Fuel injector and fuel injection device using the same

A fuel injector comprising:

• a coil generating a magnetic flux when being energized;
• a stator core generating a part of a magnetic circuit as a passage of the magnetic flux, the stator core generating an electromagnetic force;
• a movable core moved by the electromagnetic force;
• a valve body moved together with the movable core, the valve body opening an injection port;
• and
• an elastic-force applying portion being elastically deformable according to a movement of the valve body to apply an elastic force to the valve body in a valve-closing direction, wherein
• an elastic coefficient of the elastic-force applying portion is set to meet a condition that a value of (Ffx+Lx×K) is continuously increased during a time period from a time point that the movement distance becomes Lx to a time point that the movement distance becomes L, wherein among fuel-pressure valve-closing forces applied to the valve body in the valve-closing direction by a fuel pressure, the fuel-pressure valve-closing force of when the valve body is moved to a predetermined position is referred to as Ffx, the movement distance of the valve body from a time point that the valve body is closed to a time point that the valve body is moved to the predetermined position is referred to as Lx, a movement distance of the valve body from the time point that the valve body is closed to a time point that the valve body is completely opened is referred to as L, and the elastic coefficient is referred to as K.