| 摘要 |
1,206,153. Hydraulic braking systems. GOODYEAR TIRE & RUBBER CO. 25 Sept., 1967 [9 Nov., 1966], No. 43448/67. Heading F2F. [Also in Divisions G1 an H3] In an hydraulic braking system, skidding or wheel lock is prevented by a circuit which senses the wheel speed and releases the brake pressure if the speed is below a predetermined value. The system is applied to an aircraft, and comprises a transducer 10 which produces an electrical signal proportional to wheel speed. This signal is fed to a skid detector 26, which produces an output when the wheel speed falls to zero, and to a locked-wheel detector 28 which produces an output for wheel speeds below a predetermined value. This latter circuit may be inhibited by means of a switch 32. The outputs of the two detectors are fed via an amplifier 36 to actuate a valve in the braking system. The skid detector output is also fed to a circuit 34 which ensures that, after release, the brakes are applied at a lower pressure. Circuit details.-The skid detector, Fig. 2, comprises a bridge circuit with D.C. source 38 connected across one pair of diagonals, and transistor Q24 connected across the other pair. Temperature compensating diodes CR41. . . CR44 are provided in the bridge. Any sudden change in wheel speed, due to skidding is fed via capacitor C15 to point B, and unbalances the bridge sufficiently to switch on transistors Q24, Q25, Thus producing an output signal which is fed to an amplifier, Fig. 3. The amplifier output is maintained constant by a feedback path containing temperature compensating diodes CR63 . . . CR66, and is fed to a valve control solenoid. A further output from the circuit of Fig. 2 is fed to the circuit of Fig. 4 which ensures that the valve control signal is reduced after skidding. This control signal is normally determined by the voltage across capacitor C19. In the event of a skid, transistor Q20 conducts for the duration of the skid to allow capacitor C18 to commence charging. The potential to which it charges is then fed via transistor Q29 to modify the charge on capacitor C19. A further path via capacitor C17, diode CR59 and resistor R70 is also provided to modify the control signal in the event of short duration skids. |
