Patent GB-1444940-A (GB)
Title: Antilocking control system
IPC: B60T8/84
Filed: 1973-09-03
Abstract: 1444940 Anti-lock braking systems TELDIXGmbH 3 Sept 1973 [2 Sept 1972] 41396/73 Heading F2F An anti-lock braking system for the common control of the pressure at the wheel brakes of a plurality of wheels of a vehicle comprises sensors, &c., 8 to 13 for sensing a tendency to lock, evaluating means including a comparator 14 responsive to signals from the sensors, &c., and switchable into two states # 1 , # 2 , for producing, in a first switching state, a signal if any one wheel shows a tendency to lock, and for producing, in the second state, a signal if all wheels show a tendency to lock, and a gate 16 and a timing element 17 together responsive to an output signal from the evaluating means for switching over, after a first time period, the evaluating means from the first switching state to the second switching state, for a second time period. The output signal from comparator 14, amplified at 15, is applied to inlet/outlet valve 15 in a line 3 leading to brake cylinders 4, 4<SP>1</SP>. As described, cylinders 4, 4<SP>1</SP> and sensors 8, 9, are associated with the two rear wheels. 10, 11 are transducers which produce voltages dependent on the rotary speed from the sensor outputs. A circuit element 12 produces a reference voltage approximating to vehicle speed from the outputs of both transducers 10, 11 and a circuit element 13 produces a mean value from those outputs. When during a brake application the mean speed value voltage from element 13 falls below a threshold equivalent to 95% reference voltage for the first time, the output signal from the comparator 14, besides operating valve 5, passes through gate 16 to timing element 17 which acts with a delay (say 20 m.sec.) to issue an output signal of specified length (e.g. 100 m.sec.) which output signal switches over the comparator from the # 1  to the # 2  state. Simultaneously this output signal triggers a bi-stable element 18 into a position in which it blocks the gate 16 through its negated input by means of an OR gate 19, and the time for the # 2  state expires. After termination of the output signal of the timing element the bi-stable element 18 is reset on account of negator element 20. The time during which the # 2  state is operative can be varied by a feed-in of the vehicle speed voltage to the timing element 17 by means of OR gate 21; with increasing voltage the time span of the # 2  state is reduced. Vehicle deceleration can control the time constant of element 17 by means of a discriminator 22. The switch-over to the # 2  state can be prevented by means of an AND gate 23 if, because of a low vehicle deceleration, a signal appears at a terminal 24 and if, because of a steering wheel turn or an angle of bend in the case of semi-trailers, a signal appears at a terminal 25. In the modification of Fig. 3 (not shown) a measuring device (30) is operable to transmit a signal dependent on the vehicle transverse acceleration to a difference generator (31) which blocks a gate (32) to cut off the output signal of the timing element (17<SP>1</SP>) in the case of a specified change in the transverse acceleration. Instead of causing this interruption the time period of the # 2  stage can be shortened. In the embodiment of Fig. 4 (not shown) pressure meters (40, 41) at the front wheels are connected to a difference generator (42) controlling the timing element (17<SP>1</SP>). In the embodiment of Fig. 5, a normally open gate 50 is blocked by means of an AND gate 57 with the occurrence of an output signal from a front-wheel difference generator (42) at a terminal 56. A pressure meter 52 measures the different pressures involved in the two states # 1 , # 2  and a comparison signal is formed in an element 53, e.g. by averaging. This comparison signal is compared with the instantaneous pressure value; with a deviation, a control signal is formed which controls the valve by means of gate 54 and OR gate 55. Instead of the measurement of the differing brake pressures, measurement of the different response times of the front wheel valves or of the rear wheel valves could be used to determine the pressure difference and initiate switchover according to Fig. 4 or 5.