JP3396005B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is an electrophotographic image forming apparatus provided with a belt-shaped intermediate transfer member, and can be applied to printers, facsimile machines, and various electrophotographic image forming apparatuses. In particular, the present invention relates to an image forming apparatus characterized by a transfer separation unit.

[0002]

2. Description of the Related Art A belt-shaped intermediate transfer member stretched around a plurality of rollers is provided as a means of an image forming process, and transfer is performed by a charger device provided on a stretched portion of one of the plurality of rollers. A color image forming apparatus is known, which is a so-called printer unit that transfers toner to a material and a so-called scanner unit that reads an image of a document by separating it into blue, green, and red colors and converts it into an electrical image signal. Has been.

The printer section has image forming process sections such as a charging section, an exposing section, a developing section, a transferring section, and a cleaning section around the photosensitive drum. The charging unit includes a charging unit that presses the transfer bias roller against the intermediate transfer member. The exposure unit is composed of a laser emission source that converts the color image data from the color scanner into an optical signal and performs optical writing corresponding to the original image, a polygon mirror, an fθ lens, a reflection mirror, and the like. The developing unit is cyan, magenta,
It consists of developing means for each color of yellow and black. The transfer unit is composed of a belt-shaped intermediate transfer member stretched by a plurality of rollers, and is configured to come into contact with and separate from the photosensitive drum. The cleaning unit is composed of a rubber blade or the like provided so as to be in contact with the photosensitive drum.

When the copy operation is started, the scanner section reads the original document and obtains color image data of cyan, magenta, yellow and black. Next, the exposure unit and the development unit of the printer unit function to form a black toner image on the photosensitive drum. This black toner image is
It is transferred to the intermediate transfer member. Similarly, toner images of cyan, magenta, and yellow colors based on the image data of the same original are aligned and transferred to the intermediate transfer member, and a full-color toner image is formed on the intermediate transfer member. . Then, this full-color toner image is collectively transferred to a transfer material such as transfer paper.

At the time of batch transfer to the transfer material, in this image forming apparatus, as a means for transferring the toner from the intermediate transfer body to the transfer material, a bias transfer in which a transfer bias roller to which a transfer bias voltage is applied is brought into pressure contact with the transfer material. The bias roller method is used. That is, the transfer material is conveyed to the pressure contact portion between the transfer bias roller and the intermediate transfer member, and then a bias voltage having a polarity opposite to that of the toner is applied to the transfer bias roller to perform the transfer.

This image forming apparatus has the following problems. 1. The toner is reversely attached to the intermediate transfer member by applying pressure to the toner at the transfer portion. In particular, the amount of adhered toner is likely to occur in the covered portion, and an image called a bug-eating print image is formed on the transfer material, in which the image becomes a bug-eating pattern. In this insect-eating print image, the higher the transfer section pressure,
Remarkably appears.

2. Since the transfer bias roller is configured, the mechanism becomes complicated and the cost becomes high. Further, since the transfer bias roller has a nip, it must have elasticity and stable characteristics such as resistance. Further, a mechanism for cleaning the transfer bias roller, a mechanism for contacting and separating the transfer bias roller, This is because a mechanism for driving is also required.

3. When the transfer material is conveyed to the transfer portion, the intermediate transfer body and the transfer roller are in direct contact with each other on the outer side of the width of the transfer material, and the resistance is small, so that a large current flows there. The optimum bias greatly changes depending on the transfer material width. In addition, at the end of the transfer material, discharge is generated in the minute gap between the intermediate transfer body and the transfer roller, reducing the resistance of the intermediate transfer body and the transfer bias roller, and applying an appropriate transfer bias voltage. It disappears and disturbs the image.

As another example of this type of image forming apparatus, there is a technique disclosed in Japanese Patent Application Laid-Open No. 64-92771. The main point of this technique is that the transfer roller 10 around which the intermediate transfer member 100 is wound is shown in FIG.
A corona discharge type charger 102 is provided so as to face No. 1.

[0010]

In the technique of [1], the problems 1 to 3 in the technique of [1] are solved, but there are problems peculiar to this system. The problem is that the diameter of the transfer roller 101 facing the charger 102 is structurally smaller than that of the above technology, so that the transfer nip between the intermediate transfer body 100 and the transfer material is narrowed, and the transfer material and the intermediate material are That is, the adhesion to the transfer body is poor and the stability becomes unstable. Therefore, transfer rate (toner amount on transfer material / toner amount on intermediate transfer member)
Is small, and in particular, a high toner adhesion portion and the transfer rate remarkably decrease for a color image.

Further, the adhesion between the transfer material and the intermediate transfer material may be reduced, which may cause a speed difference between the intermediate transfer material and the transfer material, and the image on the transfer material may expand or contract.

Further, as compared with the above technique, since the diameter of the transfer roller 101 facing the charger 102 is structurally smaller, the transfer material transfer portion and the separation portion come closer to each other, and the separation charger has a certain degree of transfer nip. You will be approaching the club. Therefore, the separation current may affect the transfer nip portion and an abnormal image may be generated.

An object of the present invention is to obtain high quality transfer performance and separation performance for a transfer material.

[0014]

In order to achieve the above-mentioned object, the present invention comprises: (1) As a means for an image forming process, a belt-shaped intermediate transfer member stretched over a plurality of rollers is provided, and the plurality of rollers are provided. Of the two adjacent rollers, a roller on the transfer material outlet side is used in an image forming apparatus that transfers toner to a transfer material by corona discharge of a charger device provided in a stretched portion of two adjacent rollers. The transfer material is separated from the intermediate transfer member by using two adjacent rollers.
When the distance between them is L, L = 10 mm to 40 mm
And (claim 1).

(2) In the image forming apparatus described in (1), when the diameter of the roller on the transfer material outlet side is D, D ≦ 5
mm to 20 mm (claim 2).

[0016]

( 3 ) In the image forming apparatus described in (1), when the wrap angle of the intermediate transfer member with respect to the roller on the transfer material outlet side of the two adjacent rollers is θ,
= 15 ° to 90 ° (claim 3 ).

( 4 ) In the image forming apparatus described in (1), ρ = 10, where ρ is the volume resistance value of the intermediate transfer member.
^{It was 9} to 10 ¹³ Ωcm (claim 4 ).

[0019]

[Function] When the transfer material enters, the nip can be widened.
The contact state between the transfer material and the intermediate transfer member is improved (Claim 1), the curvature separability is improved (Claim 2 ), and the creep phenomenon at the roller winding portion of the intermediate transfer member is less likely to occur (Claim 1). 3 ) It is easy to keep the transfer current within the optimum range and the blurred image at the time of belt transfer (primary transfer) is eliminated (Claim 4 ).

[0020]

【Example】

(1) Description of Apparatus Suitable for Implementation Before entering the description of each claim of the present invention, a color image forming apparatus suitable for implementation of the present invention will be described with reference to FIG. This color image forming apparatus is composed of a color image reading device, a color image recording device, and the like, which are mechanical components.

A color image reading device (hereinafter referred to as a color scanner) 200 includes a contact glass 202.
An image of the original document 180 is formed on a color sensor 207 via an illumination lamp 205, mirror groups 204A, B, C and a lens 206, and color image information of the original document is displayed, for example, in blue, green and red colors. It reads each decomposed light and converts it into an electrical image signal.

In this example, the color sensor 207 is composed of blue, green, and red color separation means and a photoelectric conversion element such as a CCD (charge coupled element), and simultaneously reads three colors. And this color scanner 20
Based on the blue, green, and red color-separated image signal intensity levels obtained in 0, color conversion processing is performed by an image processing unit (not shown), and black (hereinafter, referred to as Bk), cyan (hereinafter, referred to as Bk). Color image data of C, magenta (hereinafter, referred to as M), and yellow (hereinafter, referred to as Y) are obtained.

This color image data is used as a color image recording device (hereinafter referred to as a color printer) 4 described below.
00 to visualize with Bk, C, M, and Y colors to obtain a final color copy. The operation method of the color scanner 200 for obtaining Bk, C, M, and Y images is as follows. In FIG. 4, when the illumination / mirror optical system receives a scanner start signal in time with the operation of the color printer 400. Scan the original in the direction of the left arrow, and set 1 for each scan.
Get color image data.

By repeating this operation a total of four times, sequential four-color image data is obtained. And each time,
The four color full-color images are formed by sequentially superimposing the images on the color printer 400 while visualizing the images.

Next, the outline of the color printer 400 will be described. The writing optical unit converts the color image data from the color scanner into an optical signal to perform optical writing corresponding to the original image, and the photosensitive drum 41 as a latent image carrier.
An electrostatic latent image is formed on 4.

The writing optical unit is composed of a laser emission means 441, an emission drive control section (not shown) thereof, a polygon mirror 443, a rotation motor 444 thereof, an fθ lens 442, a reflection mirror 446 and the like. ing.

The photosensitive drum 414 rotates in the counterclockwise direction as shown by the arrow.
Photoconductor cleaning unit 421, static elimination lamp 414
M, a charger 419, a potential sensor 414D, a selected developing device in the revolver developing device 420, an optical sensor 414P as a developing density pattern detector, a belt-shaped intermediate transfer member 415, and the like are arranged.

The Bk image is formed as follows.
The charger 419 causes the photoconductor drum 414 by corona discharge.
Is uniformly charged to about -700V with a negative charge. Then, the laser light emitting means 441 performs raster exposure based on the Bk signal. As described above, when the raster image is exposed, initially, the exposed portion of the photosensitive drum 414 that is uniformly charged loses the electric charge proportional to the exposure light amount, and an electrostatic latent image is formed. This electrostatic latent image is revolver developing device 420.
To be developed.

The revolver developing device 420 includes a Bk developing device 420K, a C developing device 420C, an M developing device 420M, a Y developing device 420Y and a revolver rotation drive for rotating each developing device in a counterclockwise direction as shown by an arrow. (Not shown).

In order to develop the electrostatic latent image, each developing device is
The ear of the developer is brought into contact with the surface of the photoconductor drum 414,
Rotating developing sleeves 420KS, 420CS, 420
MS, 420YS, and a developing paddle that rotates to scoop up and stir the developer.

In the standby state, the revolver developing device is
When the copy operation is started, the color scanner 200 sets Bk at a predetermined timing.
The reading of the image data is started, and based on the image data, the optical writing by the laser beam and the latent image formation are started (hereinafter, the electrostatic latent image by the Bk image data is referred to as Bk latent image. C, M and Y are also referred to. the same.).

In order to enable development from the front end of the Bk latent image, the developing sleeve 420KS is started to rotate before the front end of the latent image reaches the developing position of the Bk developing device, and the Bk latent image is formed by the Bk toner. develop. After that, the developing operation of the Bk latent image area is continued, but when the leading edge of the latent image passes the Bk developing position, the revolver developing device rapidly rotates from the Bk developing unit developing position to the next color developing position. This is completed at least before the leading edge of the latent image by the next image data arrives.

When the image forming cycle is started, the photosensitive drum 414 is rotated counterclockwise as indicated by an arrow and the intermediate transfer member 415 is rotated clockwise by a drive motor (not shown). This intermediate transfer member 41
With the rotation of 5, the Bk toner image, the C toner image, the M toner image, and the Y toner image are formed, and finally, the intermediate transfer member Bk, C, M, and Y in this order. 41
A toner image is formed on the surface of the toner image 5.

The toner in the developing device 420 is negatively charged by stirring with the ferrite carrier, and
The Bk developing sleeve 420KS of the present developing device is biased by a power supply means (not shown) with respect to the metal base layer of the photosensitive drum 414 to a potential in which a negative DC potential and an AC are superposed.

As a result, the toner does not adhere to the portion of the photosensitive drum 414 where the electric charge remains, and the portion where the electric charge does not exist,
That is, Bk toner is adsorbed on the exposed portion, and a Bk visible image similar to the latent image is formed.

The intermediate transfer member 415 has a driving roller 415.
D, a transfer opposing roller 415T, a cleaning opposing roller 415C, and a driven roller group are stretched and driven and controlled by a drive motor (not shown).

The Bk toner image formed on the photosensitive drum 414 is a belt transfer corona discharger (hereinafter referred to as a belt transfer device) 416 on the surface of the intermediate transfer member 415 which is driven at a constant speed in contact with the photosensitive member. Transcribed by Less than,
The transfer of the toner image from the photosensitive drum 414 to the intermediate transfer member 415 is called belt transfer or primary transfer.

Some untransferred residual toner on the photoconductor drum 414 is cleaned by the photoconductor cleaning unit 421 in preparation for reuse of the next color of the photoconductor drum 414. The toner collected by the photoconductor cleaning unit 421 is stored in an exhaust toner tank (not shown) via the collection pipe.

The intermediate transfer member 415 has a photosensitive drum 41.
Toner images of Bk, C, M, and Y that are sequentially formed on No. 4 are sequentially aligned on the same surface to form a belt transfer image of four-color superimposition, and then are collectively transferred to a transfer material by a corona discharge transfer device. I do.

On the side of the photosensitive drum 414, the Bk process is followed by the C process, but the C image data reading by the color scanner starts at a predetermined timing, and the C latent image is formed by laser writing with the image data. To do.

The C developing device rotates the revolver developing device with respect to the developing position after the trailing end of the previous Bk latent image has passed and before the leading end of the C latent image reaches. C
Develop the latent image with C toner.

Thereafter, the development of the C latent image area is continued, but when the trailing edge of the latent image passes, the C developing unit is rotated like the Bk developing device. This is also completed before the leading edge of the next M latent image reaches. It should be noted that the M and Y steps are the same as the steps Bk and C described above in respect of the operations of reading image data, forming a latent image, and developing, and therefore a description thereof will be omitted.

The belt cleaning device 415E is composed of an entrance seal, a rubber blade, an ejection coil and an entrance seal, a blade contacting / separating mechanism, and the like. While the color is transferred to the belt, the inlet seal and the blade are separated from the belt surface by the blade contacting / separating mechanism.

A paper transfer corona discharger 417 (hereinafter referred to as a paper transfer device), which is a charger device, applies AC + DC or a DC component by a corona discharge method to form a superimposed toner image on the intermediate transfer member. Transfer to transfer material. Transfer materials of various sizes are stored in the transfer material cassette 482 in the paper feeding bank, and the paper is fed / conveyed in the registration roller direction by the paper feeding rollers 483A, B, and C from the storage cassette of the designated size paper. To be done. Reference numeral 412B2 indicates a manual feed tray for OHP paper, thick paper, or the like.

At the time when image formation is started, the transfer material 190 made of transfer paper is fed from any one of the paper feed ports,
It stands by at the nip portion of the resist roll pair 418R.
When the front end of the toner image on the intermediate transfer body 421 reaches the paper transfer device 417, the registration roller pair 418R is driven so that the front end of the transfer material 190 exactly coincides with the front end of the image, and the registration of the paper and the image is performed. Be seen.

In this manner, the paper transfer device 41 in which the transfer material 190 is superposed on the intermediate transfer belt image and is connected to the positive potential.
Pass over 7. At this time, the transfer material is positively charged by the corona discharge current, and most of the toner image is transferred onto the transfer material. Then, the transfer material is peeled off from the intermediate transfer member and transferred onto the conveyor belt 422.

The transfer material on which the four-color superimposed toner images are collectively transferred from the belt surface as an intermediate transfer member is the paper transport belt 42.
The toner image is melted and fixed at the nip portion of the fixing roller 423A and the pressure roller 423B, which are conveyed to the fixing device 423 at a predetermined temperature 2, and is sent out of the main body by the discharge roll pair 424. Stacked face up on to get a full color copy.

The photosensitive drum 414 after the belt transfer
The surface is cleaned by a photoconductor cleaning unit 421 including a brush roller, a rubber blade, and the like, and the charge is uniformly discharged by the charge removing lamp 414M. The surface of the intermediate transfer member 415 after the toner image is transferred onto the transfer material is cleaned by pressing the belt cleaning device 415E again by the blade contacting / separating mechanism to press the blade.

In the case of repeat copying, the operation of the color scanner and the image formation on the photoconductor are carried out in the second (first color) image process at a predetermined timing after the first (fourth color) image process. move on. In the intermediate transfer member 415, the second Bk toner image is transferred to the area where the surface is cleaned by a belt cleaning device, following the batch transfer process of the first four-color superimposed image onto the transfer material. To be transcribed. After that, the same operation as the first sheet is performed.

The above is the description of the copy mode for obtaining four full colors of A4 size horizontal feed. However, in the case of the three-color copy mode and the two-color copy mode, the designated color and the number of times are the same as above. The operation will be performed.

In the case of a single color copy, only the developing device of the predetermined color of the revolver developing device 420 is in the developing operation (developing position of the predetermined color) state until the predetermined number of sheets is completed, and the blade of the belt cleaning device 415E is set. Intermediate transfer member 4
The copy operation is continuously performed while the pressure is applied to 15.

(2) Description corresponding to Claims FIG. 1 shows an intermediate transfer member unit according to Claims 1 to 4 of the present invention. The configuration of this figure conforms to the overall configuration shown in FIG. The intermediate transfer body unit includes a driving roller 415D supported by bearings on the front and rear side plates, a tension roller 450, transfer counter rollers 451A and 451B, a cleaning counter roller 415C, a driven roller 452, and a belt-shaped belt wound around these rollers. Intermediate transfer member 41
5. It has a paper transfer corona discharger 417 and the like.

[0053] In the present invention of claim 1 (Supplement there to be described later) described corresponding to claim 1, the transfer material 190 which has been conveyed by the registration roller pair 418R, by way of the pre-transfer guide 453, transfer counter roller The configuration is such that the intermediate transfer member 451A, 451B enters the stretched portion of the intermediate transfer member.

FIG. 2 partially shows such a configuration.
For comparison, both FIGS. 2 and 5 are shown at the same scale with respect to the actual product. As can be seen by comparing these two figures, it is more preferable than the structure shown in FIG. 5 in which the transfer material is inserted into the winding portion of the intermediate transfer body (belt) of one roller.
As shown in FIG. 7, the configuration in which the transfer material enters the belt winding portion of the two rollers allows the flat portion of the intermediate transfer member to be wider, so that the transfer material and the intermediate transfer member are in a close contact range. It is possible to take a large NP.

In this way, the toner is transferred to the transfer material by the charger device at the stretched portion of the two adjacent rollers, and the transfer material is transferred by the transfer facing roller 451A on the transfer material outlet side of these rollers. Since it is configured to be separated from the intermediate transfer body 415, the nip portion NP between the belt as the intermediate transfer body and the transfer material can be widened, and the transfer can be performed stably. Furthermore, the contact angle at which the transfer material contacts the intermediate transfer member can be relatively stabilized.

Description corresponding to claim 2 The transfer opposite roller 4 on the transfer material outlet side in claim 1
When the outer diameter of 51A is D, D ≦ 5 mm to 20 mm. In the case of the configuration in which the transfer material enters the belt winding portion of the single roller transfer roller 101 shown in FIG. 5, in order to secure the size of the nip portion necessary for transfer, the transfer roller 101 has a relatively large diameter. (For example, the diameter is 40 mm or more), and it is difficult to separate the transfer material from the intermediate transfer body only by the curvature separation.

However, in the case of this example, the diameter of the transfer facing roller 451A on the transfer material outlet side does not affect the formation of the nip portion for transfer, so the diameter of the roller is made small enough to allow curvature separation. be able to.

Several rollers having different diameters were prepared as the transfer facing roller 451A, and the paper transfer corona discharger 4 was used.
Increase the transfer current value of 17 from a low value to a high value,
FIG. 3 is a graph showing the experimental results of investigating the relationship between the separation performance of the transfer material and the separation roller by plotting the current value when the separation failure occurs as the total transfer current when the separation failure occurs.

In FIG. 3, the transfer total current on the vertical axis is preferably large from the viewpoint of transfer performance, but a practical value is 300 μA to 500 μA. On the other hand, the smaller the diameter of the transfer facing roller 451A as the separation roller, the better the separation performance.

From these things, the transfer counter roller 451
The diameter is 30 mm or less, but in view of variations in experimental values and safety factors, 20 mm or less, more preferably 15 mm or less is suitable. It has been confirmed that in the case of 15 mm or less, the transfer material can be separated only by the curvature separation without providing a new separating means.

On the other hand, the diameter of the transfer facing roller 451 is 5 m.
If it is less than m, there is a problem in that curling is likely to occur at the winding portion between the belt constituting the intermediate transfer member and the transfer facing roller.

From the above, when the diameter of the roller on the transfer material outlet side, that is, the transfer counter roller 451 is D,
It is preferable that D ≦ 5 mm to 20 mm. By setting the diameter of the transfer facing roller 451 in this manner, it is possible to separate the transfer material only by the curvature separation without the need for the transfer material separating means.

Supplementary explanation of claim 1 In this example , in FIG. 2, the distance L between the transfer facing roller 451A and the transfer facing roller 451B is set to 10 mm or more and 40 m.
It is specified below m. When the distance between the transfer facing roller 451B, which is a roller on the transfer material inlet side, and the transfer facing roller 451A, which is a roller on the transfer material outlet side, is made longer than necessary, the intermediate transfer body 415 between these rollers wavy and transfer. When the material enters, the contact state between the transfer material and the intermediate transfer body deteriorates, which may cause uneven transfer.

In particular, in the case of an intermediate transfer member, a resin member having a medium resistance is often used as a material. In such a case,
Rippling and curling are more likely to occur as compared with the photoconductor belt. Although there are variations depending on the material of the intermediate transfer member 415, according to an experiment, the transfer facing rollers 451A and 451 are shown.
When the distance L between B exceeds 40 mm, transfer white defects due to poor adhesion occurred. On the contrary, when L is less than 10 mm, the nip portion between the transfer material and the intermediate transfer member is too small,
It was found that the transfer was defective.

From the above, the distance L between the transfer opposing roller 451A and the transfer opposing roller 451B is set to 10 mm or more and 40 m.
When the thickness is m or less, the transfer can be performed without the influence of the wave inside the intermediate transfer belt on the transfer nip portion.

[0066] In explaining claim 4 corresponding to claim 3, in FIG. 1, the intermediate transfer member for transfer opposing roller 451A which corresponds to the transfer material outlet roller 41
The winding angle θ of No. 5 is 90 ° or less. In FIG. 1, the transfer counter roller 451A has to have a small diameter in order to ensure separability, and therefore, curling at the roller winding portion is likely to occur when left for a long time.

In the intermediate transfer member, a creep phenomenon occurs in a portion where curling is generated, and when this portion is applied to the nip portion at the time of primary transfer, toner is difficult to transfer to the creep portion. The image may appear as white bands.

According to the experiment, when the diameter of the transfer facing roller 451A is 20 mm, the image is not affected when the winding angle θ of the intermediate transfer member 415 is 90 ° or less.
However, it was found that when the winding angle θ is less than 15 °, the transfer material becomes difficult to separate from the intermediate transfer body (belt).

Therefore, in the case of the configuration of this example,
Since the winding angle θ of the intermediate transfer body 415 with respect to the transfer facing roller 451A is set to 15 ° to 90 °, the creep phenomenon of the intermediate transfer body does not easily occur in the winding section of the intermediate transfer body 415 with respect to the roller, and the transfer white of the creep section is not generated. You can prevent the omission.

Description of Claim 4 In claim 5, when the volume resistance value of the intermediate transfer member 415 is ρ in FIG. 1, ρ = 10 ⁹ Ωcm to 10 ¹³ Ω.
cm. The volume resistance value of the intermediate transfer member 415 is set to 10
It has been confirmed by experiments that when the volume resistance value is increased from ¹² Ωcm, the optimum range of the transfer current tends to be narrowed as the volume resistance value is increased.

Here, if the transfer current falls below the optimum range, transfer failure occurs, and if it rises, reverse transfer causes reverse transfer failure. Therefore, it is necessary to keep the transfer current within the optimum range. To keep the transfer current in the optimum range, it is easy to keep the transfer current in the optimum range, so that the transfer failure is less likely to occur.

The volume resistance value of the intermediate transfer member is 10 ¹² Ωcm.
However, there is still an optimum range of transfer current, which can be kept within a practically possible range. 10 ¹³ Ωcm
But it's not impossible. However, when it exceeds 10 ¹³ Ωcm, the optimum range does not exist. When the volume resistance value of the intermediate transfer body becomes high, the charges of the opposite polarity of the charges injected into the transfer material do not flow into the intermediate transfer body due to the ground, so the adhesion force between the intermediate transfer body and the transfer material weakens, which is optimal. The transfer current area is narrowed. Therefore, the volume resistance value of the intermediate transfer member is
When it is set to a high value exceeding 10 ¹³ Ωcm, it is considered that a transfer failure will occur. Conversely, ρ = 10
^If it is less than ⁹ Ωcm, a blurred image is generated during belt transfer (primary transfer) from the photosensitive drum to the intermediate transfer member.

Therefore, the two transfer opposing rollers 451
In order to perform the transfer at the stretched portion between A and 451B, the volume resistance value of the intermediate transfer member is 10 ⁹ Ωcm or more and 10 ¹³ Ωcm or less,
More desirably, the transferability can be stabilized by setting it to 10 ⁹ Ωcm or more and 10 ¹² Ωcm or less.

According to this example, since the volume resistance value of the intermediate transfer member is 10 ⁹ Ωcm or more and 10 ¹³ Ωcm or less,
The optimum range of the transfer current in the configuration of claim 1 can be sufficiently set, and a stable transfer state can be obtained.

[0075]

According to the present invention, high quality transfer performance and separation performance for a transfer material can be obtained.

[Brief description of drawings]

FIG. 1 is a front view illustrating a main part of an intermediate transfer member unit according to the present invention.

FIG. 2 is a partially enlarged front view illustrating an intermediate transfer member tension portion according to the present invention.

FIG. 3 is a table illustrating a relationship between a transfer material separating performance and a separating roller according to the present invention.

FIG. 4 is a front view illustrating the outline of an image forming apparatus suitable for implementing the present invention.

FIG. 5 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

415 Intermediate transfer body 451A Transfer facing roller (roller on the transfer material exit side) 451B Transfer facing roller

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Yukata 1-3-3 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. (72) Inventor Katsuji Watanabe 1-3-3 Nakamagome, Ota-ku, Tokyo No. 6 in Ricoh Co. Ltd. (72) Inventor Yuji Sawai 1-3-3 Nakamagome, Ota-ku, Tokyo No. 6 in Ricoh Co. Ltd. (56) Reference Japanese Patent Laid-Open No. 5-210294 (JP, A) Kaihei 5-281775 (JP, A) JP 3-196172 (JP, A) JP 59-104673 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15 / 16 G03G 15/01 114 G03G 15/14 101

Claims (4)

(57) [Claims] 1. A charger device provided with a belt-shaped intermediate transfer member stretched between a plurality of rollers as a means of an image forming process, and provided in a stretched portion of two adjacent rollers among the plurality of rollers. An image forming apparatus that transfers toner to a transfer material by corona discharge, wherein the transfer material is separated from the intermediate transfer body by a roller on the transfer material outlet side of the two adjacent rollers. , L is the distance between the two adjacent rollers
The image forming apparatus is characterized in that L = 10 mm to 40 mm . 2. The image forming apparatus according to claim 1, wherein D ≦ 5 mm to 20 mm, where D is the diameter of the roller on the transfer material outlet side. 3. The image forming apparatus according to claim 1, before
Serial out adjacent two rollers, a transfer material outlet of the roller
An image forming apparatus , wherein θ = 15 ° to 90 ° , where θ is the wrap angle of the intermediate transfer member . 4. An image forming apparatus according to claim 1, before
The image forming apparatus is characterized in that ρ = 10 ⁹ to 10 ¹³ Ωcm when the volume resistance value of the intermediate transfer member is ρ .