Inkjet recording device and ink heating unit

Abstract

To provide an inkjet recording device and an ink heating unit capable of controlling a temperature of ink with high energy efficiency.SOLUTION: An inkjet recording device 1 that forms an image by discharging ink from an inkjet head 241 to a recording medium P, includes: an ink heating device 243 that heats the ink; and a carriage 242 equipped with a plurality of inkjet heads 241. The ink heating device 243 is fixed to an outer surface of the carriage 242, and the ink heated in the ink heating device 243 is supplied to the inkjet heads 241.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an inkjet recording apparatus and an ink heating unit. [Background technology]

[0002] Conventionally, there is known an inkjet recording device that ejects ink from an inkjet head to record an image on a recording medium. Since the physical properties of ink, such as viscosity and surface tension, change depending on the temperature, the size of the ink droplets also changes. Variation in droplet size leads to a decrease in image quality, so in inkjet recording devices, it is necessary to appropriately control the temperature of the ink.

[0003] Therefore, for example, Patent Document 1 describes an ink supply device in which a heating device for heating ink is provided in an ink flow path between a main tank and a sub-tank that stores ink supplied from the main tank. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2021-133629 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the invention of Patent Document 1, the longer the distance that the ink heated by the ink heating device must travel to reach the sub-tank, the less favorable it becomes in terms of energy efficiency.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an inkjet recording apparatus and an ink heating unit capable of controlling the ink temperature with excellent energy efficiency. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides an inkjet recording device that forms an image by ejecting ink from an inkjet head onto a recording medium, comprising: an ink heating device for heating the ink; a carriage on which a plurality of the inkjet heads are mounted; the ink heating device is fixed to an outer surface of the carriage; The ink heated by the ink heating device is supplied to the inkjet head.

[0008] The invention described in claim 2 is the inkjet recording apparatus described in claim 1, A main tank for storing ink; a sub-tank that stores the ink heated by the ink heating device and supplies the ink to the inkjet head, The ink heating device heats the ink supplied from the main tank.

[0009] The invention described in claim 3 is the inkjet recording apparatus described in claim 1 or 2, The ink heating device is fixed to an end of the carriage.

[0010] The invention described in claim 4 is the inkjet recording apparatus described in claim 1 or 2, A temperature uniforming mechanism is provided to make the temperature inside the carriage approximately uniform.

[0011] The invention described in claim 5 is the inkjet recording apparatus described in claim 4, the temperature uniforming mechanism includes a first ink heating device and a second ink heating device; the first ink heating device is fixed to a first end of the carriage; The second ink heating device is secured to an exterior surface of the carriage at a second end opposite the first end.

[0012] The invention described in claim 6 is the inkjet recording apparatus described in claim 4, the temperature uniforming mechanism includes the ink heating device and a degassing module that degasses dissolved gas in the ink; the ink heating device is secured to a first end of the carriage; The degassing module is secured to an exterior surface of the carriage at a second end opposite the first end.

[0013] The invention described in claim 7 is the inkjet recording apparatus described in claim 4, The temperature uniformity mechanism includes a heat insulating member interposed between the ink heating device and the carriage.

[0014] The invention described in claim 8 is the inkjet recording apparatus described in claim 4, a first control unit for controlling the ink heating device; The first control unit controls the ink heating device so that the temperature of the ink is higher than the temperature of the ink ejected from the inkjet head.

[0015] The invention described in claim 9 is the inkjet recording apparatus described in claim 8, The first control unit controls the temperature of the ink heating device so that the temperature is 5° C. to 15° C. higher than the temperature of the ink ejected from the inkjet head.

[0016] The invention described in claim 10 is the inkjet recording apparatus described in claim 6, A second control unit is provided for controlling a temperature of the degassing module, The second control unit controls the degassing module so that the temperature of the ink is higher than the temperature of the ink ejected from the inkjet head.

[0017] The invention described in claim 11 is the inkjet recording apparatus described in claim 10, The second control unit controls the temperature of the degassing module so that the temperature is 5° C. to 15° C. higher than the temperature of the ink ejected from the inkjet head.

[0018] The invention described in claim 12 is the inkjet recording apparatus described in claim 8, the temperature uniforming mechanism includes a third control unit that individually controls temperatures of the inkjet heads, The third control unit controls the inkjet head so that the temperature of the inkjet head increases as the inkjet head is farther from the ink heating device.

[0019] The invention described in claim 13 is the inkjet recording apparatus described in claim 1 or 2, A phase change ink is used, which undergoes a reversible phase change between a solid state and a liquid state at a phase transition temperature.

[0020] The invention described in claim 14 is an ink heating unit, an ink heating device for heating the ink; a carriage having an exterior surface to which the ink heating device is secured. Effect of the Invention

[0021] According to the present invention, ink temperature control can be achieved with excellent energy efficiency. [Brief description of the drawings]

[0022] [Figure 1] FIG. 2 is a side view of the inkjet recording apparatus as viewed in the width direction. [Diagram 2] FIG. 1 is a block diagram of an inkjet recording apparatus. [Diagram 3] 1 is a schematic configuration diagram of a liquid delivery section of an inkjet recording apparatus according to a first embodiment. [Figure 4] FIG. 2 is a top cross-sectional view of the ink heating device. [Diagram 5] FIG. 11 is a schematic configuration diagram of a liquid delivery section of an inkjet recording apparatus according to a second embodiment. [Figure 6]FIG. 11 is a schematic configuration diagram of a liquid delivery section of an inkjet recording apparatus according to a third embodiment. [Figure 7] FIG. 2 is a schematic diagram of a degassing module. [Figure 8] FIG. 13 is a schematic configuration diagram of a liquid delivery section of an inkjet recording apparatus according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, an inkjet recording apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples. In the following description, components having the same functions and configurations are given the same reference numerals, and the description thereof will be omitted.

[0024] [First embodiment] [Overall configuration of inkjet recording device] Fig. 1 is a side cross-sectional view showing the main configuration of an inkjet recording apparatus 1. Fig. 2 is a block diagram showing the functional configuration of the inkjet recording apparatus 1. The inkjet recording apparatus 1 according to the first embodiment includes a paper feed unit 10, an image forming unit 20, a paper discharge unit 30, a control unit 40, and the like.

[0025] In the following description, the X direction, Y direction, and Z direction refer to the directions shown in Fig. 1. In the following description, the X direction, Y direction, and Z direction are respectively referred to as the width direction, the conveying direction, and the height direction.

[0026] (Paper feed section) The paper feed unit 10 stores the recording medium P before an image is formed on it. The paper feed unit 10 conveys the recording medium P to the image forming unit 20 under the control of the control unit 40. The paper feed unit 10 includes a paper feed tray 11, a conveying unit 12, and the like.

[0027] {Paper feed tray} The paper feed tray 11 is a plate-like member that stores recording media P. The paper feed tray 11 is provided so that one or more recording media P can be placed on it. The paper feed tray 11 moves up and down depending on the amount of recording media P placed on it. By this up and down movement, the paper feed tray 11 is held at a position where the top recording medium P is transported by the transport unit 12.

[0028] {Transportation section} The conveying unit 12 conveys the recording medium P from the paper feed tray 11 to the image forming unit 20. The conveying unit 12 includes a conveying mechanism. The conveying mechanism drives a belt 123 to convey the recording medium P on the belt 123. The belt 123 is in a ring shape, and the inner side of the ring is supported by a plurality of rollers 121 and 122.

[0029] The conveying unit 12 includes a supply unit. The supply unit delivers the top recording medium P placed on the paper feed tray 11 onto the belt 123. The conveying unit 12 conveys the recording medium P along the belt 123 by the supply unit.

[0030] (Image forming section) The image forming unit 20 performs a recording operation on the recording medium P under the control of the control unit 40. The image forming unit 20 includes an image forming drum 21, a delivery unit 22, a paper heating unit 23, a head unit 24, an irradiation unit 25, a delivery unit 26, and the like.

[0031] {Image forming drum} The image forming drum 21 carries the recording medium P along its cylindrical outer circumferential surface and conveys the recording medium P as it rotates. The conveying surface of the image forming drum 21 faces the paper heating section 23, the head unit 24, and the irradiation section 25, and performs an image forming process on the conveyed recording medium P.

[0032] {Delivery unit} The delivery unit 22 is provided at a position interposed between the transport section 12 and the image forming drum 21. The delivery unit 22 includes a claw portion 221, a delivery drum 222, and the like.

[0033] The claw portion 221 is a cylindrical member that holds one end of the recording medium P transported by the transport unit 12. The delivery drum 222 is a member that guides the recording medium P held by the claw portion 221.

[0034] The delivery unit 22 picks up the recording medium P on the transport section 12 with the claw portion 221 and moves it along the outer circumferential surface of the delivery drum 222. The delivery unit 22 delivers the recording medium P to the image forming drum 21 by this operation.

[0035] {Paper heating section} The paper heating section 23 includes, for example, an electric heating wire, and generates heat in response to the passage of electricity. The paper heating section 23 is controlled by the control section 40, and generates heat so that the recording medium P passing nearby reaches a predetermined temperature. The paper heating section 23 is disposed near the outer circumferential surface of the image forming drum 21, and is located upstream of the head unit 24 in the transport direction of the recording medium P.

[0036] A temperature sensor (not shown) is provided near the paper heating unit 23. The control unit 40 uses the temperature sensor to detect the temperature near the paper heating unit 23. The control unit 40 controls the heat generation of the paper heating unit 23 based on the detected temperature.

[0037] {Head unit} The head units 24 form an image by ejecting ink onto the recording medium P. The head units 24 are provided corresponding to the colors C (cyan), M (magenta), Y (yellow), and K (black). In Fig. 1, the head units 24 corresponding to the colors Y, M, C, and K are provided in this order from upstream with respect to the transport direction of the recording medium P.

[0038] The head unit 24 of this embodiment is configured by arranging a plurality of inkjet heads 241 (see FIG. 3) which are droplet ejection heads on a carriage 242 (see FIG. 3) for the recording medium P. The head unit 24 forms an image by ejecting ink from the carriage 242, which has a width length longer than the recording medium P, onto the conveyed recording medium P. In other words, the inkjet recording device 1 is a line head type inkjet recording device.

[0039] The number of head units 24 provided in the image forming section 20 may be three or less, or may be five or more. The inkjet recording device 1 may be of a serial head type, which forms an image by scanning a carriage 242, whose width is shorter than the recording medium P, in the width direction.

[0040] The ink ejected by the head unit 24 is, for example, an ultraviolet curable ink. The ultraviolet curable ink is a gel-like ink that changes phase between a gel state and a liquid (sol) state depending on the temperature when not irradiated with ultraviolet rays from the irradiation unit 25. The sol-gel phase transition temperature of the ultraviolet curable ink is preferably within a range of 40 to 70°C, and more preferably within a range of 50 to 65°C. A more detailed configuration of the head unit 24 will be described later.

[0041] {Irradiation unit} The irradiation unit 25 includes, for example, a fluorescent tube such as a low-pressure mercury lamp. The irradiation unit 25 irradiates energy rays such as ultraviolet rays by emitting light from the fluorescent tube. The irradiation unit 25 is provided near the outer circumferential surface of the image forming drum 21. The irradiation unit 25 is also provided so as to be located downstream of the head unit 24 in the transport direction of the recording medium P. The irradiation unit 25 irradiates the recording medium P onto which the ink has been ejected with energy rays. The ink on the recording medium P is cured by the action of the energy rays.

[0042] The fluorescent tube that emits ultraviolet rays is not limited to a low-pressure mercury lamp. The fluorescent tube may be a mercury lamp with an operating pressure of, for example, several hundred Pa to 1 MPa. The fluorescent tube may be a light source that can be used as a germicidal lamp, for example, a cold cathode fluorescent tube, an ultraviolet laser light source, a metal halide lamp, or a light-emitting diode. Among these, it is preferable that the fluorescent tube is a power-saving light source that can irradiate ultraviolet rays with a higher illuminance. The fluorescent tube is, for example, a light-emitting diode. The energy rays are not limited to ultraviolet rays, and may be energy rays that have the property of curing the ink depending on the properties of the ink. The light source is also replaced depending on the energy rays.

[0043] In the above, the head unit 24 ejects ultraviolet-curable ink, but the present invention is not limited to this. The ink ejected by the head unit 24 may be water-based ink or other ink.

[0044] {Delivery Department} The delivery unit 26 includes a transport mechanism. The transport mechanism drives a ring-shaped belt 263, the inside of which is supported by a plurality of rollers 261 and 262, to transport the recording medium P. The delivery unit 26 includes a cylindrical delivery roller 264. The delivery roller 264 delivers the recording medium P from the image forming drum 21 to the transport mechanism. The delivery unit 26 transports the recording medium P delivered onto the belt 263 by the delivery roller 264, and sends it out to the paper discharge unit 30.

[0045] (Paper ejection section) The recording medium P on which an image has been formed in the image forming section 20 is discharged to the paper discharge section 30. The paper discharge unit 30 includes a plate-shaped paper discharge tray 31. The recording medium P sent from the image forming unit 20 by the delivery unit 26 is placed on the paper discharge tray 31. The paper discharge unit 30 stores the recording medium P until the user removes it.

[0046] (Head unit) 3 is a schematic diagram of one head unit 24 according to the first embodiment. The head unit 24 includes not only a plurality of inkjet heads 241 and a carriage 242, but also an ink heating device 243 and a sub-tank 244. As shown in FIG. 3, the components of the head unit 24 except for the carriage 242 are fixed to and mounted on the carriage 242. The head unit 24 is also connected to main tanks MT that contain ink of each color and are arranged outside the carriage 242. As shown in FIG. 2, the carriage 242 and the ink heating device 243 form an ink heating unit 100.

[0047] {Main Tank} The main tank MT is a rigid tank made of resin, for example. The capacity of the main tank MT is, for example, about 30 L, but is not limited to this. As shown in FIG. 3, the main tank MT is connected to a first end of a first pipe T1, and communicates with the ink heating device 243 via the first pipe T1.

[0048] {First Pipe} The first pipe T1 is a member that connects the main tank MT and the ink heating device 243. The first pipe T1 is, for example, a tube having a predetermined elasticity. If the first pipe T1 is a tube, it becomes easy to attach and detach the first pipe T1 to the main tank MT and the ink heating device 243. Furthermore, if the inkjet recording apparatus 1 is, for example, of a serial head type, the first pipe T1 having elasticity allows the head unit 24 to freely scan in the width direction.

[0049] A supply pump P1 is provided in the first pipe T1 near the main tank MT. The supply pump P1 operates under the control of the control unit 40 to supply ink in the main tank MT to the first sub-tank 2441. When the amount of ink in the main tank MT becomes low, ink is replenished and used.

[0050] Furthermore, a supply control valve V1 is provided in the first pipe T1 downstream of the supply pump P1 in the liquid sending direction. The supply control valve V1 is an electromagnetic valve. The opening and closing of the supply control valve V1 is controlled by the control unit 40. Specifically, the supply control valve V1 is opened when the supply pump P1 supplies ink in the main tank MT to a first sub-tank 2441 (described later), and is closed at other times.

[0051] {Ink heating device} The ink heating device 243 is made of, for example, aluminum, and is connected to a second end of the first pipe T1 to heat the ink supplied from the main tank MT (first pipe T1) under the control of the control unit 40. Also, as shown in FIG. 3, the ink heating device 243 is fastened and fixed to a first end (end portion) of the outer surface of the carriage 242 by, for example, a screw.

[0052] An example of a top cross-sectional view of the ink heating device 243 is shown in Fig. 4. As shown in Fig. 4, the ink heating device 243 includes a flow path 243a that is provided in a serpentine shape. The ink heating device 243 also includes a cartridge heater 243b that crosses the flow path 243a in the transport direction, and heats the ink in the flow path 243a.

[0053] As shown by the arrows in Fig. 4, the flow path 243a is provided so as to branch into multiple branches (three branches in Fig. 4) and merge. This configuration of the flow path 243a increases the area where the ink comes into contact with the heated flow path 243a. The ink heating device 243 has a configuration in which such flow paths 243a are stacked in multiple stages (three stages in Fig. 3) in the vertical direction, which lengthens the time that the ink stays in the ink heating device 243. This configuration allows the ink heating device 243 to sufficiently heat the ink inside.

[0054] 4, the flow path 243a is shown to be branched into three branches, but the present invention is not limited to this. The number of branches in the flow path 243a may be increased to increase the contact area with the ink. However, on the other hand, as the number of branches increases, the flow path resistance increases, and the pressure required for the supply pump P1 increases. Therefore, it is preferable to appropriately set the number of branches according to a desired balance between heating efficiency and flow path resistance. The ink capacity of the ink heating device 243 is, for example, about 300 cc.

[0055] As described above, the ink discharged by the head unit 24 is a gel-like ink whose phase changes according to temperature. When the phase transition temperature of the ink is 70° C. or lower, the temperature of the ink when discharged from the inkjet head 241 is preferably about 80° C. Therefore, in order to quickly heat the ink to a temperature near 80° C., the control unit 40 preferably controls the ink heating device 243 to a temperature about 5 to 15° C. higher than 80° C., that is, about 90° C. In this way, the control unit 40 functions as a first control unit that controls the ink heating device 243 to a temperature higher than the ink discharged from the inkjet head 241.

[0056] {Second piping} Each unit mounted on the carriage 242 downstream in the liquid sending direction from the ink heating device 243 is connected to each other by the second pipe T2.

[0057] The second pipe T2 is a rigid flow path, and is made of, for example, metal. Unlike the first pipe T1, the second pipe T2 is provided, for example, on its outer circumferential surface with a heating member that heats the ink inside to an appropriate temperature. The heating member is, for example, a rubber heater in which a strip-shaped heating element is arranged in a corrugated form on a thin plate-shaped insulating heat insulator, but is not limited to this. When the heating member is a rubber heater, it directly contacts the outer surface of the second pipe T2 to heat it.

[0058] The control unit 40, which is a temperature control unit, controls the heating member of the second piping T2 that connects the ink heating device 243 and the first sub-tank 2441 so that the temperature of the ink inside becomes, for example, 90° C. The control unit 40, which is also a temperature control unit, controls the heating member of the piping that connects the first sub-tank 2441 and the second sub-tank 2442 so that the temperature of the ink inside becomes, for example, 80° C. With this configuration, ink at an appropriate temperature is supplied to each unit.

[0059] {Subtank} The ink sent from the main tank MT is temporarily stored in the sub tank 244. The sub tank 244 includes a first sub tank 2441 and a second sub tank 2442.

[0060] <First sub-tank> The first sub-tank 2441 is one or more ink chambers. The volume of the first sub-tank 2441 is smaller than that of the main tank MT. The first sub-tank 2441 stores ink that is supplied from the main tank MT and has passed through the ink heating device 243. By providing the first sub-tank 2441, pressure fluctuations caused by pulsation when the supply pump P1 supplies ink in the main tank MT are mitigated.

[0061] A liquid feed pump P2 is provided in the piping that connects the first sub-tank 2441 and the second sub-tank 2442. The liquid feed pump P2 is, for example, a diaphragm pump that includes a check valve and a diaphragm. If the liquid feed pump P2 is a diaphragm pump, the risk of foreign matter being mixed into the ink and the risk of liquid leakage are reduced.

[0062] Furthermore, the first sub-tank 2441 is in communication with the outlets of each inkjet head 241 via piping. With this configuration, of the ink supplied from the second sub-tank 2442 to the inkjet head 241, ink that has not been ejected from the nozzles can be returned to the first sub-tank 2441. In this way, by making it possible to circulate the ink among the first sub-tank 2441, the second sub-tank 2442, and the inkjet head 241, the components in the ink can be made uniform.

[0063] <Second sub-tank> The second sub-tank 2442 is a tank chamber that temporarily stores the ink supplied from the first sub-tank 2441. The capacity of the second sub-tank 2442 is not particularly limited, but is, for example, approximately the same as the capacity of the first sub-tank 2441.

[0064] The second sub-tank 2442 communicates through piping with the inlets of the inkjet heads 241. Each inkjet head 241 is supplied with ink from the second sub-tank 2442 in accordance with the amount of ink to be ejected.

[0065] 3, each sub-tank 244 is provided with an atmosphere-opening flow path T3 that communicates with the atmosphere. An air pressure pump and an individual solenoid valve are provided in the atmosphere-opening flow path T3, and the inside of each sub-tank 244 can be individually pressurized or depressurized under the control of the control unit 40. In particular, by applying an appropriate negative pressure to the inside of the second sub-tank 2442, ink is prevented from leaking from the inkjet head 241 in normal times.

[0066] Further, each subtank 244 is provided with a heat retaining member that retains heat by heating the ink inside. The heat retaining member may be a rubber heater like the heating member, and is provided, for example, so as to be in contact with the outer surface of each subtank 244. In the present invention, the temperature of the ink is adjusted in advance by the ink heating device 243 and the heating member. Therefore, the output of the heat retaining member may be minimized.

[0067] Further, the first sub-tank 2441 and the second sub-tank 2442 are each provided with a liquid amount detection unit (not shown). The liquid amount detection unit is, for example, a float sensor. When the liquid amount detection unit detects that the liquid amount falls below a preset value, the control unit 40 sends ink from a tank on the upstream side in the liquid sending direction.

[0068] (Control unit) Returning to Fig. 2, the control unit 40 controls each unit constituting the inkjet recording apparatus 1. As shown in Fig. 2, the control unit 40 is connected to each unit constituting the inkjet recording apparatus 1. The control unit 40 includes a CPU (Central Processing Unit) 41, a RAM (Random Access Memory) 42, a ROM (Read Only Memory) 43, and the like.

[0069] The CPU 41 reads out various programs, data, etc. corresponding to the processing contents from a storage device such as the ROM 43 and executes them. The CPU 41 controls the operation of each part of the inkjet recording device 1 according to the executed processing contents. The RAM 42 temporarily stores various programs, data, etc. processed by the CPU 41. The ROM 43 stores various programs, data, etc. read out by the CPU 41, etc.

[0070] [Effects of the first embodiment] As described above, in the inkjet recording apparatus 1 according to the first embodiment, the ink heating device 243 is fixed to the outer surface of the carriage 242. Then, the ink heated by the ink heating device 243 is supplied to the inkjet head 241. According to this configuration, the distance from the ink heating device 243 to the inkjet head 241 can be short, so the ink heated by the ink heating device 243 does not cool easily. Therefore, there is less need to reheat the ink in the subtank 244 or the like, and the energy efficiency is excellent. Also, since the flow path of the ink heated by the ink heating device 243 is not exposed to the outside, the ink does not cool easily, and the energy efficiency is excellent. Also, in the conventional invention, the ink may solidify due to the heated ink cooling. In this case, the ink may clog the ink flow path, causing a liquid transfer failure, but the above configuration makes it possible to prevent such a liquid transfer failure.

[0071] Furthermore, in a configuration in which the ink is reheated in the subtanks 244, heat can interfere with each other between the subtanks 244, making it difficult to control the ink temperature appropriately. However, according to the inkjet recording apparatus 1 according to this embodiment, since heating is mainly performed by the ink heating device 243, the amount of heat provided by the heat retaining member of the subtank 244 can be minimized. Therefore, it is possible to suppress the above-mentioned mutual heat interference between the subtanks 244, and to control the ink temperature appropriately.

[0072] In particular, when the ink ejected by the inkjet recording apparatus 1 is a sol-gel phase transition ink, if the temperature of the ink drops before it is supplied to the subtank 244, the ink may undergo a phase transition to a sol state, which may cause problems when pumping the ink. However, in this embodiment, the ink can be pumped in a gel state, and therefore the above problem does not occur.

[0073] [Second embodiment] An inkjet recording apparatus 1 according to the second embodiment will be described with reference to Fig. 5. Note that the same reference numerals are used to designate configurations that are substantially the same as those in the first embodiment, and detailed descriptions thereof will be omitted.

[0074] 5, the inkjet recording apparatus 1 of the second embodiment differs from the first embodiment in that it includes a first ink heating device 2431 and a second ink heating device 2432 having the same configuration as the ink heating device 243. The second ink heating device 2432 is fixed to a second end, which is the outer surface of the carriage 242 facing the first ink heating device 2431. In addition, the first pipe T1 branches into two flow paths, which communicate with the first ink heating device 2431 and the second ink heating device 2432, respectively.

[0075] [Effects of the second embodiment] When the ink heating device 243 heats the ink, the amount of heat is very large. Specifically, when the ink heating device 243 heats 300 cc of ink to 90° C., the amount of heat is approximately 7000 J. Therefore, a temperature distribution occurs in the carriage 242 between the vicinity of the ink heating device 243 and the other portions. This causes a temperature distribution of the ink ejected from the inkjet head 241 near the ink heating device 243 and the other inkjet heads 241. As a result, the ink properties vary and the size of the droplets also varies, which may result in a deterioration in image quality.

[0076] Therefore, the inkjet recording apparatus 1 of the second and subsequent embodiments includes a temperature uniforming mechanism for uniforming the temperature of the carriage 242. The temperature uniforming mechanisms in the second embodiment are a first ink heating device 2431 and a second ink heating device 2432. In detail, the ink heating device 243 generates heat on the outer surfaces on both sides of the carriage 242, so that the temperature of the carriage 242 becomes approximately uniform on both ends. Therefore, according to the configuration of the second embodiment, it becomes easier to control the ink temperature, and deterioration of image quality caused by temperature distribution in the carriage 242 can be suppressed.

[0077] [Third embodiment] An inkjet recording apparatus 1 according to a third embodiment will be described with reference to Fig. 6. Note that the same reference numerals are used to designate configurations that are substantially the same as those in the first embodiment, and detailed descriptions thereof will be omitted.

[0078] The inkjet recording apparatus 1 according to the third embodiment differs from the first embodiment in that the first sub-tank 2441 is connected to the second sub-tank 2442 via a degassing module 245 fixed to the second end, which is the outer surface of the carriage 242.

[0079] {Degassing module} FIG. 7 is a schematic diagram showing a cross section of a cylindrical degassing module 245 taken along a plane passing through the central axis thereof. The degassing module 245 has a shape in which a number of gas-permeable membranes 2456 cover the periphery of a central tube 2454 inside an outer shell 2451 made of, for example, aluminum. A first end of the central tube 2454 is connected to an ink inlet 2452, and an opposing second end is sealed by a plug 2454a. The central tube 2454 has numerous fine holes 2454b (perforations) in its outer wall. The ink that flows into the central tube 2454 from the ink inlet 2452 flows out of these fine holes 2454b to the surroundings, passes between the gas-permeable membranes 2456, and flows out of the ink outlet 2453. In this way, the degassing module 245 is in the form of an external return flow.

[0080] The gas-permeable membrane 2456 is, for example, a hollow fiber membrane, and its membrane surface is gas permeable. The hollow fiber membrane has a structure of many hollow fine fibers with one end closed. The other end of the gas-permeable membrane 2456 is connected to a gas outlet 2455, and the inside is depressurized by sucking air with a vacuum pump (not shown). In this state, when ink comes into contact with the outer membrane surface of the gas-permeable membrane 2456, the ink comes into contact with the vacuum region across the gas-permeable membrane 2456, and only the air in the ink selectively permeates the membrane surface and flows to the vacuum side, and the ink is degassed.

[0081] Further, the degassing module 245 is provided on its outer circumferential surface with an apparatus heating section 2457. The apparatus heating section 2457 is, for example, a rubber heater, and heats the ink in the degassing module 245 under the control of the control section 40.

[0082] In general, the higher the temperature of a liquid, the less the amount of dissolved gas. Therefore, the control unit 40 heats the ink in the degassing module 245 using the device heating unit 2457, thereby improving the degassing efficiency of the degassing module 245. In this way, the control unit 40 functions as a second control unit that controls the temperature of the degassing module 245 by controlling the device heating unit 2457. Specifically, it is preferable that the control unit 40 controls the device heating unit 2457 so that the temperature of the ink is about 90° C., which is about 5 to 15° C. higher than the temperature of the ink when it is discharged from the inkjet head 241, which is about 80° C.

[0083] {Effect of the degassing module} In the inkjet head 241, if foreign matter such as air bubbles is mixed in the liquid to be discharged, there is a risk of discharge defects. Therefore, by providing the above-mentioned degassing module 245 in one of the head units 24, it is possible to remove dissolved gas in the ink that has flowed in before the liquid is sent to the inkjet head 241, and to discharge the degassed ink.

[0084] The degassing module 245 of the present embodiment can usually reduce the air concentration in the ink to a level that does not adversely affect the ejection of ink with one degassing. However, as a circulable flow path, it may be possible to further reduce the air concentration in the ink by performing degassing multiple times.

[0085] [Effects of the third embodiment] Suppose that the capacity of the degassing module 245 is 300 cc, and the control unit 40, which is the third control unit, controls the device heating unit 2457 to heat the ink inside to 90° C. as described above. At this time, the heat quantity of the degassing module 245 is about 7000 J, which is about the same as that of the ink heating device 243. Therefore, in the inkjet recording device 1 according to the third embodiment, the ink heating device 243 fixed to the first end of the outer surface of the carriage 242 and the degassing module 245 fixed to the second end function as a temperature uniforming mechanism. Then, since the temperature of the carriage 242 becomes approximately uniform at both ends, it becomes easier to control the temperature of the ink.

[0086] 5 shows a configuration in which the second sub-tank 2442 is provided in the approximate center of the carriage 242, as in the first embodiment, but this is not limited to this. In the second and third embodiments, it is preferable to provide the first sub-tank 2441 and the second sub-tank 2442 at a distance from each other on the first end and second end sides of the carriage 242, as shown in Fig. 6. With this configuration, both sub-tanks 2441 and 2442 are heated by a temperature uniforming mechanism, making it easier to control the ink temperature.

[0087] [Fourth embodiment] Next, an inkjet recording apparatus 1 according to a fourth embodiment will be described with reference to Fig. 8. Note that the same reference numerals are used to designate configurations that are substantially the same as those in the first embodiment, and detailed descriptions thereof will be omitted.

[0088] The inkjet recording apparatus 1 according to the fourth embodiment differs from the first embodiment in that a heat insulating member 246, which is a temperature uniforming mechanism, is interposed between the carriage 242 and the ink heating device 243.

[0089] {Thermal insulation materials} The heat insulating member 246 may be any suitable known material as long as it has low thermal conductivity and can be fixed to the carriage 242. The heat insulating member 246 is, for example, a fluorine-based rigid resin, but is not limited to this.

[0090] [Effects of the fourth embodiment] As described above, in the inkjet recording apparatus 1 according to the fourth embodiment, the heat insulating member 246, which is a temperature uniforming mechanism, is interposed between the carriage 242 and the ink heating device 243. According to this configuration, the heat generated by the ink heating device 243 is blocked by the heat insulating member 246 and is not transmitted to the carriage 242. Therefore, the temperature distribution in the carriage 242 is suppressed, and the deterioration of image quality caused by the temperature distribution of the ink can be suppressed.

[0091] [Fifth embodiment] Next, an inkjet recording apparatus 1 according to a fifth embodiment will be described. Note that the same reference numerals are used to designate configurations that are substantially the same as those in the first to fourth embodiments, and detailed descriptions thereof will be omitted.

[0092] The inkjet recording apparatus 1 according to the fifth embodiment differs in that a heat retaining member and a thermometer (not shown) are provided in each inkjet head 241. The control unit 40 functions as a third control unit that controls the temperature of each inkjet head 241 by changing the output of each heat retaining member based on measurement data acquired from each thermometer. Specifically, the control unit 40 controls the output of the heat retaining member of each inkjet head 241 so that the temperature increases from the vicinity of the ink heating device 243 to the farther away.

[0093] [Effects of the fifth embodiment] As described above, the control unit 40 of the inkjet recording apparatus 1 according to the fifth embodiment functions as a third control unit that controls the temperature of the inkjet head 241. The third control unit controls the temperature of the inkjet head 241 so that the temperature increases as the inkjet head 241 becomes farther from the ink heating device 243. This configuration makes it possible to adjust the temperature of the ink ejected from the inkjet head 241 heated by the ink heating device 243 and the inkjet head 241 heated by the heat retaining member to be approximately the same. This makes it possible to suppress image defects caused by uneven ink temperature.

[0094] Although the present invention has been specifically described above based on the embodiment, the present invention is not limited to the above embodiment. Of course, the present invention can be modified in various ways within the scope of the invention described in the claims and its equivalents. [Explanation of symbols]

[0095] 1 Inkjet recording device 241 Inkjet head 242 Carriage 243 Ink heating device 2431 First ink heating device (temperature uniformity mechanism) 2432 Second ink heating device (temperature uniformity mechanism) 244 Subtank 245 Degassing Module 2457 Equipment heating section 246 Insulation materials 50 control unit (first control unit, second control unit, third control unit (temperature uniforming mechanism)) 100 Ink Heating Unit MT Main Tank P Recording medium

Claims

1. An inkjet recording device that forms an image by ejecting ink from an inkjet head onto a recording medium, an ink heating device for heating the ink; a carriage on which a plurality of the inkjet heads are mounted; the ink heating device is fixed to an outer surface of the carriage; an inkjet recording apparatus, in which the ink heated by the ink heating device is supplied to the inkjet head;

2. A main tank for storing ink; a sub-tank that stores the ink heated by the ink heating device and supplies the ink to the inkjet head, 2. The ink jet recording apparatus according to claim 1, wherein the ink heating device heats the ink supplied from the main tank.

3. 3. The ink jet recording apparatus according to claim 1, wherein the ink heating device is fixed to an end portion of the carriage.

4. 3. The inkjet recording apparatus according to claim 1, further comprising a temperature uniforming mechanism for making the temperature inside the carriage approximately uniform.

5. the temperature uniforming mechanism includes a first ink heating device and a second ink heating device, the first ink heating device is fixed to a first end of the carriage; 5. The ink jet recording apparatus according to claim 4, wherein the second ink heating device is fixed to a second end of the outer surface of the carriage opposite to the first end.

6. the temperature uniforming mechanism includes the ink heating device and a degassing module that degasses dissolved gas in the ink; the ink heating device is secured to a first end of the carriage; The inkjet recording apparatus according to claim 4 , wherein the degassing module is fixed to a second end of the outer surface of the carriage opposite to the first end.

7. 5. The ink jet recording apparatus according to claim 4, wherein the temperature uniforming mechanism includes a heat insulating member interposed between the ink heating device and the carriage.

8. a first control unit for controlling the ink heating device; The inkjet recording apparatus according to claim 4 , wherein the first control unit controls the ink heating device so that the temperature of the ink is higher than the temperature of the ink ejected from the inkjet head.

9. The inkjet recording apparatus according to claim 8 , wherein the first control unit controls the temperature of the ink heating device so that the temperature is 5° C. to 15° C. higher than the temperature of the ink ejected from the inkjet head.

10. A second control unit is provided for controlling a temperature of the degassing module, The inkjet recording apparatus according to claim 6 , wherein the second control unit controls the degassing module so that the temperature of the ink is higher than the temperature of the ink ejected from the inkjet head.

11. The inkjet recording apparatus according to claim 10 , wherein the second control unit controls the temperature of the degassing module so that the temperature is 5° C. to 15° C. higher than the temperature of the ink ejected from the inkjet head.

12. the temperature uniforming mechanism includes a third control unit that individually controls temperatures of the inkjet heads, The inkjet recording apparatus according to claim 8 , wherein the third control unit controls the temperature of the inkjet head so that the temperature of the inkjet head increases as the inkjet head is located farther from the ink heating device.

13. 3. The ink jet recording apparatus according to claim 1, wherein a phase change ink is used, the phase change ink being capable of reversibly changing between a solid state and a liquid state at a phase change temperature.

14. an ink heating device for heating the ink; a carriage having the ink heating device fixed to an outer surface thereof.

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