JP3129900B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[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 a photoconductive material made of a photoconductive material by various means, a latent image is formed using toner, and a toner image is transferred to a transfer material such as paper as necessary, and then overheated. ,
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. etc,
Numerous development methods are known.

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 that can obtain a good image relatively stably, but has the common disadvantages related to the two-component developer such as deterioration of the carrier and fluctuation of the mixing ratio of the toner and the carrier. Have.

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 method, a conductive magnetic toner is supported on a cylindrical conductive sleeve having magnetism therein, and is contacted 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 which avoids the problems associated with the conventional two-component toner, but on the other hand, since the toner is conductive, the developed image can be transferred from the recording medium to the final paper such as plain paper. Has the disadvantage that it is difficult to transfer electrostatically to a typical 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 the development is applied to the toner. It is possible to give.

However, also in the above-mentioned method, it is known that the chance of contact between the developing sleeve and the magnetic toner is smaller than the chance of contact between the two-component toner and the carrier in the two-component method.

It is also well known that the required number of times of contact between the magnetic toner and the developing sleeve for obtaining the amount of triboelectric charge required for the magnetic toner to be used for development varies depending on the composition of the magnetic toner. .

Therefore, in the above system, in a system in which the required number of times of contact is large in order to obtain a required amount of triboelectric charge, there is a disadvantage that a phenomenon accompanying charging instability tends to occur.

According to the study by the present inventors regarding 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.

In FIG. 6, a developing device includes a toner container 3 containing a magnetic one-component toner, a developing sleeve 1a using a non-magnetic member rotatably disposed in the opening of the toner container 3 in the direction of the arrow, and a developing device. A permanent magnet 1b fixed inside the sleeve 1a, a magnetic blade 2 fixed to the toner container 3 and using a magnetic member for regulating the thickness of the toner layer, and a toner conveying member 4 provided in the toner container 3 are provided. Have. 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. 6, 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 of 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. 8, 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.
Therefore, 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 was found that the toner was 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 between the toners, 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. 8, and the toner remaining on the developing sleeve 1a is conveyed in the rotation direction of the developing sleeve 1a. .

Therefore, as is apparent from the behavior of the toner of the conventional example and the process of applying the charge to the toner, the conventional example has a problem that the charge can be applied only to the toner near the developing sleeve 1a. there were.

In the above conventional example, as shown in FIG.
A toner accumulation portion C to which no electric charge is applied is generated. When the toner accumulation portion C becomes large, the force of holding the toner on the magnetic blade 2 side by magnetic force is weakened. Part of the toner is conveyed in the rotation direction of the developing sleeve 1a, and as a result, part of the toner conveyed on the developing sleeve 1a becomes uncharged toner. In the above-described conventional example, a phenomenon associated with unstable charging is likely to occur. There was a problem.

In order to solve the above problem, the present inventors have proposed a developing device for stabilizing the charging of the magnetic toner by returning the insufficiently charged magnetic toner into the developing container by the developer regulating member. .

That is, as shown in FIG.
As a member that regulates the application of the toner on a, a developer regulating member 6a that is made of a non-magnetic material and that is rotatably provided facing the vicinity of the developing sleeve 1a. Further, inside the developer regulating member 6a, a permanent magnet 6b is disposed near the magnetic pole N11 of the permanent magnet 1b. Further, the developer regulating member 6a
The magnetic pole S61 of the middle permanent magnet 6b is opposed to the magnetic pole N11 of the permanent magnet 1b in the developing sleeve 1a, and the rotation direction of the developer regulating member 6a is the same as the rotation direction of the developing sleeve 1a. This makes it possible to stabilize the charging by returning the magnetic toner not in contact with the surface of the developing sleeve 1a into the developing container and conveying only the sufficiently charged magnetic toner.

[0026]

As described above, the provision of the developer regulating member 6a having the permanent magnet 6b therein in a rotatable manner in the vicinity of the developing sleeve 1a stabilizes the charging of the magnetic toner. It became possible to make it.

However, also in the above-described conventional example, a combination of the magnetic pole N11 inside the developing sleeve 1a and the magnetic pole S61 inside the developer regulating body 6a, or a magnetic member is used for the developer regulating body 6, and the width of the magnetic pole N11 is changed. When the width of the developer regulating body 6 is made narrower than in the case where the rigidity of the developer regulating body 6 is low, for example, the developer regulating body 6 is bent by the magnetic force, which may cause uneven coating of the toner. there were.

Accordingly, an object of the present invention is to provide an image forming apparatus provided with a developing device capable of preventing bending of a developer regulating member due to a magnetic force and eliminating uneven toner coating.

[0029]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
A rotatable developer carrier that carries on its surface a developer containing a magnetic toner containing a magnetic material, a permanent magnet disposed inside the developer carrier, and A developer regulating body for regulating the application of the developer, wherein the developer regulating body is rotatably opposed to at least one magnetic pole of a permanent magnet disposed inside the developer carrier. In the image forming apparatus having a developing device whose rotation direction is the same as the rotation direction of the developer carrier, the image forming apparatus has a structure in which a magnetic force received by the developer regulating body from a magnetic pole in the developer carrier is provided. An image forming apparatus, wherein a force acting in a reverse direction is applied to the developer regulating member.

Preferably, the developer regulating member is provided with a permanent magnet having at least two poles therein, and at least one of the permanent magnets disposed inside the developer carrier. It is rotatably opposed to the vicinity,
At a position where the developer regulating member and the developer carrying member face each other,
One magnetic pole of the permanent magnet provided inside the developer regulating body has a different polarity from one magnetic pole of the permanent magnet inside the developer carrying body provided at the facing position.

It is preferable that the developer regulating member is made of a magnetic material, and the width thereof is smaller than the width of one magnetic pole of the permanent magnet facing the developer regulating member inside the developer carrier.

[0032] Further, it is preferable that the magnetic flux density increases from the side of the developer carrier to the side of the developer regulator at a position where the developer regulating body and the developer carrying body are opposed to each other.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings. In the embodiment described below,
The present invention will be described as being embodied in, for example, an electrophotographic image forming apparatus as shown in FIG. 10, but is not limited thereto.

Referring to FIG. 10, an electrophotographic image forming apparatus includes an electrophotographic photosensitive member, that is, a photosensitive drum 15 on a drum constituted by applying a photoconductive layer on a conductive substrate as an electrostatic latent image carrier. Rotatably provided, the photosensitive drum 15 is uniformly charged by the charger 12, and an information signal is exposed by a light emitting element 13 such as a laser to form an electrostatic latent image,
The image is visualized by the developing device 20. Next, the image is transferred to the transfer material 19 by the transfer charger 14 and further 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 With reference to FIG. 1, a first embodiment of a developing device of an image forming apparatus according to the present invention will be described. The same members as those described above are denoted by the same reference numerals.

In FIG. 1, a developing device 20 has a diameter which is a toner carrier which is formed of a non-magnetic metal member and which is made of a non-magnetic metal member and rotates in the direction of the arrow, facing the photosensitive drum 15 which is a latent image carrier at an opening of the developing container 3. It has a developing sleeve 1a of 32 mm. 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 developer regulating body 6a having a diameter of 10 mm is provided adjacent to the developing sleeve 1a and extends in the same direction, and a permanent magnet 6b having a plurality of magnetic poles is fixed therein.
The scraper 5 is attached to the developing container 3 such that one end thereof is in contact with the developer regulating body 6a. Further, a plate-shaped permanent magnet 7 having one end thereof opposed to the developer regulating body 6a is provided.
Is attached to the developing container 3.

The developer regulating member 6a is arranged so as to be rotatable in the direction of arrow b1 in the same direction as the direction of arrow b2 in the direction of rotation of the developing sleeve 1a.

In the present embodiment, the permanent magnet 6 is disposed so as to be closely opposed to the magnetic pole N11 in the permanent magnet 1b, which is located at the position where the developing sleeve 1a and the developer regulating body 6a are opposed.
b, the magnetic flux density of the magnetic pole S61 is 800 gauss and the magnetic pole N1 is
The magnetic flux density of No. 1 was 900 gauss. Further, the ratio of the width of the region showing a value of 50% or more to the peak value of the magnetic flux density of each magnetic pole (hereinafter referred to as a 50% value for convenience) is represented by ｛(50% value of magnetic pole S61) × (development The diameter of the sleeve 1a) / {(50% value of the magnetic pole N11) × (the diameter of the developer regulating member 6a)} <1.0, and the magnetic flux density of the magnetic field formed between the magnetic pole S61 and the magnetic pole N11 The configuration is such that the magnetic flux density increases as the change goes from the developing sleeve 1a to the developer regulating body 6a.

Further, the developing sleeve 1a and the developer regulating body 6
a is set to a range of 100 μm to 2 mm, and the ratio of the absolute value of the peripheral speed of the developing sleeve 1a to the absolute value of the peripheral speed of the developer regulating member 6a is defined as (absolute value of the peripheral speed of the developer regulating member 6a). Value) / (absolute value of peripheral speed of developing sleeve 1a)> 0.5.

Further, the plate-shaped permanent magnet 7 is
And a magnetic pole N7 opposed to the magnetic pole N61 in the inside, the magnetic pole S7 is set to 800 gauss, and the magnetic pole N61 is set to 80
0 gauss.

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.

In the developing device constructed as shown in FIG. 1, since the magnetic flux density increases from the developing sleeve 1a toward the developer regulating member 6a, the developing sleeve 1a
The magnetic toner present between the developer regulating body 6a and
A magnetic force acts from the developing sleeve 1a to the developer regulating body 6a. Therefore, the magnetic toner which is less sufficiently reflected than the above-mentioned magnetic force and is less reflected on the developing sleeve 1a is held on the developer regulating body 6a side.

In this embodiment, the developer regulating member 6
a is rotated in the direction of the arrow b1 in the drawing, which is the same direction as the developing sleeve 1a, so that the insufficiently charged magnetic toner held on the surface of the developer regulating body 6a by the magnetic force is less than the force by the magnetic field. Due to the frictional force with the surface of the developer regulating body 6a, a conveying force from the developer regulating body 6a to the inside of the developing container 3 is given.

In this embodiment, the magnetic pole N61 of the permanent magnet 6b in the developer regulating body 6a is used to prevent the developer regulating body 6 from bending due to the magnetic force from the permanent magnet 1b.
The magnetic pole S7 of the permanent magnet 7 is disposed at a position opposite to the magnetic force from the permanent magnet 1b. The restricting body 6a is prevented from bending.
As a result, it is possible to prevent toner coating unevenness due to bending of the developer regulating body 6a.

Therefore, the insufficiently charged magnetic toner passes through the opposing position between the developing sleeve 1a and the developer regulating member 6a, and
It is not transported to the development area.

The magnetic toner returned into the developing container 3 is scraped off the surface of the developer regulating member 6a by the scraper 5. The magnetic toner thus returned into the developing container 3 is attracted to the surface of the developing sleeve 1a by a magnetic force, and is conveyed to a position facing the magnetic pole N11 and the magnetic pole S61. At this time, the circulation route of the magnetic toner in the developing container 3 is indicated by an arrow a in FIG.
It becomes as shown in.

The magnetic toner is conveyed on the surface of the developing sleeve 1a by a magnetic force in the developing container 3 to a position where the developing sleeve 1a and the developer regulating member 6a are opposed to each other. When the developer is transported to the opposite position, the insufficiently charged magnetic toner is removed from the developing sleeve 1a and the developer regulating member 6 for the above-described reason.
The developer is returned into the developing container 3 from the position opposing a.

Therefore, the magnetic toner that has passed through the opposing position of the developing sleeve 1a and the developer regulating member 6a and is conveyed to the developing area has a higher reflection force on the developing sleeve 1a than the conveying force in the developing container 3 direction. And only a sufficiently charged magnetic toner is obtained.

That is, according to this configuration, the developer regulating member 6
The unevenness of the toner coating due to the deflection of a can be eliminated.

Embodiment 2 Next, a second embodiment of the developing device of the image forming apparatus 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. 2, a developing device 20 is a non-magnetic metal member which is opposed to the photosensitive drum 15 which is a latent image carrier at an opening of the developing container 3 and is a toner carrier which rotates in an arrow direction. It has a developing sleeve 1a of 32 mm. 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 developer regulating body 6 having a diameter of 8 mm is provided adjacent to the developing sleeve 1a and extends in the same direction.
The developer container 3 has one end thereof in contact with the developer regulating body 6.
Attached to. Further, a plate-shaped permanent magnet 7 having one end facing the developer regulating body 6 is attached to the developing container 3.

The developer regulating member 6 is arranged so as to be rotatable in the direction of arrow b1 in the same direction as the direction of arrow b2 in the direction of rotation of the developing sleeve 1a.

The developer regulating member 6 is arranged so as to be rotatable in the direction of the arrow b1 which is the same direction as the direction of the arrow b2 which is the direction of rotation of the developing sleeve 1a.

In this embodiment, the magnetic flux density of the magnetic pole N11 in the developing sleeve 1a is 900 gauss, and the magnetic pole N1
1 is in the range of 40 ° to 60 °, and the magnetic pole N1
1, the width of the developer regulating member 6 is narrowed, so that the change in the magnetic flux density of the magnetic field formed between the developer regulating member 6 and the magnetic pole N11 changes from the developing sleeve 1a to the developer regulating member. The configuration is such that the magnetic flux density becomes higher toward the sixth side.

The distance W between the developing sleeve 1a and the developer regulating member 6 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 developer regulating member 6 are further determined. Ratio (absolute value of peripheral speed of developer regulating body 6) / (development sleeve 1
(absolute value of the peripheral speed of a)> 0.5.

The plate-shaped permanent magnet 7 is disposed on a straight line passing through the center of the developing sleeve 1a and the developer regulating body 6 on the opposite side of the magnetic pole N11 with the developer regulating body 6 interposed therebetween.
000 gauss.

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.

In the developing device configured as shown in FIG. 2, the magnetic flux density increases from the developing sleeve 1a to the developer regulating body 6, so that the developing sleeve 1a and the developer regulating body 6 A magnetic force from the developing sleeve 1a to the developer regulating body 6 acts on the magnetic toner existing therebetween.
Therefore, the magnetic toner which is less sufficiently reflected than the above-mentioned magnetic force and is less reflected on the developing sleeve 1a is held on the developer regulating body 6 side.

In this embodiment, the developer regulating member 6
Is rotated in the direction of the arrow b1 in the figure, which is the same direction as the developing sleeve 1a, so that the insufficiently charged magnetic toner held on the surface of the developer regulating body 6 by the magnetic force will Due to the frictional force with the surface of the developer regulating body 6, a conveying force is applied from the developer regulating body 6 a to the inside of the developing container 3.

In this embodiment, the magnetic pole S7 of the permanent magnet 7 is provided at a position facing the developer regulating member 6 in order to prevent the developer regulating member 6 from bending due to the magnetic force from the permanent magnet 1b. The magnetic force of the magnetic pole S7 in the opposite direction to the magnetic force from the permanent magnet 1b described above is
Has given to.

As a result, it has become possible to prevent toner coating unevenness due to the deflection of the developer regulating body 6.

Accordingly, the insufficiently charged magnetic toner does not pass through the opposing position of the developing sleeve 1a and the developer regulating body 6 and is not conveyed to the developing area.

The magnetic toner returned into the developing container 3 is scraped off the surface of the developer regulating body 6 by the scraper 5. The magnetic toner thus returned into the developing device 3 is agitated with the toner by the conveying member 4, conveyed again on the surface of the developing sleeve 1 a, and conveyed to a position where the magnetic pole N 11 and the magnetic pole S 61 face each other. At this time, the circulation route of the magnetic toner in the developing container 3 is as shown by an arrow a in the figure.

The magnetic toner is charged in the developing container 3 by friction with the surface of the developing sleeve 1a. The charged magnetic toner adheres to the surface of the developing sleeve 1a due to the reflection force of the toner itself, and is conveyed to a position where the developing sleeve 1a and the developer regulating body 6 face each other. When the developer is conveyed to the opposing position, the insufficiently charged magnetic toner is returned into the developing container 3 from the opposing position of the developing sleeve 1a and the developer regulating body 6 for the above-described reason.

Accordingly, the magnetic toner that has passed through the opposing position of the developing sleeve 1a and the developer regulating body 6 and is conveyed to the developing area is reflected on the developing sleeve 1a more than the conveying force inward of the developing container 3. And only a sufficiently charged magnetic toner is obtained.

That is, according to this configuration, the developer regulating member 6
This makes it possible to eliminate toner coating unevenness due to warpage.

Embodiment 3 With reference to FIG. 3, a third embodiment of the developing device of the image forming apparatus according to the present invention will be described. The same members as those described above are denoted by the same reference numerals.

In FIG. 3, the developing device 20 has a diameter which is a toner carrier which is made of a non-magnetic metal member and is rotated in the direction of the arrow, facing the photosensitive drum 15 which is a latent image carrier at an opening of the developing container 3. It has a developing sleeve 1a of 32 mm. 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 developer regulating body 6a having a diameter of 10 mm is provided adjacent to the developing sleeve 1a and extends in the same direction, and a permanent magnet 6b having a plurality of magnetic poles is fixed therein.
The scraper 5 is attached to the developing container 3 such that one end thereof is in contact with the developer regulating body 6a. Further, a plate-shaped permanent magnet 7 having one end facing the developer regulating body 6a is attached to the developing container.

The developer regulating member 6a is arranged so as to be rotatable in the direction of arrow b1 in the same direction as the direction of arrow b2 in the direction of rotation of the developing sleeve 1a.

In this embodiment, the permanent magnet 6 is disposed so as to be closely opposed to the magnetic pole N11 in the permanent magnet 1b at the position where the developing sleeve 1a and the developer regulating body 6a are opposed.
b, the magnetic flux density of the magnetic pole S61 is 800 gauss and the magnetic pole N1 is
1 is 900 gauss, and the ratio of the 50% value of each magnetic pole is: {(50% value of magnetic pole S61) × (diameter of developing sleeve 1a)} / {(50% value of magnetic pole N11) X (diameter of the developer regulating member 6a)｝ <1.0, and the magnetic flux of the magnetic field formed between the magnetic pole S61 and the magnetic pole N11 by reducing the width of the magnetic pole S61 with respect to the width of the magnetic pole N11. The configuration is such that the magnetic flux density increases as the density changes from the developing sleeve 1a toward the developer regulating body 6a.

The developing sleeve 1a and the developer regulating member 6a
And the ratio of the absolute value of the peripheral speed of the developing sleeve 1a to the absolute value of the peripheral speed of the developer regulating member 6a is defined as (the absolute value of the peripheral speed of the developer regulating member 6a). ) / (Absolute value of peripheral speed of developing sleeve 1a)> 0.5.

The plate-shaped permanent magnet 7 is arranged with a magnetic pole S7 opposed to a magnetic pole N61 in the permanent magnet 6b and a width of ± 2 cm in the longitudinal center of the developer regulating body 6a as shown in FIG. The magnetic pole N61 was 800 gauss and the magnetic pole S7 was 800 gauss.

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.

In the developing device constructed as shown in FIG. 3, since the magnetic flux density increases from the developing sleeve 1a toward the developer regulating body 6a, the developing sleeve 1a
The magnetic toner present between the developer regulating body 6a and
A magnetic force acts from the developing sleeve 1a to the developer regulating body 6a. Therefore, the magnetic toner which is less sufficiently reflected than the above-mentioned magnetic force and is less reflected on the developing sleeve 1a is held on the developer regulating body 6a side.

In this embodiment, the developer regulating member 6
a is rotated in the direction of the arrow b1 in the figure, which is the same direction as the developing sleeve 1a, and the insufficiently charged magnetic toner held on the surface of the developer regulating member 6a by the magnetic force is not affected by the above-mentioned magnetic field. Due to the frictional force with the surface of the developer regulating body 6a, a conveying force from the developer regulating body 6a to the inside of the developing container 3 is given.

In the present embodiment, the following configuration is employed to prevent the developer regulating body 6 from being bent by the magnetic force from the permanent magnet 1b.

Since the deflection caused by the magnetic force from the permanent magnet 1b is greatest at the central portion of the developer regulating member 6a, the deflection at the central portion of the developer regulating member 6a in the longitudinal direction is ±.
With a width of 2 cm, the magnetic pole S7 of the permanent magnet 7 is disposed so as to face the magnetic pole N61 of the permanent magnet 6b in the developer regulating body 6a,
By applying a magnetic force in the opposite direction to the magnetic force from the permanent magnet 1b by the magnetic pole S7 to the center of the developer regulating body 6a, the bending of the developer regulating body 6a is prevented. As a result, it is possible to prevent toner coating unevenness due to the deflection of the developer regulating body 6a.

Therefore, the insufficiently charged magnetic toner does not pass through the opposing position of the developing sleeve 1a and the developer regulating body 6a and is not conveyed to the developing area.

The magnetic toner returned into the developing container 3 is scraped off the surface of the developer regulating body 6a by the scraper 5. The magnetic toner thus returned into the developing container 3 is attracted to the surface of the developing sleeve 1a by a magnetic force, and is conveyed to a position facing the magnetic pole N11 and the magnetic pole S61. At this time, the circulation route of the magnetic toner in the developing container 3 is indicated by an arrow a in FIG.
It becomes as shown in.

The magnetic toner is charged in the developing container 3 by friction with the surface of the developing sleeve 1a. The charged magnetic toner adheres to the surface of the developing sleeve 1a by the reflection force of the charge of the toner itself, and is conveyed to a position where the developing sleeve 1a and the developer regulating body 6a face each other. When the developer is conveyed to the opposite position, the insufficiently charged magnetic toner is removed from the developing sleeve 1a and the developer regulating member 6a for the above-described reason.
Is returned into the developing container 3 from the opposite position.

Therefore, the magnetic toner that has passed through the opposing position between the developing sleeve 1a and the developer regulating member 6a and is conveyed to the developing area is reflected on the developing sleeve 1a by a force greater than the conveying force inward of the developing container 3. And only a sufficiently charged magnetic toner is obtained.

That is, according to this configuration, it is possible to eliminate the unevenness of the toner coating due to the deflection of the developer regulating member.

Embodiment 4 Next, with reference to FIG. 5, a fourth embodiment of the developing device of the image forming apparatus according to the present invention will be described. The same members as those described above are denoted by the same reference numerals.

In FIG. 5, the developing device 20 is a developing device which is a toner carrier which is formed of a non-magnetic metal member and is rotated in the direction of the arrow, facing the photosensitive drum 15 which is a latent image carrier at an opening of the developing container 3. It has a sleeve 1a. A permanent magnet 1b having a plurality of magnetic poles is fixed inside the developing sleeve 1a. A transport member that rotates in the direction of the arrow to stir the developer and transport the developer in the direction of the developing sleeve 1a is provided inside the developing container 3. Further, a developer regulating body 6 having a diameter of 8 mm is provided adjacent to the developing sleeve 1a and extending in the same direction.

The roller 9 is located adjacent to the developer regulating body 6.
Is provided on the roller 9 and the developer regulating body 6.
Has been passed over.

Incidentally, the developer regulating member 6 includes a developing sleeve 1a.
Is arranged so as to be rotatable in the direction of arrow b1 in the same direction as the direction of arrow b2, which is the direction of rotation of.

In this embodiment, the magnetic flux density of the magnetic pole N11 in the developing sleeve 1a is set to 1000 gauss, and
The 50% value of the magnetic pole N11 is set in the range of 40 ° to 60 °,
By narrowing the width of the developer regulating body 6 with respect to the width of the magnetic pole N11, the change in the magnetic flux density of the magnetic field formed between the developer regulating body 6 and the magnetic pole N11 causes the developer to flow from the developing sleeve 1a to the developer. The configuration is such that the magnetic flux density becomes higher toward the regulating body 6 side.

The developing sleeve 1a and the developer regulating member 6a
Is set in the range of 100 μm to 2 mm, and the ratio of the absolute value of the peripheral speed of the developing sleeve 1a to the absolute value of the peripheral speed of the developer regulating member 6 is defined as (the absolute value of the peripheral speed of the developer regulating member 6). ) / (Developing sleeve 1)
(absolute value of the peripheral speed of a)> 0.5.

The film 8 is formed of a Kapton film having a thickness of 100 μm, and is arranged so as to rotate in the direction of arrow c with the rotation of the developer regulating member 6 in the direction of arrow b1.

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.

In the developing device configured as shown in FIG. 4, the magnetic flux density increases from the developing sleeve 1a toward the developer regulating body 6, so that the developing sleeve 1a and the developer regulating body 6 A magnetic force from the developing sleeve 1a to the developer regulating body 6 acts on the magnetic toner existing therebetween.
Therefore, the magnetic toner which is less sufficiently reflected than the above-mentioned magnetic force and is less reflected on the developing sleeve 1a is held on the developer regulating body 6 side.

In this embodiment, since the film 8 is rotated in the direction indicated by the arrow c in the drawing, which is the same direction as the developing sleeve 1a, the insufficiently charged magnetism held on the surface of the developer regulating body 6 by the magnetic force. The toner is conveyed from the developer regulating body 6 to the inside of the developing container 3 by the force of the magnetic field and the frictional force between the toner regulating body 6 and the toner.

In this embodiment, in order to prevent the developer regulating body 6 from bending due to the magnetic force from the permanent magnet 1b, the film 8 causes the developer regulating body 6 to move in the opposite direction to the magnetic force from the permanent magnet 1b. To pull it. As a result, it is possible to prevent toner coating unevenness due to the bending of the developer regulating body 6.

Accordingly, the insufficiently charged magnetic toner passes through the opposing position between the developing sleeve 1a and the developer regulating member 6a, and
It is not transported to the development area.

The magnetic toner returned to the developing container 3 loses its own weight when the binding force by the magnetic force is lost.
Fall from the surface.

The magnetic toner thus returned into the developing container 3 is attracted to the surface of the developing sleeve 1a by a magnetic force, and is conveyed to a position where the magnetic pole N11 and the developer regulating body 6 face each other. At this time, the circulation route of the magnetic toner in the developing container 3 is as shown by an arrow a in the figure.

The magnetic toner is charged in the developing container 3 by friction with the surface of the developing sleeve 1a. The charged magnetic toner adheres to the surface of the developing sleeve 1a due to the reflection force of the toner itself, and is conveyed to a position where the developing sleeve 1a and the developer regulating body 6 face each other. When the developer is conveyed to the opposing position, the insufficiently charged magnetic toner is returned into the developing container 3 from the opposing position of the developing sleeve 1a and the developer regulating body 6 for the above-described reason.

Therefore, the magnetic toner that passes through the position where the developing sleeve 1a and the developer regulating body 6 are opposed to each other and is conveyed to the developing area is reflected on the developing sleeve 1a more than the conveying force in the developing container 3 direction. And only a sufficiently charged magnetic toner is obtained.

That is, according to this configuration, it is possible to eliminate the uneven toner coating due to the bending of the developer regulating member.

[0100]

As is apparent from the above description, the image forming apparatus according to the present invention uses the developer regulating member to apply a force acting in the opposite direction to the magnetic force received by the developer regulating member from the magnetic pole in the developer carrying member. With this configuration, it is possible to prevent bending of the developer regulating body due to the magnetic force, and to eliminate uneven toner coating. Therefore, a good image can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a first embodiment of a developing device of an image forming apparatus 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 an explanatory diagram of an arrangement position of a plate-shaped permanent magnet in the developing device of FIG. 3;

FIG. 5 is a configuration diagram showing a fourth embodiment of the developing device according to the present invention.

FIG. 6 is a configuration diagram of an example of a conventional developing device using a magnetic blade fixed to a developer amount regulating member.

FIG. 7 is an explanatory diagram of a magnetic flux density in a developer regulating region.

FIG. 8 is an explanatory diagram of the behavior of the toner in the developer regulating region.

FIG. 9 is a configuration diagram of an example of another conventional developing device using a rotatable developer regulating member.

FIG. 10 is a schematic configuration diagram of an electrophotographic image forming apparatus capable of embodying the present invention.

[Explanation of symbols]

 1a Developing sleeve (developer carrier) 1b Permanent magnet 3 Developing container 4 Conveying member 5 Scraper 6 Developer regulating body 6a Developer regulating body 6b Permanent magnet 20 Developing device

Continuation of the front page (56) References JP-A-58-18657 (JP, A) JP-A-4-184462 (JP, A) JP-A-3-209487 (JP, A) JP-A-58-23068 (JP) , A) JP-A-55-50274 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/06-15/095

Claims (4)

(57) [Claims] A rotatable developer carrier that carries a developer containing a magnetic toner containing a magnetic material on a surface thereof; a permanent magnet disposed inside the developer carrier; A developer regulating member for regulating the application of the developer on the developer carrying member, wherein the developer regulating member is provided near at least one magnetic pole of a permanent magnet disposed inside the developer carrying member. In an image forming apparatus having a developing device rotatably opposed and having the rotation direction being the same as the rotation direction of the developer carrier, the developer regulating member receives from a magnetic pole in the developer carrier. An image forming apparatus, wherein a force acting in a direction opposite to a magnetic force is applied to the developer regulating member. 2. The developer regulating member according to claim 1, wherein a permanent magnet having at least two poles is disposed inside the developer regulating member, and at least one of the permanent magnets disposed inside the developer carrying member is located near the permanent magnet. One magnetic pole of a permanent magnet disposed inside the developer regulating member is disposed at the facing position at a position facing the developer regulating member and the developer carrying member. The image forming apparatus according to claim 1, wherein one of the permanent magnets inside the developer carrier has a different polarity. 3. The developer regulating member is made of a magnetic material.
2. The image forming apparatus according to claim 1, wherein the width is smaller than the width of one magnetic pole of the permanent magnet facing the developer regulating body inside the developer carrier. 4. The magnetic flux density increases from the side of the developer carrier to the side of the developer regulator at a position where the developer regulating body and the developer carrier are opposed to each other. An image forming apparatus according to any one of 1 to 3.