JPH11246130A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device eliminating generation of a toner stain on paper, having high both-side productivity capable of performing a both-side paper re-feed even without waiting for stack completion of one side, to be provided with a both-side device at a low cost. SOLUTION: This device is provided with a both-side paper feeder feeding one side image formed paper stacked onto a both-surface tray 18 through a reversal part paper discharger 51 to re-feed the paper to an image forming part side through a feed roller 45 brought into contact with a lower surface of the paper. Here, a paper return device 52 is provided, which is formed of a sponge roller, for instance, returning paper discharged onto the both-side tray 18 to a side of a separation feed part 28 in a condition without retaining the paper by a paper retaining member 32, paper returned by the separation feed part 28 is separated to be fed, when at least a sheet of the paper is stacked on the both-side tray 18, the paper can be re-fed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image on a transfer sheet, and more particularly to an image forming apparatus having a double-sided function for forming an image on both sides of a transfer sheet.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus such as a copying machine or a printer has a so-called double-sided function of forming an image on both sides of the same sheet and further synthesizing the image. Image forming apparatuses having such a double-sided function have become common.

FIG. 4 is a diagram showing a schematic configuration of an analog copying machine as an image forming apparatus having such a double-sided function. In this figure, this copying machine is a copying machine body 1
And an automatic double-sided document feeder (hereinafter, referred to as “ADF”) 2 mounted on the upper portion of the main body 1, a paper discharge unit 3 connected to the paper discharge side, and a It is basically composed of a finisher 4 that performs staples and punches. Inside the main body 1, a double-sided tray 1
An image is formed by the image forming device 7 on the upper surface side (one side surface) of the paper P fed from the paper feeding device 15.
After the sheet P is conveyed to the double-sided tray 18 via the branching section 14 for switching to the discharge to the outside, an image is formed by re-feeding the sheet P to the image forming apparatus 7. An image is formed on the other side that is not present, and the image is formed on both sides of one sheet.

[0004] The double-sided tray 18 is disposed below the image forming device 7 which is disposed at a position where an image is formed on the upper surface side of the paper P. The sheet P on which an image is formed on one side and which is turned upside down is sent to the double-sided tray 18 via a branching section 14 provided on the downstream side in the transport direction of the fixing device 13.

The double-sided tray 18 has a re-feeding device 19
And the horizontal transport device 30 is provided, and the paper P is stored in a state where the image forming surface is turned upside down. The accommodated paper P is in the opposite direction to the direction in which it was sent (counter-arrow A direction)
Then, the sheets are separated and fed one by one by the re-feeding device 19 in order from the lowest order, and are fed again to the photosensitive drum 8 side through the lower side of the double-sided tray 18 by the horizontal transfer device 30. Therefore, the sheet re-feeding device 19 is provided on the left side of the double-sided tray 18 in the drawing, and the horizontal transport device 30 is provided below the double-sided tray.

In the apparatus main body 1, a contact glass 5 serving as an exposure section is provided on an upper surface, and a scanning optical system including a light source 6a, a mirror group 6b including first to third mirrors, and a lens 6c is provided below the contact glass 5. Is provided. Below the exposure device 6, a photosensitive drum 8, a charging charger 9, a developing unit 36, a transfer charger 1
1, an image forming apparatus 7 including a cleaning unit 12, a fixing device 13, and the like is provided.

The paper feeder 15 includes four paper feed cassettes 16A to 16D provided below the horizontal conveyor 30 and a manual feed tray 17 provided on the right side of the horizontal conveyor 30 in the drawing. Unused paper (transfer paper) P from one of the trays
Is supplied to the image forming area of the image forming apparatus 7.

In the drawing, a solid line with an arrow indicates a sheet P
The paper P, on which an image is formed on one side by the image forming apparatus 7, is guided by the swingable switching claw of the branch portion 14, and goes straight to the outside during one-sided copying, and is discharged to the outside during two-sided copying. It is guided and stacked on the double-sided tray 18.

Since the ADF 2 is a known one, a detailed description thereof will be omitted. However, a large number of documents stacked on the document set unit 21, a so-called document stack D, are sequentially transferred from the lowest document to a feed roller 22, a transport roller 23, conveyor belt 2
4, the original is sent out onto the contact glass 5 of the exposure device 6 as shown by a solid line with an arrow, and after exposure, the original is sent out in the same direction by a transport belt 24, inverted by an inversion roller 25, and inverted by an ejection roller 26. The document is discharged to the uppermost position of the document stack.

The paper discharge unit 3 includes a paper discharge tray 31 which can be moved up and down to the outside. A number of pairs of transport rollers for transporting the paper inside the paper discharge unit 3 and a paper discharge tray 31 in a direction of the paper discharge tray 31 or a finisher are provided. And a branching claw C for selectively guiding in the direction 4. The finisher 4 includes a paper output tray 41 that can be moved up and down to the outside, and includes therein a number of pairs of transport rollers for transporting the paper, a paper alignment device 42, and a stapler 43.

In the copying machine having such a configuration, the document D placed on the document setting section 21 of the ADF 2 with the image side facing upward is sent out from the bottom, that is, from the last page to the left.
It turns downward, reaches the contact glass 5, and is left still at a predetermined exposure position. Next, the exposure device 6 irradiates the original on the contact glass 5, projects the reflected light onto the photosensitive drum 8 of the image forming device 7, and immediately before that, uniformly charges the photosensitive drum 8 by the charging charger 9. To form an electrostatic latent image on the surface of the substrate. When such an exposure process is completed, the document is re-conveyed, turned upward, and discharged
6 is discharged. In this conventional example, the document is exposed while being fixed. However, there is also a configuration in which the exposure device is fixed and the document is moved to perform exposure.

The electrostatic latent image on the photosensitive drum 8 is developed and visualized by applying toner by a developing unit 36. The visualized image is fed to the paper feeder 1
5, the unused paper P is transferred from one of the paper feed cassettes 16A to 16D and the manual feed tray 17 to the image forming area, that is, the upper surface side of the paper sent to the transfer area by the transfer charger 11, and the fixing device 13 Is heat-fixed.

After the transfer, the toner slightly remaining on the photosensitive drum 8 is cleaned by the cleaning unit 12 to prepare for the next image formation. When the double-sided copy mode for performing double-sided copy is selected, the sheet P having the image fixed on one side is guided to the branching unit 14 and sent to the first reversing device 27 so that the image side faces downward. Is turned over and stacked on the double-sided tray 18. The sheet P stacked on one side (lower surface) of the double-sided tray 18 has been copied, and the sheet P is opposite to the direction in which the sheets P are fed on the double-sided tray 18 by the re-feeding device 19 in order from the lowest stacked sheet. In FIG. 5, sheets are re-fed one by one using the frictional force by the pickup roller 45 shown in FIG. At the time of re-feeding, the uppermost sheet P3 on the double-sided tray 18 is pressed by the pressing member 32 as shown in FIG.
5 ensures that the sheet is re-fed. When two or more fed sheets P are fed out by the feed roller 46 rotating in the direction of arrow E and the separation belt 44 rotating in the direction of arrow F, they are separated into one sheet.

In this manner, the sheet P re-fed by the re-feeding device 19 is turned upside down by the feed roller 46, the separation belt 44, the guide plate 37, and the like, and the image forming surface faces upward. And is conveyed to the horizontal conveying device 30 by the horizontal conveying device 30 in the right direction in the figure. The paper P transported by the horizontal transport rollers is again inverted by the transport rollers 29 and the like, and is again transported to the image forming device 7 with the image forming surface of the paper P facing downward.
In the image forming apparatus 7, an image is transferred to an unimaged surface on the upper surface side, and copy images are formed on both sides of the sheet P.

The sheet P on which images are formed on both sides is guided by the switching claw of the branch portion 14, travels straight to the left in FIG. 4 and is discharged into the sheet discharge unit 3. In the paper discharge unit 3, the turning position of the branch claw is changed according to the selection made by the operator, and the paper P is directly discharged to the paper discharge tray 31.
And the paper is sent into the finisher 4 and the set of sheets is aligned by the sheet aligning device 42 in the page order.
The stapling is performed by the stapler 43.
In the copying machine 1, the branching unit 14, the double-sided tray 18, the re-feeding device 19, the horizontal transporting device 30, and the transporting path related thereto constitute the double-sided paper feeding device 10.

As described above, the double-sided paper feeding device 10 feeds the paper P on which an image is formed on the upper surface side by the image forming device 7 to the double-sided tray 18 via the branching unit 14 with the image surface facing downward. The fed sheet P is fed to the sheet re-feeding device 19.
Paper P in the direction opposite to the direction
The sheet P is separated one by one and re-fed, and the re-fed sheet P is conveyed to the horizontal conveyance device 30 with the sheet P facing upward, and the sheet P is again conveyed with the image face down.
Therefore, each transport system can be arranged in the up-down direction without providing a switchback path for reversing the traveling direction of the sheet, so that the up-down and left-right directions can be made compact. Further, the paper P re-fed from the double-sided tray 18 is separated one by one from the lowermost paper P under the condition that the unimaged surface is less likely to rub against the image surface of the paper P on the stop side. And the paper P is re-fed, so that double-sided copying can be performed without generating a recognized stain on the paper P.

[0017]

However, in the conventional sheet re-feeding device as shown in FIG. 5, when a plurality of sheets P are stacked on the double-sided tray 18, all the sheets to be double-sided copied on the double-sided tray 18 are used. The pressing member 32 cannot be operated until the sheet P has completed the stacking operation.
In F2, even though the preparation of the next document has been completed, the refeeding operation cannot be started immediately. For this reason, a waiting time occurs, and the productivity of the double-sided copying operation cannot be sufficiently increased.

Therefore, for example, in the invention described in Japanese Patent Application Laid-Open No. Hei 5-11537, productivity is improved by shortening the storage time in the double-sided tray and the discharge time after storage.

On the other hand, when the formed toner image is rubbed on the image surface immediately after image formation, the toner is slightly peeled off from the toner image and the toner adheres to the member on the rubbed side. When re-feeding the paper P, depending on how the paper P is handled, the toner peeled off by the rubbing described above may adhere to the adjacent paper, and the attached toner may be recognized as a stain.

Therefore, Japanese Patent Application Laid-Open No. 5-127456 discloses
According to the invention disclosed in Japanese Patent Application Laid-Open No. 9-80984, the sheets are stacked on a double-sided tray so that the image surface faces downward, and the sheet P is fed from the lowermost sheet P so that the image of the adjacent sheet is used. The surface of the paper is prevented from being contaminated to such an extent that human eyes can recognize it.

At this time, the sheets on which the image has been formed on one side of the double-sided tray are re-fed using the frictional force by the pickup roller in order from the lowermost first stacked sheet. The sheet is pressed by the pressing member so that sheet refeeding is performed. During stacking, the pressing member cannot be operated because it interferes with the conveyance. The refeeding operation can be performed only after the stacking of one side is completed. Therefore, it is unavoidable that the waiting time is caused and the productivity is reduced.

As a method in which a holding member is not used so as not to cause a waiting time, a method in which paper is vacuum-conveyed using air is also known. However, since a vacuum device is required, the cost of the device is high. At the same time, there is a problem of noise and a problem that the device itself becomes large.

The present invention has been made in view of such a situation of the prior art, and an object of the present invention is to prevent a sheet from being stained even when an image is formed on both sides and to wait for completion of stacking on one side. An object of the present invention is to provide an image forming apparatus having a low-cost double-sided apparatus capable of performing refeeding of both sides at a high productivity.

[0024]

In order to achieve the above object, a first means is to stack single-sided image-formed sheets fed through a sheet discharging means on a double-sided tray, and to contact the lower surface of the sheets. In an image forming apparatus provided with a double-sided device for re-feeding paper to an image forming unit side via a contacting feed roller, a sheet discharged onto the double-sided tray is moved to a side of a separation / feeding unit without being pressed by a sheet pressing unit. Paper return means for returning paper, the paper returned by the separation / feed means is separated and fed, and if at least one sheet is stacked on a double-sided tray, it can be re-fed. I do.

The second means is a roller according to the first means, wherein the paper return means is a roller having a weak conveying force which comes into contact with the upper surface of the paper and returns the paper until it comes into contact with the nip of the separating and feeding means. It is characterized by.

According to a third aspect, in the second aspect, the roller having a weak conveying force is a sponge roller.

A fourth means is the second means, wherein the sheet return means drives the feed roller in a state where the first sheet is discharged onto the double-sided tray to separate and feed the sheets. And a feed roller drive control means for returning the feed roller until it comes into contact with the nip.

The fifth means is different from the fourth means in that the drive control means makes contact with the second sheet when the second sheet comes into contact with the upper surface of the first sheet. The feed roller is driven while a pressing force is applied to the first sheet by pressure.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

Since the copying machine itself as an image forming apparatus is constructed in the same manner as the above-mentioned conventional example, in the following description, the same reference numerals are given to the same parts as those in the above-mentioned conventional example. Duplicate description will be omitted.

<First Embodiment> FIG. 1 is an enlarged view of a main part of a refeeding device provided in a double-sided device of the analog type copying machine shown in FIG. The return device 52 is composed of a sponge roller, is driven to rotate clockwise by a drive device (not shown), and moves in the vertical direction in the figure by a moving unit that performs a movement drive in response to a control signal from a control device (not shown). The sheet P1 on which image formation on one side has been completed is
After passing through a reversing section discharge device 51 composed of a pair of rollers and dropping on the double-sided tray 18, the paper is conveyed in the direction of the re-feeding device 19 by the return device 52 and formed by the separation belt 44 and the feed roller 44. It is sent to the entrance. As a result, it is possible to perform re-feeding without pressing the sheet by the sheet pressing device 32 in the conventional example. The paper pressing device 32 inhibits the operation only when the paper is re-fed to the double-sided tray 18 while the paper is being stacked, and when the paper is fed again when the paper is not being stacked, the toner is applied to the back surface of the paper P. Since the paper is not rubbed, the paper can be fed again by pressing the paper with the paper pressing device 32 as in the related art.

The return amount of the paper P by the return device 52 is defined by the falling time of the return device 52, in other words, the contact time with the paper P, but is set to be somewhat longer than the actual return distance. . Since the return device 52 is constituted by a sponge roller, when the leading edge of the sheet is returned on the double-sided tray 18 until it reaches the separation feeding unit 28, the feeding force is lost,
Deflection of the paper due to excessive return is naturally prevented. Note that the separation belt 44 may always be stopped, and the sheet P is re-fed with the image side facing down, so that two sheets are double fed and the lowest sheet P1 is Even if friction occurs between the sheet P2 and the next sheet P2, in that case, a part of the toner of the sheet P2 is only slightly dispersed on the back surface (upper side) of the sheet P1 over the entire length in the sheet feeding direction. , Does not result in any perceived dirt.

The return device 52, the feed roller 4
4. Control of each unit such as the sheet re-feeding device 19 and the sheet pressing device 32 is executed by a CPU (not shown) according to a program stored in a ROM (not shown). It should be noted that R that functions as a work area of the CPU for performing the calculation of this execution
It goes without saying that a plurality of sensors for detecting the paper position for calculation by the CPU are provided at predetermined positions.

With this configuration, when a plurality of sheets are stacked on the double-sided tray, if at least one sheet has been stacked, refeeding can be performed, and refeeding can be performed. Since it is not necessary to wait until all the sheets P on which the sheets are to be stacked are completed, the waiting time can be greatly reduced. As a result, the productivity of double-sided copying can be significantly improved.

In a copying machine of the type shown in FIG.
When four size papers are conveyed in the transverse direction, when the number of copies is one, the waiting time is not shortened because it is exactly the same as before, but when the number of copies is two or more, the waiting time is reduced, If the number is four or more, the waiting time becomes zero. For example, comparing the productivity when 10 single-sided originals and 10 double-sided copies are used, the conventional example shown in FIG. 5 has a single-sided copy speed of 82%, whereas the conventional example shown in FIG. With paper feeders, it has reached 97%.

<Second Embodiment> FIG. 2 is an enlarged view of a main part of a refeeding device according to a second embodiment. In this embodiment, in the conventional example shown in FIG. 5, after all sheets P to be re-fed are stacked, the sheet bundle is pressed by the sheet pressing device 32, and then the feed roller 45 is rotated counterclockwise in the drawing. Then, the separation belt 4 is separated from the lowermost sheet P1.
The sheet P, which has been fed into the nip of the feed roller 4 and the feed roller 46 and re-fed, is subjected to double-sided copying on the double-sided tray 18 by the reversing section discharging device 51 composed of a pair of rollers. After dropping an arbitrary number of sheets equal to or smaller than the set,
, An instruction to rotate in the counterclockwise direction is given, and the sheet P1 is conveyed from the lowest sheet P1 to the nip position. Then, the second and third sheets of paper P2, P3, etc.
Are sequentially re-fed. At this time, the sheets on which image formation has been completed on one side are sequentially discharged from the reversing section paper discharge device 51 and stacked on the double-sided tray 18. That is, in this embodiment, double-sided paper feeding is started when a predetermined number of sheets are stacked on the double-sided tray, and double-sided paper feeding and stacking are performed in parallel. Becomes possible.

Other configurations not particularly described are all the same as those of the above-described conventional example, and operate in the same manner.

With this configuration, when the number of copies is two or more, the waiting time is reduced as compared with the conventional apparatus, and the copy productivity can be improved. Further, since the conventional apparatus is dealt with only by the control method without adding a new mechanism, the cost does not increase with respect to the conventional apparatus.

<Third Embodiment> FIG. 3 is an enlarged view of a main part of a sheet re-feeding device according to a third embodiment. In this embodiment, the paper discharging direction of the reversing unit paper discharging device 51 including the pair of rollers of the re-feeding device in the conventional example shown in FIG. 5 or the second embodiment shown in FIG. The paper is discharged onto the double-sided tray 18 by defining it in the 45 direction, and the other configuration is the same as that of the conventional sheet re-feeding device according to the conventional example or the second embodiment, and operates similarly.

In this configuration, the sheet on which the image formation on one side has been completed falls onto the double-sided tray 18 by the reversing section paper ejection device 51. At this time, the already stacked sheets P1 are The paper P2 is nipped and pressed by the leading end thereof, so that refeeding by the feed roller 45 can be started. If refeeding is performed from an arbitrary number of sheets within one set, the same operation as in the above-described second embodiment is performed.

With this configuration, when a plurality of sheets are stacked on the double-sided tray 18, if at least one sheet has been stacked, re-feeding can be performed. Can be greatly reduced, and the productivity of double-sided copying can be significantly improved.

It should be noted that also in this embodiment, the first
As in the first embodiment, when a sheet of A4 size is conveyed in the transverse direction in a copying machine of the type shown in FIG. 2, when the number of copies is one, the waiting time is not shortened because it is completely the same as the conventional case. However, when the number of copies is two or more, the waiting time is reduced, and when the number of copies is four or more, the waiting time becomes zero. For example, 10 single-sided documents, 1 double-sided copy
Comparing the productivity at the zero copy, in the conventional example shown in FIG. 5, it is 82% of the one-sided copy speed, whereas it is 97% in the re-feeding apparatus according to the embodiment of FIG. ing.

Further, in the re-feeding device according to this embodiment, it is not necessary to add the sponge roller 52 and this driving mechanism as in the first embodiment. There is no increase in cost for such a refeeding device.

[0044]

As described above, according to the first aspect of the present invention, there is provided a paper return means for returning the paper fed onto the double-sided tray to the separation feeding means side without being pressed by the paper pressing means. Therefore, it is possible to re-feed the paper without pressing the paper, so that the re-feeding is possible if the stacking of at least one sheet is completed even if the stacking of all the sheets is not completed. As a result, the waiting time for re-feeding can be greatly reduced, and productivity in performing double-sided copying can be significantly improved. Further, since the paper pressing means is not operated, the rubbing of the toner is suppressed, and the generation of toner stain on the paper can be eliminated.

According to the second aspect of the present invention, the paper return means is constituted by a roller having a weak conveying force for contacting the paper from the upper surface and returning the paper before contacting the nip of the branch feeding means. After the sheet abuts, the conveyance force for the sheet is reduced, the bending of the sheet due to excessive return is suppressed, and the sheet can be fed again reliably.

According to the third aspect of the invention, since the sponge roller is used as the roller having a weak conveying force, it is possible to provide an inexpensive material and a low-cost roller suitable for the function of the sheet return means. .

According to the fourth aspect of the present invention, the sheet return means is driven by driving the feed roller in a state where the first sheet is discharged onto the double-sided tray, and the sheet is fed to the nip of the separating / feeding means. Since it is constituted by the drive control means of the feed roller which returns until it comes into contact, the effect of the invention described in claim 1 can be obtained at low cost by using a conventional hardware configuration.

According to the fifth aspect of the present invention, when the second sheet abuts on the upper surface of the first sheet, the first sheet is pressed against the first sheet by the contact pressure of the second sheet. , The feed roller is driven in the state given, so that the return operation can be performed more reliably.

[Brief description of the drawings]

FIG. 1 is an enlarged view of a main part of a refeeding device in an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of a refeeding device in an image forming apparatus according to a second embodiment.

FIG. 3 is an enlarged view of a main part of a refeeding device in an image forming apparatus according to a third embodiment.

FIG. 4 is a configuration diagram showing a schematic configuration of a conventional analog copying machine.

FIG. 5 is an enlarged view of a main part of a conventional sheet re-feeding device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Double-sided paper feeder 18 Double-sided tray 19 Re-feeder 28 Separation feeding part 30 Horizontal conveyance device 45 Feed roller 44 Separation belt 46 Feed roller 51 Reversing part discharge device 52 Returning device (sponge roller)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI G03G 15/00 518 G03G 15/00 518

Claims (5)

[Claims] 1. A double-sided paper feeder in which single-sided image-formed sheets fed through a sheet discharging means are stacked on a double-sided tray, and re-fed to an image forming unit via a feed roller contacting the lower surface of the sheet. An image forming apparatus provided with a paper device, further comprising: paper return means for returning the paper discharged onto the double-sided tray to the separation / feeding means side without being pressed by the paper holding means; An image forming apparatus that separates and feeds the separated sheets and, if at least one sheet is stacked on a double-sided tray, can refeed the sheets. 2. An image according to claim 1, wherein said sheet return means comprises a roller having a weak conveying force which comes into contact with the upper surface of the sheet and returns the sheet until it comes into contact with the nip of said separation / feeding means. Forming equipment. 3. The image forming apparatus according to claim 2, wherein the roller having a weak conveyance force is a sponge roller. 4. The feed roller according to claim 1, wherein the sheet return means drives the feed roller in a state where the first sheet is discharged onto the double-sided tray and returns the sheet until the sheet comes into contact with the nip of the separation / feeding means. 3. The image forming apparatus according to claim 2, further comprising drive control means. 5. The driving control means applies a pressing force to the first sheet by the contact pressure of the second sheet when the second sheet contacts the upper surface of the first sheet. The image forming apparatus according to claim 4, wherein the feed roller is driven in a state where the feed roller is moved.