Intake and exhaust system

Abstract

To suppress discharge of unburned fuel.SOLUTION: An intake and exhaust system 1 includes an engine 100 including a combustion chamber 108, an intake flow passage 200 communicating with the combustion chamber 108, a fuel injection nozzle provided in the intake flow passage 200, and a first connection flow passage 500 connecting the fuel injection nozzle and a part of the intake flow passage 200 upstream the fuel injection nozzle.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] There is an engine having a combustion chamber, an intake valve, and an exhaust valve. In such an engine, as disclosed in, for example, Patent Document 1, an intake port communicating with the combustion chamber is opened and closed by the intake valve, and an exhaust port communicating with the combustion chamber is opened and closed by the exhaust valve. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 049878 Summary of the Invention [Problem to be solved by the invention]

[0004] During the intake stroke, the intake valve opens, causing a gas flow from the intake port toward the combustion chamber. During the exhaust stroke, the exhaust valve opens, causing a gas flow from the combustion chamber toward the exhaust port. In the process of exhausting the gas, unburned fuel may be discharged. For example, when switching from the exhaust stroke to the intake stroke, a situation may occur in which both the intake valve and the exhaust valve are open. In a situation in which both the intake valve and the exhaust valve are open, a blow-by may occur in which unburned fuel remaining in the intake port is discharged through the exhaust port. From the viewpoint of improving thermal efficiency or suppressing greenhouse gas emissions, it is desirable to suppress the emission of unburned fuel.

[0005] An object of the present disclosure is to provide an intake and exhaust system capable of suppressing the emission of unburned fuel. [Means for solving the problem]

[0006] In order to solve the above problems, the intake and exhaust system of the present disclosure includes an engine having a combustion chamber, an intake flow passage communicating with the combustion chamber, a fuel injection nozzle provided in the intake flow passage, and a first connection flow passage connecting the fuel injection nozzle to the intake flow passage upstream of the fuel injection nozzle.

[0007] The engine may include a control device that performs suction of gas through a first connecting passage from the fuel injection nozzle to the intake passage, and the control device may prohibit suction of gas through the first connecting passage from the fuel injection nozzle to the intake passage while fuel is being injected by the fuel injection nozzle.

[0008] The engine may include a compressor provided in the intake passage, and the first connection passage may connect the fuel injection nozzle to a portion of the intake passage upstream of the compressor.

[0009] The engine may include a compressor provided in the intake passage, and the first connection passage may connect the fuel injection nozzle to a portion of the intake passage downstream of the compressor, and the first connection passage may be provided with a booster.

[0010] The engine may further include a second connection passage that connects an intake port, which is a portion of the intake passage within the cylinder head, to a portion of the intake passage upstream of the intake port.

[0011] The engine is provided with a control device that performs suction of gas from the intake port through a second connecting passage to the intake passage, and the control device may prohibit suction of gas from the intake port to the intake passage through the second connecting passage when the engine intake valve is open.

[0012] The control device may prohibit the suction of gas from the intake port to the intake passage via the second connection passage while the intake valve is closed, if fuel is being injected by the fuel injection nozzle.

[0013] The engine may further include a compressor provided in the intake passage, and the second connection passage may connect the intake port to a portion of the intake passage upstream of the compressor.

[0014] The compressor may be provided in the intake passage, and the second connection passage may connect the intake port to a portion of the intake passage downstream of the compressor, and the second connection passage may be provided with a booster. Effect of the Invention

[0015] According to the present disclosure, it is possible to suppress the emission of unburned fuel. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an intake and exhaust system according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a schematic diagram showing the configuration of each cylinder of the engine according to the embodiment of the present disclosure. [Diagram 3] FIG. 3 is a graph showing an example of the transition of each state quantity according to the embodiment of the present disclosure. [Figure 4] FIG. 4 is a schematic diagram showing the configuration of an intake and exhaust system according to a modified example of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present disclosure will be described with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values ​​shown in the embodiments are merely examples for ease of understanding, and do not limit the present disclosure 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 disclosure are not illustrated.

[0018] Fig. 1 is a schematic diagram showing the configuration of an intake and exhaust system 1 according to this embodiment. The intake and exhaust system 1 is a system related to the intake and exhaust of an engine 100. As shown in Fig. 1, the intake and exhaust system 1 includes an engine 100, an intake flow path 200, an exhaust flow path 300, a supercharger 400, a first connection flow path 500, a second connection flow path 600, and a control device 700. As described later, the configuration in Fig. 1 is merely an example, and various modifications may be made to the example in Fig. 1.

[0019] The engine 100 has multiple cylinders. In the example of Fig. 1, the engine 100 has a first cylinder #1, a second cylinder #2, a third cylinder #3, a fourth cylinder #4, a fifth cylinder #5, and a sixth cylinder #6. However, the number of cylinders of the engine 100 may be other than six.

[0020] Fig. 2 is a schematic diagram showing the configuration of each cylinder of the engine 100 according to this embodiment. In Fig. 2, the intake port 104a, the exhaust port 104b, the fuel injection nozzle 112, and the ignition device 114 are illustrated on the same cross section. However, the intake port 104a, the exhaust port 104b, the fuel injection nozzle 112, and the ignition device 114 do not have to be located on the same cross section.

[0021] 2, the engine 100 includes a cylinder liner 102, a cylinder head 104, and a piston 106. The piston 106 is housed within the cylinder liner 102. A combustion chamber 108 is formed by the cylinder liner 102, the cylinder head 104, and the piston 106.

[0022] An intake port 104a and an exhaust port 104b are formed in the cylinder head 104. The intake port 104a and the exhaust port 104b open to the combustion chamber 108. The intake valve 110a opens and closes the opening of the intake port 104a on the combustion chamber 108 side. The exhaust valve 110b opens and closes the opening of the exhaust port 104b on the combustion chamber 108 side. The intake valve 110a and the exhaust valve 110b open and close in accordance with the rotation of a camshaft (not shown).

[0023] A pipe forming a branch passage 202 of the intake passage 200, which will be described later, is connected to the intake port 104a. An air-fuel mixture flows into the combustion chamber 108 via the intake port 104a. As will be described later, a branch passage 602 of a second connection passage 600 is connected to the intake port 104a. A pipe forming a branch passage 302 of the exhaust passage 300, which will be described later, is connected to the exhaust port 104b. Exhaust gas is discharged from the combustion chamber 108 via the exhaust port 104b.

[0024] The fuel injection nozzle 112 is connected to a fuel supply source via a fuel supply passage 112a. The fuel supply source is, for example, a fuel tank (not shown) or a pipeline for city gas or the like. Fuel gas is supplied to the fuel injection nozzle 112 from the fuel supply source via the fuel supply passage 112a. The fuel injection nozzle 112 is provided in a branch passage 202 of the intake passage 200. The tip of the fuel injection nozzle 112 faces the intake port 104a. However, the fuel injection nozzle 112 may be provided in the intake port 104a.

[0025] The fuel injection nozzle 112 injects fuel gas into the intake port 104a. The fuel gas is generated, for example, by gasifying LNG (liquefied natural gas). The fuel gas is not limited to LNG, and may be, for example, gasified LPG (liquefied petroleum gas), light oil, heavy oil, ammonia, hydrogen, or the like. The engine 100 is a gas engine that uses fuel gas as fuel. Hereinafter, the fuel gas is also simply referred to as fuel. As described later, a branch passage 502 of the first connection passage 500 is connected to the fuel injection nozzle 112.

[0026] The ignition device 114 is provided in the cylinder head 104. A tip portion of the ignition device 114 protrudes into the combustion chamber .

[0027] The engine 100 is a four-stroke engine. During the intake stroke, fuel is injected from the fuel injection nozzle 112, the intake valve 110a opens, and the exhaust valve 110b closes. The piston 106 moves toward the bottom dead center, and intake air and fuel are drawn into the combustion chamber 108 from the intake port 104a. During the compression stroke, the intake valve 110a and the exhaust valve 110b close. The piston 106 moves toward the top dead center, and the air-fuel mixture in the combustion chamber 108 is compressed. The air-fuel mixture is ignited by the ignition device 114 and combusted, and during the combustion stroke, the piston 106 is pressed toward the bottom dead center. During the exhaust stroke, the intake valve 110a closes, and the exhaust valve 110b opens. The piston 106 moves toward the top dead center, and the exhaust gas after combustion is discharged from the combustion chamber 108 through the exhaust port 104b. Returning to FIG. 1, the description will be continued below.

[0028] The intake passage 200 communicates with the combustion chamber 108 of the engine 100. In the intake passage 200, intake air, which is air supplied to the combustion chamber 108, flows. An intake port (not shown) through which air is taken in from the outside is provided at the upstream end of the intake passage 200. The intake passage 200 has a plurality of branch passages 202 that communicate with the plurality of combustion chambers 108, respectively. The plurality of branch passages 202 are provided on the downstream side of the intake passage 200. As described above, the pipe that forms the branch passage 202 is connected to the intake port 104a of the engine 100. The intake port 104a corresponds to the downstream end of the branch passage 202. The intake port 104a is included in the intake passage 200. The intake port 104a is a portion of the intake passage 200 inside the cylinder head 104.

[0029] The exhaust flow passage 300 communicates with the combustion chamber 108 of the engine 100. Exhaust gas discharged from the combustion chamber 108 flows through the exhaust flow passage 300. An exhaust port (not shown) is provided at the downstream end of the exhaust flow passage 300, through which the exhaust gas is discharged to the outside. The exhaust flow passage 300 has a plurality of branch flow passages 302 that communicate with the plurality of combustion chambers 108, respectively. The plurality of branch flow passages 302 are provided on the upstream side of the exhaust flow passage 300. As described above, the pipe that forms the branch flow passage 302 is connected to the exhaust port 104b of the engine 100. The exhaust port 104b corresponds to the upstream end of the branch flow passage 302. The exhaust port 104b is included in the exhaust flow passage 300. The exhaust port 104b is a portion of the exhaust flow passage 300 inside the cylinder head 104.

[0030] The turbocharger 400 has a compressor 402 and a turbine 404. The impeller of the compressor 402 and the impeller of the turbine 404 rotate as a unit. The impeller of the compressor 402 and the impeller of the turbine 404 are connected by a shaft.

[0031] The compressor 402 is provided in the intake air flow path 200 upstream of the branch flow path 202. The compressor 402 compresses the intake air taken in from the intake port and sends it downstream. An intercooler C1 is provided in the intake air flow path 200 upstream of the branch flow path 202 and downstream of the compressor 402. The intake air flowing through the intercooler C1 is cooled by heat exchange with air outside the intercooler C1. The intake air that has passed through the intercooler C1 is sent to each combustion chamber 108 via each branch flow path 202. Note that the intercooler C1 may be one that uses cooling water such as engine cooling water or industrial water to cool the intake air.

[0032] The turbine 404 is provided in the exhaust passage 300 downstream of the branch passages 302. The exhaust gas discharged from the engine 100 is sent to the turbine 404 via each branch passage 302. The exhaust gas sent to the turbine 404 passes through the turbine 404 and is discharged from an exhaust port. The turbine 404 generates rotational power by rotating a blade of the turbine 404 by the exhaust gas. The rotational power generated by the turbine 404 is transmitted to the compressor 402 via a shaft.

[0033] The first connection flow passage 500 is connected to the intake flow passage 200 on the upstream side of the compressor 402. The first connection flow passage 500 branches into a plurality of branch flow passages 502 on the opposite side of the connection point with the intake flow passage 200 on the upstream side of the compressor 402. As shown in FIG. 2, each branch flow passage 502 is connected to the fuel injection nozzle 112 of each branch flow passage 202. In the example of FIG. 1, branch flow passages 502a, 502b, 502c, 502d, 502e, and 502f are provided as the branch flow passages 502. The branch flow passages 502a, 502b, 502c, 502d, 502e, and 502f are connected to the fuel injection nozzles 112 of the branch flow passages 202 connected to the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, the fifth cylinder #5, and the sixth cylinder #6, respectively.

[0034] As described above, the first connection passage 500 connects the fuel injection nozzle 112 to the intake passage 200 on the upstream side of the fuel injection nozzle 112. For example, the first connection passage 500 connects the fuel injection nozzle 112 to at least the intake passage 200 on the upstream side of the branch passage 202. The first connection passage 500 is provided to return the fuel remaining in the fuel injection nozzle 112 to the intake passage 200 on the upstream side of the fuel injection nozzle 112.

[0035] An on-off valve 504 is provided in each branch flow path 502. The on-off valve 504 is capable of opening and closing the branch flow path 502. In the example of Fig. 1, on-off valves 504a, 504b, 504c, 504d, 504e, and 504f are provided as the on-off valves 504. The on-off valves 504a, 504b, 504c, 504d, 504e, and 504f are provided in the branch flow paths 502a, 502b, 502c, 502d, 502e, and 502f, respectively.

[0036] In the intake passage 200, the fuel injection nozzle 112 is located downstream of the compressor 402. Therefore, the pressure in the intake passage 200 at the location where the fuel injection nozzle 112 is installed is higher than the pressure in the intake passage 200 upstream of the compressor 402. Therefore, when the on-off valve 504 is opened, gas is sucked from the fuel injection nozzle 112 to the branch passage 502, and the gas is sent to the intake passage 200 upstream of the compressor 402 via the first connection passage 500.

[0037] The second connection flow passage 600 is connected to the intake flow passage 200 on the upstream side of the compressor 402. The second connection flow passage 600 branches into a plurality of branch flow passages 602 on the opposite side of the connection point with the intake flow passage 200 on the upstream side of the compressor 402. As shown in FIG. 2, each branch flow passage 602 is connected to the intake port 104a of each cylinder. In the example of FIG. 1, branch flow passages 602a, 602b, 602c, 602d, 602e, and 602f are provided as the branch flow passages 602. The branch flow passages 602a, 602b, 602c, 602d, 602e, and 602f are connected to the intake ports 104a of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, the fifth cylinder #5, and the sixth cylinder #6, respectively.

[0038] As described above, the second connection passage 600 connects the intake port 104a to the intake passage 200 on the upstream side of the intake port 104a. For example, the second connection passage 600 connects the intake port 104a to at least the intake passage 200 on the upstream side of the branch passage 202. The second connection passage 600 is provided to return the fuel remaining in the intake port 104a to the intake passage 200 on the upstream side of the intake port 104a.

[0039] An on-off valve 604 is provided in each branch flow path 602. The on-off valve 604 is capable of opening and closing the branch flow path 602. In the example of Fig. 1, on-off valves 604a, 604b, 604c, 604d, 604e, and 604f are provided as the on-off valve 604. The on-off valves 604a, 604b, 604c, 604d, 604e, and 604f are provided in the branch flow paths 602a, 602b, 602c, 602d, 602e, and 602f, respectively.

[0040] In the intake flow path 200, the intake port 104a is located downstream of the compressor 402. Therefore, the pressure at the intake port 104a in the intake flow path 200 is higher than the pressure at the upstream side of the compressor 402 in the intake flow path 200. Therefore, when the on-off valve 604 is opened, gas is sucked from the intake port 104a to the branch flow path 602, and the gas is sent to the upstream side of the compressor 402 in the intake flow path 200 via the second connection flow path 600.

[0041] The control device 700 includes a central processing unit (CPU), a ROM in which programs and the like are stored, a RAM as a work area, etc. The control device 700 controls the operation of each device in the intake and exhaust system 1.

[0042] For example, the controller 700 may control the operation of the engine 100. In particular, the controller 700 may control the timing of fuel injection by the fuel injection nozzles 112.

[0043] For example, the control device 700 controls the operation of each on-off valve 504. As a result, the control device 700 can execute suction of gas from the fuel injection nozzle 112 to the intake passage 200 via the first connection passage 500. Hereinafter, suction of gas via the first connection passage 500 is also referred to as first suction. The control device 700 can control the operation of each on-off valve 504 to control the timing of the first suction.

[0044] For example, the control device 700 controls the operation of each on-off valve 604. This allows the control device 700 to execute suction of gas from the intake port 104a to the intake flow path 200 via the second connection flow path 600. Hereinafter, suction of gas via the second connection flow path 600 is also referred to as second suction. The control device 700 can control the operation of each on-off valve 604 to control the timing of the second suction.

[0045] The transition of each state quantity for one of the cylinders will be described below with reference to Fig. 3. However, the transition of each state quantity for the other cylinders is similar. As will be described later, the transition in Fig. 3 is merely an example, and various modifications may be made to the example in Fig. 3.

[0046] FIG. 3 is a graph showing an example of the transition of each state quantity according to this embodiment. In FIG. 3, the horizontal axis represents the crank angle, and the vertical axis represents the lift amount of the intake valve 110a and the exhaust valve 110b, the timing of fuel injection, the timing of the first suction, and the timing of the second suction, as state quantities. In FIG. 3, fuel injection is performed when fuel injection is ON, and fuel injection is not performed when fuel injection is OFF. In FIG. 3, the first suction is performed when the first suction is ON, and the first suction is not performed when the first suction is OFF. In FIG. 3, the second suction is performed when the second suction is ON, and the second suction is not performed when the second suction is OFF.

[0047] 3 shows the transition of the lift amount LAa of the intake valve 110a and the transition of the lift amount LAb of the exhaust valve 110b. In the example of FIG. 3, at the crank angle CA1, the lift amount LAb of the exhaust valve 110b starts to increase, and the exhaust valve 110b starts to open. At the crank angle CA4 after the crank angle CA1, the lift amount LAb of the exhaust valve 110b ends to decrease, and the exhaust valve 110b finishes closing. At the crank angle CA3 after the crank angle CA1 and before the crank angle CA4, the lift amount LAa of the intake valve 110a starts to increase, and the intake valve 110a starts to open. At the crank angle CA6 after the crank angle CA4, the lift amount LAa of the intake valve 110a ends to decrease, and the intake valve 110a finishes closing.

[0048] 3, fuel injection by fuel injection nozzle 112 begins at crank angle CA2 after crank angle CA1 and before crank angle CA3. Specifically, fuel injection by fuel injection nozzle 112 begins a time before crank angle CA3 at which intake valve 110a begins to open, taking into account the travel time of fuel from fuel injection nozzle 112 to combustion chamber 108. Fuel injection by fuel injection nozzle 112 ends at crank angle CA5 after crank angle CA4 and before crank angle CA6.

[0049] As described above, in the example of Fig. 3, a situation occurs in which both the intake valve 110a and the exhaust valve 110b are open. In this situation, unburned fuel remaining in the intake port 104a may be discharged through the exhaust port 104b, resulting in the discharge of unburned fuel. The control device 700 controls the timing of the first suction and the timing of the second suction so as to effectively suppress the discharge of unburned fuel.

[0050] For example, as shown in Fig. 3, the control device 700 prohibits the first suction during the period when fuel is injected by the fuel injection nozzle 112. In the example of Fig. 3, the control device 700 prohibits and does not execute the first suction during the period from crank angle CA2 to crank angle CA5 during which fuel is injected by the fuel injection nozzle 112. This prevents the fuel injected from the fuel injection nozzle 112 from being sucked into the first connection passage 500 without being sent to the combustion chamber 108.

[0051] Meanwhile, the control device 700 executes the first suction before the crank angle CA2 and after the crank angle CA5 at which fuel is not injected by the fuel injection nozzle 112. As a result, the fuel remaining in the fuel injection nozzle 112 is sucked by the first connection passage 500 and returned to the intake passage 200 upstream of the fuel injection nozzle 112 via the first connection passage 500.

[0052] For example, as shown in Fig. 3, the control device 700 prohibits the second suction when the intake valve 110a is open. In the example of Fig. 3, the control device 700 prohibits and does not execute the second suction during the period from crank angle CA3 to crank angle CA6 when the intake valve 110a is open. This prevents the suction of gas by the second connection passage 600 from disturbing the flow of gas in the intake port 104a and inhibiting the flow of gas from the intake port 104a into the combustion chamber 108 when the intake valve 110a is open.

[0053] Furthermore, the control device 700 prohibits the second suction when the intake valve 110a is closed and fuel is being injected by the fuel injection nozzle 112. In the example of Fig. 3, the control device 700 prohibits and does not execute the second suction during the period from crank angle CA2 to crank angle CA3 when the intake valve 110a is closed but fuel is being injected by the fuel injection nozzle 112. This prevents the fuel injected from the fuel injection nozzle 112 from being sent to the combustion chamber 108 and being sucked into the second connection passage 600.

[0054] On the other hand, the control device 700 executes the second suction before the crank angle CA2 and after the crank angle CA6 when the intake valve 110a is closed and fuel is not injected by the fuel injection nozzle 112. As a result, the fuel remaining in the intake port 104a is sucked by the second connection passage 600 and returned to the intake passage 200 upstream of the intake port 104a via the second connection passage 600.

[0055] As described above, the intake and exhaust system 1 includes the engine 100 having the combustion chamber 108, the intake passage 200 communicating with the combustion chamber 108, the fuel injection nozzle 112 provided in the intake passage 200, and the first connection passage 500 connecting the fuel injection nozzle 112 to the intake passage 200 upstream of the fuel injection nozzle 112. As a result, the fuel remaining in the fuel injection nozzle 112 can be sucked by the first connection passage 500 and returned to the intake passage 200 upstream of the fuel injection nozzle 112 via the first connection passage 500. Therefore, in a situation where both the intake valve 110a and the exhaust valve 110b are open, the blow-by of unburned fuel being discharged through the exhaust port 104b is suppressed. Therefore, the discharge of unburned fuel is suppressed. Therefore, the improvement of thermal efficiency and the suppression of greenhouse gas emissions are realized.

[0056] Furthermore, in the intake and exhaust system 1, when the intake valve 110a is closed, gas can be made to flow in the intake port 104a by suctioning the gas through the first connection passage 500. This allows the intake valve 110a to be opened while gas is flowing in the intake port 104a, thereby accelerating the initial flow of gas from the intake port 104a to the combustion chamber 108 and smoothing the flow of gas.

[0057] In particular, the intake and exhaust system 1 includes a compressor 402 provided in the intake passage 200, and the first connection passage 500 connects the fuel injection nozzle 112 to the intake passage 200 on the upstream side of the compressor 402. This eliminates the need to provide a booster unit 506 described later, unlike the case where the first connection passage 500 is connected to the intake passage 200 on the downstream side of the compressor 402, as in the intake and exhaust system 1A according to a modified example of FIG.

[0058] In particular, the intake and exhaust system 1 further includes a second connection passage 600 that connects the intake port 104a, which is a portion of the intake passage 200 inside the cylinder head 104, to the intake passage 200 upstream of the intake port 104a. As a result, the fuel remaining in the intake port 104a can be sucked by the second connection passage 600 and returned to the intake passage 200 upstream of the intake port 104a via the second connection passage 600. Therefore, in a situation where both the intake valve 110a and the exhaust valve 110b are open, the blow-by of unburned fuel being discharged through the exhaust port 104b is more effectively suppressed. Therefore, the discharge of unburned fuel is more effectively suppressed.

[0059] Furthermore, in the intake and exhaust system 1, when the intake valve 110a is closed, the gas can be made to flow more effectively in the intake port 104a by suctioning the gas through the second connection passage 600. This allows the intake valve 110a to be opened in a state in which the gas is made to flow more effectively in the intake port 104a, thereby more effectively accelerating the initial flow of gas from the intake port 104a to the combustion chamber 108 and more effectively smoothing the flow of gas.

[0060] In particular, the intake and exhaust system 1 includes a compressor 402 provided in the intake flow path 200, and the second connection flow path 600 connects the intake port 104a to the intake flow path 200 on the upstream side of the compressor 402. This eliminates the need to provide a booster unit 606 described later, unlike the case where the second connection flow path 600 is connected to the intake flow path 200 on the downstream side of the compressor 402, as in the intake and exhaust system 1A according to a modified example of FIG.

[0061] The intake and exhaust system 1 has been described above with reference to Figures 1 to 3. However, various modifications may be made to the example described above.

[0062] For example, in the above description, an example has been described in which the first connection flow path 500 and the second connection flow path 600 are provided separately. However, a part of the first connection flow path 500 and a part of the second connection flow path 600 may be realized by a common flow path. For example, a part of the first connection flow path 500 downstream of the branch flow paths 502 in the gas flow direction and a part of the second connection flow path 600 downstream of the branch flow paths 602 in the gas flow direction may be merged to form one common flow path.

[0063] For example, in the above description, an example has been described in which the second connection flow path 600 is provided in addition to the first connection flow path 500. However, of the first connection flow path 500 and the second connection flow path 600, the second connection flow path 600 does not necessarily have to be provided.

[0064] For example, in the above description, an example has been described in which the first connection flow path 500 and the second connection flow path 600 are connected to the intake flow path 200 on the upstream side of the compressor 402. However, at least one of the first connection flow path 500 and the second connection flow path 600 may be connected to the intake flow path 200 on the downstream side of the compressor 402. This example will be described later with reference to FIG.

[0065] For example, in the above example, the compressor 402 and the intercooler C1 are provided in the intake passage 200, and the turbine 404 is provided in the exhaust passage 300. However, the turbocharger 400 may be omitted, or one of the compressor 402 and the turbine 404 may be omitted. The intercooler C1 may be omitted.

[0066] For example, in the above, an example of the transition of each state quantity has been described with reference to FIG. 3. However, the transition of each state quantity is not limited to the example of FIG. 3. For example, the end timing of the first suction may be earlier than the start timing of the fuel injection. For example, the start timing of the first suction may be later than the end timing of the fuel injection. For example, the end timing of the second suction may be earlier than the start timing of the fuel injection. For example, the start timing of the second suction may be later than the timing when the intake valve 110a finishes closing. For example, the start timing of the fuel injection may be later than the timing when the intake valve 110a starts opening.

[0067] As described above, at least one of the first connection flow path 500 and the second connection flow path 600 may be connected to the intake flow path 200 downstream of the compressor 402. This example will be described with reference to Fig. 4. Fig. 4 is a schematic diagram showing the configuration of an intake and exhaust system 1A according to a modified example. In the intake and exhaust system 1A, the connection positions of the first connection flow path 500 and the second connection flow path 600 are different from those of the intake and exhaust system 1 described above.

[0068] 4, in the intake and exhaust system 1A, the first connection passage 500 has branch passages 502a, 502b, 502c, 502d, 502e, and 502f, similar to the intake and exhaust system 1 described above. The branch passages 502a, 502b, 502c, 502d, 502e, and 502f are connected to the fuel injection nozzles 112 of the branch passages 202 connected to the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, the fifth cylinder #5, and the sixth cylinder #6, respectively. The first connection passage 500 is provided to return the fuel remaining in the fuel injection nozzle 112 to the intake passage 200 upstream of the fuel injection nozzle 112.

[0069] In the intake and exhaust system 1A, unlike the above-described intake and exhaust system 1, a portion of the first connection flow path 500 downstream of the branch flow paths 502 in the gas flow direction is connected to the intake flow path 200 downstream of the compressor 402. In the example of Fig. 4, the above portion of the first connection flow path 500 is connected to the intake flow path 200 downstream of the compressor 402 and upstream of the intercooler C1. However, the above portion of the first connection flow path 500 may be connected to the intake flow path 200 downstream of the intercooler C1.

[0070] In the intake and exhaust system 1A, unlike the intake and exhaust system 1 described above, a booster 506 is provided in the first connection passage 500. The booster 506 increases the pressure of the gas sent from the fuel injection nozzle 112 to the first connection passage 500. Examples of the booster 506 include an electric fan or an electric compressor. The booster 506 makes the pressure in the first connection passage 500 higher than the pressure in the intake passage 200 downstream of the compressor 402 and upstream of the intercooler C1. Therefore, when the on-off valve 504 is opened, gas is sucked from the fuel injection nozzle 112 to the branch passage 502, and the gas is sent to the intake passage 200 downstream of the compressor 402 via the first connection passage 500.

[0071] 4, in the intake and exhaust system 1A, the second connection passage 600 has branch passages 602a, 602b, 602c, 602d, 602e, and 602f, similar to the intake and exhaust system 1 described above. The branch passages 602a, 602b, 602c, 602d, 602e, and 602f are connected to the intake ports 104a of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, the fifth cylinder #5, and the sixth cylinder #6, respectively. The second connection passage 600 is provided to return the fuel remaining in the intake port 104a to the intake passage 200 upstream of the intake port 104a.

[0072] In the intake and exhaust system 1A, unlike the above-described intake and exhaust system 1, a portion of the second connection passage 600 downstream of the branch passages 602 in the gas flow direction is connected to the intake passage 200 downstream of the compressor 402. In the example of Fig. 4, the above portion of the second connection passage 600 is connected to the intake passage 200 downstream of the compressor 402 and upstream of the intercooler C1. However, the above portion of the second connection passage 600 may be connected to the intake passage 200 downstream of the intercooler C1.

[0073] In the intake and exhaust system 1A, unlike the above-mentioned intake and exhaust system 1, a booster 606 is provided in the second connection passage 600. The booster 606 increases the pressure of the gas sent from the intake port 104a to the second connection passage 600. Examples of the booster 606 include an electric fan or an electric compressor. The booster 606 makes the pressure in the second connection passage 600 higher than the pressure in the intake passage 200 downstream of the compressor 402 and upstream of the intercooler C1. Therefore, when the on-off valve 604 is opened, gas is sucked from the intake port 104a to the branch passage 602, and the gas is sent to the intake passage 200 downstream of the compressor 402 via the second connection passage 600.

[0074] As described above, the intake and exhaust system 1A includes the compressor 402 provided in the intake passage 200, and the first connection passage 500 connects the fuel injection nozzle 112 to the intake passage 200 downstream of the compressor 402, and the booster 506 is provided in the first connection passage 500. This allows the fuel remaining in the fuel injection nozzle 112 to be sucked by the first connection passage 500 and returned to the intake passage 200 upstream of the fuel injection nozzle 112 via the first connection passage 500. Furthermore, unlike the case where the first connection passage 500 is connected to the intake passage 200 upstream of the compressor 402 as in the above-mentioned intake and exhaust system 1, the gas containing fuel is prevented from being sent to the compressor 402.

[0075] The intake and exhaust system 1A also includes a compressor 402 provided in the intake passage 200, and the second connection passage 600 connects the intake port 104a to the intake passage 200 downstream of the compressor 402, and the second connection passage 600 is provided with a booster 606. This allows the fuel remaining in the intake port 104a to be sucked by the second connection passage 600 and returned to the intake passage 200 upstream of the intake port 104a via the second connection passage 600. Furthermore, unlike the case where the second connection passage 600 is connected to the intake passage 200 upstream of the compressor 402 as in the above-mentioned intake and exhaust system 1, the gas containing fuel is prevented from being sent to the compressor 402.

[0076] In the above-described intake and exhaust system 1A, both the first connection flow path 500 and the second connection flow path 600 are connected to the intake flow path 200 on the downstream side of the compressor 402. However, one of the first connection flow path 500 and the second connection flow path 600 may be connected to the intake flow path 200 on the downstream side of the compressor 402, and the other of the first connection flow path 500 and the second connection flow path 600 may be connected to the intake flow path 200 on the upstream side of the compressor 402.

[0077] The above describes the intake and exhaust system 1A with reference to Fig. 4. However, the intake and exhaust system 1A may be modified in the same manner as the various modifications that may be made to the intake and exhaust system 1 described above.

[0078] Although the embodiments of the present disclosure have been described above with reference to the accompanying drawings, it goes without saying that the present disclosure is not limited to such embodiments. It is clear that a person skilled in the art can think of various modified or altered examples within the scope of the claims, and it is understood that these also naturally belong to the technical scope of the present disclosure.

[0079] The present disclosure can reduce unburned fuel emissions and, therefore, can contribute to, for example, Sustainable Development Goal (SDG) 7, "Ensure access to affordable, reliable, sustainable and modern energy." [Explanation of symbols]

[0080] 1. Intake and exhaust system 1A Intake and exhaust system 100 Engine 104 Cylinder head 104a Intake port 108 Combustion chamber 110a Intake valve 112 Fuel injection nozzle 200 Intake passage 402 Compressor 500 First connecting channel 506 Booster 600 Second connecting channel 606 Booster 700 Control device

Claims

1. an engine having a combustion chamber; an intake passage communicating with the combustion chamber; a fuel injection nozzle provided in the intake passage; a first connection passage that connects the fuel injection nozzle to a portion of the intake passage upstream of the fuel injection nozzle; Equipped with Intake and exhaust system.

2. a control device that performs suction of gas from the fuel injection nozzle to the intake passage through the first connection passage, the control device prohibits the suction of gas from the fuel injection nozzle to the intake passage via the first connection passage during a period when fuel is being injected by the fuel injection nozzle. The intake and exhaust system according to claim 1 .

3. A compressor is provided in the intake passage, The first connection passage connects the fuel injection nozzle and a portion of the intake passage upstream of the compressor.

3. The intake and exhaust system according to claim 1 or 2.

4. A compressor is provided in the intake passage, the first connection passage connects the fuel injection nozzle to a portion of the intake passage downstream of the compressor, The first connection flow path is provided with a pressure increasing section.

3. The intake and exhaust system according to claim 1 or 2.

5. a second connecting passage connecting an intake port, which is a portion of the intake passage within a cylinder head, to a portion of the intake passage upstream of the intake port, The intake and exhaust system according to claim 1 .

6. a control device that performs suction of gas from the intake port to the intake passage through the second connection passage, the control device prohibits the gas from being drawn from the intake port to the intake passage via the second connection passage when an intake valve of the engine is open. The intake and exhaust system according to claim 5.

7. the control device prohibits the suction of gas from the intake port to the intake passage via the second connection passage when the intake valve is closed and fuel is being injected by the fuel injection nozzle. The intake and exhaust system according to claim 6.

8. A compressor is provided in the intake passage, The second connection passage connects the intake port to a portion of the intake passage upstream of the compressor. An intake and exhaust system according to any one of claims 5 to 7.

9. A compressor is provided in the intake passage, the second connection passage connects the intake port to a portion of the intake passage downstream of the compressor, The second connection flow path is provided with a pressure increasing section. An intake and exhaust system according to any one of claims 5 to 7.

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