Engine

Abstract

To make deposits brittle.SOLUTION: An engine has exposed parts that are exposed inside a combustion chamber. The engine has an injector that has a tip portion exposed inside the combustion chamber and is connected to a gas flow passage that branches off from an exhaust system. The tip portion has an emission hole communicating with the gas flow passage and faces the exposed parts.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to engines. [Background technology]

[0002] Deposits, which are products of incomplete combustion of fuel and oil, accumulate in the combustion chambers of engines (see Patent Documents 1-3). Because such deposits are a cause of abnormal combustion such as knocking, the deposits are sometimes removed using fuel additives containing, for example, polyetheramines. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-273564 A [Patent Document 2] Patent No. 5691336 [Patent Document 3] Patent No. 5842195 Summary of the Invention [Problem to be solved by the invention]

[0004] However, because deposits in the combustion chamber are attached to the pistons and other parts, it may be difficult to remove the deposits using fuel additives, etc. For this reason, there is a demand for making the deposits that build up on the pistons and other parts brittle so that they can be easily removed. [Means for solving the problem]

[0005] According to the present disclosure, an engine includes an exposed part exposed in a combustion chamber. The engine includes an injector having a tip portion exposed in the combustion chamber and connected to a gas flow passage branched from an exhaust system. The tip portion has an emission hole communicating with the gas flow passage and faces the exposed part. Effect of the Invention

[0006] According to the present disclosure, the deposit can be made brittle. [Brief description of the drawings]

[0007] [Figure 1] 1 is a diagram illustrating an example of a vehicle equipped with an engine according to an embodiment of the present disclosure. [Diagram 2] FIG. 1 illustrates an example of an engine and control system. [Diagram 3] FIG. 11 is a diagram showing an example of an execution status of a gas release mode. [Figure 4] FIG. 13 is a diagram illustrating an example of an execution status of a water ejection mode. [Diagram 5] FIG. 2 is a diagram showing a combustion chamber of an engine and its vicinity. [Figure 6] FIG. 2 is a diagram showing a combustion chamber of an engine and its vicinity. [Figure 7] FIG. 2 is a diagram illustrating an example of a basic structure of an electronic control unit. [Figure 8] 13 is a flowchart showing an example of a procedure for executing deposit weakening control. [Figure 9] FIG. 2 illustrates a portion of an engine according to another embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following description, the same or substantially the same configurations and elements will be denoted by the same reference numerals and repeated description will be omitted.

[0009] First Embodiment <Vehicle> Fig. 1 is a diagram showing an example of a vehicle 11 equipped with an engine 10 according to an embodiment of the present disclosure. As shown in Fig. 1, the vehicle 11 has a power unit 13 consisting of the engine 10 and a transmission 12. An output shaft 14 of the power unit 13 is connected to wheels 17 via a propeller shaft 15 and a differential mechanism 16. Note that the illustrated power unit 13 is a rear-wheel drive power unit, but is not limited thereto, and may be a front-wheel drive or all-wheel drive power unit.

[0010] <Engine> FIG. 2 is a diagram showing an example of the engine 10 and the control system 100. As shown in FIG. 2, the engine 10 has a cylinder block 21 that houses a piston 20, and a cylinder head 22 that is mounted on the cylinder block 21. The piston 20 is housed in the cylinder block 21 so that it can reciprocate, and a crankshaft 23 that is connected to the piston 20 is rotatably supported. In addition, an intake port 25 that communicates with a combustion chamber 24 is formed in the cylinder head 22, and an intake valve 26 that opens and closes the intake port 25 is attached. Similarly, an exhaust port 27 that communicates with the combustion chamber 24 is formed in the cylinder head 22, and an exhaust valve 28 that opens and closes the exhaust port 27 is attached. In addition, an intake camshaft 29 that drives the intake valve 26 and an exhaust camshaft 30 that drives the exhaust valve 28 are attached to the cylinder head 22.

[0011] The cylinder head 22 is connected to an intake system 40 through which intake air flows toward the intake port 25, and an exhaust system 50 through which exhaust gas discharged from the exhaust port 27 flows. The intake system 40 is composed of an air cleaner box 41, a throttle valve 42, a surge tank 43, an intake manifold 44, and intake pipes 45, 46 connecting these components. The exhaust system 50 is composed of an exhaust manifold 51, a catalytic converter 52, a silencer 53, and exhaust pipes 54, 55 connecting these components. The intake air taken into the air cleaner box 41 is supplied to the combustion chamber 24 through the throttle valve 42, the surge tank 43, the intake manifold 44, and the intake port 25. The exhaust gas discharged from the combustion chamber 24 is discharged to the outside through the exhaust port 27, the exhaust manifold 51, the catalytic converter 52, and the silencer 53.

[0012] The engine 10 has an EGR system 60 that supplies a part of the exhaust gas (hereinafter, referred to as EGR gas) from the exhaust system 50 to the intake system 40. EGR is an abbreviation for "Exhaust Gas Recirculation." The EGR system 60 has an EGR flow path 61 that guides the EGR gas from the exhaust system 50 to the intake system 40. The EGR flow path 61 is composed of a gas pipe 62 connected to the exhaust pipe 54 of the exhaust system 50 and a gas pipe 63 connected to the surge tank 43 of the intake system 40. An EGR valve 64 is attached between the gas pipe 62 and the gas pipe 63, and an EGR cooler 65 that cools the EGR gas is attached to the gas pipe 62. By controlling the EGR valve 64 to an open state, the EGR gas is supplied from the exhaust system 50 to the intake system 40 through the gas pipes 62 and 63.

[0013] The engine 10 also has a gas emission system 70 that emits a portion of the EGR gas into the combustion chamber 24. The gas emission system 70 has a shared injector (injector) 71 attached to the cylinder head 22, a shared pipe 72 connected to the shared injector 71, and a gas pipe 73 that connects the shared pipe 72 and the gas pipe 63. That is, the shared injector 71 is connected to the exhaust system 50 via a gas flow path 74 consisting of the shared pipe 72 and the gas pipes 62, 63, and 73. In addition, an electromagnetic valve 75 and a check valve 76 are attached to the gas pipe 73 branched from the gas pipe 63. The shared injector 71 can be operated in an open state in which a discharge hole 90 at a tip portion 91, which will be described later, is opened, and in a closed state in which the discharge hole 90 at the tip portion 91 is closed.

[0014] Furthermore, the engine 10 has a water injection system 80 that injects water into the combustion chamber 24 using the above-mentioned shared injector 71. The water injection system 80 has a water supply pipe 81 connected to the shared pipe 72 of the shared injector 71, and a water tank 82 to which the water supply pipe 81 is connected. That is, the shared injector 71 is connected to the water tank 82 via a water supply passage 83 consisting of the shared pipe 72 and the water supply pipe 81. In addition, an electromagnetic valve 84 and a water pump 85 are attached to the water supply pipe 81. For example, only water may be poured into the water tank 82, a mixture of water and alcohol may be poured into the water tank 82, or a mixture of water, alcohol, and oil may be poured into the water tank 82. In addition, the water pump 85 may be structured to be driven by the intake camshaft 29, the exhaust camshaft 30, or the like, or may be structured to be driven by an electric motor.

[0015] As described above, the common injector 71 is connected to the gas flow path 74 that extends from the exhaust system 50 and guides EGR gas (exhaust gas), and is also connected to the water supply flow path 83 that extends from the water tank 82 and guides water. The common injector 71 has two operating modes: a gas discharge mode in which the common injector 71 discharges EGR gas into the combustion chamber 24, and a water injection mode in which the common injector 71 injects water into the combustion chamber 24.

[0016] Fig. 3 is a diagram showing an example of an execution state of the gas release mode. As shown in Fig. 3, when the gas release mode is executed, the EGR valve 64 and the electromagnetic valve 75 are controlled to be in an open state, and the common injector 71 is controlled to be in an open state. As a result, as shown by the arrow G1, the EGR gas is supplied from the exhaust system 50 to the common injector 71 through the gas flow path 74, and the EGR gas is released from the common injector 71 into the combustion chamber 24. In other words, the common injector 71 can be operated in a gas release state in which the EGR gas is released into the combustion chamber 24. Note that, when the gas release mode is executed, the electromagnetic valve 84 is controlled to be in a closed state, and the water pump 85 is controlled to be in a stopped state.

[0017] FIG. 4 is a diagram showing an example of the execution state of the water injection mode. As shown in FIG. 4, when the water injection mode is executed, the electromagnetic valve 84 is controlled to be in an open state, the water pump 85 is controlled to be in a driven state, and the common injector 71 is controlled to be in an open state. As a result, as shown by the arrow W1, water is supplied from the water tank 82 through the water supply passage 83 to the common injector 71, and the water is injected from the common injector 71 into the combustion chamber 24. That is, the common injector 71 can be operated in a water injection state (water discharge state) in which water is injected into the combustion chamber 24. In the water injection mode, from the viewpoint of lowering the gas temperature in the combustion chamber 24 and increasing the thermal efficiency, when it is determined that the engine operation region is in the high load region, water is injected from the common injector 71 into the combustion chamber 24. In addition, a check valve 76 is attached to the gas pipe 73, so that the water discharged from the water pump 85 does not flow into the EGR passage 61.

[0018] As shown in FIG. 2, the cylinder head 22 is provided with a fuel injector 86 for injecting fuel such as gasoline into the combustion chamber 24, and an ignition device 87 for igniting the air-fuel mixture in the combustion chamber 24. The ignition device 87 is formed of an igniter, a spark plug, or the like. A PCV hose 89 is connected to the head cover 22a of the cylinder head 22 via a PCV valve 88, and the PCV hose 89 is connected to the surge tank 43 of the intake system 40. When the PCV valve 88 is opened in response to a pressure drop in the surge tank 43, blow-by gas is supplied from the crankcase 21a of the cylinder block 21 to the surge tank 43, so that the blow-by gas, which is unburned gas, can be burned in the combustion chamber 24. PCV stands for "Positive Crankcase Ventilation."

[0019] <Mounting position of shared injector> Next, the mounting position of the shared injector 71 will be described. Figures 5 and 6 are diagrams showing the combustion chamber 24 of the engine 10 and its vicinity. As shown in the enlarged portion of Figure 5, the shared injector 71 has a valve body 92 with a tip portion 91 in which a discharge hole 90 is formed, a needle valve 93 housed in the valve body 92 for opening and closing the discharge hole 90, and a solenoid portion 94 for driving the needle valve 93. The discharge hole 90 opening at the tip portion 91 of the shared injector 71 communicates with the shared pipe 72 that constitutes the gas flow path 74.

[0020] The center line CL1 of the valve body 92, i.e., the center line CL1 of the common injector 71, intersects with the piston crown surface 20a (hereinafter, referred to as the piston crown surface 20a) of the piston 20 located at the top dead center. That is, the tip end 91 of the common injector 71 faces the piston (exposed part) 20 exposed in the combustion chamber 24. Also, as shown in FIG. 6, the center line CL1 of the common injector 71 intersects with the intake valve 26 that is pushed out during the intake stroke. That is, the tip end 91 of the common injector 71 faces the intake valve (exposed part) 26 exposed in the combustion chamber 24. Note that even when viewed from the direction indicated by the arrow X1 in FIGS. 5 and 6, the center line CL1 of the common injector 71 intersects with the piston crown surface 20a, and the center line CL1 of the common injector 71 intersects with the intake valve 26.

[0021] <Control system> As shown in FIG. 2, the engine 10 has a control system 100 consisting of an electronic control unit 101 for controlling the throttle valve 42, the EGR system 60, the gas emission system 70, the water injection system 80, the fuel injector 86, and the ignition device 87. Sensors connected to the electronic control unit 101 include an accelerator sensor 102 for detecting the amount of operation of an accelerator pedal, a brake sensor 103 for detecting the amount of operation of a brake pedal, and a vehicle speed sensor 104 for detecting the vehicle speed, which is the traveling speed of the vehicle 11. Sensors connected to the electronic control unit 101 include an engine rotation sensor 105 for detecting the engine speed, which is the rotation speed of the crankshaft 23, and a throttle opening sensor 106 for detecting the throttle opening, which is the opening of the throttle valve 42. A start switch 107 that is operated by the driver when the control system 100 is started is also connected to the electronic control unit 101.

[0022] Fig. 7 is a diagram showing an example of a basic structure of the electronic control unit 101. As shown in Fig. 7, the electronic control unit 101 has a microcontroller 112 incorporating a processor 110, a main memory 111, and the like. A predetermined program is stored in the main memory 111, and the program is executed by the processor 110. The processor 110 and the main memory 111 are connected to each other so as to be able to communicate with each other. Note that a plurality of processors 110 may be incorporated in the microcontroller 112, and a plurality of main memories 111 may be incorporated in the microcontroller 112.

[0023] The electronic control unit 101 also has an input circuit 113, a drive circuit 114, a communication circuit 115, an external memory 116, and a power supply circuit 117. The input circuit 113 converts signals input from various sensors into signals that can be input to the microcontroller 112. The drive circuit 114 generates drive signals for devices such as the throttle valve 42 described above based on signals output from the microcontroller 112. The communication circuit 115 converts signals output from the microcontroller 112 into communication signals directed to other electronic control units 101, etc. The communication circuit 115 also converts communication signals received from other electronic control units 101, etc. into signals that can be input to the microcontroller 112. The power supply circuit 117 supplies a stable power supply voltage to the microcontroller 112, the input circuit 113, the drive circuit 114, the communication circuit 115, the external memory 116, etc. The external memory 116, which is a non-volatile memory, etc., stores programs and various data, etc.

[0024] <Deposit Vulnerability Control: Flowchart> The deposit weakening control for weakening deposits will be described below. Note that deposits are products of incomplete combustion of fuel and oil that accumulate on the wall surfaces of the combustion chamber 24, etc. FIG. 8 is a flowchart showing an example of the procedure for executing deposit weakening control. Each step of the deposit weakening control shown in FIG. 8 is executed by the processor 110 constituting the control system 100. Moreover, the deposit weakening control shown in FIG. 8 is control that is executed by the control system 100 at predetermined intervals after the control system 100 is started by operating the start switch 107.

[0025] As shown in FIG. 8, the control system 100 proceeds to step S10 and sets the operation mode of the common injector 71 to a water injection mode in which water is injected when the engine 10 is in a high-load operating state. As shown in FIG. 4, when the control system 100 determines that the engine operating region is in the high-load region, that is, when the engine load exceeds a predetermined value and the engine speed exceeds a predetermined value, the control system 100 controls the solenoid valve 84, the water pump 85, and the common injector 71 to inject water into the combustion chamber 24 (arrow W1). As a result, when the engine 10 is operating at high load, the gas temperature in the combustion chamber 24 can be lowered by water injection, and the thermal efficiency of the engine 10 can be improved. Note that when the control system 100 determines that the engine operating region is outside the high-load region, the control system 100 controls the solenoid valve 84, the water pump 85, and the common injector 71 to stop water injection into the combustion chamber 24.

[0026] As shown in Fig. 8, the control system 100 proceeds to step S11 and determines whether the vehicle speed exceeds a predetermined threshold V1. If the control system 100 determines in step S11 that the vehicle speed exceeds the threshold V1, the control system 100 proceeds to step S12 and determines whether the throttle opening is below a predetermined threshold S1. If the control system 100 determines in step S12 that the throttle opening is below the threshold S1, the control system 100 proceeds to step S13 and determines whether the engine speed exceeds a predetermined threshold N1. If the control system 100 determines in step S13 that the engine speed exceeds the threshold N1, the control system 100 proceeds to step S14 and determines whether fuel injection from the fuel injector 86 is cut off.

[0027] In the above-mentioned steps S11 to S14, the control system 100 determines that the vehicle speed exceeds the threshold V1, the throttle opening is below the threshold S1, the engine speed exceeds the threshold N1, and fuel injection is cut off, which is a coasting state in which the engine brake is activated and the vehicle speed decreases gradually. When the control system 100 determines that the vehicle is in a coasting state, the process proceeds to step S15, where the operation mode of the shared injector 71 is switched from the water injection mode to the gas discharge mode, and the gas discharge mode is executed to supply EGR gas into the combustion chamber 24.

[0028] 3, when the gas release mode is executed, the control system 100 controls the EGR valve 64 and the electromagnetic valve 75 to be in an open state, and also controls the common injector 71 to be in an open state. As a result, as shown by the arrow G1, the EGR gas is supplied from the exhaust system 50 through the gas flow path 74 to the common injector 71, and the EGR gas is released from the common injector 71 into the combustion chamber 24. In this way, the coasting situation in which the gas release mode is executed is a situation in which intake air is pumped from the intake system 40 to the exhaust system 50 while the throttle valve 42 is held in a fully closed position.

[0029] That is, the pressure in the combustion chamber 24 is greatly reduced, and the pressure difference between the combustion chamber 24 and the crankcase 21a is increased, which may cause the oil α in the crankcase 21a to leak into the combustion chamber 24. In addition, the pressure in the surge tank 43 also decreases with the reduction in pressure in the combustion chamber 24, so that the PCV valve 88 opens and blow-by gas containing oil mist flows into the combustion chamber 24, as shown by the arrow β. In this way, the flow of oil into the combustion chamber 24 due to so-called oil rising or the opening of the PCV valve 88 is a factor that causes oil to adhere to the piston crown surface 20a, the intake valve 26, etc., and is a factor that causes oil-derived deposits to form on the piston crown surface 20a, the intake valve 26, etc.

[0030] Therefore, as described above, in a coasting state where oil is likely to adhere to the piston crown surface 20a, the intake valve 26, etc., the control system 100 executes the gas release mode to supply EGR gas (exhaust gas) to the combustion chamber 24. In addition, as shown in Figures 5 and 6, the tip 91 of the common injector 71 faces the piston 20 located at the top dead center and also faces the intake valve 26 pushed out during the intake stroke. This allows the EGR gas released from the common injector 71 to be sprayed against the piston crown surface 20a and the intake valve 26.

[0031] In this way, the EGR gas can be directly sprayed onto the oil and fuel, which are the deposit precursors, and the deposits formed on the piston crown surface 20a and the intake valve 26 can be made brittle. In other words, it is considered that the water (H2O) and carbon dioxide (CO2) in the EGR gas react with carbon (C), which is the main component of the oil and fuel, to form porous deposits. In other words, when carbon (C) is reacted with water (H2O) and carbon dioxide (CO2) in a temperature environment (e.g., 700°C or higher and 1000°C or lower) in the combustion chamber 24, an endothermic reaction proceeds as shown in the following thermochemical equation, and pores are formed in the deposit due to the intake of hydrogen (H2) and carbon monoxide (CO). C + H2O = CO + H2- 31kcal C + CO2 = 2CO - 41kcal

[0032] Such a gas emission mode is stopped when the coasting state is eliminated. That is, as shown in Fig. 8, when the control system 100 executes the gas emission mode in step S15, the process proceeds to step S16, where it determines whether the throttle opening exceeds a threshold value S2 that is greater than the threshold value S1. When the control system 100 determines in step S16 that the throttle opening is equal to or less than the threshold value S2, it proceeds to step S17, where it determines whether the engine speed falls below a threshold value N2 that is less than the threshold value N1. When the control system 100 determines in step S17 that the engine speed is equal to or greater than the threshold value N2, it proceeds to step S18, where it determines whether fuel injection from the fuel injector 86 is being performed.

[0033] If the control system 100 determines in step S18 that fuel is being cut, the coasting state continues, and the process returns to step S15 to continue the execution of the gas emission mode. On the other hand, if the control system 100 determines in step S16 that the throttle opening exceeds the threshold value S2, if the control system 100 determines in step S17 that the engine speed falls below the threshold value N2, or if the control system 100 determines in step S18 that fuel is being injected, the control system 100 determines that the coasting state accompanied by oil rising or blow-by gas intake has been resolved, and proceeds to step S19. Then, in step S19, the control system 100 switches the operation mode of the shared injector 71 from the gas emission mode to the water injection mode.

[0034] As described above, the tip 91 of the common injector 71 has the discharge hole 90 communicating with the common pipe 72 constituting the gas flow passage 74, and faces the piston 20 located at the top dead center. This allows the EGR gas discharged from the common injector 71 to be directly blown against the piston crown surface 20a, making it possible to weaken deposits formed on the piston crown surface 20a. The tip 91 of the common injector 71 also has the discharge hole 90 communicating with the common pipe 72 constituting the gas flow passage 74, and faces the intake valve 26 pushed out during the intake stroke. This allows the EGR gas discharged from the common injector 71 to be directly blown against the intake valve 26, making it possible to weaken deposits formed on the intake valve 26. In this way, the deposits accumulated on the piston crown surface 20a and the intake valve 26 can be made weak, and the deposits can be easily removed from the piston crown surface 20a and the intake valve 26.

[0035] In the above description, the common injector 71 is held in an open state when the gas release mode is executed, but this is not limited thereto, and the common injector 71 may be controlled to open and close based on the crank angle, etc. In other words, when EGR gas is blown toward the piston crown surface 20a, the common injector 71 may be controlled to be open at or near the top dead center, and may be controlled to be closed at other piston positions such as the bottom dead center. Also, when EGR gas is blown toward the intake valve 26, the common injector 71 may be controlled to be open during the intake stroke, and may be controlled to be closed during other strokes such as the compression stroke.

[0036] In the above description, the gas release mode is executed when it is determined that the vehicle is in a coasting state. However, the gas release mode may be executed when other vehicle conditions are satisfied. For example, under vehicle conditions in which the injection amount of fuel, which is a precursor of deposits, increases, a large amount of fuel adheres to the piston crown surface 20a and the intake valve 26, so it is desirable to execute the gas release mode to make the deposits fragile. Examples of vehicle conditions in which the fuel injection amount increases include a situation in which the engine 10 is cold started, a situation in which learning of the fuel injection amount has not been completed, and a situation in which the engine 10 is operated in a fuel increase region set from the viewpoint of cooling, etc. In addition, the gas release mode may be executed at the timing when the intake valve 26 and the exhaust valve 28 overlap, that is, at or near the top dead center. In this case, oil and fuel are likely to adhere to the intake valve 26 due to the blowback of combustion gas, so it is desirable to execute the gas release mode to make the deposits fragile.

[0037] <Second embodiment> 5 and 6, the tip 91 of the common injector 71 faces the piston 20 located at the top dead center and also faces the intake valve 26 pushed out during the intake stroke, but this is not limited to this. Figure 9 is a diagram showing a part of an engine 120 according to another embodiment of the present disclosure. Note that in Figure 9, parts similar to those shown in Figure 5 are denoted by the same reference numerals and their description will be omitted.

[0038] 9, a common injector 71 and a fuel injector 86 are attached to the cylinder head 22 of the engine 120. A center line CL2 of the common injector 71 intersects with a tip 86a of the fuel injector 86. That is, a tip 91 of the common injector 71 faces the fuel injector (exposed part) 86 exposed in the combustion chamber 24. The center line CL2 of the common injector 71 also intersects with the broken-line intake valve 26 that is pushed out during the intake stroke, and intersects with the broken-line exhaust valve 28 that is pushed out during the exhaust stroke. That is, the tip 91 of the common injector 71 faces the intake valve (exposed part) 26 and the exhaust valve (exposed part) 28 that are exposed in the combustion chamber 24. Even when viewed from the direction indicated by the arrow X1 in FIG. 9, the center line CL2 of the common injector 71 intersects with the fuel injector 86, and the center line CL2 of the common injector 71 intersects with the intake valve 26 and the exhaust valve 28.

[0039] 9 is capable of directly spraying EGR gas onto fuel injector 86, intake valve 26, and exhaust valve 28. This makes it possible to weaken deposits formed on fuel injector 86, intake valve 26, and exhaust valve 28, and makes it possible to easily remove the deposits from fuel injector 86, intake valve 26, and exhaust valve 28. In addition, the timing for executing the gas release mode may be the timing when it is determined that the vehicle is in a coasting state, as described above, or may be the timing when another vehicle condition is satisfied.

[0040] For example, under vehicle conditions where the injection amount of fuel, which is a precursor of deposits, increases, a large amount of fuel adheres to the fuel injector 86, the intake valve 26, and the exhaust valve 28, so it is desirable to execute the gas release mode to make the deposits fragile. Examples of vehicle conditions where the fuel injection amount increases include a situation where the engine 10 is cold started, a situation where the learning of the fuel injection amount is not completed, and a situation where the engine 10 is operated in a fuel increase region set from the viewpoint of cooling, etc. Also, when EGR gas is sprayed to the fuel injector 86, it is desirable to execute the gas release mode at a timing when a large amount of fuel adheres to the tip 86a of the fuel injector 86, that is, immediately after fuel injection. Also, the gas release mode may be executed at a timing when the intake valve 26 and the exhaust valve 28 overlap, that is, at or near the top dead center. In this case, it is desirable to execute the gas release mode to make the deposits fragile, because oil and fuel are likely to adhere to the intake valve 26 due to the blowback of the combustion gas.

[0041] <Other embodiments> The present disclosure is not limited to the above-described embodiment, and may be modified in various ways without departing from the spirit of the present disclosure. For example, the illustrated gas emission system 70 emits EGR gas into the combustion chamber 24 by the pressure difference between the exhaust system 50 and the combustion chamber 24, but is not limited to this. For example, the EGR gas may be pumped toward the shared injector 71 by attaching a pump for pumping the EGR gas to the gas piping 73. In addition, the illustrated gas emission system 70 uses the shared injector 71 shared with the water injection system 80, but is not limited to this, and an injector dedicated to the gas emission system may be used. Furthermore, the illustrated gas emission system 70 is structured to emit a part of the EGR gas flowing through the EGR flow passage 61 into the combustion chamber 24, but is not limited to this, and may be structured to emit exhaust gas taken out of the exhaust system 50 into the combustion chamber 24.

[0042] In the example shown in FIG. 6, the tip 91 of the common injector 71 faces the intake valve 26, and in the example shown in FIG. 9, the tip 91 of the common injector 71 faces the intake valve 26 and the exhaust valve 28, but the present invention is not limited to this. For example, the tip 91 of the common injector 71 may face the exhaust valve 28 instead of the intake valve 26. In the example shown in the figure, the tip 91 of the common injector 71 faces the intake valve 26 and the exhaust valve 28 that have been pushed out from the fully closed position, but the present invention is not limited to this, and the tip 91 of the common injector 71 may face the intake valve 26 and the exhaust valve 28 that are in the fully closed position. In the example shown in the figure, one discharge hole 90 is formed in the tip 91 of the common injector 71, but the present invention is not limited to this, and a plurality of discharge holes 90 may be formed in the tip 91 of the common injector 71. [Explanation of symbols]

[0043] 10...engine, 20...piston (exposed part), 24...combustion chamber, 26...intake valve (exposed part), 28...exhaust valve (exposed part), 50...exhaust system, 71...common injector (injector), 74...gas flow path, 82...water tank, 83...water supply flow path, 86...fuel injector (exposed part), 90...discharge hole, 91...tip, 120...engine

Claims

1. An engine having an exposed part exposed in a combustion chamber, an injector having a tip portion exposed in the combustion chamber and connected to a gas flow passage branched from an exhaust system; The tip portion has a discharge hole communicating with the gas flow path and faces the exposed component. engine.

2. 2. The engine of claim 1, The exposed part is a piston. engine.

3. 2. The engine of claim 1, The exposed part is at least one of an intake valve and an exhaust valve. engine.

4. 2. The engine of claim 1, The exposed part is a fuel injector that injects fuel. engine.

5. 2. The engine of claim 1, The injector is connected to the gas flow path and to a water supply flow path extending from a water tank, The injector is operable in a gas discharge state in which exhaust gas is discharged from the discharge hole into the combustion chamber, and in a water discharge state in which water is discharged from the discharge hole into the combustion chamber. engine.

Images