Fluid-pressure and analogous brake systems – Speed-controlled – Odd condition or device detection
Reexamination Certificate
1999-10-21
2001-11-13
Oberleitner, Robert J. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Odd condition or device detection
Reexamination Certificate
active
06315372
ABSTRACT:
BACKGROUND OF THE INVENTION
This application claims the priority of 198 48 448.8, filed Oct. 21, 1998, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a brake pressure control device of a brake system of a road vehicle with an automatic control of a main clutch and/or of a transmission for the purpose of maintaining a driving condition for the duration of traffic-caused stoppage phases by controlling brake pressure into at least one wheel brake of the road vehicle.
DE 196 11 360 C2 discloses, a device for the automatic operation of a hydraulic brake system of a road vehicle to maintain a vehicle stoppage for the duration of traffic-caused stoppage phases by coupling brake pressure from a brake pressure source, which can be activated without the driver's cooperation, into at least one wheel brake of the vehicle. This device operates with a brake pressure control device which, from a processing of sensor output signals of a sensor arrangement taking place according to plausibility criteria while the engine is running and after stoppage of the vehicle achieved after a braking operation, provides an automatic continuation of the stoppage braking. After a delay period of a defined duration has elapsed from the stoppage of the vehicle, a brake pressure, which is sufficient for a secure stoppage of the vehicle, is coupled into the wheel brake(s) utilized for the stoppage braking. When the driving operation is resumed, which can be detected from a redundant combination of sensor output signals, such as the output signal of an accelerator pedal position generator and a throttle valve position sensor or of a rotational engine speed sensor, the wheel brake(s) previously utilized for the stoppage braking is (are) released.
This known brake pressure control device endeavors to carry out maneuvering operations in a simple and secure manner irrespective of a triggering of stoppage brake operation phases which meet the demand. For this purpose, the automatic stoppage braking operation will be activated only when, within the delay period, the driver starts an operating activity which can be recognized as the driver's wish to activate the automatic stoppage braking and can be detected by the sensor arrangement. The termination of the automatic stoppage braking operation occurs only if, in addition to the sensor output signals of the sensor arrangement which demonstrate the driver's wish to resume the driving operation, sensor output signals are also present which, again on the basis of plausibility criteria, indicate the meeting of safety-relevant secondary conditions.
Thus, in the known control device, the time period is triggered by reaching the stoppage of the vehicle during a stoppage braking. The brake pedal is completely released after the triggering of the stoppage braking, and the continuation of the stoppage braking, when the accelerator pedal is operated for resuming the driving operation, is terminated only if the engine hood and the vehicle doors are closed and the driver's seat is occupied.
The goal of the known brake pressure control device of representing the function of a mechanical hill holder (free wheeling)—specifically automatic prevention of rolling on a hill against the intended driving direction—by way of a brake intervention, cannot be achieved in every operating condition or can be achieved only with high technical expenditures. In practice, problems with the operating comfort may also occur depending on the construction. For example, depending on the surrounding conditions, the vehicle will roll backwards in an undesirable manner because the existing brake pressure is not sufficient. Moreover, because the brake is operated in an undesirable manner in certain operating conditions (so that, for example, the maneuvering on the hill is more difficult) or, during active braking, noise problems occur while standing as the result of the pump of the brake system.
SUMMARY OF THE INVENTION
An object of the present invention is to implement the function of the hill holder in a brake pressure control device while avoiding the now recognized disadvantages.
The foregoing object has been advantageously achieved according to the invention by providing that the time period is triggered by the operating activity (&agr;
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) recognized as the driver's wish and the change, which can be achieved by the driver during the time period, replaces the condition for maintaining the brake pressure independent of the intervention by the driver by the condition for the adjustment of a brake pressure dependent on the intervention by the driver, and in that, at the end of the time period, the control device is necessarily brought into its condition for the adjustment of a brake pressure dependent on the intervention by the driver.
In the brake pressure control device according to the invention, the time period for the change of the condition of the control device which can be achieved by the driver is triggered by an arbitrary activity of the driver, for example, by the intentional “bridging” of the brake pedal during the stoppage of the vehicle. In this case, the alteration changes the control device from the condition for adjusting a brake pressure dependent on the intervention by the driver into the condition representing the actual “hill holder” function for maintaining a brake pressure independent of the intervention by the driver.
The elimination of this “hill holder” function, i.e., the change back into the condition of the control device for the adjustment of a brake pressure dependent on the intervention by the driver takes place automatically synchronized with the starting operation initiated by the driver by releasing the brake pedal and operating the accelerator pedal, with the automatic control of the main clutch and/or of a transmission. Should the driver not initiate this starting operation within the time period after, for example, bridging of the brake pedal, the “hill holder” function will automatically switch off. That is, the control device changes into the condition for adjusting a brake pressure dependent on the intervention by the driver, whereupon the brake pressure occurs which corresponds to the actual position of the brake pedal.
In the brake pressure control device according to the invention, the time period is usefully defined to be so short that the driver can change from the brake pedal to the accelerator pedal, without starting the movement of the vehicle. Although the brake pressure required for the stoppage of the vehicle must then be continuously modulated by the driver during the stoppage, short excitation periods are obtained thereby for the electromagnetic pressure control valves or pressure maintaining valves normally required for maintaining a brake pressure independent of the intervention by the driver. The pressure control and pressure maintaining valves heat up to an unacceptable degree during longer periods of excitation. For the usefulness of the operation of the brake pressure control device according to the invention, the active condition of the “hill holder” function is advantageously indicated in a known manner.
In the brake pressure control device according to the invention, when starting on a hill, the automatic “hill holder” function of the brake system is followed by an automatic start control function triggered by the accelerator pedal. In this case, the “hill holder” function is advantageously switched off under these circumstances only when the transmission capacity of the main clutch or of the transmission line between the engine and the vehicle wheel is recognized as being sufficient.
The logic devices of the brake pressure control device according to the invention can be integrated without additional sensors or actuators of the known brake pressure control devices, such as a wheel slip control system or an ESP in conjunction with automatically controlled clutches or transmissions in a simple manner, so that no separate logic unit is required.
The brake
Kroger Torsten
Reiter Jochen
Crowell & Moring , L.L.P.
Daimler-Chrysler AG
Kramer Devon
Oberleitner Robert J.
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