Spring energy storage type brake control system and control method

Abstract

The application provides a spring energy storage type brake control system and control method, which comprises an EPB hand control unit and an EPB processor, the EPB hand control unit is connected with the EPB processor and information interaction is carried out, the controller is further connected with a vehicle air source, a left spring brake cylinder and a right spring brake cylinder, and the controller further comprises a left displacement sensor for collecting the piston displacement of the left spring brake cylinder and a right displacement sensor for collecting the piston displacement of the right spring brake cylinder; the controller comprises an EPB electromagnetic valve and a gas pressure sensor, the controller knows the size of the brake pressure under the same displacement condition at different times according to the displacement sensor and the gas pressure sensor, so as to control the size of the brake pressure by the EPB electromagnetic valve. The spring brake cylinder has the advantages of long service life and the like.

Description

Technical Field

[0001] This invention relates to the field of brakes, and more particularly to a spring-energy-storage brake control system and control method. Background Technology

[0002] The invention patent CN201080051693.7's method for solving the problem of vehicle slippage due to insufficient spring strength in the EPB system's spring brake cylinder is based on the premise that the vehicle is equipped with a self-braking control system in addition to the EPB. For example, the Electronic Braking System (EBS), developed in recent years based on the Anti-lock Braking System (ABS) and Anti-skid System (ASR), represented by Wan'an Technology, is mainly used to improve the braking performance of trucks and has the self-braking function. However, the self-braking control system is rarely used in large-scale commercial vehicles in China.

[0003] The spring brake cylinders widely used in commercial vehicle air braking systems have a limited lifespan compared to other automotive components. When the parking brake system is released, the spring remains compressed under the force of compressed air. To maintain this state, the compressed air must maintain a certain pressure. Furthermore, current pressure calibrations typically select the maximum pressure, which, over prolonged use, leads to excessive wear on the piston and spring of the spring brake cylinder, reducing its lifespan. Summary of the Invention

[0004] This invention provides a spring-energy-storage brake control system and control method to address existing technical problems.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A spring-energy-storage brake control system includes an EPB manual control unit and an EPB processor. The EPB manual control unit is connected to the EPB processor and interacts with it. The controller is also connected to the vehicle's air supply, a left spring brake cylinder, and a right spring brake cylinder. It also includes a left displacement sensor for collecting the piston displacement of the left spring brake cylinder and a right displacement sensor for collecting the piston displacement of the right spring brake cylinder. The controller includes an EPB solenoid valve and a pressure sensor. The controller obtains the magnitude of the braking pressure under the same displacement at different times based on the displacement sensor and the pressure sensor, and then controls the EPB solenoid valve to control the magnitude of the braking pressure.

[0007] As a preferred embodiment, the EPB manual control unit includes a parking switch and a calibration switch.

[0008] A control method for a spring-energy-storage brake control system includes the following steps:

[0009] Step 1: Define the compressed air pressure value as the release threshold Pr when the vehicle is fully released from the parking state; the corresponding piston displacement value is Xr during the process of the vehicle moving from the parking state to the fully released state.

[0010] Step 2: Calibrate the initial state, release the threshold Pr = P0, the corresponding displacement value is Xr = X0, the release threshold revision number N = 0, and store it in the controller;

[0011] Step 3: During the vehicle's parking release process, record the air pressure value Py when the displacement value of the left displacement sensor is Xr, and simultaneously record the displacement value X5 when the air pressure is Pr-0.5. If Pr-Py ≥ 0.5 bar, the displacement sensor is normal, then revise Pr = Pr-0.5 and Xr = X5; the number of release threshold revisions N = N+1. Store the new Pr, Xr, and N in the EEPROM; if the conditions are not met, no adjustment is made.

[0012] Preferably, between steps two and three, there is an additional step used to verify whether the sensor is functioning correctly; the specific method is as follows:

[0013] Calibrate P1 = 1 bar, P2 = 2 bar. During calibration, record the displacements of the left displacement sensor under P1 and P2 pressures as X10 and X20, respectively. During calibration, record the displacements of the right displacement sensor under P1 and P2 pressures as X11 and X21, respectively. This is used to verify X10 and X20. The verification is successful when |X11-X10|≤Δxmin and |X21-X20|≤Δxmin. After the verification is successful, X10 and X20 are stored in the controller through the parameter writing interface during calibration.

[0014] Preferably, the system is set with a minimum release threshold Prmin, and pr should always be greater than or equal to Prmin.

[0015] Preferably, when pr is less than or equal to Prmin, the processor transmits this information to the EPB manual control unit via a CAN message. The EPB manual control unit includes an indicator light, which the processor controls to alert the driver.

[0016] Preferably, in step three, if Pr-Py ≥ 0.5 bar, indicating the displacement sensor is functioning correctly, the processor transmits a revision command to the calibration switch on the EPB manual control unit and prompts the driver to perform calibration. If the driver selects calibration, Pr is revised to Pr-0.5, Xr to X5, and the release threshold revision count N = N+1. The new Pr, Xr, and N are then stored in the EEPROM.

[0017] This solution has the following beneficial effects:

[0018] This solution utilizes the characteristic of spring decay in the spring brake cylinder to appropriately adjust the release pressure, thereby extending the service life of the brake cylinder piston and making the release more stable and timely. Attached Figure Description

[0019] Figure 1 This is a comparison chart of the pressure-displacement curves of the spring in a spring brake cylinder.

[0020] Figure 2 This is a flowchart for calibrating the release threshold.

[0021] Figure 3 The output characteristic curve of the Hall effect displacement sensor. Detailed Implementation

[0022] Example 1

[0023] A spring-energy-storage brake control system includes an EPB manual control unit and an EPB processor. The EPB manual control unit is connected to the EPB processor and interacts with it. The controller is also connected to the vehicle's air supply, a left spring brake cylinder, and a right spring brake cylinder. It also includes a left displacement sensor for collecting the piston displacement of the left spring brake cylinder and a right displacement sensor for collecting the piston displacement of the right spring brake cylinder. The controller includes an EPB solenoid valve and a pressure sensor. The controller obtains the magnitude of the braking pressure under the same displacement at different times based on the displacement sensor and the pressure sensor, and then controls the EPB solenoid valve to control the magnitude of the braking pressure.

[0024] The EPB manual control unit includes a parking switch and a calibration switch. The displacement sensor is a Hall sensor. The spring-energy-storage brake with a Hall displacement sensor adds a permanent magnet and a Hall displacement sensor to the original spring-energy-storage brake chamber. In the parking state, the displacement is zero; upon release, as pressure gradually builds up in the parking chamber, the displacement increases with increasing pressure.

[0025] Example 2

[0026] This embodiment provides a control method for a spring-energy-storage brake control system. Before introducing the method, the parking release state of the vehicle is explained. In the release state, the compressed air must maintain a certain pressure. The concept of the release threshold can be understood here as a pressure that must exist at least in the spring brake cylinder of the parking brake system so that the parking brake can be fully released. This ensures that the driver can release the parking brake and drive the vehicle directly when they wish to do so. For example, a pressure value of approximately 5 bar can be used as the release threshold. Obviously, this release threshold depends on vehicle parameters, such as vehicle weight, trailer operation, etc., and can be reduced to varying degrees.

[0027] A control method for a spring-energy-storage brake control system includes the following steps:

[0028] Step 1: Define the compressed air pressure value as the release threshold Pr when the vehicle is fully released from the parking state; the corresponding piston displacement value is Xr during the process of the vehicle moving from the parking state to the fully released state.

[0029] Step 2: Calibrate the initial state, release the threshold Pr = P0, the corresponding displacement value is Xr = X0, the release threshold revision number N = 0, and store it in the controller;

[0030] Step 3: During the vehicle's parking release process, record the air pressure value Py when the displacement value of the left displacement sensor is Xr, and simultaneously record the displacement value X5 when the air pressure is Pr-0.5. If Pr-Py ≥ 0.5 bar, the displacement sensor is normal, then revise Pr = Pr-0.5 and Xr = X5; the number of release threshold revisions N = N+1. Store the new Pr, Xr, and N in the EEPROM; if the conditions are not met, no adjustment is made.

[0031] This is because as the spring brake cylinder is used more frequently, the previously calibrated 5-bar release threshold may release at 4 bar. The displacement sensor can detect this situation. If it can detect it, we can then control the pressure of the spring brake cylinder to 4 bar for release, thereby extending the life of the spring brake cylinder. Specifically, refer to Hooke's Law: within the elastic range of a material, the spring force is directly proportional to the spring deformation. The mathematical expression is F = k·X or ΔF = k·ΔX, where k is a constant, the stiffness coefficient of the object. The change in piston area with displacement can be ignored: P = k·x, where Pmax is the maximum air pressure of the vehicle, and xmax is the maximum displacement limited by the brake cylinder. A comparison diagram of normal and aging conditions is shown in the attached figure.

[0032] To verify whether the displacement sensor is working properly, the following steps are performed between steps two and three, and the specific methods are as follows:

[0033] The calibration process involves setting P1 = 1 bar and P2 = 2 bar. During calibration, the displacements of the left displacement sensor under P1 and P2 pressures are recorded as X10 and X20, respectively, and the displacements of the right displacement sensor under P1 and P2 pressures are recorded as X11 and X21, respectively. These values ​​are used to verify X10 and X20. Verification is successful when |X11-X10| ≤ Δxmin and |X21-X20| ≤ Δxmin. After successful verification, X10 and X20 are stored in the controller via the parameter writing interface. The left and right cylinders have interconnected air circuits, and one pressure sensor simultaneously measures the air pressure of both cylinders. The two displacement sensors are symmetrically installed, and Δxmin is the set minimum displacement difference.

[0034] In this embodiment, the system has a minimum release threshold Prmin, and pr should always be greater than or equal to Prmin. When pr is less than or equal to Prmin, the processor transmits this information to the EPB manual control unit via CAN message. The EPB manual control unit includes an indicator light, which the processor controls to remind the driver. When only 3 bar is needed for release, or when other conditions are deemed ineffective for the backup service brake function (backup brake function after the service brake fails), it indicates that the lifespan of the spring brake cylinder has ended. The driver can be reminded via other vehicle display devices by sending relevant CAN messages. The frequency of reminders can be set to the first occurrence of a 3 bar release threshold and every subsequent power-on. Alternatively, the indicator light on the manual control unit can flash as a reminder. The power-on reminder can be set for a certain time, and the flashing frequency varies depending on the release threshold. Upon the first occurrence, it will continue to flash unless the vehicle is powered on again. The other display devices can be instruments or other visual devices.

[0035] The EPB system uses both a pressure sensor and a displacement sensor to monitor for air leaks (air leaks into the stroke chamber) while the vehicle is parked, preventing accidental rollover while parked. This is especially important when the vehicle is on a slope. After the engine is turned off (ignition power is off), there is a slight delay before determining whether to deactivate the EPB system.

[0036] The EPB system can use pressure sensors and displacement sensors to monitor for air leaks (external leaks in the parking chamber) in the released state, preventing accidental parking in the released state, especially while the vehicle is in motion.

[0037] This solution utilizes the characteristic of spring decay in the spring brake cylinder to appropriately adjust the release pressure, thereby extending the service life of the brake cylinder piston and making the release more stable and timely.

[0038] Example 3

[0039] The difference from Example 2 is that in step three, if Pr-Py ≥ 0.5 bar, the displacement sensor is normal. The processor then transmits a revision command to the calibration switch on the EPB manual control unit and prompts the driver to perform calibration. If the driver selects calibration, Pr is revised to Pr-0.5, Xr to X5, and the number of release threshold revisions N = N+1. The new Pr, Xr, and N are stored in the EEPROM. This part allows for manual selection to adjust the release threshold.

Claims

1. A control method for a spring-energy-storage brake control system, characterized in that: The control system includes an EPB manual control unit and an EPB processor. The EPB manual control unit is connected to the EPB processor and interacts with it. The controller is also connected to the vehicle's air supply, left spring brake cylinder, and right spring brake cylinder. It also includes a left displacement sensor for collecting the piston displacement of the left spring brake cylinder and a right displacement sensor for collecting the piston displacement of the right spring brake cylinder. The controller includes an EPB solenoid valve and a pressure sensor. Based on the displacement and pressure sensors, the controller determines the braking pressure at the same displacement over different time periods, thereby controlling the EPB solenoid valve to control the braking pressure. The EPB manual control unit includes a parking switch and a calibration switch. The control method includes the following steps: Step 1: Define the compressed air pressure value as the release threshold Pr when the vehicle is fully released from the parking state; the corresponding piston displacement value is Xr during the process of the vehicle moving from the parking state to the fully released state. Step 2: Calibrate the initial state, release the threshold Pr=P0, the corresponding displacement value is Xr=X0, the release threshold revision number N=0, and store it in the controller; Step 3: During the vehicle's parking release process, record the air pressure value Py when the displacement value of the left displacement sensor is Xr, and simultaneously record the displacement value X5 when the air pressure value is Pr-0.

5. If Pr-Py ≥ 0.5 bar, the displacement sensor is normal, then revise Pr = Pr-0.5 and Xr = X5; the number of release threshold revisions N = N+1; store the new Pr, Xr, and N in the EEPROM; if the conditions are not met, no adjustment is made.

2. The control method for a spring-energy storage brake control system according to claim 1, characterized in that: Between steps two and three, there is a further step used to verify whether the sensor is functioning correctly; the specific method is as follows: Calibrate P1=1 bar, P2=2 bar. During calibration, record the displacements of the left displacement sensor under P1 and P2 pressures as X10 and X20, respectively. During calibration, record the displacements of the right displacement sensor under P1 and P2 pressures as X11 and X21, respectively. This is used to verify X10 and X20. The verification is successful when |X11-X10|≤Δxmin and |X21-X20|≤Δxmin. After the verification is successful, X10 and X20 are stored in the controller through the parameter writing interface during calibration.

3. The control method for a spring-energy storage brake control system according to claim 1, characterized in that: The system has a minimum release threshold Prmin, and pr should always be greater than or equal to Prmin.

4. The control method for a spring-energy storage brake control system according to claim 3, characterized in that: When pr is less than or equal to Prmin, the processor transmits the information to the EPB manual control unit via CAN message. The EPB manual control unit includes an indicator light, which the processor controls to alert the driver.

5. The control method for a spring-energy storage brake control system according to claim 3, characterized in that: In step three, if Pr-Py ≥ 0.5 bar, the displacement sensor is normal. The processor will transmit the revision command to the calibration switch on the EPB manual control unit and remind the driver whether to perform calibration. If the driver selects calibration, then Pr = Pr-0.5, Xr = X5; release the threshold revision number N = N+1; and store the new Pr, Xr, and N in the EEPROM.

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