JP2001027227A - Sliding bearing made of synthetic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sliding bearing made of synthetic resin, capable of maintaining smooth steering during steering operation over a long period of time without lowering a sliding characteristic caused by the entry of dust or the like by preventing dust or the like from entering a sliding surface particularly from the inner peripheral side of a space where a sliding bearing member or a sliding bearing protruding part is disposed. SOLUTION: This sliding bearing 1 made of synthetic resin is provided with a lower case 2 made of synthetic resin, an upper case 3 made of synthetic resin and placed over the lower case 2, an outer elastic sealing means 4 disposed on the outer peripheral side between the upper and lower cases 3, 2, an inner elastic sealing means 5 disposed on the inner peripheral side between the upper and lower cases 3, 2, and a sliding bearing means 7 made of synthetic resin and disposed in a space between the upper and lower cases 3, 2 and between the outer and inner elastic sealing means 4, 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding bearing made of a synthetic resin, and more particularly to a sliding bearing made of a synthetic resin suitable for being incorporated in a strut type suspension (MacPherso type) of a four-wheeled vehicle.

[0002]

A strut type suspension used for a front wheel of a four-wheeled vehicle generally has a coil spring combined with a strut assembly having a hydraulic shock absorber incorporated in an outer cylinder integrated with a main shaft. Has a structure. In such a suspension, when the strut assembly rotates together with the coil spring in the steering operation, there are a type in which the piston rod of the strut assembly rotates and a type in which the piston rod does not rotate. In order to allow the rotation smoothly, between the mounting member of the vehicle body and the upper spring seat of the coil spring,
In some cases, a sliding bearing made of a synthetic resin is used in place of the rolling ball bearing.

A plain bearing made of a synthetic resin usually has a lower case made of a synthetic resin and an upper case made of a synthetic resin superposed on the lower case, and a space between the lower case and the upper case. Is provided with a sliding bearing member or a sliding bearing projection, but when dust, muddy water, etc. enter this space,
There is a possibility that a desired bearing function cannot be obtained. On the other hand, since the strut type suspension is mounted on the part where dust, muddy water, etc. act directly while the vehicle is running, the usage environment of the sliding bearing mounted between the mounting member of the vehicle body and the upper spring seat of the coil spring is also limited. It will be extremely harsh. Therefore, if the outer peripheral side and the inner peripheral side of the space in which the sliding bearing member or the sliding bearing protrusion is arranged are directly opened to the outside, the danger of dust and muddy water from entering the space becomes extremely high, Here, the sealing performance becomes extremely important.
Particularly, in the case of a synthetic resin sliding bearing in which the lower case and the upper case are formed by opening the inner peripheral side of the space downward so as to prevent stagnation of moisture in the space, the above danger is further increased.

The present invention has been made in view of the above-mentioned points, and prevents entry of dust and the like into a sliding surface of a space in which a sliding bearing member or a sliding bearing projection is arranged, particularly from the inner peripheral side. It is another object of the present invention to provide a synthetic resin sliding bearing capable of maintaining smooth steering operation for a long period of time without deteriorating sliding characteristics due to intrusion of dust or the like.

[0005]

According to a first aspect of the present invention, there is provided a sliding bearing made of synthetic resin, comprising: a lower case made of synthetic resin; an upper case made of synthetic resin stacked on the lower case;
Outer elastic sealing means arranged on the outer peripheral side between the upper and lower cases, inner elastic sealing means arranged on the inner peripheral side between the upper and lower cases, and between the outer and inner elastic sealing means, and And a sliding bearing made of synthetic resin disposed between the lower case and the lower case, wherein the lower case is integrally formed with a cylindrical portion having a cylindrical inner peripheral surface and one end of the cylindrical portion. The upper case has an inner peripheral surface and an outer peripheral surface concentric with the inner peripheral surface of the cylindrical portion of the lower case, and is provided in the cylindrical portion of the lower case. A cylindrical portion provided, and a second annular plate portion integrally formed at one end of the cylindrical portion, wherein the inner elastic sealing means is provided on an inner peripheral surface of the cylindrical portion of the lower case or the upper case. An annular main body attached to the outer peripheral surface of the cylindrical part, and attached to this main body Are, and an annular elastic lip portion which elastically contacts the cylindrical portion of the cylindrical portion or the lower casing of the annular end side of the upper case.

According to the sliding bearing made of synthetic resin of the first aspect, since the inner elastic sealing means disposed on the inner peripheral side between the upper and lower cases is provided, the sliding bearing from the inner peripheral side is provided. Intrusion of dust etc. into the sliding surface of the means can be prevented, smooth steering during steering operation can be maintained for a long period of time without lowering of sliding characteristics due to intrusion of dust etc. Since one end side of the elastic lip portion is in elastic contact with the cylindrical portion of the upper case or the cylindrical portion of the lower case, the sealing can be almost completely performed.

According to the second aspect of the present invention, there is provided a sliding bearing made of a synthetic resin according to the first aspect.
The main body of the inner elastic sealing means has a core metal member, and the elastic lip of the inner elastic sealing means is made of an elastic material. As the elastic material, a rubber elastic body such as natural rubber or synthetic rubber or a plastic elastomer such as polyester or polyurethane is used.

According to the sliding bearing made of synthetic resin of the second aspect, the inner elastic sealing means is mounted on the inner peripheral surface of the cylindrical portion of the lower case or the outer peripheral surface of the cylindrical portion of the upper case via the cored member. As a result, the inner elastic sealing means can be securely attached and the inner elastic sealing means can be effectively prevented from falling off, and the sealing can be almost completely achieved by the elastic lip portion made of the elastic material.

According to a third aspect of the present invention, there is provided a sliding bearing made of a synthetic resin according to the first or second aspect, wherein the elastic lip has one end portion formed on the cylindrical portion of the upper case. It is formed so as to elastically contact the outer peripheral surface or the inner peripheral surface of the cylindrical portion of the lower case.

According to a fourth aspect of the present invention, there is provided a sliding bearing made of synthetic resin according to the first or second aspect, wherein one end of the elastic lip has a cylindrical portion of the upper case. It is formed so as to elastically contact the annular end surface or the annular end surface of the cylindrical portion of the lower case.

In the sliding bearing made of synthetic resin of the present invention, even if the elastic lip portion is brought into elastic contact with the outer peripheral surface or the inner peripheral surface as in the third embodiment, the elastic lip portion does not have the same effect as in the fourth embodiment. Although they may be brought into contact with the end surfaces, they may be formed as inclined surfaces in order to obtain more sealing performance and the like.

According to a fifth aspect of the present invention, there is provided the sliding bearing made of synthetic resin according to any one of the first to fourth aspects, wherein a part of the main body has an annular portion formed in a lower case. Is seated on an annular step formed on the inner peripheral surface of the cylindrical portion or the outer peripheral surface of the cylindrical portion of the upper case, and is mounted on the inner peripheral surface of the cylindrical portion or the outer peripheral surface of the cylindrical portion.

According to a sixth aspect of the present invention, there is provided the synthetic resin plain bearing according to the fifth aspect.
The annular horizontal surface of the step on which the annular part of the main body is seated faces upward.

According to the sliding bearings made of synthetic resin of the fifth and sixth aspects, the main body is seated and mounted on the annular step, so that the mounting properties are improved and the sixth aspect is improved. In the synthetic resin sliding bearing described above, since the annular horizontal surface of the step portion faces upward, it is possible to reliably prevent the inner elastic sealing means from falling off.

According to a seventh aspect of the present invention, there is provided the synthetic resin plain bearing according to the fifth aspect.
The annular horizontal surface of the step portion on which the annular portion of the main body is seated faces downward.

According to the sliding bearing made of synthetic resin of the seventh aspect, since the annular horizontal surface of the step faces downward, the inner elastic sealing means can be mounted last in the assembling, and the productivity is improved. Can be planned.

In the synthetic resin sliding bearing according to the eighth aspect of the present invention, in the synthetic resin sliding bearing according to any one of the first to seventh aspects, the sliding bearing means comprises a first annular member of the lower case. A thrust sliding bearing disposed between the plate portion and the second annular plate portion of the upper case; and a radial sliding bearing disposed between the cylindrical portion of the lower case and the cylindrical portion of the upper case. .

According to a ninth aspect of the present invention, there is provided the synthetic resin plain bearing according to the eighth aspect, wherein:
At least one of the thrust slide bearing and the radial slide bearing is formed of a synthetic resin slide bearing member separate from the upper and lower cases.

The synthetic resin constituting the upper and lower cases according to the present invention preferably has excellent sliding and mechanical properties such as wear resistance, impact resistance and creep resistance. It is preferable that the synthetic resin constituting the sliding bearing means housed therebetween has a self-lubricating property, for example, a polyacetal resin, a polyamide resin, a polyester resin such as polybutylene terephthalate (PBT), and a polyolefin resin such as polyethylene and polypropylene. Are preferably used, and polycarbonate resins and the like can also be used.

For the upper and lower cases, the same synthetic resin as the synthetic resin constituting the sliding bearing means can be used.
In particular, it is desirable that the synthetic resin used in the sliding bearing means be a combination of a synthetic resin having a good friction characteristic and a relatively high rigidity. To illustrate the preferred combination, for the plain bearing means and the upper and lower cases, a combination of polyacetal and polyamide,
There are combinations of polyethylene and polyacetal, combinations of polyacetal and PBT, and combinations of polyacetal and polyacetal.

A labyrinth sealing means is further added to at least one of the outer elastic sealing means and the inner elastic sealing means, and the labyrinth sealing means and the elastic sealing means cooperate to form at least one of the outer peripheral side and the inner peripheral side. The sealing performance may be further improved.

Next, the present invention will be described in more detail based on an example of a preferred embodiment shown in the drawings. The present invention is not limited to these examples.

[0023]

1 and 2, a synthetic resin sliding bearing 1 of the present embodiment comprises a lower case 2 made of synthetic resin, an upper case 3 made of synthetic resin superposed on the lower case 2, and an upper case 3 made of synthetic resin. Outer elastic sealing means 4 arranged on the outer peripheral side between the lower case 2 and the lower case 2;
An inner elastic sealing means 5 arranged on the inner peripheral side between
A sliding bearing means 7 made of synthetic resin is provided between the outer and inner elastic sealing means 4 and 5 and in a space 6 between the upper and lower cases 2 and 3.

The lower case 2 includes a cylindrical portion 12 having a cylindrical inner peripheral surface 11, annular steps 13 and 14 formed on the inner peripheral surface 11 of the cylindrical portion 12, and one end of the cylindrical portion 12. An annular plate portion 15 formed integrally, annular protrusions 17 and 18 integrally formed on an upper surface 16 of the annular plate portion 15, and an annular plate portion 1;
5 has an annular step 20 formed on the lower surface 19. Each of the annular steps 13 and 14 has annular horizontal surfaces 21 and 22 facing upward, and each of the annular projections 17 and 18 projects toward the annular plate 34 of the upper case 3. The annular step 20 has an annular vertical surface 23.

The upper case 3 is provided with a cylindrical portion 12 of the lower case 2.
A cylindrical portion 33 having an inner peripheral surface 31 and an outer peripheral surface 32 concentric with the inner peripheral surface 11 of the lower case 2 and disposed in the cylindrical portion 12 of the lower case 2.
And an annular plate portion 34 formed integrally with one end of the cylindrical portion 33 so as to face the annular plate portion 15 and to be juxtaposed.
And the outer peripheral portion of the annular plate portion 34 are integrally formed,
An outer cylindrical portion 36 having an inner peripheral surface 35 concentric with the inner peripheral surface 11 of the lower case 2, annular steps 37 and 38 formed on an outer peripheral surface 32 of the cylindrical portion 33, and an inner periphery of the outer cylindrical portion 36. And a projection 39 integrally formed on the surface 35. Upper case 3
The inner peripheral surface 31 defines a through hole 43 into which the bottomed cylindrical portion 42 of the mounting member 41 on the vehicle body side shown in FIG. 3 is inserted.
The outer peripheral surface 32 has an inclined outer peripheral surface 44, the annular step portion 37 has a horizontal surface 45, and the annular protrusion 39 projects radially inward.

The outer elastic sealing means 4 comprises a cylindrical main body 5
1 and bent back from an annular one end of the cylindrical main body 51, gradually expanded in diameter, and extended toward the other end of the cylindrical main body 51, and coaxial with the cylindrical main body 51 to form a cylindrical main body. 51
An annular elastic lip 52 disposed outside of the cylindrical body 51 and a flange 54 extending integrally from the annular other end of the cylindrical main body 51 and having an annular lip 53 at an inner peripheral end thereof. The flange 54 having the portion 53, the cylindrical main body 51, and the elastic lip 52 are integrally formed from an elastic material, and a core metal 55 is attached to the cylindrical main body 51 and the flange 54. Flange 54, cylindrical main body 51, and elastic lip 52
As the elastic material forming the rubber, a rubber elastic body such as natural rubber or synthetic rubber or a plastic elastomer such as polyester or polyurethane is used. The annular distal end of the elastic lip portion 52, which is made thicker toward the free end side, elastically abuts the inner peripheral surface 35 of the outer cylindrical portion 36 of the upper case 3, and the cylindrical main body 51 is Is attached to the outer peripheral side of the annular plate portion 15 through a mandrel 55,
Reference numeral 4 denotes an annular step portion 20 formed on the outer peripheral side of the lower surface 19 of the annular plate portion 15. Annular lip 53 of collar 54
Is elastically in contact with the annular vertical surface 23 at the annular step portion 20. The outer elastic sealing means 4 forms a sealing portion on the outer peripheral side of the sliding bearing 1 made of synthetic resin.

The inner elastic sealing means 5 is mounted on the inner peripheral surface 11 of the cylindrical portion 12 of the lower case 2 and has an annular main body 62 having an annular flange 61 extending radially outward, An annular elastic lip portion that is folded from one end of the annular portion of the portion 62, gradually reduces in diameter, extends toward the other end of the main portion 62, is coaxial with the main portion 62, and is mounted inside the main portion 62. In the present embodiment, the main body 62 is a metal member 6 having an L-shaped cross section and serving as a mandrel for the elastic lip 63.
A flange 61, which is a part of an annular shape, is seated on the step portion 14 of the cylindrical portion 12 of the lower case 2, is mounted on the inner peripheral surface 11 of the cylindrical portion 12, and has an elastic lip portion 63. Is one end (inner peripheral portion) of the elastic lip portion 63 which is integrally formed from an elastic material fixed to the metal member 64 and is thinned toward the inner peripheral side which is a free end side. Are in elastic contact with the inclined outer peripheral surface 44 of the cylindrical portion 33. The inner-side elastic sealing means 5 forms a sealing portion on the outer peripheral side in the sliding bearing 1 made of synthetic resin. As the elastic material forming the elastic lip portion 63, natural rubber,
A rubber elastic body such as synthetic rubber or a plastic elastomer such as polyester or polyurethane is used.

The sliding bearing means 7 is provided in the annular space between the annular plate 15 of the lower case 2 and the annular plate 34 of the upper case 3 in the space 6.
4 and a thrust slide bearing 72 that is slidably provided on the lower surface 2 of the lower case 2 in the space 6.
In the cylindrical space between the cylindrical portion 33 of the upper case 3 and the inner peripheral surface 11 and the outer peripheral surface 3 of the cylindrical portion 12 and the cylindrical portion 33, respectively.
2 and a radial sliding bearing 73 separate from the cylindrical portion 12 and the cylindrical portion 33, respectively. The thrust sliding bearing 72 is formed of a synthetic resin annular thrust bearing. The radial sliding bearing 73 is made of
It consists of a radial sliding bearing cylindrical member made of synthetic resin. The thrust slide bearing 72 is arranged between the annular projections 17 and 18 and is positioned in the radial direction by them, and the radial slide bearing 73 is arranged between the annular steps 13 and 37 and thereby is vertical. It is positioned in the direction (axial direction).

As shown in FIG. 3, the sliding bearing 1 made of synthetic resin has the piston rod 81 of the shock absorber in the strut assembly penetrated through the insertion hole 43, and is mounted on the vehicle body to which one end of the piston rod 81 is mounted. The upper surface 84 of the upper case 3 is brought into close contact with the member 41, and the lower surface 19 of the lower case 2 is connected to the upper spring seat 8 of the coil spring 82 in the strut assembly.
3 is abutted tightly via a washer 85 and is mounted between the upper spring seat 83 and the mounting member 41 for use. At this time, the inner peripheral surface 31 is exactly in contact with the outer peripheral surface of the bottomed cylindrical portion 42 of the mounting member 41.

When the strut assembly is rotated by the steering operation, the lower case 2 is rotated with respect to the upper case 3, and this rotation of the lower case 2 is caused by a thrust slide disposed between the upper and lower cases 3 and 2. Bearing 72
And the radial sliding bearing 73 makes the operation smooth, so that the steering operation is also performed without any resistance. Intrusion of dust and the like into the space 6 between the upper and lower cases 3 and 2 is prevented by the inner elastic sealing means 5 on the inner peripheral side and by the outer elastic sealing means 4 on the outer peripheral side. Intrusion of dust or the like into each sliding surface of the thrust sliding bearing 72 and the radial sliding bearing 73 disposed between the means 4 and the inner elastic sealing means 5 is reliably prevented.

That is, according to the sliding bearing 1 made of a synthetic resin, since the inner elastic sealing means 5 disposed on the inner peripheral side between the upper and lower cases 3 and 2 is provided, the sliding bearing 1 from the inner peripheral side is provided. Intrusion of dust and the like into the sliding surface of the slide bearing means 7 can be prevented, and smooth steering force during steering operation can be maintained for a long period of time without lowering of sliding characteristics due to the intrusion of dust and the like. In addition, since one end side of the annular elastic lip portion 63 is in elastic contact with the inclined outer peripheral surface 44 of the cylindrical portion 33 of the upper case 3, the sealing can be substantially completed.

According to the sliding bearing 1 made of synthetic resin, since the inner elastic sealing means 5 is mounted on the inner peripheral surface 11 of the cylindrical portion 12 of the lower case 2 via the metal member 64, the inner elastic sealing The means 5 can be firmly attached, and the inner elastic sealing means 5 can be effectively prevented from falling off from the lower case 2,
In addition, the sealing can be achieved almost completely by the elastic lip portion 63 made of an elastic material, and further, as a result of the main body portion 62 being seated and mounted on the annular step portion 14, the mounting property is improved, and Since the annular horizontal surface 22 of the portion 14 faces upward, the falling off of the inner elastic sealing means 5 can be reliably prevented here.

In the above-described sliding bearing 1 made of synthetic resin, one end of the elastic lip 63 is connected to the inclined outer peripheral surface 4 of the cylindrical portion 33.
4, the elastic lip 63 may be elastically contacted with the annular end surface 87 of the cylindrical portion 33 of the upper case 3, as shown in FIG. 4. The inner elastic sealing means 5 may be formed on the metal member 64. Further, a metal member 64 having an L-shaped cross section serving as the main body 62 is disposed in reverse to the above, and the elastic lip 63 is attached to the flange 61. ,
The inner elastic sealing means 5 may be formed so that the main body 62 is seated on the step portion 89 of the cylindrical portion 12 forming the downwardly facing annular horizontal surface 88.

Instead of the inner elastic sealing means 5 shown in FIG. 4, as shown in FIG. 5, the elastic lip 63 is formed from an annular plate whose inner peripheral end which is one end is not bent in advance. The outer peripheral end of the elastic lip 63 is fixed to the flange 61 of the main body 62 made of a metal member 64 having an L-shaped cross section, and the inner peripheral end thereof is elastically attached to the inclined inner peripheral surface 44 of the cylindrical portion 33. The inner elastic sealing means 5 may be configured so as to make contact with the inner elastic sealing means 5. In this case, the cylindrical portion 33 of the upper case 3
The inclined inner peripheral surface 4 without forming the annular step portion 38.
4 may be provided.

Further, the inner elastic sealing means 5 as shown in FIG. 6 in which the inner elastic sealing means 5 of the form shown in FIG. 4 is reversed in the radial direction is attached to the cylindrical portion 33 of the upper case 3, and the elastic lip is provided. The outer peripheral end of the portion 63 may be brought into elastic contact with the annular end surface 91 of the cylindrical portion 12 of the lower case 2. In this case, the main body 62 of the inner elastic sealing means 5 is connected to the cylindrical portion of the upper case 3. The cylindrical portion 33 is seated on an annular step 38 formed on the outer peripheral surface 32 of the cylindrical portion 33.
It is good to attach to outer peripheral surface 32 of.

In the above description, the sliding bearing means 7 is formed by the thrust sliding bearing 72 separate from each of the annular plates 15 and 34 and the radial sliding bearing 73 separate from each of the cylindrical portion 12 and the cylindrical portion 33. Instead of this, as shown in FIG. 6, the sliding bearing means 7 is formed integrally with, for example, an annular thrust sliding bearing projection 95 formed integrally with the annular plate portion 34 and the cylindrical portion 12. And an annular radial slide bearing projection 96. In this case, the annular projections 17 and 18 for positioning and the annular steps 13 and 37 may be omitted. In the example shown in FIG. 6, the rotation of the lower case 2 with respect to the upper case 3 is performed by sliding on the upper surface 16 and the outer peripheral surface 32.

[0037]

According to the present invention, it is possible to prevent dust and the like from entering the sliding surface from the inner peripheral side of the annular space in which the sliding bearing annular member or the sliding bearing projection is arranged, particularly from the inner peripheral side. Therefore, a sliding bearing made of a synthetic resin can be provided which can maintain smooth steering at the time of steering operation for a long period of time without lowering the sliding characteristics of the bearing due to the above.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of a preferred embodiment of the present invention.

FIG. 2 is a partially enlarged sectional view of the example shown in FIG.

FIG. 3 is a cross-sectional view of an example in which the example shown in FIG. 1 is used for a strut assembly.

FIG. 4 is a partially enlarged cross-sectional view of another example of the preferred embodiment of the present invention.

FIG. 5 is a partially enlarged sectional view of still another example of the preferred embodiment of the present invention.

FIG. 6 is a partially enlarged sectional view of still another example of the preferred embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 sliding bearing made of synthetic resin 2 lower case 3 upper case 4 outer elastic sealing means 5 inner elastic sealing means 7 sliding bearing means

Claims (9)

[Claims] 1. A lower case made of synthetic resin, an upper case made of synthetic resin superposed on the lower case, outer elastic sealing means arranged on an outer peripheral side between the upper and lower cases, an upper case and a lower case An inner elastic seal means disposed on the inner peripheral side between the outer and inner elastic seal means, and a sliding bearing means made of synthetic resin disposed between the upper and lower cases, The lower case includes a cylindrical portion having a cylindrical inner peripheral surface, and a first annular plate portion integrally formed at one end of the cylindrical portion,
The upper case has an inner peripheral surface and an outer peripheral surface concentric with the inner peripheral surface of the cylindrical portion of the lower case, and is integrally formed with the cylindrical portion disposed in the cylindrical portion of the lower case and one end of the cylindrical portion. And a second annular plate formed, wherein the inner elastic sealing means comprises:
An annular main body attached to the inner peripheral surface of the cylindrical portion of the lower case or the outer peripheral surface of the cylindrical portion of the upper case; And an annular elastic lip portion elastically contacting the cylindrical portion of the bearing. 2. A sliding bearing made of synthetic resin according to claim 1, wherein the main body of the inner elastic sealing means has a cored member, and the elastic lip of the inner elastic sealing means is made of an elastic material. 3. The elastic lip portion is formed such that one end side thereof elastically contacts the outer peripheral surface of the cylindrical portion of the upper case or the inner peripheral surface of the cylindrical portion of the lower case.
A sliding bearing made of a synthetic resin as described in 1 above. 4. The elastic lip is formed such that one end thereof elastically contacts an annular end surface of the cylindrical portion of the upper case or an annular end surface of the cylindrical portion of the lower case. A sliding bearing made of a synthetic resin as described in 1 above. 5. The main body portion has an annular part seated on an annular step formed on the inner peripheral surface of the cylindrical portion of the lower case or the outer peripheral surface of the cylindrical portion of the upper case. The sliding bearing made of a synthetic resin according to any one of claims 1 to 4, which is mounted on an inner peripheral surface or an outer peripheral surface of a cylindrical portion. 6. The synthetic resin sliding bearing according to claim 5, wherein the annular horizontal surface of the step portion on which the annular portion of the main body is seated faces upward. 7. The synthetic resin sliding bearing according to claim 5, wherein the annular horizontal surface of the step portion on which the annular portion of the main body portion is seated faces downward. 8. The sliding bearing means includes: a thrust sliding bearing disposed between the first annular plate of the lower case and the second annular plate of the upper case; The sliding bearing made of a synthetic resin according to any one of claims 1 to 7, further comprising a radial sliding bearing disposed between the sliding bearing and the cylindrical portion. 9. The synthetic resin slide bearing according to claim 8, wherein at least one of the thrust slide bearing and the radial slide bearing comprises a synthetic resin slide bearing member separate from the upper and lower cases.