JP2015000518A - Ink jet recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of foreign substances (debris) in ink, dehydration of ink in a deaeration module, and reduction in life of a vacuum pump due to moisture content in ink, and to keep a dissolved oxygen amount in ink at a low level.SOLUTION: There is provided an ink jet recording device which includes: an ejection head 250 in which an ejection port is formed for ejecting ink; an ink tank 252 connected to the ejection head 250 via a supply channel 212 and housing ink to be supplied to the ejection head 250 through the supply channel 212; a deaeration module 360 that is disposed in the supply channel 212 and deairs ink; a vacuum pump 500 connected to the deaeration module 360 via a vacuum path 502 and decompressing the deaeration module 360; and vacuum degree adjustment means 504 that adjusts a decompression level of the deaeration module 360 attained by the vacuum pump 500 to a degree of vacuum that prevents a dissolved oxygen amount in ink from reaching a reference value or less.

Description

  The present invention relates to an ink jet recording apparatus, and more particularly to an ink jet recording apparatus provided with a degassing module for degassing oxygen in ink in a supply channel connecting an ejection head and an ink tank.

  In recent years, there has been an increasing demand for small number of copies in the printing industry. In offset printing, since it is necessary to create a plate, when printing a small number of copies, there has been a problem in terms of time and cost. For this reason, single-pass inkjet recording is preferably used.

  However, the single-pass method has a drawback that streaks are likely to be noticeable in the missing portion if there are nozzles that do not discharge or nozzles that cause discharge bending. A major factor causing streaks is that air bubbles are mixed in the head (increase in the amount of dissolved oxygen).

  Therefore, in order to remove bubbles, a deaeration module is provided, so that the amount of dissolved oxygen in the ink is kept at a low level by the deaeration module.

  In Patent Document 1, a membrane module using a gas-permeable membrane and a vacuum pump are provided on an ink supply path for supplying ink from an ink tank to an ejection head, and the membrane module is decompressed by the vacuum pump. An ink jet printer with a degassing device for removing dissolved gas in the ink is described.

JP 2010-58413 A

  However, the ink jet printer provided with the deaeration device described in Patent Document 1 has a problem in that the dissolved oxygen amount of the ink increases due to deterioration with time of the vacuum pump, and bubbles are mixed in the head. .

  If a vacuum pump with a high degassing capacity is provided in consideration of the deterioration of the vacuum pump over time, the dissolved oxygen amount level of the ink is excessively lowered, and foreign matter (Debris) is generated in the ink. There is a problem, a problem that the moisture in the ink is sucked and the ink is dried in the deaeration module, and a problem that the life of the vacuum pump is shortened due to the moisture in the ink.

  The present invention has been made in view of such circumstances, and the life of the vacuum pump is caused by the problem that foreign matter (Debris) is generated in the ink, the problem that the ink is dried in the deaeration module, and the moisture in the ink. It is an object of the present invention to provide an ink jet recording apparatus capable of forming a high quality image by preventing the ink from being shortened and maintaining the amount of dissolved oxygen at a low level.

  In order to achieve the above object, the present invention provides an ejection head having ejection openings for ejecting ink, and an ink connected to the ejection head via a supply channel and supplied to the ejection head through the supply channel. An ink tank to be accommodated, a deaeration module provided in the supply flow path for degassing ink, a vacuum pump connected to the deaeration module via a vacuum path, and depressurizing the deaeration module; There is provided an ink jet recording apparatus comprising: a vacuum degree adjusting means for adjusting a pressure reduction level of a degassing module with a vacuum pump at a vacuum degree at which a dissolved oxygen amount does not become a reference value or less.

  According to the present invention, by providing the vacuum degree adjusting means for adjusting the pressure reduction level of the deaeration module in the vacuum pump at a vacuum degree where the dissolved oxygen amount of the ink does not become the reference value or less, foreign matter (Debris) is contained in the ink. Generation of ink and drying of the ink in the deaeration module can be prevented, the life of the vacuum pump can be extended, and a high-quality image can be formed by maintaining the amount of dissolved oxygen at a low level.

  The “reference value for the dissolved oxygen amount of ink” and “the degree of vacuum at which the dissolved oxygen amount of the ink does not fall below the reference value” vary depending on the composition of the ink, but foreign matter (debris) is present in the ink. This refers to the limit value of the amount of dissolved oxygen that does not occur and the limit value of the degree of vacuum at which foreign matter (Debris) does not occur in the ink. The “reference value of the dissolved oxygen amount of ink” and the “degree of vacuum at which the dissolved oxygen amount of ink does not become lower than the reference value” are determined by conducting preliminary experiments on the ink and degassing module to be used.

  In the ink jet recording apparatus according to another aspect of the present invention, the vacuum degree adjusting means is preferably a vacuum regulator provided in a vacuum path.

  In the ink jet recording apparatus according to another aspect of the present invention, the vacuum degree adjusting means is preferably a speed controller having one end provided in the vacuum path and the other end opened to the atmosphere.

  In the ink jet recording apparatus according to another aspect of the present invention, the vacuum degree adjusting means is preferably a vacuum pump driving ability adjusting means for adjusting a driving ability of the vacuum pump.

  According to the ink jet recording apparatus according to another aspect of the present invention, the vacuum degree adjusting means includes a vacuum regulator provided in the vacuum path, a speed controller provided at one end in the vacuum path and the other end opened to the atmosphere, or a vacuum By being a vacuum pump driving capacity adjusting means for adjusting the driving capacity of the pump, it is possible to adjust the pressure reduction level of the deaeration module in the vacuum pump so as not to reduce the dissolved oxygen amount of the ink excessively.

  In the ink jet recording apparatus according to another aspect of the present invention, the maximum driving capability of the vacuum pump is preferably such that the degree of vacuum is −95 kPa or less. In addition, as for the maximum drive capability of a vacuum pump, it is more preferable that a vacuum degree is -97 kPa or less.

  In the ink jet recording apparatus according to another aspect of the present invention, it is preferable that the degree of vacuum adjusting means adjust the vacuum pump so that it is in the range of 85% to 100% of the maximum driving capacity of the vacuum pump. In addition, it is preferable to adjust a vacuum degree adjustment means so that it may become the range of 85%-95% of the maximum drive capability of a vacuum pump.

  In the ink jet recording apparatus according to another aspect of the present invention, it is preferable that the degree of vacuum adjusting means adjust the degree of vacuum at the time of printing higher than that at the time of non-printing.

  According to the ink jet recording apparatus according to another aspect of the present invention, since the degree of vacuum during printing is increased, the amount of dissolved oxygen in the ink can be suitably reduced.

  In the ink jet recording apparatus according to another aspect of the present invention, the degree of vacuum adjusting means adjusts the degree of vacuum during non-printing within a range of −90 kPa to −85 kPa, and the degree of vacuum during printing within a range of −100 kPa to −90 kPa. It is preferable. In addition, it is more preferable that the degree of vacuum adjusting means adjusts the degree of vacuum at the time of non-printing in the range of −88 kPa to −86 kPa and the degree of vacuum at the time of printing in the range of −100 kPa to −97 kPa.

  The preferred degree of vacuum varies depending on the deaeration module used, ink type, and acceptable printing quality, but the degree of vacuum during non-printing is in the range of −90 kPa to −85 kPa, and the degree of vacuum during printing is −100 kPa to −90 kPa. By adjusting within the range, a high-quality image can be formed.

  In the ink jet recording apparatus according to another aspect of the present invention, it is preferable that the vacuum degree switching timing in the vacuum degree adjusting means is during cleaning of the ejection head.

  According to the ink jet recording apparatus according to another aspect of the present invention, since the degree of vacuum is switched by the degree of vacuum adjusting unit during the cleaning of the ejection head, printing can be performed without waiting time. Therefore, the total printing time can be shortened.

  In the ink jet recording apparatus according to another aspect of the present invention, the vacuum degree adjusting means is preferably controlled by a system controller.

  In the ink jet recording apparatus according to another aspect of the present invention, it is preferable that a recovery flow path for recovering ink from the discharge head to the ink tank is connected between the discharge head and the ink tank.

  According to the ink jet recording apparatus according to another aspect of the present invention, since the ink is provided with the circulation flow path for circulating the ink between the discharge head and the ink tank, the vacuum pump is used so as not to reduce the dissolved oxygen amount of the ink excessively. It is particularly effective to provide a degree of vacuum adjusting means for adjusting the pressure reduction level of the degassing module.

  According to the ink jet recording apparatus of the present invention, it is possible to prevent the generation of foreign matter (Debris) in the ink and the drying of the ink in the deaeration module, and the high quality by maintaining the ink dissolved oxygen amount at a low level. Images can be formed.

1 is an overall configuration diagram of an ink jet recording apparatus. It is a block diagram which shows schematic structure of a circulation type ink supply apparatus. It is the schematic which simplified the ink supply apparatus which concerns on this application. It is the schematic which simplified the ink supply apparatus which concerns on the other aspect of this application. It is the schematic which simplified the ink supply apparatus which concerns on the other aspect of this application. It is the schematic which simplified the ink supply apparatus which concerns on the other aspect of this application. It is a block diagram of the control system of an inkjet recording device.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

<< Overall configuration of inkjet recording apparatus >>
First, an ink jet recording apparatus to which the liquid ejection apparatus of the present invention is applied will be described. FIG. 1 is a configuration diagram showing the overall configuration of an ink jet recording apparatus according to the present invention.

  In the inkjet recording apparatus 100, a recording medium 124 (sometimes referred to as “paper” for convenience) held on the impression cylinder (drawing drum 170) of the drawing unit 116 is provided with a plurality of colors from the inkjet heads 172M, 172K, 172C, 172Y. Is an impression cylinder direct drawing type ink jet recording apparatus that forms a desired color image by applying ink droplets of the ink. A treatment liquid (in this case, an aggregating treatment liquid) is applied onto the recording medium 124 before ink ejection. This is an on-demand type image forming apparatus to which a two-liquid reaction (aggregation) method for forming an image on a recording medium 124 by reacting a treatment liquid and an ink liquid is applied.

  As shown in the figure, the ink jet recording apparatus 100 mainly includes a paper feeding unit 112, a treatment liquid application unit 114, a drawing unit 116, a drying unit 118, a fixing unit 120, and a paper discharge unit 122.

(Paper Feeder)
The paper feeding unit 112 is a mechanism that supplies the recording medium 124 to the processing liquid application unit 114, and the recording medium 124 that is a sheet is stacked on the paper feeding unit 112. The paper feed unit 112 is provided with a paper feed tray 150, and the recording medium 124 is fed from the paper feed tray 150 to the processing liquid application unit 114 one by one.

  In the inkjet recording apparatus 100 of this example, a plurality of types of recording media 124 having different paper types and sizes (paper sizes) can be used as the recording medium 124. A mode is also possible in which a plurality of paper trays (not shown) for separately collecting various recording media are provided in the paper feeding unit 112 and the paper to be sent to the paper feeding tray 150 is automatically switched from among the plurality of paper trays. In addition, a mode is also possible in which the operator selects or replaces the paper tray as necessary. In this example, a sheet (cut paper) is used as the recording medium 124, but a configuration in which continuous paper (roll paper) is cut to a required size and fed is also possible.

(Processing liquid application part)
The processing liquid application unit 114 is a mechanism that applies the processing liquid to the recording surface of the recording medium 124. The treatment liquid contains a color material aggregating agent that agglomerates the color material (pigment in this example) in the ink applied by the drawing unit 116, and the ink comes into contact with the treatment liquid and the ink. And the solvent are promoted.

  As shown in FIG. 1, the treatment liquid application unit 114 includes a paper feed cylinder 152, a treatment liquid drum 154, and a coating device 156. The treatment liquid drum 154 is a drum that holds and rotates the recording medium 124. The processing liquid drum 154 includes a claw-shaped holding means (gripper) 155 on the outer peripheral surface thereof, and the recording medium 124 is sandwiched between the claw of the holding means 155 and the peripheral surface of the processing liquid drum 154. The tip can be held. The treatment liquid drum 154 may be provided with suction holes on the outer peripheral surface thereof and connected to suction means for performing suction from the suction holes. As a result, the recording medium 124 can be held in close contact with the peripheral surface of the treatment liquid drum 154.

  A coating device 156 is provided outside the processing liquid drum 154 so as to face the peripheral surface thereof. The coating device 156 includes an application tray in which the processing liquid is stored, an anilox roller (measuring roller) partially immersed in the processing liquid in the application tray, and an anilox roller and the recording medium 124 on the processing liquid drum 154. And a rubber roller (application roller) that transfers the measured processing liquid to the recording medium 124. According to the coating device 156, the processing liquid can be applied to the recording medium 124 while being measured.

  The recording medium 124 to which the processing liquid is applied by the processing liquid applying unit 114 is transferred from the processing liquid drum 154 to the drawing drum 170 of the drawing unit 116 via the intermediate transport unit 126.

(Drawing part)
The drawing unit 116 includes a drawing drum (second transport body) 170, a sheet pressing roller 174, and ink jet heads 172M, 172K, 172C, and 172Y. Similar to the treatment liquid drum 154, the drawing drum 170 includes a claw-shaped holding means (gripper) 171 on the outer peripheral surface thereof. The recording medium 124 fixed to the drawing drum 170 is conveyed with the recording surface facing outward, and ink is applied to the recording surface from the inkjet heads 172M, 172K, 172C, 172Y.

  The inkjet heads 172M, 172K, 172C, and 172Y are preferably full-line inkjet recording heads (inkjet heads) each having a length corresponding to the maximum width of the image forming area on the recording medium 124. On the ink ejection surface, a nozzle row in which a plurality of nozzles for ink ejection are arranged over the entire width of the image forming area is formed. Each inkjet head 172M, 172K, 172C, 172Y is installed so as to extend in a direction orthogonal to the conveyance direction of the recording medium 124 (the rotation direction of the drawing drum 170). The droplets of the corresponding color ink are ejected from the inkjet heads 172M, 172K, 172C, and 172Y toward the recording surface of the recording medium 124 held in close contact with the drawing drum 170, whereby the processing liquid application unit 114 performs the processing. The ink comes into contact with the treatment liquid previously applied to the recording surface, and the color material (pigment) dispersed in the ink is aggregated to form a color material aggregate. Thereby, the color material flow on the recording medium 124 is prevented, and an image is formed on the recording surface of the recording medium 124.

  In this example, the configuration of CMYK standard colors (four colors) is illustrated, but the combination of ink colors and the number of colors is not limited to this embodiment, and light ink, dark ink, and special colors are used as necessary. Ink may be added. For example, it is possible to add an inkjet head that discharges light-colored ink such as light cyan and light magenta, and the arrangement order of the color heads is not particularly limited.

  The recording medium 124 on which an image is formed by the drawing unit 116 is transferred from the drawing drum 170 to the drying drum 176 of the drying unit 118 via the intermediate conveyance unit 128.

(Drying part)
The drying unit 118 is a mechanism for drying moisture contained in the solvent separated by the color material aggregating action, and includes a drying drum 176 and a solvent drying device 178, as shown in FIG.

  Similar to the processing liquid drum 154, the drying drum 176 includes a claw-shaped holding unit (gripper) 177 on the outer peripheral surface thereof, and the holding unit 177 can hold the leading end of the recording medium 124.

  The solvent drying device 178 is disposed at a position facing the outer peripheral surface of the drying drum 176 and includes a plurality of IR heaters 182 and hot air ejection nozzles 180 disposed between the IR heaters 182.

  Various drying conditions can be realized by appropriately adjusting the temperature and air volume of the hot air blown toward the recording medium 124 from each hot air ejection nozzle 180 and the temperature of each IR heater 182.

  The surface temperature of the drying drum 176 is set to 50 ° C. or higher. Drying is accelerated by heating from the back surface of the recording medium 124, and image destruction during fixing can be prevented. The upper limit of the surface temperature of the drying drum 176 is not particularly limited, but from the viewpoint of safety of maintenance work such as cleaning ink adhering to the surface of the drying drum 176 (preventing burns due to high temperatures). It is preferably set to 75 degrees or less (more preferably 60 degrees C or less).

  It is held on the outer peripheral surface of the drying drum 176 so that the recording surface of the recording medium 124 faces outward (that is, in a state where the recording surface of the recording medium 124 is convex), and is dried while being rotated and conveyed. By doing so, it is possible to prevent the recording medium 124 from being wrinkled or lifted, and to reliably prevent unevenness in drying due to these.

  The recording medium 124 that has been dried by the drying unit 118 is transferred from the drying drum 176 to the fixing drum 184 of the fixing unit 120 via the intermediate conveyance unit 130.

(Fixing part)
The fixing unit 120 includes a fixing drum 184, a halogen heater 186, a fixing roller 188, and an inline sensor 190. Like the processing liquid drum 154, the fixing drum 184 includes a claw-shaped holding unit (gripper) 185 on the outer peripheral surface, and the leading end of the recording medium 124 can be held by the holding unit 185.

  With the rotation of the fixing drum 184, the recording medium 124 is conveyed with the recording surface facing outward. The recording surface is preheated by the halogen heater 186, fixing processing by the fixing roller 188, and by the inline sensor 190. Inspection is performed.

  The halogen heater 186 is controlled to a predetermined temperature (for example, 180 ° C.). Thereby, preheating of the recording medium 124 is performed.

  The fixing roller 188 is a roller member that heats and pressurizes the dried ink to weld the self-dispersing thermoplastic resin fine particles in the ink to form a film of the ink, and heats and pressurizes the recording medium 124. Composed. Specifically, the fixing roller 188 is disposed so as to be in pressure contact with the fixing drum 184 and constitutes a nip roller with the fixing drum 184. As a result, the recording medium 124 is sandwiched between the fixing roller 188 and the fixing drum 184 and nipped at a predetermined nip pressure (for example, 0.15 MPa), and the fixing process is performed.

  The fixing roller 188 is configured by a heating roller in which a halogen lamp is incorporated in a metal pipe such as aluminum having good thermal conductivity, and is controlled to a predetermined temperature (for example, 60 to 80 ° C.). By heating the recording medium 124 with this heating roller, thermal energy equal to or higher than the Tg temperature (glass transition temperature) of the thermoplastic resin fine particles contained in the ink is applied, and the thermoplastic resin fine particles are melted. As a result, pressing and fixing are performed on the unevenness of the recording medium 124, and the unevenness of the image surface is leveled to obtain glossiness.

  In the embodiment of FIG. 1, only one fixing roller 188 is provided, but a configuration in which a plurality of stages are provided in accordance with the image layer thickness and the Tg characteristics of the thermoplastic resin fine particles may be used.

  On the other hand, the in-line sensor 190 is a measuring means for measuring a check pattern, a moisture content, a surface temperature, a glossiness, and the like for an image fixed on the recording medium 124, and a CCD line sensor or the like is applied.

  According to the fixing unit 120 configured as described above, the thermoplastic resin fine particles in the thin image layer formed by the drying unit 118 are heated and pressurized by the fixing roller 188 and are melted. Can be fixed and fixed. Further, by setting the surface temperature of the fixing drum 184 to 50 ° C. or higher, drying is promoted by heating the recording medium 124 held on the outer peripheral surface of the fixing drum 184 from the back surface, thereby preventing image destruction during fixing. In addition, the image intensity can be increased by the effect of increasing the image temperature.

  In addition, when a UV curable monomer is contained in the ink, after the water is sufficiently volatilized in the drying unit, the image is irradiated with UV at the fixing unit equipped with a UV irradiation lamp. The monomer can be cured and polymerized to improve the image strength.

(Output section)
As shown in FIG. 1, a paper discharge unit 122 is provided following the fixing unit 120. The paper discharge unit 122 includes a discharge tray 192. Between the discharge tray 192 and the fixing drum 184 of the fixing unit 120, a transfer drum 194, a conveyance belt 196, and a stretching roller 198 are in contact with each other. Is provided. The recording medium 124 is sent to the conveyor belt 196 by the transfer drum 194 and discharged to the discharge tray 192.

  Although not shown in the drawing, the ink jet recording apparatus 100 of the present example has an ink storage / loading unit for supplying ink to each of the ink jet heads 172M, 172K, 172C, and 172Y in addition to the above-described configuration, and application of processing liquid. A means for supplying a processing liquid to the unit 114, and a head maintenance unit for cleaning each ink jet head 172M, 172K, 172C, 172Y (wiping, purging, nozzle suction, etc. of the nozzle surface), A position detection sensor for detecting the position of the recording medium 124, a temperature sensor for detecting the temperature of each part of the apparatus, and the like are provided.

≪Explanation of circulation system of inkjet head≫
Next, the circulation system of the ink jet recording apparatus will be described. FIG. 2 is a block diagram showing an outline of a circulation type ink supply device.

(overall structure)
The ink supply apparatus 200 shown in the figure has a supply channel 212 and a recovery channel 312. A supply subtank 218 is provided in the supply channel 212, and a recovery subtank 318 is provided in the recovery channel 312. The supply sub tank 218 communicates with the ink tank 252 via the supply pump 220 and a predetermined ink flow path, and the recovery sub tank 318 communicates with the ink tank 252 via the recovery pump 320 and the predetermined ink flow path.

  A head 250 shown in FIG. 2 is a head having a structure in which n head modules 251-1, 251-2,..., 251-n are connected, and each of the head modules 251 has a supply valve 214-1, , 214-n and the supply flow path 212, and also connected to the recovery flow path 312 via the recovery valves 314-1, 314-2, 314-n.

  The supply side manifold 254 and the recovery side manifold 354 are temporary storage portions for ink provided between the supply flow path 212 and the recovery flow path 312 and the head 250. The supply side manifold 254 and the recovery side manifold 354 are communicated with each other by a first bypass channel 390 and a second bypass channel 392, and the bypass channels 390 and 392 are respectively a first bypass channel valve 394 and a second bypass channel 394. Two bypass flow path valves 396 are provided.

  A tube pump is applied to the supply pump 220 and the recovery pump 320. The supply pump 220 controls the pressure (liquid feeding amount) of the supply channel 212 that supplies ink from the ink tank (buffer tank) 252 to the head 250, and the recovery pump 320 recovers ink from the head 250 to the ink tank 252. The pressure (liquid feeding amount) of the recovery channel 312 (circulated) is controlled. The supply pump 220 and the recovery pump 320 can be pumps having the same performance (capacity).

  The supply pump 220 and the recovery pump 320 rotate only in one direction during a period in which the head 250 stops operating (that is, a period in which ink flows stably), and the head 250 performs a discharge operation. When the internal pressure decreases during the period, the supply pump 220 increases the rotation speed and the recovery pump 320 reverses to increase the internal pressure of the head 250.

  The supply sub tank 218 has a structure partitioned into a liquid chamber and an air chamber by a flexible elastic film. When ink flows into the liquid chamber, the elastic film is deformed toward the air chamber according to the volume of the ink that has flowed. On the other hand, since the volume of the ink flowing out from the liquid chamber does not fluctuate, even if a pressure fluctuation occurs in the supply flow path 212, the pressure fluctuation is suppressed by the action of the supply sub tank 218. That is, the supply sub-tank 218 has a pressure adjustment function that suppresses fluctuations in the internal pressure of the head 250 and fluctuations in the internal pressure of the supply flow path 212 due to the pulsating flow caused by the operation of the supply pump 220. The liquid chamber communicates with the ink tank 252 through the drain flow path 228 and the drain valve 230. The collection sub tank 318 has the same configuration as the supply sub tank 218.

  In the ink supply device 200 shown in FIG. 2, a degassing module 360 and a one-way valve 362 for preventing the backflow of ink are provided between the ink tank 252 and the supply pump 220, and the supply pump 220 and the supply subtank 218. Between these, a filter 364 and a heat exchanger (cooling heating device) 366 are provided. The ink sent out from the ink tank 252 is deaerated by the deaeration module 360, air bubbles and foreign matters are removed by the filter 364, temperature-adjusted by the heat exchanger 366, and then sent to the supply sub tank 218. .

  In addition, a one-way valve 370 for preventing back flow of ink is provided between the deaeration module 360 and the recovery pump 320, and a filter 372 is provided, and ink is sent from the ink tank 252 to the recovery sub tank 318. Even in this case, predetermined degassing processing and filtering processing are performed.

  Further, the ink supply device 200 is provided with safety valves (relief valves) 374 and 376, and an abnormality occurs in the supply pump 220 and the recovery pump 320, so that the internal pressures of the supply channel 212 and the recovery channel 312 are a predetermined value. If the pressure rises further, the safety valves 374 and 376 operate to lower the internal pressures of the supply flow path 212 and the recovery flow path 312. In addition, one-way valves 378 and 380 are provided for preventing a reverse flow of ink when the supply pump 220 and the recovery pump 320 are reversely operated.

  The main tank 256 shown in FIG. 2 stores ink supplied to the ink tank 252. When the ink amount in the ink tank 252 decreases, the replenishment pump 382 is operated to send the ink in the main tank 256 to the ink tank 252. The main tank 256 is provided with a filter 384 inside. A liquid level sensor (not shown) is provided in the ink tank 252, and ink is supplied from the main tank 256 to the ink tank 252 when the ink in the ink tank 252 falls below the liquid level sensor.

(Explanation of circulation)
The ink supply apparatus 200 having such a configuration operates the supply pump 220 and the recovery pump 320 to provide a differential pressure between the supply side manifold 254 and the recovery side manifold 354 to circulate the ink. For example, with the supply valve 214 and the recovery valve 314 open, the supply pump 220 is rotated forward to generate negative pressure in the supply-side manifold 254, while the recovery pump 320 is operated in reverse to return to the recovery-side manifold 354. When a negative pressure lower than that on the supply side is generated, ink can flow from the supply side manifold 254 to the recovery side manifold 354 via the head 250, and further, the ink can be circulated via the recovery flow path 312, the recovery sub tank 318, and the like. .

  When the ink is circulated, the second bypass passage valve 396 provided in the second bypass passage 392 is opened, and the supply side manifold 254 and the recovery side manifold 354 are connected via the second bypass passage 392. It is good to communicate. Any one of the bypass channels 390 and 392 may be provided as long as the bypass channels 390 and 392 have a diameter that does not cause pressure loss during pressurization.

  3, 5, and 6 are schematic views illustrating a simplified ink circulation path between the ejection head 250 and the ink tank 252 illustrated in FIG. 2. As described above, in FIGS. 3, 5, and 6, ink is supplied from the ink tank 252 to the head 250, the ink that has not been ejected is collected, and returned to the ink tank 252.

  The deaeration module 360 is connected to the vacuum pump 500 via the vacuum path 502, and the amount of dissolved oxygen in the ink can be reduced by reducing the pressure of the deaeration module 360 with the vacuum pump 500.

  However, with only the configuration of the deaeration module 360, the vacuum pump 500, and the vacuum path 502, the amount of dissolved oxygen in the ink increases due to the deterioration of the vacuum pump over time, and bubbles may be mixed in the head. Therefore, in consideration of the deterioration of the vacuum pump over time, it is conceivable to provide a vacuum pump having a high degassing capacity in advance. However, if a vacuum pump with a high degassing capacity is installed in advance, the dissolved oxygen amount level of the ink will be lowered too much, and foreign matter (Debris) will be generated in the ink, or moisture in the ink will be absorbed. As a result, the ink is dried in the deaeration module and the life of the vacuum pump is shortened.

  Therefore, this embodiment is provided with a vacuum degree adjusting means for adjusting the pressure reduction level of the deaeration module in the vacuum pump at a vacuum degree at which the dissolved oxygen amount of the ink does not become the reference value or less.

<First Embodiment>
FIG. 3 is a schematic view showing a simplified ink circulation path between the ejection head 250 and the ink tank 252, and includes a vacuum regulator 504 in the vacuum path 502. By providing the vacuum regulator 504, a predetermined pressure is applied to the deaeration module 360, so that it is possible to prevent the pressure from the vacuum pump 500 from being excessively applied to the deaeration module 360.

  Therefore, by providing the vacuum regulator 504 in the vacuum path 502, the generation of foreign matter (Debris) in the ink and the drying of the ink in the deaeration module can be prevented, the life of the vacuum pump can be extended, and the ink can be dissolved. By maintaining the oxygen amount at a low level, a high-quality image can be formed.

  As for the maximum drive capability of the vacuum pump 500, the degree of vacuum is preferably −95 kPa or less. The vacuum regulator 504 is preferably adjusted so that the pressure is excessively applied to the deaeration module 360 in the range of 85% to 100% of the maximum driving capacity of the vacuum pump. The maximum driving capacity of the vacuum pump is more preferably a vacuum degree of −97 kPa or less, and the vacuum regulator is more preferably adjusted to be in the range of 85% to 95% of the maximum driving capacity of the vacuum pump. preferable.

  Here, the pressure applied to the deaeration module 360 by the vacuum pump 500 is preferably adjusted by the vacuum regulator 504 so that the degree of vacuum during printing is higher than that during non-printing. By increasing the degree of vacuum at the time of printing, the residual oxygen amount level of the ink during printing can be suitably lowered.

  Specifically, it varies depending on the deaeration module and ink type to be used and the acceptable print quality, but the vacuum degree is in the range of −90 kPa to −85 kPa when not printing, and the vacuum degree is in the range of −100 kPa to −90 kPa when printing. More preferably, the pressure is adjusted by the vacuum regulator 504. It is more preferable to adjust the degree of vacuum during non-printing in the range of −88 kPa to −86 kPa and the degree of vacuum during printing in the range of −100 kPa to −97 kPa.

  Further, the timing of switching the degree of vacuum in the vacuum regulator 504 is preferably during the cleaning of the ejection head 250. When the ink is deaerated by circulating the ink in the ink tank 252 with the head 250 as shown in FIG. 3, the capacity of the deaeration module and the time for the ink to pass through the deaeration module are used. Although it differs depending on the ink circulation, the deaeration can be almost completed by circulating the ink once, and can be completed in about 3 minutes, for example. That is, it takes about 3 minutes to bring the dissolved oxygen amount of the ink to a desired value, but by switching the degree of vacuum during cleaning of the discharge head 250, the waiting time during printing can be eliminated. , The total printing time can be reduced.

  Although the case where the circulation path including the supply flow path 212 and the recovery flow path 312 is between the ejection head 250 and the ink tank 252 has been described, the present embodiment is not limited to this, and as shown in FIG. In addition, an ink jet recording apparatus that does not include the recovery channel 312 may be used.

Second Embodiment
FIG. 5 is a schematic diagram showing a simplified ink circulation path between the ejection head 250 and the ink tank 252, and includes a speed controller 506 in the vacuum path 502 instead of the vacuum regulator 504 in FIG. 3. It is. The speed controller 506 has one end connected to the vacuum path 502 and the other end open to the atmosphere. By providing the speed controller 506, a predetermined pressure is applied to the deaeration module 360, so that it is possible to prevent the pressure from the vacuum pump 500 from being excessively applied to the deaeration module 360.

  Therefore, by providing the speed controller 506 in the vacuum path 502, the generation of foreign matter (Debris) in the ink and the drying of the ink in the deaeration module can be prevented, the life of the vacuum pump can be extended, and the ink can be dissolved. By maintaining the oxygen amount at a low level, a high-quality image can be formed.

  As for the maximum drive capability of the vacuum pump 500, the degree of vacuum is preferably −95 kPa or less. The speed controller 506 is preferably adjusted so that the pressure is excessively applied to the deaeration module 360 in the range of 85% to 100% of the maximum driving capacity of the vacuum pump. The maximum driving capacity of the vacuum pump is more preferably a vacuum degree of −97 kPa or less, and the vacuum regulator is more preferably adjusted to be in the range of 85% to 95% of the maximum driving capacity of the vacuum pump. preferable.

  Here, the pressure applied to the deaeration module 360 by the vacuum pump 500 is preferably adjusted by the speed controller 506 so that the degree of vacuum during printing is higher than that during non-printing. By increasing the degree of vacuum at the time of printing, the residual oxygen amount level of the ink during printing can be suitably lowered.

  Specifically, it varies depending on the deaeration module and ink type to be used and the acceptable print quality, but the vacuum degree is in the range of −90 kPa to −85 kPa when not printing, and the vacuum degree is in the range of −100 kPa to −90 kPa when printing. More preferably, the pressure is adjusted by the vacuum regulator 504. It is more preferable to adjust the degree of vacuum during non-printing in the range of −88 kPa to −86 kPa and the degree of vacuum during printing in the range of −100 kPa to −97 kPa.

  Further, it is preferable that the timing of switching the degree of vacuum in the speed controller 506 is during cleaning of the ejection head 250. By switching the degree of vacuum during cleaning of the ejection head 250, the waiting time during printing can be eliminated, so that the total printing time can be reduced.

  Although the case where the circulation path including the supply flow path 212 and the recovery flow path 312 is between the ejection head 250 and the ink tank 252 has been described, the present embodiment is not limited to this, and the recovery flow path 312 is provided. An inkjet recording apparatus that is not provided may be used.

<Third Embodiment>
FIG. 6 is a schematic diagram showing a simplified ink circulation path between the ejection head 250 and the ink tank 252, and the vacuum pump 500 is provided with a vacuum pump driving capability adjusting means 508 that adjusts the driving capability of the vacuum pump. It is provided. By providing the vacuum pump driving capability adjusting means 508 for adjusting the driving capability of the vacuum pump, a predetermined pressure is applied to the deaeration module 360, and therefore the pressure by the vacuum pump 500 is excessively applied to the deaeration module 360. Can be prevented. In order to adjust the driving capability of the vacuum pump 500, it is conceivable to adjust the exhaust speed of the vacuum pump 500.

  Therefore, by providing the vacuum pump drive capacity adjusting means 508 in the vacuum pump 500, it is possible to prevent the generation of foreign matter (Debris) in the ink and the drying of the ink in the deaeration module, thereby extending the life of the vacuum pump. In addition, a high-quality image can be formed by maintaining the amount of dissolved oxygen at a low level.

  As for the maximum drive capability of the vacuum pump 500, the degree of vacuum is preferably −95 kPa or less. Moreover, it is preferable that the vacuum pump drive capacity adjusting means 508 adjust the pressure so that the pressure is excessively applied to the deaeration module 360 in the range of 85% to 100% of the maximum drive capacity of the vacuum pump. The maximum driving capacity of the vacuum pump is more preferably a vacuum degree of −97 kPa or less, and the vacuum regulator is more preferably adjusted to be in the range of 85% to 95% of the maximum driving capacity of the vacuum pump. preferable.

  Here, it is preferable that the pressure applied to the deaeration module 360 by the vacuum pump 500 is adjusted by the vacuum pump drive capability adjusting means 508 so that the degree of vacuum during printing is higher than that during non-printing. By increasing the degree of vacuum at the time of printing, the residual oxygen amount level of the ink during printing can be suitably lowered.

  Specifically, it varies depending on the deaeration module and ink type to be used and the acceptable print quality, but the vacuum degree is in the range of −90 kPa to −85 kPa when not printing, and the vacuum degree is in the range of −100 kPa to −90 kPa when printing. More preferably, the pressure is adjusted by the speed controller 506. It is more preferable to adjust the degree of vacuum during non-printing in the range of −88 kPa to −86 kPa and the degree of vacuum during printing in the range of −100 kPa to −97 kPa.

  In addition, it is preferable that the vacuum degree switching timing in the vacuum pump driving capability adjusting means 508 is during cleaning of the ejection head 250. By switching the degree of vacuum during cleaning of the ejection head 250, the waiting time during printing can be eliminated, so that the total printing time can be reduced.

  Although the case where the circulation path including the supply flow path 212 and the recovery flow path 312 is between the ejection head 250 and the ink tank 252 has been described, the present embodiment is not limited to this, and the recovery flow path 312 is provided. An inkjet recording apparatus that is not provided may be used.

  Conventionally, the vacuum pump diaphragm needs to be replaced in one year, but in this embodiment, the vacuum pump diaphragm needs to be replaced in three years.

≪Control system≫
FIG. 6 is a block diagram showing a schematic configuration of a control system of the inkjet recording apparatus 100 of the present embodiment.

  As shown in the figure, the inkjet recording apparatus 100 includes a system controller 400, a communication unit 402, an image memory 404, a conveyance control unit 410, a paper feed control unit 412, a processing liquid application control unit 414, a drawing control unit 416, and a drying control. A unit 418, a fixing control unit 420, a paper discharge control unit 422, an operation unit 430, a display unit 432, and the like.

  The system controller 400 functions as a control unit that performs overall control of each unit of the inkjet recording apparatus 100 and also functions as a calculation unit that performs various calculation processes. The system controller 400 includes a CPU, a ROM, a RAM, and the like, and operates according to a predetermined control program. The ROM stores a control program executed by the system controller 400 and various data necessary for control.

  The communication unit 402 includes a required communication interface, and transmits / receives data to / from a host computer connected to the communication interface.

  The image memory 404 functions as a temporary storage unit for various data including image data, and data is read and written through the system controller 400. Image data captured from the host computer via the communication unit 402 is stored in the image memory 404.

  The conveyance control unit 410 controls a recording medium conveyance system in the inkjet recording apparatus 100. That is, the feed drum 152 in the processing liquid application unit 114, the processing liquid drum 154, the drawing drum 170 in the drawing unit 116, the drying drum 176 in the drying unit 118, the driving of the fixing drum 184 in the fixing unit 120, the intermediate transport unit 126, The drive of 128,130 is controlled.

  The conveyance control unit 410 controls the conveyance system in accordance with a command from the system controller 400 so that the recording medium 124 is conveyed from the paper supply unit 112 to the paper discharge unit 122 without delay.

  The paper feed control unit 412 controls the paper feed unit 112 according to a command from the system controller 400 so that the recording media 124 are fed one by one in order without overlapping.

  The processing liquid application control unit 414 controls the processing liquid application unit 114 in accordance with a command from the system controller 400. Specifically, the driving of the coating device 156 is controlled so that the processing liquid is applied to the recording medium conveyed by the processing liquid drum (pressure path) 154.

  The drawing control unit 416 controls the drawing unit 116 in response to a command from the system controller 400. Specifically, the drive of the inkjet heads 172M, 172K, 172C, and 172Y is controlled so that a predetermined image is recorded on the recording medium conveyed by the drawing drum 170. Further, the printing is interrupted before the printing limit time n elapses.

  The supply control unit 424 controls driving of the supply pump 220 and the recovery pump 320 to supply ink from the ink tank 252 to the inkjet heads 172M, 172K, 172C, 172Y (250) and recover ink to the ink tank 252. . Further, when the ink in the ink tank 252 is deaerated, the ink is circulated through the supply channel 212 and the recovery channel 312.

  Further, the vacuum degree adjusting means 504 (506, 508) is controlled in accordance with a command from the system controller 400 to control the pressure to the deaeration module 360. When the vacuum degree adjusting means is the vacuum pump driving ability adjusting means 508, the driving ability of the vacuum pump 500 is adjusted by the vacuum pump driving ability adjusting means 508.

  When the pressure applied to the degassing module 360 by the vacuum pump 500 is adjusted by the vacuum degree adjusting means 504 (506, 508) so that the vacuum degree during printing is higher than that during non-printing, the system controller 400 To control the vacuum degree adjusting means 504 (506, 508).

  The drying control unit 418 controls the drying unit 118 according to a command from the system controller 400. Specifically, the drive of the solvent drying device 178 is controlled so that the recording medium 124 conveyed by the drying drum 176 is dried by the IR heater 182 and the hot air jet nozzle 180.

  The fixing control unit 420 controls the fixing unit 120 in accordance with a command from the system controller 400. Specifically, the driving of the halogen heater 186 and the fixing roller 188 is controlled so that the recording medium conveyed by the fixing drum 184 is heated and pressed. Further, the operation of the inline sensor 190 is controlled so that the fixed image is read.

  The paper discharge control unit 422 controls the paper discharge unit 122 according to a command from the system controller 400. Specifically, driving of the transfer drum 194, the conveying belt 196, the stretching roller 198, and the like is controlled so that the recording medium 124 is stacked on the discharge tray 192.

  The operation unit 430 includes necessary operation means (for example, operation buttons, a keyboard, a touch panel, etc.), and outputs operation information input from the operation means to the system controller 400. The system controller 400 executes various processes in accordance with the operation information input from the operation unit 430.

  The display unit 432 includes a required display device (for example, an LCD panel or the like), and displays required information on the display device in response to a command from the system controller 400.

  As described above, the image data to be recorded on the recording medium 124 is taken into the inkjet recording apparatus 100 from the host computer via the communication unit 402. The captured image data is stored in the image memory 404.

  The system controller 400 performs necessary signal processing on the image data stored in the image memory 404 to generate dot data. Then, the driving of each inkjet head 172M, 172K, 172C, 172Y of the drawing unit 116 is controlled according to the generated dot data, and the image represented by the image data is recorded on the paper.

  The dot data is generally generated by performing color conversion processing and halftone processing on image data. The color conversion process is a process of converting image data expressed in sRGB or the like (for example, RGB 8-bit image data) into ink amount data of each color of ink used in the inkjet recording apparatus 100 (in this example, M, (Converted into ink amount data of each color of K, C, Y). The halftone process is a process of converting the ink amount data of each color generated by the color conversion process into dot data of each color by a process such as error diffusion.

  The system controller 400 performs color conversion processing and halftone processing on the image data to generate dot data for each color. Then, according to the generated dot data of each color, the drive of the corresponding ink jet head is controlled to record the image represented by the image data on the paper.

  DESCRIPTION OF SYMBOLS 100 ... Inkjet recording device, 112 ... Paper feed part, 114 ... Processing liquid provision part, 116 ... Drawing part, 118 ... Drying part, 120 ... Fixing part, 122 ... Paper discharge part, 124 ... Recording medium, 200 ... Ink supply apparatus , 212 ... supply flow path, 220 ... supply pump, 250 ... head (discharge head), 252 ... ink tank, 256 ... main tank, 312 ... collection flow path, 320 ... collection pump, 328 ... replenishment pump, 360 ... deaeration Module, 382 ... replenishment pump, 400 ... system controller, 500 ... vacuum pump, 502 ... vacuum path, 504 ... vacuum regulator (vacuum degree adjusting means), 506 ... speed controller (vacuum degree adjusting means), 508 ... vacuum pump drive capability Adjustment means (Vacuum degree adjustment means)

Claims (11)

An ejection head in which ejection openings for ejecting ink are formed;
An ink tank that is connected to the discharge head via a supply flow path and that stores the ink supplied to the discharge head through the supply flow path;
A degassing module provided in the supply flow path for degassing the ink;
A vacuum pump connected to the degassing module via a vacuum path and depressurizing the degassing module;
An ink jet recording apparatus comprising: a degree of vacuum adjusting means for adjusting a pressure reduction level of the degassing module in the vacuum pump at a degree of vacuum at which a dissolved oxygen amount of the ink does not become a reference value or less.   The inkjet recording apparatus according to claim 1, wherein the vacuum degree adjusting unit is a vacuum regulator provided in the vacuum path.   The inkjet recording apparatus according to claim 1, wherein the vacuum degree adjusting unit is a speed controller having one end provided in the vacuum path and the other end opened to the atmosphere.   The inkjet recording apparatus according to claim 1, wherein the vacuum degree adjusting unit is a vacuum pump driving capability adjusting unit that adjusts a driving capability of the vacuum pump.   5. The inkjet recording apparatus according to claim 1, wherein the maximum driving capability of the vacuum pump is a vacuum degree of −95 kPa or less.   6. The ink jet recording apparatus according to claim 1, wherein the vacuum degree adjusting unit adjusts the vacuum pump so as to be in a range of 85% to 100% of a maximum driving capacity of the vacuum pump.   The inkjet recording apparatus according to claim 1, wherein the vacuum degree adjusting unit adjusts the degree of vacuum during printing higher than that during non-printing.   The inkjet recording apparatus according to claim 7, wherein the vacuum degree adjusting unit adjusts the degree of vacuum during non-printing in a range of −90 kPa to −85 kPa and the degree of vacuum during printing in a range of −100 kPa to −90 kPa.   The inkjet recording apparatus according to claim 7 or 8, wherein the vacuum degree switching timing of the vacuum degree adjusting means is during the cleaning of the ejection head.   The inkjet recording apparatus according to claim 1, wherein the vacuum degree adjusting unit is controlled by a system controller.   11. The ink jet recording apparatus according to claim 1, wherein a recovery flow path for recovering ink from the discharge head to the ink tank is connected between the discharge head and the ink tank.

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