GB2200707A - Friction clutch release mechanism - Google Patents

Abstract

A friction clutch for a vehicle comprises a clutch release mechanism including a first member 14, a second member 16, a detent means 52 which is adapted to position the first and second members relatve to each other when the first member is moved in a first direction to a first position relative to the second member whereby at the first position, Fig 1, the detent means can transmit a clutch release force from the first member to the second member when the first member is moved in a second direction which is opposite to the first direction, and a detent releasing means which comprises a plastics slider 36 which is provided with means for engaging the detent means, the slider being held captive in a slot 24 which is provided in member 16 and being movable along the slot from a first positon relative to the detent means at which the slider does not engage the detent means to a second position (Fig 10) relative to the detent means at which the slider engages the detent means and releases the detent means whereby the first member can be moved in the second direction relative to the second member thereby to separate the first and second members. The detent means 52 may be located on the member 16 (Fig 11) and the slot 24 in the member 16. <IMAGE>

Description

FRICTION CLUTCH The present invention relates to a friction clutch and, in particular, to a friction clutch for a vehicle which has a clutch release mechanism which can readily be assembled and disassembled.

It is known to provide a friction clutch having a release mechanism which can be assembled by snap-fitting clutch release components onto the hub of a diaphragm spring.

One such friction clutch is disclosed in GB-A-2131515 and thatfriction clutch comprises a first member, a second member, and a detent arranged to locate the first member relative to the second member by moving the first member in one direction relative to the second member. To separate the first and second members, the first member is initially urged further in the said one direction to release the detent, facilitating fitting and removal of the clutch release mechanism. However, that known friction clutch suffers from the disadvantage that it can be difficult to disassemble the clutch after a number of years or miles of service of the vehicle since the detent mechanism can suffer from corrosion. Also, when the clutch is being manually assembled or disassembled the mechanic can find it difficult to know when the assembly is engaged or disengaged.Furthermore, the assembly is relatively difficult to assemble and disassemble.

The present invention aims to provide a friction clutch which can overcome these disadvantages. In particular, the present invention aism to provide a friction clutch which can be easily assembled and disassembled, even if the clutch has been in use for a considerable period of time.

Accordingly, the present invention provides a friction clutch for a vehicle, the friction clutch including a clutch release mechanism including a first member, a second member, a detent means which is adapted to position the first and second members relative to each other when the first member is moved in a first direction to a first position relative to the second member whereby at the first position the detent means can transmit a clutch release force from the first member to the second member when the first member is moved in a second direction which is opposite to the first direction, and a detent releasing means which comprises a plastics slider which is provided with means for engaging the detent means, the slider being held captive in a slot which is provided on one of the first and second members and being movable along the slot from a first position relative to the detent means at which the slider does not engage the detent means to a second position relative to the detent means at which the slider engages the detent means and releases the detent means whereby the first member can be moved in the second direction relative to the second member thereby to separate the first and second members. Embodiments of the present invention will now be described by way of example only, with reference to the accompanying drawings, in which:: Figure 1 is a part-sectional view of part of a friction clutch in an assembled configuration in accordance with a first embodiment of the present invention, Figure 2 is a plan view of a blank for a spring clip of the friction clutch of Figure 1; Figure 3 is a top view of the spring clip which has been formed from the blank of Figure 2; Figure 4 is a side view of the spring clip of Figure 3; Figure 5 is a section through a first type of tooth of the spring clip of Figure 3; Figure 6 is a section through a second type of tooth of the spring clip of Figure 3; Figure 7 is a section through a third type of tooth of the spring clip of Figure 3; Figure 8 is a sectional view of part of a release bearing assembly and a part of a release plate assembly of the friction clutch of Figure 1 prior to assembly;; Figure 9 is a sectional view of the part of the release bearing assembly and the part of the release plate assembly of the friction clutch of Figure 1 in a configuration just prior to disassembly; and Figure 10 is a sectional view of the part of the release bearing assembly and the part of the release plate assembly of the friction clutch of Figure 1 during disassembly; and Figure 11 is a part sectional view of part of a friction clutch in an assembled configuration in accordance with a second embodiment of the present invention.

Referring to Figure 1, a "pull-type" friction clutch includes a clutch release mechanism designated generally as 2, which can act to retract a clutch pressure plate (not shown) thereby to release a clutch driven plate (not shown) by applying a force in direction A to the clutch release mechanism 2. The applied force acts to retract a diaphragm spring 4. The force is applied by a release lever 6 which is rotatably mounted on an annular bearing carrier 8 by means of a pin 10 and through an annular release bearing 12, an annular bearing sleeve 14, and an annular release plate 16 on which the diaphragm spring 4 is mounted. In alternative embodiments, the release lever is not mounted on the bearing carrier by means of a pin but is adapted to act on lugs or ears which are integral with the outer case of the release bearing.The bearing sleeve 14 and the release plate 16 are releasably coupled together by a release mechansim to permit assembly and disassembly of the diaphragm spring 4. The release mechanism is referred to as a "snap assembly" or a "snap on-off" assembly.

In the illustrated arrangement, the release bearing 12 is held in the bearing carrier 8 by a retaining circlip 18. However, in an alternative arrangement the release bearing would be held in place in the bearing carrier by an outer ring of the bearing assembly which is part of the outer case of the bearing carrier. The diaphragm spring 4 is held in position on the release plate 16 by being sandwiched between a hub portion 20 of the release plate 16 and a circlip 22 and disc spring 23 assembly.

The release mechanism will now be described. The outer circumferential surface of the release plate 16 is provided with an annular slot 24 of rectangular cross-section, the slot 24 having an elongate circumferential surface 26 disposed between two annular end surfaces 28,30. The end surface 28 which is nearer the diaphragm spring 4 is referred to hereinafter as the stop surface and the end surface 30 which is remote from the diaphragm spring 4 is referred to hereinafter as the clip engaging surface. The outer edge of the clip engaging surface 30 has a chamfered face 32 and the outer edge of the release plate 16 is provided with an opposing chamfered face 34. A releasing sleeve 36 of low friction plastics material is slidably mounted and held captive in the slot 24. The releasing sleeve 36 is annular and dimensioned so as to fit snugly in the slot 24 but is provided with a radial slit (not shown) so as to permit the releasing sleeve 36 to be easily assembled to, and disassembled from, the release plate 16. The releasing sleeve is dimensioned and the radial slit is of a thickness such that the releasing sleeve 36 can have an "open" position, at which the free ends of the releasing sleeve do not meet, and a "closed" position, at which the free ends bear against each other and the diameter of the releasing sleeve 36 is reduced, but for each position the internal diameter of the releasing sleeve is greater than the diameter of the slot 26 so as to ensure that the releasing sleeve 36 can slide in the slot in either of those positions.The releasing sleeve 36 has a thickness substantially corresponding to the depth of the slot 24 and a length which is approximately one half that of the slot 24, although this latter dimension may be varied as desired provided that the releasing sleeve 36 can be slid up and down the slot 24. The releasing sleeve 36 is provided with opposed chamfered outer edges 38, 40 and an annular groove 42. The groove 42 has smooth sides so as to permit a joggle in a tooth of a spring clip (to be described hereinafter) to be withdrawn from the groove 42 in either longitudinal direction.

The bearing sleeve 14 is provided, on its inner circumferential surface which, in the assembled configuration, opposes the outer circumferential surface of the release plate 16, with an annular spring clip retaining notch 44. The notch 44 comprises a shallow portion 46 which is, in use, near the diaphragm spring 4 and an inclined portion 48 which is, in use, remote from the diaphragm spring 4. The annular surface of the inclined portion 48 is progressively inclined inwardly in a direction away from the shallow portion 46.

The outer edge 50 of the inclined portion 48 of the notch 44 is chamfered. An annular spring clip 52 is held captive in the notch 44 and is described in greater detail with reference to Figures 2 to 7.

Referring to Figures 2 to 7, the spring clip 52 is made from the flat blank 54 of a spring metal which is shown in Figure 2 by forming the blank 54 into an open annul us as shown in Figures 3 and 4. The blank 54 consists of an elongate support 56 from one side of which extend a plurality of spring teeth. The spring teeth are divided into three distinct types. A first type is a joggle tooth 58 which is shown in greater detail in Figure 5. The joggle tooth 58 is straight and co-planar with the elongate support 56 but has a deformation or "joggle" 60 which extends transversely of the joggle tooth 58 above the elongate support 56. The joggle 60 extends radially inwardly of the annular spring clip 52. A second type is a short tooth 62 which is shown in greater detail in Figure 6.The short tooth 62 is shorter in length than the joggle tooth 58 and includes an inclined portion 64 which extends radially inwardly of the annular spring clip 52 at an angle of e.g. 200 to the elongate support 56 and a flat end portion 66 which is substantially paralle-l with the elongate support 56. The third type is a long tooth 68 which is shown in greater detail in Figure 7. The long tooth 68 is substantially the same length as the joggle tooth 58 and is longer than the short tooth 62. The long tooth 68 extends radially outwardly of the annular spring clip 52 at an angle of e.g. 5 to the plane of the elongate support 56.

The spring clip 52 is provided with a particular number of each type of tooth, and the teeth are arranged around the spring clip in a particular order. In the illustrated embodiment, the spring clip 52 has three joggle teeth 58, seven long teeth 68 and twelve short teeth 62, the short teeth 62 being arranged in pairs between alternating long teeth 68 and long teeth 68/joggle tooth 58 combinations. The diameter of the elongate support 56 is slightly greater than that of the shallow portion 46 of the notch 44 so that when the spring clip 52 is held captive in the notch 44 the spring clip 52 springs outwardly and is thereby firmly held in the notch 44.The teeth of the spring clip 52 are dimensioned so that, in the assembled configuration which is shown in Figure 1, the long teeth 68 extend into the inclined portion 48 of the notch 44 with their ends being longitudinally just short of the outer edge 50 thereof. The joggle teeth 58 have their joggles 60 extending into the slot 24. The short teeth 62 extend into the slot 24 and the free ends of the short teeth 62 bear against the clip engaging surface 30 of the slot 24. In this way, the short teeth 62 prevent the bearing carrier 8, to which the bearing sleeve 14 which carries the spring clip 52 is connected via the bearing 12, from being moved axially in relation to the release plate 16 in a direction away from the diaphragm spring 4 as shown by arrow A.In the assembled configuration, the short teeth 62 transmit the clutch release load from the release lever 6 to the diaphragm spring 4.

The assembly and disassembly of the clutch will now be described with reference to Figures 8 to 10. Figure 8 shows the relationship between the bearing sleeve 14 and the release plate 16 prior to assembly.

Figure 9 shows the relationship between the bearing sleeve 14 and the release plate 16 during an initial phase of disassembly. Figure 10 shows the relationship between the bearing sleeve 14 and the release plate 16 during a final phase of disassembly. As has been described above, Figure 1 shows the bearing sleeve 14/release plate 16 combination in its assembled configuration, with the spring clip being in its engaged position, i.e. with the short teeth 62 of the spring clip 52 engaged with the clip engaging surface 30 to effect clutch release.

Referring to Figure 8, the clutch is assembled by telescoping the bearing sleeve 14 over the release plate 16. The releasing sleeve 36 is positioned at that end of the slot 24 which is near to the diaphragm spring 4 (i.e. adjacent the stop surface 28), leaving empty the other end of the slot 24 which is nearer to the bearing sleeve 14. The bearing sleeve 14 is slid over the release plate 16 and the short teeth 62 and the joggles 60 of the joggle teeth 58 engage the chamfered face 34 of the release plate 16 and are pushed by that chamfered surface 34 into the inclined portion 46 of the notch 44. A person assembling the clutch can detect that the spring clip 32 is being deformed in this way by feeling the resistance to the movement of the bearing sleeve 14.The number of joggle teeth 58 and the height of the joggles 60 are controlled so that the load required to push the bearing sleeve 14 onto the release plate 16 is not too much so as to cause bending deformation of the diaphragm spring fingers but still permits the assembler to be able to feel when engagement has occurred. The bearing sleeve 14 is slid further until the joggles 60 slide down the chamfered face 32 -of the clip engaging surface 30 and extend inwardly into the slot 24. This movement can also be felt by the person assembling the clutch. The assembly continues until the short teeth 62 are slid clear of the chamfered face 32 of the clip engaging surface 30 and spring inwardly into the slot 24. This springing can be felt by the assembler and is an indication that the clutch has been assembled. The bearing sleeve 14 is slid backwardly, if necessary, in order to engage the ends of the short teeth 62 with the clip engaging surface 30. The clutch is now ready for use.

In order to disassemble the clutch, the bearing sleeve 14 is telescoped still further over the release plate 16 in a direction towards the diaphragm spring 4 up to circlip 22. The short teeth 62 and the joggles 60 of the joggle teeth 58 are slid over the chamfered outer edge 38 of the releasing sleeve 36. The sliding is continued unti-l the joggles 60 are slid into and located within the groove 42.

The smooth sides of the groove 42 permit the joggles easily to be slid smoothly into the groove 42 but are sufficiently steep so that the person disassembling the clutch can feel when the joggles 60 have engaged the groove 42. When the joggles 60 enter the groove 42 they urge the releasing sleeve 36 inwardly. The releasing sleeve 36 is deformed elastically from its "open" position to its "closed" position at which the free ends of the releasing sleeve 36 bear against each other. This causes the releasing sleeve to become a rigid ring which urges the short teeth 62 radially outwardly in order to ensure disassembly. The circlip 22 acts as a bearing sleeve "stop" for the disassembly operation to prevent overstroking of the bearing assembly when disassembling the clutch.At this point, the short teeth 62 bear against the outer circumferential surface of the releasing sleeve 36 and extend into the inclined portion 46 of the notch 44 so that no teeth extend into the slot 24. This configuration is shown in Figure 9. The bearing sleeve 14 is then slid in the opposite direction and away from the diaphragm spring as shown by Arrow C. The joggles 60 bear against the groove 42 with sufficient force to slide the releasing sleeve 36 along the slot 24 together with the spring clip 52. The releasing sleeve 36 can slide easily in the slot 24 since it is made of a low friction plastics material. Also, the releasing sleeve 36 is easily slid up and down the slot 26 even after a number of years of service of the clutch since it is made of a non-corrodible material. The releasing sleeve 36 is slid along the slot 24 until it bears against the clip engaging surface 30.This configuration is shown in Figure 10. In this configuration, the free ends of the long teeth 68 clear the clip engaging surface 30 of the slot 24 since they are inclined outwardly away from the release plate 16. Further sliding of the bearing sleeve 14 in the direction of Arrow D of Figure 10 causes the joggles 60 of the joggle teeth 58 to be slid out of the groove 42 and the long teeth 68 to guide the remaining teeth of the spring clip 52 clear of the release plate 36.

The chamfered face 32 of the clip engaging surface 30 helps to enable the joggle teeth 58 and the short teeth 62 to be slid clear of the slot 24. The bearing sleeve 14 is slid further in the direction of Arrow D until it is clear of the release plate 16. The clutch can then be further disassembled.

In the illustrated embodiment, the spring clip is provided with a specific number and distribution of the three types of teeth so as to facilitate the assembly and disassembly operation and so as to permit satisfactory operation of the clutch in use. If there are too many short teeth and joggle teeth, particularly joggle teeth, this can require too high a load to the required in the assembly and disassembly operations and so the number of those teeth must be chosen so as to permit easy assembly and disassembly but also so as to permit sufficient load transmission by the short teeth and sufficient sliding force to be applied to the releasing sleeve and sufficient "positive feel" by the joggle teeth. The spring clip of the illustated embodiment is provided with three joggle teeth and twelve short teeth so as to optimise these various requirements.It is preferred to have one long tooth at each end of the spring clip 52 so as to aid seating of the spring clip in the notch 44. Furthermore, the relative lengths of the teeth are chosen so that the long teeth can guide the remaining teeth out of the slot by extending beyong the chamfered face of the clip engaging surface. However, it will be readily appreciated by those skilled in the art that other tooth configurations could be employed.

In the illustrated embodiment the chamfered edges 38, 40 of the releasing sleeve have different lengths and angles of inclinations to the axis of the releasing sleeve 36, and also the groove 42 is not centrally located along the length of the releasing sleeve 36 but is offset towards one end. This can lead to the disadvantage that if the releasing sleeve 36 is assembled in the slot 24 the wrong way round, disassembly of the clutch would be prevented. Accordingly, in an alternative embodiment the groove 42 is centrally located along the length of the releasing sleeve 36 and the chamfered edges 38, 40 are identical so that the releasing sleeve 36 can befitted either way within the slot 24.

The illustrated embodiment has a "positive feel" so that the person who is assembling or disassembling the clutch can feel when the clutch is engaged or disengaged. The spring clip and the releasing sleeve are both slit so as to facilitate assembly and disassembly thereof.

Generally, neither the spring clip not the releasing sleeve needs to be removed from the bearing sleeve or the release plate, respectively, during the lifeti,f the clutch. However, these components can be removed if desired and are re-usable in another clutch. Since the spring clip does not require abutting ends, it can be easily manufactured from thin strip material.

A second embodiment of the present invention is shown in Figure 11.

In this embodiment, the arrangement is similar to that of Figure 1 and like parts are numbered with like reference numerals. However, the arrangement of the spring clip and the releasing sleeve is interchanged with respect to the arrangement of Figure 1. In this embodiment, a releasing sleeve 70 is slidably mounted captive in a slot 72 disposed in the inner circumferential surface of the bearing sleeve 14 and a spring clip 74 is'mounted in a notch 76 which is disposed in the outer circumferential surface of the release plate 16. The releasing sleeve 70 has an annular groove 78 and two chamfered edges 80, 82 in its inner circumferential surface. As for the embodiment of Figures 1 to 10, the chamfered edges may, as an alternative to the illustrated arrangement, be made identical and the groove 78 may alternatively be centrally located along the length of the releasing sleeve 70.The slot 72 has a chamfered face 84 on that end face 86 of the slot 72 which is, in the assembled configuration, near to the diaphragm spring 4 and acts as a clip engaging face. The spring clip 88 has an annular elongate support 90 from which extend short teeth 92, joggle teeth 94 with joggles 96 and long teeth 98.

However, in contrast to the spring clip 52 of the first embodiment, the short teeth 92 and the joggles 96 of the joggled teeth 94 extend radially outwardly of the spring clip 88 and the long teeth 98 extend radially inwardly. The notch 76 has a shallow portion 100 which is positioned remote from the diaphragm spring 4 and in which the elongate support 90 of the-spring clip 88 is located and an inclined portion 102 which is positioned near to the diaphragm spring 4 and in which the teeth of the spring clip 88 are positioned.

The assembly and disassembly operations are similar to those employed with the first embodiment. During assembly, the bearing sleeve 14 is telescoped over the release plate 16 until the joggles 96 of the joggle teeth 94 and then the short teeth 92 enter the slot 72. In the assembled configuration, which is shown in Figure 11, the free ends of the short teeth 92 engage the clip engaging face 86 of the slot 72 and transmit the clutch release force from the release lever 6 to the diaphragm spring 4. During disassembly, the bearing sleeve 14 is telescoped further over the release plate 16 thereby to move the releasing sleeve 70 therewith until the joggles 96 of the joggle teeth 94 engage the groove 78 of the releasing sleeve 70, at which position the releasing sleeve 70 pushes the short teeth 92 into the inclined portion 102 of the notch 76. The bearing sleeve 14, and the releasing sleeve 70, are then slid together in a direction away from the diaphragm spring 4 thereby to release the joggles 96 from the groove 78 and the teeth from the slot 72. The bearing sleeve 14 is then separated from the release plate 16.

Claims (12)

CLAIMS:

1. A friction clutch for a vehicle, the friction clutch including a clutch release mechanism including a first member, a second member, a detent means which is adapted to position the first and second members relative to each other when the first member is moved in a first direction to a first position relative to the second member whereby at the first position the detent means can transmit a clutch release force from the first member to the second member when the first member is moved in a second direction which is opposite to the first direction, and a detent releasing means which comprises a plastics slider which is provided with means for engaging the detent means, the slider being held captive in a slot which is provided on one of the first and second members and being movable along the slot from a first position relative to the detent means at which the slider does not engage the detent means to a second position relative to the detent means at which the slider engages the detent means and releases the detent means whereby the first member can be moved in the second direction relative to the second member thereby to separate the first and second members.

2. A friction clutch for vehicle according to Claim 1, wherein the detent means comprises an annular spring having a plurality of longitudinally directed teeth, the teeth comprising a plurality of load transmitting teeth which are adapted to transmit the said clutch release force from the first member to the second member and a plurality of slider-engageable teeth each of which is provided with a protrusion which is engaged with the means for engaging when the slider is at the second position.

3. A friction clutch for a vehicle according to Claim 2, wherein the teeth further comprise a plurality of slot-clearing teeth, each of which is adapted to extend away from the slot whereby when the detent means is engaged by the means for engaging the slot clearing teeth guide the load transmitting teeth and the slider-engageable teeth out of the slot when the first member is moved in the second direction.

4. A friction clutch for a vehicle according to Claim 2 or Claim 3, wherein the annular spring is formed from a strip which has been deformed into an annul us with two free ends.

5. A friction clutch for a vehicle according to any one of Claims 2 to 4, wherein the protrusion of each slider-engageable tooth comprises a semi-circular joggle, the outer surface of which is adapted to be engageable with the means for engaging.

6. A friction clutch for a vehicle according to any one of Claims 2 to 5, wherein the annular spring is held captive in a notch which is provided on the other of the first and second members from that which carries the slider.

7. A friction clutch for a vehicle according to Claim 6, wherein the annular spring is held in the notch by means of an interference fit.

8. A friction clutch for a vehicle according to any one of Claims 2 to 7, wherein the slider is annular and the means for engaging comprises an annular groove in which the protrusions are disposed when the slider is at the second position.

9. .A friction clutch for a vehicle according to Claim 8, wherein the slider has a longitudinal slit therethrough whereby it can be opened out for removal from the said one of the first and second members on which it is held captive.

10. A friction clutch for a vehicle according to Claim 9, wherein the slider is dimensioned so that it has an open position, at which the two opposing free ends, which are defined by the longitudinal slit, are spaced from each other, and a closed position, at which the two opposing free ends bear against each other, and at each of those positions the internal diameter of the slider is greater than the internal diameter of the slot.

11. A friction clutch for a vehicle according to Claim 10, wherein the slider is adapted to be urged into the closed position when the protrusions engage the annular groove of the slider.

12. A friction clutch for a vehicle substantially as hereinbefore described with reference to Figures 1 to 10 or Figure 11 of the accompanying drawings.