Patent ID: 8172338

Claim:
A method of controlling vehicle brakes comprising: providing at vehicle startup and vehicle shutdown a hydraulic unboosted actuation of the vehicle brakes so that the driver modulates the brake pressure directly by depressing a brake pedal and the driver feels the brake pressure as pedal resistance; providing upon normal conditions of vehicle operation after vehicle startup for the boosted actuation of the vehicle brakes by the modulation of the brake pressure through an electrically controlled boost pressure valve operable in response to at least one sensor sensing brake pedal depression by the driver, during which period of boosted actuation the pedal is isolated from direct influence by the brake pressure and instead the driver feels pedal resistance provided by a simulator that simulates a pedal resistance in proportion to the depression of the brake pedal; upon shutdown of the boosted actuation of the vehicle brakes, operating the electrically controlled boost valve in a manner to reduce the brake pressure gradually over a calibrated period of time until the brake pressure substantially equals the pedal resistance then felt by the driver and then reestablishing the hydraulic unboosted actuation of the vehicle brakes whereby the driver is not disturbed by an abrupt change in pedal resistance upon the reversion from boosted actuation to hydraulic unboosted actuation; when after shutdown of the boosted actuation of the vehicle brakes by the vehicle shutdown and during the calibrated period of time, the driver ceases to depress the pedal and thus would not experience a pedal disturbance, at once operating the electrically controlled boost valve to reestablish the hydraulic unboosted actuation of the vehicle brakes; when after shutdown of the boosted actuation of the vehicle brakes by the vehicle shutdown and during the calibrated period of time, the vehicle shutdown is terminated, aborting the gradual reduction of the brake pressure; and, when the vehicle brakes experience a fault, reverting at once from the boosted actuation to the hydraulic unboosted actuation without delay due to the calibrated period of time and irrespective of any occurrence of pedal disturbance.