Method for operating a brake system

Abstract

A method for operating a brake system, wherein two switching valves arranged on the suction side of pumps are opened and closed in an alternating manner in order to reduce current consumption.

Claims

1. A method for operating a brake system of a motor vehicle, comprising: a first hydraulic circuit, a second hydraulic circuit, and a master brake cylinder, wherein the first hydraulic circuit has at least a first hydraulic pump and a first switching valve, and the master brake cylinder is connected via the first switching valve to a first suction port of the first hydraulic pump, wherein the second hydraulic circuit has at least a second hydraulic pump and a second switching valve, and the master brake cylinder is connected via the second switching valve to a second suction port of the second hydraulic pump, and wherein, during continuous running of the first hydraulic pump and the second hydraulic pump, the first switching valve and the second switching valve are opened and closed in an alternating manner to one another.

2. The method as claimed in claim 1, wherein the first hydraulic pump and the second hydraulic pump are driven by a single motor.

3. The method as claimed in claim 2, wherein the motor is an electric motor.

4. The method as claimed in claim 1, wherein the first switching valve and the second switching valve are opened and closed in the alternating manner to one another during an antilocking system engagement at an operating point of 150 bar to 250 bar.

5. The method as claimed in claim 1, wherein the switching valves are switched in such a way that they are open and closed for equally long times.

6. The method as claimed in claim 1, wherein the switching valves are switched in such a way that the first switching valve is open for a shorter time than the second switching valve.

7. The method as claimed in claim 6, wherein the second switching valve is open for twice as long as the first switching valve.

8. The method as claimed in claim 6, wherein, for a same speed, the second hydraulic pump has a higher delivery power than the first hydraulic pump.

9. The method as claimed in claim 8, wherein the second switching valve is open for twice as long as the first switching valve.

10. The method as claimed in claim 1, wherein times in which the switching valves are open or closed are calculated on the basis of a volume model.

11. The method as claimed in claim 1, wherein the first switching valve and/or the second switching valve are or is open for 100 ms to 200 ms.

12. The method as claimed in claim 1, wherein each hydraulic pump has a respective outlet port which is connected to a number of brake cylinders of the respective hydraulic circuit.

13. The method as claimed in claim 12, wherein an inlet valve is arranged between the outlet port and each brake cylinder, and the inlet valves are connected via an isolation valve to the master brake cylinder so as to be situated opposite to the respective brake cylinder; and/or wherein each brake cylinder is connected via a respective outlet valve to the respective low-pressure accumulator of its hydraulic circuit.

14. The method as claimed in claim 1, wherein the first switching valve and the second switching valve are opened and closed in the alternating manner to one another continuously during operation of the motor vehicle, or wherein the first switching valve and the second switching valve are opened and closed in the alternating manner to one another in response to: a supply voltage of one or both of the hydraulic pumps below a first threshold value, a temperature of one or both of the hydraulic pumps above a second threshold value, or a current of a motor, which drives the hydraulic pumps, above a third threshold value.

15. The method as claimed in claim 1, wherein the first hydraulic circuit is short-circuited by opening the first switching valve so that fluid can be pumped into the first hydraulic circuit without resistance, and the second hydraulic circuit is short-circuited by opening the second switching valve so that fluid can be pumped into the second hydraulic circuit without resistance.

16. The method as claimed in claim 1, wherein the first hydraulic pump and the second hydraulic pump are connected to different fluid reservoirs of the master brake cylinder.

17. The method as claimed in claim 1, wherein the first switching valve and the second switching valve are opened and closed in the alternating manner to one another during an antilocking system engagement at an operating point of 200 bar.

18. The method as claimed in claim 1, wherein the first switching valve and/or the second switching valve are or is open for 150 ms.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages will be gathered by a person skilled in the art from the exemplary embodiment described below with reference to the appended drawing, in which:

(2) The FIGURE shows a brake system for carrying out the method according to an aspect of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(3) The FIGURE shows a brake system or a detail of a brake system which is designed for carrying out a method according to an aspect of the invention according to an exemplary embodiment. The method according to an aspect of the invention is described with reference to this FIGURE.

(4) The brake system illustrated in the FIGURE has a master brake cylinder 5. The main brake cylinder 5 has a first fluid reservoir 7.

(5) The brake system further has a first hydraulic circuit 10. It additionally has a second hydraulic circuit. The second hydraulic circuit is not illustrated in the FIGURE. Only illustrated, rather, is the first hydraulic circuit 10 which is connected to the already mentioned first fluid reservoir 7. It should be understood that the master brake cylinder 5 further has a second fluid reservoir which is not illustrated or not explicitly described and which is connected to the second hydraulic circuit (not shown).

(6) The second hydraulic circuit (not shown) has substantially the same or a similar functionality as the illustrated first hydraulic circuit 10 described below. Corresponding differences or relationships will be discussed where appropriate.

(7) The first hydraulic circuit 10 has a first hydraulic pump 20. The first hydraulic pump 20 has a suction port 22 and an outlet port 24. It is designed to pump a brake fluid or a fluid from the suction port 22 to the outlet port 24. For this purpose, it is coupled to a motor 26, wherein the motor 26 drives not only the hydraulic pump 20, illustrated in the FIGURE, of the first hydraulic circuit 10 but also a hydraulic pump (not shown) of the second hydraulic circuit.

(8) The first hydraulic circuit 10 further has a first low-pressure accumulator 30. The first low-pressure accumulator 30 serves as an intermediate reservoir within the first hydraulic circuit 10.

(9) A first nonreturn valve 40 is arranged between the first low-pressure accumulator 30 and the suction port 22. This ensures that the brake fluid can flow only in the direction from the first low-pressure accumulator 32 to the suction port 22, but not in reverse.

(10) The suction port 22 of the first hydraulic pump 20 is further connected via a first switching valve 50 to the first fluid reservoir 7 of the master brake cylinder 5. The first switching valve 50 is an electrically actuatable valve by means of which the connection can be opened and closed.

(11) The outlet port 24 of the first hydraulic pump 20 is connected to two inlet valves 60, which in turn are connected to in each case a brake cylinder 12, 14. In the present case here, a design is chosen in which a first brake cylinder 12 operates the front left wheel and a second brake cylinder 14 operates the rear right wheel. It should be mentioned that, correspondingly, the second hydraulic circuit, which is not illustrated, likewise has two brake cylinders which operate the front right and the rear left wheel. Such a design is particularly advantageous for vehicles having front-wheel drive.

(12) The pressure generated by the hydraulic pump 20 can be channeled via the inlet valves 60 to the brake cylinders 12, 14, with the result that they can carry out a braking operation.

(13) As shown, the two inlet valves 60 are also connected to a first isolation valve 70, which in turn is connected to the first fluid reservoir 7 of the master brake cylinder 5. Consequently, a pressure which is generated by the master brake cylinder 5 and which is typically generated by a driver actuating a brake pedal can also be channeled via the two inlet valves 60 to the two brake cylinders 12, 14.

(14) The two brake cylinders 12, 14 are connected via in each case an outlet valve 65 to the low-pressure accumulator 30. In the case that an antilocking system engagement occurs, this allows pressure to be reduced in a targeted manner in the two brake cylinders 12, 14 by opening the outlet valves 65 and to be channeled away into the low-pressure accumulator 30. As a result, locking of the wheels can be prevented.

(15) This fluid or the brake fluid is then pumped back again out of the first low-pressure accumulator 30 by the first hydraulic pump 20.

(16) The motor 26 and the first hydraulic pump 20 are dimensioned in such a way that the delivery power of the first hydraulic pump 20 at the operating pressure of approximately 200 bar that is typical for such engagements is considerably higher than necessary. This is because the first hydraulic pump 20 and the motor 26 are designed in the present case for the system also to be able to implement an emergency braking function in which the vehicle has to be braked to a standstill in an automated manner. Such an emergency braking function typically occurs at a pressure of approximately 100 bar, whereas the pressure used during an antilocking system engagement is approximately 200 bar. However, the high delivery power achievable here is not required at all.

(17) In order in this situation to save current and to allow a weaker design of a vehicle electrical system, the first switching valve 50 and a second switching valve (not shown) of the second hydraulic circuit (not shown) are continuously switched in an alternating manner, with the result that one of the two hydraulic circuits is always short-circuited in alternation. The respective hydraulic pump of the short-circuited hydraulic circuit then no longer pumps any brake fluid from the respective low-pressure accumulator, but merely pumps it in the circuit, which occurs virtually without resistance This means that only ever one of the two hydraulic pumps of the brake system illustrated in the FIGURE actually provides a delivery power, with the result that the current consumption of the motor 60 is considerably reduced.

(18) Mentioned steps of the method according to an aspect of the invention can be executed in the indicated order. However, they can also be executed in a different order. In one of its embodiments, for example with a specific combination of steps, the method according to an aspect of the invention can be executed in such a way that no further steps are executed.

(19) However, in principle, further steps can also be executed, even steps of a kind which have not been mentioned.

(20) The claims that are part of the application do not represent any dispensing with the attainment of further protection.

(21) If it turns out in the course of the proceedings that a feature or a group of features is not absolutely necessary, then the applicant aspires right now to a wording for at least one independent claim that no longer has the feature or the group of features. This may be, by way of example, a subcombination of a claim present on the filing date or may be a subcombination of a claim present on the filing date that is limited by further features. Claims or combinations of features of this kind requiring rewording can be understood to be covered by the disclosure of this application as well.

(22) It should further be pointed out that configurations, features and variants of aspects of the invention that are described in the various embodiments or exemplary embodiments and/or shown in the FIGURES can be combined with one another in any way. Single or multiple features can be interchanged with one another in any way. Combinations of features arising therefrom can be understood to be covered by the disclosure of this application as well.

(23) Back-references in dependent claims are not intended to be understood as dispensing with the attainment of independent substantive protection for the features of the back-referenced subclaims. These features can also be combined with other features in any way.

(24) Features that are disclosed only in the description or features that are disclosed in the description or in a claim only in conjunction with other features may fundamentally be of independent significance essential to aspects of the invention. They can therefore also be individually included in claims for the purpose of distinction from the prior art.