Power plants – Pressure fluid source and motor – Condition responsive control of pump or motor displacement
Patent
1977-05-11
1978-05-30
Geoghegan, Edgar W.
Power plants
Pressure fluid source and motor
Condition responsive control of pump or motor displacement
60465, 60DIG2, F16H 3946
Patent
active
040916170
ABSTRACT:
An electro-hydraulic control for a hydrostatic transmission including a variable displacement hydraulic pump and fluid operable servos to vary the displacement of the pump. The electro-hydraulic control is in series between the charge pump and the standard manual controller and determines the maximum pressure of the charge fluid ported to the standard controller. The electro-hydraulic control includes a spool biased toward a first position to port fluid from the charge pump to the standard controller, and biased toward a second position to relieve to tank the pressure of fluid ported to the manual controller. The biasing toward the second direction is accomplished, in part, by pressure in a fluid chamber exerting a biasing force on the spool, the fluid chamber being in communication with drain through a variable orifice which is variable in response to a pressure command signal. This signal is generated by control logic including a torque command signal generator which is variable to correspond to a maximum desired input torque setting and circuitry providing a torque approximation signal representing the product of pump displacement and the instantaneous pressure command signal. The circuitry compares the torque command and torque approximation signals and generates a new pressure command signal tending to minimize the difference between the torque command and approximation signals. As a result, the commanded maximum system pressure varies such that the product of maximum system pressure and pump displacement (equal to input torque) is constant, for a given input torque setting.
REFERENCES:
patent: 3864915 (1975-02-01), Metailler
patent: 3924410 (1975-12-01), Cornell et al.
Eaton Corporation
Geoghegan Edgar W.
Kasper L. J.
McCloskey R. J.
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