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

Abstract

The present invention relates to a method for operating an electromechanical brake actuator (EMB) (200) for a friction brake of a vehicle, wherein a locking actuator (212) of the EMB (200) is controlled to lock a mechanism (206) of the EMB (200) when a drive (300) of the EMB (200) has moved the mechanism (206) into a braking position and a standstill of the friction brake is detected.

Description

Field of the invention

[0001] The 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. State of the art

[0002] An electromechanical brake actuator can provide braking force to a friction brake via a drive and a mechanism. As long as braking force is requested, the drive is energized. When the drive is de-energized, the braking force decreases or ceases.

[0003] Therefore, an electromechanical brake actuator can incorporate a force accumulator for a parking brake. The force accumulator can, for example, be a preloaded spring that is released when the vehicle is parked. This can prevent a vehicle from rolling away even when the brake actuator is de-energized. The force accumulator can be re-loaded by reversing the electromechanical brake actuator when the parking brake is released. Disclosure of the invention

[0004] Against this background, the approach presented here presents 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. Advantageous further developments and improvements of the approach presented here emerge from the description and are described in the dependent claims. Advantages of the invention

[0005] In an electromechanical brake actuator, the drive movement of an electric motor is reduced by a gear in order to achieve a high braking force on the friction linings of a friction brake with a small movement of the friction linings. The braking force presses the friction linings against a counterpart, such as a brake disc or brake drum, to generate friction. The gear can, for example, be a worm gear that acts on a threaded spindle to convert rotation into translation. To press the friction linings against the counterpart, the gear is moved forward. To lift the friction linings from the counterpart, the gear is moved backward. The gear can also be moved backward by a counterforce when the electric motor no longer provides drive torque. The counterforce can arise, for example, from lateral runout of the brake disc.

[0006] When a vehicle is braked to a standstill using the electromechanical brake actuator, the electric motor has already moved the friction linings at the beginning of the braking process and pressed them against their counterpart with the required braking force.

[0007] In the approach presented here, the friction linings are held at least approximately in the position reached during braking after the vehicle has come to a standstill, providing a holding torque to the counterpart through the friction linings. To this end, the reverse movement of the transmission is prevented by a switchable locking mechanism.

[0008] The approach presented here allows the electric motor to stop providing drive torque or at least reduce it after the vehicle has come to a standstill. Unintentional rolling of the vehicle is reliably prevented until the transmission lock is released. When the vehicle intentionally sets off, the holding torque or braking torque can be reduced or eliminated in a controlled manner by the electric motor being restarted.

[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 presented, wherein a locking actuator of the EMB is controlled to lock a mechanism of the EMB when a drive of the EMB has moved the mechanism into a braking position and a standstill of the friction brake is detected.

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

[0011] Ideas for embodiments of the present invention can be considered, among other things, to be based on the thoughts and findings described below.

[0012] An electric drive of an electromechanical brake actuator can, for example, be an electric motor that provides rotary motion and torque when electrically controlled. A mechanical system can be a gearbox. The mechanical system can have a gear ratio to convert a large input movement of the electric drive into a small output movement of a friction lining of a friction brake, whereby a small input force of the drive is translated into a large output force on the friction lining. The drive can move the friction lining(s) from an initial position to a braking position. In the braking position, the friction linings make contact with a counterpart of the friction brake, are pressed against the counterpart with a resulting braking force, and generate friction there. The counterpart can, for example, be a brake disc or a brake drum.

[0013] An electromechanical locking actuator can be controlled 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 element. The locking element can engage a corresponding counterpart of the mechanism to mechanically block the mechanism. By activating the locking actuator, the mechanism of the electromechanical brake system can be blocked in its current state, thus preventing the friction linings, which have been moved into the braking position by the electromechanical brake system, from returning to a non-braking position. In other words, the electromechanical brake system can be blocked and held in its braking configuration by activating the locking actuator.

[0014] A standstill of the friction brake can be detected by a sensor. In a vehicle, the sensor can be, for example, a speed sensor and / or an ABS sensor. In particular, the friction brake can be continuously or repeatedly monitored for movement, for example, by monitoring moving components in the brake or a braked wheel itself, or by monitoring other state variables that allow conclusions to be drawn about the current movement behavior of the friction brake. As soon as it is detected that the friction brake or the vehicle being braked by it has come to a standstill, the locking actuator is activated immediately or as quickly as possible to lock the EMB mechanism.

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

[0016] The mechanism can be unlocked again in response to the vehicle's accelerator pedal being depressed. An accelerator pedal can also be referred to as an accelerator pedal. When the accelerator pedal is depressed, this indicates a driver's intention to continue or begin driving. When the accelerator pedal is depressed, torque is provided by a vehicle drive. This torque can compensate for a decrease in braking force when the mechanism is unlocked.

[0017] The drive of the electromechanical brake actuator can be controlled to move the mechanism to its home position in response to the mechanism being unlocked. The drive can retract the friction linings from the counterpart to prevent dragging. Alternatively, or in addition, the friction linings can be pushed away from the counterpart by a lateral impact of the counterpart.

[0018] The locking actuator can have at least one switchable pawl as the locking element. As a counterpart, a locking device for engaging the pawl can be coupled to the mechanism. A pawl can be movable. The pawl can be moved by the locking actuator between an unlocked state or an unlocked position and a locked state or a locked position. The pawl can be coupled to a housing of the EMB. The pawl can thus be supported by the housing when the mechanism is blocked.

[0019] The locking device can be located on the drive side of the mechanism. The electric drive can be coupled to the mechanism on the drive side. On the drive side, the mechanism can be blocked or locked with a small amount of force.

[0020] The pawl and the locking device can form a switchable freewheel to prevent backward movement of the mechanism, whereby forward movement remains unblocked even when the freewheel is activated. In the forward direction, the pawl can slide off the sloped sides of the notches of the locking device and, after sliding off, engage the steep sides of the notches.

[0021] The locking mechanism may be undercut. A forward impulse from the drive may be required to disengage the pawl. The steep sides of the locking mechanism's notches may each have an undercut. When engaging in the reverse direction, the pawl can slide into the undercut and rest securely in the undercut. In the undercut, the pawl cannot move back into the unlocked position without the locking mechanism being moved slightly forward, thereby moving the pawl out of the undercut.

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

[0023] The drive can be controlled to unlock the mechanism, at least moving the mechanism forwards by the undercut of the locking device for the locking actuator. The locking pawl of the locking actuator can be securely held without power when the mechanism is locked behind the undercut of the locking device. The locking pawl cannot move out from behind the undercut without slight movement of the locking device. To release the locking pawl from the undercut, the drive can briefly press the friction linings more firmly against the counterpart in order to release the pawl. After release, the drive can drive the locking device in the reverse direction to lift the friction linings off the counterpart.

[0024] When locking, the mechanism can be moved backwards from the braking position, at least by the undercut. When the pawl engages in the locking mechanism, the brake can be released slightly until the pawl engages behind the undercut.

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

[0026] The approach presented here further creates a control unit, wherein the control unit is designed to carry out, control or implement the steps of a variant of the method presented here in corresponding devices.

[0027] The control unit can be an electrical device with at least one computing unit for processing signals or data, at least one memory unit for storing signals or data, and at least one interface and / or a communication interface for reading in 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 depending on the sensor signals. The memory unit can be, for example, a flash memory, an EPROM, or a magnetic storage unit. The interface can be designed as a sensor interface for reading in the sensor signals from a sensor and / or as an actuator interface for outputting the data signals and / or control signals to an actuator.The communication interface can be configured to read or output data wirelessly and / or via a wired connection. The interfaces can also be software modules, which are present, for example, on a microcontroller alongside other software modules.

[0028] Also advantageous is a computer program product or computer program with program code that 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 carry out, implement and / or control the steps of the method according to one of the embodiments described above, in particular when the program product or program is executed on a computer, in a control unit or a device.

[0029] It should be noted that some of the possible features and advantages of the invention are described herein with reference to different embodiments. A person skilled in the art will recognize that the features of the control device and the method can be combined, adapted, or exchanged as appropriate to achieve further embodiments of the invention. Short description of the drawings

[0030] Embodiments of the invention are described below with reference to the accompanying drawings, wherein neither the drawings nor the description are to be construed as limiting the invention. Fig. 1 shows a decision chain of a method according to an embodiment; Fig. 2 shows a sectional view through an electromechanical brake actuator according to an embodiment; and Fig. 3 shows a spatial representation of an electromechanical brake actuator according to an embodiment.

[0031] The figures are merely schematic and not to scale. Like reference numerals denote like or equivalent features. Embodiments of the invention

[0032] Fig. 1 shows a decision chain 100 of a method for operating an electromechanical brake actuator of a vehicle according to an exemplary embodiment. Initially, the vehicle is moving. If a service brake of the vehicle has been applied and the vehicle has stopped, a hill hold function of the service brake is activated. If, during this time, the vehicle's start / stop button remains activated, the driver's seat remains occupied, and the door remains closed, the "short stop" situation is detected and a locking actuator of the electromechanical brake actuator is quickly closed to lock the friction brake in the position for the hill hold function. Subsequently, an electric drive of the electromechanical brake actuator is switched off, thus ending the active hill hold function. If an accelerator pedal of the vehicle is actuated, the short stop is ended and the locking actuator is deactivated so that the brake is released and the vehicle can move off.

[0033] If, after activating the hill hold function, the start / stop button is deactivated, the driver's seat is left and / or the door is opened and / or an automatic start / stop system of the vehicle switches off the engine, the "parked" situation is detected and the parking lock actuator is closed.

[0034] The drive of the electromechanical brake actuator is then deactivated and returns to a rest position. The hill hold function is also deactivated. Parking is terminated when the start / stop button is pressed, the driver's seat is occupied, and the door is closed again after opening. This simultaneously signals the start of the journey.

[0035] Fig. Figure 2 shows a sectional view of an electromechanical brake actuator 200 according to an exemplary embodiment. The electromechanical brake actuator 200 is abbreviated to EMB 200. The EMB 200 has an electric drive. The drive acts on a worm gear 202. The worm gear 202 is coupled to a screw drive 204. In the worm gear 202, the speed of the drive is significantly reduced. In the screw drive 204, the reduced rotary motion is converted into a linear motion, and a braking force is amplified via a thread pitch. The screw drive 204 is designed as a ball screw drive. The worm gear 202 and the screw drive form a mechanism 206 of the electromechanical brake actuator 200.

[0036] A locking device 210 is coupled to a worm gear 208 of the worm gear 202. A locking actuator 212 with a movable pawl 214 is aligned with the locking device 210. The locking actuator 212 is designed to engage the pawl 214 with the locking device 210, thus locking the mechanism 206.

[0037] In one embodiment, the pawl 214 is configured to block a backward movement of the mechanism 206 and to continue to allow a forward movement of the mechanism 206.

[0038] Fig. Figure 3 shows a spatial representation of an electromechanical brake actuator 200 according to an embodiment. The brake actuator 200 essentially corresponds to the brake actuator in Fig. 2. Here, the locking actuator 212, the pawl 214, the locking device 210 and an electric drive 300 of the electromechanical brake actuator 200 are shown.

[0039] The locking device 210 is designed as a gear with sawtooth teeth. The pawl 214 is designed as a movable finger that slides over inclined flanks of the teeth when the locking device 210 is rotated in the forward direction and engages steep flanks of the teeth when the locking device 210 is rotated in the reverse direction.

[0040] When the locking actuator 212 is activated, it presses against the locking pawl 214 with a force, pushing the locking pawl 214 from an unlocked position to a locked position. The locking actuator acts against a return spring 302 of the locking pawl 214. If the force is greater than the spring force of the return spring 302, the locking pawl 214 is moved to the locked position. If the force is less than the spring force, the return spring 302 moves the locking pawl 214 back to the unlocked position.

[0041] In one embodiment, the toothing of the locking device 210 is designed with an undercut. As a result, the locking pawl 214, in the locked position, slides into the undercut 304 of at least one notch of the locking device 210 or a tooth of the locking device 210 when the drive 300 reduces its torque. The locking device 210 rotates around the undercut 304 in the reverse direction and is only then locked by the locking pawl 214. When the locking pawl 214 is engaged behind the undercut 304, the force of the return spring 302 is too small to move the locking pawl 214 back into the unlocked position.

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

[0043] In the following, possible embodiments of the invention are summarized again or presented with slightly different wording.

[0044] An electromechanical brake actuator (EMB) with a fast transfer from a hill hold function to an automatic parking brake (APB) is presented.

[0045] With the increasing electrification of automotive components, the service brake is now coming into focus, following the parking brake. Individual electromechanical brake concepts have already been installed in production vehicles.

[0046] Typically, an electric drive motor is combined with one or more gear stages with a very high overall reduction ratio, usually with geared transmissions with a linear ratio. Some concepts use cams as a transmission element, thus achieving non-linear transmission.

[0047] In the approach presented here, the "Automatic Parking Brake" (APB) function is also integrated into this EMB. The automatic parking brake has special requirements, some of which differ significantly from those for the service brake (EMB). The APB is typically designed to operate for a long time and usually only requires operating current to change its state. Little or no operating current is required to maintain an APB state (APB open + vehicle moving or APB closed + vehicle stationary).

[0048] Especially in vehicles with EMB, the hill hold function is (usually) implemented by actively (powered) holding the EMB drive motor. This requires high currents, which place a strain on the vehicle's storage battery, reducing the driving range.

[0049] The approach presented here can save electrical energy in battery-electric vehicles (BEVs) with electromechanical brakes (EMBs), thus enabling a longer range.

[0050] The core idea is the extremely fast transfer of the vehicle holding function from the hill hold function (this is assigned to the rolling vehicle and is implemented by the service brake) to the automatic parking brake function (implemented by the APB automatic parking brake / parking brake, which is usually already electromechanically operated).

[0051] This is facilitated by the functional proximity of the parking brake (electromechanical actuation) and the functional brake (electro-mech. actuation) in the EMB.

[0052] The approach presented here can save electricity for greater range.

[0053] The APB can take over the brake already applied by the service brake (hill hold) in the "closed" state. Only a small APB actuation current is required, and the time required for the transition from APB open to APB closed is close to zero or very short.

[0054] The operating current for the EMB drive motor can now be instantly reduced from high holding currents to zero. The EMB service brake can be completely released (low reversing currents) or can remain in a position close to the transfer position to the APB (low or no holding current, as it is powerless). This allows the EMB motor to be designed significantly smaller than conventionally, as it cannot overheat due to continuous current loading.

[0055] Based on other signals in the vehicle (e.g. vehicle remains in operation (no "Stop" button, no leaving the driver's seat (seat sensor), no door opening (door sensor), etc.), it can be interpreted that this is a brief stop of the vehicle, e.g. at an intersection, traffic light, etc.

[0056] Alternatively / optionally, this situation can be defined as “APB closed / short stop”, with possible effects on other vehicle functions.

[0057] If the other signals in the vehicle detect that the vehicle is parked (stop button pressed, leaving the driver's seat (seat sensor), etc.), the EMB can return to its rest position without power and with low currents, since the APB is already activated.

[0058] Alternatively / optionally, this situation can be defined as “APB closed / parked” with possible effects on other vehicle functions.

[0059] The approach presented here can also be used in mechanical-hydraulic actuation elements, even outside of motor vehicles, e.g. in mobile hydraulics and other hydraulics, motorcycles, eBikes, power tools, household appliances, industrial technology, building technology or consumer goods.

[0060] Initially, the vehicle is moving. Then, the signal is received that the service brake is applied and that the vehicle is stopped. The hill hold function then kicks in. If other signals are "YES," e.g., the "Start" button remains pressed, the driver's seat remains occupied, or the door remains closed, an "APB closed / short stop" situation is detected and the APB is quickly closed, the EMB is opened and, if possible, de-energized, and the hill hold function is terminated.

[0061] The situation is ended by pressing the accelerator pedal (=short stop ended, continue driving).

[0062] If the other signals are "No", an "APB closed / parked" situation is detected and the APB is closed for parking, the EMB is opened and goes to the rest position, the hill hold function is terminated.

[0063] The situation is ended by pressing the "Start" button, when the driver's seat is occupied, and when the door is closed again after opening. (=parking ends, driving begins)

[0064] Finally, it should be noted that terms such as "comprising," "having," etc., do not exclude other elements or steps, and terms such as "a" or "an" do not exclude a plurality. Reference signs in the claims are not to be considered limiting.

Claims

[1] Method for operating an electromechanical brake actuator (EMB) (200) for a friction brake of a vehicle, wherein a locking actuator (212) of the EMB (200) is controlled to lock a mechanism (206) of the EMB (200) when a drive (300) of the EMB (200) has moved the mechanism (206) into a braking position and a standstill of the friction brake is detected. [2] Method according to claim 1, wherein a driving force generated by the drive (300) is at least reduced in response to the locking of the mechanism (206). [3] Method according to claim 2, wherein the drive (300) is de-energized in response to the locking of the mechanism (206). [4] Method according to one of the preceding claims, wherein the mechanism (206) is unlocked in response to actuation of an accelerator pedal of the vehicle. [5] Method according to claim 4, wherein the drive (300) is controlled in response to the unlocking of the mechanism (206) to move the mechanism (206) into a starting position. [6] Method according to one of the preceding claims, in which the drive (300) for unlocking the mechanism (206) is controlled to move the mechanism (206) in a forward direction at least around an undercut (304) of a locking device (210) for the locking actuator (212). [7] Method according to claim 6, wherein the mechanism (206) is moved at least around the undercut (304) from the braking position in a reverse direction during locking. [8] Electromechanical brake actuator (EMB) (200) for a friction brake of a vehicle, wherein the EMB (200) has an electric drive (300), a mechanism (206) for transmitting a drive movement of the drive (300) to a friction brake of the vehicle and an electromechanical locking actuator (212) for locking the mechanism (206). [9] EMB (200) according to claim 8, wherein the blocking actuator (212) is open when de-energized. [10] EMB (200) according to one of claims 8 to 9, wherein the locking actuator (212) has at least one switchable pawl (214) and a latching device (210) for latching the pawl (214) is coupled to the mechanism (206). [11] EMB (200) according to claim 10, wherein the locking device (210) is arranged on a drive side of the mechanism (206). [12] EMB (200) according to one of claims 10 to 11, wherein the pawl (214) and the locking device (210) form a switchable freewheel for preventing a backward movement of the mechanism (206), wherein a forward movement is also unlocked in the activated state of the freewheel. [13] EMB (200) according to one of claims 10 to 12, wherein the locking device (210) is undercut, wherein a forward impulse of the drive (300) is required to disengage the pawl (214). [14] Control device which is designed to carry out, control or implement the method according to one of claims 1 to 7 in corresponding devices [15] Computer program product which is designed to instruct a processor, when the computer program product is executed, to carry out, implement and / or control the method according to one of claims 1 to 7. [16] A machine-readable storage medium on which the computer program product according to claim 15 is stored.

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