Abstract: A vacuum booster for a vehicle brake system provides a working pressure valve seat on a valve member axially movable with respect to an input member. A rotary electric motor within the booster has an output shaft coupled through rotary to linear motion conversion apparatus to move the valve member with its working pressure valve seat relative to the input member. The combination of elements is designed as a drop-in replacement for a standard air valve member. The motion conversion apparatus provides much greater mechanical force than a linear solenoid; and this allows a more straightforward design of the valve arrangement, particularly the use of a high friction seal such as a simple "O"-ring in a groove. In further contrast to a linear solenoid, it further provides positive control of the working pressure valve seat position and an extended range of travel with constant force throughout the range.

Abstract: A power booster is operable at relatively low apply rates and at relatively high apply rates and includes an input assembly that has a movable input rod and a primary reaction piston having a first reaction area. An output support body is responsive to movement of the input rod, with a resilient reaction disc engaging the output support body. A secondary reaction body has a second reaction area and is engageable with the reaction disc and transfers loads between the reaction disc and the input assembly at relatively low apply rates. The amount of the load transferred is a function of both the first reaction area and the second reaction area at the relatively low apply rates resulting in a first reaction ratio. The primary reaction piston is engageable with the reaction disc and transfers loads between the output support body and the input assembly during relatively high apply rates.

Abstract: A brake apply system includes a power booster in which, when released and at-rest, a leg of a stop engages a clip and an extension of a valve body engages the clip so that an annular rib of the valve body is axially spaced away from the stop by a distance G. At the same time, a first valve seat is engaged with a first annular valve element closing a pressure supply conduit off from a variable pressure chamber and a second valve seat is spaced away from a second annular valve element by a distance T, opening the variable pressure chamber to an atmospheric pressure chamber. When the power booster is applied, the second valve seat moves the distance T and engages the second annular valve element closing the variable pressure chamber off from the atmospheric pressure chamber and the first valve seat separates from the first annular valve element opening the pressure supply conduit to the variable pressure chamber.

Abstract: A method and device for brake application provides braking pressure augmentation when preferred. A power booster and master cylinder generate a braking pressure in relation to an operator's input on the brake pedal. An optional brake parameter sensor is used to determine when the power booster reaches a run-out condition. At least one control valve and pump are used to apply braking pressure in response to additional increases in brake pedal application by the operator, after the power booster reaches a run-out condition. The pump and control valve are optionally used to generate braking pressure independent of brake pedal inputs.

Abstract: A vehicle braking system that primarily operates as a pure brake-by-wire system, with optional hydraulic actuation. The system includes a set of four electrically actuated drum brakes. At least two of the wheel brakes include hydraulic actuators that operate to apply the wheel brakes independent of electric control. Each of the wheel brakes is normally operated in response to a control signal generated by the vehicle's brake processor. As such, a primary brake-by-wire system is provided at all four vehicle wheels. The rear brakes are proportioned to the front brakes electrically, according to design criteria.