JPH07271193A - Developing device - Google Patents

Abstract

PURPOSE:To provide a developing device capable of obtaining an excellent image without irregularities in a density over a long period by preventing the scattering of a developer. CONSTITUTION:A developing sleeve 21 as a developer carrier, which carries the developer 41 housed in a developing container 2 to a developing part 60 as a developing region opposite to an image carrier 1 and in which a magnet roller 22 as a magnetic field generating means is installed in immobile is freely rotatably installed in the developing container 2, an electrode plate 10 is disposed so that at least its part faces the region where the density of a magnetic flux in a direction perpendicular to the surface of the developing sleeve 21 is made smaller than that in the horizontal direction with respect to a magnetic field formed by the magnet roller 22 in the downstream side in the turning direction of the developing part 60 on the developing sleeve 21 and the width in the rotational direction of the developing sleeve 21 is longer than the shortest distance from the developing sleeve 21 and a voltage having the same polarity as that of the developer 41 is applied to the electrode plate 10 based on the DC component of a developing bias applied to the developing sleeve 21 as a reference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing apparatus utilizing electrophotography or electrostatic recording method and used for developing and visualizing a latent image formed on an image bearing member.

[0002]

2. Description of the Related Art Conventionally, in a developing device utilizing an electrophotographic method or an electrostatic recording method, a latent image formed on an image bearing member is developed by the developing device and visualized as a toner image. There is.

Various developing devices of various principles are known, and of these, the one based on the so-called magnetic brush developing method is mainly put into practical use.

FIG. 4 is a sectional view showing an example of a conventional developing device.

The present developing device includes a developing chamber 1 of a developing container 102.
A non-magnetic developing sleeve 121 as a developer carrying member is provided inside the bearing unit 45 so as to face the electrostatic latent image carrying member (hereinafter referred to as an image carrying member) 101 rotated in the direction of the arrow a ′. A magnet roller 122 as a magnetic field generating means is installed immovably, and the magnet roller 122 is S ₁ , N ₁ , S ₂ , in order from the position of substantially the top in the rotation direction of arrow b ′.
It is magnetized to N ₂ and N ₃ .

The developing chamber 145 contains a two-component developer 141 in which a toner 140 and a magnetic carrier 143 are mixed.

When the developer 141 is sent into the stirring chamber 142 of the developing container 102 through one opening (not shown) of the partition wall 148 whose upper end is open at one end of the developing chamber 145, the toner chamber 147 is stirred in the stirring chamber 142. Toner 14 supplied to
0 is replenished and mixed by the first developer agitating / conveying means 150 in the agitating chamber 142 and conveyed to the other end of the agitating chamber 142. The developer 141 conveyed to the other end of the stirring chamber 142 is returned to the inside of the developing chamber 145 through the other opening (not shown) of the partition wall 148, where the second developer inside the developing chamber 145 is discharged.
A developer agitating / conveying means 151 and a third developer agitating / conveying means 152 for conveying the developer in a direction opposite to the conveying direction by the second developer agitating / conveying means 151 inside the developing chamber 145.
Is supplied to the developing sleeve 121 while being agitated and conveyed.

The developer 1 supplied to the developing sleeve 121.
41 is magnetically restrained by the action of the magnetic force of the magnet roller 122, is carried on the developing sleeve 121, and is regulated by a blade 123 which is a developer regulating member provided substantially on the top of the developing sleeve 121. 121
The latent image carrier 10 is formed as the developing sleeve 121 is rotated in the direction of the arrow b ′ while being formed as a thin layer of the developer 141 above.
1 is conveyed to the developing unit 160 facing the image forming apparatus 1 where it is used for developing the electrostatic latent image on the latent image carrier 101. The residual developer 141 not consumed for the development is the developing sleeve 12
It is collected in the developing container 102 by the rotation of 1.

In the developing container 102, the residual developer 141 remaining after the development which is magnetically restrained on the developing sleeve 121 is peeled off by the repulsive magnetic field between N ₂ and N ₃ having the same polarity. . By the magnetic pole N ₂ described above, the developer 141
The elastic seal member 13 is provided below the developing container 102 in order to prevent the toner from scattering when the toner stands up along the lines of magnetic force.
1 is fixed and installed so that one end thereof contacts the developer 141.

[0010]

In order to obtain a high-definition image, it has been attempted to reduce the toner particle size.
Many of the small particle size toners have a small binding force to the carrier, and there is a problem such as release of the toner 140 from the developer 141 during stirring / conveying in the developing container 102.

That is, in the conventional developing device shown in FIG. 4, the developer 141 which is constrained by the developing sleeve 121 and is rotating collides with and contacts the elastic seal member 131, and the impact causes the carrier of the developer 141 to be conveyed. The toner particles bound by the particles are released or scattered, or the elastic seal member 13
1 is charged by friction with the developer 141, and the toner particles are positively attached and deposited on the elastic seal member 131 to form a toner agglomerate, from which the toner 140 is released and scattered, or the agglomerate is formed in the developing container 102. However, there is a problem that they are sequentially mixed in and appear as an abnormal image on the image obtained by development.

Further, in this configuration is essential to stripping of the developer 141 by a repulsive magnetic field N _2, N ₃ in order to obtain a pictorial image, by the repulsive magnetic field by the magnetic poles N _2, N _3, magnetic poles N ₂ Magnetic pole S ₂ whose magnetic flux lines have different polarities
In the vicinity of the magnetic pole N ₂ , the developer 14 formed on the developing sleeve 121 is concentrated in the direction and becomes dense.
Since the bristles of No. 1 are large and extend in the direction of the magnetic pole S _{2 for} a long time to become more dense, the elastic seal member 131 acts as a barrier against the developer 141 which is about to be collected from the developing unit 160 into the developing container 102. This causes the problem that the scattering is further increased as compared with the conventional configuration that does not use the repulsive pole.

For this reason, for example, Japanese Patent Laid-Open No. 58-46365 is used.
And JP-A-60-95574, JP-A-60-125863.
As described above, there has been proposed a method in which an electrode member is provided in a portion of the frame of the developing container surrounding the outside of the developing sleeve 121, which is a developer carrier, in the vicinity of the image carrier, and a voltage having the same polarity as that of the toner is applied. With such a configuration, in the case of the main developing device using the repulsive pole, the effect of removing the scattering cannot be obtained, and the toner 140 scattered on the image carrier 101 is rather conversely obtained.
Occurs, resulting in a problem such as an image with a large density unevenness.

In any case, it has been impossible to completely prevent the scattering by the conventional means.

The present invention has been made to solve the above-mentioned problems of the prior art. The object of the present invention is to prevent the scattering of the developer and to obtain a good image without density unevenness for a long period of time. To provide a device.

[0016]

In order to achieve the above object, in the present invention, a developer contained in a developing container is carried and is conveyed to a developing area facing an image carrier. In a developing device in which a developer carrier having a magnetic field generating means immovably installed therein is rotatably installed in the developing container, the magnetic field is provided on the downstream side in the rotation direction of the developing region of the developer carrier. The magnetic field formed by the generating means is such that the electrode plates are arranged such that at least a part of them face each other in a region where the magnetic flux density in the vertical direction on the surface of the developer carrier becomes smaller than the magnetic flux density in the horizontal direction. Arranged so that the width in the rotation direction of the developer carrier is longer than the shortest distance from the developer carrier, and the development is performed with reference to the DC component of the developing bias applied to the developer carrier on the electrode plate. Apply the same polarity voltage as the agent Characterized in that it pressure.

It is also possible to arrange adjacent magnetic poles of the same polarity as the magnetic field generating means on the downstream side in the rotation direction of the developer carrying member from the position where the electrode plate is arranged.

The developer is a two component composed of a magnetic carrier and a non-magnetic toner, and the voltage applied to the electrode plate is based on the DC component of the developing bias applied to the developer carrying member. It is preferable that the polarity is the same as that of the magnetic toner.

The developing bias applied to the developer carrying member may have a DC component and an AC component.

[0020]

In the developing device constructed as described above, the magnetic field formed by the magnetic field generating means is located on the downstream side in the rotating direction of the developing area of the developer carrier, and the magnetic flux density in the vertical direction on the surface of the developer carrier is horizontal. In a region smaller than the magnetic flux density of, the electrode plate is arranged so as to at least partially face each other, and the electrode plate has a width in the rotation direction of the developer carrier longer than the shortest distance from the developer carrier. And a voltage of the same polarity as the polarity of the developer is applied to the electrode plate with the direct current component of the developing bias applied to the developer carrier as a reference, so that the developer repels from the electrode plate. Receive.

By arranging adjacent magnetic poles of the same polarity as magnetic field generating means on the downstream side in the rotation direction of the developer carrying member from the position where the electrode plate is arranged, the magnetic force lines are perpendicular to the surface of the developer carrying member. .

The developer is a two component composed of a magnetic carrier and a non-magnetic toner, and the voltage applied to the electrode plate is based on the DC component of the developing bias applied to the developer carrier, and the polarity of the non-magnetic toner is used as a reference. By having the same polarity as, the non-magnetic toner released on the developer carrying side is attracted,
Then, by contacting the magnetic carrier, the magnetic carrier adheres to the magnetic carrier and is taken into the developing container.

Since the developing bias applied to the developer carrying member has a direct current component and an alternating current component, a very small amount of non-magnetic toner charged to the opposite polarity reciprocates between the developer carrying member and the electrode plate. After that, it comes into contact with the magnetic carrier and has a normal electric charge, so that it adheres to the magnetic carrier and is taken into the developing container.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view showing the whole of one embodiment of the developing device of the present invention.

The developing device develops a latent image formed on the image carrier 1 such as a photoconductor or a dielectric of the image forming device by an electrophotographic method, an electrostatic recording method or the like to visualize it as a toner image. The developing device is for use in the developing container 2,
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, and its basic configuration is the same as that of the conventional developing device shown in FIG.

In FIG. 1, an opening is formed at a position near the image carrier 1 of the developing container 2, and the developing sleeve 21 is rotatably opposed to the image carrier 1 in the opening. The blade 23 is provided at a position approximately above the top of the developing sleeve 21 with a predetermined gap. According to the present invention, the electrode plate 10 is provided below the developing sleeve 21.
Are mounted with a predetermined gap. The electrode plate 10 will be described later.

The developing sleeve 21 is made of a non-magnetic material and rotates in the direction of arrow b in the drawing during the developing operation. Inside the developing sleeve 21, a magnet roller 2 serving as a magnetic field generating means is provided.
2 is installed immovably, and the magnet roller 22 has a developing pole S ₂
And a carrier pole S ₁ for transporting the developer 41 and another pole N ₁ ,
N ₂ and N ₃ are provided by magnetizing. The magnetic poles S _{1 to} N ₃ may be a combination having opposite polarities.

The blade 23 is made of a non-magnetic material such as aluminum or non-magnetic stainless steel (SUS),
As described above, the developing sleeve 21 is mounted with a predetermined gap between it and the surface of the developing sleeve 21.
The amount of the developer 41 carried on the upper surface and conveyed to the developing unit 60 facing the latent image carrier 1, specifically, the developing sleeve 21.
The layer thickness of the upper developer 41 is regulated. Therefore, in this embodiment, both the non-magnetic toner 40 and the magnetic carrier 43 forming the developer 41 pass between the tip of the blade 23 and the surface of the developing sleeve 21 and are conveyed to the developing unit 60. It

As described above, the developer 41 is a two-component developer composed of the toner 40 and the magnetic carrier 43, and the toner 40 has a volume average particle diameter of 12 μm or less, preferably 10 μm or less. A toner for a color copying machine using a styrene-acrylic acid ester resin as a base was used, and in this embodiment, a toner having a thickness of 8 μm was used.

The magnetic carrier 43 has a weight average particle diameter of 3
0 to 80 μm, preferably 40 to 70 μm and a resistance value of 1
0 ⁷ Ωcm or more, preferably 10 ⁸ Ωcm or more resin-coated ferrite particles (maximum magnetization 60 emu /
g) can be used, and in this embodiment, the weight average particle diameter is 50 μm.
I used the one.

The toner 40 and the magnetic carrier 43 are stirred in the stirring chamber 42 in the direction of the arrow by the first developer stirring / transporting means 50, and transported to the developing chamber 45 over the partition wall 48.

The developer 41 is carried by being held on the developing sleeve 21 by the action of the magnet roller 22 and conveyed to the developing section 60, where the toner 40 in the developer 41 is used for developing. After that, it is conveyed to the magnetic pole N _{2 at the} lower portion of the developing sleeve 21 on the downstream side of the developing unit 60 while further holding. Since the magnetic pole N ₂ of the magnet roller 22 has the same pole as the magnetic pole N _{3 on} the downstream side, a repulsive magnetic field is generated between them. Therefore, the developer 41 carried to the position of the magnetic pole N _{2 while} being held by the developing sleeve 21 is
By the action of the repulsive magnetic field, it is peeled off from the developing sleeve 21 and removed, and is agitated and mixed by the second developer agitating / conveying means 51 (rotating in the arrow direction) in the developing chamber 45, while the developing sleeve 21 has The developer 41 is newly supplied in the vicinity of the magnetic pole N ₃ .

The rotation direction of the second developer agitating / conveying means 51 facilitates the conveyance of the developer 41 along the lines of magnetic force of the repulsive magnetic field formed by the magnetic poles N ₂ and N _{3 on the} magnet roller 22.

That is, the developer 41 which has received the development history on the developing sleeve 21 is separated and removed from the developing sleeve 21, and is sufficiently mixed in the conveying path by the second developer agitating / conveying means 51 so as to be on the developing sleeve 21. Since a new developer 41 is constantly supplied to, it is possible to stably obtain a good image.

Incidentally, the magnetic pole N ₂ below the developing sleeve 21.
The electrode plate 10 of the present invention is arranged in the vicinity of the developing sleeve 21 on the upstream side in the rotation direction of the developing sleeve 21. The function and effect of the electrode plate 10 will be described with reference to FIG.

As the developing sleeve 21 rotates, the developer 4
After the completion of development, 1 is conveyed to the vicinity of the magnetic pole N ₂ . Magnetic pole N
_{In the} vicinity of ₂ , the developer 4 is formed because a repulsive pole is formed with N _3.
1 sharply stands up along the magnetic lines of force. Therefore, N
_{In the} vicinity of ₂ , the developer 41 collides with each other or collides with the portion of the developing container 2 facing N _2, and the shock causes the magnetic carrier 43 and the toner 40 to be released.

Conventionally, the released toner 40 was conveyed in the direction of arrow c and scattered outside the developing container 2 to pollute the engine.

In the present invention, a bias having the same polarity as that of the toner 40 provided with the electrode plate 10 is applied so that the released toner 40 is not scattered outside the apparatus, and the toner 40 is applied to the developer 41 on the developing sleeve 21. It was attached and collected in the machine. Here, the electrode plate 10 is opposed to the developing sleeve 21,
A voltage having the same polarity as that of the toner 40 is applied based on the DC (direct current) component of the developing sleeve 21.
There is an important relationship between the position of 0 and the width, which will be described.

First, regarding the position of the electrode plate 10, the position is not limited as long as the developer 41 is collected in the developing container 2 on the downstream side of the developing section 60 which is the developing area on the developing sleeve 21. .

In the vicinity of the magnetic pole position on the developing sleeve 21,
The developer 41 is violently moving such that the developer 41 causes a spike and falls. Further, since the developer 41 stands up, the developer 41 is nonuniformly present on the developing sleeve 21.

Even if a bias toward the developing sleeve 21 is applied to the electrode plate 10 in such a state, the toner 40, which is not sufficiently collected and adhered by the magnetic carrier 43, is scattered out of the apparatus. Will end up.

Therefore, the portion where the electrodes face each other needs to be the portion where the developer 41 between the magnetic poles lies. At such a position, as shown in FIG. 2, the developer 41 does not form ears, lays on the developing sleeve 21 so as to cover it uniformly, and does not move violently to stand up. It is possible to reliably collect the toner 40 moved to the developing sleeve 21 side by the electric field of (3) by the magnetic carrier 43 and almost prevent the scattering.

Under such conditions, the magnetic flux density B in the horizontal direction is more than the magnetic flux density B in the horizontal direction on the surface of the developing sleeve 21.
The electrode plate 10 is completely filled near the region where θ is large.
It suffices that a part of B is opposed to the region of Bθ> Br.

Further, the distance d between the electrode plate 10 and the developing sleeve 21 and the width L of the electrode plate 10 in the rotating direction of the developing sleeve 21 have important relationships. When the width L of the electrode plate 10 is narrowed to be narrower than the closest distance d, the scattered toner 40 does not decrease even if the electric field of the electrode plate 10 is raised. This can be considered as follows. Since the scattered toner 40 has a low tribo (charged charge of the toner), the electric field following property is worse than that of the toner 40 that contributes to the development. Therefore, even if a force toward the developing sleeve 21 is applied by the electrode plate 10, it does not immediately follow.

The width L of the electrode plate 10 is set to at least the electrode plate 10
It is considered that the toner 40 having a poor electric field following property can reach the position of the developer 41 on the developing sleeve 21 and can be prevented from scattering by setting the closest distance d of the developing sleeve 21 or more. In many studies, it was confirmed in FIG. 2 that the scattering of the toner 40 is surely reduced by making the width L of the electrode plate 10 longer than the value of the distance d.

Next, examples of the present invention will be further described.

(First Example) Image development was performed under the following developing conditions.

The developing device was constructed as shown in FIG. 1, and the development was carried out by the above-mentioned operation.

In the reversal developing method, the developer 41 is a negatively charged toner, the developing bias is DC-400V, the developer coating amount is 50 mg / cm ² , the distance d between the electrode plate 10 and the developing sleeve 21 is 2 mm, and the electrode plate 10 has the same. Applied bias is -900
V, the width L of the electrode plate 10 is 5 mm.

Under the above conditions, images were continuously printed on 10,000 sheets, but the toner 40 was not scattered at all.

(Second Embodiment) Under the same conditions as in the first embodiment,
Development bias only DC-400V, AC (AC) 2KV
A bias of pp, 2 KHz and DC superimposed on AC was used, but the bias of the electrode plate 10 described above was sufficient to prevent scattering. In this way, even if an oscillating electric field in AC is generated,
If there is an electric field acting in the direction of the developing sleeve 21, the developer 41 is sufficiently collected.

Further, it was confirmed that the same effect can be obtained by providing a protective layer such as mylar or Teflon on the surface of the electrode plate 10.

(Third Embodiment) The structure other than the electrode plate is the same as that of the first embodiment, and the electrode plate 10 is 2 m long as shown in FIG.
Three m-width electrode plates 10a, 10b, 10c were sequentially arranged in the carrying direction, superposed on a DC bias of -800V, and a three-phase AC wave traveling toward the inside of the machine was applied. Even with such a configuration, the scattering of the toner 40 can be surely reduced.

[0054]

The present invention has the above-described structure and operation, and the magnetic field formed by the magnetic field generating means on the downstream side in the rotation direction of the developing region of the developer carrying member is in the direction perpendicular to the surface of the developer carrying member. In a region where the magnetic flux density is smaller than the horizontal magnetic flux density, the electrode plates are arranged so that at least some of them face each other, and the electrode plates rotate the developer carrier more than the shortest distance from the developer carrier. By arranging so that the width in the direction becomes long, and applying a voltage having the same polarity as the polarity of the developer to the electrode plate with reference to the direct current component of the developing bias applied to the developer carrying member, The repulsive force is received from the electrode plate, the developer is attracted to the developer carrying member side, and the developer is taken into the developing container and stabilized, so that the toner scattering as in the conventional case is prevented and a stable and good image can be obtained.

By arranging adjacent magnetic poles of the same polarity as magnetic field generating means on the downstream side in the rotation direction of the developer carrying member from the position where the electrode plate is arranged, the magnetic force lines are perpendicular to the surface of the developer carrying member. The developer easily peels off from the developer carrier.

The developer is a two component composed of a magnetic carrier and a non-magnetic toner, and the voltage applied to the electrode plate is based on the direct current component of the developing bias applied to the developer carrying member, and the polarity of the non-magnetic toner. By having the same polarity as, the non-magnetic toner released on the developer carrying side is attracted,
Then, when the magnetic toner comes into contact with the magnetic carrier and adheres to the magnetic carrier and is taken into the developing container, the free toner is hardly scattered outside the developing container.

Since the developing bias applied to the developer carrying member has a direct current component and an alternating current component, a very small amount of non-magnetic toner charged with opposite polarity reciprocates between the developer carrying member and the electrode plate. Since the magnetic toner comes into contact with the magnetic carrier and has a normal electric charge, the magnetic carrier adheres to the magnetic carrier and is taken into the developing container. Therefore, scattering of the free toner to the outside of the developing container is almost completely suppressed.

[Brief description of drawings]

FIG. 1 is a sectional view showing an entire embodiment of a developing device of the present invention.

FIG. 2 is a sectional view showing a main part of the developing device of FIG.

FIG. 3 is a sectional view showing the whole of another embodiment of the developing device of the invention.

FIG. 4 is a cross-sectional view showing another example of a conventional developing device as a whole.

[Explanation of symbols]

 d distance (shortest distance) L width 1,101 image carrier 2,102 developing container 10, 10a, 10b, 10c electrode plate 21,121 developing sleeve (developer carrier) 22,122 magnet roller (magnetic field generating means) 40 , 140 toner 41, 141 developer 43, 143 magnetic carrier 45, 145 developing chamber 60, 160 developing section (developing area)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshimitsu Amazuka 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (4)

[Claims] 1. A developer carrying body, in which magnetic field generating means is immovably installed, for carrying a developer contained in a developing container and transporting the developer to a developing area opposite to an image carrying body, In the developing device rotatably installed in the developing container, the magnetic field formed by the magnetic field generating means on the downstream side in the rotating direction of the developing region of the developer carrier is a magnetic flux in the vertical direction on the surface of the developer carrier. In a region where the density is smaller than the magnetic flux density in the horizontal direction, the electrode plates are arranged so that at least some of them face each other, and the electrode plates are arranged in the rotational direction of the developer carrier more than the shortest distance from the developer carrier. And a voltage having the same polarity as the polarity of the developer is applied to the electrode plate with reference to the DC component of the development bias applied to the developer carrying member. . 2. The magnetic poles of the same polarity which are adjacent to each other are arranged as the magnetic field generating means on the downstream side in the rotation direction of the developer carrier from the position where the electrode plate is arranged. Development device. 3. The developer is a two component composed of a magnetic carrier and a non-magnetic toner, and the voltage applied to the electrode plate is based on a direct current component of a developing bias applied to the developer carrier. The developing device according to claim 1, wherein the developing device has the same polarity as the non-magnetic toner. 4. The developing device according to claim 1, wherein the developing bias applied to the developer carrying member has a DC component and an AC component.