JP2000227727A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of cleaning defect by secondary transfer residual toner on an intermediate transfer belt or a negative ghost. SOLUTION: In image forming devices of full color for 4 colors provided with 4 units of image forming units A to D along the rotary direction of the intermediate transfer belt 1 (arrow R1 direction), the device is allowed to charge the secondary transfer residual toner by the charging roller 5, and to statically recover by a recovering drum 18b. In such a manner, since the secondary transfer residual toner on the intermediate transfer belt 1 can be excellently removed, the device is respectively prevented from the cleaning defect, the negative ghost or the like, and the occurrence of color mixture can be prevented even in the case of performing the toner re-use for respective image forming unit A to D.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus such as a copying machine and a laser beam printer.

[0002]

2. Description of the Related Art Among electrophotographic color image forming apparatuses, as a method particularly advantageous for speeding up, a single color image forming unit of yellow, magenta, cyan and, if necessary, black is provided by an intermediate transfer belt ( There has been known a method in which toner images of respective colors are arranged on a straight line along the moving direction of an intermediate transfer member, and image formation of toner images of respective colors is performed almost simultaneously (hereinafter, referred to as “tandem method”).

The tandem type image forming apparatus is classified into an intermediate transfer body type and a transfer / conveyance belt type depending on the transfer method.

First, in the case of the intermediate transfer type, the toner images of each color formed on the photosensitive drum of each single color image forming unit are sequentially primary-transferred onto the intermediate transfer body and superimposed on the intermediate transfer body. Thereafter, the plurality of toner images are collectively secondary-transferred onto a transfer material. The intermediate transfer body after the secondary transfer needs to be cleaned of toner remaining on the surface of the intermediate transfer body without being secondarily transferred to the transfer material (hereinafter referred to as “secondary transfer residual toner”) in preparation for the next image formation. .

As a cleaning method, there is a method of scraping toner with a blade, a fur brush, or the like. However, according to this method, the surface of the intermediate transfer member or the surface of the transfer belt is rubbed. There is a disadvantage that the life is shortened.

In recent years, toner particles have been reduced in particle size and made spherical due to reasons such as the reproducibility of thin lines and the improvement of transfer efficiency. However, these toners have been removed by cleaning using a blade or fur brush. It cannot be removed well.

Therefore, the secondary transfer residual toner is positively charged, for example, by a charging roller or a corona charger, and is then electrostatically attracted to a negatively charged photosensitive drum via a primary transfer nip portion. There is a method of collecting by a cleaning unit for cleaning the drum. This collection is performed simultaneously with the primary transfer to prevent a decrease in throughput. Hereinafter, such a cleaning method is referred to as “ICL method” or “ICL”. The charging means for the secondary transfer residual toner is referred to as "ICL means", and when a charging roller is used for this ICL means, this means "ICL means".
Roller ".

Next, according to the transfer / conveying belt system, first, after the transfer material is adsorbed on the transfer / conveying belt, the toner images of each color formed by each single-color image forming unit are directly transferred.
The toner images are formed by sequentially transferring and superimposing the toner images on a transfer material.

In the case of the transfer / conveying belt system, since the toner is entirely transferred onto the transfer material, the toner on the transfer / conveying belt does not become dirty. However, when a single color image forming unit forms a toner image on the photosensitive drum, a small amount of toner is developed over the entire non-image area (hereinafter, this situation is referred to as "fogging"), so that the transfer conveyance belt is soiled. Would. The cause of the fogging is that the toner charge amount when the toner is developed is controlled to be a certain value, but the toner includes a small toner charge amount, and this toner is developed in a non-image area. It is thought that it is transferred.

Further, when a jam (paper jam) occurs, the toner to be transferred to the transfer material is transferred to the transfer / transport belt, and the transfer / transport belt may be soiled.
For these reasons, it is common to install a transfer and transport belt cleaning device. The above ICL method is
The present invention is also applicable to this cleaning device.

[0011]

SUMMARY OF THE INVENTION However, ICL
The method has the following problems.

In the ICL system, the secondary transfer residual toner is
The toner is positively charged by a roller, and is collected on a photosensitive drum at a primary transfer nip portion, and at the same time, primary transfer is performed. At this time, if the amount of positive charge on the secondary transfer residual toner is weak, the force for electrically moving to the photosensitive drum is weakened, and the secondary transfer residual toner remains on the intermediate transfer member, resulting in poor cleaning. As a result, the secondary transfer residual toner appears on the next image and becomes a defective image.

Conversely, if the amount of the positive charge on the secondary transfer residual toner is too strong, the negatively charged toner originally transferred from the photosensitive drum to the intermediate transfer member is attracted to the positively charged secondary transfer residual toner and is exposed. The image returns to the position on the drum, and an image defect (hereinafter, referred to as “negative ghost”) occurs.

Further, for reasons such as space saving of the image forming apparatus and improvement of toner in recent years, the primary transfer residual toner on the photosensitive drum after the primary transfer has been collected by a blade or the like, stored in a waste toner container and discarded. Instead of using the toner, the method of sending the primary transfer residual toner to the developing container again for reuse (hereinafter referred to as “toner reuse”) has been increasing. When the toner is reused, the waste toner container becomes unnecessary.

The toner reuse system includes a system in which the primary transfer residual toner on the photosensitive drum after the primary transfer is collected by a blade or the like and conveyed into a developing container, or a method in which the primary transfer residual toner is charged to a certain amount of electric charge and the developing unit And developing again or collecting in a developing container.

When the above-mentioned ICL method is applied to an image forming apparatus adopting this toner reuse, the ICL
In the image forming unit where the secondary transfer residual toner is collected, a so-called “color mixture” in which colors other than the desired color are developed
The problem occurs. This is because the secondary transfer residual toner on the intermediate transfer member has four colors, and the secondary transfer residual toner is collected by the image forming unit and developed again.

Further, in the case of using a transfer / conveying belt in a tandem type image forming apparatus, there is a problem that the throughput is reduced when the ICL type is used. This is because in the ICL method, the secondary transfer residual toner is collected on the photosensitive drum, and therefore, in order to clean the transfer / transport belt, the transfer / transport belt needs to be rotated by one full turn, during which image formation cannot be performed. That is the problem. This is because, during image formation, the transfer material is present between the photosensitive drum and the transfer / transport belt, so that the untransferred toner on the surface of the transfer / transport belt cannot be moved to the photosensitive drum, and the simultaneous transfer cleaning cannot be performed. is there.

The present invention has been made in view of the above circumstances, and when performing tandem type image forming apparatus using an intermediate transfer member by ICL type cleaning, occurrence of image defects such as defective cleaning and negative ghost. It is another object of the present invention to provide an image forming apparatus capable of preventing the occurrence of color mixture even when toner is reused.

Another object of the present invention is to prevent the throughput from lowering when performing ICL type cleaning in a tandem type image forming apparatus using a transfer / transport belt.

[0020]

According to a first aspect of the present invention, there is provided an image forming apparatus comprising: a plurality of image forming units arranged along a moving direction of an intermediate transfer member; After the toner images formed on the respective image carriers are sequentially primary-transferred to the intermediate transfer members at respective primary transfer portions and the toner images are superimposed on the intermediate transfer members, the toner images are superimposed on the intermediate transfer members. An image forming apparatus that collectively secondary-transfers a plurality of toner images onto a transfer material at a secondary transfer unit, wherein a charging unit that charges secondary transfer residual toner remaining on the intermediate transfer body after secondary transfer; And a collection unit for electrostatically collecting the secondary transfer residual toner after charging.

According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the toner has a shape factor SF1 of 1
00 to 140, and the shape factor SF2 is 100 to 150.

According to a third aspect of the present invention, there is provided the first or second aspect.
In the above image forming apparatus, the primary transfer residual toner remaining on the image carrier after the primary transfer is returned to a developing device of the image forming unit, and is used again for development.

According to a fourth aspect of the present invention, a plurality of image forming units are provided along a moving direction of a transfer / conveying body for carrying / transferring a transfer material, and the image forming units are formed on the respective image carrying members. In the image forming apparatus in which the transferred toner images are sequentially transferred to the transfer material on the transfer conveyance body at the respective primary transfer units and the toner images are superimposed on the transfer body, the transfer remaining on the transfer conveyance body is performed. A charging unit for charging the residual toner; and a collection unit for electrostatically collecting the transfer residual toner after charging.

According to a fifth aspect of the present invention, in the image forming apparatus of the fourth aspect, the toner has a shape factor SF1 of 1
00 to 130 and the shape factor SF2 is 100 to 130.

The present invention according to claim 6 is based on claims 1, 2,
In the image forming apparatus according to any one of 3, 4, or 5, the collection unit includes a grounded collection member that collects the secondary transfer residual toner from the intermediate transfer body or the transfer conveyance body.
It is characterized by the following.

The present invention according to claim 7 is based on claims 1, 2,
In the image forming apparatus according to any one of 3, 4, and 5, the collection unit is configured to collect the secondary transfer residual toner from the intermediate transfer body or the transfer conveyance body, and a collection member charging unit configured to charge the collection unit. And having the following.

The present invention according to claim 8 is directed to claim 6 or 7.
In the above image forming apparatus, the collection unit includes a cleaning member that scrapes off the secondary transfer residual toner from the collection member.

[0028]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 shows an example of an image forming apparatus according to the present invention. The image forming apparatus shown in FIG.
This is a full-color four-color image forming apparatus of a tandem type and an intermediate transfer body type, and FIG. 1 is a longitudinal sectional view showing a schematic configuration thereof.

The image forming apparatus shown in FIG.
Image forming units A, B, C, and D are provided. These image forming units A to D are magenta,
The toner images of yellow, cyan, and black are formed.

The image forming units A to D have electrophotographic photosensitive members (hereinafter, referred to as "photosensitive drums") 11a to 11d for forming toner images of respective colors as image carriers. Further, the image forming units A to D include primary chargers 12a, 12b, 12c, 12d that uniformly charge the surfaces of the photosensitive drums 11a to 11d to a predetermined polarity and a predetermined potential.
Scanners (exposure devices) 13a, 13b, 13c, 13 for exposing the surface of each charged photosensitive drum to form an electrostatic latent image
d, developing devices 14a, 14b, 14c and 14d for attaching toner to the electrostatic latent image to develop the toner image, primary transfer chargers 15a and 15b for primarily transferring the toner image on the photosensitive drum to the intermediate transfer belt 1, 15c, 15d, toner remaining on photosensitive drum after primary transfer (primary transfer residual toner)
Cleaning devices 16a, 16b, 16c for removing
16d. The intermediate transfer belt 1 described above as an intermediate transfer member forms a nip in contact with the photosensitive drums 11a~11d in respective primary transfer portion T _1.

The intermediate transfer belt 1 has a volume resistivity of 10 ⁶
It is preferably 10 to 10 ¹² Ωcm, urethane resin, fluorine resin, nylon resin, polyimide resin, or elastic material such as silicone rubber or hydrin rubber, or by dispersing carbon or conductive powder in these. A resistance-adjusted one or the like can be used. In this embodiment, the volume resistivity is 10 ⁷ by dispersing carbon in hydrin rubber.
10 ¹³ Ω on the surface of the 0.5 mm thick base layer adjusted to Ωcm
The intermediate transfer belt 1 is constituted by providing a surface layer having a thickness of 20 μm with a fluorine resin of cm.

The intermediate transfer belt 1 is stretched over three rollers of a drive roller 1a, a separation roller 1b, and a support roller 1c, and travels (rotates) in the direction of arrow R1 as the drive roller 1a rotates in the direction of arrow. ). The tension of the intermediate transfer belt 1 when being stretched over these rollers depends on the material, but is set to a tension such that the elongation percentage is within 1%, and breakage or permanent distortion occurs in the intermediate transfer belt 1. It is desirable not to do so. In the present embodiment,
It is set so that a tension (load) of 150 N (Newton) is applied.

Each of the primary transfer portions T ₁ is provided with a primary transfer roller 15 a, 15 b, 1, 1, or 2, which is coated with an elastic material having a medium resistance (the actual resistance in forming the nip when 1 kV is applied is 10 ⁶ to 10 ¹⁰ Ω).
5c, 15d are photosensitive drums 11a, 11b, 11c, 1
1d and the intermediate transfer belt 1 are interposed therebetween.

The secondary transfer roller 19 is obtained by coating a core metal with an EPDM foam layer having a medium resistance.
The intermediate transfer belt 1 and the transfer material are disposed at a position facing the separation roller 1b.

Next, the operation of the image forming apparatus having the above configuration will be described.

The photosensitive drum 11a rotates in the direction of the arrow, is uniformly charged by the primary charger 12a, and is charged by the laser beam from the scanner 13a modulated by the image information signal sent from the host computer.
a) to form an electrostatic latent image. The intensity of the laser beam and the irradiation spot diameter are appropriately set depending on the resolution of the image forming apparatus and the desired image density, and the surface of the photosensitive drum 11a is irradiated with the laser beam at the light portion potential _VL (about -1).
00V), the dark portion potential V _D (about -700 V) when the other portion is charged by the primary charger 12a is formed to form an electrostatic latent image. The electrostatic latent image is stored on the photosensitive drum 11
The rotation of a reaches the developing unit facing the developing device 14a,
Toner charged to the same polarity (minus polarity in the present embodiment) is attached to the bright portion and developed as a toner image. In full-color image formation similarly toner image on the photosensitive drum 11a~11d corresponding to respective colors are formed, respectively intermediate transfer belt 1 at the primary transfer portion T ₁
The primary-transferred toner images of the four colors are sequentially superimposed on the intermediate transfer belt 1. Each primary transfer portion T formed by the intermediate transfer belt 1 and the photosensitive drums 11a to 11d
_{In FIG. 1} , an electric field formed in the primary transfer portion T ₁ by a voltage (+100 to +1000 V) having a polarity opposite to that of the toner applied to the conductive primary transfer rollers 15 a to 15 d in contact with the back surface of the intermediate transfer belt 1, Each photosensitive drum 11a
11d is primarily transferred onto the intermediate transfer belt 1. The intermediate transfer belt 1 is supported on the intermediate transfer belt 1 in a state in which toner images of four colors are superimposed at the stage that has passed through the primary transfer portion T ₁ of the photosensitive drum 11d, the primary transfer process is completed. On the other hand, the photosensitive drums 11a to 11d after the primary transfer of the toner image are transferred to the cleaning device 1 by the primary transfer residual toner remaining on the surface without being transferred to the intermediate transfer belt 1.
After being collected by 6a to 16d, it is subjected to the next image forming step. The toner collected by the cleaning devices 16a to 16d is transferred to a conveying device (not shown) such as a screw.
Is returned into the respective developing devices 14a to 14d by
It is reused for subsequent development.

As described above, the four color toner images superimposed on the intermediate transfer belt 1 are secondarily transferred onto a transfer material P such as paper. The transfer material P is fed by the sheet conveying apparatus from the paper cassette (not shown), it is inserted into the secondary transfer portion T _2. At this time, a voltage (+1 kV to +6 kV) having a polarity opposite to that of the toner on the intermediate transfer belt 1 is applied to the secondary transfer roller 19.
Is applied, so that the four color toner images on the intermediate transfer belt 1 are secondarily transferred collectively on the intermediate transfer material P.

The transfer material P after the secondary transfer carries an unfixed toner image of four colors and is conveyed to the fixing device 17. Transfer material P
Here, the toner images of four colors are melted and mixed by being heated and pressed, and fixed on the surface as a color image. On the other hand, the intermediate transfer belt 1 after the secondary transfer is left on the surface to remove the secondary transfer residual toner, and is prepared for the next image formation. This point will be described later in detail.

Next, the toner used in the present embodiment will be described.

In this embodiment, the developer contains 5 to 30% by weight of a low softening point substance and has a shape factor SF.
1 (described later) is 110 to 120, and the shape factor SF2 (described later)
Is 100 to 110, and the particle size produced by the suspension polymerization method is 5
A substantially spherical non-magnetic one-component fine particle polymerized toner having a diameter of about 7 μm is used.

FIG. 2 (longitudinal sectional view) shows a schematic configuration of the polymerized toner. As shown in the figure, the polymerized toner is spherical in production. In this embodiment, the core 2a contains an ester-based wax, the resin layer 2b is made of styrene-butylene acrylate, and the surface layer 2c is made of a polymerized toner having a structure of styrene-polyester. Its specific gravity is about 1.05. The reason for the three-layer structure is that the wax is included in the core 2a to obtain an effect of preventing offset in the fixing step, and the provision of the surface layer 2c in the resin layer 2b aims to increase charging efficiency. That's why. In actual use, oil-treated silica is externally added to stabilize the charge amount.

Here, the shape factor SF1 and the shape factor S
F2 will be described.

As shown in FIG. 3, the shape factor SF1 is a numerical value indicating the ratio of the roundness of the shape of the shape material (in this embodiment, “toner”), and is obtained by projecting the shape material on a two-dimensional plane. It is expressed by the value obtained by dividing the square of the maximum length (MXLNG) of the elliptical figure formed by the figure area (AREA) and multiplying by (100π / 4). That is, the shape factor SF1 is given by the following equation: SF1 = {(MXLNG) ² / (AREA)} × (10
0π / 4). In the case of a perfect sphere, the shape factor SF1 is a minimum of 100, and the smaller the numerical value, the closer to a sphere.

As shown in FIG. 4, the shape factor SF2 is a numerical value indicating the ratio of irregularities of the shape of the shape material, and is a figure perimeter (PERI) formed by projecting the shape material on a two-dimensional plane.
Is divided by the area of the figure (AREA) to obtain (100/4
π). That is, the shape factor SF
2 is the following equation: SF2 = {(PERI) ² / (AREA)} × (100
/ 4π). In the case of a perfect sphere, the shape factor SF2 is 100, which is the minimum, and the smaller this numerical value is, the smaller the unevenness of the shape is.

The shape factors SF1, S described in the present embodiment
In F2, a toner image was randomly sampled 100 times by FE-SEM (S-800) of Hitachi, Ltd., and the image information was analyzed at 200 times by an image analyzer (LUSEX3) manufactured by Nicole via an interface. , Calculated from the above equation.

Next, the cleaning of the intermediate transfer belt 1 after the transfer of the toner image onto the transfer material P, which is a characteristic part of the present invention, will be described with reference to FIGS.

FIG. 5 is a longitudinal sectional view of the ICL roller 5 as a charging means for charging the secondary transfer residual toner. The cored bar 5c was coated with a conductive rubber layer 5b in which carbon was dispersed in EPDM rubber, and the surface of the conductive rubber layer 5b was coated with a 200 μm-thick surface layer 5a of a fluorine-based resin. The actual resistance value of the roller was measured by pressing the ICL roller 5 against a metal drum to form a contact nip having a width of 3 mm, and applying a DC voltage of 1000 V between the metal drum and the cored bar 5c. . It was 5 × 10 ⁸ Ω.

The polarity of the voltage applied to the ICL roller 5 may be either positive or negative, but it is preferable to apply a voltage having the same polarity as that of the toner. This is because, when a voltage of the opposite polarity is applied, the secondary transfer residual toner adheres to the
This is because the charging performance of the CL roller 5 decreases. Also,
The AC component may be superimposed on the voltage applied to the ICL roller 5 to uniformly charge the secondary transfer residual toner.

At the downstream side of the ICL roller 5 along the rotation direction of the intermediate transfer belt 1 (the direction of arrow R1), a collecting means 18 is provided. The collecting means 18 has a collecting drum 18b as a collecting member. The collection drum 18b
An aluminum cylinder having a diameter of 30 mm was used to make GND (ground). The surface of the aluminum cylinder is preferably coated with a urethane-based resin, a fluorine-based resin, a nylon-based resin, or a polyimide resin in order to ensure releasability from the toner. In the present embodiment, a fluorine-based resin having a thickness of 20 μm is used. Coated. The secondary transfer residual toner attached to the collection drum 18b is scraped off by a urethane rubber cleaning blade 18a as a cleaning member, and the scraped-off secondary transfer residual toner is collected in a container 18c.

In order to confirm the effect of the present embodiment, the cleaning failure and the absence of the recovery drum are determined depending on whether or not the recovery drum is provided.
Negative ghost and color mixing were evaluated. The evaluation of the cleaning failure is performed on a solid white image after one blue solid image is output, and the evaluation of a negative ghost is performed on a magenta solid image after one blue solid image is output.
The evaluation of the color mixture was performed on a magenta solid image after 1000 blue solid images were output. Since the levels of cleaning failure, negative ghost, and color mixture change depending on the voltage applied to the ICL roller 5, the applied voltage was changed from 0 kV to -3 kV in 0.5 kV steps. The image evaluation was performed by displaying an image in a low-temperature and low-humidity (temperature of 10 ° C., humidity of 15%) environment having a low level of negative ghost. The results are shown in FIG. 8, with the level being good as 悪 い, the poor level as × and the middle as △.

As can be seen from the figure, there is no applied voltage that satisfies both cleaning failure and negative ghost at the same time without the recovery drum, but no negative ghost occurs with the recovery drum. The level of cleaning failure is improved from a low (absolute value) applied voltage, and no color mixing occurs.

As described above, in the image forming apparatus that performs the cleaning of the ICL system using the intermediate transfer body in the tandem system, the provision of the collection drum 5 can effectively prevent the cleaning failure, the negative ghost, and the color mixture. did it.

Second Embodiment FIG. 6 shows an image forming apparatus according to a second embodiment. FIG. 1 is a longitudinal sectional view showing the schematic configuration. The same members and the like as the members and the like shown in FIG. 1 are denoted by the same reference numerals, and the duplicate description will be omitted.

In the second embodiment, as shown in FIG. 6, a charging roller (collecting member charging means) 18d is provided adjacent to the collecting drum 18b, and the surface of the collecting drum 18b is charged by the charging roller 18d. And

As the charging roller 18d, the same charging roller as that for charging the photosensitive drum is used.
A bias having a polarity opposite to that of the ICL roller 5 is applied to the surface.
In this embodiment, since the potential contrast between the surface of the intermediate transfer belt 1 and the surface of the collection drum 18b can be increased, the force for attracting the secondary transfer residual toner on the intermediate transfer belt 1 to the collection drum 18b is increased. Can be. Accordingly, there is an advantage that even when the voltage applied to the ICL roller 5 is low, the cleaning property of the intermediate transfer belt 1 can be ensured.

In this embodiment, the charging roller 18d is used to charge the surface of the collection drum 18b, but a corona charger may be used instead. The effect in this case is the same.

Third Embodiment FIG. 7 shows an image forming apparatus according to a third embodiment. FIG. 1 is a longitudinal sectional view showing the schematic configuration. 1 and 6 are denoted by the same reference numerals, and redundant description will be omitted.

The third embodiment is characterized in that, as shown in FIG. 7, cleaning by the ICL method is applied to an image forming apparatus using a transfer conveyance belt 7b as a transfer conveyance body.

After the transfer material P is attracted to the transfer / conveying belt 7b by the attracting roller 7a, a toner image is similarly formed by the photosensitive drums 11a to 11d corresponding to each color.
Are sequentially transferred onto the transfer material P at the transfer portion T _3, toner images of four colors on the transfer material P is superimposed.

The transfer conveyance belt 7b has a volume resistivity of 10
It is preferably ⁷ to 10 ¹¹ Ωcm, and urethane-based resin, fluorine-based resin, nylon-based resin, polyimide resin, or elastic material such as silicone rubber or hydrin rubber, or carbon or conductive powder dispersed therein. Then, a resistance-adjusted one or the like can be used. Of course, a two-layer configuration or the like may be used.

The transfer / conveyance belt 7b includes a driving roller 1a,
It is stretched over three rollers of a support roller 1c and a tension roller 7c. The tension of the transfer / transport belt 7b when it is stretched, although it depends on the material, is preferably set so that the elongation rate is within 1% so that the transfer / transport belt does not break or have permanent distortion. . In the present embodiment, the tension (load) is set to 150 N (Newton).

In each transfer section T ₃ , the core metal is set to a medium resistance (the actual resistance in the nip formation when 1 kV is applied is 10 ⁶ to 10).
Transfer rollers 8a, 8b, 8 coated with an elastic material of ¹⁰ Ω)
Reference numerals c and 8d are arranged so as to sandwich the transfer conveyance belt 7b together with the photosensitive drums 11a to 11d. Transfer roller 8a-
8d, a voltage having a polarity opposite to that of the toner (+100 to
(+1000 V), the toner images on the photosensitive drums 11a to 11d are sequentially transferred onto the transfer material P by the electric field formed in the transfer portion, and the four color toner images are superimposed directly on the transfer material P. These toner images are transferred to the fixing device 17.
Is fixed on the transfer material P.

With the above configuration, in the tandem type image forming apparatus using the transfer / conveyance belt 7b, the transfer / conveyance belt 7b can be used without lowering the throughput by the ICL method.
Cleaning, and the conventional blade,
Compared with a cleaning method using a fur brush or the like, the transfer / conveying belt 7b can have a longer life by reducing rubbing. Further, even when a small size and spherical toner is used, the secondary transfer residual toner can be reduced. Since the collection is performed electrostatically instead of mechanically, the cleaning property can be improved.

[0065]

As described above, according to the present invention,
IC for tandem type image forming apparatus using intermediate transfer body
When performing the L-type cleaning, it was possible to prevent the occurrence of image defects such as cleaning defects and negative ghosts, and also to prevent the occurrence of color mixing when performing toner reuse.

When performing ICL cleaning in a tandem type image forming apparatus using a transfer conveyor (transfer conveyor belt), the transfer conveyor can be cleaned without lowering the throughput. As compared with a cleaning method using a fur brush or the like, the rubbing of the transfer conveyance body is reduced, so that the life can be extended.

Further, when the above-mentioned intermediate transfer member is used,
Regardless of the use of the transfer carrier, when using small-sized, spherical toner, the secondary transfer residual toner is not collected mechanically but is collected electrostatically. Can be planned.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to a first embodiment.

FIG. 2 is a longitudinal sectional view of the toner.

FIG. 3 is a diagram illustrating a shape factor SF1.

FIG. 4 is a view for explaining a shape factor SF2.

FIG. 5 is a longitudinal sectional view showing a configuration of an ICL roller.

FIG. 6 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to a second embodiment.

FIG. 7 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to a third embodiment.

FIG. 8 is a diagram illustrating an effect of the collection drum according to the first embodiment.

[Explanation of symbols]

Reference Signs List 1 Intermediate transfer member (intermediate transfer belt) 5 Charging means (ICL roller) 7b Transfer transfer member (transfer transfer belt) 11a to 11d Image carrier (photosensitive drum) 12a to 12d Primary charger 13a to 13d Exposure device (scanner) 14a １４14d developing device 15a〜15d primary transfer charger 16a〜16d cleaning device A, B, C, D image forming unit P transfer material T ₁ primary transfer portion T ₂ secondary transfer portion T ₃ transfer portion

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kenichi Iida 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H032 AA05 AA15 BA01 BA05 BA09 BA27 BA30 CA13

Claims (8)

[Claims] A plurality of image forming units are provided along a moving direction of an intermediate transfer body, and a toner image formed on each image carrier of each of the image forming units is transferred to a primary transfer unit at each of the primary transfer units. After the primary transfer is sequentially performed on the intermediate transfer body and the toner images are superimposed on the intermediate transfer body, the plurality of toner images on the intermediate transfer body are collectively secondary-transferred onto the transfer material at the secondary transfer unit. A charging unit for charging the secondary transfer residual toner remaining on the intermediate transfer body after the secondary transfer, and a collection unit for electrostatically recovering the charged secondary transfer residual toner. An image forming apparatus comprising: 2. The toner has a shape factor SF1 of 100.
2. The image forming apparatus according to claim 1, wherein the shape factor SF2 is from 100 to 140, and the shape factor SF2 is from 100 to 150. 3. 3. The image forming apparatus according to claim 1, wherein the primary transfer residual toner remaining on the image carrier after the primary transfer is returned to a developing device of the image forming unit and used again for development. Image forming apparatus. 4. A plurality of image forming units are arranged along the direction of movement of a transfer conveyance body that carries and conveys a transfer material, and a toner image formed on each image carrier of each of these image formation units is transferred to each of the image formation units. In an image forming apparatus for sequentially transferring a transfer material on the transfer carrier at a primary transfer unit and superimposing a toner image on the transfer body, a charging unit for charging transfer residual toner remaining on the transfer carrier An image forming apparatus, comprising: a collection unit configured to electrostatically collect the transfer residual toner after being charged. 5. The toner has a shape factor SF1 of 100.
5. The image forming apparatus according to claim 4, wherein the shape factor SF2 is 100 to 130. 6. 6. The collection unit according to claim 1, wherein the collection unit includes a grounded collection member that collects the secondary transfer residual toner from the intermediate transfer body or the transfer conveyance body. 6. The image forming apparatus according to claim 4, or 5. 7. The collection unit includes a collection member that collects the secondary transfer residual toner from the intermediate transfer body or the transfer conveyance body, and a collection member charging unit that charges the collection unit. The image forming apparatus according to claim 1, 2, 3, 4, or 5, wherein 8. The image forming apparatus according to claim 6, wherein the collection unit includes a cleaning member that scrapes off the secondary transfer residual toner from the collection member.