Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2001-03-20
2002-07-16
Nguyen, Thinh (Department: 2861)
Incremental printing of symbolic information
Ink jet
Controller
C347S011000
Reexamination Certificate
active
06419339
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recording method and an ink jet recorder, and specifically an ink jet recording method and an ink jet recorder which can control a number of ink droplets for forming a dot, and a storage medium for storing a program for driving the recorder.
2. Description of the Related Art
A known conventional ink ejector of the ink jet type has ink channels and nozzles each communicating with one of the channels. The volume of each ink channel can be changed by the deformation of a piezoelectric ceramic or the like. When the channel volume decreases, ink in the ink channel is ejected as droplets through the associated nozzle. When the channel volume increases, the ink channel is supplied with ink from an ink supply.
Such a conventional ink ejector
600
is shown in section in
FIG. 6
of the accompanying drawings. The ink ejector
600
includes an actuator substrate
601
and a cover plate
602
. The actuator substrate
601
has ink channels
613
and spaces
615
all in the form of grooves, which extend perpendicularly to a record medium set on the recorder including the ejector
600
. The ink channels
613
and spaces
615
are arrayed alternately, with side walls
617
interposed between them, which are made of piezoelectric material. Each side wall
617
consists of a lower wall
611
and an upper wall
609
, which are polarized in opposite directions P
1
and P
2
, respectively. Each ink channel
613
has a nozzle
618
formed at one end. The other ends of the ink channels
613
are connected to a manifold (not shown), through which ink can be supplied. Those ends of the spaces
615
which are adjacent to the manifold are closed so that no ink can enter the spaces.
Both sides of each side wall
617
are fitted with a pair of electrodes
619
and
621
in the form of metallized layers. Specifically, the electrodes
619
and
621
are a channel electrode
619
and a space electrode
621
, which are positioned in the adjacent ink channel
613
and space
615
, respectively. All the channel electrodes
619
are grounded. The space electrodes
621
are connected to a controller
625
(FIG.
8
), which outputs actuator drive signals. The space electrodes
621
on both sides of each ink channel
613
are connected together. The space electrodes
621
in each space
615
are insulated from each other.
When voltage is applied to the space electrodes
621
on both sides of any of the ink channels
613
, the associated side walls
617
deform piezoelectrically in such directions that the channel or channels
613
enlarge in volume. As shown in
FIG. 7
of the drawings, for example, in order to drive the side walls
617
c
and
617
d
for the ink channel
613
b
, a voltage of E volts is applied to the associated space electrodes
621
c
and
621
d
. The voltage application generates electric fields in opposite directions E in the side walls
617
c
and
617
d
. The electric fields deform the side walls
617
c
and
617
d
piezoelectrically in such directions that the ink channel
613
b
enlarges in volume, reducing the pressure in this channel
613
b
. This condition is maintained for the one-way propagation time T of a pressure wave in each ink channel
613
. This supplies ink from the manifold to the ink channel
613
b
during the propagation time T.
The one-way propagation time T is the time that it takes for a pressure wave in each ink channel
613
to be propagated longitudinally of the channel
613
. This propagation time T is L/a (T=L/a) where L is the length of the ink channel
613
and a is the sound velocity in the ink in the channel
613
.
According to the theory of pressure wave propagation, exactly when the time T passes after the voltage is applied to the space electrodes
621
c
and
621
d
, the pressure in the ink channel
613
b
reverses into a positive pressure. When the pressure becomes positive, the voltage is returned to 0 volt. This allows the deformed side walls
617
c
and
617
d
to return to their original condition (
FIG. 6
) so as to apply a positive pressure to the ink in the ink channel
613
b
. This pressure is added to the pressure which has reversed to be positive. As a result, a relatively high pressure develops in that portion of the inkchannel
613
b
which is near to the nozzle
618
b
, ejecting an ink droplet through the nozzle.
If the period after the voltage is applied and until it is returned to 0 volt differs from the one-way propagation time T, the energy efficiency for the droplet ejection lowers. If this period is roughly an even number of times the propagation time T, no ink is ejected. Therefore, in general, in order to raise the energy efficiency, for example, to drive the side walls
617
at a voltage as low as possible, it is preferable that the period be roughly equal to the propagation time T or at least roughly an odd number of times the time T.
After an ink droplet is ejected from one of the ink channels
613
in accordance with a print instruction, vibration remains on the meniscus of ink in the associated nozzle
618
. At some drive frequencies, the vibration affects the ejection of an ink droplet in accordance with the next print instruction. For example, the vibration may cause the ink droplet to be ejected in a wrong direction, or a needless ink droplet to be ejected.
FIG. 5
of the drawings shows printing with ink droplets ejected from one of the ink channels
613
in accordance with different patterns of print instructions at a higher drive frequency for printing at a higher speed. In accordance with the consecutive or serial print instructions, ink droplets can be ejected stably. In accordance with the print instruction for every other drive cycle (dot), that is a pair of print instruction and non-print instruction is repeated however, the influence of the ink meniscus in the associated nozzle
618
is amplified. This is liable to make ink droplets ejected in wrong directions and/or needless ink droplets ejected.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an ink jet recording method for good recording quality, which makes it possible to stably eject ink by changing the number of ejected ink droplets for a dot if the print instruction for the dot immediately follows and/or immediately precedes non-print instruction. It is another object to provide an ink jet recorder and a storage medium for use with such a recording method.
In accordance with a first aspect of the present invention, an ink jet recording method is provided for recording a dot pattern on a record medium by means of a recorder including an actuator, which has an ink channel filled with ink and a nozzle communicating with the ink channel. The ink channel can change in volume to eject ink from it through the nozzle. The recording method includes the steps of:
judging whether one print instruction for forming a dot immediately follows another or not and whether the one print instruction immediately precedes another or not; and
causing the actuator to eject a predetermined number of ink droplets for forming the dot depending on the result of the judgment.
The recording method makes it possible to stably eject ink, regardless of whether one print instruction for forming a dot immediately follows another or not, and regardless of whether the one print instruction immediately precedes another or not.
If the one print instruction for forming the dot immediately follows another and immediately precedes another, the predetermined number of ink droplets for forming the dot may be N which is two or more (N≦2). The number N may be three or four. If the one print instruction immediately follows and immediately precedes no others, the number of ink droplets may be M which is smaller than N (M<N). As vibration remained on the meniscus of ink in the nozzle increases, a number of ejections increases because the vibration corresponds to vibration in pressure which is accumulated thereto each time an ink droplet is ejected from the nozzle. According
Brother Kogyo Kabushiki Kaisha
Oliff & Berridg,e PLC
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