Patent GB-1337713-A (GB)
Title: Controls for engageable torque-transmitting devices
IPC: F16H61/02
Filed: 1972-04-06
Abstract: 1337713 Calculating function generators GENERAL MOTORS CORP 6 April 1972 [28 May 1971] 15843/72 Heading G4G [Also in Division F2] The engaging hydraulic pressure applied to a pressure-engaged torque-transmitting device, such as a ratio-establishing friction clutch or brake in a variable-ratio transmission on a motor - vehicle, is modulated during engagement to control the acceleration of the input member according to a predetermined programme, which provides initially a pressure exceeding that required for the desired input acceleration, positive or negative, so that rapid initial engagement and input acceleration occurs; whereafter acceleration-responsive means rapidly decrease the engaging pressure as a function of the acceleration to establish the approximate pressure for the desired acceleration; and further means varies the pressure according to a function of the difference between the desired and the actual acceleration. Modulation is provided for both the engaging and disengaging clutches during a shift, and is performed by an electronic computing circuit controlling the electrical loading of solenoids D ... G of shift-valves, which are differentially landed to supply an output pressure proportional to solenoid current. The equations for programming the pressuremodulating circuit for engagement and release pressure, P-on, P-off, during an upshift are as follows: The P-on equation for downshift differs from that above in that the constants K3, K4 change sign and R1 is replaced by K7. In the equations K1-K7, R1 and R2 are scaling factors. R1 is an input acceleration varying linearly with input speed; R2 is a constant low acceleration below a trigger point, and a constant higher value above that point. N is the input acceleration at the trigger point, which e.g. for upshift could be -250 r.p.m./sec., and for downshift + 500 r.p.m./sec. Block diaqram, Fig. 1.-Timing and logic circuits 280 ... 286, commanded by a shiftpoint control 230, issue upshift and downshift signals U2, D2 &c. to a gate 276, receiving also signals from a shift timer 300 and a pressurechange controlling modulating computer 262, the latter receiving a differentiated speed signal 260, representing input acceleration, a signal 257, representing input speed, and upshift and downshift signals 264, 266, received through diodes from the signal lines U2, D2 &c. of the timing and logic circuits. The gate 276 receives from the modulating computer 262 P-on and P-off control signals 268, 270 for the first three shift solenoids D, E, F, and 272, 274, for the fourth shift solenoid G which requires an inverted signal. The gate 276 issues modulated signals to output drivers controlling the shift solenoids D ... G. Modulation computer, Fig. 8.-Receipt of an upshift signal 264 from any of the timing and logic circuits, Fig. 1, operates switching circuits 470, 510 to apply the input acceleration signal N in the line 260 to a line 494 and to apply + 15 V to a line 522 respectively. There are similar switching circuits 506, 524 operated by the downshift signal 266 to apply the N signal to a line 508 and 15V to a line 526. A third switching circuit, including transistors 532, 538, 542, applies + 15 V to a line 546 when neither up or downshift signal 264, 266 is present, and is triggered through diodes 528 by either signal to apply -15 V to the line 546. A circuit 548, fed with the input speed signal 257, generates a signal representing the acceleration term R1 in the above equation, and applies it to a line 562 when the upshift signal 264 is present.  An integrator 570 receives at its positive input, through resistors, the signals 562 (R1); 494 (upshift N); and 526 (+15 V), from the switching circuit 524 when the downshift line 266 is energized; and at its negative input 508 (downshift N), and a feed-back 588, 592 shunted by an F.E.T. 594 which maintains the output of the integrator 570 at zero until turned off by a trigger amplifier 600, which attains a negative output when its input signal N on the line 494 during upshift reaches -250 r.p.m./sec. At this acceleration the integrator is allowed to start integration to provide the output signal term K3N-K4#(R1-N)dt in the above equation. The integrator 570 feeds an inverting amplifier 630, fed also by the trigger amplifier 600 through a potentiometer 640, adjusted to provide an output signal proportional to -K2, so that the inverter represents negatively the last three terms of the P-on upshift equation above. The output of the inverting amplifier 630 and a 12 V input are connected to the positive input of an operational amplifier 646, the negative input of which is provided from a + 15 V source through a potentiometer 654, adjusted to provide an output signal K1, the final output signal at 268 fed to the output drivers through the gate 276 being 12 V-K1 + K2-K3N + K4#(R1-N)dt, which produces a solenoid current in accordance with the upshift P-on equation above. The fourth ratio solenoid G requires current inverse to the others, and the signal operating it is inverted by an amplifier 660. During downshift, the downshift signal 266 grounds the line 494 and produces the N signal on 508 as above described. The trigger amplifier 600 switches to negative at + 500 r.p.m./sec., and an input potentiometer 580 is adjusted to provide a signal representing the term K7 in the above equation. Off-going pressure modulation, to the P-off equation above, is provided by an integrator 680 and amplifiers 682, 682 producing output signals 270 for the first three solenoids D, E, F, and 274 for the fourth, G.