METHOD FOR OPERATING A BRAKING SYSTEM

Abstract

A method for operating a braking system, wherein a switchable connection between two connection points is open in normal operation, and a voltage difference across the switchable connection is reduced by recuperation before said switchable connection is closed, which serves to compensate for a disturbance in an on-board electrical system. As a result, it is possible to avoid excess currents in the event of the closing of the switchable connection.

Claims

1-15. (canceled)

16. A braking system comprising: a first input voltage terminal; a second input voltage terminal; an electric motor; and a switchable connection between a first connection point connected to the first input voltage terminal and a second connection point connected to the second input voltage terminal and the electric motor, wherein the switchable connection is open in normal operation, and wherein in response to a detected voltage difference between the first input voltage terminal and the second input voltage terminal which is above a first threshold value, the electric motor is configured to operate in a recuperation mode, and in response to a detected voltage difference between the first connection point and the second connection point which is below a second threshold value, the switchable connection is closed.

17. The braking system as claimed in claim 16, wherein with the switchable connection closed, in response to a detected voltage difference between the first input voltage terminal and the second input voltage terminal which is below a third threshold value for a first time duration, the switchable connection is opened and the electric motor is configured to operate in normal operation.

18. The braking system as claimed in claim 17, wherein the third threshold value is identical to the first threshold value wherein the third threshold value is between 3.5 V and 4.5 V, and wherein the first time duration is between 10 ms and 30 ms.

19. The braking system as claimed in claim 18, wherein in a state in which the electric motor is operated in the recuperation mode, and the switchable connection is open, in response to the voltage difference between the first input voltage terminal and the second input voltage terminal falling below a fourth threshold value, the electric motor is configured to operate in normal operation.

20. The braking system as claimed in claim 19, wherein upon return from the recuperation mode to normal operation, or upon a predefined number of direct return from the recuperation mode to normal operation within a predefined monitoring time being exceeded, a return prohibition is activated, which remains activated for a predetermined safeguard time, wherein with the return prohibition activated, a direct return from the recuperation mode to normal operation is prevented.

21. The braking system as claimed in claim 20, wherein after activation of the return prohibition, a fault memory entry is carried out and a return to the normal state is prevented until the deactivation of an ignition.

22. The braking system as claimed in claim 21, wherein the switchable connection is closed in response to a second time duration being exceeded, in which second time duration the electric motor is operated in the recuperation mode.

23. The braking system as claimed in claim 22, wherein the second time duration is between 10 ms and 100 ms.

24. The braking system as claimed in claim 23, wherein the first threshold value is between 3.5 V and 4.5 V, and wherein the second threshold value is between 0.25 V and 2 V.

25. The braking system as claimed in claim 24, wherein in response to a detected voltage difference between the first input voltage terminal and the second input voltage terminal which is above a fifth threshold value for a third time duration, the electric motor is configured to activate a warning function.

26. The braking system as claimed in claim 25, wherein the third time duration is between 50 ms and 1 s.

27. The braking system as claimed in claim 26, wherein the first input voltage terminal is connected to a battery, and wherein the second input voltage terminal is connected to a generator.

28. The braking system as claimed in claim 27, further comprising: a first switch or a first diode connected between the first input voltage terminal and the first connection point; and a second switch or a second diode connected between the second input voltage terminal and the second connection point.

29. The braking system as claimed in claim 28, further comprising a valve arrangement connected to the first connection point.

30. The braking system as claimed in claim 29, further comprising a diode having a forward direction toward the first connection point interconnected in parallel with the switchable connection.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Embodiments will now be described with reference to the figures. In this case, in the figures:

[0039] FIG. 1 is a diagram illustrating a braking system according to an embodiment, and

[0040] FIG. 2 is a flow diagram illustrating a method of operating a braking system according to an embodiment.

DETAILED DESCRIPTION

[0041] FIG. 1 shows a braking system 5, on which a method according to an embodiment can be carried out.

[0042] The braking system 5 comprises a first input voltage terminal KL30_1 and a second input voltage terminal KL30_2. The first input voltage terminal KL30_1 is typically connected to a battery. The second input voltage terminal KL30_2 is typically connected to an on-board electrical system of a motor vehicle.

[0043] The first input voltage terminal KL30_1 is connected to a first connection node 21 via a first switch 25. The second input voltage terminal KL30_2 is connected to a second connection node 22 via a second switch 26. The switches 25, 26 can for example be embodied as transistors and serve to interrupt or enable the connection between the respective input voltage terminal KL30_1, KL30_2 and the connection node 21, 22.

[0044] A valve arrangement 15 is connected to the first connection node 21. Said valve arrangement includes a plurality of switchable valves that serve for the operation of the braking system, but they will not be discussed any further here.

[0045] The second connection node 22 is connected to an electric motor 10. The electric motor 10 typically drives a pump or a linear actuator in order to generate pressure in the braking system 5 independently of the driver.

[0046] A switchable connection 40 is formed between the first connection node 21 and the second connection node 22. Said switchable connection can be switched to be either open or closed. Consequently, the first connection node 21 and the second connection node 22 can be disconnected from one another or connected to one another in a targeted manner. A control device 45 is provided for control purposes, which control device carries out a method according to an embodiment, as will be described below with reference to FIG. 2.

[0047] The braking system 5 has a total of four voltage sensors, which are designated with their respective voltages in FIG. 1. In this regard, a first voltage V1 is measured at the first input voltage terminal KL30_1. A second voltage V2 is measured at the second input voltage terminal KL30_2. A third voltage V3 is measured at the first connection node 21. A fourth voltage V4 is measured at the second connection node 22. The procedure will now be described by way of example with reference to FIG. 2.

[0048] The braking system is initially in normal operation N with all components functioning entirely satisfactorily. In this case, a voltage difference V1-V2 between the first input voltage V1 and the second input voltage V2 is continuously monitored. If said voltage difference exceeds a first threshold value Diff1, then the braking system 5 firstly transitions to a recuperation mode R. The recuperation mode R is characterized in that the electric motor 10 is operated in recuperation for a limited time, such that it can obtain energy from its rotation that is present anyway, or from a pressure in a hydraulic area of the braking system 5. As a result, the voltage at the second connection node 22 is increased by means of the electric motor 10. The voltage difference V3-V4 otherwise present between the first connection node 21 and the second connection node 22 is reduced in this way. If said voltage difference falls below a second threshold value Diff2 or alternatively if a second time duration t2 has elapsed, the braking system 5 switches to a switched mode S, in which the switchable connection 40 is closed. Consequently, a supply of the electric motor 10 by means of the first input voltage terminal KL30_1 is now possible. In other words, if the supply by the on-board electrical system at the second input voltage terminal KL30_2 fails, this failure is compensated for by the electric motor 10 then running in battery operation.

[0049] By contrast, if in the recuperation mode the voltage difference V1-V2 between first input voltage terminal KL30_1 and second input voltage terminal KL30_2 falls below a fourth threshold value Diff4, then the switchable connection 40 is not opened, rather there is a return directly to the normal state, that is to say that the recuperation is ended. In this case, a return prohibition is directly activated, which remains active for a predetermined safeguard time period. If, with the return prohibition activated, there is again a changeover to the recuperation mode and then the event occurs again that, before the opening of the switchable connection 40, the voltage difference V1-V2 between first input voltage terminal KL30_1 and second input voltage terminal KL30_2 drops below the fourth threshold value Diff4, then a return to the normal state is prevented. Rather, there is then necessarily firstly a changeover to the switched state, specifically according to the rules already explained further above. As an alternative to the direct activation of the return prohibition, a change counter can also be incremented whenever a transition from normal operation to the recuperation mode takes place. If the counter assumes a specific value of 2, 3, 4 or 5, for example, and this occurs in particular within a predefined monitoring time of, for example, 10 s, 20 s or 50 s or else by the next ignition change, the return prohibition is activated. As a result, repeated changeover between normal operation and recuperation mode can be permitted.

[0050] If the voltage difference V1-V2 between the first input voltage terminal KL30_1 and the second input voltage terminal KL30_2 falls below a third threshold value Diff3 again at least for a first time duration t1, then the system returns to normal operation, that is to say that, in particular, the switchable connection 40 is opened again. Consequently, therefore, once again the electric motor 10 is operated exclusively from the second input voltage terminal KL30_2 and the valve unit 15 is operated exclusively from the first input voltage terminal KL30_1.

[0051] However, if the voltage difference V1-V2 between the first input voltage terminal KL30_1 and the second input voltage terminal KL30_2 is above a fifth threshold value Diff5 for a third time duration t3, then a warning message W is activated. This can be for example a display in an instrument panel of a motor vehicle. As a result, the driver is made aware that the braking system has a malfunction and he/she ought to drive more cautiously since operational restrictions of the braking system 5 should possibly be expected.

[0052] Abovementioned steps of the method according to an embodiment can be carried out in the order indicated. However, they can also be carried out in a different order, insofar as is technically appropriate. In one of its embodiments, for example with a specific combination of steps, the method according to an embodiment can be carried out in such a way that no further steps are carried out. However, in principle, further steps can also be carried out, including steps that have not been mentioned.

[0053] It is pointed out that features may be described in combination in the claims and in the description, for example in order to facilitate understanding, even though these can also be used separately from one another. A person skilled in the art will recognize that such features, independently of one another, can also be combined with other features or feature combinations.

[0054] Dependency references in dependent claims may characterize preferred combinations of the respective features but do not exclude other feature combinations.