JPS6093471A - Developing device - Google Patents

Abstract

PURPOSE:To form pictures of good quality without white stripes by setting the half-amplitude level of a magnetic pole, which is placed in an aperture part of a developing vessel, of a magnetic member to a specific ratio to the aperture width of the developing vessel to cause a great agitating action without providing an agitating mechanism. CONSTITUTION:A magnetic body 20 is provided as the magnetic member in the position of a magnetic pole S2 in the lengthwise direction of a magnet roller 2, and a half-amplitude level 23 of the magnetic pole S2 is set to 40-80% of an aperture width 11 of a hopper. Therefore, a tuft 24 is formed in a wide range to strength the diffusing action of a toner current E; and when the toner current E is circulated once to try to contact with a sleeve 1, it is agitated by the diffusing action of the tuft 24, and a toner block is loosened, and a surface layer is not generated. As the result, sufficient trioelectrification is given to the whole of a toner 5, and a sufficient quantity of toner is supplied to a blade part 3, and generation of white stripes is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION In other words, the present invention relates to a developing device that uses a magnetic developer and includes a magnet in a developer carrier.

Generally, a developer is carried on the developer carrier by the magnetic force of a magnet included in the developer carrier, and an electrostatic 1Vt image is generated by F.
1) Champing, in which the developer layer is not brought into direct contact with the electrostatic latent image holding surface, and the developer is selectively flown onto the holding surface by the '1L field of the electrostatic iWi image. 11) Conductive magnetic developer 1; Magne dry method in which a magnetic brush is formed using a conductive magnetic developer and developed by bringing it into contact with an electrostatic li~image retainer 1j; A magnetic brush method is known in which a developer having a magnetic carrier and a magnetic carrier is directly supported on a former developer carrier, and this is rotated to develop an electrostatic latent image on the surface of an electrostatic latent image carrier. ing.

Among the various insertion and development methods described above, the magnetic dry method, the magnetic brush method f:I, the developer is applied to the electrostatic latent image holding surface in both fii areas (the area where toner should originally be deposited), and the written image is Because toner contacts without distinction between areas (areas to which toner should not originally adhere), toner adhesion also occurs in non-image areas, making it impossible to avoid the occurrence of so-called ground force blur. The method described in Japanese Patent Publication No. 41-9475) is an extremely effective method in terms of preventing ground force blur because the toner layer and the electrostatic image holding surface are not in contact with each other and are developed with a gap between them. .

By the way, in a two-component development method using toner and a magnetic carrier, such as the above-mentioned magnetic brush method, since the magnetic carrier constantly stirs the toner, blocking of the toner is prevented and images with uniform density are obtained even in solid images. can be obtained. However, the one-component development method such as the jumping development method has the disadvantage that toner blocks occur, and particularly in solid image areas, band-like density unevenness of thin density occurs in the vertical direction of the image.

Conventionally, in the dual one-component development method, a stirring bar was provided as a means to prevent this type of density unevenness (hereinafter referred to as "white spot"), and it was adjusted to the rotational speed of the developer carrier. It is known that the developer is stirred once in the developer container by rotating the stirring rod at a fixed ratio. Another method is to increase the number of magnetic poles (specifically, 2 to 2) at the opening of the developer container of the magnetic roller.
(about 4 poles), there are also known devices that increase the agitation effect of the toner in the developer container. However, in this case,
When used in a small-diameter developer carrier such as 2Q@i+n, increasing the number of magnetic poles is disadvantageous in terms of cost, and there are manufacturing problems such as arranging a large number of magnetic poles in a narrow area.

The present invention has been made in order to eliminate the above-mentioned drawbacks, and provides a developing device that can obtain high-quality images without white spots even in a small-sized developing device that does not require a stirring mechanism that requires a driving means. The aim is to provide the following.

In order to achieve the above object, the present invention includes a developer carrying member containing a magnetic part having a plurality of magnetic poles, which is disposed in the open part of the developer container, and the magnetic part has a plurality of magnetic poles. One-component magnetic development is applied to the carrier by widening the half width of the magnetic pole for simultaneous development and general transport located within the opening 11 of the developer container to 40% or more and 80% or less of the opening width of the opening. It is designed to carry and transport the agent.

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

First, the toner block phenomenon that causes the above-mentioned white streaks will be described based on FIGS. 1 and 2.

The figure shows a general developing device for one-component development. Here, a longitudinally cylindrical developer carrier (hereinafter referred to as a sleeve) 1 contains a magnet Rho/l/2 as a magnetic member having a smaller diameter, and the sleeve 1 also carries a magnetic developer (hereinafter referred to as a sleeve). The magnet roller 2 is rotatably disposed in an opening 6 formed at the bottom of a developing container serving as a developing container that stores toner 5 (referred to as toner). different magnetic poles S1 + Nl +
S2 + N2 is magnetized and does not rotate itself. Furthermore, in order to regulate the thickness of the toner layer 50, a long blade 3 made of a magnetic material such as iron is attached to the sleeve 1.
It is also necessary to transfer the toner on the sleeve 1 to an electrostatic image holder (photoreceptor) (not shown) provided close to the surface of the sleeve 10. A bias power supply 7.8 for setting AC and DC voltages is connected to sleeve j.
Ru.

Therefore, when the developing device color having a series-like configuration is activated, the sleeve rotates in the direction of the arrow. Then, the toner 5 is coated in a thin layer on the sleeve 1 by the fly 3, and is carried to the developing area (around the magnetic pole 81 of the magnet roller 2), where it develops the latent image on the electrostatic image carrier (not shown). do.

On the other hand, the toner 5 in the hopper 4 flows as shown by the arrow 13 due to the rotation of the sleeve and the influence of Nl p S2 of the magnetic roller 2. However, if the degree of aggregation of the toner 5 increases during this flow, some toner blocks with high density and lack of fluidity may be formed partially in the cutting direction in the hopper 4.

FIG. 2 shows the state of the toner block 9. The toner block 9 flows as shown by arrow C as the sleeve 10 rotates, but there is a surface layer 10 with a particularly high degree of aggregation. Therefore, triboelectric charge (amount of triboelectric charge) due to friction with the sleeve 1 is not uniformly applied to the entire toner 5, and some portions do not have sufficient triboelectric charge. Furthermore, since the toner block 9 is in the form of a single lump of toner, there are portions where the blade 3 is not sufficiently supplied with toner.

For the above reasons, toner coating on the sleeve 1 is not uniformly performed, which causes white streaks to occur.

Next, using FIG. 3, the reason why the above-mentioned toner block occurs will be explained from the relationship with the half width of the magnetic pole S2. FIG. 2A shows the state of toner flow caused by the unevenness 14 on the surface of the sleeve 1 caused by the magnetic pole S2 located in the hopper opening 6, and by the influence of the magnetic poles N1 and S2.

FIG. 1 (1)) shows a magnetic flux density distribution curve showing the strength of the radial component of the sleeve 10 of the magnetic field formed on the sleeve 1 by the magnetic pole S2. Conventionally, magnetic flsz
There was only one in which the half-value width (that is, the half-value width of the above-mentioned distribution curve) 13 had a small spread (about 30% or less) with respect to the opening width 11 of the hopper opening 6. Therefore, the toner spikes 14 were small and formed only in a narrow range. Therefore, the action of the standing spikes 14 to diffuse the toner flow 1) is not sufficient, and even when the toner flow 1) goes around and comes into contact with the sleeve 1 again, it remains almost undisturbed and flows to the blade 3 without being stirred. It will be transported towards. As a result, as described above, toner blocks are likely to occur, a surface layer is formed, and white streaks are likely to occur.

Therefore, the present invention takes measures to make the half width of the magnetic pole S2 larger than the opening width of the developer container opening.

FIG. 4(a) is a schematic diagram showing an embodiment of the present invention.

This means that the magnet l-o −= la2 as a magnetic member
In the longitudinal direction, a magnetic body 2 is further placed at the position of the magnetic pole S2.
It is not necessary to set 0. Then, as shown in the magnetic flux density distribution curve in FIG. 3(1)), the half-value width 23 of the magnetic pole S2 becomes clearly wider than the half-value width 13 shown in FIG. 3(b). Therefore, the standing spikes 24 are formed over a wide range, and the effect of diffusing the toner flow E becomes stronger. Therefore, when the toner flow goes around once and tries to come into contact with the sleeve 1 again, the toner flow 1) is agitated by the diffusion effect of the spikes 24, and the toner blocks are loosened, so that the above-mentioned surface layer is no longer formed. As a result, sufficient triboelectric force is applied to the entire toner 5, and since the toner flow E is stirred, it is possible to supply enough toner to three parts of one blend, and white streaks are prevented. It is possible to prevent the occurrence of

Next, based on the following experimental results, the half width 2 described above;
The case where the ratio of 3 to the opening width J1 is specifically set will be described. The diameter of the magnet roller used in this experiment was 18zzIII+, the diameter of the sleeve was 20Ω, and the opening width of the hopper was 145° C. above the sleeve surface centered on the rotation axis of the sleeve.

Table 1 shows the relationship between the half width 230 ratio It of the magnetic pole S2 to the opening width of the hopper and the degree P of white streak occurrence, which was obtained through the above experiment. As shown in the same table, in this experiment, the degree of white streak occurrence P was determined by expressing the temperature relative to the four values of the ratio 1 (1).
× indicates poor, ◯ indicates good, and ◎ indicates very good.

Therefore, from the results shown in the same table, the width of the magnetic body 200 or the position of τ1 is determined so as to have a half-value width of 40% or more.

Since the magnetic pole N is also present in the opening 6, it is practically impossible to set R=80% or more, taking into consideration the problem of magnetizing the sleeve 1. Therefore, by setting Il=40% or more and 80% or less, the above-mentioned effects can be obtained.

In the embodiment shown in FIG. 4(a), the magnetic material 2o is provided on the magnet roller 2 as a means of widening the half-width, but other than this, for example, the method of magnetizing the magnet roller 2 may be changed. Accordingly, the same effect can be obtained by forming the magnetic pole S2 over a wide range or strongly.

As explained above, in the present invention, the half-width of the magnetic pole located at the opening of the former developing container in the magnetic section is 40% relative to the opening width of the developing container.
% or more and less than 80%, it is possible to avoid the need for a complicated stirring mechanism (which would result in a large stirring action, and also to allow the development device to be so small that it would be impossible to provide the above mechanism. It has particularly high usability, and therefore has a very excellent effect of being able to obtain high-quality images without white streaks.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing the developing device and the flow of toner inside it, FIG. 2 is a schematic explanatory diagram showing the developing device and toner blocks formed inside it, and FIG. FIG. 3(b) is a schematic explanatory diagram showing toner spikes and toner flow, and FIG. 4(a) is a magnetic flux density distribution curve on the sleeve generated by the magnetic pole S2.
) is a schematic explanatory diagram showing one embodiment of the present invention, and FIG. 4(b) is a wide magnetic flux density distribution curve obtained by the present invention. l...Developer carrier (sleeve) 2...Magnetic roller 3...Blade 6/Developer container (hopper) opening 11...Developer container (hopper) opening width 20...Magnetic material 23 ...Half price・1. .

Claims (1)

[Claims] A developer carrier containing a magnetic part having a plurality of magnetic poles is disposed in one opening of the developer container, and a one-component magnetic developer is carried on the carrier and the developer is delivered to the development area. In a developing device configured to transport developer, among the magnetic poles of the magnetic member, the half width of the magnetic flux density of the magnetic pole for transporting the developer located inside the opening of the developer container is set to 40% of the opening width of the opening.
A developing device characterized in that the ratio is above and below 80%.