JPH09311509A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an excellent transfer to both surfaces by forming toner images on both surfaces of a transfer material, while carrying the transfer material with at least a group of belt-like image forming means out of two groups of toner image forming means. SOLUTION: A belt-like photoreceptor belt 14a is extended between a driving roller 14d and a grounded driven roller 14e, provided in proximity to or contact with a photoreceptor drum 10 and rotated counterclockwise, that is, in a direction opposite to the rotational direction of the photoreceptor drum 10, shown by the arrow, in a state where the belt 14a is grounded via the driven roller 14e. Then, front surface images on the periphery of the drum 10 are transferred to the top side (front side) of a recording paper P altogether by a transfer unit 14c to which a voltage having a polarity (negative polarity) opposite to that of toner is applied. Then, rear surface images on the periphery of the belt 14a are transferred to the under side (rear side) of the recording paper P altogether by a rear surface transfer unit 14g to which the voltage having the polarity (positive polarity) opposite to that of the toner is applied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine which arranges a charging means, an image exposing means and a developing means around an image carrier to transfer and fix a toner image formed on the image carrier onto a transfer material. The present invention relates to an electrophotographic image forming apparatus such as a printer, a FAX, or the like.

[0002]

2. Description of the Related Art Conventionally, in double-sided copying, an image on one side formed on an image carrier is transferred and fixed on a transfer material, and this is temporarily stored in a two-sided reversing paper feeder, and the image bearing is again performed. A method has been adopted in which a transfer material is fed from a double-sided reversing sheet feeder in synchronization with an image formed on the body, and an image on the other surface is transferred and fixed onto the transfer material.

In this double-sided copying apparatus, as described above, the transfer of the transfer material, such as feeding to the two-sided reversing paper feeder and passing through the fixing device twice, is performed, so that the reliability of transfer of the transfer material is low. And so on. On the other hand, Japanese Patent Laid-Open No. 172280/1988 proposes a method in which a toner image is formed on both surfaces of a transfer material and then the fixing is performed once.

[0004]

That is, in the double-sided image forming apparatus according to the above-mentioned proposal, as shown in FIG. 5, charging means 911a for charging the image forming body 910a is provided around the cylindrical image forming body 910a. An image exposing means 912a for exposing the charged image forming body 910a to form a latent image, and a developing means 91 for developing the formed latent image to form a toner image.
3a is arranged to form one toner image forming means, and a toner image is formed on the image forming body 910a by charging by the charging means 911a, image exposure by the image exposing means 912a, and development by the developing means 913a. After that, transfer means 9
The toner image is transferred onto one surface of the recording paper P at 14a.

Subsequently, a cylindrical image forming body 911 provided on the surface opposite to the recording paper P on the downstream side in the traveling direction of the recording paper P.
b, the charging means 911b, the image exposing means 912b, and the developing means 913b arranged around it, constitute the other toner image forming means, and after forming the toner image on the image forming body 910b, the transferring means 914b. There is proposed a method in which the toner image is transferred to the other surface of the recording paper P, toner images are formed on both surfaces of the recording paper P, and then fixing is performed at one time. The conveyance of the recording paper P passing between the two toner image forming means provided with the bodies 910a and 910b is not stable, it is difficult to convey the toner image without disturbing it, and the double-sided image formation is well performed. There is a problem such as not.

There is also a problem that the recording paper P after passing through the transfer means 914b is apt to wind around the image forming body 910b and is difficult to separate.

SUMMARY OF THE INVENTION It is an object of the present invention to improve the above-mentioned problems, and to provide an image forming apparatus capable of stably and easily transporting a transfer material between a plurality of toner image forming means and performing good double-sided transfer. And

[0008]

The above-mentioned object is to provide a charging means for charging the image forming body around the image forming body, and an image exposing means for exposing the charged image forming body to form a latent image. And a developing means for developing a latent image formed on the image forming body to form a toner image, and charging the image forming body by the charging means, image exposing by the image exposing means, and developing by the developing means. Two sets of toner image forming means for forming a toner image by means of are provided, and two sets of toner images formed by the two sets of toner image forming means are transferred to both sides of a transfer material to form a double-sided image. In the apparatus, the image forming bodies provided in at least one of the sets are belt-like image forming bodies, and the image forming bodies provided in the two sets of toner image forming means are in contact with each other and rotate, and Front by belt-shaped image forming body While conveying the transfer material, it is achieved by an image forming apparatus, and forming the toner image on both surfaces of the transfer material.

[0009]

Embodiments of the present invention will be described below. The description of the present application does not limit the technical scope of the claims or the meaning of terms. Also, the following assertive description in the embodiment of the present invention indicates the best mode, and does not limit the meaning of the terms of the present invention or the technical scope. In the following description of the embodiment, when a color toner image is transferred to a transfer material, an image to be transferred to a surface of the transfer material facing the image carrier in the transfer area (referred to as a surface of the transfer material) will be described. The front image and the image transferred to the other surface of the transfer material (called the back surface of the transfer material) are called the back surface image.

Embodiment 1 The image forming process and each mechanism of the first embodiment of the image forming apparatus of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing a first embodiment of the present invention, and FIG. 2 is a diagram showing a toner image forming state on both sides and a paper discharge form according to the first embodiment. is there.

The cylindrical photosensitive drum 10 which is the first image forming body is provided with a cylindrical base body formed of a transparent member such as optical glass or transparent acrylic resin inside,
Transparent conductive layer, a-Si layer or organic photosensitive layer (OPC)
A photosensitive layer such as is formed on the outer periphery of the substrate, and is rotated clockwise in the state of being grounded as shown by the arrow in FIG.

Scorotron charger 11 as charging means
Is used in the image forming process of each color of yellow (Y), magenta (M), cyan (C), and black (K), and is exposed in a direction orthogonal to the moving direction of the photoconductor drum 10 as an image forming body. A control grid, which is attached to face the body drum 10 and is held at a predetermined potential with respect to the above-described organic photoconductor layer of the photoconductor drum 10, and a corona of the same polarity as the toner, using, for example, a sawtooth electrode as a discharge electrode. A charging action (negative charging in the present embodiment) is performed by the discharge, and a uniform potential is applied to the photosensitive drum 10. Other wire electrodes may be used as the discharge electrodes.

The exposure unit 12 for each color has a linear shape in which a plurality of LEDs (light emitting diodes) as image exposure light emitting elements arranged in the main scanning direction parallel to the axis of the photosensitive drum 10 are arranged in an array. The exposure element and the SELFOC lens as a unity-magnification imaging element are configured as an exposure unit attached to a holder (not shown). The exposure unit 12 for each color is attached to the holding member 20.
0 is a uniform exposure unit 12 in addition to the exposure unit 12 for each color.
2 and the transfer simultaneous exposure device 123 are attached and housed inside the substrate of the photoconductor drum 10. Image data of each color read by a separate image reading device and stored in the memory is sequentially read from the memory and input to the exposure unit 12 for each color as an electric signal.

As the exposure element, an array of a plurality of light emitting elements such as FL (fluorescent substance light emission), EL (electroluminescence), PL (plasma discharge), LED (light emitting diode) and the like is used. The emission wavelength of the light emitting element used in this embodiment is usually Y, M, C
In the range of 680 nm to 900 nm, which has a high toner transparency, is preferable, but a shorter wavelength may be used since the color toner does not have sufficient transparency because image exposure is performed from the back surface.

A developing unit 13 provided in accordance with the color order in which the image is formed and the rotating photosensitive drum in accordance with the color order
In the present embodiment, the developing units 13 for Y and M are on the left side of the photosensitive drum 10 with respect to the rotation direction of the photosensitive drum 10 indicated by the arrow in FIG. Are arranged on the right side of the photosensitive drum 10 and the Y and M developing devices 1
Below 3, there are Y and M scorotron chargers 11,
A C, K scorotron charger 11 is disposed above the C, K developing device 13.

The developing device 13 as a developing means for each color is
One-component or two-component developers of yellow (Y), magenta (M), cyan (C) and black (K) are contained respectively, and a predetermined gap is maintained with respect to the peripheral surface of the photosensitive drum 10, A developing sleeve 131 that rotates in the same direction as the rotation direction of the photosensitive drum 10 at the developing position is provided.

A developing device 13 is provided with a gap of a predetermined value, for example, 100 μm, from the photosensitive drum 10 by an abutting roller (not shown).
.About.1000 .mu.m and kept in a non-contact state, and when developing by the developing device 13 for each color, the developing sleeve 131
A developing bias to which a DC voltage or an AC voltage AC is further applied is applied to the photosensitive drum, a jumping development is performed by a one-component or two-component developer accommodated in the developing device, and the transparent conductive layer is grounded. A DC bias having the same polarity as the toner (minus polarity in the present embodiment) is applied to the drum 10 to perform non-contact reversal development in which the toner adheres to the exposed portion. At this time, the precision of the development interval needs to be about 20 μm or less in order to prevent image unevenness.

The developing device 13 for each color described above applies a developing bias voltage to the electrostatic latent image formed on the photosensitive drum 10 formed by the charging by the scorotron charger 11 and the image exposure by the exposure unit 12 described above. The toner having the same polarity as the charging polarity in a non-contact state by the non-contact developing method according to (the photosensitive drum in this embodiment is negatively charged,
Reversal development is carried out with a negative polarity toner).

An image read by an image pickup device of an image reading apparatus separate from the apparatus or an image edited by a computer as a document image is temporarily stored in a memory as image data for each color of Y, M, C and K. Are stored and stored in.

When the image recording is started, the photosensitive drum driving motor (not shown) is started to rotate the photosensitive drum 10 in the clockwise direction shown by the arrow in FIG. 1, and at the same time, the left side of the photosensitive drum 10 develops yellow (Y). Due to the charging action of the Y scorotron charger 11 arranged below the container 13, application of electric potential to the photosensitive drum 10 is started.

After the photoconductor drum 10 is applied with a potential, the first color signal, that is, Y
Exposure by an electric signal corresponding to the image data is started, and an electrostatic latent image corresponding to the Y image of the original image is formed on the photosensitive layer on the surface by rotating and scanning the drum.

The latent image is reversal-developed by the Y developing device 13 with the developer on the developing sleeve in a non-contact state, and a yellow (Y) toner image is formed according to the rotation of the photosensitive drum 10.

Next, the photoconductor drum 10 is placed on the yellow (Y) toner image, and further to the left of the photoconductor drum 10 and above the yellow (Y) image, the magenta (M) developing device 1 is provided.
An electric potential is applied by the charging action of the magenta (M) scorotron charger 11 disposed below 3, and the exposure is performed by the second color signal of the M exposure unit 12, that is, the electric signal corresponding to the M image data. That is, the non-contact reversal development by the developing unit 13 for M forms a magenta (M) toner image on the yellow (Y) toner image in order.

By the same process, the cyan (C) scorotron charger 11, the exposure unit 12 of C and the developing device 13 of C, which are arranged on the right side of the photosensitive drum 10 and above the developing device 13 of cyan (C). In addition, a cyan (C) toner image corresponding to the third color signal is formed on the right side of the photosensitive drum 10, and a black (K) color is disposed below the C color and above the black (K) developing unit 13. A black (K) toner image corresponding to the fourth color signal is sequentially superposed and formed by the scorotron charger 11, the exposure unit 12, and the developer 13 on the peripheral surface of the photosensitive drum 10 within one rotation. A color toner image is formed on (first toner image forming means).

Exposure unit 1 for Y, M, C and K
Exposure of the organic photosensitive layer of the photosensitive drum 10 by 2 is performed from the inside of the drum through the transparent substrate described above. Therefore, the exposure 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. It is possible to form an electrostatic latent image.

By the above image forming process, a superposed color toner image to be a surface image is formed on the photosensitive drum 10 as the first image forming body.

The belt-shaped photosensitive belt 14a which is the second image forming body is made of, for example, polyester, polystyrene,
A belt-shaped substrate formed of a translucent member such as polyethylene or polyethylene terephthalate is provided inside,
A light-transmitting conductive layer, a photosensitive layer such as an organic photosensitive layer (OPC), is formed on the outer periphery of the substrate, and is stretched between a driving roller 14d and a driven roller 14e that is grounded to form a first image. It is provided in the vicinity of or in contact with the photoconductor drum 10 as a body, and is rotated in the counterclockwise direction shown by the arrow in FIG. 1 in the direction opposite to the rotation direction of the photoconductor drum 10 while being grounded via the driven roller 14e. To be done.

Inside the photosensitive belt 14a, yellow (Y), magenta (M), cyan (C) and black (K).
The exposure unit 12a for each color of the photoconductor belt used in the image forming process of each color is attached to the holding member 120 in the order of image formation and is arranged in parallel with the photoconductor belt 14a in a direction orthogonal to the moving direction of the photoconductor belt 14a. They are arranged in the scanning direction. The exposure unit 12a for each color is a linear exposure element in which a plurality of LEDs (light emitting diodes) as image exposure light emitting elements arranged in the main scanning direction in parallel with the axis of the photosensitive drum 10 are arranged in an array. , A SELFOC lens as a unity-magnification image forming element is configured as an exposure unit attached to a holder (not shown). Image data of each color read by a separate image reading device and stored in the memory is sequentially read from the memory and input to the exposure unit 12 for each color as an electric signal.

Further, a scorotron charger 11a as a charging means and a vertical developing device 13a as a developing means are provided outside the photosensitive belt 14a, and yellow (Y), magenta (M), cyan (C) and black (K). ), The photosensitive belt 14 as the second image forming body in the order of the image forming process of each color.
In the direction orthogonal to the moving direction of a, the photoconductor belt 14
It is attached facing a.

A control grid held at a predetermined potential with respect to the above-mentioned organic photoconductor layer of the photoconductor belt 14a by the scorotron charger 11a, and a corona discharge having the same polarity as the toner by using, for example, a sawtooth electrode as a discharge electrode. A charging action (negative charging in this embodiment) is performed by the above, and a uniform potential is applied to the photosensitive belt 14a. Other wire electrodes may be used as the discharge electrodes.

Developing device 13a as developing means for each color
Contains one-component or two-component developers of yellow (Y), magenta (M), cyan (C), and black (K), respectively, and maintains a predetermined gap with respect to the outer peripheral surface of the photosensitive belt 14a. And the photoconductor belt 14 at the developing position.
developing sleeve 131a that rotates in the same direction as that of a
It has.

The vertical developing device 13a is kept in non-contact with the photoconductor belt 14a by abutting rollers (not shown) with a predetermined gap, for example, 100 μm to 1000 μm, and the developing action by the developing device 13a for each color. At this time, a DC voltage or an AC voltage AC is applied to the developing sleeve 131a.
Is applied to apply a developing bias, and jumping development is performed by a one-component or two-component developer accommodated in the developing device to ground the transparent conductive layer.
A non-contact reversal development in which a DC bias having the same polarity as the toner (negative polarity in the present embodiment) is applied to 4a to attach the toner to the exposed portion is performed. At this time, the precision of the development interval needs to be about 20 μm or less in order to prevent image unevenness.

The developing unit 13a for each color is the charging and exposure unit 1 by the scorotron charger 11a described above.
The electrostatic latent image formed on the photosensitive belt 14a by image exposure based on the image data of 2a and the toner of the same polarity as the charging polarity in the non-contact state by the non-contact developing method by applying the voltage of the developing bias voltage ( In the present embodiment, the photosensitive drum is negatively charged, and reversal development is performed with toner of negative polarity.

In order of the image forming process of each color of yellow (Y), magenta (M), cyan (C) and black (K),
The scorotron charger 11a, the exposure unit 12a, and the developing device 13a sequentially form toner images of respective colors in a superimposed manner, and a color toner image is formed on the peripheral surface of the photoreceptor belt 14a within one rotation (first). 2 toner image forming means).

In the same manner as the color image forming process described above, the front surface image formed on the photosensitive drum 10 and the transfer area 14b are synchronized, and the back surface image of the superimposed color toner image is the second image. It is formed on the photosensitive belt 14a as a forming body.

The recording paper P, which is a transfer material, is delivered from the paper feed cassette 15 which is a transfer material storage means by the delivery roller 15a and is conveyed to the timing roller 15b.

On the recording paper P, the color toner image of the front surface image carried on the photosensitive drum 10 and the color toner image of the back surface image carried on the photosensitive belt 14a are synchronized with each other by driving the timing roller 15b. It is taken and fed to the transfer area 14b. At this time, the recording paper P is charged to the same polarity as the toner by the paper charger 14f as a transfer material charging means, adsorbed to the photoconductor belt 14a grounded via the driven roller 14e, and supplied to the transfer area 14b. Will be sent.
By charging the paper with the same polarity as the toner, it is possible to prevent the toner image on the photoconductor belt and the toner image on the image forming body from being attracted to each other, thereby preventing the toner image from being disturbed. Further, as the transfer material charging means, it is also possible to use a conduction roller, a brush charger, or the like, which can be brought into contact with and released from the photosensitive belt.

The surface image on the peripheral surface of the photosensitive drum 10 is collectively recorded on a recording paper by a transfer unit 14c as a first transfer unit to which a voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied. It is transferred to the upper surface side (front side) of P. At this time, the rear surface image on the peripheral surface of the photoconductor belt 14a is not transferred to the recording paper P and remains on the photoconductor belt 14a. Next, the back surface image on the peripheral surface of the photosensitive belt 14a is collectively recorded on the recording paper by the back surface transfer device 14g as the second transfer means to which the voltage of the polarity opposite to the toner (plus polarity in this embodiment) is applied. Transfer to the lower surface side (back surface side) of P. During transfer by the transfer device 14c, uniform exposure is performed by a transfer simultaneous exposure device 123 using, for example, a light emitting diode, provided inside the photoconductor drum 10 so as to face the transfer device 14c so that good transfer is performed. Is done.

Since the toner images of the respective colors are overlapped with each other, it is preferable that the upper layer toner and the lower layer toner are charged with the same charge amount and the same polarity to enable batch transfer. Therefore, in double-sided image formation in which the polarity of the color toner image formed on the photosensitive belt 14a is reversed by corona charging, or the polarity of the color toner image formed on the photosensitive drum 10 is reversed by corona charging,
Since the toner of the lower layer is not sufficiently charged to the same polarity, the transfer becomes defective, which is not preferable.

Photoreceptor drum 10 as first image forming body
It is preferable to repeat the reversal development above and collectively transfer the color toner images of the same polarity, which are formed by superposition, onto the recording paper P without changing the polarity, because it contributes to the improvement of the transferability of the surface image formation. Also for reverse side image formation, reversal development is repeated on the photoconductor belt 14a as the second image forming body,
It is preferable to collectively transfer the color toner images of the same polarity, which are superposed on each other, onto the recording paper P without changing the polarity because it contributes to the improvement of the transferability of the back side image formation.

From the above, in color image formation, the first transfer means is operated to form a color toner image on the surface of the transfer material by using the above-mentioned front and back image forming methods, and then, A double-sided image forming method in which the second transfer unit is operated to form a color toner image on the back surface of the transfer material is preferably adopted.

The recording paper P on both sides of which color toner images are formed is neutralized by the paper separation AC neutralizer 14h for separating the transfer material, separated from the photosensitive belt 14a, and has a heater inside both rollers. The sheet is conveyed to a fixing device 17 as a fixing unit composed of two rollers. By applying heat and pressure between the fixing roller 17a and the pressure roller 17b, the toner adhered to the front and back of the recording paper P is fixed, and the recording paper P on which double-sided image recording has been performed is sent by the paper discharge roller 18. And discharged to a tray outside the apparatus. At the time of separating the transfer material, good separation is performed by the curvature separation of the drive roller 14d in addition to the paper separation AC static eliminator 14h.

The toner remaining on the peripheral surface of the photoconductor belt 14a after the transfer is provided in the photoconductor belt cleaning device 119 as a means for cleaning the photoconductor belt, and can be brought into contact with and released from the photoconductor belt 14a. The photosensitive belt cleaning blade 119a cleans the same, and the screw 119b collects it in a waste toner container (not shown).

After the transfer, the toner remaining on the peripheral surface of the photosensitive drum 10 is subjected to static elimination by the image forming body AC static eliminator 16 and then goes to a cleaning device 19 as a cleaning means of the photosensitive drum or exposed to light. The cleaning blade 19a made of a rubber material that is in contact with the body drum 10 scrapes it into the cleaning device 19, and the screw 19b collects it in a waste toner container (not shown).
At this time, in order to eliminate the history of the photosensitive member up to the previous printing, the peripheral surface of the photosensitive member is destaticized by exposure by the uniform exposure device 122 using a light emitting diode before charging.

The photoconductor drum 10 and the photoconductor belt 14a, from which the residual toner has been removed by the cleaning device 19 and the photoconductor belt cleaning device 119, are uniformly charged by the Y scorotron chargers 11 and 11a, respectively. Enter the back side image forming cycle.

By using the above method, the transfer material can be stably conveyed between a plurality of toner image forming means, and good double-sided transfer becomes possible. Further, in the color image formation, since the superimposed color toner images are collectively transferred, color deviation of the color image on the photoconductor belt as the second image forming member, toner scattering, rubbing, etc. are less likely to occur, resulting in image deterioration. A good double-sided color image formation is achieved.

In the above-mentioned image forming apparatus, the recording paper P on which the double-sided image is formed and the toner images on both surfaces are fixed by the fixing device 17 is normally discharged horizontally in the moving direction of the recording paper P. It is also possible to copy only one side by the image forming means or the second image forming means.

When a single-sided copy is made by the first image forming means or the second image forming means, as shown in FIG. 2, a discharge path switching member is provided downstream of the fixing device 17 in the discharge direction of the recording paper P. 17c is provided, and in the case of the back side image by the photoconductor belt 14a, when the discharge path switching member 17c is at the position shown by the solid line, the recording paper P is discharged horizontally with the toner image surface as the bottom side, and the front side image by the photoconductor drum 10 It is also possible to switch the discharge path switching member 17c to the position shown by the dotted line, invert the recording paper P, and discharge the toner image surface as the lower surface. Switching of the discharge path switching member 17c is performed by selection from an operation unit (not shown). Therefore, it is possible to form a toner image on only one surface of the transfer material, the front surface or the back surface.

Embodiment 2 FIG. 3 shows a second embodiment of the image forming apparatus of the present invention.
FIG. 3 is a sectional configuration diagram of an image forming apparatus showing a second embodiment of the present invention. In this embodiment, a monochrome image is formed instead of the color image formation of the first embodiment, and a member having the same function and structure as described in the image forming apparatus of the first embodiment is used. Are given the same reference numerals.

For example, a first image in which a substrate formed of a cylindrical aluminum member is provided inside and a photosensitive layer such as a conductive layer, an a-Si layer or an organic photosensitive layer (OPC) is formed on the outer periphery of the substrate. Cylindrical photosensitive drum 10a that is a forming body
Is rotated clockwise in the state of being grounded, as indicated by the arrow in FIG.

Further, the belt-shaped photosensitive belt 114a which is the second image forming body is provided with a base formed of, for example, a belt-shaped nickel plate material or a polyester, polystyrene, polyethylene or polyethylene terephthalate resin member inside, A photosensitive layer such as a conductive layer and an organic photosensitive layer (OPC) is formed on the outer periphery of the base, and is stretched between a driving roller 14d and a driven roller 14e that is grounded,
It is provided in proximity to or in contact with the photoconductor drum 10a as the first image forming body, and is grounded via the driven roller 14e, and is indicated by an arrow in FIG. It is rotated counterclockwise.

An exposure unit 121 as an image exposure means is a semiconductor laser as a light emitting element (not shown), and a rotary polygon mirror 12 for rotationally scanning a laser beam emitted from the semiconductor laser.
1b, an fθ lens 121c, a reflection mirror 121d, and the like, and a laser beam emitted from a semiconductor laser (not shown) is rotationally scanned by the rotary polygon mirror 121b, and rotates via the fθ lens 121c, the reflection mirror 121d, and the like. Image exposure based on image data is performed in the main scanning direction of the drum 10a to form a latent image on the photoconductor drum 10a.

Scorotron charger 11 as charging means
And a developing device as a developing means using latent image formation by image exposure based on image data by an exposure unit 121 using a laser beam as image exposure means, and reversal development with toner having the same polarity as the charge polarity. A toner image of a surface image is formed on the peripheral surface of the photoconductor drum 10a as the first image forming body by developing the electrostatic latent image on the photoconductor drum 10 by 13 (first toner image forming means). ).

Further, the surface image formed on the photosensitive drum 10a and the transfer area 14b are synchronized with each other,
Charging by a scorotron charger 11a as a charging means for the photosensitive belt, latent image formation by image exposure based on image data by an exposure unit 12a using an LED as an image exposing means for the photosensitive belt, and charging polarity. And the development of the electrostatic latent image on the photoconductor belt 114a by the vertical developing device 13a as the developing means for the photoconductor belt using the reversal development with the toner of the same polarity as the second image forming body. A toner image of the back side image is formed on the peripheral surface of the body belt 114a (second toner image forming means).

The recording paper P, which is a transfer material, is sent out from the paper feed cassette 15, which is a transfer material storage means, by the sending roller 15a and is conveyed to the timing roller 15b.

The recording paper P is synchronized with the toner image of the front surface image carried on the photoconductor drum 10a and the toner image of the back surface image carried on the photoconductor belt 114a by the driving of the timing roller 15b. And is fed to the transfer area 14b. At this time, the recording paper P is charged to the same polarity as the toner by the paper charger 14f serving as a transfer material charging means, adsorbed to the photoconductor belt 114a grounded via the driven roller 14e, and supplied to the transfer area 14b. Will be sent.

As described in the first embodiment, the surface image on the peripheral surface of the photosensitive drum 10a is recorded on the recording paper by the transfer device 14c as the first transfer means to which the voltage having the opposite polarity to the toner is applied. It is transferred to the upper surface side (front surface side) of P.
At this time, the back surface image on the peripheral surface of the photoconductor belt 114a is not transferred to the recording paper P and remains on the photoconductor belt 114a. Next, the photoreceptor belt 1 is transferred by the back surface transfer device 14g as the second transfer means to which the voltage having the opposite polarity to the toner is applied.
The rear surface image on the peripheral surface of 14a is transferred to the lower surface side (rear surface side) of the recording paper P.

The recording paper P on which color toner images are formed on both sides is neutralized by the paper separation AC static eliminator 14h for separating the transfer material, separated from the photosensitive belt 114a, and has a heater inside both rollers. The sheet is conveyed to a fixing device 17 as a fixing unit composed of two rollers.
By applying heat and pressure between the fixing roller 17a and the pressure roller 17b, the toner adhered to the front and back of the recording paper P is fixed, and the recording paper P on which double-sided image recording has been performed is sent by the paper discharge roller 18. And discharged to a tray outside the apparatus. Paper separation AC static eliminator 14h when separating transfer material
In addition to the above, good separation is achieved by the curvature separation of the drive roller 14d.

The toner remaining on the peripheral surface of the photosensitive drum 10a after the transfer is transferred to the cleaning device 19 as a cleaning means for the photosensitive drum, or the photosensitive drum 10a.
Cleaning blade 19a made of a rubber material abutting against
The toner is scraped off into the cleaning device 19 by the screw 19b and collected by a screw 19b in a waste toner container (not shown).

Further, the toner remaining on the peripheral surface of the photoconductor belt 114a after the transfer is provided in the photoconductor belt cleaning device 119 as a means for cleaning the photoconductor belt, and contacts and abuts on the photoconductor belt 114a. It is cleaned by a releasable photoreceptor belt cleaning blade 119a and collected by a screw 119b in a waste toner container (not shown).

The photoconductor drum 10a and the photoconductor belt 114a, from which the residual toner has been removed by the cleaning device 19 and the photoconductor belt cleaning device 119, are uniformly charged by the scorotron chargers 11 and 11a, and the next front and back images are formed. Enter the formation cycle.

By using the above method, the transfer material can be stably and easily conveyed between a plurality of toner image forming means, and good double-sided transfer can be performed.

Further, as described with reference to FIG. 2 of the first embodiment, in the above-mentioned image forming apparatus, the recording paper P on which the double-sided image is formed and the double-sided toner images are fixed by the fixing device 17 is usually Although the recording paper P is ejected horizontally in the moving direction, it is also possible to copy only one side by the first image forming means or the second image forming means, and the first image forming means or the second image forming means. When only one side is copied by the image forming means, the fixing device 17 is arranged in the discharge direction of the recording paper P.
A discharge path switching member (not shown) is provided on the downstream side of the recording sheet P, and when the discharge path switching member is switched, the recording paper P is discharged horizontally with the toner image surface as the lower surface in the case of the back side image by the photosensitive belt 114a. In the case of the surface image by 10a, it is possible to reverse the recording paper P and eject the toner image surface as the lower surface. Switching of the discharge path switching member is performed by selection from an operation unit (not shown).

Embodiment 3 FIG. 4 shows a third embodiment of the image forming apparatus of the present invention.
FIG. 4 is a sectional configuration diagram of an image forming apparatus showing a third embodiment of the present invention. Like the second embodiment, the present embodiment performs monochrome image formation instead of the color image formation of the first embodiment, and the image forming apparatus of the first and second embodiments has the same configuration. Same function as described above,
The same reference numerals are given to members having a structure.

In this embodiment, a belt-shaped image forming body is used for both the first image forming body on which the front side image is formed and the second image forming body on which the back side image is formed.

The photosensitive belt 114b as a first image forming body on which a surface image is formed is provided with a substrate formed of, for example, a belt-shaped nickel plate material or a polyester, polystyrene, polyethylene or polyethylene terephthalate resin member inside. , Conductive layer, organic photosensitive layer (OP
A photosensitive layer such as C) formed on the outer periphery of the substrate;
The drive roller 41, the driven roller 42, and the tension roller 43 are stretched between them and rotated clockwise as indicated by the arrow in FIG.

Further, the photosensitive belt 114a as the second image forming body on which the back side image is formed is also provided with a base body formed of, for example, a belt-shaped aluminum plate material or a resin member on the inside in the same manner as described above. A photosensitive layer such as a conductive layer, an a-Si layer, or an organic photosensitive layer (OPC) is formed on the outer periphery of the base, and is stretched between a driving roller 41a, a driven roller 42a that is grounded, and a tension roller 43a. First
The counterclockwise direction of the arrow of FIG. 4, which is opposite to the rotation direction of the photosensitive belt 114b, is provided in the vicinity of or in contact with the photosensitive belt 114b as an image forming body and is grounded via the driven roller 42a. Is rotated in the direction.

As described in the second embodiment, charging by the scorotron charger 11 as charging means,
Exposure unit 12 using laser light as image exposure means
1 to form a latent image by image exposure based on the image data, and a photoreceptor belt 114 by a developing device 13 as a developing means using a reversal development with toner having the same polarity as the charging polarity
By developing the electrostatic latent image on b, a toner image of a surface image is formed on the peripheral surface of the photosensitive belt 114b as the first image forming body (first toner image forming means).

Further, the surface image formed on the photosensitive belt 114a and the transfer area 14b are synchronized with each other, and charging by the scorotron charger 11a as a charging means and laser light as an image exposing means are used. An electrostatic latent image on the photoconductor belt 114a is formed by a vertical developing device 13a as a developing means using latent image formation by image exposure based on image data by the exposure unit 121 and reversal development with toner having the same polarity as the charging polarity. By developing the image, a toner image of the back side image is formed on the peripheral surface of the photosensitive belt 114a as the second image forming body (second toner image forming means).

The recording paper P is carried by the toner image of the front surface image carried on the front surface image photosensitive belt 114b and by the back surface image photosensitive belt 114a by the driving of a timing roller (not shown). The back side image is fed to the transfer area 14b in synchronism with the toner image. On this occasion,
The recording paper P is charged to the same polarity as the toner by the paper charger 14f as a transfer material charging means, adsorbed to the grounded photoconductor belt 114a via the driven roller 14e, and fed to the transfer area 14b. .

First voltage applied with the opposite polarity to the toner
The transfer belt 14c as a transfer means for
The surface image on the peripheral surface of 14b is transferred to the upper surface side (front surface side) of the recording paper P. At this time, the back surface image on the peripheral surface of the photoconductor belt 114a is not transferred to the recording paper P and remains on the photoconductor belt 114a. Then, the back surface image on the peripheral surface of the photoconductor belt 114a is transferred to the lower surface side (back surface side) of the recording paper P by the back surface transfer device 14g as a second transfer unit to which a voltage having a polarity opposite to that of the toner is applied.

The recording paper P having the toner images formed on both sides is
The charge is removed by the paper separation AC static eliminator 14h for separating the transfer material, is separated from the photoconductor belt 114a, and is transferred to the fixing device 17 as a fixing unit composed of two rollers having a heater inside both rollers. Be transported. Heat and pressure are applied between the fixing roller 17a and the pressure roller 17b to fix the adhered toner on the front and back of the recording paper P, and the recording paper P on which double-sided image recording is performed is discharged to a tray outside the apparatus. To be done. When separating the transfer material, paper separation A
Good separation is achieved by the curvature separation of the drive roller 41a in addition to the C static eliminator 14h.

By using the above method, the transfer material can be stably and easily conveyed between a plurality of toner image forming means, and excellent double-sided transfer can be performed.

Further, as described with reference to FIG. 2 of the first embodiment, in the above-mentioned image forming apparatus, the recording paper P on which the double-sided image is formed and the double-sided toner images are fixed by the fixing device 17 is usually , The recording paper P is discharged horizontally in the moving direction, but it is also possible to copy only one side by the first image forming means or the second image forming means. When a single-sided copy is made by the image forming means 2 of No. 2, the fixing device 1 is set in the discharge direction of the recording paper P.
7, a discharge path switching member (not shown) is provided, and by switching the discharge path switching member, the photoconductor belt 114 for the back side image is formed.
In the case of the back side image by a, the recording paper P is discharged horizontally with the toner image side as the bottom side, and the photoreceptor belt 1 for the front side image
In the case of the front surface image by 14b, it is possible to reverse the recording paper P and eject the toner image surface as the lower surface. Switching of the discharge path switching member is performed by selection from an operation unit (not shown).

[0075]

According to the first to third aspects of the invention, the transfer material can be stably and easily conveyed between a plurality of toner image forming means,
Good double-sided transfer becomes possible.

According to the fourth aspect, even when the toner image is formed on only one side of the front surface or the rear surface of the transfer material, the toner image surface on the transfer material is always aligned and ejected.

[Brief description of drawings]

FIG. 1 is a sectional configuration diagram of a color image forming apparatus showing a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a toner image formation state on both surfaces and a paper discharge form according to the first embodiment.

FIG. 3 is a sectional configuration diagram of an image forming apparatus showing a second embodiment of the present invention.

FIG. 4 is a sectional configuration diagram of an image forming apparatus showing a third embodiment of the present invention.

FIG. 5 is a diagram showing a problem of the related art.

[Explanation of symbols]

 10, 10a Photoconductor drum 11, 11a Scorotron charger 12, 12a, 121 Exposure unit 13, 13a Developing device 14a, 114a, 114b Photoconductor belt 14c Transfer device 14d, 41, 41a Drive roller 14e, 42, 42a Driven roller 14g Back transfer device 17 Fixing device P Recording paper

Claims (4)

[Claims] 1. A charging means for charging the image forming body around the image forming body, an image exposing means for exposing a charged image forming body to form a latent image, and an image forming means formed on the image forming body. A developing means for developing a latent image to form a toner image is arranged, and a toner image is formed on the image forming body by charging by the charging means, image exposure by the image exposing means, and development by the developing means. Two sets of toner image forming means are provided, and two sets of toner images formed by the two sets of toner image forming means are transferred to both sides of a transfer material to perform double-sided image formation. The provided image forming body is a belt-shaped image forming body, and the image forming bodies provided in the two sets of toner image forming means rotate while contacting with each other, and by the belt-shaped image forming body. While transporting the transfer material, Image forming apparatus and forming the toner image on both sides of Utsushizai. 2. An image forming body provided on one of the toner image forming means is a drum-shaped image forming body, and an image forming body provided on the other toner image forming means is a belt-shaped image forming body. The image forming apparatus according to claim 1, wherein the image forming apparatus is a body. 3. The image forming apparatus according to claim 1, wherein the image forming members provided in the two sets of toner image forming units are belt-shaped image forming members. 4. When a back surface image is formed on the transfer material by using only one of the toner image forming means, the transfer material is conveyed substantially horizontally and discharged to the outside of the image forming apparatus. 4. When the surface image is formed using only the other toner image forming unit, the toner image surface on the transfer material is reversed and discharged to the outside of the image forming apparatus. The image forming apparatus according to claim 1.