JPH11249390A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device equipped with a discharge wire cleaning mechanism capable of effectively removing the oxide coating film of a discharge wire and a foreign matter. SOLUTION: Since the electrophotographic image forming device utilizing corona discharge is provided with the discharge wire cleaning mechanism equipped with a pad 14 impregnated with alkali water solution, SiO2 and WO3 which are hardly removed by a dry system or neutral water are solved and removed by the alkali water solution, and the discharge wire is kept in an excellnt state. The discharge wire cleaning mechanism is constituted of at least the pad 14 and a holder 15 supporting the pad 14. Since the pad 14 is attached to the holder 15 without using an adhesive member, only the pad 14 can be attached to/detached from the holder 15, only the pad 14 can be replaced or the pad 14 can be washed and reused.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus using a corona discharge, such as a copying machine, a facsimile, and a printer, and more particularly, to an image forming apparatus having a cleaning mechanism for a corona discharge wire used in an electrophotographic process. It is about.

[0002]

2. Description of the Related Art As means for cleaning a wire of a corona discharger (charging device) used in an electrophotographic image forming apparatus such as a copying machine, for example, Japanese Patent No. 2690369 discloses "Corona discharge of image forming apparatus". A cleaning pad as disclosed in "Electric Appliance" (an invention relating to a means for reducing load resistance when reciprocating with a discharge wire held between pads).
Several means for automatically cleaning the discharge wire have been proposed. Further, in order to improve the cleaning effect, Japanese Patent Application Laid-Open No.
No. 23772, "Charging device for image forming apparatus" (cleaning of a charging wire using a pad in which hard small-diameter particles are dispersed); Using a corona wire to slide and clean).

[0003]

In an image forming apparatus such as a copying machine, a printer, or a facsimile using an electrophotographic process, the surface of an image carrier such as a photoconductor is charged uniformly.
Transfer charging when transferring an image from an image carrier to a transfer material,
2. Description of the Related Art A corona discharge device is widely used as a discharge device for performing charge removal for separation when separating a transfer material after transfer from an image carrier or the like. The corona discharge device utilizes an electric charge generated by a corona discharge phenomenon caused by a strong electric field generated between a corona discharge wire to which a high voltage is applied and a shield electrode facing the discharge wire, and uses the image carrier or the transfer material. And the like to charge or remove electricity.

FIG. 6 schematically shows a scorotron as one of the corona discharge devices. Usually, tungsten (W) is used as the discharge wire 21, and a high voltage is applied to the discharge wire 21 by a high-voltage power supply 24 to perform corona discharge. Improvement of discharge stability, and charged object 20 such as photoreceptor
In order to control the surface potential of the discharge wire 21, the periphery of the discharge wire 21 is shielded by a square or cylindrical metal called a casing 23, and a grid 22 is disposed at a position below the discharge wire 21 facing the charged object 20. Connected to the varistor 25.

At the time of corona discharge, ozone is generated from oxygen in the air. This causes oxidation of the discharge wire, and in the case of a tungsten wire, a WO ₃ film is formed on the surface. Further, dust in the image forming apparatus, evaporated matter of silicon oil applied to the fixing roller, and the like also adhere to the discharge wire. Such oxidation of the wire and adhesion of foreign matter cause uneven charging and poor charging, resulting in deterioration of image quality.

In order to avoid such a drawback, a cleaning member provided with a pad such as a felt or a sponge for holding the discharge wire is provided, and the cleaning member is reciprocated along the discharge wire to clean the discharge wire. Various cleaning mechanisms have been proposed (for example, Japanese Patent No. 2690369).
However, in the case of the type in which the wire is reciprocated simply by sandwiching the wire between the pads, a sufficient cleaning effect cannot be obtained. It has been proposed to improve the performance by using a pad containing water (Japanese Patent Application Laid-Open No. 9-197771). In the case of a pad in which small-diameter particles are dispersed, the purpose is to remove the particles by polishing.However, it is not easy to remove the foreign matters firmly adhered to the pad. There was a risk of contamination. When a pad soaked in water is used, there are many foreign substances dissolved in water and easily removed, and there is no problem such as polishing debris. However, oxidation of SiO ₂ or tungsten wire formed from silicon oil is not performed. WO ₃ or the like as a coating film could not be sufficiently removed because of its low solubility in water.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image provided with a discharge wire cleaning mechanism capable of more effectively removing an oxide film and foreign matter on a discharge wire than the prior art. It is to provide a forming device.

[0008]

In order to achieve the above object, the present invention relates to an electrophotographic image forming apparatus utilizing corona discharge, comprising a discharge wire cleaning mechanism provided with a pad impregnated with an alkaline aqueous solution. It has a structure (claim 1).

Here, as the main component of the alkaline aqueous solution impregnated in the pad, one having an alkaline buffering action is used (claim 2). The pad is provided in non-contact with the wire when not used for cleaning (claim 3). The pad is covered with a lid when not used for cleaning (claim 4). Further, the alkaline aqueous solution can be appropriately replenished to the pad (claim 5).

[0010] The discharge wire cleaning mechanism in the image forming apparatus of the present invention comprises at least a pad and a holder for supporting the pad, and the pad is attached to the holder without using an adhesive member. ). The pad is made of a member having water absorption and elasticity, and the pad has an outer diameter larger than the inner diameter of the holder. The inner diameter of the holder can be changed by a screw (claim 8).

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration and operation of the present invention will be described below in detail with reference to the drawings.

FIG. 1 schematically shows the structure of an electrophotographic image forming apparatus and an image forming process. In FIG. 1, reference numeral 1 denotes a photoreceptor serving as an image carrier, and a charging device 2, an exposing device (not shown), a developing device 3, a transfer device 4, a pre-cleaning neutralizing device 6, and a cleaning device are provided around the photoreceptor 1. 7, a static elimination lamp 8, and the like. When the image forming process is started, first, the photoconductor 1 is charged by the charging device 2, and thereafter, an exposure device (a device for exposing a document image, or optical writing corresponding to an image signal using a laser beam or the like) is used. The developing device 3 forms an electrostatic latent image by exposure to light, and develops the image with the toner of the developing device 3. continue,
An image is recorded on the transfer paper 9 by a process in which the toner on the photoreceptor 1 is transferred to the transfer paper 9 by the transfer device 4 and then fixed by the fixing device 5. The toner remaining on the photoreceptor 1 without being transferred to the transfer paper 9 is removed by the pre-cleaning charge removing device 6.
Then, the photosensitive member 1 is cleaned by a blade or the like of the cleaning device 7, the charge is removed by irradiating light from the charge removing lamp 8, and the photosensitive member 1 is used again in the image forming process. Of these processes, a corona discharge method is often used for charge, transfer, and charge removal before cleaning.

In charging, a charging device 2 using corona discharge is used in order to uniformly charge the photosensitive member 1.
In particular, it is often used in a negative discharge that generates a large amount of ozone. The transfer is a process of moving the toner adhered on the photoconductor 1 to the transfer paper 9. For this, a method utilizing an electrostatic force is generally used, and a transfer device 4 using corona discharge applies an electric charge onto a transfer paper 9 to thereby transfer the photosensitive member 1.
Then, the toner is moved to the transfer paper side by Coulomb force and held by the electric field generated between them. The cleaning is a process of removing the toner remaining on the photoconductor 1 without being transferred from the photoconductor 1, and a typical method is a method of scraping the toner with a rubber blade or a fur brush. In order to improve the cleaning property, a pre-cleaning static eliminator 6 using AC corona discharge before scraping is performed.
Thus, there is a case where a process for removing the charge of the toner and weakening the electrostatic adhesion between the toner and the photoconductor 1 is performed.

As described above, corona discharge devices are used in various places in an electrophotographic image forming apparatus. However, as described in the above-mentioned subject, as the use is continued, the discharge wire is oxidized or a foreign substance is adhered, causing charging unevenness and charging failure. In particular, poor charging of the photoreceptor directly leads to deterioration of image quality, so that it is necessary to always maintain a good state.

The present inventors have examined foreign substances adhering to the discharge wire. As a result, with the dry pad conventionally proposed,
Although effective for removing dust and paper dust, the evaporation of silicon oil applied to the fixing roller and the like is oxidized by ozone to form silica (SiO ₂ ) on the surface of the wire and adhere to the wire. In some cases, the oxide of the wire itself (W
There is not much effect on the removal of O ₃ ). Then, S
Focusing on the fact that iO ₂ and WO ₃ dissolve in an alkaline aqueous solution, using a pad impregnated with an alkaline aqueous solution, it was confirmed that the pad could be easily removed by several round trips.

Hereinafter, the configuration and operation of the present invention will be described in detail. FIG. 2 is a schematic configuration diagram of a corona discharger showing an example of the embodiment of the present invention. The corona discharger 10 is used for the charging device 2, the transfer device 4, the pre-cleaning static eliminator 6, etc. of the image forming apparatus shown in FIG. 1 and includes a discharge wire 11, a grid 12, and a casing 13. A discharge wire cleaning mechanism is provided in the casing 13, and the discharge wire cleaning mechanism has a configuration including a cleaning member including a holder 15 and a pad 14. The upper part of the casing 13 of the corona discharger 10 is open, and a part of the holder 15 goes out of the opening of the casing 13 and is connected to the motor 19 via a drive mechanism (not shown).

The cleaning of the discharge wire 11 is controlled so as to be performed at regular intervals when discharge is not being performed.
Further, when cleaning is not performed, the holder 15
The pad 14 and the discharge wire 11 are lifted above the position shown in FIG. Further, when the pad 14 is not used for cleaning, the exposed portion of the pad 14 of the holder 15 is covered with a lid 16 having a shape as shown in FIG. As such a configuration,
By impregnating the pad 14 with an alkaline aqueous solution, the pad 14 becomes conductive and avoids adversely affecting the discharge behavior. In addition, the lid 15 holds the holder 15.
By covering the exposed portion of the pad, the evaporation of moisture from the pad 14 can also be prevented.

A notch is formed in the center of the pad 14. When the holder 15 is lowered during cleaning, the discharge wire 11 is sandwiched in the notch of the pad 14, as shown in FIG. The portion of the holder 15 that is outside the casing 13 is driven by a motor 19 via a drive mechanism such as a gear (not shown), so that the cleaning mechanism can reciprocate along the discharge wire 11. In addition, the discharge wire 11 can be cleaned by rubbing with the pad 14.

The pad 11 is made of a material having water absorbency and elasticity, such as urethane foam and felt, and is impregnated with an alkaline aqueous solution. Examples of the alkaline aqueous solution include Na ₂ CO ₃ , K ₂ CO ₃ , Na ₂ CO ₃ P ₂ O ₅ ,
Na ₂ SiO ₃ , Na ₂ O · NaHSiO ₃ , NaSi
Aqueous solutions of various alkali salts having an alkaline buffering action such as O ₄ , Na ₅ P ₃ O ₁₀ , and Na ₄ P ₂ O ₇ can be used.
In the case of an aqueous solution having no alkali buffering property such as NaOH, it works well at the beginning, but it is not preferable because the pH shifts to a neutral side with time, and the cleaning effect weakens accordingly.

The pad 14 is connected to the holder 1 as shown in FIG.
In this case, the outer diameter of the pad 14 is slightly larger than the inner diameter of the holder 15,
The pad 14 can be held in the holder 1 without using an adhesive by squeezing the holder 4 into the holder 15.
5 supported. As another example, the outer diameter of the pad 14 and the inner diameter of the holder 15 are set to be substantially equal to each other.
As shown in FIG. 5, screws 17 may be attached to both side walls of the holder 15 so as to press both ends of the pad 14, and the pad 14 may be supported by the holder 15 by changing the inner diameter of the holder 15 with the screw. Alternatively, as shown in FIG. 5, the holder 15 is configured so as to open to the left and right at the center, and the portion of the flange 15 a provided at the joint portion of the holder 15 is closed with a screw 17 so that the inner diameter of the holder 15 can be reduced. Is changed so that the pad 14 can be sandwiched between the holders 15, the mounting can be performed more easily.

In any case, since the pad 14 can be supported on the holder 15 without using an adhesive, replacement of the pad 14 is easy. Further, when the degree of adhesion of the dirt on the pad 14 becomes severe and the cleaning effect is deteriorated, only the pad 14 can be removed from the holder 15, washed, replaced, and used again without replacing the entire cleaning member. Therefore, a good state can be maintained without wasting resources.

As shown in FIG. 4 or FIG. 5, the holder 15 is provided with a replenishing port 18 for an aqueous solution.
An alkaline aqueous solution can be appropriately replenished to the pad 14 from the replenishing port 18. Specifically, the replenishment of the alkaline aqueous solution to the pad 14 may be performed by inserting a tip of a dropper, a syringe, or the like into the replenishing port 18 of the holder 15 from the upper opening of the casing 13 or may be performed. May be provided and attached to the replenishing port 18 of the holder 15 via a tube or the like so that the replenishment is automatically performed as appropriate.

[Embodiment] As an embodiment of the present invention, a new corona discharger 10 having a discharge wire cleaning mechanism is attached to a charging device 2 of a photoreceptor charging section of an evaluation laser printer having a configuration as shown in FIG. And a continuous print test was performed. The cleaning member of the discharge wire cleaning mechanism is shown in FIG.
And the pad 14 has Na ₂ CO ₃ and Na
A mixture of ₅ P ₃ O ₁₀ is dissolved in water, impregnated with an alkaline aqueous solution adjusted to a pH of about 12, and an alkaline aqueous solution is automatically supplied to the pad 14 by a tank (not shown) or the like. . The discharge wire cleaning mechanism was reciprocated three times for every 10K prints (K: 1000), and a continuous test was performed for up to 1000K prints while cleaning the discharge wires 11 with the pads 14 at regular intervals. As a result, good images were obtained until the end of the test.

COMPARATIVE EXAMPLE As a comparative example, a new corona discharger 1 having a discharge wire cleaning mechanism in the photosensitive member charging section of the evaluation laser printer having the configuration shown in FIG.
0 was attached as the charging device 2, and a continuous printing test was performed. The shape of the cleaning member of the discharge wire cleaning mechanism is the same as in the above embodiment, but the pad 14 is used by impregnating with neutral water. The operation was performed at the same timing as in the above-described embodiment. As a result, the image became uneven when the number of prints was about 500K, and the unevenness became severe as the test was advanced. After the test was completed, the surface of the wire was analyzed. As a result, WO ₃ and SiO ₂ were detected, and it was considered that these could not be removed effectively with neutral water, resulting in image deterioration.

As is clear from the results of the above Examples and Comparative Examples, it is effective to use a pad impregnated with an alkaline aqueous solution for the discharge wire cleaning mechanism, and to surely remove oxide films and foreign substances on the discharge wire. It can be removed.

[0026]

As described above, the image forming apparatus according to the first aspect has a structure in which the discharge wire cleaning mechanism is provided with the pad impregnated with the alkaline aqueous solution. SiO ₂ and WO _{3 which} are difficult to dissolve can be dissolved and removed with an alkaline aqueous solution.
The discharge wire can be kept in a good state. Therefore,
The occurrence of uneven charging and poor charging due to oxidation of the discharge wire and adhesion of foreign matter can be prevented, and deterioration of image quality due to these can be prevented.

In the image forming apparatus according to the second aspect,
In addition to the configuration and effect of claim 1, the main component of the alkaline aqueous solution to be impregnated into the pad uses an alkaline buffering agent, so that the pH of the aqueous solution hardly changes over time, so that a good state can be maintained. it can.

In the image forming apparatus according to the third aspect,
In addition to the configuration and effect of the first aspect, when the pad is not used for cleaning, the pad is provided in non-contact with the wire, so that the pad does not adversely affect discharge.

In the image forming apparatus according to the fourth aspect,
In addition to the structure and effect of the first aspect, when the pad is not used for cleaning, the pad is covered with the lid, so that adverse effects on electric discharge can be prevented, and further, evaporation of moisture from the pad can be prevented.

In the image forming apparatus according to the fifth aspect,
In addition to the configuration and effect of the first aspect, the alkaline aqueous solution can be appropriately replenished to the pad, so that it can be used continuously for a long period of time.

In the image forming apparatus according to the sixth aspect,
In addition to the configuration and effect of claim 1, the discharge wire cleaning mechanism includes at least a pad and a holder that supports the pad, and the pad is attached to the holder without using an adhesive member. It is possible to attach and detach only the holder, replace only the pad,
Alternatively, the pad can be cleaned and reused.

In the image forming apparatus according to the seventh aspect,
In addition to the configuration and effect of claim 6, the pad is made of a member having water absorbency and elasticity, and the outer diameter of the pad is configured to be larger than the inner diameter of the holder.
It is possible to support the pad on the holder.

[0033] In the image forming apparatus according to the eighth aspect,
In addition to the configuration and effect of claim 6, the inner diameter of the holder can be changed by a screw, so that the pad can be easily attached and detached.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating a configuration of an electrophotographic image forming apparatus and an image forming process.

FIG. 2 is a view illustrating an example of an embodiment of the present invention, and is a schematic configuration diagram of a corona discharger having a discharge wire cleaning mechanism.

FIG. 3 is a perspective view illustrating an example of a lid that covers a pad exposure portion of a holder of the discharge wire cleaning mechanism illustrated in FIG. 2;

FIG. 4 is a diagram showing another example of the embodiment of the present invention,
(A) is sectional drawing of a discharge wire cleaning member, (b) is a perspective view of a discharge wire cleaning member.

FIGS. 5A and 5B are views showing still another example of the embodiment of the present invention, wherein FIG. 5A is a sectional view of a discharge wire cleaning member, and FIG. 5B is a perspective view of the discharge wire cleaning member.

FIG. 6 is a diagram showing a schematic configuration of a scorotron as one of the conventional corona discharge devices.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor (image carrier) 2 charging device 3 developing device 4 transfer device 5 fixing device 6 static elimination device before cleaning 7 cleaning device 8 static elimination lamp 9 transfer paper 10 corona discharger 11 discharge wire 12 grid 13 casing 14 pad 15 holder 15a Flange 16 Lid 17 Screw 18 Refill port 19 Motor

Claims (8)

[Claims] 1. An electrophotographic image forming apparatus using corona discharge, comprising: a discharge wire cleaning mechanism having a pad impregnated with an alkaline aqueous solution. 2. The image forming apparatus according to claim 1, wherein the main component of the alkaline aqueous solution impregnated in the pad has an alkali buffering action. 3. The image forming apparatus according to claim 1, wherein the pad is not in contact with the wire when not used for cleaning. 4. The image forming apparatus according to claim 1, wherein the pad is covered with a lid when not used for cleaning. 5. The image forming apparatus according to claim 1, wherein the alkaline aqueous solution can be replenished to the pad as needed. 6. An image forming apparatus according to claim 1, wherein said discharge wire cleaning mechanism comprises at least a pad and a holder for supporting said pad, and said pad is attached to said holder without using an adhesive member. Characteristic image forming apparatus. 7. The image forming apparatus according to claim 6, wherein the pad is formed of a member having water absorbency and elasticity, and an outer diameter of the pad is larger than an inner diameter of the holder. 8. The image forming apparatus according to claim 6, wherein the inner diameter of the holder can be changed by a screw.