JP2000327174A - Sheet feeding device and image forming device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve productivity by immediately detecting a non-sheet condition of a sheet loading tray on the way of sheet conveyance and immediately performing processing in a non-sheet condition. SOLUTION: This sheet feeding device is provided with a sheet loading tray 1 to load sheets P, a sheet feeding means 2 for sequentially feeding the sheets P loaded on the sheet loading tray 1, a detecting means 3 for detecting the presence or absence of the sheet P at the position near the rear end in the sheet feeding direction of the sheet P loaded on the sheet loading tray 1, and a control means 4 for performing processing in a non-sheet condition on the basis of the detected result of a non-sheet condition, obtained by the detecting means 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding apparatus for feeding sheets stacked on a sheet feeding tray, and an image forming apparatus such as a printer, a copying machine, and a facsimile using the sheet feeding apparatus.

[0002]

2. Description of the Related Art In an image forming apparatus such as a printer, a copying machine, a facsimile, etc., in order to output an image formed by an image forming unit using an electrophotographic method, generally,
Sheets (paper) that are recording materials such as paper and OHP sheets
And a sheet supply device that feeds out the sheets one by one from the paper feed tray and the paper feed cassette and supplies the sheets to the image forming unit. In recent years, image processing technology in this image forming unit has advanced, and while it is possible to form a large amount of images in a short time, there is a demand for improving the productivity by increasing the conveying speed of sheets stacked on a sheet feed tray or a sheet feed cassette. Is getting stronger.

[0003] Here, after a user (operator) stacks the sheets on the large-capacity paper feed tray or the like, in order to stably supply the sheets, the stacked sheets are lifted to a certain height. In general, a sheet feeding method of feeding one sheet at a time from the upper surface of the sheet at the lifted position is used. In order to lift the sheet, an elevator tray system that raises the bottom plate on which the sheet is loaded in parallel or a lever system that raises the other end with one end as the center of rotation is adopted, and a draw-in roll ( Nadger Roll)
(Height), and it is necessary to keep the pressure of the nager roll against the sheet almost constant. That is, in these sheet feeding apparatuses, it is necessary to provide a sheet height detection mechanism for detecting the height of the sheet in addition to the sheet presence / absence detection mechanism for detecting the presence / absence of a sheet, which is a prerequisite.

[0004] As a prior art provided with the sheet presence / absence detection mechanism and the sheet height detection mechanism, for example, Japanese Patent Laid-Open No. 5-21 is disclosed.
No. 3,483, JP-A-5-221553, JP-B-6-30753, JP-A-7-172624, and the like. In Japanese Patent Application Laid-Open No. Hei 5-213483,
Although the bottom plate does not move upward, a technique is disclosed in which the pickup roller rotates with the lowering of the sheet take-out position to detect the remaining amount of the sheet and indicates that the sheet is out. Japanese Patent Application Laid-Open No. Hei 5-221553 discloses that a rotatable cassette is pushed up once by a push-up member, and the presence or absence of a sheet is determined based on a state in which a take-out means provided at an upper portion is displaced by pushing up the cassette. A technique for detecting the Further, Japanese Utility Model Publication No. 6-30753 discloses a technique in which the detection of the height of the sheet and the detection of the out-of-sheet at the uppermost position of the sheet are shared by a single detection mechanism, thereby simplifying the configuration. I have. Further, Japanese Patent Application Laid-Open No. 7-172624 discloses a technique for detecting the absence of a sheet and the height of a sheet ascending according to the position of an arm having a lever structure provided above a sheet feeding tray.

[0005]

However, according to the technique disclosed in Japanese Patent Application Laid-Open No. Hei 5-213483, it is possible to detect the remaining amount of sheets in the middle of conveying a sheet. It is difficult to apply to quantity detection. Further, it is possible to recognize that the number of sheets is equal to or less than a predetermined amount, but the recognition accuracy is low. Further, it is not possible to recognize when the sheet has run out, and the tray switching is in a state where the remaining amount is present, which is not preferable as a specification of the apparatus. According to the technique disclosed in Japanese Patent Application Laid-Open No. Hei 5-221553, it is possible to detect the presence or absence of a sheet during the initial operation and during sheet conveyance by the bottom plate raising mechanism. Since the recognition is performed by dropping the pickup roller at the tip of the tray, the recognition of the absence of the sheet during the sheet conveyance is delayed.

Further, in the technique disclosed in Japanese Utility Model Publication No. 6-30753, the sheet detecting mechanism can be simplified, but it is intended to detect the height of the sheet and the out of sheet with one sensor. In addition, the position of the sensor needs to be installed on the downstream side in the sheet conveying direction, and the recognition of the absence of the sheet during the sheet conveyance is delayed similarly to the above-mentioned Japanese Patent Application Laid-Open No. 5-221553, and the image on the downstream side is Stopping the image formation in the forming unit is delayed, and there is a possibility that a trouble such as a stain may occur in the transfer unit that transfers the image to the sheet. Further, the technique disclosed in Japanese Patent Application Laid-Open No. 7-172624 is very excellent in that it is possible to detect the absence of a sheet and the height of rising of the sheet by a simple mechanism. In the same way as above, it is recognized that the sheet has run out in conjunction with the movement of the pickup roller, and the recognition of the absence of the sheet during the sheet conveyance is delayed, the sheet interval for printing is increased, and the productivity is reduced. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above technical problems, and is a sheet supply apparatus and an image using the same, which can quickly recognize the absence of a sheet during sheet supply. The present invention relates to a forming apparatus.

[0008]

That is, as shown in FIG. 1, a sheet feeding apparatus according to the present invention sequentially includes a sheet stacking tray 1 for stacking sheets P and sheets P stacked on the sheet stacking tray 1. Sheet feeding means 2 for feeding, detecting means 3 for detecting the presence or absence of a sheet P at a position near the rear end of the sheet P stacked on the sheet stacking tray 1 in the sheet feeding direction, and detecting the absence of a sheet by the detecting means 3 Control means 4 for executing a process when there is no sheet based on the result.

The position near the rear end in the sheet feeding direction, which is the position of the detecting means 3, is changed to the sheet-free state as soon as possible in order to secure the time necessary for the control means 4 to execute the processing when there is no sheet. Any position that can be detected is preferable, and need not be the complete edge of the sheet. Further, in consideration of the state in which the sheet is temporarily held by the sheet separating unit 7 described later, it is preferable that the distance can be detected from the sheet separating unit to the rear end of the sheet.

The processing when the sheet is absent by the control means 4 includes not only stopping the image forming processing by the image forming unit and displaying the sheet absent state on a control panel or the like, but also
As described later, there is a case where a sheet stacking tray different from the currently used sheet stacking tray is selected, and the sheet P is continuously supplied from the selected sheet stacking tray.

The sheet stacking tray 1 holds the sheets P at the rear end in the sheet supply direction of the sheets P to be stacked.
And an end guide 5 for positioning the
If the configuration is such that the presence or absence of the sheet P is detected based on the sensor attached to the end guide 5, the presence or absence of the sheet P can be detected quickly at a position near the rear end of the sheet feeding direction. Image formation can be stopped at an early stage, and problems such as contamination at the transfer portion can be prevented. The position of the end guide 5 is not limited, and if the end guide 5 is provided on the bottom plate 8 and rises following the rise of the bottom plate 8, the endless state of the sheet can be detected almost accurately. It is preferred in that respect.

Further, the sheet supply means 2 includes a sheet drawing unit 6 for supplying the sheet P from the upper surface of the stacked sheets P.
A sheet separating unit 7 provided downstream of the sheet pull-in unit 6 for separating the supplied sheet P;
Is characterized in that the presence or absence of the sheet P is detected by a sheet detection unit disposed at a position where the sheet P can be detected when the sheet P reaches the sheet separating unit 7. Even when a plurality of sheets P have been supplied in advance, it is possible to recognize no paper as soon as all the sheets P have been supplied from the sheet separating unit 7.

At this time, for example, a sheet detecting unit is provided on the bottom plate 8 so that the sheet P
Can be detected, even if the front end of the sheet P in the sheet feeding direction is in a floating state, the rear end is in contact with the bottom plate 8 due to the gravity of the sheet P, and the presence or absence of the sheet P can be accurately determined. It is preferable in that it can be detected.

Still further, the processing when there is no sheet executed by the control means 4 is to select a sheet stacking tray different from the sheet stacking tray 1.
Can quickly control the sheet P to be fed from another sheet stacking tray after recognizing no paper, avoiding the problem of reducing the sheet feeding productivity without skipping the sheet interval. can do.

Further, the image forming apparatus of the present invention comprises a sheet conveying means for conveying a sheet supplied from the sheet supplying apparatus, and an image forming means for forming an image on the sheet conveyed by the sheet conveying means. When the sheet feeding apparatus of the present invention is used in an image forming apparatus, it is possible to quickly recognize the no-paper state of the sheet feeding apparatus, and to quickly stop image formation in the image forming unit at the time of no-paper. Further, it is possible to prevent troubles such as contamination in the transfer section.

Next, the operation of the above technical means will be described. When a user (user) stacks the sheets P on the sheet stacking tray 1 and sets the end guide 5, the detecting means 3 provided on the end guide 5 detects the sheet P and outputs it to the control means 4. . The control means 4 instructs the driving of the bottom plate raising mechanism 9 to raise the bottom plate 8, and the sheet supply means 2 carries out the sheet P on the upper surface thereof in order to the downstream image forming means. Thereafter, when the supply of the last sheet P is started by the sheet supply means 2, the sheet detection unit by the detection means 3
The sheet P no longer exists at the (sensor position), and the detecting means 3 detects a state in which the sheet P has disappeared, and outputs no paper to the control means 4. Here, since the detecting means 3 is located near the rear end of the sheet feeding direction, many surfaces of the last sheet P are still in the sheet stacking tray at the stage of outputting no paper to the control means 4. The control unit 4 can instruct the execution of the process when there is no sheet based on the no-paper output from the detection unit 3. In other words, the apparatus can execute the process when there is no sheet before the sheet P exits from the sheet stacking tray 1 and, if the process when there is no sheet is switching the tray, continuously without skipping the sheet interval. Sheet can be transported, and
The formation of an image by the image forming means can be stopped promptly, and it becomes possible to prevent the transfer portion from being stained.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the accompanying drawings. FIG. 2 shows an embodiment of an image forming apparatus to which the present invention is applied. The image forming apparatus 21 includes an apparatus main body 22 that forms an image on a sheet (paper) P, and an image reading apparatus (IIT) that reads a document image.
23. The apparatus main body 22 has an image forming unit 24 for directly forming an image on a sheet P. In the figure, reference numeral 25 denotes a photosensitive drum, and 26 denotes a signal output from an image processing device (IPS) 29. Exposure device for forming an electrostatic latent image on photoreceptor drum 25 based on
Reference numeral 7 denotes a developing device for visualizing the electrostatic latent image formed on the photosensitive drum 25 with a developer such as toner, and 30 denotes a toner unfixed on the paper P by a transfer roll facing the photosensitive drum 25. A transfer device for transferring an image, 31 is a transfer device 3
This is a fixing device for fixing an unfixed toner image formed on the paper P by a pressure of 0. A heating roll and a pressure roll are brought into contact with an appropriate pressure, and the paper P is passed between the rolls and fixed. In the present embodiment, the photosensitive drum 25 and the developing device 27 are integrated into a cartridge 28 that can be attached to and detached from the device main body 22, and the cartridge 28 also serves as a tank for storing the developer. The developer is supplied to the photosensitive drum 25 via the developing roll 27a. Also, an image processing device (IPS) 2
Reference numeral 9 denotes conversion into image information that can be formed by the apparatus main body 22 based on image information output from the IIT 23 as an electronic copier and as image data from an external apparatus as a printer or a facsimile. ing. Further, the control unit 69
Controls the movement of each component of the apparatus body 22,
In response to signals from sensors and the like provided at various places in the apparatus main body 22, control is performed to convey the sheet P by controlling an actuator and the like.

The apparatus main body 22 is provided with a plurality of paper feed trays 32 for accommodating paper P by size or by paper feed direction, which are detachably provided in upper and lower stages. In these paper feed trays 32, a large number of papers P are stacked and stored on a bottom plate 33 provided therein.
2 can be inserted and pulled out from the front side (the front surface shown in FIG. 2) via the rail 50. When a tray-in sensor (not shown) detects that the paper feed tray 32 has been inserted into the apparatus main body 22, the paper feed tray 3
2, the upper surface of the sheet P comes into contact with a later-described nudger roll 35, and the lift of the bottom plate 33 is stopped after the sheet P lifts the nudger roll 35.

Further, a large-capacity paper feed tray (HCF) 70 is provided at the bottom of the apparatus main body 22. The large-capacity paper tray 70 is supported by a pair of rails 71 and is configured to be able to be pulled out or mounted from the apparatus main body 22.
The pull-out and mounting operations are detected by a tray-in sensor (not shown). A bottom plate (lifting table) 72 on which the sheets P are stacked and which can move up and down is arranged on the large-capacity sheet feeding tray 70, and the bottom plate 72 is pulled up by a winding shaft 75 via a pulley 74 by a wire 73. . The hoisting shaft 75 is rotated by a lift-up motor (not shown), and is connected to a brake (not shown). Here, the large capacity paper feed tray 70
Is set in the apparatus main body 22, upon receiving a signal from the control unit 69, the hoisting shaft 75 is rotated by the lift-up motor, the wire 73 is wound, and the bottom plate 72 is raised. On the other hand, when the large-capacity paper tray 70 is pulled out, the coupling between the lift-up motor and the hoisting shaft 75 is released, and the bottom plate 72 falls naturally. ing.

Each of the paper feed trays 32 is provided in the apparatus main body 22.
And the stacked paper P for the large-capacity paper tray 70.
The paper feed rolls 34 for feeding the paper P toward the image forming unit 24 are provided one by one from the upper surface of the paper feed roll.
In the present embodiment, a common paper feed roll group 34 is used for each paper feed tray 32 and large-capacity paper feed tray 70, and the cost is reduced by common use. These paper feed roll groups 34 are provided for the stacked sheets P lifted by raising the bottom plate 33 of the paper feed tray 32 and raising the bottom plate 72 of the large capacity paper tray 70.
Nager rolls (N
udger roll) 35 and nadger roll 35
A feed roll (Feed Roll) 36 and a retard roll (Retard Roll) 37, each of which is composed of a pair of rolls, for separating the paper P taken out of the printer.

A paper transport path 38 is formed on the left side of the apparatus main body 22 downstream of the feed roll 36 and the retard roll 37, and has a plurality of transport rolls 39 disposed therein. . The paper P supplied from the large-capacity paper feed tray 70 at the bottom is conveyed along the entire length of the paper conveyance path 38, and the paper P supplied from the paper supply tray 32 at the top is supplied to the middle of the paper conveyance path 38. The sheets are merged and conveyed to the image forming unit 24. This image forming unit 2
4, a registration roll 40 is provided. The conveyance posture and the conveyance timing of the paper P are matched, and the image forming unit 24 is controlled based on an instruction from the control unit 69.
Sent to. The sheet P on which an image is formed on the first surface after passing through the fixing device 31 via the image forming unit 24.
In the case of single-sided printing, the image is discharged onto the discharge tray 42 formed on the upper surface of the apparatus main body 22 by the first discharge roll 41 with the first surface on which the image is formed facing downward. In the case of double-sided printing, the paper P is once sent to the paper output tray 42 side, and when the rear end of the paper P reaches the position where the paper P is held by the first paper output roll 41, the gate is controlled by the instruction of the control unit 69. 43
At the same time, the first paper discharge roll 41 is reversed, the paper P is reversed with the end, which has been the rear end of the paper P, as the front end, and the automatic double-sided unit 45 from the second paper discharge roll 44 Sent to

This automatic double-sided unit 45 is
The outer shell is constituted by a relatively thin casing having a depth slightly smaller than 2, the support unit 47 of the manual feed tray 46 is fixed to the apparatus main body 22, and the automatic duplex unit 45 is located at the lower end. Are hingedly connected to the support unit 47, and the upper side is a free end, which is configured to be openable and closable with respect to the apparatus main body 22. Further, a circulating transport path 48 for double-sided printing is provided in the automatic duplex unit 45, and a plurality of transport rolls 49 are provided in the circulating transport path 48. The circulating transport path 48 is connected to a paper transport path of the apparatus main body 22, and has an opening at one end facing the second paper discharge roll 44 and an opening at the other end at the paper transport path 38.
Is opposed to the upper end. First side for double-sided printing
The paper P on which the (front side) is printed is sent from the second paper discharge roll 44 to the circulation transport path 48, transported downward by the transport roll 49, and supplied again to the paper transport path 38 of the apparatus main body 22. Thereafter, the conveyance timing is adjusted by the registration roll 40, and the second
An image is formed on the surface (back surface). Then, after the second surface is fixed via the fixing device 31, the sheet is discharged onto the sheet discharge tray 42 with the second surface facing downward.

Next, the paper feed tray 32 will be described in detail with reference to FIG. FIG. 3 shows the paper feed tray 32 in a perspective view. Bottom plate 3 in paper feed tray 32
3, a hinge mechanism 51 is provided near the end on the opposite side to the sheet feeding direction, and the sheet P is configured to be stacked thereon;
The sheet feeding tray 32 is hingedly connected to both side surfaces of the sheet feeding tray 32 so that the sheet feeding direction of the bottom plate 33 is rotatable. The sheet feeding direction side of the bottom plate 33 is raised by the operation of the lift lever 53 via the joint 54 by the rotation of the lift-up motor 55, and the conveying direction side of the sheet P is raised. It comes in contact with. Further, the bottom plate 33 is provided with an end guide 52 that presses and positions the sheet P from the rear end (upstream side in the sheet transport direction) of the stacked sheet P. The end guide 52 is configured to be movable in the sheet conveying direction, and can change its position according to the size of the sheet P.

Further, the end guide 52 is provided with a no-paper sensor 56 composed of a reflection type sensor, and detects the presence of the paper P stacked on the bottom plate 33 from below. Further, the apparatus main body 22 is provided with a size sensor 57 for detecting the size and the storing direction of the paper P stored in each paper feed tray, and detecting the size of the paper P raised by the bottom plate 33. The size information is output to the user of the apparatus by using, for example, a control panel (not shown).

FIG. 4 is an explanatory diagram showing each structure of the paper feed tray 32 and the paper feed roll group 34. Paper tray 3
In the paper feed roll group 34 provided above the roller 2, the nager roll 35, the feed roll 36, and the retard roll 37 are rolls having the same shape and the same size as each other, and both ends in the axial direction are made of rubber or the like on the surface. The elastic member has a slightly larger diameter than the central portion, and these large-diameter portions come into contact with the sheet P to carry out the transport operation of the sheet P. The nager roll 35 is cantilevered by an arm 60 that rotates about the axis of the feed roll 36. The feed roll 36 is connected to a drive gear (not shown) via a feed clutch via a feed clutch (not shown), and feeds the paper P via a feed roll shaft in a connected state of the feed clutch. Rotate forward. Further, the nager roll 35 has a gear (not shown) fixed to its shaft.
It is configured to rotate with the feed roll via this gear. Also, at this time, the Nadger roll 35
With the rotation of the shaft in the forward direction, the rotation of the arm 60 with the axis of the feed roll 36 as the rotation axis rotates in the direction of pressing the surface of the sheet P.

The retard roll 37 is rotatably supported via a supporter 61 about the axis of the transport roll 39 as a center of rotation, and the pressure of the retard roll 37 increases as the feed roll 36 rotates. Is configured. Further, a torque limiter (not shown) is provided on the shaft of the retard roll 37. When the paper P is not present, the feed roll 36 overcomes the limit force of the torque limiter because the frictional force (μ) is large when the paper P is not present. When two or more sheets P are conveyed, they rotate in the direction opposite to the sheet feeding direction by the torque limiter because the frictional force (μ) between the sheets is small, and as a result,
The feed roll 36 and the retard roll 37 have a function of blocking the second and subsequent sheets P that have been double fed, and consequently separating the sheets P one by one and transporting them downstream.

In the present embodiment, the paperless sensor 56 provided on the end guide 52 as described above
Although the presence or absence of the sheet P is detected from below the stacked sheets P, the position of the no-paper sensor 56 is separated from the surface of the end guide 52 pressing the sheet P by a distance d as shown in FIG. It is arranged. The dimension d is set slightly longer than the dimension from the leading end position of the sheet P in the sheet supply direction to the nip position between the feed roll 36 and the retard roll 37. By arranging the sheet P with a margin from the rear end position by the dimension d in this way, a plurality of sheets P are collectively pulled up by the nudger roll 35, and are sequentially held by the feed roll 36 and the retard roll 37. Even in a state where the paper is unwound, the paper P can be detected, and incorrect recognition of no paper can be prevented. Further, in the present embodiment, the no-paper sensor 56 is arranged on the bottom plate 33 side, which is the bottom of the end guide 52, and detects from below the paper P.
Thus, even when a plurality of sheets of paper P are nipped by the feed roll 36 and the retard roll 37 and the leading ends thereof are lifted, the trailing ends thereof are in contact with the bottom plate 33 and the paperless sensor 56 almost completely ensures the sheet. P
Can be detected.

On the upper side of the paper feed tray 32, the paper P
Control sensor 59 for detecting the upper surface position of
have. The face control sensor 59 is formed in a U-shape so that the end of the arm 60 can pass therethrough.
The bottom plate 33 is raised by the operation of the lift lever 53 to raise the transport direction side of the paper P, so that the upper surface of the paper P pushes up the nadger roll 35 and the end of the arm 60 passes through the sensor unit, so that the paper is It is detected that P has reached the upper surface position. That is, the face control sensor 59 is turned ON /
It is configured to detect the sheet height by turning it off.

FIG. 5 is a perspective view showing a state in which the large-capacity sheet feeding tray 70 is viewed from the rear side of the apparatus (the side opposite to the tray drawing direction). As described above, the bottom plate 72 of the large-capacity paper feed tray 70 can be supplied with the paper P by being pulled up by the winding shaft 75 via the pulley 74 by the wire 73. Although not shown in FIG. 5, a mechanism similar to the paper feed roll group 34 shown in FIG. 4 is provided above the large capacity paper feed tray 70 so that the upper surface of the paper P is A face control sensor 59 is provided for detecting the up and down movement. Further, a paperless sensor 77 is provided near the rear end of the bottom plate 72 on which the paper P is loaded in the paper transport direction. The position where the paperless sensor 77 is disposed is a position where the presence of the paper P can be detected even when the leading end of the paper P is sandwiched between the feed roll 36 and the retard roll 37 serving as a separation unit of the paper feed roll group 34. If a guide is provided, it may be provided at the end guide. In the present embodiment, however, the minimum width of the stackable paper P, that is, the expected minimum width in the paper transport direction (A4 size: 297 mm × 210 mm)
Considering the position that can be detected at 210 mm),
It is formed on the bottom plate 72. If the position of the no-paper sensor 77 can be changed according to the size of the paper P, it is possible to more quickly recognize the no-paper.

Next, the supply operation of the sheet P in the present embodiment will be described with reference to FIGS. For example,
When "no paper" is displayed from a control panel (not shown), the user (user) pulls out the paper feed tray 32 from the apparatus main body 22 and carries out the work of loading paper P on the bottom plate 33 of the paper feed tray 32. . At this time, after the sheets P are stacked, the positioning is performed by the end guide 52, and when the sheet feeding tray 32 is set by the user, the no-paper sensor 56 detects the sheets P, and the information is transmitted to the control unit of the apparatus main body 22. 69 recognizes, and the control unit 69 operates the lift-up motor 55 to
3 raises the bottom plate 33. Then, the sheet P pushes up the nudger roll 35, and the movement of the arm 60 recognizes that the sheet P is present at the transport position where the face control sensor 59 is normal, and the controller 69 stops raising the bottom plate 33.

In this manner, the paper P which has risen to the normal position is lifted from the upper surface by the nudger roll 35, separated by the feed roll 36 and the retard roll 37 as sheet separation units, and moved downstream by each sheet. Conveyed. Thereafter, when a predetermined number of sheets are conveyed, the nager roll 35 falls down, and the pressure required for pulling up the paper P cannot be obtained. This state is recognized by the face control sensor 59 by the downward movement of the arm 60, and the control unit 69
Moves the lift-up motor 55 and raises the bottom plate 33 by the lift lever 53. By repeating this operation, the paper P is conveyed in order, and when the last sheet starts to be conveyed, the sensor state of the no-paper sensor 56 immediately changes. Upon receiving the detection information from the no-paper sensor 56, the control unit 69 instructs to switch the supply to another paper feed tray if another paper feed tray in which paper of the same size exists exists. As a result, the paper feeding operation in the middle of the job can be smoothly continued, and continuous paper can be supplied without skipping the paper interval. If there is no other paper feed tray containing paper of the same size, the image processing unit 24 immediately performs image processing to be performed on the next paper following the last paper P. Instructs to stop. As a result, it is possible to prevent the toner from adhering to the photosensitive drum 25 in a state where no paper is present, and it is possible to prevent toner contamination in the transfer device 30 beforehand. In addition, the control unit 69 receives this detection information and also displays "no paper" on the control panel.

In this embodiment, the position of the no-paper sensor 56 is such that the sheet P can be detected even when the sheet P is sandwiched by the feed roll 36 and the retard roll 37 serving as a sheet separating section. is there. Therefore, in a state where the number of sheets of paper P is reduced,
Thus, even when a plurality of sheets of paper P are pulled up and held by the feed roll 36 and the retard roll 37 and are on standby, the supply operation is continued as it is. In particular, even when the leading end of the paper P is pulled up, the paper P is still in contact with the bottom plate 33 at a position near the no-paper sensor 56, and the no-paper sensor 56 can continuously detect the paper P. it can. Thereafter, when the last sheet is separated and conveyed by the sheet separating unit and conveyed, "no paper" is output by the no-paper sensor 56 for the first time, and the control unit 69 instructs execution of the above-described no-paper processing. .

Further, the sheets P stacked on the large-capacity sheet feeding tray 70 are similarly controlled. In the large-capacity paper feed tray 70 in the present embodiment, an end guide in the paper transport direction is not provided in order to improve the operability of the user during paper setting. A no-paper sensor 77 is provided at a position where the presence of the paper P can be detected even when the paper P is stopped at the separating section. Therefore, similarly to the above-described sheet feeding from the sheet feeding tray 32, when the last sheet is fed from the separation unit, "no paper" is output by the no-paper sensor 77, and the process at the time of no paper is performed. It is performed smoothly.

As described above, according to the present embodiment, the no-paper sensor 56 provided on the end guide 52 and
Since the "no paper" state is recognized by the no paper sensor 77 provided near the rear end of the bottom plate 72 in the paper transport direction, the paper P is discharged from each paper tray by detecting the no paper in each paper tray. Before it is detected. Therefore, in the case of a continuous job operation or the like, it is possible to switch the sheet feeding tray without skipping the sheet interval, and the productivity is not reduced. Further, image formation can be stopped promptly, and toner contamination near the transfer device 30 can be avoided. Also, no paper sensors 56 and 77
Is located at a position where the sheet P can be detected even when the sheet P is sandwiched by the sheet handling section.
Even when a plurality of sheets of paper P are previously pulled up by the nudger roll 35 when the number of sheets of paper P is low, it is possible to recognize the sheet of paper P, and it is possible to recognize an accurate "no paper" state.

In the present embodiment, a single no-paper sensor is disposed in each paper feed tray. However, a plurality of no-paper sensors having a predetermined interval in the paper supply direction are disposed on the bottom plate. It is also possible to adopt a configuration in which no paper is recognized immediately at the rear end of the paper P. With this configuration, even when the end guide does not exist or the end guide is not correctly fixed, it is possible to more accurately recognize the “paper out” state of the stacked paper P. .

[0036]

As described above, according to the present invention,
It is possible to quickly detect the absence of a sheet on the sheet stacking tray during sheet conveyance, and it is possible to immediately execute processing when there is no sheet.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an outline of an apparatus according to the present invention.

FIG. 2 is an explanatory diagram illustrating an outline of the image forming apparatus according to the first embodiment;

FIG. 3 is a perspective view illustrating a sheet feed tray according to the embodiment.

FIG. 4 is an explanatory diagram showing each structure of a paper feed tray and a paper feed roll group in the present embodiment.

FIG. 5 is a perspective view for explaining a large-capacity sheet feeding tray according to the embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sheet loading tray, 2 ... Sheet supply means, 3 ... Detection means, 4 ... Control means, 5 ... End guide, 6 ... Sheet retracting section, 7 ... Sheet separating section, 8 ... Bottom plate, 9 ... Bottom plate raising mechanism 21 image forming apparatus, 22 apparatus main body, 23 image reading apparatus (IIT), 24 image forming section, 25 photosensitive drum, 26 laser exposure apparatus, 2
7: developing device, 28: cartridge, 29: image processing device (IPS), 30: transfer device, 31: fixing device, 32 ...
Paper feed tray, 33: bottom plate, 34: paper feed roll group, 35: nadger roll, 36: feed roll, 3
7: retard roll, 38: paper transport path, 39: transport roll, 40: registration roll, 4
DESCRIPTION OF SYMBOLS 1 ... 1st paper discharge roll, 42 ... paper discharge tray, 50 ... rail, 51 ... hinge mechanism, 52 ... end guide, 53 ... lift lever, 54 ... joint, 55 ... lift-up motor, 56 ... no paper sensor, 57: Size sensor, 59: Face control sensor, 60: Arm, 61: Supporter, 70: Large capacity paper tray, 71:
Rail, 72 ... Bottom plate, 73 ... Wire, 74 ...
Pulley, 75: Hoisting shaft, 77: No paper sensor, P: Sheet (paper).

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasutaka Komatsu 2274 Hongo, Ebina-shi, Kanagawa F-term in Fuji Xerox Co., Ltd. (reference) 3F048 AA02 AA04 AB01 BA02 BB02 CB03 CB05 CB15 CC04 3F343 FA02 FA09 FB02 FB03 FB04 FC01 GA03 GB01 GC01 GD01 HA14 HA33 HA37 HB03 HD18 HE08 HE20 HE27 JA01 JD03 JD09 MA03 MA10 MA23 MB03 MB10 MC20 MC21

Claims (5)

[Claims] 1. A sheet stacking tray for stacking sheets, sheet feeding means for sequentially feeding sheets stacked on the sheet stacking tray, and a position near a rear end of a sheet stacked on the sheet stacking tray in a sheet feeding direction. And a control unit for executing a process when there is no sheet based on a detection result of the absence of a sheet by the detection unit. 2. The sheet stacking tray includes an end guide that positions the sheet to be stacked at a rear end in a sheet supply direction of the sheet to be stacked, and the detecting unit detects the sheet based on a sensor attached to the end guide. 2. The sheet feeding apparatus according to claim 1, wherein the presence / absence of the sheet is detected. 3. The sheet supply means includes: a sheet retraction unit that supplies a sheet from an upper surface of a stacked sheet; and a sheet release unit that is provided downstream of the sheet retraction unit and that separates the supplied sheet. 2. The sheet feeding apparatus according to claim 1, wherein the detecting unit detects the presence or absence of the sheet by a sheet detecting unit disposed at a position where the sheet can be detected when the sheet reaches the sheet separating unit. . 4. The sheet supply apparatus according to claim 1, wherein the process when there is no sheet executed by the control unit selects a sheet stacking tray different from the sheet stacking tray. 5. A sheet conveying means for conveying a sheet supplied from the sheet feeding apparatus according to claim 1, and an image forming apparatus for forming an image on the sheet conveyed by said sheet conveying means. And an image forming apparatus.