JPH08106222A - Corone discharge devce - Google Patents

Abstract

PURPOSE: To prevent the irregularities in an image from occurring due to charging when a transfer material passes the end of a guiding means for preventing entening of the transfer material into a separating means in an image forming device selectively using two kinds of toners having different charging polarities. CONSTITUTION: In an image forming device for forming a negative image or a positive image by using two kinds of toners having different charging polarites comprising an image carrier, a transfer means for transferrring a toner image on the image carrier to a transfer material, a separating means for electrostatically peeling off the transfer material from the image carrier and a guiding means provided oppositely to the separating means for preventing the transfer material peeled off from the image carrier from entering the separating means and carrying the tramsfer material, a guiding means 19 includes a first insulated transfer material entering preventing means 191 for preventing the transfer material from entering the separating means and a second conductive carrying means 193 different from the first means 191 and charging of the transfer material due to friction with the end of the first means 191 is prevented by the second means 193.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corona discharge device used in an image forming apparatus or the like, and more particularly to a corona discharge device provided with a member for preventing a transfer material from entering the corona discharge device.

[0002]

2. Description of the Related Art Conventionally, various image forming apparatuses for forming a toner image on an image carrier by electrophotography and electrostatically transferring the toner image onto a transfer material have been put to practical use. Usually, in these image forming apparatuses, the toner image formed on the image carrier is electrostatically transferred to a transfer material by corona discharge from a transfer charger, and then this toner image is transferred. The material is electrostatically peeled from the photosensitive drum by corona discharge from a separation charging device disposed adjacent to the transfer charging device. Further, a conveyance guide in which a plurality of rib-shaped members are arranged at a predetermined interval is provided on the surface of the separation charger facing the image carrier so that the transfer material separated from the image carrier does not enter the separation charger. ing. By the way, the transport guide is made of an insulating member, and the transport guide or the transfer paper is charged up to several KV due to frictional charging with the transfer material. This tendency becomes more remarkable in a low humidity environment, and the unfixed toner image on the transfer paper is disturbed.

Therefore, conventionally, as in Japanese Patent Laid-Open No. 4-301870, the above-mentioned toner disorder has been solved by appropriately selecting a resin which is triboelectrically charged with a polarity opposite to that of the toner from various insulating resins. In general, PP resin or the like is used in the case of an image forming apparatus such as a copying machine that performs regular development using positive toner, and ABS is used in an image forming apparatus such as LBP that performs reversal development using negative toner. Resin, etc. are used.

Alternatively, as in Japanese Patent Application No. 63-13590,
It has been proposed to dispose a conductive material or apply a conductive coating on the side of the guide (rib) that is the transfer material rush prevention and conveyance means facing the image carrier.

[0005]

By the way, in an image forming apparatus such as a copying machine or a laser beam printer which forms an image by using a toner having a single charging polarity as described above, an insulating resin is appropriately selected as described above. However, in an image forming apparatus such as a micro film reader printer that forms an image by using two types of toner having different charging polarities, an insulating resin is appropriately selected and two types having different charging polarities are used. It is difficult to make both toners compatible. That is, when a negatively charged PP resin is used for the transport guide, there is no problem during positive image formation, but image distortion occurs during negative image formation. On the contrary, when the (+)-charged ABS resin is used, there is no problem when forming a negative image, and there is a problem when forming a positive image.

Further, when a conductive material is provided or a conductive coating is provided on the surface of the guide (rib) facing the image carrier, it is necessary to dispose the conductive material on a part of the rib for accuracy and workability. In consideration of the above, it is difficult in reality, and when a conductive coat is used, there is a problem that the abrasion coat is peeled off together with the durable number.

Further, as a result of a study by the present inventor, the place where the above-mentioned image disorder occurs is in the fixing material side end portion (downstream side of the transfer material advancing direction) of the rib which is the conveyance guide in the transfer material advancing direction. There was found. This is because the transfer material that has passed over the separation charger moves to the transport section, and at this time, due to the step (height direction) between the transport section and the transport guide rib, the transfer sheet and the transport guide slide strongly at the end of the transport guide rib fixing unit side. This is for rubbing.

[0008]

In order to solve the above-mentioned drawbacks, the present invention provides an image carrier, transfer means for transferring a toner image on the image carrier to a transfer material, and a proximity to the transfer means. Separation means arranged to electrostatically separate the transfer material from the image carrier, and guide means arranged to face the separation means to prevent the transfer material separated from the image carrier from entering the separation means and convey the transfer material. In an image forming apparatus provided with two types of toner having different charging polarities to form a negative image or a positive image, the guide means is a first insulating transfer material for preventing the transfer paper from entering the separating means. It is characterized in that the rush prevention means and the first guide are formed of second conductive transport guide means different from each other.

With the above construction, the transfer paper peeled off by the separation charging device can be prevented from entering the charging device by the first insulating transfer material rush preventing means, and the side of the conveyance guide fixing device where image distortion occurs At the end portion, frictional charging with the transfer paper can be prevented by sliding contact with the second conductive transport guide means, so that the image on the transfer paper is not disturbed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a schematic view of an image forming apparatus applied to the present invention, and 9 is an image carrier made of an OPC photoconductor.
It is rotationally driven at a predetermined peripheral speed in the direction of arrow a in the figure. Around the image carrier 9, a primary charging device 10, a blank exposure light source (used for forming a positive image) 11, a positive developing device 12 containing positive toner, a negative developing device 13 containing negative toner,
Pre-transfer charger 14, transfer charger 15, separation charger 16,
A cleaner 17 and a pre-exposure lamp 18 are arranged in that order.

After the photosensitive drum 9 is uniformly charged by the primary charger 10, an electrostatic latent image is formed on the photosensitive drum by the image exposure E which is the magnified transmitted light of the microfilm.
Then, in the developing section, the electrostatic latent image is developed. At this time, the pressures of the positive developing device and the negative developing device are released according to the image forming mode. The developing sleeve rotates in the direction of the arrow b in the drawing, and the fixed magnet is built in the developing sleeve. A magnetic mono-component insulating toner is coated on the surface of the developing sleeve in a thin layer, and a developing bias voltage in which a DC component is superimposed on an AC component is applied to the developing sleeve in order to develop an electrostatic latent image on the image carrier. Has been done.

After the development process is completed, the pre-transfer charger 14 is provided to apply the electric charge to the toner which is the developed image on the image carrier.
Is arranged, and the direct current component and the alternating current component biased to the same polarity as the toner are superimposed. A transfer charger 15 and a separation charger 16 are arranged just below the image carrier.

The transfer material P temporarily stays on the pair of registration rollers 20, and the registration rollers operate so that the transfer material and the front end of image exposure are synchronized. As a result, the transfer material P is conveyed toward the transfer charging device 15 via the transfer entrance guide pair 21, and the transfer charging device performs corona charging having a polarity opposite to the polarity of the toner to form a developed image on the image carrier. Transfer to the transfer material P. At the time when this transfer is performed, the transfer material P is adsorbed on the image carrier by electrostatic force.

Next, the transfer material P is separated from the image carrier by the corona discharge of the separation charger 16 so that the electrostatic force acting between the image carrier and the transfer material is weakened. Here, the separation charger 1
The voltage applied to the corona wire 6 has a direct current component and an alternating current component of the opposite polarity to the polarity of the transfer charger. Next, the transfer material separated from the image bearing member is guided to the conveyance section 221 while being in contact with the guide 19, heated and fixed in a fixing section (not shown), and discharged outside the apparatus.

On the other hand, the image carrier 9 remaining in the transfer / separation process
The toner on the top is cleaned by the cleaner 17, and then the image bearing member is decharged by the pre-exposure 18.

FIG. 1 is a guide 19 for explaining the present invention, which is disposed on the side of the surface of the image carrier which is separated by the charging device and which prevents the transfer material from entering the charging device and guides the transfer material to the conveying portion. FIG. 3 is an enlarged perspective view of an essential part of FIG. In the figure, reference numeral 191 denotes a plurality of ribs formed of an insulating material which is a first insulating transfer material rush preventing means for preventing the transfer paper from rushing into the separating means, and is integrally formed with the base material 192. ABS resin. Besides the insulating material, ACS, PP, MB
S, PS, PE, PC, PA, POM, PPM, PAI
Resins such as are generally used.

Reference numeral 19 denotes a second conductive transport guide means having a volume resistivity of ¹ × 1O ¹ Ω · Cm or a surface resistivity of 7.
It is a rib formed of a conductive resin (trade name: DURACON CE-20) of X10 ¹ Ω · cm. Here, the second conveyance guide means (rib) 193 is adhered, fitted or heat-welded to the end of the ABS resin on the base material outside the opening of the transfer separation charger on the downstream side (fixer side) in the transfer material advancing direction. And other known methods.

Further, the second conveying guide means 193 is located between the ribs 191 which are the first insulating transfer material rush preventing means and is slightly higher than the height h2 of the ribs 191 (in the present embodiment, h1). It is desired that the transfer material is formed and arranged at a height of approximately 0.2 to 0.5 mm) and that the cross-sectional shape thereof has a predetermined curvature so that the transfer material can be smoothly transported as shown in the drawing.

Therefore, the transfer material rushing into the charging device can be prevented by the first insulating transfer material rushing-in preventing means, and the first insulating transfer material rushing-in preventing means at the end portion of the guide fixing device side which causes the image disturbance. The rubbing against the transfer material can be prevented by disposing the second conveyance guide means. Further, although it rubs against the second conveyance guide means, since it is formed of the conductive resin as described above, the triboelectric charge amount is greatly improved and can be suppressed to approximately 10 OV or less. Further, although the conductive resin is used as the second conveying guide means, in the present invention, the guide means is arranged at a position outside the charger opening, and between the charger shield and the guide means. Is electrically insulated by the first insulating transfer material rush prevention means, and there is no fear of leakage from the charger.

In the above-mentioned embodiment, the second conveyance guide means is arranged approximately in the middle of the first insulating transfer material rush preventing means, but the present invention is not limited to this, and the first insulating transfer material rushing means is not limited to this. It is also possible to place it adjacent to the prevention means. In short, any arrangement position or number may be used as long as the first insulative transfer material rush prevention unit and the transfer material do not rub against each other at the end portion on the guide fixing device side. Further, the material of the second conveyance guide means is not limited to this embodiment.

[0021]

As described above, according to the present invention,
The first insulating transfer material rush preventing means for preventing the transfer material from entering and the guide means for preventing the transfer material from entering the separating means and the guide means are provided by a second conductive transfer means different from the first guide. With this structure, frictional electrification at the end of the guide on the side of the fixing device can be prevented, so that image distortion does not occur during both negative image formation and positive image formation.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a corona discharge device according to the present invention.

FIG. 2 is an enlarged perspective view of a main portion of a guide in the corona discharge device of the present invention.

[Explanation of symbols]

9 ... Image bearing member 15 ... Transfer charging device 16 ... Separation charging device 19 ... Guide means 191 ... Insulating transfer material intrusion prevention means 192 ... Base material 193 ... Conductive transporting means

Claims (2)

[Claims] 1. An image carrier, a transfer means for transferring a toner image on the image carrier to a transfer material, and a separating means arranged in proximity to the transfer means to electrostatically separate the transfer material from the image carrier. And a guide unit that is arranged opposite to the separating unit to prevent the transfer material separated from the image carrier from entering the separating unit and convey the transfer material, and a negative image or a negative image using two types of toner having different charging polarities. In an image forming apparatus for forming a positive image, the guide means is a first insulating transfer material rush preventing means for preventing the transfer material from rushing into the separating means, and a second conductive transporting means different from the first means. A corona discharge device comprising: 2. The corona discharge device according to claim 1, wherein the second conductive transport means is a first insulating transfer material rush prevention part on the downstream side in the transfer material advancing direction outside the transfer separation charger opening. A corona discharge device, wherein the corona discharge device is arranged at a position different from that of the device and is slightly higher than the first insulating transfer material rush prevention device.