JP2006281532A - Inkjet printing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet printing apparatus which can remove air bubbles without deterioration of an ink, can prevent foreign substances caused by the deterioration of the air bubbles and the ink from reaching an inkjet head, and can perform a delivery which does not increase the ratio of non-delivering from the inkjet head. <P>SOLUTION: The inkjet printing apparatus has a circulation passage for the ink, a distributing instrument 28 for the ink provided in the circulation passage, the inkjet head 29 provided in the distributing instrument, and a deaerating means 20 provided in the circulation passage. In the inkjet printing apparatus, the deaerating means exists at the highest position among the circulation passage, the distributing instrument and the inkjet head. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet printing apparatus having a device for supplying ink to a head in an ink jet printer.

In an ink jet printer, bubbles are present in the supply path due to dissolved gas in ink, ink filling (for the first ink filling or ink type replacement, etc.), ink jet head replacement, permeation from an ink supply member such as a tube, etc. There are several reasons why But they are inevitable. If ink is ejected in a state where these bubbles enter the ink jet head, ejection failure such as non-ejection will occur.
For example, air entering the ink supply system not only prevents proper negative pressure control of the inkjet head, but also discharge pressure is absorbed by the air, so that exhaust pressure cannot be secured, and air enters the common liquid chamber of the inkjet head. In such a case, the discharge droplet is not formed, resulting in non-discharge or a splash phenomenon.
For this reason, removing bubbles in the ink supply path is very important in ink jet printing, and a method for this has been proposed.

For example, a proposal has been made that a branch pipe for removing air bubbles is arranged at the top of the ink supply path where air bubbles easily collect, the amount of bubbles is detected, and air bubbles are automatically removed from the branch pipe. (See Patent Document 1)
With this method, workability is improved as compared with the conventional manual bubble removal, so that it is easy to remove bubbles mixed during ink filling and head replacement operations.
In addition, it is possible to remove the gas accumulated in the branch pipe from the dissolved gas in the ink and the permeated gas from the pipe member.
JP 2005-40670 A

Leading bubbles out of the bubble reservoir can achieve the purpose of improving ejection stability at the initial stage of use of the apparatus. However, the deterioration of the ink that has come into contact with the bubbles in the bubble reservoir progresses to some extent and changes to solidified foreign matter. If such foreign matter enters the ink jet head, non-ejection may not be resolved even if maintenance (nozzle recovery processing) is performed, leading to head replacement. In addition, the denatured material of the ink also adheres to the branch pipe valve that has come into contact with the bubbles, causing a malfunction.
Further, the dissolved gas in the ink and the permeated gas from the piping member remain attached to the wall surface of the piping member until they become large bubbles to some extent, and it is difficult to lead to the bubble accumulation by buoyancy.
Therefore, the ink supply path is preferably filled with degassed ink.
Further, when bubbles are removed from the bubble reservoir, ink is always discharged together with the bubbles, so that an ink discharge path is required, and the apparatus becomes complicated.
In view of the above circumstances, an object of the present invention is to remove bubbles without deteriorating ink and prevent foreign matters from reaching the inkjet head due to bubbles and denatured ink. It is an object to enable discharge not to be performed.

The invention described in claim 1
In an ink jet printing apparatus having an ink circulation path, an ink distributor provided in the circulation path, an ink jet head provided in the distributor, and deaeration means provided in the circulation path,
An ink jet printing apparatus, wherein the deaeration means is provided at a highest position among the circulation path, the distributor, and the ink jet head, and includes a hollow fiber membrane through which the ink passes and a pressure reducing means. .

The invention described in claim 2
2. The inkjet printing apparatus according to claim 1, wherein the distributor has a tapered shape in which an inner upper surface has a height that increases from an inlet portion to an outlet portion of the ink.

The invention according to claim 3
The inkjet printing apparatus according to claim 1, wherein a valve is provided between the distributor and the inkjet head.

The invention according to claim 4
The circulation path includes a circulation means for sending the ink from the outlet portion toward the deaeration means, a rectification means for making the ink flow in one direction, and between the circulation means and the rectification means. The inkjet printing apparatus according to claim 1, further comprising a branch pipe for removing air bubbles.

The invention described in claim 5
5. The inkjet printing apparatus according to claim 4, wherein the circulation unit includes a control unit capable of changing an ink flow rate.

  According to the present invention, it is possible to remove bubbles without deteriorating the ink, prevent foreign matter due to bubbles and denatured ink from reaching the inkjet head, and perform ejection without increasing the non-ejection rate of the inkjet head. .

  For this reason, by maintaining stable discharge, the operating rate of the apparatus increases, and the production efficiency can be improved.

  Furthermore, since maintenance for recovery of non-ejection due to mixing of bubbles can be reduced, the amount of ink consumed for maintenance can be reduced, which is economical.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is an overall view of a printing apparatus having an ink supply device for an inkjet head according to an embodiment of the present invention, and includes a primary supply comprising a main ink tank 1, a primary filter 4, a primary degassing unit 6, and a sub tank 7. Part and the secondary supply part after it.
The primary supply unit and the secondary supply unit are connected by a joint 13 having a flow prevention function.

  The main ink tank 1 is provided with an ink outlet 3 and an air communication port 2, and ink in the main ink tank is sent to a primary degassing unit 6 by a liquid feed pump 5 to remove dissolved gas in the ink, It is sent to the sub tank 7.

The sub tank 7 includes an ink inlet 9, an ink outlet 10, an atmosphere communication port 8 (with an electromagnetic valve not shown), a compressed air insertion port 11 (with an electromagnetic valve not shown), and a liquid level sensor (not shown). .
The ink is sent by the liquid feed pump 5 to the compressed air insertion port 11 and the air communication port 8 to be opened, and to a preset position of the liquid level sensor. Here, the preset position of the liquid level sensor is a height that gives a good water head difference to the inkjet head nozzle surface in a state where all ink paths are filled with ink.

  The secondary supply unit is configured by a circulation path in which a distributor for supplying ink to one or more inkjet heads 29 and a deaeration unit are arranged.

Ink from the primary supply unit is sent to the secondary deaeration unit 20 (deaeration means) at the highest position of the ink supply system. The secondary deaeration unit 20 is arranged such that the deaeration part is higher than the ink inlet part and the outlet part. Thereby, it is possible to remove bubbles that have risen due to buoyancy and bubbles that have been sent by circulation by the circulation pump 15 described later.
Further, in the secondary degassing unit 20, a hollow fiber membrane (not shown) is disposed in a housing, and ink passes through the hollow fiber membrane. The casing is depressurized by so-called evacuation, and removes gas in the ink that passes through the hollow fiber membrane. (Example: PF series manufactured by Dainippon Ink and others)

FIG. 2 is a cross-sectional view showing the inside of the distributor.
The distributor is disposed downstream of the secondary degassing unit 20, and the ink 32 degassed by the secondary degassing unit 20 is supplied to the distributor 28. In addition, a valve 33 is provided between the distributor 28 and the inkjet head 29, and is closed when ink is filled and when the head is replaced to prevent ink from flowing out.
Furthermore, the upper surface inside the distributor has a tapered shape 31 that increases in height from the inlet to the outlet. As a result, bubbles in the ink jet head piping and the distributor mixed during ink filling and head replacement can be guided to the outlet side.

The ink 32 in the distributor is sucked out by the circulation pump 15 downstream of the outlet of the distributor. The circulation pump 15 needs to have a low pulsation that does not affect the discharge so that it can operate even during the discharge.
In addition, since the bubbles mixed in the path at the time of ink filling and head replacement are quickly sent to the secondary deaeration unit 20, the pump flow rate can be varied so that the bubbles can be sent at a larger flow rate than during ejection. . Further, by alternating the large flow operation and the stop, impact can be given to the microbubbles, the microbubbles adhering to the wall surface can be pulled away from the wall surface, and sent to the secondary degassing unit 20.

  An air vent branch pipe 17 is provided downstream of the circulation pump. The air vent branch pipe 17 communicates with the atmosphere when the ink is filled, and air until ink reaches the branch pipe can be discharged. After the ink 32 reaches the air bleeding branch pipe, it is communicated with the circulation path.

A reverse support valve 18 is provided on the circulation path side immediately before the merge 19 of the circulation path of the primary supply section and the secondary supply section.
Accordingly, it is possible to prevent ink from the primary supply unit from flowing into the distributor 28 and the inkjet head 29 without passing through the secondary deaeration unit 20.

  The following is a procedure for filling the ink and removing air bubbles from the secondary supply unit during ink filling.

The ink in the main ink tank is sent to the primary degassing unit 6 by the liquid feed pump 5, the dissolved gas in the ink is removed, and sent to the sub tank 7.
The sub tank 7 closes the compressed air insertion port 11 and opens the atmosphere communication port 8, and supplies the ink until the liquid level sensor reaches the set position of the water head difference from the ink jet head nozzle surface.

  Next, all the valves 33 above the ink jet head are closed, and the air vent branch pipe 17 is communicated with the atmosphere.

  In this state, the compressed air insertion port 11 of the sub tank 7 is opened, and the inside of the sub tank is pressurized. As a result, the ink is pushed out from the sub tank 7 and the secondary supply section up to the air bleeding branch pipe 17 is filled with the ink. When the ink is filled up to this point, the air vent branch pipe 17 is communicated with the circulation path.

  Next, all the valves 33 above the inkjet head are opened. As a result, the air in the upper pipe of the inkjet head floats in the distributor 28 and is guided to the distributor outlet 14 along the taper 31 in the distributor. In this state, bubbles are present at various locations in the secondary supply unit.

  In order to remove bubbles in the secondary supply section, all the inkjet head upper valves 33 are closed, the circulation pump 15 is operated at a high flow rate, and bubbles are sent into the secondary deaeration unit 20 together with ink. Thereby, bubbles can be removed.

When the bubbles have been removed, the flow rate of the circulation pump 15 is switched during discharging, and the inkjet head upper valve 33 is opened.
By the above procedure, ink filling and air removal from the secondary supply unit can be performed.

  The following is a procedure for removing air bubbles from the secondary supply unit when replacing the head.

  The valve 33 on the upper part of the ink jet head that is exchanged is closed so that the ink in the distributor does not flow out when the ink jet head 29 is attached / detached, and the ink jet head 29 is exchanged. After the replacement, when the valve 33 is communicated with the distributor 28, the air in the ink jet head and in the connecting pipe becomes air bubbles and rises to the distributor 28, and is guided to the distributor outlet 14 along the taper 31 in the distributor. It is burned.

  In order to remove the bubbles, all the inkjet head upper valves 33 are closed, the circulation pump 15 is operated at a high flow rate, and the bubbles are sent into the secondary deaeration unit 20 together with the ink. Thereby, bubbles can be removed.

When the bubbles have been removed, the flow rate of the circulation pump 15 is switched during discharging, and the inkjet head upper valve 33 is opened.
By the above procedure, it is possible to remove air bubbles from the secondary supply unit when replacing the head.

In addition, there may be a case where minute bubbles due to dissolved gas in the ink or permeation from the pipe member adhere to the inner wall of the pipe and cannot float inside the secondary supply unit due to buoyancy.
The procedure for removing air bubbles in such a case is shown below.

  All the inkjet head upper valves 33 are closed, and the circulation pump 15 alternately performs a large flow operation and a stop. As a result, the microbubbles can be impacted, separated from the wall surface, and sent to the secondary degassing unit 20.

When the bubbles have been removed, the flow rate of the circulation pump 15 is switched during discharging, and the inkjet head upper valve 33 is opened.
By the above procedure, the micro bubbles adhering to the secondary supply pipe can be removed.

  By the above method, there is no bubble accumulation and the secondary supply unit can be filled with ink.

  The above description is effective for quickly removing bubbles. However, in the present invention, the mixed air bubbles are automatically discharged by the secondary degassing unit 20, so that it is possible to perform special operations only by leaving it for several tens of minutes to 2 hours (depending on the performance of the degassing unit). Bubbles can be removed without having to

FIG. 1 is an overall view of an ink supply device for an ink jet head according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the inside of the distributor of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Main ink tank 2 ... Atmospheric communication port 3 ... Ink outlet part 4 ... Primary filter 5 ... Liquid feed pump 6 ... Primary deaeration unit 7 ... Sub tank 8 ... Atmospheric communication port 9 ... Ink inlet part 10 ... Ink outlet part 11 ... Compressed air insertion port 12 Secondary filter 13 Joint 14 with flow prevention function Distributor outlet 15 Circulating pump 16 Air venting air communication port 17 Air vent branch pipe 18 Check valve 19 Ink junction 20 ... Secondary deaeration unit 21 ... Distributor inlet 28 ... Distributor 29 ... Inkjet head 30 ... Substrate transport table 31 ... Taper 32 ... Ink 33 ... Valve

Claims (5)

In an ink jet printing apparatus having an ink circulation path, an ink distributor provided in the circulation path, an ink jet head provided in the distributor, and deaeration means provided in the circulation path,
An ink jet printing apparatus, wherein the deaeration means is provided at a highest position among the circulation path, the distributor, and the ink jet head, and includes a hollow fiber membrane through which the ink passes and a pressure reduction means.   2. The inkjet printing apparatus according to claim 1, wherein the distributor has a tapered shape in which an inner upper surface has a height that increases from an inlet portion toward an outlet portion of the ink.   The inkjet printing apparatus according to claim 1, wherein a valve is provided between the distributor and the inkjet head.   The circulation path includes a circulation means for sending the ink from the outlet portion toward the deaeration means, a rectifying means for making the ink flow in one direction, and between the circulation means and the rectifying means. The inkjet printing apparatus according to claim 1, further comprising a branch pipe for removing air bubbles.   The inkjet printing apparatus according to claim 4, wherein the circulation unit includes a control unit capable of changing an ink flow rate.

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