Thrust sliding bearing and combination mechanism of the thrust sliding bearing and a piston rod

A thrust sliding bearing includes a synthetic resin-made bearing body having a hollow cylindrical portion, an annular collar portion, an annular protruding portion, a tubular projecting portion, an engaging projecting portion, and an annular projecting portion; an annular cover having a disk portion, a tubular portion, and an engaging projecting portion; an annular metal plate having an outer disk portion and an inner disk portion; and a thrust sliding bearing which is interposed between the bearing body and an annular lower surface of the outer disk portion of the annular metal plate and renders the annular metal plate rotatable with respect to the bearing body in a direction about an axis of the bearing body.

This application is the U.S. national phase of International Application No. PCT/JP2012/000477, filed Jan. 25, 2012, which designated the U.S. and claims priority to JP Application 2011-076387, filed Mar. 30, 2011, the entire contents of each of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a thrust sliding bearing, and more particularly to a thrust sliding bearing which is suitably incorporated as a sliding bearing of a strut-type suspension (Macpherson type) in a four-wheeled vehicle, as well as a combination mechanism of the thrust sliding bearing and a piston rod.

BACKGROUND ART

In general, a strut-type suspension used for a front wheel of a four-wheeled vehicle has a structure in which a strut assembly incorporating a hydraulic shock absorber in an outer cylinder integrated with a main shaft is combined with a coil spring. Among such suspensions, there is a type in which when the strut assembly rotates together with the coil spring in the steering operation, the piston rod of the strut assembly rotates, and a type in which the piston rod does not rotate. In either type, there are cases where, instead of a rolling bearing, a synthetic resin-made thrust sliding bearing is used between a mechanism for mounting the strut assembly to the vehicle body and an upper spring seat member of the coil spring, so as to allow smooth rotation of the strut assembly.

PRIOR ART DOCUMENTS

Patent Documents

SUMMARY OF THE INVENTION

Problems that the Invention is to Solve

Incidentally, in the mechanism for mounting the strut assembly to the vehicle body, a mounting plate is used for supporting one end of the piston rod of the hydraulic shock absorber, but in the case of such a mounting mechanism, the mounting plate for supporting the end of the piston rod is not only required, but the structure becomes complex, so that high cost is entailed.

With respect to such a problem, Patent Document 6 proposes a thrust sliding bearing and a combination mechanism of the thrust sliding bearing and a piston rod which make it possible to support one end of the piston rod instead of the mounting plate of the mechanism for mounting the strut assembly to the vehicle body, thereby making it possible to simplify the mounting mechanism and attain a cost reduction.

The thrust sliding bearing according to this proposal is comprised of a synthetic resin-made annular bearing body having an annular upper surface and an annular engaging outer peripheral surface; a synthetic resin-made annular another bearing body which is superposed on this bearing body so as to be relatively rotatable about an axis of that bearing body and has an annular lower surface opposed to the annular upper surface of the bearing body; thrust sliding bearing means interposed between the annular upper surface of the bearing body and the annular lower surface of the other bearing body and having at least one of a lower surface and an upper surface which is in slidable contact with at least one of the annular upper surface of the bearing body and the annular lower surface of the other bearing body; an annular upper cover having an annular engaging inner peripheral surface engaging the annular engaging outer peripheral surface of the bearing body; and an annular metal plate interposed between an annular upper surface of the other bearing body and a lower surface of the annular upper cover such that a lower surface of the annular metal plate is brought into contact with the annular upper surface of the other bearing body and an upper surface thereof is brought into contact with the lower surface of the annular upper cover. In this thrust sliding bearing, the annular metal plate is provided with an annular inner peripheral surface having a smaller diameter than inside diameters of annular inner peripheral surfaces of the both bearing bodies and the annular upper cover, thereby effectively overcoming the above-described problem.

However, since the proposed thrust sliding bearing at the flat annular metal plate is arranged to be mounted to the threaded portion of the piston rod through the nut, there is a possibility that if a large force is applied to the annular metal plate through the piston rod, the annular metal plate can be deformed, generating abnormal noise in the relative rotation of the piston rod.

In addition, with the proposed thrust sliding bearing, there are problems in that not only does the number of component parts become large, but an increase in weight of that thrust sliding bearing is entailed, and the height of the thrust sliding bearing itself becomes large, so that the mounting mechanism supporting one end of the piston rod also becomes large, requiring a large mounting space.

The present invention has been devised in view of the above-described aspects, and its object is to provide a thrust sliding bearing and a combination mechanism of the thrust sliding bearing and a piston rod which, even if a large force is applied to the annular metal plate through the piston rod, make it possible to prevent the deformation of the annular metal plate, reduce the generation of abnormal noise in the relative rotation of the piston rod, and make the height low by reducing the number of the component parts.

Means for Overcoming the Problems

A thrust sliding bearing in accordance with the present invention comprises: a synthetic resin-made bearing body having a hollow cylindrical portion with a cylindrical inner peripheral surface defining a through hole, an annular collar portion integrally extending radially outwardly from a cylindrical outer peripheral surface of the hollow cylindrical portion, an annular protruding portion integrally protruding radially outwardly from a lower side of a cylindrical outer peripheral surface of the annular collar portion, a tubular projecting portion formed on an annular upper surface of the annular protruding portion and defining by a cylindrical inner peripheral surface thereof an annular outer recessed portion in cooperation with the cylindrical outer peripheral surface of the annular collar portion and the annular upper surface of the annular protruding portion, and an annular engaging projecting portion projecting radially outwardly from a cylindrical outer peripheral surface of the tubular projecting portion; an annular cover having a disk portion with an inner peripheral surface defining a through hole concentric with the through hole of the bearing body as well as an annular upper surface and an annular lower surface, a tubular portion formed integrally with the disk portion and having an inner peripheral surface, and an engaging projecting portion projecting radially inwardly from the inner peripheral surface of the tubular portion and adapted to engage the engaging projecting portion of the bearing body; an annular metal plate having a radially outwardly disposed outer disk portion having an annular upper surface coming into contact with the annular lower surface of the disk portion of the annular cover and a radially inwardly disposed inner disk portion formed integrally with the outer disk portion and disposed in the through hole defined by the inner peripheral surface of the disk portion of the annular cover; and a thrust sliding bearing means which is interposed between the bearing body and an annular lower surface of the outer disk portion of the annular metal plate and renders the annular metal plate rotatable in a direction about an axis of the bearing body with respect to the bearing body, wherein the inner disk portion has a cylindrical inner peripheral surface having a smaller diameter than a diameter of the inner peripheral surface of the hollow cylindrical portion of the bearing body and defining a through hole concentric with the both through holes, and the thrust sliding bearing means has an annular upper surface of the bearing body, an annular deep groove formed on an inner peripheral side of the annular upper surface, at least one annular shallow groove surrounding the annular deep groove and shallower in depth than the annular deep groove, and a lubricant which is filled in the annular deep groove and the annular shallow groove.

According to the thrust sliding bearing of the present invention, since the annular metal plate has the inner disk portion which is formed integrally with the outer disk portion and is disposed in the through hole defined by the inner peripheral surface of the annular cover, the inner disk portion functions like a reinforcing portion (rib) for the outer disk portion. As a result, even if a large force is applied to the annular metal plate through the piston rod, it is possible to prevent the deformation of the annular metal plate and reduce the generation of abnormal noise in the relative rotation of the piston rod ascribable to the deformation of the annular metal plate.

In addition, in the thrust sliding bearing in accordance with the present invention, since thrust sliding bearing means has an annular upper surface of the bearing body, an annular deep groove formed on an inner peripheral side of the annular upper surface, at least one annular shallow groove surrounding the annular deep groove and shallower in depth than the annular deep groove, and a lubricant which is filled in the annular deep groove and the annular shallow groove, the height of the thrust sliding bearing itself can be made low by reducing the number of component parts, so that the installation space of the thrust sliding bearing can be diminished, and overall cost reduction can be achieved.

In the present invention, the bearing body may be formed of a thermoplastic synthetic resin such as polyacetal resin, polyamide resin, and thermoplastic polyester resin, and the annular cover in a preferred embodiment is formed of a thermoplastic synthetic resin such as polyacetal resin, polyamide resin, and thermoplastic polyester resin, but may alternatively be formed of a reinforced thermoplastic synthetic resin in which such a thermoplastic synthetic resin is reinforced by an inorganic filler such as glass fiber, glass powder, glass beads, and carbon fiber or by an organic filler such as aramid resin fiber. The annular metal plate in a preferred embodiment is formed of a steel plate made of such as steel, stainless steel, or the like, but may alternatively be formed of a nonferrous alloy plate made of such as a copper alloy, a titanium alloy, or the like, and such an annular metal plate is preferably formed by subjecting a hot-rolled steel plate (SPHC: steel plate hot commercial) to press forming.

The thrust sliding bearing means may have a plurality of annular shallow grooves which are mutually identical in depth. Further, in the thrust sliding bearing means, the at least one annular shallow groove may have an annular wide shallow groove having a wider radial width than a radial width of the annular deep groove. Still further, the thrust sliding bearing means at the annular upper surface of the bearing body may be in contact with the annular lower surface of the outer disk portion of the annular metal plate rotatably in the direction about the axis of the bearing body, or may have a synthetic resin-made annular sheet disposed on the annular upper surface in such a manner as to cover the lubricant which is filled in the annular shallow groove and the annular deep groove. The thrust sliding bearing means having the annular sheet may be in contact at the annular upper surface of the annular sheet with the annular lower surface of the outer disk portion of the annular metal plate rotatably in the direction about the axis of the bearing body. In addition, the thrust sliding bearing means may have an electrodeposited coating which is provided on at least one of the annular lower surface of the outer disk portion of the annular metal plate. Furthermore, at least the inner disk portion of the annular metal plate may have at least one of an annular upper surface and an annular lower surface which are each coated with a ductile soft metal such as zinc, copper, or tin.

In the present invention, at least one of the lubricant, the synthetic resin-made annular sheet, and the electrodeposited coating is interposed between the annular lower surface of the outer disk portion and the annular upper surface of the bearing body of the thrust sliding bearing means, and therefore the annular upper surface of the bearing body of the thrust sliding bearing means is rendered rotatable in the direction about the axis of the bearing body with respect to the annular lower surface of the outer disk portion through at least one of the lubricant, the synthetic resin-made annular sheet, and the electrodeposited coating, with the result that the thrust sliding bearing means renders the annular metal plate rotatable with respect to the bearing body in the direction about the axis of the bearing body.

The annular cover in one embodiment has a connecting portion which is interposed between the disk portion and the tubular portion thereof and which has a cylindrical inner peripheral surface, a circular annular lower surface continuously connected to the cylindrical inner peripheral surface, and a semi spherical outer peripheral surface which is arc-shaped in cross section, and the outer disk portion of the annular metal plate has a cylindrical outer peripheral surface opposing the cylindrical inner peripheral surface of the connecting portion in the radial direction.

The annular metal plate may have an inclined connecting portion interposed between the outer disk portion and the inner disk portion and continuously connected to the inner disk portion in such a manner as to extend diagonally upwardly from an inner peripheral side of the outer disk portion and an downwardly protruding portion formed integrally with the outer disk portion and suspended downwardly from an outer peripheral side of the annular lower surface of the outer disk portion in such a manner as to envelop an upper edge portion of the outer peripheral surface of the annular collar portion.

In a preferred embodiment, the annular cover has a connecting portion interposed between the disk portion and the tubular portion thereof and having a semispherical outer peripheral surface and a semispherical inner peripheral surface which are arc-shaped in cross section, and the outer disk portion of the annular metal plate has a semispherical outer peripheral surface which opposes the semispherical inner peripheral surface of the connecting portion of the annular cover, while the inner disk portion of the annular metal plate has an annular lower surface continuously connected to the annular lower surface of the outer disk portion and flush with the annular lower surface of the outer disk portion.

A combination mechanism of a thrust sliding bearing and a piston rod, or a combination mechanism for use in a strut-type suspension in a four-wheeled vehicle in a preferred embodiment, comprises: the thrust sliding bearing according to any one of the above-described embodiment; and a piston rod of a shock absorber, wherein the piston rod includes a large-diameter portion disposed in a through hole defined by an inner peripheral surface of the hollow cylindrical portion of the bearing body, a small-diameter portion whose diameter is smaller than the large-diameter portion and which is formed integrally with the large-diameter portion and is disposed in a through hole defined by the cylindrical inner peripheral surface of the inner disk portion of the annular metal plate, and a threaded portion formed on the small-diameter portion, and wherein the annular metal plate at the inner disk portion is clamped by an annular stepped surface between the large-diameter portion and the small-diameter portion of the piston rod and an annular surface of a nut threadedly engaged with the threaded portion.

In at least the inner disk portion of such an annular metal plate, if at least one of the annular upper surface and the annular lower surface of the inner disk portion, which are clamped by the annular surface of the nut and the annular stepped surface between the large-diameter portion and the small-diameter portion of the piston rod, is coated with a ductile soft metal such as zinc, copper, or tin, at least one pair of corresponding ones between the annular stepped surface and the annular surface of the nut, on the one hand, and the annular upper surface and the annular lower surface of the inner disk portion, on the other hand, can be brought into substantially total contact with each other, thereby making it possible to avoid local contact and disperse the stress when it is applied in the axial direction from the piston rod. As a result, it is possible to avoid the occurrence of damage, such as a crack, to the inner disk portion.

Advantages of the Invention

According to the present invention, it is possible to provide a thrust sliding bearing and a combination mechanism of the thrust sliding bearing and a piston rod which, even if a large force is applied to the annular metal plate through the piston rod, make it possible to prevent the deformation of the annular metal plate, reduce the generation of abnormal noise in the relative rotation of the piston rod ascribable to the deformation of the annular metal plate, and make the height low by reducing the number of the component parts.

MODE FOR CARRYING OUT THE INVENTION

Hereafter, a more detailed description will be given of the mode for carrying out the invention on the basis of preferred embodiments illustrated in the drawings. It should be noted that the present invention is not limited to these embodiments.

InFIGS. 1 to 13, a thrust sliding bearing1of this embodiment includes a synthetic resin-made bearing body16having a hollow cylindrical portion4with a cylindrical inner peripheral surface3defining a through hole2, an annular collar portion6integrally extending radially outwardly from a cylindrical outer peripheral surface5of the hollow cylindrical portion4, an annular protruding portion8integrally protruding radially outwardly from a lower side of a cylindrical outer peripheral surface7of the annular collar portion6, a tubular projecting portion13formed integrally on an annular upper surface9of the annular protruding portion8and defining an annular outer recessed portion12, which opens at an annular upper surface11, in cooperation with the cylindrical outer peripheral surface7of the annular collar portion6and the annular upper surface9of the annular protruding portion8, an annular engaging projecting portion14integrally projecting radially outwardly from a cylindrical outer peripheral surface of the tubular projecting portion13, and an annular projecting portion15formed integrally on the inner peripheral surface3side of the hollow cylindrical portion4; an annular cover28having a disk portion24with an inner peripheral surface22defining a through hole21concentric with the through hole2of the bearing body16as well as an annular lower surface23continuously connected to a lower edge of that inner peripheral surface22, a tubular portion26formed integrally with the disk portion24and having an inner peripheral surface25constituted by a truncated conical surface, and an engaging projecting portion27integrally projecting radially inwardly from the inner peripheral surface25of the tubular portion26and adapted to elastically engage the engaging projecting portion14of the bearing body16; an annular metal plate34having a radially outwardly disposed outer disk portion32having an annular upper surface31coming into contact with the annular lower surface23of the disk portion24of the annular cover28and a radially inwardly disposed inner disk portion33formed integrally with the outer disk portion32and disposed in the through hole21defined by the inner peripheral surface22of the disk portion24of the annular cover28; and a thrust sliding bearing means36which is interposed between the bearing body16and an annular lower surface35of the outer disk portion32of the annular metal plate34and renders the annular metal plate34rotatable with respect to the bearing body16in an R direction about an axis O of the bearing body16.

In the synthetic resin-made bearing body16formed of a thermoplastic synthetic resin such as polyacetal resin, polyamide resin, and polyester resin (polybutylene terephthalate resin), the hollow cylindrical portion4has an annular lower surface40in addition to the inner peripheral surface3and the outer peripheral surface5, and a plurality of lower recesses43arranged in such a manner as to be spaced apart from each other in the R direction and a plurality of lower recesses44, each one being radially adjacent to and deeper than the lower recess43, are formed in an annular lower surface41of the annular collar portion6which is disposed higher than the annular lower surface40and in an annular lower surface42of the annular protruding portion8flush with that annular lower surface41.

The annular cover28, which is formed of a thermoplastic synthetic resin such as polyacetal resin, polyamide resin, and polyester resin (polybutylene terephthalate resin) or a reinforced thermoplastic synthetic resin in which such a thermoplastic synthetic resin is reinforced by an inorganic filler such as glass fiber, glass powder, glass beads, and carbon fiber or by an organic filler such as aramid resin fiber, has a connecting portion54which is interposed between the disk portion24and the tubular portion26and which has a cylindrical inner peripheral surface51, an annular lower surface52continuously connected to a lower edge of that cylindrical inner peripheral surface51, and a semispherical outer peripheral surface53which is arc-shaped in cross section. The disk portion24has, in addition to the inner peripheral surface22and the annular lower surface23, an annular upper surface55continuously connected at its outer edge to an upper edge of the semispherical outer peripheral surface53, and the inner peripheral surface22of the disk portion24has a truncated conical surface56, while the tubular portion26has, in addition to the inner peripheral surface25, an annular lower surface58and a cylindrical outer peripheral surface57which is continuously connected at its upper edge to a lower edge of the semispherical outer peripheral surface53.

The annular metal plate34, which is preferably formed by subjecting a hot-rolled steel plate (SPHC: steel plate hot commercial) to press forming, has, in addition to the outer disk portion32and the inner disk portion33, an inclined connecting portion61interposed between the outer disk portion32and the inner disk portion33and continuously connected to the inner disk portion33in such a manner as to extend diagonally upwardly from an inner peripheral side of the outer disk portion32, as well as an annular downwardly protruding portion62formed integrally with the outer disk portion32and suspended downwardly from an outer peripheral side of the annular lower surface35of the outer disk portion32in such a manner as to envelop an upper edge portion of the outer peripheral surface7of the annular collar portion6.

The outer disk portion32disposed between, on the one hand, the hollow cylindrical portion4and the annular collar portion6and, on the other hand, the disk portion24in the axial direction has, in addition to a cylindrical outer peripheral surface63opposed to the cylindrical inner peripheral surface51of the connecting portion54in the radial direction. The inclined connecting portion61has an inclined outer peripheral surface64opposed to the truncated conical surface56of the annular cover28in the radial direction, as well as an inclined inner peripheral surface65extending in parallel to the inclined outer peripheral surface64. The inner disk portion33which is disposed in the through hole21has an annular upper surface67continuously connected to an upper edge of the inclined outer peripheral surface64and exposed upwardly in the through hole21, an annular lower surface68extending in parallel to the annular upper surface67, and a cylindrical inner peripheral surface70having a smaller diameter than the diameter of the inner peripheral surface3of the hollow cylindrical portion4of the bearing body16and defining a through hole69concentric with both through holes2and21.

The annular metal plate34is preferably formed by subjecting a hot-rolled steel plate (SPHC) to press forming. In this case, at least the below-described annular upper surface67and annular lower surface68(clamped surfaces) of the inner disk portion33, which are clamped by an annular surface of a nut and an annular stepped surface between a large-diameter portion and a small-diameter portion of a piston rod, are preferably coated with a ductile soft metal such as zinc, copper, or tin. As such metal plating is provided, the annular stepped surface of the piston rod and the annular surface of the nut, on the one hand, and the annular upper surface67and the annular lower surface68of the inner disk portion33, on the other hand, are brought into substantially total contact with each other, thereby making it possible to avoid local contact and disperse the stress when it is applied in the axial direction from the piston rod. As a result, damage, such as a crack, to the inner disk portion33and the outer disk portion32formed integrally with the inner disk portion33does not occur.

The thrust sliding bearing means36includes an annular upper surface82of the hollow cylindrical portion4, i.e., an annular upper surface81of the bearing body16which is brought into slidable contact with the annular lower surface35of the outer disk portion32in the R direction, as well an annular upper surface83of the annular collar portion flush6with the annular upper surface82; an annular deep groove84formed in the annular upper surface82on the inner peripheral side of the annular upper surface81; annular shallow grooves85and86which are formed in the annular upper surfaces82and83on the radially outer side of the annular deep groove84in such a manner as to surround the annular deep groove84and which are shallower in depth than the annular deep groove84but are mutually identical in depth; and a lubricant87such as grease which is filled in the annular deep groove84and the annular shallow grooves85and86. The annular shallow groove85is formed in the annular upper surface82, while the annular shallow groove86is formed in the annular upper surface83on the radially outer side of the annular shallow groove85in such a manner as to surround that annular shallow groove85. Such a thrust sliding bearing means36at its annular upper surface81with the lubricant87spread thereon is in contact with the annular lower surface35of the outer disk portion32of the annular metal plate34rotatably in the R direction about the axis O.

In the above-described thrust sliding bearing1, the bearing body16and the annular cover28are superposed on and coupled to each other with the annular metal plate34clamped therebetween in the axial direction (vertical direction) by the elastic fitting (snap fitting) of the engaging projecting portion27with respect to the engaging projecting portion14making use of the flexibility of the synthetic resin. In the relative rotation of the annular metal plate34with respect to the bearing body16about the axis O in the R direction, sliding in the R direction is caused to take place between, on the one hand, the annular upper surfaces82and83of the thrust sliding bearing means36which is interposed between the bearing body16and an annular lower surface35of the outer disk portion32of the annular metal plate34and the annular lower surface35of the outer disk portion32of the annular metal plate34which is in contact with the annular upper surfaces82and83, thereby allowing the relative rotation of the annular metal plate34with respect to the bearing body16about the axis O in the R direction to be effected with low frictional torque.

As shown inFIG. 14, such a thrust sliding bearing1is used when a strut-type suspension93of a vehicle, which includes a hydraulic shock absorber (not shown) having a piston rod91therein and a coil spring92disposed so as to surround such a hydraulic shock absorber, is mounted to a vehicle body by means of a mounting mechanism94.

The strut-type suspension93of a vehicle, e.g., a four-wheeled vehicle, includes, in addition to the hydraulic shock absorber and the coil spring92, an upper spring seat member95for receiving one end of the coil spring92and a bump stopper96disposed so as to surround the piston rod91. The mounting mechanism94includes a rubber-made resilient member98with a core metal97embedded therein, as well as a spacer member99interposed between, on the one hand, the upper spring seat member95and the annular collar portion6of the bearing body16and, on the other hand, the respective annular lower surfaces41and42of the annular protruding portion8. The thrust sliding bearing1is disposed between the resilient member98of the mounting mechanism94and the upper spring seat member95of the strut-type suspension93through the spacer member99. Moreover, a lower end portion of the hollow cylindrical portion4is inserted in a central through hole100of the upper spring seat member95, to be thereby positioned by the upper spring seat member95concerning a direction perpendicular to the axis O, i.e., in the radial direction, and the inner peripheral surface of the spacer member99is in contact with the outer peripheral surface5of the hollow cylindrical portion4. The resilient member98enveloping the thrust sliding bearing1is disposed with its inner peripheral surface brought into contact with the semispherical outer peripheral surface53, the annular upper surface55, and the cylindrical outer peripheral surface57of the annular cover28.

The piston rod91includes a large-diameter portion111disposed by being passed through the through hole2, a small-diameter portion112whose diameter is smaller than the large-diameter portion111and which is formed integrally with the large-diameter portion111and is disposed by being passed through the through hole69of the annular metal plate34, and a threaded portion113formed on the small-diameter portion112. Between, on the one hand, an annular stepped surface114between the large-diameter portion111and the small-diameter portion112of the piston rod91and, on the other hand, an annular surface116of a nut115threadedly engaged with the threaded portion113, the annular metal plate34at its inner disk portion33is clamped by the annular stepped surface114and the annular surface116.

The large-diameter portion111at its outer peripheral surface121is in contact with the inner peripheral surface3of the bearing body16defining the through hole2rotatably in the R direction, and the nut115at its outer peripheral surface is in contact with an annular inner peripheral surface122of the resilient member98, is threadedly engaged with the threaded portion113so as not to rotate in the R direction with respect to the resilient member98, and is fixed to the piston rod91. The annular cover28is held by the resilient member98by means of the annular metal plate34whose inner disk portion33is clamped by the annular stepped surface114and the annular surface116, so as not to rotate in the R direction with respect to the piston rod91.

In the above-described combination mechanism of the thrust sliding bearing1and the piston rod91, when the coil spring92is rotated around the axis O in the R direction by the steering operation, the bearing body16is similarly rotated relatively in the R direction with respect to the annular metal plate34. This rotation of the bearing body16is allowed by the sliding contact in the R direction between, on the one hand, the annular upper surfaces82and83of the thrust sliding bearing means36and the lubricant87such as grease spread on the annular upper surfaces82and83and filled in the annular deep groove84and the annular shallow grooves85and86and, on the other hand, the annular lower surface35of the outer disk portion32of the annular metal plate34which is in contact therewith, so that the steering operation is performed without resistance.

With the thrust sliding bearing1, since the bearing body16is disposed rotatably in the R direction with respect to the annular lower surface35of the annular metal plate34by the annular upper surfaces82and83of the thrust sliding bearing means36and the lubricant87spread on the annular upper surfaces82and83, the thrust sliding bearing1can be constructed by three parts including the bearing body16, the annular metal plate34, and the annular cover28. As a result, the height of the thrust sliding bearing1itself can be made low by reducing the number of component parts, so that the installation space of the thrust sliding bearing1can be diminished, and overall cost reduction can be achieved. Moreover, one end of the piston rod91can be supported by the annular metal plate34, and it is possible to eliminate a mounting member for supporting one end of the piston rod91in the mechanism for mounting the strut-type suspension93to the vehicle body, thereby making it possible to simplify the mounting mechanism and attain cost reduction.

In addition, according to the thrust sliding bearing1, since the annular metal plate34has the inner disk portion33which is formed integrally with the outer disk portion32through the inclined connecting portion61and is disposed in the through hole21defined by the inner peripheral surface22of the annular cover28, the inner disk portion33functions like a reinforcing portion (rib) for the outer disk portion32. As a result, even if a large force is applied to the annular metal plate34through the piston rod91, it is possible to prevent the deformation of the annular metal plate34and reduce the generation of abnormal noise in the relative rotation of the piston rod91in the R direction ascribable to the deformation of the annular metal plate34.

In addition, with the thrust sliding bearing1, the wall thickness of the annular collar portion6and the annular protruding portion8formed integrally on the lower side of the outer peripheral surface7of the annular collar portion6can be made uniform by the lower recesses43and44formed on the annular lower surface41of the annular collar portion6and the annular lower surface42of the annular protruding portion8, thereby making it possible to overcome molding defects and dimensional defects ascribable to nonuniformity of wall thickness during molding. However, in cases where such effects are not particularly required, the lower recesses43and44may not be particularly provided.

Furthermore, according to the thrust sliding bearing1, since the annular protruding portion62is adapted to engage the outer peripheral surface7of the annular collar portion6of the bearing body16, it is possible to hold the relative radial positions of the annular metal plate34and the bearing body16.

In the thrust sliding bearing1, as at least the annular upper surface67and the annular lower surface68of the inner disk portion33, which are clamped by the annular surface116of the nut115and the annular stepped surface114between the large-diameter portion111and the small-diameter portion112of the piston rod91, are coated with a ductile soft metal such as zinc, copper, or tin, the annular stepped surface114and the annular surface116, on the one hand, and the annular upper surface67and the annular lower surface68of the inner disk portion33clamped by the annular stepped surface114and the annular surface116, on the other hand, can be brought into substantially total contact with each other, thereby making it possible to avoid local contact and disperse the stress when it is applied in the axial direction from the piston rod91. As a result, it is possible to avoid the occurrence of damage, such as a crack, to the inner disk portion33.

As shown inFIGS. 15 and 16, the thrust sliding bearing means36may have a synthetic resin-made annular sheet131disposed on the annular upper surface81in such a manner as to cover the lubricant87such as grease which is filled in the annular grooves84,85, and86, in addition to the annular upper surface81, the annular deep groove84, the annular shallow grooves85and86, and the lubricant87. The annular sheet131is interposed between the annular upper surface81and the annular lower surface35of the outer disk portion32of the annular metal plate34, and the annular sheet131at its annular upper surface132is in contact with the annular lower surface35of the outer disk portion32of the annular metal plate34, while the annular sheet131at its annular lower surface133is in contact with the annular upper surface81, so as to be rotatable in the R direction, respectively. With such a thrust sliding bearing means36, the annular metal plate34is rendered rotatable with respect to the bearing body16in the R direction about the axis O of the bearing body16by at least one of the sliding in the R direction of the annular lower surface133of the annular sheet131with respect to the annular upper surface81and the sliding in the R direction of the annular upper surface132of the annular sheet131with respect to the annular lower surface35of the annular metal plate34, and the lubricant87filled in the annular deep groove84and the annular shallow grooves85and86sealed by the annular sheet131is adapted to support the axial load from the annular sheet131.

The synthetic resin-made annular sheet131is preferably formed of a synthetic resin including at least one of polyacetal resin, polyamide resin, polyester resin, polyolefin resin, polycarbonate resin, and fluororesin, may have the annular inner peripheral surface134of an inside diameter greater than the outside diameter of the annular projecting portion15of the bearing body16and the outer peripheral surface135of an outside diameter smaller than the outside diameter of the outer peripheral surface7of the annular collar portion6, and may have an axial thickness of 0.05 mm to 1.0 mm.

In the thrust sliding bearing1shown inFIGS. 15 and 16, in the relative rotation of the annular metal plate34in the R direction about the axis O with respect to the bearing body16, the sliding of synthetic resins between the annular upper surface132of the annular sheet131and the annular lower surface35of the outer disk portion32of the annular metal plate34, or the sliding of synthetic resins between the annular lower surface133of the annular sheet131and the annular upper surface81of the bearing body16through the lubricant87, preferably the former sliding, is caused to take place, thereby allowing the relative rotation of the annular metal plate34in the R direction with respect to the bearing body16about the axis O to be effected with extremely low frictional torque. Moreover, since the arrangement provided is such that the annular sheet131having a thin thickness of 0.05 to 1.0 mm or thereabouts is merely interposed in the thrust sliding bearing means36described earlier, also with the thrust sliding bearing1shown inFIGS. 15 and 16, its own height can be made low, its installation space can be diminished, and overall cost reduction can be attained.

In each thrust sliding bearing1described above, the thrust sliding bearing means36has the annular deep groove84and the annular shallow grooves85and86, but, as shown inFIG. 17, the thrust sliding bearing means36may alternatively have the annular deep groove84, an annular wide shallow groove136having a wider width than the radial width of the annular deep groove84and the annular shallow grooves85and86, and the lubricant87filled in the annular deep groove84and the annular wide shallow groove136. The thrust sliding bearing means36shown inFIG. 17may also have the synthetic resin-made annular sheet131shown inFIGS. 15 and 16and disposed on the annular upper surface81in such a manner as to cover the lubricant87such as grease which is filled in the annular deep groove84and the annular wide shallow groove136.

In the thrust sliding bearing1shown inFIGS. 1 to 13, the thrust sliding bearing means36may have, in addition to the annular upper surface81, the annular deep groove84, and the annular shallow grooves85and86, an electrodeposited coating which is provided on the annular lower surface35of the outer disk portion32, and such an electrodeposited coating may be preferably effected by cathodic electrodeposition of resin paint so as to obtain a resin coating as an electrodeposited coating having low frictional properties, but other electrodeposition may be effected.

Such an electrodeposited coating may be applied to the thrust sliding bearing means36of the thrust sliding bearing1shown inFIGS. 15 and 16or17.

In the above-described thrust sliding bearing1, the annular cover28has the disk portion24, the tubular portion26formed integrally with the disk portion24, the engaging projecting portion27projecting radially inwardly from the inner peripheral surface25of the tubular portion26, and the connecting portion54interposed between the disk portion24and the tubular portion26, and the annular metal plate34has the outer disk portion32, the inner disk portion33formed integrally with the outer disk portion32, and the inclined connecting portion61interposed between the outer disk portion32and the inner disk portion33. However, as shown inFIG. 18, the annular cover28may alternatively be constructed by including a thin-walled disk portion141having the annular lower surface23and the cylindrical inner peripheral surface22defining the through hole21, a thin-walled tubular portion142formed integrally with the disk portion141and having the inner peripheral surface25constituted by a truncated conical surface, the engaging projecting portion27projecting radially inwardly from the inner peripheral surface25of the tubular portion142, and an annular connecting portion145interposed between the disk portion141and the tubular portion142and having a semispherical outer peripheral surface143and a semispherical inner peripheral surface144which are arc-shaped in cross section. Further, the annular metal plate34may be constructed by including the outer disk portion32having, in addition to the annular upper surface31and the annular lower surface35, a semispherical outer peripheral surface146which is arc-shaped in cross section and which opposes the cross-sectionally arc-shaped semispherical inner peripheral surface144of the connecting portion145and is continuously connected to the annular upper surface31, and by including the thick-walled inner disk portion33having, in addition to the annular upper surface67and the inner peripheral surface70defining the through hole69, the annular lower surface68continuously connected to the annular lower surface35of the outer disk portion32and flush with the annular lower surface35of the outer disk portion32, while having, instead of the inclined outer peripheral surface64, a cylindrical outer peripheral surface147opposing the cylindrical inner peripheral surface22.

In the thrust sliding bearing1shown inFIG. 18, the annular projecting portion15is integrally formed on the annular upper surface82of the hollow cylindrical portion4on the inner peripheral surface3side of the hollow cylindrical portion4so that its annular upper surface becomes located lower than the annular lower surface68with an annular gap with respect to the annular lower surface68, the downwardly protruding portion62is formed integrally on the annular lower surface35of the outer disk portion32in such a manner as to be suspended downwardly from the outer peripheral side of the annular lower surface35of the outer disk portion32such that its outer peripheral surface extends in contact with the semispherical inner peripheral surface144of the connecting portion145along that semispherical inner peripheral surface144, and the annular metal plate34is made capable of holding its relative radial position with respect to the annular cover28by the contact of the outer peripheral surface of the downwardly protruding portion62with the semispherical inner peripheral surface144.

Any one of the thrust sliding bearing means among the thrust sliding bearing means36shown inFIGS. 1 to 13, the thrust sliding bearing means36shown inFIGS. 15 and 16, the thrust sliding bearing means36shown inFIG. 17, and the thrust sliding bearing means36having the above-described electrodeposited coating may be also applied to the thrust sliding bearing1shown inFIG. 18.

In addition, also with any one of the thrust sliding bearings1shown inFIGS. 15 and 16,FIG. 17, andFIG. 18, the annular upper surface67and the annular lower surface68of the inner disk portion33, which are clamped by the annular surface116of the nut115and the annular stepped surface114between the large-diameter portion111and the small-diameter portion112of the piston rod91, may be coated with a ductile soft metal such as zinc, copper, or tin.