METHOD FOR OPERATING A BRAKE SYSTEM FOR A MOTOR VEHICLE AND CORRESPONDING BRAKE SYSTEM

Description

[0001] The invention relates to a method for operating a braking system for a motor vehicle, wherein the braking system comprises a service braking device, and the service braking device is actuated to generate a braking force on a wheel axle of the motor vehicle at least temporarily depending on the setting of a control element. The invention further relates to a braking system for a motor vehicle.

[0002] For example, DE 11 2016 001 509 T5 is known from the prior art. This document describes a brake control device comprising a brake command addition section for adding an automatic braking brake command value output by an automatic braking brake command calculation section and a pedal-operated braking command set output by a pedal-operated braking command calculation section. The pedal-operated braking command calculation section includes a pedal-operated braking command selection section, a normal braking characteristic section for maintaining a normal braking characteristic, and an automatic braking characteristic section for maintaining an automatic braking characteristic.The pedal-operating brake command selecting section selects a brake command value output from the automatic braking characteristic section when the automatic braking brake command value is more than 0, and outputs the selection result to the brake command adding section as the pedal-operating brake command value.

[0003] It is an object of the invention to propose a method for operating a brake system for a motor vehicle, which has advantages over known methods, in particular enabling the control of the service brake device in a particularly reliable manner, even after installation and / or replacement of an operating element of the brake system.

[0004] This is achieved according to the invention with a method for operating a braking system for a motor vehicle with the features of claim 1. It is provided that the generation of the braking force is carried out as a function of the setting of the operating element using a calibration data set stored in a control unit of the braking system, wherein an identifier stored in the operating element is transmitted to the control unit and used there for a compatibility check and, if the compatibility check is successful, the operating element is set up by using a generic data set stored in the control unit as the calibration data set and by transmitting an operating element-specific data set stored in the operating element to the control unit and, after transmission, using this data set as the calibration data set.

[0005] Advantageous embodiments with useful further developments of the invention are specified in the dependent claims. It should be noted that the exemplary embodiments explained in the description are not limiting; rather, variations are possible without departing from the scope of the invention defined by the claims.

[0006] The method serves to operate the braking system. This is preferably a component of the motor vehicle, but can of course also be separate from it. The braking system serves to brake the motor vehicle, i.e., to reduce the speed of the motor vehicle, in particular to a standstill, and / or to immobilize the motor vehicle at a standstill. For the former, the braking system has the service brake device, which at least temporarily exerts a braking force on at least one wheel of the motor vehicle, preferably on several or all wheels of the motor vehicle. This braking force can also be referred to as the service braking force.

[0007] If multiple wheels are present, the at least one wheel is considered a component of these multiple wheels. Where reference is made to the wheel or the at least one wheel within the scope of this description, the statements are equivalent. Furthermore, they are preferably transferable to each of the multiple wheels.

[0008] The at least one wheel is assigned to the wheel axle of the motor vehicle, to which the braking force is applied by means of the service brake device. The wheel axle is, for example, a rear wheel axle or a front wheel axle of the motor vehicle. The service brake device is preferably provided and configured to apply the braking force, at least temporarily, to several wheels of the wheel axle and / or wheels of several wheel axles. Particularly preferably, the service brake device is used to apply the braking force, at least temporarily, to several or all wheel axles of the motor vehicle or their wheels, or to brake the corresponding wheels.

[0009] The service brake device has at least one wheel brake, which is assigned to the at least one wheel or the at least one wheel axle. The service brake device preferably has a plurality of wheel brakes, each of which is assigned to a wheel or a wheel axle of the motor vehicle. Particularly preferably, the wheel brakes are present on a plurality of wheels and / or wheel axles; in particular, each wheel and / or wheel axle of the motor vehicle is assigned a separate wheel brake. The wheel brake applies the braking force to the wheel axle or the respective wheel of the motor vehicle.

[0010] The braking force applied by the service brake system can typically be adjusted as desired. This is done depending on the setting of the control element, via which a driver of the motor vehicle specifies the braking force. The control element is arranged within a passenger compartment of the motor vehicle, accessible to the driver; in particular, it is located at least partially in front of the passenger compartment or protrudes into it. The control element is particularly preferably designed as a brake pedal, i.e., it is intended, configured, and arranged accordingly for actuation by the driver's foot or for foot actuation by the driver.

[0011] The braking system evaluates the setting of the control element, for example, its position, and uses this setting to determine the braking force specified by the driver. This can also be referred to as the specified braking force. The service braking system is controlled in such a way that it applies a braking force to the wheel axle of the motor vehicle or to at least one wheel that corresponds to the specified braking force. In particular, a target braking force corresponding to the specified braking force is specified for the service braking system, and the service braking system adjusts an actual braking force acting on the wheel axle or to at least one wheel in such a way that it corresponds to the target braking force and thus to the specified braking force.

[0012] The service brake device is at least temporarily connected purely electronically to the control element, so that the control of the wheel brake(s) is / are carried out purely electronically, at least temporarily, depending on the setting of the control element. However, it can be provided that a mechanical and / or hydraulic fallback level is present between the control element and the wheel brake, so that in the event of a failure of the electronic connection, the braking force can still be applied or adjusted using the control element. However, it is particularly preferred that the control element is permanently connected purely electronically to the service brake device, or conversely, the service brake device is permanently connected purely electronically to the control element.

[0013] The braking force is generated as a function of the setting of the control element using a calibration data set stored in a control unit of the braking system. This means that the braking force does not depend exclusively on the setting of the control element, but also on the calibration data set. In particular, the setting of the control element serves as the input variable for the calibration data set, and the braking force as the output variable. Preferably, the aforementioned preset braking force is determined from the setting of the control element using the calibration data set. The target braking force corresponding to the preset braking force is subsequently set on the service braking device, which adjusts the actual braking force acting on the wheel axle of the motor vehicle such that it corresponds to the target braking force.

[0014] The calibration data set comprises, in particular, information about the control element, in particular a relationship between the setting of the control element and the braking force to be generated or the specified braking force. In particular, the calibration data set relates different values ​​for the setting of the control element to different values ​​for the braking force or the specified braking force. Preferably, the calibration data set contains a value for the braking force to be generated for different values ​​of the setting of the control element. The values ​​for the braking force to be generated are at least partially different from one another for different values ​​of the setting.

[0015] The calibration data set is available, for example, in the form of a table, a characteristic map, or a mathematical relationship. It is fundamentally important that the braking force or the specified braking force depends only indirectly on the setting of the control element, namely via the calibration data set. The calibration data set is necessary to determine the braking force from the setting of the control element.

[0016] The control element is electrically connected, preferably permanently and purely electrically, to the control unit and transmits its setting to it. The control unit uses the calibration data set to determine the corresponding braking force or the specified braking force for the setting transmitted from the control element to the control unit. The control unit then controls the service brake device to generate the braking force. The calibration data set must therefore be stored in the brake system control unit.

[0017] Preferably, the control-element-specific data set is stored in the control element. The control-element-specific data set is tailored to the control element; for example, it is determined during calibration of the control element and stored in the control element. The control element has a corresponding data memory for this purpose. For example, the control-element-specific data set is determined during production of the control element and / or before installation of the control element in the motor vehicle and stored in the control element.

[0018] The control element transmits the control element-specific data set at least once to the control unit of the braking system, preferably once after the control element has been installed in the motor vehicle. However, it can also be provided that the control element transmits the control element-specific data set to the control unit multiple times, in particular periodically. The control unit receives the control element-specific data set from the control element and, after transmission, uses it as a calibration data set. In this case, it can be provided that only the control element-specific data set transmitted for the first time by the control element is used as the calibration data set. Subsequent transmissions of the control element-specific data set from the control element to the control unit are ignored in this case and the used calibration data set is retained, at least if no replacement of the control element is detected, i.e. the control element is unchanged.

[0019] Since transferring the control-element-specific data set to the control unit takes a certain amount of time, and during this time the control-element-specific data set is not available as a calibration data set, the braking system would have to indicate an error and / or the vehicle would have to be taken out of operation to ensure a high level of safety for the driver. However, to enable the driver to start up the vehicle quickly, the identifier is stored in the control element. This identifier is transferred to the control unit, where it is used for a compatibility check. The compatibility check means that a check is carried out to determine whether the control element and its behavior are fundamentally known to the control unit.

[0020] If the compatibility check is successful, meaning the control element is fundamentally known to the control unit, the control element is configured for operation within the braking system. This configuration is performed by first using the generic data set stored in the control unit as the calibration data set. At the same time or subsequently, the control element-specific data set is transferred to the control unit in the manner described above. After the control element-specific data set has been completely transferred or after the transfer is completed, the system switches from the generic data set to the control element-specific data set, so that the control element-specific data set is subsequently used as the calibration data set and no longer the generic data set.

[0021] This procedure enables safe and reliable operation of the braking system or the vehicle while the control-element-specific data set is still being transferred from the control element to the control unit. Immediately after the control element is put into operation, the full functionality of the control element or the braking system is guaranteed, and the driver receives at least approximately the expected braking force when the control element is actuated in a defined manner.

[0022] The control element-specific data set preferably differs from the generic data set. The generic data set is determined, for example, based on a large number of similar control elements, preferably by averaging over the control element-specific data sets of these control elements. Preferably, a plurality of control elements is provided and each of the control elements is calibrated, with a control element-specific data set being created and stored in the corresponding control element. The generic data set is subsequently determined from this plurality of control element-specific data sets and stored in the control unit. The generic data set therefore already represents a good approximation of the control element-specific data set of the control element and can accordingly be used, at least temporarily, as a calibration data set to enable the operation of the braking system.

[0023] The generic data set is preferably permanently stored in the control unit, meaning it is not changed or overwritten even when the control element-specific data set is transferred. This ensures that, for example, if the control element is replaced with another control element, the generic data set is also available for operating the braking system with the other control element. In other words, the generic data set is preferably permanently stored in the control unit.

[0024] The identifier preferably has a smaller data volume than the control-element-specific data set. Accordingly, the identifier is transmitted to the control unit more quickly than the control-element-specific data set. This enables rapid commissioning of the braking system and the control element. The data volume of the identifier is preferably at most 10%, at most 5%, or at most 1% of the data volume of the control-element-specific data set. The identifier preferably consists of at most a few bits, in particular at most 16 bits, at most 8 bits, or at most 4 bits. The identifier and / or the control-element-specific data set is transmitted to the control unit, for example, via a data bus, in particular via a SENT bus, preferably via its slow channel.

[0025] In a preferred embodiment, it is also provided that several generic data sets are stored in the control unit. Each of these generic data sets is assigned to one of several different values ​​of the identifier. After the identifier stored in the control element has been transmitted to the control unit, a check is carried out to determine whether a generic data set is stored for the transmitted identifier or its value. If this is the case, the compatibility check is successful, and the control element is configured. The generic data set stored in the control unit, which is assigned to the transmitted identifier, is used as the calibration data set, and the process continues as described above.

[0026] The described procedure enables rapid commissioning of the braking system and reliable operation. In particular, the expected functionality of the braking system is achieved promptly after the control element is installed, namely based on the generic data set.

[0027] A further development of the invention provides that an identifier stored in the control element is transmitted to the control unit and compared there with a stored identifier. If there is a difference between the transmitted identifier and the identifier stored in the control unit, the control element is configured. The identifier is stored in the control element in addition to the identification.

[0028] The identification can be specific to a control element and can be represented, for example, as the serial number of the control element. When manufacturing multiple control elements, different serial numbers are preferably assigned to each control element so that the control element can be clearly identified. However, the identification can also be identical for several control units, particularly for only some of the control units, and can be represented, for example, as a part number. Differently designed control elements have different part numbers, while the part numbers of identical control elements are also identical.

[0029] The code allows the braking system to easily determine whether the control element has been replaced. For this purpose, the code stored in the control element is transmitted to the control unit. There, it is compared with the stored code. If the transmitted code differs from the stored code, it is assumed that the control element has been replaced. In this case, and preferably only in this case, the control element is configured.

[0030] Particularly preferred is the identification stored in the control element transmitted to the control unit only if there is a difference between the transmitted identification number and the identification number stored in the control unit, where it is used for the compatibility check. This means that the compatibility check is only performed if the transmitted identification number differs from the identification number stored in the control unit. If the transmitted identification number corresponds to the identification number stored in the control unit, the control element is not configured, the compatibility check is not performed, and / or the identification is not transmitted.

[0031] The identification code preferably has only a small amount of data; for example, its data volume is at most as large as the data volume of the identification code, or larger than the data volume of the identification code by a factor of at most 2, at most 4, or at most 8. Such a procedure enables efficient checking for a replacement of the control element. Preferably, after setup, in particular immediately after the control element-specific data set is transmitted to the control unit, the transmitted identification code is stored in the control unit and subsequently used for comparison with the transmitted identification code.

[0032] A further development of the invention provides that the use of the control-element-specific data set occurs by overwriting the calibration data set with the control-element-specific data set or by switching from the calibration data set to the control-element-specific data set. During the overwriting process, the control-element-specific data set is written to a memory area of ​​the control unit's data memory in which the calibration data set is already present. Otherwise, after transfer, the calibration data set and the control-element-specific data set are located in different address areas of the data memory, and switching is performed from the address area of ​​the calibration data set to the address area of ​​the control-element-specific data set in order to subsequently use the control-element-specific data set as the calibration data set. Such a procedure enables efficient integration of the control-element-specific data set.

[0033] A further development of the invention provides for a warning signal to be generated during the compatibility check and / or during setup. The warning signal serves to indicate to the driver of the motor vehicle and / or a device of the motor vehicle other than the braking system that the braking system may not be fully functional and that functional limitations must be expected. The generation of the warning signal ensures the safe operation of the braking system or the motor vehicle.

[0034] A further development of the invention provides that if the compatibility test fails, an error signal is generated and / or the control element is taught. If the compatibility test fails, it is determined that the control element cannot be operated reliably within the braking system. The error signal is generated accordingly. Additionally or alternatively, if the compatibility test fails, the control element is taught. Teaching means that the calibration data set is written into the control unit, for example, externally.

[0035] During the programming of the control element, the control unit is parameterized in such a way that the control element can be used to perform the intended operation of the braking system. The calibration data set is written into the control unit, for example, using a device that is only temporarily connected to the control unit, such as a mobile device. The device is preferably only temporarily connected to the control unit, in particular via a data bus. Before the motor vehicle or the braking system is started, the connection between the external device and the control unit is interrupted.

[0036] The described procedure allows the operation of a control element within the braking system for which the compatibility test has not been successfully completed. However, this requires more effort than for a control element for which the compatibility test can be successfully completed.

[0037] A further development of the invention provides that the warning signal and / or the error signal are suppressed for a specific period of time, in particular immediately following the start of operation of the braking system. Suppressing the warning signal or the error signal results in the respective signal not being visible externally. The control unit thus has the same external state as if the warning signal or the error signal were not generated. The warning signal and / or the error signal are suppressed for the specific period of time, for example, for at least 1 second and at most 30 seconds, at least 5 seconds and at most 20 seconds, or approximately or exactly 10 seconds or 15 seconds. The period preferably begins when the braking system starts operating, i.e., as soon as voltage is applied to terminal 15 of the motor vehicle. This suppresses unnecessary warning messages or error messages.

[0038] A further development of the invention provides that the warning signal and / or the error signal are displayed by means of a display device. The display device serves to display the warning signal or the error signal, preferably in the interior of the motor vehicle and / or for the driver of the motor vehicle. The display device is, for example, a visual or acoustic display device. In particular, the warning signal is indicated by a yellow light and the error signal by a red light. This ensures a reliable warning of a possible impairment of the operation of the braking system.

[0039] A further development of the invention provides that, within the scope of the compatibility check, the identifier is used as an input variable for a characteristic map or a table which has a compatibility characteristic as an output variable, wherein the compatibility check is classified as successful if the determined compatibility characteristic is at a first value and as failed if the determined compatibility characteristic is at a second value. The characteristic map or table is stored in the control unit. The transmitted identifier is evaluated using the characteristic map or table; it accordingly serves as the input variable. The compatibility characteristic results from the characteristic map or table as the output variable. The compatibility characteristic is therefore available as a function of the identifier and is determined from the identifier using the characteristic map or table.

[0040] Preferably, the map or table contains only two different values ​​for the compatibility parameter, namely the first value and the second value. If the map or table yields the first value for the compatibility parameter using the identifier as the input variable, it is assumed that the control element is compatible, and the compatibility check is accordingly successful. If, however, the second value is present, the control element is classified as incompatible, and the compatibility check fails. This allows for a simple check of the control element's compatibility.

[0041] A further development of the invention provides that the control unit is a first control unit and, in addition to the first control unit, there is a second control unit that operates analogously to the first control unit. The first control unit and the second control unit are designed or operated redundantly to ensure high reliability and safety of the braking system. Preferably, the first control unit and the second control unit are connected to the control element separately from one another, and the identifier is transmitted from the control element to each of the control units.

[0042] The compatibility check is also performed separately in each of the control units. Only if the compatibility check is successful in each of the control units is operation of the control element permitted using the control-element-specific data set as the calibration data set. Otherwise, the error signal is preferably generated. The control element preferably has several redundant sensors, with the control units connected to different redundant sensors of the control element. The redundant sensors each serve to detect the setting of the control element, for example, the position of the control element. This achieves the aforementioned reliability of the braking system.

[0043] The invention further relates to a braking system for a motor vehicle, in particular for carrying out a method according to the embodiments within the scope of this description, wherein the braking system has a service braking device and the service braking device is actuated to generate a braking force on a wheel axle of the motor vehicle at least temporarily as a function of a setting of an operating element.The braking system is provided and designed to generate the braking force as a function of the setting of the operating element using a calibration data set stored in a control unit of the braking system, wherein an identifier stored in the operating element is transmitted to the control unit and used there for a compatibility check and, if the compatibility check is successful, the operating element is set up by using a generic data set stored in the control unit as the calibration data set and by transmitting an operating element-specific data set stored in the operating element to the control unit and, after transmission, using this data set as the calibration data set.

[0044] The advantages of such a procedure or such a design of the braking system have already been pointed out. Both the braking system and the method for its operation can be further developed according to the explanations in this description, so reference is made to these in this regard.

[0045] The invention will be explained in more detail below with reference to the exemplary embodiments shown in the drawings, without limiting the invention. The sole Figure 1 a schematic representation of a braking system for a motor vehicle.

[0046] The Figure 1shows a highly schematic representation of a braking system 1 for a motor vehicle. The braking system 1 has a service brake device 2, which in turn has a first control unit 3 and a second control unit 4. The control units 3 and 4 are each connected to a brake actuator 5 and 6, respectively, by means of which wheel brakes 7 can be controlled to generate a braking force on a wheel or wheel axle of the motor vehicle. The control units 3 and 4 are interconnected via a data bus 8. They communicate via the data bus 8 to realize redundant operation. Accordingly, a high level of operational reliability of the braking system 1 is achieved.

[0047] The control units 3 and 4 are connected to an operating element 11 via further data buses 9 and 10, in particular purely electrically. In the exemplary embodiment shown here, the operating element 11 is in the form of a brake pedal. It has a foot pedal 12, by means of which a driver of the motor vehicle can specify a braking force. This specified braking force can also be referred to as the preset braking force. The preset braking force is only determined in the control unit 3 or 4. A setting of the operating element 11, for example a position of the operating element 11 or the foot pedal 12, is initially transmitted via the data bus 9 or 10. From this position, the preset braking force is determined in the control unit 3 or 4 using a calibration data set, and the respective brake actuator 5 or 6, and thus the wheel brakes 7, are controlled to achieve an actual braking force corresponding to the preset braking force.

[0048] The calibration data set is stored in the respective control unit 3 or 4. It is tailored to the respective control element 11. When the control element 11 is first put into operation, a control element-specific data set stored in the control element 11 is transmitted to the control unit 3 or 4 and, after transmission, is used as the calibration data set. In order to enable reliable and safe operation of the braking system 1 even before the control element-specific data set is completely transmitted to the control unit 3 or 4, an identifier also stored in the control element 11 is transmitted to the control unit 3 or 4 before the control element-specific data set is transmitted. The control unit 3 or 4 uses the identifier to perform a compatibility check.

[0049] If the compatibility check shows that the control element 11 is compatible with the braking system 1, the compatibility check is successful and the control element is set up. Setting up the control element 11 involves transferring the control element-specific data set to the control unit 3 or 4. After the transfer is complete, the control element-specific data set is used as the calibration data set. However, until the transfer is complete, i.e., until the transfer is completed, a generic data set is used as the calibration data set. The generic data set is designed in such a way that it enables a reliable and accurate determination of the specified braking force for a plurality of control elements 11 from the setting of the respective control element 11.

[0050] If the identifier transmitted to control unit 3 or 4 determines that the control element 11 is incompatible, an error signal is generated. Additionally or alternatively, the control element is taught, during which the calibration data set is stored in control unit 3 or 4, in particular by transmission from an external device. This can occur, for example, during vehicle maintenance or a visit to the workshop. The described procedure ensures safe and reliable operation of the brake system 1 in all cases. LIST OF REFERENCE SYMBOLS:

[0051] 1Brake system 2Service brake device 3First control unit 4Second control unit 5Brake actuator 6Brake actuator 7Wheel brake 8Data bus 9Data bus 10Data bus 11Control element 12Foot pedal

Claims

1. Method for operating a brake system (1) for a motor vehicle, wherein the brake system (1) has a service brake device (2) and a control for the service brake device (2) for generating a braking force on a wheel axle of the motor vehicle, performed at least temporarily as a function of an adjustment of a control element (11), characterized in that the generation of the braking force as a function of the adjustment of the control element (11) is performed using a calibration data set stored in a control device (3) of the brake system (1), wherein an identifier stored in the control element (11) is transmitted to the control device (3) and is used there for a compatibility check and, in the case of a successful compatibility check, setup of the control element (11) is performed by a generic data set stored in the control device (3) being used as a calibration data set, as well as a control element-specific data set stored in the control element (11) being transmitted to the control device (3) and being used as a calibration data set after transmission.

2. Method according to claim 1, characterized in that an identifier stored in the control element (11) is transmitted to the control device (3) and is compared there with a stored identifier, wherein, in the case of a difference between the transmitted identifier and the identifier stored in the control device (3), setup of the control element (11) is performed.

3. Method according to any of the preceding claims, characterized in that use of the control element-specific data set is performed by the calibration data set being overwritten with the control element-specific data set or being switched from the calibration data set to the control element-specific data set.

4. Method according to any of the preceding claims, characterized in that a warning signal is generated during the compatibility check and / or during setup.

5. Method according to any of the preceding claims, characterized in that in the case of a failed compatibility check, an error signal is generated and / or learning of the control element (11) is performed.

6. Method according to any one of claims 4 and 5, characterized in that the warning signal and / or the error signal are disabled for a certain period of time.

7. Method according to any one of claims 4 and 5, characterized in that the warning signal and / or the error signal are displayed by means of a display device.

8. Method according to any of the preceding claims, characterized in that, as part of the compatibility check, the identifier is used as an input variable for a characteristic diagram or a table, which has a compatibility parameter as an output variable, wherein the compatibility check is considered successful with a first value of the determined compatibility parameter and failed with a second value.

9. Method according to any of the preceding claims, characterized in that the control device (3) is a first control device (3) and, in addition to the first control device (3), there is a second control device (4), which is operated in the same way as the first control device (3).

10. Brake system (1) for a motor vehicle, in particular for implementing the method according to one or more of the preceding claims, wherein the brake system (1) has a service brake device (2) and a control for the service brake device (2) for generating a braking force on a wheel axle of the motor vehicle, performed at least temporarily as a function of an adjustment of a control element (11), characterized in that the brake system (1) is provided and designed to perform the generation of the braking force as a function of the adjustment of the control element (11) using a calibration data set stored in a control device (3) of the brake system (1), wherein an identifier stored in the control element (11) is transmitted to the control device (3) and used there for a compatibility check and, in the case of a successful compatibility check, setup of the control element (11) is performed by a generic data set stored in the control device (3) being used as a calibration data set, as well as a control element-specific data set stored in the control element (11) being transmitted to the control device (3) and being used as a calibration data set after transmission.