Solenoid valve

A solenoid valve comprising;

• a valve sleeve of cylindrical shape having an inner passage continuing in an axial direction,
• a spool arranged in a movable manner along said axial direction in said inner passage of said valve sleeve,
• a center post of cylindrical shape having a through hole connected with said inner passage of said valve sleeve and constituted from a magnetic material magnetized by a coil,
• a plunger constituted from a magnetic material and arranged in a movable manner along said axial direction against said center post by placing said center post between said spool and said plunger in said axial direction due to the magnetic force generated by the coil,
• a shaft constituted from a non-magnetic material comprising an axis part and a collar part, said axis part having one end face being contacted with said spool and other end face fixedly attached to a plunger front end face of said plunger and moving in said axial direction inside said through hole of said center post, and said collar part protruding out in a radial direction from said axis part so as to be formed as one body with said axis part and sandwiched between said plunger front end face and a step face opposing to said plunger front end face in said center post when said plunger closely approaches said center post, and
• a case part having said coil generating a magnetic force transferring to said center post and housing said center post, said plunger and said shaft in inside, wherein
• an outer diameter of said step face is almost same as or slightly larger than an outer diameter of said plunger front end face,
• a maximum diameter of said collar part is larger than an opening diameter of said through hole on said step face of said center post,
• said axis part including a first larger diameter portion having a first cross section outer peripheral shape, a second larger diameter portion having a second cross section outer peripheral shape, and a smaller diameter portion;
• said first cross section outer peripheral shape having a first plurality of arc shaped portions arranged symmetrically against a center of said axis part, and a first plurality of notch portions connecting said first plurality of arc shaped portions,
• said second cross section outer peripheral shape having a second plurality of arc shaped portions arranged symmetrically against said center of said axis part, and a second plurality of notch portions connecting said second plurality of arc shaped portions,
• said smaller diameter portion extending from and between the first and second larger diameter portions in said axial direction and having a maximum diameter smaller than a maximum outer diameter of said first and second larger diameter portions in a cross section shape,
• said collar part connected to said first plurality of arc shaped portions.