JP4225805B2 - Start-up operation method of premixed compression ignition engine and premixed compression ignition engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention shifts to a premixed compression ignition operation after performing a spark ignition operation in which a mixture is sparked in a combustion chamber when starting a premixed compression ignition engine that compresses and self-ignites the mixture in the combustion chamber. It relates to start-up operation technology.
[0002]
[Prior art]
There is a premixed compression ignition engine that actively uses self-ignition of fuel as an engine that can achieve high efficiency and low NOx by high-compression and self-ignition combustion of fuel in a lean state.
Such a premixed compression ignition engine does not inject fuel into compressed air like a diesel engine, but supplies a mixture of air and fuel to a combustion chamber like a spark ignition engine, and increases the mixture. It is configured to compress and elevate the temperature to the ignition point of the air-fuel mixture, and perform self-ignition combustion. Also, such a premixed compression ignition engine does not need to be highly compressed and injected into the combustion chamber like a diesel engine, so it can be easily applied to a gas engine using a gaseous fuel such as natural gas. Can do.
[0003]
Further, in the premixed compression ignition engine, so-called premixed compression ignition operation is performed in which the air-fuel mixture is compressed in the combustion chamber to raise the temperature to the ignition point and self-ignite, so that the temperature of the cylinder or the like is relatively low, At start-up that has not yet been warmed up, even if the air-fuel mixture is compressed, the temperature cannot be sufficiently raised to the ignition point, and stable premix compression ignition operation cannot be maintained due to the occurrence of misfire, etc. Sometimes.
[0004]
Therefore, in order to perform start-up and warm-up well in the start-up operation of the premixed compression ignition engine, an ignition plug is provided in the combustion chamber, and the supercharging pressure of the supercharger can be varied during the period when the engine is not warmed up. The mechanism lowers the supercharging pressure by the mechanism, supplies an air-fuel mixture with an equivalent ratio capable of spark ignition to the combustion chamber, performs a so-called spark ignition operation in which the air-fuel mixture is sparked by a spark plug in the combustion chamber, and the engine warm-up is performed. After completion, the supercharging pressure may be increased or heating of fresh air may be started to increase the temperature of the air-fuel mixture formed in the combustion chamber, and the premixed compression ignition operation described above may be entered. (For example, refer to Patent Documents 1-3.)
By the way, the difference between the spark ignition operation and the premixed compression ignition operation is that in the former, it is necessary to lower the temperature of the mixture formed in the combustion chamber in order to prevent knocking, whereas in the latter, self-ignition is performed. In order to promote, a high air-fuel mixture temperature is required. However, if the temperature is too high even by compression ignition, pre-ignition may occur and there may be cases where operation is not possible. Further, the required equivalence ratio is different between the premixed compression ignition operation and the spark ignition operation.
[0005]
[Patent Document 1]
Japanese Patent Laying-Open No. 2001-140681 [Patent Document 2]
JP 2001-271671 A [Patent Document 3]
Japanese Patent Laid-Open No. 2000-220484
[Problems to be solved by the invention]
However, in the above-described prior art, when performing spark ignition operation, it is necessary to set the equivalence ratio of the air-fuel mixture that is spark ignited in the combustion chamber to be within the spark ignitable range near the theoretical equivalence ratio. When performing the compression ignition operation, in order to avoid knocking due to premature ignition, it is necessary to set the equivalent ratio of the air-fuel mixture to be self-ignited within a lean range that is smaller than the spark ignition range. Therefore, when shifting from the spark ignition operation to the premixed compression ignition operation, it is necessary to rapidly reduce the equivalence ratio at the same time as the self-ignition of the air-fuel mixture is started in the combustion chamber. Since the ignition is not stable, the air-fuel mixture may not self-ignite due to a rapid decrease in the equivalence ratio, and the operation may not be maintained.
The equivalence ratio in the combustion chamber is the stoichiometric air-fuel ratio divided by the air-fuel ratio of the mixture formed in the combustion chamber. is there.
[0007]
Therefore, in view of the above circumstances, the present invention significantly reduces the equivalence ratio of the air-fuel mixture in the combustion chamber when shifting to the premixed compression ignition operation after performing the spark ignition operation in the premixed compression ignition engine. It is an object of the present invention to realize a start-up operation technique that can maintain a stable operation state.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a premixed compression ignition engine start-up operation method according to the present invention includes a premixed compression ignition engine configured to be capable of spark-igniting an air-fuel mixture in a combustion chamber and adjusting an exhaust gas recirculation amount. During start-up operation,
After performing a spark ignition operation for spark-igniting an air-fuel mixture in the combustion chamber, a premixed compression ignition operation for performing a transition operation to increase the exhaust gas recirculation amount and compressing the air-fuel mixture in the combustion chamber for self-ignition Spark ignition operation in a form in which the exhaust gas recirculation amount is reduced after the premix compression ignition operation is started and the equivalent ratio of the mixture is made higher than the equivalent ratio suitable for the premix compression ignition operation. It is characterized in that the equivalent ratio is less than the equivalent ratio suitable for the above, and the equivalent ratio suitable for the premixed compression ignition operation is lowered .
[0009]
In addition, the premixed compression ignition engine can be started and operated, and the first characteristic configuration of premixed compression ignition according to the present invention for achieving the above object is that the air-fuel mixture can be spark-ignited in the combustion chamber. A spark plug, an exhaust gas recirculation amount adjusting means capable of adjusting the exhaust gas recirculation amount, and a fuel amount adjusting valve capable of adjusting an equivalence ratio of the air-fuel mixture in the combustion chamber ,
In the start-up operation, after performing a spark ignition operation in which the spark plug is operated to spark-ignite the air-fuel mixture in the combustion chamber, a transition operation is performed to increase the exhaust gas recirculation amount by operating the exhaust gas recirculation amount adjusting means. And starting a premixed compression ignition operation in which the mixture is compressed and self-ignited in the combustion chamber, and after the premixed compression ignition operation is started , the exhaust gas recirculation amount adjusting means is operated to set the exhaust gas recirculation amount. e Bei control means for executing the activation operation control decreases to the fuel quantity adjusting valve, the equivalent ratio of the mixture in the form of higher than the equivalent ratio suitable for homogeneous charge compression ignition operation, suitable for spark ignition operation It is in the point which falls from the equivalent ratio below the equivalent ratio to the equivalent ratio suitable for premix compression ignition operation .
[0010]
In the premixed compression ignition engine, the inventors of the present invention recirculate exhaust gas to fresh air supplied to the combustion chamber, and increase the exhaust gas recirculation amount to about 50% with respect to fresh air. Even if the equivalence ratio of the air-fuel mixture in the chamber is, for example, in the vicinity of the spark ignitable range, it is found that the combustion after the self-ignition in the combustion chamber can be slowed down and stable operation avoiding knocking can be maintained, The present invention was completed by applying it to the start-up operation technology of a premixed compression ignition engine.
[0011]
That is, according to the premixed compression ignition engine and the startup operation method thereof according to the present invention, when the premixed compression ignition engine is started, the spark ignition operation is performed and then the premixed compression ignition operation is performed. It is not necessary to significantly reduce the equivalence ratio of the air-fuel mixture, and it is possible to shift to the premixed compression ignition operation while maintaining a stable operation state.
[0012]
Specifically, the control means first executes the spark ignition operation to warm up the engine, and executes the transition operation when it is determined that the warm-up is completed. In the transition operation, the temperature of the air-fuel mixture formed in the combustion chamber is gradually increased, and the recirculation amount of the exhaust gas recirculated to the combustion chamber is increased while inducing self-ignition of the air-fuel mixture in the combustion chamber. As the mixture temperature rises, the combustion state of the mixture in the combustion chamber gradually becomes slow. Then, in the transition operation, even if the equivalence ratio of the air-fuel mixture in the combustion chamber is in the vicinity of the spark ignition possible range, it is possible to shift to the premixed compression ignition operation while avoiding knocking and maintaining stable operation.
[0013]
The second characteristic configuration of the premixed compression ignition engine according to the present invention includes, in addition to the first characteristic configuration described above, in the combustion chamber based on an ion current generation state between the electrodes of the spark plug in a spark ignition stop state. Combustion state detection means for detecting the combustion state,
In the transition operation, the control means sets the spark plug in a spark ignition stop state, detects the combustion state by the combustion state detection means, and shifts to the premixed compression ignition operation based on the detected combustion state. The point is to determine completion.
[0014]
That is, according to the second feature configuration, the combustion state detecting means uses the spark plug provided in the combustion chamber as a so-called ion probe in a spark ignition stop state, and between the electrodes of the spark plug to which a potential difference is applied. The combustion state in the combustion chamber can be detected based on the generation state of the ionic current generated by the arrival of the flame. Then, by the control means, in the transition operation after the spark ignition operation of the premixed compression ignition engine, the spark plug is temporarily stopped in the spark ignition state, and the self-ignition of the air-fuel mixture in the combustion chamber is stabilized by the combustion state detection means. If it is detected that the self-ignition is stable, determine the completion of the transition to the premixed compression ignition operation, and immediately proceed to the premixed compression ignition operation. On the other hand, when it is detected that self-ignition is not stable, the ignition plug is again set to the spark ignition state, and combustion of the air-fuel mixture can be maintained until self-ignition is stabilized.
[0015]
The third characteristic configuration of the premixed compression ignition engine according to the present invention is that, in addition to the first or second characteristic configuration, the exhaust gas recirculation amount adjusting means is an advance amount with respect to the top dead center of the exhaust valve closing timing. By adjusting the amount of exhaust gas, the amount of exhaust gas remaining in the combustion chamber is adjusted, and the exhaust gas recirculation amount can be adjusted to constitute a variable valve timing mechanism.
[0016]
That is, according to the third feature configuration, the valve timing variable mechanism makes the exhaust valve closing timing in the exhaust stroke advanced from the top dead center (in other words, earlier than the top dead center). Thus, a part of the high-temperature exhaust gas (combustion gas) in the combustion chamber remains in the combustion chamber without being discharged into the exhaust passage, and the remaining exhaust gas is supplied to the combustion chamber in the next air supply stroke. So-called exhaust gas recirculation can be performed.
Therefore, by adjusting the advance amount with respect to the top dead center of the exhaust valve closing timing by the valve timing variable mechanism, the exhaust gas amount remaining in the combustion chamber can be adjusted to adjust the exhaust gas recirculation amount. In addition, the variable valve timing mechanism can function as exhaust gas recirculation amount adjusting means.
Further, the variable valve timing mechanism is made to function as an exhaust gas recirculation amount adjusting means, and in the transition operation after the spark ignition operation of the premixed compression ignition engine, the advance amount with respect to the top dead center of the exhaust valve closing timing is set. By gradually increasing the recirculation amount of high-temperature exhaust gas to fresh air, the temperature of the air-fuel mixture formed in the combustion chamber is increased at the same time, and self-ignition of the air-fuel mixture in the combustion chamber is induced. Can do.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a premixed compression ignition engine according to the present invention will be described based on the drawings.
[0018]
A premixed compression ignition engine 100 shown in FIG. 1 includes a combustion chamber 2 defined by an inner surface of a cylinder 5 and a top surface of a piston 3, and an air supply path connected to the combustion chamber 2 via an air supply valve 7. 12 and an exhaust passage 13 connected to the combustion chamber 2 via an exhaust valve 8 are provided.
[0019]
The piston 3 is swingably connected to the connecting rod 4, and the reciprocating motion of the piston 3 is obtained as a rotational movement of one crankshaft (not shown) by the connecting rod 4. There is no place to change.
[0020]
The air A (fresh air) flowing through the air supply path 12 is appropriately supercharged by a supercharger or the like, and then passes through an aftercooler 15 to be described later, and the fuel G of natural gas city gas is supplied to the mixer 18. As a result, the mixture is mixed and supplied to the combustion chamber 2.
[0021]
The premixed compression ignition engine 100 compresses the air-fuel mixture supplied to the combustion chamber 2 by raising the piston 3 and raises the temperature to the ignition point, so that the air-fuel mixture self-ignites and burns. The fuel is burned by performing the mixed compression ignition operation.
[0022]
The premixed compression ignition engine 100 is provided with an engine control unit (hereinafter referred to as ECU) 30 comprising a computer, and the ECU 30 is configured to perform various controls such as start-up operation control of the premixed compression ignition engine. Has been.
[0023]
The aftercooler 15 provided in the air supply path 12 is configured to perform heat exchange with a cooling medium that has become a high temperature by cooling the cylinder 5 or the like, or a hot medium D such as a high-temperature exhaust gas discharged from the combustion chamber 2. The air A flowing through the air supply path 12 is configured to be heatable.
Further, the temperature medium amount adjusting valve 16 adjusts the supply amount of the temperature medium D to the aftercooler 15 to adjust the temperature of the air A flowing through the air supply path 12, and the air-fuel mixture formed in the combustion chamber 2. It functions as a mixture temperature adjusting means X that can adjust the temperature.
Then, the ECU 30 adjusts the supply amount of the warm medium D to the after cooler 15 by the warm medium amount adjustment valve 16 based on the detection result of the temperature sensor 24 provided in the vicinity of the supply valve 7 of the supply passage 12. Thus, the temperature of the fresh air flowing through the air supply path 12 is controlled to be a predetermined target temperature.
[0024]
The fuel G supplied to the mixer 18 is configured so that the flow rate can be adjusted by a fuel amount adjustment valve 19. And ECU30 adjusts the supply amount of the fuel G based on the detection result of the oxygen sensor 25 which is provided in the exhaust passage 13 and can detect the oxygen concentration of exhaust gas, for example, and the equivalence of the air-fuel mixture in the combustion chamber 2 The ratio is controlled to be a predetermined target equivalent ratio.
[0025]
The premixed compression ignition engine 100 is connected to an exhaust passage 13 and an air supply passage 12 as exhaust gas recirculation amount adjusting means Y, and an EGR passage for recirculating exhaust gas in the exhaust passage 13 to the air supply passage 12. 21 and an EGR amount adjusting valve 22 for adjusting the recirculation amount of the exhaust gas are provided. Then, the ECU 30 adjusts the opening degree of the EGR amount adjustment valve 22 based on, for example, the amount of fresh intake air into the combustion chamber 2 that can be recognized by the rotation speed of the crankshaft, and the recirculation rate of the exhaust gas with respect to the fresh air. Is controlled to have a predetermined recirculation rate.
[0026]
Further, the premixed compression ignition engine 100 is provided with an ignition plug 26 capable of spark ignition of the air-fuel mixture supplied to the combustion chamber 2, and the ECU 30 starts and stops ignition by the ignition plug 26, and further, Control the ignition timing.
[0027]
Further, the premixed compression ignition engine 100 is provided with combustion state detection means 27 for detecting the combustion state in the combustion chamber 2 based on the generation state of ionic current between the electrodes of the spark plug 26 in the spark ignition stopped state. The ECU 30 is able to recognize whether or not the air-fuel mixture has been stably ignited in the combustion chamber 2 based on the detection result of the combustion state detecting means 27 once the spark plug 26 is in the spark ignition stopped state.
[0028]
Since the premixed compression ignition engine 100 performs the premixed compression ignition operation in which the air-fuel mixture is compressed and self-ignited in the combustion chamber 2 to burn the fuel G as described above, for example, the compression ratio is about 21. Therefore, low NOx can be realized because combustion can be performed in a lean state such that the equivalent ratio of the air-fuel mixture is lower than the flame propagation lower limit, for example.
[0029]
However, such a premixed compression ignition engine 100 cannot sufficiently raise the temperature even when the air-fuel mixture is compressed in the combustion chamber 2 when it is not sufficiently warmed up at the start-up operation. In some cases, it is impossible to perform the premixed compression ignition operation stably because the timing of the engine cannot be changed or the mixture cannot be self-ignited.
[0030]
Therefore, the ECU 30 of the premixed compression ignition engine 100 performs a spark ignition operation in which the air-fuel mixture is sparked by the spark plug 26 in the combustion chamber 2 during the start-up operation, and after the warm-up is completed, a predetermined transition is made. It functions as the control means Z that performs an operation and starts a premixed compression ignition operation that starts a premixed compression ignition operation that stably self-ignites the mixture in the combustion chamber 2.
[0031]
Next, the details of the startup operation method of the premixed compression ignition engine 100 will be described with reference to FIG.
FIG. 2 is a diagram illustrating a change state of the exhaust gas recirculation rate, the fresh air temperature, and the equivalence ratio with respect to time during the start-up operation of the premixed compression ignition engine 100.
[0032]
The ECU 30 operates the temperature medium amount adjustment valve 16 as a transition operation from the spark ignition operation to the premixed compression ignition operation to increase the fresh air temperature supplied to the combustion chamber 2 while increasing the EGR amount adjustment valve. 22 is operated to execute a transition operation to increase the amount of exhaust gas recirculation for fresh air.
[0033]
That is, when the premixed compression ignition engine 100 is started, the ECU 30 first performs the spark ignition operation in which the spark plug 26 is operated to sparkly ignite the air-fuel mixture in the combustion chamber 2. Adjusting the recirculation amount, setting the exhaust gas recirculation rate to a predetermined exhaust gas recirculation rate Eb (%), adjusting the supply amount of the warm medium to the aftercooler 15 by the warm medium amount adjustment valve 16, The fresh air temperature is set to a predetermined fresh air temperature Tc (° C.), the amount of fuel supplied to the mixer 18 is adjusted by the fuel amount adjustment valve 19, and the equivalence ratio of the air-fuel mixture supplied to the combustion chamber 2 is predetermined. Is set to the equivalent ratio φa. In the present embodiment, the exhaust gas recirculation rate Eb (%) set during the spark ignition operation is set to 0 or the vicinity thereof, and the fresh air temperature Tc (° C.) is supplied to the aftercooler 15 as a heating medium. It is set to a relatively low value close to the atmospheric temperature when there is not, and the equivalence ratio φa is set to 1 within the combustion chamber 2 where spark ignition is possible or within a spark ignition possible range.
[0034]
Next, the ECU 30 executes the spark ignition operation, for example, when the engine coolant temperature rises and reaches a predetermined temperature, or when the temperature of the cylinder 5 rises and reaches a predetermined temperature. Then, it is determined that the warm-up is completed, and the next transition operation is executed.
In this transition operation, the exhaust gas recirculation rate of the premixed compression ignition engine 100 is gradually increased from Eb (%) to a predetermined Ea (%) (for example, 50%), and the fresh air temperature is further increased to Tc (° C. ) To a predetermined Ta (° C.).
Then, during this transition operation, the fresh air temperature is gradually raised, and the self-ignition of the air-fuel mixture in the combustion chamber 2 is induced, while the recirculation rate of the exhaust gas to the combustion chamber 2 increases the fresh air temperature. In addition, the combustion state of the air-fuel mixture in the combustion chamber 2 is gradually reduced. Therefore, in the above transition operation, knocking can be avoided and stable operation can be maintained even if the equivalence ratio of the air-fuel mixture in the combustion chamber 2 is in the vicinity of the spark ignition possible range where the fuel is relatively high. In the transition operation, the ECU 30 sets the ignition plug 26 to the spark ignition stopped state for one or several cycles, and the air-fuel mixture is stably ignited in the combustion chamber 2 according to the detection result of the combustion state detecting means 27 described above. When it is determined that the premixed compression ignition operation has been started, it can be determined that the premixed compression ignition operation has started. The spark plug 26 may stop completely when it is determined that the premixed compression ignition operation has started, but for example, a certain time has elapsed after it is determined that the premixed compression ignition operation has started. It doesn't matter if you keep working.
[0035]
In the transition operation, the equivalence ratio in the combustion chamber 2 may be decreased from φa to φb as the exhaust gas recirculation rate increases.
[0036]
The ECU 30 is configured to execute the following fresh air temperature lowering operation and equivalent ratio lowering operation after shifting to the premixed compression ignition operation.
That is, the ECU 30 first performs an operation of lowering the exhaust gas recirculation rate until knocking is detected by the knocking sensor 31 and then reducing the fresh air temperature by a predetermined amount. The process is repeated until the temperature reaches Tb (° C.). Further, the ECU 30 lowers the exhaust gas recirculation rate until knocking is detected by the knocking sensor 31, and then performs an equivalent ratio lowering operation in which the equivalent ratio is decreased by a predetermined amount, for example, the equivalent ratio becomes the predetermined equivalent ratio φc. Repeat until
By performing such a fresh air temperature lowering operation and an equivalent ratio lowering operation, it is possible to self-ignite a lean air-fuel mixture even if the fresh air temperature is relatively low while maintaining a stable operating state by avoiding misfires and the like. Premixed compression ignition operation that can be performed can be executed, and further high efficiency and low NOx can be achieved.
[0037]
[Another embodiment]
Next, another embodiment of the present invention will be described with reference to the drawings.
[0038]
<1> In the above embodiment, the EGR flow path 21 and the EGR amount adjusting valve 22 as the exhaust gas recirculation amount adjusting means Y are provided, and the heating medium amount adjusting valve 16 of the aftercooler 15 as the mixture temperature adjusting means X. However, the exhaust gas recirculation amount adjusting means Y and the mixture temperature adjusting means X may be configured by the valve timing variable mechanism 28.
That is, the variable valve timing mechanism 28 is configured to be capable of adjusting at least the opening / closing timing of the exhaust valve 8, and by adjusting the advance amount with respect to the top dead center of the closing timing of the exhaust valve 8, the high temperature remaining in the combustion chamber 2 can be adjusted. The exhaust gas amount can be adjusted, and the exhaust gas recirculation amount and the mixture temperature can be adjusted. The ECU 30 gradually increases the advance amount with respect to the top dead center of the exhaust valve 8 when the premixed compression ignition engine 100 is shifted from the spark ignition operation to the premixed compression ignition operation. Thus, the exhaust gas recirculation amount can be easily increased while raising the fresh air temperature.
[0039]
Further, the air-fuel mixture temperature adjusting means X adjusts the power of the supercharger or the valve opening degree provided in the air supply passage 12 to adjust the compression end temperature of the fresh air, thereby You may comprise so that the temperature of the air-fuel mixture formed in the chamber 2 may be adjusted.
[0040]
<2> In the above embodiment, an example in which the premixed compression ignition engine according to the present invention is configured as a single cylinder type has been described. However, the present invention is also applied to a multicylinder type premixed compression ignition engine. can do.
Further, in the multi-cylinder type premixed compression ignition engine, it is preferable that a part of each of the plurality of cylinders is sequentially shifted from the spark ignition operation to the premixed compression ignition operation through a transition operation. In other words, during the transition operation of some cylinders, until the operation state of the cylinder during the transition operation is stabilized by another cylinder that has maintained a stable operation state before the transition or after a certain time has elapsed since the transition. The crankshaft rotation can be kept stable, and all the cylinders can be smoothly shifted to the premixed compression ignition operation.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of a premixed compression ignition engine according to the present invention. FIG. 2 is a diagram showing changes in various states during start-up operation of the premixed compression ignition engine.
2: Combustion chamber 7: Supply valve 8: Exhaust valve 12: Supply passage 13: Exhaust passage 15: After cooler 16: Heat medium amount adjustment valve 18: Mixer 19: Fuel amount adjustment valve 21: EGR passage 22: EGR Amount adjustment valve 26: Spark plug 27: Combustion state detection means 28: Variable valve timing mechanism 30: Engine control unit (ECU)
100: Premixed compression ignition engine A: Air (fresh air)
G: Fuel E: Exhaust gas H: Temperature medium X: Mixture temperature adjusting means Y: Exhaust gas recirculation amount adjusting means Z: Control means

Claims (4)

During start-up operation of a premixed compression ignition engine configured to be able to spark-ignite the air-fuel mixture in the combustion chamber and to adjust the exhaust gas recirculation amount,
After performing a spark ignition operation for spark-igniting an air-fuel mixture in the combustion chamber, a premixed compression ignition operation for performing a transition operation to increase the exhaust gas recirculation amount and compressing the air-fuel mixture in the combustion chamber for self-ignition the start,
While reducing the exhaust gas recirculation amount after the start of the premixed compression ignition operation,
The equivalent ratio of the air-fuel mixture is made higher than the equivalent ratio suitable for the premixed compression ignition operation, and the equivalent ratio less than the equivalent ratio suitable for the spark ignition operation is lowered to the equivalent ratio suitable for the premixed compression ignition operation. A starting operation method of a premixed compression ignition engine. An ignition plug capable of spark-igniting the air-fuel mixture in the combustion chamber, an exhaust gas recirculation amount adjusting means capable of adjusting the exhaust gas recirculation amount, and a fuel amount adjusting valve capable of adjusting the equivalence ratio of the air-fuel mixture in the combustion chamber ;
In the start-up operation, after performing a spark ignition operation in which the spark plug is operated to spark-ignite the air-fuel mixture in the combustion chamber, a transition operation is performed to increase the exhaust gas recirculation amount by operating the exhaust gas recirculation amount adjusting means. Performing a premixed compression ignition operation in which the air-fuel mixture is compressed and self-ignited in the combustion chamber ,
E Bei control means for executing the activation operation control by exercising the exhaust gas recirculation amount adjusting means after the start of the premixed compression ignition operation to decrease the exhaust gas recirculation amount,
The fuel amount adjusting valve is configured to change the equivalence ratio of the air-fuel mixture to be higher than the equivalence ratio suitable for the premixed compression ignition operation, and from the equivalent ratio suitable for the spark ignition operation to the premixed compression ignition operation. A premixed compression ignition engine that drops to a suitable equivalence ratio . Combustion state detection means for detecting the combustion state in the combustion chamber based on the state of generation of ionic current between the electrodes of the spark plug in the spark ignition stop state,
In the transition operation, the control means sets the spark plug in a spark ignition stop state, detects the combustion state by the combustion state detection means, and shifts to the premixed compression ignition operation based on the detected combustion state. The premixed compression ignition engine according to claim 2, wherein completion is determined.   The exhaust gas recirculation amount adjusting means adjusts the amount of exhaust gas remaining in the combustion chamber by adjusting the advance amount with respect to the top dead center of the exhaust valve closing timing, so that the exhaust gas recirculation amount can be adjusted. The premixed compression ignition engine according to claim 2 or 3, wherein the premixed compression ignition engine is constituted by a variable mechanism.

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