JPS60169872A - Image forming device - Google Patents

Abstract

PURPOSE:To reduce toner sticking on a conveying member and prevent image staining in both normal development and reversal development by using a well conductive material for an unfixed transfer material conveying member such as a conveyor roller and a conveyor roll. CONSTITUTION:The conveyor roll 122 is made of the well conductive material such as conductive resin metal, a roll shaft 126 and a shaft holding material 127 also have good conductivity, and the holding material 127 is grounded through a lead wire 130. Consequently, even when two kinds of toner which are different in electrostatic charge polarity and used for normal development and reversal development are used, the electrostatic force for attracting unfixed toner onto the conveyor roll 122 decreases greatly and the toner becomes hard to stick on the roll.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus, and more particularly, to a component toner image forming apparatus.
The present invention relates to an image forming apparatus that can obtain a copy of a positive image from either a positive original or a negative original using an image method.

In order to obtain a positive image from either a blank original or a negative original, the positive original is subjected to normal development in the same way as a normal artist forming device (for example, an electrophotographic device).
On the other hand, for negative images, it is necessary to perform reversal development, which is used in laser beam printers and microfilm printers.

First, an image forming process for obtaining a positive image from a positive original will be explained using FIG. 1. In FIG. 4
5 is a primary charger, and 5 is an image exposure device. 6 is a developing device, which includes a doctor blade 7, a magnet roller 8, and a cylinder 9.
It consists of T is a developing toner, 10 is a pre-exposure lamp, 11 is a transfer paper guide, and 12 is a transfer charger. 13
The cleaner is composed of a p1 rubber blade 14, a magnetic roller 15, a screw 16, a housing 17, and the like.

Here, an example will be described in which a phthalocyanine-based organic conductor is used for the photosensitive layer 2 and negative charging is performed.

The photosensitive drum 1 uniformly charged by the primary charger 4 receives image exposure corresponding to the image pattern of the positive original to form an electrostatic latent image. At this time, the dark part potential Vd of the latent image corresponds to the black ground part of the original, and the four part potential V/ corresponds to the white ground part.

Figure 2 shows the behavior of the drum surface potential.

As the developing toner T, a magnetic component developer having positive charging polarity is used. The toner T in the developing device is charged by mutual friction and contact friction of the cylinder 9, doctor blade 7, etc. The charged toner T is placed on the cylinder 9 with a uniform thickness by the doctor blade 7.
The cylinder 9 rotates, and at the closest point between the drum 1 and the cylinder 9, an electric field generated between the developing bias potential applied to the cylinder 9 and the latent image on the drum 1 causes the toner to be developed to the latent I#! attracted to parts. Since this is normal development, the portion corresponding to the dark potential Vd is visualized.

Afterwards, this type 1 elephant was shown on the back of the transfer paper (omitted in this figure).
The image is transferred onto the paper by applying negative corona charging by the transfer charger 12. The transferred toner image is fixed on the transfer paper by a fixing device (not shown) and is discharged outside the machine to obtain a copy.

Next, the image forming process for obtaining a positive image from a negative original will be explained using FIG. 1 as well. The mechanical configuration of the primary charger 4, developer 6, pre-exposure lamp 10, transfer guide 11, transfer charger 12, and cleaner 13 arranged around the drum 1 is basically the same as the above-mentioned normal phenomenon 1. It is the same as the case.

In this configuration, image exposure 5 corresponding to a negative original is applied to the photosensitive drum 1 which has been uniformly and uniformly negatively charged by the -order charger 4.

Through this exposure, an electrostatic latent image is formed on the drum, where the dark potential Vd corresponds to the black background portion of the negative original, and the bright potential Vt corresponds to the white background portion. In this case, since the purpose is to obtain an inverted image from a negative original, it is necessary to perform a development method in which toner is attached to the Ve portion, so-called inversion development. As the developing toner T in this case, a magnetic component developer having negative charge polarity is used. The toner T in the developing device is charged by mutual friction and contact friction with the cylinder 9, doctor blade 7, etc. The charged toner T is placed on the cylinder 9 with a uniform thickness by the doctor blade 7. As the cylinder 9 rotates, the toner is developed at the closest point between the drum 1 and the cylinder 9 due to the field generated between the voltage bias potential V applied to the cylinder 9 and the latency on the drum 1. It is attracted to the desired area, and the area corresponding to the four-part potential ■e of the latent image shown in FIG. 3 is developed.

For this purpose, the toner must have a charged polarity (in this case, negative) that exhibits a relatively high potential V/ in the positive direction. FIG. 4 conceptually shows how toner does not adhere to the negative potential portion of the background Vd, but negatively charged toner adheres to the four-part potential ■e near the ground potential.

After the latent image is visualized as described above, the transfer charger 1
2, a toner image is transferred onto the paper by applying a positive corona charge. The transferred toner image is fixed onto the transfer paper by a fixing device (not shown) and is discharged outside the machine to obtain a hard copy.

The method for obtaining a positive image from both a positive original and a negative original has been described above, but it is necessary to change the charging polarity of the toner and the electrical polarity of the transfer charging corona depending on the original.

In order to easily accomplish this, a method has been proposed in Japanese Patent Application No. 58-216794 (November 17, 1981) that uses a process cartridge that includes a primary charger, a developer, and a cleaner around the drum. (Not known) In this method, the corona discharge polarity of the transfer charger is also switched by replacing the cartridge.

As described above, it is possible to obtain a positive image from either a positive original or a negative original by replacing the cartridge in the same apparatus.

However, since two kinds of toners having different charging polarities are used, the conveying path of the transfer paper is likely to be stained, and this has caused problems such as smearing on the image.

The cause of this will be explained using FIG. 5 showing the conveyance path. In the figure, a transfer paper (not shown) is guided between a photosensitive drum 1 and a transfer charger 12 by a transfer guide 11. Transfer roller 2
0, the paper is pressed against the drum, and at this time the toner image on the drum is transferred to the back side of the paper by being given a transfer corona discharge. Thereafter, the paper is separated from the drum surface by the separation belt 23, and the paper is separated from the drum surface by the conveying roller 2, which rotates in the direction of the arrow.
A spring member 24 is used to apply tension to the separation belt 23, and is conveyed while being held between the conveyance rollers 21 and the conveyance guide 25.

A part of this conveyance path is shown in the perspective view of FIG.

An unfixed toner image 31 is placed on the transfer paper 30.

Since it is preferable that the amount of information recorded on the transfer paper 30 is large,
In many image forming apparatuses, toner images are formed right below the projections 22a of the conveying rollers 22, as shown in the cross-sectional view of FIG.

Normally, the conveying roller 22 is made of resin, and is charged to several thousand volts by friction with the paper. Therefore, the resin is selected so that the triboelectrically charged resin has the same polarity as the toner to be used. It electrostatically repels toner and prevents stains.

For example, in an image forming apparatus that uses toner that is positively charged, a resin such as polyacetal that is positively charged by friction with paper is used as the conveying roller 22, and conversely, in an apparatus that uses toner that is negatively charged, the resin is charged negatively. A resin such as tetrafluoroethylene is used.

However, when using class 211 toners with different charging polarities in one device as described above, there are cases where toners with charging polarities different from the frictional charging polarity of the resin of the roller material are used, and the roller There was a problem in that toner was electrostatically attracted and accumulated on the transfer paper and came into contact with the transfer paper, causing image stains.The present invention was made in view of the above-mentioned drawbacks of the conventional example. An object of the present invention is to provide an image forming apparatus in which toner is prevented from adhering to members disposed in a conveyance path of a transfer material, such as a conveyance roller, a conveyance roller, etc.

The present invention will be explained below based on one embodiment shown in the drawings.

The present invention is characterized in that the conveying rollers 22 shown in FIGS. 5 and 6 are made of a highly conductive material and are electrically connected to the ground, and the structure is shown in FIG. 8. show. That is, in FIG. 8, the conveying roller 122 is made of a four-conductor resin or metal, the roller shaft 126 and the shaft holding material 127 are also made of highly conductive materials, and the lead wire 130 etc. is made from the shaft holding material 127. It is connected to the ground of the image forming apparatus.

With the above configuration, the electrostatic force that attracts toner onto the conveying roller 122 is significantly reduced, making it difficult for toner to adhere to the roller. This prevents image staining, which has been a problem in the past.

FIG. 9 ta+ and +bl show another embodiment of the present invention, in which the shape of the conveying roller is changed, and the protruding portion 22a is tapered toward the tip. With such a shape, the toner 1 on the transfer paper and the protrusion 222a of the roller material are
, and the roller becomes even higher than in the above embodiment
toner becomes difficult to adhere to. Furthermore, even if toner accumulates on the roller, since there is a wide gap between the transfer paper and the protrusion 222a,
There is no contact between toner and paper, and therefore no image smearing occurs.

Of course, the shaft, holding member, etc. are made conductive, and the rollers are connected to the ground, as in the previous embodiment.

Furthermore, as another embodiment, a bias potential level of several 6 volts with both positive and negative polarities can be selected and applied to the conveying roller, and the polarity of this bias potential is determined by the cartridge to determine the charging polarity of the toner to be used. A configuration in which they are selected so that they match is also possible. With this method, a stable potential is applied to the conveying roller instead of an uncertain potential due to frictional charging as in the conventional example, and this potential prevents toner absorption, so the aforementioned conveying roller can be grounded. This embodiment is even more effective against image defects and stains.

FIG. 10 shows a block diagram of this bias voltage method, in which 200 is a cartridge detection sensor, 201 is a driver circuit, 202 is a negative (-)' power supply, 203
204 is a positive (+) ton, and 204 is a current supply circuit to the conveying roller. That is, the cartridge is provided with a bottle or the like corresponding to the polarity of the toner used, and this bottle causes one of the sensor sections of the cartridge detection sensor 200 to act. Due to this action, the driver circuit 20
1 connects the negative power supply 202 or positive power supply 203 to MIA
make it move.

Further, the present invention is not limited to conveyance rollers and conveyance rollers, but can also be applied to conveyance belts, and more broadly, can be applied to all members disposed within the transfer material conveyance path.

Since the image forming apparatus according to the present invention is as described above, it has the effect of preventing image staining due to toner.

[Brief explanation of the drawing]

FIG. 1 is a side view showing the outline of the image forming apparatus, FIG. 2 is a diagram showing the fluctuation of the drum surface potential in the case of a positive original-positive image, and FIG. figure,
FIG. 4 is a diagram conceptually showing how toner adheres, FIG. 5 is a side view showing the transfer section of the image forming apparatus, and FIG. 6 is a perspective view showing the relationship between the conveyance roller and the transfer material. FIG. 7 is a front view, FIG. 8 is a perspective view of one embodiment of the present invention, FIG. 9 ta+ is a front view of another embodiment, FIG. 9 fbl is a perspective view, and FIG. 10 is another embodiment. FIG. 2 is a block diagram of an embodiment of the invention. l...Photosensitive drum, 5...Image exposure, 6...Developer, T
...Development toner, 11...Transfer paper guide, 12...
Transfer charger, 30... Transfer paper, 31... Toner 1 elephant,
122.222... Conveyance roller, 126... Roller axis, 1
30 ・Lead wire (earth), Vd... dark area' potential,
Ve...S' part potential. Applicant Canon Co., Ltd.

Claims (1)

[Scope of Claims] fll In an image forming apparatus that uses two unique toners with different charging polarities, a member disposed in a conveyance path of a transfer material carrying toner 1 is made of a highly conductive material. , an image forming device characterized in that all of the members are at ground potential. (2) Image 1 using two types of toner with different charging polarities
The image forming apparatus is characterized in that a member arranged in a conveyance path of a transfer material carrying a toner image is made of a highly conductive material, and a bias potential of the same polarity as that of the toner is applied to the member. Device.