Inkjet recording device

Abstract

To suppress the occurrence of ink transfer failure.SOLUTION: An inkjet recording device includes: a main tank for storing ink; a sub-tank connected to an inkjet head and storing the ink that is supplied from the main tank; a heating part for heating ink that is to be supplied from the main tank to the sub-tank; and a feedback current frow channel for returning the ink that has been supplied from the main tank to the sub-tank to the heating part.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an inkjet recording apparatus. [Background technology]

[0002] An inkjet recording apparatus includes an ink supply device for supplying ink to a plurality of inkjet heads, and a prior art ink supply device is shown in Patent Document 1. The configuration of the ink supply device (referred to as an ink circulation device in Patent Document 1) described in Patent Document 1 can be briefly explained as follows.

[0003] The ink supply device includes a main tank (referred to as a refill tank in Patent Document 1) that stores ink. The ink supply device includes a first sub-tank (referred to as a circulation tank in Patent Document 1) that stores ink supplied from the main tank, and the first sub-tank is connected to the outlet sides of the multiple inkjet heads. The ink supply device includes a second sub-tank (referred to as a supply tank in Patent Document 1) that stores ink supplied from the first sub-tank, and the second sub-tank is connected to the inlet sides of the multiple inkjet heads. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-154697 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the ink supply device according to the prior art, the ink is not heated before being supplied from the main tank to the first sub-tank. Therefore, it is not easy to uniformly raise the ink temperature from room temperature to the temperature at which the ink is converted into a sol before supplying the ink to the first sub-tank. As a result, ink may become clogged inside the flow path downstream of the first sub-tank, causing problems with the ink delivery.

[0006] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide an inkjet recording apparatus capable of suppressing the occurrence of ink delivery failures. [Means for solving the problem]

[0007] One aspect of the inkjet recording apparatus of the present invention is A main tank for storing ink; a sub-tank connected to an inkjet head and configured to store ink supplied from the main tank; a heating unit that heats the ink before it is supplied from the main tank to the sub tank; The ink supply unit includes a return flow path for returning the ink to the heating unit after the ink is supplied from the main tank to the sub tank. Effect of the Invention

[0008] According to the present invention, it is possible to suppress the occurrence of poor ink delivery. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic front view of an inkjet recording apparatus according to this embodiment. [Diagram 2] FIG. 2 is a diagram showing the ink supply device according to the present embodiment. [Diagram 3] FIG. 3 is a schematic diagram showing a heating unit in the ink supply device according to the present embodiment. [Figure 4] FIG. 4 is a schematic diagram taken along line IV-IV in FIG. [Diagram 5]FIG. 5 is a schematic diagram taken along line VV in FIG. [Figure 6] FIG. 6 is a control block diagram of the inkjet recording apparatus according to this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, this embodiment will be described with reference to the drawings. In this embodiment, the transport direction refers to the transport direction in which the recording medium P is transported. The downstream side refers to the downstream side of the transport direction, and the upstream side refers to the upstream side of the transport direction. The transport width direction refers to the direction perpendicular to the transport direction.

[0011] The overall configuration of an inkjet recording apparatus 10 according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic front view of the inkjet recording apparatus 10 according to this embodiment.

[0012] As shown in FIG. 1, the inkjet recording apparatus 10 according to the present embodiment is a single-pass type recording apparatus that forms a color image on the recording medium P by ejecting four color inks toward the recording medium P at appropriate timing while moving the recording medium P in the conveying direction. As the recording medium P, in addition to paper such as plain paper and coated paper, various media capable of fixing the ink that has landed on the surface, such as fabric and resin film, can be used. In the inkjet recording apparatus 10, ink that changes phase between a gel state and a sol state (liquid state) depending on temperature is used. For example, energy ray irradiation type ink such as UV ink that is in a gel state at room temperature, changes to a sol state when heated, and is solidified when irradiated with energy rays during image formation can be used.

[0013] The inkjet recording device 10 includes a device body 12 extending in the left-right direction. The device body 12 includes a center frame 14, a first side frame 16 disposed on the right side of the center frame 14, and a second side frame 18 disposed on the left side of the center frame 14.

[0014] The first side frame 16 is provided with a paper feed section 20 for feeding recording media P. The paper feed section 20 has a plate-shaped paper feed tray 22 for placing the recording media P thereon, and the paper feed tray 22 is provided on the first side frame 16 so as to be movable in the vertical direction. The paper feed tray 22 is configured to move up and down depending on the amount of recording media P to be placed on it, and the uppermost recording medium P is held at a predetermined height position.

[0015] The paper feed unit 20 has a transport section 24 for transporting the recording medium P sent out from the paper feed tray 22 in the transport direction, and the transport section 24 is provided from the first side frame 16 to the center frame 14. The transport section 24 has a plurality of rotatable support rollers 26 and an endless belt 28 provided to be wound around the plurality of support rollers 26. The belt 28 is caused to circulate by the rotation of the plurality of support rollers 26, thereby transporting the recording medium P sent out from the paper feed tray 22 in the transport direction.

[0016] The center frame 14 is provided with an image forming section 30 for ejecting ink onto the recording medium P to form an image. The image forming section 30 has an image forming drum 32 that supports the recording medium P, and the image forming drum 32 is rotatably provided on the center frame 14. With the recording medium P supported on the outer circumferential surface (conveyance surface) of the image forming drum 32, the image forming drum 32 is rotated by driving a motor (not shown) for the image forming drum, thereby conveying the recording medium P in the conveyance direction. The image forming drum 32 has a claw portion (not shown) that presses the edge of the recording medium P, and an adsorption portion (not shown) that adsorbs the recording medium P.

[0017] The image forming section 30 has a delivery unit 34 for delivering the recording medium P from the transport section 24 to the image forming drum 32, and the delivery unit 34 is provided between the transport section 24 and the image forming drum 32 in the center frame 14. The delivery unit 34 has a swing arm 36 that supports one end of the recording medium P transported by the transport section 24, and a delivery drum 38 that delivers the recording medium P supported by the swing arm 36 to the image forming drum 32. One end of the recording medium P on the transport section 24 is supported by the swing arm 36 and delivered to the delivery drum 38, so that the recording medium P is delivered from the delivery drum 38 to the image forming drum 32.

[0018] The image forming section 30 has a media heating section 40 for heating the recording medium P supported on the image forming drum 32, and the media heating section 40 is provided on the downstream side of the delivery drum 38 in the center frame 14. The media heating section 40 is disposed facing the outer circumferential surface of the image forming drum 32. The media heating section 40 has, for example, an infrared heater or the like, and heats the image forming drum 32 and the recording medium P so that the temperature of the recording medium P transported by the image forming drum 32 falls within a predetermined range.

[0019] The image forming section 30 has a plurality of head units 42 that eject ink onto the recording medium P carried by the image forming drum 32 to form an image, and the plurality of head units 42 are disposed downstream of the medium heating section 40. The plurality of head units 42 are units corresponding to four colors of ink, namely, yellow (Y), magenta (M), cyan (C), and black (K). The plurality of head units 42 corresponding to the four colors of ink, Y, M, C, and K, are disposed at intervals from the upstream side along the conveying direction. Each head unit 42 is held by each carriage (not shown) that is provided on the center frame 14 so as to be movable in the conveying width direction. In other words, each head unit 42 is provided on the center frame 14 so as to be movable in the conveying width direction via each carriage.

[0020] Each head unit 42 has a plurality of inkjet heads 44 (see FIG. 2) that eject ink onto the recording medium P, and the inkjet heads 44 are arranged along the conveying width direction. In other words, each head unit 42 constitutes a line head including the plurality of inkjet heads 44. Each inkjet head 44 has a plurality of recording elements. Each recording element has a pressure chamber that stores ink, a piezoelectric element provided on the inner wall surface of the pressure chamber, and a nozzle that communicates with the pressure chamber. When a drive signal that causes the piezoelectric element to deform is input, the pressure chamber of the recording element is deformed by the deformation of the piezoelectric element, and the pressure in the pressure chamber changes accordingly, and ink is ejected from the nozzle. In addition, since a back pressure (negative pressure) within a certain range is applied to the ink in each inkjet head 44, the meniscus of the ink in each inkjet head 44 is held in a state of being drawn into the nozzle.

[0021] The arrangement range of the nozzles in each head unit 42 in the transport width direction covers the range in the transport width direction of an area on the recording medium P where an image is formed. During image formation (printing), the position of each head unit 42 in the transport width direction is fixed. That is, the inkjet recording device 10 is a single-pass type recording device as described above.

[0022] The image forming unit 30 has a fixing unit 46 for fixing the ink onto the recording medium P, and the fixing unit 46 is provided on the downstream side of the multiple head units 42 in the center frame 14. The fixing unit 46 is disposed facing the outer circumferential surface of the image forming drum 32. The fixing unit 46 has a light-emitting unit that irradiates energy rays such as ultraviolet rays. The light-emitting unit of the fixing unit 46 imparts a predetermined energy to the ink ejected onto the recording medium P, thereby hardening the ink and fixing it to the recording medium P.

[0023] The image forming unit 30 has a delivery unit 48 that transports the recording medium P irradiated with energy rays from the image forming drum 32 in the transport direction. The delivery unit 48 is provided across the center frame 14 to the second side frame 18. The delivery unit 48 has a plurality of rotatable support rollers 50, an endless belt 52 provided so as to be wound around the plurality of support rollers 50, and a delivery drum 54 that delivers the recording medium P from the image forming drum 32 to the belt 52. The belt 52 is caused to travel in a circular manner by the rotation of the plurality of support rollers 50, thereby transporting the recording medium P sent out from the image forming drum 32 in the transport direction.

[0024] The second side frame 18 is provided with a paper discharge section 56 for discharging the recording medium P on which an image has been formed. The paper discharge section 56 has a plate-shaped paper discharge tray 58 on which the recording medium P on which an image has been formed is placed. The paper discharge section 56 stores the recording medium P until the user removes the recording medium P from the paper discharge tray 58.

[0025] The main configuration of the ink supply device 60 according to this embodiment will be described with reference to Fig. 2 to Fig. 5. Fig. 2 is a diagram showing the ink supply device 60 according to this embodiment. Fig. 3 is a schematic diagram showing a heating unit 68 in the ink supply device 60 according to this embodiment. Fig. 4 is a schematic diagram taken along line IV-IV in Fig. 3. Fig. 5 is a schematic diagram taken along line VV in Fig. 3. The arrows in Figs. 4 and 5 indicate the flow direction of ink.

[0026] 2, the inkjet recording apparatus 10 includes an ink supply device 60 for supplying ink to each head unit 42. The ink supply devices 60 (only one is shown) correspond to the four colors of ink, Y, M, C, and K, respectively. A main tank 62 for storing ink is provided at a position separated from the carriage (not shown). The main tank 62 is a large-capacity tank capable of storing 10 L or more of ink, for example, 30 L.

[0027] The carriage is provided with a first sub-tank 64 that stores ink supplied from the main tank 62. The first sub-tank 64 is connected to the outlet sides of the multiple inkjet heads 44. The first sub-tank 64 may have a heat source such as a heater for heating the ink.

[0028] The carriage is provided with a plurality of second sub-tanks 66 that store ink supplied from the first sub-tank 64. The plurality of second sub-tanks 66 store ink supplied from the main tank 62 via the first sub-tank 64. Each of the second sub-tanks 66 is connected to the inflow sides of the plurality of inkjet heads 44. Each of the second sub-tanks 66 may have a heating source such as a heater for heating the ink.

[0029] As shown in FIGS. 2 and 3, the carriage is provided with a heating unit 68 as a heating section that heats ink before it is supplied from the main tank 62 to the first sub-tank 64. The heating unit 68 has multiple stages of heating tanks 70 (70U, 70D) for heating ink. The heating tanks 70 of each stage are made of a material with high thermal conductivity, such as an aluminum alloy, and the upper side of each stage of the heating tanks 70 is open. The heating unit 68 has flat lid members 72 (72U, 72D) provided on the upper side of each stage of the heating tanks 70 so as to cover the opening. In this embodiment, the heating tanks 70 have two stages, but may have three or more stages.

[0030] 3 to 5, a plurality of ribs 74 are formed inside the heating tank 70 of each stage, and a serpentine heating flow path 76 for circulating ink is defined inside the heating tank 70 of each stage by the plurality of ribs 74. In other words, the heating tank 70 of each stage has a serpentine heating flow path 76 defined by the plurality of ribs 74.

[0031] Two inlets 70i, 70j are formed on the side of the lower heating tank 70D for allowing ink to flow into the heating flow path 76. A communication flow path 78 is formed from the lower lid member 72D to the upper heating tank 70U for connecting the heating flow path 76 of the lower heating tank 70D to the heating flow path 76 of the upper heating tank 70U. Also, an outlet 70e is formed on the side of the upper heating tank 70U for allowing ink to flow out from the heating flow path 76. In other words, the heating unit 68 is configured so that ink flows from the heating flow path 76 of the lower heating tank 70D to the heating flow path 76 of the upper heating tank 70U.

[0032] A plurality of heaters 80 for heating the ink are provided in the center of the heating tank 70 of each stage. A temperature sensor (not shown), such as a thermistor, for detecting the ink temperature in the heating flow path 76 of the heating tank 70 of each stage is provided at an appropriate position of the heating tank 70 of each stage.

[0033] The heating unit 68 has an inlet 82 for allowing ink to flow into the heating tank 70, and the inlet 82 is provided on the side of the lower heating tank 70D. The inlet 82 communicates with the inlet 70i of the lower heating tank 70D. The inlet 82 has a heater 84 that heats the ink before it flows into the heating tank 70. A temperature sensor (not shown), such as a thermistor, that detects the temperature of the ink in the inlet 82 is provided at an appropriate position of the inlet 82.

[0034] Next, the flow path configuration of the ink supply device 60 will be described.

[0035] 2 and 4, one end of a first main flow path 86 is connected to the main tank 62, and the other end of the first main flow path 86 is connected to the inlet 82. A pump 88 for sending ink to the heating unit 68 side (first sub-tank 64 side) is disposed in the first main flow path 86. A solenoid valve 90 is disposed in the first main flow path 86 between the pump 88 and the inlet 82 as an opening / closing valve for the first main flow path that opens and closes the first main flow path 86. A pressure sensor (not shown) for detecting the ink pressure in the first main flow path 86 is provided at an appropriate position in the first main flow path 86.

[0036] 2 and 5, one end of the second main flow path 92 is connected to the outlet 70e of the upper heating tank 70U, and the other end of the second main flow path 92 is connected to the inlet port of the first sub-tank 64. A pressure sensor (not shown) that detects the ink pressure in the second main flow path 92 is provided at an appropriate position in the second main flow path 92.

[0037] As shown in FIG. 2, one end of a third main flow path 94 is connected to the outflow port of the first sub-tank 64. The third main flow path 94 has a plurality of branch flow paths 94b branched off from it at the other end, and the tip of each branch flow path 94b is connected to the inflow port of the second sub-tank 66. The plurality of branch flow paths 94b are flow paths for distributing ink to the plurality of second sub-tanks 66. Each branch flow path 94b is a branch flow path on the inflow side of each second sub-tank 66. An electromagnetic valve 96 is disposed midway along each branch flow path 94b as an opening / closing valve for the branch flow path that opens and closes each branch flow path 94b. A pressure sensor (not shown) for detecting the ink pressure in the third main flow path 94 is provided at an appropriate position in the third main flow path 94.

[0038] Here, the first main flow path 86, the second main flow path 92, and the third main flow path 94 are main flow paths for supplying ink from the main tank 62 to the second sub-tank 66 via the first sub-tank 64. The heating unit 68 is disposed upstream of the branch flow path 94b in the main flow paths.

[0039] A filter 98 for removing impurities from the ink is disposed upstream of the branching portion 94t in the third main flow path 94 (on the first sub-tank 64 side). A degassing module 100 for degassing (removing) dissolved gas from the ink is disposed between the branching portion 94t and the filter 98 in the third main flow path 94. A pump 102 for sending ink to the second sub-tank 66 side is disposed between the branching portion 94t in the third main flow path 94 and the degassing module 100. The degassing module 100 may be omitted from the configuration of the ink supply device 60.

[0040] One end of an auxiliary flow path 104 is connected between the branch point 94t of the third main flow path 94 and the pump 102, and the other end of the auxiliary flow path 104 is connected to another inlet port of the first sub-tank 64. A check valve 106 that regulates the flow of ink toward the pump 102 is disposed in the auxiliary flow path 104. A pressure sensor (not shown) that detects the ink pressure in the auxiliary flow path 104 is provided at an appropriate position in the auxiliary flow path 104.

[0041] One end of a supply flow path 108 is connected to the outlet port of each second sub-tank 66, and each supply flow path 108 has a plurality of branch flow paths 108b on the other end side. The tips of the plurality of branch flow paths 108b of each supply flow path 108 are connected to the inlet ports of the plurality of inkjet heads 44, respectively. Each second sub-tank 66 is connected to the inlet sides of the plurality of inkjet heads 44. In other words, each second sub-tank 66 is connected to the inlet sides of the plurality of inkjet heads 44 via each supply flow path 108, as described above. A pressure sensor (not shown) that detects the ink pressure in the supply flow path 108 is provided at an appropriate position of the supply flow path 108.

[0042] One end of a plurality of discharge flow paths 110 is connected between the heating unit 68 and the first sub-tank 64 in the second main flow path 92, and each discharge flow path 110 has a plurality of branch flow paths 110b at the other end side. The tip end of the branch flow paths 110b of each discharge flow path 110 is connected to the outlet ports of the inkjet heads 44, respectively. In other words, the first sub-tank 64 is connected to the outlet sides of the inkjet heads 44 via the second main flow path 92 and the plurality of discharge flow paths 110. An electromagnetic valve 112 is disposed in the middle of each discharge flow path 110 as an opening / closing valve for the discharge flow path that opens and closes each discharge flow path 110. A check valve 114 that regulates the flow of ink toward the inkjet head 44 is disposed downstream of the electromagnetic valve 112 in each discharge flow path 110. A pressure sensor (not shown) that detects the ink pressure in the discharge flow path 110 is provided at an appropriate position in the discharge flow path 110.

[0043] As shown in Figs. 2 and 4, one end of a return flow path 116 for returning ink after being supplied from the main tank 62 to the first sub-tank 64 to the heating unit 68 is connected to the middle of the branch flow path 94b on the most downstream side. The other end of the return flow path 116 is connected to the inlet 70j of the heating tank 70D on the lower stage side. The return flow path 116 connects the downstream part of the main flow path to the heating unit 68. In other words, the return flow path 116 connects the most downstream part (the most downstream side) of the branch flow path 94b to the heating unit 68. Also, a solenoid valve 118 is provided in the middle of the return flow path 116 as an opening / closing valve for the return flow path that opens and closes the return flow path 116.

[0044] In addition, when the heating unit 68 can also have the ink storage function of the first sub-tank 64 by increasing the number of stages of the heating tank 70, the first sub-tank 64 may be omitted from the configuration of the ink supply device 60. In this case, the other end of the second main flow path 92 and one end of the third main flow path 94 are connected to each other.

[0045] The control configuration of the inkjet recording apparatus 10 according to this embodiment will be described with reference to Fig. 2 and Fig. 6. Fig. 6 is a control block diagram of the inkjet recording apparatus 10 according to this embodiment.

[0046] 6, the inkjet recording apparatus 10 includes a control unit 120 that controls the paper feed unit 20, the image forming unit 30, and the ink supply unit 60. The control unit 120 is responsible for controlling the entire inkjet recording apparatus 10. The control unit 120 includes a CPU 120 (Central Processing Unit), a RAM 124 (Random Access Memory), a ROM 124 (Read Only Memory), and a storage unit 128. An input / output interface 130 is connected to the control unit 120, and an external device 132 is connected to the input / output interface 130.

[0047] The CPU 120 centrally controls the overall operation of the inkjet recording apparatus 10. The CPU 120 reads out various control programs and setting data stored in the ROM 124, stores them in the RAM 124, and executes the programs to perform various arithmetic processing. The RAM 124 also provides a working memory space for the CPU 120 and stores temporary data. The RAM 124 may include a non-volatile memory.

[0048] The ROM 124 stores various control programs and setting data executed by the CPU 120. Instead of the ROM 124, a rewritable non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory may be used. The storage unit 128 stores print jobs input from an external device 132 via an input / output interface 130 and image data related to the print jobs. As the storage unit 128, for example, a hard disk drive (HDD) may be used, or a dynamic random access memory (DRAM) or the like may be used in combination.

[0049] The input / output interface 130 mediates the transmission and reception of data between the external device 132 and the control unit 120. The input / output interface 130 is, for example, any one of various serial interfaces and various parallel interfaces, or a combination of these. The external device 132 is, for example, a personal computer, and supplies print jobs, image data, and the like to the control unit 120 via the input / output interface 130.

[0050] 2 and 6, the control unit 120 controls the heating of the heater 80 of the heating tank 70 of each stage independently based on the detection results from the temperature sensor of the heating tank 70 of each stage. In other words, the heating tank 70 of each stage is configured to be able to control the heating of the ink independently. Furthermore, the control unit 120 controls the heating of the heater 84 of the inlet 82 independently of the heater 80 of the heating tank 70 based on the detection results from the temperature sensor of the inlet 82. In other words, the inlet 82 is configured to be able to control the heating of the ink independently of the heating tank 70.

[0051] During printing, the control unit 120 controls the solenoid valve 118 to close the return flow path 116. In other words, the ink supply device 60 (inkjet recording apparatus 10) is configured to close the return flow path 116 by the solenoid valve 118 during printing.

[0052] During printing, the control unit 120 controls so as to open any one of the branch flow paths 94b by any one of the solenoid valves 96 and open any one of the discharge flow paths 110 by any one of the solenoid valves 112, and also drives and controls the pump 102. This allows ink to circulate between any one of the second sub-tanks 66 and any one of the inkjet heads 44. In other words, the ink supply device 60 is configured to circulate ink between any one of the second sub-tanks 66 and any one of the inkjet heads 44 with any one of the branch flow paths 94b open and any one of the discharge flow paths 110 open during printing. As a result, ink that has not been ejected from the inkjet head 44 is collected in the second sub-tank 66.

[0053] As a predetermined case other than during printing, when an ink delivery failure occurs, the control unit 120 controls the solenoid valve 118 to open the return flow path 116 while closing each branch flow path 94b with each solenoid valve 96, and drives and controls the pump 102. Then, ink can be circulated between the heating unit 68 and the first sub-tank 64 via the return flow path 116. When there is a high possibility of an ink delivery failure occurring, the ink supply device 60 is configured to circulate ink between the heating unit 68 and the first sub-tank 64 via the return flow path 116 by opening the return flow path 116 while closing each branch flow path 94b. Note that the control unit 120 determines that there is a high possibility of an ink delivery failure occurring when a detection value from any pressure sensor exceeds a predetermined threshold value. The predetermined threshold value is a threshold value for determining whether there is a high possibility of an ink delivery failure occurring.

[0054] As a predetermined case other than during printing, when the inkjet recording apparatus 10 is started up, the control unit 120 controls the solenoid valve 118 to open the return flow path 116 while closing each branch flow path 94b with each solenoid valve 96, and also drives and controls the pump 102. This makes it possible to circulate ink between the heating unit 68 and the first sub-tank 64 via the return flow path 116. In other words, the ink supply device 60 is configured to circulate ink between the heating unit 68 and the first sub-tank 64 via the return flow path 116 by opening the return flow path 116 while closing each branch flow path 94b at the time of starting up the inkjet recording apparatus 10.

[0055] During printing, the control unit 120 controls so as to open any one of the branch flow paths 94b by any one of the solenoid valves 96 and open any one of the discharge flow paths 110 by any one of the solenoid valves 112, and also drives and controls the pump 102. This makes it possible to circulate ink between any one of the second sub-tanks 66 and any one of the inkjet heads 44. In other words, the ink supply device 60 is configured to circulate ink between any one of the second sub-tanks 66 and any one of the inkjet heads 44 with any one of the branch flow paths 94b open and any one of the discharge flow paths 110 open during printing.

[0056] The control unit 120 controls the predetermined solenoid valve 96 to open a predetermined branch flow path 94b and the predetermined solenoid valve 112 to open a predetermined discharge flow path 110, and also drives and controls the pump 102. This makes it possible to circulate ink between a predetermined second sub-tank 66 and a predetermined inkjet head 44. In other words, the ink supply device 60 is configured to circulate ink between a predetermined second sub-tank 66 and a predetermined inkjet head 44 with the predetermined branch flow path 94b open and the predetermined discharge flow path 110 open.

[0057] According to the configuration of the inkjet recording device 10 of this embodiment, as described above, the ink supply device 60 is provided with the return flow path 116 for returning the ink supplied to the first sub-tank 64 side to the heating unit 68. Therefore, the inkjet recording device 10 can circulate the ink between the heating unit 68 and the first sub-tank 64 as necessary. As a result, the heating unit 68 can heat not only the ink flowing from the main tank 62 but also the ink returned to the heating unit 68 via the return flow path 116. As a result, the ink temperature can be uniformly increased from room temperature to a temperature at which the ink is converted into a sol (for example, about 80°C), and the dissolution of additives such as wax contained in the ink can be promoted. Therefore, according to this embodiment, clogging of ink in the flow paths such as the second main flow path 92, the third main flow path 94, the auxiliary flow path 104, the supply flow path 108, and the discharge flow path 110 can be suppressed, and the occurrence of poor ink delivery can be suppressed.

[0058] According to the configuration of the inkjet recording apparatus 10 of this embodiment, as described above, the electromagnetic valve 118 that opens and closes the return flow path 116 is disposed midway through the return flow path 116. Therefore, ink can be circulated between the heating unit 68 and the first sub-tank 64 at a predetermined time other than when printing is being performed, and the circulation of ink can be stopped during printing. As a result, according to this embodiment, the operation of the inkjet recording apparatus 10 can be stabilized.

[0059] According to the configuration of the inkjet recording apparatus 10 of this embodiment, the ink supply device 60 is configured to circulate ink between the heating unit 68 and the first sub-tank 64 via the return flow path 116 when there is a high possibility of ink delivery failure. Therefore, according to this embodiment, it is possible to more sufficiently suppress the occurrence of ink delivery failure.

[0060] According to the configuration of the inkjet recording apparatus 10 of this embodiment, as described above, the ink supply device 60 is configured to circulate ink between the heating unit 68 and the first sub-tank 64 via the return flow path 116 when the inkjet recording apparatus 10 is started up. This allows the ink to be heated from room temperature to a temperature at which the ink is converted into a sol in a short period of time. Therefore, according to this embodiment, the warm-up time required when starting up the inkjet recording apparatus 10 can be shortened.

[0061] According to the configuration of the inkjet recording apparatus 10 according to this embodiment, as described above, the ink supply device 60 is configured to circulate ink between any of the second sub-tanks 66 and any of the inkjet heads 44 during printing. Therefore, according to this embodiment, it is possible to stabilize the operation of the inkjet recording apparatus 10 during printing.

[0062] According to the configuration of the inkjet recording apparatus 10 of this embodiment, as described above, the heating tanks 70 at each stage independently control the heating of the ink. Therefore, according to this embodiment, the ink can be appropriately heated in response to changes in the ink formulation.

[0063] According to the configuration of the inkjet recording apparatus 10 of this embodiment, as described above, the heating tank 70 at each stage has a serpentine heating flow path 76 partitioned by a plurality of ribs 74. Therefore, the ink can be heated by heat transfer from the plurality of ribs 74, and the ink can be agitated by the flow path resistance of the plurality of ribs 74. As a result, according to this embodiment, it is possible to further promote dissolution of additives such as wax contained in the ink in the heating unit 68.

[0064] According to the configuration of the inkjet recording apparatus 10 of this embodiment, as described above, the heating unit 68 is configured so that ink flows from the heating flow path 76 of the lower heating tank 70D to the heating flow path 76 of the upper heating tank 70U. Therefore, according to this embodiment, air bubbles in the ink can be pushed upward, suppressing cavitation.

[0065] According to the configuration of the inkjet recording apparatus 10 of this embodiment, as described above, the inlet 82 controls the heating of the ink independently of the heating tank 70. Therefore, the ink can be preheated before flowing into the heating tank 70. As a result, according to this embodiment, ink clogging inside the heating tank 70 can be suppressed.

[0066] According to the configuration of the inkjet recording apparatus 10 of this embodiment, as described above, the ink supply device 60 is configured to circulate ink between a predetermined second sub-tank 66 and a predetermined inkjet head 44. Therefore, according to this embodiment, the predetermined inkjet head 44 can be cleaned as necessary.

[0067] Although the present embodiment has been specifically described above, the present invention is not limited to the specific embodiment described above. Various modifications and changes can be made to the specific example described in the above embodiment within the scope of the gist of the present invention described in the claims. [Industrial Applicability]

[0068] The present invention is useful as an inkjet recording apparatus capable of suppressing the occurrence of ink delivery failures. [Explanation of symbols]

[0069] 10 Inkjet recording device 12. Device body 14 Center Frame 16 First side frame 18 Second side frame 20 Paper feed section 22 Paper feed tray 24 Conveyor 26 Support Roller 28 Belt 30 Image forming section 32 Image forming drum 34 Delivery Unit 36 Swingarm 38 Delivery Drum 40 Medium heating section 42 Head Unit 44 Inkjet head 46 Fixing section 48 Delivery Department 50 Support Roller 52 Belt 54 Delivery drum 56 Paper output section 58 Output tray 60 Ink supply device 62 Main Tank 64 1st Subtank 66 Second Subtank 68 Heating Unit 70 Heating tank 70D Lower heating tank 70U Upper heating tank 70i inlet 70j inlet 70e Outlet 72 Lid member 74 Ribs 76 Heating Channel 78 Connecting Channel 80 Heater 82 Inlet 84 Heater 86 1st main channel 88 Pump 90 Solenoid valve 92 2nd main channel 94 Third main channel 94t Branch 94b Branch channel 96 Solenoid valve 98 Filters 100 Degassing Module 102 Pump 104 Auxiliary flow path 106 Check valve 108 Supply Channel 110 Exhaust flow path 112 Solenoid valve 114 Check valve 116 Return channel 118 Solenoid valve 120 Control section 122 CPU 124 RAM 126 ROM 128 Storage section 130 Input / Output Interface 132 External device P Recording medium

Claims

1. A main tank for storing ink; a sub-tank connected to an inkjet head and configured to store ink supplied from the main tank; a heating unit that heats the ink before it is supplied from the main tank to the sub tank; a return flow path for returning the ink to the heating section after the ink has been supplied from the main tank to the sub-tank side, Inkjet recording device.

2. a main flow path for supplying ink from the main tank to the sub tank; The heating unit is disposed midway through the main flow path, The return flow path connects a downstream portion of the main flow path and the heating portion. The inkjet recording apparatus according to claim 1 .

3. A plurality of the sub-tanks are provided, the main flow path includes branch flow paths for distributing ink to the plurality of sub-tanks, The heating unit is disposed upstream of the branch flow path in the main flow path, The return flow path connects the most downstream portion of the branch flow path and the heating unit. The inkjet recording apparatus according to claim 2 .

4. A return flow passage opening / closing valve is provided in the return flow passage to open and close the return flow passage. The inkjet recording apparatus according to claim 1 .

5. the heating unit has a plurality of heating tanks for heating ink, and the heating tanks in each tank independently heat the ink; The inkjet recording apparatus according to claim 1 .

6. A plurality of ribs are formed inside the heating tank of each stage, and the heating tank of each stage has a serpentine heating flow path partitioned by the plurality of ribs. The inkjet recording apparatus according to claim 5 .

7. The heating unit is configured so that ink flows from the heating flow path of the heating tank on the lower stage side to the heating flow path of the heating tank on the upper stage side. The inkjet recording apparatus according to claim 6.

8. The heating unit has an inlet for allowing ink to flow into the heating tank, and the inlet heats the ink independently of the heating tank. The inkjet recording apparatus according to claim 6.

9. The sub-tank is a first sub-tank connected to an outlet side of the inkjet heads and configured to store ink supplied from the heating unit; a plurality of second sub-tanks connected to inlet sides of the plurality of inkjet heads, respectively, for storing ink supplied from the first sub-tank; a branch passage opening / closing valve disposed in the branch passage on the inflow side of each of the second sub-tanks for opening and closing each of the branch passages; an on-off valve for the discharge flow path, which is disposed in the middle of the discharge flow path on the outflow side of each inkjet head and opens and closes each discharge flow path; The inkjet recording apparatus according to claim 4.

10. a predetermined branch flow path is opened by an on-off valve for the predetermined branch flow path and a predetermined discharge flow path is opened by an on-off valve for the predetermined discharge flow path, and ink is circulated between a predetermined second sub-tank and a predetermined inkjet head. The inkjet recording apparatus according to claim 9.

11. and in a predetermined time other than during printing, the ink is circulated between the heating unit and the first sub-tank via the return flow path by opening the return flow path with the return flow path opening / closing valve for the return flow path and closing each branch flow path with the return flow path opening / closing valve for the branch flow path. The inkjet recording apparatus according to claim 9.

12. The predetermined time is when a failure in ink delivery occurs. The inkjet recording apparatus according to claim 11.

13. the predetermined time is when the inkjet recording apparatus is started up; The inkjet recording apparatus according to claim 11.

14. During printing, the return flow path is closed by an on-off valve for the return flow path. The inkjet recording apparatus according to claim 4.

15. during printing, ink is circulated between any of the second sub-tanks and any of the inkjet heads in a state in which any of the branch flow paths is opened by an on-off valve for any of the branch flow paths and any of the discharge flow paths is opened by an on-off valve for any of the discharge flow paths. The inkjet recording apparatus according to claim 9.

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