JPH09288388A - Image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a uniform smooth image without any afterimage by obtaining an interval of the peripheral length of a photoreceptor drum, after the tailing edge part of a preceding transfer paper passes through an image transfer position and then, carrying a succeeding transfer paper to the image transfer position. SOLUTION: In an image forming device, after the tailing edge part of the preceding transfer paper passes through the image transfer position, the photoreceptor drum 201 is further rotated once and irradiated with erasing light, then, the formation of the image and the carrying of the transfer paper are starred and the succeeding transfer paper is carried to the image transfer position at the carrying interval of the peripheral length from the preceding transfer paper, to transfer the image to the succeeding transfer paper. At this time, a pretransfer discharged light irradiator 209 and a pretransfer corona charger 210 are turned on during a copying operation, to execute irradiation with discharged light and a corona charge, before the transfer is performed, so that a potential on the drum 201 can be uniformized. Thus, a uniform halftone image without the afterimage can be formed on each transfer paper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method for transferring an image formed by exposing a photosensitive drum onto a transfer paper,
In particular, it relates to improvement of accuracy of formed images.

[0002]

2. Description of the Related Art In an image forming apparatus, the electrostatic characteristic of a photosensitive drum changes depending on the environment, the condition of use over time and the like. To cope with this change, for example, in the image density adjusting device disclosed in Japanese Patent Laid-Open No. 63-237075, the surface potential of the photosensitive drum on which the image is recorded is compared with the surface potential of the reference member on which the image is recorded. However, by controlling the image forming process condition according to the difference, a stable image having an appropriate density can be obtained.

[0003]

However, the surface potential of the photosensitive drum may vary depending on the previous image forming state, and in such a case, it is not possible to obtain a uniform image density in all image areas. This depends on the electrostatic characteristics of the photosensitive drum, the spectral characteristics of various kinds of irradiation light, whether various kinds of irradiation light and corona charge impinge on the photosensitive drum via the toner layer, and the like. For example, as shown in FIG. 4, in a certain system, the surface potential of the portion that was previously irradiated with erase light is several tens of volts higher than the surface potential of the portion that was not irradiated. The F portion of FIG. 4 is the photosensitive drum 2 of the E portion.
The figure shows one cycle after 01. Since the F portion of FIG. 4 has not been irradiated with the erase light one round before, the surface potential is lower than that of the portion irradiated with the erase light. G in FIG.
Similarly, the surface potential of the portion is low because it is not irradiated with the erase light one round before. The image forming apparatus generally sets the non-image forming area (transfer sheet interval) as short as possible in order to increase the copying speed. Therefore, in the image forming apparatus in which the peripheral length of the photosensitive drum is long, the length of the non-image forming area in the transport direction is shorter than the peripheral length of the photosensitive drum, and the above-mentioned problem occurs.

Further, in the image forming apparatus, the potential on the surface of the photosensitive drum changes depending on the presence / absence of irradiation of static elimination light before transfer and the presence / absence of irradiation of corona charge before transfer. When a potential difference occurs on the surface of the photoconductor drum, an afterimage is generated in a halftone image.

The present invention has been made to solve the above disadvantages, and an object of the present invention is to form a uniform and smooth image without an afterimage by considering the electrostatic history of the photosensitive drum.

[0006]

According to the image forming method of the present invention, when the operation of transferring the image formed by exposing the photosensitive drum to the transfer paper is continuously performed on a plurality of transfer papers, After the trailing edge of the preceding transfer paper has passed the image transfer position and a gap corresponding to the peripheral length of the photoconductor drum is provided, the next transfer paper is conveyed to the image transfer position, and an accurate afterimage does not occur. Image formation is performed.

Further, depending on the image forming mode, after the trailing edge of the preceding transfer sheet passes through the image transfer position, a conveyance interval corresponding to the peripheral length of the photosensitive drum is opened, and then the next transfer sheet is imaged. And the image forming speed is increased according to the image forming mode.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The image forming method of the present invention is an image forming method for transferring a toner image formed on a photoconductor drum onto a transfer paper to form a uniform image having no afterimage.

In order to form an image having an appropriate density, the potential of the photosensitive drum may be read in the portion of the original and the portion of the white reference plate during the preliminary scanning, and the density may be adjusted according to the difference. However, since the charged state of the photoconductor drum is different between the portion that is irradiated with light or corona charger and the portion that is not irradiated, there are cases where the density cannot be adjusted accurately. According to the image forming method of the present invention, a uniform halftone image having no afterimage is obtained by always making the charged states of the photosensitive drums equal.

An image forming apparatus using the image forming method of the present invention has, for example, an exposure optical device, an image forming device and a conveying device. The exposure optical device exposes the photosensitive drum of the image forming device according to the image to be formed, and forms an electrostatic latent image on the photosensitive drum. The image forming apparatus includes, for example, a photoconductor drum, a charging corona charger, an eraser, a developing device, a transfer corona charger, a separating corona charger, a fixing device, a static eliminator, a pre-transfer static elimination light irradiator, and a pre-transfer corona charger. The photosensitive drum rotates in the transfer paper conveyance direction.
The charging corona charger uniformly charges the photosensitive drum. The exposure optical means exposes the uniformly charged photosensitive drum to form an electrostatic latent image on the photosensitive drum. The eraser irradiates the photoconductor drum with erase light to eliminate unnecessary areas of the electrostatic latent image on the photoconductor drum. The developing device develops the electrostatic latent image on the photosensitive drum into a toner image. The pre-transfer charge removal light irradiator lowers the potential of the photoconductor drum and weakens the electrostatic adhesion force between the photoconductor drum and the transfer paper. The pre-transfer corona charger mainly charges the photosensitive drum in order to control the toner charge amount.

On the other hand, the conveying device conveys the transfer paper in accordance with the toner image formed on the photosensitive drum. The transfer corona charger transfers the toner image formed on the photoconductor drum onto the transfer paper carried by the carrying means. The separation corona charger separates the transfer paper from the photosensitive drum onto which the toner image has been transferred. The fixing device fixes the toner image on the transfer paper. The static eliminator removes the residual toner on the photosensitive drum after the transfer paper is separated.

In the image forming apparatus described above, after the trailing edge of the preceding transfer sheet passes the image transfer position, a conveyance interval corresponding to the peripheral length of the photosensitive drum is provided, and the photosensitive drum is rotated once to expose the photosensitive drum. After the surface potential on the body drum is made uniform, the next transfer paper is conveyed to the image transfer position, thereby preventing image deterioration when images are continuously formed on a plurality of transfer papers.

After the trailing edge of the preceding transfer paper passes the image transfer position, the next transfer paper is transferred to the image transfer position without leaving an interval corresponding to the peripheral length of the photosensitive drum to transfer the image. Then, there is a portion which is irradiated with the erase light and a portion which is not irradiated with the erase light on the photoconductor drum on which the toner image is transferred on the preceding transfer paper. When the photoconductor drum is charged by the charging corona charger to form an electrostatic latent image on the photoconductor drum, the surface potential of the part of the photoconductor drum that has not been irradiated with erase light is irradiated with erase light. It may become lower than the surface potential of the exposed portion, and an afterimage may occur. On the other hand, as shown in the image forming method of the present invention, after the trailing edge of the preceding transfer paper passes the image transfer position, the conveyance interval corresponding to the peripheral length of the photoconductor drum is provided, and the photoconductor drum is moved. 1
After rotating for an amount of time to make the surface potential on the photosensitive drum uniform, the next transfer paper is conveyed to the image transfer position, so that the image in the case of forming images continuously on a plurality of transfer papers It is possible to prevent deterioration.

Further, in the case of, for example, a character original, the influence of the potential difference on the photoconductor drum on the image does not appear so much on the surface, so that the image forming mode on the photoconductor drum is, for example, a copy mode of the text original. In the case of forming an image in which the influence of the potential difference on the image does not appear so much on the surface, the interval between the preceding transfer sheet and the next transfer sheet may be shortened to increase the image forming speed.

[0015]

1 is a block diagram of an image forming apparatus using an image forming method of the present invention. As shown in the figure, the image forming apparatus has an exposure optical device 1, an image forming device 2, and a conveying device 3. The exposure optical device 1 includes a document table 101, a black reference portion 102,
White reference portion 103, exposure lamp 104, first mirror 10
5, a second mirror 106, a third mirror 107, a condenser lens 108, a fourth mirror 109, a fifth mirror 110, and a sixth mirror 111. The original table 101 is made of contact glass or the like and is a portion on which an original to be copied is placed.
The black reference portion 102 is a portion serving as a black reference for document density adjustment, and the white reference portion 103 is a portion serving as a white reference. The exposure lamp 104 and the first mirror 105 are mounted on a first carriage (not shown), and reciprocate in the document scanning range together with the first carriage. The exposure lamp 104 exposes the original on the original table 101, and the first mirror 105 reflects the reflected light from the original toward the second mirror 106. Second mirror 10
6 and the third mirror 107 are mounted on a second carriage (not shown) that moves at a speed half that of the first carriage,
Reciprocates with the carriage. The second mirror 106 is the first
The reflected light from the mirror 105 is reflected toward the third mirror 107, and the third mirror 107 reflects the reflected light from the second mirror 106 toward the imaging lens 108. The imaging lens 108 converges the reflected light from the third mirror 107. The fourth mirror 109 reflects the reflected light that has passed through the condenser lens 108 toward the fifth mirror 110. Fifth mirror 110
Reflects the light reflected from the fourth mirror 109 toward the sixth mirror 111. The sixth mirror 111 is the fifth mirror 110.
The reflected light from is reflected toward the image forming device 2.

The image forming device 2 includes a photosensitive drum 201, a charging corona charger 202, an eraser 203, and a developing device 2.
04, a transfer corona charger 205, a separation corona charger 206, a fixing device (not shown), a cleaning device 207, a static eliminator 208, a pre-transfer static elimination light irradiator 209, and a pre-transfer corona charger 210. The photosensitive drum 201 has a peripheral length of 210 mm or more, for example, and rotates in the transfer paper conveyance direction (counterclockwise in the drawing). The peripheral length of the photosensitive drum 201 is set to 210 mm or more because the most commonly used transfer paper size is A4 size and the lateral length of the A4 size transfer paper is 210 mm. is there. This is because, for example, when the peripheral length of the photoconductor drum 201 is considerably smaller than 210 mm which is the lateral length of the A4 size transfer paper, the peripheral length of the photoconductor 201 is often smaller than the non-image forming area.

The charging corona charger 202 uniformly charges the photosensitive drum 201. The exposure optical device 1 exposes the uniformly charged photosensitive drum 201, and the photosensitive drum 2 is exposed.
An electrostatic latent image is formed on 01. The eraser 203 irradiates the photoconductor drum 201 with erasing light to emit light to the photoconductor drum 20.
The unnecessary area of the electrostatic latent image on 1 is eliminated. Developing device 204
Develops the electrostatic latent image on the photosensitive drum 201 into a toner image. The transfer corona charger 205 transfers the toner image formed on the photosensitive drum 201 to a transfer paper. The separation corona charger 206 separates the transfer paper from the photosensitive drum 201 to which the toner image has been transferred. A fixing device (not shown) fixes the toner image on the transfer paper. The cleaning device 207 and the static eliminator 208 remove the residual toner on the photosensitive drum 201 after the transfer paper is separated. The pre-transfer charge eliminating light irradiator 209 reduces the potential of the photoconductor drum 201 to weaken the electrostatic adhesion force between the photoconductor drum 201 and the transfer paper, and facilitates separation of the transfer paper and the photoconductor drum 201. The pre-transfer corona charger 210 mainly charges the photosensitive drum 201 to control the amount of toner charge.
The transport device 3 transports the transfer paper in accordance with the toner image formed on the photosensitive drum 201.

An outline of the operation when image reading and image formation are performed by the image forming apparatus having the above configuration will be described with reference to the flowchart of FIG.

The user specifies a mode for copying an image in halftone and the number of copies, places an original to be copied on the original table 101, and depresses a start switch of an operation display unit (not shown) to start copying. When instructed (step S
1), the photosensitive drum 201 is rotationally driven by the driving force of a main motor (not shown), and the charging corona charger 20
2 uniformly charges the photosensitive drum 201 (step S
2). Further, the exposure lamp 104 moves together with the first carriage to expose the document on the document table 101. The original reflects the light from the exposure lamp 104, and the first mirror 105, the second mirror 106, and the third mirror 107 sequentially reflect the reflected light from the original and send it toward the imaging lens 108. The imaging lens 108 converges the reflected light from the third mirror 107 so as to focus on the photosensitive drum 201. The fourth mirror 109, the fifth mirror 110, and the sixth mirror 111 reflect the light from the imaging lens 108 toward the photoconductor drum 201 to perform image exposure, and form an electrostatic latent image on the photoconductor drum 201. (Step S3). The eraser 203 neutralizes the unnecessary area of the electrostatic latent image on the photosensitive drum 201. The developing device 204 has a photosensitive drum 201 from which unnecessary areas are eliminated.
The above electrostatic latent image is developed into a toner image (step S
4).

On the other hand, the carrying device 3 carries the transfer paper supplied from a paper feeding device (not shown) or the like in accordance with the toner image on the photosensitive drum 201 (step S5). The transfer corona charger 205 transfers the toner image on the photosensitive drum 201 to the transferred transfer paper (step S6). The separation corona charger 206 transfers the transfer paper to the photosensitive drum 2
Separate from 01. A fixing device (not shown) fixes the toner image on the transfer paper. The static eliminator 208 removes the residual toner on the photoconductor drum 201 after the transfer paper is separated, and prepares for the next image forming operation.

When the transfer operation has not been completed for the preset number of transfer sheets (step S7), the image forming apparatus does not perform the photosensitive operation after the trailing edge of the preceding transfer sheet has passed the image transfer position. After the body drum 201 is further rotated once to irradiate the erase light, image formation and transfer sheet conveyance are started, and the next transfer sheet is moved to the image transfer position at a conveyance interval of the peripheral length from the preceding transfer sheet. The image is transferred and transferred to the next transfer sheet (steps S8 and S9). Here, the pre-transfer charge eliminating light irradiator 209 and the pre-transfer corona charger 210 are turned on during the copying operation, and the charge eliminating light irradiation before the transfer and the corona charge irradiation before the transfer are performed. The upper potential can be made uniform. As a result, the image forming apparatus can form a uniform halftone image on each transfer sheet without an afterimage.

In the image forming apparatus having the above structure, after the trailing edge of the preceding transfer sheet passes the image transfer position, the next transfer sheet is transferred to the next transfer sheet without the gap corresponding to the peripheral length of the photosensitive drum 201. When the image is transferred to the transfer position and transferred, the photosensitive drum 201 having the toner image transferred on the preceding transfer paper has a portion irradiated with the erase light and a portion not irradiated with the erase light. When the photoconductor drum 201 is charged by the charging corona charger in order to form an electrostatic latent image on the photoconductor drum 201 by transferring the image to be transferred onto the next transfer sheet, for example, as shown in FIG.
In some cases, the surface potential of the portion of No. 01 which is not irradiated with the erase light is lower than the surface potential of the portion which is irradiated with the erase light. Part B of FIG. 3A shows the part A of the photosensitive drum 201 after one round. Since the portion B in FIG. 3A has not been irradiated with the erase light one round before, the surface potential is lower than that of the portion irradiated with the erase light. Similarly, the portions C and D in FIG. 3A have a low surface potential because they are not irradiated with the erase light one round before. On the other hand, in the image forming apparatus, after the trailing edge of the preceding transfer sheet passes the image transfer position as described above, the next transfer sheet is imaged at an interval corresponding to the circumferential length of the photosensitive drum 201. The image is transferred to the next transfer paper and transferred to the next transfer paper. As a result, as shown in FIG. 3B, the potential on the photosensitive drum 201 can be made uniform and a uniform halftone image without afterimage can be obtained. Here, in order to convey the next transfer sheet to the image transfer position with a gap corresponding to the circumferential length of the photosensitive drum 201 after the trailing edge of the preceding transfer sheet has passed the image transfer position, for example, The position of each transfer sheet may be detected by using a sensor to control the transfer sheet transfer, or the transfer sheet may be transferred a distance corresponding to two transfer sheets after the preceding transfer sheet transfer is started. It is also possible to measure the time required for the next transfer paper and then carry the next transfer paper.

When a halftone image is not copied as described above, for example, when an image on a character original is copied, even if there is a slight potential difference on the photosensitive drum 201, the effect on the copied image does not appear. When the set image forming mode is, for example, a copy mode of a text original, the copying speed may be increased by narrowing the interval between the preceding transfer paper and the next transfer paper.

[0024]

As described above, according to the present invention, after the trailing edge of the preceding transfer sheet passes through the image transfer position, the next transfer sheet is moved after a gap corresponding to the peripheral length of the photosensitive drum is provided. Since the image is conveyed to the image transfer position, accurate and stable image formation without an afterimage can be performed.

Further, depending on the type of image to be formed, after the trailing edge of the preceding transfer sheet has passed the image transfer position, a gap corresponding to the peripheral length of the photosensitive drum is provided, and then the next transfer sheet is transferred. Since the image is conveyed to the image transfer position, the image forming speed can be increased.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the image forming apparatus.

FIG. 3 is a signal chart showing the irradiation timing of erase light.

FIG. 4 is a signal chart showing a conventional irradiation timing of erase light.

[Explanation of symbols] 1 exposure optical device 104 exposure lamp 2 image forming device 201 photoconductor drum 202 charging corona charger 203 eraser 204 developing device 205 transfer corona charger 207 cleaning device 208 static eliminator 209 pre-transfer static erasing light irradiator 210 transfer Front corona charger 3 carrier

Claims (2)

[Claims] 1. In an image forming method for transferring an image formed by exposing a photosensitive drum onto a transfer paper, the rear end portion of the preceding transfer paper when the images are continuously transferred to a plurality of transfer papers. An image forming method, characterized in that after the sheet has passed through the image transfer position, a next transfer sheet is conveyed to the image transfer position after leaving an interval corresponding to the peripheral length of the photosensitive drum. 2. Depending on the image forming mode, after the trailing edge of the preceding transfer sheet has passed the image transfer position, a gap corresponding to the peripheral length of the photoconductor drum is provided, and then the next transfer sheet is transferred to the image transfer mode. The image forming method according to claim 1, wherein the image is conveyed to a transfer position.