Clutch control system with thermostatic regulator valve

A control system of a clutch engagement mechanism drivingly connected to an output shaft of an engine and an input shaft of a transmission to be shifted by a manual lever, the system comprising:

• servo means operatively connected to said clutch engagement mechanism for engaging and disengaging said clutch engagement mechanism;
• shift valve means for connecting a source of oil pressure to said servo means upon shifting of said manual lever to operate said servo means and for connecting said servo means to an oil reservoir after shifting of said manual lever to release the operation of said servo means;
• first and second drain passage means arranged in parallel and connecting said shift valve means to said oil reservoir;
• thermostatically operated valve means, disposed within said first drain passage means for controlling the flow of oil discharged from said servo means to said oil reservoir through said first drain passage means in accordance with changes of the oil temperature, said second drain passage means constantly permitting the flow of oil, which has been bypassed around said first drain passage, to said oil reservoir;
• and
• flow restriction means disposed within said second drain passage means for throttling the bypassed oil flow.