JPS5945152B2 - Dry developing device for electronic copying machines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry developing device for an electronic copying machine.

Conventionally, this type of developing device has been put into practical use with a single developing roller that applies developer to the recording photoreceptor on which an electrostatic latent image is formed, but the gradation expressivity of copies is poor. It has the following drawbacks.

Furthermore, in order to increase the speed, it has been conventionally considered that a plurality of developing rollers are provided along the photoreceptor, thereby substantially increasing the developing time for the photoreceptor. In such a multi-stage development method, in which the developer is transferred sequentially and developed,
It is necessary that the developer be transferred smoothly between the cylindrical outer peripheral surfaces. Specifically, a cylindrical sleeve made of non-magnetic material is provided around the outer periphery of a rotating magnetic roller, and in a multi-stage phenomenon sleeve system in which multiple sleeves are arranged, developer is transferred between adjacent sleeves. In order for this to occur smoothly, it is necessary to match the number of poles of adjacent magnetic rollers, and to ensure that different poles face each other at the closest opposing portion, and the rotational speed of each magnetic roller must also be completely controlled. It is something that must be matched. Also,
Even when replacing the developer, it is difficult to completely remove the old developer, so some special measures must be taken. The present invention was made in view of the above points, and allows smooth transfer of developer between sleeves, allows the number of poles, rotational speed, and relative position of the magnetic roller to be freely set, and improves development efficiency. It is an object of the present invention to provide a dry type developing device for an electronic copying machine, in which agent replacement is easy, and speeding up or gradation expression can be easily improved as required.

An embodiment of the present invention will be described based on the drawings.

First, reference numeral 1 denotes a photoconductor, which is a recording medium on which an electrostatic latent image is formed, with the bottom surface serving as a latent image holding surface.This photoconductor 1 is often formed in the shape of a drum, but for convenience, it is flat. Illustrated as Note that the photoreceptor 1 may be belt-shaped. Ξ thin-walled cylindrical sleeves 3, 4, and 5 having smooth surfaces made of conductive non-magnetic material are fixed at predetermined intervals along the latent image holding surface 2 of the photoreceptor 1. It is set up as follows. Inside these sleeves 3, 4, 5 are cylindrical magnetic rollers 6 in which a plurality of magnetic poles are arranged alternately.
7 and 8 are provided so as to be driven and rotated counterclockwise. These magnetic rollers 6, 7, and 8 may each have the same shape, or may have different magnetic pole intervals or different rotational speeds as necessary. Next, each sleeve 3, 4, 5
At the top and bottom of the gap, cylindrical magnetic bodies 9, 10, 11, and 12 having magnetism such as iron and having roughened outer peripheral surfaces are provided so as to rotate clockwise. In particular, the distance between Hijikata's magnetic bodies 9, 10 and the photoreceptor 1 is set to be larger than the distance between the sleeves 3, 4, 5 and the photoreceptor 1. Further, a magnetic body 13 whose position can be freely shifted in the horizontal direction is provided on the side of the sleeve 5 at the right end. Further, a developer supply section 15 is provided on the side of the left sleeve 3 for storing a developer 14 such as magnetic toner or a mixture of magnetic carrier and toner. Next, the sleeves 3, 4, 5 are supplied with V by the divided bias circuit 16.
Bias potentials are applied with the relationship: 3>V2>V1. The divided bias circuit 16 includes a power supply 17 and three voltage dividing bodies 1 such as a Zener diode, a varistor, and a resistor.
8 and more. In such a configuration, the photoreceptor 1, on which a latent image has been formed in the previous charging and exposure process, moves to the right, and the magnet rollers 6, 7, and 8 rotate counterclockwise. Therefore, the developer 14 that is magnetically attracted from the developer supply section 15 and adheres to the outer circumferential surface of the sleeve 3 moves in the opposite direction to the rotational direction of the magnetic roller 6 according to a known principle.
Since the magnetic body 9 provided close to the sleeve 3 is magnetized by concentrated magnetic flux due to electromagnetic induction by the magnetic pole of the magnet roller 6, the developer 14 on the sleeve 3 is magnetized by the magnetic body 9.
The developer 1 moves upward and falls on the right side of this magnetic material 9.
4 is attracted to the surface of the sleeve 4 on which the magnetic roller 7 is provided, and moves in the clockwise direction. Such an action is similarly performed between the sleeves 4 and 5 provided with the magnetic body 10. In addition, during normal development, the magnetic material 13
Since the developer 14 on the sleeve 5 moves away from the sleeve 5, the developer 14 on the sleeve 5 advances to the position of the magnetic body 11, which is provided close to the sleeves 4 and 5 at an equal distance. Therefore, the developer 14 transferred to the magnetic body 11 under the influence of both the magnet rollers 7 and 8 transfers to the surface of the sleeve 4. The same applies to the magnetic material 12, which is smoothly transferred from the sleeve 4 to the sleeve 3.
The developer 14 is transferred in this way, but the developer 14 is electrostatically attracted in the vicinity of the photoreceptor 1 of the sleeves 3, 4, 5 according to the latent image potential of the latent image holding surface 2. The image is then developed.

For example, the traveling speed of a selenium photoreceptor is 200mm/? C
Assume that the latent image potential in the dark area is 800V1 and the latent image potential in the bright area is 60V. And the bias potentials V3, V2, Vl for the sleeves 3, 4, 5 are 400, 300V.
, 220V. At this time, since the difference between the latent image potential and the bias potential is a substantial potential difference that acts on the attraction of the developer 14, high-density development is not performed all at once even in dark areas, but high-density development is gradually performed. Since the development progresses in a manner similar to that shown in FIG. Moreover, multiple sleeves 3, 4, 5
Because of this, the speed can be much increased compared to a system with only one sleeve. Next, when removing the developer 14 for replacing the replacement agent 14 of the developer 14, the magnetic body 1 is removed.
3 close to the sleeve 5.

The developer 14 on the sleeve 5 transfers to the surface of the magnetic material 13 according to the above-mentioned principle, but on the right side it falls by itself or by a scraping blade, and if a tray is placed at the bottom, it becomes a magnet. They are sequentially removed by the rotation of the rollers 6, 7, and 8. Such a means is not limited to the multi-stage sleeve system, but can also be used in a developing device provided with only one sleeve. In the above embodiment, the magnetic bodies 9 and 10 are not brought close to the photoconductor 1, but if the main purpose is to increase the speed, the magnetic bodies 9 and 10 are also brought close to the photoconductor 1, so that the magnetic bodies 9 and 10 are not brought close to the photoconductor 1. The development range may be expanded.

Further, by changing the rotational speed of the magnetic rollers 6, r, 8, the layer thickness of the developer 14 on each sleeve 3, 4, 5 changes, and it is possible to further improve gradation expression. Furthermore, the shapes of the magnetic bodies 9, 10, 11, and 12 are not limited to cylindrical shapes, and it is not an essential condition that they be rotated. Although the photoreceptor 1 has been described in the above embodiment, any material on which an electrostatic latent image can be formed may be used. In the present invention, as described above, a plurality of sleeves each having a built-in magnetic roller are provided, and a magnetic material is provided close to these sleeves, so that the developer can be smoothly transferred between the sleeves. , it is not necessary to consider the number of poles, relative position, rotation speed, etc. of the magnetic roller, developer can be easily removed using magnetic material, and it is also necessary to increase speed and improve gradation expression. This has the advantage that it can be easily carried out depending on the situation.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a longitudinal side view, and FIG. 2 is a side view of a portion of the device when the developer is removed. 1...Photoreceptor, 3-5...Sleeve,
6-8...Magnetic roller, 9-13...
magnetic material.

Claims (1)

[Claims] 1. A magnetic roller having a plurality of magnetic poles and a cylindrical sleeve made of a non-magnetic material provided on the outer periphery of the magnetic roller are provided so as to be relatively rotatable, and the plurality of sleeves are arranged so that electrostatic latent images are formed on the sleeves. fixedly arranged along the recorded recording medium,
A dry developing device for an electronic copying machine, characterized in that a rotating magnetic body is provided between these sleeves.