Electromagnetic solenoid for oil hydraulic control valves

Claim 1

An electromagnetic solenoid for oil hydraulic control valves comprising: an electromagnetic coil wound around a bobbin; a case for accommodating said electromagnetic coil, said case being made of a magnetic material; a cylindrical fixed iron core secured to a front portion of said case; a sleeve bearing being secured to an inside diameter portion on the front end side of said case and having an axially extending oil flow notch member at an outside diameter portion thereof; a magnetic path iron core being coupled with the rear end side of said case; an operating rod passing through an inside diameter portion of said fixed iron core with a gap, a front end portion of said operating rod extruding while supported by said sleeve bearing so as to be movable in an axial direction of said electromagnetic solenoid, an outside diameter portion on the rear end side of said operating rod having an axially extending oil flow notch member; a hollow movable iron core including a first inside diameter portion on the rear end side of which being secured to said outside diameter portion of said operating rod and a second inside diameter portion on the front end side of said movable iron core, said second inside diameter portion being formed so as to have an oil flow gap with respect to said outside diameter portion of said operating rod; a magnetic sleeve bearing secured to the inside diameter of said magnetic path iron core to support said hollow movable iron core; and a nonmagnetic stopper washer passing through said operating rod and inserted into an axially extending air gap formed between said fixed iron core and said movable iron core, said nonmagnetic stopper washer having an oil flow notch for allowing oil to flow in an axial direction of said electromagnetic solenoid.