Sheet feeding device

Abstract

To provide a sheet feeding device that can improve productivity while suppressing a sheet from being poorly conveyed.SOLUTION: A sheet feeding device comprises: a sheet supporting part; a sheet feeding part that performs feeding operation; an air processing part that performs spraying operation; and a control part that executes sheet-feeding control that the sheet feeding part performs the feeding operation while stopping the spraying operation after the spraying operation is performed and then the spraying operation is stopped, by which the spraying operation is executed every time when a first number of sheets are fed until printing number of sheets designated in a job are fed. In the sheet feeding control, when a second number of sheets processed by the spraying operation but not fed are left in the sheet supporting part at a time point when a first job is completed and when the number of sheets to be printed designated in a second job subsequent to the first job is equal to a third number of sheets less than the second number of sheets, the control part skips first spraying operation and starts feeding operation, for the second job.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a sheet feeding device that feeds a sheet. [Background technology]

[0002] In recent years, there has been an increasing demand for forming images on various types of sheets, and sheets with smooth surfaces, such as coated paper, are sometimes used as recording materials. When a stack of sheets with such smooth surfaces is set in a sheet feeding device that feeds the sheets, the sheets may adhere strongly to each other, making it difficult to feed the sheets. According to Patent Document 1, a sheet feeding device is proposed that blows air onto the sheet stack to release the adhesion between the sheets and separate the sheets. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2006-256819 Summary of the Invention [Problem to be solved by the invention]

[0004] A general control in which air is blown onto a stack of sheets to separate them and feed the sheets as in the above-mentioned Patent Document 1 will be described with reference to FIG. 10. As shown in FIG. 10, when the control for feeding sheets is started in response to a command such as the start of a print job (S101), first, air blowing toward the stack of sheets is started (S102). This separates the top several to several tens of sheets of the stack of sheets. Air blowing continues until a predetermined time (for example, 10 seconds) has elapsed since the start of air blowing (No in S103). Then, when the predetermined time has elapsed since the start of air blowing (Yes in S103), a feeding operation is performed to feed the sheets to the image forming unit by a pickup roller or the like (S104). Then, the feeding operation is repeated until the required number of sheets to be fed to the image forming unit based on the command of the print job is reached (No in S105), and when the required number of sheets is reached (Yes in S105), air blowing is stopped (S106) and this control is terminated (S107).

[0005] However, in the above-mentioned control, when a second job following the first job is started after the first job is finished, there may be sheets that have already been loaded and have been released from adhesion by air blowing in the first job. In this case, according to the above-mentioned control, the air blowing operation is performed in the second job on the sheets that have already been released from adhesion, which may reduce productivity.

[0006] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide a sheet feeding device capable of improving productivity while reducing sheet transport failures. [Means for solving the problem]

[0007] The present invention provides a sheet feeding control device, comprising: a sheet supporting section for supporting a sheet stack; a sheet feeding section for performing a feeding operation of contacting the top sheet of the sheet stack supported by the sheet supporting section and feeding the top sheet; an air handling section for performing a blowing operation of blowing air against a side surface of the sheet stack supported by the sheet supporting section to handle the sheets; and a sheet feeding control device for performing the blowing operation by the air handling section, and after the blowing operation is stopped, performing the feeding operation by the sheet feeding section in a state in which the blowing operation is stopped, and a control unit that executes sheet feeding control in which the blowing operation is performed each time a first number of sheets are fed until the first number of sheets have been fed, and the control unit is characterized in that, in the sheet feeding control, if a second number of sheets that have been handled by the blowing operation but not fed remain in the sheet support unit at the time when a first job is completed and the number of printed sheets in a second job following the first job is a third number that is less than the second number, omits the initial blowing operation in the second job and starts the feeding operation.

[0008] The present invention also provides a sheet feeding device comprising: a sheet supporting section that supports a sheet stack; a sheet feeding section that performs a feeding operation by contacting a top sheet of the sheet stack supported by the sheet supporting section and feeding the top sheet; an air handling section that performs a blowing operation by blowing air against sides of the sheet stack supported by the sheet supporting section to handle the sheets; and a control section that executes sheet feeding control in which the air handling section performs the blowing operation, stops the blowing operation, and then performs the feeding operation by the sheet feeding section with the blowing operation stopped, the sheet feeding control performing the blowing operation every time a first number of sheets is fed until a print number of sheets specified in a job is fed, and the control section is characterized in that in the sheet feeding control, if a fourth number, which is the number of sheets fed after the blowing operation at the time a first job is completed, is less than the first number, then in the sheet feeding control, the control section omits the initial blowing operation and starts the feeding operation in a second job following the first job. Effect of the Invention

[0009] According to the present invention, it is possible to reduce sheet transport failures. [Brief description of the drawings]

[0010] [Figure 1] 1 is an overall schematic diagram showing an image forming system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram showing a control system of the image forming system. [Diagram 3] FIG. 4 is a schematic diagram showing a configuration of a manual feeding section. [Figure 4] FIG. 11 is a schematic diagram showing a state in which an air blowing operation is performed in the manual feed section. [Diagram 5] 5 is a flowchart showing sheet feeding control according to the first embodiment. [Figure 6] 10 is a flowchart showing sheet feeding control according to a second embodiment. [Figure 7] 10 is a flowchart showing sheet feeding control according to a second embodiment. [Figure 8] 13 is a flowchart showing a sheet feeding control according to a third embodiment. [Figure 9] 5A and 5B are diagrams for explaining the generation of a rotational force due to the positional relationship between a pickup roller and a feed roller. [Figure 10] 11 is a flowchart showing a general sheet feeding control. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] <First embodiment> A first embodiment of the present invention will be described in detail below with reference to the drawings. First, an image forming system 600 including a feed deck 500 and an image forming apparatus 201 connected thereto will be described with reference to Fig. 1. Fig. 1 is a diagram showing a schematic configuration of the image forming system according to the first embodiment.

[0012] [Outline of image forming system] 1, the image forming system 600 includes an image forming apparatus 201 and a feed deck 500 connected to the image forming apparatus 201. The feed deck 500 is connected to the right side of the image forming apparatus 201 in FIG. 1, and is configured to be able to feed a sheet S to the image forming apparatus 201.

[0013] [General configuration of image forming device] 1, the image forming apparatus 201 has an image forming apparatus main body 201A including an image forming unit 201B that forms an image on a sheet, and an image reading device 202 disposed above the image forming apparatus main body 201A. Between the image reading device 202 and the image forming apparatus main body 201A, a discharge space V for discharging sheets is formed. An operation unit 730 constituted by a touch panel or the like capable of displaying a screen is disposed above the image forming apparatus main body 201A.

[0014] The image forming section 201B employs a four-drum full-color system. The image forming section 201B includes a laser scanner 210 and four process cartridges 211Y, 211M, 211C, and 211K that form toner images of four colors, yellow (Y), magenta (M), cyan (C), and black (K). Here, each process cartridge 211 includes a photosensitive drum 212, a charger 213, and a developing device 214. The image forming section 201B also includes an intermediate transfer unit 201C disposed above the process cartridge 211, and a fixing section 201E. Note that a toner cartridge 215 for supplying toner to the developing device 214 is disposed above the image forming section 201B.

[0015] The intermediate transfer unit 201C includes an intermediate transfer belt 216 wound around a drive roller 216a and a tension roller 216b. A primary transfer roller 219 is provided on the inner side of the intermediate transfer belt 216, and contacts the intermediate transfer belt 216 at a position facing the photosensitive drum 212. The intermediate transfer belt 216 is rotated in the direction of the arrow in FIG. 1 by a drive roller 216a driven by a drive unit (not shown).

[0016] Then, the toner images of each color having a negative polarity on the photosensitive drum are sequentially transferred in a multi-layer manner to the intermediate transfer belt 216 by the primary transfer roller 219. A secondary transfer roller 217 that transfers the color image formed on the intermediate transfer belt to the sheet P is provided at a position facing the driving roller 216a of the intermediate transfer unit 201C. The intermediate transfer belt 216 and the secondary transfer roller 217 form a secondary transfer section 201D. Furthermore, a fixing section 201E having a pressure roller 220a and a heating roller 220b is provided above the secondary transfer roller 217. In addition, a first discharge roller pair 225a, a second discharge roller pair 225b, and a double-sided reversing section 201F are provided at the upper left of the fixing section 201E. The double-sided reversing section 201F is provided with a reversible reversing roller pair 222 and a re-conveying passage R that conveys the sheet with an image formed on the first side to the image forming section 201B again.

[0017] A plurality of (four in this embodiment) sheet feeding units 230 are provided at the bottom of the image forming apparatus main body 201A, which feed the set sheets S to the image forming section 201B. Each sheet feeding unit 230 includes a feeding cassette 1 for storing sheets, and a sheet feeding section 5 for feeding the sheets S stored in the feeding cassette 1. The sheet feeding section 5 includes a pickup roller 2, and a feed roller 3 and a retard roller as a separation section for separating the sheets S fed from the pickup roller 2 and fed in a duplicated manner.

[0018] Further, on the right side surface of the image forming apparatus main body 201A in FIG. 1, there is provided a manual feed section 235 that feeds the set sheet S to the image forming section 201B. The manual feed section 235 includes a manual feed tray 6 as a sheet support section that supports the sheet S. The manual feed tray 6 is supported by the image forming apparatus main body 201A as a housing so as to be openable and closable. A detailed configuration of the manual feed section 235 will be described later. Further, on the right side surface of the image forming apparatus main body 201A in FIG. 1, below the manual feed section 235, there is provided a feed deck 500 that feeds the set sheet S to the image forming section 201B.

[0019] Next, the image forming operation of the image forming apparatus 201 will be described. First, image information of an original is read by the image reading device 202, and the image information is image-processed, converted into an electric signal, and transmitted to the laser scanner 210 of the image forming section 201B. In the image forming section 201B, the surface of the photosensitive drum 212, the surface of which is uniformly charged to a predetermined polarity and potential by the charger 213, is sequentially exposed to laser light. As a result, electrostatic latent images of yellow, magenta, cyan, and black are sequentially formed on the photosensitive drum of each process cartridge 211, respectively.

[0020] Thereafter, the electrostatic latent images are developed and visualized with toner of each color, and the toner images of each color on each photoconductor drum are transferred in order onto the intermediate transfer belt 216 in a superimposed manner by a primary transfer bias applied to the primary transfer roller 219. As a result, a toner image is formed on the intermediate transfer belt 216.

[0021] On the other hand, the sheet S fed by the feed roller 3 of the sheet feeding unit 230 is conveyed to a pair of registration rollers (hereinafter referred to as the registration roller pair) 240 consisting of a drive roller and a driven roller. At this time, the driving of the registration roller pair 240 is stopped, and the leading edge of the sheet S is abutted against the registration roller pair 240. As a result, the leading edge of the sheet S is made to follow the registration roller pair 240. Thereafter, as the sheet S continues to be conveyed by the feed roller 3, a flexure (loop) is formed in the sheet S, and when a predetermined loop amount is reached, the registration roller pair 240 is driven. As a result, the skew of the sheet S is corrected by the registration roller pair 240, and the sheet S with the skew corrected is conveyed to the secondary transfer portion 201D by the registration roller pair 240. Subsequently, in the secondary transfer portion 201D, the toner images are transferred collectively onto the sheet S by a secondary transfer bias applied to the secondary transfer roller 217. The sheet S onto which the toner image has been transferred is then conveyed to a fixing section 201E, where the toner of each color is melted and mixed by heat and pressure, and is fixed onto the sheet S as a color image.

[0022] Thereafter, the sheet S on which the image has been fixed is discharged to the discharge space V by the first discharge roller pair 225a or the second discharge roller pair 225b provided downstream of the fixing section 201E, and is stacked on the stacking section 223 formed on the bottom surface of the discharge space V. When an image is formed on both sides of the sheet S, after the image is fixed on the first side of the sheet S, the sheet S is transported to the re-conveyance path R by the reversing roller pair 222, and is transported again to the image forming section 201B. Then, an image is formed on the second side of the sheet S, which is opposite to the first side, and the sheet S is discharged to the stacking section 223.

[0023] [Manual feed section configuration] Next, the manual feed unit 235 as a sheet feeding device will be described in detail with reference to Fig. 1 and Fig. 3. Fig. 3 is a schematic diagram showing the configuration of the manual feed unit 235 according to the present embodiment. As shown in Fig. 1 and Fig. 3, the manual feed unit 235 includes a manual tray 6 and a sheet feed unit 506 that feeds a sheet and separates overlapped sheets.

[0024] Moreover, the sheet feeding unit 506 includes a pickup roller 501 as a feeding roller that comes into contact with the top sheet of a sheet stack supported by a sheet stacking plate 514 described later and feeds the top sheet. Furthermore, the sheet feeding unit 506 includes a feed roller 502 and a retard roller 503 as a separating unit that separates the sheet S fed from the pickup roller 501.

[0025] Further, in the manual feed section 235, downstream in the sheet feeding direction of the feed roller 502, there is disposed a pull-out roller 504 (see FIG. 1) which pulls out the sheet S from the feed roller 502 and feeds it to the image forming apparatus 201. In the sheet feeding direction, between the feed roller 502 and the pull-out roller 504, that is, downstream in the feeding direction of the sheet feeding section 506, there is disposed a feed sensor 505. This feed sensor 505 detects the passage of the sheet S by outputting a signal depending on the presence or absence of the sheet S.

[0026] 3, the manual feed tray 6 is provided with a sheet stacking plate 514 that stacks and supports a sheet bundle consisting of a plurality of sheets S, a support base 515 that supports the sheet stacking plate 514, and a sheet presence / absence sensor 401. The sheet presence / absence sensor 401 can detect the presence or absence of sheets (including a sheet bundle) on the sheet stacking plate 514. For example, the sheet presence / absence sensor 401 may be a flag sensor that detects the position of a flag that moves when pressed by a sheet stacked on the sheet stacking plate 514, or may be an optical sensor that detects light reflected by a sheet.

[0027] The manual feed tray 6 is also provided with side end regulating plates 511, 512 and a rear end regulating plate 513. The side end regulating plates 511, 512 as regulating parts regulate the positions of the widthwise ends (side ends of the sheets) of the sheets S set on the sheet stacking plate 514. The width direction W of the sheets S is a direction perpendicular to the sheet feeding direction FD of the sheets S (sheet stack). The rear end regulating plate 513 regulates the position of the upstream end (rear end of the sheets) in the feeding direction of the sheets S.

[0028] These side end regulating plates 511 and 512 are provided with air blowing sections 511A and 512A as air handling sections. The air blowing section 511A of the side end regulating plate 511 has a fan 511b driven by a fan motor 511M (see FIG. 2) and a blowing nozzle 511a that guides the air blown from the fan 511b and blows it from the side of the sheet stack. Similarly, the air blowing section 512A of the side end regulating plate 512 has a fan 512b driven by a fan motor 512M (see FIG. 2) and a blowing nozzle 512a that guides the air blown from the fan 512b and blows it from the side of the sheet stack. These blowing nozzles 511a and 512a as blowing ports have a function of a duct that guides air inside the side end regulating plates 511 and 512. The side end regulating plates 511, 512 are provided with floating suppression plates 511c, 512c in the vicinity of the blowing nozzles 511a, 512a to prevent the sheet S, to which air is blown, from floating up and climbing over the side end regulating plates 511, 512.

[0029] [Configuration of the control system of the image forming system] Next, the configuration of a control system in the image forming system 600 will be described with reference to Fig. 2. Fig. 2 is a block diagram showing the control system of the image forming system according to the present embodiment.

[0030] The control unit 100 according to the present embodiment is provided in, for example, an image forming apparatus 201. The control unit 100 includes a central processing unit (CPU) 101, a read only memory (ROM) 102, and a random access memory (RAM) 103. The ROM 102 stores various programs, and the CPU 101 reads and executes any program from the ROM 102. The RAM 103 is used as a working area for the CPU 101. The control unit 100 controls the image forming apparatus 201 and the feed deck 500. The control unit 100 is connected to a host device 900 and an operation unit 730, and performs signal processing and sequence control for various process devices while exchanging information with them. The host device 900 is an external device such as a personal computer, an image scanner, or a facsimile. The operation unit 730 that can be operated by a user will be described later.

[0031] The control unit 100 is connected to the fan control unit 402 and the feed motor 520 as a motor that drives the pickup roller 501. The control unit 100 is also connected to a torque measurement unit 520a that measures the motor torque of the feed motor 520, the feed sensor 505, the sheet presence sensor 401, and the like. The fan control unit 402 is connected to the fan motors 511M and 512M, and performs rotation control of the fans 511b and 512b by the fan motors 511M and 512M, while simultaneously detecting failures of the fans 511b and 512b. Whether the fans 511b and 512b are broken can be determined, for example, by counting the number of rotations of the fans 511b and 512b and checking whether the counted number of rotations reaches an intended number of rotations.

[0032] Note that torque measuring unit 520a measures the motor torque of feed motor 520, but may be, for example, a current sensor that detects the value of a current flowing through feed motor 520, or a torque sensor that detects the torque generated in pickup roller 501. In other words, the specific configuration of torque measuring unit 520a may be anything that can directly or indirectly measure the motor torque of feed motor 520.

[0033] [Operation and problems when blowing air] Next, the state of the sheets S when air is blown from the side of the sheet stack by the air blowing units 511A, 512A, and problems that occur when the sheets S are fed while air is being blown thereon will be described with reference to Figs. 4 and 9. Fig. 4 is a schematic diagram showing a state in which an air blowing operation (hereinafter referred to as "air blowing operation" or "blowing operation") is performed by the feeding deck according to this embodiment. Fig. 9 is an explanatory diagram for explaining the generation of a turning force due to the positional relationship between the pickup roller 501 and the feed roller 502.

[0034] 4, fans 511b, 512b of air blowing units 511A, 512A blow air toward the side of the sheet stack as indicated by arrows A1, A2 during the air blowing operation. Then, several to several tens of sheets S at the top of the sheet stack are separated and floated, while the floating suppression plates 511c, 512c suppress the floating of the sheets S. This reduces the adhesion between the floating sheets S, and makes it possible to feed the sheets S by the pickup roller 501 even if the sheets S have a smooth surface, such as coated paper.

[0035] However, due to design considerations in relation to other components, the positions of the center C1 of the pickup roller 501 and the center C2 of the feed roller 502 may be misaligned by, for example, a distance X in the width direction perpendicular to the sheet feeding direction, as shown in FIG. 9. In this case, when a transport load occurs near the pickup roller 501 due to a difference in transport speed or the like while the topmost sheet S1 is being transported by the feed roller 502, a rotating force is generated in the sheet S1 in the counterclockwise direction. As a result, the sheet S1 is fed while rotating, causing the sheet S1 to skew. Here, even if a rotating force is generated on the sheet S1, the side edges of the sheet S1 usually come into contact with the side edge regulating plates 511 and 512, and the stiffness of the sheet S1 suppresses the skew.

[0036] However, because the sheet S1 is raised by the air blowing from the air blowing sections 511A and 512A, the sheet S1 is likely to bend as shown in Fig. 9. This reduces the effect of the side end regulating plates 511 and 512 in suppressing the skew of the sheet S1, and there is a problem that the amount of skew of the sheet S1 may increase. Therefore, in this embodiment, the sheet feeding control is performed as follows.

[0037] [Sheet feeding control] Next, the sheet feeding control of the manual feed unit 235 according to the present embodiment will be described with reference to Fig. 5. Fig. 5 is a flowchart showing the sheet feeding control according to the first embodiment. The control unit 100 starts the sheet feeding control to feed a sheet when the image forming apparatus 201 starts a print job (hereinafter simply referred to as a job) (S301).

[0038] Then, first, the control unit 100 acquires the number of prints M of the job (S302). Here, an example will be described in which the number of prints M is 22. Next, the control unit 100 detects the presence or absence of the sheet S on the sheet stacking plate 514 of the manual feed tray 6 based on the detection result of the sheet presence sensor 401. Specifically, the control unit 100 detects whether the sheet presence sensor 401 has transitioned from a no state in which the sheet S is not present on the sheet stacking plate 514 to a present state in which the sheet S is present on the sheet stacking plate 514 (S303). When the user sets a new sheet stack on the sheet stacking plate 514 in a state in which no sheets are placed, the sheet presence sensor 401 transitions from the no state to the present state. Note that, hereinafter, an example will be described in which the user sets a sufficient amount of sheets for printing a job multiple times, for example, 50 sheets, on the sheet stacking plate 514.

[0039] Furthermore, if the sheet presence / absence sensor 401 remains in the absent state for a predetermined time after the job is started, the control unit 100 causes the operation unit 730 to display a screen that guides the user to set a sheet in the manual feed tray 6.

[0040] When the sheet presence / absence sensor 401 transitions from the absent state to the present state (Yes in S303), the control unit 100 starts an air blowing operation in which the air blowing units 511A, 512A blow air onto the sides of the sheet stack (S304). As a result, several to several tens of sheets S at the top of the sheet stack are separated and floated, while the floating suppression plates 511c, 512c suppress the floating of the sheets S (see FIG. 4), thereby reducing the adhesion between the sheets.

[0041] Since the fan motors 511M, 512M start rotating from a stopped state, a predetermined time, such as 10 seconds, is preset as the time required to reach a desired number of rotations (rotational speed) and the time required to stabilize the floating of the sheet S. Then, the air blowing operation is performed until the predetermined time has elapsed (No in S305), and when the predetermined time has elapsed (Yes in S305), the control unit 100 stops the air blowing operation (S306), that is, turns off the drive of the fan motors 511M, 512M.

[0042] As a result, the sheets S that were in a floated state attempt to return to the state of the sheet bundle before floating as the air between the sheets is released, but it takes a certain amount of time for the sheets S to return to the state of the sheet bundle before floating. Since the adhesion between the sheets remains reduced until the sheet bundle returns to the state of the sheet bundle before floating, it is possible to feed a predetermined number N of sheets S while preventing double feeding, even for a sheet bundle with high adhesion. The predetermined number N as the first number is information that is stored in advance in the RAM 103, and is set to 10 in this embodiment. The predetermined number N means the number of sheets that the manual feed unit 235 can feed while preventing double feeding until the air between the sheets is released and the sheet bundle returns to the state of the sheet bundle before floating.

[0043] Next, the control unit 100 starts the feeding operation of the sheet S (S307). The start of the feeding operation means that the pickup roller 501, in contact with the uppermost sheet S in the sheet stack, rotates by the feeding motor 520, thereby feeding the sheet S. Thereafter, in the case where the sheets S are fed in a double state in a separation unit composed of a feed roller 502 and a retard roller 503, the sheets S are separated, and the passage of the sheets S is detected by a feeding sensor 505.

[0044] Then, the control unit 100 judges whether or not the feeding of the sheets S of the number of printed sheets M has been completed (S308). If the feeding of the sheets S of the number of printed sheets M (22 sheets in this example) has not been completed (No in S308), the control unit 100 judges whether or not the feeding of a predetermined number N of sheets S (10 sheets in this example) has been completed (S311). If the feeding of the predetermined number N of sheets S has not been completed (No in S311), the control unit 100 returns to step S307 and performs the feeding operation on the next sheet S (S307).

[0045] On the other hand, when the feeding of the predetermined number N of sheets S (10 sheets in this example) is completed in step S311 (Yes in S311), the control unit 100 causes the air blowing units 511A, 512A to perform the air blowing operation (S304). In this manner, in the sheet feeding control, the control unit 100 causes the air blowing units 511A, 512A to perform the blowing operation every time the predetermined number N of sheets S is fed until the feeding of the number M of printed sheets S is completed (S304 to S311).

[0046] When the feeding of the sheets of the number of prints M is completed (Yes in S308), the control unit 100 calculates the number of non-contact sheets Q (S309). The number of non-contact sheets Q is the number of sheets S that have been cleared by the blowing operation but have not been fed and remain on the sheet stacking plate 514 at the time the job is completed. The number of non-contact sheets Q is calculated by subtracting the "surplus of the number of prints M by the predetermined number N" from the "predetermined number N". That is, Q = N - (M mod N) In this embodiment, since N=10 and M=22, M mod N=2. Therefore, Q=8. The calculated number of non-contact sheets Q as the second number is stored in, for example, the RAM 103. With the above, the sheet feeding control of the first job is completed (S310).

[0047] Thus, at the time when the preceding first job is completed, the sheet stacking plate 514 is loaded with eight sheets that have already been separated by the spraying operation and whose adhesion between the sheets has been reduced, as well as several unseparated sheets below them (50-22=28 sheets in this example).

[0048] Next, a case where a second job subsequent to such a first job is executed will be described as an example. As in the case of the first job, the control unit 100 acquires the number of prints M of the second job (S302). Here, a case where the number of prints M as the third number specified in the second job is 5 sheets will be described as an example. Note that since sheets S are stacked on the sheet stacking plate 514, the sheet presence / absence sensor 401 maintains the presence state. Therefore, the control unit 100 proceeds from No in step S303 to step S312.

[0049] The control unit 100 judges whether the number of printed sheets M is equal to or less than the number of non-contact sheets Q (S312). Here, since the number of printed sheets M (five sheets in this example) is equal to or less than the number of non-contact sheets Q (eight sheets in this example) (Yes in S312), the control unit 100 judges that the air blowing operation is unnecessary and performs the feeding operation without the air blowing operation (S313). In other words, the control unit 100 omits the first blowing operation of the second job. This is because all sheets to be fed in the second job have already been handled by the air blowing operation in the first job.

[0050] Next, the control unit 100 judges whether or not the feeding of the sheets S of the number of printed sheets M (five sheets in this example) is completed (S314). When the feeding of the sheets of the number of printed sheets M is completed (Yes in S314), the control unit 100 calculates a new number of non-contact sheets Q (S315). The number of non-contact sheets Q here is obtained by subtracting the number of printed sheets of the second job (five sheets in this example) from the number of non-contact sheets at the end of the first job (eight sheets in this example). That is, the new number of non-contact sheets Q is three sheets. The newly calculated number of non-contact sheets Q is stored in, for example, the RAM 103. With the above, the control unit 100 ends the sheet feeding control (S310).

[0051] Next, a case where a third job subsequent to such a second job is executed will be described as an example. As in the cases of the first and second jobs, the control unit 100 acquires the number of prints M of the third job (S302). Here, a case where the number of prints M specified in the third job is 9 sheets will be described as an example. Note that since sheets S are stacked on the sheet stacking plate 514, the sheet presence / absence sensor 401 maintains the presence state. Therefore, the control unit 100 proceeds from No in step S303 to step S312.

[0052] The control unit 100 judges whether the number of printed sheets M is equal to or less than the number of non-contact sheets Q (S312). Here, since the number of printed sheets M (9 sheets in this example) is greater than the number of non-contact sheets Q (3 sheets in this example) (No in S312), the control unit 100 judges that the air blowing operation is necessary and executes the air blowing operation (S304). That is, the control unit 100 executes the air blowing operation before the feeding operation is started. This is because, although the first three sheets fed in the third job have already been handled by the air blowing operation in the first job, the remaining six sheets have not been handled by the air blowing operation.

[0053] Thereafter, the control unit 100 proceeds to steps S305 to S309 as described above, and newly calculates the number of non-contact sheets Q (S309). The number of non-contact sheets Q here is calculated in the same manner as described for the first job. In this example, N=10 and M=9, so M mod N=9. Therefore, Q=1. That is, the new number of non-contact sheets Q is 1. The newly calculated number of non-contact sheets Q is stored in, for example, the RAM 103. With this, the control unit 100 ends the sheet feeding control (S310).

[0054] As described above, in this embodiment, the air blowing operation is performed by air blowing units 511A and 512A, so that the adhesion of sheets that have a smooth surface such as coated paper and tend to have a high adhesion between sheets can be reduced. This reduces conveyance failures such as slipping of pickup roller 501 and making it impossible to convey a sheet.

[0055] In addition, since the sheet S is fed after the air blowing operations by the air blowing units 511A and 512A are stopped, skew of the sheet can be reduced. Therefore, when correcting skew of the sheet at the registration roller pair 240, the amount of skew correction required is small, so that the variation in the position of the sheet conveyed to the secondary transfer unit 201D can be reduced and the printing precision (quality) can be improved.

[0056] In addition, in this embodiment, the number of non-contact sheets Q, which is the number of sheets S that have been separated by the blowing operation but have not been fed and remain on the sheet stacking plate 514 at the time the job is completed, is compared with the number of printed sheets M of the next job. If the number of printed sheets M is equal to or less than the number of non-contact sheets Q, the air blowing operation is omitted and a feeding operation is performed, so that it is possible to improve productivity while suppressing sheet transport defects. Also, since unnecessary blowing operations can be omitted, it is possible to reduce the power consumption of the image forming apparatus 201.

[0057] <Second embodiment> Next, a second embodiment of the present invention will be described, which is configured by modifying the sheet feeding control of the first embodiment. Therefore, the same configuration as the first embodiment will be described by omitting illustrations or by assigning the same reference numerals in the drawings.

[0058] Figures 6 and 7 are flowcharts showing sheet feeding control according to the second embodiment. Steps S401 to S415 in Figure 6 are similar to steps S301 to S315 in Figure 5, so a description thereof will be omitted. That is, the sheet feeding control in the second embodiment differs from the sheet feeding control in the first embodiment only in steps S424 to S439, which are advanced by No in S412 in Figure 6.

[0059] In the following, a case will be described where the number of non-contact sheets Q is 3 and the number of printed sheets M is 19 when the first job ends and the second job is started. As shown in FIG. 6, when the second job starts (S401), the control unit 100 acquires the number of printed sheets M of the second job (S402). In this example, the number of printed sheets M is 19. Since sheets S have already been loaded on the sheet loading plate 514, the sheet presence / absence sensor 401 maintains the presence state. Therefore, the control unit 100 proceeds from No in step S403 to step S412.

[0060] The control unit 100 judges whether the number of printed sheets M is equal to or less than the number of non-contact sheets Q (S412). Here, since the number of printed sheets M (19 sheets in this example) is greater than the number of non-contact sheets Q (3 sheets in this example) (No in S412), the control unit 100 proceeds to step S424 in Fig. 7. In other words, the control unit 100 omits the first spraying operation of the second job.

[0061] 7, the control unit 100 starts the feeding operation of the sheets S (S421). Next, the control unit 100 judges whether the feeding of the non-contact number Q (three sheets in this example) of sheets S is completed (S422). If the feeding of the non-contact number Q (three sheets in this example) of sheets S is completed (Yes in S422), the control unit 100 starts the air blowing operation by the air blowing units 511A and 512A (S424).

[0062] That is, in this example, the first three sheets fed in the second job have already been cleared by the air blowing operation in the first job, but the remaining 16 sheets have not been cleared by the air blowing operation. Therefore, the air blowing operation is not necessary for the first three sheets S, but is necessary for the remaining 16 sheets S.

[0063] Steps S424 to S427, S431, and S439 in Fig. 7 are the same as steps S304 to S307, S311, and S319 in Fig. 5. Control unit 100 performs the air blowing operation until a predetermined time has elapsed (No in S425), and when the predetermined time has elapsed (Yes in S425), it stops the air blowing operation (S426), that is, it turns off the drive of fan motors 511M and 512M.

[0064] Next, the control unit 100 starts the feeding operation of the sheets S (S427). Then, the control unit 100 judges whether the feeding of the remaining number of printed sheets (16 sheets in this example) obtained by subtracting the number of non-contact sheets Q (3 sheets in this example) from the number of printed sheets M (19 sheets in this example) is completed (S440). If the feeding of these sheets S is not completed (No in S440), the control unit 100 judges whether the feeding of a predetermined number N of sheets S (10 sheets in this example) is completed (S431). If the feeding of the predetermined number N of sheets S is not completed (No in S431), the control unit 100 returns to step S427 and performs the feeding operation on the next sheet S (S427).

[0065] When the feeding of the remaining number of printed sheets (16 sheets in this example) of sheets S is completed (Yes in S440), the control unit 100 newly calculates the number of non-contact sheets Q (S439). The number of non-contact sheets Q here is calculated by subtracting the "remainder of the difference between the number of printed sheets M and the number of non-contact sheets Q divided by the predetermined number N" from the "predetermined number N". That is, Q=N-{(MS) mod N} In this example, M=19, N=10, and the difference between the number of printed sheets M and the number of non-contact sheets Q, i.e., the remaining number of printed sheets, is 16, so (MS) mod N=6. Therefore, Q=4. The newly calculated number of non-contact sheets Q is stored in, for example, the RAM 103. With this, the control unit 100 ends the sheet feeding control (S410).

[0066] As a result, the same effects as those of the first embodiment can be achieved. In addition, in this embodiment, the air blowing operation is omitted for sheets that have already been handled in the first job and the sheets are fed, and the air blowing operation is performed for the remaining number of prints in the job, and then the sheets are fed. This makes it possible to both suppress sheet transport failures and improve productivity.

[0067] <Third embodiment> Next, a third embodiment of the present invention will be described, which is configured by modifying the sheet feeding control of the first embodiment. Therefore, the same configuration as the first embodiment will be described by omitting illustrations or by assigning the same reference numerals in the drawings.

[0068] Fig. 8 is a flowchart showing sheet feeding control according to the third embodiment. Steps S501 to S508 and S509 in Fig. 8 are similar to steps S301 to S308 and S309 in Fig. 5, and therefore a description thereof will be omitted.

[0069] In the following, a case where a first job with a print number M of 15 sheets is started will be described. As shown in FIG. 8, when the first job is started (S501), the control unit 100 acquires the print number M of the first job (S502). In this example, the print number M is 15 sheets. Next, the control unit 100 detects whether the sheet presence sensor 401 has transitioned from the absent state to the present state (S502). When the user sets a new sheet stack on the sheet stacking plate 514 in a state where no sheets are placed, the sheet presence sensor 401 transitions from the absent state to the present state. Note that in the following, an example will be described where the user sets a sufficient amount of sheets for printing multiple jobs, for example, 50 sheets, on the sheet stacking plate 514.

[0070] Steps S504 to S507 are the same as steps S304 to S307 in Fig. 5, and therefore the description will be omitted. When one sheet S is fed, the control unit 100 adds 1 to the count value of the number of sheets fed after sorting T (S551). The number of sheets fed after sorting T as the fourth number corresponds to the number of sheets fed after the air blowing operation is performed.

[0071] Then, the control unit 100 judges whether or not the feeding of the sheets S of the number of printed sheets M has been completed (S508). If the feeding of the sheets S of the number of printed sheets M (15 sheets in this example) has not been completed (No in S508), the control unit 100 judges whether or not the number of sheets fed after sorting T is equal to or greater than the predetermined number of sheets N (S552). If the number of sheets fed after sorting T is smaller than the predetermined number of sheets N (No in S552), the control unit 100 returns to step S507 and feeds the next sheet S (S507). Then, the control unit 100 repeats steps S507, S551, S508, and S552 until the predetermined number of sheets S is fed.

[0072] When 10 sheets S are fed and the number of sheets fed after sorting T becomes equal to or larger than the predetermined number N in step S552 (Yes in S552), the control unit 100 resets the number of sheets fed after sorting T to T=0 (S553). Then, the control unit 100 returns to step S504 and starts the air blowing operation (S504).

[0073] Then, when the feeding of the remaining five sheets of the first job is completed (Yes in S504 to S507, S551, and S508), the control unit 100 ends the sheet feeding control (S510). At this time, the number of sheets fed after sorting T is recorded as T=5. The number of sheets fed after sorting T is stored in, for example, the RAM 103.

[0074] Next, an example will be described in which a second job subsequent to such a first job is executed. When the second job is started (S501), the control unit 100 acquires the number of prints M of the second job (S502). In this example, the number of prints M of the second job is four. Note that since sheets S have already been loaded on the sheet stacking plate 514, the sheet presence / absence sensor 401 maintains the presence state. Therefore, the control unit 100 proceeds from No in step S503 to step S554.

[0075] The control unit 100 judges whether the number of sheets to be fed after separation T is equal to or larger than the predetermined number N (S554). If the number of sheets to be fed after separation T is smaller than the predetermined number N (No in S554), the process proceeds to step S507, where one sheet S is fed (S507). In this example, since the number of sheets to be fed after separation T=5 and the predetermined number N=10, the air blowing operation (S504 to S506) is omitted and the feeding operation (S507) is performed. That is, the control unit 100 omits the first blowing operation of the second job. This is because NT=5 sheets have already been separated and stacked on the sheet stacking plate 514 by the air blowing operation in the first job.

[0076] Then, when the feeding of four sheets, which is the number of print sheets M of the second job, is completed (Yes in S507, S551, and S508), the control unit 100 ends the sheet feeding control (S510). At this time, T=5+4=9 is recorded in the number of sheets fed after sorting T.

[0077] Next, an example will be described in which a third job subsequent to such a second job is executed. When the third job is started (S501), the control unit 100 acquires the number of prints M of the third job (S502). In this example, the number of prints M of the third job is four. Note that since sheets S have already been loaded on the sheet stacking plate 514, the sheet presence / absence sensor 401 maintains the presence state. Therefore, the control unit 100 proceeds from No in step S503 to step S554.

[0078] The control unit 100 judges whether the number of sheets to be fed after separation T is equal to or larger than the predetermined number N (S554). If the number of sheets to be fed after separation T is smaller than the predetermined number N (No in S554), the process proceeds to step S507, where one sheet S is fed (S507). In this example, since the number of sheets to be fed after separation T=9 and the predetermined number N=10, the air blowing operation (S504 to S506) is omitted and the feeding operation (S507) is performed. This is because NT=1 sheet has already been separated and stacked on the sheet stacking plate 514 by the air blowing operation in the first job.

[0079] Then, the control unit 100 feeds one sheet S, and thereby increments the count value of the number of sheets fed after separation T by 1 (S551), so that the number of sheets fed after separation T = 9 + 1 = 10. Then, the process proceeds to No in step S508 and Yes in step S552, and the control unit 100 resets the number of sheets fed after separation T (S553).

[0080] Thereafter, the control unit 100 proceeds to S504, starts the air blowing operation (S504), and performs the processes of steps S504 to S507, S551, S508, and S552 until the feeding of the remaining number of printed sheets of the third job, which is three sheets, is completed. Then, when the feeding of the sheets S of the number of printed sheets M (four sheets in this example) is completed (S508), the sheet feeding control ends (S510). At this time, the number of sheets fed after sorting T is recorded as T=3.

[0081] As a result, the same effects as those of the first and second embodiments can be achieved.

[0082] In this embodiment, the number of sheets T fed after sorting is incremented by 1 each time one sheet S is fed, and the timing of the air blowing operation is controlled, but this is not limited to this. For example, the predetermined number N (number of sheets that can be fed) may be subtracted each time one sheet S is fed, and when the predetermined number N (number of sheets that can be fed) becomes 0, the air blowing operation may be executed.

[0083] <Other embodiments> In any of the above-described embodiments, the sheet feeding control in the manual feeding section 235 having the air blowing sections 511A, 512A has been described. However, the present invention is not limited to this, and the sheet feeding control according to the present embodiment may be performed in the sheet feeding unit 230 having the feeding cassette 1 or in the feeding deck 500 having an air blowing section. In addition, when the sheet feeding control according to the present embodiment is performed in the sheet feeding unit 230, the sheet feeding control may be performed in any stage in the vertical direction. In other words, the sheet supporting section that supports the sheet stack may have any configuration.

[0084] In addition, in each of the above-described embodiments, the sheet feeding unit is provided with a pickup roller for feeding the sheets, and a feed roller and a retard roller for separating overlapped sheets, and feeding and separating the sheets is described. However, the present invention is not limited to this, and the sheet feeding unit may have any configuration for feeding the sheets, such as a unit that feeds the sheets by vacuum adsorbing the sheets to a belt or the like.

[0085] Also, in each of the above-described embodiments, the control unit 100 has been described as being provided in the image forming apparatus 201. However, this is not limiting, and the control unit may be provided in the feeding deck 500. In other words, the control unit may be disposed in any device as long as it is electrically connected to the sheet feeding unit and the air blowing unit and the control unit is capable of controlling them.

[0086] In the above embodiment, the predetermined number is set to 10, but is not limited to this number. In other words, since the number of uppermost sheets of the sheet stack that are floated by the blowing operation varies depending on the basis weight of these sheets, the predetermined number may be changed based on the attributes of the sheets to be fed, the surrounding temperature and humidity environment, etc.

[0087] In addition, in any of the above-described embodiments, air is blown onto both sides in the width direction of the sheet stack stacked on the sheet stacking plate 514, but this is not limited to this. For example, air may be blown onto only one side in the width direction of the sheet stack, or air may be blown onto the front side and the rear side of the sheet stack.

[0088] In addition, in each of the above-described embodiments, the image forming apparatus 201 including the manual feed unit 235 and the control unit 100 has been described as an example of a sheet feeding device, but the present invention is not limited to this. For example, the image forming system 600 including the feed deck 500 and the image forming apparatus 201 may be regarded as a sheet feeding device. Furthermore, the manual feed unit 235 and the control unit 100 may be regarded as a sheet feeding device.

[0089] In addition, in each of the above-described embodiments, the electrophotographic image forming apparatus 201 has been described, but the present invention is not limited to this. For example, the present invention can also be applied to an inkjet image forming apparatus that forms an image on a sheet by ejecting ink liquid from nozzles.

[0090] The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions. [Explanation of symbols]

[0091] 6: sheet support section (manual feed tray) / 100: control section / 201A: housing (image forming apparatus main body) / 201B: image forming section / 506: sheet feeding section / 511, 512: regulation section (side end regulation plate) / 511a, 512a: blowing port (blowing nozzle) / 511b, 512b: fan / 511A, 512A: air handling section (air blowing section) / FD: sheet feeding direction / M: number of printed sheets, third number / N: first number (predetermined number) / Q: second number (non-contact number) / T: fourth number (number of sheets fed after handling) / WD: width direction

Claims

1. A sheet support section that supports the sheet bundle, A sheet feeding unit that contacts the uppermost sheet of the sheet bundle supported by the sheet support unit and performs a feeding operation to feed the uppermost sheet, An air blowing unit that blows air onto the side surface of a sheet bundle supported by the sheet support unit to loosen the sheets, The system includes a control unit that, when a first job is started, performs the spraying operation using the air handling unit, and after stopping the spraying operation, performs the first sheet feeding control operation using the sheet feeding unit to feed a predetermined number of sheets while the spraying operation is stopped, If, at the time the first job is completed, the number of sheets fed after the spraying operation is less than the predetermined number, the control unit executes a second sheet feeding control when the second job following the first job is started, which does not perform the spraying operation by the air handling unit and performs the feeding operation with the spraying operation stopped. A sheet feeding device characterized by the following features.

2. The sheet further comprises a detection unit for detecting the sheet supported by the sheet support unit, If the detection result of the detection unit changes between the end of the first job and the start of the second job, the control unit executes the first sheet feeding control in the second job. The sheet feeding device according to feature 1.

3. If the number of sheets to be fed in the first job is greater than the predetermined number, the control unit repeats the first sheet feeding control until the number of sheets set for the first job has been fed. The sheet feeding device according to feature 1.

4. In the second sheet feeding control, the control unit performs the spraying operation after the sheet feeding unit has fed a number of sheets less than the predetermined number while the spraying operation is stopped. The sheet feeding device according to feature 1.

5. Further comprising a housing, The aforementioned seat support portion is positioned on the side of the housing and is supported in a manner that allows it to be opened and closed relative to the housing. The sheet feeding device according to feature 1.

6. The housing includes an image forming unit that forms an image on a sheet, The sheet feeding device according to feature 5.

7. The regulating portion is configured to restrict the position of the side surface of the sheet bundle supported by the sheet support portion and is movable in a width direction perpendicular to the sheet feeding direction, The air handling section comprises a fan that sends air, and a spray duct configured to blow the air sent from the fan onto the side surface of the sheet bundle supported by the sheet support section. The fan and the spray duct move as the restricting portion moves in the width direction. The sheet feeding device according to feature 1.

Images