Sheet feeding device and image forming device

Abstract

To suppress occurrence of separation failure of sheets.SOLUTION: A sheet feeding device includes: a support part for supporting a sheet bundle; feeding means for separating the uppermost sheet from the sheet bundle piece by piece and feeding it; an air blowing part for blowing air to an end part of the sheet bundle and reducing the adsorption force between the sheets; and control means for executing a blowing operation for blowing air to the sheet bundle by the air blowing part, and a feeding operation for feeding the uppermost sheet by the feeding means. After executing the blowing operation, in the case where predetermined time has not elapsed from the end of the blowing operation, the control means executes the feeding operation in a state where the blowing operation is stopped, and in the case where the predetermined time has elapsed from the end of the blowing operation, the control means stops the feeding operation and executes a second blowing operation, and resumes the feeding operation after the end of the second blowing operation.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a sheet feeding device that feeds sheets and an image forming apparatus that forms images on sheets. [Background technology]

[0002] Patent Document 1 describes a sheet feeding device that uses a small blower to blow air onto the sides of a sheet stack to reduce adhesion between sheets, making it easier to separate and feed sheets one by one. Patent Document 2 describes a device that blows air onto the sides of a sheet stack to separate the sheets, and then performs a sheet feeding operation with the blowing operation stopped. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 4-23747 [Patent Document 2] Japanese Patent Application Publication No. 2023-102814 Summary of the Invention [Problem to be solved by the invention]

[0004] Even if the adhesion between sheets is reduced by blowing air, it was found that the adhesive force between the sheets increases over time after the end of blowing, and there is a possibility that the sheets may not separate properly before the number of sheets specified in the job is completely fed.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a sheet feeding device and an image forming apparatus that can suppress the occurrence of sheet separation failure. [Means for solving the problem]

[0006] One aspect of the present invention is a sheet feeding device comprising: a support section that supports a sheet stack; a feeding means that separates and feeds the topmost sheet from the sheet stack one by one; an air blowing section that blows air onto the end of the sheet stack to reduce the adhesive force between the sheets; and a control means that performs a blowing operation in which the air blowing section blows air onto the sheet stack and a feeding operation in which the feeding means feeds the topmost sheet, wherein after performing the blowing operation, if a predetermined time has not elapsed since the end of the blowing operation, the control means performs the feeding operation with the blowing operation stopped; and if the predetermined time has elapsed since the end of the blowing operation, the control means stops the feeding operation and performs the blowing operation again, and resumes the feeding operation after the second blowing operation has been completed. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a sheet feeding device and an image forming apparatus that can suppress the occurrence of sheet separation failure. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram of an image forming apparatus according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing a control system of the image forming apparatus according to the embodiment. [Figure 3] FIG. 2 is a perspective view showing the inside of an optional feeding device according to the embodiment. [Figure 4] FIG. 2 is a cross-sectional view of an optional feeding device according to the embodiment. [Figure 5] 4 is a flowchart showing a control method according to the embodiment. [Figure 6] 10 shows an example of the change in adhesive force between sheets over time when the sheet stack is left as is. [Figure 7] A graph showing an enlarged portion of Figure 6. [Figure 8] Schematic diagram showing a method for measuring the adhesive force between sheets. [Figure 9] FIG. 2 is a top view of an optional feeding device according to the embodiment. [Figure 10] 10 is a flowchart showing a control method according to a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0010] (Image forming device) FIG. 1 is a schematic diagram showing a cross section of an image forming apparatus 201 according to one embodiment. The image forming apparatus 201 is a laser beam printer that uses an electrophotographic process. The image forming apparatus 201 can form (record) a full-color or monochrome image on a sheet S corresponding to image information (print image data) received from a host device 900 that is communicatively connected to the control unit 100 (FIG. 2). The sheet S, which is the recording material (recording medium), can be a variety of sheet materials of different sizes and materials, including paper such as plain paper and cardboard, surface-treated sheet materials such as coated paper, specially shaped sheet materials such as envelopes and index paper, plastic film, cloth, etc.

[0011] 2 is a control unit that controls the overall operation of the image forming apparatus 201. The control unit 100 exchanges information with the host device 900 and the operation unit 730. The control unit 100 also performs signal processing and sequence control for various process devices. Here, the host device 900 is a personal computer, image scanner, facsimile machine, etc.

[0012] As shown in Fig. 1, the image forming apparatus 201 has an image forming apparatus main body (hereinafter referred to as apparatus main body 201A), an image forming unit 201B, and an image reading device 202. The image forming unit 201B is housed in the apparatus main body 201A. The image reading device 202 is placed substantially horizontally on the top surface of the apparatus main body 201A. A discharge space V into which a sheet S on which an image has been formed is discharged is formed between the image reading device 202 and the apparatus main body 201A in the vertical direction.

[0013] Furthermore, image forming apparatus 201 includes one or more (four in the illustrated example) cassette feeding units 230 provided within apparatus main body 201A, a manual feeding unit 235 provided on the side of apparatus main body 201A, and optional feeding device 500 connected to apparatus main body 201A. The configuration of optional feeding device 500 will be described later.

[0014] Each cassette feeding section 230 has a cassette 1 (storage case) as a sheet storing means for storing sheets S, a pickup roller 2 as a feeding member for feeding sheets S, and a separation conveying section (3, 4) for separating and conveying sheets S. The separation conveying section of this embodiment has a feed roller 3 and a retard roller 4 that forms a separation nip together with the feed roller 3. The pickup roller 2, feed roller 3, and retard roller 4 function as a feeding unit that feeds sheets S one by one from the cassette 1.

[0015] The manual feed section 235 has a manual feed tray 5 on which a user can manually set a sheet S, and a feed unit that feeds the sheet S from the manual feed tray 5. The feed unit may have the same configuration as the feed units (2, 3, 5) in the cassette feed section 230.

[0016] The image forming section 201B is a tandem-type intermediate transfer electrophotographic engine and functions as an image forming means for forming an image on a sheet S. The image forming section 201B has four process cartridges 211, a laser scanner 210, an intermediate transfer unit 201C, a secondary transfer section 201D, and a fixing section 201E.

[0017] The four process cartridges 211 are process units that form toner images of yellow (Y), magenta (M), cyan (C), and black (K), respectively. Each process cartridge 211 has a photosensitive drum 212 that is an image carrier, a charging roller 213 that serves as charging means, and a developing unit 214 that serves as developing means. The developing unit 214 has a developing roller that carries toner as developer and supplies it to the photosensitive drum 212, and a developing container that contains the toner. Note that toner cartridges 215 that serve as replenishing containers that replenishing toner to each of the four developing units 214 are attached to the top of the apparatus main body 201A.

[0018] The laser scanner 210 as an exposure unit has a laser light source that emits laser light, and an exposure optical system (polygon mirror or the like) that guides the laser light toward the surface of the photosensitive drum 212 in each process cartridge 211. Note that an LED exposure device in which light-emitting elements (LEDs) are arranged in the rotation axis direction of the photosensitive drum 212 may also be used as the exposure unit.

[0019] The intermediate transfer unit 201C has an intermediate transfer belt 216, which is an intermediate transfer body, and multiple rollers (216a, 216b, 219). The intermediate transfer belt 216 is stretched over a drive roller 216a and a tension roller 216b, and is rotated by the drive roller 216a. Four primary transfer rollers 219 are disposed on the inner periphery of the intermediate transfer belt 216, at positions facing the photosensitive drums 212 with the intermediate transfer belt 216 in between.

[0020] Secondary transfer unit 201D is a transfer unit where a toner image is transferred to sheet S, and is a nip portion formed between secondary transfer roller 217 and intermediate transfer belt 216. Secondary transfer roller 217 is disposed on the outer periphery of intermediate transfer belt 216, facing drive roller 216a with intermediate transfer belt 216 sandwiched therebetween.

[0021] Fixing unit 201E includes heating member 220b (fixing member), a heat source for heating the heating member, and pressure member 220a for forming a fixing nip with the heating member. Heating member 220b and pressure member 220a may be rollers, cylindrical films, or belts stretched over multiple rollers. The heat source may be, for example, a halogen lamp that radiates heat, a ceramic heater with a heating resistor pattern printed on a ceramic substrate, or an induction heating coil unit.

[0022] Furthermore, the image forming apparatus 201 has a first discharge roller pair 225a, a second discharge roller pair 225b, and a duplex reversing unit 201F. The first discharge roller pair 225a and the second discharge roller pair 225b each function as a discharge unit capable of discharging the sheet S, on which an image has been formed by the image forming unit 201B, to a discharge space V. The duplex reversing unit 201F includes a reversing roller pair 222 that can rotate forward and backward, and a re-conveying path R along which the sheet S reversed by the reversing roller pair 222 is transported again toward the image forming unit 201B.

[0023] An operation unit 730 serving as a user interface for accepting operations from a user is provided on the upper part of the image forming apparatus 201. The operation unit 730 includes a display unit such as a liquid crystal panel that displays information to the user as an image (screen display), and an input unit such as a button or touch panel that allows the user to input setting information and instructions to the image forming apparatus 201.

[0024] (Image formation operation) Next, a series of operations (image forming operations) in which the image forming apparatus 201 forms an image on the sheet S while conveying the sheet S one by one will be described. When the control unit 100 receives an instruction to perform the image forming operation (print instruction) along with image data, the control unit 100 starts a series of tasks (image forming jobs, print jobs) to repeatedly perform the image forming operation on the number of sheets S specified by the user. The flow of the image forming operation on one sheet S will be described below.

[0025] During image formation, each photosensitive drum 212 and the intermediate transfer belt 216 are rotated at a predetermined peripheral speed (process speed). A charging voltage is applied to each charging roller 213, which uniformly charges the surface of the corresponding photosensitive drum 212 to a predetermined polarity and potential. The control unit 100 analyzes the received image data and generates a time-series signal (video signal) for driving the laser scanner 210. Based on the video signal transmitted from the control unit 100, the laser scanner 210 exposes each photosensitive drum 212 with laser light. As a result, an electrostatic latent image corresponding to a monochromatic image obtained by separating the original image data into individual color components is formed on the surface of each photosensitive drum 212. The developing unit 214 supplies toner to the photosensitive drum 212 and develops the electrostatic latent image into a toner image. As a result, a monochromatic toner image is formed on the photosensitive drum 212 in each process cartridge 211.

[0026] The toner images formed on the photosensitive drums 212 are primarily transferred onto the intermediate transfer belt 216 by applying a voltage to the primary transfer rollers 219. At this time, the four color toner images are superimposed on each other to form a full-color toner image on the intermediate transfer belt 216. The full-color toner image is carried on the intermediate transfer belt 216 and transported toward the secondary transfer unit 201D.

[0027] In parallel with the formation of the toner image by image forming unit 201B, sheets S are fed one by one toward image forming unit 201B from either cassette feeding unit 230, manual feeding unit 235, or optional feeding device 500. The fed sheets S are subjected to skew correction by a pair of registration rollers (pair of registration rollers 240) and then transported to secondary transfer unit 201D. Then, in secondary transfer unit 201D, the toner image is secondarily transferred from intermediate transfer belt 216 to sheet S by applying a voltage to secondary transfer roller 217.

[0028] Next, the sheet S onto which the toner image has been transferred is transported to a fixing unit 201E. The fixing unit 201E heats and pressurizes the toner image on the sheet S while nipping and transporting the sheet S at a fixing nip between a pressure member 220a and a heating member 220b, thereby fixing the toner image on the sheet S. The sheet S that has passed through the fixing unit 201E is discharged into a discharge space V by a first discharge roller pair 225a or a second discharge roller pair 225b, and is stacked on a stacking unit 223 (discharge tray) provided at the bottom of the discharge space V (the upper surface of the apparatus main body 201A). When images are to be formed on both sides of the sheet S, the sheet S with the image formed on its first side is reversed by a reversing roller pair 222 and transported again to a registration roller pair 240 via a re-conveyance path R. Then, after an image is formed on the second side of the sheet S by passing through the secondary transfer section 201D and the fixing nip, the sheet S is discharged into the discharge space V by the first discharge roller pair 225a or the second discharge roller pair 225b and stacked on the stacking section 223.

[0029] When forming images on multiple sheets S in one print job, the multiple sheets S are continuously fed from either the cassette feeding section 230, the manual feeding section 235, or the optional feeding device 500. Then, the image forming operation described above is performed on each of the continuously fed sheets S.

[0030] A print job includes not only image forming operations for the number of sheets S specified by the user, but also preparatory operations before the first image forming operation and adjustment operations for putting the apparatus into a standby state or stopped state after the image forming operation is completed. Preparatory operations before the image forming operation (also called pre-rotation) include, for example, cleaning of the photosensitive drum 212 and intermediate transfer belt 216, preheating of the fixing unit 201E, and adjustment of various voltages in the electrophotographic process. Adjustment operations after the image forming operation (also called post-rotation) include, for example, cleaning of the photosensitive drum 212 and intermediate transfer belt 216 and processing for terminating the output of various voltages.

[0031] Furthermore, if the control unit 100 detects that the sheets S have run out or that a transport failure (jam) has occurred after the image formation operation for the first sheet S in a print job has started, the execution of the print job may be interrupted. The running out of sheets S refers to the fact that a sheet presence / absence sensor that detects the presence or absence of sheets S has detected the absence of sheets in the feeding unit (230, 235, 500) selected as the supply source of sheets S. Furthermore, for example, the control unit 100 detects the occurrence of a jam when one or more sheet sensors arranged along the transport path in the image forming apparatus 201 do not detect the passage of sheets S at the scheduled timing.

[0032] When the control unit 100 detects that the sheets S have run out or that a transport failure (jam) has occurred, it suspends the image forming operation that is being performed, stops feeding the next sheet S, and issues a warning to the user via the operation unit 730, etc. After that, when it determines that the print job can be resumed by replenishing the sheets S or clearing the jam, the control unit 100 resumes the print job.

[0033] (Optional feeding device) The optional feeding device 500 in this embodiment is an example of a sheet feeding device equipped with an air blowing unit (air handling mechanism) that handles a sheet stack by blowing air. "Handling" a sheet stack refers to reducing adhesion between sheets and facilitating separation. The configuration of the optional feeding device 500 will be described below mainly with reference to FIGS. 3 and 4.

[0034] Fig. 3 is a schematic diagram showing the internal configuration of optional feeding device 500. Fig. 4 is a schematic diagram showing a cross section of optional feeding device 500 in a plane perpendicular to the sheet feeding direction Df.

[0035] 3 and 4, optional feeding device 500 includes a storage case 510 (FIG. 1) that stores a sheet stack, a feeding unit 500F as a feeding means that feeds sheets S, a pair of conveying rollers 504 (FIG. 1), and air blowing units 511A and 512A. Storage case 510 and optional feeding device 500 may be referred to as a feeding deck and a deck feeding device.

[0036] The feeding unit 500F includes a pickup roller 501 (first roller) as a feeding member, and a separation conveying section (502, 503). The pickup roller 501 is disposed above a lifter plate 514. The pickup roller 501 rotates while contacting the upper surface of the uppermost sheet S of the sheet stack stacked on the lifter plate 514, thereby feeding the uppermost sheet S from the storage case 510 in the sheet feeding direction Df.

[0037] The separation and conveyance unit in this embodiment is a roller pair consisting of a feed roller 502 (second roller) and a retard roller 503 (third roller). The feed roller 502 is disposed downstream of the pickup roller 501 in the sheet feeding direction Df, and conveys the sheet S received from the pickup roller 501 further in the sheet feeding direction Df. The retard roller 503 comes into contact with the feed roller 502 and forms a separation nip together with the feed roller 502. A driving force in a direction opposite to the sheet feeding direction Df is input to the retard roller 503 via a torque limiter (i.e., the retard roller 503 is retard-driven).

[0038] The storage case 510 has a lifter plate 514 that can be raised and lowered and on which sheets S are placed, regulating members (511, 512, 513) that regulate the position of the sheets S, and a storage case main body 510A (FIG. 1) that supports the lifter plate 514 and the regulating members. The lifter plate 514 is a support portion that supports the sheet stack. The lifter plate 514 is housed within the storage case main body 510A and is configured so that its elevation can be controlled based on the position of the top surface of the sheet stack by, for example, a wire reel-type elevation mechanism. The regulating members include a pair of side edge regulating plates 511, 512 that regulate the position of the end (side edge) of the sheet S in the sheet width direction Dw perpendicular to the sheet feeding direction Df, and a rear edge regulating plate 513 that regulates the position of the rear edge of the sheet S in the sheet feeding direction Df.

[0039] The side edge regulating plates 511 and 512 are arranged on one side and the other side of the conveyance center Sc (FIG. 4) in the sheet width direction Dw. The conveyance center Sc is, for example, the central position in the sheet width direction Dw of the contact area where the pickup roller 501 comes into contact with the sheet S. The side edge regulating plates 511 and 512 are connected via an interlocking mechanism such as a rack and pinion, and are configured to move in conjunction with each other so as to maintain a symmetrical positional relationship with respect to the conveyance center Sc. The rear edge regulating plate 513 is also configured so that its position can be adjusted according to the length of the sheet S in the sheet feeding direction Df. The position of the leading edge of the sheet S in the sheet feeding direction Df is regulated by the wall surface of the storage cabinet main body 510A.

[0040] Air blowing section 511A includes fan 511b, blowing nozzle 511a, and floating suppressor 511c. Similarly, air blowing section 512A includes fan 512b, blowing nozzle 512a, and floating suppressor 512c.

[0041] The air blowing units 511A and 512A of this embodiment are arranged to blow air toward the side edges of the sheet stack placed on the lifter plate 514. In this embodiment, one air blowing unit 511A is incorporated into one side edge regulating plate 511, and the other air blowing unit 512A is incorporated into the other side edge regulating plate 512. In other words, the fans 511b and 512b, which are elements of the air blowing units 511A and 512A, move integrally with the side edge regulating plates 511 and 512. It is also possible to arrange the air blowing units 511A and 512A as separate components from the side edge regulating plates 511 and 512.

[0042] The fans 511b and 512b have blade members that generate airflows (A1 and A2) by rotating, and a motor that rotates the blade members. The fans 511b and 512b may be, for example, silent sirocco fans, but other fans such as axial fans may also be used.

[0043] The air blowing nozzles 511a and 512a are openings provided on the regulating surfaces (surfaces facing the side edges of the sheet stack) of the side edge regulating plates 511 and 512. The air blowing nozzle 511a is connected to the outlet of the fan 511b through a flow path formed inside the side edge regulating plate 511. Similarly, the air blowing nozzle 512a is connected to the outlet of the fan 512b through a flow path formed inside the side edge regulating plate 512.

[0044] The floating restraints 511c and 512c are arranged to protrude inward (toward the conveyance center Sc) in the sheet width direction Dw from the regulating surfaces of the side end regulating plates 511 and 512. The floating restraints 511c and 512c have the function of preventing the sheet S, which has been floated by the air blowing, from climbing over the side end regulating plates 511 and 512 and causing a stacking error.

[0045] As shown in FIG. 2, the optional feeding device 500 includes the control unit 100, a feeding motor 520, a conveying motor 521, a feeding sensor 505, a sheet presence sensor 506, and an environment sensor 522.

[0046] The control unit 100 functions as a control means for controlling the operation of the optional feeding device 500. The control unit 100 has a ROM 102 for storing a program, a CPU 101 for reading and executing the program from the ROM 102, and a RAM 103 for providing a work space for the CPU 101. The control unit 100 realizes the operation of the optional feeding device 500 in accordance with the flow (FIG. 5) described below by the CPU 101 controlling the operation of the fans 511b, 512b and the motors (520, 521) in accordance with the program.

[0047] The environmental sensor 522 is a detection unit for detecting the environmental conditions of the space surrounding the optional feeding device 500 or the image forming device 201. The environmental sensor 522 of this embodiment can acquire information on the ambient temperature (ambient temperature) and ambient relative humidity (ambient humidity) of the optional feeding device 500 as the environmental conditions. The control unit 100 can execute control according to the environmental conditions based on the detection results of the environmental sensor 522.

[0048] The feeding sensor 505 is a sensor that detects the sheet S between the separation nip and the pair of conveying rollers 504 (FIG. 1). The control unit 100 can monitor whether the feeding of the sheet S is being performed normally based on the detection result of the feeding sensor 505. The sheet presence / absence sensor 506 is a sensor (sheet detection means) that detects the presence or absence of the sheet S on the lifter plate 514.

[0049] Furthermore, the control unit 100 can acquire information (hereinafter referred to as sheet information) relating to the attributes of the sheets S set in the storage cabinet 510, for example, through a user input via the operation unit 730. The sheet information may be one or more combinations selected from the group consisting of the size, basis weight, presence or absence of surface treatment, and brand of the sheets S.

[0050] Note that some or all of the functions of control unit 100 described below may be realized by a control circuit located outside optional feeding device 500. In other words, at least a part of control unit 100 for controlling the operation of optional feeding device 500 may be located outside optional feeding device 500. In this case, the optional feeding device 500 and the control circuit for controlling optional feeding device 500 constitute a "sheet feeding device."

[0051] (Basic operation of optional feeding device) The optional feeding device 500 performs a feeding operation in which the feeding unit 500F separates and feeds the sheets S one by one, and an air blowing operation (air handling operation) in which air is blown onto the sheet stack by the air blowing sections 511A and 512A to handle the sheets.

[0052] The feeding operation starts when the pickup roller 501 is driven to rotate while the pickup roller 501 is in contact with the uppermost sheet S on the lifter plate 514. The rotation of the pickup roller 501 feeds the uppermost sheet S in the sheet feeding direction Df, and the sheet is then separated into a single sheet at the separation nip. That is, the retard roller 503 applies a frictional force in the opposite direction to the sheet feeding direction Df to the sheet S passing through the separation nip, thereby preventing multiple sheets S from passing through the separation nip (multiple feeding). Furthermore, when only one sheet S passes through the separation nip, the retard roller 503 rotates following the feed roller 502 and the sheet S due to slippage of the torque limiter. The sheet S that has passed through the separation nip is conveyed by the conveying roller pair 504 toward the apparatus main body 201A.

[0053] The air blowing operation starts when fans 511b and 512b are activated and ends when fans 511b and 512b are stopped. When fans 511b and 512b rotate, air is blown from blowing nozzles 511a and 512a toward the side edges of the sheet stack, as shown by flow lines A1 and A2 in FIG. 4. When the air enters the gaps between sheets S, an upward force acts on the uppermost sheets S in the sheet stack, reducing the adhesive force between the sheets (the adhesion between the sheets). By reducing the adhesive force between the sheets, the feeding unit 500F can more easily transport sheets S one by one without causing separation problems, even when using coated paper, which tends to have a large adhesive force between sheets.

[0054] (Control method) The control method for the optional feeding device 500 according to this embodiment will be described below with reference to the flowchart in Fig. 5. The control unit 100 starts the processing of this flow when, for example, a print job is submitted. Below, each step of this flow is executed by the control unit 100 (Fig. 2) unless otherwise specified.

[0055] At the start of a print job, the control unit 100 determines whether or not to perform the air blowing operation (S3 to S5) (S1). If the air blowing operation is to be performed, the control unit 100 sets the operating conditions for the air blowing operation based on the environmental conditions detected by the environmental sensor 522 (S2).

[0056] In this embodiment, the control unit 100 makes a decision to perform an air blowing operation at the start of a print job (S1 Yes) if the sheet S used in the current print job is coated paper, the environmental conditions are a high temperature and high humidity environment or a normal environment, and any of the following conditions is met: a) When the current print job starts, a predetermined time τ (described later) has passed since the previous air blowing operation. b) When the control unit 100 determines that sheets have been replenished in the storage 510 between the end of the previous print job and the start of the current print job, or that there is a possibility that this has happened.

[0057] On the other hand, if the sheet S used in the current print job is not coated paper (for example, plain paper) or if the environmental conditions are a low temperature and low humidity environment, the control unit 100 determines not to perform the air blowing operation at the start of the print job (S1 No). Also, even if the sheet S is coated paper and the environmental conditions are met, if neither a) nor b) above applies, the control unit 100 determines not to perform the air blowing operation at the start of the print job (S1 No).

[0058] Note that the above is merely an example of a determination method. The control unit 100 may be configured to perform the air blowing operation when it determines that the sheets are in close contact with each other (the adhesive force between the sheets is relatively strong), and not to perform the air blowing operation when it determines that the sheets are not in close contact with each other (the adhesive force between the sheets is relatively weak). For example, in addition to the above a) to c), the air blowing operation may be performed when the supply source of the sheet S in the previous print job was other than the optional feeding device 500 and the supply source of the sheet S in the current print job is the optional feeding device 500.

[0059] In this embodiment, the operating conditions for the air blowing operation are the rotation speed of fans 511b and 512b, which corresponds to the air volume, and the length of time for which fans 511b and 512b are rotated (referred to as the blowing time). Table 1 below shows the classification of environmental conditions in this embodiment, typical temperature and humidity values, the rotation speed of fans 511b and 512b, and the set values ​​for the blowing time. The rotation speed of fans 511b and 512b is represented by the duty in PWM control for controlling the power input to fans 511b and 512b.

[0060] [Table 1]

[0061] As shown in Table 1 above, the air volume is increased and the blowing time is lengthened in a high-temperature, high-humidity environment compared to a normal environment. In other words, the controller 100 increases the intensity of the air blowing operation as the absolute moisture content of the air around the optional feeding device 500 increases. In other words, the air volume when the absolute moisture content is a first amount (e.g., an amount equivalent to 30°C / 80% RH) is greater than the air volume when the absolute moisture content is a second amount less than the first amount (e.g., an amount equivalent to 23°C / 50% RH). Furthermore, the blowing time when the absolute moisture content is the first amount is longer than the blowing time when the absolute moisture content is a second amount less than the first amount.

[0062] In this embodiment, a high temperature and low humidity environment (for example, 30°C / 10% RH) is classified as a low temperature and low humidity environment, and a low temperature and high humidity environment (for example, 15°C / 80% RH) is classified as a normal environment.

[0063] Based on the above settings, the control unit 100 activates the fans 511b and 512b in S3 to start the air blowing operation. As a result, as shown in Fig. 4, several to several tens of sheets S at the top of the sheet stack on the lifter plate 514 float up, reducing the adhesive force between the sheets. In addition, the floatation suppressors 511c and 512c prevent the sheets S floated up by the air from climbing over the side edge regulating plates 511 and 512. When the blowing time set in S2 has elapsed since the activation of the fans 511b and 512b (S4 Yes), the control unit 100 stops the fans 511b and 512b and ends the air blowing operation (S5).

[0064] This section explains how the possibility of skew of the sheet S due to the influence of air can be reduced by performing an air blowing operation at the start of a print job and then performing a feeding operation (S8) after the air blowing operation is completed. For example, as shown in FIG. 9, if the feeding operation is started in parallel with the air blowing operation, the sheet S will bend as it floats. If the side edges of the sheet S move away from the side edge regulating plates 511 and 512, the side edge regulating plates 511 and 512 will be less effective in suppressing skew. Furthermore, due to assembly tolerances or design considerations, the contact positions C1 and C2 (the points of application of the contact load on the sheet S) of the pickup roller 501 and the feed roller 502 in the sheet width direction Dw may be misaligned. In such a case, if a difference (V1>V2) occurs between the conveyance speeds V1 and V2 (V1>V2) between the pickup roller 501 and the feed roller 502 due to resistance of the sheet S from a conveyance guide or the like, a force will be generated that tends to rotate the sheet S counterclockwise in the figure. In addition, a rotational force may occur when the contact positions C1 and C2 of the rollers are shifted from the conveyance center Sc. In contrast, in this embodiment, the feeding operation (S8) is performed with the air blowing operation stopped, so that skew of the sheet S can be suppressed.

[0065] At the same time as fans 511b and 512b are stopped, control unit 100 starts measuring elapsed time T (S6). Elapsed time T represents the length of time that has elapsed since the end of the previous air blowing operation without any air blowing operation being performed.

[0066] As the elapsed time T increases, air escapes from under the sheets S that were lifted by the previous air blowing operation. As the air escapes, the suction force between the sheets gradually increases, but as long as the suction force does not exceed the separation capacity of the feeding unit 500F, the feeding unit 500F can feed the sheets S while separating them one by one. However, if the suction force becomes so large that it exceeds the separation capacity of the feeding unit 500F, separation failure may occur.

[0067] If the elapsed time T since the end of the previous air blowing operation is equal to or less than the predetermined time τ (S7 No), the control unit 100 starts the next feeding operation (S8). The start of the feeding operation refers to the rotation of the pickup roller 501 by the driving force of the feeding motor 520 while the pickup roller 501 is in contact with the uppermost sheet S. After the feeding operation starts, as described above, the separation of the sheet S at the separation nip and the conveyance of the sheet S by the conveyance roller pair 504 are performed. The value of the predetermined time τ is stored in the ROM 102 as a preset value, for example, and is read out by the CPU 101.

[0068] The control unit 100 returns to S7 and repeats the same process until the number of sheets S specified by the user when the print job was submitted has been fed (S9 No). That is, the control unit 100 repeatedly executes the feeding operation (S8) until the specified number of sheets S has been fed until the predetermined time τ has elapsed since the end of the previous air blowing operation (S7 No). If feeding of the specified number of sheets S is completed before the predetermined time τ has elapsed since the end of the previous air blowing operation (S9 Yes), the processing of this flow ends.

[0069] On the other hand, if the elapsed time T since the end of the previous air blowing operation in S7 exceeds the predetermined time τ, the control unit 100 returns to S3 without performing the next feeding operation and performs the air blowing operation (S3 to S5) again. This causes several to several tens of sheets S at the top of the sheet stack on the lifter plate 514 to float, and the adhesive force between the sheets is reduced again. When the blowing operation ends, the control unit 100 resets the elapsed time T and starts measuring it again.

[0070] In this way, when executing a job to feed a specified number of sheets, the control unit 100 (1) repeats the feeding operation until the predetermined time τ has elapsed since the end of the previous blowing operation, and (2) stops the feeding operation when the predetermined time τ has elapsed since the end of the previous blowing operation and executes the blowing operation again, repeating this process until the feeding of the specified number of sheets is completed. In this way, by performing the air blowing operation at intervals of the predetermined time τ, it is possible to suppress poor separation of the sheets S.

[0071] Here, Fig. 6 shows an example of the change in the adhesive force between sheets over time when the sheet stack is left as is after the adhesive force between sheets has been reduced. The adhesive force is measured as the force F (unit: gg) in the sheet feeding direction Df required to move the top sheet S of the sheet stack St in the sheet feeding direction Df so as to peel it off from the sheets below it, as shown in Fig. 8. The measurement in Fig. 6 was carried out in an environment with a temperature of 30°C and a humidity of 80% RH, which corresponds to the high temperature and high humidity environment mentioned above. The horizontal axis of Fig. 6 represents the basis weight of 200 g / m 2 The coated papers in the table were manually separated one by one and then stacked to form a sheet stack St, and the graph shows the time elapsed since the sheet stack St was left standing. The vertical axis of Figure 6 represents the magnitude of the suction force measured using the method in Figure 8 when a preset time had elapsed.

[0072] As shown in FIG. 6, the adhesive force between the sheets monotonically increased for approximately 300 seconds after the start of the operation, and then remained approximately constant. Therefore, if the adhesive force between the sheets, which increases with the elapsed time T after the most recent air blowing operation, exceeds the separation capability (separation limit adhesive force) of the feeding unit 500F, poor separation of the sheets S during the feeding operation may occur. The separation limit adhesive force is the maximum value of the adhesive force between the uppermost sheet S and the lowermost sheets S at which the feeding unit 500F can separate and feed the uppermost sheet S from the lowermost sheets S. In other words, the separation limit adhesive force is the maximum value of the adhesive force that is allowable during the feeding operation. The separation limit adhesive force may vary depending on the allowable torque of the torque limiter provided on the retard roller 503, the coefficient of friction between the sheets, and the coefficients of friction between the feed roller 502 and the retard roller 503 and the sheets S.

[0073] Fig. 7 is a graph showing the interval from 0 seconds to 180 seconds in Fig. 6, which can be regarded as an interval in which the suction force increases monotonically. The dashed-dotted line A in Fig. 7 shows an example of the (separation limit suction force). In this embodiment, the separation limit suction force is set to 228 gf.

[0074] When the graph in FIG. 7 is linearly approximated, the relationship between the adsorptive force (y) and the elapsed time (x) can be expressed by the following equation (1). y=2.0909x+116.06 (1)

[0075] From the above formula (1), it can be seen that in this embodiment, the suction force between sheets exceeds the separation limit suction force approximately 53 seconds after the start of the test. In other words, when a print job is executed using the same coated paper and environmental conditions as in the above test, even if an air blowing operation is performed at the start of the job, poor separation of the sheet S may occur during the feeding operation after the elapsed time T after the end of the air blowing operation exceeds 53 seconds.

[0076] Therefore, in this embodiment, a predetermined time τ is set in advance, which is shorter than the value of the elapsed time until the suction force between sheets reaches the separation limit suction force. Then, when the elapsed time T from the end of the previous air blowing operation exceeds the predetermined time τ, the feeding operation is interrupted and the air blowing operation is performed (S7Yes→S3 to S5), and the feeding operation (S8) is resumed after the air blowing operation is completed.

[0077] In other words, after performing the blowing operation, if a predetermined time τ has not elapsed since the end of the blowing operation, the control unit 100 stops the blowing operation and performs the feeding operation. Also, if a predetermined time τ has elapsed since the end of the blowing operation, the control unit 100 stops the feeding operation, performs the blowing operation again, and resumes the feeding operation after the second blowing operation has been completed. This allows the feeding operation to be performed without the adhesive force between the sheets exceeding the separation limit adhesive force, thereby preventing poor separation of the sheets S.

[0078] That is, an object of the present embodiment is to provide a sheet feeding device and an image forming apparatus that can suppress the occurrence of sheet separation failure.

[0079] A control method for the optional feeding device 500 of a comparative example to this embodiment is shown in Fig. 10. In this comparative example, after an air blowing operation (S101 to S103) is performed at the start of a print job, the feeding operation is repeated with the air blowing operation stopped (S104, S105). In this comparative example, even if a long time has passed since the air blowing operation ended, the air blowing operation is not performed again.

[0080] According to this comparative example, the feeding operation is performed with the air blowing operation stopped, so similar to the present embodiment, it is possible to reduce the occurrence of skew due to the influence of air. However, in this comparative example, even after the elapsed time since the end of the air blowing operation exceeds the predetermined time τ, the feeding operation (S104) is repeated until the number of sheets S specified in the job has been fed. Therefore, the feeding operation is performed in a state where the adhesive force between the sheets exceeds the separation limit adhesive force, which may result in poor separation of the sheets S.

[0081] In contrast, according to this embodiment, the feeding operation is interrupted before the adhesive force between the sheets exceeds the separation limit adhesive force, and the feeding operation is resumed after the air blowing operation is performed, thereby reducing the possibility of poor separation of the sheets S while reducing the occurrence of skew due to the influence of air.

[0082] Furthermore, according to this embodiment, regardless of the number of sheets fed by the feeding unit 500F since the end of the previous blowing operation, a second blowing operation is executed when the elapsed time T since the end of the previous blowing operation exceeds the predetermined time τ. In other words, if a print job is interrupted for some reason and then resumed, and the elapsed time from the end of the previous blowing operation performed before the job interruption to the resumption of the job exceeds the predetermined time τ, the feeding of sheets S is resumed after the blowing operation is executed when the job is resumed, even if the number of sheets fed from the end of the previous blowing operation to the interruption of the job was small.

[0083] Therefore, even if the adhesive force between sheets exceeds the separation limit adhesive force during the interruption of the print job, when the print job is resumed, the adhesive force is reduced by the blowing operation and feeding of the sheets S is resumed. Therefore, the blowing operation can be performed at a more appropriate timing than, for example, a configuration in which the timing of performing the blowing operation is determined based on the number of sheets fed. Note that a print job may be interrupted due to a transport failure (jam), toner depletion, an interruption instruction from the user, etc.

[0084] Furthermore, in S1 in the flow of FIG. 5, according to the above-mentioned a), if the elapsed time from the air blowing operation in the previous job to the start of the current job does not exceed the predetermined time τ, the feeding operation is started without performing the air blowing operation at the start of the current job. In other words, when a second job is executed after a first job, if the elapsed time from the end of the previous blowing operation performed during the execution of the first job to the start of the second job does not exceed the predetermined time, the control unit 100 starts the feeding operation without performing the blowing operation at the start of the second job. In this way, if the handling effect of the air blowing operation in the previous print job remains, the productivity of the optional feeding device 500 can be improved by starting the feeding of the sheet S in the current print job without performing the blowing operation.

[0085] It is also possible to simplify the control so that the air blowing operation is always performed before the feeding operation at the start of a print job, or to perform the air blowing operation at the start of a print job only if, for example, the environmental conditions have changed between the start of the previous print job and the start of the current print job.

[0086] 5, in determining whether or not an air blowing operation is required (S1), if sheets S have been replenished, the air blowing operation is executed according to the above-mentioned b), even if the elapsed time T has not exceeded the predetermined time. In other words, if the sheet presence / absence sensor 506 (sheet detection means) detects that there is a sheet on the lifter plate 514 (support portion) after detecting that there is no sheet on the lifter plate 514, the control unit 100 starts the feeding operation after executing the air blowing operation, even if the predetermined time τ has not elapsed since the end of the previous blowing operation. Because a new sheet stack placed on the lifter plate 514 may have strong adhesive forces between the sheets, performing the above control can suppress poor separation during the feeding operation after the sheet stack has been replenished.

[0087] 5, the determination of whether or not to perform the air blowing operation at the start of a job has been described based on the detection result of the sheet presence / absence sensor 506, but similar control may also be performed when the sheet presence / absence sensor 506 detects the absence of a sheet during execution of a job. That is, suppose that the sheet presence / absence sensor 506 detects the absence of a sheet during execution of a job and the job is interrupted, and then the sheet presence / absence sensor 506 detects the presence of a sheet as the user replenishes sheets S. In this case, the control unit 100 performs the air blowing operation and then resumes the feeding operation, even if the predetermined time τ has not elapsed since the end of the previous blowing operation.

[0088] Furthermore, the method of performing the air blowing operation when there is a possibility that sheets have been replenished (replaced) is not limited to the method of using the detection result of the sheet presence / absence sensor 506. For example, if the image forming apparatus 201 has been in a sleep state between the end of the previous job and the input of the current job, the control unit 100 may determine that there is a possibility that sheets S have been replenished (replaced) and perform the air blowing operation at the start of the current job. Similarly, for example, if an open / close detection sensor provided in the storage case 510 detects that the storage case 510 has been opened or closed between the end of the previous job and the input of the current job, the control unit 100 may determine that there is a possibility that sheets S have been replenished (replaced).

[0089] (Example of setting the predetermined time τ) In this embodiment, the value of the predetermined time τ that defines the time interval between air blowing operations is set to different values ​​depending on the environmental conditions at the start of the print job and the sheet information related to the sheet S used in the print job.

[0090] By selecting the value of the predetermined time τ from multiple values, it is possible to suppress separation failure of the sheets S and improve productivity at the same time. In other words, compared to when the predetermined time τ is always set to the same value (a value that can suppress separation failure of the sheets S regardless of conditions), the value of the predetermined time t can be increased under conditions where the increase in the adhesive force between sheets is relatively gradual, thereby reducing the frequency of the air blowing operation. This makes it possible to improve the productivity of the optional feeding device 500 (the number of sheets S fed per elapsed time from the start of a print job). It also makes it possible to improve the productivity of the image forming apparatus 201 (the number of images output per elapsed time from the start of a print job). Below, an example of setting the predetermined time τ will be described.

[0091] First, an example of setting the predetermined time τ according to the environmental conditions will be described. As described above, in this embodiment, the operating conditions for the air blowing operation are changed according to the environmental conditions. This is because, even for the same type of sheet S, the maximum value of the adhesive force between sheets varies depending on the environmental conditions. Similarly, the change in adhesive force according to the elapsed time after the adhesive force between sheets is reduced by the air blowing operation also varies depending on the environmental conditions. Therefore, in each of the "high temperature and humidity environment" and "normal environment" that are the targets of the air blowing operation, the change in the adhesive force of the sheet according to the elapsed time after the air blowing operation is examined, and an appropriate value for the predetermined time τ is determined in advance. As an example, the value of the predetermined time τ for each environmental classification for coated paper (coated paper 1 described below) is determined as follows:

[0092] [Table 2]

[0093] According to the above example, the interval between air blowing operations in a high-temperature, high-humidity environment is shorter than the interval between air blowing operations in a normal environment. In other words, the predetermined time τ (30 seconds) when the absolute moisture content is a first amount (e.g., an amount corresponding to 30°C / 80% RH) is shorter than the predetermined time τ (240 seconds) when the absolute moisture content is a second amount (e.g., an amount corresponding to 23°C / 50% RH) that is smaller than the first amount.

[0094] As a result, in a high-temperature, high-humidity environment where the adhesive force between sheets increases relatively quickly, the air blowing operation is performed at a high frequency, thereby making it possible to suppress poor separation of the sheets S. Furthermore, in a normal environment where the adhesive force between sheets increases relatively slowly, the air blowing operation is performed at a low frequency, thereby making it possible to improve the productivity of the optional feeding device 500.

[0095] Next, an example of setting the predetermined time τ according to the type of sheet S will be described. In this embodiment, coated paper is classified into the following three types based on basis weight, and the value of the predetermined time τ is set for each type. The control unit 100 selects an appropriate value of the predetermined time τ based on the type of sheet S used in the print job.

[0096] [Table 3]

[0097] The ease with which the adhesive force between sheets increases depends on the physical properties of the sheets S. The physical properties of the sheets S include, for example, air permeability (ease of air passing through), smoothness (surface smoothness), and rigidity (ease of deformation). Therefore, it is preferable to consider the ease with which the adhesive force increases for each type of sheet S and determine the value of the predetermined time τ in advance.

[0098] According to the above example, the interval between air blowing operations when using "Coated Paper 3" with a large basis weight is shorter than the interval between air blowing operations when using "Coated Paper 1" with a small basis weight. In other words, when the basis weight is a first value (e.g., 240 g / m 2 ), the predetermined time τ (220 seconds or 20 seconds) when the basis weight is a second value (for example, 120 g / m 2 ) is shorter than the predetermined time τ (240 seconds).

[0099] As a result, when using "coated paper 3," which tends to have a large adhesive force between sheets, the air blowing operation is performed more frequently, thereby preventing poor separation of the sheets S. Furthermore, when using "coated paper 1," which tends to have a small adhesive force between sheets, the air blowing operation is performed less frequently, thereby improving the productivity of the optional feeding device 500.

[0100] The adhesive force between sheets is also affected by the sheet size, with larger sheet sizes tending to increase the adhesive force between sheets. Therefore, it is preferable to shorten the predetermined time τ as the sheet size increases. In other words, the predetermined time τ when using a sheet S of a first size (e.g., A3 size) is shorter than the predetermined time τ when using a second size (e.g., B4 size) that is smaller in area than the first size.

[0101] As a result, when using first size sheets S, which tend to have a large adhesive force between sheets, the air blowing operation is performed more frequently, thereby preventing poor separation of the sheets S. When using second size sheets S, which tend to have a large adhesive force between sheets, the air blowing operation is performed less frequently, thereby improving the productivity of the optional feeding device 500.

[0102] It is also desirable to change the operating conditions for the air blowing operation depending on the sheet classification and sheet size. For example, when using "Coated Paper 3," the fan rotation speed may be increased and the blowing time may be extended compared to when using "Coated Paper 1." Furthermore, when using a first size sheet S, the fan rotation speed may be increased and the blowing time may be extended compared to when using a second size sheet S. This makes it possible to more reliably reduce the adhesive force between sheets with a single air blowing operation.

[0103] (Variation) In the above-described embodiment, the optional feeding device 500 has been described as an example of a sheet feeding device. However, the present technology is not limited to this, and may be applied to any sheet feeding device equipped with an air blowing unit (air handling mechanism), for example, any cassette feeding unit 230 or manual feeding unit 235. Furthermore, the present technology is not limited to a sheet feeding device that feeds sheets S as recording media toward the image forming unit 201B. For example, the present technology may be applied to a sheet feeding device that feeds sheets S as documents in an image reading device, or a sheet feeding device that feeds sheets S to be sorted in a sheet sorting device.

[0104] The feeding mechanism including the pickup roller 501, feed roller 502, and retard roller 503 described in the above embodiment is an example of a feeding unit 500F that feeds sheets S one by one. For example, a belt-conveying type feeding unit may be used in which a single sheet S is attracted to a feeding belt by negative pressure generated by a fan and conveyed. The retard roller 503 is an example of a separating member that separates the sheets S, and for example, a pad-shaped elastic member that contacts the feed roller 502 may be used as the separating member.

[0105] In the above-described embodiment, a method is exemplified in which a value of the predetermined time τ that is set in advance according to the environmental conditions and the sheet information is used. However, the present invention is not limited to this, and a configuration may be adopted in which, for example, the user can arbitrarily set the value of the predetermined time τ via the operation unit 730.

[0106] In the above-described embodiment, the value of the predetermined time τ is determined based on the environmental conditions at the start of the print job, and the value of the predetermined time τ is not changed during the print job. However, this is not limiting. For example, if the elapsed time T since the previous air blowing operation exceeds the predetermined time τ, the environmental conditions may be determined again based on the detection results of the environmental sensor 522, and the value of the predetermined time τ may be updated. In other words, if the result of S7 in the flow of FIG. 5 is No, the process may return to S2. This modification may be advantageous when the print job lasts for a long period of time, or when the image forming apparatus 201 is installed in a location where the environmental conditions change significantly.

[0107] (Other embodiments) The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions. [Explanation of symbols]

[0108] 100...control means (control unit) / 500...sheet feeding device (optional feeding device) / 500F...feeding means (feeding unit) / 511S, 512S...air blowing section / 514...support section (lifter plate) / 522...environment sensor

Claims

1. a support portion that supports the sheet stack; a feeding means for separating and feeding the topmost sheet from the sheet stack one by one; an air blowing unit that blows air onto an end of the sheet stack to reduce the suction force between the sheets; a control unit that executes a blowing operation of blowing air onto the sheet stack by the air blowing unit and a feeding operation of feeding the uppermost sheet by the feeding unit; Equipped with The control means After the blowing operation is performed, if a predetermined time has not elapsed since the end of the blowing operation, the blowing operation is stopped and the feeding operation is performed; If the predetermined time has elapsed since the end of the blowing operation, the feeding operation is stopped and the blowing operation is performed again, and after the second blowing operation is completed, the feeding operation is resumed. A sheet feeding device characterized by:

2. an environmental sensor for detecting an environmental condition around the sheet feeding device; the control means changes the length of the predetermined time in accordance with the environmental conditions based on the detection result of the environmental sensor.

2. The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device.

3. the control means changes the length of the predetermined time when the absolute moisture content of the air around the sheet feeding device is a first amount so that the predetermined time is shorter than the predetermined time when the absolute moisture content is a second amount that is smaller than the first amount.

3. The sheet feeding device according to claim 2, wherein the sheet feeding device is a sheet feeding device.

4. the control means changes the length of the predetermined time in accordance with the basis weight of the sheet supported by the support portion.

2. The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device.

5. the control means changes the length of the predetermined time so that the predetermined time when the basis weight is a first value is shorter than the predetermined time when the basis weight is a second value smaller than the first value.

5. The sheet feeding device according to claim 4.

6. the control means changes the length of the predetermined time period in accordance with the size of the sheet supported by the support portion.

2. The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device.

7. the control means changes the length of the predetermined time when the sheet size is a first size so that the predetermined time is shorter than the predetermined time when the sheet size is a second size having an area smaller than that of the first size.

7. The sheet feeding device according to claim 6, wherein the sheet feeding device is a sheet feeding device.

8. further comprising an operation unit that accepts an operation from a user, The control means determines the length of the predetermined time based on an input from a user to the operation unit.

2. The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device.

9. When a second job of feeding a sheet is executed after a first job of feeding a sheet, if the elapsed time from the end of the previous blowing operation performed during the execution of the first job to the start of the second job does not exceed the predetermined time, the control means starts the feeding operation without executing the blowing operation at the start of the second job.

2. The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device.

10. further comprising a sheet detection means for detecting the presence or absence of a sheet on the support portion; When the sheet detection means detects that a sheet is present on the support portion after the sheet detection means detects that a sheet is not present on the support portion, the control means starts the feeding operation after executing the blowing operation even if the predetermined time has not elapsed since the end of the previous blowing operation.

2. The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device.

11. When the control means interrupts a job for feeding a specified number of sheets and then resumes the job, if the elapsed time from the end of the previous blowing operation performed before the interruption of the job to the resumption of the job exceeds the predetermined time, the control means resumes the feeding operation after performing the blowing operation regardless of the number of sheets fed by the feeding means from the end of the previous blowing operation to the interruption of the job.

2. The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device.

12. When executing a job to feed a specified number of sheets, the control means repeats the feeding operation during the period from the end of the previous blowing operation until the predetermined time has elapsed, and when the predetermined time has elapsed from the end of the previous blowing operation, stops the feeding operation and executes the blowing operation again, repeating this process until feeding of the specified number of sheets is completed.

2. The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device.

13. the feeding means includes a first roller that contacts the uppermost sheet and feeds it from the support portion in the sheet feeding direction, a second roller that is disposed downstream of the first roller in the sheet feeding direction and transports the sheet in the sheet feeding direction, and a third roller that contacts the second roller to form a separation nip and applies a frictional force in a direction opposite to the sheet feeding direction to the sheet passing through the separation nip, the air blowing unit includes a fan that generates an air flow, and a nozzle that blows the air flow toward an end of the sheet stack in a sheet width direction perpendicular to the sheet feeding direction.

2. The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device.

14. a sheet feeding device according to any one of claims 1 to 13; an image forming means for forming an image on the sheet fed by the sheet feeding device; An image forming apparatus comprising:

Images