Abstract: In a fuel injector (1) configured so that fuel injection is controlled by a solenoid valve (4), the solenoid valve (4) comprises an electromagnet (43), an armature bolt (41) that has a ball (42) and a plate member (41A) attached thereto and is spring-biased in the valve closing direction by a spring member (48), a stopper member (49) that limits movement of the plate member (41A) in order to limit the maximum stroke of the ball (42) and an armature plate (44) through which the armature bolt (41) passes and which collaborates with the solenoid valve (4), the contact area (S2) between the armature plate (44) and the plate member (41A) being made larger than the contact area (S1) between the plate member (41A) and the stopper member (49).

Abstract: A planetary gear 5 is contacted at its at least one tooth of all its teeth 51n with an end edge 23d facing an inner releasing part 23c of an inner peripheral surface of a receiving hole 23a irrespective of a rotational position of the planetary gear 5. By doing so, the planetary gear 5 is prevented from moving in the radial direction. As a result, the planetary gear 5 can be prevented from vibrating in the radial direction. Thus, vibrations of a planetary gear apparatus can be reduced, and the planetary gear and a carrier can be reduced in damage.