Procedure for verifying the correct installation of an electronic parking brake of a motor vehicle and test arrangement

Abstract

Method for verifying the correct installation of an electronic parking brake of a motor vehicle (K), with actuators (19) located on the wheels (12, 13) of at least one axle for applying a parking brake force, wherein at least one evaluation and control unit (16) controls the actuators (19) of the electronic parking brake located on the wheels (12, 13) such that they are moved on the wheels (12, 13) and thereby generate an engagement or release movement (SP or LP) of the electronic parking brake, characterized in that at least one hydraulic pressure generating device (17a) generates an operating brake pressure (P) at one of the wheels (12 or 13) at least for the duration of a certain movement phase or part of the movement phase within the engagement or release movement (SP or LP) and an actual current characteristic (l) Ist) of the current (I) absorbed during the clamping or releasing movement (SP or LP) of at least one actuator (19) assigned to one of the wheels (12 or 13) with a reference current characteristic (I R ) compared and the comparison is used to assess the correct installation of the electronic parking brake and the reference current characteristic for each actuator (19) is generated by controlling the actuators (19) before the operating brake pressure (P) is generated in such a way that a clamping and a releasing movement (SP and LP) of the electronic parking brake is generated, whereby the resulting current characteristic of each actuator (19) is measured and used as the reference current characteristic (I R ) is saved.

Description

[0001] The invention relates to a method for checking the correct installation of an electronic parking brake of a motor vehicle and a test arrangement for carrying out the method

[0002] According to the state of the art known to the applicant, the verification of the correct installation of an electronic parking brake generally takes place during the end-of-line inspection during production. This involves a complex process using a roller test bench to verify the correct installation and wiring between a control unit or between control units and the actuators responsible for the electronic parking brake.

[0003] For this purpose, the roller dynamometer is accelerated to a specific speed, which depends on the roller dynamometer used and could, for example, be approximately 70 km / h. Subsequently, an actuator of the electronic parking brake is activated, which is assigned to one of the rear wheels. Correct installation of the electronic parking brake is determined if a braking torque and a reduction in speed can be measured on the roller dynamometer on the side of the rear wheels that also corresponds to the side assignment of the activated actuator. For example, if the left actuator is activated and a braking torque can actually be measured on the left rear wheel and the speed is also reduced as a result, correct installation is determined.

[0004] The disadvantage of this procedure is that a roller test bench is required and the test takes a lot of time.

[0005] DE 10 2007 050 662 A1 discloses a method for calibrating or diagnosing a motor vehicle brake system with a pulsed pump. Specifically, the motor vehicle brake system is a service brake of a motor vehicle with a dual-circuit braking system. To achieve an optimized braking process, two two-way valves located on either side of the pump must be controlled depending on the brake line pressure (pre-pressure) between a master brake cylinder and a wheel brake cylinder of a wheel brake.

[0006] First, a reference pump is operated in advance, and a parameter representing the electromotive force of the reference pump is repeatedly determined under defined conditions. A statistical characteristic is derived from this. This parameter is determined primarily from the motor voltage drop across the reference pump.

[0007] During operation of the pump to be calibrated (duty pump), the same parameter is determined under corresponding specifications, and a corresponding statistical characteristic is derived. A ratio is calculated from the characteristic calculated for the reference pump and the characteristic calculated for the duty pump. This ratio is used as a measure of the deviation of the operating behavior of the duty pump from that of the reference pump. Using this ratio, a characteristic curve of the duty pump is adjusted to a characteristic curve specified for the reference pump. However, if the ratio or the characteristic lies outside a specified tolerance range, this means that the operating pump deviates too greatly from the reference pump in its operating behavior. In such a case, the duty pump is classified as faulty.

[0008] The present invention is based on the specific object of providing a method for checking the correct installation of an electronic parking brake, which is easy to carry out and in particular can be carried out without a roller test bench.

[0009] In contrast to a motor vehicle's service brake, an electronic parking brake is a separately controllable braking device used to securely hold the vehicle when parked. Electromechanical parking brake actuators can be integrated into the calipers of the wheel brakes, i.e., the rear and / or front axle brakes. A DC motor with a multi-stage gear (reduction gear) is typically used to generate the necessary clamping force. A translatory movement is required to generate a clamping force on the brake pads; this movement is typically generated from the motor's rotational movement using a spindle or ball screw drive.

[0010] Applying (closing) the electronic parking brake is achieved by controlling the electric motors assigned to the actuators using a brake control unit. Basic electrical parameters such as voltage and current can be used to determine the developed clamping force, taking into account the actuator design, motor characteristics, and ambient conditions (e.g., temperature). In particular, the current characteristic curve can be used to draw conclusions about the actuator state, clamping force, and actuator travel. Typical current characteristics exist for the application and release movements of the electronic parking brake.

[0011] DE 10 2016 203 475 A1 discloses a method for operating a control device of an actuator unit of an electromechanical motor vehicle brake. An electrical quantity, such as a current drawn by the actuator during application or release, is measured. Based on this measured value, a current actuating state of the actuator unit can be determined, and the installed actuator model can be deduced from this.

[0012] DE 10 2004 021 534 A1 discloses an automated parking brake with a test mode. It compares normal operation and a test mode, differing in the speed at which the parking brake is applied.

[0013] DE 10 2016 203 476 A1 discloses a control device for an electric motor of a motor vehicle brake and a method for operating the control device. A test signal is applied to an electric line of the electric motor, and a resulting line voltage is detected, thereby verifying an intact line connection.

[0014] The invention is based on the object of providing a method of the generic type and a test arrangement for implementing the method, by means of which the correct installation of an electronic parking brake can be checked in a simple and reliable manner. According to the invention, this object is achieved by a method having the features recited in claim 1 and a test arrangement having the features recited in claim 8.

[0015] The invention therefore proposes a method for checking the correct installation of an electronic parking brake of a motor vehicle, comprising actuators located on the wheels of at least one axle for applying a parking braking force. At least one evaluation and control device controls the actuators of the electronic parking brake located on the wheels in such a way that they are moved on the wheels, thereby generating an application or release movement of the electronic parking brake. At least one hydraulic pressure generating device, which may consist, for example, of a hydraulic pressure actuator (e.g., electronic brake booster, ESC pump, ESC = Electronic Stability Control) and a slip control unit (ESC unit), generates a service braking pressure on one of the wheels, at least for the duration of a specific movement phase or part of the movement phase within the application or release movement.The brake pedal could also be used as a hydraulic pressure-generating device (e.g., by an operator operating the brake pedal or by a braking robot). In this case, an actual current characteristic curve of the current consumed by at least one actuator assigned to one of the wheels during the application or release movement is compared with a reference current characteristic curve. This comparison is used to assess the correct installation of the electronic parking brake.

[0016] In order to be able to provide the highest degree of meaningfulness and accuracy despite existing manufacturing tolerances, the method according to the invention proposes that the reference current characteristic for each actuator is generated by controlling the actuators before, i.e. without generating the service brake pressure, in such a way that an application and a release movement of the electronic parking brake is generated, wherein the resulting current characteristic of each actuator is measured and stored as a reference current characteristic.

[0017] This creates the basis for checking the correct installation of an electronic parking brake using simple means, without the aid of a roller test bench.

[0018] Service brake pressure within the meaning of the invention is to be understood as such a brake pressure which is generated by the actuation of an actuator within the hydraulic circuit of the service brake system and not by activation of the electronic parking brake.

[0019] According to a first development of the method, it is proposed that the service brake pressure generated by the hydraulic pressure generating device is transmitted to a rear wheel to be tested and the actual current characteristic of the actuator is compared with the reference current characteristic that is also assigned to the rear wheel to be tested.

[0020] Such a design contributes to the simplicity and comprehensibility of the process. For example, if the generated service brake pressure was transmitted to the right rear wheel, the actual current characteristic of the actuator is compared with the reference current characteristic that, at least theoretically—that is, with correct installation and wiring—should also be assigned to the right rear wheel.

[0021] If no deviation between the actual current characteristic and the reference current characteristic is subsequently detected at the actuator of the right rear wheel, although this should have occurred, it is concluded that the actuators have been mistakenly swapped or that the wiring / control of the actuators has been incorrect.

[0022] As an alternative to this, it is also conceivable to transmit the generated service brake pressure to the rear wheel not being tested and then to verify that no differences occur between the actual current characteristic and the reference current characteristic at the actuator being tested.

[0023] According to another development, it is also conceivable that the service brake pressure generated by the hydraulic pressure generating device is transmitted to a wheel to be tested and the actual current characteristic of the pressurized wheel is compared with the actual current characteristic of the non-pressurized wheel, which serves as the reference current characteristic.

[0024] It has proven to be a particularly useful further development of the method if the generation of the service brake pressure takes place for the entire duration of a tensioning movement of the electronic parking brake, i.e. for the entire duration of such a movement of the actuators which leads to the tensioning of the electronic parking brake.

[0025] Tests have shown that the clearest and most pronounced differences in the current characteristics occurred here, thus increasing the accuracy of fault diagnosis.

[0026] In order to reduce the time required for testing, a further development also proposes that the generation of the service brake pressure only takes place for the duration of a specific movement phase or only for the duration of selected movement phases or only for the duration of parts of the movement phases of the actuators within the clamping or releasing movement and that the comparison of the current characteristics is limited to this movement phase or to the selected movement phases.

[0027] For example, it is conceivable that the service brake pressure is generated during the application movement of the electronic parking brake only for the duration of a clamping force build-up phase, i.e., a phase in which the brake pads have already been applied to the brake disc by the actuator and the mechanical brake pressure is continuously increased. Here, too, it was shown that when service brake pressure was applied, a significant change in the actual current characteristic could be observed compared to the reference current characteristic.

[0028] According to another variant of the method, the service brake pressure is generated during the release movement of the electronic parking brake, and only for the duration of a clamping force reduction phase. This also showed a significant change in the actual current characteristic compared to the reference current characteristic, thus demonstrating that this procedure is well suited for verifying correct installation.

[0029] Finally, the invention also aims to protect a test setup with which the method according to the invention can be carried out. Such a test setup involves a motor vehicle that has an electronic parking brake and a hydraulic service brake.

[0030] The electronic parking brake acts by means of actuators on the same brake pads of the rear wheels of the vehicle, which are also subjected to the service brake pressure of the hydraulic service brake.

[0031] The actuators can be controlled via at least one evaluation and control device in such a way that they are moved on the rear wheels and thereby a tensioning or releasing movement of the electronic parking brake is generated.

[0032] Furthermore, the at least one evaluation and control device can be or is set to a test routine. This results in the actuators performing a movement that causes the electronic parking brake to apply or release, and a service brake pressure can be or is built up at a selected rear wheel by at least one hydraulic pressure generating device of the service brake.

[0033] Finally, the test routine also allows an actual current characteristic curve of a selected actuator, measured during a clamping or releasing movement, to be compared with a measured reference current characteristic curve of a selected actuator. The comparison of the current characteristics is therefore preferably performed within the at least one evaluation and control device itself.

[0034] To start the test routine, a test device can be used, for example, which can be connected to the evaluation and control device via a service interface. Alternatively, it is also conceivable that the test routine can be activated remotely via a suitable data transmission method, for example, via an internet connection.

[0035] Additionally or alternatively, it is conceivable that the current characteristics recorded during the test routine be displayed on a display unit, preferably a test device. This also allows a comparison of the current characteristics by visual inspection.

[0036] Preferred embodiments of the invention are illustrated in the figures and explained in more detail in the following description with reference to the figures. This also makes further advantages of the invention clear. The same reference numerals, even in different figures, refer to the same, comparable, or functionally identical components. Corresponding or comparable properties and advantages are achieved even if a repeated description or reference to them is not made. The figures are not, or at least not always, to scale. In some figures, proportions or distances may be exaggerated in order to emphasize features of an embodiment more clearly.

[0037] They show, schematically Fig. 1 a test arrangement for carrying out the method according to the invention, Fig. 2 the representation of a reference current characteristic for a tensioning movement of the electronic parking brake, Fig. 3 the representation of a reference current characteristic for a release movement of the electronic parking brake, Fig. 4 the comparison of an actual current characteristic with a reference current characteristic with a superimposed pressure application of the parking brake with service brake pressure of the service brake during the entire tensioning movement of the electronic parking brake, Fig. 5 the comparison of an actual current characteristic with a reference current characteristic with a superimposed pressure application of the parking brake with service brake pressure of the service brake exclusively during a clamping force build-up phase, Fig. 6 the comparison of an actual current characteristic with a reference current characteristic with a superimposed pressure application of the parking brake with service brake pressure of the service brake exclusively during the release movement of the electronic parking brake and Fig. 7 a representation of a flow chart to illustrate a possible procedure.

[0038] First, the Fig. 1. This figure shows a conceivable test setup or test arrangement PA for implementing the method according to the invention. A motor vehicle K and a test device 21 are shown. The motor vehicle K has two front wheels 10, 11 and two rear wheels 12, 13.

[0039] Each of the wheels 10 to 13 is provided with a brake disc 14, which can be braked by brake pads 15 when the wheel rotates. The brake pads 15 are integrated into brake calipers 15' indicated by dashed lines.

[0040] It should be noted that, in contrast to the exemplary embodiment, the method can of course also be applied to a drum brake if the brake shoes can be actuated both via a parking brake actuator and via the wheel brake cylinder.

[0041] The motor vehicle K has a service brake, which has, for example, an electronic brake booster (eBKV) as a hydraulic pressure-generating device 17a. The hydraulic pressure-generating device 17a is connected via a brake line B to another hydraulic control device 17b in the form of a slip control unit (ESC unit). The slip control unit 17b is in turn hydraulically connected via brake lines B in a dual-circuit braking system (not shown in detail) to the brake calipers 15' in such a way that when hydraulic pressure builds up through the hydraulic pressure-generating device 17a, the brake pads 15 are clamped against the brake discs 14.

[0042] The hydraulic pressure generating device 17a and the slip control unit 17b are connected to an evaluation and control device 16 via control lines S.

[0043] Motor vehicle K is further equipped with an electronic parking brake, which is formed by an actuator 19 on each of the rear wheels 12 and 13. Each actuator 19 is integrated into the brake caliper 15' in a manner not shown in detail. Thus, when actuated or moved, it can also act on the brake pads 15 and cause the rear wheels 12, 13 to clamp.

[0044] Each actuator 19 comprises, in a manner not shown in detail, an electric motor and a multi-stage reduction gear, whereby a rotary movement of the electric motor can be converted into a translatory clamping or releasing movement. The actuators 19 are each connected to the evaluation and control device 16 via control lines S.

[0045] The evaluation and control device 16 is signal-connected to a service interface 20 via a data bus 18 (CAN bus). The test device 21 can be connected to the service interface 20 either wired via a service connector or wirelessly via a near-field radio network.

[0046] To check the correct installation of the electronic parking brake, i.e. to check whether the actuators 19 of each rear wheel 12, 13 are correctly connected to the evaluation and control device 16 via the control lines S and are also correctly controlled by this, a service technician or worker on the assembly line can start a test routine using the test device 21.

[0047] Alternatively, however, it is also conceivable that the test routine can be started or is started via a remote data transmission, for example via an Internet connection (not shown).

[0048] By means of the test routine, the evaluation and control device 16 is remotely controlled or activated in such a way that it causes the electronic brake booster 17a to build up pressure. The slip control unit 17b is then controlled by the evaluation and control device 16 in such a way that it selectively applies service brake pressure to one of the two rear wheels 12, 13 via a brake line B and also activates the actuators 19.

[0049] As will be explained in more detail later, this is done in such a way that for each rear wheel 12 or 13 a reference current characteristic I R measured and stored and later compared with an actual current characteristic I ist will compare.

[0050] Each reference current characteristic I Ris measured without an overlay of the parking brake with hydraulic service brake pressure, while each actual current characteristic curve is measured during an overlay of the parking brake with a hydraulic service brake pressure.

[0051] As part of the test routine, the current characteristics I R and I ist be shown on a suitable display of the test device 21.

[0052] By comparing the current characteristics I ist and I RIt can be assessed whether the installation of the electronic parking brake is correct or not. The comparison of the current characteristics or the measured current values ​​is carried out as part of the test routine, preferably by the evaluation and control device 16 itself. Only the result of the comparison, i.e. whether a correct or incorrect installation of the electronic parking brake was determined, is shown on a suitable display of the test device 21. Alternatively or additionally, it is conceivable that the said current characteristics I R and I ist can also be shown on the display of the test device 21 and can thus be compared visually by the service technician.

[0053] Based on the Fig. 2 is a reference current characteristic I RSP (t) of an actuator 19, which results during a tensioning movement SP, i.e. when the electronic parking brake is closed.

[0054] The diagram shows the current I drawn by the actuator 19 over time t. It can be seen that the clamping movement SP can be divided into five movement phases SP1 to SP5 within the clamping movement SP of the electronic parking brake.

[0055] In an initial start-up phase SP1 (time t1 to t2), the current I rises to a maximum current value I1 and then drops steeply to a current value I2 by time t2. In a subsequent idle phase SP2, the current value I2 remains approximately constant until time t3. At this point in time, a pad application phase SP3 begins, during which the brake pads are applied to the brake discs. The pad application phase SP3 lasts until approximately time t4 and then transitions into a clamping force build-up phase SP4. The clamping force build-up phase SP4 lasts until time t5, during which the current I rises steadily to a current value I3 (the defined cut-off current) and at time t5 initially changes to a negative current value I4, which returns to the value 0 by time t6. The period from t5 to t6 is referred to as the cut-off phase SP5.

[0056] Fig. 3 shows a reference current characteristic I RLP(t) of an actuator 19, which occurs during a release movement LP of the electronic parking brake. Here, too, the release movement LP can be divided into several movement phases LP1 to LP4 within the release movement LP of the electronic parking brake.

[0057] Thus, initially (t1 to t2) a start-up phase LP1 takes place in which the current I rapidly increases to a maximum current value I1 and then drops to a current value I2. In a second, clamping force reduction phase LP2 (t2 to t3), which can also be referred to as the pad release phase, the actuator 19 releases from the brake pads 15 and the current I drops to a current value I3. The clamping force reduction phase LP2 is followed by an idle phase LP3 (t3 to t4) in which the current I remains approximately at the current value I3. The idle phase LP3 is followed by a switch-off phase LP4 (t4 to t6) in which the current I initially drops again to a negative current value I4 and then returns to the value 0 at time t6.

[0058] The Fig. 2 and Fig. 3 shown reference current characteristics I RSP (t) and I RLP (t) occur when the actuators 19 execute a tensioning or releasing movement without a hydraulic superposition, ie without generating a superimposed service brake pressure of the service brake, provided that the tension remains approximately constant.

[0059] Based on the Fig. 4 is intended to compare a reference current characteristic I RSP (t) with an actual current characteristic I istSP (t). The current characteristics I RSP (t), I istSP (t) are recorded during an entire clamping movement SP of the actuators 19.

[0060] P(t) represents the course of the service brake pressure P of the service brake.

[0061] As already mentioned, the reference current characteristic I RSP (t) without a hydraulic overlay (i.e. operating brake pressure P = 0, cf. Fig. 4a) while the actual current characteristic Ii stSP (t) with a hydraulic superposition, thus generating a service brake pressure (P = P1, cf. Fig. 4b) was generated.

[0062] When comparing, it is noticeable that due to the hydraulic pressure superposition, the actual current characteristic I istSP (t) has a significantly longer idle phase SP2 and a significantly steeper increase in the clamping force build-up phase SP4. An extended idle phase SP2 combined with a steeper clamping force build-up phase SP4 thus represent characteristics of a hydraulic superposition of an actuator 19 with a service brake pressure P.

[0063] In the embodiment shown, the hydraulic superposition takes place over the entire tensioning movement SP of the electronic parking brake.

[0064] Alternatively, a procedure is also conceivable in which hydraulic overlay is carried out only in one or several selected phases of the clamping movement SP. This should be demonstrated using the Fig. 5 are shown.

[0065] Fig. 5a again shows the reference current characteristic I RSP (t), as determined without hydraulic pressure superposition. In the Fig. In contrast, in Figure 5b, a hydraulic pressure superposition (P = P1) occurred during the tension build-up phase SP4. As can be seen, a pressure superposition beginning at time t4' leads to a weakening of the current increase. This weakening lasts until time t4" and then transitions back to a steeper increase until time t5. Depending on the applied pressure and the gradient, the slope of the current increase can also briefly become negative.

[0066] A reduced current gradient in the tension build-up phase SP4 can therefore be interpreted as an indication of hydraulic pressure superposition during this phase.

[0067] As a further alternative, the Fig. 6 shows that a hydraulic pressure superposition during the release movement LP of the electronic parking brake is also conceivable. Fig. 6a a reference current characteristic I RLP (t), which was recorded during the release movement LP of the parking brake without a hydraulic pressure overlay. In the Fig. 6b shows the actual current characteristic li stLP (t) occurs when a hydraulic superposition (P = P1) takes place during the release movement LP.

[0068] It is evident that the current requirement decreases during the clamping force reduction phase LP2 (pad release phase). In other words, the negative slope of the actual current characteristic curve l istLP(t) in the tension reduction phase LP2 is significantly lower than without a hydraulic pressure superposition.

[0069] In addition, a shortening of phase LP2 and an extension of phase LP3 are to be expected.

[0070] In addition to the variants described above, further modifications of the process are also conceivable. For example, it is also conceivable that hydraulic pressure superposition with service brake pressure P during the release movement LP occurs exclusively in the idle phase LP3.

[0071] Finally, the Fig. 7 a possible embodiment of the method according to the invention is briefly outlined in essential steps (see also Fig. 1). Thus, in a first process step S1, within the scope of a test routine, the initially open actuators 19 of the parking brake are closed in a clamping movement and then opened again in a release movement. This initially occurs without any hydraulic pressure superposition from the service brake. During these movements, the current consumed by the actuators 19 is measured using suitable measuring devices.

[0072] In a process step S2, the current characteristics thus obtained for each actuator 19 are used as reference current characteristics I R saved.

[0073] In a method step S3, a hydraulic pressure build-up and a targeted forwarding to a rear wheel 12 or 13 to be checked takes place. The targeted forwarding of hydraulic service brake pressure can be carried out with the aid of the slip control unit 17b.

[0074] In a subsequent process step S4, the actuators 19 are closed again and an actual current characteristic I ist measured and saved.

[0075] The actual current characteristic I ist is compared in a process step S5 with a stored reference current characteristic I R of the respective actuator 19. This checks whether there is a deviation between the current characteristics as shown in the Fig. 4b described.

[0076] If so, a process step S6 additionally checks whether the deviation is related to the actuator on the pressurized wheel side. If so, a process step S7 determines that the electronic parking brake is installed correctly, and a corresponding message is issued.

[0077] If it is determined in process step S6 that the deviation belongs to an actuator which cannot be assigned to the pressurised wheel side, an interchanged installation of the actuators is determined in process step S7' and an error message is issued.

[0078] Alternatively, it is also conceivable in process step S5 that no deviation can be detected between the actual current characteristic of a checked actuator 19 and its reference current characteristic. In this case, a check is carried out in process step S6' to determine whether this actuator 19, for which no deviation could be detected, belongs to the wheel side not subjected to pressure. If this is the case, the correct installation can also be determined in process step S7 with a corresponding message. Otherwise, an error message about incorrect installation is also output here in process step S7'. List of reference symbols 10, 11 wheels (front wheels) 12, 13 wheels (rear wheels) 14 brake discs 15 brake pads 15' brake calipers 16 Evaluation and control device 17a hydraulic pressure generating device 17b hydraulic control device, slip control unit (ESC) 18 Data bus (CAN) 19 actuators 20 Service interface 21 test device B Brake lines I Current I1-I4 current values I ist Actual current characteristic I R Reference current characteristic I IstSP (t) Actual current characteristic during the clamping movement I IstLP (t) Actual current characteristic during the release movement I RSP (t) Reference current characteristic during the clamping movement I RLP (t) Reference current characteristic during the release movement K Motor vehicle LP release movement of the electronic parking brake LP1-LP4 Movement phases within the release movement of the electronic parking brake LP1 start-up phase LP2 Tension reduction phase (coating release phase) LP3 idle phase LP4 shutdown phase PA test setup for checking the correct installation of an electronic parking brake P hydraulically generated service brake pressure P1 Value of the operating brake pressure P(t) Course of the operating brake pressure S control cables S1-S7 process steps S6', S7' process steps SP tensioning movement of the electronic parking brake SP1-SP5 Movement phases within the tensioning movement of the electronic parking brake SP1 start-up phase SP2 idle phase SP3 surface application phase SP4 Tension build-up phase SP5 shutdown phase t time t1-t6 time points t4', t4" Zeitpunkte

Claims

[1] Method for checking the correct installation of an electronic parking brake of a motor vehicle (K), with actuators (19) located on the wheels (12, 13) of at least one axle for applying a parking brake force, wherein at least one evaluation and control device (16) controls the actuators (19) of the electronic parking brake located on the wheels (12, 13) in such a way that they are moved on the wheels (12, 13) and thereby a tensioning or releasing movement (SP or LP) of the electronic parking brake is generated, characterized by that a service brake pressure (P) is generated at one of the wheels (12 or 13) by at least one hydraulic pressure generating device (17a) at least for the duration of a specific movement phase or part of the movement phase within the clamping or releasing movement (SP or LP) and an actual current characteristic curve (l Ist) of the current (I) absorbed during the clamping or releasing movement (SP or LP) of at least one actuator (19) associated with one of the wheels (12 or 13) with a reference current characteristic (I R ) and the comparison is used to assess the correct installation of the electronic parking brake, and the reference current characteristic for each actuator (19) is generated by controlling the actuators (19) before generating the service brake pressure (P) in such a way that a tensioning and a release movement (SP and LP) of the electronic parking brake is generated, wherein the resulting current characteristic of each actuator (19) is measured and used as a reference current characteristic (I R ) is saved. [2] Method according to claim 1, characterized by that the service brake pressure (P) generated by the hydraulic pressure generating device (17a) is transmitted to a wheel (12 or 13) to be tested and the actual current characteristic (l Ist) of the actuator (19) with the reference current characteristic (I R ) which is also assigned to the wheel to be tested (12 or 13). [3] Method according to claim 1 or 2, characterized by that the service brake pressure (P) generated by the hydraulic pressure generating device (17a) is transmitted to a wheel (12 or 13) to be tested and the actual current characteristic (l Ist ) of the pressurized wheel (12 or 13) with the actual current characteristic (l Ist ) of the non-pressurized wheel (13 or 12). [4] Method according to one of the preceding claims 1 to 3, characterized by that the generation of the service brake pressure (P) takes place for the entire duration of a tensioning movement (SP) of the electronic parking brake, [5] Method according to one of the preceding claims 1 to 3, characterized bythat the generation of the service brake pressure (P) only takes place for the duration of a specific movement phase or only for the duration of selected movement phases or parts of the movement phases (SP1, SP2, SP3, SP4, SP5; LP1, LP2, LP3, LP4) of the actuators (19) within the clamping or releasing movement (SP or LP) and the comparison of the current characteristics (I Ist and I R ) is limited to this movement phase or to the selected movement phases (SP1, SP2, SP3, SP4, SP5; LP1, LP2, LP3, LP4). [6] Method according to claim 5, characterized by that the generation of the service brake pressure (P) during the tensioning movement (SP) of the electronic parking brake only takes place for the duration of a tensioning force build-up phase (SP4). [7] Method according to claim 5, characterized by that the generation of the service brake pressure (P) during the release movement (LP) of the electronic parking brake only takes place for the duration of a clamping force reduction phase (LP2). [8] Test arrangement (PA) for carrying out the method according to one of the preceding claims, with a motor vehicle (K) which has an electronic parking brake and a hydraulic service brake, wherein the electronic parking brake acts by means of actuators (19) on the same brake pads (15) or brake shoes of wheels (12, 13) of at least one axle of the motor vehicle (K), on which a service brake pressure (P) of the hydraulic service brake also acts, and wherein the actuators (19) can be controlled via at least one evaluation and control device (16) in such a way that they are moved on the wheels (12, 13) and thereby a tensioning or releasing movement (SP or LP) of the electronic parking brake is generated, wherein the evaluation and control device (16) can be set into a test routine in such a way thatthat the actuators (19) carry out a movement causing a tensioning or releasing movement (SP or LP) of the electronic parking brake and by at least one hydraulic pressure generating device (17a) of the service brake a service brake pressure (P) can be built up or is built up at a selected wheel (12 or 13), wherein by the at least one evaluation and control device (16) an actual current characteristic (l, Ist ) of a selected actuator (19) with a measured reference current characteristic (I R) of a selected actuator (19), and the reference current characteristic for each actuator (19) is generated in that the actuators (19) are controlled before the operating brake pressure (P) is generated in such a way that a tensioning and a release movement (SP and LP) of the electronic parking brake is generated, wherein the resulting current characteristic of each actuator (19) is measured and used as a reference current characteristic (I R ) is stored, is comparable or is compared.

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