Flow diagnosis device and method of exhaust gas recirculation system and engine

Abstract

The embodiment of the invention provides a flow diagnosis device and method of an exhaust gas recirculation system and an engine. The device comprises an EGR intercooler, an EGR valve, a first temperature sensor, a second temperature sensor, a differential pressure sensor, a turbine, a gas compressor, an air filter, an intake and exhaust system, a first pipeline, a second pipeline, a third pipeline, a fourth pipeline, a fifth pipeline and a sixth pipeline. An EGR intercooler and an EGR valve are arranged on the first pipeline, a first temperature sensor is arranged in front of the EGR valve, a second temperature sensor is arranged behind the EGR valve, the two ends of the EGR valve are connected with a differential pressure sensor, the turbine is connected with a gas compressor through a third pipeline, the gas compressor is connected with an air filter through a fourth pipeline, and the air filter is connected with a second pipeline. And the turbine is connected with the intake and exhaust system through a fifth pipeline, and the gas compressor is connected with the intake and exhaust system through a sixth pipeline, so that high-flow diagnosis and low-flow diagnosis of the low-pressure EGR system can be realized, the vehicle cost is reduced, and the space of an engine compartment is saved.

Description

Technical Field

[0001] The present invention relates to the technical field of exhaust gas recirculation, and in particular to a flow rate diagnosis device, method and engine of an exhaust gas recirculation system. Background Art

[0002] Exhaust Gas Recirculation (EGR) refers to returning part of the exhaust gas discharged by the engine to the intake manifold and re-entering the cylinder together with the fresh mixed gas. Since the exhaust gas contains a large amount of polyatomic gases such as CO2, which cannot be burned but absorbs a large amount of heat due to its high specific heat capacity, the maximum combustion temperature of the mixed gas in the cylinder is reduced, thereby reducing NO x The amount of generation.

[0003] Exhaust gas recirculation of automobile engines is a key technology for automobile energy conservation and emission reduction because it can significantly reduce fuel consumption, emissions and suppress knocking. It is currently widely used. There are two common EGR application technologies for supercharged engines: high-pressure EGR technology and low-pressure EGR technology. High-pressure EGR technology takes air before the turbine and has a higher pressure, so it is called high-pressure EGR technology. Low-pressure EGR technology takes air after the turbine, and the gas pressure is lower after the turbine works (generally, air is taken after the three-way catalytic converter). Low-pressure EGR technology is more widely used due to its low cost and wide range of application conditions. However, the disadvantage of low-pressure EGR technology is that the pressure difference is low, so a mixing valve must be used in conjunction to meet the flow requirements in all working conditions, which makes the vehicle cost higher and wastes space in the engine compartment. Summary of the invention

[0004] In view of this, an embodiment of the present invention provides a flow diagnosis device, method and engine for an exhaust gas recirculation system, so as to realize high flow diagnosis and low flow diagnosis of a low-pressure EGR system, reduce vehicle costs and save space in the engine compartment.

[0005] On the one hand, an embodiment of the present invention provides a flow diagnostic device for an exhaust gas recirculation system, comprising: an EGR intercooler, an EGR valve, a first temperature sensor, a second temperature sensor, a differential pressure sensor, a turbine, a compressor, an air filter, an intake and exhaust system, a first pipeline, a second pipeline, a third pipeline, a fourth pipeline, a fifth pipeline, and a sixth pipeline; The second pipeline is connected to the first end of the first pipeline and the turbine respectively, the EGR intercooler and the EGR valve are arranged on the first pipeline, the first temperature sensor is arranged before the EGR valve, and the second temperature sensor is arranged after the EGR valve, both ends of the EGR valve are connected to the pressure difference sensor, the second end of the first pipeline is connected to the fourth pipeline, the turbine is connected to the compressor through the third pipeline, the compressor is connected to the air filter through the fourth pipeline, the turbine is connected to the intake and exhaust system through the fifth pipeline, and the compressor is connected to the intake and exhaust system through the sixth pipeline.

[0006] Optionally, it also includes: a pressure relief valve and a bypass valve; The pressure relief valve is connected to the fourth pipeline and the sixth pipeline respectively; The bypass valve is connected to the second pipeline and the fifth pipeline respectively.

[0007] Optionally, it also includes: a throttle valve and a first intake air temperature and pressure sensor, the throttle valve is installed on the sixth pipe, the compressor is connected to the intake and exhaust system through the sixth pipe and the throttle valve, and the first intake air temperature and pressure sensor is installed in the sixth pipe between the compressor and the throttle valve.

[0008] Optionally, it also includes: a second intake air temperature and pressure sensor; The intake and exhaust system includes an exhaust manifold and an intake manifold. The turbine is connected to the exhaust manifold through the fifth pipeline, and the compressor is connected to the intake manifold through the sixth pipeline. The second intake temperature and pressure sensor is installed in the intake manifold.

[0009] On the other hand, an embodiment of the present invention provides a flow rate diagnosis method for an exhaust gas recirculation system, which is applied to the flow rate diagnosis device for the exhaust gas recirculation system, comprising: After the vehicle is running and the engine is started, obtaining a pre-valve temperature value of the first temperature sensor and a post-valve temperature value of the second temperature sensor within a first time period; It is determined whether the exhaust gas recirculation system has a high flow fault according to the difference between the pre-valve pressure value and the post-valve pressure value.

[0010] Optionally, after obtaining the pre-valve temperature value of the first temperature sensor and the post-valve temperature value of the second temperature sensor within the first time period, the method further includes: When the temperature signals satisfying both the pre-valve temperature value and the post-valve temperature value are normal and the EGR valve is in a closed condition, it is determined whether the exhaust gas recirculation system has a high flow fault according to the difference between the pre-valve pressure value and the post-valve pressure value.

[0011] Optionally, judging whether the exhaust gas recirculation system has a high flow fault according to the difference between the pre-valve pressure value and the post-valve pressure value includes: When the difference between the pre-valve pressure value and the post-valve pressure value is greater than a set pressure threshold, it is determined that a high flow fault exists in the exhaust gas recirculation system.

[0012] Optionally, it also includes: When the EGR valve is in a closed state and stabilizes for a first time threshold, the engine management system sends a control request to the hybrid control unit to coordinate the engine to the working range of the EGR valve, and obtains the valve front pressure value and valve rear pressure value of the pressure difference sensor, and the valve front temperature value of the first temperature sensor; Generate an actual EGR flow rate according to the pre-valve pressure value, the post-valve pressure value and the pre-valve temperature value; It is determined whether the exhaust gas recirculation system has a low flow fault according to the actual EGR flow and the set target EGR flow.

[0013] Optionally, judging whether the exhaust gas recirculation system has a low flow fault according to the actual EGR flow and the set target EGR flow includes: When the absolute value of the difference between the actual EGR flow rate and the set target EGR flow rate is greater than a set flow rate threshold, it is determined that a low flow rate fault exists in the exhaust gas recirculation system.

[0014] On the other hand, an embodiment of the present invention provides an engine, comprising the flow diagnostic device of the exhaust gas recirculation system mentioned above.

[0015] In the technical solution provided by the embodiment of the present invention, the flow diagnostic device of the exhaust gas recirculation system includes: an EGR intercooler, an EGR valve, a first temperature sensor, a second temperature sensor, a pressure difference sensor, a turbine, a compressor, an air filter, an intake and exhaust system, a first pipeline, a second pipeline, a third pipeline, a fourth pipeline, a fifth pipeline and a sixth pipeline; the first pipeline is provided with an EGR intercooler and an EGR valve, a first temperature sensor is provided in front of the EGR valve, a second temperature sensor is provided after the EGR valve, both ends of the EGR valve are connected to the pressure difference sensor, the turbine is connected to the compressor through the third pipeline, the compressor is connected to the air filter through the fourth pipeline, the turbine is connected to the intake and exhaust system through the fifth pipeline, and the compressor is connected to the intake and exhaust system through the sixth pipeline, which can realize high flow diagnosis and low flow diagnosis of the low-pressure EGR system, reduce vehicle costs, and save space in the engine compartment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 A schematic diagram of a flow diagnostic device for an exhaust gas recirculation system provided in the related art; Figure 2 A schematic diagram of a flow diagnostic device for an exhaust gas recirculation system provided by an embodiment of the present invention; Figure 3 A schematic diagram of another flow diagnostic device for an exhaust gas recirculation system provided by an embodiment of the present invention; Figure 4 A flow chart of a method for diagnosing flow of an exhaust gas recirculation system provided by one embodiment of the present invention; Figure 5 A flow chart of another exhaust gas recirculation system flow diagnosis method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0018] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0019] It should be clear that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0021] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0022] GB18352.6-2016 standard includes the diagnostic monitoring of high and low flow of gasoline engine EGR valve as a mandatory requirement. The related technology provides a flow diagnostic device for exhaust gas recirculation system. Figure 1 A schematic diagram of a flow diagnostic device for an exhaust gas recirculation system provided in the related art is shown in FIG. Figure 1 As shown, the following schemes are available for diagnosing the high and low flow of the EGR valve in the low-pressure EGR system of a gasoline hybrid vehicle: In the related art, the flow diagnostic device of the exhaust gas recirculation system includes: an EGR intercooler 11, an EGR valve 12, a first temperature sensor 101, a pressure difference sensor 103, a catalyst 10, a turbine 13, a compressor 14, an EGR mixing valve 20, an air filter 15, a pressure relief valve 19, a bypass valve 18, a throttle valve 16, an exhaust manifold 171, an intake manifold 172, a first pipe, a second pipe, a third pipe, a fourth pipe, a fifth pipe and a sixth pipe.

[0023] The second pipeline is connected to the first end of the first pipeline and the catalyst 10 respectively, the catalyst 10 is connected to the turbine 13 through the second pipeline, the first pipeline is provided with an EGR intercooler 11 and an EGR valve 12, a first temperature sensor 101 is provided in front of the EGR valve, both ends of the EGR valve 12 are connected to the pressure difference sensor 103, the second end of the first pipeline is connected to the fourth pipeline, the turbine 13 is connected to the compressor 14 through the third pipeline, the compressor 14 is connected to the EGR mixing valve 20 and the air filter 15 through the fourth pipeline, the turbine 13 is connected to the exhaust manifold 171 through the fifth pipeline, the compressor 14 is connected to the throttle 16 and the intake manifold 172 through the sixth pipeline, the pressure relief valve 19 is connected to the fourth pipeline and the sixth pipeline respectively, and the bypass valve 18 is connected to the second pipeline and the fifth pipeline respectively. The throttle valve 16 is installed on the sixth pipeline, a first intake air temperature and pressure sensor 104 is installed in the sixth pipeline between the compressor and the throttle valve 16 , and a second intake air temperature and pressure sensor 105 is installed in the intake manifold 172 .

[0024] After the engine is started, the EGR valve 12 is closed immediately. When the intake air flow exceeds the set threshold and other conditions are met, the mixing valve is triggered to operate. After a certain period of time, the temperature rise value of the first temperature sensor 101 is calculated. When the temperature rise value is lower than the calibration threshold, a high flow fault is reported. After the EGR mixing valve 20 is opened in the fault state, the temperature rise value is smaller, and the difference from the fault-free state is obvious, so the high flow fault can be accurately reported.

[0025] There are generally two ways to obtain the intake air flow: direct acquisition and indirect calculation. Direct acquisition is to read directly from the air flow meter at the rear end of the air filter 15; indirect calculation is based on the pressure and volume of the intake manifold 172. When the engine is running, the intake volume is calculated based on factors such as speed, intake pressure, throttle body opening, and environmental condition correction. Both need to be calibrated on the engine bench before the data can be integrated into the vehicle for application.

[0026] The blockage of the EGR pipeline will cause a low flow fault, reduce the pressure difference before and after the EGR valve 12, and cause the calculated actual EGR flow to fail to keep up with the target flow. When the diagnosis is enabled, the EGR mixing valve 20 is triggered to act, and the target flow and actual flow of the EGR are integrated respectively. After a certain period of time, the deviation between the target and actual flow is calculated. If the deviation is greater than the calibration threshold, a low flow fault is reported. After the mixing valve is opened in the fault state, the target flow rises fast enough and has sufficient distinction from the actual flow, so the low flow fault can be accurately reported.

[0027] The EGR mixing valve 20 is a normally open electronically controlled valve. Its main function is to increase the vacuum behind the mixing valve by adjusting the valve opening, increase the pressure difference at both ends of the EGR pipeline, and achieve a higher EGR flow rate. When diagnosing the high and low flow of the EGR system, opening the EGR mixing valve 20 under appropriate working conditions can accurately determine the fault.

[0028] The technical solution in the related art has a high cost, the air intake pipeline for arranging the EGR mixing valve 20 occupies a large space, and the cabin layout requirements are high.

[0029] In order to solve the technical problems in the related art, an embodiment of the present invention provides a flow diagnostic device for an exhaust gas recirculation system. Figure 2 A schematic diagram of a flow diagnostic device for an exhaust gas recirculation system provided by an embodiment of the present invention is shown in FIG. Figure 2 As shown, the flow diagnostic device of the exhaust gas recirculation system includes: an EGR intercooler 11, an EGR valve 12, a first temperature sensor 101, a second temperature sensor 102, a pressure difference sensor 103, a turbine 13, a compressor 14, an air filter 15, an intake and exhaust system 17, a first pipe, a second pipe, a third pipe, a fourth pipe, a fifth pipe and a sixth pipe.

[0030] The second pipeline is connected to the first end of the first pipeline and the turbine 13 respectively, the first pipeline is provided with an EGR intercooler 11 and an EGR valve 12, a first temperature sensor 101 is provided in front of the EGR valve 12, a second temperature sensor 102 is provided after the EGR valve 12, both ends of the EGR valve 12 are connected to a pressure difference sensor 103, the second end of the first pipeline is connected to the fourth pipeline, the turbine 13 is connected to the compressor 14 through the third pipeline, the compressor 14 is connected to the air filter 15 through the fourth pipeline, the turbine 13 is connected to the intake and exhaust system 17 through the fifth pipeline, and the compressor 14 is connected to the intake and exhaust system 17 through the sixth pipeline.

[0031] In the technical solution provided by the embodiment of the present invention, the flow diagnostic device of the exhaust gas recirculation system includes: an EGR intercooler, an EGR valve, a first temperature sensor, a second temperature sensor, a pressure difference sensor, a turbine, a compressor, an air filter, an intake and exhaust system, a first pipeline, a second pipeline, a third pipeline, a fourth pipeline, a fifth pipeline and a sixth pipeline; the first pipeline is provided with an EGR intercooler and an EGR valve, a first temperature sensor is provided in front of the EGR valve, a second temperature sensor is provided after the EGR valve, both ends of the EGR valve are connected to the pressure difference sensor, the turbine is connected to the compressor through the third pipeline, the compressor is connected to the air filter through the fourth pipeline, the turbine is connected to the intake and exhaust system through the fifth pipeline, and the compressor is connected to the intake and exhaust system through the sixth pipeline, which can realize high flow diagnosis and low flow diagnosis of the low-pressure EGR system, reduce vehicle costs, and save space in the engine compartment.

[0032] An embodiment of the present invention provides another flow rate diagnostic device for an exhaust gas recirculation system. Figure 3 A schematic diagram of another exhaust gas recirculation system flow diagnostic device provided by an embodiment of the present invention, such as Figure 3 As shown, the flow diagnostic device of the exhaust gas recirculation system includes: an EGR intercooler 11, an EGR valve 12, a first temperature sensor 101, a second temperature sensor 102, a pressure difference sensor 103, a turbine 13, a compressor 14, an air filter 15, an intake and exhaust system 17, a first pipe, a second pipe, a third pipe, a fourth pipe, a fifth pipe and a sixth pipe.

[0033] The second pipeline is connected to the first end of the first pipeline and the turbine 13 respectively, the first pipeline is provided with an EGR intercooler 11 and an EGR valve 12, a first temperature sensor 101 is provided in front of the EGR valve 12, a second temperature sensor 102 is provided after the EGR valve 12, both ends of the EGR valve 12 are connected to a pressure difference sensor 103, the second end of the first pipeline is connected to the fourth pipeline, the turbine 13 is connected to the compressor 14 through the third pipeline, the compressor 14 is connected to the air filter 15 through the fourth pipeline, the turbine 13 is connected to the intake and exhaust system 17 through the fifth pipeline, and the compressor 14 is connected to the intake and exhaust system 17 through the sixth pipeline.

[0034] In the embodiment of the present invention, the flow diagnostic device of the exhaust gas recirculation system further includes: a pressure relief valve 19 and a bypass valve 18. The pressure relief valve 19 is connected to the fourth pipeline and the sixth pipeline respectively, and the bypass valve 18 is connected to the second pipeline and the fifth pipeline respectively.

[0035] In an embodiment of the present invention, the flow diagnostic device of the exhaust gas recirculation system also includes: a throttle valve 16 and a first intake air temperature and pressure sensor 104, the throttle valve 16 is installed on the sixth pipe, the compressor 14 is connected to the intake and exhaust system 17 through the sixth pipe and the throttle valve 16, and the first intake air temperature and pressure sensor 104 is installed in the sixth pipe between the compressor 14 and the throttle valve 16.

[0036] In the embodiment of the present invention, the flow diagnostic device of the exhaust gas recirculation system further includes: a second intake air temperature and pressure sensor 105. The intake and exhaust system 17 includes an exhaust manifold 171 and an intake manifold 172, the turbine 13 is connected to the exhaust manifold 171 through a fifth pipeline, and the compressor 14 is connected to the intake manifold 172 through a sixth pipeline; the second intake air temperature and pressure sensor 105 is installed in the intake manifold 172.

[0037] In the technical solution provided by the embodiment of the present invention, the flow diagnostic device of the exhaust gas recirculation system includes: an EGR intercooler, an EGR valve, a first temperature sensor, a second temperature sensor, a pressure difference sensor, a turbine, a compressor, an air filter, an intake and exhaust system, a first pipeline, a second pipeline, a third pipeline, a fourth pipeline, a fifth pipeline and a sixth pipeline; the first pipeline is provided with an EGR intercooler and an EGR valve, a first temperature sensor is provided in front of the EGR valve, a second temperature sensor is provided after the EGR valve, both ends of the EGR valve are connected to the pressure difference sensor, the turbine is connected to the compressor through the third pipeline, the compressor is connected to the air filter through the fourth pipeline, the turbine is connected to the intake and exhaust system through the fifth pipeline, and the compressor is connected to the intake and exhaust system through the sixth pipeline, which can realize high flow diagnosis and low flow diagnosis of the low-pressure EGR system, reduce vehicle costs, and save space in the engine compartment.

[0038] In the technical solution provided by the embodiment of the present invention, an EGR mixing valve is not configured, and only a pressure difference sensor 103 before and after the EGR valve 12 is configured to obtain the pressure difference before and after the EGR valve 12. The first temperature sensor 101 before the EGR valve 12 and the second temperature sensor 102 after the valve can monitor the exhaust gas temperature after the EGR valve 12.

[0039] In the technical solution provided by the embodiment of the present invention, an EGR mixing valve is not configured and only a post-valve temperature sensor (second temperature sensor 102) of the EGR valve is added. The high-flow diagnosis of the EGR valve can be achieved by using the temperature difference between the first temperature sensor 101 and the second temperature sensor 102 of the EGR valve, which can greatly reduce the vehicle cost.

[0040] In the technical solution provided by the embodiment of the present invention, the diagnostic working conditions can be flexibly adjusted according to the specific vehicle model, with a wide range of applications and a high diagnostic completion rate.

[0041] Compared with a low-pressure EGR system equipped with an EGR mixing valve, the technical solution provided by the embodiment of the present invention saves the layout space of the engine compartment and makes the engine layout more flexible.

[0042] Compared with the EGR valve high flow diagnostic solution equipped with an EGR mixing valve, the technical solution provided by the embodiment of the present invention reduces the cost per vehicle by about RMB 100.

[0043] based on Figure 2 or Figure 3 The flow rate diagnostic device of the exhaust gas recirculation system in the embodiment of the present invention provides a flow rate diagnostic method of the exhaust gas recirculation system, which can realize the high flow rate diagnosis of the low-pressure EGR system. Figure 4 A flow chart of a method for diagnosing flow of an exhaust gas recirculation system provided by an embodiment of the present invention is shown in FIG. Figure 4 As shown, the method includes: Step 102: After the vehicle engine is started, a pre-valve temperature value of a first temperature sensor and a post-valve temperature value of a second temperature sensor within a first time period are obtained.

[0044] In the embodiment of the present invention, after the vehicle engine is started, it can be determined whether there is a high flow fault by observing the temperature difference between the airflow before and after the EGR valve under a certain working condition during that period of time.

[0045] Step 104 : Determine whether there is a high flow fault in the exhaust gas recirculation system according to the difference between the pressure value before the valve and the pressure value after the valve.

[0046] In an embodiment of the present invention, when the temperature signals satisfying both the pre-valve temperature value and the post-valve temperature value are normal and the EGR valve is in a closed condition, it is determined whether the exhaust gas recirculation system has a high flow fault based on the difference between the pre-valve pressure value and the post-valve pressure value.

[0047] In the embodiment of the present invention, when the temperature signal of the pre-valve temperature value or the post-valve temperature value is abnormal, it indicates that the first temperature sensor or the second temperature sensor is faulty.

[0048] In the embodiment of the present invention, when the EGR valve cannot be stabilized in the closed working condition, it indicates that the EGR valve is stuck, cannot be closed, and has a malfunction. The engine controller can send an EGR valve closing zero position instruction, and the EGR valve can return to zero position under normal conditions. If the EGR valve cannot be closed, it means that the EGR valve is damaged, and an EGR valve fault can be reported. At this time, the high flow fault of the EGR valve cannot be diagnosed.

[0049] In the embodiment of the present invention, when the difference between the pre-valve pressure value and the post-valve pressure value is greater than a set pressure threshold, it is determined that a high flow fault exists in the exhaust gas recirculation system.

[0050] In the embodiment of the present invention, the pressure threshold can be set according to actual conditions.

[0051] based on Figure 2 or Figure 3 The flow rate diagnostic device of the exhaust gas recirculation system in the embodiment of the present invention provides another flow rate diagnostic method of the exhaust gas recirculation system, Figure 5 A flow chart of another exhaust gas recirculation system flow diagnosis method provided by an embodiment of the present invention, such as Figure 5 As shown, the method includes: Step 202: When the EGR valve is in a closed state and stabilizes at a first time threshold, the engine management system sends a control request to the hybrid control unit to coordinate the engine to the working range of the EGR valve, obtain the pre-valve pressure value and post-valve pressure value of the pressure difference sensor, and the pre-valve temperature value of the first temperature sensor.

[0052] In the embodiment of the present invention, after the EGR valve is in a closed state for a period of time (a first time threshold), the engine management system (EMS) requests the hybrid control unit (HCU) to coordinate the engine to the working range of the EGR valve, and determines whether a low flow fault exists by comparing the target EGR flow and the actual EGR flow.

[0053] Step 204: Generate an actual EGR flow rate according to the pre-valve pressure value, the post-valve pressure value, and the pre-valve temperature value.

[0054] In the embodiment of the present invention, the following formula is used The pressure before the valve, the pressure after the valve and the temperature before the valve are calculated to generate the actual EGR flow rate. Among them, P1 is the pressure before the valve, T1 is the temperature before the valve, P2 is the pressure after the valve, A T is the geometric area of ​​the EGR valve, C D is the fluid coefficient, K is the isentropic coefficient (fresh air = 1.4), r is the gas constant (fresh air = R / M = 8.314 / 0.02884 = 288.28), is the actual EGR flow rate.

[0055] In the embodiment of the present invention, the low flow fault diagnosis is mainly based on the difference between the pressure sensors before and after the EGR valve. It is necessary to comprehensively consider factors such as altitude, vehicle condition, vehicle dispersion and airflow fluctuation, and sensor measurement accuracy. The pressure difference between the valve before and after the valve is generally greater than 20hPa (specific calibration and matching is required according to the specific vehicle model) to ensure the reliability of the diagnosis and avoid the possibility of missed diagnosis and misdiagnosis.

[0056] Step 206: Determine whether there is a low flow fault in the exhaust gas recirculation system according to the actual EGR flow and the set target EGR flow.

[0057] In the embodiment of the present invention, when the absolute value of the difference between the actual EGR flow rate and the set target EGR flow rate is greater than the set flow rate threshold, it is determined that a low flow rate fault exists in the exhaust gas recirculation system.

[0058] In the embodiment of the present invention, the flow threshold can be set according to actual conditions.

[0059] In the technical solution provided in the embodiment of the present invention, a solution of a low-pressure EGR system without an EGR valve is adopted. Since the EGR valve is a key environmental protection quality assurance part, its failure mode needs to be accurately diagnosed by the on-board diagnostic system (OBD). Since the solution in the embodiment of the present invention does not have an EGR mixing valve, it is impossible to use the EGR mixing valve to create the vacuum behind the EGR valve, resulting in the pressure difference between the two ends of the EGR valve not being obvious when a high-flow fault occurs, and the pressure difference differentiation for effective diagnosis cannot be achieved (the vehicle operating condition is not stable, and the diagnostic differentiation of the pressure difference is required to be high), and the diagnosis cannot be completed.

[0060] The above technical solution was obtained through a large number of experiments and tests in the embodiment of the present invention, and it is the first application in the automotive industry. It is aimed at the leakage diagnosis of automobile engines using low-pressure EGR systems. The function realization in the embodiment of the present invention needs to consider many factors such as engine start and stop, emissions, fuel consumption, noise, vibration and harshness (NVH), rather than just measuring temperature in principle.

[0061] The installation position of the temperature sensor is determined by the temperature measurement itself. In the embodiment of the present invention, the installation position of the temperature sensor is required to measure the temperature of the center of the airflow and be a certain distance away from the EGR valve (requires multiple tests to determine) to prevent the gas after EGR throttling from being fully mixed, resulting in uneven temperature distribution of the EGR airflow and distortion of the temperature measurement. The start-stop operating conditions are affected by requirements such as emissions, fuel consumption and NVH, and the operating conditions in turn affect the temperature of the EGR airflow. The high-flow leakage diagnosis of the low-pressure EGR system is required to be completed during driving, and the diagnostic threshold needs to have sufficient discrimination to avoid missed diagnosis and misdiagnosis. Misdiagnosis causes the fault light to turn on, and the user experience is poor.

[0062] In the embodiment of the present invention, a high-flow diagnosis scheme of temperature sensors arranged before and after the EGR valve is adopted. After the operating condition calibration, the diagnosis requirement should be achieved in the shortest possible time. The temperature differentiation measured by the temperature sensors before and after the valve should be large enough (taking into account the measurement accuracy of the vehicle temperature sensor, the airflow fluctuation of the operating condition and the vehicle dispersion, etc., which is generally greater than 10°C, and the specific value needs to be calibrated and matched with the actual vehicle) to ensure the reliability of the diagnosis.

[0063] In addition, the embodiment of the present invention has also tried to implement the diagnosis scheme without adding the second temperature sensor behind the EGR valve, but at this time, the engine speed is pulled to a high load condition of more than 3500rpm, the diagnostic cycle fuel consumption increases by 0.3L / 100km, and the subjective perception of the engine noise is unacceptable. This scheme only has the first temperature sensor in front of the EGR valve. When a high flow leakage occurs (when the EGR valve is not opened and the valve plate is damaged, different apertures are generally made on the valve plate to simulate), it is judged by comparing the deviation value of the measured value (valve front temperature value) of the first temperature sensor with and without damage to the EGR valve under the corresponding intake volume. In automotive applications, the situation where the EGR valve does not work is generally cold start (the engine is cold and the EGR combustion is unstable when the EGR is turned on) and the outer characteristic area of ​​the engine (the torque loss is obvious when the EGR is turned on, and the power loss is large). In the embodiment of the present invention, a cold start of 120s without fault was tested, and the temperature difference was 2.48℃. When simulating 5mm and 8mm apertures, the temperature difference was 6.3℃ and 5.16℃ respectively, which cannot be used as a basis for diagnosis. The HCU coordinates the working condition to 3500rpm 155N.m working condition and stabilizes it, and waits for the temperature value before the EGR valve to be set to a certain threshold Ti (generally around 100℃); close the EGR valve and observe the temperature drop of the first temperature sensor (the temperature value before the valve of the first temperature sensor when there is no fault), and there is a temperature drop of about 10℃ in about 30s. In addition to increasing the cycle fuel consumption, this solution has a large output power of the engine working condition during diagnosis, poses a great challenge to the power balance of the power battery, affects environmental compliance (the emission cycle requires a deviation of ±1% in power balance), and the actual vehicle evaluation shows that the noise and vibration of the whole vehicle are unacceptable.

[0064] An embodiment of the present invention provides an engine, comprising: Figure 2 or Figure 3 The flow diagnostic device of the exhaust gas recirculation system is shown.

[0065] In the embodiment of the present invention, the engine may include a naturally aspirated engine. For example, the model of the naturally aspirated engine is S15DHE, and the vacuum degree of its intake manifold is high. Therefore, its diagnosis only requires a pre-valve temperature sensor (first temperature sensor) of the EGR valve in conjunction with the idle speed to achieve high flow diagnosis of the EGR valve.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A flow diagnostic device for an exhaust gas recirculation system, characterized in that: include: An EGR intercooler, an EGR valve, a first temperature sensor, a second temperature sensor, a differential pressure sensor, a turbine, a compressor, an air filter, an intake and exhaust system, a first pipeline, a second pipeline, a third pipeline, a fourth pipeline, a fifth pipeline, and a sixth pipeline; The second pipeline is connected to the first end of the first pipeline and the turbine respectively, the EGR intercooler and the EGR valve are arranged on the first pipeline, the first temperature sensor is arranged before the EGR valve, and the second temperature sensor is arranged after the EGR valve, both ends of the EGR valve are connected to the pressure difference sensor, the second end of the first pipeline is connected to the fourth pipeline, the turbine is connected to the compressor through the third pipeline, the compressor is connected to the air filter through the fourth pipeline, the turbine is connected to the intake and exhaust system through the fifth pipeline, and the compressor is connected to the intake and exhaust system through the sixth pipeline.

2. The flow diagnostic device according to claim 1, characterized in that: Also includes: Pressure relief valves and bypass valves; The pressure relief valve is connected to the fourth pipeline and the sixth pipeline respectively; The bypass valve is connected to the second pipeline and the fifth pipeline respectively.

3. The flow diagnostic device according to claim 1, characterized in that: Also includes: A throttle valve and a first intake air temperature and pressure sensor, wherein the throttle valve is installed on the sixth pipe, the compressor is connected to the intake and exhaust system through the sixth pipe and the throttle valve, and the first intake air temperature and pressure sensor is installed in the sixth pipe between the compressor and the throttle valve.

4. The flow diagnostic device according to claim 1, characterized in that: Also includes: a second intake air temperature and pressure sensor; The intake and exhaust system includes an exhaust manifold and an intake manifold. The turbine is connected to the exhaust manifold through the fifth pipeline, and the compressor is connected to the intake manifold through the sixth pipeline. The second intake temperature and pressure sensor is installed in the intake manifold.

5. A flow rate diagnostic method for an exhaust gas recirculation system, characterized in that: The flow diagnostic device for the exhaust gas recirculation system according to claim 1 comprises: After the vehicle is running and the engine is started, obtaining a pre-valve temperature value of the first temperature sensor and a post-valve temperature value of the second temperature sensor within a first time period; It is determined whether the exhaust gas recirculation system has a high flow fault according to the difference between the pre-valve pressure value and the post-valve pressure value.

6. The flow diagnosis method according to claim 5, characterized in that: After obtaining the pre-valve temperature value of the first temperature sensor and the post-valve temperature value of the second temperature sensor within the first time period, the method further includes: When the temperature signals satisfying both the pre-valve temperature value and the post-valve temperature value are normal and the EGR valve is in a closed condition, it is determined whether the exhaust gas recirculation system has a high flow fault according to the difference between the pre-valve pressure value and the post-valve pressure value.

7. The flow diagnosis method according to claim 6, characterized in that: The determining whether the exhaust gas recirculation system has a high flow fault according to the difference between the pre-valve pressure value and the post-valve pressure value includes: When the difference between the pre-valve pressure value and the post-valve pressure value is greater than a set pressure threshold, it is determined that a high flow fault exists in the exhaust gas recirculation system.

8. The flow diagnosis method according to claim 5, characterized in that: Also includes: When the EGR valve is in a closed state and stabilizes for a first time threshold, the engine management system sends a control request to the hybrid control unit to coordinate the engine to the working range of the EGR valve, and obtains the valve front pressure value and valve rear pressure value of the pressure difference sensor, and the valve front temperature value of the first temperature sensor; Generate an actual EGR flow rate according to the pre-valve pressure value, the post-valve pressure value and the pre-valve temperature value; It is determined whether the exhaust gas recirculation system has a low flow fault according to the actual EGR flow and the set target EGR flow.

9. The flow diagnosis method according to claim 8, characterized in that: The determining whether the exhaust gas recirculation system has a low flow fault according to the actual EGR flow and the set target EGR flow includes: When the absolute value of the difference between the actual EGR flow rate and the set target EGR flow rate is greater than a set flow rate threshold, it is determined that a low flow rate fault exists in the exhaust gas recirculation system.

10. An engine comprising the flow diagnostic device of the exhaust gas recirculation system according to any one of claims 1 to 4.

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