Patent GB-1322579-A (GB)
Title: Automatic shift-control systems for automatic transmissions
IPC: F16H61/02
Filed: 1970-10-05
Abstract: 1322579 Change-speed control TOYOTA JIDOSHA KOGYO KK and NIPPONDENSO KK 5 Oct 1970 [8 Oct 1969] 47263/70 Heading F2D An electronic control which energizes solenoids 432, 437 of 1-2 and 2-3 shift valves 430, 435 in a torque-converter-driven automatic transmission on a motor-vehicle, in response to voltage signals proportional to output speed and engine-throttle setting, includes a mountainous condition (grade) detecting circuit 100, which downshifts the transmission from third ratio by detecting a simultaneous combination of all the following features. Engine-throttle opening above; output speed below; and vehicle acceleration, for a predetermined time interval, below, specified limits, or alternatively servicebrake pressure above a predetermined limit (for engine braking). Termination of the grade condition, permitting upshift to third ratio, is detected by output speed being above and throttle setting below predetermined limits, or by a first ratio signal. The throttle setting control may be subject to time delay to prevent transient action. Gear arrangement.-The gear, Fig. 1, not shown, comprises triple-stepped planets (311) meshing an output sun (319) and two additional suns one (309) driven from the input in all foward ratios through a forward clutch (306), the other (310) meshing its planet step through an idler and driven through a direct-reverse clutch (307). The planet-carrier is held by a one-way brake (321) for automatic low or by a parallel rear band-brake (321) for two-way manual low and reverse. A front band-brake (322) holds the idler-meshing sun (310) for a planetary second ratio, and both clutches together give direct drive. Fluid circuit, Fig. 3, controlling the two clutches 306, 307 and brakes 321a, 322a, comprises a pump 401, pressure-regulator 405, manual ranging valve 420 and the 1-2, 2-3 shift valves 430, 435. The front clutch 306 is pressurized directly from the manual valve in all its forward settings. In first ratio, automatic, both shift-valve solenoids 432, 437 are energized. the front clutch 306 is engaged alone, and reaction is taken by the one-way brake. Deenergizing the solenoid 432 permits a spring to upshift the 1-2 valve 430 to the right, pressurizing the apply line 434 of the front brake 322 for 1-2 upshift. De-energizing additionally the solenoid 437 upshifts the 2-3 valve 435, pressurizing the rear clutch 307 and release chamber of the front brake 322a for 2-3 upshift. Electric circuit.-The complete circuit is described with reference to Fig. 6, individual circuit blocks being described later. The circuit responds to voltage signals 21 from a vehicle speed circuit 20, comprising a digital-analogue converter, converting a variable-frequency signal from an output-driven polarized magnetic pick-up, to a speed-variable D.C. voltage; and a throttle position circuit 10 in which the engine accelerator pedal (1001, Fig. 7, not shown) switches in resistor tappings from a voltage source, providing variable voltage output signals in four stages at an output 11, representing 1, 2, 2À5 and 3À5 quarters of full throttle opening; and also full supply voltage at terminal output 12 for one-quarter depression; at 12 and 13 for two-quarters; and at 14 for fourquarters (i.e. kickdown). The speed-throttle signals feed 1-2 and 2-3 shift signal generators 30, 40, which emit zero signals for de-energizing the shift valve solenoids 432, 437 for upshift and voltage signals for downshaft energization. Up-down hysteresis is provided in the signal generating circuits 30, 40, and is reduced for full-throttle (kickdown) when the 4-fourths terminal 14 is effective. The variable output 11 and full throttle output 14 are used for the signal generators, the remaining throttle tappings 12, 13 (quarter and half) being used for the grade detector. Grade detector circuit 100 produces a 3-2 downshift and prevents any further 2-3 upshift by sending a voltage signal 72 to a gate 70, which produces a downshift output voltage signal 73 independently of any command issued to the gate by the 2-3 signal generator 40. Voltage or zero signals in the gate-line 72, indicating respectively a grade or end thereof, are produced by driving a bi-stable memory 220 to one or other of its two stable states by grade and level road signals 221, 222 respectively. The grade signal 221 is produced when an AND circuit 180 simultaneously receives three signals, one, 112 from a throttle position discriminating circuit 110 fed by the throttle circuit tapping 13 and indicating an engine throttle opening exceeding 2 fourths; a second, 122, from a speed discriminating circuit 120, indicating vehicle speed below 45 k.p.h.; and a third, 132, also fed by the speed circuit 20, and indicating that vehicle acceleration is less than 0À05 g, and followed by a time circuit 170 which only issues the acceleration signal to the AND circuit after it has persisted for at least two seconds. Between the AND circuit 180 and the bistable memory 220 is an OR circuit 200 fed also by a switch 160 which closes when service-brake pressure exceeds 15 kg./cm.<SP>2</SP>, so that service braking can produce 3-2 downshift for engine braking on a level road or downgrade. To erase the grade signal 72 and permit 2-3 upshift, the bi-stable memory 220 is driven to its other stable position, indicating termination of the grade, by simultaneous signals 142, 152, from a second throttle position discriminating circuit 140 signalled by the throttle tapping 12 and indicating a throttle setting below one fourth, and from a second speed discriminating circuit 150, indicating vehicle speed above 50 k.p.h., the signals passing through an AND circuit 190 and an OR circuit 210 which latter also receives a downshift signal 212 from the 1-2 signal generator 30 to release the memory when the transmission is in first ratio. Individual circuits. Shift signal generators 30, 40, Fig. 8, not shown, are fed with resistoradjusted portions of the speed and throttle voltages 21, 14, the variable throttle voltage 11 being used. 12 volts positive and 6 volts negative supply are provided, and when the speed voltage predominates over the throttle, a comparator circuit (3001) switches an output transistor (3009) to erase the output voltage 34, 44, thus providing the zero upshift signal. The voltage signal reappears for downshift, hysteresis being provided by suitable resistor values. For kickdown the full throttle tapping 14 provides the downshift voltage signal at 34, 44, directly through a separate switching circuit using two transistors (3016, 3013), hysteresis in this case being less than for normal downshift. Throttle position discriminating circuit 110, Fig. 11, not shown, receives a two-fourths throttle position signal 13 and, by a two-transistor switch, produces a signal 112 from a voltage source when this throttle setting is exceeded. The other throttle position discriminating circuit 140 similarly produces a signal 142 when the throttle setting is below that of the one-fourth signal 12. In Fig. 18, not shown, these circuits are modified by the provision of a time-delay by a resistor-capacitor and Zener diode network. Speed discriminating circuit 120, Fig. 12, not shown, is a comparator circuit similar to that of the shift signal generators 30, 40, receiving an adjusted portion of the speed voltage signal 21 and comparing it with an adjusted portion of a constant voltage supply, to switch a transistor and provide an output signal 122 when vehicle speed is below 45 k.p.h. The other speed discriminating circuit 150 similarly emits a voltage signal 152 when speed is above 50 k.p.h. Acceleration discriminating circuit 130, Fig. 13, not shown, comprises a comparator circuit (1301) which directly differentiates the speed signal 21 to obtain acceleration, which it then compares in a similar circuit (1307) with a standard voltage (E(v)) to switch a transistor (1312) producing a voltage output signal 132 when acceleration is below 0À05 g. Time circuit 170, Fig. 14, not shown, uses a Zener diode (1704) and resistor-capacitor charge circuit (1701, 1703) to switch two transistors so that an output signal 172 is produced not less than two seconds after continuous receipt of the acceleration input signal 171. AND circuit 180, Fig. 15, not shown, receives three input signals 181, 182, 183 from throttle, output speed and acceleration discriminating circuits 110, 120, 130 connected to the cathodes of separate diodes (1801-1803), the anodes of which are connected in common through a resistor to a power input (1807) and directly to the base of a transistor (1804), which, when all three signals appear simultaneously is switched on, thereby switching off a second transistor (1806) which produces an output voltage signal 184. OR circuits 200, 210, Fig. 16, not shown, emit a signal 203, 213 when a transistor (2004) is switched off by a transistor (2003), switched on by a signal applied, through individual resistors, to its base by either one only of the input signals 201, 202. Bi-stable memory 220, Fig. 17, not shown, comprises two transistors arranged as a bistable multi-vibrator.