Method and device for determining a fault of a solenoid valve in a brake system

Abstract

According to at least one embodiment, the present disclosure provides a method for determining a solenoid valve failure in a brake system, the method including: a first valve operation process of opening a backup valve that controls opening and closing of a flow passage provided between a master cylinder and a pedal cylinder, and opening and closing a plurality of valves other than the backup valve in a preset manner; a first determination process of moving a piston provided in the master cylinder to a preset first position, and determining whether the backup valve is in a failure state using a pressure sensor; a second valve operation process of closing a mixing valve that controls opening and closing of a flow passage provided between a front wheel circuit and a rear wheel circuit, and opening and closing a plurality of valves other than the mixing valve in a preset manner; and a second determination process of moving the piston provided in the master cylinder to a preset second position, and determining whether the mixing valve is in a failure state using the pressure sensor.

Description

[0001] Cross-references to related applications

[0002] This application is based on and claims priority to Korean Patent Application No. 10-2021-0086228, filed on July 21, 2021, the entire disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure relates to an apparatus and method for determining a solenoid valve malfunction in a braking system. More specifically, this disclosure relates to an apparatus and method for determining a mechanical malfunction of a solenoid valve used in the hydraulic control of the braking system. Background Technology

[0004] The content described in this section simply provides background information on this disclosure and does not constitute prior art.

[0005] Typically, braking systems include: an anti-lock braking system (ABS) to prevent wheel slippage during braking; a brake traction control system (BTCS) to prevent drive wheel slippage during vehicle start-up or rapid acceleration; and an electronic stability control system (ESC) that combines the ABS and traction control to control brake fluid pressure, thereby maintaining stable vehicle operation.

[0006] The ESC integrated braking system includes a fuel tank, pedal cylinder, master cylinder, motor, wheel cylinders, control unit, and multiple hydraulic control valves. A pedal displacement sensor detects the driver's brake pedal operation and drives the motor. The motor's rotational force is converted into linear motion via a ball screw to advance a piston in the master cylinder, generating braking pressure within the cylinder. Since brake pedal operation is transmitted as an electrical signal through the pedal displacement sensor, motor, etc., a pedal simulator is provided as a means to provide the driver with pedal force or pedal feel. The pedal simulator generates hydraulic responsiveness in the pedal cylinder so that the driver can feel the appropriate pedal force or pedal feel when operating the brake pedal.

[0007] The ESC integrated braking system includes multiple hydraulic control valves. These valves, which control the opening and closing of the flow path between the pedal cylinder and the master cylinder, are always closed during braking. Therefore, if a valve malfunctions and becomes mechanically closed and stuck, there is a problem of insufficient backup pressure transmission.

[0008] Furthermore, during braking, the mixing valve, which controls the opening and closing of the flow path between the front and rear wheel circuits, remains open. Therefore, if the mixing valve malfunctions and becomes mechanically open or stuck, there is a risk of the entire brake fluid being depleted and braking failing due to circuit leakage. Summary of the Invention

[0009] According to at least one embodiment, this disclosure provides a method for determining a faulty solenoid valve in a braking system. The method includes: a first valve operation process, opening a backup valve (the backup valve controls the opening and closing of a flow channel between a master cylinder and a pedal cylinder) and opening and closing multiple valves of the braking system other than the backup valve in a preset manner; a first determination process, moving a piston disposed in the master cylinder to a preset first position and using a pressure sensor to determine whether the backup valve is in a faulty state; a second valve operation process, closing a mixing valve (the mixing valve controls the opening and closing of a flow channel between a front wheel circuit and a rear wheel circuit) and opening and closing multiple valves of the braking system other than the mixing valve in a preset manner; and a second determination process, moving a piston disposed in the master cylinder to a preset second position and using a pressure sensor to determine whether the mixing valve is in a faulty state.

[0010] According to at least one embodiment, this disclosure provides a braking device, comprising: a pedal cylinder connected to a tank storing brake fluid, generating hydraulic pressure by pressing a brake pedal; a motor driven by an electrical signal output corresponding to or indicating the displacement of the brake pedal; a master cylinder connected to the pedal cylinder and including a piston that moves forward and backward by the drive of the motor, the master cylinder using the piston to generate brake hydraulic pressure; a control unit that detects a fault in a standby valve for regulating the opening and closing of a flow passage between the master cylinder and the pedal cylinder, and a fault in a mixing valve for regulating the opening and closing of a flow passage between a front wheel circuit and a rear wheel circuit; and a plurality of valves disposed in a flow passage connecting the tank to wheel cylinders, the wheel cylinders performing braking of individual wheels, the plurality of valves opening and closing under the control of the control unit. Attached Figure Description

[0011] Figure 1 This is a hydraulic circuit diagram of a braking system according to an embodiment of the present disclosure;

[0012] Figure 2 This is a hydraulic circuit diagram of a braking system during the main braking operation according to an embodiment of the present disclosure;

[0013] Figure 3 This is a flowchart of a method for determining a solenoid valve fault in a braking system according to an embodiment of the present disclosure;

[0014] Figure 4This is a hydraulic circuit diagram for checking the closestuck of a backup valve in a braking system, according to an embodiment of the present disclosure.

[0015] Figure 5 This is a hydraulic circuit diagram for checking the open-stuck state of a mixing valve in a braking system, according to an embodiment of the present disclosure.

[0016] Figures 6A to 6C This is a diagram illustrating a method for determining a solenoid valve malfunction in a braking system, according to an embodiment of the present disclosure. Detailed Implementation

[0017] In view of the above, this disclosure provides a method for determining a solenoid valve malfunction in a braking system, which can detect a stuck valve that controls the opening and closing of the flow passage between the pedal cylinder and the master cylinder.

[0018] Furthermore, this disclosure provides a method for determining a solenoid valve malfunction in a braking system, which can detect a jammed opening of a mixing valve that controls the opening and closing of a flow path between the front wheel circuit and the rear wheel circuit.

[0019] The purposes of this disclosure are not limited to those described above, and other unmentioned purposes will be clearly understood by those skilled in the art through the following description.

[0020] Hereinafter, some embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, similar reference numerals preferably designate similar elements, even though these elements are shown in different drawings. Furthermore, in the following description of some embodiments, detailed descriptions of relevant known components and functions will be omitted when they are considered to obscure the subject matter of the present disclosure for the purpose of clarity and brevity.

[0021] Furthermore, the alphanumeric codes in the component numbers (such as first, second, i), ii), (a), (b), etc.) are used only to distinguish one component from another, and do not imply or suggest the material, order, or sequence of the components. In this specification, when a component “contains” or “includes” a component, they mean that other components are further included, but not excluded, unless specifically described to the contrary. Terms such as “unit”, “module,” etc., refer to one or more units for performing at least one function or operation, which can be implemented by hardware, software, or a combination thereof.

[0022] Figure 1 This is a hydraulic circuit diagram of a braking system according to an embodiment of the present disclosure.

[0023] refer to Figure 1According to one embodiment of the present disclosure, a braking system may include all or part of the following: an oil tank 80, a pedal cylinder 20, a motor 30, a master cylinder 40, wheel cylinders 111, 112, 113 and 114, hydraulic control valves 51, 52, 53, 54, 55 and 56, a mixing valve 57 and a control unit 100.

[0024] A fuel tank 80 is connected to the upper part of the pedal cylinder 20 to store brake fluid. The pedal cylinder 20 generates hydraulic pressure when the brake pedal 10 is pressed. The pedal cylinder 20 may include a first chamber 20a, a second chamber 20b, and a pedal simulator 21.

[0025] When the driver applies pressure to the brake pedal 10, the pedal cylinder 20 generates hydraulic pressure. This hydraulic pressure is supplied to the piston of the pedal simulator 21 to pressurize the elastic body of the pedal simulator 21, and the driver can feel the pedal sensation through the reaction force of the pressed elastic body. When the driver presses the brake pedal, a stroke sensor 94 for detecting the amount of pressure applied to the brake pedal 10 can be provided at the brake pedal 10.

[0026] The motor 30 operates via an electrical signal output in response to the displacement of the brake pedal 10. The control unit 100 can receive signals from the travel sensor 94 of the brake pedal 10 to control the drive of the motor 30. A screw (not shown) converts the rotational motion of the motor 30 into linear motion to linearly move the piston of the master cylinder 40 in the left-right direction. The master cylinder 40 is driven by the motor 30 controlled by the control unit 100 to generate hydraulic pressure and supply hydraulic pressure to the wheel cylinders 111, 112, 113, and 114 that perform the RL, RR, FL, and FR braking of each wheel. The control unit 100 may be an Electronic Control Unit (ECU), which is a representative control device of the vehicle. The master cylinder 40 may include a third chamber 40a, a fourth chamber 40b, and a piston (not shown).

[0027] For example, when the driver presses the brake pedal 10, the travel sensor 94 senses the travel of the brake pedal 10 and transmits the sensed travel to the control unit 100. The control unit 100 controls the motor 30 based on the travel of the brake pedal 10 detected by the travel sensor 94, thereby controlling the hydraulic pressure generated by the master cylinder 40. When the brake pedal 10 is pressed, the motor 30 operates under the control of the control unit 100 to generate brake hydraulic pressure based on signals output from the travel sensor 94 and the pedal cylinder pressure sensor 91, respectively.

[0028] Wheel cylinders 111, 112, 113 and 114 include a first wheel cylinder 111 for braking the left rear wheel RL of the vehicle, a second wheel cylinder 112 for braking the right rear wheel RR of the vehicle, a third wheel cylinder 113 for braking the left front wheel FL of the vehicle, and a fourth wheel cylinder 114 for braking the right front wheel FR of the vehicle.

[0029] In the hydraulic flow passage between each wheel cylinder 111, 112, 113 and 114 and the oil tank 80, there are feed valves 61, 62, 63 and 64 for controlling the brake oil supplied to each wheel cylinder 111, 112, 113 and 114, and discharge valves 71, 72, 73 and 74 for controlling the brake oil discharged from each wheel cylinder 111, 112, 113 and 114.

[0030] Hydraulic control valves 51, 52, 53, 54, 55, and 56 are disposed in hydraulic flow channels and open and close under the control of control unit 100. Hydraulic control valves 51, 52, 53, 54, 55, and 56 may include first to sixth hydraulic control valves.

[0031] The first hydraulic control valve 51 is located in the hydraulic flow channel of the first chamber 20a connecting the oil tank 80 and the pedal cylinder 20.

[0032] The second hydraulic control valve 52 is located in the hydraulic passage connecting the first chamber 20a of the pedal cylinder 20 and the fourth chamber 40b of the master cylinder 40.

[0033] The third hydraulic control valve 53 is disposed in the hydraulic passage of the second chamber 20b of the pedal cylinder 20 and the third chamber 40a of the master cylinder 40. Hereinafter, the third hydraulic control valve 53 is referred to as "standby valve 53".

[0034] The fourth hydraulic control valve 54 is located in the third chamber 40a and hydraulic passage connecting the discharge valves 73 and 74 on the front side of the vehicle, the oil tank 80, and the master cylinder 40. The fourth hydraulic control valve 54 can be omitted to reduce production costs.

[0035] The fifth hydraulic control valve 55 is located in the hydraulic passage connecting the third chamber 40a of the master cylinder 40 and the wheel cylinder.

[0036] The sixth hydraulic control valve 56 is located in the hydraulic passage connecting the fourth chamber 40b of the master cylinder 40 and the wheel cylinder.

[0037] A mixing valve 57 is disposed in the hydraulic passage connecting the fifth hydraulic control valve 55 to the wheel cylinders 113 and 114 on the front side of the vehicle, and in the hydraulic passage connecting the sixth hydraulic control valve 56 to the wheel cylinders 111 and 112 on the rear side of the vehicle. The mixing valve 57 is a valve for adjusting the hydraulic pressure to supply hydraulic pressure to multiple wheel cylinders 111, 112, 113 and 114.

[0038] The hydraulic passage connecting the fifth hydraulic control valve 55 and the wheel cylinders 113 and 114 on the front side of the vehicle is connected to the third chamber 40a of the master cylinder 40, and guides hydraulic pressure to the third and fourth wheel cylinders 113 and 114 respectively mounted on the two front wheels FL and FR. Furthermore, the hydraulic passage connecting the fifth hydraulic control valve 55 and the wheel cylinders 113 and 114 on the front side of the vehicle may include a first pressure sensor 92 for measuring hydraulic pressure.

[0039] Furthermore, the hydraulic passage connecting the sixth hydraulic control valve 56 and the wheel cylinders 111 and 112 on the rear side of the vehicle is connected to the fourth chamber 40b of the master cylinder 40, and guides hydraulic pressure to the first and second wheel cylinders 111 and 112 respectively mounted on the two rear wheels RL and RR. Additionally, the hydraulic passage connecting the sixth hydraulic control valve 56 and the wheel cylinders 111 and 112 on the rear side of the vehicle may include a second pressure sensor 93 for measuring hydraulic pressure. The second pressure sensor 93 can be removed to reduce production costs.

[0040] The first to sixth hydraulic control valves 51, 52, 53, 54, 55, and 56, as well as the mixing valve 57, can be normally operating valves or solenoid valves controlled by the control unit 100. Multiple valves adjust the pressure path. For example, the vehicle can be controlled by controlling seven normally operating valves 51 to 57, two check valves (not shown), and the braking pressure transmitted to each wheel. The check valves prevent brake fluid backflow.

[0041] Although the pressure line is illustrated as an H-shaped split in this embodiment, and the line is arranged to generate pressure from the front wheel, the pressure line is not limited to this and can be configured as an X-shaped split.

[0042] Figure 2 This is a hydraulic circuit diagram of a braking system during main braking operation according to an embodiment of the present disclosure.

[0043] refer to Figure 2 During main braking operation, the first hydraulic control valve 51, the second hydraulic control valve 52, the fifth hydraulic control valve 55, and the mixing valve 57 are open, while the standby valve 53, the fourth hydraulic control valve 54, and the sixth hydraulic control valve 56 are closed. Each hydraulic control valve 51 to 56 and the mixing valve 57 are opened and closed under the control of the control unit 100.

[0044] refer to Figure 2The backup valve 53 remains closed during main braking operations. Therefore, even if the backup valve 53 is stuck in a closed state, i.e., in a mechanical failure state, the braking system can still operate normally. Since the braking system can still function normally even if the backup valve 53 is faulty, the control unit may not be able to detect the fault. To transmit backup pressure from the pedal cylinder 20 to the wheel cylinders 111 to 114, the backup valve 53 needs to be opened, but when the backup valve 53 is stuck in a closed state due to a fault, backup pressure cannot be transmitted.

[0045] Furthermore, the mixing valve 57 remains open during main braking operation. Therefore, even if the mixing valve 57 is stuck open, i.e., in a mechanical failure state, the braking system can still function normally. Because the braking system can function normally even if the mixing valve 57 is faulty, the control unit may not be able to detect the fault. The mixing valve 57 is used to adjust the hydraulic pressure between the front and rear wheel circuits and allows hydraulic pressure to be supplied to multiple wheel cylinders 111 to 114. If the mixing valve 57 is stuck open due to a fault, there is a problem that, in the event of a circuit leak, all brake fluid may be depleted, preventing braking.

[0046] Figure 3 This is a flowchart of a method for determining a solenoid valve malfunction in a braking system according to an embodiment of the present disclosure.

[0047] When it is determined that the driver has left the vehicle after arriving at the destination (S310), a method for determining a solenoid valve malfunction in a braking system according to an embodiment of the present disclosure is run. For example, the control unit 100 operates after a predetermined time has elapsed following the closing of the brakes and ignition, the opening and closing of the door.

[0048] With the driver out of the vehicle, check if the backup valve 53 is stuck in a closed state due to a mechanical failure (S320). After determining that the backup valve 53 is mechanically faulty, check if the mixing valve 57 is stuck in an open state due to a mechanical failure. When it is determined that the backup valve 53 is faulty, check if the mixing valve 57 is faulty (S330), and illuminate a warning light indicating a valve malfunction on the instrument panel so that the driver can identify whether the valve is faulty (S350). The algorithm terminates after the warning light is illuminated.

[0049] Furthermore, even if the backup valve 53 is not in a faulty state, it is determined whether the mixing valve 57 is in a faulty state (S340). When the mixing valve 57 is in a faulty state, a warning light indicating that the valve is in a faulty state is illuminated on the instrument panel so that the driver can identify whether the valve is in a faulty state (S350). The algorithm terminates after the warning light is illuminated.

[0050] The algorithm terminates if the driver does not disembark, or if neither the backup valve 53 nor the mixing valve 57 is faulty. The method for determining mechanical faults in the backup valve 53 and the mixing valve 57 will be described in detail below.

[0051] Figure 4 This is a hydraulic circuit diagram for checking the closure of a backup valve in a braking system according to an embodiment of the present disclosure.

[0052] refer to Figure 4 The control unit 100 applies zero duty to the backup valve 53 (or sets the load on the backup valve 53 to zero) and commands the backup valve 53 to open. The control unit 100 opens and closes valves 51, 52, 54, 55, 56, and 57 of the braking system, excluding the backup valve 53, so that pressure can be generated in wheel cylinders 111 to 114 when the piston in the master cylinder 40 moves toward the third chamber 40a. For example, the first hydraulic control valve 51, the second hydraulic control valve 52, the fifth hydraulic control valve 55, and the mixing valve 57 are open, while the fourth hydraulic control valve 54 and the sixth hydraulic control valve 56 are closed. After each valve operation is completed, the control unit 100 moves the piston forward toward the third chamber 40a to a preset first position.

[0053] After a predetermined time has elapsed after the piston reaches the first position, the first pressure sensor 92 checks whether the backup valve 53 is mechanically closed and stuck. When the backup valve 53 is opened in the hydraulic circuit design, brake fluid discharged from the third chamber 40a of the master cylinder 40 is guided through the backup valve 53 to the second chamber 20b of the pedal cylinder 20. Therefore, when the backup valve 53 is open without mechanical failure, no hydraulic pressure is formed in the front wheel circuit, and thus the first pressure sensor 92 does not measure pressure. On the other hand, as Figure 4 As shown, when brake fluid discharged from the third chamber 40a of the master cylinder 40 forms hydraulic pressure in the front wheel circuit through the fifth hydraulic control valve 55, the pressure is measured by the first pressure sensor 92. Consequently, when the first pressure sensor 92 measures a pressure exceeding a certain level, it can be determined that the backup valve 53 is mechanically shut off due to a malfunction.

[0054] Figure 5 This is a hydraulic circuit diagram for checking the opening jam of the mixing valve in a braking system according to an embodiment of the present disclosure.

[0055] refer to Figure 5The control unit 100 opens the sixth hydraulic control valve 56 and controls the piston in the master cylinder 40 to be positioned at the end of the third chamber 40a. The control unit 100 applies zero load to the mixing valve 57 and controls the mixing valve 57 to close. The control unit 100 opens and closes valves 51, 52, 53, 54, 55, and 56 of the braking system, excluding the mixing valve 57, so that pressure can be generated in wheel cylinders 111 to 114 when the piston in the master cylinder 40 moves in the reverse direction toward the fourth chamber 40b. For example, the first hydraulic control valve 51, the fourth hydraulic control valve 54, the sixth hydraulic control valve 56, the second hydraulic control valve 52, the third hydraulic control valve 53, and the fifth hydraulic control valve 55 are closed.

[0056] After each valve operation is completed, the control unit 100 moves the piston in the opposite direction toward the fourth chamber 40b to a preset second position.

[0057] After a predetermined time has elapsed after the piston reaches the second position, the first pressure sensor 92 checks whether the mixing valve 57 is mechanically stuck. When the mixing valve 57 is closed in the hydraulic circuit design, brake fluid discharged from the fourth chamber 40b of the master cylinder 40 passes through the sixth hydraulic control valve 56 to create hydraulic pressure only in the rear wheel circuit. Therefore, when the mixing valve 57 is closed without mechanical failure, no hydraulic pressure is created in the front wheel circuit, and thus the first pressure sensor 92 does not measure pressure. On the other hand, as Figure 5 As shown, when brake fluid discharged from the fourth chamber 40b of the master cylinder 40 forms hydraulic pressure in the front wheel circuit through the sixth hydraulic control valve 56, the pressure is measured by the first pressure sensor 92. As a result, when the first pressure sensor 92 measures a pressure exceeding a certain level, it can be determined that the mixing valve 57 is mechanically stuck due to a malfunction.

[0058] Figures 6A to 6C This is a diagram illustrating a method for determining a solenoid valve malfunction in a braking system, according to an embodiment of the present disclosure.

[0059] Figure 6A The diagram illustrates a situation where, in a method for determining a fault in a braking system solenoid valve according to an embodiment of the present disclosure, the standby valve 53 and the mixing valve 57 are in normal condition without mechanical faults.

[0060] refer to Figure 6AIt can be seen that when the load application of the backup valve 53 is 0, that is, when the backup valve 53 is open, the circuit pressure is slightly generated at the beginning and then becomes 0. The phenomenon of slightly generated circuit pressure at the beginning is due to the bottleneck caused by the difference in cross-sectional area between the flow channels when the brake fluid discharged from the third chamber 40a of the master cylinder 40 has a high velocity. Furthermore, it can be seen that when the load application of the mixing valve 57 is 0, that is, when the mixing valve 57 is closed, the circuit pressure becomes 0. Figure 6A As shown, the signals for the standby valve 53 and the mixing valve 57 are set to 0 when there is no mechanical failure.

[0061] Figure 6B This is a diagram showing a backup valve 53 in a closed and stuck state due to mechanical failure in a method for simulating a solenoid valve failure in a braking system, according to an embodiment of the present disclosure.

[0062] Referring to section B, a load is applied to the standby valve 53 to simulate its closed-and-stuck state. When the standby valve 53 is in the closed-and-stuck state, it can be seen that, compared to when the standby valve 53 is in its normal state... Figure 6A In comparison, the circuit pressure increases significantly. The signal for the standby valve 53 being stuck in a closed state due to mechanical failure is set to 1.

[0063] Figure 6C This is a diagram showing a mixing valve 57 in an open and stuck state due to a mechanical failure in a method for simulating a solenoid valve failure in a braking system, according to an embodiment of the present disclosure.

[0064] Reference section C shows that a load is applied to mixing valve 57 to simulate its open-jammed state. When mixing valve 57 is in the open-jammed state, it can be seen that, compared to its normal state... Figure 6A In comparison, the circuit pressure increases significantly. The signal for the mixing valve 57 being stuck in the open state due to mechanical failure is set to 2.

[0065] In a method for determining a solenoid valve malfunction in a braking system according to an embodiment of this disclosure, a control unit 100 receives a circuit pressure sensed by a first pressure sensor 92 and compares the received circuit pressure with a preset circuit pressure under normal conditions. As a result of the comparison, when the circuit pressure is higher than normal, the control unit 100 determines that the backup valve 53 and / or the mixing valve 57 is in a mechanical malfunction state and sends a signal appropriate to the situation to warn the driver. Even if the backup valve 53 and / or the mixing valve 57 malfunctions, all controls under normal conditions are still possible. If the valve malfunctions, a warning light is activated during normal control to guide the driver to recognize the warning light and inspect the vehicle.

[0066] According to one embodiment, a method for determining a solenoid valve malfunction in a braking system can detect malfunctions in hydraulic valves that control the opening and closing of a flow path between the pedal cylinder and the master cylinder to ensure driver safety.

[0067] According to one embodiment, a method for determining a solenoid valve malfunction in a braking system can detect a malfunction in a mixing valve that controls the opening and closing of a flow path between the front wheel cylinder and the rear wheel cylinder to ensure driver safety.

Claims

1. A method for determining a solenoid valve malfunction in a vehicle's braking system, the method comprising: Open the backup valve and open / close multiple valves of the braking system other than the backup valve, wherein the backup valve controls the opening / closing of a first flow passage between the master cylinder and the pedal cylinder; The piston located in the master cylinder is moved to the first position, and a pressure sensor is used to determine whether the backup valve is in a faulty state. The mixing valve is closed, and the plurality of valves of the braking system, excluding the mixing valve, are opened / closed; the mixing valve controls the opening / closing of a second flow path between the front wheel circuit and the rear wheel circuit; and The piston located in the master cylinder is moved to the second position, and the pressure sensor is used to determine whether the mixing valve is in a faulty state. Specifically, before closing the mixing valve, a third flow passage is opened between the master cylinder and the rear wheel circuit; and the piston is moved from its initial position in the master cylinder to the end of the master cylinder in the direction toward the first position.

2. The method according to claim 1, wherein opening the backup valve comprises: Set the load of the backup valve to zero; and Open or close the plurality of valves of the braking system, excluding the backup valve, to create pressure in the plurality of wheel cylinders when the piston moves to the first position.

3. The method according to claim 1, wherein determining whether the standby valve is in a fault state comprises: The pressure sensor is used to detect the pressure in the front wheel circuit; and When the detected pressure in the front wheel circuit meets the preset pressure condition, it is determined that the backup valve is in a fault state.

4. The method of claim 1, wherein closing the mixing valve comprises: The load on the mixing valve is set to zero; and Open or close the plurality of valves of the braking system, excluding the mixing valve, to create pressure in the plurality of wheel cylinders when the piston moves to the second position.

5. The method of claim 1, wherein determining whether the mixing valve is in a fault state comprises: The pressure sensor is used to detect the pressure in the front wheel circuit; and When the detected pressure in the front wheel circuit meets the preset pressure condition, the mixing valve is determined to be in a fault state.

6. The method of claim 1, further comprising determining whether the driver has left the vehicle before opening the backup valve.

7. The method of claim 1, further comprising, when it is determined that the backup valve is in a faulty state, notifying the driver of the vehicle of the fault in the backup valve.

8. The method of claim 1, further comprising, when it is determined that the mixing valve is in a faulty state, notifying the driver of the vehicle of the fault in the mixing valve.

9. A braking device for a vehicle, comprising: A pedal cylinder, connected to a fuel tank, is configured to generate hydraulic pressure in response to the driver pressing the brake pedal; the fuel tank stores brake fluid. The motor is driven by an electrical signal output indicating the displacement of the brake pedal; A master cylinder, connected to the pedal cylinder, includes a piston configured to move forward or backward via the motor, the master cylinder being configured to generate brake hydraulic pressure using the piston; The control unit is configured to detect: (1) a fault in a standby valve used to regulate the opening and closing of a first flow path between the master cylinder and the pedal cylinder; and (2) a fault in a mixing valve used to regulate the opening and closing of a second flow path between the front wheel circuit and the rear wheel circuit; and Multiple valves are disposed in a flow channel connecting the oil tank to multiple wheel cylinders, the multiple wheel cylinders being configured to apply braking to each wheel. The control unit is configured to control the opening and closing of the plurality of valves. When a fault is detected in the backup valve, the control unit is configured as follows: The backup valve is opened, and the plurality of valves of the braking device, excluding the backup valve, are opened / closed. The piston located in the master cylinder is moved to a first position, and a pressure sensor is used to determine whether the backup valve is in a faulty state. When a fault is detected in the mixing valve, the control unit is configured as follows: The mixing valve is closed, and the plurality of valves of the braking device, excluding the mixing valve, are opened / closed. The piston located in the master cylinder is moved to a second position, and the pressure sensor is used to determine whether the mixing valve is in a faulty state. Specifically, before closing the mixing valve, a third flow passage is opened between the master cylinder and the rear wheel circuit; and the piston is moved from its initial position in the master cylinder to the end of the master cylinder in the direction toward the first position.

10. The braking device according to claim 9, wherein the control unit is configured to: Set the load of the backup valve to zero; Controlling the opening and closing of the plurality of valves, excluding the backup valve, to create pressure in the wheel cylinder when the piston moves forward to the first position; and Determine whether the backup valve is in a faulty state when the piston moves forward to the first position.

11. The braking device according to claim 10, wherein, When it is determined that the backup valve is in a faulty state, the control unit is configured to notify the driver of the vehicle of the fault in the backup valve.

12. The braking device according to claim 9, wherein the control unit is configured to: The load on the mixing valve is set to zero; Controlling the opening and closing of the plurality of valves, excluding the mixing valve, to create pressure in the wheel cylinder when the piston moves rearward to the second position; and Determine whether the mixing valve is in a faulty state when the piston moves backward to the second position.

13. The braking device according to claim 12, wherein, When it is determined that the mixing valve is in a faulty state, the control unit is configured to notify the driver of the vehicle of the fault in the mixing valve.

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