Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
2000-03-31
2001-02-13
Schwartz, Christopher P. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C303S020000, C303S114300
Reexamination Certificate
active
06186601
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle brake system of a motor vehicle.
In particular, the present invention relates to a vehicle brake system of a motor vehicle with an electronically controllable brake booster comprising a vacuum chamber and a pressure chamber which are separated from each other by a movable wall, a control valve arrangement which can be actuated by means of an electromagnetic actuation means and by means of which a pressure difference between the pressure chamber and the vacuum chamber is adjustable, with the movable wall changing its position as a function of the pressure conditions in the vacuum chamber and in the pressure chamber, thereby actuating a master cylinder, with the electromagnetic actuation means being supplied with current signals by an electronic control unit during operation, which the electronic control unit generates as a function of driving dynamics conditions or external influences.
Such a vehicle brake system is known, for example, from DE 43 24 205 A1.
Such vehicles brake systems are employed for motor vehicles which are equipped with vehicle-to-vehicle ranging controls and cruise controls, or with combinations of these two controls (AbstandsRegelTempomaten—automatic ranging/cruise controls). One of the problems of these systems, however, is that these controls are relatively unreliable, because for a rapid control there exists too much play, backlash, or tolerance-related free travel in the vehicle brake system.
The consequence of this is that braking distance is “given away”. At a vehicle speed of 200 km/h and a vehicle brake system-related lost time of only 200 ms, this “given away” braking distance amounts to 11 m! Compared to a braking distance of approx. 193 m (at a deceleration of 8 m/s
2
) this corresponds to approx. 6%. Moreover, the control can exhibit an unsuitable transient behaviour or an overshooting behaviour as well.
SUMMARY OF THE INVENTION
The invention considers or utilises, respectively, the friction of seals and moved components and their bearings as counterforce or as holding force, respectively. It is thereby achieved that the components moved into a play-free position by the actuated control valve arrangement are held in this position as well, so that upon a braking operation to be initiated this position can already be the starting position.
According to a preferred embodiment of the invention the vehicle brake system is further developed in that, for sensing driving dynamics conditions or external influences, or combinations thereof, the electronic control unit is connected with sensors which sense the vehicle speed, and/or the vehicle acceleration/deceleration, and/or the distance from another vehicle, and/or the shift condition of the automatic speed control (cruise control), and/or the position of the throttle, and/or the position of the gearshift lever or of the automatic transmission, and/or the fuel consumption, and/or the brightness of the environment, and/or the time of day, and/or the contact of the brake pedal by the driver, and/or other signals which are relevant for the assessment of the probability of a braking operation required in the immediate future.
On the basis of this information from these sensors, the electronic control unit can determine whether the initiation of a braking operation in the immediate future is probable.
In a first design stage, the current signals generated by the electronic control unit are dimensioned in such a manner that they control the electromagnetic actuation means to such an extent, that play, backlash, or tolerance-related free travel in the brake booster are overcome without an actuation of the master cylinder taking place.
In a second, further design stage, the current signals generated by the electronic control unit are dimensioned in such a manner that they control the electromagnetic actuation means to such an extent, that play, backlash, or tolerance-related free travel in the master cylinder are overcome without an actuation of the brake means at the wheels of the vehicle taking place.
In a further design stage, the current signals generated by the electronic control unit are dimensioned in such a manner that they control the electromagnetic actuation means to such an extent, that play, backlash, or tolerance-related free travel in the brake lines, valve arrangements, and brake means at the wheels of the vehicle are overcome without an actuation of the brake means taking place.
Preferably, the overcoming of play, backlash, or tolerance-related free travel in the brake booster, and/or the master cylinder, and/or the brake lines, valve arrangement, and brake means at the wheels of the vehicle is sensed by corresponding sensors which generate feedback signals for the electronic control unit.
The electronic control unit comprises a computer for combining the signals sensed by the sensors in accordance with predetermined rules, and a memory for storing the predetermined rules as well as empirical values obtained during the operation of the vehicle brake system. These are used for the detection of driver-specific behavioural patterns before a braking operation and for their evaluation for future braking situations.
In an embodiment of the invention, the empirical values stored in the memory are combinations of sensed sensor signals as well as of probability values by means of which upon the respective combination of sensed sensor signals being present, a braking operation was carried out within a time interval in the past.
In this manner, the current signals generated by the electronic control unit can control the electromagnetic actuation means as a function of present sensor signals compared with the empirical values stored in the memory to such an extent that with increasing probability of a braking operation to be initiated in the immediate future, play, backlash, or tolerance-related free travel is overcome at first in the brake booster, then in the master cylinder, and then in the brake lines, valve arrangements and brake means at the wheels of the vehicle, without an actuation of the brake means taking place.
In this stepwise overcoming of the free travel, the vehicle brake system can be prepared successively for a braking operation as a function of external influences, so that in the very moment in which the braking operation is actually intended by the driver through an actuation of the brake pedal, the brake can immediately “grip” without the occurrence of delays related to the vehicle brake system.
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XP 000635432 Research Disclosure—Aug. 1996 Adjustable Dead-Stroke in Braking System Disclosed by Philippe Castel.
Lucas Industries Public Limited Company
MacMillan Sobanski & Todd LLC
Schwartz Christopher P.
Talavera Melanie
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