JPH0239180A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain an image with good quality for a long period by disposing a means which regulates a gap between an image carrier and a developing means, outside the effective width of a transfer member with respect to the surface of the image carrier. CONSTITUTION:A developing roller 3 desposed at both ends of a developing sleeve 4 is set in such a position that it is inside the effective width of a primary electrifier and outside the effective width of a transfer roller 7. Even if the number of totally feeding sheets of paper to a device is increased and the surface of the image carrier 1 on which the developing roller 3 abuts is shaved by the roller 3, the transfer roller 7 does not get a leak. In the area when the developing roller 3 abuts on the image carrier 1, the surface of the image carrier is electrified in the same polarity as that of toner; therefore, even if toner passes between them, it is not stuck and fixed onto any of them. Thus, the gap between the image carrier 1 and developing sleeve 4 is accurately maintained for a long period, and an image having the good quality is obtained.

Description

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

(Prior Art and Issues to be Solved) A well-known image forming apparatus configured to electrostatically transfer a toner image formed on the surface of an image carrier using a developer (referred to as toner) to a sheet-like transfer material such as paper. An image carrier is provided with a transfer member such as a transfer roller or a transfer belt that comes into contact with the image carrier, and a transfer material is interposed between the two, and a transfer bias is applied to the transfer member to transfer the image on the image carrier side. A device in which a toner image is transferred to a transfer material has already been proposed.

FIG. 5 is a schematic perspective view of the main part of a typical device of this type showing the vicinity of the end of the development and transfer region, and is close to the cylindrical image carrier 1 rotating in the direction of arrow A. A developing device 2 is disposed in the developing device, and a developing sleeve 4 disposed in the developing device is connected to the image carrier 1 by developing rollers 3 (only one of which is shown in the figure) provided at both ends of the developing sleeve 4. It is arranged so as to maintain a predetermined distance from the surface.

An elastic transfer roller 7 made of an electrically conductive material is placed in pressure contact with the image carrier 1 on the downstream side of the developing device 2 when viewed in the running direction of the image carrier 1 to form a transfer region. A bias voltage (including ground) having a polarity opposite to that of the toner is applied.

When an electrostatic latent image formed on the surface of the image carrier by a latent image forming means (not shown) reaches the position of the sleeve 4, toner charged to a predetermined polarity is supplied from the sleeve 4 to the latent image. When this image is visualized and this visualized image arrives at the transfer site, a transfer material (not shown) is supplied to the transfer site at the same timing, and a transfer bias is applied to the transfer roller 7, so that the surface of the image carrier is The visualized image is transferred to a transfer material.

Compared to the well-known transfer means in which a corona discharger is disposed at the transfer site, this type of transfer means does not need to apply an excessive charge to the transfer material, so that toner is not deposited around the character image. High-quality images can be obtained with almost no scattering, and especially in the case of reversal development, since the charge on the surface of the image carrier and the charge on the toner are of the same polarity, the transfer bias can be low and corona radiation can be reduced. Compared to electrical appliances, it has the advantage of producing far less ozone and ozone products.

However, in this type of apparatus, as shown in FIG. 6, the developing roller 3 is usually located inside the transfer roller 7 with respect to the image carrier 1. Normally, when the cumulative number of sheets passed increases and the amount of scraping of the surface of the image carrier by the developing roller 3 increases, the transfer roller 7 leaks at the scraped part of the image carrier 1, resulting in temporary transfer failure. may occur.

Further, since the core of the image carrier is grounded, if the transfer roller leaks, noise will be added to the signal ground of one image forming device, and there is a risk that the CPU controlling the device will run out of control.

In the case of a corona discharger, this kind of situation will not occur unless an abnormal discharge occurs, but with a transfer roller,
When the transfer member is constantly in contact with the image carrier, the above-mentioned problems cannot be ignored.

The present invention has been made in order to cope with the above-mentioned situation, and in the above-described image forming apparatus, the presence of a developing roller does not have any adverse effects such as poor transfer.
It is an object of the present invention to provide an image forming apparatus that can stably perform good transfer over a long period of time.

(2) Structure of the invention (technical means for solving the problem and its operation) In order to achieve the above objects, the present invention has an image bearing member and a regulating means for regulating the gap between the image carrier. In the image forming apparatus, the regulating means includes a developing means for supplying toner to an electrostatic latent image on the surface of the image bearing member, and a transfer member that contacts the image bearing member, the regulating means is arranged on the surface of the image bearing member of the transfer member. It is characterized in that it is arranged outside of the active area.

With this configuration, in an image forming apparatus having a transfer member such as a transfer roller and a transfer belt that comes into contact with an image carrier, and/or a charging roller, leakage of these members to the image carrier can be prevented, and The function of the gap regulating means of the developing means can be stabilized.

(Description of Embodiments) FIGS. 1 and 2 are oblique views of essential parts of an image forming apparatus showing an embodiment of the present invention, and explanatory views showing the relative arrangement of an image bearing member and a developing roller. The forming apparatus basically has the same configuration as that shown in FIG. shall be.

The image carrier 1 is equipped with an OPC photosensitive layer, and a charger 1
0 to about 1,700 V, and an image signal is applied to this charged surface by an appropriate means such as scanning with an image-modulated laser beam or irradiating reflected light from the original to form an electrostatic latent image. It is formed.

As the image carrier 1 rotates, this latent image comes to a position facing the developing sleeve 4 of the developing device 2, and the negatively charged toner is attracted to the latent image to form a visible image.

As the image carrier rotates, when this image reaches a transfer site where the image carrier 1 and the transfer roller 7 come into contact, the transfer material 8 is supplied to the transfer site in time with this.

The entire transfer roller 7 has a volume resistance of 105Ω CIQ.
When the developed image on the image carrier is in a position facing the transfer material, a transfer bias is applied by the power source 14 to perform the transfer.

During transfer, residual toner that does not contribute to transfer but remains on the surface of the image carrier is removed by the cleaning blade 11, and residual charges are also removed by means such as a discharge lamp (not shown), and the image carrier is ready for the next image formation. Now you are ready to start the process.

In such an apparatus, as shown in FIG.
It is set so that it is outside the effective width of .

Therefore, the total number of sheets passed by the device increases.

Even if the surface portion of the image carrier with which it comes into contact is scraped by the developing roller 3, the transfer roller 7 does not leak, and can always perform a stable transfer function.

Furthermore, in the case of this device, in the area where the developing roller comes into contact with the image carrier, the surface of the image carrier is charged to the same polarity as the toner, so even if toner enters between the two, it will not be absorbed by either of them. There is no risk of adhesion and solidification, the distance between the image carrier and the developing sleeve can be maintained accurately at all times, and it is also possible to prevent image unevenness due to fluctuations in this distance.

FIG. 3 shows another embodiment of the present invention, which is similar to the embodiment described above except that a charging roller 13 is used instead of the primary charger as a means for charging the surface of the image carrier. It is similar to the device.

In such an apparatus, if the surface of the image carrier is scraped due to the presence of the developing roller 3, there is a risk that leakage may occur in the charging roller 13 as well as in the transfer roller. Portions where no potential is applied occur in the axial direction of the image carrier, resulting in white lines appearing on the image in the case of normal development and black edges in the case of reverse development, leading to deterioration of image quality, and noise causing CPU overload. There is a risk of it going out of control.

Therefore, in the above-mentioned apparatus, the developing roller 3 is positioned outside the effective width of the charging roller 13, as shown in FIG.

This configuration prevents leaks from occurring.
It is possible to obtain high quality images over a long period of time.

Further, in this device, as shown in FIG. 4, the effective width of the charging roller 13 is made larger than that of the transfer roller 7 so that the former completely covers the latter. When performing reversal development, it is possible to particularly prevent the end portion of the transfer roller from being contaminated by toner, making it possible to obtain high-quality images.

That is, if the effective widths of the two on the surface of the image carrier l are the same or if the effective width of the charging roller is narrow, there will be portions on both sides of the roller that are not charged within the effective ridges of the transfer roller, and these portions will not be charged. Since toner easily adheres to the transfer roller, both ends of the transfer roller may become contaminated with toner, causing stains on the back of the transfer material, and eventually causing uneven pressure contact between the transfer roller and the image carrier. However, such a situation can be avoided.

(3) As described in detail, according to the present invention, an image carrier and a transfer member such as a transfer cola that is in pressure contact with the image carrier are provided, and an electrostatic latent image on the surface of the image carrier is transferred to the image carrier. In an image forming apparatus configured to supply toner from a developing sleeve provided with a regulating member that comes into contact with the developing sleeve to regulate a gap between the regulating member and the surface of the image carrier, the regulating member prevents leakage to the image carrier. At the same time, it is possible to prevent toner from adhering to the regulating means and changing the gap between the regulating means and the image carrier, which greatly contributes to obtaining high-quality images.

[Brief explanation of the drawing]

FIG. 1 is a partial perspective view showing the main parts of an image forming apparatus according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the positional relationship between the effective It] of the transfer roller and the developing roller in the above, and FIG. FIG. 4 is an explanatory diagram showing the effective width of the transfer a-ra and the positional relationship of the developing roller in the same embodiment. FIG. 5 is a part of a known image forming apparatus. FIG. 6 is an explanatory view showing the positional relationship between the effective width of the transfer roller and the developing roller. lφΦ-image bearing member, 2-urn #ψ developer fR device, 3-e/developing roller, 4-... developing sleeve, 7... transfer roller, 13
11...Charging roller. Figure 1 Figure 2 Figure Figure Figure Figure Figure

Claims (4)

[Claims] (1) An image bearing member, a developing means having regulating means for regulating a gap between the image bearing member and supplying toner to an electrostatic latent image on the surface of the image bearing member, and a developing means that comes into contact with the image bearing member. An image forming apparatus comprising a transfer member, wherein the regulating means is disposed outside an effective width of the transfer member toward the surface of the image carrier. (2) Claim 1 in which the transfer member is a transfer roller
The image forming apparatus described in . (3) The image forming apparatus according to claim 1, wherein the image carrier is uniformly and primarily charged by a charging roller. (4) The image forming apparatus according to claim 3, wherein the regulating means is disposed outside the effective width of the charging roller toward the surface of the image carrier.