Procedure for determining the status of a parking brake system and parking brake system

Abstract

The invention relates to a method for determining the status of a parking brake system (1), wherein the parking brake system (1) comprises at least one friction brake (2) with at least one brake element (3), an actuator (4) with a movable actuator part for actuating the brake element (3), a locking device (6) for securing the position of the brake element (3) in a position in which the parking brake (1) is safely activated, and a storage unit (7) for storing status information of the parking brake system (1), wherein, in the case that no information regarding the current status of the parking brake (1) is available in the storage unit (7), the actuator (4) is controlled such that it applies a torque that acts in the direction of increasing the braking force of the friction brake (2), it is checked whether the movable part of the actuator (4) has undergone a movement as a result of the control, and the status of the parking brake is determined accordingly.

Description

[0001] The invention relates to a method for determining the status of a parking brake system and to a parking brake system.

[0002] Electrically operated parking brake systems are generally known. These systems use a friction brake with at least one brake element that interacts with a brake drum or brake disc to prevent the vehicle from rolling away through friction. The brake element is actuated by an electric actuator.

[0003] Determining the status of the parking brake system, i.e., whether the parking brake is engaged or not, after a hardware reset or during a new ignition cycle is preferably done by reading stored information from a non-volatile memory unit. However, this information may be unavailable or unreliable in the memory unit, for example, due to data loss, an incorrectly executed memory routine, or data corruption. In this case, the state of the parking brake system cannot currently be reliably determined.

[0004] This is disadvantageous because reliable knowledge of the parking brake system's status is a prerequisite for numerous vehicle operations. For example, a command to release the parking brake can be ignored if the parking brake is already reported as released. Conversely, a command to engage the parking brake can be ignored if the parking brake is already considered engaged.

[0005] Based on this, the object of the invention is to provide a method that enables a reliable determination of the state of the parking brake.

[0006] The problem is solved by a method having the features of independent claim 1. Preferred embodiments are the subject of the dependent claims. A parking brake system is the subject of dependent claim 15.

[0007] According to a first aspect, a method for determining the status of a parking brake system is disclosed. The parking brake system comprises at least a friction brake with at least one brake element, an actuator with a movable actuator part for actuating the brake element, a safety device for securing the position of the brake element in a position in which the parking brake is safely activated (i.e., the vehicle is secured against rolling away by the parking brake), and a storage unit for storing status information of the parking brake system.

[0008] The parking brake system is designed as a self-releasing parking brake, meaning that the brake element moves into a position in which it exerts no frictional force on the moving brake component, particularly the brake drum, without the need for force from the actuator or locking by the safety device. A return spring can be provided to enable the parking brake to release itself, applying a restoring force to at least one brake element. When moving the brake element in a direction that increases braking force, the actuator that moves the brake element must overcome the spring force of the return spring. The safety device is preferably designed such that it must be actively actuated to provide the locking effect, but is self-locking after activation.

[0009] The process includes the following steps: First, the system determines whether the storage unit contains information regarding the current status of the parking brake system. This information indicates whether the parking brake is activated or not. "Activated" means that the vehicle is secured against rolling away by the parking brake with a predefined minimum holding force, and this state is mechanically secured by the safety device.

[0010] If the current status of the parking brake system is unavailable, or if the current status indicates that the parking brake is not activated, the actuator is controlled in such a way that it applies a torque or force in the direction of increasing the braking force of the friction brake. The torque or force of the actuator is limited, meaning that the actuator can only apply a torque or force up to a certain threshold value. In other words, the actuator is controlled taking into account a force or torque limit, such that the torque applied by the actuator is not greater than the torque limit, or alternatively, that the applied force is not greater than the force limit (e.g., in the case of an actuator with a linearly moving actuator part).This limitation ensures that no undesirable change in the state of the parking brake occurs, for example, in the form of the actuator being overloaded or the safety device being released, and the brake mechanism can only be moved if the parking brake is not already engaged.

[0011] After the actuator is activated, it is checked whether the moving part of the actuator has performed a movement. The result of this check constitutes the test result. It should be noted that the actuator is the sole drive for at least one brake element; that is, the moving part of the actuator directly defines whether and to what extent the brake element has been moved. If the parking brake was released, the limited torque or force is sufficient for the actuator to move the brake element in the direction of increasing the braking force of the friction brake. If the parking brake was already engaged, the limited torque or force is insufficient to move the brake element, particularly to such an extent that the self-locking safety device is released.

[0012] Depending on the test result, the status of the parking brake system is determined as "parking brake released" if the moving part of the actuator has performed a movement and as "parking brake activated" if the moving part of the actuator has not performed a movement.

[0013] The technical advantage of this method lies in the fact that the status of the parking brake system can be determined safely and reliably. This leads to higher availability of the parking brake function, particularly during an ignition cycle in which the test is performed and the parking brake is intended to be used. Furthermore, the reliable determination of the parking brake system's state enables appropriate control of the parking brake system based on this state, thus allowing for more precise control of the parking brake.

[0014] According to one embodiment, the force limit or torque limit is lower than the force or torque required to release the locking device. The locking device is configured, for example, such that the parking brake's locking in the engaged state can be released by actuating the actuator in a direction that tightens the parking brake more firmly (i.e., by driving the actuator in the direction of increasing the force or torque). This can, for example, disable a mechanical positive locking mechanism within the locking device, thus releasing the parking brake's locking mechanism. The force limit or torque limit is selected such that this locking mechanism is maintained, preventing the parking brake from unintentionally entering an undefined state.

[0015] According to one embodiment, the locking device comprises a parking pawl, which can be activated by an actuator and reset by an elastically deformable element, in particular a spring, and a ratchet wheel. Actuation of the actuator allows the parking pawl to move such that a locking section of the parking pawl engages with a tooth of the ratchet wheel, and the locking section positively engages with a tooth contour of the ratchet wheel. The upper force limit or the upper torque limit is less than the force or torque that, when the parking brake is activated, causes the ratchet wheel to rotate such that the positive engagement of the locking section with the tooth contour of the ratchet wheel is released and the parking pawl is disengaged from the ratchet wheel by the elastically deformable element.This prevents the safety device from being unintentionally released by limiting the force or torque.

[0016] According to one embodiment, the actuator is controlled taking into account a minimum force or torque limit, such that the force applied by the actuator is greater than the force or torque required to move the brake element until it contacts a brake drum or disc. The minimum force or torque limit ensures that the force or torque of the actuator is always sufficient to move the brake element, provided it is not in contact with the brake drum or disc. In particular, the applied force or torque is sufficient to overcome friction and other resistances in the parking brake.

[0017] According to one embodiment, if the current status of the parking brake, stored in a memory unit, indicates that the parking brake is activated, the current position of the actuator's moving part is compared with a first position information, determined during a calibration process and therefore also referred to as the calibration position, which is stored in the memory unit. This comparison checks whether the current position of the actuator's moving part corresponds to a position in which the parking brake can be secured via the locking device. The first position information, or calibration position, corresponds to a position of the locking device in which mechanical locking of the parking brake is possible.This test determines whether, in the previous ignition cycle, the parking brake could have been secured in the current position of the actuator's moving part. Comparing the positions eliminates the need for a mechanical test. This reduces stress on the actuator over the vehicle's lifetime and also eliminates the risk of the locking device unintentionally releasing due to a mechanical test.

[0018] According to one embodiment, if the locking device consists of a ratchet wheel and a cooperating parking pawl, and if the current status of the parking brake, stored in a memory unit, indicates that the parking brake is activated, the current position of the actuator's moving part is compared with a first position information or calibration position stored in the memory unit. This comparison checks whether the current position of the actuator's moving part corresponds to a position in which the parking pawl can engage with a tooth of the ratchet wheel. In other words, the first position information indicates whether the ratchet wheel is in a rotational position in which the parking pawl can be mechanically engaged. This comparison verifies whether a basic mechanical locking mechanism for the parking brake is present.

[0019] According to one embodiment, an additional check is performed to determine whether the current position of the actuator's moving part corresponds to a second position information stored in the memory unit. This second position information indicates the position the actuator's moving part assumed after the parking brake was activated. The second position information is therefore also referred to as the "current locking position information." This check verifies whether the actuator's moving part is still in the position where the parking brake was activated and mechanically locked.

[0020] According to one embodiment, if the comparison of the first or second position information with the current position of the moving part of the actuator reveals a deviation greater than a tolerance limit, the following steps are performed: - Controlling the actuator in such a way that the actuator applies a torque to increase the braking force of the friction brake; - After activating the actuator, check whether the moving part of the actuator has performed a movement and determine a test result; - depending on the test result, setting the status of the parking brake system as parking brake released if the moving part of the actuator has performed a movement and as parking brake activated if the moving part of the actuator has not performed a movement.

[0021] This prevents an undefined state of the parking brake system by bringing the parking brake into a defined state through the control of the actuator.

[0022] According to one embodiment, the first position information indicates a position of the actuator in which the ratchet wheel coupled to the actuator assumes a rotational position in which the parking pawl can be engaged with any tooth of the ratchet wheel. Thus, the first position information allows determination of whether mechanical locking was even possible in the previous ignition cycle, based on the actuator's position.

[0023] According to one embodiment, the second position information indicates the position of the actuator at which the ratchet wheel coupled to the actuator assumes a rotational position in which the parking pawl is engaged with the tooth of the ratchet wheel that secures the parking brake since the last activation of the parking brake. Thus, the second position information allows it to be determined whether the actuator is still located at the point where the parking brake was activated and where the mechanical locking by the locking device occurred.

[0024] According to one embodiment, checking whether the moving part of the actuator has performed a movement involves comparing the position information of the moving part of the actuator, stored before the actuator was activated, with the position of the moving part of the actuator after the actuator has been activated. If the parking brake was engaged, the moving part of the actuator will not perform any movement. Therefore, the status of the parking brake can be checked by verifying whether a movement has occurred.

[0025] According to one embodiment, the actuator is activated for a predetermined duration. This allows the duration of the activation, and thus the duration of the test routine, to be limited.

[0026] According to one embodiment, the method is only executed when the vehicle's service brake is not applied. This prevents the position of the brake element or the position of the actuator's moving part from being distorted by the application of the service brake.

[0027] According to another aspect, a parking brake system is disclosed. The parking brake system comprises at least one friction brake with at least one brake element, an actuator with a movable actuator part for actuating the brake element, a safety device for securing the position of the brake element in a position in which the parking brake is safely activated, a control unit for controlling the parking brake system, and a storage unit for storing status information of the parking brake system. The control unit is configured to perform a procedure with the following steps: - Determine whether information regarding the current status of the parking brake system is available in the storage unit; - if the current status of the parking brake system is unavailable or the current status indicates that the parking brake is not activated, actuate the actuator in such a way that the actuator applies a force or torque in the direction of increasing the braking force of the friction brake, the actuation of the actuator taking into account a force limit or torque limit, such that the torque applied by the actuator is not greater than the torque limit or that the force applied is not greater than the force limit; - After activating the actuator, check whether the moving part of the actuator has performed a movement and determine a test result; - Depending on the test result, the status of the parking brake system is set to "parking brake released" if the moving part of the actuator has performed a movement, and "parking brake activated" if the moving part of the actuator has not performed a movement.

[0028] In the context of the present invention, "actuator has performed a movement" means, in particular, that the position of the moving part of the actuator, especially a rotor of a motor, differs from the position prior to the actuator being actuated by a position or angular position that is greater than a predetermined tolerance range, wherein the tolerance range is determined by the accuracy of the sensors used to determine the position of the moving part of the actuator. The tolerance range may, in particular, include an angular range greater than ±3 degrees or a translational movement of the moving part of the actuator by more than ±0.0025 mm.

[0029] In the context of the present invention, "actuator has not performed any movement" means in particular that the position of the moving part of the actuator, especially a rotor of a motor, differs from the position before the actuator is controlled by a position or angular position that is zero or smaller than a predetermined tolerance range, wherein the tolerance range is determined by the noise of the measured values ​​and the accuracy of the sensors for determining the position of the moving part of the actuator.

[0030] The terms “approximately”, “essentially” or “about” mean, within the meaning of the invention, deviations from the respective exact value by + / - 10%, preferably by + / - 5% and / or deviations in the form of changes that are insignificant for the function.

[0031] Further developments, advantages, and possible applications of the invention will also become apparent from the following description of exemplary embodiments and from the figures. All features described and / or illustrated are, individually or in any combination, fundamentally the subject matter of the invention, irrespective of their compilation in the claims or their cross-reference. The content of the claims is also incorporated into the description.

[0032] The invention will be explained in more detail below with reference to exemplary embodiments shown in the figures. The figures show: Fig. 1. An example is a schematic representation of a vehicle with a parking brake system; Fig. 2. An exemplary and schematic graphic representation of a parking brake designed as an electrically operated drum brake; Fig. 3. An example schematic representation of components of a parking brake system; Fig. 4. An example flowchart showing the detailed steps for checking the status of a parking brake system; and Fig. 5. An example block diagram illustrates the basic steps of a procedure for checking the status of a parking brake system.

[0033] Fig. Figure 1 shows, schematically and by way of example, a vehicle F that has a parking brake system 1 with at least one friction brake 2. The parking brake system 1 implements a parking brake that can assume an activated state and a deactivated state. In the activated state, the parking brake exerts braking force such that the vehicle F cannot roll away. This applies in particular even if the vehicle F is tilted. In the deactivated state, the parking brake is released, i.e., the parking brake exerts no braking force on the wheels of the vehicle, so that the vehicle F is not prevented from rolling by the parking brake.

[0034] Fig. Figure 2 shows a schematic representation of a parking brake with a friction brake 2 in the form of a drum brake, by means of which the braking torque is generated. The drum brake has a pair of braking elements 3 in the form of brake shoes, which are connected to a Fig. The two brake drums (not shown) interact. A spreading unit 5 engages the brake shoes, by means of which the brake shoes can be moved in such a way that they can be pressed against the inside of the brake drum and thus produce a braking effect.

[0035] The spreading unit 5 is operatively connected to an actuator 4. The actuator 4 can, in particular, be a motor having a rotating rotor. The actuator 4 causes movement of the brake shoes 3 via the spreading unit 5. The mechanical coupling of the actuator 4 to the spreading unit 5 is effected by a locking device 6 and preferably by a gearbox 4.1. The locking device 6 is designed to secure the parking brake in the activated state, such that this activated state is mechanically maintained even when the vehicle's ignition F is switched off and thus no electronic control of the motor 4 takes place.

[0036] In the illustrated embodiment, the locking device 6 comprises a ratchet wheel 6.1 and a parking pawl 6.2 that interacts with the ratchet wheel 6.1. The ratchet wheel 6.1 is gear-like and has a plurality of teeth 6.1.1 on its outer circumference. The parking pawl 6.2 has a locking section 6.2.1 at its free end, which is designed to interact with the ratchet wheel 6.1. The parking pawl 6.2 has an actuator by means of which the locking section 6.2.1 can be moved, preferably such that the locking section 6.2.1 can be positioned translationally into a forward position in which the locking section 6.2.1 can engage with a tooth 6.1.1 of the ratchet wheel 6.1. Furthermore, the parking pawl 6.2 has an elastic element, in particular a spring, by means of which the locking section 6.2.1 can be positioned in a retracted position, in which the locking section 6.2.1 is separated from the ratchet wheel 6.1 is defective and therefore not in engagement with a tooth 6.1.1 of the ratchet wheel 6.1.

[0037] Preferably, the teeth 6.1.1 of the ratchet wheel 6.1 are form-fitted to the locking section 6.2.1 of the parking pawl 6.2.

[0038] Preferably, the shape is adapted such that both the tooth 6.1.1 and the locking section 6.2.1 have an undercut. This undercut has the advantage that, when the parking brake is activated, the locking section 6.2.1 engages a tooth 6.1.1 of the ratchet wheel 6.1 and cannot be disengaged, despite its spring tension, until the ratchet wheel 6.1 moves in the direction of increasing the braking force of the parking brake (see arrow in). Fig. 2) is moved to such an extent that the positive locking between the tooth 6.1.1 and the locking section 6.2.1 is released and thus the locking section 6.2.1 is disengaged from the ratchet wheel 6.1.

[0039] A gearbox 4.1 can be provided between the actuator 4 and the spreading unit 5, which implements a desired transmission ratio between the actuator 4 and the spreading unit 5.

[0040] It should be noted that the friction brake 2 can also be designed as a disc brake. In this case, the brake element 3 is formed by a brake pad that interacts with a brake disc, which is in operative contact with a wheel of the vehicle F. The actuator 4 can in this case be an electric actuator by means of which at least one brake pad can be pressed against the brake disc.

[0041] Fig. Figure 3 shows a block diagram of the parking brake system 1. As previously mentioned in relation to Fig. As explained in section 2, the actuator 4 is operatively connected to the spreading unit 5 via a shaft on which the ratchet wheel 6.1 is provided and a gearbox 4.1. Furthermore, an actuator is provided by means of which the parking pawl 6.2 can be activated.

[0042] Actuator 4 and parking pawl 6.2 are controlled by a control unit 8 of the parking brake. The control unit 8 can be a separate control unit specifically for the parking brake or a higher-level control unit that also performs other control tasks in addition to controlling the parking brake.

[0043] The control unit 8 can have a control unit for the actuator 4, a control unit for the parking pawl 6.2 and a storage unit 7 in which status information of the parking brake is stored.

[0044] Preferably, when the ignition of the vehicle F is switched off, one or more of the following pieces of information are stored in the memory unit 7: - Parking brake status: Activated or deactivated; - first position information of the actuator 4, in which the ratchet wheel 6.1 assumes a rotational position in which a tooth 6.1.1 of the ratchet wheel 6.1 can engage with the parking pawl 6.2, - second position information, which indicates a position or angular position of the moving part of actuator 4 after the last activation of the parking brake at the end of the last ignition run.

[0045] Fig. Figure 4 illustrates in a flowchart the steps of a procedure for determining the state of the parking brake.

[0046] After the routine starts, for example when the vehicle F's ignition is switched on, step S1 first checks whether information about the current status of the parking brake is available in memory unit 7. This information can include, in particular, the states "parking brake activated" and "parking brake released".

[0047] If this information is not available in storage unit 7, the current position of the moving part of the motor or actuator 4, by means of which the brake element 3 can be moved, is first stored in step S2. The current position can, for example, be information about the position of a translationally displaceable actuator part or the angular position of the rotor of a motor.

[0048] Subsequently, in step S3, actuator 4 or the motor is controlled such that it produces a torque or force that is limited by an upper threshold. This control takes place over a predefined period. This period can be monitored using a timer, as shown in steps S4 to S6: a timer with a predefined time interval is initialized (S4), the timer is started (S5), and the motor is controlled until the time interval has expired (S6).

[0049] The force or torque limitation is preferably selected such that the locking device 6 of the parking brake is not released. In the case of a locking device 6 with a ratchet wheel 6.1 and a parking pawl 6.2, this means that the force or torque limitation is dimensioned such that the ratchet wheel 6.1 cannot rotate far enough, due to the contact of the brake element 3 with the brake drum or brake disc, to release the positive engagement between the locking section 6.2.1 of the parking pawl 6.2 and the tooth 6.1.1, and thus the parking pawl 6.2 is retracted due to the preload by the elastically deformable element and thus disengaged from the ratchet wheel 6.1.

[0050] Subsequently, by comparing the position of the moving part of the actuator 4 or the motor stored in step S2 with the current position in step S7, it is checked whether the moving part of the actuator 4 or the motor could be moved or not. This is preferably done taking into account a tolerance threshold, i.e., if the moving part of the actuator 4 or the motor has moved by an angle or distance smaller than the tolerance threshold, this is interpreted as "no movement".

[0051] If, in step S7, it is detected that the moving part of the actuator 4 or the motor has moved (i.e., in particular, by a greater distance than the tolerance threshold), the status of the parking brake is defined as not activated in step S8. This information is preferably also stored in the memory unit 7. This is because it must then be assumed that the safety device 6 is not securing the parking brake (i.e., for example, that the parking pawl 6.2 is not engaging the ratchet wheel 6.1) and therefore it cannot be ensured that the vehicle F is adequately secured against rolling away.

[0052] However, if in step S7 it is determined that the moving part of the actuator 4 or the motor has not moved (i.e., in particular, is smaller than the tolerance threshold), the status of the parking brake is defined as activated in step S9. This information is preferably also stored in the memory unit 7.

[0053] If step S1 determines that the parking brake status is available, a check of this stored state is preferably still performed to ensure that the stored state corresponds to the actual state of the parking brake. It should be noted that this is not always the case, for example, if the last save operation was unsuccessful and therefore an outdated state is still stored in memory unit 7.

[0054] In step S10, the system checks which parking brake status is stored in memory unit 7, i.e., whether the stored information indicates that the parking brake is activated or deactivated. If the stored information indicates that the parking brake is deactivated, the previously described steps S2 to S7 are performed to verify this information.

[0055] If step S10 determines that the information stored in memory unit 7 indicates the parking brake is engaged, step S11 compares the current position of the actuator 4 with an initial position stored in memory unit 7, specifically the current angle of the motor with an initial angle stored in memory unit 7. The initial position or angle corresponds to a position or angle in which the locking device 6 can assume a state that secures the parking brake. In the case of a locking device 6 comprising a ratchet wheel 6.1, this is a position or angular position of the actuator 4 or motor in which the parking pawl 6.2 can engage with a tooth of the ratchet wheel 6.1 (i.e., in particular, any tooth of the plurality of teeth of the ratchet wheel).For example, the stored initial angle can define an angular position in which such an intervention can take place, and based on the division of the ratchet wheel, it is possible to deduce the other angular positions in which an intervention can occur.

[0056] In step S12, it is checked whether there is a correlation between the current position of actuator 4 or the current rotation angle of the motor and the initial position or angle. This means that the current position or angle, taking into account a tolerance threshold, corresponds to the position or angle in which the locking device 6 can secure the parking brake.

[0057] If no correlation exists, the parking brake status is preferably set to undefined (step S13). This information can be stored in memory unit 7. Subsequently, the previously described routine according to steps S2 to S7 is executed to determine the parking brake status.

[0058] If, however, step S12 determines that there is a correlation between the current position of actuator 4 or the current rotation angle of the motor and the initial position or angle, step S14 checks whether the last stored position of actuator 4 or the current rotation angle of the motor is available in the storage unit 7.

[0059] If this is not the case, the parking brake status is preferably set to undefined (step S13). The previously described routine, steps S2 to S7, is then executed again to determine the parking brake status.

[0060] If, however, it is determined in step S14 that the last stored position of the actuator 4 or the current rotation angle of the motor is available in the storage unit 7, in step S15 the current position of the actuator 4 or the current rotation angle of the motor is compared with the last stored position or angle.

[0061] If these positions or angles match (step S16), the parking brake state is set to activated. This state information can also be stored in memory unit 7.

[0062] If these positions or angles do not match, the parking brake state is again set to undefined (step S13). The previously described routine, steps S2 to S7, is then executed again to determine the parking brake status.

[0063] Fig. Figure 5 shows a schematic block diagram illustrating the steps of the procedure for determining the status of the parking brake system.

[0064] First, it is determined whether information regarding the current status of the parking brake system is available in the storage unit (S20).

[0065] If the current status of the parking brake system is not available or the current status indicates that the parking brake is not activated, the actuator is controlled in such a way that the actuator applies a torque or force in the direction of increasing the braking force of the friction brake (S21).

[0066] After the actuator is activated, which can be done for a predetermined period of time, it is checked whether the moving part of the actuator has performed a movement. This check determines a test result (S22).

[0067] Depending on the test result (i.e., whether or not the moving part of the actuator has moved), the status of the parking brake system is set to "parking brake released" if the moving part of the actuator has moved, and to "parking brake engaged" if the moving part of the actuator has not moved (S23).

[0068] The invention has been described above using exemplary embodiments. It is understood that numerous modifications and adaptations are possible without thereby departing from the scope of protection defined by the patent claims. Reference symbol list 1 Parking brake system 2 friction brakes 3 Brake element 4 Actuator 4.1 Gearbox 5 Spreading unit 6 Safety device 6.1 Ratchet wheel 6.1.1 Tooth 6.2 Parking handle 6.2.1 Locking section 7 storage units 8 Control unit F vehicle

Claims

[1] Method for determining the status of a parking brake system (1), wherein the parking brake system (1) comprises at least a friction brake (2) with at least one brake element (3), an actuator (4) with a movable actuator part for actuating the brake element (3), a safety device (6) for securing the position of the brake element (3) in a position in which the parking brake (1) is safely activated, and a storage unit (7) for storing status information of the parking brake system (1), wherein the method comprises the following steps: - Determine whether information regarding the current status of the parking brake system (1) is available in the storage unit (7) (S20); - if the current status of the parking brake system (1) is not available or the current status indicates that the parking brake is not activated, actuating the actuator (4) such that the actuator (4) applies a torque or force in the direction of increasing the braking force of the friction brake (2) (S21), wherein the actuating of the actuator (4) is subject to a force limit or torque limit such that the torque applied by the actuator (4) is not greater than the torque limit or the force applied is not greater than the force limit; - After actuating the actuator (4), check whether the moving part of the actuator (4) has performed a movement and determine a test result (S22); - Depending on the test result, the status of the parking brake system (1) is set to be as parking brake released if the moving part of the actuator (4) has performed a movement and as parking brake activated if the moving part of the actuator (4) has not performed a movement (S23). [2] Method according to claim 1, characterized by , that the force limit or the torque limit is less than the force or torque required to release the locking device (6). [3] Method according to claim 1 or 2, characterized bythat the locking device (6) comprises a parking pawl (6.2) that can be activated by actuating an actuator and resettable by an elastically deformable element, and a ratchet wheel (6.1), wherein the parking pawl (6.1) is movable by actuating the actuator such that a locking section (6.2.1) of the parking pawl (6.2) is brought into operative contact with a tooth (6.1.1) of the ratchet wheel (6.1) and the locking section (6.2.1) engages positively in a tooth contour of the tooth (6.1.1) of the ratchet wheel (6.1), wherein the upper force limit or the upper torque limit is less than the force or torque which, when the parking brake is activated, causes the ratchet wheel (6.1) to rotate such that the locking section (6.2.1) engages positively in the tooth contour of the tooth (6.1.1) of the ratchet wheel (6.1) is lifted and the parking pawl (6.2) is disengaged from the ratchet wheel (6.1) by the elastically deformable element. [4] Method according to any one of the preceding claims, characterized by , that the actuator (4) is controlled taking into account a minimum force or torque limit, such that the force applied by the actuator (4) is greater than the force or torque applied by the actuator (4) is greater than the torque required to move the brake element (3) until it contacts a brake drum or brake disc. [5] Method according to any one of the preceding claims, characterized by, that in the event that the current status of the parking brake, which is stored in a memory unit, indicates that the parking brake is activated, the current position of the moving part of the actuator (4) is compared with an initial position information stored in the memory unit (7), and that by means of the comparison it is checked whether the current position of the moving part of the actuator (4) corresponds to a position at which the parking brake can be secured via the locking device (6). [6] Method according to any one of the preceding claims, characterized by, that in the event that the locking device (6) is formed by a ratchet wheel (6.1) and a cooperating parking pawl (6.2) and that when the current status of the parking brake, which is stored in a memory unit, indicates that the parking brake is activated, the current position of the moving part of the actuator (4) is compared with an initial position information stored in the memory unit (7), and that by means of the comparison it is checked whether the current position of the moving part of the actuator (4) corresponds to a position in which the parking pawl (6.2) can be engaged with a tooth (6.1.1) of the ratchet wheel (6.1). [7] Method according to claim 6, characterized by, that it is additionally checked whether the current position of the moving part of the actuator (4) corresponds to a second position information stored in the storage unit (7), wherein the second position information indicates which position the moving part of the actuator (4) has assumed after the parking brake has been activated. [8] Method according to any one of claims 5 to 7, characterized by , that if the comparison of the first or second position information with the current position of the moving part of the actuator (4) results in a deviation greater than a tolerance limit, the following steps are carried out: - Controlling the actuator (4) such that the actuator (4) applies a torque to increase the braking force of the friction brake (2); - After actuating the actuator (4), check whether the moving part of the actuator (4) has performed a movement and determine a test result; - depending on the test result, setting the status of the parking brake system (1) as parking brake released if the moving part of the actuator (4) has performed a movement and as parking brake activated if the moving part of the actuator (4) has not performed a movement. [9] Method according to any one of claims 5 to 8, characterized by , that the first position information indicates a position of the actuator (4) in which the ratchet wheel (6.1) coupled to the actuator (4) assumes a rotational position in which the parking pawl (6.2) may be engaged with any tooth (6.1.1) of the ratchet wheel (6.1). [10] Method according to any one of claims 7 to 9, characterized by, that the second position information indicates the position of the actuator (4) in which the ratchet wheel (6.1) coupled to the actuator (4) assumes a rotational position in which the parking pawl (6.2) is engaged with the tooth (6.1.1) of the ratchet wheel (6.1) which secures the parking brake since the last activation of the parking brake. [11] Method according to any one of the preceding claims, characterized by , that checking whether the moving part of the actuator (4) has performed a movement includes a comparison of position information of the moving part of the actuator (4) stored before the actuator (4) was controlled with the position of the moving part of the actuator (4) after the actuator (4) was controlled. [12] Method according to any one of the preceding claims, characterized by , that the actuator (4) is controlled for a specified duration. [13] Method according to any one of the preceding claims, characterized bythat the procedure is only carried out if the vehicle's service brake is not applied. [14] Parking brake system comprising at least a friction brake (2) with at least one brake element (3), an actuator (4) with a movable actuator part for actuating the brake element (3), a locking device (6) for securing the position of the brake element (3) in a position in which the parking brake is safely activated, a control unit (8) for controlling the parking brake system (1) and a storage unit (7) for storing status information of the parking brake system (1), wherein the control unit (8) is configured to perform a procedure comprising the following steps: - Determine whether information regarding the current status of the parking brake system (1) is available in the storage unit (7); - if the current status of the parking brake system (1) is not available or the current status indicates that the parking brake is not activated, actuating the actuator (4) such that the actuator (4) applies a force or torque in the direction of increasing the braking force of the friction brake (2), the actuating of the actuator (4) taking into account a force limit or torque limit, such that the torque applied by the actuator (4) is not greater than the torque limit or that the force applied is not greater than the force limit; - After actuating the actuator (4), check whether the moving part of the actuator (4) has performed a movement and determine a test result; - Depending on the test result, the status of the parking brake system (1) is set as parking brake released if the moving part of the actuator (4) has performed a movement and as parking brake activated if the moving part of the actuator (4) has not performed a movement.

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