Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2002-01-23
2003-09-09
Pham, Hai (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S010000
Reexamination Certificate
active
06616258
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device and method for driving an ink-jet head which performs printing by ejecting ink onto a printing medium, and to an ink-jet printing apparatus using the driving device.
2. Description of the Related Art
Printing apparatuses suitably used as image-output means in printers, copying machines, facsimiles, and the like record an image formed of a dot pattern on a printing medium such as paper, a plastic thin plate, cloth, or the like in accordance with given image information. The printing apparatuses are classified into an ink-jet type, a wire-dot type, a thermal type such as a thermal transfer type, a laser beam type, and the like according to their image-forming methods. Among these types, an ink-jet printing apparatus ejects ink (recording liquid), for example, in a droplet form from a discharge opening of an ink-jet head onto a printing medium, thereby printing an image on the printing medium.
An ink-jet head suitably used in such an ink-jet printing apparatus is known in which an electrothermal conversion element (discharge heater) is disposed in a channel which communicates with each discharge opening, and ink is discharged by using the expansion power of a bubble generated by heat which is produced by energizing the discharge heater (for example, a bubble-jet type, advocated by the present applicant, which discharges ink by producing film boiling in ink). This type of ink-jet head can be produced through a process similar to a semiconductor manufacturing process. For this reason, the size of the discharge heater disposed adjacent to the discharge opening or along the channel disposed on the inner side (the discharge opening and the channel will be generically named a “nozzle”, unless otherwise specified) can be made much smaller than that of an energy producing element which has been hitherto used to discharge ink. This enables high-density mounting of nozzles.
In an ink-jet head having multiple nozzles mounted therein, normally, discharge heaters are divided into a plurality of blocks in order to limit the number of discharge heaters to be simultaneously driven in consideration of the upper limit of the maximum power consumption, and the ink-jet head is driven block by block in a time division manner within a predetermined driving period.
A related art of such time-division driving will be described with reference to
FIGS. 1
to
4
.
FIG. 1A
shows the correspondence between nozzles arranged in the ink-jet head, and the waveforms of signals to be applied to discharge heaters corresponding to the nozzles.
An ink-jet head
1000
shown in
FIG. 1A
is schematically shown, as viewed from the front side of a discharge opening. Ink is discharged from nozzles or discharge openings
1
to
12
, and lands on a printing medium, thereby forming an image thereon. Recent ink-jet heads have a tendency to have 200 to 2000 nozzles mounted thereon for higher printing speed and higher image quality. Herein, the ink-jet head
1000
includes twelve nozzles for ease of explanation.
A timing chart on the right side of the ink-jet head
1000
shows the waveforms of signals to be applied to discharge heaters in the nozzles. The vertical axis represents the applied voltage. A state in which the voltage is high (H) means an energized (ON) state, and a state in which the voltage is low (L) means a non-energized (OFF) state. The horizontal axis represents the time.
For convenience, the nozzles
1
to
12
are arranged in numerical order from the top of the figure. The nozzles
1
to
12
are divided into four blocks of three. Each block includes discharge heaters to be simultaneously driven, and is driven individually. When the applied voltage is high, the discharge heater is energized, and ink is discharged by using the expansion power of a bubble generated by heat. In contrast, when the applied voltage is low, the discharge heater is not energized, and ink is not discharged. The nozzles
1
to
12
are driven in a time division manner, that is, the nozzles
1
,
5
, and
9
are driven at a first block time, the nozzles
2
,
6
, and
10
at a second block time, the nozzles
3
,
7
, and
11
at a third block time, and the nozzles
4
,
8
, and
12
at a fourth block time. As a result, the discharge openings of the first to fourth blocks sequentially perform discharge operation.
FIG. 2
is a circuit diagram of a driving circuit for such time-division driving in the related art, and
FIG. 3
is an operation timing chart of the components in the driving circuit.
Referring to
FIG. 2
, a one-shot circuit
100
detects the rising edge of a predetermined encoder signal, and generates a one-shot pulse signal A. For example, in a so-called serial type printing apparatus, encoder signals are generated at regular intervals during a main scanning process of the ink-jet head with respect to a printing medium. The one-shot pulse signal A is supplied to a timer circuit
114
and to a one-shot circuit
102
in parallel.
The timer circuit
114
is reset by the pulse signal A, and generates signals B at regular intervals. The timer circuit
114
is connected to a shift circuit
103
and a heating pulse generating circuit
104
so that the signals B are input thereto. The signal B serves as a reference signal for a block driving period shown in FIG.
1
A.
The configuration and operation of the timer circuit
114
will now be described with reference to
FIGS. 4A and 4B
.
FIG. 4A
is a circuit diagram of the timer circuit
114
, and
FIG. 4B
is an operation timing chart thereof. Reference numerals
110
,
111
,
112
, and
113
denote toggle flip-flops (hereinafter referred to as “TFFs”). A pulse to be input to the TFF
110
is a square wave having a frequency of, for example, 800 kHz. The TFF
110
inverts a pulse signal Q
1
output from a terminal Q at every rising edge of the input pulse signal. In this way, the TFF can reduce the frequency to half by dividing the input signal. Since four TFFs are connected in series in
FIG. 1A
, an output pulse B from the last TFF
113
is a square wave of 50 kHz.
The above-described pulse signal A is supplied to a reset input terminal R of each of the TFFs
110
to
113
. For this reason, the TFFs
110
to
113
are reset in response to every input of a one-shot pulse signal A, and output signals Q
1
, Q
2
, Q
3
, and Q
4
therefrom become low. When a pulse signal having a frequency of 800 kHz is input to the TFF
110
, the TFFs
110
to
113
are triggered at the falling edge of the signal A, and a signal B divided by the four TFFS
110
to
113
is output.
Referring to
FIGS. 2 and 3
, the one-shot circuit
102
generates a one-shot pulse signal at the falling edge of the signal B, and outputs an OR signal C between the pulse signal and the pulse signal A. The signal C is supplied to a heating-pulse generating circuit
104
. On the other hand, a shift circuit
103
of a Johnson counter type outputs pulse signals QA
1
to QA
4
in a time division manner in response to the signal B, as shown in
FIG. 3
, and inputs the pulse signals to the heating-pulse generating circuit
104
.
The heating-pulse generating circuit
104
generates signals for energizing the discharge heaters, and outputs the signals to a driver circuit
105
. Information about the ON time of the discharge heaters for discharging ink is supplied from a microcomputer or the like (not shown) serving as a control section in the printing apparatus, and the ON time (heat pulse width) of the discharge heaters is determined on the basis of the information. As shown in
FIG. 3
, the heating-pulse generating circuit
104
outputs a block driving signal BL
1
for a period, which is determined on the basis of the information at the rising edge of the pulse signal QA
1
, and supplies the signal to the driver circuit
105
. Similarly, the heating-pulse generating circuit
104
outputs block driving signals BL
2
, BL
3
, and BL
4
for the periods determined on the basis of the information at the rising edges of the pulse signals Q
Dudding Alfred
Pham Hai
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