GB2037944A

GB2037944A - Mounting Clutch Discs on Hubs

Info

Publication number: GB2037944A
Application number: GB7941428A
Authority: GB
Original assignee: Francaise du Ferodo SA
Current assignee: Valeo SE
Priority date: 1978-12-04
Filing date: 1979-11-30
Publication date: 1980-07-16
Also published as: DE2948765A1; DE7934135U1; DE2948765C2; FR2446414A1; FR2446414B1; ES486542A1; GB2037944B

Abstract

A clutch friction disc 12 comprises a hub 18 and an annular support 19 which can transmit torque to the hub 18 by teeth 24 on its inner periphery and has friction linings 20 on its outer periphery. The support 19 is mounted so as to be axially movable relative to the hub 18 and, in order to center it, between plates 13, 14, when the clutch is disengaged, it is subjected to axially acting elastic means, for example elastic lugs 26, which constantly urge it towards an axial positioning abutment 33 carried by the hub 18. This reduces or eliminates residual drag within the clutch after declutching. The invention is especially applicable to clutches used in semi- automatic transmissions. <IMAGE>

Description

SPECIFICATION Improvements in Clutches The present invention relates generally to clutches.

As is known, in a common form of clutch, a friction disc which comprises a hub and an annular support fixed by its inner periphery to said hub and provided on its outer periphery with friction linings, is mounted so as to be axially movable between two plates, one of which is also mounted so as to be axially movable relative to the other, these plates being integral in rotation with a first shaft, generally a drive shaft, and in practice the output shaft of a motor, whilst the hub of the friction disc is integral with a second shaft, generally a driven shaft, and in practice the input shaft of a gearbox.

In the position of engagement of the clutch, the friction disc is axially clamped between the plates, thus making the driven shaft rotationally integral with the drive shaft.

In the position of disengagement of the clutch, the friction disc is released, thus disconnecting the driven shaft from the drive shaft and, as the driven shaft is no longer being driven, thus enabling a gear to be engaged, in the case of a conventional manually controlled gearbox with parallel gears, or enabling a new gear ratio to be established in the case of an automatic gearbox with epicyclic gears.

However, in practice, it may happen that in the disengaged position of the clutch, adhesion is perpetuated axially between the friction disc and one and/or the other of the plates between which it is located, so that the friction disc is subjected to an untimely drive torque, known as a drag torque, on this plate.

A drag torque of this kind can be a particular problem in oil-type clutches and notably in a clutch forming part of a semi-automatic transmission; in this case, it is due to hydrodynamic adhesion which is more pronounced when the clutch is cold but may also occur when it is warmed up, and which, despite a relative rotational sliding between the friction disc and the plate in question, keeps the friction disc in the immediate vicinity of this plate and prevents it from being re-centred between this plate and the other plate. However, a drag torque may also develop in dry clutches, notably in clutches for heavy vehicles; in this case, it is due to mechanical rather than hydrodynamic adhesion of the friction disc to one or other of the plates between which it is located, with the same effects as described above.

Whichever is the case, the result is that in the disengaged position of the clutch, especially in the case of a conventional gearbox, it is difficult to engage a gear because the driven shaft is being driven; in the case of an automatic gearbox, there is a loss of power owing to the loss in yield caused by this drag torque.

The present invention relates to an arrangement for preventing or reducing such drag torque.

The invention provides a clutch of the kind comprising two plates one of which is mounted so as to be axially movable relative to the other, and a friction disc which is mounted so as to be axially movable between said plates and which comprises a hub and an annular support, the support being fixed by its inner periphery to the hub and having friction linings on its outer periphery, this clutch being characterised in that, on the one hand, the support of the friction disc is mounted so as to be axially movable relative to the hub thereof, and, on the other hand, the support is subjected to elastic means with an axial action, hereinafter referred to as elastic centering means, which constantly urge it towards a limit position so that, for the disengaged position of the clutch, urged by the elastic centering means, the support of the friction disc is automatically recentered relative to both of the plates of the clutch and is thus equally spaced from both plates.

Preferably, the limit position is defined by an axial abutment fixed relative to the hub, hereinafter referred to as the positioning abutment.

According to one embodiment of the invention, the elastic centering means for the support of the friction disc abut on a support stop integral with the hub thereof, so as to form an integral part of the friction disc.

As a variant, in another possible embodiment of the invention, the elastic centering means for the support of the friction disc abut on either of the plates of the clutch and bear either on the hub of the friction disc, this hub comprising in a transverse direction, on the side opposite said -plate, a shoulder adapted for axial driving of the support and forming the positioning abutment thereof, or on the support of the friction disc so that, for example, the elastic centering means may be borne by the plate in question, if desired.

Whichever is the case, the centering which they provide for the disengaged position of the clutch advantageously ensures, according to the invention, that any drag torque which is parasitic for the friction disc is minimised, or even eliminated.

American Patent No. 2,276,416 has already proposed a construction for a friction disc wherein the support forms a part which is separate from the hub and is urged towards an abutment integral with the latter by axially acting elastic means.

However, in this American Patent, the aim is simplyto ensure stacking of the various component parts of the friction disc in question, which comprise friction washers, and to subject this stack and hence these friction washers to an axial clamping action.

There is nothing to suggest that, on disengagement, these elastic means should intervene in any way to ensure recentering of the friction disc relative to the plates between which it is located.

In order that the invention may be more fully understood, embodiments in accordance therewith will now be described by way of example, with reference to the accompanying schematic drawings, in which: Figure 1 is an axial section through a clutch comprising a friction disc according to the invention; Figures 2 and 3 show, on a larger scale, details of Figure 1, marked by insets Il and Ill on Figure 1; Figure 4 is a perspective view of a washer used in the friction disc shown in Figures 1 to 3; Figure 5 is a view analogous to Figure 2 and shows an alternative embodiment; Figure 6 is an axial section through another embodiment of the friction disc according to the invention, taken along on the broken line VI-VI in Figure 7; Figure 7 is a cross section through this embodiment, on the line VII-VII in Figure 6;; Figures 8-9 and 10-11 1 correspond to Figures 6-7, respectively, and show other embodiments of the friction disc according to the invention, with the lines VIll-VIll, IX-IX, X-X and Xl-Xl showing the sections taken on these Figures; Figure 12 is an axial section analogous to that in Figure 1 and shows another embodiment; Figure 13 is an axial section partly reproducing Figure 12 and relating to an alternative embodiment, taken along the üne XIII-XIII in Figure 14 Figure 14 is a partial elevation of this embodiment along the arrow WIV in Figyre 13. These Figures show by way of example the appiication of the invention to a clutch 10 belonging to a semi-automatic transmission 11.

themselves, form part of the invention and will therefore not be described in defail in this specsification.

It need only be borne in mind that in the manner konwn per se, the clutch 10 comprises a friction disc li mounted so as to ';x',i - movable between two plates 13 14 one of which, plate 14, is also mounte'd"s" s to be axially movable relative to the other le plate 13 in practice, in the embodiment shown relating to a semi-automatic transmission, th, and 14 are in a cylinder-piston relationship wi each other; the plate 13 is mounted by me, means of ilvets 15 on a hub 16 which is axially fixed, and the plate 14 14 is mounted in axially movable manner on a hub 17.

Between the engaged position of the ,clutch, shown in Figure 1, in which the friction disc 12 is ciamped between the plates 13 and 14 and the disengaged position (not shown) in which the friction disc 12 is not clamped, the axial travel. or rise; of the plate 14 is C, (Figure 1).).

In the manner known per se, the friction disc 12 comprises a hub 18 and an annular support 19, the support being attached by its inner periphery to the hub 18 and having, on each side, friction linings 20 on its outer periphery, for clamping by the plates 13, 14; the plate 14 forms the pressure plate and the plate 13 forms the reaction plate.

In practice, in the embodiment shown, and in the case of a semi-automatic transmission, in order to control a valve 21 which governs an opening 22 in the support 19, the outer periphery of the hub 18 comprises teeth 23 and the inner periphery of the support 19 also comprises teeth 24 by means of which this support 1 9 engages on the hub 18, whilst a limited play is provided between the teeth 23 and 24.

As these arrangements are known peruse and are not part of the invention, they will not be described in detail here.

According to the invention, the support 19 of the friction disc 12 is mounted so as to be axially movable relative to the hub 18 thereof, and is subjected to axially acting elastic means, hereinafter referred to as elastic centering means, which constantly urge it towards an axial abutment, integral with the hub 18, which is hereinafter referred to as the positioning abutment.

In the embodiments shown in Figures 1 to 11, the elastic means thus provided according to the invention abut on a support stop which is integral with the hub.

In the embodiment shown more particularly in Figures 1 to 3 these elastic centering means exert a traction force on the support 19 they comprise one or more elastically deformable radial lugs 26 which may be carried, as shown, by a common support washer 27, and which are mountec on the support 19 by means or rivets 28 for example as shown with an interposed bracing washer 29 having a radial passage 30 for the valve 21 in this embodiment the support stop for the elastic centering means consisting of the lugs 26 is formed by a first transverse surface 31 of a washer 32, the other transverse suiface 33 of which forms the positioning abutment for the support 19 and which is mounted on the hub 18 for example by means of rivets 34 as shown and the positioning abutment 33 are directed axially opposite eachother, on the same side of the support 19 and both belong to the same washer 32 on whch the lugs 26 forming the elastic centering means engage.

in the embodiment shown the washer 32 is undulating and comprises, in an alternating circular arrangement areas 36 by which it abuts abutment 33 and areas 37 which project axially relative to the hub and form the supprt stop 31 Thus a washer which is relatively small in axial thickness is advantageously functionally equivalent to a washer having a greater axial thickness whilst still providing recesses suitable for receiving the rivets 34 needed to fix it to the hub 18, and thus reducing the increase in radial thickness caused by these rivets 34.

For the engaged position of the clutch (Figures 1 and 2), the support 1 9 of the friction disc 12 is spaced from its positioning abutment by the pressure plate 14, counter to the force exerted on it by the lugs 26 which constitute the elastic centering means, and the axial centering travel between it and its positioning abutment 33 is C2.

At the same time, for this engaged position, there is an axial play J between the hubs 17 and 18.

By its construction, this axial play J is less than the difference between, on the one hand, the travel C, of the movable plate 14 as defined above, and, on the other hand, the centering travel C2 of the support 1 9 of the friction disc 12, as defined above.

Consequently, for the disengaged position (not shown in the drawings), irrespective of the axial play of the hub 18 between the hubs 16 and 1 7, the lugs 26 constitute elastic centering means which constantly exert a force of traction on the support 19 of the friction disc 12, from plate 13 towards plate 14, as shown by the arrow F1 in Figure 2, and move the support 19 away from the plate 13 and return it to abut on its positioning abutment 33.

In this position of abutting on the positioning abutment 33, the support 19 is located substantially equidistantly between the plates 13 and 14 and is therefore not susceptible to be acted upon by any parasitic drag torque by one of these plates more precisely by the plate 13.

Prefenably for this position as shown by broken ines in Figure 2, the lugs 26 which constitute the elastie cemterimg means are still under load thus ensuring effective abutment of the support 19 on the position abutment 33 Moreover for the engaged position the positioning abutment 33 darried by the hub 18 cannor interfere with the supporrt 19 according to the embodiment described above, the friction disc and more predisely the annular support thereof is displaced axially both in a first direction, when the clutch moves form its- engaged position to ite oisengaged position and t opposite direction when ..th'e..r.Qlutc.h','retu rns to its engaged position According to the alternative embodiment shown in Figure 5 the elastic oentering means exert thrust on the annular support 19 of the friction dieo 12: these means consist for example as shown, of an wlastic washer 36 of the Belleville Washer type, which simply abuts on the support 19 and whose support stop 31 is formed by a washer 37 mounted by means of rivets 38 on the hub 18 A@ the same time the positioning abutment 33 of the support 19 is formed by a split washer 39 engagin in a groove 40 of the hub 18 in this case, the support steo 31 and the positioning abutment 33 are directed axially towards easch other and are arranged on both sides of the support 19 According to the alternative embodiments shown in Figures 6 and 7, the elastic centering means comprise at least one elastically deformable lug 40, produced by cutting out from the support 19 itself by means of a cut 41 provided in the support, and then suitably shaped.

In the embodiment shown, three lugs 40 are provided, arranged in twos at 1200.

The corresponding support stop 31 is formed by a split washer 42, engaging in a groove 43 of the hub 18, and the positioning abutment 33 of the support 19 is formed by a transverse shoulder of this hub.

The method of operation of these alternative embodiments is analogous to that described hereinbefore.

In the embodiments shown in Figures 8 to 10, the elastic centering means associated with the support 19 of the friction disc 12 comprise an elastic washer 45 which has, on its inner periphery, teeth 46 complementary to the teeth 23 on the hub 18, and the latter comprises, in a transverse direction, a groove 47 which interrupts these teeth 23 locally.

This groove 47 is thus adapted to receive the washer 45, and more precisely the toothed inner periphery of this washer; to do this, the washer 45 merely has to be engaged axially, by its teeth 46, with the teeth 23 of the hub 18, in the direction of the arrow F2 in Figure 8, then, when the washer 45 is aligned with the groove 47 of the hub 18, this washer 45 has to be rotated through an angle equal to half the pitch of its teeth, in the diection of tje arrow F3 in Figure 9 After this rotation the washer 45 axially abuts with ists teeth 46 on the side of the groove 47 of the hub 18 opposite the support 19 of the friction olise 12 this side being formed by the axial end portion of the teeth 23 of the hub 18 At the same time the washer 45 is provided with engagement means for preventing it from rntating'ori::the support 19 of the friction disc 12.

in the embodiment shown in-Figures.8-and 9, these engagement means comprise at.least one lug 49 provided axially on the elastic washer 45 for engaging in a recess 5Q provided. for this purpose in the anhular suppor 19 of the friction disc 12.

in practice, and as shown, two axial lugs 49 are provided on the washer 45, in'diahietriqal.ly"'.

opposed positions, and each of these lugs is formed by a right-angled bend of a radial lug 51 obtained by local cutting out from the washer 45 In an alternative embodiment (Figures 10 and 1 1), the engagement means which-the elastic washer 45 comprises have at least one cutout 52 provided. on;this:'elastic washer, "for example on ghe outer periphery thereof, for engaging with a projection 53. provided ax'iallyfor this" :purpase'on the support 19.

in practice, as shown, two cutouts 52 are provided, in diametrically opposite positions, and the corresponding projections 53 of the support 19 are formed by rivets mountd on the latter for this purpose.

In the foregoing, the elastic centering means associated with the support 19 of the friction disc 12 abut on the hub 1 8 thereof and thus form an integral part of this friction disc.

In an alternative embodiment (Figure 12), they may abut on either of the plates 1 3, 14 between which the friction disc 12 is arranged, and may, for example, abut on the plate 13 forming the reaction plate, as shown.

In the embodiment shown, these elastic centering means then bear on the hub 18 of the friction disc 12, and thus hub 18 comprises, transversely, on the side opposite the plate 13own which these elastic centering means abut, a shoulder 55 adapted for the axial driving of the support 19 of the friction disc 12 and forming the positioning abutment for this support on the side of the plate 13.

In the embodiment shown in Figure 12, these elastic centering means consist of an elastic washer 56, of the Belleville washer type, and are interposed between the plate 13, or more precisely the hub 1 6 thereof, and a bearing surface, for needle or ball bearings 57, abutting on the hub 18 of the friction disc 12, whilst the hub 1 6 axially comprises an annular recess 58 adapted for receiving this elastic washer 56 and this bearing surface 57.

To ensure that the support 19 is axially retained relative to the hub 18, the latter comprises, on the other side of its shoulder 55 in relation to the support 19, as shown, a split washer 60 forming a resting stop for the support 19 on the side of the plate 14.

In any case, in the engaged position, the support 1 9 of the friction disc 12 bears axially on the shoulder 55 of the hub 18 and axially holds this hub 1 8 in place counter to the elastic axial stress of the washer 56, which is compressed.

Obviously, some axial play is provided, for this position of engagement between the hub 18 and the plate 13, for all points of this hub 18.

When the clutch moves into the disengaged position, the elastic washer 56 axially pushes back the hub 18 of the friction disc 12, in the direction of arrow F4 in Figure 12, and with its shoulder 55 this hub 1 8 axially drives the support 1 9 along with it, so that the support is thus spaced from the plate 1 3 and brought into a resting position in which it is substantially equidistant from this plate 1 3 and the plate 14.

Thus, in this case, the entire friction disc assembly is axially movable into disengagement and engagement.

In the alternative embodiment shown in Figures 13 and 14, the elastic centering means associated with the friction disc 12 abut on the plate 13, as before, but they bear directly on the support 1 9 of the friction disc 12.

In the embodiment shown, these means consist of a reed or wire ring 61 which is bent axially arcuately as shown, and which is carried by the plate 13.

For this purpose, a washer 62 is mounted on this plate 13 and, in order to make the plate integral with the ring 61, this washer comprises radially at least one lug 63 by means of which it engages with the ring 61; in practice, as shown, two radial lugs 63 are provided, in diametrically opposed positions.

Preferably, and as shown, the washer 62 is mounted on the plate 13 by means of rivets 1 5 which make the plate integral with the hub 1 6 carrying it.

In the embodiment shown, the ring 61 is open and, in line with one of the radial lugs 63 of the washer 62, each of its two circumferential ends womprises a right-angled bent portion 64 engaging in an axial bore 65 in the plate 13.

In any case, -the apex of the ring 61 bears on the support 1 9 of the friction disc 12.

The invention is not limited to the embodiments described and shown, but covers all variants and/or combinations of the various elements within the scope of the appended

Claims

claims. Claims

1. A clutch of the kind comprising two plates one of which is mounted to be axially movable relative to the other, and a friction disc, which is mounted to be axially movable between said plates, and which comprises a hub and an annular support, the support being fixed by its inner periphery to the hub and having friction linings on its outer periphery, wherein said annular support is mounted to be axially movable relative to the hub thereof, and is subjected to elastic centering means having an axial action, which means constantly urge said support towards a limit position such that in the disengaged position of the clutch, the support is automatically recentered relative to both of the two plates and is thus equally spaced from both of these plates.

2. A clutch according to Claim 1, wherein said limit position is defined by an axial positioning abutment fixed relative to said hub.

3.-Aciutch according to Claim 1 or Claim 2, wherein the elastic centering means abut on a support stop which is integral with the hub of the friction disc.

4. A clutch according to Claim 3, wherein the support stop of the elastic centering means and the positioning abutment of the annular support are axially directed opposite each other, on the same side of the support, and the elastic centering means exert traction on said support and are mounted on the support for this purpose, by means such as rivets.

5. A clutch according to Claim 4, wherein the support stop of the elastic centering means and the positioning abutment of the annular support both belong to the same washer, of which they form the two transverse surfaces, and which is mounted on the hub by means such as rivets.

6. A clutch according to Claim 5, wherein said washer is an undulating washer.

7. A clutch according to Claim 3, wherein the support stop of the elastic centering means and the positioning abutment of the annular support are axially directed' towards each other, on both sides of the support, and the elastic centering means exert thrust on the support and for this purpose simply abut on the support, for example.

8. A clutch according to Claim 7, wherein the elastic centering means comprise at least one elastically deformable lug, produced by cutting out from the friction disc itself, and then suitably shaping.

9. A clutch according to Claim 7, wherein the outer periphery of the hub of the friction disc has teeth and the inner periphery of the annular support has corresponding teeth by means of which the support engages with the hub, and wherein the elastic centering means comprise an elastic washer which has on its inner periphery teeth which are complementary to those on the hub, and which is provided with engagement means adapted to prevent it from rotating on the support, and the hub comprises, in a transverse position, a groove which locally interrupts the teeth and which is adapted to receive the teeth of said washer.

10. A clutch according to Claim 9, wherein the engagement means comprise at least one lug provided axially on the elastic washer, for engaging in a recess provided for this purpose in the annular support.

11. A clutch according to Claim 9, wherein the engagement means comprise at least one cutout provided on the elastic washer, foi engaging with a projection provided axially on the annular support.

12. A clutch according to Claim 1 or Claim 2, wherein the elastic centering means abut on either of the plates and bear directly on the support of the friction disc.

13. A clutch according to Claim 12, wherein the elastic centering means are carried by the plate in question.

1 4. A clutch according to Claim 1 2 or Claim 13, wherein the elastic centering means consist of an axially deformed ring bent into an arcuate shape.

1 5. A clutch according to Claims 13 and 14 taken together, wherein the ring is made integral with the plate in question by means of a washer which comprises radially at least one lug by means of which it engages with said ring.

1 6. A clutch according to any of Claims 1 to 15, wherein, in the engaged position, there is axial centering travel between the annular support of the friction disc and its positioning abutment.

1 7. A clutch according to Claim 2, wherein the elastic centering means abut on either of the plates and bear on the hub of the friction disc, this hub comprising, transversely, on the side opposite said plate, a shoulder adapted for the axial driving of the support and forming the positioning abutment for the latter.

1 8. A clutch according to Claim 17, wherein the elastic centering means are interposed between the plate in question and a bearing surface abutting on the hub of the friction disc.

19. A clutch according to any of Claims 1 to 18, in which, in the engaged position, the axial play of the hub between the plates is less than the difference between the travel of the movable plate between the engaged position and the disengaged position and the axial centering travel of the annular support.

20. A clutch, substantially as hereinbefore described with reference to Figs. 1 to 4, Fig. 5, Figs. 6 and 7, Figs. 8 and 9, Figs. 10 and 11, Fig.

12, or Figs. 13 and 14 of the accompanying drawings.