JP6471041B2 - Injection controller for spark ignition engine - Google Patents

Description

  The present invention relates to a fuel injection control device for a spark ignition engine.

  A spark ignition engine in which liquid fuel and gaseous fuel are mixed and burned in a cylinder is widely known. For example, Japanese Patent Application Laid-Open No. 07-063076 (Patent Document 1) is disclosed. An engine that mixes and burns two types of fuel in this way is called a dual fuel engine.

  In a spark ignition engine, fuel consumption can be improved by introducing so-called lean burn, exhaust gas recirculation, or so-called EGR, in which the mixture ratio of fuel and air is excessive. However, in lean burn or EGR combustion, the ignitability of the air-fuel mixture diluted with air or exhaust gas is reduced, and there is a risk that the combustion becomes unstable. In response to this problem, for example, in the above-mentioned publication, a carburetor for supplying compressed natural gas (CNG) to the intake air in the intake stroke is provided, and ignition is performed toward a portion facing the ignition plug on the piston upper surface before ignition. The liquid fuel injection means for injecting the liquid fuel is provided, and a sufficiently rich air-fuel mixture is formed around the spark plug at the time of ignition to form a strong fire type. As a result, combustion propagation is performed smoothly with a strong fire type, and stable combustion is performed even with a fuel lean mixture.

  In general, in a dual fuel engine, the ratio of the two fuels can be variously selected. Then, since the fuel component of the air-fuel mixture formed around the spark plug changes variously, in order to perform smooth combustion by spark ignition, it is necessary to form an optimal air-fuel mixture according to the fuel component around the spark plug. is there. However, in the prior art, such mixture formation has not been considered.

  Accordingly, an object of the present invention is to provide an injection control device for a spark ignition engine that can perform lean burn and EGR combustion satisfactorily even when the ratio of two fuels varies in a dual fuel engine. To do.

  In order to solve the above problems, for example, the configuration described in the claims is adopted. That is, the present invention provides an injection control device that performs injection control of a spark ignition engine that includes a first injector that injects liquid fuel and a second injector that injects gas fuel, the first injector or the first injector 2 injectors perform ignition injection, and prior to the ignition injection, the first injector or the second injector, or the first injector and the second injector are used for main combustion. It is configured to perform injection, and the equivalent ratio around the spark plug is increased as the liquid fuel ratio in the fuel by the main combustion injection increases.

  According to the present invention, lean burn and EGR combustion can be performed satisfactorily even when the ratio of two fuels varies in a dual fuel engine.

It is a figure showing an engine system concerning one embodiment of the present invention. It is an engine driving map. It is a fuel injection timing chart at the time of lean burn operation. It is an example of setting of the ignition assist injection amount with respect to the gasoline ratio of the main combustion injection in the present embodiment. It is a form of the in-cylinder mixture at the ignition timing. It is the figure which showed the gasoline ratio of the air-fuel mixture for ignition assistance with respect to the gasoline ratio of the air-fuel mixture for main combustion. It is the figure which showed the equivalence ratio dependence of the minimum ignition energy of natural gas and gasoline. It is the figure which showed the change of the optimal equivalent ratio with respect to the ratio of a liquid fuel. It is a fuel injection timing chart at the time of lean burn operation, and is a diagram showing an example in which the timing of ignition assist injection is changed. It is the figure which showed the example which changed both the injection quantity of the injection for ignition assistance, and the injection timing according to the ratio of the gasoline injection quantity in the main combustion injection. It is a figure showing an engine composition concerning one embodiment of the present invention, and is a figure showing an engine composition which made a fuel injection valve for gasoline a port injection type, and made a fuel injection valve for natural gas direct in-cylinder injection type. . It is a figure showing an engine composition concerning one embodiment of the present invention, and is a figure showing an engine composition which made a fuel injection valve for gasoline and a fuel injection valve for natural gas direct in-cylinder type. It is a figure showing an engine composition concerning one embodiment of the present invention, and is a figure showing an engine composition which made a fuel injection valve for gasoline and a fuel injection valve for natural gas direct in-cylinder type. It is a figure showing an engine composition concerning one embodiment of the present invention, and is a top view of an engine which made a fuel injection valve for gasoline and a fuel injection valve for natural gas into a port injection type. BRIEF DESCRIPTION OF THE DRAWINGS It is the figure which showed the engine structure which concerns on one Embodiment of this invention, and is a longitudinal cross-sectional view of the engine which made the fuel injection valve for gasoline and the fuel injection valve for natural gas into the port injection type. It is a fuel injection timing chart at the time of lean burn in this embodiment. It is a form of the in-cylinder mixture at the ignition timing. It is a figure showing an engine composition concerning one embodiment of the present invention, and is a top view of an engine which made a fuel injection valve for gasoline and a fuel injection valve for natural gas into a port injection type. It is a figure which shows the relationship between the gasoline ratio of the mixture for main combustion, and the gasoline ratio which occupies for the fuel in the mixture for ignition assistance.

  Hereinafter, examples will be described with reference to the drawings.

  An engine system and an engine configuration according to an embodiment of the present invention will be described with reference to FIG.

  FIG. 1 shows an outline of the engine configuration. In the four-cycle engine of this embodiment, a combustion chamber 10 is formed by the engine head 1, the cylinder block 2, the piston 3, the intake valve 7, and the exhaust valve 8. A fuel injection valve 100 for gasoline is provided in the cylinder block 2 and its injection nozzle penetrates the combustion chamber 10 to constitute a so-called in-cylinder direct injection engine. The intake port 11 is provided with a fuel injection valve 101 for natural gas. By supplying gasoline by direct in-cylinder injection in this way, it is possible to cool the air-fuel mixture in the combustion chamber by gasoline vaporization, and there are advantages of knocking suppression and high output during high load operation. In general, gas fuel is difficult to mix with air due to its weak injection penetration. However, since the mixing distance and the mixing time can be increased by supplying natural gas by port injection, there is an advantage that air and natural gas can be mixed well.

  The piston 3 is connected to a crankshaft 18 via a connecting rod 17, and a crank angle sensor 19 capable of detecting the crank angle and the engine speed is installed on the crankshaft 18. The cylinder block 2 is provided with a water temperature sensor 20 that detects the temperature of the cooling water.

  The intake pipe 5 is provided with a throttle valve 23 capable of adjusting the amount of air to be sucked, and an air flow sensor (not shown) capable of detecting the amount of air to be sucked is provided upstream thereof.

  The exhaust pipe 6 is provided with a three-way catalyst 14, an air-fuel ratio sensor 15 is provided on the upstream side, and an O 2 sensor 16 is provided on the downstream side.

  The accelerator pedal 21 is provided with an accelerator opening sensor 22 that detects the amount of depression of the driver.

  The gasoline filled in the gasoline tank 25 is pressurized to about 5 to 30 MPa by the high-pressure fuel pump 27 and sent to the gasoline fuel injection valve 100.

  The natural gas filled in the compressed natural gas (CNG) tank 28 at a pressure of about 20 MPa is decompressed to about 300 kPa by the regulator 29 and sent to the fuel injection valve 101 for natural gas.

  The ECU 120 temporarily stores a central processing unit (CPU) 30 that executes arithmetic processing according to a set program, a read-only memory (ROM) 31 that stores a control program and data necessary for the calculation, and a calculation result. A random access memory (RAM) 32, an input circuit 33 for receiving signals from each sensor, an output circuit 34 for transmitting signals to each device from the calculation results, and the like. The ECU 120 performs injection timings of the gasoline fuel injection valve 100 and the natural gas fuel injection valve 101 based on the detection values of the accelerator opening sensor 22, the coolant temperature sensor 20, the air-fuel ratio sensor 15, the O2 sensor 16, and the like. The injection period, the ignition timing of the spark plug 4, the opening degree of the throttle valve 23, etc. are determined, control signals are transmitted to these devices, and the engine is set to predetermined operating conditions.

  The gasoline fuel injection valve 100 is driven by a drive circuit 121. More specifically, an injection command value 123 is sent from the ECU 120 to the drive circuit 121, and the drive circuit 121 sets the gasoline fuel injection valve 100 at a timing and period corresponding to the injection command value 123, and the drive current that can be opened is gasoline. Output to the fuel injection valve 100.

  The natural gas fuel injection valve 101 is driven by a drive circuit 122. More specifically, an injection command value 124 is sent from the ECU 120 to the drive circuit 122, and the drive circuit 122 generates a drive current that can open the natural gas fuel injection valve 101 at a timing and period corresponding to the injection command value 124. It outputs to the fuel injection valve 101 for natural gas.

  Next, the operation mode of the spark ignition engine in the present embodiment will be described with reference to FIG.

  FIG. 2 is a diagram showing an operation map of the spark ignition engine in the present embodiment. When the engine speed and the engine torque are lower than a predetermined value, the engine is operated in a so-called lean burn mode in which the equivalence ratio of the in-cylinder mixture is smaller than 1. In other engine speed and engine torque regions, so-called stoichiometric combustion is performed with an equivalent ratio of in-cylinder air-fuel mixture of 1.

  In general, in a spark ignition engine, when the engine load is small, the fuel efficiency deteriorates due to the pump loss caused by the throttle valve throttle. However, as described above, the throttle opening is increased by operating the low load region in the lean burn mode. Pump loss can be reduced.

  Next, the fuel injection method for the spark ignition engine in this embodiment will be described with reference to FIG.

  FIG. 3 is a chart showing the fuel injection timing during the lean burn operation of the spark ignition engine in the present embodiment. FIG. 3 shows an example of four injection patterns from (a) to (d) in a constant load operation. In the present embodiment, natural gas or gasoline, or natural gas and gasoline are supplied from the respective fuel injection valves in the exhaust stroke to the intake stroke, and after the gasoline is injected from the gasoline fuel injection valve in the compression stroke, the ignition plug Ignition by is executed.

  Hereinafter, injection from the exhaust stroke to the intake stroke is defined as main combustion injection, and injection before ignition in the compression stroke is defined as ignition assist injection. The amount of ignition assist injection is, for example, about 10 to 20% with respect to the total amount of fuel injected in one stroke. As shown by the injection patterns (a) to (b), in the main combustion injection, various injection ratios of natural gas and gasoline are set. The injection ratio of the natural gas and gasoline is determined in advance according to the engine load or the like so that the fuel consumption and emission emission of the engine are minimized. Then, the injection timing and the injection period of the natural gas fuel injection valve and the gasoline fuel injection valve are controlled by the ECU so as to obtain an appropriate ratio.

  On the other hand, with respect to the ignition assist injection, as shown in FIG. 4, the ECU controls the gasoline fuel injection valve so that the ignition assist injection amount increases as the ratio of the gasoline injection amount in the main combustion injection increases. An injection period is set.

  The form of the in-cylinder air-fuel mixture at the ignition timing of this embodiment is shown in FIG. The main combustion mixture is formed in a wide range in the cylinder by the main combustion injection, and the ignition assist mixture is formed around the electrode of the spark plug 4 by the ignition assist injection. The ignition assist mixture is formed by mixing the fuel for ignition assist injection with the main combustion mixture. Accordingly, the equivalence ratio Φi of the ignition assist mixture is higher than the equivalent ratio Φm of the main combustion mixture. By igniting an air-fuel mixture with a high equivalence ratio around the spark plug, even when the main combustion air-fuel mixture is a fuel-lean mixture (Φm <1), rapid flame propagation is performed and stable combustion is performed. Can do.

  FIG. 6 shows the gasoline ratio of the ignition assist mixture (gasoline relative to all the fuel in the ignition assist mixture) relative to the gasoline ratio of the main combustion mixture (mass ratio of gasoline to the total fuel in the main combustion mixture). It is the figure which showed (mass ratio). The ignition assist air-fuel mixture is formed by adding about 10 to 20% of the total injection amount to the main combustion air-fuel mixture, so that the gasoline ratio is slightly higher than that of the main combustion air-fuel mixture. However, as shown in FIG. 6, the gasoline ratio of the ignition assist mixture increases monotonously with the increase in the gasoline ratio of the main combustion mixture.

  FIG. 7 shows the equivalence ratio dependency of the minimum ignition energy in the natural gas-air mixture and the gasoline-air mixture. The minimum ignition energy is a minimum amount of energy required for igniting the air-fuel mixture with, for example, a spark plug, and indicates that the smaller the minimum ignition energy, the easier the ignition. As shown in FIG. 7, the minimum ignition energy varies greatly depending on the equivalence ratio, and there exists an equivalence ratio (hereinafter referred to as an optimal equivalence ratio) that minimizes the minimum ignition energy. It is known that the optimal equivalent ratio Φg of gas fuel such as natural gas or propane is smaller than the optimal equivalent ratio Φl of liquid fuel such as gasoline or alcohol. For example, the optimum equivalent ratio of natural gas is 0.9, and the optimum equivalent ratio of gasoline is about 1.8.

  Therefore, in an air-fuel mixture in which gas fuel and liquid fuel are mixed, the optimum equivalence ratio increases from Φg toward Φl as the ratio of liquid fuel occupying the entire fuel increases as shown in FIG.

  In this embodiment, as shown in FIG. 4, the injection period of the gasoline fuel injection valve is set by the ECU so that the amount of ignition assist injection increases as the ratio of the gasoline injection amount in the main combustion injection increases. Is done. Accordingly, as shown in FIG. 19, the equivalent ratio around the spark plug increases as the gasoline ratio in the fuel in the ignition assist mixture increases.

  As described above, in the air-fuel mixture composed of gas fuel, liquid fuel, and air, the higher the liquid fuel ratio in the fuel, the higher the optimal equivalent ratio, that is, the equivalent ratio that is easy to ignite with spark ignition (FIG. 8). Therefore, by setting the injection period of the fuel injection valve for gasoline so that the amount of ignition assist injection increases as the ratio of the gasoline injection amount in the main combustion injection increases, the equivalent ratio that easily ignites around the spark plug is set. A mixture is formed, and the mixture can be easily ignited. Since the high-temperature initial flame ignited by the spark plug gives large thermal energy to the surrounding main combustion mixture, rapid flame propagation is performed even if the main combustion mixture is lean. As a result, highly stable lean burn operation can be performed. In addition, even when a large amount of EGR is introduced, by performing injection control in the same manner as described above, an air-fuel mixture with a concentration that easily ignites according to the ratio of liquid fuel to gas fuel is formed around the spark plug. High EGR operation can be performed. Since the lean burn and EGR combustion are stabilized, the lean limit and the EGR limit can be extended, so that fuel consumption and emission can be reduced.

  In the above embodiment, an example in which the equivalence ratio of the ignition assist mixture is controlled by changing the ignition assist injection amount has been shown, but the same effect can be obtained by changing the timing of the ignition assist injection. .

  FIG. 9 shows an embodiment in which the timing of ignition assist injection is changed. The configuration of the engine is the same as in the above embodiment. In the present embodiment, the timing of ignition assist injection is retarded as the ratio of the gasoline injection amount in the main combustion injection increases. By retarding the injection, the time from injection to ignition is shortened, so the dispersion of the fuel injected for ignition assist is reduced and the equivalence ratio of the ignition assist mixture is increased. As a result, an air-fuel mixture having a concentration that is easily ignited according to the ratio of liquid fuel and gas fuel is formed around the spark plug, and a highly stable lean burn operation and EGR operation can be performed.

  If the equivalence ratio of the ignition assist mixture is controlled by changing the injection timing in this manner, the amount of ignition assist injection becomes constant with respect to the change in the ratio of liquid fuel to gas fuel, and the engine is easily controlled. There is an advantage to become. In other words, when the amount of ignition assist injection changes, it is necessary to correct the injection amount for main combustion in consideration of the engine torque fluctuation due to the change in the injection amount. However, if the equivalence ratio of the ignition assist mixture is controlled at the injection timing, the ignition assist injection amount does not change, so it is not necessary to correct the main combustion injection amount.

  Furthermore, as shown in FIG. 10, both the injection amount and the injection timing of the ignition assist injection may be changed according to the ratio of the gasoline injection amount in the main combustion injection. For example, if the amount of ignition assist injection is large, fuel vaporization until ignition may be insufficient. Further, if the timing of ignition assist injection is late, fuel may adhere to the piston. These cause engine emissions and fuel consumption to deteriorate. However, as shown in FIG. 10, by controlling both the injection amount and the injection timing of the ignition assist injection, the amount of change in the injection amount and the injection timing can be suppressed to be small. This reduces the problem of fuel adhesion and suppresses engine emissions and deterioration of fuel consumption.

  In the embodiments shown so far, an example of an engine configuration in which natural gas is supplied by port injection and gasoline is supplied by in-cylinder direct injection has been shown, but the fuel supply method in the present invention is not limited to this. Absent.

  For example, as shown in FIG. 11, the fuel injection valve 100 for gasoline may be mounted to be a port injection type, and the fuel injection valve 101 for natural gas may be mounted to be a direct injection type in a cylinder. In the engine having such a configuration, the main combustion injection is performed by the fuel injection valve 100 for gasoline and the fuel injection valve 101 for natural gas, or both, and the ignition assist injection is the fuel injection for natural gas. Performed with valve 101. As a result, the natural gas injected for ignition assist and the main combustion air-fuel mixture are mixed, and a fuel-rich ignition assist air-fuel mixture is formed around the spark plug.

  When natural gas is supplied by direct in-cylinder injection, the gas fuel does not adhere to the wall surface of the combustion chamber, so that no soot and unburned hydrocarbons are discharged due to the fuel wall surface adhesion. In addition, by injecting gasoline from the port, the fuel injection pressure can be lowered to about 300 kPa, for example, so that a high-pressure fuel pump for pressurizing gasoline is not required, and fuel consumption deterioration due to pump drive loss is eliminated. There are advantages such as being cheap.

  In such an engine configuration, as in the above-described embodiment, as the ratio of the gasoline injection amount in the main combustion injection increases, the amount of ignition assist natural gas injection increases or the injection of natural gas for ignition assist increases. The fuel injection valve for natural gas is controlled so that the timing is delayed. As a result, an air-fuel mixture having a concentration that is easily ignited according to the ratio of liquid fuel and gas fuel is formed around the spark plug, and a highly stable lean burn operation and EGR operation can be performed.

  Furthermore, as shown in FIG. 12 or FIG. 13, both the fuel injection valve 100 for gasoline and the fuel injection valve 101 for natural gas may be mounted so as to be in-cylinder direct injection. In such a configuration, when the fuel for ignition assist is injected using the fuel injection valve closer to the spark plug 4, it is easy to create a fuel-rich mixture for ignition assist around the spark plug. For example, in the engine configuration shown in FIG. 12, it is preferable to inject fuel for ignition assist using the fuel injection valve 101 for natural gas. In the engine configuration shown in FIG. 13, it is preferable to inject fuel for ignition assist using the fuel injection valve 100 for gasoline.

  Thus, if both the gasoline fuel injection valve and the natural gas fuel injection valve are in-cylinder direct injection, it is possible to control the combustion state by changing the distribution of the air-fuel mixture in the cylinder in various ways.

  Further, as shown in FIGS. 14 and 15, both the fuel injection valve for gasoline and the fuel injection valve for natural gas may be port injection type. FIG. 14 is a plan view of an engine in which both a fuel injection valve for gasoline and a fuel injection valve for natural gas are configured as a port injection type, and FIG. 15 is a longitudinal sectional view of the engine. In the engine of this embodiment, a fuel injection valve 101 for natural gas is provided downstream of the intake port, and a fuel injection valve 100 for gasoline is provided upstream of the intake port. The two fuel injection valves are arranged in series in the axial direction of the intake port. Natural gas is injected in a single cone shape from the fuel injection valve 101 for natural gas. The injection direction of the fuel injection valve 101 for natural gas is determined so that the center of the cone is directed to the center of the engine cylinder. On the other hand, gasoline spray is injected from the gasoline fuel injection valve 100 in two separate cone shapes. The injection direction of the gasoline fuel injection valve 100 is determined so that the center of each cone-shaped spray is generally directed to the center of the intake valve 7. In an engine having such a fuel injection valve arrangement and injected fuel configuration, fuel injection control as shown in FIG. 16 is performed during lean burn operation. That is, in the exhaust stroke, the main combustion injection is performed by the natural gas fuel injection valve 101 or the gasoline fuel injection valve 100 or both. Subsequently, the ignition assist injection is performed by the natural gas fuel injection valve 101 in the intake stroke. Then, the air-fuel mixture is ignited by the spark plug at the latter stage of the compression stroke.

  The form of the in-cylinder mixture thus formed is shown in FIG. The gasoline and natural gas injected in the exhaust stroke are widely dispersed in the combustion chamber to form a main combustion air-fuel mixture. On the other hand, the natural gas injected in the intake stroke stays in the vicinity of the center cross section of the combustion chamber and mixes with the main combustion mixture near the center cross section of the combustion chamber to form an ignition assist mixture around the spark plug 4. Is done. The equivalence ratio Φi of the ignition assist mixture is higher than the equivalent ratio Φm of the main combustion mixture.

  The equivalence ratio of the ignition assist mixture can be increased by increasing the ignition assist injection amount. Further, if the injection timing for ignition assist is retarded within the intake stroke, dispersion of the natural gas injected for ignition assist in the combustion chamber can be suppressed, so that the equivalence ratio of the ignition assist mixture can be increased. it can. Therefore, in the present embodiment, as the ratio of the gasoline injection amount in the main combustion injection increases, the amount of ignition assist natural gas injection increases, or the timing of ignition assist natural gas injection delays. Control the fuel injection valve for natural gas. As a result, an air-fuel mixture having a concentration that is easily ignited according to the ratio of liquid fuel and gas fuel is formed around the spark plug, and a highly stable lean burn operation and EGR operation can be performed.

  14 and 15, the arrangement of the gasoline fuel injection valve 100 and the natural gas fuel injection valve may be interchanged. That is, as shown in FIG. 18, the same effect can be obtained even if the gasoline fuel injection valve 100 is arranged downstream of the intake port and the natural gas fuel injection valve 101 is arranged upstream of the intake port.

  By using both the fuel injection valve for gasoline and the fuel injection valve for natural gas as port injection, there is an advantage that a high-pressure fuel pump for pressurizing gasoline is not required, the cost is reduced, and fuel consumption loss due to the high-pressure pump is eliminated. In dual fuel, injection from one fuel injection valve may be stopped for a long period of time, so in the case of direct injection in a cylinder, the fuel injection valve may become hot and coking may occur due to deterioration of the fuel. However, this problem can be avoided by setting both fuel injection valves to port injection.

DESCRIPTION OF SYMBOLS 1 ... Cylinder head, 2 ... Engine block, 4 ... Spark plug, 5 ... Intake pipe, 6 ... Exhaust pipe, 7 ... Intake valve, 8 ... Exhaust valve, 10 ... Combustion chamber, 11 ... Intake port, 24 ... Throttle valve, DESCRIPTION OF SYMBOLS 25 ... Gasoline tank, 27 ... High pressure fuel pump, 28 ... CNG tank, 29 ... Regulator, 100 ... Fuel injection valve for gasoline, 101 ... Fuel injection valve for natural gas, 120 ... ECU, 121 ... Drive circuit for gasoline fuel injection valve 122 ... Natural gas fuel injection valve drive circuit

Claims (8)

  In an injection control device that performs injection control of a spark ignition engine including a first injector that injects liquid fuel and a second injector that injects gas fuel, the first injector or the second injector is used for ignition. The first injector or the second injector or the first injector and the second injector perform the main combustion injection prior to the ignition injection. An injection control device for a spark ignition engine, wherein the equivalence ratio around the spark plug is increased as the ratio of liquid fuel in the fuel by the main combustion injection increases.   2. The injection control device for a spark ignition engine according to claim 1, wherein the means for increasing the equivalence ratio around the spark plug increases the injection amount of the injection for ignition.   The injection control device for a spark ignition engine according to claim 1, wherein the means for increasing the equivalence ratio around the spark plug retards the injection timing of the ignition injection.   The spark according to claim 1, wherein the means for increasing the equivalence ratio around the spark plug increases the injection amount of the ignition injection and retards the injection timing of the ignition injection. Injection control device for ignition engine.   The first injector that injects liquid fuel is an in-cylinder direct injection type, the second injector that injects gas fuel is a port injection type, and the first injector performs injection for ignition. The injection control device for a spark ignition engine according to claim 1.   The first injector for injecting the gas fuel is an in-cylinder direct injection type, the second injector for injecting the liquid fuel is a port injection type, and the first injector performs injection for ignition. The injection control device for a spark ignition engine according to claim 1.   The first injector for injecting liquid fuel and the second injector for injecting gas fuel are both in-cylinder direct injection types, and injection for ignition is performed by an injector disposed near the spark plug among the injectors. The injection control device for a spark ignition engine according to any one of claims 1 to 4, wherein the injection control device is a spark ignition engine.   The first injector for injecting liquid fuel and the second injector for injecting gas fuel are both port injection types, and a plurality of sprays directed to an intake valve are injected from the first injector, and the second injector The injection control device for a spark ignition engine according to any one of claims 1 to 4, wherein a gas fuel directed toward the center of the combustion chamber is injected from the injector, and injection for ignition is performed by the second injector. .

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