JP2013241921A - Egr system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an EGR system capable of suppressing a failure in an internal combustion engine caused by flow of condensed water generated in exhaust in an EGR path into an intake path while suppressing deterioration in fuel consumption.SOLUTION: An EGR system (100) includes: an EGR path (110); a bypass path (120); a flow rate control means (130) for controlling flow rate of exhaust flowing from the EGR path to an intake path (30) and flow rate of exhaust flowing from the EGR path to the bypass path; and a controller (140) for controlling the flow rate control means. When a temperature in the EGR path is lower than a specific one, the controller controls the flow rate control means so that the exhaust flows from the EGR path into the bypass path by preventing the exhaust from flowing from the EGR path into the intake path, and when the temperature in the EGR path reaches the specific one or higher, it controls the flow rate control means so that the exhaust flows from the EGR path into the intake path.

Description

  The present invention relates to an EGR system.

  2. Description of the Related Art Conventionally, an EGR (Exhaust Gas Recirculation) system that recirculates exhaust discharged from a combustion chamber of an internal combustion engine to an intake passage is known. For example, Patent Document 1 discloses that the exhaust gas flow is more than the location where the EGR passage connecting the passage of the exhaust passage and the passage of the intake passage, the EGR valve opening and closing the EGR passage, and the EGR passage of the exhaust passage are connected. An EGR system is disclosed that includes a control valve disposed on the downstream side in the direction, and an EGR valve and a control device that controls the control valve. The EGR system according to Patent Document 1 controls the EGR valve and the control valve so that the exhaust gas in the exhaust passage passes through the EGR passage and is recirculated to the intake passage when the internal combustion engine is started.

JP 2009-235946 A

  By the way, when the exhaust gas is recirculated to the intake passage when the internal combustion engine is started, if the temperature of the EGR passage is low, condensed water may be generated in the exhaust in the EGR passage. If this condensed water flows into the intake passage, there is a risk that a malfunction of the internal combustion engine such as corrosion of intake system parts, fuel injection valves, etc. may occur. On the other hand, in order to suppress the inflow of the condensed water into the intake passage, a method of waiting until the EGR passage rises in temperature and then opening the EGR passage to allow the exhaust to flow into the intake passage is conceivable. The start timing of inflow into the intake passage will be delayed. In order to solve this problem, it is conceivable to raise the temperature of the EGR passage early by separately providing a heating device such as a heater, but in this case, the fuel consumption may be deteriorated.

  The present invention provides an EGR system capable of suppressing the occurrence of a malfunction of an internal combustion engine caused by the condensed water generated in the exhaust gas in the EGR passage flowing into the intake passage while suppressing deterioration of fuel consumption. Objective.

  An EGR system according to the present invention includes an EGR passage that connects a passageway of an exhaust passage through which exhaust gas discharged from a combustion chamber of an internal combustion engine passes and a passageway of an intake passage through which intake air drawn into the combustion chamber passes. A bypass passage connecting the middle of the EGR passage and a portion of the exhaust passage downstream of the EGR passage to the exhaust flow direction, and flows into the intake passage from the EGR passage. A flow rate adjusting means for adjusting the flow rate of the exhaust gas and the flow rate of the exhaust gas flowing from the EGR passage into the bypass passage; and a control device for controlling the flow rate adjusting means, the control device comprising: When the temperature is lower than a predetermined temperature, the exhaust gas does not flow from the EGR passage to the intake passage and the exhaust gas flows from the EGR passage to the bypass passage. It controls the flow rate adjusting means so as, when the temperature of the EGR passage becomes equal to or higher than the predetermined temperature, the exhaust to the intake passage from the EGR passage for controlling the flow rate adjusting means so as to flow.

  According to the EGR system of the present invention, when the temperature of the EGR passage is lower than the predetermined temperature, the exhaust gas can be prevented from flowing into the intake passage from the EGR passage. Thereby, even when condensed water is generated in the exhaust gas in the EGR passage when the temperature of the EGR passage is lower than the predetermined temperature, the condensed water can be prevented from flowing into the intake passage. As a result, it is possible to suppress the occurrence of problems in the internal combustion engine caused by the condensed water generated in the exhaust gas in the EGR passage flowing into the intake passage. Further, even when the temperature of the EGR passage is lower than the predetermined temperature, the exhaust gas can pass through the EGR passage partway through the EGR passage, and then flow into the bypass passage and into the exhaust passage. Thereby, even when the temperature of the EGR passage is lower than the predetermined temperature and as a result, the inflow of exhaust gas to the intake passage is suppressed, the temperature of the EGR passage can be raised by the heat of the exhaust gas. As a result, it is possible to raise the temperature of the EGR passage at an early stage so that the temperature of the EGR passage becomes equal to or higher than a predetermined temperature and to let the exhaust flow into the intake passage without separately providing a heating device such as a heater for heating the EGR passage. it can. Thereby, deterioration of fuel consumption can be suppressed. As described above, according to the EGR system of the present invention, it is possible to suppress the occurrence of malfunction of the internal combustion engine caused by the condensed water generated in the exhaust gas in the EGR passage flowing into the intake passage while suppressing the deterioration of fuel consumption. can do.

  The said structure WHEREIN: The cylinder head or cylinder block which the said internal combustion engine has may be inserted in the part of the said exhaust gas flow direction upstream rather than the connection part of the said EGR passage and the said bypass passage. According to this configuration, the temperature of the EGR passage can be raised by the heat of the cylinder head or cylinder block of the internal combustion engine.

  In the above configuration, the cylinder head is provided with a refrigerant passage through which a refrigerant for cooling the internal combustion engine passes, and is located upstream of the connection portion of the EGR passage between the EGR passage and the bypass passage in the exhaust flow direction. The portion may be inserted through the cylinder head. According to this configuration, the refrigerant passage of the cylinder head can be warmed by the heat of the exhaust gas in the EGR passage. Thereby, warm-up of the internal combustion engine can be promoted.

  In the above configuration, the internal combustion engine is located downstream in the exhaust flow direction from the portion of the exhaust passage where the EGR passage is connected, and upstream of the portion of the exhaust passage where the bypass passage is connected. A supercharger driven by a turbine disposed on the side of the turbocharger, and when the supercharging pressure of the supercharger is insufficient with respect to a predetermined target value, the control device is connected to the intake passage from the EGR passage. The flow rate adjusting means is controlled so that the exhaust gas does not flow into the bypass passage from the EGR passage, and the exhaust gas flow adjustment so that the exhaust gas flows into the intake passage from the EGR passage. And the flow rate of the exhaust gas flowing into the intake passage from the EGR passage and the bypass passage from the EGR passage are prohibited. Serial flow rate of the exhaust gas may be further controlling the flow rate adjusting means to be zero.

  If the supercharging pressure of the supercharger is insufficient with respect to a predetermined target value, if a part of the exhaust gas in the exhaust passage passes through the EGR passage and flows into the intake passage or bypass passage, As a result of the insufficient flow rate of the exhaust gas supplied to the turbine, the supercharging pressure of the supercharger is further insufficient, and as a result, the acceleration response of the internal combustion engine may be deteriorated. On the other hand, according to the above configuration, when the supercharging pressure of the supercharger is insufficient with respect to the predetermined target value, the exhaust gas does not flow from the EGR passage to the intake passage and is exhausted from the EGR passage to the bypass passage. The flow rate adjusting means is controlled so as to flow in, and the flow rate adjusting means is prohibited from being controlled so that exhaust flows from the EGR passage into the intake passage, and the flow rate of exhaust gas flowing into the intake passage from the EGR passage and EGR Since the flow rate of the exhaust gas flowing into the bypass passage from the passage can be made zero, it is possible to suppress the deterioration of the acceleration response of the internal combustion engine as described above.

  In the above configuration, the flow rate adjusting means is disposed at a connection portion between the EGR passage and the bypass passage, and the exhaust gas in the exhaust passage does not flow into the intake passage from the EGR passage and bypasses from the EGR passage. A first mode in which the exhaust flows into the passage; a second mode in which the exhaust in the exhaust passage does not flow into the bypass passage from the EGR passage and flows into the intake passage from the EGR passage; and the exhaust in the exhaust passage There may be provided a switching valve for switching between a third mode that does not flow into the intake passage and the bypass passage from the EGR passage.

  According to this configuration, the configuration of the EGR system can be simplified as compared with the case where the flow rate adjusting means includes, for example, an on-off valve (for example, an EGR valve) that opens and closes the EGR passage and an on-off valve that opens and closes the bypass passage. Can do.

  According to the present invention, there is provided an EGR system capable of suppressing the occurrence of a malfunction of an internal combustion engine caused by the condensed water generated in the exhaust gas in the EGR passage flowing into the intake passage while suppressing deterioration of fuel consumption. be able to.

FIG. 1 is a schematic diagram of an internal combustion engine. Fig.2 (a)-FIG.2 (c) are the schematic diagrams for demonstrating the detail of a channel | path switching valve. FIG. 3A is a schematic diagram for explaining the control of the passage switching valve by the control unit of the control device according to the first embodiment. FIG. 3B is a schematic diagram for explaining a method for acquiring the temperature of the EGR passage by the control unit. FIG. 4 is a diagram illustrating an example of a flowchart when the control device according to the first embodiment controls the passage switching valve. FIG. 5 is a diagram illustrating an example of a flowchart when the control device according to the second embodiment controls the passage switching valve.

  Hereinafter, modes for carrying out the present invention will be described.

  An EGR (Exhaust Gas Recirculation) system 100 according to Embodiment 1 of the present invention will be described. First, the overall configuration of the internal combustion engine 10 to which the EGR system 100 is applied will be described, and then the details of the EGR system 100 will be described. FIG. 1 is a schematic diagram of an internal combustion engine 10. The type of the internal combustion engine 10 is not particularly limited, and various internal combustion engines such as a gasoline engine using gasoline as a fuel and a diesel engine using light oil as a fuel can be used. In the present embodiment, a diesel engine is used as an example of the internal combustion engine 10.

  The internal combustion engine 10 includes an internal combustion engine body 20, an intake passage 30, an exhaust passage 40, a supercharger 50, an intercooler 60, a diesel throttle 70, various sensors, and an EGR system 100. The EGR system 100 includes an EGR passage 110, a bypass passage 120, a passage switching valve 130, and a control device 140.

  The internal combustion engine body 20 includes a cylinder head 21. Further, the internal combustion engine body 20 includes a cylinder block below the cylinder head 21. A cylinder is formed in the cylinder block and the cylinder head 21. The internal combustion engine main body 20 includes a piston disposed in the cylinder and a crankshaft connected to the piston. A combustion chamber 22 is formed in a region surrounded by the cylinder block, the cylinder head 21 and the piston. The internal combustion engine main body 20 according to this embodiment includes four combustion chambers 22. The four combustion chambers 22 are arranged in the axial direction of the crankshaft. However, the number of combustion chambers 22 is not limited to four.

  The internal combustion engine body 20 has a fuel injection valve that injects fuel. Specifically, the internal combustion engine body 20 has a fuel injection valve for each combustion chamber 22. Each fuel injection valve is disposed in the internal combustion engine body 20 so as to inject fuel directly into the combustion chamber 22. However, the location of the fuel injection valve is not limited to this. For example, the fuel injection valve may be arranged in the intake passage 30 so that the fuel injected from the fuel injection valve is supplied to each combustion chamber 22.

  The internal combustion engine body 20 is provided with a refrigerant passage through which a refrigerant that cools the internal combustion engine body 20 passes. The refrigerant passage is inserted through the cylinder head 21 and the cylinder block of the internal combustion engine body 20. Hereinafter, a portion of the refrigerant passage that is inserted through the cylinder head 21 and the cylinder block may be referred to as an internal refrigerant passage.

  The intake passage 30 is a passage through which intake air taken into the combustion chamber 22 passes. In the intake passage 30 according to the present embodiment, the downstream side of the intake passage 30 in the intake flow direction is branched into a plurality and connected to each combustion chamber 22. In the present embodiment, the intake air flowing into the upstream end of the intake passage 30 in the intake flow direction is fresh air (specifically, air). The exhaust passage 40 is a passage through which the exhaust discharged from the combustion chamber 22 passes. In the exhaust passage 40 according to the present embodiment, the upstream side of the exhaust passage 40 in the exhaust flow direction is branched into a plurality and connected to each combustion chamber 22.

  The supercharger 50 is a device that compresses intake air. Although the specific structure of the supercharger 50 is not specifically limited, The supercharger 50 which concerns on a present Example is provided with the turbine 51 and the compressor 52 as an example. The turbine 51 is disposed in the exhaust passage 40. Specifically, the turbine 51 is exhausted more downstream of the exhaust passage 40 in the exhaust flow direction than a portion where an EGR passage 110 described later is connected, and more than a portion where a bypass passage 120 described later of the exhaust passage 40 is connected. Arranged upstream in the flow direction. The compressor 52 is disposed in the intake passage 30. Specifically, the compressor 52 is disposed upstream of the portion of the intake passage 30 where an intercooler 60 (described later) is disposed in the intake flow direction. The compressor 52 is connected to the turbine 51 so as to rotate integrally with the turbine 51 when the turbine 51 rotates.

  The turbine 51 rotates by receiving a force from the exhaust gas passing through the exhaust passage 40. When the turbine 51 rotates, the compressor 52 connected to the turbine 51 also rotates. As the compressor 52 rotates, the intake air in the intake passage 30 is compressed. In this way, the supercharger 50 compresses the intake air and supplies it to the combustion chamber 22 (ie, supercharging).

  The intercooler 60 is disposed downstream of the compressor 52 in the intake passage 30 in the intake flow direction. The intercooler 60 has a function as a cooling device that cools the intake air in the intake passage 30. Since the internal combustion engine 10 includes the intercooler 60, the temperature of the intake air compressed by the supercharger 50 can be suppressed from becoming too high.

  The diesel throttle 70 is disposed in the intake passage 30. Specifically, the diesel throttle 70 according to the present embodiment is located downstream of the intercooler 60 in the intake passage 30 in the intake flow direction and above the branch point where the intake passage 30 branches into a plurality of branch passages. It is arranged in the part. The diesel throttle 70 adjusts the amount of intake air that passes through the intake passage 30 and flows into the combustion chamber 22 based on an instruction from the control device 140.

  The various sensors are sensors that detect information necessary for control of the control device 140. In FIG. 1, a crank position sensor 80, a temperature sensor 81, and a temperature sensor 82 are illustrated as examples of various sensors. The crank position sensor 80 detects the position of the crankshaft and transmits the detection result to the control device 140. The control device 140 acquires the crank angle and the rotational speed (rpm) of the internal combustion engine 10 based on the detection result of the crank position sensor 80.

  The temperature sensor 81 detects the temperature of the refrigerant in the internal refrigerant passage provided in the internal combustion engine body 20 and transmits the detection result to the control device 140. Specifically, the temperature sensor 81 according to the present embodiment detects the temperature of the refrigerant in the internal refrigerant passage provided in the cylinder head 21 of the internal combustion engine body 20. However, the temperature detection location of the temperature sensor 81 is not limited to this. For example, the temperature sensor 81 may detect the temperature of the internal refrigerant passage of the cylinder block.

  The temperature sensor 82 detects the temperature of the exhaust gas in the EGR passage 110 and transmits the detection result to the control device 140. The temperature sensor 82 according to the present embodiment detects the temperature of the portion of the EGR passage 110 downstream of the portion where the internal combustion engine body 20 is inserted in the exhaust flow direction. However, the specific exhaust temperature detection location of the temperature sensor 82 is not limited to this. The internal combustion engine 10 also includes sensors other than those shown in FIG. For example, the internal combustion engine 10 also includes an air flow meter that detects the amount of intake air flowing into the intake passage 30.

  The EGR passage 110 of the EGR system 100 is a passage for recirculating a part of the exhaust gas in the exhaust passage 40 to the intake passage 30. The EGR passage 110 connects the middle of the exhaust passage 40 and the middle of the intake passage 30. Although the specific connection location of the EGR passage 110 to the exhaust passage 40 and the intake passage 30 is not particularly limited, one end of the EGR passage 110 according to the present embodiment is more than the turbine 51 of the exhaust passage 40. It is connected to a portion on the upstream side in the exhaust flow direction, more specifically, a portion where a plurality of branch passages of the exhaust passage 40 merge. Further, the other end of the EGR passage 110 according to the present embodiment is connected to a portion between a branch point where the intake throttle 30 branches into a plurality of branch passages and a location where the diesel throttle 70 is disposed.

  In the present embodiment, a part of the EGR passage 110 is inserted through the internal combustion engine body 20. Specifically, a part of the portion of the EGR passage 110 on the upstream side in the exhaust flow direction with respect to the portion where the bypass passage 120 is connected passes through the internal combustion engine body 20. A specific portion of the internal combustion engine body 20 through which the EGR passage 110 is inserted is not particularly limited, but the EGR passage 110 according to the present embodiment is inserted through the cylinder head 21. More specifically, the EGR passage 110 passes through the vicinity of the internal refrigerant passage of the cylinder head 21.

  The bypass passage 120 connects the middle of the EGR passage 110 and a portion of the exhaust passage 40 on the downstream side in the exhaust flow direction from the portion where the EGR passage 110 is connected. Specifically, one end of the bypass passage 120 according to the present embodiment is connected to a portion on the downstream side in the exhaust flow direction with respect to the portion inside the cylinder head 21 of the EGR passage 110, and the turbine 51 of the exhaust passage 40 is connected to the other end. It is connected to a portion on the downstream side in the exhaust flow direction with respect to the disposed portion. The bypass passage 120 is a passage for returning the exhaust gas flowing from the exhaust passage 40 into the EGR passage 110 to the exhaust passage 40 without flowing into the intake passage 30 (that is, bypassing the intake passage 30).

  The passage switching valve 130 is disposed at a connection portion between the EGR passage 110 and the bypass passage 120. The passage switching valve 130 is controlled by the control device 140 to adjust the flow rate of exhaust gas flowing into the intake passage 30 from the EGR passage 110 and the flow rate of exhaust gas flowing into the bypass passage 120 from the EGR passage 110. That is, the passage switching valve 130 has a function as a flow rate adjusting means for adjusting the flow rate of the exhaust gas flowing into the intake passage 30 from the EGR passage 110 and the flow rate of the exhaust gas flowing into the bypass passage 120 from the EGR passage 110. The passage switching valve 130 according to this embodiment is driven by an actuator, and the operation of the actuator is controlled by the control device 140.

  FIG. 2A to FIG. 2C are schematic views for explaining the details of the passage switching valve 130. Specifically, FIG. 2 (a) shows a portion of the passage switching valve 130 on the upstream side in the exhaust flow direction from a location where the passage switching valve 130 of the EGR passage 110 is disposed (hereinafter sometimes referred to as a valve placement location). And the bypass passage 120 are shown schematically. In FIG. 2B, the passage switching valve 130 communicates the portion on the upstream side in the exhaust flow direction with respect to the valve arrangement location of the EGR passage 110 and the portion on the downstream side in the exhaust flow direction with respect to the valve arrangement location of the EGR passage 110. The state is shown schematically. FIG. 2 (c) shows that the passage switching valve 130 is located upstream of the EGR passage 110 in the exhaust flow direction, the downstream portion of the EGR passage 110 in the exhaust flow direction, and the bypass passage 120. The state which interrupted | blocked is shown typically.

  The passage switching valve 130 has an internal passage 131 through which exhaust can pass. Further, the passage switching valve 130 is arranged at a connection portion between the EGR passage 110 and the bypass passage 120 so as to be rotated by an actuator. As shown in FIG. 2A, the actuator that has received an instruction from the control device 140 causes the internal passage 131 of the passage switching valve 130 and the bypass passage and the portion on the upstream side in the exhaust flow direction from the valve arrangement location of the EGR passage 110. When the passage switching valve 130 is rotated so as to communicate with 120, the exhaust gas that has flowed into the EGR passage 110 from the exhaust passage 40 can flow into the bypass passage 120. In this case, since the portion on the upstream side in the exhaust flow direction and the portion on the downstream side in the exhaust flow direction with respect to the valve arrangement position of the EGR passage 110 are blocked, the flow rate of the exhaust gas flowing through the EGR passage 110 and flowing into the intake passage 30 Becomes zero.

  As shown in FIG. 2B, the actuator that has received an instruction from the control device 140 causes the internal flow 131 of the passage switching valve 130 and the exhaust flow direction upstream portion of the EGR passage 110 to be upstream of the valve arrangement location. When the passage switching valve 130 is rotated so as to communicate with the portion on the downstream side in the direction, the exhaust gas flowing into the EGR passage 110 from the exhaust passage 40 can flow into the intake passage 30. In this case, the portion of the EGR passage 110 on the upstream side in the exhaust flow direction with respect to the valve arrangement location and the bypass passage 120 are blocked, so the flow rate of the exhaust gas flowing through the EGR passage 110 and flowing into the bypass passage 120 becomes zero. .

  As shown in FIG. 2C, the actuator that has received an instruction from the control device 140 causes the internal flow 131 of the passage switching valve 130 and the exhaust flow direction upstream portion of the EGR passage 110 to be upstream of the valve arrangement location. When the passage switching valve 130 is rotated such that the portion downstream in the direction is blocked and the portion upstream in the exhaust flow direction from the valve arrangement location of the EGR passage 110 and the bypass passage 120 are blocked. The exhaust gas flowing into the EGR passage 110 from the exhaust gas does not flow into the intake passage 30 and the bypass passage 120. That is, in this case, the flow rate of exhaust gas flowing from the EGR passage 110 into the intake passage 30 is zero, and the flow rate of exhaust gas flowing from the EGR passage 110 into the bypass passage 120 is also zero.

  In the following, the state shown in FIG. 2A, specifically, the state in which the exhaust gas in the exhaust passage 40 does not flow into the intake passage 30 from the EGR passage 110 but flows into the bypass passage 120 from the EGR passage 110, This is called one mode. The state shown in FIG. 2B, specifically, the state in which the exhaust gas in the exhaust passage 40 does not flow into the bypass passage 120 from the EGR passage 110 but flows into the intake passage 30 from the EGR passage 110 is referred to as a second mode. . The state shown in FIG. 2C, specifically, the state in which the exhaust gas in the exhaust passage 40 does not flow into the bypass passage 120 from the EGR passage 110 to the intake passage 30 is referred to as a third mode.

  As described above, the passage switching valve 130 according to the present embodiment is disposed at the connection portion between the EGR passage 110 and the bypass passage 120, and is controlled by the control device 140 so that the first mode, the second mode, and the second mode. It has a function as a switching valve for switching between the three modes. In this way, the passage switching valve 130 adjusts the flow rate of exhaust gas flowing from the EGR passage 110 into the intake passage 30 and the flow rate of exhaust gas flowing from the EGR passage 110 into the bypass passage 120.

  Referring to FIG. 1, control device 140 includes a control unit that controls passage control valve 130, diesel throttle 70, and fuel control valve of internal combustion engine body 20, and a storage unit that stores information necessary for the operation of the control unit. It has. An electronic control unit (Electronic Control Unit) can be used as the control device 140. In this embodiment, an electronic control device including a CPU (Central Processing Unit) 141, a ROM (Read Only Memory) 142, and a RAM (Random Access Memory) 143 is used as an example of the control device 140. The function of the control unit is realized by the CPU 141. The function of the storage unit is realized by the ROM 142 and the RAM 143.

  The control unit controls the diesel throttle 70 according to the load of the internal combustion engine 10. Further, the control unit controls the fuel injection valve so that a fuel injection amount corresponding to the intake air amount acquired based on the detection result of the air flow meter and the rotation speed acquired based on the detection result of the crank position sensor 80 is obtained. . Further, the control unit corrects the fuel injection amount according to the acceleration degree of the internal combustion engine 10, the refrigerant temperature acquired based on the detection result of the temperature sensor 81, and the like. Since the control of the diesel throttle 70 and the fuel injection valve by the control unit itself can be applied or applied to a control method of the diesel throttle and the fuel injection valve which is performed in a known internal combustion engine, detailed description is omitted.

  In addition, when the temperature of the EGR passage 110 is lower than the predetermined temperature, the control unit according to the present embodiment controls the passage switching valve 130 so that the first mode is obtained, and the temperature of the EGR passage 110 exceeds the predetermined temperature. In this case, the passage switching valve 130 is controlled so that the second mode is obtained.

  FIG. 3A is a schematic diagram for explaining the control of the passage switching valve 130 by the control unit according to the present embodiment. In FIG. 3A, the vertical axis indicates the temperature of the EGR passage 110, and the horizontal axis indicates time. Time t1 is the time when the internal combustion engine 10 is started. Specifically, the time t1 is a time when cranking of the internal combustion engine body 20 is started.

  As shown in FIG. 3A, when the internal combustion engine 10 is started, the temperature of the EGR passage 110 is assumed to be lower than a predetermined temperature. In this case, the control unit controls the passage switching valve 130 so that the first mode is obtained. That is, when the temperature of the EGR passage 110 is lower than the predetermined temperature, the control unit according to the present embodiment does not flow exhaust into the intake passage 30 from the EGR passage 110 but flows into the bypass passage 120 from the EGR passage 110. Thus, the passage switching valve 130 is controlled.

  Even when the passage switching valve 130 is controlled in this way, the exhaust gas in the exhaust passage 40 can pass through the EGR passage 110 partway through the EGR passage 110. As a result, the temperature of the EGR passage 110 rises as the EGR passage 110 is heated by the heat of the exhaust. That is, in the first mode, the temperature of the EGR passage 110 can be raised while suppressing the inflow of exhaust gas into the intake passage 30.

  When the temperature of the EGR passage 110 becomes equal to or higher than the predetermined temperature due to the temperature rise of the EGR passage 110 (time t2), the control unit controls the passage switching valve 130 so that the second mode is obtained. That is, the control unit according to the present embodiment controls the passage switching valve 130 so that the exhaust gas flows from the EGR passage 110 into the intake passage 30 when the temperature of the EGR passage 110 becomes equal to or higher than a predetermined temperature.

  In addition, although the specific value of the predetermined temperature mentioned above is not specifically limited, In this embodiment, as an example of the predetermined temperature, a dew point temperature, specifically, a temperature at which condensed water is generated in exhaust gas is used. I will do it.

  In determining whether or not the temperature of the EGR passage 110 has become equal to or higher than the predetermined temperature, the control unit can acquire the temperature of the EGR passage 110 by the following method, for example. FIG. 3B is a schematic diagram for explaining a technique for acquiring the temperature of the EGR passage 110 by the control unit. Specifically, FIG. 3B is a diagram schematically showing a cross section of the EGR passage 110. Note that hatching in the sectional view is omitted.

  The control unit according to the present embodiment uses the temperature of the wall portion 111 of the EGR passage 110 (the pipe portion of the EGR passage 110) as the temperature of the EGR passage 110. A specific method for acquiring the temperature of the wall 111 by the control unit is not particularly limited. For example, the internal combustion engine 10 includes a temperature sensor that detects the temperature of the wall 111, and the control unit can acquire the temperature of the wall 111 based on the detection result of the temperature sensor. Alternatively, the control unit can also obtain the temperature by estimating the temperature of the wall 111 based on an index having a correlation with the temperature of the wall 111.

The control part which concerns on a present Example acquires by estimating the temperature of the wall part 111. FIG. A method for estimating the temperature of the wall 111 by the control unit will be described below. First, the heat capacity of the EGR passage 110, specifically, the heat capacity of the wall portion 111 is C _pipe (J / K), and the heat capacity of the exhaust _gas in the EGR passage 110 is C _gas (J / K). Further, the temperature at a predetermined portion (referred to as a reference position) of the wall 111 after the elapse of t (s) from the start of the internal combustion engine 10 is defined as T _{pipe (t)} (° C.). The amount of heat that the wall 111 receives from the exhaust gas in the EGR passage 110 per unit time at time t (s ₎ is referred to as heat reception amount E _(t) .

Further, the exhaust _gas temperature upstream of the reference position of the EGR passage 110 after the elapse of t (s) from the start of the internal combustion engine 10 is _defined as T _{gas up (t)} (° C.), which is higher than the reference position. The temperature of the exhaust gas downstream in the exhaust flow direction is _defined as T _{gas down (t)} (° C.).

  It should be noted that where the reference position is set is not particularly limited, but in the present embodiment, as an example of the reference position, a portion inserted into the cylinder head 21 of the EGR passage 110 and the passage switching valve 130 are provided. The predetermined position of the part between the arranged parts is used. More specifically, as a reference position, a portion near the portion where the temperature sensor 81 is disposed in the internal combustion engine body 20 of the EGR passage 110, more specifically, a portion indicated by reference numeral A in FIG. I will do it.

Here, when the internal combustion engine 10 is started, the wall portion 111 of the EGR passage 110 is considered to be at the same temperature as the temperature of the refrigerant in the internal refrigerant passage of the internal combustion engine body 20. Therefore, the refrigerant temperature in the internal refrigerant passage detected by the temperature sensor 81 when the internal combustion engine 10 is started is used as the temperature (T _{pipe (0)} ) of the wall portion 111 when the internal combustion engine 10 is started. This is expressed by the following formula (1).
T _{pipe (0)} = temperature of the refrigerant in the internal refrigerant passage when the internal combustion engine 10 is started (1)

The control part which concerns on a present Example acquires the temperature (T _{pipe (0)} ) of the wall part 111 at the time of start-up of the internal combustion engine 10 based on Formula (1). Specifically, the control unit determines the temperature of the refrigerant in the internal refrigerant passage detected by the temperature sensor 81 when the internal combustion engine 10 is started (more specifically, the refrigerant temperature in the internal refrigerant passage of the cylinder head 21). Acquired as the temperature (T _{pipe (0)} ) of the wall 111 at the time of starting.

In addition, the control unit calculates the temperature rise per unit time (1 (s)) of the wall 111 after the elapse of time t (s) from the start of the internal combustion engine 10 (T _{diff (t)} ; the unit is ° C.). Ask. The temperature increase allowance T _{diff (t)} can be calculated by a value obtained by dividing the amount of heat received by the wall 111 (E _(t) ) by the heat capacity (C _pipe ) of the wall 111. This is expressed by the following formula (2).
T _{diff (t)} = E _(t) / C _pipe (2)

The amount of heat received E _(t ) in equation (2) is the exhaust temperature T _{gas up (t)} and the exhaust _{gas at} time t (s) at the upstream side of the EGR passage 110 in the exhaust flow direction at time t (s). The temperature of the exhaust on the downstream side in the flow direction can be calculated by multiplying the difference from T _{gas down (t) by} the heat capacity C _gas of the exhaust in the EGR passage 110. This is expressed by the following formula (3).
E _(t) = _Cgas * ( _{Tgasup (t)} -Tgasdown _(t) ) (3)

The control part which concerns on a present Example calculates | requires the received heat amount E _(t) based on the said Formula (3), and calculates | requires the temperature increase allowance T _{diff (t)} based on the said Formula (2). Note that the heat capacity C _gas of equation (3) and the heat capacity C _pipe of equation (2) are stored in advance in the storage unit.

Further, the control unit obtains T _{gas up (t)} of Expression (3) based on an index having a correlation therewith. As an example of this index, the load of the internal combustion engine 10, the temperature of the internal combustion engine body 20, and the like can be used. The higher the load of the internal combustion engine 10 or the temperature of the internal combustion engine body 20, the higher the temperature of the exhaust gas discharged from the internal combustion engine body 20. As a result, the exhaust gas temperature upstream of the reference position in the exhaust flow direction. This is because they tend to be higher. Although it does not specifically limit as a load of the internal combustion engine 10, For example, the rotation speed of the internal combustion engine main body 20, a fuel injection amount, etc. can be used. The control unit according to the present embodiment acquires T _{gas up (t)} based on the fuel injection amount.

In this case, the storage unit stores a map that defines the relationship between the fuel injection amount and the exhaust gas temperature upstream of the reference position in the exhaust flow direction. The control unit acquires the fuel injection amount at time t (s) from the start of the start of the internal combustion engine 10, and maps the temperature of the exhaust gas upstream in the exhaust flow direction corresponding to the acquired fuel injection amount in the storage unit map. And the acquired exhaust gas temperature is used as T _{gas up (t) in} equation (3).

Further, the control unit obtains T _{gas down (t)} in Expression (3) based on the detection result of the temperature sensor that detects the temperature of the exhaust gas downstream in the exhaust gas flow direction from the reference position. Specifically, the internal combustion engine 10 according to the present embodiment uses the detection result of the temperature sensor 82. This is because the temperature sensor 82 detects the temperature of the portion downstream of the reference position (A) in the exhaust flow direction as shown in FIG. The control unit uses the temperature of the exhaust obtained based on the detection result of the temperature sensor 82 at time t (s) as T _{gas down (t) in} Expression (3).

Note that the method of acquiring T _{gas up (t)} and T _{gas down (t)} by the control unit is not limited to the method described above. For example, the internal combustion engine 10 further includes a temperature sensor that detects the temperature of the exhaust gas upstream of the reference position in the exhaust flow direction, and the control unit acquires the detection result of this temperature sensor at time t (s), _It may be used as _{gas up (t)} . Further, the control unit may acquire T _{gas down (t)} based on an index having a correlation with the temperature of the exhaust downstream in the exhaust flow direction from the reference position.

The control unit calculates an integrated value obtained by integrating the temperature increase allowance T _{diff (t)} of the above equation (2) from the start of the internal combustion engine 10 to the time t (s), and the integrated value is expressed in equation (1). by adding to the temperature _{T pipe (0)} of the wall portion 111 at a time of starting the internal combustion engine 10 obtained on the basis of the temperature _{T PIPE (t} wall portion 111 after the time t (s) has elapsed from the start of the internal combustion engine 10 ₎ Is calculated. This is expressed by the following formula (4).
T _{pipe (t)} = T _{pipe (0)} + Integrated value of temperature rise T _{diff (t)} of wall 111 from the start to t (s) = T _{pipe (0)} + (T _{diff (1 ) + T diff (2) +} T diff (3) + ··· + T diff (t)) ··· (4)

  The control unit uses the temperature of the wall 111 calculated based on the above equation (4) as the temperature of the EGR passage 110. As a result, when the temperature of the wall 111 calculated based on the equation (4) (the temperature of the EGR passage 110) is lower than the predetermined temperature, the control unit according to the present embodiment passes through the intake passage 30 from the EGR passage 110. The passage switching valve 130 is controlled so that the exhaust gas does not flow into the bypass passage 120 from the EGR passage 110 (first mode), and the temperature of the wall 111 calculated based on the equation (4) is When the temperature exceeds a predetermined temperature, the passage switching valve 130 is controlled so that the exhaust gas flows from the EGR passage 110 into the intake passage 30 (second mode).

  FIG. 4 is a diagram illustrating an example of a flowchart when the control device 140 according to the present embodiment controls the passage switching valve 130. The control unit of the control device 140 repeatedly executes the flowchart of FIG. 4 every predetermined time. First, the control unit determines whether or not the temperature of the EGR passage 110 is lower than a predetermined temperature (step S100). Specifically, the control unit according to the present embodiment uses the temperature of the wall 111 acquired based on the equation (4) as the temperature of the EGR passage 110, and the temperature of the wall 111 is stored in the storage unit. It is determined whether the temperature is lower than a predetermined temperature (specifically, the dew point temperature of the exhaust gas).

  When it is determined in step S100 that the temperature of the EGR passage 110 is lower than the predetermined temperature, the control unit controls the passage switching valve 130 so that the first mode is obtained (step S110). Specifically, the control unit controls the passage switching valve 130 so that the exhaust does not flow into the intake passage 30 from the EGR passage 110 but flows into the bypass passage 120 from the EGR passage 110. Next, the control unit ends the execution of the flowchart.

  If it is not determined in step S100 that the temperature of the EGR passage 110 is lower than the predetermined temperature, the control unit controls the passage switching valve 130 so that the second mode is obtained (step S120). Specifically, the control unit controls the passage switching valve 130 so that the exhaust does not flow into the bypass passage 120 from the EGR passage 110 but flows into the intake passage 30 from the EGR passage 110.

  In the present embodiment, in the second mode according to step S120, the exhaust gas does not flow from the EGR passage 110 into the bypass passage 120. However, the control content of step S120 is not limited to this. If the exhaust gas flows from the EGR passage 110 into the intake passage 30 when the temperature of the EGR passage 110 is equal to or higher than the predetermined temperature, the exhaust gas is also partially passed into the bypass passage 120 when the temperature of the EGR passage 110 is higher than the predetermined temperature. It may flow in. However, the configuration in which the exhaust does not flow into the bypass passage 120 when the temperature of the EGR passage 110 is equal to or higher than the predetermined temperature as in this embodiment can increase the flow rate of the exhaust gas recirculated into the intake passage 30. preferable. After step S120 is executed, the control unit ends the execution of the flowchart.

  As described above, according to the EGR system 100 according to this embodiment, when the temperature of the EGR passage 110 is lower than the predetermined temperature, the exhaust gas can be prevented from flowing into the intake passage 30 from the EGR passage 110. Thereby, even when condensed water is generated in the exhaust gas in the EGR passage 110 when the temperature of the EGR passage 110 is lower than the predetermined temperature, the condensed water can be prevented from flowing into the intake passage 30. . As a result, it is possible to suppress the occurrence of the malfunction of the internal combustion engine 10 caused by the condensed water generated in the exhaust gas in the EGR passage 110 flowing into the intake passage 30.

  Specifically, if condensed water generated in the exhaust gas in the EGR passage 110 flows into the intake passage 30, intake system parts (parts constituting the intake passage 30) of the internal combustion engine 10, fuel injection valves, etc. Although there is a possibility of corroding by condensed water, according to the EGR system 100 according to the present embodiment, it is possible to prevent such a malfunction of the internal combustion engine 10 from occurring.

  Further, according to the EGR system 100, even when the temperature of the EGR passage 110 is lower than a predetermined temperature, the exhaust gas passes through the EGR passage 110 partway through the EGR passage 110 and then flows into the bypass passage 120. It can flow into the exhaust passage 40. Thereby, even when the temperature of the EGR passage 110 is lower than the predetermined temperature and as a result, the inflow of exhaust gas to the intake passage 30 is suppressed, the EGR passage 110 can be heated with the heat of the exhaust gas. As a result, the EGR passage 110 is heated at an early stage without separately providing a heating device such as a heater or a heat exchanger in order to heat the EGR passage 110, and the exhaust gas is exhausted by setting the temperature of the EGR passage 110 to a predetermined temperature or higher. It can flow into the intake passage 30. Thereby, deterioration of fuel consumption can be suppressed.

  From the above, according to the EGR system 100 according to the present embodiment, the condensed water generated in the exhaust gas in the EGR passage 110 flows into the intake passage 30 while suppressing deterioration in fuel consumption. The occurrence of defects can be suppressed.

  Note that the EGR system 100 according to the present embodiment includes an EGR passage 110 and a flow rate adjusting unit that adjust the flow rate of exhaust gas flowing from the EGR passage 110 into the intake passage 30 and the flow rate of exhaust gas flowing from the EGR passage 110 into the bypass passage 120. Although the passage switching valve 130 is provided at the connection portion with the bypass passage 120, the configuration of the flow rate adjusting means is not limited to this. For example, instead of providing the passage switching valve 130, the flow rate adjusting means of the EGR system 100 is arranged in the bypass passage 120 and a first on-off valve (for example, an EGR valve) that is arranged in the EGR passage 110 to open and close the EGR passage 110. And a second on-off valve that opens and closes the bypass passage 120. However, the configuration including the passage switching valve 130 as in the present embodiment is preferable in that the configuration of the EGR system 100 can be simplified.

  Further, according to the EGR system 100 according to the present embodiment, since the portion of the EGR passage 110 upstream of the connection portion between the EGR passage 110 and the bypass passage 120 passes through the cylinder head 21, The passage 110 can be heated by the heat of the cylinder head 21. Thereby, the temperature of the EGR passage 110 can be raised. As a result, the exhaust can flow into the intake passage 30 at an early stage. By causing the exhaust gas to flow into the intake passage 30 at an early stage, NOx contained in the exhaust gas can be reduced.

  Note that a portion of the EGR passage 110 on the upstream side in the exhaust flow direction with respect to the connection portion between the EGR passage 110 and the bypass passage 120 may be inserted into the cylinder block instead of the cylinder head 21. In this case, the temperature of the EGR passage 110 can be raised by the heat of the cylinder block.

  Further, according to the EGR system 100 according to the present embodiment, the cylinder head 21 is provided with the refrigerant passage, and a portion of the EGR passage 110 on the upstream side in the exhaust flow direction with respect to the connection portion between the EGR passage 110 and the bypass passage 120. Since the cylinder head 21 is inserted, the refrigerant passage of the cylinder head 21 can be warmed by the heat of the exhaust gas in the EGR passage 110. Thereby, warm-up of the internal combustion engine 10 can be promoted. As a result, the fuel efficiency of the internal combustion engine 10 can be improved.

  Next, an EGR system (hereinafter referred to as an EGR system 100a) according to Embodiment 2 of the present invention will be described. In the description of the present embodiment, the same members as those in the first embodiment will be denoted by the same reference numerals, and redundant description will be omitted. The EGR system 100a according to the present embodiment is different from the EGR system 100 according to the first embodiment in that a control device 140a is provided instead of the control device 140. The control device 140a is different from the control device 140 according to the first embodiment in the control content of the passage switching valve 130. Other configurations of the EGR system 100a and the configuration of the internal combustion engine 10 to which the EGR system 100a is applied are the same as those in the first embodiment. Therefore, illustration of the EGR system 100a and the control device 140a is omitted.

  When the supercharging pressure of the supercharger 50 is insufficient with respect to the predetermined target value, the control unit 140a according to the present embodiment prohibits the control to switch to the first mode and the second mode and The control device 140a according to the first embodiment is different from the control device 140a according to the first embodiment in that the passage switching valve 130 is further controlled to obtain the three modes.

  FIG. 5 is a diagram illustrating an example of a flowchart when the control device 140 a according to the present embodiment controls the passage switching valve 130. The control unit of the control device 140a repeatedly executes the flowchart of FIG. 5 every predetermined time. The flowchart in FIG. 5 differs from the flowchart in FIG. 4 according to the first embodiment in that step S10 and step S20 are further added.

  First, the control unit determines whether or not the supercharging pressure of the supercharger 50 is insufficient with respect to a predetermined target value (hereinafter sometimes referred to as a supercharging pressure target value) (step S10). The specific execution content of step S10 by the control unit is not particularly limited as long as it can be determined whether or not the supercharging pressure of the supercharger 50 is insufficient with respect to the supercharging pressure target value. . The control unit according to the present embodiment acquires the supercharging pressure in step S10, acquires the difference between the supercharging pressure target value stored in advance in the storage unit and the acquired supercharging pressure, and this difference is predetermined. Step S10 is executed by determining whether or not the value is greater than or equal to the value. In addition, the specific value of this predetermined value is not specifically limited, What is necessary is just to memorize | store the appropriate value of 0 or more in a memory | storage part beforehand.

  In addition, the control part which concerns on a present Example acquires supercharging pressure based on the detection result of the pressure sensor which detects supercharging pressure. In this case, the internal combustion engine 10 is provided with a pressure sensor for detecting the boost pressure on the downstream side of the intake passage 30 in the intake flow direction with respect to the compressor 52. Specifically, the internal combustion engine 10 includes a pressure sensor in a portion of the intake passage between the compressor 52 and the intercooler 60. A control part acquires a supercharging pressure based on the detection result of this pressure sensor.

  However, the method of acquiring the supercharging pressure by the control unit is not limited to the above configuration. For example, the control unit may acquire the supercharging pressure based on an index having a correlation with the supercharging pressure. As such an index, the intake air flow rate, the rotational speed of the turbine 51 or the compressor 52 of the supercharger 50, or the like can be used.

  When it is determined in step S10 that the difference between the supercharging pressure target value and the supercharging pressure is equal to or greater than a predetermined value, the control unit controls the passage switching valve 130 so as to obtain the third mode (step S20). Specifically, the control unit controls the passage switching valve 130 so that the flow rate of exhaust gas flowing into the intake passage 30 from the EGR passage 110 and the flow rate of exhaust gas flowing into the bypass passage 120 from the EGR passage 110 become zero. Next, the control unit ends the execution of the flowchart.

  As can be seen from FIG. 5, when step S10 is positively determined and step S20 is executed, the first mode and the second mode are not entered. That is, if the determination in step S10 is affirmative, the passage switching valve 130 is controlled so that the exhaust does not flow from the EGR passage 110 to the intake passage 30 and the exhaust flows from the EGR passage 110 to the bypass passage, and the EGR passage. It is prohibited to control the passage switching valve 130 so that the exhaust gas flows from 110 into the intake passage 30.

  On the other hand, if it is not determined in step S10 that the difference between the supercharging pressure target value and the supercharging pressure is greater than or equal to a predetermined value, the control unit executes step S100. The content of step S100 is the same as step S100 according to FIG. Moreover, since the content of step S110 and step S120 which concerns on FIG. 5 is also the same as step S110 and step S120 which concerns on FIG. 4, description is abbreviate | omitted.

  Even in the EGR system 100a according to the present embodiment, when a negative determination is made in step S10, steps S100, S110, and S120 are executed, so that the same effects as in the first embodiment can be exhibited. . That is, it is possible to suppress the occurrence of the malfunction of the internal combustion engine 10 caused by the condensed water generated in the exhaust gas in the EGR passage 110 flowing into the intake passage 30 while suppressing the deterioration of fuel consumption.

  Here, if the supercharging pressure of the supercharger 50 is insufficient with respect to a predetermined target value, a part of the exhaust gas in the exhaust passage 40 passes through the EGR passage 110 and flows into the intake passage 30 or the bypass passage 120. In such a case, the flow rate of the exhaust gas supplied to the turbine 51 of the supercharger 50 is insufficient, and as a result, the supercharging pressure of the supercharger 50 is further insufficient. There is a fear.

  On the other hand, according to the EGR system 100a according to the present embodiment, when the supercharging pressure of the supercharger 50 is insufficient with respect to the supercharging pressure target value, the exhaust gas flows into the intake passage 30 from the EGR passage 110. It is prohibited to control the passage switching valve 130 so that the exhaust gas flows into the bypass passage 120 from the EGR passage 110 without controlling the passage switching valve 130 so that the exhaust gas flows into the intake passage 30 from the EGR passage 110. Thus, the flow rate of the exhaust gas flowing into the intake passage 30 from the EGR passage 110 and the flow rate of the exhaust gas flowing into the bypass passage 120 from the EGR passage 110 can be made zero. Thereby, the deterioration of the acceleration responsiveness of the internal combustion engine 10 as described above can be suppressed.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 20 Internal combustion engine main body 21 Cylinder head 22 Combustion chamber 30 Intake passage 40 Exhaust passage 50 Supercharger 100 EGR system 110 EGR passage 120 Bypass passage 130 Passage switching valve 140 Control device

Claims (5)

An EGR passage that connects a passageway of an exhaust passage through which exhaust gas discharged from a combustion chamber of an internal combustion engine passes and a passageway of an intake passage through which intake air sucked into the combustion chamber passes;
A bypass passage connecting the middle of the EGR passage and a portion of the exhaust passage on the downstream side of the exhaust flow direction with respect to the portion where the EGR passage is connected;
Flow rate adjusting means for adjusting the flow rate of the exhaust gas flowing into the intake passage from the EGR passage and the flow rate of the exhaust gas flowing into the bypass passage from the EGR passage;
A control device for controlling the flow rate adjusting means,
When the temperature of the EGR passage is lower than a predetermined temperature, the control device is configured so that the exhaust does not flow from the EGR passage to the intake passage but flows from the EGR passage to the bypass passage. An EGR system that controls a flow rate adjusting unit so that when the temperature of the EGR passage becomes equal to or higher than the predetermined temperature, the flow rate adjusting unit is controlled so that the exhaust gas flows from the EGR passage into the intake passage.   2. The EGR system according to claim 1, wherein a portion of the EGR passage upstream of the connection portion between the EGR passage and the bypass passage in the exhaust flow direction passes through a cylinder head or a cylinder block of the internal combustion engine. The cylinder head is provided with a refrigerant passage through which a refrigerant for cooling the internal combustion engine passes.
3. The EGR system according to claim 2, wherein a portion of the EGR passage upstream of a connection portion between the EGR passage and the bypass passage passes through the cylinder head. The internal combustion engine is disposed downstream of the exhaust passage in the exhaust flow direction from the portion where the EGR passage is connected, and upstream of the portion of the exhaust passage where the bypass passage is connected. A turbocharger driven by a turbine
When the supercharging pressure of the supercharger is insufficient with respect to a predetermined target value, the control device does not allow the exhaust gas to flow from the EGR passage to the intake passage and from the EGR passage to the bypass passage. It is prohibited to control the flow rate adjusting means so that the exhaust flows in and to control the flow rate adjusting means so that the exhaust flows from the EGR passage into the intake passage, and from the EGR passage to the intake air 4. The flow rate adjusting means according to claim 1, further controlling the flow rate adjusting means so that a flow rate of the exhaust gas flowing into the passage and a flow rate of the exhaust gas flowing into the bypass passage from the EGR passage become zero. EGR system.   The flow rate adjusting means is disposed at a connection portion between the EGR passage and the bypass passage, and the exhaust gas in the exhaust passage does not flow into the intake passage from the EGR passage but flows into the bypass passage from the EGR passage. A first mode; a second mode in which the exhaust gas in the exhaust passage does not flow from the EGR passage into the bypass passage and flows into the intake passage from the EGR passage; and the exhaust gas in the exhaust passage from the EGR passage. The EGR system according to any one of claims 1 to 4, further comprising a switching valve that switches between a third mode that does not flow into the intake passage and the bypass passage.

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