JPS6311965A - Image forming device - Google Patents

Abstract

PURPOSE:To eliminate the occurrence of uneveness of density and color shift of a picture, by driving an image forming medium in such a way that the moving time of the medium from the location of an image writing means to the location of a transfer means can become integer times of the driving shift period of driving means. CONSTITUTION:Photosensitive drums 101-103 are arranged with prescribed distances among them, but the distances are set in such a way that the times T4 and T5 required by a transfer material carrying means 13 and transfer material P to move from the transfer position 25 of the drum 101 to that 26 of the adjacent drum 102 and from the transfer position 26 of the drum 102 to that of the adjacent drum 103 can become integer times of the driving shift period T1 of driving means 17 and 29. Since the photosensitive drums move quickly and the transfer material P quickly passes through the transfer positions, for example, an expansion in a picture produced at the time of picture writing is transferred to the transfer material P as just reversely corrected picture shrinkage and, consequently, the picture size becomes proper one on the transfer material P. In addition, the irregular pitch of the driving means can be corrected reversely and is disappeared.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generally relates to a transfer type image forming apparatus, and in particular, a plurality of image forming media such as electrophotographic photoreceptors are arranged side by side, and an electrophotographic image forming process is performed on these photoreceptors. A developed image of each color is obtained, and the developed image is sequentially transferred to a transfer material carried and conveyed by a transfer material conveying means, an intermediate transfer body, or an image carrier such as continuous paper to obtain a color image. The present invention relates not only to an electrophotographic color copying apparatus but also to a multicolor electrophotographic image forming apparatus.
It can be realized with various color printers, etc.
In particular, it can be suitably used in digital printers and laser beam printers, but in this specification it will be mainly described in relation to laser beam printers that apply electrophotography. Further, the image forming medium used in the present invention may be in any form, such as a belt or a drum, as long as it is an endlessly moving image forming medium, but in this specification, it is described as being drum-shaped. do.

Beauty. Conventionally, image forming means has been provided around an image forming medium such as a photosensitive drum for performing charging, exposure, development, and transfer processes, and in the exposure process, an image of the document is projected onto the photosensitive drum using an imaging lens. In an electrophotographic image forming apparatus, since the exposure is performed with a constant slit width, unevenness in the speed of the photosensitive drum is visually recognized simply as a decrease in resolution, so there is a large tolerance for unevenness in the speed of the photosensitive drum. .

However, in recent years, laser beam printers, LE
With the development of image forming apparatuses that write images using dot matrix or raster lines, such as D printers, liquid crystal shutter printers, thermal printers, and dot impact printers, the tolerance for speed unevenness caused by the drive of image forming media such as photosensitive drums has increased. For example, in the case of raster lines of 16 pixels/mm, pitch irregularities every 0.062 mm are detected by human vision as density irregularities, so image forming media such as photosensitive drums must be driven. Gears and the like are required to be extremely accurate compared to conventional gears.

The inventors of the present invention have researched methods for driving and controlling photosensitive drums in order to solve such problems. As a result, the driving means for driving the photosensitive drums of image forming apparatuses has a problem with inherent drive unevenness that occurs at regular intervals. The rotational speed unevenness of the photosensitive drum caused by the periodic drive unevenness, that is, the uneven density of the image, causes the drive means to move from the image writing means position of the photosensitive drum to the transfer means position. It has been found that the problem can be solved by operating the driving means so that the moving time is an integral multiple of the driving unevenness period of the driving means.

The present invention has been made based on this new knowledge.

Accordingly, an object of the present invention is to provide an image forming apparatus that eliminates density unevenness of images with a simpler structure while allowing periodic driving unevenness of an image forming medium driving means.

Another object of the present invention is to eliminate unevenness in image density and to eliminate transfer misalignment of images from each image forming medium to an image carrier such as a transfer material, that is, color misregistration, so that a high-quality color image can be obtained. An object of the present invention is to provide a forming device.

i fortune telling ruta The above object is achieved by an image forming apparatus according to the present invention.

In summary, the present invention relates to an imaging medium.

A driving means for driving the image forming medium, an image writing means for writing at least an image on the image forming medium around the image forming medium, and an image writing means for transferring the image formed on the image forming medium to an image carrier. In the image forming apparatus including an image forming means having a transfer means, the drive means is arranged such that the time it takes for the image forming medium to move from the image writing means position to the transfer means position is determined by driving unevenness of the drive means. The image forming apparatus is characterized in that the image forming medium is driven at an integral multiple of a cycle. The present invention also provides a plurality of image forming media, a common driving means for driving each of the image forming media, and an image writing means for writing an image on at least the image forming medium around each of the image forming media. and an image forming means having a transfer means for transferring the image formed on the image forming medium to an image carrier, and the driving means is configured to move each image forming medium from the image writing means position to the transfer means. A color image forming apparatus is provided in which the image forming medium is driven such that the time taken to move the image forming medium to the means position is an integral multiple of the driving unevenness period of the driving means.

Next, the image forming apparatus according to the present invention will be explained in more detail with reference to the drawings.

FIG. 1 is a schematic diagram of an electrophotographic imaging apparatus according to the Carlson process, which is well known to those skilled in the art. That is, a charger 4 is placed around an image forming medium 3, which is an electrophotographic photosensitive drum, and a laser beam optical scanning device t that is equipped with a laser light source and a polygon scanner and writes an image on the photosensitive drum 3 to form a latent image. A developing device 5 for making the latent image on the photosensitive drum 3 visible, a transfer discharger 6 for transferring the developed image on the photosensitive drum 3 onto a transfer material 7, and a transfer discharge device 6 for transferring the developed image on the photosensitive drum 3 to a transfer material 7; An image forming means consisting of a cleaner 8 for cleaning is arranged.

The photosensitive drum 3, as best illustrated in FIG.
It is driven in the direction of the arrow by the driving means. In this embodiment, the driving means includes an electric motor 9 and a driving gear 10 connected to the output shaft of the electric motor 9, and the driving gear 10 is connected to a driven gear 11 fixed to the photosensitive drum 3. They are configured to drive and rotate the photosensitive drum 3 by meshing with each other. In FIG. 2, image forming means other than the image writing means 1 and the transfer discharger 6 are omitted in order to clarify the driving relationship.

In the above configuration, according to research by the present inventors, the photosensitive drum driving means 9 and 10111 have inherent driving unevenness that fluctuates at a constant cycle, and the driving unevenness from such driving means is transmitted to the photosensitive drum 3, causing It was found that the rotation speed of drum 3 was uneven. The speed unevenness of the photosensitive drum 3 caused the image to expand and contract during image writing in the exposure process, resulting in an expanded image and a contracted image in the visible image on the transfer material.

According to the present invention, in order to solve the expansion and contraction of the image caused by the driving unevenness of the driving means, the photosensitive drum 3 is moved from the image writing means position 3a to the transfer means position g13.
The drive is controlled so that the time it takes to move to b is an integral multiple of the driving unevenness cycle of the photosensitive drum drive means. To explain more specifically, in this embodiment, the rotation period TI of the gear 10
is configured to be an integral fraction of the travel time Tz from the exposure writing position 513a to the transfer position g13b.

According to such a configuration, the cumulative pitch error and adjacent pitch error caused by the gear lO are reproduced in exactly the same way during image writing and during image transfer.

For example, assuming that the rotation period TI of the gear 10 is set to 1/2 of the travel time Tz from the exposure writing position a13a to the transfer position 113b, the pitch error (a) of the gear 10 in FIG. teeth.

It is composed of a component 10a due to eccentricity of the gear 10 and an adjacent pitch error tab superimposed thereon. As mentioned above, since TI is 172 of T2, the speed unevenness (wow and flutter) caused on the photosensitive drum 3 by the gear IO during writing is reproduced exactly the same as during writing when transfer starts 12 hours later. . As a result, for example, image elongation that occurs when writing an image is transferred to the transfer material 7 as a shrinkage of the reversely corrected image because the photosensitive drum 3 moves quickly during transfer and passes through the transfer position more quickly. As a result, the image size becomes correct on the transfer material, and the pitch unevenness of the driving means is reversely corrected and disappears.

4 to 7 show other embodiments of the present invention as a color laser beam printer using an electrophotographic method.

According to the full-color laser beam printer shown in FIG. 4, three image forming units (Pa, Pb, Pc) are arranged, and each image forming unit has a dedicated photosensitive drum 101.1.
02.103, and dedicated image forming means (laser beam exposure means 107, 108, 109) are arranged around it.
Although other parts are not shown, for example, a charging section, an exposure means, a developing section, a transfer section, a cleaning section, etc.) are arranged. On the other hand, below the photosensitive drums 101, 102, and 103, there is a moving body, that is, an endless belt 16, which is suspended from the drum 14.15 and rotates in the direction of the arrow, passing through each image forming unit (Pa, Pb, Pc). A transfer material conveying means 13 is disposed, and transfers the transfer material P fed by a paper feeding device (not shown) to the transfer position 2 of each image forming unit Pa, Pb, Pc.
5.26.27 for transport in the direction of the arrow.

In such a configuration, first of all, the first image forming unit)
A visible image of yellow toner is formed at Pa, and the yellow toner image is transferred to the transfer material P conveyed by the transfer material conveying means 16 at a transfer portion, that is, a transfer position 25. On the other hand, while this yellow image is being transferred to the transfer material P, a toner image with magenta toner is obtained in the second image forming unit Pb, and the transfer material P whose transfer has been completed in the first image forming unit Pb is When the second image forming unit (Pb) is carried into the transfer position 26, this magenta toner image is transferred to a predetermined position on the transfer material P.

Image formation is subsequently performed in the same manner for cyan color and, if desired, black color. When the superposition of the three or four color toner images on the transfer material P is completed, the transfer material P is transferred to the fixing section (not shown). is fixed, and a multicolor (full color) image is obtained on the transfer material P.

After the transfer, each photosensitive drum is cleaned of residual toner by a cleaning means (not shown) in preparation for the next latent image formation.

In this embodiment, at least two or more of the photosensitive drums 101, 102, and 103 are driven by a common driving means, and in this embodiment, all the photosensitive drums are driven by a common driving means. That is, in this embodiment, the drive means is composed of an electric motor 17 and a drive shaft 29 connected to the drive motor. Each photosensitive drum 101.102.1
03 is a worm gear 18.1 provided on the drive shaft 29
The rotational driving force from the drive shaft 2.9 is transmitted through the worm wheels 21, 22, and 23 fixed to the ends of the photosensitive drums 9.20 and 2.9.

Further, according to the present invention, each photosensitive drum 101, 102, 103 driven by a common driving means 17, 29 moves from the image writing position by the laser beam optical scanning device 107, 108, 109 to the transfer position 25, 26. The driving means is driven such that the time T for moving to .27 is an integral multiple of the driving unevenness cycle T1 of the driving means. Furthermore, according to this embodiment, the photosensitive drums 101, 102, 103 are arranged at a predetermined distance from each other, and the distance is such that the transfer material conveying means 13 and the transfer material P in this embodiment are arranged at a predetermined distance from each other. and 102
and 102. ! :103(7) Passing time T4 and T5 for passing between transfer positions 25 and 26 and 26 and 27 (T5
may be the same as T4) is configured to be a distance equal to an integral multiple of the drive unevenness period (wow and flutter) TI of the drive means 17.29 (FIG. 5).

To explain further, the inventors of the present invention have discovered that when the photosensitive drums 101, 102, and 103 are driven with the above configuration,
Similar to the embodiment described above, for example, the elongation of the image that occurs when writing the image is transferred to the transfer material 7 as a shrinkage of the reversely corrected image because the photosensitive drum 3 moves quickly during transfer and passes through the transfer position more quickly. As a result, the image becomes the correct size on the transfer material, and the pitch unevenness of the driving means is reversely corrected and disappears, and at the same time, the T3 cycle driving as shown in FIG. 4 occurring in the driving means 17.29 The unevenness, or wow and flutter, is resolved, and the transfer misalignment at each image station is eliminated.

As described above, according to this embodiment, the periodic drive unevenness inherent in the drive means for driving the photosensitive drum is completely resolved. The accuracy is not required to be as high as conventionally required.

- The embodiment described in F is applied to a multicolor electrophotographic laser beam printer in which a developed image is sequentially transferred onto a transfer material P that is rejected by a transfer material conveying means 13 having a belt to obtain a color image. Although described in this connection, the present invention can also be embodied in a multicolor electrophotographic image forming apparatus that sequentially transfers a developed image to an intermediate transfer member or an image receiving member such as continuous paper to obtain a color image. Another embodiment of the invention is illustrated in FIGS. 6 and 7.

FIG. 6 shows two photosensitive drums 101, 102, and 103 according to the present invention.
According to this embodiment, an image formed on a photosensitive drum is transferred to an intermediate transfer member, and then a developed image on the intermediate transfer member is transferred to the transfer member. An intermediate transfer member conveying means 13a is disposed below 101°, 102, and 103, and the intermediate transfer member conveying means 13a has substantially the same structure as the transfer material conveying means 13 described in connection with FIG. The only difference is that a belt-shaped intermediate transfer body 16a, for example, a belt-shaped polyester film, polyimide film, silicone rubber, urethane rubber, etc., is used instead of the conveyor belt 160. or,
In this embodiment, in order to further transfer the visible image once transferred to the intermediate transfer member 16a onto the transfer material P, a paper feeder (not shown) is used.
Transfer rollers 14a and 14b are arranged in place of the hanging drum 14 in FIG. 4 in order to press the transfer material P fed from the intermediate transfer member 16a. In this embodiment as well, the same effects as in the embodiment shown in FIG. 4 can be obtained.

FIG. 7 shows the photosensitive drums 101, 102, 103 according to the present invention.
According to this embodiment, which shows a mode realized in a multicolor electrophotographic image forming apparatus in which a color image is obtained by sequentially transferring images formed on a continuous paper Pa to an image carrier, a photosensitive drum Continuous transfer paper Pa fed out from the transfer roll paper is arranged below lO1, 102, 103,
The image on the photosensitive drum is directly transferred to the roll paper.

That is, in this embodiment, the continuous paper P is used instead of the conveying belt 16 in the transfer material conveying means explained in connection with FIG.
A is provided.

In this embodiment as well, the same effects as in the embodiment shown in FIG. 4 can be obtained.

In the above embodiments, the driving force transmission means from the driving means 17.29 to the photosensitive drum is a worm gear and a worm wheel, but the invention is not limited to this. Also, other means than the electric motor 17 and the drive shaft 29 may be used as the drive means.

The E button device No. 11 can form high-quality images with a simpler structure that eliminates image density unevenness while tolerating periodic wA drive unevenness of one image forming medium drive means. Further, according to the present invention, there is an advantage that it is possible to eliminate density unevenness in an image and to eliminate transfer deviation of images from each image forming medium to a transfer material, that is, color deviation, and to obtain a high-quality color image.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a first embodiment of an image forming apparatus according to the present invention. 2 is a perspective view of the apparatus of FIG. 1; FIG. FIG. 3 is a graph showing the drive cycle irregularities of the drive means used in the device shown in FIG. FIG. 4 is a perspective view of a second embodiment of the image forming apparatus according to the present invention. FIG. 5 is a graph showing drive cycle irregularities of the drive means used in the device of FIG. 4. FIG. 6 is a perspective view of a third embodiment of an image forming apparatus according to the present invention, and FIG. 7 is a perspective view of a fourth embodiment of an image forming apparatus according to the present invention. P, Pa: Image writing means 3.101, 102.103: Image forming medium 9.10.
11.17.29: Drive means 6.25.26.27: Transfer means 13: Transfer material transport means 16: Transfer material transport belt 16a: Intermediate transfer body Fig. 5 Fig. 6 Pc Fig. 7 c

Claims (1)

[Scope of Claims] 1) An image forming medium, a driving means for driving the image forming medium, an image writing means for writing an image on at least the image forming medium around the image forming medium, and the image forming medium. and an image forming means having a transfer means for transferring an image formed thereon to an image carrier, wherein the driving means moves the image forming medium from the image writing means position to the transfer means. An image forming apparatus characterized in that the image forming medium is driven so that the time taken to move the image forming medium to the position is an integral multiple of the driving unevenness period of the driving means. 2) a plurality of image forming media, a common driving means for driving each of the image forming media, and around each of the image forming media,
The drive means includes at least an image writing means for writing an image on the image forming medium and an image forming means having a transfer means for transferring the image formed on the image forming medium to an image carrier, and the driving means The image forming medium is driven such that the time it takes for the image forming medium to move from the image writing means position to the transfer means position is an integral multiple of the drive unevenness period of the driving means. The image forming apparatus according to item 1. 3) Each image forming medium driven by a common driving means:
The image carriers are arranged so that the passing time intervals of the image carriers passing through the transfer means positions of the adjacent image forming media are equal to an integral multiple of the drive unevenness period of the drive means. The image forming apparatus according to scope 2. 4) The apparatus according to claim 3, wherein the driving means is a drive motor and a drive shaft driven by the drive motor and transmitting driving force to two or more image forming media simultaneously. 5) The apparatus according to claim 2, 3, or 4, wherein the image carrier is a transfer material conveying means for conveying a transfer material for transferring an image formed on an image forming medium. 6) The device according to claim 2, 3 or 4, which is an image carrier or a transfer material for transferring an image formed on an image forming medium. 7) The apparatus according to claim 6, wherein the transfer material is an intermediate transfer body. 8) The apparatus according to claim 6, wherein the transfer material is a continuously supplied roll paper.