GB2197920A

GB2197920A - Friction clutches

Info

Publication number: GB2197920A
Application number: GB08726361A
Authority: GB
Inventors: Anthony John Curtis; Andrew Christopher Jam Clayton
Original assignee: Automotive Products PLC
Current assignee: Automotive Products PLC
Priority date: 1986-11-29
Filing date: 1987-11-11
Publication date: 1988-06-02
Also published as: GB8628585D0; GB8726361D0

Abstract

A friction clutch cover assembly having a cover (4) has a pressure plate (22) and a spring (16) to bias the pressure plate axially away from the cover. The pressure plate (22) is held rotationaly fast to the cover by drive straps (14) which accommodate axial movement of the pressure plate. The movement of pressure plate (22) relative to the cover is limited by radially extending stops (35), each of which is secured in a bore (37) in either the cover or pressure plate, and which loosely engage in an axially extending aperture (36) in the other of the cover or pressure plate. The stop member (35) abuts an end face of the aperture (36) to limit said movement. (Figs 3-7) depict different methods of mounting a radial stop on a pressure plate. <IMAGE>

Description

FRICTION CLUTCH COVER ASSEMBLIES This invention relates to friction clutch cover assemblies, for example to clutch cover assemblies for motor vehicles.

In a typical motor vehicle friction clutch, a driven plate, rotationally fast with the input shaft of a gearbox, is sandwiched between a flywheel on the engine crankshaft and a pressure plate. The pressure plate is usually mounted in a clutch cover assembly, and the cover assembly is in turn mounted on the flywheel. The pressure plate is rotationally fast with a cover and the flywheel, and is biased away from the cover by urging spring means to trap the driven plate between itself and the flywheel.

Drive straps hold the pressure plate rotationally fast with the cover and allow the pressure plate to move axially so as to enable the driven plate to be released or clamped between the flywheel and pressure plate as required. The drive straps are formed by leaf springs serving as release springs to pull the pressure plate towards the cover when the biasing load applied to the pressure plate by said urging spring means is relieved.

Prior to mounting such a clutch cover assembly on a vehicle flywheel, or alternatively during vehicle maintenance when the clutch cover assembly is removed from the vehicle flywheel, the pressure plate is moved by the urging spring means, typically a diaphragm spring, axially away from the cover. Also the heavy pressure plate may suddenly axially move further from the cover under the inertia of the pressure plate when a floor abruptly halts the falling cover, should the cover be accidentally dropped.

If axial movements of the pressure plate are extreme and limited by the drive straps, the latter become overstressed causing them damage which impedes their ability to retract the pressure plate when the clutch is released in use, and thus clutch drag occurs.

The present invention provides a means of limiting the axial movement of the pressure plate relative to the cover.

Accordingly there is provided a clutch cover assembly comprising a clutch cover, a pressure plate, and a spring means acting between the pressure plate and the cover to bias the pressure plate away from the cover, the pressure plate being held rotationally fast to the cover by circumferentially spaced drive straps which allow the pressure plate to move axially wherein there is provided at least one radially extending stop member on one of the cover and pressure plate, the stop member extending in and protruding from a radially extending bore in one of the cover and pressure plate, and loosely engaging in an axially extending aperture in the other of the cover and pressure plate, and the stop member being engageable with an axially facing end of the aperture to limit displacement of the pressure plate from the cover.

The stop members can be fixed to the sidewall of the cover and engage a radial bore in the peripheral edge of the pressure plate or alternatively can be secured to the pressure plate by various means and engage in an aperture in the wall of the cover. A further advantage of limiting the axial movement of the pressure plate is that it can prevent damage to the pressure plate caused by excess wear in the driven plate.

Also according to the invention there is provided a method of construction of a clutch cover Assembly comprising a clutch cover, a pressure plate, and a spring means which urges the pressure plate away from the cover, there being provided at least one radially extending stop member on one of the cover and pressure plate which loosely engages in an aperture in the other of the cover and pressure plate to limit displacement of the pressure plate away from the cover, wherein the cover, pressure plate and spring means are assembled together and then the stop means is inserted radially through the cover to engage in the aperture and is then secured in position in one of the cover or pressure plate.

The invention will be described by way of example and with reference to the accompanying drawings in which: Figure 1 is a plan view of friction clutch cover assembly according to this invention, Figure 2 is a section through the cover assembly of Figure 1 on the line II - II, Figure 3 is an enlarged sectional view of a cover assembly showing a second embodiment of the invention, and Figures 4 to 9 are enlarged sectional views of cover assemblies showing differing methods of secur ing the stop means to the clutch cover.

With reference to Figures 1 and 2 there is illustrated a friction clutch cover'assembly 2, comprising an annular cover 4, a pressure plate 22 located coaxially within the cover 4, and a coaxial diaphragm spring 16 located between the cover and the pressure plate to bias the pressure plate 22 away from the cover 4. The terms 'axial' 'axially' etc., refer to the axis of rotation of the clutch cover, and the terms 'radial', 'radially' refer to radial distances in a plane normal to said axis.

The cover 4 comprises a cylindrical sidewall 5 having a radially outwardly projecting flange 7 at one axial end thereof and a radially inwardly projecting flange 8 at the other axial end. The outwardly projecting flange 7 has a plurality of holes 6 therein whereby the cover is attached by bolts B to a flywheel on the crankshaft of a vehicle engine. The inwardly projecting flange 8 has a plurality of tabs 26 on its radially inner periphery whereby the diaphragm spring 16 is attached to the cover.

The spring 16 is a frustoconical plate spring coned away from the pressure plate 22 and having a radially outer continuous annular portion 17 with a plurality of spaced radially inwardly extending fingers 18 projecting from the radially inner periphery of the annular portion 17. The spring 16 is attached to the cover 4 by the tabs 26 on the cover, extending through respective apertures 19 at the base of the fingers 18 and being bent around the continuous portion 17 of the spring to clinch the spring to the cover. A pair of coaxial fulcrum rings 24 and 28 are located one on each side of the diaphragm spring and are located against the radially outer surface of the tabs 26 prior to the tabs be.ing bent around the spring 16. The outer margin 17 of the spring 16 acts against the pressure plate 22.

The pressure plate 22 has an annular cast iron body with a friction surface 29 on one axial side for engagement with a driven plate and is made rotationally fast with the cover 4 by three circumferentially spaced drive straps 14 which extend between the cover and lugs 23 on the outer periphery of the plate 22. The drive straps 14 allow for axial movement of the pressure plate 22 relative to the cover 4 whilst holding the two rotationally fast and serve as release straps to pull the pressure plate towards the cover when the clutch is released. Each drive strap can be in the form of a plurality of superimnosed thin leaf springs which are bundled together to form the drive strap.The drive straps 14 are secured to the cover 4 and the lug 23 by suitable means 31, for example, rivets, bolts, etc In order to limit axial movement of the pressure plate 22 away from the cover 4 when the cover assembly is not attached to a flywheel, there are provided at least one, and preferably three stop members 35 spaced around the sidewall 5 of the cover 4.

With reference to Figure 2, the stop members 35 are equiangularly spaced and are each in the form of a pin projecting substantially radially inwardly of the cover sidewall 5 and loosely engaging in an aperture 36 in the pressure plate 22 so that there is some axial lost-motion between the pin 35 and the aperture to allow for normal operational movement of the pressure plate. In this example, the pin 35 extends in a bore 37 in the cover and is secured the-rein by rivetting or by other suitable means. The aperture 36 is formed as a radial blind bore in the outer surface of the pressure plate and the stop member 35 will abut an axially facing portion of the bore wall to limit the axial displacement of the pressure plate 22 from the cover.

The clutch cover assembly is assembled together and the pin 35 rivetted In position.

With reference now to Figure 3, there is illustrated a part section through an alternative clutch cover assembly in which each stop member is constituted by a stepped steel pin 45 fixed in a radial like-stepped blind bore 47 in the outer peripheral edge margin of the pressure plate 22.

Each pin 45 engages in an axially extending aperture 49 formed in the sidewall 5 of the cover 4. Each bore 47 is formed with a radially inner re-entrant portion 48 and each pin 45 has an annealed smaller diameter end portion 46 which fits into the re-entrant portion 48 of the bore.

After assembly of the cover assembly, each pin 45 is fitted into its respective bore 47 through the respective aperture 49 in the cover and its outer end is subject to a rivetting load which deforms the inner end portion 46 of the pin causing it to fill the re-entrant portion 48 of the bore.

The aperture 49 in the cover may be in the form of an elongated slot or could be circular. Each pin 45 will abut an axially facing portion of each respective aperture to limit displacement of the pressure plate 22.

With reference now to Figure 4 to 9, there are illustrated variations of the cover assembly shown in Figure 3, in which each stop member pin has one of a variety of differing constructions.

In Figure 4, each pin 145 has a plain pin body 144 with a radiall.y inner threaded end portion 146 and a smaller diameter plain portion 149 adjacent the threaded end portion 146. Each bore 147 is a through bore having a radially inner threaded portion 148 into which a pin 145 can be screwed. The pin body 144 may be an interference fit in the bore 147 to prevent it moving axially in the bore.

When the end portion 146 of the pin 145 is screwed right through the bore 147, as shown in Figure 4, it is unlikely that the threaded end portion 146 would re-engage with the screw threaded portion 148 of the bore and allow the pin to become inadvertantly unscrewed. As an added safety measure the exposed end portion 1 46 of the pin can be deformed.

In Figure 5 there is shown a stop member 245 in the form of a 'pop' blind rivet with a collar portion 244 Which engages in a respective aperture 49 in the cover 5. After assembly of the clutch cover assembly, each pop-rivet is inserted through its respective through bore 247 in the pressure plate 22 and its shank 250 pulled in the conventional manner, causing the inter end to flare and lock the rivet in the bore 247.

In order to facilitate fitting of the blind rivet, pockets 249 may be formed in the pressure plate 22 adjacent the inner end of the respective bores 247. Alternatively, the stop can be a sleeve on a pop rivet which has a radially thin flange, instead of the radially thicker collar portion 244 of Figure 5, whereby the flange clamps the sleeve against the pressure plate.

With reference tc Figure 6, the stop member is a two diameter stepped hollow pin 345 which locates in a like stepped through bore 347 in the pressure plate 22. The radially inner end portion 346 of the pin 345 is segmented and the hollow cavity locally narrowed at that place so that if a tool is inserted through the hollow pin the end portion 346 can be flared outwardly locking the pin 345 in the bore 347.

A similar method of fixing a stop member pin 445 is shown in Figure 7. The hollow stepped pin 445 has external serrations on its smaller diameter end portion 446, which are a push fit into the smaller portion 448 of the stepped blind bore 447. The internal cavity of the hollow pin 445 is tapered so that a ball 450 or pin driven inwards into the hollow pin expands the serrated end portion to grip the smaller diameter portion of the blind bore.

In figure 8 there is shown a stop member 545 comprising a hollow pin or tube 550 in a radial blind bore 547 in the outer margin of the pressure plate 22. The tube 545 engages in an aperture 49 in the clutch cover 4. A dowl or pin 552 is driven into the hollow tube 550 to expand the tube into an interference fit with the bore and lock the tube in place. The outer surface of the tube can be smooth but preferably has a roughened surface to engage in the bore. The outer surface may be ridged, knurled or otherwise.

In Figure 9 the stop member 645 is a rivet the shank 655 of which is held fast in a radial blind bore 647 in the pressure plate and the head 653 of which engages an aperture 49 in the cover 4. The head 653 of the rivet holds a collar 654 against the outer margin of the pressure plate within the aperture 49 and the dimensions of the collar may be varied to give the desired relative axial movement of the pressure plate to the cover.

Claims

CLAIMS:

1. A clutch cover assembly comprising a clutch cover, a pressure plate, and a spring means acting between the pressure plate and the cover to bias the pressure plate away from the cover, the pressure plate being held rotationally fast to the cover by circumferentially spaced drive straps which allow the pressure plate to move axially, wherein there is provided at least one radially extending stop member on one of the cover and pressure plate, tre stop member extending in and protruding from a radially extending bore in said one of the cover and pressure plate, said stop member loosely engaging in an axially extending aperture in the other of the cover and pressure plate, and the stop member being engageable with an axially facing end of the aperture to limit displacement of the pressure plate from the cover.

2. A clutch cover assembly as claimed in Claim 1 wherein the stop member is fixed to the sidewall of the cover and engages an aperture in the pressure plate.

3. A clutch cover assembly as claimed in Claim 1 wherein the stop member is fixed to the pressure plate and engages in an aperture in the sidewall of the cover.

4. A clutch cover assembly as claimed in Claim 3 wherein the stop member is constituted by a pin which is fixed in a radial bore formed in the outer peripheral edge margin of the pressure plate.

5. A clutch cover assembly as claimed in Claim 4 wherein the pin is fixed in its bore by deformation of the radially inner end portion of the pin to lock the pin in the bore.

6. A clutch cover assembly as claimed in Claim 5 wherein the bore is a stepped blind bore with a re-entrant portion and the radially inner end of the pin is deformed to fill the re-entrant portion.

7. A clutch cover assembly as claimed in Claim 5 wherein the bore is a through bore and the radially inner end portion of the pin when fully located in the bore extends beyond the bore and the pin is fixed therein by deformation of said inner end portion.

8. A clutch cover assembly as claimed in Claim 5 or Claim 7 wherein the pin is hollow and the radially inner end portion of the hollow cavity is narrowed so that insertion of a tool or other means inwardly through the cavity causes said inner end portion to flare outwardly from the cavity.

9. A clutch cover assembly as claimed in Claim 8 when dependant upon Claim 5 wherein the pin is located in a stepped blind bore and the pin has serrations on the outer surface of its inner end portion which are deformed against the bore on flaring of said end portion.

10. A clutch cover assembly as claimed in Claim 8 wherein the pin is located in stepped through bore and the inner end portion of the pin is segmented.

11. A clutch cover assembly as claimed in Claim 4 wherein the bore is a through bore having a radially inner threaded portion, and the pin has a like threaded inner end portion for screwing into the bore so that when the pin is fully located, said inner end portion extends beyond the bore, the pin being held firmly in the bore by making an inference fit therein.

12. A clutch cover assembly as claimed in Claim 11 wherein the pin has a smaller diameter plain portion adjacent the threaded inner end portion.

13. A clutch cover assembly as claimed in Claim 2, wherein the stop member is rivetted to the sidewall, or a clutch cover assembly as claimed in Claim 3, wherein the stop member is rivetted to the pressure plate.

14. A clutch cover assembly as claimed in claim 4 wherein the pin is a hollow tube and is held in the bore by a dowl inserted therein to expand the outer surface of the tube against the bore.

15. A clutch cover assembly as claimed in claim .13 when dependent upon claim 3 wherein the head of the rivet holds a collar against the pressure plate, said collar engaging in the aperture and having dimensions so as to give the desired axial movement.

16. A clutch cover assembly substantially as described herein and as illustrated in any one of Figures 2 to 9 in the accompanying drawings.

17. A method of construction of a clutch cover assembly comprising a clutch cover, a pressure plate, and a spring means which urges the pressure plate away from the cover, there being provided at least one radially extending stop member on one of the cover and pressure plate which loosely engages in an aperture in thb other of the cover and pressure plate to limit displacement of the pressure plate aWay from the cover, wherein the cover, pressure plate and spring means are assembled together and then the stop means is inserted radially through the cover to engage in the aperture and is then secured in position in one of the cover or pressure plate.

18. h method of construction of a clutch cover assembly and which is substantially as described herein and with reference to any one of the accompanying drawings.