JP3536167B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] TECHNICAL FIELD The present invention relates to a copier, a facsimile
For image forming devices such as millimeters and printers,
While the transfer material is guided by the guide member,
It is conveyed to the opposite part of the corona discharge transfer device, and
The present invention relates to an image forming apparatus for transferring a toner image. [0002] 2. Description of the Related Art The present applicant has proposed an image forming apparatus of this type.
To a toner image carrier such as a photoconductor or an intermediate transfer belt.
A corona discharge transfer device facing each other with a predetermined gap
Transfer that supplies a transfer current to the discharge wire of the discharge transfer device
Current supply means, toner image carrier and corona discharge transfer
A guide member for guiding the transfer material is provided at a portion facing the apparatus.
Image forming deviceProposal(For example, Japanese Patent Application No.
No. 118087, Japanese Patent Application7-134317). This
In the image forming apparatus described above, the transfer material is guided by a guide member.
The toner image carrier and the corona discharge transfer device
Transfer paper to the opposite side, and the corona
By performing corona discharge with a discharge transfer device, the transfer material
Charged to the opposite polarity of the charge polarity of the toner image on the toner image carrier
To transfer the toner image on the toner image carrier to the transfer material.
You. [0003] SUMMARY OF THE INVENTION The above conventional image forming apparatus
The transfer device transfers the transfer material transported from the fixing device to the toner again.
It is necessary to supply an image to the opposing portion of the image carrier and the corona discharge transfer device.
Using a known transfer material transport device, the transfer material
Guide and corona discharge transfer
The transfer material and the toner image carrier are transported to
Transfer the toner image on the toner image carrier
Can be configured to be transferred to the back surface of the. However, a solid toner having a large amount of toner adhered to its surface
The transfer material on which a toner image such as an image has been transferred and fixed
The difference in thermal shrinkage between the material itself and the fixed toner
May curl. In particular, color on the surface of the transfer material
When a toner image is formed, a toner image of a plurality of colors is formed on the surface.
Is transferred and the toner adhesion amount tends to increase,
It is easier to curl. The curl of this transfer material is
A so-called face cover that curls with the transfer surface inside
It is. This face curl is applied to the back of the transfer material.
When the toner image is transferred, a so-called back curl occurs. As described above, the toner image is transferred to the back surface.
If the transfer material before the transfer is curled,
Passing through the tip of the guide member, and the regulating force of the guide member is released.
When removed, the curl of the transfer material itself
The trailing end of the transfer material moves away from the toner image carrier
Moves, close contact between the rear end of the transfer material and the toner image carrier
Failure may occur. Such poor adhesion
Causes transfer defects such as white spots. The present invention has been made in view of the above problems.
The purpose is to transfer the surface of the transfer material,
Prevents transfer defects such as reverse transfer during transfer to the center of the surface
As well as the back of the transfer material due to the curl of the transfer material
White spots due to poor adhesion between the rear end of the surface and the toner image carrier
To provide an image forming apparatus capable of preventing any transfer failure
It is. [0007] [0008] [0009] [0010] [0011] [0012] [0013][MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
To Claim1The invention according to
A corona discharge transfer device opposed by a gap;
Transfer current supply to supply transfer current to discharge wire of copying device
Means, the toner image carrier and the corona discharge transfer device
A guide member for guiding the transfer material to the facing portion;
Fixing device for fixing the toner image transferred to the fixing device, and the fixing device
Swaps the transfer material transferred from the machine with the front and back sides
And a transfer material transfer device for transferring the transfer material to the facing portion.
Transfer and fixing of the toner image on the surface of the transfer material.
After that, the transfer material is conveyed to the facing portion, and the back surface of the transfer material is
An image forming apparatus for transferring a toner image to
Transferred to the opposite part to transfer the toner image to
The rear end of the material leaves the tip of the guide member on the side of the facing portion.
Until the transfer of the toner image to the back side is completed.
The toner image carrier and transfer at the time of transfer of the rear end of the back surface
The peripheral speed of the material and the portion other than the rear end of the back surface of the transfer material.
Peripheral speed of the toner image carrier and transfer material during transfer
And can be set independentlyAnd the above
The toner image carrier and the toner image transfer at the time of transferring the rear end of the back side of the paper
And the peripheral speed of the transfer material,
Image carrier and transfer material at the time of transfer with respect to minute
Less than the peripheral speed ofIt is characterized by
You. This claim1In the image forming apparatus, the transfer material
Other than the rear end of the back surface, that is, the surface of the transfer material, the transfer material
From the transfer material to the top and bottom center of
Transfer failure such as reverse transfer of toner image to toner image carrier
The toner image carrier at a peripheral speed set to a size that does not
With the transfer material being moved, the toner
The transfer of the toner image to the copying material is performed. And the back side of the transfer material
Transferred to the opposite part to transfer the toner image to
The rear end of the material leaves the tip of the guide member on the side of the facing portion.
Until the transfer of the toner image to the back side is completed.
The transfer material curls with respect to the rear end of the back surface of the transfer material.
The transfer material is in close contact with the toner image carrier.
The toner image carrier at a small peripheral speed set to
With the transfer material moved, transfer material from the toner image carrier
The transfer of the toner image to the toner image is performed. [0015] BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention relates to a toner image carrier
Electrophotographic color image using an intermediate transfer belt
Suitable for an image forming apparatus (hereinafter referred to as a “color image forming apparatus”).
One embodiment used will be described. First, a color image forming apparatus according to this embodiment
The overall configuration and operation of the device will be described. Figure 2 shows the color
FIG. 3 is a schematic diagram of an image forming apparatus, and FIG.
It is a principal part enlarged view of a forming apparatus. This color image forming apparatus
Is an image reading device (hereinafter referred to as "color scanner")
1, an image forming unit (hereinafter, referred to as a “color printer”) 2,
It is composed of a paper feed bank 3 and the like. The color scanner 1 includes a contact glass.
Illumination lamp 122 and mirror
Color through groups 123a, b, c and lens 124
An image is formed on the sensor 125, and the color image information of the document 4 is
For example, Red, Green, Blue (hereinafter, respectively)
(R, G, B)
And converts it into an electrical image signal. Color sensor 125
In this example, R, G, B color separation means and a CCD (charge connection)
And a photoelectric conversion element such as
Simultaneous reading of three color images obtained by color separation of images
You. Then, the R, G, and B of the color scanner 1
Based on the color separation image signal intensity level, an image (not shown)
The color conversion processing is performed by the image processing unit, and Black (hereinafter referred to as “B
k ”), Cyan (hereinafter“ C ”), Mag
enta (hereinafter referred to as “M”), Yellow (hereinafter referred to as “M”)
(Referred to as “Y”). The color image data of the above Bk, C, M, Y
The operation of the color scanner 1 for obtaining
You. The operation and timing of the color printer 2 described later
Receiving the scanner start signal, the illumination lamp 122 and the
And the optical system composed of mirror groups 123a, b, c, etc.
The original 4 is scanned in the direction of
Obtain image data. By repeating this operation four times in total
Thus, four color image data are sequentially obtained. And that
Each time the color printer 2 visualizes the image sequentially,
Then, a final four-color full-color image is formed. The color printer 2 includes a photosensitive drum 2
00, writing optical unit 220, revolver developing unit
Unit 230, the intermediate transfer device 260, the fixing device 270, etc.
It is configured. The photosensitive drum 200 has a counterclockwise arrow.
Around the photosensitive member cleaning device 2
01, static elimination lamp 202, charger 203, charge potential detection
Potential sensor 204 as means, revolver developing unit
230 selected developing devices (C developing device 23 in the example of FIG. 2)
1C), development density pattern detector 205, intermediate transfer device
260 etc. are arranged. The writing optical unit 220
Represents the color image data from the color scanner 1 as an optical signal
And write the light corresponding to the image of the document 4
That is, an electrostatic latent image is formed on the photosensitive drum 200. This book
The recording optical unit 220 includes a semiconductor laser as a light source.
221, laser emission drive control unit (not shown)
Gon mirror 222 and its rotation motor 223, f / θ
And a reflection mirror 225 and the like. The revolver developing unit 230 is a photosensitive
As a rotary support provided near the body drum 200
Bk developing devices 231K and C
Developing device 231C, M developing device 231M and Y developing device 23
1Y is provided, and the entire unit is rotated counterclockwise.
(Not shown). In FIG.
Is located at the developing position facing the photosensitive drum 200.
C developing unit 231C, and M developing in the clockwise order in the figure.
Unit 231M, Y developing unit 231Y, Bk developing unit 231K
Has become. Each developing unit is provided with an electrostatic
In order to visualize the latent image, the developer
Built-in magnet that rotates by contacting the surface of 200
To pick up and agitate the image sleeve 232 and developer
And a developing paddle that rotates. The toner in each developing device is a ferrite carrier.
Negatively charged by stirring with
The probe 232 includes a metal substrate layer of the photosensitive drum 200.
And a negative DC voltage and AC voltage
Is applied. The intermediate transfer device 260 carries a toner image
Transfer belt 261 as a body (intermediate transfer medium),
Cleaning device 262 on the photosensitive drum 200
Primary transfer means for transferring the toner image to the intermediate transfer belt 261
Corona discharger as a stage (hereinafter referred to as "belt transfer device")
265) Transfer the toner image on the intermediate transfer belt 261
Corona discharge transfer device as secondary transfer means for transferring to paper
(Hereinafter referred to as “paper transfer device”) 263 and the like.
You. The intermediate transfer belt 261 is a transfer opposite row.
Rollers 264a, 264b, cleaning opposed roller 264
c, being stretched around the drive roller 264d and the driven roller group
The drive is controlled by a drive motor (not shown). During ~
The intermediary transfer belt 261 has a volume resistivity of 1 × 10⁸~
10¹²Ωcm, surface resistivity 1 × 10⁸-10¹¹Ω (JI
SK6911) medium resistance belt can be used,
The material is ethylene tetrafluoroethylene (ET
FE), epichlorohydrin rubber, etc.
Wear. Also, as in the present embodiment, a belt-like toner image
A drum-shaped toner image carrier may be used instead of a carrier.
No. The above-mentioned belt cleaning device 262
Mouth seal, rubber blade, discharge coil, inlet seal and
It is composed of a rubber blade contact / separation mechanism, etc.
After transferring the Bk image to the intermediate transfer belt 261,
The third and fourth color images are transferred to the intermediate transfer belt 261.
During the transfer, the intermediate transfer belt 26 is
Separate the inlet seal and blade from one surface. Ma
Further, the paper transfer unit 263 applies an AC voltage to the discharge wire 263a.
+ DC voltage or DC voltage is applied to the intermediate transfer belt 2
The superimposed toner image on 61 is collectively transferred to transfer paper. The transfer paper cassette 3 in the paper supply bank 3
Transfer papers 5 of various sizes are stored in 00a, b, and c.
And the transfer paper 5 of the designated size is
From the set, register by feeding rollers 301a, b, c
Paper is fed and conveyed in the direction of the pair of rollers 209. Also, OH
Right side of the printer 2 for manual paper feeding such as P paper and thick paper
There is a manual feed tray 210. A fixing device is provided in the color printer 2.
Replace the transfer paper transported from
Transfer for transporting to the transfer unit by the paper transfer unit 263
Equipped with a double-sided unit 207 as a material transfer device,
It is configured to be able to execute the plane mode. In the automatic double-sided mode, as shown in FIG.
Transfer paper on which the toner image has been transferred and fixed
The lower double-sided unit, which is different from the
To the "S-shaped" route as indicated by the bold line.
With the image already formed facing up
Is locked. The transfer paper entering the duplex unit 207
After passing through the paper sensor 207a and the reversing sensor 207b,
It passes between the roller 207c and the separation roller 207d.
Thus, the sheet is conveyed by the conveying rollers 207e. At this time, the bottom
The plate 207f is descending. When forming an image on the back side of the transfer paper,
As shown in FIG.
The transferred transfer paper is moved by raising the bottom plate 207f.
Contact with the feed roller 207c. And
The roller is rotated (reverse rotation from stacking).
As shown by the thick line, the transfer paper is
It is sent to the stroller pair 209. In the manual double-sided mode, once
Set the discharged transfer paper on the bypass tray 210 and
An image is formed on the surface. At this time, an operator (not shown)
By pressing the back side designation key on the work panel, the machine
Can be identified. (Hereinafter, margin) The standby state of the color image forming apparatus having the above configuration.
Then, the revolver developing unit 230 is a Bk developing device 231.
K is stopped at the development position, and the copy operation is started
And Bk color from a predetermined timing with the color scanner 1.
-Start reading the image data, and
Writing with laser light based on data, forming an electrostatic latent image
(Hereinafter, an electrostatic latent image based on Bk image data is represented by Bk
It is called a latent image. The same applies to C, M, and Y). It is possible to develop from the tip of this Bk electrostatic latent image.
Before the tip of the electrostatic latent image reaches the Bk development position,
Start rotation of the Bk developing sleeve, and transfer the Bk electrostatic latent image to Bk.
Develop with toner. Thereafter, the developing operation of the Bk electrostatic latent image area
The operation continues, but the trailing edge of the electrostatic latent image passes through the Bk development position.
At the point when the developer for the next color is
Thus, the revolver developing unit 230 rotates. This is small
The end of the electrostatic latent image from the next image data arrives without
Complete before you do. When the image forming cycle is started, first,
The light drum 200 is moved in the counterclockwise direction of the arrow,
261 is driven by a drive motor (not shown) in the clockwise direction of the arrow.
Is rotated. With the rotation of the intermediate transfer belt 261
Bk toner image formation, C toner image formation, M toner image formation,
Y toner image formation is performed, and finally Bk, C, M, Y
A toner image is formed on the intermediate transfer belt 261 in order.
It is. Here, when forming the above-mentioned superposed toner image,
And reduce the time required to align the image tip position
To move the roller supporting the intermediate transfer belt 261
As a result, the intermediate transfer is performed as shown by the two-dot chain line in FIG.
The belt 261 is separated from the photosensitive drum 200,
Fast-forwarding the intermediate transfer belt under a separated state
Is performed. First, the formation of the Bk toner image is as follows.
Done. The charger 203 is a photoconductor by corona discharge.
The drum 200 is uniformly charged to a negative charge of about -700V.
The semiconductor laser 221 is based on the Bk color image signal.
Then, raster exposure is performed. When this raster image is exposed
Of the photosensitive drum 200 initially charged uniformly
The charge proportional to the amount of exposure light disappears, and the Bk
A latent image is formed. The negatively charged Bk on the Bk developing sleeve
Contacts the Bk electrostatic latent image on the photosensitive drum 200
As a result, the charge of the photosensitive drum 200 remains.
The toner does not adhere to the part, and the part without charge, that is, the exposure
Bk toner is adsorbed to the portion where the Bk electrostatic latent image is
A similar Bk toner image is formed. Bk formed on the photosensitive drum 200
The toner image is driven at a constant speed while in contact with the photosensitive drum 200.
Belt transfer device 2 on the surface of the intermediate transfer belt 261
65 (hereinafter, the photosensitive drum 200
Transfer of the toner image to the intermediate transfer belt 261 from the “belt
Transcription). Discharge efficiency of belt transfer unit 265 (distribution
Rate) is about 20 to 40%. On the photosensitive drum 200 side, a Bk image forming process
Next, the process proceeds to the C image forming process, and the image is formed at a predetermined timing.
Reading of the C image data by the color scanner 1 starts,
By laser light writing with the C image data, C electrostatic
A latent image is formed. And the rear end of the previous Bk electrostatic latent image
After passing and before the tip of the C electrostatic latent image arrives
The rotation operation of the revolver developing unit 230 is performed,
The C developing unit 231C is set at the developing position and the C electrostatic latent image is set.
Is developed with C toner. Thereafter, development of the C electrostatic latent image area
However, when the trailing edge of the C electrostatic latent image has passed,
The revolver developing unit is similar to the case of the Bk developing unit 231B.
The rotation operation of the knit 230 is performed, and the next M developing device 231 is operated.
M is moved to the development position. This is also the next M electrostatic latent
Complete before the leading edge of the image reaches the development position. What
For the M and Y image forming steps,
Image data reading, electrostatic latent image formation, and development
The description is omitted because it is the same as the process of BK and C described above.
You. The intermediate transfer belt 261 has a photosensitive drum.
Bk, C, M, and Y toner images sequentially formed on the ram 200
Are sequentially aligned on the same surface, and a four-color superposed toner image
Are formed, and in the next transfer step, the four color toners
The images are collectively transferred to the transfer paper 5 by the paper transfer device 263. When the image forming operation is started,
Copy paper 5 can be either the transfer paper cassette or the manual feed tray.
And waited at the nip of the registration roller pair 209.
I am working. Then, an intermediate transfer belt is attached to the paper transfer unit 263.
When the leading edge of the toner image on H.261
So that the leading edge of the transfer paper 5 coincides with the leading edge of the toner image.
The registration roller pair 209 is driven, and the transfer paper 5 and the toner
Registration with the image is performed. And the transfer paper 5
Superposed on the toner image on the intermediate transfer belt 261 to have a positive potential
Pass over the paper transfer unit 263. At this time, the corona release
The transfer paper 5 is positively charged by an electric current (hereinafter referred to as “transfer current”).
And most of the four-color superimposed toner image is on the transfer paper 5.
All at once. The discharge efficiency of the paper transfer device 263 (min.
Ratio) is about 20 to 40%, and the belt transfer device 265
Is the same as From the intermediate transfer belt 261, a four-color
The transfer paper 5 on which the toner image is collectively transferred is
Separation by AC + DC corona (not shown) arranged on the left side
Static electricity is removed when passing through the portion facing the static eliminator, and intermediate transfer
The sheet is separated from the belt 261 and moves onto the conveyor belt 211.
The transfer paper 5 on the paper transport belt 211 is transported to the fixing device 270.
The fixing roller 271 controlled to a predetermined temperature
The toner image is fused and fixed at the nip portion of the roller 272 and is discharged.
It is sent out of the apparatus main body by the output roller pair 212 and is not shown.
Stacking face up on a copy tray
Get pea. On the other hand, the photosensitive drum 200 after the belt transfer
The surface of the photoconductor cleaning device 201 (brush row)
, A rubber blade), and is cleaned with a static elimination lamp 2
02, the charge is uniformly removed. Removed from photoconductor drum 200
The collected toner is collected and passed through a collection pipe (not shown).
And stored in a waste toner tank (not shown). Also,
Intermediate transfer belt 261 after transferring the toner image on paper 5
Remaining on the surface of the belt cleaning device 2
Pressing the blade 62 again with the blade contact / separation mechanism
Will be cleaned by In the case of a repeat copy, the color
Operation of Scanner 1 and Image Formation on Photoconductor Drum 200
Follows the image forming process of the fourth color (Y) of the first sheet,
Forming the second color first color (Bk) image at a predetermined timing
Proceed to process. The intermediate transfer belt 261 has one sheet.
In the batch transfer process of the four-color superimposed toner image on the transfer paper 5
Continuously, the surface is cleaned by the belt cleaning device 262.
The second Bk toner image is transferred to the belt
To be copied. After that, the operation becomes the same as the first sheet.
You. The above is a copy for obtaining a four-color full-color copy.
Mode, but three-color copy mode and two-color copy mode
In the case of cards, the above for the specified color and number of times
The same operation is performed. Also, single color copy mode
In the case of, revolver development
Only the developing unit of the predetermined color of the unit 230 is in the developing operation state.
Then, the blade of the belt cleaning device 262 is
Continuous copy operation while pressed against transfer belt 261
I do. A3 size full color copy mode
In the case of the intermediate transfer belt 261
One color toner image is formed, and four rotations form four color toner images.
Is desirable, but the whole device is small,
The peripheral length of the intermediate transfer belt 261 is reduced,
Ensure copy speed and maximum copy speed
In order not to drop the paper, the intermediate transfer belt 2
It is preferable to form a one-color toner image during the two rotations of 61.
New In this case, the Bk toner image is transferred to the intermediate transfer belt 2.
After the transfer to the next intermediate transfer belt 261,
Indicates that development and transfer in the color printer 2 are performed.
And the next rotation makes the current
Image, and the C toner image is transferred to the intermediate transfer belt 261.
It is performed sequentially so as to transfer. At this time,
Rotating operation of revolver developing unit 230 for replacement
Is performed during the idle rotation. Next, the corona discharge rolling according to the characteristic portion of the present invention is described.
Configuration and transfer of paper transfer device 263 provided as copying device
The setting of the current will be described. FIG. 5 shows a paper transfer unit 263 and an intermediate transfer belt.
261 along with the leading end of the transfer paper 5
FIG. The intermediate transfer belt 261 is connected to the paper transfer device 2
63 with a gap capable of passing paper.
Is supported by two transfer opposing rollers 264a and 264b
It has become a flat part. In FIG. 5, the right side of the paper transfer unit 263 is the transfer paper 5
The left side is the exit side of the transfer paper 5. This entrance side
The entrance is formed by plate-shaped guide members 266a to 266f.
A guide is formed. These guide members are
The transfer paper 5 is positioned at the entrance side.
The final guide is a guide made of a thin sheet of synthetic resin.
And a guide member 266f. guide
The member 266e is fixed to the guide member 266c and
And the guide member 266f is
Fixed to a guide member 266d that is a part of the
Is located on the lower side. These guide members 266e, 26
6f are opposed to each other, and the transfer paper 5
Arranged so that the facing distance gradually narrows along the feed direction
The transfer direction of the transfer paper 5 is
The flat part is specified on the part facing the transfer opposing roller 264a.
I am trying to be. Also, guide members 266e, 26
6f, the guide member 266f is the guide member 2
66e and extends slightly longer in the direction of travel of the transfer paper than 66e.
To receive the transfer paper hanging downward. Guy
End member 266f and the transfer on the intermediate transfer belt 261
The distance L from the position where the leading edge of the paper 5 starts to contact is 2 ± 1.6.
mm. On the other hand, a guide member 267 provided on the outlet side
Means that the leading end 5F of the transfer paper 5 enters the paper transfer device 263
The guide member 26
8 is further guided toward the conveyor belt 211 (see FIG. 2).
It is for the purpose. The discharge wire 263a of the paper transfer device 263 is
The intermediate transfer belt 26 extends in a direction orthogonal to the plane of FIG.
1 corresponding to the width. Discharge wire 263a and middle
The distance from the surface of the intermediary transfer belt 261 is within a range of 9 ± 3 mm.
Set within. Secondary transfer is performed on the discharge wire 263a.
The toner image formed on the intermediate transfer belt 261
Voltage of the polarity opposite to the charging polarity of the toner
Then, a predetermined transfer current flows and corona discharge is performed. This
Transfer facing rollers 264a, 264
b to cover the flat part of the intermediate transfer belt
About the end of the guide member 266f and the exit side
The area limited by the end of the guide member 267 is
In the direction perpendicular to the plane of FIG.
A transfer electric field region E is formed. As described above, the color image type of the present embodiment
The automatic forming device forms images on both sides of the transfer paper 5.
The duplex mode or the manual duplex mode can be executed. This
When an image is formed on both sides of the transfer paper 5 as shown in FIG.
Transfer paper with the toner image transferred and fixed on the surface
5 is a surface on which the toner image T is formed as shown in FIG.
Face curl with the inside. This fe
Iskar is back curl for the back side. Special
When the color toner image is transferred and fixed
Easy to curl due to large amount of adhesion. After fixing
Transfer paper curls due to heat collection between toner and transfer paper.
This is because the reduction ratios are different. The transfer paper curled in this way is printed on the back side.
In order to form an image, the paper transfer unit 263 and the intermediate transfer are again performed.
Opposite portion to belt 261 (hereinafter referred to as “transfer opposing portion”)
The rear end 5E of the transfer paper 5 is
Leave the leading end of the guide member 266f on the paper transfer unit 263 side
Then, the rear end 5E of the transfer paper 5 moves downward, and
The flat portion of the intermediary transfer belt 261 has poor adhesion. this
Poor adhesion is caused by transfer of white spots or the like at the rear end of the transfer paper 5.
It causes a defect. The center of the transfer paper 5
Is that the degree of curl at the center is light and the rear end
Is guided by the guide member, so that the paper transfer device
263 and the intermediate transfer belt 261
Sufficient adhesion is obtained, and the above-mentioned transfer failure does not occur. The color image forming apparatus according to the present embodiment
To prevent transfer failure at the rear end of the transfer paper 5
When transferring the toner image to the rear end of the surface of the transfer paper
Independently forms a toner image on the rear edge of the
It is configured to be able to set the transfer current when transferring
I have. Then, the transfer is performed to transfer the toner image to the back surface.
The trailing end 5E of the transfer paper 5 conveyed to the copying opposing portion is the guide member 2
66f from the point when the tip on the transfer opposing portion side is released
When transferring the rear end of the back surface until the transfer of the toner image to the
Transfer current (hereinafter referred to as "transfer current at the rear end of the back surface").
I) When the back surface of the transfer paper 5 is the intermediate transfer belt 601
It was set so that it adhered to. For example, in color mode
Of the toner image formed on the intermediate transfer belt 261
The polarity is negative and the toner image is
Of the transfer paper 5 conveyed to the transfer opposing portion to transfer
The rear end 5E is the tip of the guide member 266f on the side of the transfer facing portion.
Transfer of the toner image to the surface ends when the edge is left
Transfer current (hereinafter referred to as “surface
I1 is +120 μA)
At this time, the transfer current I2 at the rear end of the back surface is larger than I1.
When set to +150 μA, I2 = + 120 μA
Transfer failure at the rear end of the transfer paper 5 (white
C) can be prevented. The color image forming apparatus of the present embodiment
-You can select and execute monochrome mode in addition to mode
Table 1 shows the monochrome mode.
The setting of the transfer current I2 at the rear end of the rear surface
This indicates whether or not transfer failure has occurred. In Table 1
“O” indicates good transferability, and “X” indicates no transfer at the rear end of the transfer paper.
Good (white spots or reverse transfer when transfer current is increased)
Has occurred. As Table 1 shows,
The transfer current I2 at the rear end of the rear surface is transferred to the transfer at the rear end of the front surface.
Set the current I1 (+70 μA) to a value that increases by 10% to 150%.
When specified, more preferably to a value of 15% to 100% increase
When set, transfer failure (white spots,
Reverse transcription) could be prevented, and good results were obtained. [0057] [Table 1] In the case of the color mode, the monochrome mode
Transfer amount of toner on the transfer paper
The paper is more likely to curl. Therefore, the color image forming apparatus of the present embodiment
Indicates the transfer current I2 at the rear end of the back surface in the monochrome mode,
And the transfer current I2 'at the rear end of the
It is configured so that it can be set independently. And Monok
Transfer current I2 at the rear end of the rear surface in the
When the current is μA, the rear end of the rear
The shooting current I2 'is set to +200 [mu] A which is larger than the above I2.
When set, it is different from when I2 '= + 100 μA.
And the occurrence of transfer failure (white spots) at the rear end of the transfer paper 5
Could be prevented. Further, the color mode is set in the same manner as in Table 1 above.
Of the transfer current I2 'at the rear end of the rear surface
Table 1 shows the occurrence of transfer failure when
Similar results were obtained. According to the results, the color
The transfer current I2 'at the rear end of the back surface in the mode is monochrome.
The transfer current I2 (+100 μ
A) is better when set to a value of 10% to 200% increase in A).
Preferably, when set to a value of 20% to 100% increase,
Prevents poor transfer (white spots, reverse transfer) at the rear end of paper
And good results were obtained. As described above, according to the present embodiment, the surface of the transfer paper 5
The transfer current I1 at the rear end of the front surface is replaced with the transfer current I2 at the rear end of the rear surface,
Since it can be set to the minimum necessary independently of I2 ', the transfer paper
5 to the intermediate transfer belt 261
The occurrence of transfer failure can be prevented. Furthermore, the rear end of the back
Transfer currents I2 and I2 'are larger than the transfer current I1.
Transfer the toner image to the back by setting the transfer current
Even if the transfer paper 5 before the transfer is curled,
The rear end of the back surface may be brought into close contact with the intermediate transfer belt 261.
It is possible to eliminate white spots at the rear end of the back side of the transfer paper 5
The occurrence of transfer failure can be prevented. In particular, according to the present embodiment, the transfer paper 5
The degree of curl is smaller than the color mode
In the transfer mode, the transfer current I2 at the rear end of the
From the transfer paper 5 to the intermediate transfer belt.
Transfer failure such as reverse transfer of the toner image to the
Hateful. The color image forming apparatus of the above embodiment
Of the curl of the transfer paper 5 before the transfer of the toner image to the back surface.
The transfer current I2 at the rear end of the back surface can be set according to the degree.
You may comprise so that it may be. The degree of curl of the transfer paper 5
Is detected by some sensor,
By inputting the result of eye contact,
Can be determined. like this
In the case where the transfer paper 5 is configured,
Poor adhesion between the rear end of the paper 5 and the intermediate transfer belt 261
Transfer defects such as white spots can be more reliably prevented. Further, in the above embodiment, after the back side of the transfer paper,
To prevent transfer defects such as white spots at the edges,
The transfer current I2 at the rear end of the back side is
Although it is configured so that it can be set independently of the flow,
The transfer roller conveyed to the transfer opposing portion to transfer the toner image
The trailing end of the copying paper 5 is the tip of the guide member 266f on the side of the transfer facing portion.
Transfer of the toner image to the back surface ends when the edge is released
Transfer belt 261 at the time of transfer of the rear end portion of the back surface up to
And the peripheral speed V2 of the transfer paper 5 to other parts of the transfer paper 5.
Of the transfer paper 5
The rear end of the back surface is configured to be in close contact with the intermediate transfer belt 261.
May be implemented. More specifically, at the time of the transfer of the rear
Speed V of the intermediate transfer belt 261 and the transfer paper 5 at
2. Transfer of the rear end of the surface when transferring the toner image to the surface
Peripheral speed of the intermediate transfer belt 261 and the transfer paper 5 at the time
V1 and the rear end of the surface.
Peripheral speed V1 at the time of partial transfer
Set to the usual 105 mm / sec as in the case of transfer.
The peripheral speed V2 at the time of transfer of the rear end of the back surface is set to half of V1.
When set to 5mm / sec, V2 remains V1
Unlike the case where the transfer was performed, transfer failure (white
Omission) could be prevented. The switching of the peripheral speed V1 to V2 is performed as follows.
For example, the rear end of the transfer paper 5 passes through the registration roller pair 209
Can be performed at the same timing. In the above embodiment, the toner image carrier
Explained the example using the intermediate transfer belt as
However, according to the present invention, the toner image is carried without using the intermediate transfer belt.
Transfers a toner image from a photoreceptor drum to transfer paper
It can also be applied to things. [0067] [0068] [0069] [0070][Effect of the Invention] According to the invention, the surface of the transfer material, the transfer material
A predetermined peripheral speed
Transfer by transferring toner image carrier and transfer material
Causes poor transfer such as reverse transfer to the toner image carrier
This has the effect that it can be prevented. Moreover, the back side of the transfer paper
For the rear end, the front surface, the back end, and the center of the back
Peripheral speed set to a small value independently of the peripheral speed for the part
Transfer by transferring toner image carrier and transfer material
Thereby, even if the transfer paper is curled,
The rear end of the back surface can be in close contact with the toner image carrier
Therefore, transfer failure such as white spots at the rear end of the back surface of the transfer material
There is an effect that generation of good can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged view of an opposing portion between an intermediate transfer belt and a paper transfer device of a color image forming apparatus according to an embodiment. FIG. 2 is a schematic configuration diagram of the color image forming apparatus. FIG. 3 is an enlarged view of a main part of the color image forming apparatus. FIG. 4A is a diagram illustrating a stacking operation of a duplex unit of the color image forming apparatus. (B) is an explanatory view of a refeeding operation of the duplex unit. FIG. 5 is an enlarged view of a portion where an intermediate transfer belt and a paper transfer device of the color image forming apparatus are opposed to each other. FIG. 6 is an explanatory diagram of curling of transfer paper. [Description of Signs] 5 Transfer paper 261 Intermediate transfer belt 263 Paper transfer device 263a Discharge wires 264a, b Transfer opposing rollers 266a to f Guide member E Transfer electric field forming area

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ identification code FI G03G 21/00 384 G03G 21/00 384 (58) Investigated field (Int.Cl. ⁷ , DB name) G03G 15/16 G03G 15 / 00 106 G03G 15/00 303 G03G 15/01 114 G03G 21/00 384

Claims (1)

(57) Patent Claims 1. A preparative corona discharge transfer device opposite a predetermined gap with respect to toner image bearing member, a transfer current is supplied to transfer current to the discharge wire of the corona discharge transfer device Supply means, a guide member for guiding a transfer material to a portion facing the toner image carrier and the corona discharge transfer device, a fixing device for fixing the toner image transferred onto the transfer material, and a fixing device. A transfer material transporting device for transporting the transported transfer material to the opposite portion by exchanging the front surface and the back surface, and transferring and fixing a toner image on the surface of the transfer material, In the image forming apparatus for transferring the toner image to the back surface of the transfer material, the rear end of the transfer material conveyed to the opposed portion to transfer the toner image to the back surface, When leaving the tip on the opposite side The peripheral speed of the toner image carrier and the transfer material at the time of transfer of the rear end of the back surface until the transfer of the toner image to the back surface is completed, and the peripheral speed of the transfer material at the time of transfer to a portion other than the rear end of the back surface of the transfer material. The peripheral speed of the toner image carrier and the transfer material can be set independently.
And, the toner Zo担during backside rear end transfer of the transfer sheet
Adjust the peripheral speed of the carrier and the transfer material to
The toner image carrier during transfer to an outer portion;
An image forming apparatus, wherein the peripheral speed of the transfer material is lower than that of the transfer material .