| 摘要 |
At vehicle startup and vehicle shutdown, the driver modulates the brake pressure directly by depressing the brake pedal and the driver feels pedal resistance. During normal conditions of vehicle operation after vehicle startup, pressure boosted actuation of the vehicle brakes is provided by the modulation of boosted pressure from an accumulator via a boost valve operable in response to brake pedal depression, while an isolation valve isolates the pedal from direct influence by the brake pressure and the driver feels pedal resistance provided by a pedal simulator. Upon shutdown of boosted actuation, the boost valve reduces the brake pressure gradually over a calibrated period of time until the brake pressure substantially equals the pedal resistance then felt by the driver. Then the isolation valve reestablishes driver's feel of the brake pressure without an abrupt change in pedal resistance upon the reversion from boosted actuation to hydraulic unboosted actuation.
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