Patent GB-1400183-A (GB)
Title: Controlling working oil-pressure in control elements in motor vehicle automatic variable speed transmissions
IPC: F16H61/10
Filed: 1972-06-22
Abstract: 1400183 Measuring engine torque electrically DAIMLER BENZ A G 22 June 1972 [30 June 1971] 29292/72 Heading G1N [Also in Division F2] The level of working oil pressure applied to ratio shift elements of a torque-converter driven automatic transmission on a motor vehicle is controlled by electrical logic circuits responding to signals proportional to engine torque, and at least one other operating parameter such as engine or output speed, oil temperature, or rate of operation of the usual accelerator pedal. Various circuits and methods of torque determination for this purpose are described. In Fig. 2 engine torque is determined by crankshaft torsional deflection, measured by the pulse width issued by a bi-stable flip-flop 19, receiving signals through triggers 15, 18 from proximity pickups 14, 17, situated adjacent the starter nag-gear teeth 13 at one end of the crank-shaft 12 and a timing gear or sprocket 16 at the other end. The number of teeth in the wheel 13 is an exact multiple of that in the teeth of the wheel 16, and the phase displacement caused by torque produces output signals from the flip-flop 19 having a pulse width which increases with torque, converted to a D.C. voltage in a band-pass filter 21. In Fig. 3 (not shown), torque is derived from an electrical signal representing engine intake pressure, corrected by a function generator (23) comprising a series of biased diodes, the output of which, with any added or subtracted quantities, is fed through a summing amplifier (24) to a multiplier (26) which receives an engine speed signal by which the pressure signal is required to be multiplied to obtain a true measure of engine torque. The speed signal (27), which may be a direct D.C. voltage signal or a variable frequency pulse converted thereto, passes through a further generator (28), to obtain a required interdependence of speed and output voltage, and a summing amplifier (29) receiving further signals such as temperature to provide a corrected speed signal this being fed to the multiplier (26) the output of which, representing true torque, passes to a control element (32). In Fig. 4 (not shown), the engine torque signal is derived by measuring the instantaneous pressure in an engine cylinder, as by a quartz or strain gauge transducer, and also the piston travel from which, and the total piston stroke, the mean indicated cylinder pressure, and hence the torque can be calculated by supplying the relevant signals to a multiplier circuit (46) the output of which issues through a low-pass filter (47) as a D.C. voltage proportional to torque. The piston travel signal is derived from a stationary coil (38) within which is reciprocated an iron core (37) attached to the piston (36); or by an eccentric (41) rotating in the crankcase and reciprocating a spring-pressed iron core (43) in a coil (44). In Fig. 5 (not shown), the mean cylinder pressure is calculated from an equation involving an integral of the instantaneous cylinder pressure (determined as above), and a series expression including the crank angle α and multiples thereof, the first and second orders, sin α and sin 2α only, being determined by rotating a kidney-shaped disc (48) between a light source and a photo-cell (52, 53), the output of which corresponds to the sine function; or by a rotating cam (48) and proximity coil (57). The output torque signal is issued by a multiplier which evaluates the integral. In Fig. 6 (not shown), the instantaneous cylinder pressure signal (33) is multiplied by a rectangular function in which a signal is produced by a coil (62) pulsed at each top-dead-centre of the crank, this pulse being reversed for each up and down stroke by a bi-stable flip-flop (63) actuating a reversing switch (58), a connecting circuit (64) being provided to ensure pressure reversal at the top-deadcentre of the ignition stroke only. In Fig. 7 (not shown), the duration of the fuel injection period of an electronically fuel-injected engine is used as a measure of the torque; the pulse width of the existing electronic circuit being converted by an integrator (66) and rectifier (69) to a D.C. voltage, then further processed as in Fig.2. In Fig. 8 (not shown), the fuel injection pulses are fed through a pulse generator (72) and lowpass filter (73) to produce a voltage proportional to engine output, which is then divided in a quotient-former (74) by engine speed (provided by a pulse generator) to result in engine torque. In Fig. 9 (not shown) this quotient-former is time-division operated by ignition pulses, feeding through a differentiating circuit (83) a monostable flip-flop (84), the duration of the output pulses of which is modified by a torque-dependent corrector voltage.