JP2003057970A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of always yielding an excellent transfer image by applying specified voltage to a transfer roll even in the case of using material whose resistance fluctuation caused by environmental change such as temperature and humidity is large as material constituting a transfer roll. SOLUTION: In this image forming device, the image is formed by temporarily multiply transferring a toner image formed on an image carrier to an intermediate transfer body by a primary transfer roll and then collectively secondarily transferring the toner image multiply transferred to the intermediate transfer body to a recording medium by a secondary transfer roll or directly transferring the toner image formed on the image carrier to the recording medium by the transfer roll. The device is provided with a limiting resistance between at least one of all the transfer rolls and a high-voltage power source applying specified high voltage to the said transfer roll.

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 such as a copying machine, a printer, a facsimile, etc. to which an electrophotographic method is applied, and particularly, a toner image formed on an image carrier is transferred to an intermediate transfer member. Primary transfer in an image forming apparatus that forms a color image or a black and white image by directly transferring the toner image formed on the image carrier to the recording medium via a recording medium or directly onto the recording medium. The present invention relates to a transfer technique using a member or a secondary transfer member.

[0002]

2. Description of the Related Art Conventionally, various types of image forming apparatuses, such as copying machines, printers, and facsimiles, which have adopted the electrophotographic method have been proposed and have been actually commercialized. Among such image forming apparatuses,
As an image forming apparatus capable of forming a high-quality color image regardless of the material of the recording medium, yellow, magenta, cyan, black, etc. on the photosensitive drum are rotated every time the photosensitive drum rotates once. Toner images of four colors are sequentially formed, and toner images of four colors of yellow, magenta, cyan, black, etc., which are sequentially formed on the photoconductor drum, are primary-transferred by a primary transfer roll onto an intermediate transfer member. After that, various four-cycle intermediate transfer type image forming apparatuses for forming a color image by collectively performing secondary transfer from the intermediate transfer body onto a recording medium by a secondary transfer roll have been proposed. It has been commercialized by the present applicants.

By the way, as a primary transfer roll that multiplex-transfers toner images of yellow, magenta, cyan, black, etc., which are sequentially formed on the photosensitive drum as described above, onto the intermediate transfer body, for example, epichlorohydrite is used. A transfer roll whose main material is rubber is used.

[0004]

However, the above-mentioned prior art has the following problems. That is, in the case of the above-mentioned conventional image forming apparatus, an epichlorohydrin rubber or the like is used as a main material as a primary transfer roll for multiple-transferring the toner images sequentially formed on the photosensitive drum onto the intermediate transfer body. A transfer roll is used. However, the transfer roll mainly composed of epichlorohydrin rubber or the like has a larger resistance fluctuation due to environmental changes such as temperature and humidity as compared with the transfer roll obtained by blending urethane with an ion conductive agent. Therefore, a transfer roll mainly composed of epichlorohydrin rubber forms a transfer electric field, and when used with constant current control, the resistance of the transfer roll is significantly reduced in a high temperature and high humidity environment. The applied voltage drops significantly below 0.1 kv. Therefore, as a power source for the transfer roll, there is a problem that the output becomes unstable, the transfer electric field becomes insufficient under a high temperature and high humidity environment, and a transfer failure occurs along the axial direction of the transfer roll. It was

In addition to this problem, in the case of the above-mentioned conventional image forming apparatus, the post nip of the primary transfer portion for transferring the toner image formed on the photosensitive drum to the belt-shaped intermediate transfer member. 8A, as shown in FIG. 8A, the distance between the photosensitive drum and the belt-shaped intermediate transfer member is suddenly increased, and the peeling discharge and the charging potential of the intermediate transfer member are rapidly attenuated. There is a problem that an image quality defect called "blur" in which an image is scattered occurs.

In recent years, such a problem is particularly remarkable in the case of a toner having a shape factor of 110 to 140, which is close to a spherical shape and is used for the purpose of improving image quality by improving transferability of a toner image.

As a measure against the above problems, FIG.
As shown in (b), the lap amount of the belt-shaped intermediate transfer member with respect to the photosensitive drum is increased, and at the post-nip side of the primary transfer portion that transfers to the belt-shaped intermediate transfer member, the photosensitive drum and the belt-shaped intermediate transfer member are transferred. It is conceivable to configure the body distance so that it does not spread rapidly.

However, in this case, as described above,
Since the belt-shaped intermediate transfer member wraps more on the photosensitive drum, the system resistance between the photosensitive drum and the primary transfer roll via the belt-shaped intermediate transfer member decreases and transferability in high temperature and high humidity environment Is further reduced, and the problem that transfer defects such as color loss occur occurs becomes more significant.

Therefore, the present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a transfer roll as a material constituting a transfer roller which is resistant to environmental changes such as temperature and humidity. An object of the present invention is to provide an image forming apparatus capable of applying a predetermined voltage to the transfer roll even when a material having large fluctuations is used and always obtaining a good transferred image.

Another object of the present invention is that even when a toner having a nearly spherical shape is used,
It is an object of the present invention to provide an image forming apparatus capable of surely preventing the occurrence of transfer defects as well as the occurrence of blur.

[0011]

In order to solve the above-mentioned problems, the invention described in claim 1 temporarily multiplexes a toner image formed on an image carrier onto an intermediate transfer member by means of a primary transfer roll. Of the toner images transferred onto the intermediate transfer member in a multiple transfer manner onto the recording medium by a secondary transfer roll, or a toner image formed on the image carrier. In the image forming apparatus for forming an image by directly transferring the image onto a recording medium by a transfer roll.
A limiting resistor is provided between one transfer roll and a high-voltage power supply that applies a predetermined high voltage to the at least one transfer roll.

Further, according to the invention described in claim 2, the transfer roll provided with a limiting resistance between the transfer roll and the high-voltage power source,
This is an ionic conductive roll having a large change in resistance value due to a change in environment.

Further, in the invention described in claim 3, the minimum voltage V applied to the transfer roll for the transfer is required.
The minimum current I required for transfer and the limiting resistance T satisfy the following relationship: minimum required voltage V / minimum required current I ≦ limiting resistance R 2.

Of the above-mentioned transfer rolls, at least one transfer roll may be, for example, a primary transfer roll, but is not limited to this, and a secondary transfer roll or a normal transfer roll may be used. Alternatively, a plurality of transfer rolls may be used.

The limiting resistance may be provided between at least one transfer roll of all the transfer rolls and a high voltage power source for applying a predetermined high voltage to the at least one transfer roll, It may be provided inside the high-voltage power supply, or may be provided at an arbitrary position of the high-voltage line connecting the transfer roll and the high-voltage power supply.

Further, the toner used in the image forming apparatus is not particularly limited, and any toner can be used, but the shape factor of the toner is 110 to 110.
"Blur" when using 140 spherical toner
This is more effective in that it is possible to reliably prevent the occurrence of transfer defects and transfer defects.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 2 shows a digital full-color copying machine as an image forming apparatus according to Embodiment 1 of the present invention. It is needless to say that the image forming apparatus may be a printer, a facsimile or the like other than the copying machine.

In FIG. 2, reference numeral 1 denotes a main body of a digital full color copying machine, and an IIT2 (Image Input T) for reading an image of a document having a color image or the like is provided on an upper portion of the main body 1 of the digital full color copying machine.
terminal) is provided. The image data read by the IIT2 and the image data sent from a personal computer or the like (not shown) are, for example, red (R), green (G), and blue (B) (8 bits each).
Color image data is sent to an image processing device (not shown), and in this image processing device, shading correction, position deviation correction, lightness / color space conversion, gamma correction, frame erasing, color / moving editing are performed on the image data. Predetermined image processing such as is performed.

The image data subjected to the predetermined image processing by the image processing apparatus as described above is yellow (Y), magenta (M), cyan (C), black (BK) (each 8).
ROS3 (Rast) as four-color image data of
ER Output Scanner), and the ROS 3 performs image exposure with the laser beam LB according to the image data.

The photosensitive drum 4 as an image bearing member, which is scanned and exposed by the laser beam LB by the ROS 3, is rotationally driven at a predetermined speed in the arrow direction by a driving means (not shown). This photosensitive drum 4
The surface of is charged in advance with a predetermined polarity (for example, a negative polarity) and a potential by the scorotron 5 for primary charging, and then yellow (Y), magenta (M), cyan (C), black according to the image data. The laser light LB corresponding to each color of (BK) is sequentially scanned and exposed to form an electrostatic latent image. The electrostatic latent images sequentially formed on the photoconductor drum 4 are developed by developing devices 6Y, 6M, 6C and 6BK for four colors of yellow (Y), magenta (M), cyan (C) and black (BK). By the developing device 6 of the rotary type provided, for example, reversal development is performed with toner charged to a negative polarity which is the same polarity as the charging polarity of the photoconductor drum 4 to form a toner image of a predetermined color. The toner image formed on the photosensitive drum 4 is charged by a pre-transfer charger (not shown) as necessary, and the charge amount is adjusted.

In the digital full-color copying machine according to the present embodiment, by improving the transferability of the toner image and the like, it is possible to further improve the image quality and to eliminate oil in the fixing device. In 6M, 6C, and 6BK, instead of the amorphous toner produced by the conventional pulverization method or the like, a nearly spherical toner is used.

Specifically, the toner has an average particle size of 6
In order to improve toner graininess and obtain high transferability,
A spherical toner having a shape factor (ML ² / A) of 110 to 140 or less, and a shape factor of 120 (here, a polymerized toner) is used. An external additive is added to the spherical toner for cleaning property, transfer property and charge maintaining property. Further, the developing devices 6Y, 6M, 6C and 6BK use a two-component developer, and the toner volume (Tv) in this two-component developer is 30 or more.

The shape factor of the above toner (ML ² /
A) is represented by the following equation. Shape factor (ML ² / A) = (absolute maximum length of toner diameter) ²
/ (Projected area of toner) x π / 4 x 100

The toner images of the respective colors sequentially formed on the photosensitive drum 4 are provided on the intermediate transfer belt 7 as an intermediate transfer member arranged below the photosensitive drum 4 as a first transfer means. The images are sequentially transferred by the primary transfer roll 8 in a state of being superimposed on each other. This intermediate transfer belt 7
Is driven by a drive roll 9, a tension roll 10, a backup roll 11 and a driven roll 12 as opposed rolls forming a part of the secondary transfer means, for example, at the same moving speed as the peripheral speed of the photosensitive drum 4 in the arrow direction. It is rotatably supported along.

In the illustrated embodiment, the driven roll 12 is provided in the vicinity of the downstream side of the primary transfer roll 8, but the driven roll 12 causes the wrap amount of the intermediate transfer belt 7 with respect to the photosensitive drum 4 to be increased. It is set to a large value, and it is possible to reliably prevent the occurrence of so-called blur even when a toner having a nearly spherical shape is used.

On the intermediate transfer belt 7, yellow (Y), magenta (M), cyan (C), and black (BK) formed on the photosensitive drum 4 according to the color of the image to be formed. The toner images of all or part of the four colors are transferred by the primary transfer roll 8 in a state of being sequentially superposed. The toner image transferred onto the intermediate transfer belt 7 is transferred onto a recording sheet 13 as a recording medium that is conveyed to a secondary transfer position at a predetermined timing, and a backup roll 11 that supports the intermediate transfer belt 7 and Transfer is performed by the pressure contact force and the electrostatic attraction force of the secondary transfer roll 14 that constitutes a part of the second transfer unit that is in pressure contact with the backup roll 11. As shown in FIG. 2, the recording paper 13 includes a plurality of paper cassettes 1 arranged at the bottom of the copying machine body 1.
Sheets of a predetermined size from sheets 5, 16, and 17 are fed one by one by the feed roll 18 and the separation roll pair 19. The fed recording paper 13 is conveyed to a secondary transfer position of the intermediate transfer belt 7 at a predetermined timing by a plurality of conveying roll pairs 20 and a resist roll 21.
Then, as described above, the toner image of a predetermined color is collectively transferred from the intermediate transfer belt 7 to the recording paper 13 by the backup roll 11 and the secondary transfer roll 14 as the secondary transfer means. It has become so.

The recording paper 13 on which the toner image of a predetermined color has been transferred from the intermediate transfer belt 7 is separated from the intermediate transfer belt 7 and is then conveyed by a conveyor belt 22 to a fixing device 23 as fixing means. The toner image is conveyed, and the toner image is fixed on the recording paper 13 by heat and pressure by the heating roll 24 and the pressure roll 25 of the fixing device 23, and the main body discharge roll 26 discharges the toner image provided outside the copying machine main body 1. The sheet is discharged onto the tray 27 and the color image forming process is completed.

In FIG. 2, 28 is a cleaning device for the photoconductor for removing residual toner, paper dust, etc. from the surface of the photoconductor drum 4 after the transfer process is completed, and 29 is the intermediate transfer belt 7. An intermediate transfer belt cleaner for cleaning, 30 a cleaner for cleaning the secondary transfer roll 14, and 31 a manual feed tray. Further, the intermediate transfer belt cleaner 29 is configured to come into contact with and separate from the intermediate transfer belt 7 at a predetermined timing. Further, the toner collected by the cleaning device 28 for the photoconductor and the cleaner 29 for the intermediate transfer belt is collected and collected in the collected toner box 32.

By the way, in this embodiment, the toner images formed on the image carrier are once transferred in multiple layers onto the intermediate transfer member by the primary transfer roll, and then transferred in multiple layers onto the intermediate transfer member. In an image forming apparatus for forming an image by secondarily transferring a toner image onto a recording medium collectively by a secondary transfer roll, at least one transfer roll among all the transfer rolls and at least one of the transfer rolls. A limiting resistor is provided between the two transfer rolls and a high-voltage power supply that applies a predetermined high voltage.

Further, in this embodiment, the transfer roll having a limiting resistance provided between the transfer roll and the high-voltage power source is an ion conductive roll having a large variation in resistance value due to a change in environment.

Further, in this embodiment, the minimum voltage V required for the transfer applied to the transfer roll, the minimum current I required for the transfer, and the limiting resistance T are the minimum required voltage V / It is configured so as to satisfy the relationship of the minimum required current I ≦ limiting resistance R 2.

That is, in this embodiment, as shown in FIG. 3, the primary transfer roll 8 has a semi-circular metal shaft 35 made of SUS and a semi-conductive foam made of epichlorohydrin rubber. The conductive elastic body layer 36 is covered so as to have a predetermined outer diameter. The resistance value of the semiconductive elastic body layer 41 made of the foam of epichlorohydrin rubber is set to be 6.6 to 7.0 logΩ.

In this embodiment, unlike the primary transfer roll 8, the secondary transfer roll 14 does not use a foam of epichlorohydrin rubber, and resistance changes due to environmental changes such as temperature and humidity. However, a material that is not so large is used.

A high DC voltage is applied to the primary transfer roll 8 by a high voltage power source 40, as shown in FIG. This high-voltage power supply 40 applies a predetermined DC voltage (about 24 V) to the primary winding 42 of the high-voltage transformer 41 by the DC power supply 43, and applies the DC voltage applied to the primary winding 42 of the high-voltage transformer 41 to the primary winding 42. FE
It is turned on / off by a switch element 44 composed of T, a transistor, etc., and a predetermined high voltage is generated in the secondary winding 45 of the high voltage transformer 41. The switch element 44 is on / off controlled by the control circuit 46 at a predetermined timing, and the control circuit 46 is controlled from the main control section 47 which controls the operation of the copying machine through the D / A conversion circuit 48. At the same time, the on / off determination circuit 49 determines the on / off timing, and the on / off timing is controlled to a predetermined on / off timing. In addition, the high voltage transformer 41
The predetermined high voltage generated in the secondary winding 45 of the above is converted into a DC high voltage by the rectifying and smoothing circuit 50 and applied to the metal shaft 35 of the primary transfer roll 8. The DC high voltage output from the rectifying / smoothing circuit 50 is subjected to constant current control such that the output current and the voltage are detected by the current detection circuit 51 and the voltage detection circuit 52 and the output current becomes constant.

By the way, in this embodiment, as shown in FIG. 1, a limiting resistor 53 is provided on the output side of the rectifying / smoothing circuit 50 of the high-voltage power supply 40, and a direct current output from the rectifying / smoothing circuit 50 is provided. Is applied to the primary transfer roll 8 via the limiting resistor 53.
As the limiting resistance 53, for example, one having a resistance value of 22 MΩ is used.

Further, in this embodiment, the minimum voltage V required for transfer applied to the primary transfer roll 8, the minimum current I required for transfer, and the resistance value R of the limiting resistor 53 are as follows. It is configured to satisfy the relationship of minimum required voltage V / minimum required current I ≦ limiting resistance R 2.

More specifically, the above-mentioned primary transfer roll 8
When the resistance value of is 6.6 to 7.0 logΩ, the VI characteristic in the high temperature and high humidity environment is as shown in the graph of FIG. 4 in the range of the used current value of 20 to 30 μA in the constant current control. , 0.
Since the transfer voltage becomes 2 kv or less, and the transfer voltage applied to the primary transfer roll 8 is too low as it is, a transfer failure occurs.

By the way, it goes without saying that the primary transfer roll 8 itself has a predetermined resistance value.
The system resistance at the primary transfer portion where the primary transfer roll 8 is pressed against the surface of the photoconductor drum 1 via the intermediate transfer belt 7 is not determined only by the resistance value of the primary transfer roll 8 itself, but the conductor layer of the photoconductor drum 1 is not determined. It includes all the resistors interposed between the high voltage power supply 40 and the high voltage power supply 40 connected via the primary transfer roll 8. The system resistance for obtaining good transfer at the primary transfer portion is 21 by the constant current control.
When μA is applied, it is 10 MΩ or more in a high temperature and high humidity environment and 120 MΩ or less in a low temperature and low humidity environment.

If a limiting resistance 53 of 22 MΩ is provided between the high-voltage power supply 40 and the primary transfer roll 8, as shown in FIGS.
As is clear from the above, the applied voltage in the high temperature and high humidity environment is 0.4 kv or more and in the low temperature and low humidity environment is 2.5 kv or less, and the transfer failure does not occur, and a good transferred image can be always obtained.

In the image forming apparatus according to the present embodiment having the above-described structure, when a material having a large resistance variation due to environmental changes such as temperature and humidity is used as the material for the transfer roll, as described below. Even in this case, it is possible to apply a predetermined voltage to the transfer roll and always obtain a good transfer image.

That is, in the digital color copying machine according to this embodiment, as shown in FIG.
Yellow (Y), magenta (M), and
The four color toner images of cyan (C) and black (BK) are transferred onto the intermediate transfer belt 7 in a state of being sequentially superposed by the primary transfer rolls 8, and then transferred onto the intermediate transfer belt 7 in multiple layers. The toner images are collectively secondarily transferred onto the recording paper 13 by the secondary transfer roll 14 and fixed to form a color image.

At this time, the primary transfer roll 8 has a structure shown in FIG.
As shown in, the high voltage power supply 40 transfers a high DC voltage by constant current control. This primary transfer roll 8
As shown in FIG. 3, the metal shaft 25 made of SUS is coated with a semiconductive elastic layer 36 made of a foam of epichlorohydrin rubber so as to have a predetermined outer diameter. It is configured. The resistance value of the semiconductive elastic body layer 36 made of a foamed material of epichlorohydrin rubber that constitutes the primary transfer roll 8 largely changes due to changes in environment such as temperature and humidity.

By the way, in this embodiment, a high voltage power source 40 for applying a high DC voltage to the primary transfer roll 8 is used.
In addition, a limiting resistor 53 is provided. Therefore, even if the resistance value of the elastic layer 36 made of the foam of epichlorohydrin rubber of the primary transfer roll 8 is significantly reduced under the high temperature and high humidity environment, the primary transfer roll 8 still has the limiting resistance 53. A high DC voltage is applied through the primary transfer roll 8, and the voltage applied to the primary transfer roll 8 is about 0.4 kv when 21 μA is applied by constant current control, as shown in FIG.
Therefore, even under a high temperature and high humidity environment, a transfer voltage of about 0.4 kv can be applied to the primary transfer roll 8, and a good transferred image can be obtained without causing a transfer failure.

In a low-temperature and low-humidity environment, the resistance value of the elastic layer 36 made of a foam of epichlorohydrin rubber of the primary transfer roll rises.
As shown in FIG. 5, the high DC voltage applied through the limiting resistor 53 is about 1.0 kv or about 2.3 kv when 21 μA is applied by constant current control. Therefore, even in a low-temperature and low-humidity environment, the applied voltage to the primary transfer roll 8 can be suppressed to 2.5 kv or less, and a transfer defect does not occur due to an excessively high applied voltage to the primary transfer roll.

Second Embodiment FIGS. 6 and 7 show a second embodiment of the present invention. The same parts as those in the first embodiment will be designated by the same reference numerals and will be described below. In the form 2, the toner image formed on the image bearing member is directly transferred onto the recording medium by the transfer roll to form an image in the image forming apparatus, and at least one of the transfer rolls is transferred. A limiting resistor is provided between the roll and a high-voltage power supply that applies a predetermined high voltage to the at least one transfer roll.

That is, in the second embodiment, as shown in FIG. 7, the toner image formed on the photosensitive drum 4 is directly transferred onto the recording paper 13 by the transfer roll 8, and the toner image is transferred. By performing a fixing process on the formed recording sheet 13, a black and white image is formed.

In the second embodiment, as shown in FIG. 6, in the high voltage line 60 for applying a high voltage from the high voltage power source 40 to the transfer roll 8, the high voltage line 60 is located in front of the transfer roll 8. A limiting resistor 53 is provided.

The high-voltage power supply 40 shown in FIG. 1 has been described as an analog type.
May be of a digital type.

The other structure and operation are the same as those in the first embodiment, and the description thereof will be omitted.

[0051]

As described above, according to the present invention, even when a material having a large resistance variation due to environmental changes such as temperature and humidity is used as a material for the transfer roll, the transfer roll is used. It is possible to provide an image forming apparatus capable of applying a predetermined voltage to the image forming apparatus and always obtaining a good transferred image.

[Brief description of drawings]

FIG. 1 is a block diagram showing a high voltage power supply used in an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a digital color copying machine as an image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional configuration diagram showing a primary transfer roll.

FIG. 4 is a graph showing VI characteristics of a primary transfer roll.

FIG. 5 is a graph showing VI characteristics of a primary transfer roll.

FIG. 6 is a block diagram showing a high voltage power supply used in the image forming apparatus according to Embodiment 1 of the present invention.

FIG. 7 is a block diagram showing a digital color copying machine as an image forming apparatus according to the first embodiment of the present invention.

FIG. 8 is a schematic diagram showing a primary transfer area in a conventional image forming apparatus.

[Explanation of symbols]

4: Photosensitive drum, 8: Primary transfer roll, 35: Metal shaft, 36: Semi-conductive elastic layer, 40: High voltage power source, 53: Limiting resistance.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Mikio Kobayashi             Fuji Zero, 2274 Hongo, Ebina City, Kanagawa Prefecture             X Co., Ltd. (72) Inventor, Kunori Kono             Fuji Zero, 2274 Hongo, Ebina City, Kanagawa Prefecture             X Co., Ltd. (72) Inventor Satoru Torimaru             Fuji Zero, 2274 Hongo, Ebina City, Kanagawa Prefecture             X Co., Ltd. (72) Inventor Naoto Yoshino             Fuji Zero, 2274 Hongo, Ebina City, Kanagawa Prefecture             X Co., Ltd. (72) Inventor Makoto Ochiai             Fuji Zero, 2274 Hongo, Ebina City, Kanagawa Prefecture             X Co., Ltd. (72) Inventor Satoshi Matsuzaka             Fuji Zero, 2274 Hongo, Ebina City, Kanagawa Prefecture             X Co., Ltd. (72) Inventor Tadashi Okada             Fuji Zero, 2274 Hongo, Ebina City, Kanagawa Prefecture             X Co., Ltd. F term (reference) 2H030 AA03 BB02 BB24 BB42 BB54                 2H200 FA01 FA18 GA14 GA23 GA34                       GA45 GA47 GB12 GB22 GB25                       HA02 HA12 HA28 HB03 HB12                       HB22 HB45 HB46 HB48 JA02                       JA25 JA26 JA28 JC03 MA03                       MA08 MB02 MB06 MB08 MB09                       NA02 NA08 NA09 NA14 NA16                       NA17 NA26

Claims (3)

[Claims] 1. A toner image formed on an image bearing member is temporarily transferred onto an intermediate transfer member by a primary transfer roll, and then the toner images transferred onto the intermediate transfer member are secondarily transferred. An image forming apparatus that forms an image by collectively secondarily transferring the image on a recording medium by a transfer roll, or by directly transferring a toner image formed on an image carrier onto the recording medium by a transfer roll. In the above image forming method, a limiting resistor is provided between at least one transfer roll of all the transfer rolls and a high-voltage power supply that applies a predetermined high voltage to the at least one transfer roll. apparatus. 2. The image forming apparatus according to claim 1, wherein the transfer roll provided with a limiting resistance between the high-voltage power supply and the high-voltage power supply is an ion conductive roll having a large variation in resistance value due to a change in environment. apparatus. 3. The minimum required voltage V applied to the transfer roll for the transfer, the minimum current I required for the transfer, and the limiting resistance T are the minimum required voltage V / the minimum required current I ≦ The image forming apparatus according to claim 1, wherein the relationship of the limiting resistance R 1 is satisfied.