JP2012101366A - Ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve deaeration performance and pressure controllability.SOLUTION: An ink jet recorder includes a tank 33 for storing liquid therein, an ink jet head 25 for ejecting the liquid, supply flow channels 210, 211 for supplying the liquid in the tank 33 to the ink jet head 25, a deaeration filter 83 provided in the middle between the supply flow channels 210, 211, a depressurization chamber 85 connected to the deaeration filter 83 via a depressurization switch valve 87, and a pump 91 for reducing the pressure in the depressurization chamber 85.

Description

  The present invention relates to an ink jet recording apparatus, and more particularly to an ink jet recording apparatus that supplies good degassed ink to an ink jet head.

  Conventionally, ink is ejected from an ink jet head onto a recording surface of a recording medium to form an image on the recording medium. In such an ink jet recording apparatus, it is important that ink ejection from the recording head is stable. In particular, a certain amount of gas is usually dissolved in the ink (dissolved gas), and bubbles are formed in the ink flow path and the recording head, preventing the flow of ink and causing an undischarge phenomenon in which the ink does not fly. Adverse effects such as For this reason, an inkjet recording apparatus having a deaeration device for deaerating ink supplied to the recording head is used.

  Further, as the ink used in the ink jet recording apparatus, an ultraviolet curable ink containing a photoinitiator having a predetermined sensitivity to ultraviolet rays is used, and the ultraviolet curable ink landed on the recording medium is irradiated with ultraviolet rays. Image formation to be cured is performed. In such a UV curable ink, when the amount of dissolved oxygen is lowered, the amount of oxygen that becomes a polymerization inhibition factor is lowered, so that dark polymerization proceeds and a gel substance is generated in the ink supply channel, resulting in clogging. There was a problem.

  For example, in Patent Document 1 below, when an ink jet performs a discharge operation, ink from which dissolved gas is removed is supplied to an ink chamber in the ink jet head, and when a discharge operation is not performed, ink supplied with a gas is disclosed. An ink jet recording apparatus that fills the ink chamber is described.

JP 2006-110780 A

However, the inkjet recording apparatus described in Patent Document 1 includes a hollow portion between the sub tank and the inkjet head, and absorbs dissolved gas in the ink that passes through the hollow portion and supplies gas to the ink. This was done using a suction air pump. Therefore, since the pressure could not be changed suddenly, there was a problem that a large deaeration effect could not be obtained and the pressure controllability was not good. In addition, when the power is turned off, the pressure in the deaeration filter cannot be controlled, and there is a problem that the ink cannot be returned from the reduced pressure state.

  This invention is made | formed in view of such a situation, and it aims at improving the deaeration performance and improving pressure controllability by changing the pressure in an apparatus sharply. Moreover, it aims at returning the pressure in a deaeration filter instantaneously at the time of a power supply interruption.

  In order to achieve the above object, a first aspect of the present invention provides a tank in which a liquid is stored, an ink jet head for discharging the liquid, and a supply flow for supplying the liquid in the tank to the ink jet head. A degassing filter provided in the middle of the supply channel, a depressurization chamber connected to the degassing filter via a depressurization on-off valve, and a pump for depressurizing the pressure in the depressurization chamber. An ink jet recording apparatus is provided.

  According to the first aspect, the deaeration filter is provided in the middle of the supply flow path for supplying the liquid from the tank to the ink jet head. Then, the pressure in the deaeration filter is adjusted by using the decompression opening / closing valve and the decompression chamber to instantaneously open the decompression opening / closing valve, thereby applying abrupt decompression to the liquid. Therefore, the deaeration effect of the liquid in the deaeration filter can be improved. Moreover, since the inside of a deaeration filter can be stably pressure-reduced by using a decompression chamber, it can deaerate stably.

  According to a second aspect of the present invention, the liquid according to the first aspect of the present invention is an ultraviolet curable ink, and includes a pressure channel and a pressure switching valve for supplying oxygen or a gas containing oxygen to the liquid in the deaeration filter. And

  When UV curable ink is used as the liquid, dark polymerization proceeds in a state where the amount of dissolved oxygen is reduced, gel material is generated, and nozzles and flow paths are clogged. According to the second aspect of the present invention, since the pressurizing flow path and the pressurization opening / closing valve for supplying oxygen or a gas containing oxygen to the liquid in the degassing filter are provided, oxygen is supplied into the degassed ultraviolet curable ink. be able to. Therefore, generation | occurrence | production of a gel substance can be suppressed and generation | occurrence | production of clogging can be prevented.

  A third aspect of the present invention is the method according to the second aspect of the present invention, when the image is formed, the decompression on-off valve is opened, the pressurization on-off valve is closed, the inside of the degassing filter is decompressed, and at the time of image formation standby, the decompression on-off valve is closed. And a valve control means for opening the pressurizing on-off valve and supplying oxygen into the deaeration filter.

  According to the third aspect of the present invention, the inside of the deaeration filter is depressurized during image formation, and oxygen is supplied into the deaeration filter during image formation standby. Generation | occurrence | production can be suppressed and the fall of the amount of dissolved oxygen can be prevented at the time of image formation standby.

  A fourth aspect of the present invention is characterized in that, in the second or third aspect, the pressure reducing on-off valve is a normally closed type that closes when not energized, and the pressure on-off valve is a normally open type that opens when not energized. .

  According to the fourth aspect of the present invention, since the pressure reducing on-off valve is a normally closed type and the pressure on / off valve is a normally open type, oxygen is supplied into the deaeration filter when the power is not supplied, and the pressure is increased to atmospheric pressure or increased. Pressure. Therefore, when the apparatus power supply is momentarily interrupted, the pressure in the deaeration filter can be set to atmospheric pressure or pressurization, so that the generation of gel substance can be suppressed.

  A fifth aspect of the present invention is characterized in that, in any one of the first to fourth aspects, the pressure in the decompression chamber is 0.04 to 0.09 MPa.

  The fifth aspect defines the pressure in the decompression chamber. By setting the pressure in the decompression chamber within the above range, deaeration can be performed stably.

  A sixth aspect of the present invention is characterized in that, in any one of the first to fifth aspects, a sub-tank for temporarily storing the liquid is provided between the tank and the deaeration filter in the supply flow path.

  According to the sixth aspect, by supplying the liquid discharged from the tank to the ink jet head via the sub tank, the liquid can be stably supplied.

  A seventh aspect of the present invention is the method according to the sixth aspect, wherein the liquid passage that has passed through the deaeration filter is returned to the sub-tank, a circulation opening / closing valve provided in the middle of the circulation passage, and the tank and the sub-tank are connected to each other. A supply opening / closing valve provided in the middle of the supply flow path is provided.

  According to the seventh aspect, since the circulation passage for returning the liquid that has passed through the deaeration filter to the sub tank is provided, the amount of dissolved gas in the sub tank can be controlled efficiently.

  An eighth aspect of the present invention includes the start-up sequence according to the seventh aspect, wherein at the start of image formation, the deaeration filter is depressurized, the circulation opening / closing valve is opened, the supply opening / closing valve is closed, and the liquid in the sub tank is circulated. It is characterized by that.

  According to the eighth aspect, the amount of dissolved gas can be reduced in a short time by reducing the pressure in the degassing filter and circulating the liquid at the start of image formation.

  A ninth aspect according to the seventh or eighth aspect is the end sequence in which the inside of the deaeration filter is pressurized, the circulation on-off valve is opened, the supply on-off valve is closed, and the liquid in the sub tank is circulated at the end of image formation. It is characterized by providing.

  According to the ninth aspect, the amount of dissolved gas can be increased efficiently by pressurizing the inside of the deaeration filter and circulating the liquid at the end of image formation.

  A tenth aspect of the present invention according to any one of the sixth to ninth aspects, wherein the sub tank is connected to the decompression chamber, and the decompression chamber applies a back pressure to the liquid inside the inkjet head. It also serves as an adjustment unit.

  According to the tenth aspect, the back pressure applied to the liquid inside the ink jet head is adjusted using the decompression chamber provided in the pressure control unit. Therefore, the cost can be reduced by performing the back pressure control of the liquid in the inkjet head and the adjustment of the pressure in the deaeration filter using the same decompression chamber. Moreover, since the number of pumps can be one, the apparatus can be miniaturized.

  An eleventh aspect is characterized in that, in the tenth aspect, a pressure loss filter is provided between the sub tank and the decompression chamber.

  According to the eleventh aspect, by providing the pressure loss filter, more stable control can be performed.

  According to the ink jet recording apparatus of the present invention, the degassing filter is provided between the supply flow path connecting the tank for storing the liquid and the ink jet head, and the degassing filter is connected to the decompression chamber via the open / close valve, thereby opening and closing. The pressure in the deaeration filter can be changed rapidly by turning the valve on and off. Therefore, the deaeration performance can be improved and the pressure controllability can be improved.

1 is an external perspective view of an ink jet recording apparatus according to an embodiment of the present invention. It is explanatory drawing which shows typically the paper conveyance path of an inkjet recording device. It is a plane perspective view which shows the structural example of an inkjet head. 1 is a block diagram showing a configuration of an ink supply system according to a first embodiment of an ink jet recording apparatus. It is a block diagram which shows the structure of the ink supply system concerning 2nd Embodiment of an inkjet recording device. 9 shows a flowchart at the time of operation of an ink supply system according to a second embodiment. It is a block diagram which shows the structure of the ink supply system concerning 3rd Embodiment of an inkjet recording device. It is a block diagram which shows the structure of an inkjet recording device.

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

[Overall configuration of inkjet recording apparatus]
FIG. 1 is an external perspective view of an ink jet recording apparatus according to an embodiment of the present invention. The inkjet recording apparatus 100 is a wide format printer that records a wide drawing range, such as a large poster or a commercial wall advertisement, and includes an apparatus main body 21 and support legs 23 that support the apparatus main body 21. In addition, here, what corresponds to A3 Nobi or more is called a “wide format”.

  The apparatus main body 21 includes a multi-channel type inkjet head 25 and a fixed platen 27. The ink jet head 25 is mounted on a carriage 30 that is reciprocated in a scanning direction Y perpendicular to the recording medium conveyance direction X along a guide mechanism 29 that is a head moving means (scanning means). As the recording medium S, various media such as paper, non-woven fabric, vinyl chloride, synthetic chemical fiber, polyethylene, polyester, and tarpaulin can be used regardless of the material, regardless of whether they are permeable media or non-permeable media. it can.

  The platen 27 shown in FIG. 1 is formed in an inverted bowl shape, and the upper surface serves as a support surface of the recording medium S. A pair of scanning conveyance rollers (not shown in FIG. 1, not shown in FIG. 1 and indicated by reference numeral 43 in FIG. 2) is disposed upstream of the platen 27 in the recording medium conveyance direction X as recording medium conveyance means. The scanning conveyance roller pair moves the recording medium S on the platen 27 in the recording medium conveyance direction X. The scanning conveyance roller pair holds only the end portion in the width direction of the recording medium, and reduces the diameter of the central portion of the recording medium S, thereby preventing interference with the open / close lid of the platen 27. The inkjet head 25 is moved by a guide mechanism 29 in a scanning direction Y that is orthogonal to the recording medium conveyance direction X and parallel to the support surface of the platen 27.

  An ink cartridge mounting portion for mounting a replaceable cartridge 33 for storing ink is provided on the left front surface of the apparatus main body 21. The cartridge 33 is provided corresponding to each color ink used in the ink jet recording apparatus 100 of this example. Each cartridge 33 is connected to the inkjet head 25 by an ink supply path (not shown) formed independently, and the cartridge 33 is replaced when the remaining amount of ink of each color decreases.

  The ink jet recording apparatus 100 of this example can use either ultraviolet curable ink (UV ink) or solvent ink, and the type of ink can be changed by replacing the cartridge 33. .

  Although not shown, a maintenance unit for the inkjet head 25 is provided on the right side of the apparatus main body 21 as viewed from the front. The maintenance unit is provided with a cap for keeping the ink-jet head 25 moisturized during non-printing and a wiping member (blade, web, etc.) for cleaning the nozzle surface (ink discharge surface) of the ink-jet head 25. The cap for capping the nozzle surface of the inkjet head 25 is provided with an ink receiver for receiving ink droplets ejected from the nozzle for maintenance.

  The ink jet recording apparatus 100 includes elevating means such as a screw mechanism that elevates the ink jet head 25 up and down with respect to the platen 27, and the ink jet head according to the thickness of the recording medium S mounted on the platen 27. 25 can be moved up and down with respect to the platen 27.

[Description of paper transport path]
FIG. 2 is an explanatory diagram schematically showing a sheet conveyance path in the inkjet recording apparatus 100 shown in FIG. As shown in FIG. 2, the recording medium S fed from the feeding supply roll 41a is fed by a pair of scanning conveyance rollers 43 provided at the entrance of the printing unit (upstream in the recording medium conveyance direction X of the platen 27). It is intermittently conveyed along the recording medium conveyance direction X indicated by the arrow line. The recording medium S that has reached the printing unit immediately below the ink jet head 25 is printed by the ink jet head 25, and is taken up by the take-up roll 41b after printing. A guide 45 for the recording medium S is provided downstream of the printing unit in the recording medium conveyance direction X.

  In order to adjust the temperature of the recording medium S during printing on the back surface (the surface opposite to the surface supporting the recording medium S) of the platen 27 that supports the recording medium S in the printing unit. The temperature control unit 47 is provided. When the recording medium S at the time of printing is adjusted so as to have a predetermined temperature, the physical properties such as the viscosity of the ink droplets that have landed on the recording medium S and the surface tension become the desired values, and the desired dot diameter is set. Can be obtained. If necessary, the pre-temperature control unit 49 may be provided on the upstream side of the temperature control unit 47, or the after-temperature control unit 51 may be provided on the downstream side of the temperature control unit 47.

[Inkjet head]
FIG. 3 is a plan perspective view showing a configuration example of the inkjet head 25.

  The carriage 30 that reciprocates in the main scanning direction Y is mounted with the inkjet head 25 and the ultraviolet irradiation units 35a, 35b, 35c, and 35d in an integrated manner. The inkjet head 25 has nozzle rows 61C, 61M, 61Y, 61K, 61CL in which a plurality of nozzles are arranged at equal intervals in the recording medium conveyance direction X corresponding to the colors C, M, Y, K, CL, and W. , 61W is provided.

  In FIG. 3, the nozzle rows are indicated by broken lines, and individual illustrations of the nozzles are omitted. In the following description, the nozzle rows 61C, 61M, 61Y, 61K, 61CL, and 61W may be collectively referred to by the reference numeral 61 to represent the nozzle rows.

  In the inkjet head 25 shown in this example, the arrangement pitch (nozzle pitch) of the nozzles constituting the nozzle row 61 is 254 μm (100 dpi), the number of nozzles constituting the nozzle row 61 is 256 nozzles, and the total length of the nozzle row is about 65 μm ( 254 μm × 255 = 64.8 μm). Further, the discharge frequency is 15 kHz, and three types of discharge droplet amounts of 10 pl, 20 pl, and 30 pl can be distinguished by changing the drive waveform.

  In addition, the aspect which comprises the separate inkjet head for every color is also possible. For example, an inkjet head 25C having a nozzle row 61C, an inkjet head 25M having a nozzle row 61M, an inkjet head 25Y having a nozzle row 61Y, an inkjet head 25K having a nozzle row 61K, and an inkjet head 25CL having a nozzle row 61CL In addition, an aspect in which the inkjet heads 25W having the nozzle rows 61W are arranged at equal intervals so as to be aligned along the main scanning direction is also possible.

  Further, a nozzle row (inkjet head) corresponding to LC (light cyan) and LM (light magenta) may be added to the configuration shown in FIG. 3, or a nozzle row (inkjet head) and W corresponding to CL may be added. Instead of the nozzle row (inkjet head), nozzle rows corresponding to LC and LM may be used.

  As the ink ejection method of the inkjet head 25, a method in which ink droplets are ejected by deformation of an actuator represented by a piezo element (piezoelectric element) (piezo jet method), and a bubble is generated by heating ink with a heating element such as a heater. Any of the thermal jet methods that eject ink droplets at that pressure can be employed. However, when UV ink is used, it is preferable to employ a piezo jet method. In this embodiment, a piezo jet method is employed.

  The inkjet head 25 having such a structure is applied with multi-pass drawing control, and can change the printing resolution by changing the number of passes. In the high production mode, printing is performed at a resolution of 600 dpi × 400 dpi. In the main scanning direction, a resolution of 600 dpi is realized by two passes (two scans), dots are formed at a resolution of 300 dpi in the first scan (outward pass), and the second scan (return pass) is the first scan. Dots are formed so that the middle of the formed dots is interpolated at 300 dpi. Further, in the sub-scanning direction, dots are formed at a resolution of 100 dpi by one scan, so that a resolution of 400 dpi is realized by four passes (four scans).

  In the standard mode, printing is executed at a resolution of 600 dpi × 800 dpi, and a resolution of 600 dpi × 800 dpi is obtained by two passes in the main scanning direction and eight passes in the sub-scanning. In the high image quality mode, printing is executed at a resolution of 1200 × 1200 dpi, and a resolution of 1200 dpi × 1200 dpi is obtained with 4 passes in the main scanning direction and 12 passes in the sub-scanning direction. The main scanning speed of the carriage is 1270 mm / sec in the high production mode.

[Ultraviolet irradiation part]
The ultraviolet irradiation units 35a and 35b shown in FIG. 3 are light sources for temporarily curing the ink droplets ejected from the inkjet head 25 to the recording medium S so that the adjacent ink droplets do not coalesce. As the (pinning light source), a plurality of ultraviolet LED elements (hereinafter simply referred to as LED elements) 63 are provided. The ultraviolet irradiation units 35c and 35d include a plurality of LED elements 65c and 65d as a light source (curing light source) for finally curing (main curing) ink droplets.

  That is, ultraviolet irradiation units 35 a and 35 b that are active energy irradiation units are arranged on both the left and right sides of the main scanning direction Y of the inkjet head 25, and further, the ultraviolet irradiation unit is disposed downstream of the inkjet head 25 in the recording medium conveyance direction X. 35c and 35d are arranged. The ultraviolet irradiation units 35 a and 35 b can move together with the inkjet head 25 by the reciprocating movement of the carriage 30. When ultraviolet curable ink (UV ink) is used, the ink droplets ejected from each nozzle and landed on the recording medium S are either one of the ultraviolet irradiation units 35a and 35b that pass immediately above. The ultraviolet rays for temporary curing are irradiated by the ultraviolet irradiation portion.

  The ink droplets on the recording medium S that have passed through the printing area of the inkjet head 25 are irradiated with ultraviolet rays for main curing by the ultraviolet irradiation units 35c and 35d. The color ink on the recording medium S that has passed through the drawing region of the inkjet head 25 is used for main curing from the ultraviolet irradiation units 35c and 35d when the ultraviolet irradiation units 35c and 35d pass through the upper part by the reciprocation of the carriage 30. Ultraviolet rays are irradiated.

  The ultraviolet irradiation units 35 a and 35 b have a structure in which a plurality of LED elements 63 are arranged in a line along the sub-scanning direction X. FIG. 3 illustrates an example in which eight LED elements 63 are provided in the ultraviolet irradiation units 35a and 35b. However, the number of LED elements 63 is four, two according to the irradiation energy required for temporary curing. It is also possible to reduce the number of elements as appropriate, such as a single element. Of course, an aspect including more than eight LED elements 63 is also possible.

  The ultraviolet irradiation units 35c and 35d have a structure in which a plurality of LED elements 65c and 65d are arranged along the main scanning direction. The LED elements 65c of the ultraviolet irradiation unit 35c are arranged in the opposite direction of the nozzle row 61W, and the LED elements 65d of the ultraviolet irradiation unit 35d are arranged in the opposite direction of the nozzle row 61C. With this structure, it is possible to prevent the ultraviolet rays irradiated from the ultraviolet irradiation units 35c and 35d from reaching the nozzle rows 61C, 61M, 61Y, 61K, 61CL, and 61W and curing the ink inside the nozzles.

[Configuration of ink supply system]
Next, configuration examples (first to third embodiments) of an ink supply system (ink supply device) of the inkjet recording apparatus 100, which is a characteristic part of the present invention, will be described.

(First embodiment)
FIG. 4 is a block diagram illustrating a configuration example of the ink supply system according to the first embodiment. In FIG. 4, for convenience of explanation, only the ink supply system for one color is shown, but in the case of a plurality of colors, a plurality of components having the same configuration are provided.

  As shown in FIG. 4, the ink supply system according to the first embodiment mainly includes a cartridge 33, a sub tank 73, and a deaeration filter 83. The sub tank 73 is provided with a back pressure adjustment unit 75 for applying a predetermined back pressure to the ink inside. The deaeration filter 83 is provided with a pressure control unit 95 that degass the ink supplied from the sub tank 73 to the inkjet head 25 or supplies the gas. In the present embodiment, the cartridge corresponds to a tank.

  The ink stored in the cartridge 33 is sucked by the supply pump 71 and sent to the inkjet head 25 through the sub tank 73.

  The back pressure adjusting unit 75 includes a pressure increasing / decreasing pump 79 communicated with the sub tank 73 via the valve 77 by the back pressure adjusting flow path 214, and a pressure gauge 81 provided between the valve 77 and the pressure increasing / decreasing pump 79. Are provided.

  In the pressure control unit 95, the deaeration filter 83 and the decompression chamber 85 are connected by a deaeration decompression channel 212. A depressurization opening / closing valve is connected in the middle of the deaeration depressurization flow path 212. The decompression chamber 85 includes a decompression pump 91 for reducing the pressure in the decompression chamber 85.

  Further, a pressure channel 213 and a pressure opening / closing valve 89 for opening the deaeration filter 83 to the atmosphere are provided. In FIG. 4, the pressurizing channel 213 is provided in the middle of the degassing decompression channel 212, and a part of the degassing decompression channel 212 also serves as the pressurizing channel. It is also possible to provide it separately from the deaeration pressure reducing channel 212. Further, it is possible to supply the atmosphere into the deaeration filter 83 by providing a pressurization opening / closing valve in the deaeration pressure reduction channel 212 without providing the pressurization channel.

  The cartridge 33 is an ink supply source that stores ink to be supplied to the inkjet head 25. One end of the supply flow path 210 is connected to the cartridge 33, and the other end of the supply flow path 210 is connected to the sub tank 73 via the supply pump 71. The sub tank 73 functions as a liquid storage part (liquid buffer chamber) in which the ink supplied from the cartridge 33 is temporarily stored.

  One end of the supply flow path 211 is connected to the sub tank 73, and the other end of the supply flow path 211 is connected to the inkjet head 25 via the deaeration filter 83. The deaeration filter 83 is connected to the pressure control unit 95, and deaeration of ink supplied to the inkjet head 25 and supply of gas are performed.

  As the deaeration filter 83, a hollow fiber membrane made of a Teflon (registered trademark) tube or a silicon tube can be used. By passing the ink inside the hollow fiber membrane and reducing the pressure around the hollow fiber membrane, the pressure is increased. Adjust the dissolved gas in the ink.

  In the pressure control unit 95, a depressurization chamber 85 is connected to a deaeration filter 83 through a degassing decompression flow path 212 via a decompression opening / closing valve 87. The decompression chamber 85 includes a decompression pump 91 for decompressing the interior of the decompression chamber, and a pressure gauge 93 for measuring the pressure. Before deaeration in the deaeration filter 83, the pressure is set within the range of 0.04 to 0.09 MPa (0.4 to 0.9 atm) in the decompression chamber 85. In this state, by opening the pressure reducing opening / closing valve 87, the pressure can be instantaneously reduced and the deaeration performance can be improved. The pressure in the decompression chamber 85 is preferably 0.04 to 0.09 MPa. By setting the pressure in the decompression chamber 85 within the above range, the ink can be deaerated stably. Since the ink is degassed at the time of image formation, the ink can be degassed efficiently from the initial stage of image formation, so that the generation of a cavity in the ink pressure chamber in the inkjet head 25 can be suppressed. . Further, by using the decompression chamber 85, it is possible to suppress the pressure fluctuation in the deaeration filter 83 with respect to the contraction deformation of the deaeration pressure reduction channel 212 connecting the deaeration filter 83 and the decompression chamber 85. Can be performed stably. In the present invention, the pressure reducing on / off valve 87 is preferably a valve that switches on and off instantaneously. Moreover, even if it is a flow control valve, it can be used if it is a valve which raises a flow in steps. In addition, the valve used in the present invention is preferably an electromagnetic valve or an electric valve that opens and closes by electricity.

  Further, the deaeration filter 83 is opened to the atmosphere through a pressurization opening / closing valve 89. When ultraviolet curable ink is used as the ink, if oxygen (dissolved gas) is insufficient due to the deaeration process at the time of image formation, dark polymerization proceeds and gel substances are generated, causing clogging of the flow path and nozzle. Therefore, when waiting for image formation, it is necessary to release the reduced pressure state and supply oxygen (gas). During standby for image formation, by closing the pressure reducing on / off valve 87, opening the pressure on / off valve 89, and opening to the atmosphere, dark polymerization of the ink can be suppressed and clogging of the flow path can be prevented. In addition, although FIG. 4 demonstrated in the aspect open | released to air | atmosphere, the aspect which provides an oxygen cylinder and supplies oxygen from an oxygen cylinder is also possible.

  The pressure reducing on / off valve 87 is preferably a normally closed type that closes when not energized, and the pressure on / off valve 89 is preferably a normally open type that opens when not energized. By setting it as the said structure, since the pressure in a deaeration filter can be made into atmospheric pressure at the time of the momentary interruption of an apparatus power supply, generation | occurrence | production of a gel substance can be suppressed.

  The back pressure adjusting unit 75 applied to the sub tank 73 is a mechanism that applies a predetermined back pressure (negative pressure) to the ink inside the inkjet head 25. During normal image formation, the pressure increasing / decreasing pump 79 operates in the direction of sucking ink in the sub tank 73, and the internal pressure of the sub tank 73 and the internal pressure of the inkjet head 25 are maintained at negative pressure. Thereby, the ink meniscus of the nozzle in the inkjet head 25 can be maintained, and ink leakage from the nozzle can be prevented. On the other hand, at the time of maintenance of the ink jet head 25, the pressure increasing / decreasing pump 79 operates in a direction to pressurize the ink in the sub tank 73, and the inside of the sub tank 73 and the inside of the ink jet head 25 are forcibly pressurized. The ink inside can be discharged through the nozzle. Further, a normally closed type opening / closing valve (not shown) is provided in the middle of the supply flow path 211 connecting the deaeration filter 83 and the inkjet head 25, and the opening / closing valve is closed during standby for image formation. The pressure can be prevented from becoming atmospheric pressure. By closing the open / close valve, it is possible to prevent liquid leakage from the inkjet head 25 during standby for image formation (at atmospheric pressure).

(Second Embodiment)
Next, a second embodiment of the present invention will be described. FIG. 5 is a block diagram illustrating a configuration example of an ink supply system according to the second embodiment. Hereinafter, description of parts common to the first embodiment will be omitted, and description will be made focusing on characteristic parts of the present embodiment.

  The ink supply system according to the second embodiment is that the circulation channel 220 is provided between the supply channel 211 on the outlet side of the deaeration filter 83 and the supply channel 210 on the inlet side of the sub tank 73. It is different from the embodiment. A circulation opening / closing valve 221 is provided in the middle of the circulation flow path 220, and a supply opening / closing valve 222 is provided between the cartridge 33 and the point where the supply flow path 210 joins the circulation flow path 220. . The circulation opening / closing valve 221 is preferably a normally closed type valve, and the supply opening / closing valve 222 is preferably a normally open type valve.

  The sub tank 73 preferably has a gas-liquid interface, and is preferably formed of a gas permeable material such as low density polyethylene. When the image formation is stopped, the ink in the deaeration filter 83 is circulated through the circulation channel 220 to the sub tank 73 side. At this time, the pressure control unit 95 closes the decompression on-off valve 87 and opens the pressurization on-off valve 89 to open the deaeration filter to the atmosphere. Moreover, since the subtank 73 has a gas-liquid interface, the contact between the ink and the gas can be increased, so that the amount of dissolved gas in the ink can be increased. By this operation, it is possible to increase the dissolved gas amount of the ink staying in the sub tank 73 and the supply flow paths 210 and 211 during the standby for image formation, so that it is possible to prevent the gel substance from being generated in the flow path.

  On the other hand, at the start of image formation, the pressure control unit 95 opens the decompression on-off valve 87 and closes the pressurization on-off valve 89 to make the decompression state and circulate between the sub tank 73 and the deaeration filter 83. Thus, the amount of dissolved gas can be reduced in a short time.

  FIG. 6 shows a flowchart at the time of operation of the ink supply system in the second embodiment. When image formation starts, first, the pressure reducing on / off valve 87 is closed (S10), and the pressure reducing pump 91 is operated to reduce the pressure in the pressure reducing chamber 85 to a predetermined pressure (S20). Thereafter, the pressure on / off valve 89 is closed, the pressure on / off valve 87 is opened, and the inside of the deaeration filter 83 is depressurized (S30). Next, the circulating open / close valve 221 is opened, the supply open / close valve 222 is closed, and the supply pump 71 is operated for 3 minutes (S40), so that the dissolved gas in the ink passing through the deaeration filter 83 can be reduced. Therefore, the amount of dissolved gas in the ink in the sub tank 73 and the supply channels 210 and 211 can be reduced, so that the stagnant ink can be efficiently deaerated in a short time at the start of image formation. Thereafter, the circulation open / close valve 221 is closed, the circulation to the circulation flow path 220 is stopped (S50), and the ejection of ink from the inkjet head 25 is started (S60).

  When the image formation is completed (S70), the decompression on / off valve 87 is closed and the pressurization on / off valve 89 is opened to set the pressure in the deaeration filter 83 to atmospheric pressure (S80). Thereafter, the circulation opening / closing valve 221 is opened, the supply opening / closing valve 222 is closed, and the supply pump 71 is operated for 5 minutes (S90), whereby the amount of dissolved gas in the ink passing through the deaeration filter 83 can be increased. Therefore, it is possible to increase the amount of dissolved gas that has decreased due to deaeration during the image formation of the ink staying in the sub tank 73 and the supply flow paths 210 and 211. Therefore, ink can be held without generating a gel substance. After operating the supply pump 71 for 5 minutes, the supply pump 71 is stopped (S100), and the image forming standby state is entered. When image formation is subsequently started, the process returns to S10, where the stagnant ink is deaerated and image formation is performed.

  In FIG. 6, the method of adjusting the dissolved gas at the start of image formation and at the end of image formation (at the time of image formation standby) has been described. However, ink is applied only at the start and end of the apparatus. The dissolved gas can be adjusted by circulation.

(Third embodiment)
Next, a third embodiment of the present invention will be described. FIG. 7 is a block diagram illustrating a configuration example of an ink supply system according to the third embodiment. Hereinafter, description of parts common to the first embodiment will be omitted, and description will be made focusing on characteristic parts of the present embodiment.

  The ink supply system according to the third embodiment is different from the first embodiment in that the pressure in the sub tank 73 is adjusted using the decompression chamber 85 of the pressure control unit 310 that adjusts the pressure of the deaeration filter 83. . Thus, by combining the pump for controlling the pressure in the sub tank 73 (back pressure control for the inkjet head 25) and the decompression pump 91 for degassing the degassing filter 83, the manufacturing cost can be reduced. Further, the apparatus can be reduced in size.

The sub tank 73 is connected to the decompression chamber 85 through the back pressure adjustment opening / closing valve 312 and the back pressure adjustment flow path 214. The head back pressure is preferably in the range of −30 mmH ₂ O to −150 mmH ₂ O on the nozzle surface of the inkjet head 25, and the back pressure adjustment opening / closing valve 312 is turned on / off during image formation so as to be in this range. Control. When the pressure in the decompression chamber 85 is low and the head back pressure is on the negative side of the desired range, a pressure loss filter 314 is provided between the sub tank 73 and the decompression chamber 85 to improve the controllability of the pressure. Is possible. Further, when the pressure is lower than the desired pressure, ink can be supplied by the supply pump 71 and the pressure can be adjusted. Further, when waiting for image formation, the back pressure adjustment opening / closing valve 312 is closed to prevent the amount of dissolved gas in the subtank 73 from decreasing.

[Explanation of Block Diagram of Inkjet Recording Apparatus]
FIG. 8 is a block diagram showing a configuration of the inkjet recording apparatus 100 according to the embodiment of the present invention. As shown in the figure, the ink jet recording apparatus 100 is provided with a control device 102 as control means. As the control device 102, for example, a computer having a central processing unit (CPU) can be used. The control device 102 functions as a control device that controls the entire inkjet recording apparatus 100 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. The control device 102 includes a recording medium conveyance control unit 104, a carriage drive control unit 106, a light source control unit 108, an image processing unit 110, an ejection control unit 112, and ink supply system pressure control units 95 and 310. Each of these units is realized by a hardware circuit or software, or a combination thereof.

  The recording medium conveyance control unit 104 controls the conveyance driving unit 114 for conveying the recording medium S (see FIG. 1). The transport drive unit 114 includes a drive motor that drives the scanning transport roller pair 43 shown in FIG. 2 and a drive circuit thereof. The recording medium S conveyed on the platen 27 (see FIG. 1) is intermittently fed in the sub-scanning direction in units of swath widths in accordance with the reciprocating scanning (movement of the printing pass) in the main scanning direction Y by the inkjet head 25. .

  The carriage drive control unit 106 controls the main scanning drive unit 116 for moving the carriage 30 (see FIG. 1) in the main scanning direction Y. The main scanning drive unit 116 includes a drive motor connected to a moving mechanism of the carriage 30 and a control circuit thereof. The light source control unit 108 is a control unit that controls the light emission of the ultraviolet irradiation light sources (LED elements) 63 and 65 via the LED drive circuit 118.

  The control device 102 is connected to an input device 120 such as an operation panel and a display device 122. The input device 120 is means for inputting a manual external operation signal to the control device 102. For example, various forms such as a keyboard, a mouse, a touch panel, and operation buttons can be adopted. Various forms such as a liquid crystal display, an organic EL display, and a CRT can be adopted as the display device 122. The operator can input printing conditions and input / edit attached information by operating the input device 120, and various information such as input contents and search results can be confirmed through the display on the display device 122. it can.

  In addition, the ink jet recording apparatus 100 is provided with an information storage unit 124 that stores various types of information and an image input interface 126 for capturing image data for printing. As the image input interface, a serial interface or a parallel interface may be applied. In this part, a buffer memory (not shown) for speeding up communication may be mounted.

  Image data input via the image input interface 126 is converted into print data (dot data) by the image processing unit 110. The dot data is generally generated by performing color conversion processing and halftone processing on multi-tone image data. The color conversion process is a process of converting image data expressed in sRGB or the like (for example, 8-bit image data for each RGB color) into color data for each ink color used in the inkjet recording apparatus 100.

  The halftone process is a process for converting the color data of each color generated by the color conversion process into dot data of each color by a process such as an error diffusion method or a threshold matrix. Various known means such as an error diffusion method, a dither method, a threshold matrix method, and a density pattern method can be applied as the halftone processing means. The halftone process generally converts gradation image data having an M value (M ≧ 3) into gradation image data having an N value (N <M). In the simplest example, it is converted into binary (dot on / off) dot image data, but in halftone processing, it corresponds to the dot size type (for example, three types such as large dot, medium dot, small dot). Multi-level quantization can also be performed.

  The binary or multi-valued image data (dot data) obtained in this way controls the drive (on) / non-drive (off) of each nozzle, and in the case of multiple values, controls the droplet amount (dot size). Used as ink discharge data (discharge control data).

  The ejection control unit 112 generates an ejection control signal for the head drive circuit 128 based on the dot data generated by the image processing unit 110. Further, the discharge control unit 112 includes a drive waveform generation unit (not shown). The drive waveform generation unit is a means for generating a drive voltage signal for driving an ejection energy generating element (in this example, a piezo element) corresponding to each nozzle of the inkjet head 25. The waveform data of the drive voltage signal is stored in advance in the information storage unit 124, and waveform data to be used is output as necessary. The signal (drive waveform) output from the drive waveform generation unit is supplied to the head drive circuit 128. Note that the signal output from the drive waveform generation unit may be digital waveform data or an analog voltage signal.

  A common drive voltage signal is applied to each ejection energy generation element of the inkjet head 25 via the head drive circuit 128, and the switch element is connected to the individual electrode of each energy generation element according to the ejection timing of each nozzle. By switching on / off (not shown), ink is ejected from the corresponding nozzle.

  The ink supply system pressure controllers 95 and 310 actuate the valves 77, 87, 89, 221, 222, 312 and the pumps 71, 79, 91 based on the image formation start signal and the image formation stop signal. Then, the pressure in the deaeration filter 83 is controlled to adjust the amount of dissolved gas in the ink. As described above, based on the image formation start signal, the decompression on / off valve 87 is opened, the pressurization on / off valve 89 is closed, and the inside of the deaeration filter 83 is decompressed. Further, based on the image formation stop signal, the decompression on-off valve 87 is opened, the pressurization on-off valve 89 is closed, and the inside of the deaeration filter 83 is set to atmospheric pressure.

  The information storage unit 124 stores programs executed by the CPU of the control device 102, various data necessary for control, and the like. The information storage unit 124 stores resolution setting information according to the print mode, the number of passes (the number of scan repetitions), control information for the ultraviolet irradiation light sources 63 and 65, and the like.

  The encoder 130 is attached to the rotation shaft of the drive motor of the main scanning drive unit 116 and the rotation shaft of the drive motor of the conveyance drive unit 114, and a pulse signal corresponding to the rotation amount and rotation speed of the drive motor is generated. Is output. The pulse signal output from the encoder 130 is sent to the control device 102. The control device 102 determines the position of the carriage 30 and the position of the recording medium S (see FIG. 1) based on the pulse signal output from the encoder 130. The posture, the drawing area of the recording medium S, and the like are grasped.

  The sensor 132 is attached to the carriage 30 (see FIG. 6), and a sensor signal output from the sensor 132 is sent to the control device 102. Based on the sensor signal obtained from the sensor 132, the width of the recording medium S (the positions of both ends in the main scanning direction) is grasped. An example of the configuration of the sensor 132 is an optical sensor including a light emitting unit and a light receiving unit.

  DESCRIPTION OF SYMBOLS 21 ... Apparatus main body, 23 ... Support leg, 25 ... Inkjet head, 27 ... Platen, 29 ... Guide mechanism, 30 ... Carriage, 33 ... Cartridge, 35 ... Ultraviolet irradiation part, 43 ... Scanning conveyance roller pair, 47 ... Temperature control part , 49 ... Pre-temperature control unit, 51 ... After-temperature control unit, 61 ... Nozzle array, 63, 65 ... LED element, 71 ... Supply pump, 73 ... Sub tank, 75 ... Back pressure adjustment unit, 77 ... Valve, 79 ... Addition Decompression pump, 81 ... pressure gauge, 83 ... deaeration filter, 85 ... depressurization chamber, 87 ... depressurization on / off valve, 89 ... pressurization on / off valve, 91 ... depressurization valve, 95, 310 ... pressure control unit, 100 ... inkjet recording Device 102 control unit 104 recording medium conveyance control unit 106 carriage drive control unit 108 light source control unit 110 image processing unit 112 ejection control , 114... Transport drive unit, 116... Main scanning drive unit, 118... LED drive circuit, 120... Input device, 122. Encoder, 132 ... sensor, 210, 211 ... supply channel, 212 ... degassing decompression channel, 213 ... pressurization channel, 214 ... pressure adjustment channel, 220 ... circulation channel, 221 ... circulation on / off valve, 222 ... Supply open / close valve, 312 ... back pressure adjustment open / close valve, 314 ... pressure loss filter

Claims (11)

A tank in which liquid is stored,
An inkjet head that ejects the liquid;
A supply flow path for supplying the liquid inside the tank to the inkjet head;
A degassing filter provided in the middle of the supply flow path;
An ink jet recording apparatus comprising: a decompression chamber connected to the deaeration filter via a decompression opening / closing valve; and a pump for reducing the pressure in the decompression chamber. The liquid is an ultraviolet curable ink,
The ink jet recording apparatus according to claim 1, further comprising a pressure channel and a pressure on / off valve for supplying oxygen or a gas containing oxygen to the liquid in the deaeration filter.   During image formation, open the decompression on-off valve, close the pressurization on-off valve, reduce the pressure in the deaeration filter, and when waiting for image formation, close the decompression on-off valve, open the pressurization on-off valve, The inkjet recording apparatus according to claim 2, further comprising a valve control unit that supplies oxygen into the deaeration filter.   4. The ink jet recording apparatus according to claim 2, wherein the pressure reducing on-off valve is a normally closed type that closes when no power is supplied, and the pressure on-off valve is a normally open type that opens when no power is supplied. .   5. The inkjet recording apparatus according to claim 1, wherein the pressure in the decompression chamber is 0.04 to 0.09 MPa.   6. The inkjet recording apparatus according to claim 1, further comprising a sub tank that temporarily stores the liquid between the tank and the deaeration filter in the supply flow path.   A circulation channel that returns the liquid that has passed through the deaeration filter to the sub-tank, a circulation opening / closing valve that is provided in the middle of the circulation channel, and a middle of the supply channel that connects the tank and the sub-tank. The inkjet recording apparatus according to claim 6, further comprising a supply opening / closing valve.   8. The system according to claim 7, further comprising: a startup sequence in which the inside of the deaeration filter is depressurized at the start of image formation, the circulation opening / closing valve is opened, the supply opening / closing valve is closed, and the liquid in the sub tank is circulated. The ink jet recording apparatus described.   8. The method according to claim 7, further comprising an end sequence for pressurizing the inside of the deaeration filter at the end of image formation, opening the circulation on-off valve, closing the supply on-off valve, and circulating the liquid in the sub tank. 8. An ink jet recording apparatus according to item 8. The sub-tank is connected to the decompression chamber;
10. The ink jet recording apparatus according to claim 6, wherein the decompression chamber also serves as a back pressure adjusting unit that applies a predetermined back pressure to the liquid in the ink jet head. 11.   The inkjet recording apparatus according to claim 10, further comprising a pressure loss filter between the sub tank and the decompression chamber.

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