JPS63225273A - Developing device - Google Patents

Abstract

PURPOSE:To prevent loss of carrier particles and to permit formation of a good-quality image with high development efficiency by disposing a developing magnetic pole to face a latent image carrier and slowing down the dropping way of the magnetic flux density on the down stream side in the rotating direction of a developing sleeve. CONSTITUTION:The developing magnetic pole 3c is so set as to have the max. magnetic flux density in the part opposite to a photosensitive body, to weaken the magnetic force thereof sharply toward the upper stream side in the rotating direction of the developing sleeve 2 and to drop the magnetic force gently toward the down stream side. A developer layer, therefore, rises sharply just before the development region and is directly rubbed onto the surface of the photosensitive body 1, by which the toner detached from the carrier particles 7 generated by the movement arising from the napping of the develop layer is easily transferred to the photosensitive body 1. The detached toner is thereby prevented from splashing. The developer layer is napped and the developing sleeve surface is opened in the development region. Flying of the toner from the developing sleeve surface and the carrier particles is actively executed by alternating electric fields. Most of the toner existing in the development region are thereby subjected to the development and, therefore, the good-quality image having the extremely high development efficiency is obtd.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a two-component development type developing device that performs development using magnetic carrier particles and toner particles, particularly a developing device that applies an alternating electric field in a developing section. Regarding.

The present invention is a developing device that can be applied to various types of display devices for forming image records, printers, and facsimile electrophotographic devices.

[Conventional technology]

In a recording device such as an electrophotographic copying device, a two-component developer in which magnetic carrier particles and toner particles are mixed is supplied to a developer transporting carrier surface to form a developer push on the developer transporting carrier surface, When developing a latent image such as an electrostatic latent image or a magnetic latent image on the surface of the image carrier by the developer press, by applying an alternating electric field to the developer press, fine lines, points, differences in shading, etc. A developing method for obtaining clear, high-quality images that faithfully reproduce images has already been developed.

Even in electrophotographic copying devices, there is a demand for smaller and lighter devices due to the trends of the times. Even in a developing device using the above-mentioned developing method, a developer transport carrier (hereinafter referred to as a developing sleeve or simply a sleeve) is used to reduce the size and weight.
There is a need for smaller diameters.

In conventional devices, the diameter of the developing sleeve was φ20 or more, so it is possible to use a magnet with a relatively large diameter installed inside the developing sleeve, and there is a high degree of freedom in designing the magnet (e.g. It is easy to design the magnetic poles so that they have sufficient magnetic flux density to cover the entire development area.

Figure 2 is a cross-sectional view of the developing area of a conventional developing device with a relatively large diameter, Figure 2 a) is a diagram representing the state of carrier particles, and Figure 2 b) is a diagram representing the magnetic flux density distribution. be.

With a magnet having a large diameter, as shown in Figure 2, it is easy for the developing magnetic pole to cover the entire developing area while maintaining sufficient magnetic flux density, and the carrier particles are sufficiently raised in the developing area. As a result, the density of the developer decreases, and the toner and carrier particles are actively vibrated and ejected by the alternating electric field, making it possible to perform extremely efficient development.

Furthermore, since sufficient magnetic force can be obtained on the downstream side of the development area, carrier particles attached to the photoreceptor can be easily pulled back by magnetic force.

Therefore, it was possible to provide a developing device that has good developing characteristics and is free from adhesion of carrier particles.

[Problems to be Solved by the Invention] However, in the above embodiments, there is a limit to the miniaturization of the developing device and, by extension, the miniaturization of the electrophotographic copying machine. It is necessary to reduce the diameter of the developing sleeve. When the diameter of the developing sleeve falls below φ20, the diameter of the magnet installed inside will naturally become smaller, and the volume of the magnet will become extremely small. Therefore, it is difficult to produce a magnet with high magnetic flux density and wide width.

Furthermore, even if the sleeve diameter is larger, the magnet roll of the developing device, which consists of multiple magnetic poles such as a cutting magnetic pole, a conveying magnetic pole, and a developing magnetic pole, must be designed to suit the characteristics of each magnetic pole. As shown in Figure 2, it is almost impossible to set the width to be strong and wide.

If the magnetic force of the developing magnetic pole is reduced, it is difficult to prevent carrier particles from adhering to the photoconductor, and even if the magnetic flux density is the same as shown in Figure 3, the width of the magnetic pole is equally narrow on the upstream and downstream sides. Even in the case where the magnetic field is increased, the magnetic force on the downstream side of the developing area is insufficient, and it is difficult to prevent carrier particles from adhering to the photoreceptor.

In addition, as shown in Figure 4, tilting the magnetic pole toward the downstream side increases the magnetic force on the downstream side and prevents the adhesion of carrier particles. This is undesirable because it obstructs the flight of toner from the carrier particles on the surface or near the sleeve surface, reducing the developing efficiency.

(Object of the Invention) An object of the present invention is to provide a developing device that can solve the problem of a small-diameter developing sleeve and also improve the image quality of a developed image on a large-diameter sleeve.

SUMMARY OF THE INVENTION An object of the present invention is to provide a developing device that can significantly prevent loss of carrier particles and form high-quality images with high development efficiency.

(Summary of the Invention) According to the present invention, development is performed by applying an alternating electric field between a latent image carrier and a developing sleeve using a mixed developer containing carrier particles and toner. Because the magnetic poles face the latent image carrier and the magnetic flux density drops slowly on the downstream side in the rotational direction of the developing sleeve, the carrier particles in the developing area are sufficiently raised, resulting in good developing characteristics. In addition, since sufficient magnetic force can be obtained even downstream of the development area, it is possible to prevent carrier particles from adhering to the latent image carrier.

〔Example〕

FIG. 1 is a sectional view of a developing area of a developing device according to the present invention, FIG. 5 is an embodiment of the developing device according to the present invention, and FIG. 6 is a magnetic flux of a magnet used in the developing device of FIG. It is a density distribution map.

In FIG. 5, the latent image carrier 1 is an insulated drum for electrostatic recording or a-Se, Cds, Zn0z.

It is a photosensitive drum or photosensitive belt having a layer of photoconductive insulating material such as OPC, α-8i. The latent image carrier 1 is rotated in the direction of arrow a by a drive device (not shown). 2
A developing sleeve is in close proximity to or in contact with the latent image carrier 1, and is made of a non-magnetic material such as aluminum or 5US316. The developing sleeve 2 has a right half-circumferential surface extending into the container 11 through a horizontally elongated opening formed in the lower left wall of the developing container 11 in the longitudinal direction of the container, and a left substantially half-circumferential surface exposed outside the container and rotatably supported on a bearing. It is installed horizontally and is driven to rotate in the direction of the arrow.

Reference numeral 3 designates a fixed permanent magnet (magnet) serving as a fixed magnetic field generating means that is inserted into the developing sleeve 2 and held in the illustrated position/posture. Even when the developing sleeve 2 is rotationally driven, this magnet 3 remains in the illustrated position/posture. It remains fixed in its position. This magnet 3 has an N-pole magnetic pole 3a and an S-pole magnetic pole 3b.
, an N-pole 3c, and an S-pole 3d.

The magnet 3 may be an electromagnet instead of a permanent magnet.

Reference numeral 4 has a base fixed to the side wall of the container on the upper edge side of the opening of the developer supply device in which the developing sleeve 2 is disposed, and the tip side is made to protrude to the outside of the container 11 beyond the position of the upper edge of the opening, and extends along the longitudinal direction of the upper edge of the opening. A non-magnetic blade is placed as a developer regulating member.
For example, it is made by bending 5uS316 into a cross-sectional shape.

Reference numeral 5 denotes a magnetic particle limiting member whose upper surface is in contact with the lower surface side of the non-magnetic blade 24 and whose front end surface is a developer guide surface 51.

7 is a carrier particle, which is coated with a resin on ferrite particles (maximum magnetization 60 emu/g) to have a particle size of 30 to 100 μm, preferably 40 to 80 μm, an average particle size of about 50 μm, and a resistance value of 107 Ωcm or more, preferably 108 Ωcm or more. can be used.

8 is a non-magnetic developer toner.

Reference numeral 6 denotes a magnetic material disposed on the inner surface of the lower part of the developer container facing the developer sleeve 2 in order to prevent carrier particles or non-magnetic toner particles 8 from leaking from the lower part of the developer container 11 in which the developer sleeve 2 is disposed. For example, it is a plated iron plate.

The magnetic field between the magnetic body 6 and the S-polarity magnetic pole 3d provides a sealing effect that recovers the carrier particles 7 and prevents leakage.

Reference numeral 9 denotes a toner supplying member that supplies toner to the brush portion of the carrier particles formed by the fixed magnetic pole 3 in the developing sleeve 2. A rubber sheet is pasted on a rotatably bearing plate, and a rubber sheet is attached to the bottom surface of the developing container. The toner supply member 9 is supplied with toner by a toner transport member 10 in a toner storage container 12 .

12 and 13 are a toner storage container and a carrier particle storage container, respectively.

Reference numeral 14 denotes a sealing member for sealing the toner accumulated in the lower part of the developer container 11, which is elastic and curved in the direction of rotation of the sleeve 2, and elastically presses the surface side of the sleeve 2. The sealing member 14 has an end on the downstream side in the rotational direction of the sleeve in a contact area with the sleeve so as to allow the developer to enter the inside of the container.

Further, the S magnetic pole 3d is a magnetic field generating means for magnetic sealing to form a magnetic field from one side to the other between the S magnetic pole 3d and the magnetic member 6, and a portion thereof faces the magnetic member 6. The magnetic member 6 is
Located below the developing device at the substantial end of the developer accommodating portion of the developer container, the movement of collected magnetic carrier particles around the inside of the container causes the developer on the sleeve surface to be located below the inside of the container. toner particles. Therefore, stable collection of magnetic particles has the effect of stabilizing the developing ability.

The magnetic member 6 has a "<" or rLJ shape, and may be made of a non-permanently magnetized magnetic material such as iron. or,
When a magnet is used as the magnetic member 6, the plane 66 must have an N polarity different from the magnetism S of the magnet S.

In other words, the magnetic member 6 restrains the carrier particles, prevents loss of the carrier particles, and facilitates recovery of the carrier particles, so that the toner particles in the developer container can be prevented from leaking from inside the container.

Furthermore, by arranging the magnetic pole 3d as described above, another favorable effect can be obtained in relation to the magnetic pole 3a. That is, due to the above-mentioned relationship between the bottom of the container 11 and the magnetic pole 3d, toner particles are not formed in a coarse state (compared to a state in which they are simply stagnant) within the magnetic brush 11, so that toner particles are not formed into the carrier particles. The intake amount will not become excessive.

Excessive uptake leads to insufficient charging of the toner and causes fogging.

Note that this configuration is also effective when magnetic particles and non-magnetic or weakly magnetic toner are mixed in the developer container.

According to experiments, the distance between the developing sleeve and the magnetic member is 2.5
mm, the magnetic carrier particles were completely recovered, no leakage of toner particles was observed, and stable development was achieved.

The presence of the surface 66 in this region means that the surface 66 can appropriately disperse the magnetic force of the magnetic pole 3d and can substantially increase the magnetic force in this region, increasing the magnetic field sealing effect. Conceivable.

The distance d between the end of the non-magnetic blade 24 and the surface of the developing sleeve 2 is 50 to 800 μm, preferably 150 to 50 μm.
It is 0 μm. If this distance is smaller than 50 μm, magnetic particles, which will be described later, will become clogged between them, which will easily cause uneven developer pressing, and the developer necessary for good development will not be applied, resulting in thin and uneven density. The drawback is that only developed images can be obtained. If the diameter is larger than 800 μm, the amount of developer applied onto the developing sleeve 2 increases, making it impossible to regulate the thickness of the developer to a predetermined extent, increasing the amount of carrier particles attached to the latent image carrier, and causing the circulation of the developer as described below. However, there is a drawback that the development regulation by the developer limiting member 5 is weakened, the toner triboelectricity is insufficient, and fogging is likely to occur.

Even when the sleeve 2 is rotated in the direction indicated by the arrow, this carrier particle layer has a magnetic force 4 and a restraining force based on gravity and the sleeve 2
Due to balance with the conveying force in the direction of movement, the movement slows down as the distance from the sleeve surface increases, and above the magnetic particle layer, a stationary layer is formed that can move to some extent but is almost immobile. Of course, some things fall due to the influence of gravity.

Therefore, by appropriately selecting the arrangement positions of the magnetic poles 3a and 3d and the fluidity and magnetic properties of the magnetic particles 7, the closer the magnetic particle layer is to the sleeve, the more the magnetic particle layer is transported in the direction of the magnetic pole 3a, forming a moving layer.

Due to this movement of the magnetic particles, the magnetic particle layer (first layer) takes in the toner from the toner layer (second layer), and due to the friction with the magnetic particles 7 or the sleeve 2, the toner receives frictional electrification and due to the rotation of the sleeve 2. Along with this, the image is transported to a developing area and subjected to development.

The movement of the magnetic particle layer is determined by the fluidity and magnetic force of the developer. When the toner content in the magnetic particles is low, the stationary layer becomes small and most of the magnetic particle layer moves quickly, removing the toner from the toner layer. take in. Also, when the toner content is high, the stationary layer becomes large and the moving layer of the magnetic particle layer becomes stiff and hardly takes up toner. Therefore, some toner content is naturally maintained.

Next, the magnetic particle layer in the vicinity of the non-magnetic blade 4, which is a developer application amount regulating member, and in the vicinity of the limiting member 5 will be described. The limiting member not only mechanically prevents unnecessary entry of replenishment toner into the developer regulating section. As mentioned above, in the restricted area where the member 5 is surrounded by the sleeve, the magnetic pole N
The magnetic carrier particles conveyed by one pole as the sleeve rotates are packed along the guide surface 51 of the limiting member 5 and become denser. In this region, the carrier particles that are being conveyed into the blade are dynamically replaced by the carrier particles that are flowing out from the blade, so the carrier particles collide with each other and create a state of disturbance. It is in a substantial bucking state. For this reason, the toner is loaded onto the toner from above the carrier particles or the sleeve, and the toner is applied onto the carrier particles or the sleeve with a weak force and removed when the toner is removed.
The toner is dislodged from the carrier particles or sleeve. In other words, toner selection and uniform charging are performed. Therefore, toner to which sufficient triboelectricity is applied can be used for development. Furthermore, the non-uniformity of the carrier particles during transport is averaged out in the space, and uniformity and stabilization of the coating of the carrier particle layer can also be achieved. Therefore, the guide surface 51 is essential for the limiting member 5, and the inclination of the slope and the volume of the space have a great influence on the backing state of carrier particles in the space.

On the other hand, the magnetic pole 3 fixedly arranged with respect to this area
a rearranges the carrier particles in the backing state along the lines of magnetic force. The backing state in this space is unstable with respect to tribo-imposition, and a constant backing state is always required to stabilize it. This is because the carrier particles that have been conveyed almost tangentially on the sleeve form a magnetic brush with a force that is perpendicular to the direction, which not only has a stirring effect on the carrier particles but also has a peeling effect, and the toner particles are The uniformity and stabilization of the tribo-imparting and the application of the carrier particle layer are further promoted. At this time,
If the concentrated developer remains under a great deal of pressure due to the surrounding configuration, there is a problem that the developer will become clogged.
It is believed that by facing the developer, it is possible to prevent excessive pressure concentration in the regulated area, and to maintain developer concentration and a stable high-density carrier particle abundance ratio.

Due to the above-mentioned regulation area, a stable amount of carrier particles and sufficiently charged toner particles can be formed as a thin layer of developer on the surface of the developing sleeve.

Therefore, the development effect in the development area 102 becomes stable. And an alternating electric field forming means for forming an alternating electric field in the developing section that causes at least the toner particles carried on the surface of the developer carrying member to be transferred to the electrostatic latent image carrying member. and in the developing section,
The volume ratio occupied by carrier particles of the developer conveyed to the developing section is 1.5% to 30% with respect to the volume of the space formed by the electrostatic latent image carrier and the developer carrying member. It was confirmed that this method has a great effect on certain developing methods and devices.

FIG. 5 shows a case where a magnetic body 50 is arranged on the non-magnetic blade side of the developer limiting member 5. In this case, the magnetic material 50
It is not preferable to provide it at a position facing the magnetic pole 3a.

This is because if they face each other, a strong concentrated magnetic field will be generated between them and the magnetic pole 3a, reducing the effect of stirring and loosening the carrier particles by the magnetic pole 3a. However, it is effective to provide a magnetic material in the regulating portion and to magnetically regulate the magnetic particles between the regulating member and the sleeve internal magnet 3, since this increases the gap tolerance between the regulating member and the sleeve. Further, when comparing the toner deposited on the carrier particles or the sleeve, the amount of electrical charge of the toner deposited on the sleeve is smaller than that of the toner deposited on the carrier particles. The reason for this is that as the sleeve moves, carrier particles are also transported, so there is an opportunity for the toner on the sleeve to be rubbed by the carrier particles. I need to rub it. That is, it is necessary to have carrier particles near the sleeve surface that cause a shift in relative velocity against the movement of the sleeve.

However, it is impossible to simply reduce the transportability of carrier particles, considering the above-mentioned toner uptake effect. Furthermore, as described above, a magnetic body may be disposed in the regulating portion facing the magnetic pole 3a in the sleeve to generate a concentrated magnetic field and improve the sliding force of the carrier particles on the sleeve (as described above).
The effect of arranging the maximum magnetic force generating portion of the magnetic pole in the space created by the developer circulation regulating member 5 is reduced.

Therefore, in this embodiment, the magnetic body 50 is provided on the downstream side of the magnetic pole 3a in the direction of rotation of the sleeve, so that the lines of magnetic force on the plate side of the magnetic pole 3a are concentrated substantially in the tangential direction of the sleeve surface.

As a result, the carrier particles only near the sleeve surface formed a magnetic brush along the sleeve surface, and the toner on the sleeve was picked up, thereby increasing the triboelectricity of the toner on the sleeve.

The magnetic flux density of the magnetic pole 3a is 600G or more, preferably 7
00G or more is preferable. This is because the applied state of the developer tends to be more stable with respect to changes in the toner content of the carrier particle layer as the magnetic flux density of the cut magnetic pole is higher. In particular, in the developing device of the present invention which does not have an automatic toner replenishing device to maintain toner content, it is preferable that the magnetic flux density be 800 G or more.

In FIG. 5, the magnetic pole 3c is a developing magnetic pole, but as shown in FIG. It is designed so that its magnetic force weakens steeply towards the river, and falls more slowly towards the downstream side. The developer push conveyed as the developing sleeve 2 rotates suddenly rises just before the development area and rubs directly against the surface of the photoreceptor 1, which is caused by the movement of the developer push as it stands up. Since the toner separated from the carrier particles 7 is easily transferred to the photoreceptor 1, there is no problem that the separated toner becomes scattered toner and contaminates the inside of the electrophotographic apparatus, which is preferable.

In addition, in the development area, the developer pressure is in a standing state,
The surface of the developing sleeve is opened, and the toner is actively ejected from the developing sleeve and from the carrier particles due to the alternating electric field. Therefore, almost all of the toner present in the development area is used for development, resulting in extremely high development efficiency and high quality images.

In addition, since there is almost no decrease in magnetic force downstream of the development area,
The magnetic carrier particles adhering to the photoreceptor 1 are removed from the developing sleeve 2.
It has enough magnetic force to pull it back. For this purpose, it is desirable to maintain 70% or more of the magnetic force in the downstream part of the development facing part. It is preferable that the width X from the center of the magnetic pole to the upstream side and the downstream side reach half the value is 1:2 or more.

Therefore, it is possible to provide a good image with no toner scattering (high quality development characteristics) and no adhesion of carrier or the like.

In any case, the present invention can provide high image quality that could not be obtained with conventional developing devices, and has the excellent effect of making the developing device small and disposable.

The toner supply member 9 is located in the developer container 11, is in close proximity to or in contact with the magnetic particle layer, and is rotated in the direction of arrow d to supply the toner 8 to the carrier particle layer.

A toner storage container 12 for storing toner is disposed approximately horizontally adjacent to the developer container 11, and a toner transport member 1 for transporting toner into the developer container 11 is disposed within the toner storage container.
0 is set.

The S magnetic pole 3b is a transporting magnetic pole provided to prevent the developer uniformly applied by the non-magnetic blade 44 from being disturbed due to the large distance between the cut magnetic pole 3a and the developing magnetic pole 3C. The strength of the S magnetic pole 3b is preferably approximately equal to or slightly lower than that of the developing magnetic pole 3C so as not to disturb the developer pressure. When a 16φ developing sleeve is used, if the distance between the cut magnetic pole and the developing magnetic pole is within 110 degrees at the center angle of the sleeve, there will be little disturbance in pushing the developer on the sleeve, and it is preferable to provide a transport pole in the middle. .

The S magnetic pole 3d is a collection magnetic pole that collects the developer after development, and is arranged upstream of the tip of the magnetic seal 6 in the moving direction of the developing sleeve 2. When the magnetic pole 3d is disposed downstream from the tip of the magnetic seal 6, a spike of carrier particles is generated by the magnetic pole 3d near the toner intake port at the bottom of the developer container 11, and the toner is extremely easily taken in (and frictional charging is sufficient). If this is not done properly, it may easily cause fogging, etc.

In Fig. 5, the sleeve 2 is an aluminum sleeve with a diameter of 16 mm whose surface has been subjected to amorphous sandblasting treatment using Alundum abrasive grains, and the magnet 3 is 4-pole magnetized with N and S poles alternately placed in the sixth The one shown in the figure was used. The maximum value of the surface magnetic flux density due to magnet 3 is approximately 900
It was Gauss. The developing magnetic pole 3c has a maximum magnetic flux density at the part facing the photoreceptor, and the magnetic force sharply decreases on the upstream side thereof.
On the downstream side, the magnetic force decreases slowly, and even after passing the development area, there is still sufficient magnetic force.

The blade 4 was made of non-magnetic stainless steel with a thickness of 1.2 mm, and the angle θ was 1.5D.

As the carrier particles, ferrite (maximum magnetization 60 parts mu/g) with a particle size of 70 to 50 μm (250/350 mesh) whose surface was coated with silicone resin was used.

The non-magnetic toner is a toner powder with an average particle size of 10μ, consisting of 100 parts of a styrene/butadiene copolymer resin and 5 parts of a copper phthalocyanine pigment, and 1.0 parts of colloidal silica.
When using blue toner with external addition of %, sleeve 2
A toner coating layer with a coating length of 10-30 μm was obtained on the surface, and a layer of carrier particles with a thickness of 200-300 μm was obtained as an upper layer. The toner is attached to the surface of each carrier particle.

°The carrier particles stand up into spikes in the developing area and its vicinity due to the magnetic field generated by the magnetic pole 3c in the sleeve 2, and the maximum length is approximately 1
．． It formed a standing brush about 2 mm in diameter.

When the amount of charge was measured by the blow-off method, the amount of tripo charge of the toner on the sleeve and on the carrier particles was +12μC/
It was g.

This developing device was incorporated into a Canon Co., Ltd. FC-5 type copying machine, and a photosensitive drum 1 (made of organic photosensitive material) and a sleeve 2 were installed.
The distance from the surface was set to 350 μm. When developing was carried out using a bias power supply (not shown) with a frequency of 1600 Hz and a peak-to-peak value of 1.300 V AC voltage superimposed with a DC voltage of -300 V, a good blue image was obtained. Ta.

Further, when a solid black image was developed and the sleeve surface after development was observed, it was found that most of the toner attached to the magnetic particles and the toner on the sleeve were consumed, and development was performed with nearly 100% development efficiency.

As for development characteristics, there was no fog, and good development characteristics could be obtained.

Furthermore, it was confirmed that the effect of the magnetic member 6 was that good penetration of magnetic particles, prevention of leakage, and good circulation were achieved.

As explained above, according to this embodiment, high image density,
It is possible to perform development with high development efficiency without fogging, ghost images, uneven sweeping, or negative characteristics.

As the material of the sleeve 2, in addition to aluminum, conductive materials such as brass and stainless steel, paper tubes, and synthetic resin cylinders can be used. Furthermore, if the surfaces of these cylinders are subjected to conductive treatment or made of a conductive material, they can function as developing electrodes.

Furthermore, using a core roll, a conductive elastic body is placed on the peripheral surface of the core roll.
For example, it may be constructed by wrapping a conductive sponge around it.

Silica particles may be externally added to the toner to improve fluidity, and abrasive particles may be added to the toner to polish the surface of the photosensitive drum 1, which is a latent image holding member in a transfer image forming method, for example. A toner containing a small amount of magnetic particles may also be used. That is, magnetic toner can also be used as long as it has significantly weaker magnetism than magnetic particles and can be tribocharged.

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☆The developer particles remaining on the sleeve 2 without being subjected to development are scraped off from the rotated sleeve 2 surface by a scraper means (not shown), and the scraped sleeve surface is magnetically removed. The developer may be recoated by contacting the particle layer.

A mechanism may be provided that detects the concentration of magnetic particles and toner and automatically replenishes toner according to this output.

The developing device of the present invention can be used either as a disposable type developing device by integrating the container 11, sleeve 2, blade 4, etc., or as a regular developing device fixed to an image forming apparatus.

Further, in this embodiment, a developing sleeve with a diameter of 16 φ was used, but the present invention is applicable not only to a small diameter developing sleeve (also to a large diameter of 20 φ or more).

<Example ■> In the above example, a single pole was used as the developing magnetic pole 3C, and the magnetic force attenuated significantly on the upstream side and slowly attenuated on the downstream side, but a pole and carrier particles that improve the developing efficiency were used. The poles to be collected may be independent of each other.

A sectional view of the developing area of the developing device of such an embodiment is shown in FIG.
As shown in the figure. In FIG. 7, the developing magnetic pole 3c is the photosensitive drum 1.
N facing the magnetic pole and N facing downstream of the development area.
Consists of two repulsive magnetic poles. The N2 magnetic pole allows the developer to completely stand up in the development area, resulting in good development characteristics, and the N2 magnetic pole makes it possible to reliably collect the carrier attached to the photoreceptor 1.

Also, by making it a repulsive magnetic pole, N,,N.

A region with weak magnetic force is created between the magnetic poles, and in this region, the restraining force of the magnetic field is weak, and the carrier particles vibrate and fly extremely easily due to the alternating electric field, so that the toner is easily removed from the carrier and the sleeve. Further, there is also the effect that the fog toner on the drum can be removed more reliably.

Further, in this weak area, the toner forms a kind of powder cloud, which promotes the edge development effect.

Therefore, an image with sharp lines and sufficient solid density can be obtained.

<Embodiment 2> In FIG. 8, a magnetic plate 81 is provided between the developing magnetic pole 3c and the upstream magnetic pole 3d to sharply reduce the magnetic flux density on the upstream side of the developing magnetic pole 3C.

By providing the magnetic plate 81 as in this embodiment, it becomes possible to control the magnetic field on the upstream side of the developing section, and therefore, it becomes possible to easily control the point at which the developer particles start forming spikes, thereby making it possible to control the magnetic field upstream of the developing section. It is possible to prevent ear standing at a distance. As a result, the toner separated due to the spike movement of the developer does not become scattered toner and can be effectively used for development, so that a good developing device with less scattering can be provided.

Further, the developing magnetic pole 3c may be a repelling magnetic pole as shown in the second embodiment.

<Embodiment IV> FIG. 9 is an example in which a magnetic brush ear presser leveling member 15 is applied to the embodiment used in FIG. 1.

It is preferable that the member is provided near the upstream inclined portion of the N pole of the development pole (not limited to that shown in FIG. 1).

The shape material is a flexible polymer material, such as Mylar (
DuPont product name) with a thickness of 25 μm was used in contact with the sleeve.

By applying this member, the magnetic brush coated on the sleeve can be formed into a dense spike in the development area.

Therefore, the toner easily separates from the carrier, brush marks are less likely to appear on the image, and carrier particles are easily held or attracted onto the sleeve by the downstream magnetic force, thereby preventing carrier particles from adhering to the photoreceptor. Can be done effectively.

Further, toner scattering during transportation from the regulating blade to the developing area can also be prevented.

〔Effect of the invention〕

As explained above, according to the present invention, in the developing area, the developer is sufficiently spiked and the developing sleeve surface is opened, so that it is possible to efficiently prevent the developer from adhering to the body and to It has the effect of reducing toner scattering caused by spikes of the agent.

Particularly when a small-diameter sleeve having an outer diameter of 6 to 20 mm is used, good images can be obtained by applying the present invention.

Further, even when fine particle toner having a particle size of 10 μm or less is used, good images can be obtained by applying the present invention.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are enlarged views of the developing area of the developing device according to the present invention, and FIGS. 2(a) and 4(b) to 4(a) and (b) are respectively explanations of the conventional developing section. 5 is a sectional view of a developing device embodying the present invention, FIG. 6 is a magnetic flux pattern diagram used in the developing device of FIG. 5, FIGS. Each figure is an enlarged view of a developing area of another embodiment of the present invention. ■・・・・・・Latent image carrier 2・・・・・・Developing sleeve wa, -1-Hota hJ4-: c corner 4...
...Developer amount regulating member 5...Developer circulation area limiting member 6...Magnetic seal 7...Carrier particles 8 ......Toner 9...Toner supply member 10...Toner transport member 11...
...Developer container 12...Toner storage container 13...
...Magnetic particle storage container 14 ... ... Lower scattering prevention film 15 ... ... Presser foot leveling member diagram 1 (α) (b) [ (0-) (b) (α) (b) Figure 7 Cα) (b) 13°

Claims (1)

[Scope of Claims] 1) Development is performed by applying an alternating electric field between a latent image carrier and a developing sleeve using a mixed developer containing carrier particles and toner particles, which is contained in the sleeve. A developing device characterized in that a developing magnetic pole corresponding to a latent image carrier corresponds to the latent image carrier, and the magnetic flux density decreases sharply on the upstream side of the developing area with respect to the rotational direction of the sleeve, and decreases slowly on the downstream side. . 2) The developing device according to claim 1, wherein the developing magnetic pole forms a repelling magnetic pole. 3) The developing device according to claim 1 or 2, characterized in that a magnetic material is disposed within the sleeve on the upstream side of the developing magnetic pole. 4) The developing device according to any one of claims 1 to 3, characterized in that a developer pressing member is provided in contact with or in close proximity to the developing sleeve on the upstream side of the developing magnetic pole.