JPH03186878A - Image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus that uses an electrostatic transfer process, such as an electrostatic copying machine and a printer thereof.

(Prior Art and Problems to be Solved) Image forming apparatuses that transfer a transferable toner image formed on the surface of an image carrier onto a transfer material, mainly paper, have been widely used in the past.

FIG. 5 is a schematic side view of a typical example of such an image forming apparatus.

To briefly describe its structure and operation, the surface of an image carrier (hereinafter referred to as photoreceptor) 10 rotating in the direction of arrow An image signal I2 such as a laser beam is applied, and the potential of the corresponding portion is attenuated to form an electrostatic latent image.

Then, when the latent image reaches a development site where the photoreceptor 10 and the developing device 3 face each other, toner is supplied to the latent image to form a toner image.

When the toner image arrives at the transfer site where the photoconductor 10 and the transfer charger 16 face each other due to the rotation of the photoconductor 10, the conveyance guide 14.
A transfer material 18 is supplied from 14 in a direction such that the transfer material comes into close contact with the photoreceptor 10 at the transfer site, and at the same time, a transfer current is applied by the transfer charger 16.
The toner image on the photoreceptor lO is transferred to the transfer material 18 by the action of the electric field thus formed.

Thereafter, the transfer material 18 is separated from the photoreceptor and conveyed to a fixing site (not shown), residual toner on the surface of the photoreceptor 10 is removed by a cleaner 17, and the next image forming process is started.

The conveyance guide 14.14 is grounded via a varistor 30, a high-resistance element, etc., and especially in a high-humidity environment, transfer current may leak through the transfer material that absorbs moisture and has a low resistance, resulting in transfer failure, etc. In order to prevent transfer defects from occurring, the polarity is maintained to be the same as that of the transfer current during transfer.

However, in such a configuration, the conveyance guide 14
is expected to have the effect of reliably guiding the transfer material to a predetermined position on the photoreceptor, so its tip is located at the photoreceptor 1
The potential of the guide I4 is normally located very close to the surface of the toner, about 1 to 2 mm from the surface of the toner.As mentioned above, the potential of the guide I4 has the same polarity as the transfer current, in other words, it has the opposite polarity to that of the toner. Since the structure is such that the toner on the surface of the photoreceptor at the position immediately before transfer, the toner floating in the container
There is a problem in that the particles are electrostatically attracted to the conveyance guide 14 and adhere to it, contaminating it, and this adheres to the transfer material, resulting in deterioration of image quality.

In order to solve this problem, it has been proposed to apply a bias voltage of opposite polarity to the transfer current to the conveyance guide 14, but such a configuration tends to promote leakage of the transfer current. In the case of a transfer material that absorbs moisture and has a low resistance, the transfer current becomes insufficient and transfer omission becomes noticeable, making it completely impractical.

Furthermore, in the case of such a configuration, a large amount of transfer current flows in the direction of the conveyance guide, and the floating toner inside the device adheres to the guide 14 due to the flow of air, so that the desired effect cannot be sufficiently achieved. I couldn't have expected it.

The present invention has been made in order to cope with such a situation, and in an image forming apparatus having the above-mentioned configuration, by controlling the potential of a conveyance guide that guides the transfer material to a predetermined position on the surface of the photoreceptor. , deterioration of transfer performance due to insufficient transfer current, and contamination of the transfer material due to prevention of toner adhesion to the conveyance guide, all of which can be effectively prevented, so that stable, high-quality images can always be obtained regardless of the environment. The purpose of the present invention is to provide an image forming apparatus that can be used as an image forming apparatus.

(2) Structure of the invention (technical means for solving the problem and its operation) In order to achieve the above object, the present invention provides an image forming apparatus in which a transfer portion consisting of an image bearing member and a transfer means facing the image carrier, A conveyance guide that guides the transfer material so as to come into contact with the surface of the image carrier is composed of an insulating member and a conductive member, and a portion that contacts this when the transfer material passes is formed of the insulating member, and the conductive layer The device is characterized in that means is provided for applying a voltage of opposite polarity to the transfer bias.

With this configuration, it is possible to reliably prevent contamination of the transfer material due to toner scattering on the conveyance guide, omission of transfer in a high-temperature environment, and the like.

(Description of Embodiments) FIG. 1 is a side view of an image forming apparatus according to an embodiment of the present invention, particularly showing a transfer region and the vicinity of a conveyance guide for supplying a transfer material thereto. The means for forming an image, the means for developing it, etc. are not particularly different from those of the above-mentioned known apparatus, and are therefore omitted.

In the case of the illustrated apparatus, the polarity of the toner of the toner image on the photoreceptor is positive, and the polarity of the transfer bias is negative.

The conveyance guides 14.14 have insulating layers 14b, L4b on the side closer to the transfer material 18 and conductive layers 14a, 14 on the outer side, respectively.
The transfer material 18 is configured to overlap with the insulating layer 14b during the conveyance process.

Further, the conductive layers 14a, 14a are applied with a bias having a polarity opposite to that of the transfer bias, that is, a bias having the same polarity as that of the toner forming the l.toner image, by a power source 20.

With this structure, the toner of the toner image advancing to the transfer site is separated from the photoreceptor by electrostatic force at a position in front of the transfer site and close to the conveyance guides 14, 14, and is attracted to the conveyance guides 14, I4. In addition, it is possible to prevent floating toner inside the device from adhering to the conveyance guide.

Furthermore, since the transfer material 18 is in an electrically floating state due to the insulating layers 14b, 14b, even if the transfer material absorbs moisture and has a low resistance, leakage of transfer current through the conveyance guide is prevented. , it is also possible to prevent the occurrence of transfer omissions.

In the case of the above device, the conveyance guide 14.14 was constructed by overlapping an insulating layer and a conductive layer, but the guide 14.14 may be formed of a conductive material such as metal and coated with an insulating paint. Of course, it is also possible to use a structure such as plating with an insulating material.

FIG. 2 shows another embodiment of the present invention, and this device is equipped with developing devices 13 and 22 that store two types of toner having different polarities, and a transfer charger 16 is a positive one. The transport guide 14 has a switch 21 that switches between a power source for applying a bias and a power source for applying a negative bias using terminals A and B.
Like the one shown in the figure, it is constructed by overlapping an insulating layer and a conductive layer, and the polarity of the bias voltage applied to the conductive layer is determined by
It is configured to be switched by a switch 20 having terminals A and B.

With this configuration, when using the developing device 13, that is, toner of positive polarity, the switch 21 of the transfer charger 16. The switches 2o of the transport guide 14 are connected to the terminal A side so that a negative transfer bias is applied to the transfer charger 16 and a bias with the same polarity as the toner is applied to the transport guide 14. When using the toner 22, that is, negative polarity toner, switch 21.2
0 to terminal B, a positive bias is applied to the transfer charger 6, and a bias of the same polarity as the toner is applied to the conveyance guide 14. , it is possible to prevent the occurrence of transfer failure due to toner flying off.

FIG. 3 shows another embodiment of the present invention. In this case, the conveyance guide 14 that guides the transfer material to the transfer site is attached to rollers 14a, 14a made of a conductive material such as metal, with an insulating surface. The insulating layer 14B is formed by performing appropriate insulating treatment such as gluing a tube made of material.

It will be easily understood that such a configuration can also provide the same effect as the above-described embodiment.

In order to ensure that the transfer material is guided to a predetermined position on the surface of the photoreceptor 10, the tip of the conveyance guide 14 is disposed very close to the surface of the photoreceptor 10, or the tip is In the case where the transfer charger 16 is disposed so as to penetrate to the inner side of the shield plate, as shown in FIG. It is preferable that the insulating layer is formed on the side so as to cover the area where the transfer current can reach.

Regarding the length of the insulating layer and the conductive layer in the direction perpendicular to the direction in which the transfer material travels, the length of the insulating layer is equal to the length of the transfer material because it is maintained in an electrically floating state during the transfer material. It is preferable to make the length of the conductive layer longer than that of the insulating layer, and it is preferable to make the length of the conductive layer longer than that of the insulating layer so that there is no problem in conveying the transfer material and it is convenient to form a contact point for applying a bias. Therefore, the length of each part should be set appropriately in consideration of such a situation.

(3) As described in detail, according to the present invention, a voltage of opposite polarity to the transfer bias is applied to the conveyance guide for introducing the transfer material to a predetermined position on the image carrier. The guide does not attract toner from the toner image on the image carrier or floating toner inside the device, and
Even when using transfer materials that have lower resistance due to moisture absorption,
It effectively prevents leakage of transfer current, prevents contamination of the transfer material and occurrence of transfer omissions, and has a remarkable effect on obtaining high-quality images.

[Brief explanation of drawings]

FIG. 1 is a side view of a main part of an image forming apparatus according to an embodiment of the present invention, showing the configuration of a portion that conveys and supplies a transfer material to a transfer site. FIGS. 2, 3, and 4 are views of other embodiments. FIG. 5 is a schematic side view showing the configuration of a known image forming apparatus. lO... Image carrier (photoreceptor), 13.22... Developing device, 14... Conveyance guide, 14a... Conductive layer, 1
4b...Insulating layer, 16...Transfer charger, 18...
・Transfer material. 2

Claims (4)

[Claims] (1) At a transfer site consisting of an image carrier and a transfer means facing the image carrier, a conveyance guide that guides the transfer material so as to come into contact with the surface of the image carrier is composed of an insulating member and a conductive member, and An image forming apparatus comprising: a portion that contacts the conductive layer when it passes through the conductive layer; and a means for applying a voltage of opposite polarity to the transfer bias to the conductive layer. (2) The image forming apparatus according to claim 1, wherein the conveyance guide comprises a pair of plate-like members. (3) The image forming apparatus according to claim 1, wherein the conveyance guide comprises a pair of roller-like members. (4) The length of the conductive layer viewed in the direction perpendicular to the travel of the transfer material is
The image forming apparatus according to any one of claims 1 to 3, which is larger than that of the insulating layer.