JPH063963A - Developing device - Google Patents

Abstract

PURPOSE:To obtain a stable image over a long term by preventing the deterioration of developer by specifying a pole for drawing the developer, a pole for regulating it and a developing pole. CONSTITUTION:It is assumed that a developing part needs the peak value Z of magnetic flux density in the direction of sleeve surface normal line of magnetic pole S1 so that carrier does not adhere on an image carrier. In this case, the deterioration of the developer is affected by the magnetic force of both a magnetic pole N2 drawing the developer in a developing container and a magnetic pole S2 carrying the developer to a guide member 21 and regulating the developer to an adequate layer thickness. The peak values X and Y of the magnetic flux density in the direction of the sleeve surface normal line of the magnetic poles N2 and S2 become equal to or under 1/2 of the value Z of the magnetic pole S1 so as to suppress the deterioration and also need equal to or above 1/3 so as to accomplish carrying the developer. Under the condition, for example even when the copying of 100,000 sheets of paper is performed, an excellent image is always and stably obtained without causing fogging and lowering image density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer, etc. of an electrophotographic system or an electrostatic recording system in which a developer is adhered to an electrostatic latent image formed on an image carrier to form a visible image. The present invention relates to an image forming apparatus, and more particularly to a developing apparatus for an image forming apparatus using a two-component developer whose main component is a toner that is a developer and a magnetic carrier that gives an electric charge to the toner.

[0002]

2. Description of the Related Art In electrophotographic and electrostatic recording type image forming apparatuses, particularly color image forming apparatuses for forming full-color and multi-color images by electrophotographic method, most of the developing agents are used in terms of color developability and color mixture. The device uses a two-component developer in which non-magnetic toner particles and a magnetic carrier are mixed. As is well known, in the developing method using this two-component developer, an electric charge is applied to the toner by frictional electrification generated between carrier particles and toner particles, and the charged toner is electrostatically applied to the latent image. It is a method of forming an image by adhering.

[0003]

However, since the toner and the carrier always rub against each other,
When images are formed for a long period of time, the binder resin of the toner is fused to the surface of the carrier, resulting in spent of the carrier and silica or titanium oxide externally added to the toner to improve the fluidity of the toner. A phenomenon such as the external additive of the toner being buried in the toner occurs, and as a result, the toner cannot be stably charged, and scattering or fog occurs outside the toner or the developing device, and There is a problem that the image quality is significantly deteriorated.

[0004]

According to the present invention, the developer is pumped up to the developer carrying body in the rotary developer carrying body carrying and carrying the two-component developer in which toner and magnetic carrier particles are mixed. A magnetic pole, a magnetic pole that regulates the amount of developer conveyed to the developing area, and a magnet that forms a developing magnetic pole that forms a magnetic field in the developing area are fixedly installed, and the scooping magnetic pole, the regulating magnetic pole, and the developing magnetic pole The maximum values of magnetic flux density X, Y, and Z (Gauss) in the direction of the surface of the carrier are

[0005]

[Outside 2] By setting so as to satisfy, it is possible to obtain a stable image for a long period of time.

[0006]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram showing a main part of a first embodiment of a developing device according to the present invention.

As shown in the figure, the developing device 2 arranged to face an image carrier 1 such as an electrophotographic photosensitive member on which an electrostatic latent image is formed includes a developing container 3 and a developing sleeve as a developer carrier. 4 and a blade 5 as a developer layer thickness regulating member, which is disposed so as to face the sleeve 4. The inside of the developing container 3 is divided by a partition wall 6 into a developing chamber (first chamber) 7 and a stirring chamber (second chamber).
Room) and is sectioned. The upper portion of the partition wall 6 is open so that the two-component developer, which becomes an excess in the developing chamber 7, is collected in the stirring chamber 8 side. Development chamber 7 and stirring chamber 8
In this embodiment, the two-component developer 11 containing non-magnetic toner particles and magnetic carrier particles is contained in the.

In the developing chamber 7 and the agitating chamber 8, screw type first and second developer agitating and conveying means 1 are provided, respectively.
6 and 17 are arranged. First stirring / conveying means 1
6 agitates and conveys the developer in the developing chamber 7, and the second agitating / conveying means 17 controls the agitating / conveying means from a toner replenishing tank (not shown) under the control of the developer concentration controller. 17
The toner supplied to the upstream side of and the developer already in the agitating chamber 8 are agitated and conveyed to make the toner concentration uniform. Partition 6
In the developing chamber 7 at the front and rear end portions in FIG.
A developer passage (not shown) that connects the stirring chamber 8 and the stirring chamber 8 to each other is formed.
By the conveying force in the opposite direction, the developer in the developing chamber 7 in which the toner is consumed by the development and the toner concentration is lowered moves from the other passage into the developing chamber 7. The developing chamber 7 of the developing container 3 has an opening at a position corresponding to the developing region facing the image carrier 1, and the developing sleeve 4 is rotatably arranged so as to be partially exposed in the opening 13. Has been done. The developing sleeve 4 is made of a non-magnetic material and rotates in the direction of the arrow in the drawing during the developing operation.
A magnet 14, which is a magnetic field generating means, is non-rotatably fixed therein. The developing sleeve 4 carries and conveys the layer of the two-component developer whose layer thickness is regulated by the blade 5, and supplies the developer to the image carrier 1 in the developing area facing the image carrier 1 to develop the latent image. . In order to improve the developing efficiency, that is, the toner application rate to the latent image, a developing bias voltage in which a DC voltage and an AC voltage are superimposed is applied to the developing sleeve 4 from a power source (not shown).

In the present embodiment, the magnet 14 has a developing magnetic pole S ₁ and magnetic poles N ₁ , S ₂ , N ₂ and N ₃ which form a magnetic field in the developing area.

The blade 5 is made of a non-magnetic material such as aluminum and is arranged on the downstream side of the magnetic pole S _{2 in} the rotation direction of the developing sleeve 4, and has a gap between the blade 5 and the surface of the developing sleeve 4. And the magnetic pole S ₂ that exerts a magnetic field on it
The thickness of the developer 11 transported to the developing area on the developing sleeve 4 is regulated in cooperation with the. Therefore, in this embodiment, both the non-magnetic toner and the magnetic carrier pass between the tip of the blade 5 and the developing sleeve 4 and are sent to the developing area.

The developer remaining in the developing area without being developed is conveyed again to the developing chamber 7 by the developing sleeve 4, and the repulsive magnetic field formed by the adjacent magnetic poles N ₃ and N ₂ of the same polarity. Thus, the toner is scraped off from the developing sleeve 4 into the developing chamber 7 and collected.

On the other hand, the developer agitated and conveyed by the rotation of the first agitating and conveying means 16 is pumped up to the developing sleeve 4 by the magnetic pole N ₂ on one side of the same polarity magnetic pole and conveyed to the developer regulating portion. To be done. The developer regulating portion is composed of the blade 5 and a developer reversing guide member 21 arranged above the developing chamber 7 in the developing container 3, and the developer is indicated by a thick arrow in the drawing at the guide member 21. And the guide member 21 that moves in such a manner and is conveyed from the developer regulating portion to the developing area.
Is pushed back to reverse the traveling direction and falls into the stirring chamber 8. The developer that has dropped into the stirring chamber 8 is mixed with the developer mixed with the replenishment toner in the stirring chamber 8 and is conveyed again to the developing chamber 7 side.

What is important here is that the guide member 21 keeps the pressure applied to the developer as low as possible. For that purpose, it is necessary to reduce the magnetic force applied to the developer as much as possible at the developer inversion moving portion in the guide member 21.

More importantly, it is possible to prevent the carrier from adhering to the image carrier together with the toner in the developing area.

In order to obtain these conditions and further efficiently convey the developer to the developing section, as a result of many experiments, it was found that the following conditions were necessary.

First, it is assumed that a peak value Z (Gauss) of the magnetic flux density of the magnetic pole S _{1 in} the direction normal to the sleeve surface is required in the developing section so that the carrier does not adhere to the image carrier. In this case, the condition for preventing the developer from deteriorating was confirmed by a durability test. As a result, the magnetic pole N ₂ for pumping the developer in the developing container was confirmed.
It was found that the magnetic forces of both magnetic poles S ₂ for conveying the developer to the guide member 21 and regulating the developer to an appropriate layer thickness are related to the deterioration of the developer. In order to suppress this deterioration, the peak values X and Y (Gauss) of the magnetic flux densities of the magnetic poles N ₂ and S _{2 in} the direction normal to the sleeve surface are ₁ of the above-mentioned value Z of the magnetic pole S 1.
It has been found that it is necessary to be / 2 or less, and 1/3 or more in order to establish the transport of the developer. When 100,000 copies were made under the above conditions, fogging and reduction in image density did not occur, and stable and good images were always obtained.

FIG. 2 shows another embodiment.

In this case, the developer guide surface 2 of the guide member 21.
2 is inclined downward from the horizontal toward the upstream side in the rotation direction of the sleeve 4. With such a configuration, it is possible to further increase the effect of weakening the magnetic forces of the S ₂ and N ₂ poles as compared with the S ₁ pole as described above, and further reduce the deterioration of the developer.

FIG. 3 shows another embodiment.

In this case, the regulating magnetic pole is N ₂ and the pumping magnetic pole is S ₂ . The rotation direction of the developing sleeve depends on the first and second embodiments.
In the opposite direction, however, a stable image can be obtained for a long time also in this case by setting S ₁ to 1000 gauss and S ₂ and N ₂ to 450 gauss.

[0022]

As described above, by defining the scooping pole of the developer, the controlling pole and the developing pole, it is possible to prevent the deterioration of the developer and obtain a stable image for a long time. became.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is an explanatory view of another embodiment of the present invention.

FIG. 3 is an explanatory diagram of still another embodiment of the present invention.

[Explanation of symbols]

 4 Developing Sleeve 5 Developer Layer Thickness Control Blade 14 Magnet 21 Developer Reversing Guide Member

Claims (1)

[Claims] 1. A magnetic pole for pumping the developer to the developer carrying member, a magnetic pole for pumping the developer to the developer carrying member, and an amount of the developer carried to the developing area. And a magnet having a developing magnetic pole that forms a magnetic field in the developing area is fixedly installed, and the magnetic flux density of the scooping magnetic pole, the regulating magnetic pole, and the developing magnetic pole in the normal direction to the carrier surface. The maximum values X, Y, and Z (Gaussian) of The developing device is set so as to satisfy the above condition.