Fluid-pressure and analogous brake systems – Speed-controlled – Odd condition or device detection
Reexamination Certificate
1997-01-30
2001-03-06
Butler, Douglas C. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Odd condition or device detection
C303S168000, C303S176000, C303S020000, C303S199000
Reexamination Certificate
active
06196644
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to anti-skid or anti-slip brake control systems.
In vehicles that are equipped with an anti-skid or anti-slip brake control system, typically four and in individual cases only three rpm sensors are used, which are assigned to the individual wheels. In general, the output signals of these rpm sensors are pulselike. From the time interval between individual pulses or individual pulse edges, the rpm of the applicable wheel is ascertained.
The vehicle reference speed, which represents an essential variable for the anti-skid or anti-slip brake control is ascertained from the wheel rpm values. The vehicle reference speed is ascertained for instance from the four wheel speeds or from the wheel speed of one wheel, the so-called reference i wheel. From the wheel rpm values, a reference speed can also be formed, which is usable in the ABS control as a further controlled variable.
Since essential variables of the anti-skid or anti-slip brake control system are formed on the basis of output signals of the wheel rpm sensors, reliable monitoring of the operability of the sensors must necessarily be performed. German Patent Application P 44 05 801.2, for instance, has therefore proposed a monitoring system that is used in ABS control systems and makes it possible to detect various malfunctions of the wheel rpm sensors.
Interference signals that correspond approximately to the mains frequency of 50 Hz (or 60 Hz) have proved to be especially problematic in control systems. Such interference signals can be fed to the rpm sensors of the ABS system for instance by magnetic fields generated by vehicle heaters that are operated at the usual mains voltage. In that event, they reflect incorrect wheel speeds to the control unit, and as a result an unintended ABS control can be tripped and maintained.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method of suppressing interference signals, especially interference signals approximately at the main power source frequency of 50 or 60 Hz, that effect operation of an anti-skid or anti-slip brake control system.
It is a further object of the present invention to provide an improved anti-skid or anti-slip brake control system, in which interference signals from a vehicle power source at about a mains frequency are accounted for and faulty operation of the braking system due to those interference signals is prevented.
According to the invention the method of controlling a motor vehicle braking system of a motor vehicle to prevent wheel slip or skidding includes:
a) generating wheel speed signals indicative of wheel speeds of each of at least two wheels of the motor vehicle;
b) determining the wheel speeds from each of the wheel speed signals;
c) determining a vehicle reference speed from one of the wheel speeds determined in step b) for one of the at least two wheels;
d) determining whether or not the vehicle reference speed ascertained in step c) is within a predetermined speed range of 47 to 63 Hz, during which interference signals from a vehicle power source at about a mains frequency are generated that produce false wheel speed signals; and
e) controlling the motor vehicle braking system according to a special ABS control method when the vehicle reference speed is within the predetermined speed range according to step d), this special ABS control method comprising a accounting for the interference signals in such a manner that improper activation of or influence on the braking system due to the interference signals is prevented.
The invention also resides in an improved ABS system designed to perform the above-described method according to the invention.
The anti-skid or anti-slip brake control systems according to the invention, have the advantage that interference signals that occur at a frequency corresponding to the usual mains frequency are reliably precluded from the evaluation of the rpm sensor signals and the vehicle reference speed formed from those signals. Thus advantageously the control properties of the ABS can be maintained even in the critical speed range. Interference at mains frequency no longer trips any control, and any existing control is ended if the vehicle stops.
These advantages are attained in that the anti-blocking control, in a critical speed range in which the frequency of the wheel rpm sensor signals of the reference wheel are in the range of 50 Hz, effects a particular adjustment of the current vehicle reference speed and the so-called auxiliary reference speed. In the process, the vehicle reference speed is negatively adjusted in a range between 63 and 47 Hz. If the wheel speed is between a minimum value vmin and 47 Hz, then the signal cannot be caused by interference, and the vehicle reference speed can then be reformed reliably on the basis of the wheel speed.
Further advantageous features of the invention are attained with the provisions recited in the dependent claims.
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Butler Douglas C.
Robert & Bosch GmbH
Striker Michael J.
Williams C
LandOfFree
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