JP2001139207A - Both-side image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a carrier defective of recording paper in a switch back part for forming a both-side image. SOLUTION: Recording paper is surely guided and carried by making a difference between the height of a guide rib at the center part of a carrier width direction of recording paper and the heights of the guide ribs at both end parts and utilizing corrugation of paper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-sided image forming apparatus, and more particularly to an improvement in a recording paper transport system of a double-sided image forming apparatus.

[0002]

2. Description of the Related Art In many double-sided image forming apparatuses, a recording sheet is supplied to an image forming section to form an image on one side thereof, and then the recording sheet is supplied again to the image forming section to form an image on the other side. By forming, double-sided image formation is performed. In such double-sided image formation, a transport unit that switches back and transports the recording paper is used to reverse the recording paper on which an image is formed on one surface.

[0003]

In a transport section that performs switchback transport, that is, in a switchback section, a recording paper transport path is switched between a loading path to the switchback section and a transport path from the switchback section. Because of this, the recording paper conveyance conditions are stricter than other conveyance paths, and the inclination of the recording paper, bending of the leading end, and jams are liable to occur.
In particular, in order to reduce the size of the image forming apparatus, the recording paper is frequently bent and transported in a relatively strong manner, so that the transport condition of the recording paper in the switchback section becomes severe.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus which smoothly conveys a recording sheet in the switchback section and prevents the recording sheet from being inclined, bent at the tip, jammed or the like.

[0005]

The above object is achieved by the following invention.

(1) A first transport path for transporting the recording paper toward the image forming means, a second transport path for transporting the recording paper having an image formed on one surface by the image forming means, In an image forming apparatus having a switchback unit for switching back the recording paper conveyed through the second conveyance path and guiding the recording paper to the first conveyance path, the recording paper conveyed from the second conveyance path is rotated in one direction. Reversing conveyance means for reversing the rotation direction and conveying the recording paper toward the first conveyance path after the conveyance, and the first conveyance with the trailing end of the recording paper conveyed through the second conveyance path as a leading end A conveyance path switching means for guiding the paper to a path, and a guide means for guiding the recording paper in the vicinity of the reversing conveyance means. 2nd guidance in the department It has an inner section, the double-sided image forming apparatus according to claim guide height of the second guide means and said first guide means are different.

(2) The double-sided image forming apparatus according to (1), wherein the first guide means and the second guide means are provided on both sides of the recording paper.

(3) The difference between (1) and (2), wherein the difference between the guide height of the first guide means and the guide height of the second guide means is set between 1 and 5 mm. 2. The double-sided image forming apparatus according to 1.

(4) The first guide means guides a B5 size recording sheet, and the second guide means guides a width range of both ends of the A4 size recording sheet. The double-sided image forming apparatus according to any one of (1) to (3).

(5) The first transport path and the second transport path form a transport path for transporting recording paper up and down, and the switchback unit is located below the first transport path and the second transport path. (1) to (1), which are provided in
The double-sided image forming apparatus according to any one of (4) and (4).

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a digital image forming apparatus (hereinafter, referred to as a digital image forming apparatus).
FIG. 1 is a diagram illustrating a configuration of an image forming apparatus 100.

In FIG. 1, an image forming apparatus 100 includes an automatic document feeder (ADF) A, a document image reading unit B for reading an image of a document fed by the automatic document feeder, and a read document image. An image processing substrate C to be processed, a writing unit D including a writing unit 12 for writing on a drum-shaped photoconductor 10 as an image carrier according to data after the image processing, and a photoconductor 10 and a charging electrode around the photoconductor 10 14. Developing means 1 composed of a magnetic brush type developing device
6, transfer electrode 18, separation electrode 20, cleaning means 2
An image forming unit E including image forming means such as No. 1 and a storage unit F for paper feed trays 22 and 24 for storing recording paper P are provided.

The automatic document feeder A includes a document table 26
And a document transport processing unit 28 including a roller group including the roller R1 and switching means for appropriately switching the document movement path (no reference symbol).

The original image reading section B is located below the platen glass G and can move back and forth while maintaining the optical path length, a fixed imaging lens (hereinafter simply referred to as a lens) 33, and a line-shaped image forming section. Image sensor (hereinafter referred to as CCD
The writing unit D includes a laser light source 4
0, a polygon mirror (polarizer) 42 and the like.

When viewed from the moving direction of the recording paper P, the transfer electrode 1
Reference numeral R10 on the front side of reference numeral 8 denotes a registration roller, and H on the downstream side of the separation electrode 20 denotes a fixing unit.

In the embodiment, the fixing means H comprises a roller having a built-in heating source and a pressure roller which rotates while being pressed against the roller.

Further, Z is a cleaning means for the fixing means H, and has a cleaning web provided so as to be wound up as a main element.

One of the originals (not shown) placed on the original placing table 26 is transported by the original transport processor 28,
While passing under the roller R1, exposure by the exposure means L is performed.

Light reflected from the original passes through mirror units 30 and 31 and a lens 33 at a fixed position and a CCD 35.
Imaged on top and read.

The image information read by the document image reading section B is processed by an image processing means, encoded, and stored in a memory provided on an image processing board C.

Further, the image data is called in accordance with the image formation, and the laser light source 40 in the writing device D is driven according to the image data, so that the photosensitive member 10 is exposed.

Prior to the exposure, the photoreceptor 10 rotating in the direction of the arrow (counterclockwise) is given a predetermined surface potential by the corona discharge action of the charging electrode 14. As a result, the electrostatic latent image is formed on the photoconductor 10 according to the image data.

The electrostatic latent image is reversal-developed by the developing means 16 to become a visible image (toner image).

On the other hand, before the leading end of the toner image on the photoconductor 10 reaches the transfer area, for example, one sheet of recording paper P in the paper feed tray 22 is fed and conveyed to the registration roller R10.
And is regulated at the tip.

The recording paper P is conveyed toward a transfer area by a registration roller R10 which starts rotating in synchronization with the toner image, that is, an image area on the photoconductor 10, so as to overlap.

In the transfer area, the toner image on the photoreceptor 10 is transferred onto the recording paper P by the urging of the transfer electrode 18,
Next, the recording paper P is separated from the photoconductor 10 by the bias of the separation electrode 20.

Thereafter, the fixing unit H is pressurized and heated to
The toner image is fused and fixed on the recording paper P, and the recording paper P
Is discharged onto a discharge tray T via a discharge path 78 and a discharge roller 79.

The reference symbol S in the paper feed tray 24 is a movable plate whose free end is always urged upward by an urging means such as a coil spring (not shown). It comes into contact with the roller.

The paper feed tray 22 also has the same configuration as that described above. In the embodiment, the paper feed trays 22 and 24 are arranged in two stages in the vertical direction, but may be provided with more paper feed trays.

The bottom (the same as the bottom wall) of the sheet tray 24 arranged at the lower stage (in the embodiment, the lower stage because the sheet tray is a two-stage stack, but the lower stage). A space 25 having a predetermined gap is formed between the apparatus and the bottom wall of the apparatus main body.

The space 25 is used in a mode (mode) in which images are formed on both sides of the recording paper P, and together with the second transport path 80 for reversing the recording paper P, the recording paper P
A transport path for forming an image is formed on the back surface of the printer.

Reference numerals 50 and 53 above the leading ends of the sheet feed trays 22 and 24 (corresponding to the leading ends of the stored recording sheets P when viewed from the sheet feeding direction) denote feed rollers 51
And 54 are feed rollers, and 52 and 55 are double feed prevention rollers.

The feed rollers (50, 53) and the feed rollers (51, 54) are formed as a unit, and a drive shaft connected to a drive source provided on the apparatus main body side or a locking means provided on a paper feed unit. It has a configuration that can be easily attached to and detached from.

The double feed prevention rollers (52, 55) are also unitized, and have a structure that can be easily attached to and detached from a fixing member provided on a fixing portion of the apparatus main body.

Reference numeral 60 denotes a manual paper feed tray of the manual paper feed unit, which can be opened and closed with the lower end serving as a fulcrum with respect to the main body side wall of the image forming apparatus 100.

Reference numeral 61 denotes a feed roller formed of a roller for feeding the recording paper placed on the manual feed tray 60 with the image formation, 63 denotes a feed roller provided downstream of the feed roller 61, and 65 denotes a feed roller. Roller 6
3, a double feed prevention roller for preventing a plurality of sheets of recording paper P from being fed, and has substantially the same configuration as that of the above-described paper feed trays 22 and 24.

Reference numeral 66 denotes a conveyance path for the recording paper P sent from the manual feed tray 60, and guides the recording paper P to a later-described junction via a pair of conveyance rollers immediately to the left of the feed roller 63.

Reference numeral 70 denotes a first conveying path for forming an image on the recording paper P by transfer, and extends upward from below when viewed from the moving direction of the recording paper sent from an appropriate paper feed tray. .

Numeral 72 denotes a paper feeding path for recording paper stored in the upper paper feeding tray 22, 74 denotes a paper feeding path for recording paper stored in the lower paper feeding tray 24, and 76 denotes both trays 2.
This is a merging portion (a part of the first conveyance path 70) where the recording papers P sent from the sheets 2 and 24 merge.

Reference numeral 78 denotes a paper discharge path for discharging the recording paper on which a predetermined image has been formed onto the paper discharge tray T.

Numeral 80 denotes a second transport path for reversing the recording paper used for forming images on both sides of the recording paper.
In the upper part of the figure, the recording paper P conveyed from the first conveyance path
I will guide you.

The second transport path 80 extends downward from above when viewed from the direction of movement of the recording paper.

The lower end of the second conveying path 80 is a conveying path extending substantially vertically, and the lower end extends below the sheet feeding section of the lower sheet feeding tray 24, and the recording paper P
Are formed.

As understood from the above, the first transport path 7
0 and the second transport path 80 form a long loop in the longitudinal direction on one side wall side of the apparatus main body.

In the one-sided image forming step of forming an image on the surface of the recording paper P, the recording paper P fed by the feed roller 50 or 53 is formed on the photosensitive member 10 when passing through the transfer electrode 18. After the toner image is transferred and the transferred toner image is fixed by the fixing unit H, the toner image is discharged to the discharge tray T via the discharge path 78.

In the double-sided image forming step of forming images on both sides of the recording paper P, the recording paper P on which the toner image has been transferred and which has been subjected to the fixing process by the fixing means H is transferred to the branch guide 9.
0 guides to the second transport path 80. Second transport path 80
After the recording paper P conveyed downward is sent into the space 25 by the conveyance rollers R20 and 21 as conveyance means,
The rear end is stopped while being held by the transport rollers R20 and R21. Next, the transport rollers R <b> 20 and R <b> 21 reverse the rotation direction, and send the recording paper P to the first transport path 70. That is, the recording paper R is transported in a switchback manner by the transport rollers R20 and R21. At this time, the recording paper P is turned upside down, and the recording paper P moving above the first transport path 70 passes through the transfer electrode 18. Transfer of the toner image to the toner image.

The recording paper P on which the toner image has been transferred to the back surface is subjected to a fixing process by the fixing means H, and then is discharged to the discharge tray T via the discharge path 78.

Referring to FIGS. 2 to 4, switchback unit SB
The conveyance of the recording paper P in the above will be described.

FIGS. 2 and 3 are enlarged cross-sectional views taken along lines AA and BB in FIG. 4, and FIG. 4 is a cross-sectional view of the switchback portion SB viewed from below in FIG. .

An openable movable frame 103 is provided on the side of the image forming apparatus 100, and the upper end of the movable frame 103 is
4 between the fixed frame 101 and the movable frame 103.
When the conveyance path 801 communicating with the conveyance path 80 is formed, and the recording paper P is jammed in the conveyance path 801 and a conveyance path 803 described later, the movable frame 103 is opened in the direction of the arrow to take out the recording paper P. I can do it.

Next, the switchback section S in which the recording paper P is switchback-conveyed by the conveyance rollers R20 and R21.
The structure and operation of B will be described with reference to FIGS.

As shown in FIG. 2, two drive rollers R21 for driving are provided on a drive shaft 105 provided on a fixed frame 102 integrally formed of resin or the like and provided with a drive gear G (see FIG. 4).
Is provided. On the other hand, the movable frame 103 is provided with two transport rollers R20 that are driven via the shaft 106, respectively.
The transport rollers R21 and R20 contact each other to transport the recording paper P. The transport line indicated by L1 is the two transport rollers R2
0, a straight line connecting the contact portions of R21.

A second frame is provided between the fixed frame 101 and the movable frame 103.
A transport path 801 which is a lower part of the transport path 80 is formed, and a transport path 802 which is a lower part of the first transport path 70 is formed between the fixed frame 101 and the fixed frame 102. A transport path 803, which is an upper part of the space 25, is formed below the transport rollers R20 and R21. An elastic guide plate 704 such as a polyethylene terephthalate film is provided at a lower end of the fixed frame 101, and a lower end, which is a free end, extends to a concave portion 710 formed in the movable frame 103. The elastic guide plate 704 is switching means for switching the recording paper P from the conveyance path 801 to the conveyance path 802. The recording paper P is fixed between the transport rollers R20 and R21 and in the vicinity thereof by the fixed frame 10.
2 and guide ribs 706 as guide means provided on the movable frame 103.
And 707.

In the back image forming step, the second transport path 8
The recording paper P, which has moved downward through 0, moves down the transport path 801 and pushes the elastic guide plate 704 as shown by a dashed line, and goes straight down, and is transported by the transport rollers R20 and R21. The upper end of the recording paper P is a transport roller R20,
While being held by R21, the transport rollers R20, R
Numeral 21 reverses the rotation direction and conveys the recording paper P upward. The recording paper P is guided by the elastic guide plate 704 returned to the position indicated by the solid line, guided by the transport path 802, and transported to the first transport path 70.

Guide ribs 705 and 7 provided on the fixed frame 102
08 and guide ribs 706 and 707 provided on the movable frame 103.
Is configured as described below.

At the center of the recording paper P in the conveying path width direction, guide ribs 705 and 706 serving as first guiding means for guiding the recording paper P are symmetrically arranged at a predetermined interval H1 with respect to the conveyance line L1. The parts are configured to face each other. On the other hand, the guide rib 70 as the second guide means
7 and 708 are separated by a predetermined distance H2 from the transfer line L.
1 is formed so as to form a transport line L2 which is shifted by a predetermined distance H3. Note that the transport line L2 is a virtual line connecting an intermediate point between the guide ribs 707 and 708. Further, it is desirable that the predetermined intervals H1 and H2 are equal,
It is desirable to set it to about 1.5 to 4.0 mm.

The difference between the heights of the guide ribs 705 and 708 which provide the transfer lines L1 and L2 and the difference between the heights of the guide ribs 706 and 707 are set within a range of about 1 to 5 mm. Is desirable. The height difference is 1m
If it is less than m, a jam may easily occur,
If it exceeds 5 mm, the tip may be easily broken.

The guide ribs 705 and 706 are
The guide ribs 707 and 708 are formed at positions for guiding recording paper P of 5 sizes (257 mm), and the guide ribs
7 mm) is preferably formed at a position for guiding a wide portion at or above both ends.

With the above-described configuration of the guide ribs 705 to 708, when the recording paper P is switched from the conveyance path 801 to the conveyance path 802 in the switchback section SB, corrugation is given to the recording paper P, and recording is performed. The transport of the paper P is performed smoothly.

The above configuration ensures smooth conveyance from thin to thick paper without causing a conveyance failure such as breakage or inclination of the leading end. It goes without saying that a jam or the like in the switchback section SB is effectively prevented.

[0062]

According to the first aspect of the present invention, the recording paper is smoothly conveyed in the switchback section, and a conveyance failure such as a bent, inclined, or jammed end portion is effectively prevented.

According to the second or third aspect of the present invention, transport failures such as breaks, inclinations, jams, and the like at the front end of the switchback portion can be prevented very effectively.

According to the fourth aspect of the present invention, a large-sized recording sheet of A4 or more can be smoothly conveyed, and defective conveyance of a large-sized recording sheet is effectively prevented.

According to the invention of claim 5, a compact double-sided image forming apparatus is realized.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view taken along line AA in FIG.

FIG. 3 is an enlarged sectional view taken along line BB in FIG.

FIG. 4 is a cross-sectional view of the switchback unit as viewed from below in FIG.

[Explanation of symbols]

 Reference Signs List 10 photoreceptor 22, 24 paper feed tray 70 first transport path 80 second transport path 801 802, 803 transport path 101, 102 fixed frame 103 movable frame 705, 706, 707, 708 guide rib 702, 709 recording paper path R20 , R21 conveying roller 100 image forming apparatus P recording paper

Claims (5)

[Claims] A first conveying path for conveying recording paper toward an image forming means; a second conveying path for conveying recording paper on which an image is formed on one surface by the image forming means; An image forming apparatus having a switchback unit for switching back the recording paper conveyed along the second conveyance path and guiding the recording paper to the first conveyance path, wherein the recording paper conveyed from the second conveyance path is rotated in one direction. After transporting the recording paper, the recording paper is
Reversing conveyance means for conveying the paper toward the conveyance path, conveyance path switching means for guiding the rear end of the recording paper conveyed in the second conveyance path to the first conveyance path as a leading end, and recording near the reversing conveyance means. A guide means for guiding the paper, the guide means having first guide means for guiding at a central portion in the conveying width direction, and second guiding means for guiding at both ends in the conveying direction; And a guide height of the second guide means is different. 2. A double-sided image forming apparatus according to claim 1, wherein said first guide means and said second guide means are provided on both sides of the recording paper. 3. A guide height of said first guide means and said second guide means.
The two-sided image forming apparatus according to claim 1, wherein a difference in guide height of the guide unit is set between 1 and 5 mm. 4. The recording medium according to claim 1, wherein said first guide means guides a B5-size recording sheet, and said second guide means guides a width range of both ends of the A4-size recording sheet. The double-sided image forming apparatus according to any one of claims 1 to 3. 5. The printer according to claim 1, wherein the first and second transport paths form a transport path for transporting the recording paper up and down, and the switchback unit is disposed below the first and second transport paths. The double-sided image forming apparatus according to claim 1, wherein the double-sided image forming apparatus is provided.