Sheet feeding device and image forming apparatus having sheet feeding device

Abstract

To prevent a decrease in productivity of a device when only a single sheet is placed on a sheet support part provided with an air blowing operation.SOLUTION: A sheet feeding device comprises: a sheet support part that supports a sheet; a feeding part that performs a feeding operation of feeding a sheet supported on the sheet support part; an air separation part that performs a blowing operation of blowing air onto a side surface of a sheet bundle supported on the sheet support part to separate sheets; number-of-sheets determination means for determining whether or not the sheet bundle supported on the sheet support part is composed of a single sheet; and a control part that controls the blowing operation by the air separation part and the feeding operation by the feeding roller. When the number-of-sheets determination means determines that the sheet bundle is composed of a single sheet, the control part causes the feeding part to perform the feeding operation without causing the air separation part to perform the blowing operation.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] Image forming apparatuses such as copiers, facsimiles, and printers are equipped with a sheet feeding device for setting a stack of sheets to be supplied to an image forming unit where an image is formed. Examples of the sheet feeding device include a feeding cassette unit provided at the bottom of the image forming apparatus main body and a manual feeding unit provided on the side of the image forming apparatus main body.

[0003] In recent years, there has been an increasing demand for forming images on a variety of sheets, and sheets with smooth surfaces, such as coated paper, are often used as recording materials. When a stack of such smooth-surfaced sheets is set in a sheet feeding device, the sheets tend to adhere closely to each other, making it difficult to separate and feed a single sheet from the stack. For this reason, Patent Document 1 discloses a device that blows air between the sheets to lift them up and separate the sheets. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 4-23747 Summary of the Invention [Problem to be solved by the invention]

[0005] When a single sheet is placed on the sheet support section, there is no need to perform the air blowing operation because the sheets do not stick to each other. However, in the sheet feeding device described in Patent Document 1, the number of sheets placed on the sheet support section is unknown. Therefore, the air blowing operation must be performed as if multiple sheets were placed. In this case, even if only one sheet is actually placed on the sheet support section, the air blowing operation must be performed every time, which could reduce the productivity of the device.

[0006] Therefore, an object of the present invention is to prevent a decrease in productivity of the apparatus by not performing the air blowing operation when only one sheet is placed on the sheet support section. [Means for solving the problem]

[0007] One aspect of the present invention is characterized in that it includes a sheet support section that supports sheets, a feeding section that performs a feeding operation to feed the sheets supported by the sheet support section, an air handling section that performs a blowing operation to blow air against the sides of the sheet stack supported by the sheet support section to handle the sheets, a sheet count determination means that determines whether the sheet stack supported by the sheet support section contains one sheet, and a control section that controls the blowing operation by the air handling section and the feeding operation by the feeding section, and when the sheet count determination means determines that the sheet stack contains one sheet, the control section causes the air handling section to perform the blowing operation and the feeding section to perform the feeding operation. [Effects of the Invention]

[0008] According to the present invention, the air blowing operation is not performed when only one sheet is placed on the sheet stacking section, thereby making it possible to reduce the decrease in productivity of the apparatus. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of an image forming apparatus according to an embodiment of the present invention. [Figure 2]FIG. 2 is a control block diagram of the sheet feeding device according to the first embodiment of the present invention. [Figure 3] FIG. 2 is a schematic diagram showing the configuration of a manual feed unit according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a schematic view showing a state in which an air handling operation is performed in the manual feed section according to the first embodiment of the present invention. [Figure 5] FIG. 3 is a diagram showing a setting screen for sheet information according to the first embodiment of the present invention. [Figure 6] 5 is a flowchart showing a procedure for setting sheet information according to the first embodiment of the present invention. [Figure 7] 6 is a flowchart showing determination of the number of sheets according to the first embodiment of the present invention. [Figure 8] 10 is a display screen that notifies the user of the number of sheets according to the first embodiment of the present invention. [Figure 9] 4 is a flowchart showing air blowing control according to the first embodiment of the present invention. [Figure 10] FIG. 10 is a schematic diagram showing the configuration of a manual feed section according to a second embodiment of the present invention. [Figure 11] FIG. 10 is a control block diagram of a sheet feeding device according to a second embodiment of the present invention. [Figure 12] 10 is a flowchart showing determination of the number of sheets according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] <Embodiment 1> A first embodiment of the present invention will be described in detail below with reference to the drawings. Fig. 1 is a cross-sectional view of an image forming system according to the first embodiment. As shown in Fig. 1, an image forming system 600 includes an image forming apparatus 201 and a feeding deck 500 connected to the image forming apparatus 201. The feeding deck 500 as a sheet feeding device 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.

[0011] <Image forming device> In Fig. 1, 201 is an image forming apparatus, 201A is an image forming apparatus main body, and 201B is an image forming unit that forms an image on a sheet. 202 is an image reading device installed horizontally above the image forming apparatus main body 201A, and the image forming apparatus main body 201A is equipped with the image forming unit 201B. In addition, an ejection space V for ejecting sheets is formed between the image reading device 202 and the image forming apparatus main body 201A. Note that an operation unit 730 composed of a touch panel or the like that can display a screen is disposed above the image forming apparatus main body 201A.

[0012] Image forming unit 201B, which is an image forming means, is provided in the center of image forming apparatus main body 201A in the vertical direction and mainly includes a laser scanner 210, a process cartridge 211, and a toner cartridge 215. Image forming unit 201B also includes an intermediate transfer unit 201C and a fixing unit 201E. Process cartridge 211 is a four-drum full-color type and includes four color process cartridges (211Y, 211M, 211C, and 211K) for yellow (Y), magenta (M), cyan (C), and black (K). Each process cartridge 211 includes a photosensitive drum 212, a charger 213 serving as charging means, and a developer 214 serving as developing means.

[0013] An intermediate transfer unit 201C is disposed above the process cartridge 211. 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 disposed inside the intermediate transfer belt 216 and abuts against the intermediate transfer belt 216 at a position facing the photosensitive drum 212. The intermediate transfer belt 216 is rotated in the direction of arrow X by the drive roller 216a, which is driven by a drive unit (not shown). The negative color toner images on the photosensitive drums are superimposed and transferred to the intermediate transfer belt 216 in the order of YMCK by the primary transfer roller 219. A secondary transfer roller 217 is disposed opposite the drive roller 216a of the intermediate transfer unit 201C and transfers the color image formed on the intermediate transfer belt to a sheet S. The intermediate transfer belt 216 and the secondary transfer roller 217 constitute a secondary transfer section 201D. The toner cartridge 215 is disposed above the intermediate transfer unit 201C.

[0014] Furthermore, above the secondary transfer roller 217, a fixing unit 201E having a pressure roller 220a and a heating roller 220b is disposed.

[0015] In addition, a first discharge roller pair 225a, a second discharge roller pair 225b, and a double-sided reversing unit 201F are arranged in the upper left of the fixing unit 201E. The double-sided reversing unit 201F is provided with a reversing roller pair 222 that can rotate forward and backward, and a re-conveying path R that conveys the sheet with an image formed on one side to the image forming unit 201B again.

[0016] A sheet feeding unit 230 is provided at the bottom of the image forming apparatus main body 201A, which feeds set sheets S to the image forming section 201B. The sheet feeding unit 230 includes a feeding cassette 1 that stores sheets, and a sheet feeding section 507 that feeds the sheets S stored in the feeding cassette 1. The sheet feeding section 507 includes a pickup roller 2, and a feed roller 3 and a retard roller 4 as a separation means that separates sheets S that have been fed from the pickup roller 2 and have been fed in a multi-fed state.

[0017] Further, on the right side surface of image forming apparatus main body 201A in FIG. 1, there is provided a manual feed section 235 that feeds set sheets S to image forming section 201B. Manual feed section 235 has a manual tray 6 that supports sheets S, and, like sheet feeding unit 230, has a manual feed roller 502 and a manual retard roller 503. Further, on the right side surface of image forming apparatus main body 201A in FIG. 1, below manual feed section 235, there is provided a feed deck 500 that feeds set sheets S to image forming section 201B. Details of manual feed section 235 will be described later.

[0018] 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. After image processing, this image information is converted into an electrical signal and transmitted to the laser scanner 210 of the image forming unit 201B. In the image forming unit 201B, the surface of the photosensitive drum 212, the surface of which has been 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.

[0019] Thereafter, this electrostatic latent image is developed and visualized with toner of each color, and the toner images of each color on each photosensitive 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.

[0020] Meanwhile, the sheet S fed by the feed rollers 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 abuts against the registration roller pair 240. As a result, the leading edge of the sheet S follows the registration roller pair 240. Thereafter, as the sheet S continues to be conveyed by the feed rollers 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 all at once 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 the fixing section 201E, where the toner of each color is melted and mixed under heat and pressure, and fixed onto the sheet S as a color image.

[0021] Thereafter, the sheet S on which the image has been fixed is discharged into the discharge space V by the first discharge roller pair 225a or the second discharge roller pair 225b provided downstream of the fixing unit 201E, and is stacked on a stacking unit 223 formed on the bottom surface of the discharge space V. When images are formed on both sides of the sheet S, after the images are fixed, the sheet S is transported to a re-conveyance path R by the reversing roller pair 222, and is transported again to the image forming unit 201B.

[0022] As described above, the image forming process for forming an image and the conveying sheet conveying process for forming an image on a sheet are linked together to form an image on a sheet.

[0023] <Manual feed section> Next, the manual feeding unit 235 as a sheet feeding device will be described in detail with reference to FIGS.

[0024] First, the control configuration for sheet feeding in the manual feed unit will be described with reference to the control block diagram in FIG. 2. The control unit 100 according to this embodiment is provided in, for example, the image forming apparatus 201, and includes a CPU 101, a ROM 102, and a RAM 103. The control unit 100 is a control means that controls the image forming apparatus 201, the feed deck 500, and the manual feed unit 235 in an integrated manner. 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, image scanner, or facsimile machine.

[0025] RAM 103 stores sheet information, such as paper size and paper type, for feed cassette 1, feed deck 500, and manual feed tray 6, which is set by a sheet information setting method described later. Controller 100 is also connected to fan controller 402, feed motor 520, which drives manual feed pickup roller 501, torque measurement unit 520a, which measures the motor torque of feed motor 520, and feed sensor 505. Torque measurement unit 520a measures the motor torque of feed motor 520, but may be, for example, a current sensor that detects the value of current flowing through feed motor 520 or a torque sensor that detects the torque generated in pickup roller 501. Torque measurement unit 520a may have any specific configuration as long as it can measure the motor torque of feed motor 520. Fan controller 402 controls the rotation of fans 511a and 511b while simultaneously detecting any malfunctions. Whether or not a malfunction has occurred can be determined by counting the number of rotations of the fan and determining whether or not the intended number of rotations has been reached.

[0026] 3 is a schematic diagram showing the configuration of the manual feed unit 235 according to the first embodiment. The manual feed unit 235 includes a manual tray 6 as a sheet storage unit, and a manual sheet feed unit 506 that feeds sheets and separates the sheet stack. The manual sheet feed unit 506 also includes a manual pickup roller 501 as a feed roller that contacts the top sheet of the sheet stack and feeds the top sheet. The manual sheet feed unit 506 also includes a feed roller 502 and a retard roller 503 as a separation unit that separates the sheet S fed from the manual pickup roller 501. In the manual feed unit 235, a pull-out roller 504 is disposed downstream of the feed roller 502 in the sheet feeding direction to pull out the sheet S from the feed roller 502 and feed it to the image forming apparatus 201. Furthermore, a feed sensor 505 serving as a sheet detection unit is disposed between the feed roller 502 and the pull-out roller 504 in the sheet feeding direction, that is, downstream in the feeding direction of the manual sheet feeding unit 506. 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.

[0027] 3, the manual feed tray 6 is provided with a manual feed tray base 515 and a lifter plate 514 as a sheet support portion that supports and stacks a sheet bundle consisting of a plurality of sheets S. The lifter plate 514 is also provided with a manual feed tray sheet presence / absence detection sensor 401, which can determine whether a sheet bundle has been stacked on the lifter plate 514. The height position of the lifter plate 514 is controlled by a lifting mechanism (not shown) in accordance with the amount of stacked sheets S. The manual feed tray 6 is also provided with side edge regulating plates 511 and 512. The side edge regulating plates 511 and 512 regulate the positions of the widthwise ends (side edges of the sheets) of the sheets S set on the lifter plate 514.

[0028] Furthermore, side edge regulating plates 511 and 512 are provided with air blowing sections 511A and 512A, respectively, as air handling sections. Air blowing section 511A of side edge regulating plate 511 has fan 511b, which is an air blowing section driven by fan motor 511M (see FIG. 2), and blowing nozzle 511a, which guides the air blown from fan 511b and blows it from the side of the sheet stack. Similarly, air blowing section 512A of side edge regulating plate 512 has fan 512b, which is driven by fan motor 512M (see FIG. 2), and blowing nozzle 512a, which guides the air blown from fan 512b and blows it from the side of the sheet stack. In addition, the side end regulating plates 511, 512 are provided with floating suppression plates 511c, 512c near 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] Next, the state of sheets S when air is blown from the side of the sheet stack by air blowing units 511A and 512A will be described with reference to Fig. 4. Fig. 4 is a schematic diagram of a state in which air is blown by a fan in manual feed unit 235 (hereinafter referred to as "air blowing operation"), as viewed from the feeding direction.

[0030] As shown in FIG. 4, air is blown toward the sides of the sheet stack from fans 511b and 512b of air blowing units 511A and 512A as indicated by arrows A1 and A2. As a result, several to several tens of sheets S located at the top of the stack of sheets are raised. The uppermost raised sheet contacts lift-up suppression plates 511c and 512c, thereby restricting the lift-up of sheets S. This air-blowing action reduces the adhesion between sheets. Even sheets S with smooth surfaces, such as coated paper, can be separated and fed one by one by feed roller 502 and retard roller 503.

[0031] <Sheet information settings> Setting of sheet information such as the size and type of the sheet set in the manual feed tray 6 will be described with reference to FIGS.

[0032] Sheet settings are made from an operation unit 730. Fig. 5(a) is a diagram showing the operation unit 730 in the image forming apparatus of Fig. 1. The operation unit 730 is provided with a start key 702 for starting an image forming operation, a stop key 703 for interrupting the image forming operation, numeric keys 704 to 712 and 714 for setting numbers and the like, an ID key 713, a clear key 715, a reset key 716, and the like. In addition, a display unit 720 with a touch panel formed on the top is provided, and soft keys can be created on the screen.

[0033] When the user presses the "Paper Selection" button on the display unit 720 shown in FIG. 5(a), the CPU 101 transitions to a paper feed tray selection screen shown in FIG. 5(b) (S201). The user then selects which paper feed tray to use to feed sheets from. Here, the user selects the manual feed tray (S201, S202) and presses the "Next" button. When the button is pressed, the CPU 101 transitions to a sheet size setting screen shown in FIG. 5(c). Here, the user selects A3, which is set in the manual feed tray (S204), and presses the "Next" button, and the CPU 101 transitions to a sheet type setting screen shown in FIG. 5(d).

[0034] Here, the type of sheet set in the sheet storage section is selected (S205, S206), and when the "OK" button is pressed, the initial screen of FIG. 5(a) is displayed, and the sheet registration process is completed (S207).

[0035] The set sheet information is saved in RAM 103. After setting the sheet information, pressing start key 702 on the operation display device 700 starts the job, and a sheet is fed from the selected sheet storage unit. In other words, it is not necessary to set sheet information every time before starting a job. For example, if you set plain A3 paper in the manual feed tray and executed a job, and then want to execute a job to feed plain A3 paper from the manual feed tray again, all you have to do is press start key 702.

[0036] <Paper count detection process control> Next, a description will be given of the process control for detecting the number of sheets according to embodiment 1. When there is one sheet placed on manual tray 6, there is no need to blow air, and therefore control is performed to determine whether there is one sheet or not.

[0037] 7 is a flowchart executed by CPU 101 according to the first embodiment to determine whether the sheet stack contains one sheet. In other words, the number of sheets is determined. Since there is always a possibility that a sheet may be placed on manual feed tray 6, the flowchart starts after the device is started and is always executed.

[0038] In S401, a sequence for prompting the user to determine the number of sheets placed on the lifter plate 514 is started. In S402, the CPU 101 determines whether the manual feed tray paper presence / absence detection sensor 401 has detected ON. If ON is detected, the CPU 101 determines that paper has been placed on the lifter plate 514 and proceeds to S403. If ON is not detected, the CPU 101 determines that no paper has been placed on the lifter plate 514 and repeats S402. In S403, the CPU 101 displays a screen on the display unit 720 inquiring of the user about the number of sheets placed on the lifter plate 514. FIG. 8 shows a display screen inquiring of the number of sheets according to the first embodiment. As shown in FIG. 9, the display unit 720 displays a message saying "Is there one sheet of paper placed on the manual feed tray?" along with a button with two options, YES or NO.

[0039] In S404, CPU 101 determines whether a button displayed on display unit 720 has been pressed. If the button has been pressed, the process proceeds to S405. If the button has not been pressed, the process proceeds to S410. In S405, CPU 101 determines whether the pressed button indicates YES. If YES has been pressed, the process proceeds to S406. If NO has been pressed, the process proceeds to S407. In S406, CPU 101 determines that the number of sheets of paper loaded on lifter plate 514 is one, and therefore assigns 1 to onePapFlg stored in RAM 103. Here, onePapFlg is a variable that stores 1 when there is one sheet of paper loaded on lifter plate 514, and 0 when there are more than one sheet of paper. Then, the process proceeds to S408.

[0040] In S408, the screen of the display unit 720 displayed in S403 is closed, and the process proceeds to S409. In S409, the CPU 101 determines whether the manual feed tray paper presence / absence detection sensor 401 has detected OFF. If OFF is detected, the process proceeds to S402. If OFF is not detected, S409 is repeated.

[0041] In S404, if the button displayed on display unit 720 has not been pressed, the process proceeds to S410. In S410, CPU 101 determines whether manual tray paper presence / absence detection sensor 401 has detected OFF. If OFF is detected, it is determined that paper has been removed from lifter plate 514, and the process proceeds to S411. If OFF is not detected, it is determined that paper remains placed on the multi, and the process proceeds to S404. In S411, the screen of display unit 720 displayed in S403 is closed, and the process proceeds to S402.

[0042] Note that this flowchart is a flow for determining whether one sheet has been set in the manual feed tray, but in this embodiment, this determination is made when coated paper has been selected as the sheet type in advance in FIG. 6. That is, it determines whether multiple sheets (coated paper) with a high adhesive force between sheets have been set in the manual feed tray and there is a possibility of double feeding. In other words, if plain paper, for example, with a low adhesive force between sheets, has been selected for the manual feed tray, there is no need to perform the air blowing operation, and there is no need to determine whether multiple sheets or one sheet have been set. Therefore, in this embodiment, if plain paper has been selected, no display is displayed asking the user how many sheets to set.

[0043] As described above, the number of sheets of paper placed on the manual feed tray 6 is determined by the manual feed tray paper presence / absence detection sensor 401 and by displaying a message on the display screen to the user indicating whether one sheet is placed and allowing the user to select it.

[0044] <Sheet feeding control> Next, actual sheet feeding control in a state where the detection control of the sheet information and number of sheets has been set will be described with reference to Fig. 9. The flowchart in Fig. 9 is executed at the start of a job.

[0045] In S601, CPU 101 starts controlling the blowing of air onto sheets placed on a tray. In S602, CPU 101 determines whether the sheet feed tray from which the sheets are fed is a manual feed tray. If CPU 101 determines that the sheet feed tray is a manual feed tray, the process proceeds to S603. If the sheet feed tray is any other type, the process proceeds to S610.

[0046] In S603, it is determined whether onePapFlg stored in RAM 103 is 1. If onePapFlg is 1, it is determined that there is one sheet of paper placed on the sheet support section, and the process proceeds to S610. If onePapFlg is 0, it is determined that there is more than one sheet of paper placed on the sheet support section, and the process proceeds to S604.

[0047] In S604, CPU 101 controls fan 511b, and the process proceeds to S605. In S605, it is determined whether a predetermined time of 10 seconds has elapsed since the start of air blowing, for example. The predetermined time (10 seconds) is the time required to separate the sheets by air blowing and improve adhesion between the sheets, and is not limited to a uniform time, but may be varied depending on the type of sheet and the temperature and humidity around the device. After the predetermined time has elapsed, the process proceeds to S606. If the predetermined time has not elapsed, S605 is repeated.

[0048] In S606, since the adhesion between sheets has improved, the manual sheet feed unit performs sheet feeding. At this time, the air blowing by the fan is stopped to reduce skew of the sheets during feeding. In S607, it is determined whether the required number of sheets to be fed to the image forming unit based on the command of the print job has been reached. If feeding is complete, the process proceeds to S608, where air blowing control ends.

[0049] If feeding is not complete, the process proceeds to S609. In S609, it is determined whether or not a predetermined number of 10 sheets have been fed since the start of the feeding operation. The predetermined number (10 sheets) is the number of sheets from the top of the sheet stack where paper suction has been improved by blowing air, and may be variable. If the predetermined number of sheets has been fed, the process proceeds to S604. If the predetermined number of sheets has not been fed, S606 is repeated.

[0050] In S610, the sheet S is fed from a designated sheet feed tray other than the manual feed tray without blowing air, and the process proceeds to S608.

[0051] As described above, according to the air handling process control of the first embodiment, when feeding a sheet from the manual feed unit, if it is determined that only one sheet of paper has been placed on lifter plate 514, the sheet is fed without blowing air at the start of the job. Therefore, since the sheet is fed without the fan blowing air, it is possible to shorten the time from when the sheet is placed until it is fed, that is, to suppress a decrease in productivity of the device.

[0052] <Embodiment 2> Next, a second embodiment of the present invention will be described. In the first embodiment, whether or not there is one sheet of paper loaded on lifter plate 514 is determined by the user, whereas in the second embodiment, the number of sheets of paper placed on lifter plate 514 is automatically determined by a sensor. In describing the second embodiment, differences from the first embodiment will be described.

[0053] <Detection control of number of sheets of paper in the second embodiment> Fig. 10 is a diagram of the manual feed tray corresponding to Fig. 4 in the first embodiment. As shown in Fig. 10, in the second embodiment, a sheet number detection sensor 520, which is an ultrasonic sensor serving as a sheet number detection unit, is disposed on the lifting suppression plate 512c and the lifter plate 514. An oscillation unit 520a is attached to the lifting suppression plate 512c, and an oscillation receiving unit 520b, which is disposed opposite the oscillation unit 520a across the sheet, is attached to the lifter plate 514. Note that the installation position of the sheet number detection sensor 520 is an example and is not limited to the position shown in this embodiment.

[0054] 11, the oscillator 520a is connected to the control unit 100, for example, via a power amplifier circuit (not shown). The power amplifier circuit amplifies pulses of a predetermined frequency output from the control unit 100, and the oscillator 520a is driven in response to the amplified pulse signal to emit ultrasonic waves. The receiver 520b is connected to the control unit 100, for example, via an output amplifier circuit and a rectifying / smoothing circuit (not shown), and outputs a detection signal of a level corresponding to the intensity of the received ultrasonic waves to the control unit 100. The oscillator 520a of the sheet number detection sensor 520 emits ultrasonic waves, which are received by the receiver 520b, and the received ultrasonic waves level is measured.

[0055] Regarding the sheets of paper loaded on lifter plate 514, if only one sheet of paper is set, the reception level will be lower than the threshold, but if multiple sheets of paper are set, the reception level will be equal to or higher than the threshold, and it will be determined whether the number of sheets placed on lifter plate 514 is one or multiple. The threshold may be changed depending on the type of sheet. In this way, it is determined whether the number of sheets placed on lifter plate 514 is one or multiple.

[0056] <Control of detection process for number of sheets according to the second embodiment> 12 is a flowchart of the process of detecting the number of sheets corresponding to FIG. 7 in the first embodiment. That is, it is a flowchart executed by CPU 101 according to the first embodiment to determine whether the sheet stack contains one sheet. Since there is always a possibility that a sheet may be placed on manual tray 6, the flowchart starts after startup and is executed continuously.

[0057] In S501, a sequence is started in which the paper number detection sensor allows the user to determine the number of sheets placed on lifter plate 514. In S502, it is determined whether manual feed tray paper presence / absence detection sensor 401 has detected an ON signal. If manual feed tray paper presence / absence detection sensor 401 has detected an ON signal, the CPU determines that paper has been placed on lifter plate 514 and proceeds to S503. If manual feed tray paper presence / absence detection sensor 401 has not detected an ON signal, it determines that no paper has been placed on lifter plate 514 and repeats S502.

[0058] In S503, the sheet number detection sensor emits ultrasonic waves from oscillator 520a to determine whether there is one sheet of paper. In S504, the CPU determines whether the reception level received by receiver 520b of the sheet number detection sensor is below a threshold. If the reception level is below the threshold, the CPU determines that there is one sheet of paper, and proceeds to S505. In S505, since it has been determined that there is one sheet of paper loaded on lifter plate 514, 1 is assigned to onePapFlg stored in RAM. Then, the process proceeds to S507. In S506, since the CPU has determined that there is more than one sheet of paper loaded on lifter plate 514, 0 is assigned to onePapFlg stored in RAM. Then, the process proceeds to S507.

[0059] In S507, the ultrasonic waves emitted from the oscillator 520a of the paper number detection sensor are stopped, and the process proceeds to S508. In S508, the CPU determines whether the manual feed tray paper presence detection sensor 401 has detected an OFF state. If the manual feed tray paper presence detection sensor 401 has detected an OFF state, the process proceeds to S502. If the manual feed tray paper presence detection sensor 401 has not detected an OFF state, S508 is repeated.

[0060] As described above, it is possible to detect that one sheet of paper is placed on manual feed tray 6 using sheet number detection sensor 520. Whether or not to blow air onto manual feed tray 6 depends on the value stored in onePapFlg, as in the flowchart of FIG. 9 shown in the first embodiment.

[0061] In the above embodiment, the manual pickup roller 501 that contacts the top sheet of a sheet stack and feeds the top sheet has been exemplified as the feeding unit that feeds sheets. However, the feeding unit may also be a feeding belt that uses air to adsorb a sheet and feeds the adsorbed sheet. [Explanation of symbols]

[0062] 100 control section 201B Image forming section 235 Manual feeding unit (sheet feeding device) 501 Manual pickup roller (feed roller) 506 Manual sheet feeder 511A, 512A Air blowing section (air handling section) 511a, 512a nozzle 511b,512b Fan 514 Lifter plate (seat support part) 730 Operation unit S seat

Claims

1. a seat support portion that supports the seat; a feeding unit that performs a feeding operation to feed the sheet supported by the sheet supporting unit; an air handling unit that blows air onto a side surface of the sheet stack supported by the sheet support unit to handle the sheets; a sheet number determination means for determining whether the number of sheets supported by the sheet support portion is one; a control unit that controls the blowing operation by the air handling unit and the feeding operation by the feeding unit; when the sheet number determining means determines that the number of sheets in the sheet stack is one, the control unit causes the air handling unit to perform the blowing operation and the feeding unit to perform the feeding operation. A sheet feeding device characterized by:

2. the sheet number determination means includes an operation unit having a screen that allows a user to select whether the number of sheets placed on the sheet support unit is one or not, the control unit controls the blowing operation and the feeding operation based on information about the number of sheets selected by the operation unit.

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

3. the sheet number determining means includes a sheet number detecting unit that detects whether the number of sheets placed on the sheet support unit is one or not, the control unit controls the blowing operation and the feeding operation based on the information detected by the sheet number detection unit.

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

4. The sheet feeding device according to claim 1 ; an image forming unit that forms an image on the sheet fed by the sheet feeding device.

Images