Homogeneous charge compressed ignition engine operating method
An aspect of the invention provides a method for operating a workable homogeneous charge compressed ignition engine in which a compression ignition operation is performed by spark ignition to shorten a load input time and a load cutoff time. In the homogeneous charge compressed ignition engine operating method, a mixture gas is burned by compression ignition in a combustion chamber, and fuel and air are previously mixed to produce the mixture gas. The homogeneous charge compressed ignition engine includes a spark ignition device 53 which performs spark ignition to the mixture gas. A temperature controller 35 substantially keeps an intake air temperature of the mixture gas constant. A spark ignition operation, a spark-assist compression ignition operation in which spark ignition is supplementarily used, and a non-spark compression ignition operation in which the spark ignition is not used are switched according to magnitude of a load.
1. A homogeneous charge compressed ignition engine operating method in which a mixture gas is burned by compression ignition in a combustion chamber, fuel and air being previously mixed to produce the mixture gas,
wherein the homogeneous charge compressed ignition engine includes a spark ignition device which performs spark ignition to the mixture gas,
a temperature controller substantially keeps an intake air temperature of the mixture gas constant, and
a spark ignition operation, a spark-assist compression ignition operation, and a non-spark compression ignition operation are switched according to magnitude of a load, spark ignition being supplementarily used in the spark-assist compression ignition operation, the spark ignition being not used in the non-spark compression ignition operation.
2. The homogeneous charge compressed ignition engine operating method according to claim 1 , wherein
in the spark-assist compression ignition operation,
target compression ignition timing is previously set,
a spark ignition timing map is previously provided, spark ignition timing at which the target compression ignition timing can be realized being recorded in the spark ignition timing map,
the spark ignition is performed at the spark ignition timing after engine starting when the load is not more than a predetermined value, the spark ignition timing being selected from an operating condition by referring to the spark ignition timing map, and
when the load is not lower than the predetermined value, the target compression ignition timing and actual compression ignition timing are compared to each other, and the spark ignition timing is adjusted based on the comparison such that the actual compression ignition timing is matched with the target compression ignition timing.
3. The homogeneous charge compressed ignition engine operating method according to claim 1 , wherein an air excess ratio is lowered to perform the spark ignition operation immediately after the engine is started from a cold state.
4. The homogeneous charge compressed ignition engine operating method according to claim 3 , wherein an engine speed is raised to a rated speed or more such that engine power becomes rating, immediately after the engine is started from the cold state.
5. The homogeneous charge compressed ignition engine operating method according to claim 1 , wherein throttle valve opening is adjusted to maintain an engine speed in performing the spark-assist compression ignition operation and the non-spark compression ignition operation, and
an air excess ratio is lowered according to the throttle valve opening when the throttle valve opening is not lower than a predetermined value.
6. The homogeneous charge compressed ignition engine operating method according to claim 1 , wherein a catalyst is provided in an exhaust passage of the engine in order to purify a hazardous component contained in exhaust gas, and
a mixture gas flow rate is decreased while an air excess ratio is lowered in order that an exhaust gas temperature is raised while an engine speed is maintained, when the engine is in a low load state, or when the exhaust gas temperature is lower than a predetermined value.