Method for operating a vehicle brake system, device for operating a vehicle brake system, vehicle

Abstract

The invention relates to a method for operating a vehicle (1), in which a brake system (8) has a brake pedal (17) which can be displaced within a defined movement path, at least one actuatable friction brake device (9) and at least one actuatable hydraulic actuator (14, 16) for actuating the friction brake device (9), the brake pedal (17) is mechanically and hydraulically decoupled from the hydraulic actuator (14, 16) in such a way that the friction brake device (9) is actuated by the hydraulic actuator (14, 16) independently of the displacement of the brake pedal (17) at least when the brake pedal (17) is stuck, the hydraulic actuator (14, 16) being activated as a function of a predetermined target brake torque, and wherein the brake pedal (17) is mechanically and hydraulically decoupled from the hydraulic actuator (14, 16). Wherein a pedal position of the brake pedal (17) and an actuation force acting on the brake pedal (17) are monitored, and wherein, depending on the detected pedal position and the detected actuation force, a check is made as to whether the brake pedal (17) is stuck during the movement stroke, and wherein, if it is determined that the brake pedal (17) is not stuck, a target brake torque is specified depending on the detected pedal position. When it is determined that the brake pedal (17) is stuck, the target brake torque is specified on the basis of the detected actuation force.

Description

Technical Field

[0001] The present invention relates to a method for operating a vehicle brake system, wherein the brake system has a brake pedal that can be displaced within a limited movement stroke, at least one actuable friction brake device, and at least one triggerable hydraulic actuator for actuating the friction brake device, and wherein the brake pedal is mechanically and hydraulically decoupled from the hydraulic actuator, so that the friction brake device is actuated by the hydraulic actuator independently of the displacement of the brake pedal at least when the brake pedal is stuck, wherein the hydraulic actuator is triggered according to a preset target braking torque, wherein the pedal position of the brake pedal and the actuating force acting on the brake pedal are monitored, wherein it is checked whether the brake pedal is stuck within the movement stroke based on the detected pedal position and the detected actuating force, and wherein when it is determined that the brake pedal is not stuck, the target braking torque is preset based on the detected pedal position.

[0002] The present invention also relates to a device for operating a vehicle braking system, wherein the braking system has a brake pedal that can be displaced within a limited movement stroke, at least one actuable friction brake device and at least one triggerable hydraulic actuator for actuating the brake device, and wherein the brake pedal is mechanically and hydraulically decoupled from the hydraulic actuator and the friction brake device is actuated by the hydraulic actuator independently of the displacement of the brake pedal at least when the brake pedal is stuck, and the device has a first sensor for monitoring the pedal position of the brake pedal and a second sensor for monitoring the actuating force acting on the brake pedal.

[0003] The present invention also relates to a vehicle having a braking system, which has a brake pedal that can be displaced within a limited movement stroke, at least one actuable friction brake device and at least one triggerable hydraulic actuator for actuating the friction brake device, and wherein the brake pedal is mechanically and hydraulically decoupled from the hydraulic actuator so that the friction brake device can be actuated by the hydraulic actuator independently of the displacement of the brake pedal, at least when the brake pedal is stuck. Background Art

[0004] A braking system and method of the type described at the beginning are known, for example, from the open document DE 10 2019130 309A1. The braking system has a brake pedal that can be displaced in a limited movement stroke, at least one actuable friction brake device, and at least one triggerable hydraulic actuator for actuating the friction brake device. The brake pedal is mechanically and hydraulically decoupled from the hydraulic actuator, so that the friction brake device is actuated by the hydraulic actuator independently of the displacement of the brake pedal at least when the brake pedal is stuck. Therefore, there is no mechanical or hydraulic coupling, which forcibly converts the actuation of the friction brake device by the hydraulic actuator into a displacement of the brake pedal. In this regard, the friction brake device can still be actuated by the hydraulic actuator even when the brake pedal is stuck. In the method known from the open document DE 10 2019 130309 A1, the pedal position of the brake pedal and the actuation force acting on the brake pedal are monitored. It is checked whether the brake pedal is stuck in the movement stroke based on the detected pedal position and the detected actuation force. If it is determined that the brake pedal is not stuck during the movement stroke, a target braking torque is preset according to the detected pedal position. The magnitude of the target braking torque is therefore determined according to the detected pedal position. The hydraulic actuator is then triggered according to the preset target braking torque. This results in the driver's brake request of the vehicle driver being accurately executed. However, if it is determined that the brake pedal is stuck during the movement stroke, the emergency function is activated in the method known from the publication DE 10 2019 130 309 A1. Summary of the invention

[0005] The method according to the invention with the features of claim 1 has the advantage that the driver can precisely control the braking of the vehicle even when the brake pedal is stuck. According to the invention, it is provided that when it is determined that the brake pedal is stuck, a target braking torque is preset according to the detected operating force. This is based on the recognition that when the brake pedal is stuck during the movement stroke, the detected operating force corresponds accurately enough to the actual braking request of the driver. When the brake pedal is stuck, the magnitude of the target braking torque is determined according to the detected operating force. For example, for a detected first operating force, a target braking torque different from the detected second operating force or a target braking torque of different magnitude is preset. Preferably, the target braking torque increases with increasing operating force and decreases with decreasing operating force. Although in the method known from the publication DE 10 2019 130 309 A1, an emergency braking torque is also generated as part of the emergency function. However, the magnitude of the emergency braking torque is not determined according to the specifically detected operating force, so that the driver cannot influence the magnitude of the emergency braking torque. In the previously known method, the driver's braking request is thus downgraded. This can be avoided by the approach according to the invention. Specifically, the change from pedal position control to actuation force control occurs without downgrading the driver's brake request. According to the invention, the brake pedal can be displaced within a defined movement path, namely between a first end position of the brake pedal and a second end position of the brake pedal. If the brake pedal is stuck within the movement path, the brake pedal is stuck in a pedal position between these end positions.

[0006] According to a preferred embodiment, it is provided that when it is determined that the brake pedal is stuck, the target braking torque is preset independently of the detected pedal position. Thus, the detected pedal position is only taken into account during the check, but not when presetting the target braking torque. If the brake pedal is stuck, there is not enough correlation between the pedal position and the driver's braking request.

[0007] According to a preferred embodiment, when it is determined that the brake pedal is stuck, a target braking torque is preset according to a transfer function, which uses the detected operating force as an input variable and the target braking torque as an output variable. The desired target braking torque can be accurately assigned to the detected operating force by means of the transfer function. The transfer function preferably has a characteristic curve, a family of characteristic curves or a comprehensive characteristic diagram (Kennfeld).

[0008] According to an alternative embodiment, it is preferably provided that when it is determined that the brake pedal is stuck, the pedal position assigned to the operating force is obtained based on the detected operating force, and the target braking torque is preset according to a transfer function, which uses the obtained pedal position as an input variable and the target braking torque as an output variable. Therefore, the assigned pedal position is first obtained based on the detected operating force. Then, when the target braking torque is preset, the pedal position will be included in the transfer function as an input variable. The advantage of this is that the method can be performed using an existing control architecture (Regelungsarchitektur). Preferably, the same transfer function is used to preset the target braking torque whether the brake pedal is stuck or not. The transfer function preferably has a characteristic curve, a family of characteristic curves or a characteristic diagram.

[0009] According to a preferred embodiment, the actuating force is filtered at least when the actuating force decreases. If the driver removes his foot from the actuated brake pedal, the brake pedal is prevented from returning to its neutral position. However, the actuating force decreases suddenly. By filtering the actuating force, a sudden decrease in the actuating force is prevented from being converted into a sudden decrease in the target braking torque. This would otherwise lead to a sudden decrease in the braking torque generated by the friction brake device.

[0010] Preferably, the actuating force is filtered only when the actuating force decreases. This is sufficient to effectively prevent the aforementioned sudden decrease in the target braking torque.

[0011] According to an alternative embodiment, it is preferably provided that the actuating force is filtered with a larger filter factor when the actuating force decreases than when the actuating force increases. In principle, it is also advantageous to filter the actuating force when the actuating force increases. In this way, a sudden increase in the braking torque generated by the friction brake device can be avoided. However, a smaller filter factor is sufficient compared to the reduction in the actuating force.

[0012] According to a preferred embodiment, it is provided that the safety function is triggered when it is determined that the brake pedal has been stuck for a preset time period. For example, when it is determined that the brake pedal is stuck, a preset time period begins. If it is determined that the brake pedal is still stuck after the time period has passed, the safety function is triggered. In principle, when the brake pedal is stuck, the driver's braking request can be accurately executed. However, this state should not be maintained for a long time, so it is preferred to trigger the safety function. Different types of safety functions can be provided.

[0013] According to a preferred embodiment, within the scope of the safety function, a warning signal is provided to the driver of the vehicle. The warning signal is used to warn the driver that the brake pedal is stuck, so that the driver can take appropriate measures himself. For example, a visually, acoustically and / or tactilely perceptible warning signal is provided. Alternatively or additionally, within the framework of the safety function, the driving speed of the vehicle is limited. Alternatively or additionally, within the framework of the safety function, the vehicle is automatically decelerated to a standstill.

[0014] According to a preferred embodiment, it is provided that the pedal position existing when the brake pedal is determined to be stuck is stored as a reference position, and when a pedal position exceeding the reference position is detected, it is determined that the brake pedal is no longer stuck. The pedal position exceeding the reference position clearly indicates that the brake pedal is no longer stuck. For example, an object that was previously stuck under the brake pedal is no longer arranged under the brake pedal, so that the object no longer blocks the brake pedal. If it is determined that the brake pedal is no longer stuck, the target braking torque is preferably preset again according to the detected pedal position.

[0015] By means of the features of claim 11, the device according to the invention is characterized by a controller which is specially designed to carry out the method according to the invention when used as intended. If the controller is used as intended, the method is carried out by the controller or in the controller. This also results in the advantages already mentioned. Further preferred features and combinations of features result from the preceding description and from the claims.

[0016] The vehicle according to the invention is characterized by the device according to the invention by the features of claim 12. This also results in the advantages already mentioned. Further preferred features and feature combinations result from the preceding description and from the claims. The hydraulic actuator is preferably designed as a master brake cylinder for actuating a brake system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be explained in more detail below with reference to the accompanying drawings, in which:

[0018] Figure 1 A schematic diagram of a vehicle is shown; and

[0019] Figure 2 A method for operating a vehicle is shown. DETAILED DESCRIPTION

[0020] Figure 1 A schematic diagram shows a vehicle 1. The 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 vehicle 1 also has a hydraulic brake system 8. The brake system 8 has a plurality of friction brake devices 9. Each of the wheels 3, 4, 6 and 7 is respectively equipped with a different friction brake device 9.

[0021] The brake system 8 also has a master brake cylinder 10, which is designed as a double master brake cylinder (Tandem-Hauptbremszylinder) 10 in the present case. 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 the 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 moved into the slave cylinder of the friction brake device 9 via the hydraulic lines 11 and 13, thereby actuating the friction brake device 9 and generating a friction braking torque.

[0022] The brake system 8 has a first hydraulic actuator 14 that can be activated. The first hydraulic actuator 14 is assigned to the master brake cylinder 10 and is designed to actuate the friction brake device 9 by actuating 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 second hydraulic actuator 16 that can be activated. The second hydraulic actuator 16 is also designed to actuate the friction brake device 9 by increasing the hydraulic pressure of the hydraulic fluid. At present, the second hydraulic actuator 16 is a radial piston pump 16 integrated into the hydraulic block 12.

[0023] The brake system 8 also has a brake pedal 17 which is particularly displaceable in an infinitely variable manner. The brake pedal 17 can be actuated by the driver of the vehicle 1. Currently, the brake pedal 17 is supported in a pivotable manner. The brake pedal 17 can be displaced between a first end position and a second end position, i.e., within a defined movement stroke. The first end position is the neutral position of the brake pedal 17. In the absence of an actuating force provided by the driver and acting on the brake pedal 17, the brake pedal 17 is in a neutral position. If the driver actuates the brake pedal 17, the brake pedal 17 is displaced from the first end position toward the second end position. The brake pedal 17 is mechanically and hydraulically decoupled from the first hydraulic actuator 14 and the second hydraulic actuator 16, so that the friction brake device 9 is actuated by one of the hydraulic actuators 14 and 16 independently of the displacement of the brake pedal 17. Therefore, the friction brake device 9 can be actuated by the hydraulic actuators 14 and 16 without necessarily causing a change in the pedal position of the brake pedal 17. Instead, there is only a signal connection between the brake pedal 17 and the hydraulic actuators 14 and 16. The brake system 8 is therefore designed as a brake-by-wire system 8.

[0024] The vehicle 1 also has a device 18 for operating the brake system 8. The device 18 has a first sensor 19. The first sensor 19 is designed to monitor the pedal position of the brake pedal 17. The device 18 also has a second sensor 20. The second sensor 20 is designed to monitor the actuation force acting on the brake pedal 17. Currently, the second sensor 20 is integrated into a footrest 21 of the brake pedal 17. The device 18 also has a controller 22. The controller 22 is designed to trigger the first hydraulic actuator 14 and the second hydraulic actuator 16. The first sensor 19 and the second sensor 20 are connected to the controller 22 in terms of communication technology. The sensors 19 and 20 each provide their sensor signals to the controller 22.

[0025] The following will refer to Figure 2 An advantageous method for operating brake system 8 is explained in more detail. Figure 2 The method is illustrated using a flow chart.

[0026] In a first step S1 , the first sensor 19 monitors the pedal position of the brake pedal 17 and provides its sensor signal to the controller 22 .

[0027] In a second step S2 , the second sensor 20 monitors the actuation force acting on the brake pedal 17 and provides its sensor signal to the control unit 22 .

[0028] In the third step S3, the controller 22 checks whether the brake pedal 17 is stuck in its movement stroke according to the detected pedal position and the detected operating force. For example, if an object such as a bottle is stuck under the brake pedal 17, the brake pedal 17 is stuck. If the brake pedal 17 is stuck in its movement stroke, the brake pedal 17 is locked in a pedal position between the first end position and the second end position. Therefore, the further displacement of the brake pedal 17 from this pedal position toward the second end position is prevented. For example, the controller 22 continuously obtains actual value pairs in the third step S3, which are respectively formed by the detected pedal position and the simultaneously detected operating force. The controller 22 then compares the obtained actual value pairs with the expected target value pairs. If the comparison shows that the operating force of the actual value pair is unexpectedly high, the controller 22 determines that the brake pedal 17 is stuck.

[0029] If the comparison in the third step S3 shows that the brake pedal 17 is not stuck in the movement stroke, refer to the fourth step S4. Then, in the fourth step S4, the controller 22 presets the target braking torque according to the detected pedal position. Therefore, the magnitude of the target braking torque is determined according to the detected pedal position. Preferably, the target braking torque increases with the increase of the pedal position and decreases with the decrease of the pedal position. When the pedal position increases, the brake pedal 17 shifts toward the second end position. When the pedal position decreases, the brake pedal 17 shifts toward the first end position. To this end, the controller 22 uses a transfer function, which takes the detected pedal position as an input variable and the target braking torque as an output variable.

[0030] In the fifth step S5, the controller 22 triggers the first hydraulic actuator 14 according to the preset target braking torque. Then the vehicle 1 decelerates according to the preset target braking torque. Alternatively, the controller 22 triggers the second hydraulic actuator 16 according to the preset target braking torque in the fifth step S5. In this case, the vehicle 1 also decelerates according to the preset target braking torque.

[0031] However, if the comparison in the third step S3 shows that the brake pedal 17 is stuck in the movement stroke, refer to the sixth step S6. Then, in the sixth step S6, the controller 22 presets the target braking torque according to the detected operating force. Therefore, the size of the target braking torque is determined according to the detected operating force. Preferably, the target braking torque increases with the increase of the operating force and decreases with the decrease of the operating force. To this end, the controller 22 uses a transfer function, which takes the detected operating force as an input variable and the target braking torque as an output variable. Therefore, a transfer function different from that in step S4 is used. Preferably, the operating force or the output signal of the second sensor 20 is filtered. This makes it possible to avoid sudden changes in the target braking torque. In particular, the operating force is filtered only when the operating force decreases. Alternatively, the operating force is filtered according to a larger filter coefficient when the operating force decreases than when the operating force increases.

[0032] Even when referring to the sixth step S6, the fifth step S5 is also referred to later. Then, in the fifth step S5, the controller 22 triggers the first hydraulic actuator 22 or the second hydraulic actuator 16 according to the target braking torque preset in step S6. Since the brake pedal 17 is mechanically and hydraulically decoupled from the hydraulic actuators 14 and 16, the friction brake device 9 can still be actuated by the hydraulic actuators 14 and 16 despite the brake pedal 17 being stuck.

[0033] Currently, if it is determined that the brake pedal 17 is stuck, refer to optional step S7. In step S7, the controller 22 starts a preset time period when it is determined that the brake pedal 17 is stuck. In addition, when it is determined that the brake pedal 17 is stuck, the controller 22 stores the current pedal position of the brake pedal 17 as a reference position. Then, the controller 22 continuously compares the detected pedal position with the stored reference position. If the comparison shows that the detected pedal position exceeds the stored reference position, the controller 22 determines that the previous jamming of the brake pedal 17 has been released. If the pedal position is between the reference position and the second endpoint position, the pedal position exceeds the reference position. Then, referring to the fourth step S4, the controller 22 detects the target braking torque again based on the detected pedal position of the brake pedal 17.

[0034] However, if the preset time period has elapsed without the jam being released again beforehand, reference is made to the eighth step S8. In the eighth step S8, the safety function is then triggered. For example, within the framework of the safety function, a warning signal is provided to the driver of the vehicle 1. Alternatively or additionally, within the framework of the safety function, the driving speed of the vehicle 1 is limited. Alternatively or additionally, within the framework of the safety function, the vehicle 1 is automatically decelerated to a standstill, i.e. independently of the actuation of the brake pedal 17.

[0035] In an alternative embodiment of the method, the controller 22 determines the pedal position assigned to the operating force in the sixth step S6 based on the detected operating force. For example, the controller 22 determines the pedal position based on the characteristic curve. In the design of the method, then refer to the fourth step S4, such as Figure 2 Then, in the fourth step S4, the controller 22 presets the target braking torque according to the pedal position. To this end, the controller 22 uses the obtained pedal position instead of the detected pedal position as the input variable of the first transfer function. The implementation of this method has the following advantages: the same control architecture can be used whether the brake pedal 17 is stuck or not.

Claims

1. A method for operating a braking system of a vehicle, wherein: The brake system (8) comprises a brake pedal (17) which can be displaced within a defined movement stroke, at least one actuable friction brake device (9) and at least one triggerable hydraulic actuator (14, 16) for actuating the friction brake device (9), wherein the brake pedal (17) is mechanically and hydraulically decoupled from the hydraulic actuator (14, 16) so that the friction brake device (9) can be actuated by the hydraulic actuator (14, 16) independently of the displacement of the brake pedal (17), at least when the brake pedal (17) is stuck, wherein The hydraulic actuator (14, 16) is triggered according to a preset target braking torque, wherein the pedal position of the brake pedal (17) and the operating force acting on the brake pedal (17) are monitored, wherein it is checked whether the brake pedal (17) is stuck in the movement stroke according to the detected pedal position and the detected operating force, and wherein when it is determined that the brake pedal (17) is not stuck, the target braking torque is preset according to the detected pedal position, characterized in that when it is determined that the brake pedal (17) is stuck, the target braking torque is preset according to the detected operating force.

2. The method according to claim 1, characterized in that When it is determined that the brake pedal (17) is stuck, the target braking torque is preset independently of the detected pedal position.

3. The method according to any one of the preceding claims, characterized in that When it is determined that the brake pedal (17) is stuck, the target braking torque is preset according to a transfer function which uses the detected operating force as an input variable and the target braking torque as an output variable.

4. The method according to any one of claims 1 and 2, characterized in that When it is determined that the brake pedal (17) is stuck, a pedal position assigned to the operating force is determined based on the detected operating force, and the target braking torque is preset based on a transfer function, which uses the determined pedal position as an input variable and the target braking torque as an output variable.

5. The method according to any one of the preceding claims, characterized in that The actuating force is filtered at least when the actuating force decreases.

6. The method according to claim 5, characterized in that The actuation force is filtered only when it decreases.

7. The method according to claim 5, characterized in that When the actuating force decreases, the actuating force is filtered using a larger filter factor than when the actuating force increases.

8. The method according to any one of the preceding claims, characterized in that When it is determined that the brake pedal (17) is stuck for a predetermined period of time, a safety function is triggered.

9. The method according to claim 8, characterized in that Within the framework of the safety function, a warning signal is provided to the driver of the vehicle (1), the driving speed of the vehicle (1) is limited within the framework of the safety function, and / or the vehicle (1) is automatically decelerated to a stationary state within the framework of the safety function.

10. The method according to any one of the preceding claims, characterized in that The pedal position existing when it is determined that the brake pedal (17) is stuck is stored as a reference position, and when it is detected that the pedal position exceeds the reference position, it is determined that the sticking of the brake pedal (17) is released.

11. A device for operating a braking system of a vehicle, wherein: The braking system (8) comprises a brake pedal (17) which can be displaced within a limited movement stroke, at least one actuable friction brake device (9) and at least one triggerable hydraulic actuator (14, 16) for actuating the friction brake device (9), wherein the brake pedal (17) is mechanically and hydraulically decoupled from the hydraulic actuator (14, 16) so that the friction brake device (9) can be actuated by the hydraulic actuator (14, 16) independently of the displacement of the brake pedal (17) at least when the brake pedal (17) is stuck, the device comprises a first sensor (19) for monitoring the pedal position of the brake pedal (17) and a second sensor (20) for monitoring the actuating force acting on the brake pedal (17), and is characterized in that the device comprises a controller (22) which is specially designed to execute a method according to any of the preceding claims when used in accordance with the regulations.

12. A vehicle having a brake system (8), the brake system having a brake pedal (17) which can be displaced within a defined movement range, at least one actuable friction brake device (9) and at least one triggerable hydraulic actuator (14, 16) for actuating the friction brake device (9), and wherein: The brake pedal (17) is mechanically and hydraulically decoupled from the hydraulic actuator (14, 16), so that the friction brake device (9) can be actuated by the hydraulic actuator (14, 16) independently of the displacement of the brake pedal (17), at least when the brake pedal (17) is stuck, characterized in that the vehicle has a device (18) for operating the brake system (8) according to the preceding claim.

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