JPH07295371A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device capable of obtaining the output of a large-sized image without the unevenness of the density of an image in the longitudinal direction of a latent image carrier (photoreceptor drum). CONSTITUTION:In image forming device provided with a photoreceptor drum l and a developing device arranged to face it, the developing device has first and second developer containers 2a and 2b and they have first and second developing sleeves respectively. The lengths in the longitudinal direction of the first and second developing sleeves 3a and 3b are shorter than that of the photoreceptor drum 1, each of the first and second developing sleeves 3a and 3b is arranged so as to face the photoreceptor drum 1 and form an overlapped region C on the end parts and moreover, an electrode 15 controlling the quantity of the developer is provided on the downstream side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method such as an electronic copying apparatus and an information recording apparatus, and an apparatus therefor.

[0002]

2. Description of the Related Art Conventionally, a developing device using a magnetic developer has been widely used as a means for visualizing a latent image on a latent image carrier in an image forming apparatus such as an electronic copying apparatus or an information recording apparatus. .

Various constructions of a developing device using a magnetic developer have been proposed. As a typical example thereof, a non-magnetic cylinder (hereinafter referred to as "sleeve" as a developer supporting means in a developing container containing the developer is proposed. ) Is rotatably disposed, and a plurality of magnetic field generating means, that is, a magnet roller having magnets is fixedly disposed in this sleeve. Such a developing device mainly supplies the developer from the inside of the developing container onto the sleeve by the rotation of the sleeve, and also regulates the developer so as to convey the developer by a constant amount (hereinafter, referred to as “developing member”). A blade), a magnet (hereinafter referred to as a “cut pole”) that is substantially opposed to the blade, and a regulated developer that is substantially opposed to an image carrier (hereinafter referred to as a “photosensitive drum”) carrying a latent image. In order to transport it to the developed position,
A magnet (hereinafter referred to as "developing magnetic pole") is disposed at a developing position in the sleeve substantially facing the photosensitive drum.

Examples of the magnetic developer used for these include a one-component magnetic developer composed of magnetic toner particles, a non-magnetic toner particle or a two-component developer composed of magnetic toner particles and a magnetic carrier.

With such a structure, it is possible to easily charge the toner particles by applying the magnetic force to both the developers, and it is possible to obtain a good image.

[0006]

However, in the construction of the developing device having the magnet roller in the sleeve as described above, a large-sized image (image size such as A1 or A0) is formed.
If a sleeve that is long in the longitudinal direction of the photosensitive drum is used in order to cope with this, uneven density of images may occur in the longitudinal direction of the photosensitive drum. There was a risk of contact and damage.

As shown in FIG. 6, this problem is caused by the fact that the longer the sleeve 101 and the magnet roller 102 are in the longitudinal direction of the photosensitive drum, the more the magnet roller 102 bends at its ends.

As a cause of the bending of the magnet roller 102, as shown in FIG. 7, in the portion where the magnetic force is strong, such as the above-mentioned cut pole 103, the magnetic developer 104 is formed.
The magnetic material such as the magnetic blade 105 and the magnetic blade 105
The force F that strongly attracts 2 and the like can be mentioned.

On the other hand, the image density in the development is as shown in FIG.
The amount of 06, the cutting d1 of the sleeve surface and the magnet roller 102
(Magnetic force depends on distance), sleeve and photosensitive drum 107
Is controlled by a delicate balance such as the distance d2 (the developing electric field depends on the distance).

As described above, this balance is distorted due to the bending of the magnet roller 102, resulting in uneven density of image density.

Therefore, an object of the present invention is to provide an image forming apparatus capable of solving the above-mentioned problems of the prior art and obtaining excellent image formation.

Another object of the present invention is to obtain a large format image without unevenness of image density in the longitudinal direction of the latent image carrier.

[0013]

In order to achieve the above-mentioned object, the present invention comprises a latent image carrier and a developer carrying means arranged so as to face the latent image carrier. In the image forming apparatus, wherein the developer carrying means is provided with a magnetic field generating means for supplying a developer therein, and the latent image on the latent image carrier is visualized by the developer, the developer carrying means comprises:
The developer carrier comprises a plurality of developer carriers, each developer carrier having a length in the longitudinal direction shorter than the length of the latent image carrier in the longitudinal direction, and each developer carrier along the longitudinal direction of the latent image carrier. It is arranged.

Further, as a preferred example, the plurality of developer carrying members are arranged so as to have respective overlapping regions for the same latent image on the latent image carrying member.

Further, as a preferred example, the image forming apparatus has an electrode facing the latent image carrier on the downstream side of the plurality of developer carriers, and applies an alternating voltage to the electrodes. .

Further, as a preferred example, the developer carrying member has a rotatable non-magnetic cylinder and a magnet roller fixedly arranged in the non-magnetic cylinder and for generating a magnetic field.

[0017]

According to the image forming apparatus of the present invention, as shown in the conventional example, when a long developer carrying member corresponding to a large-sized image is used, problems such as unevenness in image density and damage occur. In the present invention, development is carried out by using a plurality of developer carriers each having a length shorter than the length of the latent image carrier. By using such a short developer carrier, it is possible to suppress the deflection of the internal magnetic field generator, for example, the magnet roller, and the magnetic field generator and the developer carrier do not come into contact with each other even when used for a long time. .

Further, by the image forming apparatus of the present invention, the latent image is visualized without causing unevenness in the density of the image in the longitudinal direction of the latent image carrier (for example, shown in FIG. 3 of the embodiment). . That is, since a plurality of developer carrying members are arranged along the longitudinal direction of the latent image carrying member and each has an overlapping region for the same latent image, each developer carrying member is There are developed regions A and B, and a developed region C in the overlapping region of both developer carrying members. In this case, the amount of the developer to be developed differs between the area A and the area B due to the dark decay (potential drop) of the latent image carrier.
Further, in the overlappingly developed region C, the development is performed darker than the other regions A and B. As described above, in each of the areas A, B, and C having different amounts of the developer, by applying an alternating voltage to the latent image carrier and the electrode (claim 3),
An alternating electric field formed between the latent image carrier and the electrodes acts, and thus the excessively developed developer is collected by the electrodes.

As a result, a proper amount of the developer to be developed is developed on the latent image carrier, and an image having no unevenness in light and shade can be formed in the longitudinal direction thereof.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a developing device applied to an image forming apparatus of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a diagram showing the construction of a developing device using the two-component developer of the first embodiment.

As shown in FIG. 1, a developing device used in an electronic copying apparatus for developing the latent image on the photosensitive drum 1 includes a first developer container 2a, a second developer container 2b, and an electrode. It is equipped with 15. First developer container 2a and second
The developer container 2b is arranged to face the same latent image surface in the longitudinal direction of the photosensitive drum 1 so as to form an area C for overlapping development. It has developing sleeves 3a and 3b. The length of the first and second developing sleeves 3a and 3b in the longitudinal direction is shorter than the length of the photosensitive drum 1 in the longitudinal direction.

The details of the developer container will be described below with reference to FIG.

As shown in FIG. 2, the interiors of the first developer container 2a and the second developer container 2b are partitioned by a partition wall 5 into a developing chamber (first chamber) S1 and an agitating (second chamber) S2. ,
A toner storage chamber S3 is formed above the stirring chamber S2 with an inclined partition wall 6 interposed therebetween, and a replenishment toner (non-magnetic toner) 81 is stored in the toner storage chamber S3. The partition wall 6 is provided with a replenishment port 6a, and the replenishment toner 8 in an amount commensurate with the amount of toner consumed through the replenishment port 6a.
1 drops into the stirring chamber S2 and is replenished.

On the other hand, the developer 8 is contained in the developing chamber S1 and the stirring chamber S2. The developer 8 is a two-component developer including a non-magnetic toner 81 and magnetic particles (carriers) 82. The non-magnetic toner 81 has a volume average particle diameter of 10 μm or less. The magnetic particles 82 are composed of resin-coated ferrite particles (maximum magnetization 60 emu / g), have a weight average particle diameter of 30 to 80 μm, and have a resistance value of 10 ⁷ Ωcm or more. The magnetic permeability of the magnetic particles 82 is about 5.0. The weight average particle diameter of the magnetic particles 82 is preferably 40 to 70 μm,
It is preferable that the resistance value is 10 ⁸ Ωcm or more.

An opening 14 is provided in a portion of the developer container 2a, 2b near the photosensitive drum 1.
A developing sleeve 3 made of a non-magnetic material is rotatably incorporated in the reference numeral 4. The developing sleeve 3 is positioned so as to be spaced from the photosensitive drum 1 by 800 μm so as to project from the opening 14 to the outside. The outer diameter of the developing sleeve 3 is 32 mm, and the peripheral speed when rotated is 280 mm / s. The developing sleeve 3
Since the rotating mechanism is known, its description is omitted here.

Inside the developing sleeve 3, a magnet roller 13 as a magnetic field generating means is fixed. Magnet roller 1
3 has a cylindrical shape arranged concentrically with the developing sleeve 3, and a slight gap 2 mm is uniformly formed in the circumferential direction with respect to the developing sleeve 3. The gap is not limited to "2 mm", but may be any distance as long as the magnet roller 13 and the developing sleeve 3 do not come into contact with each other.

The magnet roller 13 has a developing magnetic pole N ₁ , a magnetic pole S ₁ located downstream thereof, and magnetic poles N ₂ , S ₂ and S ₃ for carrying the developer 8. The developing magnetic pole N ₁ of the magnet roller 13 is arranged inside the developing sleeve 3 so as to face the photosensitive drum 1. The developing magnetic pole N ₁ is
A magnetic field is formed in the vicinity of the developing section between the developing sleeve 3 and the photosensitive drum 1, and this magnetic field forms a magnetic brush.

Above the developing sleeve 3, the developer container 2 is provided.
A blade 4 fixed to a and 2b is arranged at a predetermined distance from the developing sleeve 3. The distance between the developing sleeve 3 and the blade 4 is 500 μm. Blade 4
Is made of a non-magnetic material such as aluminum or SUS316, and regulates the layer thickness of the developer 8 on the developing sleeve 3.

A conveying screw 9 is housed in the developing chamber S1. The conveying screw 9 is rotated in the direction indicated by the arrow A in the figure, and the rotational driving of the conveying screw 9 conveys the developer 8 in the developing chamber S1 in the longitudinal direction of the developing sleeve 3.

A conveying screw 10 is housed in the stirring chamber S2, and the conveying screw 10 is rotationally driven in a direction indicated by an arrow B in the figure, so that the developer 8 in the stirring chamber S2 extends in the longitudinal direction of the developing sleeve 3. It is conveyed in the direction.

A conveying screw 11 is housed in the storage chamber S3. The conveying screw 11 conveys the toner 81 along the longitudinal direction of the developing sleeve 3 by its rotation, and the toner 81 freely falls from the replenishing port 6a into the stirring chamber S2.

An electrode 15 is provided further downstream of the first developer container 2a and the second developer container 2b. The electrode 15 is a cylindrical fixed electrode extending in the longitudinal direction of the developing sleeve 3. The diameter dimension of the electrode is 15 mm. The electrode 15 is arranged so that the distance between the outer peripheral surface thereof and the outer peripheral surface of the photosensitive drum 1 is 300 μm.

An alternating voltage from a power source (not shown) is applied to the electrode 15. The power supply section applies an alternating voltage to the electrode 15 and also generates an alternating voltage applied to the developing sleeve 3. An alternating voltage obtained by superimposing a DC voltage of −350 V on an AC voltage having a frequency of 2000 Hz and a voltage of 2000 Vpp is applied to the electrode 15.

On the other hand, a dark potential of -6 is applied to the developing sleeve 3.
50V, bright potential -200V, frequency 2000H
An alternating voltage in which a DC voltage of −350 V is superimposed on an AC voltage of z and a voltage of 2000 Vpp is applied.

Next, the operation of this embodiment will be described.

When developing the latent image on the photosensitive drum 1, the photosensitive drum 1, the first developing sleeve 3a and the second developing sleeve 3b are rotated. The peripheral speed of the photosensitive drum 1 is 160
mm / s, and the peripheral speeds of the first developing sleeve 3a and the second developing sleeve 3b are 280 mm / s.

The first developing sleeve 3a and the second developing sleeve 3b carry the developer 8 at a position near the magnetic pole N ₂ .
With the rotation of the developing sleeve 3a (3b), the developer 8 is conveyed toward the developing section. When the developer 8 reaches the vicinity of the developing portion, the magnetic particles 82 of the developer 8 rise from the developing sleeve 3a (3b) while being connected by the magnetic force of the magnetic pole N ₁ , and a magnetic brush of the developer 8 is formed. The tip of the magnetic brush rubs against the surface of the photosensitive drum 1, and the developing sleeve 3a (3
Due to the alternating voltage between b) and the photosensitive drum 1, the toner 81 of the magnetic brush is attached to the latent image portion of the photosensitive drum 1.

However, the image density formed by the first developing sleeve 3a and the second developing sleeve 3b is developed by the first sleeve 3a shown in FIG. 3 due to characteristics such as dark decay (potential drop) of the photosensitive drum 1. There is a difference between the area A and the area B developed by the second sleeve 3b. Further, in the area C where the first sleeve 3a and the second sleeve 3b are overlapped with each other, the image density is increased because the image is excessively developed. As described above, the areas A, B, and C have different amounts of the developer.

Therefore, when the portion where the visible image having the density difference is formed approaches the electrode 15 in each portion in the longitudinal direction, the toner 81 of the visible image receives the electric field due to the alternating voltage of the electrode 15. Since the toner 81 is reciprocated between the electrode 15 and the photosensitive drum 1, a proper amount of the toner 81 is attached to each target portion of the visible image, and the excess toner is removed by the electrode 15. As a result, it is possible to obtain a uniform and good image without unevenness in light and shade.

In this embodiment, a cylindrical fixed electrode is used as the electrode 15, but as shown in FIG.
A better image can be obtained by peeling off the rotating electrode 25 that rotates in the same direction as the rotation direction of the photosensitive drum and the developer collected and adhered to the electrode as a surplus developer using, for example, a scraper 26. . still,
The stripped developer can be reused.

Further, the same effect can be obtained with respect to either a digital latent image formed by a laser beam or an analog latent image formed by a halogen lamp, a fluorescent lamp or the like.

In the present embodiment, an example using a photosensitive drum is shown, but a sheet-like one such as a photosensitive belt or a plate-like one such as a photosensitive plate does not impair the effects of the present invention. Needless to say.

In this embodiment, an example in which non-magnetic toner particles and magnetic particles (carriers) are used as the magnetic developer has been described, but the present invention is not limited to this. For example, magnetic toner particles and magnetic particles may be used. Particle (carrier)
The same effect can be obtained by using a two-component developer or a one-component magnetic toner.

That is, the present invention is effective for a developing system in which a magnetic developer is developed using a magnet roller.

(Second Embodiment) Although the two developer containers 2a and 2b and the two sleeves 3a and 3b are used in the above-described first embodiment, the present invention is not limited to this. For example, the effect of the present invention can be obtained even if the developing container is provided with three or more, or if the developing container is provided with three or more sleeves.

Further, as shown in FIG. 5, if one developer container 2 is provided with two or more sleeves 3a and 3b, the effect of the present invention can be obtained and at the same time, space can be saved. You can

As described above, according to the developing device of this embodiment, a large-sized image (A0, A1, etc.) can be formed as a uniform and good image without unevenness in the longitudinal direction and without roughness. Obtainable.

[0049]

As described above, according to the present invention,
Since a plurality of developer carrying members are provided and these are arranged along the longitudinal direction of the latent image carrying member, the magnetic field generating means in each developer carrying member is also divided into a plurality of parts. Alternatively, the supply is also preferably performed, it is possible to eliminate the unevenness of the lightness and darkness of the entire image, and it is possible to perform highly accurate image formation.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a developing device of an electronic copying apparatus according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing the configuration of a two-component developer container used in the first embodiment of the present invention.

FIG. 3 is a diagram showing changes in an image due to development in the first embodiment of the present invention.

FIG. 4 is a diagram showing another configuration example of the electrode in the first embodiment of the present invention.

FIG. 5 is a configuration diagram showing a developing device according to a second embodiment of the present invention in which a plurality of sleeves are provided in one developer container.

FIG. 6 is a diagram showing a sleeve and a magnet roller in a conventional developing device when they are elongated in a longitudinal direction.

FIG. 7 is a cross-sectional view of a developer carrier in a conventional developing device.

FIG. 8 is a cross-sectional view showing a relationship between a latent image carrier and a developing carrier in a developing portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2a, 2b 1st, 2nd developer container 3a, 3b 1st, 2nd developing sleeve 4 Blade 15 Electrode

Claims (4)

[Claims] 1. A latent image carrier, and a developer carrying unit arranged so as to face the latent image carrier. The developer carrying unit includes a magnetic field generating unit for supplying a developer. In an image forming apparatus which is provided inside and visualizes a latent image on the latent image carrier by the developer, the developer carrying means comprises a plurality of developer carrying bodies,
Each developer carrier has a length in the longitudinal direction shorter than the length in the longitudinal direction of the latent image carrier and is arranged along the longitudinal direction of the latent image carrier. Image forming apparatus. 2. The developer carrier according to claim 1, wherein the plurality of developer carrying members are arranged so as to have respective overlapping regions with respect to the same latent image on the latent image carrying member. Image forming apparatus. 3. The image forming apparatus according to claim 2, further comprising an electrode facing the latent image carrier on the downstream side of the plurality of developer carriers, and applying an alternating voltage to the electrodes. An image forming apparatus characterized by. 4. The developer carrier according to claim 1, wherein the developer carrier is disposed in a rotatable non-magnetic cylinder and fixed in the non-magnetic cylinder to generate a magnetic field. An image forming apparatus having a magnet roller.