Sheet feeder and image forming device

Abstract

To prevent multi-feeding caused by sheet adhesion.SOLUTION: This sheet feeder comprises: a sheet loading unit; blowing means for separating upper sheets of a sheet bundle stacked on the sheet loading unit for each of a plurality of sheets; suction means for sucking an uppermost sheet of the sheet bundle by air; conveyance means having a feeder belt to convey the sheet sucked by the suction means; and lifting means for lifting the sheet loading unit. The lifting means raises the sheets separated by the blowing means, stops the rising of the sheet loading unit so as to suck the uppermost sheet of the sheet bundle with the suction means when the sheet loading unit rises up to a position where the uppermost sheet of the sheet bundle and the feeder belt come into contact with each other, and lowers the sheet loading unit to a prescribed position after the uppermost sheet of the sheet bundle is sucked by the suction means. The conveyance means feeds the sucked sheet.SELECTED DRAWING: Figure 7

Description

[Technical field]

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

[0002] There are known paper feeders (sheet feeders) that pull out and transport paper from a paper stack (sheet stack) loaded on a loading tray for sheets such as paper, and image forming apparatuses equipped with the same. One such paper feeder includes a paper stacking tray on which the paper stack is loaded, a paper transport belt (sheet transport belt) disposed above the paper stacking tray, and a fan that draws in air through the ventilation holes in the paper transport belt, and the air is sucked in through the ventilation holes in the paper transport belt to adsorb the topmost paper of the paper stack to the paper transport belt and transport it.

[0003] For example, Patent Document 1 discloses a paper feeding device that includes a paper loading platform for loading a stack of paper, a lifting section for raising and lowering the paper loading platform, and a paper transport member for adsorbing and transporting paper from the paper stack by suctioning air, and a control section for lowering the paper loading platform a specified amount by controlling the lifting section during the suction period when the paper is adsorbed to the paper transport member by suctioning air, and for starting transport of paper by the paper transport member during or after the paper loading platform has been lowered the specified amount.

[0004] Here, it becomes difficult for the paper transport belt to attract heavy paper. The force of attraction varies depending on the environment. In addition, when the top surface of the paper stack is brought closer to the paper transport belt, not only the topmost paper in the paper stack but also the next paper that overlaps the topmost paper is likely to be attracted to the paper transport belt. In some cases, this can cause double feeding due to the paper sticking tightly to each other. Therefore, it is necessary to make the paper transport belt attract the paper well and effectively prevent double feeding of paper. Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to prevent double feeding due to tight contact of sheets. [Means for solving the problem]

[0006] In order to solve the above problem, the invention of claim 1 comprises a sheet stacking section for stacking a stack of sheets, an air blowing means for separating the top sheet of the sheet stack stacked on the sheet stacking section into multiple sheets, a suction means for sucking the top sheet of the sheet stack with air, a conveying means for transporting the sheet sucked by the suction means and having a feed belt, and a lifting means for raising and lowering the sheet stacking section, wherein the lifting means raises the sheet separated by the air blowing means, and when the sheet stacking section has risen to a position where the top sheet of the sheet stack and the feed belt contact each other, the lifting means stops the lifting of the sheet stacking section to allow the suction means to suck the top sheet of the sheet stack, and after the suction means has sucked the top sheet of the sheet stack, the sheet stacking section is lowered to a predetermined position, and the conveying means feeds the sucked sheet. Effect of the Invention

[0007] According to the present invention, it is possible to prevent double feeding due to sheets sticking to each other. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing the overall configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2A] FIG. [Figure 2B] FIG. 2 is an external view of a suction unit and a transport unit according to the embodiment. [Diagram 3] FIG. 2 is a block diagram showing a control system according to the embodiment. [Figure 4A] 5A to 5C are diagrams illustrating a feeding preparation operation in the embodiment according to the present invention. [Figure 4B] 5A to 5C are diagrams illustrating a feeding preparation operation in the embodiment according to the present invention. [Figure 4C]5A to 5C are diagrams illustrating a feeding preparation operation in the embodiment according to the present invention. [Figure 4D] 5A to 5C are diagrams illustrating a feeding preparation operation in the embodiment according to the present invention. [Diagram 5] 5A and 5B are diagrams for explaining a configuration for detecting an upper limit position of a paper stacking unit in the embodiment. [Figure 6] 5A and 5B are diagrams for explaining a configuration for detecting a lower limit position of a paper stacking unit in the embodiment. [Figure 7] FIG. 11 is a diagram showing an example of a control flow of a feeding preparation operation according to the embodiment. [Figure 8] FIG. 13 shows another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] <Embodiments of the present invention> DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

[0010] In addition, in each drawing for explaining the embodiments of the present invention, components such as parts and components having the same function or shape are given the same symbols as far as possible to distinguish them, and once they have been explained, their explanations will be omitted.

[0011] [Configuration of image forming device] 1 is a diagram showing the overall configuration of an image forming apparatus according to the present embodiment, First, the overall configuration and operation of the image forming apparatus 1 will be described with reference to FIG.

[0012] In FIG. 1, reference numeral 1 denotes a copier as an image forming apparatus, reference numeral 2 denotes an original reading unit that optically reads image information of an original D, and reference numeral 3 denotes an exposure unit that irradiates exposure light L based on the image information read by the original reading unit 2 onto a photosensitive drum 5.

[0013] Also, reference numeral 4 denotes an image creating unit which forms a toner image (image) on the photosensitive drum 5, reference numeral 7 denotes a transfer roller which abuts against the photosensitive drum 5 via a transfer transport belt 8 to form a transfer nip, reference numeral 8 denotes a transfer transport belt which transfers the toner image formed on the photosensitive drum 5 onto paper P0 and transports it, and reference numeral 10 denotes an original transport unit (automatic original transport device) which transports the set original D to the original reading unit 2.

[0014] Also, reference numerals 12 and 13 denote paper feed cassettes (feeding devices) in which paper P0, which is an example of a sheet, is stored, and reference numeral 17 denotes registration rollers (timing rollers) that transport paper P0 toward the transfer nip.

[0015] In addition, reference numeral 20 denotes a fixing device that fixes the toner image (unfixed image) carried on the paper P0, 21 denotes a fixing roller installed in the fixing device 20, 22 denotes a pressure roller installed in the fixing device 20, 31 denotes a paper output tray on which the paper P0 discharged from the device main body 1 is loaded, 70 denotes a feeding section (large-capacity feeding device) in which a large volume of paper P0 is stored, and 100 denotes an operation display panel on which various information about the device is displayed or on which operation buttons for performing operations are displayed.

[0016] With reference to FIG. 1, the operation of image forming apparatus 1 during normal image formation will be described.

[0017] First, the document D is transported (fed) from the document table in the direction of the arrow in the figure by the transport rollers of the document transport unit 10, and passes over the document reading unit 2. At this time, the document reading unit 2 optically reads image information of the document D passing above it.

[0018] The optical image information read by the document reading unit 2 is converted into an electrical signal and then transmitted to the exposure unit 3 (writing unit). The exposure unit 3 then emits exposure light L, such as a laser beam, based on the image information of the electrical signal toward the photoconductor drum 5 of the imaging unit 4.

[0019] Meanwhile, in the image creating unit 4, the photosensitive drum 5 rotates clockwise in FIG. 1, and after going through a predetermined image creating process (charging process, exposure process, and development process), an image (toner image) corresponding to the image information is formed on the photosensitive drum 5.

[0020] Then, the image formed on the photosensitive drum 5 is transferred onto the paper P0 transported by the registration roller 17 at the transfer nip (the position where the transfer roller 7 contacts the photosensitive drum 5 via the transfer transport belt 8).

[0021] On the other hand, the paper P0 transported to the transfer nip operates as follows. First, one of the multiple paper feed cassettes 12, 13 in the main body of the image forming apparatus 1 is automatically or manually selected (for example, the topmost paper feed cassette 12 is selected). Then, the topmost sheet of paper P0 stored in the paper feed cassette 12 is fed by the paper feed mechanism 52 (comprised of a feed roller, a pickup roller, a backup roller, etc.) and transported toward the transport path. Thereafter, the paper P0 passes through the transport path on which multiple transport rollers are arranged, and reaches the position of the registration rollers 17.

[0022] In addition, when the feeding section 70, which is a large-capacity sheet feeding device installed on the side of the main body of the image forming apparatus 1, is selected, the uppermost sheet P0 of the multiple sheets P0 stacked on the loading section 72 of the feeding section 70 is fed by the conveying belt 90C of the conveying section 90, which is a conveying device, toward a conveying path on which a pair of conveying rollers is installed, and then reaches the position of the registration roller 17.

[0023] The paper P0 that has reached the position of the registration roller 17 is transported toward the transfer nip in time for alignment with the image formed on the photosensitive drum 5.

[0024] After the transfer process, the paper P0 passes through the transfer nip position, and is then transported by the transfer transport belt 8 to the fixing device 20. The paper P0 that has reached the fixing device 20 is fed between the fixing roller 21 and the pressure roller 22, where the toner image is fixed by the heat from the fixing roller 21 and the pressure from both members 21 and 22 (the fixing process). The paper P0 after the fixing process with the toner image fixed is sent out from between the fixing roller 21 and the pressure roller 22 (the fixing nip), and is then discharged from the main body of the image forming apparatus 1 and stacked on the paper output tray 31 as an output image. In this way, a series of image forming processes are completed.

[0025] [About the feeding section] 2A is a diagram showing an outline of the feeding section. The feeding section 70 (an example of a sheet feeding device) feeds paper (an example of a sheet) one by one to the transport path R. The feeding section may also be called a paper feeding section or a sheet feeding section.

[0026] As shown in FIG. 2A, the feeding section 70 includes a paper stacking section 72, a blower section 79, a transport section 90, a suction section 95, a pinch feeding section 114, a lifting mechanism 115, and a feeding detection sensor 117.

[0027] The paper stacking section 72 (an example of a sheet stacking section) is a tray or cassette on which multiple sheets of paper can be stacked. The paper stacking section 72 is configured so that the user can replenish the paper. The paper stacking section 72 is supported by the frame of the feeding section 70 so that it can be raised and lowered within a predetermined lifting range by the lifting mechanism 115. The lifting mechanism 115 (an example of a lifting means) can be configured to raise and lower the paper stacking section 72 by, for example, lifting or lowering a wire using a lifting motor 115A, which is a drive motor.

[0028] The air blowing section 79 is disposed above the paper stacking section 72 (positive side in the Y-axis direction) and below the suction section 95 (negative side in the Y-axis direction). The air blowing section 79 is disposed in a position in the horizontal direction (X-axis direction) where it can face the paper stack P stacked in the paper stacking section 72. The air blowing section 79 blows air from the side toward the multiple sheets of paper stacked in the paper stacking section 72, thereby lifting up some of the sheets located at the top of the stack of paper stack P and separating the sheets. Note that in this specification, separating the sheets is also referred to as "sorting the sheets."

[0029] The blower 79 includes a floating fan (blower fan) 79A, which is an example of a blower means, a blower shutter 79C, which is a blower blocking means, and a blower port 79B, and generates air to float the paper. The floating fan 79A is provided inside the housing of the blower 79. For convenience of explanation, in FIG. 2A and subsequent figures, the floating fan 79A is shown pointing to the housing of the blower 79. The blower port 79B blows the air generated by the floating fan (blower fan) 79A obliquely upward (positive side in the Y-axis direction) toward the stack of paper P loaded on the paper stacker 72. The controller 120, which will be described later, controls the lifting mechanism 115 to lift and lower the paper stacker 72 so that the topmost paper P1 is positioned on the path of the air blown from the blower port 79B, thereby floating the topmost paper P1. Moreover, the airflow shutter 79C (an example of an airflow blocking means) is a mechanism that blocks the airflow by blocking the path from the floating fan 79A to the airflow opening 79B. This makes it possible to stop (block) the airflow sent from the floating fan 79A to the paper. The airflow shutter 79C can be configured to be driven by pulling it with a solenoid, for example.

[0030] The suction unit 95 is disposed above the paper stacking unit 72 and the blower unit 79 (on the positive side in the Y-axis direction). The suction unit 95 is disposed upstream in the feeding direction (on the negative side in the X-axis direction) of the nip and feed unit 114 having the nip rollers 114A and 114B and the feed detection sensor 117. The suction unit 95 adsorbs the paper floated by the blower unit 79 and transports it in the feeding direction (X-axis direction) along the feeding path R. The suction unit may also be called an adsorption unit.

[0031] The suction section 95 has a suction fan 95A, which is an example of a suction means, a suction shutter 95B, a suction port 95C, a duct 95D, a suction chamber 95F, and a suction unit 95G. The suction port 95C is disposed between the conveyor belts 90C described later and opens downward (Y-axis direction negative side). The suction fan 95A sucks air below the suction section 95 through the suction port 95C and the through-holes of the conveyor belts 90C. The suction shutter 95B (an example of a suction blocking means) is a mechanism that blocks air by blocking the path from the suction fan 95A to the suction port 95C. This makes it possible to stop the suction of the suction fan 95A. The suction shutter 95B can be configured to be driven by pulling it with a solenoid, for example.

[0032] The conveying section 90 (an example of a conveying means) has conveying rollers 90A and 90B and a conveying belt 90C. In this embodiment, the conveying roller 90A is a driving roller, and the conveying roller 90B is a driven roller. The conveying rollers 90A and 90B are rotatably supported at positions spaced apart in the feeding direction. The conveying belt 90C is an endless annular belt that is stretched around the conveying rollers 90A and 90B. The conveying belt 90 has through holes on a part or the entire surface of the belt that can communicate with the suction port 95C of the chamber 95F.

[0033] FIG. 2B is an external view of a suction unit and a transport unit according to the embodiment.

[0034] As shown in FIG. 2B, first, the suction section 95 has the suction unit 95G, the chamber 95F, and the duct 95D as described above.

[0035] The suction unit 95G includes a suction fan 95A, and is capable of sucking in air by the rotation of the suction fan 95A. The suction unit 95G is also capable of exhausting air from an exhaust port that the suction unit 95G has.

[0036] The suction unit 95G can also be used in combination with an intake port conversion unit as shown in Fig. 2B. The intake port conversion unit includes, for example, a duct 95D and a chamber 95F.

[0037] The duct 95D extends in the depth direction (Z-axis direction) and is a path connecting the chamber 95F to an air intake port of the suction unit 95G equipped with the suction fan 95A, and guides the air taken into the chamber 95F to the suction unit 95G. The suction shutter 95B described above is provided between the suction unit 95G and the duct 95D. The suction shutter 95B blocks the air flowing between the suction unit 95G and the chamber 95F. The suction shutter 95B may be provided inside the duct 95D or in another location.

[0038] Chamber 95F is a hollow body with a box-like or cylindrical appearance, and has an opening (suction port 95C) that serves as an air intake port at a location where air is to be taken in. Suction port 95C of chamber 95F is provided on the bottom surface of chamber 95F, and chamber 95F draws air in the Y-axis direction in the figure when suction fan 95A is driven.

[0039] Further, in the conveying section 90, a chamber 95F of the suction section 95 is provided in a space provided between the conveying rollers 90A and 90B inside the conveying belt 90C of the conveying section 90. As described above, the conveying belt 90 is provided with through holes in a part or the entire surface of the belt that can communicate with the suction port 95C of the chamber 95F. Further, a stack of paper sheets P is stacked below the conveying belt surface on the side facing the suction port 95C of the chamber 95F (negative side in the Y-axis direction).

[0040] In the above configuration, when the suction operation by the suction unit 95G is started, the uppermost sheet P1 from the stack of sheets P is sucked onto the belt surface of the conveyor belt 90C by the suction of air from the chamber 95F. The conveyor belt 90C that has sucked in the sheet P1 rotates in the feeding direction (X-axis direction) as the conveyor roller 90A, which is a driving roller, is rotated in the same direction, and sends out the sheet P1 in the feeding direction (X-axis direction).

[0041] Here, a case where the paper conveying force of the conveyor belt is increased will be described. First, the paper conveying force F [N] of the conveyor belt 90C can be expressed as "F = μJ (1)" using the suction force J [N] generated in the suction chamber 95F and the coefficient of friction μ between the paper sheets of the conveyor belt 90C. The suction force M [N] is expressed as follows: 2 ], then J can be expressed as "J = UA (2)". From this, the paper conveying force F can be expressed as "F = μ·UA (3)". From this, it is possible to increase the paper conveying force F by increasing the suction area A.

[0042] [About the control system] 3 is a block diagram showing a control system according to this embodiment. The control unit 120 controls the driving of each device in the image forming apparatus, and includes a CPU (Central Processing Unit), a RAM (Random Access Memory) as a data storage means, and a ROM (Read Only Memory) as a data storage means. For example, the control unit controls the driving of various devices and executes predetermined arithmetic processing based on a program stored in the ROM.

[0043] The control unit 120 is connected to the floating fan (air blower fan) 79A of the blower unit 79 and the air blower shutter 79C. The control unit 120 drives the floating fan 79A to generate air that separates the stack of paper sheets P into individual sheets. The control unit 120 also drives the air blower shutter 79C to close the path from the floating fan 79A to the air blower opening 79B. This makes it possible to stop the air blown from the floating fan 79A to the stack of paper sheets P.

[0044] The control unit 120 is also connected to the suction fan 95A and suction shutter 95B of the suction unit 95. The control unit 120 drives the suction fan 95A to generate suction, which causes the paper to be sucked onto the conveyor belt 90C through the suction port 95C and the through-holes of the conveyor belt 90C. The control unit 120 also controls the suction shutter 95B to close the path from the suction fan 95A to the suction port 95C. This makes it possible to stop the suction of the suction fan 95A.

[0045] In addition, the control unit 120 is connected to the lift motor 115A of the lift mechanism 115, the upper limit detection sensor 130, and the lower limit detection sensor 140. The control unit 120 can raise or lower the paper stacking unit 72 by driving the lift motor 115A.

[0046] Furthermore, the upper limit detection sensor 130 detects that the paper stacking unit 72 has risen and reached a predetermined position. When the upper limit detection sensor 130 detects that the paper stacking unit 72 has reached a predetermined position, the control unit 120 controls the lifting motor 115A of the lifting mechanism 115 to stop the lifting of the paper stacking unit 72.

[0047] Then, the lower limit detection sensor 140 detects that the paper stacking unit 72 has descended to a predetermined position. When the lower limit detection sensor 140 detects that the paper stacking unit 72 has descended to a predetermined position, the control unit 120 controls the lifting motor 115A of the lifting mechanism 115 to stop the descent of the paper stacking unit 72.

[0048] The lift motor 115A etc. are also connected to the suction fan 95A etc. of the suction unit 95. The upper limit detection sensor 130 and the lower limit detection sensor 140 will be described in detail later.

[0049] The control unit 120 is connected to a transport roller 90A which is a drive roller of the transport unit 90. The control unit 120 drives and rotates the transport roller 90A to send out the paper attracted to the transport belt 90C in the feeding direction (X-axis direction). Note that the transport roller 90B and the transport belt 90C which are driven rollers rotate together with the rotation of the transport roller 90A.

[0050] [Sheet Feeding Preparation Operation in the Present Embodiment] 4A to 4D are diagrams showing a sheet feeding preparation operation in an embodiment of the present invention. A series of sheet feeding preparation operations, which are a characteristic feature of the present invention, will be described with reference to these figures. Note that the lifting mechanism 115 is omitted in Figs. 4A to 4D. Also, an outline of the sheet feeding preparation operation will be described here, and a detailed control flow will be described later.

[0051] First, the control unit 120 moves the lifting mechanism 115 to raise and lower the paper stacking unit 72. Then, the paper stack P loaded on the paper stacking unit 72 rises to the position of the conveyor belt 90C. Then, when the paper stack P rises, the control unit 120 moves the ventilation shutter 79C away from the path. At this time, the control unit 120 also moves the floating fan (blower fan) 79A of the blower unit 79 to blow air K from the ventilation port 79B to the paper stack P. As a result, several sheets on the top side of the paper stack P are separated by the wind K (FIG. 4A). In this embodiment, about 10 sheets of 300 gsm paper can be separated, and FIG. 4A shows a state in which three sheets (paper sheets P1, P2, and P3) have been separated for convenience.

[0052] The control unit 120 also moves the suction shutter 95B of the suction unit 95 to block the suction air Q. This is to prevent the paper from being inadvertently sucked in order to prevent paper misalignment during suction. The suction shutter 95 appears to be inside the chamber 95F in the figures from FIG. 4A onwards, but as described above, it is provided between the suction unit 95G and the duct 95D, and is actually located in the depth direction (Z-axis direction) of the chamber 95F. The suction air Q may be blocked by stopping the suction fan 95A instead of moving the suction shutter 95B. Alternatively, the suction air Q may be blocked by both stopping the suction fan 95A and moving the suction shutter 95B.

[0053] Thereafter, when the paper stacking unit 72 reaches a position where the topmost paper sheet P1 of the separated papers comes into contact (close contact) with the conveyor belt 90C, the control unit 120 retracts the suction shutter 95B. At this time, the control unit 120 also operates the suction fan 95A of the suction unit 95 to release the suction air Q (FIG. 4B). As a result, the topmost paper sheet P1 is adsorbed to the conveyor belt 90C.

[0054] Then, control unit 120 moves lift mechanism 115 to lower paper stacking unit 72 (FIG. 4C), thereby separating the topmost paper sheet P1 from the paper sheet P2 located below it, preventing double feeding.

[0055] At this time, the control unit 120 also moves the air blower shutter 79C to block the air K being blown to the paper stack P, preventing the second and subsequent sheets (those sheets in the paper stack P that are located below paper P1) from being inadvertently floated up. In this way, it is possible to prevent the sheets from being fed together with paper P1. Note that this blocking of the air blowing may be achieved by stopping the floating fan (air blower fan) 79A instead of moving the air blower shutter 79C. Alternatively, this blocking of the air blowing may be achieved by both stopping the floating fan (air blower fan) 79A and moving the air blower shutter 79C.

[0056] Thereafter, the control unit 120 operates the conveying rollers 90A, 90B of the conveying unit 90, the conveying belt 90C, and the pinching rollers 114A, 114B of the pinching and feeding unit 114 to convey the sucked paper P1 toward the conveying path R (FIG. 4D). In this way, the paper P1 is fed. At this time, the suction fan 95A of the suction unit 95 is operated and the suction shutter 95B is retracted, so that the suction air Q is released and the paper P1 is in a state of being adsorbed to the conveying belt 90C.

[0057] Furthermore, the paper stacking section 72 and the second and subsequent sheets of paper (sheets of the paper stack P that are located below paper P1) move down to a predetermined position.

[0058] With the above-described configuration, the present invention makes it possible to prevent double feeding due to the sheets sticking to each other during conveyance.

[0059] Furthermore, for heavy paper, for example, electrostatic adsorption is affected by humidity, resulting in variation in the adsorption force. When the transport force is taken as suction force (adsorption force), the adsorption force is electrostatic adsorption force, which is mainly influenced by humidity. When humidity is high, electrical resistance decreases, resulting in a low adsorption force, whereas when humidity is low, electrical resistance increases, resulting in a high adsorption force. This results in variation in the adsorption force and transport force.

[0060] In contrast, in the embodiment according to the present invention, suction is performed by air, so that the above-mentioned variations can be prevented even for heavy paper.

[0061] [Detection of the upper and lower positions of the paper stacking section] FIG. 5 is a diagram for explaining a configuration for detecting the upper limit position of the paper stacking unit in this embodiment.

[0062] 5, the feeding section 70 in this embodiment is configured to have an upper limit detection sensor 130 (an example of a means for detecting the upper limit position of stacked sheets) and a filler 131 at a position about the same height as the conveying section 90. This allows the control section 120 to detect that the paper stacking section 72 has risen and reached a predetermined position, and also to detect the position at which the uppermost paper sheet P1 is adsorbed to the conveying belt 90C by the suction section 95.

[0063] In this embodiment, the detection of the reaching of the upper limit position of the paper stacking section 72 is configured to see a change in the upper limit detection sensor 130 accompanying the movement of the filler 131. As shown in FIG. 5(a), when the paper stacking section 72 has not reached the predetermined position, the upper limit detection sensor 130 detects that the filler 131 has not moved and is in an undetected state. On the other hand, as shown in FIG. 5(b), when the paper stacking section 72 reaches the predetermined position, the paper P1 located at the top of the paper stack P stacked on the paper stacking section 72 comes into contact with the filler 131, which causes the filler 131 to move. The upper limit detection sensor 130 detects the moved filler 131. The control section 120 can grasp that the paper stacking section 72 has reached the predetermined position by the detection of the upper limit detection sensor 130.

[0064] In this embodiment, a filler or the like is used to detect when the paper stacking section 72 has risen and reached a predetermined position, but this is merely one example, and the present invention is not limited to this.

[0065] FIG. 6 is a diagram for explaining a configuration for detecting the lower limit position of the paper stacking unit in this embodiment.

[0066] As shown in Fig. 6, the feeding section 70 in this embodiment is configured to have a lower limit detection sensor 140 (an example of a stacked sheet lower limit position detection means) near the blower section 79. This allows the control section 120 to detect that the paper stacking section 72 has lowered to a predetermined position. Also, the paper stacking section 72 needs to be lowered at least to a position where the uppermost adsorbed paper sheet P1 and the paper sheet P2 immediately below it are not fed in a double feed. Therefore, in this embodiment, the predetermined position is a position where such double feeding can be prevented.

[0067] In this embodiment, the lower limit detection sensor 140 is a reflective sensor.

[0068] As shown in Fig. 6(a), when the paper stacking section 72 has not yet reached the predetermined position, the lower limit detection sensor 140 is in a state of detecting the paper stack P. On the other hand, as shown in Fig. 6(b), when the paper stacking section 72 reaches the predetermined position, the distance between the paper P2 on the paper stack P stacked on the paper stacking section 72 and the uppermost paper P1 becomes sufficiently large, making it possible to prevent the above-mentioned double feeding. At this time, the lower limit detection sensor 140 no longer detects the paper stack P, which enables the control section 120 to grasp that the paper stacking section 72 has reached the predetermined position.

[0069] In addition, the above configuration can be said to be another configuration in which, when lower limit detection sensor 140 detects the upper part of paper sheet P2 that has now become the uppermost sheet of paper stack P, it stops the lowering of paper stacking section 72.

[0070] Further, in this embodiment, a reflective sensor is used to detect when the paper stacking section 72 has descended and reached a predetermined position, but this is merely an example and the present invention is not limited to this.

[0071] [Control flow according to this embodiment] 7 is a diagram showing an example of a control flow of the feeding preparation operation according to the present embodiment. Note that this control flow is executed by the control unit 120.

[0072] 7, in this embodiment, when a feeding preparation operation for feeding paper (sheets) is started in association with printing (Step 001), the control unit 120 controls the feeding unit 70 to perform an air blowing operation (Step 011). Specifically, the air blowing operation is performed by the control unit 120 to move the floating fan 79A of the air blowing unit 79, to move the air blowing shutter 79C away from the path, and to blow air K from the air blowing port 79B to the paper stack P. This is to separate (sort) the paper at the top of the paper stack P with the air K.

[0073] Then, the control unit 120 controls the feeding unit 70 to perform a suction cutoff operation (Step 021). Specifically, the suction cutoff operation is performed by the control unit 120 moving the suction shutter 95B of the suction unit 95 to cut off the suction air Q. Note that the cutoff of the suction air Q may be performed by stopping the suction fan 95A instead of moving the suction shutter 95B. Alternatively, the cutoff of the suction air Q may be performed by both stopping the suction fan 95A and moving the suction shutter 95B.

[0074] Moreover, the control unit 120 performs a stacking unit lifting operation for lifting and lowering the paper stacking unit 72 by moving the lifting mechanism 115 (Step 031).

[0075] Then, when the upper limit detection sensor 130 detects that the paper stacking unit 72 has risen to a predetermined position (YES in Step 041), the control unit 120 stops the lifting mechanism 115 to stop the lifting of the paper stacking unit 72 (Step 051). On the other hand, when the control unit 120 does not detect that the paper stacking unit 72 has risen to the predetermined position (NO in Step 041), the control unit 120 operates the lifting mechanism 115 to continue lifting the paper stacking unit 72 until it reaches the predetermined position.

[0076] After the rising of the paper stacking unit 72 stops, the control unit 120 controls the feeding unit 70 to perform a suction operation (Step 061). Specifically, the suction operation is performed by the control unit 120 to operate the suction fan 95A of the suction unit 95, retract the suction shutter 95B, and release the suction air Q. As a result, the uppermost paper P1 is attracted to the conveyor belt 90C.

[0077] Thereafter, the control unit 120 controls the feeding unit 70 to perform an air blowing cutoff operation (Step 071). Specifically, the air blowing cutoff operation is performed by the control unit 120 moving the air blowing shutter 79C to cut off the air K being blown to the paper stack P, so as to prevent the second and subsequent sheets (those sheets in the paper stack P that are located below paper P1) from being inadvertently floated up. Note that this cutoff of the air blowing may be achieved by stopping the floating fan (air blowing fan) 79A instead of moving the air blowing shutter 79C. Alternatively, this cutoff of the air blowing may be achieved by both stopping the floating fan (air blowing fan) 79A and moving the air blowing shutter 79C.

[0078] Moreover, the control unit 120 operates the lifting mechanism 115 to perform a stacking unit lowering operation for lowering the paper stacking unit 72 (Step 081).

[0079] Then, when the lower limit detection sensor 140 detects that the paper stacking unit 72 has descended to a predetermined position (YES in Step 091), the control unit 120 stops the lifting mechanism 115 to stop the descent of the paper stacking unit 72 (Step 101). On the other hand, when the control unit 120 does not detect that the paper stacking unit 72 has descended to the predetermined position (NO in Step 091), the control unit 120 operates the lifting mechanism 115 to continue the descent of the paper stacking unit 72 until it reaches the predetermined position.

[0080] After the downward movement of the paper stacking unit 72 stops, the control unit 120 controls the feeding unit 70 to perform a sheet feeding operation (Step 111). Specifically, in the sheet feeding operation, the control unit 120 operates the conveying rollers 90A and 90B of the conveying unit 90, the conveying belt 90C, and the pinching rollers 114A and 114B of the pinching and feeding unit 114 to convey the sucked paper P1 toward the conveying path R. In this way, the paper P1 is fed. At this time, the suction fan 95A of the suction unit 95 is operated and the suction shutter 95B is retracted, so that the suction air Q is released and the paper P1 is in a state of being sucked by the conveying belt 90C.

[0081] Then, if the printing operation is to be ended (YES in Step 121), the control unit 120 ends the feeding preparation operation (Step 131). This ends the series of control flows. On the other hand, if the printing operation is to be continued (NO in Step 121), the control unit 120 starts the next feeding preparation operation in order to continue the printing operation. At this time, the control flow returns to Step 011, and the control unit 120 performs the air blowing operation again. That is, when the control unit 120 raises the paper stacking unit 72 again, it cancels the air blowing blocking operation. The control flow thereafter is as described above.

[0082] [Another embodiment of the present invention] Fig. 8 is a diagram showing another embodiment (modification) of the present invention. In the embodiments up to now, the paper stacking section is raised and lowered to perform the feeding preparation operation. On the other hand, in the embodiment shown in Fig. 8, the feeding preparation operation is performed by raising and lowering the suction section and the like without changing the position of the paper stacking section or the topmost paper of the paper stack loaded on the paper stacking section.

[0083] As shown in FIG. 8(a), the control unit 120 lowers the suction unit 95 and the transport unit 90. During the lowering, the control unit 120 retracts the ventilation shutter 79C from the path. At this time, the control unit 120 also operates the floating fan (blower fan) 79A of the ventilation unit 79 to send wind (air) K to the paper stack P from the ventilation port 79B. As a result, several sheets on the uppermost side of the paper stack P are separated by the wind K. In this embodiment, about 10 sheets are separated, and FIG. 8(a) shows a state in which three sheets (paper sheets P1, P2, and P3) have been separated for convenience.

[0084] 8(b), suction unit 95 and transport unit 90 are lowered to a position where they come into contact with sheet P1 located at the top of sheet stack P. At this time, control unit 120 also moves ventilation shutter 79C to block air K being blown to sheet stack P, so as to prevent second and subsequent sheets (sheets in sheet stack P located below sheet P1) from being inadvertently floated up. Note that this blocking of air flow may be achieved by stopping levitation fan (air blower fan) 79A instead of moving ventilation shutter 79C. Alternatively, this blocking of air flow may be achieved by both stopping levitation fan (air blower fan) 79A and moving ventilation shutter 79C.

[0085] At this time, the control unit 120 also operates the suction fan 95A of the suction unit 95, retracts the suction shutter 95B, and releases the suction air Q. As a result, the paper P1 is attracted to the conveyor belt 90C.

[0086] Thereafter, the control unit 120 causes the suction unit 95 and the transport unit 90 to rise to a position where the adsorbed P1 can be fed.

[0087] The above-described configuration can also provide the intended effect of the present invention. As a means for raising and lowering the suction unit 95 and the conveying unit 90, for example, a mechanism for raising and lowering the wire by using a drive motor, or a link mechanism, cam mechanism, or the like can also be used.

[0088] As described above, this embodiment includes the sheet stacking section 72 on which the sheet stack P is stacked, the air blowing means 79 (79A) that separates the uppermost sheets of the sheet stack P stacked on the sheet stacking section 72 into a plurality of sheets, the suction means 95 (95A) that sucks the uppermost sheet P1 of the sheet stack with air, the conveying means 90 that conveys the sheets sucked by the suction means 95 (95A) and has the feeding belt 90C, and the lifting means 115 (115A) that lifts and lowers the sheet stacking section. 115A) lifts the sheets separated by the air blowing means 79 (79A) and, when it has risen to a position where the top sheet P1 of the sheet stack P contacts the paper feed belt 90C, stops the lifting of the sheet stacking section 72 to allow the suction means 95 (95A) to suck in the top sheet P1 of the sheet stack P, and after the suction means 95 (95A) has sucked in the top sheet P1 of the sheet stack P, it lowers the sheet stacking section 72 to a predetermined position and the conveying means 90 feeds the sucked sheet.

[0089] This makes it possible to prevent double feeding due to paper (sheet) sticking together.

[0090] As described above, this embodiment has a suction cut-off means 79C that cuts off the suction by the suction means 95 (95A), and the suction cut-off means 79C cuts off the suction while the sheet stacking section 72 is rising, and opens the suction by the suction means 95 (95A) when the topmost sheet P1 has risen to a predetermined position.

[0091] This makes it possible to prevent the position of the paper (sheet) from being shifted.

[0092] As described above, this embodiment has an air blowing blocking means 79C that blocks the air blowing by the air blowing means 79 (79A), and the air blowing blocking means 79C sucks in the topmost sheet P1 and blocks the air blowing means 79 (79A) when the sheet stacking section 72 is lowered.

[0093] This makes it possible to prevent double feeding due to paper (sheets) sticking together, and also to prevent paper (sheets) from floating up accidentally.

[0094] As described above, in this embodiment, when the sheet stacking portion 72 rises again, the blocking of the air blowing means 79 (79A) is released.

[0095] This makes it possible to prevent double feeding due to paper (sheet) sticking together.

[0096] As described above, this embodiment has a stacked sheet upper limit position detection means 130 that detects the upper limit position of the topmost sheet P1 of the sheet stack P, and when the stacked sheet upper limit position detection means 130 raises the sheet stacking section 72 and detects the upper limit position, it stops the lifting of the sheet stacking section 72.

[0097] This makes it possible to accurately grasp the position of the stacked sheets.

[0098] As described above, this embodiment has a stacked sheet lower limit position detection means 140 that detects the position of the topmost sheet P1 of the sheet stack P when the sheet stacking section 72 is being lowered, and the stacked sheet lower limit position detection means 140 lowers the sheet stacking section 72 after the suction means 95 (95A) has sucked in the sheet, and stops the descent of the sheet stacking section 72 when it detects a position where the sheet can be transported by the transport means 90.

[0099] This makes it possible to accurately grasp the position of the stacked sheets.

[0100] The above description is merely an example, and the present invention provides unique effects for each of the following aspects.

[0101] [First aspect] The first aspect includes a sheet stacking section (paper stacking section 72) for stacking a sheet stack (e.g., a paper stack P), a blowing unit (e.g., blowing unit 79, levitation fan 79A) for separating an upper sheet of the sheet stack stacked on the sheet stacking section into a plurality of sheets, a suction unit (e.g., suction unit 95, suction fan 95A) for sucking the uppermost sheet of the sheet stack with air, a conveying unit (e.g., conveying unit 90) for conveying the sheet sucked by the suction unit and having a feeding belt (e.g., conveying belt 90C), and a lifting unit for lifting and lowering the sheet stacking section. (e.g., lifting mechanism 115, lifting motor 115A), and the lifting means lifts the sheets separated by the air blowing means, and when the lifting means has lifted to a position where the top sheet of the sheet stack contacts the paper feed belt, stops lifting of the sheet stacking unit to allow the suction means to suck in the top sheet of the sheet stack (e.g., paper P1), and after the suction means has sucked in the top sheet of the sheet stack, the sheet stacking unit is lowered to a predetermined position, and the conveying means feeds the sucked sheet.

[0102] [Second aspect] The second aspect is characterized in that in the first aspect, the device has a suction cut-off means (e.g., suction shutter 90B) that cuts off the suction by the suction means, and the suction cut-off means cuts off the suction while the sheet stacking section is rising and releases the suction by the suction means when the top sheet has risen to a predetermined position.

[0103] [Third aspect] The third aspect is characterized in that, in the first or second aspect, it has an air blowing blocking means (e.g., an air blowing shutter 79C) that blocks the air blown by the air blowing means, and the air blowing blocking means sucks in the topmost sheet and blocks the air blowing means when the sheet stacking section is lowered.

[0104] [Fourth aspect] A fourth aspect is any one of the first to third aspects, characterized in that when the sheet stacking portion rises again, the blocking of the air blowing means is released.

[0105] [Fifth aspect] A fifth aspect is characterized in that, in any of the first to fourth aspects, it has a stacked sheet upper limit position detection means (e.g., upper limit detection sensor 130) that detects the upper limit position of the top sheet of the sheet stack, and when the stacked sheet upper limit position detection means raises the sheet stacking section and detects the upper limit position, it stops the lifting of the sheet stacking section.

[0106] [Sixth aspect] The sixth aspect is characterized in that, in any of the first to fifth aspects, it has a stacked sheet lower limit position detection means (e.g., lower limit detection sensor 140) that detects the position of the topmost sheet of the sheet stack when the sheet stacking section is lowered, and the stacked sheet lower limit position detection means lowers the sheet stacking section after the suction means has sucked in the sheet, and stops the descent of the sheet stacking section when it detects a position where the sheet can be transported by the transporting means.

[0107] [Seventh aspect] A seventh aspect is an image forming apparatus (for example, the image forming apparatus 1) including the sheet feeding device (for example, the feeding section 70) according to any one of the first to sixth aspects. [Explanation of symbols]

[0108] 1: Image forming device (image forming device main body) 70: Feeding section (paper feeding section, sheet feeding section) 72: Paper stacking section (sheet stacking section) 79: Blower section 79A: Levitation fan (blower fan) 79B: Air outlet 79C: Ventilator shutter 90: Transport section 90A: Transport roller (drive roller) 90B: Transport roller (driven roller) 90C:Conveyor belt 95:Suction part 95A: Suction fan 95B: Suction shutter 95C: Suction port 95D: Route (duct) 95F: Chamber 95G: Suction unit 114: Gripping feeding section 115: Lifting mechanism 115A: Lift motor 117: Feeding detection sensor 120: Control unit 130: Upper limit detection sensor 131: Filler 140: Lower limit detection sensor [Prior art documents] [Patent documents]

[0109] [Patent Document 1] JP 2014-005091 A

Claims

1. a sheet stacking section for stacking a sheet bundle; a blowing unit for separating an upper sheet of the sheet stack stacked on the sheet stacking section into a plurality of sheets; a suction means for sucking the top sheet of the sheet stack by air; a conveying means for conveying the sheet sucked by the suction means and having a feeding belt; a lifting means for lifting and lowering the sheet stacking portion, the lifting means lifts the sheets separated by the air blowing means, and when the sheet has been lifted to a position where the top sheet of the sheet stack contacts the paper feed belt, stops lifting of the sheet stacking unit to allow the suction means to suck the top sheet of the sheet stack, and after the suction means has sucked the top sheet of the sheet stack, lowers the sheet stacking unit to a predetermined position; The sheet feeding device is characterized in that the conveying means conveys the sucked sheet.

2. a suction cut-off means for cutting off the suction by the suction means, 2. The sheet feeding apparatus according to claim 1, wherein the suction cut-off means cuts off suction while the sheet stacking portion is rising, and releases suction by the suction means when the top sheet rises to a predetermined position.

3. The air blowing device has an air blowing cutoff means for cutting off the air blown by the air blowing means, 2. The sheet feeding apparatus according to claim 1, wherein the air blowing blocking means sucks the uppermost sheet and blocks the air blowing means when the sheet stacking unit is lowered.

4. 2. The sheet feeding apparatus according to claim 1, wherein the blocking of the air blowing means is released when the sheet stacking portion is raised again.

5. a stacked sheet upper limit detection means for detecting an upper limit position of a topmost stacked sheet of the sheet bundle; 2. The sheet feeding apparatus according to claim 1, wherein the stacked sheet upper limit position detection means stops lifting of the sheet stacking portion when the upper limit position is detected by lifting the sheet stacking portion.

6. a lower limit position detection means for detecting the position of the top sheet of the sheet stack when the sheet stacking portion is lowered; 2. The sheet feeding device according to claim 1, wherein the lower limit position detection means lowers the sheet stacking section after the suction means has sucked in the sheet, and when the lower limit detection means detects a position at which the sheet can be transported by the transporting means, stops the lowering of the sheet stacking section.

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

Images