JPS63182681A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent image blurring caused by a shock in contact with a roll, and to eliminate a disorder of an image, by allowing a transfer roller to contact, by pressing, before forming a latent image on an image carrying body. CONSTITUTION:Due to a contacting shock of a transfer roller 9, a photosensitive drum generates a shift by a vibration in the upward direction, therefore, when an exposure for forming a latent image is started after the transfer roller 9 is allowed to contact, by pressing, thee generation of image blurring can be eliminated. Also, in order to soften a shock in contact with a roll, it is desirable that the transfer roller is rotated beforehand. In such a way, a disorder of an image due to a shock in contact with the roll is eliminated, and when a transfer paper of a small area corresponding to the diminished diameter of the photosensitive drum is used, the possibility that the transfer roller comes into contact and separated with and from the photosensitive drum in the course of exposure becomes high, therefore, its serviceability is raised.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus having a removable roller.

[Conventional technology]

2. Description of the Related Art Conventionally, image forming apparatuses, particularly electrophotographic copying machines, have been constructed 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 being applied directly to the photoconductor in the event of a jam. Was.

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.
This caused the image to become distorted.

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. It had drawbacks such as image disturbance in the exposure section 2.

[Means for solving problems]

According to the present invention, by bringing the transfer roller into contact with the image carrier before forming a latent image on the image carrier, it is possible to prevent image blurring due to shock at the time of contact.

〔Example〕

FIG. 1 is a diagram of a copying apparatus that best represents the features of the present invention. In the 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 a certain document on the document table 13, passes through the short focus element array lens 2, hits the photosensitive drum 8, and forms an electrostatic latent image on the drum as the document table moves. do. 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, by the transfer roller 9,
The image (developer) is transferred from the photosensitive drum 8 to the paper, and sent by the conveyor belt 6 to a fixing device (not shown). Further, the developer remaining on the drum 8 without being transferred during the transfer is completely removed by the cleaner unit 7, and the photosensitive drum is neutralized by the pre-static eliminating device 4, and the process proceeds 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 time point (2) is developed. Next, when the paper detection device confirms that the transfer paper has come to the registration roller, the transfer roller comes into contact with the drum at time point (3). At this time, the exposure of the latent image forming step is still in progress, and the photosensitive drum 8 is caused to shift due to upward vibration due to the contact shock of the transfer roller 9.

At this time, if the lens 2 at position 2-a in Fig. 1 is used, image distortion will not occur if the upward shift is within the focal depth of the lens, but if the lens 2 at position 2-b in Fig. 1 is used, image distortion will not occur. If this is used, the surface of the photoreceptor drum will be displaced in the lateral direction relative to the lens 2 by an upward displacement distance of 5 inO, resulting in the formation of a shaky latent image and disturbance in the image. .

In this way, depending on the position of the lens 2, the transfer roller 9
The shock caused by the contact causes disturbances in the image, but this is because the transfer roller 9 contacts during the formation of the latent image.

As shown in the timing chart shown in FIG. 6, by starting exposure for forming a latent image after contacting the transfer roller 9, the above-mentioned image blurring can be prevented.

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 arranged inside a photosensitive drum 8 which has a photosensitive layer on a transparent substrate drum 2 made of glass or the like, and information is transmitted by light generated from a halogen lamp 15 driving a liquid crystal shutter array 11. The light passes through the array lens 2 and is applied to the photosensitive layer from inside the transparent photosensitive drum 8, and is simultaneously developed by the developing device 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 in the previous example, when simultaneous exposure and development was performed after contacting the transfer roller, no image disturbance occurred.

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 is public relations number 8747, etc.

〔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, after the transfer roller is in contact with the photoreceptor drum, the information light 15 of the latent image forming process...
・・・・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・ Starting the exposure of the halogen lamp has the effect of eliminating disturbances in the image caused by the shock at the time of contact, and the smaller the diameter of the photoreceptor drum is, the smaller the If a large area transfer paper is used, the possibility of the transfer roller coming into contact with and separating from the photoreceptor drum during exposure to the information light becomes extremely high, so that the effect is enhanced.

[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 diagram showing the sequence of the copying apparatus when the present invention is not applied, and FIG. 6 is a diagram showing the sequence when the present invention is applied.

Claims (2)

[Claims] (1) An image forming apparatus having an image bearing member and a removable transfer roller, characterized in that the transfer roller contacts the image bearing member before starting formation of a latent image. (2) The image forming apparatus according to claim 1, wherein development is performed simultaneously in the latent image forming section.