JPS5926371Y2 - developing device - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to an apparatus for developing a latent image with magnetic toner.

Dry development methods can be roughly divided into two component development methods and one-component development methods.

The two-component development methods include a magnetic brush method using an iron powder carrier, a cascade method using a bead carrier, a fur brush method using fur, etc., depending on the type of carrier that charges and transports the toner.

However, all of these methods have problems such as an increase in the size of the apparatus and deterioration of the carrier, and recently there has been an urgent need to develop a one-shot development method.

The most important points in the one-component development method are how to charge the developer, how to support the developer on the developer carrier, and how to transport the developer to the developing section. That's the point.

Regarding these points, we focused on using magnetic force, using a non-magnetic sleeve containing a magnetic roll as a toner carrier, and applying a magnetic developer onto the sleeve surface using a specific application means, and using the sleeve or application means as a toner carrier. It can be said that the method of charging the developer by friction is an extremely excellent method.

On the other hand, a major problem with the -a development method is the deterioration of the developer.

This occurs when the developer continues to receive a specific force or movement during the process of applying or transporting the developer, and is a phenomenon in which the initial characteristics of the developer particles themselves deteriorate or disappear. In a magnetic toner developing device using a magnetic sleeve, if development is performed and toner consumption continues, no problem will occur. However, if only the snow is rotated for a long time without development, and then development is performed, the developed density will be lower than the initial value. There may be a phenomenon where this happens.

Therefore, in this case, if a large number of copies with a small image width are made and then switched to a copy with a large image width, uneven shading will occur in the copied image.

The present invention aims to solve such problems and provide a developing device that can agitate the developer in the axial direction and homogenize it using an extremely simple method, thereby suppressing the above-mentioned image deterioration phenomenon and providing long-term stability. This is the purpose.

Hereinafter, details of embodiments of the developing device according to the present invention will be described with reference to the drawings.

In FIG. 1, 1 is a non-magnetic sleeve that rotates in the direction of the arrow, and 2 is a magnet roll consisting of eight magnetic poles, and the sleeve surface magnetic flux density at the main pole B located in the developing section is 800 Gauss.

Reference numeral 3 denotes a blade as a magnetic material coating means, which is disposed at a position facing the coating soil pole A while maintaining a gap of 200 μm from the sleeve surface, and controls the thickness of the magnetic toner 4 on the sleeve by magnetic force. Coating (Patent application 1986-10)
9240).

The components of the magnetic toner include polyester resin 7Q, for example.
wt%, magnetite) 28wt%, charge control agent 2wt%
0.2wt of colloidal silica to improve fluidity.
% is added externally.

Reference numeral 6 denotes a latent image holder for electrostatic images, etc., which moves in the direction of the arrow and is developed by a uniform layer of toner at a position facing the main magnetic pole B.

As shown in FIGS. 2 and 3 (developed view), the axial length of each magnetic pole of the magnet roll is equal between the coating means 3 and the developing position T (A-B), Once it passes, it becomes shorter (CD), and when it reaches the coating means 3, it becomes longer again.

By having such a magnetic pole configuration, the toner applied to the sleeve end by the application means is moved inward by the end magnetic field of the magnetic pole after passing through the developing section, and as a result, homogenization of the toner in the axial direction is achieved. effective.

In a normal document, the image area is concentrated in the center of the document, and the edges are often blank spaces.

Furthermore, even when making continuous copies of small-sized originals, the developer at the ends of the sleeve is hardly consumed, and when a normal magnetic roll is used, the developer at these ends gradually deteriorates. This tends to cause unevenness in image shading.

However, by using the above-mentioned magnetic roll in the device of the present invention, the toner present at the ends is also moved toward the center during one rotation of the sleeve, and new toner is always mixed, thus toner is removed in the axial direction. This has the effect of achieving homogenization and providing stable images over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of one embodiment of the developing device according to the present invention,
FIG. 2 is a front view of the magnet roll, and FIG. 3 is a developed view of the magnetic poles of the magnet roll. 1...Sleeve, 2...Magnetic roll, 3...Applying member, 4...Magnetic toner 5...Hotsunoku-

Claims (1)

[Claims for Utility Model Registration] A rotating non-magnetic sleeve, a fixed magnet roll having a plurality of poles contained in the sleeve, a container for supplying magnetic toner, and a member for applying the toner to the sleeve. In the developing device, when viewed according to the rotational direction of the sleeve, the length of the magnetic pole of the magnet roll in the axial direction becomes shorter once after the developing section, and becomes longer again before reaching the coating member or at the position of the coating member. A developing device characterized by being configured as follows.