PURPOSE: To prevent starting malfunction of an engine on account of freezing of a valve and so on, by opening a closing valve in case of low temperature starting of the engine, which carries out an adiabatically compressing air intake by means of a valve to be quickly released in case of prescribed negative pressure inside of an intake pipe due to be provided at a downstream portion of an intake passage having the closing valve.
CONSTITUTION: An intake passage (b) which takes in air through a valve 10 is opened at a downstream portion of an intake passage 6a having a closing valve 7. In case that the closing valve 7 is closed, and when negative pressure of the intake air caused by a descent of a piston2 exceeds a prescribed value, the valve 10 is quickly released to take in air so that charging efficiency is enhanced by its adiabatic compression. When an engine is going to start under cold condition, the valve 10 can't sometimes work on account of freezing, and air intake can't be carried out. Therefore, a control circuit 25 releases the closing valve 7 in such a situation.
KASHIMOTO MASAAKI
SAKURAI SHIGERU
