JPH02247672A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent toner from flying from on toner image on a transfer material by arranging conductive plates close to but not in contact with the transfer material on a transfer material conveying path and applying a voltage of polarity the same as the toner triboelectrifying polarity to the conductive plates. CONSTITUTION:The conductive plates 20b to 20d are provided on the whole undersurfaces of developing units 3b to 3d in second, third and fourth image forming parts Pb, Pc and Pd respectively, and the conductive plate 21 is provided on the whole undersurface of a cleaning part 5d in the fourth image forming part Pd. The conductive plates 20b to 20d and 21 are arranged close to but not in contact with the transfer material 6 on a belt 8 and the voltage of polarity the same as the toner triboelectrifying polarity for toner forming a toner image on the transfer material 6 is applied to the plates 20b to 20d and 21. With the constitution, the scattering of toner from the toner image on the transfer material 6 is electrically restrained and moreover, unfixed toner can be prevented from scattering from a toner image transferred to the transfer material 6 to the member arranged close to the transfer material conveying path.

Description

DETAILED DESCRIPTION OF THE INVENTION -$1) The present invention provides a single-color or multi-color image forming apparatus that forms an image using an electrophotographic method or an electrostatic recording method, and transfers the image onto a transfer material. The present invention relates to an image forming apparatus, and particularly relates to a one-color or multi-color image forming apparatus that prevents toner from scattering from an image transferred onto a transfer material before being fixed.

Conventionally, the system is equipped with a plurality of image forming sections, each of which forms toner images of different colors, and sequentially transfers and superimposes the toner images onto the same transfer material. A variety of multi-color image forming apparatuses, so-called color image forming apparatuses, that produce multi-color images on transfer materials have been proposed, but the most commonly used color electrophotographic copying apparatus is a multicolor electrophotographic method. be.

An example of such a color copying device will be explained based on FIG.
, third and fourth image forming sections Pa, Pb, Pc and Pd are arranged in parallel. The image forming sections Pa, Pb, Pc, and Pd each include dedicated image carriers, in this example, electrophotographic photosensitive drums la, 1b, IC, and 1d.

The photosensitive drums 1a', lb, 1c, and 1d have latent image forming portions 2a, 2b, 2c, 2d, and developing devices 3a, 3 on their outer peripheral sides.
transfer chargers 4a, 4b, 4c, 4d, and cleaning sections 5a, 5b, 5C15d are arranged.

The transfer material 6 is conveyed by the conveyor belt 8 from the right side to the left side in FIG.
Pb, Pc, Pd+7) Transfer charger 4a, 4b, 4C1
4d.

In such a configuration, first, the photosensitive drum l of the first image forming section Pa is
A latent image of the yellow component color of the original image is formed by the Hg image forming section 2a on the image forming area a. The latent image is made into a visible image by a developer containing yellow toner in a developing device 3a, and the yellow toner image is transferred onto a transfer material 6 by a transfer charger 4a.

On the other hand, while the yellow toner image is being transferred to the transfer material as described above, a latent image of the magenta component color is formed in the second image forming portion pb, and then the toner with the magenta toner is developed by the developing device 3b. An image is obtained. The magenta toner image is transferred to the transfer material 6 when the transfer material 6, which has been transferred at the first image forming section Pa, is carried into the transfer section 4b.
is transferred to a predetermined position.

Thereafter, the third and fourth image forming sections P are
Cyan and black images are formed using cyan and Pd, and the cyan and black toner images are transferred to predetermined positions on the same transfer material. When such an image forming process is completed, the image transferred onto the transfer material is fixed to the transfer material by the fixing section 7, and a multicolor image is obtained. On the other hand, the remaining toner is removed from the photosensitive drums la, 1b, 1c, and 1d by the cleaning sections 5a, 5b, 5c, and 5d after the transfer, and the drums are prepared for the next latent image formation to be performed subsequently.

However, in general, in image forming apparatuses, the toner image transferred onto the transfer material is transported in an undefined state until it is fixed in the fixing unit. In multi-color image forming apparatuses where toner tends to scatter easily from the toner image on the material, each part is reduced as much as possible in order to reduce the overall size of the apparatus. is extremely close to the transfer material conveyance path,
Toner from the toner image on the transfer material easily scatters and adheres to these developing sections, cleaning sections, and the like.

Furthermore, when the member close to the transfer material conveyance path is a conductor, for example, and the main body is grounded, toner easily scatters from the toner image on the transfer material. Even if the member close to the transfer material conveyance path is an insulator, toner scattering may occur if the insulator is charged to the opposite polarity to that of the toner due to some reason, such as internal friction charging inside the unit. .

Such toner scattering increases as the number of copies increases, and these scattered toners cause stains inside the machine, resulting in stains on the transfer material and an increase in maintenance time due to cleaning.

The problem of toner scattering as described above can be solved by providing one image carrier in common for each color toner image of a multi-color image, forming each color toner image sequentially on the common image carrier, and sequentially forming each color toner image on the transfer material. A similar problem occurs in a multi-color image forming apparatus that transfers images individually. Further, even in color image forming apparatuses, the problem of toner scattering occurs to some extent.

Therefore, in view of the above-mentioned current situation, an object of the present invention is to easily prevent toner from scattering from a toner image transferred onto a transfer material to a member close to the transfer material conveyance path before the toner image is unfixed, and to prevent the toner from scattering. An object of the present invention is to provide a single-color or multi-color image forming apparatus that can eliminate stains inside the apparatus and stains on transfer materials caused by toner.

The above objects are achieved by the image forming apparatus of the present invention. In summary, the present invention provides an image forming apparatus that obtains an image on a conveyed transfer material by transferring a toner image formed on an image carrier by developing with a frictionally charged toner onto the transferred transfer material. characterized in that a conductive plate is disposed close to the conveyance path of the transfer material onto which the toner image has been transferred without contacting the transfer material, and a voltage having the same polarity as the friction charging polarity of the toner is applied to the conductive plate. This is an image forming apparatus. According to one aspect of the present invention, one image carrier is provided for each color toner image of a multi-color image, or one image carrier is provided in common, and each of the image carriers or the common The toner images of each color sequentially formed on the image carrier 2 are sequentially transferred and superimposed onto the transfer material to obtain a plurality of color images on the transfer material, and The applied voltage has a higher potential as the transfer material passing through the conductor plate is at a stage where the toner images of the respective colors have been transferred.

1 Presentation J Next, one embodiment of the image forming apparatus according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an image forming apparatus according to the present invention. As shown in FIG. 1, the forming device includes a first
Second, third and fourth image forming sections Pa, Pb, Pc and P
d are arranged in parallel, and a drive roller 11 is provided below the image forming section.
．． 12 and 96 and these rollers 11.12.9
A transfer material conveying means is provided, which also includes a conveyor belt 8 wound around the conveyor belt 6 . The conveyor belt 8 is rotated in the direction of the arrow.

For the conveyor belt 8, a material is selected that has little elongation and allows efficient transmission of the rotational control of the drive roller, and at the same time, it is desired that it has a structure that does not significantly affect the transfer corona flow associated with the transfer process. As such a conveyor belt 8, there is a polyurethane belt (for example, a commercially available polyurethane belt manufactured by Hokushin Kogyo Co., Ltd.),
The thickness of the belt is approximately 1100p, the rubber hardness is 97°D, and the tensile modulus is 16000Kg/cm''. In FIG. The transfer material 6 is fed onto the conveyor belt 8 via the conveyor belt 8 .

First, second, third and fourth image forming sections Pa, Pb, Pc
and Pd are photosensitive drums 1a, lb, l as image carriers.
primary chargers 15a, 15b on the left side of each of the photosensitive drums la, Lb, 1c and 1d;
, 15c and 15d are provided. In this embodiment, OPC photosensitive drums are used for the photosensitive drums 1a, 1b, lc and 1d, and chargers 15a, 15b, 15c and 15d are provided.
As a result, the surface potential of each is charged to approximately -600V. Developing units 3a, 3b, 3C and 3d are further provided on the upper right side of each of the photosensitive drums la, 1b, lc and 1d, and transfer chargers 4a, 4b, 4c and 3d are provided below each with a belt 8 in between. 4d is provided.

Above the photosensitive drums la, lb, lc, 1d,
Laser boom scanner 16a, 16b, 16c, 16
d are arranged respectively. These laser boom scanners 16a, 16b, 16c, 16d are semiconductor lasers,
Chargers 15a, 15b, 15c, and 15d are composed of a polygon mirror fθ lens, etc., and receive an input of an electrical digital image signal and emit a laser beam modulated in accordance with the signal.
and the developing devices 3a, 3b, 3c, and 3d.
A, 1b, lc, and 1d are scanned in the generatrix direction and exposed to light to form a latent image.

To explain in detail, the laser scanner 1 of the first image forming section Pa
6a forms a yellow component latent image on the photosensitive drum la by exposure based on pixel signals corresponding to the yellow component image of the color image. The laser scanner 16b of the second image forming section Pb forms a magenta component latent image on the photosensitive drum lb in the same manner. And a third image forming section Pc
The laser scanner 16c and the laser scanner 16d of the fourth image forming section Pd respectively form a cyan component latent image on the photosensitive drum lc and a black component latent image on the photosensitive drum ld.

The yellow component color latent image formed on the photosensitive drum la as described above is developed with a developer containing yellow toner in the developing device 3a, and the yellow toner image is transferred onto the transfer material 6 by the transfer charger 4a. It is now transcribed into . Similarly, the latent image of the magenta component color on the photosensitive drum lb is
A latent image of a cyan component color on the photosensitive drum lc is formed by a developer containing magenta toner in the developing device 3b, and a latent image of a black component color on the photosensitive drum ld is formed by a developer containing cyan toner in the developing device 3C. The magenta toner image, the cyan toner image, and the black toner image obtained by the development are sequentially transferred onto the transfer material 6 by the transfer chargers 4b and 4C14d, respectively. It looks like this.

In this embodiment, the above development is performed by reversal development using a two-component developer consisting of toner and carrier.
Each color toner is triboelectrically charged with negative polarity.

The paper feeding mechanism 13 includes a paper feeding guide 51 and a sensor 52. When the transfer material 6 is inserted into the paper feeding guide 51, the sensor 52 detects the tip of the transfer material 6, and the photosensitive drums la, lb are detected.
, lc, and ld, and at the same time drive the drive rollers 11, 12, and 96 to rotate the conveyor belt 8. Further, the transfer material 6 fed to the conveyor belt 8 receives corona discharge from the attraction chargers 59 and 62, and is reliably attracted to the surface of the conveyor belt 8. The polarities of the high voltages of the attraction chargers 59 and 62 are set to be opposite to each other, and the charger 62 has the same polarity as the transfer chargers 4a, 4b, and 4C14d.

The tip of the transfer material 6 is connected to each sensor Boa, 60b, 60c,
When the signal 60d is cut off, image formation on the rotating photosensitive drums la, lb, tc, and td is sequentially started based on the signal. Thus, as described above, a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are sequentially transferred and superimposed on the transfer material 6 to obtain a color image. When the transfer material 6 passes through the fourth image forming section Pd, the charge is removed from the transfer material 6 by a static eliminator 61 to which an AC voltage is applied, and the transfer material 6 is separated from the conveyor belt 8 .

Next, the transfer material 6 enters the fixing device 7 and after fixing the image,
The discharge port 14 is also discharged to the outside of the apparatus main body 10.

According to the present invention, a conductor plate is installed on a member close to the conveyance path of the transfer material 6 onto which the toner image has been transferred, in order to prevent the toner from scattering from the toner image on the transfer material 6. Ru. In this embodiment, the second, third, and fourth image forming sections P
Conductive plates 20b, 20c, and 20d are provided on the entire lower surface of the developing units 3b and 3C13d of the developing devices 3b, Pc, and Pd, and a conductive plate 21 is provided on the entire lower surface of the cleaning section 5d of the fourth image forming section Pd. These conductor plates 20b, 20c, 20d, and 21 are arranged close to and not in contact with the transfer material 6 on the belt 8, and are spaced from the transfer material 6 by approximately 4 mm. Note that the reason why the conductor plate 20b and the like are provided on the lower surface of the developing device 3b is to facilitate the stepwise installation.
b, etc. may be provided apart from the lower surface of the developing device 3b, etc.

A voltage having the same polarity as the friction charging polarity of the toner is applied to the conductive plates 20b, 20c, 20d, and 21 in order to electrically suppress scattering of the toner from the toner image on the transfer material 6. Since the potential of the toner is very high after the toner image is transferred onto the transfer material 6, the voltage to suppress the scattering of the toner is as follows.
It is preferable that the transfer material 6 passing through the conductor plates 20b, 20c, 20d, and 21 has a higher potential as the transfer of the toner image progresses, that is, the transfer material 6 with the yellow toner image transferred passes through it. The conductor plate 20c, through which the transfer material 6 with the magenta toner image transferred onto the yellow toner image passes, is better than the conductor plate 20b, and the transfer material 6 with the cyan toner image further transferred onto the magenta toner image passes through the conductor plate 20c. The conductor plate 20d through which the material 6 passes is also
It is preferable to apply a higher voltage to the conductor plate 21 through which the transfer material 6, which has further transferred the black toner image onto the cyan toner image, than d. Since it is charged, the first, second,
Third. DC -400V, -500V of the developing bias voltage applied to the sleeves (not shown) in the developing devices 3a, 3b, 3C13d of the fourth image forming sections Pa, Pb, Pc, Pd
The same voltages are applied to the conductor plates 20b, 20c, 20d, and 21 using V, -600V, and -700V, respectively.

Therefore, in the present invention, the transfer material 6 to which the yellow toner image has been transferred by the transfer charger 4a of the first image forming section Pa is transferred to the second image forming section Pa.
As shown in the figure, when the developing device 3b passes under the developing device 3b of the second image forming section Pb by being conveyed by the belt 8, the developing device 3
Since an electric field acts on the toner image on the transfer material 6 in a direction that suppresses the toner due to the voltage applied to the conductor plate 2ob on the lower surface of the yellow toner image, the toner from the yellow toner image does not scatter to the developing device 3b.Similarly, The transfer material 6 on which the magenta toner image has been transferred onto the yellow toner image by the transfer charger 4b of the second image forming section pb is transferred to the developing device 3 of the third image forming section Pc.
When passing under c, the toner from the magenta toner image does not scatter to the developing device 3C, and the transfer material 6 with the cyan toner image transferred onto the magenta toner image is transferred to the fourth image forming portion Pd. When passing under the developing device 3d, the toner from the cyan toner image does not scatter to the developing device 3d, and in the same way, the black toner image is transferred onto the cyan toner image at the fourth image forming section Pd. When the transfer material 6 passes below the cleaning section 5d of the image forming section Pd, the toner from the black toner image is removed from the cleaning section 5d.
There is no chance of splashing.

Incidentally, the image forming apparatus of this example was used with the various assumed values mentioned above in a low temperature, low humidity environment where toner scattering is likely to occur (1
Approximately 5,000 copies were made at 0° C. and 10% R) (), and the scattering of toner on the developing devices 3b, 3C53d and cleaning section 5d was investigated. Only a small amount of toner was attached to 20b, 20c, 20d, and 21, and there was almost no toner scattering. On the other hand, the conductor plate 20b,
When an image forming apparatus is used with a conventional configuration in which 20c, 20d, and 21 are not provided, the amount of toner deposited on the developing devices 3b, 3c, 3d and the lower part of the cleaning section 5d when approximately 5,000 copies are made is quite large. It was observed that a large amount of toner was scattered onto the developing device 3b and the like.

In the above embodiment, the conductive plates 2°b, 20c, and 2 are used as the conductive plates to which a voltage of the same polarity as the frictional charging polarity of the toner is applied.
0d and 21 are provided in the developing units 3b, 3C53d and cleaning section 5d, but the installation of such conductor plates is
Any member may be used as long as it is close to the conveyance path of the transfer material 6 to which the toner image has been transferred, for example, the first, second, . Third
Cleaning sections 5a, 5 of image forming sections Pa, Pb, Pc
By installing conductor plates on the cleaning parts 5a, 5b, and 5c, it is possible to similarly prevent toner from scattering from the toner image on the transfer material 6 to the cleaning parts 5a, 5b, and 5c.

FIG. 3 is a schematic configuration diagram showing another embodiment of the image forming apparatus of the present invention. This embodiment is applied to an image forming apparatus that includes one common image carrier for each color toner image of a multi-color image.

Since the basic configuration of this image forming apparatus is well known, a detailed explanation thereof will be omitted. CG 131, which has a transfer drum 32 below, and transfers a yellow component color latent image formed by dew drop onto a photoreceptor drum 30 which rotates in the direction of the arrow a, into a developing device 31 which rotates in the direction of the arrow. The yellow toner image is developed in the developing section A by the yellow component color developer 31a, and the resulting yellow toner image is transferred by the transfer charger 4 onto the transfer material 6 held on the transfer drum 32 rotating in the direction of arrow C. Transfer in part B. Similarly, exposure, development,
By repeating the transfer, a color image in which a magenta toner image, then a cyan toner image, and then a black toner image are superimposed on the yellow toner image is obtained on the transfer material 6.

Note that the developing device 31 includes a developing device 3 for yellow component color.
In addition to 1a, developing units 31b, 31c, and 31d for magenta, cyan, and black component colors are installed.

In this image forming apparatus, the drum 32 is placed on the conveyance path of the transfer material 6 held via the support belt 33 stretched on the outer circumferential surface of the transfer drum 32, that is, on a circular orbit around the outer circumference of the transfer drum 32.
A pair of left and right conductor plates 34 are installed concentrically. These conductive plates 34 are arranged close to the transfer material 6 with a gap of about 4 mm and are not in contact with the transfer material 6, and one of the conductor plates 34 extends from approximately directly below the transfer drum 32 to the transfer portion B of the upper part of the transfer drum 32. The other conductive plate 34 is connected to the transfer drum 3 from the paper feed guide 35 below the transfer drum 32.
It reaches the level of the transfer material separation claw 36 at the upper part of No. 3.

In this embodiment as well, the voltage applied to the conductor plate 34 is set to a higher potential as the transfer material 6 passing through the conductor plate 34 is at a stage where the transfer of the toner image is advanced. That is, as the yellow toner image, magenta toner image, cyan toner image, and black toner image are transferred onto the transfer material 6 in this order, a higher voltage is applied to the conductor plate 34.

Incidentally, when copying is performed using the image forming apparatus of this embodiment, as in the case of the image forming apparatus described with reference to FIG. -400V on 34, -500V after magenta toner image transfer, -5oov after cyan toner image transfer
After the black toner image was transferred, when a DC voltage of -700 V was sequentially switched and applied, only a small amount of toner adhered to the conductive plate 34, and similarly, toner scattering was almost completely prevented.

In the following embodiments, explanations have been given by taking a multi-color image forming apparatus as an example, but the present invention can also be applied to a single-color image forming apparatus, and the transfer material is placed on the conveyance path of the transfer material onto which the toner image has been transferred. By arranging the conductor plates close to each other in a non-contact manner and applying a voltage having the same polarity as the frictional polarity of the toner to the conductor plates, it is possible to prevent the toner from scattering from the toner image on the transfer material.

Since the image forming apparatus of the present invention is configured as described above, it is possible to prevent toner from scattering from the toner image transferred onto the transfer material to members close to the transfer material conveyance path before the toner image is unfixed. can be easily prevented. Therefore, it is possible to prevent the inside of the device from being stained and the transfer material to be stained due to scattered toner.

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

FIG. 2 is a partial diagram showing main parts of the image forming apparatus shown in FIG. 1. FIG.

FIG. 3 shows image formation according to the present invention? FIG. 3 is a schematic configuration diagram showing another embodiment in which

FIG. 4 is a schematic configuration diagram showing a conventional image forming apparatus.

1a, 1b, lc, ld, 30: photosensitive drum 3a,
3b, 3C13d, 31a, 31b, 3
1c, 31d: Developing devices 4a, 4b, 4c, 4d, 4: Transfer charger 6: Transfer material 8: Conveyor belts 20b, 20c, 20d, 21.34: Conductor plate 32: Transfer drum 33: Support belt

[Brief explanation of drawings]

No. figure Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1) Image formation in which a toner image formed on an image carrier by development with triboelectrically charged toner is transferred onto a conveyed transfer material to obtain an image on the transfer material. In the apparatus, a conductor plate is disposed close to the conveyance path of the transfer material onto which the toner image has been transferred without contacting the transfer material, and a voltage having the same polarity as the friction charging polarity of the toner is applied to the conductor plate. Features of the image forming device. 2) One image carrier is provided for each color toner image of a multi-color image, and the toner images of each color sequentially formed on each image carrier are sequentially transferred and superimposed onto the transfer material. , to obtain a multi-color image on the transfer material,
1. The voltage applied to the conductor plate is higher in potential as the transfer material passing through the conductor plate is at a stage where the transfer of the toner image of each color is advanced.
The image forming apparatus described above. 3) One image carrier is provided in common for each color toner image of a multi-color image, and the toner images of each color sequentially formed on the common image carrier are sequentially transferred and superimposed onto the transfer material. The voltage applied to the conductor plate is set such that the more the transfer material passes through the conductor plate, the more the toner images of the respective colors are transferred, the more the toner image of each color is transferred. The image forming apparatus according to claim 1, wherein the image forming apparatus has a high potential.