JPS63182669A - Image forming device - Google Patents

Abstract

PURPOSE:To suppress the disorder of an image in image formation as much as possible by providing a position where a photosensitive body is exposed to information light oppositely to a transfer roller which is attachable to and detachable from the photosensitive body when the transfer roller is brought into contact. CONSTITUTION:An image forming device which has the transfer roller 9 which is attachable to and detachable from the photosensitive drum is provided with an information light exposure part 2 oppositely to the transfer roller 9 almost at 180 deg.. Therefore, even if the transfer roller comes into contact during exposure to generate a shock, there is such effect that the image is not disordered. As the diameter of the photosensitive drum is smaller and smaller, the possibility that the transfer roller 9 contacts and leaves the photosensitive drum during the exposure to the information light is higher and higher when transfer paper of small area is used, so the effect is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus, and particularly to an image forming apparatus having a transfer roller that can be attached and removed.

[Conventional technology]

Conventionally, an image forming apparatus, particularly an electrophotographic copying machine, has a configuration as shown in FIG. 3, and when an image on a drum is transferred to paper or the like in a copying process, a transfer charger 5 performs the transfer. However, since it requires a power source to generate high voltage, it is expensive and difficult to miniaturize. For this reason, as shown in FIG. 4, a transfer roller 9 has been provided in place of the transfer charger.

However, the transfer roller 9 is in constant contact with the photoconductor drum 8, which may cause abrasion or deterioration of the photoconductor during long-term use, or may damage the photoconductor due to transfer bias applied directly to the photoconductor in the event of a jam. etc. In addition, the transfer roller 9 may become dirty due to developer scattering, etc., preventing proper transfer, the roller itself may become deformed if left unused for a long period of time, or pressure marks may be left on the photoreceptor drum, causing image disturbance. was.

Therefore, the transfer roller 9 is configured to be detachable from the photosensitive drum so that it does not come into contact with the photosensitive drum except during transfer, thereby preventing the above-mentioned drawbacks. However, when the transfer roller 9 is brought into contact with the photosensitive drum 8 during transfer, uneven rotation of the photosensitive drum 8 occurs, and the drum moves in the vertical direction, causing misalignment of the latent image. In the exposure section 2, there were drawbacks such as image disturbance.

[Failure to solve the problem]

In the present invention, when the removable transfer roller is brought into contact with the photoreceptor drum, the position where the photoreceptor is exposed to the information light is provided to face the transfer roller. This structure is designed to minimize image disturbance during image formation.

〔Example〕

FIG. 1 is a diagram of a copying apparatus that best represents the features of the present invention, and in this figure, a photosensitive drum 8 is negatively charged by a primary charger 1 by a power source (not shown). Incidentally, the charging potential was -600V.

Next, the light emitted from the halogen lamp 12 hits the document placed on the document table 13, passes through the short focal length element array lens 2, hits the photosensitive drum 8, and forms an electrostatic latent image on the drum as the document table moves. Form. Next, the formed latent image is developed by a developing device 3, the leading edge of the image is synchronized with the position of the transfer paper by a registration roller 4, and the transfer paper is detected by a paper detection device (not shown) on the transfer roller 9. After that, it is brought into contact with the photosensitive drum 8.

At this time, a transfer bias is applied to the transfer roller 9. Although it is desirable to apply the voltage after the leading edge of the transfer paper enters the nip between the photosensitive drum 8 and the transfer roller 9, it may be applied before that. Next, the developer image is transferred from the photoreceptor to the transfer paper by the transfer roller 9, and is sent to a fixing device (not shown) by the conveyor belt 6. Furthermore, the developer remaining on the photosensitive drum without being transferred during the transfer is completely removed by the cleaner unit 7. On the other hand, the photoreceptor drum is neutralized by the pre-static eliminating device 14, and the process moves to the next cycle.

Here, the behavior at the latent image forming portion before and after transfer will be explained in detail. FIG. 5 shows a timing chart of latent image, development, and transfer in the copying process. At time point (2), an electrostatic latent image begins to be formed on the photoreceptor, and at time point (2), the latent image formed at the above-mentioned time point is developed. Next, when it is confirmed by the transfer paper detection device that the leading edge of the transfer paper has reached the registration roller, the transfer roller swings and comes into contact with the photosensitive drum at time point (3). At this time, the latent image forming process is still in progress, and the transfer roller 9
The contact shock causes the photosensitive drum 8 to vibrate upward.

At this time, if the short focal length lens 2 at position 2-a in FIG. 1 is used, the fine movement in the upward direction will not cause image disturbance as long as it is within the focal depth of the lens. However, if the arrangement of the lens 2 at position 2-b in Figure 1 is applied, the photosensitive drum surface will be displaced in the lateral direction with respect to the lens 2 by 5 inO of the upward vibration width, resulting in vibration. This results in the formation of a latent image, resulting in image disturbance.

When we actually modified a Canon copier NP-1502 and investigated the impact of shock when the transfer roller came into contact with it, we found that a commercially available short focus When the element array lens was installed, no image disturbance was observed at all. However, when the lens was installed at a position where the angle θ was 45 degrees counterclockwise from the opposing position, pitch unevenness of exposure occurred in the wavy lines, and deviations occurred in the characters and lines. Incidentally, the volume resistance of the transfer roller was 104 Ωcm, 20φ, and the transfer bias was -500V.

In addition, the charging, optical system, developing,
The fixing cleaning method is outside the scope of the present invention, and any known method may be used. Further, it is desirable to rotate the transfer roller in advance in order to soften the shock upon contact.

FIG. 2 is a sectional view of an image forming apparatus representing another embodiment of the present invention. In this device, an optical system unit is placed inside a photosensitive drum 8, which has a photosensitive layer provided on a transparent base drum such as glass, and the light generated from a halogen lamp 15 drives a liquid crystal shutter array 11 to generate information. When the light passes through the array lens 2 and hits the photosensitive layer from inside the transparent photosensitive drum 8, it is developed by the simultaneous developer 3. Incidentally, conductive magnetic toner is used as the developer, and the developing bias at this time may be about several tens of volts.

Next, the position of the leading edge of the image and the transfer paper are synchronized by the registration roller 4, and the transfer roller 9 is brought into contact with the transparent photoreceptor drum 8 after the transfer paper is detected by a paper detection device (not shown). At this time, a transfer bias is applied to the transfer roller 9. Although it is desirable to apply the voltage after the leading edge of the transfer paper enters the nip between the photosensitive drum 8 and the transfer roller 9, it may be applied before that.

Next, the image is transferred from the photoreceptor to paper by a transfer roller 9, and sent to a fixing device (not shown) by a conveyor belt 6. Further, the developer remaining without being transferred during transfer returns to the developing section and is reused. In this case as well, as in the previous example, when simultaneous exposure and development was performed at a position facing the transfer roller, no disturbance of the image occurred even if the transfer roller 9 came into contact with it during development.

This time, we used a liquid crystal shutter array for the exposure system, but the L
A known method such as an ED array or a laser beam may be used. Examples of the image forming principle of the apparatus shown in FIG.
There are publications such as No. 8747.

〔Effect of the invention〕

As explained above, in an image forming apparatus having a transfer roller that can be attached to and detached from a photoreceptor drum, the information light exposure section is disposed at a position facing the transfer roller at approximately 180 degrees, so that the transfer roller can be moved during exposure. This has the effect that the image will not be disturbed even if a shock is caused by contact, and as the diameter of the photoreceptor drum becomes smaller, using a transfer paper with a smaller area will prevent the transfer roller from coming into contact with the photoreceptor drum during exposure to information light. The effect increases because the possibility of letting go becomes extremely high.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a copying apparatus according to the present invention, FIG. 2 is a sectional view of an image forming apparatus according to the present invention, FIG. 3 is a sectional view of a general copying apparatus, and FIG. 4 is a transfer roller. FIG. 5 is a cross-sectional view of a copying apparatus using the copying apparatus, and FIG. 5 is a diagram showing the sequence of the copying apparatus.

Claims (2)

[Claims] (1) An image forming apparatus having a cylindrical image bearing member and a removable transfer roller, characterized in that an information light exposure section for the image bearing member is located at a position facing the transfer roller. image forming device. (2) The image forming apparatus according to claim 1, wherein development is performed simultaneously in the latent image forming section.