Patent Application
20240198695
The present disclosure relates to a printing apparatus having a drying unit and to a drying control method.
Inkjet printing apparatuses that print an image on a printing medium using the inkjet method have been conventionally known. A technique of blowing hot air against a printing medium printed with ink to dry the ink is known to be used in an inkjet printing apparatus. Japanese Patent Laid-Open No. 2010-082937 (called Literature 1 below) discloses a technique of drying a printing medium by circulating hot air in a casing of a drying unit with the printing medium being present on a conveyance surface of the casing. What is disclosed is a configuration in which while there is no printing medium in the casing, air to be heated and circulated in the casing is heated with a temperature higher than the temperature for drying the printing medium in order to shorten the heating time. In the technique in Literature 1, the heating time cannot be shortened while a printing medium is in the casing.
What is sought is a technique for shorting heating time even while a printing medium may be in the casing.
According to an aspect of the present disclosure, an inkjet printing apparatus includes a printing unit configured to perform printing by ejecting ink to a printing medium, and a drying unit configured to dry the printing medium, wherein the drying unit includes an air blower having an entry and an exit, a heater configured to heat air sent from the exit of the air blower, a casing having a first portion configured to communicate with the heater, and a second portion that is configured to communicate with the first portion and is configured to pass the printing medium through the second portion, a first collection path configured to communicate with the first portion and the entry of the air blower, a second collection path configured to communicate with the second portion and the entry of the air blower, and an exhaust amount regulator configured to switch between a first regulation state in which air circulates through the first portion and the first collection path and a second regulation state in which air circulates through the second portion and the second collection path, wherein the exhaust amount regulator is a regulation value disposed in each of the first and second collection paths.
Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
A drying unit of a printer dries a printing medium using a drying temperature and heats air in a casing using a heating temperature. By making the heating temperature higher than the drying temperature, the time it takes for the air in the drying unit to reach the drying temperature is shortened. However, a high heating temperature with a printing medium in the casing causes air at the high heating temperature to flow toward the printing medium in the casing due to air circulation in a step of bringing the temperature to the drying temperature, and part of the air at the high heating temperature acts on the printing medium.
In drying of a cut sheet of paper, sheet conveyance to the drying unit is intermittent, and therefore, in the intervals, air in the casing of the drying unit can be heated at a temperature higher than the drying temperature. Meanwhile, in drying of a roll of paper, in a case where the temperature in the drying unit drops, a need arises to heat the air with a sheet being present in the casing because there is no timing of sheet breaks. Thus, the heating temperature cannot be higher than the drying temperature.
The following describes embodiments of the present disclosure in concrete terms with reference to the drawings. In the present disclosure, an X-axis, a Y-axis, and a Z-axis are used appropriately as axes of directions used to illustrate, e.g., the layout of the inkjet printing apparatus. The X-axis and the Y-axis are orthogonal to each other on the horizontal plane. The Z-axis is a vertical axis orthogonal to the X-axis and the Y-axis. As will be described later, the X-axis is the same as the direction in which a printing medium travels in conveyance of the printing medium.
A printing apparatus 1 of the present disclosure is a high-speed line printer that uses a rolled continuous printing medium and is suitable for, e.g., mass printing or large-format printing. A printing apparatus having a drying unit and a drying control method of the present disclosure may be used for printers using latex ink, water pigment, solvent ink, or the like.
The printing medium supply unit 2 is a unit for holding and supplying the printing medium M. The printing medium M may be rolled into the shape of a roll 12. The printing medium supply unit 2 includes the roll 12 and draws the printing medium M from the roll 12 and supplies the printing medium M. Two or more rolls may be housed in the supply unit 2, and the supply unit 2 may select one of the plurality of rolls and supply the printing medium M therefrom. Alternatively, the continuous printing medium M may be in the shape such that, for example, perforations are provided per unit length, bent along the perforations, and stacked.
The first conveyance roller pair 3 is a unit for feeding the printing medium M along the printing medium conveyance route (the solid line S), and the printing medium M is conveyed to pass the meandering correction unit 4, the tension detection unit 5, the printing unit 6, and the post-treatment unit 8, in this order. The first conveyance roller pair 3 applies tension to the printing medium M by cooperating with the second conveyance roller pair 9 to be described later. The first conveyance roller pair 3 is rotated by a motor (not shown) and conveys the printing medium M while applying tension thereto.
The meandering correction unit 4 is a unit for correcting the meandering of the printing medium in the width direction thereof during conveyance of the printing medium M. The meandering correction unit 4 includes meandering correction rollers 4a and a meandering detection sensor (not shown) that detects meandering of the printing medium M. The meandering correction rollers 4a can be changed in their slant relative to the printing medium M by a motor (not shown) and correct the meandering of a printing medium by changing their slant based on measurements by the meandering detection sensor. In this event, a meandering correction function can be enhanced by the printing medium being wound around the meandering correction rollers 4a.
The tension detection unit 5 is a unit for detecting tension applied to the printing medium M between the first conveyance roller pair 3 and the second conveyance roller pair 9. The tension detection unit 5 can detect tension during conveyance of the printing medium M.
The printing unit 6 is a printing medium processing unit that uses printheads 13 to perform printing processing, from above, on the printing medium M being conveyed. Guide rollers 14 arranged to form an arc shape form a conveyance route for the printing medium M. By receiving certain tension and coming into contact with the guide rollers 14 arranged to form an arc shape, the printing medium M has a clearance from the printheads 13. The printheads 13 are, like the conveyance route formed by the guide rollers 14, a plurality of printheads arranged to form an arc shape in the conveyance direction. The plurality of printheads 13 are integrally held by a head holder 15 capable of moving in the Z-axis direction, and the clearance between the printing medium M and the printheads 13 can be changed by the head holder 15 moving in the Z-axis direction.
In the present disclosure, the printheads 13 may be four line-type printheads supporting four colors: Bk (black), Y (yellow), M (magenta), and C (cyan). The number of colors and the number of printheads 13 may be fewer than four or more than four. The inkjet method employed by the printing unit 6 may be a method using heat generating elements, a method using piezoelectric elements, a method using electrostatic elements, a method using MEMS elements, or the like. Ink of each color is supplied to the corresponding printhead 13 from an ink tank (not shown) through an ink tube (not shown).
The head cleaning unit 7 includes cleaning units (not shown) that clean the ink ejection surfaces of the printheads 13 and cap units 16 that keep moisture on the ink ejection surfaces of the printheads 13. Each cap unit 16 shields the ejection nozzles of the printhead 13 from outside air by coming into contact with the ejection nozzles and thereby prevents them from drying out.
The plurality of cleaning units and cap units 16 are arranged to form arc shapes in such a manner as to correspond to the respective printheads 13 and are integrally held by a cleaning holder 17.
The post-treatment unit 8 is a unit that vaporizes moisture contained in the ink applied to a printing medium by the printing unit 6 to enhance the fixation between the printing medium and the ink. The post-treatment unit 8 includes a drying unit 20, a fixation unit 30, and a cooling unit 40.
The drying unit 20 dries ink applied to the printing medium M by heating the printed printing medium M. Details will be described later.
The fixation unit 30 heats, with a predetermined temperature, the printing medium M which has been dried by the drying unit 20, thereby softens and melts the ink, and enhances the fixation of the ink to the printing medium. In the fixation unit 30, hot air is applied, at least from the −Z-axis direction, to the printing medium M passing therethrough to fixate the ink onto the printing medium M. The hot air in the fixation unit 30 may be at a temperature equal to or higher than the temperature of the hot air in the drying unit 20. Alternatively, the fixation method may be a method involving application of electromagnetic waves (such as ultraviolet or infrared rays) to the surface of the printing medium M, a method involving application of heat and pressure by sandwiching the printing medium M with heat generators, or a combination of the above.
The cooling unit 40 cools the printing medium M which has been heated by the fixation unit 30 to solidify the softened ink. Solidifying the ink helps prevent a change in the state of the printing medium and of the ink in the process downstream in the printing apparatus. In the cooling unit 40, the printing medium M being conveyed therethrough is cooled by receiving air at a temperature lower than the printing medium M at least from the −Z-axis direction side. Alternatively, the cooling method may be a heat conduction and transfer method bringing a heat release member into contact, or a combination of the above.
The second conveyance roller pair 9 is a unit that adjusts the tension of the printing medium M in cooperation with the first conveyance roller pair 3 so that the printing medium M may be conveyed under tension. The second conveyance roller pair 9 is rotated by a motor (not shown). A tension control unit 100 adjusts the tension of a printing medium using a clutch (not shown) capable of controlling a drivingly-coupled torque according to a tension value detected by the tension detection unit 5. Alternatively, the tension detection unit 5 may adjust the tension of the printing medium M by controlling the speed of the second conveyance roller pair 9. Two tension control methods may be employed: a torque controlling method which controls a torque value transmitted from the clutch and a speed controlling method which controls the roller speed of the second conveyance roller pair. These two tension control methods may be switched according to the purpose or may be used at the same time.
The printing medium collection unit 10 is a unit for winding in the printing medium M which has undergone the printing processing. The printing medium collection unit 10 has a winding core. Alternatively, the printing medium collection unit 10 may have two or more winding cores and select one of the winding cores to collect the printing medium M. Note that depending on the type of processing the printing medium M will be subjected to after the printing, the following configuration may be employed instead of the configuration in which the printing medium M is wound around the winding core. Specifically, the continuous printing medium M may be cut using a cutter, and cut pieces of the printing medium M may be stacked.
The control unit 11 is a unit that performs overall control of the units of the printing apparatus. The control unit 11 has a controller including a CPU, a storage apparatus, and various control units, an external interface, and an operation unit 18 for user input and output. The operation of the printing apparatus 1 is controlled based on commands from the controller or from the host apparatus 19 connected to the controller via the external interface, such as a hot computer.
The casing 201 has a first portion 210 (also referred to as a “pressure chamber”) and a second portion 222. The casing 201 has a vent surface 240 provided between the first portion 210 and the second portion 222. The vent surface 240 has a plurality of opening portions 245 communicating with the first portion 210 and the second portion 222. The printing medium M is conveyed through the second portion 222.
The hot air supply port 235 and the first exhaust port 250 are disposed at the first portion 210, and the second exhaust port 260 is disposed at the second portion 222.
An air blower 220 is disposed between the supply path 280 and the merge path 286. An exit 222 of the air blower 220 communicates with the supply path 280, while an entry 224 of the air blower 220 communicates with the merge path 286. A heater 230 is disposed inside the supply path 280. The heater 230 is provided with a temperature detection unit (not shown). Heating of the heater 230 is controlled according to a predetermined hot air temperature based on the temperature detected by the temperature detection unit. Air supplied from the air blower 220 to the first portion 210 is heated by the heater 230, and is sent back to the air blower 220 from the first exhaust port 250 or the second exhaust port 260. A pressure difference generated by the air blower causes air to circulate, and the first portion 210 may be pressurized.
An exhaust amount regulator 270 is disposed in the first collection path 282 and the second collection path 284. As will be described later, the exhaust amount regulator 270 causes air to be circulated in the drying unit between the air blower 220 and the first portion 210 in a first regulation state and between the air blower 220, the first portion 210, and the second portion 222 in a second regulation state. Circulating and heating air in the drying unit 20 may reduce the amount of heat to be applied by the heater 230 and cut down power consumption. The exhaust amount regulator 270 may be disposed in one of the first collection path 282 and the second collection path 284.
While the printing medium M is being dried, the humidity inside the casing 201 of the drying unit is increased by evaporation of the moisture of the ink applied to the printing medium M. Because excessively high humidity decreases the drying efficiency, the casing 201 includes an air ventilator (not shown) in every embodiment of the present disclosure. Periodically changing the air inside the casing 201 using the air ventilator may help control humidity increase.
In the first regulation state, the first regulation valve 270a is open, the second regulation valve 270b is closed, and air is circulated and heated through the air blower 220 and the first portion 210 (
Meanwhile, movement of hot air in direction A2′ is restricted because the second regulation valve 270b is closed and the opening portions provided in the vent surface 240 are small, restricting the flow amount. Thus, hot air circulates in the first portion 210 and moves in direction A2 from the first exhaust port 250. Air exhausted from the first exhaust port 250 is sent in direction A4 through the first regulation valve 270a and is returned to the air blower 220. Thus, in the first regulation state, hot air is circulated and heated between the air blower 220 and the first portion 210.
Movement of hot air in direction A2 is restricted in the second regulation state because the first regulation valve 270a is closed and the second regulation valve 270b is open. Thus, hot air flows in direction A2′ through the plurality of opening portions 245 of the vent surface 240, flows into the second portion 222, heats the printing medium, and is then exhausted from the second exhaust port 260 in direction A3. The air exhausted from the second exhaust port 260 is sent in direction A4 through the second regulation valve 270b and is returned to the air blower 220. Thus, in the second regulation state, hot air is circulated between the air blower 220, the first portion 210, and the second portion 222 and heats and dries the printing medium M.
The first exhaust port 250 and the second exhaust port 260 may be placed at any positions, and there may be a plurality of them. For example, the configuration shown in
In the first regulation state shown in
In the second regulation state shown in
In the first regulation state shown in
In the second regulation state shown in
In the first regulation state shown in
In the second regulation state shown in
The opener-closer 370 of the fourth embodiment may be used solely. Alternatively, the opener-closer 370 may be combined with any of the valves of the other embodiments. Although combined with the flapper valve 570 in the third embodiment in
In any of the embodiments, the drying unit 20 may be configured such that the area of the first exhaust port 250 is larger than the area of the plurality of opening portions 245 of the vent surface 240. Alternatively, in any of the embodiments, the exhaust amount regulator 270 may form an intermediate state, instead of the first and second regulation states described above, where the first and second collection paths are open so that less amount of hot air may pass through the second portion to heat the printing medium. The degree of opening of the first and second collection paths in the intermediate state may be 50%. In any of the embodiments, although the hot air supply port 235, the first exhaust port 250, and the second exhaust port 260 are formed in the Y-direction, the present disclosure is not limited to this, and they may be disposed in various disposition directions and at various disposition angles.
Next, using the flowchart in
In Step S6, it is determined whether drying preparation has been started. If it is determined that drying preparation has been started, in Step S7 the drying unit 20 is brought to the second regulation state, and the operation to be performed before drying the printing medium M ends. After the printing medium has been heated, the exhaust amount regulator may be brought back to Step S1.
Although the printing medium is inside the drying unit 20 all the time from the above-described pre-drying operation to completion of drying, the above-described steps make it possible to heat the air in a short period of time while reducing damage on the printing medium by controlling blowing of hot air against the printing medium. Specifically, thermal deformation of the printing medium in the dryer is reduced, and in turn, generation of creases resulting from the thermal deformation can be reduced. Also, in a case where a printing medium which has been dried is unwound and used again for printing, influence of heat in drying may be reduced, and quality can be improved. In examples, a warm air state is determined based on whether the temperature of hot air has exceeded the temperature for heating the printing medium and whether the surface temperature of the pressure chamber 210 has exceeded a particular temperature; however, the present disclosure is not limited to this.
Embodiments of the present disclosure can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described Embodiments and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described Embodiments, and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described Embodiments and/or controlling the one or more circuits to perform the functions of one or more of the above-described Embodiments. The computer may include one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read-only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc™ (BD)), a flash memory device, a memory card, and the like.
While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the disclosure is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2022-203763, filed Dec. 20, 2022, which is hereby incorporated by reference wherein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-203763 | Dec 2022 | JP | national |
