JPH07301994A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent unnecessary load from being imposed on nonmagnetic toner and magnetic particles to avoid the deterioration of both of them and to prevent the non-magnetic toner used for a long time from being melt-stuck on a toner layer thickness regulating body. CONSTITUTION:A pole N11 and a pole S61 which are different poles are disposed at a position where a developing sleeve 1a and the toner layer thickness regulating body 6a are opposed, and a pole S62 having the same polarity as the pole S61 is disposed adjacently to the pole S61 on a downstream side in the rotating direction of the regulating body 6a. The magnetic particles carried to the opposed position by the sleeve 1a are carried in a direction shown by an arrow (a) by the rotation of the regulating body 6a, and peeled from the regulating body 6a between the magnetic poles S61 and 62 by their repulsive force, and only the magnetic particles are restored in a developer container 3. Thus, only the magnetic particles are restored in the container 3 without applying pressure to the magnetic particles and the non-magnetic toner.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, as an electrophotographic image forming apparatus, US Pat.
As described in Japanese Patent Publication No. 23910 and Japanese Examined Patent Publication No. 43-24748, many methods are known. Generally, various means are used to form an electric latent image on a photoconductor of a photoconductive substance. Then, the latent image is developed with toner to form a toner image, and the toner image is transferred to a transfer material such as paper, if necessary, and then fixed by heating or solvent vapor to obtain a copy. Is what you get. Various methods for visualizing an electric latent image using toner are also known.

Further, as a developing method, for example, a magnetic brush developing method described in US Pat. No. 2,877,403, a powder cloud method and a fur brush developing method, and a liquid developing method described in US Pat. etc,
Many developing methods are known.

Among these developing methods, a magnetic brush method, a cascade method, a liquid developing method and the like, which use a developer mainly composed of toner and carrier, are widely put into practical use. All of these methods are excellent methods in which a good image can be obtained relatively stably, but on the other hand, they have the common drawbacks of two-component developers such as deterioration of the carrier and variation of the mixing ratio of the toner and the carrier. Have.

In order to avoid such drawbacks, various developing methods using a one-component developer consisting of only toner have been proposed. For example, US Pat. No. 3,909,258 proposes a method of developing using a magnetic toner having conductivity. In this method, a conductive magnetic toner is supported on a cylindrical conductive sleeve having a magnetic force inside, and the conductive magnetic toner is brought into contact with an electrostatic image for development. At this time, a conductive path is formed between the surface of the recording material and the surface of the sleeve by the toner particles in the developing area, and the electric charge is introduced from the sleeve to the toner particles through the conductive path, and the Coulomb force between the electrostatic image area is formed. As a result, toner particles adhere to the image area and are developed.

This developing method using a 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 is transferred from the recording medium to plain paper. It has a defect that it is difficult to electrostatically transfer it to a final support member such as.

In order to solve this problem, as a developing method using a high resistance toner capable of being electrostatically transferred, Japanese Patent Application Laid-Open No. 52-94140 discloses a developing method utilizing dielectric polarization of toner particles. It is shown. However, such a method has a drawback that the developing speed is slow and the density of a developed image cannot be sufficiently obtained, and it is practically difficult. As another method of using high resistance toner,
A method is known in which toner particles are triboelectrically charged by friction between the toner particles, friction between the toner particles and a sleeve, and the toner particles are brought into contact with an electrostatic holding member for development. However, in these methods, the number of contact between the toner particles and the friction member is small, and triboelectric charging tends to be insufficient, or when the Coulomb force between the charged toner particles and the sleeve is strong, the toner particles tend to aggregate. It has been pointed out that it has many drawbacks in practice and is difficult in practical use.

On the other hand, Japanese Laid-Open Patent Publication No. 54-43036 proposes a new developing method which eliminates the above-mentioned drawbacks. In this method, toner is applied very thinly on a developing sleeve, triboelectrically charged, and then brought very close to an electrostatic image under the action of a magnetic field and opposed without contacting with the electrostatic image for development.

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

According to the study by the present inventors concerning the charge imparting of the one-component developing method, it was found that the behavior of the toner in the charge imparting portion is as follows.

First, an example of a conventional developing device using the magnetic one-component toner will be described with reference to FIG. The developing device 60 faces the photosensitive drum 50, and is connected to the developing container 53.
A developing sleeve 51a made of a non-magnetic material, which is rotatably arranged in the arrow direction, and a permanent magnet 51b fixed inside the developing sleeve 51a. A magnetic one-component toner T is stored in the developing container 53, and a transport member 54 that transports the magnetic one-component toner T toward the photosensitive drum 50 is provided. Further, the magnetic blade 5 formed of a magnetic member is located very close to the developing sleeve 51a.
2 are arranged such that the distance W _{1 from} the developing sleeve 51a is a constant value. The distance W ₁ is generally set within the range of 100 μm to 1 mm.

In the developing device 60 shown in FIG.
The component toner T is thinly coated on the developing sleeve 51a. The layer thickness of this toner layer is determined by the position of the cut line L shown in FIG. 7, as will be described later.

According to a study made by the present inventors, when the magnetic toner T passes between the developing sleeve 1a and the magnetic blade 52, an electric charge is applied to the magnetic toner T and the behavior of the magnetic toner T at that time. Was found to be as follows.

That is, as shown in FIG. 6, considering a plane perpendicular to the straight line connecting the developing sleeve 51a and the magnetic blade 52, the surface close to the magnetic blade 52 is S _1, and the surface close to the developing sleeve 51a is S ₂ . Then, the width of the generally magnetic blade 52, which are set narrower than the width of the permanent magnet 51b, S ₁ side, considering the respective magnetic flux density at S ₂ side, the magnetic flux in the S ₁ side The density is higher than the magnetic flux density on the S ₂ plane. Therefore, the magnetic toner T receives a force between the developing sleeve 51a and the magnetic blade 52 in the direction of the arrow in FIG. 6, that is, a force toward the magnetic blade 52 side, depending on the strength of the magnetization of the magnetic toner.

As a result, the magnetic toner T forms ears in the B state as shown in FIG. 7, and the ears are formed from the magnetic blade 52 toward the developing sleeve 51a.
Further, the charging of the magnetic toner T is performed by the developing sleeve 51a.
And the toner t _{1 at} the tip of the ears formed from the magnetic blade 52 come into contact with each other, and an electric charge is applied to the toner t ₁ at the tip.

Further, it has been found that the toner is conveyed between the developing sleeve 51a and the magnetic blade 52 as follows.

As described above, since the toner t ₁ at the tip of the brush that comes into contact with the developing sleeve 51a is charged,
A force in the direction of the developing sleeve 51a acts due to the mirroring force, and the developing sleeve 51a is frictionally contacted with the developing sleeve 51a.
A conveying force in the rotation direction of a is given. Further, the toner particles, since the work is some cohesion to one another, the conveying force is generated which also via the cohesive force to the toner t ₂ in contact with the toner t _1. Further, the toner t ₃ in the upper layer portion similarly has a carrying force via the cohesive force.

However, the magnetic force in the direction of the magnetic blade 52 is also applied to the toner T between the developing sleeve 51a and the magnetic blade 52, as described above. Therefore, at the position where the conveying force applied to the toner T overcomes the magnetic force, that is, at the position of the cut line L in FIG.
The ears of the toner are torn and the toner T remaining on the developing sleeve 51a
Are conveyed in the rotation direction of the developing sleeve 51a.

Therefore, the magnetic toner has a high degree of aggregation,
In a system that requires a large number of contacts for obtaining the necessary triboelectric charge, there is a problem in that insufficiently charged toner that is not in contact with the developing sleeve is transported to the developing area and a phenomenon associated with poor charging easily occurs. there were.

Further, in the one-component developing method using the magnetic toner as described above, the fixing property is poor at the time of thermally fixing the toner image transferred to the transfer material, and the color toner is used because the magnetic substance is internally added to the toner itself. There is a drawback that it is impossible to use

On the other hand, a powder cloud method, an impression developing method and the like are known as a one-component developing method using a non-magnetic toner. Among these, for example, a fur brush developing method in which a soft brush such as a beaver is formed into a cylindrical brush, and a developer is attached to the brush to perform development, or an impression is used in which the developer is attached to a roller such as a velvet. The developing method and the like are well known.
These developing methods do not use a toner to which a magnetic material is internally added when developing an electrostatic latent image, and use a carrier particle to form a complicated device for maintaining a constant ratio of the toner and the carrier particle. Is a developing method that does not require.

However, the developing method using such a non-magnetic toner is disclosed in FIG.
There is a problem that a uniform predetermined toner layer thickness cannot be obtained even if the same magnetic blade disclosed in Japanese Patent No. 6 is used, which causes uneven coating of toner on the surface of the developing sleeve, which results in image density. It appears as unevenness.
Further, it is possible to regulate the toner layer thickness by using an elastic blade as the doctor blade,
The latitude of the pressing force of the elastic blade against the developing sleeve is very narrow, and if it is too low, a uniform predetermined toner layer thickness cannot be obtained, and if it is too high, it damages the toner and the developing sleeve. There is a drawback that.

In order to solve such a drawback, the developing methods described in JP-B-58-90668 and JP-B-58-143360 are known. FIG. 8 shows an example of a developing device for carrying out such a developing method. In the figure, a developing device 80 includes a toner container 73 containing a non-magnetic toner 81 and magnetic particles 82, and a non-magnetic developing sleeve which is disposed at an opening of a toner container 83 so as to face the photosensitive drum 85. 71 a, a permanent magnet 71 b fixed inside the developing sleeve 71 a, and a magnetic blade 72 fixed to the toner container 73 and regulating the layer thickness of the toner supported and conveyed to the photosensitive drum 85 side. The gap between the magnetic blade 72 and the developing sleeve 1a is set to about 250 μm.

In the developing device 80 thus constructed, the magnetic particles 82 form a brush 82a along the magnetic field between the magnetic blade 72 and the permanent magnet 71b, and are constrained within the magnetic field. Here, the non-magnetic toner 81 moves while being dragged by the developing sleeve 71a having a rough surface,
At the same time, the particles are charged by friction with the magnetic particles 82 and the developing sleeve 71a and adhere to the magnetic particles 82 and the developing sleeve 71a due to the mirroring force. However, the magnetic particles 82 cannot move due to the above-mentioned magnetic field constraint, and thus the developing sleeve. Only the non-magnetic toner 81 adhering to 71a is a brush 81 of magnetic particles.
When the developing sleeve 71a rotates, a uniform layer of the non-magnetic toner 81 is formed on the surface of the developing sleeve 71a.

In the above conventional system, the magnetic particles are
A magnetic brush must be formed in a system in which a large amount of toner is present, the toner must be applied onto the developing sleeve, and the amount of toner must be regulated. At the same time, it must have a function of supplying toner while circulatingly moving, and it is not preferable that the magnetic particles pass between the magnetic blade and the developing sleeve. Therefore, in order to satisfy these functions, the magnetic brush has an appropriate restraining force generated by a magnetic field, yet exhibits appropriate circulation property, and the state of the formed magnetic brush enables uniform application. Therefore, it must have a suitable hardness and density.

For example, a relatively sparse brush tends to easily cause insufficient regulation streaks on the developing sleeve, and conversely, when the brush is dense, the toner layer on the developing sleeve tends to be extremely thin. .

If the circulation of the magnetic particles is too good, the toner layer becomes thick and fog may occur on the image, or the magnetic particles may pass through the magnetic blade. On the contrary, when the circulation property is poor, the toner cannot be sufficiently charged, so that an image defect called so-called ghost, in which the image on the first circumference of the sleeve is dark and thin thereafter, is likely to occur.

That is, there is a problem that the latitude of the brush satisfying the function of the above magnetic particles is very narrow.

[0029]

Therefore, the present inventors
In order to solve the above problems, the non-magnetic toner, the magnetic particles and the non-magnetic toner are uniformly coated on the sleeve surface without applying pressure, and the magnetic particles are circulated without being conveyed to the developing area. And a developer having a wide latitude in which the brush of magnetic particles is in an appropriate state, which can sufficiently charge the toner by sufficiently agitating the toner with the toner.

That is, as shown in FIG.
Is provided with a non-magnetic developing sleeve 91a, which is disposed in the opening of the developing container 93 and faces the photosensitive drum 95, and a permanent magnet 91b fixed inside the developing sleeve 91a. Further, a developer containing non-magnetic toner and magnetic particles is contained in the developing container 93, and a conveying member 94 for conveying the developer in the container toward the developing sleeve 91a is provided inside the developing container 93. ing. Further, the developing sleeve 91
A cylindrical toner layer thickness regulating member 96a made of a non-magnetic metal material is disposed very close to a, and a permanent magnet 96b is inserted inside the toner layer thickness regulating member 96a. The toner layer thickness regulator 96a is rotatably provided in the same direction e as the rotation direction d of the developing sleeve 91a, and the distance W ₂ between them is set to 1 mm or less.

The permanent magnet 9 in the developing sleeve 91a is
1b has three north poles and three south poles alternately arranged, while one permanent magnet 96b in the toner layer thickness regulating body 96a.
Has one north pole and one south pole. At this time, the magnetic poles of the portions facing each other are different, that is, the magnetic pole N of the permanent magnet 91b in the developing sleeve 91a as shown in FIG.
11 and the magnetic pole S61 of the permanent magnet 96b of the toner layer thickness regulator 96a are arranged to face each other.

With the above structure, the surface of the developing sleeve is uniformly coated with the non-magnetic toner without applying pressure to the non-magnetic toner, the magnetic particles and the developing sleeve, and the magnetic particles are applied to the developing area. It is possible to improve the circulation property without carrying the toner to the toner, sufficiently charge the toner by sufficiently stirring it with the toner, and widen the latitude of the magnetic particles in a proper state of the brush.

However, the conventional developing device 100 described above is used.
Is required to scrape off the magnetic toner from the surface of the toner layer thickness regulating member 6a by the scraper 95. As a result, the non-magnetic toner and the magnetic particles may be overloaded when scraped off, resulting in non-magnetic toner and magnetic There is a problem that the deterioration of the body particles is promoted and that the non-magnetic toner is fused to the toner layer thickness regulating body 6a during long-time use.

Therefore, an object of the present invention is to provide a non-magnetic toner,
Non-magnetic toner is uniformly coated on the surface of the toner carrier without applying unnecessary pressure to the magnetic particles or the toner carrier,
In addition, the circulation of the magnetic particles is improved without being conveyed to the developing area, and the nonmagnetic toner is sufficiently agitated with sufficient stirring with the nonmagnetic toner, so that the magnetic particles have a proper brush state. The developing device which can widen the latitude of the non-magnetic toner and prevent the deterioration of the non-magnetic toner and the magnetic particles and the fusion of the non-magnetic toner to the toner carrier, and can always obtain a proper developed image even when used for a long time. An image forming apparatus having the above is provided.

[0035]

The above object can be achieved by an image forming apparatus according to the present invention. In summary, the present invention is
A developing container containing a developer containing a non-magnetic toner and magnetic particles, a rotatably arranged toner carrier carrying a non-magnetic toner on its surface, and a plurality of toner carriers arranged inside the toner carrier. A first magnetic field generating means having a magnetic pole; and a toner layer thickness regulating body for regulating the layer thickness of the non-magnetic toner applied on the toner carrier, the toner layer thickness regulating body comprising:
In an image forming apparatus including a developing device that is rotatably disposed near the toner carrier and has a rotation direction that is the same as the rotation direction of the toner carrier, the toner layer thickness regulator is at least inside thereof. A second magnetic field generating means having two poles, one magnetic pole of the second magnetic field generating means and the first magnetic field generating means;
One magnetic pole of the magnetic field generating means is disposed at a substantially opposed position,
Further, the two magnetic poles arranged at the substantially opposite positions are made to have different polarities from each other, and the second magnetic field generating means is arranged so that the one magnetic pole arranged at the substantially opposite position has a rotation direction of the toner layer thickness regulator. The magnetic recording medium further includes one or more magnetic poles on the downstream side, the magnetic poles being arranged at the substantially opposed positions, and the one or more magnetic poles arranged on the downstream side in the rotation direction of the toner layer thickness regulating body. In the image forming apparatus, at least two magnetic poles having the same polarity are arranged adjacent to each other in the arrangement in the toner layer thickness regulating body.

The toner layer thickness regulating member is located on the downstream side in the rotation direction of the toner layer thickness regulating member from the substantially opposed position of one magnetic pole of the second magnetic field generating unit and one magnetic pole of the first magnetic field generating unit. It is preferable to provide a third magnetic field generating means near the body.

The magnetic poles on the toner layer thickness regulating body side of the third magnetic field generating means have at least two adjacent magnetic poles.
It is preferably the same polarity as one or more magnetic poles.

It is preferable that the magnetic flux density becomes higher from the toner carrier toward the toner layer thickness regulator.

It is preferable that the 50% value of the magnetic poles of the toner layer thickness regulating body disposed at substantially opposite positions is 1.0 or less of the 50% value of the magnetic poles of the toner carrier.

It is preferable that the ratio of the absolute value of the peripheral speed of the toner layer thickness regulating member to the absolute value of the peripheral speed of the toner carrier is greater than 0.5.

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to the present invention will be described below in more detail with reference to the drawings. In the examples described below,
The present invention is described as being embodied in, for example, an electrophotographic image forming apparatus as shown in FIG. 4, but is not limited to this.

In FIG. 4, the electrophotographic image forming apparatus rotatably includes a photosensitive drum 10 constituted by coating a photoconductive layer on a conductive substrate as an electrostatic latent image carrier, and the photosensitive drum 15 is provided. Is uniformly charged by a primary charger 12, and then an information signal is exposed by a light emitting element 13 such as a laser to form an electrostatic latent image, and the developing device 20 visualizes it. Next, the visible image is transferred onto the transfer paper 16 by the transfer charger 14 and further fixed by the fixing device 17. Further, the transfer residual toner on the photosensitive drum 10 is cleaned by the cleaning device 11.

First Embodiment A first embodiment of the developing device of the image forming apparatus according to the present invention will be described with reference to FIG.

In FIG. 1, the developing device 20 is a toner carrier which faces the photosensitive drum 10, which is an electrostatic latent image carrier, and is rotatably arranged in the direction of the arrow at the opening of the developing container 3. It is provided with a developing sleeve 1a made of a magnetic metal member and a permanent magnet 1b as a first magnetic field generating means arranged inside the developing sleeve 1a. Further, a magnetic toner is stored in the developing container 3, and a carrying member 4 for carrying the magnetic toner toward the developing sleeve 1a is provided. Further, a cylindrical toner layer thickness regulating member 6a made of a non-magnetic metal material is arranged in the developing container 3 in close proximity to the developing sleeve 1a, and the toner layer thickness regulating member 6a has a first toner layer thickness regulating member 6a. A permanent magnet 6b, which is a means for generating two magnetic fields, is inserted and fitted. The toner layer thickness regulator 6a is arranged upstream of the developing area in the rotation direction of the developing sleeve 1a, and the rotation direction a of the non-magnetic member 6a is the same as the rotation direction b of the development sleeve 1a. ing.

Incidentally, the permanent magnet 1b in the developing sleeve 1a.
Has three N poles and three S poles alternately arranged, while the permanent magnet 6b of the toner layer thickness regulating body 6 has an S61 pole.
It has two poles, a pole and an S62 pole. At this time, the magnetic poles of the portions facing each other are different, that is, as shown in FIG. 1, the magnetic pole N of the permanent magnet 1b in the developing sleeve 1a.
11 and the magnetic pole S6 of the permanent magnet 6b of the toner layer thickness regulator 6a
1 and 1 are arranged so as to face each other closely.

In this embodiment, the magnetic pole (N11) in the permanent magnet 1b at a position where the developing sleeve 1a and the toner layer thickness regulating member 6a substantially face each other, and the permanent magnet 6b disposed so as to closely face the magnetic pole N11. The change in the magnetic flux density of the magnetic field formed between the magnetic poles (S61) inside the inner magnetic poles becomes higher from the developing sleeve 1a toward the toner layer thickness regulating body 6a side. The width of the area showing 50% or more of the density peak value
Value)) (50% value of magnetic pole S61) / (50% value of magnetic pole N11)
≦ 1.0, preferably (50% value of magnetic pole S61) / (magnetic pole N11
50% value of ≦ 0.8, and in the present embodiment, (50% value of magnetic pole S61) / (50% value of magnetic pole N11)
By setting ≈0.8, the change in the magnetic flux density of the magnetic field formed between the magnetic pole S61 and the magnetic pole N11 becomes higher from the developing sleeve 1a toward the toner layer thickness regulator 6a. did.

In this embodiment, the maximum value of each magnetic flux density is set to 900 gauss for the magnetic pole N11 and 800 gauss for the magnetic pole S11.

Further, 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. The ratio of (the absolute value of the peripheral speed of the toner layer thickness regulating member 6a) / (the absolute value of the peripheral speed of the developing sleeve 1a)> 0.5.

The magnetic toner has a weight average diameter of 5 μm or more, and the magnetic particles have a weight average diameter of 20 to 100.
An ordinary magnetic carrier of μm was used.

The magnetic pole inside the permanent magnet 1b (N11 in the present embodiment) and the magnetic pole inside the permanent magnet 6b (S61 in the present embodiment) at the position where the developing sleeve 1a and the toner layer thickness regulating member 6a face each other. By setting the size so that the width of the magnetic pole S61 is narrower than the width of the magnetic pole N11, the change in the magnetic flux density of the magnetic field formed between the magnetic pole S61 and the magnetic pole N11 changes from the developing sleeve 1a to the toner layer thickness. Regulator 6
The magnetic flux density is increased toward the side a.

Developing device 20 constructed as shown in FIG.
The toner layer thickness regulating member 6 from the developing sleeve 1a.
Since the magnetic flux density increases toward the a side, the magnetic particles existing between the developing sleeve 1a and the toner layer thickness regulating body 6a may have a magnetic field from the developing sleeve 1a to the toner layer thickness regulating body 6a side. Power works. As a result, a brush of magnetic particles is formed along the magnetic field between the magnetic pole N11 and the magnetic pole S61.

The non-magnetic toner is charged by friction between the magnetic particles and the surface of the developing sleeve 1a, adheres to the magnetic particles and the developing sleeve 1a by a mirroring force, and is conveyed on the developing sleeve 1a. For the above reason, since the developing sleeve 1a and the toner layer thickness regulating member 6a are returned to the inside of the developing device 3 from the facing position, only the sufficiently charged non-magnetic toner adhering to the surface of the developing sleeve 1a is absorbed in the brush of magnetic particles. It becomes possible to pass.

Further, since the toner layer thickness regulating member 6a is configured to rotate in the same direction as the developing sleeve 1a, that is, the direction of the arrow a in the figure, the magnetic force retained by the magnetic force on the surface of the toner layer thickness regulating member 6a. The body particles and a part of the non-magnetic toner attached to the magnetic particles are moved from the toner layer thickness regulating body 6a to the inside of the developing device 3 by the force of the magnetic field and the frictional force between the surface of the toner layer thickness regulating body 6a. Transfer power is given. Therefore, the magnetic particles do not pass through the position where the developing sleeve 1a and the toner layer thickness regulating member 6a face each other and are not conveyed to the developing area.

Further, in this embodiment, the permanent magnet 6b is used.
In the two adjacent magnetic poles S61 and S62 of the same polarity, the magnetic forces repel each other, the magnetic force lines are not connected between the two magnetic poles, and the direction of the magnetic force lines is outward from the surface of the toner layer thickness regulator 6a. Therefore, the magnetic particles and the non-magnetic toner conveyed on the surface of the toner layer thickness regulating body 6a receive a magnetic force so as to be separated from the surface of the toner layer thickness regulating body 6a between the two poles. Therefore, the magnetic particles and the non-magnetic toner having a weak carrying force on the surface of the toner layer thickness regulator 6a are peeled off from the surface of the toner layer thickness regulator 6a by the magnetic force.

That is, the magnetic particles and the non-magnetic toner can be scraped off from the toner layer thickness regulating member 6a without applying pressure to the magnetic particles and the non-magnetic toner.

The magnetic particles returned to the developing container 3 in this way are agitated with the toner by the carrying member 4 and again carried on the surface of the developing sleeve 1a, and the magnetic pole N11 and the magnetic pole S are fed.
It is conveyed to a position substantially opposite to 61, and is conveyed so as to return from the position of the magnetic pole S62 into the developing container 3. The circulation path of the magnetic particles in the developing container 3 at this time is as shown by an arrow c in the figure.

That is, according to this structure, the non-magnetic toner can be uniformly coated on the developing sleeve in a desired layer thickness without applying a high pressure that damages the toner, the magnetic particles and the developing sleeve. In addition, the circulation function of the magnetic particles can be improved without leaking the magnetic particles to the developing area, and the toner in the developing device can be sufficiently charged, and the toner layer By scraping off the magnetic particles and the non-magnetic toner conveyed to the surface of the thickness control body 6a without contact, the magnetic particles and the non-magnetic toner are deteriorated, and the non-magnetic toner is fused to the toner layer thickness control body 6a. As a result, it is possible to always obtain a proper developed image even when used for a long time.

Second Embodiment 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.

In FIG. 2, the developing device 20 is a toner carrier which is disposed in the opening of the developing container 3 so as to face the photosensitive drum 10 which is an electrostatic latent image carrier and is rotatable in the arrow direction. It is provided with a developing sleeve 1a made of a magnetic metal member and a permanent magnet 1b as a first magnetic field generating means arranged inside the developing sleeve 1a. Further, a magnetic toner is stored in the developing container 3, and a carrying member 4 for carrying the magnetic toner toward the developing sleeve 1a is provided. Further, a cylindrical toner layer thickness regulating member 6a made of a non-magnetic metal material is arranged in the developing container 3 in close proximity to the developing sleeve 1a, and the toner layer thickness regulating member 6a has a first toner layer thickness regulating member 6a. A permanent magnet 6b, which is a means for generating two magnetic fields, is inserted and fitted. The toner layer thickness regulator 6a is arranged upstream of the developing area in the rotation direction of the developing sleeve 1a, and the rotation direction a of the toner layer thickness regulator 6a is the same as the rotation direction b of the developing sleeve 1a. It is said that.

The permanent magnet 1b in the developing sleeve 1a is
Has three N poles and three S poles alternately arranged, while the permanent magnet 6b of the toner layer thickness regulating body 6 has an S61 pole.
It has three poles, N61 and N62.

In the present embodiment, the magnetic pole (N11) in the permanent magnet 1b at a position where the developing sleeve 1a and the toner layer thickness regulating member 6a substantially face each other, and the permanent magnet 6b arranged so as to closely face and substantially face the magnetic pole N11. Since the change in the magnetic flux density of the magnetic field formed between the magnetic poles (S61) inside the inner magnetic poles becomes higher from the developing sleeve 1a toward the toner layer thickness regulating body 6a side, the magnetic flux density of each magnetic pole is 50%. % Ratio (50% value of magnetic pole S61) / (50% value of magnetic pole N11)
≦ 1.0, preferably (50% value of magnetic pole S61) / (magnetic pole N11
50% value of ≦ 0.8, and in the present embodiment, (50% value of magnetic pole S61) / (50% value of magnetic pole N11)
By setting ≈0.8, the change in the magnetic flux density of the magnetic field formed between the magnetic pole S61 and the magnetic pole N11 becomes higher from the developing sleeve 1a toward the toner layer thickness regulator 6a. did.

In this embodiment, the maximum value of each magnetic flux density is set to 900 gauss for the magnetic pole N11 and 800 gauss for the magnetic pole S11.

Further, the distance W between the developing sleeve 1a and the toner layer thickness regulating body 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 body 6a. The ratio of (the absolute value of the peripheral speed of the toner layer thickness regulating member 6a) / (the absolute value of the peripheral speed of the developing sleeve 1a)> 0.5.

The magnetic toner has a weight average diameter of 5 μm or more, and the magnetic particles have a weight average diameter of 20 to 100.
An ordinary magnetic carrier of μm was used.

Developing device 20 constructed as shown in FIG.
At the permanent magnet 6b, the magnetic pole S61 at the facing position is
And the magnetic pole N6 on the downstream side in the rotational direction of the toner layer thickness regulator 6a.
1, the magnetic lines of force are connected, and the magnetic particles attracted to the toner layer thickness regulating member 6a side by the magnetic force at the opposing position and a part of the nonmagnetic toner attached to the magnetic particles are indicated by the arrow c. As shown by, the surface of the toner layer thickness regulating member 6a is conveyed. As a result, it is possible to more reliably remove the insufficiently charged magnetic toner from the developer regulating section.

Two magnetic poles N61 and N62 of the same polarity are also used.
Is disposed on the downstream side of the magnetic pole S61 in the rotation direction of the toner layer thickness regulating body 6a, so that the magnetic layer and a part of the non-magnetic toner adhered to the magnetic layer are not pressed, and the toner layer is It has become possible to scrape off a part of the non-magnetic toner attached to the thickness regulator 6a.

Therefore, even in the developing device configured as shown in FIG. 2, it is possible to scrape off the magnetic particles and a part of the non-magnetic toner adhering to the magnetic particles in a non-contact manner. The same effect as was obtained.

Third Embodiment Next, a third embodiment of the developing device of the image forming apparatus according to the present invention will be described with reference to FIG.

In FIG. 3, the developing device 20 is a toner carrier which is disposed in the opening of the developing container 3 so as to face the photosensitive drum 10 which is an electrostatic latent image carrier and is rotatable in the arrow direction. It is provided with a developing sleeve 1a made of a magnetic metal member and a permanent magnet 1b as a first magnetic field generating means arranged inside the developing sleeve 1a. Further, a magnetic toner is stored in the developing container 3, and a carrying member 4 for carrying the magnetic toner toward the developing sleeve 1a is provided. Further, a cylindrical toner layer thickness regulating member 6a made of a non-magnetic metal material is arranged in the developing container 3 in close proximity to the developing sleeve 1a, and the toner layer thickness regulating member 6a has a first toner layer thickness regulating member 6a. A permanent magnet 6b, which is a means for generating two magnetic fields, is inserted and fitted. The toner layer thickness regulator 6a is arranged upstream of the developing area in the rotation direction of the developing sleeve 1a, and the rotation direction a of the non-magnetic member 6a is the same as the rotation direction b of the development sleeve 1a. ing. Further, a permanent magnet 7 as a plate-shaped third magnetic field generating means extending from the inside of the developing container 3 toward the toner layer thickness regulating body 6a is fixed to an end portion of the developing container 3 facing the toner layer thickness regulating body 6a. Has been done.

The permanent magnet 1b in the developing sleeve 1a is
Has three N poles and three S poles alternately arranged, while the permanent magnet 6b of the toner layer thickness regulating body 6 has an S61 pole.
It has three poles, N61 and N62. Further, the plate-shaped permanent magnet 7 has an N7 pole having the same polarity at a position facing the magnetic poles N61 and N62.

In this embodiment, the magnetic pole (N11) in the permanent magnet 1b at a position where the developing sleeve 1a and the toner layer thickness regulating member 6a substantially oppose each other, and the permanent magnet 6b arranged so as to closely oppose the magnetic pole N11. Since the change in the magnetic flux density of the magnetic field formed between the magnetic poles (S61) inside the inner magnetic poles becomes higher from the developing sleeve 1a toward the toner layer thickness regulating body 6a side, the magnetic flux density of each magnetic pole is 50%. % Ratio (50% value of magnetic pole S61) / (50% value of magnetic pole N11)
≦ 1.0, preferably (50% value of magnetic pole S61) / (magnetic pole N11
(50% value of magnetic pole S61) ≦ 0.8, and in the present embodiment, (50% value of magnetic pole S61) / (50% value of magnetic pole N11)
By setting ≈0.8, the change in the magnetic flux density of the magnetic field formed between the magnetic pole S61 and the magnetic pole N11 becomes higher from the developing sleeve 1a toward the toner layer thickness regulator 6a. did.

In this embodiment, the maximum value of each magnetic flux density is set to 900 gauss for the magnetic pole N11 and 800 gauss for the magnetic pole S11.

Further, 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. The ratio of (the absolute value of the peripheral speed of the toner layer thickness regulating member 6a) / (the absolute value of the peripheral speed of the developing sleeve 1a)> 0.5.

The magnetic toner has a weight average diameter of 5 μm or more, and the magnetic particles have a weight average diameter of 20 to 100.
An ordinary magnetic carrier of μm was used.

In the developing device constructed as shown in FIG. 3, the magnetic pole S6 of the permanent magnet 6b of the toner layer thickness regulating member 6a.
Lines of magnetic force are connected between the magnetic pole 1 and the magnetic pole N61, and a conveying force in the developing container 3 acts on the magnetic particles between the two poles.

The magnetic particles having a brush formed by the magnetic field between the magnetic pole N11 and the magnetic pole 61 are the same magnetic pole N as in the first embodiment.
In addition to the magnetic force between the magnetic pole 11 and the magnetic pole S61 and the frictional force on the surface of the toner layer thickness regulating member 6a, the magnetic pole S61 and the magnetic pole N indicated by the arrow c.
The magnetic force of 61 is applied to the developing device 3 so that it is conveyed. The magnetic particles carried on the surface of the toner layer thickness regulating member 6a are repelled by a strong magnetic force by the magnetic pole N61, the magnetic pole N62, and the magnetic pole N7, and even when the cohesiveness of the developer is high, the magnetic particles are non-contact. The particles and the non-magnetic toner can be scraped off, and as a result, the same effect as that described in the first embodiment can be obtained.

[0077]

As is apparent from the above description, in the image forming apparatus according to the present invention, the toner layer thickness regulator has the second magnetic field generating means having at least two poles therein, and the second magnetic field generating means. One magnetic pole and one magnetic pole of the first magnetic field generating means disposed inside the toner carrying member are disposed at substantially opposing positions, and the two magnetic poles disposed at the substantially opposing positions are different from each other. The second magnetic field generating means is polar and further has one or more magnetic poles on the downstream side in the rotation direction of the toner layer thickness regulator of one magnetic pole arranged at the substantially opposite position, and the second magnetic field generating means is provided at the substantially opposite position. At least two magnetic poles having the same polarity in the arrangement in the toner layer thickness regulating body of one magnetic pole arranged and one or more magnetic poles arranged on the downstream side in the rotation direction of the toner layer thickness regulating body. Has a developing device in which , The non-magnetic toner, the magnetic particles and the toner carrier are uniformly coated on the surface of the toner carrier without applying unnecessary pressure, and the magnetic particles are circulated without being conveyed to the developing area. By sufficiently stirring the non-magnetic toner with the non-magnetic toner, the non-magnetic toner is sufficiently charged, the latitude of the magnetic particle brush in an appropriate state is widened, and the non-magnetic toner and the magnetic particle are dispersed. It is possible to prevent deterioration and fusion of the non-magnetic toner to the toner carrier, and always obtain a proper developed image even when used for a long time.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing 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 of the image forming apparatus according to the present invention.

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

FIG. 4 is a schematic configuration diagram showing an example of an image forming apparatus in which the present invention is embodied.

FIG. 5 is a configuration diagram showing a first example of a conventional developing device.

FIG. 6 is an explanatory diagram showing the movement of magnetic force lines of the developing device of FIG.

FIG. 7 is an explanatory diagram showing the behavior of the toner in the toner layer thickness regulating portion in the developing device of FIG.

FIG. 8 is a configuration diagram showing a second example of a conventional developing device.

FIG. 9 is a configuration diagram showing a third example of a conventional developing device.

[Explanation of symbols]

 1a Developing sleeve (toner carrier) 1b Permanent magnet (first magnetic field generating means) 3 Developing container 6a Toner layer thickness regulating body 6b Permanent magnet (second magnetic field generating means) 7 Permanent magnet (third magnetic field generating means)

Claims (6)

[Claims] 1. A developing container for accommodating a developer containing a non-magnetic toner and magnetic particles, a rotatably arranged toner carrier for carrying a non-magnetic toner on the surface, and a toner container inside the toner carrier. A first magnetic field generating means having a plurality of magnetic poles provided, and a toner layer thickness regulating body for regulating the layer thickness of the non-magnetic toner applied onto the toner carrier, the toner layer thickness regulating body comprising: In an image forming apparatus including a developing device that is rotatably disposed near the toner carrier and has a rotation direction that is the same as a rotation direction of the toner carrier, the toner layer thickness regulator is at least inside thereof. The first magnetic field generating means 1 is equipped with a second magnetic field generating means having two poles.
One magnetic pole and one magnetic pole of the second magnetic field generating means are disposed at substantially opposing positions, and the two magnetic poles disposed at the substantially opposing positions have mutually different polarities. The toner having one or more magnetic poles arranged at the substantially opposed position, and further having one or more magnetic poles on the downstream side in the rotation direction of the toner layer thickness regulating body, and the magnetic pole arranged at the substantially opposed position, and the toner. In the arrangement in the toner layer thickness regulating body with one or more magnetic poles arranged on the downstream side in the rotation direction of the layer thickness regulating body, at least two or more magnetic poles of the same polarity are arranged adjacent to each other. Image forming apparatus. 2. The toner layer on the downstream side in the rotation direction of the toner layer thickness regulating member from the substantially opposed position of one magnetic pole of the second magnetic field generating means and one magnetic pole of the first magnetic field generating means. The image forming apparatus according to claim 1, further comprising a third magnetic field generating unit near the thickness regulator. 3. The image according to claim 2, wherein the magnetic poles of the third magnetic field generating means on the toner layer thickness regulating body side have the same polarity as the at least two magnetic poles arranged adjacent to each other. Forming equipment. 4. The image forming apparatus according to claim 1, wherein the magnetic flux density increases from the toner carrier toward the toner layer thickness regulator. 5. The 50% value of the magnetic poles of the toner layer thickness regulating body arranged at substantially opposite positions is not more than 1.0% of the 50% value of the magnetic poles of the toner carrier. Four
Image forming device. 6. The ratio between the absolute value of the peripheral speed of the toner layer thickness control member and the absolute value of the peripheral speed of the toner carrier is greater than 0.5. One image forming device.