DUAL PLATE FRICTION CLUTCH

Abstract: A dual plate friction clutch has opposed hydraulic cylinders (16,17) and a single interposed reaction plate (13). The plate (13) is driven by a plurality of cylindrical pins (25) extending between the housings of the cylinders (16,17) and passing through apertures of the plate (13). Pressure plates (26) are provided between each cylinder and a respective driven member of the clutch, the plates (26) also being driven by the pins. One or more pins (25) may be hollow to provide a fluid feed duct to one of the hydraulic cylinders.

Description: "Dual Plate Friction Clutch" This invention relates to fluid actuated dual plate friction clutches particularly though not exclusively for use in motor vehicle automatic transmissions. Such clutches provide two seperately engagable output drives from a single input drive. In motor vehicle transmissions it is important that components be as small as possible for maximum space utilisation. It is also desirable that wearing components, such as those having friction material facings, are renewable without major dismantling of the transmission. British Patent Specification No. 594 950 discloses a compact dual plate clutch arrangement having facing hydraulic cylinders and a single interposed reaction member. Pressure plates are inserted between the pistons of the respective cylinder and a respective driven plate, the plates being driven and guided for movement axially of the clutch by lugs engaged in slots of the reaction member. One or more fluid ducts are also provided in the reaction member for the passage of fluid under pressure from one side of the clutch to the other. The lugs and slots of the prior art construction are difficult and expensive to manufacture to the required standard. The present invention provides improved means for driving and guiding the pressure plates in the clutch. Convenient means for supplying fluid under pressure from one side of the clutch to the other are also provided. According to the present invention there is provided a dual plate friction clutch comprising a drive member, a cover member fixed for rotation with the drive member, two facing hydraulic cylinders provided one each in said drive and cover members, an annular reaction member extending between the cylinders and fixed for rotation with the drive member, two driven members interposed one each between the reaction member and a respective hydraulic cylinder and two pressure plates fixed for rotation with the drive member and interposed one each between a respective driven member and hydraulic cylinder, characterised thereby that a plurality of guide pins are provided between said drive and cover members, the guide pins passing through apertures of the pressure plates to both hold the pressure plates for rotation with the drive member and guide the pressure plates for movement axially of the clutch. Such pins eliminate the need for lugs and slots or splines or keyways which have been used hitherto to locate and guide the pressure plates in the drive member. Cylindrical pins may be used and made from bar stock; the corresponding apertures are drilled in the drive member and pressure plates on an indexing machine tool. Relatively expensive milling of slots or splines for the pressure plates is eliminated. In a preferred embodiment one or more of the guide pins is hollow to provide part of a fluid feed duct to one of the hydraulic cylinders. Such an arrangement reduces the need for accurate machining between component part of the driven member to define the feed duct. Other features of the invention are disclosed in the following description of a preferred embodiment shown, by way of example only, in the accompanying drawing which is an axial section through a dual plate clutch according to the invention. With reference to the drawing there is shown a dual wet plate clutch for use in a motor vehicle transmission. An input shaft 11 has a generally bowl shaped clutch drive member 12 splined thereto. The outer wall of the drive member 12 is internally splined to receive a reaction plate 13 and a cover 14 which are retained against relative movement by a circlip 15. No relative axial movement between the drive member 12, reaction plate 13 and cover 14 is permitted and the splines need to be sufficiently accurately machined only to hold the members together against relative rotation. Alternative means, such as bolts could be used to retain the members together. Both the drive member 12 and cover 14 define hydraulic cylinder 16, 17 having facing pistons 18,19. Clutch driven plates 21,22 are disposed respectively between the pistons 18,19 and the reaction plate 13. The driven plates 21,22 are splined to respective output shafts 23,24 co-axial about the input shaft 11. A plurality of cylindrical pins 25 retained in co-operating bore of the drive member 12 and cover 14 support supplementary pressure plates 26 between each piston and its respective driven plate. Each plate 26 is axially movable on the pins 25 to clamp the respective driven plate on outward movement of the appropriate piston. The pistons 18,19 are preferably die cast in aluminium for accuracy and low weight whereas the plates 13 and 26 are of steel to provide uniform friction properties and low wear rate. The transmission housing 27 and end covers 28,29 enclose the clutch, bearings 31-33 supporting the shafts for rotation. Each hydraulic cylinder 16,17 has a respective fluid feed duct 34,35 from the end cover 29 which serves as a manifold. The duct for cylinder 17 passes conveniently through one or more of the pins 25. The cylinders each having a centrifugal relief valve 36 (only that for cylinder 17 shown) to prevent partial engagement of a driven plate due to centrifugal build up of pressure in the cylinders. The valves comprise a ball 37 and tapered seat 38. Under pressure the ball is forced against its seat to close the valve, centrifugal force otherwise urging the ball up the taper of its seat to open the valve as shown. Several of the pins 25 may retain light coiled compression springs 39 which act between the pressure plates 26 to return the pistons 18,19. A sleeve 41 is pressed into the drive member 12, which may be of aluminium, to serve as a bearing member for the end cap 29. Engagement of either clutch is effected by pressurisation of the appropriate cylinder to clamp the respective driven plate, the clutches are independently operable. Renewal of either clutch plate is effected by removal of the end covers 28,29 and withdrawal of the clutch assembly from shafts 11, 23 and 24. The clutch assembly may then be dismantled for inspection and replacement of plates 21 and 22 by removal of the circlip 15.

Claims: Claims 1. A dual plate friction clutch comprising a drive member (12), a cover member (14) fixed for rotation with the drive member (12), two facing hydraulic cylinders (16,17) provided one each in said drive and cover members, an annular reaction member (13) extending between the cylinders (16,17) and fixed for rotation with the drive member (12), two driven members (21,22) interposed one each between the reaction member (13) and a respective hydraulic cylinder and two pressure plates (26) fixed for rotation with the drive member (12) and interposed one each between a respective driven member and hydraulic cylinder, characterised thereby that a plurality of guide pins (25) are provided between said drive and cover members, the guide pins passing through apertures of the pressure plates (26) to both hold the pressure plates for rotation with the drive member and guide the pressure plates for movement axially of the clutch. 2. A clutch according to Claim 1, characterised thereby that one or more of the guide pins (25) is hollow and comprises part of a fluid feed duct to one of said hydraulic cylinders. 3. A clutch according to Claim 2, characterised thereby that the pressure plates (26) are uged apart by a plurality of equispaced coiled compression springs (39) located on the guide pins (25).

Inventors: BURKE, JOHN PIUS
Applicants: AUTOMOTIVE PRODUCTS PUBLIC LIMITED COMPANY
Application year: 1982
Main classification: F16D25
IPC codes: F16D25