Motor vehicles – Having four wheels driven – With differential means for driving two wheel sets at...
Patent
1990-05-24
1992-04-14
Hill, Mitchell J.
Motor vehicles
Having four wheels driven
With differential means for driving two wheel sets at...
B60K 2304
Patent
active
051039303
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention concerns an apparatus for electrohydraulic actuation of a clutch that locks a transfer differential transmission of a motor vehicle having an actuation piston actuatable with pressurized fluid via a main control line depending on the position of an electrically actuatable pressure-control valve wherein the pressure-control valve, when actuated, pressurelessly diverts pressurized fluid to the tank and wherein the transfer differential transmission is situated at the rear of an automatic transmission.
BACKGROUND OF THE INVENTION
In an already known apparatus of this kind (DE-A 32 12 195), a transfer differential transmission situated on the transmission output and connected with both axles of the motor vehicle is locked by means of a multi-disc clutch in accordance with the parameters of the motor vehicle such as travel speed, steering angle, or engine torque. For said purpose, the multi-disc clutch is engaged by a hydraulic working pressure of a main control line against a disengaging spring, the working pressure in the main control line being adjusted as result of said parameters, by means of an electro-magnetically actuated pressure-control valve, and therewith the locking effect of the multi-disc clutch. A separate hydraulic system is provided for said actuation of the multi-disc clutch. Besides, upon actuation of the pressure-control valve in direction of the opening, vibrations can appear in the main control line pressure which lead to an indifferent control behavior of the whole pressure system.
SUMMARY OF THE INVENTION
Accordingly, the problem to be solved by this invention is, in order to reduce the construction cost, to combine an apparatus for electro-hydraulic actuation of a clutch of a transfer differential transmission with a hydraulic system already existing in the motor vehicle whereby pressure fluctuations, which are produced by parallel control operations of the control system and can result in pressure drops of the system and natural vibrations of the pressure-control valve, should have no effect upon the actuation of the apparatus of the general type.
Said problem is solved in an apparatus of the above mentioned kind by the fact that the main control line is connected to a main pressure system of a control unit of the automatic transmission, that starting from the main pressure system a reduced constant pressure is obtained by a pressure-reducing valve in a pilot control line in which the pressure-control valve is situated and which via a control space acts upon a control piston of a clutch valve situated in the main control line whose spout, spring-loaded on the other side, activates the actuation piston with pressurized fluid from the main control line, and that damping means, preferably a spring-accumulator damper, is situated in the pilot control line for reducing pressure vibrations Accordingly, pressurized fluid is fed to the actuation piston from the main pressure system of the automatic transmission via the main control line in accordance with the position of the clutch valve or the actuation piston is pressure-relieved The clutch valve is actuated here via the pilot control line where a reduced, constant pressure is obtained by the pressure-reducing valve. Consequently, the pressure-reducing valve already eliminates pressure fluctuations which can occur in the main pressure system of the automatic transmission and thus faulty controls of the clutch can be prevented. Since the pressure-control valve in which a pilot control line having reduced working pressure is situated and which acts only upon the spool of the clutch valve which, on the other hand, is spring-loaded, the danger of producing vibrations can be reduced considerably But for reasons of safety, a damping means in the form of a spring-accumulator damper is also situated in the pilot control line which reduces the natural vibrations of the pressure control valve. damping piston of the spring-accumulator damper can interact with safety valve front-mounted on a clutch valve and
REFERENCES:
patent: 4787471 (1988-11-01), Kobayashi
patent: 4874059 (1989-10-01), Kasegawa
Hill Mitchell J.
Zahnradfabrik Friedrichshafen AG
LandOfFree
Apparatus for electrohydraulic actuation of a clutch assembly fo does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus for electrohydraulic actuation of a clutch assembly fo, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus for electrohydraulic actuation of a clutch assembly fo will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2343081