Sheet discharge device and image forming apparatus

Abstract

To provide a sheet discharge device capable of further suppressing blocking.SOLUTION: The sheet ejection device includes a rotation mechanism (40) that moves a part of a placement surface (14a) of the sheet ejection tray on which the ejected sheet is placed, and a controller (90) that determines whether there is a possibility of occurrence of blocking, wherein the rotation mechanism (40) moves the part of the placement surface (14a) when the controller (90) determines that there is a possibility of occurrence of blocking.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] 2. Description of the Related Art Conventionally, a sheet discharge device is known that includes a discharge tray onto which sheets having toner fixed thereon are discharged.

[0003] Patent Document 1 describes an image forming apparatus equipped with the sheet discharge device. In the image forming apparatus of Patent Document 1, a toner image is formed on a sheet, and a fixing device applies heat and pressure to the sheet on which the toner image has been formed, thereby fixing the toner image on the sheet and forming an image on the sheet. It also describes that when the sheets are discharged onto a paper output tray and stacked, a blower fan blows air onto the sheets stacked on the paper output tray to cool them. It also describes that this can prevent the occurrence of so-called blocking, in which sheets stick together due to softened toner that has not cooled and solidified. Summary of the Invention [Problem to be solved by the invention]

[0004] However, there is a risk that blocking cannot be sufficiently suppressed. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems, the present invention provides a sheet discharge device having a discharge tray onto which a sheet having a toner fixed thereon is discharged, the device comprising: a moving unit that moves a part of a placement surface on which the discharged sheets of the discharge tray are placed, and a determining unit that determines whether or not blocking is likely to occur, The moving means is characterized in that, when the determining means determines that there is a risk of blocking occurring, it moves a part of the placement surface. [Effects of the Invention]

[0006] According to the present invention, blocking can be further suppressed. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention; [Figure 2] FIG. 4 is a schematic diagram showing a tray drive unit that raises and lowers the paper discharge tray. [Figure 3] FIG. 2 is a diagram showing an example of a hardware block configuration of the image forming apparatus 1. [Figure 4] FIG. 2 is a schematic configuration diagram of a paper discharge tray according to the embodiment. [Figure 5] FIG. 2 is a schematic configuration diagram illustrating an example of a rotation mechanism that rotates a tray movable part. [Figure 6] FIG. 4 is a schematic diagram of a detection mechanism for detecting the upper limit of paper discharge. [Figure 7] 10 is a flowchart of a paper shifting operation in the present embodiment. [Figure 8] 10A and 10B are diagrams illustrating the state of a plurality of sheets on the sheet output tray when the placement surface of the sheet output tray is folded. [Figure 9] FIG. 10 is a schematic plan view showing an example in which side fences are provided on both ends of the paper discharge tray in the width direction. [Figure 10] FIG. 10 is a schematic diagram showing an example in which the tray movable part is rotated so that one widthwise end of the placement surface is positioned lower than the widthwise center of the placement surface. [Figure 11] FIG. 10 is a schematic diagram showing an example in which the tray movable part is rotated so that both ends in the width direction of the placement surface are positioned lower than the center in the width direction of the placement surface. [Figure 12] FIG. 10 is a schematic diagram showing an example in which the tray movable part is rotated so that both ends of the placement surface in the width direction are positioned above the center of the placement surface in the width direction. [Figure 13] FIG. 10 is a diagram showing a modified example of the paper discharge tray. DETAILED DESCRIPTION OF THE INVENTION

[0008] The best mode for carrying out the present invention will be described below with reference to the drawings. Note that a person skilled in the art can easily modify or alter the present invention within the scope of the claims to create other embodiments, and these modifications and alterations are included within the scope of the claims. The following description is an example of the best mode for carrying out the present invention and does not limit the scope of the claims.

[0009] FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus 1 of this embodiment. In the following description, the front-to-rear direction of the image forming apparatus or the width direction of the paper is referred to as the X direction, the left-to-right direction of the image forming apparatus or the paper ejection direction is referred to as the Y direction, and the up-down direction (also the vertical direction) is referred to as the Z direction. In the figure, image forming apparatus 1 is a copying machine that uses an electrophotographic system and is equipped with the following devices: That is, the image forming apparatus is equipped with an image forming device 5 (including a photoreceptor 11, a charging device 32, a developing device 12, a transfer device 31, a cleaning device 33, etc.) as an image forming section. The image forming apparatus also is equipped with a reversing and discharging device 6, a reading device 7, a writing device 8, a paper feeding device 9, a fixing device 10, and a rotating mechanism 40 as a moving means.

[0010] In the image forming apparatus 1, an original document placed on the document placement table of the reading device 7 is read. The read original image is converted into image information and used in image formation processing by the image creating device 5 in accordance with this image information. In the image creating device 5, the surface of the photoreceptor 11 is uniformly charged by the charging device 32, and then the writing device 8 irradiates the photoreceptor 11 with exposure light L based on the image information to form an electrostatic latent image on the photoreceptor 11. The electrostatic latent image is visualized by the developing device 12 to form a toner image. The toner that forms the toner image is electrostatically transferred by the transfer device 31 onto a sheet of paper supplied from the paper feeder 9, and the toner on the transferred paper is fixed to the paper by the fixing device 10.

[0011] The paper fed from the paper feed device 9 by the paper feed roller 9a is transported by the transport roller pair 13a toward the image forming device 5, as shown by arrow 13. Then, the registration timing for the paper relative to the photosensitive member 11 is set by the registration roller pair 13b, and the paper is transported to the transfer device 31, where the toner image is transferred. After the transfer, the paper is transported to the fixing device 10, which applies heat and pressure to the paper on which the toner image has been formed, thereby softening and melting the toner that makes up the toner image on the paper, and fixing the toner image to the paper. The paper on which the toner image has been fixed by the fixing device 10 is transported toward the paper output tray 14 or the reverse discharge device 6.

[0012] In the reversing discharge device 6, the paper is either reversed and discharged to the paper discharge tray 14, or reversed and can be circulated again toward the photosensitive member 11, which is the image carrier on the imaging device 5 side. After passing through the fixing device 10, the paper is discharged to the paper discharge tray 14 via the paper discharge rollers 15 when being discharged straight (normally) out of the image forming apparatus.

[0013] Furthermore, when the paper is transported to the reversing and discharging device 6, it is transported along the path indicated by arrow 16. In this case, the paper transported along the path indicated by arrow 16 is transported to reversing rollers 29 via a pair of transport rollers 19. Reversing rollers 29 are rollers that can rotate forward and backward, and reverse and switch back the paper that has been transported along the path indicated by arrow 16 and has an image formed on one side. When the paper that has been switched back by reversing rollers 29 is to be discharged outside the device, it is transported via a pair of re-conveying rollers 20 along the path indicated by arrow 17 to paper discharge rollers 15, and then discharged to paper discharge tray 14.

[0014] Furthermore, when the paper is reversed and recirculated to the image forming device 5 for image formation on both sides thereof, the paper is switched back by the reversing roller 29 and conveyed along the path indicated by the arrow 18 via the re-conveying roller pair 20 and the conveying roller pair 21. At this time, the paper passes through a curved reversing conveying path provided between the re-conveying roller pair 20 and the conveying roller pair 21 and is guided to the conveying roller pair 21. After passing through the conveying roller pair 21 and having its face reversed, the paper is conveyed by the conveying roller pairs 22a, 22b, 22c, and 22d and is recirculated again toward the photosensitive member 11, which is the image carrier in the image forming device 5, and is discharged to the paper discharge tray 14 via the paper discharge roller 15.

[0015] Paper heated by the fixing device 10 is discharged to the paper output tray 14 at a high temperature, and the toner on the paper discharged to the paper output tray 14 has not cooled and solidified but is in a softened state. If the next paper is discharged on top of this softened toner, there is a risk that the softened toner will cause sheets to stick together (blocking). To prevent this blocking, a cooling fan is installed between the fixing device 10 and the paper output roller 15, and this cooling fan blows air onto the paper as it is discharged straight out of the image forming apparatus to cool the paper. This allows paper to be discharged onto the paper output tray 14 with cooled and solidified toner, thereby preventing blocking.

[0016] The paper discharge tray 14 is configured to be able to move up and down and is capable of stacking a large amount of paper (3500 sheets in this embodiment). FIG. 2 is a schematic diagram showing the tray driving unit 50 that raises and lowers the paper discharge tray 14. As shown in FIG. The tray driving unit 50 includes an elevator motor 51 and a drive transmission unit 55 that transmits the driving force of the elevator motor 51 to a drive shaft 52. Pulleys 56 are attached to both ends of the drive shaft 52, which is disposed above the image forming apparatus, and to both ends of a driven shaft 58, which is disposed below the image forming apparatus. A timing belt 54 is stretched between the pulleys provided at one end of the drive shaft 52 and one end of the driven shaft 58, and between the pulleys provided at the other end of the drive shaft 52 and the other end of the driven shaft 58.

[0017] A base portion 57 on which the paper discharge tray 14 is attached is fixed to each timing belt 54. The driving force of the lifting motor 51 is transmitted to the drive shaft 52 via the drive transmission portion 55, and the timing belt 54 rotates, thereby lifting and lowering the paper discharge tray 14.

[0018] Paper heated by the fixing device 10 is discharged to the paper output tray 14 at a high temperature, and the toner on the paper discharged to the paper output tray 14 has not cooled and solidified but is in a softened state. If the next paper is discharged on top of this softened toner, there is a risk that the softened toner will cause sheets to stick together (blocking). To prevent this blocking, a cooling fan is installed between the fixing device 10 and the paper output roller 15, and this cooling fan blows air onto the paper as it is discharged straight out of the image forming apparatus to cool the paper. This allows paper to be discharged onto the paper output tray 14 with cooled and solidified toner, thereby preventing blocking.

[0019] However, in devices with high paper transport speeds to increase productivity, paper passes through a paper cooling area provided by a cooling fan in a short time. As a result, the paper cannot be sufficiently cooled while passing through the paper cooling area. As a result, even if the toner on the paper can be cooled below its softening temperature, as the number of sheets of paper on the paper output tray increases, heat that cannot be completely cooled by the cooling fan accumulates in the paper. This can cause the internal temperature of the paper stack to reach the temperature at which the toner softens, resulting in blocking. In particular, when the paper output tray 14 is capable of holding a large number of sheets and is loaded with a large number of sheets, as in this embodiment, blocking is likely to occur due to an increase in the internal temperature of the paper stack.

[0020] The blocking occurs when the paper discharged and stacked on the paper output tray 14 does not move while the softened toner cools and solidifies. Even if blocking occurs, re-adhesion can be prevented by removing the toner from the paper discharged on top. Therefore, in this embodiment, a rotation mechanism 40, which serves as a moving means, rotates and moves a portion of the sheet surface on which the discharged paper is placed on the paper output tray 14, bending the sheet surface. By bending the sheet surface, the paper stacked on the paper output tray is deformed and moved. This prevents blocking from occurring even when paper is stacked on softened toner. Even if blocking occurs, the paper movement can remove the toner from the paper. The following describes the features of this embodiment with reference to the accompanying drawings.

[0021] FIG. 3 is a diagram showing an example of a hardware block configuration of the image forming apparatus 1. As shown in FIG. The image forming apparatus 1 includes a controller 90. The controller 90 includes a CPU 90a, a ROM 90b, a RAM 90c, a printer control unit 90d, an image reading control unit 90e, a storage control unit 90f, an input control unit 90g, and an output control unit 90h, and the components constituting the controller 90 are connected by a bus 90i.

[0022] The printer control unit 90d of the controller 90 functions as an interface for the CPU 90a to control each piece of printer-related hardware, such as the image forming unit 5, paper feed unit 9, writing unit 8, reverse discharge unit 6, fixing unit 10, and rotation mechanism 40. The image reading control unit 90e functions as an interface for the CPU 90a to control the reading unit 7.

[0023] The storage control unit 90f functions as an interface for the CPU 90a to control the storage (storage device) 93 included in the image forming apparatus 1. The input control unit 90g functions as an interface for the CPU 90a to control the input unit 94. The output control unit 90h functions as an interface for the CPU 90a to control the output unit 95.

[0024] The controller 90 including the CPU 90a controls the entire image forming apparatus 1. The CPU 90a starts the OS by a boot program stored in the ROM 90b. Then, the CPU 90a executes the control programs stored in the storage 93 and the ROM 90b on the OS.

[0025] The RAM 90c is used as a temporary storage area such as the main memory or work area of ​​the CPU 90a. The storage 93 is a readable / writable nonvolatile storage device such as an HDD. This storage 93 stores various data such as programs for controlling the entire image forming apparatus 1, various application programs, data for managing consumable parts, and videos showing a series of tasks required to resolve a maintenance event. The CPU 90a accesses the storage 93 via a storage control unit 90f.

[0026] The CPU 90a reads out control programs and application programs from the storage 93 and the ROM 90b, and controls the image forming apparatus 1 by executing the programs loaded in the RAM 90c.

[0027] In the image forming apparatus 1 of this embodiment, one CPU executes each process shown in the flowcharts described below using a program loaded in one memory (RAM), but other configurations are also possible. For example, multiple processors, RAM, ROM, and storage may cooperate to execute each process shown in the flowcharts described below. Also, some processes may be executed using hardware circuits such as ASICs and FPGAs.

[0028] The CPU 90a controls the reading device via the image reading control unit 90e to read the image on the document and generate image data. The CPU 90a forms an image on paper in cooperation with each piece of hardware in the printer control unit 90d. The CPU 90a also controls the lifting and lowering of the paper output tray 14 in cooperation with the tray drive unit 50 and the paper output upper limit detection sensor 35 of the printer control unit 90d, and detects the number of sheets stacked on the paper output tray 14. The CPU 90a also performs a paper shifting operation to shift the paper output onto the paper output tray (described later) in cooperation with the rotation mechanism 40, home position sensor 44, temperature sensor 60, etc. of the printer control unit 90d.

[0029] The input control unit 90g connects the input unit 94 to the controller 90 and accepts user operation instructions from the input unit 94, such as a touch panel or hard keys. The output control unit 90h connects the output unit 95 to the controller 90 and controls the output unit 95, which has a display unit such as an LCD or CRT, to display operation screens and videos to the user. In this embodiment, the output unit 95 is described as a display unit that performs display output, but the output unit 95 may also have a speaker that performs audio output in addition to display output. Furthermore, the input unit 94 may also have a microphone that performs audio input in addition to input from the touch panel, hard keys, etc.

[0030] 4A and 4B are schematic diagrams of the discharge tray 14 of this embodiment, with FIG. 4A being a perspective view and FIG. 4B being a side view. 4, the paper output tray 14 provided on the side of the image forming apparatus 1 of this embodiment has a tray fixed portion 14b and a tray movable portion 14a. With the center of the paper width direction, which is orthogonal to the paper discharge direction, as the base point, the tray fixed portion 14b is on the left side in the drawing, i.e., the side farthest from the front of the image forming apparatus 1 (rear side), and the tray movable portion 14a is on the right side in the drawing, i.e., the side closer to the front of the image forming apparatus 1 (front side). Having the tray movable portion 14a on the side closer to the front of the image forming apparatus 1 has the advantage of making it easier to check the movement from the front side.

[0031] The tray fixed portion 14b is fixed to the base portion 57 shown in FIG. 2. The tray movable portion 14a is provided so as to be rotatable (rotatable) by a predetermined angle, with the center of the paper width direction of the paper output tray 14 as a fulcrum. The loading surface 140 can take an initial position shown by the dashed line in the figure and a deformed position shown by the solid line in the figure. In the initial position, the loading surface of the tray fixed portion 14b, which extends straight in the paper width direction, and the loading surface of the tray movable portion 14a are flush with each other. In the deformed position, the loading surface 140 is bent upward from the initial position, with the center of the paper width direction as the base point. Note that the reference numeral 30 shown in FIG. 4 denotes a paper output port from which paper is output, and the loading surface 140 of the paper output tray 14 is longer in the paper width direction, perpendicular to the paper output direction, than the opening length of the paper output port 30.

[0032] In this embodiment, when the tray movable part 14a is in the initial position, the loading surface 140 is parallel to the horizontal. However, as long as the paper does not fall off the loading surface, for example, the loading surface may be inclined in the paper ejection direction so that the downstream side in the paper ejection direction is positioned higher or lower than the upstream side. Also, a home position sensor 44 is provided to detect when the tray movable part 14a is in the initial position.

[0033] FIG. 5 is a schematic diagram illustrating an example of a rotation mechanism 40 that rotates the tray movable portion 14a. The tray movable part 14a is rotatably supported on a pivot 34 that is provided on the tray fixed part 14b or the main body of the image forming apparatus and extends in the paper discharge direction. The rotation mechanism 40 includes a motor 43 as a drive source, an arc-shaped rack gear 42 centered on the center of the pivot 34 that is provided on the end of the tray movable part 14a in the paper width direction, and a pinion gear 41 that meshes with the rack gear 42. The pinion gear 41 is attached to a drive shaft 43a of the motor 43. The driving force of the motor 43 may be transmitted to the pinion gear 41 via multiple gears.

[0034] 5, the temperature sensor 60 is a thermocouple, thermistor, or the like, and is provided near the upstream end of the paper discharge tray 14 in the paper discharge direction, at the center of the paper width direction of the paper discharge tray 14 (see also FIG. 6). The temperature sensor 60 detects the temperature of the bottom surface of the paper stack Pt on the paper discharge tray 14 (the surface temperature of the bottommost paper of the paper stack Pt).

[0035] FIG. 6 is a schematic diagram of a detection mechanism 70 that detects the upper limit of paper discharge. The detection mechanism 70 has a detection feeler 36 and a paper discharge upper limit detection sensor 35. The detection feeler 36 is rotatably attached to the main body of the image forming apparatus. As shown in Figure 6(b), the detection feeler 36 is located in the center of the paper width direction, making it less susceptible to the effects of paper curl.

[0036] When the number of sheets stacked on the paper output tray 14 reaches a predetermined number, the tip of the detection feeler 36 comes into contact with the topmost sheet of the paper stack Pt on the paper output tray 14. As more sheets are discharged from this state onto the paper output tray 14, the detection feeler 36 rotates clockwise in the figure. Then, when the predetermined number of sheets have been placed on the paper output tray 14, the paper output upper limit detection sensor 35 detects the detection feeler 36 and detects that the paper output upper limit has been reached. Upon detecting the paper output upper limit, the controller 90 drives the lift motor 51 to lower the paper output tray 14. By lowering the paper output tray 14, the detection feeler 36 rotates counterclockwise in the figure, and the paper output upper limit detection sensor 35 no longer detects the detection feeler 36.

[0037] The timing for stopping the lift motor 51 (lowering the paper output tray 14) may be when the paper output upper limit detection sensor 35 no longer detects the detection feeler 36, or when a predetermined time has elapsed. This series of controls for lowering the paper output tray 14 is performed until the paper output tray 14 reaches its lowermost position. After the paper output tray 14 reaches its lowermost position, if the paper output upper limit detection sensor 35 detects the detection feeler 36 and determines that the paper output tray 14 is at its upper limit, paper output to the paper output tray 14 is stopped, and the output unit 95 issues an instruction to the user to remove the paper from the paper output tray 14.

[0038] The inventors have confirmed through experiments that blocking rarely occurs in single-sided printing because the toner on stacked sheets does not come into contact with each other, but that blocking is more likely to occur in double-sided printing because the toner on stacked sheets comes into contact with each other. Furthermore, the inventors have confirmed through experiments that even if the toner is not softened when the sheets are discharged to the output tray, the toner softens and blocking is more likely to occur as the number of sheets stacked on the output tray increases. This is thought to be due to the following: As the number of sheets discharged to the output tray 14 increases, the sheets accumulate heat. As a result, the internal temperature of the stack of sheets exceeds the toner softening temperature, softening the toner, and the pressure increases as the number of sheets stacked on the output tray 14 increases. That is, in the case of double-sided printing, blocking does not occur when the number of stacked sheets is small, but as the number of stacked sheets increases, blocking becomes more likely to occur.

[0039] Therefore, in this embodiment, during double-sided printing, a paper shifting operation is performed, which is an operation of rotating the tray movable portion 14a, based on the temperature of the paper discharged onto the paper discharge tray 14 and the number of sheets stacked.

[0040] FIG. 7 is a flowchart of the paper shifting operation in this embodiment. At the start of printing, the tray movable portion 14a is located in the initial position indicated by the solid line in Figure 4. When the double-sided printing job is completed or the paper output tray 14 is full (upper limit: 3,500 sheets) (YES in S1), the controller 90 checks whether the number of sheets placed on the paper output tray 14 is equal to or greater than a predetermined number (S2). If the number of sheets is equal to or greater than the predetermined number (YES in S2), the temperature sensor 60 detects the temperature of the bottom surface of the paper stack (S3). If the temperature detected by the temperature sensor 60 is equal to or greater than the first temperature (YES in S3), the controller 90 determines that blocking may occur and performs a paper shifting operation.

[0041] Whether the number of sheets of paper placed on the paper discharge tray 14 is equal to or greater than the predetermined number can be determined by counting the number of printed sheets. Alternatively, whether the number of sheets of paper is equal to or greater than the predetermined number can be determined from the cumulative driving time of the lift motor 51, the number of times the paper discharge tray 14 has been lowered, etc.

[0042] To confirm the relationship between paper temperature and blocking, the inventors of the present application conducted an experiment in which a thermocouple was inserted into a stack of paper for every 100 sheets, duplex printing was performed up to 3,500 sheets, the maximum number that can be loaded into the paper output tray 14, and the internal temperature of the stack of paper was measured to confirm whether blocking occurred. The printing conditions were also high-speed printing mode, which is a printing mode that is prone to causing blocking.

[0043] This experiment confirmed that blocking is likely to occur when the maximum temperature inside the stack of sheets exceeds 65°C. This experiment also confirmed that the internal temperature of the stack of sheets rises sharply when the number of sheets stacked exceeds 300, and exceeds 65°C at which blocking occurs when the number of sheets stacked reaches around 800. Therefore, in this embodiment, the temperature sensor 60 is configured to check the temperature of the bottom surface of the stack of sheets when the number of sheets placed on the paper output tray 14 is 700 or more. Note that this is just one example, and the temperature can be set appropriately depending on the configuration of the device, the type of toner, etc.

[0044] Furthermore, in this embodiment, the temperature sensor 60 detects the temperature of the bottom surface of the paper stack, but the above-mentioned experiment has shown that the temperature of the bottom surface of the paper stack is lower than the temperature inside the paper stack. The experiment results have confirmed that the temperature of the bottom surface of the paper stack is 60°C or higher and the temperature inside the paper stack exceeds 65°C, so in this embodiment, the first temperature at which the paper shifting operation is performed is set to 60°C. Note that the first temperature is just an example, and may be set appropriately depending on the configuration of the device, the type of toner, etc.

[0045] When the paper shifting operation is performed, the motor 43 is driven to rotate the pinion gear 41, and depending on the direction of rotation, the tray movable part 14a together with the rack gear 42 is rotated counterclockwise in Fig. 5 around the pivot 34 (S4). Then, the tray movable part 14a rotates upward, and when it reaches the deformation position shown by the dashed line in Fig. 5 (Yes in S5), the driving of the motor 43 is stopped, and the rotation of the tray movable part 14a is stopped (S6).

[0046] If the motor 43 is a stepping motor, whether or not the tray movable part 14a has reached the deformation position can be determined from the number of steps. If the motor 43 is a DC motor, whether or not the tray movable part 14a has reached the deformation position can be determined from the driving time of the motor 43. A detection sensor for detecting the tray movable part 14a may be provided, and the detection sensor may detect whether or not the tray movable part 14a has reached the deformation position.

[0047] 8, when the tray movable part 14a moves from the initial position to the deformed position, the loading surface 140 of the paper output tray 14 is bent from the center in the paper width direction as a base point so that the right end in the figure (the end on the front side of the image forming apparatus), which is one end in the paper width direction of the loading surface 140, is positioned above the center in the paper width direction. When the loading surface 140 is bent in this way, the multiple sheets of paper placed on the loading surface 140 are deformed in accordance with the bending of the loading surface 140, and the right end in the figure, which is on the tray movable part 14a side, of the overlapping sheets of paper can be shifted in the paper width direction.

[0048] Note that the left end of the paper, which is the tray fixed portion 14b side in the figure, shifts toward the opposite side from the front side (left side in the figure) due to the weight of the overlapping paper, but the shift is smaller than the right end, which is the tray movable portion 14a side in the figure. Therefore, at the right end of the overlapping paper in the figure, the upper paper shifts toward the front side of the image forming device (right side in the figure) more than the lower paper. This makes it possible to suppress the occurrence of blocking. Furthermore, by shifting the overlapping paper in the paper width direction, the toner particles sticking together can be separated, and blocking can be eliminated.

[0049] When a predetermined time has elapsed since the placement surface 140 was bent (Yes in S7), the motor 43 is reversed, causing the tray movable part 14a to rotate in the reverse direction (clockwise in FIG. 5) (S8), returning the tray movable part 14a from the deformed position to the initial position. By returning the tray movable part 14a to the initial position, the misalignment of the right end (front side) in the drawing, which is the tray movable part 14a side of the stacked sheets, moves in the direction of returning. When the home position sensor 44 detects that the tray movable part 14a has reached the initial position (Yes in S9), the drive of the motor 43 is stopped, and the reverse rotation of the tray movable part 14a is stopped (S10).

[0050] Furthermore, in S3, if the temperature of the bottom surface of the paper stack Pt detected by the temperature sensor 60 is sufficiently higher than the first temperature, the toner may be softened and the paper sheets may be firmly stuck together. Therefore, in this embodiment, if the temperature of the bottom surface of the paper stack Pt detected by the temperature sensor 60 in S3 is equal to or higher than a second temperature higher than the first temperature (60°C), the paper shifting operation shown in S4 to S10 is performed multiple times. In this embodiment, if the temperature is equal to or higher than the second temperature higher than the first temperature (60°C), the paper shifting operation is performed twice.

[0051] Therefore, in S3, if the temperature of the bottom surface of the paper stack Pt detected by the temperature sensor 60 is equal to or higher than a second temperature higher than the first temperature (60°C) (Yes in S11), it is checked whether the paper shifting operation has been performed twice (S12). The second temperature may be set appropriately depending on the toner used, the configuration of the image forming apparatus, etc. The second temperature may also be set based on the ambient temperature of the image forming apparatus, etc. If the paper shifting operation has been performed once, the paper shifting operation shown in S4 to S10 is performed again. In this way, by performing the paper shifting operation multiple times, blocking can be effectively suppressed even when the temperature of the bottom surface of the paper stack is high, equal to or higher than the second temperature.

[0052] In this embodiment, when the temperature is equal to or higher than the second temperature, the sheet shifting operation is performed multiple times, but when the temperature is equal to or higher than the second temperature, the tray movable part 14a may be rotated by a larger amount, and the sheets may be shifted by a larger amount, compared to when the temperature is lower than the second temperature. Even with this configuration, even when the temperature of the bottom surface of the stack of sheets is high at or above the second temperature, the toner has softened, and the sheets are firmly stuck together, the sheets can be effectively separated and blocking can be effectively suppressed.

[0053] In this embodiment, the paper shifting operation is performed immediately after a double-sided printing job is completed or when the paper output tray 14 is full (at its maximum stacking capacity). This is because, after a print job is completed or when the paper output tray 14 is full (at its maximum stacking capacity), the paper is not discharged to the output tray, heat is no longer supplied to the stack of paper on the output tray 14, the stack of paper cools, and there is a risk that the toner will cool completely and cause the sheets to stick together firmly. Therefore, by performing the paper shifting operation immediately after a double-sided printing job is completed or when the paper output tray 14 is full (at its maximum stacking capacity), the paper can be deformed and shifted before the toner cools completely, thereby preventing blocking. Furthermore, the toner can be separated from the sheets, effectively preventing blocking. Furthermore, because the toner is separated from the sheets before they cool completely and become strongly adhered to each other, problems such as image peeling can also be prevented. Furthermore, once the toner particles are separated by the paper shifting operation, they will hardly ever stick together again, so even if the stack of paper sheets is left on the paper output tray for a long period of time after the paper shifting operation, blocking will almost never occur.

[0054] In this embodiment, if the number of sheets placed on the paper output tray 14 is less than a predetermined number (No in S2 in FIG. 7) or if the temperature of the bottom surface of the paper stack is less than the first temperature (No in S3 in FIG. 7), the controller 90 determines that blocking is unlikely to occur and does not perform the paper shifting operation. This makes it possible to reduce the number of times the paper shifting operation is performed compared to performing the paper shifting operation every time a double-sided printing job is completed or when the paper output tray 14 is full (upper limit). This allows for power savings in the image forming apparatus and effectively suppresses blocking.

[0055] In addition, in this embodiment, in a double-sided printing job, the controller 90 performs a paper shifting operation when it determines that blocking is likely to occur based on the temperature of the bottom surface of the stack of sheets and the number of sheets loaded. However, depending on the toner used, even in single-sided printing, softened toner may stick to the sheets and cause blocking. In such cases, even at the end of a single-sided printing job, it may be determined whether or not blocking is likely to occur based on the number of sheets loaded on the paper output tray 14 and the temperature of the bottom surface of the stack of sheets, and if blocking is likely to occur, the paper shifting operation may be performed. In single-sided printing, blocking is less likely to occur than in double-sided printing, and blocking only occurs under higher pressure. Therefore, the number of sheets on the paper output tray 14 used to determine whether or not to perform a paper shifting operation may be greater than in double-sided printing.

[0056] In the above description, whether or not blocking is likely to occur is determined based on the number of sheets placed on the paper output tray 14 and the temperature of the bottom surface of the paper stack, but whether or not blocking is likely to occur may also be determined based only on the temperature of the bottom surface of the paper stack. As a result, when the number of sheets placed on the paper output tray 14 is less than the predetermined number (700 sheets) and the temperature of the bottom surface of the paper stack is equal to or higher than the first temperature (60°C), and there is a risk of blocking, a paper shifting operation can be performed, and blocking can be effectively suppressed.

[0057] Furthermore, when the number of sheets placed on the paper output tray 14 exceeds a certain threshold, the paper shifting operation may be performed multiple times. The more sheets placed on the paper output tray 14, the greater the pressure applied to the sheets at the bottom of the paper stack. Therefore, even if the temperature of the bottom surface of the paper stack is below the second temperature, the above pressure may cause the sheets at the bottom of the paper stack to firmly stick together. Therefore, by performing the paper shifting operation multiple times when the number of sheets placed on the paper output tray 14 exceeds a certain threshold, the sheets can be effectively separated even if they are firmly stuck together due to the above pressure, and blocking can be effectively suppressed.

[0058] Although the tray movable part 14a is rotated using a rack and pinion in the above description, the tray movable part 14a may be rotated, for example, by using an actuator to raise and lower the end (front end) of the tray movable part 14a opposite to the pivot 34. Also, a gear or a motor connected to the pivot 34 connected to the tray movable part 14a may be attached inside the image forming apparatus 1 to rotate the tray movable part 14a.

[0059] In this embodiment, the paper output tray 14 is provided with an end fence. However, the length in the discharge direction is shorter than the length in the transport direction of the maximum paper size that the image forming apparatus can transport, and some paper may protrude from the downstream end of the paper output tray 14 in the discharge direction. Therefore, in such cases, the end fence provided on the paper output tray 14 can be removed or retracted. Because the length in the paper width direction of the paper output tray 14 is longer than the width of the maximum paper size, side fences 141 can be provided on both ends of the paper width direction of the paper output tray 14, as shown in FIG. 9.

[0060] By providing the side fence 141, even if the left edge of the paper on the tray fixed portion 14b side slides in the paper width direction when the tray movable portion 14a is positioned in the upper deformation position, for example, in the case of paper with a smooth, slippery surface, the side fence 141 can catch the paper. This prevents the paper from falling from the edge of the paper output tray 14 in the paper width direction. Note that, as described below, when the tray movable portion 14a is positioned in the lower deformation position, the upper sheet of stacked paper is shifted toward the front of the image forming device more than the lower sheet, thereby suppressing blocking. At this time, the right edge (front side) of the paper on the tray movable portion 14a side may slide in the paper width direction due to the weight of the paper and move along with the movement of the tray movable portion 14a. However, the side fence 141 catches the paper, preventing it from falling from the edge of the paper output tray 14 on the front side of the image forming device.

[0061] 10, the tray movable part 14a may be rotated so that one end of the placement surface 140 in the paper width direction is positioned below the center of the placement surface 140 in the paper width direction. Even with this configuration, as shown in FIG. 10(b), the placement surface 140 of the paper output tray 14 bends with the center of the paper width direction as the base point, and the paper P placed on the placement surface 140 can be deformed along the bend of the placement surface 140. This makes it possible to move the surface of the paper that is in contact with the toner, thereby preventing or eliminating blocking.

[0062] 11, the paper ejection tray may be configured with two tray movable parts 14a1 and 14a2 and two rotation mechanisms that rotate the tray movable parts 14a1 and 14a2, and the placement surface 140 may be bent so that both ends of the paper width direction of the paper ejection tray 14 are positioned below the center. Furthermore, as shown in FIG. 12, the placement surface 140 may be bent so that both ends of the paper width direction of the paper ejection tray are positioned above the center.

[0063] When one of the output trays 14 is a fixed tray part, the portion of the paper placed on the fixed tray part 14b moves less in the paper width direction, but the blocking suppression effect can still be achieved. Furthermore, as shown in Figures 11 and 12, by making both the left and right sides of the figure movable tray parts that rotate around the center of the paper width direction using their respective rotation mechanisms, both the left and right sides of the paper in the figure can move significantly in the paper width direction relative to the toner, as shown in Figures 11(b) and 12(b). This further effectively suppresses the occurrence of blocking.

[0064] In the above description, the tray movable part 14a is moved (rotated) so that the paper width direction end of the loading surface 140 is either above or below the center in the paper width direction. However, the paper width direction end of the loading surface 140 may be moved both above and below the center in the paper width direction to increase the movement range. This allows the paper to move relative to the toner twice, once when the paper width direction end of the loading surface 140 is moved upward and once when it is moved downward, thereby improving the effectiveness of removing the adhering toner. This further effectively suppresses the occurrence of blocking. Furthermore, when the bottom temperature of the paper stack is equal to or higher than the first temperature but lower than the second temperature, the tray movable part 14a is moved (rotated) so that the paper width direction end of the loading surface 140 is either above or below the center in the paper width direction. On the other hand, when the bottom temperature of the paper stack is equal to or lower than the second temperature, the paper width direction end of the loading surface 140 may be moved both above and below the center in the paper width direction to increase the movement range.

[0065] In the above description, the paper output tray 14 is divided into two in the paper width direction, and the placement surface 140 of the paper output tray 14 is folded around the center of the paper width direction, but this is not limited to this. For example, as shown in Fig. 13(a), the paper output tray 14 may be divided into three in the paper width direction, with the center in the paper width direction as the tray fixed part 14b and both sides in the paper width direction as the tray movable parts 14a, and the placement surface 140 may be folded around two points in the paper width direction as base points. Also, as shown in Fig. 13(b), the paper output tray may be divided into two in the paper discharge direction, and the placement surface 140 may be folded around the center in the paper discharge direction as base point.

[0066] In the above description, the loading surface 140 of the tray movable part 14a and the entire lower surface of the tray movable part 14a rotate. However, as shown in FIG. 13(c), the loading surface 140 of the tray movable part 14a may rotate while the lower surface of the tray movable part 14a remains stationary and does not rotate. While the tray movable part 14a rotates around the pivot 34, as shown in FIG. 13(d), the tray movable part 14a may be moved horizontally in the vertical direction to create a step between the loading surface of the tray fixed part 14b and the loading surface of the tray movable part 14a. Even with this configuration, sheets placed on the loading surface may be misaligned, preventing blocking. Alternatively, the tray movable part 14a may be configured to bend relative to the tray fixed part 14b, thereby curving the loading surface.

[0067] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to such specific embodiments, and unless otherwise specifically limited in the above description, various modifications and variations are possible within the spirit and scope of the present invention as set forth in the claims.

[0068] The above description is merely an example, and each of the following aspects provides unique effects. (Aspect 1) In a sheet discharge device having a discharge tray such as a paper discharge tray 14 onto which sheets such as paper P with fixed toner are discharged, the device is provided with a moving means such as a pivoting mechanism 40 that moves a part of a loading surface 140 on which the discharged sheets from the discharge tray are placed, and a determining means such as a controller 90 that determines whether or not blocking is likely to occur, and the moving means moves a part of the loading surface when the determining means determines that blocking is likely to occur. The above-mentioned blocking occurs when the stacked sheets discharged onto the discharge tray do not move while the softened toner cools and solidifies. In aspect 1, by moving a portion of the sheet receiving surface using a moving means such as a rotation mechanism 40, when multiple sheets are stacked on the discharge tray, the portion of the sheet receiving surface can be moved to deform the sheets stacked on the sheet receiving surface and shift the stacked sheets (moving the sheets). This prevents blocking even when the next sheet is discharged onto the softened toner that forms the image on the sheet but has not yet cooled and solidified. This allows for effective prevention of blocking even in highly productive devices. Furthermore, if the determining means determines that blocking may occur, the moving means can move a portion of the placement surface to displace overlapping sheets (move the sheets), thereby effectively suppressing blocking.

[0069] (Aspect 2) In aspect 1, a temperature detection means such as a temperature sensor 60 is provided that detects the temperature of a sheet placed on an output tray such as the output tray 14, and a judgment means such as a controller 90 judges that there is a risk of blocking occurring when the temperature of the sheet detected by the temperature detection means is equal to or higher than a first temperature. As described in the embodiment, when the sheet temperature is equal to or higher than the first temperature, the toner on the sheet is in a softened state, and this toner cools and hardens, which may cause blocking. In the second aspect, when the sheet temperature is equal to or higher than the first temperature, the determining means such as the controller 90 determines that blocking may occur, and shifts overlapping sheets (moves the sheets) by moving a part of the placement surface using the moving means such as the rotating mechanism 40. This makes it possible to effectively suppress the occurrence of blocking. Furthermore, when the sheet temperature is lower than the first temperature, the toner is not softened, and blocking is unlikely to occur, the determining means determines that there is no risk of blocking occurring and does not perform the sheet shifting operation, thereby reducing the number of times the sheet shifting operation is performed and achieving power saving.

[0070] (Aspect 3) In aspect 2, a judgment means such as the controller 90 judges that there is a risk of blocking occurring when a sheet with toner fixed on both sides is discharged to an output tray and the temperature of the sheet detected by the temperature detection means is equal to or higher than a first temperature. As described in the embodiment, when a sheet with toner fixed on both sides is discharged to the discharge tray, such as during a double-sided printing job, and the sheet temperature is equal to or higher than the first temperature and the toner is softened, the toner particles may come into contact with each other, causing blocking. Therefore, in aspect 3, when a sheet with toner fixed on both sides is discharged to an output tray and the temperature of the sheet detected by a temperature detection means such as temperature sensor 60 is equal to or higher than a first temperature, the judgment means determines that there is a risk of blocking occurring and moves a portion of the loading surface 140a, thereby effectively suppressing the occurrence of blocking. Furthermore, when a sheet with toner fixed on one side is discharged to the discharge tray, such as in a one-sided printing job where blocking is unlikely to occur, the determining means determines that there is no risk of blocking occurring and does not perform the sheet shifting operation, thereby reducing the number of times the sheet shifting operation is performed and achieving power saving.

[0071] (Aspect 4) In aspect 2 or 3, a sheet number detection means (in this embodiment, a controller 90) is provided for detecting the number of sheets discharged onto an output tray such as the output tray 14, and a judgment means such as the controller 90 judges that there is a risk of blocking occurring when the number of sheets detected by the sheet number detection means is equal to or greater than a specified number and the temperature of the sheets detected by a temperature detection means such as the temperature sensor 60 is equal to or greater than a first temperature. As explained in the embodiment, as the number of sheets stacked on an output tray such as output tray 14 increases, heat is accumulated in the sheets, and when the specified number of sheets is exceeded, the internal temperature of the sheet stack exceeds the temperature at which the toner softens, and further, blocking becomes more likely to occur due to the pressure on the sheets. Therefore, in aspect 4, when the number of sheets is equal to or greater than the specified number and the temperature of the sheets is equal to or greater than the first temperature, a judgment means such as the controller 90 judges that there is a risk of blocking occurring, and performs a shifting operation to move a portion of the loading surface 140a using the moving means, thereby effectively suppressing blocking. When the conditions of the specified number of sheets or more and the first temperature or more are not satisfied, the determining means determines that there is no risk of blocking occurring and does not perform the sheet shifting operation, so that the number of times the sheet shifting operation is performed can be reduced and power saving can be achieved.

[0072] (Aspect 5) In any of the second to fourth aspects, the moving means such as the rotation mechanism 40 moves a part of the placement surface multiple times when the temperature of the sheet detected by the temperature detecting means is equal to or higher than a second temperature higher than the first temperature. As described in the embodiment, when the temperature is equal to or higher than the second temperature, which is higher than the first temperature, the toner softens and the sheets may stick together firmly. Therefore, when the temperature is equal to or higher than the second temperature, by moving part of the mounting surface multiple times to increase the effect of peeling off the stuck toner, blocking can be effectively suppressed.

[0073] (Aspect 6) In any of the first to fifth aspects, a temperature detection unit such as the temperature sensor 60 detects the temperature of the bottom surface of the stack of sheets stacked on a discharge tray such as the discharge tray 14 . This allows the internal temperature of the sheet stack to be estimated more accurately than when detecting the temperature of the top surface of the sheet stack stacked on the discharge tray. As a result, when there is a risk of blocking due to softening of the toner on the sheets, part of the loading surface 140a can be moved to suppress blocking.

[0074] (Aspect 7) In any of aspects 1 to 6, a determination means such as the controller 90 determines whether or not blocking is likely to occur when a print job is completed or when the number of sheets loaded on an output tray such as the output tray 14 reaches the maximum number of sheets that the output tray can hold. As described in the embodiment, after a print job is completed or the number of sheets stacked on an output tray such as output tray 14 reaches the maximum number that the output tray can hold, no sheets heated by the fixing device are discharged to the output tray, and heat is no longer supplied to the sheet stack stacked on the output tray such as output tray 14. Therefore, after a print job is completed or the number of sheets stacked on an output tray such as output tray 14 reaches the maximum number that the output tray can hold, the temperature of the sheet stack drops, and the softened toner cools, which could cause strong blocking. In the seventh aspect, when a print job is completed or when the number of sheets stacked on an output tray such as output tray 14 reaches the maximum number that the output tray can hold, a determination means such as controller 90 determines whether or not blocking is likely to occur, and if there is a risk of blocking occurring, a moving means such as rotation mechanism 40 can move part of placement surface 140. This makes it possible to deform the sheets stacked on placement surface 140a and shift overlapping sheets (move the sheets) before the softened toner cools down completely, thereby effectively suppressing the occurrence of blocking. Furthermore, if there is no risk of blocking occurring, the operation of moving a portion of the sheet placement surface (hereinafter referred to as the sheet shifting operation) is not performed. This reduces the number of times the sheet shifting operation is performed, thereby enabling power savings, compared to when the sheet shifting operation is performed each time a print job is completed or when the number of sheets stacked on an output tray such as output tray 14 reaches the maximum number that the output tray can hold.

[0075] (Aspect 8) In an image forming apparatus equipped with an image forming means for forming a toner image on a sheet such as paper, and a sheet discharging device for discharging the sheet on which the image has been formed by the image forming means to the outside of the apparatus body, the sheet discharging device used was any one of the sheet discharging devices of embodiments 1 to 7. This makes it possible to effectively suppress blocking. [Explanation of symbols]

[0076] 1: Image forming device 10: Fixing device 14: Paper output tray 14a: Tray moving part 14b: Tray fixing part 15: Paper ejection roller 30: Paper output slot 34: Axis 35: Paper ejection upper limit detection sensor 36:Detection filler 40: Rotating mechanism 41: Pinion gear 42: Rack gear 43: Motor 43a: Drive shaft 44: Home position sensor 50: Tray drive unit 51: Lifting motor 52: Drive shaft 54: Timing belt 55: Drive transmission unit 56: Pulley 57: Base 58: Driven axis 60: Temperature sensor 70: Detection mechanism P:Paper Pt:Paper stack [Prior art documents] [Patent documents]

[0077] [Patent Document 1] Japanese Patent Application Publication No. 2019-139160

Claims

1. A sheet ejection device having an ejection tray onto which a sheet having a toner fixed thereon is ejected, a moving means for moving a part of a placement surface of the discharge tray on which the discharged sheets are placed; a determination means for determining whether or not blocking is likely to occur; The sheet ejection device, wherein the moving means moves a part of the placement surface when the determining means determines that there is a risk of blocking occurring.

2. 2. The sheet ejection device according to claim 1, a temperature detecting means for detecting the temperature of the sheet placed on the discharge tray; The sheet discharge device is characterized in that the determining means determines that there is a risk of blocking occurring when the temperature of the sheet detected by the temperature detecting means is equal to or higher than a first temperature.

3. 3. The sheet ejection device according to claim 2, The sheet discharge device is characterized in that the judgment means determines that there is a risk of blocking when a sheet with toner fixed on both sides is discharged to the discharge tray and the temperature of the sheet detected by the temperature detection means is higher than a first temperature.

4. 3. The sheet ejection device according to claim 2, a sheet number detecting means for detecting the number of sheets discharged onto the discharge tray; The sheet discharge device is characterized in that the judgment means judges that there is a risk of blocking when the number of sheets detected by the sheet number detection means is equal to or greater than a specified number and the temperature of the sheets detected by the temperature detection means is equal to or greater than the first temperature.

5. 3. The sheet ejection device according to claim 2, The sheet ejection device is characterized in that the moving means moves a portion of the placement surface multiple times when the temperature of the sheet detected by the temperature detection means is equal to or higher than a second temperature that is higher than a first temperature.

6. 3. The sheet ejection device according to claim 2, The sheet discharge device is characterized in that the temperature detection means detects the temperature of the bottom surface of the stack of sheets stacked on the discharge tray.

7. 2. The sheet ejection device according to claim 1, The sheet discharge device is characterized in that the judgment means determines whether there is a risk of blocking when a print job is completed or when the number of sheets loaded on the discharge tray reaches the maximum number that the discharge tray can hold.

8. an image forming means for forming a toner image on a sheet; an image forming apparatus including a sheet discharge device that discharges a sheet on which an image is formed by the image forming means to the outside of the apparatus body, 10. An image forming apparatus, comprising: a sheet ejection device according to claim 1;

Images