Method for operating a braking system, computer program product and vehicle

Abstract

The invention relates to a method (100) for operating a brake unit (10) comprising at least one wheel brake (11) and an operating element (12) for actuating the wheel brake, comprising controlling (101) the brake unit to perform a first braking operation (201) in which a brake element (13) of the wheel brake and a rotation element (14) of the wheel brake are contacted by a first approach movement (201.1) with a first progression (211) of a brake force amplification (210) to decelerate the vehicle (1). The invention further relates to a computer program product and a vehicle (1).

Description

[0001] The invention relates to a method for operating a braking system, a computer program product and a vehicle.

[0002] It is known to use wheel brakes for vehicles, which comprise a brake disc and brake pads. The brake disc is connected to the vehicle wheel to be braked, while the brake pads are mounted on fixed parts. When the brake is activated, the brake pads are pressed against the brake disc by a brake booster, such as that known from document DE 10 2015 223 392 A1. This creates friction and slows or stops the moving part. After the brake pressure is released and the brake pads are lifted from the brake disc, a small amount of friction typically remains between the pads and the disc, creating a so-called residual drag torque.

[0003] To reduce fuel consumption and CO2 emissions, wheel brakes are increasingly being used which reliably provide a large clearance after the brake is released to minimize residual braking torque. The increased clearance must first be "overridden" when the brake pedal is depressed during the next braking application before pressure is built up. The brake pedal travel, particularly in the acceleration range, is longer than with conventional wheel brakes. A longer brake pedal travel can be perceived negatively by the driver. In particular, the return movement for the clearance can lead to an undesirable, variable pedal feel between release and re-application when the brake pedal is depressed again during the return movement.

[0004] It is an object of the present invention to at least partially remedy the above-mentioned disadvantages known from the prior art. In particular, it is an object of the present invention to improve the operation of a braking system with a wheel brake and an operating element with regard to the braking behavior of the wheel brake and / or the haptics of the operating element during repeated braking of the vehicle.

[0005] The above object is achieved by a method having the features of claim 1, a computer program product having the features of claim 9, and a vehicle having the features of claim 10. Further features and details of the invention emerge from the respective subclaims, the description, and the drawings. Features and details described in connection with the method according to the invention naturally also apply in connection with the computer program product according to the invention and / or the vehicle according to the invention, and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is always made to each other.

[0006] According to a first aspect of the invention, a method is provided for operating a braking system of a vehicle having a braking unit that has at least one wheel brake and an operating element for actuating the wheel brake. The method comprises, in particular in the form of method steps: - controlling the brake unit to carry out a first braking operation, in which a braking element of the wheel brake and a rotation element of the wheel brake are contacted by a first feed movement in order to brake the vehicle, in particular by a control unit of the vehicle, - Terminating the first braking operation so that a return movement to achieve a predefined distance between the braking element and the rotating element takes place, in particular by the control unit, - detecting a braking signal for carrying out a second braking operation in response to an actuation of the control element, in particular by the control unit, - Controlling the braking unit to carry out the second braking operation as a function of the braking signal and the return movement, in particular by the control unit, so that the braking element and the rotation element are contacted by a second feed movement with a brake force boosting curve determined as a function of the braking signal and the return movement in order to brake the vehicle.

[0007] The vehicle can be a motor vehicle, preferably in the form of an electric vehicle. The braking system can preferably be a hydraulic braking system. The control element can be hydraulically connected to the braking element. Furthermore, it is conceivable that the resistance behavior of the control element can be adapted depending on the braking element and / or the brake booster.

[0008] Preferably, the wheel brake is a residual-torque-optimized wheel brake. The distance can be adjusted by the reset movement to avoid or reduce residual braking torque. The distance can be a minimum distance between the braking element and the rotating element. In particular, the distance can form a clearance for the wheel brake.

[0009] The advancing movement and the return movement are, in particular, relative movements of the braking element and the rotating element. Preferably, the distance during the advancing movement and / or the return movement can be reduced and / or overcome by a movement of the braking element, in particular while the rotating element remains in its position with respect to the distance. The brake force booster serves, in particular, to reduce the braking force to be applied to the control element in order to facilitate the braking process for the driver. The control element can preferably comprise a brake pedal of the vehicle. The wheel brake can be configured, for example, as a disc brake or a drum brake. In particular, the rotating element can be a brake disc and the braking element a brake caliper and / or a brake pad.

[0010] The first braking action can be triggered depending on a further braking signal. The end of the first braking action can be triggered, for example, by the driver interrupting an operation of the control element, for example, by releasing the brake pedal. The braking signal can be triggered by a further operation of the control element. For example, the driver can operate the control element several times in succession for the first and second braking actions.

[0011] The brake unit can, in particular, comprise a brake booster for applying the brake force boost. When the brake unit is activated, the brake booster for the wheel brake can be activated to execute the first and / or second delivery movement. The return movement can be executed automatically upon completion of the first braking operation. For example, the brake element can be spring-loaded to execute the return movement depending on a brake pressure and / or a brake force.

[0012] The braking signal can be detected, in particular, during the return movement. The course of the braking force boost can be determined and / or adjusted as a function of the braking signal and the return movement when the braking unit is activated to carry out the second braking operation, and preferably when the braking unit is activated to carry out the first braking operation. For example, the course of the braking force boost can be determined and / or calculated as a function of a point in time at which the braking signal is detected after the start of the return movement and / or a distance traveled by the braking element during the return movement until the braking signal is detected. The distance traveled during the return movement can, in particular, be calculated or measured.

[0013] The course of the brake force boost for the second feed movement can thus be determined, i.e. in particular calculated and / or selected, when the brake unit is activated to carry out the second braking operation and / or before the brake unit is activated to carry out the second braking operation as a function of the brake signal and the return movement. The second braking operation is in particular a repeated braking operation. It has therefore been recognized within the scope of the present invention that, in particular with residual torque-optimized brakes, the driver's feeling when actuating the control element can depend on an interaction between the start of the second braking operation by the brake signal and the return movement. Because the course of the brake force boost occurs as a function of the brake signal and the return movement, the behavior of the braking system, in particular of the control element, can be influenced.For example, it can be provided that the resistance of the control element when actuating the wheel brake is the same or almost the same during the entire return movement via the brake force booster.

[0014] Furthermore, in a method according to the invention, it can advantageously be provided that the course of the brake force boost comprises a characteristic curve which is determined as a function of the return movement. The characteristic curve can be selected and / or calculated from a plurality of pre-stored characteristic curves based on the return movement. For example, the pre-stored characteristic curves can be pre-defined, in particular at the factory, and stored in a memory unit of the control unit. Different characteristic curves can be pre-stored for a plurality of travel sections and / or time periods of the return movement in order to determine the respectively assigned characteristic curve based on the respective current travel section and / or time period of the return movement when the brake signal is detected. Thus, a finite selection of characteristic curves can be predetermined. However, it is also conceivable that a calculation of the characteristic curve, e.g.based on boundary conditions, driving conditions, and / or the current travel and / or time segment of the return movement. In particular, the calculation of the characteristic curve can be based on pre-stored characteristic curves. The pre-stored characteristic curves can limit the computational effort required to determine the brake force boosting curve. In addition, an individual characteristic curve can be specified for each travel and / or time segment to enable the brake force boosting to be adjusted to the situation. By calculating the characteristic curve, intermediate sections can also be taken into account to improve the accuracy of determining the brake force boosting curve.

[0015] Furthermore, in a method according to the invention, it can advantageously be provided that the course of the brake force boost is determined as a function of a first support point of a course of the return movement. The first support point can thus be predetermined. The course of the return movement can comprise a time and / or distance function of the return movement. The first support point can define a time and / or distance section, in particular a time and / or distance point, of the return movement. Preferably, the first support point can be defined by a start point and / or an end point of the return movement. It can be provided that a pre-stored characteristic curve is stored for the first support point, in particular in order to calculate the course of the brake force boost based on the pre-stored characteristic curve and the first support point. For example, the course of the brake force boost can be determined as a function of the first support point.The function can preferably include a factor and / or an offset. The first reference point can be used to control and / or define a calculation of the brake boost curve, particularly at the factory. However, a situational calculation can be performed to enable high accuracy and / or continuous determination of the brake boost.

[0016] Preferably, a method according to the invention can provide for the course of the brake force boost to be determined as a function of a second support point of the course of the return movement, in particular wherein an interpolation process is carried out between the first and second support points to determine the course of the brake force boost. The second support point can be predetermined, in particular at the factory. The additional, second support point can enable a more precise definition when determining the course of the brake force boost. The interpolation process can comprise calculating an interpolation between the first and second support points for the course of the brake force boost. For example, a characteristic curve can be predetermined for each of the first and second support points.Based on the characteristic curves assigned to the first and second support points, an additional characteristic curve can be calculated for the current path and / or time segment of the return movement through the interpolation process, depending on the return movement. This enables a continuous determination of the characteristic curve.

[0017] Furthermore, in a method according to the invention, it is conceivable that the first support point is defined by an end point of the return movement and / or the second support point is defined by a start point of the return movement. The end point and the start point can be time and / or path points in the sequence of the return movement. As a result, the return movement, which can in particular be a linear or nearly linear movement, can be completely defined for the interpolation process. The end point of the return movement can be reached when the predefined distance between the braking element and the rotating element is reached. The starting point of the return movement can be determined depending on the end of the first braking process. In particular, the starting point can be defined by predetermined boundary conditions. Thus, the first and second support points can form reference points in order to map the sequence of the return movement.

[0018] Within the scope of the invention, it is further conceivable that the course of the brake force boost is determined as a function of a reference time of a time-dependent reference sequence of the return movement, in particular wherein the first and / or second support point comprise times of the reference sequence after the end of the first braking process. The reference time can in particular be a time in the reference sequence which can be or is assigned to a current time of the return movement and thus to a current distance between the rotation element and the braking element. The time-dependent reference sequence can be predefined and stored. However, it is also conceivable that the reference sequence is represented by the first and / or second support point.For example, a relationship between the reference time and the course of the brake force boost can be determined or will be determined by the first and / or second support point on the basis of the reference sequence. This is based in particular on the consideration that, based on the reference time, it can be estimated, for example, how large the distance between the braking element and the rotating element is in order to determine the course of the braking force determination and, in doing so, to control and / or regulate the existing distance in relation to the actuation feel on the control element. In particular, the time-dependent reference sequence, preferably with the first and / or second support point, may make it unnecessary to actually measure the return movement. Thus, the course of the return movement can be detected by the control unit through a time measurement, in particular by a timer, and / or can be used to determine the course of the return movement.

[0019] Preferably, a method according to the invention can provide that, upon termination of the first braking operation, an actuation travel of the control element and / or a braking parameter for measuring the braking force of the wheel brake are measured, wherein a time measurement is carried out to determine the reference time of the reference sequence as a function of the actuation travel and / or the braking parameter. The braking parameter can preferably comprise a braking pressure of the wheel brake. The actuation travel can, for example, comprise a pedal travel of a brake pedal, in particular starting from an unconfirmed position of the brake pedal. Thus, the termination of the first braking operation can be detected based on the actuation travel and / or the braking parameter. For example, a time measurement can be started when the control element is released starting from the first braking operation.This can be detected by detecting a pressure drop below 1 bar and / or a brake pedal travel of 1 mm. This allows the time at which the first braking action is completed and the return movement begins to be determined. The actuation travel and / or the braking parameter can thus be used to determine when the return movement begins or has already begun. This allows the reference time to determine how far the return movement has progressed when the brake signal is detected, allowing the brake booster to be adjusted accordingly.

[0020] Furthermore, a method according to the invention can advantageously provide for the brake boost to be limited when the first reference point is exceeded in the reference sequence, in particular when the first reference point defines the end point of the return movement. Limiting the reference sequence can, for example, provide that after the first reference point is exceeded, the brake boost curve is predefined for each point in time and / or the characteristic curve assigned to the first reference point is used to determine the brake boost curve. This can prevent a calculation of the brake boost curve from running off, in particular when using the interpolation process.

[0021] According to a further aspect of the invention, a computer program product is provided. The computer program comprises instructions which, when executed by a control unit, cause the control unit to execute a method according to the invention.

[0022] Thus, a computer program product according to the invention brings with it the same advantages as have already been described in detail with reference to a method according to the invention. The method can in particular be a computer-implemented method. The computer program product can be implemented as computer-readable instruction code. Furthermore, the computer program product can be stored on a computer-readable storage medium such as a data disk, a removable drive, a volatile or non-volatile memory, or a built-in memory / processor. Furthermore, the computer program product can be provided or made available in a network such as the Internet, from which it can be downloaded by a user or executed online as needed. The computer program product can be implemented both by means of software and by means of one or more special electronic circuits, i.e., in hardware or in any hybrid form, ie, by means of software components and hardware components.

[0023] According to a further aspect of the invention, a vehicle is provided. The vehicle has a braking system with a braking unit. The braking unit comprises at least one wheel brake and an operating element for actuating the wheel brake. Furthermore, the vehicle has a control unit for executing a method according to the invention for operating the braking system.

[0024] Thus, a vehicle according to the invention offers the same advantages as have already been described in detail with reference to a method according to the invention and / or a computer program product according to the invention. The vehicle, in particular the brake unit, can preferably comprise a brake booster for applying the brake force boost. The control unit can comprise a processor and / or a microprocessor. Furthermore, the control unit can be at least partially or completely integrated into a central control unit of the vehicle. However, it is also conceivable for the control unit to be at least partially or completely integrated into one or more decentralized control units.

[0025] Further advantages, features, and details of the invention will become apparent from the following description, which describes embodiments of the invention in detail with reference to the drawings. The features mentioned in the claims and in the description may be essential to the invention individually or in any combination. They show schematically: Fig. 1 a wheel brake of a braking system of a vehicle according to the invention, Fig. 2 a sequence of a return movement of the wheel brake upon completion of a first braking operation, Fig. 3 the vehicle with the braking system, Fig. 4 shows a sequence of a method according to the invention for operating the brake system, and Fig. 5 characteristic curves for the course of a brake force boost of the brake system.

[0026] In the following description of some embodiments of the invention, the same reference numerals are used for the same technical features even in different embodiments.

[0027] Fig. Figure 1 shows a wheel brake 11 of a brake system 2 of a vehicle 1 according to the invention in a first exemplary embodiment. In the exemplary embodiment shown, the wheel brake 11 is in particular a disc brake, preferably in the form of a residual braking torque-optimized brake. However, other embodiments of the wheel brake 11 are also conceivable. As shown in Fig. 1, the wheel brake 11 comprises at least one brake element 13, here two brake elements 13 in the form of brake pads, and a rotation element 14, here in the form of a brake disc.

[0028] Vehicle 1 is equipped with braking system 2 in Fig. 3. The vehicle 1 comprises a braking system 2 with a braking unit 10, which has the wheel brake 11 and an operating element 12, here in the form of a brake pedal, for actuating the wheel brake 11. Furthermore, the braking unit 10 comprises a brake booster 17 for applying a braking force booster 210 to the wheel brake 11. Preferably, the braking unit 10 comprises two or more wheel brakes 11, which are coupled to the brake booster 17. The vehicle 1 further comprises a control unit 16 for executing a method 100 according to the invention for operating the braking system 2. For this purpose, a computer program product can be provided which comprises commands which, when executed by the control unit 16, cause the control unit 16 to execute the method 100. A sequence of the method 100 is shown in Fig. 4 shown.

[0029] In the method 100, the brake unit 10 is first actuated 101 to perform a first braking operation 201. During the first braking operation 201, the braking element 13 of the wheel brake 11 and the rotating element 14 of the wheel brake 11 are contacted by a first feed movement 201.1 in order to brake the vehicle 1. If, for example, the driver of the vehicle 1 interrupts or terminates the actuation of the control element 12, the first braking operation 201 is terminated 102. The braking element 13 performs a return movement 202 in order to achieve a predefined distance 15 between the braking element 13 and the rotating element 14. When the distance 15 is reached, a release play of the wheel brake 11 can be formed, which reduces or prevents a residual braking torque. Upon termination 102 of the first braking operation 201, an actuation path 12.1 of the control element 12, e.g. in the form of a brake pedal travel, and / or a braking parameter 11.1 for measuring the braking force of the wheel brake 11, e.g. in the form of a brake pressure, as shown in . Fig. 2 shown.

[0030] Preferably, during the return movement 202, a braking signal 220 is detected 103 to execute a second braking operation 203 as a function of an actuation of the operating element 12, and the braking unit 10 is controlled 104 to carry out the second braking operation 203. Thus, the second braking operation 203 represents, in particular, a repeated braking operation, preferably shortly after the termination 102 of the first braking operation 201.

[0031] In particular, in order to reduce or avoid the influence of the feed path of the braking element 13 in the direction of the rotating element 14, which is changed due to the return movement 202 depending on the time of the second braking operation 203, on the actuation feeling of the operating element 12, the control 104 of the braking unit 10 to carry out the second braking operation 203 takes place in dependence on the braking signal 220 and the return movement 202. As a result, the braking element 13 and the rotating element 14 are contacted by a second feed movement 203.1 with a profile 212 of a brake force booster 210, which is determined in dependence on the braking signal 220 and the return movement 202, in order to brake the vehicle 1. Profiles 212 of the brake force booster 210 are shown in Fig. 5 versus a time t.

[0032] As in Fig. As shown in Figure 2, the curve 212 of the brake booster 210 is preferably determined as a function of a reference time 211.1 of a time-dependent reference sequence 211 of the return movement 202. A time measurement can be performed to determine the reference time 211.1 of the reference sequence 211 as a function of the actuation path 12.1 and / or the braking parameter 11.1. The reference sequence 211 can be determined, for example, based on laboratory measurements of a standardized return movement 202. This eliminates the need to measure the return movement 202 of the braking element 13 itself.

[0033] The curve 212 of the brake booster 210 can be determined depending on a first support point 202.1 of a sequence of the return movement 202. For this purpose, for example, a functional relationship can be provided between the time measurement, the reference time 211.1, and the first support point 202.1 of the return movement 202. The first support point 202.1 and / or the functional relationship can map a sequence of the return movement 202 in order to adapt the brake booster 210 based on it.

[0034] Furthermore, it can be provided that the curve 212 of the brake force boost 210 is determined as a function of a second interpolation point 202.2 of the sequence of the return movement 202. The second interpolation point 202.2 can define an additional point in the sequence of the return movement 202 in addition to the first interpolation point 202.1. For example, an interpolation process can be carried out using the first and second interpolation points 202.1, 202.2 to determine the curve 212 of the brake force boost 210 between the first and second interpolation points 202.1, 202.2. It is advantageous if the first and second interpolation points 202.1, 202.2 comprise times of the reference sequence 211 after the termination 102 of the first braking process 201. For example, the first support point 202.1 can be defined by an end point of the return movement 202 and the second support point 202.2 can be defined by a start point of the return movement 202 in order to map the entire return movement 202.In this case, the brake force boost 210 can be limited if the first support point 202.1 in the reference sequence 211 is exceeded, in particular in order to prevent the calculation from running away for later points in time.

[0035] As in Fig. As shown in Figure 5, the curve 212 of the brake booster 210 can include a characteristic curve determined as a function of the return movement 202. A characteristic curve can be predefined for each of the first and second support points 202.1, 202.2. For all reference times 211.1 between the first and second support points 202.1, 202.2, the respectively assigned characteristic curve can be determined, for example, by the interpolation process.

[0036] The above explanation of the embodiments describes the present invention exclusively by way of examples. Of course, individual features of the embodiments can be freely combined with one another, provided they are technically feasible, within the scope of protection defined by the patent claims, without departing from the scope of the present invention. List of reference symbols 1 vehicle 2 brake system 10 Brake unit 11 Wheel brake 11.1 Braking parameters 12 Control element 12.1 Actuation travel 13 Brake element 14 Rotation element 15 distance 16 Control unit 17 Brake booster 100 procedures 101 Control of 10 for 201 102 Exit 103 Capture 104 Control of 10 for 203 201 first braking operation 201.1 first delivery movement 202 Return movement 202.1 first support point 202.2 second support point 203 second braking operation 203.1 second delivery movement 210 Brake booster 211 Reference process 211.1 Reference time 212 History 220 brake signal QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] DE 10 2015 223 392 A1

[0002]

Claims

[1] Method (100) for operating a brake system (2) of a vehicle (1) with a brake unit (10) which has at least one wheel brake (11) and an operating element (12) for actuating the wheel brake (11), comprising - controlling (101) the brake unit (10) to carry out a first braking operation (201), in which a braking element (13) of the wheel brake (11) and a rotation element (14) of the wheel brake (11) are contacted by a first feed movement (201.1) in order to brake the vehicle (1), - terminating (102) the first braking operation (201) so that a return movement (202) takes place to achieve a predefined distance (15) between the braking element (13) and the rotation element (14), - detecting (103) a braking signal (220) for carrying out a second braking operation (203) in response to an actuation of the operating element (12), - controlling (104) the brake unit (10) to carry out the second braking operation (203) as a function of the brake signal (220) and the return movement (202), so that the brake element (13) and the rotation element (14) are contacted by a second feed movement (203.1) with a course (212) of a brake force booster (210) determined as a function of the brake signal (220) and the return movement (202) in order to brake the vehicle (1). [2] Method (100) according to claim 1, characterized by that the course (212) of the brake force booster (210) comprises a characteristic curve which is determined as a function of the return movement (202). [3] Method (100) according to claim 1 or 2, characterized by that the course (212) of the brake force boost (210) is determined as a function of a first support point (202.1) of a course of the return movement (202). [4] Method (100) according to one of the preceding claims, characterized bythat the course (212) of the brake force boost (210) is determined as a function of a second support point (202.2) of the course of the return movement (202), wherein an interpolation process is carried out between the first and second support points (202.1, 202.2) to determine the course (212) of the brake force boost (210). [5] Method (100) according to one of the preceding claims, characterized by , that the first support point (202.1) is defined by an end point of the return movement (202) and / or the second support point (202.2) is defined by a starting point of the return movement (202). [6] Method (100) according to one of the preceding claims, characterized bythat the course (212) of the brake force boost (210) is determined as a function of a reference time (211.1) of a time-dependent reference course (211) of the return movement (202), wherein the first and / or second support point (202.2) comprise times of the reference course (211) after the termination (102) of the first braking process (201). [7] Method (100) according to one of the preceding claims, characterized by that upon termination (102) of the first braking operation (201), an actuation path (12.1) of the operating element (12) and / or a braking parameter (11.1) for measuring the braking force of the wheel brake (11) are measured, wherein a time measurement is carried out for determining the reference time (211.1) of the reference sequence (211) as a function of the actuation path (12.1) and / or the braking parameter (11.1). [8] Method (100) according to one of the preceding claims, characterized bythat the brake force boost (210) is limited when the first support point (202.1) is exceeded in the reference sequence (211). [9] Computer program product comprising instructions which, when executed by a control unit (16), cause the control unit (16) to carry out a method (100) according to one of the preceding claims. [10] Vehicle (1), comprising a brake system (2) with a brake unit (10) having at least one wheel brake (11) and an operating element (12) for actuating the wheel brake (11), and a control unit (16) for carrying out a method (100) according to one of claims 1 to 8 for operating the braking system (2).

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