Actuator

An actuator for operation of a fuel injector in a fuel injection system of an internal combustion engine, comprising:

• one of:
• i) a piezoelectric element, or ii) a magnetostrictive element;
• and
• a prestressing device that one of surrounds and passes through the one of the piezoelectric element and magnetostrictive element to exert an axial prestressing force on the one of the piezoelectric element and magnetostrictive element;
• wherein the piezoelectric element or magnetostrictive element is composed of a plurality of layers arranged in a stack;
• wherein ends of the piezoelectric element or magnetostrictive element are sealed off by a cover plate and a bottom plate;
• and
• wherein sheathing surrounds the layers.

An actuator for operation of a fuel injector in a fuel injection system of an internal combustion engine, comprising:

• one of:
• i) a piezoelectric element, or ii) a magnetostrictive element;
• and
• a prestressing device that one of surrounds and passes through the one of the piezoelectric element and magnetostrictive element to exert an axial prestressing force on the one of the piezoelectric element and magnetostrictive element;
• wherein the piezoelectric element or magnetostrictive element is composed of a plurality of layers arranged in a stack;
• wherein ends of the piezoelectric element or magnetostrictive element are sealed off by a cover plate and a bottom plate;
• wherein sheathing surrounds the layers;
• and
• wherein a projecting end of the sheathing is provided around the edge of the cover plate and the bottom plate by flanging so that an axial prestressing force is exerted on the layers arranged between the cover plate and the bottom plate.

An actuator for operation of a fuel injector, comprising:

• an actuator element including one of a piezoelectric element and a magnetostrictive element;
• a cover plate and a bottom plate for sealing off ends of the actuator element;
• and
• a sheathing surrounding the actuator element and including a first flange and a second flange, the first flange surrounding an edge of the cover plate and exerting a first axial force component on the cover plate, the second flange surrounding an edge of the bottom plate and exerting a second axial force component on the bottom plate.

An actuator for operation of a fuel injector in a fuel injection system of an internal combustion engine, comprising:

• one of:
• i) a piezoelectric element, or ii) a magnetostrictive element;
• and
• a prestressing device that axially surrounds the one of the piezoelectric element and magnetostrictive element to exert an axial prestressing force on the one of the piezoelectric element and magnetostrictive element;
• wherein an outer surface of the prestressing device is substantially flat.

An actuator for operation of a fuel injector in a fuel injection system of an internal combustion engine, comprising:

• one of:
• i) a piezoelectric element, or ii) a magnetostrictive element;
• and
• a prestressing device that one of surrounds and passes through the one of the piezoelectric element and magnetostrictive element to exert an axial prestressing force on the one of the piezoelectric element and magnetostrictive element;
• wherein an outer surface of the prestressing device is substantially flat;
• wherein the piezoelectric element or magnetostrictive element is composed of a plurality of layers arranged in a stack;
• wherein ends of the piezoelectric element or magnetostrictive element are sealed off by a cover plate and a bottom plate;
• and
• wherein sheathing surrounds the layers.