Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
1999-06-18
2001-06-12
Schwartz, Christopher P. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C303S113200, C303S116400
Reexamination Certificate
active
06244670
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for the open-loop control of a vehicle hydraulic braking system having an anti-lock system (ABS), the vehicle having two axles to which wheels are attached having wheel brakes that are coupled to a pedal-actuated master brake cylinder via hydraulic lines in which valve devices are provided. When the anti-lock system is triggered at at least one wheel of an axle, an active brake-pressure buildup is carried out at the wheel brakes of the other axle in order to attain a fully developed deceleration of the vehicle, the initial pressure between the master brake cylinder and the valve devices being used as the control criterion for the active brake-pressure buildup.
BACKGROUND INFORMATION
A previously proposed method is known, for example, from the German Published Patent Application No. 195 41 601. In response to a lock-up tendency occurring once at a front wheel, the method described therein provides for increasing the braking force at the rear axle above and beyond the specified driver input. The system pressure, determined with the aid of a sensor, is evaluated as a further criterion for the pressure buildup at the rear axle. The braking force at the rear axle should always be increased in particular when a situation has been recognized, according to which a driver demand for optimal utilization of the transferable braking force is probable. Such a situation is detected when the antilock protection controller has reduced the braking force at at least one front wheel. As soon as the driver releases the brake pedal, the brake pressure in the wheel brakes is reduced according to the driver's command.
German Published Patent Application No. 196 15 805 describes a method for controlling the braking system of a vehicle in open loop, with which, inter-alia, a maximum adhesion is adjusted during one control phase. Starting from a standby phase, there is a change into the control phase when various switch-on conditions are met. For example, the initial pressure adjusted by the driver is evaluated for this purpose. Implemented ABS interventions are not taken into consideration in this connection. As soon as a switch-off condition is met, there is a reversion from the control phase into the standby phase. For example, the initial pressure is evaluated in this connection, as well.
German Patent No. 43 38 065 describes a method for carrying out an automatic braking operation for motor vehicles having an anti-lock system. If the lock-up limit is reached at one wheel of the vehicle, an automatic braking process is carried out. During the automatic braking process, a braking pressure is produced which is greater than the braking pressure resulting from the position of the brake pedal. The braking pressure continues to be increased until, at each axle of the vehicle, the attainment of the lock-up limit for at least one wheel of the axle is determined by the anti-lock system.
German Patent No. 43 25 940 describes a method for determining a threshold value for the actuation speed of the brake pedal. If this threshold value is exceeded, an automatic braking process is triggered, during which a braking pressure is built up which is greater than the braking pressure resulting from the position of the brake pedal. The automatic braking process continuous until a discontinuation criterion is met.
The triggering of the automatic braking process by an ABS-controlled wheel can lead to an instability of the vehicle when the braking pressure at the other wheels is raised into the control range of the ABS. This is particularly the case on roadways having different road-surface coverings. In addition, irregularities in the roadway can lead to false triggerings. In response to the triggering of the support function, the driver can be irritated by the ABS function. The automatic braking process is first broken off with the release of the brake pedal. This means that a quite substantial force hysteresis occurs which holds the brake pedal forward.
SUMMARY OF THE INVENTION
An object of the present invention is to improve existing methods and devices for the open-loop control of the active pressure buildup in a hydraulic braking system. The particular intention is that the driver experience no disturbance due to an unwanted movement of the brake pedal in response to the switch-off of the fully developed deceleration.
Given a method for the open-loop control of a vehicle hydraulic braking system having an anti-lock system, the vehicle having two axles to which wheels are attached having wheel brakes that are coupled to a pedal-actuated master brake cylinder via hydraulic lines in which valve devices are provided. When the anti-lock system is triggered at at least one wheel of an axle, an active brake-pressure buildup is carried out at the wheel brakes of the other axle in order to attain a fully developed deceleration of the vehicle, the initial pressure between the master brake cylinder and the valve devices being used as the control criterion for the active brake-pressure buildup. The object of the present invention is achieved in that, in response to the fulfillment of a switch-off condition for the fully developed deceleration, the fully developed deceleration is advantageously switched off using a delay ramp. In this manner, abrupt switch-offs are avoided during which, given a pressure piling possibly still existing in the brake circuits, the brake pedal could strike unpleasantly against the driver's foot due to the sudden equalization of pressure. Another advantage of the delay function is that the brake pressure is reduced slowly.
The fully developed deceleration is advantageously reduced linearly within a predefined time to a predefined final value.
The initial pressure between the master brake cylinder and the valve devices is used as the control criterion for the active braking-pressure buildup. This has the advantage that a meaningful measured value, which is suitable as a control criterion, can be acquired in a simple manner using only one sensor. The initial pressure can be used both as a switch-on criterion, by which a fully developed deceleration is triggered, and as a switch-off criterion, by which the fully developed deceleration is switched off, and as a switchover criterion, with which a switchover from the fully developed deceleration to a smaller deceleration is carried out. In the last indicated case, it is particularly advantageous if the smaller deceleration is proportional to the initial pressure.
A fully developed deceleration of the vehicle is triggered in response to the fulfillment of a switch-on condition. The fully developed deceleration of the vehicle is effected by an active buildup of brake pressure. The pressure buildup in the wheel-brake cylinders which is not attributable to the braking force of the driver is designated as the active braking-pressure buildup. An active braking-pressure buildup is particularly necessary in situations in which the braking force of the driver only extends to an ABS control of the wheels of one axle. With the beginning of the closed-loop ABS control, the braking force is also frequently no longer increased by the driver as soon as one axle becomes ABS-controlled. However, a fully developed deceleration of the vehicle can only be achieved by an ABS control at all four wheels.
One particular specific embodiment of the present invention is characterized in that at least one of the following is used as a switch-on condition for the fully developed deceleration:
a) The anti-lock braking system is functioning faultlessly. For safety, the operation of the valve devices and the return pumps of the anti-lock system is monitored.
b) A pressure sensor for detecting the initial pressure has been successfully tested. The test of the pressure sensor is used to prevent an unwanted full braking because of a defective sensor.
c) The vehicle is not traveling in reverse. The speeds normally reached in reverse gear are not so high that an active pressure buildup is necessary.
d) The speed exceed
Bayer Stefan
Toelge Thomas
Wagner Jochen
Kenyon & Kenyon
Robert & Bosch GmbH
Schwartz Christopher P.
LandOfFree
Method for controlling a hydraulic braking system in open loop does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for controlling a hydraulic braking system in open loop, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for controlling a hydraulic braking system in open loop will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2443442