Patent ID: 7850091

Claim:
In a fuel injector, having an injector body, having a fuel inlet which is in communication with a high-pressure fuel source outside the injector body, having an actuator received in a hollow chamber from which hollow chamber a high-pressure inlet extends to an injection valve member, and as a function of the pressure in a first hydraulic chamber, fuel is injected into the combustion chamber of an internal combustion engine when the injection valve member lifts out of a seat, the improvement comprising a stepped piston acted directly on by the actuator, and a control piston which moves relative to the stepped piston and in which the injection valve member is guided, a step of the stepped piston defining the first hydraulic chamber on a first end of the first hydraulic chamber and an end face of the control piston defining the first hydraulic chamber on a second end of the first hydraulic chamber, the first hydraulic chamber acting on the end face of the control piston, the stepped piston acting on a second hydraulic chamber, which second hydraulic chamber is embodied in the control piston and which communicates hydraulically with a third hydraulic chamber disposed in the control piston, wherein an end face of the injection valve member protrudes into the third hydraulic chamber, and wherein the stepped piston is embodied with a first diameter and a second diameter, the first diameter exceeds the second diameter, the first diameter is acted on by the actuator, and the second diameter acts on the second hydraulic chamber.