GB2209577A

GB2209577A - Torsional damper

Info

Publication number: GB2209577A
Application number: GB8820947A
Authority: GB
Inventors: Denzil John William Symonds
Original assignee: Automotive Products PLC
Current assignee: Automotive Products PLC
Priority date: 1987-09-09
Filing date: 1988-09-07
Publication date: 1989-05-17
Also published as: GB8820947D0; GB8721155D0

Abstract

A torsional damper, for example for damping vibrations which arise in vehicle engines and transmissions, comprises a hub (11), a flange (13) extending radially outwardly from the hub, and an outer member comprising an annular side plate (15, 16) arranged one to each side of the flange and having a central aperture such that the side plate surrounds the hub with a clearance, the side plate being capable of limited angular movement relative to the flange. At least one compression coil spring (22) is directed circumferentially of the damper and acts between the flange (13) and the side plate (15, 16) to control the angular movement. The spring (22) is made from a material which has a longer cross- sectional dimension in the direction of a major axis (A) of the section and a shorter sectional dimension in the direction of a minor axis (B) of the section. Axes (A) and (B) may be inclined to the spring axes (Fig 4, 5). <IMAGE>

Description

TORSIONAL DAMPER The present invention relates to a torsional damper particularly, but not exclusively, for damping vibrations which arise in vehicle engines and transmissions.

Increasingly, torsional vibration dampers are being used to solve various drive line vibration problems. However, such torsional vibration dampers take up space in a clutch driven plate and it is therefore desirable to provide torsional vibration dampers or parts thereof which occupy as little space as possible. One reason why space is important is that in the interests of reducing costs, weight and size of engine - transmission combinations, it is desirable to be able to fit assemblies such as friction clutches into a small space.

It is an object of the present invention to provide a torsional damper incorporating a circumferentially directed spring which occupies less space while maintaining the performance of the spring.

According to one aspect of the present invention there is provided a torsional damper comprising a hub, a flange extending radially outwardly from the hub, an outer member comprising an annular side plate arranged to one side of the flange and having a central aperture such that the side plate surrounds the hub with a clearance, the side plate being capable of limited angular movement relative to the flange, and at least one compression coil spring directed circumferentially of the damper and acting between the flange and the side plate to control the angular movement, the spring being made from a material which has a longer cross-sectional dimension in the direction of a major axis of the section and a shorter sectional dimension in the direction of a minor axis of the section.

The major axis may extend substantially parallel to the axis of the spring. Alternatively, the major axis may be inclined relative to the axis of the spring.

The material forming the spring may be substantially rectangular in section. Alternatively, the end portions of the material in the direction of the major axis may be substantially semi-circular in section.

According to a further aspect of the present invention there is provided a friction clutch driven plate incorporating a torsional damper as defined above.

For a better understanding of the present invention and to show more clearly how it may be carried into effect reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 is a cross-sectional view of a clutch driven plate incorporating a torsional vibration damper according to the present invention; Figure 2 is an elevational view, partly cut away, of the damper spring shown in Figure 1; Figure 3 is an elevational view, partly cut away, of an alternative damper spring.

Figure 4 is an elevational view, partly cut away, of a further alternative damper spring; and Figure 5 is an elevational view, partly cut away, of another alternative damper spring.

The clutch driven plate shown in Figure 1 comprises a hub 11 having splines 12 for driving a gearbox input shaft. A radial flange 13 is formed integrally on hub 11.

A friction facing carrier 14 incorporates two side plates 15 and 16, one to each side of flange 13. The side plates 15,16 are rotatably mounted on hub 11 by way of bearing elements 26,27 respectively. The side plates are spaced apart from each other and joined together by stop pins 17.

The stop pins lie within circumferentially elongated openings 18 in the outer periphery of the flange to limit angular deflection between the flange 13 and the friction facing carrier. The side plates 15 and 16 are provided with mutually aligned windows 19 and 20 and the flange 14 has corresponding windows 21. Circumferentially directed compression coil springs 22 are arranged in these windows in such a way as to provide circumferentially acting torsion damping springing. Springs 22 control the load required to deflect the flange 13 circumferentially with respect to the friction facing carrier 14 within limits set by the stop pins in openings 18. Springs 22 will be described in more detail hereinafter.

The friction facing carrier 14 also incorporates a ring of outwardly extending spring segments 23 carrying friction facings 24 and 25.

Spring 22 is shown in more detail in Figure 2 and it can be seen that in contrast to the usual circular cross-section, the spring is substantially rectangular in cross-section having a major axis A extending in the direction of the longer sectional dimension and a minor axis B extending in the direction of the shorter sectional dimension. The major axis A extends parallel to the axis of the spring.

The use of such a spring having an axial cross-sectional dimension greater than the radial cross-sectional dimension permits the index ratio (mean diameter of spring/radial cross-sectional thickness) to be kept high. That is the radial sectional thickness is small for the mean diameter of the spring. Such a spring can provide a bump stop when compressed to its limit and can replace the function of the stop pins 18 in this respect. Such a spring can have a smaller overall diameter compared with a conventional spring of circular cross-section. This enables a saving of space to be achieved compared with the use of a conventional spring.

The spring shown in Figure 3 is similar to the spring shown in Figure 2 in that the axial cross-sectional dimension of the spring is greater than the radial cross-sectional dimension thereof. However, the spring 28 shown in Figure 3 has substantially semi-circular end portions in the axial directions.

The spring shown in Figure 4 is similar to the spring shown in Figure 2. However, the material of the spring 29 shown in Figure 2 has a major axis A which is not parallel to the axis of the spring, but is inclined thereto with the angle of inclination preferably being relatively small. The use of such a spring also provides the benefits of a high index ratio and thus a relatively small mean diameter.

The spring shown in Figure 5 is similar to the spring shown in Figure 4 in that the material forming the spring has a major axis A extending in the direction of the longer sectional dimension and a minor axis B extending in the direction of the shorter sectional dimension, the major axis A being inclined relative to the axis of the spring.

However, the spring 30 shown in Figure 5 has substantially semi-circular end portions in the direction of the major axis A. In addition to the benefits of a high index ratio and a relatively small overall diameter, the overall length of the spring can be reduced and this can be beneficial for certain energy/space requirements.

Clearly it is also possible for the spring to have other cross-sectional configurations provided that the sectional dimension in the direction of the major axis is greater than the sectional dimension in the direction of the minor axis.

Claims

1. A torsional damper comprising a hub, a flange extending radially outwardly from the hub, an outer member comprising an annular side plate arranged to one side of the flange and having a central aperture such that the side plate surrounds the hub with a clearance, the side plate being capable of limited angular movement relative to the flange, and at least one compression coil spring directed circumferentially of the damper and acting between the flange and the side plate to control the angular movement, the spring being made from a material which has a longer cross-sectional dimension in the direction of a major axis of the section and a shorter sectional dimension in the direction of a minor axis of the section.

2. A torsional damper as claimed in claim 1, wherein the major axis extends substantially parallel to the axis of the spring.

3. A torsional damper as claimed in claim 1, wherein the major axis is inclined relative to the axis of the spring.

4. A torsional damper as claimed in any one of the claims 1 to 3, wherein the material forming the spring is substantially rectangular in section.

5. A torsional damper as claimed in any one of claims 1 to 3, wherein the end portions of the material in the direction of the major axis are substantially semi-circular in section.

6. A torsional damper substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

7. A friction clutch driven plate incorporating a torsional damper as claimed in any preceding claim.