Sheet feeding device and image forming apparatus

Abstract

To provide a sheet feeding device that can properly feed sheets regardless of the number of sheets stacked on a sheet stacking part.SOLUTION: A sheet feeding device repeatedly executes the process of feeding sheets floated by an air blowing part to the suction feeding part (S801) and counting the number of sheets detected by a feeding detection sensor (S803), when the number of sheets is less than the threshold number (S804: No), every time sheets are detected by the feeding detection sensor, drives a lifting mechanism so that the sheet stacking part rises by the amount determined based on the thickness of the sheets stacked on a sheet stacking part (S806 / S807), and when the number of sheets reaches the threshold number (S804: Yes), stops the sheet stacking part from lifting until no sheet is detected by the elevation detection sensor (S808: No).SELECTED DRAWING: Figure 8

Description

[Technical Field]

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

[0002] Conventionally, a sheet feeding device has been known that includes a sheet stacking section on which multiple sheets are stacked in a stacked state, an air blowing section that blows air from the side of the multiple sheets stacked on the sheet stacking section to lift the top sheet, and an adsorption feeding section that is positioned above the sheet stacking section and adsorbs the sheet that has been lifted by the air blowing section and feeds it in the feeding direction.

[0003] In such a sheet feeding device, when the number of sheets stacked on the sheet stacking section decreases, the air blown from the air blowing section passes above the sheets, making it impossible to properly lift the sheets. Therefore, there is a technology in which, when there are few sheets stacked on the sheet stacking section, the sheet stacking section is raised by a fixed amount X each time a sheet is fed (see, for example, Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0004] However, the actual thickness of the sheets stacked on the sheet stacking section does not necessarily match the lift amount X. Therefore, if the error between the actual thickness of the sheets and the lift amount accumulates due to repeated lifting of the sheet stacking section, multiple sheets may float up together, causing multiple feeding.

[0005] The present invention has been made to solve such problems, and aims to provide a technology for appropriately feeding sheets in a sheet feeding device that floats and feeds sheets, regardless of the number of sheets stacked in a sheet stacking section. [Means for solving the problem]

[0006] In order to solve the above problem, one aspect of the present invention includes a sheet stacking section on which a plurality of sheets are stacked in a stacked state, an air blowing section that blows air from the side of the plurality of sheets stacked on the sheet stacking section to lift the topmost sheet, a suction feeding section that is arranged above the sheet stacking section and sucks the sheet lifted by the air blowing section and feeds it in a feeding direction, a lifting mechanism that lifts and lowers the sheet stacking section, a lifting detection sensor that detects that a sheet stacked on the sheet stacking section has reached a detection position between the sheet stacking section and the suction feeding section, a feeding detection sensor that detects the sheet fed by the suction feeding section, and a detection mechanism for the lifting detection sensor and the feeding detection sensor. and a controller that controls operations of the air blower, the suction feeding unit, and the lifting mechanism based on the result of the counting, wherein the controller feeds the sheets floated by the air blower to the suction feeding unit and repeatedly executes a process of counting the number of sheets detected by the feeding detection sensor, and when the number of sheets is less than a threshold number, drives the lifting mechanism so that the sheet stacking unit lifts by an amount determined based on a sheet thickness t of the sheets stacked on the sheet stacking unit each time the feeding detection sensor detects a sheet, and when the number of sheets reaches the threshold number, stops lifting of the sheet stacking unit until no sheets are detected by the lifting detection sensor. The controller determines the amount of lift by multiplying the sheet thickness t by a correction value α (α is a value greater than 1). It is characterized by: [Effects of the Invention]

[0007] According to the present invention, in a sheet feeding device that floats and feeds sheets, it is possible to appropriately feed sheets regardless of the number of sheets stacked on a sheet stacking section. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram illustrating an internal configuration of an image forming apparatus. [Figure 2] FIG. [Figure 3] FIG. [Figure 4] FIG. 2 is a diagram showing the hardware configuration of an image forming apparatus. [Figure 5] Functional block diagram of the controller. [Figure 6] 10 is a flowchart of an increase amount calculation process. [Figure 7] 6 is a graph showing the correspondence between basis weight and paper thickness range stored in memory. [Figure 8] 10 is a flowchart of a feeding process. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a schematic diagram showing the internal configuration of an image forming apparatus 100. As shown in Fig. 1, the image forming apparatus 100 mainly includes a feeding section 110 (sheet feeding device), a conveying section 120, an image forming section 130, and a paper discharge tray 140. A plurality of sheets M (sheets) before images are formed thereon are stored in a stacked state in the feeding section 110. The paper discharge tray 140 stores sheets M on which images have been formed.

[0010] Paper sheet M is an example of a sheet that is fed from feeding unit 110, transported by transport unit 120, and on which an image is formed by image forming unit 130. However, the sheet is not limited to paper, and may be an overhead projector sheet, cloth, or the like. Inside image forming apparatus 100, a transport path R1 is formed, which is a space through which paper sheet M is transported. Transport path R1 is a path that runs from feeding unit 110 to a position facing image forming unit 130, and then to paper output tray 140.

[0011] The feeding section 110 stacks a plurality of sheets of paper M in a stacked state, and supplies (feeds) the stacked sheets of paper M one by one to the conveying section 120. More specifically, the feeding section 110 floats and feeds the topmost sheet of paper M from the stack. The detailed configuration of the feeding section 110 will be described later with reference to FIGS. 2 and 3.

[0012] The transport unit 120 transports the paper sheet M fed from the feeding unit 110 along the transport path R1. Specifically, the transport unit 120 transports the paper sheet M stored in the feeding unit 110 along the transport path R1 to a position facing the image forming unit 130. The transport unit 120 also discharges the paper sheet M, on the surface of which an image has been formed by the image forming unit 130, onto the paper output tray 140 along the transport path R1.

[0013] The conveying section 120 includes a plurality of conveying rollers 121 and 122. The conveying rollers 121 and 122 are configured, for example, with a drive roller that rotates when the driving force of a motor is transmitted, and a driven roller that contacts the drive roller and rotates accordingly. The sheet M is conveyed along the conveying path R1 by the drive roller and the driven roller rotating while sandwiching the sheet M therebetween.

[0014] The transport roller 121 is disposed upstream in the transport direction from the image forming unit 130. The transport roller 122 is disposed downstream in the transport direction from the image forming unit 130. However, the installation positions of the transport rollers are not limited to the two locations shown in FIG.

[0015] The image forming unit 130 is disposed between the conveying rollers 121 and 122, facing the conveying path R1. The image forming unit 130 forms an image on the surface of the paper M conveyed by the conveying unit 120. The image forming unit 130 according to the embodiment forms an image on the paper M conveyed along the conveying path R1 by an electrophotographic method. However, the image forming method of the image forming unit 130 may also be an inkjet recording method in which an image is formed by ejecting ink onto the paper M.

[0016] More specifically, image forming unit 130 has a configuration in which photosensitive drums 131Y, 131M, 131C, and 131K (hereinafter collectively referred to as "photosensitive drum 131") of each color are arranged along transfer belt 132, which is an endless moving means. That is, along transfer belt 132, on which an intermediate transfer image to be transferred to paper M fed from feed unit 110 is formed, multiple photosensitive drums 131Y, 131M, 131C, and 131K are arranged in this order from the upstream side in the conveying direction of transfer belt 132.

[0017] Toner stored in a toner bottle is supplied to the photosensitive drum 131. Then, a full-color image is formed by superimposing and transferring the images of each color developed with toner on the surface of the photosensitive drum 131 of each color onto the transfer belt 132. The full-color image formed on the transfer belt 132 is then transferred onto the paper M by a transfer roller 133 at a position closest to the conveyance path R1.

[0018] Furthermore, image forming unit 130 includes a fixing roller 134 arranged downstream of transfer roller 133 in the conveying direction. Fixing roller 134 includes a drive roller driven by a motor and a driven roller that contacts and drives the drive roller. Then, in the process in which the drive roller and the driven roller rotate while nipping sheet M, the image transferred by transfer roller 133 is fixed to sheet M by heating and pressing sheet M.

[0019] Fig. 2 is a schematic diagram of the feeding unit 110. Fig. 3 is a diagram showing the operation of the feeding unit 110. The feeding unit 110 feeds paper M one sheet at a time to a transport path R1 via a feeding path R0. As shown in Fig. 2, the feeding unit 110 mainly includes a paper stacking unit 111 (sheet stacking unit), a blower 112, a suction feeding unit 113, a clamping feeding unit 114, a lifting mechanism 115, a lifting detection sensor 116, a feeding detection sensor 117, and a remaining amount detection sensor 118.

[0020] The paper stacking unit 111 is a tray or cassette that can hold a plurality of sheets of paper M stacked on top of each other. The paper stacking unit 111 is configured so that the user can replenish the paper sheets M. The paper stacking unit 111 is supported by the frame of the feeding unit 110 so that it can be raised and lowered by the lifting mechanism 115 within a predetermined lifting range.

[0021] The air blowing section 112 is disposed above the paper stacking section 111 and below the suction feeding section 113. The air blowing section 112 is disposed at a position where it can face the paper sheets M stacked in the paper stacking section 111 in the horizontal direction. As shown in FIG. 3A, the air blowing section 112 blows air from the side of the multiple paper sheets M stacked in the paper stacking section 111, thereby floating the topmost paper sheet M.

[0022] The air blowing section 112 mainly includes, for example, a floating blower 112a and an air outlet 112b. The floating blower 112a generates air that floats the sheets M. The air outlet 112b blows the air generated by the floating blower 112a obliquely upward toward the sheets M stacked in the sheet stacking section 111. The top sheet M is then floated by raising and lowering the sheet stacking section 111 with the lifting mechanism 115 so that the top sheet M is positioned on the path of the air blown from the air outlet 112b.

[0023] The suction feed section 113 is disposed above the sheet stacking section 111, the air blower 112, and the lift detection sensor 116. The suction feed section 113 is disposed upstream in the feeding direction from the pinch feed section 114 and the feeding detection sensor 117. The suction feed section 113 adsorbs the sheet M floated by the air blower 112, and transports the sheet M in the feeding direction along a feeding path R0. The feeding path R0 is connected to a transport path R1.

[0024] The suction feed unit 113 mainly includes, for example, a drive pulley 113a, a driven pulley 113b, an endless circular belt 113c, a feed motor 113d, a suction port 113e, and a suction fan 113f. The drive pulley 113a and the driven pulley 113b are rotatably supported at positions spaced apart in the feed direction. The endless circular belt 113c is stretched over the drive pulley 113a and the driven pulley 113b. A plurality of through-holes are formed in the surface of the endless circular belt 113c. The feed motor 113d rotates the drive pulley 113a. The suction port 113e is disposed between the endless circular belt 113c and opens downward. The suction fan 113f sucks air below the suction feeding unit 113 through the suction port 113e and the through-holes of the endless circular belt 113c.

[0025] As shown in Fig. 3(B), an upward air flow is generated by driving the suction fan 113f. As a result, the sheet M floated by the blower 112 is adsorbed to the lower surface of the endless circular belt 113c. Also, as shown in Fig. 3(C), by driving the feed motor 113d, the drive pulley 113a (in other words, the endless circular belt 113c) rotates counterclockwise. As a result, the sheet M adsorbed to the lower surface of the endless circular belt 113c is supplied to the nip feed unit 114 along the feed path R0.

[0026] The nip feed unit 114 is disposed downstream in the feeding direction from the suction feed unit 113 and upstream in the feeding direction from the feeding detection sensor 117. The nip feed unit 114 feeds the paper M supplied from the suction feed unit 113 in the feeding direction along the feeding path R0. The nip feed unit 114 mainly includes, for example, a drive roller 114a, a driven roller 114b, and a feeding motor 114c.

[0027] The drive roller 114a and the driven roller 114b are each rotatably supported. The drive roller 114a and the driven roller 114b are in contact with each other with the feed path R0 sandwiched therebetween. The feed motor 114c rotates the drive roller 114a. The nip feed unit 114 then nip the sheet M that has entered between the drive roller 114a and the driven roller 114b between the drive roller 114a and the driven roller 114b and feeds it. As a result, the sheet M is fed to the transport path R1.

[0028] The lifting mechanism 115 raises and lowers the paper stacking unit 111. The lifting mechanism 115 mainly includes, for example, a lifting motor 115a and a drive force transmission unit that transmits the drive force of the lifting motor 115a to the paper stacking unit 111. The drive force transmission unit may be configured, for example, with a rotatably supported pulley and a belt that is stretched around the pulley and has one end connected to the paper stacking unit 111 and the other end connected to the output shaft of the lifting motor 115a. As shown in FIG. 3(D), the lifting mechanism 115 raises the paper stacking unit 111 by rotating the lifting motor 115a in a first direction. The lifting mechanism 115 also lowers the paper stacking unit 111 by rotating the lifting motor 115a in a second direction opposite to the first direction.

[0029] The lifting / lowering detection sensor 116 is fixed to a detection position above the paper stacking unit 111 and below the suction feed unit 113. More specifically, the lifting / lowering detection sensor 116 is located above the paper stacking unit 111, which is located at the upper end of the lifting range. The lifting / lowering detection sensor 116 is also located a height h below the lower surface of the endless circular belt 113c. The lifting / lowering detection sensor 116 is also located at a position where it can face the paper sheets M stacked on the paper stacking unit 111 in the horizontal direction. The lifting / lowering detection sensor 116 detects that the paper sheets M stacked on the paper stacking unit 111 have reached the detection position.

[0030] The lifting / lowering detection sensor 116 is, for example, a reflective optical sensor equipped with a light-emitting unit and a light-receiving unit. The light-emitting unit emits light horizontally from a detection position. The light-receiving unit receives light that is emitted from the light-emitting unit and reflected by the sheets M stacked in the sheet stacking unit 111. When the light-receiving unit of the lifting / lowering detection sensor 116 receives light, the lifting / lowering detection sensor 116 outputs an arrival signal indicating that the sheets M have reached the detection position to the controller 150, which will be described later. On the other hand, when the light-receiving unit of the lifting / lowering detection sensor 116 does not receive light, the lifting / lowering detection sensor 116 stops outputting the arrival signal to the controller 150.

[0031] The feeding detection sensor 117 is disposed downstream in the feeding direction from the suction feeding section 113 and the pinch feeding section 114. The feeding detection sensor 117 is disposed facing the feeding path R0. The feeding detection sensor 117 detects that the paper M has passed through the feeding path R0 (i.e., that the paper M has been fed).

[0032] The feeding detection sensor 117 is, for example, a reflective optical sensor equipped with a light-emitting unit and a light-receiving unit. The light-emitting unit emits light toward the feeding path R0. The light-receiving unit receives light that is emitted from the light-emitting unit and reflected by the paper M passing through the feeding path R0. When the light-receiving unit of the feeding detection sensor 117 receives light, the feeding detection sensor 117 outputs a feeding signal indicating that the paper M has been fed to the controller 150. On the other hand, when the light-receiving unit of the feeding detection sensor 117 does not receive light, the feeding detection sensor 117 stops outputting the feeding signal to the controller 150.

[0033] The remaining amount detection sensor 118 is disposed, for example, in a position in the horizontal direction where it can face the sheets M stacked on the sheet stacking section 111. The remaining amount detection sensor 118 is configured to be able to move up and down together with the sheet stacking section 111, slightly above the upper surface of the sheet stacking section 111. The remaining amount detection sensor 118 detects the remaining amount of sheets M stacked on the sheet stacking section 111. The remaining amount of sheets M is indicated, for example, as a percentage, with the maximum amount (maximum number of sheets) of sheets M that can be stacked on the sheet stacking section 111 being set to 100%.

[0034] The remaining amount detection sensor 118 is, for example, a reflective optical sensor including a light-emitting unit and a light-receiving unit. The light-emitting unit emits light in a horizontal direction. The light-receiving unit receives light that is emitted from the light-emitting unit and reflected by the sheets M stacked in the sheet stacking unit 111. When the light-receiving unit of the remaining amount detection sensor 118 receives light, the remaining amount detection sensor 118 outputs a remaining amount signal to the controller 150, indicating that the remaining amount of the sheets M stacked in the sheet stacking unit 111 is equal to or greater than the threshold remaining amount X%. On the other hand, when the light-receiving unit of the remaining amount detection sensor 118 does not receive light, the remaining amount detection sensor 118 stops outputting the remaining amount signal to the controller 150.

[0035] 4 is a diagram showing the hardware configuration of image forming apparatus 100. Image forming apparatus 100 has a configuration in which a CPU (Central Processing Unit) 101 as a control means, a RAM (Random Access Memory) 102 as a memory, a ROM (Read Only Memory) 103 as a memory, an HDD (Hard Disk Drive) 104 as a memory, and an I / F 105 as an interface are connected via a common bus 109 as a communication means. CPU 101, RAM 102, ROM 103, and HDD 104 are examples of a controller 150.

[0036] The CPU 101 is a computing unit that controls the overall operation of the image forming apparatus 100. The RAM 102 is a volatile storage medium that can read and write information at high speed, and is used as a work area when the CPU 101 processes information. The ROM 103 is a read-only nonvolatile storage medium that stores programs such as firmware. The HDD 104 is a nonvolatile storage medium that can read and write information and has a large storage capacity, and stores an OS (Operating System), various control programs, application programs, etc.

[0037] Image forming apparatus 100 processes a control program stored in ROM 103, an information processing program (application program) loaded into RAM 102 from a storage medium such as HDD 104, and the like using the arithmetic functions of CPU 101. This processing constitutes a software control unit including various functional modules of image forming apparatus 100. The software control unit thus constituted is combined with hardware resources installed in image forming apparatus 100 to constitute functional blocks that realize the functions of image forming apparatus 100.

[0038] I / F 105 is an interface that connects feeding unit 110, conveying unit 120, image forming unit 130, and operation panel 160 to common bus 109. That is, controller 150 controls the operations of feeding unit 110, conveying unit 120, image forming unit 130, and operation panel 160 through I / F 105.

[0039] Operation panel 160 is a user interface that includes a display that displays current setting values, a selection screen, etc., and an operation unit (for example, a touch panel, push buttons, etc.) that accepts input operations from the user.

[0040] 5 is a functional block diagram of controller 150. Controller 150 mainly includes a feeding processing unit 151, a counting unit 152, a correction value acquisition unit 153, a thickness acquisition unit 154, a lift amount determination unit 155, a threshold determination unit 156, and an elevation processing unit 157. Each of the functional blocks 151 to 157 constituting controller 150 is realized, for example, by CPU 101 executing a program stored in memory. Each of the functional blocks 151 to 157 shown in FIG. 5 operates in conjunction with each other to feed a plurality of sheets M stacked in sheet stacking unit 111 to conveyance path R1 one sheet at a time.

[0041] As shown in Figures 3(A) to 3(C), the feeding processing unit 151 drives the floating blower 112a, the suction fan 113f, and the feeding motors 113d and 114c to feed multiple sheets of paper M stacked in the paper stacking unit 111 one by one in sequence to the conveying path R1.

[0042] Counting unit 152 counts the number of sheets M fed by feeding processing unit 151. More specifically, counting unit 152 increments the number of fed sheets N (number of sheets) stored in HDD 104 (memory) by 1 each time a feeding signal is output from feeding detection sensor 117. The number of fed sheets N is reset (assigned an initial value of 0) when sheets M are replenished in paper stacking unit 111 or in step S809 of FIG. 8.

[0043] The correction value acquisition unit 153 acquires the correction values ​​α1 and α2 from the user of the image forming apparatus 100 via the operation panel 160. The correction values ​​α1 and α2 according to this embodiment are numerical values ​​greater than 1 (α1>1, α2>1). Furthermore, the correction value α2 is a value greater than the correction value α1 (α2>α1).

[0044] The thickness acquisition unit 154 acquires the paper thickness t (sheet thickness) of the paper sheets M loaded on the paper stacking unit 111 from the user via the operation panel 160. As one example, the user may directly input the paper thickness t via the operation panel 160. As another example, the user may input the basis weight of the paper sheets M via the operation panel 160. Then, the thickness acquisition unit 154 may read the paper thickness t corresponding to the input basis weight (for example, the paper thickness tmin, paper thickness tavg., and paper thickness tmax in FIG. 7) from memory. Note that the feeding unit 110 may be equipped with a thickness detection sensor that detects the paper thickness t. Then, the thickness acquisition unit 154 may acquire the paper thickness t detected by the thickness detection sensor.

[0045] Lift amount determination unit 155 determines lift amounts H1, H2 of paper stacking unit 111 by lift processing unit 157 based on correction values ​​α1, α2 acquired by correction value acquisition unit 153 and paper thickness t acquired by thickness acquisition unit 154. Lift amount H1 (first lift amount) is the lift amount of paper stacking unit 111 when the paper remaining amount detected by remaining amount detection sensor 118 is equal to or greater than the threshold remaining amount X%. Lift amount H2 (second lift amount) is the lift amount of paper stacking unit 111 when the paper remaining amount detected by remaining amount detection sensor 118 is less than the threshold remaining amount X%. Lift amount H2 is set to a value greater than lift amount H1.

[0046] 6 is a flowchart of the rise amount calculation process. The rise amount determination unit 155 acquires the correction values ​​α1 and α2 through the correction value acquisition unit 153 (S601, S602). The rise amount determination unit 155 also acquires the paper thickness t through the thickness acquisition unit 154 (S603). The rise amount determination unit 155 then determines the rise amount H1 by multiplying the paper thickness t by the correction value α1 (S604). The rise amount determination unit 155 also determines the rise amount H2 by multiplying the paper thickness t by the correction value α2 (S605). Because the correction values ​​α1 and α2 are greater than 1, the rise amounts H1 and H2 are greater than the paper thickness t.

[0047] However, the method for determining the rise amounts H1 and H2 is not limited to the example in FIG. 6. As another example, the rise amount determination unit 155 may determine the rise amount H1 by adding a correction value α1 to the paper thickness t, and may determine the rise amount H2 by adding a correction value α2 to the paper thickness t. In this case, the correction values ​​α1 and α2 are positive values. As yet another example, the rise amount determination unit 155 may obtain the rise amounts H1 and H2 from the user via the operation panel 160.

[0048] The threshold number determination unit 156 determines a threshold number of sheets Nth. The threshold number of sheets Nth is the value of the number of sheets N to be fed when the process of raising the paper stacking unit 111 is stopped. In other words, the threshold number of sheets Nth is a value to be compared with the number of sheets to be fed N. The threshold number of sheets Nth may be a fixed value, but can be determined, for example, by the following method.

[0049] 7 is a graph showing the correspondence between basis weight and paper thickness ranges stored in memory. As shown in FIG. 7, the HDD 104 (memory) stores correspondence between multiple basis weights 0 to 9 and paper thickness ranges. The basis weight is the number of sheets of paper M per 1 m 2 The paper thickness range refers to the weight per sheet. The paper thickness range refers to the maximum value (paper thickness tmax) and minimum value (paper thickness tmin) of the paper thickness of the paper M of the corresponding basis weight. The HDD 104 may also store an average paper thickness (paper thickness tavg.) corresponding to each basis weight. Furthermore, the actual paper thickness of the paper M fed from the feeding unit 110 is set as the set paper thickness t0 (set sheet thickness). The set paper thickness t0 may be set by the user via the operation panel 160, for example, or may be the paper thickness corresponding to the basis weight stored in the HDD 104.

[0050] For example, the threshold value determination unit 156 reads out from the HDD 104 the paper thickness tmin corresponding to the basis weight input via the operation panel 160. Then, the threshold value determination unit 156 determines the threshold number of sheets Nth based on the following formula 1. Note that α in the following formula 1 is either the correction value α1 or α2 acquired by the correction value acquisition unit 153. Threshold number Nth = h × 1000 / (α × t0 - tmin) (Equation 1)

[0051] As another example, the threshold value determination unit 156 may determine the threshold number Nth based on the following formula 2. Note that α in the following formula 2 is either the correction value α1 or α2 acquired by the correction value acquisition unit 153. In this case, the correspondence relationship shown in FIG. 7 can be omitted. Threshold number Nth = h × 1000 / (α × t0-t) (Equation 2)

[0052] The lifting / lowering processing unit 157 causes the lifting mechanism 115 to lift the paper stacking unit 111 based on signals output from the various sensors 116 to 118, the number of fed sheets N counted by the counting unit 152, the lift amounts H1 and H2 determined by the lift amount determining unit 155, and the threshold number Nth determined by the threshold determining unit 156. In addition, the lifting / lowering processing unit 157 causes the lifting mechanism 115 to lower the paper stacking unit 111 when the paper stacking unit 111 is replenished with paper sheets M.

[0053] 8 is a flowchart of the feeding process. Controller 150 executes the feeding process when an image formation instruction is input to image forming apparatus 100. Furthermore, controller 150 repeatedly executes the feeding process when forming images on multiple sheets of paper M. The feeding process is executed by feeding processing unit 151, counting unit 152, and lifting / lowering processing unit 157. Meanwhile, it is assumed that the processes of correction value acquisition unit 153, thickness acquisition unit 154, lift amount determination unit 155, and threshold value determination unit 156 are executed before the start of the feeding process.

[0054] First, the feeding processing unit 151 drives the floating blower 112a, the suction fan 113f, and the feeding motors 113d and 114c (S801). As a result, one sheet of paper M is fed to the transport path R1, as shown in Figures 3(A) to 3(C). Then, execution of the processes from step S803 onward is awaited until a feeding signal is output from the feeding detection sensor 117 (S802: No).

[0055] Then, in response to the output of a feeding signal from the feeding detection sensor 117 (S802: Yes), the counting unit 152 increments the number of fed sheets N stored in the HDD 104 (N=N+1) (S803). In addition, in response to the output of a feeding signal from the feeding detection sensor 117 (S802: Yes), the lifting / lowering processing unit 157 executes the processes of steps S804 to S809. Furthermore, in parallel with the processes of steps S803 to S809, the conveying unit 120 and the image forming unit 130 convey the sheet M fed from the feeding unit 110 along the conveying path R1 and form an image on the sheet M.

[0056] The lifting / lowering processing unit 157 compares the number of fed sheets N counted by the counting unit 152 with the threshold number Nth determined by the threshold determination unit 156 (S804). If the number of fed sheets N is less than the threshold number Nth (S804: No), the lifting / lowering processing unit 157 determines whether a remaining amount signal is being output from the remaining amount detection sensor 118 (i.e., whether the remaining amount of paper is equal to or greater than the threshold remaining amount X%) (S805).

[0057] Then, in response to the fact that a remaining amount signal is being output from the remaining amount detection sensor 118 (i.e., the remaining amount of paper is equal to or greater than the threshold remaining amount X%) (S805: Yes), the lifting / lowering processing unit 157 drives the lifting mechanism 115 so that the paper stacking unit 111 rises by the amount of lift H1 determined by the amount of lift determination unit 155 (S806). Also, in response to the fact that the output of the remaining amount signal from the remaining amount detection sensor 118 has stopped (i.e., the remaining amount of paper is less than the threshold remaining amount X%) (S805: No), the lifting / lowering processing unit 157 drives the lifting mechanism 115 so that the paper stacking unit 111 rises by the amount of lift H2 determined by the amount of lift determination unit 155 (S807).

[0058] On the other hand, when the number of fed sheets N reaches the threshold number of sheets Nth (S804: Yes), the lift processing unit 157 determines whether or not an arrival signal is being output from the lift detection sensor 116 (i.e., whether or not paper sheet M is present at the detection position) (S808). Then, when the arrival signal is being output from the lift detection sensor 116 (i.e., paper sheet M is present at the detection position) (S808: Yes), the lift processing unit 157 ends the feeding process without executing the processes of steps S805 to S809. Also, when the output of the arrival signal from the lift detection sensor 116 has stopped (i.e., paper sheet M is not present at the detection position) (S808: No), the lift processing unit 157 resets the number of fed sheets N stored in the HDD 104 (substituting an initial value of 0) without executing the processes of steps S805 to S807 (S809).

[0059] That is, while repeatedly executing the feeding process, if the number of fed sheets N counted by counting unit 152 is less than the threshold number of sheets Nth (S804: No), lifting / lowering processing unit 157 lifts paper stacking unit 111 each time a feeding signal is output from feeding detection sensor 117 (S805-S807). Also, while repeatedly executing the feeding process, if the number of fed sheets N counted by counting unit 152 reaches the threshold number of sheets Nth (S804: Yes), lifting / lowering processing unit 157 stops lifting paper stacking unit 111. Furthermore, lifting / lowering processing unit 157 resumes lifting paper stacking unit 111 from the next feeding process after which the number of fed sheets N is reset (S809).

[0060] According to the above embodiment, for example, the following advantageous effects are achieved.

[0061] According to the above embodiment, by raising the paper stacking unit 111 each time one sheet of paper M is fed, the topmost sheet of paper M stacked on the paper stacking unit 111 can be positioned on the airflow path from the airflow unit 112. As a result, it is possible to prevent the paper M from being unfeeded during the feeding process. Furthermore, by setting the lift amounts H1 and H2 to values ​​greater than the paper thickness t, it is possible to more effectively prevent the paper M from being unfeeded during the feeding process.

[0062] However, repeated lifting of the paper stacking unit 111 accumulates an error between the total paper thickness t of the multiple sheets of paper M that have been fed and the total amount of lift of the paper stacking unit 111. Therefore, as in the above embodiment, the accumulated error can be reset by temporarily stopping the lifting of the paper stacking unit 111 in response to the feeding of the threshold number Nth of sheets of paper M. As a result, it is possible to prevent multiple sheets of paper M from floating up together.

[0063] Furthermore, non-feeding and double feeding are more likely to occur when the stack height of sheets M on sheet stacking section 111 is low. Therefore, as in the above embodiment, by setting the amount of lift H2 when the amount of remaining sheets is small to a value greater than the amount of lift H1 when the amount of remaining sheets is large, sheets M can be properly fed even when the stack height of sheets M on sheet stacking section 111 is low. However, the amount of lift of sheet stacking section 111 may be set to the same regardless of the amount of remaining sheets. In other words, steps S602 and S605 in FIG. 6 and steps S805 and S807 in FIG. 8 can be omitted.

[0064] Furthermore, as in the above embodiment, by setting the threshold number of sheets Nth using equation 1 or equation 2 and stopping the rise of the paper stacking section 111 when the number of sheets N fed reaches the threshold number of sheets Nth, it is possible to prevent double feeding of paper sheets M caused by the paper stacking section 111 and the endless circular belt 113c coming too close to each other.

[0065] Each function of the above-described embodiments can be realized by one or more processing circuits. Here, the term "processing circuit" in this specification includes a processor programmed to perform each function by software, such as a processor implemented by an electronic circuit, as well as devices such as an ASIC (Application Specific Integrated Circuit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or a conventional circuit module designed to perform each function described above.

[0066] The present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the technical gist thereof. The present invention covers all technical matters included in the technical ideas described in the claims. The above-described embodiments are preferred examples, but a person skilled in the art can realize various modifications from the disclosed content. Such modifications are also included in the technical scope described in the claims. [Explanation of symbols]

[0067] 100: Image forming device 101: CPU 102: RAM 103:ROM 104: HDD 105: Interface 109: Common bus 110: Feeding section 111: Paper stacking section 112: Ventilation section 112a: Floating blower 112b: Ventilation outlet 113: Adsorption feeding section 113a: Drive pulley 113b: driven pulley 113c: Endless circular belt 113d,114c: Feeding motor 113e: Suction port 113f: Suction fan 114: Gripping feeding section 114a: drive roller 114b: driven roller 115: Lifting mechanism 115a: Lifting motor 116: Lift detection sensor 117: Feed detection sensor 118: Remaining amount detection sensor 120: Transport unit 121, 122: Transport roller 130: Image forming unit 131C, 131K, 131M, 131Y: Photosensitive drum 132: Transfer belt 133: Transfer roller 134: Fuser roller 140: Paper output tray 150: Controller 151: Feeding processing section 152:Counting section 153: Correction value acquisition unit 154: Thickness acquisition unit 155: Lift amount determination unit 156: Threshold determination unit 157: Lifting processing section 160: Operation panel [Prior art documents] [Patent documents]

[0068] [Patent Document 1] Japanese Patent Application Publication No. 2019-119605

Claims

1. a sheet stacking section on which a plurality of sheets are stacked; an air blowing unit that blows air from the side of the plurality of sheets stacked on the sheet stacking unit to lift up the top sheet; a suction feeding section disposed above the sheet stacking section, which suctions the sheet floated by the air blowing section and feeds the sheet in a feeding direction; a lifting mechanism for lifting and lowering the sheet stacking unit; a lifting / lowering detection sensor that detects that the sheets stacked on the sheet stacking unit have reached a detection position between the sheet stacking unit and the suction feeding unit; a feeding detection sensor that detects the sheet fed by the suction feeding unit; a controller that controls operations of the air blower, the suction feeding unit, and the lifting mechanism based on detection results of the lifting / lowering detection sensor and the feeding detection sensor, The controller repeatedly performs a process of feeding the sheets floated by the air blowing unit to the suction feeding unit and counting the number of sheets detected by the feeding detection sensor. When the number of sheets is less than a threshold number, each time a sheet is detected by the feeding detection sensor, the lifting mechanism is driven so that the sheet stacking unit is lifted by an amount determined based on a sheet thickness t of the sheets stacked on the sheet stacking unit; When the number of sheets reaches the threshold number, the lifting of the sheet stacking unit is stopped until the lifting / lowering detection sensor no longer detects the sheets; The sheet feeding apparatus according to claim 1, wherein the controller determines the amount of lift by multiplying the sheet thickness t by a correction value α (α is a value greater than 1).

2. a remaining amount detection sensor for detecting the remaining amount of sheets stacked in the sheet stacking section; The controller When the remaining amount of sheets detected by the remaining amount detection sensor is equal to or greater than a threshold remaining amount, the lifting mechanism is driven so that the sheet stacking unit is lifted by a first lift amount; 2. The sheet feeding device according to claim 1, wherein when the remaining sheet amount detected by the remaining amount detection sensor is less than the threshold remaining amount, the lifting mechanism is driven so that the sheet stacking section rises by a second lift amount that is greater than the first lift amount.

3. 3. The sheet feeding device according to claim 1, wherein the feeding detection sensor is disposed downstream of the suction feeding section in the feeding direction, facing the sheet feeding path, and detects the sheet passing through the feeding path.

4. a thickness detection sensor for detecting the sheet thickness t; 4. The sheet feeding device according to claim 1, wherein the controller determines the amount of lift based on the sheet thickness t detected by the thickness detection sensor.

5. an operation unit that accepts input operations from a user; 4. The sheet feeding apparatus according to claim 1, wherein the controller determines the amount of lift based on the sheet thickness t input through the operation unit.

6. an operation unit that accepts input operations from a user; 6. The sheet feeding apparatus according to claim 1, wherein the controller determines the amount of lift based on the correction value α input through the operation unit.

7. a memory for storing a correspondence between the basis weight of a sheet and a range of sheet thickness; The sheet feeding device of any one of claims 1 to 6, characterized in that the controller determines the threshold number of sheets based on the following formula 1, where h is the height from the detection position to the suction feeding section, t0 is the set sheet thickness, and tmin is the minimum sheet thickness corresponding to the basis weight of the sheets loaded in the sheet stacking section. Threshold number=h×1000 / (α×t0−tmin) (Equation 1)

8. The sheet feeding device according to any one of claims 1 to 6, characterized in that the controller determines the threshold number of sheets based on the following formula 2, where h is the height from the detection position to the suction feeding section and t0 is the set sheet thickness: Threshold number=h×1000 / (α×t0−t) (Equation 2)

9. a sheet feeding device according to any one of claims 1 to 8; an image forming apparatus comprising: an image forming unit that forms an image on the sheet fed by the sheet feeding device;

Images