Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
1999-09-30
2001-08-07
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
Reexamination Certificate
active
06271618
ABSTRACT:
BACKGROUND OF THE INVENTION:
Field of the Invention
The invention concerns a method and a configuration for driving an actuator, in particular a piezoelectrically operated fuel injection valve of an internal combustion engine.
Published, Non-Prosecuted German Patent Application DE 196 53 666 A1 discloses a method for quickly driving capacitive loads in which a control circuit is controlled by a control device. In this method, the interaction of an upward and downward controller in the control circuit and an evaluation of a load voltage and load current values together with a fast digital controller make it possible to produce to a great extent any desired voltage characteristics at the capacitive load.
Published, Non-Prosecuted German Patent Application DE 196 52 807 A1 discloses transferring predeterminable energy to an actuator by transferring the charge of a charging capacitor partially to the actuator via a ring-around coil. A deviation in the metered amount of energy supplied in a driving operation is established on the basis of a family of characteristic maps or fields and is corrected incrementally in the next driving operations. The family of characteristic maps are determined experimentally from the predetermined component values of the configuration and the temperature-dependent actuator capacitance.
This method of driving an actuator presupposes that the capacitance of the charging capacitor and the inductance of the ring-around coil are precisely known. However, coils and capacitors usually have production-related tolerances of approximately ±10%; in addition, their values change during operation in dependence on temperature and aging. By measuring an inductance and a capacitance at the end of the line, component tolerances can be detected and taken into account in the driving method. A further solution is to use components with low production tolerances, which however leads to high component prices. External influences during operation, such as temperature influences or aging of the components for example, are not taken into account in the two solutions.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method and a configuration for driving a capacitive actuator which overcome the above-mentioned disadvantages of the prior art methods and devices of this general type, in which component tolerances of the driving circuit are detected and compensated for.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for driving a capacitive actuator being driven by a driving circuit having a series resonance circuit with a charging capacitor and a coil, the method compensating for component tolerances of the driving circuit, which includes:
reversing a charge of the charging capacitor, previously charged to a predetermined calibrating voltage, via the coil and detecting current values of a flowing charge-transfer current at different instants;
determining a charging capacitance of the charging capacitor and an inductance of the coil from the predetermined calibrating voltage, the different instants and the current values with an aid of laws applicable in series resonance circuits;
determining a starting voltage and a charging time from a predeterminable energy, the charging capacitance and the inductance on a basis of characteristic maps; and
transferring the predeterminable energy to the capacitive actuator by the charging capacitor charged to the starting voltage and having its charge transferred during the charging time to the capacitive actuator.
With the foregoing and other objects in view there is further provided, in accordance with the invention, a driving circuit that self-compensates for component tolerances of components of the driving circuit, including:
a series circuit having a charging capacitor with a charging capacitance, a coil having an inductance disposed in series with the charging capacitor, and an adjuster circuit disposed in series with the coil and has an actuator;
a main switch connected to the charging capacitor and to be connected to an energy source is provided for supplying the charging capacitor via the main switch;
a switching branch disposed in parallel with the adjuster circuit and has an auxiliary switch and a measuring resistor connected to the auxiliary switch;
the charging capacitor, the coil and the switching branch form a measuring branch; and
a controller connected to the series circuit and the main switch perform the above-noted operating steps.
The essential idea of the invention is to carry out in the measuring branch of the configuration, having the charging capacitor, the ring-around coil and the switching branch with a switch, an LC measuring operation. The LC measuring operation includes carrying out a charge-transfer (reversal) operation in the measuring branch and, during this operation, recording in the measuring branch current and voltage measurements, for subsequently determining capacitance and inductance values, and using the values determined for subsequent driving of the actuator.
A major advantage is that low-cost capacitors and coils with high tolerances can be used in the configuration. Furthermore, the service life of the configuration increases, since age-dependent influences are compensated. The range of use of the configuration is extended, since temperature-related influences are also compensated for.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and a configuration for driving a capacitive actuator, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
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Freudenberg Hellmut
Gerken Hartmut
Hoffmann Christian
Greenberg Laurence A.
Lerner Herbert L.
Medley Peter
Ramirez Nestor
Siemens Aktiengesellschaft
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