JPH0342187B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inkjet recording apparatus, and more particularly to a bubble removal method for removing harmful bubbles in a flow path.

An inkjet recording device that performs recording by ejecting liquid ink from a nozzle is expected to be a recording device that produces less noise and can record on plain paper.
However, air bubbles generated in the ink have adverse effects such as deterioration of printing quality and inability to eject ink.
In particular, in ink-on-demand type ink jets using piezoelectric elements, the influence of air bubbles is very large.

Conventionally, harmful air bubbles generated in the recording head are sucked out along with the ink by a vacuum device placed in contact with the front surface of the nozzle, or are flushed out along with the ink from the nozzle by pressurizing the ink container. However, once air bubbles form on the wall of the ink channel, a non-ink surface 2 is formed that is not wetted by ink 1, as shown in Figure 6, and even if ink 1 is flowed in the direction of the arrow, the air bubbles 3 will only deform, making it difficult to Non-ink surface 2 of channel wall 4
I couldn't get rid of it. Particularly when the recording head is made of plastic, which is easily mass-produced, the wettability of the ink to the channel walls tends to decrease, making it difficult to remove air bubbles.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for removing air bubbles that easily discharges harmful air bubbles adhering to the inner wall of an ink flow path from a nozzle.

The gist of the present invention is to cause a liquid containing a large number of bubbles to flow in an ink channel, and to discharge harmful bubbles from a nozzle along with the large number of bubbles, thereby eliminating non-ink surfaces on the walls of the ink channel. be.

An embodiment of the present invention is shown in FIGS. 1 and 2. FIG. Figure 1 shows the attempt to remove harmful bubbles, and Figure 2 shows the
The figure shows normal ink ejection after removing harmful air bubbles.

In Fig. 1, 1 is ink, 2 is a non-ink surface formed on a part of the wall 4 of the ink flow path, 3 is a harmful air bubble, 5 is a recording head, 6 is a nozzle, and 7 is an ink container (Fig. 2). 10) and a connecting needle with the foam container 8, 8 is a foam container made of soft polyethylene made by blow molding, and 9 is a cleaning foam. The foam container 8 contains approximately 1/3 of the volume of a 20% sodium oleate aqueous solution and 2/3 of the volume.
3 air is sealed. When harmful air bubbles 3 are generated and ink ejection becomes impossible, the user shakes the foam container 8 strongly to generate cleaning foam 9 inside the foam container 8. The ink container 10 is removed from the coupling needle 7, the foam container 8 is coupled to the coupling needle 7 instead, and the foam container 8 is pressurized with a finger. The cleaning foam 9 in the foam container 8 passes through the connecting needle 7 and flows out from the nozzle 6 through the ink flow path.
At this time, the harmful air bubbles 3 are discharged from the nozzle 6 together with the cleaning foam 9, the non-ink surface 2 disappears, and the channel wall 4 is completely wetted with the sodium oleate aqueous solution.

Next, remove the foam container 8 from the connecting needle 7, and insert the ink container 10 made of a polyethylene bag into the connecting needle 7.
Connect as shown in the figure and pressurize the ink container 10 with your finger to push out the cleaning foam and sodium oleate aqueous solution from the ink 6 in the ink flow path. When the ink 1 fills all the ink channels, normal recording operation begins.

Next, specific effects of the above embodiment will be described.
With harmful air bubbles 3 generated in the ink flow path and a non-ink surface 2 formed, the ink fuser 1 is removed as shown in FIG.
The ink container 10 was pressurized to about 1 mm with a pressure of about 30 KPa while the ink container 10 was kept attached to the coupling needle 7, but harmful air bubbles could not be discharged. Next, replace all the ink in the ink container 10 with a 20% sodium oleate solution.
Although the pressure was applied at 30KPa for about 1 minute, harmful bubbles could not be expelled. However, as in the embodiment shown in FIG.
When the ink was flowed into the ink channel for about 5 seconds at a pressure of 1KPa,
After the harmful air bubbles were discharged, ink was flowed for about 5 seconds, and all the cleaning bubbles were discharged from the nozzle 6, and the ink flow path was completely filled with ink.

As mentioned above, it is much more effective to remove harmful air bubbles by mixing a large number of air bubbles with a surfactant than by simply flowing ink or surfactant. The reason for this is not necessarily clear, but the adsorption force between the cleaning foam and harmful air bubbles is strong, and the apparent viscosity decreases because the speed at which the cleaning foam passes through the ink flow path is faster than the speed at which the liquid passes through the ink flow path. It is thought that the cleaning foam volume changes as the cross-sectional area of the ink flow path changes, causing the cleaning foam to flow to every corner of the flow path, and that the cleaning foam collides with harmful air bubbles and blows them away.

There is a question that the cleaning foam may remain in the flow path and become harmful bubbles, but this is not a problem at all. This is because it is difficult to expel harmful air bubbles.
This is because the non-ink surface 2 exists, and if the flow path wall 4 is completely wetted with the ink 1, the bubbles are extremely easily discharged from the nozzle 6 together with the ink 1. In other words, when the harmful air bubbles 3 are discharged with the cleaning foam 9, the non-ink surface 2 is wetted with the sodium oleate aqueous solution, which mixes with the ink that flows next, and the ink channel wall 4 is completely wetted with ink, so that no air bubbles remain. be.

FIG. 3 shows a foam container according to another embodiment of the present invention.
41 is a bellows with a ventilation hole 42 at one end,
The other end is long and extends into an air chamber 44 of the cleaning liquid container 43.
is connected to. The cleaning liquid container 43 is a porous member 4
5 into an air chamber 44 and a cleaning liquid chamber 46. The cleaning liquid chamber 46 is filled with an aqueous solution of sodium oleate. In the above configuration, in the same way as the example shown in FIG. 2, when harmful air bubbles are generated, the cleaning liquid container 43 is connected to the coupling needle 7 as shown in FIG. The air in the bellows 41 passes through the air chamber 44 and through the pores of the porous member 45 into the cleaning liquid chamber 46 as shown by the arrow, generating a large number of cleaning bubbles 48 in the sodium oleate aqueous solution. This cleaning bubble 48 flows into the ink flow path through the coupling needle 7 and discharges harmful bubbles.

The embodiment shown in FIG. 3 is different from the embodiment shown in FIG.
Although it is mechanically complex, it is unnecessary for the user to shake the foam container, and when the user removes his or her finger to stop pressing and the bellows 41 returns to its original shape, the air is passed through the ventilation hole 42 to the outside. Since the air flows into the bellows 41, the air does not flow backward from the nozzle 6 shown in FIG. Therefore, there is no possibility that the nozzle will become clogged due to the inflow of external dust or the like from the nozzle 6.

FIG. 4 shows another embodiment of the invention. In this example, the cleaning liquid container 51 is almost the same as the foam container 8 of FIG. 1, but it is filled with an aqueous surfactant solution 52 and does not contain air. When harmful air bubbles are generated, the cleaning liquid container 51 is connected to the foam container 7, and the cleaning liquid container 51 is pressurized in the direction of arrow A with a finger. When the finger is then released, the cleaning liquid container 51 returns to the direction of arrow B, sucks air bubbles from the tip of the nozzle 6, and generates cleaning foam 53. By repeating the movements of arrows A and B several times, harmful bubbles 3 and cleaning bubbles 5 can be
3, and the non-ink surface 2 disappears. According to this embodiment, since cleaning bubbles are created by the backflow of surfactant from the nozzle 6, the structure and operation are simple.

FIG. 5 shows another embodiment of the invention. 61 is a polyethylene ink container made by blow molding, and 62 is a ventilation hole, which is made into a long and thin hole to hold the ink 1.
evaporation is suppressed. Specifically, the diameter is 0.2mm
If the length is 5 mm or more, if the diameter is 0.4 mm, the length is 15
mm or more, if the diameter is 0.6 mm, the length is 30 mm or more,
1g per year at 60℃ even with the vent open
The amount of water evaporation can be as follows. ink 1
contains a surfactant to wet the channel walls 4 of the head.

In the above configuration, when normal ink ejection is performed, as ink is consumed, the vent hole 62
External air flows into the ink container through the ink container.
When harmful bubbles occur in the ink flow path, hold the ink container 61 in the connecting needle 7 and press the index finger 63.
to close the ventilation hole 62, and press the side wall of the ink container 61 in the direction of the arrow with the thumb 64 and middle finger 65. When the pressure is released, the ink container made by blow molding returns to its original shape due to its own elasticity. Therefore, by repeating this operation several times, the air bubbles sucked in from the nozzle tip become cleaning bubbles and peel off the harmful air bubbles from the inner wall of the ink flow path, as in the embodiment shown in FIG. Thereafter, while blocking the ventilation hole 62 with the index finger 63, strong pressure is applied with the thumb 64 and middle finger 65, and the cleaning foam in the flow path is discharged from the nozzle together with the harmful air bubbles and ink. Then release the index finger 63 and thumb 6
4. If the middle finger 65 is released, there is no backflow of air from the nozzle, the ink flow path is filled with ink, and ink can be ejected. The embodiment shown in FIG. 5 has the advantage that since the ink itself serves as the cleaning liquid, there is no need to prepare a separate cleaning liquid or its container, and the structure is simple.

In each of the above embodiments, a method is described in which the cleaning liquid is pushed out from the ink supply section side, but a method in which the cleaning liquid is sucked out from the nozzle side using a vacuum may also be used. Further, although sodium oleate is used as the cleaning liquid, various other surfactants may be used.

It is also conceivable to automate the generation of cleaning bubbles by using a combination of a solenoid-driven pump and a pulp that switches the flow paths between the ink and the cleaning liquid, instead of manually.

As can be seen from the above description, according to the present invention, a large number of cleaning bubbles are made to flow in the ink flow path, harmful air bubbles are peeled off from the flow path wall, and the flow path wall is wetted with ink. Stable ink ejection is made possible by expelling harmful air bubbles from the nozzle along with cleaning bubbles. The present invention can be applied to various devices such as printers, plotters, facsimile machines, and copying machines.

[Brief explanation of drawings]

1 and 2 are diagrams showing one embodiment of the bubble removal method of the present invention, FIG. 3 is a diagram showing another embodiment of the present invention, and FIG. 4 is a diagram showing still another embodiment of the present invention. FIG. 5 is a diagram showing still another embodiment of the present invention, and FIG. 6 is a diagram showing a conventional bubble removal method. 1... Ink, 2... Non-ink surface, 3... Harmful bubbles, 4... Channel wall, 8... Foam container, 9,48,
53...Cleaning foam, 10,61...Ink container, 4
3, 51...Cleaning liquid container, 52...Cleaning liquid.

Claims (1)

[Scope of Claims] 1. A method for removing air bubbles from a recording head having a nozzle for ejecting liquid ink and a flow path communicating with the nozzle, wherein the flow path in the recording head is provided with an inner wall of the flow path. A liquid that thoroughly wets the skin and a large number of cleaning bubbles contained in the liquid are forced to flow, and the liquid containing the cleaning bubbles is forced to flow together with the bubbles staying in the flow path. Eject from recording head,
A method for removing air bubbles, characterized in that the flow path of the recording head is then filled with the liquid ink.