Brakes – Wheel – Axially movable brake element or housing therefor
Reexamination Certificate
1999-06-01
2001-09-11
Swann, J. J. (Department: 3611)
Brakes
Wheel
Axially movable brake element or housing therefor
C188S071800, C180S065310
Reexamination Certificate
active
06286635
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vehicle braking system for electric, hybrid electric, and conventional vehicles having an actively controlled brake caliper retractor mechanism.
2. Description of Related Art
As vehicle manufacturers increase the fuel economy of conventional vehicles using internal combustion engines, so-called parasitic fuel economy penalties previously considered trivial must be reduced. One such parasitic loss is attributable to disc brake caliper drag which occurs as a result of intentionally maintaining the brake pads in light contact with the brake rotor at all times of vehicle operation to provide a familiar and consistent brake feel to the vehicle driver. Although small, this friction imposes a fuel economy penalty, especially at high vehicle speeds and contributes to brake wear.
For electric vehicles (EV) and hybrid electric vehicles (HEV), parallel and series regenerative braking systems have been investigated. In the parallel system, a fixed relationship is imposed between the regenerative braking power applied by the vehicle drive motor, vehicle speed, accelerator pedal position, and brake pedal pressure, with the driver maintaining control of the hydraulic brakes. In order to collect a large fraction of the braking energy available in typical urban driving, the regenerative braking force must be equivalent to that which would be applied by the driver using conventional disk brakes of the vehicle, but with no driver input from the brake pedal. This results in either unfamiliar vehicle characteristics (e.g. rapid deceleration when the accelerator pedal is released) or curtailment of regenerative braking in order to achieve a more familiar vehicle “coast down” behavior. A series regenerative braking system typically includes an additional brake-by-wire system to intervene in driver control of the hydraulic brakes and optimally partition the driver-demanded braking force between the vehicle electric drive motor and friction brakes. Although the series regenerative braking system is efficient and maintains familiar vehicle behavior, it is expensive and adds to vehicle weight.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a vehicle braking system having a brake rotor and a brake pedal-actuated hydraulic piston that actuates a brake caliper to engage a friction brake with the rotor and further having a brake caliper retractor mechanism including an actuator for actively controlling retraction of the friction brake relative to the rotor. The brake caliper retractor mechanism is actively controlled to provide either 1) a friction brake force versus pedal brake force curve where the friction brake initially contacts the rotor such that braking force from the brake pedal begins at zero pedal force or 2) a friction brake force versus pedal brake force curve that is displaced where the friction brake initially is positioned out of contact with the rotor such that braking force from the brake pedal begins at a finite preselected brake pedal force greater than zero. In an electric or hybrid electric vehicle, the displaced friction brake force versus pedal brake force curve permits series regenerative braking by an electric drive (e.g. electric drive motor or transmission) of the vehicle. In a conventional vehicle powered only by an internal combustion engine, the displaced friction brake force versus pedal brake force curve avoids brake drag.
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Brown Gregory P.
Coughlin William J.
Divine David
Ford Global Technologies Inc.
Swann J. J.
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