Electromechanical brake actuator (EMB) for a friction brake of a vehicle and method for operating the same

Abstract

The invention relates to a method for operating an electromechanical brake actuator (EMB) (200) for a friction brake of a vehicle, in which a locking actuator (212) of the EMB (200) is triggered in order to lock a mechanical device (206) of the EMB (200) when a drive (300) of the EMB (200) moves the mechanical device (206) into a braking position and it is detected that the friction brake is stopped.

Description

Technical Field

[0001] The present invention relates to a method for operating an electromechanical brake actuator (EMB) for a friction brake of a vehicle, a corresponding computer program product, and an electromechanical brake actuator (EMB) for a friction brake of a vehicle. Background Art

[0002] An electromechanical brake actuator can supply braking force to a friction brake through a drive and a mechanical device. Once braking force is required, the drive is powered on. If the drive is powered off, the braking force decreases or stops.

[0003] Therefore, an electromechanical brake actuator can have an accumulator for a parking brake. The accumulator can be, for example, a preloaded spring that is released when the vehicle is parked. Thereby, even when the brake actuator is powered off, the vehicle can be prevented from rolling away. When the parking brake is released, the accumulator can be preloaded again by reverse operation of the electromechanical brake actuator. Summary of the Invention

[0004] In this context, the solution proposed in the present application provides a method for operating an electromechanical brake actuator (EMB) for a friction brake of a vehicle, an electromechanical brake actuator (EMB) for a friction brake of a vehicle, and a corresponding computer program product according to the independent claims of the present invention. Advantageous improvements and enhancements of the solution proposed in the present application are obtained from the description and described in the dependent claims.

[0005] In an electromechanical brake actuator, the driving motion of the electric motor is decelerated by a transmission so that a large braking force can be obtained on the friction lining of the friction brake even with a small movement of the friction lining. The friction lining is pressed against a corresponding component, such as a brake disc or a brake drum, by the braking force to generate friction. The transmission can be, for example, a worm gear transmission that acts on a lead screw to convert rotation into translation. To press the friction lining against the corresponding component, the transmission moves in the forward direction. To lift the friction lining from the corresponding component, the transmission moves in the reverse direction. When the electric motor no longer provides a driving torque, the transmission can also move in the reverse direction due to a reaction force. This reaction force can be generated, for example, due to a lateral impact on the brake disc.

[0006] When using an electromechanical brake actuator to brake a vehicle to a stop, at the beginning of the braking process, the electric motor has already moved the friction lining and pressed it against its corresponding component with the required braking force.

[0007] In the solution proposed in the present application, after the vehicle has come to a stop, the friction lining remains at least approximately in the position it reached during the braking process, in order to provide a holding torque on the corresponding component via the friction lining. For this purpose, the reverse movement of the transmission is blocked by a switchable locking mechanism.

[0008] With the solution proposed in the present application, after the vehicle has come to a stop, the electric motor stops or at least reduces the provision of the driving torque. This reliably prevents the vehicle from accidentally rolling (Anrollen) until the locking of the transmission is released. When driving is intentionally started, the holding torque or the braking torque can be controllably reduced or decreased by running the electric motor again.

[0009] According to a first aspect of the invention, a method for operating an electromechanical brake actuator (EMB) for a friction brake of a vehicle is proposed, in which, when the drive of the EMB moves a mechanical device into the braking position and it is recognized that the friction brake has stopped working, the locking actuator of the EMB is triggered to lock the mechanical device of the EMB.

[0010] According to a second aspect of the invention, an electromechanical brake actuator (EMB) for a friction brake of a vehicle is proposed, wherein the EMB has an electric drive, a mechanical device for transmitting the driving movement of the electric drive to the friction brake of the vehicle, and an electromechanical locking actuator for locking the mechanical device.

[0011] The idea of the embodiments of the present invention can furthermore be seen as being based on the ideas and insights described below.

[0012] The electric drive of the electromechanical brake actuator can for example be an electric motor, which provides a rotational movement and a torque when it is electrically started. The mechanical device can be a transmission. The mechanical device can have a variable transmission ratio in order to convert a larger input movement of the electric drive into a smaller output movement of the friction lining of the friction brake, wherein a smaller input force of the drive is converted into a larger output force acting on the friction lining. The drive can shift one or more friction linings from an initial position into the braking position. In the braking position, the friction lining contacts the corresponding component of the friction brake, presses against the corresponding component using the generated braking force, and generates friction there. The corresponding component can for example be a brake disc or a brake drum.

[0013] The electromechanical locking actuator can be triggered by an electrical control signal. The locking actuator can, for example, have an electromagnetic drive. The locking actuator can act on at least one movable locking mechanism. The locking mechanism can engage into a corresponding mating part of the machine in order to mechanically lock the machine. By activating the locking actuator, the machine of the EMB can thus be locked in its current state in order to thereby prevent the friction lining that has been displaced by the EMB into the braking position from being displaced back into the non-braking position. In other words, by activating the locking actuator, the EMB can be locked and held in its braking configuration.

[0014] It can be detected by a sensor whether the friction brake has stopped working. For a vehicle, the sensor can be, for example, a speed sensor and / or an ABS sensor. In particular, the movement of the friction brake can be continuously or repeatedly monitored, for example, by monitoring the moving parts in the brake or the wheel being braked itself, or by monitoring other state variables that can infer the current movement behavior of the friction brake. Once it is recognized that the friction brake has stopped working or the vehicle that is being braked with it has stopped, the locking actuator is activated immediately or as quickly as possible in order to lock the machine of the EMB.

[0015] The driving force generated by the drive can be at least reduced in response to the locking of the machine. The drive can be de-energized, in particular, in response to the locking of the machine. The driving force can drop rapidly. The driving force can drop to zero. The drive can be disconnected. Energy can be saved by reducing the driving force.

[0016] The machine can be unlocked again in response to the actuation of the accelerator pedal of the vehicle. The accelerator pedal can be referred to as the throttle pedal. When the accelerator pedal is actuated, it indicates that the driver wishes to continue or start the journey. When the accelerator pedal is actuated, torque is provided by the drive of the vehicle. This torque can compensate for the reduced braking force when unlocking the machine.

[0017] The drive of the electromechanical brake actuator can be triggered in response to the unlocking of the machine in order to move the machine to its initial position. The drive can pull the friction lining back from the mating part in order to prevent dragging. Alternatively or additionally, the friction lining can be pushed away from the mating part by a lateral impact of the mating part.

[0018] The locking actuator can have at least one switchable locking pawl as the locking mechanism. As the mating part, a latching device for latching the locking pawl can be coupled to the machine. The locking pawl can be movable. The locking pawl can be moved between an unlocked state or an unlocked position and a locked state or a locked position by the locking actuator. The locking pawl can be coupled to the housing of the EMB. Thus, the locking pawl can be supported by the housing when the machine is locked.

[0019] The latching device can be arranged on the drive side of the mechanical device. The electric drive can be coupled to the mechanical device on the drive side. On the drive side, the mechanical device can be latched or locked with a very small force.

[0020] The locking pawl and the latching device can form a switchable overrunning clutch for preventing reverse movement of the mechanical device, wherein forward movement is not prevented even in the activated state of the overrunning clutch. In the forward direction, the locking pawl can slide on the inclined side of the latching part of the latching device and, after sliding, latch on the steep side of the latching part.

[0021] The latching device can be undercut. To release the latching of the locking pawl, a forward impact of the drive is required. The steep sides of the latching part of the latching device can each have an undercut. When snapping in in the reverse direction, the locking pawl can slide into the undercut and rest firmly therein. In the undercut, the locking pawl does not move back to the unlocked position unless the latching device moves slightly in the forward direction and thereby moves the locking pawl out of the undercut.

[0022] The locking actuator can be normally open in the case of power failure. To lock the mechanical device, the locking actuator can be actively energized. The locking actuator can be monostable. The locking actuator or the locking pawl can be held in the unlocked state by a spring, for example. This unlocked state can then be a stable state. When energized, the locking actuator can act against the spring and move the locking pawl into the locked state. If the locking pawl is in the locked state and the locking actuator is de-energized, the spring pulls the locking actuator or the locking pawl back into the unlocked state again, unless the locking pawl is held in the locked state due to a mechanical obstacle of the latching device. This obstacle can be an undercut on the latching device, for example. In the locked state, the locking pawl can be held stable due to the mechanical locking of the undercut as long as the undercut holds the locking actuator. If it actively leaves the undercut, i.e., the latching device moves actively against the locking direction, the spring pulls the locking pawl or the locking actuator back into the unlocked state.

[0023] The drive can be triggered to unlock the mechanical device, which moves in the forward direction at least past the undercut for the locking actuator of the latching device. When the mechanical device is locked, the locking pawl of the locking actuator can be reliably held behind the undercut of the latching device in the case of power failure. If the latching device does not move slightly, the locking pawl cannot escape behind the undercut. To release the locking pawl from the undercut, the drive can briefly press the friction lining more firmly against the corresponding part in order to release the locking pawl. After release, the drive can drive the latching device in the reverse direction in order to disengage the friction lining from the corresponding part.

[0024] When locked, the mechanical device can move in the reverse direction from the braking position by at least passing through the undercut portion. When the locking claw is latched in the latching device, the brake can be slightly released until the locking claw is latched after the undercut portion.

[0025] The method is preferably implemented by a computer and can be implemented, for example, in the form of software or hardware or in a hybrid form of software and hardware, such as in a driver assistance system.

[0026] The solution proposed in this application also provides a controller, wherein the controller is configured to execute, trigger or implement the steps of a variant of the method proposed in this application in the corresponding device.

[0027] The controller can be an electrical device having at least one computing unit for processing signals or data, at least one storage unit for storing signals or data, and at least one interface and / or communication interface for reading or outputting data embedded in a communication protocol. The computing unit can be, for example, a signal processor, a so-called system ASIC or a microcontroller for processing sensor signals and outputting data signals according to the sensor signals. The storage unit can be, for example, a flash memory, an EPROM or a magnetic storage unit. The interface can be a sensor interface for reading sensor signals from sensors and / or an actuator interface for outputting data signals and / or control signals to actuators. The communication interface can be used to read or output data wirelessly and / or wiredly. The interface can also be a software module that exists, for example, on a microcontroller together with other software modules.

[0028] A computer program product or computer program having program code is also advantageous, and the program code can be stored on a machine-readable carrier or storage medium, such as a semiconductor memory, a hard disk memory or an optical memory, and is used to execute, implement and / or trigger the steps of the method according to any one of the above embodiments, especially when the program product or program is executed on a computer, in a controller or in a device.

[0029] It should be noted that this application describes some possible features and advantages of the present invention with reference to different embodiments. Those skilled in the art will recognize that the features of the controller and the method can be combined, adjusted or exchanged in a suitable manner to obtain additional embodiments of the present invention. Description of the Drawings

[0030] Embodiments of the present invention will be described below with reference to the drawings, where neither the drawings nor the description are to be considered as limiting the present invention.

[0031] Figure 1 A decision chain of a method according to an embodiment is shown;

[0032] Figure 2 shows a cross-sectional view of an electromechanical brake actuator according to an embodiment; and

[0033] Figure 3 shows a spatial illustration of an electromechanical brake actuator according to an embodiment.

[0034] The drawings are merely schematic and not to scale. The same reference numerals denote the same or functionally equivalent features. Detailed Description

[0035] Figure 1 shows a decision chain 100 according to an embodiment of a method for operating an electromechanical brake actuator of a vehicle. At the beginning, the vehicle is in a driving state. If the service brake of the vehicle has been actuated and the vehicle has stopped, the hill hold function of the service brake is activated. If at this time the start / stop button of the vehicle remains activated, the driver's seat remains occupied and the doors remain closed, a "short stop" situation is recognized and the locking actuator of the electromechanical brake actuator is quickly switched on in order to lock the friction brake in the position for the hill hold function. Next, the electric drive of the electromechanical brake actuator is disconnected, thereby ending the active hill hold function. When the accelerator pedal of the vehicle is actuated, the short stop ends and the locking actuator is deactivated, thereby releasing the brake and enabling the vehicle to start moving.

[0036] If after activation of the hill hold function, the start / stop button is deactivated, the driver leaves the seat and / or the doors are opened and / or the vehicle's start / stop system shuts down the engine, a "parked" situation is recognized and the locking actuator is switched on for parking. Then the drive of the electromechanical brake actuator is disconnected and the drive moves to the inoperative position. The hill hold function also ends. When the start / stop button is actuated, the driver's seat is occupied and the doors are closed again after being opened, the parking ends. This simultaneously marks the start of a journey.

[0037] Figure 2 shows a cross-sectional view of an electromechanical brake actuator 200 according to an embodiment. The electromechanical brake actuator 200 is abbreviated as EMB 200. The EMB 200 has an electric drive. The drive acts on a worm gear drive 202. The worm gear drive 202 is coupled to a thread drive 204. The rotational speed of the drive is significantly reduced in the worm gear drive 202. The decelerated rotational movement is converted into a linear movement in the thread drive 204 and the braking force is increased by the pitch. The thread drive 204 is a ball screw drive. The worm gear drive 202 and the thread drive form the mechanical device 206 of the electromechanical brake actuator 200.

[0038] The latching device 210 is coupled to the worm wheel 208 of the worm gear drive 202. The locking actuator 212 aligns a movable locking claw 214 with the latching device 210. The locking actuator 212 is used to latch the locking claw 214 onto the latching device 210 and thus lock the mechanical device 206.

[0039] In one embodiment, the locking claw 214 prevents reverse movement of the mechanical device 206 and additionally allows forward movement of the mechanical device 206.

[0040] Figure 3 A spatial illustration of an electromechanical brake actuator 200 according to one embodiment is shown. The brake actuator 200 corresponds substantially to Figure 2 the brake actuator in. The locking actuator 212, the locking claw 214, the latching device 210 and the electric drive 300 of the electromechanical brake actuator 200 are shown here.

[0041] The latching device 210 is a gear with a serrated tooth portion. The locking claw 214 is a movable finger that slides along the inclined tooth surface of the tooth portion when the latching device 210 rotates in the forward direction, and the finger latches onto the steep tooth surface of the tooth portion when the latching device 210 rotates in the reverse direction.

[0042] When the locking actuator 212 is activated, it presses hard on the locking claw 214 and pushes the locking claw 214 from the unlocked position to the locked position. Here, the locking actuator overcomes the return spring 302 of the locking claw 214. If the force is greater than the spring force of the return spring 302, the locking claw 214 moves to the locked position. If the force is less than the spring force, the return spring 302 moves the locking claw 214 back to the unlocked position.

[0043] In one embodiment, the tooth portion of the latching device 210 is configured with an undercut. Thus, when the drive 300 reduces its torque, the locking claw 214 slides into at least one latching portion of the latching device 210 or the undercut 304 of the teeth of the latching device 210 in the locked position. In this case, the latching device 210 rotates in the reverse direction, rotates past the undercut 304, and is then locked by the locking claw 214. If the locking claw 214 is locked after the undercut 304, the force of the return spring 302 is too small to move the locking claw 214 back to the unlocked position.

[0044] To move the locking claw 214 back to the unlocked position, the drive 300 rotates the entire mechanical device 206 with the latching device in the forward direction, rotating at least past the undercut 304. Then the locking claw 214 slides out of the undercut 304 and the return spring 302 pulls the locking claw 214 back to the unlocked position.

[0045] The possible design options of the present invention are summarized again below, or introduced using slightly different wording.

[0046] An electromechanical brake actuator (EMB) is proposed that can quickly transfer the ramp parking function to an automatic parking brake (APB).

[0047] During the continuous electrification of equipment in motor vehicles, the focus is now also on service brakes following parking brakes. Electromechanical brakes of various designs have been installed in large quantities of vehicles.

[0048] Electric drive motors are usually combined with one or more gear stages with a very high overall reduction ratio, usually with a gear transmission with a linear reduction ratio. Individual solutions use cams as the speed-changing mechanism and thus change speed non-linearly.

[0049] In the solution proposed in this application, the "automatic parking brake" APB function is also integrated into the EMB. The automatic parking brake has special requirements, some of which are significantly different from those of the service brake EMB. The APB is usually used for long-term operation and usually only requires operating current to change its state. Only a small or no operating current is required to maintain the APB state (APB off and vehicle moving or APB on and vehicle stationary).

[0050] In particular, in a vehicle with an EMB, the ramp parking function is (usually) achieved by actively (energized) position holding of the engine driven by the EMB. For this, a large current is required, which burdens the vehicle's battery and thus shortens the driving range.

[0051] Through the solution proposed in this application, electrical energy can be saved in a battery electric vehicle (BEV) with an electromechanical brake (EMB), and thus a greater driving range can be achieved.

[0052] [[ID=2I]]The core idea here is to very quickly transfer the vehicle parking function from the ramp parking function (which is related to a rolling vehicle and is achieved by the service brake) to the automatic parking brake function (achieved by the APB automatic parking brake / parking brake, which is usually already operated electromechanically).

[0053] This is made easier due to the functional proximity of the parking brake (electromechanically operated) and the service brake (electromechanically operated) in the EMB.

[0054] Through the solution proposed in this application, electrical power can be saved to achieve a greater driving range.

[0055] The APB can take over the brakes (ramp parking / hill stop) that have already been engaged by the service brake in the "engaged" state. Only a very small APB operating current is required, and the duration from APB disengagement to APB engagement is close to zero or very short.

[0056] The operating current for the EMB drive motor can now immediately drop from a large holding current to zero. The service brake EMB can be fully released (small reverse movement current), or can be held in a position close to the handover position on the APB (holding current is small or there is no holding current because there is no force). Thus, the motor of the EMB can be designed much smaller than conventional ones because it does not overheat due to continuous current loading.

[0057] Based on other signals within the vehicle (such as the vehicle is still running (the "stop" button has not been pressed), the driver's seat has not been vacated (seat sensor), the doors have not been opened (door sensor), etc.), it can be interpreted that the vehicle is only stopped briefly, for example, at an intersection, traffic light, etc.

[0058] Alternatively / Optionally, this situation can be defined as "APB engaged / short stop", which may have an impact on other functions of the vehicle.

[0059] If it is recognized based on other signals in the vehicle that the vehicle has been parked (the "stop" button has been pressed, the driver's seat has been vacated (seat sensor), etc.), the EMB can return to its non-operating position without applying force and with a small current, and the APB has already been actuated.

[0060] Alternatively / Optionally, this situation can be defined as "APB engaged / parked", which may have an impact on other functions of the vehicle.

[0061] The solution proposed in this application can also be used in mechanical-hydraulic actuators, and even outside motor vehicles, for example, for automotive hydraulic systems and other hydraulic systems, motorcycles, electric bicycles, power tools, household appliances, industrial technology, construction technology, or consumer goods.

[0062] At the beginning, the vehicle is moving. Then a signal is received that the service brake has been actuated and the vehicle has stopped. Then the hill-hold function is activated. If the additional signal is "yes" (for example: the "start" button remains pressed, the driver's seat remains occupied, the doors remain closed), then the situation of "APB engaged / short stop" is recognized and the APB is quickly engaged, the EMB is disengaged and powered off as much as possible, and the hill-hold function is stopped.

[0063] This situation ends by actuating the accelerator pedal (i.e., ending the short stop and continuing to drive).

[0064] If the additional signal is "No", the situation of "APB ON / already parked" is recognized, and the APB is turned on for parking, the EMB is disconnected and moved to the inoperative position, and the ramp parking function ends.

[0065] This situation ends (i.e., parking ends and the journey begins) by pressing the "Start" button and when the driver's seat is occupied and the door is opened and then closed.

[0066] Finally, it should be noted that terms such as "comprising", "including" do not exclude other elements or steps, and terms such as "a" or "an" do not exclude a plurality or multiplicity. The reference signs in the claims should not be regarded as limiting.

Claims

1. A method of operating an electromechanical brake actuator (EMB) (200) for a friction brake of a vehicle, wherein, When the drive (300) of the EMB (200) moves the mechanical device (206) to the braking position and identifies that the friction brake has stopped working, the locking actuator (212) of the EMB (200) is triggered to lock the mechanical device (206) of the EMB (200).

2. The method according to claim 1, wherein In response to the locking of the mechanical device (206), at least reduce the driving force generated by the drive (300).

3. The method according to claim 2, wherein, In response to the locking of the mechanical device (206), power off the drive (300).

4. The method according to any one of the preceding claims, wherein, In response to the manipulation of the accelerator pedal of the vehicle, unlock the mechanical device (206).

5. The method according to claim 4, wherein In response to the unlocking of the mechanical device (206), trigger the drive (300) to move the mechanical device (206) to the initial position.

6. The method according to any one of the preceding claims, wherein, Trigger the drive (300) to unlock the mechanical device (206), and the mechanical device (206) moves in the forward direction at least past the undercut portion (304) of the latching device (210) for the locking actuator (212).

7. The method according to claim 6, wherein, When locked, the mechanical device (206) moves in the reverse direction at least past the undercut portion (304) from the braking position.

8. An electromechanical brake actuator (EMB) (200) for a friction brake of a vehicle, wherein, The EMB (200) has an electric drive (300), a mechanical device (206) for transmitting the driving motion of the electric drive (300) to the friction brake of the vehicle, and an electromechanical locking actuator (212) for locking the mechanical device (206).

9. The EMB (200) according to claim 8, wherein, The locking actuator (212) is normally open when powered off.

10. The EMB (200) according to any one of claims 8 to 9, wherein The locking actuator (212) has at least one switchable locking pawl (214), and a latching device (210) for latching the locking pawl (214) is coupled to the mechanical device (206).

11. The EMB (200) according to claim 10, wherein, The latching device (210) is arranged on the drive side of the mechanical device (206).

12. The EMB (200) according to any one of claims 10 to 11, wherein, The locking pawl (214) and the latching device (210) form a switchable overrunning clutch for preventing the reverse movement of the mechanical device (206), wherein forward movement is not blocked even in the activated state of the overrunning clutch.

13. The EMB (200) according to any one of claims 10 to 12, wherein, The latching device (210) is undercut, and a forward impact of the drive (300) is required to release the latching of the locking pawl (214).

14. A controller for executing, triggering or implementing the method according to any one of claims 1 to 7 in a corresponding device.

15. A computer program product for instructing a processor to execute, implement and / or trigger the method according to any one of claims 1 to 7 when the computer program product is executed.

16. A machine-readable storage medium on which the computer program product according to claim 15 is stored.

Images