Solenoid valve having a hollow cap mounted on a leading end of a movable iron core

A solenoid valve constructed by arranging, along a valve axis, a fixed iron core and a movable iron core assembly that adhere to each other by a magnetic force generated by energizing an exciting coil, a valve seat formed in a flow path, a valve member for opening and closing the flow path by detaching from and attaching to the valve seat with an action of the movable iron core assembly, and a transmission member for transmitting an acting force of the movable iron core assembly to the valve member,

• the movable iron core assembly comprising a movable iron core that adheres to the fixed iron core, a hollow cap mounted on a leading end of the movable iron core such that a forward movement thereof relative to the movable iron core is restricted, and a pressing member that fits into an interior of the cap so as to be displaceable between a position at which it abuts on the cap and a position at which it abuts on the movable iron core and operate so as to press the valve member against the valve seat via the transmission member,
• the movable iron core having a flange portion at an outer circumference of a leading end thereof for locking,
• the cap having an iron core fitting bore into which the movable iron core fits, an iron core locking portion at which the flange portion of the movable iron core is locked, a pressing member housing in which the pressing member is housed, and abutting seat surfaces formed on the pressure member housing on which the pressing member abuts, in an interior thereof, and a spring seat for the iron core return spring, at an outer circumference of a leading end thereof, and the cap being biased by an iron core return spring in a direction in which the movable iron core detaches from the fixed iron core,
• the pressing member being disk-shaped and having abutting shoulders for abutting on the abutting seat surface,
• the movable iron core and the pressing member being biased by a cushioning spring provided therebetween in directions in which the movable iron core and the pressing member detach from each other, the valve member being biased by a valve return spring in a direction in which it detaches from the valve seat, biasing forces F1 F2, and F3 of the iron return spring, the cushioning spring, and the valve return spring being related to each other so as to be F1>F2>F3,
• and the solenoid valve being constructed such that when the movable iron core assembly occupies an initial position by a biasing force of the iron core return spring and the pressing member presses the valve member against the valve seat via the transmission member while the exciting coil is not energized, gaps x and y exist between the pressing member and the movable iron core and between the pressing member and the cap, respectively.