JP2001356555A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a tension part formed when an intermediate transfer belt travels to circulate at the installation position of an image forming unit and the transfer position of a toner image to a recording medium. SOLUTION: This device is provided with the image forming units 5, 6, 7 and 8 storing toner whose color is different from each other and arrayed in tandem, the endless intermediate transfer belt 3 traveling to circulate along in the arraying direction of the units 5, 6, 7 and 8 so that a color toner image may be formed by successively superposing and transferring plural color toner images formed on photoreceptor drums 5a, 6a, 7a and 8a, a tension roller 14 installed near the upstream side of a belt supporting roller 2 in the traveling direction of the belt 3 and applying tension to the belt 3, and a secondary transfer roller 11 arranged at a position opposed to the roller 2 and pressing the roller 2 through the belt 3 so that a synthetic toner image formed on the belt 3 may be collectively transferred to paper P.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus for forming a composite image by superimposing image information using electrophotographic technology or the like.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus employing an electrophotographic technique, a photosensitive member as an image carrier is charged by a charger, and the photosensitive member is irradiated with light according to image information to form a latent image. Is formed, and the latent image is developed by a developing device, and the visualized toner image is transferred to a sheet material or the like to form an image.

On the other hand, a plurality of image carriers on which such a series of image forming processes are developed in accordance with colorization of an image are provided, and each color image of a cyan image, a magenta image, a yellow image, and preferably a black image is provided. Is formed on each image carrier, and a full-color image is formed by superimposing and transferring each color image on a recording medium at a transfer position of each image carrier, or a toner image of each color is formed on the image carrier. A number of tandem-type color image forming apparatuses have been proposed in which, after formation, the images are sequentially transferred to an intermediate transfer member, and the superimposed full-color toner images are collectively transferred onto a recording medium.

[0004] Such a tandem type color image forming apparatus has an image forming section for each color, and is considered to be advantageous for speeding up.

FIG. 3 is a schematic diagram showing a configuration of a conventional color image forming apparatus using a tandem system.

As shown in FIG. 3, the color image forming apparatus includes yellow (Y), magenta (M), cyan (C),
Image forming units 15, 16, 17, and 18 for forming toner images of respective colors of black (K); and image forming units 15, 16, 17, and 1 that output image signals.
8, the photosensitive drums 15a, 16a, 17a,
An exposure unit 19 for forming an electrostatic latent image on the intermediate transfer belt 18a, an intermediate transfer belt 20 formed and running in a closed loop,
A primary transfer roller 47 for transferring the toner image formed on the photoconductor drums 15a, 16a, 17a, and 18a to the intermediate transfer belt 4; The toner image is transferred, and the toner image is fixed on the paper P by the fixing device 48.

Image forming units 15, 16, 17, 18
Inside is, for example, a yellow (Y) image forming unit 1.
Reference numeral 5 denotes a photosensitive drum 15a on which an electrostatic latent image is formed by a laser beam from the exposure device 19, a charger 15b for charging the outer peripheral surface of the photosensitive drum 15a to a predetermined potential, and a photosensitive member 15b. A developing roller 15c for applying toner to the electrostatic latent image formed on the drum 15a and visualizing the toner;
And a cleaner 15 for removing residual toner on the photosensitive drum 15a after transferring the toner image to the intermediate transfer belt 20.
d. The other image forming units 16, 17, and 18 have the same configuration.

The intermediate transfer belt 20 is stretched around a belt drive roller 24, a belt support roller 25, a tension roller 26, and an idle roller 27. Inside the intermediate transfer belt 20, the intermediate transfer from the photosensitive drums 15a, 16a, 17a, 18a is performed. A primary transfer roller 21 for transferring a toner image to the belt 20 is provided. The belt support roller 25 is
Between the belt drive roller 24 and the intermediate transfer belt 2
0 is pressed against the photosensitive drums 15a, 16a, 17a, and 18a, and the tension roller 26 applies a predetermined tension to the intermediate transfer belt 20.

The belt drive roller 24 needs to run stably without slipping due to the contact between the outer peripheral surface and the inner peripheral surface of the intermediate transfer belt 20. Therefore, a rubber material having a high friction coefficient is rolled on the outer peripheral surface. It is formed in a shape.

FIG. 4 is an explanatory view showing the running state of the intermediate transfer belt in the color image forming apparatus of FIG. 3, and the behavior of the intermediate transfer belt 20 in the running state is shown by a solid line in FIG. The belt drive roller 24, the photosensitive drums 15 a, 16 a, 17 a, 18 a and the belt support roller 25 deform in a wavy manner.

In the color image forming apparatus having such a configuration, for example, first, the yellow (Y) photosensitive drum 15
A is uniformly charged by the charger 15b, and a laser beam is radiated based on the image information transmitted from the host computer (not shown) to the exposure device 19, thereby forming a yellow component color latent image. This latent image is visualized as a yellow toner image by the toner thinned on the developing roller 15c. The visualized toner image is transferred to the photosensitive drum 15
When a transfer voltage is applied to the primary transfer roller 21 from the inner surface of the intermediate transfer belt 20 that is traveling in contact with a (circle A in the drawing), the image is transferred onto the intermediate transfer belt 20.

In the meantime, a magenta component latent image of the next color is formed, and a magenta toner image of magenta toner is visualized by the developing roller 16c. Then, the magenta toner image is transferred to the intermediate transfer belt 20 on which the transfer of the yellow toner image has been completed, and is superimposed on the yellow toner image.

Thereafter, image formation is performed on the cyan toner image and the black toner image in the same manner, and the superposition of the four color toner images on the intermediate transfer belt 20 is completed.

Thereafter, after the toner image on the intermediate transfer belt 20 is transferred to the sheet P taken out of the sheet cassette 23 and conveyed by the transfer roller 28, the sheet P passes through a fixing device 48 so that the toner is fixed. The sheet is discharged in the direction of arrow B.

After the toner image is transferred onto the sheet P, the toner remaining on the intermediate transfer belt 20 without being transferred onto the sheet P is removed by the belt cleaner 29.

[0016]

However, in the image forming apparatus having the above-mentioned conventional configuration, when the intermediate transfer belt is rotated around, a tension portion and a slack portion are formed between the belt driving roller and the tension roller (see FIG. 1). (Fig. 4). And
Because the image forming unit is provided in the loose part,
Fluctuations in the belt length caused by tension extension or thermal extension of the intermediate transfer belt cause variations in the contact pressure between the photosensitive drum and the intermediate transfer belt and in the nip width, making it impossible to perform ideal transfer, and causing the toner images to overlap. This will cause a shift or a disturbance of the transferred toner image.

Further, if the batch transfer to the sheet is performed at the slack portion, the nip width between the secondary transfer roller and the intermediate transfer belt varies, causing the transfer toner image to be disturbed.

Therefore, the present invention provides a color image forming apparatus capable of forming a tension portion formed when the intermediate transfer belt circulates, at the installation position of the image forming unit and the transfer position of the toner image onto the recording medium. The purpose is to provide.

[0019]

In order to solve this problem, a color image forming apparatus according to the present invention comprises a photosensitive drum on which an electrostatic latent image is formed by exposure means and a toner attached to the electrostatic latent image. A plurality of image forming units containing toners of mutually different colors and arranged in tandem and a plurality of rollers, and arranged in a direction in which the image forming units are arranged. An endless intermediate transfer belt on which a plurality of color toner images formed on a photoconductor drum are sequentially superimposed and transferred to form a color toner image while traveling around the same, and image formation in the running direction of the intermediate transfer belt. A tension roller installed near the upstream side of the roller located near the upstream side of the unit and applying tension to the intermediate transfer belt, and a roller located near the upstream side of the image forming unit Are disposed on opposite positions, it is through the intermediate transfer belt that is configured to include a transfer roller which collectively transferred to a recording medium the composite toner image formed on the intermediate transfer belt by pressing the roller.

Thus, the tension roller is installed near the upstream side of the roller located near the upstream side of the image forming unit with respect to the running direction of the intermediate transfer belt. Can be formed at the installation position of the image forming unit and the transfer position of the toner image to the recording medium.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a photosensitive drum on which an electrostatic latent image is formed by exposure means, and a developing method for forming a toner image by attaching toner to the electrostatic latent image. A plurality of image forming units containing toners of mutually different colors and arranged in tandem; and a plurality of rollers. An endless intermediate transfer belt on which a plurality of color toner images formed on the body drum are sequentially superimposed and transferred to form a color toner image; and A tension roller installed near the upstream side of the image forming unit to apply tension to the intermediate transfer belt, and a roller located near the upstream side of the image forming unit, facing the intermediate transfer belt. And a transfer roller that collectively transfers the synthetic toner image formed on the intermediate transfer belt to the recording medium by pressing the roller through the transfer roller, and the tension roller moves in the running direction of the intermediate transfer belt. Is installed near the upstream side of the roller located near the upstream side of the image forming unit. Therefore, when the intermediate transfer belt travels around the belt, the stretched portion is positioned between the image forming unit and the transfer position of the toner image onto the recording medium. It has the effect that it becomes possible to form it.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In these drawings, the same members are denoted by the same reference numerals, and duplicate description is omitted.

FIG. 1 is a schematic diagram showing a configuration of a color image forming apparatus according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing a running state of an intermediate transfer belt in the color image forming apparatus of FIG.

In FIG. 1, an intermediate transfer belt 3 driven and driven by a belt drive roller (roller) 1 includes a belt drive roller 1, a belt support roller (roller) 2, a tension roller 14 for applying tension to the intermediate transfer belt 3, and , The intermediate transfer belt 3
(Recording medium) P from a paper cassette 10 disposed below the intermediate transfer belt 3 and a secondary transfer roller (transfer roller) 11 pass through a fixing device 12. ing.

That is, an exposure device (exposure means) for irradiating a laser based on image information is provided above the intermediate transfer belt 3.
9 are arranged between the exposing device 9 and the intermediate transfer belt 3, yellow (Y), magenta (M), cyan (C),
Black (K) image forming units 5, 6, 7, and 8 are sequentially arranged along the running direction of the intermediate transfer belt 3. The color toner image formed on the intermediate transfer belt 3 is transferred to the secondary transfer roller 11 that presses the belt support roller 2 via the intermediate transfer belt 3 and the intermediate transfer belt 3.
Is transferred to the sheet P by the nip, and the transferred toner image is fixed on the sheet P by the fixing device 12.

A belt cleaning unit 4 for removing the toner image remaining on the intermediate transfer belt 3 without being transferred onto the paper P is disposed between the image forming unit 5 and the belt support roller 2. .

It should be noted that the present invention is not limited to the present embodiment as long as it comprises a black or monochrome image forming unit and a color image forming unit for at least two colors such as yellow.

Each of the image forming units 5, 6, 7, and 8 has the same structure, and the photosensitive drums 5a, 6
a, 7a, 8a and these photosensitive drums 5a, 6a,
Corona-type chargers 5b, 6b, 7b, 8b for uniformly charging the surfaces of 7a, 8a to a predetermined potential, and cleaning for removing residual toner from the surfaces of photosensitive drums 5a, 6a, 7a, 8a. Blades 5c, 6c, 7c, 8c
And a waste toner screw 5 for transporting waste toner scraped by the cleaning blades 5c, 6c, 7c, 8c.
d, 6d, 7d, 8d and the photosensitive drums 5a, 6a, 7
a, developing rollers (developing means) 5e, 6e, which apply toner to an electrostatic latent image formed on
7e, 8e and these developing rollers 5e, 6e, 7e,
The supply rollers 5f, 6f, 7f, 8f for supplying toner from a toner tank (not shown) to the surface of the developing roller 5e, and the toner thickness on the developing rollers 5e, 6e, 7e, 8e is made uniform and charged to a predetermined potential. 5g thinning blade,
6g, 7g, and 8g.

Further, primary transfer rollers 13Y, 13M, 13C and 13B are provided at positions corresponding to the photosensitive drums 5a, 6a, 7a and 8a on the inner peripheral side of the intermediate transfer belt 3.

Here, since the belt drive roller 1 needs to run the intermediate transfer belt 3 made of polycarbonate without slipping, a urethane rubber material having a high frictional force is wound around an aluminum core bar in a roll shape. It consists of what was done. Further, the belt support roller 2, the tension roller 14
And primary transfer rollers 13Y, 13M, 13C, 13B
Is made of metal, and rotates following the movement of the intermediate transfer belt 3. The belt support roller 2 is grounded to regulate the flow of current applied to the secondary transfer roller 11, and the primary transfer rollers 13Y, 13M, 13
A voltage for transferring a toner image from the photosensitive drums 5a, 6a, 7a, 8a to the intermediate transfer belt 3 is applied to C and 13B.

As shown, the tension roller 14
Is a roller located near the upstream side of the belt support roller 2 with respect to the running direction of the intermediate transfer belt 3, that is, near the upstream side of the image forming units 5, 6, 7, and 8 with respect to the running direction of the intermediate transfer belt 3. It is installed near the upstream side of.

FIG. 2 shows the behavior of the intermediate transfer belt 3 having such a structure during running. Note that FIG.
, The solid line indicates the behavior of the intermediate transfer belt 3 during traveling, and the dashed line indicates the behavior of the intermediate transfer belt 3 when traveling is stopped.

Next, the operation of the color image forming apparatus of this embodiment will be described.

When a print start signal is output, the intermediate transfer belt 3 starts traveling in the direction of arrow A. here,
As described above, since the tension roller 14 is installed near the upstream side of the belt support roller 2 with respect to the running direction of the intermediate transfer belt 3, the belt drive roller 1 and the tension roller 14 are attached to the intermediate transfer belt 3. The tension portion C where the tension acts more strongly on the boundary than at the time of stop is formed in the image forming units 5 and 5.
Loose portion D formed on 6, 7, 8 side, and on the contrary, tension decreases
Are formed on the opposite side. That is, the tension portion C formed when the intermediate transfer belt 3 travels around is formed at the installation positions of the image forming units 5, 6, 7, and 8 and the transfer position of the toner image onto the paper P.

Therefore, the change in the circumferential length of the intermediate transfer belt 3 caused by the extension by tension or heat is absorbed by the amount of deflection of the slack portion D and the spring force of the tension roller 14, so that the photosensitive drums 5a, 6a, 7a , 8a can always be maintained at a constant tension, and the contact condition between the photosensitive drums 5a, 6a, 7a, 8a and the intermediate transfer belt 3 does not change.

Next, in the image forming unit 5, the surface of the photosensitive drum 5a is uniformly charged by the charger 5b, and an electrostatic latent image is formed in accordance with the yellow component color image information output from the exposure unit 4. On the developing roller 5e, the yellow toner supplied from the supply roller 5f is triboelectrically charged by the thinning blade 5g and is uniformly formed as a thin layer.
Is attached to the latent image on the photosensitive drum 5a by the potential difference of the voltage applied between the photosensitive drum 5a and the visible image. The visualized yellow toner is transferred as a yellow toner image onto the intermediate transfer belt 3 by applying a high potential voltage to the primary transfer roller 13Y.

On the other hand, while the yellow toner image is being transferred to the intermediate transfer belt 3, the magenta image forming unit 6 also applies the magenta component color electrostatic latent image to the photosensitive drum 6 a similarly to the yellow image forming unit 5. The magenta toner image is formed on the developing roller 6e, and then the magenta toner image is visualized by the magenta toner uniformly thinned. And
When a high potential voltage is applied to the primary transfer roller 13M, the magenta toner image is transferred from the photosensitive drum 6a so as to be superimposed on the intermediate transfer belt 3 on which the transfer of the yellow toner image has been completed in the previous image forming unit 5.

Thereafter, image formation is similarly performed on the cyan toner image and the black toner image by the image forming units 7 and 8, and when a high potential voltage is applied to the primary transfer rollers 13 C and 13 B, the image is formed on the intermediate transfer belt 3. Are superimposed on toner images of four colors.

Thereafter, when the sheet P conveyed from the sheet cassette 4 passes between the intermediate transfer belt 3 and the secondary transfer roller 11, the combined toner images of four colors are collectively transferred.
Then, the transferred toner image is heated and fixed on the sheet P by the fixing device 12, and is discharged out of the machine body.

As described above, according to the present embodiment, since the tension roller 14 is installed near the upstream side of the belt support roller 2 with respect to the traveling direction of the intermediate transfer belt 3, the tension roller 14 The stretched portion C formed during the circuit running is formed at the installation position of the image forming units 5, 6, 7, and 8 and the transfer position of the toner image onto the paper P.

As a result, it is possible to obtain a high-quality image free from color misregistration and toner image disturbance.

[0042]

As described above, according to the present invention, the tension roller is installed near the upstream side of the roller located near the upstream side of the image forming unit with respect to the running direction of the intermediate transfer belt. An advantageous effect is obtained in that it is possible to form the tension portion during the orbital movement of the intermediate transfer belt at the installation position of the image forming unit and the transfer position of the toner image on the recording medium.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a color image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a running state of an intermediate transfer belt in the color image forming apparatus of FIG.

FIG. 3 is a schematic view showing a configuration of a conventional color image forming apparatus using a tandem system.

FIG. 4 is an explanatory diagram showing a running state of an intermediate transfer belt in the color image forming apparatus of FIG.

[Explanation of symbols]

 Reference Signs List 1 belt drive roller (roller) 2 belt support roller (roller) 3 intermediate transfer belt 5, 6, 7, 8 image forming unit 5a, 6a, 7a, 8a photoconductor drum 5e, 6e, 7e, 8e developing roller (developing means) 9) Exposure device (exposure means) 11 Secondary transfer roller (transfer roller) 14 Tension roller P Paper (recording medium)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Yoshihara 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Yuji Nagai 1006 Odaka Kadoma Kadoma City Osaka Pref. 72) Inventor Kazuhiro Ogata 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.F-term (reference) 2H030 AA01 AB02 BB42 BB46 BB53 2H032 AA05 BA09 BA19 BA23

Claims (1)

[Claims] A photosensitive drum on which an electrostatic latent image is formed by exposure means; and a developing means for forming a toner image by attaching toner to the electrostatic latent image. A plurality of image forming units housed and arranged in tandem; and a plurality of rollers of a plurality of colors formed on the photosensitive drum by being wrapped around a plurality of rollers and running around in the arrangement direction of the image forming units. An endless intermediate transfer belt on which a toner image is sequentially superimposed and a color toner image is formed; and near an upstream side of the roller located near an upstream side of the image forming unit with respect to a running direction of the intermediate transfer belt. A tension roller that is installed and applies tension to the intermediate transfer belt; and a tension roller that is disposed at a position facing the roller that is located near the upstream side of the image forming unit; Through a copy belt color image forming apparatus characterized by comprising a transfer roller for collectively transferred to a recording medium the composite toner image formed on the intermediate transfer belt by pressing the roller.