Method for controlling an electromechanical brake

Abstract

The invention relates to a method for controlling an electromechanical brake (10). The electromechanical brake comprises an electric motor (14) which acts on a brake regulator (28) via a transmission unit (22) in order to generate a braking force (FB). In order to lock the transmission unit (22), a switchable and bistable overrunning clutch locking mechanism (36) is provided, by means of which the brake release direction of the brake actuator (28) can be locked. The method comprises the following steps: after the braking process, returning (B) the brake actuator (28) for a fixed, predetermined distance; and triggering (C) the locking mechanism (36) to fix the brake regulator (28) in the return position.

Description

Technical Field

[0001] The present invention relates to a method for controlling an electromechanical brake and also to an electromechanical brake for carrying out the method. Background Art

[0002] Typically, the service brake uses brake fluid to press the brake piston and brake pads against the brake disc to brake the vehicle. The parking brake, on the other hand, is an electromechanical brake. With the increasing electrification of components in motor vehicles, the service brake should also be an electromechanical brake, eliminating the need for brake fluid and the complex valves and piping associated with it. This electromechanical brake also significantly reduces maintenance requirements.

[0003] Document US2012 / 0073912 A1 discloses a pneumatically or electromechanically actuated disc brake having a brake caliper that surrounds a brake disc. Furthermore, a brake actuation mechanism comprising a rotating lever and at least one axially displaceable adjustment spindle is disclosed, wherein the brake actuation mechanism is arranged in the brake caliper. A wear adjustment mechanism is disclosed, which is arranged in the brake caliper. The wear adjustment mechanism can be actuated by the rotating lever and is used to compensate for wear-induced changes in the clearance between the brake pad and the brake disc by axially adjusting the at least one adjustment spindle. The wear adjustment mechanism comprises a spur gear segment that engages in a crown gear that is functionally coupled to the at least one adjustment spindle. The spur gear segment extends in the pivoting direction of the rotating lever and is arranged on the rotating lever. Summary of the Invention

[0004] The object of the present invention is to be able to adjust the wear of brake pads in a simple and economical manner.

[0005] This object is achieved by a method having the subject matter of claim 1. Preferred embodiments can be derived from the dependent claims.

[0006] The present invention provides a method for controlling an electromechanical brake. The electromechanical brake includes an electric motor that acts on a brake actuator via a transmission unit to generate a braking force. A switchable and bistable overrunning clutch locking mechanism is provided to lock the transmission unit, and the brake release direction of the brake actuator can be locked by the locking mechanism.

[0007] The electromechanical brake is preferably a service brake. The transmission unit can be formed by one or more transmission elements, which convert rotational motion into translational motion. The transmission unit can also include transmission elements that establish a transmission ratio. A brake actuator is a component that applies the braking force of the transmission to a brake disc or drum to generate a braking torque. The brake actuator preferably includes a brake piston and / or an S-cam, as well as brake pads.

[0008] According to the present invention, the electromechanical brake includes a bistable overrunning clutch locking mechanism. This locking mechanism can be used to lock the movement of the transmission unit, and thus the movement of the brake actuator. Accordingly, the locking mechanism has two switchable positions: a locked position in which the transmission unit is locked, and an unlocked position in which the transmission unit can operate freely. Due to its bistable nature, the locking mechanism remains stable in both positions. In other words, it remains stable in both positions when the power is off. Furthermore, the locking mechanism has an overrunning clutch characteristic. This means that the locking mechanism only locks one direction of rotation of the transmission unit, while the opposite direction of rotation remains free. According to the present invention, the brake release direction of a releasable brake can be locked. Therefore, when the locking mechanism is in the locked position, the brake can still be applied.

[0009] The method comprises the following steps: after a braking operation, returning the brake adjuster by a fixed, predefined distance; and triggering a locking mechanism to secure the brake adjuster in the returned position. The return movement of the brake adjuster can be induced actively by an electric motor or passively, for example, by a spring. The fixed return distance is constant throughout the entire service life and preferably corresponds to the distance between the brake pad and the brake disc or drum. As a result, even as the brake pad wears, a constant distance between the friction pairs is maintained, thereby compensating for the wear. By securing the brake adjuster in this position, it can be held at this distance even when the power is off.

[0010] In a preferred embodiment of the present invention, the locking mechanism is actively pulled back before the brake is actuated. By actively pulling back the locking mechanism, friction caused by the locking mechanism is avoided, thereby avoiding delays caused by the deactivation of the locking mechanism and thus allowing for faster braking.

[0011] In another preferred embodiment of the present invention, the locking mechanism is deactivated by actuating the brake. The advantage of deactivating by actuating the brake is that the locking mechanism can still be deactivated even after active deactivation fails, so that the locking mechanism has a fail-safe function.

[0012] Preferably, in a stationary state, when the brake is applied, the locking mechanism is activated, thereby forming a parking brake. By activating the locking mechanism, the brake is locked in the brake release direction. The locking mechanism is stably maintained in this position so that the motor vehicle can maintain the brake when parked and stationary.

[0013] In an advantageous refinement, the fixed, predetermined distance is determined starting from the contact point between the friction pairs of the brake. At this contact point, the friction pairs abut against each other. Starting from this contact point, the distance between the friction pairs remains constant over the entire service life, even in the event of wear.

[0014] Advantageously, the contact point is determined by means of values ​​from a force sensor and / or a torque sensor and / or a force / torque estimation. Thus, the contact point can be determined by a simple force measurement or torque measurement / estimation. This allows for a continuous and precise measurement of the contact point.

[0015] In another advantageous embodiment, the contact point is determined by the values ​​of the motor current, the motor speed and / or the motor position. Motor values ​​are usually already measured. Therefore, no additional sensors are required to determine the contact point.

[0016] The objects of the present invention are additionally achieved by an electromechanical brake for performing the method. The electromechanical brake includes an electric motor that acts on a brake actuator via a transmission unit to generate a braking force. A switchable and bistable overrunning clutch locking mechanism is provided to lock the transmission unit, which can lock the brake release direction of the brake actuator. Furthermore, the electromechanical brake includes a control device that is configured to trigger the locking mechanism to secure the brake actuator after a return movement of the brake actuator. This electromechanical brake substantially achieves the advantages of the above-described method.

[0017] According to an advantageous embodiment, the brake is a drum brake. The advantage of a drum brake is that, due to its encapsulated structure, it is less susceptible to dust. Furthermore, a drum brake does not release any brake dust. Furthermore, drum brakes are significantly less expensive than disc brakes.

[0018] According to another advantageous embodiment, the brake is a disc brake. The advantage of a disc brake is that it is much lighter than a drum brake, thereby improving suspension comfort. In addition, a disc brake also has better heat dissipation properties.

[0019] Since electromechanical brakes can be used with both disc brakes and drum brakes, the optimal brake selection can be made according to the required requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Embodiments of the present invention are shown in the accompanying drawings and explained in more detail in the following description.

[0021] Figure 1 An electromechanical brake according to a first embodiment of the present invention is shown;

[0022] Figure 2 An embodiment of a bistable locking mechanism is shown;

[0023] Figure 3 shows an electromechanical brake according to a second embodiment of the present invention; and

[0024] Figure 4 An exemplary embodiment of a method for controlling an electromechanical brake is shown. DETAILED DESCRIPTION

[0025] Figure 1 An electromechanical brake 10 according to a first embodiment of the invention is shown. The electromechanical brake 10 comprises an electric motor 14 which acts on a lead screw 18 of a transmission unit 22 which is designed as a lead screw drive assembly. In the embodiment shown, the lead screw drive assembly 22 is a ball screw drive assembly. The lead screw drive assembly 22 also has a lead screw nut 24 which acts on a brake adjuster 28 to apply a braking force F B The electromechanical brake 10 also includes a control device 30 , via which the electric motor 14 can be activated. In the illustrated embodiment, the brake actuator 28 has a brake piston 28 a and a brake pad 28 b . The brake pad 28 b interacts with a brake disk 32 to apply a braking torque.

[0026] The electromechanical brake 10 further comprises a locking mechanism 36 , by means of which the transmission unit 22 can be locked. The locking mechanism 36 can also be triggered by the control device 30 . Figure 2 An embodiment of such a locking mechanism 36 is shown. Here, the locking mechanism 36 is configured as a bistable overrunning clutch locking mechanism 36. For this purpose, the locking mechanism 36 has a ratchet 40, which is fixed to the screw shaft 18. The ratchet 40 is configured as a gear, wherein the ratchet 40 has teeth 44 in the form of saw teeth. The locking mechanism 36 also has a locking pawl 48, which can be engaged or disengaged with the ratchet 40 by means of a bistable electromagnet 52, thereby switching the overrunning clutch. Here, Figure 2 The position shown is the pushed-in position.

[0027] The electromagnet 52 has a block-shaped armature 56 to which the locking pawl 48 is fixed. The side of the housing 60 of the electromagnet 52 facing the ratchet 40 is closed by a permanent magnet 64. A compression spring 68 is arranged between the armature 56 and the permanent magnet 64, which exerts a separating force between the armature 56 and the permanent magnet 64. The electromagnet 52 also has a coil 72, which pulls the armature 56 toward the permanent magnet 64. Even when the coil 72 is de-energized, the armature 56 remains stably held in position by the magnetic force between the permanent magnet 64 and the armature 56.

[0028] Due to the serrated configuration of the ratchet 40 and the corresponding configuration of the locking pawl 48, when the locking mechanism 36 is in the pushed-in position, the ratchet 40 is locked in one direction while still being free-running in the other direction. Here, the locking direction corresponds to the release direction of the brake 10. Thus, the braking force F is applied by the rotation of the ratchet 40 in the free-running direction. B When rotating in the free-running direction, the locking pawl 48 is pressed upward by the teeth 44, causing the armature 56 to separate from the permanent magnet 64. The spring force presses the armature 56 to the second stable position. In this position, the locking mechanism 36 is in the pushed-out position.

[0029] Therefore, the brake 10 can be stopped in the braking position by the locking mechanism 36, thereby forming a parking brake. The locking mechanism 36 does not hinder the movement of the brake adjuster 28 in the braking direction.

[0030] Figure 3 FIG. 1 shows an electromechanical brake 10 according to a second embodiment of the present invention. Figure 1 Unlike the conventional brake 10, the brake 10 is a drum brake. In this embodiment, the electric motor 14 also drives the brake actuator via the transmission unit 22. The transmission unit 22 comprises a plurality of spur gears 22a and a screw drive assembly, which is used to apply two drum brake pads 76 to the wheel brake drum 80 to brake the wheel. The two drum brake pads 76 are connected to each other by a tension spring 84, thereby loading them in the release direction. In addition, there is also a Figure 2 3. The locking mechanism 36 is shown in detail in FIG. 3, with which the transmission unit 22 can be locked.

[0031] Figure 4 An exemplary embodiment of a method for controlling an electromechanical brake 10 is shown. In a first step A of the method, the contact point between the friction pair (e.g., the brake pad 28b and the brake disk 32 of the brake 10) is determined. For this purpose, a force sensor (not shown) is used, for example, to determine the braking force F to be applied. B Here, the braking force F BThe contact point is determined. In the next step B of the method, the brake adjuster 28 is returned to a fixed, predetermined distance after the braking process. In order to ensure that the brake adjuster 28 can be retained when the power is off, the locking mechanism 36 is triggered in the next step C to fix the brake adjuster 28. Here, the locking mechanism 36 is placed in the pushed-in position. Although the brake pad 28b will wear during its service life, these steps will still ensure that the distance s between the brake pad 28b, 76 and the brake disc 32 or brake drum 80 is constant (see Figure 1 ).

[0032] Before the E-brake 10 is actuated, the locking mechanism 36 can be actively pulled back D. The brake 10 is then triggered to brake the wheel E. Alternatively, the locking mechanism 36 can also be automatically deactivated by actuating the E-brake 10 .

Claims

1. A method for controlling an electromechanical brake (10), comprising an electric motor (14) which acts on a brake regulator (28) via a transmission unit (22) to generate a braking force (F B ),in, In order to lock the transmission unit (22), a switchable and bistable overrunning clutch locking mechanism (36) is provided, by which the brake release direction of the brake regulator (28) can be locked, wherein the method comprises the following steps: - after the braking process, returning (B) the brake actuator (28) by a fixed, predetermined distance; and - activating (C) the locking mechanism (36) to secure the brake adjuster (28) in the returned position.

2. The method according to claim 1, characterized in that Prior to actuating the brake (10), the locking mechanism (36) is actively retracted (D).

3. The method according to claim 1 or 2, characterized in that The locking mechanism (36) is deactivated by operating the brake (E).

4. The method according to any one of the preceding claims, characterized in that In a stationary state, when the brake is applied, the locking mechanism (36) is activated, thereby forming a parking brake.

5. The method according to any one of the preceding claims, characterized in that The fixed, predetermined distance is determined starting from a contact point between friction pairs (28b, 32) of the brake (10).

6. The method according to claim 5, characterized in that The contact point is determined by means of the values ​​of a force sensor and / or a torque sensor.

7. The method according to claim 5, characterized in that The contact point is determined by the values ​​of the motor current, the motor speed and / or the motor position.

8. An electromechanical brake (10) for carrying out the method according to any one of the preceding claims, comprising: An electric motor (14) acts on a brake regulator (28) via a transmission unit (22) to generate a braking force (F B ); wherein, in order to lock the transmission unit (22), a switchable and bistable overrunning clutch locking mechanism (36) is provided, by which the brake release direction of the brake regulator (28) can be locked; and a control device (30) is configured to trigger the locking mechanism (36) to fix the brake regulator (28) after the return movement of the brake regulator (28).

9. The electromechanical brake (10) according to claim 8, characterized in that The brake (10) is a drum brake.

10. The electromechanical brake (10) according to claim 8, characterized in that The brake (10) is a disc brake.

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