Patent GB-1306249-A (GB)
IPC: F16H61/00
Filed: 1970-12-15
Abstract: 1306249 Change-speed control NISSAN MOTOR CO Ltd and HITACHI Ltd 15 Dec 1970 [22 Dec 1969] 59531/70 Heading F2D [Also in Division G4] Servo pressure applied through solenoid valves to friction clutches and brakes in a torque converter-driven planetary automatic transmission on a motor-vehicle, is electronically controlled in response to signals representing engine torque (manifested by intake depression); the speed of the torque-converter turbine (or an approximation thereof derived from vehicle speed); and the actual ratio-shift, whereby, at constant engine torque, servo pressure is inversely proportional to increase in turbine speed up to a predetermined speed, above which it is maintained constant, and the level of pressure is reduced for a predetermined interval during shift. General.-A servo pressure-control unit 19, not described, responds to three signals through diodes 98, 101, 62. Diode 98 provides a constant voltage signal from the supply bus 35, which is extinguished by a monostable multivibrator 83 during shift; 101 establishes a constant minimum pressure; whilst 62 receives the smoothed output of an astable multivibrator 43 providing a square-wave pulse amplitude-modulated by the torque-signal 22 and width-modulated by the turbine speed signal 21. Circuit detail.-The signal voltage of the speed sensor 21 increases with turbine speed (Fig. 5a, not shown) and biases an NPN transistor 30 fed from the positive bus 35. The output signal at the collector of the transistor 30 decreases with turbine speed increase, and is clamped at a constant minimum voltage above a predetermined speed (Fig. 5b, not shown) by a diode 34 and potential divider 32, 33. The voltage signal from the torque sensor 22 increases with increase in engine intake depression (Fig. 5c, not shown) and is inverted to decrease with depression (Fig. 5d, not shown) by an NPN transistor 37, the collector output of which is applied to the collector of a transistor 41 to modulate a square-wave pulse (Fig. 5e, not shown) provided by an astable multivibrator 43, biasing the transistor 41, the collector output of which is thus a square-wave pulse amplitude-modulated in inverse accordance with intake depression (Fig. 5f, not shown). Output of the transistor 41 is applied through a capacitor 54 to the base of an NPN transistor 52, the collector of which receives the inverse speed-responsive output of the transistor 30 through a resistor 53. Also applied to the base of the transistor 52 is the constant current generated by a circuit 55. The output at the collector of the transistor 52 is a square-wave pulse, determined by the alternate charge and discharge of the capacitor 54, the height of which is inversely proportional to intake depression, whilst the width is inversely proportional to turbine speed (Fig. 5a, not shown). This output, resistance-capacity smoothed 60, 61, (Fig. 5h, not shown) is applied to the diode 62 of the pressure control unit 19. Also applied to the unit 19 through the diode 101 is the fixed potential of a divider 99, 100, establishing a fixed minimum servo pressure. The third diode 98 feeds a fixed voltage signal to the pressure control unit 19, which is extinguished during shift, to reduce servo pressure, by a ratio-shift detector 70, issuing signals 71, 72, 73 corresponding to the three gear ratios and connected through differentiating circuits 74 and diodes to apply a negative pulse to trigger a monostable multivibrator 83 into its metastable state, to produce an output biasing a transistor 95 to conduct during shift, to cancel the voltage signal applied to the third diode 98, thereby establishing a reduced servo pressure for a period determined by a capacitor 94 and resistor 90 of the multivibrator 83.