Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1998-07-08
2001-09-25
Tran, Huan (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S011000, C347S005000, C347S009000
Reexamination Certificate
active
06293639
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink-jet recording apparatus, and more particularly, to a technique for controlling the driving of an ink-jet head provided in an ink-jet recording apparatus.
2. Related Art
An ink-jet head which expels ink droplets by inducing variations in the volume of ink through use of a heating element has been known as an ink-jet head to be used with an ink-jet recording apparatus such as an ink-jet printer. Another known type of ink-jet head is one which expels ink droplets by changing the volume of an ink chamber (a pressure generation chamber) in communication with an ink nozzle. A vibrating plate is formed in part of a circumferential wall so as to become resiliently deformable in an outward direction relative to the surface of a circumferential wall with which an ink chamber is partitioned, as well as to correspond to one dot. Ink droplets are expelled expelled from the ink nozzle in communication with the ink chamber by application of a drive signal to a piezoelectric vibrator (or a pressure generating element) mounted on the vibrating plate to thereby vibrate the vibrating plate.
Of the foregoing ink-jet heads, an ink-jet head which expels ink droplets by changing the volume of the ink chamber through use of the piezoelectric vibrator is classified into known types, i.e., an ink-jet head of catapult-like expelling type and an ink-jet head of pressurized expelling type. In the ink-jet head of catapult-like expelling type, by actuation of a piezoelectric vibrator, a vibrating plate constituting part of the ink chamber is displaced beforehand in a direction in which positive pressure develops in the ink chamber as a result of a reduction in its volume. In this state, the vibrating plate is displaced in a direction in which negative pressure develops in the ink chamber as a result of an increase in its volume, as a result of which an ink meniscus is withdrawn into a discharge port. At the instant when the ink meniscus is withdrawn to the innermost position, the vibrating plate is displaced in the reverse direction, thus expelling an ink droplet from the ink nozzle.
In contrast, in the ink-jet head of pressurized expelling type, after having been displaced in a direction in which negative pressure develops in the ink chamber as a result of an increase in the volume of the ink chamber, the vibrating plate is displaced in a direction in which positive pressure develops in the ink chamber as a result of a decrease in the volume of the ink chamber the instant when the ink meniscus formed in the ink discharge port becomes stationary, thus expelling an ink droplet. To perform expelling operations such as those set forth, a drive control section applies, between electrodes of the piezoelectric vibrator, a drive signal Vnco having a waveform, such as that shown in FIG.
19
A. In the drive signal Vnco, a period from time t
21
to time t
31
corresponds to one drive cycle. Immediately before commencement of a current drive operation (i.e., during a period from time t
19
to time t
21
), the vibrating plate is displaced in a direction in which the volume of the ink chamber decreases, by application of a first drive voltage V
1
to the piezoelectric vibrator. In a case where an ink droplet is expelled by means of the current driving operation, the voltage applied to the piezoelectric vibrator is changed from the first drive voltage V
1
to a second drive voltage V
2
during a period from time t
21
to time t
22
, thus displacing the vibrating plate in a direction in which the volume of the ink chamber increases. This state is maintained for a period from time t
22
to time t
23
. Subsequently, the voltage applied to the piezoelectric vibrator is changed from the second drive voltage V
2
to a third drive voltage V
3
during a period from time t
23
to time t
24
, thus displacing the vibrating plate in a direction in which the volume of the ink chamber decreases. Such a state is maintained for a period from t
24
to time t
25
, and an ink droplet is expelled from the ink nozzle. Subsequently, during a period from time t
25
to time t
26
, the voltage applied to the piezoelectric vibrator is changed from the third drive voltage V
3
to an intermediate voltage (Vm) between the first and second drive voltages V
1
and V
2
or between the third drive voltage V
3
and the second drive voltage V
2
, to thereby displace the vibrating plate in a direction in which the volume of the ink chamber is increased to its intermediate level, thus interrupting the flow of ink by means of the ink discharge port. After expelling of ink, the voltage applied to the piezoelectric vibrator is maintained at an intermediate voltage Vm during a period from time t
26
to time t
28
without regard to whether or not ink is expelled during the next drive cycle, whereby the volume of the ink chamber is maintained at its intermediate level. Immediately before commencement of the next drive operation (during a period from time t
28
to time t
29
), the voltage applied to the piezoelectric vibrator is changed from the intermediate voltage Vm to the first drive voltage V
1
, thus displacing the vibrating plate in a direction in which the volume of the ink chamber decreases. Such a state is maintained for a period from time t
29
to time
31
.
In contrast, in a case where the expelling of an ink droplet from the ink nozzle is suspended for the period of time corresponding to one dot during the current drive cycle, a drive signal Vnco having a waveform such as that shown in
FIG. 19B
is applied between the electrodes of the piezoelectric vibrator. Immediately before commencement of the current drive operation (during a period from time t
18
to time t
21
), the vibrating plate is displaced in a direction in which the volume of the ink chamber decreases from its intermediate level by means of the first drive voltage V
1
, as in the case described by reference to
FIG. 19A
in which an ink droplet is expelled during the current drive operation. During a period from time t
21
to time
31
at which the next drive operation is commenced, the volume of the ink chamber is maintained at a reduced value by application of the first drive voltage V
1
to the piezoelectric vibrator.
Here, the first and third drive voltages V
1
and V
3
may be respectively set to different potentials or to an identical potential as in the case such as that shown in FIG.
19
A.
However, in a case where each vibrating plate is driven as has been conventionally practiced, if the piezoelectric vibrator is driven according to print data without consideration of the result of a previous driving operation or of a drive history such as the next driving conditions, neither improvement of print quality nor higher speed operation can be accomplished.
Specifically, in order to expel ink droplets from an ink nozzle, the vibrating plate is displaced during a period from time t
12
to time
13
during the previous drive cycle until the ink nozzle becomes prepared for a squiring operation. The vibrating plate is then displaced during a period from time t
13
to time t
14
in a direction in which the volume of the ink chamber decreases. The vibrating plate is further displaced during a period from time t
13
to time t
14
in a direction in which the volume of the ink chamber decreases. Subsequent
1
y, the vibrating plate is displaced during a period from time t
15
to time t
16
until the volume of the ink chamber reaches an intermediate value. As shown in
FIG. 19C
, the vibrating plate keeps oscillating even after time t
16
, and the ink meniscus also oscillates in the same manner. As shown in FIG.
19
A, in such a case, if the expelling of the ink droplet is continually carried out, a stable driving operation can be ensured by bringing the movement of the piezoelectric vibrator into synchronization with the movements of the vibrating plate or the ink meniscus. Alternatively, in a state in which the vibration of the vibrating plate or the ink meniscus has become sufficiently stationary,
Do An H.
Seiko Epson Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
Tran Huan
LandOfFree
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