GB2192244A - Clutch cover and method of manufacture - Google Patents

Abstract

A method of manufacture of a friction clutch cover includes the formation of an intermediate sheet metal pressing which can be used to make either a push-type clutch cover or a pull-type clutch cover. The annular sheet metal pressing (32) for use as a friction clutch cover has a sidewall (33) and a radially inwardly projecting flange (34) on which a diaphragm spring (16A) is pivoted. The flange (34) has an annular boss (36) adjacent the sidewall (33) on which the diaphragm spring (16A) can pivot for manufacture of a pull- type clutch and the flange (34) extends inwards so that if desired tabs (38) can be formed on the radially inner margin of the flange (34) for securing the diaphragm spring to the cover (32) for manufacture of a push-type clutch. When the pressing (32) is used for a pull-type clutch the inner margin of the flange (34) is removed along a circular path (39). <IMAGE>

Description

SPECIFICATION A friction clutch cover and a methodn of making the same This invention relates to friction clutches and in particular to covers for friction chutches, and to a method of manufacture of the covers.

A motor vehicle friction clutch generally comprises a driven plate sandwiched between a flywheel and a pressure plate. The flywheel is usually rotationally fast with the vehicle engine crankshaft, and the driven plate is rotationally fast with the vehicle gearbox input shaft. The pressure plate is usually biased by a spring or springs towards the flywheel and in the drive mode, traps the driven plate between itself and the flywheel. To release the driven. plate, the pressure plate is moved away from the flywheel against the spring bias. The pressure plate and spring(s) are held within an annular clutch cover which is mounted on the flywheel so that the pressure plate, cover, and flywheel are rotationally fast whilst the pressure plate can move axially relative to the flywheel and cover to release or trap the driven plate as is required.

The release of the driven plate by movement of the pressure plate away from the flywheel is usually effected through lever mechanisms mounted on the cover. These lever mechanisms are in turn operated by a clutch release bearing, usually mounted on a fork device which is under the control of the vehicle driver.

For the purpose of this invention a 'pushtype' clutch is a clutch in which the release bearing has to be moved towards the pressure plate in order to effect release of the driven plate, and a 'pull-type' clutch is a clutch in which the release bearing is moved away from the pressure plate in order to release the driven plate.

The friction clutch covers for pull-type clutches and push-type clutches generally differ in construction, especially for diaphragm spring clutches. For diaphragm spring clutches, the frustoconical spring itself acts as the lever mechanism to release the pressure plate. In a pull-type clutch the spring is pivotted at its outer periphery for movement relative to the clutch cover; and in push-type clutches the spring is pivotted at the base of the inwardly projecting spring finger. These differences in the way of pivotting the diaphragm spring and operation of the release mechanism, mean that the respective clutch covers have different constructions.

The present invention provides a clutch cover formed from an intermediate sheet metal pressing which is suitable for subsequent use in either a pull-type clutch or a pushtype clutch.

According to the present invention there is provided an annular sheet metal pressing intended in use for a friction clutch cover and having an axially extending annular sidewall having at one axial end an inwardly projecting flange having at its radially outer margin adjacent the sidewall a raised annular boss projecting towards the other end of the sidewall and which is adaptable to form an annular pivot for a diaphragm spring and said flange extending radially inwardly so as to be capable of being used for securing a diaphragm spring to a cover formed from the pressing and which is for a push-type clutch, and when said pressing is utilised for forming a pull-type clutch cover the radially inner margin of said flange is removed.A clutch cover for a pull-type will include the above pressing with the annular boss further press formed to provide an annular pivot for a diaphragm spring, and a clutch cover for a push-type clutch may include the above pressing with radially inwardly extending projections formed at the inner margin thereof for securing a diaphragm spring to the cover.

Also according to this invention there is provided a method of manufacture of a friction clutch cover and including press forming a sheet metal annular intermediate cover with an axially extending annular sidewall havingvat one axial end thereof an inwardly projecting flange having at its radially outer margin a raised annular boss projecting towards the other end of the sidewall and which is adaptable to form a pivot for a diaphragm spring, said flange extending radially inwardly so as to be capable of being used for securing a diaphragm spring to a cover formed from the pressing and which is for a push-type clutch cover, and when the pressing is utilised for forming a pull-type clutch cover, the radially inner margin of the flange is removed.

The invention will be described by way of example and with reference to the accompanying drawings in which: Figure 1 is a cross-section through a typical prior art clutch cover assembly for a pushtype clutch, Figure 2 is a fragmentary plan view of a clutch cover from an annular intermediate pressing both according to this invention, Figure 3 is a cross-section on the line Ill-Ill of Figure 2, and Figure 4 is a schematic section through a cover according to this invention showing a diaphragm spring in-situ in both a pull-type construction and a push-type construction, both being derived from the same annular sheet metal pressing.

With rererence to Figure 1 there is illustrated a typical prior friction clutch cover assembly for an automobile push-type friction clutch. The cover assembly 11 comprises an annular clutch cover 12 which envelopes a pressure plate 14 and a spring 16. The cover 12 has an annular flange 13 used for mount ing the cover on a flywheel (not shown). The annular pressure plate 14 is held rotationally fast with the cover 12 by circumferentially spaced sets of straps 15 which allow axial movement of the pressure plate relative to the cover.

The spring 16 is a frustoconical diaphragm spring 16 located between the cover 12 and the pressure plate 14 to bias the pressure plate away from the cover. The diaphragm spring 16 comprises an outer annular margin 17 with a plurality of inwardly extending spaced spring fingers 18 projecting therefrom.

The spring 16 is held to the cover by tabs 19 integral with a portion of the cover and which pass through apertures at the base of the spring fingers 18 to clinch the spring to the cover. A pair of fulcrum rings 21 and 22 lo cated on each side of the spring 16 are also held in position by the tabs 19 and are lo cated at the- bases of the spring fingers 18.

The outer margin of the spring acts on the pressure plate 12, so that when a load A is applied to the inner ends of the spring fingers the spring pivots about the rings 21 and 22 so that the outer margin of the spring moves away from the pressure plate, thus, in use, releasing the clutch driven plate.

Now -with- respect to Figure 2 and Figure 3, there is illustrated a clutch cover 32 according to this invention, for a push-type diaphragm spring clutch. The cover 32 has a substantially cylindrical sidewall portion 33 having a radially inwardly projecting flange 34 at one axial end.

By-the term 'axial' is meant along the axis x-x of rotation of the cover, A flange 35 at the other end, is used for mounting the cover 32 on a flywheel and the inwardly projecting flange 34, is utilised for securing a diaphragm spring to the cover (as in Figure 1), or by any other means, for example by use of rivets in the flange 34.

The- radially outer margin of the flange 34, adjacent the sidewall 33, has an inwardly pro jecting annular boss or rib 36 thereon which projects axially towards the flange 35. The boss 36 is press-formed into the cover 32.

The flange 34 extends radially inwardly and may have- at thins stage a plurality circumferen tially spaced projections 37 and 38 formed on its radially inner periphery in anticipation of the use of the cover for a pushtype clutch.

If the margin 34 is formed with projection 37 and 38 then every other projection 38 may be bent axially with respect to the cover to form a tab for clinching a diaphragm spring to the cover and the other projections 37 to project radially inwardly between the tabs to serve as abutments for the fulcrum ring 21.

If the cover 32 as illustrated, is adapted for use in a pull-type clutch, then the boss 36 is more accurately formed to provide a pivot four the diaphragm spring and the inner peripheral margin of the flange 34 is cut-off around the line 39 forming a circular inner peripheral edge to the narrowed flange.

This can be more easily seen in Figure 4, which illustrates an annular sheet metal pressing which can be used to make either a pulltype cover or push-type cover. For a pull-type cover the diaphragm spring 1 6A in the relaxed mode is coned away from the flange 34 with the outer periphery of the spring 16A pivotting on the annular boss 36. To release the clutch, the inner ends of the spring finger 1 8A are moved axially towards the flange 34 so that the spring becomes coned in the opposite direction, as illustrated in Figure 4 for the spring 16A. The flange 34 is sheared around the circular line 39 forming the inner peripheral edge 39.

For a push-type version of the cover 32, the spring 16B in the relaxed mode is coned towards the flange 34 and is pivotted on a pair of fulcrum rings located around the radially outer face of the axially projecting tabs 38 which are subsequently bent to clinch the spring 16B to the cover 32. The spring 16B is illustrated in Figure 4 in the clutch released mode in which the spring fingers 1 8A have been moved from their position in the spring relaxed mode, away from the flange 34 to cone the diaphragm spring in the opposite sense as illustrated. The boss 36 is present but will not have been formed to its final size as for the pull-type version.

Claims (11)

1. An annular sheet metal pressing intended in use for a friction clutch cover and having an axial!y extending annular sidewall having at one axial end an inwardly projecting flange having.at its radially outer margin adjacent the sidewall a raised annular boss projecting towards the other end of the sidewall and which is adaptable to form an annular pivot for a diaphragm spring and said flange extending radially inwardly so as to be capable of being used for securing a diaphragm spring to a cover formed from the pressing and which is for a pushtype clutch, and when said pressing is utilised for forming a pull-type clutch cover the radially inner margin of said flange is removed.

2. An annular clutch cover for a pull-type clutch including the sheet metal pressing of Claim 1, wherein the annular boss is further press formed in the inwardly projecting flange to provide a pivot for a diaphragm spring.

3. An annular clutch cover for a push-type clutch including the sheet metal pressing of Claim 1, wherein there are circumferentially spaced projections formed on the inner periphery of the radially inwardly projecting flange, at least some of said projections being used for securing a diaphranm spring to the cover.

4. An annular clutch cover for a push-type clutch including the sheet metal pressing as claimed in Claim 1, wherein a fulcrum ring is secured to the inner periphery of the flange by securing means provided on the flange.

5. A method of manufacture of a friction clutch cover and including press forming a sheet metal annular intermediate cover with an axially extending annular sidewall having at one axial end thereof an inwardly projecting flange having at its radially outer margin a raised annular boss projecting towards the other end of the sidewall and which is adaptable to form a pivot for a diaphragm spring, said flange extending radially inwardly so as to be capable of being used for securing a diaphragm spring to a cover formed from the pressing and which is for a push-type clutch cover, and when the pressing is utilised for forming a pull-type clutch cover, the radially inner margin of the flange is removed.

6. A method of manufacture of a cover as claimed in Claim 5 and which is for a pull-type friction clutch, wherein the intermediate cover is subject to further pressing operations in which the annular boss is further formed to provide its final desired form, said annular boss in use providing a fulcrum for diaphragm spring.

7. A method of manufacture as claimed in Claim 6, wherein during one of said further pressing operations, the radially inner margin of the flange is removed.

8. A method of manufacture of a friction clutch cover as claimed in Claim 5, and which is for a push-type clutch wherein the intermediate cover is subject to further pressing operations in which radially inwardly extending projections are blanked out of the radially inner margin of the flange.

9. A method as claimed in Claim 8, wherein during one of said pressing operations at least some of said projections are further bent to form axially extending tabs subsequently used to attach a diaphragm spring to the cover.

10. A method of manufacture of a friction clutch cover for a pull-type clutch or a pushtype clutch and which is substantially as described herein.

11. A clutch cover for a friction clutch and which is substantially as described herein.