Method for operating a brake system for a motor vehicle and corresponding brake system

Abstract

A method for operating a brake system for a motor vehicle, wherein the brake system comprises an eddy current brake mechanically coupled to at least one wheel of the motor vehicle for providing a braking force acting on the wheel, wherein an electric machine is mechanically coupled or can be coupled to the wheel and is electrically connected to the eddy current brake. In this case, it is provided that, in an emergency braking mode for braking the wheel, the eddy current brake is supplied in parallel with energy provided by means of the electric machine operating as a generator and with electrical energy taken from an energy accumulator. The disclosure furthermore relates to a brake system for a motor vehicle.

Claims

1. A method for operating a brake system for a motor vehicle, comprising: an eddy current brake mechanically coupled to at least one wheel of the motor vehicle for providing a braking force acting on the wheel; an electric machine that is mechanically coupled or can be coupled to the wheel and that is electrically connected to the eddy current brake; and an energy accumulator, wherein, in an emergency braking mode for braking the wheel, the eddy current brake is supplied in parallel with electrical energy provided by means of the electric machine operating as a generator and with electrical energy taken from the energy accumulator, wherein in a braking mode, the electric machine and the eddy current brake are actuated to brake the wheel, wherein the eddy current brake is electrically decoupled from the energy accumulator and supplied with electrical energy provided by the electric machine.

2. The method as claimed in claim 1, wherein the electric machine is operated as a motor in a driving mode for driving the wheel.

3. The method as claimed in claim 1, wherein the electric machine is operated as a generator in a recuperation mode for braking the wheel, wherein the electrical energy accruing thereby is at least partly stored temporarily in the energy accumulator.

4. The method as claimed in claim 3, wherein in the recuperation mode the eddy current brake is operated to release the wheel.

5. The method as claimed in claim 1, wherein in the braking mode, the electric machine is decoupled from the energy accumulator.

6. The method as claimed in claim 1, wherein in the braking mode, when a target braking force exceeds a maximum braking force produced on the wheel by the electric machine, the electric machine is adjusted to generate the maximum braking force, and a proportion of the electrical energy provided by the electric machine and supplied to the eddy current brake is adjusted in such a way that the electric machine and the eddy current brake together bring about a braking force on the wheel corresponding to the target braking force.

7. The method as claimed in claim 1, wherein in the emergency braking mode, the electric machine is adjusted to generate the maximum braking force and the electrical energy provided by the electric machine is supplied entirely to the eddy current brake.

8. A brake system for a motor vehicle, wherein the brake system comprises: an eddy current brake mechanically coupled to at least one wheel of the motor vehicle for providing a braking force acting on the wheel an electric machine that is mechanically coupled or can be coupled to the wheel and that is electrically connected to the eddy current brake; and an energy accumulator, wherein, in an emergency braking mode for braking the wheel, the brake system is designed for the purpose of supplying the eddy current brake in parallel with energy provided by means of the electric machine operating as a generator and with electrical energy taken from the energy accumulator, wherein in a braking mode, the electric machine and the eddy current brake are actuated to brake the wheel, wherein the eddy current brake is electrically decoupled from the energy accumulator and supplied with electrical energy provided by the electric machine.

9. The brake system as claimed in claim 8, wherein the electric machine and the eddy current brake are arranged on a common shaft.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention shall now be explained more closely with the aid of exemplary embodiments represented in the drawing, without resulting in limiting the invention. Shown herein are:

(2) FIG. 1 a schematic representation of a brake system for a motor vehicle in a recuperation mode;

(3) FIG. 2 a schematic representation of the brake system in a braking mode; and

(4) FIG. 3 a schematic representation of the brake system in an emergency braking mode.

DETAILED DESCRIPTION

(5) FIG. 1 shows a schematic representation of a brake system 1 for a motor vehicle. The brake system 1 serves for applying a braking force to a wheel of the motor vehicle, which is not shown here. The brake system 1 comprises an electric machine 2 and an eddy current brake 3. The electric machine 2 has a stator 4 and a rotor 5, which is mounted rotatably with respect to the stator 4.

(6) The electric machine 2 or its rotor 5 are mechanically coupled or at least can be coupled to the wheel of the motor vehicle. In the latter case, for example, the wheel may be mechanically connected to the rotor 5 by way of a shift clutch. The eddy current brake 3 likewise has a stator 6 and a rotor 7. Here as well, the rotor 7 is mounted rotatably with respect to the stator 6. The rotor 7 is mechanically coupled or at least can be coupled to the wheel of the motor vehicle. Especially preferred, the rotor 7 is in permanent operative connection to the wheel.

(7) A braking force may be imposed on the wheel of the motor vehicle both by means of the electric machine 2 and by means of the eddy current brake 3. The brake system 1 is represented in a recuperation mode, in which the braking force is applied to the wheel solely by means of the electric machine 2. The eddy current brake 3, on the other hand, is adjusted to release the wheel or is operated to release the wheel.

(8) By applying the braking force to the wheel by means of the electric machine 2, kinetic motion energy of the wheel is transformed into electrical energy. This energy is stored temporarily in an energy accumulator 8. This is indicated by the arrow 9. Likewise shown is the braking force exerted on the wheel by the electric machine 2, namely, by the arrow 10.

(9) FIG. 2 shows the brake system 1 in a schematic representation where the brake system 1 is in a braking mode. In this case, the braking force acting on the wheel is produced jointly by the electric machine 2 and the eddy current brake 3. This is represented by the arrows 10 and 11. In the braking mode, the electrical energy provided by means of the electric machine 2 is supplied to the eddy current brake 3 for the braking of the wheel. This is indicated by the arrow 12.

(10) This means that the energy accumulator 8 is preferably decoupled from the electric machine 2 and the eddy current brake 3, so that the entire energy provided by the electric machine 2 is drawn upon by the eddy current brake 3 to generate the braking force on the wheel. In such a procedure, the proportions of braking force from the electric machine 2 and the eddy current brake 3 preferably lie in the same order of magnitude; for example, they are identical or at least almost identical.

(11) FIG. 3 again shows a schematic representation of the brake system 1, wherein it is operated in an emergency braking mode. In this mode, the electric machine 2 is operated similar to the braking mode for transforming kinetic energy of the wheel into electrical energy. Once again, the energy is supplied to the eddy current brake 3. Accordingly, both the electric machine 2 and the eddy current brake 3 contribute to generating the braking force on the wheel of the motor vehicle.

(12) However, in addition, it is now provided to supply electrical energy to the eddy current brake 3, having been drawn from the energy accumulator 8. This is indicated by the arrow 13. Accordingly, the eddy current brake 3 can provide a considerably larger proportion of the braking force on the wheel than is possible during the braking mode. This is indicated by the double arrow 11.

(13) For example, the proportion of the eddy current brake 3 in the braking force on the wheel that is produced by the electric machine 2 and the eddy current brake 3 is at least 60%, at least 70%, at least 75% or at least 80%. Accordingly, a very large braking force is realized on the wheel, so that a rapid reduction in speed of the motor vehicle occurs.

(14) On the whole, with the brake system 1 according to the statements in the context of this description, an extremely energy-efficient operation is realized and at the same time excellent safety is achieved. Thus, in the emergency braking mode, on the one hand, a very large braking force is produced on the wheel. On the other hand, it is ensured that, even if one energy source is defective, such as the electric machine 2 or the energy accumulator 8, a sufficiently large braking force will continue to be applied to the wheel by means of the eddy current brake 3. Accordingly, in this case as well, an adequate deceleration of the motor vehicle is realized.