JP2003146485A - Sheet feeder and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet feeder certainly correcting skew of a sheet having a non-rectangular shape represented by tab paper, and to provide an image forming device with it. SOLUTION: This image forming device typically comprises a skew detection means detecting the skew of the sheet; a skew correction means comprising two or more carrying roller pairs with variable carrying speed which are disposed on this side and on the inner side in a sheet carrying direction; and a skew amount calculation means correcting information from the skew detection means on the basis of sheet shape information to find a skew amount. The skew correction means corrects the skew of the sheet on the basis of the corrected skew amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying apparatus for correcting skew in an image forming apparatus for forming an image on a sheet, and an image forming apparatus including the sheet conveying apparatus.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus for forming an image on a sheet, when the conveyed sheet is skewed, the image is formed in a state of being relatively inclined with respect to the sheet. Therefore, various means are used to correct the skew of the conveyed sheet.

For example, a pair of registration rollers disposed on the upstream side of the image forming section in the sheet conveying direction is stopped, and a sheet separated and fed from the sheet stacking section is abutted against the nip to form a loop. Due to this, a configuration for correcting skew is often used. Further, a plurality of shutter members capable of projecting and comparing in the sheet transport path are provided on the upstream side of the pair of transport rollers, and the skew is corrected by bringing the leading edge of the sheet into contact with the projecting shutter member. A configuration is also used in which the skew is corrected by retracting. In either case, the skew of the sheet is corrected by the tip of the sheet following the nip of the pair of registration rollers or the shutter member depending on the waist of the sheet.

In addition to the above-mentioned structure, two or more pairs of conveying rollers having variable conveying speeds are provided on the front side and the rear side (left and right sides) in the sheet conveying direction, and both sides are conveyed in accordance with the skew amount of the sheet. There is a configuration in which the speed of the roller is controlled and the skew of the sheet is corrected.

[0005]

However, in recent years, the demand for image formation on various sheets is increasing, and it is always desired to pass non-rectangular sheets such as tab sheets to the image forming apparatus. . Here, the tab paper is
This refers to a sheet with tabs on the edges for entering headings for the purpose of classification. However, the position of the tab portion is not fixed, and the tab portion is provided in a plurality of stages so that it is cheap to check the headline and the like written on the tab portion.

The conventional skew correcting means may not always work effectively for such a sheet having a non-rectangular shape. That is, when the tab portion is fed as the leading end in the conveying direction, it is difficult to correct the skew feeding by the registration roller pair,
When the tab portion is fed as the side surface in the transport direction, it is difficult to correct the skew feeding by the shutter member.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a sheet transporting device capable of surely correcting skew of a non-rectangular sheet represented by a tab sheet, and an image forming apparatus including the sheet transporting device.

[0008]

In order to solve the above-mentioned problems, a typical structure of an image forming apparatus according to the present invention is a skew detecting means for detecting skew of a sheet and a front side in the sheet conveying direction. And a skew correction unit that is disposed on the back side and includes two or more transport roller pairs with variable transport speeds, and a skew that determines the skew amount by correcting the information from the skew detection unit based on the sheet shape information. And a skew amount correcting means for correcting skew of the sheet based on the corrected skew amount.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION [First Embodiment] An embodiment of a sheet conveying apparatus and an image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of an image forming apparatus according to the present embodiment, FIG. 2 is a diagram illustrating a pair of registration rollers and an image forming unit, FIG. 3 is a diagram illustrating a skew correction state,
FIG. 4 is a flow chart for explaining the image forming operation, and FIG. 5 is a block diagram for explaining the skew feeding correction operation.

(Overall Configuration) First, the overall configuration of the image forming apparatus according to the present embodiment will be described with reference to FIG. The image forming apparatus shown in the figure is a color copying machine adopting an electrophotographic method, and has two cassette feeding units 1 and 2 and one manual feeding unit 3, and each feeding unit 1 The sheet S is selectively fed from a few points. The sheets S are stacked on the cassettes 4 and 5 or the tray 6 of each of the feeding units 1, 2, and 3, and are picked up by the pickup roller 7 in order from the topmost one. And the pickup roller 7
The sheet S fed out by the feed roller 8a as a conveying means and the retard roller 8b as a separating means.
Only the uppermost sheet is separated by the separation roller pair 8 consisting of and is sent to the registration roller pair 12 whose rotation is stopped. In this case, the sheet S fed from the cassettes 4, 5 having a long distance to the registration roller pair 12 is relayed to the plurality of conveyance roller pairs 9, 10, 11 and sent to the registration roller pair 12.

A long transfer belt 13 (endless belt), which is a transfer member, is provided downstream of the registration roller pair 12 as a driving roller 13.
The transfer belt 13 is stretched around a, the driven roller 13b and the tension roller 13c, and the transfer belt 13 rotates counterclockwise in the drawing. On the upper surface of the horizontal portion of the transfer belt 13, a plurality of photosensitive drums 14, 15, 16, 17 for forming and carrying color toner images of different colors are sequentially arranged along the rotation direction of the transfer belt 13.
The photoconductor drums 14 to 17 carry toner images of magenta, cyan, yellow, and black, respectively, from the upstream side in the rotation direction of the transfer belt.

In the color image forming apparatus of this embodiment, a plurality of originals (not shown) are sequentially set on the original table 19 (platen glass) at predetermined positions by the automatic original feeder 18. . Then, the image of the document set on the document table 19 (here, a color image) is read by the reading optical system 20. The read color image is separated by the CCD element 21 into color components of magenta, cyan, yellow, and black, and temporarily stored in an image memory (not shown). The image information stored in the image memory includes a laser scanner and a writing optical system 22.
Thus, each color component is sequentially written on the photosensitive drums 14 to 17 which are rotating clockwise.

First, the projection of the laser beam L (M) based on the image of the magenta component is started on the most upstream photosensitive drum 14, and an electrostatic latent image is formed on the photosensitive drum 14. This electrostatic latent image is visualized by magenta toner supplied from the developing device 23. Similarly, a cyan component laser beam L (C), a yellow component laser beam L (Y), and a black component laser beam L (B) are projected onto the photosensitive drums 15 to 17 to form an electrostatic latent image. , And is visualized by the toner of each color supplied from the developing devices 24, 25 and 26. Around the photosensitive drums 14 to 17, primary chargers 27, 28, 29, 30 for uniformly charging the photosensitive drums 14 to 17 and on the photosensitive drums 14 to 17 after the toner image transfer are performed. Cleaners 31, 32, 33, 34 and the like for removing the toner adhering to the are installed.

The sheet S sent from the registration roller pair 12 and corrected in the skewed state is transferred onto the transfer belt 13 at a timing for aligning the position of the toner image on the most upstream photosensitive drum 14 with the sheet front end. Sent. While the sheet S sent to the transfer belt 13 is conveyed downstream by the transfer belt 13, a transfer portion between the photoconductor drum 14 and the transfer charger 90, as well as the photoconductor drums 15 to 17 and the transfer charger. 91, 92, 93
The toner images of magenta, cyan, yellow, and black are transferred to the surface of the sheet S in an overlapping manner by sequentially passing through the transfer portion between the sheet S and the sheet. The sheet S that has passed the most downstream transfer unit is sent by the transfer belt 13 to the fixing roller pair 35 that constitutes a fixing device. Then, the sheet S is overheated by the fixing roller 35a in the fixing roller pair 35, and the pressure roller
The transfer toner image is pressed by 35b to be fixed on the sheet surface. Sheet S that has undergone the fixing process after passing through the pair of fixing rollers 35
Is sent to the discharge roller pair 37 by the transport roller pair 36 and further discharged onto the discharge tray 38 outside the machine.

In this image forming apparatus, double-sided mode image formation is possible. Hereinafter, the configuration of the image forming apparatus will be further described along the flow of the sheet S in the double-sided mode. If duplex mode is specified, the fuser roller pair
The fixing-processed sheet S that has passed 35 is sent to the reverse path 59 through the vertical path 58. In this case, flapper 60 is vertical pass 58
The sheet S that has been fixed
It is conveyed by 36, 61, 62 and a pair of reverse rotation rollers 63.
When the trailing edge of the fixing processed sheet S conveyed in the direction of arrow a by the reverse rotation roller pair 63 passes the point P, the reverse rotation roller pair 63 rotates in the reverse direction, and the fixing processed sheet S
Is conveyed in the direction of arrow b, with the rear end side as the leading end. By this operation, the toner image transfer surface of the fixing-processed sheet S is on the upper side. At point P, the vertical path 58 to the reverse path 59
Allows the sheet S to enter the space, and the vertical path from the reverse path 59
The flapper 64 with a flexible sheet that allows the sheet S to enter the 58 and the sheet S from the reversing path 59 to the vertical path 58 and that the sheet rear end has passed the same point P. A detection lever 65 for detecting is provided.

The fixed sheet S conveyed in the direction of arrow b by the reverse rotation of the reversing roller pair 63 is fed into the re-feeding path 67, and a plurality of re-feeding path conveying roller pairs 68 and conveying roller pairs are provided.
It is relayed at 11 and again paired with registration rollers 12 to form an image.
Sent to. The fixing processed sheet S is a pair of registration rollers.
After the skewed state is corrected by 12, the sheet is sent to the transfer belt 13. Then, the second image formation is performed based on the image data stored in the image memory (not shown) in which the magnification correction in the main scanning direction and the sub-scanning direction is performed, and thereafter, the same process as the one-sided image formation is performed. Is discharged to the outside of the aircraft.

Next, sheet skew correction will be described. As shown in FIG. 2, the registration roller pair 12 as the skew correction means is composed of a front registration roller pair 12F and a back registration roller pair 12R which are arranged on the front side and the back side (both left and right sides) in the sheet conveying direction. A skew sensor 75 is provided as skew detection means for detecting skew of a sheet before registration. The front registration roller pair 12F and the back registration roller pair 12R have stepping motors 76F and 76, respectively.
R is connected. When the sheet S is conveyed from the feeding section, the skew sensor 75 detects the skew amount of the sheet S,
Based on this skew detection signal, the CPU 82, which is a skew amount calculating means,
(See FIG. 5) to control the stepping motors 76F and 76R to correct the skew of the sheet S. The skew-corrected sheet S is sent to the transfer belt 13, and images of magenta, cyan, yellow, and black are formed.

The operation of image formation and skew correction will be described along the flow of the sheet S with reference to FIGS. First, when image formation is started, the sheet S is fed from the feeding section (S1), and the skew feeding amount is detected by the skew feeding sensor 75 (S2). Here, the sheet shape information such as the tab portion dimension x, the tab shape, and the position registered in advance in the storage means or the like is read (S3), and it is determined whether the sheet shape is rectangular plain paper or irregular shape. (S4). When it is determined that the sheet is plain paper, the skew feeding of the sheet S is performed by the stepping motor 76F according to the skew feeding amount detected as in the conventional case.
The sheet is corrected with 76R (S6), an image is formed (S7), and the sheet is discharged outside the apparatus (S8).

On the other hand, when it is determined that the sheet S is irregularly shaped (S5) and the tab portion is located on the upstream side in the conveying direction as shown in FIG. 3 (a), it is the same as the rectangular sheet. In addition, the skew feeding of the irregularly shaped sheet S (tab sheet) is simply performed according to the skew feeding amount detected by the sensor 75.
Correct with F and 76R (S6) and perform image formation (S
7).

Further, as shown in FIG. 3 (b), the irregularly shaped sheet S
Even when the tab portion of is located on the downstream side in the transport direction, when the tab portion is between the skew sensors 75, the skew amount detected by the skew sensor 75 is not affected. .
Therefore, also in this case, similarly to the rectangular sheet, the skew feeding of the irregularly shaped sheet S is simply corrected by the stepping motors 76F and 76R according to the skew feeding amount detected by the sensor 75 (S
6), image formation is performed (S7).

On the other hand, as shown in FIG. 3 (c), the irregularly shaped sheet S
If the tab part of is located on the downstream side in the transport direction and the tab part is located at the skew sensor 75, the skew sensor 75
The skew amount detected by cannot be used as it is. Therefore, as shown in FIG. 5, the skew amount calculated by the skew amount (sheet skew information 80) detected by the sensor 75 is calculated by using the tab portion dimension x (sheet shape information 81) registered in advance. Corrected by CPU 82, corrected skew amount 83
To calculate. Then, according to the corrected skew feed amount 83, the stepping motors 76F, 76R correct the skew feed of the sheet S (S6), and perform image formation (S7).

With the above-described structure, a sheet conveying apparatus represented by a tab sheet and having a concave-convex shape on the edge of the sheet, that is, a sheet conveying apparatus capable of surely correcting the skew feeding of a non-rectangular sheet is provided. It can be an image forming apparatus.

[Second Embodiment] A second embodiment of the sheet conveying apparatus and the image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 6 is an overall configuration diagram of the image forming apparatus according to the present embodiment, FIG. 7 is a diagram illustrating a pair of registration rollers and an image forming unit, and FIG. 8 is a diagram illustrating how skew is corrected. The same parts as those of the embodiment will be designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 6, the image forming apparatus according to this embodiment is similar to the transfer belt 13 shown in the first embodiment.
Instead, an intermediate transfer belt 40 is provided, and a secondary transfer roller pair 41 is added to the secondary transfer portion T2 that transfers toner from the intermediate transfer belt 40 to the sheet S.

As shown in FIG. 7, the registration roller pair 12 includes a front registration roller pair 12F and a rear registration roller pair 12R which are arranged on the front side and the rear side (both left and right) in the sheet conveying direction.
And a skew feeding detection CCD 77 for detecting skew feeding of the sheet before registration. Skew detection CCD
Reference numeral 77 is a CCD array arranged in the sheet width direction, and is a skew detecting means for detecting skew of the sheet and a shape detecting means for detecting the shape of the edge of the sheet. Further, similarly to the first embodiment, the front registration roller pair 12F and the rear registration roller pair 12R are respectively provided with a stepping motor 76.
F and 76R are connected.

When the sheet S is conveyed from the feeding section,
The skew detection CCD 77 detects the skew amount of the sheet S, and the CPU 82 controls the stepping motors 76F and 76R based on the skew detection signal to correct the skew of the sheet S. The skew-corrected sheet S is sent to the secondary transfer roller pair 41 of the intermediate transfer belt 40 and image formation is performed. Shaped sheet S
The skew feed correction of (tab sheet) is the same as that in FIGS. 3 (a) to 3 (c).

Further, in this embodiment, since the skew detection CCD 77 is used in place of the skew sensor 75 of the first embodiment, even if the sheet S has a wavy edge as shown in FIG. The shape of the tip of S can be detected. That is, when an image is formed on the irregularly shaped sheet S (wavy edge paper), the skew detection CCD 77 detects the shape and skew amount of the sheet S, and the skew amount detected by the skew detection CCD 77 is used as the sheet. It is possible to perform correction in accordance with the shape of S, and to correct the skew of the sheet S by the stepping motors 76F and 76R in accordance therewith to perform appropriate image formation.

In the present embodiment as well, the sheet shape information may be registered in advance and the skew amount detected by the skew detection CCD 77 may be corrected according to this information. Further, although the correction in the irregularly shaped sheet having the wavy edges is shown here, the sheet can be applied to any sheet having any other shape.

[0029]

EFFECTS OF THE INVENTION With the above-mentioned structure, a sheet typified by a tab sheet having an irregular shape on the edge of the sheet,
That is, it is possible to provide a sheet conveying device capable of surely correcting skew of a non-rectangular sheet and an image forming apparatus including the sheet conveying device. In particular, when images are formed on both sides of a tab sheet, skew feeding can be corrected regardless of the direction of the tab portion, so that automatic double-sided recording on the tab sheet, which has been difficult until now, becomes possible.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an image forming apparatus according to a first embodiment.

FIG. 2 is a diagram illustrating a pair of registration rollers and an image forming unit.

FIG. 3 is a diagram illustrating a state of skew correction.

FIG. 4 is a flowchart illustrating an image forming operation.

FIG. 5 is a block diagram illustrating an operation of skew correction.

FIG. 6 is an overall configuration diagram of an image forming apparatus according to a second embodiment.

FIG. 7 is a diagram illustrating a pair of registration rollers and an image forming unit.

FIG. 8 is a diagram illustrating a manner of skew correction.

[Explanation of symbols]

P ... point S ... sheet T2 ... Secondary transfer part 1, 2 ... Cassette paper feeder 3 ... Manual feeding section 4, 5 ... cassette 6 ... Tray 7 ... Pickup roller 8 ... Separation roller pair 8a ... Feed roller 8b ... Retard roller 9, 10, 11 ... Pair of transport rollers 12… Registration roller pair 12F… Roller pair before registration 12R: Pair of resist inner rollers 13… Transfer belt 13a ... Drive roller 13b ... driven roller 13c Tension roller 14-17 ... Photosensitive drum 18 Automatic document feeder 19… Platen 20 ... Reading optical system 21… CCD element 22… Writing optical system 23-26 ... Developer 27-30 ... Primary charger 31-34… Cleaner 35 ... Fixing roller pair 35a ... Fusing roller 35b ... Pressure roller 36… Conveyor roller pair 37… Ejection roller pair 38… Ejection tray 40… Intermediate transfer belt 41… Secondary transfer roller pair 58… Vertical path 59… Inversion path 60… Flapper 61, 62 ... Pair of transport rollers 63… Reverse roller pair 64… Flapper with flexible sheet 65… Detection lever 67… Re-delivery pass 68… Pair of transport rollers in the re-feed path 75… Skew sensor 76F, 76R ... Stepping motor 77… Skew detection CCD 80… Sheet skew information 81… Sheet shape information 82 ... CPU 83… Skew amount 90-93… Transfer charger

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3F048 AA01 AB01 BA11 BA20 BA21                       BA27 BB02 BB05 BB08 CA09                       CC03 CC12 DA07 DB03 DB06                       DB12 DC13 EB35                 3F102 AA01 AB01 BA02 BB02 BB07                       CA04 CB01 DA08 EA03

Claims (5)

[Claims] 1. A skew detecting unit for detecting skew of a sheet, a skew correcting unit for correcting skew of a sheet, and correcting information from the skew detecting unit based on sheet shape information. A skew feeding amount calculating means for determining a skew feeding amount, wherein the skew feeding correcting means corrects the skew feeding of the sheet based on the corrected skew feeding amount. 2. The skew correcting means is arranged on the front side and the back side in the sheet conveying direction, and comprises at least one pair of conveying rollers having a variable rotational speed, and controlling the rotational speed. The sheet conveying apparatus according to claim 1, wherein skew feeding of the sheet is corrected. 3. The sheet conveying apparatus according to claim 1, further comprising shape detecting means for detecting the shape of the conveyed sheet. 4. The sheet conveying apparatus according to claim 1, wherein the sheet is a tab sheet provided with a tab portion on an end side for entering a headline or the like for the purpose of classification. 5. An image forming apparatus comprising: an image forming unit for forming an image on a sheet; and the sheet conveying device according to claim 1.