Patent GB-1514971-A (GB)
Title: Electronic control devices for automatic gear boxes
IPC: F16H61/10
Filed: 1975-05-23
Abstract: 1514971 Change speed control ROBERT BOSCH GmbH 23 May 1975 [11 Oct 1974] 22447/75 Heading F2D An electronic control for ratio shift in an automatic transmission on a motor vehicle comprises a manual selector lever 26 producing electrical signals corresponding to selected ratios and also exercising hydraulic control; trigger stages 53 ... 58 associated one with each of a number of ratio-establishing solenoid valves 22, 23, and responding to signals from sensors of output speed 25, and engine load, e.g. throttle setting 34; and at least one resistor network between each trigger stage and the load and/or speed sensor. In Fig. 3 the resistor network is between the throttle potentiometer 34 and the trigger circuits 53 ... 58 and is in the form of a matching circuit 38 which is replaceable to suit different installations, whilst in Fig. 8, duplicated matching circuits can be selectively switched in. Adjustable hysteresis, engine excess speed downshift protection and inhibition of reverse establishment during forward movement are provided. In Fig. 3 hydraulically engaged clutches and brakes of a planetary gear, not shown, are controlled by three solenoid valves, a first 22, for second ratio; a second 23 for third; and a third 24 for loading a main regulator valve controlling servo system pressure. Battery power is voltage stabilized at 52, and circuit input parameters are the output driven alternator 25, producing speed responsive frequency converted to a D.C. analogue at 41 for supply to the trigger stages 39; a manual selector switch 26 for reverse and first and second ratio hold; an engine throttle control 28 operating a potentiometer 34 (e.g. a ten stage one) supplying the trigger stages 39 through the matching circuit 38; and also operating a further potentiometer, controlling, through an engine characteristic 35, low-pass filter 36 and amplifier 37, the pressure regulator load solenoid 24; and an accelerator-operated kickdown switch 49. In the case of the pressure regulator solenoid 24 the potentiometer-controlled current is compared with a desired current to eliminate the effects of fluctuations in supply voltage, pressure and temperature-dependent coil resistance. The trigger stages 39 control the ratio solenoids 22, 23 through switching logic 62 and hysteresis logic circuits 59, 61. Two trigger stages 53, 54 control 1-2 and 2-3 upshift; 55, 56 the 3-2 and 2-1 downshift; and 57, 58 the 2-1 and 3-2 kickdown. Two trigger stages 53, 56 (or 54, 55) are detailed in Fig. 9, not shown, and comprise two operational amplifiers (158, 159) acting as comparators with speed and load input as in Fig. 3 and their outputs both connected to a four-transistor output network (162 ... 165), so arranged that the second transistor (162) which is rendered conductive by the increasing potential output of the upshift comparator (159) to produce upshift, can no longer be rendered non-conductive by a fall in potential of that comparator (159), and is so rendered, to produce downshift, only by a fall in potential of the downshift comparator (158) thereby introducing hysteresis. In Fig. 10, providing similar hysteresis, the four transistor network is replaced by a single transistor (171) and a thyristor (172) which, when fired by an upshift pulse from the upshift comparator, remains so fired until blocked by a fall in potential of the downshift comparator. In Fig. 4 (not shown) the components are represented in integrated circuits, whilst in Fig. 5 (not shown) the discrete components are shown as part of a complete circuit not further described.