GB2128272A - Friction clutch with power take-off - Google Patents

Abstract

A clutch comprises a cover 3 fastened at the driving side of a flywheel 1. A pressure plate 11 freely is supported by said cover 3 so as to be axially displaceable, a clutch disc 28 interconnected to an output shaft 30 being sandwiched between friction surface 27 of the flywheel 1 and the pressure plate 11. An inner peripheral part of the cover 3 and power take-off shaft 9 are interconnected through a damper disc 45 the function of which is to absorb torque vibration and minimise noise. <IMAGE>

Description

SPECIFICATION Semi-dual clutch This invention relates to semi-dual clutches for use in cases where two distinct output shafts, for example for driving a tractor and attached working equipment respectively, are required to be driven, for instance pn an agricultural tractor or a tiller.

A dual clutch, combining two clutches, may be used when two separate output shafts are required, as in case of a conventional tractor.

However, semi-dual clutches have been proposed recently for the purpose of simplifying such a clutch mechanism. The term semi-dual clutch is a general term for a clutch mechanism in which the one output shaft is driven freely disconnectedably through one clutch mechanism and the other output shaft is directly interconnected to the driving side to be always driven, as compared with a dual clutch in which two distinct clutch mechanisms are incorporated, are for each shaft.

Fig. 1 of the accompanying drawings illustrates a typical embodiment of a known construction of dual clutch, being a diametrical sectional side elevation of the dual clutch, with the arrow F indicating the front of the clutch.

The known embodiment of dual clutch illustrated in Fig. 1 comprises a cylindrical flange 2 provided integrally on the outer periphery of an engine flywheel 1, and a disc-shaped clutch cover 3 is secured to the annular rear surface thereof by means of plural bolts 4. A hub 5, concentric with the flywheel 1, fits in a hole in an inner peripheral part of the cover 3, and an annular flange 6 of the hub 5 and the cover 3 are integrally fastened together by means of plural rivets 7. An internal spline 8, concentric with the hub 5, is formed in the hub 5, and an external spline 10 of a power take-off shaft 9 fits therein. The rear end of the power take-off shaft 9 is connected to working equipment (not shown) for example rotary equipment, e.g. by way of a reducing gearing or other transmission.

An annular-type pressure plate 11, approximately parallel to the cover 3, is disposed in a space defined by the cover 3 and the flywheel 1, and three projections 12 are fomed integrally on a surface of the cover side of the plate 11 at circumferentially equal intervals in such dispositions that the projections project substantially parallel to the shaft 9. The projections 12 locate in corresponding holes 1 3 provided in the cover 3, and respective tip ends of the projections 12 project through the holes 1 3 to the back face 3a of the cover 3. A hole 14 is formed through the plate 11 in register with each projection 12, substantially parallel to the shaft 9 and a respective lever bolt 1 5 extends therethrough from the front side.A hole 17, provided on an outer peripheral part of a release lever 1 6, fits over an end portion of the bolt 1 5 projecting beyond the projection 12, and a nut 1 6 screws onto the bolt 1 5 to provide a stop or abutment for the lever 1 6. The tip end of a lever seat 20 fastened to the cover 3 by a rivet 1 9 fits into a hole 21 so that the lever 16 is supported so as to be swingable in the directions indicated by the arrow X, by using the seat 20 as its centre of rotation or fulcrum and an inner peripheral part of the lever 1 6 contacts with an annular lever plate 22 parallel with the cover 3.The plate 22 is movable in the directions indicated by arrow X2 by operating a clutch pedal (not shown in the Figure) being biassed in the direction of contact against the lever 16, by means of a return spring 23. Further, the pressure plate 11 is constantly pressed towards the flywheel 1 by means of pressure springs 25 which are accommodated so as to be substantially parallel to the shaft in respective flanged spring caps 24 fitted from the front side in respective holes 3b in the cover 3.

Annular facings 29 provided on an outer peripheral part of a clutch disc 28 are disposed between a friction surface 26 at the flywheel side of the pressure plate 11 and a friction surface 27 of the flywheel 1 opposite thereto. The clutch disc 28 has, at its centre, a hub 31 which spline fits onto a main output shaft 30, and the hub 31 has an integral annular flange 32 on its outer peripheral surface. Friction members 33, 34 (such as friction washers, corn springs, dished springs or the like) are disposed along inner peripheral parts of both sides of the flange 32, and a pair of plates comprising an annular clutch plate 35 and a retaining plate 36 are disposed one on each side of the flange 32 in such a manner as to sandwich the friction members 33, 34.

At positions near to the outer peripheries of the flange 32 and the two plates 35, 36, there are plural window holes 37, 38, 39 (one only of each of which is shown) having spaces left in the circumferential direction of the clutch disc 28.

These window holes 37, 38, 39 register with each other in the direction parallel to the output shaft 30, and respective torsion springs 40 are accommodated in each set consisting of the three registering window holes 37, 38 and 39. Each such spring 40 extends in the circumferential direction of the clutch disc 28, the flange 32 and both plates 35, 36 thereby being elastically interconnected by means of the spring 40. Outer peripheral parts of the two plates 35, 36 are integrally interconnected by means of a stop pin 41.An inner peripheral part of a cushioning plate 42 disposed substantially coplanar with and projecting radially outwards from the outer peripheral part of the clutch plate 35 is fastened to such outer peripheral part of the clutch plate 35 by means of rivets 43, and the annular facings 29 are fixed to both sides of the plate 42 by means of plural rivets 44.

When the semi-dual clutch as shown in Fig. 1 is employed, for example, in an agricultural tractor.

the rear end of the main output shaft 30 will, for example, be connected to a change gear or gear box for driving, and the power take-off shaft 9 will be connected to a hydraulic clutch provided in a rear change gear. Then, working equipment coupled to the power take-off shaft 9 will be turned ON and OFF by operation of the hydraulic clutch.

It will be evident that the semi-dual clutch as illustrated in Fig. 1 has disadvantages arising from the fact that the flywheel 1 and the power take-off shaft 9 are directly interconnected with each other. These disadvantages are: a) Shock and noise arising from the engagement of the hydraulic clutch for power take-off; and b) Generation of abnormal noise and vibration during operation.

An object of the present invention is to obviate or minimise the above-discussed disadvantages.

In order to accomplish this above object, in the clutch of this invention, a cover is fastened to a flywheel on a driving side thereof and the arrangement comprises a pressure plate, freely slidable along its centre axis and supported by the cover, a clutch disc interconnected to an output shaft being sandwiched between a friction surface of the flywheel and the pressure plate, and an inner peripheral part of said cover and a power take-off shaft being interconnected by way of a damper disc so as to absorb torque vibration.

The invention will be described further, by way of example, with reference to the accompanying drawings, of which Fig. 1 has already been described in detail. In the drawings: Fig, 2 is a radial section through a semi-dual clutch constructed in accordance with the present invention.

In Fig. 2, ail these components which are similar to those already described with reference to Fig. 1 have been allocated similar reference numerals and are only described in more detail where this is necessary for the understanding of the invention.

In the embodiment of the semi-dual clutch of the invention as shown in Fig. 2, a damper disc 45 having a vibration-absorbing mechanism similar to that of the clutch disc 28 is provided between an inner peripheral part of the clutch cover 3 and power take-off shaft 9. Thus, in the arrangement of Fig, 2, a spline hub 46 of the damper disc 45 fitting with a spline 10 of the power take-off shaft 9 has an integral annular flange 47 around its outer periphery, and friction members 48 and 49 are disposed around the two sides of the inner periphery of the flange 47.Further, a pair of plates comprising an annular main-plate 52 and a sub plate 53 are disposed one on each side of the flange 47 so as to sandwich the friction members 48 and 49, and the two plates 52, 53 fit freely onto the hub 46 so as to be rotatable, with slight play (clearances 50,51) therebetween. At positions near to their outer peripheries the flange 47 and the two plates 52 and 53 are formed with plural window holes 54, 55 and 56 (only one of which is shown for each), and these are provided with spaces left in the circumferential direction of the damper disc 45. The window holes 54, 55 and 56 register with each other in the direction parallel to the power take-off shaft 9, and a respective torsion spring 57 is fitted in each set consisting of the three window holes 54, 55 and 56.Each such spring 57 extends in the circumferential direction of the damper disc 45, and the flange 47 and the two plates 52 and 53 are accordingly elastically interconnected by means of the spring 57. The radial width of the hole 54 is longer than the diameter of the spring 57. Outer peripheral parts of the two plates 52 and 53 are integrally interconnected by means of a stop pin (not shown), and an outer peripheral part or parts of the plate 52 is or are fastened to an inner peripheral part of the clutch cover 3 by means of one or more rivets (not shown).

The operation of the clutch of Fig. 2 is as follows. Torque from the flywheel 1, from the driving side, is transmitted through the clutch cover 3, the plates 52 and 53, the spring 57, the flange 47, and the hub 46, to the power take-off shaft 9. During this, the spring 57 is compressed in correspondence with the transmitted torque and the two plates 52 and 53 are turned reiative to the flange 47 so that slippage occurs at the friction members 48 or 49. The compression of the spring 37 together with the slippage of the friction mernbers 48 and 49 is effective to absorb torque vibration and eliminate abnormal vibration and abnormal noise in the power transmitting mechanism for the power take-off.When a clutch pedal (not shown) is operated and the lever plate 22 is moved forward, the release lever 1 6 moves the pressure plate 11 rearward, with its fulcrum point located at the lever seat 20, so that the grip on the facing 29 of the clutch disc 28 is relaxed to bring the clutch into its disengaged state. On the other hand, when the plate 22 is moved rearwards, force holding the plate 11 backward is removed and the plate 11 is pressed forward by the pressure spring 25 (Fig. 1): then, the facing 29 is sandwiched between and firmly gripped between the plate 11 and the flywheel 1 and torque from the fiywheel 1 is transmitted through the clutch disc 28 to the main output shaft 30, the clutch being in its engaged state.Since the clutch disc 28 has a vibration absorbing mechanism similar to that of the damper disc 45, such mechanism similarly functions to eliminate abnormal vibration and abnormal noise.

In tie construction shown in Fig. 2, the plates 52 and 53 fit on the hub 46 with slight play (clearances 50 and 51) left therebetween and the radial extent of each hole 54 is longer than the diameter of the spring 57, so that premature wear of the spline of the hub 46 and the spline 10 is avoided, owing to the fact that slight eccentricity can occur between the plates 52 and 53 and the hub 46, even when a slight eccentricity exists between the clutch cover 3 and the power take-off shaft 9.

As will be understood from the above description, in the arrangement according to this invention, the cover 3 is fastened to the flywheel 1 at the driving side thereof. The pressure plate 11 is freely slidable along its centre axis and is supported by the cover 3. The clutch disc 28 interconnected to the output shaft 30 is sandwiched between the friction surface 27 of the flywheel 1 and the pressure plate 11, and the inner peripheral part of said cover 3 and the power take-off shaft 9 are interconnected through the damper disc 45 the function of which is to absorb torque vibration. Thus, the advantage is obtained that abnormal vibration and abnormal noise in the power transmitting mechanism for power take-off are minimised and the service life thereof is improved. Further, there is another advantage that optimum clutch design becomes possible by appropriate selection of the characteristics of the damper disc 45.

Moreover, in the embodiment shown in Fig. 2, the plates 52 and 53 are fitted onto the hub 46 with slight play (clearances 50, 51) left therebetween and the radial extent of the hole 54 is greater than the diameter of the spring 57, so that the advantage is obtained that premature wear of the spline of the hub 46 and the spline 10 due to eccentricity between the cover 3 and the power take-off shaft 9 can be avoided.

In the clutch of the present invention the construction of the damper disc 45 is not limited to that shown in Fig. 2, but instead other forms of damper disc for absorbing torque vibration, such as those utilizing, for example, rubber or fluid, can be employed.

Claims (4)

1. A semi-dual clutch comprising a cover fastened to a flywheel on a driving side thereof, a pressure plate, freely slidable along its centre axis, being supported by said cover, a clutch disc connected to an output shaft being sandwiched between a friction surface of the flywheel and the pressure plate, and an inner peripheral part of said cover and a power take-off shaft being interconnected by way of a damper disc so as to absorb torque vibration.

2. A semi-dual clutch as claimed in claim 1 in which the damper disc is so constructed that an annular flange is formed integrally with a splined hub of an output side, and a main-plate and a subplate of an input side are disposed one on each side of said annular flange, said plates being elastically interconnected to the flange by torsion springs, and friction members are interposed between said plates and the flange.

3. A semi-dual clutch as claimed in claim 2 in which the main-plate and the sub-plate are fitted onto an outer peripheral surface of the splined hub with clearance therebetween.

4. A semi-dual clutch substantially as hereinbefore described with reference to and as illustrated in Fig. 2 of the accompanying drawings.