Method for operating brake of motor vehicle, brake system and storage medium

Abstract

The invention relates to a method for operating a brake of a motor vehicle, the brake having an actuator which is moved along a path into a plurality of positions, a braking torque travel characteristic curve being recorded during a movement of the motor vehicle and used to hold the motor vehicle in a parked state. The invention also relates to an associated brake device and to an associated storage medium.

Description

[0001] The invention relates to a method for operating the brakes of a motor vehicle, to an associated brake system and to an associated storage medium.

[0002] Brakes are typically used in motor vehicles in order to decelerate the motor vehicle in a targeted manner and / or to hold the motor vehicle in a parked state in a reliable manner. Brakes typically generate a braking torque which leads to a deceleration of the vehicle and / or to holding the vehicle in a parked state. However, it has proven difficult to operate the brakes in a parked state in such a way that they are held reliably and without the need for reapplication / subsequent adjustment.

[0003] An object of the present invention is to provide a method for operating the brakes of a motor vehicle, which method is performed in an alternative or superior manner to the known embodiments. In addition, an object of the present invention is to provide an associated braking device. In addition, an object of the present invention is to provide an associated storage medium.

[0004] According to the invention, these objects are achieved by a method, a brake device and a storage medium according to the respective independent claims. Advantageous developments can be found, for example, in the respective dependent claims. The contents of the claims are incorporated into the contents of the description by explicit reference.

[0005] The invention relates to a method for operating a brake of a motor vehicle. The brake has an actuator which moves along a path to a plurality of positions and generates a braking torque depending on the position. The method comprises the following steps:

[0006] - recording a braking torque-travel characteristic curve of the brake during driving of the motor vehicle,

[0007] - in order to keep the motor vehicle parked with a specified braking torque,

[0008] - determining the position corresponding to the specified braking torque with the aid of the recorded braking torque-travel characteristic curve,

[0009] -Move the actuator to the corresponding position.

[0010] By means of the procedure described in this document, a braking torque-travel characteristic curve can be recorded using typical service brake operations. Such service brake operations are regularly performed during typical operation of a motor vehicle. The braking torque-travel characteristic curve obtained can then be used to move to a suitable position of the actuator when the vehicle is stationary, without the need for separate measurements for this purpose. It can thus be ensured that the brake is able to apply the required braking torque after the actuator has been moved to this position.

[0011] In particular, the brake can be considered as a component of the motor vehicle. However, in principle, the brake is a component which is contained in the motor vehicle and can also be independently actuated. The path can be specified, for example, along a straight section. For example, a braking torque-travel characteristic curve can assign a corresponding braking torque to each position or a plurality of positions along the path. The braking torque is typically measured, for example, in a support. Positions can also be assigned to braking torques. The braking torque-travel characteristic curve can be given in particular in table form or as a function.

[0012] In the exemplary embodiments described in this document, it is advantageously possible to dispense with the measurement of the braking torque while the motor vehicle remains parked.

[0013] In particular, the braking torque-travel characteristic curve can be recorded during a service brake operation. Thus, it is not necessary to read out an additional braking process in order to record only the braking torque-travel characteristic curve. Service brake operations are typically used to decelerate a motor vehicle due to general traffic conditions, road traffic regulations or dangerous situations. Service brake operations occur regularly during the travel of a motor vehicle, in particular in public places. The service brake operation can be triggered in particular by the driver pressing the brake pedal or by a driver assistance function requesting a brake operation.

[0014] The vehicle can be kept parked, in particular in response to activation of the parking brake function. This can be triggered, for example, by means of a switch or button. This allows the driver to typically indicate that the vehicle is to be parked, that is, that the vehicle movement is temporarily not desired.

[0015] In particular, the specified braking torque can be determined based on the operating state of the vehicle. For example, this allows factors such as load, ground gradient, temperature or wear of the brakes to be taken into account.

[0016] In particular, the braking torque-stroke characteristic curve can be recorded at specified time intervals and / or according to specified operating states. For example, after a predetermined time interval has elapsed, it is always possible to wait until the next service brake operation is triggered, and then the braking torque-stroke characteristic curve can be recorded for this service brake operation. The braking torque-stroke characteristic curve can also be recorded in a targeted manner under different operating states, for example at different temperatures or under different load conditions. This can be taken into account accordingly when moving to a position for keeping the motor vehicle in a parked state. For example, a braking torque-stroke characteristic curve can be used to keep the motor vehicle in a parked state, which braking torque-stroke characteristic curve was recorded under equivalent operating parameters, for example at the same temperature or at a temperature within a predetermined range around the current temperature.

[0017] In particular, it can be provided that no re-action takes place after the movement to the corresponding position while the motor vehicle is held in the parked state. The process described in this document can be used to ensure that sufficient braking force is available to keep the motor vehicle in the parked state. This means that re-action can be omitted. In particular, no means for re-action can be provided, which, for example, require additional sensors and / or monitoring functions.

[0018] In particular, the braking torque can be measured by means of a braking force sensor. The braking force sensor can be located, for example, in a support of a drum brake. In particular, the position can be measured by means of a position sensor, in particular a motor position sensor. This allows the position to be adjusted in a targeted manner. As an alternative, the position can also be deterministically derived, for example, from the number of revolutions of the electric motor.

[0019] In particular, the actuator can be an electromagnetic actuator. This has proven to be advantageous for typical applications. However, other types of actuators can also be used.

[0020] The invention further relates to a brake system for a motor vehicle. The brake system has an actuator and an electronic control device, which is configured to carry out the method as described in this document. With regard to the method, reference may be made to all embodiments and variants described.

[0021] The invention further relates to a non-volatile computer-readable storage medium comprising a program code which, when executed, causes a processor to perform the method as described in this document. With regard to this method, reference may be made to all embodiments and variants described in this document.

[0022] The method described in this document may in particular be used for an electromechanical drum brake.The brake device may in particular be an electromechanical drum brake.

[0023] In other words, the motor current can be used in particular to control the electromechanical parking brake. The motor current typically shows a correlation with the expansion force. Due to efficiency fluctuations / effective coefficient fluctuations in the transmission device, a large dispersion / discreteness can occur when determining the expansion force based on the motor current. Generally, the expansion force is required and the estimated friction coefficient is used to determine the maximum possible braking torque, which should be greater than the required downhill torque in order to safely hold the vehicle. There can be a very high degree of dispersion in the set braking torque, from the motor current, via the expansion force and then to the braking torque. This can lead to overloading of components or to the need to increase the robustness of components.

[0024] The embodiments described in this document can be used in particular for identifying parking brake actuations of electromechanical drum brakes. The increase in the number of sensors can in particular allow new possible solutions, for example in order to reduce the uncertainty of known electric parking brake systems in ensuring that the vehicle is parked, and to avoid the disadvantages of increased loads.

[0025] In particular, in the case of electromechanical drum brakes, which have a braking torque measuring device and generally a motor position sensor, a motor position / braking torque characteristic curve can be generated. This can be regarded as a synonym for the braking torque travel characteristic curve. The parking brake actuation can be based on the travel braking torque characteristic curve. This can also be regarded as a synonym for the braking torque travel characteristic curve.

[0026] The braking torque-based position control of the parking brake offers the following advantages in particular: increased hill-holding reliability, no need for force tip compensation and the associated reduction in software expenditure, avoidance of system overstressing by more precise control with reduced load distribution, reduced robustness requirements at increased cycle times, and a wide range of diagnostic possibilities.

[0027] A person skilled in the art will derive further features and advantages from the exemplary embodiments described below with reference to the accompanying drawings, in which:

[0028] Figure 1 shows a braking device,

[0029] Figure 2 Shows Figure 1 Another view of the brake system,

[0030] Figure 3 shows the braking torque stroke characteristic curve,

[0031] Figure 4 A block diagram is shown.

[0032] Figure 1 A brake system BA is shown with a drum brake TB and a control device SV. The control device SV is configured to carry out the method according to the invention according to one embodiment. This will be discussed in more detail later.

[0033] A drum brake TB is to be understood to mean in particular a service brake having a parking brake function.

[0034] The drum brake TB has a back plate a on which brake shoes b, c are mounted. These brake shoes are arranged in a brake drum f. The drum brake TB also has an expansion unit g, which presses the brake shoes b, c against the inner side of the brake drum f. The reaction forces of the brake shoes b, c are supported here on supports d, e. These supports are equipped with force sensors, as a result of which the braking torque can be determined by calculating the two variables supplied by the force sensors.

[0035] Figure 2 A plan view of a drum brake TB is shown. It can be seen that the drive expansion unit g has an actuator h, which in turn has a motor position sensor i. By way of example, the actuator h is designed as an electrically commutated brushless DC motor.

[0036] The measurement of the braking torque is a prerequisite for the further method steps disclosed in this document and can also be carried out in other ways, for example.

[0037] By measuring the two variables braking torque and motor position, a motor position braking torque characteristic curve, also called braking torque travel characteristic curve, can be determined during application of the service brake (while the vehicle is in motion). This can be calibrated continuously, in particular during service brake operation, since the characteristic curve can change due to wear and changes in the friction coefficient. The characteristic curve determined while the vehicle is in motion represents the boundary cases / limiting cases in the braking torque travel characteristic curve, in which a unique braking torque is generated depending on the motor position. This is, for example, Figure 3 This applies to the current conditions (wear, friction coefficient) for the maximum possible braking torque at a given position. In the parking state (stationary), this relationship no longer exists, since the braking torque generated by the brake is only as high as the load torque acting from the outside (especially downhill torque). The braking torque generated in the parking state is therefore not influenced by the motor position as long as the current conditions are below the limiting characteristic curve. This area is Figure 3 It is called "safe hold".

[0038] If the braking torque required for safe holding in the respective situation is clearly defined for the vehicle, the corresponding motor position is therefore also known. This can be adjusted via the motor position controller so that the parking brake permanently holds this position in the case of a power failure.

[0039] The braking torque-travel characteristic allows the prediction of a safely maintained braking torque. In this method, a re-action strategy is usually no longer necessary. In particular, overstressing of the system is prevented due to the precise prediction and activation.

[0040] By measuring the motor position, braking torque and current, the system can be checked, which results in a diagnostic capability. In this way, for example, the efficiency can be inferred in the event of an excessively high current demand.

[0041] Figure 4 A block diagram of the method is shown. In the figure, firstly the calibration during a service brake operation is shown at the top. The torque sensor and the motor position sensor are used to determine the Figure 3 The characteristic curve is similar to the characteristic curve of and distributes the braking torque to the corresponding motor position (also called stroke).

[0042] The function of the parking brake is shown in the box below. First, a target torque is specified, which ultimately represents the desired maximum braking torque for keeping the vehicle in a parked state. A setpoint motor position is determined based on the characteristic curve further determined above. The setpoint motor position is supplied to a controller, which in turn controls an actuator. In particular, the actuator can be in the form of an electric motor. The actuator is monitored by a motor position sensor, which provides an input variable to the controller. In the event that the setpoint motor position is reached, the vehicle is in a safe state.

[0043] Overall, the process described in this document can save effort and still ensure that the motor vehicle remains safely parked.

[0044] The steps mentioned in the method according to the invention can be performed in the specified order. However, as far as technically feasible, these steps can also be performed in a different order. The method according to the invention can be performed in one of its embodiments, for example by a specific group of steps, so that other steps are not performed. However, in principle, other steps can also be performed, even steps not mentioned.

[0045] It should be noted that in the claims and the specification, feature combinations may be described, for example to facilitate understanding, but these features can also be used separately from each other. Those skilled in the art will recognize that these features independent of each other can also be combined with other features or feature combinations.

[0046] The dependent references in the dependent claims may characterize preferred combinations of the respective features, but do not exclude other combinations of features.

[0047] List of Reference Numerals

[0048] BA Braking Systems

[0049] TB drum brake

[0050] SV Control Unit

[0051] a Back panel

[0052] b, c brake shoe

[0053] d.e Support

[0054] f Brake drum

[0055] g Expansion unit

[0056] h Actuator

[0057] i Motor position sensor

Claims

1. A method for operating a brake (TB) of a motor vehicle, The brake (TB) has an actuator (h) which moves along a path to a plurality of positions and generates a braking torque depending on the position, The method comprises the following steps: - recording a braking torque-travel characteristic curve of a brake (TB) during driving of the motor vehicle, - in order to keep the motor vehicle parked with a specified braking torque, - determining the position corresponding to the specified braking torque with the aid of the recorded braking torque-travel characteristic curve, -Move the actuator (h) to the corresponding position.

2. The method according to claim 1, wherein a braking torque-travel characteristic curve is recorded during a service brake operation.

3. A method according to any one of the preceding claims, - wherein the vehicle is maintained in a parked state in response to activation of the parking brake function.

4. A method as claimed in any one of the preceding claims, - wherein the specified braking torque is determined based on the operating state of the vehicle.

5. A method as claimed in any one of the preceding claims, -in, The braking torque-travel characteristic curve is recorded at defined time intervals and / or according to defined operating states.

6. A method as claimed in any one of the preceding claims, - wherein no re-action takes place after the movement into the corresponding position while the motor vehicle remains in the parked state.

7. A method as claimed in any one of the preceding claims, wherein the braking torque is measured by means of a braking force sensor, and / or -in, The position is measured with the aid of a motor position sensor (i).

8. A method as claimed in any one of the preceding claims, -in, The actuator (h) is an electromagnetic actuator.

9. A braking system (BA) for a motor vehicle, the braking system comprising - an actuator (h), and - An electronic control unit (SV) configured to carry out the method as claimed in any one of the preceding claims.

10. A non-volatile computer-readable storage medium, the non-volatile computer-readable storage medium containing program code, which, when executed, causes a processor to perform the method of any one of claims 1 to 8.

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