Drying apparatus, image forming apparatus

Abstract

The present invention provides a drying apparatus and an image forming apparatus that can effectively dry a sheet while preventing deterioration of the sheet to be dried. [Solution] The control unit 90 of the drying unit 12 includes a position control unit 94 that controls the position of the shielding member 122. The position control unit 94 drives and controls the motor 123 based on the above-mentioned sheet characteristic index value (sheet characteristic value) that affects the drying time of the image-formed sheet, to move the shielding member 122 and change the position of the shielding member 122.

Description

Technical Field

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

Background Art

[0002] An image forming device capable of forming an image by an inkjet recording method is known. This image forming device includes a sheet drying device that heats and dries printing paper (sheet) after ink image formation. For example, a heating device that changes the heating range across the width direction according to the width size of the printing paper to be heated is known (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, the characteristics of the printing paper (sheet characteristics) to be dried by the sheet drying device may differ for each printing paper. For example, the amount of ink ejected onto the surface of the printing paper varies depending on the content of the image to be formed. Also, the heat capacity of the printing paper varies depending on the type and thickness of the printing paper. Further, the water content of the printing paper varies depending on the type, thickness, or storage state of the printing paper. When different paper characteristics exist in the printing paper, if a uniform amount of heat is radiated onto the printing paper, the printing paper may not be sufficiently dried, or the printing paper may be overheated and deteriorated. If the amount of heat of the heater is adjusted with electricity for each printing paper, the above problems can be solved. However, when adjusting with electricity, since the responsiveness of the heater is poor, it is necessary to wait for the sheet until the amount of heat reaches an appropriate temperature as the drying temperature of the next sheet, resulting in poor efficiency.

[0005] The object of the present invention is to provide a drying apparatus and an image forming apparatus that can prevent deterioration of the sheet to be dried and effectively dry the sheet. [Means for solving the problem]

[0006] A drying apparatus according to one aspect of the present invention is a drying apparatus for drying a sheet on which an image has been formed on its surface, comprising: a heater that radiates heat toward the sheet supported by a predetermined support; a shielding member provided between the heater and the support, which is movable between an unshielded position that allows heat radiated from the heater to pass to the support and a shielded position that shields the heat radiated from the heater; a drive unit that applies a driving force to the shielding member to move the shielding member between the unshielded position and the shielded position; and a shielding control unit that controls the drive unit based on sheet characteristic values ​​that affect the drying time of the sheet to change the position of the shielding member.

[0007] An image forming apparatus according to another aspect of the present invention includes the drying apparatus.

[0008] According to the present invention, it is possible to prevent deterioration of the sheet to be dried and to dry the sheet effectively. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows the configuration of an inkjet recording apparatus according to an embodiment of the present invention. [Figure 2] Figure 2 is a cross-sectional view showing the configuration of a drying unit and a second conveying unit according to an embodiment of the present invention. [Figure 3] Figure 3(A) is a cross-sectional view showing the configuration of a drying unit according to an embodiment of the present invention, and Figure 3(B) is a plan view of the drying unit. [Figure 4] Figures 4(A) to 4(C) show the movement state of the shielding member according to an embodiment of the present invention. [Figure 5] Figure 5 is a block diagram showing the configuration of an inkjet recording device. [Figure 6] Figure 6 is a flowchart showing an example of the procedure for the heat quantity adjustment process performed by the control unit of an inkjet recording device. [Figure 7] Figure 7 is a plan view showing the configuration of a drying unit according to another embodiment of the present invention. [Modes for carrying out the invention]

[0010] The embodiments of the present invention will be described below with reference to the attached drawings. Note that the following embodiments are merely examples of the present invention and do not limit the technical scope of the present invention.

[0011] First, with reference to Figure 1, an inkjet recording apparatus X1 (hereinafter abbreviated as "recording apparatus X1") according to an embodiment of the present invention will be described. Figure 1 shows the state in which the first transport unit 5 of the recording apparatus X1 is positioned at a recording position where printing by the recording unit 3 is possible. In Figure 1, the first transport unit 5 is shown by a dashed line when it is positioned at a retracted position at a predetermined distance below the recording position.

[0012] The recording device X1 is an example of an image forming apparatus according to the present invention, and records an ink image on a sheet based on an inkjet recording method. As shown in Figure 1, the recording device X1 includes a paper feed cassette 1, a paper feed unit 2, a recording unit 3 (an example of an image forming unit), a first transport unit 5, a lifting mechanism 6, a second transport unit 7, a maintenance unit 8, a drying unit 12 (an example of a drying apparatus according to the present invention), an operation display unit 14 (see Figure 5), a control unit 90 (see Figure 5), and a housing 11 that houses or supports these.

[0013] Inside the housing 11, there are four transport paths 15 (15A, 15B, 15C, 15D). The first transport path 15A guides the sheet from the paper feed cassette 1 to the recording unit 3. The second transport path 15B guides the sheet from the second transport unit 7 to the output port 17. The third transport path 15C guides the sheet from the second transport unit 7 to the intermediate tray 13 for switchback, and is generally also called the switchback transport path. The fourth transport path 15D guides the sheet with recorded images from the intermediate tray 13 to the recording unit 3.

[0014] Furthermore, the transport path 15 is equipped with multiple sheet detection sensors 61 (an example of a sheet detection unit) that detect the presence or absence of a sheet, or the leading or trailing end of a sheet. The sheet detection sensors 61 are connected to the control unit 90.

[0015] The recording device X1 is a printer that performs printing processing based on the input image data. The image forming apparatus of the present invention is not limited to printers that record images on sheets based on an inkjet recording method, but can also be applied to copiers, facsimile machines, multifunction devices, etc., that have printing capabilities.

[0016] The paper feed cassette 1 is located at the bottom of the housing 11. The paper feed cassette 1 contains the sheets to be printed by the recording device X1. The sheets are recording media of a specified size (such as A4 or B5 size) formed in sheet form, such as so-called printing paper. Of course, the sheets are not limited to printing paper; they may also be recording media such as OHP sheets or cloth. Furthermore, the sheets may be long rolls of paper supplied from a reel or the like.

[0017] The operation display unit 14 (see Figure 5) is the user interface of the recording device X1. The operation display unit 14 comprises a display unit and an operation unit. The display unit displays various information in response to control instructions from the control unit 90 (see Figure 5). For example, the display unit is a liquid crystal display. The operation unit inputs various information to the control unit 90 in response to user operations. For example, the operation unit is a touch panel.

[0018] The user stores the sheet on which the user wants to record an image in the paper feed cassette 1, operates the recording device X1, and records an image on the sheet. In order to improve the image recording quality, various information such as the type, material, basis weight, and thickness of the sheet stored in the paper feed cassette 1 is input by the user via the operation display unit 14 (see FIG. 5). The various input information is stored in the RAM 93 of the control unit 90 or the internal memory in the operation display unit 14 or the like.

[0019] The paper feed unit 2 is a feeding mechanism including a pickup roller 21 and a feed roller 22. A retard roller 221 is provided at a position facing the feed roller 22. The pickup roller 21 takes out sheets one by one from the paper feed cassette 1. The feed roller 22 feeds the sheet taken out by the pickup roller 21 to the first conveyance path 15A.

[0020] In the first conveyance path 15A, a pair of conveyance rollers 23 for conveying the sheet is provided at appropriate positions. The pair of conveyance rollers 23 includes a driving roller and a driven roller that are pressed against each other. The pair of conveyance rollers 23 conveys the sheet fed to the first conveyance path 15A toward the registration roller pair 24.

[0021] The registration roller pair 24 is provided in front of the recording unit 3. The registration roller pair 24 includes a driving roller and a driven roller that are pressed against each other. The registration roller pair 24 conveys the sheet to the recording unit 3 at a predetermined conveyance timing (image writing timing).

[0022] Downstream of the registration roller pair 24 in the conveyance direction D1, a first conveyance unit 5 and a recording unit 3 are arranged.

[0023] The recording unit 3 has multiple line heads 31 corresponding to black, cyan, magenta, and yellow, and a head frame 35 that supports them. The head frame 35 is supported by the housing 11. In this embodiment, the recording unit 3 has four line heads 31 corresponding to the four colors mentioned above. Note that the number of line heads 31 is not limited to the four mentioned above, and it is sufficient to have at least one.

[0024] The line head 31 is a so-called line head type recording head. That is, the recording device X1 is a so-called line head type inkjet recording device. The line head 31 is long in the width direction perpendicular to the sheet transport direction D1 (the direction perpendicular to the paper surface in Figure 1), and specifically, the width of the line head 31 is the length corresponding to the width of the sheet with the maximum width being transported. In other words, the line head 31 has a plurality of ink nozzles capable of ejecting ink (an example of the liquid developer of the present invention) over the entire width of the sheet. Therefore, the line head 31 can record an ink image on the sheet without scanning in the width direction.

[0025] Each line head 31 is spaced at a predetermined interval along the sheet transport direction D1. The lower surface of each line head 31 is the ink ejection surface. The ink ejection surface is provided with numerous ink nozzles for ejecting ink.

[0026] The recording unit 3 records images on sheets transported by the first transport unit 5. The recording unit 3 records images on sheets by ejecting ink from ink nozzles of each line head 31. As for the ink ejection method of the line head 31, for example, a piezoelectric method that uses a piezoelectric element to eject ink, or a thermal method that generates bubbles by heating to eject ink is employed.

[0027] The recording device X1 includes ink tanks (not shown) containing inks corresponding to black, cyan, magenta, and yellow. Each of the ink tanks is connected to a line head 31 by an ink tube (not shown). The line heads 31 are supplied with ink from the corresponding ink tanks through the ink tubes.

[0028] The first transport unit 5 is located below the recording unit 3. The first transport unit 5 transports the sheet in the transport direction D1 while keeping the sheet facing the ink ejection surface of the line head 31. Specifically, the first transport unit 5 includes a paper transport belt 37 on which the sheet is placed, a plurality of tension rollers 38 that tension the paper transport belt 37, and a unit frame (not shown) that supports them.

[0029] The distance between the paper transport belt 37 and the ink ejection surface is adjusted so that the gap between the surface of the sheet and the ink ejection surface during image recording is a specified length (for example, 1 mm).

[0030] When the tension roller 38 is rotated by the driving force transmitted from a drive unit such as a motor, the paper transport belt 37 rotates. This enables the first transport unit 5 to transport the sheet in the transport direction D1. When the sheet supplied from the paper feeding unit 2 reaches the first transport unit 5, the sheet is transported by the first transport unit 5 through the recording unit 3 to the second transport unit 7. The first transport unit 5 may also be equipped with a suction unit (not shown) that draws in air through a number of through holes formed in the paper transport belt 37 in order to attract the sheet to the paper transport belt 37.

[0031] The lifting mechanism 6 is located below the first transport unit 5. The lifting mechanism 6 supports the first transport unit 5 from below and moves the first transport unit 5 up and down relative to the line head 31. In other words, the lifting mechanism 6 moves the first transport unit 5 and the line head 31 apart and closer together by moving the first transport unit 5 up and down. Specifically, the lifting mechanism 6 moves the first transport unit 5 between a recording position where printing by the recording unit 3 is possible (shown by a solid line in Figure 1) and a retracted position located a predetermined distance below the recording position (shown by a dashed line in Figure 1).

[0032] The aforementioned retracted position is the position in the vertical direction where the first transport unit 5 is at its lowest position and furthest from the line head 31. When the first transport unit 5 is in the retracted position, any sheets remaining on the first transport unit 5 can be removed. Also, when the first transport unit 5 is in the retracted position, the maintenance unit 8 can move into the space below the recording unit 3.

[0033] The maintenance unit 8 is positioned in a predetermined standby position (shown in Figure 1) when not printing. This standby position is located below the second transport unit 7, which is downstream of the recording unit 3 in the transport direction D1. The maintenance unit 8 is a mechanism for maintaining or restoring the ejection performance of the line head 31 and includes a cap unit 9 and a wipe unit 10. With the maintenance unit 8 positioned in the space below the recording unit 3, the cap unit 9 can perform a capping operation to cover the ink nozzles on the ink ejection surface, and the wipe unit 10 can perform a wiping operation.

[0034] As shown in Figure 1, the second transport unit 7 is located downstream of the recording unit 3 in the transport direction D1. The second transport unit 7 transports the sheet on which the ink image has been recorded on its upper surface by the recording unit 3 in the transport direction D1. As shown in Figure 2, the second transport unit 7 includes a transport belt 7A on which the sheet is placed (an example of the support part and transport belt of the present invention), a pair of tension rollers 7B and 7C that tension the transport belt 7A, and a frame that supports these. The image-formed sheet (image-formed sheet) on which the ink image has been recorded on its upper surface by the recording unit 3 is transported in the transport direction D1 (an example of a predetermined direction) by the second transport unit 7 while being held on the upper surface of the transport belt 7A.

[0035] As shown in Figure 1, a drying unit 12 is provided above the second transport unit 7. The drying unit 12 is a heating device that radiates heat toward the image recording surface (upper surface) of the image-formed sheet on the transport belt 7A, thereby heating the sheet and drying the ink image on the sheet.

[0036] As shown in Figure 2, the drying unit 12 comprises a plurality of heaters 121 (an example of a heater according to the present invention), a shielding member 122 (an example of a shielding member according to the present invention), and a motor 123 (an example of a drive unit according to the present invention).

[0037] The heater 121 radiates heat toward the image-formed sheet supported on the conveyor belt 7A. The heater 121 is, for example, an infrared heater that emits infrared rays in response to power supply. The heater 121 has a long shape in the width direction perpendicular to the conveying direction D1. In this embodiment, four heaters 121 are provided at equal intervals along the conveying direction D1. When a sheet to be heated is conveyed onto the conveyor belt 7A of the second conveying unit 7, the control unit 90 drives the heater 121 to start heating. Then, when the last sheet to be dried is discharged from the conveyor belt 7A toward the conveying direction D1, the control unit 90 stops driving the heater 121.

[0038] The shielding member 122 is provided between the heater 121 and the conveyor belt 7A. The shielding member 122 is supported so as to be movable between an unshielded position that allows heat radiated from the heater 121 to pass to the conveyor belt 7A and a shielded position that shields the heat radiated from the heater 121. In this embodiment, the shielding member 122 is supported so as to be movable in the housing 125 of the drying unit 12 by a slide guide (not shown) provided in the housing 125 of the drying unit 12. The shielding member 122 may also be supported in the housing 11 of the recording device X1.

[0039] The motor 123 is provided in the housing 125 of the drying unit 12. The motor 123 is a drive unit for moving the shielding member 122, and applies driving force to the shielding member 122 to move it between the unshielded position and the shielded position. The motor 123 is driven and controlled by the control unit 90 (see Figure 5). The motor 123 may also be provided in the housing 11 of the recording device X1.

[0040] The drying unit 12 has a housing 125 that houses a heater 121, a shielding member 122, and a motor 123. The housing 125 is made of a material that is resistant to heat from the heater 121. Multiple openings 127 are formed in the bottom plate 126 of the housing 125. The bottom plate 126 is the surface of the housing 125 that faces the conveyor belt 7A.

[0041] Each opening 127 is formed in the bottom plate 126 at a position corresponding to the heater 121. Specifically, the openings 127 are formed below the heater 121. Each opening 127 is formed in a rectangular shape that is elongated in the longitudinal direction of the heater 121. Therefore, if the openings 127 are not blocked, the heat radiated from the heater 121 passes through the openings 127 to the conveyor belt 7A. In other words, the openings 127 are through-holes that allow the heat radiated from the heater 121 to pass to the image-formed sheet on the conveyor belt 7A.

[0042] As shown in Figure 3, in this embodiment, the shielding member 122 is provided on the housing 125 so that the opening 127 can be opened and closed. Specifically, the shielding member 122 is supported on the upper surface of the bottom plate 126 and is supported so as to be slidable along the upper surface of the bottom plate 126 in the same direction as the transport direction D1.

[0043] The shielding member 122 has four through-holes 128 formed at positions corresponding to the four openings 127. The through-holes 128 are formed to be approximately the same size and shape as the openings 127. When the shielding member 122 is positioned in a position where the through-holes 128 and the openings 127 coincide (open position), it allows the heat radiated from the heater 121 to pass downward through the openings 127. Also, when the shielding member 122 is positioned in a position where the shielding portion 129 other than the through-holes 128 coincides with the openings 127 (closed position), it blocks the heat radiated from the heater 121 from radiating to the outside. In other words, the non-shielding position of the shielding member 122 is the open position in which the openings 127 are fully open, and the shielding position is the closed position in which the openings 127 are closed.

[0044] As shown in Figure 3, the housing 125 is provided with an elastic member 130 that applies a biasing force to the shielding member 122, causing the shielding member 122 to be positioned in the unshielded position (i.e., the open position). The elastic member 130 is, for example, a coil spring in a compressed state. Therefore, in the housing 125, when the motor 123 is not operating, the shielding member 122 is initially positioned in the unshielded position (see Figure 4(A)). The elastic member 130 can be an elastically contractible leaf spring, a rubber member, or the like.

[0045] The motor 123 has a pulley 131 on its rotating shaft. A wire 132, which acts as a connector, is wound around the pulley 131. One end of the wire 132 is connected to the end 122A of the shielding member 122. When the motor 123 is rotated by a predetermined amount in the forward rotation direction by the control unit 90, the shielding member 122 moves against the biasing force of the elastic member 130 by the amount of rotation from the initial unshielded position (open position) to the shielded position (closed position), and stops at a position separated from the unshielded position by the amount of rotation (see Figure 4(B)). Then, when it is rotated further in the forward rotation direction, the shielding member 122 moves to the shielded position and stops at that position (see Figure 4(C)).

[0046] On the other hand, if the drive control of the motor 123 by the control unit 90 is stopped or rotated in the reverse direction, the shielding member 122 is moved from its current position to the unshielded position (open position) by the biasing force of the elastic member 130.

[0047] The sheet that has passed through the drying unit 12 is transported to either the second transport path 15B or the third transport path 15C. For example, when the sheet is to be discharged from the discharge port 17, the sheet is transported to the second transport path 15B. On the other hand, when printing is to be done on the opposite side of the sheet, the sheet is transported to the third transport path 15C.

[0048] As shown in Figure 1, a flap 19 for changing the direction of sheet transport is provided at the branching point between the second transport path 15B and the third transport path 15C. The direction of sheet transport is changed when this flap 19 is displaced by the driving force of a solenoid or motor. Specifically, the control unit 90 controls the drive unit such as a solenoid or motor to switch the destination of the dried sheet to either the second transport path 15B or the third transport path 15C.

[0049] The second transport path 15B is a passage that extends straight from the second transport unit 7 to the left in Figure 1, and leads to the discharge port 17 formed on the left side of the housing 11 in Figure 1.

[0050] The third transport path 15C extends upward along the left side of the housing 11 in Figure 1, bends to the right near the top of the housing 11, extends toward the right side of the housing 11, curves downward near the front of the right side of the housing 11, and reaches the intermediate tray 13.

[0051] If double-sided recording is not performed on the sheet, the sheet is transported to the second transport path 15B and discharged from the discharge port 17, which is the exit of the second transport path 15B, into the output tray (not shown).

[0052] An intermediate tray 13 is provided at the top of the housing 11, between the recording unit 3 and the third transport path 15C. The intermediate tray 13 is a sheet support that temporarily retracts the sheet when a switchback operation is performed to reverse the front and back sides of the sheet.

[0053] When double-sided recording is performed on a sheet, the sheet with the image recorded on the first side (image recording side) is transported to the third transport path 15C. Once the sheet is fed into the third transport path 15C, it is further transported downstream in the transport direction by a plurality of transport roller pairs 25 provided in the third transport path 15C. Each transport roller pair 25 comprises a drive roller 25A and a driven roller 25B that are pressed against each other. During transport by the transport roller pair 25, the drive roller 25A contacts the non-image recording side, and the driven roller 25B contacts the image recording side.

[0054] A pair of transport rollers 28 is provided near the entrance of the intermediate tray 13. The transport roller pair 28 comprises a drive roller 28A and a driven roller 28B that are pressed against each other. When the transport roller pair 28 is used for transport, the drive roller 28A contacts the non-image recording surface, and the driven roller 28B contacts the image recording surface. The transport roller pair 28 transports the sheet from the third transport path 15C to the intermediate tray 13. After that, the operation of the transport roller pair 28 is temporarily paused, and then the rotation direction of the drive roller 28A is reversed. This allows the front and back sides of the sheet to be reversed, and the sheet on the intermediate tray 13 to be transported to the fourth transport path 15D.

[0055] The fourth transport path 15D extends to the right from the intermediate tray 13, bends downward, curves back to the left by approximately 180 degrees, and reaches the pair of resist rollers 24.

[0056] A pair of transport rollers 29 is provided in the fourth transport path 15D. The transport roller pair 29 comprises a drive roller 29A and a driven roller 29B that are pressed against each other. When the transport roller pair 29 is used for transport, the drive roller 29A contacts the non-image recording surface, and the driven roller 29B contacts the image recording surface. When the inverted sheet is fed into the fourth transport path 15D, the sheet is transported further downstream in the transport direction by the transport roller pair 29 to reach the register roller pair 24. The inverted sheet is then transported back to the first transport unit 5 with the second surface, which does not have an image recorded on it, facing upwards. As a result, the recording unit 3 records an ink image on the second surface.

[0057] Incidentally, the characteristics (sheet characteristics) of the sheets to be dried by the drying unit 12 may differ from sheet to sheet. Here, the sheet characteristics are those that affect the drying time of the image-formed sheet. For example, the amount of ink ejected onto the surface of the sheet (an example of sheet characteristics) differs depending on the content of the image to be formed. Also, the heat capacity of the sheet (an example of sheet characteristics) differs depending on the type and thickness of the sheet. Furthermore, the water content in the sheet (an example of sheet characteristics) differs depending on the type, thickness, or storage conditions of the sheet. If a uniform amount of heat is radiated onto the sheet when the sheet characteristics differ, the sheet to be dried may not dry sufficiently, or the sheet may be overheated, discolored, burnt, or deteriorated. While it might be possible to resolve the above problem by adjusting the heat output of the heater 121 using electricity for each sheet to be dried, adjusting the heat output of the heater 121 using electricity results in poor responsiveness of the heater 121. This would require the sheet to wait before the drying unit 12 until it reaches a suitable temperature for drying the next sheet, resulting in poor drying efficiency and a longer first print time in the recording device X1, which is undesirable.

[0058] In contrast, in this embodiment, even if the sheet characteristic value, which is an index value indicating the degree of the sheet characteristics, differs for each sheet to be dried, the amount of heat supplied to the sheet to be dried is adjusted based on the sheet characteristic value, making it possible to efficiently dry the image-formed sheet without causing deterioration of the sheet.

[0059] [Configuration of the control unit 90] Next, the configuration of the control unit 90 will be described with reference to Figure 5.

[0060] The control unit 90 comprehensively controls the recording device X1 and, as shown in Figure 5, comprises a CPU 91, ROM 92, and RAM 93. The CPU 91 is a processor that performs various arithmetic operations. The ROM 92 is a non-volatile memory device in which information such as control programs for instructing the CPU 91 to perform various operations is pre-stored. The RAM 93 is a volatile or non-volatile memory device used as temporary storage memory (work area) for the various operations performed by the CPU 91. The CPU 91 executes the various control programs pre-stored in the ROM 92. This allows for comprehensive control of the recording device X1.

[0061] As shown in Figure 5, the control unit 90 includes a position control unit 94 (an example of a shielding control unit of the present invention) that controls the position of the shielding member 122, and an ink amount determination unit 95 that determines the amount of ink to be discharged onto the sheet to be dried, and other control processing units.

[0062] The ROM 92 of the control unit 90 contains a control program that causes the CPU 91 to function as the position control unit 94 described above. The CPU 91 then functions as the position control unit 94 by executing the control program stored in the ROM 92.

[0063] The 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 flash memory provided in the recording device X1.

[0064] The position control unit 94 drives the motor 123 based on the above-mentioned sheet characteristic index values ​​(sheet characteristic values) that affect the drying time of the image-formed sheet, and moves the shielding member 122 to change the position of the shielding member 122. Here, the sheet characteristic values ​​are an index value indicating the degree of ink discharged onto the surface of the sheet, an index value indicating the thickness of the sheet, and an index value (humidity) indicating the water content in the sheet.

[0065] Specifically, the position control unit 94 positions the shielding member 122 in its initial position, the unshielded position (open position), when the sheet characteristic value is greater than a predetermined reference value. Furthermore, when the sheet characteristic value is smaller than the reference value, the position control unit 94 determines a movement amount corresponding to the difference between the reference value and the sheet characteristic value, and moves the shielding member 122 from the unshielded position (open position) towards the shielded position (closed position) by the specified movement amount, holding the shielding member 122 in that position. This adjusts the opening degree of the opening 127 by the shielding member 122, thereby adjusting the amount of heat supplied downward from the opening 127. In other words, the position control unit 94 performs a process to adjust the amount of heat supplied downward from the opening 127.

[0066] Furthermore, if a conveying malfunction occurs in the conveyor belt 7A for the image-formed sheet to be dried, the position control unit 94 moves the shielding member 122 to the shielding position to prevent heat from radiating downward from the opening 127. Specifically, if a sheet is detected for a predetermined set time or longer by the sheet detection sensor 61A (see Figure 2) located in front of the conveyor belt 7A, the control unit 90 determines that a sheet jam has occurred on the conveyor belt 7A. In this case, the position control unit 94 of the control unit 90 drives the motor 123 to move the shielding member 122 to the shielding position and holds the shielding member 122 in the shielding position until the release condition is met.

[0067] The ink amount determination unit 95 determines the amount of ink to be discharged onto the sheet to be dried by accumulating the amount of ink discharged calculated from the image data printed on the sheet. This ink amount is the amount of ink used to form an image on the sheet surface (an example of sheet characteristics) and varies depending on the content of the image. In other words, the ink amount determined by the ink amount determination unit 95 is an example of an index value indicating the degree of ink discharged onto the sheet to be dried.

[0068] The ink amount determination unit 95 is not limited to performing a process to determine the amount of ink based on image data. For example, if a density sensor for detecting the density of the surface of the sheet after image formation is provided in front of the drying unit 12, the ink amount determination unit 95 may determine the amount of ink ejected onto the sheet based on the density detected by the density sensor.

[0069] As shown in Figure 5, in addition to the sheet detection sensor 61, the control unit 90 is connected to several other detection sensors, including a thickness sensor 62 for detecting the thickness of the sheet and a moisture absorption sensor 63 for detecting the moisture content of the sheet.

[0070] The thickness sensor 62 is provided, for example, in the first transport path 15A from the paper feeding unit 2 to the recording unit 3. The thickness sensor 62 is a sensor that detects the thickness of a sheet, and is a well-known sensor that has, for example, a light-emitting unit that irradiates light onto the sheet being transported, and a light-receiving unit that receives either the amount of transmitted light that passes through the sheet or the amount of reflected light (specular reflected light amount or diffuse reflected light amount) that is reflected by the sheet, and detects the amount of transmitted light or the amount of reflected light. The control unit 90 measures the thickness of the sheet based on the detection signal (output signal) output from the thickness sensor 62.

[0071] The thickness of a sheet is proportional to its heat capacity (an example of a sheet characteristic). Therefore, sheet thickness is an example of an indicator value that shows the degree of heat capacity of the sheet being dried.

[0072] In this embodiment, an example of a process for measuring the sheet thickness based on the detection signal of the thickness sensor 62 is described. However, for example, the control unit 90 may acquire the sheet thickness that has been pre-input by the user via the operation display unit 14 (see Figure 5).

[0073] The moisture absorption sensor 63 is provided, for example, in the first transport path 15A. The moisture absorption sensor 63 is a well-known sensor that clamps the transported sheet between a pair of electrodes and detects the capacitance and resistance of the sheet. The control unit 90 measures the humidity of the sheet based on the detection signal (output signal) output from the moisture absorption sensor 63, utilizing the fact that the capacitance and resistance change according to the moisture content of the sheet.

[0074] The humidity of a sheet is proportional to its water content (an example of a sheet characteristic). Therefore, the humidity of a sheet is an example of an indicator value that shows the degree of water content of the sheet being dried.

[0075] [Heat adjustment process] Hereinafter, an example of the procedure for the heat quantity adjustment process performed by the control unit 90 will be described with reference to Figure 6. The present invention can also be considered as an invention of a heat quantity adjustment method that performs one or more steps included in the heat quantity adjustment process. Here, Figure 6 is a flowchart showing an example of the procedure for the heat quantity adjustment process.

[0076] The heat quantity adjustment process is performed by the control unit 90 executing a control program stored in the ROM 92 or the like. The heat quantity adjustment process is performed while the heater 121 is being heated by the drying unit 12 during the execution of the image forming process in the recording device X1.

[0077] Furthermore, the execution order of each step included in the heat quantity adjustment process described below may differ to the extent that similar effects are produced. In addition, each step of the heat quantity adjustment process described below may be executed by a processor corresponding to the control unit 90, which is the main unit executing the process, or each step may be distributed and executed by the processor corresponding to the control unit 90 and other processors that operate in cooperation with said processor.

[0078] <Step S11> In step S11, the control unit 90 obtains the thickness of the sheet to be dried based on the detection signal from the thickness sensor 62. If the sheet thickness is obtained, the obtained sheet thickness is stored as the sheet characteristic value in the RAM 93 or other internal memory of the control unit 90.

[0079] <Step S12> In the next step S12, the control unit 90 acquires the humidity of the sheet to be dried based on the detection signal from the moisture absorption sensor 63. If the humidity of the sheet is acquired, the acquired humidity of the sheet is stored as the sheet characteristic value in the RAM 93 or other internal memory of the control unit 90.

[0080] <Step S13> In the next step S13, the control unit 90 acquires the amount of ink ejected onto the sheet. Once the amount of ink on the sheet is acquired, the acquired amount of ink on the sheet is stored as the sheet characteristic value in the RAM 93 or other internal memory of the control unit 90.

[0081] <Step S14> In the next step S14, the control unit 90 determines whether or not the leading edge of the sheet to be dried has been detected based on the detection signal from the sheet detection sensor 61A (see Figure 2).

[0082] <Step S15> When the leading edge of the sheet to be dried is detected, in step S15, the control unit 90 determines whether the sheet thickness, sheet humidity, and sheet ink amount are equal to or greater than predetermined reference values ​​(thresholds) for each sheet characteristic value. For example, the control unit 90 determines whether the sheet thickness obtained in step S11 is equal to or greater than a predetermined thickness reference value defined for sheet thickness. The control unit 90 also determines whether the sheet humidity obtained in step S12 is equal to or greater than a predetermined humidity reference value defined for sheet humidity. The control unit 90 also determines whether the sheet ink amount obtained in step S13 is equal to or greater than a predetermined ink amount reference value defined for sheet ink amount. If in step S15 it is determined that any of the sheet characteristic values ​​are equal to or greater than the reference value, the process proceeds to step S16. If in step S15 it is determined that any of the sheet characteristic values ​​are less than the reference value, the process proceeds to step S17.

[0083] <Step S16> In step S16, the control unit 90 maintains the shielding member 122 in the unshielded position (open position). In other words, the control unit 90 does not move the shielding member 122, leaving it in the initial position. As a result, the opening 127 is fully open, and the maximum amount of heat that the drying unit 12 can supply is supplied from the heater 121 to the sheet to be dried.

[0084] <Step S17> In step S17, the control unit 90 performs a process to verify the amount of movement of the shielding member 122 based on one of the sheet characteristic values: the sheet thickness, the sheet humidity, or the amount of ink on the sheet. For example, the control unit 90 calculates the difference between one of the sheet characteristic values ​​and the reference value, and determines the amount of movement corresponding to that difference. One possible method for determining the amount of movement is to select the amount of movement corresponding to the calculated difference from a lookup table that associates the difference with the amount of movement.

[0085] In step S17, for example, the control unit 90 calculates the difference for the sheet thickness, the sheet humidity, and the amount of ink in the sheet, and selects the corresponding displacement amount from the lookup table. The control unit 90 then determines the displacement amount of the shielding member 122 to be the one with the shortest displacement among the three selected displacement amounts, that is, the one with the largest opening of the opening 127. Alternatively, the control unit 90 may determine the displacement amount of the shielding member 122 to be the average value of the three selected displacement amounts.

[0086] <Step S18> In the next step S18, the control unit 90 moves the shielding member 122 toward the open position by the amount of movement determined in step S17. As a result, the opening 127 is adjusted to an opening degree corresponding to the sheet characteristics of the sheet to be dried.

[0087] <Step S19> In step S19, the control unit 90 determines whether or not a sheet jam has occurred in the recording device X1.

[0088] <Step S20> If no sheet jam occurs, the control unit 90 determines in the next step S20 whether there is another sheet to be dried. If there is another sheet, it performs the processing from step S11 onwards for that sheet. If there is no other sheet, it proceeds to step S21.

[0089] <Step S21> In step S21, the control unit 90 stops the heater 121 of the drying unit 12 and stops the heating operation.

[0090] <Step S22> Subsequently, in step S22, the control unit 90 returns the shielding member 122 to its initial position, the unshielded position. This completes the series of processes.

[0091] <Step S23> If it is determined in step S19 that a sheet jam has occurred, the control unit 90 stops the transport control of all sheets in the next step S23 and also emergency stops the heater 121 of the drying unit 12 to interrupt the heating operation.

[0092] <Step S24> Furthermore, in step S24, the control unit 90 moves the shielding member 122 to the shielding position (closed position) to completely close the opening 127. As a result, the heat from the heater 121 immediately after stopping is blocked by the shielding member 122, preventing that heat from being applied to the sheet, thus preventing discoloration, scorching, and ignition of the sheet.

[0093] As described above, in the embodiment of the present invention, since the heat quantity adjustment process described above is performed, the amount by which the shielding member 122 is moved is determined based on one of the sheet characteristic values: the thickness of the sheet to be dried, the humidity of the sheet, or the amount of ink in the sheet, and the shielding member 122 is moved by that amount. As a result, the opening 127 is adjusted to an opening degree corresponding to the sheet characteristic value. Consequently, the amount of heat supplied by the heater 121 to the sheet to be dried is reduced to an amount corresponding to the opening degree of the opening 127. As a result, even if the index value indicating the degree of the sheet characteristics (sheet characteristic value) differs for each sheet to be dried, the amount of heat supplied to the sheet to be dried is adjusted based on the sheet characteristic value, making it possible to efficiently dry the image-formed sheet without causing deterioration of the sheet.

[0094] [Other embodiments] In the above-described embodiment, an example was given of a configuration in which a single shielding member 122 is provided to open and close the opening 127, but the present invention is not limited to such a configuration. For example, as shown in Figure 7, a configuration in which a plurality of shielding members 1221 (an example of a shielding member of the present invention) are provided between the heater 121 and the conveyor belt 7A may be used. Figure 7 is a plan view showing the configuration of the drying unit 12. In Figure 7, the motor 123 and the elastic member 130 are not shown.

[0095] The multiple shielding members 1221 shown in Figure 7 differ from the shielding member 122 described above only in that their length in the width direction perpendicular to the transport direction D1 is shorter; otherwise, their configuration is the same as the shielding member 122. Furthermore, in order to enable each of the multiple shielding members 1221 to be moved individually and independently, a motor 123 is provided corresponding to each of the multiple shielding members 1221. In this configuration, the control unit 90 individually determines the amount of movement of each shielding member 1221 based on the sheet characteristic value in the irradiation area on the image-formed sheet corresponding to each shielding member 1221, and individually changes the position of the shielding members 1221. In this case, it is necessary to obtain the ink ejection amount (sheet characteristic value) in each of the multiple irradiation areas into which the sheet to be dried is divided in the width direction, and to obtain the humidity (sheet characteristic value) in each of the irradiation areas.

[0096] [Notes on the invention] The following is an overview of the invention extracted from the above-described embodiments. Note that each configuration and processing function described below can be selected and combined as desired.

[0097] <Note 1> A drying apparatus for drying a sheet on which an image has been formed on its surface, A heater that radiates heat toward the sheet supported by a predetermined support part, A shielding member is provided between the heater and the support portion, and is movable between an unshielded position that allows heat radiated from the heater to pass to the support portion and a shielded position that shields the heat radiated from the heater. A drive unit that applies a driving force to the shielding member to move the shielding member between the unshielded position and the shielded position, A drying apparatus comprising: a shielding control unit that controls the drive unit based on sheet characteristic values ​​that affect the drying time of the sheet and changes the position of the shielding member; and a shielding control unit.

[0098] <Note 2> The shielding control unit is, If the sheet characteristic value is greater than a predetermined reference value, the shielding member is placed in the initial position, which is the non-shielding position. The drying apparatus according to Appendix 1, wherein, when the sheet characteristic value is smaller than the reference value, a displacement amount corresponding to the difference between the reference value and the sheet characteristic value is determined, and the shielding member is moved from the non-shielding position toward the shielding position by the displacement amount.

[0099] <Note 3> The support portion is a conveyor belt that supports the sheet and transports it in a predetermined direction. The drying apparatus according to Appendix 1 or 2, wherein the shielding control unit moves the shielding member to the shielding position when a conveying failure of the sheet occurs on the conveying belt.

[0100] <Note 4> Multiple shielding members are provided between the heater and the support portion. The drive unit is provided in multiple locations corresponding to the multiple shielding members, The drying apparatus according to any one of the appendices 1 to 3, wherein the shielding control unit individually changes the position of the shielding members based on the sheet characteristic value in the irradiation area on the sheet corresponding to each shielding member.

[0101] <Note 5> A housing for the heater, The housing further comprises an opening provided on the opposing surface facing the support portion, which allows heat radiated from the heater to pass to the sheet, The shielding member is provided in the housing so as to be able to open and close the opening, The drying apparatus according to any one of the appendices 1 to 4, wherein the non-shielded position is an open position in which the opening is opened, and the shielded position is a closed position in which the opening is closed.

[0102] <Note 6> The drying apparatus according to any one of the appendices 1 to 5, wherein the sheet characteristic value is one or more of the following: an index value indicating the amount of liquid developer contained in the sheet, an index value indicating the heat capacity of the sheet, and an index value indicating the water content of the sheet.

[0103] <Note 7> An image forming apparatus equipped with a drying apparatus as described in any of the appendices 1 to 6. [Explanation of Symbols]

[0104] 3: Records Department 7A: Conveyor belt 11: Cabinet 12: Drying Unit 14:Operation display section 15: Conveyor path 31: Line Head 35: Head frame 61: Sheet detection sensor 62: Thickness sensor 63: Moisture absorption sensor 90: Control Unit 94: Position Control Unit 95: Ink quantity determination unit 121: Heater 122: Shielding member 123: Motor 125: Enclosure 126:Bottom plate 127 :Aperture 128: Through-hole 129: Shielding part 130: Elastic member 131: Pulley 132: Wire 1221: Shielding member

Claims

1. A drying apparatus for drying a sheet on which an image has been formed on its surface, A heater that radiates heat toward the sheet supported by a predetermined support part, A shielding member is provided between the heater and the support portion, and is movable between an unshielded position that allows heat radiated from the heater to pass to the support portion and a shielded position that shields the heat radiated from the heater. A drive unit that applies a driving force to the shielding member to move the shielding member between the unshielded position and the shielded position, A drying apparatus comprising: a shielding control unit that controls the drive unit based on sheet characteristic values ​​that affect the drying time of the sheet and changes the position of the shielding member; and a shielding control unit.

2. The shielding control unit is, If the sheet characteristic value is greater than a predetermined reference value, the shielding member is placed in the initial position, which is the non-shielding position. The drying apparatus according to claim 1, wherein, when the sheet characteristic value is smaller than the reference value, the amount of movement corresponding to the difference between the reference value and the sheet characteristic value is determined, and the shielding member is moved from the non-shielding position toward the shielding position by the amount of movement.

3. The support portion is a conveyor belt that supports the sheet and transports it in a predetermined direction. The drying apparatus according to claim 1 or 2, wherein the shielding control unit moves the shielding member to the shielding position when a conveying failure of the sheet occurs on the conveying belt.

4. Multiple shielding members are provided between the heater and the support portion. The drive unit is provided in multiple locations corresponding to the multiple shielding members, The drying apparatus according to claim 1 or 2, wherein the shielding control unit individually changes the position of each shielding member based on the sheet characteristic value in the irradiation area on the sheet corresponding to each shielding member.

5. A housing for the heater, The housing further comprises an opening provided on the opposing surface facing the support portion, which allows heat radiated from the heater to pass to the sheet, The shielding member is provided in the housing so as to be able to open and close the opening, The drying apparatus according to claim 1 or 2, wherein the non-shielded position is an open position that opens the opening, and the shielded position is a closed position that closes the opening.

6. The drying apparatus according to claim 1 or 2, wherein the sheet characteristic value is one or more of the following: an index value indicating the amount of liquid developer contained in the sheet, an index value indicating the heat capacity of the sheet, and an index value indicating the water content of the sheet.

7. An image forming apparatus comprising the drying apparatus described in claim 1.

Images