An exhaust gas recirculation system including an air compressor and a variable-section turbine and a control method thereof

Abstract

The present application discloses an exhaust gas recirculation system and control method including an air compressor and a variable-section turbine, and relates to the field of exhaust gas recirculation technology. The exhaust gas recirculation system includes an EGR control module, an exhaust gas circulation branch and an air compressor branch; the exhaust gas circulation branch includes an EGR cooler, an EGR valve and a first non-return valve in sequence along the airflow direction; the air compressor branch includes an air compressor and a second non-return valve in sequence along the airflow direction, and the air compressor branch is arranged on both sides of the first non-return valve; the exhaust gas turbine adopts a variable-section turbine, and the EGR control module, the variable-section turbine and the EGR valve are connected to the vehicle-mounted ECU; the EGR control module adjusts the switch state of the EGR valve and the opening of the variable-section turbine through the vehicle-mounted ECU. The exhaust gas recirculation system and control method of the present application improve the EGR rate through the air compressor branch and the variable-section turbine to solve the problem of a low EGR rate in the traditional exhaust gas recirculation system.

Description

Technical Field

[0001] The present application relates to the technical field of exhaust gas recirculation, and in particular to an exhaust gas recirculation system including an air compressor and a variable-section turbine and a control method thereof. Background Art

[0002] At present, exhaust gas recirculation (EGR) is increasingly widely used. Specifically, the EGR valve controls a certain amount of exhaust gas to be introduced into the combustion chamber through the pipeline and mixed with fresh air passing through the intercooler before being sent into the cylinder for combustion, so as to reduce the emission of NOx and CO2 gases. This is an effective measure to meet emission requirements.

[0003] In the related art, in the traditional exhaust gas recirculation system, the exhaust gas is divided into two paths after coming out of the exhaust manifold of the engine, one path reaches the exhaust gas turbine normally, and the other path returns to the engine intake manifold through the EGR valve.

[0004] However, the traditional exhaust gas recirculation system has a relatively low EGR rate. With the development of automobile technology, the upgrading of exhaust emission standards, and the after-treatment system's demand for original exhaust gas in the engine and aging problems, the EGR rate (also known as the proportion of exhaust gas recirculation) needs to be further improved.

[0005] Therefore, those skilled in the art are in urgent need of designing new technical solutions to further improve the EGR rate. Summary of the invention

[0006] In view of the defects existing in the prior art, the purpose of this application is to provide an exhaust gas recirculation system and control method including an air compressor and a variable-section turbine, which improves the EGR rate through the air compressor branch and the variable-section turbine to solve the problem of low EGR rate in traditional exhaust gas recirculation systems.

[0007] To achieve the above objectives, in the first aspect, the technical solution adopted is: an exhaust gas recirculation system including an air compressor and a variable-section turbine, comprising a main branch, wherein the main branch is a supercharger, an intercooler, an intake manifold, an engine body, an exhaust manifold and an exhaust gas turbine in sequence along the airflow direction; the exhaust gas recirculation system comprises an EGR control module, an exhaust gas circulation branch arranged between the intake manifold and the exhaust manifold, and an air compressor branch connected in parallel to the exhaust gas circulation branch; the exhaust gas circulation branch comprises an EGR cooler, an EGR valve and a first one-way valve in sequence along the airflow direction, and the flow direction of the first one-way valve is from the intake manifold to the exhaust manifold;

[0008] The air compressor branch is an air compressor and a second one-way valve in sequence along the air flow direction, and the air compressor branch is arranged on both sides of the first one-way valve; the flow direction of the second one-way valve is from the air compressor to the intake manifold; the air outlet of the second one-way valve is connected to the pipeline between the first one-way valve and the intake manifold through a pipeline;

[0009] The exhaust gas turbine adopts a variable-section turbine, and the EGR control module, the variable-section turbine and the EGR valve are connected to the vehicle-mounted ECU; the EGR control module adjusts the switching state of the EGR valve and the opening degree of the variable-section turbine through the vehicle-mounted ECU.

[0010] On the basis of the above technical solution, the EGR valve is in a normally closed state; the air compressor is connected to the pipeline between the EGR valve and the first one-way valve through a bypass intake pipeline, and a bypass valve is arranged on the bypass intake pipeline; the EGR valve and the bypass valve are both connected to the vehicle-mounted ECU, and the EGR valve and the bypass valve are opened or closed at the same time.

[0011] On the basis of the above technical solution, the EGR control module receives the engine speed signal and the engine torque signal in real time. When the engine speed is greater than or equal to the first speed threshold and the engine torque is greater than or equal to the first torque threshold, the EGR control module controls the EGR valve and the bypass valve to open simultaneously through the on-board ECU, and the air compressor draws exhaust gas from the exhaust gas circulation branch; the EGR control module can also reduce the opening of the variable-section turbine from the conventional opening through the on-board ECU.

[0012] On the basis of the above technical solution, the EGR cooler is in a normally closed state, and the EGR cooler is connected to the vehicle-mounted ECU; the vehicle-mounted ECU controls the EGR cooler and the EGR valve to be opened or closed at the same time.

[0013] On the basis of the above technical solution, the EGR control module includes a parameter relationship table of the rotation speed, torque, opening of the variable-section turbine, power of the air compressor and EGR rate.

[0014] Based on the above technical solution, when the EGR valve is opened, when the EGR control module monitors that the engine speed is less than or equal to the second speed threshold or the engine torque is less than or equal to the second torque threshold, the on-board ECU controls the EGR valve and the bypass valve to be closed at the same time, and the on-board ECU controls the variable-section turbine to return to the normal opening.

[0015] On the basis of the above technical solution, an air filter is further arranged before the supercharger, and the pipeline between the supercharger and the air filter is connected to the bypass intake pipeline through the air compressor intake pipeline, and a solenoid valve is arranged on the air compressor intake pipeline; a two-position three-way conversion valve is arranged between the air compressor and the second one-way valve, and one interface of the two-position three-way conversion valve is connected to the air storage tank through a pipeline; the solenoid valve and the two-position three-way conversion valve are both connected to the on-board ECU; the opening and closing states of the solenoid valve and the EGR valve are always opposite; when the EGR valve is closed, the solenoid valve is opened, and the air passes through the air filter, the air compressor intake pipeline, enters the air compressor and then enters the air storage tank.

[0016] On the basis of the above technical solution, the exhaust gas recirculation system further includes a dryer and a pressure sensor arranged on the gas tank, the dryer is arranged between the two-position three-way conversion valve and the gas tank, and the pressure sensor is connected to the vehicle-mounted ECU; when the pressure inside the gas tank reaches a set threshold, the high-pressure gas is discharged into the atmosphere through the unloading hole of the dryer; at the same time, the vehicle-mounted ECU controls the solenoid valve and the air compressor to close.

[0017] In a second aspect, the present application further discloses a control method based on the above-mentioned exhaust gas recirculation system, wherein the EGR valve is in a normally closed state, the air compressor branch is in a non-working state when the EGR valve is closed, the variable cross-section turbine is in a normal opening when the EGR valve is closed, and the EGR control module receives an engine speed signal and an engine torque signal in real time; the control method comprises the following steps:

[0018] The EGR control module detects that the engine speed is greater than or equal to a first speed threshold and the engine torque is greater than or equal to a first torque threshold, and the EGR control module controls the EGR valve to open through the vehicle-mounted ECU;

[0019] The EGR control module obtains the optimal power of the air compressor and the optimal opening of the variable cross-section turbine by looking up the table, controls the air compressor to operate according to the optimal power, adjusts the variable cross-section turbine from the conventional opening to the optimal opening, and the air compressor sucks the exhaust gas from the exhaust gas circulation branch;

[0020] The main branch, exhaust gas circulation branch and air compressor branch work simultaneously, and the exhaust gas enters the intake manifold through the exhaust manifold, EGR cooler, EGR valve and the first one-way valve; the air compressor draws the exhaust gas from between the EGR valve and the first one-way valve and circulates it to the intake manifold; at the same time, fresh air enters the intake manifold through the supercharger and intercooler, and the fresh air and exhaust gas are mixed and enter the engine body.

[0021] On the basis of the above technical solution, the EGR valve is in a normally closed state; the air compressor is connected to the pipeline between the EGR valve and the first one-way valve through a bypass intake pipeline, and a bypass valve is arranged on the bypass intake pipeline; the EGR valve and the bypass valve are both connected to the vehicle-mounted ECU, and the EGR valve and the bypass valve are opened or closed at the same time;

[0022] The EGR control module receives the engine speed signal and the engine torque signal in real time. When the engine speed is greater than or equal to the first speed threshold and the engine torque is greater than or equal to the first torque threshold, the EGR control module controls the EGR valve and the bypass valve to open simultaneously through the on-board ECU, and the air compressor draws exhaust gas from the exhaust gas circulation branch. The EGR control module can also reduce the opening of the variable-section turbine from the normal opening through the on-board ECU.

[0023] The beneficial effects of the technical solution provided by this application include:

[0024] 1. The exhaust gas recirculation system and control method containing an air compressor and a variable-section turbine of the present application are equipped with an exhaust gas circulation branch, an air compressor branch and a variable-section turbine, which can adjust the EGR rate from two aspects. The exhaust gas of the exhaust gas circulation branch can be sucked by the air compressor branch, and the opening of the variable-section turbine can be adjusted to change the EGR rate. In actual work, the air compressor branch and the variable-section turbine can be changed to select one or two to work as needed, thereby improving the EGR rate. Compared with the existing main branch and the exhaust gas circulation branch, the ratio of the exhaust gas volume is constant and the EGR rate is small. The present application can greatly improve the EGR rate and improve the energy utilization rate. Furthermore, the variable-section turbine can achieve coarse adjustment of the EGR rate, while the air compressor can achieve fine adjustment of the EGR rate. The combination of the two makes the control accuracy of the EGR rate higher and more safe and reliable.

[0025] 2. The exhaust gas recirculation system and control method containing an air compressor and a variable-section turbine of the present application, by setting clear trigger conditions, the exhaust gas circulation branch does not work at ordinary times. When the engine speed is greater than or equal to a first speed threshold and the engine torque is greater than or equal to a first torque threshold, the exhaust gas circulation branch is triggered to start working, thereby realizing automatic control, effectively improving the EGR rate, and being safe and reliable; at the same time, the opening of the variable-section turbine and the power of the air compressor are coordinated to adjust the EGR rate, so the EGR rate can be finely adjusted with high efficiency.

[0026] 3. In the exhaust gas recirculation system and control method including an air compressor and a variable-section turbine of the present application, the air compressor not only plays the role of sucking exhaust gas, but also plays the role of storing high-pressure gas; the pipeline between the supercharger and the air filter is connected to the bypass intake pipeline through the air compressor intake pipeline, and a solenoid valve is arranged on the air compressor intake pipeline. The opening and closing states of the solenoid valve and the EGR valve are always opposite, so that the air compressor of the exhaust gas recirculation system can also play the function of storing high-pressure gas, that is, the exhaust gas recirculation system including the air compressor branch of the present application can share the original air compressor for storing high-pressure gas, without the need to set up an additional air compressor separately, without taking up additional space, and greatly saving costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 A schematic diagram of the exhaust gas recirculation disclosed in the embodiment of the present application;

[0029] Figure numerals: 1. air filter; 2. supercharger; 3. intercooler; 4. intake connecting pipe; 5. intake manifold; 6. engine body; 7. exhaust manifold; 8. variable-section turbine; 9. EGR intake pipe; 10. EGR cooler; 11. EGR valve; 12. first one-way valve; 13. EGR outlet pipe; 14. bypass valve; 15. bypass intake line; 16. air compressor intake line; 17. solenoid valve; 18. air compressor; 19. conversion valve; 20. dryer; 21. air tank; 22. air compressor bypass outlet line; 23. second one-way valve; 24. pressure sensor; 25. vehicle-mounted ECU; 26. EGR control module. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present application clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] The purpose of the present application is to provide an exhaust gas recirculation system and control method including an air compressor and a variable-section turbine. By connecting the air compressor branch and the variable-section turbine 8 in parallel to the exhaust gas circulation branch, the variable-section turbine 8 adjusts the gas output of the exhaust gas turbine, and the air compressor branch cleverly extracts the exhaust gas, thereby improving the EGR rate to solve the problem of the low EGR rate of the traditional exhaust gas recirculation system and further reduce the emission of Nox and CO2 gases.

[0032] like Figure 1 As shown, the present application discloses an embodiment of an exhaust gas recirculation system including an air compressor and a variable-section turbine, wherein the exhaust gas recirculation system comprises a main branch, and the main branch is sequentially connected to a supercharger 2, an intercooler 3, an intake manifold 5, an engine body 6, an exhaust manifold 7 and an exhaust gas turbine along the airflow direction; wherein the supercharger 2 and the exhaust gas turbine are linked by a shaft and rotate synchronously. Specifically, the main branch is a classic structure of an engine, and this application will not repeat it.

[0033] The exhaust gas recirculation system includes a variable cross-section turbine 8, an EGR control module 26, an exhaust gas circulation branch and an air compressor branch. The exhaust gas circulation branch is arranged between the intake manifold 5 and the exhaust manifold 7. The air compressor branch is connected in parallel to the exhaust gas circulation branch, so that negative pressure is formed inside the exhaust gas circulation branch, thereby increasing the flow rate of the exhaust gas. The variable cross-section turbine 8 changes the gas output of the exhaust turbine.

[0034] The exhaust gas circulation branch includes an EGR cooler 10 , an EGR valve 11 and a first one-way valve 12 in sequence along the air flow direction. The flow direction of the first one-way valve 12 is from the exhaust manifold 7 to the intake manifold 5 .

[0035] In the exhaust gas circulation branch of the present application, the EGR valve 11 is arranged at the rear end of the EGR cooler 10, that is, the EGR valve 11 works at the cold end, and the working temperature of the EGR valve 11 is low. Compared with the EGR valve 11 working at the hot end in the prior art solution, the reliability is high, and the EGR valve 11 can be effectively protected and the service life can be extended. A first one-way valve 12 is arranged in the exhaust gas circulation branch, which can prevent fresh air from flowing back into the exhaust gas branch, and can effectively prevent the occurrence of reflux, which is safe and reliable.

[0036] Specifically, the air compressor branch is the air compressor 18 and the second one-way valve 23 in sequence along the air flow direction, and the air compressor branch is arranged on both sides of the first one-way valve 12; the flow direction of the second one-way valve 23 is from the air compressor 18 to the intake manifold 5. The air inlet of the air compressor 18 is connected to the pipeline between the EGR valve 11 and the first one-way valve 12 through a pipeline, and the air outlet of the second one-way valve 23 is connected to the pipeline between the first one-way valve 12 and the intake manifold 5 through a pipeline. The second one-way valve 23 can prevent the exhaust gas of the exhaust gas circulation branch from flowing back to the air compressor branch.

[0037] When the exhaust gas circulation branch is working, the air compressor 18 of the air compressor branch sucks the exhaust gas of the exhaust gas circulation branch, so that the exhaust gas circulation branch is in a negative pressure state, thereby increasing the EGR rate. Specifically, the EGR rate is the amount of exhaust gas flowing through the exhaust gas circulation branch divided by the amount of exhaust gas flowing out of the exhaust manifold. The EGR valve 11 is connected to the vehicle-mounted ECU 25, and the vehicle-mounted ECU 25 is connected to the EGR control module 26. The EGR control module 26 controls the opening and closing state of the EGR valve 11 through the vehicle-mounted ECU 25.

[0038] The exhaust gas turbine adopts a variable cross-section turbine 8, and the EGR control module 26, the variable cross-section turbine 8 and the EGR valve 11 are connected to the vehicle ECU 25. The EGR control module 26 adjusts the switch state of the EGR valve 11 and the opening degree of the variable cross-section turbine 8 through the vehicle ECU 25.

[0039] When the exhaust gas circulation branch is working, the EGR rate can be adjusted from two aspects. On the one hand, it is the operating power of the air compressor 18 of the air compressor branch. The greater the power, the greater the suction force; on the other hand, it is the opening of the variable cross-section turbine 8.

[0040] The exhaust gas recirculation system containing an air compressor and a variable-section turbine of the present application is equipped with an exhaust gas circulation branch, an air compressor branch and a variable-section turbine 8, which can adjust the EGR rate from two aspects. The exhaust gas of the exhaust gas circulation branch can be sucked by the air compressor branch, and the opening of the variable-section turbine 8 can be adjusted to change the EGR rate. In actual work, the air compressor branch and the variable-section turbine 8 can be changed as needed to select one or two to work, thereby improving the EGR rate. Compared with the existing main branch and the exhaust gas circulation branch, the ratio of the exhaust gas volume is constant and the EGR rate is small, and the present application can greatly improve the EGR rate. Furthermore, the variable-section turbine 8 can achieve rough adjustment of the EGR rate, and the air compressor 18 can achieve fine adjustment of the EGR rate. The two cooperate to make the control accuracy of the EGR rate higher, safer and more reliable.

[0041] In one embodiment, the EGR valve 11 is in a normally closed state, the air compressor 18 is connected to the pipeline between the EGR valve 11 and the first check valve 12 through the bypass intake pipeline 15, and the bypass valve 14 is provided on the bypass intake pipeline 15. The EGR valve 11 and the bypass valve 14 are both connected to the vehicle-mounted ECU 25, and the EGR valve 11 and the bypass valve 14 are opened or closed at the same time, that is, the bypass valve 14 is opened only when the exhaust gas circulation branch is working.

[0042] The exhaust gas recirculation system containing an air compressor and a variable-section turbine of the present application has a bypass valve 14 arranged on the bypass intake pipe 15, which not only serves to disconnect the air compressor branch, but also can separate the air compressor 18 from the exhaust gas circulation branch when the exhaust gas circulation branch is not working, so that the air compressor 18 can be used for other purposes.

[0043] In one embodiment, the EGR control module 26 receives the engine speed signal and the engine torque signal in real time. When the engine speed is greater than or equal to the first speed threshold and the engine torque is greater than or equal to the first torque threshold, the EGR control module 26 controls the EGR valve 11 and the bypass valve 14 to open simultaneously through the onboard ECU 25, and the air compressor 18 sucks the exhaust gas from the exhaust gas circulation branch. At the same time, the EGR control module 26 can also reduce the opening of the variable cross-section turbine 8 from the conventional opening through the onboard ECU 25. For example, the conventional opening is 90%, and after the exhaust gas circulation branch is working, the variable cross-section turbine 8 can be reduced to increase the EGR rate.

[0044] Furthermore, the EGR valve 11 and the bypass valve 14 are opened for EGR circulation, which can be opened automatically or directly controlled by inputting instructions through the EGR control module 26; the opening adjustment of the variable-section turbine 8 can be adjusted automatically or by inputting instructions through the EGR control module 26.

[0045] Specifically, the air compressor 18 is connected to the vehicle-mounted ECU. After the bypass valve 14 is opened, the vehicle-mounted ECU controls the air compressor 18 to operate at optimal power and controls the variable-section turbine 8 to adjust to an optimal opening. The optimal power of the air compressor 18 and the optimal opening of the variable-section turbine 8 correspond to the maximum EGR rate under the current state.

[0046] Specifically, when the opening of the variable-section turbine 8 and the power of the air compressor 18 are coordinated to adjust the EGR rate, coarse adjustment, i.e., adjustment of the opening of the variable-section turbine 8, is performed first, and then fine adjustment, i.e., adjustment of the power of the air compressor 18, is performed.

[0047] The exhaust gas recirculation system containing an air compressor and a variable-section turbine of the present application sets clear trigger conditions. The exhaust gas circulation branch does not work normally. When the engine speed is greater than or equal to a first speed threshold and the engine torque is greater than or equal to a first torque threshold, the exhaust gas circulation branch is triggered to start working, thereby realizing automatic control, effectively improving the EGR rate, and being safe and reliable. At the same time, the opening of the variable-section turbine 8 and the power of the air compressor 18 cooperate to adjust the EGR rate, so that the EGR rate can be finely adjusted with high efficiency.

[0048] In one embodiment, the EGR cooler 10 is in a normally closed state, and the EGR cooler 10 is connected to the vehicle-mounted ECU 25; the vehicle-mounted ECU 25 controls the EGR cooler 10 and the EGR valve 11 to be opened or closed at the same time. The function of the EGR cooler 10 is to allow the EGR valve 11 to work at the cold end, to provide the EGR valve with a good working environment, and thus to improve the efficiency of the EGR valve.

[0049] In one embodiment, the EGR control module 26 includes a parameter relationship table of the speed, torque, opening of the variable-section turbine 8, power of the air compressor 18 and EGR rate. Specifically, the EGR control module 26 includes a parameter relationship table of the speed, torque, opening of the variable-section turbine 8, power of the air compressor 18 and EGR rate, which is a table established in advance through a large number of experiments. When the exhaust gas circulation branch is involved in the work, the EGR control module 26 can directly look up the table to control the air compressor 18 and the variable-section turbine 8, so as to increase the EGR rate as much as possible.

[0050] In one embodiment, when the EGR valve 11 is opened, when the EGR control module 26 monitors that the engine speed is less than or equal to the second speed threshold or the engine torque is less than or equal to the second torque threshold, the on-board ECU controls the EGR valve 11 and the bypass valve 14 to be closed at the same time, and the exhaust gas circulation is no longer performed. At the same time, the on-board ECU controls the variable-section turbine 8 to return to the normal opening.

[0051] The exhaust gas recirculation system containing an air compressor and a variable-section turbine of the present application specifically sets clear exhaust gas circulation branch participation working conditions (first speed threshold and first torque threshold) and exit working conditions (second speed threshold and second torque threshold) for the engine, which can realize automatic control, maximize the EGR rate, and be safe and reliable.

[0052] In one embodiment, an air filter 1 is further provided before the supercharger 2 , and the pipeline between the supercharger 2 and the air filter 1 is connected to the bypass air intake pipeline 15 through the air compressor air intake pipeline 16 , and a solenoid valve 17 is provided on the air compressor air intake pipeline 16 .

[0053] A two-position three-way conversion valve 19 is provided between the air compressor 18 and the second one-way valve 23, and one interface of the two-position three-way conversion valve 19 is connected to the air tank 21 through a pipeline. Specifically, the three interfaces of the two-position three-way conversion valve 19 are respectively connected to the air compressor 18, the air tank 21 and the second one-way valve 23. The solenoid valve 17 and the two-position three-way conversion valve 19 are both connected to the vehicle-mounted ECU 25, and the vehicle-mounted ECU 25 controls the switch of the solenoid valve 17 and controls the connection direction of the two-position three-way conversion valve 19.

[0054] The opening and closing states of the solenoid valve 17 and the EGR valve 11 are always opposite, that is, when the exhaust gas circulation branch is working, the solenoid valve 17 remains closed, and the air compressor plays the role of sucking exhaust gas; when the exhaust gas circulation branch is not working, the solenoid valve 17 is opened, and the air compressor 18 plays the role of inflating the air tank 21, and the high-pressure air in the air tank 21 is used for the braking system.

[0055] When the EGR valve 11 is closed, the solenoid valve 17 is opened, and the air passes through the air filter 1, the air compressor intake pipe 16, enters the air compressor 18 and then enters the air storage tank 21 for use by the brake system.

[0056] In the exhaust gas recirculation system containing an air compressor and a variable-section turbine of the present application, the air compressor 18 not only plays the role of sucking exhaust gas, but also plays the role of storing high-pressure gas; the pipeline between the supercharger 2 and the air filter 1 is connected to the bypass intake pipeline 15 through the air compressor intake pipeline 16, and a solenoid valve 17 is arranged on the air compressor intake pipeline 16. The opening and closing states of the solenoid valve 17 and the EGR valve 11 are always opposite, so that the air compressor 18 of the exhaust gas recirculation system can also play the function of storing high-pressure gas, that is, the exhaust gas recirculation system containing an air compressor branch of the present application can share the original air compressor 18 for storing high-pressure gas, without the need to set up an additional air compressor 18 separately, without taking up additional space, and greatly saving costs.

[0057] In one embodiment, the exhaust gas recirculation system further includes a dryer 20 and a pressure sensor 24 disposed on the air tank 21 . The dryer 20 is disposed between the two-position three-way switching valve 19 and the air tank 21 , and the pressure sensor 24 is connected to the vehicle-mounted ECU 25 .

[0058] When the pressure of the gas tank 21 reaches the set threshold, the high-pressure gas is discharged into the atmosphere through the unloading hole of the dryer 20 and no longer enters the gas tank 21; at the same time, the vehicle-mounted ECU 25 controls the electromagnetic valve 17 and the air compressor 18 to be closed. Specifically, the air compressor 18 is electrically connected to the vehicle-mounted ECU 25 and is controlled by the vehicle-mounted ECU 25 to be turned on, off, and adjust the power.

[0059] In one embodiment, the output port of the intercooler 3 is connected to the intake manifold 5 through the intake connecting pipe 4, and the first one-way valve 12 is connected to the intake connecting pipe 4 through the EGR outlet pipe 13. That is, the intake connecting pipe 4 and the EGR outlet pipe 13 are first cross-connected and then connected to the intake manifold 5. The two-position three-way switching valve 19 is connected to the EGR outlet pipe 13 through the air compressor bypass outlet pipe 22, and the second one-way valve 23 is arranged on the air compressor bypass outlet pipe 22.

[0060] The present application also discloses a control method based on the above-mentioned exhaust gas recirculation system, wherein the EGR valve 11 is in a normally closed state, the air compressor branch is in a non-working state when the EGR valve 11 is closed, the variable-section turbine 8 is in a normal opening when the EGR valve 11 is closed, and the EGR control module 26 receives the engine speed signal and the engine torque signal in real time.

[0061] The control method comprises the following steps:

[0062] The EGR control module 26 detects that the engine speed is greater than or equal to the first speed threshold and the engine torque is greater than or equal to the first torque threshold, the exhaust gas circulation loop is triggered to open, and the EGR control module 26 controls the EGR valve 11 to open through the on-board ECU.

[0063] The EGR control module 26 obtains the optimal power of the air compressor 18 and the optimal opening of the variable cross-section turbine 8 by looking up the table. The on-board ECU controls the air compressor 18 to operate according to the optimal power. At the same time, the on-board ECU control can also control the opening of the variable cross-section turbine 8 to be reduced from the normal opening to the optimal opening. The air compressor 18 sucks the exhaust gas from the exhaust gas circulation branch. The optimal power of the air compressor 18 and the optimal opening of the variable cross-section turbine 8 correspond to the maximum EGR rate of the current state.

[0064] Specifically, the opening of the variable-section turbine 8 and the power of the air compressor 18 cooperate to adjust the EGR rate, which can improve the EGR rate control accuracy and efficiently adjust to the maximum EGR rate. Specifically, when the opening of the variable-section turbine 8 and the power of the air compressor 18 cooperate to adjust the EGR rate, the coarse adjustment, i.e., the opening adjustment of the variable-section turbine 8, is prioritized, and then the fine adjustment, i.e., the power of the air compressor 18, is performed.

[0065] The main branch, the exhaust gas circulation branch and the air compressor branch work simultaneously, and the exhaust gas enters the intake manifold 5 through the exhaust manifold 7, the EGR cooler 10, the EGR valve 11 and the first non-return valve 12; the air compressor 18 draws the exhaust gas from between the EGR valve 11 and the first non-return valve 12 and circulates it to the intake manifold 5; at the same time, fresh air enters the intake manifold 5 through the supercharger 2 and the intercooler 3, and the fresh air and the exhaust gas are mixed and enter the engine body.

[0066] In the exhaust gas recirculation system containing an air compressor and a variable-section turbine of the present application, when the EGR control module 26 monitors that the engine speed is greater than or equal to a first speed threshold and the engine torque is greater than or equal to a first torque threshold, the exhaust gas circulation branch participates in the operation, and the EGR control module 26 looks up the table to obtain the optimal power of the air compressor 18 and the optimal opening of the variable-section turbine 8, and the on-board ECU controls the air compressor 18 to operate at the optimal power, which can maximize the EGR rate.

[0067] Specifically, when the EGR control module 26 obtains the optimal power of the air compressor 18 and the optimal opening of the variable-section turbine 8 by looking up the table, the minimum opening of the variable-section turbine 8 is determined first, and the rest is satisfied by the power of the air compressor 18 .

[0068] Regarding the control method of the exhaust gas recirculation system, in one embodiment, the EGR valve 11 is in a normally closed state, the air compressor 18 is connected to the pipeline between the EGR valve 11 and the first check valve 12 through the bypass intake pipeline 15, and the bypass valve 14 is arranged on the bypass intake pipeline 15. The EGR valve 11 and the bypass valve 14 are both connected to the vehicle-mounted ECU 25, and the EGR valve 11 and the bypass valve 14 are opened or closed at the same time, that is, the bypass valve 14 is opened only when the exhaust gas circulation branch is working.

[0069] In the control method of the present application, the bypass valve 14 provided on the bypass intake pipe 15 not only serves to disconnect the air compressor branch, but also can separate the air compressor 18 from the exhaust gas circulation branch when the exhaust gas circulation branch is not working, so that the air compressor 18 can be used for other purposes.

[0070] Regarding the control method of the exhaust gas recirculation system, in one embodiment, the EGR control module 26 receives the engine speed signal and the engine torque signal in real time. When the engine speed is greater than or equal to the first speed threshold and the engine torque is greater than or equal to the first torque threshold, the EGR control module 26 controls the EGR valve 11 and the bypass valve 14 to open simultaneously through the onboard ECU 25, and the air compressor 18 sucks the exhaust gas from the exhaust gas circulation branch; at the same time, the EGR control module 26 can also reduce the opening of the variable cross-section turbine 8 from the conventional opening through the onboard ECU 25. For example, the conventional opening is 90%, and after the exhaust gas circulation branch is working, the variable cross-section turbine 8 can be reduced to increase the EGR rate.

[0071] Furthermore, the EGR valve 11 and the bypass valve 14 are opened for EGR circulation, which can be opened automatically or directly controlled by inputting instructions through the EGR control module 26; the opening adjustment of the variable-section turbine 8 can be adjusted automatically or by inputting instructions through the EGR control module 26.

[0072] Specifically, the air compressor 18 is connected to the vehicle-mounted ECU. After the bypass valve 14 is opened, the vehicle-mounted ECU controls the air compressor 18 to operate at optimal power and controls the variable-section turbine 8 to adjust to an optimal opening. The optimal power of the air compressor 18 and the optimal opening of the variable-section turbine 8 correspond to the maximum EGR rate under the current state.

[0073] Specifically, when the opening of the variable-section turbine 8 and the power of the air compressor 18 are coordinated to adjust the EGR rate, coarse adjustment, i.e., adjustment of the opening of the variable-section turbine 8, is performed first, and then fine adjustment, i.e., adjustment of the power of the air compressor 18, is performed.

[0074] The control method of the present application sets clear trigger conditions, and the exhaust gas circulation branch does not work normally. When the engine speed is greater than or equal to the first speed threshold and the engine torque is greater than or equal to the first torque threshold, the exhaust gas circulation branch is triggered to start working, which can realize automatic control, effectively improve the EGR rate, and is safe and reliable. At the same time, the opening of the variable-section turbine 8 and the power of the air compressor 18 cooperate to adjust the EGR rate, which can finely adjust the EGR rate with high efficiency.

[0075] Regarding the control method of the exhaust gas recirculation system, in one embodiment, the EGR cooler 10 is in a normally closed state, and the EGR cooler 10 is connected to the vehicle-mounted ECU 25; the vehicle-mounted ECU 25 controls the EGR cooler 10 and the EGR valve 11 to be opened or closed at the same time. The function of the EGR cooler 10 is to allow the EGR valve 11 to work at the cold end, to provide the EGR valve with a good working environment, and thus to improve the efficiency of the EGR valve.

[0076] Regarding the control method of the exhaust gas recirculation system, in one embodiment, the EGR control module 26 includes a parameter relationship table of the speed, torque, opening of the variable-section turbine 8, power of the air compressor 18 and EGR rate. Specifically, the EGR control module 26 includes a parameter relationship table of the speed, opening of the variable-section turbine 8, power of the air compressor 18 and EGR rate, which is a table established in advance through a large number of experiments. When the exhaust gas circulation branch is involved in the work, the EGR control module 26 can directly look up the table to control the air compressor 18 and the variable-section turbine 8, so as to increase the EGR rate as much as possible.

[0077] Regarding the control method of the exhaust gas recirculation system, in one embodiment, when the EGR valve 11 is opened, when the EGR control module 26 detects that the engine speed is less than or equal to the second speed threshold or the engine torque is less than or equal to the second torque threshold, the on-board ECU controls the EGR valve 11 and the bypass valve 14 to be closed at the same time, and the exhaust gas circulation is no longer performed. At the same time, the on-board ECU controls the variable-section turbine 8 to return to the normal opening.

[0078] The control method of the present application specifically sets clear exhaust gas circulation branch participation working conditions (first speed threshold and first torque threshold) and disengagement working conditions (second speed threshold and second torque threshold) for the engine, which can realize automatic control, maximize the EGR rate, and be safe and reliable.

[0079] Regarding the control method of the exhaust gas recirculation system, in one embodiment, an air filter 1 is further arranged before the supercharger 2, and the pipeline between the supercharger 2 and the air filter 1 is connected to the bypass intake pipeline 15 through the air compressor intake pipeline 16, and a solenoid valve 17 is arranged on the air compressor intake pipeline 16.

[0080] A two-position three-way conversion valve 19 is provided between the air compressor 18 and the second one-way valve 23, and one interface of the two-position three-way conversion valve 19 is connected to the air tank 21 through a pipeline. Specifically, the three interfaces of the two-position three-way conversion valve 19 are respectively connected to the air compressor 18, the air tank 21 and the second one-way valve 23. The solenoid valve 17 and the two-position three-way conversion valve 19 are both connected to the vehicle-mounted ECU 25, and the vehicle-mounted ECU 25 controls the switch of the solenoid valve 17 and controls the connection direction of the two-position three-way conversion valve 19.

[0081] The opening and closing states of the solenoid valve 17 and the EGR valve 11 are always opposite, that is, when the exhaust gas circulation branch is working, the solenoid valve 17 remains closed, and the air compressor plays the role of sucking exhaust gas; when the exhaust gas circulation branch is not working, the solenoid valve 17 is opened, and the air compressor 18 plays the role of inflating the air tank 21, and the high-pressure air in the air tank 21 is used for the braking system.

[0082] When the EGR valve 11 is closed, the solenoid valve 17 is opened, and the air passes through the air filter 1, the air compressor intake pipe 16, enters the air compressor 18 and then enters the air storage tank 21 for use by the brake system.

[0083] In the control method of the present application, the air compressor 18 not only plays the role of sucking exhaust gas, but also plays the role of storing high-pressure gas; the pipeline between the supercharger 2 and the air filter 1 is connected to the bypass intake pipeline 15 through the air compressor intake pipeline 16, and the air compressor intake pipeline 16 is provided with a solenoid valve 17, and the opening and closing states of the solenoid valve 17 and the EGR valve 11 are always opposite, so that the air compressor 18 of the exhaust gas recirculation system can also play the function of storing high-pressure gas, that is, the exhaust gas recirculation system containing the air compressor branch of the present application can share the original air compressor 18 for storing high-pressure gas, without the need to set up an additional air compressor 18 separately, without taking up additional space, and greatly saving costs.

[0084] Regarding the control method of the exhaust gas recirculation system, in one embodiment, the exhaust gas recirculation system also includes a dryer 20 and a pressure sensor 24 arranged in the air tank 21, the dryer 20 is arranged between the two-position three-way switching valve 19 and the air tank 21, and the pressure sensor 24 is connected to the vehicle-mounted ECU 25.

[0085] When the pressure of the gas tank 21 reaches the set threshold, the high-pressure gas is discharged into the atmosphere through the unloading hole of the dryer 20 and no longer enters the gas tank 21; at the same time, the vehicle-mounted ECU 25 controls the electromagnetic valve 17 and the air compressor 18 to be closed. Specifically, the air compressor 18 is electrically connected to the vehicle-mounted ECU 25 and is controlled by the vehicle-mounted ECU 25 to be turned on, off, and adjust the power.

[0086] In the description of the present application, it should be noted that the terms "upper", "lower", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0087] It should be noted that, in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0088] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. An exhaust gas recirculation system including an air compressor and a variable-section turbine, comprising a main branch, wherein the main branch is sequentially connected along the airflow direction to a supercharger (2), an intercooler (3), an intake manifold (5), an engine body (6), an exhaust manifold (7) and an exhaust turbine, characterized in that: The exhaust gas recirculation system comprises an EGR control module (26), an exhaust gas circulation branch arranged between an intake manifold (5) and an exhaust manifold (7), and an air compressor branch connected in parallel to the exhaust gas circulation branch; the exhaust gas circulation branch comprises an EGR cooler (10), an EGR valve (11) and a first one-way valve (12) in sequence along the air flow direction, and the flow direction of the first one-way valve (12) is from the exhaust manifold (7) to the intake manifold (5); The air compressor branch is connected to the air compressor (18) and the second one-way valve (23) in sequence along the air flow direction, and the air compressor branch is arranged across both sides of the first one-way valve (12); the flow direction of the second one-way valve (23) is from the air compressor (18) to the intake manifold (5); the air outlet of the second one-way valve (23) is connected to the pipeline between the first one-way valve (12) and the intake manifold (5) through a pipeline; The exhaust gas turbine adopts a variable cross-section turbine (8); the EGR control module (26), the variable cross-section turbine (8) and the EGR valve (11) are connected to the vehicle-mounted ECU (25); the EGR control module (26) adjusts the switch state of the EGR valve (11) and the opening degree of the variable cross-section turbine (8) through the vehicle-mounted ECU (25); The EGR valve (11) is in a normally closed state; the air compressor (18) is connected to the pipeline between the EGR valve (11) and the first one-way valve (12) through a bypass air intake pipeline (15), and a bypass valve (14) is provided on the bypass air intake pipeline (15); the EGR valve (11) and the bypass valve (14) are both connected to an on-board ECU (25), and the EGR valve (11) and the bypass valve (14) are opened or closed at the same time; An air filter (1) is also arranged before the supercharger (2); the pipeline between the supercharger (2) and the air filter (1) is connected to the bypass air intake pipeline (15) through the air compressor air intake pipeline (16); and a solenoid valve (17) is arranged on the air compressor air intake pipeline (16); A two-position three-way conversion valve (19) is provided between the air compressor (18) and the second one-way valve (23); one interface of the two-position three-way conversion valve (19) is connected to the air storage tank (21) via a pipeline; the solenoid valve (17) and the two-position three-way conversion valve (19) are both connected to the vehicle-mounted ECU (25); the opening and closing states of the solenoid valve (17) and the EGR valve (11) are always opposite; When the EGR valve (11) is closed, the solenoid valve (17) is opened, and air passes through the air filter (1), the air compressor intake pipe (16), enters the air compressor (18), and then enters the air storage tank (21).

2. An exhaust gas recirculation system comprising an air compressor and a variable-section turbine as claimed in claim 1, characterized in that: The EGR control module (26) receives an engine speed signal and an engine torque signal in real time. When the engine speed is greater than or equal to a first speed threshold and the engine torque is greater than or equal to a first torque threshold, the EGR control module (26) controls the EGR valve (11) and the bypass valve (14) to open simultaneously through the on-board ECU (25), and the air compressor (18) draws exhaust gas from the exhaust gas circulation branch. The EGR control module (26) can also reduce the opening of the variable-section turbine (8) from a normal opening through the on-board ECU (25).

3. An exhaust gas recirculation system comprising an air compressor and a variable-section turbine as claimed in claim 1, characterized in that: The EGR cooler (10) is in a normally closed state, and the EGR cooler (10) is connected to an on-board ECU (25); the on-board ECU (25) controls the EGR cooler (10) and the EGR valve (11) to be opened or closed at the same time.

4. An exhaust gas recirculation system comprising an air compressor and a variable-section turbine as claimed in claim 1, characterized in that: The EGR control module (26) includes a parameter relationship table of rotation speed, torque, opening degree of the variable cross-section turbine (8), power of the air compressor (18) and EGR rate.

5. An exhaust gas recirculation system comprising an air compressor and a variable-section turbine as claimed in claim 2, characterized in that: When the EGR valve (11) is open, when the EGR control module (26) detects that the engine speed is less than or equal to a second speed threshold or the engine torque is less than or equal to a second torque threshold, the on-board ECU controls the EGR valve (11) and the bypass valve (14) to close simultaneously, and the on-board ECU controls the variable-section turbine (8) to return to a normal opening.

6. An exhaust gas recirculation system comprising an air compressor and a variable-section turbine as claimed in claim 1, characterized in that: The exhaust gas recirculation system further comprises a dryer (20) and a pressure sensor (24) arranged on the gas storage tank (21); the dryer (20) is arranged between the two-position three-way conversion valve (19) and the gas storage tank (21), and the pressure sensor (24) is connected to an on-board ECU (25); when the pressure inside the gas storage tank (21) reaches a set threshold, the high-pressure gas is discharged into the atmosphere through the unloading hole of the dryer (20); at the same time, the on-board ECU (25) controls the solenoid valve (17) and the air compressor (18) to close.

7. A control method for the exhaust gas recirculation system according to claim 1, characterized in that: The EGR valve (11) is in a normally closed state, the air compressor branch is in a non-operating state when the EGR valve (11) is closed, the variable cross-section turbine (8) is in a normal opening when the EGR valve (11) is closed, and the EGR control module (26) receives an engine speed signal and an engine torque signal in real time; The control method comprises the following steps: The EGR control module (26) detects that the engine speed is greater than or equal to a first speed threshold and the engine torque is greater than or equal to a first torque threshold, and the EGR control module (26) controls the EGR valve (11) to open through the on-board ECU; The EGR control module (26) obtains the optimal power of the air compressor (18) and the optimal opening of the variable cross-section turbine (8) by looking up a table, controls the air compressor (18) to operate according to the optimal power, and adjusts the variable cross-section turbine (8) from a normal opening to an optimal opening, and the air compressor (18) sucks exhaust gas from the exhaust gas circulation branch; The main branch, the exhaust gas circulation branch and the air compressor branch operate simultaneously, and the exhaust gas enters the intake manifold (5) through the exhaust manifold (7), the EGR cooler (10), the EGR valve (11) and the first check valve (12); the air compressor (18) draws the exhaust gas from between the EGR valve (11) and the first check valve (12) and circulates it to the intake manifold (5); at the same time, fresh air enters the intake manifold (5) through the supercharger (2) and the intercooler (3), and the fresh air and the exhaust gas are mixed and enter the engine body.

8. The control method according to claim 7, characterized in that: The EGR valve (11) is in a normally closed state; the air compressor (18) is connected to the pipeline between the EGR valve (11) and the first one-way valve (12) through a bypass air intake pipeline (15), and a bypass valve (14) is provided on the bypass air intake pipeline (15); the EGR valve (11) and the bypass valve (14) are both connected to an on-board ECU (25), and the EGR valve (11) and the bypass valve (14) are opened or closed at the same time; The EGR control module (26) receives an engine speed signal and an engine torque signal in real time. When the engine speed is greater than or equal to a first speed threshold and the engine torque is greater than or equal to a first torque threshold, the EGR control module (26) controls the EGR valve (11) and the bypass valve (14) to open simultaneously through the on-board ECU (25), and the air compressor (18) draws exhaust gas from the exhaust gas circulation branch. The EGR control module (26) can also reduce the opening of the variable-section turbine (8) from a normal opening through the on-board ECU (25).

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