GB2157398A - Friction clutch driven plate - Google Patents

Abstract

This invention relates to clutch driven plates for motor vehicles and which comprise a hub 11 having a flange 12 which is connected to an intermediate driving plate 24 through a toothed connection 13, 25 incorporating circumferential free play. The intermediate plate 24 is connected to a friction facing carrier 14 carrying friction facings 19 and 21 by means of main torsion damping springs 27. Auxiliary springing providing some circumferential movement under very light loads is provided by auxiliary springs 32 arranged in windows in plate members 35 and 36 connected respectively to the intermediate plate and the hub. An inertia damper 39 is mounted on the hub 11 and held by a dished spring washer 44 against bearing member 43 to provide a friction drive between the hub and the inertial mass of the damper. The inertia damper, particularly in conjunction with the auxiliary springing tends to damp out idle rattle in a gearbox associated with the clutch driven plate. <IMAGE>

Description

SPECIFICATION Friction clutch driven plate This invention relates to friction clutch driven plates and particularly, but not exclusively, to driven plates which are utilised in the friction clutches of automobiles.

A problem associated with some automobiles is that during the periods when the transmission drive is under no load, rotary oscillations occur in the gearbox producing a phenomenon known as idle-rattle.

In order to damp out the vibrations which generate idle-rattle it is known to utilise a friction clutch driven plate in which the torque load through the driven plate passes through two sets of damping springs arranged in series with each other. Very light loads applied to the driven plate are taken through soft auxiliary vibration damping springing.

When the limited angular movement controlled by the auxiliary damping springing has been taken up, normal drive load passes through a set of main torsion damping springs. In this way, very soft springing is provided over a limited range of movement for very light loads and this arrangement tends to prevent idle-rattle. Such a driven plate is known from French Patent Publication No. 1501465.

There have also been other proposals for providing very soft springing during the initial part of the movement between a hub and a friction facing carrier.

Despite the various attempts to overcome idle rattle, this is still a problem which exists in some installations.

An object of the present invention is to provide a friction clutch driven plate incorporating an improved torsional vibration damping means.

According to the present invention there is provided a friction clutch driven plate comprising a hub, a friction facing carrier mounted on the hub co-axially therewith for limited relative angular movement, torsion damping springing interposed between the hub and the carrier and an inertia damper connected to the hub.

Preferably the inertia damper is connected to the hub through a friction drive.

Preferably the torsion damping springing is such that initial movement of the carrier with respect to the hub from a central position is controlled by springing much softer than the main torsion damping springing. The soft springing is intended to provide control over idle rattle and the inertia damper is intended to provide further control over idle rattle, particularly in conjunction with operation of the soft springing.

The hub may be provided with main torsion damping springing to damp out normal load fluctuations when a vehicle including the driven plate is being driven and with auxiliary torsion damping springing to control limited movement against low resistance for idle rattle damping.

An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a cross section through a friction clutch driven plate in accordance with the invention; and Figure 2 is an end elevation in the direction of arrow II showing the same driven plate but with an inertia damper removed for clarity.

The driven plate incorporates a hub 11 splined at iO for mounting on and driving a gearbox input shaft (not shown). Hub 11 incorporates an external radial flange 1 2 which is provided with outwardly directed teeth 1 3 around its periphery.

The clutch driven plate also incorporates a friction facing carrier 1 4 which in turn includes two axially spaced annular side plates 1 5 and 1 6 which are connected together by three equally spaced stop pins 1 7. The stop pins are in effect large shouldered rivets. A friction facing carrier plate 1 8 is held against the side plate 1 5 by being rivetted thereto by the stop pins 1 7. This carrier plate extends out beyond the side plates and carries around its outer periphery two annular friction facings 19 and 21. As seen in Figure 2, carrier plate 1 8 is divided near its outer periphery into eight segments 22 to which the friction facings are secured by rivets 23.Side plate 1 5 extends inward towards the hub 11 and has a central aperture corresponding to the outer diameter of the hub 11 so that it acts as a guide for constraining the friction facing carrier with respect to the hub.

A driving connection between the friction facing carrier 14 and the hub 11 includes an intermediate drive means constituted by a plate 24 which will hereinafter be referred to as the intermediate plate. The intermediate plate is generally annular and around its inner periphery incorporates inwardly directed teeth 25 which mesh, by way of a circumferential clearance best seen in Figure 1, with the outwardly directed teeth 1 3 of the hub 11.

The clearance provides a lost-motion connection between hub and intermediate plate which in this example allows relative movement of 6o.

The intermediate plate is also provided with six circumferentially directed windows such as the window 26 of figure 2 which receive main torsion damping springs 27. Torsion damping springs 27 are also received in windows 28 and 29 in the side plates 1 5 and 1 6 respectively. As can be seen in figure 1, the six sets of windows are of varying lengths and incorporate springs of differing lengths and stiffnesses. As is conventional, some of the windows in the intermediate plate have a circumferential clearance with respect to their associ ated springs so they do not come into effect until after some relative movement between the intermediate plate and the carrier 14.The main torsion damping springs such as 27 in their respective windows 26, 28 and 29 constitute a driving connection between the friction facing carrier 14 and the intermediate plate 24 which operates in a manner to be described subsequently.

The driven plate also incorporates auxiliary torsion damping spring connection between the intermediate plate 14 and the hub 11 to control the relative angular rotation between the hub and the intermediate plate which is permitted by the teeth 1 3 and 25. This connection is effected by three circumferentially directed auxiliary springs 32 which, as shown in figure 2, are arranged in windows in plate members 35 and 36 respectively. Plate member 36 closely surrounds the hub 11 and is held against rotation with respect to the hub by virtue of lugs 37 engaged in slots 38.

Plate member 35 is freely rotatable on the hub 11 but has outward annular extensions terminating in bent over lugs 40 which engage in notches 30 at the inner edges of three of the windows such as 26 to provide a positive driving connection between plate member 35 and the intermediate plate 24.

Thus the auxiliary springs 32 provide a driving connection between the intermediate plate 24 and the hub 11 through the intermediary of the plate members 35 and 36. The significance of this driving connection and its relationship with the main driving connection through springs 27 will be described subsequently.

In accordance with the present invention the hub 11 also carries an inertia damper 39 constituted by a carrier plate 41 rotatable on hub 11 and an annular inertia weight 42 welded to plate 41. At its mounting with the hub 11, the carrier plate 41 is separated from plate member 36 by a friction washer 43 and is held against this friction washer by a dished spring clip 44 arranged in a peripheral groove near the outer edge of the hub 11.

The relative location of the friction facing carrier, hub and intermediate member includes several axially directed annular bearing members and associated axially directed annular springs. In particular, the inner extension of the side plate 1 5 of friction facing carrier 14 is held in position against the side of flange 1 2 by a bearing member 45, an axially directed annular spring 46 and a circlip 47 providing reaction for spring 46. This arrangement provides location between the hub 11 and friction facing carrier 1 4.

An annular bearing member 48 is interposed between side plate 1 5 and intermediate plate 24. On the opposite side of intermediate plate 24, an annular spring 49, the plate member 35 and a bearing member 50 are interposed between the intermediate plate 24 and side plate 16. By this means, the intermediate plate is located axially with respect to the friction facing carrier 14 and the plate member 35 is also located axially.

The arrangement described allows limited angular movement between the hub and the intermediate plate and between the intermediate plate and the friction facing carrier under the control of torsion damping springs. The nature of this movement as torque is applied to the friction facings of the friction facing carrier from an engine for transmission through the hub to a gearbox is described in greater detail in our co-pending Italian Patent Application No. 24663A/82. The following brief description should suffice for the purposes of the present invention. The main and auxiliary torsion damping springs hold the components of the driven plate in the rotational positions shown, with clearance for movement in both angular directions.When a light load or small displacement is applied to the carrier 14, this is transmitted through the two springs in windows 31 to intermediate plate 24 and from the intermediate plate 24 through auxiliary springs 32 to the hub. Because the springs 32 are much softer than springs 27, there is a direct drive without spring compression through the springs 27 and the initial angular movement occurs between intermediate plate and hub under the control of auxiliary springs 32. This is the situation for movement up to 3" in either direction as allowed by the co-operating teeth 1 3 and 25 of the hub and intermediate plate respectively.After this movement of 3" in either direction, teeth 1 3 and 25 allow no further relative rotation between hub and intermediate member so the torque required to produce further deflection increases more rapidly because this deflection is associated with compression of main damping springs such as 27 in window 31. As previously described, some of the main damping springs may come into operation at different stages of rotation due to variations in their lengths and in the width of the windows in the intermediate plate 24. This results in stepped increases in the stiffness of the main torsion damping springing.

One or more of the bearing members 45, 48 or 50 may be made of a friction material so as to provide a significant degree of friction between the relatively rotatable parts of the driven plate and thus assist in the damping out of vibrations. Generally, some friction damping is desirable in conjunction with the movement controlled by the main torsion damping springs.

The present invention is concerned particularly with the inter-relationship between the initial relative movement between the friction facing carrier and hub controlled by the auxiliary damping springing and the action of the inertia damper. During an acceleration phase of a torsional vibration generated by the vehicle engine and with the engine gearbox in neutral, the friction facing carrier is accelerated at the same rate as the engine. The hub tends to lag behind the engine due to the drive through the auxiliary torsion damping springing to the hub, the shaft driven thereby, associated inertia in the gearbox connected to this shaft and the inertia damper 39. For vibratory accelerations greater than a predetermined level, slip occurs between the hub and plate 41 of the inertia damper, thereby introducing friction damping into the system. Also during the transition from auxiliary to main torsion damping springing which normally imposes a very sudden acceleration on the hub, the inertia of the damper 39 acting through its friction drive can moderate this sudden acceleration and help to provide smooth operation. It is believed that due to these effects, the provision of the inertia reduces the tendency to idle rattle. It has been found that idle rattle is particularly difficult to overcome with diesel engined vehicles and the present invention is particularly useful with such engines.

Although the drawings show an inertia damper incorporating a friction drive, other forms of drive may be employed. For example the friction drive could be replaced by a viscous drive or a spring based drive or any combination of these.

Claims (7)

1. A friction clutch driven plate comprising a hub, a friction facing carrier mounted on the hub coaxially therewith for limited relative angular movement, torsion damping springing interposed between the hub and the carrier and an inertia damper connected to the hub.

2. A friction clutch driven plate as claimed in claim 1 wherein the inertia damper incorporates a friction drive through which it is connected to the hub.

3. A friction clutch driven plate as claimed in claim 1 or claim 2 wherein the torsion damping springing is such that initial movement of the carrier with respect to the hub from a central position is controlled by springing much softer than the main torsion damping springing.

4. A friction clutch driven plate as claimed in claim 3 wherein the hub is provided with main torsion damping springing to damp out normal load fluctuations when the vehicle including the driven plate is being driven and with auxiliary torsion damping springing to provide limited relative movement against low resistance to provide idle rattle damping.

5. A friction clutch driven plate as claimed in any one of the preceding claims wherein the inertia damper comprises a plate mounted for rotation on the hub and an annular inertia weight secured to the hub.

6. A friction clutch driven plate as claimed in claim 5 wherein the plate is urged axially by a spring to provide friction between the plate and the hub.

7. A friction clutch driven plate substantially as described with reference to and as illustrated by the accompanying drawings.