PURPOSE: T perform simple regulation of the opening and closing motion characteristics of a check valve by means of regulating screw by providing an energizing mechanism to energize s valve body in an opening and closing direction and a regulating screw to regulate an energizing force.

CONSTITUTION: Since a regulating spring 25 energizes a valve body 20 in a direction in which a valve is opened, a synthetic force in a closing direction on a valve body exerted on a valve body by a return spring 21 and a regulating spring 25 produces a difference between the elastic forces of the two springs 25 and 21. Of course, a spring sufficiently stronger than the regulating spring 25 is used for the return spring 21. Through regulation of the axial position of the regulating spring by rotating the regulating spring 26 by means of a proper tool, a compression amount of the regulating spring 25 is changed, and an elastic force in a closing direction exerted on the valve body is regulatable. Through regulation of a force in a closing direction, the opening and closing characteristics of a check valve 17 are regulated. Taking the operation condition of an engine and the motion characteristics of the check valve of other cylinder into consideration, optimum opening and closing characteristics can be provided.