JP2013006470A - Steering apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering apparatus that can achieve quieter operation while providing good steering feeling.SOLUTION: The steering apparatus includes: a rack shaft 5 which is reciprocatably provided in an axial direction in a rack housing 21; and a cylindrical rack bush 23 which supports the rack shaft 5 to be slidable by being interposed between the rack housing 21 (end housing 27) and the rack shaft 5, wherein a radially outward protrusion 35 is formed around the cylindrical rack bush 23, and a recess 34 into which the radially outward protrusion 35 is inserted is formed in the end housing 27, and O-rings 31 each mounted on the outer circumference of the cylindrical rack bush 23 are sandwiched in the axial direction between the radially outward protrusion 35 and the recess. Additionally, each opposed face 41 in the recess 34 is slanted with respect to the axial direction so that the O-rings 31 can radially inwardly push the cylindrical rack bush 23 by being compressed when the cylindrical rack bush 23 is moved in the axial direction.

Description

  The present invention relates to a rack and pinion type steering apparatus.

  2. Description of the Related Art Conventionally, some vehicle steering devices convert a rotation of a pinion shaft accompanying a steering operation into a reciprocating motion of a rack shaft by engaging a pinion shaft and a rack shaft. Usually, in such a rack-and-pinion type steering device, the rack shaft is supported in the radial direction by one or more rack bushes interposed between the cylindrical housing (for example, a patent) Reference 1).

  By the way, since the rack shaft is in sliding contact with the rack bush, the steering force exceeds the friction force (static friction force) acting between the rack shaft and the rack bush at the start of steering (when the rack shaft starts moving). The steering wheel must be steered by the steering wheel, and this causes a so-called catching feeling, resulting in deterioration of the steering feeling. In particular, when it is desired to slightly change the traveling direction of the vehicle, it may be difficult to perform delicate steering that slightly moves the rack shaft due to the above-described catching.

  Thus, for example, Patent Document 2 discloses a steering device in which a rack bush is provided in a housing so that a gap is formed on both sides in the axial direction of the rack bush, and an elastic member such as an O-ring is interposed in the gap. Has been. In this steering apparatus, the elastic member is elastically deformed at the start of steering so that the rack shaft moves integrally with the rack bush in the axial direction, which reduces the feeling of catching that occurs at the start of steering. Steering feeling can be realized.

JP 2007-1331025 A Japanese Patent No. 4192626

  By the way, a tie rod connected to a steered wheel is rotatably connected to a shaft end portion of the rack shaft via a ball joint. Since this tie rod is normally inclined with respect to the rack shaft, a bending load acts on the rack shaft when the rack shaft moves in the axial direction. As a result, the rack shaft reciprocates in a bent state, and when the rack shaft reciprocates in the axial direction, the rack bush moves in the radial direction and collides with the housing, and noise is likely to occur. Become.

  Here, in the steering device of Patent Document 2, the rack bush is fitted in a gap fitting state in which a slight gap is provided between the housing and the elastic member is mounted on the outer peripheral surface thereof. In the same housing, it is elastically supported in the radial direction. Thereby, the impact when the rack bush collides with the housing is alleviated, and the generation of abnormal noise is suppressed.

  However, in recent years, more and more quietness is demanded in vehicles, and it is the actual situation that the above-described configuration cannot be said to have reached the required level. Therefore, measures for realizing higher silence have been strongly demanded.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a steering device that can realize a higher level of quietness while realizing a good steering feeling. There is.

  In order to achieve the above object, according to a first aspect of the present invention, there is provided a rack shaft provided in a housing so as to be capable of reciprocating in an axial direction, and the rack shaft interposed between the housing and the rack shaft. In the steering apparatus including a cylindrical rack bush that is slidably supported, a convex portion protruding radially outward is formed on the rack bush, and a concave portion into which the convex portion is inserted in the housing And an elastic member sandwiched in the axial direction between the convex portion and the concave portion is provided on an outer periphery of the rack bush, and an opposing surface of the convex portion facing in the axial direction of the rack shaft, At least one of the opposing surfaces of the recess has an inclined surface inclined with respect to the axial direction of the rack shaft, and the inclined surface is moved by the elastic member by the movement of the rack bush in the axial direction. And summarized in that formed so as to press the Kkubusshu radially inward.

  According to the above configuration, when the steering is started, the elastic member is compressed in the axial direction between the convex portion and the concave portion, so that the rack bush is moved in the axial direction integrally with the rack shaft, and the hook feeling is felt. It is possible to achieve a good steering feeling by reducing the above. The elastic member presses the rack bush radially inward by being compressed by the inclined surface when the rack bush (rack shaft) moves in the axial direction. As a result, when the rack shaft reciprocates in the axial direction, it is possible to increase the radial support rigidity of the rack bush by the elastic member, and it is difficult to move the rack bush in the radial direction and collides with the housing. This can be suppressed. Therefore, it is possible to suppress the generation of abnormal noise during steering and to realize even higher silence.

  The invention according to claim 2 is characterized in that, in the steering device according to claim 1, the convex portion, the concave portion and the elastic member are each formed in an annular shape extending in a circumferential direction of the rack bush. .

  According to the said structure, since a convex part, a recessed part, and an elastic member are each formed in cyclic | annular form, when a rack axis | shaft reciprocates to radial direction, an elastic member is compressed to radial direction over the perimeter. Therefore, the pressing force inward in the radial direction from the elastic member acts on the rack bush over the entire circumference. As a result, when the rack shaft reciprocates, the support stiffness in the radial direction of the rack bush by the elastic member can be stably increased, and the generation of abnormal noise can be effectively suppressed during steering.

  The gist of the invention according to claim 3 is that, in the steering device according to claim 1, the convex portion is formed in a columnar shape, and the concave portion is formed in a hole shape corresponding to the convex portion. .

  According to the said structure, it can suppress that a rack bush rattles in the circumferential direction because a convex part engages with the circumferential direction of a rack bush with respect to a recessed part.

  ADVANTAGE OF THE INVENTION According to this invention, the steering apparatus which can implement | achieve still higher silence can be provided, implement | achieving favorable steering feeling.

The schematic block diagram of a steering device. The expanded sectional view of the end housing vicinity of this embodiment. The expanded sectional view of the rack bush vicinity of this embodiment. Sectional drawing of the rack bush of this embodiment. Explanatory drawing which shows the state which the rack axis | shaft of this embodiment started moving to the axial direction one end side. The schematic diagram which shows the pressing force which acts on a rack bush from an O-ring. The expanded sectional view of another rack bush vicinity. (A) The front view of another rack bush, (b) The expanded sectional view of the rack bush vicinity of (a).

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
As shown in FIG. 1, in the steering device 1, a steering shaft 3 to which a steering (steering wheel) 2 is fixed is connected to a pinion shaft 4, and the pinion shaft 4 is meshed with a rack shaft 5. That is, the steering shaft 3 is connected to the rack shaft 5 via a well-known rack and pinion mechanism, and the rotation of the steering shaft 3 accompanying the steering operation is converted into a reciprocating linear motion of the rack shaft 5.

  A tie rod 12 is rotatably connected to the shaft end portion 5a of the rack shaft 5 via a ball joint 11, and a knuckle with a steered wheel assembled to the tip of the tie rod 12 (not shown). Are connected. The tie rod 12 is connected in an inclined state with respect to the rack shaft 5 for the convenience of mounting space in the vehicle. The connecting portion between the rack shaft 5 and the tie rod 12 is surrounded by a resin boot 13 formed in a bellows shape. Then, the reciprocating linear motion of the rack shaft 5 accompanying the rotation of the steering shaft 3 is transmitted to the knuckle through the tie rods 12 connected to both ends of the rack shaft 5, so that the steering angle of the steered wheels, that is, the vehicle The direction of travel is changed.

  The steering device 1 according to the present embodiment is configured as a so-called rack assist type electric power steering device (EPS) using a motor 15 coaxially arranged with the rack shaft 5 as a drive source. Specifically, the rotation of the hollow motor shaft 16 through which the rack shaft 5 is inserted is converted into the reciprocating motion of the rack shaft 5 by the ball screw mechanism 17. The axial pressing force based on the motor torque is applied to the steering system as an assist force for assisting the steering operation.

Next, the rack shaft support structure will be described.
In the rack housing 21, one end side (the right side in FIG. 1) of the rack shaft 5 is supported by the rack guide device 22, and the other end side (the left side in FIG. 1) is supported by the rack bush 23. It is accommodated so as to be capable of reciprocating in the axial direction.

  More specifically, the rack housing 21 is provided on the gear housing 25 in which the pinion shaft 4 is accommodated, the actuator housing 26 that accommodates the motor 15 while being provided on one end side of the gear housing 25, and the one end side of the actuator housing 26. And an end housing 27. The gear housing 25 is provided with a rack guide device 22, and the rack shaft 5 is supported while being pressed against the pinion shaft 4 by the rack guide device 22. As shown in FIG. 2, a cylindrical rack bush 23 is provided coaxially with the rack shaft 5 in the end housing 27, and the rack shaft 5 is supported in the radial direction by the rack bush 23. ing.

(Rack shaft support structure with rack bush)
Next, the rack shaft support structure by the rack bush of this embodiment will be described in detail.
As shown in FIGS. 2 and 3, the rack bush 23 is elastically supported by an O-ring 31 as an elastic member in an end housing 27 as a housing, and the O-ring 31 is elastically deformed at the start of steering. Accordingly, it is provided so as to move integrally with the rack shaft 5 in the axial direction.

  More specifically, as shown in FIG. 2, the end housing 27 is formed in a substantially cylindrical shape, and in the vicinity of the other end in the axial direction, the inner portion of the end housing 27 is partially reduced so that the accommodating portion 32 is formed. The rack bush 23 is provided in the housing portion 32. As shown in FIG. 3, an annular housing groove 33 is formed on the inner peripheral surface of the housing portion 32. The axial length of the accommodation groove 33 is formed longer than the axial length of the rack bush 23, and the rack bush 23 is accommodated so as to be movable in the axial direction. An annular recess 34 extending in the circumferential direction of the rack bush 23 is formed on the bottom surface of the housing groove 33.

  On the other hand, the rack bush 23 is made of a resin material and is formed in a substantially cylindrical shape. The outer diameter of the rack bush 23 is formed smaller than the inner diameter of the accommodating portion 32, and the rack bush 23 is fitted in a gap fitting state in which a slight gap is provided between the rack bush 23 and the end housing 27. Further, the inner diameter of the rack bush 23 (more precisely, the other axial end portion) is formed to be slightly smaller than the outer diameter of the rack shaft 5 so that the rack shaft 5 is lightly press-fitted and can slide smoothly. It has become.

  On the outer peripheral surface of the rack bush 23, a circular portion extending in the circumferential direction and a convex portion 35 inserted into the concave portion 34 are formed. The O-ring 31 is formed in an annular shape extending in the circumferential direction of the rack bush 23 and is mounted on both sides in the axial direction of the convex portion 35 on the outer peripheral surface of the rack bush 23.

  The O-ring 31 is provided in a state of being sandwiched in the radial direction between the rack bush 23 and the recess 34 of the housing portion 32, and elastically supports the rack bush 23 in the radial direction. The O-ring 31 is sandwiched between the convex portion 35 and the concave portion 34 in the axial direction of the rack shaft 5. When the steering is started (when the movement of the rack shaft 5 is started), the O-ring 31 is compressed in the axial direction, so that the rack bush 23 moves integrally with the rack shaft 5 in the axial direction.

  By the way, the tie rod 12 rotatably connected to the rack shaft 5 via the ball joint 11 is normally inclined with respect to the rack shaft 5, and therefore when the rack shaft 5 moves in the axial direction. In addition, a bending load acts on the rack shaft 5. As a result, the rack shaft 5 reciprocates in a bent state, and the rack bush 23 moves in the radial direction and easily collides with the end housing 27 when the rack shaft 5 reciprocates in the axial direction. .

  In consideration of this point, each opposing surface 41 of the concave portion 34 facing the convex portion 35 in the axial direction moves the O-ring 31 radially inward with the outer peripheral surface of the rack bush 23 by the axial movement of the rack bush 23. It is formed to compress. Specifically, the opposing surface 41 is formed in a tapered shape that is inclined so that its inner diameter decreases linearly as the distance from the convex portion 35 increases. That is, the facing surface 41 is formed to be linear in a cross section along the axial direction of the rack shaft 5. In the present embodiment, the entire opposing surface 41 is formed in a tapered shape, and the entire opposing surface 41 is configured as an inclined surface. Further, each facing surface 42 facing the concave portion 34 of the convex portion 35 in the axial direction is formed in a planar shape orthogonal to the axial direction of the rack shaft 5.

  As shown in FIG. 4, the rack bush 23 is formed with a slit 43 extending from one end to the other end so that the diameter can be reduced. Then, after the rack bush 23 with the O-ring 31 mounted is reduced in diameter, the rack bush 23 is inserted into the rack housing 21 and then returned to its original shape, so that the rack bush 23 is brought into the rack housing 21 as described above. It can be assembled.

  In the steering apparatus 1 configured as described above, the O-ring 31 is compressed in the axial direction between the convex portion 35 and the concave portion 34 at the start of steering, so that the rack bush 23 is integrated with the rack shaft 5 as a shaft. It is designed to move in the direction. Specifically, when the rack shaft 5 moves to one end side in the axial direction, the O-ring 31 disposed on one end side in the axial direction of the convex portion 35 is compressed in the axial direction as shown in FIG. Thus, the rack bush 23 moves integrally with the rack shaft 5 in the axial direction. Similarly, when the rack bush 23 moves to the other end side in the axial direction, the O-ring 31 disposed on the other end side in the axial direction of the convex portion 35 is compressed in the axial direction, so that the rack bush 23 is rack-mounted. It moves integrally with the shaft 5 in the axial direction. When the pressing force F1 (see FIG. 6) in the axial direction of the rack bush 23 acting on the rack bush 23 from the O-ring 31 becomes larger than the sliding resistance between the rack bush 23 and the rack shaft 5, the rack The shaft 5 slides with respect to the rack bush 23.

  Here, as shown in FIG. 6, when the rack shaft 5 moves in the axial direction, the opposed surface 41 is formed in a tapered shape, so that the O-ring 31 is also compressed in the radial direction of the rack bush 23. Therefore, the radially inward pressing force F2 acting on the rack bush 23 from the O-ring 31 is increased. Thereby, when the rack shaft 5 reciprocates in the axial direction, the radial support rigidity of the rack bush 23 by the O-ring 31 is increased.

As described above, according to the present embodiment, the following operational effects can be achieved.
(1) The steering device 1 is interposed between the rack shaft 5 provided in the rack housing 21 so as to be capable of reciprocating in the axial direction, and between the rack housing 21 (end housing 27) and the rack shaft 5. And a cylindrical rack bush 23 for slidably supporting 5. The rack bush 23 is formed with a convex portion 35 projecting radially outward, and the end housing 27 is formed with a concave portion 34 into which the convex portion 35 is inserted. An O-ring 31 that is sandwiched in the axial direction is provided. Then, the O-ring 31 is compressed by the axial movement of the rack bush 23 on each facing surface 41 of the recess 34, so that the O-ring 31 presses the rack bush 23 radially inward with respect to the axial direction. Tilted.

  According to the above configuration, the O-ring 31 is compressed in the axial direction between the convex portion 35 and the concave portion 34 at the start of steering so that the rack bush 23 moves in the axial direction integrally with the rack shaft 5. Therefore, it is possible to achieve a good steering feeling by reducing the feeling of catching. In the above configuration, the O-ring 31 presses the rack bush 23 radially inward by being compressed by the facing surface 41 when the rack bush 23 (rack shaft 5) moves in the axial direction. Thereby, when the rack shaft 5 reciprocates in the axial direction, it becomes possible to increase the radial support rigidity of the rack bush 23 by the O-ring 31, and it is difficult to move the rack bush 23 in the radial direction, The collision with the end housing 27 can be suppressed. Therefore, it is possible to suppress the generation of abnormal noise during steering and to realize even higher silence.

  (2) The convex portion 35, the concave portion 34, and the O-ring 31 are each formed in an annular shape extending in the circumferential direction of the rack bush 23. According to the above configuration, when the rack shaft 5 moves in the axial direction, the O-ring 31 is compressed in the radial direction over the entire circumference. Therefore, the pressing force F2 radially inward from the O-ring 31 increases on the rack bush 23 over the entire circumference. Thereby, when the rack shaft 5 reciprocates, the radial support rigidity of the rack bush 23 by the O-ring 31 can be stably increased, and the generation of abnormal noise can be effectively suppressed during steering. it can.

  (3) Since the facing surface 41 of the recess 34 is formed to be linear in the cross section along the axial direction of the rack shaft 5, it is formed to be curved in the cross section along the axial direction of the rack shaft 5. Compared with the case, the opposing surface 41 can be easily formed.

  (4) Since the slits 43 extending from one end to the other end are formed in the rack bush 23, the rack bush 23 can be easily reduced in diameter, and its assembling property can be improved.

In addition, the said embodiment can also be implemented in the following aspects which changed this suitably.
In the above embodiment, the opposing surfaces 41 of the recesses 34 are inclined so as to compress the O-ring 31 in the radial direction as the rack bush 23 moves in the axial direction, and the opposing surfaces 41 of the protrusions 35 are adjusted to the rack shaft 5. It was formed in a planar shape orthogonal to the axial direction. However, the present invention is not limited thereto, and the opposing surface 42 of the convex portion 35 may be inclined so as to compress the O-ring 31 in the radial direction as the rack bush 23 moves in the axial direction. Specifically, for example, as shown in FIG. 7, the opposing surface 41 of the concave portion 34 is formed in a planar shape orthogonal to the axial direction of the rack shaft 5, and each opposing surface 42 of the convex portion 35 is formed on the concave portion 34. You may form in the taper shape in which the outer diameter becomes linearly small as it approaches each opposing surface 41. As shown in FIG. Further, both the opposing surfaces 41 of the concave portions 34 and the opposing surfaces 42 of the convex portions 35 may be inclined so as to compress the O-ring 31 in the radial direction as the rack bush 23 moves in the axial direction.

  In the above embodiment, the convex portion 35, the concave portion 34, and the O-ring 31 (elastic member) are each formed in the rack bush 23 in an annular shape extending in the circumferential direction, but the present invention is not limited to this, for example, FIG. ), The convex portion 51 may be formed in a cylindrical shape protruding outward in the radial direction of the rack bush 23, and the concave portion 52 may be formed in a round hole shape corresponding to the convex portion 51. Specifically, as shown in the figure, a plurality of (for example, three) convex portions 51 are formed at equal angular intervals on the outer peripheral surface of the rack bush 23, and are convex on the inner peripheral surface of the accommodating portion 32. A plurality of concave portions 52 are formed at positions corresponding to the portions 51. An O-ring 55 extending in the circumferential direction of the convex portion 51 is provided between the outer peripheral surface 53 of the convex portion 51 and the inner peripheral surface 54 of the concave portion 52. The outer peripheral surface 53 of the convex portion 51 is formed in a cylindrical shape having a constant outer diameter, and the inner peripheral surface 54 of the concave portion 52 has its inner diameter linearly toward the radially outer side of the rack shaft 5. It is formed in a tapered shape that becomes smaller. Therefore, the entire inner peripheral surface 54 is configured as an inclined surface.

  With this configuration, in addition to the effects (1), (3), and (4) of the above embodiment, the convex portion 51 is engaged with the concave portion 52 in the circumferential direction of the rack bush 23. The rack bush 23 can be prevented from rattling in the circumferential direction. Further, when the rack shaft 5 moves in the axial direction, the pressing force inward in the radial direction from the O-ring 55 acts on the rack bush 23 at equal angular intervals. Thereby, when the rack shaft 5 reciprocates in the axial direction, the radial support rigidity of the rack bush 23 by the O-ring 55 can be stably increased, and the generation of abnormal noise is effectively suppressed during steering. can do.

  In addition, in the structure shown in FIG. 8, while forming the convex part 51 in polygonal column shape, you may make the recessed part 52 the shape which the convex part 51 can insert. Further, the plurality of convex portions 51 and concave portions 52 may not be provided at equal angular intervals in the circumferential direction of the rack bush 23. Furthermore, you may form the outer peripheral surface 53 of the convex part 51 in a taper shape.

  In the above embodiment, the entire facing surface 41 of the recess 34 is configured as an inclined surface, but a part of the facing surface 41 compresses the O-ring 31 in the radial direction as the rack bush 23 moves in the axial direction. You may make it become the inclined surface inclined in the axial direction.

  In the above-described embodiment, each facing surface 41 of the recess 34 is formed to be linear in a cross section along the axial direction of the rack shaft 5, but is not limited thereto, and is, for example, a curved shape such as an arc shape. You may form as follows.

  In the above embodiment, the steering device 1 is configured to include only one rack bush 23. However, the configuration is not limited thereto, and the steering device 1 may be configured to include two or more rack bushes 23. In this case, for example, two rack bushes 23 in total can be provided at both ends of the rack housing 21, that is, near the outer ends of the end housing 27 and the gear housing 25.

  In the above embodiment, the present invention is embodied in the steering device 1 in which the rack housing 21 is configured by the gear housing 25, the actuator housing 26, and the end housing 27. However, the present invention is not limited thereto, and the present invention may be embodied in a steering apparatus having an integral rack housing in which the gear housing 25, the actuator housing 26, and the end housing 27 are integrally formed.

  In the above embodiment, the present invention is embodied in a steering device configured as a rack assist type electric power steering device (EPS). However, the present invention is not limited to this, and the present invention may be applied to, for example, a so-called column assist type EPS, a non-rack assist type EPS, a hydraulic power steering device, or a non-assist type steering device.

Next, technical ideas that can be understood from the above embodiments and other examples will be described below together with their effects.
(A) In the steering apparatus according to claim 3, the rack bush is formed with a plurality of convex portions at equal angular intervals in the circumferential direction of the rack bush, and the housing is provided with the plurality of concave portions. A steering apparatus characterized by being formed at equal angular intervals in the circumferential direction of the rack bush. According to the above configuration, since the convex portion and the concave portion are formed at equal angular intervals in the circumferential direction of the rack bush, when the rack shaft moves in the axial direction, the rack bush has a radial inward direction from the elastic member. The pressing force acts at equiangular intervals. As a result, when the rack shaft reciprocates, the support stiffness in the radial direction of the rack bush by the elastic member can be stably increased, and the generation of abnormal noise can be effectively suppressed during steering.

  (B) In the steering apparatus according to any one of claims 1 to 3 and (A), the inclined surface is formed to be linear in a cross section along the axial direction of the rack shaft. A steering apparatus characterized by that. According to the said structure, compared with the case where the cross section along the axial direction of a rack shaft is formed in curve shape, an inclined surface can be formed easily.

  DESCRIPTION OF SYMBOLS 1 ... Steering device, 5 ... Rack shaft, 11 ... Ball joint, 12 ... Tie rod, 21 ... Rack housing, 23 ... Rack bushing, 25 ... Gear housing, 26 ... Actuator housing, 27 ... End housing, 31, 55 ... O-ring , 32 ... accommodating portion, 34, 52 ... concave portion, 35, 51 ... convex portion, 41, 42 ... facing surface, 43 ... slit, 53 ... outer peripheral surface, 54 ... inner peripheral surface.

Claims (3)

A steering wheel including a rack shaft that is reciprocally movable in an axial direction in a housing, and a cylindrical rack bush that is interposed between the housing and the rack shaft and slidably supports the rack shaft. In the device
The rack bush is formed with a convex portion protruding radially outward, and the housing is formed with a concave portion into which the convex portion is inserted,
On the outer periphery of the rack bush, an elastic member is provided that is sandwiched in the axial direction between the convex portion and the concave portion,
At least one of the opposing surface of the convex portion and the opposing surface of the concave portion facing each other in the axial direction of the rack shaft has an inclined surface inclined with respect to the axial direction of the rack shaft,
The steering apparatus according to claim 1, wherein the inclined surface is formed such that the elastic member presses the rack bush radially inward by the axial movement of the rack bush. The steering apparatus according to claim 1, wherein
The steering device, wherein the convex portion, the concave portion, and the elastic member are each formed in an annular shape extending in a circumferential direction of the rack bush. The steering apparatus according to claim 1, wherein
The steering device, wherein the convex portion is formed in a column shape, and the concave portion is formed in a hole shape corresponding to the convex portion.

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