Patent GB-1342623-A (GB)
Title: Friction clutch control system
Inventor: BRITTAIN WILLIAM J
IPC: F16D48/06
Filed: 1971-02-23
Abstract: 1342623 Clutch control FORD MOTOR CO Ltd 23 Feb 1971 5202/71 Heading F2L A power operated clutch control system for a motor vehicle comprises an input acceleration comparator 26 which, when the clutch input speed exceeds the clutch output speed, provides a clutch engaging signal when the clutch input acceleration exceeds a control value K3. Electronic circuit.-Voltages V1, V2 proportional to clutch input and outut speed are applied to a circuit 21 which subtracts the output voltage from the input voltage and applies the difference through a line 22 to a comparator 23 which compares the voltage difference with a predetermined value K1. If the voltage difference is less than the predetermined value the comparator 23 supplies a signal through an OR gate 25 to and AND gate 31 which when enabled supplies a clutch engaging signal through an OR gate 32 to a clutch actuating circuit 10. The input voltage V1 is additionally supplied through a differentiating circuit to the comparator 26 which, when the input acceleration exceeds the control value K3 supplies a signal to an AND gate 29. The voltage difference signal 22 is applied to the other input of the AND gate 29 so that when the input speed is greater than the output speed and the input acceleration exceeds the control value K3 the gate 29 applies a signal through OR gate 25 to the AND gate 31 for clutch engagement. The voltage difference signal 22 is also applied through an inverter 56 to an AND gate 30 and the absence of a signal from the comparator 26 causes an inverter 57 to apply a signal to the AND gate 30 so that, when the output speed is greater than the input speed and the input acceleration is less than the control value K3, the AND gate 30 is enabled and applies a signal through OR gate 25 to the AND gate 31 for clutch engagement. The control value K3 is dependent upon engine speed and throttle pedal position and is supplied to the comparator 26 by a comparator 50. A second input to the AND gate 31 is supplied by a circuit including a normally open gear change switch 38. During ratio shift the switch 38 is closed to disable the AND gate 31 and thus effect clutch disengagement. A third input through the AND gate 31 is supplied through an OR gate 44 either from a vehicle speed comparator 41 or a throttle switch circuit 46. The comparator 41 supplies a signal when the vehicle speed exceeds a predetermined minimum value corresponding to engine stall speed. The throttle switch circuit includes a switch 45 which is opened when the throttle pedal is depressed to provide a signal to the gate 31. A neutral switch 39 which is opened when the gear is in neutral supplies a signal to an AND gate which by-passes the gate 31 the other input of the AND gate being supplied from the gear change circuit. When the gear is in neutral and the shift lever is not being moved the AND gate supplies a clutch engaging signal through the OR gate 32 to the clutch actuating circuit 10. The clutch actuating circuit 10 includes transistor switches 34, 35 which supply a positive clutch disengaging current to a solenoid controlled hydraulic or pneumatic valve in the absence of a control signal to the actuator 10 and supplies a negative clutch engaging current to the valve when a signal is applied to the clutch actuator 10. The valve controls the supply and exhaust of liquid or air to a clutch disengaging servo-motor (Fig. 2, not shown). Operation.-When the vehicle is at rest with a gear engaged, initial depression of the accelerator pedal opens the switch 45 to supply a signal to the third input of the AND gate 31. When the input acceleration exceeds the control value K3 a signal is applied to the input 11  of the AND gate 31 which is thus enabled and supplies a clutch engaging signal to the clutch actuating circuit 10. During ratio shifts the clutch is disengaged by closing the gear shift lever switch 38 which disenables the AND gate 31. When the vehicle slows down with the clutch engaged the comparator circuit 41 disenables the AND gate 31 for clutch disengagement when the engine stall speed is approached.