JP2007245689A - Inkjet printer and inkjet image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet printer which is simple in structure, unerringly and quickly discharges dust and bubbles existing in ink supply routes and recording heads without damaging the ink supply routes and the recording heads and without causing ink leakage, and its ink supply method. <P>SOLUTION: The inkjet printer has ink tanks storing inks, a pump which transfers the ink stored in the ink tank to a plurality of recording heads, a plurality of ink channels between the pump and the recording heads, and a control section which opens the ink channels connected to unblocked recording heads at the time when blocked recording heads exist among the recording heads and control the ink channels connected to the blocked recording heads while transferring the inks from the ink tanks by the pump. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inkjet recording apparatus and an inkjet image forming method.

  In recent years, the inkjet recording method can easily and inexpensively create an image, and thus has been applied to various printing fields such as photographs, various printing, marking, and special printing such as a color filter.

  Ink jet printers have a serial printing method in which printing is performed while the recording head is reciprocated in the paper width direction and the paper is conveyed intermittently, and ejection heads are arranged throughout the paper width direction to fix the recording head. There is a line head system that performs printing. The recording head is supplied with ink directly from an ink tank or through an ink tube. The recording head has problems such as clogging of the recording head at the time of ink ejection and ejection failure due to increased viscosity of the ink.

  Therefore, a group including a channel where ink discharge failure occurs by dividing a large number of ink discharge channels into a plurality of groups and providing a plurality of manifolds for distributing ink from the ink supply source to the ink discharge channels for each group. Only the valve corresponding to is opened, and ink is pressurized and supplied by a pump. This forcibly discharges bubbles and thickened ink, reduces the amount of ink that is wasted for recovery operations, and reduces the chances that the ink discharge channels that were normally discharged are blocked by bubbles. In addition, a method for efficiently performing a recovery operation in a short time has been proposed (see, for example, Patent Document 1).

Further, a method has been proposed in which ink is pressure-fed from an ink tank at the time of cleaning and recovery of the recording head, and foreign matters such as dust and bubbles in the recording head are ejected together with ink from the ejection port (for example, see Patent Document 2) ).
JP 2002-225302 A JP-A-3-184872

  However, in the invention described in Patent Document 1, since the ink supply path is made of a hard material tank or tube, when the ink is pumped to the flow path filled with ink, the flow path and the inside of the recording head are rapidly changed. There is a risk of ink leakage from the joint of the flow path due to pressure.

  Further, in the invention described in Patent Document 2, if the printer is not used for a long time, if pressure maintenance is performed by a pump when all the nozzles of the printer are clogged, a sudden pressure change occurs. Similarly, there is a risk of ink leakage from the joint portion of the ink supply path.

  Therefore, the present invention discharges dust, bubbles, etc. existing in the ink supply path and the print head with a simple structure reliably and quickly without damaging the ink supply path and the print head and without causing ink leakage. It is an object of the present invention to provide an ink jet recording apparatus and an ink supply method thereof.

The object of the present invention can be achieved by the following constitution.
(1)
A plurality of recording heads having a plurality of ejection openings for ejecting ink and forming an image on a recording medium with the ejected ink;
An ink jet recording apparatus having an ink supply unit for supplying ink to the recording head;
An ink tank for storing ink;
A pump for pumping ink stored in the ink tank to the plurality of recording heads;
A plurality of ink flow paths between the pump and the plurality of recording heads;
When there is a clogged recording head among the plurality of recording heads, the ink flow path connected to the recording head without clogging is opened, and the ink is pumped from the ink tank by the pump. An ink jet recording apparatus comprising: a control unit that controls to open an ink flow path connected to the clogged recording head.
(2)
When there are a plurality of print heads that are clogged, the control unit pumps ink from the ink tank with the pump, and the ink flow connected to the first print head that is clogged. After the path is opened, the ink flow path is closed, and the ink flow path connected to the other recording head that is clogged is controlled to be repeatedly opened and closed sequentially. The inkjet recording apparatus according to (1).
(3)
The control unit performs control so as to notify an error without pumping ink from the ink tank with the pump when all of the recording heads are clogged (1) or The ink jet recording apparatus according to (2).
(4)
The control performed by the control unit on the clogged recording head is performed based on the result of printing on the recording paper or the result of inspection of the recording head (1) to ( The inkjet recording apparatus according to any one of 3).
(5)
The ink contains at least water, a water-soluble organic solvent, and a pigment, and the water content is 10% by mass or more and less than 50% by mass of the total ink mass, and is contained most in the water-soluble organic solvent. The SP value of the water-soluble organic solvent is 16.5 or more and less than 24.6, and the content of the water-soluble organic solvent is 30% by mass or more of the total ink mass (1) to (4) The ink jet recording apparatus according to any one of the above.
(6)
In an inkjet image forming method for forming an image on a recording medium by ejecting ink supplied from an ink supply unit from a plurality of recording heads,
When there is a clogged recording head among the plurality of recording heads, the ink flow path connected to the recording head without clogging is opened, and
An ink-jet image forming method, wherein ink is pumped from an ink tank, and an ink flow path connected to the clogged recording head is opened to eliminate the clogging.
(7)
In the image forming method, when there are a plurality of clogged recording heads, the ink is pumped from the ink tank by the pump and connected to the first clogged recording head. After opening the ink flow path, the ink flow path is closed, and the ink flow path connected to the recording head that has caused other clogging is controlled to be repeatedly opened and closed sequentially. The inkjet image forming method as described in (6), which is characterized in that
(8)
In the image forming method, when all the recording heads are clogged, control is performed so as to notify an error without pumping ink from the ink tank with the pump (6). Or the image formation method of the inkjet system as described in (7).

  According to the present invention, when the head is recovered by pressurizing and extruding ink to the head, the ink is simultaneously pressurized to the clogged head and the head without clogging. The ink is pushed out from the nozzle, and a sudden pressure change can be absorbed.

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

  FIG. 4 is an example of a cross-sectional view of the ink jet recording apparatus according to the present invention.

  A denotes the entire inkjet recording apparatus, and 3 denotes a paper discharge unit on which a recording medium (paper) P on which an image is recorded is discharged and stacked. The ink jet recording apparatus A includes a recording head 50, an ink tank 11, a liquid feed pump (pump) 22, an intermediate tank 31, a transport unit 2, and a recording medium P that constitute a liquid ejecting apparatus according to the invention. A paper section 1 is provided.

  The control unit 4 operates various means constituting the ink jet recording apparatus according to a program stored in the ROM, for example, reads image information of a document, or from an external information device via an interface (not shown). Printer function that executes a series of image information recording control that inputs image information etc., stores that information, and records and outputs it on a recording medium, and adjustment and maintenance of various means so that the printer function can be executed reliably Maintenance function to perform etc.

  For the recording head 50, for example, recording heads having a plurality of ejection openings are provided for four colors in order to eject each ink of cyan (C), magenta (M), yellow (Y), and black (BK). In addition, although not shown, for example, a drive circuit or the like for performing an ink discharge operation corresponding to each recording head is integrated.

  The maintenance stand 60 is provided with a cap that covers the vicinity of the discharge port so that dust or dust adheres to the discharge port of the recording head 50 or the ink does not dry and become clogged when the printing operation is interrupted for a while. Recover the clogged state by installing or cleaning the discharge port before starting the next print operation after suspending the print operation or at regular intervals. Thus, a normal ink ejection operation can be performed.

  For transporting the recording medium P, the recording medium P stored in the paper feeding unit 1 is taken out one by one by the feed roller R1. The pair of rollers R2 sends the taken recording medium P in the direction of the pair of rollers R3. The recording medium P sandwiched between the rollers R3 is further sent to the transport unit 2.

  The recording medium P conveyed via the conveying unit 2 faces the recording head 50 and records an image while being conveyed at a constant speed.

  Thereafter, a paper discharge conveyance operation is executed, and the recording medium P on which an image is recorded is sandwiched by a pair of rollers R8 and discharged to the paper discharge unit 3.

  FIG. 1 is a schematic diagram illustrating an example of the configuration of an ink supply and head recovery system in an ink jet recording apparatus according to the present invention.

  The back pressure required for the recording head 50 is set by the water head difference between the intermediate tank 31 made of a flexible bag and the discharge port of the recording head 50.

  At the time of printing, the ink is supplied by the ejection of the individual head 51 from the intermediate tank 31 through the supply valve 33, the common channel 34, the distributor 41, and the individual head supply channel (ink channel) 45. Replenishment to the intermediate tank 31 is pumped from the ink tank 11 through the replenishment flow path 21 by the liquid feed pump 22 when the bulge detection sensor 32 determines that replenishment is necessary, and is supplied to the replenishment valve 23 and the intermediate tank 31 by a predetermined amount. The liquid is supplied. A distributor 41 provided in the middle of the common flow path 34 is provided to equalize the flow path resistance of the ink supplied to the individual heads 51 constituting the print head 50, and serves as a short-time supply source.

  When the recording head 50 recovers, the ink is fed by rotating the liquid feed pump 22 forward, and is selected by the individual head valve 46 via the pressurization valve 25 and the pressurization flow path 24 that bypass the intermediate tank 31. It is extruded from the nozzle of the individual head 51. After the ink drops from the nozzles of the individual heads are settled, the nozzle surface is wiped by the wiper blade 61 disposed on the maintenance table 60.

  An air vent channel 71 having an air vent valve 44 is piped from the upper part of the distributor 41, and air is discharged from this channel at the time of initial ink introduction and when air enters the ink supply channel. The pressure sensor 42 is used for overpressure detection during pressure extrusion.

  2 and 3 are examples of flowcharts of the recording head recovery operation according to the present invention. By performing the operations of the flowcharts of FIGS. 2 and 3, clogging that discharges dust, bubbles, etc. present in the ink supply path and the print head without damaging the ink supply path and the print head and without causing ink leakage. An ink jet image forming method can be realized.

The operation will be described with reference to FIG.
<Embodiment 1>
FIG. 2 is a flowchart of a recovery operation performed on a clogged head that the user wants to perform a head recovery operation.

  In step S1, the supply valve 33 and the supply valve 23 are closed.

  In step S2, the individual head valve 46 of the flow path 45 connected to the clogged head (hereinafter referred to as a defective head) is closed.

  In step S3, the individual head valve 46 of the flow path 45 connected to the head without clogging (hereinafter referred to as a normal head) is opened.

  In step S4, the pressurizing valve 25 is opened. Here, the intermediate tank 31 is cut off, and ink is supplied to the recording head via the pressure channel 24.

  In step S5, the liquid feeding pump 22 is driven to feed ink from the ink tank to the recording head. Ink is pressurized and pushed out from the discharge port of the open normal head.

  In step S6, the individual head valve 46 of the flow path 45 connected to the defective head designated by the user among the defective heads is opened. Ink is also pressed and pushed out from the defective head, and dust and bubbles in the head are pushed out. If there is no user designation, the individual head valve 46 of the flow path 45 connected to all defective heads is opened.

  Here, the user's instruction is previously notified to the control unit 4 by an input from an operation unit (not shown).

  In step S7, the liquid feed pump 22 is stopped.

  In step S8, the pressurizing valve 25 is closed.

  In step S9, the supply valve 33 and the supply valve 23 are opened. Here, the intermediate tank 31 is connected, and printing is enabled with respect to ink supply.

  In step S10, a wiping operation is performed, and dust and ink droplets adhering to the nozzle surface of the head are wiped with the wiper blade 61.

  The user inputs the result of printing or the inspection of the recording head in advance from an operation unit (not shown), and notifies the control unit 4 of the result. The control unit 4 recognizes whether the connected recording head is normal or defective.

  When receiving a head recovery operation instruction from a user or a connected PC (Personal Computer), the control unit 4 determines that all the connected recording heads are defective heads before executing step S1. An error is reported to the display of the operation unit.

According to the present invention, when all the connected recording heads are defective heads, the head recovery operation is not performed and the error is notified to the display unit of the operation unit, so that time and ink can be saved. .
<Embodiment 2>
FIG. 2 is a flowchart of a recovery operation in which the head recovery operation is performed for each of the clogged heads.

  In step S21, the supply valve 33 and the supply valve 23 are closed.

  In step S22, the individual head valve 46 of the flow path 45 connected to the clogged head (hereinafter referred to as a defective head) is closed.

  In step S23, the individual head valve 46 of the flow path 45 connected to the head without clogging (hereinafter referred to as a normal head) is opened.

In step S24, one of the individual head valves 46 of the flow path 45 connected to the defective head is opened. (In the flowchart, it is described as individual head valve a)
In step S25, the pressurizing valve 25 is opened.

  In step S26, the liquid feeding pump 22 is driven to feed ink from the ink tank to the recording head. Ink is pressurized and pushed out from the ejection head of the opened normal head and the defective head whose individual valve is opened in step S24.

  In step S27, the individual head valve 46 of the flow path 45 connected to the normal head is closed. Here, pressurization and extrusion to the normal head are stopped, and ink is pressurized and pushed out only from the ejection port of the defective head whose individual valve is opened in step S24.

  In step S28, one of the individual head valves 46 of the flow path 45 connected to the defective head, which is different from the one opened in step S24, is opened. (In the flowchart, it is described as individual head valve b) Here, the individual head valves a and b are pressurized and extruded.

  In step S29, the individual head valve a is closed.

  In step S30, it is determined whether there is still a defective head that has not been subjected to pressurization and extrusion processing. If there is still a defective head (step S30: YES), the process returns to step S28, and if there is no defective head (step S30: NO), the process proceeds to step S31.

  If there is a defective head, in step S28, the next individual head valve (for example, individual head valve c) and further individual head valves d, e. . . . And repeatedly pressurizing and extruding.

  In step S31, the liquid feed pump 22 is stopped.

  In step S32, the pressurizing valve 25 is closed.

  In step S33, the supply valve 33 and the supply valve 23 are opened.

  In step S34, a wiping operation is performed, and dust and ink droplets adhering to the nozzle surface of the head are wiped by the wiper blade 61.

  According to the present invention, since the head recovery operation of the defective head is performed one by one, the ink is saved. In addition, the ink pressurization is constant, and reliable head recovery is possible.

  Next, an example of ink used in the ink jet recording apparatus will be described.

  Ink for an ink jet recording apparatus (hereinafter also simply referred to as ink) contains at least water, a water-soluble organic solvent, and a pigment. Here, the water-soluble organic solvent is not particularly limited as long as it can be mixed with water. Two or more water-soluble organic solvents can be used in combination. However, in order to suppress the occurrence of cavitation when continuously emitting light, the SP value of the most water-soluble organic solvent among the water-soluble organic solvents is 16.5 or more and less than 24.6, It is preferable that the content of the water-soluble organic solvent having an SP value of 16.5 or more and less than 24.6 is 30% by mass or more of the total ink mass. Since this solvent composition contains a large amount of a water-soluble organic solvent having a higher hydrophobicity than water, the solubility of the entire ink is high, and as a result, cavitation is unlikely to occur during continuous emission.

  The solvent solubility parameter (SP value) is a value expressed by the square root of the molecular cohesive energy. F. Fedors, Polymer Engineering Science, 14, p147 (1974). The unit is (MPa) 1/2, and refers to the value at 25 ° C.

  Hereinafter, examples of water-soluble organic solvents having an SP value of 16.5 or more and less than 24.6 are shown together with the SP value. Needless to say, the present ink is not limited to this.

Ethylene glycol monomethyl ether (SP value: 24.5)
Ethylene glycol monoethyl ether (23.5)
Ethylene glycol monobutyl ether (22.1)
Ethylene glycol monoisopropyl ether (22.3)
Diethylene glycol monomethyl ether (23.0)
Diethylene glycol monoethyl ether (22.4)
Diethylene glycol monobutyl ether (21.5)
Diethylene glycol diethyl ether (16.8)
Triethylene glycol monomethyl ether (22.1)
Triethylene glycol monoethyl ether (21.7)
Triethylene glycol monobutyl ether (21.1)
Propylene glycol monomethyl ether (23.0)
Propylene glycol monophenyl ether (24.2)
Dipropylene glycol monomethyl ether (21.3)
Tripropylene glycol monomethyl ether (20.4)
1,3-dimethyl-2-imidazolidinone (21.8)
In this ink, in addition to the water-soluble organic solvent having an SP value of 16.5 or more and less than 24.6, conventionally known various water-soluble organic solvents can be used in combination.

  Examples of water-soluble organic solvents preferably used as the solvent used in combination include alcohols (for example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexane). Hexanol, benzyl alcohol, etc.), polyhydric alcohols (eg, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, Thiodiglycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanedio , 1,2-pentanediol, 1,2-hexanediol, 1,2,6-hexanetriol, etc.), amines (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine) , Morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), heterocyclic rings (for example, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, 2-oxazolidone, etc.), sulfoxides For example, dimethyl sulfoxide, etc.), sulfones (e.g., sulfolane), urea, acetonitrile, and acetone.

  As the pigment that can be used in the present ink, conventionally known pigments can be used without particular limitation, and any of water-dispersible pigments, solvent-dispersible pigments, and the like can be used, for example, organic pigments such as insoluble pigments and lake pigments, An inorganic pigment such as carbon black can be preferably used. This pigment is present in a dispersed state in the ink, and the dispersion method may be any of self-dispersion, dispersion using a surfactant, polymer dispersion, and microcapsule dispersion. Dispersion is particularly preferred from the standpoint of fixability.

  The insoluble pigment is not particularly limited. Dioxazine, thiazole, phthalocyanine, diketopyrrolopyrrole and the like are preferable.

  Specific pigments that can be preferably used include the following pigments.

  Examples of the magenta or red pigment include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. Pigment red 202, C.I. I. Pigment red 222, C.I. I. Pigment violet 19 and the like.

  Examples of the pigment for orange or yellow include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 15: 3, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 94, C.I. I. And CI Pigment Yellow 138.

  Examples of the pigment for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.

  Examples of black pigments include C.I. I. Pigment black 1, C.I. I. Pigment black 6, C.I. I. Pigment black 7 and the like.

  The average particle size of the dispersed state of the pigment contained in the ink is preferably 50 nm or more and less than 200 nm. When the average particle size of the pigment dispersion is less than 50 nm or 200 nm or more, the stability of the pigment dispersion tends to deteriorate, and the storage stability of the ink tends to deteriorate.

  The particle size of the pigment dispersion can be determined by a commercially available particle size measuring instrument using a dynamic light scattering method, an electrophoresis method, or the like. Accurate and often used.

  The pigment to be used is preferably used after being dispersed by a disperser together with a dispersant and other additives necessary for various desired purposes. As the disperser, a conventionally known ball mill, sand mill, line mill, high-pressure homogenizer, or the like can be used. In particular, the particle size distribution of the ink produced by dispersion with a sand mill is sharp and preferable. The material of the beads used for sand mill dispersion is preferably zirconia or zircon from the viewpoint of contamination of bead fragments and ionic components. Furthermore, the bead diameter is preferably 0.3 mm to 3 mm.

  In the present ink, it is preferable to use a polymer dispersant in the dispersion.

  The polymer dispersant has a polymer component having a molecular weight of 5000 or more and 200000 or less. The polymer dispersant is selected from styrene, styrene derivatives, vinyl naphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid and fumaric acid derivatives. Examples thereof include a block copolymer comprising at least one kind of monomer, a random copolymer and salts thereof, polyoxyalkylene, and polyoxyalkylene alkyl ether.

  In the case of an acidic polymer dispersant, it is preferably added after neutralization with a neutralizing base. Here, the neutralizing base is not particularly limited, but is preferably an organic base such as ammonia, monoethanolamine, diethanolamine, triethanolamine, or morpholine.

  Moreover, it is preferable that it is 10-100 mass% with respect to a pigment as addition amount of a polymer dispersing agent.

  In this ink, in addition to the above description, if necessary, various known additions may be made depending on the purpose of improving the emission stability, compatibility with the print head and ink cartridge, storage stability, image storage stability, and other various performances. Agents, for example, polysaccharides, viscosity modifiers, specific resistance regulators, film forming agents, ultraviolet absorbers, antioxidants, anti-fading agents, antifungal agents, rust inhibitors, etc. can be appropriately selected and used, For example, oil droplet fine particles such as liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476, 57-74192, 57-87989, 60-72785, 61-146591, JP-A-1-95091 and 3-13376, etc. Anti-fading agents, fluorescent whitening agents described in JP-A-59-42993, JP-A-59-52689, JP-A-62-280069, JP-A-61-228771, JP-A-4-219266, etc. be able to.

  The ink having the above-described structure preferably has an ink surface tension of 25 to 40 mN / m at 25 ° C., more preferably 25 to 35 mN / m, and still more preferably 30 to 35 mN / m. . The ink viscosity is preferably 1 to 40 mPa · s at 25 ° C., more preferably 5 to 40 mPa · s, and still more preferably 5 to 20 mPa · s.

  Of course, the ink jet recording apparatus is not limited to the ink described above.

  The detailed configuration and detailed operation of each component constituting the ink jet recording apparatus can be changed as appropriate without departing from the spirit of the present invention.

1 is a schematic diagram illustrating an example of a configuration of an ink supply and head recovery system in an ink jet recording apparatus according to the present invention. 4 is an example of a flowchart of a recording head recovery operation according to the present invention. 4 is an example of a flowchart of a recording head recovery operation according to the present invention. It is an example of sectional drawing of the inkjet recording device which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Ink tank 21 Supply path 22 Liquid feed pump 31 Intermediate tank 45 Individual head supply path 46 Individual head valve 51 Individual head 61 Wiper blade

Claims (8)

A plurality of recording heads having a plurality of ejection openings for ejecting ink and forming an image on a recording medium with the ejected ink;
An ink jet recording apparatus having an ink supply unit for supplying ink to the recording head;
An ink tank for storing ink;
A pump for pumping ink stored in the ink tank to the plurality of recording heads;
A plurality of ink flow paths between the pump and the plurality of recording heads;
When there is a clogged recording head among the plurality of recording heads, the ink flow path connected to the recording head without clogging is opened, and the ink is pumped from the ink tank by the pump. An ink jet recording apparatus comprising: a control unit that controls to open an ink flow path connected to the clogged recording head. When there are a plurality of print heads that are clogged, the control unit pumps ink from the ink tank with the pump, and the ink flow connected to the first print head that is clogged. After the path is opened, the ink flow path is closed, and the ink flow path connected to the other recording head that is clogged is controlled to be repeatedly opened and closed sequentially. The inkjet recording apparatus according to claim 1. 2. The control unit according to claim 1, wherein when the recording head is a recording head in which all the recording heads are clogged, control is performed so as to notify an error without pumping ink from the ink tank with the pump. 2. An ink jet recording apparatus according to item 2. 4. The control performed by the control unit on the clogged recording head is performed based on a result of printing on the recording paper or an inspection result of the recording head. The ink jet recording apparatus according to any one of the above. The ink contains at least water, a water-soluble organic solvent, and a pigment, and the water content is 10% by mass or more and less than 50% by mass of the total ink mass, and is contained most in the water-soluble organic solvent. The SP value of the water-soluble organic solvent is 16.5 or more and less than 24.6, and the content of the water-soluble organic solvent is 30% by mass or more of the total ink mass. The inkjet recording apparatus of any one. In an inkjet image forming method for forming an image on a recording medium by ejecting ink supplied from an ink supply unit from a plurality of recording heads,
When there is a clogged recording head among the plurality of recording heads, the ink flow path connected to the recording head without clogging is opened, and
An ink-jet image forming method, wherein ink is pumped from an ink tank, and an ink flow path connected to the clogged recording head is opened to eliminate the clogging. In the image forming method, when there are a plurality of clogged recording heads, the ink is pumped from the ink tank by the pump and connected to the first clogged recording head. After opening the ink flow path, the ink flow path is closed, and the ink flow path connected to the recording head that has caused other clogging is controlled to be repeatedly opened and closed sequentially. The ink-jet image forming method according to claim 6. 7. The image forming method according to claim 6, wherein when all the recording heads are clogged, the ink is not pumped from the ink tank by the pump and an error is reported. Or an inkjet image forming method described in 7;

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