GB2104982A - Friction clutches - Google Patents

Abstract

A vehicle friction clutch has a driven plate (14) with central hub assembly (21) for mating with a gearbox input shaft (22). In order to detect wear to the driven plate friction facings (17) and (18) the hub assembly (21) carries a resilient projection (27) which is engagable with a projection (30) on the clutch pressure plate (15) after a predetermined wear has taken place to the adjacent facing (18) which exhibits maximum wear. The striking of the driven plate projection (27) with the pressure plate projection (30) will only occur during operation of the clutch and can be used to operate a warning device. <IMAGE>

Description

SPECIFICATION Friction clutches This invention relates to friction clutches and in particular to friction clutches for use on automobiles.

A problem associated with automobile friction clutches is that generally there is no way of monitoring the wear on the friction clutch driven plate and to examine the driven plate it is necessary to dismantle the vehicle gearbox from the engine. The first indications to a driver that the vehicle clutch is worn may be a slipping clutch.

It is the object of the present invention to provide a means of altering a vehicle driver that a predetermined amount of wear to a clutch driven plate has taken place.

Accordingly there is provided a friction clutch having a flywheel with a clutch cover assembly secured thereto and a driven plate having friction faces damped between flywheel and pressure plate and a central hub assembly for attachment to a gearbox input shaft, characterised in that the hub assembly on its side adjacent the pressure plate has a resilient projection thereon which is engageable with a projection of the adjacent face of the pressure plate after a predetermined wear has taken place at the friction faces, said engagement operating a warning device.

Preferably there is intermittent contact between the two projections which produces an audible warning sound.

The invention will be described by way of example and with reference to the accompanying drawings in which: Fig. 1 is a section through a friction clutch according to this invention; and Fig. 2 is a detailed section on the line Il-Il of Fig. 1.

With reference to Fig. 1 and Fig. 2 of the drawing a motor vehicle friction clutch comprises a flywheel 11 attached to the crankshaft 12 of an internal combustion engine, a cover assembly 1 3 and a driven plate 14. The driven plate 14 is clamped between the flywheel 11 and the pressure plate 1 5 of the cover assembly under the load of the diaphragm spring 1 6.

The driven plate 14 consists of a pair of annular friction facings 1 7 and 1 8 mounted on a central hub assembly 21. The hub assembly 21 comprises a hub member 25, with a facing carrier plate 26, and retainer plate 23 mounted thereon. The carrier plate and retainer plate are secured together by stop pins 29 and hub assembly is splined onto a gearbox input shaft 22.During the operational life of the clutch it is usual for the facing 18 adjacent the pressure plate 1 5 to wear at a faster rate than the facing 1 7 adjacent the flywheel 11. Indeed when a driven plate is fully worn most of the wear will have occurred in the facing 17 and only negligible wear in the facing 1 8. Therefore, during the life of the clutch, the axial position of the hub assembly retainer plate 23 will remain substantially constant relative to the flywheei 11 and the pressure plate 1 5 will gradually move axially towards the flywheel as the facing 1 8 wears.

A spring steel resilient tab 27 is held in position on the face of the retainer plate 23 adjacent the pressure plate 1 5 by one of the rivets 29. The tab 27 is arranged to be engageable with a projection 30 on the pressure plate after a predetermined amount of wear to the facing 1 8 has taken place, so that as the pressure plate 15 and driven plate 14 rotate relative to each other the tab 27 intermittently strikes the projection 30. The tab 27 is resilient and bends to allow the projection to pass over. Each time the projection 30 strikes the tab an audible noise is limited, and the constant rapid striking of the tab on the projection during gear changes will warn the vehicle driver that the driven plate is worn.

Whilst the two projections 27 and 30 are arranged to strike each other intermittently to limit an audible warning it is envisaged that after a degree of wear two projections on the driven plate and pressure plate could come into continuous contact to complete an electric circuit to illuminate a warning light.

1. A friction clutch having a flywheel with a clutch cover assembly secured thereto and a driven plate having friction faces damped between flywheel and pressure plate and a central hub assembly for attachment to a gearbox input shaft, characterised in that the hub assembly on its side adjacent the pressure plate has a resilient projection thereon which is engageable with a projection on the adjacent face of the pressure plate after a predetermined wear has taken place at the friction faces, said engagement operating a warning device.

2. A friction clutch as claimed in Claim 1, wherein the engagement of the two projections occurs intermittently when there is relative rotational movement between the cover assembly and driven plate.

3. A friction clutch as claimed in Claim 2, wherein the intermittent contact between the two projections produces an audible warning signal.

4. A friction clutch substantially as described herein and as illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Friction clutches This invention relates to friction clutches and in particular to friction clutches for use on automobiles. A problem associated with automobile friction clutches is that generally there is no way of monitoring the wear on the friction clutch driven plate and to examine the driven plate it is necessary to dismantle the vehicle gearbox from the engine. The first indications to a driver that the vehicle clutch is worn may be a slipping clutch. It is the object of the present invention to provide a means of altering a vehicle driver that a predetermined amount of wear to a clutch driven plate has taken place. Accordingly there is provided a friction clutch having a flywheel with a clutch cover assembly secured thereto and a driven plate having friction faces damped between flywheel and pressure plate and a central hub assembly for attachment to a gearbox input shaft, characterised in that the hub assembly on its side adjacent the pressure plate has a resilient projection thereon which is engageable with a projection of the adjacent face of the pressure plate after a predetermined wear has taken place at the friction faces, said engagement operating a warning device. Preferably there is intermittent contact between the two projections which produces an audible warning sound. The invention will be described by way of example and with reference to the accompanying drawings in which: Fig. 1 is a section through a friction clutch according to this invention; and Fig. 2 is a detailed section on the line Il-Il of Fig. 1. With reference to Fig. 1 and Fig. 2 of the drawing a motor vehicle friction clutch comprises a flywheel 11 attached to the crankshaft 12 of an internal combustion engine, a cover assembly 1 3 and a driven plate 14. The driven plate 14 is clamped between the flywheel 11 and the pressure plate 1 5 of the cover assembly under the load of the diaphragm spring 1 6. The driven plate 14 consists of a pair of annular friction facings 1 7 and 1 8 mounted on a central hub assembly 21. The hub assembly 21 comprises a hub member 25, with a facing carrier plate 26, and retainer plate 23 mounted thereon. The carrier plate and retainer plate are secured together by stop pins 29 and hub assembly is splined onto a gearbox input shaft 22.During the operational life of the clutch it is usual for the facing 18 adjacent the pressure plate 1 5 to wear at a faster rate than the facing 1 7 adjacent the flywheel 11. Indeed when a driven plate is fully worn most of the wear will have occurred in the facing 17 and only negligible wear in the facing 1 8. Therefore, during the life of the clutch, the axial position of the hub assembly retainer plate 23 will remain substantially constant relative to the flywheei 11 and the pressure plate 1 5 will gradually move axially towards the flywheel as the facing 1 8 wears. A spring steel resilient tab 27 is held in position on the face of the retainer plate 23 adjacent the pressure plate 1 5 by one of the rivets 29. The tab 27 is arranged to be engageable with a projection 30 on the pressure plate after a predetermined amount of wear to the facing 1 8 has taken place, so that as the pressure plate 15 and driven plate 14 rotate relative to each other the tab 27 intermittently strikes the projection 30. The tab 27 is resilient and bends to allow the projection to pass over. Each time the projection 30 strikes the tab an audible noise is limited, and the constant rapid striking of the tab on the projection during gear changes will warn the vehicle driver that the driven plate is worn. Whilst the two projections 27 and 30 are arranged to strike each other intermittently to limit an audible warning it is envisaged that after a degree of wear two projections on the driven plate and pressure plate could come into continuous contact to complete an electric circuit to illuminate a warning light. CLAIMS

1. A friction clutch having a flywheel with a clutch cover assembly secured thereto and a driven plate having friction faces damped between flywheel and pressure plate and a central hub assembly for attachment to a gearbox input shaft, characterised in that the hub assembly on its side adjacent the pressure plate has a resilient projection thereon which is engageable with a projection on the adjacent face of the pressure plate after a predetermined wear has taken place at the friction faces, said engagement operating a warning device.

2. A friction clutch as claimed in Claim 1, wherein the engagement of the two projections occurs intermittently when there is relative rotational movement between the cover assembly and driven plate.

3. A friction clutch as claimed in Claim 2, wherein the intermittent contact between the two projections produces an audible warning signal.

4. A friction clutch substantially as described herein and as illustrated in the accompanying drawings.