Fluid-pressure and analogous brake systems – Electric control
Reexamination Certificate
1998-07-27
2001-05-08
Graham, Matthew C. (Department: 3613)
Fluid-pressure and analogous brake systems
Electric control
C303S007000, C303S122080
Reexamination Certificate
active
06227626
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device and a method for controlling the brake system of a motor vehicle.
BACKGROUND INFORMATION
A plurality of different brake system embodiments are known. An overview of brake systems is shown, for example, in Bosch Kraftfahrtechnische Taschenbuch, 21st edition, pp. 594-643 (Bosch Automotive Handbook, 3
rd
edition, pp. 594-643). Such brake systems can be designed as hydraulic, pneumatic, or electromechanical brake systems. Electrical actuation of such brake systems may consist, for example, of actuating the valves affecting the braking pressure in the wheel brakes hydraulically or pneumatically. In the case of an electromechanical brake system, the wheel brakes are actuated electromechanically. For brake systems of motor vehicles of a certain size, the law mandates that, in addition to the service brakes, with which the driver can reduce the vehicle speed during normal operation, an auxiliary brake system and a parking brake system be provided. The auxiliary brake system allows the driver to stepwise reduce the speed or the acceleration of the vehicle or bring the vehicle to a stop in the event of a failure of the service brake system. The parking brake system ensures that the vehicle can be held at a standstill on an inclined roadway by mechanical means, in particular in the absence of the driver.
An electromechanical brake system is described, for example, in International Publication No. WO-A 94/24453, where a wheel brake in which the brake application force is generated by an electric motor. It is particularly important in such electromecanically actuated wheel brakes, as well as generally in the other electrically controlled wheel brakes, to ensure the reliable operation of the brake system, especially reliability of the voltage supply provided by the batteries. In particular, the operating reliability of the brake system must be guaranteed even if sufficient braking action can no longer be applied due to the insufficient amount of electric energy stored.
German Patent Application No. 35 02 100 describes a pneumatic brake system for motor vehicles, where two energy storage devices are provided for supplying power to the brake system; depending on the charge status of one energy storage device, the system allows a switchover to the other storage device. An excessively low charge status can be reported to the driver of the vehicle visually and/or acoustically.
German Patent Application No. 39 36 638 describes an electric supply in a motor vehicle, where, depending on the charge status of the vehicle battery, those loads that are not essential for safe vehicle operation can be shut off.
German Patent Application No. 19548560.2 describes a brake system with electrically actuated wheel brakes, which includes a parking brake that can be actuated by the driver. At vehicle start, a test sequence is initiated to test the functionality of the brake system; during this sequence, at least one wheel brake is supplied with a control signal that corresponds to a predefined minimum braking effect. The parking brake is not released if the predefined minimum braking effect on at least one wheel is not achieved. The charge status of the battery or batteries is not measured.
The object of the present invention is to prevent safety-critical situations in electrically controlled brake systems.
SUMMARY OF THE INVENTION
The present invention relates to the control of units arranged in the power train of a motor vehicle. Furthermore, the vehicle has electrically actuated wheel brakes preferably designed with one or two motors that control the functions of at least one of the units arranged in the power train and/or the function of the wheel brakes and influence the potential of at least one of these units in response to a signal supplied. At least one electric energy storage means arrangement is effectively connected to the electrically actuated wheel brakes to supply them with power. One of the advantages of the present invention consists of the fact that diagnostic means are provided through which the potential of at least one energy storage means is detected. The diagnostic means arrangement generate the signal, as a function of the detected potential of at least one of the units arranged in the power train, so that the potential of at least one of the units arranged in the power train is adjusted to the potential detected with a view to driving safety and/or the function of the wheel brakes is influenced to apply a predefinable braking effect.
The present invention offers the advantage that, in the event that an insufficient amount of power is supplied by the energy storage means, safety-critical situations are avoided through intervention in the power train and/or the wheel brakes.
The potential of the energy storage means can be represented by the energy charge status of the energy storage means. In particular, the diagnostic means detect at least two different energy charge states of the energy storage means and the signal generated represents the different energy charge states. With this embodiment, the measures aiming at driving safety can be easily adjusted to the available energy.
The potential of one of the units arranged in the power train or the potential of the entire power train can be represented by the drive power output and/or the drive torque of the vehicle, in particular by the maximum possible drive power output and/or the maximum possible drive torque. The instantaneous or maximum possible power output or the instantaneous or maximum drive torque of the vehicle is adjusted to the energy available for braking.
At least one vehicle engine, in particular an internal combustion engine, a clutch a transmission, a retarder, and/or an exhaust valve can be provided in the vehicle power train. The drive torque and/or the drive power output can be adjusted to the energy available for braking by suitably controlling these units.
In another embodiment, the potential of at least one unit arranged in the power train is adjusted to the potential of at least one of the energy storage means to affect at least one of the units arranged in the power train to support the vehicle braking effect so that a vehicle braking effect is achieved. In this embodiment, the driver's intention to decelerate can be supported by using the signal according to the present invention in that the drive torque and/or the drive power output is reduced even to negative values, according to the potential of the energy storage means. Such negative drive values act as a drag torque on the driven vehicle wheels. If there is just a little energy available for braking, a wheel drag torque is achieved in this manner, which supports the service brake functions (auxiliary and parking brake effects) and thus increases driving safety. In particular, control of the vehicle engine is provided in order to induce a motor drag torque.
In particular, it may be provided that, in response to the signal, i.e., in the event of insufficient power available, the function of at least one of the units arranged in the power train, in particular, of the vehicle engine, is affected so that vehicle start, in particular, engine start, is disabled. It is advantageous that the vehicle engine start is disabled by locking a switch in the appropriate position.
In another embodiment, when the signal represents a potential of at least one of the energy storage devices that is insufficient to start the vehicle engine arranged in the power train, the vehicle motor start is disabled. Also in this case, the start of the vehicle engine can be disabled by locking a switch in the appropriate position. The background of this embodiment is that the energy storage devices are normally used both for supplying power to the brakes and for starting the vehicle engine. High-current capability, i.e., the ability of the energy storage device to supply a high current for starting the vehicle engine, normally decreases with the potential, i.e., the charge status. If the potential of the energy storage dev
Graham Matthew C.
Kenyon & Kenyon
Robert & Bosch GmbH
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