Incremental printing of symbolic information – Ink jet – Controller
Patent
1997-07-17
1999-11-16
Moses, Richard
Incremental printing of symbolic information
Ink jet
Controller
347 15, B41J 2938
Patent
active
059844485
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a circuit for driving an ink-jet head using a piezoelectric actuator and a method of driving the same, more particularly to a circuit for driving an ink-jet head to record a gradation of density on a recording medium such as a printing paper and a method of driving the same.
BACKGROUND TECHNOLOGY
An ink-jet printer is known which uses an ink-jet recording system that jets a liquid ink droplet through a nozzle of the ink-jet head onto a recording medium such as a printing paper, thereby recording characters, image and the like on the medium.
The ink-jet printer using the foregoing system has advantages as follows:
(1) the mechanism, construction, and printing process of the system are comparably simple, and no noise is emitted in printing;
(2) being capable of discharging a minimal ink droplet, high resolution printing is possible;
(3) arranging plural color inks facilitates color printing;
(4) the system does not consume much power; and
(5) the price is comparably low.
Owing to these advantages, the ink-jet printer using this system has been spreading rapidly as a printer for not only personal computers but also for various office automation apparatus.
Of the ink-jet printer, the so-called drop-on-demand (DOD) type ink-jet printer, which discharges ink droplets only when a printing instruction is issued to minimize the ink consumption, is the most popular.
As major techniques to discharge ink by this DOD type ink-jet printer, there are the piezoelectric system that applies a pressure to the ink chamber by a force induced by the piezoelectric actuator as an electromechanical transducer and the bubble system that utilizes an expansion pressure of bubbles produced by an instantaneous vaporization of ink by an electric heater.
As a conventional example, a circuit for driving an ink-jet head using the piezoelectric actuator and a method of driving the same will be described with reference to FIG. 14 and FIG. 15.
In the circuit for driving an ink-jet head shown in FIG. 14, the emitter of an NPN transistor Q2 and one terminal of a piezoelectric actuator PZ are connected to the ground terminal GND as the earth potential.
A power source voltage VH for the ink-jet head is applied to the emitter of a PNP transistor Q1, one terminal of a second resistor R2, and one terminal of a third resistor R3.
A control signal S for driving the piezoelectric actuator PZ enters input terminals of a first inverter U1 of the open collector type and a second inverter U2. The output of the first inverter U1 is given through a first resistor R1 to the other terminal of the second resistor R2 and the base of the PNP transistor Q1.
The output of the second inverter U2 is given to the other terminal of the third resistor R3 and the base of the NPN transistor Q2. The collector of the NPN transistor Q2 is connected through a fifth resistor R5 to one terminal of a fourth resistor R4 and to the other terminal of the piezoelectric actuator PZ. The other terminal of the fourth resistor R4 is connected to the collector of the PNP transistor Q1.
The foregoing driving circuit drives the ink-jet head as follows.
Applying a pulse waveform voltage to the piezoelectric actuator PZ deforms a part of a wall in an ink chamber to increase the volume of the ink chamber, and ink is supplied in the increased space inside the ink chamber. And, stopping the voltage supply to the piezoelectric actuator PZ, or applying a pulse waveform voltage of the reverse polarity against the foregoing pulse waveform deforms the part of the wall in the ink chamber in the reverse direction to decrease the volume of the ink chamber, thus discharging ink droplets through the nozzle.
FIG. 15 illustrates waveforms of the control signal S, a driving voltage signal VCp applied to the piezoelectric actuator PZ, and a displacement X of the piezoelectric actuator in the conventional circuit for driving an ink-jet head shown in FIG. 14.
In FIG. 15, an initial period T0, a charge period T1 having a pulse change, and a discharge period T2 const
REFERENCES:
patent: 5327166 (1994-07-01), Shimada
patent: 5343231 (1994-08-01), Suzuki
Citizen Watch Co. Ltd.
Moses Richard
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