JP2004263663A - Starting operation method of premixed compression ignition engine and premixed compression ignition engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize technology of starting operation for keeping stable operating condition without remarkable lowering of equivalence ratio of mixture in a combustion chamber in transition to the premixed compression ignition operation after spark ignition operation of spark igniting the mixture in the combustion chamber in the starting operation of the premixed compression ignition engine adapted to perform self-ignition by compressing the mixture in the combustion chamber. <P>SOLUTION: After spark ignition operation is performed, the transition to increase exhaust gas recirculation quantity is performed to start the premixed compression ignition operation. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
According to the present invention, when starting the premixed compression ignition engine that compresses the air-fuel mixture in the combustion chamber and self-ignites, the operation proceeds to the premixed compression ignition operation after performing the spark ignition operation of spark-igniting the air-fuel mixture in the combustion chamber. Related to startup driving technology.
[0002]
[Prior art]
As an engine capable of realizing high efficiency and low NOx by highly compressing fuel in a lean state and performing self-ignition combustion, there is a homogeneous charge compression ignition engine that actively utilizes self-ignition of fuel.
Such a premixed compression ignition engine does not inject fuel into compressed air as in 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 raise the temperature up to the ignition point of the air-fuel mixture to perform self-ignition combustion. In addition, such a homogeneous charge compression ignition engine does not need to highly compress fuel and inject it into a combustion chamber unlike a diesel engine, so that it can be easily applied to a gas engine using a gaseous fuel such as natural gas. Can be.
[0003]
Further, in the premixed compression ignition engine, a so-called premixed compression ignition operation in which the mixture is compressed in the combustion chamber to raise the temperature to the ignition point and self-ignite is performed. During start-up, etc., which 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 a stable premixed compression ignition operation cannot be maintained due to the occurrence of misfire or the like. Sometimes.
[0004]
Therefore, in the starting operation of the homogeneous charge compression ignition engine, an ignition plug is provided in the combustion chamber in order to satisfactorily start and warm up the engine, and when the engine is not warmed up, the supercharging pressure of the supercharger is changed. While reducing the supercharging pressure by the mechanism, the mixture is supplied to the combustion chamber at an equivalence ratio capable of spark ignition, and a so-called spark ignition operation is performed in which the mixture is spark-ignited by a spark plug in the combustion chamber. After completion, the supercharging pressure may be increased or the heating of fresh air may be started to raise the temperature of the air-fuel mixture formed in the combustion chamber, and the operation may shift to the premixed compression ignition operation described above. (For example, refer to Patent Documents 1-3.)
By the way, the difference between the spark ignition operation and the homogeneous charge compression ignition operation is that in the former, it is necessary to lower the temperature of the air-fuel mixture formed in the combustion chamber in order to prevent knocking, whereas in the latter, self-ignition is required. In order to promote this, a high mixture temperature is required. However, if the temperature is too high even by compression ignition, premature ignition may occur, and operation may not be performed well. Further, the required equivalence ratio differs between the premixed compression ignition operation and the spark ignition operation.
[0005]
[Patent Document 1]
JP 2001-140681 A [Patent Document 2]
Japanese Patent Application Laid-Open No. 2001-271671 [Patent Document 3]
JP 2000-220484 A
[Problems to be solved by the invention]
However, in the above-described prior art, when performing the spark ignition operation, the equivalent ratio of the air-fuel mixture to be spark ignited in the combustion chamber needs to be within a spark ignitable range near the stoichiometric equivalent ratio. When performing the compression ignition operation, the equivalent ratio of the air-fuel mixture to be self-ignited needs to be within a lean range smaller than the spark ignition range in order to avoid knocking due to premature ignition. Therefore, when shifting from the spark ignition operation to the premixed compression ignition operation, the self-ignition of the air-fuel mixture is started in the combustion chamber, and at the same time, it is necessary to rapidly decrease the equivalent ratio. Since the ignition is not stable, the mixture may not self-ignite due to a sharp decrease in the equivalent ratio, and the operation may not be maintained.
Note that the equivalence ratio in the combustion chamber is obtained by dividing the stoichiometric air-fuel ratio by the air-fuel ratio of the air-fuel 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 homogeneous charge compression ignition operation after performing the spark ignition operation in the homogeneous charge compression ignition engine. An object of the present invention is to realize a startup operation technique that does not need to be performed and can maintain a stable operation state.
[0008]
[Means for Solving the Problems]
A starting operation method of a premixed compression ignition engine according to the present invention for achieving the above object is a premixed compression ignition engine configured to be capable of spark ignition of an air-fuel mixture in a combustion chamber and capable of adjusting an exhaust gas recirculation amount. During startup operation of
After performing the spark ignition operation of spark-igniting the air-fuel mixture in the combustion chamber, a transition operation for increasing the exhaust gas recirculation amount is performed, and the premix compression ignition operation in which the air-fuel mixture is compressed and self-ignited in the combustion chamber. Is characterized by the fact that
[0009]
Further, the starting operation method of the homogeneous charge compression ignition engine is configured to be executable, and the first characteristic configuration of the homogeneous charge compression ignition according to the present invention for achieving the above object is that a mixture can be spark-ignited in a combustion chamber. An ignition plug and exhaust gas recirculation amount adjusting means capable of adjusting the exhaust gas recirculation amount,
At the time of the start-up operation, after performing the spark ignition operation of spark-igniting the air-fuel mixture in the combustion chamber by operating the spark plug, a transition operation for increasing the exhaust gas recirculation amount by operating the recirculation amount adjusting unit is performed. And a control means for executing a start-up operation control for starting a premixed compression ignition operation for compressing the air-fuel mixture in the combustion chamber for self-ignition.
[0010]
In the premixed compression ignition engine, the present inventors recirculate exhaust gas to fresh air supplied to the combustion chamber, and increase the amount of exhaust gas recirculation to about 50% of the fresh air to achieve combustion. Even when the equivalence ratio of the air-fuel mixture in the combustion chamber is, for example, in the vicinity of a spark ignitable range, it has been found that combustion after self-ignition in the combustion chamber can be slowed to maintain stable operation avoiding knocking. The present invention has been completed by applying the technology to the starting operation of a homogeneous charge compression ignition engine.
[0011]
That is, according to the homogeneous charge compression ignition engine and the start-up operation method thereof according to the present invention, when the homogeneous charge compression ignition engine is started, the spark ignition operation is performed and then the transition to the homogeneous charge compression ignition operation is performed. There is no need to significantly reduce the equivalent ratio of the air-fuel mixture, and the operation can be shifted to the premix compression ignition operation while maintaining a stable operation state.
[0012]
More specifically, the control unit executes the spark ignition operation to warm up the engine, and executes the shift operation when it is determined that the warm-up is completed. Then, in the shift operation, the temperature of the air-fuel mixture formed in the combustion chamber is gradually increased, and while the self-ignition of the air-fuel mixture in the combustion chamber is induced, the amount of the exhaust gas recirculated to the combustion chamber is reduced. The combustion state of the air-fuel mixture in the combustion chamber gradually becomes slower as the air-fuel mixture temperature rises. Then, in the above transition operation, even if the equivalent ratio of the air-fuel mixture in the combustion chamber is near the spark ignitable range, it is possible to transition to the premix compression ignition operation while avoiding knocking and maintaining stable operation.
[0013]
A second characteristic configuration of the premixed compression ignition engine according to the present invention further includes, in addition to the first characteristic configuration, a configuration in the combustion chamber based on an ion current generation state between the electrodes of the spark plug in a spark ignition stopped state. A combustion state detecting means for detecting a combustion state,
In the shift operation, the control means sets the spark plug to a spark ignition stop state, detects the combustion state by the combustion state detection means, and shifts to the premix compression ignition operation based on the detected combustion state. The point is to determine completion.
[0014]
That is, according to the second characteristic configuration, by the combustion state detecting means, the spark plug provided in the combustion chamber is used as a so-called ion probe in a spark ignition stop state, and is applied between the electrodes of the ignition plug that gives a potential difference. The combustion state in the combustion chamber can be detected based on the generation state of the ion current generated by the arrival of the flame. The control means causes the homogeneous charge compression ignition engine to temporarily stop the spark plug in the transition operation after the spark ignition operation, and the self-ignition of the air-fuel mixture in the combustion chamber is stabilized by the combustion state detecting means. If it is detected that self-ignition is stable, it is determined that the transition to homogeneous charge compression ignition has been completed, and the transition to homogeneous charge compression ignition must be made immediately. On the contrary, if it is detected that the self-ignition is not stable, the ignition plug is again set to the spark ignition state, and the combustion of the air-fuel mixture can be maintained until the self-ignition is stabilized.
[0015]
A third characteristic configuration of the homogeneous charge compression ignition engine according to the present invention is the above-described first or second characteristic configuration, in which the exhaust gas recirculation amount adjusting means includes an advance amount with respect to a top dead center of an exhaust valve closing timing. By adjusting the amount of exhaust gas remaining in the combustion chamber by adjusting the amount of exhaust gas, the variable valve timing mechanism is capable of adjusting the amount of exhaust gas recirculation.
[0016]
That is, according to the third characteristic configuration, the closing timing of the exhaust valve in the exhaust stroke is set to a timing advanced from the top dead center (in other words, a timing earlier than the top dead center) by the variable valve timing mechanism. Then, part of the high temperature exhaust gas (combustion gas) of the combustion chamber remains in the combustion chamber without being discharged to the exhaust passage, and the remaining exhaust gas is supplied to the combustion chamber in the next air supply stroke. And so-called exhaust gas recirculation.
Therefore, by adjusting the amount of advance of the closing timing of the exhaust valve with respect to the top dead center by the variable valve timing mechanism, the amount of exhaust gas remaining in the combustion chamber can be adjusted, and the amount of exhaust gas recirculation can be adjusted. Thus, the variable valve timing mechanism can function as the exhaust gas recirculation amount adjusting means.
Further, the variable valve timing mechanism functions as 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 of the closing timing of the exhaust valve with respect to the top dead center is determined. Increasing the temperature of the air-fuel mixture formed in the combustion chamber at the same time by increasing the amount of high-temperature exhaust gas recirculated to the fresh air by gradually increasing it, thereby inducing self-ignition of the air-fuel mixture in the combustion chamber Can be.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of a homogeneous charge compression ignition engine according to the present invention will be described with reference to the drawings.
[0018]
In the homogeneous charge compression ignition engine 100 shown in FIG. 1, 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 passage 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 the exhaust valve 8.
[0019]
The piston 3 is swingably connected to the connecting rod 4, and the reciprocating motion of the piston 3 is obtained by the connecting rod 4 as a rotating motion of one crankshaft (not shown). There is no change.
[0020]
The air A (fresh air) flowing through the air supply passage 12 is appropriately supercharged by a supercharger or the like, and then passes through an aftercooler 15 described later, and the fuel G of the natural gas-based city gas is supplied to the mixer 18. As a result, the air-fuel mixture is 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 homogeneous charge compression ignition engine 100 is provided with an engine control unit (hereinafter, referred to as an ECU) 30 including a computer. The ECU 30 is configured to perform various controls such as start-up operation control of the homogeneous charge compression ignition engine. Have been.
[0023]
The aftercooler 15 provided in the air supply passage 12 exchanges heat with cooling medium that has cooled the cylinder 5 and the like and has a high temperature, or with a warm medium D such as a high-temperature exhaust gas discharged from the combustion chamber 2. The air A flowing through the air supply passage 12 can be heated.
Further, the heating medium amount adjusting valve 16 adjusts the supply amount of the heating medium D to the aftercooler 15 to adjust the temperature of the air A flowing through the air supply passage 12, and adjusts the air-fuel mixture formed in the combustion chamber 2. It functions as air-fuel mixture temperature adjusting means X capable of adjusting the temperature.
Then, the ECU 30 adjusts the supply amount of the warm medium D to the aftercooler 15 by the warm medium amount adjusting valve 16 based on the detection result of the temperature sensor 24 provided near the air supply valve 7 in the air supply passage 12. Thus, the temperature of the fresh air flowing through the air supply passage 12 is controlled to be a predetermined target temperature.
[0024]
The flow rate of the fuel G supplied to the mixer 18 can be adjusted by a fuel amount adjusting valve 19. The ECU 30 adjusts the supply amount of the fuel G based on the detection result of the oxygen sensor 25 provided in the exhaust passage 13 and capable of detecting the oxygen concentration of the exhaust gas, for example, so that the equivalent amount of the air-fuel mixture in the combustion chamber 2 is adjusted. The ratio is controlled so as to be a predetermined target equivalent ratio.
[0025]
An exhaust gas recirculation amount adjusting means Y connects the exhaust path 13 and the air supply path 12 to the homogeneous charge compression ignition engine 100, and an EGR flow path for recirculating exhaust gas in the exhaust path 13 to the air supply path 12. 21 and an EGR amount adjusting valve 22 for adjusting the recirculation amount of the exhaust gas. Then, the ECU 30 adjusts the opening degree of the EGR amount adjustment valve 22 based on, for example, the amount of fresh air taken into the combustion chamber 2 that can be recognized based on the number of revolutions of the crankshaft, and recirculates 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-igniting the air-fuel mixture supplied to the combustion chamber 2. The ECU 30 starts and stops ignition by the ignition plug 26, Control ignition timing.
[0027]
Further, the homogeneous charge compression ignition engine 100 is provided with a combustion state detecting means 27 for detecting a combustion state in the combustion chamber 2 based on a state of generation of an ion current between the electrodes of the spark plug 26 in which the spark ignition has been stopped. The ECU 30 temporarily stops the spark plug 26 in the spark ignition state, and can recognize whether or not the air-fuel mixture is stably self-ignited in the combustion chamber 2 based on the detection result of the combustion state detecting means 27.
[0028]
As described above, 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. For example, the compression ratio is about 21. Therefore, it is possible to achieve high efficiency because the fuel gas can be set at a high value, and it is possible to burn the mixture in a lean state with the equivalent ratio of the air-fuel mixture being equal to or lower than the flame propagation lower limit, for example, thereby realizing low NOx.
[0029]
However, when the premixed compression ignition engine 100 has not been sufficiently warmed up during the start-up operation, the temperature of the mixture cannot be sufficiently raised even if the air-fuel mixture is compressed in the combustion chamber 2. May not be able to change, or the air-fuel mixture may not self-ignite, and the premixed compression ignition operation may not be stably performed.
[0030]
Therefore, the ECU 30 of the premixed compression ignition engine 100 performs the spark ignition operation of spark-igniting the air-fuel mixture in the combustion chamber 2 by the ignition plug 26 in the above-described start-up operation. By performing the operation, it functions as the control means Z for executing the start-up operation method for starting the premix compression ignition operation for stably igniting the air-fuel mixture in the combustion chamber 2.
[0031]
Next, the details of the startup operation method of the homogeneous charge compression ignition engine 100 will be described with reference to FIG.
FIG. 2 is a diagram showing how the exhaust gas recirculation rate, the fresh air temperature, and the equivalence ratio change over time during the startup operation of the homogeneous charge compression ignition engine 100.
[0032]
The ECU 30 controls the EGR amount adjustment valve while operating the heating medium amount adjustment valve 16 to increase the temperature of fresh air supplied to the combustion chamber 2 as a transition operation from the spark ignition operation to the premix compression ignition operation. 22 is operated to execute a transition operation for increasing the amount of exhaust gas recirculation for fresh air.
[0033]
That is, during the start-up operation of the premixed compression ignition engine 100, the ECU 30 first operates the spark plug 26 to perform the spark ignition operation of spark-igniting the air-fuel mixture in the combustion chamber 2 so that the EGR amount adjustment valve 22 controls the exhaust gas. The recirculation amount is adjusted to set the exhaust gas recirculation rate to a predetermined exhaust gas recirculation rate Eb (%), and the supply amount of the warm medium to the aftercooler 15 is adjusted by the warm medium amount adjusting 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 adjusting valve 19, and the equivalent ratio of the air-fuel mixture supplied to the combustion chamber 2 is determined. Is set to the equivalent ratio φa. In the present embodiment, the exhaust gas recirculation rate Eb (%) set at the time of the spark ignition operation is set at or near 0, and the fresh air temperature Tc (° C.) supplies a heating medium to the aftercooler 15. The equivalent ratio φa is set to a relatively low value close to the atmospheric temperature when there is no temperature, and the equivalent ratio φa is set to 1 in which spark ignition is possible in the combustion chamber 2 or within a spark ignitable range in the vicinity thereof.
[0034]
Next, the ECU 30 performs 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 shift operation is performed.
In this transition operation, the exhaust gas recirculation rate of the homogeneous charge compression ignition engine 100 is gradually increased from Eb (%) to a predetermined Ea (%) (for example, 50%), and further, the fresh air temperature is raised to Tc (° C). )) To a predetermined Ta (° C.).
Then, during this transition operation, the fresh air temperature is gradually increased, and while the self-ignition of the air-fuel mixture in the combustion chamber 2 is induced, the recirculation rate of the exhaust gas to the combustion chamber 2 increases to the above-described fresh air temperature increase. The combustion state of the air-fuel mixture in the combustion chamber 2 is gradually increased. Therefore, in the above shifting operation, even if the equivalent ratio of the air-fuel mixture in the combustion chamber 2 is near the spark ignitable range where the fuel is relatively large, knocking can be avoided and stable operation can be maintained. In the transition operation, the ECU 30 sets the spark plug 26 to the spark ignition stop state for one or several cycles, and the air-fuel mixture stably self-ignites in the combustion chamber 2 based on the detection result of the combustion state detecting means 27 described above. When it is determined that the ignition operation is being performed, it can be determined that the above-described homogeneous charge compression ignition operation has started. The spark plug 26 may be completely stopped when it is determined that the premixed compression ignition operation has started. However, for example, after a lapse of a predetermined time after it is determined that the premixed compression ignition operation has started, You can keep working.
[0035]
Note that, in the transfer operation, the equivalence ratio in the combustion chamber 2 may be reduced from φa to φb as the exhaust gas recirculation rate increases.
[0036]
Further, the ECU 30 is configured to execute the following fresh air temperature lowering operation and equivalent ratio lowering operation after shifting to the premix compression ignition operation.
That is, the ECU 30 first performs a fresh air temperature lowering operation of lowering the fresh air temperature by a predetermined amount after reducing the exhaust gas recirculation rate until knocking is detected by the knocking sensor 31, for example. The process is repeated until the temperature reaches Tb (° C.). Further, the ECU 30 performs an equivalence ratio lowering operation of reducing the equivalence ratio by a predetermined amount after reducing the exhaust gas recirculation rate until knocking is detected by the knocking sensor 31, for example, the equivalence ratio becomes a predetermined equivalence ratio φc. Repeat until
By performing such a fresh air temperature lowering operation and an equivalent ratio lowering operation, self-ignition of a lean air-fuel mixture even when the fresh air temperature is relatively low while maintaining a stable operation state by avoiding a misfire or the like. , The premixed compression ignition operation can be performed, and further higher efficiency and lower 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 hot medium amount adjusting valve 16 of the aftercooler 15 as the air-fuel mixture temperature adjusting means X is provided. Although the temperature of the fresh air is adjusted by the above, the exhaust gas recirculation amount adjusting means Y and the air-fuel mixture temperature adjusting means X may be separately constituted by the variable valve timing mechanism 28.
That is, the variable valve timing mechanism 28 is configured to be able to adjust at least the opening / closing timing of the exhaust valve 8, and by adjusting the advance amount of the closing timing of the exhaust valve 8 with respect to the top dead center, the high temperature remaining in the combustion chamber 2 is adjusted. The exhaust gas amount can be adjusted to adjust the exhaust gas recirculation amount and the mixture temperature. Then, the ECU 30 gradually increases the amount of advance of the closing timing of the exhaust valve 8 with respect to the top dead center in the transition operation from the spark ignition operation of the homogeneous charge compression ignition engine 100 to the homogeneous charge compression ignition operation. Thus, the amount of exhaust gas recirculation can be easily increased while increasing the fresh air temperature.
[0039]
Further, by adjusting the air-fuel mixture temperature adjusting means X by adjusting the power of the supercharger or by adjusting the valve opening provided in the air supply passage 12 to adjust the compression end temperature of the fresh air, combustion is performed. The temperature of the air-fuel mixture formed in the chamber 2 may be adjusted.
[0040]
<2> In the above embodiment, an example was described in which the homogeneous charge compression ignition engine according to the present invention was configured as a single cylinder type. However, the present invention is also applied to a multi-cylinder homogeneous charge compression ignition engine. can do.
In the multi-cylinder homogeneous charge compression ignition engine, it is preferable that a part of the plurality of cylinders is sequentially shifted from the spark ignition operation to the homogeneous charge compression ignition operation through a shift operation. That is, at the time of the transition operation of some cylinders, until the operation state of the cylinder during the transition operation is stabilized by another cylinder that maintains a stable operation state after a predetermined time has elapsed before or after the transition. In addition, it is possible to smoothly shift all cylinders to the premix compression ignition operation while maintaining stable rotation of the crankshaft.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of a homogeneous charge compression ignition engine according to the present invention; FIG. 2 is a diagram showing a change tendency of various states during startup operation of the homogeneous charge compression ignition engine;
2: Combustion chamber 7: Air supply valve 8: Exhaust valve 12: Air supply path 13: Exhaust path 15: Aftercooler 16: Heat medium amount adjusting valve 18: Mixer 19: Fuel amount adjusting valve 21: EGR passage 22: EGR Amount adjusting valve 26: Spark plug 27: Combustion state detecting 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: Hot medium X: Air-fuel mixture temperature adjusting means Y: Exhaust gas recirculation amount adjusting means Z: Control means

Claims (4)

In the startup operation of the premixed compression ignition engine configured to be capable of spark ignition of the air-fuel mixture in the combustion chamber, and capable of adjusting the exhaust gas recirculation amount,
After performing a spark ignition operation of spark-igniting the air-fuel mixture in the combustion chamber, a transition operation for increasing the exhaust gas recirculation amount is performed, and a premix compression ignition operation in which the air-fuel mixture is compressed and self-ignited in the combustion chamber. To start the premixed compression ignition engine starting operation method. An ignition plug capable of spark ignition of the air-fuel mixture in the combustion chamber, and an exhaust gas recirculation amount adjusting means capable of adjusting an exhaust gas recirculation amount,
At the time of the start-up operation, after performing the spark ignition operation of spark-igniting the air-fuel mixture in the combustion chamber by operating the spark plug, a transition operation for increasing the exhaust gas recirculation amount by operating the recirculation amount adjusting unit is performed. A premixed compression ignition engine comprising control means for executing start-up operation control for starting a premixed compression ignition operation in which the air-fuel mixture is compressed and self-ignited in the combustion chamber. Combustion state detection means for detecting a combustion state in the combustion chamber based on a state of generation of an ion current between electrodes of the spark plug in a spark ignition stopped state,
In the shift operation, the control means sets the spark plug to a spark ignition stop state, detects the combustion state by the combustion state detection means, and shifts to the premix compression ignition operation based on the detected combustion state. The homogeneous charge 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 closing timing of the exhaust valve, so that the exhaust gas recirculation amount can be adjusted. The homogeneous charge compression ignition engine according to claim 2 or 3, wherein the engine is configured by a variable mechanism.

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