Method and control unit for checking whether a parking brake actuator is connected correctly to the control unit

Abstract

The invention relates to a method for checking whether a controllably adjustable parking brake actuator (1) for braking or locking a wheel (2) of a motor vehicle is connected correctly, in particular on the correct side, to a control unit (10) for controlling a parking brake actuator. In detail, the method comprises at least three obligatory measures a), b) and c). According to a first measure a), is generated in a hydraulic medium (HM) present in a hydraulic line (3) for hydraulically adjusting the parking brake actuator (1). In a second measure b) carried out after measure a), at least one control signal (SSIG) for adjusting the parking brake actuator (1) is output by the control unit (10) to an electrical signal output connector (11) of the control unit (10) assigned to this wheel (2). In a measure c) carried out after measure b), a determination is made as to whether outputting of the at least one control signal (SSIG) in measure b) is accompanied by a change in the hydraulic pressure (p1) of the hydraulic medium (HM) which is present in the hydraulic line (3).

Description

[0001] PROCEDURE AND CONTROL UNIT FOR CHECKING WHETHER A PARKING BRAKE ACTUATOR IS CORRECTLY CONNECTED TO THE CONTROL UNIT

[0002] The invention relates to a method for checking whether a controllable and adjustable parking brake actuator for braking or locking a wheel of a motor vehicle is correctly connected to a control unit for controlling such a parking brake actuator. The invention further relates to a control unit configured or programmed to carry out this method.

[0003] Motor vehicles with an automated parking brake often include functions that generate braking force or brake force assistance in dynamic driving situations through electromechanical parking brake actuators. With this type of control, the wheel movement is monitored, and the braking force generated by the parking brake actuator is reduced as soon as the wheel locks. To ensure that the braking force is reduced at the correct wheel, it is important that the relevant parking brake actuator is connected correctly—in particular, "correctly"—to the control unit controlling the parking brake actuators.In the context of the present invention, "correctly oriented" and "inverted oriented" therefore mean that a parking brake actuator for generating a braking force acting on a specific wheel is also connected to the electrical signal output connection of the control unit assigned to this wheel, and not to an electrical signal output connection assigned to a different wheel of the motor vehicle. This ensures that control signals generated by the control unit for a specific parking brake actuator are also executed by this specific parking brake actuator and not by the parking brake actuator assigned to a different wheel. It is therefore an object of the present invention to provide an improved method with which it can be checked whether a specific parking brake actuator of a parking brake is also correctly connected to the respective control unit for controlling two or more parking brake actuators of this parking brake.In particular, a procedure is to be created which can be carried out in a particularly simple technical manner and without the need for special testing equipment.

[0004] This object is achieved by the subject matter of the independent patent claims. Preferred embodiments are the subject matter of the dependent patent claims.

[0005] The basic idea of ​​the invention is therefore to utilize, in the aforementioned interchangeability test, the fact that a parking brake actuator arranged in a hydraulic line and hydraulically coupled to a hydraulic medium present in the hydraulic line, as well as being electromechanically adjustable, causes a pressure change in the hydraulic pressure of the hydraulic medium present in the hydraulic line when electromechanically adjusted. This pressure change is caused by the electromechanical adjustment of the parking brake actuator or a piston as part of the parking brake actuator resulting in the volume formed jointly by the parking brake actuator and the hydraulic line either increasing or decreasing, depending on whether the parking brake actuator or its piston is adjusted towards the brake disc of the associated wheel, i.e., toward a closed position, or in the opposite direction away from the brake disc, i.e., toward a released position.Using a suitable pressure sensor for determining the hydraulic pressure of the hydraulic medium in the hydraulic line or in the parking brake actuator, such a change in the hydraulic pressure can be detected and thus indirectly determined whether the parking brake actuator has been or is being moved. This effect of a change in hydraulic pressure when the parking brake actuator is moved is utilized in the method according to the invention. For this purpose, the control unit controlling the parking brake or its parking brake actuator generates a control signal at a signal output connection assigned to a specific wheel including the parking brake actuator. This control signal causes an adjustment of the parking brake actuator connected to this signal output connection. With the aid of the hydraulic pressure monitoring explained above, it can thus be determined whether an adjustment of the desired parking brake actuator actually takes place in response to said control signal.Since this absolutely requires that the parking brake actuator in question is also connected to the correct signal output connection of the control unit, it can be determined in this way whether such a correct connection, in particular a "correct side" connection of the parking brake actuator in question to the control unit, exists or not, as explained at the beginning.

[0006] A particularly advantageous feature of the method described above is that no additional hardware is required for the parking brake to implement this procedure; both the parking brake actuator and the aforementioned hydraulic pressure sensor are generally already present in a conventional parking brake. It goes without saying that the procedure described above can also be implemented for all parking brake actuators present in the parking brake and assigned to the various wheels of the vehicle without any major additional effort.

[0007] The method according to the invention presented here is therefore used to check whether a controllably adjustable parking brake actuator for braking or locking a wheel of a motor vehicle is correctly connected, in particular in the correct direction, to a control unit for controlling a parking brake actuator. Specifically, the method comprises at least three mandatory measures a), b), and c). According to a first measure a), a specific hydraulic pressure is generated in a hydraulic medium present in a hydraulic line, to which the parking brake actuator is hydraulically coupled. In a second measure b), carried out after measure a), at least one control signal for electromechanically adjusting the parking brake actuator is output by the control unit to an electrical signal output connection of the control unit assigned to this wheel.In step c), which is performed after step b), it is checked whether the output of at least one control signal in step b) is accompanied by a change in the hydraulic pressure of the hydraulic medium present in the hydraulic line. This determination can be made using a hydraulic pressure sensor located in the hydraulic line, which is connected to the control unit for signal and thus also data transmission and transmits the corresponding hydraulic pressure sensor data to the control unit, so that the control unit has the appropriate hydraulic pressure information available for implementing step c).

[0008] In a preferred embodiment of the method according to the invention, in step c), a change in the hydraulic pressure is determined to have occurred if a difference between the hydraulic pressure before the output of the at least one control signal for adjusting the parking brake actuator and after the output of the at least one control signal according to step b) exceeds a predetermined threshold value. Since exceeding such a threshold value is accompanied by an adjustment of the parking brake actuator, if the threshold value is set appropriately, it can be reliably determined without risk of incorrect evaluation whether the parking brake actuator has been moved. Alternatively, in this embodiment, in step c), a change in the hydraulic pressure can be determined to have occurred if an expected increase or decrease in the previous hydraulic pressure is detected during the adjustment of the parking brake actuator according to step b).According to a third alternative of this embodiment, in measure c), a change in the hydraulic pressure can be determined to have occurred if, after the lapse of a predetermined period of time, measured from the output of the at least one control signal according to measure b), a change, in particular an increase or a decrease, in the hydraulic pressure has been detected.

[0009] Particularly preferably, an additional parking brake actuator for braking or locking another wheel of the motor vehicle is hydraulically decoupled from the hydraulic line before performing measures b) and c). This prevents an adjustment of the other parking brake actuator from leading to a change in the hydraulic pressure in the hydraulic line, which could lead to an erroneous determination in measure c) that the parking brake actuator being tested—and not the other one—was moved, even though this is not the case.

[0010] According to an advantageous development of the method according to the invention, in an additional measure d1) following measure c), the parking brake actuator is classified as correctly connected to the control unit, in particular as connected to the correct signal output connection, if a change in the hydraulic pressure was detected in measure c). In contrast, in an additional measure d2) following measure c), the parking brake actuator is classified as incorrectly connected to the control unit, in particular as not connected to the correct signal output connection of the control unit, if no change in the hydraulic pressure was detected in measure c.

[0011] According to an advantageous further development, an error signal can be generated by and / or in the control unit, and in particular, output if it was determined in additional measure d2) that the parking brake actuator was incorrectly connected to the control unit. This allows further processing of the finding that the tested parking brake actuator is obviously connected incorrectly, but in any case incorrectly, to the parking brake control unit, thus potentially resulting in a safety-critical error condition.

[0012] The method according to the invention can be implemented during parking brake fault diagnosis when the motor vehicle equipped with the parking brake, including the parking brake actuator, the control unit, and the wheel to be braked, is not currently in transit mode, allowing the proper functioning of the parking brake to be specifically tested. However, the method presented here is also advantageously suitable for implementation during transit mode of a motor vehicle.

[0013] According to a further advantageous development, in the course of the method according to the invention, measures a), b) and c) can be carried out as measures a'), b') and c)' with a further parking brake actuator for braking or blocking another wheel of the motor vehicle.

[0014] Thus, by means of the method according to the invention, an interchange check of two or more parking brake actuators of the parking brake can be carried out at least partially simultaneously, i.e. with a temporal overlap.

[0015] In a further preferred embodiment, measures a'), b'), and c') are performed at least partially simultaneously, i.e., with a temporal overlap, with measures a), b), and c). This allows the test duration required for the method to be kept as short as possible, particularly when two or more parking brake actuators are to be tested for their correct electrical connection to the control unit.

[0016] In an alternative variant, however, it is also conceivable to begin testing a further, i.e., second, parking brake actuator by performing the aforementioned steps a'), b'), and c') only after the first parking brake actuator has been tested by performing steps a), b), and c). This completely eliminates any potential interference between the two test procedures, which could potentially occur when they are performed simultaneously.

[0017] Particularly preferably, measures a'), b'), and c') can be carried out at a time staggered from measures a), b), and c). This avoids or at least counteracts electrical overload of the control unit due to undesirable electrical current peaks caused by the simultaneous adjustment of two or more parking brake actuators. Due to the at least partially simultaneous execution of two test procedures, testing is accelerated. In this variant, implementation of measure a') therefore begins after implementation of measure a).

[0018] The invention also relates to a control unit for a motor vehicle, which is configured / programmed to implement the above-described method according to the invention. The above-explained advantages of the method according to the invention are therefore transferred to the control unit according to the invention.

[0019] Further important features and advantages of the invention emerge from the subclaims, from the drawings and from the associated description of the figures based on the drawings.

[0020] It is understood that the features mentioned above and those to be explained below can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the present invention. Preferred embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

[0021] They show, schematically:

[0022] Fig. 1 shows an example of the structure of a parking brake including a control unit of the parking brake, by means of which the method according to the invention can be carried out.

[0023] Fig. 2 shows an exemplary flow diagram of the method according to the invention.

[0024] Figure 1 illustrates schematically, in a highly simplified representation and by way of example, the structure of a parking brake 4 with two hydraulically acting and each electromechanically adjustable parking brake actuators 1, 1*, as well as with a control unit 10, in which the method according to the invention can be carried out. Each of the parking brake actuators 1, 1* comprises a movable piston 5, 5*, which can be hydraulically adjusted using a hydraulic medium HM. For this purpose, a volume of the parking brake actuator 1, 1*, in which the piston 5, 5 * is adjustably arranged, communicates with a hydraulic line 3, in which the hydraulic medium HM is provided. The hydraulic line 3 can in turn be in fluid connection with a hydraulic medium reservoir 6, in which the hydraulic medium HM is stored and from which hydraulic medium HM can consequently be introduced into the hydraulic line 3 and via this into the parking brake actuator 1, 1*. By means of the adjustable piston 5 or5*, a braking force can be exerted on a brake disc 7 or 7*, which is arranged on the associated wheel 2, 2*.

[0025] The respective parking brake actuator 1, 1* or piston 5, 5* or can thus be adjusted with the aid of the hydraulic medium HM, but also electromechanically between a released position, in which no such braking force is generated, and a closed position, in which such braking force acts on the brake disc 7. Since, during electromechanical adjustment of the parking brake actuator 1, 1* or its piston 5, 5* towards the closed position, the volume of the parking brake actuator 1, 1* that is in fluid communication with the hydraulic line 3 is increased, the hydraulic pressure p of the hydraulic medium HM decreases towards the closed position during such an electromechanical adjustment. Because, during electromechanical adjustment of the parking brake actuator 1, 1* orwhose piston 5, 5* towards the release position, the volume of the parking brake actuator 1, 1 fluidly communicating with the hydraulic line 3 is reduced, the hydraulic pressure p of the hydraulic medium HM increases with such an adjustment towards the release position.

[0026] To adjust the parking brake actuator 1, 1* or its piston 5, 5*, the latter is controlled by the control unit 10 by transmitting corresponding control signals SSIG generated by the control unit 10. These control signals SSIG are transmitted from the control unit 10 to the respective parking brake actuator 1, 1* via a respective signal line 13, 13*.

[0027] For correct signal transmission to the parking brake actuator 1, it is imperative that the signal line 13 electrically connected to the parking brake actuator 1 is also connected to the signal output connection 11 assigned to this parking brake actuator 1, since only at this connection are the control signals SSIG required to adjust the parking brake actuator 1 provided. Connecting the signal line 13 to the signal output connection 11*, at which control signals for controlling the parking brake actuator 1* are generated by the control unit 10, would thus result in the parking brake actuator 1* being adjusted in error and not the parking brake actuator 1 as intended. Whether the signal line 13 is correctly connected to the assigned signal output connection 11 can be checked using the method according to the invention, which is explained below by way of example using the flow diagram in Figure 2.In the example of Figure 2, the procedure includes three mandatory measures a), b) and c).

[0028] According to a first measure a), the hydraulic medium HM present in the hydraulic line 3, to which the parking brake actuator 1 is hydraulically coupled, is pressurized so that the hydraulic medium HM has a hydraulic pressure p1. This can be achieved by introducing additional hydraulic medium HM from the pressurized hydraulic medium reservoir 6 with the aid of an actuator 8 controllable by the control unit 10. As soon as the hydraulic medium HM in the hydraulic line 3 has the desired hydraulic pressure p1, the fluidic connection between the hydraulic line 3 and the hydraulic medium reservoir 6 can be interrupted with the aid of the actuator 8. However, a configuration is also conceivable in which the fluidic connection between the hydraulic line 3 and the hydraulic medium reservoir 6 is first interrupted by adjusting the actuator 8 and the desired hydraulic pressure p1 is then generated by further adjusting the actuator 8.The determination of the instantaneous hydraulic pressure p of the hydraulic medium HM in the hydraulic line 3 can be carried out by means of a hydraulic pressure sensor 14 arranged in the hydraulic line 3 or fluidically communicating with the hydraulic line 3, which transmits sensor data corresponding to the measured hydraulic pressure p to the control unit 10 via a signal line 21.

[0029] Following measure a), a fluidic connection between the parking brake actuator 1* not to be tested and the pressure sensor 14 is interrupted using a valve device 9* arranged in the hydraulic line 3 between the pressure sensor 14 and the parking brake actuator 1*. The parking brake actuator 1* is thus fluidically isolated from the parking brake actuator 1 and the pressure sensor 14. Accordingly, before carrying out measure a), it must be ensured that a fluidic connection between the parking brake actuator 1 and the pressure sensor 14 is not interrupted using a valve device 9 arranged in the hydraulic line 3 between the pressure sensor 14 and the parking brake actuator 1. By means of the aforementioned measures, a closed hydraulic system 15 is created comprising the parking brake actuator 1 and the pressure sensor 14, which are hydraulically or fluidly connected to one another via the hydraulic medium HM in the hydraulic line 3.

[0030] In a second measure b) carried out after measure a), the control unit 10 now outputs a control signal SSIG for adjusting the parking brake actuator 1 to the electrical signal output connection 11 of the control unit 10 assigned to the wheel 2.

[0031] If the parking brake actuator 1 is correctly connected to this signal output connection 11 via the signal line 13 as shown in Figure 1, the control signal SSIG is transmitted to the parking brake actuator 1 via the signal line 13 and causes the parking brake actuator 1 to be adjusted either to the closed position or to the released position.

[0032] The adjustment of the parking brake actuator 1, as described above, is accompanied by an increase or decrease in the hydraulic pressure p of the hydraulic medium HM compared to the previously set hydraulic pressure p1. Such a change in the hydraulic pressure p to a value that is increased or decreased compared to the hydraulic pressure p1 is detected by the pressure sensor 14 and transmitted to the control unit 10 via the signal line 21.

[0033] Thus, in a measure c) carried out after measure b), the pressure sensor 14 is used to check whether the output of the control signal SSIG in measure b) has caused a change in the hydraulic pressure p1 of the hydraulic medium HM present in the hydraulic line 3 or whether this is not the case.

[0034] In a sub-measure c1) of measure c), a change in the hydraulic pressure p1 is determined to have occurred if a difference Ap between the hydraulic pressure p1 before the output of the at least one control signal SSIG for adjusting the parking brake actuator 1 and after the output of the control signal SSIG according to measure b exceeds a predetermined threshold value ps. As an alternative to sub-measure c1), in a sub-measure c2) of measure c), a change in the hydraulic pressure p1 can be determined to have occurred if, after the expiration of a predetermined time period T, measured from the output of the at least one control signal SSIG according to measure b), a change, in particular an increase or a decrease, in the hydraulic pressure p1 is detected.

[0035] In an additional measure d1) following measure c), the parking brake actuator 1 is classified as correct, i.e. as connected to the correct signal output connection 11 on the control unit 2, if in measure c) - as explained above for two alternatives - a change in the hydraulic pressure p1 was detected. In contrast, as an alternative to additional measure d1), in an additional measure d2) also following measure c), the parking brake actuator 1 is classified as incorrect, i.e. not connected to the correct signal output connection 11 of the control unit 10, if in measure c no change in the hydraulic pressure p1 was detected. This is the case if the signal line 13 leading to the parking brake actuator 1 is connected in the wrong direction to the signal output connection 11* assigned to the other parking brake actuator 1*.

[0036] Optionally, in a further additional measure e) following additional measure d2), it can be provided to generate and output an error signal ERR in the control unit 10 if it was determined in measure c) or in additional measure d2) that the parking brake actuator 1 was incorrectly connected to the control unit 10, in particular to the output connection 11* assigned to the other wheel 2*.

[0037] In a further development of the example, in the course of the method according to the invention, measures a), b) and c can be carried out as measures a'), b') and c ') with the further parking brake actuator 1* for braking or blocking the other wheel 2* of the motor vehicle.

[0038] Measures a'), b'), and c') can preferably be implemented staggered, but with a temporal overlap with measures a), b), and c). For this purpose, the implementation of measure a') begins after the start of the implementation of measure a).

[0039] Alternatively, a synchronous implementation of measures a), b), c) and measures a'), b') and c' is also conceivable.

[0040] In the example, the method according to the invention described above is carried out as a diagnostic method, i.e., not during the vehicle's ferry operation. However, it is also conceivable that it could be carried out during the vehicle's ferry operation.

[0041] *****

Claims

Patent claims 1 . Method for checking whether an electromechanically adjustable and hydraulically acting parking brake actuator (1) for braking or locking a wheel (2) of a motor vehicle is correctly connected, in particular in the correct direction, to a control unit (10) for controlling such a parking brake actuator (1), comprising the following measures: a) generating a specific hydraulic pressure (p1) in a hydraulic medium (HM) present in a hydraulic line (3), to which hydraulic medium the parking brake actuator (1) is hydraulically coupled, b) outputting at least one control signal (SSIG) for electromechanically adjusting the parking brake actuator (1) by the control unit (10) to an electrical signal output connection (11) of the control unit (10) assigned to this wheel (2); c) Checking whether the output of the at least one control signal (SSIG) in measure b) is accompanied by a change in the hydraulic pressure (p1) of the hydraulic medium (HM) present in the hydraulic line (3).

2. Method according to claim 1, characterized in that in measure c) a change in the hydraulic pressure (p1) is determined to have occurred if a difference (Ap) between the hydraulic pressure (p1) before the output of the at least one control signal (SSIG) for adjusting the parking brake actuator (1) and after the output of the at least one control signal (SSIG) according to measure b) exceeds a predetermined threshold value (ps); or that in measure c) a change in the hydraulic pressure (Ap) is determined to have occurred if, during the expected adjustment of the parking brake actuator (1) according to measure b), an increase or decrease in the previous hydraulic pressure (p1) is detected; or that in measure c) a change in the hydraulic pressure (p1) is determined to have occurred if, after the lapse of a predetermined period of time (T), measured from the output of the at least one control signal (SSIG) according to measure b), a change (D), in particular an increase or a decrease, in the hydraulic pressure (p) is detected.

3. Method according to claim 1 or 2, characterized in that a further parking brake actuator (1*) for braking or blocking another wheel (2*) of the motor vehicle is hydraulically decoupled from the hydraulic line (3) before carrying out measures b) and c).

4. Method according to one of claims 1 to 3, characterized in that in an additional measure d1) following measure c) the parking brake actuator (1) is classified as being correctly connected to the control unit (10), in particular as being connected to the correct signal output connection (11) of the control unit (10), if a change in the hydraulic pressure (p1) was detected in measure c); or / and in an additional measure d2) following measure c) the parking brake actuator (1) is classified as being incorrectly connected to the control unit (10), in particular as not being connected to the correct signal output connection (11) of the control unit (10), if no change in the hydraulic pressure (p1) was detected or the change was too small.

5. Method according to one of the preceding claims, characterized in that an error signal (ERR) is generated by and / or in the control unit (10) if it was determined in measure c) and / or d2) that the parking brake actuator (1) was incorrectly connected to the control unit (10).

6. Method according to one of the preceding claims, characterized in that the method is carried out during the driving operation of the motor vehicle which has the wheel (2), the parking brake actuator (1) and the control unit (10).

7. Method according to one of the preceding claims, characterized in that in the course of the method, measures a), b) and c) are carried out as measures a'), b') and c)' with a further parking brake actuator (1*) for braking or blocking another wheel (2*) of the motor vehicle.

8. Method according to claim 7, characterized in that the measures a'), b') and c') are carried out with a temporal overlap with the measures a), b) and c) or synchronously with the measures a), b) and c).

9. Method according to claim 7 or 9, characterized in that the measures a'), b') and c') are carried out with a time delay to the measures a), b) and c), and the implementation of the measure a') begins after the start of the implementation of the measure a).

10. Control device for a motor vehicle, characterized in that the control device (10) is set up / programmed to carry out the method according to one of the preceding claims.

Images