Patent GB-1310625-A (GB)
Title: Modulated clutch-toque converter transmission having a hydraulic control system for limiting torque
IPC: F16H45/00
Filed: 1970-12-23
Abstract: 1310625 Clutch control TWIN DISC Inc 23 Dec 1970 [5 Jan 1970] 61257/70 Headings F2C and F2L In a transmission system for a motor vehicle wherein power is transmitted through a hydraulically operated continuously slipping friction clutch CL, a torque converter TC and a change speed gear, the torque applied to the transmission output is limited by a torque limiting valve B which limits the maximum value of a control pressure 14 applied to a clutch control valve 16. Friction clutch.-The clutch CL may be of the type described in Specification 1,133,698 wherein a control valve 16 varies the pressure supplied through a line 10 to a clutch engaging servo 7 to maintain the clutch output speed constant for a predetermined control pressure 14. A variation in the control pressure 14 adjusts the output speed of the clutch CL which automatically maintains its output speed proportional to the control pressure. Fluid system components.-A pump 9 supplies control pressure 14 to the valve 16 through the torque limiting valve B which limits the maximum value of the control pressure below a predetermined output speed, a range selector valve C which permits the control pressure to by-pass the torque limiting valve B when the change speed gear is in a high ratio, and a manually controlled modulator valve D. The pump supply pressure is regulated by a valve E which reduces the pump supply pressure to a predetermined minimum value during a shift from forward to reverse ratios or vice versa in the manner described in Specification 1,293,475. Exhaust fluid from the regulating valve E passes through the plates of the clutch CL to the torque converter TC. Exhaust pressure 37 from the torque converter TC is maintained at a predetermined value by a pressure relief valve 13c. An output driven pump A applies pressure proportional to output speed to the end of the torque limiting valve B. Operation.-With the circuit conditioned as shown a selector valve TR establishes a third ratio in the change speed gear and vents the right-hand end of the range selector valve C. A spring 36 moves the range selector valve spool 33 right to the position shown. The control pressure thus by-passes the torque limiting valve B and is only regulated by the manually controlled modulating valve D. When the selector valve TR establishes first ratio in the change speed gear it additionally supplies pressure liquid through a line 35 to the righthand end of the valve spool 33 which moves left against the bias of the spring 36 to connect the torque limiting valve B in the clutch control pressure supply circuit. With a low output speed the torque limiting valve B is conditioned as shown and limits the clutch supply pressure to a predetermined maximum value. As the output speed rises the pump A supplies pressure liquid to the right-hand end of a loading plunger 25 of the torque limiting valve B which plunger acts through a spring to move left the valve spool 26 and thus increase the maximum clutch control pressure. The maximum control pressure determined by a torque limiting valve B when the vehicle is stationary may be adjusted through a linkage 24.