JPH01174461A - Ink jet head drive method - Google Patents

Abstract

PURPOSE:To enable an ink drip to be jetted out even under a low-voltage drive by applying a negative voltage and a positive voltage successively to a piezoelectric element and applying a positive voltage to the other piezoelectric element with a time lag. CONSTITUTION:In the front and rear parts of an ink jet nozzle body 1, ink pressurizing chambers 2a, 2b are respectively formed. In the ink pressurizing chambers 2a, 2b, piezoelectric elements 3, 4 are disposed, respectively. In the piezoelectric elements 3, 4, a negative voltage is applied to the piezoelectric element 4 to reduce the pressure in the ink pressurizing chamber 2b to suck a meniscus once. Thereafter, a positive voltage is applied to the other piezoelectric element 3 to impart a pressure wave to the meniscus to accelerate it toward a nozzle injection port 1a. At the same time, a positive voltage is applied to the piezoelectric element 4 to further accelerate the meniscus to jet it out of the injection port 1a as an ink drip.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a drop-on-demand type inkjet head, and particularly to a method for driving an inkjet nozzle.

[Prior Art] Conventionally, this type of inkjet nozzle has only one ink pressurizing chamber per nozzle, and ink is ejected by pressurizing the ink pressurizing chamber.

[Problems to be Solved by the Invention] In the conventional inkjet nozzle described above, in order to obtain an appropriate ejection speed of ink droplets, the voltage of the applied pulse applied to the piezoelectric element, which is the pressurizing means, is increased or the pulse waveform is changed. has a complex waveform, so the power consumption is large.
Another disadvantage is that the waveform forming circuit becomes complicated.

An object of the present invention is to provide an inkjet head driving method that eliminates the above-mentioned problems.

[Means for Solving the Problems] The present invention has an inkjet nozzle internally equipped with two ink pressurizing chambers that can be pressurized or depressurized separately, and the ink pressurizing chamber on the nozzle exit side is depressurized. This inkjet head driving method is characterized in that ink is ejected by performing a subsequent pressurizing operation and an ink pressurizing chamber on the ink supply side with a time difference.

[Example] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, the present invention is an inkjet nozzle body 1.
Ink pressurizing chambers 2a and 2b are formed at the front of the nozzle body 1, piezoelectric elements 3 and 4 are installed in each ink pressurizing chamber 2a and 2b, and an ink jetting port 1a is roughly opened at the front end of the nozzle body 1. At the same time, an ink supply port 1b is opened at the rear end.

FIGS. 2(a) and 2(b) are diagrams showing applied voltage waveforms applied to two sets of piezoelectric elements 3 and 4. FIG. One piezoelectric element 3 has a second
The applied voltage shown in FIG. 2(a) is applied, and the applied voltage shown in FIG. 2(b) is applied to the other piezoelectric element 4.

In the present invention, the ink pressure chamber 2b on the side of the ink ejection port 1a is depressurized and then pressurized, and the operation of pressurizing the ink pressure chamber 2a on the side of the ink supply port 1b is performed with a time difference. It is something that gushes out. In other words, the voltage applied to the piezoelectric element 4 reduces the pressure in the ink pressurizing chamber 2b of the nozzle body 1, and the meniscus is once drawn in (FIG. 4(a)), and the voltage applied to the piezoelectric element 3 causes a meniscus to be drawn in. When the pressure wave reaches the meniscus and is accelerated toward the nozzle exit, a positive voltage is applied to the piezoelectric element 4 to accelerate the pressure wave and eject an ink droplet. Figure 3 (a
) to (f) show the movement of ink near the ink supply port. Figures 3(a) and 3(f) are the initial state, Figure 3(b) is the state where the meniscus is retracted, Figure 3(C) is the state showing the start of ink ejection, and Figure 3(d) is the state where the meniscus is retracted. FIG. 3(e) shows a state in which an ink droplet is formed and a state in which a meniscus is drawn.

FIGS. 4(a) and 4(b) are diagrams showing the ink velocity when the inside of the nozzle near the nozzle exit is negative.

Figure 4(b) shows the case of the conventional driving method, and Figure 4(a)
FIG. 3 is a diagram showing the case of the driving method according to the present invention.

In the case of the conventional driving method, the ink forms a column and is ejected from the nozzle outlet, breaks at p2, and is ejected as droplets. The meniscus is then drawn into the nozzle and returns to the initial state q2. In the case of the driving method of the present invention, after the meniscus is once drawn in, the ink forms a column and is ejected from the nozzle outlet, broken by pl, and ejected as droplets. After the meniscus is once drawn into the nozzle, it returns to the initial state q1.

By doing this, the time q1 required to return to the initial state with the drive method of the present invention is shorter than the time q2 required to return to the initial state with the conventional drive method, so the repetition frequency of droplet ejection can be increased. can.

[Effects of the Invention] As explained above, the present invention has two piezoelectric elements, and a negative voltage and a positive voltage are continuously applied to one piezoelectric element, and a time lag is applied to the other piezoelectric element. By applying a positive voltage at the same time, ink droplets can be ejected even when driven at low voltage, and the amount of ink in the ink pressurizing chamber can be replenished from the ink supply port in a short time. This has the effect of increasing the critical repetition frequency of ink droplet ejection.

[Brief explanation of the drawing]

Fig. 1 is an overview diagram showing one embodiment of the present invention, Fig. 2(a)
, (b) is a diagram showing the applied voltage waveform applied to the piezoelectric element,
3(a) to 3(f) are diagrams showing the movement of ink in the vicinity of the ink ejection port, and FIGS. 4(a) and 4(b) are diagrams showing the velocity of ink within the nozzle.

Claims (1)

[Claims] (1) having an inkjet nozzle internally equipped with two ink pressurizing chambers that can each be pressurized or depressurized separately; an operation of depressurizing the ink pressurizing chamber on the nozzle exit side and then pressurizing the ink pressurizing chamber;
An inkjet head driving method characterized in that ink is ejected by performing an operation of pressurizing an ink pressurizing chamber on an ink supply side with a time difference.