Liquid discharge device and liquid temperature control method

Abstract

A liquid discharge device according to the present invention comprises: a liquid discharge head (45) including a nozzle for discharging a liquid; a supply tank (51) for storing the liquid to be supplied to the liquid discharge head (45); a liquid supply passage (56) connecting the liquid discharge head (45) and the supply tank (51); and a temperature adjustment unit (77) including a microchannel heat exchanger (80) for heating the liquid to be supplied to the liquid discharge head (45). The present invention also provides a temperature control method.

Description

Liquid dispensing device and liquid temperature control method

[0001] This disclosure relates to a liquid dispensing device and a method for controlling the temperature of a liquid.

[0002] In liquid ejection devices that eject liquids, such as inkjet printers, depending on the liquid to be ejected, it may be necessary to heat it to reduce its viscosity before ejection because it has high viscosity at room temperature. Japanese Patent Publication No. 2012-000883, International Publication No. 2021 / 245808, or Japanese Patent Publication No. 2024-093608 discloses a printing device equipped with a heating means for heating ink between an inkjet head (corresponding to a liquid ejection head) that ejects ink and an ink tank that stores the ink supplied to the inkjet head.

[0003] Japanese Patent Publication No. 2012-000883 and International Publication No. 2021 / 245808 employ a heat exchange method in which heat is transferred to the ink via a thermal conductor (specifically, a heated flow path) as the heating means. Furthermore, Japanese Patent Publication No. 2024-0936083 employs a method in which the ink is directly heated using a heater placed inside the ink flow path as the heating means.

[0004] In methods that directly heat the ink using a heater, controlling the temperature of the heater surface and the flow of ink on the heater surface is difficult, which can lead to localized temperature increases. In heat exchange methods, the laminar flow of ink in the flow channel is heated. In laminar flow ink, the ink near the flow channel wall is heated by the high temperature of the flow channel wall, but in the center, heat is transferred by heat conduction between ink particles, resulting in relatively low heat transfer efficiency and a tendency for temperature distribution to occur.

[0005] For example, when using inks such as UV-curing inks, which can cause aggregation or gelation if the temperature is raised too high, there is a need to suppress localized increases in ink temperature while heating the overall liquid temperature to a temperature suitable for ejection.

[0006] To heat ink without exceeding the localized temperature at which aggregation is a concern, a heat exchange method is more suitable than direct heating. However, when using a heat exchange method, in order to heat the ink to the target ink temperature in a short time, it is necessary to make the heat exchange distance in the heat exchanger (in this case, the flow path) relatively long and heat it slowly. This can lead to disadvantages such as an increase in the size of the heat exchanger, resulting in larger equipment and increased equipment weight.

[0007] The purpose of this disclosure is to provide a liquid dispensing device and a liquid temperature control method that enable the uniform supply of liquid to the liquid dispensing head at a stable temperature.

[0008] The liquid dispensing device of this disclosure comprises a liquid dispensing head equipped with a nozzle for dispensing liquid, a supply tank for storing liquid supplied to the liquid dispensing head, a liquid supply path connecting the liquid dispensing head and the supply tank, and a temperature control unit equipped with a microchannel heat exchanger for heating the liquid supplied to the liquid dispensing head.

[0009] The cross-sectional area of ​​the liquid flow path in the microchannel heat exchanger is 10 mm². ２ The following is preferable:

[0010] Preferably, the system further includes a first temperature sensor positioned between the supply tank and the liquid discharge head to detect the liquid temperature, and the temperature control unit controls heating based on the liquid temperature detected by the first temperature sensor.

[0011] It is preferable that the sensor portion of the first temperature sensor is positioned in a direction opposite to the flow of liquid.

[0012] Preferably, the system further includes a second temperature sensor for detecting the temperature of the liquid, which is located in at least one of the temperature control section and the flow path through which the liquid flowing out of the temperature control section passes, and a processor that reduces the heating output of the temperature control section when the temperature of the liquid detected by the second temperature sensor exceeds a predetermined threshold.

[0013] Preferably, the print bar includes a liquid supply path, a circulation path for circulating liquid between a liquid discharge head and a supply tank, and a circulation pump for circulating liquid within the circulation path, wherein the temperature control unit is located in the circulation path between the liquid recovered from the liquid discharge head and the supply tank, and the liquid discharge head, supply tank, temperature control unit, circulation path, and circulation pump are all arranged in a single housing.

[0014] Preferably, the circulation path located inside the casing of the print bar is further provided with a filter and a degassing module through which the liquid passes.

[0015] The system further comprises a liquid storage section for storing liquid, and a liquid replenishment section connecting the liquid storage section to the circulation path, the liquid replenishment section being equipped with a replenishment pump for supplying liquid to the circulation path, wherein the liquid replenishment section is preferably connected to the circulation path upstream of the filter and degassing module in the circulation direction.

[0016] It is preferable that the combined volume of the supply tank and the liquid supply path is greater than the volume of the flow path of the microchannel heat exchanger.

[0017] Preferably, the liquid has a viscosity higher than the appropriate liquid viscosity for the liquid dispensing head at room temperature, its viscosity decreases when heated, and its properties change when the temperature exceeds the temperature at which the appropriate liquid viscosity is reached. Furthermore, it is preferable that the liquid has a lower thermal conductivity and lower specific heat than water.

[0018] The liquid may be an ultraviolet-curing ink.

[0019] The liquid temperature control method of the present disclosure is a liquid dispensing device comprising: a liquid dispensing head equipped with a nozzle for dispensing liquid; a supply tank for storing liquid supplied to the liquid dispensing head; a liquid supply path connecting the liquid dispensing head and the supply tank; and a temperature control unit equipped with a microchannel heat exchanger for heating the liquid supplied to the liquid dispensing head. The method adjusts the heating output of the temperature control unit that heats the liquid based on the temperature of the liquid supplied to the liquid dispensing head, and monitors the temperature of at least one of the liquid in the temperature control unit and the liquid that has flowed out of the temperature control unit. When the temperature exceeds a predetermined threshold, the heating output of the temperature control unit is reduced.

[0020] When reducing the heating output of the temperature control unit, the heating output may be set to zero.

[0021] According to the liquid dispensing device and temperature control method of this disclosure, the temperature of the liquid supplied to the liquid dispensing head can be made uniform, and the liquid can be supplied to the liquid dispensing head at a stable temperature.

[0022] This is an overall configuration diagram of an inkjet printing apparatus according to an embodiment. This is a perspective view showing the configuration of the print bar. This is a schematic configuration diagram of the ink supply mechanism. This is a perspective view of the flow channel members constituting the microchannel heat exchanger. This is a cross-sectional view of the flow channel in the heat exchanger, where (A) and (B) are cross-sectional views of the microchannel, and (C) is a cross-sectional view of the flow channel of a reference example. This is an explanatory diagram of the method for manufacturing the microchannel heat exchanger.

[0023] Hereinafter, an embodiment of the liquid dispensing device and liquid circulation control method of this disclosure will be described with reference to the drawings. Here, an inkjet printing apparatus will be used as an example of an embodiment of the liquid dispensing device. Furthermore, ink will be given as an example of a liquid, and a method for controlling ink circulation to the inkjet head in an inkjet printing apparatus will be described as an embodiment of a liquid circulation control method. In each figure, the same elements are denoted by the same reference numerals.

[0024] "Configuration of Inkjet Printing Apparatus" Figure 1 is an overall configuration diagram of the inkjet printing apparatus 1. The inkjet printing apparatus 1 is an inkjet-type color digital printing apparatus that forms a desired image on a sheet of paper P. The inkjet printing apparatus 1 is a single-sided printing apparatus that forms an image on only one side of the paper P. However, the technology of this disclosure is also applicable to a double-sided printing apparatus that forms an image on both sides of the paper P. Paper P is an example of a recording medium.

[0025] As shown in Figure 1, the inkjet printing apparatus 1 comprises a transport mechanism 10, a paper feeder 20, an image forming unit 40, and an accumulation device 90.

[0026] The transport mechanism 10 transports the paper P with its recording surface (i.e., paper surface) Pa facing the print bar of the image forming unit 40, which will be described later. In Figure 1, the transport path 12 through which the paper P is transported is shown by a dashed line.

[0027] The transport mechanism 10 includes a plurality of transport members along the transport path 12. The plurality of transport members include a plurality of transport roller pairs 14, a paper feed drum 16 and an output drum 18, and a drawing drum 41, which will be described later. Each transport roller pair 14 includes a drive roller 14a and a pinch roller 14b arranged opposite each other. The transport roller pair 14 grips the paper P between the drive roller 14a and the pinch roller 14b and rotates to feed out the paper P. The transport members may also include a transport drum, a belt conveyor, a chain gripper and a transport guide. The transport mechanism 10 also includes a drive unit such as a motor (not shown) and a motor drive circuit (not shown) as a power source. The paper P is transported along the transport path 12 by these elements constituting the transport mechanism 10.

[0028] The paper feeder 20 is an example of a paper feed section that houses the paper P to be transported toward the image forming unit 40. The paper feeder 20 is equipped with a paper feed tray on which a stack of multiple sheets of paper P is placed. The type of paper P is not particularly limited, but for example, cellulose-based printing paper such as fine paper, coated paper, and art paper can be used. The maximum paper size that can be used in the inkjet printer 1 is, for example, A0 size (841 mm x 1189 mm).

[0029] The paper feeder 20 takes out the stack of paper P set inside, one sheet at a time from the top, and supplies it to the transport path 12.

[0030] The image forming unit 40 performs image formation by ejecting droplets onto the recording surface Pa of the paper P. The image forming unit 40 includes a drawing drum 41 and a head unit 42. The drawing drum 41 receives the paper P from the paper feed drum 16, subjects the received paper P to image formation by the head unit 42, and discharges the paper P from the discharge drum 18. The drawing drum 41 is equipped with a gripper (not shown) on its circumferential surface, and by gripping the leading edge of the paper P with the gripper and rotating it, the paper P is wrapped around the circumferential surface of the drum and transported. The drawing drum 41 is also equipped with a suction mechanism (not shown), which suctions the paper P wrapped around the circumferential surface of the drum and transports it. Negative pressure is used for suction. The drawing drum 41 is equipped with numerous suction holes on its circumferential surface, and by suction from inside the drawing drum 41 through these suction holes, the paper P is suctioned to the circumferential surface of the drawing drum 41.

[0031] The head unit 42 includes print bars 43C, 43M, 43Y, and 43K. In the following, when it is not necessary to distinguish between print bars 43C, 43M, 43Y, and 43K, they will be referred to as print bar 43. The print bar 43 comprises a rectangular parallelepiped housing 44, and inkjet heads 45, a circuit board 46, and a flexible cable 47, each housed within the housing 44. As shown in Figure 2, the inkjet head 45 includes a plurality of head modules 48, which are arranged along the longitudinal direction A. Each head module 48 has a plurality of nozzles for ejecting liquid, and the nozzle surface 48a having the nozzles is positioned to face the recording surface Pa. The inkjet head 45 is an example of a "liquid ejection head" in the technology of this disclosure.

[0032] In the image forming unit 40, the print bar 43 is arranged such that its longitudinal direction A intersects (orthogonal in this example) with the paper transport direction T of the paper P. Furthermore, as shown in Figure 1, multiple print bars 43C, 43M, 43Y, and 43K are arranged sequentially along the transport direction T.

[0033] Print bar 43C is equipped with an inkjet head 45 that ejects droplets of cyan ink. Print bar 43M is equipped with multiple inkjet heads 45 that eject droplets of magenta ink. Print bar 43Y is equipped with an inkjet head 45 that ejects droplets of yellow ink. Print bar 43K is equipped with multiple inkjet heads 45 that eject droplets of black ink.

[0034] Furthermore, each inkjet head 45 of print bars 43C, 43M, 43Y, and 43K is supplied with ink corresponding to its respective state by an ink supply mechanism 50 (see Figure 3), which is not shown in Figure 1. For example, ultraviolet-curing ink is used as the ink for drawing in the inkjet printing device 1. Other inks such as water-based ink, oil-based ink, and solvent-based ink can also be used for drawing. The ink supply mechanism 50 will be described later.

[0035] In the image forming unit 40, ink droplets are ejected toward the paper P being transported by the drawing drum 41, and an image is formed on the paper P as the ejected droplets adhere to the paper P.

[0036] In this example, a configuration using four CMYK inks is illustrated, but the combination of ink colors and the number of colors is not limited to this embodiment. Print bars equipped with inkjet heads that eject light ink, dark ink, spot ink, etc., may be added as needed. Furthermore, there are no particular limitations on the arrangement order of the print bars for each color.

[0037] The stacking device 90 stacks the paper sheets P on which images have been formed. The stacking device 90 receives the paper sheets P discharged from the transport path 12 and stacks the paper sheets P in bundles on a stacking tray (not shown).

[0038] The inkjet printer 1 is equipped with a processor (not shown). The processor includes a CPU (Central Processing Unit). The processor functions as a processing unit and / or control unit that performs various processes by executing program instructions stored in a memory device. The processor comprehensively controls the transport mechanism 10, the paper feed device 20, the image forming unit 40, the ink supply mechanism 50, and the integrator 90.

[0039] (Configuration of the ink supply mechanism) Next, with reference to Figure 3, the configuration of the ink supply mechanism 50 that supplies ink to the inkjet head 45 will be described. Note that each inkjet head 45 of print bars 43C, 43M, 43Y, and 43K is provided with an ink supply mechanism 50, and they have the same configuration as each other.

[0040] The ink supply mechanism 50 is driven at least during printing processing by the inkjet printing apparatus 1. The ink supply mechanism 50 supplies ink to the inkjet head 45, collects ink that has not been ejected from the inkjet head 45, and implements ink circulation that returns the ink to the inkjet head 45 again. More specifically, the ink supply mechanism 50 supplies ink to each of the head modules 48 of the inkjet head 45, and collects ink from each of the head modules 48. That is, supplying ink to each of the head modules 48 means supplying ink to the inkjet head 45, and collecting ink from each of the head modules 48 means collecting ink from the inkjet head 45. As shown in FIG. 3, the ink supply mechanism 50 includes a supply tank 51, a collection tank 52, a liquid supply path 56, a liquid collection path 57, a connection path 58, and a temperature adjustment unit 77.

[0041] The supply tank 51 stores ink to be supplied to the head modules 48. The supply tank 51 is connected to the head modules 48 via the liquid supply path 56, and is connected to the collection tank 52 via the connection path 58.

[0042] The collection tank 52 stores ink collected from the head modules 48. The ink collected from the head modules 48 is ink that has not been ejected from the nozzles of the head modules 48.

[0043] The liquid supply path 56 connects the supply tank 51 and the head module 48. The liquid supply path 56 is a flow path for ink supplied from the supply tank 51 to the head module 48. In the present embodiment, a supply-side manifold 61 is provided midway along the liquid supply path 56. The liquid supply path 56 includes an upstream supply path 56A and a downstream supply path 56B. The upstream supply path 56A has one end connected to the supply tank 51, and the other end connected to the supply-side manifold 61. The downstream supply path 56B includes a plurality of branch paths 56B1, one end of each of which is connected to the supply-side manifold 61, and the other end of each of which is connected to each of the plurality of head modules 48. That is, the liquid supply path 56 branches into the plurality of branch paths 56B1 respectively connected to the plurality of head modules 48 in the downstream supply path 56B via the supply-side manifold 61. Note that in FIG. 3, one head module 48 is shown as a representative. The supply-side manifold 61 temporarily stores ink to be supplied to each of the plurality of head modules 48. Ink is supplied to each head module 48 via the supply-side manifold 61 and each branch path 56B1.

[0044] The liquid recovery path 57 is a flow path for ink recovered from the head module 48 to the recovery tank 52. In the present embodiment, a recovery-side manifold 62 is provided midway along the liquid recovery path 57. The liquid recovery path 57 includes an upstream recovery path 57A and a downstream recovery path 57B. The upstream recovery path 57A includes a plurality of branch paths 57A1, one end of each of which is connected to each of the plurality of head modules 48, and the other end of each of which is connected to the recovery-side manifold 62. The downstream recovery path 57B has one end connected to the recovery-side manifold 62, and the other end connected to the recovery tank 52. Ink recovered from the plurality of head modules 48 is temporarily stored in the recovery-side manifold 62.

[0045] The connecting passage 58 connects the recovery tank 52 and the supply tank 51. The connecting passage 58 is the flow path for ink supplied from the recovery tank 52 to the supply tank 51. The connecting passage 58 is equipped with a circulation pump 59. The circulation pump 59 is controlled by a circulation pump control unit (not shown). For example, based on the output of a liquid level sensor installed in the recovery tank 52, the amount of ink discharged by the circulation pump 59 is controlled so that the amount of ink in the recovery tank 52 remains constant.

[0046] The ink circulation path is composed of a supply tank 51, a liquid supply path 56, an inkjet head 45 (more specifically, a head module 48), a liquid recovery path 57, a recovery tank 52, and a connecting path 58. The liquid supply path 56, the liquid recovery path 57, and the connecting path 58 of the circulation path are collectively referred to as the circulation path 55.

[0047] The temperature control unit 77 is located on the circulation path 55, between the point where the ink recovered from the inkjet head 45 is returned to the supply tank 51. In this example, the temperature control unit 77 is located on the connecting path 58 that connects the recovery tank 52 and the supply tank 51. The supply tank 51, recovery tank 52, temperature control unit 77, circulation path 55, and circulation pump 59 are all located within the housing 44 of the print bar 43.

[0048] The temperature control unit 77 is located on a connecting passage 58 that connects the recovery tank 52 and the supply tank 51. The temperature control unit 77 adjusts the temperature of the ink being sent from the recovery tank 52 to the supply tank 51 and the ink being supplied from the ink storage unit 71 (described later). As a result, temperature-controlled ink is supplied to the supply tank 51, and consequently, temperature-controlled ink is supplied to the inkjet head 45. Through temperature control, for example, if the ink is UV ink, the viscosity is adjusted to be within the recommended viscosity range for the inkjet head 45.

[0049] The temperature control unit 77 includes a microchannel heat exchanger 80 that heats the ink supplied to the inkjet head 45. The microchannel heat exchanger 80 has a flow channel member 82 with a plurality of microchannels 81 (see Figure 4) through which the ink flows, and a heating unit 84 that heats the flow channel member 82. The microchannel heat exchanger 80 heats the flow channel member 82 with the heating unit 84, and heats the ink by transferring the heat from the heated flow channel member 82 to the ink. Figure 4 is a perspective view of an example of a flow channel member 82.

[0050] In this specification, a microchannel refers to a channel in which the distance d between at least one pair of opposing walls is 1 μm or more and 1 mm or less. The microchannel 81 in Figure 4 has a rectangular cross-section, but the cross-section may be circular, elliptical, or semicircular. In the case of a circular channel, the diameter corresponds to the distance d between the opposing pair of cross-sections; in the case of an elliptical channel, the minor axis corresponds to the minor axis; and in the case of a semicircular channel, the radius corresponds to the radius. The cross-sectional area of ​​the microchannel 81 is 1 μm. ２ Above 10mm ２ The following is preferable:

[0051] The microchannel 81 preferably has a flattened cross-section, as shown in Figures 5(A) and 5(B). In Figure 5(A), it has a cross-section of 1 mm × 5 mm, and in Figure 5(B), it has a cross-section of 1 mm × 9 mm. Figure 5(C) shows a cross-section of a reference example channel 181. As shown in Figure 5(C), in the case of channel 181 having a cross-section of 3 mm × 3 mm, the temperature gradient between the center of the channel and the vicinity of the wall surface is larger compared to the microchannel 81 shown in Figures 5(A) and 5(B). When the cross-section is flattened as in Figures 5(A) and 5(B), even with the same channel cross-section, the area in contact between the ink per unit length and the wall surface (hereinafter referred to as the contact area) can be increased. For example, in both Figure 5(B) and Figure 5(C), the channel cross-sectional area is 9 mm ２ However, the contact area per unit length (1 mm) in Figure 5(C) is 12 mm². ２ In contrast, the contact area per unit length in Figure 5(B) is 20 mm². ２Therefore, compared to the flow path 181 shown in Figure 5(C), the microflow path 81 in Figure 5(B) can reduce the temperature gradient and increase the efficiency of heat exchange.

[0052] As shown in Figure 5(A) or (B), if the distance d between at least one pair of opposing walls is 1 mm or less, a large temperature gradient will not be generated in the ink flowing through the channel. Therefore, the ink can be heated in a short time while preventing a localized temperature rise. Furthermore, as shown in Figure 4, by providing multiple microchannels 81, the flow rate can be increased, making it possible to heat the ink more efficiently.

[0053] The flow channel member 82 is a member in which microchannels 81 are formed on a thermally conductive substrate, and is composed of a highly thermally conductive substrate, such as a metal plate. The flow channel member 82 is obtained, for example, as shown in Figure 6, by stacking metal plates 82a to 82c in which grooves g are formed by etching or the like, and a metal plate 82d without grooves, and by applying pressure at a high temperature to cause metal diffusion and join the metal surfaces together.

[0054] The heating unit 84 is, for example, a heater. The flow channel member 82 is heated by the heater, and the heat from the flow channel member 82 is transferred to the ink to heat the ink. Alternatively, the flow channel member 82 may be configured to heat the ink by flowing a heat source medium through a part of the microchannel 81 and ink through a part of it, thereby transferring the heat from the heat source medium to the ink via the flow channel member 82. For example, in a group of four layers of microchannels 81A to 81D, the heat source medium may be flowed through the first and third layers of microchannels 81A and 81C, and ink may be flowed through the second and fourth layers of microchannels 81B and 81D. In this case, the heat source medium and the mechanism for flowing the heat source medium through the microchannels constitute the heating unit.

[0055] The temperature adjustment unit 77 adjusts the temperature of the ink supplied to the inkjet head 45 so that the temperature of the ink falls within a predetermined set range. The set range is, for example, 30°C to 60°C. The temperature adjustment unit 77 is controlled by the temperature adjustment control unit 78. In this embodiment, the supply-side manifold 61 is equipped with a supply-side temperature sensor 63 for detecting the temperature of the ink supplied to the inkjet head 45, and the recovery-side manifold 62 is equipped with a recovery-side temperature sensor 64 for detecting the temperature of the ink recovered from the inkjet head 45. The temperature adjustment control unit 78 performs feedback control based on the ink temperatures detected by the supply-side temperature sensor 63 and the recovery-side temperature sensor 64. For feedback control, proportional (P) control, integral (I) control, differential (D) control, or PI control, PD control, PID control, etc., can be used. PID control is particularly preferred because it has the highest error suppression effect. As an example, the temperature control unit 78 controls the heating output by the temperature adjustment unit 77 so that the average value of the ink temperature detected by the supply-side temperature sensor 63 and the ink temperature detected by the recovery-side temperature sensor 64 falls within a predetermined range. The supply-side temperature sensor 63 is an example of the "first temperature sensor" in this disclosure. Here, the temperature adjustment unit 77 is controlled using the average value of the ink temperatures detected by the supply-side temperature sensor 63 and the recovery-side temperature sensor 64, but the temperature control unit 78 may be configured to control the temperature adjustment unit 77 based only on the ink temperature detected by the supply-side temperature sensor 63.

[0056] The temperature control unit 78 includes a processor and can be configured by a computer such as a PLA (Programmable Logic Controller).

[0057] Each temperature sensor 63 and 64 is positioned so that its sensor portion faces the flow of ink. That is, the supply-side temperature sensor 63 has its sensor portion (sensor surface 63a) facing the flow of ink F from the supply tank 51 towards the inkjet head 45. ｉｎIt is positioned to face the other side. The recovery-side temperature sensor 64 has its sensor part (sensor surface 64a) facing the ink flow F from the inkjet head 45 towards the recovery tank 52. ｏｕｔ It is positioned opposite to it.

[0058] The ink supply mechanism 50 may further include a temperature sensor 86 that monitors at least one of the temperature of the ink in the temperature adjustment unit 77 and the temperature of the ink immediately after it flows out of the temperature adjustment unit 77. In this case, it is preferable that the temperature adjustment control unit 78 is configured to reduce the heating output of the temperature adjustment unit 77 when the temperature detected by the temperature sensor 86 exceeds a predetermined threshold. The temperature adjustment control unit 78 may also be configured to set the heating output of the temperature adjustment unit 77 to 0 when the temperature detected by the temperature sensor 86 exceeds a predetermined threshold. The temperature sensor 86 is an example of a "second temperature sensor" in the technology of this disclosure.

[0059] The temperature sensor 86 is positioned, for example, on the outer wall of the flow channel member 82. Because the microchannels 81 of the flow channel member 82 are small, it is not possible to position the temperature sensor 86, and it is difficult to measure the ink temperature within the microchannels 81. Therefore, in this specification, detecting the ink temperature includes not only cases where the temperature sensor is brought into contact with the ink to directly detect the ink temperature, but also cases where the ink temperature is detected indirectly from outside the flow channel. In this example, in order to directly measure the ink temperature, the temperature sensor 86 may be positioned in the flow channel through which the ink flowing out of the flow channel member 82 in the temperature adjustment unit 77 passes, or near the outlet of the temperature adjustment unit 77 in the connecting passage 58.

[0060] Furthermore, the circulation path 55 may also be equipped with a filter 87 and a degassing module 88 through which the ink passes. These are arranged together with the circulation path 55 within the housing 44 of the print bar 43. Preferably, the filter 87 and degassing module 88 are located upstream of the temperature control unit 77 and directly before the temperature control unit 77 in the circulation direction of the circulation path 55. This is because the area directly before the temperature control unit 77 is where the ink temperature is lowest in the circulation path 55. The appropriate operating temperature for the filter 87 and degassing module 88 is relatively low, and if the ink temperature is high, the attackiness of the ink may increase. If the ink passing through the filter 87 and degassing module 88 is at a relatively low temperature before heating, the decrease in the durability of the filter 87 and degassing module 88 can be suppressed.

[0061] The ink supply mechanism 50 further includes an ink storage section 71 and a liquid replenishment passage 72. A replenishment pump 73 is provided in the liquid replenishment passage 72. The ink storage section 71 stores the ink supplied to the circulation passage 55. The ink storage section is an example of a "liquid storage section" in the technology of this disclosure. The liquid replenishment passage 72 connects the ink storage section 71 and the circulation passage 55. The liquid replenishment passage 72 is the flow path for the ink sent from the ink storage section 71 to the circulation passage 55. In this example, the liquid replenishment passage 72 is connected to a connecting passage 58, and the ink from the ink storage section 71 is supplied to the connecting passage 58. The liquid replenishment passage 72 is connected to the circulation passage 55 (in this case, the connecting passage 58 within the circulation passage 55) upstream of the filter 87 and the degassing module 88 in the circulation direction.

[0062] The supply tank 51 is equipped with a liquid level sensor (not shown), and the replenishment pump 73 is driven so that the sum of the liquid level readings from the supply tank 51 and the recovery tank 52 approaches a target value, and new ink is supplied from the ink storage section 71 to the circulation path 55.

[0063] The ink supply mechanism 50 further includes a supply-side pressure adjustment unit 66 and a recovery-side pressure adjustment unit 67.

[0064] The supply-side pressure adjustment unit 66 adjusts the pressure of the ink stored in the supply tank 51 using the air pressure inside the supply tank 51. The supply-side pressure adjustment unit 66 adjusts the inflow of air into the supply tank 51 and the outflow of air from the supply tank 51 so that the air pressure inside the supply tank 51 becomes a preset supply-side target air pressure.

[0065] The supply-side pressure adjustment unit 66 is composed of, for example, an air pressure adjustment valve, an air pressure supply source, a primary air pipeline, a secondary air pipeline, and an air pressure sensor. The air pressure supply source includes, for example, a compressor and a vacuum pump, with the compressor used for pressurization and the vacuum pump for depressurization. The primary air pipeline is a pipeline connecting the air pressure supply source and the air pressure adjustment valve. The secondary air pipeline is a pipeline connecting the air pressure adjustment valve and the supply tank 51. The air pressure sensor detects the air pressure in the secondary air pipeline. The air pressure in the secondary air pipeline connected to the supply tank 51 is equivalent to the air pressure inside the supply tank 51. The air pressure adjustment valve obtains the air pressure in the secondary air pipeline from the air pressure sensor and controls the air pressure supply source to allow air to flow into the supply tank 51 or to discharge air from the supply tank 51 so that this air pressure becomes the supply-side target air pressure. The target air pressure on the supply side is determined in relation to the desired ink pressure of the ink stored in the supply tank 51.

[0066] The recovery-side pressure adjustment unit 67 adjusts the pressure of the ink stored in the recovery tank 52 using the air pressure inside the recovery tank 52. The recovery-side pressure adjustment unit 67 adjusts the inflow of air into the recovery tank 52 and the discharge of air from the recovery tank 52 so that the air pressure inside the recovery tank 52 becomes a preset recovery-side target air pressure.

[0067] The recovery-side pressure adjustment unit 67 has a similar configuration to the supply-side pressure adjustment unit 66, but includes, for example, a pneumatic adjustment valve, a pneumatic supply source, a primary air pipeline, a secondary air pipeline, and a pneumatic sensor. Here, the secondary air pipeline is a pipeline connecting the pneumatic adjustment valve and the recovery tank 52. The pneumatic sensor detects the air pressure in the secondary air pipeline. The air pressure in the secondary air pipeline connected to the recovery tank 52 is equivalent to the air pressure inside the recovery tank 52. The pneumatic adjustment valve obtains the air pressure in the secondary air pipeline from the pneumatic sensor and controls the pneumatic supply source to allow air to flow into the recovery tank 52 or to discharge air from the recovery tank 52 so that this air pressure becomes the recovery-side target air pressure. The recovery-side target air pressure is determined in relation to the pressure of the ink stored in the recovery tank 52.

[0068] The target air pressure on the supply side and the target air pressure on the recovery side are set so that the pressure of the ink stored in the supply tank 51 is higher than the pressure of the ink stored in the recovery tank 52. In other words, the supply side pressure adjustment unit 66 and the recovery side pressure adjustment unit 67 are configured to adjust the air pressure in the supply tank 51 and the air pressure in the recovery tank 52 so that the ink pressure in the supply tank 51 is higher than the ink pressure in the recovery tank 52. This is because the ink is sent from the supply tank 51 through the head module 48 to the recovery tank 52 in the ink circulation path.

[0069] A brief explanation of the method for adjusting the ink temperature in the ink supply mechanism 50 configured as described above will now be given. In the inkjet printing apparatus 1, the ink temperature is adjusted so that the temperature of the ink supplied to the inkjet head 45 reaches the appropriate ejection temperature.

[0070] Temperature control by the temperature control control unit 78 is performed as follows.

[0071] The temperature control unit 78 acquires detection results from the supply-side temperature sensor 63 located on the liquid supply path 56 (in this case, inside the supply-side manifold 61) and the recovery-side temperature sensor 64 located on the liquid recovery path 57 (in this case, inside the recovery-side manifold 62). Based on the average value of the ink temperature detected by the supply-side temperature sensor 63 and the recovery-side temperature sensor 64, the temperature control unit 78 provides feedback control to the heating output of the temperature adjustment unit 77 so that the average value is, for example, between 30°C and 60°C.

[0072] The feedback control by the temperature control unit 78 can use P control, I control, D control, or PI control, PD control, PID control, etc. PID control is particularly preferred because it has the highest error suppression effect.

[0073] Furthermore, the temperature control unit 78 acquires detection results from the temperature sensor 86 provided in the temperature adjustment unit 77. When the ink temperature detected by the temperature sensor 86 exceeds a predetermined threshold, the temperature control unit 78 reduces the heating output of the temperature adjustment unit 77, for example, to 0.

[0074] By implementing this control, the temperature of the ink supplied to the inkjet head 45 can be adjusted to always remain within a certain range. Furthermore, the inclusion of a microchannel heat exchanger 80 enables rapid heating of the temperature control unit 77, which can suppress overheating of the ink.

[0075] As described above, the inkjet printing apparatus 1 of this embodiment includes a temperature control unit 77 equipped with a microchannel heat exchanger 80 in the ink supply mechanism 50. By including the microchannel heat exchanger 80, as described above, local temperature rises of the ink are suppressed, the temperature of the ink supplied to the inkjet head 45 is made uniform, and ink can be supplied to the inkjet head 45 at a stable temperature. Because the temperature stability of the ink supplied to the inkjet head 45 can be improved, high-quality ink ejection can be achieved, and as a result, the image quality can be improved.

[0076] In this embodiment, the temperature sensors 63 and 64 are positioned so that their sensor portions face the flow of ink. This allows for more accurate measurement of the temperature of the flowing ink.

[0077] As previously described, in this embodiment, the ink supply mechanism 50 is equipped with a temperature sensor 86 that monitors at least one of the temperature of the ink in the temperature control unit 77 and the temperature of the ink immediately after it flows out of the temperature control unit 77. The temperature control control unit 78 is configured to reduce the heating output of the temperature control unit 77 when the temperature detected by the temperature sensor 86 exceeds a predetermined threshold. Since the ink is heated in the microchannel 81 in the temperature control unit 77, the ink is prone to temperature increases. During startup of the device or in the event of a runaway operation, the ink may be overheated. When a rapid temperature rise occurs that causes the ink temperature to exceed the threshold, the heating output of the temperature control unit 77 can be forcibly reduced or forcibly stopped to suppress overheating of the ink and prevent deterioration such as ink aggregation.

[0078] In this embodiment, the print bar 43 has a configuration in which an inkjet head 45, a supply tank 51, a temperature control unit 77, a circulation path 55, and a circulation pump 59 are arranged in a single housing 44. By arranging the circulation path 55 within the print bar 43, the flow path length from the temperature control unit 77 to the inkjet head 45 and the flow path length from the inkjet head 45 to the temperature control unit 77 are made shorter. Therefore, the temperature drop of the ink heated in the temperature control unit 77 as it returns to the temperature control unit 77 via the inkjet head 45 can be suppressed.

[0079] In the ink supply mechanism 50, it is preferable that the total volume of the supply tank 51 and the liquid supply passage 56 is greater than the volume of the flow path of the microchannel heat exchanger 80. Here, the volume of the flow path of the microchannel heat exchanger 80 is the volume of the microchannel 81, and if there are multiple microchannels 81, it is the total volume of the multiple microchannels 81.

[0080] When ink is newly introduced into the circulation path 55 from the replenishment path 72, the temperature of the microchannel heat exchanger 80 may decrease due to the ink. Even in such cases, if the ink volume up to the head module 48 is greater than the ink volume of the microchannel heat exchanger 80, large temperature fluctuations in the liquid supplied to the head module 48 can be suppressed.

[0081] The ink supply mechanism 50 of this embodiment is particularly effective when the ink has a higher viscosity than the appropriate ink viscosity of the inkjet head 45 at room temperature, its viscosity decreases when heated, and its liquid properties change when the temperature exceeds the temperature at which the appropriate ink viscosity is reached, and it has a lower thermal conductivity and specific heat than water. Examples of such inks include ultraviolet-curable inks.

[0082] The inkjet printing apparatus 1 may include a pretreatment liquid coating unit and a pretreatment liquid drying unit upstream of the image forming unit 40. Alternatively, the inkjet printing apparatus 1 may include a drying unit downstream of the image forming unit 40.

[0083] The term "recording medium" is a general term encompassing various things that are called by different names, such as paper, recording paper, printing paper, printing media, printing medium, printed medium, image-forming medium, image-receiving medium, and ejected medium.

[0084] Although the above embodiments describe an inkjet printing apparatus that ejects ink to form an image, the technology of this disclosure can also be applied to liquid ejection apparatus that ejects liquids other than ink, such as coating solvents.

[0085] The embodiments of the present invention described above can be modified, added to, or deleted as appropriate without departing from the spirit of the invention. The present invention is not limited to the embodiments described above, and many modifications are possible within the technical concept of the present invention by those with ordinary skill in the equivalent related field.

[0086] Furthermore, the processor may be configured by one or more pieces of hardware, and the type of hardware is not limited. For example, the processor may be a programmable logic device such as a CPU (Central Processing Unit), an MPU (Micro Processing Unit), or an FPGA (Field Programmable Gate Array), a dedicated circuit for executing specific processing such as an ASIC (Application Specific Integrated Circuit), or hardware such as a GPU (Graphic Processing Unit) or an NPU (Neural Processing Unit). Further, the type of hardware may be a combination of different types of hardware. When a plurality of pieces of hardware are configured to execute one or more processes of a certain processor, the plurality of pieces of hardware may be present in physically separate devices from each other, or may be present in the same device. Also, in any of the embodiments, the order of each process performed by the processor is not limited to the order described above, and may be changed as appropriate. Note that the hardware is configured by an electric circuit (circuitry) or the like in which circuit elements such as semiconductor elements are combined.

[0087] Regarding the above embodiment, the following supplementary notes are further disclosed. <Supplementary Note 1> A liquid ejection apparatus, comprising: a liquid ejection head including a nozzle that ejects liquid; a supply tank that stores liquid to be supplied to the liquid ejection head; a liquid supply path that connects the liquid ejection head and the supply tank; and a temperature adjustment unit including a microchannel heat exchanger that heats the liquid supplied to the liquid ejection head. <Supplementary Note 2> The cross-sectional area of the flow path through which liquid passes in the microchannel heat exchanger is 10 mm ２The liquid dispensing device described in Appendix 1 is as follows: <Appendix 3> The liquid dispensing device described in Appendix 1 or Appendix 2, further comprising a first temperature sensor located between the supply tank and the liquid dispensing head for detecting the temperature of the liquid, wherein the temperature control unit controls heating based on the temperature of the liquid detected by the first temperature sensor. <Appendix 4> The liquid dispensing device described in Appendix 3, wherein the sensor portion of the first temperature sensor is located in a direction opposite to the flow of the liquid. <Appendix 5> The liquid dispensing device described in Appendix 3 or Appendix 4, further comprising a second temperature sensor located in at least one of the temperature control unit and the flow path through which the liquid discharged from the temperature control unit passes for detecting the temperature of the liquid, and a processor that reduces the heating output of the temperature control unit when the temperature of the liquid detected by the second temperature sensor exceeds a predetermined threshold. <Note 6> A liquid dispensing device according to any one of Notes 1 to 5, further comprising a circulation path that includes a liquid supply path and circulates liquid between a liquid dispensing head and a supply tank, and a circulation pump that circulates liquid within the circulation path, wherein the temperature control unit is located in the circulation path between the liquid recovered from the liquid dispensing head and the supply tank, and the liquid dispensing head, supply tank, temperature control unit, circulation path, and circulation pump are arranged in a single housing. <Note 7> A liquid dispensing device according to Note 6, further comprising a filter and a deaeration module through which liquid passes, located on the circulation path arranged in the housing of the print bar. <Note 8> A liquid dispensing device according to Note 7, further comprising a liquid storage section for storing liquid, and a liquid replenishment path connecting the liquid storage section and the circulation path, which includes a replenishment pump that delivers liquid to the circulation path, wherein the liquid replenishment path is connected to the circulation path upstream of the filter and deaeration module in the circulation direction of the circulation path. <Note 9> A liquid discharge device according to any one of Notes 1 to 8, wherein the total volume of the supply tank and the liquid supply path is greater than the volume of the flow path of the microchannel heat exchanger.<Note 10> A liquid dispensing device according to any one of Notes 1 to 9, wherein the liquid has a higher viscosity than the appropriate liquid viscosity of the liquid dispensing head at room temperature, its viscosity decreases when heated, and its liquid properties change when the temperature exceeds the temperature at which the appropriate liquid viscosity is obtained, and the liquid has a lower thermal conductivity and lower specific heat than water. <Note 11> A liquid dispensing device according to Note 10, wherein the liquid is an ultraviolet-curable ink. <Note 12> A liquid dispensing device comprising: a liquid dispensing head equipped with a nozzle for dispensing liquid; a supply tank for storing the liquid supplied to the liquid dispensing head; a liquid supply path connecting the liquid dispensing head and the supply tank; and a temperature control unit equipped with a microchannel heat exchanger for heating the liquid supplied to the liquid dispensing head, wherein the heating output of the temperature control unit for heating the liquid is adjusted based on the temperature of the liquid supplied to the liquid dispensing head, and the temperature of at least one of the temperature of the liquid in the temperature control unit and the temperature of the liquid discharged from the temperature control unit is monitored, and the heating output of the temperature control unit is reduced when the temperature exceeds a predetermined threshold. <Note 13> The temperature control method described in Note 12, wherein the heating output of the temperature control unit is set to 0 when the heating output is reduced.

[0088] The disclosure of Japanese Patent Application No. 2025-052702, filed on 26 March 2025, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted to be incorporated by reference.

Claims

1. A liquid dispensing device comprising: a liquid dispensing head equipped with a nozzle for dispensing liquid; a supply tank for storing the liquid supplied to the liquid dispensing head; a liquid supply path connecting the liquid dispensing head and the supply tank; and a temperature control unit equipped with a microchannel heat exchanger for heating the liquid supplied to the liquid dispensing head.

2. The cross-sectional area of ​​the flow path through which the liquid passes in the microchannel heat exchanger is 10 mm². ２ The liquid dispensing device according to claim 1, which is as follows:

3. The liquid dispensing device according to claim 1 or 2, further comprising a first temperature sensor disposed between the supply tank and the liquid dispensing head for detecting the temperature of the liquid, wherein the temperature adjustment unit controls the heating based on the temperature of the liquid detected by the first temperature sensor.

4. The liquid dispensing device according to claim 3, wherein the sensor portion of the first temperature sensor is arranged in a direction opposite to the flow of the liquid.

5. The liquid discharge device according to claim 3, further comprising: a second temperature sensor for detecting the temperature of the liquid, which is disposed in at least one of the temperature control section and the flow path through which the liquid discharged from the temperature control section passes; and a processor that reduces the heating output of the temperature control section when the temperature of the liquid detected by the second temperature sensor exceeds a predetermined threshold.

6. A liquid dispensing device according to claim 1 or 2, further comprising a circulation path that includes the liquid supply path and circulates the liquid between the liquid dispensing head and the supply tank, and a circulation pump that circulates the liquid within the circulation path, wherein the temperature control unit is located in the circulation path between the liquid recovered from the liquid dispensing head and the supply tank, and the liquid dispensing head, the supply tank, the temperature control unit, the circulation path, and the circulation pump are arranged in a single housing.

7. The liquid dispensing device according to claim 6, further comprising a filter and a degassing module through which the liquid passes, located on the circulation path disposed within the housing of the print bar.

8. The liquid discharge device according to claim 7, further comprising: a liquid storage section for storing the liquid; a liquid replenishment section connecting the liquid storage section and the circulation path, the liquid replenishment section being equipped with a replenishment pump for supplying the liquid to the circulation path, wherein the liquid replenishment section is connected to the circulation path upstream of the filter and the degassing module in the circulation direction.

9. The liquid discharge device according to claim 1 or 2, wherein the combined volume of the supply tank and the liquid supply path is greater than the volume of the flow path of the microchannel heat exchanger.

10. The liquid dispensing device according to claim 1 or 2, wherein the liquid has a viscosity higher than the appropriate liquid viscosity of the liquid dispensing head at room temperature, its viscosity decreases when heated, and its properties change when the temperature exceeds the temperature at which the appropriate liquid viscosity is obtained, and the liquid has a lower thermal conductivity and a lower specific heat than water.

11. The liquid dispensing apparatus according to claim 10, wherein the liquid is an ultraviolet-curable ink.

12. A liquid dispensing device comprising: a liquid dispensing head equipped with a nozzle for dispensing liquid; a supply tank for storing the liquid supplied to the liquid dispensing head; a liquid supply path connecting the liquid dispensing head and the supply tank; and a temperature control unit equipped with a microchannel heat exchanger for heating the liquid supplied to the liquid dispensing head, wherein the heating output of the temperature control unit for heating the liquid is adjusted based on the temperature of the liquid supplied to the liquid dispensing head, and the temperature of at least one of the temperature of the liquid in the temperature control unit and the temperature of the liquid discharged from the temperature control unit is monitored, and the heating output of the temperature control unit is reduced when the temperature exceeds a predetermined threshold.

13. The temperature control method according to claim 12, wherein the heating output of the temperature adjustment unit is reduced, and the heating output is set to 0.

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