Power plants – Pressure fluid source and motor – Pulsator
Patent
1997-05-30
1999-03-02
Richter, Sheldon J.
Power plants
Pressure fluid source and motor
Pulsator
60545, 310328, F15B 2108, F02M 5106, H01L 4109
Patent
active
058756329
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
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>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.
SUMMARY OF THE INVENTION
It is, therefore, an advantage of the present to provide an operationally reliable electrohydraulic drive which has a compact design, operates within a large temperature range and has good dynamic properties. To this end, in an embodiment, an electrohydraulic drive is provided having an actuator and a lift transformer arranged in a housing filled with a hydraulic medium. The length of the actuator varies in a controllable fashion. A first piston is arranged in an axially displaceable fashion in a housing bore. A second piston acts on a spring element and a control element wherein the first piston is driven by the actuator. The first piston has an axial bore in which the second piston moves in an opposite direction to the first piston. A balancing element is arranged between the actuator and the lift transformer wherein the balancing element is formed of a spherical segment and is supported in an actuator side depression of the first piston and is capable of sliding freely on the actuator.
The advantage which can be achieved with the present invention consists, in particular, in that even a comparatively large decentering of one of the multiply guided parts does not impair the functionality of the drive. The drive can, therefore be, produced with a substantially lower outlay and in a more cost effective fashion.
BRIEF DESCRIPTION OF THE DRAWINGS
Additional features and advantages of the present invention are described in, and will be apparent from, the detailed description of the presently preferred embodiments and from the drawings.
FIG. 1 illustrates a sectional view of an embodiment of an electrohydraulic drive for a fuel injection valve.
FIG. 2 illustrates a sectional view of an embodiment of a bipartite reciprocating piston of the force/travel transmission drawn.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
The design and method of functioning of the electrohydraulic drive will be described in conjunction and with reference to FIGS. 1 and 2 wherein like numerals refer to like parts.
FIG. 1 shows essentially only the components of a high-speed fuel injection valve which relate to the drive according to the invention; such a valve is disclosed for example, in German Patent No. DE 43 06 073 C1 or described in more detail in the German Patent Application DE 4406522. As drive element, the injection valve contains an electromechanical actuator P which acts on a hydraulic lift transformer DK/HK and which
REFERENCES:
patent: 3635016 (1972-01-01), Benson
patent: 5233834 (1993-08-01), Tsukamoto
Kappel Andreas
Mock Randolf
Richter Sheldon J.
Siemens Aktiengesellschaft
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