Patent GB-1261956-A (GB)
Title: Working-oil pressure control systems for automatic transmissions with torque converters
IPC: F16H41/04
Filed: 1969-11-17
Abstract: 1,261,956. Change-speed control. NIPPONDENSO K.K., and TOYOTA JIDOSHA KOGYO K.K. 17 Nov., 1969 [2 May, 1969], No. 56099/69. Heading F2D. [Also in Division G4] The level of working pressure in a liquid pressure servo circuit, actuating friction ratioselectors in an automatic change-speed gear on a motor-vehicle, is controlled in accordance with the slip-ratio in an hydrodynamic torqueconverter through which the gear is driven, the pressure control comprising an electronic circuit in which the slip-ratio is represented by a constant amplitude, variable width square wave C, Fig. 6, which chops the sawtooth wave T of an oscillator, to provide pulses of variable duration, which are amplified and fed to a solenoid 50 of a valve 60, Fig. 2, which, through a line 73 applies upward pressure to a main regulator valve 30 in opposition to its constant loading spring 33, whereby regulated pressure 72 is decreased with increase in slip-ratio. Fluid circuit.-Pressure is supplied to the regulator 30 at 70, and to the load-control valve 60 at 71. The valve 60 has a permanent restricted exhaust 66 and a damping-piston 64. Electric circuit.-Variable-frequency outputs 10, 20, Fig. 4, from polarized pick-ups arranged near toothed discs rotating with the converter impeller and turbine respectively have their waveform converted to fixed amplitude, variable width pulses in RPM operational circuits 110, 120, which provide a D.C. voltage output N 1 , N 2  proportional to speed. These feed a slipratio circuit 200, the output N 2 /N 1  of which is the square-wave pulse C, Fig. 6, which, in a comparator circuit 150, Fig. 4, is compared with the sawtooth output T, Fig. 6, of an oscillator 140, Fig. 4. The comparator signal ceases when the sawtooth voltage T exceeds the square-wave slip-ratio voltage S, the resultant output signal being a gapped sawtooth omitting the peaks for a variable duration (dotted in Fig. 6). After amplification at 160 this wave feeds the solenoid 50 of the regulator load-control valve 60 which is thereby intermittently opened for variable periods of time corresponding to the gapped sawtooth pulses. The effective pressure of the main regulator valve is thereby caused to follow a law P=10-65, and varies between 10 and 4 kg./cm<SP>2</SP>. The slip-ratio circuit 200, Fig. 4, is detailed in Fig. 7. It includes two comparator circuits 280, 240, one, 280, comparing N 2  with N 1  after N 1  has been reduced in a coefficient circuit 210 by a specified denominator (depending on the number of significant figures required in the output) and integrated at 220; the other, 240, comparing the integrated N 1  with N 1  itself. The output of both comparators 240, 280 feeds a re-set pulse generator 290 which may be a multivibrator producing a constant-time pulse and provides the time limits for converting to a definite integral the indefinite integral of the first integrating circuit 220 and a second integrating circuit 260, receiving the output of a constant voltage circuit 250. The output of the second integrating circuit passes through a smoothing circuit 270 to form the output of the circuit shown as 200 in Fig. 4.