Braking system air leakage judgment and control method

Abstract

The invention discloses a method for judging and controlling air leakage of a brake system. The method comprises the following steps: starting self-inspection; if yes, the air pressure of the brake air tank uploaded by the air pressure sensor is received; judging whether the air pressure of the brake air tank reaches a driving permitting condition or not; if yes, allowing the vehicle READY, or not allowing the vehicle READY; whether the air pressure of the brake air tank meets the air pump closing condition or not is judged, if yes, the VCU instructs the air pump to continue working, and if not, the VCU instructs the air pump to stop working; judging whether the working time is greater than a time threshold set by the VCU or not; if yes, the VCU sends an inflation timeout alarm to the instrument through the CAN bus, and otherwise, the VCU instructs the air pump to continue working; judging whether the actual vehicle speed is smaller than a vehicle speed threshold value set by the VCU or not; if yes, the VCU instructs the air pump to stop working; otherwise, vehicle READY is allowed; by the adoption of the technical scheme, it is ensured that braking air pressure exists in the traveling process, and traveling safety is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of vehicle air brake systems, and more specifically, relates to a brake system air leakage judgment and control method. Background Art

[0002] New energy vehicles are becoming intelligently connected, and as chip computing power increases, domain control is gradually being carried out, and the VCU (vehicle controller) performs key strategy control in the entire control system.

[0003] The braking system of commercial heavy trucks is mainly driven by gas compression to drive the mechanical mechanism to move, and perform drum / disc braking at the wheel end. The high-pressure gas is driven by the air pump controller (electric air compressor controller) to drive the air pump (electric air compressor) to compress the air and store it in the gas tank; on new energy vehicles, the air pump is not allowed to work for a long time. The air pump controller generally collects the working current, voltage, and temperature of the air pump controller and the air pump (including the controller temperature, the air pump motor temperature, and the compressor temperature), and sets the protection threshold for overload protection.

[0004] However, when the overload protection is triggered, the air pump controller generally shuts down and stops pumping before the driver stops in time to avoid danger, causing the vehicle to lose sufficient effective brake pressure before stopping, creating hidden dangers for vehicle and personal safety; and the air pump controller and air pump overload temperature failure is generally caused by the long-term operation of the air pump. There are many reasons for the long-term operation of the air pump, such as the capacity design of the air tank, the capacity design of the air pump controller, the displacement design of the air pump, etc. The abnormal reason is mainly the leakage of the brake system, which causes the brake system pressure to fail to meet the air pump shutdown conditions and keeps pumping.

[0005] The design of the gas tank capacity, the air pump controller capacity, and the air pump displacement can be completed in the hardware design stage. Problems can be found and corrected during the design driving test. However, it is not easy to determine the abnormal cause. Without adding hardware equipment such as sensors, the existing technology has not proposed a corresponding judgment strategy.

[0006] The solutions adopted in the prior art have the following problems:

[0007] 1. Failure to effectively monitor and correctly judge the air leakage of the brake system;

[0008] 2. Only protect the air pump controller and air pump against current and temperature overload, phase loss and short circuit;

[0009] 3. If the air pump current, temperature overload, phase loss or short circuit protection is triggered during driving, the air pump will be directly shut down.

[0010] Therefore, the defects of the prior art are:

[0011] The existing control strategy only monitors the air tank pressure of the brake system to control the operation and frequency of the air compressor to achieve energy-saving effects. However, there is a lack of fault settings when the pressure is always at the lower limit, and there is a lack of corresponding protection strategies, which cannot effectively improve driving safety. This leads to the deterioration of the air pump and its controller fault, resulting in over-temperature and over-current protection, and the failure to stop pumping when the driver stops in time to avoid danger, which in turn causes the vehicle to lose brake pressure when it is not parked, resulting in vehicle and personal safety accidents.

[0012] The following search results were obtained by searching the existing public technical literature using keywords such as "brake system; air tank; pressure (or air leakage); judgment; control":

[0013] 1. Chinese patent document: "Electric vehicle vacuum brake leakage detection and emergency brake system", patent (application) number: 201710360744.8; the technical solution recorded is:

[0014] "The leakage detection and emergency braking system for vacuum brake of electric vehicles includes a vehicle controller, a motor controller, a drive motor, a vehicle speed signal acquisition sensor, a vacuum pressure sensor, a vacuum pump, a brake pedal opening sensor and a combination instrument, including the following steps: Step A, collecting the opening signal and calculating the opening signal change rate; Step B, collecting the vacuum pressure signal and calculating the pressure signal change rate; Step C, collecting the vacuum pump speed data and calculating the vacuum pumping rate; Step D, judging whether there is a vacuum system leak and distinguishing and rating the leak; Step E, if the leak level is low, the vehicle controller generates a speed reduction signal to the motor controller to control the drive motor to slow down; Step F, if the leak level is high, the drive motor controller controls the drive motor to apply a counter torque to reduce the vehicle speed until it stops directly";

[0015] The technical effects recorded are:

[0016] "The overall setting is reasonable, the usage stability is good, the applicability is strong and the practicality is good."

[0017] 2. Chinese patent document: "A vehicle brake pressure control method based on a pneumatic wire control brake system", patent (application) number: 202010121004.0; the technical solution recorded is:

[0018] "A calibration method and acquisition device for pressure increase and pressure reduction characteristics of a pneumatic wire-controlled brake system, a vehicle brake pressure control method, and a vehicle brake system control method, wherein the pressure increase and pressure reduction characteristics are used in a pneumatic wire-controlled brake system, and the pressure increase and pressure reduction characteristics are expressed as a brake pressure increase characteristic curve and a brake pressure reduction characteristic curve, and the steps for acquiring the two include: changing the duration of each opening of the intake valve and the exhaust valve and periodically controlling the opening and closing of the intake valve or the exhaust valve of the brake chamber according to the pressure holding period until the pressure in the brake chamber no longer changes, and recording the change of the pressure of the brake chamber over time each time, and then obtaining the brake pressure increase characteristic curve and the brake pressure reduction characteristic curve by data processing";

[0019] The technical effects recorded are:

[0020] "The pressure increase and decrease characteristics obtained using the above calibration method can bring convenience to the regulation of the vehicle's brake pressure, thereby improving the regulation efficiency of the vehicle's brake pressure regulation method."

[0021] However, the technical solutions recorded in the above-mentioned technical documents and the existing publicly applied related technical solutions have not been able to solve the problems and defects existing in the prior art of "inability to effectively monitor and correctly judge the leakage of the braking system; the vehicle loses brake air pressure when it is not parked, causing vehicle and personal safety accidents." Summary of the invention

[0022] The invention provides a method for judging and controlling air leakage of a brake system, the purpose of which is to ensure that there is brake air pressure during driving and to improve driving safety.

[0023] In order to achieve the above object, the technical solution adopted by the present invention is:

[0024] The brake system leakage judgment and control method of the present invention is controlled by the VCU of the vehicle; the brake system includes an air pump and an air pump controller; the steps of the leakage judgment and brake control method are:

[0025] 1) Power-on wake-up self-test;

[0026] 2) Determine whether the self-test is successful; if yes, proceed to the next step; if no, return to the previous step;

[0027] 3) Receive the air pressure information of the brake air tank uploaded by the air pressure sensor;

[0028] 4) Determine whether the air pressure of the brake air tank reaches the condition for allowing driving; if yes, proceed to the next step; if no, the vehicle is not allowed to be READY;

[0029] 5) Allow the vehicle to be READY;

[0030] 6) Determine whether the air pressure of the brake air tank reaches the condition for shutting down the air pump; if yes, proceed to step 11); if no, proceed to the next step;

[0031] 7) VCU instructs the air pump to continue working;

[0032] 8) Determine whether the working time is greater than the time threshold set by the VCU; if yes, proceed to the next step; if no, return to step 7);

[0033] 9) VCU sends an inflation timeout alarm to the instrument through the CAN bus;

[0034] 10) Determine whether the actual vehicle speed is less than the speed threshold set by the VCU; if yes, proceed to the next step; if no, return to step 7);

[0035] 11) VCU instructs the air pump to stop working.

[0036] Regarding step 4), when the braking system adopts 8 bar or 10 bar braking pressure, the setting value of the condition allowing driving is 7 bar.

[0037] For step 6), when the braking system adopts 8 bar braking pressure, the setting value of the air pump closing condition is 10 bar; when the braking system adopts 10 bar braking pressure, the setting value of the air pump closing condition is 10.5 bar.

[0038] In the step 8), the time threshold set by the VCU is 15 minutes.

[0039] In the step 10), the vehicle speed threshold set by the VCU is 5 km / h.

[0040] The air pump controller sets a safety protection threshold and a fault protection trigger condition; when the air pump controller detects that the air pump controller itself and the air pump have a fault that endangers safety, the air pump is shut down for protection.

[0041] The safety protection thresholds include an overload protection threshold, an undervoltage protection threshold and a temperature rise protection threshold.

[0042] The fault protection triggering conditions include phase loss signal and short circuit signal.

[0043] The VCU determines whether the brake system is leaking, and reports the brake system leakage fault through the CAN bus, and the instrument performs sound, light, and text alarms and reminders; until the vehicle is powered off and the key is inserted again, the VCU will not automatically restore to the state before the fault.

[0044] The VCU is based on the air pump working status sent by the air pump controller via the CAN bus; when the VCU receives the air pump working status as "yes", it indicates that the air pump is in working condition, and the VCU internal chip starts timing; when the VCU receives the air pump working status as "no", it indicates that the air pump has stopped working, and the timing is reset.

[0045] The present invention adopts the above-mentioned technical scheme, and optimizes the working characteristics of the braking system through software strategies without adding additional hardware. It can judge whether the braking system is leaking through logical analysis of the air pressure and the working time of the air pump; identify the braking risk through leakage judgment, and warn the driver to avoid risks in time through sound, light, and text alarms and prompts on the instrument; during driving (vehicle speed > 5km / h), before the air pump controller makes an overload protection, the VCU does not shut down the air pump due to leakage fault, and continues to keep the air pump enabled to ensure that there is brake pressure during driving, thereby improving driving safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The contents shown in the attached drawings are briefly described as follows:

[0047] Figure 1 It is a control flow chart of the present invention. DETAILED DESCRIPTION

[0048] The specific implementation modes of the present invention are further explained in detail below by describing the embodiments with reference to the accompanying drawings, so as to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0049] like Figure 1 The control flow chart of the present invention is a method for judging and controlling air leakage in a brake system, wherein the brake system is controlled by a VCU of a vehicle; the brake system includes an air pump and an air pump controller. The present invention proposes a judgment principle for air leakage in a brake system and provides a fault handling strategy after air leakage in the brake system.

[0050] In order to solve the problems existing in the prior art and overcome its defects, to achieve the invention purpose of ensuring the presence of brake air pressure during driving and improving the safety of driving, the technical solution adopted by the present invention is:

[0051] like Figure 1 As shown, the brake system leakage judgment and control method of the present invention comprises the following steps:

[0052] 1) Power-on wake-up self-test;

[0053] 2) Determine whether the self-test is successful; if yes, proceed to the next step; if no, return to the previous step;

[0054] 3) Receive the air pressure information of the brake air tank uploaded by the air pressure sensor;

[0055] 4) Determine whether the air pressure of the brake air tank reaches the condition for allowing driving; if yes, proceed to the next step; if no, the vehicle is not allowed to be READY;

[0056] 5) Allow the vehicle to be READY;

[0057] 6) Determine whether the air pressure of the brake air tank reaches the condition for shutting down the air pump; if yes, proceed to step 11); if no, proceed to the next step;

[0058] 7) VCU instructs the air pump to continue working;

[0059] 8) Determine whether the working time is greater than the time threshold set by the VCU; if yes, proceed to the next step; if no, return to step 7);

[0060] 9) VCU sends an inflation timeout alarm to the instrument through the CAN bus;

[0061] 10) Determine whether the actual vehicle speed is less than the speed threshold set by the VCU; if yes, proceed to the next step; if no, return to step 7);

[0062] 11) VCU instructs the air pump to stop working.

[0063] READY means the vehicle is ready to start.

[0064] Explanation of step 4) above:

[0065] Because different brake air pressures bring different braking forces, the brake system is designed according to the braking force requirements of the vehicle, among which the brake air pressure is one of the key parameters of the braking force;

[0066] Before driving, in order to ensure that the air pressure inside the gas tank meets the basic braking requirements of the vehicle, it is necessary to set a minimum air pressure threshold that allows the vehicle to be READY. This is a calibrable quantity, which is related to the braking system design of the OEM, for example:

[0067] For a braking system with 8 bar brake pressure, the set value is 7 bar; for a braking system with 10 bar brake pressure, the set value is also 7 bar;

[0068] Because 7 bar is the minimum requirement for the vehicle's brake pressure, the minimum brake pressure threshold is set to 7 bar;

[0069] The "reached" here refers to the real-time air pressure value of the gas tank (including when the air pressure drops, rises, and is stationary).

[0070] Explanation of step 6) above:

[0071] In order to prevent the brake system from over-pressurizing, it is necessary to stop pumping when the air pressure in the air tank reaches the maximum threshold. According to the design of the vehicle's brake system, the brake air pressure of the designed brake system is different, and the maximum air pressure threshold is also different. It is a calibrable quantity, for example:

[0072] The brake system uses 8 bar brake pressure, and the set value is 10 bar;

[0073] For a brake system with 10 bar brake pressure, the set value is 10.5 bar;

[0074] It can be seen that the thresholds of the maximum inflation pressure are different for systems with different brake pressures;

[0075] The "reached" here means that when the air pressure is inflated, the air pressure rise value reaches the threshold value.

[0076] The above brake system air leakage judgment strategy of the present invention sets a pump working time threshold for the VCU; during driving, the VCU judges the air pumping time according to the working state of the pump controller. When the VCU controls the pump controller to drive the pump to start working, the VCU starts timing.

[0077] By controlling the air pump according to the above logic, it can not only provide routine protection for the inflation system, but also make a logical judgment on whether the inflation system is leaking based on the inflation time. It can promptly remind the driver and passengers of vehicle malfunctions and enable them to pull over to the side of the road in time to avoid danger, thus preventing vehicle and personal accidents.

[0078] In the step 8), the time threshold set by the VCU is 15 minutes.

[0079] In the step 10), the vehicle speed threshold set by the VCU is 5 km / h.

[0080] Brake system leakage protection: During driving, the VCU determines whether the brake system is leaking and whether the current vehicle speed is ≤5km / h. If not, the VCU continues to enable the air pump; if yes, the VCU stops enabling the air pump. Before driving, the VCU determines whether the brake system is leaking, stops enabling the air pump, and exits the READY state.

[0081] Set the VCU to set the air pump working time threshold, and VCU to make a logical judgment on the brake system leakage; VCU performs air pump control protection based on the logical judgment of the brake system leakage: the air pump is not shut down during driving, and the air pump is shut down only when the vehicle speed is ≤5km / h.

[0082] When the air pump controller drives the air pump to work continuously for 15 minutes (calibrable) or more, the VCU records it as an air pump overtime operation and determines it as a brake system leakage. The VCU reports the brake system leakage fault through the CAN bus, and the instrument gives sound, light, and text alarms and prompts until the vehicle is powered off. The next time the vehicle is powered on again with the key inserted, the VCU resets the alarm signal; otherwise, the VCU does not automatically recover from the fault; at the same time, the VCU continues to control the air pump controller to keep the air pumping state until the vehicle speed is ≤5km / h, at which time the VCU stops enabling the air pump controller and stops pumping.

[0083] In view of the defects of the prior art, the present invention makes the following strategies based on the existing air pump control protection strategy:

[0084] 1. The air pump controller itself does not set the inflation time threshold, and continues to set the overload protection threshold of the air pump controller. When the air pump controller detects that itself and the air pump have overload, phase loss, undervoltage, short circuit and other faults, the air pump is shut down for protection to ensure that the air pump and the controller will not be irreversibly damaged.

[0085] 2. VCU sets the upper pressure threshold for stopping the air pump and the lower pressure threshold for stopping the air pump according to the air tank pressure; when the air tank pressure is lower than the lower pressure threshold, VCU controls the air pump controller to drive the air pump to work; when the air tank pressure is higher than the upper pressure threshold, VCU controls the air pump controller to stop the air pump.

[0086] 3. Before driving, if the inflation time does not exceed the set threshold, continue to accumulate time points during driving and perform strategic protection after driving.

[0087] On the basis of the above technical solution, the present invention continues to set the air pump controller and the air pump current, temperature overload, phase loss, short circuit protection:

[0088] The air pump controller sets a safety protection threshold and a fault protection trigger condition; when the air pump controller detects that the air pump controller itself and the air pump have a fault that endangers safety, the air pump is shut down for protection.

[0089] The specific safety protection thresholds and fault protection triggering conditions are:

[0090] The safety protection thresholds include an overload protection threshold, an undervoltage protection threshold and a temperature rise protection threshold.

[0091] The fault protection triggering conditions include phase loss signal and short circuit signal.

[0092] Note: The overload protection threshold, undervoltage protection threshold, and temperature rise protection threshold set by the air pump controller itself are set based on the characteristics of the air pump motor in the brake system and the parameter requirements of the air pump controller itself. They are calibrable values, for example:

[0093] For example, the air pump motor parameters that can be used in the present invention are shown in Table 1 below:

[0094] Table 1: Air pump motor parameters

[0095] Rated power (kW) 4 Peak power (kW) 8 Peak frequency (Hz) 65 Rated frequency(Hz) 55 Pole pairs 3 Rated speed (r / min) 1100 Rated voltage(VAC) 380 Peak speed (r / min) 1300 Rated current(A) 8.3 Peak current(A) 16.6 Rated torque(Nm) 34.7 Peak torque(Nm) 69.4 Temperature sensor type No temperature sensation Cooling method / Insulation class H Protection level IP68 D-axis inductance(mH) 28.3 Q-axis inductance(mH) 67.5 Stator resistance(Ω) 1.92 Supplier Name *** Supplier Model *** Heavy Industry Material Number ***

[0096] The protection thresholds set by the air pump controller are as follows, among which the overload protection threshold is:

[0097] (1) The controller output current value > the controller rated current;

[0098] (2) The duration of the controller outputting high current is greater than the protection time set by the hardware;

[0099] When (1) AND (2) occur together, it is considered that overload protection occurs;

[0100] The air pressure protection threshold is: the DC bus voltage of the air pump controller < the controller undervoltage point 300V;

[0101] Temperature rise protection threshold: air pump controller temperature > controller over-temperature point 105°C;

[0102] The above mentioned parameters refer to real-time parameters (including descent, ascent and stationary).

[0103] The VCU determines whether the brake system is leaking, and reports the brake system leakage fault through the CAN bus, and the instrument performs sound, light, and text alarms and reminders; until the vehicle is powered off and the key is inserted again, the VCU will not automatically restore to the state before the fault.

[0104] The VCU is based on the air pump working status sent by the air pump controller via the CAN bus; when the VCU receives the air pump working status as "yes", it indicates that the air pump is in working condition, and the VCU internal chip starts timing; when the VCU receives the air pump working status as "no", it indicates that the air pump has stopped working, and the timing is reset.

[0105] When the air pump controller controls the air pump to work, it will report the fault status of the air pump controller through the CAN bus; voltage, current, temperature value, and working status; for example: when the air pump is working, the air pump controller sends the working status as "yes", and when the air pump stops working, the air pump controller sends the working status as "no";

[0106] Air pump working timeout threshold: The air pump controller has working time requirements for the air pump, such as "15 minutes"; Braking system leakage judgment: VCU integrates the working time of the air pump. If the working time is ≥15 minutes, VCU judges that the braking system is leaking.

[0107] The beneficial effects of adopting the above technical solution are:

[0108] 1. Without adding any additional hardware, the working characteristics of the brake system can be optimized through software strategies, and the air pressure and the working time of the air pump can be used to logically analyze whether the brake system is leaking;

[0109] 2. Identify the braking risk through air leakage judgment, and warn the driver to avoid danger in time through sound, light, and text alarms and prompts on the instrument;

[0110] 3. During driving (vehicle speed > 5km / h), before the air pump controller is overload protected, the VCU does not shut down the air pump due to leakage, but continues to enable the air pump to ensure that there is brake pressure during driving.

[0111] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for judging and controlling air leakage in a brake system, which is controlled by a vehicle's VCU; the brake system comprises an air pump and an air pump controller; characterized in that: The steps of the air leakage judgment and brake control method are as follows: 1) Power-on wake-up self-test; 2) Determine whether the self-test is successful; If yes, go to the next step; if no, return to the previous step; 3) Receive the air pressure information of the brake air tank uploaded by the air pressure sensor; 4) Determine whether the air pressure of the brake air tank reaches the conditions for allowing driving; If yes, go to the next step; if no, do not allow the vehicle to be READY; 5) Allow the vehicle to be READY; 6) Determine whether the air pressure of the brake air tank reaches the condition for shutting down the air pump; if yes, proceed to step 11); if no, proceed to the next step; 7) VCU instructs the air pump to continue working; 8) Determine whether the working time is greater than the time threshold set by the VCU; If yes, go to the next step; if no, return to step 7); 9) VCU sends an inflation timeout alarm to the instrument through the CAN bus; 10) Determine whether the actual vehicle speed is less than the speed threshold set by the VCU; if yes, proceed to the next step; if no, return to step 7); 11) VCU instructs the air pump to stop working.

2. The brake system leakage judgment and control method according to claim 1, characterized in that: Regarding step 4), when the braking system adopts a braking pressure of 8 bar or 10 bar, the setting value of the condition allowing driving is 7 bar.

3. The brake system leakage judgment and control method according to claim 1, characterized in that: For step 6), when the braking system adopts 8 bar braking pressure, the setting value of the air pump closing condition is 10 bar; when the braking system adopts 10 bar braking pressure, the setting value of the air pump closing condition is 10.5 bar.

4. The brake system leakage judgment and control method according to claim 1, characterized in that: In the step 8), the time threshold set by the VCU is 15 minutes.

5. The brake system leakage judgment and control method according to claim 1, characterized in that: In the step 10), the vehicle speed threshold set by the VCU is 5 km / h.

6. The brake system leakage judgment and control method according to claim 1, characterized in that: The air pump controller sets a safety protection threshold and a fault protection trigger condition; when the air pump controller detects that the air pump controller itself and the air pump have a fault that endangers safety, the air pump is shut down for protection.

7. The brake system leakage judgment and control method according to claim 6, characterized in that: The safety protection thresholds include an overload protection threshold, an undervoltage protection threshold and a temperature rise protection threshold.

8. The brake system leakage judgment and control method according to claim 1, characterized in that: The fault protection triggering conditions include phase loss signal and short circuit signal.

9. The brake system leakage judgment and control method according to claim 1, characterized in that: The VCU determines whether the brake system is leaking, and reports the brake system leakage fault through the CAN bus, and the instrument performs sound, light, and text alarms and reminders; until the vehicle is powered off and the key is inserted again, the VCU will not automatically restore to the state before the fault.

10. The brake system leakage judgment and control method according to claim 1, characterized in that: The VCU is based on the air pump working status sent by the air pump controller via the CAN bus; when the VCU receives the air pump working status as "yes", it indicates that the air pump is in working condition, and the VCU internal chip starts timing; when the VCU receives the air pump working status as "no", it indicates that the air pump has stopped working, and the timing is reset.

Images