JPH11109685A - Double side image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an image to be formed on both surfaces at a high speed, to reduce paper jam to the utmost, to facilitate the processing of the paper jam when it happens and to facilitate the exchange of process units forming a toner image. SOLUTION: The first process unit 20A and the second process unit 20B are arranged in turn from the lower part of an intermediate transfer body 10 and a downstream side in the moving direction of the transfer body 10. Then, a transfer material is supplied from a gap between both units 20A and 20B and brought into contact with the transfer body 10. The back-surface image is formed on the transfer body 10 by the unit 20B and the front-surface image is formed on the front surf ace of the transfer material by the unit 20A. After the image is formed on both surfaces of the transfer material by transferring the back-surface image formed on the transfer body 10 on the transfer material, the transfer material is carried to a fixing device 18 and the image is simultaneously fixed on both surfaces. By rotating an upper machine body 1A including the transfer body 10, the carrying path of the transfer material can be opened. By opening the carrying path, the first and the second units 20A and 20B can be taken out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a double-sided image forming apparatus,
In particular, the present invention relates to a double-sided image forming apparatus for forming an image by an electrophotographic method. The double-sided image forming apparatus according to the present invention can be used for a copying machine, a printer, a facsimile, and the like.

[0002]

2. Description of the Related Art A double-sided image forming apparatus for forming an image on both sides of paper is useful in terms of saving paper and compressing a document amount.
Widely used. In a conventional double-sided image forming apparatus, a process of forming a toner image on an image forming body, transferring a toner image from the image forming body to a transfer material such as paper, and fixing the toner image on the transfer material is performed on a front image and a back image. The double-sided image formation is repeatedly performed. Such a conventional image forming apparatus has drawbacks in that the transfer material transport path is long and complicated, so that the transfer material tends to jam, and the image forming speed is low.

As a double-sided image forming apparatus in which such disadvantages are improved, Japanese Patent Publication No. 49-37538 and Japanese Patent Publication No.
JP-A-28740 and JP-A-4-214576 propose a method in which a toner image is formed on both sides of a transfer material using an intermediate transfer member and then fixed once.

[0004]

However, these proposals have not been sufficient for high-speed double-sided image formation. Accordingly, an object of the present invention is to provide a double-sided image forming apparatus capable of performing double-sided image formation at a high speed. It is another object of the present invention to provide a double-sided image forming apparatus in which the occurrence rate of a transfer material jam is significantly improved. It is still another object of the present invention to provide a double-sided image forming apparatus which can easily perform processing when a transfer material jam occurs, and facilitate maintenance and replacement of a process unit.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
A first process unit and a second process unit each comprising an image forming body
And a process unit, the first process unit being disposed downstream in the transport direction of the intermediate transfer body and the second process unit being disposed upstream, and the second process unit being disposed between the two process units. The toner image formed in the two-process unit is transferred directly to one surface of the transfer material via the intermediate transfer member, and the toner image formed in the first process unit is directly transferred to the other surface of the transfer material. In the double-sided image forming apparatus for forming an image on both sides of the image forming apparatus, the first process unit and the second process unit are arranged below the intermediate transfer body, and the transfer material is placed below the first process unit and the second process. Transported between the units and brought into close contact with the intermediate transfer body,
This is achieved by a double-sided image forming apparatus, which transfers a toner image from the image forming body to a transfer material and transfers a toner image from the intermediate transfer body to a transfer material.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) The configuration and functions of a duplex image forming apparatus according to Embodiment 1 of the present invention will be described with reference to FIG. FIG.
FIG. 1 is a diagram showing a configuration of Embodiment 1 of the present invention.

Embodiment 1 shown in FIG. 1 comprises an upper body 1A and a lower body 1B. The upper body 1A is connected to the lower body 1B by an axis 1C, and is rotatable with respect to the lower body 1B. As shown in FIG.
0, the transfer units 14A and 14B are configured as an intermediate transfer body unit, and these are integrally rotated to a position shown by a two-dot chain line in the figure to open the transfer path of the transfer material. Also,
Although the process units 20A and 20B are provided in the lower body 1B, the upper body 1A having the intermediate transfer body unit is provided.
Is displaced upward, is indicated by a two-dot chain line, and arrows d,
It can be taken out from the lower body 1B as shown by e. Such a configuration is a configuration for processing the transfer material jam and replacing and maintaining the process unit,
The configuration in which the process unit is disposed below the intermediate transfer body 10 makes it very easy to perform processing of the transfer material jam, replacement of the process unit, maintenance, and the like.

The intermediate transfer member 10 is an endless belt capable of holding a toner image on a peripheral surface. For example, modified polyimide, thermosetting polyimide, ethylene tetrafluoroethylene copolymer, polyvinylidene fluoride, nylon A conductive material dispersed in engineering plastics such as an alloy, having a thickness of 0.1 to 1.0 mm and a resistance of 10 ¹⁰ to 10
^This is a seamless belt having a two-layer structure in which a fluororesin coating having a thickness of 5 to 50 μm is preferably formed on the outside of a semiconductive film substrate of ¹⁶ Ωcm, preferably as a toner filming preventing layer. In addition to this, a semiconductive 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 also be used as the belt base. The intermediate transfer member 10 includes a driving roller 11
A, the driven roller 11B, and the tension roller 13 extend in a horizontal direction, and are circulated clockwise as indicated by an arrow b by a power (not shown) transmitted to the drive roller 11A.

The first and second process units 20A and 20B, which are arranged below the rotating intermediate transfer body 10 and from the downstream side, respectively, include a photosensitive drum 21 as an image forming body, a scorotron charger 22, A developing device 23 and a cleaning device 24 are provided. The scorotron charger 22 may be attached to the image forming apparatus main body separately from the process units 20A and 20B.

The photosensitive drum 21 is formed by forming a conductive layer and an organic photosensitive layer (OPC) on the outer periphery of a cylindrical aluminum substrate, and is indicated by an arrow a by the power of the apparatus main body with the conductive layer grounded. The intermediate transfer body 1
It is driven and rotated at the same speed as the peripheral speed of 0.

The scorotron charger 22 is composed of a corona discharge electrode composed of a sawtooth electrode or a wire electrode, and a control grid maintained at a constant potential, and is orthogonal to the moving direction of the photosensitive drum 21. The photoconductor drum 21 is attached to face the photoconductor drum 21 in the direction. The scorotron charger 22 performs corona discharge (negative charging in the present embodiment) having the same polarity as the toner, and
1 is given a uniform potential.

An exposure unit 30 installed in the main body of the image forming apparatus separately from the above-described process units.
Reference numerals A and 30B denote a linear light-emitting element array composed 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 21 and a single-magnification imaging element. It consists of a selfoc lens. As the light emitting element, a linear light emitting element array such as FL (phosphor emission), EL (electroluminescence), and PL (plasma discharge) is used. Exposure unit 30
A and 30B are read by a separate image reading device (not shown), and perform image exposure on the photosensitive drum 21 based on image data stored in a memory.
A latent image is formed thereon. The exposure units 30A and 30B may be provided in the first and second process units 20A and 20B, respectively.

The developing device 23 has a thickness of, for example, 0.5 to 0.5.
It has a cylindrical developing sleeve 230 made of non-magnetic stainless steel or aluminum material having a diameter of 1 mm and an outer diameter of 15 to 25 mm, and contains a one-component or two-component developer therein. The developing sleeve 230 rotates in the forward direction with respect to the rotation direction of the photosensitive drum 21, and has the same polarity as the toner with respect to the developing sleeve 230 (negative polarity in the present embodiment).
By applying a DC bias or a developing bias to which an AC is further applied, the reversal development is performed on the exposed portion of the photosensitive drum 21 in a non-contact or contact state.

The transfer units 14A and 14B are each constituted by a corona charger, and are provided with a photosensitive drum 21 of the intermediate transfer body 10.
The surface opposite to the surface opposite to the toner is charged to the opposite polarity to the toner, and an electric field is formed between the intermediate transfer member 10 and the photosensitive drum 21 to move the toner from the photosensitive drum 21 to the intermediate transfer member 10. The transfer unit 14A is on the upper surface of the transfer material to which the toner image on the photosensitive drum 21 in the first process unit is supplied, while the transfer unit 14B is the intermediate transfer of the toner image on the photosensitive drum 21 in the second process unit. Transfer onto the body 10 respectively.

The transfer material charger 14C is a brush-shaped charger, and is disposed between the first process unit 20A and the second process unit 20B. When the sheet P is conveyed to the intermediate transfer member 10, the sheet P comes into sliding contact with the supplied transfer material P and is charged to the same polarity as the toner. Due to this charging, the transfer material P is attracted to the intermediate transfer member 10 and conveyed to the transfer area without disturbing the toner image on the intermediate transfer member 10. The transfer material charger 14C may be a corona charger. The intermediate transfer body 10 is backed up by a grounded roller 14F at a position facing the transfer material charger 14C.

The transfer unit 14D is constituted by a corona charger, and transfers the toner image on the intermediate transfer body 10 to the upper surface of the transfer material by applying a voltage having a polarity opposite to that of the toner to the lower surface of the transfer material. It is arranged so as to face the peripheral surface of the grounded drive roller 11A.

Further, the fixing device 18 is a heat roller type fixing device comprising a first roller 18A and a second roller 18B, both of which have a heater inside. The transfer device separated from the intermediate transfer body 10 by a charge remover 14E. The toner images transferred to the upper and lower surfaces are simultaneously heated and fixed by nipping and transporting the material. Reference numeral 11C denotes an intermediate transfer member cleaning device for cleaning the intermediate transfer member 10.

At the start of image formation, input of image data of a document from a separate image reading device (not shown) is started. Each image data on the front and back of the document is temporarily stored in the memory after being read by the image reading device. The first and second processing units 20A, 20A and 2
The photosensitive drum 21 of 0B rotates in a counterclockwise direction indicated by an arrow a. In the second process unit 20B, following the charging by the charger 22, the LE by the LED driving signal formed by the image data by the exposure unit 30B.
An electrostatic latent image is formed on the photosensitive drum 21 by the light emission of D. Subsequently, the photosensitive drum 2 is developed by the developing action of the developing device 23.
A toner image on the back surface of the document is formed on the peripheral surface of No. 1, and this toner image is once transferred onto the peripheral surface of the intermediate transfer body 10 by the transfer device 14B.

The transfer material P is transferred from the paper feed cassette 15 to a discharge roller 15A in parallel with the formation and transfer of the toner image on the back surface of the document.
The supply of the transfer material P is started by the operation of
And is fed to the timing roller 17 via.

Next, the image data on the front side of the original is shifted to the first side by a predetermined time difference from the input of the image data on the back side of the original.
Exposure unit 30 corresponding to the process unit 20A of FIG.
A, the first process unit 20A forms a toner image on the surface of the original document on the peripheral surface of the photosensitive drum 21A by the operation of the charger 22 and the developing unit 23 described above. The image data is converted in advance so that the surface toner image formed on the peripheral surface of the photosensitive drum 21 has a mirror image relationship with the previously formed rear surface toner image.

First and second process units 20A, 20
The operation of the timing roller 17 is started in synchronization with the formation of the toner image on the front and back surfaces of the original on the peripheral surface of the photosensitive drum 21 in B, and the transfer to the intermediate transfer member 10 described above, and the transfer material P is transferred to the intermediate transfer member. 10 is introduced. The synchronous control of the formation of the front and back images and the operation of the timing roller 17 is performed such that the tops of the front and back images coincide, and the front and back images are formed at predetermined positions of the transfer material.

The transfer material P is brought into close contact with the intermediate transfer member 10 by the charging of the transfer material charger 14C, and is conveyed integrally with the intermediate transfer member 10. First, the photosensitive drum of the first process unit 20A is provided on the lower surface thereof. The transfer unit 14A transfers the toner image on the front surface of the document carried by the transfer unit 21, and then transfers the toner image on the back surface of the document on the intermediate transfer body 10 transferred from the photosensitive drum 21 of the second process unit 20B to the top surface. Retransfer by 14D.

The transfer material P on which the toner images have been transferred to the front and back surfaces is discharged by the discharger 14E, separated from the peripheral surface of the intermediate transfer body 10, and guided by the spur 31.
It is introduced into the fixing device 18. After the toner images on the front and back surfaces of the transfer material P are fixed in the fixing device 18, the transfer material P is discharged to a tray 19. When the curvature separation is used, the static eliminator 14E can be omitted. In addition, a separation claw may be provided close to the intermediate transfer body 10 in order to further ensure separation. On the other hand, each of the photosensitive drums 21 on which the transfer of the toner image has been completed is cleaned by the cleaning device 24 so that the next toner image can be formed. The intermediate transfer member 10 is also provided with an intermediate transfer member cleaning device 14.
The toner image is cleaned by 0, and the next toner image can be transferred.

This image forming apparatus has a manual paper feed table 163. The transfer material introduced by manual feed is fed by a paper feed roller 162 and conveyed to a timing roller 17.

In this embodiment, the formation of the front side image is delayed from the formation of the back side image only by the time required for the intermediate transfer body 10 to move from the position of the second process unit 20B to the position of the first process unit 20A. The time required for image formation on both sides is almost the same as that for single-sided image formation, and is greatly reduced as compared with the conventional double-sided image forming apparatus. As a result, the time required for recording a two-sided image is significantly reduced, and the image recording speed is significantly improved.

(Embodiment 2) The configuration and functions of a double-sided image forming apparatus according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 2 is a diagram showing a configuration of the second embodiment of the present invention. The same members as those in the first embodiment are denoted by the same reference numerals,
The description is omitted.

In this embodiment, a color image is formed by superimposing a color image on two photosensitive drums, and a color image is formed on both surfaces of a transfer material.

The first process unit 40A and the second process unit 40B include a photosensitive drum 41 as an image forming body and chargers 42Y and 42 disposed around the photosensitive drum 41, respectively.
M, 42C, 42K, developing units 43Y, 43M, 43C,
43K, cleaning device 44 and exposure unit 45
Y, 45M, 45C, and 45K. Y, M, C, and K in the reference numerals indicate process means for forming yellow, magenta, cyan, and black color toner images, respectively. For example, 42Y indicates a charger for forming a yellow toner image, and The container has a toner of a color corresponding to the code.

Also in this embodiment, the upper body 1A
Can be rotated with respect to the lower body 1B to open the transfer material conveyance path.
The process unit can be taken out as indicated by the chain line.

When the image formation is started, the photosensitive drum 41 rotates counterclockwise as indicated by an arrow a, and
The intermediate transfer member 10 rotates the photosensitive drum at the same peripheral speed in the direction indicated by the arrow b. The photosensitive drum 41 is charged by the charger 42Y, image exposure by the exposure unit 45Y, yellow toner image by reversal development by the developing unit 43Y, charging by the charger 42M, image exposure by the exposure unit 45M, and reversal development by the developing unit 43M. Magenta toner image, charging by charger 42C, exposure unit 45C
, A black toner image is sequentially formed by the reversal development by the developing unit 43C, the charging by the charger 42K, the image exposure by the exposure unit 45K, and the reversal development by the developing unit 43K, and these four color toner images are formed. To form a back color toner image. The back color toner image formed on the photosensitive drum 41 of the second process unit 40B is transferred to the intermediate transfer body 10 by the transfer unit 14B.

On the other hand, the photosensitive drum 41 of the first process unit 40A undergoes the same process as that of the second process unit 40B with a predetermined time delay with respect to the image formation in the second process unit 40B. A surface color toner image is formed on 41. The surface color toner image is transferred from the first process unit 40A to the lower surface of the transfer material supplied to the intermediate transfer body 10 in synchronization with the formation of these color toner images from the first process unit 40A. The back side color toner image formed in the second process unit and transferred to the intermediate transfer body 10 first is transferred to the transfer unit 14.
D transfers from the intermediate transfer body 10 to the upper surface of the transfer material P. In this way, the transfer material having the color toner images formed on both sides is fixed by the fixing device 18 and
Is discharged.

In this embodiment, the double-sided image formation is not only shortened as compared with the conventional one, but also the color image formation is performed in a time period for one rotation of the photosensitive drum 21.
Significant speedup of double-sided color image formation is achieved.

Also in this image forming apparatus, the upper body 1A having the intermediate transfer unit can be rotated about the axis 1C to a position shown by a two-dot chain line. Then, the process units 20A and 20B can be taken out with the transfer material conveying path opened, as indicated by the two-dot chain line.

Third Embodiment The configuration and functions of a double-sided image forming apparatus according to a third embodiment of the present invention will be described with reference to FIG. FIG. 3 is a diagram showing a configuration of the third embodiment of the present invention. The same members as those in the first embodiment are denoted by the same reference numerals,
The description is omitted.

In this embodiment, the first process unit includes a plurality of color process units 50AY and 50A.
M, 50AC, and 50AK, and the second process unit includes a plurality of color process units 50BY and 50B.
M, 50BC, and 50BK. As in the second embodiment, Y, M, C, and K in the codes correspond to yellow, magenta, cyan, and black, respectively. Each of these color process units has a photosensitive drum 51, a charger 52, a developing unit 53, and a cleaning device 54, and has a common structure. The developing device 53 includes color process units 50AY, 50AM,
Each of 50AC and 50AK has a specific toner, that is, yellow, magenta, cyan, and black toners. In this embodiment, as the exposure unit, an exposure unit including a laser scanning optical system provided in the image forming apparatus main body is used. 55AY, 55AM, 5
Exposure units 5AC and 55AK each include a yellow, magenta, cyan, and black image forming laser scanning optical system corresponding to the first process unit.
BY, 55BM, 55BC, and 55BK are exposure units having a laser scanning optical system configuration for forming images of yellow, magenta, cyan, and black corresponding to the second process unit.

When the image formation is started, the intermediate transfer member 10
Rotates in the direction indicated by the arrow b. The photosensitive drum 51 rotates in the direction of the arrow a in synchronization with the operation of the intermediate transfer body 10,
Each color process unit 50Y, 50M, 50C, 50K of the second process unit 50B operates. A yellow toner image is formed on the photosensitive drum 51 of the color process unit 50BY by charging by the charger 52, exposure by light beam irradiation based on the yellow image signal by the exposure unit 55BY, and development by the developing unit 53 to transfer. The yellow toner image is transferred to the intermediate transfer body 10 by the device 14B. Subsequently, a magenta toner image, a cyan toner image, and a black toner image are sequentially formed in the respective color process units 50BM, 50BC, and 50BK.
0, and a surface color toner image is formed on the intermediate transfer member 10 by superimposing these color toner images. The timing of forming each of these color toner images is controlled so that registration can be performed on the intermediate transfer member 10.

The transfer material P is supplied to the intermediate transfer body 10, and in the first process unit in synchronization with the intermediate transfer body 10 and the transfer material P, each color process unit 50AY, 50AM, 50AC,
From 50 AK, a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are transferred to the transfer material P in this order, and a surface color toner image is formed on the intermediate transfer body 10. Further, the back color toner image on the intermediate transfer member 10 is transferred to the transfer material P by the transfer device 14D, and the transfer material P
A color toner image is formed on both sides of the. The transfer material P on which the color toner images are formed on both sides is conveyed to the fixing device 18, and the fixing device 18 simultaneously fixes the color toner images formed on both surfaces of the transfer material P to form a two-sided color image. .

In the present embodiment, the transfer material transport path is opened by rotating the upper body 1A to the position shown by the two-dot chain line as shown, and then each color process unit is shown by the two-dot chain line. Color process unit 50A
Y and 50BY, it can be taken out individually. With such a structure for attaching and detaching color process units, each color process unit can be replaced as needed, and an image forming apparatus that always forms a color image with a uniform color tone has been realized.

[0039]

The image can be formed on both sides of the transfer material in a time almost equal to the time required to form an image on one side, so that high-speed double-sided printing can be performed. In addition, the rate of occurrence of paper jams is extremely low, and even when paper jams occur, the processing is very easy. Further, maintenance such as replacement of the process unit becomes very easy.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a second embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a third embodiment of the present invention.

[Explanation of symbols]

1A Upper body 1B Lower body 1C axis 10 Intermediate transfer body 14A, 14B, 14D Transfer device 18 Fixing device 20A, 40A First process unit 20B, 40B Second process unit 21, 41, 51 Photoconductor drum 22, 42Y, 42M, 42C, 42K, 52 Chargers 23, 43Y, 43M, 43C, 43K, 53 Developers 24, 44, 54 Cleaning Devices 30A, 30B, 45Y, 45M, 45C, 45K Exposure Units 55AY, 55AM, 55AC, 55AK Exposure Unit 55BY , 55BM, 55BC, 55BK Exposure unit 50AY, 50AM, 50AC, 50AK Color process unit 50BY, 50BM, 50BC, 50BK Color process unit

Claims (11)

[Claims] 1. A first process unit and a second process unit each including an image forming body are arranged in the order of the first process unit at a downstream portion and the second process unit at an upstream portion in a transport direction of an intermediate transfer body. Then, a toner image formed in the second process unit on the transfer material supplied from between the two process units is formed on one surface of the transfer material via the intermediate transfer body in the first process unit. In a double-sided image forming apparatus for forming an image on both sides of a transfer material by directly transferring the formed toner image to the other surface of the transfer material, the first process unit and the second process unit are disposed below the intermediate transfer body. And transferring the transfer material from below to a position between the first process unit and the second process unit so that the transfer material is in close contact with the intermediate transfer body. A double-sided image forming apparatus for transferring a toner image from a formed body to a transfer material and transferring a toner image from the intermediate transfer body to a transfer material. 2. An upper body of the double-sided image forming apparatus having the intermediate transfer body is rotatably connected to a lower body of the double-sided image forming apparatus around an axis, and the transfer material is rotated by rotation of the upper body. 2. The double-sided image forming apparatus according to claim 1, wherein the conveying path is opened. 3. The image forming apparatus according to claim 1, wherein the first and second process units can be taken out of the image forming apparatus after the transfer material conveying path is opened.
2. The double-sided image forming apparatus according to 1. 4. The double-sided image forming apparatus according to claim 1, wherein each of the first and second process units has at least a developing device. 5. The double-sided image forming apparatus according to claim 1, wherein each of the first and second process units has at least a charger. 6. The double-sided image forming apparatus according to claim 1, wherein each of the first and second process units has at least an exposure unit. 7. The double-sided image forming apparatus according to claim 1, wherein an exposure unit is attached to an apparatus main body of the double-sided image forming apparatus. 8. The method according to claim 1, wherein each of said first and second process units has a plurality of developing units for forming toner images of different colors, and can form a color image. A two-sided image forming apparatus according to claim 1. 9. The image forming apparatus according to claim 1, wherein each of the first and second process units has a plurality of image forming bodies, and toner images on the plurality of image forming bodies are individually transferred to the intermediate transfer body. The double-sided image forming apparatus according to claim 1. 10. The double-sided image forming apparatus according to claim 1, wherein a transfer material conveying path for manual paper feed is provided below the second process unit. 11. The apparatus according to claim 1, wherein each of said first and second process units is divided into a plurality of color process units for forming color toner images of different colors, and said color process units can be individually taken out of said double-sided image forming apparatus. The double-sided image forming apparatus according to claim 1 or claim 9, wherein