JPH10319724A - Developing device with developer spinning chamber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device in the form of actively using the rotation of developer. SOLUTION: Developer as a mixture of carrier and toner is attracted to the surface of a developing roller 40 formed with a cylindrical permanent magnet of pole interval λ and the developing roller 40 is rotated to put the developer in contact with or in proximity to a static latent image so that the static latent image can be actualized. A doctor blade 50 is provided on the upstream side where the developer is put in contact with or in proximity to the static latent image and a cavity shaped spinning chamber 51 for the developer to be rotatable is provided on the upstream side adjacent to the doctor blade 50, and the maximum distance ρ between the spinning chamber 51 and the developing roller 40 is no less than 1/2 to no more than three times of a magnetic pole interval λ.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a developing device provided in an image forming apparatus, and more particularly, to a developing device having a spin chamber for a developer.

[0002]

2. Description of the Related Art Conventionally, copiers, printers, facsimile machines and the like have been widely used as image forming apparatuses. Among these image forming apparatuses, in an apparatus using an electrophotographic method or an electrostatic recording method, an electrostatic latent image formed on a surface of a photoconductor is transferred to a toner supplied from a developer transport mechanism provided in proximity to the photoconductor. A method is adopted in which a visible image is formed by the adhesion of the image.

Further, for the purpose of improving image quality and reducing the cost and size of the image forming apparatus, a sleeve provided around the magnet body, which is employed for magnetically attracting and holding the developer, is provided. There is no proposed configuration, that is, a configuration of sleeveless development, which has been applied.

As a known example of such a sleeveless developing configuration, a plurality of examples are disclosed, including the one disclosed in Japanese Patent Application Laid-Open No. Hei 7-234588. Common to these configurations is a doctor blade (hereinafter referred to as a “doctor blade”) that uses a sleeveless magnet roller as a developing roller and regulates a developer containing toner, which is attracted and held by the magnet roller, to a constant layer thickness. (Abbreviated).

[0005]

However, in the conventional configuration as described above, the doctor is made of a linear member, and is not configured to positively use the rotation of the developer. As a result, there have been cases in which the toner concentration becomes unstable, the amount of charge of the toner becomes insufficient, and background contamination and toner scattering occur.

Further, the charging of the toner (and the developer) is mainly performed in the process of scraping off the excess developer adsorbed on the developing roller at the tip of the doctor to a predetermined amount.
This force at the tip of the doctor tends to concentrate on a narrow area, which causes a problem of deteriorating the developer.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the prior art, and an object of the present invention is to provide a developing device having a configuration for positively utilizing the rotation of a developer.

[0008]

According to a first aspect of the present invention, there is provided a developing device comprising: a powder containing a ferromagnetic material and functioning as a carrier; and a powder containing a coloring material and functioning as a toner. Is adsorbed on the surface of a developing roller constituted by a cylindrical permanent magnet with a pole interval λ, and the developer is brought into contact with or close to the electrostatic latent image by rotating the developing roller. In a developing device for visualizing the electrostatic latent image, upstream of the developer contacting or approaching the electrostatic latent image, a member that regulates the developer amount on the developing roller to be substantially constant. And a hollow spin chamber in which the developer is rotatable on the upstream side adjacent to the doctor. The maximum distance ρ between the spin chamber and the developing roller is one half of the magnetic pole interval λ. It is characterized by being more than 3 times or less To.

According to the above construction, the developer blocked by the doctor is provided with a force for rotating the developer, thereby making it possible to frictionally charge the toner without deteriorating the developer.

According to a second aspect of the present invention, in the configuration of the first aspect, the distance between the entrance of the developer into the spin chamber and the developing roller (the spin chamber entrance gap Gi) is equal to the gap between the doctor and the developing roller. And is smaller than the maximum distance ρ between the spin chamber and the developing roller.

According to the above configuration, it is difficult for the developer to exit from the entrance of the spin chamber, the rotation of the developer in the spin chamber becomes smoother, and the pressure of the developer in the spin chamber increases, so that the development is performed. The toner can be frictionally charged without deteriorating the agent.

According to a third aspect of the present invention, there is provided the developing device according to the first aspect, wherein an entrance of the spin chamber is covered with a developer.

According to the above configuration, since the entrance of the spin chamber is covered with the developer, mixing of the lump of the toner into the spin chamber is prevented, and thus the toner which is not triboelectrically charged is transported to the development area. Is prevented.

According to a fourth aspect of the present invention, there is provided a developing device comprising: a developer which is a mixture of a powder containing a ferromagnetic material and functioning as a carrier and a powder containing a coloring agent and functioning as a toner;
The developer is brought into contact with or close to the electrostatic latent image by rotating the developing roller by attracting the developer to the surface of the developing roller constituted by a cylindrical permanent magnet having a pole interval λ, and In the developing device for visualizing, upstream, the developer comes into contact with or close to the electrostatic latent image, a doctor is provided as a member for regulating the developer amount on the developing roller to a substantially constant amount. An adjacent upstream side has a hollow spin chamber in which the developer is rotatable, an entrance of the spin chamber is located below the spin chamber, and a spin chamber entrance gap enters the spin chamber. Characterized in that the thickness is larger than

According to the above configuration, since the entrance of the spin chamber is located below the spin chamber, it is not electrically attached to the carrier that cannot be held on the developing roller by the magnetic force or the carrier that is attracted to the developing roller. The toner falls by gravity and is discharged out of the spin chamber. As a result, the toner in the spin chamber can maintain a charge amount equal to or higher than a certain value.

According to a fifth aspect of the present invention, in the configuration of the fourth aspect, the length from the doctor to the entrance of the spin chamber is longer than the maximum distance between the spin chamber and the developing roller. .

According to the above construction, while the developer scraped off from the developing roller by the doctor at the upper part of the spin chamber falls a long distance to the exit of the spin chamber, the developer is attracted to the developing roller and rises. The agent is rubbed and charged.

[0018]

Embodiments of the present invention will be described below. FIG. 1 is a schematic sectional view of a main part of a first embodiment of a developing device having a developer spin chamber according to the present invention. FIG. 2 is a schematic sectional view of a peripheral portion of the drum in the developing device of FIG.

As shown in FIG. 1, in a developing device 1 according to the present invention, a spin chamber 51 is provided in a doctor blade (doctor) 50. The spin chamber 51 is located on the upstream side in the rotation direction of the developing roller 40 and has a concave dent. The shape of the dent is approximately one-eighth of the circumference as shown in the figure.
It is a circular arc of a degree. The spin chamber 51 assists rotation of the developer inside. The spin chamber 51 having the shape of the present embodiment does not have a shape that sufficiently wraps the developer, but can generate an effective spin.

A magnetic field is formed around the developing roller 40 by the magnetic charge of the developing roller 40. When this is observed at a fixed position, for example, at the distal end position of the doctor 50, it appears that the magnetic field is rotating with the rotation of the developing roller 40. Here, assuming that the peripheral speed of the developing roller 40 is Vr, the rotation speed fr of the magnetic field is given by fr = λ / Vr.

By the rotation of the magnetic field, a force for rotating the developer blocked by the doctor 50 is applied. On the other hand, the magnetic field generated by the developing roller 40 decreases rapidly as the distance from the roller surface increases. The distance over which the magnetic field can effectively act on the developer is determined by many parameters including the magnitude of the magnetic charge of the developing roller 40 and the saturation magnetic charge of the developer. Without moving to the photoconductor 30 side, and
When the doctor 50 regulates the amount of the developer 41 on the developing roller 40 to be substantially constant, the strength is preferably such that an excessive load does not occur.

In operation, the developer 41 passed through the doctor blade 50 and held on the developing roller 40 gives at least a part of the toner to the photosensitive member 30 at a stage where the developer 41 contacts or approaches the photosensitive member 30. Then, the latent image formed on the photoconductor 30 is visualized by the amount of toner. As a result, a part of the toner is consumed.

As described above, the developer 41 that has been developed by contacting or approaching the photoreceptor 30 and giving the amount of toner returns to the developing device 39 with the movement of the developing roller 40, and the toner 41 Contact and adsorb this.

However, at this stage, the newly adsorbed toner may harden in a state where the toners are aggregated, and have little electric charge yet. When the toner enters the spin chamber 51, the toner agglomerates due to vigorous rotation of the developer, and the finely-divided toner is rubbed against the carrier constituting the developer and is softly triboelectrically charged. The developer receives a strong shearing force at the stage of exiting the spin chamber 51 and passing through the doctor 50, and is sufficiently charged. In this way, the toner can be frictionally charged without deteriorating the developer.

FIG. 2 is an overall view around the drum of the apparatus of the first embodiment. The photoreceptor 30 is provided with an electrostatic image by irradiation with the laser writing light Lr carrying the image and charging by the charging roller. Developing roller 4
The image developed by 0 and revealed by toner is transferred to output paper. The surface of the photoconductor 30 after the transfer is cleaned by the cleaning blade 15.

FIG. 3 is a schematic cross-sectional view of a main part of a second embodiment of a developing device having a developer spin chamber according to the present invention. As shown in FIG. 3, the developing device 2 according to the second embodiment of the present invention is configured such that the distance between the entrance of the developer into the spin chamber and the developing roller, that is, the spin chamber entrance gap Gi is between the doctor 50 and the developing roller 40. , And smaller than the maximum distance ρ between the spin chamber 52 and the developing roller 40.

Thus, the spin chamber entrance gap Gi is
By setting the distance between the spin chamber 52 and the developing roller 40 to be smaller than the maximum distance ρ, the spin chamber 52 sufficiently wraps the developer, and the frictional resistance between the container wall and the developer is reduced. Less than the internal shear friction, and thus the spin chamber 52
The rotation of the developer can be assisted in the rotation, and the developer can be smoothly and largely rotated. In addition to such an effect of making the rotation of the developer in the spin chamber 52 smoother, the developer hardly goes out from the entrance of the spin chamber 52, thereby increasing the pressure of the developer in the spin chamber 52. Thus, triboelectric charging can be performed more effectively.

FIG. 4 is a schematic cross-sectional view of a main part of a third embodiment of a developing apparatus having a developer spin chamber according to the present invention. As shown in FIG. 4, the developing device 3 according to the third embodiment of the present invention has a configuration in which the developer D covers the entrance 53a of the spin chamber 53, and the toner cannot directly enter the spin chamber 53. It has become.

After the development, the developer returns to the developing device 39 in accordance with the movement of the developing roller 40, comes into contact with the toner, adsorbs the toner, and replenishes the consumed toner. However, at this stage, as described above, the newly adsorbed toner has little electric charge because the toner may still be aggregated and hardened. Therefore, the toner is in a state of being softly laid on the developer. When this enters the developer reservoir 38 that covers the spin chamber 53, the toner is blocked by the developer, and only the toner adhering to the surface layer of the developer adsorbed by the developing roller 40 sneaks into the developer reservoir 38. Thereby, it is possible to prevent excessive toner from entering the spin chamber 53.

FIG. 5 is a schematic cross-sectional view of a main part of a fourth embodiment of a developing device having a developer spin chamber according to the present invention. As shown in FIG. 5, in the developing device 4 according to the fourth embodiment of the present invention, the entrance 54a of the spin chamber 54 is
4, the entrance gap of the spin chamber is larger than the layer thickness of the developer entering the spin chamber.

In front of the spin chamber 54, the paddle wheel 60
The developer (contains a sufficient amount of toner) lifted to the vicinity of the developing roller 40 is attracted by the magnetic field. Spin room entrance 5 located below spin room 54
At 4a, the developer adsorbed on the developing roller 40 enters the spin chamber 54 as the developing roller 40 rotates.

Here, the developer scraped off by the doctor 50 rotates in the spin chamber 54. At this time, the toner that has not adhered to the developer with sufficient force is peeled off from the developer by centrifugal force or the like. According to gravity, spin chamber entrance 54a
From the spin chamber 54. That is, since the spin chamber entrance 54a is located below the spin chamber 54, a carrier that cannot be held on the developing roller 40 by magnetic force,
The toner not electrically attached to the carrier adsorbed on the developing roller 40 falls due to gravity and goes out of the spin chamber 54. As a result, the toner that has not been triboelectrically charged is not carried to the developing area, and the toner in the spin chamber maintains a charge amount equal to or more than a certain value.

FIG. 6 is a schematic sectional view of a main part of a fifth embodiment of a developing apparatus having a developer spin chamber according to the present invention. As shown in FIG. 6, a developing device 5 according to a fifth embodiment of the present invention includes a
The length up to 5a is longer than the maximum distance between the spin chamber 55 and the developing roller 40.

The developer (contains a sufficient amount of toner) lifted up to the vicinity of the developing roller 40 by the paddle wheel 60 just before the entrance 55a of the spin chamber is attracted by the magnetic field. At the spin chamber entrance 55a located below the spin chamber 55, the developer adsorbed on the developing roller 40
As the developing roller 40 rotates, it enters the spin chamber 55.

Since the doctor 50 is located above the developing roller 40, the developer scraped by the doctor 50 rotates in the spin chamber 55, and moves on the developer layer adsorbed on the surface of the developing roller 40 by gravity. Spin room entrance 55 by
Fall in the a direction. That is, the developer layer drops on the surface of the developing roller 40 in a direction opposite to the traveling direction (upward direction) of the developer layer. During this time, while falling a long distance to the spin chamber entrance 55a, the developer adsorbed on the surface of the developing roller 40 is rubbed and charged. In this manner, the developer that enters one after another and the developer that falls are rubbed to charge the toner.

In this way, it is possible to frictionally charge the toner without deteriorating the developer, and to prevent the non-frictionally charged toner from being carried to the development area. As a result, background contamination and toner scattering hardly occur.

[0037]

As described in detail above, claim 1 of the present invention
With this configuration, the force of the rotating magnetic field can be effectively used for the rotational movement of the developer. During the vigorous rotational movement of the developer in the spin chamber, the friction between the developers and the entrance of the spin chamber. Thus, the toner can be frictionally charged by friction with the developer coming and going. In addition, since the friction is performed at a place relatively distant from the developing roller, the pressure on the friction surface is weak, and there is an effect that the developer is not deteriorated.

According to a second aspect of the present invention, in the configuration of the first aspect, the spin chamber entrance gap is set to be small to make it difficult for the developer to flow out from the spin chamber entrance.
In addition, the rotation of the developer in the spin chamber can be made smoother, and the pressure of the developer in the spin chamber can be increased to make the frictional charging more effective, so that the toner can be frictionally charged without deteriorating the developer. .

According to a third aspect of the present invention, the constitution in which the entrance of the spin chamber is covered with the developer in the first aspect can prevent toner agglomerates from being mixed into the spin chamber, so that toner that has not been triboelectrically charged can be removed. This has the effect of preventing transport to the development area.

According to the fourth aspect of the present invention, the carrier that cannot be held on the developing roller by the magnetic force or the toner that is not electrically attached to the carrier adsorbed on the developing roller is dropped by gravity, and the outside of the spin chamber is removed. Therefore, the toner in the spin chamber can be maintained at a charge amount equal to or higher than a certain value.

According to a fifth aspect of the present invention, while the developer scraped off from the developing roller by the doctor at the upper part of the spin chamber falls a long distance to the exit of the spin chamber, it is attracted to the developing roller and rises. By employing a configuration in which the developer is charged by friction, the toner can be frictionally charged without deteriorating the developer, and a configuration in which non-frictionally charged toner is not carried to the development area can be achieved. As a result, there is an effect that background stain and toner scattering hardly occur.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a main part of a developing device according to a first embodiment of the present invention.

FIG. 2 is a schematic sectional view of a peripheral portion of a drum in the developing device of FIG.

FIG. 3 is a schematic sectional view of a main part of a developing device according to a second embodiment of the present invention.

FIG. 4 is a schematic sectional view of a main part of a developing device according to a third embodiment of the present invention.

FIG. 5 is a schematic sectional view of a main part of a developing device according to a fourth embodiment of the present invention.

FIG. 6 is a schematic sectional view of a main part of a developing device according to a fifth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Developing device of the present invention 10 Transfer belt 15 Cleaning blade 20 Charging roller 30 Photoconductor 39 Developing device 40 Developing roller 41 Developer on developing roller 50 Doctor blade 51 Spin chamber ρ Maximum distance between spin chamber and developing roller λ Magnetic pole spacing

Claims (5)

[Claims] 1. A developer comprising a mixture of a powder containing a ferromagnetic material and functioning as a carrier and a powder containing a colorant and functioning as a toner, is developed by a cylindrical permanent magnet with a pole interval of λ. A developing device that attracts the developer to the surface of the roller and rotates the developing roller to contact or approach the developer with the electrostatic latent image to visualize the electrostatic latent image; A cavity as a member that regulates the amount of the developer on the developing roller to be substantially constant upstream of contact with or close to the electrostatic latent image; and a cavity in which the developer can rotate on the upstream side adjacent to the doctor. A maximum distance ρ between the spin chamber and the developing roller is at least half to three times the magnetic pole interval λ. 2. The method according to claim 1, wherein the distance between the entrance of the developer into the spin chamber and the developing roller (spin chamber entrance gap Gi) is larger than the gap between the doctor and the developing roller and smaller than the maximum distance ρ between the spin chamber and the developing roller. Claim 1
The developing device as described in the above. 3. The developing device according to claim 1, wherein an entrance of the spin chamber is covered with a developer. 4. A developer comprising a mixture of a powder containing a ferromagnetic material and functioning as a carrier and a powder containing a colorant and functioning as a toner, is developed by a cylindrical permanent magnet with a pole interval λ. A developing device that attracts the developer to the surface of the roller and rotates the developing roller to contact or approach the developer with the electrostatic latent image to visualize the electrostatic latent image; A cavity as a member that regulates the amount of the developer on the developing roller to be substantially constant upstream of contact with or close to the electrostatic latent image; and a cavity in which the developer can rotate on the upstream side adjacent to the doctor. A spin chamber, wherein the entrance of the spin chamber is located below the spin chamber,
A developing device wherein a spin chamber entrance gap is larger than a layer thickness of the developer entering the spin chamber. 5. The developing device according to claim 4, wherein the length from the doctor to the entrance of the spin chamber is longer than the maximum distance between the spin chamber and the developing roller.