JP2001337546A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device by which the occurrence of transfer unevenness is prevented by removing the residual electric charge on a belt-like intermediate transfer body. SOLUTION: After a toner image on an intermediate transfer body is transferred to a transfer material by a secondary transfer means, preliminary electrification having the same polarity as that of toner is performed by a preliminary electrifying means for the transfer area of the toner image on an image carrier to at least the intermediate transfer body on the intermediate transfer body after transfer residual toner on the intermediate transfer body is removed by an intermediate transfer body cleaning means and before the toner image on the image carrier is transferred to the intermediate transfer body by a primary transfer means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to copying in which a charging means, an image writing means and a developing means are arranged around an image carrier to transfer and fix a toner image formed on the image carrier onto a transfer material. More particularly, the present invention relates to an image forming apparatus that forms a toner image on both surfaces of a transfer material, such as an image forming apparatus, a printer, and a facsimile.

[0002]

2. Description of the Related Art Conventionally, in forming a double-sided image, an image on one side formed on an image carrier is transferred and fixed onto a transfer material, and this is temporarily stored in a double-sided reversal feeding device, and the image is re-supported. 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.

As described above, in the double-sided image forming apparatus, as described above, the transfer of the transfer material such as feeding to the double-sided reverse feeding device and passing through the fixing device twice is performed. This is a cause of 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 Nos. 4-214576 and 4-214576 propose a method in which a toner image is formed on both surfaces of a transfer material using an image carrier and an intermediate transfer member, and then fixed once.

Further, the present inventors dispose a plurality of sets of toner image forming means including a charging means, an image writing means, a developing means and the like around a photosensitive drum (image carrier), and place the toner image forming means on the photosensitive drum. The formed superimposed color toner image is once transferred onto a belt-shaped intermediate transfer body at one time, and then a superimposed color toner image is formed again on the photoconductor drum, and the toner image on the photoconductor drum and the intermediate transfer body are formed again. The toner image on the photosensitive drum is transferred as a surface image (surface toner image) onto both surfaces of the transfer material which is fed in time with the toner image of the intermediate transfer member and conveyed by the intermediate transfer member. After transferring the toner image as a backside image (backside toner image), the transfer material is separated from the intermediate transfer member by discharging the transfer material, and the toner image on the transfer material is fixed by a fixing unit to form a double-sided color image. JP-image forming apparatus and an image forming method for forming a (one-pass double-sided image forming method) 9-2584
No. 92 and JP-A-9-258516.

[0006]

However, in an image forming apparatus (one-pass double-sided image forming apparatus) for forming an image on both sides of a transfer material using the belt-like intermediate transfer body as described above, an image carrier (photosensitive) is used. When the toner image on the drum is transferred to the belt-shaped intermediate transfer member, residual charges remain on the belt surface of the intermediate transfer member, and the transfer conditions change due to the memory due to the residual charges, resulting in band-shaped transfer unevenness. The problem that occurs occurs.

SUMMARY OF THE INVENTION It is a first object of the present invention to solve the above-mentioned problems and to provide an image forming apparatus which removes residual charge of a belt-like intermediate transfer member and prevents occurrence of transfer unevenness.

Further, in an image forming apparatus for forming an image on both surfaces of a transfer material using the belt-shaped intermediate transfer member,
When a toner image on an image carrier (photosensitive drum) is transferred to a belt-shaped intermediate transfer member, a separation discharge occurs at a separation portion between the photosensitive drum and the belt surface of the intermediate transfer member, and a part of toner is discharged. The toner polarity changes, the polarity becomes the opposite positive polarity, or the charge amount (Q / M) changes, causing the charge of the toner image to be disturbed and causing the toner image to be transferred onto the intermediate transfer member. There is a problem that image disturbance or transfer omission occurs when the toner image on the intermediate transfer member is transferred onto the transfer material.

The present invention also solves the above problems, and makes the toner charge of the toner image on the belt-like intermediate transfer member uniform,
It is a second object of the present invention to provide an image forming apparatus which prevents occurrence of image disturbance of a toner image on an intermediate transfer member and prevents transfer omission when transferring a toner image on the intermediate transfer member onto a transfer material. And

In an image forming apparatus for forming an image on both surfaces of a transfer material using the belt-shaped intermediate transfer member,
When a toner image on an image carrier (photosensitive drum) is transferred onto a belt-shaped intermediate transfer member, a separation discharge occurs at a separation portion between the photosensitive drum and the belt surface of the intermediate transfer member, and the intermediate transfer member is separated. When the toner image on the transfer drum is disturbed or when the toner image on the transfer drum is transferred onto the transfer material, a separation discharge occurs at the separation portion between the transfer drum and the transfer drum, and the toner image on the transfer material is removed. The problem arises that the data is disturbed.
In particular, when a toner image on an image carrier (photosensitive drum) is transferred onto a transfer material, a peeling discharge at a separation portion between the photosensitive drum and the transfer material occurs during monochrome image formation and color image formation. Different depending on environmental conditions,
There is a problem in that the toner image varies depending on the type of the transfer material and the toner image on the transfer material is disturbed.

The present invention also solves the above-mentioned problems, and separates the image carrier from the belt-like intermediate transfer member when transferring the toner image on the image carrier onto the belt-like intermediate transfer member. Of the toner image on the intermediate transfer member due to the peel discharge at the time of transfer and transfer of the toner image on the image carrier onto the transfer material by the peel discharge at the separation portion between the image carrier and the transfer material Provided is a double-sided image forming apparatus for preventing disturbance of a toner image on a material, and a monochrome unit in a separation unit between the image carrier and the transfer material when a toner image on the image carrier is transferred onto a transfer material. Peeling discharge that occurs differently during image formation and color image formation, peeling discharge that occurs differently under environmental conditions, and disturbance of the toner image on the transfer material due to peeling discharge that occurs differently depending on the type of transfer material Providing an image forming apparatus for preventing It is referred to as third object of.

[0012]

A first object of the present invention is to provide an image bearing member for carrying a toner image formed by a toner image forming means on a surface thereof, and transferring and transferring the toner image on the image bearing member. While carrying the toner image on the surface, a transfer material charged by a transfer material charging unit is brought into close contact with the belt, and a belt-shaped intermediate transfer body that supports and conveys the transfer material, and the toner image on the image carrier is Primary transfer means for transferring the toner image on the intermediate transfer member or the front surface of the transfer material, secondary transfer means for re-transferring the toner image on the intermediate transfer member to the back surface of the transfer material, and transferring the toner image on the transfer material In an image forming apparatus having a fixing unit for fixing and an intermediate transfer body cleaning unit for cleaning the intermediate transfer body, after transferring the toner image on the intermediate transfer body to the transfer material by the secondary transfer unit, Intermediate transfer member After cleaning the residual toner on the intermediate transfer member by cleaning means, the 1
Before the transfer of the toner image on the image carrier to the intermediate transfer member by the next transfer means, at least a transfer area of the toner image on the image carrier to the intermediate transfer member on the intermediate transfer member, An image forming apparatus (first invention) for performing pre-charging of the same polarity as toner by pre-charging means, and a second device for carrying a toner image formed on the surface by the first toner image forming means. (1) an image carrier, a second image carrier for carrying the toner image formed by the second toner image forming means on the surface thereof, and the toner image on the first image carrier is transferred and transferred. A belt-shaped intermediate transfer body that supports the transfer material, while supporting the transfer material charged by the transfer material charging means while supporting the toner image on the surface, and a toner on the first image support. First primary transfer for transferring an image to the intermediate transfer body Means, second primary transfer means for transferring the toner image on the second image carrier to the surface of the transfer material, and retransfer of the toner image on the intermediate transfer material to the back surface of the transfer material In an image forming apparatus including a secondary transfer unit, a fixing unit for fixing a toner image on the transfer material, and an intermediate transfer body cleaning unit for cleaning the intermediate transfer body, the intermediate transfer body by the secondary transfer unit After transferring the upper toner image to the transfer material, the intermediate transfer body cleaning means cleans the transfer residual toner on the intermediate transfer body, and then the first primary transfer means carries the first image bearing member. Before the transfer of the toner image on the body to the intermediate transfer member, at least a transfer area of the toner image on the first image carrier to the intermediate transfer member on the intermediate transfer member is determined by preliminary charging means. ,toner It is achieved by an image forming apparatus, characterized in that the preliminary charging of the same polarity (the second invention).

A second object of the present invention is to provide an image bearing member for carrying a toner image formed on a surface thereof by a toner image forming means, a toner image on the image bearing member being transferred, and transferring the transferred toner image. A belt-shaped intermediate transfer body that supports and transports a transfer material, a transfer material supply unit that supplies the transfer material to the intermediate transfer body, and transfers the toner image on the image carrier to the intermediate transfer body. Primary transfer means for transferring the toner image on the body or the surface of the transfer material, secondary transfer means for retransferring the toner image on the intermediate transfer body to the back surface of the transfer material, and fixing the toner image on the transfer material In an image forming apparatus having a fixing unit and an intermediate transfer member cleaning unit for cleaning the intermediate transfer member, a toner image transferred from the image carrier to the intermediate transfer member by the primary transfer unit is re-used. For charging means An image forming apparatus (third invention), wherein the transfer material is recharged to the same polarity as the toner, and after the recharge by the recharge means, the transfer material is fed by the transfer material feeding means. A first image carrier for carrying on the surface a toner image formed by the first toner image forming means, and a second image carrier for carrying on the surface a toner image formed by the second toner image forming means A toner image on the first image carrier, and a belt-shaped intermediate transfer body that supports and transports the transferred toner image while supporting the transferred toner image on the surface; Transfer material supply means for supplying the intermediate transfer member, first primary transfer means for transferring the toner image on the first image carrier to the intermediate transfer member, and toner on the second image carrier Second primary transfer means for transferring an image to the surface of the transfer material; Secondary transfer means for re-transferring the toner image on the serial intermediate transfer member to the back surface of the transfer material, and a fixing unit for fixing the toner image on the transfer material,
An image forming apparatus having an intermediate transfer member cleaning unit for cleaning the intermediate transfer member, wherein the toner image transferred from the first image carrier to the intermediate transfer member by the first primary transfer unit is provided. An image forming apparatus wherein the transfer material is recharged to the same polarity as the toner by the recharge means, and the transfer material is fed by the transfer material feed means after the recharge by the recharge means. invention)
Achieved by

A third object of the present invention is to provide an image bearing member for carrying a toner image formed on a surface thereof by a toner image forming means, a toner image transferred on the image bearing member, and the transferred toner image. And a belt-like intermediate transfer body that supports and transports the transfer material, and transfers the toner image on the image carrier to the surface of the intermediate transfer body or the transfer material.
An image forming apparatus comprising: a secondary transfer unit; a secondary transfer unit that re-transfers the toner image on the intermediate transfer member to the back surface of the transfer material; and a fixing unit that fixes the toner image on the transfer material. In the vicinity of a separation portion between the intermediate transfer member and the image carrier, an auxiliary discharge unit for performing a discharge having the same polarity as the toner is provided, and the toner image on the image carrier by the primary transfer unit is formed on the intermediate transfer member A discharge condition by the auxiliary discharge unit when the toner image on the image carrier is transferred onto the transfer material by the primary transfer unit is weaker than a discharge condition by the auxiliary discharge unit during transfer to the transfer member. An image forming apparatus (fifth invention), an image carrier, a toner image forming means for forming a color toner image or a monochrome toner image on the image carrier, and the image carrier The upper color toner image Is a belt-like intermediate transfer member on which a monochrome toner image is transferred and which carries the transferred color toner image or monochrome toner image on the surface thereof and supports and conveys a transfer material; and a color toner image or a monochrome toner image on the image carrier. A primary transfer unit for transferring a toner image to the surface of the intermediate transfer member or the transfer material; a secondary transfer unit for retransferring a color toner image or a monochrome toner image on the intermediate transfer member to a back surface of the transfer material; An image forming apparatus having a fixing unit for fixing a color toner image or a monochrome toner image on the transfer material, wherein a discharge having the same polarity as the toner is performed in the vicinity of a separation portion between the intermediate transfer member and the image carrier. An auxiliary discharge unit is provided, and the primary transfer unit transfers a color toner image or a monochrome toner image on the image carrier onto the transfer material. An image forming apparatus characterized by than by discharge conditions the auxiliary discharge means during monochrome image formation, setting strongly discharge condition by said auxiliary discharge means during color image formation (sixth invention),
An image carrier that carries the toner image formed by the toner image forming means on the surface thereof; a toner image on the image carrier is transferred; the transferred toner image is carried on the surface; A belt-shaped intermediate transfer body for supporting and conveying, a primary transfer means for transferring the toner image on the image carrier to the surface of the intermediate transfer body or the transfer material, and a transfer of the toner image on the intermediate transfer body In an image forming apparatus having a secondary transfer unit for retransferring to the back surface of a material and a fixing unit for fixing a toner image on the transfer material, a toner is provided near a separation portion between the intermediate transfer body and the image carrier. And an auxiliary discharge means for performing a discharge having the same polarity as that of the auxiliary discharge means. When the primary transfer means transfers the toner image on the image carrier onto the transfer material, the auxiliary discharge means Change discharge conditions An image forming apparatus (seventh invention), an image carrier that carries a toner image formed by a toner image forming unit on a surface thereof, and the toner image on the image carrier is transferred and transferred. A belt-shaped intermediate transfer member that carries the transferred toner image on the surface and supports and conveys the transfer material; and a primary transfer device that transfers the toner image on the image carrier to the surface of the intermediate transfer member or the transfer material. An image forming apparatus comprising: a transfer unit; a secondary transfer unit configured to re-transfer the toner image on the intermediate transfer member to the back surface of the transfer material; and a fixing unit configured to fix the toner image on the transfer material. In the vicinity of a separation portion between the transfer body and the image carrier, an auxiliary discharge unit that performs discharge of the same polarity as the toner is provided, and the primary transfer unit transfers the toner image on the image carrier onto the transfer material. During transfer, depending on the type of transfer material An image forming apparatus (eighth invention), wherein the discharge condition of the auxiliary discharge means is changed, and a first image forming apparatus which carries a toner image formed on the surface by the first toner image forming means. An image carrier, a second image carrier for carrying on its surface a toner image formed by a second toner image forming means,
A toner image on the image carrier, and a belt-shaped intermediate transfer member that supports the transferred toner image on the surface and supports and conveys a transfer material; and a toner image on the first image carrier. A first primary transfer unit for transferring the image to the intermediate transfer member,
Second primary transfer means for transferring the toner image on the second image carrier to the surface of the transfer material, and secondary transfer for retransferring the toner image on the intermediate transfer material to the back surface of the transfer material And an image forming apparatus having a fixing unit for fixing a toner image on the transfer material.
A first auxiliary discharge unit for performing a discharge having the same polarity as that of the toner is provided in the vicinity of a separation portion between the image carrier and the toner, and a toner and A second auxiliary discharge means for performing a discharge of the same polarity;
The second primary transfer unit is more than the discharge condition of the first auxiliary discharge unit when the toner image on the first image carrier is transferred onto the intermediate transfer member by the primary transfer unit. The discharge condition of the second auxiliary discharge unit when the toner image on the second image bearing member is transferred onto the transfer material by the above-described method is set to be weak. And a first image carrier, and a first image carrier for forming a color toner image or a monochrome toner image on the first image carrier.
Toner image forming means, a second image carrier, a second toner image forming means for forming a color toner image or a monochrome toner image on the second image carrier, and the first image carrier A belt-shaped intermediate transfer body that transfers the color toner image or the monochrome toner image thereon, carries the transferred color toner image or the monochrome toner image on the surface, and supports and conveys a transfer material; A first primary transfer unit for transferring a color toner image or a monochrome toner image on a carrier to the intermediate transfer body; and a color toner image or a monochrome toner image on the second image carrier for transferring the color toner image or the monochrome toner image to the surface of the transfer material. Second transfer means for transferring the toner image on the intermediate transfer member to the back surface of the transfer material, and fixing a color toner image or a monochrome toner image on the transfer material. Sure And a second auxiliary discharge means for performing a discharge having the same polarity as that of the toner near the separation portion between the intermediate transfer member and the second image carrier. When the color toner image or the monochrome toner image on the second image carrier is transferred onto the transfer material by the primary transfer unit, the discharge condition by the second auxiliary discharge unit at the time of monochrome image formation is smaller than the discharge condition by the second auxiliary discharge unit. An image forming apparatus (tenth aspect) in which the discharge condition of the second auxiliary discharge unit during color image formation is set strongly, and the toner image formed by the first toner image forming unit is A first image carrier carried on the surface, a second image carrier carrying the toner image formed by the second toner image forming means on the surface, and a toner image on the first image carrier are formed. Transcribed, transcribed A belt-shaped intermediate transfer member that supports the toner image on the surface and supports and conveys a transfer material; and a first primary transfer unit that transfers the toner image on the first image carrier to the intermediate transfer member. , The second
A second primary transfer means for transferring the toner image on the image carrier to the surface of the transfer material, a secondary transfer means for retransferring the toner image on the intermediate transfer body to the back surface of the transfer material, An image forming apparatus having a fixing unit for fixing the toner image on the transfer material, wherein a discharge having the same polarity as the toner is performed in the vicinity of a separation portion between the intermediate transfer member and the second image carrier. An auxiliary discharge means provided at the time of transferring the toner image on the second image carrier onto the transfer material by the second primary transfer means in accordance with environmental conditions; An image forming apparatus (eleventh invention), wherein a discharge condition by means is changed, a first image carrier for carrying on the surface a toner image formed by the first toner image forming means, The toner image formed by the second toner image forming means is displayed. And a belt-shaped intermediate transfer for transferring the toner image on the first image carrier, supporting the transferred toner image on the surface, and supporting and transferring the transfer material. Body, first primary transfer means for transferring the toner image on the first image carrier to the intermediate transfer body, and transfer of the toner image on the second image carrier to the surface of the transfer material An image having: a second primary transfer unit for performing transfer; a secondary transfer unit for retransferring the toner image on the intermediate transfer member to the back surface of the transfer material; and a fixing unit for fixing the toner image on the transfer material. In the forming apparatus, a second auxiliary discharge unit for performing a discharge having the same polarity as that of the toner is provided in the vicinity of a separation portion between the intermediate transfer member and the second image bearing member. When transferring the toner image on the second image carrier onto the transfer material, Depending on the type of Utsushizai, the achieved by a second auxiliary discharge means an image forming apparatus characterized by changing the discharge conditions according to (twelfth invention).

[0015]

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. 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, the surface of the transfer material supported and conveyed by the intermediate transfer member, the surface on the side facing the image carrier is the front surface, and the other surface, that is, the surface on the side facing the intermediate transfer member is the back surface. That is, an image transferred to the front surface of the transfer material is called a front image, and an image transferred to the back surface of the transfer material is called a back image.

First, a first common feature of claims 1 and 2, claims 5 to 8, and claims 13 to 17 of the present invention is as follows.
Image forming process of an embodiment of the image forming apparatus of the example of
Each mechanism will be described with reference to FIGS. FIG. 1 shows claim 1 or 2 of the present invention, claims 5 to 8,
FIG. 2 is a sectional configuration view of a color image forming apparatus showing an embodiment of an image forming apparatus of a first example common to claims 13 to 17, and FIG. 2 is a side sectional view of the image carrier of FIG. FIG. 3 is a view showing a toner image forming state in the image forming apparatus of FIG. 1, and FIG. 3 (A) shows a state in which a back side image formed on an image carrier is transferred onto a belt-shaped intermediate transfer body. FIG. 3B is a diagram illustrating a toner image forming state, and FIG. 3B is a diagram illustrating a toner image forming state when a front image is formed on an image carrier in synchronization with a back image on a belt-shaped intermediate transfer member. FIG. 3 (C) is a diagram showing double-sided image formation on a transfer material.

In FIG. 1, 10 is a photosensitive drum as an image carrier, 11 is a scorotron charger as charging means for each color, 12 is an exposure optical system as image writing means for each color, and 13 is an exposure optical system for each color. A transfer device as a belt-like intermediate transfer member; and 14c, a primary transfer device for transferring the toner image on the image carrier onto the surface of the belt-like intermediate transfer member and the transfer material. The primary transfer roller 14g is a secondary transfer unit that is a secondary transfer unit that transfers the toner image on the belt-shaped intermediate transfer body to the back surface of the transfer material.
4 m is a static eliminator as a static elimination means, 150 is a paper charger as a transfer material electrification means, 14 h is a transfer material static eliminator as a transfer material static elimination means, 160 is a separation claw 210 as a nail member and a spur 162 as a spur member. Reference numeral 17 denotes a fixing device as a fixing unit, reference numeral 19 denotes a photoconductor cleaning device as an image carrier cleaning unit, and reference numeral 190 denotes an intermediate transfer body cleaning device as an intermediate transfer body cleaning unit.

The photosensitive drum 10 serving as an image carrier 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), which is rotated at a linear speed of, for example, 80 to 400 mm / sec in a clockwise direction indicated by an arrow in FIG. Is done.

The photosensitive drum 10 is, as shown in FIG.
Flange members 10A and 1A at both ends for engaging and fixing it
The photoreceptor drive gear G integrated with the flange member 10B is supported by the bearings B1 and B2 fitted into the photoreceptor drum shaft 30 mounted and fixed to the apparatus main body so as to be rotatable. The drive gear is driven at a constant speed in a predetermined direction by being engaged with and driven by a drive gear (not shown) on the side.

The toner image forming means for forming a toner image on the image carrier is a scorotron charger 11, which is a charging means.
An exposure optical system 12 serving as an image writing unit and a developing unit 13 serving as a developing unit. These units constitute an image of each color of yellow (Y), magenta (M), cyan (C), and black (K). Four sets are provided for the forming process, and are arranged in the order of Y, M, C, and K with respect to the rotation direction of the photosensitive drum 10 indicated by the arrow in FIG.

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 saw-tooth electrode, and faces the photosensitive layer of the photosensitive drum 10. And installed
The charging operation is performed by corona discharge having the same polarity as the toner (the polarity of the toner used in this embodiment is set to minus polarity, and the charging by the scorotron charger 11 serving as a charging unit in this embodiment is performed negatively). 10 is given a uniform potential. 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 includes a plurality of LEDs (light emitting diodes) as light emitting elements of image exposure light (image writing light) arranged in the main scanning direction in parallel with the drum axis 30. Linear exposure elements 12a arranged in an array, and a light converging light transmitter (trade name: Selfoc lens array) 12b as an imaging element
And a lens holder 12c that holds the SELFOC lens array 12b, and is attached to the holding member 20. In addition to the exposure optical system 12 for each color, a transfer simultaneous exposure device 12d and a uniform exposure device 12e are attached to the holding member 20, and the photosensitive drum 1 is integrally formed.
0 is accommodated inside the light-transmitting substrate. The exposure optical system 12 for each color writes an image on the photosensitive layer of the photosensitive drum 10 from the back side in accordance with image data of each color read by a separate image reading device and stored in the memory.
An electrostatic latent image is formed thereon. As the exposure element 12a, L
In addition to the ED, it is also possible to use a plurality of light-emitting elements such as FL (phosphor light emission), EL (electroluminescence), and PL (plasma discharge) arranged in an array.
The emission wavelength of the light emitting element of the image exposure light (image writing light) is usually 780 to 90, which is highly transparent to the Y, M, and C toners.
In the present embodiment, since the image is written from the back surface, a shorter wavelength than 40 nm which does not have sufficient transparency to the color toner is used in this embodiment.
The wavelength may be from 0 to 780 nm. In addition, 80 of the image exposure light
% Or more is absorbed by the photosensitive layer of the photoconductor drum 10, so that the effect of reflection and absorption by the color toner on the surface of the photoconductor drum 10 can be neglected. Generally, the order of development of the color toner is preferably Y, M, C, and K from the relation of the color mixture to the toner image and the developing device 13. In FIG. 2, W
A 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 at a developing position in the forward direction of the rotating direction of the photosensitive drum 10. It has a cylindrical developing sleeve 131 made of non-magnetic stainless steel or aluminum having a diameter of 5 to 1 mm and an outer diameter of 15 to 25 mm, and a developing casing 138. Inside the developing casing 138, yellow (Y) is provided. , Magenta (M), cyan (C) and black (K) one-component or two-component developers. The developing sleeve 131 of each developing unit 13 is separated from the photosensitive drum 10 by a contact roller (not shown) with a predetermined gap, for example, 100 to 500 μm. 10 is maintained in a non-contact state with the developing sleeve 131. By applying a developing bias in which a DC voltage (in the present embodiment, the same polarity as the toner polarity used and a negative polarity) is superimposed on an AC voltage, the developing bias is applied to the developing sleeve 131. Contact reversal development is performed to form a toner image on the photosensitive drum 10.

Intermediate transfer bell which is a belt-shaped intermediate transfer member
G preferably has a volume resistivity of 10⁹Ω · cm or less
Above, 10¹²Less than Ω · cm, surface resistance is 10⁹-10¹²Ω
/ Cm ^TwoAnd the surface resistance is between 1 and
It is an endless belt with a value of 100 times.
Imide, thermoset polyimide, ethylene-tetrafluoro
Ethylene copolymer, polyvinylidene fluoride, nylon
Separating conductive materials into engineering plastics such as Roy
Sputtered semiconductive film substrate having a thickness of 0.1 to 1.0 mm
Outside, preferably as a toner filming prevention layer
Two-layer structure with fluorine coating of 5 to 50 μm thickness
It is a seamless belt. Of the intermediate transfer belt 14a
In addition to the above, silicon rubber or urethane
0.5 to 2.0 mm thick conductive material dispersed in rubber etc.
A semiconductive rubber belt can also be used. Intermediate transfer
The belt 14a is an intermediate transfer member stretching roller member.
A certain drive roller 14d and a secondary transfer opposing roller 14j
Moving roller 14e, guide roller 14f and tension roller
1a and stretched counterclockwise as indicated by the arrow in FIG.
Rotated. Guide roller 14f, driven roller 14e,
Secondary transfer opposing roller 14j and drive roller 14d are fixed
The tension roller 14i is rotated at the position shown in FIG.
It is movably supported and rotated by the elasticity of the spike. Unfortunate
Drive roller driven by the photoconductor drive motor shown
14d is rotated, and the intermediate transfer belt 14a is driven to rotate.
Invert. Secondary transfer by rotation of the intermediate transfer belt 14a
Opposing roller 14j, driven roller 14e, guide roller 1
4f and the tension roller 14i are driven and rotated.
You. The belt slack of the rotating intermediate transfer belt 14a is
It is tensed by the shock roller 14i. Intermediate transfer belt
The transfer material is placed at a position where 14a is stretched over the driven roller 14e.
A recording sheet P is supplied, and is supplied by the intermediate transfer belt 14a.
Supported and transported. The middle stretched around the drive roller 14d
Curvature portion KT at end of transfer belt 14a on fixing device 17 side
The recording paper P is separated from the intermediate transfer belt 14a at
You.

A contact-type transfer roller member is used,
A primary transfer roller 14c, which is a primary transfer unit for transferring the toner image on the image carrier onto the surface of a belt-shaped intermediate transfer body or a transfer material, is disposed on the photosensitive drum 10 for each color with the intermediate transfer belt 14a interposed therebetween. The intermediate transfer belt 14a is provided so as to face the intermediate transfer belt 14a, and forms a transfer area (no reference numeral) between the intermediate transfer belt 14a and the photosensitive drum 10. 1
A DC voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied to the next transfer roller 14c, and the toner image on the photosensitive drum 10 is transferred onto the intermediate transfer belt 14a or the surface of the recording paper P as a transfer material. Transfer to It is also possible to use a corona discharger as the primary transfer means.

A secondary transfer device 1 as a secondary transfer means for retransferring the toner image on the belt-like intermediate transfer member to the back surface of the transfer material.
4 g is constituted by a corona discharger, and the primary transfer roller 1
4c and the drive roller 14d, the intermediate transfer belt 14
a, a DC voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied to record the toner image on the intermediate transfer belt 14a. The image is transferred to the back surface of the paper P.

The static eliminator 14m, which is a static eliminator, is constituted by a corona discharger, and is provided in parallel with the primary transfer roller 14c on the downstream side of the primary transfer roller 14c with respect to the moving direction of the intermediate transfer belt 14a. AC voltage is applied and 1
The charge of the intermediate transfer belt 14a charged by the voltage application of the next transfer roller 14c is eliminated.

The paper charger 150, which is a transfer material charging means, is preferably constituted by a corona discharger, is provided opposite to a driven roller 14e, which is grounded with the intermediate transfer belt 14a interposed, and has the same polarity as the toner (this embodiment). (In the embodiment, a negative polarity) is applied, and the recording paper P is charged and attracted to the intermediate transfer belt 14a. As the transfer material charging means, in addition to the corona discharger, a saw-tooth electrode, a brush-like or roller-like charger capable of contacting and releasing contact with the intermediate transfer belt 14a, and the like can be used.

Transfer material static eliminator 14h as transfer material static elimination means
Is constituted by a corona discharger, and the intermediate transfer belt 14a
Of the recording paper P at the end of the fixing device 17 side of the intermediate transfer belt 14
In the vicinity of the position where the intermediate transfer belt 14a is separated from the driving roller 14d, the charging amount (Q /
M) An AC voltage on which a DC voltage is superimposed for preventing separation discharge at the time of separation of the surface toner image having a high surface is applied, and 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 has a separation claw 210 as a transfer material separation assisting means and a spur 162 as a spur member.
The intermediate transfer belt 14 a is provided between the fixing device 17 and a curvature portion KT at the end of the intermediate transfer belt 14 a on the fixing device 17 side. Transport unit 160
Is transferred to the intermediate transfer belt 14 by heat from the fixing device 17.
a, the toner image carried on the intermediate transfer belt 14a becomes less likely to be transferred because the toner image tends to be fused, and the toner is prevented from being fixed on the intermediate transfer belt 14a.

The separation claw 210, which is a transfer material separation assisting means, is close to the curvature portion KT of the intermediate transfer belt 14a, and has a predetermined distance from the intermediate transfer belt 14a, preferably 0.1 to 2.0.
When the recording paper P is separated from the intermediate transfer belt 14a, the recording paper P is bent toward the intermediate transfer belt 14a to be conveyed when the recording paper P is separated from the intermediate transfer belt 14a. To assist the curvature separation of the recording paper P.

The spur 162, which is a spur member, is made of an insulating resin material such as polyacetal or polyamide, has a plurality of protrusions 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 toner image on the back side of the recording sheet P having the toner images 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 disposed on the side opposite to the photosensitive drum 10 with respect to the transfer material conveying surface on the intermediate transfer belt 14a or its extension surface.
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.

The fixing device 17 serving as a fixing means includes a first fixing roller 17a having a heater therein and a second fixing roller 1a.
7b, which is composed of two roller-shaped fixing members, and by applying heat and pressure while nipping and transporting the recording paper P at a nip portion T between the first fixing roller 17a and the second fixing roller 17b. Then, the toner image on the recording paper P is fixed.

The photoconductor cleaning device 19, which is an image carrier cleaning unit, includes a photoconductor drum 10 rotating direction,
The photoreceptor cleaning blade 19a, which is provided downstream of the transfer area (no symbol) of the primary transfer roller 14c and is made of a rubber material that contacts the photoreceptor drum 10, remains on the peripheral surface of the photoreceptor drum 10 after the transfer. Clean transfer residual toner. The toner cleaned by the photoconductor cleaning blade 19a is collected by a screw 19b into a not-shown waste toner container.

The intermediate transfer member cleaning device 190, which is an intermediate transfer member cleaning means, includes an intermediate transfer belt 14a.
The intermediate transfer belt cleaning blade 191a, which is provided opposite to the guide roller 14f, is made of a rubber material, and can be brought into contact with and released from the intermediate transfer belt 14a, on the peripheral surface of the intermediate transfer belt 14a after transfer. The remaining toner remaining on the back side toner image after the transfer is cleaned. The toner cleaned by the intermediate transfer member cleaning blade 191a is collected by a screw 190b into a waste toner container (not shown).

Next, the image forming process will be described. The photosensitive drum 10 is rotated clockwise as indicated by an arrow in FIG. 1 by the start of a photosensitive member drive motor (not shown) at the start of image recording, and at the same time, a yellow (Y) scorotron charger 1.
By the charging operation of 1, the application of the potential to the photosensitive drum 10 is started.

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 reversely developed in a non-contact state by the Y developing device 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 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, an exposure optical system 12 for K, and a developing device 13 for K. A superimposed 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. .

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.

The superimposed color toner image (reverse toner image), which is the reverse image formed on the photosensitive drum 10 as the image carrier by the above-described image forming process, is transferred to the transfer area (unsigned) of the primary transfer roller 14c. 3), the image is collectively transferred onto an intermediate transfer belt 14a, which is a belt-shaped intermediate transfer member, by a primary transfer roller 14c (FIG. 3).
(A)). 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 charge on the intermediate transfer belt 14a charged by the primary transfer roller 14c is removed by a charge remover 14m serving as an intermediate transfer member discharging means.

The toner remaining on the peripheral surface of the photoreceptor drum 10 after the transfer is discharged by the photoreceptor drum AC static eliminator 16 and then enters the photoreceptor cleaning device 19 or contacts the photoreceptor drum 10. The cleaning is performed by the cleaning blade 19a. In addition, the history of the photosensitive drum 10 in the previous image formation on the peripheral surface of the photosensitive drum 10 is eliminated by, for example, exposure by the uniform exposure device 12e before charging using a light emitting diode.

After the superimposed color toner image serving as the back surface image is formed on the intermediate transfer belt 14a as described above, the front surface image is continuously formed on the photosensitive drum 10 in the same manner as the above-described color image forming process. A superimposed color toner image (surface toner image) is formed as shown in FIG.
(B)). At this time, the image data is changed so that the front surface image formed on the photosensitive drum 10 is a mirror image of the rear surface image formed on the photosensitive 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 the timing roller 15b drives the front surface image color toner image formed on the photosensitive drum 10 to synchronize with the back surface image color toner image carried on the intermediate transfer belt 14a. Is fed to the transfer area (no symbol) of the primary transfer roller 14c. 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 front surface side of the recording paper P, and is attracted to the intermediate transfer belt 14a to be charged to the primary transfer belt. The sheet is conveyed to the transfer area (no symbol) of the transfer roller 14c. By charging the paper with the same polarity as that of the toner, the toner is prevented from being attracted to the toner image on the intermediate transfer belt 14a and the toner image on the photosensitive drum 10, thereby preventing the toner image from being disturbed.

In the transfer area (no sign) of the primary transfer roller 14c, the primary transfer roller 14c to which a voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied. The color toner images (surface toner images) are collectively transferred to the surface of the recording paper P. At this time, the color toner image (backside toner image) of the backside image on the intermediate transfer belt 14a is present on the intermediate transfer belt 14a without being transferred to the recording paper P. At this time, a transfer simultaneous exposure unit 12d using, for example, a light emitting diode is provided inside the photosensitive drum 10 so as to oppose a transfer area (no reference numeral) of the primary transfer roller 14c so that good transfer is performed. May be performed.
The charge on the intermediate transfer belt 14a charged by the primary transfer roller 14c is removed by a charge remover 14m serving as an intermediate transfer member discharging means.

The recording paper P on which the color toner image has been transferred is conveyed to a secondary transfer unit 14g to which a voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied. By 14g, the color toner image (backside toner image) of the backside image on the peripheral surface of the intermediate transfer belt 14a is collectively retransferred to the backside of the recording paper P (FIG. 3C).

The recording paper P on which the color toner images are formed on both sides is provided with a curvature of the curvature portion KT of the intermediate transfer belt 14a and a transfer material neutralizer 14h as a transfer material neutralization means provided at an end of the intermediate transfer belt 14a. Of the intermediate transfer belt 14a with the separation claw 210 provided on the conveyance unit 160 at a predetermined interval from the intermediate transfer belt 14a.
From the nip portion T between the first fixing roller 17a and the second fixing roller 17b, and is conveyed to the fixing device 17 as a fixing unit through a spur 162 provided in the conveying portion 160. By applying heat and pressure in the portion T, the toner images on the front and back sides of the recording paper P are fixed, and a front surface image of the recording paper P and a back surface image of the rear surface are formed. 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.

The toner remaining on the peripheral surface of the intermediate transfer belt 14a after the transfer is cleaned by an intermediate transfer member cleaning blade 191a that comes into contact with the intermediate transfer belt 14a.

Further, the toner remaining on the peripheral surface of the photosensitive drum 10 after the transfer is subjected to static elimination by the photosensitive drum AC static eliminator 16 and then cleaned by the photosensitive body cleaning device 19 to uniformly remove the toner before charging. The history of the photosensitive drum 10 in the previous image formation is eliminated by the exposure device 12e, and the process proceeds to the next image formation cycle.

Since the superposed 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.

Next, an embodiment of an image forming apparatus according to a second example which is common to claims 3 or 4, 9 to 12 and 18 to 22 of the present invention will be described with reference to FIG. I do. FIG. 4 is a cross-sectional view of a main part of a color image forming apparatus showing an embodiment of an image forming apparatus according to a second example which is common to claims 3 or 4, 9 to 12, and 18 to 22 of the present invention. It is a block diagram. The members having the same functions and structures as those of the members described in the image forming apparatus of the first example are given the same numbers.

In the image forming apparatus of this embodiment, as shown in FIG. 4, a photosensitive drum 10b as a first image carrier for forming a toner image to be a back image (back toner image) and a front image are formed. A photoconductor drum 10a as a second image carrier for forming a toner image (front toner image) is separately provided, and the back toner image formed on the photoconductor drum 10b has a polarity opposite to that of the toner (in the present embodiment). Is a belt-like intermediate transfer member by a first primary transfer roller 114b which is a first primary transfer unit to which a voltage of a negative polarity is used for the toner to be used and a positive polarity voltage is applied in the present embodiment. Is transferred onto the intermediate transfer belt 114a,
The recording paper P, which is a transfer material, is supplied between the photosensitive drum 10b and the photosensitive drum 10a onto the intermediate transfer belt 114a by a timing roller 15b as a transfer material feeding unit, and grounded through the intermediate transfer belt 114a. Roller 14
The recording paper P is transferred to the intermediate transfer belt 114 by the charging of the paper charger 150 which is a transfer material charging unit provided opposite to the recording paper P.
a, and is conveyed on the transfer material conveying surface of the intermediate transfer belt 114a and the extended surface thereof, and the surface toner image formed on the photosensitive drum 10a in synchronization with the conveyance of the recording paper P is changed in polarity opposite to the toner ( After transfer to the surface of the recording paper P by a second primary transfer roller 114c, which is a second primary transfer unit to which a voltage having a positive polarity in this embodiment is applied,
The back side toner image on the intermediate transfer belt 114a is re-transferred to the back side of the recording paper P by a secondary transfer unit 14g which is a secondary transfer unit to which a voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied. Then, the recording paper P on which the front and back toner images are formed on the recording paper P, and the color toner images are formed on both sides, is applied to the curvature of the curvature portion KT of the intermediate transfer belt 114a and the end of the intermediate transfer belt 114a. Recording that is conveyed on the transfer material conveyance surface by the charge elimination action of the transfer material charge eliminator 14h as the provided transfer material charge elimination means and the separation claw 210 provided on the conveyance unit 160 at a predetermined interval from the intermediate transfer belt 114a. The paper P is separated from the intermediate transfer belt 114a, and is provided in a transport unit 160 provided between the fixing device 17 and a curvature portion KT at the end of the intermediate transfer belt 114a on the fixing device 17 side. The sheet is conveyed to a fixing device 17 as a fixing unit through a spur member 162 as a spur member, and the front and back toner images on the recording paper P are fixed at a nip portion T between the first fixing roller 17a and the second fixing roller 17b. To obtain a two-sided image. The charge of the intermediate transfer belt 14a charged by the first primary transfer roller 114b or the second primary transfer roller 114c is applied to the charge eliminator 11 as an intermediate transfer body charge eliminator provided on the downstream side, respectively.
The charge is removed by 4 m or the charge remover 114n.

The toner remaining on the peripheral surfaces of the photoconductor drums 10b and 10a after the transfer is transferred to a photoconductor cleaning device 19 (FIG. 1) serving as image carrier cleaning means provided on the first and second image carriers, respectively. (Not shown in FIG. 4), or a photoconductor cleaning blade 19a made of a rubber material that comes into contact with the photoconductor drums 10b and 10a, respectively.
(See FIG. 1, not shown in FIG. 4). The transfer residual toner of the back toner image remaining on the peripheral surface of the intermediate transfer belt 114a after the transfer is an intermediate transfer member cleaning unit provided opposite the guide roller 14f with the intermediate transfer belt 114a interposed therebetween. The body cleaning device 190 is cleaned by an intermediate transfer body cleaning blade 190a made of a rubber material and capable of abutting on and releasing from the intermediate transfer belt 114a.

The photosensitive drums 10a and 10b and the intermediate transfer belt 114a in the image forming apparatus of this embodiment are the same as those of the first embodiment.
The same function and structure as those of the photosensitive drum 10 and the intermediate transfer belt 14a described in the image forming apparatus of the example are used. The intermediate transfer belt 114a is stretched in contact with the drive roller 140, the secondary transfer opposing roller 14j, the ground roller 14k, the driven roller 14e, the guide roller 14f, and the tension roller 14i, and is counterclockwise indicated by an arrow in FIG. Is rotated.

Toner image serving as backside image (backside toner image)
On the photosensitive drum 10b as a first image carrier, and a toner image (surface toner image) as a surface image on a photosensitive drum 10a as a second image carrier. The second toner image forming unit to be formed includes the same yellow (Y), magenta (M), cyan (C), and black (K) image forming units as those used in the above-described image forming apparatus. Four sets of scorotron chargers 11 (charging means), an exposure optical system 12 (image writing means), and a developing device 13 (developing means) for the process are composed of the photosensitive drum 10b,
10a (see FIG. 1, not shown in FIG. 4), respectively, to form a toner image of a back side image and a toner image of a front side image.

Even when the above-described image forming apparatus is used, since the superimposed color toner images are collectively transferred, color shift of the color image on the intermediate transfer belt 114a, scattering or rubbing of the toner, and the like are less likely to occur, and image deterioration is reduced. A small and favorable double-sided color image is formed.

In each of the above-described examples of the image forming apparatus, the toner image is formed directly on the image bearing member. It may be carried on an image carrier. Also, although the color image forming apparatus has been described as an example of each of the above image forming apparatuses, the present invention is not necessarily limited to this, and a monochrome image formed by a process similar to that described with reference to FIG. 1 or FIG. The present invention is also applied to a forming apparatus. Further, although the image writing unit is provided inside the image carrier, the first image carrier, and the second image carrier, it may be provided outside.

Further, in the image forming apparatus of the present invention, in addition to the double-sided image forming for forming an image on both sides of the transfer material as described in each of the above-described image forming apparatuses, the image forming apparatus may be provided on one side of only the front surface or the back surface of the transfer material. It goes without saying that single-sided image formation for forming an image can also be performed.

Embodiment 1 However, in an image forming apparatus for forming an image on both surfaces of a transfer material using a belt-like intermediate transfer body as described above, a toner image on an image carrier (photosensitive drum) is transferred to a belt-like form. When transferring to the intermediate transfer member (intermediate transfer belt), residual charges remain on the belt surface of the intermediate transfer member, and the transfer condition changes due to the memory due to the residual charges, thereby causing band-like transfer unevenness.

A method for removing the residual charge of the belt-like intermediate transfer body to solve this problem will be described with reference to FIG. 5 or FIG. FIG. 5 is a diagram showing a method of removing the residual charge of the belt-like intermediate transfer body in the image forming apparatus of the first example described with reference to FIG. 1, and FIG.
FIG. 11 is a diagram illustrating a method for removing residual charges from a belt-shaped intermediate transfer body in the image forming apparatus of the example.

According to FIG. 5, as described in FIG.
Double-sided image formation is performed by the photosensitive drum 10 serving as an image carrier and the intermediate transfer belt 14a serving as a belt-shaped intermediate transfer member. In order to set the surface of the intermediate transfer belt 14a at the time of forming the backside toner image (previous) to an initial state, preliminary charging is performed to remove residual charges.

Basically, after the transfer of the toner image on the intermediate transfer belt 14a to the recording paper P by the secondary transfer device 14g,
After the transfer residual toner on the intermediate transfer belt 14a is cleaned by the intermediate transfer body cleaning device 190, 1
Before the transfer of the back toner image on the photosensitive drum 10 to the intermediate transfer belt 14a by the next transfer roller 14c, the back toner image area (intermediate transfer belt 1) on the intermediate transfer belt 14a
(A transfer area of the backside toner image on the photosensitive drum 10 to the photosensitive drum 4a) by a preliminary charger YT1 as a preliminary charging means provided between the primary transfer roller 14c and the intermediate transfer body cleaning device 190. And applying a pre-charging bias VYa in which a DC voltage (minus polarity in the present embodiment) of the same polarity as the toner is superimposed on the AC voltage,
Preliminary charging is performed on the intermediate transfer belt 14a, and memory removal of residual charges remaining on the intermediate transfer belt 14a is performed.
The entire area of the portion where the back toner image is not carried on the intermediate transfer belt 14a, including the cleaning area for the transfer residual toner of the back toner image by the intermediate transfer body cleaning device 190 on the It is preferable to perform preliminary charging.

The charging condition of the preliminary charger YT1 is such that an AC voltage having a frequency of 1 kHz and a peak-to-peak voltage of 4 kV _pp is superimposed on a weakly charged DC voltage of, for example, about -200 V so as not to damage the intermediate transfer belt 14a. The applied preliminary charging bias VYa is applied.

Further, as shown by a dotted line in FIG. 5, a pair of preliminary chargers YT1 may be provided on the back side of the intermediate transfer belt 14a to constitute preliminary charging means.

Further, in the image forming apparatus of the present embodiment, a paper charger as a transfer material charging means to which a DC voltage having the same polarity as that of the toner (minus polarity in this embodiment) is applied as described above with reference to FIG. The paper charger 150 can be used also as a preliminary charging unit. In this case, when the paper charger 150 functions as the paper charger 150, the paper charger 150 uses a DC voltage of the same polarity as the toner (in this embodiment, a negative polarity).
The discharge of the negative polarity by the paper charger 150 at the time of acting as the pre-charging means is weaker than the discharge of.

The pre-charging may be performed before the first image formation or after the image formation. As a result, the residual charge of the belt-shaped intermediate transfer member is removed, and good image formation with less transfer unevenness, particularly, belt-like transfer unevenness can be achieved.

According to FIG. 6, as described with reference to FIG. 4, the photosensitive drum 10b as the first image carrier, the photosensitive drum 10a as the second image carrier, and the belt-shaped intermediate transfer. Double-sided image formation is performed with the intermediate transfer belt 114a, which is a body.
In order to set the surface 4a or the surface of the intermediate transfer belt 114a at the time of forming the back surface toner image before the start of the process (before the start of printing) to the initial state, preliminary charging is performed and residual charges are removed.

Basically, after the transfer of the toner image on the intermediate transfer belt 14a to the recording paper P by the secondary transfer device 14g,
After the transfer residual toner on the intermediate transfer belt 14a is cleaned by the intermediate transfer body cleaning device 190, the photosensitive drum 10b is driven by the first primary transfer roller 114b.
Before the upper back toner image is transferred to the intermediate transfer belt 114a, it is synchronized with the back toner image area on the intermediate transfer belt 114a (the transfer area of the back toner image on the photosensitive drum 10b to the intermediate transfer belt 114a). A preliminary charger YT as a preliminary charging means provided between the first primary transfer roller 114b and the intermediate transfer body cleaning device 190
According to 1, a pre-charging bias VYa in which a DC voltage having the same polarity as the toner (in this embodiment, a negative polarity) is superimposed on an AC voltage is applied to pre-charge the intermediate transfer belt 114a and remain on the intermediate transfer belt 114a. The pre-charging of the intermediate transfer belt 114a includes the cleaning area of the residual toner of the back toner image by the intermediate transfer body cleaning device 190 on the intermediate transfer belt 114a.
It is preferable that the entire area of the portion where the back surface toner image is not carried is set as the preliminary charging area, and the preliminary charging is performed over the entire area.

The charging condition of the preliminary charger YT1 is such that an AC voltage having a frequency of 1 kHz and a peak-to-peak voltage of 4 kV _pp is superimposed on a weakly charged DC voltage of, for example, about -200 V so as not to damage the intermediate transfer belt 114a. The applied preliminary charging bias VYa is applied.

As shown by the dotted line in FIG. 6, a pair of preliminary chargers YT1 may be provided on the back side of the intermediate transfer belt 114a to constitute a preliminary charging means. A preliminary charger YT1 may be provided between the next transfer roller 114b and the intermediate transfer body cleaning device 190, facing the driven roller 14e provided with the intermediate transfer belt 114a interposed therebetween.

The preliminary charging may be performed before the first image formation or after the image formation. As a result, the residual charge of the belt-shaped intermediate transfer member is removed, and good image formation with less transfer unevenness, particularly, belt-like transfer unevenness can be achieved.

Embodiment 2 In an image forming apparatus for forming an image on both surfaces of a transfer material using the belt-shaped intermediate transfer member, a back toner image on an image carrier (photosensitive drum) is transferred to a belt-shaped intermediate transfer member. During transfer to a transfer member (intermediate transfer belt), peeling discharge occurs at the separation portion between the photosensitive drum and the belt surface of the intermediate transfer member, and the toner polarity of some toner changes, and the positive polarity has the opposite polarity. Or the charge amount (Q / M) changes, and the charge of the back toner image is disturbed, and the image of the back toner image transferred onto the intermediate transfer member is disturbed and the back toner on the intermediate transfer member is disturbed. Transfer omission occurs when an image is transferred onto a transfer material.

A method for equalizing the toner charge of the back side toner image on the belt-shaped intermediate transfer body to solve this problem will be described with reference to FIG. 7 or FIG. FIG.
FIG. 8 is a diagram showing a method for equalizing the toner charge of the back surface toner image on the belt-like intermediate transfer member in the image forming apparatus of the first example described with reference to FIG. 1, and FIG. FIG. 13 is a diagram illustrating a method for equalizing the toner charge of the back surface toner image on the belt-shaped intermediate transfer body in the image forming apparatus of the second example described above.

According to FIG. 7, as explained in FIG.
An image is formed by the photosensitive drum 10 serving as an image carrier and the intermediate transfer belt 14a serving as a belt-shaped intermediate transfer member.
A part of the toner image transferred above has a toner polarity that changes due to peeling discharge at the time of separation between the photosensitive drum 10 and the intermediate transfer belt 14a. Or the charge amount (Q / M) changes, so that after the transfer of the backside toner image by the primary transfer roller 14c and before the feeding of the recording paper P by the timing roller 15b as the transfer material feeding means. The back toner image transferred from the photosensitive drum 10 to the intermediate transfer belt 14a by the primary transfer roller 14c is transferred to the toner by a recharger ST1 as a recharging means provided opposite the tension roller 14i, for example. A recharging bias VSa in which a DC voltage of the same polarity (minus polarity in the present embodiment) is superimposed on an AC voltage is applied to the back surface of the intermediate transfer belt 14a. The toner image is recharged, the toner charge and the toner charge amount of the back side toner image on the intermediate transfer belt 14a are uniformly adjusted to a negative polarity in this embodiment, and then the recording paper P is fed by the timing roller 15b. Then, the back side toner image is formed on the recording paper P by the secondary transfer device 14g.
Is to be transferred to the back surface.

The charge amount Q2 of the toner on the back toner image on the intermediate transfer belt 14a upon recharging by the recharger ST1
(ΜC / g) is the charge amount Q1 (μC
/ G) 1.0 to 1.5 times (Q2 = (1.0 to 1.
5) Q1) is preferable, and Q2 is 1.0 of Q1.
If it is less than 2 times, toner of opposite polarity remains,
The toner charge is not made uniform. Further, if Q2 is increased beyond 1.5 times Q1, the intermediate transfer belt 14a
Lightning strikes on the surface or disturbance of the backside toner image may occur. Accordingly, the charge amount Q2 of the toner of the back surface toner image on the intermediate transfer belt 14a at the time of recharging by the recharger ST1.
(ΜC / g) is changed to the charge amount Q1 (μC
/ G) to about 1.0 to 1.5 times the recharging condition of the recharging device ST1 as -200 to -400.
DC voltage of about V, frequency 1 kHz, peak-to-peak voltage 4
Recharging bias VS with AC voltage of ~ 5 kV _pp superimposed
a is applied.

The recharging device ST1 is arranged such that after the transfer of the back toner image to the back surface of the recording paper P by the secondary transfer device 14g, the timing roller 15b moves from the separation position of the recording paper P by the transfer material discharging device 14h. Intermediate transfer belt 14
a between the position where the recording paper P is fed to
Rotation direction of intermediate transfer belt 14a, intermediate transfer belt 14
The cleaning roller 190 is disposed upstream (before the position of the intermediate transfer member cleaning device 190) upstream of the intermediate transfer member cleaning device 190 for cleaning the residual toner on the transfer roller a (in this example, opposed to the tension roller 14i in front of the intermediate transfer member cleaning device 190). The transfer residual toner on the intermediate transfer belt 14a may be discharged by the recharger ST1.

As described above, the toner charge of the backside toner image on the belt-shaped intermediate transfer body is made uniform, the toner of the opposite polarity and the change in the amount of charge are corrected, and the backside toner image on the intermediate transfer body is corrected. The occurrence of image disturbance and the occurrence of transfer omission when transferring the back surface toner image on the intermediate transfer member onto the transfer material are prevented, and satisfactory image formation is performed.

According to FIG. 8, as described with reference to FIG. 4, the photosensitive drum 10b as the first image bearing member, the photosensitive drum 10a as the second image bearing member, and the belt-shaped intermediate transfer A surface image is formed by the intermediate transfer belt 114a as a body, and the back toner image transferred from the photosensitive drum 10b to the intermediate transfer belt 114a is separated when the photosensitive drum 10b and the intermediate transfer belt 114a are separated. Due to the peeling discharge of the toner, the toner polarity of some of the toner changes, and in the present embodiment, the polarity becomes the opposite positive polarity or the charge amount (Q / M) changes. After the transfer of the back toner image by the roller 114b, the recording paper P is transferred by the timing roller 15b as a transfer material feeding unit.
Before the feeding, the back toner image transferred from the photosensitive drum 10b to the intermediate transfer belt 114a by the first primary transfer roller 114b is transferred to, for example, a tension roller 14i.
Recharger ST as recharging means provided opposite to
According to 1, a recharging bias VSa in which a DC voltage having the same polarity as the toner (in the present embodiment, a negative polarity) is superimposed on an AC voltage is applied to recharge the back toner image on the intermediate transfer belt 114a, and In the present embodiment, the toner charge and the toner charge amount of the back side toner image on the transfer belt 114a are made uniform with a negative polarity, and then the recording paper P is fed by the timing roller 15b, and the back side is fed by the secondary transfer unit 14g. The toner image is transferred onto the back surface of the recording paper P.

The charge amount Q2 of the toner on the back side toner image on the intermediate transfer belt 114a at the time of recharging by the recharger ST1
1 (μC / g) is the charge amount Q11 of the toner before recharging.
(ΜC / g) 1.0 to 1.5 times (Q21 = (1.0
1.5) Q11) is preferable, and Q21 is Q
If it is less than 1.0 times smaller than 11, the toner of the opposite polarity remains or the toner charge is not made uniform. Also,
If Q21 is made larger than 1.5 times Q11, a lightning strike on the surface of the intermediate transfer belt 114a may occur, or the back side toner image may be disturbed. Therefore, the charge amount Q21 (μC / g) of the toner of the back toner image on the intermediate transfer belt 114a in the recharging by the recharger ST1 is 1 to the charge amount Q11 (μC / g) of the toner before the recharge. As a condition for recharging by the recharger ST1, an AC voltage having a frequency of 1 kHz and a peak-to-peak voltage of 4 to 5 kV _pp was superimposed on a DC voltage of about -200 to -400 V in order to make the voltage about 0.0 to 1.5 times. A recharge bias VSa is applied.

The arrangement of the recharger ST1 is such that after the transfer of the back toner image to the back of the recording paper P by the secondary transfer device 14g, the photosensitive drum 10b is moved from the separation position of the recording paper P by the transfer material discharging device 14h. The intermediate transfer belt 114a is disposed between the first primary transfer roller 114b to which the next upper back toner image is transferred, and the intermediate direction for cleaning the transfer residual toner on the intermediate transfer belt 114a. The intermediate transfer belt is provided upstream (in front of the intermediate transfer member cleaning device 190) of the transfer member cleaning device 190 (in this example, opposed to the tension roller 14i in front of the intermediate transfer member cleaning device 190). 114
It is also possible to adopt a configuration in which the transfer residual toner on a is neutralized by the recharger ST1.

As described above, the toner charge of the backside toner image on the belt-like intermediate transfer member is made uniform, the toner of the opposite polarity and the change in the charge amount are corrected, and the backside toner image on the intermediate transfer member is corrected. The occurrence of image disturbance and the occurrence of transfer omission when transferring the back surface toner image on the intermediate transfer member onto the transfer material are prevented, and satisfactory image formation is performed.

Embodiment 3 In an image forming apparatus for forming an image on both surfaces of a transfer material using the belt-shaped intermediate transfer member, a back toner image on an image carrier (photosensitive drum) is transferred to a belt-shaped intermediate transfer member. At the time of transfer onto the transfer member, a peeling discharge occurs at a separation portion between the photosensitive drum and the belt surface of the intermediate transfer member, and the toner image on the back surface on the intermediate transfer member is disturbed, or the surface on the photosensitive drum is disturbed. When the toner image is transferred onto the transfer material, a peeling discharge occurs at a separation portion between the photosensitive drum and the transfer material, and the surface toner image on the transfer material may be disturbed. In particular, when a surface toner image on an image carrier (photosensitive drum) is transferred onto a transfer material, a peeling discharge at a separation portion between the photosensitive drum and the transfer material is generated during monochrome image formation and color image formation. , Or depending on environmental conditions, or depending on the type of transfer material, and the surface toner image on the transfer material may be disturbed.

In order to solve this problem, when a backside toner image on an image carrier is transferred onto a belt-shaped intermediate transfer member, a separation discharge occurs at a separation portion between the image carrier and the belt-shaped intermediate transfer member. In addition to preventing the rear toner image from being disturbed on the intermediate transfer member, when the front toner image on the image carrier is transferred onto the transfer material, the transfer material is separated from the transfer member by the separation discharge at the separation portion between the image carrier and the transfer material. A method for preventing disturbance of a surface toner image, and a method for forming a monochrome image and a color image at a separation section between an image carrier and a transfer material when transferring a surface toner image on an image carrier onto a transfer material The purpose of the present invention is to prevent the peeling discharge that occurs differently during image formation, the peeling discharge that occurs differently under environmental conditions, and the disturbance of the surface toner image on the transfer material due to the peeling discharge that occurs differently depending on the type of transfer material. See Figure 9 or It will be described with reference to the 12. FIG. 9 is a diagram illustrating the intermediate state between the image carrier and the belt when the back toner image on the image carrier is transferred onto the belt-shaped intermediate transfer body in the image forming apparatus of the first example described with reference to FIG. In addition to preventing the rear toner image on the intermediate transfer member from being disturbed by the peeling discharge at the separation portion from the transfer member, the transfer between the image carrier and the transfer material when transferring the front toner image on the image carrier onto the transfer material is prevented. A method for preventing disturbance of a surface toner image on a transfer material due to a peeling discharge in a separation unit, and a method for transferring a surface toner image on an image carrier onto a transfer material, between the image carrier and the transfer material In the separation section, peeling discharge that occurs differently between monochrome image formation and color image formation, peeling discharge that occurs differently under environmental conditions, and peeling discharge that occurs differently depending on the type of transfer material on the transfer material For preventing surface toner image disturbance Is an explanatory view of FIG. 10 is a control block diagram of the image forming method and auxiliary discharge means 9, 11
Are the first image carrier and the first image carrier when the back toner image on the first image carrier is transferred onto the belt-shaped intermediate transfer body in the image forming apparatus of the second example described with reference to FIG. In addition to preventing the rear toner image on the intermediate transfer member from being disturbed due to the peeling discharge at the separation portion from the belt-shaped intermediate transfer member, the second step is performed when the front toner image on the second image carrier is transferred onto the transfer material. A method for preventing the surface toner image on the transfer material from being disturbed due to the peeling discharge at the separation portion between the image carrier and the transfer material, and the surface toner image on the second image carrier onto the transfer material At the time of transfer, in the separation portion between the second image bearing member and the transfer material, a peel discharge that occurs differently during monochrome image formation and a color image formation, a peel discharge that occurs differently under environmental conditions, Surface on transfer material due to peeling discharge generated differently depending on the type of transfer material Is an explanatory view of a method for preventing the disturbance of the toner image, FIG. 12, an image forming method and the first auxiliary discharge means 11 is a control block diagram of a second auxiliary discharge means.

In the following, in the image forming apparatus of the first example described with reference to FIG. 1, the image carrier and the belt-shaped toner image are transferred when the back side toner image on the image carrier is transferred onto the belt-shaped intermediate transfer member. The image carrier and the transfer material when transferring the front toner image on the image carrier onto the transfer material while preventing the rear toner image on the intermediate transfer body from being disturbed by the peeling discharge at the separation portion from the intermediate transfer body A method for preventing the surface toner image on the transfer material from being disturbed due to the peeling discharge at the separation portion from the above will be described.

According to FIG. 9 or FIG. 10, as shown in FIG. 10, when an image forming mode is selected by an operation unit (not shown), an image forming mode selection signal is sent to the control unit (CP).
U), and the image forming process described in FIG. 1 is executed by the image forming program stored in the ROM.

When the monochrome image formation in the double-sided image formation mode is selected, the monochrome image formation program P1 of the double-sided image formation program stored in the ROM is selected, and the double-sided image formation with the monochrome image is performed through the control unit. . When the color image formation in the double-sided image formation mode is selected, the color image formation program P2 of the double-sided image formation program stored in the ROM is selected, and the double-sided image formation with the color image is performed through the control unit. Further, when the single-sided image forming mode of the single-sided image forming mode is selected, the single-sided single-sided image forming program P11 of the single-sided image forming program stored in the ROM is selected. The single-sided image formation of only the front side of the monochrome image is performed through the unit. When the single-sided single-sided color image formation in the single-sided image formation mode is selected, the single-sided single-sided color image formation program P21 of the single-sided image formation program stored in the ROM is selected. Image formation of only one surface of a color image is performed. When the single-sided image forming mode is selected, the single-sided single-sided image forming program P12 of the single-sided image forming program stored in the ROM is selected. A single-sided image formation of only the back side of the monochrome image is performed through the unit. When the color image formation of the single-sided image formation on the back side in the single-sided image formation mode is selected, the single-sided color image formation program P22 on the back side of the single-sided image formation program stored in the ROM is selected. A single-sided image formation of only the back side of the color image is performed.

As described with reference to FIG. 1, an image is formed by the photosensitive drum 10 as an image carrier and the intermediate transfer belt 14a as a belt-shaped intermediate transfer member. When transferring the toner image onto the intermediate transfer belt 14a, the value V1 (volt) of the primary transfer bias VTa due to the DC voltage having the opposite polarity (positive polarity in this embodiment) to the toner on the primary transfer roller 14c is The primary transfer bias VTa is set to be lower than a value V2 (volt) of a primary transfer bias VTa by a positive DC voltage (constant voltage power supply) when the surface toner image on the photosensitive drum 10 is transferred onto the recording paper P (see FIG. V1 <V2). This is because when transferring the surface toner image on the photosensitive drum 10 onto the recording paper P, there is a transfer material (with paper), and the toner image on the back surface on the photosensitive drum 10 is transferred to the intermediate transfer belt 14a. This is because there is no transfer material (no paper) when transferring to the upper side. As the primary transfer bias VTa, a constant current power supply is used in addition to the above constant voltage power supply.

As described above, when the back surface toner image on the photosensitive drum 10 is transferred onto the intermediate transfer belt 14a,
Separation discharge occurs at a separation portion between the photoconductor drum 10 and the intermediate transfer belt 14a, and the rear surface toner image is disturbed or the front surface toner image on the photoconductor drum 10 is transferred onto the recording paper P. Separation discharge occurs in the separation portion between the drum 10 and the recording paper P, and the surface toner image is disturbed. Therefore, in the vicinity of the separation portion between the intermediate transfer belt 14a and the photosensitive drum 10, the same polarity as the toner (this embodiment) , An auxiliary discharge bias VH by a DC voltage of
The auxiliary discharge device HT1 is provided as an auxiliary discharge means for applying a discharge and a discharge. The discharge of the auxiliary discharge device HT1 causes the back surface toner image on the photosensitive drum 10 to be transferred to the intermediate transfer belt 14a.
When the toner image is transferred upward, the rear toner image is disturbed due to the peeling discharge at the separation portion between the photosensitive drum 10 and the intermediate transfer belt 14a, and when the front toner image on the photosensitive drum 10 is transferred onto the recording paper P. In addition, the surface toner image is prevented from being disturbed due to the peeling discharge at the separation portion between the photosensitive drum 10 and the recording paper P. At this time, the voltage or current applied by the primary transfer bias VTa of the primary transfer roller 14c is greater than when there is no paper (when the backside toner image on the photosensitive drum 10 is transferred onto the intermediate transfer belt 14a). (When the surface toner image on the photosensitive drum 10 is transferred onto the recording paper P) is set larger (stronger), the auxiliary discharge device HT
1 discharges the paper (the surface toner image on the photosensitive drum 10 is transferred to the recording paper P) from the absence of the paper (when transferring the back toner image on the photosensitive drum 10 onto the intermediate transfer belt 14a). (When transferring to the top) is set smaller (weaker). Further, if the recording paper P is discharged with a large applied voltage or applied current when paper is present due to the low resistance, a current flows into the primary transfer portion through the recording paper P and a transfer failure occurs, so that the discharge by the auxiliary discharger HT1 is performed. When there is no paper (the backside toner image on the photosensitive drum 10 is transferred to the intermediate transfer belt 14a).
Than when there is paper (photosensitive drum 10).
The upper surface toner image is transferred onto the recording paper P).
The current value ratio is set to be small (weak) about 30 to 80%. As shown in FIG. 10, the value of the auxiliary discharge bias is applied with reference to the value of each auxiliary discharge bias that is experimentally obtained in advance and stored in the ROM of the storage unit. Further, the discharge by the auxiliary discharger HT1 is started when the paper is present (when the backside toner image on the photosensitive drum 10 is transferred onto the intermediate transfer belt 14a) or when the paper is present (when the surface toner on the photosensitive drum 10 is present). Even if the value of (when an image is transferred onto the recording paper P) is set to be smaller (weaker), the recording paper P has low resistance, so that discharge unevenness hardly occurs. The discharge of the auxiliary discharger HT1 stably charges the backside toner image when there is no paper (when the backside toner image on the photosensitive drum 10 is transferred onto the intermediate transfer belt 14a), so that the secondary transfer device 14g Is prevented, the image quality of the back side image is improved, and the voltage applied to the secondary transfer unit 14g can be kept low.

In the above description, when forming a color toner image, the discharge condition by the auxiliary discharger HT1 is set to the same condition as when there is no paper (when transferring the backside toner image on the photosensitive drum 10 onto the intermediate transfer belt 14a). When paper is present (when the surface toner image on the photosensitive drum 10 is transferred onto the recording paper P), it is preferable to set a strong setting to prevent disturbance of the color toner images on the back and front surfaces.

As described above, when the back side toner image on the image carrier is transferred onto the belt-shaped intermediate transfer body, peeling discharge at the separation portion between the image carrier and the belt-shaped intermediate transfer body is prevented. Disturbance of the backside toner image on the intermediate transfer body is prevented, and peeling discharge at the separation portion between the image carrier and the transfer material when transferring the frontside toner image on the image carrier onto the transfer material is prevented. As a result, disturbance of the surface toner image on the transfer material is prevented, and favorable double-sided image formation is performed. Further, a good color toner image is formed.

Further, in the image forming apparatus of the first example described with reference to FIG. 1, when the surface toner image on the image carrier is transferred onto the transfer material, the separation portion between the image carrier and the transfer material is used. Surface toner image on transfer material due to peel discharge that occurs differently between monochrome image formation and color image formation, peel discharge that occurs differently under environmental conditions, and peel discharge that occurs differently depending on the type of transfer material Hereinafter, a method for preventing the disturbance will be described.

According to FIG. 9 or FIG. 10, as shown in FIG. 10, when an image forming mode is selected by an operation unit (not shown), an image forming mode selection signal is transmitted to the control unit (CP).
U), and the image forming process described in FIG. 1 is executed by the image forming program stored in the ROM.

When the monochrome image formation in the double-sided image formation mode is selected, the monochrome image formation program P1 of the double-sided image formation program stored in the ROM is selected, and the double-sided image formation with the monochrome image is performed through the control unit. . When the color image formation in the double-sided image formation mode is selected, the color image formation program P2 of the double-sided image formation program stored in the ROM is selected, and the double-sided image formation with the color image is performed through the control unit. Further, when the single-sided image forming mode of the single-sided image forming mode is selected, the single-sided single-sided image forming program P11 of the single-sided image forming program stored in the ROM is selected. The single-sided image formation of only the front side of the monochrome image is performed through the unit. When a single-sided single-sided image forming color image formation in the single-sided image forming mode is selected, a single-sided single-sided color image forming program P12 of the single-sided image forming program stored in the ROM is selected. A single-sided image formation of a color image only on the front side is performed. When the single-sided image forming mode is selected, the single-sided single-sided image forming program P21 of the single-sided image forming program stored in the ROM is selected. A single-sided image formation of only the back side of the monochrome image is performed through the unit. When the color image formation of the single-sided image formation on the back side in the single-sided image formation mode is selected, the single-sided color image formation program P22 on the back side of the single-sided image formation program stored in the ROM is selected. A single-sided image formation of only the back side of the color image is performed.

As described with reference to FIG. 1, the photosensitive drum 10 serving as an image carrier and the intermediate transfer belt 14a serving as a belt-like intermediate transfer member form a monochrome image or a color image by selecting the image forming mode. Although the formation is performed, the polarity (in the present embodiment, positive polarity) opposite to that of the toner on the primary transfer roller 14c when the monochrome toner image of the surface toner image on the photosensitive drum 10 is transferred onto the recording paper P The value V11 (volts) of the primary transfer bias VTa due to the DC voltage is a positive polarity DC voltage (constant voltage power supply) when the color toner image of the surface toner image on the photosensitive drum 10 is transferred onto the recording paper P. ) Is set lower than the value V21 (volt) of the primary transfer bias VTa (V11 <V).
21). This is because when the color toner image of the surface toner image on the photoconductor drum 10 is transferred onto the recording paper P, the amount of toner adhering to the color toner image is large.
The value V21 (volt) of the primary transfer bias VTa by the positive polarity DC voltage (constant voltage power supply) when transferring the color toner image of the surface toner image on the recording paper P onto the photosensitive drum 10 When the monochrome toner image of the surface toner image is transferred onto the recording paper P, the polarity is opposite to the toner applied to the primary transfer roller 14c (positive polarity in the present embodiment).
V11 of the primary transfer bias VTa by the DC voltage of
(V) (V21> V11).

For this reason, as described above, the photosensitive drum 1
When the surface toner image on the recording paper P is transferred onto the recording paper P, recording is performed by a separation discharge that occurs differently between monochrome image formation and color image formation in a separation portion between the photosensitive drum 10 and the recording paper P. Since the surface toner image on the paper P is disturbed, an auxiliary discharge by a DC voltage having the same polarity as the toner (in the present embodiment, a negative polarity) is provided near the separation portion between the photosensitive drum 10 and the recording paper P. An auxiliary discharge device HT1 is provided as auxiliary discharge means for applying the bias VHa, and discharge is performed by the auxiliary discharge device HT1 when the primary transfer roller 14c transfers the surface toner image on the photosensitive drum 10 to the recording paper P. In the discharge of the auxiliary discharger HT1 when the surface toner image on the photosensitive drum 10 is transferred to the recording paper P by the primary transfer roller 14c, the color toner of the surface toner image on the photosensitive drum 10 is changed. When transferring an image onto the recording paper P,
The discharge voltage or the discharge current is set to be stronger (greater) than the discharge voltage or the discharge current when the monochrome toner image of the surface toner image on the photosensitive drum 10 is transferred onto the recording paper P. As shown in FIG. 10, the value of the auxiliary discharge bias is experimentally obtained in advance and stored in the ROM of the storage unit.
Each of them is applied with reference to the value of the auxiliary discharge bias according to monochrome image formation or color image formation.

As described above, when the color toner image or the monochrome toner image of the surface toner image on the image carrier is transferred onto the transfer material, the color toner of the surface toner image at the separation portion between the image carrier and the transfer material is transferred. Disturbance of the color toner image or the monochrome toner image of the surface toner image on the transfer material due to the peeling discharge caused by the difference between the image and the monochrome toner image is prevented, and excellent color image formation and monochrome image formation are performed.

Further, according to FIG. 9, when the surface toner image on the photosensitive drum 10 is transferred onto the recording paper P as described above, the environment in the separation portion between the photosensitive drum 10 and the recording paper P is changed. Since the surface toner image on the recording paper P is disturbed by the peeling discharge generated differently under the conditions, the same polarity as the toner (in the present embodiment) near the separation portion between the photosensitive drum 10 and the recording paper P An auxiliary discharge device HT1 is provided as an auxiliary discharge means for applying an auxiliary discharge bias VHa with a DC voltage having a negative polarity. When the primary transfer roller 14c transfers the surface toner image on the photosensitive drum 10 to the recording paper P, Discharge is performed by the auxiliary discharger HT1, and the discharge voltage or discharge current of the discharge of the auxiliary discharger HT1 when the surface toner image on the photosensitive drum 10 is transferred to the recording paper P by the primary transfer roller 14c. , For example, normal temperature and humidity (20 ± 5
℃, 45 ± 10%), high temperature and high humidity (30 ± 5 ℃, 70 ±
10%), low temperature and low humidity (10 ± 5 ° C., 15 ± 10%). Temperature and humidity are detected by a temperature detecting means (temperature detecting sensor) and a humidity detecting means (humidity detecting sensor) (not shown) provided inside the apparatus. As shown in FIG. 10, the value of the auxiliary discharge bias is experimentally obtained in advance and stored in the ROM of the storage unit.
It applies with reference to the value of the auxiliary discharge bias according to the environmental conditions.

As described above, when the surface toner image on the image carrier is transferred onto the transfer material, the surface on the transfer material due to peeling discharge caused by a difference in environmental conditions at the separation portion between the image carrier and the transfer material. Disturbance of the toner image is prevented, and good image formation is performed.

According to FIG. 9, when the surface toner image on the photosensitive drum 10 is transferred onto the recording paper P as described above, the transfer is performed at the separation portion between the photosensitive drum 10 and the recording paper P. Since the surface toner image on the recording paper P is disturbed by the peeling discharge generated differently depending on the type of the material, the same polarity as the toner (in the present embodiment) is provided near the separation portion between the photosensitive drum 10 and the recording paper P. An auxiliary discharge device HT1 is provided as auxiliary discharge means for applying an auxiliary discharge bias VHa by a DC voltage having a negative polarity in the embodiment (primary transfer roller 14c).
When the surface toner image on the photosensitive drum 10 is transferred to the recording paper P by the auxiliary discharge device HT1, the surface toner image on the photosensitive drum 10 is transferred to the recording paper P by the primary transfer roller 14c. The discharge voltage or discharge current of the discharge of the auxiliary discharger HT1 at the time is, for example, 45 to 60 kg / m
² plain paper or thin paper less than 45 kg / m ² or 60 kg / m ²
Is changed according to the type of the transfer material, such as thick paper or OHT (overhead transparency). For example, the type of transfer material is determined based on the value of the conduction current of a detection roller as a transfer material type detection unit (not shown) provided up to the entrance position of the paper charger 150. As shown in FIG. 10, the value of the auxiliary discharge bias is experimentally obtained in advance as the value of the auxiliary discharge bias and stored in the ROM of the storage unit with reference to the value of the auxiliary discharge bias according to the type of the transfer material.

As described above, when the surface toner image on the image carrier is transferred onto the transfer material, the separation portion between the image carrier and the transfer material causes a difference in the type of the transfer material on the transfer material due to the peeling discharge. Of the surface toner image is prevented, and good image formation is performed.

Next, in the image forming apparatus of the second example described with reference to FIG. 4, the first toner image is transferred when the back toner image on the first image carrier is transferred onto the belt-shaped intermediate transfer member. Along with preventing the rear toner image on the intermediate transfer member from being disturbed by the peeling discharge at the separation portion between the image carrier and the belt-shaped intermediate transfer member,
When transferring the surface toner image on the second image carrier onto the transfer material, the surface toner image on the transfer material is prevented from being disturbed by peeling discharge at the separation portion between the second image carrier and the transfer material. Will be described.

According to FIG. 11 or FIG. 12, as shown in FIG. 12, when an image forming mode is selected by an operation unit (not shown), an image forming mode selection signal is sent to the control unit (CP
U), the image forming process described in FIG. 4 is executed by the image forming program stored in the ROM.

When the monochrome image formation in the double-sided image formation mode is selected, the monochrome image formation program P3 of the double-sided image formation program stored in the ROM is selected, and the double-sided image formation with the monochrome image is performed through the control unit. . When the color image formation in the double-sided image formation mode is selected, the color image formation program P4 of the double-sided image formation program stored in the ROM is selected, and the color image is formed through the control unit. When the single-sided image forming mode is selected, the single-sided image forming program P31 of the single-sided image forming program stored in the ROM is selected. The single-sided image formation of only the front side of the monochrome image is performed through the unit. When the single-sided single-sided color image formation in the single-sided image formation mode is selected, the single-sided single-sided color image formation program P41 of the single-sided image formation program stored in the ROM is selected. A single-sided image formation of a color image only on the front side is performed. When the single-sided image forming mode is selected, the single-sided single-sided image forming program P32 of the single-sided image forming program stored in the ROM is selected. A single-sided image formation of only the back side of the monochrome image is performed through the unit. When the color image formation of the single-sided image formation on the back side in the single-sided image formation mode is selected, the single-sided color image formation program P42 of the single-sided image formation program stored in the ROM is selected, and is transmitted through the control unit. A single-sided image formation of only the back side of the color image is performed.

As described with reference to FIG. 4, the photosensitive drum 10b as the first image carrier, the photosensitive drum 10a as the second image carrier, and the intermediate transfer belt 114a as a belt-like intermediate transfer member An image is formed by the above process, but the intermediate transfer belt 14a of the back toner image on the photosensitive drum 10a is formed.
The value V3 of the first primary transfer bias VTb by a DC voltage (constant voltage power supply) of the opposite polarity (positive polarity in the present embodiment) to the toner to the first primary transfer roller 114b during the upward transfer. (Volt) is a direct current having a polarity opposite to that of the toner to the second primary transfer roller 114c (positive polarity in the present embodiment) when the surface toner image on the photosensitive drum 10a is transferred onto the recording paper P. The value is set lower than the value V4 (volt) of the second primary transfer bias VTc by the voltage (constant voltage power supply) (V3 <V4). This is because the transfer material is present (there is paper) when the front toner image on the photosensitive drum 10a is transferred onto the recording paper P, and the back toner image on the photosensitive drum 10b is transferred to the intermediate transfer belt 14a. This is because there is no transfer material (no paper) when transferring to the upper side.
As the first primary transfer bias VTb and the second primary transfer bias VTc, a constant current power supply is used in addition to the constant voltage power supply.

As described above, when the backside toner image on the photosensitive drum 10b is transferred onto the intermediate transfer belt 14a, a separation discharge occurs at the separation portion between the photosensitive drum 10b and the intermediate transfer belt 14a, and the backside toner image is generated. Since the image is disturbed, the intermediate transfer belt 14a and the photosensitive drum 10b
A first auxiliary discharge bias VHb with a DC voltage of the same polarity as the toner (in the present embodiment, a negative polarity) is applied to the vicinity of the separation portion, and a first auxiliary discharge unit as a first auxiliary discharge unit for performing discharge is performed. An auxiliary discharger HT21 is provided, and when the first auxiliary discharger HT21 discharges the back toner image on the photosensitive drum 10b onto the intermediate transfer belt 14a, the transfer between the photosensitive drum 10b and the intermediate transfer belt 14a is performed. The rear surface toner image is prevented from being disturbed due to peeling discharge in the separation section. Further, when the surface toner image on the photosensitive drum 10a is transferred onto the recording paper P, a peeling discharge occurs at a separation portion between the photosensitive drum 10a and the recording paper P, and the surface toner image is disturbed. A second auxiliary discharge bias VHc with a DC voltage of the same polarity as the toner (minus polarity in the present embodiment) is applied to the vicinity of the separation portion between the body drum 10a and the recording paper P, and the second auxiliary discharge for discharging is performed. A second auxiliary discharger HT22 is provided as a discharging means, and the discharge of the second auxiliary discharger HT22 causes the photosensitive drum 10a to transfer the surface toner image on the photosensitive drum 10a onto the recording paper P. The surface toner image is prevented from being disturbed due to peeling discharge at the separation portion from the recording paper P. At this time, the applied voltage or applied current when no paper is present (the backside toner image on the photosensitive drum 10b is transferred onto the intermediate transfer belt 14a) by the first primary transfer bias VTb of the first primary transfer roller 114b. (The applied voltage or the applied current by the first primary transfer bias VTb at this time) from the second primary transfer roller 114.
c, the applied voltage or applied current in the presence of paper due to the second primary transfer bias VTc (based on the second primary transfer bias VTc when transferring the surface toner image on the photosensitive drum 10a onto the recording paper P). Since the applied voltage or the applied current is set to be larger (stronger), the first auxiliary discharger HT21 discharges the paper (transfers the backside toner image on the photosensitive drum 10b onto the intermediate transfer belt 14a when there is no paper). (Discharge when the surface toner image on the photosensitive drum 10a is transferred onto the recording paper P) by the second auxiliary discharger HT22 when there is paper is smaller (weaker) than when the paper is present. Set. Due to the low resistance of the recording paper P, if a large applied voltage or current is discharged when paper is present, a current flows through the recording paper P to the second primary transfer portion, resulting in poor transfer. The discharge by the second auxiliary discharger HT22 when there is paper is set smaller (weaker) by about 30 to 80% as a ratio of the current value than the discharge by the first auxiliary discharger HT21. As shown in FIG. 12, the value of the first auxiliary discharge bias, which is obtained in advance experimentally and stored in the ROM of the storage unit, as the value of the first auxiliary discharge bias and the value of the second auxiliary discharge bias Alternatively, it is applied with reference to the value of the second auxiliary discharge bias.

Also, the first auxiliary discharger HT when there is no paper
21, the second auxiliary discharger H with paper
Even if the discharge by T22 is set smaller (weaker), the recording paper P has a low resistance, so that the discharge unevenness hardly occurs. Further, by discharging the first auxiliary discharger HT21, the back toner image is stably charged when there is no paper (when the back toner image on the photosensitive drum 10b is transferred onto the intermediate transfer belt 14a). The occurrence of transfer unevenness at the time of the next transfer unit 14g is prevented, and the image quality of the back side image is improved.
The voltage applied to the next transfer device 14g can be kept low.

In the above description, when forming a color toner image, the discharge condition by the first auxiliary discharger HT21 when there is no paper (when transferring the back toner image on the photosensitive drum 10b onto the intermediate transfer belt 14a). Also, the discharge condition of the second auxiliary discharger HT22 when paper is present (when the surface toner image on the photosensitive drum 10a is transferred onto the recording paper P) is set strongly, and the color toner images on the back and front surfaces are set. It is preferable to prevent disturbance.

As described above, when the back toner image on the first image carrier is transferred onto the belt-shaped intermediate transfer member, the first image carrier is separated from the belt-shaped intermediate transfer member at the separation portion. Disturbance of the backside toner image on the intermediate transfer member due to electric discharge is prevented, and the transfer of the frontside toner image on the second image carrier onto the transfer material causes the transfer between the second image carrier and the transfer material. Disturbance of the surface toner image on the transfer material due to peeling discharge at the separation portion is prevented, and favorable double-sided image formation is performed. Also,
A good color toner image is formed.

Further, in the image forming apparatus of the second example described with reference to FIG. 4, when the surface toner image on the image carrier is transferred onto the transfer material, the separation portion between the image carrier and the transfer material is used. Surface toner image on transfer material due to peel discharge that occurs differently during monochrome image formation and color image formation, peel discharge that occurs differently under environmental conditions, and peel discharge that occurs differently depending on the type of transfer material Hereinafter, a method for preventing the disturbance will be described.

According to FIG. 11 or FIG. 12, as shown in FIG. 12, when an image forming mode is selected by an operation unit (not shown), an image forming mode selection signal is sent to the control unit (CP).
U), the image forming process described in FIG. 4 is executed by the image forming program stored in the ROM.

When the monochrome image formation in the double-sided image formation mode is selected, the monochrome image formation program P3 of the double-sided image formation program stored in the ROM is selected, and the double-sided image formation with the monochrome image is performed through the control unit. . When the color image formation in the double-sided image formation mode is selected, the color image formation program P4 of the double-sided image formation program stored in the ROM is selected, and the color image is formed through the control unit. When the single-sided image forming mode is selected, the single-sided image forming program P31 of the single-sided image forming program stored in the ROM is selected. The single-sided image formation of only the front side of the monochrome image is performed through the unit. When the single-sided single-sided color image formation in the single-sided image formation mode is selected, the single-sided single-sided color image formation program P41 of the single-sided image formation program stored in the ROM is selected. A single-sided image formation of a color image only on the front side is performed. When the single-sided image forming mode is selected, the single-sided single-sided image forming program P32 of the single-sided image forming program stored in the ROM is selected. A single-sided image formation of only the back side of the monochrome image is performed through the unit. When the color image formation of the single-sided image formation on the back side in the single-sided image formation mode is selected, the single-sided color image formation program P42 of the single-sided image formation program stored in the ROM is selected, and is transmitted through the control unit. A single-sided image formation of only the back side of the color image is performed.

As described with reference to FIG. 4, the photosensitive drum 10b serving as the first image carrier, the photosensitive drum 10a serving as the second image carrier, and the intermediate transfer belt 114a serving as a belt-shaped intermediate transfer member. Thus, the monochrome image formation and the color image formation in the above-described image formation mode selection are performed. However, when the monochrome toner image of the surface toner image on the photosensitive drum 10a is transferred onto the recording paper P, the second one is performed. Next transfer roller 11
4c is a second primary transfer bias VT due to a DC voltage of the opposite polarity (positive polarity in this embodiment) to the toner.
The value c of V31 (volt) is the second primary transfer using a positive polarity DC voltage (constant voltage power supply) when the color toner image of the surface toner image on the photosensitive drum 10a is transferred onto the recording paper P. It is set lower than the value V41 (volt) of the bias VTc (V31 <V41). This is because the color toner image of the surface toner image on the photosensitive drum 10a is transferred to the recording paper P.
When the color toner image is transferred upward, the second primary transfer roller is used to transfer the color toner image of the surface toner image on the photosensitive drum 10 a onto the recording paper P because the amount of toner adhered to the color toner image is large. The value V41 (volt) of the second primary transfer bias VTc by a DC voltage (constant voltage power supply) having a polarity opposite to that of the toner 114c and the toner is transferred to the photosensitive drum 10
When transferring the monochrome toner image of the surface toner image on the recording paper P onto the recording paper P, the second primary transfer bias VTc by the DC voltage (constant voltage power supply) of positive polarity by the second primary transfer roller 114c. It is set higher than the value V31 (volt) (V41> V31).

Therefore, as described above, the photosensitive drum 1
When the surface toner image on the recording paper P is transferred onto the recording paper P, recording is performed by a peeling discharge that occurs differently between the monochrome image formation and the color image formation in the separation portion between the photosensitive drum 10a and the recording paper P. Since the surface toner image on the paper P is disturbed, a second DC voltage of the same polarity as the toner (minus polarity in the present embodiment) is applied near the separation portion between the photosensitive drum 10a and the recording paper P. Auxiliary discharge bias VH
A second auxiliary discharger HT22 is provided as a second auxiliary discharge means for applying the second c. The second auxiliary discharger HT22 is used when the surface toner image on the photosensitive drum 10a is transferred to the recording paper P by the second primary transfer roller 114c. Is discharged by the auxiliary discharge device HT22 of the second auxiliary discharge device HT22. When the second primary transfer roller 114c transfers the toner image on the surface of the photosensitive drum 10a to the recording paper P, the discharge of the second auxiliary discharge device HT22 is performed. Body drum 10
a transfer voltage or discharge current when the color toner image of the surface toner image on the recording medium P is transferred onto the recording paper P;
It is set to be stronger (greater) than the discharge voltage or discharge current when transferring to the upper side. As shown in FIG. 12, the value of the second auxiliary discharge bias according to monochrome image formation or color image formation, which is previously experimentally obtained as the value of the second auxiliary discharge bias and stored in the ROM of the storage unit. Refer to the values and apply each one.

As described above, when the color toner image or the monochrome toner image of the surface toner image on the second image carrier is transferred onto the transfer material, the separation portion between the second image carrier and the transfer material is used. Disturbance of the color toner image and the monochrome toner image of the surface toner image on the transfer material due to the peeling discharge caused by the difference between the color toner image and the monochrome toner image of the surface toner image is prevented, and excellent color image formation and monochrome image formation are achieved. Done.

According to FIG. 11, when the surface toner image on the photosensitive drum 10a is transferred onto the recording paper P as described above, the environment in the separation section between the photosensitive drum 10a and the recording paper P is changed. Since the surface toner image on the recording paper P is disturbed by the peeling discharge generated differently under the conditions, the same polarity as the toner (in the present embodiment) near the separation portion between the photosensitive drum 10a and the recording paper P A second auxiliary discharger HT22 is provided as a second auxiliary discharge means for applying a second auxiliary discharge bias VHc by a DC voltage having a negative polarity. Is discharged by the second auxiliary discharger HT22 when the surface toner image is transferred to the recording paper P, but the surface toner image on the photosensitive drum 10 is transferred to the recording paper P by the second primary transfer roller 114c. Second auxiliary discharger Utsushiji HT22
For example, when the discharge voltage or discharge current of the electric discharge is normal temperature and normal humidity (20 ± 5 ° C., 45 ± 10%), high temperature and high humidity (30 ± 5
℃, 70 ± 10%), low temperature and low humidity (10 ± 5 ℃, 15 ± 15%)
10%) to be changed according to environmental conditions such as time. Temperature and humidity are detected by a temperature detecting means (temperature detecting sensor) and a humidity detecting means (humidity detecting sensor) (not shown) provided inside the apparatus. As shown in FIG. 12, the value of the second auxiliary discharge bias RO
Each of the values is applied with reference to the value of the second auxiliary discharge bias according to the environmental condition stored in M.

As described above, when the surface toner image on the second image carrier is transferred onto the transfer material, the peeling discharge caused by the difference in the environmental conditions in the separation portion between the second image carrier and the transfer material. This prevents the toner image on the transfer material from being disturbed due to the above-mentioned process, thereby forming a good image.

According to FIG. 11, when the surface toner image on the photosensitive drum 10a is transferred onto the recording paper P as described above, the transfer is performed at the separation section between the photosensitive drum 10a and the recording paper P. Since the surface toner image on the recording paper P is disturbed by the peeling discharge generated differently depending on the type of the material, the same polarity as that of the toner (this embodiment) A second auxiliary discharger HT22 is provided as a second auxiliary discharge means for applying a second auxiliary discharge bias VHc with a DC voltage having a negative polarity in the embodiment, and the photosensitive drum is driven by a second primary transfer roller 114c. When the surface toner image on 10a is transferred to the recording paper P, the second
Is discharged by the auxiliary discharge device HT22, but the second auxiliary discharge device HT at the time of transferring the surface toner image on the photosensitive drum 10a to the recording paper P by the second primary transfer roller 114c.
The discharge voltage or discharge current of the discharge of No. 22 is, for example, 45 to
60 kg / m ² plain paper, thin paper less than 45 kg / m ²
Change according to the type of transfer material, such as thick paper exceeding 0 kg / m ² or OHT (overhead transparency). For example, the type of transfer material is determined based on the value of the conduction current of a detection roller as a transfer material type detection unit (not shown) provided up to the entrance position of the paper charger 150. As shown in FIG. 12, refer to the value of the second auxiliary discharge bias according to the type of the transfer material, which is obtained experimentally in advance as the value of the second auxiliary discharge bias and stored in the ROM of the storage unit. And apply each.

As described above, when the surface toner image on the second image carrier is transferred onto the transfer material, the difference is caused by the difference in the type of the transfer material in the separation section between the second image carrier and the transfer material. Disturbance of the surface toner image on the transfer material due to peeling discharge is prevented, and good image formation is performed.

[0121]

According to the first to fourth aspects, the residual charge of the belt-shaped intermediate transfer member is removed by the pre-charging means, and good image formation with less transfer unevenness can be achieved.

According to the fifth to twelfth aspects, the recharging means makes the toner charge of the backside toner image on the belt-shaped intermediate transfer member uniform, and corrects the change in the toner of the opposite polarity and the change in the charge amount. Thus, occurrence of image disorder of the backside toner image on the intermediate transfer body and occurrence of transfer omission when transferring the backside toner image on the intermediate transfer body onto the transfer material are prevented, and satisfactory image formation is performed.

According to the thirteenth aspect, when the back side toner image on the image carrier is transferred onto the belt-shaped intermediate transfer member, the separation discharge at the separation portion between the image carrier and the belt-shaped intermediate transfer member is performed. The transfer material is prevented from being disturbed by the back surface toner image on the intermediate transfer body, and is caused by peeling discharge at a separation portion between the image carrier and the transfer material when the front surface toner image on the image carrier is transferred onto the transfer material. Disturbance of the upper surface toner image is prevented, and favorable double-sided image formation is performed.

According to the fourteenth aspect, a good color toner image is formed. According to claim 15, when the color toner image or the monochrome toner image of the surface toner image on the image carrier is transferred onto the transfer material, the color of the surface toner image at the separation section between the image carrier and the transfer material Disturbance of the color toner image and the monochrome toner image of the surface toner image on the transfer material due to the peeling discharge caused by the difference between the toner image and the monochrome toner image is prevented, and excellent color image formation and monochrome image formation are performed.

According to the sixteenth aspect, when the surface toner image on the image carrier is transferred onto the transfer material, the transfer by the separation discharge caused by the difference in environmental conditions in the separation portion between the image carrier and the transfer material. Disturbance of the surface toner image on the material is prevented,
Good image formation is performed.

According to the seventeenth aspect, at the time of transferring the surface toner image on the image carrier to the transfer material, the peeling discharge caused by the difference in the type of the transfer material at the separation portion between the image carrier and the transfer material. This prevents the toner image on the transfer material from being disturbed due to the above-described process, thereby forming a good image.

According to the eighteenth aspect, when the toner image on the back side of the first image carrier is transferred onto the belt-like intermediate transfer member, the first image carrier and the belt-like intermediate transfer member are transferred. Disturbance of the back surface toner image on the intermediate transfer member due to the peeling discharge in the separation unit is prevented, and the second image carrier and the second image carrier when the front surface toner image on the second image carrier is transferred onto the transfer material. Disturbance of the surface toner image on the transfer material due to separation discharge at the separation portion from the transfer material is prevented, and favorable double-sided image formation is performed.

According to the nineteenth aspect, a good color toner image is formed. According to the twentieth aspect, when the color toner image or the monochrome toner image of the surface toner image on the second image carrier is transferred onto the transfer material, the separation portion between the second image carrier and the transfer material is used. Disturbance of the color toner image and the monochrome toner image of the surface toner image on the transfer material due to the peeling discharge caused by the difference between the color toner image and the monochrome toner image of the surface toner image is prevented. The formation takes place.

According to the twenty-first aspect, when the surface toner image on the second image carrier is transferred onto the transfer material, the difference in the environmental conditions in the separation section between the second image carrier and the transfer material. Disturbance of the surface toner image on the transfer material due to peeling discharge caused by the discharge is prevented, and a good image is formed.

According to the present invention, when the surface toner image on the second image carrier is transferred onto the transfer material, the type of the transfer material in the separation section between the second image carrier and the transfer material The toner image on the transfer material is prevented from being disturbed due to the peeling discharge caused by the difference in the image quality, and a good image is formed.

[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 of a first example.

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

FIG. 3 is a diagram illustrating a toner image forming state in the image forming apparatus of FIG. 1;

FIG. 4 is a cross-sectional configuration diagram of a main part of a color image forming apparatus showing an embodiment of the image forming apparatus of a second example.

FIG. 5 is a diagram illustrating a method of removing a residual charge of a belt-shaped intermediate transfer body in the image forming apparatus of the first example described with reference to FIG.

FIG. 6 is a diagram illustrating a method for removing the residual charge of the belt-shaped intermediate transfer member in the image forming apparatus of the second example described with reference to FIG.

FIG. 7 is a diagram illustrating a method for equalizing the toner charge of the back surface toner image on the belt-shaped intermediate transfer member in the image forming apparatus of the first example described with reference to FIG.

FIG. 8 is a diagram illustrating a method for equalizing the toner charge of the back surface toner image on the belt-shaped intermediate transfer member in the image forming apparatus of the second example described with reference to FIG.

FIG. 9 is an explanatory diagram of a method for preventing disturbance of a surface toner image on a transfer material due to peeling discharge.

10 is a control block diagram of the image forming method of FIG. 9 and an auxiliary discharge unit.

FIG. 11 is an explanatory diagram of a method for preventing disturbance of a surface toner image on a transfer material due to peeling discharge that occurs differently depending on environmental conditions and the type of transfer material.

FIG. 12 is a control block diagram of the image forming method of FIG. 11 and first and second auxiliary discharge units.

[Explanation of symbols]

 10, 10a, 10b Photoreceptor drum 11 Scorotron charger 12 Exposure optical system 13 Developing device 14a, 114a Intermediate transfer belt 14c Primary transfer roller 14f Guide roller 14g Secondary transfer device 14h Transfer material eliminator 14j Secondary transfer opposed roller 14m , 114m, 114n Static eliminator 15b Timing roller 17 Fixing device 114b First primary transfer roller 114c Second primary transfer roller 150 Paper charger 190 Intermediate transfer member cleaning device HT1 Auxiliary discharger HT21 First auxiliary discharger HT22 Second auxiliary discharger P Recording paper ST1 Recharger YT1 Precharger VHa Auxiliary discharge bias VHb First auxiliary discharge bias VHc Second auxiliary discharge bias VSa Recharge bias VYa Precharge bias

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tetsu Haneda 2970 Ishikawacho, Hachioji-shi, Tokyo Konica Corporation F-term (reference) 2H028 BA06 BA16 BB04 2H030 AD17 BB02 BB23 BB42 BB44 BB46 BB55 BB56 BB63 2H032 AA02 AA05 AA15 BA09 BA18 BA23 BA26 BA29 BA30 CA04 CA13 DA03 DA12 DA22 DA28

Claims (22)

[Claims] An image carrier for carrying a toner image formed by a toner image forming means on a surface thereof; a toner image on the image carrier being transferred, and carrying the transferred toner image on a surface; A belt-shaped intermediate transfer member that closely contacts a transfer material charged by a transfer material charging unit and supports and conveys the transfer material; and transfers a toner image on the image carrier to the surface of the intermediate transfer member or the transfer material. A primary transfer unit that performs the following steps: a secondary transfer unit that retransfers the toner image on the intermediate transfer member to the back surface of the transfer material; a fixing unit that fixes the toner image on the transfer material; An intermediate transfer member cleaning unit for cleaning, wherein after the toner image on the intermediate transfer member is transferred to the transfer material by the secondary transfer unit, the intermediate transfer member is cleaned by the intermediate transfer member cleaning unit. After cleaning the transfer residual toner on the transfer member, and before transferring the toner image on the image carrier to the intermediate transfer member by the primary transfer means, at least to the intermediate transfer member on the intermediate transfer member An image forming apparatus, wherein a pre-charging means performs pre-charging of the same polarity as toner on a transfer area of the toner image on the image carrier. 2. The image forming apparatus according to claim 1, wherein said preliminary charging means is used as said transfer material charging means. 3. A first image carrier for carrying on the surface a toner image formed by the first toner image forming means, and a first image carrier for carrying on the surface a toner image formed by the second toner image forming means. 2, the toner image on the first image carrier is transferred, the transferred toner image is carried on the surface, and the transfer material charged by the transfer material charging unit is brought into close contact with the image carrier. A belt-shaped intermediate transfer member that supports and conveys a transfer material; a first primary transfer unit that transfers a toner image on the first image carrier to the intermediate transfer member; A second primary transfer unit for transferring the toner image on the transfer material to the front surface of the transfer material; a secondary transfer unit for retransferring the toner image on the intermediate transfer body to the back surface of the transfer material; Fixing means for fixing the toner image; and cleaning the intermediate transfer member. An image forming apparatus having a transfer member cleaning unit, wherein after the transfer of the toner image on the intermediate transfer member to the transfer material by the secondary transfer unit, the transfer residue on the intermediate transfer member is determined by the intermediate transfer member cleaning unit. After cleaning the toner, before transferring the toner image on the first image carrier to the intermediate transfer body by the first primary transfer unit, at least to the intermediate transfer body on the intermediate transfer body An image forming apparatus, wherein a pre-charging means performs pre-charging of the same polarity as toner on a transfer area of the toner image on the first image carrier. 4. An image forming apparatus according to claim 3, wherein said preliminary charging means is used as said transfer material charging means. 5. An image carrier for carrying a toner image formed by a toner image forming means on the surface, a toner image on the image carrier being transferred, and carrying the transferred toner image on the surface. A belt-shaped intermediate transfer body that supports and conveys a transfer material, a transfer material supply unit that supplies the transfer material to the intermediate transfer body, and a surface of the intermediate transfer body or the transfer material that transfers the toner image on the image carrier to the intermediate transfer body Primary transfer means for transferring the toner image on the intermediate transfer body to a back surface of the transfer material; fixing means for fixing the toner image on the transfer material; An intermediate transfer member cleaning unit for cleaning the body, wherein the toner image transferred from the image carrier to the intermediate transfer member by the primary transfer unit is made to have the same polarity as the toner by a recharging unit. While recharging, the after re-charging by recharging unit, the image forming apparatus characterized by feeding the transfer material by said transfer material feeding means. 6. The toner image transferred on the intermediate transfer body is recharged by the recharging means to form a toner image of 1.0 to 1.
The image forming apparatus according to claim 5, wherein the charge amount is five times (μC / g). 7. The image forming apparatus according to claim 5, wherein a recharging bias in which an AC voltage is superimposed on a DC voltage is applied by the recharging unit. 8. After the transfer of the toner image on the intermediate transfer member to the transfer material by the secondary transfer unit, and before the transfer residual toner on the intermediate transfer member is cleaned by the intermediate transfer member cleaning unit, 8. The image forming apparatus according to claim 5, wherein the re-charging unit removes the charge of the transfer residual toner.
The image forming apparatus according to claim 1. 9. A first image carrier for carrying a toner image formed by a first toner image forming means on a surface thereof, and a first image carrier for carrying a toner image formed by a second toner image forming means on a surface thereof. A belt-like intermediate transfer body that transfers the toner image on the first image carrier, carries the transferred toner image on the surface, and supports and conveys a transfer material; Transfer material supply means for supplying a transfer material to the intermediate transfer member, first primary transfer means for transferring a toner image on the first image carrier to the intermediate transfer member, and second image carrier A second primary transfer unit for transferring a toner image on a body to a front surface of the transfer material; a secondary transfer unit for retransferring a toner image on the intermediate transfer body to a back surface of the transfer material; Fixing means for fixing the upper toner image; and cleaning the intermediate transfer member. An image forming apparatus having an intermediate transfer body cleaning means, wherein the toner image transferred from the first image carrier to the intermediate transfer body by the first primary transfer means is transferred to a toner by a recharging means. An image forming apparatus, wherein the transfer material is fed by the transfer material feeding means after being recharged to the same polarity and recharged by the recharging means. 10. The toner image transferred on the intermediate transfer member is recharged by the recharging means to a toner image of 1.0 to 1.0.
The image forming apparatus according to claim 9, wherein the charge amount is 1.5 times (μC / g). 11. The image forming apparatus according to claim 9, wherein a recharging bias in which an AC voltage is superimposed on a DC voltage is applied by the recharging unit. 12. After the toner image on the intermediate transfer member is transferred to the transfer material by the secondary transfer unit, before the transfer residual toner on the intermediate transfer member is cleaned by the intermediate transfer member cleaning unit, 10. The method according to claim 9, wherein the transfer residual toner is neutralized by the recharging unit.
12. The image forming apparatus according to claim 11. 13. An image carrier for carrying a toner image formed by a toner image forming means on the surface, a toner image on the image carrier being transferred, and carrying the transferred toner image on the surface. A belt-shaped intermediate transfer member that supports and conveys a transfer material; a primary transfer unit that transfers a toner image on the image carrier to the surface of the intermediate transfer member or the transfer material; a toner image on the intermediate transfer member And a fixing unit for fixing a toner image on the transfer material, in the vicinity of a separation portion between the intermediate transfer member and the image carrier. And auxiliary discharge means for performing a discharge having the same polarity as the toner, and discharge conditions of the auxiliary discharge means when the toner image on the image carrier is transferred onto the intermediate transfer body by the primary transfer means. Than the primary Image forming apparatus and sets weak discharge condition by said auxiliary discharge means during the transfer to the transfer material onto the toner image on the image carrier by the shooting unit. 14. The image forming apparatus according to claim 13, wherein when forming a color toner image, a discharge condition of the auxiliary discharge unit is set strongly. 15. An image carrier, a toner image forming means for forming a color toner image or a monochrome toner image on the image carrier, and a color toner image or a monochrome toner image on the image carrier is transferred and transferred. A belt-like intermediate transfer body that supports the transferred color toner image or monochrome toner image on the surface, and supports and conveys a transfer material; and the color toner image or monochrome toner image on the image carrier is the intermediate transfer body or A primary transfer unit for transferring the color toner image or the monochrome toner image on the intermediate transfer member to a back surface of the transfer material; a primary transfer unit for transferring the color toner image on the intermediate transfer body; and a color toner image on the transfer material. Or, in an image forming apparatus having a fixing unit for fixing a monochrome toner image, in the vicinity of a separation portion between the intermediate transfer member and the image carrier, a toner having the same polarity as toner. An auxiliary discharge unit for performing a discharge; and a transfer of the color toner image or the monochrome toner image on the image carrier onto the transfer material by the primary transfer unit. An image forming apparatus, wherein a discharge condition by the auxiliary discharge unit in forming a color image is set stronger than a discharge condition. 16. An image carrier for carrying a toner image formed by a toner image forming means on the surface, a toner image on the image carrier being transferred, and carrying the transferred toner image on the surface. A belt-shaped intermediate transfer member that supports and conveys a transfer material; a primary transfer unit that transfers a toner image on the image carrier to the surface of the intermediate transfer member or the transfer material; a toner image on the intermediate transfer member And a fixing unit for fixing a toner image on the transfer material, in the vicinity of a separation portion between the intermediate transfer member and the image carrier. And an auxiliary discharge means for performing a discharge having the same polarity as the toner, and when the primary transfer means transfers the toner image on the image carrier onto the transfer material, the auxiliary discharge means may be provided in accordance with environmental conditions. Discharge by discharge means Image forming apparatus and changes the matter. 17. An image carrier for carrying a toner image formed by a toner image forming means on the surface, a toner image on the image carrier being transferred, and carrying the transferred toner image on the surface. A belt-shaped intermediate transfer member that supports and conveys a transfer material; a primary transfer unit that transfers a toner image on the image carrier to the surface of the intermediate transfer member or the transfer material; a toner image on the intermediate transfer member And a fixing unit for fixing a toner image on the transfer material, in the vicinity of a separation portion between the intermediate transfer body and the image carrier. An auxiliary discharge unit for performing a discharge having the same polarity as the toner, and at the time of transferring the toner image on the image carrier onto the transfer material by the primary transfer unit, according to a type of the transfer material. By the auxiliary discharge means Image forming apparatus characterized by changing the electrostatic conditions. 18. A first image carrier for carrying a toner image formed by a first toner image forming means on a surface thereof, and a first image carrier for carrying a toner image formed by a second toner image forming means on a surface thereof. A belt-like intermediate transfer body that transfers the toner image on the first image carrier, carries the transferred toner image on the surface, and supports and conveys a transfer material; A first primary transfer unit for transferring the toner image on the first image carrier to the intermediate transfer body; and a second primary transfer unit for transferring the toner image on the second image carrier to the surface of the transfer material. An image forming apparatus comprising: a primary transfer unit; a secondary transfer unit that re-transfers the toner image on the intermediate transfer body to the back surface of the transfer material; and a fixing unit that fixes the toner image on the transfer material. In the vicinity of the separation portion between the intermediate transfer member and the first image bearing member, A first auxiliary discharge means for performing a discharge of the same polarity as the toner, and a second auxiliary discharge for performing a discharge of the same polarity as the toner near the separation portion between the intermediate transfer member and the second image carrier. Means for discharging the toner image on the first image carrier onto the intermediate transfer member by the first primary transfer means, the discharge condition being higher than the discharge condition by the first auxiliary discharge means. An image characterized by weakly setting a discharge condition of the second auxiliary discharge unit when the toner image on the second image carrier is transferred onto the transfer material by a second primary transfer unit. Forming equipment. 19. A method for forming a color toner image, comprising:
19. The image forming apparatus according to claim 18, wherein a discharge condition by the auxiliary discharge unit and a discharge condition by the second auxiliary discharge unit are set strongly. 20. A first image carrier, first toner image forming means for forming a color toner image or a monochrome toner image on the first image carrier, a second image carrier, A second toner image forming means for forming a color toner image or a monochrome toner image on the second image carrier; and a color toner image or a monochrome toner image on the first image carrier is transferred and transferred. A belt-shaped intermediate transfer member that supports the color toner image or the monochrome toner image on the surface and supports and conveys a transfer material; and a color toner image or a monochrome toner image on the first image bearing member, the intermediate transfer member. A first primary transfer unit for transferring a color toner image or a monochrome toner image on the second image carrier to a surface of the transfer material; and an intermediate transfer member. Top toner image An image forming apparatus comprising: a secondary transfer unit that retransfers to the back surface of the transfer material; and a fixing unit that fixes a color toner image or a monochrome toner image on the transfer material. A second auxiliary discharge unit for performing a discharge of the same polarity as the toner is provided in the vicinity of a separation portion from the carrier, and a color toner image or a monochrome image on the second image carrier by the second primary transfer unit is provided. At the time of transferring the toner image onto the transfer material, the discharge condition by the second auxiliary discharge unit at the time of color image formation is set stronger than the discharge condition by the second auxiliary discharge unit at the time of monochrome image formation. An image forming apparatus comprising: 21. A first image carrier for carrying on the surface a toner image formed by the first toner image forming means, and a first image carrier for carrying on the surface a toner image formed by the second toner image forming means. A belt-like intermediate transfer body that transfers the toner image on the first image carrier, carries the transferred toner image on the surface, and supports and conveys a transfer material; A first primary transfer unit for transferring the toner image on the first image carrier to the intermediate transfer body; and a second primary transfer unit for transferring the toner image on the second image carrier to the surface of the transfer material. An image forming apparatus comprising: a primary transfer unit; a secondary transfer unit that re-transfers the toner image on the intermediate transfer body to the back surface of the transfer material; and a fixing unit that fixes the toner image on the transfer material. Near the separation portion between the intermediate transfer member and the second image bearing member, And a second auxiliary discharge unit for performing a discharge having the same polarity as the first primary transfer unit. When the second primary transfer unit transfers the toner image on the second image carrier to the transfer material, the second auxiliary discharge unit performs An image forming apparatus, wherein a discharge condition of the second auxiliary discharge unit is changed according to a condition. 22. A first image carrier for carrying a toner image formed by a first toner image forming means on a surface thereof, and a first image carrier for carrying a toner image formed by a second toner image forming means on a surface thereof. A belt-like intermediate transfer body that transfers the toner image on the first image carrier, carries the transferred toner image on the surface, and supports and conveys a transfer material; A first primary transfer unit for transferring the toner image on the first image carrier to the intermediate transfer body; and a second primary transfer unit for transferring the toner image on the second image carrier to the surface of the transfer material. An image forming apparatus comprising: a primary transfer unit; a secondary transfer unit that re-transfers the toner image on the intermediate transfer body to the back surface of the transfer material; and a fixing unit that fixes the toner image on the transfer material. Near the separation portion between the intermediate transfer member and the second image bearing member, And a second auxiliary discharge means for performing a discharge having the same polarity as that of the first primary transfer means, and transferring the toner image on the second image carrier onto the transfer material by the second primary transfer means. An image forming apparatus, wherein a discharge condition of the second auxiliary discharge unit is changed according to a type of a material.