JP6841688B2 - How to control a two-stage supercharged exhaust turbocharger, an engine, and a two-stage supercharged exhaust turbocharger - Google Patents

Description

The present invention relates to a two-stage supercharged exhaust turbocharger including a high-pressure stage supercharger and a low-pressure stage supercharger, an engine, and a method for controlling a two-stage supercharged exhaust turbocharger.

In diesel engines, an exhaust gas recirculation (EGR) device that circulates a part of exhaust gas to the intake system is applied in order to suppress the generation of NOx. In addition, a supercharger (turbocharger) is applied as a method of improving the output of a diesel engine. For example, in Patent Document 1, in an engine equipped with a low-pressure stage turbocharger and a high-pressure stage mechanical supercharger, EGR is performed in an EGR mode selected from a plurality of EGR modes of high-pressure EGR, medium-pressure EGR, and low-pressure EGR. The technology is disclosed.

Japanese Unexamined Patent Publication No. 2016-3614

In the conventional two-stage supercharged exhaust turbocharger, it is difficult to improve the EGR rate when the engine is operating in a state close to the turbo limit value and the load is high.

The present invention has been made in view of such a problem, and is a two-stage supercharged exhaust turbocharger, an engine, and a two-stage supercharger that can improve the EGR rate at high load of the engine. An object of the present invention is to provide a control method for an exhaust turbocharger.

The two-stage supercharged exhaust turbocharger of the present invention has a low-pressure stage turbocharger and a low-pressure stage compressor, and is a low-pressure stage turbocharger connected to the intake / exhaust system of the engine body, and a high-pressure stage turbine and a high-pressure stage. A high-pressure turbocharger having a compressor and connected to an intake / exhaust system between the low-pressure turbocharger and the engine body, and an upstream side of the high-pressure turbocharger in the intake / exhaust system and the high-pressure stage. A high-pressure exhaust recirculation device that is connected to the downstream side of the compressor and recirculates the exhaust gas of the engine body, and at least one of the low-pressure stage turbine and the high-pressure stage turbine has the exhaust movable vane in the state of the first opening. A supercharger control unit for recirculating the exhaust gas to the high-pressure exhaust recirculation device is provided, and the supercharger control unit is in a state where the exhaust movable vane is narrowed down to the first opening degree. When the high-pressure exhaust recirculation device recirculates the exhaust gas and the load of the engine body exceeds a predetermined load, the second exhaust movable vane is opened from the first opening degree. It is characterized by changing to the opening degree.

The two-stage supercharged exhaust turbocharger of the present invention is connected to the downstream side of the low-pressure stage turbine and the upstream side of the high-pressure stage compressor in the intake / exhaust system, and is in a state where the exhaust gas can be recirculated. Further provided with a low-pressure exhaust recirculation device capable of switching between a state in which recirculation is impossible and a state in which recirculation is impossible, the supercharger control unit sets the exhaust movable vane to a second opening in a state of being opened from the first opening. When changed, the low-pressure exhaust recirculation device can be switched to a state in which the exhaust gas can be recirculated.

The engine of the present invention includes the above-mentioned two-stage supercharged exhaust turbocharger, an engine body connected to the two-stage supercharged exhaust turbocharger, an engine control unit that controls the engine body, and the like. The engine control unit is characterized in that when the torque of the engine body decreases, the fuel injection amount of the engine body increases.

The control method of the two-stage supercharged exhaust turbocharger of the present invention includes a low-pressure stage turbocharger and a low-pressure stage compressor, and the low-pressure stage turbocharger connected to the intake / exhaust system of the engine body and the high-pressure stage turbocharger. A high-pressure turbocharger having a high-pressure turbocharger and a high-pressure turbocharger connected to an intake / exhaust system between the low-pressure turbocharger and the engine body, and an upstream side of the high-pressure turbocharger in the intake / exhaust system. It is a control method executed by a two-stage supercharged exhaust turbocharger including a high-pressure exhaust recirculation device connected to the downstream side of the high-pressure stage compressor and recirculating the exhaust gas of the engine body. A step of bringing the exhaust movable vane of at least one of the low-pressure stage turbine and the high-pressure stage turbine into a state of the first opening and recirculating the exhaust gas to the high-pressure exhaust recirculation device, and a load of the engine body. Is characterized by including a step of changing the exhaust movable vane to a second opening degree which is open from the first opening degree when the load exceeds a predetermined load.

According to the two-stage supercharged exhaust turbocharger and the control method of the present invention, the high-pressure exhaust recirculation device is in a state where at least one of the low-pressure stage turbine and the high-pressure stage turbine has the exhaust movable vane narrowed to the first opening degree. When the load of the engine body exceeds the predetermined load when the exhaust gas is recirculated, the exhaust movable vane of the turbocharger is changed to the second opening in a state where it is opened from the first opening. Can be done. As a result, the two-stage supercharged exhaust turbocharger and the control method can open the opening of the high-pressure exhaust gas recirculation device by the margin due to the decrease in the rotation speed of the low-pressure turbine, so that the engine is in a high load state. The EGR rate in can be improved. As a result, the two-stage supercharged exhaust turbocharger and the control method can improve the cleanliness of the exhaust gas.

According to the two-stage supercharged exhaust turbocharger of the present invention, when the exhaust movable vane of the low-pressure stage turbine is opened to the second opening, the low-pressure exhaust recirculation device can recirculate the exhaust gas. By switching to, the flow rate of gas flowing through the turbocharger, engine, etc. can be increased. As a result, the two-stage supercharged exhaust turbocharger can increase the exhaust gas to be recirculated, so that the EGR rate in a high load state of the engine can be further improved.

According to the engine of the present invention, the two-stage supercharged exhaust turbocharger exhausts high pressure in a high load state of the engine in which the exhaust movable vane of at least one of the low pressure stage turbine and the high pressure stage turbine is narrowed to the first opening. When the exhaust gas is recirculated by the recirculation device, the exhaust movable vane of the turbocharger is changed to the second opening that is open from the first opening, and when the torque of the engine body decreases, the fuel is fueled. The injection amount can be increased. As a result, the engine can improve the EGR rate while maintaining the engine output.

According to the present invention, the EGR rate under high load of the engine can be improved.

FIG. 1 is a configuration diagram showing an example of a diesel engine including a two-stage supercharged exhaust turbocharger according to an embodiment. FIG. 2 is a map showing the relationship between the engine speed, torque, and mode of a diesel engine. FIG. 3 is a diagram showing the relationship between the opening degree of the low-pressure turbocharger and the engine load. FIG. 4 is a diagram showing the relationship between the EGR rate and the load state of the diesel engine. FIG. 5 is a diagram showing the relationship between the control and operation of the diesel engine in a high load state. FIG. 6 is a diagram showing the relationship between the turbo speed and the load state of the diesel engine. FIG. 7 is a diagram showing the relationship between the pressure ratio and the load state of the diesel engine. FIG. 8 is a diagram showing the relationship between the torque and the load state of the diesel engine. FIG. 9 is a diagram showing the relationship between the fuel injection amount and the load state of the diesel engine. FIG. 10 is a diagram showing the relationship between the net fuel consumption rate and the load state of the diesel engine. FIG. 11 is a flowchart showing a processing procedure of an example of control for switching the opening degree of the low-pressure turbocharger by the control device. FIG. 12 is a diagram showing an example of control for a two-stage supercharged exhaust turbocharger using a map executed by the control device. FIG. 13 is a configuration diagram showing another example of the diesel engine including the two-stage supercharged exhaust turbocharger according to the embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to this embodiment. In addition, the components in the following embodiments include those that can be easily replaced by those skilled in the art, or those that are substantially the same. Further, the components described below can be appropriately combined, and when there are a plurality of embodiments, each embodiment can be combined.

The diesel engine 100 to which the two-stage supercharged exhaust turbocharger 1 is applied will be described with reference to FIG. FIG. 1 is a configuration diagram showing an example of a diesel engine 100 including a two-stage supercharged exhaust turbocharger 1 according to an embodiment. The diesel engine 100 is mounted on, for example, a vehicle, a ship, or the like. The diesel engine 100 includes an engine main body 101, a two-stage supercharged exhaust turbocharger 1, and a control device 10.

The engine body 101 has an injector 102 that injects fuel into the fuel chamber. The injector 102 can inject the indicated injection amount of fuel. The engine body 101 is connected to an intake flow path 113 that supplies intake gas to the engine body 101 and an exhaust flow path 121 that discharges exhaust gas from the engine body 101.

The two-stage supercharged exhaust turbocharger 1 includes a low-pressure stage supercharger 2, a high-pressure stage supercharger 3, a high-pressure exhaust recirculation device 4, a low-pressure exhaust recirculation device 5, and an intake bypass valve 6. , Exhaust bypass valve 7. In the present embodiment, the two-stage supercharged exhaust turbocharger 1 includes a supercharger control unit 10A of the control device 10. The two-stage supercharged exhaust turbocharger 1 may be configured to be controlled by an external supercharger control unit 10A.

The low-pressure turbocharger 2 is connected to the intake / exhaust system of the diesel engine 100. The low-pressure stage turbocharger 2 includes a low-pressure stage turbine 21 and a low-pressure stage compressor 22. The low-pressure stage turbine 21 is driven by the exhaust gas from the engine body 101. The low-pressure stage turbine 21 operates in a single stage when the operating state of the diesel engine 100 is a high load state and the flow rate of exhaust gas is large. The low-pressure stage turbine 21 and the low-pressure stage compressor 22 are integrally and rotatably connected by a rotating shaft 23. The low-pressure stage compressor 22 is driven by power from the low-pressure stage turbine 21 via the rotating shaft 23. The low-pressure stage turbine 21 is connected to the exhaust flow path 122 on the upstream side and to the exhaust flow path 123 on the downstream side. The low-pressure stage compressor 22 is connected to the intake flow path 111 on the upstream side and to the intake flow path 112 on the downstream side.

The low-pressure stage turbocharger 2 has a nozzle vane (exhaust movable vane) 21a provided around the low-pressure stage turbine 21. For example, a plurality of nozzle vanes 21a may be arranged at equal intervals in the circumferential direction around the low pressure stage turbine 21. The opening degree of the nozzle vane 21a can be adjusted by an actuator or the like. The low-pressure stage turbine 21 can increase the flow rate of the exhaust gas flowing through the low-pressure stage turbine 21 and the like by reducing (squeezing) the opening degree of the nozzle vane 21a.

The high-pressure turbocharger 3 is connected to an intake / exhaust system between the low-pressure turbocharger 2 and the engine body 101. The high-pressure turbocharger 3 includes a high-pressure turbine 31 and a high-pressure compressor 32. The high-pressure stage turbine 31 operates when the operating state of the diesel engine 100 is a low load state and the flow rate of the exhaust gas is small. The high-pressure stage turbine 31 and the high-pressure stage compressor 32 are integrally and rotatably connected by a rotating shaft 33. The high-pressure stage turbine 31 is connected to the exhaust flow path 121 on the upstream side and to the exhaust flow path 122 on the downstream side. The upstream side of the high-pressure compressor 32 is connected to the intake flow path 112, and the downstream side is connected to the intake flow path 113.

The high-pressure stage turbocharger 3 has a nozzle vane 31a of the high-pressure stage turbine 31 like the low-pressure stage turbocharger 2. For example, a plurality of nozzle vanes 31a may be arranged at equal intervals in the circumferential direction around the high-pressure stage turbine 31. The opening degree of the nozzle vane 31a can be adjusted by an actuator or the like. The high-pressure stage turbine 31 can increase the flow rate of the exhaust gas flowing through the high-pressure stage turbine 31 and the like by reducing (squeezing) the opening degree of the nozzle vane 31a.

The high-pressure exhaust gas recirculation device 4 has an EGR (Exhaust Gas Recirculation) passage 41 and an EGR valve 42 provided in the EGR passage 41. The EGR passage 41 circulates the exhaust gas of the engine body 101 as EGR gas to the engine body 101. The EGR passage 41 is connected to an exhaust flow path 121 between the high-pressure stage turbine 31 and the engine body 101, and an intake flow path 113 between the high-pressure stage compressor 32 and the engine body 101. The EGR passage 41 is a passage that bypasses the engine body 101. The EGR valve 42 can adjust the flow rate of the exhaust gas recirculated in the engine body 101.

The low-pressure exhaust gas recirculation device 5 has an EGR passage 51 and an EGR valve 52 provided in the EGR passage 51. The EGR passage 51 recirculates the exhaust gas of the engine main body 101 via the low-pressure stage turbine 21 to the engine main body 101 as EGR gas via the low-pressure stage compressor 22. The EGR passage 51 is connected to the exhaust flow path 123 and the intake flow path 111. The EGR passage 51 is a passage that bypasses the engine body 101. The EGR valve 52 can adjust the flow rate of exhaust gas or the like circulating from the low-pressure stage turbine 21 to the low-pressure stage compressor 22.

The intake bypass valve 6 is provided in the intake bypass flow path 131 connected to the intake flow path 112 and the intake flow path 113. The intake bypass flow path 131 is a flow path that bypasses the high-pressure stage compressor 32. The intake bypass valve 6 is a valve that is opened and closed by an actuator (not shown). By opening and closing the intake bypass valve 6, the flow rate of the intake gas flowing through the intake bypass flow path 131 can be adjusted. When the intake bypass valve 6 is in the open state, the intake gas passes through the intake bypass flow path 131 and bypasses the high-pressure stage compressor 32.

The exhaust bypass valve 7 is provided in the exhaust bypass flow path 132 connected to the exhaust flow path 121 and the exhaust flow path 122. The exhaust bypass valve 7 is a flow path that bypasses the high-pressure stage turbine 31. The exhaust bypass valve 7 is a valve that is opened and closed by an actuator (not shown). By opening and closing the exhaust bypass valve 7, the flow rate of the exhaust gas flowing through the exhaust bypass flow path 132 can be adjusted. When the exhaust bypass valve 7 is in the open state, exhaust gas passes through the exhaust bypass flow path 132 and bypasses the high-pressure stage turbine 31.

The control device 10 is composed of a memory and a CPU (Central Processing Unit). The control device 10 may be realized by dedicated hardware, or may realize the function by loading and executing a program for realizing the function of the control device 10 in a memory. Good.

The control device 10 comprehensively controls the diesel engine 100. The control device 10 includes a supercharger control unit 10A and an engine control unit 10B.

The supercharger control unit 10A controls the operation of each part of the two-stage supercharged exhaust turbocharger 1. The supercharger control unit 10A acquires the load information of the engine body 101. For example, the load information includes detection results of an engine speed sensor, an accelerator opening sensor, a pressure sensor, a temperature sensor, and the like. The supercharger control unit 10A can adjust the opening degrees of the nozzle vanes 21a and 31a based on the load state of the engine. The supercharger control unit 10A can control the EGR valves 42 and 52, and can adjust the opening degree of the EGR valves 42 and 52 based on the engine operating state.

The engine control unit 10B controls the operation of the engine body 101. The engine control unit 10B controls the operation of the engine body 101 based on various input conditions such as a required load and the results detected by various sensors. The engine control unit 10B controls the fuel injection timing to the cylinder, the injection amount, and the opening / closing timing of the exhaust valve to control the fuel input amount and the rotation speed of the engine body 101 and the combustion in the combustion chamber. The engine control unit 10B controls the engine output of the engine body 101 by controlling the fuel input amount and the rotation speed.

In the present embodiment, the diesel engine 100 describes a case where the control device 10 has a supercharger control unit 10A and an engine control unit 10B, but the present invention is not limited to this. For example, in the diesel engine 100, the supercharger control unit 10A and the engine control unit 10B may be independent hardware.

The control device 10 controls the intake bypass valve 6 and the exhaust bypass valve 7 according to the operating state of the engine body 101. More specifically, the control device 10 controls the actuator to close the exhaust bypass valve 7 when the operating state of the engine body 101 is in a low load state, and causes the actuator to be closed when the operating state of the engine body 101 is in a high load state. The exhaust bypass valve 7 is controlled and opened.

Next, the flow path through which the intake gas flows in the engine 100 will be described. The flow path through which the intake gas flows is configured by connecting the intake flow path 111, the intake flow path 112, and the intake flow path 113 in order from the upstream side. The intake flow path 111 takes in air from the outside. The upstream side of the intake flow path 111 is open to the outside, and the downstream side is connected to the low pressure stage compressor 22. The upstream side of the intake flow path 112 is connected to the low pressure stage compressor 22, and the downstream side is connected to the high pressure stage compressor 32. The upstream side of the intake flow path 113 is connected to the high-pressure compressor 32, and the downstream side is connected to the engine body 101. The intake gas is supplied to the engine body 101 through the flow path configured in this way.

Next, the flow path through which the exhaust gas flows in the engine 100 will be described. The flow path through which the exhaust gas flows is configured by connecting the exhaust flow path 121, the exhaust flow path 122, and the exhaust flow path 123 in order from the upstream side. The exhaust flow path 121 discharges exhaust gas from the engine body 101. The upstream side of the exhaust flow path 121 is connected to the engine body 101, and the downstream side is connected to the high-pressure turbine 31. The upstream side of the exhaust flow path 122 is connected to the high-pressure stage turbine 31, and the downstream side is connected to the low-pressure stage turbine 21. The upstream side of the exhaust flow path 123 is connected to the low pressure stage turbine 21. Exhaust gas is discharged from the engine body 101 through the flow path configured in this way.

In the two-stage supercharged exhaust turbocharger 1 configured in this way, when the operating state of the engine 100 is in a high load state, the low-pressure turbine 21 rotates with the exhaust gas discharged from the engine main body 101. Then, the rotation of the low-pressure stage turbine 21 is transmitted via the rotation shaft 23, and the low-pressure stage compressor 22 rotates. Then, the low-pressure stage compressor 22 compresses the intake gas and supplies it to the engine body 101 via the intake flow path 112. In the two-stage supercharged exhaust turbocharger 1, when the operating state of the engine 100 is in a low load state, the high-pressure stage turbine 31 rotates with the exhaust gas discharged from the engine main body 101 through the exhaust flow path 121. Then, the rotation of the high-pressure stage turbine 31 is transmitted via the rotation shaft 33, and the high-pressure stage compressor 32 rotates. Then, the high-pressure stage compressor 32 compresses the intake gas and supplies it to the engine body 101 via the intake flow path 113.

An example of the mode used for controlling the diesel engine 100 will be described with reference to FIG. FIG. 2 is a map 11 showing the relationship between the engine speed, torque, and mode of the diesel engine 100. In FIG. 2, the horizontal axis represents the engine speed and the vertical axis represents the torque.

The control device 10 controls the two-stage supercharged exhaust turbocharger 1 by switching between modes 1, mode 2, and mode 3 shown in FIG. 2 based on the engine speed, torque, and map 11. Mode 1 is a mode in which the operating state of the diesel engine 100 is a low speed state. The mode 2 is a mode in which the operating state of the diesel engine 100 is in the process of shifting from the low speed state to the high speed state (hereinafter, referred to as "medium speed state"). Mode 3 is a mode in which the operating state of the diesel engine 100 is a high-speed state. In the diesel engine 100, the full load performance curve of the map 11 shows the relationship between the engine speed and the torque operating in a state close to the turbo limit value. The turbo limit value includes, for example, a limit value such as a rotor speed, a back temperature, and a compressor outlet temperature. The diesel engine 100 controls the two-stage supercharged exhaust turbocharger 1 so that the relationship between the engine speed and the torque does not exceed the turbo limit value.

The control device 10 adjusts the opening degrees of the nozzle vanes 21a and 31a in the two-stage supercharged exhaust turbocharger 1 so that the exhaust pressure of the exhaust flow path 121 becomes higher than the intake pressure of the intake flow path 113. As a result, the exhaust gas in the exhaust flow path 121 flows from the EGR passage 41 to the intake flow path 113.

The control device 10 increases the opening degree of the EGR valve 42 to allow a large amount of EGR gas to pass through the EGR passage 41 when the diesel engine 100 is operating, that is, when the combustion temperature is high and a high concentration of NOx is likely to be generated. Return to the engine body 101. As a result, in the diesel engine 100, the combustion temperature in the combustion chamber is lowered by the returned EGR gas, and the amount of NOx generated can be reduced as the combustion temperature is lowered.

The control device 10 reduces the opening degree of the nozzle vane 21a to increase the speed of the exhaust gas flowing to the low-pressure turbine 21 when the diesel engine 100 is in operation, that is, in a low load state where the output is insufficient. As a result, the diesel engine 100 rotates the low-pressure stage turbine 21 and the low-pressure stage compressor 22 at high speed by the high-speed exhaust gas flow, and the low-pressure stage compressor 22 compresses the intake air to increase the filling efficiency and improve the engine output. Can be done.

An example of control of the low-pressure turbocharger 2 by the diesel engine 100 will be described with reference to FIG. FIG. 3 is a diagram showing the relationship between the opening degree of the low-pressure turbocharger 2 and the engine load. In FIG. 3, the horizontal axis represents the engine load of the diesel engine 100, and the vertical axis represents the opening degree of the low-pressure turbocharger 2. On the horizontal axis, the left side is in the low load state and the right side is in the high load state. The vertical axis opens toward the upper side and closes toward the lower side.

The graph G11 shown in FIG. 3 shows the relationship between the engine load and the opening degree (VG opening degree) of the supercharger when the recirculation is not executed. Graph G12 shows the relationship between the engine load and the opening degree (VG opening degree) of the turbocharger when the recirculation is executed and the opening degree of the EGR valve 42 is narrowed down. Graph G13 shows the relationship between the engine load and the opening degree (VG opening degree) of the turbocharger when the recirculation is executed and the opening degree of the EGR valve 42 is opened. Graph G14 shows the relationship between the engine load of the present embodiment and the opening degree (VG opening degree) of the supercharger.

When there is no EGR, the diesel engine 100 keeps the EGR valve 42 closed. No EGR means that the diesel engine 100 does not apply EGR. As shown in the graph G11 of FIG. 3, in the case of no EGR, the diesel engine 100 narrows the opening degree of the supercharger as the engine load of the engine body 101 changes from the low load state to the high load state. When the diesel engine 100 has EGR, the EGR valve 42 is in an open state. With EGR means that the diesel engine 100 applies EGR. As shown in the graph G14 of FIG. 3, the diesel engine 100 of the present embodiment is a low-pressure turbocharger 2 of the low-pressure turbocharger 2 until the engine load reaches a predetermined load when the diesel engine 100 has an EGR. The exhaust gas is recirculated to the high-pressure exhaust recirculation device 4 according to the first opening degree in which 21 is narrowed down, that is, the relationship of the graph G12. Then, when the engine load exceeds a predetermined load, the diesel engine 100 changes the low-pressure stage turbine 21 to a second opening degree which is open from the first opening degree. Specifically, the valve opening degree is adjusted according to the relationship of the graph G13 of FIG.

As a result, the diesel engine 100 can open the opening degree of the high-pressure exhaust gas recirculation device 4 by the margin due to the decrease in the rotation speed of the low-pressure stage turbine 21, so that the exhaust gas (EGR gas) of the exhaust flow path 121 is EGR. It can be introduced from the passage 41 to the intake flow path 113. In the diesel engine 100, since the combustion temperature is lowered by the EGR gas and the generation of NOx can be suppressed, the EGR rate in a high load state of the engine can be improved. As a result, the diesel engine 100 can improve the cleanliness of the exhaust gas.

For example, in the case of the diesel engine 100 with EGR, the exhaust gas can be circulated to the engine body 101 by narrowing the opening degree of the nozzle vanes 21a, 31a, etc. of the supercharger. However, in the diesel engine 100, when the engine body 101 is in a high load state, if the opening degrees of the nozzle vanes 21a and 31a are reduced (throttled), the flow rate of the exhaust gas flowing through the low-pressure stage turbine 21 and the like increases, so that the turbo Due to the limit value of, the opening degrees of the nozzle vanes 21a and 31a cannot be reduced. On the other hand, in the diesel engine 100 of the present embodiment, when the engine body 101 is in a high load state, the opening degrees of the nozzle vanes 21a and 31a are opened, so that the EGR rate is improved without exceeding the turbo limit value. Can be done.

Using FIG. 4, when the engine load exceeds a predetermined load with EGR, the diesel engine 100 opens the opening degree of the low-pressure turbocharger 2 and does not open the opening degree. An example of the relationship between the rate and the engine load will be described. FIG. 4 is a diagram showing the relationship between the EGR rate and the load state of the diesel engine 100. In FIG. 4, the horizontal axis represents the engine load of the diesel engine 100, and the vertical axis represents the EGR ratio of the diesel engine 100. On the horizontal axis, the left side is in the low load state and the right side is in the high load state. On the vertical axis, the upper side has a higher EGR rate, and the lower side has an EGR rate of 0. Graph G22 shows the relationship between the engine load and the EGR rate when recirculation is executed and the opening degree of the EGR valve 42 is narrowed (setting of graph G12). Graph G23 shows the relationship between the engine load and the EGR rate when recirculation is executed and the opening degree of the EGR valve 42 is opened (setting of graph G13). Graph G24 shows the relationship between the engine load and the EGR rate when the opening degree of the EGR valve 42 is set (setting of graph G14) in the present embodiment.

The diesel engine 100 of the present embodiment changes the valve opening degree in relation to the graph G14, and as shown in the graph G24 of FIG. 4, EGR at the first inclination until the engine load reaches a predetermined load. The rate drops. When the engine load of the diesel engine 100 exceeds a predetermined load, the EGR rate of the diesel engine 100 decreases at a second inclination that is gentler than the first inclination. On the other hand, the graph G22 performs a simulation or an engine test on the diesel engine 100, and has an EGR, and the engine load and the EGR rate when the opening of the supercharger is not opened even if the engine load exceeds a predetermined load. Shows the relationship with. In the graph G22, the EGR rate decreases until the engine load reaches a predetermined load, as in the graph G12. Then, in the graph G22, when the engine load exceeds a predetermined load, the EGR rate decreases until it becomes zero. As described above, in the diesel engine 100 of the present embodiment, when the engine load exceeds a predetermined load, the EGR rate is improved as compared with the result when the opening degree of the supercharger is not opened. Further, in the diesel engine 100 of the present embodiment, when the engine load is equal to or less than a predetermined load, the EGR rate can be made higher than the setting in which the opening degree of the EGR valve 42 is opened.

Next, an example of the relationship between the control and the operation of the diesel engine 100 will be described with reference to FIGS. 5 to 11. FIG. 5 is a diagram showing the relationship between the control and operation of the diesel engine 100 in a high load state. In this embodiment, the relationship between the opening degree of the EGR valve 42 and the engine load is set based on the relationship shown in FIG.

When the engine load of the diesel engine 100 exceeds a predetermined load, the diesel engine 100 opens the opening degree of the low-pressure stage turbine 21 (step S100). For example, the diesel engine 100 controls an actuator or the like based on the graph G12 of FIG. 3 to open the nozzle vane 21a of the low-pressure stage turbine 21 in the closed state. As a result, in the diesel engine 100, the rotation speed of the low-pressure turbocharger 2 decreases (state ST11). That is, the turbo speed of the diesel engine 100 decreases. In the diesel engine 100, if the opening degree of the low pressure stage turbine 21 is opened too much, the back temperature becomes excessive. The back temperature includes the temperature of the exhaust gas.

In the diesel engine 100, the pressure ratio decreases as the turbo speed decreases (state ST12). That is, in the diesel engine 100, the air flow rate of the intake / exhaust system is reduced. In the diesel engine 100, when the atmospheric pressure ratio decreases, the torque of the engine decreases (state ST13). That is, in the diesel engine 100, the engine output is reduced by opening the opening degree of the low pressure stage turbine 21.

The diesel engine 100 increases the fuel injection amount after the opening degree of the low-pressure stage turbine 21 is opened (step S200). For example, the diesel engine 100 injects the fuel injection amount into the engine body 101 based on the state of the engine load. As a result, the diesel engine 100 can inject the engine main body 101 with a fuel injection amount that offsets the decrease in the torque of the engine in the state ST13.

In the diesel engine 100, when the fuel injection amount is increased, the net fuel consumption rate may deteriorate (state ST21). The net fuel consumption rate indicates the fuel consumed per hour in terms of the amount of work per horsepower or 1 km. For example, in the diesel engine 100, the net fuel consumption rate may be deteriorated by having EGR in the state where the low-pressure stage turbine 21 is closed. The diesel engine 100 may increase the fuel injection amount within a range in which the deterioration of the net fuel consumption rate in the state where the low-pressure stage turbine 21 is closed is suppressed to the same level of deterioration as in the state where the low-pressure stage turbine 21 is closed.

In the diesel engine 100, the torque of the engine is increased by increasing the fuel injection amount (state ST22). That is, the diesel engine 100 can offset the decreased engine output by opening the opening degree of the low-pressure turbine 21 with the increased engine output. As a result, the diesel engine 100 can open the EGR valve 42 of the high-pressure exhaust gas recirculation device 4 by the margin due to the decrease in the rotation speed of the low-pressure stage turbocharger 2, so that the EGR rate can be improved.

When the diesel engine 100 includes the low-pressure exhaust gas recirculation device 5, the EGR valve 52 of the low-pressure exhaust gas recirculation device 5 is opened after increasing the fuel injection amount (step S300). For example, the diesel engine 100 controls an actuator or the like to open an EGR valve 52 in a closed state.

In the diesel engine 100, when the engine load exceeds a predetermined load, the rotation speed of the low-pressure stage turbocharger 2 increases by opening the EGR valve 52 of the low-pressure exhaust gas recirculation device 5 (state ST31). That is, the turbo speed of the diesel engine 100 increases. In the diesel engine 100, if the opening degree of the EGR valve 52 is opened too much, the rotation speed of the low-pressure turbocharger 2 and the outlet temperature of the low-pressure compressor 22 exceed the limit values, and the net fuel consumption rate may deteriorate. It may exceed the range.

In the diesel engine 100, the pressure ratio increases as the turbo speed increases (state ST32). That is, in the diesel engine 100, the air flow rate of the intake / exhaust system increases. Then, in the diesel engine 100, the torque of the engine increases as the atmospheric pressure ratio increases (state ST22). As a result, the diesel engine 100 can offset the decreased engine output by opening the opening degree of the low-pressure turbine 21 with the increased engine output by increasing the fuel injection amount and opening the EGR valve 52. As a result, the diesel engine 100 can open the EGR valve 42 of the high-pressure exhaust gas recirculation device 4 by the margin due to the decrease in the rotation speed of the low-pressure stage turbocharger 2, so that the EGR rate can be improved.

As described above, the diesel engine 100 describes a VG table for obtaining the second opening degree from the engine load in the memory or the like of the control device 10 when the engine load exceeds a predetermined load. When the load of the engine body 101 exceeds a predetermined load, the control device 10 obtains a second opening degree that is wider than the first opening degree of the low-pressure stage turbocharger 2 based on the load and the VG table. be able to.

Further, in the diesel engine 100, when the exhaust gas is recirculated by the high pressure exhaust recirculation device 4 in a state where the nozzle vane 21a of the low pressure stage turbine 21 is narrowed down to the first opening degree, the nozzle vane 21a of the low pressure stage turbine 21 If is changed to the second opening in a state of being opened more than the first opening, the output of the engine is reduced. However, the diesel engine 100 can recover the reduced engine output by increasing the fuel injection amount of the engine body 101. As a result, the diesel engine 100 can improve the EGR rate while maintaining the engine output in a high load state of the engine. As a result, the diesel engine 100 can improve the cleanliness of the exhaust gas under a high load state of the engine.

Next, the relationship between other parameters when the diesel engine of the present embodiment is used for control will be described. FIG. 6 is a diagram showing the relationship between the turbo speed and the load state of the diesel engine. In FIG. 6, a simulation or an engine test is performed on the diesel engine 100, and the horizontal axis represents the engine load of the diesel engine 100 and the vertical axis represents the turbo speed. On the horizontal axis, the left side is in the low load state and the right side is in the high load state. On the vertical axis, the upper side has a higher rotation speed, and the lower side has a lower rotation speed. Graph G31 shows the relationship between the engine load and the turbo speed when the recirculation is not executed. Graph G32 shows the relationship between the engine load and the turbo speed when recirculation is executed and the opening degree of the EGR valve 42 is narrowed (setting of graph G12). Graph G33 shows the relationship between the engine load and the turbo speed when recirculation is executed and the opening degree of the EGR valve 42 is opened (setting of graph G13). Graph G34 shows the relationship between the engine load and the turbo speed when the opening degree of the EGR valve 42 is set (setting of graph G14) in the present embodiment.

In the case of no EGR, as shown in the graph G31 of FIG. 6, the turbo speed of the diesel engine 100 increases as the engine load of the engine body 101 changes from a low load state to a high load state. On the other hand, in the case of having EGR, as shown in the graph G34 of FIG. 6, the diesel engine 100 changes in the same relationship as the graph G32 until the engine load reaches a predetermined load, and is higher than the graph G31. With the number of revolutions, the number of turbo revolutions is increasing. Then, when the engine load exceeds a predetermined load, the diesel engine 100 changes in the same relationship as the graph G33, decreases to a lower rotation speed than the graph G31, and then has a turbo rotation speed lower than the graph G31. Will increase.

FIG. 7 is a diagram showing the relationship between the pressure ratio and the load state of the diesel engine. In FIG. 7, a simulation or an engine test is performed on the diesel engine 100, and the horizontal axis represents the engine load of the diesel engine 100 and the vertical axis represents the pressure ratio. On the horizontal axis, the left side is in the low load state and the right side is in the high load state. On the vertical axis, the pressure ratio is higher toward the upper side and lower at the lower side. Graph G41 shows the relationship between the engine load and the pressure ratio when the recirculation is not executed. Graph G42 shows the relationship between the engine load and the pressure ratio when recirculation is executed and the opening degree of the EGR valve 42 is narrowed (setting of graph G12). Graph G43 shows the relationship between the engine load and the pressure ratio when recirculation is executed and the opening degree of the EGR valve 42 is opened (setting of graph G13). Graph G44 shows the relationship between the engine load and the pressure ratio when the opening degree of the EGR valve 42 is set (setting of graph G14) in the present embodiment.

In the case of no EGR, as shown in the graph G41 of FIG. 7, the pressure ratio of the diesel engine 100 increases as the engine load of the engine body 101 changes from a low load state to a high load state. On the other hand, in the case of EGR, as shown in the graph G44 of FIG. 7, the pressure ratio of the diesel engine 100 is increased in a state higher than that of the graph G41 until the engine load reaches a predetermined load. .. Then, when the engine load exceeds a predetermined load, the diesel engine 100 decreases to a pressure ratio lower than that of the graph G41, and then increases the pressure ratio in a state lower than that of the graph G41.

FIG. 8 is a diagram showing the relationship between the torque and the load state of the diesel engine. In FIG. 8, a simulation or an engine test is performed on the diesel engine 100, and the horizontal axis represents the engine load of the diesel engine 100 and the vertical axis represents the torque. On the horizontal axis, the left side is in the low load state and the right side is in the high load state. On the vertical axis, the torque is larger toward the upper side and smaller toward the lower side. Graph G51 shows the relationship between the engine load and the torque when the recirculation is not executed. Graph G52 shows the relationship between the engine load and torque when recirculation is executed and the opening degree of the EGR valve 42 is narrowed (setting of graph G12). Graph G53 shows the relationship between the engine load and torque when recirculation is executed and the opening degree of the EGR valve 42 is opened (setting of graph G13). Graph G54 shows the relationship between the engine load and torque when the opening degree of the EGR valve 42 is set (setting of graph G14) in the present embodiment.

The diesel engine 100 maintains the required output by adjusting various conditions to keep the torque constant under any of the conditions. In the graphs G51, G52, G53, and G54, the torque increases as the engine load changes from the low load state to the high load state.

FIG. 9 is a diagram showing the relationship between the fuel injection amount and the load state of the diesel engine. In FIG. 9, a simulation or an engine test is performed on the diesel engine 100, and the horizontal axis represents the engine load of the diesel engine 100 and the vertical axis represents the fuel injection amount. On the horizontal axis, the left side is in the low load state and the right side is in the high load state. On the vertical axis, the fuel injection amount is larger toward the upper side, and the fuel injection amount is 0 at the lower side. Graph G61 shows the relationship between the engine load and the fuel injection amount when the recirculation is not executed. Graph G62 shows the relationship between the engine load and the fuel injection amount when recirculation is executed and the opening degree of the EGR valve 42 is narrowed (setting of graph G12). Graph G63 shows the relationship between the engine load and the fuel injection amount when recirculation is executed and the opening degree of the EGR valve 42 is opened (setting of graph G13). Graph G64 shows the relationship between the engine load and the fuel injection amount when the opening degree of the EGR valve 42 is set (setting of graph G14) in the present embodiment.

In the case of the diesel engine 100 without EGR, as shown in the graph G61 of FIG. 9, the fuel injection amount increases as the engine load of the engine body 101 changes from the low load state to the high load state. In the case of EGR, when the control of the present embodiment is executed, the diesel engine 100 has a higher fuel injection amount than the graph G61 and an engine load from a low load state to a high load state, as shown in the graph G64 of FIG. As the fuel injection amount increases, the fuel injection amount increases. Further, when the control of the present embodiment is executed, the diesel engine 100 has the same fuel injection amount as the graph G63 when the opening degree of the EGR valve is increased, and the opening degree of the EGR valve is narrowed in the high load band. The fuel injection amount is larger than that of the graph G62 in the case.

FIG. 10 is a diagram showing the relationship between the net fuel consumption rate and the load state of the diesel engine. In FIG. 10, a simulation or an engine test is performed on the diesel engine 100, and the horizontal axis represents the engine load of the diesel engine 100 and the vertical axis represents the net fuel consumption rate. On the horizontal axis, the left side is in the low load state and the right side is in the high load state. On the vertical axis, the net fuel consumption rate is higher toward the upper side, and the net fuel consumption rate is 0 at the lower side. Graph G71 shows the relationship between the engine load and the net fuel consumption rate when recirculation is not performed. Graph G72 shows the relationship between the engine load and the net fuel consumption rate when recirculation is executed and the opening degree of the EGR valve 42 is narrowed (setting of graph G12). Graph G73 shows the relationship between the engine load and the net fuel consumption rate when recirculation is executed and the opening degree of the EGR valve 42 is opened (setting of graph G13). Graph G74 shows the relationship between the engine load and the net fuel consumption rate when the opening degree of the EGR valve 42 is set (setting of graph G14) in the present embodiment.

In the case of no EGR, as shown in the graph G71 of FIG. 10, the diesel engine 100 increases the net fuel consumption rate as the engine load of the engine body 101 changes from the low load state to the high load state. In the case of the control of the present embodiment, the diesel engine 100 consumes more fuel as the engine load changes from a low load state to a high load state with a fuel injection amount higher than that of the graph G71, as shown in the graph G74 of FIG. The rate is high. When the net fuel consumption rate deteriorates, the diesel engine 100 causes the engine body 101 to inject a fuel injection amount based on the graph G72 and the state of the engine load. As a result, the diesel engine 100 can inject the engine main body 101 with a fuel injection amount that offsets the decrease in the torque of the engine in the state ST13.

FIG. 11 is a flowchart showing a processing procedure of an example of control for switching the opening degree of the low-pressure turbocharger 2 by the control device 10. The processing procedure shown in FIG. 11 is realized by the control device 10 executing a control program or the like. The processing procedure shown in FIG. 11 is executed by the control device 10 when the diesel engine 100 has EGR.

As shown in FIG. 11, the control device 10 of the diesel engine 100 narrows the opening degree of the low-pressure turbocharger 2 to the first opening degree (step S51). For example, the control device 10 controls the actuator of the low-pressure turbocharger 2 to close the opening degree of the low-voltage turbocharger 2 to the first opening degree. The control device 10 opens the EGR valve 42 of the high-pressure exhaust gas recirculation device 4 (step S52). As a result, the diesel engine 100 can recirculate the exhaust gas of the engine body 101 as EGR gas to the engine body 101 under a high load state.

The control device 10 detects the state of the diesel engine 100 (step S53). For example, the control device 10 detects the load state of the diesel engine 100 from the detection results of an engine speed sensor, an accelerator opening degree sensor, a pressure sensor, a temperature sensor, and the like (not shown).

The control device 10 determines whether or not the load exceeds a predetermined load based on the detected load state of the diesel engine 100 (step S54). When the control device 10 determines that the load does not exceed the predetermined load (No in step S54), the control device 10 returns the process to step S53 already described. When the control device 10 determines that the load exceeds a predetermined load (Yes in step S54), the control device 10 proceeds to the process in step S55.

The control device 10 opens the opening degree of the low-pressure stage turbocharger 2 from the first opening degree to the second opening degree (step S55). For example, the control device 10 obtains a second opening degree based on the load state of the diesel engine 100 and the VG table, and causes the opening degree of the low-pressure turbocharger 2 to be opened by the second opening degree. Then, the control device 10 specifies the fuel injection amount corresponding to the amount at which the opening degree of the low-pressure stage turbocharger 2 is opened (step S56). For example, the control device 10 specifies the fuel injection amount by using a table for specifying the fuel injection amount from the relationship between the fuel injection amount and the load and the second opening degree shown in FIG. 9, a calculation program, and the like.

The control device 10 requests the engine body 101 to inject the specified fuel injection amount (step S57). For example, the engine control unit 10B of the control device 10 causes the injector 102 of the engine body 101 to inject fuel at the fuel injection amount. Then, the control device 10 opens the EGR valve 52 of the low-pressure exhaust gas recirculation device 5 (step S58). As a result, the diesel engine 100 can recirculate the exhaust gas from the low-pressure stage turbine 21 as EGR gas to the low-pressure stage compressor 22. Then, when the control device 10 opens the EGR valve 52, the processing procedure shown in FIG. 11 is completed.

In the diesel engine 100, the high-pressure exhaust recirculation device 4 recirculates the exhaust gas under the state of the engine load in which the nozzle vanes 21a of the low-pressure turbine 21 are narrowed down to the first opening degree. In this case, the diesel engine 100 opens the nozzle vane 21a (exhaust movable vane) of the low-pressure turbine 21 to the second opening degree based on the limit value of the two-stage turbo of the high-pressure turbocharger 3 and the low-pressure turbocharger 2. It is possible to restore the output of the engine as well as change it to. As a result, the diesel engine 100 can further improve the EGR rate in a high load state of the engine in which the EGR rate cannot be increased due to the turbo limit value or the like.

When the nozzle vane 21a of the low-pressure stage turbine 21 is opened to the second opening, the diesel engine 100 switches the low-pressure exhaust recirculation device 5 to a state in which exhaust gas can be recirculated, whereby the low-pressure stage compressor 22 and the engine The flow rate of the gas flowing through the main body 101 and the like can be increased. As a result, the diesel engine 100 can improve the EGR rate in a high load state and suppress an increase in fuel consumption.

Next, an example of the operation mode of the diesel engine 100 and the operating state of the supercharger will be described with reference to FIG. FIG. 12 is a diagram showing an example of control for the two-stage supercharged exhaust turbocharger 1 using the map 11 executed by the control device 10.

When the operation mode of the diesel engine 100 is mode 1, the control device 10 controls the two-stage supercharged exhaust turbocharger 1 when the operating state of the diesel engine 100 is a low speed state. The control device 10 closes the exhaust bypass valve 7 and the intake bypass valve 6, opens the high-pressure stage turbine 31 from small to medium open, and opens the low-pressure stage turbine 21 to medium open. Nakahiraki is more open than small opening. As a result, the exhaust gas flows into the high-pressure stage turbine 31 and the low-pressure stage turbine 21. As a result, in the two-stage supercharged exhaust turbocharger 1, two stages of the low-pressure stage supercharger 2 and the high-pressure stage supercharger 3 operate.

When the operation mode of the diesel engine 100 is mode 2, the control device 10 controls the two-stage supercharged exhaust turbocharger 1 while the operating state of the diesel engine 100 is a medium speed state. The medium speed state is faster than the low speed state. The control device 10 opens the exhaust bypass valve 7, closes the intake bypass valve 6, opens the high-pressure stage turbine 31 fully, and opens the low-pressure stage turbine 21 from small to medium. As a result, the exhaust gas flows into the high-pressure stage turbine 31 and the low-pressure stage turbine 21. As a result, in the two-stage supercharged exhaust turbocharger 1, two stages of the low-pressure stage supercharger 2 and the high-pressure stage supercharger 3 operate. In this case, the high-pressure turbocharger 3 operates as an auxiliary to the low-pressure turbocharger 2.

When the operation mode of the diesel engine 100 is mode 3, the control device 10 controls the two-stage supercharged exhaust turbocharger 1 while the operating state of the diesel engine 100 is in a high speed state. The high speed state is faster than the medium speed state. In the control device 10, the exhaust bypass valve 7 is fully opened, the intake bypass valve 6 is opened, the high-pressure stage turbine 31 is fully opened, and the low-pressure stage turbine 21 is fully opened from the middle open. That is, the control device 10 can switch the opening degree of the low-pressure stage turbine 21 between the first opening degree and the second opening degree. As a result, the exhaust gas flows into the low-pressure stage turbine 21. As a result, in the two-stage supercharged exhaust turbocharger 1, one stage of the low-pressure stage supercharger 2 operates. In this case, the high-pressure turbocharger 3 is stopped.

In the above embodiment, the diesel engine 100 has described the case where the opening degree of the nozzle vane 21a of the low-pressure turbine 2 is opened when the load of the engine body 101 exceeds a predetermined load, but the present invention is not limited to this. The diesel engine 100 of the present embodiment expands the vane opening of the turbocharger to reduce the rotation speed of the turbine, and the margin generated by this decrease increases the opening of the EGR valve to increase the EGR rate. explained. In the diesel engine 100 of the present invention, the supercharger to be opened can be changed according to the specifications of the engine and the supercharger. For example, the diesel engine 100 may reduce the rotation speed of the turbine by opening the opening degree of the nozzle vane 31a of the high-pressure stage turbine 3 when the load of the engine body 101 exceeds a predetermined load. For example, in the diesel engine 100, when the load of the engine body 101 exceeds a predetermined load, the turbine rotates by opening the opening degrees of both the nozzle vane 21a of the low-pressure stage turbine 2 and the nozzle vane 31a of the high-pressure stage turbine 3. The number may be reduced.

In the above embodiment, the diesel engine 100 has described the case where the two-stage supercharged exhaust turbocharger 1 includes the low-pressure exhaust gas recirculation device 5, but the present invention is not limited to this. FIG. 13 is a configuration diagram showing another example of the diesel engine 100 including the two-stage supercharged exhaust turbocharger according to the embodiment. FIG. 13 has the same reference numerals for the same components as those in FIG. As shown in FIG. 13, in the diesel engine 100, the two-stage supercharged exhaust turbocharger 1 does not have to include the low-pressure exhaust gas recirculation device 5. That is, the two-stage supercharged exhaust turbocharger 1 includes a low-pressure stage supercharger 2, a high-pressure stage supercharger 3, a high-pressure exhaust recirculation device 4, an intake bypass valve 6, and an exhaust bypass valve 7. , The configuration may include the control device 10. In this case, the control device 10 executes steps S57 to S57 of the predetermined procedure shown in FIG. 11, and does not execute the process of step S58.

In the above embodiment, the case where the two-stage supercharged exhaust turbocharger 1 is used for the diesel engine 100 has been described, but the present invention is not limited to this. For example, the two-stage supercharged exhaust turbocharger 1 may be applied to a gasoline engine.

1 Two-stage turbocharger 2 Low-pressure stage turbocharger 21 Low-pressure stage turbocharger 22 Low-pressure stage turbocharger 3 High-pressure stage turbocharger 31 High-pressure stage turbocharger 32 High-pressure stage compressor 4 High-pressure exhaust gas recirculation device 41 EGR passage 42 EGR Valve 5 Low-pressure exhaust gas recirculation device 51 EGR passage 52 EGR valve 6 Intake bypass valve 7 Exhaust bypass valve 10 Control device 10A Supercharger control unit 10B Engine control unit 100 Diesel engine (engine)
101 engine body

Claims (4)

A low-pressure turbocharger that has a low-pressure turbine and a low-pressure compressor and is connected to the intake / exhaust system of the engine body.
A high-pressure turbocharger having a high-pressure turbine and a high-pressure compressor and connected to an intake / exhaust system between the low-pressure turbocharger and the engine body.
A high-pressure exhaust recirculation device connected to the upstream side of the high-pressure stage turbine and the downstream side of the high-pressure stage compressor in the intake / exhaust system to recirculate the exhaust gas of the engine body.
At least one of the low-pressure stage turbine and the high-pressure stage turbine is brought into a state of a first opening degree smaller than the opening degree when recirculation by the high-pressure exhaust recirculation device is not performed, and the exhaust gas is discharged. The supercharger control unit that recirculates the high-pressure exhaust gas recirculation device,
With
The supercharger control unit
In a state in which the targeted exhaust movable vane to said first opening, when the high-pressure exhaust gas recirculation system is recirculating the exhaust gas, when the load of the engine body exceeds a predetermined load, the exhaust The movable vane is changed to a second opening that is larger than the opening when recirculation by the high-pressure exhaust recirculation device is not performed and is open from the first opening. Feeding exhaust turbocharger. Low-pressure exhaust recirculation that is connected to the downstream side of the low-pressure stage turbine and the upstream side of the high-pressure stage compressor in the intake / exhaust system and can switch between a state in which the exhaust gas can be recirculated and a state in which recirculation is not possible. Equipped with a circulation device
The supercharger control unit
Wherein Changing the exhaust movable vanes in the second opening of the opened than the first opening, wherein, characterized in that switching between the low pressure exhaust gas recirculation system to recycle a state capable of the exhaust gas Item 1. The two-stage supercharged exhaust turbocharger according to Item 1. The two-stage supercharged exhaust turbocharger according to claim 1 or 2,
The engine body connected to the two-stage supercharged exhaust turbocharger,
An engine control unit that controls the engine body and
With
The engine control unit is an engine characterized in that when the torque of the engine body decreases, the fuel injection amount of the engine body increases. A low-pressure turbocharger that has a low-pressure turbine and a low-pressure compressor and is connected to the intake / exhaust system of the engine body.
A high-pressure turbocharger having a high-pressure turbine and a high-pressure compressor and connected to an intake / exhaust system between the low-pressure turbocharger and the engine body.
A high-pressure exhaust recirculation device connected to the upstream side of the high-pressure stage turbine and the downstream side of the high-pressure stage compressor in the intake / exhaust system to recirculate the exhaust gas of the engine body.
It is a control method executed by a two-stage supercharged exhaust turbocharger equipped with.
At least one of the low-pressure stage turbine and the high-pressure stage turbine is brought into a state of a first opening degree smaller than the opening degree when recirculation by the high-pressure exhaust recirculation device is not performed, and the exhaust gas is discharged. The step of recirculating the high-pressure exhaust recirculation device and
When the load of the engine body exceeds a predetermined load, the opening of the exhaust movable vane is larger than the opening when the recirculation by the high-pressure exhaust recirculation device is not performed, and the opening is larger than the first opening. Steps to change to 2 opening and
A control method for a two-stage supercharged exhaust turbocharger, which comprises.

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