JPS59140068A - Method for filling up ink into ink jet recorder - Google Patents

Abstract

PURPOSE:To initially fill up ink with a little mixture of bubbles, by a method wherein an ink circulation system is filed up with ink by operating a pump under the condition where the nozzle front surface of ink jet head is closed by means of cleaning, and then the front surface of nozzle is opened. CONSTITUTION:When ink is initially filled up from a tank 11 to a head 13 after carrying out the exchange or the like of ink tank 11 and ink jet head 13, at first a pump 12 is operated by making the means of cleaning 17 in close contact to the nozzle part on the front surface of head 13, and the ink is circulated via the reservoir 24 of head 13 and a valve 14 from the tank 11. Thereafter, the means of cleaning 17 is separated from the front surface of head and the ink is filled up to the nozzle part 33 via pressure chambers 22 from the reservoir 24.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ink filling method for an inkjet recording apparatus that performs recording by directly jetting ink onto a recording medium.

In the past, many attempts have been made to research and improve inkjet recording, and some of them have reached the point of practical application.

As known from many documents, inkjet valve control can be broadly classified into the following two methods.

One method is to divide ink into continuous regular particles, apply an electric direction to the ink particles, and deflect them in an electrostatic field to record predetermined characters or the like.

The other one is to make part of the ink chamber of the jet head a flexible wall,
By bending the wall sharply in response to an electric pulse, ink is ejected toward the entire recording medium in the ink chamber to perform recording (on-demand system disclosed in JP-A-51-55251).

In the former, the means to create regular ink droplets is complicated;
In addition to requiring commercial voltage for deflection, it also has the disadvantage of making the device larger and more complex, such as collecting unnecessary ink that is not used for recording, but it is advanced in principle and is currently in practical use. Most things are of this type.

On the other hand, in the latter case, ink is ejected in response to a restraint pulse only when necessary, so unnecessary ink is not generated all at once, which is not only efficient, but also eliminates the need for cylinder voltage for deflection, so the device can be simplified. Therefore, it can be made into a compact, low-cost recording device. However, there are many practical examples of this method;
The level of perfection as a product is also low. The reason for this is due to deficiencies in peripheral devices including the structure of the ink jet head.

In a conventional example of this Yuzu head, as shown in Figure 1, a common ink chamber 2, a pressure chamber 5, a nozzle 4, etc. are formed as shallow grooves by etching or other methods on a substrate 1 such as glass, and the upper part of the pressure chamber 5 is A piezoelectric element 5 is disposed in the ink, and by applying an electric pulse 6 according to a recording signal to the piezoelectric element, mechanical displacement is caused to increase the liquid pressure of the ink in the pressure chamber, and the ink is ejected from the nozzle 4. As is clear from this principle, ink is ejected only when an electric pulse is applied, and H
Unlike IJ, there is no unnecessary ink generation, and the device is very simple. However, on the other hand, ink jetting is not performed normally. Alternatively, troubles such as ink clogging near the nozzle may occur. To explain these in detail, it is clear from the principle that ink ejection cannot be performed normally unless the ink liquid pressure in the pressure chamber reaches a required value.

This condition can occur if air bubbles are mixed in the ink near the pressure chamber. This is because the bulk modulus of air is extremely smaller than that of ink (water). Further, regarding clogging, it is disadvantageous because the nozzle 5 is relatively small and the ink pressure during ink ejection is lower than that of the continuous particle generation type.

The problem of clogging of the nozzle has been solved by putting a lid on the tip of the nozzle. However, the structure of the lid is often complex. Concerning the 611 persons, no complete information has been obtained regarding prevention of air contamination and countermeasures in case of contamination. These shortcomings have delayed the practical application of the on-demand method.

The above-mentioned inclusion of air bubbles will be explained in more detail. Conditions for bubbles to occur include, first, when the flow of ink is stagnant at some point during the initial filling of ink into the head, bubbles are generated due to unfilled ink. This is due to the head structure, and the head of tights (double cavity type), in which the liquid is divided into two, as shown in JP-A No. 48-9622, completely fills the initial filling. Therefore, it is necessary to have a liquid chamber structure that is easy to fill with ink.During operation, air bubbles may be sucked in from the nozzle due to impact, etc.Furthermore, there is a problem with the tubes leading from the ink tank to the head, etc. Air bubbles may be introduced due to evaporation of ink from the piping section.Air bubbles may also be introduced when replacing the ink tank.

It will be difficult to put the recording device into practical use unless the means for removing bubbles is rational and simple to take advantage of these possible situations. Conventional methods to prevent air bubbles from entering include preventing initial unfilling by improving the head structure, increasing the amount of agent to prevent air bubbles from entering when replacing the tank, and using deaerating ink, but all of the above cases can be addressed. The fact that no air bubbles are mixed in is similar to Komachi Noh. Even if one improves the head structure, the above-mentioned double cavity type ink filling means is extremely complicated (% 15159/1983), and there are also examples in which air bubble traps, etc. are installed in the middle of the piping. Not only is it large and complicated, but it is less effective against microbubbles. On the other hand, as a means for controlling air bubbles, a method has been adopted in which air bubbles are discharged from the nozzle tip together with the ink, but this is undesirable as it consumes a large amount of wasted and wasted ink.
1-55251).

As another example, in the case of the exhaust device in the head described in JP-A No. 52-49052, there is a risk that air bubbles accumulated at the top may enter the nozzle due to an impact, or the wall surface of the exhaust pipe may The adsorbed microbubbles are difficult to float to the top, and the ink must be made to flow in order to be discharged, resulting in wasted ink consumption. Furthermore, depending on the inclination of the head (the posture of the device), it is difficult for air bubbles to float.

In order to eliminate the drawbacks of the various conventional examples mentioned above, Japanese Unexamined Patent Publication No. 54-1
No. 59227 and Japanese Patent Application Laid-open No. 160142/1984 propose a method of removing air bubbles while circulating ink. In both of these methods, a pump means is provided in the middle of the ink supply path to forcibly flow the ink to remove air bubbles and, in some cases, to eliminate clogging, but they have several drawbacks.

Regarding JP-A-54-159227, the specification No. 2
If you drive the pump with the configuration shown in the figure, some ink will always be 7%.
/ Inject from X Le Nz. However, air bubbles were found in the tube near the ink tank. In this case, in order to circulate these bubbles together with the ink and discharge them into the ink tank, a corresponding amount of paper ink is consumed through the nozzle NZ. Therefore, in the same embodiment, head 1q
A gutter is installed on the i1 side to collect this consumed ink. However, such a gutter not only reduces the number of parts in the apparatus, but also causes dust, dirt, etc. in the air to be mixed into the recovered ink, reducing the life of the filter 6.

Originally, it is desirable that the ink of Ink@4 be made under sufficiently controlled manufacturing conditions in order to prevent contamination with dirt and to obtain long-term productivity.

In this embodiment, harmful components in the air are likely to be mixed into the ink liquid. In addition, other pump devices or the like are required to promptly guide the ink collected in the gutter to the ink tank, and if this is not done, the gutter will not be able to perform its function. This is a serious drawback, especially when using quick-drying inks suitable for inkjet printing. In addition, two valve system connections are required, and the number of piping connections increases, which is unfavorable in terms of 1-gram pourability and cost.

Next, in Japanese Patent Application Laid-Open No. 54-160242, a large amount of wasted ink is consumed through the nozzle 4 during ink circulation, resulting in poor efficiency. In order to eliminate blemishes, it is necessary to eject ink from the tip of the d nozzle, but in daily use, the most likely cause is air bubbles, and this is caused by air bubbles entering the head from the ink tank. Piping that sends ink (
tube system). That is, when constructing a recording device, in order to make the head movable 5J, it is necessary to make the tube system flexible, and it is necessary to use a plastic tube system.
There will be 14j. However, the water vapor and air permeability of these tubes is quite low, and these values increase significantly, especially at high temperatures, and evaporation of ink can occur anywhere in the tube system, which requires considerable length. obtain. Even a small amount of air bubbles that enter through the tube wall to balance this ink evaporation will adversely affect ink jetting performance if they enter the pressure chamber in the head. Compared to clogging, etc., air bubbles in the tube occur at a much higher probability, and in the IO, l embodiment, during circulation, air bubbles in the tube are not always reliably discharged into the ink tank, and may be sent into the head. can also be considered. At this time, if air bubbles climb up the head structure, they may accumulate in the corners of the head, and the air bubbles may no longer function as a bubble remover. Therefore, it is preferable to completely expel the air bubbles in the tube and then flow the ink into the pressure chamber side of the head.

Furthermore, in the configuration of FIG. 1 of the same embodiment, in addition to the frequent use of ID valves, there are many complicated features such as bypasses in the pump section.

The present invention eliminates the above-mentioned drawbacks by improving the head structure and creating an extremely simple means for removing air bubbles, thereby achieving reliable and efficient air removal and complete ink filling. .

Specific examples of the present invention will be described below based on human examples. FIG. 2 schematically shows the configuration of the recording apparatus of the present invention. In the figure, 11 is the ink tank 12, which is the 10th stage.
16 is a recording head, 14 is a square, and 15 & 16 are piping such as tubes. Furthermore, a cleaning means 17 is provided on the front surface of the head 15 so as to face the head 16 at a position away from the range where the head 15 performs the cleaning. In the head 16 of the present invention, as shown in FIG. 6(a), grooves for the pressure chambers 22, nozzles 25, etc. are formed by etching on both sides of a glass substrate 210, and a comparison is made in which the ink is guided to the pressure chambers 22 of JL et al. Ink is supplied from the vibrators 15 and 16 via an ink reservoir m24' having a large internal volume. To describe the structure of this head in a little more detail, a glass piece 25 of the same thickness as the glass substrate z1 with grooves formed on both sides is placed side by side as shown in FIG. 6(b), and a diaphragm ( Relatively thin glass plates 26 and 27, which will become the flexible walls (El flexible walls), are bonded together by a method such as fusion bonding. At this time, the glass substrate 24, the glass piece 25, and the glass plate 26.2
7 forms a reservoir 24. Therefore, this space has a sufficiently large volume and has a small resistance to the ink fluid compared to the etched groove portions of the pressure chamber 22, nozzle 25, etc., which have a depth of 1 μm to several 100 μm. Furthermore, by simultaneously forming a part of the filter 29 by enching between the reservoir 24 and the pressure chamber 22, the configuration can be simplified without requiring a filter in the middle of the pipe as seen in the embodiment described in m. It will be done. Above the diaphragms 26 and 27 (the part corresponding to the pressure chamber 22) there is pressure! An element (not shown) is arranged so that ink flows into the nozzle 23 according to the electric pulse.
Points such as being injected from
-552.51 etc.). In order to improve the light jetting properties of the ink, island-shaped protrusions 28 are provided at the front and rear of the circular pressure chamber 22 to direct the flow of ink along the wall surface as shown by the arrow.

FIG. 2, FIG. 6 I/c Therefore, the operation of filling ink in the recording apparatus will be described. The cleaning means 17 made of a member such as rubber is connected to the nozzle 2514i when recording is stopped.
It has a can on one side and can also serve as a lid means to prevent clogging due to drying of ink in the nozzle part. Although various structures for the cleaning means 17 are conceivable, a rotary cleaning device having a notch 18 (one stage is shown as an example) is suitable for the purpose of the present invention.
Now, when you are about to start recording (prepare the initial light or when replacing the ink tank, etc.), rotate the bonder 12 while keeping the lid means 17 close to the nozzle part. . Force〕14 is a structure that normally remains open (normally open valve)
By setting the ink to the ink tank, the ink circulates from the ink tank 11 to the head 15 (reservoir) to the ink tank 11, and at this time, the air bubbles in the tubes 15 and 16 are also discharged into the ink tank 11 along with the ink, and the air bubbles are removed from the air bubble vent hole 19 of the ink tank.
ρ) are excluded from the outside. It is desirable that these vent holes be made of a collection of sufficiently small holes or that an air filter or the like be installed in order to prevent people from entering the room. In this state, inside the tube 15, 16 and part 2 of the 9 parts of the head 15.
The air bubbles in step 4 are completely removed without wasting a single drop of ink. Furthermore, this circulation also has the effect of refreshing the entire ink. [7] After that, the cleaning means 17 is rotated to clean the front surface of the head, and the notch 18 is positioned on the nozzle 1 surface as shown by the dashed line in FIG. 2, thereby opening the nozzle.

In this state, by further rotating the bonder 12 fully, a portion of the ink is sent from the reservoir/<-24 to the pressure chamber 22 and the nozzle 25. Since this ink is an ink that does not produce any bubbles in the first operation of the eel, the inside of the head is completely filled with ink just by flowing out a very small amount of ink from the tip of the nozzle 25. Through the series of operations described above, the head becomes ready for recording, and is moved to recording 1iZK by a carriage (not shown) or the like. Here, the valve 14 is the only one that operates, but during normal printing, it remains open and the ink is completely supplied during printing. If the ink remains near the chamber 22 and printing cannot be performed, or if the nozzle tip becomes clogged due to a very long period of idle use, closing the valve 14 and rotating the pump 12 will allow the ink to be pumped. Since the liquid is extruded from the tip of the nozzle 25 at high speed under the same pressure, all troubles caused by air bubbles and clogging can be eliminated. The cleaning means as described above cleans the front surface of the nozzle 25 while it is rotating, but in order to ensure this, the pump 12 is operated while the cleaning means 17 is being rotated.
Since the cleaning means rotates while ink pressure is applied to the nozzle, there is no need to worry about pushing dirt, fluff, etc. into the fine nozzle.

In general, inkjet recording, especially in on-demand printing, the nozzles are fine and the ink droplet jetting speed is relatively slow, and the direction of the droplet jetting is disturbed by the influence of minute dust and residual ink on the front of the nozzle, which affects printing quality. Not as good as that. Therefore, even when removing air bubbles or eliminating clogging, pushing out ink from the nozzle and immediately starting the printing operation in good condition will lead to undesirable results.Especially in a multi-nozzle head like the present invention, where the nozzles are close together. Therefore, the influence of residual ink is large. Therefore, the leaning action as in this embodiment brings about a great effect.

The above series of operations, i.e., ink circulation (bubble expulsion)
→ Nozzle opening resistance ink leaks from some heads → Pulp closure (depending on conditions such as air bubbles and clogging) → The cycle of being in a recordable state does not necessarily have to be performed every time a recording operation is performed, and the recording pause time If the ink circulation is short (when there is little possibility of air bubbles being mixed in), it may be possible to record without ink circulation, or with only a small amount of ink circulation.Also, during initial filling, when replacing the ink tank,
If air bubbles get mixed in due to an unexpected impact, etc., circulate the ink, and in case of clogging due to a long recording stop or air bubbles that are difficult to flow inside the head, you can close the valve and jet ink from the head. A more practical configuration can be achieved by setting the operating mode according to the situation.

For example, it is conceivable to automatically set the operation mode using the built-in tie 4- depending on the length of the recording pause time.

FIG. 4 shows an example in which the above-mentioned components are combined as a recording device. 51, 52, and 55 are frames. For example, a printing standby position is set on the left side of the recording device, and a cleaning means 17 and a bong 112 are installed between the frames 51 and 55.
etc., and a series of operations such as ink circulation will be performed at this standby position. Recording is performed by moving the head 15 to a portion of the grating 54 provided between frames 52 and 55. When recording is finished, return the head 15 to the standby position and close the lid (in this embodiment, the cleaning means 17
Of course, during recording, if data is not received and recording is stopped for a long time, return the head 15 to the standby position (and close the lid). By setting it in place, it is possible to immediately respond to ink circulation, etc. at the start of recording.

If the lid is not used as the cleaning means 17, the lid may be installed on the left side of the cleaning means 17.

As explained above, the present invention is a method for solving the problem of air bubbles, which is a drawback of conventional on-demand type inkjet recording apparatuses.
→Construction of an ink circulation system called an ink tank
This not only makes it possible to fill ink completely eliminating air bubbles in all situations, but also organically combines with the lid of the reservoir to prevent clogging, resulting in a simple configuration and great effects. It will be recognized.

[Brief explanation of the drawing]

FIG. 1 shows an example of a conventional in/out recorder. FIG. 2 shows a schematic configuration example of an ink jet recording apparatus of the present invention. FIGS. 5(a) and 5(b) show an example of a recording head used in the present invention. FIG. 4 shows an example of the recording apparatus of the present invention. 1...Glass substrate 2...Common ink chamber 6...
・Pressure chamber 4... Nozzle 5... Piezoelectric element
6... Drive signal 11... Ink tank 12
...Pump means 15...Recording hand 14...
Valve device 15, 16...Tube 17...Cleaning means 18...Lid notch 19...Bubble removal,
Hole 21...Glass 22...Pressure chamber Z5...
・Nozzle 24...Reservoir part 25...Glass piece 26.27...Thin glass plate 29...Filter 51.52.55...Frame 54...
・Above the platen Figure 1 Figure 2 (0) Figure 3

Claims (2)

[Claims] (1) An ejection head, a part provided in the ejection head and having an ink inlet, an ink outlet, and an ink supply port to a pressure chamber in the head, and an ink tank with the ink inlet and outlet; piping means for connecting the ink inlet and the ink tank, and an ink provided in the middle of the piping means for connecting the ink inlet and the ink tank, for allowing a portion of the ink in the ink tank to flow out of the reservoir and feeding it back into the ink tank. A stopper means forming a circulation system is provided in the middle of the piping means connecting the ink outlet and the ink tank, and is normally open during recording and closed as necessary during the ink circulation. only one valve means, a cleaning means disposed opposite the head at a position outside the recording range, and closing the nozzle of the head within a predetermined period of time during the circulation operation; (a) sealing the nozzle by the cleaning means; (1) driving the pump means while keeping the valve means open; and (c) removing a portion of the reservoir from the ink inlet. (d) Thereafter, the cleaning means is removed from the nozzle, and the flow path from a part of the reservoir to the nozzle is filled with ink. How to fill ink in a recording device. (2) The ink filling method for an ink-end recording apparatus according to claim 1, item 8, wherein the cleaning means also serves as a means for closing the nozzle while recording is stopped.