Electro-hydraulic parking brake mechanism control method

Abstract

The application discloses an electro-hydraulic parking brake mechanism control method, which is used for diagnosing and processing electro-hydraulic parking function failure on the basis of brake and unlocking control of the parking mechanism according to requirements, thereby improving the availability of the vehicle while ensuring the parking safety of the vehicle. In order to ensure the reliability of the parking unlocking control function, the parking electromagnetic valve is controlled to be continuously pressurized during the parking unlocking process, the parking electromagnetic valve is closed after the parking piston moves to a parking unlocking limit position, and under the resetting force of the return spring, when the parking piston moves from the parking unlocking limit position to the parking unlocking position, the locking piece passes through the locking groove, the locking groove has sufficient width, and the locking piece can successfully fall into the locking groove during the return movement of the piston, thereby ensuring the reliable parking unlocking control. The application further discloses that the parking unlocking limit position reached by the parking piston is self-learned, and the parking unlocking limit position reached by each mechanism is automatically determined, so as to cover the manufacturing and assembly tolerances.

Description

Technical Field

[0001] This invention belongs to the field of automotive electronics technology, specifically relating to a control method for an electro-hydraulic parking brake mechanism. Background Technology

[0002] With the development of automotive electronics technology, electro-hydraulic parking mechanisms have gradually replaced traditional mechanical cable-operated manual parking mechanisms in automatic transmissions to achieve vehicle parking braking. In new energy vehicles, electro-hydraulic parking mechanisms can be integrated into the hybrid transmission as a separate parking mechanism from the EPB (Electronic Parking Brake) system, improving the reliability of the vehicle's parking braking function and ensuring parking safety. The electro-hydraulic parking control system interacts closely with other controllers on the vehicle. As a mechanical, electrical, and hydraulic coupled system, it has numerous control input factors. Failure of the electro-hydraulic parking control function can affect vehicle functional safety and the driver's intuitive operating experience.

[0003] During the parking unlocking control process, the electro-hydraulic parking control system controls the target pressure of the parking solenoid valve, causing hydraulic oil to flow into the parking piston cylinder through the solenoid valve. This overcomes the spring return force and pushes the parking piston in the parking unlocking direction. If the solenoid valve is closed when the piston reaches the parking unlock position, the locking plate may not fall into the locking groove in time, and the parking piston may return to its initial position under the action of the return spring, resulting in the failure of the parking mechanism's parking unlocking control.

[0004] Because the actual stroke of the parking piston is very small, and manufacturing and assembly tolerances exist during the manufacturing and assembly process, ensuring that the parking solenoid valve closes after the parking piston reaches a certain fixed position, thus accurately locking the parking piston in the parking unlock position, places very high demands on the manufacturing process and significantly increases manufacturing costs. Therefore, this invention proposes a self-learning method to automatically determine the parking unlock limit position achievable by each mechanism, covering manufacturing and assembly tolerances, based on the parking piston's achievable limit position. Summary of the Invention

[0005] In order to solve the technical problems existing in the background art, the present invention aims to provide a control method for an electro-hydraulic parking brake mechanism.

[0006] To solve the technical problem, the technical solution of the present invention is as follows:

[0007] A control method for an electro-hydraulic parking brake mechanism, wherein the system is based on an electro-hydraulic parking brake mechanism; the parking piston of the electro-hydraulic parking brake mechanism has several characteristic position parameters, namely, a parking brake position, an intermediate position, a parking unlock position, and a parking unlock limit position, which are used to control the parking and unlocking functions of the parking brake mechanism;

[0008] The parking brake position is where the control push rod pushes the parking pawl into the parking ratchet, thus achieving the parking piston position when the vehicle is parked and locked.

[0009] The middle position is the parking piston position that ensures the locking piece leaves the locking groove area, meaning that even if the electromagnet is de-energized and the locking piece falls, it will not enter the locking groove. In this position, the pawl and ratchet are also separated.

[0010] The parking unlock position is the parking piston position when the control push rod removes the force applied to the parking pawl, ensuring that the pawl and ratchet can disengage.

[0011] The parking unlock limit position is the limit position that the parking piston can reach when it moves in the direction of the parking unlock position.

[0012] Furthermore, the self-learning process for the parking unlock limit position includes:

[0013] S1: When the parking mechanism's parking unlock limit position self-learning function is triggered, the parking control system will first check the current vehicle status to determine whether it meets the conditions for parking unlock limit position self-learning, such as the engine being in an idling state, the parking system currently having no faults, and the vehicle being in a braking state.

[0014] S2: After the judgment condition is met, the parking unlock limit position self-learning function is activated. The parking control system controls the target pressure of the parking pressure valve. When the continuously given pressure reaches the time threshold 1, the parking piston position 1 is measured and recorded. When the continuously given pressure reaches the time threshold 2, the parking piston position 2 is measured and recorded.

[0015] S3: If the absolute value of the difference between parking piston position 1 and position 2 is less than the threshold, the system is considered stable and the learning process is effective during the parking unlock limit position learning process. The larger value between parking piston position 1 and position 2 is recorded as the parking unlock limit position learning value. Otherwise, the self-learning is judged to have failed.

[0016] S4: The parking control system will judge the rationality of the learning value of the parking unlock limit position. If the learning value is within the manufacturing tolerance range, the self-learning result is considered valid. At the same time, in order to avoid the influence of the piston position sensor sampling deviation on the learning result, the calculation result after subtracting a deviation value from the learning value is used as the final learning result of the parking unlock limit position.

[0017] Furthermore, the self-learning process for determining the parking unlock limit position also includes:

[0018] After the parking mechanism has successfully completed self-learning at the limit position of parking unlock, the control system will store the final learning result and self-learning completion signal information into the EEPROM memory, which will then be used for the subsequent parking and unlocking process control of the parking mechanism.

[0019] Furthermore, the parking unlocking control process includes:

[0020] S1: In the initial state, the parking piston is in the parking position. When the driver's parking unlocking request is detected, the electro-hydraulic parking control system first determines whether there is a fault in the current parking mechanism that prevents the parking unlocking function. If there is a fault, the control process ends and the parking piston is kept in the current parking position. If there is no fault, the parking mechanism parking unlocking control process is carried out.

[0021] S2: While activating the parking mechanism parking unlock control, the control system times the entire control process and adds timeout protection to prevent the control system from being unable to exit due to timeout. When the timeout exceeds the timeout protection threshold, the parking mechanism unlock control process is judged to be successful based on whether the parking piston has reached the parking unlock position at this time.

[0022] S3: By controlling the output pressure of the solenoid valve, the parking piston is pushed to the parking unlock limit position. After the solenoid valve is closed, the control system starts timing to reserve time for the parking piston to retract and lock. When the timing reaches the threshold, if the parking piston reaches the parking unlock position, it is determined that the parking mechanism parking unlock control is successful and the current gear information is fed back to the driver.

[0023] S4: During engine start-up, the starter motor may cause the vehicle's 12V power supply voltage to drop too low, leading to abnormalities in the parking mechanism actuators and sensors or failure to execute control commands correctly. However, the 12V power supply voltage will return to normal after the engine starts successfully. In order to respond to the driver's operation needs as quickly as possible and avoid the impact of parking mechanism failure due to low power supply voltage during engine start-up, when parking unlock control fails, the parking control system will determine the engine's starting status during the parking unlock control process. If the engine is starting, after starting, it will re-control the parking mechanism to execute the parking unlock function according to the driver's current intention. If the engine is not starting, it will determine that the parking mechanism parking unlock control has failed and will feed this fault information back to the driver in the form of audible and visual signals for alarm purposes.

[0024] Furthermore, the parking control process specifically includes:

[0025] S1: In the initial state, the parking piston is in the parking unlock position. When the driver's parking request is detected, the electro-hydraulic parking control system first determines whether there is a fault in the current parking mechanism that prevents it from performing the parking function. If there is a fault, the control ends and the parking position is maintained in the current state. If there is no fault, the parking mechanism parking control process is carried out.

[0026] S2: While activating the parking mechanism parking control, the control system times the entire control process and adds timeout protection to prevent the control system from failing to exit due to timeout; when the timeout exceeds the timeout protection threshold, the parking mechanism parking control is judged to be successful based on whether the parking mechanism piston has reached the parking position at this time.

[0027] S3: During the parking control process, the parking control system energizes the electromagnet of the locking mechanism and uses the electromagnetic force generated by the electromagnet to disengage the locking plate from the locking groove on the parking piston. Then, the parking piston moves to the parking position under the action of the return spring. When the piston position sensor detects that the parking piston has moved to the middle position and the energization time of the electromagnet reaches the minimum time threshold, the system de-energizes the electromagnet of the locking mechanism. Since the parking control has a direct impact on achieving the functional safety goals of the entire vehicle, a minimum time threshold for energizing the electromagnet of the locking mechanism is set to eliminate interference from abnormal jumps in the position sensor on the judgment of the parking process and avoid unexpected vehicle movement caused by parking control errors.

[0028] S4: After the electromagnet of the locking mechanism is de-energized, the control system starts timing and reserves time for the parking piston to move to the parking position. When the timing reaches the threshold, if the parking piston reaches the parking position, it is determined that the parking mechanism parking control is successful and the current gear information is fed back to the driver.

[0029] S5: Similar to the parking unlock control process, a drop in vehicle power supply voltage caused by engine starting may also lead to parking control failure. Therefore, when parking control fails, the parking control system will determine the engine starting status during the parking control process. If the engine is starting, it will re-control the parking mechanism to execute the parking control function after starting. If the engine is not starting, it will determine that the parking mechanism has failed to control the parking and will feed back the fault information to the driver in the form of audible and visual signals for alarm purposes. At the same time, the vehicle's backup parking function, such as the electronic parking brake (EPB), will be activated.

[0030] Compared with the prior art, the advantages of the present invention are as follows:

[0031] This invention proposes a control method for an electro-hydraulic parking brake mechanism. Based on driver-defined braking and unlocking control of the parking mechanism, it diagnoses and addresses malfunctions in the electro-hydraulic parking function, improving vehicle availability while ensuring parking safety. To ensure the reliability of the parking unlocking control function, this invention continuously pressurizes the parking solenoid valve during the parking unlocking process, moving the parking piston to its limit position before closing the solenoid valve. Under the restoring force of the return spring, as the parking piston moves from the limit position to the unlock position, the locking plate passes through the locking groove. The locking groove has sufficient width to ensure that the locking plate successfully falls into the groove during the piston's retraction, guaranteeing reliable parking unlocking control. This invention proposes a self-learning mechanism to automatically determine the parking unlocking limit position achievable by each mechanism, covering manufacturing and assembly tolerances. Attached image description:

[0032] Figure 1 This is a schematic diagram of the electro-hydraulic parking mechanism;

[0033] Figure 2 The parking piston position curve for the parking mechanism during parking unlocking and parking processes;

[0034] Figure 3 The self-learning process unlocks the extreme positions for parking;

[0035] Figure 4 For the electro-hydraulic parking mechanism parking unlock control process;

[0036] Figure 5 This describes the parking control process for the electro-hydraulic parking mechanism.

[0037] Figure label:

[0038] 1- Parking ratchet, 2- Parking pawl, 3- Hydraulic piston push rod, 4- Electromagnetic locking mechanism, 5- Hydraulic piston, 6- Hydraulic piston return spring, 7- Main controller, 8- Parking pawl return spring, 9- Hydraulic control solenoid valve, 10- Hydraulic cylinder, 11- Piston position sensor. Detailed Implementation

[0039] The specific implementation of the present invention is described below with reference to embodiments:

[0040] It should be noted that the structures, proportions, sizes, etc. shown in this specification are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which the present invention can be implemented. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0041] Furthermore, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity of description and are not intended to limit the scope of the invention. Any changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0042] Example 1:

[0043] like Figure 1 As shown, the main controller 7 receives the piston position signal transmitted by the piston position sensor 11, identifies the driver's operating intention, and sends control signals to the electromagnet-controlled locking mechanism 4 and the hydraulic control solenoid valve 9 to control the on / off state of the electromagnet and solenoid valve. The hydraulic control solenoid valve 9 is connected to the hydraulic cylinder 10 via an oil passage to control the filling and draining of the hydraulic cylinder. During filling, hydraulic pressure is generated on the left side of the hydraulic piston 5, overcoming the force of the hydraulic piston return spring 6 and pushing the hydraulic piston 5 to move the parking push rod 3 in the parking unlocking direction. When the push rod 3 leaves the pawl, the parking pawl 2 can disengage from the parking ratchet 1 under the action of the parking pawl return spring 8, thus unlocking the vehicle. During draining, the hydraulic pressure on the left side of the hydraulic piston 5 is removed, the electromagnet-controlled locking mechanism 4 unlocks, and the hydraulic piston 5 moves the push rod 3 in the parking direction under the action of the return spring 6. Under the pushing action of the parking push rod 3, the parking pawl 2 can engage with the parking ratchet 1, realizing parking braking.

[0044] Figure 1 This is a schematic diagram of the control system structure of the present invention. The parking piston of the electro-hydraulic parking mechanism has several characteristic position parameters: parking brake position, intermediate position, parking unlock position, and parking unlock limit position, which are used to control the parking and unlocking functions of the parking mechanism. The parking brake position is the parking piston position where the control push rod can push the parking pawl into the parking ratchet, achieving vehicle parking lock. The intermediate position is the parking piston position ensuring that the locking plate leaves the locking groove area, i.e., the locking plate will not enter the locking groove even when the electromagnet is de-energized and falls, and the pawl and ratchet are also separated in this position. The parking unlock position is the parking piston position when the control push rod removes the force applied to the parking pawl, ensuring that the pawl and ratchet can disengage. The parking unlock limit position is the maximum position that the parking piston can reach when moving towards the parking unlock position. Figure 2 The parking piston position curve for the parking mechanism during parking unlocking and parking processes.

[0045] like Figure 3 As shown, the specific self-learning process for the parking unlock limit position is as follows:

[0046] S1: When the parking mechanism's parking unlock limit position self-learning function is triggered, the parking control system will first check the current vehicle status to determine whether it meets the conditions for parking unlock limit position self-learning, such as the engine being in an idling state, the parking system currently having no faults, and the vehicle being in a braking state.

[0047] S2: After the judgment condition is met, the parking unlock limit position self-learning function is activated. The parking control system controls the target pressure of the parking pressure valve. When the continuously given pressure reaches the time threshold 1, the parking piston position 1 is measured and recorded. When the continuously given pressure reaches the time threshold 2, the parking piston position 2 is measured and recorded.

[0048] S3: If the absolute value of the difference between parking piston position 1 and position 2 is less than the threshold, the system is considered stable and the learning process is effective during the parking unlock limit position learning process. The larger value between parking piston position 1 and position 2 is recorded as the parking unlock limit position learning value. Otherwise, the self-learning is judged to have failed.

[0049] S4: The parking control system will judge the rationality of the learning value of the parking unlock limit position. If the learning value is within the manufacturing tolerance range, the self-learning result is considered valid. At the same time, in order to avoid the influence of the piston position sensor sampling deviation on the learning result, the calculation result after subtracting a deviation value from the learning value is used as the final learning result of the parking unlock limit position.

[0050] S5: After the parking mechanism has successfully completed self-learning at the limit position of parking unlock, the control system will store the final learning result and self-learning completion signal into the EEPROM memory, and use it for subsequent parking and parking unlocking process control of the parking mechanism.

[0051] like Figure 4 As shown, the parking unlock control process:

[0052] S1: Initial state: The parking piston is in the parking position. When the driver's parking unlocking request is detected, the electro-hydraulic parking control system first determines whether there is a fault in the current parking mechanism that prevents the parking unlocking function from being realized. If a fault is found, the control process ends, maintaining the parking piston in the current parking position; if there is no fault, the parking mechanism parking unlocking control process is initiated.

[0053] S2: While activating the parking mechanism's parking unlock control, the control system times the entire control process and adds timeout protection to prevent the control system from failing to exit due to timeout. When the timeout protection threshold is exceeded, the success of the parking mechanism unlock control process is determined by whether the parking piston has reached the parking unlock position at that time.

[0054] S3: By controlling the output pressure of the solenoid valve, the parking piston is pushed to the parking unlock limit position. After the solenoid valve closes, the control system starts timing to allow time for the parking piston to retract and lock. When the timing reaches the threshold, if the parking piston reaches the parking unlock position, it is determined that the parking mechanism has successfully unlocked, and the current gear information is fed back to the driver.

[0055] S4: During engine start-up, the starter motor may operate, potentially causing a low 12V power supply voltage for the entire vehicle. This could lead to malfunctions in the parking mechanism actuators and sensors, or prevent them from correctly executing control commands. However, the 12V power supply voltage will return to normal after the engine starts successfully. To respond to driver requests as quickly as possible while avoiding the impact of parking mechanism failure due to low power supply voltage during engine start-up, the parking control system will determine the engine's starting status during the parking unlock control process if the parking unlock control fails. If the engine is starting, the system will re-control the parking mechanism to perform the parking unlock function after startup is complete, based on the driver's current intention. If the engine is not starting, the system will determine that the parking mechanism's parking unlock control has failed and will provide this fault information to the driver via sound and light as a warning.

[0056] like Figure 5 As shown, the parking control process:

[0057] S1: Initially, the parking piston is in the parking unlock position. When the driver's parking request is detected, the electro-hydraulic parking control system first determines whether there is a fault in the current parking mechanism that prevents it from performing the parking function. If there is a fault, the control ends and the parking position is maintained in the current state; if there is no fault, the parking mechanism parking control process is initiated.

[0058] S2: While activating the parking mechanism's parking control, the control system times the entire control process and adds timeout protection to prevent the control system from failing to exit due to timeout. When the timeout exceeds the protection threshold, the success of the parking mechanism's parking control is determined by whether the parking mechanism piston has reached the parking position at that time.

[0059] S3: During parking control, the parking control system energizes the electromagnet of the locking mechanism, using the electromagnetic force generated by the electromagnet to disengage the locking plate from the locking groove on the parking piston. The parking piston then moves to the parking position under the action of the return spring. When the piston position sensor detects that the parking piston has moved to the intermediate position and the energization time of the electromagnet reaches the minimum time threshold, the system de-energizes the electromagnet of the locking mechanism. Since parking control directly impacts the achievement of vehicle functional safety objectives, a minimum time threshold for energizing the locking mechanism electromagnet is set to eliminate interference from abnormal fluctuations in the position sensor during the parking process, preventing unexpected vehicle movement due to parking control errors.

[0060] S4: After the locking mechanism electromagnet is de-energized, the control system starts timing and allows time for the parking piston to move to the parking position. When the timing reaches the threshold, if the parking piston reaches the parking position, it is determined that the parking mechanism has successfully controlled the parking and the current gear information is fed back to the driver.

[0061] S5: Similar to the parking unlock control process, a drop in vehicle power supply voltage during engine starting can also cause parking control failure. Therefore, when parking control fails, the parking control system will determine the engine's starting status during the parking control process. If the engine is starting, it will re-control the parking mechanism to perform the parking control function after starting is complete, based on the driver's current intention. If the engine is not starting, the parking mechanism is deemed to have failed, and fault information will be fed back to the driver through sound, light, etc., for alarm purposes. At the same time, the vehicle's backup parking function, such as the electronic parking brake (EPB), will be activated.

[0062] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

[0063] Many other changes and modifications can be made without departing from the concept and scope of this invention. It should be understood that this invention is not limited to the specific embodiments, and the scope of this invention is defined by the appended claims.

Claims

1. A control method for an electro-hydraulic parking brake mechanism, characterized in that, The method is based on an electro-hydraulic parking mechanism, which includes a parking piston, a locking mechanism electromagnet, a locking plate, a parking pawl, and a parking ratchet. The method includes: During the parking control process, the electromagnet of the locking mechanism is energized, causing the locking plate to disengage from the locking groove on the parking piston. Then, the parking piston moves to the parking position under the action of the return spring, and pushes the parking pawl to engage with the parking ratchet. The position of the parking piston is detected by a piston position sensor; When the parking piston is detected to have moved to the middle position and the energization time of the locking mechanism electromagnet reaches the shortest time threshold, the energizer of the locking mechanism electromagnet is de-energized. The intermediate position is the parking piston position when the locking piece leaves the locking groove area and the parking pawl separates from the parking ratchet. The minimum time threshold is set to eliminate interference from abnormal piston position sensor fluctuations in the parking process judgment, so as to avoid unexpected vehicle movement caused by parking control errors.

2. The control method for an electro-hydraulic parking brake mechanism according to claim 1, characterized in that, The self-learning process for unlocking the vehicle at its extreme positions includes: S1: When the parking mechanism's parking unlock limit position self-learning function is triggered, the parking control system will first check the current vehicle status to determine whether it meets the conditions for parking unlock limit position self-learning, including the engine being in an idling state, the parking system currently having no faults, and the vehicle being in a braking state. S2: After the judgment condition is met, the parking unlock limit position self-learning function is activated. The parking control system controls the target pressure of the parking pressure valve. When the continuously given pressure reaches the time threshold 1, the parking piston position 1 is measured and recorded. When the continuously given pressure reaches the time threshold 2, the parking piston position 2 is measured and recorded. S3: If the absolute value of the difference between parking piston position 1 and parking piston position 2 is less than the threshold, the system is considered stable and the learning process is effective during the parking unlock limit position learning process. The larger value between parking piston position 1 and parking piston position 2 is recorded as the parking unlock limit position learning value. Otherwise, the self-learning is judged to have failed. S4: The parking control system will judge the rationality of the learning value of the parking unlock limit position. If the learning value is within the manufacturing tolerance range, the self-learning result is considered valid. At the same time, in order to avoid the influence of the piston position sensor sampling deviation on the learning result, the calculation result after subtracting a deviation value from the learning value is used as the final learning result of the parking unlock limit position.

3. The control method for an electro-hydraulic parking brake mechanism according to claim 2, characterized in that, The self-learning process for determining the parking unlock limit position also includes: After the parking mechanism has successfully completed self-learning at the limit position of parking unlock, the control system will store the final learning result and self-learning completion signal information into the EEPROM memory, which will then be used for the subsequent parking and unlocking process control of the parking mechanism.

4. The control method for an electro-hydraulic parking brake mechanism according to claim 3, characterized in that, The parking unlocking process control includes: S1: In the initial state, the parking piston is in the parking position. When the driver's parking unlocking request is detected, the electro-hydraulic parking control system first determines whether there is a fault in the current parking mechanism that prevents the parking unlocking function. If there is a fault, the control process ends and the parking piston is kept in the current parking position. If there is no fault, the parking mechanism parking unlocking control process is carried out. S2: While activating the parking mechanism parking unlock control, the control system times the entire control process and adds timeout protection to prevent the control system from being unable to exit due to timeout. When the timeout exceeds the timeout protection threshold, the parking mechanism unlock control process is judged to be successful based on whether the parking piston has reached the parking unlock position at this time. S3: By controlling the output pressure of the solenoid valve, the parking piston is pushed to the parking unlock limit position. After the solenoid valve is closed, the control system starts timing to reserve time for the parking piston to retract and lock. When the timing reaches the threshold, if the parking piston reaches the parking unlock position, it is determined that the parking mechanism parking unlock control is successful and the current gear information is fed back to the driver. S4: During engine start-up, the starter motor may cause the vehicle's 12V power supply voltage to drop too low, leading to abnormalities in the parking mechanism actuators and sensors or failure to execute control commands correctly. However, the 12V power supply voltage will return to normal after the engine starts successfully. In order to respond to the driver's operation needs as quickly as possible and avoid the impact of parking mechanism failure due to low power supply voltage during engine start-up, when parking unlock control fails, the parking control system will determine the engine's starting status during the parking unlock control process. If the engine is starting, after starting, it will re-control the parking mechanism to execute the parking unlock function according to the driver's current intention. If the engine is not starting, it will determine that the parking mechanism parking unlock control has failed and will feed this fault information back to the driver in the form of audible and visual signals for alarm purposes.

5. The control method for an electro-hydraulic parking brake mechanism according to claim 3, characterized in that, The parking control process specifically includes: S1: In the initial state, the parking piston is in the parking unlock position. When the driver's parking request is detected, the electro-hydraulic parking control system first determines whether there is a fault in the current parking mechanism that prevents it from performing the parking function. If there is a fault, the control ends and the parking position is maintained in the current state. If there is no fault, the parking mechanism parking control process is carried out. S2: While activating the parking mechanism parking control, the control system times the entire control process and adds timeout protection to prevent the control system from failing to exit due to timeout; when the timeout exceeds the timeout protection threshold, the parking mechanism parking control is judged to be successful based on whether the parking mechanism piston has reached the parking position at this time. S3: During the parking control process, the parking control system energizes the electromagnet of the locking mechanism and uses the electromagnetic force generated by the electromagnet to disengage the locking plate from the locking groove on the parking piston. Then, the parking piston moves to the parking position under the action of the return spring. When the piston position sensor detects that the parking piston has moved to the middle position and the energization time of the electromagnet reaches the minimum time threshold, the system de-energizes the electromagnet of the locking mechanism. Since the parking control has a direct impact on achieving the functional safety goals of the entire vehicle, a minimum time threshold for energizing the electromagnet of the locking mechanism is set to eliminate interference from abnormal jumps in the position sensor on the judgment of the parking process and avoid unexpected vehicle movement caused by parking control errors. S4: After the electromagnet of the locking mechanism is de-energized, the control system starts timing and reserves time for the parking piston to move to the parking position. When the timing reaches the threshold, if the parking piston reaches the parking position, it is determined that the parking mechanism parking control is successful and the current gear information is fed back to the driver. S5: Similar to the parking unlock control process, a drop in vehicle power supply voltage caused by engine starting may also lead to parking control failure. Therefore, when parking control fails, the parking control system will determine the engine starting status during the parking control process. If the engine is starting, it will re-control the parking mechanism to execute the parking control function after starting. If the engine is not starting, it will determine that the parking mechanism has failed to control the parking and will feed back the fault information to the driver through audible and visual signals for alarm purposes. At the same time, the vehicle's backup parking function, including the electronic parking brake (EPB), will be activated.

Images