JPH0436781A - image forming device - Google Patents

Abstract

PURPOSE:To prevent toner from adhering to a carrying member and to prevent the contamination of a transfer material by forming a non-magnetic conductive member at the edge part of the carrying member and allowing it to be electrically in a float state or biasing it so that it may have the same polarity as the toner. CONSTITUTION:A toner image formed on a photosensitive drum 1 arrives at a transfer pat opposed to an electrostatic transfer roller 3 by the rotation of the drum 1. Meanwhile, the transfer material such as paper, etc., is guided by the carrying member 2 and arrives at the transfer part, where the toner image is transferred to the transfer material. The member 2 is constituted of two plates 2b and 2c arranged nearly in parallel, and a non-magnetic metallic member or conductive member 2d is provided over the end faces on the casing 5 side and the drum 1 side of a developing device at the edge part of the plate 2b. In the case that the toner is negative, the member 2d is biased to be negative by a power source A.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention comprises a pair of plate-shaped conveying members disposed approximately parallel to each other in the vicinity of an image carrier, and the above-mentioned The present invention relates to an image forming apparatus in which a transfer material is guided in the direction of an image carrier, and in particular to an image forming apparatus having a feature in a transfer material conveying device portion of an image forming apparatus that utilizes an electrostatic transfer process. be.

[Prior Art] Image forming apparatuses that have been put into practical use are shown in FIG.
As shown in Fig. 4, there is a type in which the casing of the developing device is also used as a conveyance member, and as shown in Fig. 5, there is a type in which it is constructed as a separate body. .

The former device is generally composed of a photosensitive drum 10 whose rotating shaft is perpendicular to the plane of the paper and rotates in the direction of arrow A, and a transfer roller 30 disposed close to the photosensitive drum 10, and a transfer roller 30 located upstream of the photosensitive drum 10 when viewed in the rotational direction of the photosensitive drum. A transfer material conveying member 20 consisting of a pair of members 20a and 20b is disposed on the side, and a conveying member 40 for conveying the transferred transfer material to the next step is disposed on the downstream side.

Further, in the conventional image forming apparatus shown in FIG.
It is formed from a separate member.

In the above-mentioned apparatus, a sheet-shaped transfer material (not shown) mainly made of paper is guided by the conveyance member 2,
At the transfer site where the transfer roller 30 and the photosensitive drum come into contact, the toner image on the photosensitive drum is transferred to the transfer material, and then the transfer material is separated from the photosensitive drum and transported to the next process by the transport means 40. ing.

[Il the invention tries to solve! By the way, in the image forming apparatus of the type shown in FIGS. 3 and 4, in which the conveying member is also used as a casing, even if the conveying member becomes dirty with toner during long-term use, it is difficult to replace the developing device. At the same time, the conveyance member is renewed, so that staining of the transfer material can be prevented for a long period of time, and cost can be reduced by providing two functions to one plate 20a.

However, in the above-mentioned conventional example, when there is no transfer material as shown in FIG. However, as shown in Figure 's4, when the leading edge of the transfer material P advances while coming into contact with the photosensitive drum for transfer, the path of the air flow is suddenly blocked. Therefore, airflow turbulence Fd occurs in the space between the photosensitive drum and the upper plate 20a.

On the other hand, since the toner image formed on the surface of the photosensitive drum is only electrostatically attached to the photosensitive drum, a portion of the toner is peeled off due to such turbulence of airflow.

When peeled, the peeled toner accumulates on the plate 20a, and the effect on the image is as follows for normal image patterns such as characters.
Since the amount of peeled toner is extremely small, there is no problem within the life of the developing device, but in image patterns with a high printing rate such as solid black, the amount of peeled toner increases significantly, so a large amount accumulates on the plate 20a and is transported one by one. This causes the inconvenience of falling onto the transfer material and contaminating it.

Furthermore, in the image forming apparatus shown in FIG. 5, the conveying member 2b is separate from the developing casing 5, and there is a gap G between the conveying member 2b and the casing 5. Since the air current flows, the air turbulence Fd' is smaller than the former turbulence Fd. Therefore, although the amount of release toner is small, the release toner accumulates in the hollow portion in the figure. Since this storage position is located apart from the conveying member, the influence on the image is generally small. However, when used for a long period of time, the conveyance section is contaminated by the peeled toner, which inevitably stains the transfer material.

Particularly in electrostatic printers that use a reversal development system process, the charged polarity of the photosensitive layer of the photosensitive drum and that of the toner are the same, so the photosensitive drum has a weak ability to retain the toner. The occurrence of the above-mentioned inconveniences is remarkable.

Therefore, the present invention prevents the toner from falling and accumulating on the conveying member, despite the turbulence of airflow in the space near the image carrier caused by the supply of the transfer material, and prevents contamination of the transfer material and various parts within the device. It is an object of the present invention to provide an image forming apparatus that can prevent such problems.

[Means for Solving the 81 Problems] In order to achieve the above object, the present invention comprises a pair of plate-shaped conveyance members disposed approximately parallel to each other in the vicinity of an image carrier. In an electrophotographic image forming apparatus in which a transfer material is guided between members toward the image carrier, the tip of the conveyance member on the image carrier side guides the image carrier side of the transfer material. The portion is made of a non-magnetic conductive member, and the non-magnetic conductive member is electrically floated or biased to have the same polarity as the toner. In another aspect of the invention, the nonmagnetic conductive member is formed at the tip of the image carrier side of the conveyance member that guides the image carrier surface of the transfer material, and at a position that does not contact the transfer material.

[Function] According to the present invention, the non-magnetic conductive member is formed at the tip of the conveying member, and is electrically floated or biased to the same polarity as the toner, so that it is not affected by the transfer material during image formation. There is little toner peeling, toner is prevented from adhering to the conveying member, and the transfer material is not contaminated.
Good quality images can be obtained.

Furthermore, as in other inventions, if the non-magnetic conductive member is formed at a position where it does not come into contact with the transfer material, in addition to the above effects,
In a high-temperature environment, even if a transfer material such as paper absorbs moisture and its surface resistance value decreases, there will be no electrical short-circuit between the conveying member and the transfer roller. Therefore, no transfer defects occur.

[Example] The present invention will be explained in detail below with reference to FIGS. 1, 2, 6, and 7. In this example, the image carrier is a photosensitive drum. There is.

FIG. 1 is a diagram showing a first embodiment of the present invention. As shown in the figure, an image forming apparatus includes a cylindrical photosensitive drum 1 extending perpendicularly to the paper surface and rotating in the direction of arrow A. and an electrostatic transfer roller 3 provided close to this drum.

As is well known, around the photosensitive drum 1, members necessary for image formation such as a charger, an image signal applying means, and a cleaning means are arranged (not shown), and their actions cause the surface of the photosensitive drum to be affected. The formed toner image arrives at a transfer site facing the electrostatic transfer roller 3 due to the rotation of the photosensitive drum. On the other hand, a sheet-like transfer material (not shown) such as paper supplied from a cassette or the like temporarily waits at the position of the registration roller 2a, and is guided through the conveying member 2 in synchronization with the toner image on the photosensitive drum. The toner image on the photosensitive drum is transferred to the transfer material at this position, separated from the photosensitive member, and transported to the next step by the transport means 4. As shown in the figure, the conveying member 2 consists of two plates 2b and 2c arranged substantially parallel to each other, and the upper plate 2b is constituted by the bottom surface of the casing of the replaceable power-testing type developing device 5. It is something that A non-magnetic metal member or a conductive member 2 is provided at the tip of the plate 2b between the casing 5 side of the developing device and the end surface of the photosensitive drum 1 side.
d is provided. This conductive member 2d is negatively biased by power source A since the toner is negative in the illustrated embodiment.

According to this example, it was experimentally confirmed that contamination by toner on the transfer material was prevented.

Although the detailed mechanism of the effect of the non-magnetic metal member has not been elucidated, it is presumed as follows.

As shown in FIG. 1, when there is no transfer material in the conveyance member 2, the airflow generated by the rotation of the photoreceptor is
As explained in the figure, the toner flows smoothly along the surface of the photoconductor, but if there is a transfer material between the conveying members, turbulence in the airflow occurs as in the case of Figure 4, and a portion of the toner is Trying to separate from the photosensitive drum.

However, since the non-magnetic conductive member 2d is biased to the same polarity as the toner, the toner on the photosensitive drum 1 is electrostatically pressed against the drum and is difficult to peel off. This is thought to be because they electrostatically repel each other and are difficult to adhere to the plate. Therefore, according to this embodiment, the amount of toner that adheres to the transfer material or plate 2b per copy sheet is extremely small and cannot be discerned with the naked eye, and even if it accumulates, the amount is very small. Yes, and since it is replaced with a new one when the developing device is replaced,
There are no negative effects of the toner even after long-term use.

FIG. 2 shows a second embodiment, and parts common to those in the first embodiment are given the same reference numerals as in FIG. 1, and redundant explanation will be omitted.

In this embodiment, the conveyance member 2 is made up of two plates 2b and 2c arranged approximately parallel to each other as shown in the figure, and the upper plate 2b is formed by the bottom surface of the casing of the developing device 5. The casing is made of resin. 2e is a non-magnetic metal member such as aluminum or stainless steel placed at the tip of the plate 2b and is electrically floated. The transfer material is conveyed through the gap between the two.

According to the research experiments conducted by the present inventors, the above device eliminates the inconvenience of toner contaminating the transfer material.
It has also been confirmed that if the non-magnetic metal member is made into a float, the voltage will be 500 cm in absolute value with the same polarity as the toner.

FIG. 6 shows a third embodiment, and the same members as those in the first and second embodiments are designated by the same reference numerals as in FIG. 1 and will not be described again.

In this embodiment, the conveyance member 2 is made up of two plates 2b and 2c arranged approximately parallel to each other as shown in the figure, and the upper plate 2b is formed by the bottom surface of the casing of the developing device 5. The casing is made of resin. 2f indicates a non-magnetic metal member such as aluminum or stainless steel arranged at the tip of the plate 2b, and is electrically connected to AC and D.
Another high-voltage power source (for example, a bias power source for development, etc., on which C is superimposed) is half-wave rectified (not shown), and a bias having the same polarity as that of the toner is applied by power source B.

In this embodiment, the same effects as those of the above-mentioned embodiment can be obtained, but in addition, a dedicated high-voltage power supply is not required,
It is effective and can be implemented at low cost.

FIG. 7 shows a fourth embodiment of the invention. In this embodiment as well, parts common to those in the previous embodiment are given the same reference numerals and will not be described repeatedly.

According to this embodiment, the non-magnetic conductor 2g made of aluminum, stainless steel, etc. is provided only at the tip of the plate 2d and at the portion facing the casing 5 of the developing device, and does not come into contact with the transfer material. There is.

This embodiment also provides the same effect as the above-mentioned embodiment, but furthermore, since the transferred transfer material does not come into contact with the plate 2g, the transfer material such as paper absorbs moisture in a high-temperature environment. This reduces the surface resistance value, and eliminates the disadvantage of electrical short-circuiting between the plate 2g and the transfer roller 3, which causes transfer defects.

[Effects of the Invention] As explained above, according to the present invention, the tip of the plate for guiding the transfer side of the transfer material of the transfer material conveying member having a pair of parallel plates is made of non-magnetic metal, Since this is electrically floated or a bias voltage with the opposite polarity to the toner is applied, it is a simple structure and there is no need for a complicated structure to prevent toner from adhering to the plate, saving space and making it easier to use. It is possible to inexpensively prevent the toner separated from the photosensitive drum from falling and accumulating on the plate, thereby preventing contamination of the transfer material, which has the effect of obtaining high-quality images.

[Brief explanation of the drawing]

FIGS. 1 and 2 illustrate the first aspect of the present invention. FIG. 3 is a schematic side view showing the second embodiment. 5 is a side view showing different conventional examples, and FIG. 4 is a side view showing different conventional examples. The side views, FIGS. 6 and 7, showing the operation of the conventional example shown in FIG. FIG. 2 is a schematic side view similar to FIG. 1 and FIG. 2 showing a fourth embodiment, respectively. 1... Photosensitive drum 2... Conveying member 5...
Casing 2b of the developing device...Plate bodies 2d, 2e, 2f, 2g...-Nonmagnetic conductive members A, B...
・・Power supply diagram

Claims (1)

[Scope of Claims] 1. Consisting of a pair of plate-shaped conveying members arranged approximately parallel to each other in the vicinity of the image carrier, and a transfer material is guided between the plate-shaped conveying members toward the image carrier. In an electrophotographic image forming apparatus, the tip of the conveyance member on the image carrier side that guides the image carrier side of the transfer material is
An image forming apparatus comprising a non-magnetic conductive member, the non-magnetic conductive member being electrically floated or biased to have the same polarity as the toner. 2. An image forming apparatus according to claim 1, wherein the conveying member for guiding the image bearing surface side of the transfer material is constituted by a casing of a developing device. 3. The non-magnetic electrically conductive member according to claim 1 or 2 is formed at a distal end portion on the image bearing member side of the conveyance member that guides the image bearing surface side of the transfer material and at a position that does not contact the transfer material. Device.