JPH05107989A - Cleaning device - Google Patents

Abstract

PURPOSE:To maintain excellent image quality over a long period by completely removing a carrier on a surface of a toner image carrier removed with a brush, therefrom, and preventing the occurrence of resticking to the surface of the toner image carrier, and the scratch of the surface of the toner image carrier caused by the arrival of the carrier at a blade. CONSTITUTION:In this cleaning device used for an image forming device adopting a two-component developing system, and having the blade 2 whose top end elastically contacts with the toner image carrier 1 such as the photosensitive body, the brush 3 coming into contact with the surface of the toner image carrier 1, and rotating, on the upstream side of the blade 2, and a flicker 4 removing a developer G stuck to the brush 3, a magnetically attracting means 5 is provided on the downstream side of the flicker 4 of the brush 3, as a characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning device for removing a developer such as toner adhered to the surface of an image bearing member such as a photosensitive member by a brush and a blade after transfer in an image forming apparatus such as an electrophotographic copying machine. Is.

[0002]

2. Description of the Related Art Conventionally, as a cleaning device in an image forming apparatus such as an electrophotographic copying machine, a cleaning device disclosed in, for example, Japanese Patent Application Laid-Open No. 1-312578 is widely known. This makes the rotating direction of the brush the same as the moving direction of the photoconductor, and the brush also serves as a conveying member for guiding the toner scraped off by the blade to the developer collecting auger. A flick cover is provided in the portion so that the toner and the like adhering to the brush surface can be removed easily and effectively.

More specifically, as shown in FIG. 9, the transfer residual toner T existing on the surface of the photosensitive member 21 is
As the photoconductor 21 moves (arrow A), it is removed from the photoconductor 21 by the brush 11. The toner that cannot be removed by the brush 11 is completely removed by the blade 12 arranged on the downstream side of the brush 11. When the toner removed by the blade 12 is accumulated to some extent, the toner falls by its own weight and rides on the brush 11 disposed upstream of the blade 12, that is, below the blade 12. That is, on the surface of the brush 11, there are toner removed by the brush itself from the photoconductor 21 and toner removed by the blade 12, and the toner moves according to the rotation of the brush 11 (arrow B) and comes into contact with the flicker 13. Toner is removed from the brush 11 and flicked toward the recovery auger 16 in the direction of arrow D.

[0004]

However, in the image forming apparatus using the two-component developing method, there is a phenomenon that not only the toner but also the carrier enters the cleaning apparatus. In particular, the reversal developing method is used. In the type that employs the method of adhering toner to the exposed portion as the image portion, even if the carrier C on the surface of the photoconductor 21 is removed by the brush 11, it is mechanically contacted with the tip of the brush 11. It is difficult to completely remove the carrier C electrostatically attached to the brush 11 by the flicker 13 present,
The carrier C attached to the brush 11 is redeposited on the surface of the photoconductor 21 and a part of the carrier C reaches the tip of the blade 12 to damage the surface of the photoconductor 21 during cleaning with the blade 12 (X in the figure). However, there was a technical problem that it causes a serious deterioration of image quality.

As a means for solving such a technical problem, there has been proposed one in which a carrier collecting means is provided between the brush 11 and the blade 12 (Japanese Patent Laid-Open No. 61-212).
880), some of the carriers C redeposited on the surface of the photoconductor 21 have a very small amount, but very high electric charge, and they are very strong with the surface of the photoconductor 21. Since the carrier C is attached, it is not possible to completely remove the carrier C redeposited by the carrier collecting means, and the photoconductor 21 is accompanied by the arrival of the carrier C at the tip of the blade 12.
It is not sufficient as a means for preventing the surface scratching phenomenon.

As a result of the inventors' earnest studies on such technical problems, the following reasoning was obtained. For example, it is assumed that the potential on the surface of the photoconductor 21 becomes as shown in FIG. 10A when a latent image is formed by laser beam light. That is, the image area to which the toner should be attached in the developing device is lowered to about -200 V by the irradiation of the laser beam light, and the non-image area where the toner is not attached is about -200 V because there is no light irradiation.
It holds 600V. In the developing device, the toner and the carrier are frictionally charged with each other, the toner is negatively charged, the carrier is positively charged, and the negative bias (about −
500 V) is applied. A developing electric field is formed between the surface of the photoconductor and the developing device by the developing bias. Then, in the image area, since the photoconductor apparently has a positive electric field, the toner having a negative charge moves from the developing device to the surface of the photoconductor by electrostatic force and is developed, and in the non-image area, it has a negative electric field. There is no movement of toner.

However, the surface potential of the photosensitive member and the developing bias value in the image area and the non-image area fluctuate due to environmental changes, changes in the electrical characteristics of the photosensitive member with time, and changes in the charger and the developing bias power source. Often. Figure 10
(B) schematically shows this state, in which the photoconductor surface potential in the non-image area becomes higher than usual, and as a result, the negative electric field becomes stronger and the positively charged carriers are electrostatically charged. It adheres to the surface of the photoconductor. It can be seen that the carrier adhered to the non-image area in this way adheres to a portion where the surface potential of the photoconductor is very high, and therefore the adhesive force is also very high.

Further, in the transfer device, the polarity opposite to that of the toner,
That is, in this example, since a positive charge is applied, a potential difference occurs between the surface of the photoconductor and the back side of the recording paper in the transfer area.
Due to this potential difference, the toner is electrostatically moved from the surface of the photoconductor to the recording paper and the transfer is performed. However, the non-image area enters the transfer area with the very high surface potential as described above.
Abnormal discharge (void discharge and peeling discharge) occurs between the surface of the photoconductor and the recording paper at the exit. Although the mechanism of occurrence of this abnormal discharge is not clear, as a result, it is known that the surface of the photoconductor is strongly positively charged and the recording paper side is negatively charged. Therefore, the carrier attached to the above-mentioned non-image area originally had a positive charge, but due to this abnormal discharge, it will be further charged with a strong charge, and the adhesion to the photoconductor will become stronger and stronger. is there.

As shown in FIG. 9, the carrier C firmly adhered to the non-image area has the parameters of the brush 11 of the cleaning device 10 (for example, rotation speed of the brush,
It can be removed once by appropriately setting the pressure applied to the photoconductor, etc.), but it still adheres to the surface of the brush 11 since it still retains a strong electric charge. A part of the carrier C electrostatically attached to the surface of the brush 11 is mechanically removed when the brush 11 comes into contact with the flicker 13, but most of the carrier C has a weak adhesive force, and the carrier C is exposed again. It reaches the surface of the body 21. At this time, if there is a portion where the potential on the surface of the photoconductor 21 is still high, the carrier C is attached again to this region. Since this adhesion is still electrostatic,
Since the adhesive force is high, it is difficult to first remove it by the carrier collecting means described in JP-A-61-212880.

The present invention has been made in view of such circumstances, and the carrier on the surface of the toner image bearing member removed by the brush is completely removed from the brush, and the re-adhesion to the surface of the toner image bearing member occurs. The present invention provides a cleaning device that maintains good image quality for a long period of time by preventing the occurrence of scratches on the surface of the toner image carrier due to the carrier reaching the blade.

[0011]

That is, the present invention is
As shown in FIG. 1, a blade 2 used in an image forming apparatus adopting a two-component developing method has its tip elastically contacting a toner image carrier 1 such as a photoconductor, and a toner image carrier upstream of the blade 2. Assuming a cleaning device having a brush 3 rotating in contact with one surface and a flicker 4 for removing the developer G adhering to the brush 3, a magnetic attraction means 5 is provided on the downstream side of the flicker 4 of the brush 3. It is characterized by that.

In such a technical means, the magnetic attraction means 5 may be any magnetic attraction means which is installed on the downstream side of the flicker 4 and has a magnetic force sufficient to attract the carrier of the developer G adhering to the brush 3. The design may be changed as appropriate, such as a permanent magnet arranged in a non-contact state with the surface of the brush 3, but from the viewpoint of improving the carrier removal efficiency, for example, a rotatable magnet that comes into contact with the surface of the brush 3 is rotatable. A non-magnetic sleeve, a magnet body fixedly arranged in the sleeve to generate an attractive magnetic field at a contact portion of the sleeve with the brush 3, and a scraper arranged in contact with an arbitrary portion of the non-magnetic sleeve. As configured, it is preferred to design the carrier removed from the brush 3 to be surely disposed of elsewhere.

[0013]

According to the technical means as described above, the brush 3
When a small amount of the carrier present on the surface of the toner image carrier 1 is cleaned, the carrier electrostatically adheres to the surface of the brush 3 together with the toner, but the adhesive force of the carrier to the surface of the brush 3 is mechanical impact due to contact with the flicker 4. Slightly weakens. For this reason, the magnetic attraction means 5 installed on the downstream side of the flicker 4 attracts the carrier, whose adhesion to the surface of the brush 3 is weakened, by magnetic force, and prevents the carrier from being reattached to the toner image carrier 1. Further, at this time, the toner on the surface of the brush 3 that has not been scraped off by the flicker 4 is entangled by the carrier, so that the brush 3 can be made more clean.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the embodiments shown in the accompanying drawings. [Embodiment 1] FIG. 2 is a process block diagram of an electrophotographic copying machine including Embodiment 1 of the cleaning apparatus to which the present invention is applied.
In the figure, the electrophotographic copying machine includes a developing device 24, a transfer device 27, a fixing device 29, and a cleaning device using a two-component developer including a photoconductor 21, a charging device 22, an exposing device 23, a toner 25 and a carrier 25. It is composed of 10.

In this embodiment, first, the surface of the photoconductor 21 is uniformly charged by the charger 22. The exposure device 23 irradiates the light to remove the charged electric charge in the exposed portion to form an electrostatic latent image. For example, in the case of a digital electrophotographic copying machine in which an organic photoconductor is used as the photoconductor 21 and a laser beam light is used as the exposure device 23, the surface of the photoconductor 21 is negatively charged by the charger 22 and the laser beam light is applied. As a result, a dot-shaped digital latent image is formed, and toner is applied by the developing device 24 to a portion exposed to the laser beam light to form a visible image. In this case, a negative bias is applied to the developing device 24. Next, the recording paper 28 is superposed on this toner image, a charge having a polarity opposite to that of the toner is applied to the recording paper 28 from the back side of the recording paper 28, and the toner image is transferred to the recording paper 28 by electrostatic force. The transferred toner image is fused with the recording paper 28 by applying heat or pressure to form a permanent image. On the other hand, the toner T remaining on the photoconductor 21 without being transferred is removed by the cleaning device 10. One cycle is completed by a series of processes from this charging to cleaning.

FIG. 3 is a schematic enlarged view of the cleaning device used in the first embodiment. In the figure, the brush 11 comes into contact with the surface of the photoconductor 21 and rotates in the same direction (arrow B) as the moving direction (arrow A) of the photoconductor 21 to remove the transfer residual toner 51 on the photoconductor surface. , Then the flicker 13 comes into contact with the brush 11
1 is configured to remove the toner.

Further, in this embodiment, the flicker 1
3, a magnetic force suction device 15 is installed between the flicker 13 and the photoconductor 21 on the downstream side of the magnetic force suction device 15.
4, the non-magnetic cylindrical sleeve 16 that comes into contact with the surface of the brush 11 and rotates in the direction opposite to the rotating direction of the brush 11, and is fixedly arranged in the cylindrical sleeve 16. Magnet roll 17 and the cylindrical sleeve 16
And a scraper 18 which is disposed in contact with a predetermined position of the.

More specifically, the cylindrical sleeve 16 described above.
For this, a stainless tube having an outer diameter of 10 mm is used, and the biting amount of the sleeve 16 with respect to the brush 11 is about 1 mm. The magnet roll 17 is the brush 1
A main magnetic pole (S pole: surface magnetic flux density of about 600 gauss in this embodiment) 171 is arranged at a contact portion between the first magnetic pole 1 and the cylindrical sleeve 16, and a magnetic pole having a polarity opposite to that of the main magnetic pole 171 at a position apart from the main magnetic pole 171 A repulsive magnetic field is formed by arranging (N pole) 172, 173 at a constant interval. Further, the scraper 18 is arranged in a region where the repulsive magnetic field of the magnet roll 17 is generated.

In this case, since the sleeve 16 contacts the surface of the brush 11 and the main magnetic pole 171 is arranged at a position corresponding to this contact portion, the carrier C which cannot be removed by the flicker 13 is more effective. Removed from the surface. Further, the sleeve 16 rotates in the direction opposite to the rotation direction of the brush 11 (direction E in the figure), and the scraper 18 scrapes off the carrier C magnetically attached to the surface of the sleeve 16, so that the surface of the sleeve 16 is always clean. Since it comes into contact with the brush, there is no possibility that the carrier C adsorbed on the sleeve 16 side reattaches to the brush 11 side.

FIG. 5 shows the number of carrier particles existing on the surface of the photoconductor before and after passing the brush when the cleaning device according to the first embodiment and the conventional type cleaning device (comparative example) shown in FIG. 9 are used. It is a comparison. The conditions for this test are as follows. -Photoreceptor: Organic photoreceptor-Developer: Toner average particle size 7 microns Carrier average particle size 40 microns-Process speed: 160 mm / sec-Brush: Material Beltron B12N (trade name, manufactured by Kanebo Co., Ltd.) Denier / Density 10d (160/16), 48,000 fibers / inch ² Fiber length 6.5 mm Brush diameter 20 mm Interference with photoconductor 1 mm Interference with flicker 1 mm Rotation speed Approx. 100-450 mm / sec Rotation direction Contact with photoconductor Same direction as the photoconductor on the shaft Shaft earth ground ・ Magnetic generation means: 10mm outer diameter Surface magnetic flux density 600 gauss Rotation speed about 100-450mm / sec Rotation direction Opposite to the brush at the contact point with the brush ・ Photoconductor surface potential: Image Area -200V, non-image area -600V ・ Development bias: -500V

According to this test, in the comparative example, as shown by the dotted line in FIG. 5, the amount of change in the carrier amount before and after the brush increases due to the increase in the number of rotations of the brush, that is, the re-adhesion of the carrier from the brush to the photosensitive member. As a result, it is confirmed that the carrier after brushing is increased, but the carrier adhesion amount is decreased in the example 1 as shown by the solid line in FIG. In FIG. 5, the brush peripheral speed ratio is the brush tip speed (mm / sec) / process speed (mm / s).
ec), and the carrier amount ratio (%) before and after the brush is {(the number of carriers on the photoconductor after passing the brush) / (the number of carriers on the photoconductor before passing through the brush)}.
It means x100.

FIGS. 6 and 7 show the degree of scratches on the surface of the photoconductor in Example 1 and the comparative example, respectively, and the grade of image quality deterioration that occurs as a result. The conditions at this time are: brush and sleeve rotation speed 320 mm / se
c, blade manufactured by Hokushin Kogyo Co., Ltd. (hardness 70 degrees, thickness 2 mm)
The test conditions are the same as the test conditions shown in FIG.
As for the grade of image quality deterioration, an index of graininess, which represents the roughness of image quality, is used. For example, density variation data measured while scanning a micro densitometer
It is calculated by using the formula called ner spectrum. Here, the relationship between the image quality deterioration grade and the graininess data is generally as follows. Image quality degradation grade Graininess data Actual image quality 1 1.0 or less White stripes can finally be confirmed with a magnifying glass. 2 1.0 to 1.2 White streaks can finally be visually confirmed. 3 to 1.5 White streaks can be visually confirmed. 4 to 2.0 White lines can be clearly seen, which is an eyesore. 5 2.0 or higher The image quality of the copy is no longer present.

According to FIG. 6, it was confirmed that the degree of scratches on the surface of the photoconductor was smaller in Example 1 (shown by the solid line in the figure) than in Comparative Example (shown by the dotted line in the figure). According to the comparative example (indicated by the dotted line in the figure), the image quality obviously deteriorates as the number of copies increases, but in the example 1 (indicated by the solid line in the figure), It is confirmed that the image quality is sufficiently secured even if the number of sheets increases.

Example 2 FIG. 8 shows Example 2 of the cleaning device to which the present invention is applied. In the figure, a magnetic attraction device 15 installed downstream of the flicker 13 with respect to the rotation direction of the brush 11.
Is a permanent magnet 19 disposed in the vicinity of the tip of the flicker 13, for example, below the fixed support member 14 of the flicker 13, in a non-contact state with the brush 11.

According to this embodiment, the tip of the brush 11 is repelled in the direction of the arrow D by contact with the flicker 13, and most of the toner T and carrier C are scraped off at that time, but the surface of the brush 11 is firm. Even if the carrier C attached to the carrier C does not separate from the brush 11, the carrier C has a very weak adhesive force, so that it is easily collected by the magnetic force of the permanent magnet 19 arranged near the flicker 13. Therefore, the carrier C is removed from the surface of the brush 11 and the photoconductor 2
Redeposition of the carrier C on the surface 1 is effectively prevented.

However, unlike the first embodiment, the carrier C adhering to the permanent magnet 19 is not naturally removed, so that the carrier C is gradually deposited on the permanent magnet 19 portion, so that the carrier C is applied to the brush 11. From the viewpoint of preventing reattachment, regularly clean the permanent magnet 19 portion, or define the life of the cleaning device within a range in which the amount of carrier C deposited does not affect reattachment to the brush 11. is necessary.

[0027]

As described above, according to claims 1 to 3.
According to the invention described in any one of the above, when a small amount of the carrier present on the surface of the toner image bearing member is cleaned with a brush, the magnetic force is applied to the carrier whose adhesion to the brush surface is slightly weakened by a mechanical shock caused by contact with flicker. Since it is designed to be efficiently removed by using, it is possible to reliably prevent reattachment of the carrier to the toner image carrier,
As a result, it is possible not only to effectively avoid the situation where the carrier reaches the blade portion and damages the toner image carrier, causing image quality deterioration, but also entangles the toner on the brush surface that was not scraped off by flicker with the carrier. Since it can be removed, the brush itself can always be kept in a clean state, and the cleaning performance of the brush can be kept excellent accordingly.

Particularly, according to the second aspect, it is possible to provide a simple and inexpensive magnetic attraction means, and according to the third aspect, it is possible to ensure the removal efficiency of the carrier on the brush surface. it can.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a cleaning device according to the present invention.

FIG. 2 is a process configuration diagram of an electrophotographic copying machine including a cleaning device according to a first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing the basic configuration of the cleaning device according to the first embodiment.

FIG. 4 is a detailed view thereof.

FIG. 5 is a graph showing changes in the number of carrier particles on the surface of the photoconductor before and after passing the brush when the cleaning devices of Example 1 and the comparative example are used.

FIG. 6 is a graph showing the relationship between the number of copies and the surface roughness (RZ) of the photoconductor when the cleaning devices of Example 1 and the comparative example are used.

FIG. 7 is a graph showing the relationship between the number of copies and the grade of image quality deterioration when the cleaning devices of Example 1 and the comparative example are used.

FIG. 8 is an explanatory diagram showing a second embodiment of the cleaning device to which the present invention is applied.

FIG. 9 is an explanatory diagram showing an example of a conventional cleaning device.

FIG. 10 is a schematic diagram of a photoreceptor surface potential state for explaining a phenomenon in which a carrier reaches a blade portion in a conventional cleaning device.

[Explanation of symbols]

1 ... Toner image carrier, 2 ... Blade, 3 ... Brush, 4 ...
Flicker, 5 ... Magnetic attraction means

Claims (3)

[Claims] 1. A blade (2) used in an image forming apparatus adopting a two-component developing method, the tip of which is in elastic contact with a toner image carrier (1), and a toner image carrier on the upstream side of this blade (2). (1) In a cleaning device having a brush (3) rotating in contact with the surface and a flicker (4) for removing the developer (G) adhering to the brush (3), the flicker (4) of the brush (3) is ), A magnetic attraction means (5) is provided on the downstream side of the cleaning apparatus. 2. The cleaning device according to claim 1, wherein the magnetic attraction means (5) is composed of a permanent magnet arranged in a non-contact state with the brush surface. 3. The magnetic attraction means (5) according to claim 1, wherein said magnetic attraction means (5) is a rotatable non-magnetic sleeve in contact with the brush surface and a brush of said sleeve fixedly arranged in this sleeve. The cleaning device according to claim 1, wherein the cleaning device comprises a magnet body that generates an attractive magnetic field at a contact portion with the scraper, and a scraper that is disposed in contact with an arbitrary portion of the non-magnetic sleeve.