JP2003322165A - Bush bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bush bearing favorably used to slidably support a shaft member such as a rack shaft, particularly in a steering mechanism of an automobile, capable of slidably supporting the rack shaft, etc., with certain rigidity in the radial direction and with low friction resistance in the axial direction and of suppossing the change of performance according to a heat history. <P>SOLUTION: The bush bearing 1 has an inside surface 3 in a cylindrical shape with which the rack shaft 2 slidably contacts in the axial direction A and at least one slit 6 extending from one end face about the axial direction A to the other end face 5 so that the inside surface can expand and contract and is provided with a bush body 10 made of synthetic resin having ring-shaped grooves 8 and 9 at its cylindrical peripheral surface 7, and endless and ring- shaped resilient members 11 and 12 fitted in the grooves 8 and 9 and having an outside diameter R2 larger than the diameter R1 of the peripheral surface 7 of the bush body 10. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bush bearing, and more particularly to a bush bearing suitable for slidably supporting a rack shaft in a steering mechanism of an automobile.

[0002]

Various bush bearings made of synthetic resin have been proposed, but such bush bearings made of synthetic resin usually support a shaft member slidably with an interference. It has become.

By the way, in a bush bearing made of synthetic resin, when a large interference is provided for a shaft member to be supported, a large misalignment of the shaft member does not occur, and
The shaft member can be firmly supported with a predetermined rigidity in the radial direction so as not to create a gap with the shaft member, but since the shaft member is tightened tightly, sliding friction resistance increases and the shaft member is good. While it is not possible to support with good sliding characteristics, if a small tightening margin is provided for the supporting shaft member, good sliding characteristics with low sliding friction resistance with respect to the shaft member can be expected, but shaft member A large misalignment is likely to occur, and a gap is likely to be formed between the shaft member and the radial rigidity, which reduces rigidity support.
Moreover, when such a gap is generated, a tapping sound is generated between the shaft member and the shaft member when the shaft member slides.

Further, in the bush bearing made of synthetic resin, due to the stress relaxation of the synthetic resin due to the heat history, a gap is generated between the shaft bearing and the mounting member to which the shaft member is mounted, so that the rigidity in the radial direction is increased. If the synthetic resin is stress-relieved, and especially in the radial direction, the tightening margin for the shaft member increases and sliding friction resistance increases. There is a risk that it will grow.

The present invention has been made in view of the above points, and an object thereof is to slide a shaft member such as a rack shaft with a predetermined rigidity in the radial direction and a low frictional resistance in the axial direction. In addition to being freely supported,
It is an object of the present invention to provide a bush bearing which is capable of reducing the change in performance due to heat history and is particularly suitable for slidably supporting a rack shaft in a steering mechanism of an automobile.

[0006]

A bush bearing according to a first aspect of the present invention has a cylindrical inner peripheral surface with which a shaft member to be supported slidably contacts, and the inner peripheral surface has a reduced diameter. It has at least one slit extending from one end face in the axial direction to the other end face so that
A bush body made of synthetic resin having at least one annular groove on the outer peripheral surface, and an endless annular elastic member mounted on the groove of the bush body and having an outer diameter larger than the diameter of the outer peripheral surface of the bush body. It has.

According to the bush bearing of the first aspect, the bush body made of synthetic resin having the cylindrical inner peripheral surface with which the shaft member to be supported, for example, the rack shaft in the steering mechanism of an automobile slidably contacts. While having at least one slit extending from one end face in the axial direction to the other end face, the endless annular elastic member has an outer diameter larger than the diameter of the outer peripheral surface of the bush body made of synthetic resin. Therefore, it is possible to fit the endless annular elastic member into the through hole of the mounting member of the rack shaft with a gap between the outer peripheral surface of the bush main body and the elastic elastically deformed endless ring member.
Thus, a large radial displacement of the shaft member due to a radial force that resists the elastic repulsive force of the endless annular elastic member due to crushing can be restricted by the outer peripheral surface of the bush body, and the endless annular shape due to crushing As a result of tightening the bush body to the shaft member by the elastic force of the elastic member, the shaft member can be slidably supported with a predetermined rigidity in the radial direction and a low frictional resistance in the axial direction, and at the same time, a synthetic resin accompanying heat history It is possible to prevent a gap from occurring between the cylindrical inner peripheral surface and the shaft member or between the endless annular elastic member and the mounting member to which the bush bearing is mounted due to the stress relaxation of As a result of being able to reduce the influence on the interference due to the contraction in the direction, it is possible to reduce the performance change in the thermal history.

As the synthetic resin as the material for forming the bush main body, it is preferable to use a synthetic resin having excellent wear resistance and low frictional properties, and having a predetermined flexibility and rigidity and having little thermal expansion and contraction. Examples of the resin include synthetic resin containing at least one of polyamide resin, polyolefin resin and fluororesin.

In the present invention, the cylindrical inner peripheral surface of the bush main body is in a state where the endless annular elastic member is mounted in the groove of the bush main body, and the shaft member to be supported is the inner peripheral surface of the bush main body. It is formed so that its diameter is substantially the same as the diameter of the outer peripheral surface of the shaft member to be supported minus the tightening margin in the state where it is not inserted into the prescribed through hole. It is preferable that the slit has a width that can absorb stress relaxation of the synthetic resin due to thermal history when the cylindrical inner peripheral surface comes into close contact with the outer peripheral surface of the shaft member without any gap. In addition, when the endless annular elastic member is mounted in the groove of the bush body, the cylindrical inner peripheral surface has a reduced diameter like the bush bearing of the second aspect of the present invention. Set the inner diameter that gives elastic force to the bush body so that it has the above diameter. Alternatively, instead of this, the cylindrical inner peripheral surface may have an inner diameter which simply contacts the bush body in the groove so as to exhibit the above diameter without substantially reducing the diameter, Here, when an endless annular elastic member having an inner diameter that reduces the diameter of the cylindrical inner peripheral surface is used, the slit can absorb the stress relaxation of the synthetic resin due to the thermal history, and also the endless annular elastic member. It is required to have a width that allows the diameter reduction of the cylindrical inner peripheral surface due to the elastic force of the member. When the cylindrical inner peripheral surface has a diameter of 24 mm, a width of the slit of about 1 mm can be presented as a preferable example.

The slit may extend parallel to the axial direction, but preferably, it has an inclined slit portion inclined to the axial direction like the bush bearing of the third aspect of the present invention. More preferably, as in the bush bearing of the fourth aspect of the present invention, in addition to the inclined slit portion, it is arranged continuously with the inclined slit portion with the inclined slit portion interposed therebetween in the axial direction and the shaft. It has a pair of axial slits extending parallel to the direction.

The slit may be a single slit or a plurality of slits. In this case, as in the bush bearing of the fifth aspect of the present invention, the bush main body is composed of at least a pair of split bodies.

Although the bush body may have only one annular groove, it may have a plurality of annular grooves as in the bush bearing of the sixth aspect of the present invention. Well, in this case, the endless annular elastic member is mounted in each groove.

The endless annular elastic member preferably has a circular, elliptical or flat oval cross section, like the bush bearing of the seventh aspect of the present invention, but the present invention is not limited to these. , Other shapes, and preferably, like the bush bearing of the eighth aspect of the present invention,
It is made of natural rubber or synthetic rubber. A commonly used O-ring can be preferably used as the endless annular elastic member.

Even if the bush main body has at least one recess on its cylindrical inner peripheral surface, like the bush bearing of the ninth aspect of the present invention, the bush of the tenth aspect of the present invention. Like a bearing, it may have a plurality of small-diameter circular recesses discretely arranged on its cylindrical inner peripheral surface, and like the bush bearing of the eleventh aspect of the present invention. It may have an annular recess arranged so as to divide the cylindrical inner peripheral surface in the axial direction.

When the bush body has a recess as in the bush bearing of the eleventh aspect, preferably the endless annular elastic member is the same as the bush bearing of the twelfth aspect of the present invention. In addition, it is mounted in an annular groove arranged corresponding to the divided cylindrical inner peripheral surface.

When the bush main body has the recess as described above, as in the bush bearing of the thirteenth aspect of the present invention, such a recess is provided with a solid or fluid lubricant. It is preferable that it has been done.

Further, preferably, the bush main body is continuous with the cylindrical inner peripheral surface on both sides in the axial direction of the cylindrical inner peripheral surface, like the bush bearing of the fourteenth aspect of the present invention. The endless annular elastic member has a pair of tapered inner peripheral surfaces that are arranged and have a diameter increasing from the cylindrical inner peripheral surface toward the end surface in the axial direction. Like the bush bearing of the fifteenth aspect, it is preferable that the bush bearing is mounted in an annular groove arranged corresponding to the boundary between the cylindrical inner peripheral surface and the tapered inner peripheral surface.

In the present invention, the annular groove is preferably an endless member mounted in the groove, like the bush bearing of the sixteenth aspect thereof, from the viewpoint of sufficiently obtaining elasticity of the endless annular elastic member. The volume is larger than the volume of the annular elastic member, but instead of this, like the bush bearing of the seventeenth aspect thereof, the volume is smaller than the volume of the endless annular elastic member mounted in the groove. May have.

With the annular groove having a volume like that of the bush bearing of the seventeenth aspect, when the endless annular elastic member is largely crushed by the radial force and spreads to the full extent of the groove, the annular endless elastic member is formed. The rigidity of the shaft member can be increased, and this also enables the shaft member to be supported with a predetermined rigidity in the radial direction.

In addition to the bush body, the bush bearing of the present invention has a synthetic resin collar portion integrally formed with the bush body on the outer peripheral surface of the bush body, like the bush bearing of the eighteenth aspect. You may have more,
When such a collar portion is provided, the bush bearing can be attached to the opening end side of the through hole of the attachment member so as not to move in the axial direction.

Further, the bush bearing of the present invention can be used for slidably supporting a rotating shaft member, a shaft member that moves linearly in the axial direction, and the like, and particularly, the bush bearing of the nineteenth aspect thereof. As described above, it is suitable for slidably supporting a rack shaft in a steering mechanism of an automobile as a shaft member, and by using the rack shaft in the radial direction of the rack shaft based on vibration applied from the road surface. The center deviation is preferably absorbed by the elastic deformation of the endless annular elastic member, so that the rack shaft can be linearly moved in the axial direction and can be rigidly supported with low friction resistance.

The present invention will now be described in more detail with reference to the preferred embodiments shown in the drawings. The present invention is not limited to these examples.

[0023]

1 to 3, a rack shaft 2 (see FIG. 4) in a steering mechanism of an automobile is moved in an axial direction A.
The bush bearing 1 of this example for slidably supporting the
A rack shaft 2 as a shaft member to be supported has a cylindrical inner peripheral surface 3 that slidably contacts in the axial direction A, and one of the axial direction A is arranged so that the inner peripheral surface 3 can be reduced in diameter. Has at least one slit extending from the end face 4 to the other end face 5, and in this example one slit 6, and
A bush body 10 made of synthetic resin having at least one annular groove, in this example, two annular grooves 8 and 9 on a cylindrical outer peripheral surface 7, and a bush body 10 fitted in the grooves 8 and 9, respectively. In addition, the bush body 10 has an outer diameter R2 that is larger than the diameter R1 of the outer peripheral surface 7, and the circular endless annular elastic members 11 and 12 are made of natural rubber or synthetic rubber. The outer peripheral surface 7 is provided with a collar 13 made of synthetic resin integrally formed with the bush body 10.

The slit 6 is arranged continuously with the inclined slit portion 21 which is inclined with respect to the axial direction A and the inclined slit portion 21 with the inclined slit portion 21 in the axial direction A. And a pair of axial slit portions 22 and 23 extending in parallel with the inclined slit portion 21 and the axial slit portions 22 and 23 have a width t of about 1 mm in this example.

Each of the annular grooves 8 and 9 is, in this example, an endless annular elastic member 11 fitted in each of the grooves 8 and 9.
And 12 have a volume larger than that of the bushes 10, so that the grooves 8 and 9 do not project from the outer peripheral surface 7 of the bush body 10 due to the endless annular elastic members 11 and 12 being elastically deformed and crushed. Even so, the endless annular elastic members 11 and 12 that are elastically deformed and crushed are not completely filled.

In addition to the cylindrical inner peripheral surface 3 having a wide width in the axial direction A, the bush main body 10 is continuously arranged on the cylindrical inner peripheral surface 3 on both sides of the inner peripheral surface 3 in the axial direction A. In addition, a pair of annular tapered inner peripheral surfaces 25 and 26 having a diameter increasing from the cylindrical inner peripheral surface 3 toward the end surfaces 4 and 5 in the axial direction A, respectively, and an annular surface on the end surface 5 side. Chamfer 27
And have.

Each of the endless annular elastic members 11 and 12 is
The bush body 10 has an inner diameter R4 that gives an elastic force to the bush body 10 by reducing the inner peripheral surface 3 to a diameter R3.

The diameter R3 of the inner peripheral surface 3 of the bush body 10 is
If the tightening margin is δ mm, 2δ is larger than the diameter R5 of the rack shaft 2.
Only small. In addition, the inner peripheral surface 3 of such a bush body 10
In principle, when the rack shaft 2 is inserted into the through hole 28 defined by the inner peripheral surface 3 of the bush body 10 (the case shown in FIG. 4) and when it is not (the case shown in FIG. 1). In the former case, the radius R3 of the inner peripheral surface 3 is sufficiently large with respect to the interference δ. When the tightening margin δ is extremely small, for example, the diameter R3 of the inner peripheral surface 3 is about 24 mm and the tightening margin δ is about 0.7 mm at the maximum, even if the rack shaft 2 is inserted into the through hole 28. It can be considered that the elastic deformation including the bending of the bush main body 10 substantially conforms to the outer surface 29 of the rack shaft 2.

In the bush bearing 1 described above, as shown in FIG. 4, the endless annular elastic members 11 and 12 are elastically deformed into an elliptical shape in a cross section and crushed, and the flange 13 is provided on the end surface 32 of the mounting member 31. In the abutting state, the inner peripheral surface 33 is defined by the inner peripheral surface 33 of the mounting member 31 and is attached to the through hole 34 having a diameter R6 smaller than the outer diameter R2 of the endless annular elastic members 11 and 12, and The rack shaft 2 is inserted into the through hole 28 defined by 3 and is used to support the rack shaft 2 slidably in the axial direction A with respect to the mounting member 31.

In a normal state, the bush bearing 1 is shown in FIG.
And as shown in FIG. 5, the inner peripheral surface 33 of the mounting member 31.
An annular gap 35, for example, an annular gap 35 having a width in the radial direction R of 0.17 mm to 0.19 mm, is formed between the cylindrical outer peripheral surface 7 and the cylindrical outer peripheral surface 7. The rack shaft 2 is slidably supported in the axial direction A with an elastic pressing force based on the diameter expansion of 12 and its elastic deformation into an elliptical shape and an interference δ.

Even if the rack shaft 2 supported by the bush bearing 1 is displaced in the radial direction R and the center of the rack shaft 2 is deviated, the bush bearing 1 is provided with a small displacement force in the radial direction R. Restricts the elastic deformation of the endless annular elastic members 11 and 12 while the displacement force in the radial direction R is large, as shown in FIG.
After the large elastic deformation of 1 and 12, the gap 35 disappears so that the outer peripheral surface 7 of the bush bearing 1 abuts the inner peripheral surface 33 of the mounting member 31 so that the gap 35 disappears and is rigidly regulated.

As described above, according to the bush bearing 1, the gap 35 is formed between the bush main body 10 and the outer peripheral surface 7.
Moreover, the endless annular elastic members 11 and 12 can be fitted into the through holes 34 of the mounting member 31 in a crushed state,
Thus, the endless annular elastic members 11 and 12 caused by the crushing
The radial displacement of the rack shaft 2 due to the radial force that opposes the elastic repulsive force can be restricted by the outer peripheral surface 7 of the bush body 10, and the elastic force of the endless annular elastic members 11 and 12 caused by the crushing can be controlled. Therefore, the bush body 10 is attached to the rack shaft 2
As a result, the rack shaft 2 can be slidably supported with a predetermined rigidity in the radial direction and a low friction resistance in the axial direction A.

Further, according to the bush bearing 1, the bush body 10 has the slit 6, the endless annular elastic members 11 and 12 are mounted in the grooves 8 and 9 of the bush body 10, respectively, and the bush body 10 is provided. Outer peripheral surface 7
Since the outer diameter R2 is larger than the diameter R1 of the inner peripheral surface 3 and the rack shaft 2 due to the stress relaxation of the synthetic resin due to the heat history, or the endless annular elastic members 11 and 12 and the mounting member 31. It is possible to prevent a gap from being formed between the inner peripheral surface 33 and the inner peripheral surface 33, and to reduce the influence on the interference δ due to the radial contraction due to the stress relaxation of the synthetic resin. .

Further, the bush bearing 1 is composed of the bush body 1
The endless annular elastic members 11 and 12 having the outer diameter R2 larger than the diameter R1 of the outer peripheral surface 7 of 0 are provided, and the endless annular elastic members 11 and 12 are fitted to the mounting member 31 through the endless annular elastic members 11 and 12. Bush body 1 in addition to excellent vibration and noise reduction characteristics
0, the rack shaft 2, the mounting member 31 and the like have manufacturing errors, but can be absorbed by the elastic deformation of the endless annular elastic members 11 and 12, resulting in the prying of the rack shaft 2 in the sliding in the axial direction A. It is possible to reduce the situation such as.

Further, in the bush bearing 1, since the bush body 10 has the annular chamfered surface 27 on the end face 5 side thereof, the endless annular elastic members 11 and 12 are extremely mounted in the grooves 8 and 9. It can be done easily.

In the bush bearing 1 and the bush bearing of the comparative example which does not have the endless annular elastic members 11 and 12, the slit 6 and the grooves 8 and 9, the tightening margin δ (mm) and the sliding force (friction resistance) (N) Fig. 7 shows the measurement results of the relationship between the two before, and Fig. 8 shows the one after the heat history after heating at 120 ° C for 1 hour. With respect to the bush bearing of the example, the measurement results of the relationship between the tightening margin δ (mm) and the deflection amount (mm) are shown in FIG. 9 before the thermal history, and in FIG.
The heat history after heating for 1 hour at 0 ° C. is shown respectively. In FIGS. 7 to 10, the curve 41 shows the case of the bush bearing 1, and the curve 42 shows the case of the bush bearing of the comparative example. .

As is clear from FIGS. 7 to 10, according to the bush bearing 1, a low sliding force (friction resistance) (N) which is constant and does not change even after the thermal history is maintained regardless of the tightening margin. In addition to the above, it is possible to support the rack shaft 2 with a predetermined rigidity by suppressing the misalignment below a certain value.

By appropriately changing the width of the annular gap 35 in the radial direction R, the allowable amount of misalignment of the bush bearing 1 with respect to the rack shaft 2, that is, the rigidity in the radial direction R can be adjusted to an optimum value.

The bush body 10 of the bush bearing 1 described above.
Has a smooth and flat inner peripheral surface 3, but instead of this, as shown in FIG. 11, a plurality of small-diameter circles discretely arranged on the cylindrical inner peripheral surface 3 are provided. 12, the cylindrical inner peripheral surface 3 is arranged so as to be divided into two inner peripheral surfaces 3a and 3b in the axial direction, as shown in FIG. In the bush bearing 1 shown in FIG. 12, the endless annular elastic members 11 and 12 are arranged corresponding to the divided cylindrical inner peripheral surfaces 3a and 3b. It may be mounted in the grooves 8 and 9. Further, a solid or fluid lubricant may be disposed in the recesses 51 and 52 as needed to further reduce the sliding friction resistance.

Further, the bush body 10 of the bush bearing 1 has a pair of annular tapered inner peripheral surfaces 2 having a narrow width in the axial direction A.
5 and 26, instead of this, as shown in FIG. 13, in addition to the cylindrical inner peripheral surface 3, both sides of the cylindrical inner peripheral surface 3 in the axial direction A have the cylindrical shape. Is continuously arranged on the inner peripheral surface 3 of the pair, and has a large diameter in the axial direction A that increases from the cylindrical inner peripheral surface 3 toward the end surfaces 4 and 5 in the axial direction A, respectively. You may have the taper inner peripheral surface 55 and 56, and in this case, the endless annular elastic members 11 and 12 are made into the cylindrical inner peripheral surface 3 and the taper inner peripheral surface 55 and 56.
Grooves 8 and 9 arranged corresponding to the boundary portions 57 and 58 with
It may be attached to the.

As shown in FIGS. 11 to 13, the flange portion 13 may be omitted to form the bush bearing 1. In this case, an annular chamfered surface 59 similar to the chamfered surface 27 is used as the end surface. Four
It may be provided on the side.

Further, in the bush bearing 1 described above, the circular endless annular elastic members 11 and 12 are mounted in the grooves 8 and 9, respectively, but instead of this, as shown in FIG. Also in the bush bearing 1, one endless annular elastic member 61 having a flat oval shape in a cross section having an outer diameter R7 larger than the diameter R1 of the outer peripheral surface 7 of the main body 10 is attached to one groove 62 of the bush main body 10. Good.

Further, instead of making the volumes of the grooves 8, 9 and 62 larger than the volumes of the endless annular elastic members 11, 12 and 61, for example, as shown in FIG. The volume of the endless annular elastic member 11 is set smaller than that of the endless annular elastic member 11 as shown in FIG.
Is elastically deformed by the force in the radial direction R and is crushed, the endless annular elastic member 11 is spread over the groove 8.
The rigidity of the endless annular elastic member 11 may be increased.

As shown in FIG. 17, the bush body 10 may be provided with two slits 6a and 6b, and the bush body 10 may be composed of a pair of divided bodies 10a and 10b. According to the bush main body 10 including the divided bodies 10a and 10b having the divided bodies 10a and 6b, it is sufficient to form either one of the divided bodies 10a and 10b, which makes the manufacturing extremely simple.

[0045]

According to the present invention, the shaft member can be slidably supported with a predetermined rigidity in the radial direction and a low sliding frictional resistance in the axial direction, and at the same time, a change in performance due to heat history can be reduced. In particular, it is possible to provide a bush bearing suitable for being used for slidably supporting a rack shaft in a steering mechanism of an automobile.

[Brief description of drawings]

FIG. 1 is a sectional view taken along the line I-I of FIG. 2 showing an example of a preferred embodiment of the present invention.

FIG. 2 is a left side view of the example shown in FIG.

FIG. 3 is an external view of the example shown in FIG.

FIG. 4 is a diagram for explaining the operation of the example shown in FIG.

5A and 5B are operation explanatory views of the example shown in FIG.

FIG. 6 is a diagram for explaining the operation of the example shown in FIG.

FIG. 7 is an explanatory diagram of an effect of the example shown in FIG.

FIG. 8 is an explanatory diagram of an effect of the example shown in FIG.

FIG. 9 is an explanatory diagram of an effect of the example shown in FIG.

FIG. 10 is an explanatory diagram of an effect of the example shown in FIG.

FIG. 11 is a sectional explanatory view of another example of the preferred embodiment of the present invention.

FIG. 12 is a cross sectional view showing still another example of the preferred embodiment of the present invention.

FIG. 13 is a cross sectional view showing still another example of the preferred embodiment of the present invention.

FIG. 14 is a cross sectional view showing still another example of the preferred embodiment of the present invention.

FIG. 15 is a cross sectional view showing still another example of the preferred embodiment of the present invention.

FIG. 16 is a cross sectional view showing still another example of the preferred embodiment of the present invention.

FIG. 17 is an explanatory diagram corresponding to FIG. 2 of still another example of the preferred embodiment of the present invention.

[Explanation of symbols]

1 Bush bearing 2 rack axes 3 Inner surface 4,5 end face 6 slits 7 outer peripheral surface 8, 9 groove 10 Bush body 11,12 Endless annular elastic member

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Haruhiko Sudo             8 Kirihara Town, Fujisawa City, Kanagawa Prefecture             Fujisawa business site F-term (reference) 3J011 AA03 BA02 DA02                 3J017 AA06 DA01 DB04

Claims (20)

[Claims] 1. A shaft member to be supported has a cylindrical inner peripheral surface that slidably contacts, and from one end surface in the axial direction to the other end surface so that the inner peripheral surface can be reduced in diameter. It has at least one elongated slit, and
A bush body made of synthetic resin having at least one annular groove on the outer peripheral surface, and an endless annular elastic member mounted on the groove of the bush body and having an outer diameter larger than the diameter of the outer peripheral surface of the bush body. Bush bearing equipped. 2. The bush bearing according to claim 1, wherein the endless annular elastic member has an inner diameter that gives the bush body an elastic force that reduces the inner peripheral surface of the bush body. 3. The bush bearing according to claim 1, wherein the slit has an inclined slit portion that is inclined with respect to the axial direction. 4. The slit has a pair of axial slit portions that are arranged continuously with the inclined slit portion in the axial direction with the inclined slit portion in between and extend parallel to the axial direction. Item 3. The bush bearing according to Item 3. 5. The bush bearing according to claim 1, wherein the bush body is composed of at least a pair of divided bodies and has a plurality of slits. 6. The bush bearing according to claim 1, wherein the bush main body has a plurality of annular grooves, and the endless annular elastic member is mounted in each groove. 7. The bush bearing according to claim 1, wherein the endless annular elastic member is a circular, elliptical or flat oval in cross section. 8. The bush bearing according to claim 1, wherein the endless annular elastic member is made of natural rubber or synthetic rubber. 9. The bush bearing according to claim 1, wherein the bush main body has at least one recess on its cylindrical inner peripheral surface. 10. The bushing body according to claim 1, wherein the bushing body has a plurality of small-diameter circular recesses discretely arranged on the cylindrical inner peripheral surface thereof. Bush bearing. 11. The bush according to claim 1, wherein the bush main body has an annular recess arranged so as to axially divide the cylindrical inner peripheral surface of the bush main body. bearing. 12. The bush bearing according to claim 11, wherein the endless annular elastic member is mounted in an annular groove arranged corresponding to the divided cylindrical inner peripheral surface. 13. The bush bearing according to claim 9, wherein a lubricant is provided in the recess. 14. The bush main body is continuously arranged on both sides of the cylindrical inner peripheral surface in the axial direction, and the bush main body extends from the cylindrical inner peripheral surface to the end surface in the axial direction. The bush bearing according to any one of claims 1 to 13, which has a pair of tapered inner peripheral surfaces that become larger in diameter as they go toward each other. 15. The bush bearing according to claim 14, wherein the endless annular elastic member is mounted in an annular groove arranged corresponding to a boundary portion between the cylindrical inner peripheral surface and the tapered inner peripheral surface. 16. The bush bearing according to claim 1, wherein the annular groove has a volume larger than that of the endless annular elastic member mounted in the groove. 17. The bush bearing according to claim 1, wherein the annular groove has a volume smaller than the volume of the endless annular elastic member mounted in the groove. 18. The bush bearing according to claim 1, further comprising a synthetic resin collar portion integrally formed with the bush main body on an outer peripheral surface of the bush main body. 19. The bush bearing according to claim 1, which is used for slidably supporting a rack shaft in a steering mechanism of an automobile as a shaft member. 20. A rack shaft as a shaft member, the bush bearing according to any one of claims 1 to 19, which slidably supports the rack shaft, and a penetrating body to which the bush bearing is attached. A steering mechanism for an automobile, comprising: a mounting member having a hole, wherein an annular gap is formed between an inner peripheral surface defining a through hole of the mounting member and an outer peripheral surface of the bush body.