JP2002318491A - Two-component developer - Google Patents

Abstract

(57) [Problem] To improve the mixing of a toner and a developer at the time of toner replenishment and to properly charge the toner replenished to a developing unit even in a miniaturized developing device having a small developer capacity. It is another object of the present invention to provide a two-component developing device capable of outputting an image free from background contamination. A notch portion (21a) for forming a stagnant portion of a developer is provided in a part of a right conveying screw (21) located on a toner supply port side. The magnetic body 28a is arranged in a part of the notch 21a. Due to the magnetic material 28a, ears due to the carrier are generated in this portion. The replenished toner sneaks into the developer at the cutout portion and passes through the ears of the carrier, so that the toner is more easily charged. By conveying the sufficiently charged toner to the developing roller side, a good image without background contamination can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-component developing device mounted on an image forming apparatus such as a copying machine, a laser printer, and a facsimile, and more particularly, to sufficiently charge toner in a small developing device having a small developing capacity. The present invention relates to a two-component developing device that prevents generation of background fouling.

[0002]

2. Description of the Related Art Conventionally, an image output using an electrophotographic image forming apparatus includes a background portion which should not be developed,
There is a problem that the toner is developed in the white portion.
This is because the replenished toner is not sufficiently charged in the developing device, but is weakly charged and / or reversely charged, and these toners are developed into a background portion or a white portion during development.

A specific description will be given with reference to FIG. FIG.
(A) is a perspective view of a two-component developing device, and (b) is an external view. The toner replenished from the toner replenishing port 24 shown in FIG. The replenished toner is hardly charged and has a large difference in charge amount from the toner already present in the developer, so that the replenished toner is not mixed into the developer and slips on the surface of the developer. Easy to be transported. The replenishment toner conveyed from the right conveyance screw 21 so as to slide on the developer surface as described above is left as it is on the left conveyance screw 22.
When the toner is transferred to the printer, the supply toner is insufficiently charged, which causes soiling of the background.

Therefore, in order to prevent such soiling,
Various proposals have been made in the conventional electrophotographic technology.
An example is shown below. FIG. 3 is a sectional view of the right transport screw 21. A cut-out portion 21a is provided in a part of the right conveying screw 21 to form a stagnant portion of the developer. The stagnant portion of the developer makes it easy for the replenishment toner to be taken into the developer, and the replenishment toner is sufficiently charged.

In addition, as in the developing device disclosed in Japanese Patent Application Laid-Open No. 2000-19821, the agitation and conveyance of toner by the agitating screw on the toner supply side and the agitating screw on the developing sleeve are improved to improve the developing device. There have been proposals to improve the agitation of the replenished toner supplied to the toner.

On the other hand, in recent years, the size of the image forming apparatus has been required to be reduced in size, and accordingly, the built-in components in the apparatus have also been reduced in size. When a certain amount of toner is replenished to a small amount of developer in a miniaturized developing device, the replenished toner cannot be charged sufficiently as compared with a large developing device. In addition, the problem that weakly charged and / or reversely charged toner causes background fouling has become remarkable.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention has been made to improve the mixing of toner and developer at the time of toner replenishment even in a downsized developing device having a small developer capacity. It is an object of the present invention to provide a two-component developing device capable of outputting an image free from background stain by appropriately charging toner supplied to a unit.

[0008]

In order to solve the above-mentioned problems, the invention according to claim 1 is provided with a structure in which a developer composed of a carrier and a toner is circulated in a developing roller axial direction by a plurality of conveying members. In this two-component developing device, a partition plate with a cutout at the lower portion is provided at a developer transfer portion from the conveying member on the toner supply port side to the conveying member on the developing roller side. According to a second aspect of the present invention, in the two-component developing device according to the first aspect, the shape of the notch portion at the lower portion of the partition plate becomes wider as approaching the developer transfer portion. Developing device.

The invention described in claim 3 is the first or second invention.
In the two-component developing device described in (1), a two-component developing device is provided in which a magnetic material is arranged on a part of a conveying member that is not directly opposed to the developing roller downstream of the toner supply port in the toner conveying direction.
According to a fourth aspect of the present invention, there is provided the two-component developing device according to the third aspect, further comprising: a two-component developing device having a magnetic material at a position on the case of the developing device facing the magnetic material disposed on the transport member. I do. The invention according to claim 5 is the two-component developer according to claim 4, wherein the magnetic two-component developer is a developer having a developer capacity of 300 g or less.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG.
FIG. 3 is a cross-sectional view illustrating a configuration of a component developing device. FIG.
2A is a perspective view of a two-component developing device, and FIG. 2B is an external view. Toner conveyed from a toner bottle (not shown) is fed from the right
1 replenished. The replenishment toner is conveyed to the front side in the figure while being stirred with the developer by the right conveyance screw 21, and is transferred to the left conveyance screw 22 on the developing roller 20 side from the front side in the figure. The left transport screw 22 supplies the developer to the opposing developing roller 20 while transporting the developer to the back side in the drawing. The amount of the developer on the developing roller 20 is regulated by the doctor blade 28 and is conveyed to the developing nip between the developer and the photoreceptor 10. Left transport screw 2
The developer conveyed to the rear side in the figure by 2 is transferred again to the right conveying screw 21 on the rear side in the figure, and thus the developer circulates. Note that a partition plate 23 is provided between the right transport screw 21 and the left transport screw 22 so that the developer is not mixed on the way. Further, in the figure, two transport screws as the developer transport member are used, but the invention is not limited to this, and a configuration may be employed in which a plurality of transport members are further provided.

In the developing device of the present invention, the toner supplied to the right transport screw 21 is not mixed well with the developer during the transport, and the right transport screw 21 is connected to the left transport screw 21 in order to prevent the toner from being insufficiently charged. The partition plate 23 located between the conveying screws 22 has the following shape. FIG.
It is a figure which shows the 1st shape of a partition plate. Conventionally, the partition plate 23 has a shape in which the whole is cut out at the developer transfer portion. However, in the developing device of the present invention, only the lower portion is cut out. With such a configuration, it is possible to transfer the replenished toner from the right transport screw 21 to the left transport screw 22 in a state where the replenishment toner has surely entered the developer.

Further, in the configuration of the two-axis stirring type developing device as shown in FIG. 1, a deviation tends to occur in the toner density between the near side and the far side of the developing device in FIG. Especially when replenishing toner,
On the front side in which the developer replenished with toner from the back side of the drawing is transferred to the left conveying screw 22 on the developing roller 2 side, the toner concentration tends to increase, and such developer is supplied to the developing roller 2. This causes soiling. Then, the shape of the notch below the partition plate 23 is as follows. FIG. 5 is a diagram illustrating a second shape of the partition plate. As shown in FIG. 5, the shape of the cutout portion at the lower part of the partition plate 23 becomes wider as approaching the developer transfer portion. With such a configuration, the toner replenished on the front side of the drawing does not concentrate, the unevenness of the toner density can be eliminated, and the background stain can be prevented.

The right conveying screw 21 shown above is used.
Is a notch 2 in a part of the screw as shown in FIG.
1a may be provided. By providing such a notch 21a, a developer stagnation portion is formed, and an effect of making the replenishment toner sneak into the developer can be obtained.

In the developing device of the present invention, in order to sufficiently charge the replenished toner, the configurations of the transport screw and the developing device case are as follows. FIG.
FIG. 3 is a cross-sectional view illustrating a configuration of a right transport screw. FIG.
The magnetic body 29a is arranged in a part of the notch 21a of the right transport screw 21 shown in FIG. Due to the magnetic material 29a, ears due to the carrier are generated in this portion. The replenished toner sneaks into the developer at the cutout portion and passes through the ears of the carrier, so that the toner is more easily charged.

FIG. 7 is a view showing the structure of the transport screw and the developing device case. FIG. 7A is a perspective view of the developing device.
FIG. 7B is an external view. A magnetic material 29a similar to that shown in FIG. 6 is disposed on the right conveying screw 21, and a fixed magnetic material 29b is also disposed at a position facing the magnetic material 29a of the developing device case 27. With such a configuration, the toner is conveyed while rubbing in the ears of the carrier, so that the toner is more easily charged.

The following are test examples suitable for explaining the present invention. (Test Example 1) An example using a developing device provided with a partition plate with a cutout at the lower portion shown in FIG. 4 is referred to as a first embodiment, and the shape of the cutout portion shown in FIG. In Example 2, an example in which a developing device provided with a partition plate having a configuration that became wider as approaching was used was used, and the amount of developer was changed to evaluate background contamination in an output image at the time of toner supply. Further, as Comparative Example 1, the same evaluation was performed using a developing device having a partition plate with both ends cut out. Table 1 shows the results.

[0017]

[Table 1]

As shown in Table 1, the evaluation of the background stain was carried out in two regions of a troubled end portion to a width of 30 mm and a width of 30 mm to 100 mm. ○ is a good image without background stains, Δ is an image with light background stains, and X is an image with noticeable background stains. 400 g of the developer amount of Comparative Example 1 and 35
At the time of toner replenishment, the developer containing the replenished toner shows that the developer containing the replenished toner has a poorer result than the area having a width of 30 mm to 100 mm in the evaluation result of 0 g. It can be seen that it is easy to occur from the front side supplied to the developing roller. In Comparative Example 1,
Irrespective of the amount of the developer, background stains in the region from the front end to the width of 30 mm were remarkable. The result is that the replenished toner is not sufficiently taken into the developer.

On the other hand, in Example 1 according to the configuration of the partition plate of the present invention, up to 300 g of the developer amount, and in Example 2, up to 250 g of the developer amount, a good image without background contamination was obtained. As a result of improving the shape of the partition plate, the replenishment toner and the developer are mixed well, and a uniform toner concentration is obtained. Further, as the amount of the developer is smaller, the background stain during toner replenishment is more likely to occur. However, by using the developing device of the present invention, the level of the background stain is particularly large even with a small amount of developer of 300 g or less. It can be seen that it has been improved.

(Test Example 2) An example in which a developing device provided with a magnetic material in the right transport screw shown in FIG. 6 is used in Example 3, and a magnetic material is provided in the developing device case together with the right transport screw shown in FIG. Example 4 using a developing device provided with a developing device was used as an example 4, and the amount of developer was changed to evaluate background contamination in an output image at the time of toner supply. The same evaluation was performed using the developing device of Comparative Example 1 as in Test Example 1 and the developing device of Comparative Example 1 in which a notch was provided in the right transport screw of Comparative Example 1. Table 2 shows the results.

[0021]

[Table 2]

The evaluation results are indicated by ○, Δ, and × as in Table 1. In Comparative Example 2 using a developing device having a notch in the right transport screw, an improvement effect was observed at a developer amount of 350 g as compared with Comparative Example 1. The image was conspicuously stained.
On the other hand, in Embodiments 3 and 4 in which the magnetic body of the present invention is provided, background dirt is greatly reduced. By the right conveying screw or the magnetic material provided in the developing device case,
This is a result of the replenishment toner being sufficiently charged during conveyance. In particular, in the fourth embodiment in which the magnetic material is also provided in the developing device case together with the right conveying screw, even if the developer amount is as small as 200 g, the toner in the developer is uniformly charged and appropriately charged. As a result, a good image free from background contamination could be obtained. This is a result that can sufficiently cope with downsizing of the developing device.

[0023]

As described above, according to the present invention, a partition plate having a notched lower portion is provided at a developer transfer portion from a toner supply port side conveying member to a developing roller side conveying member. By adopting a configuration in which a magnetic material is arranged in a part of the transport member on the supply port side and the opposite developing device case,
Even in a miniaturized developing device with a small developer capacity, the mixture of toner and developer at the time of toner replenishment is improved and the toner concentration is made uniform. Can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a two-component developing device to which the present invention is applied.

FIGS. 2A and 2B are diagrams illustrating a configuration of a two-component developing device, wherein FIG. 2A is a perspective view and FIG.

FIG. 3 is a sectional view of a right conveying screw.

FIG. 4 is a view showing a first shape of a partition plate.

FIG. 5 is a view showing a second shape of the partition plate.

FIG. 6 is a cross-sectional view illustrating a configuration of a right transport screw.

FIGS. 7A and 7B are diagrams showing a configuration of a transport screw and a developing device case, wherein FIG. 7A is a perspective view of the developing device, and FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoreceptor unit 10 photoreceptor 2 developing unit 20 developing roller 21 right transport screw 21a notch 22 left transport screw 23, 23a, 23b partition plate 24 toner supply port 25 toner density sensor 26 developer cartridge 27 developer case 28 doctor Blade 29a, 29b Magnetic material

Claims (5)

[Claims] In a two-component developing device having a configuration in which a developer composed of a carrier and toner is circulated in a developing roller axial direction by a plurality of conveying members, a conveying member on a toner supply port side to a conveying member on a developing roller side. 2. A two-component developing device, wherein a partition plate having a cut-out lower portion is arranged in the developer transfer section. 2. The two-component developing device according to claim 1, wherein a shape of a cutout portion at a lower portion of the partition plate becomes wider as approaching a developer transfer portion. Component developer. 3. The two-component developing device according to claim 1, wherein a magnetic material is disposed on a part of the conveying member that is not directly opposed to the developing roller downstream of the toner supply port in the toner conveying direction. Characteristic two-component developing device. 4. The two-component developing device according to claim 3, further comprising a magnetic material on a case of the developing device at a position facing the magnetic material disposed on the transport member. . 5. The two-component developing device according to claim 4, wherein said two-component developing device is a developing device having a developer capacity of 300 g or less.