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 braking installation (8) comprising at least one controllable first hydraulic actuator (14) and a controllable second hydraulic actuator (16). 【Means for solving the problem】 The motor vehicle (1) is decelerated by controlling one of the selected hydraulic actuators (14, 16) depending on the deceleration setting. The current wear state (V1) of the first hydraulic actuator (14) is determined, the current wear state (V2) of the second hydraulic actuator (16) is determined, and it is intended that the selection of one of the hydraulic actuators (14, 16) is made depending on the determined wear states (V1, V2).

Description

Technical Field

[0001] The present invention relates to a method for operating a motor vehicle having a hydraulic brake installation comprising at least one controllable first hydraulic actuator and a controllable second hydraulic actuator, wherein the motor vehicle is decelerated by controlling one of the selected hydraulic actuators depending on a requested deceleration setting.

[0002] Furthermore, the present invention relates to a device for operating a motor vehicle having a hydraulic brake installation comprising at least one controllable first hydraulic actuator and a controllable second hydraulic actuator.

[0003] Furthermore, the present invention relates to a motor vehicle having a hydraulic brake installation comprising at least one controllable first hydraulic actuator and a controllable second hydraulic actuator.

Background Art

[0004] Methods and motor vehicles of the kind mentioned at the beginning are known from the prior art. Motor vehicles typically have a hydraulic brake installation. At this time, a brake installation having at least one controllable first hydraulic actuator and a controllable second hydraulic actuator is known. In such a kind of brake installation, the frictional brake torque for decelerating the motor vehicle can be generated either by controlling the first hydraulic actuator or by controlling the second hydraulic actuator. Typically, one of these hydraulic actuators is selected, i.e., the first hydraulic actuator or the second hydraulic actuator is selected, and the selection of one of the hydraulic actuators can be made situationally. When there is a deceleration setting for the motor vehicle, the motor vehicle is decelerated by controlling the selected hydraulic actuator.

Summary of the Invention

[0005] The method of the present invention having the constituent elements of claim 1 has the advantage that the service life of the hydraulic actuator can be maximized. Therefore, according to the present invention, the current wear state of the first hydraulic actuator is determined, the current wear state of the second hydraulic actuator is determined, and it is intended that the selection of one of the hydraulic actuators is made depending on the determined wear state. That is, the current wear state of the hydraulic actuator is taken into account when making the selection of one of the hydraulic actuators. By taking the current wear state into account, it is possible to affect the future wear of the hydraulic actuator. It is preferable that the hydraulic actuator with the lower current wear state is preferentially or more frequently selected. Thereby, the future wear of the other hydraulic actuator can be reduced. In particular, it is realized that the first hydraulic actuator and the second hydraulic actuator wear at substantially the same rate over the service life of the vehicle, whereby the current wear state of the first hydraulic actuator is always at least substantially equivalent to the current wear state of the second hydraulic actuator. When making the selection of one of the hydraulic actuators, it is preferable that at least one other piece of information is taken into account in addition to the wear state of the hydraulic actuator.

[0006] In a preferred embodiment, it is intended that the wear state of at least one of the hydraulic actuators is determined depending on the determined load spectrum of the corresponding hydraulic actuator. When the wear state of the first hydraulic actuator is determined, the determined load spectrum of the first hydraulic actuator is taken into account at that time. When the wear state of the second hydraulic actuator is determined, the determined load spectrum of the second hydraulic actuator is taken into account at that time. It is preferred that both the wear state of the first hydraulic actuator and the wear state of the second hydraulic actuator are determined depending on the determined load spectrum of the corresponding hydraulic actuator. With reference to the load spectrum up to that point, the wear state of the corresponding hydraulic actuator can be accurately determined. The load spectrum preferably represents the transition of the load acting on the corresponding hydraulic actuator, particularly after the start of the first use of the hydraulic actuator. The load is preferably determined depending on the hydraulic pressure of the hydraulic fluid of the braking equipment. As an alternative, the load is preferably determined depending on the motor current of the electric motor of the corresponding hydraulic actuator.

[0007] In a preferred embodiment, a threshold load is set, and it is intended that only loads exceeding the threshold load are taken into account in the determination of the load spectrum. The underlying finding is that the wear state of the hydraulic actuator hardly decreases due to low loads below the threshold load. As described above, it is preferred that the wear state of both hydraulic actuators is determined depending on the determined load spectrum of the corresponding hydraulic actuator. In particular, in that case, the same threshold load is set for the first hydraulic actuator and the second hydraulic actuator. As an alternative, a threshold load different from that of the second hydraulic actuator is set for the first hydraulic actuator.

[0008] In a preferred embodiment, a plurality of load regions are defined, and it is intended that the generated load is weighted differently in the determination of the load spectrum depending on its attribution to one of the load regions. The underlying finding is that the wear state of the hydraulic actuator is affected differently by loads of different magnitudes. High loads are preferably weighted more strongly than low loads in the determination of the load spectrum.

[0009] In a preferred embodiment, a maximum load spectrum is set, and it is intended that the wear state is determined depending on the difference between the determined load spectrum and the maximum load spectrum. By setting the maximum load spectrum, a reference value for the determined load spectrum is defined in a preferred manner, thereby enabling an accurate determination of the current wear state. As described above, it is preferred that the current wear state of both hydraulic actuators is determined depending on the determined load spectrum of the corresponding hydraulic actuator. In that case, it is preferred that different maximum load spectra are set for each hydraulic actuator.

[0010] The selection of one of the hydraulic actuators is preferably made depending on the target of the deceleration setting and the pressure generation dynamics. That is, the target of the deceleration setting and the pressure generation dynamics are considered in addition to the current wear state in the selection of one of the hydraulic actuators. Typically, each hydraulic actuator differs with respect to its maximum pressure generation dynamics. Under the target pressure generation dynamics that exceed the threshold pressure generation dynamics, it is preferably always the hydraulic actuator with the greater maximum pressure generation dynamics that is selected. If another hydraulic actuator is selected, the resulting pressure generation dynamics may undesirably become too small.

[0011] In a preferred embodiment, the functional readiness state of the hydraulic actuator is checked, and it is intended that the selection of one of the hydraulic actuators be made depending on the functional readiness state of the hydraulic actuator. For example, for one of the hydraulic actuators, when there is information regarding the fact that the functional readiness state of the hydraulic actuator is restricted, it is preferable that, regardless of the current wear state of the hydraulic actuator, another hydraulic actuator is always selected.

[0012] The selection of one of the hydraulic actuators is preferably made depending on the noise level in the passenger area of the motor vehicle. Typically, one of the hydraulic actuators generates less noise than the other hydraulic actuators under equal volumetric delivery rates. Under a corresponding level below the threshold noise level, it is preferable that, regardless of the current wear state of the hydraulic actuator, the hydraulic actuator that generates less noise is always selected. This is particularly comfortable for the passengers of the motor vehicle from the perspective of noise generation. The noise level in the passenger area of the motor vehicle is preferably detected, for example, by a microphone. As an alternative, it is preferable that an amount corresponding to the noise level in the passenger area is detected, and the noise level in the passenger area is estimated depending on the detected amount. For example, the driving speed of the motor vehicle is detected as this amount.

[0013] In a preferred embodiment, it is intended that the selection of one of the hydraulic actuators be made depending on the detected actual temperature. The underlying finding is that the use of a hydraulic actuator under low temperatures can be more critical than the use of other hydraulic actuators. Accordingly, under a low actual temperature, for example, under an actual temperature below a threshold temperature, other hydraulic actuators are preferentially selected. For example, the ambient temperature is detected as the actual temperature.

[0014] In a preferred embodiment, one of the selections of the hydraulic actuators is intended to be made depending on a set target - load ratio that represents the load to be applied by the first hydraulic actuator relative to the load to be applied by the second hydraulic actuator, and the target - load ratio is set depending on the determined wear state. Thereby, the desired split of the braking load to each hydraulic actuator can be dynamically adapted. For example, if the first hydraulic actuator has more wear than the second hydraulic actuator, the target - load ratio is preferably changed such that the load to be applied by the first hydraulic actuator in the future becomes lower.

[0015] The device according to the invention is characterized, according to the features of claim 11, in that the device has at least one control device and is specifically configured to carry out the method according to the invention by the control device during normal use. Thereby, the advantages already described are also brought about. Other preferred features and combinations of features will become apparent from the above description as well as from the claims.

[0016] In a preferred embodiment, the device is intended to have a first control device for controlling the first hydraulic actuator and a second control device for controlling the second hydraulic actuator, and one of the control devices is configured to select one of the hydraulic actuators and provide information regarding the selected hydraulic actuator to the other control device. That is, the arbiter logic for selecting one of the hydraulic actuators is implemented in only one of the control devices. Thereby, it is avoided that different hydraulic actuators are selected by both control devices respectively.

[0017] The motor vehicle according to the invention is characterized by having the device according to the invention by the constituent features of claim 13. By this also, the advantages already mentioned are brought about. Other preferred constituent features and combinations of constituent features will become apparent from the above description as well as from the claims. The first hydraulic actuator is preferably configured to operate the master brake cylinder of the braking equipment. The second hydraulic actuator is preferably the radial piston pump of the hydraulic block of the braking equipment. The brake pedal of the braking equipment is preferably mechanically and hydraulically disconnected from the master brake cylinder. That is, there is no mechanical or hydraulic link acting between the brake pedal and the master brake cylinder that forcibly converts the operation of the brake pedal into the operation of the master brake cylinder. In a motor vehicle having a braking equipment of this kind, the implementation of the method according to the invention is particularly preferred. In that case, the pedal feeling received by the user when operating the brake pedal is not impaired by the selection of one of the hydraulic actuators.

[0018] Next, the present invention will be described in detail with reference to the drawings.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0020] FIG. 1 schematically shows a motor vehicle 1. The motor vehicle 1 has a front wheel axle 2 having two wheels 3 and 4, and a rear wheel axle 5 having two wheels 6 and 7. Furthermore, the motor vehicle 1 has a hydraulic braking equipment 8. The braking equipment 8 has a plurality of friction brake devices 9. A separate friction brake device 9 is attached to each of the wheels 3, 4, 6 and 7.

[0021] Furthermore, the braking equipment 8 has a master brake cylinder 10 configured as a tandem master brake cylinder 10 in this example. The master brake cylinder 10 is hydraulically connected to the hydraulic block 12 of the braking equipment 8 by two first hydraulic pipes 11. The hydraulic block 12 is hydraulically connected to the slave cylinder of the friction brake device 9 by a plurality of second hydraulic pipes 13. When the master brake cylinder 10 is operated, the hydraulic fluid is transferred through the hydraulic pipes 11 and 13 to the slave cylinder of the friction brake device 9, thereby operating the friction brake device 9 to generate a friction brake torque.

[0022] The braking equipment 8 has a controllable first hydraulic actuator 14. The first hydraulic actuator 14 is attached to the master brake cylinder 10 and is configured to operate the friction brake device 9 by operating the master brake cylinder 10. The first hydraulic actuator 14 and the master brake cylinder 10 jointly constitute a reciprocating piston pump 15. Furthermore, the braking equipment 8 has a controllable second hydraulic actuator 16. The second hydraulic actuator 16 is also configured to operate the friction brake device 9 by increasing the hydraulic pressure of the hydraulic fluid. In this example, the second hydraulic actuator 16 is a radial piston pump 16 integrated into the hydraulic block 12.

[0023] Furthermore, the braking equipment 8 has a brake pedal 17 that can be operated by the user of the vehicle 1. By operating the brake pedal 17, the user can provide a deceleration setting for the vehicle 1. In the embodiment shown in FIG. 1, the brake pedal 17 is mechanically and hydraulically disconnected from the master brake cylinder 10. That is, there is no mechanical or hydraulic link between the brake pedal 17 and the master brake cylinder 10 that forcibly converts the operation of the brake pedal 17 into the operation of the master brake cylinder 10. Accordingly, this braking equipment 8 is configured as a brake-by-wire braking equipment 8.

[0024] Furthermore, the vehicle 1 has a device 18 for operating the braking equipment 8. The device 18 has a first control device 19. The first control device 19 is configured to control the first hydraulic actuator 14. Furthermore, the device 18 has a second control device 20. The second control device 20 is configured to control the second hydraulic actuator 16. The control devices 19 and 20 are connected to each other in a communication engineering manner.

[0025] Next, with reference to FIG. 2, a preferred method for operating the vehicle 1 will be described in detail. FIG. 2 illustrates this method using a flowchart.

[0026] In a first step S1, the first control device 19 determines the load spectrum of the first hydraulic actuator 14 up to that point. The first control device 19 preferably determines the load spectrum depending on the sensor signal of a pressure sensor (not shown), and the pressure sensor is configured to monitor the hydraulic pressure of the hydraulic fluid of the braking equipment 8. The first control device 19 continuously determines the load spectrum, so that the current load spectrum of the first hydraulic actuator 14 can always be utilized. From the viewpoint of determining the load spectrum of the first hydraulic actuator 14, various methods are conceivable. For example, when determining the load spectrum of the first hydraulic actuator 14, the first control device 19 only considers loads exceeding a set threshold load. The first control device 19 preferably defines a plurality of load regions and assigns the occurring loads to one of the load regions respectively. Then, various loads can be weighted differently depending on their attribution to one of the load regions when determining the load spectrum.

[0027] In the second step S2, the first control device 19 determines the current wear state V1 of the first hydraulic actuator 14 depending on the load spectrum of the first hydraulic actuator 14. For this purpose, it is preferable that the first control device 19 first determines the difference between the determined load spectrum and the set maximum load spectrum. Then, the first control device 19 determines the current wear state V1 of the first hydraulic actuator 14 depending on this difference.

[0028] In the third step S3, the second control device 20 determines the load spectrum of the second hydraulic actuator 16 up to that point. It is preferable that the control device 20 determines the load spectrum depending on the sensor signal of the pressure sensor. The second control device 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 can always be utilized. In determining the load spectrum of the second hydraulic actuator 16, it is also preferable that the second control device 20 only considers loads exceeding the set threshold load. At this time, a different threshold load can be set for the second hydraulic actuator 16 than for the first hydraulic actuator 14. However, an equal threshold load can also be set. It is preferable that the second control device 20 defines a plurality of load regions and assigns the generated load to one of the load regions respectively.

[0029] In the fourth step S4, the second control device 19 determines the current wear state V2 of the second hydraulic actuator 16 depending on the load spectrum of the second hydraulic actuator 16. For this purpose, it is preferable that the second control device 20 first determines the difference between the determined load spectrum and the set maximum load spectrum. Then, the second control device 20 determines the current wear state V2 of the second hydraulic actuator 16 depending on this difference. Further, in step S4, the second control device 20 provides the first control device 19 with information regarding the determined wear state V2 of the second hydraulic actuator 16. In another embodiment, the second control device 20 provides the first control device 19 with information regarding the determined load spectrum of the second hydraulic actuator 16, or provides information regarding the determined difference. Then, the first control device 19 determines the current wear state V2 of the second hydraulic actuator 16 by itself from this. In another embodiment, the first control device 19 determines the load spectrum of the second hydraulic actuator 16 and determines the current wear state V2 of the second hydraulic actuator 16 from this.

[0030] In the fifth step S5, it is monitored whether there is a deceleration setting for the vehicle 1. For example, the deceleration setting exists when the brake pedal 17 is operated by the user of the vehicle 1. When it is confirmed that the deceleration setting exists, the process proceeds to the sixth step S6.

[0031] And in the sixth step S6, the first control device 19 selects one of the hydraulic actuators 14 and 16. At this time, the first control device 19 selects the hydraulic actuator 14 or 16 to be controlled to decelerate the vehicle 1 according to the existing deceleration setting. When selecting one of the hydraulic actuators 14 and 16, the first control device 19 takes into account the current wear states V1 and V2 of the hydraulic actuators 14 and 16 determined previously. 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 preferentially or more frequently selected in step S6. When selecting one of the hydraulic actuators 14 and 16, the first control device 19 preferably also takes into account at least one other piece of information in addition to the current wear states V1 and V2.

[0032] The first control device 19 preferably makes a selection of one of the hydraulic actuators 14 and 16 depending on the target - pressure generation dynamics of the deceleration setting. When the target - pressure generation dynamics exceed the threshold - pressure generation dynamics, the first control device 19 preferably always selects the second hydraulic actuator 16. The second hydraulic actuator 16 configured as a radial piston pump 16 can typically generate greater pressure generation dynamics than the first hydraulic actuator 14. That is, in that case, the selection is made regardless of the current wear states V1 and V2 of the hydraulic actuators 14 and 16.

[0033] As an alternative or in addition, the first control device 19 preferably makes a selection depending on the noise level in the passenger compartment of the motor vehicle 1. In particular, the noise level is detected by a microphone assigned to the passenger compartment and provided to the first control device 19. If the noise level in the passenger compartment of the motor vehicle 1 is below a threshold noise level, the first control device 19 preferably always selects the first hydraulic actuator 14. The first hydraulic actuator 14 typically generates less noise than the second hydraulic actuator 16 under the same volumetric delivery rate. In this sense, under a low noise level in the passenger compartment, the selection of the first hydraulic actuator 14 is preferred.

[0034] As an alternative or in addition, the first control device 19 preferably makes a selection depending on the detected actual temperature. For example, the first control device 19 always selects the same hydraulic actuator under an actual temperature below a set threshold temperature.

[0035] In step S6, the first control device 19 preferably checks the functional readiness of the hydraulic actuators 14 and 16. If the first control device 19 ascertains that one of the hydraulic actuators 14 and 16 is not in a functionally ready state, or is only marginally in a functionally ready state, the first control device 19 always selects the other hydraulic actuator 14 or 16.

[0036] In the seventh step S7, the first control device 19 provides the second control device 20 with information regarding which of the hydraulic actuators 14 and 16 has been selected.

[0037] In the eighth step S8, the selected hydraulic actuator 14 or 16 is controlled such that the motor vehicle 1 is decelerated in accordance with the deceleration setting. If the first hydraulic actuator 14 is selected, the first control device 19 controls the first hydraulic actuator 14 in step S8. However, if the second hydraulic actuator 16 is selected, the second control device 20 controls the second hydraulic actuator 16 in step S8.

[0038] When selecting one of the hydraulic actuators 14 or 16, by considering the current wear states V1 and V2 of the hydraulic actuators 14 and 16, the maximum service life of the hydraulic actuators 14 and 16 can be extended. In particular, it is possible to avoid one of the hydraulic actuators 14 and 16 wearing out earlier than the other of the hydraulic actuators 14 or 16.

[0039] In the method described with reference to FIG. 2, the method steps S6 and S7 are executed by the first control device 19. In another embodiment, these method steps are executed by the second control device 20. In that case, accordingly, the second control device 20 selects one of the hydraulic actuators 14 and 16 and provides information regarding which of the hydraulic actuators 14 and 16 has been selected to the first control device 19.

Explanation of Reference Numerals

[0040] 1 Motor vehicle 8 Hydraulic braking equipment 14 First hydraulic actuator 16 Second hydraulic actuator 18 Device 19 First control device 20 Second control device 20 V1, V2 Wear state

Claims

1. A method for operating a motor vehicle having a hydraulic braking facility (8) comprising at least one controllable first hydraulic actuator (14) and a controllable second hydraulic actuator (16), wherein the motor vehicle (1) is decelerated by control of one selected from the hydraulic actuators (14, 16) depending on a deceleration setting. In the method, 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 a selection of one of the hydraulic actuators (14, 16) is made depending on the determined wear states (V1, V2).

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

3. The method according to claim 2, characterized in that a threshold load is set and only loads exceeding the threshold load are considered in determining the load spectrum.

4. The method according to any one of claims 2 or 3, characterized in that a plurality of load regions are defined and the occurring loads are weighted differently in determining the load spectrum depending on their attribution to one of the load regions.

5. The method according to any one of claims 2 to 4, characterized in that a maximum load spectrum is set and the wear states (V1, V2) are determined depending on the difference between the determined load spectrum and the maximum load spectrum.

6. The method according to any one of claims 1 to 5, characterized in that a selection of one of the hydraulic actuators (14, 16) is made depending on the target-pressure generation dynamics of the deceleration setting.

7. The method according to any one of claims 1 to 6, characterized in that a functional readiness state of the hydraulic actuators (14, 16) is checked and a selection of one of the hydraulic actuators (14, 16) is made depending on the functional readiness state of the hydraulic actuators (14, 16).

8. The method according to any one of claims 1 to 7, characterized in that the selection of one of the hydraulic actuators (14, 16) is made depending on the noise level in the passenger area of the motor vehicle (1).

9. The method according to any one of claims 1 to 8, characterized in that the selection of one of the hydraulic actuators (14, 16) is made depending on the detected actual temperature.

10. The method according to any one of claims 1 to 9, characterized in that the selection of one of the hydraulic actuators (14, 16) is made depending on a set target - load ratio that represents the load to be applied by the first hydraulic actuator (14) relative to the load to be applied by the second hydraulic actuator (16), and the target - load ratio is set depending on the determined wear state (V1, V2).

11. In a device for operating a motor vehicle having a hydraulic brake installation (8) comprising at least one controllable first hydraulic actuator (14) and a controllable second hydraulic actuator (16), the device (18) has at least one control device (19, 20) and is specially configured to carry out the method according to any one of claims 1 to 10 by means of the control device (19, 20) during regular use.

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

13. A motor vehicle having a hydraulic brake installation (8) comprising at least one controllable first hydraulic actuator (14) and a controllable second hydraulic actuator (16), characterized by having the device (18) according to any one of claims 11 and 12.

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