Differential expansion absorption mechanism and fuel injection valve comprising same

The present invention provides a fuel injection valve which moves a needle valve (10) via a viscous fluid and a piston (7) by having an actuator (9) move a cylinder (3). The fuel injection valve comprises a sealing member (27) for sealing a gap between the cylinder (3) and piston (7), and a linking hole (29) formed in the piston (7) for connecting two chambers (5, 6) to each other. The size and/or shape of the linking hole (29) is set such that when a force for moving the cylinder (3) or piston (7) at a lower speed than the driving speed of the actuator (9) is generated due to differential thermal expansion between members, the viscous fluid moves between the two chambers (5, 6) through the linking hole (29), and when a force for moving the cylinder (3) at a higher speed than the force generated by the differential thermal expansion is generated by the actuator (9), the viscous fluid cannot pass through the linking hole (29).