JPH0480037A - Driving method of ink jet recorder - Google Patents

Abstract

PURPOSE:To restrain dispersion in a jet direction of ink and make an ink receiving component useless for a non-printing area by a method wherein an electric signal of a range within which ink never jets out at the same timing into non- printing area from all nozzles to be used for printing is applied to an energy generating element. CONSTITUTION:Though a nozzle from which no ink jets exists in a printing area, microvibration is given to piezoelectric elements 7 of a group of all print ing nozzles 5 by applying an electric signal of a range within which no ink jets at same timing to the piezoelectric elements 7 of the group of all printing nozzles 5 in non-printing area, and ink is made to ooze around their nozzle holes. By making ink reservoirs around the nozzle holes of the group of all printing nozzles homogeneous thus prior to printing, a fly angle of an ink drop from the printing nozzle is stabilized in the printing area even in initial printing. An electric signal to be applied to the piezoelectric element 7 of the printing nozzle 5 in non-printing area is varied, concretely, as follows, (1) discharge time Pwd is shortened, (2) drive voltage VH to be applied to the piezoelectric element 7 is lessened, (3) discharging resistance is increased, (4) charging resis tance is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for driving an inkjet recording apparatus used in a printer or the like, which performs recording by ejecting ink according to an input signal.

[Conventional technology]

An ink ejection head used in a conventional inkjet recording device is shown in FIG. 1, a substrate 1 having grooves corresponding to flow paths formed therein.
The ink flow path and nozzle 5 are formed by welding a substrate 2 made of the same material as the ink flow path and the nozzle 5. Ink is supplied from an ink tank not shown in the drawings through the ink supply port 3 and filled into the ink supply preparation chamber 4. This ink supply preparation chamber 4 is connected with a supply pipe 1 for each nozzle, and has branched flow paths.

There is a pressure chamber 6 in the middle of the flow path of the printing nozzle 5, and a piezoelectric element 7 is bonded to the opposite position, and when an electric signal is applied to this, pressure is applied to the pressure chamber 6 through the substrate 2, and the nozzle tip 51
Ink droplets are ejected from.

When a signal is applied to the piezoelectric element 7 and an ink droplet is ejected from the nozzle tip 51, the ink spreads around the nozzle hole on the nozzle surface to form an ink wall.

The wall of ink generated during ink ejection has a large effect on the ejection angle of the ejected ink droplets.

Specifically, as shown in the front view of FIG. 2(a) and the side view of FIG. 2(b), when an uneven pool of ink occurs around the nozzle hole, the ejected ink droplets are It becomes a wall and is pushed by the smaller ink pool as it flies. This phenomenon occurs particularly at the beginning of a line feed, etc. In the printing area shown in Figure 3, if there are two or more idle nozzles consecutively on the same nozzle surface as shown in Figure 4 (&''),
), a non-uniform wetting (ink puddle 10) is formed. Although this wetting is once drawn into the nozzle in the non-printing area, it does not disappear completely and a thin ink layer 101 is formed as shown in FIG. 4(C). For this reason, when ink is ejected from the dormant nozzle in the printing area again, the ink pool around the nozzle hole of the dormant nozzle is the fourth in the initial stage of printing.
As shown in Figure (d), the ink droplets are attracted to the smaller side of the puddle, causing the ink droplets to fly towards the target, and printing continues for some time until the size of the ink puddle becomes approximately the same, as shown in Figure 4 ( The flight becomes stable as shown in e). Conventionally, as a countermeasure against this problem, a method has been adopted in which ink droplets are periodically ejected in the non-printing area to form a stable wet state.

[Problem to be solved by the invention]

However, with conventional methods, ink droplets are wasted in non-printing areas, resulting in high ink running costs, and a member or waste ink reservoir is required to catch the ejected ink droplets in these non-printing areas. This has been a problem when miniaturizing printers.

[Means to solve the problem]

In order to solve the problem with the inkjet head of the present invention, all nozzles are driven at the same timing in the non-printing area by applying an electric signal within a range that does not cause ink to jump out to their piezoelectric elements, and printing is performed. The present invention is characterized in that the ejection angle of ink droplets of the printing nozzle group during printing is controlled by uniformly wetting the periphery of the nozzle holes of the printing nozzle group with ink before the timing.

[Effect]

When the nozzles are arranged as described above and a plurality of printing nozzles are used for printing in the printing area, the non-printing nozzle is placed at the same timing as the piezoelectric element of the printing nozzle used for printing.
When driven by applying an electric signal within a range that does not cause ink to fly out, the ink pool that oozes from the non-printing nozzle hole connects with the ink pool around the printing nozzle hole, making the wetting by ink around the nozzle hole of the printing nozzle group uniform. Therefore, it is possible to control the ink ejection angle and eject ink in a direction perpendicular to the nozzle surface.

〔Example〕

In this embodiment, as shown in FIG. 5, even if there is a nozzle that does not eject ink in the printing area [FIG. 5(a)],
In the non-printing area, the piezoelectric elements of all the printing nozzle groups are given an electrical signal in a range that does not eject ink at the same timing, giving slight vibrations to the piezoelectric elements of all the printing nozzle groups,
Let the ink smear around the nozzle hole [Figure 5 (b)
)).

This makes the ink pools around the nozzle holes of all printing nozzle groups uniform before printing, thereby stabilizing the flight angle of the ink droplets of the printing nozzles in the printing area even in the early stages of printing [Figure 5 ( c)), Figure 5 (d) and (e)
The state is repeated as in (a) and (b) above.

Figure 6 shows another example in which all printing nozzles are driven to the extent that no ink drops are ejected in the non-printing area by changing the driving conditions of the piezoelectric elements of the printing nozzles between the printing area and the non-printing area. This is an example. FIG. 6(a) shows the driving waveform of the piezoelectric element of the printing nozzle group. vH is the drive voltage applied to the piezoelectric element, Pwd is the time required for the charge to be discharged from the piezoelectric element, Pwc is the time required for the piezoelectric element to be charged, and the discharge curve A and the charge curve B are the capacitance of the piezoelectric element and These curves are caused by discharge and charging resistance and the drive voltage applied to the piezoelectric element. In the standby state, voltage VH is applied in the direction that the piezoelectric element contracts, causing the piezoelectric element to bend. When the voltage applied to the piezoelectric element is released, the voltage element no longer bends, and the pressure inside the pressure chamber is reduced, causing the pressure near the nozzle to decrease. Ink is supplied from the ink and ink supply path.

Next, when voltage is applied to the piezoelectric element again, the piezoelectric element contracts and pressure is applied to the ink, causing the ink to be ejected from the nozzle. Thereafter, due to the surface tension in the nozzle, ink is supplied and the meniscus is stabilized at the nozzle orifice, and the nozzle enters a standby state. In this embodiment, the printing energy in the non-printing area is made smaller than the energy applied to the piezoelectric element in the printing area by changing the driving conditions for the piezoelectric element, and the piezoelectric element is applied to the piezoelectric element to the extent that ink droplets are not ejected. This gives gI vibration to. Specifically, the electrical signal applied to the piezoelectric element of the printing nozzle in the non-printing area is changed as follows.

(1) Shorten the discharge time Pwd. Figure 6(b)(2)
The drive voltage VH applied to the piezoelectric element is reduced. Figure 6 (
c) (3) Increase the discharge resistance. Figure 6(d) (4) Increase the charging resistance. 6 (e), when multiple nozzles are used for printing simultaneously on the same substrate, by driving all the nozzles under the above conditions in the non-printing area, the ink is released from the nozzle holes. The ink cannot be ejected, and the ink smears around the nozzle holes, and the ink pools around the nozzle holes of the print nozzle group become uniform before the printing timing.

Note that in the case of the recording medium liquid ejection method in which an electrothermal transducer is provided in the flow path instead of the piezoelectric element and the ink in the nozzle is ejected using thermal energy, the same applies.
The same effect as in the above embodiment can be obtained by changing the driving current and voltage application time so as to apply energy to the heat generating part in the flow path of the printing nozzle in the non-printing area to the extent that the ink does not fly out. It will be done. The present invention does not limit the type of drive source.

〔Effect of the invention〕

As explained above, the inkjet head of the present invention has the effect of suppressing variations in the ink ejection direction by making the ink pools around all printing nozzle holes uniform in the non-printing area before the printing timing. Further, since unnecessary ink droplets are not ejected, ink can be used effectively only for printing. Furthermore, since no member such as an ink receiver is required in the non-printing area, a compact printer can be realized.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a conventional device. FIGS. 2 and 4 are diagrams showing the state of ink accumulation around a nozzle hole in a conventional device. FIG. 3 is a diagram showing print areas and non-print areas in a conventional device. FIG. 5 is a side view of the nozzle hole, showing the state of ink accumulation around the nozzle hole in this embodiment. FIG. 6 is a detailed explanatory diagram of the present invention. 1...First substrate 2...Second substrate 3...Ink supply port 4...Ink supply preparation chamber 5...Printing nozzle 6...Pressure chamber 7...Piezoelectric element Figure 2 Figure 3 (c) (d) (e) Figure 4 (c) (d) Figure 5

Claims (1)

[Claims] An inkjet in which a substrate is formed with a closed groove to serve as an ink flow path, and the flow path is composed of a plurality of pressure chambers and a group of nozzles corresponding to the pressure chambers, and a driving source is provided at a position corresponding to the pressure chambers. 1. A method for driving an inkjet recording device, characterized in that all nozzles used for printing in the recording device apply electrical signals within a range that does not cause ink to jump out at the same timing in a non-printing area to an energy generating element.