JP2008194966A - Inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording device in which ink whose dissolved-gas quantity exceeds a predetermined value is not supplied to an inkjet head. <P>SOLUTION: The inkjet recording device comprises an inkjet head 2 for discharging ink droplets according to a signal, an ink tank 1 for storing the ink, an ink supply passage 3 for communicating the inkjet head 2 with the ink tank 1, a deaeration means 5 installed in the ink supply passage, a liquid pumping means installed in the ink supply passage 3 and a sub tank 6 which is installed in the ink supply passage and the position nearest to the inkjet head 2 while enabling the temporary storage of the ink. In the inkjet recording device, dissolved-gas sensors are installed between the sub tank and the deaeration means, and also between the ink tank and the deaeration means, respectively. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus using an ink jet head, and more particularly to ink supply and deaeration means.

  In the ink jet recording technique, in particular, when mechanical power by a piezoelectric actuator is used for ink ejection, cavitation occurs when recording gas contains a predetermined amount or more of dissolved gas, resulting in ejection failure. Therefore, the dissolved gas amount of the recording ink must be adjusted to a predetermined amount or less. As a method for adjusting the dissolved gas amount of recording ink, a method of degassing by reducing the pressure in a vacuum furnace before sealing the ink pouch at the ink cartridge preparation stage is general.

  However, in recent years, in the field of large format printing, the amount of ink consumed is enormous, and the frequency of replacement of a general-purpose ink cartridge having a capacity of 2 L or less cannot be ignored. For this reason, the supply of ink is shifting to a form in which a main tank having a large capacity of about 20 to 50 L is installed and deaerated on the ink jet recording apparatus instead of in the form of a cartridge. As a result, the frequency of cartridge replacement can be reduced, and a degassing step at the time of cartridge production is not required, leading to a reduction in ink manufacturing cost.

  A conventional example of deaeration on an ink jet recording apparatus is shown in FIG. 4 (for example, Patent Document 1). In the ink jet recording apparatus shown in FIG. 4, a large-capacity ink tank 1 communicates with an ink jet head 2 through an ink supply path 3, and in the ink supply path, a liquid feed pump 4 serving as an ink liquid feed means, ink removal, and the like. It is composed of a deaeration unit 5 serving as an air unit and a sub tank 6 for storing deaeration ink, and has a layout as shown in FIG. Although not shown in FIG. 4, the deaeration is performed by reducing the pressure with a vacuum pump.

As a deaeration means, a small vacuum furnace may be installed, but it is suitable for miniaturization to use a deaeration module composed of a hollow fiber bundle made of a gas permeable material and a decompression space. In addition, since stable deaeration quality can be obtained, it is becoming popular in recent years (for example, Patent Document 2).
JP-A-11-48491 JP-A-11-209670

  However, since the conventional method operates without knowing the amount of dissolved gas in the ink, even if the amount of dissolved gas does not reach the predetermined amount when the performance of the deaeration module is poor, ink is introduced into the inkjet head. May end up. In this case, stable ejection cannot be maintained, and stable ejection cannot be restored unless the ink that has been introduced into the inkjet head is wiped out and refilled with ink whose dissolved gas amount is equal to or less than a predetermined amount. That is, waste ink and cost for recovery work are generated.

  The initial dissolved gas amount of ink varies depending on the lot, and the deaeration level by the deaeration module depends on the ink dissolved gas amount at the time of introduction. Specifically, the smaller the amount of dissolved gas at the time of introduction, the shorter the time required to reach a predetermined amount or less. For this reason, in the conventional method, the ink feeding speed is set and operated on the basis of the maximum value of the initial variation in dissolved gas amount. That is, it is not efficient as a degassing treatment method.

  In order to solve the above problems, in the present invention, an inkjet head that ejects ink droplets in response to an electrical signal, an ink tank that stores ink, an ink supply path that communicates the inkjet head and the ink tank, Temporary storage of degassing means installed in the ink supply path, liquid feeding means installed in the ink supply path, and ink installed in the ink supply path and closest to the inkjet head An ink jet recording apparatus comprising: a first sub-tank; a first dissolved gas sensor installed between the sub-tank and the degassing means; and a second dissolved gas sensor installed between the ink tank and the degassing means. An ink jet recording apparatus comprising: a gas sensor.

  In addition, an ink jet head that discharges ink droplets in response to an electrical signal, an ink tank that stores ink, an ink supply path that communicates the ink jet head and the ink tank, and a plug installed in the ink supply path. In an ink jet recording apparatus comprising: air means; liquid feeding means installed in the ink supply path; and a sub tank capable of temporarily storing ink installed in the ink supply path and at a position closest to the ink jet head An ink jet recording apparatus comprising a dissolved gas sensor between the ink tank and the deaeration means.

  In addition, an ink jet head that discharges ink droplets in response to an electrical signal, an ink tank that stores ink, an ink supply path that communicates the ink jet head and the ink tank, and a plug installed in the ink supply path. In an ink jet recording apparatus comprising: air means; liquid feeding means installed in the ink supply path; and a sub tank capable of temporarily storing ink installed in the ink supply path and at a position closest to the ink jet head A first dissolved gas sensor installed between the sub tank and the degassing means, and a second dissolved gas sensor installed between the ink tank and the degassing means. Inkjet recording apparatus.

  2. The apparatus according to claim 1, further comprising a control mechanism that varies a liquid feeding speed of the liquid feeding unit based on a measured value by the dissolved gas sensor and a deaeration characteristic of the deaeration unit and ink. 3 was used.

  Further, the ink jet recording apparatus is characterized in that the deaeration means comprises a deaeration module comprising a gas permeable hollow fiber bundle and a decompression space.

  The ink jet recording apparatus is characterized in that the dissolved gas sensor is a dissolved oxygen meter.

  By the above means, it is possible to avoid an error that introduces ink whose dissolved gas amount does not reach the predetermined amount to the inkjet head, and it is possible to perform deaeration processing at a liquid feeding speed according to the dissolved gas amount at the time of introduction. Therefore, the time for the deaeration process can be shortened.

  Examples of the present invention will be described below. However, the present invention is not limited to the examples described below.

(Example 1)
FIG. 1 shows a schematic configuration diagram of an ink jet recording apparatus according to a first embodiment of the present invention. In the ink jet recording apparatus shown in FIG. 1, a large-capacity ink tank 1 communicates with an ink jet head 2 via an ink supply path 3 as in the prior art, and a liquid feed pump 4 serving as an ink feed means in the ink supply path. 4 includes a deaeration unit 5 serving as an ink deaeration unit and a sub tank 6 for storing the deaeration ink, and has a layout as shown in FIG. Here, a dissolved gas sensor 8 is provided between the sub tank and the deaeration means.

  Moreover, the controller 9 which has the measurement function of a dissolved gas sensor and the speed control function of a liquid feeding pump is comprised. In this embodiment, the deaeration means is a deaeration module made up of a gas permeable hollow fiber bundle. This deaeration means may be a small vacuum furnace. A dissolved oxygen meter was used as the dissolved gas sensor. If this is a dissolved gas sensor that can monitor the amount of dissolved gas in the ink, such as a dissolved nitrogen meter, the type of detection gas is not specified. Various types of dissolved oxygen meters are commercially available, and any type of polaro type or fluorescent type may be used as long as they have resistance to the ink used. Here, in order to detect the deaeration level after deaeration as early as possible, the location where the dissolved gas sensor is installed should be as close as possible to the deaeration means. In recent fluorescent dissolved oxygen meters and the like, an optical fiber-sized ultrafine form is also commercially available, so that it can be easily installed in a local region.

Here, the deaeration characteristic in the deaeration module will be described. FIG. 2 shows an example of ink degassing level and ink flow rate characteristics in the degassing module. FIG. 2 shows a degassing module having a membrane area of 1.2 m ² which is the surface area of a hollow fiber bundle, and an aqueous pigment ink having an initial dissolved oxygen amount of about 5.0 to 7.0 mg / l is applied with a vacuum degree of about −96 kPa. It is the measurement result which deaerated by depressurizing with. As shown in FIG. 2, it can be seen that the ink deaeration level is approximately proportional to the ink flow rate and the initial dissolved oxygen amount. The deaeration module has a structure in which 10000 hollow fibers having a diameter of about 200 μm are bundled, and has a high viscosity of about 10 cp for all of these hollow fibers, and depends on a component such as a surfactant. It is difficult to airtightly fill ink that easily generates bubbles, and the actual filling rate varies. As a result, the deaeration level also varies.

  As described above, the amount of dissolved oxygen in the ink after passing through the deaeration module varies greatly depending on the state of the ink introduced into the deaeration module and the state of the deaeration module.

  In the present invention, as described above, since the dissolved gas sensor is installed immediately after the deaeration module, the dissolved gas amount of ink immediately after the deaeration module can be monitored. Then, a threshold value of the dissolved gas amount that lowers the ejection stability is set, and when the dissolved gas amount of the ink to be monitored exceeds the threshold value, the following control may be performed. For example, when the deaeration means has an extreme performance deterioration, the deaeration means may be fatally damaged. Therefore, the liquid feeding is immediately stopped, and the operation is resumed after replacement or maintenance of the deaeration means. In addition, if the performance deterioration is gradual and the life of the deaeration means is considered to be long-lasting, the deaeration level can be finely adjusted by reducing the liquid feed speed, so the deaeration level to be monitored What is necessary is just to always feed back the adjustment of the liquid feeding speed according to. In addition, when the threshold value is exceeded due to variations in the amount of dissolved gas in the ink degassing means, the adjustment of the liquid feeding speed according to the degassing level to be monitored may be constantly fed back as described above (in this case, degassing). Since the air level has the characteristics shown in FIG. 2, if the deaeration level characteristic of the ink to be used is known in advance, the flow rate can be adjusted actively in accordance with the characteristic) . By the control method as described above, it is possible to avoid the inflow of ink exceeding the threshold value to the inkjet head.

  As a specific example, depending on the specifications of the ink jet head and the ink physical properties, for example, in the case of water-based ink in which the total dissolved gas amount can be monitored by the dissolved oxygen amount, the dissolved oxygen amount is about 3.0 mg / l. That is, when the amount of dissolved oxygen is 3.0 mg / l or less, stable discharge is secured, and when it is 3.0 mg / l or more, stable discharge cannot be secured. Therefore, in this case, the above-described threshold value may be set to 3.0 mg / l.

(Example 2)
FIG. 3 is a schematic configuration diagram of the ink jet recording apparatus according to the second embodiment of the present invention. Since the basic configuration is the same as that of the first embodiment, the description of overlapping items is omitted, but the difference from the first embodiment is that the dissolved gas sensor 8 is installed upstream of the degassing means 5. Thereby, the deaeration level of the ink can be monitored before being introduced into the deaeration means. As a result, if the characteristics of the deaeration performance between the deaeration means and the ink are known in advance, the deaeration process can be performed at the maximum liquid feeding speed that does not exceed the threshold value. As a result, the time for the deaeration process can be shortened.

  As a specific example, in the case of the deaeration characteristics of the deaeration module and ink as shown in FIG. 2, if the dissolved oxygen amount threshold is 3.0 mg / l, the initial dissolved oxygen amount is 5.0 mg / l and 7 In the case of 0.0 mg / l, the maximum flow rates not exceeding the threshold value are 500 ml / min and 190 ml / min, respectively. In the case of the conventional method, the condition that does not exceed the threshold value of the dissolved oxygen amount under any condition must be uniquely set. Therefore, in the case of FIG. 2, the condition is inevitably 190 ml / min. However, in the case of the present invention, the amount of dissolved gas before being introduced to the degassing means can be monitored at all times, and the maximum flow rate not exceeding the threshold according to the amount of dissolved gas at that time can be set. When the initial dissolved oxygen amount is 5.0 mg / l and the threshold value is 3.0 mg / l under various characteristic conditions, the ink flow rate can be set up to 500 ml / min at the maximum. As a result, the processing speed can be improved by a factor of two or more compared to the conventional case.

(Example 3)
FIG. 4 is a schematic configuration diagram of the ink jet recording apparatus according to the third embodiment of the present invention. Since the basic configuration is the same as in the first and second embodiments, detailed description is omitted. However, the difference from the first and second embodiments is that the dissolved gas sensor 8 is installed both upstream and downstream of the degassing means 5. It is that you are. This makes it possible to satisfy the functions of the first and second embodiments at the same time. In addition, since the deaeration level before and after the deaeration means can be monitored at any time, if the performance of the deaeration means is known in advance, the life of the deaeration means is determined by the amount of deviation from the original performance of the deaeration means. Changes can be monitored and can be used as a criterion for replacement of the deaeration means life. Here, the deaeration performance of the deaeration unit alone cannot be monitored only by detecting the deaeration level of either one before or after the deaeration unit.

BRIEF DESCRIPTION OF THE DRAWINGS The structure schematic diagram of Example 1 of this invention. Characteristics of ink flow rate and deaeration level by deaeration module The structure schematic diagram of Example 2 of the present invention. The structure schematic of Example 3 of this invention. 1 is a schematic configuration diagram of a conventional inkjet recording apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ink tank 2 Inkjet head 3 Ink supply path 4 Liquid feed pump 5 Deaeration means 6 Vacuum pump 7 Ink 8 Dissolved gas sensor 9 Controller

Claims (6)

An ink jet head that ejects ink droplets in response to an electrical signal, an ink tank in which ink is stored, an ink supply path that communicates the ink jet head and the ink tank, and a deaeration unit installed in the ink supply path An ink jet recording apparatus comprising: a liquid feeding means installed in the ink supply path; and a subtank capable of temporarily storing ink installed in the ink supply path and at a position closest to the ink jet head. ,
An ink jet recording apparatus, wherein a dissolved gas sensor is provided in the ink supply path between the sub tank and the deaeration means. An ink jet head that ejects ink droplets in response to an electrical signal, an ink tank in which ink is stored, an ink supply path that communicates the ink jet head and the ink tank, and a deaeration unit installed in the ink supply path An ink jet recording apparatus comprising: a liquid feeding means installed in the ink supply path; and a subtank capable of temporarily storing ink installed in the ink supply path and at a position closest to the ink jet head. ,
An ink jet recording apparatus, wherein a dissolved gas sensor is provided in the ink supply path between the ink tank and the deaeration means. An ink jet head that ejects ink droplets in response to an electrical signal, an ink tank in which ink is stored, an ink supply path that communicates the ink jet head and the ink tank, and a deaeration unit installed in the ink supply path An ink jet recording apparatus comprising: a liquid feeding means installed in the ink supply path; and a subtank capable of temporarily storing ink installed in the ink supply path and at a position closest to the ink jet head. ,
A first dissolved gas sensor is provided in the ink supply path between the sub tank and the degassing means, and a second dissolved gas sensor is provided in the ink supply path between the ink tank and the degassing means. An ink jet recording apparatus.   4. The apparatus according to claim 1, further comprising a control mechanism for controlling a liquid feeding speed of the liquid feeding unit based on a measured value by the dissolved gas sensor and a deaeration characteristic of the deaeration unit and ink. The ink jet recording apparatus described.   5. An ink jet recording apparatus according to claim 1, wherein said deaeration means comprises a deaeration module comprising a gas permeable hollow fiber bundle and a decompression space.   6. The ink jet recording apparatus according to claim 1, wherein the dissolved gas sensor is a dissolved oxygen meter.

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