JP2002162806A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently transfer a toner image on each photoreceptor drum to an intermediate transfer body by firmly pressing the photoreceptor drum and the intermediate transfer body to each other by means of a simple structure, and applying a uniform transfer bias voltage to the firmly pressed portion, in an image forming device of a system in which unfixed toner images formed on the separate photoreceptor drums are transferred one on the other on the belt-like intermediate transfer body. SOLUTION: The photoreceptor drums 2 and support rolls 9 are arranged along an imaginary circle 14 so that the central angles of the photoreceptor drums in the range where the intermediate transfer body 6 is in contact with peripheral faces of the photoreceptor drums 2 are equal to each other. Therefore, the intermediate transfer body 6 is pressed against the photoreceptor drums 2 in the constant state without providing a special member used for pressing the intermediate transfer body 6 to the drums 2. Thus, a substantially uniform transfer bias can be applied to the intermediate transfer body 6 by a transfer electrifier 7. Each of the color toner images on the photoreceptor drums is primarily transferred efficiently under almost same conditions. Accordingly, high quality image can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to an image forming apparatus that forms a visible image by transferring a toner to a latent image due to a difference in electrostatic potential, such as an electrostatic recording method and ionography, and more specifically, relates to a toner image formed on an image carrier. The present invention relates to an image forming apparatus that transfers a toner image on an intermediate transfer member and superimposes the toner image on the intermediate transfer member to perform secondary transfer to a recording medium.

[0002]

2. Description of the Related Art An image forming apparatus for forming a visible image using a powdery toner such as an electrophotographic system or an electrostatic recording system has been widely used as a copying machine, a facsimile, a printer, and the like. Such an image forming apparatus includes a method of directly transferring a toner image formed on an image carrier to a recording medium such as paper, and a method of temporarily transferring a toner image formed on an image carrier to an intermediate transfer body once, Further, there is a method of performing secondary transfer from an intermediate transfer member to a recording medium. Among these, the latter device using an intermediate transfer member is particularly suitable for a color image forming apparatus, in which primary transfer of a toner image is performed under stable conditions, whereby a toner image of a plurality of colors is formed on the intermediate transfer member. Superimposed. Therefore, a high-quality color image can be obtained.

In the primary transfer of the toner image, a method of forming an electric field between an image carrier and an intermediate transfer member to transfer charged toner is widely used. This is because even when the image carrier has a photoconductor layer having no heat resistance, good transfer is possible without exerting a thermal influence on the photoconductor.

FIG. 7 is a schematic configuration diagram showing a color image forming apparatus for electrostatically performing primary transfer of a toner image. This image forming apparatus includes four image forming units 201a, 201
1b, 201c, and 201d. A plurality of photosensitive drums 202a,
02b, 202c, and 202d, and charging devices 203a, 203b, 203c, and 203d that charge the surface of the photosensitive drum substantially uniformly around each photosensitive drum.
And an optical scanning device 204 that scans the surface of each photoconductor drum with a laser beam to write an electrostatic latent image, and that yellow, magenta, cyan, or black toner is applied to each latent image formed on the photoconductor drum. Developing devices 205a, 205b, 205c, and 205d that transfer and form toner images, and respective photosensitive drums 202a, 202b, and 202c;
An endless belt-shaped intermediate transfer member 206 arranged so as to abut on the intermediate transfer member 202d; a transfer charger 207a for primarily transferring a toner image on each photosensitive drum onto the intermediate transfer member 206;
207b, 207c, and 207d.

The intermediate transfer member 206 is stretched around a plurality of support rolls 208a and 208b and a transfer opposing roll 209 and driven to rotate. The transfer facing roll 20
A transfer roll 210 is disposed at a position facing the transfer roll 9 via an intermediate transfer body 206. This transfer facing roll 2
09 and the transfer roll 210, the recording paper is fed,
The toner image on the intermediate transfer member is secondarily transferred onto recording paper.
The recording paper carrying the unfixed toner image is heated and pressed when passing through the fixing device 211, and the toner image is pressed against the recording paper.

[0006] The transfer charger 207 is a corona discharger having a grid and electrode wires.
6 are arranged at positions facing the respective photosensitive drums. Then, a high voltage is applied to the electrode wires, and a predetermined voltage is applied to the grid to generate corona discharge, thereby applying charges to the back side of the intermediate transfer body 206.

In the above image forming apparatus, a transfer charger made of a flexible sheet member can be used. A conductive material is dispersed in the sheet-like member, and a leading end portion is pressed against the intermediate transfer member to apply a transfer bias voltage.

Further, a roll-shaped transfer charger can be used as the transfer charger. The transfer charger is made of a conductive or semiconductive roll-shaped member, and applies a transfer bias voltage to the photosensitive drum.

[0009]

In order to efficiently transfer a toner image to an intermediate transfer member using the above-described transfer charger, it is necessary to form a stable electric field in a transfer area.
For this reason, when a corona discharger is used, a voltage is applied in a state in which a film-shaped member made of an elastic body is pressed from the back side of the intermediate transfer body and the photosensitive drum and the intermediate transfer body are in contact with each other. Also, in a sheet-shaped transfer charger,
The intermediate transfer member is pressed against the photosensitive drum by the elastic force of the sheet member. However, there is a possibility that the film-like member or the sheet-like member made of the elastic body may be broken or deformed by the pressing force on the intermediate transfer member. In addition, a mechanism for retracting these members when the intermediate transfer member or the like is replaced is required, which increases the cost of the apparatus.

On the other hand, when a transfer charger in the form of a roll is used, the roll itself is pressed against the intermediate transfer body to bring the photosensitive drum into contact with the intermediate transfer body. However, a mechanism for retracting the roll is necessary. Therefore, the cost of the apparatus increases.

Further, when a plurality of photosensitive drums are arranged in a horizontal direction along the intermediate transfer member as in the above color image forming apparatus, the length of the intermediate transfer member stretched between the rolls becomes large. In some cases, the intermediate transfer member may be bent. Then, the bending may cause minute vertical vibrations of the intermediate transfer body, and there is a possibility that the superposition of the toner images of the respective colors on the intermediate transfer body may be defective. In order to eliminate such bending of the intermediate transfer body, it is necessary to support the intermediate transfer body at a plurality of locations, and the cost of the apparatus increases due to the addition of members.

Further, when the electrostatic transfer of the toner image is performed in a state where the photosensitive drum and the intermediate transfer member are not in contact with each other, the moving distance of the toner particles flying electrostatically becomes large. May be scattered to cause an image defect called blur. This is largely because the electric field formed between the toner image on the photosensitive drum and the intermediate transfer member does not become an ideal parallel electric field in the pre-nip region and the nip region. Also, when a high voltage is applied in a state where the photosensitive drum and the intermediate transfer member are separated from each other, discharge occurs at a certain threshold or more, and the effective electric field decreases. May cause These also cause image defects.

The invention according to the present application has been made in view of the above circumstances, and has as its object to press-contact a photosensitive drum and an intermediate transfer member with a simple structure, and to apply a uniform transfer bias to the press-contact portion. An object of the present invention is to provide an image forming apparatus that efficiently transfers a toner image on each photosensitive drum to an intermediate transfer member by applying a voltage.

[0014]

Means for Solving the Problems To solve the above problems, the invention according to claim 1 has a cylindrical peripheral surface,
A plurality of image carriers on which a toner image is formed by toner selectively transferred onto the peripheral surface; and an endless belt-shaped member which is stretched around two or more support rolls and driven to rotate, the image comprising: An image forming apparatus comprising: an intermediate transfer member on which a toner image on a carrier is primarily transferred onto an outer peripheral surface; and a secondary transfer device for transferring the toner image on the intermediate transfer member to a recording medium. The carrier is in contact with the outer peripheral surface of a portion of the intermediate transfer member stretched between support rolls, and a central angle of a range in which the intermediate transfer member contacts along the peripheral surface of the image carrier is plural. An image forming apparatus is characterized in that the image forming members are equal.

In the above-described image forming apparatus, the intermediate transfer member is suspended in a state where tension is introduced, and a predetermined area of the peripheral surface of the image carrier is arranged so as to come into contact with the intermediate transfer member. A pressure contact force is applied to a region where the carrier is in contact with the intermediate transfer member. For this reason, the toner image formed on the image carrier is likely to be primarily transferred to the intermediate transfer member, and the toner image is less likely to be disturbed during transfer. Also, there is no need to particularly provide a member for pressing. Since the plurality of image carriers are in contact with the intermediate transfer body in substantially equal ranges, the contact pressures in the respective contact ranges are also substantially equal. Therefore, the toner images on the respective image carriers are efficiently transferred to the intermediate transfer member under the same conditions, and are superimposed on the intermediate transfer member.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the plurality of image carriers are separated from the support roll between two support rolls which stretch the intermediate transfer body. And the center of a range where the intermediate transfer member contacts each of the image carriers depending on the relative position between the intermediate transfer member and the adjacent image carrier or the support roll, which are in contact with the intermediate transfer member at intervals. It is characterized in that the corners are set equal.

In the above-described image forming apparatus, each of the plurality of image carriers and the intermediate transfer member may be provided without providing a dedicated pressurizing member or increasing the number of support rolls. A substantially equal contact pressure can be applied to the contact portion. Therefore, the toner image on each image carrier can be efficiently transferred to the intermediate transfer member without increasing the cost of the apparatus by adding a member. Also,
The replacement of the intermediate transfer member and the like can be easily performed, and the time required for maintenance can be reduced.

According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, two image carriers and support rolls are arranged in parallel on both sides of the image carrier, and the intermediate transfer body has an outer peripheral surface having the outer peripheral surface. The support roll is in contact with two image carriers, and is stretched on a common tangent line between the two image carriers, and the support roll is in contact with an inner peripheral surface of the intermediate transfer member, and the intermediate transfer member is attached to the image transfer member. It is arranged so as to be wound around the peripheral surface of the carrier.

In the above image forming apparatus, in the image forming apparatus according to the first aspect, a contact pressure substantially equal to a contact portion between the plurality of image carriers and the intermediate transfer member is applied without using a dedicated pressing member. In addition, the toner image on each image carrier can be efficiently transferred to the intermediate transfer body.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first, second or third aspect, at least one of the support rolls is driven to rotate, whereby the intermediate transfer member is rotated. Wherein the image bearing member rotates in accordance with the circumferential movement of the intermediate transfer member.

In the above-described image forming apparatus, a portion is provided between the image carrier and the intermediate transfer member, and the image carrier is driven by the orbital movement of the intermediate transfer member due to frictional resistance in the contact area. Rotate. Therefore, a device for driving the image carrier is not required, and the cost of the device can be reduced.

According to a fifth aspect of the present invention, in the image forming apparatus according to the first aspect, the intermediate transfer member has conductivity and flexibility at a downstream portion of a portion where the intermediate transfer member contacts the peripheral surface of the image carrier. A transfer member made of a member having the contact member is in contact with the inner peripheral surface of the intermediate transfer member.

In the above-described image forming apparatus, a substantially uniform contact pressure is applied to a contact portion between the image carrier and the intermediate transfer body without pressing the intermediate transfer body against the image carrier with the transfer member. Therefore, it is easy to apply a uniform transfer bias to the intermediate transfer member, and the primary transfer of the toner image can be efficiently performed. Further, since the image carrier and the intermediate transfer member are in contact with each other, the electric field formed therebetween becomes a parallel electric field, and the toner image formed on the image carrier becomes a toner image when transferred to the intermediate transfer member. Disturbance hardly occurs, and a high-quality image can be obtained. Further, the transfer member does not need to apply a large pressing force to the intermediate transfer member, and can prevent the transfer member from being broken or deformed.

According to a sixth aspect of the present invention, in the image forming apparatus of the first aspect, the intermediate transfer member is stretched so that a circumferential shape is line-symmetric. Of the portions stretched between the support rolls of the intermediate transfer member, two portions are abutted on two line-symmetric portions at two line-symmetric positions.

In the above-described image forming apparatus, the length of the intermediate transfer member stretched between the rolls is longer than that in the case where all the image carriers are arranged in parallel at the portion where the intermediate transfer member is stretched linearly. Decrease. For this reason, without adding a support member,
It is possible to prevent large bending of the intermediate transfer member,
The mechanism for supporting the intermediate transfer member is simple. Also,
A plurality of image carriers are pressed by substantially the same pressing force to positions at which the circumferential shape of the intermediate transfer member is line-symmetric. For this reason, the pressing forces applied to the line-symmetric positions act so as to cancel each other, and the load on the member supporting the intermediate transfer member is reduced. Therefore, the intermediate transfer member can be firmly supported with a simple structure. Further, the load on the driving of the intermediate transfer member acts in a distributed manner, and vibration in the driving direction during driving can be suppressed to a small level. As a result, smooth circular driving without unevenness in speed becomes possible.

According to a seventh aspect of the present invention, there are provided a plurality of image carriers having a cylindrical peripheral surface on which a toner image is formed by a toner selectively transferred on the peripheral surface; An endless belt-shaped member which is stretched around a roll and driven to rotate, wherein an intermediate transfer member on which a toner image on the image carrier is primarily transferred onto an outer peripheral surface; and a toner image on the intermediate transfer member is recorded. An image forming apparatus having a secondary transfer device for transferring to a medium, wherein the intermediate transfer body is between support rolls,
Two of the stretched portions are arranged so as to face each other, and two of the image carriers are respectively in contact with two opposed stretched portions of the intermediate transfer member,
The inside of the stretched intermediate transfer member,
An image forming apparatus, wherein one transfer device is provided between the two image carriers, and the transfer device forms a transfer electric field between the two image carriers. It is.

In the above-described image forming apparatus, since a pressing force is applied between the image carrier and the intermediate transfer body at a position facing the intermediate transfer body, the primary transfer of the toner image can be efficiently performed. Further, since a single transfer device can form a transfer electric field between two opposing image carriers, the size and weight of the device can be reduced.

According to an eighth aspect of the present invention, in the image forming apparatus according to the seventh aspect, the transfer device is a roll-shaped member to which a transfer bias voltage is applied, and the two opposite image carriers are provided with: It is characterized in that it is pressed into contact with the intermediate transfer member.

In the image forming apparatus, a substantially uniform transfer bias is applied by the transfer device including the roll-shaped member, and the primary transfer of the toner image can be efficiently performed. Further, when the intermediate transfer member is driven to rotate, the transfer device including the roll member is also driven to rotate, so that the driving load on the intermediate transfer member can be reduced.

According to a ninth aspect of the present invention, in the image forming apparatus according to the eighth aspect, the transfer device, which is a roll-shaped member, includes: each of the image carriers; It is characterized by being pressed in the downstream part of the contact area.

In the above image forming apparatus, it is possible to prevent an electric field from being formed on the upstream side of the contact area between the image carrier and the intermediate transfer member. For this reason, it is possible to prevent the toner image on the image carrier from flying between the non-contact intermediate transfer body and the image to be disturbed, and to provide a good image in the contact range between the image carrier and the intermediate transfer body. Transfer can be performed.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. This image forming apparatus includes:
An endless belt-shaped intermediate transfer body 6 whose peripheral surface is rotatably supported is provided.
Four image forming units 1a, 1b, 1c, 1d for forming yellow, magenta, cyan, and black toner images
Are arranged.

Each of the image forming units 1a, 1b, 1c, 1
d is a photosensitive drum 2a on the surface of which an electrostatic latent image is formed,
Charging devices 3a, 3b, 3c, and 3d around the respective photoconductor drums, which charge the surfaces of the photoconductor drums substantially uniformly, respectively. An image exposure device 4 that irradiates image light to write an electrostatic latent image, and transfers a yellow, magenta, cyan, or black toner to each latent image formed on the photosensitive drum to form a toner image Developing devices 5a, 5b, 5c, 5
d, and transfer chargers 7a, 7b, 7c, 7d for primarily transferring the toner images on the respective photosensitive drums onto the intermediate transfer member 6.

The intermediate transfer member 6 is supported by a support roll 9a with tension applied by a belt tensioner 8.
9b and the transfer opposing roll 10 rotatably support. Each of the photosensitive drums is pressed against the outer peripheral surface of the intermediate transfer member 6, and is provided with a photosensitive drum 2a, 2b, 2c,
d and the supporting rolls 9a and 9b are arranged such that the central angles of the respective photosensitive drums in the range where the intermediate transfer body 6 contacts along the peripheral surfaces of the photosensitive drums 2a, 2b, 2c and 2d are equal. I have. The intermediate transfer member 6 moves around by rotating one of the support rolls 9a, and the photosensitive drums 2a, 2b, 2c, and 2d move the intermediate transfer member 6a.
Rotates following the orbital movement of.

A transfer roll 11 for transferring the toner image on the intermediate transfer body 6 to recording paper is provided at a position facing the transfer opposed roll 10 via the intermediate transfer body 6. In a pressure contact portion between the transfer roll 11 and the transfer roll 11,
Recording paper is fed from the paper tray 12. Further, on the downstream side of the pressing portion, the toner image on the recording paper is heated and melted,
A fixing device 13 for pressing the recording paper is provided.

Hereinafter, each component constituting this embodiment will be described in more detail. The photosensitive drums 2a, 2b, 2c and 2d are S
Those having various inorganic photoreceptor layers such as e, a-Si, a-SiC and CdS, or those having various organic photoreceptor layers can be used.

The charging devices 3a, 3b, 3c and 3d are:
A film of a resin mixed with a powder of a conductive material such as carbon is rubbed on the peripheral surface of the photosensitive drum 2, and a charging bias voltage is applied to the photosensitive drum 2.
As a result, a discharge is generated in the minute gap with the photosensitive drum 2, and the surface of the photosensitive drum 2 is uniformly charged.

The image exposure devices 4a, 4b, 4c, 4d
Is an array of LEDs for each pixel, and irradiates image light to the surface of the photosensitive drum by blinking of a light emitting element. As a result, the potential is attenuated in the uniformly charged exposed portion of each photosensitive drum, and a latent image is formed due to the difference in electrostatic potential.

The developing devices 5a, 5b, 5c and 5d are
Developing devices containing yellow, magenta, cyan, and black toners are arranged so as to be close to and opposed to the respective photosensitive drums, and transfer toner to latent images to form visible images. is there.

The transfer chargers 7a, 7b, 7c, 7d
Is a corona discharger that applies a charge to the back surface of the intermediate transfer member 6 so that the toner image on each photosensitive drum is efficiently transferred to the intermediate transfer member 6.

The belt-like intermediate transfer member 6 has a base layer and a surface layer, and the base layer is made of a heat-resistant polyimide film to which carbon black is added. The surface layer has a rubber hardness of 40 degrees and a thickness of 50 μm to transfer the toner image from the intermediate transfer member 5 to the recording paper so that the intermediate transfer member 5 and the recording paper are in close contact with each other with the toner image interposed therebetween. A silicone copolymer is used.

The transfer roll 11 is formed of a conductive or semi-conductive roll-like member, and a voltage is applied between the intermediate transfer body 6 and the opposing transfer opposing roll 10 to apply a voltage to the intermediate transfer body 6. The toner image is collectively transferred to recording paper.

The fixing device 13 heats and fuses the toner image by sandwiching a recording paper carrying an unfixed toner image between a heating roll having a built-in heat source and a pressing roll pressed against the heating roll. , Which is pressed against recording paper.

The toner used in the image forming apparatus is
It is made of a thermoplastic binder containing yellow, magenta, cyan, and black dyes, and can be formed by a known material. In this embodiment, a polyester toner having a weight average molecular weight of 540,000, a softening point of 113 ° C., and an average particle diameter of 7 μm is used.

Next, the operation of the image forming apparatus will be described. In each of the image forming units 1a, 1b, 1c and 1d arranged around the belt-like intermediate transfer body 6, the photosensitive drums 2a, 2b, 2c and 2d
a, 3b, 3c, and 3d cause the charging to be substantially uniform. Thereafter, the image exposure device 4 which is turned on / off in accordance with the image signal
Image light is irradiated by a, 4b, 4c, and 4d to form an electrostatic latent image.

The electrostatic latent images on the photosensitive drums 2a, 2b, 2c, and 2d are developed by developing devices 5a, 5b, and 5 containing yellow, magenta, cyan, and black toners, respectively.
c, 5d, and a so-called digital image expressing density by area modulation is formed on each of the photosensitive drums 2a, 2d.
b, 2c, and 2d are formed as toner images. A transfer charger 7a is provided between each photosensitive drum and the intermediate transfer member 6.
Electric fields are formed by 7b, 7c, and 7d, and the toner images of the respective colors are sequentially and efficiently transferred to the intermediate transfer body 6 in a primary manner.

The toner image superimposed on the intermediate transfer member 6 is conveyed to a position facing the transfer roll 11 and the transfer opposing roll 10 by the orbital movement of the intermediate transfer member 6, and the recording paper fed from the paper tray 12. Contacted. A transfer bias voltage is applied between the transfer roll 11 and the transfer opposing roll 10, and the toner image is secondarily transferred onto the recording paper. The recording paper P carrying the unfixed toner image is conveyed to the fixing device 13 and is heated and pressed between the heating roll and the pressing roll of the fixing device 13 so that the toner image is melted and pressed on the recording paper.

In the above-described image forming apparatus, the photosensitive drum 2 and the support roll 9 are arranged along a virtual circle 14, and the intermediate transfer member 6 is pressed against each photosensitive drum 2 in the same state. Therefore, each color toner image is primarily rotated under substantially the same conditions, and a high quality image can be obtained. Further, replacement of the intermediate transfer member and the like can be easily performed, and the time required for maintenance can be reduced.

FIG. 2 shows claim 1, claim 2, or claim 4.
1 is a schematic configuration diagram illustrating an image forming apparatus according to another embodiment of the present invention. This image forming apparatus includes image forming units 21a, 21b, 21c, 21d, an intermediate transfer body 26, and the like having the same configuration as those used in the image forming apparatus shown in FIG.
The image forming apparatus includes transfer chargers 27a, 27b, 27c, and 27d, a transfer opposing roll 30, a transfer roll 31, and a fixing device 33. The image forming units 21a, 21b, 21c, and 2
Developing device 25 containing 1d arrangement and black toner
d is different.

In the above-described image forming apparatus, among the plurality of photosensitive drums, the photosensitive drums 22a, 22b, and 22c on which yellow, magenta, and cyan toner images are formed have the same distance between adjacent photosensitive drums. It is arranged as follows. On the other hand, the photoconductor drum 22d on which the black toner image is formed is adjacent to one photoconductor drum 22c, and is arranged so that the interval therebetween is wide.

Developing device 2 for forming black toner image
Reference numeral 5d designates a larger toner storage section than the other developing devices 25a, 25b, and 25c. In general, black toner is frequently used also in a color image forming apparatus. However, by arranging the photosensitive drums 25a, 25b, 25c, and 25d as described above, the toner accommodating portion of the black developing device 25d is enlarged. be able to.

Each photosensitive drum and supporting rolls 29a, 2
9b are arranged at different intervals as described above, but due to their relative positional relationship, the intermediate transfer body 26 can be attached to the photosensitive drums 22a, 22b, 22c, and 22d.
Are arranged so that the center angles of the respective photosensitive drums in the range of contact along the peripheral surface of the photosensitive drums are equal.

FIG. 3 is a schematic diagram of the first, third, fourth, and fourth aspects of the present invention.
FIG. 9 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. This image forming apparatus has the configuration shown in FIG.
In comparison with the image forming apparatus shown in FIG.
a, 42b, 42c, 42d and support rolls 48a, 4
8b, 48c and transfer chargers 47a, 47b, 4c.
7c and 47d are different from each other, and other components are the same as those of the image forming apparatus of FIG.

The photosensitive drums 42a, 42b, 42
c and 42d indicate that the intermediate transfer member 46 has three support rolls 48.
a, 48b, and 48c are press-contacted in two portions on a portion stretched between them. The intermediate transfer member 46 is wound around a predetermined length of the peripheral surface of the photosensitive drums 42a, 42b, 42c, and 42d by the relative positional relationship between the adjacent photosensitive drums and the support rolls adjacent thereto. Are located.

The transfer chargers 47a, 47b, 47c,
47d is the photosensitive drums 42a, 42b, 42c, 4
On the downstream side of the area where the intermediate transfer body 46 is wound around 2d,
It is in contact via an intermediate transfer member 46. The transfer chargers 47a, 47b, 47c, and 47d are film transfer units made of a flexible member in which a conductive material is dispersed, and apply a transfer bias voltage by bringing a leading end portion into contact with the intermediate transfer body 46. .

In this image forming apparatus, the transfer charger 4
Even without strongly pressing the intermediate transfer members 7a, 47b, 47c, and 47d against the intermediate transfer member 46, the intermediate transfer member 46 is pressed against the photosensitive drum, and a uniform electric field is formed by applying a transfer bias voltage. For this reason, the toner images of the respective colors are superposed on the intermediate transfer member 46 satisfactorily, and a high-quality image can be obtained. Further, the transfer chargers 47a, 47b, 47
It is not necessary to strongly press the intermediate transfer body 46 with c and 47d, and the transfer charger can have a simple structure. Furthermore, since an electric field is hardly formed on the upstream side of the contact portion between each photosensitive drum and the intermediate transfer body 46, good primary transfer without toner image disturbance can be performed.

FIG. 4 is a schematic configuration diagram showing an image forming apparatus according to an embodiment of the present invention. The image forming apparatus includes an endless belt-shaped intermediate transfer body 66 whose peripheral surface is rotatably supported. Along the peripheral surface of the intermediate transfer member 66, yellow, magenta, cyan, and black are provided. Four image forming units 6 for forming toner images
1a, 61b, 61c and 61d are provided.

Each image forming unit 61a, 61b, 61
c, 61d are photosensitive drums 62a, 62b, 62c,
62d, charging devices 63a, 63b, 63c and 63d, and an image exposing device 64 around each photosensitive drum.
a, 64b, 64c, 64d and developing devices 65a, 65
b, 65c, 65d and transfer chargers 67a, 67b, 6
7c and 67d.

The intermediate transfer member 66 includes a driving roll 68
, The support roll 69 and the transfer opposing roll 70 are stretched so that the circumferential shape is line-symmetric, and the intermediate transfer body 66 is rotated by the driving roll 68 being rotated. The intermediate transfer member 66 is stretched over a photosensitive drum 62a for a yellow image and a photosensitive drum 62d for a black image, and a photosensitive drum 62b for a magenta image and a photosensitive drum 62c for a cyan image. Is abutted at a line symmetrical position of the portion. Further, the transfer chargers 67a, 67b, 67c, 67d abut on the downstream side of the contact portion between the photosensitive drums 62a, 62b, 62c, 62d and the intermediate transfer member 66 via the intermediate transfer member 66. Have been.

The transfer opposing roll 70 and the intermediate transfer member 66
A transfer roll 71 is provided at a position opposed to the transfer roll 71, and a recording sheet is fed from a paper tray (not shown) to a pressure contact portion between the transfer opposed roll 70 and the transfer roll 71. Further, a fixing device 72 that heats and melts the toner image on the recording paper and presses the toner image on the recording paper is provided downstream of the pressing portion. In the image forming apparatus, each of the image forming units 61a, 61b, 61c, 61d, the photosensitive drums 62a, 62b, 62c, 62d, the charging devices 63a, 63b, 63c, 63d, and the image exposing device 64
a, 64b, 64c, 64d and developing devices 65a, 65
For b, 65c, 65d, the intermediate transfer member 66, the transfer opposing roll 70, the transfer roll 71, and the fixing device 72, those similar to those in the image forming apparatus shown in FIG. 1 are used.

The transfer chargers 67a, 67b, 67c,
Reference numeral 67d denotes a film transfer device made of a flexible member in which a conductive material is dispersed, and a transfer bias voltage is applied by bringing the leading end portion into contact with the intermediate transfer member 66. Since a pressing force is applied to a contact portion between each photosensitive drum and the intermediate transfer member 66, a substantially uniform electric field is formed when a transfer bias voltage is applied. Therefore, the toner images formed on the respective photosensitive drums are all in good condition,
6 is efficiently transferred onto the intermediate transfer body 6
6 are superimposed well.

The photosensitive drums 62a, 62b, 62
The intermediate transfer member 66 is divided into two parts which are stretched over the intermediate transfer member 66 so as to be symmetrical with each other. It is possible to reduce the length that is stretched between them. Therefore, the intermediate transfer member 66 can be stretched in a stable state. Further, since the contact pressures of the respective photosensitive drums are applied to the line symmetrical positions in the circumferential direction of the intermediate transfer body 66, the contact pressures at the opposing positions cancel each other against the support mechanism of the intermediate transfer body 66. Act like so. Therefore, the supporting member can strongly support the intermediate transfer body 66 with a simple structure. further,
When the photosensitive drums are pressed against each other, the intermediate transfer member 6 is pressed.
Although the load acts on the drive of No. 6, the operation positions of the load are dispersed, and stable drive with less speed unevenness is possible.

FIG. 5 is a schematic structural view showing an image forming apparatus according to an embodiment of the present invention. In this image forming apparatus, each image forming unit 81a, 81b, 81
c, 81d, and photosensitive drums 82a, 82b, 82c,
82d and charging devices 83a, 83b, 83c, 83d
, Image exposing devices 84 a, 84 b, 84 c, 84 d, developing devices 85 a, 85 b, 85 c, 85 d, an intermediate transfer body 86, a driving roll 88, a transfer facing roll 89, a transfer roll 90, and a fixing device 91. Means the same as the image forming apparatus shown in FIG.

In the above image forming apparatus, the intermediate transfer member 86
However, by the drive roll 88 and the transfer opposing roll 89,
It is stretched so that it can go around. One of two corresponding stretched portions of the intermediate transfer body 86 has a photosensitive drum 82a for a yellow image and a photosensitive drum 82b for a magenta image.
Is in contact with the photosensitive drum 82
The photosensitive drum 82d for a black image and the photosensitive drum 82c for a cyan image are in contact with each other at a position facing a and 82b. Further, the transfer chargers 87a and 87b are arranged inside the endless intermediate transfer body 86 and between two sets of opposing photosensitive drums 82a, 82d and 82b and 82c.

The transfer chargers 87a and 87b extend an electrode wire and apply a high voltage to the electrode wire to generate a corona discharge. As a result, an electric charge is applied to the inner peripheral surface of the intermediate transfer member 86, and the toner image is electrostatically transferred to the intermediate transfer member 86. At this time, since a pressing force is applied to the contact portion between each photoconductor drum and the intermediate transfer member 86, an electric field is formed between the intermediate transfer member and the photoconductor drum in a stable state. Therefore, the toner images formed on the respective photosensitive drums are sequentially and efficiently transferred onto the intermediate transfer member 86 in good condition, and the toner images of the respective colors are superimposed on the intermediate transfer member 86 satisfactorily. You.

FIG. 6 is a schematic diagram showing an image forming apparatus according to an embodiment of the present invention. This image forming apparatus differs from the image forming apparatus shown in FIG. 5 in the configuration of the transfer chargers 107a and 107b and the arrangement of the photosensitive drums 102a, 102b, 102c and 102d. 5 has the same configuration as the image forming apparatus.

The transfer chargers 107a and 107b are made of a conductive or semiconductive roll-shaped member, and are in contact with the back side of the intermediate transfer member 106 to apply a transfer bias voltage. The transfer chargers 107a and 107b
Are disposed downstream of the portions where the respective photosensitive drums 102 and the intermediate transfer member 106 are in contact with each other, and are rotationally driven as the intermediate transfer member 106 rotates.

Since a contact pressure is applied to the contact portion between each photosensitive drum and the intermediate transfer member 106, the transfer charger 1
07a and 107b form a stable electric field between the intermediate transfer member 106 and the photosensitive drum 102. The transfer charger 1 is located downstream of the process at the contact portion.
Since 07 is in contact, almost no electric field is formed upstream of the contact portion. For this reason, it is possible to prevent the toner image on each photosensitive drum from flying between the non-contact intermediate transfer body 106 and each color toner image.
06 is superimposed satisfactorily, and a high-quality image can be obtained.

[0069]

As described above, in the image forming apparatus according to the present invention, there is no need to strongly press the transfer charger against the intermediate transfer member or to provide a member for pressing the intermediate transfer member against the photosensitive drum. The intermediate transfer member is pressed against each photosensitive drum in the same state, and an electric field is formed between each photosensitive drum and the intermediate transfer member in a stable state. For this reason,
The respective color toner images on the photosensitive drum are primarily transferred efficiently under substantially the same conditions, and a high quality image can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing an image forming apparatus according to another embodiment of the present invention according to claim 1, 2 or 4.

FIG. 3, Claim 3, Claim 4, and Claim 5
1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention.

FIG. 4 is a schematic configuration diagram showing an image forming apparatus as one embodiment of the invention according to claim 6;

FIG. 5 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention;

FIG. 6 is a schematic configuration diagram showing an image forming apparatus according to an embodiment of the invention according to claims 8 and 9;

FIG. 7 is a schematic configuration diagram illustrating a conventional image forming apparatus.

[Explanation of symbols]

1, 21, 41, 51, 81, 101, 201 Image forming unit 2, 22, 42, 52, 82, 102, 202 Photoconductor drum 3, 23, 43, 53, 83, 103, 203 Charging device 4, 24 , 44, 54, 84, 104 Exposure device 5, 25, 45, 55, 85, 105, 205 Developing device 6, 26, 46, 56, 86, 106, 206 Intermediate transfer member 7, 27, 47, 57, 87 , 107, 207 Transfer charger 8, 28 Belt tensioner 9, 29, 48, 69, 208 Support roll 68, 88, 108 Driving roll 10, 30, 49, 70, 89, 109, 209 Transfer opposing roll 11, 21, 50, 71, 90, 110, 210 Transfer roll 12, 22, 51 Paper tray 13, 23, 52, 72, 91, 111, 211 Fixing device 204 Scanning device

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Yutaka Kanai 2274 Hongo, Ebina-shi, Ebina-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. On-site F term (reference) 2H030 AA06 AB02 AD17 BB23 BB42 BB43 BB46 BB54 BB71 2H032 AA02 AA05 AA15 BA01 BA09 BA23 CA02 CA13

Claims (9)

[Claims] A plurality of image carriers having a cylindrical peripheral surface on which a toner image is formed by toner selectively transferred onto the peripheral surface; An endless belt-shaped member to be driven, wherein an intermediate transfer body on which the toner image on the image carrier is primarily transferred onto an outer peripheral surface; and a secondary for transferring the toner image on the intermediate transfer body to a recording medium. An image forming apparatus having a transfer device, wherein the image carrier is in contact with an outer peripheral surface of a portion stretched between support rolls of the intermediate transfer body, and the intermediate transfer body is An image forming apparatus, wherein a central angle of a range contacting along a peripheral surface is equal for a plurality of image carriers. 2. The image transfer member according to claim 1, wherein the plurality of image carriers are in contact with the intermediate transfer member at a distance from the support roll and at an interval between two support rolls on which the intermediate transfer member is stretched. 2. The central angle of a range in which the intermediate transfer member contacts each of the image carriers is set to be equal according to a relative position with respect to an adjacent image carrier or a support roll. Image forming apparatus. 3. An intermediate transfer member having two image carriers and support rolls arranged in parallel on both sides thereof, wherein an outer peripheral surface of the intermediate transfer member is in contact with the two image carriers, and The support roll is stretched on a common tangent line, and the support roll is in contact with an inner peripheral surface of the intermediate transfer body, and is arranged so as to wind the intermediate transfer body around the peripheral surface of the image carrier. The image forming apparatus according to claim 1. 4. The image forming apparatus according to claim 1, wherein at least one of the support rolls is driven to rotate, so that the intermediate transfer body rotates in a circumferential direction, and the image carrier rotates following the circumferential movement of the intermediate transfer body. The image forming apparatus according to claim 1, wherein the image forming apparatus is provided. 5. A transfer member made of a conductive and flexible member is provided on an inner peripheral surface of the intermediate transfer body at a downstream portion of a portion where the intermediate transfer body contacts the peripheral surface of the image carrier. The image forming apparatus according to claim 1, wherein the image forming apparatus is in contact with the image forming apparatus. 6. The intermediate transfer body is stretched so that a circumferential shape thereof is line-symmetric, and the image carrier is a line of a portion stretched between support rolls of the intermediate transfer body. 2. The image forming apparatus according to claim 1, wherein two symmetric portions are abutted at two symmetrical positions. 3. 7. A plurality of image carriers having a cylindrical peripheral surface on which a toner image is formed by toner selectively transferred onto the peripheral surface; An endless belt-shaped member to be driven, wherein an intermediate transfer body on which the toner image on the image carrier is primarily transferred onto an outer peripheral surface; and a secondary for transferring the toner image on the intermediate transfer body to a recording medium. An image forming apparatus having a transfer device, wherein the intermediate transfer member is disposed such that two of the stretched portions are opposed to each other between support rolls, and the image carrier is the intermediate transfer member. The two abutted portions of the intermediate transfer member are respectively abutted, and the two abutted portions are inside the stretched intermediate transfer member and are opposed to each other.
An image forming apparatus, wherein one transfer device is provided between two image carriers, and the transfer device forms a transfer electric field between the two image carriers. 8. The image forming apparatus according to claim 1, wherein the transfer device is a roll-shaped member to which a transfer bias voltage is applied, and is in pressure contact with the two opposing image carriers via the intermediate transfer member. Item 8. The image forming apparatus according to Item 7. 9. The transfer device, which is a roll-shaped member,
The image forming apparatus according to claim 8, wherein each of the image carriers is pressed into contact with the image carrier at a downstream portion of a range where the image carrier contacts the intermediate transfer member.