) is connected to a torsion bar (not shown), and the other end is linked to the rack bar 3.

[0016] Specifically, pinion teeth (not shown) are formed on the outer periphery of the other end of the output shaft 22, and these pinion teeth (not shown) mesh with rack teeth (not shown) of the rack bar 3, thereby converting and transmitting the rotational movement of the output shaft 22 into axial movement of the rack bar 3. Also, a torque sensor TS is disposed on the outer periphery of the steering shaft 2 to detect the steering torque input to the steering shaft 2 by the driver. This torque sensor TS detects the steering torque based on the amount of displacement in the relative rotation between the input shaft 21 and the output shaft 22.

[0017] Both ends of the rack bar 3 are linked to left and right steered wheels (not shown) via tie rods 4, 4 and knuckle arms (not shown). That is, the rack bar 3 moves in the axial direction, and the knuckle arms (not shown) are pushed and pulled via the tie rods 4, 4 in accordance with the axial movement of the rack bar 3, thereby changing the direction of the steered wheels (not shown). In addition, the tie rods 4, 4 are connected to both ends of the rack bar 3 via ball joints 40, 40, which are shaft couplings.

[0018] Here, the vicinity of the axial end of the rack bar 4, i.e., the vicinity of the rack end, is covered by rubber boot members 5, 5, which protect the ball joints 40, 40 from water and dust. The boot members 5, 5 have a bellows cylindrical shape that can expand and contract as the rack bar 3 moves in the axial direction, and one end is fixed to the rack bar accommodating portion 13 and the other end is fixed to the tie rods 4, 4, thereby surrounding the ball joints 40, 40.

[0019] The steering assist mechanism AM has an electric motor 61 that generates the steering assist force, a control device 62 that controls the drive of the electric motor 61, and a transmission mechanism 63 that transmits the drive force of the electric motor 61 to the rack bar 3. In other words, the steering assist mechanism AM assists the axial movement of the rack bar 3 with the drive force of the electric motor 61, which is drive-controlled by the control device 62 based on the detection results of various sensors such as the torque sensor TS and a vehicle speed sensor (not shown).

[0020] FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, showing a cross-sectional view of the adjustment mechanism 7 in the steering device.

[0021] 2, the steering device has an adjustment mechanism 7 that is disposed at an engagement portion between pinion teeth 220 formed on the steering shaft 2 (output shaft 22) and rack teeth 30 formed on the rack bar 3, and adjusts the engagement of the rack teeth 30 with the pinion teeth 220. The adjustment mechanism 7 has a rack retainer 71 that supports the rack rear surface portion 31 of the rack bar 3, a coil spring 72 that biases the rack retainer 71 toward the rack bar 3, and a spring holding member 73 that holds the coil spring 72 and adjusts the biasing force of the coil spring 72. That is, the adjustment mechanism 7 adjusts the engagement of the rack teeth 30 with the pinion teeth 220 by having the rack retainer 71 that supports the rack rear surface portion 31 of the rack bar 3 bias the rack bar 3 toward the output shaft 22 based on the biasing force of the coil spring 72 held by the spring holding member 73.

[0022] The rack retainer 71 is formed into a generally cylindrical shape from a metal material such as an aluminum alloy, and is housed inside the retainer housing portion 12 of the housing 1 so as to be movable along an axis Y perpendicular to the central axis X of the rack bar 3. The rack retainer 71 has, at its axial end facing the rack rear surface portion 31, a retainer abutment portion 710 formed in the shape of a concave arc groove having a curvature corresponding to the curvature of the rack rear surface portion 31, which abuts against the rack rear surface portion 31. A sliding member 74 made of a material (e.g., PTFE resin) having lower friction resistance than the rack retainer 71 is attached to the retainer abutment portion 710.

[0023] Furthermore, an annular seal retaining groove 711 cut out along the circumferential direction is formed on the outer periphery of the rack retainer 71. An annular seal member 75, such as a well-known O-ring, that can elastically contact the inner periphery of the retainer accommodating portion 12 is fitted into the seal retaining groove 711. That is, the seal member 75 slides against the inner periphery of the retainer accommodating portion 12, thereby preventing water and dust from entering through the outer opening end of the retainer accommodating portion 12 and entering the rack bar accommodating portion 13.

[0024] The coil spring 72 is accommodated between a first spring seat 712 formed in a concave shape at the axial end opposite the retainer abutment portion 710 of the rack retainer 71, and a second spring seat 731 formed in a concave shape at the end of the spring holding member 73 facing the rack retainer 71, in a compressed state with a predetermined preload.

[0025] The spring holding member 73 has a male thread portion 730 on its outer periphery, and is threaded into a female thread portion 120 formed on the inside of the outer open end of the retainer accommodating portion 12. In other words, by adjusting the amount by which the spring holding member 73 is threaded into the retainer accommodating portion 12, the compression amount of the coil spring 72 can be adjusted, and the biasing force of the rack retainer 71 can be adjusted. Note that a lock nut 76 is threaded onto the male thread portion 730 exposed from the retainer accommodating portion 12, so that the amount by which the spring holding member 73 is threaded into the retainer accommodating portion 12 can be maintained.

[0026] FIG. 3 is a cross-sectional view taken along line BB in FIG. 1, showing a cross-sectional view of the vicinity of the axial end of the rack bar accommodating portion 13 in the steering device.

[0027] As shown in FIG. 3, the rack bar accommodating portion 13 of the housing 1 has a rack bar insertion hole 130 having a cross section corresponding to the outer shape of the rack bar 3. The rack bar insertion hole 130 is formed to penetrate along the axial direction of the rack bar 3. The rack bar insertion hole 130 also has enlarged diameter portions 131 at both axial ends that widen in a stepped manner axially outward. The enlarged diameter portions 131 have an inner diameter sufficient to receive the ball joint 40 (see FIG. 1) provided at the axial end of the rack bar 3, which is the rack end. A step portion 132 is also formed between the enlarged diameter portion 131 and the rack bar insertion hole 130. The step portion 132 functions as a restricting portion that restricts movement of the ball joint 40 by abutting against the ball joint 40.

[0028] Furthermore, a rack relief portion 133 is provided at the axial end of the rack bar insertion hole 130 and inside the step portion 132. The rack relief portion 133 avoids both widthwise ends 301, 302 of the rack teeth 30 of the rack bar 3 when an external force (for example, a road surface) acts on the rack bar 3 and the axial end side of the rack bar 3 is deflected toward the rack teeth 30 (in the direction Q in FIG. 3). The rack relief portion 133 is provided on the opposite side of the retainer accommodating portion 12 across the central axis X of the rack bar 3, and is formed so that the cross section (cross section perpendicular to the central axis X of the rack bar 3) shown in FIG. 3 has a concave arc shape by recessing the outer circumferential surface of the rack insertion hole 130 radially outward.

[0029] FIG. 4 shows an enlarged view of the vicinity of the axial end (left end in FIG. 1) of the rack bar 3 shown in FIG.

[0030] As shown in FIG. 4, the rack bar accommodating portion 13 of the housing 1 has a rack bar insertion hole 130 having a cross section corresponding to the outer shape of the rack bar 3. The rack bar insertion hole 130 is formed to penetrate along the axial direction of the rack bar 3. The rack bar insertion hole 130 also has enlarged diameter portions 131 at both axial ends that widen in a stepped manner axially outward. The enlarged diameter portions 131 have an inner diameter sufficient to receive a ball joint 40 (a socket portion 41, described later) attached to the axial end of the rack bar 3, which is the rack end. A step portion 132 is formed between the enlarged diameter portion 131 and the rack bar insertion hole 130. The step portion 132 functions as a restricting portion that restricts movement of the ball joint 40 by abutting against an end face (abutment surface 414, described later) of the socket portion 41 of the ball joint 40.

[0031] Furthermore, the step portion 132 has a buffer member receiving portion 134 formed in an inner region facing the ball joint 40 (abutment surface 414 described later), which sandwiches the buffer member 8 described later between the step portion 132 and the ball joint 40. The buffer member receiving portion 134 has an inner diameter smaller than the abutment surface 414 described later of the ball joint 40, but larger than the buffer member 8. As a result, the step portion 132 has a restriction surface 135 that can abut against the abutment surface 414 described later of the ball joint 40 to restrict movement of the rack bar 3, and the buffer member receiving portion 134 has a predetermined radial gap C1 between itself and the outer peripheral surface of the buffer member 8 when the buffer member 8 is in an uncompressed state.

[0032] A ball joint 40, which is an axle coupling that connects the rack bar 3 and tie rod 4 (see FIG. 1), is attached to the axial end of the rack bar 3. The ball joint 40 has a socket portion 41 as an attachment base that is attached to the rack bar 3, and a stud portion 43 as an axle that is supported via a ball portion 42 that is rotatably held in the socket portion 41. A bellows-shaped cylindrical boot member 5 that surrounds and protects the ball joint 40 is attached to the end of the rack bar accommodating portion 13 via a boot band 50.

[0033] The socket portion 41 has a socket body portion 411 provided at one axial end and surrounding the ball portion 42, and a screw portion 412 provided integrally with the socket body portion 411 at the other axial end and screwed into the axial end of the rack bar 3. The socket body portion 411 is formed in a cylindrical shape that gradually narrows toward the tip, and is provided with a concave ball receiving portion 413 therein that receives the ball portion 42. The socket body portion 411 has an outer diameter that is larger than the inner diameter of the rack bar insertion hole 130. On the other hand, the screw portion 412 has an outer diameter that narrows in a stepped manner relative to the socket body portion 411 and is smaller than the outer diameter of the rack bar 3. A male thread portion 413 that meshes with a female threaded hole 32 formed at the axial end of the rack bar 3 is formed on the outer periphery of the screw portion 412.

[0034] The socket portion 41 has an abutment surface 414 between the socket body 411 and the screw portion 412 that can abut against the step portion 132 of the rack bar accommodating portion 13 of the housing 1. The abutment surface 414 is formed of a flat surface that is approximately perpendicular to the central axis X of the rack bar 3. The socket portion 41 is attached to the rack bar 3 with the inner circumferential side of the abutment surface 414 abutting against the axial end face of the rack bar 3.

[0035] Furthermore, a roughly annular buffer member 8 is attached to the outer periphery of the axial end of the rack bar 3. The buffer member 8 has integrally formed convex portions 83 that protrude radially inward, and is attached to the rack bar 3 by the convex portions 83 engaging with concave portions 33 that are recessed radially inward from the outer periphery of the axial end of the rack bar 3.

[0036] Fig. 5 is an enlarged view of a main part of Fig. 3, showing the state of the buffer member 8 before deformation. Fig. 6 is an enlarged view of a main part of Fig. 3, showing the state of the buffer member 8 after deformation in the locked end state. For convenience of explanation, in Figs. 5 and 6, the steering shaft 2 (see Fig. 1) side in the axial direction of the rack bar 3 (direction along the central axis X) is defined as a first end side X1, and the tie rod 4 (see Fig. 1) side is defined as a second end side X2.

[0037] 5, the buffer member 8 is made of a predetermined rubber material and is formed in a continuous annular shape along the circumferential direction of the rack bar 3. Specifically, the buffer member 8 integrally includes a thick-walled portion 81 having a relatively wide axial width, a thin-walled portion 82 formed radially inward of the thick-walled portion 81 so as to be stepped relative to the thick-walled portion 81 and having a narrower axial width than the thick-walled portion 82, and a convex portion 83 formed on the inner circumferential side of the thin-walled portion 82 and protruding toward the rack bar 3, and capable of engaging with a concave portion 33 provided in the rack bar 3. In this embodiment, the buffer member 8 is formed symmetrically with respect to the axial center P of the convex portion 83.

[0038] The housing 1 has a buffer member receiving portion 134 that receives an end portion of the buffer member 8 on the first end X1 side, at the axial end of the rack bar accommodating portion 13 and the inner peripheral end portion of the step portion 132. The buffer member receiving portion 134 has a first opposing surface 134a that faces the buffer member 8 in the axial direction, and a second opposing surface 134b that faces the buffer member 8 in the radial direction. Here, the inner diameter of the buffer member receiving portion 134, i.e., the inner diameter R1 of the second opposing surface 134b, is set to be larger than the outer diameter R2 of the buffer member 8 in an uncompressed state as shown in FIG. 5, for example, and a predetermined radial gap C1 is secured between the buffer member 8 (thick-walled portion 81) and the buffer member receiving portion 134 (second opposing surface 134b). As shown in FIG. 6, it is desirable that the radial gap C1 be set to a size that allows the thick portion 81 (the third abutment surface 813 described later) of the buffer member 8 to abut against the second opposing surface 134b of the buffer member receiving portion 134 when the buffer member 8 is compressed and deformed.

[0039] The thick portion 81 is provided on the outermost peripheral side of the buffer member 8, and exhibits a buffering effect by being sandwiched between the abutment surface 414 of the socket portion 41 of the ball joint 40 and the buffer member receiving portion 134 of the rack bar accommodating portion 13 of the housing 1. Specifically, the thick portion 81 has a first abutment surface 811 that faces and abuts against the first opposing surface 134a of the buffer member receiving portion 134, a second abutment surface 812 that faces and abuts against the abutment surface 414 of the ball joint 40, and a third abutment surface 813 that faces and abuts against the second opposing surface 134b of the buffer member receiving portion 134.

[0040] The first contact surface 811 has a radial width T that is smaller than the radial width Wz of the first opposing surface 134a of the buffer member receiving portion 134. Furthermore, since the buffer member 8 is formed symmetrically with respect to the axial center P, the first contact surface 811 and the second contact surface 812 have approximately the same radial width T. In the uncompressed state shown in FIG. 5 , the third contact surface 813 has an axial width W1 that is larger than the axial width Wx of the second opposing surface 134b.

[0041] The thin-walled portion 82 is formed by narrowing both axial sides in a stepped manner relative to the thick-walled portion 81. In other words, a predetermined axial gap C2 is secured between the thin-walled portion 82 and the abutment surface 414 and the first opposing surface 134a. Specifically, the axial width W2 of the thin-walled portion 82 is set to approximately half (50%) of the axial width W1 of the thick-walled portion 81 in an uncompressed state. The axial width W2 of the thin-walled portion 82 can be set arbitrarily depending on the axial gap C2 to be secured between the abutment surface 414 and the first opposing surface 134a, for example, depending on the specifications of the steering device.

[0042] Here, a tapered width-reducing portion 84 is formed between the thin-walled portion 82 and the thick-walled portion 81, in which the axial width W1 of the thick-walled portion 81 gradually decreases radially inward. In other words, the thin-walled portion 82 and the thick-walled portion 81 are smoothly connected via a tapered step (tapered width-reducing portion 84) that is non-perpendicular (non-parallel to the central axis X). This prevents stress from concentrating at the boundary between the thick-walled portion 81 and the thin-walled portion 82 during elastic deformation, which will be described later.

[0043] Furthermore, the thin-walled portion 82 has a flat surface 820 on the inner peripheral side where the convex portion 83 is formed, which is generally parallel to the direction of the central axis X of the rack bar 3. The flat surface 820 is formed so as to be able to abut against the outer peripheral surface of the rack bar 3 when the buffer member 8 is in an uncompressed state. In this way, the buffer member 8 is held in an uncompressed state with the flat surface 820 abutting against the outer peripheral surface of the rack bar 3, thereby preventing the buffer member 8 from tilting when it is compressed and deformed.

[0044] The protrusion 83 has a tapered shape in which the axial width W3 gradually decreases, and is formed in a continuous ring shape along the circumferential direction of the rack bar 3. Specifically, the protrusion 83 has a first rounded surface 831 and a second tapered surface 832, which are a pair of arcuate surfaces formed by tapering so that the axial width W3 decreases, and a tip rounded surface 833 that smoothly connects the first rounded surface 831 and the second rounded surface 832.

[0045] On the other hand, the recess 33 with which the protrusion 83 engages is formed so that its axial width gradually decreases radially inward and is asymmetric in the axial direction with respect to a groove center Px (which coincides with the axial center P of the buffer member 8 in FIG. 5 ) passing through the bottom portion 330. Specifically, the recess 33 has a first inclined surface 331 facing the first rounded surface 831, a second inclined surface 332 facing the second rounded surface 832, and a bottom surface 333 having an arc-shaped cross section formed by smoothly connecting the first inclined surface 331 and the second inclined surface 332. Note that, although the present embodiment illustrates an example in which the first inclined surface 331 and the second inclined surface 332 are formed in a substantially flat shape, the first inclined surface 331 and the second inclined surface 332 may be formed in a so-called rounded shape, i.e., the cross section shown in FIG. 5 may be formed in an arc-shaped shape. In other words, the first inclined surface and the second inclined surface according to the present invention include the above-described rounded surface (arcuate surface) in addition to the flat surface disclosed in this embodiment.

[0046] The first inclined surface 331 has a first inclination angle θ1, which is an inclination angle that generally corresponds to the first rounded surface 831 of the convex portion 83. Here, when the first inclined surface 331 is a flat surface, the inclination angle θ1 corresponds to the angle between the flat surface and a horizontal line H that passes through the bottom portion 330, and when the first inclined surface 331 is a rounded surface (arcuate surface), the inclination angle θ1 corresponds to the angle between a tangent to the rounded surface and the horizontal line H that passes through the bottom portion 330. Note that in this embodiment, the first inclined surface 331 is exemplified as being formed in a generally flat shape.

[0047] The second inclined surface 332 has a second inclination angle θ2 that is gentler (smaller) than the first inclined surface 331. As with the first inclination angle θ1, when the second inclined surface 332 is a flat surface, the second inclination angle θ2 corresponds to the angle between the flat surface and a horizontal line H passing through the bottom 330. When the second inclined surface 332 is a rounded surface (arcuate surface), the second inclined surface 332 corresponds to the angle between a tangent to the rounded surface and the horizontal line H passing through the bottom 330. In this embodiment, the second inclined surface 332 is exemplified as being formed in a substantially flat shape. In this embodiment, the second inclined angle θ2 is set to approximately half (50%) of the first inclined angle θ1, such that the distance L2 from the center P to the edge of the second inclined surface 332 is approximately twice the distance L1 from the center P to the edge of the first inclined surface 331.

[0048] (Cushioning effect of the buffer member at the lock end) The cushioning effect of the cushioning member 8 at the lock end will be described below with reference to FIGS.

[0049] In the steering device according to this embodiment, when the buffer member 8 is in an uncompressed state immediately before the lock end, as shown in Fig. 5 , the second abutment surface 812 of the buffer member 8 abuts against the abutment surface 414 of the ball joint 40 and the convex portion 83 of the buffer member 8 contacts the bottom portion 330 of the recessed portion 33, that is, the buffer member 8 is held on the outer circumferential side of the rack bar 3 in a state in which the axial center P of the buffer member 8 and the groove center Px of the recessed portion 33 coincide with each other. Eventually, the first abutment surface 811 of the buffer member 8 abuts against the first opposing surface 134a of the buffer member receiving portion 134 of the housing 1, with the axial center P and the groove center Px of the recessed portion 33 remaining in a coincident state.

[0050] Subsequently, as the buffer member 8 approaches the locked end, as shown in FIG. 6 , the thick portion 81 of the buffer member 8 is sandwiched between the abutment surface 414 of the ball joint 40 and the first opposing surface 134a of the buffer member receiving portion 134, and the buffer member 8 is compressed in the axial direction. Then, the convex portion 83 of the buffer member 8 moves toward the second end side X2 so that the convex portion 83 climbs the second inclined surface 332, and the second rounded surface 832 or the tip rounded surface 833 of the convex portion 83 abuts against the second inclined surface 332. As the thick portion 81 compresses and deforms, the thick portion 81 expands radially, and the third abutment surface 813 abuts against the second opposing surface 134b of the buffer member receiving portion 134. Eventually, when the buffer member 8 reaches approximately its maximum compressed deformation, the abutment surface 414 of the ball joint 40 abuts against the step portion 132 of the housing 1. This restricts axial movement of the first end side X1 of the rack bar 3, and the buffer member 8 is placed in the locked end state. In this way, the cushioning member 8 is compressed and deformed, thereby mitigating the impact of the contact surface 414 of the ball joint 40 against the step portion 132.

[0051] (Effects of this embodiment) In the conventional steering device, the recesses 33 provided on the outer periphery of the rack bar 3 are formed symmetrically with respect to the groove center Px, and the buffer member 8 is fixed to the rack bar 3 by engaging with the protrusions 73 having a shape corresponding to the recesses 33. For this reason, at the stroke end (lock end) of the rack bar 3, there is a risk that part of the thick portion 81 of the buffer member 8, which has been deformed to bulge in the radial direction due to compressive deformation in the axial direction, may become pinched between the housing 1 (rack bar insertion hole 130) and the rack bar 3. This makes it difficult to ensure stable buffering characteristics of the buffer member 8, and there is room for improvement.

[0052] In contrast to this, the steering device according to this embodiment can solve the problems of the conventional steering devices by achieving the following advantageous effects.

[0053] The steering device includes a housing 1 formed in a cylindrical shape extending in the vehicle width direction, a rack shaft (rack bar 3) accommodated inside the housing 1 so as to be movable in the vehicle width direction, and whose movement is restricted by restricting portions (contact surfaces 414 of the ball joint 40) provided at both ends in the vehicle width direction contacting the housing 1, a pinion shaft (output shaft 22 of the steering shaft 2) engaging with the rack bar 3, a transmission mechanism 63 that transmits a driving force generated by a driving source (a motor 61 in this embodiment) to the rack bar 3, and a pinion shaft (output shaft 22 of the steering shaft 2) that is provided at an axial end of the rack bar 3 in a ring shape that continues in the circumferential direction of the rack bar 3 and that is provided on the radially inner side of the rack bar 3. and a buffer member 8 attached to the recess 33 and sandwiched between the regulating portion (contact surface 414 of the ball joint 40) and the housing 1 at the stroke end of the rack bar 3, the recess 33 having a first inclined surface 331 and a second inclined surface 332 that are asymmetric on both sides of a bottom 330 that is the deepest recess in an axial cross section of the rack bar 3, and the second inclined surface 332 located on the opposite side of the regulating portion (contact surface 414 of the ball joint 40) from the bottom 330 has a smaller inclination angle than the first inclined surface 331 located on the regulating portion (contact surface 414 of the ball joint 40) side from the bottom 330.

[0054] As described above, in this embodiment, the recess 33 has a first inclined surface 831 and a second inclined surface 832 that are asymmetric in the axial direction of the rack bar 3, and the second inclined surface 832 has a gentler inclination than the first inclined surface 831. Therefore, when the buffer member 8 is sandwiched between the abutment surface 414 of the ball joint 40 and the first opposing surface 134a of the buffer member receiving portion 134 of the housing 1 at the stroke end (lock end) of the rack bar 3, the buffer member 8 can be guided toward the second inclined surface 832. That is, when the thick-walled portion 81 is compressively deformed between the ball joint 40 and the housing 1 at the lock end, the protrusion 83 floats so as to climb up the second inclined surface 832, and is displaced within the recess 33 toward the second inclined surface 832, i.e., toward the side away from the housing 1 (rack bar accommodating portion 13) (see FIG. 6 ). This makes it possible to suppress changes in the cushioning characteristics at the lock end caused by a part of the thick-walled portion 81 that has been radially expanded in response to axial compressive deformation of the cushioning member 8 being pinched between the housing 1 (rack bar insertion hole 130) and the rack bar 3. As a result, stable cushioning characteristics of the cushioning member 8 can be ensured.

[0055] In this embodiment, the buffer member 8 is formed symmetrically with respect to the axial center P, and the recess 33 is formed asymmetrically with respect to the groove center Px, thereby forming the floating structure of the buffer member 8 as described above. With this configuration, the buffer member 8 has no front or back, which makes it possible to prevent the buffer member 8 from being incorrectly assembled to the rack bar 3.

[0056] In addition, in this embodiment, the buffer member 8 has an annular protrusion 83 on the inner side facing the recess 33 that can engage with the recess 33, and is attached to the rack bar 3 by the protrusion 83 engaging with the recess 33.

[0057] In this manner, in this embodiment, the buffer member 8 is attached to the rack bar 3 by engaging the annularly formed convex portion 83 with the concave portion 33. This increases the attachment rigidity of the buffer member 8, thereby ensuring stable buffering characteristics of the buffer member 8.

[0058] In addition, the buffer member 8 may have a plurality of protrusions 83 on the inner side facing the recess 33 that can engage with the recess 33, and may be attached to the rack bar 3 by the plurality of protrusions 83 engaging with the recess 33.

[0059] 5 and 6, it is sufficient for the relationship between the convex portions 83 and the concave portions 33 to be configured as shown in the cross sections in Figures 5 and 6. Therefore, specific illustrations are omitted, but the convex portions 83 of the buffer member 8 may be provided in a plurality of positions, for example, spaced apart along the circumferential direction, and the buffer member 8 may be attached to the rack bar 3 by engaging the plurality of convex portions 83 with the concave portions 33. In such a configuration, it is possible to attach the buffer member 8 to the rack bar 3 (engage the convex portions 83 with the concave portions 33) with less force than when the convex portions 83 are formed in an annular shape, and the work of attaching the buffer member 8 can be improved.

[0060] In addition, in this embodiment, the width (axial width W2) of the buffer member 8 on the inner side (thin portion 82) where the convex portion 83 is provided is smaller than the width (axial width W1) of the outer side (thick portion 81) in the radial direction of the rack bar 3.

[0061] As described above, in the present embodiment, the axial width W2 of the thin-walled portion 82 of the buffer member 8 is set smaller than the axial width W1 of the thick-walled portion 81. Therefore, a compression allowance can be secured on the inner circumferential side of the buffer member 8 when the buffer member 8 is sandwiched between the ball joint 40 (the abutment surface 414) and the housing 1 (the first opposing surface 134a of the buffer member receiving portion 134). This ensures more stable buffering characteristics of the buffer member 8 compared to when the axial width of the buffer member 8 is constant in the radial direction of the rack bar 3.

[0062] In this embodiment, the buffer member 8 has a flat portion 820 on the inner circumferential side where the convex portion 83 is formed, and the flat portion 820 is provided on the outer circumferential side of the convex portion 83.

[0063] As described above, in this embodiment, the flat portion 820 is provided on the inner peripheral side of the buffer member 8 and further outward than the protrusion 83. Therefore, when the buffer member 8 is sandwiched between the ball joint 40 (contact surface 414) and the housing 1 (first opposing surface 134a of the buffer member receiving portion 134) at the lock end, the flat portion 820 abuts against the outer peripheral surface of the rack bar 3, thereby making it possible to prevent the buffer member 8 from tilting. This ensures more stable buffering characteristics of the buffer member 8.

[0064] In this embodiment, the housing 1 (rack bar accommodating portion 13) has a rack clearance portion 133 at the end of the rack bar 3 in the axial direction, which avoids the rack teeth 30 of the rack bar 3.

[0065] As described above, in this embodiment, rack clearance portions 133 that avoid the rack teeth 30 (both widthwise ends 301, 302) are provided at the axial ends of the rack bar insertion holes 130 of the rack bar accommodating portion 13. Therefore, when the rack bar 3 is flexibly deformed by an external input, interference with the rack teeth 30 (both widthwise ends 301, 302) is reduced, and the stress received from the rack teeth 30 (both widthwise ends 301, 302) can be dispersed in stages.

[0066] In this embodiment, the housing 1 has a retainer accommodating portion 12 that accommodates a rack retainer 71 for supporting the rack bar 3 on the opposite side of the rack clearance portion 133 in the radial direction of the rack bar 3.

[0067] As described above, in this embodiment, in the housing 1, the retainer accommodating portion 12 that accommodates the rack retainer 71 for supporting the rack bar 3 is provided on the radially opposite side of the rack recess portion 133 across the central axis line X of the rack bar 3. This makes it possible for the rack retainer 71 to appropriately support the rack bar 3, which helps to ensure stable cushioning characteristics by the cushioning member 8.

[0068] In addition, in this embodiment, when the buffer member 8 is sandwiched between the regulating portion (contact surface 414 of the ball joint 40) and the housing 1 at the stroke end of the rack bar 3, the outer peripheral surface (third contact surface 813) contacts the housing 1 (second opposing surface 134b of the buffer member receiving portion 134).

[0069] In this manner, in this embodiment, when the buffer member 8 is compressed and deformed at the lock end, the third abutment surface 813 of the buffer member 8 can abut against the second opposing surface 134b of the buffer member receiving portion 134 of the housing 1. This restricts the elastic deformation of the buffer member 8 toward the outside in the radial direction, thereby ensuring more stable buffering characteristics of the buffer member 8.

[0070] (Variation) In the above embodiment, the recess 33 is formed in a continuous ring shape along the circumferential direction of the rack accommodating section 13. However, within the technical concept of the present invention, a configuration may be adopted in which a plurality of recesses 33 are provided intermittently along the circumferential direction of the rack accommodating section 13, and a plurality of protrusions 83 provided on the inner circumferential side of the buffer member 8 are engaged with the recesses 33. Furthermore, it is sufficient that at least some of the recesses 33 are asymmetric with respect to the groove center Px, i.e., the second inclined surface 332 has a gentler slope than the first inclined surface 331. In other words, when a plurality of recesses 33 are provided, the present invention includes a configuration in which the second inclined surface 332 is gentler than the first inclined surface 331 for all of the recesses 33, as well as a configuration in which the second inclined surface 332 is gentler than the first inclined surface 331 for some of the recesses 33.

[0071] That is, as another aspect of the steering device according to the present invention, there is provided a housing 1 formed in a cylindrical shape extending in the vehicle width direction, a rack shaft (rack bar 3) accommodated inside the housing 1 so as to be movable in the vehicle width direction, and the movement of which is restricted by restricting portions (abutment surfaces 414 of the ball joint 40) provided at both ends in the vehicle width direction abutting against the housing 1, a pinion shaft (output shaft 22 of the steering shaft 2) that meshes with the rack bar 3, a transmission mechanism 63 that transmits a driving force generated by a driving source (a motor 61 in this embodiment) to the rack bar 3, and a plurality of recesses 3 that are provided in parallel in the circumferential direction of the rack bar 3 at the axial end of the rack bar 3 and recessed radially inward of the rack bar 3. 3, and a buffer member 8 attached to the recess 33 and sandwiched between the regulating portion (contact surface 414 of the ball joint 40) and the housing 1 at the stroke end of the rack bar 3, some of the recesses 33 have a first inclined surface 331 and a second inclined surface 332 that are asymmetric on both sides with respect to a bottom 330 that is the deepest in an axial cross section of the rack bar 3, and the second inclined surface 332 located on the opposite side of the regulating portion (contact surface 414 of the ball joint 40) from the bottom 330 may have a gentler inclination than the first inclined surface 331 located on the regulating portion (contact surface 414 of the ball joint 40) side from the bottom 330.

[0072] (Other technical ideas) The present invention is not limited to the configuration of the above-described embodiment, and can be freely modified according to the specifications of the steering device to which it is applied, as long as the configuration can achieve the effects of the present invention.

[0073] In the above embodiment, as described above, by forming the second inclined surface 332 of the recess 33 to be gentler than the first inclined surface 331, the buffer member 8 can float away from the housing 1 (rack bar accommodating portion 13) in the locked end state, thereby preventing a part of the thick portion 81 that has bulged radially due to compression deformation from becoming pinched between the housing 1 (rack bar insertion hole 130) and the rack bar 3.

[0074] However, the problem of part of the thick portion 81 being radially bulged and deformed due to the compressive deformation of the cushioning member 8 becoming pinched between the housing 1 (rack bar insertion hole 130) and the rack bar 3 is determined by the relative relationship between the recess 33 of the rack bar 3 and the protrusion 83 of the cushioning member 8.

[0075] Therefore, the problem of part of the buffer member 8 getting pinched between the housing 1 (rack bar insertion hole 130) and the rack bar 3 can be resolved not by the recess 33 but by setting the inclination angle of the second curved surface 832 of the protrusion 83 to be relatively small compared to the inclination angle of the first curved surface 831.

[0076] The concave-convex relationship between the rack bar 3 and the buffer member 8 may also be reversed, with a convex portion provided on the outer periphery of the rack bar 3 and a concave portion provided on the inner periphery of the buffer member 8. In this case, the inclined surface of the concave portion provided on the buffer member 8 side may be formed asymmetrically with respect to the bottom (center of the groove) of the concave portion, and the inclination angle of the inclined surface on the inner side (closer to the housing 1) of the concave portion may be set to be gentler than the inclination angle of the inclined surface on the outer side (farther from the housing 1). [Explanation of symbols]

[0077] 1...housing, 2...steering shaft (pinion shaft), 3...rack bar (rack shaft), 3...rack bar, 30...rack teeth, 33...recess, 330...bottom, 40...ball joint (regulating portion), 61...motor (driving source), 63...transmission mechanism, 8...buffer member, 83...convex portion, 831...first inclined surface, 832...second inclined surface,

Claims

1. a housing formed in a cylindrical shape extending in the vehicle width direction; a rack shaft accommodated in the housing so as to be movable in the vehicle width direction, the rack shaft having restriction portions provided at both ends in the vehicle width direction that come into contact with the housing to restrict movement; a pinion shaft that meshes with the rack shaft; a transmission mechanism that transmits a driving force generated by a driving source to the rack shaft; a recessed portion provided in an axial end portion of the rack shaft so as to have a continuous annular shape in a circumferential direction of the rack shaft and recessed radially inward of the rack shaft; a buffer member attached to the recess and sandwiched between the restricting portion and the housing at a stroke end of the rack shaft; Equipped with the recess has a first inclined surface and a second inclined surface that are asymmetrical on both sides of a bottom portion that is recessed most deeply in an axial cross section of the rack shaft, the second inclined surface located on the opposite side of the restricting portion from the bottom has an inclination angle smaller than that of the first inclined surface located on the restricting portion side from the bottom; A steering device characterized by:

2. 2. The steering device according to claim 1, the buffer member has an annular convex portion on an inner circumferential side facing the concave portion, the annular convex portion being engageable with the concave portion, and the buffer member is attached to the rack shaft by the convex portion engaging with the concave portion. A steering device characterized by:

3. 2. The steering device according to claim 1, the buffer member has a plurality of protrusions on an inner circumferential side facing the recessed portion, the protrusions being engageable with the recessed portion, and the buffer member is attached to the rack shaft by the plurality of protrusions engaging with the recessed portion; A steering device characterized by:

4. The steering device according to claim 2 or 3, the buffer member has a width on an inner circumferential side where the convex portion is provided that is smaller than a width on an outer circumferential side in the radial direction of the rack shaft; A steering device characterized by:

5. 5. The steering device according to claim 4, the buffer member has a flat portion on the inner circumferential side where the convex portion is formed, The flat portion is provided on the outer circumferential side of the protruding portion. A steering device characterized by:

6. 2. The steering device according to claim 1, the housing has a rack clearance portion at an axial end of the rack shaft for avoiding rack teeth of the rack shaft; A steering device characterized by:

7. 7. The steering device according to claim 6, the housing has a retainer accommodating portion that accommodates a rack retainer for supporting the rack shaft, on the opposite side of the rack relief portion in the radial direction of the rack shaft. A steering device characterized by:

8. 2. The steering device according to claim 1, When the buffer member is sandwiched between the restricting portion and the housing at the stroke end of the rack shaft, an outer peripheral surface of the buffer member abuts against the housing. A steering device characterized by:

9. a housing formed in a cylindrical shape extending in the vehicle width direction; a rack shaft accommodated in the housing so as to be movable in the vehicle width direction, the rack shaft having restriction portions provided at both ends in the vehicle width direction that come into contact with the housing to restrict movement; a pinion shaft that meshes with the rack shaft; a transmission mechanism that transmits a driving force generated by a driving source to the rack shaft; a plurality of recesses provided in parallel in a circumferential direction of the rack shaft at an axial end portion of the rack shaft, the recesses being recessed radially inward of the rack shaft; a buffer member attached to an outer periphery of the rack shaft via a protrusion that engages with the recess, and sandwiched between the restricting portion and the housing at a stroke end of the rack shaft; Equipped with Some of the recesses among the plurality of recesses have a first inclined surface and a second inclined surface that are asymmetric on both sides of a bottom portion that is recessed most deeply in an axial cross section of the rack shaft, the second inclined surface located on the opposite side of the restricting portion from the bottom has an inclination angle smaller than that of the first inclined surface located on the restricting portion side from the bottom; A steering device characterized by:

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