JP2002160647A - Bush for steering rack housing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bush for steering rack housing of novel structure capable of dampingly limiting the occurrence of an abrupt change point at the rise of load-deflection characteristics as well as realizing a slightly under steering characteristic by setting smaller a spring constant in the lateral direction of a vehicle while maintaining the steering stability of the vehicle by setting larger the spring constant in the longitudinal direction of the vehicle. SOLUTION: A pair of recessed parts 54 and 54 are formed in a body rubber elastic body 30 for elastically connecting an inner shaft member 28 to an outer tube member 22, and a damping projection 42 projected from the inner shaft member 28 to the outer tube member 22 is formed on the center part of the recessed part 54.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bush for a steering rack housing for supporting a housing accommodating a steering rack for steering of an automobile in a vibration-proof manner with respect to a vehicle body, and a vibration-proof supporting structure for a steering rack housing using the same. , Especially when mounted on the vehicle,
TECHNICAL FIELD The present invention relates to a bush for a steering rack housing having a novel structure capable of stably obtaining a desired non-linear load-deflection characteristic in the lateral direction of a vehicle, and a vibration isolating support structure for the steering rack housing using the bush.

[0002]

2. Description of the Related Art Conventionally, an anti-vibration bush is mounted on a mounting portion of a steering rack housing to a vehicle body in order to suppress transmission of vibration from a wheel side to the vehicle body. In recent years, in order to achieve weak under steering performance while securing the running stability of the vehicle,
Tuning is required for the anti-vibration support system for the steering rack housing to the vehicle body, while securing the static spring constant in the vehicle front-rear direction and the vertical direction, and sufficiently reducing the static spring constant in the vehicle left-right direction. ing.

[0003] Therefore, Japanese Patent No. 2618353 discloses that an inner shaft metal fitting fixed to a vehicle body is inserted through an outer cylindrical metal fitting fixed to a steering rack housing and extending in the vehicle vertical direction. The inner shaft fitting and the outer tube fitting are connected by the main rubber elastic body, and extend between the opposing surfaces of the inner shaft fitting and the outer tube fitting on both sides in the radial direction sandwiching the inner shaft fitting in the vehicle lateral direction over the entire length in the axial direction. A structure of a steering rack housing bush provided with a pair of bulges is disclosed. In the bush having such a structure, the main rubber elastic body that elastically connects the inner shaft fitting and the outer cylindrical fitting in the radial direction is substantially removed in the vehicle left-right direction by a pair of burrs, and the vehicle left-right direction is used. Since the spring ratio in the front-rear direction can be set large, the static spring constant in the vehicle left-right direction can be set small while securing the static spring constant in the vehicle front-rear direction.

[0004] However, Japanese Patent No.
In the bush described in Japanese Unexamined Patent Publication No. 3 (1994), since a pair of bulge portions facing each other in the vehicle lateral direction are formed,
When a large load is input in the lateral direction of the vehicle, the inner shaft fitting and the outer cylindrical fitting are directly brought into contact with each other, and the spring characteristic in the lateral direction of the vehicle changes greatly. It was difficult to avoid the occurrence of a sudden change point at the rise of. Therefore, for example, when an excessive load is input in the vehicle lateral direction due to, for example, a case where the steering wheel is suddenly operated to a position where the steering angle is maximized, or a case where a large external force is applied by contact with a curb or the like. However, there was a problem that a sense of shock was easily felt.

[0005]

The present invention has been made in view of the above-described circumstances, and an object of the present invention is to control a vehicle by setting a large spring constant in the longitudinal direction of the vehicle. By setting the spring constant in the lateral direction of the vehicle to be small while ensuring stability, a weak under steering performance is realized, and a sudden change point occurs in the rise of the load-deflection characteristic with respect to the input load in the lateral direction of the vehicle. It is an object of the present invention to provide a steering rack housing bush having a novel structure capable of alleviating or avoiding the above problem, and a vibration damping support structure for a steering rack housing having a novel structure using the steering rack housing bush.

[0006]

An embodiment of the present invention which has been made to solve such a problem will be described below. The components employed in each of the embodiments described below can be employed in any combination as possible. In addition, aspects or technical features of the present invention are not limited to those described below, but are described in the entire specification and drawings, or based on the invention ideas that can be understood by those skilled in the art from the descriptions. It should be understood that it is recognized on the basis of.

That is, according to a first aspect of the present invention, the inner shaft member and the outer cylinder member which are radially separated from each other are elastically connected to each other by the rubber elastic body, and the inner shaft member and the outer cylinder member are connected to each other. Either one is fixed to the vehicle body and the other is fixed to the steering rack housing, so that the steering rack housing is mounted with the center axis substantially in the vehicle vertical direction, and the steering rack housing is fixed to the vehicle body. In a bush for a steering rack housing adapted to be supported for vibration isolation, the inner shaft member is made longer in the axial direction than the outer cylindrical member, and the main rubber elastic body is vulcanized on the outer peripheral surface of the inner shaft member. The inner shaft member is spread in the direction perpendicular to the axis at both ends in the axial direction of the inner shaft member while being bonded and press-fitted into the outer cylinder member. Then, stopper portions, which are axially separated from and opposed to both end surfaces in the axial direction of the outer cylinder member, are fixed to the inner shaft member, and the main rubber elastic body is fixed to the inner shaft member and the inner shaft member. A radial connecting portion interposed between the radially opposed surfaces of the outer cylindrical member, and a gap between the axially opposed end surfaces of the outer cylindrical member and the stopper portion of the inner axial member on both axial sides of the inner shaft member. And a pair of axial connecting portions interposed between the inner shaft member and the outer cylindrical member at both radial sides of the radial connecting portion sandwiching the inner shaft member in the vehicle lateral direction. And a pair of bulges extending in the axial direction over the entire length between the radially opposed surfaces, and projecting radially from the inner shaft member toward the outer cylinder member at a central portion of each of the bulges. Almost one With tapered cross-section extending in the circumferential direction buffer protrusion, that is integrally formed in the main rubber elastic body, and wherein.

In the steering rack housing bush having the structure according to this aspect, a pair of bulges are formed on both sides of the inner shaft member in the vehicle lateral direction. The constant can be set smaller than the spring constant in the vehicle longitudinal direction. As a result, while maintaining the steering stability of the vehicle obtained by the large spring constant in the vehicle front-rear direction, it is possible to realize the weak under steering performance obtained by the small spring constant in the vehicle lateral direction. Moreover, since the spring constant in the vertical direction of the vehicle is also set to be large, the steering stability of the vehicle can be more advantageously secured.

[0009] Each of the bulges is provided with a tapered buffering projection projecting from the inner shaft member toward the outer cylinder member, so that the buffer is applied when a large load is input in the lateral direction of the vehicle. When the projection abuts on the outer cylinder member, a sudden change in the rise of the load-deflection characteristic can be mitigated, so that a smooth load-deflection characteristic can be imparted to the bush. Therefore, it is possible to reduce the shock feeling when an excessive load is input in the lateral direction of the vehicle, and it is possible to improve the riding comfort of the vehicle.

Further, in the bush for a steering rack housing according to this aspect, the cushioning projection is formed so as to extend in the circumferential direction with a substantially constant cross-sectional shape.
When the inner shaft member to which the main rubber elastic body is vulcanized and bonded is press-fitted into the outer cylinder member, even if the buffer protrusion is mounted at a position shifted in the circumferential direction due to a circumferential mounting error or the like, such a buffer is provided. The protrusion can be positioned opposite to the outer cylinder member in the vehicle lateral direction. Therefore,
Even if there is a variation in the mounting direction of the main rubber elastic body, the buffer effect by the buffer protrusion can be stably exhibited, and as a result, the improvement of the workability of assembling the bush and the stability of the characteristics are improved. It can be realized both.

According to a second aspect of the present invention, there is provided a bush for a steering rack housing having a structure according to the first aspect, wherein the bulge is formed in a circumferential direction around the center axis of the inner shaft member. The feature is that it is 120 degrees. In such a steering rack housing bush having the structure according to this aspect,
Since the spring ratio in the lateral direction of the vehicle and the longitudinal direction of the vehicle can be further increased, it is possible to achieve a steering performance of a weaker under level while advantageously securing the steering stability of the vehicle. In addition, since the diameter of the bulging portion is set to 60 degrees or more in the circumferential direction, the free length of the main rubber elastic body can be advantageously secured when a large load is input in the lateral direction of the vehicle. As a result, the durability can be improved. The size in the circumferential direction of the hollow portion is more preferably 60 to 100 degrees.

According to a third aspect of the present invention, there is provided a bush for a steering rack housing having a structure according to the first or second aspect, wherein a radial direction in which the burrs are opposed to each other and a diameter perpendicular to the radial direction. It is characterized in that the ratio of the static spring constant in the direction is 1: 2.5 to 6 in the initial stage of elastic deformation. In the steering rack housing bush having the structure according to this aspect, the ratio of the static spring constant in the vehicle front-rear direction and the vehicle lateral direction is increased, so that the steering stability of the vehicle is advantageously secured. At the same time, it is possible to more advantageously realize a weak under steering performance.

According to a fourth aspect of the present invention, there is provided a bush for a steering rack housing having a structure according to any one of the first to third aspects, wherein a circumferential length of the cushioning projection is set to the inner shaft. It is characterized in that it is not less than 20 degrees in the circumferential direction around the central axis of the member and shorter than the circumferential length of the hollow portion. In the steering rack housing bush having such a structure according to this aspect, the buffer protrusion is formed to have a length of 20 degrees or more in the circumferential direction, so that an assembling error in a range of ± 10 degrees at the time of press-fitting is considered. In addition, the intended support characteristics of the steering rack housing based on the buffer effect by the buffer projection can be stably exhibited.

Further, since the cushioning projection is formed at a circumferential angle of 20 degrees or more around the center axis of the inner shaft member, a sufficient volume of the cushioning projection in the circumferential direction can be ensured. The load resistance and durability of the buffer projection against the input load can be advantageously secured.

The maximum value of the circumferential length of the buffer projection is
In consideration of a realistic size of an assembling error and the like, it is preferable that the inner shaft member is formed in a range of 70 degrees or less in the circumferential direction around the central axis.

According to a fifth aspect of the present invention, in the bush for a steering rack housing having a structure according to any one of the first to fourth aspects, the cushioning projection does not reach the outer cylinder member. It is characterized by being formed at a protruding height. In the steering rack housing bush having such a structure according to this aspect, since a gap is formed between the protruding distal end portion of the buffer projection and the outer cylinder member, at least until the buffer projection comes into contact with the outer cylinder member. In the stroke range described above, the low spring characteristics of the vehicle in the lateral direction due to the hollow portion are exhibited without being affected by the shock-absorbing projection, and the desired weak under steering performance can be more advantageously achieved.

According to a sixth aspect of the present invention, in a bush for a steering rack housing having a structure according to any one of the first to fifth aspects, the projecting tip of the cushioning projection is formed in an arc shape. It is characterized in that it is formed so as to extend in the circumferential direction in a sectional shape. In the bush for a steering rack housing having the structure according to the present aspect, at the initial stage when the cushioning projection comes into contact with the outer cylinder member, the bushing comes to a point contact in the axial direction and a line contact in the direction perpendicular to the axis. Therefore, a non-linear load-deflection characteristic based on the buffering action of the buffer projection can be stably obtained irrespective of a circumferential assembly error of the bush. Local stress concentration at the protrusion is reduced,
The load resistance and durability can also be improved.

According to a seventh aspect of the present invention, there is provided a bush for a steering rack housing having a structure according to any one of the first to sixth aspects, wherein the axial connecting portion is connected to a shaft of the outer cylinder member. It is characterized in that a pressure is applied in the axial direction over the entire circumference in the circumferential direction between the end face in the direction and the stopper portion of the inner shaft member. In the steering rack housing bush having such a structure according to this aspect, since the axial connecting portion is formed over the entire circumference in the circumferential direction, the circumferential mounting direction of the axial connecting portion is large. There is no need to consider.
In addition, by ensuring that the volume of the axial connection portion is substantially uniform over the entire circumference and large as a whole, the load resistance and durability in the axial direction can be improved.

The present invention also provides a steering rack housing bush having a structure according to any one of the first to seventh aspects mounted between the steering rack housing and the vehicle body. An anti-vibration support structure of the steering rack housing in which the steering rack housing is supported in an anti-vibration manner with respect to the vehicle body is also characterized.

In the anti-vibration support structure of the steering rack housing having the structure according to this embodiment,
By employing the specific bush having the structure according to the present invention as described above, even if an assembly error occurs in the same direction when the bush is assembled to the steering rack housing, a small spring constant occurs in the vehicle lateral direction. It is possible to stably exhibit both a weak under steering performance and a steering cushioning performance due to a gentle spring constant rising characteristic.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, in order to clarify the present invention more specifically, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an anti-vibration support structure of a steering rack housing as one embodiment of the present invention. In FIG. 1, reference numeral 10 denotes a steering rack housing which has a long hollow tubular shape.
Although not explicitly shown in the drawing, a steering rack is accommodated and disposed in the hollow interior so as to be movable in the longitudinal direction. When the pinion meshed with the steering rack is driven to rotate in accordance with the steering operation of the rotary operation shaft 12, the tie rod ends 1 protruding from both sides in the longitudinal direction via the steering rack.
4 and 14 are driven to apply a steering force to a front wheel (not shown). The steering rack housing further includes two steering rack housing bushes 16 on both sides of the central axis in one direction perpendicular to the axis, and the steering rack housing 10 is not shown by these bushes 16. The anti-vibration support is provided for the vehicle body.

More specifically, the steering rack housing 10 is formed of a metal material such as an iron-based metal or an aluminum alloy by casting, pressing, or the like. Although not shown in the drawing, a straight line is formed on the center axis. Extending,
It has a hole for disposing the steering rack. Further, hollow shell-shaped covers 18 having a bellows structure are attached to both ends of the steering rack housing 10, and the protruding portions of the tie rod ends 14, 14 are covered. Furthermore, the steering rack housing 1
0, a pinion housing 20 is fixed to the housing 20 so as to protrude substantially vertically upward, and the rotational driving force exerted on the rotary operation shaft 12 protruded from the housing 20 is transmitted to the pinion via a hydraulic auxiliary mechanism or the like. Has been affected.

Further, the steering rack housing 1
0, two outer cylinder portions 2 as outer cylinder members projecting from both sides of the central axis in a substantially horizontal direction.
2 and 22 are fixedly formed by integral formation or the like. Each of the outer cylinder portions 22, 22 is connected to the steering rack housing 1.
0 are provided near both ends in the longitudinal direction, and each has a circular assembling hole extending in a substantially vertical direction. Then, the bush body 2 is
6 are assembled, thereby forming a total of four steering rack housing bushes 16.

As shown in FIGS. 2 and 3, the bush body 26 has an inner cylindrical member 28 as an inner shaft member.
And a main rubber elastic body 30. This inner tube fitting 28
Has a thick cylindrical shape extending with a substantially constant cross section. Further, the main rubber elastic body 30 has a substantially cylindrical shape as a whole, and the central portion in the axial direction has a smaller diameter than both end portions in the axial direction. A portion 32 is formed, and a large-diameter portion 34 as an axial connection portion is formed at both axial ends. In addition, the small diameter part 32 is larger than the large diameter part 34.
The axial length is set large, and in the present embodiment,
The small-diameter portion 32 is formed with an axial length of approximately 1/2 to 3/4 of the entire length of the main rubber elastic body 30.

The small-diameter portion 32 and the large-diameter portion 3
4 and 34 are respectively vulcanized and bonded to the outer peripheral surface of the inner cylinder 28 so that the main rubber elastic body 30 can be integrally vulcanized and formed with the inner cylinder 28. Have been. The axial length of the entire rubber elastic body 30 is smaller than that of the inner cylinder 28, and the inner cylinder 2
8, both ends in the axial direction are slightly projected outward in the axial direction from the main rubber elastic body 30, respectively.

Further, the small diameter portion 32 of the rubber elastic body 30 is provided.
A pair of recesses 36, 36 are formed on both sides in the radial direction with the inner tube fitting 28 sandwiched in one direction (vertical direction in FIG. 3). The pair of recesses 36, 36 respectively
The small-diameter portion 32 is formed on the outer peripheral surface of the small-diameter portion 32 so as to extend straightly over the entire length in the axial direction with a substantially constant cross-sectional shape. The depth of each recess 36 is set so as not to reach the inner cylindrical fitting 28, and the circumferential widths of the two recesses 36 are the same. Furthermore, in the present embodiment, the angle α formed by the two radial lines 40 extending from the central axis O of the inner cylindrical fitting 28 to the wall surfaces 38 on both sides in the circumferential direction of the recess 36 is 60 to 60.
100 degrees.

Further, an elastic projection 42 as a buffer projection is provided on the bottom surface of each of the recesses 36 so as to project radially outward. The elastic protrusion 42 is formed integrally with the main rubber elastic body 30 and positioned at the axial center portion of the bottom surface of the recess 36, and has a substantially constant cross-sectional shape.
6 at a predetermined length in the circumferential direction. Also, the elastic projection 4
The projecting height of 2 is slightly smaller than the depth dimension of the recess 36 so that the elastic projection 42 does not project from the recess 36.

That is, in the present embodiment, the elastic projection 42 has a semi-elliptical cross-sectional shape whose minor axis is the direction of projection, and the major axis ratio of the major axis to the minor axis is approximately 2/5. As a whole, it has a curved crab shape extending in the circumferential direction in the recess 36. Further, the projecting height of the elastic projection 42 is set so that the elastic projection 42 does not reach the wall surface of the outer cylinder (22) when the bush body 26 is assembled to the outer cylinder (22). In this embodiment,
The top of the elastic projection 42 has a radius of curvature approximately 1 mm smaller than the radius of curvature of the small-diameter portion 32 around the central axis O.
It has a ridge shape extending in the circumferential direction around O. Also,
In the present embodiment, the angle β formed by the radial lines 44 extending from the central axis O of the inner cylindrical metal fitting 28 to the circumferential both ends of the top of the elastic projection 42 A, A, Circumferential angle: smaller than α and 20 to 70 degrees. As a result, the elastic projections 42 protruding into the recesses 36 form the small-diameter portions 32 forming the circumferential side walls of the recess 36 and the large-diameter portions forming the axial side walls of the recess 36. 3
4, 34, each is formed substantially independently.

As shown in FIG. 4, first circumferential grooves 46, 46 are formed at both ends in the axial direction of the small diameter portion 32 of the main rubber elastic body 30. This first circumferential groove 46
Has a U-shaped cross-sectional shape, is formed on the outer peripheral surface of the small diameter portion 32, and is formed over the entire circumference. Further, the depth dimension of the first peripheral groove 46 is set to a size that does not reach the inner cylindrical fitting 28, and in the present embodiment, is set to be substantially the same as the depth dimension of the recess 36. Thereby, in the formation site of the recess 36, the first peripheral grooves 46, 46 constitute both axial end portions of the recess 36, and the pair of recesses 36, 36
At both ends in the axial direction, the first peripheral grooves 46 are connected to each other.

Further, large-diameter portions 34, 34 are integrally formed at both ends in the axial direction of the small-diameter portion 32, respectively. These large-diameter portions 34, 34 have an annular block shape extending over the entire circumference in a circumferential direction with a substantially rectangular constant cross section. The above-described first peripheral groove 46 is formed. That is, the large diameter portion 3
4 is formed by one wall surface of the first circumferential groove 46.

Also, on the axially outer surface of each large diameter portion 34,
A second peripheral groove 48 extending circumferentially along the inner peripheral edge is formed. The second circumferential groove 48 has a substantially U-shaped cross-sectional shape that expands toward the opening side, and has a large diameter portion 34.
And is continuously formed with a substantially constant cross-sectional shape over the entire circumference. In addition, the depth dimension of the second circumferential groove 48 is set to a size that does not reach the small diameter portion 32, and in the present embodiment, is approximately １ ／ of the axial size of the large diameter portion 34. Further, an opening portion of the inner peripheral side wall surface in the second peripheral groove 48 is formed by the outer peripheral surface of the inner cylinder fitting 28.

Further, the large diameter portion 34 is inclined in the axial direction by a predetermined angle: γ so as to gradually extend inward in the axial direction from the inside to the outside in the radial direction. Thereby, the axial inner surface 50 and the axial outer surface 52 of the large diameter portion 34 are inclined inward in the axial direction with respect to the surface perpendicular to the axis by the angle: γ, and the outer peripheral surface of the large diameter portion 34 is The central axis is inclined inward in the axial direction by an angle γ with respect to the cylindrical surface around O.

As shown in FIGS. 5 and 6, the bush body 26 having such a structure is assembled into the rack housing (10) by being pressed into the outer cylinder 22. ing. The outer cylindrical portion 22 is formed in a large-diameter cylindrical shape,
6 has an axial length substantially equal to the axial length of the small diameter portion 32. The inner diameter of the outer cylinder 22 is slightly smaller than the outer diameter of the small diameter portion 32 of the bush body 26, and the outer diameter of the outer cylinder 22 is larger than the larger diameter 34 of the bush body 26. Is larger than the outer diameter dimension of.

The bush body 26 is assembled to the outer cylinder 22 such that the center axes of the inner cylinder fitting 28, the rubber elastic body 30 and the outer cylinder 22 are substantially coaxial. The inner peripheral surface of the outer cylindrical portion 22 is pressed against the outer peripheral surface of the small-diameter portion 32 of the main rubber elastic body 30, and both axial end surfaces of the outer cylindrical portion 22 have the large diameter of the main rubber elastic body 30. Since the bush body 26 is pressed against the inner surface 50 in the axial direction of the portion 34, the drag force of the bush body 26 in the axial direction with respect to the outer cylindrical portion 22 is exerted.

In such an assembled state, the pair of recesses 36, 36 provided in the bush main body 26 are covered with the outer cylinder 22 to form a pair of bulges 54, 54. I have. These bulges 54, 54 are formed continuously over the entire length of the outer cylinder 22 in the axial direction, and at portions opposed to each other on both sides of the inner cylinder 28 in the vehicle lateral direction, the inner cylinders are formed. 28 and the outer cylindrical portion 22 are respectively positioned over the entire length in the axial direction between the radially opposed surfaces of the outer cylindrical portion 22.

Further, the pair of large-diameter portions 34, 34 of the bush main body 26 have their respective axial inner surfaces 50 pressed against the axial end surfaces of the outer cylindrical portion 22 based on their respective elasticity. Thereby, the large-diameter portions 34 protrude outward in the axial direction from both axial end surfaces of the outer cylindrical portion 22. In addition, each large diameter portion 34
Is elastically deformed so as to be pushed outward in the axial direction by the press-contact of the outer cylindrical portion 22, so that the axially outer surface 52 is smaller than the axially end surface of the inner cylindrical fitting 28 by a predetermined dimension: t. It protrudes outward in the direction.

As described above, since the large diameter portion 34 is formed to be inclined inward in the axial direction, the bush body 2
6, the press-fitting workability into the outer cylinder portion 22 can be advantageously ensured. Further, when the bush main body 26 is press-fitted into the outer cylindrical portion 22, the first peripheral groove 46 and the second peripheral groove 48 are elastically deformed.
It is a rubber relief of 0. And the bush body 2
6 is press-fitted into the outer cylindrical portion 22, the first peripheral groove 46 is substantially eliminated except for the portion where the bulging portion 54 is formed, and the width dimension of the second peripheral groove 48 is reduced. Is reduced so that the rubber elastic body 3
0, the stress generated is reduced, and the durability is improved.

Further, in each of the burrs 54 formed between the radially opposed surfaces of the inner cylindrical fitting 28 and the outer cylindrical part 22, the protruding distal end face of the elastic projection 42 projecting from the inner cylindrical fitting 28 side. Slight gap between (top) and outer cylinder 22:
δ is formed. In the present embodiment, the gap δ is set to a predetermined size within a range of 0.1 to 1.0 mm.

Further, as shown in FIG. 7, stopper plates 56, 56 as stopper portions are fixedly mounted on both axial sides of the inner cylindrical fitting 28. The stopper plate 56 is formed in a thick disk shape formed of a rigid material such as metal, and has a through hole 58 formed in a central portion thereof so as to penetrate in the thickness direction. The radial dimension of the through-hole 58 is substantially the same as the inner diameter of the inner cylinder fitting 28, and the outer diameter of the stopper plate 56 is substantially the same as the outer diameter of the outer cylinder 22. I have.

Then, a bolt 60 is inserted from one side in the axial direction into the inner cylindrical fitting 28 and the stopper plates 56, 56 superposed on both sides in the axial direction. By screwing the nut 62, the stopper plates 56, 56 are tightened and fixed to both axial ends of the inner cylindrical fitting 28, and are axially perpendicular to the axially opposite ends of the inner cylindrical fitting 28. It is spread and fixed.

Although not explicitly shown in the drawings, the stopper plates 56 are fixed to the vehicle body directly or via bolts 60. As a result, the inner cylinder fitting 28 and the outer cylinder 22 are elastically connected by the main rubber elastic body 30 to form the bush 16, and the inner cylinder 28 is fixed to the vehicle body, and the outer cylinder 22 is fixed to the vehicle body. The steering rack housing 10 on which is fixed is provided with an anti-vibration support structure which is elastically supported on the vehicle body via four bushes 16.

In each bush 10, the stopper plates 56, 56 fixed to the inner cylinder fitting 28 are respectively
In the outer peripheral portion, the large-diameter portions 34 of the main rubber elastic body 30 are pressed against the respective axial end surfaces.
Thus, each large-diameter portion 34 is disposed over the entire circumference in the axial direction between the outer cylindrical portion 22 and the axially opposed surface of the stopper plate 56 while being pressed in the axial direction.

The bush body 26 has a radial direction in which the pair of bulges 54, 54 are opposed to each other and a radial direction orthogonal thereto, respectively, are defined as a vehicle lateral direction and a vehicle longitudinal direction, respectively. Body 2
The axial direction of 6 is the vehicle vertical direction. As a result, a shear deformation is mainly generated for an input load in a vehicle lateral direction, while a compression / tensile deformation is mainly generated for an input load in a vehicle vertical direction and a vehicle front-rear direction. Thus, it is possible to set the spring characteristics in the vehicle lateral direction softly while securing a large spring rigidity in the vehicle longitudinal direction and the vehicle vertical direction. In particular, in the present embodiment, the ratio of the static spring constant in the radial direction in which the pair of bulges 56 and 56 are opposed to each other and the static spring constant in the radial direction perpendicular thereto is determined until the elastic protrusion 42 contacts the outer cylinder 22. Is set to a predetermined value in the range of 1: 2.5 to 6 in the initial stage of the elastic deformation of the steering rack housing 10 so that the steering spring stability of the steering rack housing 10 in the vehicle lateral direction can be secured while ensuring the steering stability of the vehicle. Is softened, and a weak under steering characteristic can be advantageously provided.

In the vibration isolating support structure of the steering rack housing 10 having the above-described structure, an elastic projection 42 is formed on a straight portion 54 of each bush 16, and the elastic projection 42 is formed on the outer cylinder. Due to the buffering effect obtained by contacting the portion 22, a sudden change in the rise of the load-deflection characteristic is mitigated. As a result, a smooth load-deflection characteristic is imparted to the bush 16, and the shock feeling when a large load is input in the vehicle lateral direction can be advantageously reduced.

In addition, when a small load is input, the elastic projection 4
2 is maintained in a non-contact state with the outer cylinder portion 22, so that a soft supporting spring characteristic is exerted on the steering rack housing 10 in the lateral direction of the vehicle, and the desired steering characteristic is effectively achieved. It can be demonstrated.

The elastic projection 42 has a substantially elliptical shape in a section in the axial direction and is extended at a predetermined length in the circumferential direction. The contact surface is substantially in contact with the line, and while the input load is small, an excellent cushioning effect based on sufficiently soft spring characteristics is exhibited. On the other hand, when the input load is large, the elastic protrusion 42 With a large volume (volume), a large load bearing performance is exhibited, and also excellent durability is exhibited.

Further, since the elastic projection 42 is formed to have a substantially constant cross-sectional shape and a predetermined length in the circumferential direction, for example, when the bush main body 26 is press-fitted to the outer cylindrical portion 22 in the circumferential direction, Due to the assembly error of the pair of recesses 36,
Even when the facing direction of 36 is shifted from the lateral direction of the vehicle, the state in which the elastic projection 42 faces the outer cylinder 22 with a gap of the target size: δ stably appears. Therefore, the above-described intended buffer effect of the elastic projection 42 can be effectively and stably exhibited with excellent reliability.

Specifically, for example, if the circumferential length (α) of the elastic projection 42 is set to 25 degrees, even if there is an assembly error of about ± 10 degrees in the circumferential direction, Thus, the intended buffer effect according to 42 can be effectively obtained.

FIG. 8 shows the results of actually measuring the load-deflection characteristics of the bush 16 having the structure according to the present embodiment as described above. In this experiment, FIG.
In the actual mounting state as shown in FIG. 5, the load input direction is the direction perpendicular to the axis at which the pair of bulges 54 and 54 are opposed to each other. The load applied in this direction is measured using a load cell, and the load is applied. Inner metal fitting 28 when the
And the relative displacement of the outer cylinder 22 in the direction perpendicular to the axis was recorded by an XY recorder using a displacement meter such as a differential transformer. In addition, as a conventional structure example, using a bush in which a pair of bulges are not provided with cushioning protrusions, a similar experiment was performed on a bush having such a conventional structure, and the result was also compared with FIG. 8 as a comparative example. Show.

As is clear from the measurement results shown in FIG. 8, in the bush 16 of the embodiment, the soft spring characteristic is substantially the same as that of the bush of the comparative example until the buffer projection 42 comes into contact with the outer cylindrical portion 22. It is recognized that the load-deflection characteristics based on the above are exhibited. Further, after the load increases and the buffer protrusion 42 comes into contact with the outer cylindrical portion 22, the bush 16 of the embodiment has a sharp change in the bending with respect to the increase in the load as compared with the bush of the comparative example. It is clearly observed that it is relaxed and exhibits smoother load-deflection properties.

Although the embodiment of the present invention has been described in detail above, this is merely an example, and the present invention is not to be construed as being limited by the specific description in the embodiment. .

For example, in the above-described embodiment, the large-diameter portion 34 of the main rubber elastic body 30 is formed over the entire circumference. However, it is not always necessary to form the large-diameter portion 34 over the entire circumference. Specifically, at the circumferential position where the recess 36 is formed, a concave groove extending in a direction perpendicular to the axial direction on the inner surface of the large diameter portion 34 in the axial direction, a through hole penetrating the large diameter portion 34 in the axial direction, and the like are provided. It may be formed.

In the above embodiment, the elastic projection 4
It is also possible to provide a plurality of 2 in one burring portion 54. In this case, it is desirable to adopt a configuration in which the elastic protrusions are arranged side by side in the axial direction of the bulging portion and extend in the circumferential direction in parallel with each other, whereby the circumferential length of each elastic protrusion is set to be large. It is possible to do.

Further, the number of bushes 16 used for supporting one steering rack housing 10 on the body in a vibration-proof manner is not limited to four, but is three.
Less than or five or more bushes may be employed.
Further, it is desirable that all of the plurality of bushes be constituted by a bush having a structure according to the present invention, but at least one of the plurality of bushes should be constituted by a bush having a structure according to the present invention. Thus, the effects of the present invention can be effectively exhibited.

In addition, although not enumerated one by one, the present invention
Based on the knowledge of those skilled in the art, the present invention can be implemented in a form in which various changes, modifications, improvements, and the like are added.
It goes without saying that all such embodiments are included in the scope of the present invention without departing from the spirit of the present invention.

[0057]

As is apparent from the above description, the steering rack housing bush having the structure according to the present invention employs a specific shape elastic projection extending in the circumferential direction with a substantially constant cross-sectional shape. In addition, the adverse effects of working errors at the time of press-fitting and assembling of the bush are reduced or avoided, and the smooth load-deflection characteristics exhibited based on the buffering action of the elastic projections are stable with high reliability. It can be demonstrated.

Further, in the anti-vibration support structure of the steering rack housing according to the present invention, by adopting the steering rack housing bush having the structure according to the present invention, the anti-vibration support characteristic of the intended steering rack housing, and furthermore, This makes it possible to stably obtain the steering stability and riding comfort of the vehicle.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an anti-vibration support structure of a steering rack housing as one embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a bush main body constituting a bush having a structure according to the present invention employed in the vibration isolating support structure of the steering rack housing shown in FIG. 1;
FIG. 4 is a diagram corresponding to a II-II section in FIG. 3.

FIG. 3 is a sectional view taken along the line III-III in FIG. 2;

FIG. 4 is an enlarged view of a main part in FIG. 2;

FIG. 5 is a longitudinal sectional view showing a state in which the bush body shown in FIG. 2 is press-fitted into an outer cylinder portion,
It is a figure corresponding to a cross section.

FIG. 6 is a sectional view taken along line VI-VI in FIG. 5;

FIG. 7 is a longitudinal sectional view of a bush having a structure according to the present invention employed in the vibration isolating support structure of the steering rack housing shown in FIG. 1;

FIG. 8 is a graph showing the measurement results of the load-deflection characteristics of the bush in this example, together with the measurement results of the comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Steering rack housing 16 Bush 22 Outer cylinder part 28 Inner cylinder fitting 30 Rubber elastic body 32 Small diameter part 34 Large diameter part 42 Elastic projection 54 Straightening part 56 Stopper plate

Claims (8)

[Claims] 1. An inner shaft member and an outer cylinder member which are radially separated from each other are elastically connected by a rubber elastic body, and one of the inner shaft member and the outer cylinder member is fixed to a vehicle body. And a steering rack having the other fixed to a steering rack housing so that the center axis is substantially in the vertical direction of the vehicle so that the steering rack housing is supported on the vehicle body in a vibration-proof manner. In the housing bush, the inner shaft member is longer in the axial direction than the outer tube member, and the main rubber elastic body is vulcanized and adhered to the outer peripheral surface of the inner shaft member to be pressed into the outer tube member. At the same time, the outer cylindrical member is axially extended at both axial end portions of the inner shaft member so as to be assembled. The stopper portion for opposition spaced apart from each axial direction with respect to allowed fixed to the inner shaft member,
The main rubber elastic body, a radial connecting portion interposed between the radially opposed surfaces of the inner shaft member and the outer cylindrical member, and an axial end surface of the outer cylindrical member on both axial sides of the inner shaft member. And a pair of axial connecting portions interposed between the opposing surfaces of the inner shaft member and the stopper portion. The radial connecting portion further includes a diameter that sandwiches the inner shaft member in a vehicle lateral direction. A pair of bulges extending in the axial direction over the entire length between the inner shaft member and the radially opposed surface of the outer cylindrical member on both sides in the direction, and the inner shaft member is formed at a central portion of each of the bulges. A cushioning projection projecting radially toward the outer cylinder member and extending in the circumferential direction with a substantially constant tapered cross-sectional shape integrally formed with the rubber elastic body. Interview. 2. The steering rack housing bush according to claim 1, wherein the bulge is formed at a circumferential angle of 60 to 120 degrees around a center axis of the inner shaft member. 3. The method according to claim 1, wherein the ratio of the static spring constant in the radial direction in which the bulge is opposed to the radial direction and the static spring constant in the radial direction perpendicular thereto is 1: 2.5 to 6 in the initial stage of the elastic deformation. A bush for a steering rack housing as described. 4. A circumferential length of said buffer projection is not less than 20 degrees in a circumferential direction around a central axis of said inner shaft member and shorter than a circumferential length of said hollow portion.
The bush for a steering rack housing according to any one of the above. 5. The bush for a steering rack housing according to claim 1, wherein the cushioning projection has a projecting height that does not reach the outer tubular member. 6. The bush for a steering rack housing according to claim 1, wherein the projecting tip of the cushioning projection is formed so as to extend in a circumferential direction with an arc-shaped cross section. 7. The axial connection portion is pressed in the axial direction between the axial end surface of the outer cylinder member and the stopper portion of the inner shaft member over the entire circumference in the circumferential direction. A bush for a steering rack housing according to any one of claims 1 to 6. 8. A plurality of bushes for a steering rack housing according to claim 1, which are mounted between said steering rack housing and said vehicle body, and said steering rack housing is attached to said vehicle body. An anti-vibration support structure for a steering rack housing, characterized in that it is supported by anti-vibration.