1. Field of Invention
This invention relates to a diesel engine, and in particular, a diesel engine in which a priming operation required at the time of restarting of the engine after a lack of fuel, etc., can be performed.
2. Description of the Related Art
In case that air mixes into a fuel passage of a diesel engine caused by a lack of fuel or an exchange of a fuel filter, etc., a priming operation is required to remove the mixed air from the fuel passage.
In a conventional diesel engine, a manual priming pump is provided between a fuel tank and a high-pressure pump (injection pump) which supplies the fuel in the fuel tank to an injector, and the priming operation can be done by an operator such as a driver manually operating the priming pump. This type of priming pump is disclosed in, for example, Japanese laid-open Patent Application No. 10-252599.
However, since the operator needs to manually operate the priming pump in such a conventional diesel engine, burden on the operator is much. For example, a certain type of the priming pump may need to be moved up and down hundreds of times in order to remove the mixed air completely from the fuel passage. Moreover, since the operator is required to judge by his sense that the mixed air is completely removed from the fuel passage, this also increases the operator's burden.
Another type of diesel engine which has been proposed is that an electric pump is provided between the fuel tank and the high-pressure pump, and this electric pump automatically supplies the fuel in the fuel tank to the high-pressure pump to remove the mixed air. This type of diesel engine is disclosed in, for example, Japanese Patent Publication No. 7-103836.
However, in this diesel engine, neither judgment as to the necessity for the priming operation (judgment as to whether the air is mixed in the fuel passage) nor judgment as to a timing to stop the electric pump (judgment as to whether the mixed air is removed from the fuel passage) can be done automatically, and thus the priming operation does not come to be completely automated.
This is explained in more detail. In the diesel engine disclosed in the above Japanese Patent Publication No. 7-103836, since the above judgment cannot be done automatically, the electric priming pump is periodically driven. Consequently, the electric priming pump is driven also when the priming operation is not required. This decreases efficiency. Furthermore, in this diesel engine, driving and stopping of the electric priming pump is switched when the operator turns a switch to ON or OFF. That is, the above judgment is put into the operator's hand, and therefore the operator's burden still exists.
Thus, even if the electric priming pump is provided, a present state is that the priming operation is not completely automated. In the meantime, in the diesel engine equipped with a common rail type fuel injection system adoption of which is rapidly promoted in recent years, electronic control (automation) for the whole of the control system is promoted and it is also strongly desired to completely automate the priming operation.