JP2658103B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly, to transfer a color image from a photoreceptor onto an intermediate transfer member to form a multicolor image, and transfer the image at once. The present invention relates to an image forming apparatus configured to transfer an image on a material.

(Prior Art) For example, Japanese Patent Application Laid-Open No. 56-147166 discloses an image forming apparatus in which an image formed on a photoreceptor is primarily transferred to an intermediate transfer member and then secondary transferred to a transfer material. There is disclosed an apparatus in which a cleaning device for an intermediate transfer member is made inoperative when multiple transfer is performed. However, the intermediate transfer member and the photoreceptor are always in pressure contact with each other, and cannot be separated.

(Problems to be Solved by the Invention) However, in the above-described image forming apparatus, since the photoconductor and the intermediate transfer body are always in pressure contact with each other, even when only one of them needs to be driven, if one of them is stopped, the damage is caused. Therefore, it is necessary to drive both, and even if both are driven, physical damage due to contact will occur.Further, frictional charging and peeling discharge will be repeated because contact and separation are repeated at the contact part of both. ,
There are problems such as electrical fatigue.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described conventional problems, and has as its object to provide an image forming apparatus capable of performing a pressing / separating operation of a photoconductor, an intermediate transfer body, and a cleaning device.

(Means for Solving the Problems) In order to achieve the above object, the present invention electrostatically transfers a visible image obtained by developing an electrostatic latent image formed on a photoreceptor to an intermediate transfer member. Is performed for each of the plurality of colors, and the images of the plurality of colors formed on the intermediate transfer body are electrostatically re-transferred to the transfer material at once, and then the residual toner on the intermediate transfer body is removed by a cleaning device. In the image forming apparatus,
Position switching means for moving the intermediate transfer member between a first position pressed against the photosensitive member and separated from the cleaning device and a second position separated from the photosensitive member and pressed against the cleaning device is provided. It is characterized by.

In a preferred embodiment, the intermediate transfer member is an intermediate transfer belt wound around a pressing roller for pressing the intermediate transfer member against the photosensitive member and a cleaner pressing roller for pressing the intermediate transfer member against the cleaning device. The position switching means comprises a rocking lever having the pressing roller and the cleaner pressing roller attached to both ends.

(Operation) Since the present invention has the above-described structure, the intermediate transfer member is pressed against the photosensitive member at the time of primary transfer, and the intermediate transfer member is separated from the cleaning device to be in a non-operating state. Separating the body from the photoreceptor reduces damage and electrical fatigue on the photoreceptor and the intermediate transfer body, and presses the intermediate transfer body against the cleaning device to remove residual toner on the intermediate transfer body. It is possible to perform both operations in cooperation with each other, so that only a single driving means is required, which is advantageous in terms of space and cost.

In addition, by using an intermediate transfer belt as the intermediate transfer body and switching the position of the intermediate transfer body by swinging the swing lever, the secondary transfer unit is used for switching the position of the intermediate transfer body. Not only does it have no effect, the tension of the intermediate transfer belt can be kept constant during both operations, and a stable image without expansion and contraction can be obtained.

(Embodiment) An embodiment in which the present invention is applied to a color copying machine will be described below with reference to FIGS.

In FIG. 1, reference numeral 1 denotes a platen glass on which a document is placed. Below the platen glass 1, an exposure lamp 2,
An optical system including first to fifth mirrors 3a to 3e, a lens 4, and a color separation filter unit 5 is provided. As shown in FIG. 2, the color separation filter unit 5 includes a blue filter plate 5B, a green filter plate 5G, and a red filter plate.
5R are supported in parallel by the frame 51, and the drive motor 52 and the position sensors 53a, 53b filter plates 5B, 5B.
It is configured so that one of G and 5R can be selectively positioned in the exposure light path.

Reference numeral 6 denotes a photosensitive drum, around which an erase lamp 7, a charging charger 8, a developing unit 9, and an intermediate transfer belt 1 are provided.
0, a drum cleaner 11 is provided. The developing unit 9
Is provided with a yellow developing unit 9Y, a magenta developing unit 9M, and a cyan developing unit 9C. Each developing unit is provided with a developing sleeve, a cutting shutter, a toner concentration detector, a toner replenishing device, and the like.

The intermediate transfer belt 10 is formed of an endless belt made of a flexible dielectric material having good environmental resistance and dimensional stability, for example, a polyimide film having a thickness of about 50 to 100 μm.

Around the intermediate transfer belt 10, a primary transfer charger 12 for transferring an image from the photosensitive drum 6 to the intermediate transfer belt 10, secondary transfer pretreatment chargers 13 a and 13 b, and an image is transferred from the intermediate transfer belt 10 to a transfer material. Secondary transfer charger
14, a static elimination charger 15, a belt cleaner 16 and the like are provided.

Further, as shown in detail in FIG. 3, the intermediate transfer belt 10 has pressing rollers 17 and 18 on both sides of the primary transfer charger 12.
And four straight rollers of a secondary transfer roller 19 and a cleaner pressing roller 20. The one pressure contact roller 18 and the cleaner pressure contact roller 20 are connected to a pivot shaft 21 at an intermediate portion.
Are attached to both ends of a swing lever 22 which is swingably supported by. By swinging the swing lever 22 with the solenoid 23, the intermediate transfer belt 10 is pressed against the photosensitive drum 6 by the press rollers 17 and 18, and the cleaner press roller 20 is moved by the cleaning blade 16a of the belt cleaner 16. The intermediate transfer belt 10 is separated from the photosensitive drum 6 and the intermediate transfer belt is moved by the cleaner pressure contact roller 20.
The position of the intermediate transfer belt 10 is switched between a second position where the intermediate transfer belt 10 is pressed against the cleaning blade 16a.

Reference numeral 24 denotes a paper cassette, reference numeral 25 denotes a registration roller, reference numeral 26 denotes a transfer paper transport belt, and reference numeral 27 denotes a fixing device provided with a fixing roller having a built-in heater.

Next, the operation will be described. The original placed on the original platen glass 1 is sequentially scanned in the horizontal direction, and the reflected light is reflected by the first to third mirrors 3a to 3c, the color separation filter unit 5,
An image is formed on the photosensitive surface of the photosensitive drum 6 via the lens 4 and the fourth and fifth mirrors 3d and 3e. Photoconductor drum 6
After being subjected to exposure and elimination by the erase lamp 7, it is charged to, for example, a negative constant potential by the charging charger 8, and is rotated and exposed in synchronization with the scan. When the photosensitive surface receives the reflected light from the original, the surface potential changes according to the intensity of the light, and an electrostatic latent image is formed.

This electrostatic latent image is stored in a yellow developing unit 9Y of the developing unit 9;
Each of the magenta developing device 9M and the cyan developing device 9C develops with the toner of each color. For example, in the color separation filter unit 5, if the blue filter plate 5B is located in the optical path, the yellow developing device which is a complementary color of blue
9Y is selected, and the other developer units 9M and 9C scrape off the developer on the developing sleeve by the ear-cutting shutters behind the respective developing sleeves. The latent image is developed and visualized. Note that the toner is charged to, for example, a positive potential opposite to the photosensitive drum 6.

The intermediate transfer belt 10 is driven at the same speed as the photosensitive drum 6 in synchronization with the photosensitive drum 6, and a positive potential toner image on the photosensitive drum 6 is formed by the primary transfer charger 12 to which a negative potential is applied. The image is transferred to the intermediate transfer belt 10. Thereafter, the photosensitive surface of the photosensitive drum 6 is cleaned by the drum cleaner 11, and the exposure-development-primary transfer process is completed.

In the case of a full-color copy, when the first exposure-development-primary transfer process for yellow is completed, a green filter plate 5G is selected by the color separation filter unit 5, is positioned on the optical path, and passes therethrough. The photosensitive surface of the photosensitive drum 6 is exposed by the reflected light of the original to form an electrostatic latent image, which is visualized by a magenta developing device 9M, which is a complementary color of green, and is formed on the yellow toner image on the intermediate transfer belt 10. The magenta toner image is superimposed and transferred.

When the second exposure-development-primary transfer step is completed, the third time, the red filter plate 5R is selected by the color separation filter unit 5 and positioned on the optical path, and the photosensitive member is reflected by the original reflected light passing therethrough. The photosensitive surface of the drum 6 is exposed to form an electrostatic latent image, which is visualized by a cyan developing device 9C, which is a complementary color of red, and is superimposed on the yellow and magenta toner images on the intermediate transfer belt 10 by cyan toner. The image is transferred, and a full-color toner image of yellow, magenta, and cyan is formed.

During this primary transfer step, the solenoid 23 is turned on, and the swing lever 22 swings clockwise as shown by the solid line in FIGS. Is pressed against the photosensitive drum 6 at
The cleaner pressing roller 20 is separated from the cleaning blade 16a of the belt cleaner 16, and the toner image transferred onto the intermediate transfer belt 10 is not erased.

Next, when the primary transfer step is completed, the solenoid 23 is turned off, and the swing lever 22 swings counterclockwise by urging means (not shown) as shown by a broken line in FIGS. As a result, the pressing roller 18 moves to move the intermediate transfer belt.
10 is separated from the photosensitive drum 6, and the cleaner pressing roller 20 is moved to the belt cleaner via the intermediate transfer belt 10.
Press against 16 clean blades 16a. in this way,
By pressing the intermediate transfer belt 10 against the photosensitive drum 6 only in the primary transfer step and separating the intermediate transfer belt 10 at other times, the photosensitive member 6 can be stopped when the primary transfer is completed. Further, since the photoreceptor 6 and the intermediate transfer belt 10 are separated from each other, there is no occurrence of such damage and electrical fatigue due to repeated frictional charging and peeling discharge.

Next, the full-color toner image on the intermediate transfer belt 10 is pre-processed and charged by the secondary transfer pre-processing chargers 13a and 13b. That is, the same positive potential as the toner image is applied to the pretreatment charger 13a on the front side of the intermediate transfer belt 10,
The opposite negative potential is applied to the pre-processing charger 13b on the back side, so that the charged state of the toner image is strengthened prior to the secondary transfer, and then the toner image moves to the secondary transfer charger.

On the other hand, at a predetermined timing according to a signal from a position detecting device (not shown) of the intermediate transfer belt 10, transfer paper is fed out from the paper feed cassette 24 by the paper feed roller
The transfer paper is sent to the secondary transfer charger 14 at a predetermined timing by the registration roller 25,
The full-color toner image of the positive potential on the intermediate transfer belt 10 is electrostatically attracted by the secondary transfer charger 14 to which the negative potential is applied, and is transferred to the transfer paper.

The transfer paper on which the toner image has been transferred is discharged by applying an AC potential by the charge removing charger 15, separated from the intermediate transfer belt 10, sucked and transferred by the transfer paper transfer belt 26, and sent to the heated fixing unit 27. It is fixed and discharged.

On the other hand, the residual toner on the intermediate transfer belt 10 after the secondary transfer is cleaned because the intermediate transfer belt 10 is pressed against the cleaning blade 16a by the cleaner pressing roller 20 as described above.

Photoconductor drum 6, intermediate transfer belt in the above steps
FIG. 4 shows the operating states of the solenoid 10 and the solenoid 23.

As described above, the charge state of the toner image is enhanced by the pre-processing chargers 13a and 13b prior to the secondary transfer, so that the charge of the toner image transferred in the first and second primary transfer steps is reduced to the second time. Or the toner image formed by the first primary transfer even if the toner image is reduced during the third primary transfer, and the toner image formed by the second primary transfer and the single color portion over which the toner image was not formed during the third primary transfer. As described above, even in a portion where the charge is easily reduced by the second and subsequent primary transfer, sufficient charge is held by recharging, and the toner image is efficiently and stably transferred.

In the above description, the photosensitive drum 6, the primary transfer charger 12, the back-side image pre-processing charger 13b, and the secondary transfer charger 14 are negatively charged, and the toner and the front-side pre-processing charger 3a are positively charged. Although an example has been described, charging may be performed in reverse.

Further, in the above description, the primary transfer is performed on the intermediate transfer belt 10 for three times.
Although the example in which the full-color toner image is formed by repeating the transfer and transferred to the transfer paper has been described, it goes without saying that a mode in which a single-color image is formed and transferred may be provided. In that case, the pre-processing charger may or may not be activated.

Further, in the above-described embodiment, the intermediate transfer belt 10 is exemplified as the intermediate transfer body, but an intermediate transfer drum can be used.

(Effect of the Invention) According to the image forming apparatus of the present invention, as described above, at the time of the primary transfer, the intermediate transfer member is pressed against the photosensitive member, and the intermediate transfer member is separated from the cleaning device to be in a non-operating state. Conversely, during transfer, the intermediate transfer body is separated from the photoreceptor to reduce scratches and electrical fatigue on the photoreceptor and the intermediate transfer body, and the intermediate transfer body is pressed against the cleaning device to remain on the intermediate transfer body. The toner can be removed.

In addition, if the intermediate transfer belt is used as the intermediate transfer body and the position of the intermediate transfer body is switched by the swing operation of the swing lever, the secondary transfer unit is affected by the switching of the position of the intermediate transfer body. Not only give
A great effect can be obtained, for example, the tension of the intermediate transfer belt can be kept constant during both operations, and a stable image without expansion and contraction can be obtained.

[Brief description of the drawings]

1 to 4 show an embodiment in which the present invention is applied to a full-color copying apparatus. FIG. 1 is an overall schematic diagram, FIG. 2 is a perspective view of a color selection filter unit, and FIG. FIG. 4 is a perspective view around the belt, and FIG. 6. Photoconductor drum 10 Intermediate transfer belt 16 Belt cleaner 17, 18 Pressure roller 20 Cleaner pressure roller 22 Swing lever 23 Solenoid

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshiyuki Sakai 2-30 Azuchicho, Higashi-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Camera Co., Ltd. (72) Katsuhiko Takeda 2--30 Azuchicho, Higashi-ku, Osaka-shi, Osaka Address: Osaka International Building Minolta Camera Co., Ltd. (72) Inventor Hideo Kitakubo 2-30 Azuchicho, Higashi-ku, Osaka City, Osaka Prefecture Osaka International Building Minolta Camera Co., Ltd. (56) References JP-A-59-133581 (JP, A) JP-A-59-104673 (JP, A)

Claims (2)

(57) [Claims] A step of electrostatically transferring a visible image obtained by developing an electrostatic latent image formed on a photoreceptor to an intermediate transfer member for each of a plurality of colors to form a latent image on the intermediate transfer member. An image forming apparatus in which a plurality of color images formed on the intermediate transfer member are electrostatically re-transferred to the transfer material at a time, and then the residual toner on the intermediate transfer member is removed by a cleaning device. Image forming means for moving between a first position pressed against the body and separated from the cleaning device and a second position separated from the photoreceptor and pressed against the cleaning device. apparatus. 2. The intermediate transfer member comprises a pressure roller for pressing the intermediate transfer member against the photoreceptor, and an intermediate transfer belt wound around a cleaner pressure roller for pressing the intermediate transfer member against the cleaning device. 2. An image forming apparatus according to claim 1, wherein said position switching means comprises a swing lever having said pressing roller and said cleaner pressing roller attached to both ends.