JPH0895350A - Electrifier for image forming device - Google Patents

Abstract

PURPOSE: To remove even firmly stuck toner, to attain the prolongation of effect and prevention of filming in a cleaning member and to repeatedly use it by making the hardness of the cleaning member coming into contact with an electrifying roller lower than its hardness. CONSTITUTION: A cleaning roller 21 coming into contact with the electrifying roller 2 is installed in a position adjacent to the electrifying roller 2. The cleaning roller 21 is of a roller shape and an elastic member 212 formed on the outer periphery of a shaft center 211. As the elastic member 212, one having low hardness in itself and the hardness lower than that of the electrifying roller 2 can be used. Both ends of the shaft center 211 are freely rotatably supported by bearings 213 and in press-contact with the electrifying roller 2 by the pressing of springs 214. By such a constitution, the rotation of the electrifying roller 2 is transmitted to the cleaning roller 21. Since the surface of the cleaning roller 21 is made of a material with low hardness, close contactness with the surface of the electrifying roller 2 becomes high and friction becomes strong as well.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device for an image forming apparatus, and more particularly to a charging device provided with a charging roller for contacting and charging a photoreceptor.

[0002]

2. Description of the Related Art A photosensitive layer on the surface of an image bearing member is uniformly charged by a charging means, optical image information is applied to the photosensitive layer to form an electrostatic latent image, and usually powdery toner is supplied to the electrostatic latent image. An image forming apparatus that repeats the process of electrostatically transferring the toner image onto a sheet-like transfer paper after visualizing the latent image has been widely used as a copying machine, a facsimile, a printer, etc. It is well known that this is done.

In such an image forming apparatus, it is well known that selenium, cadmium sulfide, zinc oxide or the like is used as an inorganic photoconductive material as a photoconductive material used as a photosensitive layer. However, various organic compounds have come to be used recently.

Examples of this type of substance include poly-
Organic photoconductive polymers such as N-vinylcarpazole and polyvinylanthracene, low molecular weight organic photoconductive members such as carpazole, anthracene, pyrazolines, oxadiazoles, hydrazones, polyallyl alkanes, phthalocyanine pigments, Organic dyes and pigments such as azo pigments, cyanine dyes, polyquinone pigments, perylene pigments, indigo dyes, thioindigo dyes and squaric acid methine dyes are used. These are easier to synthesize than the above-mentioned inorganic materials,
Since it is easy to form a material exhibiting photoconductivity in an appropriate wavelength range, it is increasingly used. For example, US Pat. Nos. 4,123,270, 4,251,613 and 4,
No. 251624, No. 4256821, No. 426067
No. 2, 4268596, No. 4287747, No. 42
Japanese Patent No. 93628 discloses a photosensitive layer having a charge-generating layer and a charge-transporting layer which are functionally differentiated from each other.

By the way, in the image forming process using the photoconductor as described above, as a means for charging the photoconductor, a charger in which a metal wire is spread is generally used, and a direct current of 5 to 8 KV is applied to the metal wire. In many cases, it was charged by corona generated by applying a high voltage.

However, this type of means may generate ozone or nitrogen oxides associated with corona discharge, which may damage the photoreceptor itself or adhere to it, causing deterioration of image quality. However, the discharge stream itself has a problem that the amount of flow in the direction of the photoconductor is as small as 5 to 30% and the efficiency is poor.

In order to avoid such a defect, a direct charging system has been proposed in which a charging member is brought into direct contact with a photosensitive member. As the direct charging method, a technique has been proposed in which a charging roller, a belt, or the like is brought into contact with a photoconductor and a DC voltage or a voltage obtained by superimposing an AC on a DC is applied to these charging members.

However, in this type of system, since the charging member is in direct contact with the photosensitive member, toner, paper powder, etc. are likely to adhere, resulting in poor image quality (charging potential corresponding to the adhesion position). There is a possibility that white spots, etc.) may occur due to deterioration of

As a technique for solving this kind of problem, for example, Japanese Patent Laid-Open No. 2-301777 is known.
Here, it is proposed to clean the contact charging member (charging belt made of medium-resistance conductive rubber) with a cleaning means (roller, pad) made of felt material.

[0010]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The technique disclosed in Japanese Patent Laid-Open No. 7-74 is intended to prevent deterioration of image quality due to adhesion of toner, paper powder, etc. by cleaning the contact charging member with a cleaning means. However, the felt member is used as the cleaning member. There's a problem.

Since the felt material has a gap between the fibers capable of trapping the toner on its surface, it is possible to release the toner from the surface of the charging member, but it has no ability to attract the toner. However, the toner firmly adhered to the charging member cannot be removed.

On the other hand, a charging roller generally used as a contact charger requires elasticity because it comes into contact with the photoconductor, and therefore a rubber material is usually used. Since the rubber material and the toner are the same organic substance, they have a good compatibility with each other, and the longer they are left in the adhered state, the stronger the adhesive force becomes. This is a serious problem in a small electrophotographic apparatus that is often left unattended for a long time, and toner at the uncleaned area from the photosensitive member to the cleaning member and the contact area between the cleaning member and the photosensitive member at the end of the operation may not be removed. For the above-mentioned reasons, the toner often adheres firmly to the roller and cannot be removed even in the next cleaning operation. Such a roller causes a charging failure depending on the adhered area, resulting in white spots on the image.

The first aspect of the present invention has been made to solve the above-mentioned problems, and an object thereof is to provide a cleaning member capable of removing and cleaning even strongly adhered toner. Further, claim 2 particularly extends the life of the effect of claim 1, claim 3 prevents filming of the cleaning member of claim 1 or 2, and claim 4 claims 1, 2 or Three
The purpose is to enable repeated use of the cleaning member.

[0014]

In order to solve the above-mentioned problems, in the invention of claim 1, an image is provided with a photoconductor for forming an image, and a charging roller for contacting the photoconductor and giving an electric charge to the photoconductor. The charging device of the forming apparatus includes a cleaning member that comes into contact with the charging roller, and the hardness of the cleaning member is smaller than the hardness of the charging roller.

According to the second aspect of the invention, the hardness (JISA) of the cleaning member is set to 30 degrees or less.

Further, in the invention of claim 3, the cleaning member has a roller shape, and the cleaning member rotates together with the rotation of the charging roller in a state where the cleaning member and the charging roller are in contact with each other. To configure.

In the invention of claim 4, the hardness (JISA) of the cleaning member is set to 24 degrees or more.

[0018]

[Action]

(Operation and effect corresponding to claim 1) Since the hardness of the cleaning member is smaller than the hardness of the charging roller,
When the cleaning member is brought into contact with the charging roller, the degree of adhesion of the toner to both rollers is compared, and since the cleaning member (for example, the cleaning roller) is larger than the charging roller, the toner easily sticks to the cleaning member. Therefore, the transfer from the charging roller to the cleaning member can be promoted, and the toner once attached to the cleaning member can be prevented from re-adhering to the charging roller. Even for toner that has adhered firmly,
It can be cleaned to a level that does not affect the image.

(Operation and effect corresponding to claim 2) Since the hardness of the cleaning member is set to 30 degrees or less, the surface shape of the cleaning member changes along with the concave portion of the charging roller, so that they are pressed against each other. The operation is completely performed. Therefore, the effect of the first aspect can be sufficiently exerted also on the toner attached to the concave portion, and as a result, the cleaning performance of the charging roller can be extended.

(Effect corresponding to claim 3) Since the cleaning member has a roller shape and rotates around the charging roller, the charging roller surface and the cleaning member surface can be closely contacted and separated from each other without rubbing. You can This allows
Toner filming on the charging roller can be prevented, and the life can be extended.

(Effect corresponding to claim 4) Since the hardness of the cleaning member is particularly 24 degrees or more, the cleaning member having poor cleaning performance can be completely restored to the initial state by washing with water and repeatedly used. Is possible.

[0022]

EXAMPLE FIG. 1 shows an example of the configuration of an image forming apparatus using a contact type charger. An outline of the image forming process in the image forming apparatus shown in FIG. 1 will be described.

In advance, the surface of the photoconductor 1 is charged to a uniform potential by the charging roller 2. Then, by irradiation of light 3 from an optical writing device (not shown), a potential distribution corresponding to the image pattern, that is, an electrostatic latent image is formed on the surface of the photoconductor 1. The developing device 4 attaches toner according to the potential distribution of the electrostatic latent image on the photoconductor 1 to visualize the electrostatic latent image. Recording paper is fed from the conveyance path 5 at the same timing as this image formation. Then, the toner image is transferred onto the recording paper by the transfer device 6, passes through the separator 7, and reaches the conveyance path 8. On the other hand, the transfer residual toner on the photoconductor 1 is cleaned by the cleaning device 9
It is then dammed up, separated from the photoconductor 1, and collected in the cleaning device 9. Photoreceptor 1 after toner removal
Is photo-electrified by a quenching lamp 10 (hereinafter abbreviated as QL10) to eliminate potential unevenness and prepare for the next image formation.

Even in the structure as shown in FIG. 1, the ozone generation is 40 to 60% as compared with the type using the charger.
Will be reduced. However, in the case of aiming for complete ozoneless, it is desirable to replace the transfer device 6 and the separator 7 in FIG. 1 with a transfer belt, a transfer roller, or the like. The present invention can be implemented with any configuration.

FIG. 2 shows the detailed structure of the charger of the image forming apparatus shown in FIG. This will be described with reference to FIG. The charging roller 2 has, as a material of its shaft core 201, a SUS material,
A metal rod material such as SECC material or Al material is used. Axis 2
An intermediate layer 202 is formed on the outer periphery of 01. The intermediate layer 202 is made of a conductive material (carbon plaque, metal powder, etc.) in a medium resistance elastic body such as epichlorohydrin rubber having a thickness of about 1 mm to 4 mm and synthetic rubber such as silicon rubber, ethylene propylene rubber, nitrile rubber, norponene rubber. ) Is mixed with the composition. The material required for the material of the intermediate layer 202 has a volume resistance of 10 ⁵ Ωcm or less, preferably 1
0 ³ Ωcm or less, rubber hardness (JIS / A) 20 degrees to 4
The common angle is 5 degrees, preferably 25 to 40 degrees.

The outermost layer 203 is formed on the outer periphery of the intermediate layer 202. The layer thickness of the outermost layer 203 is 3 μm to
It is set to 25 μm, preferably 4.5 μm to 12 μm. As the material forming the outermost layer 203, synthetic rubber in which epichlorohydrin rubber, lumiflon and silica are dispersed and mixed, lumiflon in which tin oxide is dispersed and mixed, nylon, cellulose and the like can be used. Further, the volume resistance characteristic required for the material forming the outermost layer 203 is 10 ⁵ Ω to 10 ¹³ Ω · cm, and 10 ⁶ to
10 ¹² cm is more preferable. The volume resistance from the intermediate layer 202 to the outermost layer 203 is 10 ⁶ to 10 ¹² Ω.
-It is desirable to have conductivity of about cm.

Both ends of the shaft core 201 are rotatably supported by bearings 204, and the charging roller 2 is pressed against the photoconductor 1 by the pressing of the spring 205. Of course, the mode of supporting the charging roller 2 and pressing it against the photoconductor is not limited to this, and the point is that the driving of the photoconductor is transmitted by friction between the charge roller and the photoconductor, and the charge roller rotates together. If

A power supply 206 for supplying electric power to the charging roller 2.
The control means (not shown) controls the power application timing. Electric power supplied from the power supply 206 is applied to the photoconductor 1 through the power feeding receptacle 207 abutted on the shaft 201, the shaft 201, the intermediate layer 202, the outermost layer 203, and the photoconductor 1. . With this power,
The photoconductor is charged. Also in this power feeding system, as long as the above-described current flow is formed, particularly in FIG.
It is not limited to this form. For example, the power supply 206 may be connected to the spring 205 and the bearing 204 may be formed of a conductive member.

Next, a means for cleaning the charging roller 2 will be described. As shown in FIG. 2, the charging roller 2
The cleaning roller 21 that is in contact with the cleaning roller 21 is installed at a position adjacent to the cleaning roller 21. The cleaning roller 21 has a roller shape and has a structure similar to that of the charging roller 2. That is, the elastic member 212 is formed on the outer periphery of the shaft core 211. The elastic member 212 has a small hardness,
In addition, the hardness may be lower than that of the charging roller 2, and specific materials thereof include polyurethane rubber, silicon rubber, ethylene propylene rubber, nitrile rubber, norbornene rubber and the like.

Both ends of the shaft core 211 are rotatably supported by bearings 213, and are pressed against the charging roller 2 by pressing of springs 214. With this configuration, the rotation of the charging roller is transmitted to the cleaning roller 21. Since the surface of the cleaning roller 21 is formed of a material having low hardness, the degree of close contact with the surface of the charging roller is large. As a result, friction also increases. Therefore, when the rotational movement is transmitted from the photoconductor → the charging roller → the cleaning roller, the spring 205 is strongly pressed so that the friction with the cleaning roller does not cause the photoconductor and the charging roller to slip. It is necessary to weakly press. In short, the three rotating bodies (photoreceptor 1, charging roller 2, cleaning roller 21) are pressed against each other to cause friction,
It is sufficient that the driving force is transmitted from the photoconductor 1 to the cleaning roller 21.
It does not need to be limited to 14.

The charging roller 2 having the above structure
The cleaning operation will be described with reference to FIGS. First, the mechanism of toner adhesion to the charging roller will be described with reference to FIG. The cleaning device 9 includes the photoconductor 1
Most of the above toner is scraped off, but it is easy to pass minute toner with a particle size of 1 μm. Further, in the blade cleaning 91 of the photoconductor 1, although the edge of the blade vibrates due to sliding with the photoconductor, it is resonated with the drive of the photoconductor, the vibration of the scanner of the copying machine, and the like, so that the blade edge The squeezing state may become sluggish, and the toner may partially leak in a streak shape. If these stripes adhere to the charging roller 2, defective charging tends to occur in the form of white stripes,
Cleaning of the charging roller is necessary to maintain performance.

When the charging roller 2 and the photosensitive member 1 are in pressure contact with each other, not all of the toner on the photosensitive member 1 is transferred to the charging roller 2, but the recessed position on the charging roller 2 and the minute amount on the photosensitive member 1. It is known from the experimental results that the toner is likely to remain on the charging roller when the position of the small-diameter toner coincides. The reason will be considered with reference to FIG. The toner adhering to the convex portion may be brought into pressure contact with the photoconductor 1 and brought to the photoconductor side when the surface of the photoconductor 1 and the surface of the charging roller 2 are re-contacted. Since the photoconductor 1 is close to a flat surface, a gap is formed even when the photoconductor 1 and the charging roller 2 are re-contacted with each other. If the toner adhered in the gap has a large particle size, it may come into contact with the photoconductor 1 again and be taken to the photoconductor 1. However, the toner having a small particle size does not contact the photoconductor 1 and remains attached. Imagine becoming. In the mass production process, it is difficult to reduce the surface roughness of the charging roller 2 to 3 μm or less by the current technology.
Even if it could be achieved in terms of quality, it cannot be said that it would be cost effective to put it on the market. At present, it is considered that 5 μm or more is a reasonable value that achieves both quality and cost, but for toner with a particle size of 1 μm or less, it means that the toner adheres to the bottom of the hole 5 times or more, so that it is flat (the surface of the photoconductor). It can be said that the pressure welding of is not enough to reach the bottom.

Next, the cleaning mechanism of the charging roller 2 by the cleaning roller 21 will be described with reference to FIG. The difference between FIG. 5 and FIG. 4 is that the hardness of the cleaning roller 21 pressed against the charging roller 2 is much lower than that of the photoconductor 1. Therefore, the charging roller 2 and the cleaning roller 21 are pressed against each other along the concave portion (contact state), and no gap is generated. Therefore, it can be said that it is possible to remove the fine particle toner attached to the concave portion. Moreover,
Since the hardness of the cleaning roller 21 is lower than that of the charging roller 2, the cleaning roller 21 has a higher degree of adhesion with the toner than the charging roller 2. That is, it can be said that the cleaning roller 21 is more likely to adhere toner than the charging roller 2 in terms of material. As a result, not only the toner firmly attached to the charging roller 2 can be removed, but even if the cleaning roller surface with the toner is brought into contact with the charging roller 2 again, the toner is removed from the cleaning roller 21 to the charging roller 2. It can be said that it is difficult to retransfer to the 2 side.

Also, in this embodiment, the cleaning roller 2
Since 1 is made into a roller shape and rotated around,
The surface of the charging roller 2 and the surface of the cleaning roller 21 can be brought into close contact with and separated from each other without rubbing against each other. If the surface of the charging roller 2 and the surface of the cleaning member are displaced by the rubbing operation, the action of rubbing the toner onto the charging roller 2 (toner filming) will occur. Is important in.

In order to evaluate the cleaning-related performance of the charging roller 2 in the above embodiment, the following experiment was conducted. Here, level 1 corresponds to the apparatus of the embodiment, and level 2 and level 3 correspond to the conventional apparatus. The evaluation results are shown in Table 1.

(Conditions) Photoconductor: φ80 OPC Photoconductor linear velocity: 150 mm / sec Charging roller: Rubber roller: φ14 × 300 Material Intermediate layer: Epichlorohydrin rubber Outermost layer: Epichlorohydrin rubber + Lumiflon + Silica Hardness: 40 degrees (JIS A) Charge applied voltage: -1700V Paper size: A4 Development method: Dry two-component photoconductor cleaning method: Counter blade Level 1: Cleaning roller: Rubber roller part: φ10 × 294: Material: Polyurethane rubber Hardness: 30 degrees (JIS A ) Level 2: Contact with felt material (pad shape: see Fig. 6) Level 3: No cleaning member Evaluation method: After 5000 sheets have been continuously fed, left for 1 week, and after half-life, halftone image (A3) Image defect evaluation

[0037]

[Table 1]

From the above results, it can be said that the cleaning performance of the charging roller is Level 1> Levels 2 and 3. In the case where there is no cleaning member of level 3, it can be said that the toner leaked from the photoconductor cleaning blade adheres to the charging roller in the form of streaks and the above-mentioned white streaks are generated on the image. Level 2 shows that the streak adhesion to the level 3 charging roller was cleaned by the felt material during continuous paper feeding, but after the paper feeding is completed, as shown in FIG. 7, the portion from the photosensitive member outlet to the felt material inlet vicinity It can be said that the black streaks remained on the charging roller and could not be removed because they were firmly attached at the end of standing. Similarly to Level 2, Level 1 had streaks of toner adhering from the photosensitive member outlet to the cleaning roller inlet at the end of leaving, but after the halftone image was sampled, streaks on the charging roller caused image defects. Not cleaned to a level. Therefore, the high cleaning performance of this embodiment can be seen.

In order to evaluate the cleaning durability of the charging roller 2 in the examples, the experiments described below were carried out. The evaluation results are shown in Table 2.

(Conditions) Photoconductor: φ80 OPC Photoconductor linear velocity: 120 mm / sec Charging roller: Rubber roller part: φ14 × 300 Material Intermediate layer: Epichlorohydrin rubber Outermost layer: Epichlorohydrin rubber + Lumiflon + Silica Hardness: 40 degrees (JIS A) Charge applied voltage: -1500V Paper size: A4 Development method: Dry 2-component photoconductor cleaning method: Counter blade cleaning roller: Rubber roller: φ10 × 294: Material: Polyurethane rubber Hardness of cleaning roller Level 1:45 degrees ( JISA) Level 2:35 degrees (JISA) Level 3:30 degrees (JISA) Level 4:24 degrees (JISA) Level 5:20 degrees (JISA)

[0041]

[Table 2]

From the above results, the durability is in the order of Level 3, Level 4, Level 5> Level 2 >> Level 1. This allows
It is considered that when the rubber hardness of the cleaning roller 21 is smaller than that of the charging roller 2, the durability of the charging roller cleaning is improved (level 2> level 1, the effect of claim 1). Further, it can be said by experiments that the cleaning durability is further improved (level 3, 4, 5> level 2, the effect of claim 2) particularly when the rubber hardness of the cleaning roller is 30 degrees or less.

Next, an attempt was made to regenerate the cleaning roller which became unusable after the above evaluation. Level 1, 2, 3,
As a result of cleaning the rollers of Nos. 4 and 5 with water while washing them with hands, it was possible to completely wash off the toner adhering to the surface except for the rollers of level 5 (rubber hardness 20 degrees). Only the cleaning roller of level 5 had some toner filming on the surface and could not be removed by rubbing with a finger.

The principle of releasing the toner of the cleaning roller of the present invention from the charging roller is that the hardness of the cleaning roller is low and that the surface is exposed. If the surface is exposed again by washing with water. Since the hardness does not change, it can be reused by returning to the initial state.

[0045]

【The invention's effect】

(Effect corresponding to claim 1) Since the hardness of the cleaning member is smaller than the hardness of the charging roller, when the cleaning member is brought into contact with the charging roller, the degree of adhesion of toner to both rollers is compared. Since the cleaning member (for example, the cleaning roller) is larger than the charging roller, the toner easily sticks to the cleaning member. Therefore, the transfer from the charging roller to the cleaning member can be promoted, and the toner once attached to the cleaning member can be prevented from re-adhering to the charging roller. It is possible to perform cleaning to a level that does not affect the image even for the toner that is strongly adhered.

(Effect corresponding to claim 2) Since the hardness of the cleaning member is set to 30 degrees or less, the surface shape of the cleaning member changes along with the concave portion of the charging roller, so that they are pressed against each other. The operation is complete. Therefore, the effect of the first aspect can be sufficiently exerted also on the toner attached to the concave portion, and as a result, the cleaning performance of the charging roller can be extended.

(Effect corresponding to claim 3) Since the cleaning member is formed in the shape of a roller and rotates around the charging roller, the charging roller surface and the cleaning member surface can be closely contacted and separated without sliding. it can. As a result, toner filming on the charging roller can be prevented, and the life can be extended.

(Effect corresponding to claim 4) Since the hardness of the cleaning member is particularly set to 24 degrees or more, the cleaning member having poor cleaning performance can be completely returned to the initial state by washing with water and can be repeatedly used. It will be possible.

[Brief description of drawings]

FIG. 1 is a front view showing a configuration of an image forming apparatus according to an embodiment.

FIG. 2 is a side view showing a part of FIG. 1 in an enlarged manner.

3 is a front view showing a part of FIG. 1 in an enlarged manner. FIG.

FIG. 4 is a front view showing a part of FIG. 1 in an enlarged manner.

FIG. 5 is a front view showing a part of FIG. 1 in an enlarged manner.

FIG. 6 is a perspective view showing configurations of Level 2 and Level 3.

FIG. 7 is a perspective view showing configurations of Level 2 and Level 3.

[Explanation of symbols]

 1: Photoconductor 2: Charging roller 3: Light 4: Developing device 5, 8: Conveying path 6: Transfer device 7: Separator 9: Cleaning device 10: Quenching lamp 21: Cleaning roller 201: Shaft core 202 : Middle layer 203: Outermost layer 204: Bearing 205: Spring 206: Power supply 207: Power feeding receptacle 211: Shaft core 212: Elastic member 213: Bearing 214: Spring

Claims (4)

[Claims] 1. A charging device of an image forming apparatus, comprising: a photoconductor for forming an image; and a charging roller for contacting the photoconductor to give a charge to the photoconductor, the cleaning device comprising a cleaning member in contact with the charging roller. At the same time, the hardness of the cleaning member is smaller than the hardness of the charging roller. 2. The hardness (JISA) of the cleaning member is 30.
The charging device for an image forming apparatus according to claim 1, wherein the charging device has a temperature of not more than a degree. 3. The cleaning member has a roller shape, and the cleaning member rotates together with the rotation of the charging roller when the cleaning member and the charging roller are in contact with each other. The charging device for an image forming apparatus according to claim 1 or 2. 4. The hardness (JIS A) of the cleaning member is 24.
The claim 1, claim 2, or claim 3, which is at least a degree.
A charging device for an image forming apparatus as described above.