Sheet drying device, and image forming device

Abstract

To provide a sheet drying device and an image forming device that can stably suction a sheet to be dried onto a conveyor belt even when the exhaust volume varies depending on the installation environment.SOLUTION: When a state of a sheet to be dried is acquired, a control unit reads a set pressure corresponding to the state of the sheet from a memory device (S12), extracts, from corresponding data, an opening-degree measurement value corresponding to a pressure measurement value with a numerical value equivalent to the set pressure (S13), and drives an actuator of an exhaust flow adjustment unit to control a valve to make an opening degree same as indicated by the extracted opening-degree measurement value (S14).SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a sheet drying device and an image forming apparatus. [Background technology]

[0002] An image forming apparatus capable of forming an image by an inkjet method is equipped with a sheet drying device that heats and dries a sheet after an ink image has been formed on it. As this type of sheet drying device, for example, a recording apparatus equipped with a sheet conveying device that uses an intake fan to adsorb the sheet to be dried onto a conveying belt and convey the sheet is known (see Patent Document 1).

[0003] The recording device includes a duct section that releases air discharged from an intake fan to the outside, and a pressure adjustment section that can adjust the pressure difference between the pressure inside the duct section and the pressure outside the duct section. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-34764 Summary of the Invention [Problem to be solved by the invention]

[0005] Depending on the installation environment of the sheet drying apparatus, an external exhaust duct may be provided to guide the exhaust air discharged from the sheet drying apparatus to another space (e.g., outdoors). The external exhaust duct may be provided with an exhaust fan to promote exhaust, or may not be provided with such an exhaust fan. Even if an exhaust fan is provided, the air volume of the exhaust fan may vary depending on the installation environment. Therefore, the performance of the exhaust fan may vary depending on the installation environment of the sheet drying apparatus, which may cause the sheet suction force of the intake fan in the sheet drying apparatus to become unstable, resulting in unstable sheet transport by the transport belt.

[0006] An object of the present invention is to provide a sheet drying device and an image forming apparatus that can stably adsorb a sheet to be dried onto a conveyor belt even when the exhaust volume varies depending on the installation environment. [Means for solving the problem]

[0007] a heater disposed opposite the upper surface of the conveyor belt and configured to heat the sheet being conveyed by the conveyor belt; a chamber disposed below the conveyor belt and having an opening facing the lower surface of the conveyor belt; a first fan configured to draw air from inside the chamber and create a negative pressure inside the chamber; an internal exhaust duct configured to guide air discharged from the intake fan to the outside; an adjustment unit attached to the internal exhaust duct and configured to adjust the exhaust flow in the internal exhaust duct by changing the opening of a passage in the internal exhaust duct using driving force from a drive source; and an opening adjustment control unit configured to control the adjustment unit so that the air pressure inside the chamber becomes a set pressure determined for the sheet based on correspondence data indicating a correspondence between an opening measurement value indicating the opening of the adjustment unit and a pressure measurement value indicating the pressure inside the chamber, the opening measurement value being measured in advance during operation of a second fan and the first fan.

[0008] An image forming apparatus according to another aspect of the present invention includes the sheet drying device described above. [Effects of the Invention]

[0009] According to the present invention, even if the exhaust capacity differs depending on the installation environment, it is possible to stably adsorb the sheet to be dried onto the conveyor belt. [Brief explanation of the drawings]

[0010] [Figure 1]FIG. 1 is a block diagram showing the configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing the configuration of the drying device of the image forming apparatus according to the embodiment of the present invention. [Figure 3] FIG. 3 is a perspective view showing a cross section of an internal exhaust duct and a conveyor belt of a drying device according to an embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view of the conveyor belt of the drying device according to the embodiment of the present invention, as viewed from the direction of the arrow IV in FIG. [Figure 5] FIG. 5 is a diagram showing an example of an exhaust flow adjustment unit of a drying apparatus according to an embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing another example of the exhaust flow adjustment unit of the drying apparatus according to the embodiment of the present invention. [Figure 7] FIG. 7 is a flowchart showing an example of a procedure of a valve adjustment process executed by the control unit of the drying device according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the following embodiment is an example of a specific embodiment of the present invention and does not limit the technical scope of the present invention.

[0012] First, with reference to FIG. 1, the configuration of an image forming apparatus 100 according to an embodiment of the present invention will be described.

[0013] The image forming apparatus 100 is an inkjet printer that forms an image on a sheet by inkjet printing. Note that the image forming apparatus 100 may also be a fax machine, a copier, a multifunction peripheral, or the like that is capable of forming an image by inkjet printing.

[0014] As shown in FIG. 1, the image forming apparatus 100 includes a paper feed unit 1, an image forming unit 2, a drying device 3 (an example of a sheet drying device of the present invention), an operation display unit 4, and a control unit 5 (an example of an opening adjustment control unit of the present invention).

[0015] The paper feed unit 1 supplies sheets on which images are to be formed to the image forming unit 2. The paper feed unit 1 includes one or more paper feed cassettes that store sheets, and a paper feed unit. The paper feed unit 1 takes out a sheet from a pre-specified paper feed cassette and feeds it to the image forming unit 2.

[0016] The image forming unit 2 uses an inkjet system to form an ink image on a sheet supplied by the paper feed unit 1. The image forming unit 2 has four line heads that eject C (cyan), M (magenta), Y (yellow), and K (black) ink onto the sheet. Each line head is provided with a recording head having multiple nozzles that eject ink, and ink is ejected from each nozzle based on image data. After the ink image has been formed by the image forming unit 2, the sheet is transported to a drying device 3.

[0017] The drying device 3 dries the sheet on which the ink image has been formed by the image forming unit 2. The sheet on which the ink image has been formed and dried by the drying device 3 is discharged to a discharge tray (not shown).

[0018] The operation display unit 4 is a user interface of the image forming apparatus 100. The operation display unit 4 includes a display unit and an operation unit. The display unit displays various information in response to control instructions from the control unit 5. For example, the display unit is a liquid crystal display. The operation unit inputs various information to the control unit 5 in response to user operations. For example, the operation unit is a touch panel.

[0019] [Configuration of Drying Device 3] Next, the configuration of the drying device 3 will be described with reference to FIGS. 2 to 4. Here, FIG. 2 is a cross-sectional view showing the configuration of the drying device 3 placed on the installation surface of the image forming apparatus 100. Also, FIG. 3 is a perspective view showing a cross section of the internal exhaust duct 27 and the conveyor belt 32 of the drying device 3. Also, FIG. 4 is a view of the conveyor belt 32 as seen from the upstream side of the sheet conveyance path X1 (see FIGS. 2 and 3). Note that in FIG. 2, the sheet conveyance path X1 is indicated by a two-dot chain line with an arrow. Also, in FIG. 3, the drying unit 23 is omitted.

[0020] As shown in FIG. 2, the drying device 3 includes a housing 21, a sheet conveying section 22 (an example of a sheet conveying section of the present invention), a drying unit 23, a sheet adsorption section 24, an internal exhaust duct 27 (an example of an internal exhaust duct of the present invention), and an exhaust flow adjustment unit 40 (an example of an adjustment section of the present invention).

[0021] The housing 21 houses the sheet conveying section 22, the drying unit 23, and the sheet adsorption section 24. The housing 21 is formed in a substantially rectangular parallelepiped shape. The drying device 3 does not necessarily have to be provided with the housing 21. In this case, the drying device 3 may be provided in a housing that houses the image forming section 2 and the like.

[0022] The sheet conveying unit 22 conveys the sheet on which the ink image has been formed, conveyed from the image forming unit 2, along a conveying path X1 (see FIG. 2) to the discharge tray (not shown). The conveying path X1 is a path along a horizontal plane. In the drying device 3, the sheet is conveyed in a position along the horizontal plane.

[0023] As shown in FIG. 2, the sheet conveying section 22 includes a conveying belt 32 (an example of the conveying belt of the present invention), a driving roller 33, a driven roller , and a second conveying roller pair .

[0024] The conveyor belt 32 conveys the sheet on which the ink image has been formed, conveyed from the image forming unit 2, downstream of the conveyance path X1.

[0025] The conveyor belt 32 is an endless belt. The conveyor belt 32 holds a sheet on which an ink image has been formed on its upper outer peripheral surface and conveys the sheet along the conveying path X1. The conveyor belt 32 is stretched by a drive roller 33 and a driven roller 34. As shown in FIG. 2, the drive roller 33 and the driven roller 34 are provided at intervals along the conveying path X1. The drive roller 33 and the driven roller 34 are both hollow rollers. The conveyor belt 32 is stretched by the drive roller 33 and the driven roller 34, so that tension is applied to the conveying belt 32 in the direction along the conveying path X1.

[0026] The conveyor belt 32 has a plurality of ventilation holes penetrating in the thickness direction. For example, the conveyor belt 32 has a belt body formed in a mesh shape from a metal such as stainless steel, and a coating layer formed on the outer circumferential surface of the belt body. The coating layer is formed from a heat-resistant material such as silicone, polyimide, or fluorine-based resin.

[0027] The drive roller 33 rotates by receiving a driving force supplied from a motor (not shown). As a result, the conveyor belt 32 stretched around the drive roller 33 travels in a travel direction D1 shown in Fig. 2. Therefore, the sheet on which the ink image has been formed and held on the outer peripheral surface of the conveyor belt 32 is transported along a transport path X1.

[0028] The sheet adsorption unit 24 is a sheet adsorption device that adsorbs the sheet to be dried onto the upper outer peripheral surface of the conveyor belt 32. The sheet adsorption unit 24 has a chamber 25 (see FIG. 2) and an intake fan 26 (see FIG. 4). The intake fan 26 is an example of the first fan of the present invention.

[0029] 2, the chamber 25 is disposed inside the conveyor belt 32, and more specifically, is disposed below the upper belt portion 32A on the upper side of the conveyor belt 32. The chamber 25 is formed in the shape of a hollow flat rectangular parallelepiped, and on its upper surface is provided a support plate 25A that supports the lower surface of the upper belt portion 32A of the conveyor belt 32. A plurality of ventilation holes (an example of the openings of the present invention) are formed in the support plate 25A so as to face the lower surface of the upper belt portion 32A.

[0030] 4, the intake fan 26 is provided on the side of the chamber 25. The intake fan 26 is controlled by the control unit 5 so as to be driven at a predetermined set rotation speed.

[0031] The intake fan 26 is an electric intake device that draws air from inside the chamber 25 to create a negative pressure inside the chamber 25. When the intake fan 26 is driven, air is exhausted from inside the chamber 25, and as a result, air above the upper belt portion 32A of the conveyor belt 32 is drawn into the chamber 25 via the numerous intake holes formed in the support plate 25A and the numerous intake holes formed in the conveyor belt 32. In this state, when a sheet to be dried is brought onto the upper surface of the upper belt portion 32A of the conveyor belt 32, the sheet after the ink image formation is adsorbed to the outer peripheral surface of the upper belt portion 32A of the conveyor belt 32, and the conveyor belt 32 then conveys the sheet along the conveyance path X1 while holding the sheet adsorbed to its outer peripheral surface.

[0032] The air drawn in by the intake fan flows from the exhaust port of the intake fan into the first internal duct 27A.

[0033] Intake fan 26 may be provided in first internal duct 27A or in second internal duct 27B, which will be described later. The installation position of intake fan 26 is not limited as long as it can suck air from inside chamber 25 and exhaust the air to the outside of housing 21 through internal exhaust duct 27.

[0034] 2, the drying unit 23 is provided above the upper belt portion 32A of the conveyor belt 32 so as to face the upper surface of the upper belt portion 32A. The drying unit 23 is a heating device that heats the sheet conveyed by the conveyor belt 32.

[0035] The drying unit 23 includes, for example, a heater 23A that emits infrared rays in response to power supply, a reflector (not shown) above the heater 23A that reflects the infrared rays emitted from the heater 23A downward, and a hot air fan (not shown) above the reflector that blows air downward. The drying unit 23 heats the sheet by blowing hot air onto the sheet conveyed by the conveyor belt 32 from above the conveyor belt 32. The drying unit 23 is not limited to the above configuration, and may have any configuration as long as it can heat the sheet conveyed by the conveyor belt 32.

[0036] 3, the internal exhaust duct 27 is provided inside the housing 21 of the drying device 3. The internal exhaust duct 27 has a first internal duct 27A and a second internal duct 27B.

[0037] The first internal duct 27A is provided on the side of the conveyor belt 32. The first internal duct 27A extends in the same direction as the conveyor path X1, with one end connected to the exhaust port of the intake fan 26 and the other end connected to the second internal duct 27B. The air discharged from the intake fan 26 flows into the second internal duct 27B through the first internal duct 27A.

[0038] In addition, the first internal duct 27A and the second internal duct 27B do not have to be connected, and the other end of the first internal duct 27A and the intake port 28 of the second internal duct 27B may be close to each other, and each internal duct 27A, 27B may be positioned so that air can flow from the other end of the first internal duct 27A into the second internal duct 27B.

[0039] The second internal duct 27B is disposed above the conveyor belt 32 and downstream of the conveyor path X1. An intake port 28 is formed near the lower end of the second internal duct 27B. This intake port 28 is connected to the other end of the first internal duct 27A. The second internal duct 28B extends from near the upper belt portion 32A of the conveyor belt 32 to the upper part of the housing 21 and is connected to an exhaust port 21A formed on the upper surface of the housing 21. As a result, air that flows into the second internal duct 27B through the first internal duct 27A passes through the second internal duct 27B and is discharged to the outside from the exhaust port 21A.

[0040] In this embodiment, an exhaust fan 29 is provided inside the housing 21. The exhaust fan 29 is provided in the second internal duct 27B. The exhaust fan 29 is used to send air inside the second internal duct 27B to the exhaust port 21A. The exhaust fan 29 is controlled by the control unit 5 so as to be driven at a predetermined set rotation speed. Note that the exhaust fan 29 does not necessarily have to be provided in the second internal duct 27B, and the exhaust fan 29 does not necessarily have to be provided in the housing 21.

[0041] 2, the exhaust flow adjustment unit 40 is attached to the exhaust port 21A of the housing 21. The exhaust flow adjustment unit 40 is attached between the exhaust port 21A and an external exhaust duct 47 provided outside the drying apparatus 3. The exhaust flow adjustment unit 40 is a device capable of adjusting the exhaust flow in the second internal duct 27B. The exhaust flow adjustment unit 40 adjusts the exhaust flow that passes through the second internal duct 27B and is discharged from the exhaust port 21A by changing the opening degree of the passage in the second internal duct 27B.

[0042] In this embodiment, the exhaust flow adjustment unit 40 is detachably attached between the external exhaust duct 47 and the exhaust port 21A. When the exhaust flow adjustment unit 40 is not required in the drying apparatus 3, the external exhaust duct 47 is directly connected to the exhaust port 21A.

[0043] The exhaust flow adjustment unit 40 may be provided inside the housing 21, for example, in the second internal duct 27B.

[0044] 5 and 6 are diagrams showing an example of the exhaust air flow adjustment unit 40 of the drying apparatus 3. As shown in Fig. 5 and 6, the exhaust air flow adjustment unit 40 includes a connecting duct 41, a valve 42 attached to the connecting duct 41, and an actuator 43 for operating the valve 42.

[0045] The connecting duct 41 is, for example, a cylindrical duct. A lower end 41A of the connecting duct 41 is connected to the exhaust port 21A, and an upper end 41B is connected to the intake port of the external exhaust duct 47.

[0046] 5, the valve 42 of the exhaust flow regulating unit 40 is, for example, a butterfly valve 421 that can rotate between a fully open position where the passage in the second internal duct 27B is fully opened and a fully closed position where the passage in the second internal duct 27B is fully closed. The actuator 43 is a motor 431, such as a stepping motor, whose output shaft is connected to a rotation shaft 422 of the butterfly valve 421. In this case, the opening degree of the passage in the second internal duct 27B adjusted by the exhaust flow regulating unit 40 can be expressed as the opening degree (amount of rotation or rotation angle) of the butterfly valve 421. The adjustment range (adjustment width) of the opening degree ranges, for example, from a rotation angle θ1 (=0°) when the butterfly valve 421 is in the fully closed position to a rotation angle θ2 (=90°) when the butterfly valve 421 is in the fully open position. The motor 431 is driven and controlled by the control unit 5, thereby changing the opening degree (amount of rotation or rotation angle) of the butterfly valve 421. The motor 431 is driven and controlled by the control unit 5, thereby changing the opening of the butterfly valve 421, thereby changing the opening of the passage in the second internal duct 27B and adjusting the exhaust flow in the second internal duct 27B.

[0047] 6, the valve 42 of the exhaust flow regulation unit 40 may be, for example, a slide valve 423 that can slide between a fully open position where the passage in the second internal duct 27B is fully opened and a fully closed position where the passage in the second internal duct 27B is fully closed. The actuator 43 includes a motor 431, such as a stepping motor, having a pinion gear 433 connected to an output shaft, and a rack gear 434 formed on the slide valve 423. The pinion gear 433 is meshed with the rack gear 434. In this case, the opening degree of the passage in the second internal duct 27B adjusted by the exhaust flow regulation unit 40 can be represented by the opening degree (slide amount or movement amount) of the slide valve 423. The adjustment range (adjustment width) of the opening degree ranges, for example, from position P1 when the slide valve 423 is in the fully closed position to position P2 when the slide valve 423 is in the fully open position. The motor 431 is driven and controlled by the control unit 5, thereby changing the opening degree (slide amount or movement amount) of the slide valve 423. The motor 431 is driven and controlled by the control unit 5, thereby changing the opening of the slide valve 423, thereby changing the opening of the passage in the second internal duct 27B and adjusting the exhaust flow in the second internal duct 27B.

[0048] In the present embodiment, the exhaust flow adjustment unit 40 has the configuration shown in Fig. 5 or 6, but the exhaust flow adjustment unit 40 is not limited to the configuration shown in Fig. 5 or 6. For example, if the outer diameter of the connecting duct 41 is flexible enough to expand and contract in the radial direction, the exhaust flow adjustment unit 40 may be configured to adjust the opening degree of the passage in the second internal duct 27B by narrowing the outer diameter of the connecting duct 41 using the power of a motor or the like.

[0049] Depending on the installation environment of the drying device 3, an external exhaust duct 47 (see FIG. 2) may be provided to further guide the exhaust air discharged from the drying device 3 to another location (e.g., outdoors). The external exhaust duct 47 may be provided with an exhaust fan 48 (one example of the second fan of the present invention, see FIG. 2) to promote exhaust. The installation environment of the drying device 3 is not necessarily the same in different locations, and the specifications and capabilities of the exhaust fan 48 may vary. In other words, the air volume of the exhaust fan 48 may differ depending on the installation environment of the drying device 3. Therefore, the capacity of the exhaust fan 48 may vary depending on the installation environment of the drying device 3, causing the air pressure in the chamber 25 due to the intake air of the intake fan 26 of the drying device 3 to become unstable. This may result in an unstable adhesion force of the sheet to the conveyor belt 32, which may cause the sheet to be transported unstably by the conveyor belt 32.

[0050] In contrast, in this embodiment, the exhaust flow adjustment unit 40 is controlled by the control unit 5, so even if the amount of exhaust air from the second internal duct 27B to the external exhaust duct 47 varies depending on the installation environment, the sheet to be dried can be stably adsorbed onto the conveying belt 32, and the sheet can be stably transported by the conveying belt 32.

[0051] [Configuration of control unit 5] Next, the configuration of the control unit 5 will be described with reference to FIG.

[0052] The control unit 5 controls the image forming apparatus 100 in an overall manner, and as shown in FIG. 1, includes a CPU 11, a ROM 12, and a RAM 13. The CPU 11 is a processor that executes various types of arithmetic processing. The ROM 12 is a non-volatile storage device that stores information such as control programs for causing the CPU 11 to execute various types of processing in advance. The RAM 13 is a volatile or non-volatile storage device that is used as a temporary storage memory (work area) for the various types of processing executed by the CPU 11. The CPU 11 executes the various control programs stored in the ROM 12 in advance. This allows the image forming apparatus 100 to be controlled in an overall manner.

[0053] 1, the control unit 5 includes a processing unit such as a drive control unit 51. The sheet drying apparatus of the present invention includes a drying device 3 and the control unit 5. Note that the drying device 3 may be provided with a control device corresponding to the drive control unit 51 of the control unit 5.

[0054] An operation control program for causing the CPU 11 to function as each of the above-mentioned functional units is stored in advance in the ROM 12 of the control unit 5. The CPU 11 executes the operation control program stored in the ROM 12 to function as each of the above-mentioned processing units.

[0055] The operation control program may be recorded on a computer-readable recording medium such as a CD, DVD, or flash memory, and may be read from the recording medium and stored in a non-volatile storage device such as a flash memory provided in image forming apparatus 100. Some or all of the functional units included in control unit 5 may be configured with electronic circuits. The operation control program may also be a program for causing multiple processors to function as the functional units included in control unit 5.

[0056] The drive control unit 51 controls the exhaust flow adjustment unit 40. The drive control unit 51 drives and controls the motor 431 of the exhaust flow adjustment unit 40 to control the aperture of the valve 42 of the exhaust flow adjustment unit 40 so that the air pressure inside the chamber 25 becomes a predetermined set pressure for the sheet to be dried. This makes it possible to adjust the aperture of the passage inside the second internal duct 27B within a range of the fully closed position of the valve 42. The set pressure value is stored in a storage device such as the ROM 12 or RAM 13 of the control unit 5 or another internal memory.

[0057] Specifically, the drive control unit 51 controls the exhaust flow adjustment unit 40 based on correspondence data prepared in advance. The correspondence data is created after the drying device 3 is installed at a predetermined installation location, and is then stored in the ROM 12 of the control unit 5 or another storage device readable by the control unit 5.

[0058] After the drying device 3 is installed at a predetermined installation location, the external exhaust fan 48 and intake fan 26 are driven to draw air from the outlet of the second internal duct 27B. The correspondence data includes actual measurements taken while the exhaust fan 48 and intake fan 26 are operating after the installation of the drying device 3. Here, the actual measurements are an opening measurement value indicating the opening of the valve 42 of the exhaust flow regulation unit 40 and a pressure measurement value indicating the pressure of the air inside the chamber 25. The correspondence data is data that associates the opening measurement value with the pressure measurement value when the valve 42 is displaced to a predetermined opening. The correspondence data is lookup table data that is referenced when the drive control unit 51 controls the exhaust flow regulation unit 40.

[0059] The pressure measurement value includes a numerical value equivalent to the set pressure predetermined for the sheet to be dried. For example, if the sheet to be dried can take multiple states, multiple set pressures are determined for each of the sheet states. In this case, the pressure measurement value includes a numerical value equivalent to each of the multiple set pressures determined according to the sheet state. In other words, the correspondence data includes multiple pressure measurement values ​​corresponding to the multiple set pressures determined according to the sheet state, and multiple opening measurement values ​​corresponding to these multiple pressure measurement values.

[0060] The state of the sheet may be classified into a plurality of states according to the type of the sheet, or a plurality of states according to the amount of ink ejected onto the sheet, for example.

[0061] The type of the sheet may be identified by various factors such as the basis weight of the sheet fed from the paper feed unit 1 in the image forming apparatus 100, the thickness of the sheet, whether the sheet is coated, the thickness of the coating layer, etc. In other words, examples of the state of the sheet include a state classified according to differences in each of these factors, or a state classified according to a combination of these factors.

[0062] For example, when the basis weight or thickness of the sheet is less than a predetermined reference value, air can easily pass through in the thickness direction of the sheet, so the set pressure for adhering the sheet to the conveyor belt 32 is set higher. On the other hand, when the basis weight or thickness of the sheet is equal to or greater than a predetermined reference value, air cannot easily pass through in the thickness direction of the sheet compared to when the basis weight or thickness is less than the reference value, so the set pressure for adhering the sheet to the conveyor belt 32 is set lower. Therefore, the set pressure is set to a pressure value that is inversely proportional to the basis weight or thickness of the sheet.

[0063] In addition, in the case of an uncoated sheet, air can easily pass through in the thickness direction of the sheet, so the set pressure for adhering the sheet to the conveyor belt 32 is set higher. On the other hand, in the case of a coated sheet, air cannot easily pass through in the thickness direction of the sheet compared to an uncoated sheet, so the set pressure for adhering the sheet to the conveyor belt 32 is set lower.

[0064] Furthermore, in coated sheets, it is more difficult for air to pass through in the thickness direction of the sheet when the coating layer is thicker than when the coating layer is thin, so the set pressure is set to a pressure value that is inversely proportional to the thickness of the coating layer.

[0065] For example, if sheet information including information about the type of sheets accommodated in the paper feed cassette of the paper feed unit 1 is stored in a storage device such as the ROM 12 or RAM 13 of the control unit 5 or another internal memory, the drive control unit 51 acquires the type information of the sheets to be dried from the storage device and determines the type of the sheets. Also, if the image forming apparatus 100 is provided with a thickness sensor capable of detecting the thickness of the sheets to be dried, the drive control unit 51 may determine the thickness of the sheets based on the output value of the thickness sensor. Also, if sheet type information is input together with a print output instruction when the print output instruction is input from an external information processing device, the drive control unit 51 may determine the type of the sheets to be dried based on the input type information.

[0066] Furthermore, the states classified by the ink amount can be, for example, a plurality of states classified by the number of effective pixels of the image data used in the image formation process for one sheet by the image forming unit 2. For example, the amount of ink ejected onto the sheet differs between a case where half of all pixels in the image data have color information and a case where all pixels have color information.

[0067] For example, when the number of effective pixels of the image data is half the total number of pixels, the amount of ink ejected is relatively small and air easily passes through in the thickness direction of the sheet, so the set pressure for adhering the sheet to the conveyor belt 32 is set higher. On the other hand, when the number of effective pixels of the image data is the same as the total number of pixels, the amount of ink ejected is relatively large and air does not easily pass through in the thickness direction of the sheet, so the set pressure for adhering the sheet to the conveyor belt 32 is set lower than when the number of total pixels is half. Therefore, the set pressure is set to a pressure value that is inversely proportional to the amount of ink ejected.

[0068] For example, the drive control unit 51 determines the number of effective pixels based on the image data and uses the number of effective pixels as an index value indicating the amount of ink ejection. Furthermore, if the image forming apparatus 100 or the drying device 3 is provided with a sensor such as an image sensor or line sensor that can detect the presence or absence of an image and the image density on the image surface of the sheet to be dried after image processing, the drive control unit 51 may determine the proportion of the ink image on the entire sheet based on the output value of the sensor and use the proportion as an index value indicating the amount of ink ejection. Furthermore, during the image formation process by the image forming unit 2, the number of times ink is ejected from the nozzles of the recording head may be counted and the count value may be used as an index value indicating the amount of ink ejection.

[0069] The opening measurement value is, for example, a value obtained by manually measuring the opening of the valve 42 by an operator, or a value of the opening when the control unit 5 controls the valve 42 to be driven to a predetermined opening. The pressure measurement value is, for example, a value obtained by actually measuring the air pressure inside the chamber 25 by an operator using a portable pressure measuring device when the valve 42 is placed at the opening indicated by the opening measurement value. If the drying device 3 is provided with an air pressure sensor (not shown) capable of detecting the pressure inside the chamber 25, the pressure measurement value is a pressure value indicated by the output value of the air pressure sensor. The operator creates table data including the manually measured opening measurement values ​​and the pressure measurement values ​​corresponding to the opening measurement values, and stores the table data in ROM 12.

[0070] The correspondence data may be created manually by an operator, or may be automatically created by the control unit 5 on the condition that a creation instruction is input to the image forming apparatus 100 while the drying device 3 is in operation. For example, when the creation instruction is input, the control unit 5 sequentially changes the opening of the valve 42 to a plurality of openings within the adjustment range, calculates a pressure value based on the output value of the air pressure sensor each time the opening is changed, and creates, as the correspondence data, data that associates the numerical value of each opening (actual opening value) with the pressure value (measured pressure value) for each opening.

[0071] In this embodiment, the drive control unit 51 extracts the opening measurement value corresponding to the pressure measurement value, which is equal to the set pressure determined for the sheet to be dried, from the corresponding data, and controls the drive of the valve 42 of the exhaust flow adjustment unit 40 so that the opening is the opening indicated by the extracted opening measurement value.

[0072] In addition, when multiple set pressures are set for each state of the sheet, the drive control unit 51 detects the state of the sheet to be dried before it is transported to the drying unit 23, extracts from the corresponding data the opening measurement value corresponding to the pressure measurement value that is equal to the set pressure corresponding to the detected state, and drives and controls the valve 42 of the exhaust flow adjustment unit 40 so that the opening is the opening indicated by the extracted opening measurement value.

[0073] [Valve adjustment processing] An example of the procedure of the valve adjustment process executed by the control unit 5 will be described below with reference to Fig. 7. Note that the present invention can also be understood as an invention of a valve adjustment method that executes one or more steps included in the valve adjustment process. Here, Fig. 7 is a flowchart showing an example of the procedure of the valve adjustment process.

[0074] The valve adjustment process is performed by the control unit 5 executing a control program stored in the ROM 12 or the like.

[0075] The steps included in the valve adjustment process described below may be executed in a different order as long as the same operational effect is achieved. Furthermore, the check-in process described below may be executed by a processor corresponding to the control unit 5, which is the main processor executing the process, or the steps may be executed in a distributed manner by the processor corresponding to the control unit 5 and another processor operating in cooperation with the processor.

[0076] In step S11, the control unit 5 acquires the state of the sheet to be dried.

[0077] In step S12, the control unit 5 reads out the set pressure corresponding to the state of the seat acquired in step S11 from the storage device such as the ROM 12, the RAM 13, or another internal memory (S12).

[0078] In step S13, the control unit 5 extracts, from the correspondence data, the opening measurement value that corresponds to the pressure measurement value that is the same numerical value as the set pressure.

[0079] Thereafter, in step S14, the control unit 5 drives the actuator 43 of the exhaust flow regulation unit 40 to control the valve 42 so that the opening becomes equal to the opening indicated by the extracted opening measurement value.

[0080] As described above, in the embodiment of the present invention, the valve adjustment process described above is performed, so that the air pressure in the chamber 25 caused by the intake fan 26 of the drying device 3 can be stabilized at the set pressure according to the state of the sheet to be dried, even if there is a difference in the capacity of the exhaust fan 48 depending on the installation environment of the drying device 3. As a result, even if the amount of exhaust air from the second internal duct 27B to the external exhaust duct 47 varies depending on the installation environment, the sheet to be dried can be stably attracted to the conveyor belt 32, and the sheet can be stably conveyed by the conveyor belt 32.

[0081] [Notes on the Invention] The following is a summary of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0082] <Appendix 1> a sheet conveying section having a conveying belt with air holes formed therein, which conveys a sheet after ink image formation held on an upper surface of the conveying belt; a heater provided opposite to an upper surface of the conveyor belt and configured to heat the sheet conveyed by the conveyor belt; a chamber disposed below the conveyor belt and having an opening facing the lower surface of the conveyor belt; a first fan that draws air from the inside of the chamber to create a negative pressure inside the chamber; an internal exhaust duct that guides the air discharged from the first fan to the outside; an adjustment unit attached to the internal exhaust duct, receiving a driving force from a drive source and changing an opening degree of a passage in the internal exhaust duct to adjust the exhaust flow in the internal exhaust duct; an opening adjustment control unit that controls the adjustment unit so that the air pressure inside the chamber becomes a set pressure determined for the seat, based on correspondence data that indicates a correspondence relationship between an opening measurement value that indicates the opening of the adjustment unit measured in advance while the second fan that sucks air from the outlet of the internal exhaust duct and the first fan are operating and a pressure measurement value that indicates the pressure inside the chamber; A sheet drying device comprising:

[0083] <Appendix 2> The sheet drying device described in Appendix 1, wherein the opening adjustment control unit extracts the opening measurement value corresponding to the pressure measurement value that is equal to the set pressure from the corresponding data, and controls the adjustment unit so that the opening is the opening indicated by the extracted opening measurement value.

[0084] <Appendix 3> A plurality of set pressures are determined for each state of the seat, the correspondence data includes a plurality of the pressure measurement values ​​corresponding to a plurality of the set pressures, and a plurality of the opening measurement values ​​corresponding to a plurality of the pressure measurement values, The sheet drying device described in Appendix 2, wherein the opening adjustment control unit detects the state of the sheet transported by the sheet transport unit, extracts from the corresponding data the opening measurement value corresponding to the pressure measurement value that is equal to the set pressure corresponding to the detected state, and controls the adjustment unit so that the opening is the opening indicated by the extracted opening measurement value.

[0085] <Appendix 4> 4. The sheet drying device according to claim 3, wherein the state of the sheet is one of a plurality of states classified according to the type of the sheet or a plurality of states classified according to the amount of ink ejected onto the sheet.

[0086] <Appendix 5> the adjustment unit has a butterfly valve that is rotatable between a fully open position that fully opens the passage in the internal exhaust duct and a fully closed position that fully closes the passage, 5. The sheet drying device according to claim 1, wherein the opening degree of the adjustment unit is a rotation amount of the butterfly valve from the fully closed position to the fully closed position.

[0087] <Appendix 6> the adjustment unit has a slide valve that is slidable between a fully open position that fully opens the passage in the internal exhaust duct and a fully closed position that fully closes the passage, 5. The sheet drying device according to claim 1, wherein the opening degree of the adjustment unit is a sliding distance of the slide valve from the fully closed position to the fully closed position.

[0088] <Appendix 7> An image forming apparatus comprising the sheet drying device according to any one of appendixes 1 to 6. [Explanation of symbols]

[0089] 1 Paper feed section 2 Image forming unit 3 Drying equipment 4 Operation display section 5. Control section 21. Cabinet 22 Sheet transport section 23 Drying unit 24 Exhaust flow adjustment unit 32 conveyor belt 33 Drive roller 34 Driven roller 41 Blower fan 42 First temperature sensor 43 Second temperature sensor 51 Drive control unit 100 Image forming device

Claims

1. a sheet conveying section having a conveying belt with air holes formed therein, which conveys a sheet after ink image formation held on an upper surface of the conveying belt; a heater provided opposite to an upper surface of the conveyor belt and configured to heat the sheet conveyed by the conveyor belt; a chamber disposed below the conveyor belt and having an opening facing the lower surface of the conveyor belt; a first fan that draws air from the inside of the chamber to create a negative pressure inside the chamber; an internal exhaust duct that guides the air discharged from the first fan to the outside; an adjustment unit attached to the internal exhaust duct, receiving a driving force from a drive source and changing an opening degree of a passage in the internal exhaust duct to adjust the exhaust flow in the internal exhaust duct; an opening adjustment control unit that controls the adjustment unit so that the air pressure inside the chamber becomes a set pressure determined for the seat, based on correspondence data that indicates a correspondence relationship between an opening measurement value that indicates an opening of the adjustment unit measured in advance during operation of the second fan and the first fan that suck air from the outlet of the internal exhaust duct and a pressure measurement value that indicates a pressure inside the chamber; A sheet drying device comprising:

2. 2. The sheet drying device according to claim 1, wherein the opening adjustment control unit extracts the opening measurement value corresponding to the pressure measurement value having a numerical value equivalent to the set pressure from the corresponding data, and controls the adjustment unit so that the opening is the opening indicated by the extracted opening measurement value.

3. A plurality of set pressures are determined for each state of the seat, the correspondence data includes a plurality of the pressure measurement values ​​corresponding to a plurality of the set pressures, and a plurality of the opening measurement values ​​corresponding to a plurality of the pressure measurement values, The sheet drying device of claim 2, wherein the opening adjustment control unit detects the state of the sheet being transported by the sheet transport unit, extracts from the corresponding data the opening measurement value corresponding to the pressure measurement value that is equal to the set pressure corresponding to the detected state, and controls the adjustment unit so that the opening is the opening indicated by the extracted opening measurement value.

4. The sheet drying device according to claim 3 , wherein the state of the sheet is a plurality of states classified according to the type of the sheet or a plurality of states classified according to the amount of ink ejected onto the sheet.

5. the adjustment unit has a butterfly valve that is rotatable between a fully open position that fully opens the passage in the internal exhaust duct and a fully closed position that fully closes the passage, The sheet drying apparatus according to claim 1 or 2, wherein the opening degree of the adjustment unit is a rotation amount of the butterfly valve from the fully closed position to the fully closed position.

6. the adjustment unit has a slide valve that is slidable between a fully open position that fully opens the passage in the internal exhaust duct and a fully closed position that fully closes the passage, The sheet drying apparatus according to claim 1 or 2, wherein the opening degree of the adjustment unit is a sliding amount of the slide valve from the fully closed position to the fully closed position.

7. An image forming apparatus comprising the sheet drying device according to claim 1 or 2.

Images