WO2014095630A1

WO2014095630A1 - Coupling mechanism

Info

Publication number: WO2014095630A1
Application number: PCT/EP2013/076540
Authority: WO
Inventors: Martin Brenninger; Richard Heindl
Original assignee: Agco International Gmbh
Priority date: 2012-12-21
Filing date: 2013-12-13
Publication date: 2014-06-26

Abstract

A clutch mechanism for a utility vehicle comprises a rotatable first body (51), a second rotatable body (52) rotatable relative to the first body (51), at least one first clutch disc (56a) which is non-rotatable relative to the first body (51), and at least one second rotating clutch disc (56b) which is fixed for rotation with the second rotatable body (52). An actuating member (57) is operable to press the first clutch disc (56a) and the second clutch disc (56b) against each other to close the clutch. A spring (70) which exerts a closing force on the actuating member (57) via intermediate part (72) presses the first and second clutch discs (56a, 56b) against each other to close the clutch. A clutch release means (71,73) is operable to exert a clutch release force which counteracts the closing force of the spring so that the actuating member (57) no longer presses the first and second clutch discs (56a, 56b) against each other. A clutch applying means (60) exerts a pushing force on the actuating member (57) in the same direction as the closing force to press the first clutch disc (56a) and the second clutch disc (56b) against each other to close the clutch.

Description

COUPLING MECHANISM

The present invention relates to clutch mechanisms for utility vehicles and

particularly, but not exclusively, to such mechanisms for use in coupling front and rear driven axles of such vehicles.

Standard drivelines for All Wheel Drive (AWD) utility vehicles, especially for tractors, comprise an AWD clutch between front and rear axles providing an engaged and disengaged position. AWD is disengaged when the vehicle is passing a curve and the inner wheel and outer wheel rotate at different speeds. For a steering brake function, AWD is also disengaged, so that only the rear wheels transmit brake forces to ground. The engaged position is chosen for high traction work, typically on the field.

For controlling the torque distributed to front and rear axles in dependence on traction demands for example, it would be advantageous to have a clutch

mechanism which provides an operating position in-between the disengaged and engaged positions. Depending on the operating position, the torque transmitted to rear and front axle can be split in a controlled manner. This technique, called torque- vectoring, may be realized in AWD-cars with, for example, a Haldex coupling between front and rear axles.

However, for utility vehicles and especially tractors, the requirements vary compared to passenger cars. In particular, the parking brake function is different compared to other vehicle types. In general, the parking brake function is realised by a parallel brake system to the service brake which mainly acts on one axle only, generally the rear axle. For passenger cars and trucks, this function is suitable. Looking at a tractor, the main difference is that a tractor is often used with a trailer with no brakes. As a result, in a park position on a hill, with a parking brake acting on the rear axle only, the rear wheels have to bear the load of about 40 tonnes. This may result in unplanned movement of the tractor when the rear wheels alone are not capable to handle the load. To avoid this, it is common to engage the AWD clutch during parking to increase the number of wheels transmitting brake force. To avoid any unintended disengagement, most AWD clutches are designed so that the engagement is kept even if the engine or power source is failing. Such normally-engaged arrangements can cause problems, however, if it is also desired to implement torque-vectoring.

It is an object of the present invention to provide a clutch system optimised for AWD applications which provides both a fail-safe On/Off engagement, for example for parking brake function, together with a variable engagement for torque distribution. In accordance with the present invention there is provided a clutch mechanism for a utility vehicle, comprising: a rotatable first body, a second rotatable body rotatable relative to the first body, at least one first clutch disc which is non-rotatable relative to the first body, at least one second rotating clutch disc which is fixed for rotation with the second rotatable body, an actuating member which can press the first clutch disc and the second clutch disc against each other to close the clutch, a spring means which exerts an closing force on the actuating member via an intermediate part to press the first clutch disc and the second clutch disc against each other to close the clutch, a clutch release means which can exert a clutch release force which counteracts the closing force of the spring so that the actuating member no longer presses the first clutch disc and the second clutch disc against each other, and a clutch applying means which can exert a pushing force on the actuating member in the same direction as the closing force to press the first clutch disc and the second clutch disc against each other to close the clutch. The mechanism provides a fail-safe arrangement whereby the spring means forces engagement of the clutch plates unless forcibly counteracted by the clutch release means. Variable engagement is provided by operation of both the clutch release means and clutch applying means. The invention further provides a continuously variable transmission arrangement and an AWD utility vehicle utilising such a clutch mechanism as a coupling mechanism between front and rear driven axles. Further optional features of the invention are recited in the attached sub-claims to which reference should now be made and which are incorporated herein by reference.

Embodiments of the present invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:

Figure 1 shows a drivetrain arrangement for an AWD vehicle suitable to incorporate a clutch mechanism according to the invention; Figure 2 is a sectional view of a first embodiment of clutch mechanism;

Figure 3 is a sectional view of a second embodiment of clutch mechanism; and

Figure 4 shows a further drivetrain arrangement incorporating the clutch mechanism.

Figure 1 schematically shows a drivetrain arrangement for a utility vehicle, in this case a tractor, comprising:

- engine 1

- flywheel 1 a

- rear axle 2

- rear axle differential 2a

- rear axle brakes 2b

- rear axle final drives 2c

- rear axle wheels 2d

- front axle 3 (part)

- front axle differential 3a

- front axle brake 3b

- front axle final drive 3c

- front axle wheel 3d

- a gearbox 4 to adapt gear ratios in stepped or infinitely variable mode

- All Wheel Drive (AWD) clutch 5 One side of the front axle assembly is omitted for reasons of clarity. Additionally shown in Figure 1 is a power take-off (PTO) shaft drive arrangement 6 driven by the engine 1 via a further clutch arrangement 7.

A first embodiment of a clutch arrangement according the present invention used suitably for the clutch 5 in Figure 1 is shown in sectional view in Figure 2.

The clutch arrangement 50 shown in Figure 2 has a first body (input element 51 ) and a second body (output element 52), both pivotably mounted and axially fixed via bearings 53 in a housing 54, which is only shown schematically for better clarity. The housing 54 may be a front wheel driveline housing. A further bearing 55 is provided between input element 51 and output element 52. First clutch discs 56a are pivotably fixed but axially movable attached to the input element 51 via engaging toothing. Similarly, second clutch discs 56b (in between first clutch discs 56a) are pivotably fixed but axially movable attached to the output element 52 via engaging toothing. The clutch discs 56a, 56b are brought into contact by first annular piston 57 moving in the direction shown by arrow A. The clutch discs 56a, 56b are of wet-type operating under oil supply.

The actuation of the clutch is now described for the two different actuating modes. A first actuation (clutch applying) means for Variable Adjustment mode is provided by a first actuation chamber 60 which can be pressurized with hydraulic fluid to move a first actuating member (annular piston 57) in direction A. The first actuation chamber 60 is connected to a hydraulic supply system via ducts 52a in output element 52, a rotary feedthrough arrangement 62 (including seals 62a) and a duct 54a in housing 54. If the first actuation chamber 60 is not pressurized, the first annular piston 57 is moved in the opposite direction to A by reset behaviour (caused by friction and oil adulteration) of the clutch discs 56a, 56b. When the engine is off and the oil supply system is off, leakage in the pipes etc. may result in the clutch arrangement 50 becoming disengaged over time. This may happen if the vehicle is parked for a long time. However, the fluid actuation allows a very fine dosing which is needed for controlled torque distribution between the front and rear axles. A second actuation means, for ON/OFF mode, comprises Belleville spring washer 70 which applies a force in direction A on a second annular piston 71 which is

connected to five intermediate parts 72 placed on a circular path around the output element. Second annular piston 71 can be moved in an opposite direction to A by pressurizing second actuation chamber 73, with the piston 71 and chamber 73 providing a clutch release means. The second actuation chamber 73 is connected to a hydraulic supply system via ducts 52b in output element 52, a rotary feedthrough arrangement 62 (including seals 62a) and a duct 54b in housing 54. Due to the Belleville spring washer 70, the second actuation means is always closed when the second actuation chamber 73 is disconnected from the oil supply. When using Belleville spring washers, friction forces between the washers result in a certain hysteresis. This hysteresis makes it difficult to realise a fine adjustment of the clutch engagement but, on the other hand, Belleville springs allow high forces in a very compact installation space.

Due to the connection of both activation means via intermediate parts 72, first piston 57 can only disengage the clutch discs if the second piston 71 is in the left position (in the orientation of the Figure) from piston chamber 73 being pressurized. On the other hand, as intermediate part 72 is not fixed to first piston 57, movement of the second piston 71 does not automatically move first piston 57 in the direction opposite to A.

By combining both actuation means in one coupling arrangement 50, the problems mentioned above are mitigated while allowing a very compact design. In the embodiment of Figure 1 , the clutch arrangement 50 would be connected coaxially to the driveline via toothing on the shaft end 51 a of input element 51 and via toothing on the shaft end 52c of output element 52. In an alternative configuration, if an axial offset is needed, input element 51 and/or output element 52 could be equipped with toothing on circumferential surfaces shown in dashed lines at 51 b and 52d, which toothing then engages a

correspondingly toothed gear. Referring back to Figure 1 , the clutch 7 in the PTO driveline may also comprise a clutch mechanism according to the invention.

Figure 3 shows another embodiment of the coupling arrangement clutch mechanism 500 whereby input element 510 is designed for a non-coaxial connection via circumferential toothing 510a. In similar manner to the arrangement of Figure 2, output element 520 offers a shaft end 520a for coaxial connection and a

circumferential toothing 520b. Due to this design, the routing of the oil supply to the respective actuation chambers 600 and 730 is different, but the actuation is as before.

The possibility of having multiple connecting points 51 a, 51 b, 52c, 52d, 510a, 520a and 520b to the input and output elements allows a special application in a driveline as shown in Figure 4. The driveline comprises

- engine 1

- flywheel 1 a

- rear axle 2

- rear axle differential 2a

- rear axle brakes 2b

- rear axle final drives 2c

- rear axle wheels 2d

- front axle 3

- front axle differential 3a

- front axle brakes 3b

- front axle final drives 3c

- front axle wheels 3d

The transmission arrangement shown in Figure 4 is of a hydrostatic-mechanical power split type with a mechanical branch and a hydrostatic branch 100 comprising:

- A pump 101 (driven by the engine 1 )

- A first hydraulic motor 102

- A second hydraulic motor 103 Further details of such a transmission arrangement may be found in WO 2009/059700 A2.

The first hydraulic motor 102 is connected to the rear axle 2 and can be connected via clutch 500 to the front axle 3. If the clutch 500 is disengaged, motor 102 is not connected to front axle 3 and only drives the rear axle (e.g. for transport on the road). The second hydraulic motor 103 is connected via clutch 300 to the front axle 3. This clutch is a standard On/Off clutch similar to a standard AWD clutch.

Clutch 500 also serves as a means to sum up the torque delivered by motor 102 (connected to shaft end 51 a of first body (input element) 51 as shown in Figure 2) and the torque supplied by motor 103 (connected to shaft end 52c of second body (output element) 52 as shown in Figure 2) for connection with the front axle 3 via circumferential toothed portion 52d (as shown in Figure 2) resulting in there being three elements for torque input/output. Although not shown, it will be readily understood that the clutch mechanism embodiment of Figure 3 could also be used in the driveline of Figure 4. Alternatively, both motors 102, 103 could be connected to the circumferential toothing 510a, 520b (51 b, 52d) for torque input while torque output could be provided at shaft ends 51 a, 52c, 520a. In the foregoing the applicant has described a clutch mechanism for a utility vehicle which comprises a rotatable first body 51 , a second rotatable body 52 rotatable relative to the first body 51 , at least one first clutch disc 56a which is non-rotatable relative to the first body 51 , and at least one second rotating clutch disc 56b which is fixed for rotation with the second rotatable body 52. An actuating member 57 is operable to press the first clutch disc 56a and the second clutch disc 56b against each other to close the clutch. A spring 70, which exerts a closing force on the actuating member 57 via intermediate part 72, presses the first and second clutch discs 56a, 56b against each other to close the clutch. A clutch release means 71 ,73 is operable to exert a clutch release force which counteracts the closing force of the spring so that the actuating member 57 no longer presses the first and second clutch discs 56a, 56b against each other. A clutch applying means 60 exerts a pushing force on the actuating member 57 in the same direction as the closing force to press the first clutch disc 56a and the second clutch disc 56b against each other to close the clutch.

From reading of the present disclosure, other modifications will be apparent to those skilled in the art and the scope of the invention is limited only by the following claims.

Claims

A clutch mechanism for a utility vehicle, comprising: a rotatable first body (51 ), a second rotatable body (52) rotatable relative to the first body (51 ), at least one first clutch disc (56a) which is non-rotatable relative to the first body (51 ), at least one second rotating clutch disc (56b) which is fixed for rotation with the second rotatable body (52), an actuating member (57) which can press the first clutch disc (56a) and the second clutch disc (56b) against each other to close the clutch, a spring means (70) which exerts a closing force on the actuating member (57) via an intermediate part (72) to press the first clutch disc (56a) and the second clutch disc (56b) against each other to close the clutch, a clutch release means (71 ,73) which can exert a clutch release force which counteracts the closing force of the spring so that the actuating member (57) no longer presses the first clutch disc (56a) and the second clutch disc (56b) against each other, and a clutch applying means (60) which can exert a pushing force on the actuating member (57) in the same direction as the closing force to press the first clutch disc (56a) and the second clutch disc (56b) against each other to close the clutch.

2. A clutch mechanism as claimed in claim 1 , wherein the actuating member (57) is a first piston slidable in a bore in the second rotatable body (52).

3. A clutch mechanism as claimed in claim 2, wherein the clutch applying means (60) is a first hydraulic cylinder acting on the actuating member (57).

4. A clutch mechanism as claimed in any of claims 1 to 3, wherein the clutch release means is a further piston (71 ) slidable in a bore in the second rotatable body (52), said further piston being positioned between the spring means (70) and the intermediate part (72).

5. A clutch mechanism as claimed in claim 4, wherein the clutch release

mechanism comprises a further hydraulic chamber (73) acting on the further piston (71 ) to oppose the closing force of the spring means (70).

6. A clutch mechanism as claimed in claim 4 or claim 5, wherein the further piston (71 ) is an annular piston.

7. A clutch mechanism as claimed in any preceding claim, further comprising a fixed housing (54) within which the first and second bodies (51 , 52) are at least partially rotatably mounted.

8. A clutch mechanism as claimed in claim 3, further comprising a first rotary feedthrough connecting a duct (54a) delivering pressurised fluid through a fixed housing (54) to a first annular opening in the second rotatable body (52), which first annular opening is in fluid communication (52a) with the first hydraulic chamber (60).

9. A clutch mechanism as claimed in claim 5, further comprising a second rotary feedthrough connecting a duct (54b) delivering pressurised fluid through a fixed housing (54) to a second annular opening in the second rotatable body

(52), which second annular opening is in fluid communication (52b) with the further hydraulic chamber (73).

10. A clutch mechanism as claimed in any preceding claim, wherein at least one of the first and second bodies (51 , 52) is shaped to provide an axially extending shaft (52c) for drivable connection thereto.

1 1 .A clutch mechanism as claimed in any preceding claim, wherein at least one of the first and second bodies (51 , 52) has a circumferential toothed portion (51 a, 52d) for driving engagement with a correspondingly toothed gear.

12. A clutch mechanism as claimed in any preceding claim, wherein the clutch discs are of wet type.

13. An all-wheel drive utility vehicle having an engine driving front and rear axles, wherein a clutch mechanism according to any of claims 1 to 12 is provided in the driveline between front and rear axles.

14. A PTO driveline for a utility vehicle, wherein a clutch mechanism according to any of claims 1 to 12 is provided in the driveline between transmission and PTO shaft.

15. A continuously variable transmission comprising first and second hydraulic motors and connection means operable to separately and selectively connect each motor to drive one or two axles of a vehicle, wherein the connection means include a clutch mechanism as claimed in any of claims 1 to 12 connectable to sum the torque from the motors.

16. A continuously variable transmission as claimed in claim 15, wherein one of the motors is connected directly to the first body (51 ) of the clutch mechanism and the other is connectable to the second body (52) through the operation of an additional clutch.

17. A continuously variable transmission as claimed in claim 15, wherein both of the first and second bodies (51 , 52) has a circumferential toothed portion in driving engagement with a respective one of the first and second hydraulic motors.