Sheet feeding device and image forming device

Abstract

To provide a sheet feeding device capable of suppressing occurrence of double feeding or non-feeding even in a high temperature and high humidity environment or when a sheet has high rigidity.SOLUTION: A sheet feeding device 70 including: a loading platform 72 for loading sheets S; a feeding mechanism for feeding the topmost sheet S from among the sheets S loaded on the loading platform 72 in a predetermined feeding direction; a regulation part 73 for regulating the positions of both ends of the sheets S loaded on the loading platform 72 in a direction perpendicular to the feeding direction; and an air applying mechanism 77 provided in the regulation part 73 for applying air to upper parts of both ends of the sheets S loaded on the loading platform 72; and a sheet pressing part 74 capable of pressing a center part between both ends of a sheet is provided above the loading platform 72, and the loading platform 72 is provided by the sheet feeding device 70 which is formed so that both ends of the sheets S are positioned higher than the center in the loading direction of the sheets S.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] Conventionally, a type of feeding device is known in which nozzles are provided above a regulating portion (guide portion) that regulates the side ends of sheets (papers), and air from a blower fan provided in the guide portion is blown onto the upper side end surfaces of the sheets stacked on the paper feed table (FIG. 10).

[0003] In this type of feeding device, the stacked sheets are separated by the air fed through the nozzles between the stacked sheets (i.e., between the papers), and thus, double feeding during sheet feeding can be prevented (FIG. 11).

[0004] However, in the conventional feeding device, in an environment where the adhesive force between the sheets extremely increases, such as in a high-temperature and high-humidity environment, the adhesion of the sheets cannot be released only by the air from the blower fan, and double feeding or non-feeding has occurred.

[0005] Also, in order to surely release the adhesion of the sheets, it may be considered to increase the output of the blower fan and apply stronger air to the sheets. However, by increasing the output of the blower fan, more power is consumed.

[0006] Patent Document 1 discloses a feeding device having a bottom plate on which sheets are stacked such that the side surfaces of the sheets are higher than the central portion in order to easily introduce air between the sheets. However, since a sheet with high stiffness like a thick paper is difficult to deform following the shape of the bottom plate, the side surface of the sheet may not be higher than the central portion.

Summary of the Invention

Problems to be Solved by the Invention

[0007] Therefore, an object of the present invention is to provide a sheet feeding device capable of suppressing double feeding and non-feeding even in a high-temperature and high-humidity environment or with a sheet having high rigidity.

Means for Solving the Problems

[0008] This problem is solved by a sheet feeding device including a stacking table on which sheets are stacked, a feeding mechanism that feeds the uppermost sheet from the sheets stacked on the stacking table in a predetermined feeding direction, a restricting portion that restricts positions of both ends of the sheet stacked on the stacking table in a direction orthogonal to the feeding direction, and an air applying mechanism that is provided in the restricting portion and applies air to upper portions of both ends of the sheet stacked on the stacking table, the sheet feeding device including a sheet pressing portion above the stacking table that can press a central portion between both ends of the sheet, and the stacking table being formed such that both ends of the sheet are positioned above the central portion in a stacking direction of the sheet.

Effects of the Invention

[0009] It is possible to suppress double feeding and non-feeding even in a high-temperature and high-humidity environment or with a sheet having high rigidity.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0011] <Configuration of the Image Forming Apparatus> FIG. 1 is a schematic configuration diagram showing an example of an image forming apparatus according to an embodiment of the present invention. The illustrated image forming apparatus is a printer that forms an image by an electrophotographic method. The printer 1000 includes an image forming unit 1, a transfer unit 2, a sheet supply unit 3, a fixing unit 4, a sheet return unit 5, a sheet discharge unit 6, an exposure unit 7, and the like. Here, the image forming unit 1, the transfer unit 2, and the exposure unit 7 are examples of "image forming means".

[0012] The image forming unit 1 includes a plurality of image forming units 10A, 10B, 10C, 10D. Since the image forming units 10A to 10D have the same or equivalent configurations, they are collectively referred to as the image forming unit 10 when not particularly distinguished.

[0013] The image forming units 10A to 10D form toner images of different colors. For example, the image forming unit 10A forms a yellow (Y) toner image, and the image forming unit 10B forms a magenta (M) toner image. The image forming unit 10C forms a cyan (C) toner image, and the image forming unit 10D forms a black (K) toner image.

[0014] The number and color arrangement order of the image forming units 10 are not limited to the above. The number of the image forming units 10 may be three or less, or may be five or more. The color arrangement order of the image forming units 10 may be appropriately determined according to the specifications of the image forming units, toner characteristics, etc. Further, the image forming section 1 may include an image forming unit that uses a special color toner other than Y, M, C, and K. The special color is not necessarily limited to a colored one, and may include a colorless one such as a clear toner.

[0015] The image forming unit 10 includes a photoreceptor 11, a charging roller 12, a developing roller 13, a cleaner 14, etc. The photoreceptor 11 is, for example, a cylindrical photoreceptor drum. The photoreceptor 11 is rotationally driven clockwise (in the direction of the arrow) in the figure. The charging roller 12 applies charges to the surface of the photoreceptor 11 and charges the surface of the photoreceptor 11 to a predetermined potential.

[0016] The developing roller 13 carries, on its surface, for example, a two-component developer containing toner and a magnetic carrier. The developing roller 13 applies toner to the electrostatic latent image formed by exposing the surface of the photoreceptor 11 charged to a predetermined potential by the exposure section 7 described later, and forms a toner image on the surface of the photoreceptor 11. The cleaner 14 includes cleaning members such as a cleaning roller and a cleaning blade, for example. The cleaner 14 cleans the surface of the photoreceptor 11 that has passed through the transfer section 2 described later.

[0017] The transfer section 2 is disposed, for example, below the image forming section 1. The transfer section 2 includes a plurality of transfer rollers 20, a transfer belt 21, etc. The transfer roller 20 is provided at a position facing the photoreceptor 11 included in the image forming unit 10. The transfer roller 20 is provided so as to be able to contact the photoreceptor 11 via the transfer belt 21, and a nip (hereinafter referred to as a transfer nip) is formed between the photoreceptor 11 and the transfer belt 21 by pressing the transfer roller 20 against the photoreceptor 11 side. A transfer bias is applied to the transfer roller 20 to form an electric field in the transfer nip.

[0018] The transfer belt 21 is an endless belt composed of materials such as vinylidene fluoride, ethylene-tetrafluoroethylene copolymer, polyimide, and polycarbonate, which are configured in a single layer or multiple layers. The transfer belt 21 is stretched over a plurality of support rollers and moves counterclockwise in the figure.

[0019] The sheet supply unit 3 is disposed, for example, at the lower part of the printer 1000. The sheet supply unit 3 includes a tray 30 for stacking the sheets S, and a feeding mechanism 31 for feeding out the sheets S one by one from the tray 30. Further, the sheet supply unit 3 includes a pair of synchronous rollers 33 for conveying the sheet S to the transfer unit 2 at a predetermined timing, and a conveying roller 32 for conveying the sheet S sent from the feeding mechanism 31 to the pair of synchronous rollers 33.

[0020] Among these, the feeding mechanism 31 includes a chamber 336 for sucking the uppermost sheet S from the sheets S stacked on the tray 30, a feeding section 310 for sending the sucked sheet S in a predetermined direction, and a feeding-out section 320 for feeding out the sheet S sent from the feeding section 310 to the conveying roller 32.

[0021] The fixing unit 4 is disposed, for example, downstream of the transfer unit 2 in the sheet conveying direction. The fixing unit 4 includes a heating roller 40, a pressure roller 41, and the like. The heating roller 40 and the pressure roller 41 can be brought into contact with each other, and a nip (hereinafter referred to as a fixing nip) is formed by their contact with each other. The sheet S onto which the toner image is transferred in the transfer unit 2 is heated and pressurized at the fixing nip, and the toner image is fixed to the sheet S.

[0022] The sheet discharge unit 6 is disposed, for example, downstream of the fixing unit 4 in the sheet conveying direction. The sheet discharge unit 6 includes switching mechanisms 60a, 60b, etc. for switching the discharge destination of the sheet S, and conveys the sheet S toward the outside of the machine or the sheet return unit 5 described later by the switching mechanisms 60a, 60b.

[0023] The sheet return section 5 is disposed, for example, below the sheet discharge section 6, the fixing section 4, and the transfer section 2. The sheet return section 5 includes a return path 50 provided with a plurality of conveying rollers. The end point of the return path 50 merges with the sheet supply section 3 and conveys the sheet S sent from the sheet discharge section 6 toward the transfer section 2 again.

[0024] The exposure unit 7 is disposed, for example, above the image forming unit 1. The exposure unit 7 scans the photosensitive member 11 charged to a predetermined potential by the charging roller 12 with a laser beam L to form an electrostatic latent image on the surface of the photosensitive member 11.

[0025] In the above configuration, when the printer 1000 receives image data from an external computer or the like, it shifts to a print job and starts driving the transfer belt 21 and the like. Then, in the image forming unit 1, the surface of the rotating photosensitive member 11 is uniformly charged to a predetermined charging potential by the charging roller 12.

[0026] On the surface of the charged photosensitive member 11, electrostatic latent images for respective colors are formed by optical scanning using the laser beam emitted from the exposure unit 7 based on the image data. After the electrostatic latent image is developed into a toner image by the developing roller 13, it is sequentially transferred onto the surface of the sheet S conveyed by the transfer belt 21 to form a toner image in which the respective colors are superimposed. After the toner image is transferred to the sheet S, the photosensitive member 11 is cleaned by the cleaner 14, and toner and the like remaining on the surface of the photosensitive member 11 are removed from the surface of the photosensitive member 11.

[0027] The sheet S sent out from the feeding mechanism 31 of the sheet supply section 3 is conveyed until it hits the synchronous roller pair 33, and if the sheet S hits the synchronous roller pair 33, the conveyance is temporarily stopped. Then, the synchronous roller pair 33 resumes the conveyance in accordance with the timing when the toner image on the photosensitive member 11 reaches the transfer nip. The toner image is transferred to the sheet S resumed from the conveyance by the synchronous roller pair 33 in synchronization with the toner image on the photosensitive member 11 at the transfer nip.

[0028] After transfer, the sheet S moves to the fixing unit 4, and the fixing unit 4 applies heat and pressure to the toner image on the sheet S to fix the toner image on the sheet S. Thereafter, the sheet S moves to the sheet discharge unit 6, and according to the guidance of the switching mechanisms 60a and 60b, the sheet S is sent outside the machine or to the sheet return unit 5. The sheet return unit 5 is mainly used when the sheet S is inverted in the vertical direction (front and back) and re-fed to the transfer nip. After the toner image is transferred to the back surface of the sheet S at the transfer nip, the sheet S is discharged from the sheet discharge unit 6.

[0029] In the printer 1000 having the above configuration, for example, as the tray 30 and the feeding mechanism 31, the sheet feeding device of the present invention can be applied. Thereby, even when various types of sheets are used, the sheet S is supplied to the image forming unit 1 one by one, and the operation reliability of the printer 1000 can be improved.

[0030] Note that the image forming apparatus is not limited to a printer that forms an image by an electrophotographic method, and may be a printer that forms an image by another method such as an inkjet method.

[0031] <Configuration of the Sheet Feeding Device> FIG. 2 is a schematic perspective view of a sheet feeding device according to an embodiment of the present invention, and FIG. 3 is a schematic front view of the sheet feeding device according to an embodiment of the present invention. FIG. 3 is a schematic front view of the sheet feeding device 70 as viewed in the feeding direction. The sheet feeding device 70 has a stacking table 72 for stacking the sheet S and a lifting mechanism for lifting and lowering the stacking table 72. The sheet feeding device 70 also has a feeding mechanism for feeding the uppermost sheet S from the sheets S stacked on the stacking table 72 in a predetermined feeding direction, and a guide portion 73 as a regulating portion for regulating the positions of both ends of the sheet in the direction orthogonal to the feeding direction of the sheets S stacked on the stacking table 72. The sheet feeding device 70 also has a blower fan 77 as an air supply mechanism provided in the guide portion 73 for applying air to the upper portions of both ends of the sheet S stacked on the stacking table 72.

[0032] In the sheet feeding device 70, for example, it is possible to apply the delivery mechanism 31 as a feeding mechanism.

[0033] Further, the sheet feeding device 70 has a paper center pressing portion 74 as a sheet pressing portion capable of pressing the central portion between both ends of the sheet above the stacking table 72. The stacking table 72 is formed such that both ends of the sheet are positioned above the central portion of the sheet S when viewed in the stacking direction or the feeding direction of the sheet S. In other words, the stacking table 72 has a shape in which both end portions of the sheet S stacked thereon are lifted with respect to the central portion. For example, the paper center pressing portion 74 is installed on the bottom surface of the delivery mechanism 31, and does not press the sheet S by its own weight, but receives power from a drive portion provided in the sheet feeding device 70 and presses the sheet S downward with an appropriate pressing force.

[0034] When the central portion of the sheet S stacked on the stacking table 72 is pressed by the paper center pressing portion 74, the sheet S deforms following the shape of the stacking table 72, both ends of the sheet are lifted, and it becomes a bent state. Thereby, even in the case of a sheet S in a high temperature and high humidity environment or a sheet with high rigidity, air easily enters between the stacked sheets, and the adhesion of the sheet S can be easily released.

[0035] Further, a blower fan 77 is attached to the upper portion outside each guide portion 73, and a nozzle 78 for ejecting the air generated by the blower fan 77 opens on the inner surface of the guide portion 73. The air from the nozzle 78 is blown onto the upper side end surface of the sheet S stacked on the stacking table 72. Above the nozzle 78, a sheet retainer 75 for pressing the sheet S stacked on the stacking table 72 projects from the inner surface of the guide portion 73.

[0036] The stacking table 72 is vertically movable by a lifter motor as a lifting mechanism provided in the sheet feeding device 70. When the user pulls out the tray 30 from the device to set the sheet S, it is detected by a sensor, and the lifter motor acts so that the stacking table 72 descends to the lower limit position, and when the tray 30 is stored in the device, the stacking table 72 is configured to rise.

[0037] As shown in FIG. 3, since both ends of the loading table 72 (the loading portion of the loading table 72) are lifted more than the central portion, both ends of the sheet S loaded on the loading table 72 are lifted following the shape of the loading table 72 and are in a deflected state.

[0038] FIG. 4(a) is an enlarged view of the paper side end portion of the conventional example, and FIG. 4(b) is an enlarged view of the paper side end portion of the present invention. As shown in FIG. 4(a), when air is blown onto the sheets stacked flat, since the sheets are in close contact with each other, it is difficult for air to enter between the sheets, and there may be a case where the sheets do not separate well. On the other hand, as shown in FIG. 4(b), when air is blown onto the deflected sheet S, the close contact between the sheet S and the sheet S is loosened, air easily enters between the sheets (between the papers), and the close contact between the sheets is easily released.

[0039] FIG. 5 is a schematic explanatory view showing a state in which a sheet with high rigidity is placed on the loading table according to the conventional example. As shown in the figure, a sheet with stiffness like cardboard and high rigidity is difficult to deform following the shape of the bottom plate of the loading table 72. Therefore, the sheets still remain in close contact at the upper parts of both ends of the sheet, and ultimately it is difficult for air to enter between the sheets.

[0040] Therefore, according to the embodiment of the present invention shown in FIG. 6, by pressing the central portion of the paper with the paper central pressing portion 74, the sheet S is made to follow the shape of the loading table 72 and deformed. Here, FIG. 6 is a schematic front view showing the pressing state of the sheet S by the paper central pressing portion 74. FIG. 6(a) shows the case where the paper central pressing portion 74 is at a high pressing position, and FIG. 6(b) shows the case where the paper central pressing portion 74 is at a low pressing position.

[0041] In the embodiment shown in FIG. 6, the paper center pressing portion 74 is provided so as to be vertically movable in the stacking direction of the sheet S. In FIG. 6(a) where the paper center pressing portion 74 is at a high pressing position, both ends of the sheet are moderately bent and deformed, whereas in FIG. 6(b) where the paper center pressing portion 74 is at a low pressing position, the sheet S is pressed more downward, and both ends of the sheet are bent and deformed more greatly. Thus, by providing the paper center pressing portion 74 of the sheet feeding device 70 so as to be movable, the sheet feeding device 70 can correspond to various sheets S having various stiffnesses.

[0042] The paper center pressing portion 74 of the sheet feeding device 70 is vertically movable, for example, by the power from a lifter motor as a lifting mechanism provided in the sheet feeding device 70. Note that a common lifter motor may be used for the stacking table 72 and the paper center pressing portion 74, or a separate lifter motor may be provided for the paper center pressing portion 74.

[0043] FIG. 7 is a schematic front view showing a sheet feeding device according to another embodiment of the present invention. In the sheet feeding device 70 of the present embodiment, the guide portion 73 is disposed at a position narrower than the width of the sheet S stacked on the stacking portion. Thereby, as shown in the figure, both ends of the sheet are further lifted and further bent, and air more easily enters between the stacked sheets.

[0044] FIG. 8 is a schematic perspective view showing a sheet feeding device according to another embodiment of the present invention. In the sheet feeding device 70 of the present embodiment, the guide portion 73 is movable in a direction orthogonal to the feeding direction of the sheet S. Further, the guide portion 73 has a lifting portion 79 that acts on the sheet S so as to lift both ends of the sheet at the lower part in the stacking direction of the sheet S. That is, the guide portion 73 is not flat, and has a lifting portion 79 having a lifted shape at the lower part on the inner surface of the guide portion 73. As a result, when the guide portion 73 is moved in the width direction of the sheet S (the direction orthogonal to the feeding direction) with the sheet S set on the loading table 72, it can be smoothly moved without being caught by the sheet S.

[0045] FIG. 9 is an explanatory view of a sheet feeding device according to another embodiment of the present invention. In the sheet feeding device 70 of the present embodiment, the guide portion 73 is movable in a direction orthogonal to the feeding direction of the sheet S. Further, the angle of the air blown from the nozzle 78 can be changed according to the position of the guide portion 73 in the width direction of the sheet S or the sheet width. Specifically, in FIG. 9(a), the two guide portions 73 are in a narrower position, and since both ends of the sheet are greatly bent, the inclination angles of the air blown to the nozzle 78 and both ends of the sheet are large. In FIG. 9(b), the two guide portions 73 are in a middle position, and since both ends of the sheet are bent relatively greatly, the inclination angles of the nozzle 78 and the air are in the middle. In FIG. 9(c), the two guide portions 73 are in a wider position, and since the bending of both ends of the sheet is smaller, the inclination angles of the nozzle 78 and the air are substantially flat and horizontal. In other words, since the loading table 72 has a shape that rises upward from the central portion toward the guide portion 73, the angles of both end portions of the sheet S become larger as they move away from the central portion.

[0046] For example, as shown in FIG. 9, the angle of the nozzle 78 can be set in three steps, and the user can appropriately select the angle of the nozzle 78 according to the position of the guide portion 73 or the sheet width. Alternatively, a link mechanism that links the position of the guide portion 73 and the angle of the nozzle 78 may be provided in the sheet feeding device 70, whereby the angle of the nozzle 78 is automatically adjusted according to the position of the guide portion 73 or the sheet width.

[0047] According to the present embodiment, by making it possible to change the angle of the nozzle 78, the air can be applied to the sheet S at an optimal angle for the sheet S to be used.

[0048] The above-described embodiments can be used not only individually but also in combination with each other.

Explanation of Reference Numerals

[0049] 70 Sheet Feeding Device 72 Loading Table 73 Guide Part (Restricting Part) 74 Sheet Center Pressing Part (Sheet Pressing Part) 77 Blower Fan (Air Applying Mechanism) 79 Lifting Part 1000 Image Forming Apparatus S Sheet

Prior Art Documents

Patent Documents

[0050]

Patent Document 1

Claims

1. A loading table for loading sheets, A feeding mechanism for feeding the topmost sheet from the sheets loaded on the loading table in a predetermined feeding direction, A restricting portion for restricting the positions of both ends of the sheet in the direction perpendicular to the feeding direction of the sheet loaded on the loading table, An air supply mechanism provided in the restricting portion for applying air to the upper portions of both ends of the sheet loaded on the loading table, a sheet feeding device comprising: Above the loading table, comprising a sheet pressing portion capable of pressing the central portion between both ends of the sheet, The loading table is formed such that both ends of the sheet are positioned above the central portion in the sheet loading direction. A sheet feeding device characterized by the above.

2. The sheet feeding device according to claim 1, wherein the sheet pressing portion is movable in the sheet loading direction.

3. The sheet feeding device according to claim 1, wherein the restricting portion is arranged at a position narrower than the width of the sheet loaded on the loading table.

4. The restricting portion is movable in the direction perpendicular to the feeding direction, and the restricting portion has a lifting portion that acts on the sheet in a direction of lifting both ends of the sheet at the lower part in the sheet loading direction. The sheet feeding device according to claim 1.

5. The restricting portion is movable in the direction perpendicular to the feeding direction, and the angle of the air supplied from the air supply mechanism can be changed according to the position of the restricting portion. The sheet feeding device according to claim 1.

6. Image forming means for forming an image on a sheet, The sheet feeding device according to any one of claims 1 to 5 for feeding the sheet toward the image forming means, An image forming apparatus characterized by comprising the above.

Images