JPH01235968A - Image forming device - Google Patents

Abstract

PURPOSE:To bring an intermediate transfer belt into tight contact with a driving roller so as to eliminate slips and to attain sure driving by electrostatically charging said belt by an attraction charger to act electrostatic attraction force between the belt and the grounded driving roller. CONSTITUTION:The attraction charger 22 is used to electrostatically charge the intermediate transfer belt 10 to attract the belt to the driving roller 17. The driving roller 17 is grounded. The intermediate transfer belt 10 is, therefore, polarized as the surface thereof is electrostatically charged positive. A negative potential is induced in the grounded driving roller 17 and the intermediate transfer belt 10 is electrostatically and powerfully attracted to the driving roller 17. The intermediate transfer belt is thereby surely driven without generating the slips.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus that transfers images of each color from a photoreceptor onto an intermediate transfer member to form a multicolor image, which is then transferred at once. The present invention relates to an image forming apparatus that performs image transfer onto a transfer material.

(Prior Art) For example, Japanese Patent Publication No. 49-209 discloses an apparatus for printing multicolor images on flexible materials such as cloth by applying electrophotography, which transfers each color image to an intermediate transfer member, A multicolor image formed on this intermediate transfer member is transferred to a flexible material under pressure under an electrostatic voltage.

In addition, the images of each color formed on the photoreceptor are sequentially transferred to an intermediate transfer body to form a multicolor image on the intermediate transfer body, and then electrostatically transferred all at once to transfer paper, so that there is no image shift. Devices for forming multicolor images are also already known.

(Problems to be Solved by the Invention) By the way, when an intermediate transfer belt is used as an intermediate transfer member in the image forming apparatus as described above, it is necessary to have a smooth surface, so that the friction coefficient is small and there is no charge. Since it is necessary to use a thin dielectric belt for ease of use, there is a problem in that it is difficult to accurately drive this intermediate transfer belt without slippage.

Generally, in order to drive the belt without slipping, a rubber roller is used as the drive roller, or a belt with teeth or perforations is used. There are various problems, such as that it is not suitable as such.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, it is an object of the present invention to provide an image forming apparatus that can reliably drive an intermediate transfer belt without causing slippage.

(Means for Solving the Problems) In order to achieve the above object, the present invention electrostatically transfers a developed image obtained by developing an electrostatic latent image formed on a photoreceptor to an intermediate transfer belt. In an image forming apparatus that performs the step of retransferring the images formed on the intermediate transfer belt to the transfer material at once by electrostatically retransferring the images formed on the intermediate transfer belt to the transfer material, the intermediate transfer belt is wrapped around the image forming apparatus. It is characterized in that an adsorption charger is disposed opposite the drive roller, and the drive roller is grounded.

(Function) Since the present invention has the above configuration, even if the intermediate transfer belt is made of a dielectric material with a smooth surface, a small coefficient of friction, and a thin thickness, it is possible to transfer the adsorption chart by utilizing the dielectric material. By charging the intermediate transfer belt with electricity, an electrostatic attraction force can be exerted between the intermediate transfer belt and the grounded drive roller, and the intermediate transfer belt can be brought into close contact with the drive roller and driven reliably without slipping.

(Embodiment) An embodiment in which the present invention is applied to a color copying apparatus will be described below with reference to FIGS. 1 to 4.

In FIG. 1, reference numeral 1 denotes a document table glass on which a document is placed. Below the document table glass 1, an exposure lamp 2, first to fifth mirrors 3a to 3e, a lens 4, and a color separation filter unit 5 are provided. An optical system consisting of 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 supported in parallel by seven frames 51, and a drive motor 52 and a position sensor. At 53a and 53b, one of the filter plates 5B, 5G, and SR can be selectively positioned in the exposure optical path.

Reference numeral 6 denotes a photosensitive drum, around which are an erase lamp 7, a charging charter 8, a developing section 9, and an intermediate transfer belt 10.
, a drum cleaner 11 are provided. The developing section 9
A yellow developer 9Y, a magenta developer 9M, and a cyan developer 9C are installed. Further, each developing device is equipped with a developing sleeve, a grain cutting shutter, a toner concentration detector, a toner replenishing device, and the like.

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

Around the intermediate transfer belt 10, there are a primary transfer charger 12 that transfers an image from the photosensitive drum 6 to the intermediate transfer belt 10, an adsorption charger 22, secondary transfer pretreatment chargers 13a and 13b, and a transfer material from the intermediate transfer belt 10. A secondary transfer charger 14 for transferring an image, a static elimination charger 15, a belt cleaner 16, etc. are provided.

Further, as shown in detail in FIG.
The pressure roller 18, the secondary transfer roller 219, and the belt cleaner roller 20 are tensioned by four straight rollers, and the pressure roller 18 is connected to a solenoid 21a.
By moving the intermediate transfer belt 10 at , the intermediate transfer belt 10 is switched between a first position where it is in pressure contact with the photoreceptor drum 6 and a second position where it is spaced apart from the photoreceptor drum 6. 211] is a solenoid that presses and separates the belt cleaner 16 from the intermediate transfer belt 10. The adsorption charter 22 is for charging the intermediate transfer belt 10 and adsorbing it to the drive roller 17, and the drive roller 17 is made of a conductive material and is grounded as shown in FIG. There is.

23 is a paper feed cassette, 24 is a registration roller, 25 is a transfer paper conveyance belt, and 26 is a fixing device equipped with a fixing roller having a built-in heater.

Next, to explain the operation, a document placed on the document table lath 1 is sequentially scanned in the horizontal direction, and the reflected light is transmitted to the first to third mirrors 3a to 3c and the color separation filter unit 5.
, lenses 4 and 14, and fifth mirrors 3cl and 3e, an image is formed on the photosensitive surface of the photosensitive drum 6. After the photosensitive drum 6 is exposed and neutralized by the erase lamp 7,
It is charged to, for example, a constant negative potential by the charger 8, rotates in synchronization with the scanning, and is exposed. When the photosensitive surface is irradiated with reflected light from the original, the surface potential changes depending on the intensity of the light, and an electrostatic latent image is formed.

This electrostatic latent image is formed by the yellow developing device 9Y of the developing section 9,
The image is developed with toner of each color in either the magenta developer 9M or the cyan developer 9C. For example, in the color M filter unit 5, the blue filter plate 5B
is located in the optical path, the yellow developing device 9Y, which is a complementary color to blue, is selected, and the developer on the developing sleeve is scraped off by the ear-cutting shutter at the rear of each developing sleeve in the other developing devices 9M and 9C. After that, the yellow developing device 9Y is driven, and the electrostatic latent image is developed with yellow toner and made visible. Note that the toner is stored on the photoreceptor drum 6.
It is charged to the opposite potential, for example, to a positive potential.

The intermediate transfer bell 10 is driven at a constant speed with the photosensitive drum 6 in synchronization with the photosensitive drum 6, and the photosensitive drum 6 is driven by the primary transfer churner 12 to which a negative potential is applied.
The upper positive potential toner image is transferred to this intermediate transfer bell (10). Thereafter, the photosensitive surface of the photosensitive drum 6 is cleaned by a drum cleaner 11, and the exposure-development and primary transfer steps are completed.

In the case of full-color copying, when the first exposure, development and primary transfer steps for yellow are completed, the green filter plate 5G is selected in the color separation filter unit 5 and positioned on the optical path. The photosensitive surface of the photosensitive drum 6 is exposed to the reflected light of the original that has passed through the photosensitive drum 6, and an electrostatic latent image is formed.
The magenta toner image is transferred onto the yellow toner image on the intermediate transfer belt 10 .

When the second exposure-development and primary transfer process is completed,
For the third time, the red filter plate 5R is selected in the color separation filter unit 5 and positioned on the optical path, and the light reflected from the original that passes through it exposes the photosensitive surface of the photosensitive drum 6 to form an electrostatic latent image. The image is visualized by a cyan developer 9C, which is a complementary color to red, and the cyan toner image is transferred onto the intermediate transfer belt 10 overlapping the yellow and magenta toner images, resulting in a full-color toner image of yellow, magenta, and cyan. is formed.

During this next transfer process, the belt cleaner 16 of the intermediate transfer belt 10 is separated from the intermediate transfer belt 10 by turning off the solenoid 211). On the other hand, when the -next transfer process is completed, the solenoid 21a is turned off, and the pressure roller 21a is turned off.
18 and transfer the intermediate transfer belt 10 to the photosensitive drum 6.
In this state, the intermediate transfer belt 10 is driven as it is. In this way, since the intermediate transfer belt 10 is brought into pressure contact with the photoreceptor drum 6 only in the next transfer process, and is kept apart at other times, the photoreceptor drum 6 is stopped when the second transfer is completed.

Next, the full-color toner image on the intermediate transfer belt 10 is pre-charged by a secondary transfer pre-treatment charter 13a113b. That is, the same positive potential as that of the toner image is applied to the pretreatment charger 13a on the front side of the intermediate transfer belt 10, and the opposite negative potential is applied to the pretreatment charger 131 on the back side, so that the charged state of the toner image is changed. The toner image is intensified prior to secondary transfer, and then moved to secondary transfer charger 14. In this way, by strengthening the charging state of the toner image prior to the secondary transfer in the pre-treatment charter 13a113'l), the charge of the toner image transferred in the first or second primary transfer step is increased in the second transfer process. Ya 3
Even if the charge is reduced during the first primary transfer, sufficient charge is retained by being charged again, and the toner image is efficiently and stably transferred.

On the other hand, at a predetermined timing based on a signal from a position detection device (not shown) of the intermediate transfer belt 10, the transfer paper is fed out from the grade cassette 23 by the paper feed roller 23a and sent to the Leno stroller 24. The transfer paper is fed to the secondary transfer charger 14 at a predetermined timing, and the full-color toner image with a positive potential on the intermediate transfer belt 10 is electrostatically attracted by the secondary transfer charger 14 to which a negative potential is applied, and transferred. transferred to paper.

An alternating current potential is applied to the transfer paper on which the toner image has been transferred, and the charge is removed by the charger 15, and the transfer paper is transferred to the intermediate transfer belt 10.
The paper is separated, transported by suction by a transfer paper transport belt 25, sent to a heated fixing device 26, fixed, and discharged.

On the other hand, the solenoid 21b is turned on and the belt cleaner 16 is pressed to clean the intermediate transfer belt 10 that has completed the secondary transfer, and is ready for the next process.

During the above-described operation of the intermediate transfer belt 10, the drive roller 17 is grounded, and the intermediate transfer belt 10 is charged by positive discharge by the adsorption charter 22, so that the intermediate transfer belt 10 is electrostatically and strongly applied to the drive roller. 17, the driving force is reliably transmitted, and the drive is performed with high precision without slipping. That is, as shown in FIG. 4, the intermediate transfer belt 1 is
0 has a positive charge on its surface and is polarized, which induces a negative potential in the grounded drive roller 17, and the intermediate transfer belt 10 is attracted to the drive roller 17.

Photosensitive drum 6 and intermediate transfer belt 1 in the above steps
The operating states of 0, the adsorption charter 22, the -next transfer charger 12, the pretreatment charters 13a and 13b, and the secondary transfer charger 14 are shown in Figure @5.

In the above explanation, the adsorption charger 22 was positively discharged, but in this embodiment, the pretreatment chargers 13a and 13b
Since the charge is adjusted by , the adsorption charter 22 can be negatively charged, -11- or alternating current discharge. On the other hand, the adsorption charter 22 may also be used as a pretreatment charter. In addition, the secondary transfer roller 19 is grounded as a driving roller, and the secondary transfer charger 14 and the separation charger 15
Alternatively, the adsorption charger may also be used.

Further, in the above description, the photosensitive drum 6, the secondary transfer charger 12, the back side pretreatment charge 13b, and the secondary transfer charger 14 are negatively charged, and the toner and the front side pretreatment charger 3a are positively charged. Although an example has been described in which charging is performed in the opposite direction.

In addition, in the above description, three primary transfers are performed on the intermediate transfer belt 10.
Although an example has been shown in which a full-color toner image is formed by rotating the toner image and transferred to a transfer paper, it goes without saying that a mode in which a monochromatic color image is formed and transferred may also be provided. In that case, the pretreatment charger may or may not be activated.

(Effects of the Invention) According to the image forming apparatus of the present invention, as described above, the intermediate transfer belt is charged by the adsorption charger by utilizing the fact that it is a dielectric material, and is electrostatically attracted between it and the grounded drive roller. By applying force, the intermediate transfer belt can be brought into close contact with the drive roller, and even if the intermediate transfer belt is made of a thin dielectric material with a smooth surface and a small coefficient of friction, it can be ensured without slippage. This has the effect that it can be driven to

[Brief explanation of the drawing]

! @Figures 1 to 5 show an embodiment in which the present invention is applied to a full-color copying apparatus, in which Figure 1 is a general schematic diagram, Figure 2 is a perspective view of a color selection filter unit, and Figure 3 is an intermediate transfer unit. FIG. 4 is a perspective view of the belt and its surroundings, FIG. 4 is an explanatory diagram of the operation of the drive roller and suction charter, and FIG. 5 is a diagram showing the operation timing of each part.

Claims (1)

[Claims] (1) A step of electrostatically transferring the developed image obtained by developing the electrostatic latent image formed on the photoreceptor to the intermediate transfer belt is performed for each of multiple colors to form the image on the intermediate transfer belt. In an image forming device that electrostatically retransfers multiple color images onto a transfer material at once, an adsorption charger is disposed opposite to a drive roller around which an intermediate transfer belt is wrapped, and the drive roller is grounded. An image forming apparatus characterized by: