Inkjet recording device and ink agitation method

Abstract

To provide an inkjet recording device and an ink agitation method that can make ink containing a wax component even.SOLUTION: An inkjet recording device includes: an ink tank 241B storing ink containing a wax component; and an inkjet head 242 including a plurality of nozzles that discharge ink. The ink tank 241B agitates ink.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an inkjet recording apparatus and an ink agitation method for discharging ink onto a recording medium to form an image.

Background Art

[0002] Conventionally, an inkjet recording apparatus including an inkjet head provided with a plurality of nozzles is known. The inkjet recording apparatus discharges ink from the plurality of nozzles toward a recording material such as paper to record an image on the recording material. And the inkjet recording apparatus includes an ink tank for storing ink.

[0003]

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] ​The inkjet printer described in Patent Document 1 is effective in suppressing the sedimentation of pigment particles contained in the pigment ink by stirring. On the other hand, in the case of ultraviolet curable ink, when there is no sedimentation component such as pigment particles, stirring of the ink in the ink tank was considered unnecessary. However, in ultraviolet curable ink, it was found that the wax component contained in the ink separates when the temperature of the ink changes. As a result, unevenness in the ink concentration occurs, and the ink components become non-uniform, resulting in a problem of deterioration in image quality.

[0006] In view of the above-described conventional problems, an object of the present invention is to provide an inkjet recording apparatus and an ink stirring method capable of homogenizing ink containing a wax component.

Means for Solving the Problems

[0007] In order to achieve at least one of the above-described objects, an inkjet recording apparatus reflecting one aspect of the present invention includes an ink tank for storing ink containing a wax component, and an inkjet head having a plurality of nozzles for discharging the ink. The ink tank stirs the ink.

[0008] Also, an ink stirring method reflecting one aspect of the present invention includes a heating step of heating ink containing a wax component in the inkjet recording apparatus of the present invention, and a stirring step of stirring the ink heated in the heating step.

Effects of the Invention

[0009] According to the present invention, the ink containing the wax component can be stirred to homogenize the ink containing the wax component.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Mode for Carrying Out the Invention

[0011] Hereinafter, an inkjet recording apparatus according to an embodiment of the present invention and an example of an ink stirring method will be described with reference to the drawings. Note that the present invention is not limited to the following examples. In each of the drawings described below, common members are denoted by the same reference numerals.

[0012] 1. First Embodiment 1-1. Overall Configuration of Inkjet Recording Apparatus FIG. 1 is an overall configuration diagram of an inkjet recording apparatus 1 according to the first embodiment of the present invention. As shown in FIG. 1, the inkjet recording apparatus 1 according to the first embodiment includes a recording material supply unit 10, an image recording unit 20, a recording material discharge unit 30, an ink supply unit 40, and a control unit 100 (see FIG. 9). The inkjet recording apparatus 1 conveys the recording material P stored in the recording material supply unit 10 to the image recording unit 20 under the control of the control unit 100. Then, the inkjet recording apparatus 1 records an image on the recording material P in the image recording unit 20, and discharges the recording material P on which the image has been recorded to the recording material discharge unit 30.

[0013] [Recording Material Supply Unit] The recording material supply unit 10 includes, for example, a paper feed tray 11 that stores the recording material P made of paper or the like, and a conveyance unit 12 that conveys the recording material P from the paper feed tray 11 to the image recording unit 20.

[0014] The paper feed tray 11 is a plate-shaped member provided so that one or a plurality of recording materials P can be placed thereon. The paper feed tray 11 moves up and down according to the amount of the recording material P placed on the paper feed tray 11. The uppermost recording material P among the recording materials P placed on the paper feed tray 11 is disposed at a supply position where it is delivered to the conveyance unit 12.

[0015] The conveyance unit 12 includes a conveyance mechanism that conveys the recording material P, and a supply mechanism (not shown) that delivers the recording material P placed on the paper feed tray 11 to the conveyance mechanism. The conveyance mechanism includes two rollers 121 and 122, and an endless belt 123 stretched between the rollers 121 and 122.

[0016] The conveyance mechanism of the conveyance unit 12 rotates the two rollers 121 and 122 to drive the belt 123. The supply mechanism places the recording material P on the belt 123. The driven belt 123 conveys the placed recording material P to the image recording unit 20. Note that the rollers of the conveyance mechanism are not limited to two, and may be three or more.

[0017] [Image Forming Unit] The image recording unit 20 includes an image recording drum 21, a transfer unit 22, a heating unit 23, a head unit 24, an irradiation unit 25, a delivery unit 26, and an image reading sensor 27.

[0018] The image recording drum 21 is a cylindrical member. The image recording drum 21 rotates about a rotation axis extending in the horizontal direction by a drive motor (not shown). The image recording drum 21 holds the recording material P along its outer peripheral surface and conveys the recording material P as it rotates. The outer peripheral surface of the image recording drum 21 faces the heating unit 23, the head unit 24, and the irradiation unit 25. The heating unit 23, the head unit 24, and the irradiation unit 25 perform respective processes related to image recording on the recording material P conveyed by the image recording drum 21.

[0019] The transfer unit 22 is disposed between the conveyance unit 12 of the recording material supply unit 10 and the image recording drum 21. The transfer unit 22 has a claw portion 221 and a cylindrical transfer drum 222.

[0020] The claw portion 221 of the transfer unit 22 holds one end of the recording material P conveyed by the conveyance unit 12. The transfer drum 222 guides the recording material P held by the claw portion 221. The claw portion 221 holds the recording material P on the conveyance unit 12 and aligns it along the outer peripheral surface of the transfer drum 222. The transfer drum 222 guides the recording material P in a direction along the outer peripheral surface of the image recording drum 21 and delivers it to the image recording drum 21.

[0021] The heating unit 23 is disposed upstream of the head unit 24 in the conveyance direction of the recording material P by the image recording drum 21. The heating unit 23 has, for example, a heating wire or the like. The heating unit 23 generates heat in response to energization of the heating wire and heats the recording material. The heating unit 23 generates heat based on control by the control unit 100 (see FIG. 9). Thereby, the recording material P held by the image recording drum 21 and passing through the opposing portion of the heating unit 23 is heated to a predetermined temperature.

[0022] In the vicinity of the heating unit 23, a temperature sensor (not shown) is disposed. The control unit 100 controls the calorific value of the heating unit 23 based on the temperature near the heating unit 23 detected by the temperature sensor so that the recording material P held by the image recording drum 21 and passing through the opposing portion of the heating unit 23 reaches a predetermined temperature.

[0023] The head unit 24 discharges ink onto the recording material P held by the image recording drum 21 to record an image. The head unit 24 is provided individually for each color of C (cyan), M (magenta), Y (yellow), and K (black). In FIG. 1, the head units 24 corresponding to the respective colors of Y, M, C, and K are arranged in order from upstream with respect to the conveyance direction of the recording material P conveyed as the image recording drum 21 rotates.

[0024] The length of the head unit 24 in the direction perpendicular to the conveyance direction of the recording material P (the width direction of the recording material P) is set to a length that covers the entire recording material P. That is, the inkjet recording apparatus 1 is a one-pass type line head type inkjet recording apparatus. The head unit 24 can configure a line head by arranging a plurality of inkjet heads.

[0025] The head unit 24 has a plurality of inkjet heads 242 (see FIG. 2). The plurality of inkjet heads 242 discharge ink to record an image on the recording material P held by the image recording drum 21.

[0026] The irradiation unit 25 is disposed on the downstream side of the head unit 24 in the conveyance direction of the recording material P by the image recording drum 21. The irradiation unit 25 irradiates energy rays for curing the ink after the ink used in the inkjet recording apparatus 1 is discharged onto the recording material P. The irradiation unit 25 has, for example, a fluorescent tube such as a low-pressure mercury lamp, and emits the fluorescent tube to irradiate energy rays such as ultraviolet rays.

[0027] Examples of fluorescent tubes that emit ultraviolet rays include, in addition to low-pressure mercury lamps, mercury lamps having an operating pressure of about several hundred Pa to 1 MPa, light sources that can be used as germicidal lamps, cold cathode tubes, ultraviolet laser light sources, metal halide lamps, light-emitting diodes, and the like. Among these, a light source that can irradiate ultraviolet rays with higher illuminance and consume less power (for example, a light-emitting diode or the like) is more desirable. Further, the energy ray is not limited to ultraviolet rays, and any energy ray having the property of curing the ink according to the properties of the ink may be used, and the light source is also replaced according to the wavelength of the energy ray and the like.

[0028] The ink used in the inkjet recording apparatus 1 is, for example, a gel ink containing a wax component. The wax functions as a gelling agent, for example. Wax is typically a compound that can gel and temporarily fix (pin) the ink droplets that have landed on the recording material. When the ink that has landed on the recording material gels and is pinned, the wet spread of the ink is suppressed and it becomes difficult for adjacent dots to be the same, so that a higher-definition image can be formed. Further, when the ink is in a gel state, the entry of oxygen in the environment into the ink droplets is suppressed and it becomes difficult for oxygen to inhibit curing, so that a higher-definition image can be formed at a higher speed. The wax may be contained alone or in two or more kinds in the inkjet ink.

[0029] The content of the wax is preferably 0.01% by mass or more and 15.0% by mass or less based on the total mass of the ink. By setting the content of the wax to 0.5% by mass or more, the pinning property of the ink can be sufficiently enhanced and a higher-definition image can be formed. By setting the content of the wax to 10.0% by mass or less, it becomes difficult for the wax to precipitate on the surface of the formed image, the gloss of the image can be made closer to the gloss of the image formed by other inks, and the ink ejection property from the inkjet head can be further enhanced. From the above viewpoints, the content of the wax in the ink is more preferably 0.5% by mass or more and 10.0% by mass or less.

[0030] Also, from the following viewpoints, it is preferable that the wax crystallizes in the ink at a temperature below the gelation temperature of the ink. The gelation temperature refers to the temperature at which the ink undergoes a phase transition from a sol to a gel and the viscosity of the ink changes abruptly when the ink solubilized or liquefied by heating is cooled. Specifically, the solubilized or liquefied ink can be cooled while measuring the viscosity with a rheometer (for example, MCR300 manufactured by Physica), and the temperature at which the viscosity rises abruptly can be defined as the gelation temperature of the ink.

[0031] When the wax crystallizes in the ink, a structure may be formed in which the active energy ray curable compound is encapsulated in the three-dimensional space formed by the wax crystallized in a plate shape (such a structure is hereinafter referred to as a "card house structure"). When the card house structure is formed, since the liquid active energy ray curable compound is retained in the above-mentioned three-dimensional space, the ink droplets are less likely to wet and spread, and the pinning property of the ink is further enhanced. When the pinning property of the ink is enhanced, the ink droplets landing on the recording medium are less likely to coalesce, and a higher definition image can be formed.

[0032] From the viewpoint of facilitating the formation of the card house structure, it is preferable that the active energy ray curable compound dissolved in the ink and the wax are compatible. On the other hand, when the active energy ray curable compound dissolved in the ink and the wax are phase-separated, it may be difficult to form the card house structure.

[0033] Examples of waxes suitable for forming the card house structure by crystallization include ketone waxes, ester waxes, petroleum waxes, plant waxes, animal waxes, mineral waxes, hydrogenated castor oil, modified waxes, higher fatty acids, higher alcohols, hydroxystearic acid, fatty acid amides including N-substituted fatty acid amides and special fatty acid amides, higher amines, esters of sucrose fatty acids, synthetic waxes, dibenzylidene sorbitol, dimer acids, and dimer diols.

[0034] Examples of ketone waxes include lignoceryl ketone, dibehenyl ketone, distearyl ketone, dieicosyl ketone, dipalmitoyl ketone, dilauryl ketone, dimyristyl ketone, myristyl palmitoyl ketone, and palmitoyl stearyl ketone.

[0035] Examples of ester waxes include behenyl behenate, icosyl icosanoate, stearyl stearate, palmitoyl stearate, cetyl palmitate, myristyl myristate, cetyl myristate, myricyl cerotate, stearyl stearate, oleyl palmitate, glycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, ethylene glycol fatty acid ester, and polyoxyethylene fatty acid ester.

[0036] Examples of oil waxes include paraffin wax, microcrystalline wax, and petroleum waxes including petrolactam. Examples of plant waxes include candelilla wax, carnauba wax, rice wax, wood wax, jojoba oil, jojoba solid wax, and jojoba ester. Examples of animal waxes include beeswax, lanolin, and spermaceti. Examples of mineral waxes include montan wax and hydrogenated wax.

[0037] Examples of modified waxes include montan wax derivatives, paraffin wax derivatives, microcrystalline wax derivatives, 12-hydroxystearic acid derivatives, and polyethylene wax derivatives. Examples of higher fatty acids include behenic acid, arachidic acid, stearic acid, palmitic acid, myristic acid, lauric acid, oleic acid, and erucic acid. Examples of higher alcohols include stearyl alcohol and behenyl alcohol.

[0038] Examples of hydroxystearic acid include 12-hydroxystearic acid. Examples of fatty acid amides include lauric acid amide, stearic acid amide, behenic acid amide, oleic acid amide, erucic acid amide, ricinoleic acid amide, and 12-hydroxystearic acid amide. Examples of N-substituted fatty acid amides include N-stearyl stearic acid amide and N-oleyl palmitic acid amide.

[0039] Examples of special fatty acid amides include N,N'-ethylenebisstearylamide, N,N'-ethylenebis-12-hydroxystearylamide, and N,N'-xylylenebisstearylamide. Examples of higher amines include dodecylamine, tetradecylamine, and octadecylamine.

[0040] Examples of esters of sucrose fatty acids include sucrose stearic acid and sucrose palmitic acid. Examples of synthetic waxes include polyethylene wax and α-olefin maleic anhydride copolymer wax. Examples of dibenzylidene sorbitol include 1,3:2,4-bis-O-benzylidene-D-glucitol.

[0041] The wax component in the ink of this embodiment is set to be 0.01% by mass or more and less than 15% by mass. Further, this ink contains a photoactive radiation curable compound. Furthermore, this ink contains inorganic fine particles having an average particle diameter of 5 nm or more and less than 60 nm.

[0042] When the ink containing the wax component is heated, the wax component with a high melting point separates from the other ink components. Then, the wax component floats on the liquid surface. When an image is recorded using the ink with the wax component remaining separated, unevenness occurs in the ink density and the image quality deteriorates. In addition, there is a risk that the separated wax component clogs the ink flow path, leading to a failure of the inkjet recording apparatus 1.

[0043] The delivery unit 26 conveys the recording material P irradiated with energy rays by the irradiation unit 25 from the image recording drum 21 to the recording material discharge unit 30. The delivery unit 26 includes two rollers 261 and 262, an endless belt 263 spanned over the rollers 121 and 122, and a transfer drum 264. The rollers 261 and 262 and the belt 263 constitute a conveyance mechanism for conveying the recording material P.

[0044] The conveyance mechanism of the delivery unit 26 rotates the two rollers 261 and 262 to drive the belt 263. The transfer drum 264 receives the recording material P from the image recording drum 21 and places the received recording material P on the belt 263. The driven belt 263 conveys the placed recording material P to the recording material discharge unit 30. Note that the rollers of the conveyance mechanism are not limited to two and may be three or more.

[0045] The image reading sensor 27 is composed of an in-line sensor or the like. The image reading sensor 27 reads the image recorded on the recording material P conveyed by the delivery unit 26. The data of the read image is sent to the control unit 100.

[0046] [Recording material discharge unit] The recording material discharge unit 30 stores the recording material P conveyed by the delivery unit 26. The recording material discharge unit 30 has a plate-shaped paper discharge tray 31. The recording material P after image recording is placed on the paper discharge tray 31.

[0047] [Ink supply unit] The ink supply unit 40 has a main tank 420 (see FIG. 2) for storing ink, and supplies each color of ink to the head unit 24 of the image recording unit 20. The ink supplied to the head unit 24 of the image recording unit 20 is ejected from the respective nozzles of the inkjet head 242 (see FIG. 2).

[0048] 1-2. Configuration of the ink supply system Next, the configuration of the ink supply system will be described with reference to FIG. 2. FIG. 2 is a configuration diagram of an ink supply system according to the inkjet recording apparatus 1. In FIG. 2, an ink supply system of a head unit 24Y that discharges yellow ink is shown.

[0049] As shown in FIG. 2, the ink supply unit 40 includes a main tank 420 in which ink is stored, an ink dissolving unit 421 that dissolves the ink, and a pump 422. The main tank 420, the ink dissolving unit 421, and the pump 422 are provided individually corresponding to each of the colors Y, M, C, and K.

[0050] The main tank 420 communicates with the ink dissolving unit 421 via a first supply channel 451. The pump 422 is disposed in the first supply channel 451. The pump 422 sends the ink stored in the main tank 420 to the ink dissolving unit 421.

[0051] The main tank 420 has a stirring mechanism, a replenishing port, and a lid member. The stirring mechanism includes a stirring blade inserted into the main tank 420 and a motor that rotates the stirring blade. The stirring blade stirs the ink in the main tank 420 by rotating. The lid member opens and closes the replenishing port. And the lid member is lockable by a lid lock mechanism so that it can be unlocked.

[0052] The ink dissolving unit 421 communicates with a first ink tank 241A (to be described later) of the head unit 24Y via a second supply channel 452. The ink dissolving unit 421 heats and dissolves the ink supplied from the main tank 420. And the ink dissolving unit 421 supplies the dissolved ink to the first ink tank 241A.

[0053] The head unit 24Y includes a first ink tank 241A, a second ink tank 241B, an inkjet head 242, and a pump 243.

[0054] The first ink tank 241A communicates with the ink dissolution unit 421 via the second supply channel 452. As a result, the ink supplied from the ink dissolution unit 421 flows into the first ink tank 241A. Further, the first ink tank 241A communicates with the second ink tank 241B via the first circulation channel 251 and the second circulation channel 252.

[0055] The ink stored in the first ink tank 241A flows into the second ink tank 241B through the first circulation channel 251. A pump 243 and a check valve 255 are arranged in the first circulation channel 251. The pump 243 sends the ink in the first ink tank 241A to the second ink tank 241B. The check valve 255 prevents the ink passing through the first circulation channel 251 from flowing backward from the second ink tank 241B to the first ink tank 241A.

[0056] The ink stored in the second ink tank 241B flows into the first ink tank 241A through the second circulation channel 252. A check valve 256 is arranged in the second circulation channel 252. The check valve 256 prevents the ink passing through the second circulation channel 252 from flowing backward from the first ink tank 241A to the second ink tank 241B. That is, by driving the pump 243, the ink in the first ink tank 241A and the second ink tank 241B circulates.

[0057] The first ink tank 241A and the second ink tank 241B each have a heater 244 and a temperature detection unit 247 (see FIG. 10). The heater 244 heats the ink stored in the corresponding ink tank. The temperature detection unit 247 detects the temperature of the ink stored in the corresponding ink tank.

[0058] The second ink tank 241B communicates with the inkjet head 242 via the ink supply channel 253. The ink stored in the second ink tank 241B is supplied to the inkjet head 242 through the ink supply channel 253. The ink supplied to the inkjet head 242 is heated to a predetermined temperature in the second ink tank 241B.

[0059] The inkjet head 242 has a plurality of nozzles. The plurality of nozzles face the recording material P conveyed by the image recording drum 21 (see FIG. 1). The inkjet head 242 discharges ink from the plurality of nozzles toward the recording material P held by the image recording drum 21. Thereby, an image is recorded on the recording material P.

[0060] The inkjet head 242 communicates with the first ink tank 241A via the ink return channel 254. The ink that has not been discharged from the plurality of nozzles in the inkjet head 242 is returned to the first ink tank 241A through the ink return channel 254. A check valve 257 is disposed in the ink return channel 254. The check valve 257 prevents the ink passing through the ink return channel 254 from flowing backward from the first ink tank 241A to the inkjet head 242.

[0061] 1-3. Ink Stirring Method Next, a method for stirring the ink in the ink tanks 241A and 241B will be described with reference to FIG. 3. FIG. 3 is a diagram for explaining an ink stirring method in the inkjet recording apparatus 1.

[0062] As shown in FIG. 3, in the present embodiment, the ink in the second ink tank 241B that supplies ink to the inkjet head 242 is stirred. That is, in the present embodiment, the ink is stirred immediately before the ink is supplied to the inkjet head 242.

[0063] The second ink tank 241B has a tank body 271 and a central protrusion 272 disposed inside the tank body 271. The tank body 271 is formed in a hollow cylindrical shape. The tank body 271 has a circular top surface portion and bottom surface portion, and a cylindrical side wall portion. The axial direction of the tank body 271 is substantially parallel to the vertical direction.

[0064] The central protrusion 272 is formed in a cylindrical shape concentric with the tank body 271. The diameter of the central protrusion 272 is smaller than the diameter of the tank body 271. The axial length of the central protrusion 272 is equal to the axial length of the tank body 271. Note that the height of the central protrusion 272 only needs to be higher than the height of the liquid level when the storage amount of ink in the tank body 271 is maximum.

[0065] The central protrusion 272 serves as an obstacle that inhibits the ink from progressing in the radial direction of the tank body 271. Thereby, the ink that has flowed into the tank body 271 rotates around the central protrusion 272. That is, the ink that has flowed into the tank body 271 progresses in the circumferential direction of the tank body 271. Thereby, the ink in the tank body 271 is agitated.

[0066] The central protrusion 272 may be a float floating in the ink in the tank body 271. The float is a remaining amount detection unit that detects the remaining amount of ink in the tank body 271. It is formed in a cylindrical shape and has a specific gravity that floats in the liquid. A support shaft that penetrates the float in the axial direction is disposed in the tank body 271. The support shaft is formed, for example, in a cylindrical shape concentric with the tank body 271. The float moves vertically along the support shaft in response to a change in the amount of ink in the tank body 271.

[0067] Such a float, like the central protrusion 272, serves as an obstacle that inhibits the ink from progressing in the radial direction of the tank body 271. Thereby, the ink that has flowed into the tank body 271 rotates around the float. Thereby, the ink in the tank body 271 is agitated.

[0068] The first ink tank 241A has the same configuration as the second ink tank 241B. Therefore, similar to the second ink tank 241B, when ink flows into the first ink tank 241A, the ink inside is agitated. As described above, ink that has passed through the second supply channel 452 and ink that has passed through the second circulation channel 252 flow into the first ink tank 241A (see FIG. 2).

[0069] Note that the agitation of the ink in the first ink tank 241A may be at least one of when the ink that has passed through the second supply channel 452 is made to flow in and when the ink that has passed through the second circulation channel 252 is made to flow in. Also, the ink may be agitated before being supplied to the inkjet head 242. Therefore, the inkjet recording apparatus according to the present invention may be configured not to agitate the ink in the first ink tank 241A.

[0070] 1-4. Ink Inflow Position of Ink Tank Next, with reference to FIG. 4, the ink inflow position of the ink tank and the distance from the inner wall surface of the ink tank to the central protrusion will be described. FIG. 4 is a diagram for explaining the ink inflow position of the ink tank according to the first embodiment and the distance from the inner wall surface of the ink tank to the central protrusion.

[0071] As shown in FIG. 4, the ink inlet of the ink tank is provided on the side wall of the tank body 271. The ink inflow position can be set at any position between the bottom surface position in contact with the bottom surface portion of the tank body 271 and the liquid surface position of the ink. When the ink inflow position is higher than the liquid surface position of the ink, it is difficult to make the ink in the tank body 271 progress in the circumferential direction of the tank body 271. Therefore, the ink inflow position is preferably at or below the same level as the liquid surface position of the ink.

[0072] The distance S from the inner wall surface of the ink tank (tank body 271) to the outer wall surface of the central protrusion 272 can be arbitrarily set. The smaller the distance S, the faster the flow rate of the ink in the tank body 271. As a result, the stirring performance of the ink in the tank body 271 can be enhanced.

[0073] On the other hand, the smaller the distance S, the less the amount of ink that can be stored in the tank body 271. And to ensure the amount of ink that can be stored in the tank body 271, it is necessary to increase the diameter of the tank body 271. As a result, the tank body 271 becomes larger. Therefore, the distance S is preferably set appropriately in consideration of the diameter of the tank body 271 and the flow rate of the ink in the tank body 271.

[0074] 1-5. Ink Inflow Direction into the Ink Tank Next, the ink inflow direction into the ink tank will be described with reference to FIG. 5. FIG. 5 is a diagram for explaining the ink inflow direction into the ink tank according to the first embodiment.

[0075] As shown in FIG. 5, the ink inflow direction into the ink tank (tank body 271) can be considered as a first inflow direction and a second inflow direction. The first inflow direction is the normal direction to the outer wall surface of the tank body 271. The second inflow direction is the tangential direction to the outer wall surface of the tank body 271.

[0076] 1-6. Evaluation of Inflow Position, Inflow Direction, and Stirring Performance Next, the evaluation of the inflow position, inflow direction, and stirring performance of the ink tank will be described with reference to FIGS. 6 and 7. FIG. 6 is a table showing the liquid surface flow velocity and stirring performance with respect to the flow rate when the ink inlet in the ink tank is at the liquid surface position. FIG. 7 is a table showing the liquid surface flow velocity and stirring performance with respect to the flow rate when the ink inlet in the ink tank is at the bottom surface position.

[0077] The inventor verified the ink agitation performance when changing the ink flow rate with respect to the ink inflow position and the ink inflow direction in the ink tank. The inner diameter of the ink tank (tank body) was set to 76 mm, the distance S was set to 18 mm, and the time for ink inflow was set to 60 S.

[0078] The ink agitation performance was evaluated as effective when the 1 g wax component floating on the ink liquid surface became invisible. "Effective" indicates that the ink could be agitated until it was in a state where it could be supplied to the inkjet head 242.

[0079] As shown in FIG. 6, when the ink inlet was at the liquid surface position, even when ink was made to flow in the first inflow direction (normal direction), the ink that flowed into the tank body 271 did not rotate around the central protrusion 272. Therefore, the liquid surface flow velocity could not be measured and the agitation performance could not be evaluated (indicated by "-" in FIG. 6).

[0080] On the other hand, when the ink inlet was at the liquid surface position, when ink was made to flow in at a flow rate of 3.61×10 -6 m 3 / S in the second inflow direction (tangential direction), the flow velocity at the inlet was 18.38×10 -3 m / S and the liquid surface flow velocity was 14.43×10 -3 m / S. The agitation performance in this case was effective. Also, when ink was made to flow in at a flow rate of 2.14×10 -6 m 3 / S in the second inflow direction (tangential direction), the flow velocity at the inlet was 10.89×10 -3 m / S and the liquid surface flow velocity was 8.55×10 -3 m / S. Also in this case, the agitation performance was effective.

[0081] Furthermore, when ink was made to flow in at a flow rate of 1.16×10 -6 m 3 / S in the second inflow direction (tangential direction), the flow velocity at the inlet was 5.89×10 -3 m / S and the liquid surface flow velocity was 3.85×10 -3m / s. Even in this case, the stirring performance was effective. From the above evaluation, when the ink inlet is at the liquid surface position, if the inflow direction is set to the second inflow direction (tangential direction) and the liquid surface flow velocity is set to a flow rate of ink of 3.85×10 -3 m / s or more, it was found that the stirring performance becomes effective.

[0082] As shown in Fig. 7, when the ink inlet is at the bottom surface position, even if the ink is made to flow in at a flow rate of 23.22×10 -6 m 3 / s in the first inflow direction (normal direction), the liquid surface flow velocity was low. Therefore, when the ink was made to flow in the first inflow direction (normal direction), the stirring performance was not effective (indicated by "×" in Fig. 7).

[0083] On the other hand, when the ink inlet is at the bottom surface position, if the ink is made to flow in at a flow rate of 23.22×10 -6 m 3 / s in the second inflow direction (tangential direction), the flow velocity at the inlet is 118.30×10 -3 m / s and the liquid surface flow velocity was 15.48×10 -3 m / s. The stirring performance in this case was effective (indicated by "○" in Fig. 7). Also, when the ink was made to flow in at a flow rate of 8.51×10 -6 m 3 / s in the second inflow direction (tangential direction), the flow velocity at the inlet is 43.36×10 -3 m / s and the liquid surface flow velocity was 5.67×10 -3 m / s. Even in this case, the stirring performance was effective.

[0084] When the ink is made to flow in at a flow rate of 6.06×10 -6 m 3 / s in the second inflow direction (tangential direction), the flow velocity at the inlet is 30.87×10 -3 m / s and the liquid surface flow velocity was 4.04×10 -3 m / s. Even in this case, the stirring performance was effective. When the ink is made to flow in at a flow rate of 4.59×10 -6 m 3When the ink is made to flow in at the flow rate of / S, the flow velocity at the inlet is 23.38×10 -3 m / S, and the surface flow velocity was 3.06×10 -3 m / S. The stirring performance in this case was not effective (indicated by "×" in Fig. 7). From this, it was found that the second inflow direction (tangential direction) is preferable for the inflow direction of the ink regardless of the position of the ink inlet.

[0085] When the ink is made to flow in at the flow rate of 3.61×10 -6 m 3 / S in the second inflow direction (tangential direction), the flow velocity at the inlet is 18.38×10 -3 m / S, and the surface flow velocity was 2.40×10 -3 m / S. The stirring performance in this case was not effective. When the ink is made to flow in at the flow rate of 2.14×10 -6 m 3 / S in the second inflow direction (tangential direction), the flow velocity at the inlet is 10.89×10 -3 m / S, and the surface flow velocity was 1.42×10 -3 m / S. The stirring performance in this case was not effective.

[0086] Thus, when the ink inlet of the ink tank is at the bottom surface position, in order to obtain a surface flow velocity at which the stirring performance is effective, it is necessary to increase the flow rate more than when the ink inlet is at the surface position. And when the ink inlet is at the bottom surface position, by setting the inflow direction to the second inflow direction (tangential direction) and setting the flow rate of the ink to be 4.04×10 -3 m / S or more, it was found that the stirring performance becomes effective.

[0087] 1-7. Relationship between the ink flow rate and the distance S Next, with reference to Fig. 8, the relationship between the ink flow rate and the distance S for ensuring a surface flow velocity of 4.0×10 -3 m / S will be described. Fig. 8 is a graph showing the relationship between the ink flow rate and the distance S for ensuring a surface flow velocity of 4.0×10 -3 m / S.

[0088] The vertical axis of the graph shown in FIG. 8 indicates the flow rate of the ink flowing in from the inlet of the ink tank. The horizontal axis of the graph shown in FIG. 8 indicates the distance S (see FIG. 4). Also, the ink inflow direction into the ink tank is set to the second inflow direction (tangential direction). When the flow rate is constant, the liquid surface flow velocity becomes slower as the distance S increases. Therefore, to obtain a liquid surface flow velocity of 4.0×10 -3 m / S, it is necessary to set the value of the flow rate according to the distance S. Note that the liquid surface flow velocity is not limited to 4.0×10 -3 m / S, and it can be set to any value as long as the stirring performance is evaluated as effective.

[0089] As shown in FIG. 8, to set the distance S to about 10 mm and ensure a liquid surface flow velocity of 4.0×10 -3 m / S, the inlet of the ink tank can be set at either the liquid surface position or the bottom surface position. For example, when setting the inlet of the ink tank at the liquid surface position, the flow rate needs to be set to about 4×10 -6 m 3 / S. On the other hand, when setting the inlet of the ink tank at the bottom surface position, the flow rate needs to be set to about 20×10 -6 m 3 / S.

[0090] As shown in FIG. 8, when setting the distance S to about 22 mm and ensuring a liquid surface flow velocity of 4.0×10 -3 m / S, if the inlet of the ink tank is set at the bottom surface position, a flow rate of about 33×10 -6 m 3 / S or more is required. However, the maximum value of the ink flow rate that the pump 243 in this embodiment can deliver is about 23×10 -6 m 3 / S. Therefore, when setting the distance S to about 22 mm, it is necessary to set the inlet of the ink tank at the liquid surface position. When setting the inlet of the ink tank at the liquid surface position, the flow rate needs to be set to about 5×10 -6 m 3 / S or more.

[0091] Also, when setting the distance S to 100 mm, to ensure a liquid surface flow velocity of 4.0×10 -3 m / S, the ink tank inlet should be set at the liquid surface position, and the flow rate needs to be set to 23×10 -6 m 3 / S or more. As described above, the maximum value of the ink flow rate that the pump 243 of this embodiment can deliver is approximately 23×10 -6 m 3 / S. Therefore, when using the pump 243 of this embodiment, the maximum value of the distance S is approximately 100 mm.

[0092] 1-8. Configuration of the control system Next, the control system regarding the ink supply of the inkjet recording apparatus 1 will be described with reference to FIGS. 9 and 10. FIG. 9 is a block diagram of the control system regarding the ink supply of the inkjet recording apparatus 1. FIG. 10 is a functional block diagram related to the control of the head unit 24 in the control unit of the inkjet recording apparatus 1.

[0093] The control unit 100 shown in FIG. 9 controls the entire system constituting the inkjet recording apparatus 1. Therefore, the control unit 100 is connected to the recording material supply unit 10, the image recording unit 20, and the input / output interface 70 via the system bus 80, respectively.

[0094] The control unit 100 is composed of, for example, a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, and a storage unit 104, etc. Various functions of the control unit 100 are realized by the CPU 101 executing a predetermined processing program stored in the ROM 102. Various functions of the control unit 100 include, for example, the drive control of the conveyance unit 12 in the recording material supply unit 10, and the operation control regarding image recording of the image recording drum 21 and the head unit 24 in the image recording unit 20.

[0095] The ROM 102 stores various processing programs for controlling each part of the inkjet recording apparatus 1, parameters and table data necessary for the execution of the programs, various files, etc. The ROM 102 is used as an example of a computer-readable non-transitory recording medium storing the programs executed by the CPU 101. Therefore, the programs are permanently stored in the ROM 102.

[0096] The RAM 103 is, for example, a volatile semiconductor memory. The RAM 103 forms a work area for temporarily storing various processing programs, input or output data, parameters, etc. read from the ROM 102 in various processes executed under the execution control of the CPU 101.

[0097] The storage unit 104 consists of a hard disk drive (HDD) or the like as a mass storage device. The storage unit 104 stores data information of the images read by the image reading sensor 27.

[0098] The CPU 101 of the control unit 100 is connected to an external device via the input / output interface 70. The external device is, for example, a personal computer, a facsimile device, or the like. The input / output interface 70 receives image data from the external device. The input / output interface 70 outputs the received image data to the control unit 100.

[0099] The control unit 100 performs image processing such as shading correction, image density adjustment, image compression, etc. on the image data received from the input / output interface 70 as necessary. Then, the control unit 100 controls the operation of the image recording unit 20 based on the image-processed image data, and causes the inkjet head 242 (see FIG. 2) to eject ink to a predetermined position on the recording material P. Thereby, an image is recorded on the recording material P.

[0100] As shown in FIG. 10, the head unit 24 includes a pump 243, a heater 244, a head driving unit 245, a remaining amount detection unit 246, and a temperature detection unit 247. Since the pump 243, the heater 244, and the temperature detection unit 247 have been described above, their descriptions will be omitted.

[0101] The head driving unit 245 causes the inkjet head 242 (see FIG. 2) of the head unit 24 to eject ink. The remaining amount detection units 246 are respectively arranged in the first ink tank 241A and the second ink tank 241B. The remaining amount detection unit 246 is, for example, the above-described float, and respectively detects the remaining amount of ink in the first ink tank 241A and the remaining amount of ink in the second ink tank 241B.

[0102] The control unit 100 includes a pump control unit 111, a temperature control unit 112, a discharge control unit 113, a remaining amount detection unit 114, and a temperature detection unit 115.

[0103] The pump control unit 111 is electrically connected to the pump 243. The pump control unit 111 controls the driving of the pump 243 to send ink from the first ink tank 241A to the second ink tank 241B.

[0104] The temperature control unit 112 is electrically connected to the heater 244. The temperature control unit 112 controls the driving of the heater 244 to heat the ink in the first ink tank 241A and the ink in the second ink tank 241B respectively. The discharge control unit 113 is electrically connected to the head driving unit 245. The discharge control unit 113 controls the driving of the head driving unit 245 to cause the inkjet head 242 (see FIG. 2) to eject ink.

[0105] The remaining amount detection unit 114 is electrically connected to the remaining amount detection unit 246. It receives the detection result of the remaining amount detection unit 246 and detects the remaining amount of ink in the first ink tank 241A and the remaining amount of ink in the second ink tank 241B. The temperature detection unit 115 is electrically connected to the temperature detection unit 247. The temperature detection unit 115 receives the detection result of the temperature detection unit 247 and detects the temperature of the ink in the first ink tank 241A and the temperature of the ink in the second ink tank 241B.

[0106] 1-9. Ink Stirring Process Next, the ink stirring process executed by the inkjet recording apparatus 1 will be described with reference to FIG. 11. FIG. 11 is a flowchart showing an example of the ink stirring process in the inkjet recording apparatus 1.

[0107] First, the temperature control unit 112 of the control unit 100 performs an ink heating process (S1). In step S1, the temperature control unit 112 controls the driving of the heater 244 to heat the ink in the first ink tank 241A and the ink in the second ink tank 241B, respectively. The ink heating process in step S1 corresponds to the ink heating step according to the present invention.

[0108] Next, the temperature detection unit 115 of the control unit 100 determines whether the temperatures of the ink in the first ink tank 241A and the ink in the second ink tank 241B are equal to or higher than a predetermined value (S2). In step S2, when it is determined that the temperatures of the ink in the first ink tank 241A and the ink in the second ink tank 241B are not equal to or higher than the predetermined value (when S2 is a NO determination), the temperature detection unit 115 of the control unit 100 continues the ink heating process in step S1.

[0109] In step S2, when it is determined that the temperatures of the ink in the first ink tank 241A and the ink in the second ink tank 241B are equal to or higher than the predetermined value (when S2 is a YES determination), the pump control unit 111 of the control unit 100 performs a pump driving process (S3).

[0110] In step S3, the pump control unit 111 controls the driving of the pump 243 to send ink from the first ink tank 241A to the second ink tank 241B. As a result, the ink in the second ink tank 241B is agitated. Thereafter, the control unit 100 ends the ink agitation process. The pump driving process in step S3 corresponds to the agitation step according to the present invention.

[0111] When sending ink from the second ink tank 241B to the inkjet head 242 (see FIG. 2), it is necessary to set the temperature of the ink to a predetermined value or higher. However, since the ink contains a wax component, when the temperature is set to a predetermined value or higher, the wax component separates from the other ink components.

[0112] Therefore, the pump control unit 111 sends ink from the first ink tank 241A to the second ink tank 241B to rotate the ink in the second ink tank 241B in the circumferential direction of the second ink tank 241B. As a result, the ink in the second ink tank 241B can be agitated. Consequently, the separation of the wax component can be eliminated.

[0113] 2. Second Embodiment The part where the inkjet recording apparatus according to the second embodiment differs from the inkjet recording apparatus 1 according to the first embodiment is the ink supply system of the head unit. Therefore, here, the ink supply system according to the second embodiment will be described, and the description of the configuration overlapping with the first embodiment will be omitted.

[0114] 2-1. Configuration of Ink Supply System Next, the configuration of the ink supply system according to the second embodiment will be described with reference to FIG. 12. FIG. 12 is a configuration diagram of the ink supply system according to the second embodiment. In FIG. 12, the ink supply system of the head unit 24Y that discharges yellow ink is shown.

[0115] As shown in FIG. 12, the ink supply unit 40 includes a main tank 420 in which ink is stored, an ink dissolution unit 421 that dissolves the ink, and a pump 422. The configuration of the ink supply unit 40 is the same as that of the first embodiment. The main tank 420, the ink dissolution unit 421, and the pump 422 are provided individually corresponding to each of the colors Y, M, C, and K.

[0116] The head unit 24Y includes a first ink tank 241A, a second ink tank 241B, an ink jet head 242, and a pump 243.

[0117] The first ink tank 241A communicates with the ink dissolution unit 421 via the second supply channel 452. Thus, the ink supplied from the ink dissolution unit 421 flows into the first ink tank 241A. The first ink tank 241A communicates with the second ink tank 241B via the first channel 281. That is, the ink supply system according to the second embodiment does not have a circulation channel between the first ink tank 241A and the second ink tank 241B that does not pass through the ink jet head 242.

[0118] The ink stored in the first ink tank 241A flows into the second ink tank 241B through the first channel 281. A pump 243 and a check valve 255 are arranged in the first channel 281. The pump 243 sends the ink in the first ink tank 241A to the second ink tank 241B. The check valve 255 prevents the ink passing through the first channel 281 from flowing backward from the second ink tank 241B to the first ink tank 241A.

[0119] The second ink tank 241B communicates with the ink jet head 242 via the ink supply channel 253. The ink stored in the second ink tank 241B is supplied to the ink jet head 242 through the ink supply channel 253. The ink supplied to the ink jet head 242 is heated to a predetermined temperature in the second ink tank 241B.

[0120] The inkjet head 242 communicates with the first ink tank 241A via the ink return channel 254. Ink that has not been ejected from a plurality of nozzles in the inkjet head 242 is returned to the first ink tank 241A through the ink return channel 254. A check valve 257 is disposed in the ink return channel 254. The check valve 257 prevents the ink passing through the ink return channel 254 from flowing backward from the first ink tank 241A to the inkjet head 242.

[0121] Also in the second embodiment, the ink agitation process is executed in the same manner as in the first embodiment. That is, the pump 243 sends ink from the first ink tank 241A to the second ink tank 241B and rotates the ink in the second ink tank 241B in the circumferential direction of the second ink tank 241B. Thereby, the ink in the second ink tank 241B can be agitated. As a result, the separation of the wax component can be eliminated.

[0122] As described above, embodiments of the inkjet recording apparatus and the ink agitation method of the present invention have been described including their operational effects. However, the inkjet recording apparatus and the ink agitation method of the present invention are not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the invention described in the claims.

[0123] For example, in the above-described embodiment, the ink was agitated by flowing the ink into the ink tanks 241A and 241B formed in a hollow cylindrical shape and controlling the flow of the ink. However, the inkjet recording apparatus of the present invention may use other configurations to agitate the ink as long as it can agitate the ink containing the wax component and eliminate the separation of the wax component.

[0124] For example, the ink tanks 241A and 241B may have stirring vanes (stirrers). The stirring vanes are respectively disposed in the ink tanks 241A and 241B and are rotationally driven using a motor. The stirring vanes rotate to agitate the ink in the ink tanks 241A and 241B.

Description of Signs

[0125] 1…Inkjet recording apparatus, 10…Recording material supply unit, 11…Paper feed tray, 12…Conveying unit, 20…Image forming unit, 21…Image forming drum, 22…Transfer unit, 23…Paper heating unit, 24, 24Y…Head unit, 25…Irradiation unit, 26…Delivery unit, 27…Image reading sensor, 30…Recording material discharge unit, 31…Paper discharge tray, 40…Ink supply unit, 100…Control unit, 101…CPU, 102…RAM, 103…ROM, 104…Storage unit, 111…Pump control unit, 112…Temperature control unit, 113…Discharge control unit, 114…Remaining amount detection unit, 115…Temperature detection unit, 241A…First ink tank, 241B…Second ink tank, 242…Inkjet head, 243…Pump, 244…Heater, 245…Head drive unit, 246…Remaining amount detection unit, 247…Temperature detection unit, 251…First circulation flow path, 252…Second circulation flow path, 253…Discharged ink flow path, 254…Return ink flow path, 255, 256, 257…Check valve, 271…Tank body, 272…Central protrusion, 281…First flow path, 420…Main tank, 421…Ink dissolution unit, 422…Pump, 451…First supply flow path, 452…Second supply flow path

Claims

1. An ink tank in which ink containing a wax component is stored, and an inkjet head having a plurality of nozzles for discharging the ink, wherein the ink tank stirs the ink. An inkjet recording apparatus.

2. The ink tank is formed in a hollow cylindrical shape that stirs the ink inside when the ink flows in. The inkjet recording apparatus according to claim 1.

3. The ink contains two or more wax components having different melting points. The inkjet recording apparatus according to claim 1.

4. A flow path for supplying the ink to the ink tank, and a pump for sending the ink to the ink tank. The inkjet recording apparatus according to claim 1.

5. The inflow direction of the ink flowing from the flow path into the ink tank is a tangential direction with respect to the side circumferential surface of the ink tank. The inkjet recording apparatus according to claim 4.

6. The liquid surface flow velocity of the ink is 3.8×10 －３ m / sec or more. The inkjet recording apparatus according to claim 5.

7. A plurality of the ink tanks are provided, and the plurality of ink tanks communicate with each other via a circulation flow path to circulate the ink. The inkjet recording apparatus according to claim 4.

8. A plurality of the ink tanks are provided, and the plurality of ink tanks and the inkjet head communicate with each other via an ink flow path to circulate the ink. The inkjet recording apparatus according to claim 4.

9. Comprising an obstacle disposed at the central portion inside the ink tank The inkjet recording apparatus according to claim 1.

10. The ink tank supplies the ink to the inkjet head through an ink supply passage The inkjet recording apparatus according to claim 1.

11. The inflow of the ink into the ink tank is performed after heating the ink The inkjet recording apparatus according to claim 1.

12. The ink contains a wax component of 0.01 mass% or more and less than 15 mass% The inkjet recording apparatus according to claim 1.

13. The ink contains a photoactive radiation curable compound The inkjet recording apparatus according to claim 1.

14. The ink contains inorganic fine particles having an average particle diameter of 5 nm or more and less than 60 nm The inkjet recording apparatus according to claim 13.

15. An ink stirring method performed by an inkjet recording apparatus including an ink tank, comprising: A heating step of heating the ink containing a wax component; And a stirring step of stirring the ink heated in the heating step. An ink stirring method.

16. The ink tank is formed in a hollow cylindrical shape that stirs the internal ink when the ink flows in, In the stirring step, the ink heated in the heating step is caused to flow into the ink tank The ink stirring method according to claim 15. Claim 17 In the heating step, the ink stored in the ink tank is heated The ink stirring method according to claim 15

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