Patent GB-1531434-A (GB)
Title: Automatic gearboxes for vehicles
IPC: F16H61/02
Filed: 1976-04-15
Abstract: 1531434 Change speed control AUTOMOTIVE PRODUCTS Ltd 15 April 1976 [15 April 1975] 15458/75 Addition to 1420307 Heading F2D An electronic control system for a motor vehicle change speed gear of the type described in the main Specification 1,420,307 wherein the electronic circuits comprise one or more integrated circuits. The circuit is generally similar to that of Specification 1,420,307, and comprises, for each of three ratio-shifts, a level detector in the form of an operational amplifier 170, 171, 172 for the 1-2, 2-3 and 3-4 shift respectively, each receiving at its inverting input 165, 166, 167, a speed-throttle signal, derived from an output speed signal 110 through square-wave-producing operational amplifiers 116, 117 and transistor pump circuits 122, 123, and a throttle signal 150, which decreases with increase in throttle opening, from a throttle-operated potentiometer 151, the speed and throttle signals being combined in summing junctions 134, 135 and 136. The non-inverting inputs of the level detector amplifiers 170 are connected to earth through resistors 175 and to the amplifier outputs through resistors 182 and diodes 185 the values of which resistors determine the operational hysteresis. The output of each of the level detector amplifiers 170, 171, 172 is connected directly to the inverting input of one operational amplifier 191, 198, 205, and, through an inverter transistor 193, 199, 206, to the inverting input of a second operational amplifier 195, 202, 208, the paired amplifiers 191, 195 &c. producing an overlapped shift as follows. When, in response to attainment of a predetermined level of the speed-throttle signal, e.g. 165, the detector amplifier 170 changes state, its output falls rapidly from a high to a low value, which causes the output of the amplifier 191 to rise slowly as a capacitor 210 discharges, whilst the output of the paired amplifier 195, initially high because of the inverter transistor 193, falls rapidly as a capacitor 211 quickly charges, so that, whilst a summing junction 240 and output circuit 242 cause instantaneous energization of an on-going second ratio brake valve solenoid 245, a similar output circuit 230 causes slow de-energization of a valve solenoid 237 of the off-going firstreverse brake, producing overlapped shift. The remaining operational amplifier pairs 198. 202 and 205, 208 act similarly for the third ratio brake and direct-reverse clutch valve solenoids 255, 260, and a similar delayed release of offgoing solenoids is produced for downshifts. Manual switch 300 has three wafers 301, 302, 303. In the first embodiment, the first wafer 301 ensures that, in any setting except D, the positive voltage line +V is connected to the inverting input of the operational amplifier 116, thereby disabling the speed signal. The second wafer 302 connects the +V line in D, N and P to the output of the operational amplifier 191, thereby preventing energization of the lowreverse brake valve solenoid 237, and in 2 and 3 settings respectively connects +V to the inverting inputs of the 1-2 and 2-3 level detector amplifiers 170, 171 to hold them in the upshift state, and in R setting connects +V to the output circuit 231 to energize the lowreverse brake valve solenoid 237. The switch wafer 303, in settings D, 3, 2 and 1, completes an earth return from the forward clutch valve solenoid 309 for engaging the forward clutch, whilst in R setting it causes the earth line E to trigger the output circuit 257 to energize the direct-reverse clutch valve solenoid 260. Integrated circuits.-The three level-detector amplifiers 170, 171, 172, plus an unused amplifier 174, are integrated in a single integrated circuit 173, whilst two additional integrated circuits are provided by the amplifiers 116, 117, 191, 195 and 198, 202, 205, 208. Modifications.-Figs. 4 to 7 (not shown) modify the hold connections of the manual switch as follows. Fig. 4 (not shown) has an additional 4 setting for fourth ratio hold. In Fig. 5 (not shown) the speed signal is not suppressed and the 1, 2 and 3 settings are connected to the level-detector amplifiers 170, 171, 172, so that ratios shift automatically as in D but only up to the selected setting. In Fig. 6 (not shown), negative signals are applied to the respective summing junctions preceding the level detectors 170, 171, 172, reducing the speed-throttle signal so that upshift from a selected ratio occurs automatically at speeds excessively higher than those of normal upshift. In Fig. 7 (not shown), there is a similar excess speed protection, together with sequencing to a selected ratio at normal automatic shift speeds. In Fig. 1 (not shown), a solenoid valve (27) is opened at throttle openings above and output speeds below predetermined values to increase servo pressure. A terminal 132, Fig. 2A, is provided for connection to an electronic speedometer.