Normally closed solenoid valve includes a fixed core, a valve portion including a valve seat and a valve body, a movable core disposed between the fixed core and the valve seat, a resilient biasing member for biasing the movable core in a valve-closing direction and a coil.

When energized, the coil generates an attracting force between the movable core and the fixed core against a biasing force by the resilient biasing member to cause the movable core to retreat from an initial position where the valve seat is in a closed state. When a characteristic graph line of spacing distance/attracting force that defines the attracting force in relation with a spacing distance between the fixed core and the movable core provides an inclination A (N/mm) at the initial position, the compression resiliency coefficient of the resilient biasing member is set to A (N/mm).

Conventionally, there are two types of solenoid valves for opening and closing a flow path of a hydraulic fluid, one of which is a normally closed solenoid valve that is normally closed and is opened by excitation of a fixed core and a movablecore when a current is rendered to flow into a coil, and the other of which is a normally open valve that is normally opened and is closed by excitation of a fixed core and a movable core when a current is rendered to flow into a coil.

Such a normallyclosed solenoid valve is provided with a valve seat for opening and forming a flow path of a hydraulic fluid and a valve body formed at the tip end of a movable core capable of being brought into contact with the valve seat and moving away therefrom. Ina demagnetized state, the movable core is seated on the valve body by a spring force of a spring member secured between the movable core and fixed core and is pressed into the direction of closing the valve. In a magnetized state where a current isrendered to flow into a coil, an attracting force works between the fixed core and movable core, and when the attracting force exceeds the spring force of the spring member, the valve body is separated from the valve seat, wherein the flow path of ahydraulic fluid can be opened.