Thrust bearing

A thrust bearing which is formed by stamping a plate made of a bearing alloy material or a plate having a bearing alloy layer has an annular shape. The thrust bearing is disposed in a circumferential direction and has a plurality of recesses and projections deformed in the direction of the thickness of the bearing. The thrust bearing may have a positioning and retaining portion.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a ring-shaped thrust bearing formed by 
stamping a plate. 
2. Statement of the Related Art 
A bush with a collar in which the collar is deformed into a corrugated 
shape in the direction of its thickness is disclosed in Japanese Utility 
Model Unexamined Publication No. 16442/1977. In this prior art, the collar 
is provided around the outer periphery of an end portion of a sleeve, and 
this bush with a collar constitutes a thrust and radial sliding bearing. 
It is very difficult to manufacture thrust and radial sliding bearings as 
compared with manufacturing bearings without collars, so that it is very 
difficult to ensure high accuracy this type of bearing, and productivity 
is therefore low. Furthermore, according to normal usage, the radial 
bearing portions are used to support a high load, while the thrust bearing 
portions are used to support a low load. However, if the bush is 
constructed such as to be integrally formed with a collar, the same 
bearing material is inevitably used for the two portions, with the result 
that the costs become high. 
SUMMARY OF THE INVENTION 
To overcome this problem, in accordance with the present invention, a 
thrust bearing is formed separately from a radial bearing. 
According to one aspect of the invention, there is provided a ring-shaped 
thrust bearing formed by stamping a plate made of a bearing alloy material 
or a plate having a bearing alloy layer. A plurality of circumferentially 
arranged indented portions obtained by deforming the thrust bearing are 
formed in the thrust bearing. 
According to another aspect of the invention, a positioning and retaining 
portion which is adapted to position the thrust bearing and serves as a 
stopper therefor is formed in addition to the plurality of recesses and 
projections. 
According to the present invention, both the indented portions and (or) the 
positioning and retaining portion can be formed simultaneously by stamping 
a plate. The projections constitute surfaces of contact with a shaft, 
while the recesses constitute channels for influx of lubricating oil. The 
positioning and retaining portion serves to position the thrust bearing in 
a housing or the like and serves as a stopper.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A bimetal 3 shown in FIGS. 4 and 5, for instance, is used as a material of 
a thrust bearing, and this bimetal 3 comprises a steel backing layer 1 and 
a bearing alloy 2. The bimetal 3 is stamped out into an annular shape 4, 
as shown in FIGS. 1 to 3 and 6, by using a press. At the same time, a 
plurality of recesses 5a, 5b, and a plurality of projections 6a, 6b are 
formed by deforming the peripheral portion of the stamped piece in the 
direction of the thickness thereof. Furthermore, a protrusion 7 protruding 
radially outwardly and serving as a positioning and retaining member is 
formed thereon. 
In a thrust bearing 8 thus formed by stamping, the plurality of projections 
6a serve as sliding surfaces for supporting a load in the direction of a 
thrust, while the plurality of recesses 5a serve as oil grooves. 
Meanwhile, the plurality of projections 6b serve as surfaces engaging with 
a housing, for instance, and the protrusion 7 is fitted with a 
corresponding groove or hole of the housing and functions as a positioning 
and retaining portion. 
In the above-described embodiment, although the protrusion 7 protruding 
radially outwardly is provided as the positioning and retaining portion, a 
protrusion 7' having an L-shape, as shown in FIG. 7, may be provided as 
the positioning and retaining portion. This protrusion 7' is fitted with a 
corresponding groove or hole in the housing to serve as a positioning and 
retaining portion. 
Furthermore, an arrangement in which a hole or a groove (not shown) is 
simply provided at a predetermined position of the thrust bearing 8 may 
alternatively be provided as the positioning and retaining portion. A 
projecting portion provided on the housing is fitted with this hole or 
groove, thereby positioning and retaining the thrust bearing 8. 
The protrusion 7, the protrusion 7', the hole, or the groove constitute 
examples of the arrangement of the positioning and retaining portion in 
accordance with the present invention. However, the positioning and 
retaining portion should not be restricted to these examples. In short, 
the positioning and retaining portion may be provided with any form within 
a range in which stamping can be performed, insofar as it is capable of 
positioning and retaining the thrust bearing with respect to the housing. 
In the embodiment described above, although the thrust bearing has a 
positioning and retaining portion, such a positioning and retaining 
portion may be omitted depending on usage. In cases where the positioning 
and retaining portion is not provided, the thrust bearing may be used by 
being provided on both surfaces thereof with a sliding surface formed by a 
sliding material (e.g., a solid sliding bearing alloy) and by being fitted 
between a side surface of the housing and a side surface of a rotary 
shaft. In such an arrangement, the thrust bearing is so arranged in design 
that it can be rotated between the side surface of the housing and the 
side surface of the rotary shaft. 
FIG. 8 shows a cross-section of another embodiment of the present 
invention, in which the tops of the projections 6a are respectively formed 
into a planar shape. 
FIG. 9 shows a cross-section of still another embodiment of the present 
invention, in which are tops of the projections 6a are formed in such a 
manner that central portions thereof are slightly raised. 
It should be noted that, although in the foregoing embodiments a bimetal is 
used as the material, the material should not be restricted to the same, 
and it goes without saying that a plate formed of a solid bearing alloy 
material may be used. 
The present invention has the following advantages: 
(1) Since the collar of a bush with a collar in the prior art is separated 
in the present invention, and the thrust bearing is formed separately, 
production by stamping is faciliated, and a high dimensional accuracy can 
be obtained. As a result, a material for the thrust bearing suited to a 
given situation can be selected regardless of the radial bearing. 
Accordingly, there are advantages in that this arrangement leads to a 
reduction in costs, and that the thrust bearing excels in performance and 
is easy for user to handle. 
(2) Since a plurality of indented portions deformed in the direction of the 
thickness are provided, the rigidity of the thrust bearing increases. The 
recesses constitute passages for influx of lubricating oil to sliding 
surfaces to improve lubrication, while the indented portions are 
distributed in the circumferential direction. As a result, this thrust 
bearing exhibits a resilient structure and demonstrates a multi-pad 
effect. In addition, if projections in which central portions thereof are 
slightly raised, as shown in FIG. 9, are provided, an oil film can be 
formed more easily on the sliding surfaces. Furthermore, by virtue of 
these indented portions, misalignment can be absorbed favorably, and it 
becomes possible to assemble the thrust bearing and a housing with no gap 
by making use of the resilient effect of the thrust bearing. This results 
in an effect of checking the vibration of a shaft. Hence, the material 
costs can be reduced and the thrust bearing becomes light in weight as 
compared with a thrust bearing which is not provided with indented 
portions. 
(3) Since a positioning and retaining portion can be formed in a very 
simple arrangement, even if the thrust bearing is formed separately from 
the radial bearing, no particular inconveniences arise in installing the 
thrust bearing.