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.

Description

INCORPORATION BY REFERENCE[0001]The disclosure of Japanese Patent Application No. 2017-026602 filed on Feb. 16, 2017 including the specification, drawings and abstract is incorporated herein by reference in its entirety.BACKGROUND1. Technical Field[0002]The present disclosure relates to a control device that stops the supply of fuel to an engine and ignition of the fuel to stop the operation of the engine, and particularly, to a spark discharge caused by an ignition plug for each cylinder.2. Description of Related Art[0003]Generally, a system (stop and start system), which automatically stops an engine of a vehicle during idling or the like and then automatically restarts the engine, is well-known in the related art. When the engine is stopped in the system as described above, normally, a throttle valve is closed, supply of fuel by an injector is stopped (fuel cut), and then, a spark discharge caused by an ignition plug is continued for a while, and the spark discharge caused by the...

AI Technical Summary

Benefits of technology

[0018]That is, even when the crankshaft is reversely operated after the start of the energization to the ignition coil resulting from the spark discharge caused by the ignition plug as described above and the energization cutoff timing is not reached, there is no case where the energization time becomes extremely long as described above. Therefore, the wasteful power consumption can be further suppressed, and the premature degradation of the ignition coil can be further restrained.

[0019]According to the control device of the aspect of the present disclosure as described above, when the operation of the engine is stopped, the spark discharge caused by the ignition plug is continued for a while even after the supply of the fuel is stopped. Accordingly, the unburned fuel within the cylinder can be combusted. In the first aspect of the present disclosure, when the rotation speed of the crankshaft decreases gradually and becomes equal to or lower than the threshold value, the spark discharge caused by the ignition plug is stopped. Accordingly, the wasteful power consumption can be further suppressed, and a situation in which the energization time to the ignition coil becomes extremely long can be further suppressed.

[0020]In the second aspect of the present disclosure, the energization start timing to the ignition coil is retarded as the rotation speed of the crankshaft decreases gradually as described above. Accordingly, the wasteful power consumption can be further suppressed, and a situation in which the energization time to the ignition coil becomes extremely long can also be further suppressed. In the third aspect of the present disclosure, the energization is cut off when the crankshaft is reversely operated. Accordingly, the energization time can be further restrained from becoming extremely long.

[0021]Therefore, by virtue of the first to third aspects of the present disclosure, the wasteful power consumption can be further suppressed without causing the aggravation of emissions when the engine is stopped, the premature degradation of the ignition coil resulting from the energization time becoming extremely long can be further restrained.

Problems solved by technology

However, in a case where the spark discharge caused by the ignition plug is continued for a while after a fuel cut as described above, the duration time of the spark discharge caused by the ignition plug becomes a problem.

That is, when the time for which the spark discharge caused by the ignition plug is continued is significantly shorter than usual, the unburned fuel within the cylinder cannot be sufficiently combusted and may be released into the ambient air.

Thus, there is a possibility that aggravation of emissions is caused.

On the other hand, continuing an unneeded spark discharge caused by the ignition plug until after unburned fuel is substantially exhausted leads to an increase in wasteful power consumption.

Energization time may become extremely long due to the reverse operation of a crankshaft immediately before the stop of the engine.

As a result, degradation of the ignition coil may be accelerated, and there is also a possibility that the service life of the ignition coil is shortened.

Thus, the crankshaft is not able to exceed a top dead center in a compression stroke of one of the cylinders.

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