Planetary gear transmission systems or components – Fluid drive or control of planetary gearing – Fluid controlled mechanical clutch or brake
Patent
1996-09-11
1998-07-14
Bonck, Rodney H.
Planetary gear transmission systems or components
Fluid drive or control of planetary gearing
Fluid controlled mechanical clutch or brake
475141, 475127, 192 8713, B60K 2302
Patent
active
057795860
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a driving device, in particular for driving the wheels of a motor vehicle, having a drive and a mechanical gear connected downstream thereof and two hydraulically shiftable friction clutches or friction brakes by which the drive may be connected with the gear and which carry out the function of a parking brake.
BACKGROUND OF THE INVENTION
In relation to powershift transmissions, such as used in industrial vehicles like wheel excavators and loaders, it is known to provide an auxiliary uncoupling device by which the power train of the industrial vehicle may be interrupted thus making it possible to tow away a horizontally lying vehicle.
DE 43 05 763 has disclosed a driving device with a hydromotor and a mechanical gear connected downstream thereof which has a mechanically actuated auxiliary uncoupling device. In the driving device disclosed in said publication, the friction clutch can be locked in the open position by a mechanical device for the towing operation so that the vehicle can be towed without problem.
However, it is a disadvantage that the uncoupling of the power train is carried out mechanically wherefore this solution is very complicated and thus expensive in view of the multiplicity of separate parts needed.
SUMMARY OF THE INVENTION
Therefore, this invention is based on the problem of providing a driving device with which a vehicle lying in horizontal state can be towed without problem and which is of reasonable cost.
According to the invention, this problem is solved by connecting the friction clutches or friction brakes, via control pressure lines, with an auxiliary uncoupling device which has an adjustable accumulator piston and gearshift pistons cooperating therewith, wherein when the accumulator piston is actuated by the gearshift pistons, the volume of the accumulator piston can be supplied through the control pressure lines to the friction clutches for uncoupling.
By proving a hydraulic auxiliary uncoupling device having an adjustable accumulator piston and gearshift pistons cooperating therewith it is possible, to a great extent, to eliminate mechanical parts so that the driving device, according to the invention, can be produced and assembled economically.
To prevent the control pressure of the gear of the vehicle from acting upon the hydraulic auxiliary uncoupling device, an automatic sealing is effected when actuating the hydraulic auxiliary uncoupling device so as to ensure a reliable and perfect function of the driving device.
The seals here can be provided directly upon the gearshift pistons.
It can be advantageously provided that the auxiliary uncoupling device be equipped with a sealed oil volume which, during normal operation of the vehicle, is kept pressureless.
Since the auxiliary uncoupling device constitutes a self-contained hydraulically regarded system, the hydraulic parts needed for the auxiliary uncoupling device can be dimensioned, as needed, for actuating the auxiliary uncoupling device, that is, over-dimensions of the individual parts can be eliminated and thus the auxiliary uncoupling device can be produced at reasonable cost.
Since the auxiliary uncoupling device is kept pressureless during the normal operation of the vehicle, the necessary hydraulic parts can be made small in relation to the other parts of the transmission.
To prevent oil from leaking into the control pressure lines of the transmission, in case of buildup of pressure in the sealed circuit, the oil volume of the auxiliary uncoupling device can be separated by seals from the control pressure lines of the transmission.
By providing such seals, it is prevented that oil from the sealed oil volume penetrates into the control pressure lines, and that the oil volume within the auxiliary uncoupling device thus diminishes, which eventually can lead to a breakdown of the auxiliary uncoupling device.
The seals additionally prevent that oil from the control lines of the transmission, which are under high pressure, flows into the sealed oil volume and that thus the auxiliary coupli
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patent: 5509860 (1996-04-01), Legner
Gebhard Wolfgang
Heilig Eduard
Bonck Rodney H.
Kwon Peter T.
ZF Friedrichshafen AG
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