Patent GB-1462957-A (GB)
Title: Device for the automatic shifting of multistep change-speed gearboxes
IPC: F16H61/12
Filed: 1974-05-10
Abstract: 1462957 Counting apparatus DAIMLERBENZ AG 10 May 1974 [27 July 1973] 20816/74 Heading G4D [Also in Division F2] An automatic electronic control for the stepped speed ratios of a motor vehicle transmission comprises a store, in which are stored upper and lower limits of output speed threshold values fH, fR, derived from the established ratio setting and engine torque demand (accelerator setting), such values being fed to a speed comparison unit DV, in which they are compared with actual measured output speed fab to produce, when the limits are exceeded, upshift and downshift signals H<SP>1</SP>, R<SP>1</SP>, the store comprising a programmable permanent memory ROM, which, in addition, stores acceleration and retardation limit values bH, bR for each speed ratio, which are compared, in an acceleration comparison unit BV, with actual output acceleration (derived from the speed signal fab) to produce, when the limits are exceeded in either direction, acceleration signals bH<SP>1</SP>, bR<SP>1</SP>, which are supplied, through a control unit ESE, to the memory ROM, and change the shiftcontrolling output speed limit threshold values fH, fR, and thereby produce, for supply to the speed comparison unit DV, additional sets of speed limit values. The speed comparison unit DV, detailed below, comprises two backwards counters receiving the upper and lower speed limits fH, fR, and the prevailing output speed fab, the latter represented by a series of pulses at speedresponsive frequency, which are counted backwards during timed intervals measured by a central clock generator ZTG, to emit an appropriate upshift or downshift signal H<SP>1</SP> or R<SP>1</SP> if the counter reaches zero before the end of the interval.  The acceleration comparison unit BV compares the acceleration limit values bH, bR from the memory ROM with the prevailing acceleration in two counters, corresponding to upper and lower limits, and counted first forwards, against speed pulses measured in one time interval, and, following a delay, counted backwards during a second interval, an appropriate acceleration signal bH<SP>1</SP> or bR<SP>1</SP> being issued if zero is reached during backward counting. In the block diagram, Fig. 1, ratio-establishing clutches and brakes of a six-ratio gear are engaged by electromagnetic valves VT, controlled by a valve unit VA. Individual store cells (not described) of the memory ROM are triggered by the electronic control ESE (not described), which processes the following signals. Selected ratio range signals from a selector programme unit WPE, responding to six settings W1 ... W6 of a range selector lever Wi, giving the following ratio ranges: G1; G1, G2; G1 to G3; G1 to G4; G1 to G5; G3 to G6; and to a signal SR representing the cut-off point of the engine fuel injection pump, the selector lever also having directly acting PNR settings; six torque steps Mi, provided by dividing the accelerator travel into four steps M1 ... M4, followed by full throttle VG and kickdown KD; a signal G representing the established speed ratio and derived from measured input and output speeds fan, fab, sensed by inductive or optical pick-ups producing rectangular pulses at speed - proportional frequency ; the abovedescribed acceleration comparison signals bH<SP>1</SP>, bR<SP>1</SP> and the data signal D. The upshift and downshift signals H<SP>1</SP>, R<SP>1</SP> issue from the speed comparator DV to the selector lever programme unit WPE which receives also the prevailing ratio signal G and itself issues a signal RZ to the programme control unit ESE, preventing upshift while the signal RZ persists, thus determining the selected ratio range. The selector programme unit WPE issues upshift and downshift signals H, R to a gear speed store GS comprising a forwards counter for upshift and a backwards counter for downshift, and actuating a logic gate valve control unit VA energizing the shift valves VT. A failure protector GAS blocks the gear speed store GS to prevent any further automatic shift on sudden failure of the output speed signal fab. A gear ratio monitor GV provides further safety by comparing input-output transmission speed ratio, fan to fab, with the actual ratio stored at GS, and if these ratios do not agree, emits a disturbance signal S. Speed comparator DV, Figs. 1 and 3, comprises backwards counters ZO, ZU, receiving the upper and lower speed limit signals issued by the programmed memory ROM; cyclestarting signals EfH, EfR from the central clock generator ZTG; and signals from AND circuits 7, 10. The latter receive the output speed signal pulses fab, a time signal T, measuring time for backward counting the fab pulses, and feedbacks from the negative outputs of inverters 8, 11 through which the counters ZO, ZU are connected respectively to the resetting and setting inputs K9, J12 of bi-stable flip-flops 9, 12, the setting and re-setting inputs of which are connected directly to the counters. The timing inputs of the flip-flops 9, 12 receive pulses  from the central clock generator ZTG. In operation the upper output speed limit fH is entered into the counter ZO from the memory ROM on appearance of a starting pulse EfH from ZTG, the limit fH corresponding to the number of fab pulses which must be received within a measured time T if the actual speed fab is to correspond to the limit value fH. During the interval T the counter ZO is counted backwards with fat pulses, and on expiry of the measuring time T the counter is stopped, thus inhibiting fab at the AND circuit, and the cycle recommences. If, during the measuring time T, the counter reaches zero; i.e. fab has exceeded the limit fH, the counter ZO is stopped and produces an L signal at the setting input J9 of the flip-flop 9 and an O signal at its re-set input K9, whereupon the flip-flop issues an upshift signal H<SP>1</SP>, provided that when the  pulse arrives the counter ZO still has the L signal. Action of the downshift counter ZU is similar, with a cycle start signal EfR for the lower limit fR and inverted set connections to the flip-flop 12. The acceleration comparator BV, Fig. 5, not shown, is similar to DV, but uses forwardsbackwards counters (ZOB, ZUB), counted first forwards at output speed frequency during a time interval TV, followed by a delay interval TP, and a backwards counting interval TR. The counter state is thus the sum of the acceleration limit bH from the memory plus the difference between the pulse rates during the forward and backwards counts divided by the total time interval. If either counter reaches zero during the backward count the corresponding upper or lower acceleration limit is exceeded in the appropriate direction and a corresponding acceleration signal bH<SP>1</SP> or bR<SP>1</SP> is issued to the control unit ESE and takes effect by modifying the output speed threshold limits supplied to the speed comparator DV.  The gear ratio monitor GV, detailed in Figs. 7 and 8, not shown, compares the actual transmission ratio, obtained from the input and output speeds fan, fab, with the established ratio obtained from the gear ratio store GS, and emits the disturbance signal S if they are dissimilar. The monitor comprises a counter (GZ) which counts forward with input speed fan and back to zero with output speed fab. With a fixed interval for forward count, the speed ratio depends on the backward interval. Commands for counting are received from the central clock generator ZTG, together with coded pulses (T1 ... T6) of differing length representing each of the six ratios of the transmission, and stored in a register store (REG), to which a pulse (Sp) is issued when the backwards count reaches zero, which determines the actual speed ratio as the intersection with the particular ratio pulse. This ratio is then compared with the established ratio in the gear ratio store GS and if not coincident the disturbance signal S is emitted. The gear ratio store may also provide an indication of the ratio established.