JPS62205385A - Developing device - Google Patents

Abstract

PURPOSE:To sufficiently cut the conveyance of a developer by providing a magnet that is installed at a part starting the conveyance of the developer and approaches to one conveyance pole at the time of stopping the conveyance of the developer and facing said conveyance pole with a pole surface with the reverse polarity of the former pole. CONSTITUTION:Doctor blades 17 and 18 are installed on the inner bottom parts of the upper and lower developing units 3 and 4, and regulate the layer thicknesses of the developers t1 and t2. The magnets 19 and 20 are installed on the upper parts of the doctor blades 17 and 18 and brought close to the 1st magnetic poles 7 and 13 at the time of stopping the conveyance of the developer, and the surface of the polarities of their poles N are opposite to that of the reverse polarities of poles S. Upon the completion of development, the 1st-5th magnetic poles 7-11 of a developing roll 3 are displaced at positions shown by dotted lines. As figure shows, the 1st magnetic pole 7 faces the magnet 19 of the doctor blade 17 to form a magnetic intensity line S between the magnet 19 and said pole 7. The magnetic intensity line S cuts forcibly the conveyance of the developer t1. In terms of black development as well, the developer t2 is similarly cut.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a developing device that is provided in, for example, an electronic copying machine and conveys developer using magnetic force.

(Prior Art) This type of developing device has two parts: a developing roller having a plurality of magnetic poles disposed within a rotating sleeve; A magnetic brush of developer is formed on the photosensitive drum, and this magnetic brush is brought into sliding contact with the electrostatic latent image formed on the photosensitive drum by the rotation of the rotating sleeve, thereby developing the image.

The magnetic pole of the developing roller is rotatably provided, and when the development is stopped, the magnetic pole is rotationally displaced so that the conveyance of the developer is stopped.

(Problem to be Solved by the Invention) However, in the conventional device, the conveyance of the developer is simply stopped by rotating the position of the conveyance pole. Because of these factors, it was not possible to sufficiently cut the developer transport, resulting in poor reliability6.Furthermore, there was a problem in that the magnetic properties of the developer used were limited, reducing the degree of freedom in material development.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to sufficiently reduce developer transport without being affected by environmental conditions, developer fatigue level, density, etc. It is an object of the present invention to provide a developing device in which the magnetic properties of the developer used are not limited.

[Structure of the invention]

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention is provided at a developer transport start site, and is located close to one of the transport poles when the developer transport is stopped, and is located close to one of the transport poles when the developer transport is stopped. It is characterized by being equipped with a magnet that has polar faces of opposite polarity facing each other.

(Function) By the above means, lines of magnetic force are formed between the transport pole and the magnet, and the transport of the developer is forcibly cut by the lines of magnetic force.

(Example) The present invention will be described below with reference to an example shown in the drawings. In the figure, 1 is a photosensitive drum installed in a copying machine, for example.
A developing device 2 is provided adjacent to the photosensitive drum 1. The developing device 2 is composed of upper (for red) and lower (for black) developers 3.4. Developing rolls 5a and 5b are disposed within the developing device 3.4, respectively. The developing roll 5a includes a rotating sleeve 6 and first to fifth magnetic poles 7 to 11 disposed within the rotating sleeve 6. These first to fifth magnetic poles 7 to 11 are at the position shown by the solid line when the developer (magnetic toner) 11 is being conveyed, and are rotated by a solenoid (not shown) to the position shown by the dotted line when the conveyance is stopped. It has become. Among the first to fifth magnetic poles 7 to 11, the first.
The third and fifth magnetic poles 7, 9, 11 are north poles, and the second and fourth magnetic poles 8, 10 are south poles. Also.

The developing roll 5b includes a rotating sleeve 12 and first to fourth magnetic poles 13 to 16 disposed within the rotating sleeve 12.
It is composed of. The first to fourth magnetic poles 13
1 to 16 are in the position shown by the solid line when the developer (magnetic toner) 1 is being conveyed, and are rotationally displaced by a solenoid (not shown) to the position shown by the dotted line when the conveyance is stopped. Among the first to fourth magnetic poles 13 to 16, the first and third magnets 13. IS is N pole, second and fourth magnet 1
4.16 is the south pole.

In addition, doctor blades 17 and 18 are provided at the inner bottoms of the upper and lower developing devices 3 and 4, respectively, and the layer thickness of the developer jl*fl is regulated by these doctor blades 1'17 and 1B. It looks like this. Magnets 19 and 20 are provided on the upper surfaces of these doctor blades 17 and 18, as shown in FIG. The magnets i9, 2o are close to the first magnetic poles 7, 13 when the developer transport is stopped, and have a polarity (N pole) opposite to the first magnetic pole (S pole).
The two poles are arranged to face each other. The surface magnetic flux density of the magnets 19 and 20 is 100 Gauss.

In addition, 21.22 in the figure is the developer 11si! of the above-mentioned upper and lower developing devices 2.4! A detector that detects the concentration of 23.2
4 is a replenishment hopper for replenishing the developer tl j tl.

For example, when developing a red color, the developing roll 30 rotating sleeve 6 of the upper developing device 3 rotates, the layer thickness of the developer t1 on the surface thereof is regulated by the doctor blade 17, and the developing agent t1 is conveyed. The developer (developer brush) 11 comes into sliding contact with the electrostatic latent image formed on the surface of the photosensitive drum 1 and is developed.

After this development is completed, the first to fifth magnetic poles 7 to 11 of the developing roll 3 are rotationally displaced to the positions shown by dotted lines. At this time, as shown in FIG.
and the magnet 19 of the doctor blade 11 face each other.
A line of magnetic force 8 is formed between the two 7 and 19, and the line of magnetic force S forcibly cuts the conveyance of the developer tl.

On the other hand, in the case of black development, the conveyance of the developer t1 by the above-mentioned upper developing device 3 is stopped, and the lower developing device rotates 30 times. J-7'' 12 is rotated, and the layer thickness of the developer t! on its surface is regulated by a doctor blade 18 before being conveyed, and the developer (developing brush) is formed directly on the surface of the photosensitive drum 1. It is developed by sliding into contact with the electrostatic latent image.

After this development is completed, the first to fifth magnetic poles 13 to 16 of the developing roll 5b are rotationally displaced to the positions shown by dotted lines. At this time, the first magnetic pole 13 and the magnet 20 of the doctor blade 18 closely face each other, and lines of magnetic force S are formed between the two 12.20, and the conveyance of the developer image t1 is forcibly cut.

As mentioned above, developer! When the conveyance of lp1m is stopped, the developer figt! is forced by the action of the magnetic force line S. , it is possible to reliably cut the developer without being affected by environmental conditions, developer fatigue, concentration, etc., and the magnetic properties of the developer are not limited, allowing for greater freedom in material development. .

It should be noted that the present invention is not limited to the above-mentioned embodiment, and it goes without saying that various modifications can be made within the scope of the invention.

〔Effect of the invention〕

As explained above, according to the present invention, the transport of the developer can be sufficiently cut, the developer is not affected by environmental conditions, developer fatigue level, concentration, etc., and the magnetic properties of the developer are not limited. This has the effect of increasing the degree of freedom in material development.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is an explanatory diagram showing a cut state of developer conveyance, and FIG. 2 is a configuration diagram showing a developing device. 7-11.13-16...Transport pole, 19.20...
Magnet, *1*fl...developer.

Claims (2)

[Claims] (1) In a device that has a plurality of transport poles for transporting the developer and stops the transport of the developer by displacing the positions of these transport poles, the developer transport A developing device comprising a magnet that is close to one of the transport poles when stopped and has a pole face of opposite polarity to the transport pole facing the transport pole. (2) The developing device according to claim 1, wherein the surface magnetic flux density of the magnet is 50 Gauss or more.