An epb parking release control method and control system thereof

Abstract

The application discloses an EPB parking release control method and a control system thereof, and the control method comprises the following steps: when the EPB parking is pulled up, the rotating angle of the working process of an EPB motor is acquired; the acquired rotating angle is recorded and stored; when the next parking release operation is performed, the rotating angle of the EPB motor when the last parking is pulled up is read, and the motor is reversely rotated by the same angle according to the rotating angle when the parking is pulled up to release the parking. The motor is reversely rotated by the same number of turns according to the motor rotating angle when the last parking is pulled up, the parking release control method makes the drum brake EPB parking release control adaptive, and the parking release control method can well adapt to the differences of single brake and the changes of brake clearance during the use of the vehicle, so that the motor rotating angle during each parking release operation matches the actual brake clearance, the abnormal alarm of the system is avoided, and the reliability of the vehicle function is improved.

Description

Technical Field

[0001] This invention relates to the field of automotive electronic parking system control technology, and in particular to an EPB parking release control method and its control system. Background Technology

[0002] With the upgrading of the needs of light commercial vehicles, electronic parking brake (EPB) systems are now widely adopted. Due to the limitations of vehicle weight and cost, most light commercial vehicles use rear drum brakes, which use a motor and a worm gear screw mechanism to replace the manual cable for parking and starting. The system's control program is integrated into the ABS / ESC. Parking is initiated by monitoring the motor's stall current threshold, while parking is released without stalling. The industry generally uses a method of calibrating a fixed motor operating time to determine when the parking brake is fully released.

[0003] The existing control scheme has certain flaws and is prone to triggering EPB current overload alarms. During mass production of vehicles, the consistency of drum brake clearance is poor, as illustrated by the drum brake connection and installation structure with electronic parking brake function disclosed in patent CN210565923U. Wear of the brake pads and abnormalities in the self-adjusting mechanism during vehicle use can lead to brake clearances that are too small and exceed the calibrated range. When the parking brake is released, the motor continues to operate after the lead screw reaches its limit position, causing stalling, excessive current, and triggering a fault alarm. This problem is solely caused by a mismatch between the control duration and the actual clearance; it does not cause wheel drag and does not affect normal vehicle operation, but the mismatch between the parking brake release time and the actual braking clearance can cause a high current alarm. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an EPB parking release control method and its control system, which can avoid the problem of excessive motor operating current alarm during parking release caused by mismatch between parking release time and actual brake clearance.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] This application provides an EPB parking release control method, including the following steps:

[0007] S1. When the EPB parking brake is pulled up, obtain the rotation angle of the EPB motor during its operation.

[0008] S2. Record and store the acquired rotation angle;

[0009] S3. When performing the next parking release operation, read the EPB motor rotation angle when the parking was pulled up last time, and make the motor rotate in the opposite direction by the same angle to release the parking.

[0010] In step S1, the number of rotations of the EPB motor during the process of fully raising the parking brake is obtained, and the number of rotations is converted into a rotation angle.

[0011] In step S2, the acquired rotation angle is converted into a digital signal and stored in the system memory.

[0012] In the control method, the initial release rotation angle of the EPB is set as follows: based on the design brake clearance range given by the brake, the vehicle model obtains the rotation angle of the MGU motor when the parking brake is fully released through the EPB system calibration. The number of encoder pulses , When a new vehicle rolls off the production line or during a system reset, the EPB brake is in the fully released parking position, and the EPB system stores the initial value of the pulse corresponding to the parking release rotation angle. The initial pulse value of the motor is all according to .

[0013] In the control method, the misoperation compatibility control checks whether the EPB motor actually rotates after the parking switch is pulled, thereby eliminating the possibility of accidental switch activation and the possibility that the vehicle is actually in the parking state when the switch is pulled.

[0014] This application provides a drum brake EPB parking release control system, including a drum brake, an MGU unit, and a parking cable. The MGU unit includes a motor and a transmission structure. The motor is connected to the parking cable through the transmission structure. It also includes a storage module and a controller. The MGU unit has a data acquisition component for acquiring the rotation angle of the motor. The data acquisition component is connected to the storage module. The storage module and the motor are both connected to the controller.

[0015] The acquisition component is an angle sensor or encoder integrated into the motor.

[0016] The encoder includes a code disk, a photosensitive element, and a light source; the code disk is connected to the motor's rotating shaft, and the photosensitive element and the light source are respectively arranged on both sides of the code disk.

[0017] The encoder is a magnetic encoder.

[0018] The bottom of the motor is a hollow structure, and the inner end of the motor's rotating shaft is located inside the hollow structure. The encoder, photosensitive element, and light source are all located inside the hollow structure.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] The EPB parking release control method and its control system are reasonably designed. By adjusting the motor rotation angle based on the previous parking pull-up, the motor rotates in the opposite direction by the same number of turns during the parking release process. This parking release control method makes the EPB parking release control of the drum brake adaptive. It can well accommodate the differences in individual brake components and the changes in brake clearance during vehicle use, ensuring that the motor rotation angle during each parking release matches the actual brake clearance, avoiding abnormal system alarms and improving the reliability of vehicle functions. Attached Figure Description

[0021] The following is a brief explanation of the contents of each of the accompanying drawings and the markings in the drawings:

[0022] Figure 1 This is a schematic diagram of the control steps of the present invention.

[0023] Figure 2 This is a schematic diagram of the workflow of the control method of the present invention.

[0024] Figure 3 This is a schematic diagram of the drum brake integrating the MGU according to the present invention.

[0025] Figure 4 This is a schematic diagram illustrating the working principle of the MGU of the present invention.

[0026] Figure 5 This is a schematic diagram of the internal structure of the motor of the present invention.

[0027] In the picture:

[0028] 1. Drum brake, 2. MGU unit, 3. Parking cable, 4. Motor, 401. Motor rotating shaft, 5. Worm gear, 6. Lead screw, 7. Encoder, 8. Photosensitive element, 9. Light source. Detailed Implementation

[0029] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and through the description of the examples.

[0030] Although the invention has been shown and described herein with reference to specific embodiments, it is not intended to be limited to the details shown. Rather, various modifications in detail may be made within the equivalent scope and scope of the claims without departing from the invention. In the drawings, the same item numbers refer to the same elements.

[0031] Throughout this disclosure, various terms are used to describe the physical shape or arrangement of features. Many of these terms are used to describe features conforming to a cylindrical or generally cylindrical geometry with the feature as its radius and a central axis perpendicular to that radius. Unless otherwise specified, the terms are given the following meanings: The terms “longitudinal,” “longitudinal,” “axial,” and “axial” refer to a direction, dimension, or orientation parallel to the central axis. The terms “radial” and “radially” refer to a direction, dimension, or orientation perpendicular to the central axis. The terms “inward” and “inner” refer to a direction, dimension, or orientation extending radially toward the central axis. The terms “outward” and “outer” refer to a direction, dimension, or orientation extending radially away from the central axis.

[0032] In this specification, relative terms such as “horizontal,” “vertical,” “upward,” “downward,” “top,” and “bottom,” and their derivatives (e.g., “horizontal,” “downward,” “upward,” etc.) should be interpreted as referring to the direction described or the direction shown in the accompanying drawings. These relative terms are for ease of description and are not generally intended to require a specific direction.

[0033] With the rapid development of the automotive industry and the continuous improvement of people's living standards, domestic light commercial vehicle users have higher requirements for interior space, ease of operation and driving comfort. Light commercial vehicles are becoming increasingly well-equipped, and electronic parking brakes (EPB) are increasingly being adopted.

[0034] Light commercial vehicles have a large total mass, requiring high braking performance and cost control; therefore, drum brakes are commonly used for the rear brakes. For example... Figure 3 As shown, the rear drum brake using an electronic parking system has a motor and a worm gear screw transmission mechanism arranged on the base plate of the rear drum brake. The motor drives the screw to replace manual tensioning and release of the cable connecting the brake shoes, thereby realizing the function of raising and releasing the parking device.

[0035] The control software of an electronic parking brake system is generally integrated with ABS or ESC. The control methods for fully engaging and fully disengaging the parking brake are generally as follows: Based on the motor's operating current characteristics, when the motor stops rotating, its operating current gradually increases from a smooth, stable value. During the parking brake engagement process, the EPB control system monitors the motor current to determine whether the parking brake is fully engaged. That is, after the brake shoes fully engage with the brake drum, the motor stops rotating, and the motor current increases. A certain value during this current increase is used as a threshold; when the current reaches the threshold, the parking brake is considered fully engaged. This current threshold is obtained through calibration.

[0036] For the parking brake release process, since there is no motor stall during normal release, it is impossible to determine whether the parking brake is fully released by using the threshold current. Currently, drum brake EPB systems generally use a "fixed motor working time" as the control method for complete parking brake release. That is, the motor working time of the EPB brake for this model from the pulled-up state to the fully released state is obtained by calibration, and this working time is used as the length of time the motor works during the EPB release process.

[0037] Using a fixed working time length as the parking release control for the EPB drum brake, during mass production and vehicle use, issues such as excessive motor operating current alarms may occur in the EPB system due to problems with the clearance between the brake shoes and the brake drum. The causes are as follows: 1. To prevent burnout from excessive motor operating current, the EPB system has an alarm safety strategy: when the motor operating current reaches the maximum allowable current, the system will stop the motor and illuminate the EPB instrument panel fault light; 2. When the clearance between the brake shoes and the brake drum of the EPB drum brake is too small, exceeding the caliper range, when the parking brake is engaged, the screw moves a distance... 1. When the distance is shorter than the calibrated minimum distance, the motor continues to operate according to the calibrated motor working time when releasing the parking brake in this state. After the screw moves to the bottom, the motor continues to work because the set motor working time has not yet been reached. The lead screw continues to move, but at this time the lead screw has already moved to the bottom, which will cause the motor to stall. The motor working current will continue to increase and exceed the current alarm threshold, triggering a system alarm. 2. The gap between the brake shoes and the brake drum of a drum brake is generally controlled between 0.20 and 0.40 mm. When developing a vehicle model to match the EPB system of drum brakes, the motor working time during EPB parking brake release will be calibrated according to the gap range provided by the brake manufacturer. However, due to the limitations of the level of consistency control of the brake gap of drum brakes, the brake gap may exceed the calibrated range during mass production. 3. During vehicle use, with continuous braking, the friction shoes of the left and right drum brakes wear, and the gap between the friction shoes and the brake surface inside the brake drum changes. The brake gap self-adjustment mechanism may adjust the brake gap to be too small, exceeding the design calibration range.

[0038] The above reasons lead to an alarm issue of excessive motor current during parking release when using the current parking release control method. However, this situation of insufficient brake clearance will not cause wheel drag and will not affect the normal driving of the vehicle. The excessive current alarm is only caused by the mismatch between the parking release time and the actual brake clearance.

[0039] Due to the inherent structural characteristics of drum brakes, a certain percentage of individual brake components may have a brake clearance exceeding the specified range. However, as long as the brake drag force does not exceed the specified range, the vehicle's basic braking function is normal, meaning there will be no brake drag or locking malfunction. However, because of the EPB (Electronic Parking Brake) system, a brake clearance smaller than the specified range can cause the EPB motor to stall during parking release, resulting in excessive motor current triggering a system alarm and rendering the EPB parking pull-up and release functions ineffective.

[0040] In response to the above technical issues, such as Figures 1 to 5 As shown, this application provides an EPB parking release control method and its control system, which can effectively solve the problem of excessive motor operating current alarm during parking release caused by differences in the state of individual brake components and by the mismatch between the parking release time and the actual brake clearance during vehicle use.

[0041] like Figure 1 As shown, this application provides an EPB parking release control method, including the following steps:

[0042] S1. When the EPB parking brake is pulled up, obtain the rotation angle of the EPB motor during its operation.

[0043] S2. Record and store the acquired rotation angle;

[0044] S3. When performing the next parking release operation, read the EPB motor rotation angle when the parking was pulled up last time, and make the motor rotate in the opposite direction by the same angle to release the parking.

[0045] In step S1, the number of rotations of the EPB motor during the process of fully raising the parking brake is obtained and converted into a rotation angle.

[0046] In step S2, the acquired rotation angle is converted into a digital signal and stored in the system memory.

[0047] In some embodiments, the initial release rotation angle of the EPB is set as follows: based on the design brake clearance range given by the brake, the vehicle model obtains the rotation angle of the MGU motor when the parking brake is fully released through the EPB system calibration. The number of encoder pulses , When a new vehicle rolls off the production line or during a system reset, the EPB brake is in the fully released parking position, and the EPB system stores the initial value of the pulse corresponding to the parking release rotation angle. The initial pulse value of the motor is all according to The EPB performs vehicle model calibration based on the brake clearance design of the brake, and determines the MGU motor rotation angle and encoder pulse parameters under the fully released parking condition. When a new vehicle rolls off the production line or the system is reset, the brake remains in the fully released state. The system stores the initial reference of the release pulse under this condition, and the initial pulses of all motors are uniformly set according to this calibration reference.

[0048] Misoperation compatibility control checks whether the EPB motor actually rotates after the parking switch is pulled, thus eliminating the possibility of accidental switch activation and situations where the vehicle is actually in the parking state when the switch is pulled.

[0049] like Figures 2 to 5 As shown, this application provides a drum brake EPB parking release control system, including a drum brake 1, an MGU unit 2, a parking cable 3, a storage module, and a controller; the MGU unit is integrated on the drum brake; the MGU unit includes a motor 4 and a transmission structure, the motor being connected to the parking cable through the transmission structure; the MGU unit has a data acquisition component for acquiring the motor rotation angle, the data acquisition component being connected to the storage module, and both the storage module and the motor being connected to the controller.

[0050] In some embodiments, the transmission structure includes a worm gear 5 and a lead screw 6. The worm is disposed at the end of the motor rotating shaft 401 of the motor, and the worm gear is disposed on the lead screw. The worm and the worm gear mesh with each other. When the motor works, it drives the lead screw to move, thereby driving the parking cable. The transmission structure may also use a multi-gear structure to drive the lead screw.

[0051] The data acquisition component is an angle sensor or encoder integrated into the motor. The encoder can be a photoelectric encoder or a magnetic encoder.

[0052] Preferably, a photoelectric encoder is used; specifically, the encoder includes a code disk 7, a photosensitive element 8, and a light source 9; the code disk is connected to the motor rotation shaft of the motor, and the photosensitive element and the light source are respectively arranged on both sides of the code disk.

[0053] The bottom of the motor is hollow, and the inner end of the motor's rotating shaft is located inside the hollow structure. The encoder, photosensitive element, and light source are all housed within the hollow structure, resulting in a compact design.

[0054] This application discloses a drum brake EPB parking release control system, comprising a drum brake, an integrated MGU unit, a parking cable, a storage module, and a controller. The MGU unit is integrated into the drum brake body and consists of a motor and a transmission structure. The motor drives the transmission structure to move the parking cable, achieving parking and release actions. The motor's built-in acquisition components (angle sensor / encoder) collect motor angle data, which is then buffered in the storage module and transmitted to the controller to achieve closed-loop control. The transmission structure supports both worm gear and lead screw structures and multi-gear transmission structures. The acquisition component preferably uses a built-in photoelectric encoder, and the system employs a hollow integrated layout at the bottom of the motor to achieve miniaturization and compact structure.

[0055] In some embodiments, for harsh driving conditions involving high temperatures, dust, and severe vibration (mountainous areas, construction sites), a fully enclosed magnetoelectric encoder is used to replace the ordinary photoelectric encoder. The light source and transparent code disk are eliminated, and a combination structure of magnets and Hall effect sensors is adopted, which is entirely sealed within the hollow structure of the motor. This provides dustproof, oil-proof, high-temperature resistant, and vibration-resistant characteristics, and can adapt to a wide temperature range of -40℃ to 150℃, overcoming the shortcomings of photoelectric encoders that are easily obscured by dust and prone to aging and failure at high temperatures.

[0056] Meanwhile, a dual-mode acquisition and calibration function has been added. The storage module has a built-in standard angle-displacement calibration database. The controller can automatically calibrate the acquisition error based on the motor's real-time angle data, running time, and ambient temperature data. There is no cumulative deviation after long-term use, which greatly improves the system's durability.

[0057] In some embodiments, the transmission structure employs a composite transmission structure of planetary gears and a lead screw. Compared to ordinary multi-gear transmissions, the planetary gear structure offers advantages such as a large transmission ratio, small size, smooth transmission, and low noise. The motor output shaft connects to the planetary gear set, and the output end of the planetary gear set is connected to the lead screw. This allows for high torque output within a compact space, making it suitable for medium-sized freight vehicles. It solves the problems of insufficient torque in ordinary gear transmissions and low efficiency in worm gear transmissions, improving transmission efficiency by 15% to 20% and resulting in faster parking release response.

[0058] In some embodiments, in addition to the encoder acquisition component, a temperature sensor, a vibration sensor, and a current acquisition sensor are added inside the hollow cavity of the motor. All of these are integrated into the hollow structure, without requiring additional external installation space.

[0059] Multi-dimensional sensors can collect real-time data on motor operating temperature, vibration amplitude, and operating current, and transmit this data synchronously to the controller and storage module. The controller can then implement overheat protection, abnormal vibration fault identification, and overload current power-off protection based on these multi-dimensional parameters. This addresses the shortcomings of the original system, which only collected rotation angle data and could not monitor the motor's operating status, significantly improving system safety. Simultaneously, the hollow cavity employs a sealed potting compound design, achieving waterproofing, dustproofing, and electromagnetic interference protection, making it suitable for complex driving environments.

[0060] In some embodiments, the MGU unit is integrated on the outside of the drum brake base plate. The motor is equipped with a high-precision lead screw drive structure, and the output end of the lead screw is directly hinged to the brake shoes, eliminating the need for a parking cable. The motor's forward and reverse rotation drives the lead screw to extend and retract linearly, directly driving the brake shoes to open and close, completing the parking brake and release actions. The data acquisition component collects the motor rotation angle and lead screw travel data in real time and feeds it back to the controller to form a closed-loop control.

[0061] The EPB parking release control method and its control system in this application are reasonably designed. By adjusting the motor rotation angle based on the previous parking pull-up, the motor rotates in the opposite direction by the same number of turns during the parking release process. This parking release control method makes the EPB parking release control of the drum brake adaptive. It can well accommodate the differences in individual brake components and the changes in brake clearance during vehicle use, ensuring that the motor rotation angle during each parking release matches the actual brake clearance, avoiding abnormal system alarms and improving the reliability of vehicle functions.

[0062] like Figures 1 to 5 As shown, the preferred embodiment of this application is as follows:

[0063] A method for controlling the parking release of a drum brake EPB includes the following steps:

[0064] Obtain the number of rotations (angles) of the EPB motor during the process of fully raising the parking brake;

[0065] Record the rotation angle of the EPB motor and store it in the system memory;

[0066] When performing the next parking release operation, the EPB motor rotation angle when the parking was pulled up is read, and the motor is rotated by the same angle as when the parking was pulled up to release the parking.

[0067] The specific control method is as follows:

[0068] like Figure 1 and Figure 2 As shown, the method provided in this embodiment of the invention includes the following steps S1 to S3.

[0069] S1, when the parking brake is pulled up, obtain the rotation angle of the left and right motors of the MGU.

[0070] like Figure 3 As shown, the main components of the drum brake assembly with electronic parking brake include the drum brake, MGU, and parking cable. Figure 4 As shown, the main components of the MGU include a motor, a worm gear, and a lead screw.

[0071] When the EPB switch is pulled up, the parking brake is engaged. The MGU motor is energized and rotates in the forward direction, driving the worm gear mechanism to rotate and move the lead screw to the top of the housing. The other end of the lead screw is connected to the parking cable. The movement of the lead screw drives the parking arm to pull up through the parking cable, causing the brake shoes to open and press against the working surface inside the brake drum to generate braking force and achieve parking.

[0072] The EPB system monitors the operating current of the MGU motor in real time. The EPB control system determines whether the tightness between the brake shoes and the brake drum reaches the required parking braking force by using the current threshold. When the operating current of the MGU motor reaches the threshold current, the MGU motor stops rotating, and the parking is lifted.

[0073] like Figure 5 As shown, an incremental encoder is installed on an MGU motor. Its main components include a light source, a code disk, and a photosensitive element. The code disk has radially spaced, equally spaced light-transmitting slits, with each adjacent slit representing one incremental cycle. The detection grating has two sets of light-transmitting slits, A and B, corresponding to those on the code disk. These slits allow light to pass through or block light from the light source and the photoelectric detection device. Their spacing is equal to that on the code disk, and the two sets of slits are staggered by 1 / 4 of the spacing, ensuring that the signals output by the photoelectric detection device are 90° out of phase.

[0074] The code disk is coaxial with the motor. When the motor rotates, the code disk rotates at the same speed as the motor, while the detection grating remains stationary. The fiber optic head illuminates the photoelectric detection device through the gaps on the code disk and the detection grating. The photoelectric detection device outputs two sets of sinusoidal electrical signals with a 90° phase difference. The sinusoidal waves are processed by the conversion circuit to obtain a rectangular pulse signal.

[0075] The encoder generates a value corresponding to 360° rotation of the motor. A pulse signal, then the motor rotation angle corresponding to a unit pulse signal is The number of pulses generated by the encoder during one revolution is obtained through the encoder's characteristics.

[0076] During the parking brake engagement process, from the fully released parking brake state to the fully engaged parking brake state, the left and right motor encoders of the MGU output the following pulse counts respectively. and The corresponding rotation angles of the left and right motors of the MGU. and ,in,

[0077] , .

[0078] S2 converts the acquired rotation angle into software-recognizable digital information and stores it in system memory.

[0079] EPB initial release rotation angle setting. Based on the brake's designed brake clearance range, the vehicle model's MGU motor rotation angle when the parking brake is fully released is determined through EPB system calibration. Calculate the corresponding MGU motor rotation angle At that time, the number of encoder pulses , When a new vehicle rolls off the production line or during a system reset, the EPB brake is in the fully released parking position, and the EPB system stores the initial value of the pulse corresponding to the parking release rotation angle. The initial pulse values ​​of the left and right motors of the MGU are both set according to... .

[0080] Accidental operation compatibility. The system checks if the motor rotation angle is valid, i.e., whether the EPB motor actually rotates after the parking switch is pulled. This eliminates the possibility of accidental switch activation and situations where the vehicle is actually in the parking position when the switch is pulled. , At this time, the EPB switch is accidentally activated, or the vehicle is already in the parking state when the switch is activated. The EPB system stores the parking release rotation angle unchanged, that is, it is still the previous stored value.

[0081] The MGU motor rotation angle is obtained when the parking brake is engaged and the vehicle is in normal working order. The left and right motors of the MGU rotate by their respective angles. and , , At this point, it is determined that the parking brake is effectively engaged, and the valid value is set. and Store them separately as the rotation angle pulse values ​​that the MGU motor should execute the next time the parking brake is released.

[0082] Brake clearance abnormality alarm mechanism and logic, brake drag alarm. The normal clearance between the brake shoes and the working surface of the brake drum in a drum brake is... The minimum braking clearance corresponding to the allowable drag torque was obtained through bench testing. Minimum allowable brake clearance At that time, the rotation angle of the MGU motor was measured through bench tests from the time the parking brake was fully released to the time the parking brake was fully engaged. The corresponding encoder output minimum number of pulses The parking pull-up process is complete when the encoder of the MGU motor outputs a certain number of pulses. If the system determines that the brake clearance is too small, which will cause brake drag, the EPB system will output a corresponding fault code and illuminate the EPB warning light. The current fault level is set to a low-level alarm, which does not limit the vehicle's power output or disable the parking brake function; it only reminds the driver to inspect the parking brake system.

[0083] The system includes an alarm mechanism and logic for abnormal brake clearance, specifically an alarm for excessive difference in brake clearance between the left and right wheels. According to GB 7258 requirements for bench testing of braking force balance, the braking force difference should be ≤8%. This means that the ratio of the maximum difference in braking force between the left and right wheels measured simultaneously throughout the entire braking force increase process to the greater of the maximum braking forces measured on the left and right wheels of the axle during the entire process should be ≤8%. Based on practical production experience, when the difference in brake clearance between the left and right brakes on the rear axle is too large, it will affect the directional stability during braking, leading to brake pull. The minimum difference in brake clearance between the left and right brakes that does not cause brake pull or brake clearance discrepancies is determined through real vehicle testing and bench testing. The minimum difference in the output pulses of the encoders of the left and right MGU motors is measured using a test bench. After the parking brake pull-up process ends, if the difference in the number of output pulses from the encoders of the left and right MGU motors exceeds the minimum allowable value, a fault of excessive brake clearance is identified, and the EPB warning light illuminates. The current fault level is set to a low-level alarm; it does not restrict the vehicle's power output, does not restrict or disengage the parking brake function, and only reminds the driver to inspect the parking brake system.

[0084] S3, execute EPB parking release.

[0085] Read the rotation angle information stored in the system, i.e., the number of pulses that the left and right motor encoders of the MGU should output. and The number of pulses corresponds to the actual output value of the left and right brakes when the parking brake was last engaged. That is, the brake cable and lead screw move a corresponding distance according to the brake gap, the worm gear mechanism rotates a corresponding angle, the motor rotates a corresponding angle, and the encoder outputs a corresponding number of pulses.

[0086] The EPB system controls the left and right motors of the MGU to rotate in opposite directions. The worm gear mechanism drives the lead screw to move towards the brake base plate, releasing the tension of the parking cable connected to the other end of the lead screw. The encoders of the left and right motors of the MGU continuously output pulse signals. and .

[0087] The EPB control system receives the pulse values ​​output from the left and right motor encoders of the MGU in real time, and converts the left and right pulse values ​​into values ​​respectively. and and and When comparing, When the system determines that the left parking brake has been fully released, it controls the left motor of the MGU to stop rotating; when When the system determines that the right brake has been fully released, it controls the right motor of the MGU to stop rotating. The left and right motors of the MGU are controlled separately according to their respective pulse values, without interfering with each other.

[0088] The system controls the release of the parking brake based on the motor rotation angle of the previous parking brake pull. Each time the parking brake is pulled, the motor rotation angle for release is determined based on the actual rotation angle of the parking brake pull. This allows the system to adapt to individual differences. Even if the initial braking clearance of the left and right brakes is slightly out of tolerance, the system can still adapt to changes in the braking clearance due to brake wear during vehicle use. This avoids the problem of the screw hitting the bottom and the motor stalling, which would cause an alarm if the release was performed for a uniform fixed working time.

[0089] The drum brakes integrated with the EPB system are affected by multiple factors, including the consistency control of component processing, the working characteristics of the brake's self-adjusting mechanism, and long-term wear of the brake pads. During mass production and vehicle service, the brake clearance is prone to being less than the calibrated lower limit. When the clearance is too small, the parking pull-up screw stroke is shorter than the calibrated stroke. During the release phase, the motor continues to run for the preset duration. After the screw reaches its mechanical limit, the motor is forced to stall, causing a sudden increase in operating current that exceeds the system protection threshold, triggering the EPB fault light alarm and causing abnormal parking start-stop function. The root cause of the fault is simply the mismatch between the fixed release duration and the real-time brake clearance. Existing control strategies cannot adapt to the discreteness of the brake clearance and wear changes. Therefore, this patent proposes an adaptive EPB parking release control scheme and supporting control system based on parking pull-up angle tracing.

[0090] This invention abandons the fixed release time mode and adopts a closed-loop adaptive approach, consisting of three main steps: parking angle acquisition and storage, data retrieval, and reverse angle release. The first step, under EPB parking pull-up conditions, relies on the encoder or angle sensor integrated into the motor to acquire the actual rotation angle and encoder pulse data of the left and right MGU motors from full release to parking lock. Parking pull-up uses a mature current threshold judgment logic; the system monitors the motor current and stops when it reaches the calibrated stall threshold, simultaneously latching the actual rotation angle parameters. The second step digitizes the acquired rotation angle pulse signals and stores them in the vehicle controller's storage module. Simultaneously, it sets initial calibration rules for new vehicle production and system reset: when the vehicle leaves the factory or the controller is reset, the brake is in a fully released state, and the calibrated baseline release angle and corresponding encoder pulse initial value are used as the system initialization baseline parameters. An additional misoperation detection logic is added, filtering out invalid operations such as user accidental touches of the parking switch or repeated pulling of the handbrake while the vehicle is parked by judging whether the actual motor rotation angle is a valid change. Misoperation triggering conditions do not refresh the stored rotation angle; historical valid data is used instead. The third step is that when the next parking release command is issued, the controller retrieves the stored independent rotation angle pulse data of the left and right wheels from the previous parking pull-up, controls the left and right MGU motors to rotate independently in opposite directions at the same angle, and the encoder provides real-time feedback of rotation pulses. When the actual pulse reaches the stored value, the power supply of the corresponding side motor is cut off separately. The left and right wheel drive control do not interfere with each other, so that the release stroke is adaptively adjusted according to the actual braking gap of a single parking.

[0091] This application adds a dual-layer fault warning logic to provide early fault alerts without limiting the vehicle's power and parking function. The first layer is a single-wheel brake clearance too small warning. Based on bench calibration, the minimum clearance corresponding to the allowable drag torque of the brake and the minimum rotation angle pulse of the matching motor are obtained. If the pulse collected during a single parking pull-up is less than this benchmark value, it is determined that the clearance is too small and there is a risk of dragging. The system reports a low-priority fault code and illuminates the fault light to remind maintenance. The second layer is a left and right wheel clearance deviation warning. In accordance with the GB7258 regulation that braking force balance should not exceed 8%, the maximum allowable pulse difference between the left and right brakes is calibrated using bench and real vehicle calibration. When the left and right pulse difference exceeds the standard during parking, a fault warning is triggered to avoid the risk of brake pull due to significant clearance differences.

[0092] The control system is based on a drum brake, an integrated MGU power unit, a parking cable, a storage module, and a vehicle controller. The MGU unit is integrated into the brake base plate and consists of a drive motor, a transmission mechanism, and a rotation angle acquisition component. The transmission structure offers three optional configurations: the conventional scheme uses a worm gear + screw transmission structure, which is suitable for basic vehicle models; the optimized scheme uses a planetary gear and screw composite transmission, which has a larger transmission ratio, a more compact structure, and a 15%~20% increase in transmission efficiency compared to ordinary gear transmission, and provides high torque output suitable for medium and heavy-duty light trucks; the simplified scheme eliminates the external parking cable, and the end of the screw is directly hinged to the brake shoe. The motor drives the screw to extend and retract linearly to directly open and close the brake shoe, reducing intermediate transmission losses. The corner acquisition component prioritizes the use of a coaxial built-in photoelectric encoder. The code disk, light source, and photosensitive components are all arranged in the hollow cavity of the motor, resulting in a compact structure that saves installation space. For harsh working conditions such as construction sites and mountainous areas with high temperatures, dust, and strong vibrations, a fully sealed magnetoelectric encoder can be used instead. It relies on magnets and Hall chips to acquire signals. After sealing and potting, it can work stably under poor road conditions, solving the shortcomings of photoelectric devices such as easy dust accumulation and high-temperature aging failure.

[0093] Furthermore, three types of auxiliary sensors—temperature, vibration, and current—are integrated into the hollow cavity of the motor. All sensors are internally sealed, requiring no additional openings. Multi-dimensional sensor data is fed into the controller, enabling multiple protections including motor overheat protection (power-off), abnormal vibration detection, and overload current limiting. This addresses the shortcomings of the original system, which only monitored rotation angle and could not monitor the motor's overall operating status. The storage module incorporates a rotation angle-displacement calibration database. The controller automatically corrects encoder acquisition errors based on real-time rotation angle, ambient temperature, and operating time, suppressing cumulative measurement deviations after long-term vehicle use and improving control stability throughout the entire lifecycle.

[0094] This solution addresses the inherent shortcomings of traditional timed release systems from both control logic and hardware structure perspectives. It defines the release stroke by reverse-engineering the actual stroke of each parking maneuver, naturally accommodating the dynamic changes in brake clearance caused by individual component manufacturing tolerances, progressive brake pad wear, and fine-tuning of the self-adjusting mechanism. Regardless of whether the clearance of a single wheel is too small or the clearances of the left and right wheels are inconsistent, the motor's rotation stroke automatically shortens to follow the actual clearance during release, preventing the lead screw from reaching its mechanical limits and eliminating stall and overcurrent alarm faults at their source. The entire system requires no modification to the drum brake structure; it can be implemented simply by upgrading the EPB control strategy and optimizing the MGU's built-in data acquisition devices. This balances mass production modification costs with overall vehicle reliability, effectively improving the environmental adaptability and product durability of drum brake EPB systems in light commercial vehicles.

[0095] The above description is merely an illustration of preferred embodiments of the present invention, and the above technical features can be arbitrarily combined to form multiple embodiments of the present invention.

[0096] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the concept and technical solution of the present invention, or the direct application of the concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. An EPB parking release control method, characterized in that: Includes the following steps: S1. When the EPB parking brake is pulled up, obtain the rotation angle of the EPB motor during its operation. S2. Record and store the acquired rotation angle; S3. When performing the next parking release operation, read the EPB motor rotation angle when the parking was pulled up last time, and make the motor rotate in the opposite direction by the same angle to release the parking.

2. The EPB parking release control method as described in claim 1, characterized in that: In step S1, the number of rotations of the EPB motor during the process of fully raising the parking brake is obtained, and the number of rotations is converted into a rotation angle.

3. The EPB parking release control method as described in claim 1, characterized in that: In step S2, the acquired rotation angle is converted into a digital signal and stored in the system memory.

4. The EPB parking release control method as described in claim 1, characterized in that: In the control method, the initial release rotation angle setting of EPB is as follows: according to the design braking gap range given by the brake, the vehicle model obtains the rotation angle of the MGU motor when the parking brake is fully released and the number of encoder pulses through the EPB system calibration; when the new car is off the production line and the system is reset, the EPB brake is in the fully released parking state, the EPB system stores the initial pulse value corresponding to the parking release rotation angle, and the initial pulse value of the motor is set according to the specified conditions.

5. The EPB parking release control method as described in claim 1, characterized in that: In the control method, the misoperation compatibility control checks whether the EPB motor actually rotates after the parking switch is pulled, thereby eliminating the possibility of accidental switch activation and the possibility that the vehicle is actually in the parking state when the switch is pulled.

6. A drum brake EPB parking release control system, comprising a drum brake, an MGU unit, and a parking cable, wherein the MGU unit includes a motor and a transmission structure, the motor being connected to the parking cable via the transmission structure, characterized in that: It also includes a storage module and a controller. The MGU unit has a data acquisition component for acquiring the rotation angle of the motor. The data acquisition component is connected to the storage module. Both the storage module and the motor are connected to the controller.

7. The EPB parking release control system for drum brakes as described in claim 6, characterized in that: The acquisition component is an angle sensor or encoder integrated into the motor.

8. The EPB parking release control system for drum brakes as described in claim 7, characterized in that: The encoder includes a code disk, a photosensitive element, and a light source; the code disk is connected to the motor's rotating shaft, and the photosensitive element and the light source are respectively arranged on both sides of the code disk.

9. The EPB parking release control system for drum brakes as described in claim 7, characterized in that: The encoder is a magnetic encoder.

10. The EPB parking release control system for drum brakes as described in claim 8, characterized in that: The bottom of the motor is a hollow structure, and the inner end of the motor's rotating shaft is located inside the hollow structure. The encoder, photosensitive element, and light source are all located inside the hollow structure.

Images