Inkjet printing equipment

Abstract

To suppress variation in ink temperature in a plurality of heads for discharging ink on an inkjet printing device.SOLUTION: An inkjet printing device 1 includes: a plurality of heads (first head 11 and second head 12) for discharging ink IK; a plurality of circulation parts (first circulation part 30 and second circulation part 40) for circulating the ink IK through the one or more different heads (11, 12); and a transfer part 50 for transferring the ink IK circulating through each of the circulation parts (30, 40) to the other circulation part.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an inkjet printing apparatus including a circulation unit that circulates ink.

Background Art

[0002] Conventionally, a horizontal printing method for performing inkjet printing horizontally on the side surface of cardboard, paper, etc. is known. In this horizontal printing method, an image recording apparatus is proposed that includes a common liquid chamber divided vertically and a plurality of sub-tanks that supply the same liquid to these common liquid chambers, and adjusts the negative pressure of each common liquid chamber according to the difference in the water head height of these plurality of sub-tanks (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in an inkjet printing apparatus, a method of adjusting the ink temperature is performed by a heating operation by a heater and a cooling operation by a cooling fan so as to maintain an ink temperature suitable for printing (for example, 30 to 35°C).

[0005] In particular, in an inkjet printing apparatus including an inkjet head having a plurality of heads arranged in the height direction and ejecting ink in the horizontal direction, since a water head difference occurs in each head, there may be a case where a plurality of circulation units that circulate ink to one or more heads are provided. <00000​​However, even if each of these multiple circulation units circulates the ink while adjusting its temperature, variations in ink temperature occur between circulation units due to factors such as the drive status of the heads corresponding to each circulation unit. As a result, even if the head drive voltage and head drive waveform are selected in relation to the ink temperature, slight differences in image quality may occur, or the cooling fan may be driven more frequently due to an imbalance in the driven heads.

[0007] The objective of the present invention is to provide an inkjet printing apparatus that can suppress variations in ink temperature across multiple ink ejection heads. [Means for solving the problem]

[0008] In one embodiment, the inkjet printing apparatus comprises a plurality of heads for ejecting ink, a plurality of circulation units for circulating ink to one or more different heads, and a transfer unit for transferring the ink circulating in each of the plurality of circulation units to the other circulation units. [Effects of the Invention]

[0009] According to the above embodiment, variations in ink temperature among multiple print heads that eject ink can be suppressed. [Brief explanation of the drawing]

[0010] [Figure 1] This is a left side view showing a schematic configuration of an inkjet printing apparatus according to one embodiment. [Figure 2] This is a front view showing an inkjet head in one embodiment. [Figure 3] This is a diagram showing the configuration of the first circulation unit and the like in one embodiment. [Figure 4] This is a perspective view showing a temperature control unit in one embodiment. [Figure 5] This figure shows the control configuration of an inkjet printing apparatus according to one embodiment. [Figure 6]This graph shows the change in ink temperature of the first and second heads in one embodiment and a comparative example. [Figure 7] This is an explanatory diagram illustrating the change in ink temperature in one embodiment. [Figure 8] This figure illustrates the switching mechanism in a first modified example of one embodiment. [Figure 9] This diagram illustrates the ink transfer in the first to third circulation sections in a second modified example of one embodiment. [Modes for carrying out the invention]

[0011] Hereinafter, an inkjet printing apparatus according to one embodiment of the present invention will be described with reference to the drawings.

[0012] Figure 1 is a left side view showing a schematic configuration of an inkjet printing apparatus 1 according to one embodiment. Figure 2 is a front view showing the inkjet head 10.

[0013] Note that the front-back, left-right, and up-down directions in Figures 1 and 2 are merely illustrative examples for the purpose of explaining the process when the conveying direction D1 of the printed material M by the conveyor 100 is to the right. The front-back and left-right directions are horizontal, and the up-down direction is vertical.

[0014] The inkjet printing apparatus 1 shown in Figure 1 comprises an inkjet head 10, a first circulation unit 30, a second circulation unit 40, a transfer unit 50, and a control unit 71, a storage unit 72, and an interface unit 73 as shown in Figure 4. A system comprising the inkjet printing apparatus 1 and a conveyor 100 can be called a printing system. For example, the conveyor 100 is a belt conveyor positioned as part of a box-making machine. The conveyor 100 may also be a conveyor other than a belt conveyor, such as a roller conveyor.

[0015] The inkjet head 10 shown in Fig. 1 has a plurality of first heads 11, a plurality of second heads 12, distributors 13, 14, and aggregators 15, 16. The inkjet head 10 is disposed on the front side of the conveyor 100.

[0016] The plurality of first heads 11 and the plurality of second heads 12 are an example of a plurality of heads that discharge ink IK (see Fig. 3). For example, three of each of the first heads 11 and the second heads 12 are arranged for each of the colors black, cyan, magenta, and yellow. These first heads 11 and second heads 12 are arranged in the height direction such that the first heads 11 are located above the second heads 12, and discharge the ink IK in the lateral direction D2 that intersects this height direction. This lateral direction D2 is a direction (rearward in Fig. 1) that intersects the height direction (vertical direction in Fig. 1) and the conveyance direction D1 of the printed material M (rightward in Fig. 2), and is, for example, a horizontal direction. However, the lateral direction D2 in which the first heads 11 and the second heads 12 discharge the ink IK is not limited to the horizontal direction, and may be a direction inclined upward or downward with respect to the horizontal direction.

[0017] As shown in Fig. 2, three of each of the first heads 11 and the second heads 12 for each color are arranged in the height direction while staggering their positions in the left-right direction (conveyance direction D1). Note that since the first heads 11 and the second heads 12 are located on the rear side of the inkjet head 10 that is not shown in Fig. 2, they are illustrated by dashed lines, which are hidden lines.

[0018] Then, the inkjet head 10 performs printing of a printed image Ma on the side surface (front surface) of the printed material M in, for example, four colors (full color) of black, cyan, magenta, and yellow. Note that the printed material M is, for example, a box such as cardboard, but may be paper or the like, and is not particularly limited.

[0019] The dispenser 13 shown in FIG. 1 distributes the ink IK supplied from the first circulation unit 30 to the three first heads 11. The dispenser 14 distributes the ink IK supplied from the second circulation unit 40 to the three second heads 12. Note that the dispenser 13 and the dispenser 14 are arranged for each color.

[0020] The collector 15 collects the ink IK not consumed by the first heads 11 from the three first heads 11. The ink IK collected by the collector 15 flows into the first circulation unit 30. The collector 16 collects the ink IK not consumed by the second heads 12 from the three second heads 12. The ink IK collected by the collector 16 flows into the second circulation unit 40. Note that the collector 15 and the collector 16 are also arranged for each color.

[0021] Although not shown in FIGS. 1 and 2, the printed object M conveyed on the conveyor 100 may be printed while being guided by a conveyance guide arranged on the rear side of the conveyor 100.

[0022] The three first heads 11 and the three second heads 12 for each color that the above-described inkjet head 10 has are merely examples, and the inkjet head 10 may perform single-color printing, and the number of heads may be plural. Further, the first heads 11 and the second heads 12 are not limited to being arranged in the height direction and discharging the ink IK in the lateral direction D2. For example, they may be arranged horizontally and discharge the ink IK downward, or may be arranged on different inkjet heads for the first heads 11 and the second heads 12.

[0023] FIG. 3 is a configuration diagram showing the first circulation unit 30 and the like.

[0024] The above-described first heads 11 and second heads 12 of the inkjet head 10 shown in FIG. 3 have an ink chamber (not shown) for storing the ink IK and a plurality of nozzles (not shown) for discharging the ink IK. For example, a piezo element (not shown) is arranged in the ink chamber, and the ink IK is discharged from the nozzles by driving this piezo element.

[0025] The first circulation unit 30 includes a pressurized tank 31, a negative pressure tank 32, a common pressurized air chamber 33, a common negative pressure air chamber 34, an air pump 35, a temperature control unit 36, ink circulation pipes 37a and 37b, and an ink supply unit 38, and circulates ink IK to three first heads 11. The second circulation unit 40, although not shown in its entirety in Figure 3, has the same configuration as the first circulation unit 30, including the pressurized tank 41, the negative pressure tank 42, and the ink circulation pipes 47a and 47b, and circulates ink IK to three second heads 12. Therefore, the explanation of the first circulation unit 30 will be used, and the explanation of the second circulation unit 40 will be omitted. Note that each of the first circulation unit 30 and the second circulation unit 40 is provided for each color of ink IK, except for the common pressurized air chamber 33, the common negative pressure air chamber 34, the air pump 35, and the temperature control unit 36.

[0026] Here, the first circulation unit 30 and the second circulation unit 40 are examples of multiple circulation units that circulate ink IK to one or more different heads. In this embodiment, since the first head 11 is located above the second head 12, the first circulation unit 30 and the second circulation unit 40 can be said to circulate ink IK to one or more heads at different heights. Furthermore, the circulation units are not limited to just the first circulation unit 30 and the second circulation unit 40, but may consist of three or more units.

[0027] The pressurized tank 31 stores the ink IK supplied to the first head 11. The pressurized tank 31 supplies the ink IK to the inkjet head 10 (distributor 13) via the ink circulation pipe 37b. An air layer is formed above the liquid surface of the ink IK inside the pressurized tank 31. The pressurized tank 31 is positioned lower than the inkjet head 10.

[0028] The negative pressure tank 32 recovers and stores ink IK that was not consumed by the inkjet head 10 (first head 11) from the inkjet head 10 (collector 15). The negative pressure tank 32 also stores ink IK supplied from the ink cartridge 38a of the ink supply unit 38, which will be described later. An air layer is formed above the liquid surface of the ink IK inside the negative pressure tank 32. The negative pressure tank 32 is positioned at the same height as the pressurized tank 31.

[0029] The pressurized common air chamber 33 is an air chamber for equalizing the pressure in multiple pressurized tanks 31 corresponding to each color of ink IK. The pressurized common air chamber 33 has an atmospheric release valve 33a and a pressure sensor 33b. The atmospheric release valve 33a switches the pressurized common air chamber 33 between a sealed state (isolated from the atmosphere) and an open state (accessible to the atmosphere). The pressure sensor 33b detects the pressure inside the pressurized common air chamber 33.

[0030] The negative pressure common air chamber 34 is an air chamber for equalizing the pressure in multiple negative pressure tanks 32 corresponding to each color of ink IK. The negative pressure common air chamber 34 has an atmospheric release valve 34a and a pressure sensor 34b. The atmospheric release valve 34a switches the negative pressure common air chamber 34 between a sealed state (isolated from the atmosphere) and an open state (connected to the atmosphere). The pressure sensor 34b detects the pressure inside the negative pressure common air chamber 34.

[0031] The air pump 35 sends air from the negative pressure common air chamber 34 to the pressurized common air chamber 33. When the air pump 35 is driven, the atmospheric release valve 33a of the pressurized common air chamber 33 is closed, sealing the pressurized common air chamber 33 and generating pressure (positive pressure) in the pressurized common air chamber 33. Also, when the air pump 35 is driven, the atmospheric release valve 34a of the negative pressure common air chamber 34 is closed, sealing the negative pressure common air chamber 34 and generating pressure (negative pressure) in the negative pressure common air chamber 34. Since the pressurized tank 31 and the pressurized common air chamber 33 are in communication, and the negative pressure tank 32 and the negative pressure common air chamber 34 are in communication, the air pump 35 functions as an example of a pressure adjustment unit that adjusts the gas pressure in the tanks (pressurized tank 31 and negative pressure tank 32). The control unit 71, described later, can adjust the gas pressure in the pressurized common air chamber 33 and the negative pressure common air chamber 34, and consequently the gas pressure in the pressurized tank 31 and the negative pressure tank 32, by controlling the air pump 35 based on the detection results of the pressure sensors 33b and 34b.

[0032] The temperature control unit 36 ​​is located in the ink circulation pipe 37b between the pressurized tank 31 and the inkjet head 10. As shown in Figure 4, the temperature control unit 36 ​​includes, for example, a cooling fan 36a, a plurality of fins 36b, a heater 36c, and a heat transfer member 36d, and collectively cools and heats the inks IK flowing through the ink circulation pipes 37b for each of the black (K), cyan (C), magenta (M), and yellow (Y) colors.

[0033] The cooling fan 36a cools the ink IK of each color flowing through the ink circulation tube 37b by blowing air onto the multiple fins 36b whose temperature rises due to heat conduction from the ink circulation tube 37b. The heater 36c cools the ink IK of each color flowing through the ink circulation tube 37b by heat conduction via the heat transfer member 36d.

[0034] As shown in Figure 3, the ink circulation pipe 37a connects the inkjet head 10 (collector 15) and the negative pressure tank 32. Ink IK flows from the inkjet head 10 to the negative pressure tank 32 through the ink circulation pipe 37a. The ink circulation pipe 37b connects the pressurized tank 31 and the inkjet head 10 (distributor 13). Ink IK flows from the pressurized tank 31 to the inkjet head 10 through the ink circulation pipe 37b.

[0035] The ink supply unit 38 supplies ink IK to the negative pressure tank 32 of the first circulation unit 30. The ink supply unit 38 includes an ink cartridge 38a, an ink supply valve 38b, and an ink supply pipe 38c.

[0036] The ink cartridge 38a contains the ink IK used for printing by the inkjet head 10. The ink IK in the ink cartridge 38a is supplied to the negative pressure tank 32 of the first circulation unit 30 via the ink supply pipe 38c.

[0037] The ink supply valve 38b is a solenoid valve that opens and closes the flow path of ink IK in the ink supply pipe 38c. When supplying ink IK to the negative pressure tank 32, the ink supply valve 38b is opened by the control of the control unit 71, which will be described later.

[0038] The ink supply tube 38c connects the ink cartridge 38a to the negative pressure tank 32. Ink IK flows from the ink cartridge 38a to the negative pressure tank 32 through the ink supply tube 38c.

[0039] The transfer unit 50 has transfer pumps 51 and 52 and ink circulation pipes 53 and 54, and transfers the ink IK circulating in the first circulation unit 30 to the second circulation unit 40, and transfers the ink IK circulating in the second circulation unit 40 to the first circulation unit 30. In this way, the transfer unit 50 transfers the ink IK circulating in each of the multiple circulation units to the other circulation units.

[0040] The transfer pump 51 transfers ink IK from the negative pressure tank 32 of the first circulation section 30 to the pressurized tank 41 of the second circulation section 40. The transfer pump 52 transfers ink IK from the negative pressure tank 42 of the second circulation section 40 to the pressurized tank 31 of the first circulation section 30. The transfer pump 51 is installed in the middle of the ink circulation pipe 53, and the transfer pump 52 is installed in the middle of the ink circulation pipe 54.

[0041] Figure 5 shows the control configuration of the inkjet printing device 1.

[0042] The control unit 71 shown in Figure 5 has a processor (e.g., CPU: Central Processing Unit) that functions as an arithmetic processing unit that controls the operation of the entire inkjet printing apparatus 1. The control unit 71 controls each part of the inkjet printing apparatus 1, such as the inkjet head 10, the first circulation unit 30, the second circulation unit 40, and the transport unit 50.

[0043] The memory unit 72 includes, for example, a ROM (Read Only Memory), which is a read-only semiconductor memory in which a predetermined control program is pre-recorded, and a RAM (Random Access Memory), which is a semiconductor memory that can be written to and read at any time and used as a working memory area as needed when the processor executes various control programs.

[0044] The interface unit 73 exchanges various types of information with external devices such as a print control device and a user terminal. For example, the interface unit 73 receives print jobs containing image data to be printed from external devices.

[0045] Next, the operation of the transfer unit 50 will be described with reference to Figures 6 and 7.

[0046] Figure 6 is a graph showing the change in ink temperature of the first head 11 and the second head 12 in this embodiment and comparative example.

[0047] As shown by the dashed line in Figure 6, before printing starts, the heater 36c of the temperature control unit 36 ​​shown in Figure 3 is turned ON, and the ink temperature rises.

[0048] Then, at time t1, which is the start time of printing, the heater 36c is turned OFF. Here, we will describe an example in which the first head 11 repeatedly prints a solid image Ma (see Figure 2) onto multiple substrates M in succession, and the second head 12 does not perform any printing.

[0049] In this case, in the comparative example where the transfer unit 50 is not provided, that is, in the example where ink is not transferred between the first circulation unit 30 and the second circulation unit 40, the ink temperature of the first head 11 (shown by a thick solid line in Figure 6) rises, and when it reaches the upper limit temperature of, for example, 35°C (time t2), the control unit 71 turns on the cooling fan 36a of the temperature adjustment unit 36, and the ink temperature of the first head 11 decreases. On the other hand, the ink temperature of the second head 12 (shown by a thin solid line in Figure 6) decreases because the second head 12 is not driven. As a result, a temperature difference is created between the ink temperature of the first head 11 and the ink temperature of the second head 12. When the ink temperature of the second head 12 reaches the lower limit temperature of, for example, 30°C, the control unit 71 turns on the heater of the second circulation unit 40 (the same as the heater 36c of the first circulation unit 30).

[0050] On the other hand, in this embodiment, since the transfer unit 50 transfers ink IK between the first circulation unit 30 and the second circulation unit 40, a temperature difference is unlikely to occur in the ink temperature of the first head 11 and the second head 12 (shown by dashed lines in Figure 6).

[0051] Figure 7 is an explanatory diagram illustrating the change in ink temperature.

[0052] Regarding Figure 7, similar to the example in Figure 6, we will describe an example in which the first head 11 repeatedly prints a solid image Ma onto multiple substrates M in succession, while the second head 12 does not perform any printing.

[0053] Here, ink (1) shown in Figure 7 is the ink IK initially located in the first circulation section 30 upstream of the first head 11, and ink (2) is the ink IK initially located in the second circulation section 40 upstream of the second head 12. One circulation cycle in Figure 7 is the cycle from when the ink located upstream of the first head 11 (or second head 12) circulates to the upstream side of the second head 12 (or first head 11).

[0054] As shown in Figure 7, the ink (1) heats up as it passes through the first head 11 due to the drive of the first head 11 (shown by a dashed line). Subsequently, the ink (1) passes through the negative pressure tank 32, the ink circulation pipe 53, and the pressurized tank 41 of the second circulation unit 40, and then through the temperature control unit of the second circulation unit 40 (same as the temperature control unit 36). As it passes through the fins of the temperature control unit of the second circulation unit 40 (same as the fins 36b of the first circulation unit 30), its temperature decreases due to natural cooling (shown by a dashed line; cooling fan is OFF). As a result, after one circulation cycle, the ink (1) heats up slightly more than its initial temperature.

[0055] On the other hand, the ink (2) does not heat up when it passes through the second head 12 because the second head 12 is not driven. Subsequently, the ink (2) passes through the negative pressure tank 42, the ink circulation pipe 54, and the pressurized tank 31 of the first circulation unit 30, and then through the temperature control unit 36. As it passes through the fins 36b of the temperature control unit 36, its temperature drops slightly from the initial temperature due to natural cooling.

[0056] In the next second circulation cycle, the ink (1) does not heat up as it passes through the second head 12 because the second head 12 is not driven. Subsequently, the ink (1) passes through the negative pressure tank 42, the ink circulation pipe 54, the pressurized tank 31 of the first circulation unit 30, and then through the temperature control unit 36. As it passes through the fins 36b of the temperature control unit 36, its temperature decreases due to natural cooling and returns to its initial temperature.

[0057] Meanwhile, the ink (2) heats up as it passes through the first head 11 due to the drive of the first head 11. Subsequently, the ink (2) passes through the negative pressure tank 32, the ink circulation pipe 53, and the pressurized tank 41 of the second circulation unit 40, and then through the temperature control unit of the second circulation unit 40 (same as the temperature control unit 36). As it passes through the fins of the temperature control unit of the second circulation unit 40 (same as the fins 36b of the first circulation unit 30), its temperature drops due to natural cooling. As a result, the ink (2) returns to its initial temperature.

[0058] Next, in the third and fourth cycles, since they are identical to the first and second cycles, even after the fourth cycle, ink (1) and ink (2) return to their initial temperature, just as they did after the second cycle. Thus, a temperature difference between ink (1) and ink (2) is unlikely to occur.

[0059] Next, the first and second modified examples of this embodiment will be described with reference to Figures 8 and 9.

[0060] Figure 8 is a diagram illustrating the switching mechanism in the first modified example.

[0061] The switching valves 61-64 shown in Figure 8 are an example of a switching mechanism, and are, for example, solenoid valves. The switching valves 61-64 switch between a state in which the ink path of the transfer unit 50 is blocked so that ink IK circulates in each of the multiple circulation units (first circulation unit 30 and second circulation unit 40), and a state in which the ink paths of the first circulation unit 30 and the second circulation unit 40 are blocked so that the transfer unit 50 transfers ink IK to the other circulation unit, the second circulation unit 40 or the first circulation unit 30.

[0062] Specifically, the switching valve 61 is positioned to open and close the ink path of the first circulation section 30 from the negative pressure tank 32 to the pressurized tank 31. The switching valve 62 is positioned to open and close the ink path of the second circulation section 40 from the negative pressure tank 42 to the pressurized tank 41.

[0063] The switching valve 63 is positioned to open and close the ink path from the negative pressure tank 32 to the pressurized tank 41. The switching valve 64 is positioned to open and close the ink path from the negative pressure tank 42 to the pressurized tank 31.

[0064] The control unit 71 shown in Figure 5, for example, before continuously printing the same print image Ma on multiple substrates M, opens the switching valves 61 and 62 and closes the switching valves 63 and 64 to circulate the ink IK in the first circulation unit 30 and the second circulation unit 40, respectively, if the transfer unit 50 is not used based on the print content (such as the difference between the ejection amount of the first head 11 and the ejection amount of the second head 12) or user operation. Also, if the transfer unit 50 is used, the control unit 71 closes the switching valves 61 and 62 and opens the switching valves 63 and 64 to transfer the ink IK from the first circulation unit 30 to the second circulation unit 40 and transfers the ink IK from the second circulation unit 40 to the first circulation unit 30.

[0065] Figure 9 is a diagram illustrating the transfer of ink IK in the first circulation unit 30, the second circulation unit 40, and the third circulation unit 80 in a second modified example.

[0066] In the above description, two circulation units, the first circulation unit 30 and the second circulation unit 40, were described as an example of multiple circulation units. However, as shown in Figure 9, the inkjet printing apparatus 1 may further include a third circulation unit 80, and have three or more circulation units. In the third circulation unit 80, only the pressurized tank 81 and the negative pressure tank 82 are shown, but it is assumed to have the same configuration as the first circulation unit 30 and the second circulation unit 40. Furthermore, the third circulation unit 80 may circulate ink IK to one or more heads at different heights than the head (first head 11) to which the first circulation unit 30 circulates ink IK, and the head (second head 12) to which the second circulation unit 40 circulates ink IK.

[0067] In the example shown in Figure 9, a transfer pump 51 located in the middle of the ink circulation pipe 53 transfers ink IK from the negative pressure tank 32 of the first circulation section 30 to the pressurized tank 41 of the second circulation section 40. A transfer pump 52 located in the middle of the ink circulation pipe 54 transfers ink IK from the negative pressure tank 42 of the second circulation section 40 to the pressurized tank 81 of the third circulation section 80. A transfer pump 55 located in the middle of the ink circulation pipe 56 transfers ink IK from the negative pressure tank 82 of the third circulation section 80 to the pressurized tank 31 of the first circulation section 30. Furthermore, even when the inkjet printing apparatus 1 has three or more circulation units, as in this modified example, the switching valves 61-64 (switching mechanism) of the first modified example described with reference to Figure 8 may be used to switch between a state in which the ink path of the transfer unit 50 is blocked so that ink IK circulates in each of the multiple circulation units (first circulation unit 30, second circulation unit 40, and third circulation unit 80), and a state in which the ink path of the first circulation unit 30, second circulation unit 40, and third circulation unit 80 is blocked so that the transfer unit 50 transfers ink IK to the other circulation units.

[0068] In the embodiment described above, the inkjet printing apparatus 1 comprises a plurality of heads (first head 11 and second head 12) that eject ink IK, a plurality of circulation units (first circulation unit 30 and second circulation unit 40) that circulate ink IK to one or more different heads (11, 12), and a transfer unit 50 that transfers the ink IK circulating in each of the plurality of circulation units (30, 40) to other circulation units.

[0069] In this way, the transfer unit 50 transfers the ink IK circulating in each of the multiple circulation units to the other circulation units, so that even if the drive status of the heads corresponding to each circulation unit is uneven, the ink IK flows through each circulation unit, and the ink temperature is equalized in each circulation unit. Therefore, according to this embodiment, variations in ink temperature in the heads (first head 11 and second head 12) can be suppressed. Furthermore, because variations in ink temperature can be suppressed, it is possible to prevent differences in image quality between the first head 11 and the second head 12, and fine temperature control of the temperature adjustment unit 36 ​​in the first circulation unit 30 and the second circulation unit 40 becomes unnecessary, thus simplifying control and saving power.

[0070] In this embodiment, the multiple heads (first head 11 and second head 12) are arranged in the height direction and eject ink IK in the horizontal direction D2 that intersects the height direction. The multiple circulation units (first circulation unit 30 and second circulation unit 40) each circulate ink to one or more heads (first head 11 and second head 12) of different heights.

[0071] As a result, when the first circulation unit 30 and the second circulation unit 40 are arranged to adjust for the difference in ink head caused by the difference in height between the first head 11 and the second head 12, the ink temperature is equalized in these circulation units. Therefore, variations in ink temperature in the heads (first head 11 and second head 12) can be suppressed.

[0072] Furthermore, in this embodiment, each of the multiple circulation units (first circulation unit 30 and second circulation unit 40) has a negative pressure tank 32 for recovering ink IK from the heads (first head 11 and second head 12) and a pressurized tank 31 for supplying ink IK to the heads, and the transfer unit 50 transfers ink IK from the negative pressure tanks 32 and 42 to the pressurized tanks 41 and 31 of the other circulation units.

[0073] This allows the ink IK in the negative pressure tanks 32 and 42 immediately after being recovered from the print head to be transferred to other circulation units. As a result, the ink temperature is further equalized across multiple circulation units.

[0074] Furthermore, in the first modified example of this embodiment, the inkjet printing apparatus 1 further includes switching valves 61 to 64, which are an example of a switching mechanism. The switching valves 61 to 64 switch between a state in which the ink path of the transfer unit 50 is blocked so that ink IK circulates in each of the multiple circulation units (first circulation unit 30 and second circulation unit 40) (switching valves 61 and 62 are open and switching valves 63 and 64 are closed) and a state in which the ink path of the circulation unit is blocked so that the transfer unit 50 transfers ink IK to the other circulation unit (switching valves 61 and 62 are closed and switching valves 63 and 64 are open).

[0075] This allows for power saving by stopping the operation of the first circulation unit 30 or the second circulation unit 40 when the first head 11 or the second head 12 is not used for printing.

[0076] Furthermore, in a second modified example of this embodiment, the multiple circulation units consist of three or more circulation units (a first circulation unit 30, a second circulation unit 40, and a third circulation unit 80), and the transfer unit 50 transfers the ink IK circulating in each of the three or more circulation units to the other circulation units.

[0077] As a result, even with three or more circulation units, the ink temperature is equalized in each circulation unit, effectively suppressing variations in ink temperature at the print head.

[0078] It should be noted that the present invention is not limited to the above-described embodiment, and the components can be modified and implemented in the implementation stage without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the above-described embodiment. For example, all the components shown in the embodiment may be combined as appropriate. It goes without saying that various modifications and applications are possible without departing from the spirit of the invention. The invention described in the original claims of this application is listed below.

[0079] [Note 1] Multiple print heads that eject ink, Multiple circulation units that circulate ink to one or more different print heads, A transfer unit that transfers the ink circulating in each of the plurality of circulation units to other circulation units. An inkjet printing apparatus characterized by comprising the following features.

[0080] [Note 2] The aforementioned plurality of heads are arranged in the height direction and eject ink in a horizontal direction intersecting the height direction. Each of the aforementioned multiple circulation units circulates ink to one or more heads of different heights. An inkjet printing apparatus as described in Appendix 1, characterized by the features described herein.

[0081] [Note 3] Each of the aforementioned multiple circulation units includes a negative pressure tank for recovering ink from the head and a pressurized tank for supplying ink to the head. The transfer unit transfers ink from the negative pressure tank to the pressurized tank of the other circulation unit. An inkjet printing apparatus as described in Appendix 1, characterized by the features described herein.

[0082] [Note 4] The system further includes a switching mechanism that switches between a state in which the ink path of the transfer unit is blocked so that ink circulates in each of the plurality of circulation units, and a state in which the ink path of the circulation unit is blocked so that the transfer unit transfers ink to the other circulation units. An inkjet printing apparatus as described in Appendix 1, characterized by the features described herein.

[0083] [Note 5] The aforementioned plurality of circulation units consist of three or more circulation units. The transfer unit transfers the ink circulating in each of the three or more circulation units to the other circulation units. An inkjet printing apparatus as described in Appendix 1, characterized by the features described herein. [Explanation of Symbols]

[0084] 1. Inkjet printing device 10 inkjet heads 11 First Head 12 Second Head 13,14 distributor 15,16 collector 30 1st Circulation Department 31 Pressurized tank 32. Vacuum Tank 33 Pressurized common air chamber 33a Atmospheric release valve 33b Pressure sensor 34 Negative pressure common air chamber 34a Atmospheric release valve 34b Pressure Sensor 35 Air pump 36 Temperature adjustment section 36a Cooling Fan 36b fin 36c heater 36d Heat transfer component 37a, 37b Ink circulation tube 38 Ink Refill Section 38a Ink Cartridge 38b Ink refill valve 38c Ink Refill Tube 40 2nd Circulation Department 41 Pressurized tank 42. Vacuum Tank 47a, 47b Ink circulation tube 50 Transfer section 51, 52, 55 Transfer pumps 53, 54, 56 Ink transfer tubes 61-64 Switching valve 71 Control Unit 72 Memory section 73 Interface section 80 Third Circulation Department 81 Pressurized tank 82. Vacuum Tank 100 Conveyors D1 Conveying direction D2 Horizontal IK Ink M Printing material Ma Printed Image

Claims

1. Multiple print heads that eject ink, Multiple circulation units that circulate ink to one or more different print heads, A transfer unit that transfers the ink circulating in each of the plurality of circulation units to other circulation units. An inkjet printing apparatus characterized by comprising the following features.

2. The aforementioned plurality of heads are arranged in the height direction and eject ink in a horizontal direction intersecting the height direction. Each of the aforementioned multiple circulation units circulates ink to one or more heads of different heights. The inkjet printing apparatus according to claim 1, characterized in that it is the same as described in claim 1.

3. Each of the aforementioned multiple circulation units includes a negative pressure tank for recovering ink from the head and a pressurized tank for supplying ink to the head. The transfer unit transfers ink from the negative pressure tank to the pressurized tank of the other circulation unit. The inkjet printing apparatus according to claim 1, characterized in that it is the same as described in claim 1.

4. The system further includes a switching mechanism that switches between a state in which the ink path of the transfer unit is blocked so that ink circulates in each of the plurality of circulation units, and a state in which the ink path of the circulation unit is blocked so that the transfer unit transfers ink to the other circulation units. The inkjet printing apparatus according to claim 1, characterized in that it is the same as described in claim 1.

5. The aforementioned plurality of circulation units consist of three or more circulation units. The transfer unit transfers the ink circulating in each of the three or more circulation units to the other circulation units. The inkjet printing apparatus according to claim 1, characterized in that it is the same as described in claim 1.

Images