JP7650135B2 - Sheet Feeding Device - Google Patents

Description

The present invention relates to a sheet feeding device that stores sheets to be fed to an image forming device, and in particular to a sheet feeding device that blows air onto stacked sheets to separate and feed the stacked sheets one by one.

In image forming devices such as copiers and printers, sheets are separated one by one from a deck that stores stacked sheets, removed, subjected to image formation processing, and discharged. However, if the adhesion between sheets increases when they are stacked on the deck, the separability of the sheets deteriorates. As a result, when sheets are supplied from the deck, double feeding, in which multiple sheets are fed in an overlapping state, and misfeeds such as delayed sheet transport are likely to occur. In particular, in high humidity environments, a greater adhesion force acts between sheets, making double feeding and misfeeds more likely to occur.

For this reason, it has been proposed to provide a so-called air handling separation mechanism in which an air outlet is provided in a side fence that regulates the side position of the sheet in the width direction, and air is blown from a fan connected to the air outlet, so that air gets in between the sheets before they are fed and assists in separation by blowing air against the sides of the sheets (see, for example, Patent Document 1).

JP 2005-96994 A

The sheet feeding device is configured to remove a sheet from the sheet stacking device and feed it when the sheet position detection means detects that the top surface of the sheet stack supported by the liftable sheet stacking device has reached a position where feeding by the sheet feeding device is possible.

However, when using the air handling separation mechanism, depending on the type of sheet, the strength of the air blowing may push up the topmost sheet in the stack, reducing the accuracy of the detection means for detecting the removal position and making stable paper feeding impossible. In particular, for sheets with a basis weight above a certain level, the topmost sheet may be lifted by the air blowing, leaving a large gap between it and the next sheet, making the supply of the next sheet unstable.

The present invention aims to provide a sheet feeding device that eliminates the instability of the next sheet removal position caused by air blowing without compromising separation performance during sheet feeding.

In order to solve the above problems, a sheet feeding device according to the present invention includes a stacking means on which sheets are stacked in a predetermined stacking direction, a sheet taking-out means for taking out a sheet stacked on the stacking means and located at a predetermined take-out position in a feeding direction, a moving means for moving the stacking means upward in the stacking direction so that the sheet reaches the take-out position after the sheet is taken out by the sheet taking-out means, a blowing means for blowing air from a direction intersecting both the stacking direction and the feeding direction so as to sort the sheets located at the take-out position, a detection means for detecting whether a sheet stored in the stacking means is located at the take-out position, a basis weight recognition means for recognizing basis weight information of the sheets stacked on the stacking means, and the moving means. and a control means for controlling the sheet stacking means to move the sheets stored in the stacking means to the removal position when the detection means detects that the sheets are not at the removal position when the basis weight information recognized by the basis weight recognition means is less than a predetermined basis weight, and when the basis weight information recognized by the basis weight recognition means is equal to or greater than the predetermined basis weight, regardless of the detection result by the detection means, the control means controls the moving means to lift the moving means by a predetermined amount so that the sheet removal means removes a predetermined number of sheets that are subjected to air blowing from the air blowing means and then positions the sheets stored in the stacking means to the removal position.

In addition, the sheet removal means moves in the stacking direction according to the height position of the topmost sheet stored in the stacking means, and the detection means is controlled to detect that the sheet stored in the stacking means is not at the removal position when the sheet removal means reaches the lower limit of a preset movement range .

As a result, when the basis weight of the stored sheet type is small, the lifting means can control the linear lifting and lowering of the stacking means according to the height position of the stacked sheets, allowing for efficient sheet feeding.

In one embodiment, the sheet removal means moves in accordance with the height position of the topmost sheet stored in the stacking means, and the detection means detects that the sheet stored in the stacking means is not at the removal position when the sheet removal means reaches the limit of its movable range.

In addition, when the air blowing means stops blowing air, the control means controls the lifting means to position the sheets stored in the stacking means at the removal position when the sheet removal means removes the sheets. When the sheets are set so that they will not be lifted by the air blowing, it is preferable to linearly control the lifting and lowering of the stacking means by the lifting means according to the height position of the stacked sheets.

According to the present invention, by controlling the lifting and lowering of the stacking means by the lifting and lowering means in accordance with the number of sheets to be removed, even when the gap between the top sheet and the next sheet is large due to the blowing of air, the next sheet is reliably positioned at the removal position, and the sheets can be fed stably.

1 shows a schematic configuration diagram of an image forming system according to an embodiment. FIG. 2 shows a front view of a multi-stage feeding deck according to an embodiment. FIG. 2 is a side view showing a state in which a storage cabinet of the multi-stage feeding deck according to the embodiment is pulled out. FIG. 2 is an enlarged side view showing a state in which a storage cabinet of a multi-stage feeding deck according to an embodiment is pulled out; FIG. 2 is an enlarged perspective view showing a state in which a storage cabinet of a multi-stage feeding deck according to an embodiment is pulled out; 1 is an explanatory diagram showing a state in which sheets are set in a storage unit of a multi-stage feeding deck according to an embodiment; 1 is an explanatory diagram of a main configuration of a sheet feeding device according to the present invention; 4 shows a flowchart relating to the operation of the sheet feeding device of the present invention. 4 shows a flowchart relating to the operation of the sheet feeding device of the present invention. FIG. 1 is an explanatory diagram of the problem to be solved by the present invention. FIG. 1 is an explanatory diagram of the problem to be solved by the present invention.

Specific embodiments of the present invention will be described in detail below with reference to the drawings.

[Image forming system]
1 is a cross-sectional view showing an example of an image forming system 1000 including a multi-stage deck 200 having a plurality of sheet feeding devices according to the present invention arranged vertically, and an image forming apparatus 100. In the following description, an image forming apparatus having an image forming section will be described using a laser printer system (hereinafter simply referred to as a printer) using an electrophotographic method as an example. Note that the image forming apparatus constituting the image forming system may be a copier, a facsimile, a multifunction machine, etc., in addition to a printer. Also, the image forming apparatus may be configured using other methods such as an inkjet method, regardless of the electrophotographic method.

The multi-stage deck 200, the schematic configuration of which will be described later, can feed sheets to the image forming device 100 from multiple sheet feeders, each capable of storing multiple sheets. Examples of sheets include plain paper, thin paper, thick paper, plastic sheets, etc.

The image forming device 100 forms a toner image (image) on a sheet in response to an image signal from a document reading device (not shown) connected to the image forming device main body or a host device such as a personal computer connected to the image forming device main body so as to be able to communicate with the image forming device main body.

The image forming apparatus 100 includes an image forming section 110, a plurality of sheet storage devices 120, a sheet conveying device 130, and the like. Each section of the image forming apparatus 100 is controlled by a control section 140. The control section 140 has a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The CPU controls each section while reading out a program corresponding to a control procedure stored in the ROM. In addition, working data and input data are stored in the RAM, and the CPU performs control by referring to the data stored in the RAM based on the aforementioned programs, etc.

Each of the sheet storage devices 120 includes a cassette 121 for storing sheets S, a pickup roller 122, and a separation and conveying roller pair 125 consisting of a feed roller 123 and a retard roller 124. The sheets S stored in the cassette 121 are separated and fed one by one by the pickup roller 122 and the separation and conveying roller pair 125, which move up and down and rotate at a predetermined timing.

The sheet conveying device 130 includes a conveying roller pair 131, a pre-registration roller pair 132, and a registration roller pair 133. The sheet S fed from the sheet storage device 120 is passed through the sheet conveying path 134 by the conveying roller pair 131 and the pre-registration roller pair 132, and then guided to the registration roller pair 133. The sheet S is then fed into the image forming unit 110 at a predetermined timing by the registration roller pair 133.

The sheet transported from the multi-stage deck 200 (described later) via the transport roller pair 201 is transported into the image forming apparatus 100 via a connection path 202 with the image forming apparatus 100. The sheet transported from the multi-stage deck 200 into the image forming apparatus 100 is then sent to the image forming section 110 at a predetermined timing via the pre-registration roller pair 132 and the registration roller pair 133, in the same way as the sheet transported from the sheet storage device 120 in the image forming apparatus 100.

The image forming unit 110 includes a photosensitive drum 111, a charger 112, a laser scanner 113, a developing unit 114, a transfer charger 115, a separation charger 116, a cleaner 117, and the like. During image formation, the photosensitive drum 111 is rotated in the direction of the arrow in the figure, and the surface of the photosensitive drum 111 is first uniformly charged by the charger 112. Then, a laser beam emitted from the laser scanner 113 in response to an image signal is reflected by a mirror 118 and irradiated onto the charged photosensitive drum 111, forming an electrostatic latent image on the photosensitive drum 111. The electrostatic latent image thus formed on the photosensitive drum 111 is then visualized as a toner image by the developing unit 114.

The toner image on the photosensitive drum 111 is then transferred to the sheet S by the transfer charger 115 in the transfer section 115a. Furthermore, the sheet S onto which the toner image has been transferred in this manner is electrostatically separated from the photosensitive drum 111 by the separation charger 116. Residual toner remaining on the photosensitive drum 111 after transfer is removed by the cleaner 117. The sheet S onto which the toner image has been transferred is transported by the transport belt 119 to the fixing device 150 where the toner image is fixed, and then discharged outside the machine by the discharge rollers 151.

[Multi-deck]
The multi-stage deck 200 has a plurality of sheet feeding devices 210 according to the present invention, each of which stores a plurality of sheets and sends them out to the image forming apparatus 100. The plurality of sheet feeding devices 210 are arranged vertically in a plurality of stages. Each sheet feeding device 210 can be pulled out and inserted into the housing 204 of the multi-stage deck 200. The sheet feeding devices 210 have the same basic configuration, except that they can store different numbers of sheets. Note that the number of sheets that can be stored may be the same.

The sheets fed from each sheet feeding device 210 are transported to a connection path 202 (FIG. 1) via a transport path not shown. Each part of the multi-stage deck 200 is controlled by a control unit 203 (FIG. 1). The control unit 203 has a CPU, ROM, and RAM, similar to the control unit 140. The control unit 203 can communicate with the control unit 140 of the image forming apparatus 100, and controls the timing of sheet feeding by communicating with the control unit 140.

The multi-stage deck 200 has a button 205 as an operation unit for pulling out the sheet feeding device 210. The button 205 is provided on the front of each sheet feeding device 210. For example, when an operator presses the button 205, a locking mechanism that has locked the sheet feeding device 210 in the mounting position is released, and the sheet feeding device 210 is pushed out of the housing 204 by a spring (not shown). This allows the operator to pull out the sheet feeding device 210 to a position where the sheets can be stored, as shown in Figures 3 to 5. Note that the configuration may also be such that pressing the button 205 causes a motor or the like to automatically move the storage to a position where the sheets can be stored.

As shown in Figs. 4 to 7, the sheet feeding device 210 has a storage section 220 capable of storing sheets S, and a sheet feeding section 230 that feeds sheets S from the storage section 220 toward the image forming device 100. As shown in Fig. 5, the storage section 220 has a stacking tray 221 on which sheets S are stacked, abutment section 222, a trailing end regulating plate 223, a side regulating member 224R, etc. The stacking tray 221 can be raised and lowered in the vertical direction by a lifter 243 that changes the height of the stacking tray 221 by winding up a wire connected to a pulley driven by a motor (not shown).

The abutting portion 222 is disposed downstream in the sheet feeding direction in the storage space 225 in which the sheets are stored, and the downstream end (leading end) of the sheet stacked on the stacking tray 221 abuts against the abutting portion 222. The rear end regulating plate 223 is disposed upstream in the sheet feeding direction in the storage space 225, and the upstream end (rear end) of the sheet stacked on the stacking tray 221 abuts against the abutting portion 222, thereby regulating the rear end position of the sheet. The rear end regulating plate 223 is movable in the sheet feeding direction, and the rear end regulating position of the sheet can be adjusted according to the sheet size. The side regulating members 224 are disposed on both sides in the width direction perpendicular to the sheet feeding direction of the storage space 225, and regulate the width direction end positions of the sheet. The side regulating members 224R and 224F are movable in the width direction, and the regulating position of the sheet in the width direction can be adjusted according to the sheet size.

As shown in FIG. 6, one of the side regulating members 224R has two air outlets 240 at the top. These are for blowing air sent by an air blowing means 241 provided inside the side regulating member 224R onto the side edge portion of the sheet P. In this embodiment, two air outlets 241 are provided, but the present invention is not limited to this embodiment.

As shown in FIG. 7, the sheet feeding section 230 has a pickup roller 231 as a sheet removal means, a separation conveying roller pair 234 consisting of a conveying roller 232 and a retard roller 233, a conveying roller pair 235, etc. As shown in FIG. 5, the pickup roller 231 and the separation conveying roller pair 234 are disposed at the downstream end in the sheet feeding direction above the storage space 225 and approximately in the center in the width direction.

The pickup roller 231 is provided above the stacking tray 221 and contacts the top sheet of the sheets S stacked on the raised stacking tray 221 to feed it. For this reason, as shown in FIG. 7, the pickup roller 231 is pivoted so as to be able to swing freely in the sheet stacking direction, i.e., in the vertical direction, so that it can press the top sheet on the stacking tray 221 with an appropriate force near the leading edge of the sheet S in the sheet feeding direction. The swing range is the feedable range indicated by the arrow in FIG. 11, and a sheet located within this range is removed from the stacking tray 221 by the rotation of the pickup roller 231 and sent out in the feed direction.

When two or more overlapping sheets are picked up from the pickup roller 231, the separation conveying roller pair 234 separates them and conveys only one of the sheets. That is, the conveying roller 232 of the separation conveying roller pair 234 rotates in the sheet conveying direction and conveys the sheet picked up by the pickup roller 231. On the other hand, the retard roller 233 rotates in the opposite direction to the conveying roller 232 and returns the sheets other than the topmost sheet of the two or more sheets sent from the pickup roller 231 to the stacking tray 221 side. Note that the retard roller 233 has a built-in torque limiter (not shown), and when only one sheet is sent to the separation conveying roller pair 234, the drive of the conveying roller 232 is transmitted to the separation conveying roller pair 234, and the sheet being conveyed is pinched and rotated.

The sheet separated and conveyed by the separation conveying roller pair 234 is conveyed by the conveying roller pair 235 to a conveying path (not shown) in the multi-stage feeding device 200, and is conveyed to the image forming device 100 via the connection path 202 (Figure 1) as described above.

The blowing means 241 is a fan mechanism that blows air, and the air outlet 240 that blows the air is arranged on the surface of the side regulating member 224R that the sheet abuts against. The air blown from the blowing means 241 passes through the air passage and is blown from the air outlet 240 to the topmost sheet P and several sheets stacked below it. The blown air is blown between the sheets, so that the sheets float up one by one and are handled. Note that information on the type of sheet may be obtained from the image forming device 100 before the air blowing operation is performed, and the strength of the blown air may be varied according to the information to adjust the air volume to an appropriate level. Note that in this embodiment, a device equipped with two blowing means in one storage space is disclosed, but various forms may be adopted, such as blowing air from one blowing means through multiple air outlets or providing multiple blowing means.

The floating restriction members 242 are arranged in four positions above the air outlet 240, and are rotatable around a swinging rotation axis provided on the side restriction member 224 side, and are provided in a state where they protrude above the sheet P so as to be able to restrict the floating of the sheet P that abuts against the side restriction member 224. As a result, the sheet P that has been floated by the air blown from the air outlet 240 abuts against the floating restriction members 242, and is prevented from floating higher than that position. Therefore, sufficient air is sent between the sheets S, and the sheets are held in the appropriate position where they can be fed while being separated, preventing double feeding.

The sheet storage section 220 includes a liftable stacking tray 221 on which sheets S are stacked, and a rear end regulating plate 223 that is a regulating member that regulates the position of the rear end of the sheets S, which is the upstream end in the sheet feeding direction. The rear end regulating member 223 is supported so as to be movable in a direction parallel to the sheet feeding direction, moves along a long hole (not shown) formed in the center of the stacking tray 221, and includes a size detecting means 14 provided on the path to detect the position information of the rear end regulating member 223 as the size of the sheet.

When feeding the sheets S, the liftable pickup roller 231, which lowers to feed the top sheet S1 of the sheets S stacked on the stacking tray 221, also serves as a sheet feed position sensor flag to stop the stacking tray 221 at the removal position (height). That is, as the lifting action of the lifter 243 raises the stacking tray 221, the pickup roller 231 is lifted and the stacking tray 221 rises to a predetermined range. When the sheet feed position sensor 231S detects the pickup roller 231, it stops the lifter 243 and stops the lifting of the stacking tray 221.

Next, the sheet feeding operation of the sheet feeding device 1 will be described. The pickup roller 231 descends to contact the sheet on the stacking tray 221, and rotates to feed the top sheet of the stacked sheets S on the stacking tray 221 in the feeding direction. Before such sheet feeding, air is blown out from the air outlet 240 by the air blowing means 241, and the blown air is blown onto the end of the sheet S. Air continues to be blown during the sheet feeding operation, and air blowing ends at the same time as the sheet feeding operation ends. The air blowing means 241 is provided with a fan and at least one heater, and air is blown by the rotation of the fan. The heater is installed at the suction port of the fan, and the necessity of heater operation is determined at the same time as the type of sheet is specified, and if operation is necessary, the heater is raised to the specified temperature. When air is blown, the air heated to an appropriate temperature by passing through the temperature-controlled inside of the heater is sucked into the fan and discharged from the air outlet 240.

As a result, air blown out from the air outlet 240 gets in between the sheets, and the sheets S within the area where the air is blown rise one by one, thereby separating the sheets S. This air blowing is performed continuously while the sheets are being fed, but it may also be performed intermittently.

After blowing air in this manner to separate the top sheets S of the stack one by one, the pickup roller 231 descends and contacts the top sheet. The pickup roller 231 then sends the top sheet to the separation nip formed by the feed roller 232 and the retard roller 7233. If the top sheet S1 has not been completely separated from the next sheet by the air, the top sheet S1 is separated from the next sheet and transported as it passes through the separation nip.

The sheet presence/absence discrimination sensor 10 detects the presence or absence of a sheet S on the stacking tray 221 by detecting a sheet presence/absence discrimination flag 11 that can rotate up and down around a rotation axis. An opening 12 is formed in the stacking tray 221 at a position corresponding to the sheet presence/absence discrimination flag 11, and when no sheet S is loaded on the stacking tray 221, the sheet presence/absence discrimination flag 11 rotates downward around the rotation axis and its tip enters the opening 12. When the sheet presence/absence discrimination flag 11 rotates downward in this manner, the optical axis of the sheet presence/absence discrimination sensor 10 is opened. Based on the detection signal from the sheet presence/absence discrimination sensor 10, the control unit 203 determines that no sheet S is loaded on the stacking tray 221.

Next, the operation of the sheet feeding device 1 during sheet feeding will be described. Before starting to feed the sheet S, air is blown out from the air outlet 240 by the air blowing means 241, so that the entire sheet floats along the side regulating member 224, and the entire sheet floats in a direction approximately perpendicular to the flow path of the air blown against the sheet S, so that the stacked sheets can be handled reliably.

For example, coated paper has the characteristics of high smoothness, low breathability, and high moisture absorption, so the adhesion between sheets tends to increase when stacked, and this tendency becomes more pronounced in high humidity environments, making separation poorer than that of plain paper, and making it more likely that double feeding or non-feeding will occur when feeding. For this reason, the air coming out of the air outlet 240 can be heated using the heating means 13, and the hot air can be applied to remove moisture from the sheets, improving the air handling effect.

However, as shown in FIG. 10, the air separation effect causes the top sheet S1 on the stack tray 221 to rise to a position higher than the feeding surface detected when the air separation is not working (when there is no air layer between the sheets). In particular, the gap between the top sheet S1 and the next sheet S2 is noticeable in the case of sheets with a large basis weight and high stiffness.

The next waiting sheet S2 to be fed, which is below the top sheet S1, also floats up due to the air handling effect, just like the top sheet S1, but the amount of lift is always unstable. Also, the air handling effect is only exerted on sheets within a certain range from the feeding surface, and sheets outside the range where the air handling effect is exerted do not float up, and the gap between them and sheet S1 becomes large.

As a result, even if an attempt is made to feed sheet S2, which is located outside the range where the air clearance effect cannot be obtained, immediately after sheet S1, which has risen significantly as shown in FIG. 11, is fed, the position of the pickup roller 231 will be significantly lower than the feedable range shown in the figure, increasing the possibility of a malfunction in which the sheet is not fed. As a result, the interval between sheets sent to the image forming device may be distorted, causing a jam. Furthermore, if the stacking tray 221 is not raised appropriately, waiting sheets located below sheet S2 are not given enough time to obtain air clearance, increasing the possibility of double feeding even after the jam is cleared.

To solve this problem, the control unit 203 uses two types of paper surface position control: a method of detecting the actual paper surface, and a method of not detecting the actual paper surface but raising the stack tray 221 after a certain number of sheets have been fed according to the sheet information. The paper surface position control by the control unit 203 will be described in detail below with reference to the flowcharts in Figures 8 and 9.

First, the initial operation will be described with reference to FIG. 8. As already described, the sheet feeding device 1 is configured to be able to be pulled out from the device housing, and when sheets are stored in the sheet storage unit 220 and set in the device housing (storage unit closed), the control unit 203 starts the initial operation of the sheet feeding device 1 using a closing signal from the open/close sensor triggered by the closing (St1).

In the initial operation, the control unit 203 uses the lifter 243 to raise the stacking tray 221, which is lowered to a certain height before the sheet feeding device 1 is pulled out (St2). Then, the control unit 203 raises the stacking tray 221 until the pickup roller 231 comes into contact with the top surface of the sheet and the sheet feed position sensor 231S turns on (St3), and the lifter 243 stops lifting the stacking tray 221 (St4). This completes the initial operation. The sheet feed position sensor 231S is a sensor that turns on when the pickup roller 231 comes into contact with the top surface of the sheet, so in the figures and the flowchart of FIG. 9, the sheet feed position sensor 231S is called the "top surface detection sensor."

The paper feeding operation that starts when a job is input to the image forming system 1000 is described with reference to FIG. 9.

When the sheet feeding operation starts (St10), the control unit 203 acquires sheet information from the control unit 140 of the image forming apparatus 100 (St11). The sheet information includes information on whether air separation is necessary and information on whether the sheet is of a type exceeding a predetermined basis weight (less than 350 g/ ^m2 ). The user inputs information on the necessity of air separation to the control unit 140 in advance by operating the operation panel of the image forming apparatus 100.

Then, when the acquired sheet information indicates that air handling is required ("Y" in St12), the control unit 203 operates the blower means 241 to turn on air handling (St13). Note that when air handling is not required ("N" in St12), the control unit 203 proceeds to the processing of St19 described below.

Next, the control unit 203 judges whether the sheet type is a sheet that does not exceed a predetermined basis weight (St14). Air gets in between the sheets S by air handling, but if the sheet does not exceed the predetermined basis weight, specifically, if the sheet has a basis weight of less than 350 g/ ^m2 , the height of the sheet surface does not shift significantly even if the sheet tries to float up, because it is pressed down by the pickup roller 231. However, if the sheet has a basis weight of 350 g/ ^m2 or more, the pickup roller 231 is pushed up, causing a large shift in the height of the sheet surface.

If the sheet has a basis weight of less than 350 g/m ² ("N" in St14), the control unit 203 starts the sheet feeding operation to the image forming apparatus 100 and drives each conveyance roller to perform the sheet feeding operation (St19).

At this time, if the sheet feed position sensor 241S (upper surface detection sensor) detects the pickup roller 231 ("Y" in St20), it determines whether the required number of sheets has been fed (St23), and if not, returns to the process of St19. Therefore, the sheet feed operation continues until the required number of sheets has been fed. During this time, as the sheets are fed, the sheet surface stored in the stack tray 221 gradually lowers and the pickup roller 231 also gradually lowers. When the sheets leave the sensing range of the sheet feed position sensor 241S, the sheet feed position sensor 241S turns off ("Y" in St20), and the lifter 243 (stack tray 221) is raised to a predetermined height at which the sheet feed position sensor 241S returns to on (St21, St22).

When the control unit 203 determines that the required number of sheets has been fed ("Y" in St23), the sheet feeding operation ends, the rollers stop, and the air blowing for air separation also stops.

On the other hand, the control unit 203 determines that air separation is necessary ("Y" in St12), turns on air separation (St13), and then determines whether the sheet has a predetermined basis weight (350 g/ ^m2 ) or more (St14). If the sheet has a predetermined basis weight or more, it determines from the above-mentioned sheet identification information how many sheets the lifter 243 (stack tray 221) should be raised by a predetermined distance, for example, 1 mm, for each sheet that is conveyed (St15). Then, each conveyance roller is driven to perform a sheet feeding operation to the image forming apparatus 100 (St16).

When the preset number of sheets is fed to the image forming device 100, the control unit 203 drives the lifter 243 to raise the stack tray 221 by 1 mm (St17). Therefore, when air clearance is required and the sheets are equal to or greater than the predetermined basis weight, the control unit 203 controls the lifting operation of the lifter 243 without relying on a detection signal from the sheet feed position sensor 241S.

The control unit 203 determines whether the required number of sheets has been supplied to the image forming device 100 (St18), and if not, returns to the process of St16. Therefore, the sheet feeding operation continues until the required number of sheets has been supplied, and the lifter 243 (loading tray 221) continues to rise each time a predetermined number of sheets are fed until the feeding is completed. When the required number of sheets has been fed ("Y" in St18), the feeding operation ends and the blower fan also stops (St24).

On the other hand, when the sheet information as described above indicates that air handling is not required, the process of St12 judges as "N" and proceeds to process St19, and the amount of lift of the stack tray 221 is controlled while detecting the feeding surface by the sheet feeding position sensor 241S.

In this embodiment, when performing air separation on sheets exceeding a predetermined basis weight (350 g/ ^m2 ), the lifter 243 (loading tray 221) is raised every time a predetermined number of sheets are transported without using the results of paper surface detection, but this operation is effective when applied when the sheet floats up and causes a large gap between the sheet and the next sheet. Therefore, for sheets with a large basis weight, sheets with a coated surface, or sheets that require improved separation performance such as synthetic paper, the air volume may be set stronger than for normal sheets, and the stronger air volume may be used as a trigger to raise the lifter 243 (loading tray 221) every time a predetermined number of sheets are transported to start the operation.

This control does not take into account errors in the thickness of the sheet itself or mechanical variations. This may result in deviation from the actually detected feeding surface, so after a certain number of lifts using this control, the feeding surface may be detected with the air blowing stopped, and then a reset control of the feeding surface may be performed.

The method of acquiring sheet information may be based on information from the main unit, using a pre-installed control table corresponding to the sheet type, or control may be performed by external input.

In this way, in this embodiment, by controlling the movement of the stacking tray 221 using information calculated in advance based on the sheet size and type, it is possible to eliminate instability in the pick-up position and perform stable air handling and paper feeding operations even when air is being blown.

In the above explanation, a sheet feeding device has been described in which air is blown toward the ends of sheets stacked on the stacking tray 221 to float the sheets and separate them, and then the sheets are fed by the pickup roller 231. However, the present invention is not limited to this, and can also be applied to a sheet feeding device in which air is used to float the sheets and separate them one by one, and then the floated top sheet is attracted to a conveyor belt and conveyed. Furthermore, in the above explanation, a sheet feeding device in which air is blown toward the sides of the sheets has been described, but air may also be blown toward the leading or trailing ends of the sheets.

In addition, in this embodiment, the lift amount of the lifter 243 (loading tray 221) is 1 mm at a time, and the amount of lifting is changed by 1 mm for each sheet fed according to the sheet information to accommodate various types of sheets, but it is also possible to increase or decrease the number of times it is lifted and vary the amount of lifting per time to 2 mm or 3 mm, etc. This has the advantage of reducing the number of times the lifter 243 operates in cases where there is relatively little variation in air handling even for sheets with a large basis weight and transport problems are unlikely to occur.

In addition, since the condition of the sheet varies greatly depending on the environment in which the device is installed, the control table may be set taking into account the conditions of the installation environment, such as temperature and humidity.

100 Image forming apparatus 203 Control unit (control means)
210 Sheet feeding device 221 Loading tray (loading means)
231 Pickup roller (sheet removal means)
231S Paper feed position sensor (detection means)
243 Lifter (lifting means)
241 Air blowing means 1000 Image forming system S Sheet S1 Top sheet

Claims (4)

A stacking means for stacking sheets in a predetermined stacking direction;
a sheet removal means for removing a sheet stacked on the stacking means and located at a predetermined removal position in a sheet feeding direction;
a moving means for moving the stacking means upward in the stacking direction so that the sheet reaches the stacking position after the sheet is taken out by the sheet taking-out means;
a blowing unit that blows air from a direction intersecting both the stacking direction and the feeding direction so as to separate the sheets at the removal position;
a detection means for detecting whether the sheet stored in the stacking means is at the removal position;
a basis weight recognition means for recognizing basis weight information of the sheets loaded on the loading means;
A control means for controlling the moving means,
The control means
a control unit for controlling the moving means to position the sheets stored in the stacking means at the removal position when the detection unit detects that the sheets are not at the removal position when the basis weight information recognized by the basis weight recognition unit is less than a predetermined basis weight, and when the basis weight information recognized by the basis weight recognition unit is equal to or greater than a predetermined basis weight, regardless of the detection result by the detection unit, the sheet removal unit removes a predetermined number of sheets that are subjected to air blowing from the air blowing unit, and then controls the moving means to lift a predetermined amount to position the sheets stored in the stacking means at the removal position. the sheet removal means moves in the stacking direction in accordance with the height position of the top sheet stored in the stacking means,
2. The sheet feeding apparatus according to claim 1 , wherein said detection means detects that the sheets stored in said stacking means are not at said take-out position when said sheet take-out means reaches a lower limit of a preset movement range. The sheet feeding device according to claim 2, wherein the control means controls the moving means to position the sheet stored in the stacking means at the removal position when the sheet removal means removes a sheet when the air blowing means stops blowing air. A sheet feeding device according to any one of claims 1 to 3,
an image forming apparatus for forming an image on a sheet fed from the sheet feeding apparatus;
An image forming system comprising:

Images