Patent ID: 7581711

Claim:
An electromagnetic fuel injection valve comprising: a valve housing ( 8 ) comprising a valve seat member ( 10 ) having a valve seat ( 13 ) and a cylindrical magnetic body ( 9 ) having a front end thereof coaxially connected to the valve seat member ( 10 ); a valve assembly ( 17 ) comprising a valve body ( 20 ) housed in the valve housing ( 8 ) so that the valve body ( 20 ) can be seated on the valve seat ( 13 ) and a movable core ( 18 ) coaxially connected to the valve body ( 20 ) with a rear end face of the movable core ( 18 ) as a movable side attracting face ( 41 ), the valve assembly ( 17 ) being spring-biased in a direction that seats the valve body ( 20 ) on the valve seat ( 13 ); a cylindrical non-magnetic body ( 26 ) having the front end thereof coaxially joined to the rear end of the cylindrical magnetic body ( 9 ) so as to surround a part of the movable core ( 18 ); and a fixed core ( 22 ) having at a front end thereof a fixed side attracting face ( 42 ) facing the movable side attracting face ( 41 ) and having a front portion thereof fitted into and fixed to a rear portion of the cylindrical non-magnetic body ( 26 ); characterized in that the movable core ( 18 ) comprises a tubular sliding portion ( 18 a ) having an outer peripheral face that is in sliding contact with an inner peripheral face of a rear portion of the cylindrical magnetic body ( 9 ) over a predetermined length along the axis of the cylindrical magnetic body ( 9 ), a rear tubular opposing portion ( 18 b ) that has the movable side attracting face ( 41 ) at a rear end thereof, is connected coaxially and integrally to the rear end of the tubular sliding portion ( 18 a ), and has the outer periphery thereof facing the inner periphery of the cylindrical magnetic body ( 9 ), and a front tubular opposing portion ( 18 c ) that has the outer periphery thereof facing the inner periphery of the cylindrical magnetic body ( 9 ) and is connected coaxially and integrally to the front end of the tubular sliding portion ( 18 a ), and when the diameter of the rear tubular opposing portion ( 18 b ) is D 1 , the diameter of the front tubular opposing portion ( 18 c ) is D 2 , and the diameter of the tubular sliding portion ( 18 a ) is D 3 , they are set so that D 1 <D 2 <D 3 .