Electromechanical brake actuator (EMB) for friction brake of vehicle, and method for operating such brake actuator

Abstract

To provide a method for operating an electromechanical brake actuator (EMB) for a friction brake of a vehicle.SOLUTION: A method for operating an electromechanical brake actuator (EMB) for a friction brake of a vehicle is provided. In the method, when a drive of the EMB moves a mechanism of the EMB to a braking position and a standstill of the friction brake is recognized, a locking actuator of the EMB is driven and controlled to lock the mechanism.SELECTED DRAWING: Figure 1

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 technology]

[0002] An electromechanical brake actuator may provide braking force to a friction brake via a drive and mechanism. The drive is energized while braking force is required. When the drive is de-energized, braking force decreases or is eliminated.

[0003] Therefore, the electromechanical brake actuator may have a force storage means for the parking brake. The force storage means may be, for example, a biased spring, which is released when the vehicle is parked. This may protect the vehicle from rolling away even when the brake actuator is de-energized. The force storage means may be re-energized by reverse operation of the electromechanical brake actuator when the parking brake is released. Summary of the Invention

[0004] Against this background, the approach presented here provides a method for operating an electromechanical brake actuator (EMB) for friction brakes of a vehicle, an electromechanical brake actuator (EMB) for friction brakes of a vehicle, and a corresponding computer program product according to the independent claims. Advantageous developments and refinements of the approach presented here can be seen from the description and are set forth in the dependent claims. [Effects of the Invention]

[0005] In electromechanical brake actuators, the drive motion of an electric motor is slowed down by a transmission in order to obtain a large braking force at the friction lining of a friction brake with a small movement of the friction lining. The braking force presses the friction lining against a counter element, such as a brake disc or brake drum, to generate friction. The transmission can be, for example, a worm transmission, which acts on a threaded spindle to convert rotation into translation. To press the friction lining against the counter element, the transmission is moved in a forward direction. To lift the friction lining from the counter element, the transmission is moved in a reverse direction. The transmission can also be reversed by a reaction force when the electric motor no longer provides a drive moment. This reaction force can be caused, for example, by lateral deflection of the brake disc.

[0006] When a vehicle is braked to a standstill using an electromechanical brake actuator, the electric motor already sets the friction linings in motion at the start of the braking process, pressing them against their mating components with the required braking force.

[0007] In the approach presented here, the friction linings are held at least approximately in the position they achieved during the braking process after the vehicle has come to a standstill, so that a holding moment can be applied by the friction linings to the counter element, and for this purpose, reverse movement of the transmission is prevented by a switchable blocking mechanism.

[0008] The approach presented here allows the electric motor to cease providing or at least reduce the driving torque after the vehicle has come to a standstill. The vehicle is reliably prevented from starting to roll unintentionally until the transmission is unblocked. When it is desired to start moving again, the holding or braking torque can be reduced or eliminated in a controlled manner by the electric motor being started up again.

[0009] According to a first aspect of the present invention, a method of operating an electromechanical brake actuator (EMB) for a friction brake of a vehicle is presented, wherein a drive unit of the EMB moves a mechanism of the EMB to a braking position and, when a stopped state of the friction brake is recognized, drives and controls a lock actuator of the EMB to lock the mechanism.

[0010] According to a second aspect of the present invention, there is provided an electromechanical brake actuator (EMB) for a friction brake of a vehicle, the EMB comprising an electric drive unit, a mechanism for transmitting the drive motion of the drive unit to the friction brake of the vehicle, and an electromechanical lock actuator for locking the mechanism.

[0011] The ideas that led to the embodiments of the present invention may be considered to be based, inter alia, on the thoughts and realizations described below.

[0012] The electric drive of the electromechanical brake actuator can be, for example, an electric motor, which, when controlled by the electric drive, provides rotational motion and torque. The mechanism can be a transmission. The mechanism can have a gear ratio to convert a large input motion of the electric drive into a small output motion of the friction linings of the friction brake, whereby a small input force of the drive is converted into a large output force on the friction linings. The drive can displace one or more friction linings from an initial position to a braking position. In the braking position, the friction linings contact a mating member of the friction brake and press against the mating member with the resulting braking force, generating friction therebetween. The mating member can be, for example, a brake disc or a brake drum.

[0013] The electromechanical locking actuator can be driven by an electrical control signal. The locking actuator can have, for example, an electromagnetic drive. The locking actuator can act on at least one movable locking element. The locking element can engage in a corresponding counter element of the mechanism to mechanically block the mechanism. By actuating the locking actuator, the mechanism of the EMB can be blocked in its current state, thereby preventing the friction linings displaced by the EMB into the braking position from displacing back to the non-braking position. In other words, by actuating the locking actuator, the EMB can be blocked and held in a braked configuration.

[0014] The stalled state of the friction brake can be detected by a sensor. In the case of a vehicle, this can be, for example, a speed sensor and / or an ABS sensor. In particular, the friction brake can be monitored permanently or repeatedly for motion, for example by monitoring moving components within the brake or the braked wheel itself, or by monitoring another state variable that allows the current motion behavior of the friction brake to be estimated. As soon as the friction brake, or the vehicle braked by the friction brake, recognizes that it has come to a standstill, a lock actuator is activated immediately or as soon as possible to lock the EMB mechanism.

[0015] The drive force generated by the drive unit may be at least reduced in response to the locking of the mechanism. The drive unit may be specifically switched off in response to the locking of the mechanism. The drive force may drop rapidly. The drive force may drop to zero. The drive unit may be switched off. By reducing the drive force, energy may be saved.

[0016] The mechanism may be unlocked again in response to actuation of the vehicle's accelerator pedal, sometimes referred to as a gas pedal. When the accelerator pedal is actuated, this indicates the driver's desire to continue or start driving. When the accelerator pedal is actuated, torque is provided by the vehicle's drive. This torque can compensate for the braking force that weakens when the mechanism is unlocked.

[0017] A drive unit of the electromechanical brake actuator may be driven and controlled in response to unlocking the mechanism to move the mechanism to its initial position. The drive unit may retract the friction lining from the mating member to prevent dragging. Alternatively or additionally, the friction lining may be pushed away from the mating member by lateral deflection of the mating member.

[0018] The lock actuator may have at least one switchable lock pawl as a locking member. A locking device for locking the lock pawl may be coupled to the mechanism as a counter member. The lock pawl may be movable. The lock pawl may be moved by the lock actuator between an unlocked state or unlocked position and a locked state or locked position. The lock pawl may be coupled to the housing of the EMB. The lock pawl may thus be supported by the housing when blocking the mechanism.

[0019] The locking device can be arranged on the drive side of the mechanism, and an electric drive can be connected to the mechanism on the drive side, where the mechanism can be blocked or locked with a small force.

[0020] The locking pawl and the locking device may form a switchable freewheel that prevents reverse movement of the mechanism, while forward movement is unlocked even when the freewheel is activated. In the forward direction, the locking pawl may slide along the angled surface of the locking device's locking portion and, after sliding, lock onto the steep surface of the locking portion.

[0021] The locking device may have an undercut. A forward impulse of the drive may be required to unlock the locking pawl. Each steep surface of the locking part of the locking device may have an undercut. When locking in the reverse direction, the locking pawl may slide into the undercut and rest securely in the undercut. In the undercut, the locking pawl cannot return to the unlocked position unless the locking device is slightly moved forward, thereby moving the locking pawl out of the undercut.

[0022] The lock actuator can be de-energized and open. To lock the mechanism, the lock actuator can be actively energized. The lock actuator can be monostable. The lock actuator or lock pawl can be held in an unlocked state, for example, by a spring. This unlocked state can be a stable state. When energized, the lock actuator can act against the spring and move the lock pawl to the locked state. If the lock pawl is in the locked state and the lock actuator is de-energized, the spring again pulls the lock actuator or lock pawl to the unlocked state, unless the lock pawl is held in the locked state by some mechanical obstruction in the locking device. This obstruction can be, for example, an undercut in the locking device. In the locked state, the lock pawl can be stable due to the mechanical block provided by the undercut, as long as the undercut holds the lock actuator. When the undercut is actively moved away, i.e., when the locking device is actively moved in the opposite direction to the locked position, the spring pulls the lock pawl or lock actuator back into the unlocked position.

[0023] To unlock the mechanism, the drive unit may be controlled to move the mechanism in a forward direction at least the distance of the undercut of the locking device for the lock actuator. The locking pawl of the lock actuator can be securely held in the undercut of the locking device without being energized when the mechanism is locked. The locking pawl cannot move out of the undercut without slight movement of the locking device. The drive unit can press the friction lining more firmly against the mating member for a short period of time to release the locking pawl from the undercut. After release, the drive unit can drive the locking device in a reverse direction to lift the friction lining from the mating member.

[0024] The mechanism may be moved in reverse from the brake position by at least the undercut when locked. When the lock pawl is locked into the locking device, the brake may be released slightly until the lock pawl is locked deep into the undercut.

[0025] The method is preferably computer-implemented and may be implemented, for example, in software or hardware or in a mixed form consisting of software and hardware, for example in a driver assistance system.

[0026] The approach presented herein further provides a control device that is configured to perform, control or otherwise implement the steps of one of the variants of the method presented herein within a corresponding device.

[0027] The control device may 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 may be, for example, a signal processor, a so-called system ASIC, or a microcontroller for processing sensor signals and outputting data signals in response to the sensor signals. The storage unit may be, for example, a flash memory, an EPROM, or a magnetic storage unit. The interface may be configured as a sensor interface for reading sensor signals from sensors and / or as an actuator interface for outputting data and / or control signals to actuators. The communication interface may be configured for reading or outputting data wirelessly and / or via a wired connection. The interface may also be a software module, which may reside alongside another software module, for example on the microcontroller.

[0028] Also advantageous is a computer program product or computer program having a program code, which can be stored on a machine-readable carrier or storage medium, such as a semiconductor memory, a hard disk storage device or an optical memory, and which is used for performing, realizing and / or controlling the steps of the method according to one of the aforementioned embodiments, in particular when the program product or program is run on a computer, in a control device or in any device.

[0029] Additionally, some of the possible features and advantages of the present invention will now be described with reference to different embodiments, and it will be apparent to those skilled in the art that the features of the control device and method may be suitably combined, adapted or interchanged to arrive at further embodiments of the present invention.

[0030] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, neither the drawings nor the description should be construed as limiting the present invention. [Brief explanation of the drawings]

[0031] [Figure 1] FIG. 1 illustrates a decision chain for a method according to an embodiment. [Figure 2] 1 is a cross-sectional view of an electromechanical brake actuator according to one embodiment. [Figure 3] 1 is a three-dimensional view of an electromechanical brake actuator according to one embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0032] The drawings are only schematic and are not to scale. Like reference numerals refer to like features or features of like action.

[0033] FIG. 1 illustrates a decision chain 100 for a method of operating a vehicle electromechanical brake actuator according to one embodiment. Initially, the vehicle is moving. When the vehicle's service brakes are applied and the vehicle is stopped, the service brake's hill-holding function is activated. If the vehicle's start / stop button remains activated, the driver's seat remains occupied, and the door remains closed, this situation is recognized as a "short stop" and the locking actuator of the electromechanical brake actuator is quickly closed to block the friction brakes in the hill-holding function position. Subsequently, the electric drive of the electromechanical brake actuator is switched off, thus ending the active hill-holding function. When the vehicle's accelerator pedal is operated, the short stop is ended and the locking actuator is deactivated, allowing the brakes to be released and the vehicle to move off.

[0034] After the hill-holding function has been activated, if the start / stop button is deactivated, the driver's seat is removed and / or a door is opened and / or the vehicle's automatic start / stop system switches off the prime mover, the situation is recognized as "parking" and the lock actuator is closed for parking. The drive for the electromechanical brake actuator is then switched off and moved to its rest position. The hill-holding function is also terminated. Parking is terminated when the start / stop button is operated, the driver's seat is removed and the door is opened and then closed again, which simultaneously signals the start of driving.

[0035] FIG. 2 shows a cross-sectional view of an electromechanical brake actuator 200 according to an embodiment. The electromechanical brake actuator 200 is referred to as EMB 200 for short. The EMB 200 comprises an electric drive. The drive acts on a worm gear 202. The worm gear 202 is connected to a thread drive 204. In the worm gear 202, the rotational speed of the drive is strongly reduced. In the thread drive 204, this reduced rotational movement is converted into linear movement and the braking force is multiplied via the thread pitch. The thread drive 204 is configured as a ball screw drive. The worm gear 202 and the thread drive form a mechanism 206 of the electromechanical brake actuator 200.

[0036] A locking device 210 is coupled to the worm wheel 208 of the worm transmission 202. A lock actuator 212, including a movable lock pawl 214, is aligned with the locking device 210. The lock actuator 212 is configured to lock the lock pawl 214 to the locking device 210, thereby locking the mechanism 206.

[0037] In one embodiment, locking pawl 214 is configured to lock mechanism 206 against reverse motion and still allow mechanism 206 to move forward.

[0038] Figure 3 shows a three-dimensional view of an electromechanical brake actuator 200 according to one embodiment. The brake actuator 200 substantially corresponds to the brake actuator shown in Figure 2. The view shows the lock actuator 212, lock pawl 214, locking device 210, and electric drive 300 of the electromechanical brake actuator 200.

[0039] The locking device 210 is formed as a gear with saw-tooth teeth, and the locking pawl 214 is formed as a movable finger that slides over the slanted flanks of the tooth row when the locking device 210 is rotated in the forward direction and locks against the steep flanks of the tooth row when the locking device 210 is rotated in the reverse direction.

[0040] When the lock actuator 212 is actuated, it applies a force to the lock pawl 214, urging the lock pawl 214 from the unlocked position to the locked position. In doing so, the lock actuator acts against the return spring 302 of the lock pawl 214. If the force is greater than the spring force of the return spring 302, the lock pawl 214 is moved to the locked position. If the force is less than the spring force, the return spring 302 returns the lock pawl 214 to the unlocked position.

[0041] In one embodiment, the teeth of the locking device 210 are configured with undercuts so that, in the locked position, the lock pawl 214 slides into the undercut 304 of at least one locking portion of the locking device 210 or one tooth of the locking device 210 when the driver 300 reduces the torque of the driver 300. At that time, the locking device 210 rotates in the reverse direction by the undercut 304, and only then is it locked by the lock pawl 214. When the lock pawl 214 is locked deep within the undercut 304, the force of the return spring 302 is too small to return the lock pawl 214 to the unlocked position again.

[0042] To return the lock pawl 214 to the unlocked position, the driver 300 rotates the entire mechanism 206, including the locking device, in a forward direction at least the width of the undercut 304. The lock pawl 214 then slides out of the undercut 304, and the return spring 302 pulls the lock pawl 214 back to the unlocked position.

[0043] In the following, possible configurations of the invention are summarized once again, or expressed in slightly different wording.

[0044] This paper presents an electromechanical brake actuator (EMB) with a fast handover from hill hold function to automatic parking brake (APB).

[0045] As the electrification of in-vehicle devices continues, service brakes are now in focus, following on from parking brakes, and several electromechanical brake concepts are already being integrated into production vehicles.

[0046] In most cases, an electric drive motor is combined with one or more transmission stages with a very strong overall reduction ratio, usually a toothed transmission with a linear transmission ratio. Some concepts use cams as the speed-changing element, thereby varying the speed nonlinearly.

[0047] In the approach presented here, the function "automatic parking brake" APB is also integrated into this EMB. Automatic parking brakes have special requirements, which in some cases differ significantly from those for the service brake EMB. APBs are usually designed for long periods of time and often only require an operating current to change the APB state. Maintaining the APB state (APB open + vehicle moving or APB closed + vehicle stationary) requires little or no operating current.

[0048] Especially in vehicles with EMB, the hill hold function is (mostly) achieved by the EMB drive motor actively (powered) holding the position, which requires high current, which puts a strain on the vehicle's battery in the sense that the driving range is reduced.

[0049] The approach presented here can save electrical energy in battery-electric vehicles (BEVs) with electromechanical braking (EMB), thus enabling a higher driving range.

[0050] The core idea here is the extremely rapid transfer of the vehicle-holding function from the hill-hold function (which is assigned to the rolling vehicle and is realized by the service brake) to the automatic parking brake function (which is realized in most cases by the APB (automatic parking brake) which is already electro-mechanically operated).

[0051] This is facilitated by the functional proximity of the function brake (electro-mechanically operated) and the parking brake (electro-mechanically operated) in the EMB.

[0052] With the approach presented here, current can be saved for greater driving range.

[0053] The APB can take over the brakes already closed by the service brakes (hill hold) in the "closed" state. The APB operating current required to transition from APB-open to APB-closed is very small and the time is almost zero or very short.

[0054] The operating current for the EMB drive motor can now be instantly reduced from a high holding current to zero. The service brake EMB can be released completely (low reversing current) or can remain in a position close to the handover position to the APB (low or no holding current due to powerlessness). This means that the EMB motor can be designed significantly smaller than previously customary, since it cannot overheat due to continuous current load.

[0055] Based on other signals in the vehicle (e.g. the vehicle is in motion (no button "stop", no driver's seat is left (seat sensor), no door is opened (door sensor), etc.), the stop can be interpreted as a short stop of the vehicle, e.g. at an intersection, traffic lights, etc.

[0056] Alternatively / optionally, this situation may be defined as "APB closed / short stop", possibly with impact on other functions of the vehicle.

[0057] Based on other signals within the vehicle, when it recognizes that the vehicle is parked (pressing the "Stop" button, leaving the driver's seat (seat sensor), etc.), the EMB can return to its rest position without any force and with a small current, and the APB is already operated.

[0058] Alternatively / optionally, this situation may be defined as "APB Closed / Parking", possibly with implications for other functions of the vehicle.

[0059] The approach presented here can be used in mechanical and hydraulic operating elements outside of automobiles, e.g. in mobile hydraulic systems or other hydraulic systems, motorcycles, e-bikes, power tools, household appliances, industrial technology, building technology or everyday items.

[0060] At the start, the vehicle is moving. Then it receives a signal that the service brakes are applied and the vehicle is stopped. Accordingly, the hill hold function is initiated. If a further signal is "YES (JA)", for example: the "Start" button is still pressed, the driver's seat is still occupied, and the door is still closed, it recognizes the situation as "APB closed / short stop" and quickly closes the APB, opens the EMB, reduces the current as much as possible, and ends the hill hold function.

[0061] This situation is ended by operating the accelerator pedal (= ending the short-term stop and resuming driving).

[0062] If the further signal is "No", the system recognizes the situation as "APB Closed / Parking", closes the APB for parking, opens the EMB, moves it to the rest position and ends the hill hold function.

[0063] This situation is ended by pressing the "Start" button and when the driver's seat is occupied and the door is opened and then closed again (=end of parking, start of driving).

[0064] Finally, it should be noted that the word "comprises" does not exclude other elements or steps, and the word "indefinite article" does not exclude a plurality. Reference signs in the claims are not to be regarded as limiting. [Explanation of symbols]

[0065] 100 decision chain 200 Electromechanical Brake Actuator, EMB 202 Worm transmission 204 Thread Drive 206 Mechanism 208 Worm Wheel 210 Locking device 212 Lock Actuator 214 Locking Claw 300 Electric drive unit 302 Return spring 304 Undercut

Claims

1. 1. A method for operating an electromechanical brake actuator (EMB) (200) for a friction brake of a vehicle, comprising: a drive unit (300) of the EMB (200) moving a mechanism (206) of the EMB (200) to a braking position; and, when a stopped state of the friction brake is recognized, driving and controlling a lock actuator (212) of the EMB (200) to lock the mechanism (206).

2. The method of claim 1, further comprising at least reducing the drive force generated by the drive portion (300) in response to the locking of the mechanism (206).

3. The method of claim 2, further comprising de-energizing the drive (300) in response to the locking of the mechanism (206).

4. 4. The method of claim 1, wherein the mechanism (206) is unlocked in response to actuation of a vehicle accelerator pedal.

5. The method of claim 4, further comprising controlling the drive unit (300) to move the mechanism (206) to an initial position in response to the unlocking of the mechanism (206).

6. 6. The method according to claim 1, further comprising controlling the drive unit (300) to move the mechanism (206) in a forward direction at least by an amount corresponding to an undercut (304) of a locking device (210) for the lock actuator (212) to unlock the mechanism (206).

7. 7. The method of claim 6, wherein the mechanism (206) moves in a reverse direction from the braking position at least the distance of the undercut (304) when locked.

8. An electromechanical brake actuator (EMB) (200) for a friction brake of a vehicle, the EMB (200) comprising: an electric drive unit (300); a mechanism (206) for transmitting a drive motion of the drive unit (300) to the friction brake of the vehicle; and an electromechanical lock actuator (212) for locking the mechanism (206).

9. The EMB (200) of claim 8, wherein the lock actuator (212) is normally open.

10. The EMB (200) of claim 8 or 9, wherein the lock actuator (212) has at least one switchable lock pawl (214), and a locking device (210) for locking the lock pawl (214) is connected to the mechanism (206).

11. The EMB (200) of claim 10, wherein the locking device (210) is located on a drive side of the mechanism (206).

12. 12. The EMB (200) of claim 10 or 11, wherein the locking pawl (214) and the locking device (210) form a switchable freewheel that blocks reverse movement of the mechanism (206), and forward movement is unlocked even when the freewheel is activated.

13. 13. The EMB (200) of any one of claims 10 to 12, wherein the locking device (210) is undercut and requires a positive impulse of the drive (300) to release the lock of the lock pawl (214).

14. 8. A control device, the control device being configured to implement, control or realize the method according to any one of claims 1 to 7 in a corresponding device.

15. 8. A computer program product configured to instruct a processor, when executed, to perform, implement and / or control a method according to any one of claims 1 to 7.

16. 16. A machine-readable storage medium having stored thereon the computer program product of claim 15.

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