JP2000035699A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize excellent fixation for cardboard or the like without changing a processing condition by decreasing the speed of an intermediate transfer body and a fixing means, providing a mode for forming a toner image only on the rear surface of transfer material and making a fixing rotating member for fixing an image on the rear surface side softer than that for fixing the image on the front surface side in the fixing means. SOLUTION: The transfer material is carried into a timing roller 15b functioning as a transfer material feeding means at ordinary speed and stands by. Next, the driving speed of the fixing device 17, a photoreceptor drum 10 and an intermediate transfer belt 14a is made lower than the ordinary speed before the leading edge of the toner image on the belt 14a abuts on the drum 10. The device 17 is provided with a 1st (2nd) fixing roller 17a (17b) as the upper (lower) roll type fixing rotating member for fixing the toner image being a front surface image (rear surface image). In such a case, by making the rotating member for fixing the image on the rear surface side softer than that for fixing the image on the front surface side and performing fixation by a soft and wide fixing part, the excellent fixation for OHT and the like performed in a one-side image forming process for the rear surface is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus for transferring and fixing a toner image formed on an image forming body onto a transfer material to form an image in a copying machine, a printer, a facsimile or the like. In particular, an image is formed on both the front and back surfaces of the transfer material by transferring the toner image on the image forming body to the front surface of the transfer material or temporarily transferring the toner image on the intermediate transfer body and then to the back surface of the transfer material. The present invention relates to an image forming apparatus capable of performing such operations.

[0002]

2. Description of the Related Art Conventionally, in double-sided image formation, an image on one side formed on an image forming body is transferred and fixed on a transfer material, and this is temporarily stored in a double-sided reversal feeding device and formed again. A method has been adopted in which a transfer material is fed from a two-sided reversing feed device in synchronization with an image formed on a body, and an image on the other surface is transferred and fixed onto the transfer material.

In this double-sided image forming apparatus, as described above,
The transfer of the transfer material, such as feeding to the two-sided reversing feed device or passing through the fixing device twice, is performed, so that the reliability of transfer of the transfer material is low, causing jams and wrinkles of the transfer material. .

On the other hand, JP-B-49-37538 and JP-B-54-28740, and JP-A-1-44457.
Japanese Patent Application Laid-Open Publication No. 4-214576 and the like propose a method in which a toner image is formed on both surfaces of a transfer material using an image forming body and an intermediate transfer body, and then fixed once.

Further, the present inventors have arranged a plurality of sets of toner image forming means including a charging means, an image writing means, a developing means, etc. around a photosensitive drum (image forming body), and provided on the photosensitive drum. After the formed superimposed color toner image is once transferred to the belt-shaped intermediate transfer body by the first transfer means, the superimposed color toner image is formed again on the photoconductor drum, and the toner on the photoconductor drum is formed. The transfer material fed in time with the image and the toner image on the intermediate transfer body is charged by the transfer material charging means and adsorbed on the intermediate transfer body,
On both sides of the transfer material conveyed by the intermediate transfer body,
The toner image on the photosensitive drum is transferred as a front image by a second transfer unit (using the same one as the first transfer unit), and the toner image on the intermediate transfer body is transferred as a back image by a third transfer unit. Fixing device (fixing means)
The curvature of the roller member provided on the side and stretching the intermediate transfer member,
And an image forming apparatus and an image forming method for separating a transfer material from an intermediate transfer body by static elimination by a transfer material separating unit provided as necessary, and fixing a toner image on the transfer material by a fixing device to form a double-sided color image Is disclosed in JP-A-9-25849.
No. 2 and JP-A-9-258516.

[0006]

However, in a double-sided image forming apparatus for forming a double-sided image by transferring the front and back toner images of the image forming body and the belt-shaped intermediate transfer body onto a transfer material as described above. When an image is formed by using an OHT (overhead transparency) or a thick paper as a material, or when an image having a glossiness is formed, a large amount of fixing heat is required. In general, fixing is carried out at a low speed, but it is difficult because it interferes with an image forming process such as image exposure or development, and the variable range is limited. Further, when the driving speeds of the image forming process members such as the driving speed of the fixing unit, the driving speed of the intermediate transfer member, the driving speed of the image forming body, the transfer material conveying unit, and the driving speed of the developing unit are reduced, the image forming The problem is that the total copy speed required for the image processing is greatly reduced. Further, there arises a problem that process conditions such as charging or development change.

The present invention solves the above-mentioned problems, and can fix glossiness fixing, OHT, cardboard, etc., which require a large fixing heat capacity, without slowing down the total copy speed and without changing the process conditions. It is an object to provide an image forming apparatus that performs well.

[0008]

An object of the present invention is to transfer a toner image formed on an image forming member to a surface of a transfer material, and to transfer the toner image formed on the image forming member to an intermediate transfer member. And transferring the toner image to the back surface of the transfer material through the intermediary transfer medium, thereby reducing the speed of the intermediate transfer body and the fixing device in an image forming apparatus in which toner images are formed on both surfaces of the transfer material and fixed by a fixing unit. An image having a mode comprising a step of forming a toner image only on the back surface of the transfer material, wherein the fixing rotating member on the back side of the fixing means is softer than the fixing rotating member on the front side. This is achieved by a forming device.

It is another object of the present invention to transfer a toner image formed on an image forming member to a surface of a transfer material, and to transfer the toner image formed on the image forming member via an intermediate transfer member. In the image forming apparatus in which toner images are formed on both surfaces of the transfer material and fixed by a fixing unit, the speed of the intermediate transfer body and the fixing unit is reduced, and the transfer material is This is achieved by an image forming apparatus having a mode including a step of forming a toner image only on the back surface, and changing a linear velocity in accordance with designation of glossiness of fixing of a toner image by the fixing unit. .

[0010]

Embodiments of the present invention will be described below. Note that the description in this column does not limit the technical scope of the claims and the meaning of terms. Further, the following assertive description in the embodiment of the present invention indicates the best mode, and does not limit the meaning or technical scope of the terms of the present invention. In the following description of the embodiment, the surface of the transfer material on the side facing the image forming body in the transfer area is called the front surface, and the other surface of the transfer material, that is, the surface of the transfer material on the side facing the intermediate transfer body is called the back surface. The image transferred to the front surface of the transfer material is called a front image, and the image transferred to the back surface of the transfer material is called a back image.

An image forming process and each mechanism of an embodiment of the image forming apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is a sectional configuration view of a color image forming apparatus showing an embodiment of the image forming apparatus according to the present invention, FIG. 2 is a side sectional view of the image forming body of FIG. 1, and FIG. FIG. 3A is a diagram illustrating a toner image forming state in the image forming apparatus according to the present invention, and FIG. 3A is a diagram illustrating a toner image forming state when a back surface image formed on an image forming body is transferred onto an intermediate transfer body. FIG. 3B is a diagram illustrating a toner image forming state when a front surface image is formed on an image forming body in synchronization with a back side image on the intermediate transfer body.
(C) is a diagram showing double-sided image formation on a transfer material,
FIG. 4 is a diagram showing an example of a document image reading unit.
6 is a control circuit block diagram of the image forming apparatus, and FIG.
6A and 6B are diagrams illustrating image formation when a mode such as OHT, cardboard, or gloss is selected, FIG. 6A is a diagram illustrating backside image formation, and FIG. FIG. 7 is a diagram showing upper and lower fixing rotating members. In the image forming process described below, the step of transferring the toner image formed on the image forming body to the surface of the transfer material is a first step, and the step of transferring the toner image formed on the image forming body is an intermediate step. The step of transferring the image to the back surface of the transfer material via the transfer body is referred to as a second step.

A mode selection (shown in FIG. 5) which requires a large amount of fixing heat at the time of fixing when forming an image such as OHT (overhead transparency), thick paper or glossiness, which will be described later, is selected from an operation unit (not shown). In the case where the image forming state is a non-glossy gloss and the recording material is a plain recording paper of 45 to 60 kg / m ² as a transfer material, the image forming process is performed at a low speed when a mode selection described later is performed. The image forming process of all the image forming process members is performed at a normal speed higher than the image forming process.
For example, the driving speed of the fixing unit, the image forming body, the intermediate transfer body, the transfer material feeding unit, the developing unit, etc. is a normal speed, and the charging unit, the first transfer unit, the second transfer unit, the third transfer unit Current or voltage control of the means, transfer material charging means, transfer material separating means, etc. is performed at a current value or voltage value corresponding to a normal speed.

As shown in FIGS. 4 and 5, a document image reading device 500 as document image reading means provided integrally with the image forming device main body or in an external device such as an external printer or a scanner includes a reading device main body 501, A document storage plate 505 for storing a document PS, a document sending roller 502, a transparent plate 503, a document conveying roller 504, and a document discharge plate 50.
6 and line-shaped original image reading sensors PS1 and PS2 which are provided with the transparent plate 503 interposed therebetween to read the original image of the original PS from above and below, and are provided with signal lines incorporated in a color image forming apparatus described below. Connected to control unit.

When the original PS sent by the original sending roller 502 passes through the transparent plate 503, the original PS is converted to a one-sided original by original image reading sensors PS1 and PS2 provided above and below the transparent plate 503. Determination of whether the document is a double-sided document (single-sided or double-sided) and reading of image data of the document PS are performed.

In this embodiment, one-sided / two-sided discrimination and image data reading are performed by one set of upper and lower sensors. However, a plurality of sensors respectively corresponding to image data reading and one-sided / two-sided discrimination may be provided. For example, image data may be read after a single-sided or double-sided discrimination has been performed using a plurality of sensors respectively corresponding to each other. Original image reading sensor PS1
Alternatively, image data of one bundle of originals PS is read by PS2 and stored in the RAM through the control unit.

When the image is determined to be a double-sided image,
The image data of the original PS is read into the RAM through the control unit by the original image reading means shown in FIG. 4, and the double-sided image forming program P1 stored in the ROM shown in FIG.
Is read into the RAM through the control unit, and the control unit executes the double-sided image forming program P1 to perform the image forming process.

In FIG. 1, reference numeral 10 denotes a photosensitive drum as an image forming body; 11, a scorotron charger as charging means for each color; 12, an exposure optical system as image writing means for each color; The developing device 14a is an intermediate transfer belt which is an intermediate transfer member, and 14c is a first and a second transfer belt.
14g, a backside transfer unit as a third transfer unit, 14m, a neutralizer as a neutralization unit, and 150g.
Is a paper charger which is a transfer material charging means, 14h is a paper separation AC static eliminator which is a transfer material separating means, 160 is a conveying section having a separation claw 210 which is a claw member and a spur 162 which is a spur member, and 17 is a fixing member. It is a fixing device as a means.

The photosensitive drum 10, which is an image forming body, has a transparent conductive layer, a, on the outer periphery of a cylindrical substrate formed of a transparent member such as optical glass or transparent acrylic resin.
-A photosensitive layer such as an Si layer or an organic photosensitive layer (OPC) is formed, and is rotated clockwise as indicated by an arrow in FIG. 1 with the conductive layer grounded.

The photosensitive drum 10 is, as shown in FIG.
Flange members 10A and 1A at both ends for engaging and fixing it
The gear G integrated with the flange member 10B is supported by the bearings B1 and B2 fitted into the drum body 0B and supported rotatably by the drum shaft 30 erected and fixed to the apparatus main body. When driven by meshing with the drive gear, it is rotated at a constant speed in a predetermined direction.

A scorotron charger 11, which is a charging unit for each color, an exposure optical system 12, which is an image writing unit for each color, and a developing unit 13, which is a developing unit for each color, form a set of yellow (Y) ), Magenta (M), cyan (C), and black (K) are provided for the image forming process, and four sets are provided.
With respect to the rotation direction of 0, they are arranged in the order of Y, M, C, K.

The scorotron charger 11, which is a charging means for each color, has a control grid maintained at a predetermined potential and a discharge electrode 11a composed of, for example, a sawtooth electrode, and faces the photosensitive layer of the photosensitive drum 10. And installed
The charging operation (minus charging in the present embodiment) is performed by corona discharge having the same polarity as the toner, and the photosensitive drum 1 is charged.
A uniform potential is given to 0. As the discharge electrode 11a, a wire electrode or a needle electrode may be used.

Exposure optical system 1 as image writing means for each color
2 indicates that the exposure position on the photosensitive drum 10 is the photosensitive drum 1 with respect to the scorotron charger 11 for each color described above.
It is arranged inside the photoconductor drum 10 so as to be located on the downstream side in the rotation direction of 0. As shown in FIG. 2, each exposure optical system 12 has a line in which a plurality of LEDs (light emitting diodes) as light emitting elements of image exposure light arranged in the main scanning direction in parallel with the drum shaft 30 are arranged. An exposure unit composed of an exposure element 12a in the shape of a circle, a light-converging light transmitter (trade name: Selfoc lens array) 12b as an imaging element, and a lens holder 12c, which is attached to the holding member 20. . In addition to the exposure optical system 12 for each color, the transfer simultaneous exposure unit 12d and the uniform exposure unit 12e are attached to the holding member 20, and are housed integrally inside the light-transmitting substrate of the photosensitive drum 10. Exposure optical system 1 for each color
Reference numeral 2 denotes an image exposure of the photosensitive layer of the photosensitive drum 10 from the back side in accordance with image data of each color read by the document image reading device 500 (see FIG. 5) and stored in the memory, and an electrostatic latent image is formed on the photosensitive drum 10. To form As the exposure element 12a, in addition to an LED, an element in which a plurality of light emitting elements such as FL (phosphor light emission), EL (electroluminescence), and PL (plasma discharge) are arranged in an array can be used. The emission wavelength of the image exposure light emitting element is usually Y,
780-900n with high transparency to M and C toners
m is used, but in the present embodiment, since the image exposure is performed from the back surface, the color toner does not have sufficient transparency to the color toner.
The wavelength may be 80 nm. Further, since 80% or more of the image exposure light is absorbed by the photosensitive layer of the photosensitive drum 10, the influence of the reflection and absorption by the color toner on the surface of the photosensitive drum 10 can be neglected. Generally, the development order of the color toners is Y,
The order of M, C and K is preferred. In FIG. 2, WA is a lead wire from a light emitting element (LED) for image exposure light.

The developing device 13 as a developing means for each color keeps a predetermined gap with respect to the peripheral surface of the photosensitive drum 10 and rotates in a forward direction with respect to the rotating direction of the photosensitive drum 10, for example, 0.5 to 1 mm in thickness. And a developing casing 131 formed of a cylindrical nonmagnetic stainless steel or aluminum material having an outer diameter of 15 to 25 mm, and a developing casing 138. Inside the developing casing 138, yellow (Y) and magenta ( M), cyan (C) and black (K) one-component or two-component developers. Each developing unit 13
Is maintained in a non-contact state with a predetermined gap, for example, 100 to 500 μm, from the photosensitive drum 10 by an abutting roller (not shown), and applies a developing bias in which a DC voltage and an AC voltage are superimposed on the developing sleeve 131. By doing
Non-contact reversal development is performed to form a toner image on the photosensitive drum 10.

The intermediate transfer belt 14a, which is an intermediate transfer member, has a volume resistivity of 10 ⁸ Ω · cm to 10 ¹⁴ Ω · cm, preferably 10 ⁹ Ω · cm.
It is an endless belt of 〜１０10 ¹² Ωcm, for example, modified polyimide, thermosetting polyimide, ethylene tetrafluoroethylene copolymer, polyvinylidene fluoride, a thickness of 0.1 to 0.1 to which a conductive material is dispersed in engineering plastic such as nylon alloy This is a seamless belt having a two-layer structure in which a 1.0-mm semiconductive film substrate is coated with a fluorine coating having a thickness of 5 to 50 μm, preferably as a toner filming preventing layer. In addition, a semiconductive rubber belt having a thickness of 0.5 to 2.0 mm in which a conductive material is dispersed in silicon rubber, urethane rubber, or the like can be used as the base of the belt. The intermediate transfer belt 14a is
Each of them is stretched in contact with a driving roller 14d, a ground roller 14j, a driven roller 14e, a guide roller 14f, and a tension roller 14i, which are roller members, and is rotated in a counterclockwise direction indicated by an arrow in FIG. Guide roller 14
f, the driven roller 14e, the ground roller 14j, and the drive roller 14d are fixedly rotated, and the tension roller 14
i is movably supported and rotated by the elastic force of a spring or the like (not shown). The drive roller 14d is rotated by a drive from a drive motor (not shown), and drives and rotates the intermediate transfer belt 14a. The rotation of the intermediate transfer belt 14a causes the ground roller 14j, the driven roller 14e, the guide roller 14f, and the tension roller 14i to be driven and rotated. The slack of the rotating intermediate transfer belt 14a is tensioned by the tension roller 14i. The recording paper P, which is a transfer material, is supplied to a position where the intermediate transfer belt 14a is stretched around the driven roller 14e, and is conveyed by the intermediate transfer belt 14a. The recording paper P is separated from the intermediate transfer belt 14a at a curvature portion KT at an end of the intermediate transfer belt 14a stretched around the drive roller 14d on the fixing device 17 side.

Transfer device 14 as first and second transfer means
c denotes the photosensitive drum 10 with the intermediate transfer belt 14a interposed therebetween.
A transfer area 14b is formed between the intermediate transfer belt 14a and the photosensitive drum 10. A DC voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied to the transfer device 14c, and the toner image on the photosensitive drum 10 is transferred onto the intermediate transfer belt 14a or onto the surface of the recording paper P as a transfer material. Transcribe.

The back transfer device 14g, which is the third transfer means, is preferably constituted by a corona discharger, and is provided with a transfer device 14c.
And a driving roller 14d are provided opposite to a conductive ground roller 14j that is grounded with the intermediate transfer belt 14a interposed therebetween, and a DC voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied. , Intermediate transfer belt 14
a is transferred to the back surface of the recording paper P.

The static eliminator 14m, which is a static eliminator, is preferably constituted by a corona discharger, and is provided downstream of the transfer unit 14c, which is the first and second transfer unit, with respect to the moving direction of the intermediate transfer belt 14a. 14c is provided in parallel with
An AC voltage on which a DC voltage having the same polarity or opposite polarity to the toner is superimposed is applied, and the charge of the intermediate transfer belt 14a charged by the voltage application of the transfer device 14c is eliminated.

The paper charger 150, which is a transfer material charging means, is preferably constituted by a corona discharger, is provided to face a driven roller 14e, which is grounded across the intermediate transfer belt 14a, and has the same polarity as the toner (this embodiment). (In the embodiment, negative polarity) is applied, and the recording paper P is charged and attracted to the intermediate transfer belt 14a. In addition to the corona discharger, a paper charging brush or a paper charging roller that can abut and release the intermediate transfer belt 14a can be used as the paper charger 150.

Paper separation AC neutralizer 1 as transfer material separating means
Reference numeral 4h denotes a driving roller 14 which is preferably constituted by a corona discharger, and which is grounded to the end of the intermediate transfer belt 14a on the side of the fixing device 17 as required.
d, and an AC voltage obtained by superimposing a DC voltage of the same polarity or opposite polarity to the toner is applied as necessary.
The recording paper P conveyed by the intermediate transfer belt 14a is discharged and separated from the intermediate transfer belt 14a.

The transport section 160 includes a separation claw 210 as a claw member.
And a spur 162 serving as a spur member. The transport unit 160 includes the fixing device 1
7, the intermediate transfer belt 14a is deformed, the toner image carried on the intermediate transfer belt 14a tends to be fused, and the transfer becomes difficult.
4a is prevented from sticking to the toner.

The separation claw 210, which is a claw member, is close to the curvature portion KT of the intermediate transfer belt 14a.
Is fixed to the support shaft 221 at a predetermined interval, preferably 0.1 to 2.0 mm, and when the recording paper P is separated from the intermediate transfer belt 14a, the intermediate transfer belt 14
The leading end of the recording paper P that is to be bent and conveyed in the direction a is brought into contact with the recording paper P to assist the separation of the recording paper P.

The spur 162, which is a spur member, has a plurality of projections 162a on its peripheral surface, and is provided rotatably about a rotation support shaft 165. The spur 162 guides the back side of the recording sheet P to convey the recording sheet P, prevents the back side toner image of the recording sheet P having the toner image on both sides from being disturbed, and also fixes the recording sheet P to the fixing device 17. The recording paper P is stably conveyed to the fixing device 17 while keeping the entering direction constant.

The separation claw 210 and the spur 162 are positioned between the transfer material conveying surface of the intermediate transfer belt 14a or the extension surface thereof.
It is arranged on the opposite side of the photosensitive drum 10. It is also possible to provide spurs 162 as spur members on both sides of the transfer material conveying surface or an extension surface thereof.

A fixing device 17 as a fixing means includes a first fixing roller 17a as an upper (front side) roll-shaped fixing rotating member for fixing a toner image of a front side image (upper side image), and a back side. A second fixing roller 17b as a roll-shaped fixing rotating member on the lower side (back side) for fixing the toner image of the image (image on the lower side);
The recording paper P is nipped by a nip portion T formed between the first fixing roller 17a and the second fixing roller 17b, and the toner image on the recording paper P is fixed by applying heat and pressure.
Halogen heaters 171c are disposed inside the first fixing roller 17a and the second fixing roller 17b, respectively (see FIG. 6).

Next, the image forming process will be described.

The photosensitive drum 10 is rotated clockwise as indicated by an arrow in FIG. 1 by starting a photosensitive member driving motor (not shown) at the start of image recording, and is simultaneously exposed to light by the charging action of a yellow (Y) scorotron charger 11. Body drum 1
Application of a potential to 0 starts.

After the photosensitive drum 10 is applied with a potential, the Y exposure optical system 12 starts image writing with a first color signal, that is, an electric signal corresponding to the Y image data. An electrostatic latent image corresponding to the Y image of the original image is formed on the front surface.

The latent image is reversal-developed in a non-contact state by the Y developing unit 13, and a yellow (Y) toner image is formed on the photosensitive drum 10.

Next, a potential is applied to the photosensitive drum 10 from above the Y toner image by the charging action of the magenta (M) scorotron charger 11, and the second color signal, that is, the M color signal, is applied by the M exposure optical system 12. Image writing is performed by an electric signal corresponding to the image data, and the magenta (M) toner image is superimposed on the yellow (Y) toner image by non-contact reversal development by the M developing unit 13. It is formed.

By the same process, the cyan (C) toner image corresponding to the third color signal is further superimposed by the cyan (C) scorotron charger 11, the exposure optical system 12 of C and the developing device 13 of C. The black (K) toner image corresponding to the fourth color signal is sequentially superimposed thereon by a black (K) scorotron charger 11, a K exposure optical system 12, and a K developing device 13. A superposed color toner image of four colors of yellow (Y), magenta (M), cyan (C) and black (K) is formed on the peripheral surface within one rotation of the photosensitive drum 10. (Toner image forming means).

These Y, M, C and K exposure optical systems 12
Image writing on the photosensitive layer of the photosensitive drum 10 is performed from the inside of the drum through the above-described translucent substrate. Therefore, the writing of the images corresponding to the second, third and fourth color signals is performed without any influence from the previously formed toner image, and is equivalent to the image corresponding to the first color signal. Can be formed.

In the transfer area 14b, the superimposed color toner image serving as the back surface image formed on the photosensitive drum 10 as the image forming body by the above-described image forming process is formed.
By the transfer device 14c as a first transfer unit, the transfer (1) is collectively performed on the intermediate transfer belt 14a as the
The next transfer is performed (FIG. 3A). At this time, uniform exposure may be performed by the simultaneous transfer exposure device 12d provided inside the photosensitive drum 10 so that good transfer is performed.

The toner remaining on the peripheral surface of the photoconductive drum 10 after the transfer is subjected to static elimination by the photoconductive drum AC static eliminator 16, and then enters a cleaning device 19 as image forming body cleaning means. The toner is cleaned by a cleaning blade 19a made of a rubber material in contact with the toner, and collected by a screw 19b in a toner discharge container (not shown). Further, the peripheral surface of the photosensitive drum 10
For example, a uniform exposure device 12 before charging using a light emitting diode
The history of the photosensitive drum 10 in the previous image formation is eliminated by the exposure by e.

The charge on the intermediate transfer belt 14a charged by the transfer unit 14c is removed by a charge removal unit 14m which is a charge removal unit provided in parallel with the transfer unit 14c.

After the superimposed color toner image serving as the back side image is formed on the intermediate transfer belt 14a as described above, the front side image is continuously formed on the photosensitive drum 10 in the same manner as the above color image forming process. Is formed (FIG. 3B). On this occasion,
The image data is changed so that the front surface image formed on the photoconductor drum 10 becomes a mirror image with respect to the rear surface image formed on the photoconductor drum 10.

With the formation of a surface image on the photosensitive drum 10, recording paper P as a transfer material is sent out from a paper feed cassette 15 as a transfer material storage means by a feed roller 15a, and is used as a transfer material feeding means. Timing roller 1
5b, and driven by the timing roller 15b, the first toner image formed on the photosensitive drum 10 is a surface toner color toner image and the intermediate transfer belt 14
The sheet is fed to the transfer area 14b in synchronization with the color toner image of the back side image, which is the second toner image carried on the transfer area 14b. At this time, the fed recording paper P is charged to the same polarity as the toner by a paper charger 150 which is a transfer material charging means provided on the surface side of the recording paper P, and the intermediate transfer belt 14a
And is fed to the transfer area 14b. By charging the paper with the same polarity as the toner, the toner image is prevented from being attracted to the toner image on the intermediate transfer belt 14a or the toner image on the photoconductor drum 10, thereby preventing the toner image from being disturbed.

In the transfer area 14b, a second voltage to which a voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied.
The surface image on the photosensitive drum 10 is collectively transferred onto the surface of the recording paper P by the transfer device 14c as the transfer means (2).
Next transfer). At this time, the back side image on the intermediate transfer belt 14a is not transferred to the recording paper P and the intermediate transfer belt 1
4a. Transfer device 14 as second transfer means
In the case of secondary transfer by c, so that good transfer is performed,
The uniform exposure may be performed by a simultaneous transfer exposure device 12d using, for example, a light emitting diode, provided inside the photosensitive drum 10 so as to face the transfer area 14b. Further, the intermediate transfer belt 14a charged by the transfer device 14c
Is removed by the charge remover 14m.

The recording paper P on which the color toner image has been transferred to the front surface is conveyed to a back transfer device 14g as a third transfer means to which a voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied. Then, the back side image on the peripheral surface of the intermediate transfer belt 14a is collectively transferred (tertiary transfer) to the back side of the recording paper P by the back side transfer unit 14g (FIG. 3C).

The recording paper P on which the color toner images are formed on both sides is formed by the curvature of the curvature portion KT of the intermediate transfer belt 14a and the paper as transfer material separating means provided at the end of the intermediate transfer belt 14a as necessary. The spur 162 provided on the transport unit 160 is separated from the intermediate transfer belt 14a by the static elimination action of the separation AC neutralizer 14h and the separation claw 210 provided on the transport unit 160 at a predetermined interval from the intermediate transfer belt 14a. Fixing device 17 as fixing means through
The toner image on the recording paper P is fixed by applying heat and pressure at a nip portion T between the first fixing roller 17a and the second fixing roller 17b. The recording paper P on which double-sided image recording has been performed is sent upside down, and is discharged by a discharge roller 18 to a tray outside the apparatus. Further, as shown by a dashed line in FIG. 1, a switching member (not shown) may be provided at the exit of the fixing device 17 so that the sheet is discharged to a tray outside the device without turning over the front and back.

The toner remaining on the peripheral surface of the intermediate transfer belt 14a after the transfer is provided to face the guide roller 14f with the intermediate transfer belt 14a interposed therebetween, and is applied to the intermediate transfer belt 14a with the support shaft 142 as a rotation fulcrum. The intermediate transfer member is cleaned by an intermediate transfer member cleaning device 140 which is an intermediate transfer member cleaning unit having an intermediate transfer member cleaning blade 141 capable of contacting and releasing contact.

The toner remaining on the peripheral surface of the photoreceptor drum 10 after the transfer is removed by a photoreceptor drum AC static eliminator 16 and then cleaned by a cleaning device 19. By 12e, the history of the photosensitive drum 10 in the previous image formation is eliminated, and the next image formation cycle is started.

Since the superimposed color toner images are collectively transferred by using the above-described method, color shift of the color image on the intermediate transfer belt 14a, scattering or rubbing of the toner, and the like are less likely to occur, and the image deterioration is small. Double-sided color image formation is performed.

In the original image reading apparatus 500,
When the image data of the document PS read by the document image reading unit shown in FIG. 4 is copied as a single-sided image of only the surface of the photosensitive drum 10 when the image is determined to be a single-sided image or a double-sided image The RO shown in FIG.
A single-sided image forming program P2 of the front surface by the photosensitive drum 10 as an image forming body stored in M is read into the RAM through the control unit, and the single-sided image forming program P2 of the front surface is executed by the control unit. The image forming process for only the surface by the photosensitive drum 10 described above is continuously performed.

When the image data is determined to be a single-sided image or a double-sided image, the image data of the original PS read by the original image reading means shown in FIG. In the case of copying as an image, a single-sided image forming program P3 on the back surface of the intermediate transfer belt 14a as an intermediate transfer member stored in the ROM shown in FIG. The image forming program P3 is executed, and the image forming process for only the back surface by the intermediate transfer belt 14a described in FIG. 1 is continuously performed.

In the above, in the double-sided image forming process and the image forming process only on the back surface, the fixing device 17 is used.
The fixing of the toner image on the transfer material is performed intermittently every other sheet, and the fixing of the toner image on the transfer material by the fixing device 17 is performed continuously in the image forming process of only the front surface.

As shown in FIG. 5, selection of a transfer material such as OHT (overhead transparency) or thick paper exceeding 60 kg / m ² , or mode selection that requires a large amount of fixing heat at the time of image formation such as glossiness. Is selected from the operation unit (not shown), the image data of the document PS read by the document image reading unit is transferred to the intermediate transfer belt 1.
4A, a single-sided image forming program P3 for forming an image as a single-sided image on the back side alone is executed. However, the fixing of the single-sided image formation on the back side is performed intermittently, and is performed in the same manner as described with reference to FIG. First, a toner image is formed on the photosensitive drum 10 at a high normal speed.
Transfer device 14c as a first transfer unit
Is transferred onto the intermediate transfer belt 14a. On this occasion,
Photoreceptor drum 10, intermediate transfer belt 14a, developing unit 13
Drive speed is normal speed, and the scorotron charger 1
1. Current or voltage control of the transfer device 14c or the like as the first transfer means is performed at a current value or voltage value corresponding to the normal speed.

As shown in FIG. 6A, the transfer material is transferred at a normal speed to a timing roller 15b as a transfer material feeding means.
The fixing device 17, the photosensitive drum 10, and the intermediate transfer belt 14 come into contact with each other before the leading end of the toner image on the intermediate transfer belt 14 a contacts the photosensitive drum 10.
Each of the driving speeds a (fixing speed, image forming body speed, and intermediate transfer body speed) is set to a lower speed than the normal speed, and as shown in FIG. 15b, the toner image formed as the back surface image on the intermediate transfer belt 14a is transferred to the lower surface of the transfer material fed in synchronization with the toner image on the intermediate transfer belt 14a as the third transfer means. Is transferred by the container 14g. At this time, a paper charger 1 as a transfer material charging unit
The current or voltage control of the 50 and the back transfer device 14g as the third transfer means is performed at a current value or a voltage value corresponding to a low speed higher than the normal speed.

A toner image is formed on the back surface in a state where the driving speeds (fixing speed, image forming member speed, and intermediate transfer member speed) of the fixing device 17, the photosensitive drum 10, and the intermediate transfer belt 14a are low. Transfer material is the intermediate transfer belt 1
4a, the curvature of the curvature portion KT, the neutralization effect of the paper separation AC neutralizer 14h as a transfer material separating means provided as necessary at the end of the intermediate transfer belt 14a, and a predetermined interval from the intermediate transfer belt 14a. The belt is separated from the intermediate transfer belt 14a by a separation claw 210 provided in the conveyance unit 160, and is conveyed to a fixing device 17 as a fixing unit through a spur 162 provided in the conveyance unit 160. The toner image on the transfer material is fixed by applying heat and pressure at a nip portion T between the second fixing roller 17b. At this time, the current or voltage control of the paper separating AC static eliminator 14h as a transfer material separating unit is performed at a current value or a voltage value corresponding to a higher speed than a normal speed and a low speed.

Further, the fixing device 17 is a first fixing roller 17 as an upper (front surface) roll-shaped fixing rotating member for fixing a toner image of a front surface image (upper surface side image).
a, and a second fixing roller 17b as a lower (rear side) roll-shaped fixing rotating member for fixing the toner image of the back side image (lower side image), and the first fixing roller 17a The recording paper P is nipped by a nip portion T formed between the recording paper P and the second fixing roller 17b, and the toner image on the recording paper P is fixed by applying heat and pressure. As shown in FIG. 7, the first fixing roller 17a for fixing the toner image of the front surface image has a Teflon coat applied to the outer peripheral surface by baking or coating.
For example, a cylindrical metal pipe 1 made of aluminum, steel, etc.
It is configured as a hard roller formed at 71a. A halogen heater 171c is provided inside the metal pipe 171a. Further, the second fixing roller 17b for fixing the toner image of the back side image includes a cylindrical metal pipe 172a using, for example, an aluminum material, and a metal pipe 172a using, for example, a silicon material on the outer peripheral surface of the metal pipe 172a. It is configured as a soft roller on which a rubber roller 172b having a thickness of 20 mm is formed. The halogen heater 171 is provided inside the metal pipe 172a.
c is provided.

Between the upper hard roller and the lower soft roller, a nip T having a width of about 2 to 10 mm and having a convex lower side is formed, and the toner image is fixed.

With the configuration of the fixing device 17 as described above, the back side is made softer than the front side, and the fixing is carried out by a soft and wide fixing section (nip section). Gloss fixing and OH
The fixing property of T, cardboard, etc. is performed more favorably.

The fixing temperature is usually controlled in the same control state as at the time of high speed. However, the fixing temperature setting condition may be changed according to the mode selection such as OHT, thick paper, or glossiness. Further, the linear speed such as the fixing speed, the speed of the image forming member, and the speed of the intermediate transfer member are completely separated from the image forming, and can be freely changed. As shown in FIG. 5, when fixing, a gloss level such as gloss level 1 for forming an image with gloss and gloss level 2 for forming an image with super gloss can be selected. Preferably, the fixing speed is changed and the fixing temperature setting condition is changed according to each mode selection.

In the above description, since the image formation in the mode selection such as OHT, thick paper, or glossiness has a toner image on the back surface of the transfer material, the fixing of the toner image in the fixing device 17 is performed intermittently by one sheet. The fixing is performed by the second fixing roller 17b as a lower (rear side) roll-shaped fixing rotating member for fixing the toner image of the rear side image (lower side image).

As described above, the step of transferring the toner image formed on the image forming member to the surface of the transfer material, and the step of transferring the toner image formed on the image forming member to the back surface of the transfer material via the intermediate transfer member. By the step of transferring, a toner image is formed on both sides of the transfer material, and the image forming apparatus is fixed by a fixing unit.
After the toner image formed on the image forming member is once transferred to the intermediate transfer member, the fixing speed, the image forming member speed and the intermediate transfer member are set before the leading end of the toner image on the intermediate transfer member contacts the image forming member. Since the image is formed by reducing the linear speed such as the speed and forming the toner image only on the back surface of the transfer material, the process of transferring the toner image formed on the image forming body to the intermediate transfer body is a linear speed. It is done at a fast normal speed without slowing down. As a result, glossiness fixing and OHT (overhead transparency), which require a large fixing heat capacity, without slowing down the total copy speed and without changing the process conditions such as charging means, image exposing means and developing means. Fixing of thick paper etc. is performed favorably. In addition, since the fixing is performed intermittently every other sheet, the fixing of glossiness and the fixing of OHT, thick paper, etc., which require a large fixing heat capacity, are performed favorably. In particular, by changing the linear velocity in accordance with the specification of the glossiness, more appropriate and good glossiness fixing can be achieved.

Although the color image forming apparatus has been described as the image forming apparatus, the present invention is not necessarily limited to this. The present invention is also applicable to a monochrome image forming apparatus having the same process as that described with reference to FIG. Is what is done.

[0066]

According to the first or third aspect, the step of transferring the toner image formed on the image forming member to the surface of the transfer material, and the step of transferring the toner image formed on the image forming member to the intermediate transfer member. And forming a toner image on both sides of the transfer material by a process of transferring the toner image to the back surface of the transfer material through a fixing unit, and fixing the image by a fixing unit. After the toner image formed on the image forming body is once all transferred to the intermediate transfer body, the fixing speed, the image forming body speed, and the like before the leading end of the toner image on the intermediate transfer body contacts the image forming body. Since the image is formed by reducing the linear speed such as the speed of the intermediate transfer member and forming the toner image only on the back surface of the transfer material, the process until the toner image formed on the image forming member is transferred to the intermediate transfer member Is performed at a high normal speed without slowing down the linear speed . As a result, glossiness fixing and OHT (overhead transparency), which require a large fixing heat capacity, without slowing down the total copy speed and without changing the process conditions such as charging means, image exposing means and developing means. Fixing of thick paper etc. is performed favorably. Further, since the fixing is performed intermittently every other sheet, gloss fixing which requires a large fixing heat capacity and good fixability of OHT, thick paper, etc. are performed satisfactorily. In particular, the fixing rotating member on the back side of the fixing means. Is made softer than the rotating member for fixing on the front surface side, the fixability of glossiness and the fixability of OHT, thick paper and the like are further improved.

According to the second or third aspect, a step of transferring the toner image formed on the image forming body to the surface of the transfer material;
Transferring the toner image formed on the image forming member to the back surface of the transfer material via the intermediate transfer member, thereby forming a toner image on both surfaces of the transfer material and fixing the toner image by a fixing unit. Uses the one-sided image formation of the back side, which is performed intermittently every other sheet, and once the toner image formed on the image forming body is once transferred to the intermediate transfer body, the leading end of the toner image on the intermediate transfer body forms the image. Before contacting the image forming member, the linear speed such as the fixing speed, the image forming member speed, and the intermediate transfer member speed is reduced, and the image is formed by forming the toner image only on the back surface of the transfer material. The process up to the transfer of the toner image formed on the intermediate transfer member is performed at a normal high speed without reducing the linear speed. As a result, glossiness fixing and OHT (overhead transparency), which require a large fixing heat capacity, without slowing down the total copy speed and without changing the process conditions such as charging means, image exposing means and developing means. Fixing of thick paper etc. is performed favorably. In addition, since the fixing is performed intermittently every other sheet, glossiness fixing which requires a large fixing heat capacity and good fixability of OHT, thick paper, etc. are performed satisfactorily.
By changing the linear velocity, more appropriate and good gloss fixing can be achieved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a side sectional view of the image forming body of FIG. 1;

FIG. 3 is a diagram illustrating a toner image forming state in the image forming apparatus according to the present invention.

FIG. 4 is a diagram illustrating an example of a document image reading unit.

FIG. 5 is a control circuit block diagram of the image forming apparatus.

FIG. 6 is a diagram illustrating image formation when a mode such as OHT, thick paper, or glossiness is selected.

FIG. 7 is a diagram illustrating upper and lower fixing rotating members.

[Explanation of symbols]

 Reference Signs List 10 photoconductor drum 11 scorotron charger 12 exposure optical system 13 developing device 14a intermediate transfer belt 14c transfer device 14g back surface transfer device 14h paper separation AC neutralizer 14m static neutralizer 15b timing roller 17 fixing device 17a first fixing roller 17b second fixing Roller P recording paper

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Kuki Nagase, Inventor 2970, Ishikawa-cho, Hachioji-shi, Tokyo Konica Corporation F-term (reference) 2H027 DC05 ED16 EE03 FA13 FA28 2H028 BA06 BA16 BB02 2H030 AD04 AD05 BB23 BB42 2H033 AA46 BA08 BB04 CA13 CA36

Claims (3)

[Claims] A step of transferring a toner image formed on the image forming member to a surface of a transfer material; and a step of transferring the toner image formed on the image forming member to a back surface of the transfer material via an intermediate transfer member. In the image forming apparatus that forms a toner image on both surfaces of the transfer material and fixes the same by a fixing unit, the speed of the intermediate transfer body and the fixing unit is reduced, and only the back surface of the transfer material is An image forming apparatus having a mode including a step of forming a toner image, wherein the fixing rotating member on the back side of the fixing unit is softer than the fixing rotating member on the front side. 2. A step of transferring a toner image formed on an image forming member to a front surface of a transfer material, and a step of transferring the toner image formed on the image forming member to a back surface of the transfer material via an intermediate transfer member. In the image forming apparatus that forms a toner image on both surfaces of the transfer material and fixes the same by a fixing unit, the speed of the intermediate transfer body and the fixing unit is reduced, and only the back surface of the transfer material is An image forming apparatus having a mode including a step of forming a toner image, wherein the linear velocity is changed in accordance with designation of glossiness of fixing of the toner image by the fixing unit. 3. After transferring the toner image to the intermediate transfer member, before the toner image on the intermediate transfer member contacts the image forming member,
The image forming apparatus according to claim 1, wherein the speed of the intermediate transfer body is reduced, and the transfer material is carried into a fixing unit.