GB2246183A

GB2246183A - Thrust washer

Info

Publication number: GB2246183A
Application number: GB9015747A
Authority: GB
Inventors: Peter Adalpho Connor
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-07-17
Filing date: 1990-07-17
Publication date: 1992-01-22
Anticipated expiration: 2010-07-17
Also published as: GB9015747D0; GB2246183B

Abstract

A thrust washer which can accommodate a range of tolerances in a single washer and provide a specific axial thrust, comprises a spring (3) consisting of an annulus of a resilient thin sheet material having a plurality of radially spaced apertures (5, Fig 1) therearound, the annulus being deformed into an S-shape in cross-section. By varying the number and size of the apertures, the loading of the washer can be set to a desired value. The spring is preferably located between two annular end plates or shells (6 and 7). <IMAGE>

Description

THRUST WASHER This invention relates to a thrust washer, for example for use in gearboxes.

Thrust washers are used to reduce end float or axial movement of rotary members in machinery, for example gears and gearshafts in gearboxes. Typically, thrust washers consist of a simple annulus of a hardened bearing material, a range of such washers of different thicknesses being provided so that the appropriate washer or washers may be selected to compensate for manufacturing tolerances. In applications where high precision is required, for example in automatic gearboxes for automobiles, the components are measured during assembly and the thrust washers are selected according to the measured end-float. This requires the use of skilled workers and is open to error. The conventional assembly method is also costly.

The present invention provides a thrust washer which can accommodate a range of tolerances in a single washer and provide a specific axial thrust. The thrust washer is suitably designed to occupy an engineered space between internal dynamic mechanisms and their end bearing positions in vehicle transmission systems, where the clearances can vary considerably due to the aggregate tolerance variations.

Accordingly, the invention provides a thrust washer comprising a spring consisting of an annulus of a resilient thin sheet material having a plurality of radially spaced apertures there around, the annulus being deformed such that the outer and inner edges thereof lie in respective planes which are spaced apart axially and relatively movable axially in response to an axial load on the washer.

Preferably each side of the annulus, when viewed in cross-section, is generally S-shaped.

The spring is preferably located between two annular end plates or shells to form a thrust washer assembly. To prevent relative rotation of the components of the assembly, the inner edge of the annulus may be secured to one of the shells and the outer edge may be secured to the other of the shells, for example by crimping the edges of the spring into the shells. Alternatively, each shell may be provided with posts which engage in the apertures in the spring to prevent rotation whilst still permitting compression.

The shells may be of a bearing metal such as a bronze bearing metal. The spring is suitably formed of a spring steel, and may be formed by stamping a blank from a steel sheet, and either pressing to deform the blank into shape followed by punching to cut-out the apertures, or punching the flat blank and then deforming. The spring is then suitably annealed to ensure that it has the necessary spring characteristics.

The axial thrust provided by the thrust washer may be selected by varying the size and number of the apertures, and the thickness of the sheet material from which the spring is formed.

The thrust washer of the invention may be used to advantage where the application of selective thickness of conventional axial thrust washers is not convenient. For example, when a closing surface is installed, access to check internal clearances is thereby removed. By designing into the assembly a datum space from which the tolerance variations can be computed, a thrust washer in accordance with the invention, of appropriate dimensions and axial thrust rating, may be inserted. The thrust washer of the invention will also perform a noise dampening action.

Reference is made to the drawings, in which: Figures 1 and 2 are respectively front and side elevations of the annular spring forming part of a thrust washer in accordance with one embodiment of the invention; Figure 3 is a cross-sectional side view of the assembled thrust washer; Figure 4 is an enlarged view of the thrust washer shown in Figure 3; Figures 5 and 6 are respectively front and side elevations of an annular spring forming part of a thrust washer assembly according to a second embodiment of the invention; Figure 7 is an enlarged view of the upper part of the spring shown in Figure 6; Figure 8 is a side elevation of one bearing shell of the assembly; Figure 9 is a side elevation of the completed assembly; Figure 10 is a cross-sectional side elevation of the other bearing shell of the assembly shown in Figure 9;; Figure 11 is a partially cut-away front elevation showing the two end shells of a thrust washer according to a further embodiment of the invention; and Figure 12 is a sectional side-elevation of the thrust washer assembly of which Figure 11 shows the bearing shells.

Referring first to Figures 1 - 4, the spring 1 is formed by punching an annulus from thin sheet steel of 35 S.W.G. (0.2134mm thickness). The annulus is then pressed to form a profile such that, in cross-section, at each side of the central aperture thereof an S-shaped configuration 3 is formed with a flange 2 and 4 at each end of the S-shape lying in a plane normal to the axis of the spring 1. A plurality of pairs of apertures 5, for example twelve equally-spaced pairs of apertures, are then punched through the spring in the configuration illustrated in Figure 1.

Two bearing plates or shells 6 and 7 are formed from high ductility high tensile alloy steel. Each has a portion 6a or 7a which, during assembly, is folded over onto the respective flange 2 or 4 of the spring 1 and then clinched to give a high torque resistance to ensure that relative rotation of the three components does not occur in use. The two shells 6 and 7 have different internal diameters, the washer being suitable for applications where the larger bore shell engages by press-fit onto the machined diameter of a bearing case and is fixed, while the smaller bore is a running fit on a shaft of a rotating mechanism. The configuration shown can fit into a very limited space.

In use, an axial load on the shell 7 having the smaller internal diameter causes the spring element 1 to compress by a rolling action about the S-shaped portion 3, the width of the lands 8 between the apertures 5 determining the extent to which the lands 8 can tend to spread outwardly to permit the rolling action to take place and thereby determining the loading of the thrust washer.

In an example of a thrust washer according to this embodiment of the invention, having an overall external diameter of 90mm and with the shell 7 designed to fit onto a 60mm diameter rotating shaft, the pre-load during assembly of the spacer is 4kg, the recoverable deflection 3mm, the load at 2mm deflection is 8kg and at full deflection llkg.

Referring now to Figures 5 to 10, illustrating a second embodiment of the invention, the spring 10 is formed by punching an annular blank from 35 S.W.G. sheet steel as in the first embodiment illustrated in Figure 1 to 4. However, apertures 11 spaced radially around the spring are also formed at the punching stage before the spring is pressed into the configuration seen from Figures 6 and 7, i.e. having a generally S-shaped cross-sectional curved section 12 terminating at each end in a curved annular flange 13 or 14 adapted to be a snap fit into a corresponding groove 15, (Figure 8) and 16 (Figure 10) in the two shells 17 and 18, which are formed of bronze alloy bearing material. The completed assembly may be seen from Figure 9.The rear shell 18 has a series of axially extending pegs 19 spaced around the inner edge thereof which engage in corresponding grooves formed in the inner surface of the front shell 17. This prevents relative rotation of the component parts of the assembly. As with the first embodiment, the washer is designed to fit between a restating mechanism and its static bearing surface, and the front shell 17 engages by press-fit onto a machined diameter of the bearing case. The snap-in construction of the assembly permits the use of different rated springs for different axial thrust load conditions.

By way of example, an assembly as illustrated in Figure 5 to 10, having an overall diameter of 102mm and an internal diameter of 74mm, has a pre-load of 5kg, a recoverable deflection of 3mm, and a load at 2mm deflection of lOkg.

Figures 11 and 12 illustrate a thrust washer assembly intended for siting between two sub-assembly mechanisms.

The internal diameter is a running fit on a 34mm shaft, for example, and the front 20 and rear 21 shells are of bronze bearing material to provide low friction good wearing qualities between the adjacent surfaces. The spring 22 is of generally similar configuration to that shown in Figures 5 to 10, with curved annular flanges 23 and 24 arranged to snap-fit into corresponding grooves in the two shells, where they are each an interference fit.

Figure 11 shows the two shells 20 and 21, the Figure being partially cut-away to show the one shell 20 behind the other 21. In this case, relative rotation of the component parts of the thrust washer assembly is prevented by the provision of matching pegs 25 and 26 extending from the front and rear shells 20 and 21 respectively. The pegs are arranged in pairs, the pairs being equally spaced so that the pair of pegs 25 on the front shell 20 locate equi-distantly between adjacent pairs of pegs 26 on the rear shell 21. The configuration is such that a peg 25 from the front shell 20 and a peg 26 from the rear shell 21 project through each of the apertures 27 in the spring 22. This arrangement prevents relative rotation of the component parts.

By way of example, for a thrust washer of the configuration illustrated in Figures 11 and 12 having an external diameter of 55mm and an internal diameter of 34mm, the pre-load is 2kg, the recoverable deflection 2.5mm, and the load at 1.6mm deflection is 4kg.

The applications described above require means for preventing relative rotation of the components of the thrust washer. However, the thrust washer of the invention, having an appropriate dimensional and performance specification, may also ideally be fitted between a rotating element and its end bearing, where this is an angular contact ball bearing and where a prescribed axial end thrust has to be maintained. In this particular application where the inner ring of the bearing rotates with the shaft, whilst the outer ring of the bearing remains stationary in the bearing housing, the one shell of the thrust washer is designed to make contact with the inner ring of the bearing only, while the other shell of the thrust washer makes contact with the rotating element. In such a location where all the items are rotating in unison, it is unnecessary to include in the design of the thrust washer a means of restricting relative rotation of the parts of the thrust washer assembly.

Claims

CLAIMS 1. A thrust washer, comprising a spring consisting of an annulus of a resilient thin sheet material having a plurality of radially spaced apertures therearound, the annulus being deformed such that the outer and inner edges thereof lie in respective planes which are spaced apart axially and relatively movable axially in response to an axial load on the washer. 2. A thrust washer according to Claim 1, wherein each side of the annulus, when viewed in cross-section, is generally S-shaped. 3. A thrust washer according to Claim 1 or 2, wherein the spring is located between two annular end plates or shells. 4. A thrust washer according to Claim 3, wherein the inner edge of the spring is secured to one of the shells and the outer edge is secured to the other of the shells. 5. A thrust washer according to Claim 4, wherein the edges of the spring are secured to the respective shells by crimping the edges of the spring into the shells. 6. A thrust washer according to Claim 3, wherein each shell is provided with posts which engage in the apertures in the spring to prevent rotation of the shells relative to the spring while still permitting compression of the spring. 7. A thrust washer according to any of Claims 3 to 6, wherein the shells are formed from a bearing metal. 8. A thrust washer according to Claim 7, wherein the shells are formed from bronze bearing metal. 9. A thrust washer according to any preceding claim, wherein the spring is formed of spring steel. 10. A thrust washer, substantially as described with reference to, or as shown in, the drawings. AMENDMENTS TO THE CLAIMS HAVE BEEN FILED ASFOLLOWS.

1. A thrust washer, comprising a pair of annular end plates or shells with a spring mounted therebetween, the spring consisting of an annulus of a resilient thin sheet material having a plurality of apertures spaced therearound, the annulus being deformed such that the outer and inner edges thereof lie in respective planes which are spaced apart axially and relatively movable axially in response to an axial load on the washer.

2. A thrust washer according to Claim 1, wherein each side of the annulus, when viewed in cross-section, is generally S-shaped.

3. A thrust washer according to Claim 1 or 2, wherein the inner edge of the spring is secured to one of the shells and the outer edge is secured to the other of the shells.

4. A thrust washer according to Claim 3, wherein the edges of the spring are crimped into the respective shells.

5. A thrust washer according to Claim 1 or 2, wherein each shell is provided with posts which extend through the apertures in the spring to prevent rotation of the shells relative to the spring while still permitting compression of the spring.

6. A thrust washer according to any preceding claim, wherein the shells are formed from a bearing metal.

7. A thrust washer according to Claim 6, wherein the shells are formed from bronze bearing metal.

8. A thrust washer according to any preceding claim, wherein the spring is formed of spring steel.

9. A thrust washer according to any preceding claim, wherein the width of the lands between the apertures is selected according to the desired axial loading and compression of the washer.

10. A thrust washer according to any preceding claim, wherein two sets of apertures are provided, the sets being spaced apart radially.

11. A thrust washer, substantially as described with reference to, or as shown in, the drawings.