Method for operating a motor vehicle, device for operating a motor vehicle, motor vehicle

Abstract

The invention relates to a method for operating a motor vehicle (1) having a hydraulic brake system (8), which has at least one controllable first hydraulic actuator (14) and a controllable second hydraulic actuator (16), the motor vehicle (1) is decelerated by controlling a selected one of the hydraulic actuators (14, 16) according to a deceleration command. According to the invention, a current wear state (V1) of the first hydraulic actuator (14) is determined, a current wear state (V2) of the second hydraulic actuator (16) is determined, and one of the hydraulic actuators (14, 16) is selected as a function of the determined wear states (V1, V2).

Description

Technical Field

[0001] The invention relates to a method for operating a motor vehicle having a hydraulic brake system with at least one controllable first hydraulic actuator and a controllable second hydraulic actuator, wherein the motor vehicle is decelerated by controlling a selected hydraulic actuator according to a requested deceleration command.

[0002] The invention further relates to a device for operating a motor vehicle having a hydraulic brake system with at least one first controllable hydraulic actuator and one second controllable hydraulic actuator.

[0003] The invention further relates to a motor vehicle having a hydraulic brake system with at least one first controllable hydraulic actuator and one second controllable hydraulic actuator. Background Art

[0004] Methods and motor vehicles of the type described above are known in the prior art. Motor vehicles usually have a hydraulic brake system. A brake system having at least one controllable first hydraulic actuator and a controllable second hydraulic actuator is known. In such a brake system, a friction braking torque for decelerating the motor vehicle can be generated by controlling both the first hydraulic actuator and the second hydraulic actuator. Usually, one of the hydraulic actuators is selected, namely the first hydraulic actuator or the second hydraulic actuator, wherein one of the hydraulic actuators can be selected depending on the situation. When there is a deceleration command for the motor vehicle, the motor vehicle is decelerated by controlling the selected hydraulic actuator. Summary of the invention

[0005] The method according to the invention having the features of claim 1 has the advantage of being able to maximize the service life of the hydraulic actuator. To this end, it is provided according to the invention that a current wear state of the first hydraulic actuator is determined, a current wear state of the second hydraulic actuator is determined, and one of the hydraulic actuators is selected in dependence on the determined wear state. Thus, the current wear state of the hydraulic actuator is taken into account when selecting one of the hydraulic actuators. By taking into account the current wear state, further or future wear of the hydraulic actuator can be influenced. Preferably, a hydraulic actuator with a lower current wear state is preferred or selected more frequently. Further or future wear of the other hydraulic actuator can thereby be reduced. In particular, it is achieved that the first hydraulic actuator and the second hydraulic actuator wear at approximately the same rate during the service life of the motor vehicle, so that the current wear state of the first hydraulic actuator always corresponds at least substantially to the current wear state of the second hydraulic actuator. When selecting one of the hydraulic actuators, in addition to the wear state of the hydraulic actuator, at least one further information is preferably also taken into account.

[0006] According to a preferred embodiment, it is provided that the wear state of at least one of the hydraulic actuators is determined based on the determined load spectrum of the relevant hydraulic actuator. If the wear state of the first hydraulic actuator is determined, the determined load spectrum of the first hydraulic actuator is taken into account. If the wear state of the second hydraulic actuator is determined, the determined load spectrum of the second hydraulic actuator is taken into account. Preferably, both the wear state of the first hydraulic actuator and the wear state of the second hydraulic actuator are determined based on the determined load spectrum of the relevant hydraulic actuator. Based on the previous load spectrum, the wear state of the relevant hydraulic actuator can be accurately determined. The load spectrum preferably describes the trend of the load acting on the relevant hydraulic actuator, in particular since the hydraulic actuator was first put into use. Preferably, the load is determined based on the hydraulic pressure of the hydraulic fluid of the brake system. Alternatively, the load is preferably determined based on the motor current of the electric motor of the relevant hydraulic actuator.

[0007] According to a preferred embodiment, it is provided that a threshold load is predefined and that only loads exceeding the threshold load are taken into account when determining the load spectrum. This is based on the recognition that the wear state of the hydraulic actuator is hardly influenced by small loads below the threshold load. As described above, the wear state of the two hydraulic actuators is preferably determined based on the determined load spectrum of the relevant hydraulic actuators. In particular, the same threshold load is predefined for the first hydraulic actuator and the second hydraulic actuator. Alternatively, a different threshold load is predefined for the first hydraulic actuator than for the second hydraulic actuator.

[0008] According to a preferred embodiment, it is provided that a plurality of load ranges are defined and that when determining the load spectrum, the occurring loads are weighted differently depending on their membership in one of the load ranges. This is based on the recognition that loads of different magnitudes have different effects on the wear state of the hydraulic actuator. Preferably, when determining the load spectrum, high loads are given a greater weight than low loads.

[0009] According to a preferred embodiment, it is provided that a maximum load spectrum is predefined and the wear state is determined as a function of the deviation of the determined load spectrum from the maximum load spectrum. By predefining the maximum load spectrum, a reference value for the determined load spectrum is advantageously defined, so that the current wear state can be precisely determined. As described above, the current wear state of the two hydraulic actuators is preferably determined as a function of the determined load spectrum of the associated hydraulic actuator. Preferably, different maximum load spectra are predefined for the hydraulic actuators.

[0010] Preferably, one of the hydraulic actuators is selected depending on the target pressure build-up dynamics of the deceleration command. Thus, when selecting one of the hydraulic actuators, in addition to the current wear state, the target pressure build-up dynamics of the deceleration command are taken into account. Typically, the maximum pressure build-up dynamics of the hydraulic actuators differ. Preferably, if the target pressure build-up dynamics exceeds a threshold pressure build-up dynamic, the hydraulic actuator with the higher maximum pressure build-up dynamic is always selected. If another hydraulic actuator is selected, the resulting pressure build-up dynamic may be too low.

[0011] According to a preferred embodiment, it is provided that the functional readiness of the hydraulic actuators is checked and one of the hydraulic actuators is selected as a function of the functional readiness of the hydraulic actuators. For example, if there is information for one of the hydraulic actuators that the functional readiness of this hydraulic actuator is restricted, then preferably the other hydraulic actuator is always selected regardless of the current wear state of the hydraulic actuator.

[0012] Preferably, one of the hydraulic actuators is selected as a function of the noise level in the passenger area of ​​the motor vehicle. Typically, at the same volume delivery rate, one of the hydraulic actuators generates less disturbing noise than the other of the hydraulic actuators. Preferably, if the noise level is below a threshold noise level, the hydraulic actuator that generates less disturbing noise is always selected, regardless of the current wear state of the hydraulic actuator. In view of the disturbing noise that is generated, this is particularly comfortable for the passengers of the motor vehicle. Preferably, the noise level in the passenger area of ​​the motor vehicle is detected, for example by means of a microphone. Alternatively, preferably a variable corresponding to the noise level in the passenger area is detected, and the noise level in the passenger area is estimated as a function of the detected variable. For example, the speed of the motor vehicle is detected as the variable.

[0013] According to a preferred embodiment, it is provided that one of the hydraulic actuators is selected according to the detected actual temperature. This is based on the recognition that it may be more difficult to use one of the hydraulic actuators than the other hydraulic actuator at low temperatures. Therefore, if the actual temperature is lower, for example, the actual temperature is lower than a threshold temperature, the other hydraulic actuator is preferably selected. For example, the ambient temperature is detected as the actual temperature.

[0014] According to a preferred embodiment, it is provided that one of the hydraulic actuators is selected as a function of a predetermined target load ratio, wherein the target load ratio describes the ratio of the load to be applied by the first hydraulic actuator to the load to be applied by the second hydraulic actuator, and the target load ratio is predetermined as a function of the determined wear state. As a result, the desired distribution of the braking load on the hydraulic actuators can be adjusted dynamically. For example, if the first hydraulic actuator has greater wear than the second hydraulic actuator, the target load ratio is preferably changed in such a way that the load to be applied by the first hydraulic actuator in the future is reduced.

[0015] The device according to the invention having the features of claim 11 is characterized in that it has at least one controller and is specifically configured to carry out the method according to the invention by means of the controller when used as intended. This also leads to the advantages already mentioned. Further preferred features and feature combinations result from the above description and the claims.

[0016] According to a preferred embodiment, the device has a first control unit for controlling the first hydraulic actuator and a second control unit for controlling the second hydraulic actuator, wherein one of the control units is designed to select one of the hydraulic actuators and to provide information about the selected hydraulic actuator to the other control unit. Thus, the arbitration logic for selecting one of the hydraulic actuators is implemented in only one control unit. This prevents the two control units from selecting different hydraulic actuators.

[0017] A motor vehicle according to the invention having the features of claim 13 is characterized by a device according to the invention. This also leads to the advantages already mentioned. Further preferred features and combinations of features result from the above description and the claims. The first hydraulic actuator is preferably designed for actuating a master brake cylinder of a brake system. The second hydraulic actuator is preferably a radial piston pump of a hydraulic block of the brake system. Preferably, the brake pedal of the brake system is mechanically and hydraulically decoupled from the master brake cylinder. Therefore, there is no active mechanical or hydraulic connection between the brake pedal and the master brake cylinder, which inevitably converts the actuation of the brake pedal into the actuation of the master brake cylinder. It is particularly advantageous to carry out the method according to the invention in a motor vehicle having such a brake system. The pedal feel felt by the user when actuating the brake pedal is not influenced by the selection of one of the hydraulic actuators. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be explained in more detail below with reference to the accompanying drawings, wherein:

[0019] Figure 1 shows a schematic diagram of a motor vehicle,

[0020] Figure 2 A method of operating a motor vehicle is shown. DETAILED DESCRIPTION

[0021] Figure 1 A motor vehicle 1 is shown in a schematic diagram. The motor vehicle 1 has a front axle 2 with two wheels 3 and 4 and a rear axle 5 with two wheels 6 and 7. The motor vehicle 1 also has a hydraulic brake system 8. The brake system 8 has a plurality of friction brake devices 9. A different one of the friction brake devices 9 is assigned to each of the wheels 3, 4, 6 and 7.

[0022] The brake system 8 further comprises a master brake cylinder 10, which in the present case is designed as a tandem master brake cylinder 10. The master brake cylinder 10 is fluidically connected to a hydraulic block 12 of the brake system 8 via two first hydraulic lines 11. The hydraulic block 12 is fluidically connected to a slave cylinder of the friction brake device 9 via a plurality of second hydraulic lines 13. If the master brake cylinder 10 is actuated, hydraulic fluid is pushed into the slave cylinder of the friction brake device 9 via the hydraulic lines 11 and 13, so that the friction brake device 9 is actuated and generates a friction braking torque.

[0023] The brake system 8 has a controllable first hydraulic actuator 14. The first hydraulic actuator 14 is assigned to the master brake cylinder 10 and is configured to control the friction brake device 9 by controlling the master brake cylinder 10. The first hydraulic actuator 14 and the master brake cylinder 10 together form a reciprocating piston pump 15. The brake system 8 also has a controllable second hydraulic actuator 16. The second hydraulic actuator 16 is also configured to control the friction brake device 9 by increasing the hydraulic pressure of the hydraulic fluid. In the present case, the second hydraulic actuator 16 is a radial piston pump 16 integrated into the hydraulic block 12.

[0024] The brake system 8 also has a brake pedal 17 which can be operated by a user of the motor vehicle 1. By operating the brake pedal 17, the user can provide a deceleration command for the motor vehicle 1. Figure 1 In the illustrated embodiment, the brake pedal 17 is mechanically and hydraulically decoupled from the master brake cylinder 10. Therefore, there is no mechanical or hydraulic connection between the brake pedal 17 and the master brake cylinder 10, which would inevitably convert an actuation of the brake pedal 17 into an actuation of the master brake cylinder 10. The brake system 8 is therefore designed as a brake-by-wire brake system 8.

[0025] The motor vehicle 1 further has a device 18 for operating the brake system 8. The device 18 has a first controller 19. The first controller 19 is configured to control the first hydraulic actuator 14. The device 18 further has a second controller 20. The second controller 20 is configured to control the second hydraulic actuator 16. The controllers 19 and 20 are in communication connection with each other.

[0026] Refer to the following Figure 2 An advantageous method for operating a motor vehicle 1 is explained in more detail. Figure 2 The method is illustrated using a flow chart.

[0027] In a first step S1, the first controller 19 determines the previous load spectrum of the first hydraulic actuator 14. The first controller 19 preferably determines the load spectrum based on sensor signals of a pressure sensor, not shown, wherein the pressure sensor is configured to monitor the hydraulic pressure of the hydraulic fluid of the brake system 8. The first controller 19 continuously determines the load spectrum so that the current load spectrum of the first hydraulic actuator 14 is always available. Various methods are conceivable with regard to determining the load spectrum of the first hydraulic actuator 14. For example, when determining the load spectrum of the first hydraulic actuator 14, the first controller 19 only takes into account those loads that exceed a predetermined threshold load. The first controller 19 preferably defines a plurality of load ranges and assigns the occurring loads to one of the load ranges respectively. When determining the load spectrum, different loads can be weighted differently according to their membership in one of the load ranges.

[0028] In the second step S2, the first controller 19 determines the current wear state V1 of the first hydraulic actuator 14 based on the load spectrum of the first hydraulic actuator 14. To this end, the first controller 19 preferably first determines the deviation of the determined load spectrum from the predetermined maximum load spectrum. Then, the first controller 19 determines the current wear state V1 of the first hydraulic actuator 14 based on the deviation.

[0029] In a third step S3, the second controller 20 determines the previous load spectrum of the second hydraulic actuator 16. The controller 20 preferably determines the load spectrum based on the sensor signal of the pressure sensor. The second controller 20 also continuously determines the load spectrum of the second hydraulic actuator 16, so that the current load spectrum of the second hydraulic actuator 16 is always available. When determining the load spectrum of the second hydraulic actuator 16, the second controller 20 preferably also only takes into account those loads that exceed a pre-given threshold load. Here, a different threshold load can be pre-given for the second hydraulic actuator 16 than for the first hydraulic actuator 14. However, the same threshold load can also be pre-given. The second controller 20 preferably defines a plurality of load ranges and assigns the occurring loads to one of the load ranges, respectively.

[0030] In the fourth step S4, the second controller 19 determines the current wear state V2 of the second hydraulic actuator 16 based on the load spectrum of the second hydraulic actuator 16. To this end, the second controller 20 preferably first determines the deviation of the determined load spectrum from the predetermined maximum load spectrum. Then, the second controller 20 determines the current wear state V2 of the second hydraulic actuator 16 based on the deviation. In addition, in step S4, the second controller 20 provides the first controller 19 with information about the determined wear state V2 of the second hydraulic actuator 16. According to another embodiment, the second controller 20 provides the first controller 19 with information about the determined load spectrum of the second hydraulic actuator 16 or information about the determined deviation. Then, the first controller 19 thereby determines the current wear state V2 of the second hydraulic actuator 16. According to another embodiment, the first controller 19 determines the load spectrum of the second hydraulic actuator 16 and thereby determines the current wear state V2 of the second hydraulic actuator 16.

[0031] In a fifth step S5, it is monitored whether there is a deceleration command for the motor vehicle 1. For example, there is a deceleration command when the user of the motor vehicle 1 operates the brake pedal 17. If it is determined that there is a deceleration command, reference is made to a sixth step S6.

[0032] In a sixth step S6, the first control unit 19 selects one of the hydraulic actuators 14 and 16. Here, the first control unit 19 selects the hydraulic actuator 14 or 16 that should be controlled in order to decelerate the motor vehicle 1 according to the existing deceleration command. When selecting one of the hydraulic actuators 14 and 16, the first control unit 19 takes into account the previously determined current wear states V1 and V2 of the hydraulic actuators 14 and 16. If one of the hydraulic actuators 14 or 16 has a lower wear state than the other of the hydraulic actuators 14 and 16, the hydraulic actuator 14 or 16 with the lower wear state is preferably or more preferably selected in step S6. When selecting one of the hydraulic actuators 14 and 16, the first control unit 19 preferably takes into account at least one further information in addition to the current wear states V1 and V2.

[0033] Preferably, the first controller 19 selects one of the hydraulic actuators 14 and 16 according to the target pressure buildup dynamics of the deceleration command. If the target pressure buildup dynamics exceeds the threshold pressure buildup dynamics, the first controller 19 preferably always selects the second hydraulic actuator 16. The second hydraulic actuator 16, which is configured as a radial piston pump 16, can generally generate a greater pressure buildup dynamics than the first hydraulic actuator 14. Then, the selection is therefore made independently of the current wear states V1 and V2 of the hydraulic actuators 14 and 16.

[0034] Alternatively or additionally, the first controller 19 preferably makes a selection depending on the noise level in the passenger area of ​​the motor vehicle 1. In particular, the noise level is detected by a microphone assigned to the passenger area and provided to the first controller 19. If the noise level in the passenger area of ​​the motor vehicle 1 is below a threshold noise level, the first controller 19 preferably always selects the first hydraulic actuator 14. At the same volume delivery rate, the first hydraulic actuator 14 generally generates less disturbing noise than the second hydraulic actuator 16. If the noise level in the passenger area is low, the selection of the first hydraulic actuator 14 is advantageous in this respect.

[0035] Alternatively or additionally, the first controller 19 preferably makes the selection according to the detected actual temperature. For example, when the actual temperature is lower than a predetermined threshold temperature, the first controller 19 always selects the same hydraulic actuator.

[0036] Preferably, the first controller 19 checks the functional readiness of the hydraulic actuators 14 and 16 in step S6 and always selects the other hydraulic actuator 14 or 16 if the first controller 19 determines that one of the hydraulic actuators 14 and 16 is not functionally ready or is functionally ready only to a limited extent.

[0037] In a seventh step S7 , the first controller 19 provides the second controller 20 with information on which one of the hydraulic actuators 14 and 16 is selected.

[0038] In the eighth step S8, the selected hydraulic actuator 14 or 16 is controlled so that the motor vehicle 1 decelerates according to the deceleration instruction. If the first hydraulic actuator 14 is selected, the first controller 19 controls the first hydraulic actuator 14 in step S8. However, if the second hydraulic actuator 16 is selected, the second controller 20 controls the second hydraulic actuator 16 in step S8.

[0039] By considering the current wear states V1 and V2 of the hydraulic actuators 14 and 16 when selecting one of the hydraulic actuators 14 and 16, the maximum service life of the hydraulic actuators 14 and 16 can be increased. In particular, it is possible to avoid one of the hydraulic actuators 14 and 16 from wearing faster than the other of the hydraulic actuators 14 and 16.

[0040] In reference Figure 2 In the method described, method steps S6 and S7 are performed by the first controller 19. According to another embodiment, these method steps are performed by the second controller 20. Therefore, the second controller 20 then selects one of the hydraulic actuators 14 and 16 and provides information to the first controller 19 about which of the hydraulic actuators 14 and 16 is selected.

Claims

1. A method for operating a motor vehicle, the motor vehicle having a hydraulic brake system (8) having at least one first controllable hydraulic actuator (14) and one second controllable hydraulic actuator (16), wherein: The motor vehicle (1) is decelerated by operating a selected one of the hydraulic actuators (14, 16) according to a deceleration instruction, characterized in that a current wear state (V1) of the first hydraulic actuator (14), a current wear state (V2) of the second hydraulic actuator (16) is determined, and one of the hydraulic actuators (14, 16) is selected according to the determined wear state (V1, V2).

2. The method according to claim 1, characterized in that The wear state (V1, V2) of at least one of the hydraulic actuators (14, 16) is determined based on the determined load spectrum of the associated hydraulic actuator (14, 16).

3. The method according to claim 2, characterized in that A threshold load is predefined and only loads exceeding the threshold load are taken into account when determining the load spectrum.

4. The method according to any one of claims 2 and 3, characterized in that A plurality of load ranges are defined and, when determining the load spectrum, the occurring loads are respectively weighted differently depending on their membership in one of the load ranges.

5. The method according to any one of claims 2 to 4, characterized in that A maximum load spectrum is predefined, and the wear state (V1, V2) is determined as a function of a deviation of the determined load spectrum from the maximum load spectrum.

6. The method according to any one of the preceding claims, characterized in that One of the hydraulic actuators (14, 16) is selected according to the target pressure establishment dynamics of the deceleration command.

7. The method according to any one of the preceding claims, characterized in that The functional readiness of the hydraulic actuators (14, 16) is checked and one of the hydraulic actuators (14, 16) is selected depending on the functional readiness of the hydraulic actuators (14, 16).

8. The method according to any one of the preceding claims, characterized in that One of the hydraulic actuators (14, 16) is selected depending on the noise level in a passenger area of ​​the motor vehicle (1).

9. The method according to any one of the preceding claims, characterized in that One of the hydraulic actuators (14, 16) is selected based on the detected actual temperature.

10. The method according to any one of the preceding claims, characterized in that One of the hydraulic actuators (14, 16) is selected based on a predetermined target load ratio, which describes the ratio of the load to be applied by the first hydraulic actuator (14) to the load to be applied by the second hydraulic actuator (16), and the target load ratio is predetermined based on the determined wear state (V1, V2).

11. Device for operating a motor vehicle, the motor vehicle having a hydraulic brake system (8) having at least one first controllable hydraulic actuator (14) and one second controllable hydraulic actuator (16), characterized in that: The device (18) has at least one controller (19, 20) and is specifically designed to carry out a method according to any of the preceding claims via the controller (19, 20) when used as intended.

12. The device according to claim 11, characterized in that The device (18) has a first controller (19) for controlling the first hydraulic actuator (14) and a second controller (20) for controlling the second hydraulic actuator (16), wherein one of the controllers (19, 20) is configured to select one of the hydraulic actuators (14, 16) and to provide information about the selected hydraulic actuator (14, 16) to the other controller (19, 20).

13. A motor vehicle having a hydraulic brake system (8) having at least one first controllable hydraulic actuator (14) and one second controllable hydraulic actuator (16), characterized in that: The motor vehicle has a device (18) according to any one of claims 11 and 12.

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