Fluid-pressure and analogous brake systems – Speed-controlled – Sensing jerk – acceleration – or deceleration
Reexamination Certificate
1999-02-09
2001-07-03
Butler, Douglas C. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Sensing jerk, acceleration, or deceleration
C303S191000, C303S020000, C188S00111E
Reexamination Certificate
active
06254203
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method for determining a deceleration of a motor vehicle from the vehicle brake system.
The requirements for modern brake systems for motor vehicles are becoming increasingly stringent now a days. For example, antilock braking devices, driving stability controllers, drive slip controllers and traction controls are making wheel-selective brake actions necessary. This is achieved by brake systems which have an electromechanical wheel brake actuator on each wheel, mounted on the wheel brake caliper such as those described in German Patent DE 196 15 186 C1.
A critical criterion for the effectiveness of such additional functions is that the current total deceleration of the motor vehicle be defined as exactly as possible. As long as the wheel rotation speeds are proportional to the vehicle speed, that is to say the wheels show no tendency to become locked and the wheel slip is thus negligible, the total deceleration is essentially defined by the deceleration by the vehicle brake, called the braking deceleration in the following text.
The braking deceleration is a function of the contact-pressure forces of the brake pads on the brake disk and, in the case of hydraulic servo-assistance, the pressures (which are directly proportional to the contact-pressure forces) in the wheel brake cylinders (brake pressures) can, in particular, also be used as function variables here. Knowledge of the precise relationship between the braking deceleration and the contact-pressure force is of major importance for modern brake systems.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for determining the deceleration of a motor vehicle that overcomes the above-mentioned disadvantages of the prior art methods of this general type, which allows the braking deceleration of a motor vehicle to be defined as a function of the contact-pressure forces. The proportionality factor between these variables is intended to be matched to the vehicle mass and to the brake temperature.
With the foregoing and other objects in view there is provided, in accordance with the invention, an improved method for determining a deceleration of a motor vehicle due to a vehicle brake, the improvement which includes: calculating the deceleration as a product of a contact-pressure force of the vehicle brake and a proportionality factor being dependent on the contact-pressure force, a brake temperature and a vehicle mass without the brake temperature and the vehicle mass being explicitly defined.
The invention has the advantage that sensors for detecting the contact-pressure forces, in particular brake pressure sensors, provide relatively accurate and low-noise results, so that the sensor signals need not necessarily be averaged or filtered. Short-term availability of current braking deceleration values is thus also ensured. In this case, these values can also be associated with the individual wheels. While the influence of the load being carried is evident even before the start of a braking process, brake fading starts to occur only in the course of braking. It is thus possible to distinguish between the two effects. Since the respectively current relationship between the contact-pressure force and the braking deceleration is now known, a fixed characteristic can be defined between the brake pedal force and the braking deceleration. In the process, a matched contact-pressure force is associated with any given brake pedal position. Furthermore, if the wheels have a tendency to lock, that is to say when wheel slip increases, the braking deceleration calculated from the contact-pressure forces can advantageously be used to define the vehicle deceleration which is actually occurring, without having to define the coefficient of friction explicitly for this purpose.
With the foregoing and other objects in view there is also provided, in accordance with the invention, an improved method for determining a total deceleration of a motor vehicle, the improvement which includes: calculating a braking deceleration as a product of a contact-pressure force of a vehicle brake and a proportionality factor being dependent on the contact-pressure force, a brake temperature and a vehicle mass without the brake temperature and the vehicle mass being explicitly defined; determining an engine deceleration; determining a wind deceleration; determining a friction deceleration; determining a grade deceleration; and deriving the total deceleration by adding together the braking deceleration, the engine deceleration, the wind deceleration, the friction deceleration and the grade deceleration.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for determining the deceleration of a motor vehicle, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
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Published International Application No. 97/03869 (Maisch), dated Feb. 6, 1997.
Butler Douglas C.
Greenberg Laurence A.
Lerner Herbert L.
Siemens Aktiengesellschaft
Stemer Werner H.
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