Ink supply device and image forming apparatus

Abstract

To provide an ink supply device that quickly supplies ink of a viscosity suitable for discharging, to an inkjet head, to suppress temperature unevenness of the ink, and an image forming device.SOLUTION: An ink supply device includes: a main tank that stores ink; a sub-tank that stores the ink supplied from the main tank and supplies the stored ink to a plurality of connected inkjet heads; and a heating part that heats the ink before the ink flows into the sub-tank. The heating part includes a plurality of ink outlet parts capable of supplying inks of different temperatures to the sub-tank, in the middle of a flow path of the ink to be heated.SELECTED DRAWING: Figure 3

Description

Technical Field

[0004]

[0001] The present invention relates to an ink supply device and an image forming apparatus.

Background Art

[0002] Conventionally, an inkjet image forming apparatus that ejects ink from an inkjet head to form an image on a recording medium is known.

[0003] In addition, a relatively large inkjet image forming apparatus forms an ink flow path in which a plurality of tanks for storing ink are connected by pipes to transfer ink, and supplies ink from an upstream tank to an inkjet head through a downstream tank. It has an ink supply device.

[0004] In such an inkjet image forming apparatus, there is a problem that the temperature of the ink ejected from the nozzles of a plurality of inkjet heads varies, and as a result, the quality of the image printed on the recording medium deteriorates. In response to this, for example, in Patent Document 1, an inkjet recording apparatus is disclosed that has temperature control means capable of heating or cooling the temperature inside the inkjet head at all times to maintain a constant appropriate temperature regardless of use in tropical or cold regions, and the temperature of the ejected ink can be adjusted. <(

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the inkjet image forming apparatus described above, which has an ink supply device, if the ink temperature of the inkjet head is changed to a different temperature from the initially set temperature in order to eliminate temperature variations in the ink, the temperature of the temperature adjustment means is changed to a different temperature, which requires time for heating and presents a problem in that it cannot be addressed immediately.

[0007] The object of the present invention is to provide an ink supply device and an image forming apparatus that rapidly supply ink with a suitable viscosity for ejection to an inkjet head and suppress temperature unevenness of the ink. [Means for solving the problem]

[0008] The ink supply device according to the present invention is The main tank for storing ink, A sub-tank that stores the ink supplied from the main tank and supplies the stored ink to a plurality of connected inkjet heads, A heating unit that heats the ink before it flows into the sub-tank, It has, The heating unit has a configuration that includes a plurality of ink outlets in the middle of the ink flow path to be heated, each capable of supplying ink at a different temperature to the sub-tank.

[0009] The image forming apparatus according to the present invention is The ink supply device with the above configuration, The device has a configuration comprising an inkjet head that ejects the ink supplied from the ink supply device toward a recording medium, and a carriage that integrally includes the sub-tank. [Effects of the Invention]

[0010] According to the present invention, ink with a suitable viscosity for ejection can be rapidly supplied to the inkjet head, thereby suppressing temperature unevenness of the ink. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows a schematic configuration of an inkjet image forming apparatus having an ink supply device according to Embodiment 1. [Figure 2] This figure shows a block diagram illustrating the main functional configuration of the inkjet image forming apparatus in Embodiment 1. [Figure 3] This is a schematic diagram illustrating the general configuration of the ink supply device in Embodiment 1. [Figure 4] This is a plan view showing the main components of the lowermost heating channel in the ink heating section of the ink supply device according to the embodiment. [Figure 5] Figure 4 is a schematic perspective view showing the flow path of the ink heating section. [Figure 6] This is a characteristic graph illustrating the relationship between the heating channel section and ink temperature at each stage. [Figure 7] This is a schematic diagram illustrating the general configuration of the ink supply device in Embodiment 2. [Figure 8] This is a schematic plan view showing an example of the ink heating section in the ink supply device according to Embodiment 2. [Modes for carrying out the invention]

[0012] This embodiment will be described in detail below with reference to the drawings.

[0013] (Embodiment 1) Figure 1 is a schematic diagram showing an example of an inkjet image forming apparatus 1 including an ink supply device 15 in Embodiment 1.

[0014] The inkjet image forming apparatus 1 includes a paper feeding unit 10, an image forming unit 20, a paper discharge unit 30, and a control unit 40 (see Figure 2), etc. Under the control of the control unit 40, the inkjet image forming apparatus 1 transports the recording medium P stored in the paper feeding unit 10 to the image forming unit 20, forms an image on the recording medium P in the image forming unit 20, and transports (discharges) the recording medium P with the image formed on it to the paper discharge unit 30.

[0015] As the recording medium P, in addition to paper such as plain paper and coated paper, various media capable of fixing the ink landed on the surface, such as cloth or sheet-like resin, can be used.

[0016] The paper feeding unit 10 includes a paper feeding tray 11 for storing the recording medium P, and a medium supply unit 12 for conveying and supplying the recording medium P from the paper feeding tray 11 to the image forming unit 20.

[0017] The paper feeding tray 11 is a plate-like member provided so that one or a plurality of recording media P can be placed thereon. The paper feeding tray 11 is provided so as to move up and down according to the amount of the recording medium P placed on the paper feeding tray 11, and in the vertical movement direction, the uppermost recording medium P is held at a position where it is conveyed by the medium supply unit 12.

[0018] The medium supply unit 12 includes an annular belt supported by two rollers on the inside, and by rotating the rollers with the recording medium P placed on this belt, the recording medium P is conveyed from the paper feeding tray 11 to the image forming unit 20.

[0019] The image forming unit 20 includes a conveyance drum 21, a delivery unit 22, a medium heating unit 23, an ink head unit (hereinafter referred to as "head unit") 24, a fixing unit 26, and a delivery unit 27.

[0020] The conveyance drum 21 rotates around a rotation axis extending in a direction perpendicular to the plane of FIGURE 1 (hereinafter referred to as "orthogonal direction") while holding the recording medium P on the outer peripheral curved surface (conveyance surface) in a cylindrical shape, thereby conveying the recording medium P in the conveyance direction along the conveyance surface (refer to the arrow in FIGURE 1).

[0021] The conveyance drum 21 includes a claw portion and an air intake portion (not shown) for holding the recording medium P on its conveyance surface. The recording medium P is held on the conveyance surface by the end portion being pressed by the claw portion and being sucked toward the conveyance surface by the air intake portion.

[0022] The transport drum 21 has a transport drum motor (not shown) for rotating the transport drum 21, and rotates by an angle proportional to the amount of rotation of the transport drum motor. The transport drum 21 and the transport drum motor are responsible for transporting the recording medium P so that it is facing the inkjet head 242 of the head unit 24 (see Figures 2 and 3).

[0023] The transfer unit 22 transfers the recording medium P, which has been transported by the media supply unit 12 of the paper feeding unit 10, to the transport drum 21. The transfer unit 22 is located between the media supply unit 12 of the paper feeding unit 10 and the transport drum 21, and holds one end of the recording medium P transported from the media supply unit 12 with its swing arm 221 to pick it up and transfers it to the transport drum 21 via the transfer drum 222.

[0024] The medium heating unit 23 is located between the position of the transfer drum 222 and the position of the head unit 24, and heats the transport surface of the transport drum 21 and the recording medium P so that the recording medium P transported by the transport drum 21 reaches a temperature within a predetermined range. The medium heating unit 23 has, for example, an infrared heater, and generates heat by supplying power to the infrared heater based on a control signal supplied from the control unit 40 (see Figure 2).

[0025] The head unit 24 records (forms) an image by ejecting ink onto the recording medium P from nozzle openings (hereinafter referred to as "nozzles") provided on the ink ejection surface of the transport drum 21 facing the transport surface, at an appropriate timing corresponding to the rotation of the transport drum 21 in which the recording medium P is held. The head unit 24 is positioned such that there is a predetermined distance between the ink ejection surface (hereinafter referred to as "nozzle surface 24a") and the transport surface.

[0026] In the inkjet image forming apparatus 1 of this embodiment, there are four head units 24, each corresponding to one of four ink colors: yellow (Y), magenta (M), cyan (C), and black (K). The four head units 24 are arranged at predetermined intervals from the upstream side in the transport direction of the recording medium P, in the order of colors Y, M, C, and K.

[0027] Each head unit 24 is equipped with an inkjet head 242 (see Figure 2). The inkjet head 242 is provided with multiple recording elements, each having a pressure chamber for storing ink, a piezoelectric element provided on the wall of the pressure chamber, and a nozzle. When a drive signal is input to deform the piezoelectric element, the pressure chamber deforms due to the deformation of the piezoelectric element, changing the pressure inside the pressure chamber, and ink is ejected from the nozzle communicating with the pressure chamber.

[0028] The arrangement range of the nozzles in the inkjet head 242 in the orthogonal direction covers the width in the orthogonal direction of the area on the recording medium P transported by the transport drum 21 where the image is formed. The head unit 24 is used with its position fixed relative to the rotation axis of the transport drum 21 during image formation. In other words, the inkjet image forming apparatus 1 is a single-pass apparatus.

[0029] The head unit 24 is mounted on a carriage 60 (see Figure 3). The carriage 60 is configured to be movable in a predetermined direction by a head transport mechanism (not shown). Details of the carriage 60 will be described later.

[0030] The head transport mechanism moves the head unit 24 (carriage 60) under the control of the control unit 40 as follows: During image formation, the head transport mechanism moves the nozzle surface 24a of the inkjet head 242 to a position (printing area) facing the circumferential surface of the transport drum 21. On the other hand, during various maintenance procedures, the head transport mechanism moves the nozzle surface 24a of the inkjet head 242 to a position (maintenance area) facing a cleaning device (not shown).

[0031] The fixing unit 26 has light-emitting units arranged across the width of the transport drum 21 in a direction perpendicular to the drum. Under the control of the control unit 40, the fixing unit 26 irradiates the recording medium P placed on the transport drum 21 with energy rays such as ultraviolet light from the light-emitting units. The light-emitting units of the fixing unit 26 apply a predetermined amount of energy to the ink ejected onto the recording medium P, thereby curing the ink and fixing it to the recording medium P.

[0032] The delivery unit 27 includes a belt loop 272 having a ring-shaped belt supported on the inside by two rollers, and a cylindrical transfer drum 271 that transfers the recording medium P from the transport drum 21 to the belt loop 272. The delivery unit 27 transports the recording medium P that has been transferred from the transport drum 21 to the belt loop 272 by the transfer drum 271, and sends the recording medium P to the paper discharge unit 30.

[0033] The paper output unit 30 has a plate-shaped paper output tray 31 on which the recording medium P sent out from the image forming unit 20 by the delivery unit 27 is placed.

[0034] Figure 2 is a block diagram showing the main functional configuration of the inkjet image forming apparatus 1. The inkjet image forming apparatus 1 includes a media heating unit 23, an inkjet head drive unit (referred to as "head drive unit" in the figure) 241 and an inkjet head 242 of the head unit 24, a fuser unit 26, a coverage detection unit 33, an atmosphere detection unit 35, a control unit 40, a transport drive unit 51, an input / output interface 52, and an ink supply device 15, which will be described later. The coverage detection unit 33 detects the coverage amount of the recording medium P and outputs it to the control unit 40. The amount of ink used increases according to the coverage amount, and the ink temperature of the inkjet head 242 rises. The atmosphere detection unit 35 detects the internal temperature of the machine where the head unit 24 (carriage 60) is located. The atmosphere detection unit 35 is composed of a temperature sensor such as a thermistor and outputs the detected internal temperature to the control unit 40. The atmosphere detection unit 35 may be other elements or devices that can be used to detect temperatures other than a thermistor.

[0035] The inkjet head drive unit 241 supplies a drive signal to the recording element of the inkjet head 242 at an appropriate timing, based on the control of the control unit 40, causing the piezoelectric element to deform according to the image data. As a result, the inkjet head drive unit 241 ejects an amount of ink from the nozzle of the inkjet head 242 corresponding to the pixel value of the image data. In reality, multiple inkjet heads 242 are arranged within the head unit 24.

[0036] The control unit 40 is responsible for controlling the entire inkjet image forming apparatus 1. The control unit 40 includes a CPU 41 (Central Processing Unit), RAM 42 (Random Access Memory), ROM 43 (Read Only Memory), and a storage unit 44.

[0037] The CPU 41 reads various control programs and setting data stored in the ROM 43, stores them in the RAM 42, and executes the programs to perform various calculations. The CPU 41 also provides overall control over the operation of the inkjet image forming apparatus 1.

[0038] RAM42 provides the CPU41 with a working memory space and stores temporary data. RAM42 may also include non-volatile memory.

[0039] ROM43 stores various control programs and setting data executed by the CPU41. Alternatively, rewritable non-volatile memory such as EEPROM (Electrically Erasable Programmable Read Only Memory) or flash memory may be used instead of ROM43.

[0040] The storage unit 44 stores print jobs (print commands) and image data related to those print jobs that are input from the external device 2 via the input / output interface 52. For example, an HDD (Hard Disk Drive) may be used as the storage unit 44, and DRAM (Dynamic Random Access Memory) may also be used in combination.

[0041] The transport drive unit 51 supplies a drive signal to the transport drum motor of the transport drum 21 based on a control signal supplied from the control unit 40, causing the transport drum 21 to rotate at a predetermined speed and timing. The transport drive unit 51 also supplies drive signals to motors that operate the medium supply unit 12, the transfer unit 22, and the delivery unit 27 based on a control signal supplied from the control unit 40. As a result, the motors that receive the drive signals supply the recording medium P to the transport drum 21 and discharge it from the transport drum 21.

[0042] The input / output interface 52 mediates the transmission and reception of data between the external device 2 and the control unit 40. The input / output interface 52 is composed of, for example, various serial interfaces, various parallel interfaces, or a combination thereof.

[0043] External device 2 is, for example, a personal computer, which supplies image formation commands (print jobs) and image data, etc., to the control unit 40 via the input / output interface 52.

[0044] The ink supply device 15 stores the ink used in the inkjet image forming apparatus 1 in advance and supplies the ink to the inkjet head 242 while adjusting (controlling) the ink temperature during printing.

[0045] In this embodiment, an ink that undergoes a phase change between gel and liquid states depending on temperature is used. For example, an energy-ray irradiation type ink such as a UV ink, which is gel-like at room temperature, changes to a liquid state when heated, and solidifies when irradiated with energy rays during image formation, can be used.

[0046] As shown in Figure 2, the main components of the ink supply device 15 include, in order from the upstream side of the ink flow path, an ink storage tank 16 for storing ink, an ink heating unit 17, a first sub-tank 18, a second sub-tank 19, an outlet temperature detection unit 37, and a group of temperature detection units 39.

[0047] In this embodiment, the ink storage tank 16 corresponds to the "main tank" of the present invention. In the ink supply device 15, the ink heating unit 17 specifically heats the ink flowing through the ink channel from the ink storage tank 16 to the first sub-tank 18, raising its temperature and supplying inks of different temperatures to the inkjet head 242 via the first sub-tank 18 as appropriate. The ink in the inkjet head 242, which is continuous with the first sub-tank 18, is subjected to a back pressure (negative pressure) within a certain range by back pressure control. As a result, the ink meniscus is held retracted into the nozzle so that the ink is ejected appropriately.

[0048] Next, with reference to Figure 3, a more specific configuration of the ink supply device 15 will be described. Figure 3 is a schematic diagram illustrating the general configuration of the ink supply device in Embodiment 1. Figure 3 shows the ink supply device for each color in the inkjet image forming apparatus 1. Specifically, Figure 3 shows a carriage 60 having one of the four head units 24 shown in Figure 1, and the corresponding ink heating unit 17.

[0049] As shown in Figure 3, the ink supply device 15 has a flow path or circuit for circulating ink formed by connecting pipes t(t1, t3~t6) that serve as ink flow paths between the above-mentioned components (16~19) and at the outlet and inlet of the inkjet head 242. A detailed explanation of these pipes will be given later.

[0050] Furthermore, each component (16-19) of the ink supply device 15 or a predetermined pipe t is equipped with pumps 152, 155 and valves such as solenoid valves (flow valves) 153, 154a-154c, 156. These pumps 152, 155 and solenoid valves 153, 154a-154c, 156, etc. are operated under the control of the control unit 40, so that ink is supplied from the upstream ink storage tank 16 to the inkjet head 242 via the various parts downstream.

[0051] The ink supply device 15 is equipped with a heating source (not shown) such as a heater for heating the incoming ink in a predetermined tank (for example, the first sub-tank 18 and the second sub-tank 19). These heating sources are, for example, provided to contact the outer surface of each tank (18, 19).

[0052] Furthermore, each of the above-mentioned components (16-19) of the ink supply device 15, a predetermined tank or predetermined piping t, is equipped with a temperature sensor such as a thermistor (including an outlet temperature detection unit 37 and a temperature detection unit group 39) for detecting the ink temperature.

[0053] Furthermore, among the temperature sensors, the temperature sensor serving as the outlet temperature detection unit 37 is provided in the ink heating unit 17 together with the heater 70 (see Figure 4).

[0054] The outlet temperature detection unit 37 is provided in the ink heating unit 17 and detects the temperature of the ink flowing through multiple ink outlets 146a that supply ink to the first sub-tank 18. The detected temperature is output to the control unit 40.

[0055] Furthermore, among the temperature sensors, the temperature sensor group 39 detects the temperature when it is installed and outputs the result to the control unit 40. The temperature detection group 39 includes multiple temperature sensors that act as detection units, respectively, to detect the temperature inside the ink storage tank 16, the first sub-tank 18, the second sub-tank 19, and the inkjet head 242.

[0056] The control unit 40 controls the output (amount of heat generated) of the heating source based on the ink temperature detected by the temperature sensor. The control unit 40 adjusts the temperature of the ink flowing out of the heating unit 17, in particular, based on the ink temperature detected by the temperature sensor.

[0057] The ink storage tank 16 acts as the main tank for containing or storing ink at the upstream end of the ink flow path. In Figure 3, the ink storage tank 16 is actually a large-capacity tank capable of storing 10 liters or more of ink, such as 30 liters.

[0058] Generally, the ink supply device 15 has an ink heating unit 17, which will be described in detail later, connected downstream of the ink storage tank 16, and a first sub-tank 18 is connected to the outlet 176a of the ink heating unit 17 via piping t3. The piping t3 is connected to each of the multiple outlets of the heating unit 17, and as an example of a valve capable of opening and closing each ink outlet, solenoid valves 154 (154a~154c) for opening and closing the ink outlets are arranged.

[0059] The solenoid valve in the pipe t3 connected to the ink outlet 176a, which discharges the hottest ink, is an NO valve 154c that is normally open (closed when energized), while the solenoid valves in the pipe t3 connected to the outlets that discharge ink at other temperatures are NC valves 154a and 154b that are normally closed (open when energized).

[0060] The first sub-tank 18 stores ink supplied from the ink storage tank 16 (main tank) during image formation and primarily supplies the stored ink to a plurality of inkjet heads 242 located downstream via piping t4. The first sub-tank 18 is also connected to the second sub-tank 19 via a pump 155, which can supply ink to it. The first sub-tank 18 and the inkjet heads 242 are connected via piping t4.

[0061] The second sub-tank 19 is connected to the first sub-tank 18 via piping containing a pump 155, and is connected to the ink outlet (return port) of the corresponding inkjet head 242 via piping t5.

[0062] The second sub-tank 19 can recover any remaining ink from the ink supplied from the first sub-tank 18 to the inkjet head 242, i.e., ink that was not ejected by the inkjet head 242, through piping t5 via the operation of a pump 155 or the like. The recovered ink is supplied to the ink heating unit 17 via piping t6.

[0063] Alternatively, the second sub-tank 19 may be configured, through the action of a pump 155 or the like, to return (recover) the ink recovered from the inkjet head 242 into the first sub-tank 18. The recovered ink is supplied to the first sub-tank 18 from the heating unit 17 via piping t3. The ink returned from the second sub-tank 19 to the first sub-tank 18 is then reused by being supplied again to the inkjet head 242 via piping t4 or the like from the first sub-tank 18.

[0064] For simplicity, Figure 3 shows only four inkjet heads 242, but in reality, more inkjet heads 242 can be added. In this case, the number of second sub-tanks 19 and piping t4~t6 should be increased by the number of additional inkjet heads 242.

[0065] The inkjet head 242 has an ink outlet (return port) connected to a second sub-tank 19 via piping t5. Piping t5 is connected to piping t6, and piping t6 connects the inkjet head 242 to a first sub-tank 18. Piping t6 is equipped with a normally closed NC valve 157 that opens and closes the flow path between the inkjet head 242 and the heating unit 17.

[0066] Pipe t5, together with pipe t6, forms a return flow path from the inkjet head 242. Pipe t5 is equipped with a normally closed NC valve 156 that controls the return of ink from each inkjet head 242 to the second sub-tank 19 or the heating unit 17.

[0067] Conventional ink supply systems are configured to supply room-temperature ink stored in an ink storage tank 16 to a first sub-tank 18, and to heat the ink using a heating source (not shown) such as a heater provided in the first sub-tank 18. Alternatively, a heating source for heating the ink in the ink storage tank 16 may also be provided. These configurations have the problem of temperature unevenness (variation in ink temperature) occurring in the ink in the first sub-tank 18.

[0068] Specifically, a temperature distribution occurs depending on the position of the ink in the first sub-tank 18 (in other words, the distance from the heating source), which may cause variations (temperature differences) in the temperature of the ink supplied from the first sub-tank 18 to each inkjet head 242. Variations in the temperature of the ink ejected from each inkjet head 242 can lead to a decrease in image quality during image formation and ink drying (curing), potentially resulting in image defects.

[0069] To address this, attempts were made to improve the placement of the heating source in the first storage tank 18, or to control the temperature using a heating source in the ink storage tank 16, but these did not yield sufficient results. It should be noted that if the inkjet head 242 is equipped with a heating source such as a heater or a temperature sensor, the ink temperature can be controlled within the inkjet head 242. However, when controlling the ink temperature immediately before image formation, the ink tends to overheat, which is a problem.

[0070] To address these issues, the ink supply device 15 in Embodiment 1 includes an "ink heating unit 17" that heats the ink supplied from the ink storage tank 16 before it flows into the first sub-tank 18. This ink heating unit 17 can quickly supply inks of various different temperatures, i.e., inks of different viscosities, to the first sub-tank 18.

[0071] In this way, the ink supply device 15 adjusts itself to a state where it can supply ink that has been appropriately adjusted to various temperatures in advance on the upstream side of the first sub-tank 18, so that heating by the heating source in the first sub-tank 18 (amount of heating borne by the heating source) is not performed, or is performed as little as possible.

[0072] The ink supply device 15 controls the ink flow path by controlling the pump 152, solenoid valves 153, 154a-154c, 156, and pump 155. By controlling the ink flow path, the ink supply device 15 can supply ink at a suitable temperature from the ink storage tank 16 to the first sub-tank.

[0073] According to the ink supply device 15, the ink is heated in the ink flow path upstream of the first sub-tank 18 that supplies ink to multiple inkjet heads 242, and the ink is supplied to the first sub-tank 18 through a selected flow path (pipe t3) corresponding to the ink that has been heated to a desired temperature.

[0074] The ink stored in the first sub-tank 18 is at an appropriately set temperature. In other words, temperature variations in the ink supplied to each inkjet head 242 branchly from the outlet of the first sub-tank 18, and furthermore, temperature variations in the ink ejected from the inkjet head 242, can be suppressed or minimized. In addition, the output of the heating source of the first sub-tank 18 (the amount of heat required), or in other words, the power that should be supplied to the heating source of the first sub-tank 18, which is used to eliminate temperature variations, can be reduced to the minimum necessary, or the heating source of the first sub-tank 18 can be eliminated altogether.

[0075] The ink heating unit 17 has an ink inlet (inlet section) connected to the ink storage tank 16 via piping t1, a heating channel (corresponding to piping t2), and a plurality of ink outlets (outlet sections) provided along the channel, each connected to the first sub-tank 18 via piping t3.

[0076] The ink heating section 17 is constructed by stacking multiple heating channel sections (block bodies) 17A to 17C that constitute the flow path. The ink heating section 17 is configured such that the temperature of the ink entering from the lower ink inlet increases as it moves from the lower to the upper section, reaching the required maximum temperature at the top.

[0077] The configuration of the ink heating unit 17 will be described in detail below with reference to Figures 4 to 6.

[0078] Figure 4 is a plan view showing the main components of the lowest heating channel section in the ink heating unit of the ink supply device of Embodiment 1. Figure 4 shows the lowest heating channel section 17A of the ink heating unit 17. Figure 5 is a schematic perspective view showing the flow path of the ink heating unit shown in Figure 4. Note that in actual use, a cover (cover member) is attached to the heating channel section 17A. For the sake of explanation, Figure 4 shows the state with the cover member removed. Also, when the heating channel sections 17A to 17C are stacked, if the upper opening is closed at the bottom surface without any gaps so that the internal flow paths are partitioned, a cover member may not be necessary, and the ink inlet of the upper section becomes integrated with the ink outlet of the lower section. In this configuration, the top opening of the uppermost section is closed by the cover member.

[0079] Furthermore, the heating channel sections 17B and 17C are configured in the same way as heating channel section 17A, and heating channel section 17B is stacked with its horizontal orientation changed by 180 degrees so that it is connected to both heating channel section 17A and heating channel section 17C, forming a single channel. In Figure 5, the position of the ink outlet in heating channel section 17B has been changed from the position indicated by ink outlet 176a to the position indicated by ink outlet 1766a (for example, a position that is vertically aligned with the ink outlet 176a of heating channel sections 17A and 17C).

[0080] The heating channel section 17A is a block body having stackable upper and lower surfaces, and a channel is formed inside the main body 171 that is connected to an ink inlet and an ink outlet disposed on the outer surface. The heating channel section 17A is formed in a rectangular shape when viewed from above. The heating channel section 17A is preferably made of a material with high thermal conductivity, such as a metal such as aluminum.

[0081] The heating channel section 17A has an ink inlet 172, an ink connection port 178, an ink outlet 176a, and channel chambers 173, 175, and 177 that connect the ink inlet 172, the ink connection port 178, and the ink outlet 176a to form a channel.

[0082] The ink inlet 172 and ink connection port 178 are provided on the surfaces (upper and lower surfaces) where the main body 171 is stacked. The ink inlet 172 and ink connection port 178 are positioned to connect to the ink inlet of the other heating channel when another heating channel (the upper heating channel 17B in Figure 3) is stacked on top of the heating channel 17A.

[0083] In the heating channel section 17A, the ink inlet 172 and ink connection port 178 are arranged to be diagonally opposite each other in a plan view, and are connected to the channel chambers 173, 175, 177 and connecting sections 174, 176 within the heating channel section 17 to form a single channel.

[0084] The ink inlet 172 and ink connection port 178 are formed in a point-symmetric position with respect to the center of the rectangular surface of the main body 171, which is rectangular in plan view. As a result, the ink connection port 178 can be connected to the ink inlet 172 of the heating channel section 17B when the heating channel section 17B, which is formed in the same way as the heating channel section 17A, is placed on top of the heating channel section 17A with its horizontal orientation changed by 180 degrees.

[0085] The flow path chambers 173, 175, and 177 extend in one direction (longitudinal direction) inside the main body 171 and have hollow sections arranged parallel to each other. The flow path chambers 173, 175, and 177 are connected via connecting sections 174 and 176, and together with the connecting sections 174 and 176, they form a single meandering flow path. In the main body 171, ink inlets 172 and ink connection ports 178 open on the upper and lower surfaces at both ends of the meandering flow path.

[0086] Ribs 179 are erected within the flow chambers 173, 175, and 177, extending along their longitudinal direction. The ribs 179 increase the contact area with the ink flowing through the flow chambers 173, 175, and 177. When the flow chambers 173, 175, and 177 are heated by the heater 70, the ink flowing through them comes into contact with the ribs 179, allowing for a more effective temperature increase. In addition, the ribs 179 guide the flow of ink within the flow chambers 173, 175, and 177 so that the ink flows in one direction from the ink inlet 172 side to the other.

[0087] The connecting sections 174 and 176 connect adjacent flow chambers 173, 175, and 177, respectively. The connecting sections 174 and 176 can be configured in any way as long as they connect adjacent flow chambers 173, 175, and 177, respectively. The connecting sections 174 and 176 may be cylindrical bodies that connect adjacent flow chambers 173, 175, and 177 within the main body 171, or they may be concave notches, such as those with a semicircular cross-section, formed in the main body 171 to connect the flow chambers 173, 175, and 177 to each other.

[0088] The connecting portion 176 connects one end of the flow path chamber 175 to one end of the flow path chamber 177, and is also connected to an ink outlet 176a that communicates with the outside within the flow path chamber 177.

[0089] The ink outlet 176a is located in the middle of the flow path of the heating section 17, and the ink is discharged to the outside at a predetermined temperature by flowing the ink out in the flow path. The ink outlet 176a is located in each of the heating flow path sections 17A to 17C, and has a solenoid valve (NC valve), and is connected to the first sub-tank 18 via solenoid valves (NC valves) 154a to 154c.

[0090] In the heating channel section 17A, the heater 70 is positioned to heat the entire flow chambers 173, 175, and 177. In Figure 4, the orientation of the heater 70 relative to the heating channel section 17B may be changed in the horizontal direction of the heating channel section 17B so that the cable 72 is led out to the outside from the side of the ink outlet 176a.

[0091] For example, using the heating channel section 17A in Figure 4, an example of the configuration of the heating channel section 17B can be described. In the configuration of the heating channel section 17A, the ink outlet 176a continuous with the connecting section 176 is closed, and an ink outlet is formed continuous with the communication section 174, connecting the communication section 174 to the outside. The heating channel section 17B configured in this way is stacked on the heating channel section 17A, rotated 180 degrees so that the ink connection port 178 of the heating channel section 17A and the ink inlet 172 of the heating channel section 17B are connected, and the heating channel section 17C is stacked on top of that. The heating channel section 17C is configured in the same way as the heating channel section 17A, and when placed on the heating channel section 17B in the same orientation as the heating channel section 17A, the lower ink connection port 178 and the upper ink inlet 172 are connected, and the heating section 17 is constructed. Furthermore, in the heating section 17, the ink connection port 178 on the upper surface of the heating channel section 17C is closed. Thus, the heating channel sections constituting each stage of the heating section 17, which have a channel and an ink outlet 176a from that channel, are formed in the same manner. This makes it possible to easily adjust the length of the heated channel, that is, to increase or decrease the number of inks with different temperatures supplied to the first sub-tank, and also reduces the manufacturing cost of the configuration.

[0092] Figure 6 is a characteristic graph illustrating the relationship between each stage and ink temperature. As shown in Figure 6, in the ink heating unit 17, the ink supplied from the ink storage tank 16 enters the interior from the lower ink inlet 172 and is configured to rise through the flow path, with the ink temperature increasing as it moves upward. In other words, the temperature of the ink passing through the flow path increases by lengthening the flow path. The ink heating unit 17 is configured to discharge ink at different temperatures in three stages, and the temperatures T1, T2, and T3 of the ink flowing through the flow paths of lengths D1, D2, and D3, which extend from the lower stage to the middle and upstream stages, increase in proportion to the length of the ink flow.

[0093] As a result, the heating section 17 is configured in multiple stages by stacking the heating channel sections 17A to 17C, which makes the heated ink channel longer. This allows for a wider temperature range for the ink, enabling the supply of ink at a wide range of different temperatures to the first sub-tank 18.

[0094] <Effects> The ink supply device 15 of the inkjet image forming apparatus 1 heats the ink in the ink supply device 15 before supplying it to the first sub-tank 18 in the carriage 60 from the ink storage tank 16. This suppresses temperature variations in the ink ejected from the inkjet head 242.

[0095] Furthermore, in the inkjet image forming apparatus 1, if the inkjet head 242 is cold, such as immediately after power-up, the ink supply device 15 supplies ink from the ink outlet 176a of the uppermost heated flow channel section 17C, which has the highest temperature.

[0096] Then, once the internal temperature stabilizes, the ink is switched to the heating channel section 17B in the middle and supplied to the first sub-tank 18. As a result, the inkjet head 242 is supplied with ink that is at a lower temperature than before, thereby lowering the ink temperature.

[0097] If the temperature of the inkjet head 242 rises too high due to printing such as high-coverage continuous injection, the ink supply device 15 supplies ink from the lower heating channel section 17A. This allows the ink temperature of the inkjet head 242 to be lowered more effectively.

[0098] Furthermore, the ink supply device 15 is provided with multiple ink outlets 176a in the flow path of the heated ink, and inks at different temperatures are supplied to the first sub-tank 18 through these ink outlets 176a.

[0099] Therefore, in the valves of the ink outlets 176a that discharge multiple inks at different temperatures, multiple valves can be opened simultaneously to supply ink to the first sub-tank 18. In other words, multiple inks at different temperatures flow into the first sub-tank 18, and the inks mix inside and their temperatures are adjusted, so it is possible to supply even more inks at different temperatures than the ink discharged from each of the upper, middle, and lower stages. In short, more inks at different temperatures than the number of stages can be supplied to the first sub-tank 18, making the ink at a more suitable temperature and supplying it to the inkjet head 242, thus enabling ink ejection without temperature unevenness.

[0100] Furthermore, the ink supply device 15 can discharge ink at a temperature corresponding to the coverage amount from the heating unit 17 and supply it to the first sub-tank 18. This allows the temperature of the inkjet head 242, which heats up in accordance with the increase in coverage amount, to be lowered to a suitable temperature for ejection.

[0101] Furthermore, the ink supply device 15 can supply ink at a temperature corresponding to the detected temperature from the heating unit 17 to the first sub-tank 18, based on the temperature detected by the temperature sensing unit group 39. This eliminates temperature unevenness among multiple inkjet heads 242, allowing ink to be ejected at a suitable temperature. In addition, for inkjet heads 242 that eject different colors, ink of different colors can be ejected at the same appropriate temperature for each.

[0102] The heating channel sections 17A to 17C are stacked and connected so that each channel is configured as a single continuous channel. By stacking the heating channel sections 17A to 17C in multiple stages, the heated channel becomes longer, allowing ink to be discharged to the outside at an appropriate length. This widens the temperature range of the discharged ink. In addition, each heating channel section 17A to 17C is provided with a heater 70 to heat the channel. The heater 70 is connected to the control unit 40 via a cable 72.

[0103] According to the inkjet image forming apparatus 1, ink with a suitable viscosity suitable for ejection from the inkjet head 242 can be rapidly supplied to the inkjet head 242, thereby suppressing temperature unevenness of the ink.

[0104] In the ink supply device 15, the heating channel is adjusted to change the ink temperature, eliminating the need to variably control the temperature of the heater 70 that heats the ink. This results in a simpler configuration and reduces manufacturing costs.

[0105] (Embodiment 2) Figure 7 is a schematic diagram illustrating the general configuration of the ink supply device in Embodiment 2, and Figure 8 is a schematic plan view showing an example of the ink heating section in the ink supply device in Embodiment 2. Note that Figure 8 is a view from arrow A in Figure 7.

[0106] The ink supply device 90 shown in Figure 7 differs from the inkjet image forming apparatus 1 shown in Figure 1 only in the configuration of the ink supply device and carriage; the other basic configurations are the same.

[0107] The ink supply device 90 includes a plurality of ink storage tanks 162 to 165 for each color, carriages 62 to 65 each having an inkjet head 242 for each color, and a heating device 80 interposed between the ink storage tanks 162 to 165 and the carriages 62 to 65.

[0108] Ink storage tanks 162-165 store four different colors of ink: yellow (Y), magenta (M), cyan (C), and black (K). These inks are supplied to the heating device 80 via piping t11 by a pump (not shown). The piping t11 is also equipped with solenoid valves (normally closed NC valves) (not shown) that can stop the ink supply from each of the ink storage tanks 162-165.

[0109] Carriages 62 to 65 are configured similarly to carriage 60 shown in Figure 3, and each has a sub-tank for temporarily storing ink and an inkjet head 242 for ejecting ink supplied from the sub-tank. Carriages 62 to 65 also have a temperature sensing unit for detecting the temperature of the sub-tank, and the control unit 40 (see Figure 2) controls the temperature of the ink flowing out from the heating device 80 based on the temperature sensing result.

[0110] In Figure 7, carriages 62-65 are arranged side by side, with yellow (Y), magenta (M), cyan (C), and black (K) carriages 62-65 adjacent to each other. The ink temperatures within these carriages 62-65 are set to the same temperature. However, when the machine is in operation, the inner carriages 63 and 64, sandwiched between carriages 62 and 65, dissipate heat less efficiently than the outer carriages 62 and 65. As a result, the temperature of the magenta (M) and cyan (C) inks stored in the inner carriages 63 and 64 becomes higher than the temperature of the yellow (Y) and black (K) inks stored in the outer carriages 62 and 65.

[0111] The heating device 80 has integrated flow paths for each of the four ink colors: yellow (Y), magenta (M), cyan (C), and black (K), separated by partitions.

[0112] The heating device 80 has flow channel steps 81 to 83, each having a heating flow channel section 800 for each color, and the flow channel steps 81 to 83 are stacked so as to connect the flow channels of each heating flow channel section 800 for each color.

[0113] The heating device 80 is provided with heaters (for example, heaters similar to the heater 70 in Embodiment 1) in each of the flow path steps 81 to 83 to heat the flow path of the heating flow path 800.

[0114] The heating channel section 800 is similar to the heating channel section 17A shown in Figure 4, and each has a channel inside, an ink inlet 802 and an ink connection port 808 connected to both ends of the channel, and an ink outlet 806 for draining the ink from the channel to the outside.

[0115] In the flow channel sections 81-83 of the heating device 80, in the lower flow channel section 81, pipes t11 connected to ink storage tanks 162-165 are connected to the ink inlets of the heating flow channel sections 800, which differ for each color. As a result, each heating flow channel section 800 in the flow channel section 81 is supplied with ink corresponding to its respective color from the ink storage tanks 162-165.

[0116] The heating channel section 800 is configured to be stacked to form a single channel, similar to the heating channel section 17A. Furthermore, each ink outlet 806 of the heating channel section 800 in each channel step section 81-83 is fitted with a solenoid valve that can be opened and closed as needed between it and the connected pipe t12. This allows for the appropriate selection of ink from each ink outlet 806 of the heating channel section 800 in channel step sections 81-83 and supplying it to the carriages 62-65.

[0117] In the ink supply device 90 shown in Figures 7 and 8, the temperature of the magenta (M) and cyan (C) stored in the inner carriages 63 and 64, sandwiched between the carriages 62 and 65 on both sides, is higher than that of the yellow (Y) and black (K) stored in the outer carriage.

[0118] Therefore, in the heating device 80, in order to raise the temperature of the ink flowing through the internal channel, The ink outlet 806 of the lowest channel section 81 is closed, and the ink of each color flows into the channels within the heated channel sections 800 of each color, and then flows into the heated channel sections 800 of the middle and upper sections.

[0119] Since magenta (M) and cyan (C) have higher temperatures than yellow (Y) and black (K), the heating device 80 discharges magenta (M) and cyan (C) at the temperature of the middle channel step 82, and yellow (Y) and black (K) at the temperature of the upper channel step 83. In other words, carriages 63 and 64 are supplied with ink at a lower temperature than the ink supplied to carriages 62 and 65.

[0120] The sub-tanks of carriages 62-65 are supplied with inks at different temperatures (the ink in carriages 63 and 64 is at a lower temperature than that in carriages 62 and 65), which lowers the temperature of the ink in carriages 63 and 64 to the same temperature as the ink in carriages 62 and 65.

[0121] This suppresses temperature variations in the ink ejected from the inkjet head 242, thereby enabling the formation of a more suitable image. In the heating device 80, the ink outlets 806 for each color in each flow path step 81 to 83 can be opened and closed as appropriate.

[0122] Therefore, when setting the carriages 62-65 to a suitable temperature, or the ink temperature of the inkjet head 242 to a desired temperature, the openings can be selectively opened as needed to supply ink at the desired temperature to each color carriage 62-65. This allows for effective adjustment of the ink temperature ejected by the inkjet head 242 with a simple configuration and control.

[0123] In this way, even when inks at different temperatures are required to be ejected by the inkjet head 242, the inkjet head 242 can be supplied with ink at the appropriate temperature, thereby suppressing temperature unevenness and ejecting ink at a suitable temperature, i.e., ink with a suitable viscosity.

[0124] Furthermore, the above embodiments are merely examples of how the present invention may be implemented, and the technical scope of the present invention should not be limited by them. In other words, the present invention can be implemented in various ways without departing from its gist or its main features. [Industrial applicability]

[0125] According to the inkjet printing apparatus described herein, it is possible to rapidly supply ink with a suitable viscosity for ejection to the inkjet head, thereby suppressing temperature unevenness of the ink. [Explanation of symbols]

[0126] 1. Inkjet image forming apparatus (image forming apparatus) 2 External device 10 Paper feed section 11 Paper feed tray 12 Media supply section 15. Ink supply device 16. Ink storage tank (main tank) 17. Ink heating section 17A, 17B, 17C Heating channel section 18. First Sub-tank (Sub-tank) 19. Second Sub-tank 20 Image forming unit 21 Conveyor Drum 22 Transfer Unit 23 Medium heating section 24 Head Units 24a Nozzle surface 26 Fixing section 27 Delivery Department 30 Paper output section 31 Paper output tray 40 Control Unit 41 CPU 42 RAM 43 ROM 44 Memory section 51 Conveyor drive unit 52 Input / Output Interfaces 60, 62, 63, 64, 65 Carriage 70 Heater 72 Cables 80 Heating device 81, 82, 83 Channel step section 90 Ink supply device 152, 155 pumps 153, 154a, 154b, 154c, 156, 157 Solenoid valves (flow valves) 162, 163, 164, 165 Ink storage tanks 171 Main unit 172 Ink Inlet 173, 175, 177 Flow channel space 174, 176 Communication part 176a, 1766a Ink outlet 177 Flow channel space 178 Ink connection port 179 Rib 221 Swingarm section 222 drums 241 Inkjet head drive unit (head drive unit) 242 Inkjet Heads 271 Drums 272 Belt Loops 800 Heating channel section 806 Ink outlet 808 Ink outlet t, t1, t3, t4, t5, t6, t11, t12 piping t2 channel

Claims

1. The main tank for storing ink, A sub-tank that stores the ink supplied from the main tank and supplies the stored ink to a plurality of connected inkjet heads, A heating unit that heats the ink before it flows into the sub-tank, It has, The heating unit has a plurality of ink outlets in the middle of the flow path of the ink to be heated, each capable of supplying the ink at a different temperature to the sub-tank. Ink supply device.

2. The heating unit has a plurality of flow path valves that can open and close each of the plurality of ink outlets, and the plurality of ink outlets supply the heated ink to the sub-tank by switching the flow path valves. The ink supply device according to claim 1.

3. The heating unit includes an outlet temperature detection unit that detects the ink temperature of the ink flowing through the plurality of ink outlets. The plurality of ink outlets supply the ink to the sub-tank via the flow path valves, which are switched based on the temperature detected by the outlet temperature detection unit. The ink supply device according to claim 2.

4. The aforementioned multiple ink outlets supply multiple inks at different temperatures simultaneously. The ink supply device according to claim 1.

5. The ink supply device according to claim 1, The system comprises an inkjet head that ejects the ink supplied from the ink supply device toward a recording medium, and a carriage that integrally includes the sub-tank. Image forming apparatus.

6. The image forming apparatus has an atmosphere detection unit that detects the ambient temperature inside the main body of the image forming apparatus where the carriage is located. The heating unit has a plurality of flow path valves that can open and close each of the plurality of ink outlets, The ink supply device switches the flow path valve based on the detected ambient temperature to supply the ink to the sub-tank. The image forming apparatus according to claim 5.

7. It has a coverage detection unit that detects the coverage of recorded images, The heating unit has a plurality of flow path valves that can open and close each of the plurality of ink outlets, The ink supply device switches the flow path valve based on the detected coverage to supply the ink to the sub-tank. The image forming apparatus according to claim 5.

8. The system includes a flow path from the sub-tank to the inkjet head and a temperature detection unit for detecting the downstream ink temperature within the inkjet head. The heating unit has a plurality of flow path valves that can open and close each of the plurality of ink outlets, Based on the detected downstream ink temperature, the flow path valve is switched to supply the ink. The image forming apparatus according to claim 5.

9. The device has at least one of the following detection units: an atmosphere detection unit that detects the ambient temperature inside the main body of the device, a coverage detection unit that detects the coverage of the recorded image, and a temperature detection unit that detects the flow path from the sub-tank to the inkjet head and the ink temperature inside the inkjet head. The heating unit has a plurality of flow path valves that can open and close each of the plurality of ink outlets, Based on the detection result from the at least one detection unit, the flow path valve is switched to supply the ink. The image forming apparatus according to claim 5.

10. The temperature of the ink supplied from the ink outlet of the heating unit is less than or equal to the temperature of the ink in the sub-tank. The image forming apparatus according to claim 5.

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