Method for re-tensioning electromechanical parking brake device of vehicle
By diagnosing and optimizing the re-tightening process of the electromechanical parking brake device, the problem of reduced clamping force after high-temperature cooling was solved, achieving safe and reliable parking and efficient clamping force management.
Patent Information
- Application Number
- CN202510754157.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-06-10
- Filing Date
- 2025-06-06
- Publication Date
- 2025-12-12
AI Technical Summary
Electromechanical parking brakes reduce clamping force after cooling from high temperatures, leading to unsafe parking. Existing strategies may damage brake components or cause loss of clamping force, and there is a risk of locking failure when re-tightening.
By diagnosing and checking the operability of the parking brake system, it is only re-tightened when there is no fault. The clamping and locking of the brake pads are controlled by electromechanical actuators and locking devices. The clamping force is optimized by combining the hysteresis effect, and measures are taken to compensate for the loss of clamping force.
It minimizes the risk of clamping force loss, ensures parking safety, reduces mechanical load on braking components, and improves energy efficiency.
Smart Images
Figure CN121106147A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a method for retensioning an electromechanical parking brake device of a vehicle. BACKGROUND
[0002] Electromechanical brakes (EMB) usually have a very high efficiency and, due to their design, are to some extent self-inhibiting. The focus is on converting the electrical energy used to drive the EMB as efficiently as possible into braking energy and to reduce internal friction as much as possible so that in the event of a failure, i.e. when the EMB cannot be actively or electrically actuated, the service brake can apply pressure by means of the energy stored in the brake caliper.
[0003] However, since electromechanical brakes have a very low self-inhibiting capability, they must be equipped with an accessible locking device, for example a pawl, in order to achieve a parking brake. After the locking device has been accessed, the brake can be switched to a current-free state, since the applied clamping force is sufficient for parking.
[0004] However, this clamping force usually decreases, especially when the brake disc and the lining have a temperature of several hundred degrees Celsius at the time of parking. During the subsequent cooling to ambient temperature, the clamping force decreases in proportion to the length change and the system stiffness.
[0005] In order to enable the vehicle to be parked safely, the parking brake can be, for example, pressed with a higher clamping force so as to thereby ensure that a defined clamping force still exists even after the cooling process. The disadvantage here, however, is that the mechanical load acting on the brake components is higher, which can lead to the brake linings sticking to the brake disc at high temperatures.
[0006] Alternatively, the parking brake can be retensioned after a predetermined period of time after the vehicle has been parked in order to compensate for the decreasing clamping force. This strategy is gentler on the components than a strategy based on force increase, since an increase in force can be avoided. However, for electromechanical brakes, it must be ensured that the parking brake can be relocked after retensioning, otherwise there is a risk of further loss of clamping force. SUMMARY
[0007] It is an object of the present invention to provide a method for retensioning an electromechanical parking brake device with which the loss of clamping force when the parking brake device is retensioned can be minimized.
[0008] According to a first aspect of the present disclosure, a method for retensioning an electromechanical parking brake device of a vehicle is provided, wherein the electromechanical parking brake device has a first electromechanical brake and a second electromechanical brake, each electromechanical brake having a brake disc, at least one brake pad, an electromechanical actuator for pressing the at least one brake pad against the brake disc to generate a braking effect, and a locking device for locking the at least one brake pad in a state of being pressed against the brake disc, wherein the method comprises:
[0009] determining whether a retensioning of the first electromechanical brake is required,
[0010] if a retensioning is required, performing a diagnosis to check a retensioning operability of the parking brake device, and
[0011] only when no fault is identified within the framework of the diagnosis, retensioning the first electromechanical brake, wherein the retensioning comprises:
[0012] manipulating the locking device of the first electromechanical brake to unlock,
[0013] pressing the at least one brake pad of the first electromechanical brake against the brake disc of the first electromechanical brake by the electromechanical actuator of the first electromechanical brake with a predetermined force,
[0014] manipulating the locking device of the first electromechanical brake to lock the at least one brake pad of the first electromechanical brake in a state of being pressed against the brake disc of the first electromechanical brake.
[0015] According to the method, by performing a diagnosis to check a retensioning operability of the parking brake device before retensioning and only retensioning the first electromechanical brake when no fault is identified within the framework of the diagnosis, the risk of a loss of clamping force can be minimized.
[0016] Within the framework of the diagnosis, it can be checked, for example, whether the parking brake device is able to provide sufficient electrical power for the retensioning, whether an electrical short circuit is present or whether the parking brake device is free of mechanical faults. Furthermore, it can be provided that, for diagnosing the parking brake device, a profile of the electrical power supplied to the actuator or the behavior of the actuator itself is monitored.
[0017] The necessity of a retensioning can be determined, for example, depending on the brake temperature. Thus, for example, it can be expected that a loss of clamping force due to thermal contraction after parking of the vehicle can be expected starting from a predetermined brake temperature (about 200°C).
[0018] Before or during the re-tensioning of the first electromechanical brake, a residual clamping force between the at least one brake pad of the first electromechanical brake and the brake disc of the first electromechanical brake can be determined. For example, the residual clamping force can be determined from the electrical power supplied to the electromechanical actuator. The electromechanical actuator of the first electromechanical brake and / or of the second electromechanical brake can comprise, for example, an electric motor. For an electromechanical actuator designed in this way, the electrical power supplied to the electric motor can be increased until the shaft of the electric motor begins to rotate. The electrical power supplied can be used as an indicator of the residual clamping force.
[0019] After the re-tensioning of the first electromechanical brake, it can be checked whether the locking of the at least one brake pad of the first electromechanical brake was successful. For example, this check can be made with the aid of the electromechanical actuator. Here, the electromechanical actuator can be actuated to release the at least one brake pad from the brake disc, i.e. in the release direction. If the electrical power supplied exceeds a predetermined threshold value, the locking can be considered successful.
[0020] If the locking of the at least one brake pad of the first electromechanical brake is successful, the second electromechanical brake can subsequently be re-tensioned, wherein the re-tensioning of the second electromechanical brake can take place analogously to the re-tensioning of the first electromechanical brake, i.e. the re-tensioning can comprise:
[0021] actuating the locking device of the second electromechanical brake to release the locking of the second electromechanical brake,
[0022] pressing the at least one brake pad of the second electromechanical brake against the brake disc of the second electromechanical brake by means of the electromechanical actuator of the second electromechanical brake with a predetermined force,
[0023] actuating the locking device of the second electromechanical brake to lock the at least one brake pad of the second electromechanical brake in the state of being pressed against the brake disc of the second electromechanical brake.
[0024] If, however, the locking of the at least one brake pad of the first electromechanical brake is not successful, it can be provided that the electrical power supplied to the electromechanical actuator of the first electromechanical brake is first reduced, wherein the reduction of the electrical power takes place at such a rate of reduction that, due to a hysteresis, at least a predetermined residual clamping force remains between the at least one brake pad of the first electromechanical brake and the brake disc after the electrical power supply to the electromechanical actuator of the first electromechanical brake is switched off. In this way, it can be ensured that, despite the failed locking, a residual clamping force remains due to the hysteresis, in particular the hysteresis caused by internal friction. The electrical power can be reduced over a period of time of between one second and a few minutes. During this period of time, the brake continues to cool, which leads to an increase in the internal friction and thus to a higher residual clamping force.
[0025] Since the first and the second electromechanical brake are usually constructed similarly or identically and they therefore have a similar hysteresis behavior, conclusions about the residual clamping force of the second electromechanical brake can be drawn from the previously determined residual clamping force of the first electromechanical brake in order to be able to decide whether a retensioning attempt should be made on the second electromechanical brake after a lockup failure of the first electromechanical brake.
[0026] It can be provided here that the second electromechanical brake is retensioned if the residual clamping force determined between the at least one brake pad of the first electromechanical brake and the brake disc of the first electromechanical brake is smaller than the clamping force that would be expected due to hysteresis, wherein the retensioning can comprise:
[0027] the lockup device of the second electromechanical brake is actuated to release the lockup of the second electromechanical brake,
[0028] the at least one brake pad of the second electromechanical brake is pressed by the electromechanical actuator of the second electromechanical brake against the brake disc of the second electromechanical brake with a predetermined force,
[0029] the lockup device of the second electromechanical brake is actuated to lock the at least one brake pad of the second electromechanical brake in the state of being pressed against the brake disc of the second electromechanical brake.
[0030] If the residual clamping force in the first electromechanical brake is smaller than the clamping force that would be expected due to hysteresis, it is assumed that the residual clamping force in the second electromechanical brake is also smaller than the clamping force that would be expected due to hysteresis, so that the risk of a failed retensioning attempt of the second electromechanical brake can be accepted, because even in the case of a failed retensioning attempt the clamping force will be higher due to hysteresis than previously.
[0031] It can also be checked here whether the lockup of the at least one brake pad of the second electromechanical brake was successful.
[0032] If the lockup of the at least one brake pad of the second electromechanical brake was not successful, the electrical power supplied to the electromechanical actuator of the second electromechanical brake can be reduced, wherein the reduction of the electrical power takes place at a reduction rate such that, due to hysteresis, at least a predetermined residual clamping force remains between the at least one brake pad and the brake disc of the second electromechanical brake after the electrical power supply to the electromechanical actuator of the second electromechanical brake is switched off. The electrical power can be reduced over a period of time of between one second and a few minutes. During this period of time, the brake continues to cool, which leads to an increase in the internal friction and thus to a higher residual clamping force.
[0033] However, if it is determined that the residual clamping force determined between the at least one brake pad of the first electromechanical brake and the brake disc is not smaller than the clamping force that can be expected due to hysteresis, it can be provided that the second electromechanical brake is not re-tensioned, because here a re-tensioning attempt that fails would lead to or face a loss of clamping force.
[0034] Furthermore, further measures can also be taken to compensate for or prevent a loss of clamping force. For example, assuming that the first electromechanical brake and the second electromechanical brake described above are provided at the rear wheels of the vehicle, the residual clamping force of the brakes at the front axle can also be increased in order to ensure standstill. To this end, the clamping force at the front axle is significantly greater than the residual braking torque. The clamping force is then slowly reduced, so that an increased clamping force is achieved due to internal friction (hysteresis).
[0035] If the procedure is carried out only a few minutes after reaching the standstill state, not only can a loss of clamping force be compensated for (by length changes caused by heat), but also the "cooled" electromechanical brake can be utilized, which has a slightly worse efficiency and increases the residual clamping force compared to a hot brake.
[0036] The re-tensioning of the electromechanical brake at the front axle can already be carried out before the re-tensioning at the rear axle in order to provide the highest possible residual clamping force reserve in the "vehicle" system.
[0037] Furthermore, for reasons of energy efficiency, it can be provided that the electromechanical brake at the front axle is only re-tensioned if an error occurs in the re-tensioning process at the rear axle.
[0038] It can also be considered to re-tension the electromechanical brake at the front axle, in particular when the vehicle is parked on a very steep slope (e.g. slope > 20%). This can be done independently of the estimated or measured temperature of the brake system. For situations in which the road friction coefficient can be slightly lower, the holding capacity is further increased.
[0039] According to a second aspect of the present disclosure, a parking brake device is provided, the parking brake device comprising a first electromechanical brake and a second electromechanical brake, each electromechanical brake having a brake disc, at least one brake pad, an electromechanical actuator for pressing the at least one brake pad against the brake disc to produce a braking effect, a locking device for locking the at least one brake pad in a state pressed against the brake disc, and a control device for carrying out the method described above. BRIEF DESCRIPTION OF DRAWINGS
[0040] The application will be explained in more detail below with reference to the drawings.
[0041] Figure 1 is a schematic illustration of an electromechanical parking brake device.
[0042] Figure 2is a diagram showing the relationship between the control current of an electromechanical brake and the clamping force.
[0043] Figure 3 is a diagram of the actuation of electromechanical brakes at parking and retensioning.
[0044] Figure 4 is a flow chart of an exemplary method for retensioning electromechanical parking brake devices. DETAILED DESCRIPTION
[0045] Figure 1 is a schematic diagram of an electromechanical parking brake device 100. The parking brake device 100 has a first electromechanical brake 102, a second electromechanical brake 104 and a control device 106 for actuating the first electromechanical brake 104 and the second electromechanical brake 106. The control device 106 can be in data exchange connection with the first electromechanical brake 102 and the second electromechanical brake 104 via associated data lines 108-1, 108-2. The first electromechanical brake 102 and the second electromechanical brake 104 can be arranged, for example, on the same axle, for example the rear axle, of a vehicle.
[0046] The first electromechanical brake 102 has a brake disc 102-1, a brake pad 102-2, an electromechanical actuator 102-3 for pressing the brake pad 102-2 against the brake disc 102-1 to produce a braking effect, and a locking device 102-4 for locking the brake pad 102-2 in a state in which it is pressed against the brake disc 102-1. The electromechanical actuator 102-3 can have, for example, an electric motor and possibly a rotary / translation transmission for converting the rotary motion of the electric motor into a translational motion of the brake pad 102-2. The locking device 102-4 can have, for example, a pawl or be configured as a pawl.
[0047] The second electromechanical brake 104 can be configured similarly or identically to the first electromechanical brake 102. The second electromechanical brake 104 has a brake disc 104-1, a brake pad 104-2, an electromechanical actuator 104-3 for pressing the brake pad 104-2 against the brake disc 104-1 to produce a braking effect, and a locking device 104-4 for locking the brake pad 104-2 in a state in which it is pressed against the brake disc 104-1. The electromechanical actuator 104-3 can have, for example, an electric motor and possibly a rotary / translation transmission for converting the rotary motion of the electric motor into a translational motion of the brake pad 104-2. The locking device 104-4 can have, for example, a pawl or be configured as a pawl.
[0048] Figure 2is a diagram showing the relationship between the actuation current and the clamping force in the first electromechanical brake 102 and the second electromechanical brake 104. Purely by way of example, Figure 2 and Figure 3 The description of the embodiments only relates to the first electromechanical brake 102. However, the embodiments are likewise applicable analogously to the second electromechanical brake 104.
[0049] In Figure 2 , a diagram is plotted of the current I supplied to the electromechanical actuator 102-3 in relation to the clamping force F between the brake disc 102-1 and the brake pad 102-2.
[0050] As shown in Figure 2 , the current I must first be increased to a threshold value I thr in order to overcome the internal friction in the actuator 102-3.
[0051] An increase in the current beyond the threshold value I thr causes an increase in the force in the actuator 102-3, as shown by the arrow marked 1, until the target clamping force F z is reached.
[0052] If the current I is reduced after the target clamping force F z is reached, the target clamping force F z is initially maintained, as shown by the arrow marked 2.
[0053] If the current I is further reduced, as shown by the arrow marked 3, the clamping force F is reduced to a residual clamping force F R , which depends, inter alia, on the speed at which the current is reduced. If the current I is reduced over a period of approximately one second to a few minutes, a considerable residual clamping force F R can be maintained, which is sufficient to be able to brake the vehicle. If, however, no residual clamping force is required, for example when driving is imminent, the current I can be reduced quickly, or a target acceleration in the release direction can be achieved by electrical actuation, thereby resulting in a coasting phase in the currentless state, as shown by the arrow 4.
[0054] Figure 3 An exemplary actuation of the first electromechanical brake 102 and the second electromechanical brake 104 is shown when parking and retensioning. For the sake of simplicity, only reference is made here to the first brake 102.
[0055] As shown in Figure 2 , the current I must first be increased to a threshold value I thr in order to overcome the internal friction in the actuator 102-3.
[0056] An increase in the current beyond the threshold value I thrThis will cause the force in actuator 102-3 to increase, as indicated by the arrow with reference number 11, until the target clamping force F z .
[0057] If the target clamping force F z is reached, the brake pad 102-2 is locked by the locking device 102-4 (in the state shown with reference number 12). The target clamping force F z may for example be 10 kN.
[0058] Due to the locking, no power needs to be supplied to the actuator 102-3 to maintain the clamping force. Therefore, the power supply can be stopped, i.e. the current supplied to the actuator 102-3 is reduced, as indicated by arrow 13, to approximately zero.
[0059] However, due to thermal relaxation, the clamping force will decrease, as indicated by arrow 14. The higher the temperature of the brake disc 102-1 and the brake pad 102-2 at the time of locking, the greater the decrease in clamping force.
[0060] To counteract the decrease in clamping force, a retensioning can be performed. At retensioning, the current I must be increased until the clamping force starts to increase again (arrow 15). A further increase in current will cause the force in the actuator to increase accordingly (arrow 16). If the target clamping force F z is reached, the locking is performed again.
[0061] However, retensioning carries the risk of loss of clamping force, especially in the event of an electrical or mechanical failure. Therefore, a retensioning strategy is required which minimizes the risk of loss of clamping force at retensioning.
[0062] Figure 4 A flowchart of an exemplary method 200 for retensioning the parking brake device 100 is shown, by which the risk of loss of clamping force can be minimized.
[0063] The method 200 starts (202) after the vehicle has been parked and the parking brake device 100 has been activated.
[0064] Subsequently, it is determined in step 204 whether a retensioning of the first electromechanical brake 102 is required. The necessity of retensioning can for example be determined from the brake temperature. Thus, for example, based on the fact that from a predetermined brake temperature (approximately 200 °C) it can be expected that a loss of clamping force due to thermal contraction will occur after the vehicle has been parked.
[0065] If it is determined in step 204 that no retensioning is required, the method is terminated (jump to 300).
[0066] If, however, it is determined in step 204 that a retensioning is required, a diagnosis is made to check the retensioning operability of the parking brake device 100. Within the framework of the diagnosis, it can first be checked whether the available voltage is sufficient (step 206). If it is determined that the available voltage is insufficient, the method is terminated (jump to 300).
[0067] If, however, it is determined that the available voltage is sufficient, it is checked in a subsequent step 208 whether an electrical fault is present, for example whether the line has a predetermined resistance. If it is determined that an electrical fault is present, the method is terminated (jump to 300).
[0068] According to the method 200, if a fault is identified within the framework of the diagnosis of steps 204 or 206, no retensioning is performed. The fault identified in these steps can result, for example, in the inability to relock after a successful establishment of the clamping force. Thus, by diagnosing and aborting the retensioning of the brake when a fault is determined within the framework of the diagnosis, a loss of clamping force can be prevented in a simple and effective manner.
[0069] The two tests according to steps 204 and 206 are merely examples. Of course, the diagnosis can be more extensive. Thus, for example, it can also be checked whether a mechanical fault is present.
[0070] If it is determined within the framework of the diagnosis that no fault is present, the first electromechanical brake 102 is retensioned (step 210), wherein the retensioning comprises:
[0071] the locking means 103-4 of the first electromechanical brake 102 are actuated to unlock,
[0072] the electromechanical actuator 102-3 of the first electromechanical brake 102 is actuated to press the brake lining 102-2 of the first electromechanical brake 102 against the brake disc 102-1 of the first electromechanical brake 102 with a predetermined force, and
[0073] the locking means 102-4 of the first electromechanical brake 102 are actuated to lock the brake lining 102-2 of the first electromechanical brake 102 in the state of being pressed against the brake disc 102-1 of the first electromechanical brake 102.
[0074] Before or during the re-tensioning of the first electromechanical brake 102, a residual clamping force between the at least one brake pad 102-2 of the first electromechanical brake 102 and the brake disc 102-1 of the first electromechanical brake 102 can be determined (step 212). For example, the residual clamping force can be determined from the electrical power supplied to the electromechanical actuator 102-3. As mentioned before, the electromechanical actuator 102-3 can comprise, for example, an electric motor. In electromechanical actuators designed in this way, in order to determine the residual clamping force, the electrical power supplied to the electric motor can be increased until the shaft of the electric motor starts to rotate. The electrical power supplied can be used as an indicator for the residual clamping force.
[0075] After the re-tensioning of the first electromechanical brake 102, it can be checked whether the locking of the at least one brake pad 102-2 of the first electromechanical brake 102 was successful (step 214). For example, this check can be made with the aid of the electromechanical actuator 102-3. Here, the electromechanical actuator can be manipulated to release the at least one brake pad 102-2 from the brake disc 102-1, i.e. in the release direction. If the electrical power supplied exceeds a predetermined threshold value, the locking can be considered successful.
[0076] If the locking of the brake pad 102-2 of the first electromechanical brake 102 was successful, the second electromechanical brake can subsequently be re-tensioned (step 216), wherein the re-tensioning of the second electromechanical brake 104 can be carried out analogously to the re-tensioning of the first electromechanical brake 102, i.e. the re-tensioning can comprise:
[0077] manipulating the locking device 104-4 of the second electromechanical brake 104 to release the locking of the second electromechanical brake 104,
[0078] pressing the brake pad 104-2 of the second electromechanical brake 104 against the brake disc 104-1 of the second electromechanical brake 104 by the electromechanical actuator 104-3 of the second electromechanical brake 104 with a predetermined force,
[0079] manipulating the locking device 104-4 of the second electromechanical brake 104 to lock the at least one brake pad 104-2 of the second electromechanical brake 104 in the state of being pressed against the brake disc 104-2 of the second electromechanical brake 104.
[0080] However, if the locking of the brake lining 102-2 of the first electromechanical brake 102 is not successful, the power supplied to the electromechanical actuator 102-3 of the first electromechanical brake 102 can first be reduced (step 218), wherein the reduction of the power is performed at such a rate that, due to hysteresis, at least a predetermined residual clamping force remains between the brake lining 102-2 and the brake disc 102-1 of the first electromechanical brake 102 after the supply of power to the electromechanical actuator 102-3 of the first electromechanical brake 102 is switched off. This hysteresis behavior has been described previously by reference to Figure 2 Thereby it can be ensured that despite the locking failure, a residual clamping force remains due to hysteresis, in particular caused by internal friction. The power can be reduced over a period of time between one second and a few minutes. During this period of time, the brake continues to cool, which leads to an increase in internal friction and thus to a higher residual clamping force.
[0081] Since the first electromechanical brake 102 and the second electromechanical brake 104 are similarly or identically configured and thus have a similar hysteresis behavior, conclusions can be drawn about the residual clamping force of the second electromechanical brake 104 from the previously determined residual clamping force of the first electromechanical brake 102 in order to be able to decide whether a retensioning attempt should be made on the second electromechanical brake 104 after the locking failure of the first electromechanical brake 102.
[0082] Thus, after step 218, it can be checked whether the residual clamping force of the first electromechanical brake 102 is less than the clamping force that would be expected due to hysteresis (step 220).
[0083] If it is determined that the resulting residual clamping force between the brake lining 102-2 and the brake disc 102-1 of the first electromechanical brake 102 is not less than the clamping force that would be expected due to hysteresis, the second electromechanical brake 104 can not be retensioned, since a loss of clamping force would result or be threatened in this case when the retensioning attempt fails. The method 200 can be terminated in this case (jump to 300).
[0084] However, if it is determined in step 220 that the determined residual clamping force between the brake lining 102-2 of the first electromechanical brake 102 and the brake disc 102-1 of the first electromechanical brake 102 is less than the clamping force that would be expected due to hysteresis, the second electromechanical brake 104 can be retensioned, i.e. the method can continue with the previously described step 216.
[0085] If the residual clamping force in the first electromechanical brake 102 is smaller than the clamping force that can be expected due to hysteresis, it is assumed that the residual clamping force in the second electromechanical brake 104 is also smaller than the clamping force that can be expected due to hysteresis, so that the risk of a failed re-tensioning attempt in the second electromechanical brake 104 can be accepted, because even in the event of a failed re-tensioning attempt, the clamping force will be higher due to hysteresis than previously.
[0086] Here, it can also be checked subsequently whether the locking of the brake pad 104-2 of the second electromechanical brake 104 was successful.
[0087] If the locking was successful, the method 200 can be terminated.
[0088] On the other hand, if the locking of the brake pad 104-2 of the second electromechanical brake 104 was not successful, the power supplied to the electromechanical actuator 104-3 of the second electromechanical brake 104 can be reduced (step 224), wherein the reduction of the power takes place at a reduction rate such that, due to hysteresis, at least a predetermined residual clamping force remains between the brake pad 104-2 and the brake disc 104-1 of the second electromechanical brake 104 after the supply of power to the electromechanical actuator 104-3 of the second electromechanical brake 104 is switched off. The power can be reduced over a period of time of between one second and a few minutes. During this period of time, the brake 104 continues to cool, which leads to an increase in internal friction and thus to a higher residual clamping force.
[0089] Furthermore, further measures can also be taken to compensate for or prevent a loss of clamping force. For example, assuming that the first electromechanical brake 102 and the second electromechanical brake 104 described above are provided at the rear wheels of the vehicle, the residual clamping force of the brakes at the front axle can also be increased in order to ensure the stationary state. To this end, the clamping force at the front axle is significantly greater than the residual braking torque. The clamping force is then slowly reduced, so that an increased clamping force is achieved due to internal friction (hysteresis).
[0090] If the process is carried out only a few minutes after the stationary state has been reached, not only can the loss of clamping force be compensated for (by length changes caused by heat), but also the "cooled" electromechanical brake can be utilized to have a slightly worse efficiency and to increase the residual clamping force compared to a hot brake.
[0091] The re-tensioning of the electromechanical brakes at the front axle can already take place before the re-tensioning at the rear axle in order to provide the highest possible residual clamping force reserve in the "vehicle" system.
[0092] Furthermore, for reasons of energy efficiency, it can be provided that the electromechanical brakes at the front axle are only re-tensioned if a fault occurs in the re-tensioning process at the rear axle.
[0093] It can also be considered to re-tighten the electromechanical brake at the front axle, especially when the vehicle is parked on a very steep slope (e.g. slope > 20%). This can be done independently of the estimated or measured temperature at the brake system. The holding capability is further improved for situations where the road surface friction coefficient can be slightly lower.
Claims
1. A method (200) for re-tensioning an electromechanical parking brake device (100) of a vehicle, wherein, The electromechanical parking brake device (100) has a first electromechanical brake (102) and a second electromechanical brake (104), each electromechanical brake having: a brake disc (102-1, 104-1); at least one brake pad (102-2, 104-2); an electromechanical actuator (102-3, 104-3) for pressing the at least one brake pad (102-2, 104-2) against the brake disc (102-1, 104-1) to produce a braking effect; and a locking device (102-4, 104-4) for locking the at least one brake pad (102-2, 104-2) against the brake disc (102-1, 104-1), wherein the method (200) includes: Determine whether the first electromechanical brake (102) needs to be re-tensioned (204). If retightening is required, a diagnostic test is performed to check the retightening operability (206, 208) of the parking brake device (100), and The first electromechanical brake (102) is re-tensioned (210) only if no fault is identified within the framework of the diagnosis, wherein the re-tensioning includes: The locking device (102-4) of the first electromechanical brake (102) is operated to release the lock. The electromechanical actuator (102-3) of the first electromechanical brake (102) presses at least one brake pad (102-2) of the first electromechanical brake (102) against the brake disc (102-1) of the first electromechanical brake (102) with a predetermined force. The locking device (102-4) of the first electromechanical brake (102) is operated to lock at least one brake pad (102-2) of the first electromechanical brake (102) in a state that presses against the brake disc (102-1) of the first electromechanical brake (102).
2. The method (200) according to claim 1, wherein, Before or during the retensioning of the first electromechanical brake (102), determine the residual clamping force (212) between at least one brake pad (102-2) of the first electromechanical brake (102) and the brake disc (102-1) of the first electromechanical brake (102).
3. The method (200) according to claim 1 or 2, wherein, It also includes checking whether the locking of at least one brake pad (102-2) of the first electromechanical brake (102) is successful (214).
4. The method (200) according to claim 3, wherein, It also includes: if the locking of at least one brake pad (102-2) of the first electromechanical brake (102) is successful, then the second electromechanical brake (104) is re-tensioned (216), wherein the re-tensioning includes: Operate the locking device (104-4) of the second electromechanical brake (104) to release the lock of the second electromechanical brake (104). The electromechanical actuator (104-3) of the second electromechanical brake (104) presses at least one brake pad (104-2) of the second electromechanical brake (104) against the brake disc (104-1) of the second electromechanical brake (104) with a predetermined force. Operate the locking device (104-4) of the second electromechanical brake (104) to lock at least one brake pad (104-2) of the second electromechanical brake (104) in a state that presses against the brake disc (104-1) of the second electromechanical brake (104).
5. The method (200) according to claim 3 or 4, wherein, If locking of at least one brake pad (102-2) of the first electromechanical brake (102) is unsuccessful, the power supply (218) to the electromechanical actuator (102-3) of the first electromechanical brake (102) is reduced, wherein the reduction of power is carried out at a rate such that, due to hysteresis, after the power supply to the electromechanical actuator (102-3) of the first electromechanical brake (102) is cut off, at least a predetermined residual clamping force is maintained between at least one brake pad (102-2) of the first electromechanical brake (102) and the brake disc (102-1).
6. The method (200) according to claims 2 and 5, wherein, It also includes: if the residual clamping force determined between at least one brake pad (102-2) of the first electromechanical brake (102) and the brake disc (102-1) of the first electromechanical brake (102) is less than the clamping force that could be expected due to hysteresis, then the second electromechanical brake (104) is re-tensioned (216), wherein the re-tensioning includes: Operate the locking device (104-4) of the second electromechanical brake (104) to release the lock of the second electromechanical brake (104). The electromechanical actuator (104-3) of the second electromechanical brake (104) presses at least one brake pad (104-2) of the second electromechanical brake (104) against the brake disc (104-1) of the second electromechanical brake (104) with a predetermined force. Operate the locking device (104-4) of the second electromechanical brake (104) to lock at least one brake pad (104-2) of the second electromechanical brake (104) in a state that presses against the brake disc (104-1) of the second electromechanical brake (104).
7. The method (200) according to claim 4 or 6, wherein, Also includes: Check (222) whether the locking of at least one brake pad (104-2) of the second electromechanical brake (104) is successful.
8. The method (200) according to claim 7, wherein, If locking of at least one brake pad (104-2) of the second electromechanical brake (104) is unsuccessful, the power supplied to the electromechanical actuator (104-3) of the second electromechanical brake (104) is reduced (224), wherein the power reduction is carried out at such a rate that, due to hysteresis, after the power supply to the electromechanical actuator (104-3) of the second electromechanical brake (104) is cut off, at least a predetermined residual clamping force is maintained between at least one brake pad (104-2) of the second electromechanical brake (104) and the brake disc (104-1).
9. The method (200) according to claims 2 and 5, wherein, If the residual clamping force determined between at least one brake pad (102-2) of the first electromechanical brake (102) and the brake disc (102-1) is not less than the clamping force that can be expected due to hysteresis, then the second electromechanical brake (104) is not retightened.
10. A parking brake device (100) comprising a first electromechanical brake (102) and a second electromechanical brake (104), each electromechanical brake having: a brake disc (102-1, 104-1); at least one brake pad (102-2, 104-2); an electromechanical actuator (102-3, 104-3) for pressing the at least one brake pad (102-2, 104-2) against the brake disc (102-1, 104-1) to produce a braking effect; a locking device (102-4, 104-4) for locking the at least one brake pad (102-2, 104-2) against the brake disc (102-1, 104-1); and a control device (106) for performing the method (200) according to any one of claims 1 to 9.