Failure detection circuit for a vehicle anti-skid braking system
First Claim
1. An anti-skid braking system including a plurality of wheel speed sensors, a plurality of wheel slip detection circuits associated with the respective wheel speed sensors, a plurality of brake release solenoids connected to the respective slip detection circuits so as to energise a solenoid if the corresponding slip detection circuit detects slippage of the associated wheel, and a failure detection circuit comprising solenoid energisation detection means connected to said solenoids and producing an output signal when any one of the solenoids is energised, a timing circuit connected to the solenoid energisation detection means so as to be triggered into operation thereby, warning means operable by said timing circuit if the latter remains in operation for more than a predetermined time, means for detecting the back e.m.f. produced when each solenoid is switched off, and timer circuit reset means controlled by said back e.m.f. detecting means for resetting the timer circuit when any solenoid is switched off.
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Abstract
An anti-skid braking system including a plurality of independent solenoid energizing circuits which are controlled in accordance with the outputs of sensors on separate wheels of a vehicle, has a failure detection circuit comprising a timer triggered into operation each time any one of the solenoids is energized, and reset when a back e.m.f. generated by the deactivation of any solenoid is detected. If the timer is not reset within a fixed period the system is disabled and a warning lamp is energized. The system also includes a circuit utilizing the back e.m.f. signals for testing the system each time it is switched on.
15 Citations
9 Claims
- 1. An anti-skid braking system including a plurality of wheel speed sensors, a plurality of wheel slip detection circuits associated with the respective wheel speed sensors, a plurality of brake release solenoids connected to the respective slip detection circuits so as to energise a solenoid if the corresponding slip detection circuit detects slippage of the associated wheel, and a failure detection circuit comprising solenoid energisation detection means connected to said solenoids and producing an output signal when any one of the solenoids is energised, a timing circuit connected to the solenoid energisation detection means so as to be triggered into operation thereby, warning means operable by said timing circuit if the latter remains in operation for more than a predetermined time, means for detecting the back e.m.f. produced when each solenoid is switched off, and timer circuit reset means controlled by said back e.m.f. detecting means for resetting the timer circuit when any solenoid is switched off.
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9. An anti-skid braking system, comprising
a wheel sensor providing an output in response to wheel speed, means operatively connected to said sensor output and providing a slippage output in response to sensed wheel slippage, coil means operatively connected to said slippage means and selectively energized in response to said slippage output to provide a brake control output, means operatively connected to said coil means and selectively providing a timing sequence in response to the energisation of said coil means and providing a warning output in response to a timing sequence of a predetermined duration, detecting means operatively connected to said coil means and providing a back e.m.f. responsive output in response to the deactivation of said coil means, and reset means operatively connected to said detecting means and resetting said timing sequence of said timing means in response to said back e.m.f. responsive output.
Specification