Patent GB-1314372-A (GB)
Title: Automatic oil pressure control systems for torque converter automatic transmissions
IPC: F16H61/02
Filed: 1970-08-14
Abstract: 1314372 Change-speed control TOYOTA JIDOSHA KOGYO KK and NIPPONDENSO KK 14 Aug 1970 [13 Sept 1969 11 Nov 1969 27 Dec 1969 (2)] 39385/70 Heading F2D In a torque-converter-driven automatic transmission on a motor-vehicle, wherein ratio selecting engaging devices are engaged by fluid pressure 72 at a level controlled by a pressureregulating valve 30, which is loaded by a spring 33 alone to regulate a fixed maximum pressure (10<SP>-14</SP> kg./cm.<SP>2</SP>) and is negatively loaded to regulate to a fixed minimum pressure (4 kg./cm.<SP>2</SP>) by fluid pressure 73 supplied to its lower chamber by energizing a solenoid 50, to open a valve 61, supplying delivery pressure 71 to the control line 73, pressures intermediate between this maximum and minimum are provided under control of vehicle speed, engine load, and optionally ratio setting, which parameters timepulse the solenoid 50 electronically in accordance with equations described below. Pressure fluctuations in the control line 73 are damped by a spring-loaded valve piston 64 moving between throttled exhausts 66, 67. In all the several embodiments described the, electronic circuit includes an integrating circuit generating a constant-frequency saw-tooth wave which feeds a comparator circuit jointly with speed and load signals, which trigger the sawtooth wave constant amplitude rectangular pulses of variable time width, which are fed to the solenoid 50 to provide the graduated servo pressure control. In Fig. 5 a constant-frequency sawtooth wave, generated at 160 from a power source 150, is fed to a comparator 170 with a signal 142 produced by vehicle speed and engine load detectors 10, 20. Vehicle speed is detected as a variable frequency signal 13 from a magnetic pick-up adjacent a notched disc rotating with the output shaft, and is converted to a D.C. voltage signal 112 in an analogue converter 110. Engine load is detected at 20 by an arm actuated by the engine throttle control, Figs. 4a, 4b (not shown) tracking a resistor or resistor tappings to provide a voltage signal 27, which, together with the speed signal 112, is fed to a differential amplifier 120, producing a voltage signal 122 only when K # V #  exceeds K s V s , where K # K s  are constants and V # V s  engine load and vehicle speed. The speed signal 112 feeds a speed-setting circuit 130, which issues a constant D.C. voltage signal 132(a) whenever the vehicle speed exceeds a near-zero value, thus signal 132 feeding a twostage amplifier 140 together with the signal 122 to produce a signal 142 which is now K # V # - K s V s  + a. In a comparator 170, the speed-throttle signal 142 triggers the sawtooth wave signal 162 at a point t 1  in time between zero and a complete time integration To, providing that the signal voltage 142 is lower than the maximum sawtooth voltage at time To. This produces a rectangular wave signal in which zero to time t 1  is zero voltage, and To-t 1  is a constant voltage during which the pressure-reducing solenoid 50 is energized. An equation is derived connecting the ratio t 1 /To, by which the main regulated fluid pressure 72 is reduced, in terms of constants, V # , V s , V (the source voltage 150) and a, the speed setting voltage 132. With the vehicle at rest V #  and V s  and a are all zero, and only a constant remains, which results in a minimum pressure of 4 kg./cm.<SP>2</SP>, the maximum operating pressure being 10 kg./cm. 2  In Fig. 6, not shown, the differential amplifier 120 and speed setting circuit 130 are omitted, and the sawtooth wave generator is arranged between the speed signal generator and the comparator, so that the saw-tooth wave is now generated by integrating the D.C. speed signal, which provides hyperbolic pressure-load lines, Fig. 7 (not shown). In Figs. 8 and 10, (not shown), the sawtooth wave is generated by integrating the D.C. load signal, and thus provides linear pressure-load lines of differing slope, Fig. 9, not shown. Fig. 10, not shown, also includes a pulse width limiter arranged between the comparator and the power amplifier, and fed also with signals indicating the first gear setting and that of second and third gears. This limiter, Fig. 11, not shown, comprises two monostable multivibrators, two AND circuits and an OR circuit, and its effect is to limit servo pressure in first gear to 10 kg./cm.<SP>2</SP>, and in second and third to 8 kg./ cm.<SP>2</SP> An additional vibrator and AND circuit may be provided to limit third gear to a lower pressure, 6 kg./cm.<SP>2</SP>