JPH0511615A - Developing device - Google Patents

Abstract

PURPOSE:To form a uniform developer layer on a developer carrier with high image density and to obtain an even image by maintaining an agitating member of a magnetic material of a cylindrical shape in contact with the developer carrier surface by magnetic force. CONSTITUTION:Toner T inside a developer container T is carried in a developing sleeve (developer carrier) 4 by magnetic force of the magnetic roll 3 covering its interior, and the toner T is carried to a developing part where a photosensitive drum 10 and the developing sleeve 4 are faced by having the sleeve rotated. In this case, the cylindrical shaped agitating member 1 of the magnetic material is brought into contact with the developing sleeve 4 by the magnetic force of the magnetic roll 3, and a guide member 11 is provided on a side of a developer container T so that a constant position is maintained. Thus, by providing the agitating member 1, the toner in the vicinity of the developing sleeve 4 is agitated, the circulation of the toner is promoted, and an even smoother toner layer is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device applied to develop an electrostatic latent image formed on an image carrier in an image forming apparatus such as an electrophotographic apparatus.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic apparatus, an electrostatic latent image formed on an image carrier is developed by a developing device to be visualized as a toner image.

As a developing method in such a developing device,
In Japanese Patent Laid-Open No. 54-43036, a magnetic toner is used as a one-component developer, a very thin toner is applied on a developing sleeve, and the toner is triboelectrically charged. A method has been proposed in which under the action of a magnetic field, the electrostatic latent image on the image bearing member is brought very close to the electrostatic latent image and opposed to the electrostatic latent image without making contact with the electrostatic latent image.

In this method, the toner is applied very thinly on the developing sleeve to increase the chances of contact between the developing sleeve and the toner, enabling sufficient triboelectrification of the toner, and the toner being magnetically applied to the developing sleeve. By supporting the top of the toner and moving the magnet and the toner relative to each other, the agglomeration of the toner particles is released, the toner is sufficiently rubbed with the developing sleeve, and the toner is supported by the magnetic force. By developing the electrostatic latent image so that it is opposed to the electrostatic latent image without being in contact with the electrostatic latent image, an excellent image can be obtained by preventing fog.

Further, as a developer regulating method, a developer regulating member made of an elastic member such as urethane rubber is brought into contact with the developing sleeve, so that the developing sleeve and the developer regulating member come into contact with each other (nip portion). A method of applying toner in a thin layer on a developing sleeve has been proposed. In this method, since the toner is positively charged at the contact portion of the elastic blade with the developing sleeve, there is an advantage that the image density is increased and a much better image can be obtained.

[0006]

However, the performance of the above conventional method is greatly affected by the temperature and humidity conditions or the surface properties of the developer regulating member and the developing sleeve. For example, when the fluidity of the toner is lowered at high temperature or high humidity, the aggregation of the toner cannot be sufficiently released by the magnetic force, resulting in a decrease in image quality and image density. .

In any of the developing methods using a one-component developer, it is necessary to form a relatively thin and uniform toner layer on the developing sleeve. However, the formation of such a toner layer depends on environmental conditions and physical properties of the toner. , A uniform toner layer cannot be obtained depending on the physical properties of the developing sleeve surface, etc.
Since unevenness may occur, especially in the initial stage of durability, the charged state of the toner, the circulation of the toner in the vicinity of the developing sleeve in the container, and the packing state may become unstable, resulting in uneven toner layer conveyed to the developing area. Therefore, there is a problem in that density unevenness occurs in the image.

Further, in the developing device in which the elastic member is brought into contact with the developing sleeve to regulate the toner layer, the toner is positively charged at the contact portion to enhance the developability of the toner, so that it is apparent. Unevenness should be improved, but there was a problem that the effect was not sufficient in practice.

The present invention is intended to solve the above problems. That is, it is an object of the present invention to provide a developing device capable of forming a uniform developer layer on a developer carrying member and having a high image density and capable of obtaining an image without unevenness. Is.

[0010]

In order to achieve the above object, the present invention provides a developer carrier having a magnet for carrying a magnetic developer, and a layer thickness of the developer carried to a developing area. In a developing device having a regulating member for regulating the pressure, a cylindrical stirring member made of a magnetic material was held in contact with the surface of the developer carrying member by magnetic force, and disposed in the developing container.

[0011]

According to the present invention, a cylindrical stirring member made of a magnetic material is brought into contact with a developer carrier having a built-in magnet by a magnetic force to keep a constant contact position with the developer carrier, and the magnet and the developer. When the carrier is relatively rotated, the agitating member agitates the developer in the vicinity of the developer carrier to assist the circulation of the developer and to uniformly disperse the developer on the developer carrier. By application, a uniform developer layer can be formed on the developer carrying member.

[0012]

FIG. 1 shows the first embodiment of the present invention.
This embodiment shows a developing device used in a laser beam printer using the reversal developing method.

In FIG. 1, 1 is a stirring member, 3 is a magnet roll, 4 is a developing sleeve, 5 is a toner layer thickness regulating member, 6 is a bias power source, 7 is a developing container, and 10 is an electrostatic latent image. It is an electrophotographic photosensitive drum.

That is, the photosensitive drum 10 is uniformly charged to a negative potential V _d , for example, V _d of −650 V by a primary charger (not shown), and then exposed to a laser beam or the like (not shown). And exposed to form a negative electrostatic latent image having a V _e of −100 V, for example.

As shown in FIG. 1, the present developing device includes a developing sleeve 4 disposed opposite to the photosensitive drum 10 in a developing container 7 containing a negatively charging high resistance magnetic toner T of a one-component developer. Is equipped with.

The developing sleeve 4 is made of a non-magnetic conductive material such as aluminum, and its surface is roughened by sandblasting or the like. The developing sleeve 4 carries the toner T in the developing container 7 by the magnetic force of the magnet roll 3 contained therein, rotates in the direction of arrow a, and develops the toner T so that the photosensitive drum 10 and the developing sleeve 4 face each other. To the department.

A toner layer thickness regulating member 5 made of an elastic material such as urethane rubber is in contact with the developing sleeve 4, and the toner T carried on the developing sleeve 4 is regulated by the toner layer thickness regulating member 5 so that the developing section is exposed to light. A layer of toner T, which is thinner than the minimum gap between the drum 10 and the developing sleeve 4, is formed on the developing sleeve 4. The toner layer on the developing sleeve 4 is erected by the developing magnetic pole N of the magnet roll 3.

A bias power source 6 is attached to the developing sleeve 4.
Applies a developing bias. The developing bias is, for example, a peak-to-peak voltage of 1400 V and a frequency of 1800 Hz.
An alternating current voltage such as a rectangular wave is used to superpose a direct current voltage of -500 V, and an oscillating electric field is formed in the developing portion, so that the toner T forming the toner layer on the developing sleeve 4 is transferred onto the photosensitive drum 10. The electrostatic latent image is developed.

According to the present invention, the developer (toner T) in the vicinity of the developer carrying member (developing sleeve 4) is agitated to assist the circulation of the toner T, and further, the toner T is uniformly provided with tribo. A stirring member 1 is provided to perform the above.

That is, the cylindrical stirring member 1 having a diameter of 50 Φ of magnetic SUS and a weight of 50 g is used as the developing sleeve 4.
And the magnetic force of the magnet of the magnet roll 3 make contact with each other. In this embodiment, the stirring member 1 draws up the toner T and is arranged at a magnetically stable position in the vicinity of the carrier pole S, and is held by providing a guide member 11 on the side surface of the developing container 7 so as to maintain a constant position. did.

Next, the function and function of the stirring member 1 will be described with reference to FIG.

The stirring member 1 rotates in the direction of arrow b at a speed equal to or lower than a constant speed as the developing sleeve 4 rotates in the direction of arrow a.

The toner T moves as follows. That is, the flow t ₁ of the toner conveyed from below the contact point 12 of the developing sleeve 4 and the agitating member 1 is partially returned by the agitating member 1 as t ₂ , and the other flows through the contact 12 to t. Transported as ₃ . Further, as the stirring member 1 rotates in the direction of the arrow b, the circulation of the toner is promoted at t ₄ . Further, the toner passing through the contact 12 is sufficiently frictionally charged by the contact between the developing sleeve 4 and the stirring member 1.

As described above, by providing the agitating member 1, the toner in the vicinity of the developing sleeve 4 is agitated, the circulation of the toner is promoted, and further, sufficiently high.
By forming a uniform toner layer, the image density is sufficiently high and it is possible to stably form an image without unevenness.

Further, since the stirring member 1 rotates in accordance with the rotation of the developing sleeve 4 and the surface in contact with the developing sleeve 4 moves, toner is fused to the surfaces of the stirring member 1 and the developing sleeve 4 and scratches are generated. It also has the effect of preventing the occurrence.

Although a magnetic SUS rod is used as the stirring member 1 in the present embodiment, the material is not limited to this.
It may be formed by sintering a resin in which a metal such as iron or the like and a ferrite powder are mixed and molding the mixture into a cylindrical shape.

FIG. 3 shows a second embodiment of the present invention.

In the present embodiment, the stirring member 1 is arranged in contact with the developing sleeve 4 in the vicinity of the cut pole N of the magnet roll 3 upstream of the toner layer thickness regulating member 5.

The regulating member 5 made of a ferromagnetic material is arranged with a constant gap from the developing sleeve 4 and a magnetic field formed by the cut pole N of the magnet roll 3 forms a magnetic brush of magnetic toner to form a toner layer. In the developing device that regulates the thickness, since the magnetic energy at the regulation portion is high, the packing density of toner at the back side portion of the regulation member 5 becomes high. There, the resistance against the movement of the toner becomes large and the movement becomes poor, so that the balance between the pressure for pushing the toner out of the regulating portion and the regulating force becomes unbalanced, and the toner layer conveyed to the developing area becomes unbalanced. It was sometimes uniform.

According to this embodiment, since the stirring member 1 is arranged in the vicinity of the regulating member 5, the toner flow as described above can be created, and the toner packing in the vicinity of the regulating member 5 is possible. By reducing the density and supplying the toner that has passed between the developing sleeve 4 and the stirring member 1 to the layer thickness regulating portion, it is possible to form a uniform toner layer.

FIG. 4 shows a third embodiment of the present invention.

In this embodiment, the stirring member 1 is arranged on the bottom surface of the developing container 7 so as to contact the developing sleeve 4.

In the case of this embodiment, the effect of dynamically promoting the circulation and stirring of the toner in the vicinity of the developing sleeve 4 is small, but the effect of uniformly charging the toner is sufficient.

Further, since the gap between the developing sleeve 4 and the bottom surface of the developing container 7 is closed, it also has an effect of preventing the toner from blowing and leaking from the bottom surface.

In the above embodiment, the case where the magnet roll 3 is fixed and the developing sleeve 4 is rotated to convey the toner is described.
The present invention is not limited to this.

FIG. 5 shows a fourth embodiment of the present invention.

In this embodiment, toner is carried on the developing sleeve 4 by rotating the magnet roll 3 having alternating N and S poles in the direction opposite to the rotating direction of the developing sleeve 4.
The developing device is configured to be transported.
It has the same effect as when the magnet roll 3 is fixed.

FIG. 6 shows a fifth embodiment of the present invention.

This embodiment is an example of a two-component toner developing device.

In the two-component development, the image quality greatly changes depending on the ratio of the carrier and the toner in the developer on the developing sleeve 4, and the stirring and mixing states. In particular, improving the uniformity of the developer by stirring and mixing the image density,
This is a very important point for fogging.

In FIG. 6, 13 is a toner replenishing member, 1
4 and 15 are rotary stirring members.

The stirring member 1 arranged immediately after the developer layer regulating member 5 rotates in accordance with the rotation of the developing sleeve 4,
It has the effect of improving carrier circulation and stirring.

Since the stirring member 1 contacts the developing sleeve 4 and regulates the movement of the carrier, it also acts to make the distribution of the carrier uniform in the longitudinal direction.

As a result, the uniformity of the developer is further improved, the density is high, fog is reduced, and good image formation without unevenness can be performed.

[0045]

As described above, according to the present invention,
A cylindrical stirring member made of a magnetic material is brought into contact with a developer carrier having a built-in magnet by magnetic force to keep a constant contact position with the developer carrier, and relatively rotate the magnet and the developer carrier. At this time, the developer in the vicinity of the developer carrying member is agitated by the agitating member to assist the circulation of the developer and at the same time, the developer on the developer carrying member is uniformly tribo-applied. A uniform developer layer can be formed on the body.

Therefore, the developer can be sufficiently tribo-charged at the contact portion between the developer carrying member and the stirring member, a sufficiently high density can be obtained, and an even image can be obtained, and the developer carrying member can be obtained. There is an effect that the fusion of the developer on the surface of the above and the surface of the stirring member can be prevented and the occurrence of scratches can be prevented.

[Brief description of drawings]

FIG. 1 is a sectional side view showing a first embodiment of the present invention.

FIG. 2 is a partial explanatory view around a developing sleeve in FIG.

FIG. 3 is a sectional side view showing a second embodiment of the present invention.

FIG. 4 is a sectional side view showing a third embodiment of the present invention.

FIG. 5 is a sectional side view showing a fourth embodiment of the present invention.

FIG. 6 is a sectional side view showing a fifth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Stirring member 3 ... Magnet roll 4 ... Development sleeve 5 ... Toner layer thickness regulation member 6 ... Bias power supply 7 ... Development container 10 ... Photosensitive drum 11 ... Guide member 12 ... Contact point

Claims (2)

[Claims] 1. A developing device having a developer carrying body containing a magnet for carrying a magnetic developer and a regulating member for regulating a layer thickness of the developer conveyed to a developing area, wherein a magnetic material cylinder is used. A developing device characterized in that a stirring member having a shape is held in contact with the surface of a developer carrier by magnetic force and is arranged in a developing container. 2. A developer layer regulating member made of a magnetic material is disposed with a constant gap from a developer carrying member to regulate the layer thickness of the magnetic developer by magnetic force, and the stirring member is near the layer regulating member. 2. The developing device according to claim 1, wherein the developing device is disposed upstream in the rotation direction of the developer carrying member.