Electricity: motive power systems – Braking
Patent
1998-01-21
1999-12-28
Nappi, Robert E.
Electricity: motive power systems
Braking
188 721, H02K 710
Patent
active
060086041
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an electric motor wheel brake for motor vehicles.
BACKGROUND INFORMATION
Electric motor wheel brakes for motor vehicles are known. For example, World Patent No. WO-A 94/24453 describes a wheel brake where the brake application force is generated by an electric motor. If the brake system of a motor vehicle is composed of such electric motor wheel brakes, special attention must be devoted to reliable functioning of such a brake system to guarantee vehicular driving stability of the vehicle when braking in the partial braking range.
Therefore, the object of the present invention is to design a brake system of electric motor wheel brakes in such a way as to guarantee driving stability of the vehicle in braking and uniform brake wear.
SUMMARY OF THE INVENTION
A brake system with electric motor application of brake force is created to guarantee driving stability of the vehicle even in the partial braking range.
It is especially advantageous that this permits reliable and fault-tolerant determination of the braking torque and the braking forces on the wheels. This in turn leads to uniform brake wear in an advantageous manner.
Special advantages are achieved when using stepping motors or electronically commutated motors, where wear and tolerance effects can be compensated by adapting the point of brake application and brake release to gradual changes.
It is especially advantageous that a method of reliable monitoring of sensors for detecting the braking forces is provided with which a defective element can be detected.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a block diagram of a brake system according to an embodiment of the present invention with electric motor application of the brakes.
FIG. 2 illustrates a flow chart of an embodiment, according to the present invention, for determining the braking torque values formed at each wheel brake.
FIG. 3 illustrates a flow chart of an embodiment, according to the present invention, for comparing the braking torque values for wheel brakes on the same axle.
FIG. 4 illustrates a method, according to an embodiment of the present invention, for adapting the point of application and release of the brakes to gradual changes when using stepping motors or electronically commutated motors.
DETAILED DESCRIPTION
FIG. 1 shows a block diagram of a brake system of a motor vehicle with electric motor application of brake force on the example of an axle. This shows an electronic controller 10 that drives electric motors 16 and 18 over output lines 12 and 14. The electric motors are part of braking actuators 20 and 22 that act on braking elements 28 and 30 of wheels 32 and 34 respectively by way of mechanical connections 24 and 26. A similar arrangement is provided on additional axles of the vehicle. In the preferred embodiment, electric motors 16 and 18 are d.c. motors. In this case, as indicated with dotted lines, a quantity representing the current flowing through the motors is sent to control unit 10 over lines 36 and 38 respectively. This quantity is determined in a known way, e.g., by means of a resistor connected to ground in the H bridge output stage for the d.c. motor. Furthermore, there are force sensors 40 and 42 whose signals are sent to control unit 10 over lines 44 and 46. These force sensors determine the supporting forces of the braking actuators and in this way determine a measure of the operative braking forces and braking torques. In the preferred embodiment, these sensors are wire strain gauges. In other advantageous embodiments, the pressing force of the brake linings is detected by sensors (e.g., piezoelectric sensors), or the movement of the brake linings or an actuating lever of the wheel brake is determined (e.g., by displacement sensors) as an indirect measure of the braking force or the braking torques.
For the sake of thoroughness, FIG. 1 shows input lines 48 through 50 connecting control unit 10 to measuring devices 52 through 54. The latter detect additional operating quantitie
REFERENCES:
patent: 4327414 (1982-04-01), Klein
patent: 4658939 (1987-04-01), Kircher et al.
patent: 4685745 (1987-08-01), Reinecke
patent: 4784244 (1988-11-01), Carre et al.
patent: 4995483 (1991-02-01), Moseley et al.
patent: 5234262 (1993-08-01), Walenty et al.
Duda Rina I.
Nappi Robert E.
Robert & Bosch GmbH
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