JPH02184449A - Driver for ink jet head - Google Patents

Abstract

PURPOSE:To enable high-quality printing with favorable accuracy of dot positions and without satellite particles or collapse of particle shape by a method wherein the internal volume of an ink chamber is increased and then returned to an initial condition to eject an ink, and before the ink is cut off from a nozzle, the internal volume of the ink chamber is again increased to cut off the ink. CONSTITUTION:An ink chamber 1 is formed as though it were closed by a vibrating plate 22, and a piezoelectric element 21 is attached firmly to an outside surface of the vibrating plate 22. The piezoelectric element 21 is flat unless a voltage is applied thereon. When a voltage is applied, the element 21 is deformed inward, and the vibrating plate 22 is also deformed inward, thereby reducing the internal volume of the ink chamber 1. The first variation in the voltage exerted on the element 21 increases the volume of the ink chamber 1, whereby an ink is sucked from an ink tank 11, and an ink-air interface is drawn into a nozzle 3. With the subsequent return to an initial voltage, the internal volume is decreased, whereby the ink is ejected outward through the nozzle 3. The second variation in the voltage increases the interval volume again, whereby an ink particle 31 being ejected is cut off in a short form from the nozzle 3, and is permitted to fly toward a recording paper.

Description

[Detailed Description of the Invention] [Summary] To provide an inkjet head drive device that drives the ejection head in an inkjet printer, and to perform high-quality printing with good dot position accuracy and without satellite particles or deformation. The ink chamber internal volume control means that changes the internal volume of the ink chamber has an ink ejection operation that increases the internal volume of the ink chamber and then returns to the original state to eject ink from the nozzle. The internal volume of the ink chamber is increased again before the ink ejected from the nozzle is cut off from the nozzle, and an ink cutting operation is performed to cut the ejected ink from the nozzle.

[Industrial Application Field] The present invention relates to an inkjet head drive device that drives an ejection head in an inkjet printer.

Printers used as output devices for computers, word processors, and the like are required to have high print quality and low noise. Inkjet printers, laser printers, etc. are used for this purpose, but in the case of inkjet printers, when one dot is recorded by one ink droplet, small particles (so-called satellite particles) are scattered around the dot, reducing the print quality. It is necessary to prevent this.

[Conventional smoking technique] As a conventional inkjet head drive device, the first
As shown in Figure 0, the ink chamber 5 is opened from the standby state (G).
By reducing the internal volume of the ink chamber 51, ink is ejected from the nozzle 52 (H), and then the ink chamber 51 is gradually restored to its original volume (I).
-23237) and as shown in Figure 11,
From the standby state (J), the internal volume of the ink chamber 51 is increased (K), and then the ink chamber 51 is reduced to its original internal volume, and ink is ejected from the nozzle 52 (L) (Tokuko Showa) 62-26912).

[Problems to be Solved by the Invention] However, among the above-mentioned inkjet head drive devices,
First, the 12th one reduces the internal volume of the ink chamber.
As shown in the figure, satellite particles 62 are generated behind the main ink particles 61, resulting in printing mixed with ghost-like unnecessary dots as shown in Fig. 13, resulting in poor print quality. can't get it. (M
) to CP) show changes in ink movement over time, and FIG. 14 shows changes in the voltage applied to the piezoelectric element that changes the internal volume of the ink chamber. It is a waveform.

Note that by slowing down the flying speed of the main particles 61, it is possible to prevent such satellite particles 62 from being generated. However, if the flight speed becomes slow, the positional accuracy of printed dots decreases, making it impossible to obtain good printing quality.

On the other hand, a device that first increases the internal volume of the ink chamber and then restores it to the original internal volume to eject ink particles can increase the flying speed of the ink particles and improve the dot position accuracy. will be good. However, the 15th
As shown in the figure, since the ejected ink particles 71 fly in the form of strings, elongated, misshapen dots are formed on the recording paper, as shown in FIG. 16. This phenomenon can be caused by increasing the frequency for high-speed printing,
This problem becomes particularly noticeable in so-called draft printing in which the head scans two to three times the normal speed, making it impossible to obtain good printing quality. (Q) to U) in Figure 15 show changes in the movement of ink over time, and Figure 17 shows changes in the movement of the ink to the piezoelectric element that changes the internal volume of the ink chamber. This is a drive waveform showing changes in applied voltage.

It is an object of the present invention to provide an inkjet head drive device that eliminates the above-mentioned conventional drawbacks and can perform high-quality printing with good dot position accuracy and without satellite particles or deformation. purpose.

[Means for Solving the Problems] In order to achieve the above object, the inkjet head driving device of the present invention includes an ink chamber 1 containing ink, and an ink chamber 1, which contains ink, as shown in FIG. an ink chamber internal volume control means 2 that changes the internal volume of the ink chamber 1; a nozzle 3 that is formed in communication with the ink chamber 1 and that jets ink outward from the ink chamber 1 according to a change in the internal volume of the ink chamber 1;
an ink ejection operation in which the ink chamber internal volume control means 2 increases the internal volume of the ink chamber 1 and then returns it to the original state to eject ink from the nozzle 3; 3, before the ink ejected from the nozzle 3 is cut off, the internal volume of the ink chamber 1 is increased again, and an ink cutting operation is performed to cut the ejected ink from the nozzle 3. shall be.

[Operation] In the present invention, ink is ejected from the nozzle 3 by first increasing the internal volume of the ink chamber 1 and then returning the ink chamber 1 to its original state. If the internal volume of the ink chamber 1 is increased again before the ejected ink is cut off from the nozzle 3, the ejected ink is strongly sucked from behind in the opposite direction to the ejecting direction, so the ejected ink Particles are quickly released from nozzle 3,
cut short. Due to this operation, the total length of the flying ink particles does not extend much, so that dots having a shape close to a circle are formed on the recording paper.

[Example] Examples will be described with reference to the drawings.

FIG. 2 shows an ink jet head 10 (hereinafter simply referred to as "head 10") of an ink jet printer. For example, 24 ink chambers l containing ink are formed in the head 10, and each ink chamber l
is in communication with a nozzle 3 that ejects ink toward recording paper (not shown). The nozzles 3 are arranged, for example, in two rows of 12 in a staggered manner.

On the other hand, each ink chamber 1 communicates with an ink tank 11 arranged at the rear lower part, and the ink in the ink tank 11 is sucked into the ink chamber 1 by the operation of changing the internal volume of the ink chamber 1. It has become. A piezoelectric element 21 is deformed by applying a voltage, and is provided for each ink chamber.

FIG. 3 shows an enlarged view of the vicinity of the ink chamber l. The ink chamber 1 is covered from one direction by a diaphragm 22 made of, for example, a stainless steel plate, and the parts other than the nozzle 3 are sealed. Vibration plate 2
A piezoelectric element 21 is closely fixed to the outer surface of 2. The piezoelectric element 21 is flat as shown in FIG. 3 when no voltage is applied, and when a voltage is applied to the piezoelectric element 21,
As shown in FIG. 4, the piezoelectric element 21 is deformed inward, and the diaphragm 22 is thereby deformed in the same direction, reducing the internal volume of the ink chamber 1.

In FIG. 3, 23 is an applied voltage control circuit that controls the voltage applied to the piezoelectric element 21, and the piezoelectric element 21, the diaphragm 22, this applied voltage control circuit 23, etc.
Ink chamber internal volume control means for changing the internal volume of the ink chamber 1 is formed. In this embodiment, in the standby state, a constant voltage of, for example, 80 volts is constantly applied to the piezoelectric element 21, so that the piezoelectric element 21 deforms inward as shown in FIG. The internal volume of is in a small state.

FIG. 5 is a block diagram showing the configuration of the applied voltage control circuit 23, and FIG. 6 is a time chart showing its operation. ti3 to Wataru) indicate the signal at each position.

The first pulse width generation circuit 231 receives a pulse instructing printing from a print control circuit (not shown) and outputs a pulse of a predetermined width (@). Further, the pulse from the print control circuit is input to the delay circuit 232, and the delayed signal output from there is input to the second pulse width generation circuit 233 (■).

The second pulse width generation circuit 233 generates a pulse shorter than the pulse output from the first pulse width generation circuit 233.
It is output from the first pulse width generation circuit 231 after a predetermined time delay (@).

Next, the first and second pulse width generation circuits 231 and 233
The output pulses from the piezoelectric element drive circuit 235 are combined by an OR circuit 234 and input to a piezoelectric element drive circuit 235 (fα), and the piezoelectric element drive circuit 235 applies a voltage change corresponding to the input pulse width to the piezoelectric element 21.

In this way, the piezoelectric element 21 to which a constant voltage of, for example, 8° Port is applied in the standby state, when printing,
As shown by Y in the figure, after first discharging to O ports, a constant voltage of 80 ports is applied again, and after a certain period of time (for example, 0 to 1 ms), the discharge is continued until the voltage drops to, for example, 20 to 40 ports.

FIG. 7 shows changes in the movement of ink when the above-described voltage changes are applied to the piezoelectric element 21.

In the standby state, a constant voltage of 80 volts is applied to the piezoelectric element 21, deforming it inwardly, and the ink chamber 1 remains stable with its internal volume reduced as shown in FIG. There is. At this time, the ink-air interface of the nozzle 3 is in equilibrium, creating a meniscus that is slightly drawn into the nozzle 3 (A).

The initial voltage change (discharge to O port) causes the internal volume of the ink chamber 1 to increase. As a result, ink is drawn from the ink tank 11 into the ink chamber 1, and the ink-air interface is drawn into the nozzle 3 (CB).

Subsequently, when the voltage returns to the original voltage (80 ports), the internal volume of the ink chamber 1 decreases and returns to its original state, and ink is ejected outward from the nozzle 3 (C).

Next, after a predetermined period of time after the first voltage change, the applied voltage is lowered by a second voltage change before the ejected ink is cut off from the nozzle 3. As a result, the internal volume of the ink chamber 1 increases again, and the ejected ink particles 31 are quickly and briefly cut off from the nozzle 3 (D, E) and fly toward the recording paper (not shown).

When the applied voltage is returned to a constant voltage again, the internal volume of the ink chamber 1 decreases and returns to its original state (F).

Note that it is the ink particle 3 that finally returns the applied voltage to a constant voltage.
The applied voltage may be applied after the ink droplet 31 is cut off from the nozzle 3, but in order to stably perform the ink ejection operation for the next dot, the applied voltage should be returned to a constant voltage immediately before the ink droplet 31 is cut off from the nozzle 3. , it is better to return the meniscus to its original state.

In this way, nearly circular dots as shown in FIG. 8 are formed on the recording paper.

FIG. 9 shows changes in the voltage applied to the piezoelectric element 21 (drive waveform), the displacement of the meniscus (X), and the meniscus velocity (ΔX). The meniscus displacement X is shown in FIG. 7(C).

The diagram in FIG. 9 starts from the point where the print command is input and the internal volume of the ink chamber 1 is increased (
T=O). At this time, the meniscus vibrates at a resonance period T unique to the head, so after 0°5T time, the piezoelectric element is electrically charged again to contract, and the displacement of the meniscus moves toward the outside of the nozzle 3 at a speed Accelerate to eject ink.

The ejected ink then continues to fly outward due to inertia, whereas the meniscus velocity acts in a direction to direct the meniscus toward the ink chamber 1 after 0.75T has elapsed.

From this point on, a suction force, ie, a cutting force, begins to act on the ejected ink. Then, when time T has elapsed, the suction force becomes maximum. In this embodiment, the piezoelectric element 21 is driven (discharged) so as to increase the internal volume of the ink chamber 1 at this time.
I'm letting you do it. As a result, as shown in FIG. 9(a), a larger suction force is instantaneously generated against the ink droplets, and the ink is quickly cut off to form short ink droplets.

[Effects of the Invention] According to the inkjet head driving device of the present invention, the internal volume of the ink chamber is first increased and then restored to its original size to cut the ink from the nozzle, thereby increasing the flying speed of ink particles. This makes it possible to improve the positional accuracy of the dots, and since the internal volume of the ink chamber is increased again before the ejected ink is cut off from the nozzle and the ink is cut off from the nozzle, there are no satellite particles. In addition, ink particles can be cut into short lengths. As a result, a beautiful dot shape close to a circular shape is obtained, which has the excellent effect of allowing high-quality printing to be performed at high speed.

[Brief explanation of the drawing]

Fig. 1 is a diagram of the principle of the present invention, Fig. 2 is a schematic diagram of the head of the embodiment, Figs. 3 and 4 are cross-sectional views of the ink chamber of the embodiment, and Fig. 5 is the configuration of the applied voltage control circuit. Figure 6 is a time chart of the applied voltage control circuit, Figure 7 is an enlarged diagram showing the movement of ink in the example, Figure 8 is an enlarged diagram showing the dot shape in the example, and Figure 9 is the actual example. 10 and 11 are cross-sectional views of the ink chamber of the conventional example; FIG. 12 is an enlarged view showing the movement of ink in the conventional example; 13. Figure 14 is an enlarged diagram showing the dot shape of the conventional example. Figure 14 is a diagram showing the drive waveform of the conventional example. Figure 15 is an enlarged diagram showing the movement of ink in the conventional example. Figure 16 is the dot shape of the conventional example. The enlarged view shown in FIG. 17 is a diagram showing drive waveforms of a conventional example. In the figure, ■... Ink chamber, 2... Ink chamber internal volume control means, 3... Nozzle.

Claims (1)

[Scope of Claims] An ink chamber (1) containing ink, an ink chamber internal volume control means (2) for changing the internal volume of the ink chamber (1), and an ink chamber communicating with the ink chamber (1). The ink chamber (1
); and a nozzle (3) that ejects ink outward from the ink chamber (1) according to a change in the internal volume of the ink chamber (1), wherein the ink chamber internal volume control means (2) controls the contents of the ink chamber (1). an ink ejecting operation of ejecting ink from the nozzle (3) by returning to the original state after increasing the product; and before the ink ejected from the nozzle (3) is cut off from the nozzle (3). An inkjet head driving device characterized in that the internal volume of the ink chamber (1) is increased again and an ink cutting operation is performed to cut the ejected ink from the nozzle (3).