A brake assist pressure circuit and fault detection method for a brake-by-wire control system

Abstract

The application discloses a kind of brake-by-wire control system's auxiliary pressure loop and fault detection method, comprising: liquid storage tank;The output of the liquid storage tank is connected with analog circuit and pressure loop by check isolation valve;Under normal brake assist, the analog circuit is closed, the pressure loop is communicated, and pressure brake is carried out to wheel cylinder, under the activation of ABS brake assist, the liquid supplement valve of the pressure loop is opened, and pressure is built again;Through auxiliary pressure loop, and in the fault diagnosis method in ABS activation condition, the generation of the problem of the decrease of assist performance when the vehicle mechanical backup cannot be timely cut to due to circuit leakage can be prevented, to ensure the driving safety of driver.

Description

Technical Field

[0001] This invention relates to the field of automotive chassis braking systems, and more particularly to a power assist pressure build-up circuit and fault detection method for a brake-by-wire control system. Background Technology

[0002] In a car's brake-by-wire control system, the hydraulic circuit of the booster pressure building circuit establishes hydraulic pressure to the wheel cylinders for braking during normal operation. When ABS is activated, the fluid volume in the booster pressure building circuit fluctuates with the actions of the booster and depressurization valves. Therefore, if leakage occurs in the booster pressure building circuit when ABS is activated, it will affect the triggering of the ABS function, thus impacting vehicle safety. Since ABS activation involves the booster valve's pressurization and pressure holding, as well as the depressurization valve's depressurization, current methods to prevent false detections and accurately detect abnormalities in the booster pressure building circuit, such as leak testing using pressure holding after pressure building or using pressure combined with stroke during the pressure building process, cannot detect the pressure and flow rate of the booster pressure building circuit during ABS activation. When ABS is triggered by emergency braking, if a malfunction occurs and the backup booster pressure building circuit cannot be switched on, it can easily lead to safety issues for the vehicle. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies by proposing an assist pressure build-up circuit and fault detection method for a brake-by-wire control system.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a boost pressure build-up circuit for a brake-by-wire control system, comprising: liquid storage tank; The output end of the liquid storage tank is connected to a simulation circuit and a pressure building circuit via an inspection isolation valve; Under normal braking assistance, the simulation circuit is closed, and the pressure-building circuit is connected, thus applying pressure-building braking to the wheel cylinder. With ABS brake assist activated, the fluid replenishment valve of the pressure building circuit is opened to build up pressure again.

[0005] As a further description of the above technical solution: the simulation circuit includes a simulation master cylinder, one side of which is connected to a pedal, and a displacement sensor is provided on the pedal.

[0006] As a further description of the above technical solution: the output end of the simulated master cylinder is connected to a simulator isolation valve and two simulated master cylinder isolation valves via a first pressure sensor, and the output end of the simulator isolation valve is connected to the pedal simulator.

[0007] As a further description of the above technical solution: the pressure building circuit includes a pressure building main cylinder, the liquid storage tank is connected to the pressure building main cylinder, and the liquid replenishment valve is connected in parallel between the liquid storage tank and the pressure building main cylinder.

[0008] As a further description of the above technical solution: the output end of the pressure-building master cylinder is connected in parallel to two pressure-building master cylinder isolation valves through a second pressure sensor.

[0009] As a further description of the above technical solution: the output ends of the two pressure-building master cylinder isolation valves are respectively connected to the output ends of the two simulated master cylinder isolation valves.

[0010] As a further description of the above technical solution: the output end of any of the pressure-building master cylinder isolation valves is connected to two inlet valves, and the output end of the inlet valves is connected to the wheel cylinder.

[0011] As a further description of the above technical solution: a liquid outlet valve is connected to one side of the wheel cylinder, and the output end of the liquid outlet valve is connected to the pressure-building main cylinder or the liquid storage tank.

[0012] As a further description of the above technical solution: When the ABS brake assist is activated, the outlet valve opens, allowing the brake fluid in the pressure-building master cylinder to flow through the pressure-building master cylinder isolation valve, the inlet valve, and the outlet valve before returning to the reservoir. When the brake fluid in the pressure-building master cylinder is nearly drained, the pressure-building master cylinder isolation valve is closed, causing the pressure-building master cylinder to retract to its initial position. This process generates negative pressure, opening the replenishment valve and allowing brake fluid to enter the pressure-building master cylinder from the reservoir to build pressure again.

[0013] It also includes a fault detection method, which is applicable to the boost pressure-building circuit described in any one of the above technical solutions, comprising: Obtain the displacement information of the piston in the pressure-building master cylinder, and filter it to obtain the first liquid volume; The second fluid volume during assisted braking is obtained based on the preset wheel cylinder pressure gauge; the third fluid volume output by the four outlet valves is obtained when ABS brake assist is activated. The gradient calculation model is used to obtain the gradient of the deviation between the first liquid volume and the sum of the second and third liquid volumes. It is then determined whether the gradient exceeds a preset threshold. If it does, the pressure-building circuit is considered to be leaking; otherwise, it is considered to be normal.

[0014] The above technical solution has the following advantages or beneficial effects: The power assist pressure build-up circuit designed in this application, along with the fault diagnosis method in ABS activation mode, can prevent the power assist performance from being reduced due to circuit leakage and the inability to switch to the vehicle's mechanical backup in a timely manner, thus ensuring the driver's driving safety. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of the pressure-building circuit proposed in this invention; Figure 2 This is a flowchart of the fault detection method proposed in this invention.

[0017] Legend: 1. Liquid reservoir; 2. Inspection isolation valve; 3. Wheel cylinder; 4. Liquid replenishment valve; 5. Simulated master cylinder; 6. Pedal; 7. Displacement sensor; 8. First pressure sensor; 9. Simulator isolation valve; 10. Simulated master cylinder isolation valve; 11. Pedal simulator; 12. Pressure building master cylinder; 13. Second pressure sensor; 14. Pressure building master cylinder isolation valve; 15. Inlet valve; 16. Outlet valve. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Reference Figure 1 The present invention provides an embodiment of a boost pressure-building circuit for a brake-by-wire control system, comprising: a reservoir 1; the output end of the reservoir 1 is connected to a simulation circuit and a pressure-building circuit via a check isolation valve 2; under normal braking assistance, the simulation circuit is closed and the pressure-building circuit is connected to perform pressure-building braking on the wheel cylinder 3; under activated ABS braking assistance, the replenishment valve 4 of the pressure-building circuit is opened to perform pressure building again.

[0020] In this embodiment, brake fluid is stored inside the reservoir 1. The inspection isolation valve 2 is located at the output end of the reservoir 1 and is used to control the flow of brake fluid. The analog circuit is used to provide pedal feel, the pressure building circuit is used to actively build pressure, the drive wheel cylinder 3 realizes braking, and the replenishment valve 4 is located on the pressure building circuit for rapid replenishment of oil and re-building pressure under ABS conditions.

[0021] Under normal braking assistance, the simulation circuit is closed and does not participate in pressure building. The pedal feel is fed back by the pedal simulator 11, the fluid replenishment valve 4 is closed, and the piston is moved by the motor of the pressure building master cylinder 12 to assist in pressure building.

[0022] When ABS brake assist is activated, the replenishment valve 4 opens, drawing brake fluid from the reservoir 1 into the pressure-building master cylinder 12 for pressure build-up. This achieves stable, rapid, and continuous brake pressure output, effectively improving braking stability and safety under ABS conditions. It can prevent the reduction in assist performance caused by circuit leakage when the vehicle's mechanical backup cannot be switched in time, ensuring driver safety.

[0023] The simulation circuit includes a simulation master cylinder 5, one side of which is connected to a pedal 6, and a displacement sensor 7 is provided on the pedal 6; the output end of the simulation master cylinder 5 is connected to a simulator isolation valve 9 and two simulation master cylinder isolation valves 10 through a first pressure sensor 8, and the output end of the simulator isolation valve 9 is connected to a pedal simulator 11.

[0024] In this embodiment, a pedal 6 is connected to one side of the simulated master cylinder 5 to receive input from the driver pressing the pedal 6, generating simulated braking pressure. A displacement sensor 7 collects the movement position information of the pedal 6 in real time. A first pressure sensor 8 collects the simulated pressure value output by the simulated master cylinder 5 in real time to determine the driver's braking intention. The simulator isolation valve 9 controls the on / off state of the pedal simulator 11, which provides feedback on the pedal feel. Under normal braking assistance, when the brake pedal 6 is pressed, the simulator isolation valve 9 opens, and the simulated master cylinder isolation valve 10 closes.

[0025] The pressure-building circuit includes a pressure-building main cylinder 12, a liquid storage tank 1 connected to the pressure-building main cylinder 12, and a replenishing valve 4 connected in parallel between the liquid storage tank 1 and the pressure-building main cylinder 12. The output end of the pressure-building main cylinder 12 is connected in parallel to two pressure-building main cylinder isolation valves 14 through a second pressure sensor 13. The output ends of the two pressure-building main cylinder isolation valves 14 are respectively connected to the output ends of two analog main cylinder isolation valves 10. The output end of any pressure-building main cylinder isolation valve 14 is connected in parallel to two inlet valves 15, and the output end of the inlet valve 15 is connected to a wheel cylinder 3. One side of the wheel cylinder 3 is connected to an outlet valve 16, and the output end of the outlet valve 16 is connected to the pressure-building main cylinder 12 or the liquid storage tank 1.

[0026] In this embodiment, under normal braking assistance, when the brake pedal 6 is depressed, the pressure-building master cylinder isolation valve 14 opens and the fluid replenishment valve 4 closes. The motor of the pressure-building master cylinder 12 drives the piston to move, thus assisting in pressure building. The second pressure sensor 13 is located at the output end of the pressure-building master cylinder 12 to collect the pressure value at the output end of the pressure-building master cylinder 12 in real time for pressure monitoring and fault diagnosis. There are two pressure-building master cylinder isolation valves 14, and the output end of each pressure-building master cylinder isolation valve 14 is connected to two fluid inlet valves 15. The four fluid inlet valves 15 are respectively connected to the four wheel cylinders 3 of the vehicle to control the entry of brake fluid into the wheel cylinders 3, thereby achieving pressure boosting or pressure holding control. The output end of the discharge valve 16 is connected to the pressure-building master cylinder 12 or the fluid reservoir 1 for pressure reduction and pressure relief control of the wheel cylinders 3.

[0027] When the ABS brake assist is activated, the outlet valve 16 opens, allowing the brake fluid in the pressure-building master cylinder 12 to flow through the pressure-building master cylinder isolation valve 14, the inlet valve 15, and the outlet valve 16 before returning to the reservoir 1. When the brake fluid in the pressure-building master cylinder 12 is almost completely drained, the pressure-building master cylinder isolation valve 14 is closed, causing the pressure-building master cylinder 12 to retract to the initial position. This process generates negative pressure, opening the replenishment valve 4, allowing brake fluid to enter the pressure-building master cylinder 12 from the reservoir 1 and build up pressure again.

[0028] In this embodiment, when the ABS brake assist mode is activated, the outlet valve 16 is opened, and the brake fluid in the pressure-building master cylinder 12 flows sequentially through the pressure-building master cylinder isolation valve 14, the inlet valve 15, and the outlet valve 16 before flowing back to the reservoir 1. When the brake fluid in the pressure-building master cylinder 12 is nearly emptied, the pressure-building master cylinder isolation valve 14 is closed, causing the pressure-building master cylinder 12 to retract to the starting position. During the retraction process, a negative pressure is formed in the pressure-building master cylinder 12. The negative pressure drives the replenishment valve 4 to open, and the brake fluid enters the pressure-building master cylinder 12 from the reservoir 1 through the replenishment valve 4. After the replenishment is completed, the pressure-building master cylinder 12 performs the pressure-building action again to achieve automatic replenishment and prevent the cavity in the pressure-building master cylinder 12 from being sucked into the air.

[0029] Reference Figure 2 It also includes a fault detection method, which is applicable to the boost pressure circuit of any of the above technical solutions, including: S1. Obtain the displacement information of the piston in the pressure-building master cylinder, and filter it to obtain the first liquid volume; S2. Obtain the second fluid volume during assisted braking based on the preset wheel cylinder pressure gauge; obtain the third fluid volume output by the four outlet valves when ABS brake assist is activated; S3. The gradient of the deviation between the first liquid volume and the sum of the second and third liquid volumes is obtained by processing the gradient calculation model. It is then determined whether the deviation is greater than the preset threshold. If it is, it is determined that the pressure-building circuit has leaked. If not, it is determined to be normal.

[0030] In this embodiment, when the ABS is activated during vehicle operation, the displacement S1 of the piston in the pressure-building master cylinder 12 within the pressure-building chamber is first determined based on the diameter D1 of the pressure-building chamber, and then the fluid volume V1 in the pressure-building circuit is obtained. After filtering according to the hydraulic braking standard, the fluid volume V1F passes through the piston position.

[0031] Based on the wheel cylinder pressure gauges of the four wheel cylinders 3, the second fluid volume V2 during power-assisted braking is obtained by referring to the table. At the same time, the third fluid volume V3 flowing out through the four outlet valves 16 during ABS activation is calculated. That is, fluid volume V = flow rate Q * time T. The third step is to calculate the pressure estimate of the liquid volume for the liquid volume compensation of the liquid outlet valve 16, which is the sum of the second liquid volume and the third liquid volume: V2+V3. The gradient DVDt of the deviation DV between the first liquid volume and the sum of the second and third liquid volumes is calculated by the gradient calculation model. When the gradient DVDt is greater than the preset threshold, it indicates that the booster pressure building circuit has leaked and the ABS function needs to be downgraded. At the same time, the backup braking circuit is switched.

[0032] The gradient calculation model is as follows:

[0033] The first liquid volume V1F is 0.25π×D1. 2 ×S1; Q1, Q2, Q3, and Q4 are the flow rates flowing out through the outlet valve 16 during the ABS activation process; T1, T2, T3, and T4 are the opening times of the outlet valve 16; the third fluid volume V3 is calculated; t is the power assist braking operation time.

[0034] By utilizing the power assist pressure build-up circuit and fault diagnosis methods during ABS activation, the reduced power assist performance caused by circuit leakage during timely switching to the vehicle's mechanical backup can be prevented, thus ensuring driver safety.

[0035] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0036] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A booster pressure build-up circuit for a brake-by-wire control system, characterized in that, include: Liquid storage tank(1); The output end of the liquid storage tank (1) is connected to a simulation circuit and a pressure building circuit through an inspection isolation valve (2); Under normal braking assistance, the simulated circuit is closed, and the pressure-building circuit is connected, thus applying pressure-building braking to the wheel cylinder (3). With the ABS braking assist activated, the fluid replenishment valve (4) of the pressure building circuit is opened to build up pressure again.

2. The pressure-building circuit according to claim 1, characterized in that: The simulation circuit includes a simulation master cylinder (5), one side of which is connected to a pedal (6), and a displacement sensor (7) is provided on the pedal (6).

3. The pressure-building circuit according to claim 2, characterized in that: The output end of the simulated master cylinder (5) is connected to the simulator isolation valve (9) and two simulated master cylinder isolation valves (10) via the first pressure sensor (8). The output end of the simulator isolation valve (9) is connected to the pedal simulator (11).

4. The pressure-building circuit according to claim 3, characterized in that: The pressure building circuit includes a pressure building main cylinder (12), the liquid storage tank (1) is connected to the pressure building main cylinder (12), and the liquid replenishment valve (4) is connected between the liquid storage tank (1) and the pressure building main cylinder (12).

5. The pressure-building circuit according to claim 4, characterized in that: The output end of the pressure-building master cylinder (12) is connected in parallel to two pressure-building master cylinder isolation valves (14) via a second pressure sensor (13).

6. The pressure-building circuit according to claim 5, characterized in that: The output ends of the two pressure-building master cylinder isolation valves (14) are respectively connected to the output ends of the two simulated master cylinder isolation valves (10).

7. The pressure-building circuit according to claim 5, characterized in that: The output end of any of the pressure-building master cylinder isolation valves (14) is connected to two inlet valves (15), and the output end of the inlet valves (15) is connected to the wheel cylinder (3).

8. The pressure-building circuit according to claim 7, characterized in that: One side of the wheel cylinder (3) is connected to the liquid outlet valve (16), and the output end of the liquid outlet valve (16) is connected to the pressure building main cylinder (12) or the liquid storage tank (1).

9. The pressure-building circuit according to claim 8, characterized in that: When the ABS brake assist is activated, the outlet valve (16) opens, allowing the brake fluid in the pressure-building master cylinder (12) to flow through the pressure-building master cylinder isolation valve (14), the inlet valve (15), and the outlet valve (16) before returning to the reservoir (1). When the brake fluid in the pressure-building master cylinder (12) is almost completely drained, the pressure-building master cylinder isolation valve (14) is closed, causing the pressure-building master cylinder (12) to retract to the starting position. This process generates negative pressure, opening the replenishment valve (4), allowing the brake fluid to enter the pressure-building master cylinder (12) from the reservoir (1) and build up pressure again.

10. A fault detection method, characterized in that, The fault detection method is applicable to the boost pressure circuit of any one of claims 1-9, and includes: Obtain the displacement information of the piston in the pressure-building master cylinder, and filter it to obtain the first liquid volume; The second fluid volume during assisted braking is obtained based on the preset wheel cylinder pressure gauge; the third fluid volume output by the four outlet valves is obtained when ABS brake assist is activated. The gradient calculation model is used to obtain the gradient of the deviation between the first liquid volume and the sum of the second and third liquid volumes. It is then determined whether the gradient exceeds a preset threshold. If it does, the pressure-building circuit is considered to be leaking; otherwise, it is considered to be normal.

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