JPH0313977A - developing device - Google Patents

Abstract

PURPOSE:To improve the circulating fetch of developer, to prevent the occurrence of toner aggregate caused by sliding, and to stabilize an image by sealing the inner and the outer sides of the developing container of a developing sleeve by means of a magnet brush including a longitudinal direction and both edge parts. CONSTITUTION:The device is provided with a magnet plate 24 which does not come into contact with the both edge parts of the developing sleeve 21 along its part of peripheral surface. Then, the sleeve 21 is magnetized by a magnet roller provided in the sleeve 21, and the magnet brush constituted of developer is formed on the hollow part between the sleeve 21 and the developing container. Thus, along the sleeve 21, developer leaking from the space between the sleeve 21 and the container side wall 2a is inhibited. In addition, as an auxiliary seal member, magnets 25 are provided on both edge parts, and developer leakage is prevented by the magnet brush formed on the hollow part between the sleeve 21 and the container. Therefore, the developer circulation is improved and the occurrence of toner scattering and aggregate is prevented; moreover, a stable image can be obtained for a long time.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a developing device for developing an electrostatic latent image formed on an image carrier by an electrophotographic method or an electrostatic recording method. be.

[Prior art]

In order to prevent the developer from leaking out from the end of the developing sleeve, it has been conventional practice to press a sealing member such as felt or sponge onto the end of the sleeve.

It also prevents excessive developer from overflowing into the outlet of the developer from the developer container toward the development area and the developer return port from the development area, or from scattering as the sleeve rotates. To do this, apply relatively strong pressure to the developer layer on the sleeve of the plastic sheet.

Pressing a rubber sheet or the like has also been conventionally practiced.

On the other hand, in recent years, in order to obtain high-definition image quality, especially in color image forming devices, toner particles have become smaller, and in order to improve color mixing during heat fixing, toners that use polyester resin as a binder have become available. came into use. Furthermore, an alternating electric field is formed in the developing area in order to improve the developing ability.

[Problem that the invention is trying to solve]

However, in the conventional configuration, a small amount of small-particle developer enters the peripheral surface of the end seal member and the developing sleeve. Therefore, when the developing device is used for a long period of time, this developer causes fusion and aggregation between the end seal member and the sleeve. In particular, when polyester resin is used as a binder for toner, or when the toner has a small particle size,
This phenomenon is remarkable.

Some of these aggregates will be taken into the developer, but if the aggregates are large, they will be caught by the developer layer regulating blade, creating areas where the developer is not coated on the developing sleeve, resulting in a white image. Streaks may occur.

In addition, if the aggregates are small, the developing ability is improved by the alternating electric field, so they are developed together with the developer, and especially in the case of a solid image, the developed aggregates cause transfer gaps, causing the image to deteriorate. A white spot-like defect occurs on the top, significantly reducing the image quality. If the adhesion of the end seal member is increased in order to prevent this, extremely large stress will be applied to the developing sleeve, increasing the load on the developing sleeve drive motor, and will completely prevent developer from entering over a long period of time. It was difficult to prevent it.

Furthermore, when the developer used for development is taken into the developer container by the rotation of the sleeve, it comes into contact with the scattering prevention member that touches the developer layer relatively strongly.

At such times, toner that has weak adhesion to the magnetic particles (carrier), toner that was originally not sufficiently charged, toner that was oppositely charged, etc., becomes liberated from the carrier and scatters. In particular, toner for full-color image formation is made with a polyester binder composition that has a small toner particle size and exhibits sharp melt characteristics, taking into consideration high image quality, high color mixing properties, etc., as described above. Such toners have excellent image quality, but the triboelectric charging ability of the toner itself changes (decreases) due to environmental changes (especially in high humidity).
Shi, it was easy to scatter. Furthermore, such toner tends to form minute aggregates even when it comes into relatively strong contact with the scattering prevention member.

Further, if excessive developer comes out from the outlet of the developer container, the above-mentioned toner tends to scatter. Unless the developer layer thickness at the outlet is regulated so that the mechanical stress is relatively small, the above-mentioned toner is likely to deteriorate.

The present invention aims to solve these disadvantages.

[Means to solve the problem]

According to the present invention, the above goal can be achieved by taking the following measures.

It has a developer container containing a developer containing magnetic particles, and a developer carrier that is rotatably supported by the developer container and has a magnet inside to support and transport the developer on its surface. In the developing device, a first magnetic member is disposed at both ends of the developer carrier along at least a part of the circumferential surface of the developer carrier with a gap between the surface and the developer carrier. , and a portion where the developer exits the developer container;
In the part returning to the developer container, along the longitudinal direction of the developer carrier, there are provided a second and a third, respectively, with the surface of the developer carrier and the gap.
, and the first magnetic member is arranged. Second. A developing device characterized in that the third magnetic member is positioned in a magnetic field formed by a magnet disposed inside the developer carrier.

〔Example〕

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

FIG. 1 is a sectional view of a first embodiment in which the present invention is applied to a copying machine using a drum-type photoreceptor. Although not shown in the figure, a charging mechanism, an image exposure mechanism, a transfer mechanism, a cleaning mechanism, a static elimination mechanism, etc., which are well-known electrophotographic processes, are arranged around the photosensitive drum 1.

The developing device develops a latent image formed on a latent image carrier 1 such as a photoreceptor or dielectric by electrophotography, electrostatic recording, etc. It is configured to include a developing sleeve 21° as a developer carrying member, a blade 23 as a developer layer regulating member, and the like. That is, an opening is formed in the developing container 2 at a position close to the latent image carrier 1, and the developing sleeve 21 is rotatably provided in this opening. A blade 23 is attached with a predetermined gap therebetween, and a magnetic member IO is attached below the developing sleeve 21 with a predetermined gap provided therebetween. The developing sleeve 21 is made of a non-magnetic material, rotates in the direction indicated by the arrow during the developing operation, and has a magnet 22 fixed therein as a magnetic field generating means.
c (S pole) and a magnetic pole 22a that transports developer 41, which will be described later.
(S pole), 22b (N pole), 22d (N pole)
.

22e (N pole). Here, the polarities of the magnetic poles may be reversed.

The blade 23 includes a blade 23b made of a non-magnetic material such as aluminum or non-magnetic stainless steel, and a blade 23b made of iron.

A blade 23a made of a magnetic material such as magnetic stainless steel is integrated with the blade 23b so that the tip of the blade 23b is closer to the sleeve than the tip of the blade 23a. The sleeve is attached along the longitudinal direction with a predetermined gap between the sleeves, and this gap determines the amount of developer 41 conveyed on the developing sleeve 21 to the developing section, specifically, the amount of the developer 41 on the developing sleeve 21.
Regulate the thickness of 1.

The magnetic blade 23a forms a magnetic brush by receiving the magnetic force lines of the magnetic pole 22a, thereby helping the blade 23b to regulate the layer thickness and reducing the stress applied to the developer during regulation.

In this embodiment, both non-magnetic toner and magnetic particles pass between the tip of the blade 23 and the surface of the developing sleeve 21 and are sent to the developing section.

The developer 41 is a two-component developer consisting of a non-magnetic toner 40 and magnetic particles (carrier).

This developer 41 is transported to the developing section 101, and the magnetic pole 2
Since 2d and 22e are configured to have the same polarity (N pole), a repulsive magnetic field is generated between them. Therefore, sleeve 2
The developer conveyed to the magnetic pole 22d while being held at the magnetic pole 22d is removed from the sleeve 21 by the action of this repulsive magnetic field, stirred and mixed by the first stirring and conveying means 51, and transferred to the magnetic pole 22d.
The developing sleeve 21 is newly supplied with developer near 2e.

That is, the developer that has undergone the development history on the sleeve 21 is peeled off and thoroughly mixed, and new developer is transferred to the sleeve 21.
Since the image is constantly supplied to the image sensor, it is possible to stably obtain good images.

Next, below the sleeve 21, which is the main point of the present invention,
The magnetic member 10 provided along the longitudinal direction of the sleeve at a position slightly downstream of the magnetic pole 22d in the rotational direction of the sleeve may be made of a magnetic material such as iron or a magnet.

In this example, the thickness is 0.5 mm and the width is 5 mm.
iron parts were used. As in the present invention, the magnetic poles 22d and 22
In a developing device that uses a repulsive magnetic field with the magnetic poles e having the same polarity, the lines of magnetic force due to the magnetic pole 22d do not wrap around in the direction of the magnetic pole 22e, but thicken (concentrate) toward the magnetic pole 22c, which has a different polarity, and the lines of force from the magnetic pole 22d to 22c Magnetic flux density increases.

Therefore, in the configuration in which the magnetic member 10 is not provided as in this embodiment, the spikes of the developer 41 formed on the sleeve 21 near the position of the magnetic pole 22d are large and long, extending in the direction of the magnetic pole 22c, and becoming more dense. In addition, it acts as a barrier against the developer that is restrained and conveyed from the developing section 101 to the sleeve 21 and is about to be collected in the developer container, and the toner may be scattered due to impact or the developer 41 may not enter the developer container. It was confirmed through experiments that the uptake was poor.Furthermore, in experiments using the aforementioned color toners, especially polyester toners that tend to form into paint, it was found that dense, large and long spikes of developer near the magnetic pole 22d were found in the developing container. It has also been experimentally confirmed that strong contact and rubbing with the lower seal member 11 causes the toner to be liberated, melted and agglomerated, and the agglomerates are successively mixed into the developing container, resulting in an abnormal image appearing on the actual image.

Therefore, when the magnetic member 10 is provided as in the present embodiment of the present invention, the lines of magnetic force caused by the magnetic pole 22d do not concentrate greatly toward the magnetic pole 22c, but some of the lines of magnetic force concentrate on the magnetic member 10 and then form a large arc. Since the magnetic flux flows toward the magnetic pole 22c, a large magnetic flux is not formed from the magnetic pole 22d to the magnetic pole 22c.

Therefore, the spikes of developer 41 formed on the sleeve 21 near the position of the magnetic pole 22d in cooperation with the magnetic member IO are concentrated on the magnetic member 10, and a magnetic sealing effect is produced by the magnetic brush, which leads to the direction from the magnetic pole 22d to the magnetic pole 22c. The spikes of developer from the developing section 101 to the sleeve 2 are small.
It was confirmed that the layer thickness of the developer that was restrained and conveyed by the developer container 1 and about to be collected in the developer container did not increase (and that the spikes of developer did not come into contact with the lower seal member 11 of the developer container).

Here, the magnetic brush formed between the magnetic member 10 and the magnetic pole 22d has a static restraint force such as a magnetic restraint force and a mirror force, and the sleeve 2
Due to the balance of frictional force caused by the rotation of No. 1, some of the toners accumulate in the magnetic member, while others are sequentially taken into the developing container and fall into the container due to the repulsive magnetic field.

In addition, since the magnetic brush formed between the magnetic pole 22d and the magnetic member 10 acts as a sealing member for the developer itself which rotates sequentially, the developer is transported from the developing section 101 to the sleeve 21 and is not collected in the developer container. It acts as a soft sealing member for the developing agent, and exhibits a good sealing effect without causing the toner to scatter due to impact or impairing the uptake of the developing agent 41 into the developing container. This was confirmed by experiment.

It was also confirmed that, as in the above-mentioned comparative example in which the member 10 was not provided, free agglomerates of toner were formed, agglomerates were mixed into the developing container one after another, and did not appear as an abnormal image on the actual image.

Next, the present invention will be explained regarding the positional relationship between the magnetic member 10 and the developing sleeve 21.

In FIG. 2, the rotation center of the sleeve 21 and the magnetic pole 22d
, 22e are the angles formed by each straight line connecting the pole centers of the sleeve 21, and furthermore, the angles formed by the respective straight lines connecting the rotation center of the sleeve 21, the pole center of the magnetic pole 22d, and the closest point of the magnetic member 10 to the sleeve 21 are θ1. Assuming θ2, first of all, if θ2 = 0 or negative (here, negative means that the position of the magnetic member 1O is upstream of the magnetic pole 22d with respect to the rotational direction of the sleeve 21), then the lines of magnetic force due to the magnetic pole 22d will cause the magnetic member 10 will be strongly concentrated. Therefore, the spikes of the developer 41 formed on the sleeve 21 near the position of the magnetic pole 22d are thick (strong (dense), and from the developing section 101 to the sleeve 21
1 and becomes a complete barrier to the developer trying to be collected into the developer container, and the developer is not taken in and overflows out of the container, which is contrary to the intention of the present invention.

Furthermore, as the magnetic member 10 is located downstream of the magnetic pole 22d with respect to the rotational direction of the sleeve 21 (closer to the magnetic pole 22e), the concentration of magnetic lines of force on the magnetic pole 22d becomes weaker, and the magnetic sealing effect becomes weaker.

According to experiments conducted by the present applicant, it has been found that in the range of 0 to θ2<5°, the above-mentioned magnetic sealing effect, developer uptake effect, and toner release scattering effect are not sufficient and are not satisfactory. In addition, it was found that the magnetic member has no effect at all in the range of %θ1 to θ2, and the range in which the magnetic seal effect, developer uptake effect, and toner release scattering effect can be fully exhibited exists in 5°≦θ2≦Aθ1. This was confirmed by experiment.

Next, the relationship between the gap between the magnetic member IO and the developing sleeve 21 and the gap between the developer regulating member blade 23 and the developing sleeve 21 will be described.

In FIG. 2, the side gap is designated gz+g+. The amount (thickness t) of the developer 41 formed on the sleeve 21 is g! regulated by. t is approximately equal to gl.

Further, in the magnetic brush portion formed between the magnetic pole 22d and the magnetic member 10, as described above, a portion of the developer accumulates on the magnetic member 10 side, so that the magnetic brush portion is substantially connected to the sleeve 21 and the magnetic member 10.
The thickness of the developer passing between 0 becomes smaller than g2.

Therefore, in an experiment using a developing device configured according to the present invention, it was found that g+<g2 for good developer uptake.

Next, both ends of the developing sleeve will be explained with reference to FIGS. 1 and 3.

According to the present invention, at both ends of the developing sleeve 21,
A plate-shaped magnetic member 24 is disposed around the developing sleeve 21 so as to surround the members 10 to 23 along the sleeve rotation direction, and is attached to the side wall 2a of the developer container. The magnetic member 24 is an iron plate, a nickel plate, or a cobalt plate with a thickness (1) of about 0.2 to 1 mm.

It is preferable that the magnet be made of a ferromagnetic material such as a plate made of or an alloy thereof. These materials are (1/2)・(BH)
max is 0.7 J/rd or less. (BH)max is the maximum value of BXH and indicates the maximum energy product, where B is the residual magnetic flux density and H is the coercive force. The gap (L) between the developing sleeve 21 and the circumferential surface is not limited to 0.
．． The thickness is appropriately selected within the range of 3 to 2 mm.

In this embodiment, in order to form a gap (L) between the magnetic member, that is, the magnetic plate 24 and the circumferential surface of the developing sleeve 21,
Although it is annular in shape and has a width (W) that is co-centered with the developing sleeve 21, its shape is not limited to the shape shown in the drawings, and the designer can create various shapes as desired. I can do it. What is important is that the magnetic plate 24 is arranged along the circumferential surface of the developing sleeve 21 in a non-contact manner. Further, the angle that the side surface of the magnetic plate 24 forms with the normal to the circumferential surface of the developing sleeve 21 is preferably 45 degrees or less in order to more reliably prevent leakage of the developer. In the illustrated embodiment, the angle is 0 degrees, that is, the side surface of the magnetic plate 24 is
It is perpendicular to the circumferential surface of 0b.

Further, although it is preferable that the magnetic plate 24 be disposed over the entire circumference of the developing sleeve 21, it does not have to be formed over the entire circumference of the developing sleeve 21 as shown in FIG.

In this way, by arranging the magnetic plates at both ends of the developing sleeve 21, the magnetic plate 24 is magnetized by the magnetic force of the magnetic roller 10a provided inside the developing sleeve 21, and the magnetic plate 24 is connected to the magnetic roller 22. A magnetic circuit is formed between them, and the magnetic field is concentrated at the tip of the magnetic plate 24 on the side of the developing sleeve 2I, so that a dense magnetic brush formed by the developer is formed in the gap (L) between the magnetic plate and the developing sleeve 21. is formed. The magnetic brush functions to prevent the developer from entering the bearing 30 along the developing sleeve 21 through the gap between the developer container side wall 2a and the surface of the developing sleeve 21. In other words, the gap between the magnetic plate 24 and the developing sleeve 21 (
The developer-based magnetic brush formed in L) functions as an end sealing member.

In particular, when the magnetic pole arrangement is as in this example, 22
The air gap area (L
), the formation of a magnetic brush by the developer tends to be weaker than in other cases. Therefore, if developer enters the bearing 30 from such a gap, this developer will be captured. For this purpose, a magnet 25 can be provided as an auxiliary sealing member.

The magnet 25 is an annular magnet formed along the circumferential surface of the developing sleeve 21 over the same area as the magnetic plate 24,
Rubber magnets and plastic magnets with magnet powder dispersed inside can be applied, and in this example, the inner surface is magnetized to the S pole and the outer surface is magnetized to the N pole. In particular, the developer from the 22d pole and 22e pole regions configured to seal against leaks. According to this embodiment, the developer captured by the magnet 25 forms a magnetic brush in the gap between the magnet 25 and the surface of the developing sleeve 21, and then enters from the 22d pole and 22e pole regions. It is also effective to seal using an elastic body such as a plastic sheet that is in contact with the sleeve as an auxiliary sealing member.

In this embodiment, the magnet disposed inside the developer carrier has five repelling poles, but
The present invention relates to the configuration and method of the above embodiments.

It is not limited by dimensions or the like.

Further, as another embodiment, a case where the present invention is applied to a full-color image output device will be described. In this case, it is required to reproduce everything from solid areas in high-density areas to minute parts, and even higher image quality is essential. In order to cope with this, a toner with finer particle size is used to increase resolution and improve fixing performance, and a sharp melt toner is required. The inventors of the present invention have conducted numerous experiments and discovered that good images can be obtained when the following developer is used.

1. The non-magnetic toner particles of the developer include toner particles whose volume average particle size is M, and whose particle size is 90 volume percent or more, and whose particle size is 99 volume percent or more in the range O<γ<2M. Contains particles, and M is 12 μm or less.

2. As carriers which are magnetic particles, resin-coated ferrite particles (maximum magnetization 60
e m u / g ).

If the developer deviates from the conditions described in 1.2 above, the toner particles' triboelectric properties and cohesiveness will greatly change due to environmental changes (particularly changes in temperature and humidity), making it difficult to put them into practical use. .

However, since the developer (particularly toner) with the above characteristics easily fuses even with a slight stress, and also has a large effect on the transfer characteristics, it is recommended to use a developing device with the same configuration as in Example 1. It was confirmed that this method can prevent fusion, etc., and provide stable images over a long period of time.

The toner used polyester resin as its binder to improve the color mixing properties when the image was heated and melted and fixed.

Next, a method for measuring particle size distribution in the present invention will be explained. The measuring device is a Coulter counter TA-II type (
CX-1 and an interface (manufactured by Nikkaki) that outputs the number average distribution and volume average distribution using
A personal computer (manufactured by Canon) is connected, and a 1% NaCl aqueous solution is prepared using primary sodium chloride as an electrolyte.

As a measuring method, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and 0.5 to 50 mg of a measurement sample is added.

The electrolytic solution in which the sample was suspended was subjected to a dispersion treatment for about 1 to 3 minutes using an ultrasonic disperser, and the particle size distribution of particles of 2 to 40 μm was measured using a 100 μm aperture as an aperture using the Coulter Counter TA-II model. to find the volume average distribution. The volume average particle diameter is obtained from these determined volume average distributions.

In addition, the resistance value of the magnetic particles is measured using the measurement electrode area dc r
d. Using a sandwich type cell with an inter-electrode gap of 0.4 cm, an applied voltage E (V/cm) between both electrodes was applied to one electrode under a pressure of 1 kg, and the magnetic property was determined from the current flowing through the circuit. The method used is to obtain the resistance value of the particles.

Referring to FIG. 4, there is shown an overall schematic configuration of a full-color electrophotographic copying machine as an embodiment of an image forming apparatus to which the present invention can be applied.
A photosensitive drum 1 as an image carrier having an electrophotographic photosensitive layer on its surface is disposed approximately in the center of the copying machine, and is driven to rotate in the direction of arrow X (counterclockwise).

A one-shot electrifier A is disposed approximately directly above the photosensitive drum l, a rotary developing device B is disposed to the left of the photosensitive drum l, and a transfer device ( A transfer drum) 5 is disposed, and a cleaning device C is disposed on the right side of the photosensitive drum 1.

Further, an optical system is disposed in the upper part of the electrophotographic copying machine, and this optical system transfers the image of the document 0 on the transparent platen 7, such as a glass plate, to the charger A and the rotating type. Developing device 1
00 and is configured to project (slit exposure) onto the photosensitive drum 100 at the exposure unit 3 located between the two. Although any optical system can be used as such an optical system, in this embodiment, the first scanning mirror 111
second and third scanning mirrors E and 13 moving in the same direction at half the speed of the image forming lens F1;
It is equipped with 5. Since this optical system is a well-known slit exposure type optical system, detailed explanation will be omitted here.

The document illumination light source G is configured to move together with the first scanning mirror 11, and the color separation filter 17 is arranged between the fourth fixed mirror 15 and the exposure section 3.

The reflected light image of the document 0 scanned by the first Φ second and third scanning mirrors 11 and E-13 passes through the lens F, and then the fourth
The light is color-separated by a color separation filter 17 via a fixed mirror 15, and an image is formed on a photosensitive drum 100 at an exposure section 3.

Further, on the right side of the full-color electrophotographic copying machine, a fixing device I and a paper feeding device J are arranged, and the transfer device 5
Transfer material conveying systems 25 and 35 are provided between the fixing device I and the paper feeding device J, respectively.

In the above configuration, the photosensitive drum 100 includes the color separation filter 1
7, charging and exposing each separated color.

A series of image forming processes such as transfer and cleaning steps are performed by a blower A, a nine-rotation developing device B with an optical system, a transfer device f5, and a cleaning device C.

Here, the above-described rotary developing device B has a rotary support body 30
0, and at an angular interval of approximately 90' to this rotating support 300,
In this embodiment, yellow developing unit 10IY,
Magenta developer units) IOIM.

The four developer units (cyan developer unit 1OIC and black developer unit 1oIBk) are provided, and the latent images of each color separated and formed on the surface of the photosensitive drum 100 are transferred to the corresponding developer unit. It is visualized using a developer. That is, by controlling the rotation angle of the rotating support 300 in approximately 90° increments, the developing roller of a desired developing unit is moved to a predetermined developing position facing the photosensitive drum 100, and development is performed by this developing unit. be done. During development, an oscillating voltage such as an AC voltage, an AC voltage superimposed on a DC voltage, a sine wave, a rectangular wave, etc. is applied to the developing roller as a developing bias voltage, and the process of repeatedly attaching and detaching toner from the photosensitive drum is performed. After that, the latent image is developed. In addition, in FIG. 5, the black developing unit 101B is connected to the photosensitive drum 1.
This shows the state where the two are located opposite to each other.

The developed image in this way is transferred to the transfer device 5.
The image is transferred onto a transfer material P supplied from a paper feeder J. That is, the transfer device 5 typically has a transfer material P on its peripheral surface.
1, that is, a transfer drum 5b having a gripper 5a for gripping transfer paper, and this transfer device 5 is provided with a transfer drum 5b having a gripper 5a for gripping transfer paper, and this transfer device 5 receives paper from a transfer material cassette 31 or 32 of a paper feeding device J via a transfer material conveying system 35. The gripper 5 holds the tip of the transferred transfer material P.
a and rotate it to transfer the developed image of each color on the photosensitive drum 100. Note that a transfer charger 5C is arranged inside the transfer drum 5 in the transfer area.

(Thus, the transfer material P to which the developed image of each color, that is, the toner image formed by the developer has been sequentially transferred, is released from the gripper 5a and peeled off from the transfer drum 5b by the separating claw 8.

Next, the transfer material P peeled off from the transfer drum 5b is sent to the heat fixing device I by the transfer material conveyance system 25, and the toner image on the transfer material P is transferred by the fixing device I to the transfer material P.
The transfer material P is heated and fused onto the toner, and then the transfer material P is released onto the toner.

〔Effect of the invention〕

As explained above, with the above structure, the inside and outside of the developing container of the developing sleeve are sealed with magnetic curtains at both ends in the longitudinal direction, and the developer itself is well-circulated and taken in with less toner scattering from the developing device. Furthermore, it is possible to provide a highly durable developing device, and it is also possible to stably supply good images without creating toner aggregates due to rubbing.
Moreover, even after long-term use, there is an effect of providing a developing device that does not hinder the movement of the developer-carrying body and can always perform smooth developing operations.

In particular, when using a developer for full-color image output as in this example, in order to achieve high image quality, when using sharp-melt toner with small particle size that is prone to agglomeration, it is necessary to prevent the formation of toner aggregates. has a huge effect.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of one embodiment of the present invention, FIG. 3 is an end sectional view of the same embodiment, and FIG. 4 is an explanatory diagram of a color copying machine to which the present invention can be applied. 2 is a developing container, 21 is a developing sleeve, 22 is a fixed magnet, and 10.23a and 24 are magnetic bodies. A digit diagram

Claims (1)

[Scope of Claims] (1) A developer container containing a developer containing magnetic particles;
In the developing device, the developer carrying member is rotatably carried by the developing container and has a magnet therein to carry and transport the developer on its surface, wherein both ends of the developer carrying member include: A first magnetic member is arranged along the circumferential surface of at least a portion of the developer carrier with a gap between the surface and the developer carrier, and a portion where the developer exits the developer container and a portion where the developer returns to the developer container. second and third magnetic members are respectively disposed along the longitudinal direction of the developer carrier with a gap between the surface of the developer carrier and the first, second and third magnetic members, A developing device characterized in that the developing device is positioned in a magnetic field formed by a magnet disposed inside the developer carrier. (2) The developing device according to claim 1, further comprising an auxiliary seal member disposed adjacent to the first magnetic member. (3) The developing device according to claim 2, wherein the auxiliary seal member is an elastic sheet or a magnet. (4) The developer is 1/2M<γ<3/2, where M is the volume average particle size of the toner and γ is the particle size of the toner particles.
4. The developer according to claim 1, wherein the toner particles include 90 volume percent or more of toner particles in the range of M, 99 volume percent or more of toner particles in the range of 0<γ<2M, and M is 12 μm or less. Device. (5) The developing device according to claim 4, wherein the developer has a carrier having a weight average particle diameter of 30 to 80 μm and a resistance value of 10^7 Ωcm or more, and is resin-coated ferrite particles. (6) The developing device according to claim 4 or 5, wherein the binder of the toner is a polyester resin.