Fluid-pressure and analogous brake systems – Speed-controlled – Braking pressure demand or braking force desire
Reexamination Certificate
2000-03-09
2001-12-04
Oberleitner, Robert J. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Braking pressure demand or braking force desire
C303S113400
Reexamination Certificate
active
06325471
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to brake systems for wheeled motor vehicles, and more specifically it relates to a brake-by-wire system.
2. Background Information
A brake-by-wire system may comprise a pedal that depresses a master cylinder plunger to perform the service brake function for a motor vehicle. The service brake function is performed by selectively applying electrically boosted hydraulic brakes or regenerative brakes. Hydraulic brakes generally apply friction forces to the wheels to dissipate energy as heat. Regenerative brakes may take any of various forms, but are often considered to comprise a rotary electric machine load that is applied to one or more driven wheels. When a regenerative brake is applied, energy flows from the wheels to operate the electric machine as a generator that converts the energy into electricity. The electricity is often used to charge an energy storage device, such as a battery. Whether hydraulic or regenerative brakes are applied is determined by an electronic brake controller.
The ability to operate a motor vehicle is typically controlled by a key-operated switch, sometimes referred to as an ignition switch. Such switches may assume various forms, but perhaps the most common in present motor vehicles is a mechanical switch that is turned by a metal key. When a proper key is used, the switch may operated from an OFF position to additional positions, such as START, RUN (i.e. ON), and ACCESSORY, to deliver electric power to electric circuits and devices that perform certain functions related to vehicle starting and operation.
Certain electric circuits need to be energized for a brake-by-wire system to properly operate. Placing the energization of such circuits under the control of the ignition switch is desirable so that they do not needlessly, drain the battery when the ignition switch is OFF. However, turning the ignition switch off to de-energize those circuits may remove power from devices that when powered, aid in reducing the pedal effort required to apply the brakes via the master cylinder. Hence, brake pedal effort may increase significantly when the ignition switch is turned off.
Governmental regulation applicable to certain motor vehicles proposes to mandate certain consistency in brake pedal effort that is independent of whether the ignition switch is OFF or ON. In the case of a brake system that comprises only boosted hydraulic brakes, a vacuum reservoir is used to provide a vacuum reserve that allows the booster to aid the pedal effort for several brake applications after the ignition switch is turned off to stop the engine. In the case of certain brake-by-wire systems, the de-energization of associated electric circuits that occurs when the ignition switch is turned off, precludes continuance of the ability to aid the pedal effort that was present when the ignition switch was on.
A preliminary novelty search developed the following U.S. Pat. Nos.: 5,139,121; 5,752,748; 5,769,509; 5,800,025; 5,834,854; and 5,923,096.
SUMMARY OF THE INVENTION
The present invention relates to a strategy that is believe suitable for accomplishing the intent of the aforementioned regulatory proposal in a brake-by-wire system.
One general aspect of the invention relates to a motor vehicle comprising an electric powered brake system for braking road-engaging wheels of the motor vehicle. The vehicle has an ignition switch for turning the motor on and off, including controlling the application of electric power to the electric powered brake system. A control maintains application of full electric power to the electric powered brake system when the ignition switch is operated from ON to OFF so long as at least one parameter related to a respective component of the vehicle and indicative of a need to maintain full electric power application to the brake system continues to exist. The control discontinues application of full electric power to the brake system when all of selected ones of several such parameters are indicative of lack of need to maintain full electric power application to the brake system.
Another general aspect of the invention relates to a method for use in a motor vehicle that has an electric powered brake system for braking road-engaging wheels of the vehicle. The vehicle has an ignition switch for turning the motor on and off, including controlling the application of electric power to the electric powered brake system. A control controls the application of electric power to the brake system and functions to maintain application of full electric power to the electric powered brake system when the ignition switch is operated from ON to OFF so long as at least one parameter related to a respective component of the vehicle and indicative of a need to maintain full electric power application to the brake system continues to exist. The control also discontinues application of full electric power to the brake system when all of selected ones of several such parameters are indicative of lack of need to maintain full electric power application to the brake system.
Further aspects will be seen in various features of two presently preferred embodiments of the invention that will be described in detail.
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patent: 5752748 (1998-05-01), Schramm et al.
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patent: 5923096 (1999-07-01), Manak
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Crombez Dale Scott
Curran Patrick Joseph
Napier Steven Lee
Brown Gregory P.
Coughlin William J.
Ford Global Technologies Inc.
Oberleitner Robert J.
Williams Thomas J.
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