Delphi Technologies, Inc.

Mark P Roden

Bryan Todd Fulmer

Joseph Allen Elliott

A vehicle hydraulic braking system responds to detection of an operator intended high braking intensity event to isolate vehicle brakes from the master cylinder and activate a motor driven pump to generate a maximum predetermined supply pressure, calibrated to provide activation of an anti-lock braking system, to the brake apply valves for an initial predetermined time. Thereafter, the supply pressure is reduced via an electrically controllable pressure relief valve responsive to sensed vehicle deceleration so as to decrease the supply pressure provided to the apply valve to a level just sufficient to provide the sensed vehicle deceleration. The high intensity braking event is detected via a rate of change of master cylinder pressure, pedal force or pedal travel.

Vehicle brake boost assist control

A substantially constant brake assist gain is provided in a vehicle braking system having a vacuum booster providing braking assist to a brake fluid master cylinder in response to an operator input braking force, even though the gain of the booster falls off from its maximum value in a non-linear manner in a runout initiating portion of the working vacuum range near zero booster vacuum. A brake fluid pump, such as is used in an ABS/TCS modulator, is used to supplement the booster output as it falls so as to maintain a constant, linear brake system gain into runout. In the runout initiating portion of the working vacuum range, a runout assist gain is derived from stored data expressing booster assist gain as a function of booster vacuum, and a target wheel pressure is calculated from the derived runout boost assist gain and a corresponding change in master cylinder pressure. A target wheel pressure error is calculated from the difference between the derived target wheel pressure and the master cylinder pressure and used to control the brake fluid pressure added by the pump to the master cylinder pressure.

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Fenton, MI, United States of America

Mark P Roden