Method and device for operating electromechanical wheel brake mechanism, electromechanical wheel brake mechanism and brake system

Abstract

The invention relates to a method for determining a wear value of an electromechanical wheel brake mechanism (2) of a motor vehicle, the wheel brake mechanism (2) having a displaceable actuator element (6) which can be moved towards a brake disc (12) of the wheel brake mechanism (2) by means of an actuatable actuator (4) having an electric motor (13), the invention relates to a wheel brake device (2) having a rotor (14) which is rotatably mounted and is operatively connected to an actuator element (6), the wear value of the wheel brake device (2) being determined as a function of the displacement of the actuator element. According to the invention, in order to determine the wear value, the actuator element (6) is first displaced against the end stop (19), then the actuator element (6) is moved towards the brake disc (12), the number of revolutions of the rotor (14) is monitored during the movement of the actuator element (6) from the end stop (19) towards the brake disc (12), and the wear value of the wheel brake mechanism (12) is determined as a function of the detected number of revolutions.

Description

Technical Field

[0001] The invention relates to a method for determining a wear value of an electromechanical wheel brake mechanism of a motor vehicle, wherein the wheel brake mechanism has a displaceable actuator element, which can be displaced relative to a brake disc of the wheel brake mechanism by a controllable actuator to generate a braking force, wherein the actuator has an electric motor with a rotor which is supported in a rotatable manner and is operatively connected to the actuator element, wherein the wear value of the wheel brake mechanism is determined as a function of the displacement.

[0002] The invention also relates to a device for carrying out the above-mentioned method, an electromechanical wheel brake mechanism having such a device, and a brake system having at least one such electromechanical wheel brake mechanism. Background Art

[0003] Methods of the type mentioned at the beginning are known in the prior art. For example, patent document EP 3 908 490B1 discloses a method for operating an electromechanical wheel brake mechanism, wherein an actuator element is displaced to a first end position, in which the wheel brake mechanism is in a non-tensioned state, and from the first end position is displaced to a second end position, in which the actuator element is pressed against the brake disc to generate a braking force. Here, the rotor position and / or motor current of the electric motor of the wheel brake mechanism are continuously monitored to determine the clearance or shoe wear degree according to the contact position of the determined actuator element impacting the brake disc. Summary of the invention

[0004] The method according to the invention with the features of claim 1 has the advantage that continuous monitoring of the current position of the actuator element is omitted and an absolute movement path of the actuator element can be determined, which absolute movement path always has the same starting point. To this end, it is provided according to the invention that, in order to determine the wear value, the actuator element is first displaced against the end stop, then the actuator element is moved toward the brake disc, and the number of revolutions of the rotor is monitored during the movement of the actuator element from the end stop toward the brake disc, and the wear value of the wheel brake mechanism is determined based on the detected number of revolutions. Therefore, the invention proposes that the actuator does not move the actuator element in the direction of the brake disc from a rest position at an arbitrary distance from the brake disc, but that the actuator always moves the actuator element in the direction of the brake disc starting from the end stop, which defines the starting position of the actuator element in a form-fitting manner. Here, the end stop advantageously interacts with the actuator element in the direction of movement of the actuator element away from the brake disc, so that the actuator element is pulled back against the end stop and then moves toward the brake disc. The fixed end stop ensures that the movement of the actuator element always starts from the same starting position and thus also determines the absolute movement path of the actuator element and / or the wear value or degree of wear of the wheel brake mechanism. Since the number of revolutions of the rotor is monitored, the complex rotor position monitoring carried out in the prior art is also omitted. Since the end stop ensures a greater distance of the end stop from the brake disk and thus a greater distance of the starting position from the brake disk compared to the prior art, the number of revolutions can be advantageously used and evaluated.

[0005] According to a preferred development of the invention, the rotor is equipped with a rotational speed sensor, wherein the rotational speed is detected by means of the rotational speed sensor. This creates a cost-effective solution, since, for example, a rotational speed sensor that is already assigned to the electric motor can be used.

[0006] Furthermore, it is preferably provided that the reaching of the actuator element to the brake disk is determined based on the operating current of the electric motor and / or data from a rotational speed sensor. For example, when the actuator element strikes the brake disk, the operating current suddenly increases, so that as soon as the operating current exceeds, for example, a predetermined limit value, a conclusion of the impact is drawn. Alternatively or additionally, the rotational speed sensor is monitored and as soon as it is detected that the previously detected number of revolutions no longer changes, a conclusion is drawn that the actuator element has reached the brake disk.

[0007] Furthermore, it is preferably provided that the reaching of the actuator element at the end stop is determined as a function of the operating current of the electric motor and / or data from a rotational speed sensor, in particular in the manner described above with regard to the reaching of the brake disk.

[0008] Furthermore, it is preferably provided that the absolute movement path of the actuator element is determined and stored as a function of the number of revolutions, and the wear value is determined as a function of this movement path or a change in the movement path. Preferably, the current movement path is compared with a movement path determined at an earlier point in time in order to detect a change in the movement path. If a change in the movement path is detected, a change in the wear value can be determined. Alternatively, preferably the wear value of the wheel brake mechanism is determined directly as a function of the detected movement path, for example as a function of an expected movement path.

[0009] Particularly preferably, the method is performed at regular intervals, in particular after each start-up of a motor vehicle with a wheel brake mechanism, after a replacement of the brake shoe and / or a replacement of the brake disc. Changes in the wear value can thus be detected in a timely manner. In addition, the replacement of the brake shoe and / or the brake disc can be automatically identified by detecting the absolute movement path (for example if the detected path does not increase but decreases). In previous methods, such replacement could not be automatically detected due to the use of relative path measurement. In the prior art, the replacement of the brake shoe or the replacement of the brake disc must be actively input by the user into the software of the control unit.

[0010] The device according to the invention having the features of claim 7 is characterized by a control unit which is specially designed to carry out the method according to the invention when used as intended. This leads to the advantages already mentioned above.

[0011] The wheel brake mechanism according to the invention having the features of claim 8 is characterized by the above-mentioned arrangement. This leads to the advantages already mentioned above.

[0012] The brake system according to the invention having the features of claim 9 is characterized by at least one wheel brake mechanism according to the invention and at least one device according to the invention. Optionally, the brake system has a plurality of electromechanical wheel brake mechanisms which are designed in the manner described above and are operated in particular by a common device according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Further advantages and preferred features and feature combinations are particularly apparent from the above description and the claims. The invention will be explained in more detail below with reference to the accompanying drawings. In which:

[0014] Figure 1 An advantageous braking system for a motor vehicle is shown in a simplified illustration.

[0015] Figure 2 A flow chart is shown for explaining the advantageous method. DETAILED DESCRIPTION

[0016] Figure 1A simplified sectional view of a brake system 1 for a motor vehicle (not shown here) is shown. The brake system 1 has an electromechanical wheel brake mechanism 2, which is assigned to a wheel of the motor vehicle. The wheel brake mechanism has a brake caliper 3. The brake caliper 3 carries a controllable actuator 4, which is connected to an actuator element 6 via a transmission mechanism 5, so that the actuator element 6 can be linearly moved. For this purpose, the transmission mechanism 5 according to the present embodiment has a spindle drive 7 and a spindle that can be driven by the actuator 4, and a spindle nut 9 is arranged on the spindle in a non-rotatable manner relative to the brake caliper 3, so that the spindle nut 9 is longitudinally moved by the rotation of the spindle 8. The transmission mechanism 5 is in particular a ball screw transmission mechanism or a linear converter. The spindle nut 9 is connected to the actuator element 6, which is configured as a pressure piston 10 in the present case and has a brake shoe 11 on its end face. The brake shoe 11 is arranged opposite to the brake disc 12 of the wheel brake mechanism 2, which is only shown here, wherein the brake disc 12 is preferably surrounded by the brake caliper 3 on both sides, so that there is another brake shoe on the side of the brake disc 12 facing away from the actuator element 6. The actuator 4 is configured as an electric motor 13, which has a rotor 14 supported in a rotatable manner and is connected to the main shaft 8 via a transmission mechanism 5. Alternatively, not shown here, the rotor 14 is directly connected to the main shaft 8 in a non-rotatable manner. In this case, the rotor 14 is also equipped with a speed sensor 5 and a current sensor 16.

[0017] The brake system 1 according to the present invention further comprises a control unit 17 , which is connected to the actuator 4 to control the actuator and also obtains a rotation speed signal output by the rotation speed sensor 5 .

[0018] The actuator 4 has a housing 18 in which the actuator element 6 is substantially located and guided. The housing 18 has a stop 19 on the side of the actuator element 6 facing away from the brake disc 12, to which the actuator element 6 can be moved away from or returned to the brake disc 12 to the greatest extent. Here, the stop 19 is so far from the brake disc 12 that the actuator element 6 can be returned to the stop 19 further than the distance required for the gap set between the shoe 11 and the brake disc 12.

[0019] Reference Figure 2 , an advantageous method for determining a wear value of the wheel brake mechanism 2 is described below, which method is executed by the control unit 17 during intended use.

[0020] The method starts in step S1 with the activation of the brake system 1. In a subsequent step S2, it is checked whether the prerequisites for carrying out a wear determination exist. In particular, the prerequisites are assumed to exist when a predetermined period of time has elapsed since the last wear determination and / or when the brake system 1 is put into operation, so that the method is carried out every time the brake system 1 is activated.

[0021] If the prerequisite is detected as being met in step S2, the electric motor 13 is controlled in a subsequent step S3 to displace the actuator element 6 back to the end stop 19. The actuator element 6 is thereby brought to a defined starting position or initial position for carrying out the wear determination. Reaching the end stop is detected, for example, in that the rotation speed sensor does not detect any further rotation of the rotor 14 and / or the current sensor 16 detects an increase in the operating current exceeding a predetermined limit value.

[0022] In the subsequent step S4, the electric motor 14 is controlled to move the actuator element 6 in the opposite direction (i.e., in the direction toward the brake disc 12) until the actuator element 6 hits the brake disc 12 with the brake shoe 11, thereby applying a braking force or a deceleration torque to the brake disc 12. In particular, as described above for the end stop 19, the arrival of the actuator element 6 at the brake disc 12 is detected by monitoring the rotation speed and / or the operating current of the electric motor 13. Before reaching the brake disc 12, the number of revolutions of the rotor 13 is detected by the rotation speed sensor 15 and stored by the control unit 17. Based on the number of revolutions, the wear or wear value of the wheel brake mechanism 2 is determined. If, for example, the number of revolutions changes when the wear determination is performed again later, it is recognized that the wear of the wheel brake mechanism 2 has changed or more precisely increased. Because the actuator element 6 moves from the end stop 19 in the direction toward the brake disc 12, the absolute wear value of the wheel brake mechanism 2 can be determined. The movement path of the actuator element 6 is determined based on the number of revolutions. If the movement path increases, the wear value of the wheel brake mechanism 2 increases. This ensures reliable monitoring of the wear condition of the wheel brake mechanism 2. For example, if the determined wear value exceeds a predetermined limit value, a warning message is issued to the driver of the motor vehicle.

Claims

1. A method for determining a wear value of an electromechanical wheel brake mechanism (2) of a motor vehicle, wherein: The wheel brake mechanism (2) has a displaceable actuator element (6), which can be moved toward a brake disc (12) of the wheel brake mechanism (2) by a controllable actuator (4) to generate a braking force, wherein the actuator (4) has an electric motor (13), which has a rotor (14) supported in a rotatable manner and operatively connected to the actuator element (6), and wherein a wear value of the wheel brake mechanism (2) is determined based on the displacement of the actuator element, characterized in that in order to determine the wear value, the actuator element (6) is first displaced to abut against an end stop (19), and then the actuator element (6) is moved toward the brake disc (12), and the number of revolutions of the rotor (14) is monitored during the movement of the actuator element (6) from the end stop (19) to the brake disc (12), and the wear value of the wheel brake mechanism (12) is determined based on the detected number of revolutions.

2. The method according to claim 1, characterized in that: The rotor (14) is equipped with a rotation speed sensor (15), and the rotation speed is detected by means of the rotation speed sensor (15).

3. The method according to any one of the preceding claims, characterized in that The arrival of the actuator element (6) at the brake disk (12) is determined based on the operating current of the electric motor (13) and / or data from the rotational speed sensor (15).

4. The method according to any one of the preceding claims, characterized in that The reaching of the end stop (19) by the actuator element (6) is determined based on the operating current of the electric motor (13) and / or the data of the rotational speed sensor (15).

5. The method according to any one of the preceding claims, characterized in that The absolute movement path of the actuator element (6) is determined and stored as a function of the number of revolutions, and the wear value is determined as a function of the movement path or a change in the movement path.

6. The method according to any one of the preceding claims, characterized in that The method is carried out at regular intervals, in particular after each start of a motor vehicle having the wheel brake mechanism (2).

7. A device for operating an electromechanical wheel brake mechanism (2) of a motor vehicle, wherein: The wheel brake mechanism (2) has a displaceable actuator element (6), which can be moved toward a brake disc (12) of the wheel brake mechanism (2) by a controllable actuator (4) to generate a braking force, wherein the actuator (4) has an electric motor (13), which has a rotor (14) supported in a rotatable manner and operatively connected to the actuator element (6), characterized in that, when used as intended, the method according to any one of claims 1 to 6 is performed by a control unit (17) specially designed for this purpose.

8. An electromechanical wheel brake mechanism (2), wherein: The wheel brake mechanism (2) has a displaceable actuator element (6), which can be moved toward a brake disc (12) of the wheel brake mechanism (2) by a controllable actuator (4) to generate a braking force, wherein the actuator (4) has an electric motor (13), which has a rotor (14) which is supported in a rotatable manner and is operatively connected to the actuator element (6), characterized in that it has a device according to claim 7.

9. A brake system (1) for a motor vehicle, comprising one or more electromechanical wheel brake mechanisms (2) according to claim 8 and at least one device according to claim 7.

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