Inkjet printing device

Abstract

A drying mechanism (30) has a first heater unit (31), a second heater unit (32), a duct (33), a temperature sensor (35), and a flow regulating unit. The first heater unit (31) has a radiant heat source (311) that radiates radiant heat toward a print medium and a first housing (312) that has a first opening (313) through which the radiant heat passes and that surrounds the radiant heat source (311). The second heater unit (32) has a warm air source (321) that generates warm air and a second housing (322) that has a second opening (328) through which the warm air passes and that surrounds the warm air source (321). The duct (33) communicates the atmosphere inside the first housing (312) with the atmosphere inside the second housing (322) into communication with each other. The temperature sensor (35) detects the temperature of the warm air from the warm air source (321). The flow regulating unit regulates, on the basis of a detection result provided by the temperature sensor (35), the flow of an air current which passes through the duct (33).

Description

Inkjet printing device

[0001] The present invention relates to an inkjet printing apparatus that performs printing by ejecting ink onto a print medium such as paper.

[0002] Conventionally, there has been known a printing apparatus that performs printing by ejecting ink onto the surface of a long, strip-shaped continuous substrate while the continuous substrate is transported by a plurality of transport rollers or the like. Such a printing apparatus is provided with a drying mechanism that dries the ink ejected onto the continuous substrate while the continuous substrate is transported. An inkjet printing apparatus provided with such an ink drying mechanism is described, for example, in Patent Document 1.

[0003] JP 2012-016949 A

[0004] In the offset printing press (1) of Patent Document 1, a discharge device (5) is provided downstream of printing mechanisms (8a-8f) that print on sheets. In the discharge device (5), dryer units (11a-11d) are arranged in sequence in the sheet transport direction (paragraph 0017). The dryer units (11a-11d) are composed of a hot air dryer, an infrared dryer, a UV dryer, or a combination dryer. In the case of a combination dryer, the sheets are dried using both hot air and light energy (paragraph 0020).

[0005] However, when using a hot air dryer or an infrared dryer, the hot air dryer takes significantly longer to start up after being turned on than the infrared dryer. Specifically, a hot air dryer may take as long as several tens of minutes after being started until it can generate hot air at a predetermined temperature. This may result in a decrease in work efficiency.

[0006] The present invention has been made in consideration of these circumstances, and aims to provide a technology that can shorten the time required for a hot air dryer to start up after being turned on when drying printing media using a hot air dryer and an infrared dryer.

[0007] To solve the above problems, a first invention of the present application is an inkjet printing device that prints by ejecting ink onto a print medium, and includes a transport mechanism, an ejection head, and a drying mechanism. The transport mechanism transports the print medium along a predetermined transport path. The ejection head ejects droplets of the ink onto the surface of the print medium transported by the transport mechanism. The drying mechanism heats the print medium onto which the ink droplets have been ejected, downstream of the ejection head along the transport path. The drying mechanism includes a first heater unit, a second heater unit, a duct, a temperature sensor, and a flow rate adjuster. The first heater unit includes a radiant heat source that radiates radiant heat toward the print medium, and a first housing that has a first opening that allows the radiant heat to pass through and surrounds the radiant heat source. The second heater unit is provided separately from the first heater unit. The second heater unit includes a hot air source that generates hot air and a second housing that has a second opening through which the hot air passes and surrounds the hot air source. The duct connects a first communication hole that communicates an internal space of the first housing with an external space at a position separated from the first opening and a second communication hole that communicates an internal space of the second housing with an external space at a position separated from the second opening, thereby communicating an atmosphere within the first housing with an atmosphere within the second housing. The temperature sensor detects the temperature of the hot air generated from the hot air source. The flow rate adjustment unit adjusts the flow rate of air passing through the internal passage of the duct based on the detection result by the temperature sensor.

[0008] The second invention of the present application is an inkjet printing device of the first invention, wherein the flow rate adjustment unit is a blower fan provided in the duct and whose rotation speed is adjustable, and when the blower fan rotates, an airflow is generated from within the first housing to within the second housing.

[0009] A third aspect of the present invention is the inkjet printing apparatus of the first aspect, wherein the flow rate adjusting unit is an on-off valve provided in the duct and capable of adjusting the opening degree thereof.

[0010] A fourth invention of the present application is an inkjet printing device according to any one of the first to third inventions, wherein the first heater unit further has a shutter plate that can open and close the first opening from outside the first housing, and a blackbody surface is formed on the opposing surface of the shutter plate that faces the radiant heat source when the first opening is closed.

[0011] A fifth invention of the present application is an inkjet printing device according to any one of the first to fourth inventions, wherein the first housing further has a warm air introduction hole that is spaced apart from the first communication hole and the first opening and that connects the internal space of the first housing with the external space, and the drying mechanism further has a second duct whose upstream end faces the second opening or communicates with the atmosphere inside the second housing and whose downstream end communicates with the warm air introduction hole and through whose internal passage the warm air passes.

[0012] According to the first to fifth aspects of the present invention, when the atmosphere inside the second housing is low, the atmosphere heated by the radiant heat source inside the first housing can be supplied to the second housing through the duct. This can support the heating of the warm air generated inside the second housing, thereby shortening the time it takes for the warm air to reach a predetermined temperature. Furthermore, after the warm air reaches the predetermined temperature, the supply of the atmosphere inside the first housing can be stopped, thereby preventing the warm air from heating up too much.

[0013] In particular, according to the fourth aspect of the present invention, the black body absorbs radiant heat and generates heat, thereby making it possible to heat the atmosphere inside the first housing more efficiently.

[0014] In particular, according to the fifth aspect of the present invention, the hot air generated from the hot air source until it reaches a predetermined temperature can be supplied into the first housing through the second duct, thereby more efficiently raising the temperature of the atmosphere inside the first housing.

[0015] FIG. 1 is a diagram conceptually illustrating the configuration of an inkjet printing apparatus of a first embodiment; FIG. 2 is a vertical cross-sectional view illustrating the schematic configuration of a drying mechanism of the first embodiment; FIG. 3 is a block diagram illustrating connections between a control unit of the first embodiment and each unit of the inkjet printing apparatus; FIG. 4 is a flowchart illustrating a procedure for starting up the drying mechanism of the first embodiment; and FIG. 5 is a vertical cross-sectional view illustrating the schematic configuration of a drying mechanism of a second embodiment.

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the components described in these embodiments are merely examples and are not intended to limit the scope of the present invention. Furthermore, in the drawings, the dimensions and numbers of each part may be exaggerated or simplified as necessary to facilitate understanding.

[0017] <1. First Embodiment> <1-1. Configuration of Inkjet Printing Apparatus> FIG. 1 is a conceptual diagram illustrating the configuration of an inkjet printing apparatus 1 according to a first embodiment of the present invention. The inkjet printing apparatus 1 is an inkjet printer that records characters and images on the surface of a long, strip-shaped continuous substrate 9 by ejecting droplets of aqueous ink from multiple ejection heads 21 toward the continuous substrate 9 while transporting the continuous substrate 9. However, the long, strip-shaped continuous substrate 9 is merely one example of a print medium. The print medium may be paper, or may be a substrate made of plastic film, cardboard, metal foil, or glass. In other words, the inkjet printing apparatus 1 may be any device that ejects ink onto a print medium to perform printing.

[0018] As shown in FIG. 1 , the inkjet printing apparatus 1 includes a transport mechanism 10 , a printing mechanism 20 , a drying mechanism 30 , and a control unit 90 .

[0019] The transport mechanism 10 transports the continuous substrate 9 along a predetermined transport path TR in a transport direction that is parallel to the longitudinal direction of the continuous substrate 9. The transport mechanism 10 transports the continuous substrate 9 using a roll-to-roll method. The transport mechanism 10 includes a feed roller 11, multiple transport rollers 12, a take-up roller 13, and a rotation drive unit 15. The feed roller 11, the multiple transport rollers 12, and the take-up roller 13 are rotatable about horizontal axes extending perpendicular to the transport direction. The rotation drive unit 15 rotates the take-up roller 13 by driving a motor or the like (not shown). Note that the rotation drive unit 15 may also rotate rollers other than the take-up roller 13 (such as the transport roller 12).

[0020] The feed roller 11 pays out the continuous base material 9 wound in a roll. Each transport roller 12 is arranged along the transport path TR of the continuous base material 9. The multiple transport rollers 12 support the continuous base material 9 fed from the feed roller 11 on the predetermined transport path TR. The take-up roller 13 winds up the continuous base material 9 that has passed through the transport path TR into a roll. In FIG. 1, the transport direction of the continuous base material 9 along the transport path TR is appropriately indicated by an arrow.

[0021] The printing mechanism 20 has multiple ejection heads 21. In this embodiment, the printing mechanism 20 has four ejection heads 21. Each of the four ejection heads 21 has a printable width greater than the size of the continuous substrate 9 in the lateral direction. Note that the "lateral direction" refers to a direction perpendicular and substantially horizontal to the transport direction, and indicates a direction perpendicular to the paper surface of FIG. 1 . The four ejection heads 21 have the same structure. The four ejection heads 21 are arranged in sequence along the transport path TR at intervals from each other in the transport direction. Each of the four ejection heads 21 ejects ink droplets from multiple nozzles (not shown) toward the surface (top surface) of the continuous substrate 9 transported by the transport mechanism 10. The four ejection heads 21 eject ink droplets of each color, K (black), C (cyan), M (magenta), and Y (yellow), in sequence downstream of the transport path to record a single-color image on the surface (top surface) of the continuous substrate 9. The droplets of K, C, M, and Y inks become the color components of a color image, and a multicolor image is formed on the upper surface of the continuous substrate 9 by superimposing the four single-color images.

[0022] The drying mechanism 30 is disposed downstream of the printing mechanism 20 in the transport direction. The drying mechanism 30 heats the continuous substrate 9 onto which ink droplets have been ejected by the four ejection heads 21 while being transported by the transport mechanism 10, downstream of the four ejection heads 21 in the transport path. The drying mechanism 30 dries the ink ejected onto the upper surface of the continuous substrate 9 by heating the continuous substrate 9. Note that the drying mechanism 30 in this embodiment is disposed above the transport path TR of the continuous substrate 9. However, the position at which the drying mechanism 30 is disposed is not limited to this.

[0023] Fig. 2 is a vertical cross-sectional view showing a schematic configuration of the drying mechanism 30. As shown in Fig. 2, the drying mechanism 30 has a first heater unit 31, a second heater unit 32, a duct 33, a temperature sensor 35, a first blower fan 331, a second blower fan 332, and a third blower fan 336.

[0024] The first heater unit 31 includes multiple radiant heat sources 311 and a first housing 312. In this embodiment, the first heater unit 31 includes two radiant heat sources 311. The radiant heat sources 311 are heating elements formed from so-called carbon heaters. The radiant heat sources 311 are connected to a power source via an ON / OFF circuit (not shown). When energized, the radiant heat sources 311 generate heat by passing electricity through the carbon fibers inside the radiant heat sources 311, and radiate radiant heat such as infrared rays. The radiant heat sources 311 radiate radiant heat toward the continuous substrate 9, which is the printing medium. This heats the continuous substrate 9 being transported near the first heater unit 31. This allows the water content, primarily in the ink ejected onto the top surface of the continuous substrate 9, to evaporate. Furthermore, the heat generated by the radiant heat sources 311 itself can warm the atmosphere within the first housing 312.

[0025] The first housing 312 is a housing that forms the outer wall of the first heater unit 31. In this embodiment, the first housing 312 has a rectangular parallelepiped shape composed of side walls 317, a bottom 318, and a top plate 319. However, the shape of the first housing 312 is not limited to this. Two radiant heat sources 311 are housed in the internal space of the first housing 312. That is, the first housing 312 surrounds each radiant heat source 311. In addition, the inner surface of the first housing 312 is mirror-finished. In particular, the lower surface of the top plate 319 is mirror-finished. This allows radiant heat from the two radiant heat sources 311 to be reflected and more radiant heat to be radiated to the continuous substrate 9 outside the first housing 312 through each first opening 313 (described later). Note that the first housing 312 may be further covered from the outside with a heat insulating material (not shown). This makes it possible to further increase the temperature of the atmosphere inside the first housing 312 when each radiant heat source 311 is energized.

[0026] A plurality of first openings 313 are provided in the bottom 318 of the first housing 312. In the present embodiment, two first openings 313 are provided in the bottom 318 of the first housing 312. Each of the two first openings 313 penetrates the bottom 318 and connects the internal space of the first housing 312 to the external space. The two first openings 313 can expose the internal space of the first housing 312 to the external space below the first housing 312. This allows each first opening 313 to pass radiant heat from the radiant heat source 311 and radiate the radiant heat to the continuous substrate 9 being transported below the first housing 312.

[0027] A shutter plate 36 and a shutter movement mechanism (not shown) are disposed near each first opening 313 of the first housing 312. Each shutter plate 36 extends in a plate shape along the lower surface of the bottom 318 of the first housing 312. Furthermore, when the first housing 312 is viewed from below, each shutter plate 36 is larger than the first opening 313. This allows each shutter plate 36 to close the first opening 313 from below without any gaps when it is in a closing position Pc (described later).

[0028] The shutter movement mechanism reciprocates the shutter plate 36 along the bottom 318 of the first housing 312 between a closed position Pc and an open position Po. The closed position Pc is a position where the shutter plate 36 tightly closes the first opening 313 from below. The open position Po is a position where the shutter plate 36 is separated horizontally from the closed position Pc and opens the first opening 313. Note that in FIG. 2 , the shutter plate 36 positioned at the open position Po is illustrated by a dashed line. This allows the shutter plate 36 to open and close the first opening 313 from outside the first housing 312. However, the structure for opening and closing the first opening 313 is not limited to this.

[0029] In this embodiment, the upper surface of the shutter plate 36 is coated with a black body to form a black paint. The black body is, for example, soot or platinum black. As a result, a black body surface 361 is formed on the upper surface of the shutter plate 36. That is, the black body surface 361 is formed on the surface of the shutter plate 36 that faces the radiant heat source 311 when the first opening 313 is closed. When the shutter plate 36 closes the first opening 313, the black body that forms the black body surface 361 absorbs the radiant heat radiated from the radiant heat source 311 and generates heat. As a result, the atmosphere inside the first housing 312 can be heated more efficiently. However, instead of forming the black body surface 361 on the upper surface of the shutter plate 36, an infrared absorbing film or the like may be formed.

[0030] Furthermore, a first communication hole 314 is formed in the side wall 317 of the first housing 312. The first communication hole 314 penetrates the side wall 317 of the first housing 312 and connects the internal space of the first housing 312 with the external space. However, the position where the first communication hole 314 is formed is not limited thereto. The first communication hole 314 may be provided in a position separated from the first opening 313.

[0031] Furthermore, a plurality of outside air introduction holes 315 are formed in the top plate 319 of the first housing 312. In this embodiment, three outside air introduction holes 315 are formed in the top plate 319 of the first housing 312. Each of the three outside air introduction holes 315 penetrates the top plate 319 of the first housing 312 and connects the internal space of the first housing 312 with the external space. This allows outside air to be appropriately taken in from the external space of the first housing 312 to the internal space. However, the positions at which each outside air introduction hole 315 is formed are not limited thereto. Each outside air introduction hole 315 may be provided at a position separated from the first opening 313 and the first communication hole 314.

[0032] The second heater unit 32 is provided separately from the first heater unit 31. The second heater unit 32 has multiple hot air sources 321 and a second housing 322. In this embodiment, the second heater unit 32 has three hot air sources 321. The hot air sources 321 are configured as so-called sheath heaters. The hot air sources 321 have nichrome wires, which are heating elements covered by metal pipes. The nichrome wires are spiral resistors connected to a power source via an ON / OFF circuit (not shown). When energized, the nichrome wires generate heat as electricity flows through them, warming the air that comes into contact with them. This allows the hot air source 321 to generate hot air (including hot air) at temperatures ranging from several tens of degrees Celsius to several hundred degrees Celsius. The hot air source 321 generates hot air and supplies it toward the continuous substrate 9 being transported near the second heater unit 32. As a result, it is possible to dry mainly the solvent component in the ink ejected onto the upper surface of the continuous substrate 9 .

[0033] Here, the warm air source 321 takes a much longer time to start up after being turned on than the radiant heat source 311. Specifically, if no measures are taken, the warm air source 321 may take a long time, on the order of several tens of minutes, after being turned on until it can generate warm air (including hot air) at a predetermined temperature.

[0034] The second housing 322 is a housing that forms the outer wall of the second heater unit 32. The second housing 322 of this embodiment has a hollow shape composed of a side wall 323, a bottom 324, and a top plate 325. The side wall 323 has a substantially cylindrical three-dimensional shape. The bottom 324 is a funnel-shaped portion that gradually converges downward from the lower end of the side wall 323. The top plate 325 covers the upper part of the side wall 323. Note that the shape of the second housing 322 is not limited to this. For example, the side wall 323 of the second housing 322 may be a rectangular cylinder.

[0035] Three hot air sources 321 are housed in the internal space of the second housing 322. That is, the second housing 322 surrounds each of the hot air sources 321. The second housing 322 may be further covered from the outside with a heat insulating material (not shown). This allows the temperature of the atmosphere inside the second housing 322 to be further increased when the hot air sources 321 are energized.

[0036] A second opening 328 is provided in the center of the bottom 324 of the second housing 322. The second opening 328 connects the internal space of the second housing 322 with the external space. The second opening 328 exposes the internal space of the second housing 322 to the external space below the second housing 322. This allows the hot air generated from the hot air source 321 to pass through the second opening 328. The second opening 328 is also provided with a plurality of nozzle valves (not shown). The hot air generated from the hot air source 321 is supplied from the plurality of nozzle valves to the continuous substrate 9 being transported below the second housing 322.

[0037] Furthermore, a second communication hole 326 is formed in the side wall 323 of the second housing 322. The second communication hole 326 penetrates the side wall 323 of the second housing 322 and connects the internal space of the second housing 322 with the external space. However, the position at which the second communication hole 326 is formed is not limited thereto. The second communication hole 326 may be provided in a position separated from the second opening 328.

[0038] A temperature sensor 35 is mounted near the second opening 328 of the second housing 322. The temperature sensor 35 detects the temperature of the warm air passing through the second opening 328. The temperature sensor 35 is also electrically connected to the control unit 90. The temperature sensor 35 outputs data related to the detection result of the warm air temperature to the control unit 90. However, the position where the temperature sensor 35 is mounted is not limited to this. The temperature sensor 35 may be any sensor that detects the temperature of the warm air (including hot air) generated from the warm air source 321 and outputs the detection result to the control unit 90.

[0039] The duct 33 is a pipe for passing a high-temperature airflow through its internal passage. The duct 33 is formed from a material having thermal insulation properties or is externally covered with a thermal insulation material (not shown). This prevents a decrease in the temperature of the airflow passing through the internal passage of the duct 33. The upstream end of the duct 33 is connected to the first communication hole 314 of the first housing 312, and the downstream end is connected to the second communication hole 326 of the second housing 322. In other words, the duct 33 connects the first communication hole 314 and the second communication hole 326, thereby communicating the atmosphere inside the first housing 312 with the atmosphere inside the second housing 322.

[0040] A first blower fan 331 is inserted in an internal passage near the upstream end of duct 33. A second blower fan 332 is inserted in an internal passage near the downstream end of duct 33. That is, first blower fan 331 and second blower fan 332 are each provided inside duct 33. Each of first blower fan 331 and second blower fan 332 uses an axial flow fan motor that rotates an impeller using the driving force of a motor (not shown) to generate an airflow from the upstream end of duct 33 to the downstream end of duct 33. As first blower fan 331 and second blower fan 332 rotate, an airflow is generated from inside first housing 312 to inside second housing 322.

[0041] The rotation speed of each of the first blower fan 331 and the second blower fan 332 is adjustable. The first blower fan 331 and the second blower fan 332 are electrically connected to the control unit 90. The control unit 90 adjusts the rotation speed of each of the first blower fan 331 and the second blower fan 332 based on data input from the temperature sensor 35. This allows the flow rate of the airflow passing through the internal passage of the duct 33 to be adjusted. That is, the first blower fan 331 and the second blower fan 332 can adjust the flow rate of the airflow passing through the internal passage of the duct 33 based on the detection result of the temperature sensor 35. The first blower fan 331 and the second blower fan 332 are each an example of a "flow rate adjustment unit" according to the present invention.

[0042] A branch pipe 38 is connected to a branch position Pb between the upstream end and downstream end of the duct 33. The upstream end of the branch pipe 38 is open to the space outside the branch pipe 38. Preferably, the upstream end of the branch pipe 38 is open to the space outside the inkjet printing apparatus 1. Furthermore, the internal passage of the branch pipe 38 is connected in communication with the internal passage of the duct 33 at the branch position Pb where the downstream end of the branch pipe 38 is located.

[0043] A third blower fan 336 is inserted in the internal passage near the upstream end of the branch pipe 38. The third blower fan 336 uses an axial flow fan motor that rotates an impeller using the driving force of a motor (not shown) to generate an airflow from the upstream end side (external space) of the branch pipe 38 toward the downstream end side (branch position Pb) of the branch pipe 38. The rotation of the third blower fan 336 generates an airflow that flows from the external space through the internal passage of the branch pipe 38 toward the internal passage of the duct 33.

[0044] The rotation speed of the third blower fan 336 is adjustable. The third blower fan 336 is electrically connected to the control unit 90. The control unit 90 adjusts the rotation speed of the third blower fan 336 based on data input from the temperature sensor 35. This makes it possible to adjust the flow rate of the airflow passing through the internal passage of the branch pipe 38. In other words, the third blower fan 336 can adjust the flow rate of the airflow passing through the internal passage of the branch pipe 38 based on the detection result of the temperature sensor 35.

[0045] Next, the control unit 90 will be described. The control unit 90 is an information processing device for controlling each unit of the inkjet printing apparatus 1. Fig. 3 is a block diagram showing the connection between the control unit 90 and each unit of the inkjet printing apparatus 1. As conceptually shown in Fig. 3, the control unit 90 has a processor 91 such as a CPU, a memory 92 such as a RAM, and a storage unit 93 such as a hard disk drive. The storage unit 93 stores a computer program 90P for executing a printing process while transporting the continuous substrate 9 and for drying the continuous substrate 9 onto which ink has been ejected.

[0046] 3, the control unit 90 is communicatively connected to the transport mechanism 10, the four ejection heads 21 of the printing mechanism 20, the two radiant heat sources 311 of the first heater unit 31 of the drying mechanism 30, the three hot air sources 321 of the second heater unit 32, the first blower fan 331, the second blower fan 332, the third blower fan 336, and the temperature sensor 35. The processor 91 of the control unit 90 controls the operation of each of these units in accordance with a computer program 90P. This allows the transport and printing process of the continuous substrate 9 to proceed, and the drying process of the continuous substrate 9 onto which the ink has been ejected to proceed.

[0047] 1-2. Procedure for Starting Up the Drying Mechanism and Performing the Drying Process Next, a procedure for starting up the drying mechanism 30 from a low-temperature state and performing the drying process on the continuous substrate 9 onto which ink has been ejected will be described. Fig. 4 is a flowchart showing the procedure for starting up the drying mechanism 30.

[0048] When starting up the drying mechanism 30, the control unit 90 first drives the shutter movement mechanism of the first heater unit 31 to move each shutter plate 36 to the closed position Pc and close each first opening 313. Then, the control unit 90 turns on the power to the radiant heat source 311 of the first heater unit 31 to energize it, and turns on the power to the hot air source 321 of the second heater unit 32 to energize the nichrome wire inside. The control unit 90 also drives the first blower fan 331, the second blower fan 332, and the third blower fan 336 (step S1). At this time, the rotation speed of the first blower fan 331 is set to be significantly higher than the rotation speed of the third blower fan 336. Note that the third blower fan 336 does not necessarily have to be driven at this time. The control unit 90 also turns on the power to the temperature sensor 35.

[0049] As a result, first, the radiant heat source 311 generates heat, and the black body forming the blackbody surface 361 of the shutter plate 36 absorbs the radiant heat radiated from the radiant heat source 311 and generates heat. Then, the atmosphere inside the first housing 312 and the outside air flowing into the first housing 312 through each outside air inlet 315 become hot due to thermal conduction from the radiant heat source 311 and the blackbody surface 361. The hot atmosphere inside the first housing 312 then flows into the internal passage of the duct 33 via the first communication hole 314 and into the second housing 322 via the second communication hole 326. Furthermore, the atmosphere inside the second housing 322 and the atmosphere flowing into the second housing 322 through the second communication hole 326 come into contact with the nichrome wire of the hot air source 321 and are slightly warmed. The slightly warmed atmosphere inside the second housing 322 is then discharged downward from a plurality of nozzle valves provided in the second opening 328 .

[0050] Furthermore, the temperature sensor 35 starts detecting the temperature of the hot air sent out from the second opening 328 of the second heater unit 32. In this embodiment, as described above, the atmosphere heated by the radiant heat source 311 in the first housing 312 is supplied into the second housing 322 via the duct 33, thereby supporting the temperature increase of the hot air generated in the second housing 322. This reduces the time required for the temperature of the hot air sent out from the multiple nozzle valves of the second opening 328 of the second housing 322 to reach or exceed a predetermined temperature.

[0051] Next, the control unit 90 gradually reduces the rotation speed of the first blower fan 331 to a predetermined rotation speed or less while confirming that the temperature of the hot air blown out from the multiple nozzle valves of the second opening 328 is gradually increasing based on data input from the temperature sensor 35. More specifically, the control unit 90 gradually reduces the rotation speed of the first blower fan 331 until it approaches substantially zero. This substantially stops the airflow from inside the first housing 312 to inside the second housing 322. Meanwhile, the control unit 90 gradually increases the rotation speed of the third blower fan 336 (step S2).

[0052] Next, when the rotation speed of the first blower fan 331 falls below a predetermined rotation speed, the control unit 90 determines whether the temperature of the hot air blown out from the plurality of nozzle valves of the second opening 328, as detected by the temperature sensor 35, is equal to or higher than the value necessary to dry the ink (step S3). More specifically, the control unit 90 determines whether the temperature of the hot air blown out from the plurality of nozzle valves of the second opening 328 is equal to or higher than a predetermined lower limit. If the detection result by the temperature sensor 35 is below the predetermined lower limit (step S3: No), the control unit 90 determines that the temperature of the hot air blown out from the hot air source 321 is not yet sufficiently high. Then, the control unit 90 again slightly increases the rotation speed of the first blower fan 331 (step S4) and again executes steps S2 to S3.

[0053] On the other hand, if the detection result by the temperature sensor 35 is equal to or higher than the value (predetermined lower limit) required to dry the ink (step S3: YES), the control unit 90 determines that the temperature of the hot air blown out from the hot air source 321 has risen sufficiently, and determines that startup of the drying mechanism 30 has been completed. The control unit 90 then starts transport of the continuous substrate 9 and the printing process. The control unit 90 drives the shutter movement mechanism of the first heater unit 31 to move each shutter plate 36 to the open position Po and open each first opening 313. As a result, radiant heat radiated from the radiant heat source 311 passes through the first openings 313 and travels downward.

[0054] The control unit 90 then operates the transport mechanism 10 to transport the continuous substrate 9 in the longitudinal direction along a predetermined transport path TR, while controlling the four ejection heads 21 to eject ink droplets onto the surface (upper surface) of the continuous substrate 9. This records an image on the surface of the continuous substrate 9. Thereafter, when the continuous substrate 9 arrives below the drying mechanism 30 located downstream of the printing mechanism 20, the radiant heat emitted from the radiant heat source 311 mainly evaporates the water content of the ink ejected onto the surface of the continuous substrate 9. Furthermore, the hot air supplied from the hot air source 321 dries mainly the solvent component of the ink, causing it to fix on the surface of the continuous substrate 9. As a result, the drying process of the image recorded on the surface of the continuous substrate 9 is completed.

[0055] As described above, in this embodiment, when the atmosphere inside the second housing 322 is low, the atmosphere heated by the radiant heat source 311 inside the first housing 312 can be supplied into the second housing 322 via the duct 33. This can support the increase in temperature of the warm air generated inside the second housing 322, thereby shortening the time required for the warm air to reach a predetermined temperature. Furthermore, after the warm air reaches the predetermined temperature, the supply of the atmosphere inside the first housing 312 is stopped, thereby preventing the warm air sent out from the second housing 322 from rising too high in temperature.

[0056] 2. Second Embodiment Next, the configuration of an inkjet printing apparatus according to a second embodiment of the present invention will be described. The following description will focus on differences from the first embodiment, and some overlapping descriptions of portions that are the same as those in the first embodiment will be omitted. Figure 5 is a vertical cross-sectional view showing the schematic configuration of a drying mechanism 30B according to this embodiment.

[0057] 5 , the drying mechanism 30B includes a first heater unit 31B, a second heater unit 32B, a duct 33B, a temperature sensor 35B, a second duct 37B, a first blower fan 331B, a second blower fan 332B, a third blower fan 336B, a fourth blower fan 371B, a fifth blower fan 372B, and a sixth blower fan 373B. The duct 33B, the temperature sensor 35B, the first blower fan 331B, the second blower fan 332B, and the third blower fan 336B of this embodiment have the same configurations as the duct 33, the temperature sensor 35, the first blower fan 331, the second blower fan 332, and the third blower fan 336 of the first embodiment.

[0058] In this embodiment, a plurality of outside air introduction holes 315B and a plurality of warm air introduction holes 316B are formed in the top plate 319B of the first housing 312B of the first heater unit 31B. In this embodiment, two outside air introduction holes 315B are formed in the top plate 319B. Each of the two outside air introduction holes 315B penetrates the top plate 319B of the first housing 312B and connects the internal space of the first housing 312B with the external space. This allows outside air to be appropriately introduced from the external space into the internal space of the first housing 312B.

[0059] The warm air introduction hole 316B penetrates the top panel 319B of the first housing 312B and connects the internal space of the first housing 312B with the external space. However, the position where the warm air introduction hole 316B is formed is not limited thereto. The warm air introduction hole 316B may be provided in a position in the first housing 312B that is separated from the first communication hole 314B to which the duct 33B is connected and the first opening 313B through which radiant heat from the radiant heat source 311B passes.

[0060] Furthermore, a hot air outlet hole 327B is formed in the bottom 324B of the second housing 322B of the second heater unit 32B of this embodiment. The hot air outlet hole 327B penetrates the bottom 324B of the second housing 322B and connects the internal space of the second housing 322B with the external space.

[0061] The second duct 37B is a pipe for passing hot air through its internal passage. The second duct 37B is formed from a thermally insulating material or is externally covered with a thermal insulating material (not shown). This prevents the temperature of the airflow passing through the internal passage of the second duct 37B from decreasing. The upstream end of the second duct 37B is connected to the hot air outlet hole 327B of the second housing 322B, and the downstream end is connected to the hot air inlet hole 316B of the first housing 312B. In other words, the second duct 37B connects the hot air outlet hole 327B and the hot air inlet hole 316B, thereby communicating the atmosphere inside the second housing 322B with the atmosphere inside the first housing 312B.

[0062] However, the second housing 322B does not necessarily have to be provided with the hot air outlet hole 327B. In this case, the upstream end of the second duct 37B may be disposed so as to face the second opening 328B of the second housing 322B, or may be inserted into the second housing 322B through the second opening 328B. That is, the upstream end of the second duct 37B may face the second opening 328B or communicate with the atmosphere inside the second housing 322B, and the downstream end may communicate with the hot air introduction hole 316B.

[0063] A fourth blower fan 371B is inserted in an internal passage near the upstream end of the second duct 37B. A fifth blower fan 372B is inserted in an internal passage near the downstream end of the second duct 37B. The fourth blower fan 371B and the fifth blower fan 372B each use an axial flow fan motor that rotates an impeller using the driving force of a motor (not shown) to generate an airflow from the upstream end of the second duct 37B toward the downstream end of the second duct 37B. The rotation of the fourth blower fan 371B and the fifth blower fan 372B generates an airflow from inside the second housing 322B toward inside the first housing 312B.

[0064] The rotation speeds of the fourth blower fan 371B and the fifth blower fan 372B are each adjustable. The fourth blower fan 371B and the fifth blower fan 372B are also electrically connected to a control unit. The control unit adjusts the rotation speeds of the fourth blower fan 371B and the fifth blower fan 372B based on data input from the temperature sensor 35B. This allows the flow rate of the airflow passing through the internal passage of the second duct 37B to be adjusted. That is, the fourth blower fan 371B and the fifth blower fan 372B can each adjust the flow rate of the airflow passing through the internal passage of the second duct 37B based on the detection results of the temperature sensor 35B.

[0065] A branch pipe 39B is connected to a branch position Pd between the upstream and downstream ends of the second duct 37B. The upstream end of the branch pipe 39B is open to the outside. The internal passage of the branch pipe 39B is connected to the internal passage of the second duct 37B at the branch position Pd where the downstream end of the branch pipe 39B is located.

[0066] A sixth blower fan 373B is inserted in the internal passage near the upstream end of the branch pipe 39B. The sixth blower fan 373B uses an axial fan motor that rotates an impeller using the driving force of a motor (not shown) to generate an airflow from the upstream end side (external space) of the branch pipe 39B toward the downstream end side (branch position Pd) of the branch pipe 39B. The rotation of the sixth blower fan 373B generates an airflow that flows from the external space through the internal passage of the branch pipe 39B toward the internal passage of the second duct 37B.

[0067] The sixth blower fan 373B has an adjustable rotation speed. The sixth blower fan 373B is electrically connected to the control unit. The control unit adjusts the rotation speed of the sixth blower fan 373B based on data input from the temperature sensor 35B. This allows the flow rate of the airflow passing through the internal passage of the branch pipe 39B to be adjusted. In other words, the sixth blower fan 373B can adjust the flow rate of the airflow passing through the internal passage of the branch pipe 39B based on the detection result of the temperature sensor 35B.

[0068] In this embodiment, when the drying mechanism 30B is started up to perform a drying process on the continuous base material onto which ink has been ejected, the same procedures as steps S1 to S4 described in the first embodiment are performed, and in step S1, the fourth blower fan 371B, the fifth blower fan 372B, and the sixth blower fan 373B are also driven. At this time, the rotation speed of the fourth blower fan 371B is set to be significantly higher than the rotation speed of the sixth blower fan 373B. At this time, the sixth blower fan 373B does not necessarily have to be driven.

[0069] As a result, in step S1, until the warm air generated from warm air source 321B reaches a predetermined temperature, the atmosphere heated by radiant heat source 311B in first housing 312B can be supplied into second housing 322B via duct 33B, and warm air slightly warmed by warm air source 321B in second housing 322B can be supplied into first housing 312B via second duct 37B. In other words, the warm air generated until the warm air generated from warm air source 321B reaches a predetermined temperature can be supplied into first housing 312B via second duct 37B rather than being sent downward (discarded) from second opening 328B. This makes it possible to more efficiently heat the atmosphere in first housing 312B.

[0070] In step S2, it is desirable to gradually decrease the rotation speed of the fourth blower fan 371B until it reaches a predetermined rotation speed or less. More specifically, it is desirable to gradually decrease the rotation speed of the fourth blower fan 371B until it approaches substantially zero. On the other hand, it is desirable to gradually increase the rotation speed of the sixth blower fan 373B.

[0071] 3. Modifications Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments.

[0072] In the drying mechanism of the above embodiment, a first blower fan and a second blower fan are provided to adjust the flow rate of the airflow passing through the internal passage of the duct. However, an on-off valve whose opening degree can be adjusted may be provided instead of the first blower fan. That is, the "flow rate adjustment unit" of the present invention may be an on-off valve provided in the duct and whose opening degree can be adjusted. This makes it possible to adjust the flow rate of the airflow passing through the internal passage of the duct, as in the first embodiment. Furthermore, an on-off valve whose opening degree can be adjusted may be provided instead of the third blower fan. This makes it possible to adjust the flow rate of the airflow passing through the internal passage of the branch pipe, as in the first embodiment.

[0073] In this modification, when the drying mechanism is started to dry the continuous substrate onto which ink has been ejected, the same procedures as steps S1 to S4 described in the first embodiment are performed, and in step S1, the on-off valves provided in place of the first and third blower fans are opened. The opening degree of the on-off valve provided in place of the first blower fan is then set to a value significantly larger than the opening degree of the on-off valve provided in place of the third blower fan. As in the first embodiment, this allows the high-temperature atmosphere inside the first housing to flow through the internal passage of the duct and further into the second housing 322.

[0074] In step S2, it is desirable to gradually decrease the opening of the on-off valve provided in place of the first blower fan until it is equal to or smaller than a predetermined opening. More specifically, it is desirable to gradually decrease the opening of the on-off valve provided in place of the first blower fan until it is almost closed. On the other hand, it is desirable to gradually increase the opening of the on-off valve provided in place of the third blower fan.

[0075] Similarly, in the second embodiment, the fourth blower fan 371B and the sixth blower fan 373B may each be provided with an on-off valve whose opening degree can be adjusted, thereby similarly adjusting the flow rate of the airflow passing through the internal passages of the second duct 37B and the branch pipe 39B.

[0076] Furthermore, the elements appearing in the above-described embodiments and modifications may be combined as appropriate within the scope of not causing any contradiction.

[0077] REFERENCE SIGNS LIST 1 Inkjet printing device 9 Continuous substrate 10 Transport mechanism 20 Printing mechanism 21 Discharge head 30, 30B Drying mechanism 31, 31B First heater unit 32, 32B Second heater unit 33, 33B Duct 35, 35B Temperature sensor 36 Shutter plate 37B Second duct 38 Branch pipe 39B Branch pipe 90 Control unit 311, 311B Radiant heat source 312, 312B First housing 313, 313B First opening 314, 314B First communication hole 315, 315B Outside air introduction hole 316B Warm air introduction hole 321, 321B Warm air source 322, 322B Second housing 326 Second communication hole 327B Warm air outlet hole 328, 328B Second opening 331, 331B First blower fan 332, 332B Second blower fan 336, 336B Third blower fan 361 Blackbody surface 371B Fourth blower fan 372B Fifth blower fan 373B Sixth blower fan Pb Branch position (on duct) Pc Closed position (of shutter plate) Pd Branch position (on second duct) Po Open position (of shutter plate)

Claims

1. An inkjet printing device that prints by ejecting ink onto a printing medium, comprising: a transport mechanism that transports the printing medium along a predetermined transport path; an ejection head that ejects droplets of the ink onto a surface of the printing medium transported by the transport mechanism; and a drying mechanism that heats the printing medium onto which the ink droplets have been ejected, downstream of the ejection head on the transport path; wherein the drying mechanism comprises: a first heater unit having a radiant heat source that radiates radiant heat to the printing medium and a first housing that has a first opening through which the radiant heat passes and surrounds the radiant heat source; and a second heater unit provided separately from the first heater unit and has a hot air source that generates hot air and a second housing that has a second opening through which the hot air passes and surrounds the hot air source. an inkjet printing device comprising: a duct that connects a first communication hole that is spaced apart from the first opening and that communicates an internal space of the first housing with an external space, and a second communication hole that is spaced apart from the second opening and that communicates an internal space of the second housing with an external space, and that communicates an atmosphere within the first housing with an atmosphere within the second housing; a temperature sensor that detects a temperature of the hot air generated from the hot air source; and a flow rate adjustment unit that adjusts a flow rate of air passing through an internal passage of the duct based on a detection result by the temperature sensor.

2. An inkjet printing device as described in claim 1, wherein the flow rate adjustment unit is a blower fan provided within the duct and whose rotation speed is adjustable, and an airflow is generated from within the first housing to within the second housing as the blower fan rotates.

3. An inkjet printing device according to claim 1, wherein the flow rate adjusting section is an opening / closing valve provided within the duct and capable of adjusting the opening degree.

4. An inkjet printing device as described in any one of claims 1 to 3, wherein the first heater unit further has a shutter plate capable of opening and closing the first opening from outside the first housing, and a blackbody surface is formed on the opposing surface of the shutter plate that faces the radiant heat source when the first opening is closed.

5. An inkjet printing device as described in any one of claims 1 to 4, wherein the first housing further has a hot air introduction hole spaced apart from the first communication hole and the first opening, communicating the internal space of the first housing with the external space, and the drying mechanism further has a second duct having an upstream end facing the second opening or communicating with the atmosphere inside the second housing, and a downstream end communicating with the hot air introduction hole, and allowing the hot air to pass through its internal passage.

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