EGR (Exhaust Gas Recirculation) system for preventing gas leakage and control method

Abstract

The invention provides an EGR (Exhaust Gas Recirculation) system for preventing gas leakage and a control method, and belongs to the technical field of engine exhaust gas recirculation control. The EGR valve is used for controlling the flow of exhaust gas extracted from the exhaust pipe; the EGR cooler is used for cooling flowing waste gas; an air inlet of the EGR proportional valve is connected with a vehicle compressed air source, and an air outlet of the EGR proportional valve is connected with the EGR valve cylinder through an air path pipeline; the engine ECU controller is used for controlling the output pressure of the EGR proportional valve; the engine ECU controller is configured to control the EGR proportional valve to output preset holding pressure if the EGR valve does not need to be opened at present after the engine is powered on; the value of the holding pressure is set to enable the sealing structure in the cylinder of the EGR valve to be sealed and to be lower than a pressure threshold value required for starting to open the EGR valve. The air leakage abnormal sound of the EGR system is effectively solved, the sealing performance and reliability are improved, the cost is optimized, and the user experience is enhanced.

Description

Technical Field

[0001] This application belongs to the field of engine exhaust gas recirculation control technology, specifically relating to an EGR system and control method for preventing gas leakage. Background Technology

[0002] EGR is an abbreviation for Exhaust Gas Recirculation.

[0003] In modern internal combustion engines, especially commercial vehicle engines, precise control of the EGR valve is crucial for reducing nitrogen oxide emissions. Currently, widely used EGR systems often employ pneumatic actuators, which control the supply of compressed air through an EGR proportional valve. This, in turn, drives the EGR valve cylinder to adjust the valve opening, ultimately controlling the rate of exhaust gas recirculation introduced into the cylinder.

[0004] However, in practical applications, when the vehicle is powered on but the engine control unit (ECU) has not issued an EGR valve opening command, the EGR proportional valve should be closed. However, due to its relatively high input air pressure (typically 8.5-10.5 bar), and limitations imposed by the mechanical structure, a small amount of gas leakage can still occur even when closed. This leaked compressed air continuously enters the downstream EGR valve cylinder, creating a low-pressure environment (approximately 0.3-1.8 bar). This pressure is insufficient to allow the internal cylinder sealing structure to function effectively, causing gas to continuously escape from the pressure relief port, producing a noticeable hissing noise. This persistent abnormality in non-operating conditions is easily misinterpreted by users as a system malfunction such as a pipeline leak or valve damage, severely impacting user experience and product reputation, and potentially leading to unnecessary after-sales repairs and increased maintenance costs.

[0005] To address the aforementioned air leakage and abnormal noise issues, existing technologies typically employ the following solutions: First, improving the sealing materials and structural design of the EGR proportional valve itself to fundamentally reduce the leakage rate in its closed state. However, this method usually involves precision manufacturing processes and high-performance materials, significantly increasing the manufacturing cost of individual components. Second, installing a mechanical silencer or damping element at the pressure relief port of the EGR valve cylinder. While this method can reduce leakage noise to some extent, it only alleviates the noise and does not solve the fundamental problem of gas leakage, and it adds extra parts and assembly steps.

[0006] Therefore, there is an urgent need for an innovative solution that can fundamentally eliminate standby air leakage noise in EGR systems without significantly increasing hardware costs and complexity. Summary of the Invention

[0007] In a first aspect, embodiments of this application provide an EGR system to prevent air leakage, including an exhaust pipe, an EGR valve, an EGR cooler, an EGR proportional valve, and an engine ECU controller. The exhaust pipe is connected to the engine's exhaust manifold and is used to guide engine exhaust gas. The intake port of the EGR valve is connected to the exhaust pipe through the EGR intake line to control the flow rate of exhaust gas extracted from the exhaust pipe. The outlet port of the EGR valve is connected to the intake pipe of the engine through the EGR delivery line. An EGR cooler is installed on the EGR delivery pipeline to cool the flowing exhaust gas; The inlet of the EGR proportional valve is connected to the vehicle's compressed air source, and the outlet of the EGR proportional valve is connected to the drive mechanism of the EGR valve through an air passage. The engine ECU controller is connected to the EGR proportional valve and is used to control the output pressure of the EGR proportional valve; The driving mechanism of the EGR valve is an EGR valve cylinder. The engine ECU controller is configured to: after the engine is powered on, if it is determined that the EGR valve does not need to be opened at present, control the EGR proportional valve to output a preset holding pressure; The holding pressure is set to a value that enables the internal sealing structure of the EGR valve cylinder to achieve a sealed state, and is lower than the pressure threshold required to drive the EGR valve to start opening.

[0008] Furthermore, the EGR valve cylinder is equipped with a one-way sealing structure, which can achieve a seal under the holding pressure to prevent gas from leaking from the exhaust port or gaps of the EGR valve cylinder.

[0009] Furthermore, it also includes a first pressure sensor; The first pressure sensor is installed in the input air path of the EGR proportional valve to detect the input air pressure and transmit it to the engine ECU controller; The engine ECU controller is also configured to: after the engine is powered on, read the input air pressure signal collected by the first pressure sensor, and when the input air pressure is lower than a first preset pressure threshold, generate a fault code and restrict the activation of the EGR function.

[0010] Furthermore, the preset holding pressure is 2.0 bar ± 0.3 bar; The first preset pressure threshold is 7.0 bar ± 0.2 bar.

[0011] Furthermore, it also includes a second pressure sensor; The second pressure sensor is located in the output air path of the EGR proportional valve or integrated inside the EGR proportional valve, and is used to detect the output pressure of the EGR proportional valve and feed it back to the engine ECU controller. The engine ECU controller performs closed-loop control of the EGR proportional valve based on the output pressure signal fed back by the second pressure sensor, so as to stabilize the output pressure of the EGR proportional valve at the target pressure value.

[0012] Secondly, embodiments of this application also provide a control method for the EGR system for preventing leakage as described in the first aspect, comprising the following steps: S1. After the vehicle is powered on, determine whether the conditions for performing pressure maintenance control are met; the conditions for performing pressure maintenance control include at least: the engine is powered on and there is currently no EGR rate requirement; S2. When the conditions for the execution pressure holding control are met, the EGR proportional valve is controlled to output a preset holding pressure to the EGR valve cylinder, so that the internal sealing structure of the EGR valve cylinder remains sealed, and the holding pressure output mode is entered. S3. In the pressure holding output mode, the output pressure of the EGR proportional valve is monitored in real time, and the control signal of the EGR proportional valve is adjusted through a closed-loop control algorithm to keep the actual output pressure within the allowable error range of the holding pressure. S4. When an EGR rate demand is received, exit the pressure holding output mode, calculate the target EGR valve opening based on the EGR rate demand, and then control the corresponding working pressure of the EGR proportional valve to drive the EGR valve to operate and adjust the exhaust gas flow from the exhaust pipe through the EGR cooler to the engine intake pipe.

[0013] Furthermore, the specific steps of step S1 are as follows: S11. After the vehicle is powered on, the engine ECU controller executes the EGR self-learning process, calibrates the fully open position parameters and fully closed position parameters of the EGR valve, and establishes a mapping relationship table between the EGR valve opening degree, control parameters and EGR valve cylinder pressure, which is stored in the non-volatile memory of the engine ECU controller; the control parameters are the duty cycle of the PWM signal driving the EGR proportional valve. S12. The engine ECU controller obtains the input air pressure value of the EGR proportional valve through the first pressure sensor. And determine the input air pressure value of the EGR proportional valve. Does it meet the requirements? ;in, The first preset pressure threshold; If so, the input air pressure is determined to be normal, and the process proceeds to step S13; Otherwise, an insufficient pressure fault code will be output, and the process will end. S13. Based on engine speed, load, and coolant temperature parameters, the engine ECU controller queries a pre-calibrated EGR rate MAP and calculates the required EGR rate. ; S14. Determine whether any of the following conditions are met: Current required EGR rate ; The engine is idling; The coolant temperature is lower than the set temperature. If so, it is determined that there is currently no requirement for EGR valve opening, and the conditions for performing pressure maintenance control are met; If not, determine that the conditions for maintaining pressure control are not met, and return to step S12.

[0014] Furthermore, the specific steps of step S2 are as follows: S21. The engine ECU controller determines and outputs a corresponding PWM control signal to the EGR proportional valve based on the preset holding pressure value, so as to drive the EGR proportional valve to output the holding pressure. ; S22. When the output pressure of the EGR proportional valve reaches and stabilizes at the holding pressure... When the error is within the allowable range, confirm that you are entering the pressure holding output mode.

[0015] Furthermore, the specific steps of step S3 are as follows: S31. The engine ECU controller reads the actual output pressure value of the EGR proportional valve in real time via the second pressure sensor. ; S32. Calculate the control increment using a PID closed-loop control algorithm. :

[0016]

[0017] in, , , These are the proportional, integral, and differential coefficients, respectively. The pressure deviation at the k-th sampling point; It is the cumulative sum of pressure deviations from the 0th sample to the kth sample; The current pressure is to maintain [stability / security]. It is the actual output pressure value of the EGR proportional valve at the kth sampling time; S33. Based on the control quantity increment Adjust the output PWM duty cycle:

[0018] in, This represents the PWM duty cycle output at the k-th sampling time. Through iteration, the actual output pressure of the EGR proportional valve is obtained. Maintaining stability under current pressure Within the permissible error range.

[0019] Furthermore, the specific steps of step S4 are as follows: S41. When the engine ECU controller calculates the required EGR rate At that time, based on the pre-calibrated EGR rate MAP, the required EGR rate is... Convert to target EGR valve opening ; S42. Based on the established mapping table, query the target EGR valve opening. Corresponding target work pressure ; S43. Control the output pressure of the EGR proportional valve from the current holding pressure. Smooth transition to target work pressure Furthermore, the transition process employs a ramp function, and the slope of the pressure change does not exceed a set slope threshold. S44. During the EGR working phase, at the target working pressure. As the target value for closed-loop control of the EGR proportional valve; S45. During the EGR operation phase, perform closed-loop control of step S3 on the EGR proportional valve to drive the EGR valve to maintain the target EGR valve opening. Corresponding opening degree; S46. After the EGR operation is completed, control the output pressure of the EGR proportional valve to return to the target operating pressure. Smooth transition back to maintaining pressure Furthermore, the transition process employs a ramp function.

[0020] As can be seen from the above technical solutions, this application has the following advantages: The EGR system and control method for preventing air leakage provided in this application employs intelligent pressure control and a closed-loop feedback mechanism to ensure stable operation of the EGR system under various working conditions, enhancing the system's reliability and adaptability. It eliminates the need for large-scale modifications to existing hardware; functional optimization can be achieved solely through software upgrades, reducing costs and simplifying the system structure. While ensuring sealing, it does not affect the normal function of the EGR valve, ensuring the EGR system can respond quickly when needed, maintaining good dynamic performance. This solves the problem of air leakage and abnormal noise in the EGR system's standby state, improving user experience, reducing misdiagnosis as faults, and lowering after-sales maintenance costs. Attached Figure Description

[0021] To more clearly illustrate the technical solution of this application, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the EGR system for preventing air leakage according to the present invention.

[0023] Figure 2 This is a schematic flowchart of the control method for the EGR system to prevent leakage according to the present invention.

[0024] Among them, 1-Engine ECU controller; 2-EGR cooler; 3-Engine; 4-Exhaust pipe; 5-EGR valve; 6-EGR valve cylinder; 7-EGR proportional valve; 8-First pressure sensor; 9-Second pressure sensor; 10-Vehicle compressed air source. Detailed Implementation

[0025] The various embodiments of this disclosure will be described more fully in the following detailed description of the leak-proof EGR system. This disclosure may have various embodiments, and adjustments and changes may be made therein. However, it should be understood that there is no intention to limit the various embodiments of this disclosure to the specific embodiments disclosed herein, but rather this disclosure should be understood to cover all adjustments, equivalents, and / or alternatives falling within the spirit and scope of the various embodiments of this disclosure.

[0026] For example, in the exhaust gas recirculation (EGR) system of modern internal combustion engines, especially commercial vehicle engines, the precise control of the EGR valve plays a crucial role in reducing nitrogen oxide emissions. Currently, EGR systems generally employ pneumatic actuators, which control the compressed air supply through the EGR proportional valve, driving the EGR valve cylinder to actuate, adjusting the EGR valve opening, and thus controlling the exhaust gas recirculation rate.

[0027] However, in practical applications, when the vehicle is powered on but the engine control unit (ECU) does not issue an EGR valve opening command, the EGR proportional valve, although closed, will still experience a small amount of gas leakage due to the relatively high input air pressure (8.5-10.5 bar) and mechanical limitations. This leaked gas enters the EGR valve cylinder, creating a low-pressure environment of approximately 0.3-1.8 bar, insufficient to activate the internal cylinder seals, causing continuous gas escape and producing a hissing noise. This abnormal phenomenon in non-operating conditions is often misdiagnosed as a pipeline leak or valve body damage, severely impacting user experience and product reputation, and increasing after-sales maintenance costs.

[0028] To address this issue, existing technologies primarily employ two methods: one is to improve the sealing materials and structural design of the EGR proportional valve to reduce the leakage rate in the closed state, but this significantly increases manufacturing costs; the other is to add mechanical silencers or damping elements, which can alleviate noise but fail to fundamentally solve the leakage problem and also increase the number of parts and assembly steps. Therefore, there is an urgent need for an innovative solution that does not increase hardware costs or complexity, fundamentally eliminating the abnormal noise caused by leakage in the EGR system during standby.

[0029] To address the aforementioned issues, this embodiment provides an EGR system that prevents air leakage and abnormal noises, optimizes sealing performance, improves system reliability, requires no hardware modifications, and reduces costs.

[0030] 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.

[0031] Please see Figure 1 The diagram shown is a schematic of an EGR system for preventing air leakage in a specific embodiment. The system includes an exhaust pipe 4, an EGR valve 5, an EGR cooler 2, an EGR proportional valve 7, and an engine ECU controller 1. The exhaust pipe 4 is connected to the exhaust manifold of the engine 3 and is used to guide engine exhaust gas. It should be noted that exhaust pipe 4 guides the engine exhaust gas to the EGR system, providing a stable airflow channel for exhaust gas recirculation, ensuring that the exhaust gas can smoothly enter the EGR cooler and improve the system operating efficiency; exhaust pipe 4 is tightly connected to the engine exhaust manifold, reducing the risk of exhaust gas leakage; The intake port of EGR valve 5 is connected to the exhaust pipe 4 through the EGR intake pipe to control the exhaust gas flow rate extracted from the exhaust pipe 4. The outlet port of EGR valve 5 is connected to the intake pipe of engine 3 through the EGR delivery pipe. It should be noted that EGR valve 5 precisely adjusts the flow rate of exhaust gas extracted from the exhaust pipe by controlling the opening of the intake and exhaust ports, meeting the engine's EGR rate requirements under different operating conditions and effectively reducing nitrogen oxide emissions; EGR valve 5 works in conjunction with EGR valve cylinder 6 to achieve sealing under pressure, preventing gas leakage when not in operation, thus solving the leakage problem in traditional EGR systems. EGR cooler 2 is installed on the EGR delivery pipeline to cool the flowing exhaust gas; It should be noted that the EGR cooler 2 cools the exhaust gas flowing through it, reducing the temperature of the exhaust gas entering the engine intake manifold, increasing the intake air density, optimizing the combustion process, and enhancing engine performance; the cooled exhaust gas reduces the heat load on the engine intake system and combustion chamber components, extending the engine's service life. The air inlet of the EGR proportional valve 7 is connected to the vehicle's compressed air source, and the air outlet of the EGR proportional valve 7 is connected to the drive mechanism of the EGR valve 5 through an air passage pipe. It should be noted that the EGR proportional valve 7, according to the instructions of the engine ECU controller 1, precisely outputs compressed air of different pressures to provide power to the EGR valve cylinder 6, thereby achieving precise control of the opening degree of the EGR valve 5; when the engine is powered on and the EGR valve 6 does not need to be opened, it outputs a preset holding pressure to ensure that the EGR valve cylinder 6 is sealed, prevent air leakage and abnormal noise, and improve the reliability of the system and the user experience. The engine ECU controller 1 is connected to the EGR proportional valve 7 and is used to control the output pressure of the EGR proportional valve 7; The driving mechanism of the EGR valve 5 is the EGR valve cylinder 6. The engine ECU controller 1 is configured to: after the engine is powered on, if it is determined that the EGR valve 5 does not need to be opened at present, control the EGR proportional valve 7 to output a preset holding pressure; The holding pressure is set to a value that enables the internal sealing structure of the EGR valve cylinder 6 to achieve a sealed state, and is lower than the pressure threshold required to drive the EGR valve 5 to start opening. It should be noted that the engine ECU controller 1 adjusts the output pressure of the EGR proportional valve 7 in real time according to the operating status of the engine 3 and the EGR requirements, thereby realizing intelligent control of the EGR system. In cooperation with the pressure sensor, it can detect abnormal input air pressure in a timely manner and generate fault codes to restrict the activation of the EGR function, avoid system failure due to insufficient air pressure, and enhance the safety and reliability of the system.

[0032] This embodiment effectively solves the problem of standby air leakage and abnormal noise in EGR systems, improving sealing performance and reliability. Through intelligent control, it optimizes costs, enhances user experience, adapts to various operating conditions, and ensures stable system operation.

[0033] Furthermore, as a refinement and extension of the specific implementation of the above embodiments, in order to fully illustrate the specific implementation process in this embodiment, another EGR system for preventing air leakage is provided, which includes an exhaust pipe 4, an EGR valve 5, an EGR cooler 2, an EGR proportional valve 7, and an engine ECU controller 1. The exhaust pipe 4 is connected to the exhaust manifold of the engine 3 and is used to guide engine exhaust gas. The intake port of EGR valve 5 is connected to the exhaust pipe 4 through the EGR intake pipe to control the exhaust gas flow rate extracted from the exhaust pipe 4. The outlet port of EGR valve 5 is connected to the intake pipe of engine 3 through the EGR delivery pipe. EGR cooler 2 is installed on the EGR delivery pipeline to cool the flowing exhaust gas; The air inlet of the EGR proportional valve 7 is connected to the vehicle's compressed air source, and the air outlet of the EGR proportional valve 7 is connected to the drive mechanism of the EGR valve 5 through an air passage pipe. The engine ECU controller 1 is connected to the EGR proportional valve 7 and is used to control the output pressure of the EGR proportional valve 7; The driving mechanism of the EGR valve 5 is the EGR valve cylinder 6. The engine ECU controller 1 is configured to: after the engine is powered on, if it is determined that the EGR valve 5 does not need to be opened at present, control the EGR proportional valve 7 to output a preset holding pressure; The holding pressure is set to a value that enables the internal sealing structure of the EGR valve cylinder 6 to achieve a sealed state, and is lower than the pressure threshold required to drive the EGR valve 5 to start opening. The EGR valve cylinder 6 is equipped with a one-way sealing structure inside. The one-way sealing structure can achieve a seal under the holding pressure to prevent gas from leaking from the exhaust port or gap of the EGR valve cylinder 6. It also includes a first pressure sensor 8; The first pressure sensor 8 is installed on the input air path (or vehicle compressed air storage device) of the EGR proportional valve 7 to detect the input air pressure and transmit it to the engine ECU controller 1; The engine ECU controller 1 is also configured to: after the engine is powered on, read the input air pressure signal collected by the first pressure sensor 8, and when the input air pressure is lower than a first preset pressure threshold, generate a fault code and restrict the activation of the EGR function; The preset holding pressure is 2.0 bar ± 0.3 bar; The first preset pressure threshold is 7.0 bar ± 0.2 bar; It also includes a second pressure sensor 9; The second pressure sensor 9 is located in the output air path of the EGR proportional valve 7 or integrated inside the EGR proportional valve 7, and is used to detect the output pressure of the EGR proportional valve 7 and feed it back to the engine ECU controller 1. The engine ECU controller 1 performs closed-loop control on the EGR proportional valve 7 based on the output pressure signal fed back by the second pressure sensor 9, so as to stabilize the output pressure of the EGR proportional valve 7 at the target pressure value. For example, the engine ECU controller 1 uses a high-performance microprocessor with a main frequency of not less than 1GHz, has a built-in 1MB non-volatile memory for storing calibration parameters and mapping relationship tables, supports CAN bus communication rate of 500kbps, has multi-channel PWM signal output function (output accuracy ±1%), and can process pressure sensor feedback signals in real time and execute closed-loop control algorithms. EGR cooler 2 adopts a plate-fin structure with a cooling efficiency of ≥85%, a rated operating temperature range of -40℃ to 400℃, a maximum allowable exhaust gas flow of 120kg / h, and a pressure loss of ≤5kPa (at rated flow). It is adapted to the engine exhaust temperature characteristics to ensure that the exhaust gas meets the requirements of the intake system after cooling. Engine 3 uses the MC07(H) series commercial internal combustion engine with a displacement of 7L, a maximum power of 245kW, and a maximum torque of 1200N. m, coolant temperature normal operating range 80℃~90℃, idle speed 650r / min±50r / min, supports EGR rate adjustable from 0~30%; The exhaust pipe 4 is made of stainless steel with an inner diameter of φ80mm. It is connected to the engine exhaust manifold flange and the connection is sealed with a high-temperature resistant gasket. The leakage rate is ≤0.5L / min (at 1 bar pressure) to ensure no leakage during the exhaust gas delivery process. EGR valve 5 adopts a pneumatic butterfly valve structure with a valve diameter of φ50mm, a fully open response time of ≤150ms, a fully closed sealing pressure of ≥0.3bar, and an opening adjustment accuracy of ±1%. It is rigidly connected to EGR valve cylinder 6 to ensure consistent action under pressure drive. The EGR valve cylinder 6 is a single-acting cylinder with a cylinder diameter of φ40mm and a stroke of 20mm. It has a built-in one-way sealing structure (using fluororubber seals), a sealing activation pressure of ≤1.7bar, and an opening pressure threshold of 3.8bar±0.2bar, ensuring reliable sealing under the holding pressure without affecting normal opening action. The EGR proportional valve 7 is an electronically controlled proportional pressure valve with an input pressure range of 6~12 bar, an output pressure adjustment range of 0~8 bar, a pressure control accuracy of ±0.1 bar, a response time of ≤20ms, a built-in pressure feedback channel, and supports PWM signal control (control voltage 12V, duty cycle 0~100%). The first pressure sensor 8 has a range of 0~16 bar, a measurement accuracy of ±0.5%FS, and an output signal of 4~20mA. It is installed on the air pipeline between the vehicle's compressed air source and the EGR proportional valve, with a sampling frequency of 100Hz, and is used to detect the input air pressure in real time. The second pressure sensor 9 is integrated inside the EGR proportional valve 7, with a range of 0~10 bar, a measurement accuracy of ±0.3%FS, an output signal of 0~5V, a sampling frequency of 200Hz, and real-time feedback of the proportional valve output pressure.

[0034] The vehicle compressed air source 10 uses an air tank with a volume of 20L, a rated output pressure of 9.5bar±0.5bar, and a pressure stability of ≤±0.2bar / min, providing a continuous and stable supply of compressed air to the EGR proportional valve 7; One end of the exhaust pipe 4 is fixedly connected to the exhaust manifold of the engine 3 via a flange, and the other end extends to the exhaust gas treatment device. The EGR intake pipe branches off in the middle of the exhaust pipe 4 and is sealed to the intake port of the EGR valve 5 via a quick-connect fitting. The outlet of EGR valve 5 is connected to the intake pipe of engine 3 through EGR delivery pipeline. EGR cooler 2 is connected in series on EGR delivery pipeline, and both ends are connected by clamp-type sealing to ensure that exhaust gas flows through the cooler throughout the entire process. The vehicle compressed air source 10 is connected to the air inlet of the EGR proportional valve 7 through a high-pressure air pipeline. The first pressure sensor 8 is connected in series in the air pipeline, and the sensor signal line is connected to the analog signal input channel of the engine ECU controller 1. The outlet of the EGR proportional valve 7 is connected to the inlet of the EGR valve cylinder 6 through an air passage pipe. The detection end of the second pressure sensor 9 is located inside the air passage pipe. The feedback signal line is directly connected to the signal interface of the EGR proportional valve 7 and then communicates with the engine ECU controller 1 through the CAN bus. The engine ECU controller 1 is connected to the control terminal of the EGR proportional valve 7 and the sensor group (speed sensor, load sensor, coolant temperature sensor) of the engine 3 through the control wiring harness to realize signal acquisition and command output.

[0035] like Figure 2 As shown, the following are embodiments of the control method for preventing leakage of an EGR system provided in this disclosure. This method belongs to the same inventive concept as the EGR system for preventing leakage in the above embodiments. For details not described in detail in the embodiments of the control method for preventing leakage of an EGR system, please refer to the embodiments of the EGR system for preventing leakage described above.

[0036] The method includes the following steps: S1. After the vehicle is powered on, determine whether the conditions for performing pressure maintenance control are met; the conditions for performing pressure maintenance control include at least: the engine is powered on and there is currently no EGR rate requirement; It should be noted that by determining whether the engine is powered on and whether there is currently no EGR rate requirement, the system can accurately determine whether pressure maintenance control needs to be performed, thus avoiding unnecessary control operations and improving the system's operating efficiency. S2. When the conditions for the execution pressure holding control are met, the EGR proportional valve is controlled to output a preset holding pressure to the EGR valve cylinder, so that the internal sealing structure of the EGR valve cylinder remains sealed, and the holding pressure output mode is entered. It should be noted that when the conditions for pressure holding control are met, the EGR proportional valve is controlled to output a preset holding pressure, which keeps the internal sealing structure of the EGR valve cylinder sealed, effectively solving the air leakage problem in the standby state and improving the system's sealing performance and reliability. By monitoring the output pressure in real time and confirming that it is stable within the allowable error range, the system is ensured to smoothly enter the holding pressure output mode, avoiding the impact of pressure fluctuations on the system. S3. In the pressure holding output mode, the output pressure of the EGR proportional valve is monitored in real time, and the control signal of the EGR proportional valve is adjusted through a closed-loop control algorithm to keep the actual output pressure within the allowable error range of the holding pressure. It should be noted that the PID closed-loop control algorithm is used to adjust the output pressure of the EGR proportional valve in real time, so that it is kept within the allowable error range of the holding pressure, which improves the control accuracy and stability of the system and ensures that the EGR valve cylinder can reliably seal under the holding pressure. The PWM duty cycle is dynamically adjusted by the closed-loop control algorithm, which enables the system to adapt to changes in air pressure in real time, thereby enhancing the adaptability and reliability of the system. S4. When an EGR rate demand is received, exit the pressure holding output mode, calculate the target EGR valve opening based on the EGR rate demand, and then control the corresponding working pressure of the EGR proportional valve to drive the EGR valve to operate and adjust the exhaust gas flow from the exhaust pipe through the EGR cooler to the engine intake pipe. It should be noted that when an EGR rate demand is received, the system can quickly exit the pressure-maintaining output mode, calculate the target EGR valve opening according to the demand, and control the EGR proportional valve to output the corresponding working pressure, thus realizing flexible switching of the system under different operating conditions.

[0037] This embodiment effectively solves the problem of air leakage and abnormal noise in the EGR system in standby mode through intelligent pressure control and closed-loop feedback mechanism, improving the system's sealing performance and reliability; no hardware modifications are required, and functional optimization is achieved only through software upgrades, reducing costs while enhancing the system's dynamic response performance and adapting to various operating conditions.

[0038] Furthermore, as a refinement and extension of the specific implementation of the above embodiments, in order to fully illustrate the specific implementation process of this embodiment, another control method for preventing air leakage in an EGR system is provided. The specific steps of this control method are as follows: S1. After the vehicle is powered on, determine whether the conditions for performing pressure maintenance control are met; the conditions for performing pressure maintenance control include at least: the engine is powered on and there is currently no EGR rate requirement; the specific steps of step S1 are as follows: S11. After the vehicle is powered on, the engine ECU controller executes the EGR self-learning process, calibrates the fully open position parameters and fully closed position parameters of the EGR valve, and establishes a mapping relationship table between the EGR valve opening degree, control parameters and EGR valve cylinder pressure, which is stored in the non-volatile memory of the engine ECU controller; the control parameters are the duty cycle of the PWM signal driving the EGR proportional valve. For example, after the vehicle is powered on (12V power is connected), the engine ECU controller 1 immediately starts the EGR system self-learning process, which takes about 2 seconds. The specific process is as follows: The PWM signal output by the engine ECU controller 1 increases linearly from 0% to 100% (gradual change time 500ms), driving the EGR proportional valve 7 to increase the output pressure from 0 bar to the maximum output pressure. The PWM duty cycle (calibrated value about 85%) and the corresponding EGR valve cylinder 6 pressure (calibrated value about 6.2 bar) when the EGR valve 5 reaches the fully open position are recorded. Subsequently, the PWM signal duty cycle linearly decreased from 100% to 0% (gradual change time 500ms), and the PWM duty cycle (calibrated value about 5%) and the corresponding cylinder pressure (calibrated value about 0.2bar) when EGR valve 5 reached the fully closed position were recorded. Based on the above calibration parameters, a three-dimensional mapping table of EGR valve opening (0%~100%), PWM signal duty cycle (5%~85%) and EGR valve cylinder pressure (0.2bar~6.2bar) is established and stored in the ECU's non-volatile memory for subsequent control calls. S12. The engine ECU controller obtains the input air pressure value of the EGR proportional valve through the first pressure sensor. And determine the input air pressure value of the EGR proportional valve. Does it meet the requirements? ;in, The first preset pressure threshold; If so, the input air pressure is determined to be normal, and the process proceeds to step S13; Otherwise, an insufficient pressure fault code will be output, and the process will end. For example, after the self-learning process is completed, the engine ECU controller 1 acquires the input air pressure signal through the first pressure sensor 8, with a sampling time of 500ms, and takes the average value of 100 sampling points as the detection result: If the detected input air pressure is ≥7.0 bar ±0.2 bar (i.e. 6.8 bar ~ 7.2 bar), the input air pressure is determined to be normal, and the EGR rate requirement judgment stage is entered. If the detected input air pressure is <6.8 bar, the engine ECU controller 1 immediately generates a fault code P0XXX (a custom fault code that indicates insufficient input pressure of the EGR system), sends it to the vehicle instrument panel via the CAN bus, and restricts the activation of the EGR function until the input air pressure returns to normal and the fault code is cleared. S13. Based on engine speed, load, and coolant temperature parameters, the engine ECU controller queries a pre-calibrated EGR rate MAP and calculates the required EGR rate. ; S14. Determine whether any of the following conditions are met: Current required EGR rate ; The engine is idling; The coolant temperature is lower than the set temperature (e.g., 60°C). If so, it is determined that there is currently no requirement for EGR valve opening, and the conditions for performing pressure maintenance control are met; If not, determine that the conditions for maintaining pressure control are not met, and return to step S12; For example, the engine ECU controller 1, based on the real-time operating parameters of the engine 3, including engine speed (obtained via a crankshaft position sensor), load (calculated jointly by a throttle pedal position sensor and an intake pressure sensor), and coolant temperature (obtained via a coolant temperature sensor), queries a pre-calibrated EGR rate MAP to calculate the current required EGR rate. If any of the following conditions are met, it is determined that there is currently no EGR valve opening requirement, and the conditions for performing pressure maintenance control are met: The calculated current required EGR rate is ≤0% (i.e., there is no need for exhaust gas recirculation). The engine is idling (speed 650r / min ± 50r / min). Coolant temperature < 60℃ (cold start condition).

[0039] If none of the above conditions are met, it is determined that there is an EGR valve opening requirement. Pressure maintenance control is not performed, and the EGR working mode is directly entered according to the EGR rate requirement. S2. When the conditions for maintaining the pressure are met, the EGR proportional valve is controlled to output a preset maintaining pressure to the EGR valve cylinder, so that the internal sealing structure of the EGR valve cylinder remains sealed, and the system enters the maintaining pressure output mode; the specific steps of step S2 are as follows: S21. The engine ECU controller determines and outputs a corresponding PWM control signal to the EGR proportional valve based on the preset holding pressure value, so as to drive the EGR proportional valve to output the holding pressure. ; S22. When the output pressure of the EGR proportional valve reaches and stabilizes at the holding pressure... When the error is within the allowable range, confirm entry into the pressure holding output mode; For example, when the pressure holding control condition is met, the engine ECU controller 1 performs the following operations: Query the PWM signal duty cycle (calibrated value approximately 25%) corresponding to the preset holding pressure (2.0 bar ± 0.3 bar, i.e. 1.7 bar ~ 2.3 bar) from the mapping table, and output the PWM control signal with this duty cycle to the EGR proportional valve 7; According to the received PWM signal, the EGR proportional valve 7 outputs a holding pressure of 1.7 bar to 2.3 bar to the EGR valve cylinder 6. This pressure acts on the one-way sealing structure inside the cylinder, so that the seal tightly fits the sealing surface and prevents gas from leaking from the cylinder exhaust port or gaps. The engine ECU controller 1 monitors the output pressure in real time through the second pressure sensor 9. When the output pressure stabilizes within the range of 1.7 bar to 2.3 bar (fluctuation range ≤ ±0.1 bar, duration 100 ms), it confirms that it has entered the pressure holding output mode. S3. In the pressure holding output mode, the output pressure of the EGR proportional valve is monitored in real time, and the control signal to the EGR proportional valve is adjusted through a closed-loop control algorithm to maintain the actual output pressure within the allowable error range of the holding pressure; the specific steps of step S3 are as follows: S31. The engine ECU controller reads the actual output pressure value of the EGR proportional valve in real time via the second pressure sensor. ; S32. Calculate the control increment using a PID closed-loop control algorithm. :

[0040]

[0041] in, , , These are the proportional, integral, and differential coefficients, respectively. The pressure deviation at the k-th sampling point; It is the cumulative sum of pressure deviations from the 0th sample to the kth sample; The current pressure is to maintain [stability / security]. It is the actual output pressure value of the EGR proportional valve at the kth sampling time; S33. Based on the control quantity increment Adjust the output PWM duty cycle:

[0042] in, This represents the PWM duty cycle output at the k-th sampling time. Through iteration, the actual output pressure of the EGR proportional valve is obtained. Maintaining stability under current pressure Within the allowable error range; For example, in the pressure-maintaining output mode, the engine ECU controller 1 uses a PID closed-loop control algorithm to maintain stable output pressure, and the specific process is as follows: The second pressure sensor 9 collects the actual output pressure value of the EGR proportional valve 7 in real time at a frequency of 200Hz and feeds it back to the engine ECU controller 1. Engine ECU controller 1 calculates the pressure deviation at the kth sampling point. (in (Set to 2.0 bar). Calculate the control increment based on the PID algorithm :

[0043] The proportionality coefficient =2.5, integral coefficient =0.5, differential coefficient =0.1; Based on the control increment Adjust the output PWM duty cycle: ,in The PWM duty cycle is set at the k-th sampling time, ensuring that the PWM duty cycle is within the effective range of 5% to 85%. Through the above iterative control, the actual output pressure of EGR proportional valve 7 is stabilized within the allowable error range of 2.0 bar ± 0.3 bar, with a fluctuation range ≤ ± 0.1 bar; S4. When an EGR rate demand is received, exit the pressure-maintaining output mode, calculate the target EGR valve opening based on the EGR rate demand, and then control the corresponding working pressure of the EGR proportional valve to drive the EGR valve to operate, thereby adjusting the exhaust gas flow from the exhaust pipe through the EGR cooler to the engine intake pipe; the specific steps of step S4 are as follows: S41. When the engine ECU controller calculates the required EGR rate At that time, based on the pre-calibrated EGR rate MAP, the required EGR rate is... Convert to target EGR valve opening ; S42. Based on the established mapping table, query the target EGR valve opening. Corresponding target work pressure ; S43. Control the output pressure of the EGR proportional valve from the current holding pressure. Smooth transition to target work pressure Furthermore, the transition process employs a ramp function, and the slope of the pressure change does not exceed a set slope threshold (e.g., 0.3 bar / 10 ms). S44. During the EGR working phase, at the target working pressure. As the target value for closed-loop control of the EGR proportional valve; S45. During the EGR operation phase, perform closed-loop control of step S3 on the EGR proportional valve to drive the EGR valve to maintain the target EGR valve opening. Corresponding opening degree; S46. After the EGR operation is completed, control the output pressure of the EGR proportional valve to return to the target operating pressure. Smooth transition back to maintaining pressure Furthermore, the transition process employs a ramp function; For example, when the engine operating conditions change and the required EGR rate calculated by the engine ECU controller 1 is > 0%, the start-up mode switching process is as follows: The engine ECU controller 1 queries the EGR rate MAP based on the calculated required EGR rate and converts it into the target EGR valve opening (e.g., an EGR rate of 15% corresponds to a target opening of 50%). Based on the target EGR valve opening, the corresponding target working pressure is queried from the three-dimensional mapping table (e.g., a target opening of 50% corresponds to a target pressure of 3.5 bar). The output pressure of the EGR proportional valve 7 is smoothly transitioned from the current holding pressure to the target working pressure. The transition process uses a ramp function with a pressure change slope ≤ 0.3 bar / 10 ms (i.e., 30 bar / s) to avoid sudden pressure changes that could cause shock to the EGR valve. After entering the EGR working stage, the target working pressure is used as the target value for closed-loop control. The PID closed-loop control process of step S3 is repeated to drive the EGR valve 5 to maintain the position corresponding to the target opening, and precisely adjust the exhaust gas flow from the exhaust pipe 4 through the EGR cooler 2 to the engine intake pipe to achieve the target EGR rate. When EGR operation ends (required EGR rate ≤ 0%), the output pressure of the EGR proportional valve 7 smoothly transitions from the target operating pressure back to the holding pressure (2.0 bar ± 0.3 bar) according to the same ramp function, and re-enters the holding pressure output mode.

[0044] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0045] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An EGR system for preventing air leakage, characterized in that, Includes exhaust pipe (4), EGR valve (5), EGR cooler (2), EGR proportional valve (7) and engine ECU controller (1); The exhaust pipe (4) is connected to the exhaust manifold of the engine (3) and is used to guide engine exhaust gas; The intake port of the EGR valve (5) is connected to the exhaust pipe (4) through the EGR intake pipe to control the exhaust gas flow rate extracted from the exhaust pipe (4). The outlet port of the EGR valve (5) is connected to the intake pipe of the engine (3) through the EGR delivery pipe. The EGR cooler (2) is installed on the EGR delivery pipeline to cool the exhaust gas flowing through it; The air inlet of the EGR proportional valve (7) is connected to the vehicle compressed air source (10), and the air outlet of the EGR proportional valve (7) is connected to the drive mechanism of the EGR valve (5) through an air passage. The engine ECU controller (1) is connected to the EGR proportional valve (7) and is used to control the output pressure of the EGR proportional valve (7); The driving mechanism of the EGR valve (5) is the EGR valve cylinder (6). The engine ECU controller (1) is configured to: after the engine is powered on, if it is determined that the EGR valve (5) does not need to be opened at present, control the EGR proportional valve (7) to output a preset holding pressure; The holding pressure is set to a value that enables the internal sealing structure of the EGR valve cylinder (6) to achieve a sealed state and is lower than the pressure threshold required to drive the EGR valve (5) to start opening.

2. The EGR system for preventing air leakage according to claim 1, characterized in that, The EGR valve cylinder (6) is equipped with a one-way sealing structure inside. The one-way sealing structure can achieve a seal under the holding pressure to prevent gas from leaking from the exhaust port or gap of the EGR valve cylinder (6).

3. The EGR system for preventing air leakage according to claim 1, characterized in that, It also includes a first pressure sensor (8); The first pressure sensor (8) is installed in the input air path of the EGR proportional valve (7) to detect the input air pressure and transmit it to the engine ECU controller (1). The engine ECU controller (1) is also configured to: after the engine is powered on, read the input air pressure signal collected by the first pressure sensor (8), and when the input air pressure is lower than the first preset pressure threshold, generate a fault code and restrict the activation of the EGR function.

4. The EGR system for preventing air leakage according to claim 3, characterized in that, The preset holding pressure is 2.0 bar ± 0.3 bar; The first preset pressure threshold is 7.0 bar ± 0.2 bar.

5. The EGR system for preventing air leakage according to claim 1, characterized in that, It also includes a second pressure sensor (9); The second pressure sensor (9) is located in the output air path of the EGR proportional valve (7) or integrated inside the EGR proportional valve (7) to detect the output pressure of the EGR proportional valve (7) and feed it back to the engine ECU controller (1). The engine ECU controller (1) performs closed-loop control on the EGR proportional valve (7) based on the output pressure signal fed back by the second pressure sensor (9) so that the output pressure of the EGR proportional valve (7) is stabilized at the target pressure value.

6. A control method for an EGR system for preventing leakage as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. After the vehicle is powered on, determine whether the conditions for performing pressure maintenance control are met; the conditions for performing pressure maintenance control include at least: the engine is powered on and there is currently no EGR rate requirement; S2. When the conditions for the execution pressure holding control are met, the EGR proportional valve is controlled to output a preset holding pressure to the EGR valve cylinder, so that the internal sealing structure of the EGR valve cylinder remains sealed, and the holding pressure output mode is entered. S3. In the pressure holding output mode, the output pressure of the EGR proportional valve is monitored in real time, and the control signal of the EGR proportional valve is adjusted through a closed-loop control algorithm to keep the actual output pressure within the allowable error range of the holding pressure. S4. When an EGR rate demand is received, exit the pressure holding output mode, calculate the target EGR valve opening based on the EGR rate demand, and then control the corresponding working pressure of the EGR proportional valve to drive the EGR valve to operate and adjust the exhaust gas flow from the exhaust pipe through the EGR cooler to the engine intake pipe.

7. The control method for an EGR system to prevent leakage according to claim 6, characterized in that, The specific steps of step S1 are as follows: S11. After the vehicle is powered on, the engine ECU controller executes the EGR self-learning process, calibrates the fully open position parameters and fully closed position parameters of the EGR valve, and establishes a mapping relationship table between the EGR valve opening degree, control parameters and EGR valve cylinder pressure, which is stored in the non-volatile memory of the engine ECU controller. The control parameter is the duty cycle of the PWM signal driving the EGR proportional valve; S12. The engine ECU controller obtains the input air pressure value of the EGR proportional valve through the first pressure sensor. And determine the input air pressure value of the EGR proportional valve. Does it meet the requirements? ;in, The first preset pressure threshold; If so, the input air pressure is determined to be normal, and the process proceeds to step S13; Otherwise, an insufficient pressure fault code will be output, and the process will end. S13. Based on engine speed, load, and coolant temperature parameters, the engine ECU controller queries a pre-calibrated EGR rate MAP and calculates the required EGR rate. ; S14. Determine whether any of the following conditions are met: Current required EGR rate ; The engine is idling; The coolant temperature is lower than the set temperature. If so, it is determined that there is currently no requirement for EGR valve opening, and the conditions for performing pressure maintenance control are met; If not, determine that the conditions for maintaining pressure control are not met, and return to step S12.

8. The control method for an EGR system to prevent leakage according to claim 7, characterized in that, The specific steps of step S2 are as follows: S21. The engine ECU controller determines and outputs a corresponding PWM control signal to the EGR proportional valve based on the preset holding pressure value, so as to drive the EGR proportional valve to output the holding pressure. ; S22. When the output pressure of the EGR proportional valve reaches and stabilizes at the holding pressure... When the error is within the allowable range, confirm that you are entering the pressure holding output mode.

9. The control method for an EGR system to prevent leakage according to claim 8, characterized in that, The specific steps of step S3 are as follows: S31. The engine ECU controller reads the actual output pressure value of the EGR proportional valve in real time via the second pressure sensor. ; S32. Calculate the control increment using a PID closed-loop control algorithm. : in, , , These are the proportional, integral, and differential coefficients, respectively. The pressure deviation at the k-th sampling point; It is the cumulative sum of pressure deviations from the 0th sample to the kth sample; The current pressure is to maintain [stability / security]. It is the actual output pressure value of the EGR proportional valve at the kth sampling time; S33. Based on the control quantity increment Adjust the output PWM duty cycle: in, This represents the PWM duty cycle output at the k-th sampling time. Through iteration, the actual output pressure of the EGR proportional valve is obtained. Maintaining stability under current pressure Within the permissible error range.

10. The control method for an EGR system to prevent leakage according to claim 9, characterized in that, The specific steps of step S4 are as follows: S41. When the engine ECU controller calculates the required EGR rate At that time, based on the pre-calibrated EGR rate MAP, the required EGR rate is... Convert to target EGR valve opening ; S42. Based on the established mapping table, query the target EGR valve opening. Corresponding target work pressure ; S43. Control the output pressure of the EGR proportional valve from the current holding pressure. Smooth transition to target work pressure Furthermore, the transition process employs a ramp function, and the slope of the pressure change does not exceed a set slope threshold. S44. During the EGR working phase, at the target working pressure. As the target value for closed-loop control of the EGR proportional valve; S45. During the EGR operation phase, perform closed-loop control of step S3 on the EGR proportional valve to drive the EGR valve to maintain the target EGR valve opening. Corresponding opening degree; S46. After the EGR operation is completed, control the output pressure of the EGR proportional valve to return to the target operating pressure. Smooth transition back to maintaining pressure Furthermore, the transition process employs a ramp function.

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