JP4203792B2 - Rack bush - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rack bush that is used, for example, in an automobile steering device and supports a rack shaft in a slidable manner.
[0002]
[Prior art]
Some rack bushes are formed in a cylindrical shape surrounding the rack shaft, the entire inner periphery thereof is brought into contact with the outer periphery of the rack shaft, and the outer periphery thereof is press-fitted into a holding hole of the housing (for example, (See Patent Document 1).
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-315990
[Problems to be solved by the invention]
However, as a result of the inner periphery of the press-fitted rack bush tightening the rack shaft, the sliding resistance of the rack shaft may increase.
On the contrary, if the rack bush is dimensioned with respect to the rack shaft so that the sliding resistance of the rack shaft is reduced, a gap may be generated between the rack bush and the rack shaft, and noise may be generated.
[0005]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a rack bush that solves the above technical problems, can reduce the sliding resistance of the rack shaft, and can suppress the generation of abnormal noise.
[0006]
[Means for Solving the Problems and Effects of the Invention]
A first aspect of the present invention is a rack bushing fitted and held in a holding hole of a housing and slidably supporting a rack shaft, and an inscribed portion spaced apart from the rack shaft and inscribed in an inner periphery of the holding hole of the housing A plate that connects the adjacent inscribed parts with an annular shape in which circumferentially arranged outer parts separated from inner circumferences of the holding holes of the housing and arranged with low friction members that circumscribe the rack shaft are alternately arranged in the circumferential direction. Due to the elasticity of the spring, the low friction member between the inscribed portions connected by the leaf spring is urged to the rack shaft, and the inscribed portion has an inward and outward direction with respect to the radial direction of the rack bush. The low-friction member of the circumscribed portion is disposed inside and outside of the leaf spring with respect to the radial direction of the rack bush .
[0007]
According to the first invention, the inscribed portion is urged toward the inner periphery of the holding hole by the leaf spring, and the circumscribed portion is urged to the rack shaft, so that the rack shaft can be held on the housing without rattling. Generation of sound can be suppressed. Since the rack shaft is in contact only with the low friction member of the circumscribed portion that is a part of the circumferential direction, the sliding resistance of the rack shaft can be reduced. Moreover, since we arranged synthetic resin member in the inscribed portion, when mounting the rack bushing retaining hole, it is not necessary to damage the inner circumference of the holding hole.
[0008]
According to a second invention, in the first invention, the leaf spring includes two leaf springs disposed at both ends of the rack bush in the axial direction.
According to a third invention, in the second invention, the circumscribed portion includes a first circumscribed portion coupled to one of the two leaf springs and a second circumscribed portion coupled to the other, The first and second circumscribed portions are separated from each other in the axial direction.
According to a fourth invention, in the first , second, and third inventions, the leaf spring is formed of a metal material. According to this invention, since it can be thinned while obtaining high elasticity, the amount of adjustment of the inner and outer diameters at the time of mounting can be increased.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a steering device using a rack bush according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a partial cross-sectional front view schematically showing a main part of a steering apparatus according to an embodiment of the present invention, and also shows a schematic configuration.
The steering apparatus 1 is fixed to a pinion 4 that rotates in conjunction with a steering wheel 2 via a steering shaft 3, a rack shaft 6 provided with a rack 5 that meshes with the pinion 4, and a vehicle body (not shown). A cylindrical housing 7 that generally accommodates the rack shaft 6, and a substantially cylindrical rack bush 9 that is held by the housing 7 and supports the rack shaft 6 slidably in the axial direction.
[0010]
The rack shaft 6 is a long rod-like member having a substantially circular cross section, and the rack 5 is formed in a predetermined range along the axial directions S1 and S2 on the outer periphery 11 thereof.
A pair of ball joint units 13 as joint members are provided at both ends 12 (only one end is shown) of the rack shaft 6, and wheels (not shown) are connected to the ball joint units 13 via tie rods 14 and the like. ) Are linked to each other. When the steering wheel 2 is operated, the pinion 4 rotates, and accordingly, the rack shaft 6 moves along the axial directions S1 and S2, and the wheel can be steered.
[0011]
The steering device 1 is configured in substantially the same manner at both end portions 16 (only one end portion is shown) of the housing 7. In the following, the explanation will be made focusing on one end portion 16 shown in FIG.
A holding hole 18 is formed in the end 16 of the housing 7, and the rack bush 9 is held in the holding hole 18 in a fitted state. An annular rack stopper 17 is disposed at the opening end of the holding hole 18. The rack stopper 17 is in contact with a part of the ball joint unit 13, thereby restricting the sliding range of the rack shaft 6 when the rack shaft 6 enters the housing 7.
[0012]
With reference to the enlarged cross-sectional view of FIG. 2, the rack bush 9 is restricted from moving in the axial direction S <b> 1 by the side wall 19 of the holding hole 18, and restricted from moving in the axial direction S <b> 2 by the rack stopper 17. The side wall 19 and the rack stopper 17 of the holding hole 18 function as positioning means for positioning the rack bush 9 in the axial directions S1 and S2.
2 and 3, the rack bush 9 is mounted in an annular space between the outer periphery 11 of the rack shaft 6 and the inner periphery 20 of the holding hole 18. The annular space has a radial dimension L1 shown in FIG. 3 of about 5 mm, for example.
[0013]
The rack bush 9 has a plurality of, for example, three low friction members 30 circumscribing the rack shaft 6, a plurality of, for example, three synthetic resin members 31 inscribed in the inner periphery 20 of the holding hole 18 of the housing 7, and an annular shape. And a leaf spring 32 formed. The leaf springs 32 connect the synthetic resin members 31 and the low friction members 30 and are alternately arranged in the circumferential direction T.
The leaf spring 32 is made of metal, for example, spring steel, so as to be elastically deformable in the radial direction. As shown in FIG. 5, the leaf spring 32 in the free state has a substantially polygonal shape, for example, a substantially triangular shape. The leaf spring 32 has a plurality of, for example, three spring portions 33 that connect the adjacent synthetic resin members 31 in the circumferential direction T and function as leaf springs, and each spring portion 33 extends substantially straight. Make each side of the triangle. The synthetic resin member 31 is disposed at each apex of the substantially triangular shape, and the low friction member 30 is disposed in the middle between the synthetic resin members 31 in each spring portion 33.
[0014]
When the steering device 1 is assembled, first, the rack bush 9 in a free state is fitted to the rack shaft 6. Thereby, the low friction member 30 in the middle of each spring portion 33 is displaced radially outward U, and each spring portion 33 is flexibly bent radially outward U. Next, the rack bush 9 is inserted into the holding hole 18 together with the rack shaft 6, and the rack bush 9 is fitted into the holding hole 18. The rack bush 9 may be fitted in the holding hole 18 in advance, and then the rack shaft 6 may be fitted in the rack bush 9.
[0015]
3 and 4, in the mounted state, the intermediate portion of the spring portion 33 is bent outwardly and bent, and the rack bush 9 is formed in an annular shape, for example, a substantially hexagonal annular shape as a substantially polygonal annular shape. Make. In this state, due to the elasticity of each spring portion 33, the synthetic resin member 31 at both ends of each spring portion 33 is elastically urged and inscribed toward the inner periphery 20 of the holding hole 18. The low friction member 30 in the intermediate portion is elastically biased toward the rack shaft 6.
[0016]
The mounted rack bush 9 has a plurality of, for example, three inscribed portions 41 arranged with the above-described synthetic resin member 31 and inscribed in the inner periphery 20 of the holding hole 18 of the housing 7 away from the rack shaft 6 via a gap. And a plurality of, for example, three circumscribed portions 42 that are arranged with the low friction member 30 and circumscribe the outer periphery 11 of the rack shaft 6 away from the inner periphery 20 of the holding hole 18 of the housing 7 via a gap. ing. The inscribed portions 41 and the circumscribed portions 42 are alternately arranged at substantially equal intervals in the circumferential direction T. Only the inscribed portions 41 are inscribed in the inner circumference 20 of the holding hole 18, and only the circumscribed portions 42 are circumscribed on the rack shaft 6. is doing.
[0017]
The low friction member 30 is made of a first synthetic resin material. Examples of the first synthetic resin material include polyamide (PA) such as nylon, polyurethane, and polytetrafluoroethylene (PTFE). The portion of the low friction member 30 that is the inner periphery of the rack bush 9 has a flat surface that circumscribes the rack shaft 6, and can substantially make linear contact with the outer periphery 11 of the rack shaft 6.
The synthetic resin member 31 is formed of a second synthetic resin material. In the present embodiment, the first and second synthetic resin materials are of the same type.
[0018]
With reference to FIG. 3, in the present embodiment, the leaf spring 32 urges the inscribed portion 41 toward the inner periphery 20 of the holding hole 18, and urges the circumscribed portion 42 toward the outer periphery 11 of the rack shaft 6. The rack shaft 6 can be held on the housing 7 without rattling, and abnormal noise can be suppressed. Since the rack shaft 6 is contacted only by the low friction member 30 of the circumscribed portion 42 that is a part of the circumferential direction T, the sliding resistance of the rack shaft 6 can be reduced.
Therefore, when this rack bush 9 is used for the steering device 1, it is easy to steer by reducing the sliding resistance, which can contribute to improving the driving stability of the automobile, and can achieve noise reduction.
[0019]
Further, since the metal leaf spring 32 can be thinned while obtaining high elasticity, the amount of adjustment of the inner and outer diameters when the rack bush 9 is mounted can be increased.
Further, since the synthetic resin member 31 is disposed in the inscribed portion 41, when the rack bush 9 is attached to the holding hole 18, it is not necessary to damage the inner periphery 20 of the holding hole 18, and further contributes to prevention of abnormal noise. . In particular, in the case of the metal leaf spring 32, it is preferable because the concern that the holding hole 18 tends to be damaged can be solved.
[0020]
Further, the low friction member 30 is formed of a synthetic resin material, and more preferably used in combination with the synthetic resin member 31, thereby further contributing to prevention of abnormal noise generation.
By forming the synthetic resin member 31 and the low-friction member 30 with the same kind of synthetic resin material, they can be molded in a lump, and labor can be saved.
For example, the low friction member 30 and the synthetic resin member 31 are insert-molded and fixed integrally with a metal leaf spring 32 held as an insert in a molding die. In this case, as shown in FIGS. 2 and 3, a hole 50 (only a part of which is shown) is formed in the leaf spring 32, and the resin formed through the hole 50 is used to reduce the low friction member 30 and the synthetic resin member. 31 and the leaf spring 32 are locked together, and at least a part of the leaf spring 32 is embedded in the resin. The low-friction member 30, the synthetic resin member 31, and the leaf spring 32 can be positioned with high accuracy using a mold.
[0021]
In addition, the rack bush 9 of this invention is not limited to the above-mentioned thing, The following embodiments can be considered. In the following description, differences from the above-described embodiment will be mainly described, and the description of the same configuration will be omitted and the same reference numerals will be given.
As shown in FIG. 6, a plurality of, for example, two annular leaf springs 32a and 32b may be rack bushes 9a arranged side by side in the axial directions S1 and S2. The corresponding end portions of the synthetic resin members 31 and the low friction members 30 that are alternately arranged in the circumferential direction of the rack bush 9a are connected by corresponding leaf springs 32a and 32b, respectively. In this case, rattling of the rack shaft 6 at both ends of the rack bush 9a can be reliably prevented.
[0022]
The embodiment shown in FIG. 7 differs from the embodiment shown in FIG. 6 in the following points. That is, instead of the low-friction members 30 shown in FIG. 6, a plurality of, for example, two low-friction parts are arranged as the first and second circumscribed portions spaced apart from each other in the axial directions S1 and S2 as shown in FIG. The members 30a and 30b are provided to constitute the rack bush 9b. The low friction members 30a and 30b spaced apart in the axial directions S1 and S2 and the corresponding end portions 31a and 31b of the synthetic resin member 31 are connected by corresponding plate springs 32a and 32b. Thereby, while ensuring the fitting length between the rack bush 9b and the rack shaft 6, the sliding contact length between the low friction members 30a and 30b and the rack shaft 6 can be shortened, and the sliding resistance of the rack shaft 6 is suppressed. it can.
[0023]
Further, with respect to the circumferential direction T, the number of the inscribed portions 41 and the circumscribed portions 42 may be four or more, and at least three are essential. In addition, as in each of the above embodiments, a single circumscribed portion 42 may be disposed between adjacent inscribed portions 41, but each circumscribed portion 42 is divided into a plurality of portions in the circumferential direction, and these are adjacent to each other. Alternatively, the inscribed portions 41 may be arranged side by side. Similarly, each inscribed portion 41 may be divided into a plurality of portions with respect to the circumferential direction T.
[0025]
In each of the embodiments described above, the entire surface of the annular metal leaf springs 32, 32a, 32b is coated with a low-friction synthetic resin material, and a part of the inner periphery thereof is disposed on the circumscribed portion 42. The low friction members 30, 30 a, and 30 b may function, and a part of the outer periphery may function as the synthetic resin member 31 disposed on the inscribed portion 41.
In each of the above embodiments, the leaf springs 32, 32a, and 32b may be made of synthetic resin.
[0026]
Moreover, in each said embodiment, it is also considered that the synthetic resin member 31 distribute | arranged to the inscribed part 41 has a higher friction coefficient than the low friction members 30, 30a, and 30b distribute | arranged to the inscribed part 42. . As a result, the rack bushes 9, 9a, 9b can be prevented from moving relative to the holding holes 18 as the rack shaft 6 slides. For example, the rack bushes 9, 9a, 9b are axially moved to the holding holes 18. The structure for positioning to S1 and S2 can be simplified or omitted.
[0027]
In each said embodiment, the leaf | plate springs 32, 32a, and 32b may use a thing with an end in the circumferential direction T, may connect the edge parts, and may form it cyclically | annularly. The positions of the end portions of the leaf springs 32, 32a, 32b in the circumferential direction are not limited, and the leaf springs 32, 32a, 32b may be annular as a whole.
Further, as the present steering device 1, one end 12 of the rack shaft 6 is supported by the rack bushes 9, 9a, 9b of the present embodiment, and the other end (not shown) of the rack shaft 6 is A support member (not shown) disposed on the opposite side of the pinion 4 with the rack shaft 6 interposed therebetween may be supported by the pinion 4. Further, the present steering device 1 may be a power steering device having an electric motor or a hydraulic cylinder for obtaining a steering assist force, in addition to a manual operation type that cannot obtain a steering assist force. In addition, various modifications can be made within the scope of the claims of the present invention.
[Brief description of the drawings]
FIG. 1 is a partially sectional front view schematically showing a main part of a steering apparatus using a rack bush according to an embodiment of the present invention, and also shows a schematic configuration of the steering apparatus.
FIG. 2 is a cross-sectional view of the steering device showing an enlarged view of a portion II in FIG.
FIG. 3 is a cross-sectional view of the steering device showing a cross section taken along the line III-III in FIG. 1;
4 is a perspective view of the rack bush in FIG. 1. FIG.
FIG. 5 is a side view of the rack bush of FIG. 1 in a free state.
FIG. 6 is a cross-sectional view of a steering apparatus using a rack bush according to another embodiment of the present invention, and shows an enlarged view of a portion II in FIG.
7 is a cross-sectional view of a steering apparatus using a rack bush according to still another embodiment of the present invention, and shows an enlarged view of a portion II in FIG.
[Explanation of symbols]
6 Rack shaft 7 Housing 9, 9a, 9b Rack bush 18 Holding hole 20 Inner circumference of holding hole 30 Low friction member
30a Low friction member (first circumscribed part)
30b Low friction member (second circumscribed part)
31 Synthetic resin member 32, 32a, 32b Leaf spring 41 Inscribed part 42 Outer part T Circumferential direction

Claims (4)

In the rack bush that is fitted and held in the holding hole of the housing and slidably supports the rack shaft,
An inscribed portion that is spaced apart from the rack shaft and inscribed in the inner periphery of the holding hole of the housing; An annular ring arranged alternately in the circumferential direction, and the low friction member between the inscribed portions connected by the leaf springs is biased to the rack shaft by the elasticity of the leaf springs connecting the adjacent inscribed portions ,
In the inscribed portion, synthetic resin members are arranged on the inside and outside of the leaf spring with respect to the radial direction of the rack bush,
The rack bush, wherein the low-friction member of the circumscribed portion is disposed inward and outward of the leaf spring in the radial direction of the rack bush. The rack bush according to claim 1 , wherein the leaf spring includes two leaf springs disposed at both ends of the rack bush in the axial direction . 3. The rack bush according to claim 2, wherein the circumscribed portion includes a first circumscribed portion coupled to one of the two leaf springs and a second circumscribed portion coupled to the other, The rack bush, wherein the second circumscribed portions are spaced apart from each other in the axial direction. The rack bush according to any one of claims 1 to 3, wherein the leaf spring is formed of a metal material.

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