An injection valve is generally known from German Patent No. DE4306073 C1 that contains a drive having a of compact design and also having very good dynamic properties that still operates reliably even at high operating frequencies (f&gt;1 kHz). Since the drive permits valve opening and closing times in the range of .tau..ltoreq.0.1 ms, it is possible to inject even the smallest fuel quantities into the combustion chamber of an engine in a precisely metered and reproducible fashion. The main components of the drive are a piezoelectric actuator, which generates the primary operating travel, and a hydraulic lift transformer which essentially has a pressure piston driven by the piezoelectric actuator and a reciprocating piston which is mounted in an axially displaceable fashion in a pressure piston bore and is connected to the valve needle. The piezoelectric actuator arranged in one of the hydraulic chambers is supported on the housing side on a spherical cap bearing. This measure ensures that the actuator always bears with full surface contact against the pressure piston even should its end surfaces are not parallel for production reasons, and that no loss of lift occurs.
The design of this known valve places high demands on the axial symmetry and dimensional accuracy of the individual components. In particular, the multiply guided reciprocating piston must be produced accurately down to a few .mu.m in order to prevent canting or jamming. This complicates mass production and makes production of the valve substantially more expensive.
USPTO Backgrounds
USPTO Backgrounds