Engine control device

Abstract

An engine control device includes an electronic control unit. The electronic control unit is configured to perform a spark discharge with an ignition plug for each cylinder by cutting off energization after elapse of a predetermined period from start of energization to an ignition coil for each cylinder of the engine, to stop the spark discharge caused by the ignition plug for each cylinder after supply of fuel to the engine is stopped when operation of the engine is stopped, and to control an ignition plug so as to stop the spark discharge caused by the ignition plug from a cylinder after a rotation speed of a crankshaft decreases gradually and the rotation speed of the crankshaft reaches a preset threshold value or less, after the stop of the supply of fuel to the engine.

What is claimed is: 
     
         1 . An engine control device comprising an electronic control unit configured to
 perform a spark discharge with an ignition plug for each cylinder by cutting off energization after elapse of a predetermined period from start of energization to an ignition coil for each cylinder of the engine,   stop the spark discharge caused by the ignition plug for each cylinder after supply of fuel to the engine is stopped when operation of the engine is stopped, and   control the ignition plug so as to stop the spark discharge caused by the ignition plug from a cylinder after a rotation speed of a crankshaft decreases gradually and the rotation speed of the crankshaft reaches a preset threshold value or less, after the stop of the supply of fuel to the engine.   
     
     
         2 . The engine control device according to  claim 1 , wherein the threshold value is set to such a rotation speed that the crankshaft is reversely operated in accordance with a compression reaction force of the cylinder when the rotation speed of the crankshaft becomes lower than the threshold value. 
     
     
         3 . An engine control device comprising an electronic control unit configured to
 perform a spark discharge with an ignition plug for each cylinder by cutting off energization after elapse of a predetermined period from start of energization to the ignition coil for each cylinder of the engine,   stop the spark discharge caused by the ignition plug for each cylinder of the engine after supply of fuel to the engine is stopped when operation of the engine is stopped, and   retard an energization start timing to the ignition coil as a rotation speed of a crankshaft becomes lower when the rotation speed of the crankshaft decreases gradually after the stop of the supply of fuel to the engine.   
     
     
         4 . The engine control device according to  claim 3 , wherein the electronic control unit is configured to retard the energization start timing to the ignition coil until after a compression top dead center of a cylinder when the rotation speed of the crankshaft becomes equal to or lower than a preset threshold value. 
     
     
         5 . An engine control device comprising an electronic control unit configured to
 perform a spark discharge with an ignition plug for each cylinder by cutting off energization after elapse of a predetermined period from start of energization to an ignition coil for each cylinder of the engine,   stop the spark discharge caused by the ignition plug for each cylinder of the engine after supply of fuel to the engine is stopped when operation of the engine is stopped, and   cut off the energization to the ignition coil even before the elapse of the predetermined period in a case where a crankshaft is reversely operated after the start of energization to the ignition coil.