JP2852784B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus, and more particularly to an image forming apparatus having a blade cleaning device.

[Conventional technology]

Many methods and apparatuses have been proposed for obtaining a color image using electrophotography. For example, as disclosed in JP-A-61-100770, a latent image is formed and developed on a photosensitive drum as an image carrier in accordance with the number of separated colors of a document image.
There is a method in which a multicolor image is formed on a transfer drum by transferring to a transfer drum each time of development and then transferred to a transfer material to obtain a color copy. In the apparatus according to this method, it is necessary to provide a transfer drum having a size capable of transferring one image on the peripheral surface in addition to the photosensitive drum, and the apparatus has a large and complicated structure. Inevitable.

Further, as disclosed in, for example, JP-A-61-149972, a latent image is formed and developed in accordance with the number of separated colors of a document image on a photosensitive drum, which is an image carrier, and transferred at each development. This is a method of obtaining a multicolored color copy by transferring onto a material.
In this method, it is difficult to accurately superimpose multi-color images, and a high-quality color copy cannot be obtained.

Further, there is a method in which a latent image is formed on the photosensitive drum in accordance with the number of separated colors of the original image and development with color toner is repeated, and a color image is obtained by superimposing and transferring color toner on the photosensitive drum. The basic process of forming a multicolor image is described in Japanese Patent Application Laid-Open Nos. 60-75850 and 60-76766 by the present applicant.
Nos. 60-9556, 60-95458 and 60-158475. In such a multi-color image forming apparatus that obtains a color image by superposition development, a high-quality color image with little color shift can be obtained.

In the image forming apparatus, after a multicolor image is formed by superposition development, a toner image formed on a photosensitive drum is transferred onto a transfer sheet, and the remaining toner is cleaned to form a next image. Preparations are made.

Various methods and apparatuses have been proposed as the cleaning apparatus. Recently, however, a flat cleaning blade 19A as shown in FIG. A cleaning edge e, which is an abutting portion of the end portion, is pressed against the photosensitive drum 10 as an image carrier to remove residual toner;
Blade cleaning devices are widely used.

As shown in FIG. 6 (a), the blade cleaning device includes a counter type in which a supporting portion 19C of a cleaning blade 19A (hereinafter, simply referred to as a blade) is positioned on the downstream side with respect to the rotation of the photosensitive drum 10; As shown in FIG. 6 (b), there is a trail type in which the support portion 19C of the blade 19A is positioned on the upstream side. Compared to the trail type, the counter type has slightly better cleaning efficiency, can reduce the load on the image carrier at the contact point, and has less fluctuation in the rotation speed of the image carrier. Often.

In FIG. 6A, θ is the contact angle between the tangent of the contact portion of the blade 19A of the photosensitive drum 10 and the angle formed by the blade 19A,
t is the thickness of the blade 19A, 1 is the support 19C of the blade 19A.
Free length from to the tip.

Although the blade 19A is always kept in pressure contact with the photoconductor drum 10, for example, in the above-described apparatus for performing the overlay development, the blade 19A is separated from the photoconductor drum 10 during formation of a plurality of toner images. After the transfer step is completed, it is necessary to perform cleaning by pressure bonding, and to release the pressure when cleaning is completed.

[Problems to be solved by the invention]

During the cleaning operation by pressing the blade 19A against the photoconductor drum 10, the portion vibrates and collides irregularly with the photoconductor drum 10 (this is referred to as "bounding"). Of the image carrier (abutting portion becomes scrambled) or scratches on the surface of image carrier 10. This is because, in the apparatus for performing the overlay development, the blade 19A is constantly pressed and pressed.
Since the release is performed, the above-described bounding is likely to occur, and it is also likely to occur when the blade 19A performs the reversal development with the counter type.However, it also occurs in a normal image forming apparatus, and particularly in the width of the photosensitive drum 10. On the other hand, when the size of the transfer material is small and a large number of continuous copies are made in this state, there is a problem that the occurrence rate of such bounding is high.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus capable of solving these problems, preventing occurrence of bounding, and performing good cleaning over a long period of time.

[Means for solving the problem]

The above object is to transfer the toner image superimposed on the image carrier by repeating the cycle of charging, image exposure and development a plurality of times to the transfer material, and to remove the residual toner remaining on the image carrier after the transfer. In an image forming apparatus that performs cleaning by pressing a cleaning blade that has been separated from an image carrier against an image carrier, at least one of a plurality of cycles in at least a main scanning direction in a plurality of cycles. The image forming apparatus is characterized in that a toner image is formed at least outside the image width in the main scanning direction.

〔Example〕

Hereinafter, an experimental example on which the present invention is based will be described with reference to the drawings, and then an example of the present invention will be described.

FIG. 3 is a configuration diagram showing a bounding experiment apparatus. In the experimental apparatus, a cleaning device 19 having a charger 14, a charge erasing lamp 15 composed of a red LED, a blade 19A, a toner collecting roller 19B, and the like is arranged on the periphery of the photosensitive drum 10.

The relationship between the charging state of the photosensitive drum 10 and the occurrence of bounding was tested under the following conditions using the above apparatus.

Experimental conditions Material of blade 19A: urethane rubber hardness 70 ゜ Contact angle θ: 14 ゜ Counter pressure contact load (component force in the direction perpendicular to the photoreceptor surface at the tip of blade 19A) 18g / cm Shape of blade 19A (thickness t) × Free length 1) ... 4 types of 2 × 8, 2 × 10, 2 × 12, 3 × 10 Photoconductors: 2 types of organic photoconductors (OPC) and Se-Te type photoconductors Toner: Early in the experiment Replenishment / adhesion of toner onto photoreceptor Experimental result: The results were almost independent of the shape of blade 19A and the type of photoreceptor, and were almost equal in each case.

(A) Charging of the photosensitive drum 10; when reaching the cleaning device 19 at about -500 V, bounding occurs around 500 copies.

(B) Charging of the photosensitive drum 10; When the portion where the pressure of the blade 19A starts to be pressed and the portion where the blade 19A is released from the state of (A) are discharged to about -50V, bounding occurs at 15,000 copies or more.

(C) Charge of the photosensitive drum 10; when the entire area reaching the cleaning device 19 is discharged to about -50 V, bounding occurs at 25,000 copies or more.

In addition, in the state of (B), 15 mg of toner T
Was supplied uniformly over the entire width (approximately 300 mm) of the blade 19A and the toner T was always present at the tip of the blade 19A, no bounding occurred even with 30,000 copies or more.

Further, when the toner T at the tip of the blade 19A was intentionally removed using the above-described experimental apparatus and an experiment was conducted on occurrence of bounding, bounding occurred in one copy under any of the experimental conditions.

As described above, the bounding occurrence rate is related to the charging of the photosensitive drum 10 and the presence or absence of toner at the tip of the blade 19A. It was found that when toner T was present at the tip of blade 19A, almost no bounding occurred.

Further, the toner T adhering to the tip of the blade 19A
The following experiment was conducted to see the relationship between the flight of the photoconductor drum 10 and the charge of the photoconductor drum 10.

FIG. 4 is a side view showing an experiment apparatus for flying toner.
In the figure, e is a cleaning edge that comes into contact with the photosensitive drum 10 at the tip of the blade 19A, and p is an insulating layer A that imitates a photosensitive layer made of polyethylene terephthalate (PET).
(Thickness: 75 μm) is a pseudo photosensitive plate spread on a grounded conductive metal plate M, and d is the distance between the cleaning edge e and the surface of the pseudo photosensitive plate p.

With this experimental apparatus, the surface of the pseudo photosensitive plate p was increased by +1200
When charged to V, the relationship between the number of the negatively charged toner T flying and moving from the cleaning edge e to the pseudo photosensitive plate p and the distance d was experimentally determined.

As a result, as shown in FIG. 5, the number of moving toner particles increases as the distance d decreases. The number on the vertical axis in FIG. 5 is the number of toners T moved to the area of 100 × 100 μm on the pseudo photosensitive plate p. This is because the Coulomb force acts on the toner T due to the electric charge on the surface of the photosensitive drum 10 and the toner T
If the charge of the opposite polarity, move toward the photoconductor drum 10, if the same polarity, move in the opposite direction to the photoconductor drum 10,
This indicates that the greater the Coulomb force, the greater the decrease in the toner T at the cleaning edge e.

According to the above experiment, when the toner T is present at the cleaning edge e, the toner T acts as a lubricant and the bounding is unlikely to occur, but the toner T decreases and the toner T attached to the cleaning edge e disappears. It is thought that bounding occurs easily. As a result, as shown in FIG. 7, when the recording paper is small in size relative to the width of the photoreceptor drum 10, the toner T is applied to the outside n of the image area 21 when copying is continuously performed in this state. It can be understood that the occurrence of the bounding becomes high in this portion because the does not exist.

FIG. 1 is a block diagram showing an embodiment of the present invention, in which reversal development is performed. In the figure, 1 is an image reading unit, 2 is a laser writing unit, and 3 is an image reproducing and recording unit, which forms a color image by the following process.

In the image reading unit 1, a document stored on a document table is illuminated by a reading optical system that moves in a horizontal direction in synchronization with the rotational peripheral speed of a photosensitive drum 10 serving as an image carrier.
The light is scanned and the reflected light is guided to a lens reading unit including a lens, a color separation prism or a color filter, a color CCD, and the like. The reflected light of the document is converged by the lens and is imaged on a light receiving surface of a CCD which is a light receiving element.

For example, the image signals of B, G, and R output from the color CCD are subjected to processing such as color correction in an image information processing unit, and the color signals subjected to color correction according to the colors of the Y, M, and C toners T are output. And output to the laser writing unit 2 as an exposure unit.

In the laser writing unit 2, the laser beam L generated by the semiconductor laser is rotationally scanned by the rotating polygon mirror, the optical path is bent by the mirror via the fθ lens, and the electric charge is applied in advance by the charger 14 as the charging means. The exposed surface of the photosensitive drum 10 is scanned and exposed.

When the scanning is started, the modulation of the laser beam L by the first color signal is started, and the modulated laser beam L scans the peripheral surface of the photosensitive drum 10. Accordingly, an electrostatic latent image for the first color is formed on the peripheral surface of the photosensitive drum 10 by the main scanning by the laser beam L and the sub-scanning by the rotation of the photosensitive drum 10. This latent image is reversely developed by a developing unit 16 loaded with, for example, yellow (Y) toner as a developing unit, to form a visible toner image. The obtained toner image, while being held on the photosensitive drum 10, passes below the cleaning device 19, which is a cleaning means separated from the peripheral surface of the photosensitive drum 10, and enters the next copy cycle.

In the next copy cycle, the photosensitive drum 10 is
And the second color signal output from the image information processing unit is input to the writing unit 2 and written on the peripheral surface of the photosensitive drum 10 in the same manner as in the case of the first color signal described above. Is performed to form a latent image. This latent image is reversal-developed by a developing device 17 loaded with, for example, magenta (M) toner T as a second color. The magenta (M) toner image is formed so as to overlap the already formed yellow (Y) toner image.

The developing device 18 is a developing device having cyan (C) toner, and forms a cyan (C) toner image on the photosensitive drum 10 based on an image signal generated by an image information processing unit.
DC and AC bias voltages are applied to the developing sleeves of these developing units 16, 17, and 18, and the two-component developer causes
The non-contact development in which the developing sleeve does not contact the photosensitive drum 10 is performed.

The color toner image formed on the peripheral surface of the photosensitive drum 10 in this manner is transferred from a paper cassette 40 by a paper feed roller 41 and a registration roller 42 to a transfer unit 43 provided as a transfer unit. The image is transferred onto a recording paper P as a material. The recording paper P on which the color toner image has been transferred is separated by a separator.
The transfer belt is separated from the photosensitive drum 10 by 44
The toner image is conveyed to the fixing device 46 via the fixing device 45, and the toner image is fixed.

On the other hand, the blade 19A of the cleaning device 19 contacts the photosensitive drum 10 from which the recording paper P is separated by its peripheral surface to remove the remaining toner T, and after that, is separated from the drum peripheral surface again. The process for forming a new color image is started.

In the image forming apparatus of the present invention, the photoconductor drum is irradiated with the laser beam L outside the copy image area for each copy.
A controller is formed so as to form a fine line latent image which is orthogonal to the rotation direction of the blade 10 and approximates the width of the blade 19A, and develops this to form a fine line toner image 20 as shown in FIG. 2 (a). CPU
The program is built in. The fine line toner image 20 may be any of cyan (C), magenta (M), and yellow (Y). Thus, an appropriate amount of the toner T is supplied to the cleaning edge e. The supply of the toner T need not be performed for each copy, but may be performed intermittently, for example, for every 100 copies. Further, the toner to be supplied to the cleaning edge e may be only outside the image width as shown in FIG. 2 (b).

In the first embodiment described above, an image forming apparatus in which reversal development is performed is described. In the case where the cleaning blade 19A is repeatedly pressed and released from the photosensitive drum 10 to easily cause bounding. By forming the thin line toner image 20 outside the image area, toner is supplied to the tip of the cleaning blade 19A to prevent occurrence of bounding.

Further, in an image forming apparatus that transfers a toner image via a belt-shaped or drum-shaped transfer body, by forming the thin line toner image 20 on the transfer body as well as on the photoconductor, The occurrence of bounding of the cleaning blade acting on the transfer member can be prevented.

In this case, the thin line toner images 20 shown in FIGS. 2A and 2B are formed outside the image area, inside the transfer area on the photoconductor and outside the transfer area, respectively.
Is transferred to the outside of the image area of the transfer body to supply toner to a cleaning blade acting on the transfer body. In addition, the thin line toner image in the transfer area is not transferred, and remains on the photoreceptor to supply the toner to a cleaning blade for cleaning the photoreceptor.

 Hereinafter, a description will be given based on a specific example.

FIG. 8 (a) shows an example of a color image forming apparatus having a drum-shaped photoconductor and a belt-shaped transfer body, and the peripheral surface of the drum-shaped photoconductor 100A is charged every rotation thereof. Upon exposure, each single color toner image is developed, and a color toner image is formed by superimposing the toner images.
Therefore, during image formation, the cleaning blade 103 and the transfer body 1
The press-contact of 00B to photoconductor 100A has been released.

The multicolor toner image formed on the photoreceptor 100A is transferred onto a transfer material fed to a press-contact portion of a belt-shaped transfer member 100B that has turned into a press-contact state. The transfer material having received the transfer of the toner image is fed to a fixing device 105 via a conveying member, and the photosensitive member 100A and the transfer member 100B from which the transfer material has been separated are cleaned by respective cleaning blades 103 or 104.

At the time of transfer, the fine line toner image 20 in the transfer area is
The thin line toner image 20 outside the transfer area remains on the photosensitive member 100A and is turned into a pressed state.
To supply toner.

For the fine line toner image 20, only one single color toner image is sufficient, so that the photosensitive member 100A and the transfer member
The cleaning action for 100B is effectively performed, and it is possible to obtain a high-quality copy with excellent back quality and excellent image quality.

FIG. 8 (b) shows an example of a color image forming apparatus including a drum-shaped photosensitive member and a drum-shaped transfer member. The peripheral surface of the drum-shaped photosensitive member 100A is charged every rotation thereof. Upon exposure, each single-color toner image is formed by development. Each time the toner image is transferred onto a transfer material wound around a drum-shaped transfer member 100B, it is removed by a cleaning blade 103. In this manner, a multicolor toner image is transferred and formed on the transfer material by rotating the photosensitive member 100A and the transfer member 100B in synchronization with the photosensitive member 100A a plurality of times. Therefore, the pressing action of the transfer body 100B against the photoconductor 100A is released during the formation of a single-color toner image on the photoconductor 100A, and the cleaning blade 10 against the transfer body 100B during the transfer to the transfer material.
The pressure welding of 4 has also been released.

The transfer material having the multicolor toner image for which the transfer of the toner image has been completed is
Separated from 00B and fed to the fixing device 105 via the conveying member,
On the other hand, the transfer member 100B is cleaned by the cleaning blade 104 which has newly turned into the pressure contact state.

During the transfer, the thin line toner image in the transfer area is transferred to the outside of the image area of the transfer body 100B and supplies the toner to the cleaning blade 104, while the thin line toner image 20 outside the transfer area remains on the photoreceptor 100A. Cleaning blade 103
To supply toner.

FIG. 8C shows an example of an image forming apparatus having a plurality of drum-shaped photoconductors and a belt-shaped transfer body.
The multicolor toner image is directly transferred onto the transfer material by sequentially transferring and superimposing the single-color toner images formed on the drum-shaped photoconductors 100A onto the transfer material conveyed by the belt-shaped transfer body 100B. Is formed. Therefore, in this case, the transfer member 100B is always kept in pressure contact with the photosensitive member 100A, and the cleaning blades 103 and 104 provided respectively are also kept in pressure contact with the photosensitive member 100A or the transfer member 100B.

The transfer material to which the toner image has been transferred is separated from the transfer body 100B and fed to the fixing device 105, where each photoconductor 100A and the transfer body 100B are transferred.
Are the cleaning blades 103 and 1 provided for each
Cleaned by 04.

In this case, the thin line toner image 20 outside the transfer area is
The thin toner line 20 in the transfer area is formed on any one of the photoconductors 100A and is transferred to the transfer body 100B.
Is transferred to

Thereby, the former thin line toner image 20 outside the transfer area supplies toner to each cleaning blade 103, and the latter thin line toner image 20 inside the transfer area becomes the cleaning blade 104.
To supply toner.

FIG. 8 (d) shows an example of an image forming apparatus provided with a belt-shaped photosensitive member and a belt-shaped transfer member. The peripheral surface of the belt-shaped photosensitive member 100A is charged and exposed for each rotation. In response to this, single-color toner images are formed by development, and each time the toner images are transferred to the belt-shaped transfer member 100B, and then removed by the cleaning blade 103. In this manner, a multicolor toner image is transferred and formed on the transfer member 100B by rotating the photosensitive member 100A and the transfer member 100B in synchronization with the photosensitive member 100A a plurality of times. The multicolor toner image transferred and formed on the transfer member 100B is transferred to a transfer material fed to a transfer unit, and the transferred transfer material is passed through a transport member to a fixing device 105.
Is sent to

Therefore, when transferring the toner image from the transfer body 100B to the transfer material, the cleaning blade 10 acting on the transfer body 100B is used.
Reference numeral 4 denotes a state in which the pressure contact is released, and when the transfer is completed, the state returns to the pressure contact state and the transfer member 100B is cleaned.

Also in this case, a thin line toner image 20 is formed by any one single color, one of which remains on the photoreceptor 100A, and the other is transferred to the transfer body 100B to supply toner to the respective cleaning blades 103 or 104. Become.

In addition, 101 shown in each figure is a charger, 102 (102A) is a transfer device,
Reference numeral 106 denotes a paper feed cassette, and Y, M, C, and K represent developing units containing yellow, magenta, cyan, and black toners, respectively.

〔The invention's effect〕

According to the present invention, as described above, by forming a toner image at least outside the image width in the main scanning direction, the toner is supplied to the cleaning blade at the time of cleaning. To provide an image forming apparatus capable of preventing damage to the image, performing good cleaning over a long period of time, and obtaining a high-quality image. Further, since the toner image is formed in any of a plurality of cycles, wasteful toner consumption can be suppressed, and the unit cost of printing and the amount of waste toner can be suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIGS. 2 (a) and 2 (b) are development views showing a thin line toner image of the embodiment of FIG. 1, and FIG. 3 shows a bounding experiment apparatus. FIG. 4 is a side view showing an experimental apparatus for flying toner, FIG. 5 is a graph showing the relationship between the distance d between the blade edge and the pseudo photoconductor and the number of flying toners, and FIGS. 6 (a) and (b). FIG. 7 is a side view showing two contact states of the cleaning blade, and FIG. 7 is a developed view showing a case of a recording sheet having a size smaller than the width of the photosensitive drum. 8 (a), (b), (c) and (d) are configuration diagrams showing other embodiments. DESCRIPTION OF SYMBOLS 1 ... Image reading part, 2 ... Laser writing part 3 ... Image reproduction recording part, 10 ... Photoreceptor drum 14 ... Charger, 15 ... Charge erasing lamp 16, 17, 18 ... Developing device, 19 cleaning device 19A cleaning blade 19B toner collecting roller 19C support 20 fine line toner image 21 image area e cleaning edge L laser beam T toner

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 21/10-21/12 G03G 15/01

Claims (1)

(57) [Claims] 1. A method according to claim 1, wherein a toner image superposed on the image carrier by repeating a cycle of charging, image exposure and development a plurality of times is transferred to a transfer material, and residual toner remaining on the image carrier after the transfer is transferred. An image forming apparatus that performs cleaning by pressing a cleaning blade that has been separated from the image carrier against the image carrier, and in at least one of a plurality of cycles, the toner image is formed at least outside the image width in the main scanning direction. Forming an image.