Patent GB-1383042-A (GB)
Title: Digital type vehicle brake control system
IPC: B60T8/58
Filed: 1972-03-17
Abstract: 1383042 Anti-skid braking systems AISIN SEIKI KK 17 March 1972 [20 March 1971(2)] 12540/72 Addition to 1364476 Heading F2F A digital anti-skid brake control system for an hydraulic brake circuit of a vehicle comprises means for sensing'the rotational speed of each of one or more vehicle wheels and producing a pulse signal representing that speed or the sum of those speeds, means for counting the numbers of pulses produced in two time periods, of which the second commences after the first, and subtracting the number of pulses in the second time period from that produced in the first to obtain the difference, means for comparing the difference with first and second predetermined values, the braking pressure being relieved in response to the result of the first comparison, and means for varying the rate of relief of the braking pressure in response to the result of the second comparison. As shown in Fig. 1, wheel cylinders 15, 15a and 16, 16a of front and rear wheels 13, 13a and 14, 14a respectively are actuated by a master cylinder 11, and a controller 27, which receives electrical output signals from sensors 25, 25a and 26, 26a, applies signals to modulators 19, 20 which by the aid of electromagnetic solenoids valves 21, 24 and 23, 24 control the fluid braking pressure of the master cylinder and thus to the wheel cylinders. The modulators 19, 20 each comprise a housing 38 divided by a spring-loaded diaphragm 40 into a chamber 48 connected to the engine intake manifold and a chamber 49 connected to an electromagnetic switching valve 51; a cylinder 30 has therein a plunger 36 connected to the diaphragm and formed with an extension 37 contacting a spring-loaded ball valve 42. Each switching valve 51 includes a solenoid 22 (or 24) which when energized draws, against the force of a spring 64, a plunger 61 to the left to move a valve 62 from a seat 65 on to a seat 67. The passage 53 communicates with the chamber 49 and the passages 54, 55 are connected to the passage 60 of an electromagnetic switching valve 58 connected via the passage 77 thereof to the engine intake manifold and having an air filter 74. In the state wherein the solenoids 21 (22) are not excited the plunger 68 prevents communication between the passages 60, 75 and establishes communication between passage 60 and the manifold, the chamber 49 being at negative pressure via valve 51; the chamber 48 is at negative pressure and the diaphragm 40 through the plunger 36 holds the ball valve 42 off the seat 43 whereby the fluid pressure from the master cylinder 11 is communicated equally to the wheel cylinders. Upon the application of electric current to the solenoid 21 (23) the plunger 68 moves to the left to prevent communication between passages 60, 77 so that atmospheric pressure is applied to the chamber 49 through the valve 51, the diaphragm 40 being then displaced against the bias of the spring 45 and so that the valve 42 is applied to the seat 43 to interrupt the transmission of fluid pressure from the master cylinder to the wheel cylinders, the volume of the chamber 35 increasing to allow reduction of-the fluid pressures in the wheel cylinders. De-activation of the solenoids 21 (23) causes the valves 58 and 42 to revert to the original positions as shown and allows full master cylinder pressure to be again applied to the wheel cylinders. With the valve 51 in the position shown, the pipes 57, 50 communicate with each other and since the pipe 57 is smaller than the pipe 56 the rate of pressure variation in the chamber 49, i.e. from negative to atmospheric pressure or vice versa, is slower than when the pressure in the chamber is varied via the pipe 56; the rate of moving of the diaphragm 40 and therefore the plunger 36 is caused to be slower and the pressure-reducing rate and pressure-restoring rate of the wheel cylinders are caused to be slow. Application of electric current to the solenoids 22 (24) of the valve 51 causes the plunger 61 to move to the left so that communication between the pipes 50, 57 is cut off while the pipes 50, 56 are connected; the pipe 56 being larger than the pipe 57 allows the variation of pressure in the chamber 49, from negative to atmospheric pressure or vice versa, to be quicker than in the previous case. When the pipes 57, 50 are in communication, the moving rates of the diaphragm 40 and plunger 36 and therefore the pressure-reducing and pressure-restoring rates are quicker. Figs. 3(a), 3(b) illustrate the controller 27 comprising circuits I, II and III and IV, V and VI respectively controlling the modulators 19 and 20 for the front and rear wheels of the vehicle.