GB2134605A

GB2134605A - Hydraulically operated multiple disc clutch

Info

Publication number: GB2134605A
Application number: GB08400679A
Authority: GB
Inventors: Rensaku Fukuchi
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1983-01-31
Filing date: 1984-01-11
Publication date: 1984-08-15
Also published as: GB8400679D0; JPS59140925A; FR2540203A1; DE3402158A1

Abstract

First and second ball check valves (40, 42) are installed on a clutch piston (14) for drawing off oil from an oil chamber for thereby preventing centrifugal force acting on oil in the oil chamber (22) from causing development of oil pressure in the oil chamber (22) when a hydraulically operated multiple disc clutch (10) should be held disengaged. The first ball check valve (40) is arranged close to the outer circumferential periphery of the clutch piston (14) and the second ball check valve (42) is arranged radially inwardly of the first ball check valve (40). The second ball check valve (42) has a larger clearance between a ball (42a) and the bore of that part of a hole (42b) in which it is accommodated than that in the first valve (40). <IMAGE>

Description

SPECIFICATION Hydraulically operated multiple disc clutch The present invention relates to hydraulically operated clutches and more particularly to hydraulically operated multiple disc clutches for automatic transmissions and the like.

A hydraulically operated multiple disc clutch consists of a clutch drum rotatable with an input shaft, a clutch piston mounted in the clutch drum in a manner to define an oil chamber, and an alternating series of drive plates and driven plates constituting a clutch pack. For engagement of the clutch, oil pressure is supplied into the oil chamber to cause the piston to move toward the clutch pack and axially compress the same. This kind of clutch encounters the problem that even when there is no supply of pressurized oil into the oil chamber, oil pressure is developed in the oil chamber by centrifugal force acting on the oil in the oil chamber.By the effect of such centrifugal force, the piston is therefore urged to move toward the clutch pack and axially compress the same with a relatively small force when the clutch drum is rotating at a low speed and with a relatively large force when rotating at a high speed. This inevitably leads to dragging, overheating, rapid wear and the like. Furthermore, when such a clutch is used in a car, unexpected movement of the car may possibly occur, which is quite dangerous.

In order to solve such a problem, it has been proposed to mount on the clutch drum or piston a check valve consisting of a ball and a ball accommodation hole. The check valve is adapted to open and close depending upon the opposing forces acting on the ball, i.e., a centrifugal force and a force resulting from oil pressure in the oil chamber. More specifically, the check valve is constructed so that the ball is forced to seat, i.e., the check valve is closed, when the force resulting from the oil pressure is larger than the centrifugal force and the ball is forced to unseat, i.e., the check valve is opened, when the former force is smaller than the latterforce.

With a view to efficiently drawing off oil pressure from the oil chamber when the clutch should remain disengaged, it has been practiced to arrange the check valve as close as possible to the outer circumferential periphery of the clutch drum or piston, i.e., as remote as possible from the axis of rotation of the clutch drum. In the case of more than two check valves being installed, they were arranged on a common circle and as close as possible to the outer circumferential periphery of the clutch drum or piston.

When so arranged, the check valve requires the gap between the ball and the ball accommodation hole to be quite small so that the check valve can assuredly close even when the clutch drum is rotating at a high speed, i.e., when the centrifugal force acting on the check valve ball is quite large. With such a small gap, efficient drawing-off operation of the check valve cannot be attained. On the contrary, when the ball accommodation hole is made large to provide a large gap, assured and reliable operation of the check valve cannot be obtained.

The prior art clutch of the described kind encounters such a dilemma, and complete solution of the foregoing problem could not be attained by such a prior art device.

Acccrdingly, it is an object of the present invention to provide an improved hydraulically operated multiple disc clutch which is completely free from the problem noted above, i.e., dragging, overheating, rapid wear and the like resulting from centrifugal force acting on the clutch.

In carrying out the above object as well as other objects of the present invention, the hydraulically operated multiple disc clutch comprises a clutch pack having an alternating series of drive plates and driven plates, a clutch drum rotatable about an axis and drivingly coupled with the drive plates for rotation therewith, a clutch piston mounted in the clutch drum to define therebetween an oil chamber, the clutch piston being axially movable toward and away from the clutch pack depending upon oil pressure in the oil chamber, the clutch pack being operative to hold the clutch drum for rotation with the driven plates when axially compressed by the clutch piston, and means for drawing off oil from the oil chamber for thereby preventing centrifugal force acting on oil in the oil chamber from causing development of oil in the oil chamber when the clutch should be held disengaged, the means including at least two, first and second ball check valves which are arranged to be different in distance from the axis of rotation of the clutch drum.

In one embodiment, the first ball check valve is arranged close to the outer circumferential periphery of the clutch piston, and the second ball check valve is arranged radially inwardly of the first ball check valve.

By the above structure, the second ball check valve, which is located closer to the axis of rotation of the clutch drum, can have between its ball and bail accommodation hole a larger gap than that of the first ball check valve without causing any defect in operation. By this, oil can be rapidly and efficiently drawn off through the second ball check valve, and oil remaining in a part of the oil chamber radially outwardly of the other ball check valve can be drawn off through the first ball check valve.

The features and advantages of the hydraulically operated multiple disc clutch according to the present invention will become more clearly appreciated from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate like or corresponding parts and in which: Fig. 1 is a hydraulically operated multiple disc clutch according to an embodiment of the present invention; and Fig. 2 is a view similar to Fig. 1 but showing a modification according to the present invention.

Referring first to Fig. 1 , a hydraulically operated multiple disc clutch is generally designated by 10 and shown as comprising a clutch drum 12, a clutch piston 14 and an alternating series of drive plates 1 6 and driven plates 1 8 constituting a clutch pack 20. The clutch drum 1 2 is formed from two parts integrally joined at 1 2a and is splined at its hub portion 1 2b to an input member or shaft (not shown) for rotation together therewith. The clutch piston 14 is mounted in the clutch drum 1 2 for axial movement and cooperates therewith to define therebetween a sealingly closed oil chamber 22.To this end, the clutch piston 14 is adapted to be slidable at the inner and outer peripheries on the clutch drum 1 2 and to have mounted thereat seal rings 24 and 26 for providing a seal between the mating surfaces of the clutch drum 12 and the clutch piston 14.

The clutch drum 12 is formed with an opening 27 for providing communication between the oil chamber 22 and a source of oil under pressure (not shown). On the clutch drum 12 is also mounted a spring retainer 28 which is held in place by a snap ring 30. Between the spring retainer 28 and the clutch piston 14 there are disposed in a circular array a plurality of coil springs 32 which urge the clutch piston 1 4 in the direction away from the clutch pack 20. On the clutch drum 12 is also mounted a retainer plate 34 which is held in place by a snap ring 36 and which is splined to the clutch drum 12 for rotation together therewith. Between the retainer plate 34 and the clutch piston 14 there are disposed the drive plates 16, the driven plates 1 8 interleaved with the drive plates 1 6 and a dish plate 36.The drive plates 1 6 are friction plates and splined at the outer periphery thereof to the clutch drum 12, while the driven plates 1 6 are steel plates and splined at the inner periphery thereof to an output member or shaft (not shown) for rotation together therewith.

The foregoing structure substantially follows the conventional fashion. In accordance with the present invention, the clutch piston 1 4 is provided with two check valves, i.e., a first ball check valve 40 and a second ball check valve 42. The first ball check valve 40 is arranged close to the outer circumferential periphery of the clutch piston 14, and the second ball check valve 42 is arranged radially more inside or interior than the first check valve 40, i.e., the second ball check valve is arranged closer to the axis of rotation of the clutch drum 12 than the first check valve. The first ball check valve 40 consists of a ball 40a and a ball accommodation hole 40b.The ball accommodation hole 40b includes, though not designated, a smaller diameter hole section (the left-hand hole section in the drawing), a larger diameter hole section (the right-hand hole section) in which the ball 40a is movably accommodated, and a conical valve seat or hole section interconnecting the smaller and larger hole sections. The larger diameter hole section is slightly larger in diameter than the ball 40a to provide therebetween a gap through which oil is drawn off when the ball 40a is held unseated from the valve seat. After insertion of the ball 40a into the ball accommodation hole, an end of the large diameter hole section is caulked so that the ball 40a is assuredly retained within the larger diameter hole section.The second ball check valve 42 consists of a ball 42a and a ball accommodation hole 42b similar to the first ball check valve 40. The second ball check valve 42 is small-sized as compared with the first ball check valve 40, i.e., the ball 42a is smaller than the ball 40a. However, the second ball check valve 42 is constructed to provide between the ball 42a and the ball accommodation hole 42b a gap which is larger than the corresponding gap of the first ball check valve 40, i.e., the gap of the second ball check valve 42 provides an oil passage of which sectional area is larger than the corresponding sectional area of the first ball check valve 40.

In operation, when oil pressure is supplied through the opening 27 into the oil chamber 22, the balls 40a and 42a of the first and second ball check valves 40 and 42 are forced to seat on the respective valve seats, that is, the check valves 40 and 42 are closed. The oil pressure in the oil chamber 22 is thus caused to rise and applies on the clutch.piston 14 a leftward force in the drawing. The clutch piston 14 is pushed toward the clutch pack 20 and axially compresses the same between it and the retainer plate 34. As a result, the driven plates 1 8 are put into friction engagement with the drive plates 1 6 and rotate together therewith, that is, the clutch is engaged.

So long as oil pressure is being supplied into the oil chamber 22, the ball check valves 40 and 42 are kept closed, that is, even when the clutch is rotated at its maximum speed, the forces resulting from the oil pressure in the oil chamber 22 and acting on the balls 40a and 42a are sufficiently large not to permit the balls to be forced to unseat by centrifugal forces acting on the same.

When supply of oil pressure into the oil chamber 22 is stopped, the clutch piston 14 is pushed back away from the clutch pack 20, i.e., pushed rightwardly in the drawing, by the springs 32. Disengagement of the clutch thus results.

However, there remains oil in the oil chamber 22, and the oil is subjected to centrifugal force since the clutch drum 12 continues rotating with the input shaft. By this, oil pressure is developed in the oil chamber 22. In this instance, since the first and second ball check valves 40 and 42 are forced to open by centrifugal force acting on the balls 40a and 42a, the pressurized oil is drawn off from the oil chamber 22. In this connection, oil can be rapidly drawn off through the second ball check valve 42 since a relatively large gap is provided between the ball 42a and the ball accommodation hole 42b. Oil remaining in a part of the oil chamber 22 radially outwardly of the second ball check valve 42 is drawn off through the first ball check valve 40. By the provision of such two ball check valves 40 and 42 at radially different locations, there cannot be developed in the oil chamber such a large oil pressure that causes the clutch piston 14 to move toward the clutch pack 20 to axially compress the same.

While provided with such a large gap, the second ball check valve 42 can close assuredly and instantly when there is supply of oil pressure into theoil chamber 22 since it is situated closer to the axis of rotation of the clutch drum 12 and accordingly centrifugal force acting on the ball 42a is smaller than the corresponding force acting on the ball 40a of the first ball check valve 40.

Fig. 2 shows a modified embodiment which is substantially similar to the previous embodiment except that the first and second ball check valves 40 and 42 are mounted on the clutch drum 12.

This embodiment can produce substantially the same effect as the previous embodiment.

Claims

1. A hydraulically operated multiple disc clutch comprising: a clutch pack having an alternating series of drive plates and driven plates; a clutch drum rotatable about an axis and drivingly coupled with said drive plates for rotation therewith; a clutch piston mounted in said clutch drum to define therebetween an oil chamber, said clutch piston being axially movable toward and away from said clutch pack depending upon oil pressure in said oil chamber; said clutch pack being operative to hold said clutch drum for rotation with said driven plates when axially compressed by said clutch piston; and means for drawing off oil from said chamber for thereby preventing centrifugal force acting on oil in said oil chamber from causing development of oil in said oil chamber when said clutch should be held disengaged, said means including at least two ball check valves which are arranged to be different in distance from the axis of rotation of said clutch drum.

2. A hydraulically operated multiple disc clutch as set forth in claim 1, in which said ball check valves are mounted on said clutch piston.

3. A hydraulically operated multiple disc clutch as set forth in claim 2, in which one of said ball check valves is arranged close to an outer circumferential periphery of said clutch piston, and the other ball check valve is arranged radially inwardly of said one ball check valve.

4. A hydraulically operated multiple disc clutch as set forth in claim 1, in which said ball check valves are mounted on said clutch drum.

5. A hydraulically operated multiple disc clutch as set forth in claim 4, in which one of said ball check valves is arranged close to an outer circumferential periphery of said clutch drum, and the other ball check valve is arranged radially inwardly of said one ball check valve.

6. A hydraulically operated multiple disc clutch as set forth in claim 3, in which each of said ball check valves comprises a ball and a ball accommodation hole formed in said clutch piston, and in which said ball accommodation hole has a smaller diameter hole section, a larger diameter hole section in which said ball is movably received and a conical hole section interconnecting said smaller and larger diameter hole sections.

7. A hydraulically operated multiple disc clutch as set forth in claim 5, in which each of said ball check valves comprises a ball and a ball accommodation hole formed in said clutch drum, and in which said ball accommodation hole has a smaller diameter hole section, a larger diameter hole section in which said ball is movably received and a conical hole section interconnecting said smaller and larger diameter hole sections.

8. A hydraulically operated multiple disc clutch as set forth in claim 6 or 7, in which said other ball check valve has between said ball and said ball accommodation hole a larger gap than that of said one ball check valve.

9. A hydraulically operated multiple disc clutch as set forth in claim 8, in which said ball of said other ball check valve is smaller than that of said one ball check valve.

10. A hydraulically operated multiple disc clutch as hereinbefore described with reference to and as illustrated in Fig. 1, or Fig. 2 of the accompanying drawings.