WO1994009284A1

WO1994009284A1 - Multi-plate clutch

Info

Publication number: WO1994009284A1
Application number: PCT/AU1993/000526
Authority: WO
Inventors: John Woollams
Original assignee: APPLIED FRICTION PTY Ltd
Current assignee: APPLIED FRICTION PTY Ltd
Priority date: 1992-10-13
Filing date: 1993-10-13
Publication date: 1994-04-28
Anticipated expiration: 1995-04-13
Also published as: ZA937612B

Abstract

A multi-plate clutch or brake unit having a number of reaction plates (8) interleaved with friction plates (7) and cooled by liquid such as oil pumped from a central area (15) through galleries (14) in the reaction plates. The reaction plates may optionally be formed from two floating plate members with an oil gallery therebetween and having a raised area on their mating faces allowing the oil in the gallery to react the closing force of the clutch during engagement.

Description

"MULTI-PLATE CLUTCH" TECHNICAL FIELD This invention relates to a multi-plate clutch and has been devised particularly though not solely for use in situations where prolonged periods of slip between input and output shafts are necessary.

BACKGROUND ART

There are many applications in mechanical drive systems where it is necessary for the power of an input shaft to be applied progressively to an output shaft to prevent shock loadings on the output shaft and to prevent damage to driven or driving components. Typical applications are in the automotive field and in various types of drives for conveying apparatus such as conveyor belt drives. Where it is necessary to transmit high torque loadings or to handle high power applications, it is common to use multi-plate clutches to distribute the frictional loading over a plurality of friction plates.

In some situations such as the start-up of a laden conveyor belt it is necessary to provide a controlled amount of slippage through the clutch between the input and the output shafts to enable the speed of the output shaft to be progressively equalised with the speed of the input shaft over a prolonged period. Such operation can cause overheating and ultimately component failure in conventional arrangements. Attempts have been made to overcome the heating problem by immersing the clutch plates in an oil bath but even this is not sufficient to avoid component failure in extreme operating situations. DISCLOSURE OF INVENTION

The present invention therefore provides a multi- plate clutch or brake unit comprising a set of friction plates interleaved between a set of reaction plates, one set being keyed to a central shaft and the other set being keyed to a peripheral drive member, and actuation means arranged to pressure the interleaved sets of plates against one another, characterised by the provision within either the reaction plates or the friction plates of generally radially extending galleries, and means supplying cooling liquid to the central area of the set of plates such that in use the cooling liquid is caused to flow outwardly from the central area through the galleries, cooling the plates.

The galleries may be of any desired configuration e.g. straight and radially extending or curved with a tangential component to the inner diameter of the plate or at any desired angle to a radius of the reaction plate.

Preferably the reaction plates are provided with a plurality of generally radially extending slots in their faces which mate with the friction plates, configured to wipe oil from the face of the friction plate.

Preferably the friction plates are segmented with generally radially extending passages between the segments. In one form of the invention one or more said reaction plates comprise two plate members movable relative to one another in a direction along the central shaft forming a said gallery therebetween.

Preferably at least one said plate member has one or more raised areas on a face facing the other said plate member.

Preferably said one or more raised areas comprise an annulus on the said plate.

BRIEF DESCRIPTION OF DRAWINGS Notwithstanding any other forms that may fall within its scope, one preferred form of the invention will now be described by way of example only with reference to the accompanying drawings, in which: -

Fig. 1 is a vertical cross-section through the longitudinal axis of a multi-plate clutch according to the invention, Fig. 2 is a transverse section through the axis of the clutch plates of the multi-plate clutch^" shown in Fig. 1, showing one friction plate and one reaction plate with portions cut away for clarity, and Fig. 3 is a cross-section on the line III-III of Fig. 2 showing the construction of an alternative form of reaction plate.

MODES FOR CARRYING OUT THE, INVENTION

In the preferred form of the invention a multi-plate clutch (1) is provided having an input shaft (2) and a coaxial output shaft (3) . The input shaft is journaled in suitable bearings (4) in a casing (5) and is provided with keyed splines (6) which engage corresponding notches on the inner edges of friction plates (7) . The set of friction plates are arrayed in a conventional multi-plate clutch configuration interleaved between a set of reaction plates (8) which in turn have notched outer peripheries keyed to a peripheral drive member (9) .

The drive member (9) is in turn keyed to the output shaft (3) journaled in bearings (10) within the casing (5) .

The clutch is actuated by actuation means in the form of hydraulic operation in conjunction with a spring pack (11) operable about a return pin (12) to move the friction plates and reaction plates into and out of pressured engagement for transmitting drive from the input shaft (2) to the output shaft (3) under controlled slip conditions .

As described thus far the arrangement is typical of a conventional multi-plate clutch.

In order to provide enhanced load carrying capacity and the ability to operate under sustained slip conditions, the multi-plate clutch is provided with cooling means arranged to supply cooling liquid, and typically oil, under pressure into the area (13) surrounding the input shaft (2) and thence to the central area (15) of the set of plates (7) and (8) .

Each of the reaction plates (8) is provided with generally radially extending galleries (14) (Fig. 2) permitting oil to flow from the central area (15) outwardly through the galleries (14) , cooling the reaction plate.

The configuration of the galleries may be to any desired shape or configuration such as radially straight galleries as shown in Fig. 2 separated by vanes (16) . This form of gallery is most suitable where the reaction plate is formed from two plate components machined to the desired configuration and sandwiched together forming the galleries (14) between the vanes (16) . Alternatively the reaction plates may be formed from solid material with the galleries drilled or otherwise machined through the thickness of the plate from the inner area (15) to the outer periphery (17) . The galleries may be of any number and configuration, i.e. they may be radially straight or curved with a tangential component to the inner area (15) .

Although the galleries have been described as incorporated in the reaction plates, they can alternatively be incorporated in the friction plates, or in both the reaction and the friction plates. In an alternative form of reaction plate as shown in Fig. 3, the reaction plate is formed from two plate components as described above, but the two components are not secured together but are free to float relative to one another along the line of the axis of the shafts (2) and (3) . The reaction plate is formed from a first plate member (20) and a second plate member (21) having outer circumferences (22) and (23) respectively and being spaced apart by the oil gallery (24) .

Oil being pumped through the gallery (24) in the direction of arrow (25) (as previously described) causes a pressure F_op to be exerted as a reaction pressure between the two plates (20) and (21) which reacts against the clutch activating pressure F exerted on the outside or friction surfaces (26) of the two plate members.

The facing surfaces (27) and (28) of the plate members (20) and (21) respectively are provided with at least one raised area formed by step (29) in at least one of the faces (27) and (28) forming an annulus portion (30) of the plate member which will contact the opposing face (27) before the remainder of the face (28) . The raised area could however take other forms.

As the clutch pack is compressed by the actuating piston in the clutch mechanism, F is increased by the segments (20) and (21) being brought together. The pressure F_op opposes the closing force F and offers a dampening medium. This allows the control of torque being transmitted by the force F to be regulated more accurately in the critical wet to dry transition zone as the friction plates and reaction plates of the clutch pack are brought together. The stepped plate member (21) acted upon over its entire face area by the force F_op gives an exponential response to the closing pressure F_p which is inverse to the detrimental friction characteristics of the clutch material at the point of clutch lock-up. It has been found in use that using stepped reaction plates of the type shown in Fig. 3 enables much more accurate control of the torque being transmitted by the clutch particularly in the area leading to solid lock-up of the clutch mechanism, i.e. to virtually identical rotation speeds between the input and output shafts.

Although the step (29) has been shown in the plate member (21) it will be appreciated that it could be incorporated in both the surfaces (27) and (28) of the plates (20) and (21) respectively or alternatively could be arranged so that the thicker portion of plate (21) (as seen in Fig. 3) is located nearer to the axis of rotation of the reaction plate.

The reaction plates are also preferably provided with a plurality of generally radially extending slots (18) in each face of the plate, where the plate contacts the friction plate (7) , allowing the major volume of oil to be scraped from the face of the friction plate preventing hydrodynamic lock or floating between the reaction plate and the friction plate.

To this end, the friction plates are also preferably provided in segments separated by slots (19) to allow the major volume of oil to be scraped from the reaction plates.

Once the cooling oil has passed through the galleries (14) or through the slots (18) or (19) it is collected in the outer area (17) where it is recirculated by a pump (not shown) , and optionally through an oil cooler, and returned under pressure to the inner areas (13) and (15) for recirculation. In this manner the heat is quickly and effectively removed from the interface between the friction plates and the reaction plates, allowing the clutch to operate under high load situations with large degrees of slip maintained for prolonged periods of time. Where it is desired to achieve controlled amounts of slip, i.e. in a speed reduction situation, the pressure applied to the clutch pack may be carefully monitored and modulated by electronic controlled circuitry to maintain the desired degree of speed reduction.

In a typical application on a conveyor belt, the signals for clutch pressure control may come from the belt speed at various points and compared with the output speed of the clutch shaft. This allows maximum acceleration or deceleration of the belt without stretch or induced shock waves, lengthening the life of the belt and components. Use of the clutch in this manner also reduces the drive motor power required. In mobile transport situations, signals from wheel rotational speed give a controlled rate of deceleration or can be used to prevent lock-up when the clutch is used in a braking situation. Although the invention has been described for use in a multi-plate clutch, typically when used with a drive motor in a start-up or speed change situation, it will be

<» appreciated that the invention can also be used as a brake or as a rapid cycling clutch-brake unit in machinery applications.

CLAIMS : -

1. A multi-plate clutch or brake unit comprising a set of friction plates interleaved between a set of reaction plates, one set being keyed to a central shaft and the other set being keyed to a peripheral drive member, and actuation means arranged to pressure the interleaved sets of plates against one another, characterised by the provision within either the reaction plates or the friction plates of generally radially extending galleries, and means supplying cooling liquid to the central area of the set of plates such that in use the cooling liquid is caused to flow outwardly from the central area through the galleries, cooling the plates.

2. A multi-plate clutch or brake unit as claimed in claim 1 wherein one or more said reaction plates comprise two plate members movable relative to one another in a direction along the central shaft forming a said gallery therebetween.

3. A multi-plate clutch or brake unit as claimed in claim 2 wherein at least one said plate member has one or more raised areas on a face facing the other said plate member.

4. A multi-plate clutch or brake unit as claimed in claim 3 wherein said one or more raised areas comprise an annulus on the said plate.

5. A multi-plate clutch or brake unit as claimed in claim 1 wherein there are a plurality of galleries in each said plate.

6. A multi-plate clutch or brake unit as claimed in claim 5 wherein the galleries are straight and radially extending.

7. A multi-plate clutch or brake unit as claimed in claim 5 wherein the galleries are curved with a tangential component to the inner diameter of the plate. 8. A multi-plate clutch or brake unit as claimed in any one of the preceding claims wherein the reaction plates are provided with a plurality of generally radially extending slots in their faces which mate with the friction plates, configured to wipe oil from the face of the friction plate.

9. A multi-plate clutch or brake unit as claimed in any one of the preceding claims wherein the friction plates are segmented with generally radially extending passages between the segments.