Motors: expansible chamber type – Plural relatively movable or rigidly interconnected working... – Condition responsive means for modifying working member...
Patent
1989-10-03
1991-12-03
Look, Edward K.
Motors: expansible chamber type
Plural relatively movable or rigidly interconnected working...
Condition responsive means for modifying working member...
91518, 91528, 91532, 137529, 137538, F15B 1100, F16K 1500
Patent
active
050691112
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a hydraulic pressure-control device, specially for powershift transmissions of motor vehicles according to the preamble of claim 1.
Such a pressure-control device has been disclosed in German patent 25 57 585. In that pressure-control device a main pressure valve serves to produce a certain main pressure for actuating shift elements such as clutches and brakes. In the case of powershift transmissions the torque converter is bypassed by a lock-up clutch at high speeds. When the lock-up clutch is open, the main pressure is elevated in order that the higher torques effected by the torque converter during the gas give off can be transmitted by the clutches. If in this state of operation the speed of the pump is low--for example, when the vehicle is stationary and at low speeds of the vehicle and low speeds of the motor (idling speed)--then the leakages associated with the delivery rate of the pump are high. Thereby the low-pressure comsumer devices attached to the drain pipe of the main pressure valve such as the torque converter and a lubrication circuit attached thereto are supplied with a correspondingly smaller amount of fluid.
The problem to be solved by the invention is to improve the pressure-control device known already in the sense of reducing the leakages occurring in said state of operation at low driving speeds of the fluid pump.
This problem is solved by the hydraulic pressure-control device characterized in claim 1. Advantageous and convenient embodiments are given in the sub-claims. The invention is not limited to the combinations of features of the claims. Other important possible combinations result for the expert from the claims and individual features of the claims on the basis of the stated problem.
By the parallel connection of the second pressure-relief valve to the main pressure valve and by an added throttle site it is obtained that at low driving speeds and thus with a small fluid current, a relatively low working pressure be adjusted. Through the second pressure-relief valve, a sufficiently large current of fluid flows toward the lubrication circuit. The outcropping pressure on the shift elements is relatively low so that the leakages can likewise be kept small. The rear-mounted throttle site permits that, as the driving speeds of the fluid pump increase and the current of fluid thus becomes larger, the working pressure be adjusted also to a level required for actuating the shift elements.
In a convenient embodiment, due to the parallel connection of the compression springs of the main pressure valve and of the second pressure-relief valve in the corresponding state of operation, both compression springs act upon a valve piston which carries the functions of the main pressure valve and of the second pressure-relief valve. Therefore, the actual compression spring of the main pressure valve can be reduced.
The compression spring having the stronger initial stressing force is bound, that is, limited in its expansion. Thereby the common valve piston can regulate with uninterrupted transition two different heights of pressure. The parallel connection and encasing into each other of the two compression springs of the main pressure valve and of the second pressure-relief valve result in a simpler and space-saving construction of the pressure-control device.
The invention is explained in detail herebelow with reference to an embodiment shown in the drawing. In the drawing:
FIG. 1 is a fundamental illustration of the pressure-control device of the first embodiment with the shifting arrangement of the main pressure valve and of the second pressure-relief valve,
FIG. 2 is a fundamental illustration of the pressure-control device of the second embodiment with the shifting arrangement of FIG. 1, but with the function of the second pressure-relief valve with the function of the second pressure-relief valve integrated in the main pressure valve,
FIG. 3 is a constructional embodiment of the pressure-control device of FIG. 2.
The hydraulic pressure-control device of FIG. 1 conta
REFERENCES:
patent: 1308165 (1919-07-01), Clark
patent: 2011333 (1935-08-01), Clifton
patent: 4034563 (1977-07-01), Orth
patent: 4541451 (1985-09-01), Wittren et al.
patent: 4556078 (1985-12-01), Wittren
patent: 4869288 (1989-09-01), Toshio et al.
Loffler Alfons
Marte Walter
Wiggermann Peter
Look Edward K.
Ryznic John
Zahnradfabrik Friedrichshafen AG
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