Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-01-31
2002-11-26
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S068000, C347S069000, C347S070000, C347S071000, C347S072000
Reexamination Certificate
active
06485133
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an actuator device operated by a drive signal, an ink jet recording apparatus typified by an ink jet printer and a recording medium in which a program for driving the same is stored.
An actuator unit operated by a drive signal is utilized in various purposes. For example, as an ink jet recording head, which is one embodiment of such an actuator, used with an ink jet recording apparatus such as an ink jet printer, for example, an ink jet recording head is known wherein a piezoelectric actuator is deformed, thereby expanding or contracting a cavity (pressure generating chamber) for jetting an ink drop through an nozzle orifice.
A recording head of this kind has an extremely high resolution, for example, 720 dpi or 1440 dpi and thus requires very high work accuracy in &mgr;m units.
Variations in jetting characteristics of ink drops for each recording head occur because of a shift from the reference length of the free end portion of a piezoelectric actuator caused by an attachment error, work accuracy of the piezoelectric actuator and cavity, and the like. Then, an optimum drive voltage is set for each recording head for correcting variations for making uniform jetting characteristics of ink drops, whereby the recording head quality is stabilized and the yield of the recording heads is improved.
There is disclosed a drive signal generating device for driving an ink jet recording head as one embodiment of the actuator in Japanese Patent No. 2940542. In the device, a drive signal a waveform of which is varied in accordance with ambient temperature is programmably generated to correct variations of the ink drop jetting characteristics of the respective recording heads.
SUMMARY OF THE INVENTION
The present invention is provided in view of the above circumstance and it is therefore an object of the present invention is to provide an actuator unit using a suitable drive signal selected flexibly even if the actuator unit has inherent variations of characteristics thereof.
Another object of the present invention is to provide an ink jet recording apparatus incorporating the actuator, the yield of which can be improved.
In order to achieve the above objects, there is provided an ink jet recording apparatus comprising:
a recording head including a piezoelectric actuator for varying the volume of a pressure generating chamber by the deformation thereof to eject an ink drop from a nozzle communicating with the pressure generating chamber;
a drive signal generator for generating a drive signal including:
an expansion potential for deforming the piezoelectric actuator so as to expand the pressure generating chamber;
a contraction potential for deforming the piezoelectric actuator so as to contract the pressure generating chamber;
an ejection element for varying a potential of the drive signal from the expansion potential to the contraction potential to eject the ink drop from the nozzle; and
a contraction holding element for holding the contraction potential to keep the contracted state of the pressure generating chamber,
an ejection period information storage for storing a plurality values of a duration of the ejection element; and
a contraction holding period information storage for storing a plurality values of a duration of the contraction holding element,
wherein the drive signal generator selects one duration of the ejection element and one duration of the contraction holding element respectively from the ejection period information storage and the contraction holding information storage such that the duration of the ejection element is matched with a natural period of the piezoelectric actuator, and a resulting value by adding the duration of the ejection element and the duration of the contraction holding element is matched with a natural period of the pressure generating chamber.
Preferably, the apparatus further comprises:
an ejection period identifier storage for storing ejection period identifiers each of which is associated with the respective values stored in the ejection period information storage; and
a contraction holding period identifier storage for storing contraction holding period identifiers each of which is associated with the respective values stored in the contraction holding period information storage.
Here, the drive signal generator refers to the ejection period identifier and the contraction holding period identifier to determine the application periods of the ejection element and the contraction holding element.
Preferably, the drive signal includes a variable intermediate potential which is between the expansion potential and the contraction potential, and a damping element for varying the potential of the drive signal from the contraction potential to the intermediate potential for restoring the contracted pressure generating chamber to an initial state. The drive signal generator determines a duration of the damping element so as to match with the natural period of the piezoelectric actuator.
Preferably, the apparatus further comprises:
intermediate potential information storage means for storing a plurality values of the intermediate potential.
Here, the drive signal generator selects one potential value from the intermediate potential information storage means in accordance with jetting amount of the ink drop.
Preferably, the apparatus further comprises:
an intermediate potential identifier storage for storing intermediate potential identifiers each of which is associated with the respective values stored in the intermediate potential information storage.
Here, the drive signal generator refers to the intermediate potential identifier to determine the value of the intermediate potential.
Preferably, the drive signal is so arranged as to eject a plurality of ink drops having the same weight successively within the same driving period.
Preferably, the respective potentials and the respective elements in the drive signal is programmably defined.
According to the present invention, there is also provided an ink jet recording apparatus comprising:
a recording head including a piezoelectric actuator for varying the volume of a pressure generating chamber by the deformation thereof to eject an ink drop from a nozzle communicating with the pressure generating chamber; and
a drive signal generator for generating a drive signal including:
an expansion potential for deforming the piezoelectric actuator so as to expand the pressure generating chamber;
a contraction potential for deforming the piezoelectric actuator so as to contract the pressure generating chamber;
an intermediate potential which is between the expansion potential and the contraction potential;
an ejection element for varying a potential of the drive signal from the expansion potential to the contraction potential to eject the ink drop from the nozzle;
a contraction holding element for holding the contraction potential to keep the contracted state of the pressure generating chamber; and
a damping element for varying the potential of the drive signal from the contraction potential to the intermediate potential for restoring the contracted pressure generating chamber to an initial state; and
a characteristic information storage for storing characteristic information of the recording head which is referred by the drive signal generator and reflected to at least one of the expansion potential, the contraction potential, the intermediate potential, the ejection element, the contraction holding element and the damping element to generate the drive signal.
Preferably, the characteristic information includes at least one of a natural period of the piezoelectric actuator, a natural period of the pressure generating chamber and a natural period of meniscus of ink in the nozzle.
Preferably, the respective potentials and the respective elements in the drive signal is programmably defined.
According to the present invention, there is also provided an actuator device comprising:
an actuator;
a drive signal generator for generating a drive signal driving the actuat
Hosono Satoru
Teramae Hirofumi
Barlow John
Seiko Epson Corporation
Sughrue & Mion, PLLC
Tran Ly T.
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