CN117028562A - Control method of electrohydraulic parking brake mechanism - Google Patents

Abstract

The invention discloses a control method of an electrohydraulic parking brake mechanism, which is used for diagnosing and processing the failure of the electrohydraulic parking function on the basis of braking and unlocking control of the parking mechanism according to requirements, so that the parking safety of a vehicle is ensured and the usability of the vehicle is improved. In order to ensure the reliability of the parking unlocking control function, the parking electromagnetic valve is controlled to continuously pressurize in the parking unlocking process, so that the electromagnetic valve is closed after the parking piston moves to the parking unlocking limit position. Under the restoring force action of the return spring, when the parking piston moves from the parking unlocking limit position to the parking unlocking position, the locking piece can pass through the locking groove, and the locking groove has enough width to ensure that the locking piece can successfully fall into the locking groove in the piston rollback moving process, so that reliable parking unlocking control is ensured. The method is used for automatically learning the parking unlocking limit position reached by the parking piston and automatically determining the parking unlocking limit position reached by each mechanism so as to cover manufacturing and assembly tolerances.

Description

Control method of electrohydraulic parking brake mechanism

Technical Field

The invention belongs to the technical field of automobile electronics, and particularly relates to a control method of an electrohydraulic parking brake mechanism.

Background

With the development of automobile electronic technology, an electro-hydraulic parking mechanism in an automatic transmission gradually replaces a traditional mechanical guy cable type manual parking mechanism and is used for realizing a parking braking function of a vehicle. The electrohydraulic parking mechanism on the new energy vehicle can be integrated in a hybrid gearbox to be used as another set of parking mechanism independent of an EPB (electronic parking) system, so that the reliability of the parking braking function of the vehicle is improved, and the parking safety of the vehicle is ensured. The electrohydraulic parking control system is closely interacted with other node controllers on the whole vehicle, and simultaneously serves as a mechanical, electrical and hydraulic coupling system, so that a plurality of control input factors are generated, and the failure of the electrohydraulic parking control function can influence the safety of the vehicle function and the visual operation feeling of a driver.

In the parking unlocking control process, the electro-hydraulic parking control system controls the target pressure of the parking electromagnetic valve, so that hydraulic oil flows into the parking piston cylinder through the electromagnetic valve, overcomes the spring restoring force and pushes the parking piston to move towards the parking unlocking direction. If the solenoid valve is closed when the piston reaches the parking unlocking position, the situation that the locking piece does not timely fall into the locking groove and the parking piston returns to the initial position under the action of the return spring possibly occurs, so that the parking unlocking control of the parking mechanism is failed.

Since the actual stroke of the parking piston is small, and during the manufacturing and assembly process, there may be manufacturing and assembly tolerances. If the parking solenoid valve is closed after the parking piston reaches a certain fixed position through the manufacturing process, the parking piston can be accurately locked at the parking unlocking position, the requirement on the manufacturing process is high, and the manufacturing cost is obviously increased. Therefore, the invention proposes to self-learn the parking-release limit position reached by the parking piston, automatically determine the parking-release limit position reached by each mechanism, and cover manufacturing and assembly tolerances.

Disclosure of Invention

The invention aims to solve the technical problems in the background art and provides a control method of an electrohydraulic parking brake mechanism.

In order to solve the technical problems, the technical scheme of the invention is as follows:

an electrohydraulic parking brake mechanism control method, the system is based on an electrohydraulic parking mechanism; the parking piston of the electro-hydraulic parking mechanism is arranged in a parking braking position, a middle position, a parking unlocking position and a parking unlocking limit position, and is used for controlling the parking and unlocking functions of the parking mechanism;

the parking brake position is a parking piston position when the control push rod pushes the parking pawl to enter the parking ratchet wheel to realize parking locking of the vehicle;

the middle position is a parking piston position for ensuring that the locking piece leaves a locking groove area, namely, the electromagnet is powered off, the locking piece does not enter the locking groove even if falling down, and the pawl and the ratchet wheel are in a separated state at the position;

the parking unlocking position is a parking piston position when the control push rod removes acting force applied to the parking pawl so as to ensure that the pawl and the ratchet wheel can be separated;

the parking unlocking limit position is a limit position which can be reached when the parking piston moves towards the parking unlocking position.

Further, the self-learning process of the parking unlocking limit position includes:

s1: when the self-learning function of the parking unlocking limit position of the parking mechanism is triggered, the parking control system firstly checks the state of the current vehicle to judge whether the state of the current vehicle meets the condition of carrying out the self-learning of the parking unlocking limit position, such as that the engine is in an idle state, the parking system is not faulty currently, and the vehicle is in a braking state;

s2: after judging that the condition is met, activating a parking unlocking limit position self-learning function, controlling target pressure of a parking pressure valve by a parking control system, measuring and recording the parking piston position 1 at the moment when the continuous given pressure reaches a time threshold value 1, and measuring and recording the parking piston position 2 at the moment when the continuous given pressure reaches a time threshold value 2;

s3: if the absolute value of the difference between the parking piston position 1 and the parking piston position 2 is smaller than a threshold value, the system is considered to be stable in the learning process of the parking unlocking limit position, the learning process is effective, a larger value between the parking piston position 1 and the parking piston position 2 is taken as the learning value of the parking unlocking limit position, and if not, the self-learning is failed;

s4: the parking control system judges the rationality of the learning value of the parking unlocking limit position, if the learning value is within the range of the manufacturing tolerance, the self-learning result is considered to be effective, and in order to avoid the influence of the sampling deviation of the piston position sensor on the learning result, the calculation result obtained by subtracting one deviation value from the learning value is taken as the final learning result of the parking unlocking limit position.

Further, the self-learning process of the parking unlocking limit position further includes:

after the self-learning of the parking unlocking limit position of the parking mechanism passes, the control system stores the final learning result and the self-learning completion mark signal information into the EEPROM memory, and is used for the parking and parking unlocking process control of the follow-up parking mechanism.

Further, the parking-unlock control process includes:

s1: the parking piston is in a parking position in an initial state, when the parking unlocking requirement of a driver is identified, the electro-hydraulic parking control system firstly judges whether a fault which cannot realize the parking unlocking function exists in the current parking mechanism, if the fault exists, the control process is ended, and the parking piston is maintained in the current parking position; if no fault exists, the parking unlocking control process of the parking mechanism is carried out;

s2: when the timing time exceeds the overtime protection threshold, judging whether the parking mechanism unlocking control process is successful or not according to whether the parking piston reaches the parking unlocking position at the moment;

s3: the parking piston is pushed to reach the parking unlocking limit position by controlling the output pressure of the electromagnetic valve, after the electromagnetic valve is closed, the control system starts timing to reserve time for the backspacing and locking of the parking piston, after the timing time reaches a threshold value, if the parking piston reaches the parking unlocking position, the parking unlocking control of the parking mechanism is judged to be successful, and the current gear information is fed back to a driver;

s4: in the engine starting process, the power supply voltage of the whole vehicle 12V is too low due to the operation of a starting motor, so that an executor and a sensor of the parking mechanism are abnormal or a control instruction cannot be correctly executed, but after the engine is successfully started, the power supply voltage of the parking mechanism is recovered to be normal, in order to avoid the influence caused by the failure of the action of the parking mechanism due to the too low power supply voltage during the engine starting process when the operation requirement of a driver is responded as soon as possible, when the parking unlocking control is unsuccessful, the parking control system judges the starting state of the engine in the parking unlocking control process, if the engine is in the starting process, after the starting process is completed, the parking mechanism is controlled again according to the current intention of the driver, if the engine is not in the starting process, the parking unlocking control failure of the parking mechanism is judged, and the failure information is fed back to the driver in the form of sound and light signals for prompting an alarm.

Further, the parking control process specifically includes:

s1: the parking piston in the initial state is positioned at a parking unlocking position, and when the parking requirement of a driver is identified, the electro-hydraulic parking control system firstly judges whether the current parking mechanism has a fault which cannot realize the parking function; if the vehicle has a fault, ending the control and maintaining the parking position in the current state; if no fault exists, carrying out a parking control process of the parking mechanism;

s2: when the parking control of the parking mechanism is activated, the control system times the whole control process, and timeout protection is added to prevent the control system from being unable to exit due to timeout; when the timing time exceeds the supermarket protection threshold value, judging whether the parking control of the parking mechanism is successful according to whether the parking mechanism piston reaches the parking position at the moment;

s3: in the parking control process, the parking control system controls the electromagnet of the locking mechanism to be electrified, and makes the locking piece separate from the locking groove on the parking piston by utilizing electromagnetic force generated by the electromagnet, and then the parking piston moves towards the parking position under the action of the return spring; when the piston position sensor detects that the parking piston moves to the middle position and the energizing time of the electromagnet reaches the shortest time threshold, the electromagnet of the locking mechanism is controlled to be deenergized; because the parking control has direct influence on realizing the safety target of the whole vehicle function, the threshold value of the shortest electrifying time of the electromagnet of the locking mechanism is set, so that the method is used for eliminating the interference of abnormal jump of the position sensor on the judgment of the parking process and avoiding the unexpected movement of the vehicle caused by the judgment error of the parking control;

s4: after the electromagnet of the locking mechanism is powered off, the control system starts timing, reserves time for the parking piston to move to the parking position, judges that the parking control of the parking mechanism is successful if the parking piston reaches the parking position after the timing time reaches a threshold value, and feeds back the current gear information to a driver;

s5: the same as the parking unlocking control process, the whole vehicle power supply voltage reduction caused in the engine starting process also possibly causes the failure of the parking control process, so that when the parking control is unsuccessful, the parking control system can judge the starting state of the engine in the parking control process; if the engine is in the starting process, after the starting is completed, the parking mechanism is controlled again to execute the parking control function according to the current intention of the driver; if the engine is not in the starting process, judging that the parking control of the parking mechanism fails, and feeding back fault information to a driver in an acoustic and optical signal mode for prompting and alarming; and simultaneously, a backup parking function of the vehicle, such as an electronic parking EPB, is started.

Compared with the prior art, the invention has the advantages that:

the invention provides a control method of an electrohydraulic parking brake mechanism, which is used for carrying out corresponding diagnosis treatment on failure of the electrohydraulic parking function on the basis of braking and unlocking control of the parking mechanism according to the requirement of a driver, so that the parking safety of a vehicle is ensured and the usability of the vehicle is improved. In order to ensure the reliability of a parking unlocking control function, the invention controls the parking electromagnetic valve to continuously pressurize in the parking unlocking process, so that the parking piston moves to the parking unlocking limit position and then closes the electromagnetic valve. Under the restoring force action of the return spring, when the parking piston moves from the parking unlocking limit position to the parking unlocking position, the locking piece can pass through the locking groove, and the locking groove has enough width to ensure that the locking piece can successfully fall into the locking groove in the piston rollback moving process, so that reliable parking unlocking control is ensured. The invention provides a method for automatically learning the parking unlocking limit position reached by a parking piston and automatically determining the parking unlocking limit position reached by each mechanism so as to cover manufacturing and assembly tolerances.

Description of the drawings:

FIG. 1 is a schematic diagram of an electro-hydraulic parking mechanism;

FIG. 2 is a park piston position profile for a park release and park process for a park mechanism;

FIG. 3 is a park-unlock limit position self-learning flow;

FIG. 4 is a park-unlock control flow for an electro-hydraulic park mechanism;

fig. 5 is a parking control flow of the electro-hydraulic parking mechanism.

Reference numerals:

the device comprises a 1-parking ratchet wheel, a 2-parking pawl, a 3-hydraulic piston push rod, a 4-electromagnet control locking mechanism, a 5-hydraulic piston, a 6-hydraulic piston return spring, a 7-main controller, an 8-parking pawl return spring, a 9-hydraulic control electromagnetic valve, a 10-hydraulic cylinder and an 11-piston position sensor.

Detailed Description

The following describes specific embodiments of the present invention with reference to examples:

it should be noted that the structures, proportions, sizes and the like illustrated in the present specification are used for being understood and read by those skilled in the art in combination with the disclosure of the present invention, and are not intended to limit the applicable limitations of the present invention, and any structural modifications, proportional changes or size adjustments should still fall within the scope of the disclosure of the present invention without affecting the efficacy and achievement of the present invention.

Also, the terms such as "upper," "lower," "left," "right," "middle," and "a" and the like recited in the present specification are merely for descriptive purposes and are not intended to limit the scope of the invention, but are intended to provide relative positional changes or modifications without materially altering the technical context in which the invention may be practiced.

Example 1:

as shown in fig. 1, the main controller 7 is configured to receive a piston position signal transmitted from the piston position sensor 11, recognize the operation intention of the driver, and send control signals to the electromagnet control lock mechanism 4 and the hydraulic control solenoid valve 9 to control the on/off of the electromagnet and the solenoid valve. The hydraulic control electromagnetic valve 9 is connected with the hydraulic cylinder 10 through an oil duct to realize oil filling and oil draining control of the hydraulic cylinder. In the oil filling process, hydraulic pressure is formed on the left side of the hydraulic piston 5, the acting force of the hydraulic piston return spring 6 is overcome to push the hydraulic piston 5 to drive the parking push rod 3 to move towards the parking unlocking direction, and when the push rod 3 leaves the pawl, the parking pawl 2 can be separated from the parking ratchet wheel 1 under the action of the parking pawl return spring 8, so that the parking of a real vehicle is unlocked. In the oil drainage process, hydraulic pressure on the left side of the hydraulic piston 5 is removed, the electromagnet controls the locking mechanism 4 to unlock, the hydraulic piston 5 drives the push rod 3 to move towards the parking direction under the action of the return spring 6, and the parking pawl 2 can be clamped on the parking ratchet wheel 1 under the pushing action of the parking push rod 3, so that the parking brake is realized.

FIG. 1 is a schematic diagram of a control system according to the present invention; the parking piston of the electro-hydraulic parking mechanism has a parking braking position, an intermediate position, a parking unlocking position and a parking unlocking limit position, and is used for controlling the parking and unlocking functions of the parking mechanism. The parking brake position is a parking piston position when the control push rod can push the parking pawl to enter the parking ratchet wheel to realize parking locking of the vehicle; the middle position is the parking piston position for ensuring that the locking piece leaves the locking groove area, namely the electromagnet is powered off, the locking piece does not enter the locking groove after falling down, and the pawl and the ratchet wheel are in a separated state at the position; the parking unlocking position is a parking piston position when the control push rod removes acting force applied to the parking pawl and ensures that the pawl and the ratchet wheel can be separated; the parking-unlocking limit position is a limit position which can be reached when the parking piston moves towards the direction of the parking-unlocking position, and fig. 2 is a parking piston position curve of the parking-unlocking and parking processes of the parking mechanism.

As shown in fig. 3, a specific parking-unlock limit position self-learning procedure is as follows:

s1: when the self-learning function of the parking unlocking limit position of the parking mechanism is triggered, the parking control system firstly checks the state of the current vehicle to judge whether the state of the current vehicle meets the condition of carrying out the self-learning of the parking unlocking limit position, for example, the engine is in an idle state, the parking system is not faulty currently, the vehicle is in a braking state and the like.

S2: after the judging condition is met, a parking unlocking limit position self-learning function is activated, the parking control system controls the target pressure of the parking pressure valve, the parking piston position 1 at the moment is measured and recorded when the preset pressure continuously reaches the time threshold value 1, and the parking piston position 2 at the moment is measured and recorded when the preset pressure continuously reaches the time threshold value 2.

S3: if the absolute value of the difference between the parking piston position 1 and the parking piston position 2 is smaller than the threshold value, the system is considered to be stable in the learning process of the parking unlocking limit position, the learning process is effective, a larger value between the parking piston position 1 and the parking piston position 2 is taken as the learning value of the parking unlocking limit position, and otherwise, the self-learning failure is judged.

S4: the parking control system judges the rationality of the learning value of the parking unlocking limit position, if the learning value is within the range of the manufacturing tolerance, the self-learning result is considered to be effective, and in order to avoid the influence of the sampling deviation of the piston position sensor on the learning result, the calculation result obtained by subtracting one deviation value from the learning value is taken as the final learning result of the parking unlocking limit position.

S5: after the parking unlocking limit position of the parking mechanism passes through self-learning, the control system stores the final learning result, the self-learning completion mark signal and other information into the EEPROM memory, and is used for controlling the parking and the parking unlocking processes of the follow-up parking mechanism.

As shown in fig. 4, the parking-unlock control procedure:

s1: the parking piston is in a parking position in an initial state. When the parking unlocking requirement of a driver is identified, the electro-hydraulic parking control system firstly judges whether the current parking mechanism has a fault which can not realize the parking unlocking function. If the control process is finished, the parking piston is maintained at the current parking position; and if no fault exists, performing a parking unlocking control process of the parking mechanism.

S2: when the parking unlocking control of the parking mechanism is activated, the control system times the whole control process, and timeout protection is added to prevent the control system from being unable to exit due to timeout. And when the timing time exceeds the overtime protection threshold, judging whether the unlocking control process of the parking mechanism is successful according to whether the parking piston reaches the parking unlocking position at the moment.

S3: the parking piston is pushed to reach the parking unlocking limit position by controlling the output pressure of the electromagnetic valve. After the solenoid valve is closed, the control system begins timing to reserve time for retraction and locking of the parking piston. And when the timing time reaches the threshold value, if the parking piston reaches the parking unlocking position, judging that the parking unlocking control of the parking mechanism is successful, and feeding back the current gear information to the driver.

S4: during the starting process of the engine, the starting motor works, so that the power supply voltage of the whole vehicle 12V is possibly too low, the parking mechanism actuator and the sensor are abnormal or cannot execute control instructions correctly, and the power supply voltage of the vehicle 12V can be recovered to be normal after the engine is started successfully. In order to avoid the influence caused by failure of the action of the parking mechanism due to the too low power supply voltage during the starting of the engine while responding to the operation requirement of the driver as soon as possible, the parking control system judges the starting state of the engine during the parking unlocking control when the parking unlocking control is unsuccessful. If the engine is in the starting process, after the starting is completed, the parking mechanism is controlled again to execute the parking unlocking function according to the current intention of the driver. If the engine is not in the starting process, judging that the parking unlocking control of the parking mechanism fails, and feeding back the failure information to a driver in the forms of sound, light and the like for prompting and alarming.

As shown in fig. 5, the parking control process:

s1: the parking piston in the initial state is positioned at the parking unlocking position, and when the parking requirement of a driver is identified, the electro-hydraulic parking control system firstly judges whether the current parking mechanism has a fault which cannot realize the parking function. If the vehicle has a fault, ending the control and maintaining the parking position in the current state; and if no fault exists, performing a parking control process of the parking mechanism.

S2: when the parking control of the parking mechanism is activated, the control system times the whole control process, and timeout protection is added to prevent the control system from being unable to exit due to timeout. And when the timing time exceeds the supermarket protection threshold value, judging whether the parking control of the parking mechanism is successful according to whether the parking mechanism piston reaches the parking position at the moment.

S3: in the parking control process, the parking control system controls the locking mechanism electromagnet to be electrified, and the electromagnetic force generated by the electromagnet is utilized to enable the locking piece to be separated from the locking groove on the parking piston, and then the parking piston moves towards the parking position under the action of the return spring. When the piston position sensor detects that the parking piston moves to the middle position and the energizing time of the electromagnet reaches the shortest time threshold, the locking mechanism electromagnet is controlled to be deenergized. Because the parking control has direct influence on realizing the safety target of the whole vehicle function, the threshold value of the shortest electrifying time of the electromagnet of the locking mechanism is set, and the threshold value is used for eliminating the interference of abnormal jump of the position sensor on the judgment of the parking process and avoiding the unexpected movement of the vehicle caused by the judgment error of the parking control.

S4: after the locking mechanism electromagnet is powered off, the control system starts timing and reserves time for the parking piston to move to the parking position. And after the timing time reaches the threshold value, if the parking piston reaches the parking position, judging that the parking control of the parking mechanism is successful, and feeding back the current gear information to the driver.

S5: the same as the parking unlocking control process, the whole vehicle power supply voltage reduction caused in the engine starting process also possibly causes the failure of the parking control process, so that when the parking control is unsuccessful, the parking control system can judge the starting state of the engine in the parking control process. If the engine is in the starting process, after the starting is completed, the parking mechanism is controlled again to execute the parking control function according to the current intention of the driver. If the engine is not in the starting process, judging that the parking control of the parking mechanism fails, and feeding back fault information to a driver in the forms of sound, light and the like for prompting and alarming. At the same time, a backup parking function of the vehicle, such as an electronic parking EPB, is started.

While the preferred embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various changes may be made without departing from the spirit of the present invention within the knowledge of those skilled in the art.

Many other changes and modifications may be made without departing from the spirit and scope of the invention. It is to be understood that the invention is not to be limited to the specific embodiments, but only by the scope of the appended claims.

Claims (5)

1. An electrohydraulic parking brake mechanism control method is characterized in that the method is based on an electrohydraulic parking mechanism; the parking piston of the electro-hydraulic parking mechanism is arranged in a parking braking position, a middle position, a parking unlocking position and a parking unlocking limit position, and is used for controlling the parking and unlocking functions of the parking mechanism;

the parking brake position is a parking piston position when the control push rod pushes the parking pawl to enter the parking ratchet wheel to realize parking locking of the vehicle;

the middle position is a parking piston position for ensuring that the locking piece leaves a locking groove area, namely, the electromagnet is powered off, the locking piece does not enter the locking groove even if falling down, and the pawl and the ratchet wheel are in a separated state at the position;

the parking unlocking position is a parking piston position when the control push rod removes acting force applied to the parking pawl so as to ensure that the pawl and the ratchet wheel can be separated;

the parking unlocking limit position is a limit position which can be reached when the parking piston moves towards the parking unlocking position.

2. The control method of an electro-hydraulic parking brake mechanism according to claim 1, wherein the self-learning process of the parking-unlock limit position includes:

s1: when the self-learning function of the parking unlocking limit position of the parking mechanism is triggered, the parking control system firstly checks the state of the current vehicle to judge whether the state of the current vehicle meets the condition of carrying out the self-learning of the parking unlocking limit position, such as that the engine is in an idle state, the parking system is not faulty currently, and the vehicle is in a braking state;

s2: after judging that the condition is met, activating a parking unlocking limit position self-learning function, controlling target pressure of a parking pressure valve by a parking control system, measuring and recording the parking piston position 1 at the moment when the continuous given pressure reaches a time threshold value 1, and measuring and recording the parking piston position 2 at the moment when the continuous given pressure reaches a time threshold value 2;

s3: if the absolute value of the difference between the parking piston position 1 and the parking piston position 2 is smaller than a threshold value, the system is considered to be stable in the learning process of the parking unlocking limit position, the learning process is effective, a larger value between the parking piston position 1 and the parking piston position 2 is taken as the learning value of the parking unlocking limit position, and if not, the self-learning is failed;

s4: the parking control system judges the rationality of the learning value of the parking unlocking limit position, if the learning value is within the range of the manufacturing tolerance, the self-learning result is considered to be effective, and in order to avoid the influence of the sampling deviation of the piston position sensor on the learning result, the calculation result obtained by subtracting one deviation value from the learning value is taken as the final learning result of the parking unlocking limit position.

3. The control method of an electro-hydraulic parking brake mechanism according to claim 2, wherein the self-learning process of the parking-unlock limit position further includes:

after the self-learning of the parking unlocking limit position of the parking mechanism passes, the control system stores the final learning result and the self-learning completion mark signal information into the EEPROM memory, and is used for the parking and parking unlocking process control of the follow-up parking mechanism.

4. A control method of an electro-hydraulic parking brake mechanism according to claim 3, wherein the parking-unlock control process includes:

s1: the parking piston is in a parking position in an initial state, when the parking unlocking requirement of a driver is identified, the electro-hydraulic parking control system firstly judges whether a fault which cannot realize the parking unlocking function exists in the current parking mechanism, if the fault exists, the control process is ended, and the parking piston is maintained in the current parking position; if no fault exists, the parking unlocking control process of the parking mechanism is carried out;

s2: when the timing time exceeds the overtime protection threshold, judging whether the parking mechanism unlocking control process is successful or not according to whether the parking piston reaches the parking unlocking position at the moment;

s3: the parking piston is pushed to reach the parking unlocking limit position by controlling the output pressure of the electromagnetic valve, after the electromagnetic valve is closed, the control system starts timing to reserve time for the backspacing and locking of the parking piston, after the timing time reaches a threshold value, if the parking piston reaches the parking unlocking position, the parking unlocking control of the parking mechanism is judged to be successful, and the current gear information is fed back to a driver;

s4: in the engine starting process, the power supply voltage of the whole vehicle 12V is too low due to the operation of a starting motor, so that an executor and a sensor of the parking mechanism are abnormal or a control instruction cannot be correctly executed, but after the engine is successfully started, the power supply voltage of the parking mechanism is recovered to be normal, in order to avoid the influence caused by the failure of the action of the parking mechanism due to the too low power supply voltage during the engine starting process when the operation requirement of a driver is responded as soon as possible, when the parking unlocking control is unsuccessful, the parking control system judges the starting state of the engine in the parking unlocking control process, if the engine is in the starting process, after the starting process is completed, the parking mechanism is controlled again according to the current intention of the driver, if the engine is not in the starting process, the parking unlocking control failure of the parking mechanism is judged, and the failure information is fed back to the driver in the form of sound and light signals for prompting an alarm.

5. A control method of an electro-hydraulic parking brake mechanism according to claim 3, wherein the parking control process specifically comprises:

s1: the parking piston in the initial state is positioned at a parking unlocking position, and when the parking requirement of a driver is identified, the electro-hydraulic parking control system firstly judges whether the current parking mechanism has a fault which cannot realize the parking function; if the vehicle has a fault, ending the control and maintaining the parking position in the current state; if no fault exists, carrying out a parking control process of the parking mechanism;

s2: when the parking control of the parking mechanism is activated, the control system times the whole control process, and timeout protection is added to prevent the control system from being unable to exit due to timeout; when the timing time exceeds the supermarket protection threshold value, judging whether the parking control of the parking mechanism is successful according to whether the parking mechanism piston reaches the parking position at the moment;

s3: in the parking control process, the parking control system controls the electromagnet of the locking mechanism to be electrified, and makes the locking piece separate from the locking groove on the parking piston by utilizing electromagnetic force generated by the electromagnet, and then the parking piston moves towards the parking position under the action of the return spring; when the piston position sensor detects that the parking piston moves to the middle position and the energizing time of the electromagnet reaches the shortest time threshold, the electromagnet of the locking mechanism is controlled to be deenergized; because the parking control has direct influence on realizing the safety target of the whole vehicle function, the threshold value of the shortest electrifying time of the electromagnet of the locking mechanism is set, so that the interference of abnormal jump of the position sensor on the judgment of the parking process is eliminated, and the unexpected movement of the vehicle caused by the judgment error of the parking control is avoided;

s4: after the electromagnet of the locking mechanism is powered off, the control system starts timing, reserves time for the parking piston to move to the parking position, judges that the parking control of the parking mechanism is successful if the parking piston reaches the parking position after the timing time reaches a threshold value, and feeds back the current gear information to a driver;

s5: the same as the parking unlocking control process, the whole vehicle power supply voltage reduction caused in the engine starting process also possibly causes the failure of the parking control process, so that when the parking control is unsuccessful, the parking control system can judge the starting state of the engine in the parking control process; if the engine is in the starting process, after the starting is completed, the parking mechanism is controlled again to execute the parking control function according to the current intention of the driver; if the engine is not in the starting process, judging that the parking control of the parking mechanism fails, and feeding back fault information to a driver in an acoustic and optical signal mode for prompting and alarming; and simultaneously, a backup parking function of the vehicle, such as an electronic parking EPB, is started.