Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1999-09-14
2001-12-11
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S010000, C347S068000
Reexamination Certificate
active
06328398
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an ink-jet recording head driving method and an ink-jet recording device wherein a piezoelectric element is formed on a part of a pressure generating chamber communicating with a nozzle opening from which an ink droplet is jetted via a diaphragm and an ink droplet is jetted by the displacement of the piezoelectric element.
Typically, an ink-jet recording head includes a pressure generating chamber communicating with a nozzle opening from which an ink droplet is jetted. The ink-jet recording head comprises a diaphragm which is deformed by a piezoelectric element and ink in a pressure generating chamber is pressurized to jet an ink droplet from a nozzle opening. Two variations of this type of ink-jet recording head are known. One such device uses a method whereby a piezoelectric actuator is used in a longitudinal vibration mode in which a piezoelectric element is extended or contracted in an axial direction. A second type uses a method whereby a piezoelectric actuator is used in a flexural vibration mode.
In the former method, the volume of a pressure generating chamber can be varied by touching the end face of a piezoelectric element to a diaphragm and a head suitable for high density printing can be manufactured. However, a problem arises with this method in that it is difficult to cut each piezoelectric element in the required shape, that of the teeth of a comb. This particular shape is required due to the arrangement pitch of nozzle openings. Further, it is difficult to position and attach the cut piezoelectric element onto a pressure generating chamber as required, leading to further complications in the manufacturing process.
The second known method provides the advantage that a piezoelectric element can be fixed onto a diaphragm in a relatively simple process. In this process, a piezoelectric material is baked resulting in a piezoelectric material corresponding to the shape of a pressure generating chamber.
However, not withstanding the advantages provided by the second method, there is a problem in that a piezoelectric actuator in the flexural vibration mode requires a larger area for displacement than a piezoelectric actuator in the longitudinal vibration mode. Consequently, the volume of a pressure generating chamber is increased and the quantity of ink in a jetted ink droplet is also increased, resulting in difficulties in forming the minute ink drop sizes required in certain graphics printing applications.
Further, there is also a problem in that the vibration of a meniscus after an ink droplet is jetted effects the jetting of the next ink droplet. To solve such problems, a driving method wherein vibrations are inhibited has been proposed. However, there is a problem in that the whole driving method is extended and cannot correspond to high frequency printing.
SUMMARY OF THE INVENTION
The present invention addresses the aforementioned problems by providing an ink-jet recording head driving method and an ink-jet recording device wherein the quantity of ink comprising an ink droplet is reduced as much as possible and the vibration of a meniscus after ink is jetted can be avoided, keeping a driving cycle short.
A preferred embodiment of the present invention relates to a method of driving an ink-jet recording head for contracting a pressure generating chamber by driving a piezoelectric element provided on the pressure generating chamber communicating with a nozzle opening and a reservoir and jetting an ink droplet. The invention further relates to an ink-jet recording head driving method characterized in that a process for preparing for the jetting of ink by expanding a pressure generating chamber and backing a meniscus from the surface of the nozzle opening is provided before a first contraction process for contracting the pressure generating chamber and jetting ink from a nozzle opening. The time in which a driving signal is applied in the preparatory process is equivalent to ½ or less of the Helmholtz vibrational cycle, Tc, of the pressure generating chamber and the quantity of contraction in the first contraction process is equivalent to 50% or less of the quantity of expansion in the preparatory process. According to this preferred embodiment, a small ink droplet can be effectively jetted.
An additional aspect of this embodiment of the present invention relates to an ink-jet recording head driving method wherein a second contraction process for contracting a pressure generating chamber so that the backing of a meniscus is reduced by reaction upon the first contraction process. According to this aspect, the backing of a meniscus after ink is jetted can be inhibited to prepare for the next jetting of ink and high speed stable driving can be realized.
Another aspect of this embodiment of the present invention relates to an ink-jet recording head driving method characterized in that the above second contraction process is started between time t
1
when the backing of a meniscus starts and time t
2
when the meniscus backs most respectively after the end of an ink droplet is jetted from a nozzle opening. According to this aspect, the backing of a meniscus after ink is jetted can be effectively inhibited and high speed stable driving can be realized.
An additional aspect of this embodiment of the present invention relates to an ink-jet recording head driving method characterized in that the above second contraction process is started in a range of [t
1
+(t
2
−t
1
)×¾] from time t
1
when the backing of a meniscus starts after the end of an ink droplet is jetted from a nozzle opening. According to this aspect, the backing of a meniscus after ink is jetted can be more effectively inhibited and high speed stable driving can be realized.
Another aspect of this embodiment of the present invention relates to an ink-jet recording head driving method characterized in that the above-mentioned second contraction process is started in a range of [t
1
+(t
2
−t
1
)/2] from time t
1
when the backing of a meniscus starts after the end of an ink droplet is jetted from a nozzle opening. According to this aspect, the backing of a meniscus after ink is jetted can be more effectively inhibited and high speed stable driving can be realized.
Another aspect of this embodiment of the present invention relates to an ink-jet recording head driving method characterized in that after the above first contraction process, a process for gently contracting a pressure generating chamber is provided to a certain defined state including a reference state before the above preparatory process. According to this embodiment, a certain state is gently restored to the reference state after ink is jetted.
Yet another aspect of this embodiment of the present invention relates to an ink-jet recording head driving method wherein after the above second contraction process or after a certain state is restored to the above defined state, a first expansion process for expanding a pressure generating chamber so that vibration after ink is jetted is inhibited is provided. According to this embodiment, the vibration of a meniscus after ink is jetted can be effectively inhibited and the next jetting of ink can be prepared.
An additional aspect of this embodiment of the present invention relates to an ink-jet recording head driving method characterized in that time between the start of the above first contraction process and the start of the above first expansion process is substantially equivalent to Helmholtz vibrational cycle, Tc, of a pressure generating chamber. According to this embodiment, the vibration of a meniscus after ink is jetted can be effectively inhibited and the next jetting of ink can be prepared.
Another aspect of this embodiment of the present invention relates to an ink-jet recording head driving method wherein after the above first expansion process, a third contraction process for contracting a pressure generating chamber so that vibration after ink is jetted is inhibited is pr
Barlow John
Dudding Alfred E.
Seiko Epson Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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