JP4840383B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to a technique for performing exhaust gas recirculation for returning exhaust gas to a combustion space in a cylinder in an internal combustion engine.

  In gasoline engines and diesel engines, a part of the exhaust gas is mixed into the combustion air and burned with a mixture of fuel and air, thereby suppressing the generation of nitrogen oxides and reducing fuel consumption. A technique called EGR (Exhaust Gas Recirculation) is used. In Patent Document 1, each cylinder is provided with a primary port and a secondary port, and each is provided with a fuel injection valve. Further, when the secondary port is fully closed and exhaust gas recirculation is performed, the exhaust gas is used as the secondary port. A technology for injecting fuel from a fuel injection valve provided in the primary port while disclosing the exhaust port and introducing exhaust gas from the secondary port by closing the fully closed valve when performing exhaust gas recirculation is disclosed. ing.

JP 2003-314288 A (0048-0053, FIG. 3)

  In an internal combustion engine in which the piston reciprocates in the cylinder, the heat energy of the combustion gas that burns the mixture of fuel and air is taken away from the inner surface of the cylinder, and the generated heat cannot be used effectively, resulting in cooling loss. There are things to do. Further, when combustion is performed in a state where exhaust gas and air-fuel mixture are mixed in the cylinder, combustion tends to become unstable as the amount of exhaust gas increases. In particular, in the vicinity of the inner surface of the cylinder, flame extinguishing that the flame disappears easily occurs, and the combustion state may deteriorate. Patent Document 1 does not mention this point, and there is room for improvement.

  The present invention has been made in view of the above, and achieves at least one of reducing the cooling loss and suppressing the deterioration of the combustion state when the exhaust gas is recirculated to the combustion space in the cylinder. The purpose is to do.

  In order to solve the above-described problems and achieve the object, an internal combustion engine according to the present invention is a space in a cylinder in which a piston reciprocates, a combustion space in which a mixture of fuel and air burns, A first intake passage and a second intake passage that are connected to the combustion space and open, and the first intake passage is provided inside the first intake passage, and the first intake passage is disposed on the inner surface side and the central axis side of the cylinder. A partition member that is partitioned into two, a first fuel supply means that supplies fuel to the first intake passage on the center axis side of the cylinder partitioned by the partition member, and a fuel that is supplied to the second intake passage A second fuel supply means that opens to the first intake passage on the inner surface side of the cylinder partitioned by the partition member, and introduces exhaust gas discharged from the combustion space into the first intake passage Exhaust Characterized in that it comprises scan inlet and, a.

  With such a configuration, an exhaust gas layer is formed in the vicinity of the inner surface of the cylinder, and an air-fuel mixture layer is formed inside the exhaust gas layer. When the air-fuel mixture is ignited in this state and the air-fuel mixture burns, the heat loss by the exhaust gas near the inner surface of the cylinder can reduce the cooling loss, and the quenching can be suppressed near the inner surface of the cylinder. Deterioration can be suppressed.

  As a preferred aspect of the present invention, in the internal combustion engine, when the exhaust gas discharged from the combustion space is introduced from the exhaust gas inlet into the first intake passage, the operation of the first fuel supply means is performed. It is desirable to stop and supply the fuel only from the second fuel supply means.

  As a preferred aspect of the present invention, in the internal combustion engine, the inner portion of the first intake passage, the upstream of the partition member on the upstream side in the flow direction of the air flowing through the first intake passage. It is desirable to provide passage switching means for opening and closing the first intake passage on the upstream side in the air flow direction.

  In a preferred aspect of the present invention, in the internal combustion engine, when the exhaust gas discharged from the combustion space is introduced from the exhaust gas inlet into the first intake passage, the passage switching means causes the first intake air to flow. It is desirable to close the passage.

  As a preferred aspect of the present invention, in the internal combustion engine, it is desirable to direct the direction of the fuel supplied from at least the second fuel supply means toward the center of the cylinder.

  As a preferred aspect of the present invention, in the internal combustion engine, it is desirable that the piston has a convex shape at the top.

  The present invention can achieve at least one of reducing the cooling loss and suppressing the deterioration of the combustion state when the exhaust gas is recirculated to the combustion space in the cylinder.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited by the best mode for carrying out the invention (hereinafter referred to as an embodiment). In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art, or those that are substantially the same, so-called equivalent ranges.

  The following embodiment is a space in a cylinder in which a piston reciprocates, a combustion space in which a mixture of fuel and air burns, a first intake passage connected to the combustion space, and a second intake passage. When the exhaust gas is recirculated to the combustion space, the exhaust gas is introduced from the first intake passage into the combustion space, and the combustion space is introduced from the second intake passage. The fuel and the air are introduced into the combustion space to form a layer of the exhaust gas and a mixture of the fuel and air in the combustion space.

(Embodiment 1)
In Embodiment 1, in the internal combustion engine, fuel supply means is provided in each of the first intake passage and the second intake passage connected to the combustion space in one cylinder, and the first intake passage is connected to the cylinder by a partition member. An exhaust gas inlet that opens to the first intake passage on the inner surface side of the cylinder partitioned by the partition member is provided, and is discharged from the combustion space from the exhaust gas inlet. The exhaust gas which is the air-fuel mixture after combustion is introduced into the first intake passage. Here, supplying fuel from the fuel supply means to the intake passage of the internal combustion engine is synonymous with supplying fuel to the internal combustion engine.

  FIG. 1 is an explanatory diagram illustrating an internal combustion engine according to the first embodiment. FIG. 2 is a plan view showing a state in which the internal combustion engine according to the first embodiment is viewed from the cylinder head side. 3 is a cross-sectional view taken along the line XX of FIG. FIG. 4 is a plan view showing the internal combustion engine according to the first embodiment as viewed from the cylinder head side. FIG. 5 is a schematic diagram illustrating a state in which exhaust gas recirculation is executed in the internal combustion engine according to the first embodiment. In the first embodiment, a single cylinder provided in the internal combustion engine 1 is taken out and described. However, the present invention can be applied regardless of a multi-cylinder internal combustion engine or a single-cylinder internal combustion engine. The internal combustion engine 1 is a so-called reciprocating internal combustion engine in which a piston 5 reciprocates inside a cylinder 1S.

  The internal combustion engine 1 is controlled by an engine ECU (Electronic Control Unit) 50. The cylinder 1S of the internal combustion engine 1 is a cylindrical structure having one end attached to the cylinder head 1H and the other end attached to the crankcase 1C. A space 1B surrounded by the inner surface 1SW of the cylinder 1S, the top surface of the piston 5, and the inner surface of the cylinder head 1H is a space in which the fuel F supplied to the internal combustion engine 1 burns. This space 1B is called combustion space 1B. The fuel F supplied to the internal combustion engine 1 is a fuel containing hydrocarbons, for example, gasoline.

  A water jacket WJ is formed in the cylinder 1S. During operation of the internal combustion engine 1, water (cooling water) for cooling the internal combustion engine 1 is passed through the water jacket WJ to cool the internal combustion engine 1. The temperature of the cooling water is detected by the cooling water temperature sensor 42, taken into the engine ECU 50, and used for controlling the internal combustion engine 1.

  The cylinder head 1H has a first intake port 4A that is a first intake passage for introducing air (combustion air) A for combustion of the fuel F into the combustion space 1B and a second intake passage that is a second intake passage. An intake port 4B is formed. Further, the cylinder head 1H is formed with an exhaust port 9 which is an exhaust passage for discharging the combustion gas (exhaust gas) Ex after the fuel F is burned in the combustion space 1B to the outside of the combustion space 1B.

  The first intake port 4A, the second intake port 4B, and the exhaust port 9 are connected to the combustion space 1B, respectively, and one end of each opens to the combustion space 1B to form an opening, and the other end The part is connected to an intake air introduction passage 8 that is an intake passage. A first intake valve 10A and a second intake valve 10B are disposed in the opening 4Ao of the first intake port 4A that opens to the combustion space 1B and the opening 4Bo of the second intake port 4B, respectively, and open to the combustion space 1B. An exhaust valve 15 is disposed in the opening 9 o of the exhaust port 9. The first intake valve 10A and the second intake valve 10B open and close the opening 4Ao of the first intake port 4A and the opening 4Bo of the second intake port 4B that open to the combustion space 1B, and the exhaust valve 15 opens and closes the combustion space 1B. Open and close the opening 9o of the exhaust port 9 that opens to the front.

  The internal combustion engine 1 includes a first port injection valve 2A as first fuel supply means for injecting fuel F into the first intake port 4A and supplying the fuel F to the internal combustion engine 1, and the fuel F into the second intake port 4B. The second port injection valve 2B is provided as a second fuel supply means for injecting and supplying the fuel to the internal combustion engine 1. In the present embodiment, the first port injection valve 2A and the second port injection valve 2B are attached to the cylinder head 1H. A spark plug 7 is attached to the cylinder head 1H of the internal combustion engine 1 as an ignition means for igniting a mixture of fuel and air A formed in the combustion space 1B. The air-fuel mixture in the combustion space 1B is ignited by the discharge from the spark plug 7 and burns. Thus, the internal combustion engine 1 is a so-called spark ignition type internal combustion engine. The number of intake ports that are intake passages is not limited to two, and the number of port injection valves that are fuel supply means is not limited to two.

  The first port injection valve 2 </ b> A and the second port injection valve 2 </ b> B included in the internal combustion engine 1 are attached to the port injection valve fuel distribution pipe 20, and their operations are controlled by the engine control unit 54 of the engine ECU 50. The first port injection valve 2 </ b> A and the second port injection valve 2 </ b> B are supplied with fuel from the fuel injection pipe 20 for port injection valves, and the air A and the second intake port in the first intake port 4 </ b> A of the internal combustion engine 1. Fuel F is injected and supplied to air A in 4B. Thereby, an air-fuel mixture in which the fuel F and the air A are sufficiently mixed is formed.

  A throttle valve 14 is attached to the intake introduction passage 8 connected to the first intake port 4A and the second intake port 4B. The throttle valve 14 includes a valve body 14V and a throttle valve actuator 14A that is attached to and operates the valve body 14V. By adjusting the opening of the valve body 14V, the passage cross-sectional area of the intake passage changes, and the amount of air A introduced into the combustion space 1B is adjusted. An air flow sensor 40 is disposed upstream of the valve body 14V of the throttle valve 14 in the flow direction of the air A, and flows into the combustion space 1B, that is, the flow rate (mass flow rate) of the air A flowing through the intake passage. The flow rate of air A is measured. The flow rate of the air A measured by the air flow sensor 40 is taken into the engine ECU 50 and used for controlling the internal combustion engine 1. An air cleaner 70 is arranged upstream of the air flow sensor 40 in the flow direction of the air A. The air cleaner 70 flows into the intake air introduction passage 8 and dust or dust from the air A flowing into the combustion space 1B of the internal combustion engine 1. Is removed.

  The fuel F supplied from the first port injection valve 2A and the second port injection valve 2B into the first intake port 4A and the second intake port 4B is stored in the fuel tank 13. A feed pump 13 </ b> P is disposed inside the fuel tank 13. The feed pump 13P and the port injector fuel distribution pipe 20 are connected by a fuel pipe 18, and the fuel F in the fuel tank 13 discharged from the feed pump 13P passes through the fuel pipe 18 and is a fuel for the port injector. It is sent to the distribution pipe 20. The operation of the feed pump 13P is controlled by the engine control unit 54 of the engine ECU 50.

  When the first intake valve 10A and the second intake valve 10B are opened and the piston 5 moves toward the bottom dead center, the opening 4Ao of the first intake port 4A and the opening 4Bo of the second intake port 4B move toward the combustion space 1B. Then, an air-fuel mixture of air A and fuel F flows (intake stroke). Here, the fuel F is supplied from the first port injection valve 2A and the second port injection valve 2B to the first intake port 4A and the second intake port 4B before the intake stroke. When the piston 5 passes the bottom dead center and the piston 5 heads to the top dead center (that is, the direction of the cylinder head 1H) with the first intake valve 10A, the second intake valve 10B, and the exhaust valve 15 closed, the combustion space The mixture of fuel F and air A formed in 1B is compressed (compression stroke).

  Before the piston 5 reaches top dead center, the spark plug 7 discharges and ignites the compressed air-fuel mixture. Thereby, the air-fuel mixture in the combustion space 1B burns. Here, the ignition timing of the spark plug 7 is controlled by the engine control unit 54 of the engine ECU 50.

  The piston 5 moves toward the bottom dead center by the combustion pressure when the air-fuel mixture burns (expansion stroke). The piston 5 that has passed through the bottom dead center moves again toward the top dead center. At this time, the exhaust valve 15 is opened, and the combustion gas (exhaust gas Ex) in the combustion space 1B passes through the opening 9o to the exhaust port. 9 (exhaust stroke). This completes one cycle of the internal combustion engine. For example, during the exhaust stroke, the fuel F of the next cycle is supplied from the first port injection valve 2A and the second port injection valve 2B into the first intake port 4A and the second intake port 4B.

  When the piston 5 comes close to top dead center, the first intake valve 10A and the second intake valve 10B are opened, the exhaust valve 15 is closed, and the next cycle of the internal combustion engine 1 is started. Thus, the internal combustion engine 1 is a four-stroke one-cycle internal combustion engine in which one cycle is completed while the piston 5 reciprocates twice within the cylinder 1S. The reciprocating motion of the piston 5 is transmitted to the crankshaft 6 in the crankcase 1C via the connecting rod 3 and converted into rotational motion.

  The rotation angle of the crankshaft 6 is detected by a crank angle sensor 41. The engine control unit 54 of the engine ECU 50 takes in the rotation angle of the crankshaft 6 detected by the crank angle sensor 41, and calculates the rotation speed (engine rotation speed) of the crankshaft 6 based on this. Here, the engine rotational speed is the rotational speed of the crankshaft 6 per unit time.

  The exhaust gas Ex is led to the purification catalyst through the exhaust passage 9M connected to the exhaust port 9, and after being purified here, it is discharged into the atmosphere. As shown in FIGS. 1 and 2, the exhaust passage 9 </ b> M and the first intake port 4 </ b> A are connected by an exhaust gas recirculation passage 16. An exhaust gas inlet 16I opens in the exhaust passage 9M. The exhaust gas inlet 16I is an opening where the exhaust gas recirculation passage 16 opens into the exhaust passage 9M, and introduces the exhaust gas in the exhaust passage 9M into the exhaust gas recirculation passage 16.

  The exhaust gas recirculation passage 16 is provided with a valve device 17 controlled by the engine ECU 50. The valve device 17 has a function of changing the cross-sectional area of the exhaust gas recirculation passage 16 (the cross-sectional area perpendicular to the flow direction of the exhaust gas Ex flowing through the exhaust gas recirculation passage 16). Accordingly, the exhaust passage 9M and the first intake port 4A are communicated with each other through the exhaust gas recirculation passage 16, and the communication between the exhaust passage 9M and the first intake port 4A is blocked. As a result, the exhaust gas Ex in the exhaust passage 9M can be introduced into the first intake port 4A, or the introduction of the exhaust gas Ex into the first intake port 4A can be stopped.

  The valve device 17 can use an ON-OFF valve or a flow rate adjusting valve. When an ON-OFF valve is used for the valve device 17, the amount of exhaust gas Ex flowing through the exhaust gas recirculation passage 16 can be adjusted by changing the ratio between the open time and the close time. When a flow rate adjusting valve is used as the valve device 17, the exhaust gas recirculation passage 16 is adjusted by adjusting the opening degree of the valve device 17, that is, by changing the cross-sectional area of the exhaust gas recirculation passage 16 by the valve device 17. The amount of flowing exhaust gas Ex can be adjusted.

  When exhaust gas recirculation (hereinafter referred to as EGR) is performed during operation of the internal combustion engine 1, the valve device 17 is opened, and the exhaust gas recirculation passage 16 is discharged from the combustion space 1B via the first intake port 4A. The exhaust gas Ex is returned to the combustion space 1B. And the air-fuel mixture of the fuel F and the air A is burned in the state where the exhaust gas Ex exists in the combustion space 1B. This suppresses generation of nitrogen oxides and reduces fuel consumption.

  As shown in FIGS. 2 and 3, a partition member 30 is provided inside the first intake port 4A. The partition member 30 partitions the first intake port 4A into the inner surface 1SW side of the cylinder 1S and the central axis Z side of the cylinder 1S. The first port injection valve 2A supplies the fuel F to the first intake port 4A on the central axis Z side of the cylinder 1S, which is partitioned by the partition member 30. The first intake port 4A on the central axis Z side of the cylinder 1S that is partitioned by the partition member 30 is referred to as an air passage 32.

  An exhaust gas inlet 16E opens in the first intake port 4A on the inner surface 1SW side of the cylinder 1S, which is partitioned by the partition member 30. The exhaust gas introduction port 16E is an opening through which the exhaust gas recirculation passage 16 opens to the first intake port 4A. During EGR, the exhaust gas Ex that has passed through the exhaust gas recirculation passage 16 is introduced into the first intake port 4A. . Here, a space surrounded by the partition member 30 and the first intake port 4A on the inner surface 1SW side of the cylinder 1S is referred to as an air / exhaust gas passage 31.

  On the upstream side of the air / exhaust gas passage 31 (that is, the upstream side in the flow direction of the air A flowing through the first intake port 4), an air / exhaust gas passage inlet 31i is opened. Further, a passage switching valve 19 as a passage switching means is provided upstream of the air / exhaust gas passage inlet 31i. The passage switching valve 19 is driven by a passage switching valve driving actuator 19A shown in FIG. 1 to open and close the first intake port 4A. The passage switching valve driving actuator 19A is controlled by the engine ECU 50.

  When the passage switching valve 19 is closed, the first intake port 4A is shut off, and the air A does not flow downstream from the passage switching valve 19, that is, to the combustion space 1B. In this case, the exhaust gas Ex flows through the air / exhaust gas passage 31 to the combustion space 1B. When the passage switching valve 19 is opened, the upstream side and the downstream side of the passage switching valve 19 communicate with each other, so that the air A flows downstream from the passage switching valve 19 and the air A flows into the combustion space 1B. In this case, the air A flows into the combustion space 1B through the air / exhaust gas passage 31 and the air passage 32, that is, the entire first intake port 4A.

  In the present embodiment, the passage switching valve 19 is switched between open and closed depending on whether or not EGR is executed. When EGR is not executed, the passage switching valve 19 is opened as shown in FIG. 2, and the air A flows through the entire first intake port 4A, that is, both the air / exhaust gas passage 31 and the air passage 32. In this case, in order to reduce the resistance when the air A flows as much as possible, it is preferable that the passage switching valve 19 be parallel to the flow direction of the air A.

  When EGR is not executed in the present embodiment, as shown in FIG. 2, air A is introduced into the combustion space 1B from both the first intake port 4A and the second intake port 4B. Then, the fuel F is supplied to the internal combustion engine 1 by both the first port injection valve 2A and the second port injection valve 2B. In this case, as shown in FIG. 2, the fuel spray Fm is injected from the fuel injection hole 2o of the first intake port 4A and the fuel injection hole 2o of the second intake port 4B.

  When performing EGR, as shown in FIG. 4, the passage switching valve 19 is closed, and the air A does not flow downstream from the passage switching valve 19. When the valve device 17 is opened in this state, the exhaust gas Ex in the exhaust passage 9M passes through the exhaust gas recirculation passage 16 and flows into the air / exhaust gas passage 31 from the exhaust gas inlet 16E. As described above, the air / exhaust gas passage 31 is formed on the inner surface 1SW side of the cylinder 1S of the first intake port 4A. Therefore, the exhaust gas Ex flowing through the air / exhaust gas passage 31 flows into the combustion space 1B from between the first intake valve 10A and the opening 4Ao (FIG. 1) of the first intake port 4A, as shown in FIG. And flows along the inner surface 1SW of the cylinder 1S.

  When performing EGR in this embodiment, as shown in FIG. 4, exhaust gas Ex is introduced into the combustion space 1B from the air / exhaust gas passage 31 of the first intake port 4A, and air A is injected into the combustion space from the second intake port 4B. Introduce to 1B. Then, the operation of the first port injection valve 2A is stopped, and the fuel F is supplied to the internal combustion engine 1 using only the second port injection valve 2B. In this case, as shown in FIG. 4, the fuel spray Fm is injected only from the fuel injection hole 2o of the second intake port 4B. Therefore, in the present embodiment, when EGR is executed, approximately twice as much fuel F is supplied from the second port injection valve 2B as compared with the case where EGR is not executed.

  When EGR is executed in the present embodiment, as shown in FIGS. 4 and 5, the exhaust gas Ex in the air / exhaust gas passage 31 flows along the inner surface 1SW of the cylinder 1S (in the direction of arrow R in FIG. 5), and the cylinder An exhaust gas Ex layer (exhaust gas layer) Ex_R is formed in the vicinity of the inner surface 1SW of 1S. Then, from the second intake port 4B, an air-fuel mixture of the fuel F supplied from the second port injection valve 2B and the air A flowing through the second intake port 4B flows into the combustion space 1B, as shown in FIG. In addition, an air-fuel mixture layer (air-fuel mixture layer) Gm_R is formed at the central portion in the cylinder 1S where the exhaust gas Ex layer is not formed.

  In the present embodiment, at the time of EGR, as shown in FIG. 5, the air-fuel mixture is burned with the exhaust gas layer Ex_R formed in the vicinity of the inner surface 1SW of the cylinder 1S and the air-fuel mixture layer Gm_R formed inside the exhaust gas layer Ex_R. . Thereby, a good combustion state is obtained. Further, in this embodiment, since the heat insulation effect by the exhaust gas layer Ex_R existing in the vicinity of the inner surface 1SW of the cylinder 1S is obtained, the cooling loss is reduced, and the extinguishing of the flame in the vicinity of the inner surface 1SW of the cylinder 1S is suppressed. . As a result, fuel consumption is suppressed and unburned components are reduced. Here, the cooling loss means that the combustion gas generated by the combustion of the air-fuel mixture comes into contact with the inner surface 1SW of the cylinder 1S and the heat of the combustion gas is taken to the cylinder 1S.

  In the internal combustion engine 1, as shown in FIG. 4, the fuel injection hole 2 o of the first port injection valve 2 </ b> A opens to the air passage 32. When performing EGR, since the exhaust gas Ex passes through the air / exhaust gas passage 31, it is possible to avoid direct contact between the fuel injection hole 2o of the first port injection valve 2A and the exhaust gas Ex. Thereby, it is possible to suppress the accumulation of carbon and combustion debris in the fuel injection hole 2o of the first port injection valve 2A.

  When executing EGR, if the exhaust gas Ex in the air / exhaust gas passage 31 leaks from the air / exhaust gas channel inlet 31i, the amount of exhaust gas Ex flowing along the inner surface 1SW of the cylinder 1S is reduced, and the heat insulation effect by the exhaust gas layer Ex_R is reduced. May decrease. For this reason, it is preferable that the air / exhaust gas passage inlet 31i is closed by the passage switching valve 19 when the passage switching valve 19 is closed. Thereby, the possibility that the heat insulation effect by the exhaust gas layer Ex_R may be reduced can be reduced.

  When the fuel F is supplied from the second port injection valve 2B, when the fuel spray Fm is formed toward the center of the second intake valve 10B, that is, the stem 11, the fuel spray Fm is dispersed by the umbrella portion 12 of the second intake valve 10B. Then, the fuel F also diffuses into the exhaust gas layer Ex_R formed in the vicinity of the inner surface 1SW of the cylinder 1S. Since the exhaust gas layer Ex_R has little oxygen for combustion, the fuel F diffused in the exhaust gas layer Ex_R is discharged from the combustion space 1B without burning. As a result, problems such as an increase in unburned HC and an increase in fuel consumption may occur.

  Therefore, when the fuel F is supplied from the second port injection valve 2B, the fuel spray Fm of the fuel F supplied from the second port injection valve 2B is directed to the central axis Z of the cylinder 1S as shown in FIG. It is preferable. That is, it is preferable to deflect the fuel spray Fm of the fuel F supplied from the second port injection valve 2B toward the first port injection valve 2A. More specifically, the fuel spray Fm is formed between the stem 11 of the first intake valve 10A and the stem 11 of the second intake valve 10B. As a result, the air-fuel mixture layer Gm_R in the cylinder 1S is formed around the central axis Z of the cylinder 1S as shown in FIG. 4, and therefore, the fuel to the exhaust gas layer Ex_R formed in the vicinity of the inner surface 1SW of the cylinder 1S. F diffusion can be suppressed. As a result, the amount of fuel F that is not used for combustion can be reduced, so that an increase in unburned HC and fuel consumption can be suppressed.

  It is sufficient that at least the fuel spray Fm formed by the second port injection valve 2B is directed to the central axis Z of the cylinder 1S. However, considering the distribution of the air-fuel mixture formed in the cylinder 1S when EGR is not performed, the fuel spray Fm formed by the first port injection valve 2A is also the central axis of the cylinder 1S as shown in FIG. It is preferable that it is suitable for Z. As a result, even when EGR is not executed, an air-fuel mixture layer can be formed around the central axis Z of the cylinder 1S as shown in FIG. Further, since the amount of the fuel F adhering to the inner surface 1SW of the cylinder 1S can be reduced, the increase in unburned HC and fuel consumption can be suppressed, and the fuel dilution of the lubricating oil that lubricates the sliding portion of the internal combustion engine 1 can be suppressed. Can also be suppressed.

  As shown in FIGS. 1 and 5, the top 5T of the piston 5 of the internal combustion engine 1 is formed in a convex shape. Thereby, the exhaust gas layer Ex_R of the inner surface 1SW of the cylinder 1S is held, and mixing of the exhaust gas layer Ex_R and the air-fuel mixture layer Gm_R is suppressed. As a result, the amount of fuel F that is not used for combustion can be reduced, so that an increase in unburned HC and fuel consumption can be suppressed.

  In the example described above, the passage switching valve 19 is used, but the passage switching valve 19 is not necessarily used. The passage switching valve 19 may not be provided in the first intake port 4A, and the exhaust gas Ex may be introduced into the combustion space 1B by introducing the exhaust gas Ex into the air / exhaust passage inlet 31i only by operating the valve device 17 during EGR. Even in this case, the exhaust gas layer Ex_R along the inner surface 1SW of the cylinder 1S can be formed. Note that it is more preferable to use the passage switching valve 19 because the exhaust gas layer Ex_R along the inner surface 1SW of the cylinder 1S can be reliably formed.

  Next, the engine ECU 50 will be described. The engine ECU 50 includes an input / output unit 50IO, a processing unit 50P, and a storage unit 50M that stores various maps used for controlling the internal combustion engine 1. The input / output unit 50IO includes an air flow sensor 40, a crank angle sensor 41, a coolant temperature sensor 42, an accelerator opening sensor 43, a first port injection valve 2A, a second port injection valve 2B, a spark plug 7, a feed pump 13P, A throttle valve actuator 14A and a passage switching valve driving actuator 19A are connected. The input / output unit 50IO receives input signals from the air flow sensor 40, the crank angle sensor 41, and the like, and output signals to the first port injection valve 2A, the second port injection valve 2B, the passage switching valve drive actuator 19A, and the like. Perform input / output.

  The processing unit 50P includes, for example, a memory and a CPU (Central Processing Unit). The processing unit 50P includes a control condition determination unit 51, an EGR control unit 52, a fuel supply control unit 53, and an engine control unit 54. The storage unit 50M is a non-volatile memory such as a flash memory, a memory that can only be read such as a ROM (Read Only Memory), a memory that can be read and written such as a RAM (Random Access Memory), or a combination thereof. Can be configured. The storage unit 50M stores a control program used for controlling the internal combustion engine 1, a control data map, and the like. Next, a method for operating the internal combustion engine according to the present embodiment will be described. This operating method of the internal combustion engine relates to EGR.

  FIG. 6 is a flowchart illustrating a procedure of the operation method of the internal combustion engine according to the first embodiment. FIG. 7 is a schematic diagram of an EGR rate setting map in which the EGR rate is described. In executing the operation method of the internal combustion engine according to the present embodiment, in step S101, the control condition determination unit 51 constituting the processing unit 50P of the engine ECU 50 determines the cooling water temperature Tw of the internal combustion engine 1 from the cooling water temperature sensor 42. get.

  If the internal combustion engine 1 is not sufficiently warmed up, EGR is not executed, so the process proceeds to step S102, where the control condition determination unit 51 determines the coolant temperature Tw acquired in step S101 and the coolant temperature threshold Tc. And compare. The cooling water temperature threshold value Tc is a cooling water temperature threshold value for determining whether or not the condition is such that EGR can be executed. When it is determined No in step S102, that is, when the control condition determination unit 51 determines that Tw ≦ Twc, the internal combustion engine 1 is operated without executing EGR, and thus the process proceeds to step S103.

  In step S103, the EGR control unit 52 constituting the processing unit 50P of the engine ECU 50 sets the EGR rate to zero. This is because Tw ≦ Twc, which is not a condition for executing EGR. Here, the EGR rate is Qe / (Qe + Qa) × where Qe is the amount of exhaust gas Ex introduced into the combustion space 1B and Qa is the amount of air A introduced into the combustion space 1B (intake air amount). 100 (%).

  Next, the process proceeds to step S104, where the EGR control unit 52 opens the passage switching valve 19 as shown in FIG. 2, and in step S105, the fuel supply control unit 53 constituting the processing unit 50P of the engine ECU 50 Fuel F is supplied to the internal combustion engine 1 by both the injection valve 2A and the second port injection valve 2B. Here, if the total fuel supply amount determined by the operating condition of the internal combustion engine 1 is τa, the first port injection valve 2A and the second port injection valve 2B supply the fuel F by τa / 2 respectively. The engine control unit 54 sets an appropriate ignition timing according to the operating conditions of the internal combustion engine 1, discharges from the spark plug 7, and ignites the air-fuel mixture in the combustion space 1B.

  Next, it returns to step S102 and demonstrates. When it is determined Yes in step S102, that is, when the control condition determination unit 51 determines that Tw> Twc, it is a condition under which EGR can be executed. In this case, the process proceeds to step S106. Since the EGR is not executed when the accelerator opening OP is large, it is determined in step S106 whether or not the conditions under which the EGR can be executed are based on the accelerator opening OP. In step S106, the control condition determination unit 51 acquires the accelerator opening OP from the accelerator opening sensor 43 and compares it with a predetermined accelerator opening threshold OPc.

  When it is determined No in step S106, that is, when the control condition determination unit 51 determines that OP ≧ OPc, it is determined that the condition is not such that EGR can be executed. In this case, since the internal combustion engine 1 is operated without executing EGR, steps S103 to S105 are executed.

  If it is determined Yes in step S106, that is, if the control condition determining unit 51 determines that OP <OPc, the process proceeds to step S107. In step S107, the control condition determination unit 51 determines whether or not the internal combustion engine 1 is operating in a region where EGR is executed. The region where EGR is executed is determined by the load factor KL of the internal combustion engine 1 and the engine speed Ne.

  The EGR rate setting map 60 shown in FIG. 7 describes the EGR rate according to the load factor KL of the internal combustion engine 1 and the engine speed Ne. A region where the EGR rate is outside 0% is a region where EGR is not executed, that is, the EGR rate = 0. The control condition determination unit 51 obtains the engine speed Ne based on the signal of the crankshaft 6 detected by the crank angle sensor 41 shown in FIG. 1, and the intake air amount of the internal combustion engine 1 obtained from the signal detected by the airflow sensor 40. A load factor KL is obtained based on Qa. When the load factor KL and the engine speed Ne are obtained, the control condition determination unit 51 gives the load factor KL and the engine speed Ne to the EGR rate setting map 60 shown in FIG. It is determined whether 1 is operated.

  When it determines with No by step S107, it determines with the internal combustion engine 1 not being drive | operated in the area | region which performs EGR. For example, when the control condition determination unit 51 gives the load factor KL and the engine speed Ne to the EGR rate setting map 60 and obtains a result of EGR rate = 0%, the internal combustion engine 1 is in the region where EGR is executed. Is determined not to be driven. In this case, since the internal combustion engine 1 is operated without executing EGR, steps S103 to S105 are executed. When it determines with Yes by step S107, ie, when the control condition determination part 51 determines with the internal combustion engine 1 being drive | operated in the area | region which performs EGR, EGR is performed. In this case, the process proceeds to step S108.

  In step S108, the EGR control unit 52 obtains a necessary EGR rate. For example, the EGR control unit 52 obtains the EGR rate obtained by giving the load factor KL and the engine speed Ne of the internal combustion engine 1 to the EGR rate setting map 60 shown in FIG. EGR rate

  When the necessary EGR rate is obtained, the process proceeds to step S109, and the EGR control unit 52 closes the passage switching valve 19 as shown in FIG. In step S110, the fuel supply control unit 53 stops the operation of the first port injection valve 2A and supplies the fuel F to the internal combustion engine 1 using only the second port injection valve 2B. Here, if the total fuel supply amount determined by the operating conditions of the internal combustion engine 1 is τa, the second port injection valve 2B supplies the fuel F of τa. The engine control unit 54 sets an appropriate ignition timing according to the operating conditions of the internal combustion engine 1, discharges from the spark plug 7, and ignites the air-fuel mixture in the combustion space 1B.

  As described above, in the present embodiment, when performing EGR, exhaust gas is introduced from the first intake port into the combustion space, fuel and air are introduced from the second intake port into the combustion space, and exhaust gas is introduced into the combustion space. And a mixture of fuel and air. In order to realize this, in the present embodiment, a first port injection valve and a second port injection valve are provided in the first intake port and the second intake port connected to the combustion space in one cylinder, respectively. In addition, the first intake passage is divided into an inner surface side and a central axis side of the cylinder by a partition member, and an exhaust gas introduction port that opens to the first intake port on the inner surface side of the cylinder partitioned by the partition member is provided. Then, exhaust gas (air mixture after combustion) discharged from the combustion space is introduced into the first intake port from the exhaust gas inlet.

  As a result, an exhaust gas layer is formed in the vicinity of the inner surface of the cylinder, and an air-fuel mixture layer is formed inside the cylinder. In this state, the air-fuel mixture is ignited and the air-fuel mixture burns. As a result, the heat insulation action by the exhaust gas in the vicinity of the inner surface of the cylinder provides the effect of reducing the cooling loss and suppressing the extinction in the vicinity of the inner surface of the cylinder. For this reason, in addition to obtaining effects such as NOx reduction, pump loss reduction, and fuel consumption reduction by EGR, fuel consumption is suppressed and unburned components are reduced.

  In addition, an exhaust gas layer is formed in the vicinity of the inner surface of the cylinder, and an air-fuel mixture layer is formed on the inner side thereof. Therefore, combustion deterioration due to the mixture of the exhaust gas introduced into the combustion space by EGR and the air-fuel mixture occurs. It is suppressed. As a result, a good combustion state can be obtained, so that even if more exhaust gas is introduced into the combustion space, the combustion state is unlikely to deteriorate. As a result, it is possible to introduce more exhaust gas into the combustion space and further reduce NOx, pump loss, and fuel consumption.

(Embodiment 2)
In the second embodiment, a tumble flow is formed in the combustion space, and two intake passages (intake ports) are connected to the combustion space for opening, and a fuel supply means (port injection valve) is provided in each intake passage. In the internal combustion engine, an exhaust gas introduction passage for introducing exhaust gas into the combustion space is provided in both intake passages, and one of the intake passages is provided with an air passage switching means upstream of the exhaust gas introduction port in the exhaust gas flow direction. There is a feature in the point to do.

  FIG. 8 is an explanatory diagram showing an internal combustion engine according to the second embodiment. 9 and 10 are plan views showing the internal combustion engine according to the second embodiment as viewed from the cylinder head side. FIG. 11 is a schematic diagram showing a state in which exhaust gas recirculation is executed in the internal combustion engine according to the second embodiment. Since the internal combustion engine 1a has substantially the same configuration as the internal combustion engine 1 described in the first embodiment, the description of the common configuration is omitted. As shown in FIG. 8, when the first intake valve 10A and the second intake valve 10B are opened, air A and fuel F flow from the opening 4Ao of the first intake port 4A and the opening 4Bo of the second intake port 4B. To do. The air A and the fuel F form a tumble flow (longitudinal vortex) T in the combustion space 1B. The tumble flow T is directed from the first intake port 4A and the second intake port 4B to the exhaust port 9 on the cylinder head 1H side, and from the exhaust port 9 to the first intake port 4A and the second intake port near the top 5T of the piston 5. This is a flow toward the intake port 4B. The direction of the tumble flow T is not limited to this, and may be the opposite direction.

  As shown in FIGS. 9 to 11, the internal combustion engine 1a includes a first spark plug 7A and a second spark plug 7B as ignition means. The first spark plug 7A is disposed in the vicinity of the central axis Z of the cylinder 1S, that is, in the center portion of the cylinder 1S, and the second spark plug 7B is disposed on the inner surface 1SW side of the cylinder 1S on the second intake port 4B side. .

  As shown in FIGS. 8 to 10, the exhaust passage 9M and the first intake port 4A are connected by a first exhaust gas recirculation passage 16A. A first exhaust gas inlet 16EA opens in the first intake port 4A. The first exhaust gas introduction port 16EA is an opening in which the first exhaust gas recirculation passage 16A opens to the first intake port 4A. During EGR, the first exhaust gas recirculation passage 16A passes the first exhaust gas recirculation passage 16A through the first exhaust gas recirculation passage 16A. It introduces into the intake port 4A. Further, the second exhaust gas inlet 16EB opens in the second intake port 4B. The second exhaust gas introduction port 16EB is an opening in which the second exhaust gas recirculation passage 16B opens to the second intake port 4B. During EGR, the second exhaust gas recirculation passage 16B passes the second exhaust gas recirculation passage 16B through the second exhaust gas recirculation passage 16B. It introduces into the intake port 4B.

  The first exhaust gas recirculation passage 16A is provided with a first valve device 17A controlled by the engine ECU 50. Similarly, the exhaust passage 9M and the second intake port 4B are connected by a second exhaust gas recirculation passage 16B. A second valve device 17B controlled by the engine ECU 50 is provided in the second exhaust gas recirculation passage 16B. The first valve device 17A and the second valve device 17B are the same as the valve device 17 described in the first embodiment, and the first valve device 17A and the second valve device 17B are controlled by the engine ECU 50. The internal combustion engine 1a adjusts the opening degree of the first valve device 17A and the opening degree of the second valve device 17B to adjust the inside of the combustion space 1B through at least one of the first intake port 4A and the second intake port 4B. Exhaust gas Ex can be introduced.

  A passage switching valve 19a, which is passage switching means, is provided upstream of the first exhaust gas introduction port 16EA. The passage switching valve 19a is driven by a passage switching valve driving actuator 19Aa shown in FIG. 8 to open and close the first intake port 4A. The passage switching valve driving actuator 19Aa is controlled by the engine ECU 50.

  When the passage switching valve 19a is closed, the first intake port 4A is shut off, and the air A does not flow downstream from the passage switching valve 19a, that is, to the combustion space 1B. In this case, the exhaust gas Ex flows from the first exhaust gas inlet 16EA to the combustion space 1B through the first intake port 4A. When the passage switching valve 19a is opened, the upstream side and the downstream side of the passage switching valve 19a communicate with each other, so that the air A flows downstream from the passage switching valve 19a and the air A flows into the combustion space 1B. In this case, the air A flows to the combustion space 1B through the entire first intake port 4A.

  In the present embodiment, opening or closing of the passage switching valve 19a is switched depending on whether or not EGR is executed. Further, even when EGR is executed, when the exhaust gas Ex and the air-fuel mixture are mixed in the cylinder 1S (referred to as homogeneous EGR), the exhaust gas Ex layer and the air-fuel mixture layer are formed in the cylinder 1S. In order to selectively use the case (called stratified EGR), the passage switching valve 19a is switched between open and closed.

  First, when EGR is not executed in the present embodiment, as shown in FIG. 9, air A is introduced into the combustion space 1B from both the first intake port 4A and the second intake port 4B. Then, the fuel F is supplied to the internal combustion engine 1 by both the first port injection valve 2A and the second port injection valve 2B. In this case, as shown in FIG. 9, fuel is supplied from the fuel injection hole 2o of the first intake port 4A and the fuel injection hole 2o of the second intake port 4B to form a fuel spray Fm. When EGR is not executed, the air-fuel mixture in the cylinder 1S is ignited using the first spark plug 7A.

  When EGR is not executed, as shown in FIG. 9, the passage switching valve 19a is opened, and the air A flows through the entire first intake port 4A. In this case, in order to reduce the resistance when the air A flows as much as possible, it is preferable that the passage switching valve 19a be parallel to the flow direction of the air A.

  When the exhaust gas Ex and the air-fuel mixture are mixed in the cylinder 1S, that is, when the homogeneous EGR is performed, as shown in FIG. 9, the combustion space is discharged from both the first intake port 4A and the second intake port 4B. Air A is introduced into 1B. Then, the fuel F is supplied to the internal combustion engine 1 by both the first port injection valve 2A and the second port injection valve 2B. In this state, the first valve device 17A and the second valve device 17B are opened, and in the first intake port 4A and the second intake port 4B through the first exhaust gas recirculation passage 16A and the second exhaust gas recirculation passage 16B. Exhaust gas Ex is introduced. In this case, as shown in FIG. 9, fuel is supplied from the fuel injection hole 2o of the first intake port 4A and the fuel injection hole 2o of the second intake port 4B to form a fuel spray Fm.

  During homogeneous EGR, the air-fuel mixture present in the cylinder 1S is ignited using the first spark plug 7A. When performing the homogeneous EGR, the fuel F is supplied from the first port injection valve 2A and the second port injection valve 2B before the intake stroke, and the heat is generated by the heat of the first intake port 4A and the second intake port 4B. Homogenization in the combustion space 1B is promoted by vaporization of the fuel F and mixing by a small valve lift.

  When the exhaust gas Ex layer and the air-fuel mixture layer are formed in the cylinder 1S, that is, when the stratified EGR is executed, the passage switching valve 19a is closed and downstream of the passage switching valve 19a as shown in FIG. Air A does not flow to the side. When the first valve device 17A is opened in this state, the exhaust gas Ex in the exhaust passage 9M passes through the first exhaust gas recirculation passage 16A and flows into the first intake port 4A from the first exhaust gas inlet 16EA. The exhaust gas Ex flows into the combustion space 1B from between the first intake valve 10A and the opening 4Ao (FIG. 8) of the first intake port 4A, and the exhaust gas Ex layer is formed on the first intake port 4A side of the cylinder 1S. (Exhaust gas layer) Ex_R is formed.

  When executing the stratified EGR, as shown in FIG. 10, the exhaust gas Ex is introduced into the combustion space 1B from the first intake port 4A, and the air A is introduced into the combustion space 1B from the second intake port 4B. Then, the operation of the first port injection valve 2A is stopped, and the fuel F is supplied to the internal combustion engine 1 using only the second port injection valve 2B. In this case, as shown in FIG. 10, fuel is supplied only from the fuel injection hole 2o of the second intake port 4B, and the fuel spray Fm is formed. Therefore, in the present embodiment, when the stratified EGR is executed, approximately twice as much fuel F is supplied from the second port injection valve 2B as compared with the case where the stratified EGR is not executed.

  When the stratification EGR is executed, as shown in FIGS. 10 and 11, the exhaust gas Ex forms an exhaust gas layer Ex_R on the first intake port 4A side in the cylinder 1S. From the second intake port 4B, a mixture of the fuel F supplied from the second port injection valve 2B and the air A flowing through the second intake port 4B flows into the combustion space 1B, as shown in FIG. In addition, an air-fuel mixture layer Gm_R is formed on the second intake port 4B side in the cylinder 1S. When executing the stratified EGR, the fuel F is supplied only from the second port injection valve 2B in synchronism before the intake stroke.

  In the internal combustion engine 1a, a tumble flow is formed in the cylinder 1S. The exhaust gas Ex flowing into the cylinder 1S from the first intake port 4A forms a first tumble flow TA in the cylinder 1S, and the fuel F and air A flowing into the cylinder 1S from the second intake port 4B are the cylinder 1S. To form a second tumble flow TB. As a result, the exhaust gas layer Ex_R becomes the first tumble flow TA and the air-fuel mixture layer Gm_R becomes the second tumble flow TB, so that mixing of both is suppressed. In addition, two concave portions 5U extending from the first intake port 4A and the second intake port 4B toward the exhaust port 9 are formed in the top portion 5Ta of the piston 5a. Thereby, mixing of the exhaust gas layer Ex_R and the air-fuel mixture layer Gm_R is further suppressed.

  During the stratified EGR, the second spark plug 7B is used to ignite the air-fuel mixture layer Gm_R that is unevenly distributed on the second intake port 4B side in the cylinder 1S and hardly contains the exhaust gas Ex. As a result, the air-fuel mixture can be reliably ignited and the air-fuel mixture can be burned well. As a result, in the stratified EGR, equal or higher combustion can be ensured at a higher EGR rate than the homogeneous EGR. Next, a method for operating the internal combustion engine according to the present embodiment will be described. This operating method of the internal combustion engine relates to EGR.

  FIG. 12 is a flowchart illustrating a procedure of an operating method of the internal combustion engine according to the second embodiment. FIGS. 13 to 16 are schematic diagrams of data maps in which control data used for the operation method of the internal combustion engine according to the second embodiment is described. Since step S201 and step S202 of the operating method of the internal combustion engine according to the present embodiment are the same as step S101 and step S102 of the operating method of the internal combustion engine according to the first embodiment, description thereof will be omitted. If it is determined No in step S202, that is, if the control condition determining unit 51 shown in FIG. 8 determines that Tw ≦ Twc, the internal combustion engine 1a is operated without executing EGR, and the process proceeds to step S203. .

  In step S203, the EGR control unit 52 shown in FIG. 8 sets the EGR rate to zero. That is, EGR is not executed. Next, it progresses to step S204 and the EGR control part 52 opens the passage switching valve 19a as shown in FIG. In step S205, the fuel supply control unit 53 shown in FIG. 8 determines the fuel supply amount and the fuel supply timing.

  In the present embodiment, when EGR is not executed, the fuel F is supplied to the internal combustion engine 1a using both the first port injection valve 2A and the second port injection valve 2B. Therefore, if the total fuel supply amount determined by the operating conditions of the internal combustion engine 1a is τa, the fuel supply control unit 53 supplies the fuel F by τa / 2 by the first port injection valve 2A and the second port injection valve 2B, respectively. Each fuel supply amount is set so that it does. Further, the fuel supply control unit 53 determines the fuel supply timing. When the EGR is not executed, the fuel supply timing is determined so that the fuel F is supplied from the first port injection valve 2A and the second port injection valve 2B before the intake stroke.

  When the fuel supply amount and the fuel supply timing are determined, the process proceeds to step S206, and the fuel supply control unit 53 supplies the fuel F to the internal combustion engine 1a by both the first port injection valve 2A and the second port injection valve 2B. . When EGR is not executed, the first valve device 17A and the second valve device 17B are closed. In step S207, the engine control unit 54 sets an appropriate ignition timing according to the operating conditions of the internal combustion engine 1a, and discharges from the first spark plug (central spark plug) 7A to mix in the combustion space 1B. I ignite my mind.

  Next, it returns to step S202 and demonstrates. If it is determined Yes in step S202, that is, if the control condition determination unit 51 determines that Tw> Twc, the condition is such that EGR can be executed. In this case, the process proceeds to step S208. Since step S208 is the same as step S106 of the operating method of the internal combustion engine according to the first embodiment, description thereof is omitted.

  If it is determined No in step S208, that is, if the control condition determination unit 51 determines that OP ≧ OPc, it is determined that the condition is not such that EGR can be executed. In this case, since the internal combustion engine 1a is operated without executing EGR, steps S203 to S207 are executed.

  If it is determined Yes in step S208, that is, if the control condition determining unit 51 determines that OP <OPc, the process proceeds to step S209. In step S209, the control condition determination unit 51 determines whether or not the internal combustion engine 1a is operated in the region where the stratified EGR is executed. The region where the stratified EGR is executed is determined by the load factor KL of the internal combustion engine 1a and the engine speed Ne.

  The determination map 61 shown in FIG. 13 describes a region L of stratified EGR and a region N of homogeneous EGR. When the internal combustion engine 1a is operated at the load factor KL and the engine speed Ne in the region L of the determination map 61, the stratification EGR is executed. Further, when the internal combustion engine 1a is operated at the load factor KL and the engine speed Ne in the region N of the determination map 61, the homogeneous EGR is executed.

  The control condition determination unit 51 obtains the engine speed Ne based on the signal of the crankshaft 6 detected by the crank angle sensor 41 shown in FIG. 8, and the intake air amount of the internal combustion engine 1a obtained from the signal detected by the airflow sensor 40 A load factor KL is obtained based on Qa. When the load factor KL and the engine speed Ne are obtained, the control condition determination unit 51 gives the load factor KL and the engine speed Ne to the determination map 61 shown in FIG. 13 and executes the stratified EGR in the region where the stratified EGR is executed. It is determined whether or not the vehicle is operating.

  When it determines with No by step S209, it determines with the internal combustion engine 1a being drive | operated in the area | region which performs homogeneous EGR. In this case, the process proceeds to step S210, and the EGR control unit 52 obtains an EGR rate necessary for the homogeneous EGR. For example, the EGR control unit 52 obtains the EGR rate obtained by giving the load factor KL and the engine speed Ne of the internal combustion engine 1a obtained in the determination of step S209 to the homogeneous EGR rate setting map 63 shown in FIG. Thus, the EGR rate required for homogeneous EGR is set. Next, step S204 to step S207 are executed. In this case, in step S206, the EGR control unit 52 opens the first valve device 17A and the second valve device 17B to an opening that can realize the EGR rate obtained in step S210.

  Next, it returns to step S209 and demonstrates. When it determines with Yes in step S209, it determines with the internal combustion engine 1a being drive | operated in the area | region which performs stratified EGR. In this case, the process proceeds to step S211, and the EGR control unit 52 obtains an EGR rate necessary for the stratified EGR. For example, the EGR control unit 52 obtains the EGR rate obtained by giving the load factor KL and the engine speed Ne of the internal combustion engine 1a obtained in the determination in step S209 to the stratified EGR rate setting map 62 shown in FIG. Thus, the EGR rate required for the stratified EGR is set.

  Next, it progresses to step S212 and the EGR control part 52 closes the channel | path switching valve 19a as shown in FIG. In step S213, the fuel supply control unit 53 determines the fuel supply amount and the fuel supply timing. In the present embodiment, when the stratified EGR is executed, the first port injection valve 2A is stopped, and the fuel F is supplied to the internal combustion engine 1a using only the second port injection valve 2B. Therefore, if the total fuel supply amount determined by the operating conditions of the internal combustion engine 1a is τa, the fuel supply control unit 53 sets the fuel F of τa to be supplied by the second port injection valve 2B alone.

  Further, the fuel supply control unit 53 determines the fuel supply timing. When executing the stratified EGR, the fuel F is supplied from the second port injection valve 2B in synchronization with the intake stroke. In the present embodiment, the fuel supply timing is determined by the stratified EGR-time fuel supply timing map 64 shown in FIG. For example, the fuel supply control unit 53 gives the load factor KL and engine speed Ne of the internal combustion engine 1a obtained in the determination in step S209 to the stratified EGR-time fuel supply timing map 64, and sets the corresponding fuel supply timing IT. To do. Here, the fuel supply timing IT2 is more advanced than the fuel supply timing IT1.

  When the fuel supply amount and the fuel supply timing are determined, the process proceeds to step S214, where the fuel supply control unit 53 stops the operation of the first port injection valve 2A, and uses only the second port injection valve 2B, in step S213. Fuel F is supplied to the internal combustion engine 1a at the determined fuel supply amount and fuel supply timing. In step S215, the engine control unit 54 sets an appropriate ignition timing in accordance with the operating conditions of the internal combustion engine 1a, and discharges from the second ignition plug 7B (side ignition plug) to allow the mixture in the combustion space 1B. Ignition.

  As described above, in the present embodiment, when performing EGR, exhaust gas is introduced from the first intake port into the combustion space, fuel and air are introduced from the second intake port into the combustion space, and exhaust gas is introduced into the combustion space. And a mixture of fuel and air. In order to realize this, in the present embodiment, a tumble flow is formed in the cylinder, and each of the first intake port and the second intake port connected to the combustion space in one cylinder is provided. A first port injection valve and a second port injection valve are provided. A first exhaust gas inlet that opens to the first intake port and a second exhaust gas inlet that opens to the second intake port are provided, and an air passage switching valve is provided upstream of the first exhaust gas inlet. When performing EGR, exhaust gas discharged from the combustion space (combusted air-fuel mixture) is introduced into the first intake port from the first exhaust gas inlet, and air is introduced from the second intake port. Fuel is introduced into the combustion space.

  As a result, in the cylinder, an exhaust gas layer is formed on the first intake port side, and an air-fuel mixture layer is formed on the second intake port side. Then, the air-fuel mixture layer in which the exhaust gas Ex is hardly mixed is ignited by the second spark plug disposed on the second intake port side. As a result, the air-fuel mixture can be reliably ignited and the air-fuel mixture can be burned well. Thus, in this embodiment, since a favorable combustion state is obtained by stratified EGR, even if more exhaust gas is introduced into the combustion space, the combustion state is unlikely to deteriorate. As a result, it is possible to introduce more exhaust gas into the combustion space and further reduce NOx, pump loss, and fuel consumption.

  In the present embodiment, the homogeneous EGR and the stratified EGR are switched according to the operating condition of the internal combustion engine. Accordingly, for example, by using the stratified EGR at a low load, it is possible to operate by introducing more exhaust gas into the combustion space, so that fuel consumption can be further reduced. In addition, since the deterioration of combustion is suppressed by the stratified EGR, the EGR can be executed even under the operating condition where the EGR could not be executed so far.

  Furthermore, the following invention is grasped | ascertained from Embodiment 1 and Embodiment 2 mentioned above. A first aspect of the present invention is a space in a cylinder in which a piston reciprocates, a combustion space in which a mixture of fuel and air burns, a first intake passage that is connected to the combustion space and opens, and When the exhaust gas discharged from the combustion space is recirculated to the combustion space of the internal combustion engine having two intake passages, the exhaust gas is introduced into the combustion space from the first intake passage, and the second The fuel and the air are introduced into the combustion space from an intake passage of the exhaust gas, and a layer of the exhaust gas and a mixture of the fuel and air are formed in the combustion space. An operation method of an internal combustion engine.

  As a result, in the cylinder, an exhaust gas layer is formed on the first intake passage side, and an air-fuel mixture layer is formed on the second intake passage side. Then, the air-fuel mixture layer in which the exhaust gas is hardly mixed is ignited by the ignition means arranged on the second intake passage side. As a result, the air-fuel mixture can be reliably ignited and the air-fuel mixture can be burned well.

  As a preferred aspect of the present invention, in the first aspect of the present invention, the exhaust gas layer is formed along the inner surface of the cylinder, and the mixture layer is formed inside the exhaust gas layer. An internal combustion engine operating method (second present invention). In the second aspect of the present invention, an exhaust gas layer is formed in the vicinity of the inner surface of the cylinder, and an air-fuel mixture layer is formed inside the cylinder. In this state, the air-fuel mixture is ignited and the air-fuel mixture burns. As a result, the effect of reducing the cooling loss and suppressing the extinguishing of the flame in the vicinity of the inner surface of the cylinder can be obtained by the heat insulating action by the exhaust gas in the vicinity of the inner surface of the cylinder.

  As described above, the internal combustion engine according to the present invention is useful when exhaust gas recirculation is performed, and is particularly suitable for reducing the cooling loss and suppressing the deterioration of the combustion state.

1 is an explanatory diagram showing an internal combustion engine according to Embodiment 1. FIG. FIG. 2 is a plan view showing a state in which the internal combustion engine according to the first embodiment is viewed from the cylinder head side. It is XX sectional drawing of FIG. FIG. 2 is a plan view showing a state in which the internal combustion engine according to the first embodiment is viewed from the cylinder head side. In the internal combustion engine which concerns on Embodiment 1, it is a schematic diagram which shows the state which performed exhaust gas recirculation. 3 is a flowchart illustrating a procedure of an operation method for the internal combustion engine according to the first embodiment. It is a schematic diagram of the EGR rate setting map in which the EGR rate is described. FIG. 5 is an explanatory diagram showing an internal combustion engine according to a second embodiment. FIG. 6 is a plan view showing a state in which an internal combustion engine according to a second embodiment is viewed from the cylinder head side. FIG. 6 is a plan view showing a state in which an internal combustion engine according to a second embodiment is viewed from the cylinder head side. FIG. 6 is a schematic diagram showing a state in which exhaust gas recirculation is executed in an internal combustion engine according to a second embodiment. 6 is a flowchart showing a procedure of an operation method for an internal combustion engine according to a second embodiment. FIG. 6 is a schematic diagram of a data map in which control data used for an internal combustion engine operation method according to Embodiment 2 is described. FIG. 6 is a schematic diagram of a data map in which control data used for an internal combustion engine operation method according to Embodiment 2 is described. FIG. 6 is a schematic diagram of a data map in which control data used for an internal combustion engine operation method according to Embodiment 2 is described. FIG. 6 is a schematic diagram of a data map in which control data used for an internal combustion engine operation method according to Embodiment 2 is described.

Explanation of symbols

1, 1a Internal combustion engine 1B Combustion space (space)
1C Crankcase 1S Cylinder 1SW Inner surface 1H Cylinder head 2A 1st port injection valve 2B 2nd port injection valve 3 Connecting rod 4A 1st intake port 4B 2nd intake port 5, 5a Piston 5T, 5Ta Top part 6 Crankshaft 7 Spark plug 7A 1st spark plug 7B 2nd spark plug 8 Intake inlet passage 9 Exhaust port 9M Exhaust passage 10A First intake valve 10B Second intake valve 15 Exhaust valve 16 Exhaust gas recirculation passage 16A First exhaust gas recirculation passage 16B Second exhaust gas recirculation Passage 16E Exhaust gas inlet 16EA First exhaust gas inlet 16EB Second exhaust gas inlet 17 Valve device 17A First valve device 17B Second valve device 18 Fuel pipe 19, 19a Passage switching valve 19A, 19Aa Passage switching valve drive actuator 20 port Fuel distribution pipe for injection valve 30 partition member 31 air / exhaust gas passage 31i air / exhaust gas passage inlet 32 air passage 40 air flow sensor 41 crank angle sensor 42 cooling water temperature sensor 43 accelerator opening sensor 50 engine ECU
50IO Input / output unit 50M Storage unit 50P Processing unit 51 Control condition determination unit 52 EGR control unit 53 Fuel supply control unit 54 Engine control unit 60 EGR rate setting map 61 Determination map 62 Stratified EGR rate setting map 63 Homogeneous EGR rate setting map 64 Stratification EGR fuel supply timing map

Claims (6)

A space in the cylinder in which the piston reciprocates, and a combustion space in which a mixture of fuel and air burns;
A first intake passage and a second intake passage which are connected to the combustion space and open;
A partition member provided inside the first intake passage and partitioning the first intake passage into an inner surface side and a central axis side of the cylinder;
First fuel supply means for supplying fuel to the first intake passage on the central axis side of the cylinder partitioned by the partition member;
Second fuel supply means for supplying fuel to the second intake passage;
An exhaust gas introduction port that opens to the first intake passage on the inner surface side of the cylinder partitioned by the partition member and introduces the exhaust gas discharged from the combustion space into the first intake passage;
An internal combustion engine comprising:   When the exhaust gas discharged from the combustion space is introduced from the exhaust gas inlet into the first intake passage, the operation of the first fuel supply unit is stopped, and only from the second fuel supply unit The internal combustion engine according to claim 1, wherein fuel is supplied.   The first intake air inside the first intake passage and upstream in the air flow direction from the end of the partition member on the upstream side in the air flow direction flowing through the first intake passage. The internal combustion engine according to claim 1 or 2, further comprising passage switching means for opening and closing the passage.   4. The first intake passage is closed by the passage switching means when the exhaust gas discharged from the combustion space is introduced into the first intake passage from the exhaust gas inlet. Internal combustion engine.   5. The internal combustion engine according to claim 1, wherein the direction of the fuel supplied from at least the second fuel supply means is directed toward the center of the cylinder.   The internal combustion engine according to claim 1, wherein a top portion of the piston has a convex shape.

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