Method for testing the functionality of an electromechanical wheel brake system in an automobile, wheel brake system, brake system

Abstract

The present invention relates to a method for testing the functionality of an electromechanical wheel brake system (1) of an automobile. [Solution] The wheel brake device (1) comprises at least a first electromechanical actuator (2) for operating the wheel brake device (1) and a second electromechanical actuator (3) for blocking the wheel brake device (1) for parking braking. The second actuator (3) is controlled to block the wheel brake device (1), the first actuator (2) is controlled to operate the wheel brake device (1), the motion variables of the first actuator (2) are detected, the second actuator (3) is recognized as functioning if the motion variables fall below a predetermined limit value, and otherwise the second actuator (3) is recognized as defective.

Description

Technical Field

[0001] The present invention relates to a method for inspecting the functionality of an electromechanical wheel brake device of a motor vehicle, the wheel brake device comprising at least a first electromechanical actuator for actuating the wheel brake device and a second electromechanical actuator for blocking the wheel brake device for parking brake (Parkbremsung).

[0002] Furthermore, the present invention relates to an electromechanical wheel brake device and an electromechanical brake system comprising such a wheel brake device.

Background Art

[0003] Hydraulically operable wheel brake devices are known as service brakes of motor vehicles, and the parking brake mechanism is implemented by a separate actuator. For example, an electromechanical parking brake that usually has an electric motor, a reduction gear connected thereto, and a spindle mechanism, and these are incorporated into a hydraulic brake caliper or act on a drum brake is known. Since these actuators are usually designed together with a self-locking gear spindle mechanism, parking brake is guaranteed even when the stopped motor vehicle is in a non-powered state after operation.

[0004] Furthermore, a fully electromechanically operated wheel brake system is known as the service brake of an automobile. This also typically has an electric motor, a connected reduction gear, and a spindle mechanism. However, unlike a parking brake actuator, the components of a service brake must be designed to be non-self-locking so that if an abnormality occurs during operation (Fehlerfall), such as a power outage, the brake will open to prevent compromising the vehicle's driving stability. A known possibility for incorporating a parking brake mechanism into such a non-self-locking electromechanical service brake is the use of a second actuator that can block the service brake mechanism in the closed position. For this purpose, for example, a shape-coupled claw mechanism (Klinkenmechanismus) that can block the motor pinion of the service brake is used. This mechanism ensures that the service brake remains closed when the vehicle is unpowered and parked, allowing the service brake to be blocked to ensure secure parking. To that extent, the structural difference of this type of parking brake mechanism is that, compared to the aforementioned actuator combination (a service brake that can be operated by hydraulics and an electromechanical parking brake), the generation of parking brake torque does not occur independently of the generation of service brake torque.

[0005] Furthermore, since the proper functioning of service brake and parking brake actuators is safety-critical, various functional and validation checks (Plausibilisierung) are known for these. For example, the proper functioning of the parking brake is safety-critical, especially in driving situations where the driver cannot actively intervene in the event of a malfunction. This is true, for example, when parking remotely (RCP). In such cases, for example, the functionality of the parking brake actuator can be checked before remote parking, thereby ensuring that it can be properly engaged after parking. In conventional electromechanical parking brake actuators used in combination with hydraulically operated service brakes, for example, power consumption can be validated and / or the movement of the actuator can be detected when the clamping force increases. [Overview of the Initiative]

[0006] The method according to the present invention having the features of claim 1 is characterized in that a second actuator is controlled to block a wheel brake device, a first actuator is controlled to actuate a wheel brake device, a motion variable of the first actuator is detected, and the second actuator is recognized as functioning if the motion variable falls below a predetermined limit, and otherwise is recognized as defective. This ensures a particularly advantageous, simple, and reliable inspection of the second actuator as a parking brake actuator. The test is preferably performed with the brake open so that no brake torque is generated during test control. This allows the test to be performed even while driving (at low speed) without the driver noticing. The test procedure is advantageously performed very quickly and further simulates realistic load conditions for the parking brake actuator. Further advantageously, the check of the second actuator as a parking brake actuator is based on the first actuator as an independent service brake actuator, and to that extent, the control unit and sensor system used for inspection are independent of the parking brake actuator itself. This advantageously ensures reliable detection of mechanical and electrical abnormalities in the parking brake mechanism, such as sticking or damage. Therefore, as stated at the beginning, the method according to the present invention provides an advantageous operating strategy for checking the function of a parking brake actuator in an automobile equipped with an electromechanical service brake. In this case, the second actuator is configured to block the first actuator, in particular, as an actuator for a locking pawl in a transmission mechanism, as described at the beginning. Therefore, the possibility of checking the power consumption and / or detecting the movement of the actuator when the clamping force increases, as described at the beginning, is eliminated. This is because the brake torque itself is always increased by the first actuator as the service brake actuator, and not by a separate parking brake actuator.If a vehicle stops on a slope or even with sufficient drive torque, it may be possible to check whether the brake torque increases normally. This requires at least the following method steps: tightening the brakes with the service brake, engaging the parking brake, de-energizing the service brake, potentially increasing the drive torque, and verifying the brake torque. To that extent, such a method cannot be performed without the driver's awareness and would therefore be a time-consuming test routine that could be unpleasant for the driver. In contrast, the operational strategy according to the present invention has the advantage of checking the functionality of a second actuator as part of the parking brake mechanism without the driver's awareness, which helps to make the driver feel comfortable. This test control is preferably initiated before a situation arises where the normal functioning of the parking brake is particularly safety critical, for example, before the vehicle is remotely parked. The method according to the present invention can be used in all electromechanical service brakes with a parking brake mechanism, in which the actuator responsible for the parking brake mechanism blocks the wheel brake device, particularly the service brake. For example, this applies to a wheel brake device in which the pinion of the motor shaft of the first actuator of the service brake is blocked by a pin. The pin is inserted via a second actuator, which is particularly formed as a coil or linear motor. Preferably, the pin is inserted, i.e., the parking brake mechanism is activated, and then the first actuator is controlled to adjust the torque corresponding to the brake return torque at the maximum clamping force required for parking. If the motor shaft does not move or moves only slightly, the parking brake is properly engaged. The same applies to parking brake mechanisms in which a freewheel in a parking operation switchable by the second actuator prevents reverse rotation of the transmission of the first actuator. Shape / friction-coupled parking brake mechanisms, for example, which have a friction brake device acting on the motor pinion of the first actuator that is actuated by the second actuator, can also be checked in the same way.Preferably, before performing the method according to the present invention, particularly as a preliminary step, the first actuator as a service brake is checked for its functionality. In particular, the inspection according to the present invention is performed on each wheel of an automobile having corresponding actuators, including a parking function, for example when the automobile is unlocked and / or when it departs. In particular, the inspection is performed in parallel on all corresponding wheel brake devices. Typically, the actuators are designed to ensure that the first actuator can always continue to tighten the service brake, so accordingly, the inspection is preferably performed simultaneously while driving. Otherwise, each wheel brake device is preferably inspected individually or each wheel is inspected sequentially.

[0007] According to a preferred development of the present invention, the second actuator is intended to be controlled to block the rotation of the rotor shaft of the first actuator, and the change in the rotor position of the rotor shaft is to be detected as a motion variable. This provides a particularly advantageous possibility for testing the functionality of the second actuator when the first actuator is formed as a rotary actuator, in particular as an electric rotary drive. For example, if the rotor position is measured by a rotor position sensor of an actuator formed as an electric motor, and it does not change or remains at least below a predetermined threshold, the parking brake mechanism is properly engaged.

[0008] Particularly preferably, the second actuator is controlled to block the translational displacement of the components of the first actuator, particularly the rotor (Laeufer), and the change in the displacement distance of the components is intended to be detected as a kinetic variable. This provides a particularly advantageous possibility for testing the functionality of the second actuator when the first actuator is formed as a linear actuator, particularly an electric linear drive.

[0009] According to a preferred development of the present invention, the second actuator is intended to be controlled such that a locking member, particularly a claw, cooperates shape-coupled and / or force-coupled with a mating member, particularly a pinion, positioned or formed on or on a rotor shaft or component, in order to displace the locking member. When formed and controlled in this manner, the advantages of the method according to the present invention become particularly clear. In particular, the block is formed by shape coupling and / or friction coupling.

[0010] Particularly preferably, the mechanical stiffness, in particular play, of at least one actuator is to be detected depending on the detected motion variables. This provides the advantage that, in addition to functionality, other characteristic quantities can be determined particularly easily without the need for additional control or measurement.

[0011] According to a preferred development of the present invention, when the second actuator is controlled, the first actuator is intended to be controlled to actuate the brake pads of the wheel brake device in the tightening direction. That is, the two actuators are operated simultaneously, or a favorable superposition of their corresponding movements is achieved. In this case, the parking brake mechanism is engaged during the operation of the service brake, preferably at a very low speed, so that the action of the second actuator, in particular the aforementioned locking, is reliably confirmed based on the dynamic behavior during the tightening movement observed in that case.

[0012] Particularly preferably, the first actuator is intended to be controlled to actuate the brake pads of the wheel brake system in the disengagement direction. This provides the advantage that the motion variables are detected particularly accurately, even when the wheel brake system is already fully engaged. Preferably, the actuator is controlled to apply a predetermined control current such that a force and / or torque of the same order and direction as that which acts as a return torque to the parking brake using the second actuator, particularly when the clamping force is at its maximum, i.e., when the wheel brake system is fully engaged.

[0013] In a preferred development of the present invention, the vehicle's speed is detected, and the method is intended to be executed only when the speed falls below a predetermined limit. This also advantageously ensures that the impact on driving safety in the event of a malfunction is minimized.

[0014] Particularly preferable, the vehicle is monitored for the presence or absence of a brake request, and the method is intended to be executed only if no brake request is detected. This has the advantage, as described above, that it does not affect the continuation and results of braking and inspection that are normally possible to perform simultaneously.

[0015] In a preferred development of the present invention, the vehicle is monitored to determine whether a parking process, particularly an autonomous parking process, is scheduled, and the method is intended to be executed when it is recognized that a parking process is scheduled. This also advantageously ensures that functionality is confirmed before the use of a second actuator that is subsequently scheduled. The method is time-coordinated with the scheduled parking process, in particular, so that it is completed before the parking process begins, but at least before the vehicle is in a parking position.

[0016] Particularly preferable is the idea that the vehicle is monitored for the start of driving after a parking process, especially one performed using a second actuator, and that the method is executed when the start of driving is recognized. This has the advantage that functionality is regularly checked at the start of each drive.

[0017] In a preferred development of the present invention, the vehicle doors of an automobile are monitored for the presence or absence of an unlocking process, and the method is intended to be performed if an unlocking process is recognized. This is advantageously ensured that functionality is checked regularly, particularly before or at the start of driving, since the start of driving usually occurs with a certain time delay following the unlocking process. If the time delay is considered sufficient to perform the method, the method is preferably performed before the actual driving has started.

[0018] An electromechanical wheel brake device according to the present invention having the features of claim 13 comprises at least a first electromechanical actuator for operating the wheel brake device and a second electromechanical actuator for blocking the wheel brake device for parking braking. The device features a control device specifically configured to perform the method of the present invention. This results in the advantages already described. The control device is particularly formed as a central control device and is located, for example, in a vehicle or is individually assigned to the wheel brake device. Preferably, the wheel brake device comprises a brake caliper having at least one brake pad and a brake disc, with at least a first actuator coupled to the brake pad. In particular, at least one of the actuators is formed as an electric motor.

[0019] The electromechanical brake system according to the present invention having the features of claim 14 is characterized in particular by at least one wheel brake device according to the present invention which can be assigned to or is assigned to a different wheel of an automobile. This also results in the advantages described above. In particular, the brake system is designed without hydraulic pressure, i.e., has components that can or are actuated solely by electromechanism.

[0020] Other desirable features and combinations of features will become apparent from what has been stated above and from the claims. [Brief explanation of the drawing]

[0021] [Figure 1A] It is a diagram of a wheel brake device. [Figure 1B] It is a diagram of a wheel brake device. [Figure 2] It is a diagram of a method for operating a wheel brake device.

Embodiments for Carrying Out the Invention

[0022] Hereinafter, the present invention will be described in detail with reference to the drawings.

[0023] Figs. 1A and 1B schematically show only the components of a known wheel brake device 1 for an electromechanical brake system of a motor vehicle not shown in detail.

[0024] In that case, Fig. 1A shows a first cross-sectional view, and Fig. 1B shows a second cross-sectional view in the plane A-A shown in Fig. 1A. The wheel brake device 1 has at least a first electromechanical actuator 2 for operating the wheel brake device 1 and a second electromechanical actuator 3 for blocking the wheel brake device 1 for parking braking. In that case, the actuators 2, 3 are each formed as an electric motor here.

[0025] In that case, here the first actuator 2 is formed as a rotary actuator and has a rotor shaft 4 on which a gear formed as a pinion 5 is non-rotatably arranged. The pinion 5 is part of a transmission assembly 6 for operating the wheel brake device 1 in particular. The wheel brake device 1 accordingly has, in particular, a brake caliper not shown including at least one brake disc and brake pads, and the actuator 2 is coupled to the brake pads via the transmission assembly 6 and displaces it in the direction of the brake disc to generate a braking torque.

[0026] The second actuator 3 is here formed as a linear actuator and is formed to linearly displace the first locking member 7 as indicated by the first double-headed arrow 8. The locking member 7 is, for example, partially received in an opening 9 of a second locking member 10 formed as a claw. The locking member 10 is linearly displaceable as indicated by a second double-headed arrow 12 in the direction of the pinion 5 as the mating member assigned thereto, against the biasing force of the spring member 11.

[0027] In that case, the first locking member 7 has a cavity 13, and the geometry of the cavity is selected such that when the locking member 7 is displaced in the direction of the second actuator 3 by appropriate control of the second actuator 3, the locking member 10 abuts against the pinion 5 at one end and blocks it in the rotational direction by form-fit, as can be recognized in FIG. 1B. Free rotation is guaranteed in the other rotational direction, in particular by the arrangement and the geometric shape.

[0028] Furthermore, a control device 14 formed to control the actuators 2, 3 is also assigned to the actuators 2, 3.

[0029] In the following, a preferred method for operating the wheel brake device 1 will be described while referring to FIG. 2. For this purpose, FIG. 2 shows the method based on a flowchart. In particular, it is ensured by the method that the functionality of the actuator system of the parking brake mechanism in particular is inspected. The method is preferably executed using the control device 14.

[0030] As described above, the method is advantageously applicable to similar wheel brake devices having a corresponding functional relationship, in particular when the parking brake actuator is formed in the wheel brake device such that it blocks, for example, its service brake actuator of the wheel brake device.

[0031] In step S1, the method is initiated when one or more conditions for initiating the method are monitored. Preferably, the vehicle's speed is detected, and the method is performed only if the speed falls below a predetermined limit. Alternatively or additionally, the vehicle is monitored for the presence or absence of a brake request, and the method is performed only if no brake request is detected.

[0032] Particularly preferably, the vehicle is monitored for whether a parking process, in particular an autonomous parking process, is scheduled, and the method is executed if it is recognized that a parking process is scheduled. Alternatively or additionally, the vehicle is monitored for the start of driving after a parking process, in particular using the second actuator 3, and the method is executed if it is recognized that a start of driving has occurred. Further alternative or additionally, the vehicle doors of the vehicle are monitored for whether an unlocking process has occurred, and the method is executed if it is recognized that an unlocking process has occurred.

[0033] As soon as certain conditions or more conditions are met, the method proceeds to step S2. In step S2, the second actuator 3 is controlled to block the wheel brake device 1. Preferably, when the second actuator 3 is controlled, the first actuator 2 is controlled to actuate the brake pads of the wheel brake device 1 in the tightening direction.

[0034] With respect to the wheel brake device 1 shown in Figures 1A and 1B, the second actuator 3 is controlled to block the rotation of the rotor shaft 4 of the first actuator 2 by displacing the locking members 7 and 10 accordingly, as described above. Alternatively, the second actuator 3 is controlled to block the translational displacement of the components of the first actuator 2, particularly the rotor.

[0035] In particular, the second actuator 3 is controlled to displace the locking members, in the illustrated exemplary embodiments of locking members 7 and 10, and in the illustrated exemplary embodiments of locking member 10, so as to cooperate in shape-coupled and / or force-coupled manner with a mating member, in the illustrated exemplary embodiments of pinion 5, which is located on or formed on the rotor shaft or component.

[0036] In the subsequent step S3, the first actuator 2 is controlled to actuate the wheel brake device 1. Particularly preferably, the first actuator 2 is controlled to disengage the brake pads of the wheel brake device 1. In this case, the motion variables of the first actuator 1 are detected.

[0037] Regarding the wheel brake device 1 shown in Figures 1A and 1B, the change in rotor position of the rotor shaft 4 is detected as a motion variable. Alternatively, the change in the displacement distance of the components is detected as a motion variable. In particular, the mechanical stiffness, especially the play, of at least one actuator 2, 3 is detected depending on the detected motion variable.

[0038] In step S4, the motion variables are compared to predetermined limit values. These limit values ​​are either zero or, for example, the expected play of at least one actuator 2, 3. If the motion variables fall below the predetermined limit values ​​or reach them at most, the second actuator 3 is recognized as functioning. The method ends in step S6. If the motion variables exceed the predetermined limit values, the second actuator is recognized as defective. In that case, the method proceeds to step S5.

[0039] In step S5, an error message is output to a display device that can be assigned to or is assigned to the driver of the vehicle, and / or to a computer device via a wireless communication connection, so that appropriate countermeasures can be taken. The method similarly ends in step S6. [Explanation of Symbols]

[0040] 1. Wheel brake system 2. First electromechanical actuator 3. Second electromechanical actuator 4 rotor shafts 5 pinion 7 Locking member 8. First double-headed arrow 9 aperture 10 Locking member 11 Spring member 12. Second double-headed arrow 13 Blanks 14 Control device

Claims

1. A method for testing the functionality of an electromechanical wheel brake system (1) of an automobile, wherein the wheel brake system (1) comprises at least a first electromechanical actuator (2) for operating the wheel brake system (1) and a second electromechanical actuator (3) for blocking the wheel brake system (1) for parking braking, - The second actuator (3) is controlled to block the wheel brake device (1), - The first actuator (2) is controlled to operate the wheel brake device (1), - The motion parameters of the first actuator (2) are detected, A method characterized in that the second actuator (3) is recognized as functioning when the motion variable falls below a predetermined limit value, and otherwise the second actuator (3) is recognized as defective.

2. The method according to claim 1, characterized in that the second actuator (3) is controlled to block the rotation of the rotor shaft (4) of the first actuator (2), and a change in the rotor position of the rotor shaft (4) is detected as a motion variable.

3. The method according to claim 1, characterized in that the second actuator (3) is controlled to block the translational displacement of the components of the first actuator (2), particularly the rotor, and that a change in the displacement distance of the components is detected as a motion variable.

4. The method according to claims 2 and 3, characterized in that the second actuator (3) is controlled to cooperate in shape-coupled and / or force-coupled with a mating member, particularly a pinion (5), which is positioned on or formed on the rotor shaft (4) or the component, in order to displace the locking members (7, 10), particularly the claws.

5. The method according to any one of claims 1 to 4, characterized in that the mechanical stiffness, particularly play, of at least one of the actuators (2, 3) is detected depending on the detected motion variable.

6. The method according to any one of claims 1 to 5, characterized in that when the second actuator (3) is controlled, the first actuator (2) is controlled to actuate the brake pads of the wheel brake device (1) in the tightening direction.

7. The method according to any one of claims 1 to 6, characterized in that the first actuator (2) is controlled to actuate the brake pads of the wheel brake device (1) in the disengagement direction.

8. The method according to any one of claims 1 to 7, characterized in that the speed of the vehicle is detected, and the method is performed only when the speed falls below a predetermined limit.

9. The method according to any one of claims 1 to 8, characterized in that the vehicle is monitored for the presence or absence of a brake request, and the method is performed only when no brake request is recognized.

10. The method according to any one of claims 1 to 9, characterized in that the vehicle is monitored for whether a parking process, particularly an autonomous parking process, is scheduled, and the method is executed when it is recognized that a parking process is scheduled.

11. The method according to any one of claims 1 to 10, characterized in that the automobile is monitored for the start of driving after a parking process performed in particular using the second actuator (3), and the method is performed when the start of driving is recognized.

12. The method according to any one of claims 1 to 11, characterized in that the vehicle door of the automobile is monitored for whether or not an unlocking process is underway, and the method is executed when an unlocking process is recognized.

13. An electromechanical wheel brake device (1), comprising at least a first electromechanical actuator (2) for operating the wheel brake device (1) and a second electromechanical actuator (3) for blocking the wheel brake device (1) for parking braking, wherein the electromechanical wheel brake device is characterized by a control device (14) specifically configured to perform the method according to any one of claims 1 to 12.

14. An electromechanical brake system, characterized in part by at least one wheel brake device (1) according to claim 13, which can be assigned to or is assigned to another wheel of an automobile.

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