Patent GB-1517430-A (GB)
Title: Motor vehicle clutch control apparatus
IPC: F16D48/06
Filed: 1976-06-24
Abstract: 1517430 Clutch control NISSAN MOTOR CO Ltd 24 June 1976 [25 June 1975] 26333/76 Heading F2L In a clutch control for a motor vehicle therein an electromagnetically operated valve 44 connects a clutch disengaging servo 30 to a vacuum source 48 for clutch disengagement on closure of a touch sensitive gear shift lever switch 68 and a pair of electromagnetically operated valves 54, 56 having air ports 58, 62, 64 of different crosssectional areas are selectively connected to the servo 30 in response to clutch engaging movement and accelerator pedal position to control the rate of clutch re-engagement, clutch engagement at an intermediate rate is extended by prolonged energization of the valve 56 when the clutch temperature exceeds a predetermined value to compensate for a reduction in the coefficient of friction of the clutch plate due to the temperature rise. The clutch temperature is sensed by a sensor 80 having a reed relay 106 which is closed by a permanent magnet 104 when the clutch temperature exceeds the predetermined value. In Fig. 3 the magnet 104 is carried by a piston 96 of a wax-filled thermostat 92 housed in the clutch driving plate 18. As the clutch temperature rises the magnet 104 is moved towards a fixed plate 108 and when the temperature exceeds the predetermined value closes the reed relay 106 once each revolution - of the driving plate. In Fig. 5 the magnet 104 is secured to a plate 114 of ferro-magnetic material having a Curie point at the predetermined temperature. The plate 114 is separated from the driving plate by a paramagnetic material 112. When the clutch temperature is below the predetermined value the plate 114 is magnetically conductive and the flux of the magnet 104 passes therethrough but when the clutch temperature exceeds the predetermined value the plate 114 becomes magnetically non- conducting and the magnet 104 closes the read relay 106. Operation.-On movement of the gear shift lever the switch 68 is closed to energize the valve 44 which connects the vacuum source 48 to the servo 30 for clutch disengagement. On completion of ratio shift the valve 44 is deenergized to connect the servo 30 to the valve 54. During free movement of the clutch control linkage the valve 54 is energized through a closed switch 74 to connect the servo 30 to the air port 58 whereupon the servo piston 42 moves rapidly in the clutch engaging direction until the free movement is taken up and the switch 74 opened to de-energize the valve 54. Thereafter air is supplied to the servo 30 through the air port 62 or 64 of the valve 56 for intermediate or low rate of clutch engagement. Energization of the valve 56 is controlled by an electronic circuit, Fig. 8, in response to initial clutch engagement, vehicle speed, and accelerator pedal position. If the vehicle speed is below a predetermined value (e.g. 15 k.p.h.) and the engine throttle opening is less than # maximum, logic 1 signals are applied to inputs 158, 170 of a NAND gate 150 which produces a logic 0 output that triggers a single shot multivibrator 160 which produces a pulse at its first output Q. The width of the pulse is determined by a R-C circuit 140, 142, 146 and the pulse is applied through an OR gate 168 to the base of a transistor 122 which is rendered conducting to energize the coil 56a of the valve 56. The valve 56 thus opens the port 62 for clutch engagement at the intermediate rate. If the throttle valve is opened beyond #, # or 6/8 subsequent pulses from multivibrators 162, 164, 166 maintain the intermediate clutch engagement rate. If the clutch temperature exceeds the predetermined value and the reed relay 106 is closed, a transistor 138 is rendered non-conducting to increase the pulse width from the multivibrator 160 and thus the duration of the intermediate rate of clutch engagement. In Fig. 10 (not shown), the reed relay 106 is provided with a holding relay (178).