Method for preparing an external power braking system for expected degradation

Abstract

The invention relates to a method for preparing an electric-assisted braking system (10) for anticipated degradation. The method comprises the steps of detecting (B) an abnormal state value (Z) of at least one component necessary for electric-assisted braking, and evaluating (C) a probability of failure (W). A ) of the external power braking system (10) during braking, and of adapting (D) a brake pedal travel-brake pressure curve or brake pedal travel-deceleration curve according to the probability of failure (W A), so that a shorter brake pedal travel is required for the same brake pressure or deceleration. In a further step, the external power braking system (10) is activated (E) so that braking is carried out with a brake fluid volume provided by a change in brake pedal travel initiated by the driver, should a failure of at least one component necessary for braking be detected during braking.

Description

[0001] The present invention relates to a method for preparing an external power braking system for anticipated degradation. The invention further relates to an external power braking system with which such a method can be carried out. State of the art

[0002] In automotive engineering, braking systems play a central role in safety and driving dynamics. Particularly innovative simulator braking systems, such as the integrated power brake (IPB) and the decoupled power brake (DPB), brake autonomously while the driver transfers the brake fluid to a simulator via the brake pedal. This simulator provides the driver with only a sensation of braking. In the event of a malfunction, however, the brake system's valves can still be switched over, allowing the brake fluid to be transferred to the wheel cylinders via the brake pedal, thus guaranteeing a high level of reliability for these braking systems. This valve switching is also possible during braking, so the driver always has the option of braking the vehicle, even if the braking system fails during the braking process.

[0003] Document DE 10 2020 214 507 A1 describes a method for preparing an auxiliary brake application in a hydraulic vehicle braking system that includes a pedal travel simulator. In the event of a failure of the externally powered brake pressure generator, an auxiliary brake application can be performed by manually actuating the master brake cylinder. Alternatively, auxiliary brake pressure is generated in the pedal travel simulator by activating the externally powered brake pressure generator while certain valves are opened. This establishes a hydraulic connection between the brake pressure generator and the simulator. After the auxiliary brake pressure has been generated, various valves can be closed to stabilize the braking force.

[0004] The object underlying the invention is to provide a method for an external power braking system with which a higher deceleration can be achieved during a fault in the external power braking system.

[0005] The problem is solved by a method with the subject matter of claim 1. Preferred embodiments can be found in the dependent claims. Disclosure of the invention

[0006] The invention provides a method for preparing an electric-assisted braking system for anticipated degradation. The method comprises the steps of detecting an abnormal state value of at least one component necessary for electric-assisted braking, evaluating the probability of failure of the electric-assisted braking system during braking, and adjusting a brake pedal travel-brake pressure curve or brake pedal travel-deceleration curve according to the probability of failure, so that a shorter brake pedal travel is required for the same brake pressure or deceleration. In a further step, the electric-assisted braking system is controlled so that braking is performed with a brake fluid volume provided by a change in brake pedal travel initiated by the driver, should a failure of at least one component necessary for braking be detected during braking.

[0007] When the power-assisted braking system deteriorates, braking via the power-assisted brake pressure generator is no longer possible, meaning the vehicle must be braked manually by the driver. Before deterioration, the power-assisted braking system is still operational; however, an abnormal condition can already be detected based on its state values. For each component of the power-assisted braking system, state values ​​are defined that are considered normal, and values ​​outside this range are abnormal. Based on the component detected as abnormal and the determined state values, a probability of an impending failure during a braking maneuver can be calculated.

[0008] A brake pedal travel-brake pressure curve indicates the brake pressure to be generated by the externally applied brake pressure generator for a given brake pedal travel. Similarly, a brake pedal travel-deceleration curve indicates the desired deceleration of the vehicle for a given brake pedal travel. The externally applied brake pressure generator is controlled according to this deceleration value. By modifying these curves according to the invention, the same brake pressure or deceleration can be achieved with a shorter brake pedal travel. Consequently, the driver transfers a smaller volume of brake fluid into the brake force simulator.

[0009] In the event of a failure of the power-assisted braking system during braking, the system switches from generating brake pressure from the power-assisted brake pressure generator to generating brake pressure from the master brake cylinder. Due to the shorter brake pedal travel, a larger volume of brake fluid is available for braking in the event of a failure. Consequently, the increased fluid volume allows for greater deceleration. The vehicle can therefore be brought to a stop sooner, thus increasing safety.

[0010] In a preferred embodiment of the invention, the brake pedal travel-brake pressure curve or brake pedal travel-deceleration curve is modified when a defined failure probability is exceeded. For low failure probabilities below the defined value, the brake pedal travel-brake pressure curve or brake pedal travel-deceleration curve remains unchanged. This ensures that driving comfort for the driver is not impaired, particularly at low failure probabilities.

[0011] In a further preferred embodiment of the invention, upon detection of an abnormal condition, the brake pedal travel-brake pressure curve or brake pedal travel-deceleration curve is modified to the same extent as the failure probability changes, so that with higher failure probabilities, a shorter brake pedal travel is required for the same brake pressure or deceleration. The curves are thus continuously modified. Unlike a change occurring at a threshold, a continuous change remains imperceptible to the driver, so driving comfort is not affected. Furthermore, even at low failure probabilities, a larger volume of brake fluid is available for braking in the event of a failure of the external braking system, thus improving deceleration.

[0012] Preferably, if the failure probability changes during braking, the existing brake pedal travel-brake pressure curve or brake pedal travel-deceleration curve is approximated to a new brake pedal travel-brake pressure curve or brake pedal travel-deceleration curve. The curve is thus not changed abruptly but transitions to the new curve over a predetermined period. Therefore, the driver cannot perceive any difference between the changes in the curves, thus maintaining a good driving feel.

[0013] The invention further provides an external power braking system for carrying out the method. The external power braking system comprises an external power brake pressure generator for generating a brake pressure according to a predetermined brake pedal travel-brake pressure curve or brake pedal travel-deceleration curve, a master brake cylinder in which at least one piston is arranged that can be moved via a brake pedal and over which a volume of brake fluid can be moved, and a brake force simulator by which a braking sensation can be simulated for a driver.In addition, the power-assisted braking system includes a valve system for regulating the brake fluid flow and a control unit that receives information on the status values ​​of the components necessary for power-assisted braking and is configured to define a brake pedal travel-brake pressure curve or brake pedal travel-deceleration curve for the power-assisted brake pressure generator. In the event of a failure of a component necessary for braking, the control unit activates the valve system so that braking is performed using a volume of brake fluid supplied by the master cylinder. With such a power-assisted braking system, the advantages and effects described above are achieved.

[0014] Furthermore, a motor vehicle equipped with such an external power braking system is described. Such a motor vehicle exhibits the aforementioned advantages and effects.

[0015] Exemplary embodiments of the invention are shown in the drawing and explained in more detail in the following description. It shows: Fig. 1. Illustration of an exemplary embodiment of an external power braking system during normal operation, Fig. 2. Illustration of an embodiment of the external force braking system in a degraded state, Fig. 3. Description of a first embodiment of a method for preparing the external power braking system for expected degradation, and Fig. 4. Presentation of a second embodiment of a method for preparing the external power braking system for expected degradation.

[0016] In Fig. Figure 1 shows an embodiment of an assisted braking system 10 during normal operation. The assisted braking system 10 comprises an assisted braking pressure generator 14, which axially displaces a motor-driven assisted braking piston 18 in an assisted braking cylinder 22 to generate braking pressure for assisted braking. The assisted braking system 10 includes a master brake cylinder 26 in which a first and a second piston 30a, 30b are axially displaceable. The first piston 30a is coupled to a brake pedal 34. A displacement sensor 38 is arranged on the brake pedal 34 to detect brake pedal travel.

[0017] The power-assisted braking system 10 additionally includes a brake fluid reservoir 42, from which brake fluid is supplied. A valve system 46 is also provided, through which, in normal operation, the power-assisted brake pressure generator 14 is connected to an ESP unit 50. Wheel brakes 54, which are pressurized with brake fluid for braking, are connected to this ESP unit 50. The master brake cylinder 26 is decoupled from the ESP unit 50 via the valve system 46 and hydraulically connected to a brake force simulator 58. This brake force simulator 58 provides the driver with a braking sensation. Pressure sensors 62 are arranged at various points in the power-assisted braking system 10 to monitor the brake pressure.

[0018] Furthermore, a control unit 66 is provided, which monitors the state values ​​Z of the components necessary for braking and controls the valve system 46. A brake pedal travel-brake pressure curve or a brake pedal travel-deceleration curve can be defined via this control unit 66. The externally applied brake pressure generator 14 is thus controlled according to the brake pedal travel and the brake pressure or deceleration.

[0019] Fig. Figure 2 shows an embodiment of the power-assisted braking system 10 in a degraded state. In a degraded state, at least one component necessary for power-assisted braking has failed. In this state, the valve system 46 is configured such that the power-assisted brake pressure generator 14 is hydraulically isolated from the ESP unit 50. In contrast, the master brake cylinder 26 is hydraulically connected to the ESP unit 50 via the valve system 46. The brake force simulator 58 is correspondingly isolated from the master brake cylinder 26. The wheel brakes 54 are thus braked by a volume of brake fluid supplied by the master brake cylinder 26.

[0020] Fig. Figure 3 shows a representation of a first embodiment of a method for preparing the powered braking system 10 for expected degradation. In a first step A of the method, state values ​​Z of the components necessary for the powered braking are determined. Subsequently, the state values ​​Z are compared with state values ​​Z defined as normal. N compared. If the state values ​​Z are in the interval of the normal state values ​​[Z N The state values ​​Z should continue to be determined continuously. In the event that at least one component should have a state value Z that is outside the interval [Z] defined as normal, the state values ​​Z will continue to be determined. N If the condition should be [not specified], then in the next step B an abnormal state is detected for the corresponding component.

[0021] In a subsequent process step C, a failure probability W is calculated based on the component and the determined state value Z. A The failure probability W of the external power braking system 10 was determined during braking. A is then combined with a fixed value for the probability of failure W. G compared. If the value of the probability of failure W A the fixed value W G If the value of the probability of failure W does not exceed this value, the process is restarted with the first step A. A , however greater than the specified value W G In a further step D, a brake pedal travel-brake pressure curve or a brake pedal travel-deceleration curve is modified according to a specification. Thus, a shorter brake pedal travel is required for the same brake pressure or deceleration.

[0022] If a modified brake pedal travel-brake pressure curve or a modified brake pedal travel-deceleration curve already exists, the new brake pedal travel-brake pressure curve or the new brake pedal travel-deceleration curve will be approximated to the corresponding existing curve, ensuring a smooth transition between the curves. This adjustment of these curves will therefore remain imperceptible to the driver.

[0023] The system then continuously checks whether a component has failed. If not, the process restarts with step A. However, if the component required for power braking fails during braking, the power braking system 10 is degraded in a further step E. In this step, the valve system 46 is controlled in such a way that braking is performed with a brake fluid volume provided by a change in the brake pedal travel initiated by the driver. Since a change in the brake pedal travel-pressure curve or the brake pedal travel-deceleration curve results in a shorter brake pedal travel required before the power braking system 10 fails, a larger brake fluid volume can be supplied via the master brake cylinder 26.Accordingly, in the event of a fault in the external force braking system 10, a greater deceleration can be achieved than without a prior adjustment of the brake pedal travel-brake pressure curve or the brake pedal travel-deceleration curve.

[0024] In Fig. Figure 4 shows a representation of a second embodiment of a method for preparing an external power braking system 10 for expected degradation. The method according to Fig. 4 differs from the procedure according to Fig. 3 by the fact that a change in the brake pedal travel-brake pressure curve or the brake pedal travel-deceleration curve does not only occur when a specified value for the probability of failure W is exceeded G The brake pedal travel-brake pressure curve or the brake pedal travel-deceleration curve is thus continuously updated in step D according to the failure probability W. A changed. With increasing probability of failure W AThe brake pedal travel-brake pressure curve or the brake pedal travel-deceleration curve is changed in the direction of a shorter pedal travel. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2020 214 507 A1

[0003]

Claims

[1] Method for preparing an external force braking system (10) for expected degradation, comprising the steps: - Detecting (B) an abnormal state value (Z) of at least one component necessary for external braking, - Evaluating (C) a probability of failure (W) A ) of the external power braking system (10) during braking, - Adjusting (D) a brake pedal travel-brake pressure curve or brake pedal travel-deceleration curve according to the probability of failure (W) A ), so that a shorter brake pedal travel is required for the same brake pressure or deceleration, - Activation (E) of the external power braking system (10) so that braking is carried out with a brake fluid volume which is provided by a change in the brake pedal travel made by the driver, if a failure of at least one component necessary for braking is detected during braking. [2] Method according to claim 1, characterized by , that if a specified value for the probability of failure (W) is exceeded G ) the brake pedal travel-brake pressure curve or brake pedal travel-deceleration curve is changed. [3] Method according to claim 1, characterized by , that upon detection (B) of an abnormal condition, the brake pedal travel-brake pressure curve or the brake pedal travel-deceleration curve is changed to the same extent as the failure probability (W) A ) changes, so that with higher failure probabilities (W A) a shorter brake pedal travel is required for the same brake pressure or deceleration. [4] Method according to any one of the preceding claims, characterized by , that in the event of a change in the probability of failure (W A ) during braking, the existing brake pedal travel-brake pressure curve or brake pedal travel-deceleration curve is approximated to a new brake pedal travel-brake pressure curve or new brake pedal travel-deceleration curve. [5] External force braking system (10) for carrying out the method according to any of the preceding claims, comprising: - External force brake pressure generator (14) for generating a brake pressure according to a predetermined brake pedal travel-brake pressure curve or brake pedal travel-deceleration curve, - a master brake cylinder (26) in which at least one piston (30a, 30b) is arranged which can be moved via a brake pedal (34) and over which a volume of brake fluid can be moved, - Brake force simulator (58), which allows a driver to simulate the feeling of braking, - Valve system (46), for regulating the brake fluid flow, - Control unit (66), which receives information on state values ​​(Z) of the components necessary for external braking and is set up to define a brake pedal travel-brake pressure curve or brake pedal travel-deceleration curve for the external brake pressure generator (14) and, in the event of a failure of a component necessary for braking, controls the valve system (46) so that braking is carried out by a volume of brake fluid provided by the master brake cylinder (26). [6] Motor vehicle comprising an external power braking system (10) according to claim 5.

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