JP2008149523A - Ink jet recorder and method for deaerating ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To supply highly reliable and efficient ink jet recording ink to an ink jet head without wasting ink of a lowered deaeration level in the deaeration method of ink jet recording ink. <P>SOLUTION: The ink jet recorder comprises a means for feeding ink of lowered deaeration level which is left in an ink supply passage 12 without being used for printing reversely to a position where the ink can be deaerated, and a jet head for providing an ink jet head with ink which can be ejected stably by deaerating the ink of a lowered deaeration level again through a deaerator 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus that ejects liquid droplets from an ink jet head and records an image on a recording medium, and an ink deaeration apparatus.

  As shown in FIG. 4, a conventional general inkjet recording apparatus includes an ink tank 1 that supplies ink that can be replaced or replenished to an inkjet head 3 that ejects ink droplets of a desired volume onto a recording medium. The ink supply path 12 is connected.

  An ink jet recording apparatus has a structure in which an ink supply tank is a housing in a recording apparatus that performs a large amount of printing in relation to printing by reciprocating an ink jet head that receives ink supply from an ink supply tank in the paper width direction of the recording paper. And a method of supplying ink to the ink-jet head via an ink supply path. By the way, the ink jet recording apparatus pressurizes the ink in the pressure generating chamber to generate liquid droplets. Therefore, if the ink contains bubbles, the pressure applied to the ink decreases and the liquid droplet ejection performance also decreases. Therefore, it is necessary to supply ink that does not contain dissolved air to the inkjet head. For this reason, ink that has been sufficiently deaerated at the factory is accommodated in a cartridge or a pouch and packed in an airtight container as a product.

  However, in an inkjet recording apparatus that prints a poster or the like using a large format recording medium, a large amount of ink is consumed during printing. Therefore, a degassing system is incorporated in the ink supply path to remove non-depleted air bubbles. The ink supply tank is configured as a tank capable of injecting ink from the outside so that even ink can be supplied, and the ink in this ink supply tank is passed through a deaeration means comprising a hollow fiber bundle that receives negative pressure from the outside. In some cases, the ink jet head is supplied to the ink jet head.

  In driving the inkjet head, it is necessary to control the water pressure applied to the ejection nozzle surface of the inkjet head within a certain range in order to ensure stable operation. For this water pressure, in order to avoid unintentional outflow and dripping that are not related to the ink discharge from the nozzle, the water pressure is such that the negative negative pressure is less than a certain value so as not to disturb the ink discharge. The appropriate range is determined by the inkjet head.

  In the case of a small-capacity ink tank, this water pressure control can be performed by arranging the height in the ink jet printing apparatus at a position relative to the height of the ink jet head. However, in that case, the water pressure applied to the inkjet head varies depending on whether the amount of ink in the ink tank is maximum or when the ink tank is nearly empty.

  When the pressure fluctuation range exceeds the appropriate range for stable driving of the inkjet head, a sub tank 9 is further provided in the middle of the ink supply path connecting the ink tank and the inkjet head, as shown in FIG. Thus, a configuration is employed in which the ink is once stored in the interior and then supplied to the inkjet head.

  In such a configuration, the water level of the ink in the sub tank is measured by the ink amount monitoring sensor, and before the water level falls and the water pressure applied to the inkjet head falls below the lower limit of the appropriate range, the ink is transferred from the ink tank to the sub tank. The water pressure applied to the ink jet head is controlled within a range that does not exceed the upper limit of the appropriate range.

  For this purpose, a pump 7a for pumping ink is arranged between the ink tank and the sub-tank. This pump is a tube pump that can easily control the generated pressure, flow rate, flow velocity, etc., and has a simple configuration. Is often used.

  When the printing apparatus itself is large, the ink supply path length is long and the supply path diameter is also large. Therefore, a large amount of ink passes through the supply path from the deaerator to the inkjet head. It has been found that the ink passing through the deaeration device and in the supply path or the ink jet head has a lower deaeration level over time, making it difficult to eject. Therefore, in the past, ink with a high deaeration level was sent to the inside of the ink jet head and the ink that remained in the supply path and the deaeration level was lowered was forcibly discharged, but a large amount of ink was discarded. The waste was great.

  Means for supplying ink immediately after deaeration by adjoining a deaeration device to the inkjet head for the purpose of reducing the waste of ink without causing printing defects caused by a decrease in the deaeration level as described above Has been proposed (for example, Patent Document 1).

Similarly, a means has been proposed in which an ink container having low gas permeability is used so as not to lower the deaeration level, and the gas is deaerated in the vacuum container and supplied to the inkjet head (for example, Patent Document 2).
JP2006-239859 JP 2006-231809

  As described above, the degassing level of the ink in the supply path or the ink jet head decreases with time, making it difficult to eject. For this reason, ink with a high deaeration level is fed to the inside of the inkjet head, and the ink with a low deaeration level is forcibly discharged. However, this method discards a large amount of ink. There is a lot of wasted ink. For example, when the deaeration device is adjacent to the head (for example, Patent Document 1), the ink jet head becomes large, and the attachment area to the ink jet recording device increases accordingly. Furthermore, there are problems such as complication of production. In a very complicated ink supply system in which a new deaeration device needs to be installed (for example, Patent Document 2), the conventionally used ink supply system cannot be applied.

  The present invention has been made in view of such circumstances, and the object of the present invention is to recycle without deteriorating a special mechanism even if the ink has a reduced deaeration level. It is an object of the present invention to provide an ink jet recording apparatus capable of doing this.

  The inkjet recording apparatus of the present invention includes an inkjet head that ejects ink onto a recording medium, an ink supply tank that supplies ink to the inkjet head, an ink supply path that connects the inkjet head and the ink supply tank, and the ink A degassing device provided in the supply path; and an ink reverse feeding means for reversely feeding the ink after degassing to a position where the ink can be degassed again by the degassing device.

  As a result, even ink with a reduced deaeration level can be reused without being discarded.

  The ink back feeding means is a liquid feeding device that is installed between the ink supply tank and the ink jet head and is capable of feeding back the degassed ink.

  As a result, the ink feeding device and the reverse feeding device can be used together.

  The ink back feeding means is an ink supply tank position adjusting device that changes a height position of the ink supply tank.

  Accordingly, it is not necessary to give a reverse feed sequence to the ink liquid feeding device, and at the same time, the water head value changes due to a change in the position of the ink supply tank, and ink supply or reverse feed is possible.

  Further, the ink reverse feeding means is a pressure variable device that negatively or pressurizes the inside of the ink supply tank.

  Accordingly, it is not necessary to give a reverse feed sequence to the ink liquid feeding device, and at the same time, ink supply or reverse feed is possible due to a pressure change in the ink supply tank.

  The ink jet recording apparatus of the present invention includes a water head value management device that manages the water head value of the ink supply tank between the ink supply tank and the ink jet head.

  Accordingly, the water head value is kept constant regardless of the change in the ink amount in the ink supply tank, and stable droplet ejection is enabled.

  The ink jet recording apparatus of the present invention has at least one stop valve capable of stopping the flow of ink and gas in the ink supply path between the ink reverse feeding means and the ink jet head.

  Accordingly, it is possible to stop the pressure due to the ink and air at an arbitrary timing, and even if the deaeration level of the ink inside the deaeration device is lowered, it is possible to prevent the diffusion of the ink having the lowered deaeration level.

  In the ink degassing method of the present invention, the ink degassed by the degassing device provided in the ink supply path is transferred from the degassing device to the ink supply tank side by the ink back feed means. This is a method of reverse feeding and deaeration again by a deaeration device.

  As a result, it is possible to deaerate and efficiently supply ink with a reduced deaeration level without the need to provide a new path.

  In the present invention, the ink whose deaeration level has been lowered can be sent back to the position where deaeration can be performed, and the deaeration can be performed again. By increasing the deaeration level, the ink can be used again. As a result, it is possible to use ink having a reduced deaeration level that has been disposed of conventionally, and the ink cost is greatly reduced.

  Example 1 will be described with reference to FIG. Although only one inkjet head 3 is shown in FIG. 1, a plurality of inkjet heads 3 can be configured. First, the basic configuration is described below.

  This ink jet recording apparatus has a configuration in which an ink tank 1 for storing ink, a deaeration device 2, a sub tank 9, and an ink jet head 3 are connected by an ink supply path 12. The ink is deaerated by the deaeration device 2 from the ink tank 1 through the ink supply path 12.

  The deaeration device 2 includes a vacuum line 4 and a vacuum pump 5. This degassing device 2 is, for example, a device using a hollow fiber filter method, a method of degassing by putting ink in a sealed container and evacuating the gas phase part, or adding ultrasonic waves to the degassing efficiency. There is a method of raising The hollow fiber filter system is highly degassed because the ink is degassed by vacuuming the vacuum line outside the tube when it passes through a large number of tubes made of gas permeable membrane. There is. The vacuum pump 5 is preferably a dry pump whose performance does not deteriorate even when water enters. However, when an oil rotary vacuum pump is used, water is mixed into the pump oil and the pump performance deteriorates. It is desirable to attach a trap using a refrigerant for adsorption.

  Next, an ink amount monitoring sensor capable of monitoring the ink amount is attached to the sub tank 9. This is because normal ejection cannot be performed when the water head value indicating the ink surface water level of the ink tank 1 is too high or too low with respect to the head. The ink amount monitoring sensor is built in the sub tank 9 and detects the ink amount position in the sub tank as an ON / OFF signal.

  Therefore, the control unit 13 controls the water head value by driving the liquid feed pump 7a so that the ink reduction due to printing or the like can be self-detected and the water head value can be controlled to a predetermined position. For example, the control unit 13 reads the value of the ink amount monitoring sensor, and when the value is lower than the specified value, the control unit 13 drives the tubing pump 7a to control it to always be the specified amount.

  Further, the flow of ink and air can be stopped by providing a stop valve 8a, a stop valve 8b, and the like in the ink supply path. Thus, even when the deaeration device is turned off for maintenance or the like and left unattended, it is possible to prevent the ink having a lowered deaeration level from diffusing.

  Tubing pumps are used as the liquid feeding pumps 7a and 7b for feeding ink. For this reason, the ink supply path flowing in the ink supply path is generally hermetically sealed regardless of ink or gas.

  In the present embodiment, by providing the bypass path 6 to the liquid feed pump 7b, the flow load due to the stop of the liquid feed pump 7b can be released and ink can be supplied to the inkjet head 3. By providing the stop valve 8b in the bypass path 6, the control unit can make the sub-tank 9 and the ink jet head 3 flow freely regardless of the state of the liquid feed pump 7b, and perform the liquid feed normally. Is possible. Here, in the case of the liquid feeding means in which the ink supply path is not closed, it is not necessary to provide a bypass path.

  Next, ink supply will be described. In the present configuration example 1 configured as described above, the ink is fed by the liquid feed pump 7a in order to provide the ink jet head 3 with the ink whose deaeration level has been raised. Thereafter, the ink is deaerated in the deaerator 2 and is filled in the sub tank 9 as it is. When the water head value of the sub tank 9 is in the specified value state, the control unit operates the liquid feed pump 7b to supply ink to the inkjet head 3. As a result, the ink jet head 3 can be filled with ink. As a filling method other than the above, a method such as suction filling performed by attaching a suction jig to the inkjet head 3 may be used.

  Since the ink filled by the above means follows the path after passing through the deaeration device 2, the deaeration level is lowered if the ink is left for a long period of time, and the ink jet head 3 cannot perform normal ejection.

  In order to solve the above problem, the signals from the control unit 13 to the liquid feeding pump 7a and the liquid feeding pump 7b, which are liquid feeding means used for filling, are reversed and reversed with respect to the liquid feeding direction. Let me send you. As a result, it is possible to return to a position where deaeration can be performed again by following a path opposite to that when the sub-tank 9 is filled with the ink after deaeration.

  That is, in order to send the ink, which has been degassed in the ink jet head 3 and the ink supply path, to the ink supply tank 1 side, the stop valve 8b is closed according to an instruction from the control unit, and the liquid feed pump 7a and 7b is sent to the main tank side.

  Here, the control unit causes the ink returned between the supply tanks from the introduction unit of the deaeration device 2 to be fed by the liquid feed pump 7a, and the ink is supplied to the deaeration device 2 and filled in the sub tank 9 as it is. At this time, if the water head value of the sub tank 9 indicates a specified value, the control unit operates the liquid feeding pump 7b to supply ink to the inkjet head 3. By newly deaeration in this way, ink is not wasted and normal ejection from the inkjet head 3 can be performed.

  Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. Although only one inkjet head 3 is shown in FIG. 1, a plurality of inkjet heads 3 can be configured.

  FIG. 2 is a configuration diagram schematically showing a basic configuration relating to ink supply of the ink jet recording apparatus of the present invention. Since the equipment used is the same as that of the first embodiment, the above-described ones are omitted.

  In the second embodiment, an ink supply tank position adjusting device 10 that can change the height position of the ink supply tank 1 or the inkjet head is disposed. The ink supply tank position adjusting device 10 causes ink to be fed by changing the water head value of the supply tank 1 relative to the inkjet head. Specifically, the control unit 13 raises the ink supply tank 1 and raises the water head value by the ink supply tank position adjusting device 10.

  Here, a bypass path is provided for the liquid feed pump 7a, and effects similar to those of the liquid feed pump 7b and the stop valve 8b in the first embodiment are provided. As a result, the ink passes through the bypass path, is deaerated in the deaeration device 2, and is directly filled in the sub tank 9. The control unit operates the liquid feed pump 7b in a state where the water head value of the sub tank 9 is a specified value, and supplies and fills the ink jet head 3 with ink.

  Here, as a filling technique up to the sub tank, a pressure device is installed in the ink supply tank 1 (ink reverse feeding means), and ink is fed using a technique such as pressurizing the inside of the ink supply tank 1. Is possible.

  Even in such a form, if the ink supplied to the inkjet head 3 is left unattended, the deaeration level is lowered and normal ejection cannot be performed. Therefore, in order to raise the deaeration level of the ink, the ink is fed to a position where deaeration can be performed. For example, the ink moves to the supply tank side by lowering the water head value of the supply tank relative to the ink jet head or by making the inside of the supply tank have a negative pressure. Thereby, this ink can be deaerated again, and it becomes possible to supply ink with a high deaeration level.

  Next, a third embodiment of the present invention will be described with reference to the drawings. Although only one inkjet head 3 is shown in FIG. 1, a plurality of inkjet heads 3 can be configured.

  FIG. 3 is a configuration diagram schematically showing a basic configuration relating to ink supply of the ink jet recording apparatus of the present invention. Since the equipment used is the same as in the first and second embodiments, the above-described ones are omitted. To do.

  In the third embodiment, a pressure variable device 14 that can vary the pressure inside the sealed ink supply tank 1 is disposed in the ink supply tank 1. Ink is sent out to the flow path by the pressure variable device 14 (ink reverse feeding means) to feed the ink. The pressure changing device 14 in this embodiment has a piston shape, and the internal pressure decreases when the piston is pulled, and the internal pressure decreases when the piston is pushed. For example, a pump device or the like can be used as one that produces a similar action. Further, it is desirable that the ink supply tank be sealed from the atmosphere only when the pressure variable device 14 is in operation.

  The control unit 13 increases the pressure inside the ink supply tank 1 by the pressure variable device 14 and sends out the ink to the flow path. Here, a bypass path is provided for the liquid feed pump 7a. Since this bypass passage has the same effect as the liquid feed pump 7b and the stop valve 8b in the first embodiment, the ink passes through the bypass passage, is deaerated in the deaeration device 2, and is filled in the sub tank 9 as it is. In a state where the water head value of the sub-tank 9 is the specified value, the control unit operates the liquid feed pump 7b so as to supply ink to the ink jet head 3, thereby filling the ink jet head 3 with ink.

  Even in such a form, if the ink supplied to the inkjet head 3 is left unattended, the deaeration level is lowered and normal ejection cannot be performed. Therefore, in order to increase the deaeration level, the pressure inside the ink supply tank is made negative using the pressure variable device 11 so that the ink moves to the supply tank side and is sent to a position where deaeration can be performed. This makes it possible to supply ink with a high deaeration level.

FIG. 2 is a diagram schematically illustrating a basic configuration relating to ink supply of the ink jet recording apparatus according to the first embodiment of the present invention. It is a figure which shows typically the basic composition which concerns on the ink supply of the inkjet recording device which concerns on the 2nd Example of this invention. It is a figure which shows typically the basic composition which concerns on the ink supply of the inkjet recording device which concerns on the 3rd Example of this invention. It is a figure which shows the basic composition which concerns on the ink supply of the conventional inkjet recording device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ink supply tank 2 Deaeration apparatus 3 Inkjet head 4 Vacuum line 5 Vacuum pump 6 Bypass path 7a, 7b Liquid feed pump 8a, 8b, 8c Stop valve 9 Sub tank 10 Ink supply tank position adjustment apparatus 11 Signal line 12 Ink supply path 13 Control unit 14 Variable pressure device

Claims (7)

  An ink jet head that discharges ink to a recording medium, an ink supply tank that supplies ink to the ink jet head, an ink supply path that connects the ink jet head and the ink supply tank, and an ejector provided in the ink supply path An ink jet recording apparatus comprising: an air device; and an ink back feeding means for feeding the ink after degassing back to a position where the ink can be degassed again by the degassing device.   2. The ink jet according to claim 1, wherein the ink reverse feeding means is a liquid feeding device that is installed between the ink supply tank and the ink jet head and that can reversely feed the ink after deaeration. Recording device.   3. The ink jet recording apparatus according to claim 1, wherein the ink reverse feeding unit is an ink supply tank position adjusting device that changes a height position of the ink supply tank. 4.   4. The ink jet recording apparatus according to claim 1, wherein the ink back feeding means is a pressure variable device that makes the inside of the ink supply tank have a negative pressure.   The ink jet recording apparatus according to claim 1, further comprising a water head value management device that manages a water head value of the ink supply tank between the ink supply tank and the ink jet head.   6. The ink jet recording apparatus according to claim 1, further comprising at least one stop valve capable of stopping the flow of ink and gas in the ink supply path between the ink back feeding means and the ink jet head.   The ink deaerated by the deaeration device provided in the ink supply path is sent back from the deaeration device to the ink supply tank side by the ink reverse feeding means, and again by the deaeration device. An ink degassing method comprising degassing.

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