Patent GB-1361881-A (GB)
Title: Vehicle drive control systems
IPC: F16H59/42
Filed: 1971-12-07
Abstract: 1361881 Controlling variable speed gearing FERRANTI Ltd 6 Dec 1972 [7 Dec 1971] 56661/71 Heading F2D A vehicle gear-box is controlled by comparator means incorporating first and second counters into which are set magnitudes the ratio between which is representative of a selected gear ratio, and first and second transducers producing signals representative of the speeds of the input and output shafts of the gear-box which signals are applied to change the magnitudes, the arrangement being such that engagement of the selected gear is permitted only if any difference between the selected ratio and the ratio of the input and output shaft speeds, expressed as a proportion of the selected ratio, is less than a predetermined maximum value. In the embodiment described, selection of a desired ratio in a seven-ratio gear-box 10 results in a signal indicative of the selected ratio being fed from one of seven outputs I ... VII to two number generating means 13, 14, each of which has a store whereby in response to a particular output I ... VII from the gear-box, it provides a digital signal, the ratio between the two digital signals being equal to the ratio of the gear selected. Transducers 16, 17 driven by the input and output shafts 11, 12 of the gear-box feed pulses at frequencies proportional to the speeds of the shafts through interface units 21, 22 to counters 19, 20. When a gear is selected a sequence counter 30 which is driven by pulses from the transducer 16 delivers a pulse from an output P to the number generating means 13, 14 to cause the digital signals from these means to be set in the counters 19, 20. The digital signals set in the counters may take into account prevailing conditions, e.g. the gear already engaged and/or the speed of the input or output shaft of the gear-box. A subsequent pulse from an output Q of the counter 30 to the counters 19, 20 causes the digital signals set in these counters to be counted down by the pulses from the transducers 16, 17 until one of the counters reaches zero when the count-down is stopped and the signal remaining in the counter 19 is fed, in binary-coded form, by way of outputs a ... h to a logic gating means 24. If this signal is such, e.g. between one and eight, as to indicate that the ratio between input and output shaft speeds lies within the limit for smooth engagement of the selected gear the gating means activates a mechanism 25 to release a latch 35 and enable the gear to be engaged. If the signal is greater than eight a mechanism 26 is activated to increase the speed of the input shaft, e.g. by adjusting a fuel injection pump of the vehicle engine, or if the signal is zero a mechanism 27 is activated to decrease the speed of the input shaft, e.g. by admitting oil under high pressure into the gear-box. When either mechanism 26 or 27 is activated, the sequence counter 30 is set to recycle. A by-pass means 40, which overrides the other parts of the control system, causes engagement of a selected gear if the speed of the output shaft, or of both the output and input shafts, as determined by a transducer 41 is below a threshold value, e.g. 10 r.p.m. The control apparatus may be embodied largely as an integrated circuit semi-conductor device.