Intake and exhaust system

Abstract

To secure a recirculation amount of EGR gas regardless of an engine load.SOLUTION: An intake and exhaust system includes: a compressor provided in an intake passage connected to an engine; a supercharger having a turbine provided in an exhaust passage connected to the engine; an intercooler provided downstream from the compressor in the intake passage; a bypass flow passage connecting the upstream side and the downstream side of the intercooler in the intake flow passage; an EGR flow passage connecting the upstream side of the turbine in the exhaust flow passage and the bypass flow passage; and an orifice portion provided at a connection with the EGR flow passage in the bypass flow passage.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an intake and exhaust system. [Background technology]

[0002] As an example of an intake and exhaust system for an engine, as disclosed in Patent Document 1, there is a system capable of performing exhaust gas recirculation (EGR). Such an intake and exhaust system is provided with an EGR passage that connects an exhaust passage and an intake passage. In the EGR, a part of the exhaust gas flowing through the exhaust passage is recirculated to the intake passage via the EGR passage. This reduces the combustion temperature in the engine. Therefore, the generation of NOx is suppressed, and the amount of NOx emissions is reduced. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-291795 A Summary of the Invention [Problem to be solved by the invention]

[0004] In an intake and exhaust system equipped with a turbocharger, a compressor of the turbocharger may be provided upstream of a connection part of the intake passage with the EGR passage, and a turbine of the turbocharger may be provided downstream of a connection part of the exhaust passage with the EGR passage. In this case, as the load of the engine increases, the pressure of the connection part of the intake passage with the EGR passage (i.e., the pressure at the downstream end of the EGR passage) increases. Therefore, at the time of high load, the pressure difference between the upstream end and the downstream end of the EGR passage may become small, or the pressure at the downstream end of the EGR passage may become higher than the pressure at the upstream end. Therefore, it may be difficult to sufficiently secure the EGR return flow rate, which is the flow rate of exhaust gas flowing through the EGR passage and returning to the intake passage.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide an intake and exhaust system that can ensure an adequate EGR recirculation amount regardless of the engine load. [Means for solving the problem]

[0006] In order to solve the above problems, an intake and exhaust system according to one embodiment of the present invention comprises: a turbocharger having a compressor provided in an intake passage connected to an engine and a turbine provided in an exhaust passage connected to the engine; an intercooler provided in the intake passage downstream of the compressor; a bypass flow passage connecting an upstream side and a downstream side of the intercooler in the intake flow passage; an EGR flow passage connecting a portion of the exhaust flow passage upstream of the turbine with the bypass flow passage; a throttle portion provided at a connection portion of the bypass passage with the EGR passage; A control device having one or more processors and one or more memories coupled to the processors; Equipped with 、 A bypass valve is provided in the bypass flow path, An EGR valve is provided in the EGR passage, The processor, Executing a process including controlling opening degrees of the EGR valve and the bypass valve based on a target EGR recirculation amount, which is a target value of a flow rate of exhaust gas flowing through the EGR passage; A process is executed that includes controlling the opening degree of the EGR valve and the bypass valve based on a differential pressure between an upstream end and a downstream end of the bypass passage in addition to the target EGR recirculation amount. . Effect of the Invention

[0007] According to the present invention, it is possible to ensure a sufficient amount of EGR recirculation regardless of the engine load. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing a schematic configuration of an intake and exhaust system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram showing an example of a functional configuration of the control device according to the embodiment of the present invention. [Diagram 3]FIG. 3 is a flowchart showing an example of a flow of processing related to EGR performed by the control device according to the embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing the flow of intake air and exhaust gas during EGR in the intake and exhaust system according to the embodiment of the present invention. [Diagram 5] FIG. 5 is a flowchart showing an example of a flow of processing related to idling operation performed by the control device according to the embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing the flow of intake air and exhaust air during idling in the intake and exhaust system according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The specific dimensions, materials, numerical values, etc. shown in the embodiment are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are given the same reference numerals to avoid repeated explanations, and elements not directly related to the present invention are not shown.

[0010] <Intake and exhaust system configuration> The configuration of an intake and exhaust system 1 according to an embodiment of the present invention will be described with reference to FIGS.

[0011] Fig. 1 is a schematic diagram showing a schematic configuration of an intake and exhaust system 1. The intake and exhaust system 1 is mounted on a vehicle 100. As shown in Fig. 1, the intake and exhaust system 1 includes an engine 11, an intake passage 12, an exhaust passage 13, a bypass passage 14, an EGR passage 15, a supercharger 16, and a control device 17. The supercharger 16 has a compressor 16a and a turbine 16b. The compressor 16a and the turbine 16b are connected via a shaft and rotate integrally.

[0012] The engine 11 is, for example, a spark-ignition internal combustion engine (that is, a gasoline engine). The engine 11 has a plurality of cylinders. A piston is slidably provided inside each cylinder, and a combustion chamber is defined by the piston. Each cylinder is provided with a fuel injection valve that injects fuel toward the combustion chamber. A mixture containing air and fuel is formed in the combustion chamber, and the mixture is burned by ignition of an ignition plug provided toward the combustion chamber. This causes the piston to perform a linear reciprocating motion, and power is transmitted to a crankshaft connected to the piston of each cylinder.

[0013] Each combustion chamber of the engine 11 communicates with an intake passage 12 via an intake port, and communicates with an exhaust passage 13 via an exhaust port. Each cylinder is provided with an intake valve capable of opening and closing the intake port, and an exhaust valve capable of opening and closing the exhaust port. By driving the intake valve and exhaust valve, air (i.e., intake air) is supplied to the combustion chamber, and exhaust gas is discharged from the combustion chamber.

[0014] The intake flow path 12 is connected to the engine 11, and is a flow path through which air (i.e., intake air) supplied to a combustion chamber of the engine 11 flows. An intake port 12a is provided at the upstream end of the intake flow path 12, through which outside air is taken in from outside the vehicle 100. An air cleaner 21 is provided in the intake flow path 12 downstream of the intake port 12a. The air cleaner 21 removes foreign matter contained in the air flowing through the intake flow path 12. A compressor 16a of a turbocharger 16 is provided in the intake flow path 12 downstream of the air cleaner 21. The compressor 16a compresses the air and discharges it downstream.

[0015] An intercooler 22 is provided in the intake passage 12 downstream of the compressor 16a. The intake air flowing through the intercooler 22 is cooled by exchanging heat with air outside the intercooler 22. A throttle valve 23 is provided in the intake passage 12 downstream of the intercooler 22. The throttle valve 23 adjusts the flow rate of the intake air flowing through the intake passage 12 (i.e., the flow rate of the intake air sent to the engine 11). The flow rate of the intake air flowing through the intake passage 12 is adjusted by adjusting the opening degree of the throttle valve 23. An intake manifold 24 is provided in the intake passage 12 downstream of the throttle valve 23. The intake manifold 24 branches toward each cylinder of the engine 11 and is connected to the intake port of each cylinder.

[0016] In the intake flow path 12, outside air (i.e., intake air) is taken in from an intake port 12a as shown by a white arrow. The taken in intake air passes through an air cleaner 21, and then through a compressor 16a of the turbocharger 16. The intake air then passes through an intercooler 22, a throttle valve 23, and an intake manifold 24 in this order, before being sent to the engine 11.

[0017] A first pressure sensor 25 and a second pressure sensor 26 are provided in the intake passage 12. The first pressure sensor 25 detects the pressure of the intake air downstream of the compressor 16a and upstream of the intercooler 22 in the intake passage 12. The first pressure sensor 25 is provided, for example, near the upstream end of the intercooler 22. The second pressure sensor 26 is provided in the intake manifold 24 and detects the pressure of the intake air in the intake manifold 24.

[0018] The exhaust flow path 13 is connected to the engine 11, and is a flow path through which exhaust gas discharged from a combustion chamber of the engine 11 flows. An exhaust port 13a through which exhaust gas is discharged to the outside of the vehicle 100 is provided at the downstream end of the exhaust flow path 13. An exhaust manifold 31 is provided in the exhaust flow path 13. The exhaust manifold 31 branches toward each cylinder of the engine 11, and is connected to the exhaust port of each cylinder.

[0019] A turbine 16b of the turbocharger 16 is provided downstream of the exhaust manifold 31 in the exhaust flow path 13. The turbine 16b converts the kinetic energy of the fluid into rotational energy. When the turbine 16b is rotated by the exhaust gas flowing through it, the rotational power is transmitted to the compressor 16a via the shaft, causing the compressor 16a to rotate. A catalyst 32 is provided downstream of the turbine 16b in the exhaust flow path 13. The catalyst 32 purifies harmful components in the exhaust gas into harmless components. The catalyst 32 includes, for example, a three-way catalyst.

[0020] In the exhaust flow path 13, as shown by the black arrows, the exhaust gas discharged from the engine 11 passes through an exhaust manifold 31 and then passes through a turbine 16b of the turbocharger 16. The exhaust gas then passes through a catalyst 32 and is discharged from an exhaust port 13a.

[0021] The bypass passage 14 connects the intake passage 12 at the upstream side and downstream side of the intercooler 22. During execution of EGR, which will be described later with reference to Fig. 4, a portion of the intake air flowing through the intake passage 12 flows into the bypass passage 14 from the upstream side of the intercooler 22. The intake air that has flowed into the bypass passage 14 bypasses the intercooler 22 and is sent to the intake passage 12 at the downstream side of the intercooler 22.

[0022] As described above, the bypass flow passage 14 bypasses the intercooler 22. Since a large pressure loss occurs in the intercooler 22, by providing the bypass flow passage 14 so as to bypass the intercooler 22, it is possible to increase the pressure difference between the upstream end and the downstream end of the bypass flow passage 14. This makes it easier to generate a flow of intake air in the bypass flow passage 14.

[0023] The upstream end of the bypass flow passage 14 is connected to the intake air flow passage 12 downstream of the compressor 16a and upstream of the intercooler 22. Specifically, the upstream end of the bypass flow passage 14 is connected to the intake air flow passage 12 near the upstream end of the intercooler 22. The downstream end of the bypass flow passage 14 is connected to the intake manifold 24. In other words, a portion of the intake air flowing through the intake air flow passage 12 flows into the bypass flow passage 14 from the intake air flow passage 12 near the upstream end of the intercooler 22, and is sent to the intake manifold 24 through the bypass flow passage 14.

[0024] However, the connection position of the upstream end of the bypass flow passage 14 and the connection position of the downstream end of the bypass flow passage 14 are not limited to the example in Fig. 1. For example, the connection portion of the intake flow passage 12 with the upstream end of the bypass flow passage 14 may be closer to the compressor 16a than the intercooler 22. Also, for example, the downstream end of the bypass flow passage 14 may be connected to the intake flow passage 12 downstream of the intercooler 22 and upstream of the intake manifold 24. In this case, the downstream end of the bypass flow passage 14 may be disposed upstream of the throttle valve 23 or downstream of the throttle valve 23.

[0025] A bypass valve 41 is provided in the bypass flow passage 14. The bypass valve 41 adjusts the flow rate of intake air flowing from the intake flow passage 12 into the bypass flow passage 14 (i.e., the flow rate of intake air flowing through the bypass flow passage 14). The flow rate of intake air flowing from the intake flow passage 12 into the bypass flow passage 14 is adjusted by adjusting the opening degree of the bypass valve 41. Various valves can be used as the bypass valve 41. However, from the viewpoint of improving the accuracy of flow rate adjustment, it is preferable to use a butterfly valve, for example, as the bypass valve 41.

[0026] The EGR passage 15 connects the exhaust passage 13 upstream of the turbine 16b with the bypass passage 14. During EGR, which will be described later with reference to FIG. 4, a portion of the exhaust gas flowing through the exhaust passage 13 flows into the EGR passage 15. Specifically, an upstream end of the EGR passage 15 is connected to an exhaust manifold 31. Therefore, a portion of the exhaust gas flowing through the exhaust passage 13 flows from the exhaust manifold 31 into the EGR passage 15.

[0027] The exhaust gas that flows into the EGR passage 15 is sent to the bypass passage 14, bypassing the engine 11. The exhaust gas sent from the EGR passage 15 to the bypass passage 14 is recirculated to the intake passage 12 (specifically, the intake manifold 24). The exhaust gas that has been recirculated to the intake manifold 24 is then sent from the intake manifold 24 to the engine 11. This technology of recirculating a portion of the exhaust gas to the engine 11 is called EGR. The combustion temperature in the engine 11 is lowered by performing EGR. Therefore, the generation of NOx is suppressed, and the amount of NOx emissions is reduced.

[0028] An EGR cooler 51 is provided in the EGR passage 15. Exhaust gas flowing through the inside of the EGR cooler 51 is cooled by exchanging heat with air outside the EGR cooler 51. An EGR valve 52 is provided in the EGR passage 15 downstream of the EGR cooler 51. The EGR valve 52 adjusts the EGR recirculation amount, which is the flow rate of exhaust gas flowing through the EGR passage 15 and recirculating to the intake passage 12. The opening degree of the EGR valve 52 is adjusted to adjust the EGR recirculation amount.

[0029] In this embodiment, a throttle section 14a is provided at a connection portion of the bypass passage 14 with the EGR passage 15. The throttle section 14a is a portion in which the flow passage cross-sectional area is smaller than other portions of the bypass passage 14. The downstream end of the EGR passage 15 is connected to the throttle section 14a. The flow passage cross-sectional area of ​​the bypass passage 14 is locally smaller at the throttle section 14a. Therefore, the flow velocity of the intake air flowing through the bypass passage 14 is higher at the throttle section 14a than at other portions. Therefore, the pressure in the bypass passage 14 is locally lower at the throttle section 14a.

[0030] Here, as the load of the engine 11 increases, the boost pressure increases. In this embodiment, as described above, the throttle portion 14a is provided at the connection portion of the bypass passage 14 with the EGR passage 15, and the pressure in the bypass passage 14 is locally lowered at the throttle portion 14a. In particular, when the load increases, the flow rate of the intake air flowing through the bypass passage 14 increases, and the pressure in the throttle portion 14a decreases. Therefore, even when the load is high, the pressure at the downstream end of the EGR passage 15 can be prevented from increasing. This prevents the pressure difference between the upstream end and the downstream end of the EGR passage 15 from decreasing, and prevents the pressure at the downstream end of the EGR passage 15 from becoming higher than the pressure at the upstream end. Therefore, the EGR return amount can be secured regardless of the load of the engine 11.

[0031] The control device 17 has one or more processors 17a and one or more memories 17b connected to the processors 17a. The processor 17a includes, for example, a CPU (Central Processing Unit). The memory 17b includes, for example, a ROM (Read Only Memory) which is a storage element that stores programs and computation parameters used by the CPU, and a RAM (Random Access Memory) which is a storage element that temporarily stores parameters that change as appropriate during execution of the CPU.

[0032] The control device 17 communicates with each device (e.g., the throttle valve 23, the first pressure sensor 25, the second pressure sensor 26, the bypass valve 41, the EGR valve 52, etc.) provided in the intake and exhaust system 1. The communication between the control device 17 and each device is realized, for example, by using CAN (Controller Area Network) communication.

[0033] Fig. 2 is a block diagram showing an example of a functional configuration of the control device 17. For example, as shown in Fig. 2, the control device 17 has an acquisition unit 171 and a control unit 172. Note that various processes including the processes described below performed by the acquisition unit 171 or the control unit 172 may be executed by the processor 17a.

[0034] The acquisition unit 171 acquires various information used in the processing performed by the control unit 172, and outputs the information to the control unit 172. For example, the acquisition unit 171 acquires information from the first pressure sensor 25 and the second pressure sensor .

[0035] The control unit 172 controls the operation of each device in the intake and exhaust system 1. For example, the control unit 172 includes a throttle valve control unit 172a, an EGR valve control unit 172b, and a bypass valve control unit 172c.

[0036] The throttle valve control unit 172a controls the throttle valve 23. Specifically, the throttle valve control unit 172a controls the flow rate of the intake air flowing through the intake passage 12 by controlling the opening degree of the throttle valve 23.

[0037] The EGR valve control unit 172b controls the EGR valve 52. Specifically, the EGR valve control unit 172b controls the opening degree of the EGR valve 52 to control the EGR recirculation amount (that is, the flow amount of exhaust gas flowing through the EGR passage 15).

[0038] The bypass valve control unit 172c controls the bypass valve 41. Specifically, the bypass valve control unit 172c controls the flow rate of the intake air flowing through the bypass flow passage 14 by controlling the opening degree of the bypass valve 41. Here, when the flow rate of the intake air flowing through the bypass flow passage 14 changes, the EGR recirculation amount also changes. In other words, not only the opening degree of the EGR valve 52 but also the opening degree of the bypass valve 41 correspond to parameters that change the EGR recirculation amount.

[0039] The functions of the control device 17 according to the present embodiment may be divided among multiple control devices, or multiple functions may be realized by one control device. When the functions of the control device 17 are divided among multiple control devices, the multiple control devices may be connected to each other via a communication bus such as a CAN.

[0040] <Operation of the intake and exhaust system> Next, the operation of the intake and exhaust system 1 according to the embodiment of the present invention will be described with reference to FIGS.

[0041] Fig. 3 is a flowchart showing an example of the flow of processing related to EGR performed by the control device 17. The control flow shown in Fig. 3 is started repeatedly after it is ended. During the execution of the control flow shown in Fig. 3, the opening degree of the throttle valve 23 is controlled according to, for example, the accelerator opening degree.

[0042] 3 is started, first, in step S101, the control unit 172 determines a target EGR recirculation amount. The target EGR recirculation amount is a target value of the EGR recirculation amount.

[0043] The control unit 172 determines, as the target EGR recirculation amount, an EGR recirculation amount that makes the combustion temperature of the engine 11 low enough to appropriately reduce the amount of NOx emissions. For example, the control unit 172 determines the target EGR recirculation amount based on the load of the engine 11, the rotation speed of the engine 11, the temperature of the intake air, the flow rate of the intake air taken in through the intake port 12a, and the like. However, the parameters used to determine the target EGR recirculation amount are not limited to the above examples.

[0044] Next, in step S102, the control unit 172 determines the pressure difference between the upstream end and the downstream end of the bypass flow passage 14 (hereinafter, also simply referred to as the pressure difference of the bypass flow passage 14).

[0045] For example, the control unit 172 uses the detection value of the first pressure sensor 25 as the pressure at the upstream end of the bypass flow path 14. The control unit 172 also uses the detection value of the second pressure sensor 26 as the pressure at the downstream end of the bypass flow path 14. Then, the control unit 172 specifies a value obtained by subtracting the detection value of the second pressure sensor 26 from the detection value of the first pressure sensor 25 as the differential pressure of the bypass flow path 14.

[0046] Next, in step S103, the control unit 172 determines the target openings of the EGR valve 52 and the bypass valve 41 based on the target EGR recirculation amount and the pressure difference of the bypass passage 14. The target openings are target values ​​for the openings of each valve.

[0047] FIG. 4 is a diagram showing the flow of intake air and exhaust air during EGR in the intake and exhaust system 1. In FIG. 4, the intake air is indicated by a white arrow, and the exhaust air is indicated by a black arrow. EGR is performed by opening the EGR valve 52 and the bypass valve 41. As shown in FIG. 4, during EGR, part of the intake air flowing through the intake passage 12 flows into the bypass passage 14 from the upstream side of the intercooler 22. In addition, part of the exhaust air flowing through the exhaust passage 13 flows from the exhaust manifold 31 into the EGR passage 15.

[0048] Here, the greater the opening of the EGR valve 52, the greater the amount of EGR recirculation.

[0049] Furthermore, the greater the opening of the bypass valve 41, the greater the flow rate of the intake air flowing through the bypass passage 14, and the lower the pressure at the throttle section 14a. In other words, the greater the opening of the bypass valve 41, the greater the pressure difference in the EGR passage 15 (specifically, the pressure difference between the upstream end and the downstream end of the EGR passage 15), and the greater the EGR return flow rate.

[0050] In addition, the greater the pressure difference in the bypass passage 14, the greater the flow rate of the intake air flowing through the bypass passage 14, and the lower the pressure at the throttle portion 14a. In other words, the greater the pressure difference in the bypass passage 14, the greater the pressure difference in the EGR passage 15, and the greater the EGR return flow rate.

[0051] As described above, the EGR recirculation amount changes depending on the pressure difference in the bypass passage 14, the opening degree of the EGR valve 52, and the opening degree of the bypass valve 41. In other words, each of the pressure difference in the bypass passage 14, the opening degree of the EGR valve 52, and the opening degree of the bypass valve 41 corresponds to a parameter that changes the EGR recirculation amount.

[0052] In step S103, the control unit 172 determines, as the target opening degrees of the EGR valve 52 and the bypass valve 41, such that the EGR recirculation amount becomes the target EGR recirculation amount, based on the differential pressure of the bypass flow passage 14. For example, the control unit 172 can determine the target opening degrees of the EGR valve 52 and the bypass valve 41 by using a map showing the relationship among the differential pressure of the bypass flow passage 14, the opening degree of the EGR valve 52, the opening degree of the bypass valve 41, and the EGR recirculation amount.

[0053] Next, in step S104, the control unit 172 controls the opening degrees of the EGR valve 52 and the bypass valve 41 to the target opening degrees, and the control flow shown in FIG. 3 ends.

[0054] In the control flow illustrated in FIG. 3 described above, the control unit 172 controls the opening degrees of the EGR valve 52 and the bypass valve 41 based on the differential pressure of the bypass passage 14 in addition to the target EGR recirculation amount. However, the control unit 172 may control the opening degrees of the EGR valve 52 and the bypass valve 41 regardless of the differential pressure of the bypass passage 14. For example, by regarding the differential pressure of the bypass passage 14 as a fixed value, a map showing the relationship between the opening degree of the EGR valve 52, the opening degree of the bypass valve 41, and the EGR recirculation amount can be obtained. By using the map obtained in this manner, the control unit 172 can determine the target opening degrees of the EGR valve 52 and the bypass valve 41 and control the opening degrees of the EGR valve 52 and the bypass valve 41.

[0055] Fig. 5 is a flowchart showing an example of a process flow related to idling operation (specifically, idling operation of the engine 11) performed by the control device 17. The control flow shown in Fig. 5 is started, for example, every time the control flow shown in Fig. 3 is executed for a predetermined cycle.

[0056] During idling (i.e., while the determination in step S201 described later is YES), the control flow shown in Fig. 3 is not started after the control flow shown in Fig. 5 ends, and the control flow shown in Fig. 5 is started repeatedly. Then, when the idling of the engine 11 ends (i.e., when the determination in step S201 described later is NO), the control flow shown in Fig. 3 is started.

[0057] 5 is started, first, in step S201, the control unit 172 determines whether the engine 11 is idling. If it is determined that the engine 11 is idling (if the determination in step S201 is YES), the process proceeds to step S202. On the other hand, if it is determined that the engine 11 is not idling (if the determination in step S201 is NO), the control flow shown in FIG. 5 ends.

[0058] If the determination in step S201 is YES, in step S202, the control unit 172 closes the EGR valve 52. Next, in step S203, the control unit 172 closes the throttle valve 23. Next, in step S204, the control unit 172 opens the bypass valve 41, and the control flow shown in FIG 5 ends.

[0059] FIG. 6 is a diagram showing the flow of intake air and exhaust air during idling operation in the intake and exhaust system 1. In FIG. 6, the intake air is indicated by a white arrow, and the exhaust air is indicated by a black arrow. As described above, during idling operation, the throttle valve 23 is closed, and the bypass valve 41 is opened. Therefore, as shown in FIG. 6, the intake air taken in from the intake port 12a passes through the air cleaner 21 and the compressor 16a, and then flows into the bypass flow passage 14 from the upstream side of the intercooler 22. Then, the intake air passes through the bypass flow passage 14 and the intake manifold 24 in this order, and is sent to the engine 11.

[0060] During idling operation, the required flow rate of intake air supplied to the engine 11 (i.e., the required amount) is smaller than when idling operation is not performed. Here, the accuracy of adjusting the intake air flow rate by the throttle valve 23 is not very high. Therefore, it is difficult to accurately adjust the intake air flow rate supplied to the engine 11 to the required amount by adjusting the opening degree of the throttle valve 23.

[0061] Therefore, during idling operation, the flow rate of intake air supplied to the engine 11 can be adjusted to a required amount by closing the throttle valve 23 and opening the bypass valve 41, thereby adjusting the opening degree of the bypass valve 41. Therefore, during idling operation, the flow rate of intake air supplied to the engine 11 can be controlled with high accuracy. For example, in step S204, the control unit 172 controls the opening degree of the bypass valve 41 to a predetermined opening degree such that the required flow rate of intake air supplied to the engine 11 is obtained.

[0062] <Effects of the intake and exhaust system> Next, the effects of the intake and exhaust system 1 according to the embodiment of the present invention will be described.

[0063] The intake and exhaust system 1 according to this embodiment includes a bypass passage 14 that connects the intake passage 12 upstream of the intercooler 22 with the downstream side. The intake and exhaust system 1 also includes an EGR passage 15 that connects the exhaust passage 13 upstream of the turbine 16b with the bypass passage 14. In the intake and exhaust system 1, a throttle section 14a is provided at a connection portion of the bypass passage 14 with the EGR passage 15. This makes it possible to prevent the pressure at the downstream end of the EGR passage 15 from becoming high even under high load. Therefore, the EGR recirculation amount can be secured regardless of the load on the engine 11.

[0064] In addition, in the intake and exhaust system 1 according to this embodiment, it is preferable that a bypass valve 41 is provided in the bypass passage 14. This makes it possible to adjust the flow rate of the intake air flowing from the intake passage 12 to the bypass passage 14 (i.e., the flow rate of the intake air flowing through the bypass passage 14). Therefore, the EGR recirculation amount can be more appropriately controlled.

[0065] In addition, in the intake and exhaust system 1 according to this embodiment, it is preferable that the control unit 172 controls the opening degree of the EGR valve 52 and the bypass valve 41 based on a target EGR reflux amount, which is a target value of the flow rate of the exhaust gas flowing through the EGR passage 15 (i.e., the EGR reflux amount). This makes it possible to appropriately control the EGR reflux amount to the target EGR reflux amount.

[0066] Furthermore, in the intake and exhaust system 1 according to this embodiment, it is preferable that the control unit 172 controls the opening degree of the EGR valve 52 and the bypass valve 41 based on the target EGR reflux amount as well as the differential pressure between the upstream end and the downstream end of the bypass passage 14. This makes it possible to more appropriately control the EGR reflux amount based on the target EGR reflux amount.

[0067] Moreover, in the intake and exhaust system 1 according to this embodiment, it is preferable that the control unit 172 closes the throttle valve 23 and opens the bypass valve 41 during idling operation of the engine 11. This makes it possible to precisely control the flow rate of the intake air supplied to the engine 11 during idling operation.

[0068] The above describes a preferred embodiment of the present invention with reference to the attached drawings. However, it goes without saying that the present invention is not limited to the above-described embodiment, and various modified or altered examples within the scope of the claims also fall within the technical scope of the present invention.

[0069] For example, the processes described herein using flowcharts do not necessarily have to be performed in the order shown in the flowcharts, and additional process steps may be employed or some process steps may be omitted. [Explanation of symbols]

[0070] 1. Intake and exhaust system 11 Engine 12 Intake passage 13 Exhaust flow path 14 Bypass flow path 14a Squeezing section 15 EGR passage 16 Turbocharger 16a Compressor 16b Turbine 17 Control device 17a Processor 17b Memory 22 Intercooler 23 Throttle valve 41 Bypass valve 52 EGR valve

Claims

1. a turbocharger having a compressor provided in an intake passage connected to an engine and a turbine provided in an exhaust passage connected to the engine; an intercooler provided in the intake passage downstream of the compressor; a bypass flow passage connecting an upstream side and a downstream side of the intercooler in the intake flow passage; an EGR flow passage connecting a portion of the exhaust flow passage upstream of the turbine with the bypass flow passage; a throttle portion provided at a connection portion of the bypass passage with the EGR passage; A control device having one or more processors and one or more memories coupled to the processors; Equipped with A bypass valve is provided in the bypass flow path, An EGR valve is provided in the EGR passage, The processor, Executing a process including controlling opening degrees of the EGR valve and the bypass valve based on a target EGR recirculation amount, which is a target value of a flow rate of exhaust gas flowing through the EGR passage; A process is executed that includes controlling opening degrees of the EGR valve and the bypass valve based on a differential pressure between an upstream end and a downstream end of the bypass passage in addition to the target EGR recirculation amount. Intake and exhaust system.

2. A throttle valve is provided in the intake passage, The processor executes a process including closing the throttle valve and opening the bypass valve during an idling operation of the engine. The intake and exhaust system according to claim 1 .

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