192 clutches and power-stop control – Clutches – Operators
Patent
1998-06-01
1999-11-09
Bonck, Rodney H.
192 clutches and power-stop control
Clutches
Operators
192103F, F16D 43284, B60K 1735
Patent
active
059796316
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a device for transmitting torque between two rotatable, coaxial shaft members in a stationary housing, the device containing a number of alternate clutch discs, connected to the two shaft members and engageable to counteract differential rotational speed between the shaft members, and a hydraulic arrangement, driven by the speed differential between the two shaft members and including the housing coaxially with the shaft members and are intended to create a hydraulic pressure in the arrangement and thereby to engage the clutch discs at a differential rotational speed between the two shaft members, engaging the other of the shaft members via cams, which are angularly offset in relation to each other, so as to impart to the pistons a reciprocating movement at a differential rotational speed between the shaft members, and hydraulic lines containing check-valves.
BACKGROUND OF THE INVENTION
A device of the kind described above is known through our own EP-A-94200571.1, to which reference is made for further information about the technical field and certain features common for this prior device and the device according to the present invention. With this known device it has become possible to obtain a reasonably even or non-fluctuating differential rotational speed decrease or braking action in the device. With one embodiment of the prior device it is also possible to obtain the desired, even action also in a second rotational direction, i e in the reverse gear, if the device is used as a so called differential brake in a connection between the front and the rear axle of a road vehicle.
However, a supply piston in the hydraulic arrangement of the prior device is spring biassed into engagement with its cam, and the hydraulic system itself is of the open type, sucking oil from a reservoir and delivering it back after use in the system.
A drawback with this device is that it is impossible to obviate or switch-off its action, which for example means that towing away of a vehicle provided with such a device is very difficult. A present requirement on a device of the kind referred to is that it shall make a towing away at a speed of 50 km/h possible.
THE INVENTION
This may according to the invention be attained in that the hydraulic line system is a closed system and in that oil is supplied to the system from a reservoir by means of a pump and may be removed from the system to the reservoir via an overflow valve. There is no spring bias on any piston in the device.
By switching off the pump or rather its motor, which is done by means of the ignition key of the vehicle, the clutch discs in the device will not be imparted any braking force at towing, and there is no risk for burnt clutch discs.
The pump motor may have a very low power consumption, and in a practical case it only provides some 3% of the maximum working pressure.
In order to control the device, the hydraulic line system is provided with an electrically controlled throttle valve.
In order to level out certain variations in the hydraulic flow, the hydraulic line system may be provided with an accumulator.
It is of the greatest importance that the function of the device is as smooth as possible.
This is in a first practical embodiment, in which a cam disc provided with a circular cam curve is arranged to engage the clutch discs and in which a thrust washer in engagement with the housing over a needle bearing is arranged at the opposite side of the clutch discs, obtained in that four piston actuating members are in engagement with the cam curve of the cam disc for imparting to four pistons a reciprocating movement at a differential rotational speed between the shaft members.
In this embodiment all reaction forces are used to engage the clutch discs.
In a second embodiment of the same general design one piston actuating member is in engagement with the cam curve of the cam disc, whereas two piston actuating members are in engagement with a circular cam curve on an axial end surface of a hub on the first s
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patent: 5070975 (1991-12-01), Tanaka et al.
patent: 5087228 (1992-02-01), Johansson
patent: 5103642 (1992-04-01), Suzuki et al.
patent: 5358455 (1994-10-01), Lundstrom
patent: 5405293 (1995-04-01), Severinsson
patent: 5469950 (1995-11-01), Lundstrom et al.
Bonck Rodney H.
Haldex Traction AB
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