Hydraulic control system for power transmission having a modulated friction clutch

Claim 1

In a control system for a power transmission having a hydraulically operated, modulated friction type clutch connnected in driving relationship to a torque converter, said modulated clutch including hydraulically shiftable piston means for causing clutch clamp-up and a centrifugal hydraulic valve for regulating the amount of pressure fluid admitted to said piston means, and a multi-ratio, hydraulically operated gear shift mechanism driven by said torque converter, said shift mechanism having a plurality of hydraulically operated clutches, a selector valve for selectively operating any one of said mechanism clutches; a set pressure regulator for admitting a fixed fluid pressure to said selector valve, a source of fluid pressure for said hydraulically operated modulated clutch including a fluid pump, a modulating valve between said source of fluid pressure and said modulated clutch, said source of pressure fluid connected directly to said pressure regulator and to said modulating valve, whereby a fixed fluid pressure is delivered to both said selector valve and to said modulating valve, said modulating valve having an operator shiftable element for controlling flow of fluid pressure to said modulated clutch, said modulating valve also having an acutating means for said shiftable element including a pressure regulating chamber, and an operator foot operated control valve in fluid communication with said regulating chamber and having adjustable orifice means for dumping pressure fluid from said regulating chamber and reducing the power output from torque converter to the gear shift mechanism.