JP3103726B2 - Developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an electrophotographic or electrostatic recording type image forming apparatus such as a laser printer or a copying machine.

[0002]

2. Description of the Related Art Conventionally, many electrophotographic methods are known as described in U.S. Pat. No. 2,297,691, Japanese Patent Publication No. 42-23910 and Japanese Patent Publication No. 43-24748. However, in general,
An electric latent image is formed on the photoconductive material photoreceptor by various means, then the latent image is developed using toner, and if necessary, a toner image is transferred to a transfer material such as paper. ,
Alternatively, a copy is obtained by fixing with a solvent vapor or the like. Also, various methods for visualizing an electric latent image using toner have been known.

As a developing method, for example, a magnetic brush developing method described in US Pat. No. 2,870,063, a powder cloud method and a fur brush developing method described in US Pat. Many development methods are known, such as the development method.

In these developing methods, in particular, a magnetic brush method using a developer mainly composed of toner and carrier,
The cascade method, liquid developing method, and the like have been widely put to practical use.
Each of these methods is an excellent method to obtain a relatively stable and good image, but on the other hand, deteriorates the carrier, changes the mixing ratio of the toner and the carrier, complicates the apparatus,
It has common drawbacks associated with the two-component developer, such as scattering of toner and uneven stripes caused by carriers.

In order to avoid such disadvantages, various developing methods using a one-component developer consisting of only a toner have been proposed. For example, US Pat. No. 3,909,258 proposes a method of developing using a conductive magnetic toner. In this technique, a conductive magnetic developer is supported on a cylindrical conductive sleeve having magnetism therein, and the conductive magnetic developer is brought into contact with an electrostatic image for development. At this time, a conductive path is formed between the surface of the recording medium and the surface of the sleeve by the toner particles in the developing area, and electric charges are guided to the toner particles from the sleeve via the conductive path. As a result, the toner particles adhere to the image area and are developed. The developing method using the conductive magnetic toner is an excellent method that avoids the problems associated with the conventional two-component developing method. However, since the toner is conductive, the developed image can be transferred from a recording medium to a plain paper or the like. It has the drawback that it is difficult to transfer electrostatically to the final support member.

To solve this problem, Japanese Patent Application Laid-Open No. 52-94140 discloses a developing method using dielectric polarization of toner particles as a developing method using a high-resistance toner capable of electrostatic transfer. It is shown. However, such a method has a drawback that the developing speed is essentially low and a sufficient density of a developed image cannot be obtained, and is practically difficult. Other methods using high resistance toners include:
There is known a method in which toner particles are frictionally charged by friction between toner particles, friction between the toner particles and a sleeve, and developed by contacting the toner particles with an electrostatic holding member. However, in these methods, the number of times of contact between the toner particles and the friction member is small, and the triboelectricity is likely to be insufficient, or the toner particles are likely to aggregate when the Coulomb force between the charged toner particles and the sleeve is strong. It is pointed out that there are many practically difficult points.

On the other hand, Japanese Patent Application Laid-Open No. 54-43036 proposes a new developing method which eliminates the above-mentioned disadvantages. This involves applying a very thin layer of toner on a developing sleeve, triboelectrically charging the toner, and then bringing the toner very close to the electrostatic image under the action of a magnetic field and facing the electrostatic image without contact, and then developing. .

According to this method, the magnetic toner is applied very thinly, so that the chance of contact between the magnetic toner and the developing sleeve is increased, and the amount of triboelectric charge required for development is reduced to the toner. It is possible to give.

According to the present inventors' studies on the charge application in the one-component development system, it has been found that the behavior of the toner in the charge application section in the one-component development system is as follows.

First, FIG. 5 shows an example of a developing device using the magnetic one-component toner. In FIG. 5, the developing device is
A toner container 3 containing a magnetic one-component toner, a developing sleeve 1a using a non-magnetic member disposed rotatably in the direction of the arrow at the opening of the toner container 3, and a permanent magnet 1b fixed inside the developing sleeve 1a Is fixed to the toner container 3,
The image forming apparatus includes a magnetic blade 2 using a magnetic member that regulates a layer thickness of the toner, and a toner conveying member 4 provided in a toner container 3. Note that the magnetic blade 2 is disposed on the developing sleeve 1a such that the distance thereof becomes a constant value W. Generally, the distance is often set to a value within the range of 100 μm to 1 mm.

In the developing device shown in FIG. 5, a magnetic one-component toner is thinly coated on the developing sleeve 1a. The thickness of the toner layer is determined by the position of the cut line L shown in FIG.

According to the study by the present inventors, it has been found that when the magnetic toner T passes between the developing sleeve 1a and the magnetic blade 2, an electric charge is applied to the magnetic toner T. It was also found that the behavior of the magnetic toner at that time was as follows.

As shown in FIG. 6, a plane perpendicular to a straight line connecting the developing sleeve 1a and the magnetic blade 2 is considered, and a surface close to the magnetic blade 2 is S1 and a surface close to the developing sleeve 1a is S2. Since the width of the magnetic blade 2 is set to be narrower than the width of the permanent magnet 1b,
Considering the respective magnetic flux densities on the surface and the S2 surface, the magnetic flux density on the S1 surface is larger than the magnetic flux density on the S2 surface.
Accordingly, the magnetic toner T receives a force between the developing sleeve 1a and the magnetic blade 2 in the direction of the arrow in FIG.

Therefore, as shown in FIG.
Form a spike (state B), and the spike is formed from the magnetic blade 2 toward the developing sleeve 1a. The charging of the magnetic toner T is performed by bringing the developing sleeve 1a into contact with the toner t1 at the tip of the ear formed by the magnetic blade 2 so that a charge is applied to the tip.

Further, it has been found that the toner is transported between the developing sleeve 1a and the magnetic blade 2 as follows.

As described above, a charge is applied to the toner t1 at the tip of the ear in contact with the developing sleeve 1a.
A force in the direction of the developing sleeve 1a by the mirror force acts, and a conveying force in the rotating direction of the developing sleeve 1a is given by a frictional force with the developing sleeve 1a.

Further, since a certain amount of cohesive force acts on the toner particles, the toner t2 in contact with the toner t1 also generates a conveying force via the cohesive force. Further, a conveying force via cohesive force is similarly generated in the toner t3 in the upper layer.

However, between the developing sleeve 1a and the magnetic blade 2, as described above, the magnetic blade 2
Is also applied to the toner. Accordingly, the toner is torn off at the point where the conveying force applied to the toner overcomes the magnetic force, that is, at the cut line L in FIG. 7, and the toner remaining on the developing sleeve 1a is conveyed in the rotation direction of the developing sleeve 1a. .

Therefore, a system in which the degree of aggregation of the magnetic toner is high,
In systems where the number of necessary contacts to obtain the necessary amount of triboelectric charge is large, insufficiently charged toner that is not in contact with the developing sleeve is transported to the developing area, and the phenomenon associated with poor charging is likely to occur. there were.

In order to solve this problem, the present inventors have
As shown in FIG. 8, a developing container 3 containing a developer composed of a magnetic toner and magnetic particles, a rotatable developing sleeve 1a carrying a magnetic toner on a surface, and a developing sleeve 1a inside the developing sleeve 1a. A permanent magnet 1b is provided, and a toner layer thickness regulator 6a that regulates the application of the magnetic toner on the developing sleeve 1a. The toner layer thickness regulator 6a is rotatably disposed near the developing sleeve 1a. And
The arrangement position is in the vicinity of the magnetic pole N11 of the permanent magnet 1b disposed inside the developing sleeve 1a, and the rotating direction is the same as the rotating direction of the developing sleeve 1a. 1a to toner layer thickness regulating body 6a
The developing device 20 in which the magnetic flux density becomes higher toward the side is proposed.

As a result, the number of contacts for the magnetic toner to obtain a triboelectric charge is increased, only the sufficiently charged magnetic toner is uniformly coated on the surface of the developing sleeve 1a, and only the sufficiently charged magnetic toner is Can be transported.

[0022]

However, in the above conventional example, depending on the combination of the magnetic toner and the magnetic material particles, the environment, etc., the sufficiently charged magnetic toner adheres to the magnetic material particles by the mirror force, and the developing container 3 In some cases, the amount of magnetic toner conveyed together with the magnetic particles and conveyed to the developing area on the developing sleeve 1a becomes insufficient, and the density of the output image becomes insufficient.

Accordingly, an object of the present invention is to provide a developing device which can always obtain a proper developed image regardless of the combination of magnetic particles and magnetic toner, environment and the like.

[0024]

The above object is achieved by a developing apparatus according to the present invention. In summary, the present invention provides a developing container containing a developer having a magnetic toner and magnetic particles, a toner carrier that carries the magnetic toner and rotates, and is provided inside the toner carrier. A permanent magnet, and a toner layer thickness regulator that is provided opposite to the toner carrier and regulates a layer thickness of the magnetic toner on the toner carrier. The toner layer thickness regulator itself is the toner layer. A component that is rotatable in the same direction as the carrier or that is rotatable in the same direction as the toner carrier; the magnetic flux density increases from the toner carrier toward the toner layer thickness regulator; In a developing device in which only a magnetic toner of a developer in a container is conveyed to a developing area, a voltage is applied between the toner carrier and the toner layer thickness regulating body to cause the magnetic particles adhering to the magnetic particles. Replace the toner with the toner A developing device for causing fly into lifting body.

The toner layer thickness regulating body has a permanent magnet having at least two poles therein, and one magnetic pole of the permanent magnet and one magnetic pole of the permanent magnet disposed inside the toner carrier are provided. It is preferable that the two magnetic poles are disposed at positions substantially opposed to each other, and the two magnetic poles disposed substantially opposed to each other have mutually different polarities.

It is preferable to have an AC power supply for generating an alternating electric field between the toner carrier and the toner layer thickness regulating body.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The developing device according to the present invention will be described below in more detail with reference to the drawings. In the embodiments described below, the present invention is described as being used in an electrophotographic image forming apparatus as shown in FIG. 9, for example, but is not limited thereto.

Referring to FIG. 9, an electrophotographic image forming apparatus in which the developing device according to the present invention is used is an image forming apparatus in which a photoconductive layer is coated on a conductive substrate as an electrostatic latent image carrier. An electrophotographic photosensitive member, that is, a photosensitive drum 15 is rotatably provided, the photosensitive drum 15 is uniformly charged by a charger 12, and an information signal is exposed by a light emitting element 13 such as a laser to form an electrostatic latent image. It is formed and visualized by the developing device 20. Next, the image is transferred to the transfer material 19 by the transfer charger 14,
Further, the image is fixed to the fixing device 16 to obtain a permanent image. The transfer residual toner on the photosensitive drum 15 is removed by the cleaning device 11.

Embodiment 1 A first embodiment of the developing device according to the present invention will be described with reference to FIG. The same members as those described above are denoted by the same reference numerals.

In FIG. 1, a developing device 20 is a developer carrier which is formed of a non-magnetic metal member and rotates in the direction of the arrow, facing the photosensitive drum 15 as a latent image carrier at the opening of the developing container 3. It has a developing sleeve 1a. A permanent magnet 1b having a plurality of magnetic poles is fixed inside the developing sleeve 1a. A transport member 4 is provided inside the developing container 3 so as to be rotatable in the direction of the arrow in order to transport the developer in the direction of the developing sleeve 1a. Further, a toner layer thickness regulator 6a is provided adjacent to the developing sleeve 1a and extending in the same direction. The toner layer thickness regulating body 6a is composed of a cylindrical non-magnetic metal member, and has a permanent magnet 6b having a plurality of magnetic poles inside. Further, the scraper 5 whose one end is in contact with the toner layer thickness regulating body 6a is
Attached to.

Incidentally, the toner layer thickness regulating body 6a has an arrow b _{1 in the} same direction as the rotation direction indicated by the arrow b ₂ of the developing sleeve 1a.
It is rotatable in the direction of. Further, the developing sleeve 1
DC power supply 7 is connected to a and the toner layer thickness regulating body 6a.

In this embodiment, the permanent magnet 1b is located substantially opposite the developing sleeve 1a and the toner layer thickness regulating body 6a.
The change in the magnetic flux density of the magnetic field formed between the magnetic pole N11 in the inside and the magnetic pole S61 in the permanent magnet 6b disposed so as to be close to and substantially opposite to the magnetic pole N11 is caused by the change in the magnetic flux density from the developing sleeve 1a to the toner layer thickness regulating body 6a. In order to increase the magnetic flux density toward the side, the ratio of the width (hereinafter referred to as 50% value for convenience) of the region showing a value of 50% or more with respect to the peak value of the magnetic flux density of each magnetic pole, (50% value of magnetic pole S61) / (50% value of magnetic pole N11)
≦ 1.0 Preferably, (50% value of magnetic pole S61) / (50% value of magnetic pole N11)
≦ 0.8, and in this embodiment, (50% value of the magnetic pole S61) / (50% value of the magnetic pole N11)
By setting ≒ 0.8, the magnetic flux density of the magnetic field formed between the magnetic pole S61 and the magnetic pole N11 changes such that the magnetic flux density increases from the developing sleeve 1a toward the toner layer thickness regulating body 6a. did.

In this embodiment, the maximum value of the magnetic flux density of the magnetic pole is 900 gauss, the magnetic pole N11 is 900 gauss, and the magnetic pole S1 is
1 was 800 gauss.

The distance W between the developing sleeve 1a and the toner layer thickness regulating member 6a is set in the range of 100 μm to 2 mm, and the absolute value of the peripheral speed of the developing sleeve 1a and the absolute value of the peripheral speed of the toner layer thickness regulating member 6a. (Absolute value of peripheral speed of toner layer thickness regulating body 6a) / (absolute value of peripheral speed of developing sleeve 1a)> 0.5.

The magnetic toner has a weight average diameter of 5 μm or more,
The weight of the magnetic substance added to the magnetic toner was 10% or more of the weight of the magnetic toner, and the magnetic particles were ordinary magnetic carriers having a weight average diameter of 20 to 100 μm.

The power source 7 uses a DC power source, and the negatively charged magnetic toner is transferred from the toner layer thickness regulating body 6a to the developing sleeve 1
A bias was applied so as to apply a Coulomb force in the a direction.

The developing device 20 constructed as shown in FIG.
, The toner layer thickness regulating body 6
Since the magnetic flux density becomes higher toward the side a, the magnetic particles existing between the developing sleeve 1a and the toner layer thickness regulating body 6a include the toner particles from the developing sleeve 1a to the toner layer thickness regulating body 6a.
A magnetic force acts on the a side. As a result, a brush of magnetic particles is formed along the magnetic field between the magnetic pole N11 and the magnetic pole S61.

In this embodiment, the toner layer thickness regulating member 6a is moved in the same direction as the developing sleeve 1a by an arrow b in the drawing.
_{Since the} rotation is made in _one direction, the magnetic particles held by the magnetic force on the surface of the toner layer thickness regulating body 6a cause the toner layer thickness to be reduced by the force of the magnetic field and the frictional force with the surface of the toner layer thickness regulating body 6a. A transport force in the developing container 3 inward direction is given from the regulating body 6a. Therefore, the magnetic particles do not pass through the opposing position of the developing sleeve 1a and the toner layer thickness regulating body 6a and are not transported to the developing area.

The magnetic particles returned in the developing container 3 are scraped off from the surface of the toner layer thickness regulating body 6a by the scraper 5. The magnetic particles returned into the developing container 3 in this manner are stirred with the toner by the transport member 4,
It is transported again on the surface of the developing sleeve 1a and is transported to a position where the magnetic pole N11 and the magnetic pole S61 face each other. The circulation path of the magnetic particles in the developing container 3 at this time is as shown by an arrow a in the figure.

The magnetic toner is charged in the developing container 3 by friction between the magnetic particles and the surface of the developing sleeve 1a. The charged magnetic toner adheres to the surface of the developing sleeve 1a and the magnetic particles due to the reflection force of the charge of the toner itself, and is conveyed to a position where the developing sleeve 1a and the toner layer thickness regulating body 6a are opposed to each other. When the developer is conveyed to the opposing position, the magnetic particles become the developing sleeve 1a for the above-described reason.
Is returned into the developing container 3 from a position facing the toner layer thickness regulating body 6a. Insufficiently charged magnetic toner that has been conveyed to the opposing position due to cohesion or the like receives a magnetic force in the direction of the toner layer thickness regulating body 6a between the magnetic pole N11 and the magnetic pole S61,
Due to the frictional force with the surface of the toner layer thickness regulating body 6a and the cohesive force between the magnetic toners, a conveying force in the rotation direction of the toner layer thickness regulating body 6a (inside the developing container 3) is obtained.

In this embodiment, the bias is applied by the DC power supply 7 so that the magnetic toner negatively charged by frictional charging with the magnetic particles receives Coulomb force from the toner layer thickness regulating body 6a toward the developing sleeve 1a. Have been hung. Therefore, the magnetic toner, which is negatively charged due to frictional charging with the magnetic particles and adheres to the magnetic particles by the mirroring force, is applied by the power source 7 in the vicinity of the toner layer thickness regulating body 6a and the developing sleeve 1a. Due to the applied bias, the magnetic particles separate from the magnetic particles and fly to the developing sleeve 1a.

Accordingly, the magnetic toner that passes through the position where the toner layer thickness regulating body 6a and the developing sleeve 1a face each other and is conveyed to the developing area is reflected on the developing sleeve 1a by a force that exceeds the conveying force in the developing container 3 direction. The magnetic toner is sufficiently charged by the frictional charging between the magnetic toner particles and the sufficiently charged magnetic toner, and the magnetic toner flies to the developing sleeve 1a by the bias from the power supply 7.

That is, according to the present configuration, it is possible to sufficiently charge the magnetic toner by mixing the magnetic particles and the magnetic toner, and to prevent the magnetic particles from leaking to the developing region, Regardless of the combination of body particles and magnetic toner, environment, etc., only a sufficient amount of magnetic toner that is sufficiently charged to maintain image density can be coated on the sleeve surface and transported to the development area. Was.

Embodiment 2 Next, a second embodiment of the developing device according to the present invention will be described with reference to FIG.
This will be described below. The same members as those described above are denoted by the same reference numerals.

In FIG. 2, a developing device 20 is a developer carrying member which is made of a non-magnetic metal member and rotates in the direction of the arrow, facing the photosensitive drum 15 as a latent image carrying member at the opening of the developing container 3. It has a developing sleeve 1a. A permanent magnet 1b having a plurality of magnetic poles is fixed inside the developing sleeve 1a. A transport member 4 is provided inside the developing container 3 so as to be rotatable in the direction of the arrow in order to transport the developer in the direction of the developing sleeve 1a. Further, a toner layer thickness regulator 6a is provided adjacent to the developing sleeve 1a and extending in the same direction. The toner layer thickness regulating body 6a is composed of a cylindrical non-magnetic metal member, and has a permanent magnet 6b having a plurality of magnetic poles inside. A scraper 5 whose one end is in contact with the toner regulating body 6a is attached to the developing container 3.

The toner layer thickness regulating body 6a has an arrow b _{1 in the} same direction as the direction of rotation of the developing sleeve 1a as indicated by an arrow b ₂ .
It is rotatable in the direction of. Further, the developing sleeve 1
The DC power source 7 and the AC power source 8 are connected in series with the toner layer thickness control body 6a and the toner layer thickness regulating body 6a.

In this embodiment, the permanent magnet 1b is located substantially opposite the developing sleeve 1a and the toner layer thickness regulating body 6a.
The change in the magnetic flux density of the magnetic field formed between the magnetic pole N11 in the inside and the magnetic pole S61 in the permanent magnet 6b disposed so as to be close to and substantially opposite to the magnetic pole N11 is caused by the change in the magnetic flux density from the developing sleeve 1a to the toner layer thickness regulating body 6a. In order to increase the magnetic flux density toward the side, the ratio of the width (hereinafter referred to as 50% value for convenience) of the region showing a value of 50% or more with respect to the peak value of the magnetic flux density of each magnetic pole, (50% value of magnetic pole S61) / (50% value of magnetic pole N11)
≦ 1.0 Preferably, (50% value of magnetic pole S61) / (50% value of magnetic pole N11)
≦ 0.8, and in this embodiment, (50% value of the magnetic pole S61) / (50% value of the magnetic pole N11)
By setting ≒ 0.8, the magnetic flux density of the magnetic field formed between the magnetic pole S61 and the magnetic pole N11 changes such that the magnetic flux density increases from the developing sleeve 1a toward the toner layer thickness regulating body 6a. did.

In this embodiment, the maximum value of the magnetic flux density of the magnetic pole is 900 gauss for the magnetic pole N11 and the maximum value of the magnetic pole S1 for the magnetic pole N11.
1 was 800 gauss.

The distance W between the developing sleeve 1a and the toner layer thickness regulating member 6a is set in the range of 100 μm to 2 mm, and the absolute value of the peripheral speed of the developing sleeve 1a and the absolute value of the peripheral speed of the toner layer thickness regulating member 6a. (Absolute value of peripheral speed of toner layer thickness regulating body 6a) / (absolute value of peripheral speed of developing sleeve 1a)> 0.5.

The magnetic toner has a weight average diameter of 5 μm or more,
The weight of the magnetic substance added to the magnetic toner was 10% or more of the weight of the magnetic toner, and the magnetic particles were ordinary magnetic carriers having a weight average diameter of 20 to 100 μm.

The toner layer thickness regulating body 6a and the developing sleeve 1a
In the meantime, a bias was applied to the AC bias from the AC power supply 8 so that a Coulomb force from the toner layer thickness regulator 6a toward the developing sleeve 1a was applied to the magnetic toner negatively charged with the DC bias from the DC power supply 7. .

The developing device 20 constructed as shown in FIG.
, The toner layer thickness regulating body 6
Since the magnetic flux density becomes higher toward the side a, the magnetic particles existing between the developing sleeve 1a and the toner layer thickness regulating body 6a include the toner particles from the developing sleeve 1a to the toner layer thickness regulating body 6a.
A magnetic force acts on the a side. As a result, a brush of magnetic particles is formed along the magnetic field between the magnetic pole N11 and the magnetic pole S61.

In this embodiment, the toner layer thickness regulating member 6a is moved in the same direction as the developing sleeve 1a by an arrow b in the drawing.
_{Since the} rotation is made in _one direction, the magnetic particles held by the magnetic force on the surface of the toner layer thickness regulating body 6a cause the toner layer thickness to be reduced by the force of the magnetic field and the frictional force with the surface of the toner layer thickness regulating body 6a. A transport force in the developing container 3 inward direction is given from the regulating body 6a. Therefore, the magnetic particles do not pass through the opposing position of the developing sleeve 1a and the toner layer thickness regulating body 6a and are not transported to the developing area.

The magnetic particles returned in the developing container 3 are scraped off from the surface of the toner layer thickness regulating body 6a by the scraper 5. The magnetic particles returned into the developing container 3 in this manner are stirred with the toner by the transport member 4,
It is transported again on the surface of the developing sleeve 1a and is transported to a position where the magnetic pole N11 and the magnetic pole S61 face each other. The circulation path of the magnetic particles in the developing container 3 at this time is as shown by an arrow a in the figure.

The magnetic toner is charged in the developing container 3 by friction between the magnetic particles and the surface of the developing sleeve 1a. The charged magnetic toner adheres to the surface of the developing sleeve 1a and the magnetic particles due to the reflection force of the charge of the toner itself, and is conveyed to a position where the developing sleeve 1a and the toner layer thickness regulating body 6a are opposed to each other. When the developer is conveyed to the opposing position, the magnetic particles become the developing sleeve 1a for the above-described reason.
Is returned into the developing container 3 from a position facing the toner layer thickness regulating body 6a. Insufficiently charged magnetic toner that has been conveyed to the opposing position due to cohesion or the like receives a magnetic force in the direction of the toner layer thickness regulating body 6a between the magnetic pole N11 and the magnetic pole S61,
Due to the frictional force with the surface of the toner layer thickness regulating body 6a and the cohesive force between the magnetic toners, a conveying force in the rotation direction of the toner layer thickness regulating body 6a (inside the developing container 3) is obtained.

In this embodiment, the bias is applied by the DC power supply 7 so that the magnetic toner negatively charged by frictional charging with the magnetic particles receives Coulomb force from the toner layer thickness regulating body 6a toward the developing sleeve 1a. Have been hung. Further, since an AC bias is applied between the toner layer thickness regulating body 6a and the developing sleeve 1a by the AC power supply 8, even when the adhesive force between the magnetic toner and the magnetic particles is large, the effect of the AC bias causes The magnetic toner is easily peeled off from the magnetic particles. Therefore, the magnetic toner, which is negatively charged due to frictional charging with the magnetic particles and adheres to the magnetic particles by the mirroring force, is applied by the power source 7 in the vicinity of the toner layer thickness regulating body 6a and the developing sleeve 1a. Due to the applied bias, the magnetic particles separate from the magnetic particles and fly to the developing sleeve 1a.

Therefore, the magnetic toner which passes through the position where the toner layer thickness regulating body 6a and the developing sleeve 1a face each other and is conveyed to the developing area is reflected on the developing sleeve 1a which exceeds the conveying force in the developing container 3 direction. The magnetic toner is sufficiently charged by the frictional charging of the magnetic toner particles and the magnetic particles that are sufficiently charged, and the magnetic toner flies to the developing sleeve 1a by the bias from the power supplies 7 and 8.

That is, according to this configuration, it is possible to sufficiently charge the magnetic toner by mixing the magnetic particles and the magnetic toner, and to prevent the magnetic particles from leaking to the developing region and to reduce the magnetic toner. Regardless of the combination of body particles and magnetic toner, environment, etc., only a sufficient amount of magnetic toner that is sufficiently charged to maintain image density can be coated on the sleeve surface and transported to the development area. Was.

Embodiment 3 Next, a third embodiment of the developing device according to the present invention will be described with reference to FIG.
This will be described below. The same members as those described above are denoted by the same reference numerals.

In FIG. 3, a developing device 20 is a developer carrier which is formed of a non-magnetic metal member and is rotated in the direction of the arrow, facing the photosensitive drum 15 as a latent image carrier at the opening of the developing container 3. It has a developing sleeve 1a. A permanent magnet 1b having a plurality of magnetic poles is fixed inside the developing sleeve 1a. A transport member 4 is provided inside the developing container 3 so as to be rotatable in the direction of the arrow in order to stir the developer and transport the developer in the direction of the developing sleeve 1a. Further, a toner layer thickness regulator 6a is provided adjacent to the developing sleeve 1a and extending in the same direction. Toner layer thickness regulating body 6a
Is composed of a cylindrical non-magnetic metal member, has a permanent magnet 6b having a plurality of magnetic poles inside, and further has a drive roller 6c. A roller 9 is disposed inside the developing container 3 so as to be rotatable in the direction of arrow e. A conductive belt member 10 is wound around the roller 9 and a driving roller 6c of the toner layer thickness regulating body 6a. ing.

The driving roller 6c is positioned near the developing sleeve 1a by an arrow b _{1 in the} same direction as the rotation direction of the developing sleeve 1a.
In such a manner as to drive the conductive belt 10 in the direction of.

In this embodiment, the permanent magnet 1b is located substantially opposite the developing sleeve 1a and the toner layer thickness regulating body 6a.
The change in the magnetic flux density of the magnetic field formed between the magnetic pole N11 in the inside and the magnetic pole S61 in the permanent magnet 6b disposed so as to be close to and substantially opposite to the magnetic pole N11 is caused by the change in the magnetic flux density from the developing sleeve 1a to the toner layer thickness regulating body 6a. In order to increase the magnetic flux density toward the side, the ratio of the width (hereinafter referred to as 50% value for convenience) of the region showing a value of 50% or more with respect to the peak value of the magnetic flux density of each magnetic pole, (50% value of magnetic pole S61) / (50% value of magnetic pole N11)
≦ 1.0 Preferably, (50% value of magnetic pole S61) / (50% value of magnetic pole N11)
≦ 0.8, and in this embodiment, (50% value of the magnetic pole S61) / (50% value of the magnetic pole N11)
By setting ≒ 0.8, the magnetic flux density of the magnetic field formed between the magnetic pole S61 and the magnetic pole N11 changes such that the magnetic flux density increases from the developing sleeve 1a toward the toner layer thickness regulating body 6a. did.

In this embodiment, the maximum value of the magnetic flux density of the magnetic pole is 900 gauss, the magnetic pole N11 is 900 gauss, and the magnetic pole S1 is
1 was 800 gauss.

The distance W between the developing sleeve 1a and the toner layer thickness regulating member 6a is set in the range of 100 μm to 2 mm, and the absolute value of the peripheral speed of the developing sleeve 1a and the absolute value of the peripheral speed of the toner layer thickness regulating member 6a are set. (Absolute value of peripheral speed of toner layer thickness regulating body 6a) / (absolute value of peripheral speed of developing sleeve 1a)> 0.5.

The magnetic toner has a weight average diameter of 5 μm or more,
The weight of the magnetic substance added to the magnetic toner was 10% or more of the weight of the magnetic toner, and the magnetic particles were ordinary magnetic carriers having a weight average diameter of 20 to 100 μm.

A DC power supply was used as the power supply 7 and a bias was applied so that a negatively charged magnetic toner exerted a Coulomb force from the conductive belt 10 toward the developing sleeve 1a.

The developing device 20 constructed as shown in FIG.
In, magnetic particles forming the brush by the magnetic field between the pole N11 and the magnetic pole S61 is the frictional force between the conductive belt 10, is conveyed in the direction of rotation shown in FIG arrow b _1,
It is returned into the developing container 3 and falls into the developing container 3 by gravity.

Further, in this embodiment, the magnetic toner adhered to the magnetic particles due to the reflection force or the like due to the effect of the bias from the power source 7 is applied to the developing sleeve 1 a and the conductive belt 1.
At a position close to 0, it flies to the developing sleeve 1a.

As a result, the same effects as those of the developing device of the first embodiment were obtained.

Embodiment 4 Next, a fourth embodiment of the developing device according to the present invention will be described with reference to FIG.
This will be described below. The same members as those described above are denoted by the same reference numerals.

[0071]

In FIG. 4, the developing device 20 is a developer carrier which is made of a non-magnetic metal member and is rotated in the direction of the arrow, facing the photosensitive drum 15 as a latent image carrier at the opening of the developing container 3. It has a developing sleeve 1a. A permanent magnet 1b having a plurality of magnetic poles is fixed inside the developing sleeve 1a. A transport member 4 is provided inside the developing container 3 so as to be rotatable in the direction of the arrow in order to stir the developer and transport the developer in the direction of the developing sleeve 1a. Further, a toner layer thickness regulating body 6 extending in the same direction adjacent to the developing sleeve 1a is provided. The toner layer thickness regulating body 6 is formed of a cylindrical non-magnetic metal member, and includes a permanent magnet 6 b having a plurality of magnetic poles therein.
c. A roller 9 is disposed inside the developing container 3 so as to be rotatable in the direction of arrow e. A conductive belt member 10 is wound around the roller 9 and a driving roller 6c of the toner layer thickness regulating member 6. ing.

The driving roller 6c is provided near the developing sleeve 1a with an arrow b _{1 in the} same direction as the rotation direction of the developing sleeve 1a.
In such a manner as to drive the conductive belt 10 in the direction of.

In this embodiment, the permanent magnet 1b is located substantially opposite the developing sleeve 1a and the toner layer thickness regulating body 6a.
The change in the magnetic flux density of the magnetic field formed between the magnetic pole N11 in the inside and the magnetic pole S61 in the permanent magnet 6b disposed so as to be close to and substantially opposite to the magnetic pole N11 is caused by the change in the magnetic flux density from the developing sleeve 1a to the toner layer thickness regulating body 6a. In order to increase the magnetic flux density toward the side, the ratio of the width (hereinafter referred to as 50% value for convenience) of the region showing a value of 50% or more with respect to the peak value of the magnetic flux density of each magnetic pole, (50% value of magnetic pole S61) / (50% value of magnetic pole N11)
≦ 1.0 Preferably, (50% value of magnetic pole S61) / (50% value of magnetic pole N11)
≦ 0.8, and in this embodiment, (50% value of the magnetic pole S61) / (50% value of the magnetic pole N11)
By setting ≒ 0.8, the magnetic flux density of the magnetic field formed between the magnetic pole S61 and the magnetic pole N11 changes such that the magnetic flux density increases from the developing sleeve 1a toward the toner layer thickness regulating body 6a. did.

In this embodiment, the maximum value of the magnetic flux density of the magnetic pole is 900 gauss, the magnetic pole N11 is 900 gauss, and the magnetic pole S1 is
1 was 800 gauss.

The distance W between the developing sleeve 1a and the toner layer thickness regulating member 6a is set in the range of 100 μm to 2 mm, the absolute value of the peripheral speed of the developing sleeve 1a and the absolute value of the peripheral speed of the toner layer thickness regulating member 6a. (Absolute value of peripheral speed of toner layer thickness regulating body 6a) / (absolute value of peripheral speed of developing sleeve 1a)> 0.5.

The magnetic toner has a weight average diameter of 5 μm or more,
The weight of the magnetic substance added to the magnetic toner was 10% or more of the weight of the magnetic toner, and the magnetic particles were ordinary magnetic carriers having a weight average diameter of 20 to 100 μm.

Between the conductive belt 10 and the developing sleeve 1a, an AC bias from the power source 8 and a DC bias from the power source 7 are applied to the negatively charged magnetic toner.
Are superimposed so that a Coulomb force is applied in the direction of the developing sleeve 1a.

The developing device 20 constructed as shown in FIG.
In, magnetic particles forming the brush by the magnetic field between the pole N11 and the magnetic pole S61 is the frictional force between the conductive belt 10, is conveyed in the direction of rotation shown in FIG arrow b _1,
It is returned into the developing container 3 and falls into the developing container 3 by gravity.

In this embodiment, the effect of the AC bias by the power supply 8 makes it easy for the magnetic toner to be peeled off from the magnetic particles even when the adhesive force between the magnetic toner and the magnetic particles is large. The magnetic toner attached to the magnetic particles due to the mirror force or the like flies to the developing sleeve 1a at a position close to the developing belt 1a and the conductive belt 10 due to the effect of the bias due to the bias.

As a result, the same effect as the developing device of the first embodiment was obtained.

[0082]

As is apparent from the above description, the present invention is directed to a developing container containing a developer having a magnetic toner and magnetic particles, a toner carrier rotating to carry a magnetic toner, and a toner container. A permanent magnet provided inside the carrier,
A toner layer thickness regulator that is provided opposite to the toner carrier and regulates a layer thickness of the magnetic toner on the toner carrier, and the toner layer thickness regulator itself can rotate in the same direction as the toner carrier. Or a component member rotatable in the same direction as the toner carrier. The magnetic flux density is higher as going from the toner carrier to the toner layer thickness regulator, and only the magnetic toner of the developer in the developing container is in the developing area. In the developing device conveyed to the toner carrier, a voltage is applied between the toner carrier and the toner layer thickness regulating body to cause the magnetic toner attached to the magnetic particles to fly to the toner carrier. By mixing the body particles and the magnetic toner, the magnetic toner can be sufficiently charged, and the magnetic particles do not leak to the developing area, and the combination of the magnetic particles and the magnetic toner, environment, etc. About Instead, only a sufficient amount of magnetic toner, which is sufficiently charged to maintain the image density, can be coated on the surface of the toner carrier and conveyed to the developing area, so that a proper developed image can always be obtained. A high quality image can be obtained by using the image forming apparatus.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a developing device according to the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of the developing device according to the present invention.

FIG. 3 is a configuration diagram showing a third embodiment of the developing device according to the present invention.

FIG. 4 is a configuration diagram showing a fourth embodiment of the developing device according to the present invention.

FIG. 5 is a cross-sectional view of an example of a conventional developing device using a magnetic blade fixed to a developer amount regulating member.

FIG. 6 is an explanatory diagram of a magnetic flux density in a developer regulating section.

FIG. 7 is an explanatory diagram of a behavior of the toner in the developer regulating unit.

FIG. 8 is a configuration diagram illustrating an example of a developing device using a rotatable toner layer thickness regulating body.

FIG. 9 is a schematic configuration diagram of an electrophotographic image forming apparatus that can realize the developing device according to the present invention.

[Explanation of symbols]

 1a Developing sleeve (toner carrier) 1b Permanent magnet 3 Developing container 4 Conveying member 6a Toner layer thickness regulating body 6b Permanent magnet 6c Driving roller 7 DC power supply 8 AC power supply 9 Roller 10 Conductive belt

Continuation of front page (56) References JP-A-56-47050 (JP, A) JP-A-5-35106 (JP, A) JP-A-4-214581 (JP, A) JP-A-1-144075 (JP) JP-A-55-50274 (JP, A) JP-A-56-5573 (JP, A) JP-A-58-37657 (JP, A) JP-A-1-191163 (JP, A) 4-184462 (JP, A) JP-A-7-152245 (JP, A) JP-A-61-46557 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/06 -15/095

Claims (3)

(57) [Claims] 1. A developing container containing a developer having a magnetic toner and magnetic particles, a toner carrier rotatably supporting the magnetic toner, and a permanent magnet provided inside the toner carrier. A toner layer thickness regulator that is provided to face the toner carrier and regulates a layer thickness of the magnetic toner on the toner carrier. The toner layer thickness regulator itself is the same as the toner carrier. A component that is rotatable in the same direction or includes a component rotatable in the same direction as the toner carrier, and the magnetic flux density is higher as going from the toner carrier to the toner layer thickness regulator side,
In the developing device in which only the magnetic toner of the developer in the developing container is conveyed to the developing area, a voltage is applied between the toner carrier and the toner layer thickness regulating body to adhere to the magnetic particles. Wherein the magnetic toner is caused to fly to the toner carrier. 2. The toner layer thickness regulating body has therein a permanent magnet having at least two poles, and one of the permanent magnets.
Two magnetic poles and one magnetic pole of a permanent magnet disposed inside the toner carrier are disposed at positions substantially opposed to each other, and the two magnetic poles disposed at substantially opposite positions have mutually different polarities. 2. The developing device according to claim 1, wherein: 3. The developing device according to claim 1, further comprising an AC power supply for generating an alternating electric field between said toner carrier and said toner layer thickness regulating body.