JPH0212271A - Transfer device for electrophotographic device - Google Patents

Abstract

PURPOSE:To prevent dislocation between toner images by arranging a transfer body so that one cycle of transfer is completed when a driving shaft rotates by an integer number of times and the rotational angle reference position of the driving shaft is constantly corresponded with the transfer starting position of the transfer body when the transfer is completed. CONSTITUTION:When a toner image is transferred from a photosensitive-body belt 25 to an intermediate transfer belt 3, one cycle of transfer is completed when a driving roller 7 rotates twice from the rotational angle reference position corresponded with the transfer starting position of the intermediate transfer belt 3, and the rotational angle reference position is corresponded again with the transfer starting position. As a result, when there is a position error with a toner image transferred in a position where a visible image is to be formed due to the peripheral speed of the intermediate transfer belt 3 varying with the rotation of the drying shaft 9, an identical position error occurs in an identical position on the intermediate transfer belt 3 when a subsequent toner image is overlapped and transferred. The dislocation between overlapped toner images can be thereby prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transfer device in an electrophotographic apparatus such as an electrostatic copying type color copying machine.

[Conventional technology]

Generally, copying machines, which are one type of electrophotographic apparatus, include monochrome copying machines that use one color of toner for development, and color copying machines that use two or more color toners for development.

Since the above-mentioned monochrome copying machine uses one color of toner, one visible image is formed by transferring one toner image.

On the other hand, in a color copying machine, a plurality of toner images developed with toners of two or more colors out of two or four colors are sequentially transferred from a photoreceptor belt or the like onto the surface of a transfer member such as an intermediate transfer belt or the like. A monochrome color copying machine that overlaps and transfers to form a visible image, and then transfers this visible image onto paper to form a monochrome color image, and a plurality of toner images developed with toner of two or more colors. , a full color image that is sequentially superimposed and transferred from a photoreceptor belt, etc. to the surface of an intermediate transfer belt 1, etc. so as to approximate natural colors to form a visible image, and then transferred onto paper to form a full color image. There is a copy machine.

In the color copying machine mentioned above, in order to form a monochrome or full-color copy image, multiple toner images formed for each toner color are sequentially superimposed from a photoreceptor belt etc. onto the surface of an intermediate transfer belt etc. After transcribing,
Furthermore, the position of the visible image formed on the intermediate transfer belt and the position of each toner image on the photoreceptor belt must be determined so that each toner image will not be shifted on the surface of the intermediate transfer belt etc. Transfer must be performed in synchronization with the position of the image.

By the way, the drive shaft that rotates the intermediate transfer belt is provided with a drive roller, and there is a special difference between the roller diameter of this drive roller, the belt length of the intermediate transfer belt, and the rotation speed of the drive shaft. There is no fixed relationship, and the relationship is set around the peripheral speed of the intermediate transfer belt, which is the transfer speed.

For example, if the peripheral speed of the intermediate transfer belt is 200 (ai/5
ec), if the diameter of the drive roller is 60 (tm), the number of rotations (N) of the drive roller is N = 200 / (7E ・60 ) - 1,06 (rotations/s), that is, 1 per second It becomes .06 revolutions.

[Problem to be solved by the invention]

However, in the transfer device of the electrophotographic device used in the conventional color copying machine, etc., multiple toner images formed on the photoreceptor belt are superimposed and transferred to an intermediate transfer belt rotated by a drive roller. When trying to
The rotation angle reference position of the drive shaft that determines the contact position with the intermediate transfer belt on the drive roller surface is not constant.

Therefore, each time a plurality of toner images are superimposed and transferred from the photoreceptor belt onto the intermediate transfer belt, the rotational angle reference position of the drive shaft is different, and the , the transfer will be performed from a different position from the previous transfer. This is not a problem if the cross section of the drive roller is a perfect circle, but the actual drive roller is not a perfect circle and has variations in roundness within the tolerance and is eccentric. There is.

For this reason, the peripheral speed of the intermediate transfer belt is set to 200 (mn+
/5ec), and the roller diameter of the drive roller is 60 (t
rm ), and the rotation speed of the drive roller is 1.06 (rotations/s).
Even if set to arise.

If the above ripple is 1% of the circumferential speed, the magnitude of this ripple is 2 (InIl/5ec), and the positional error occurring in the visible image on the intermediate transfer belt is 5cos ωLdt = (1/6. 6) ・si
n ωtO815·sin ωt In other words, a positional error of 0.15 (m 2 ) occurs before and after the position where a visible image is to be formed on the intermediate transfer belt. This is shown by the solid line in Figure 3,
The first transferred toner image has a ripple size of 0.3 (mm) representing the occurrence of positional error.

Then, in the case of further transfer, the rotation angle reference position of the drive shaft in the previous transfer is 180° so that the position error of the toner image occurs in the opposite direction before and after the position where the visible image is to be formed. When transfer is performed in a rotated state corresponding to the rotation angle reference position, as shown by the broken line in FIG. 3, the toner image transferred for the second time is different from the first toner image shown by the solid line. During this time, a maximum deviation of 0°3 (mm) will occur.

As a result, the resolution deteriorates, and when full-color copying is performed, a color image with a color different from that of the original is formed, which is disadvantageous. [Means for Solving the Problems] In order to solve the above-mentioned problems, the transfer device of the electrophotographic apparatus according to the present invention has a transfer body that is rotated by a drive shaft.
Transfer the toner images multiple times so as to overlap them one after another,
In a transfer device of an electrophotographic device that forms one visible image on the transfer body and a color image on paper in one transfer, when the drive shaft rotates an integral number of times, the transfer body rotates once. The rotational angle reference position of the drive shaft at the time of completion of the transfer is set to always coincide with the transfer start position of the transfer body.

(Function) With the above configuration, when a plurality of toner images are sequentially superimposed and transferred to form a visible image on the transfer body,
Because the rotational angle reference position at the end of transfer on the drive shaft that rotates the transfer body always matches the transfer start position of the transfer body, the transfer of the toner image is controlled by the peripheral speed of the transfer body, which changes with the rotation of the drive shaft. Even if a positional error occurs, the same positional error will occur at the same position on the transfer body when the toner images are further superimposed and transferred. Therefore, it is possible to eliminate misalignment between toner images that would cause a decrease in resolution or form a visible image in a color different from the color of the original when copying in full color.

〔Example〕

An embodiment of the present invention will be described below based on FIG.

As shown in FIG. 1, a full-color copying machine (hereinafter referred to as a copying machine) serving as an electrophotographic apparatus is provided with a document table 11 on which a document 40 is placed at the top of a machine frame 39. Below the document table 11, a copy lamp 12, a mirror 15...
- an optical system section 41 that includes a lens 13 and a filter device 14 having blue, red, and green filters, and scans the original 40 to expose it to form an electrostatic latent image on the photoreceptor belt 25, which will be described later;
is provided.

A photoreceptor belt 25 made of an organic photoreceptor (OPC photoreceptor) is provided below the optical system section 41 . This photoreceptor belt 25 is passed between a driving roller 24 and a driven roller 23 which are arranged in parallel at a constant interval. Around this photoreceptor belt 25, there is a charger 2.
2. Developing devices 16, 17, and 18, a cleaner 27, and a static elimination lamp 21 are provided facing the photoreceptor belt 25, respectively, and the developing devices 16, 17, and 18 are provided with yellow, cyan, and magenta toners, respectively. is stored.

An intermediate transfer mechanism 10 is provided near the drive roller 24. This intermediate transfer mechanism 10 includes a drive roller 2
Driven rollers 6 and 8 are arranged in a substantially triangular shape parallel to 4.
An intermediate transfer belt 3, which is a transfer member, is passed between the drive roller 7 provided on the drive shaft 9, and between the driven roller 6 and the drive roller 7,
The surface of the photoreceptor belt 25 located on the outer periphery of the drive roller 24 is in contact with the surface.

A photoreceptor belt 2 is placed around the intermediate transfer belt 3.
An intermediate transfer charger 26, a transfer charger 32, a peeling charger 33, a timing sensor 5, a static elimination charger 34, a cleaner 35, etc. are provided facing the inner and outer circumferences of the intermediate transfer belt 3 in order from the contact position with the intermediate transfer belt 3. .

Here, in the drive roller 7 in this embodiment, the position set as the rotation angle reference position on the drive shaft 9 coincides with the transfer start position, and the photoreceptor belt is rotated exactly two times from the rotation angle reference position. One toner image is transferred from the surface of 25 to the intermediate transfer belt 3, and the driving roller 7 is moved again so that the rotation angle reference position coincides with the transfer start position.
The roller diameter is set.

Note that the number of rotations for setting the roller diameter of the drive roller 7 is not limited to two rotations; the rotation angle reference position and the transfer start position coincide, and the surface of the photoreceptor belt 25 is rotated exactly an integral number of times. It is sufficient if the rotation angle reference position coincides with the transfer start position after the transfer from the start position is completed.

A paper 30 is provided on the paper feed side to the intermediate transfer mechanism 10 described above.
Paper cassettes 19 and 2o containing ... are attached above and below. Paper feed rollers 28 and 29 and a timing roller 31 are provided between the upper part of each paper cassette 19 and 20 and the intermediate transfer mechanism 10. Further, on the paper discharge side with respect to the intermediate transfer mechanism 10, a conveyance belt 36, a fixing device 37, and a stray paper section 38 are provided.

In the above configuration, when the copying machine performs a copying operation, timing is determined by the timing sensor 5 reading an index indicating the transfer start position on the intermediate transfer belt 3, and the timing is determined by the timing sensor 5 reading the index indicating the transfer start position on the intermediate transfer belt 3. copy lamp 12
and mirror 15 . . . move back and forth on the lower surface of the original stacking table 11 in the directions of arrows C and D to scan the original 40.

The reflected light of the light irradiated onto the original 40 from the copy lamp 12 is reflected by the mirrors 15...1 as shown by the dashed line in the figure.
．． The light reaches the surface of the photoreceptor belt 25 through the lens 13 and filter device 14, and forms an electrostatic latent image on the photoreceptor belt 25. The document 40 is sequentially scanned three times, and the filter device 14 inserts the three color filters into the optical path one by one during each scan to sequentially form three electrostatic latent images on the photoreceptor belt 25. form.

On the other hand, the paper 30 stored in the paper cassettes 19 and 20 is fed one by one to a timing roller 31 by paper feed rollers 28 and 29, and the timing roller 31 transfers the paper 30 to the intermediate transfer belt 3 in synchronization with the intermediate transfer belt 3. It is conveyed between the transfer belt 3 and the transfer charger 32.

Then, the electrostatic latent image described above is sequentially developed with yellow, cyan, and magenta toners by the developing devices 16, 17, and 18.
Three toner images are formed.

When the drive shaft 9 rotates twice from the rotational angle reference position that corresponds to the transfer start position of the intermediate transfer belt 3, the first toner image is transferred from the surface of the photoreceptor belt 25 onto the intermediate transfer belt 3 by the intermediate transfer charger 26. The rotation angle reference position coincides with the transfer start position again.

Next, as the drive shaft 9 rotates twice, the second toner image formed on the intermediate transfer belt 3 is transferred onto the first toner image, and the rotation angle of the drive shaft 9 is referenced. The position corresponds to the transfer start position. Further, when the drive roller 7 rotates twice, the rotational angle reference position of the drive shaft 9 coincides with the transfer start position, and the yellow, cyan, and magenta toner images are all superimposed on the intermediate transfer belt 3. , a visible image is formed. Then, the intermediate transfer belt 3
The upper visible image is transferred as a color image onto the paper 30 conveyed by the transfer charger 32.

The paper 30 after the transfer is peeled off from the intermediate transfer belt 3 by the peeling charger 33, guided to the fixing device 37 by the conveyor belt 36, fixed by heating and pressure, and then discharged to the outside from the ejecting section 38. Ru.

In this way, from above the photoreceptor belt 25 to the intermediate transfer belt 3
When a toner image is transferred onto the intermediate transfer belt 3, one transfer is completed when the drive roller 7 rotates exactly two times from the rotation angle reference position that corresponds to the transfer start position of the intermediate transfer belt 3.
When the rotation angle reference position is set to match the transfer start position again, the position where a visible image is to be formed is determined by the circumferential speed of the intermediate transfer belt 3, which changes with the rotation of the drive shaft 9. Even if a positional error occurs in the toner image transferred to the intermediate transfer belt 3, the same positional error will occur at the same position on the intermediate transfer belt 3 when the next toner image is superimposed and transferred. Errors are also transferred in an overlapping manner at the same time, making it possible to eliminate misalignment between the overlapping toner images. In other words, it is possible to prevent a decrease in resolution and, when copying in full color, to prevent a color image from being formed in a color different from that of the original.

In this embodiment, the intermediate transfer belt 3 is used as the transfer body, but in addition to this, a photoreceptor drum or the like may be used as the transfer member. If it is being driven, the ratio of the number of teeth between the photosensitive drum side and the drive shaft side may be set to be an integer.

(Effects of the Invention) As described above, the transfer device of the electrophotographic apparatus according to the present invention transfers toner images multiple times onto the transfer body rotated by the drive shaft so as to sequentially overlap the toner images. In a transfer device of an electrophotographic device that forms one visible image on the paper and a color image on the paper in one transfer, the transfer body transfers one transfer when the drive shaft rotates an integral number of times. The rotation angle reference position of the drive shaft at the time of completion of transfer is set to always coincide with the transfer start position of the transfer member.

This eliminates the occurrence of misalignment between multiple toner images that are superimposed to form one visible image, prevents a decrease in resolution7, and when copying in full color, the color of the original This has the effect that it is possible to form a color image with colors very similar to those of the above.

[Brief explanation of the drawing]

FIG. 1 shows one embodiment of the present invention, and is an overall configuration diagram of a full-color copying machine. FIGS. 2 and 3 show conventional examples.
The figure is a graph showing the circumferential speed of the intermediate transfer belt due to the eccentricity of the drive roller, and FIG. 3 is a graph showing the position error of the intermediate transfer belt due to the eccentricity of the drive roller. 3 is an intermediate transfer belt (transfer body), 5 is a timing sensor, 6 and 8 are driven rollers, 7 is a drive roller, 9 is a drive shaft, 10 is an intermediate transfer mechanism, 16, 17, and 18 are developing devices,
25 is a photoreceptor belt, 26 is an intermediate transfer charger, 30
32 is a transfer charger, 33 is a peeling charger, 34 is a static elimination charger, and 35 is a cleaner.

Claims (1)

[Claims] 1. A toner image is transferred onto a transfer body rotated by a drive shaft multiple times in a sequentially overlapping manner to form one visible image on the transfer body, and one visible image is transferred onto a sheet of paper. In a transfer device of an electrophotographic apparatus that forms a color image by transferring a color image once, the transfer body is set to complete one transfer when the drive shaft described above rotates an integral number of times, and at the time of completion of transfer. 1. A transfer device for an electrophotographic apparatus, characterized in that a rotation angle reference position of a drive shaft is always set to coincide with a transfer start position of a transfer body.