JPH07333974A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To provide an electrophotographic device outputting a high-quality image without density unevenness or fogging. CONSTITUTION:Two sets of adjacent fixed magnets 33 and 34, 43 and 44 whose polarity are different from each other are respectively disposed on the inside of a photoreceptor drum 31 and an electrode roller 40. Then, magnetic flux generated by the fixed magnet 33 in the drum 31 positioned on an upstream side in the moving direction of the drum 31 is made larger than the magnetic flux generated by the magnet 34 in the drum 31 positioned on a downstream side in the moving direction of the drum 31. Besides, the magnetic flux generated by the fixed magnet 43 in the roller 40 positioned on the upstream side in the moving direction of the roller 40 is made larger than the magnetic flux generated by the fixed magnet 34 in the drum 31 positioned on the downstream side in the moving direction of the drum 31. Therefore, since magnetic restricting force is formed along the moving direction of toner from the roller 40 to the drum 31, the developer is stably supplied to the drum 31. Besides, since magnetic recovering force is made strong at a developing nip part, the image is formed without making the quantity of the toner excessive at the developing nip part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus applicable to printers, facsimiles and the like.

[0002]

2. Description of the Related Art Conventionally, a two-component developing method using a developer composed of a toner and a carrier has been widely used in an electrophotographic apparatus, but in recent years, one component has been used for downsizing and cost reduction of an image forming portion. Development of developing method is progressing. As an electrophotographic apparatus using such a one-component developing method, the electrostatic latent image holding drum and the electrode roller proposed by the present applicant in Japanese Patent Application Laid-Open No. 5-72890 have a fixed magnet contained therein, respectively. A magnetic developer was supplied to the electrostatic latent image formed on the electrostatic latent image holder, and the electrode roller applied with an alternating voltage adhered to the electrostatic latent image non-image area on the electrostatic latent image holder drum. There are electrophotographic devices that remove magnetic developers.

The features of this apparatus are as follows: (1) Unlike the conventional developing method in which the developer is attached to the image area, the developer is attached to the entire surface of the electrostatic latent image, and then the developer is attached to the non-image area. The thin line can be faithfully developed. (2) Unlike the conventional developing method in which the developer is formed on the electrostatic latent image with the developing roller having the developer layer formed thereon, after the developer is attached to the electrostatic latent image holding member, the electrode surface is changed. Since the method of removing the developer in the non-image area with the exposed electrode roller,
There is no so-called sleeve ghost phenomenon that occurs due to variations in the amount of developer charge on the developing roller. (3) Unlike the conventional developing method in which the developer layer on the developing roller is regulated by a regulating member such as a blade, since there is no member for directly applying pressure to the developer particles, the developer external additive is the developer base. It is excellent in stability over time of the developing device without being detached from the developer or driven into the developer base.

And the like. Japanese Patent Application No. 4-24
As described in Japanese Patent Application No. 1590, Japanese Patent Application No. 5-3779, Japanese Patent Application No. 5-16110, etc., it is formed between an electrostatic latent image carrier and an electrode roller. A method has been proposed in which a magnetic field that is parallel to the tangent line of the outer periphery of the electrostatic latent image holding member is formed in a region where development is performed by an alternating electric field, that is, a developing nip, and an image with high image density and no fog is output.

[0005]

However, in the above-mentioned method, the problem that density unevenness occurs when a solid image is output and that fog occurs in the non-image portion immediately after the solid image is output. Had a point. Regarding the former of the above problems, the amount of developer adhered to the surface of the electrostatic latent image carrier drum on which the electrostatic latent image is formed, or the amount of developer adhering to the surface of the electrostatic latent image carrier is conveyed to the developing nip. Occurs when the developer amount up to The latter occurs when the amount of developer in the developing nip becomes excessive. That is, the above problems occur when the amount of developer in the developing nip is not always constant.
In the above method, the mechanism for charging the developer particles is such that the electrostatic latent image carrier, the electrode roller, or the developer particles are reciprocated by the reciprocating motion of the developer particles according to the alternating electric field formed near the developing nip. This is because it depends on collision. That is, if the amount of the developer in the developing nip is unstable, stable reciprocating motion of the developer particles cannot be performed between the electrostatic latent image holding member and the electrode roller.

The amount of the developer in the developing nip becomes unstable because the developer, which has been attached to the surface of the electrostatic latent image carrier and then conveyed to the developing nip, is collected by the electrode roller and brought into contact with the electrode roller. This is because a series of the developer is not circulated stably in the developing section until the developer is scraped off by the scraping member and then conveyed and supplied again to the surface of the electrostatic latent image holding member. . The driving force for circulating the developer described above is the mechanical adhesion force between the surface of the electrostatic latent image carrier and the developer,
It is governed by two forces: the electrostatic latent image holder and the magnetic force of a fixed magnet contained in the electrode roller. Of these, regarding the magnetic force, the above-mentioned Japanese Patent Application No. 4-241590, Japanese Patent Application No. 5-3779, and Japanese Patent Application No. 5-16110.
As described in the specification, a method of forming a magnetic field parallel to the tangent line of the outer peripheral surface of the electrostatic latent image holding member or the tangent line of the outer peripheral surface of the electrode roller is mentioned. Since the range of the magnetic force to be applied is only in the vicinity of the developing nip, the magnetic pole configuration does not control the developer circulation until the developer scraped from the electrode roller is again conveyed and supplied to the surface of the electrostatic latent image holding member.

In view of the above problems, the present invention collects the developer, which has been attached to the surface of the electrostatic latent image carrier and then conveyed to the developing nip, by an electrode roller and is in contact with the electrode roller. After scraping with the scraping member, a series of developer circulation is stabilized until it is conveyed / supplied to the surface of the electrostatic latent image carrier again, and uneven density and fog in the non-image area immediately after outputting a solid image It is an object of the present invention to provide an electrophotographic apparatus capable of obtaining a high quality image without such a problem.

[0008]

In order to solve the above-mentioned problems, the electrophotographic apparatus of the present invention comprises an electrostatic latent image holding member that rotates and moves, a magnetic developer, a developer reservoir, and the electrostatic latent image. A fixed magnet A included in the image holding member and forming a magnetic field on the outer surface of the electrostatic latent image holding member; and included in the electrostatic latent image holding member.
A fixed magnet B, which is adjacent to the fixed magnet A on the downstream side in the moving direction of the electrostatic latent image holding member as viewed from the fixed magnet A and has a polarity different from that of the fixed magnet A, and the electrostatic latent image holding member. And an electrode roller installed via a gap and rotating in the opposite direction to the electrostatic latent image holding member, and a fixed magnet C included in the electrode roller and having a polarity different from that of the fixed magnet A.
And a fixed magnet D which is included in the electrode roller, is adjacent to the fixed magnet C on the downstream side in the moving direction of the electrode roller when viewed from the fixed magnet C, and has the same polarity as the fixed magnet A.
And a power supply for applying a voltage for removing the magnetic developer in the non-image area on the electrostatic latent image holder to the electrode roller, wherein the fixed magnet A is the electrostatic latent image holder. When the magnetic flux generated on the outer surface is Φ _A and the magnetic flux generated by the fixed magnet B on the outer surface of the electrostatic latent image holding body is Φ _B , | Φ _A | − | Φ _B |> 0 is established. It was done.

Further, when the magnetic flux generated by the fixed magnet C on the outer surface of the electrode roller is Φ _C and the magnetic flux generated by the fixed magnet D on the outer surface of the electrode roller is Φ _D , │Φ _A │-│Φ _B │> │ Φ _C | − | Φ _D |> 0.

In the electrophotographic apparatus of the present invention, the electrostatic latent image holding member that rotates, the magnetic developer, the developer reservoir, and the electrostatic latent image holding member are included in the electrostatic latent image holding member. A fixed magnet A that forms a magnetic field on the outer surface of the body, and a fixed magnet A that is included in the electrostatic latent image holding body and is located downstream of the fixed magnet A in the moving direction of the electrostatic latent image holding body. Adjacent to
A fixed magnet B having a polarity different from that of the fixed magnet A, an electrode roller that is installed through a gap with the electrostatic latent image holder, and rotates and moves in a direction opposite to the electrostatic latent image holder, and the electrode. A fixed magnet C included in the roller and having a polarity different from that of the fixed magnet A; and a fixed magnet C included in the electrode roller and adjacent to the fixed magnet C downstream of the fixed magnet C in the moving direction of the electrode roller. In the electrophotographic apparatus, a fixed magnet D having the same polarity as the fixed magnet A and a power source for applying a voltage for removing the magnetic developer in the non-image area on the electrostatic latent image holding member to the electrode roller are provided. , Φ _B is the magnetic flux generated by the fixed magnet B on the outer surface of the electrostatic latent image carrier,
When the magnetic flux generated by the fixed magnet C on the outer surface of the electrode roller is Φ _C , | Φ _B | ≦ | Φ _C |

Further, in the electrophotographic apparatus of the present invention, the electrostatic latent image holder that rotates, the magnetic developer, the developer reservoir, and the electrostatic latent image holder that protrudes from the inlet of the developer reservoir are provided. The developing device entrance seal, which is in contact with the developing device entrance seal, is included in the electrostatic latent image holding member, and is located downstream of the tip of the developing device entrance seal in the moving direction of the electrostatic latent image holding member. A fixed magnet that forms a magnetic field on the outer surface of the electrostatic latent image holder, an electrode roller that is installed via a gap with the electrostatic latent image holder, and rotates and moves in the opposite direction to the electrostatic latent image holder, And a power supply for applying a voltage for removing the magnetic developer in the non-image area on the electrostatic latent image holder to the electrode roller.

[0012]

According to the present invention having the above-mentioned structure, the developer, which is attached to the surface of the electrostatic latent image carrier and then conveyed to the developing nip,
A series of circulation of the developer is stabilized until it is collected by the electrode roller, scraped by the developer scraping member in contact with the electrode roller, and then conveyed and supplied again to the surface of the electrostatic latent image holding member.

That is, by making the magnetic flux generated by the fixed magnet A larger than the magnetic flux generated by the fixed magnet B, excess magnetic flux is generated from the fixed magnet A, and the developer or developer storage portion scraped from the electrode roller is discharged. The newly supplied developer can be magnetically attracted to the surface of the electrostatic latent image holding member. Therefore, the developer adhering to the surface of the electrostatic latent image carrier does not become mottled, and the consumed amount of the circulating developer can be reliably replenished. Therefore, an image without density unevenness can be obtained.

Further, the magnetic flux generated by the fixed magnet C is set to be larger than the magnetic flux generated by the fixed magnet B, so that the magnetic developer on the electrostatic latent image carrier is more magnetically conveyed to the developing nip than the electrode. The force for magnetically moving the magnetic developer on the roller from the developing nip can be increased. As a result, the developer amount in the vicinity of the developing nip does not become excessive, so that the developer can be uniformly charged. Therefore, an image without density unevenness and fog can be obtained.

Further, the fixed magnet inside the electrostatic latent image holding member is arranged on the downstream side of the tip of the developing device entrance seal, so that the developing nip is applied to all the magnetic developers supplied on the electrostatic latent image holding member. It is possible to impart a conveying force to the. Therefore, a high-density image can be obtained.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An electrophotographic apparatus of the present invention will be described below with reference to the drawings.
Will be described with reference to. (Embodiment 1) FIGS. 1A and 1B are electrophotographic apparatus of the present invention.
FIG. 3 is a configuration diagram and an enlarged view of a main part showing an embodiment of the present invention. Figure 1
A first embodiment of the present invention will be described using the above apparatus. Figure
In No. 1, 31 is aluminum with a diameter of 30 mm and a wall thickness of 1 mm.
A photoconductor drum with an organic photoconductive film coated on a substrate.
It 32 is a diameter of 6 mm coaxial with the photosensitive drum 31,
It is a photoconductor drum shaft made by Nessless. 33 and 34
With a fixed magnet bonded to the photoconductor drum shaft 32,
The fixed magnet 33 on the upstream side of the optical drum 31 in the rotation direction is S
The fixed magnets 34 on the pole and the downstream side are magnetized to the N pole,
Shown θ₁And θ ₂Are 40 and 30 degrees, respectively
Has been done. Further, the fixed magnet 33 and the fixed magnet 34 are exposed to light.
Placed at a distance of 0.5 mm from the back of body drum 31
Has been. Reference numeral 35 indicates that the photosensitive drum 31 is negatively charged.
A corona charger 36 is provided to emit signal light. 37 is a developer
Reservoir, 38 is the average particle size stored in developer reservoir 37 about 8μ
It is a magnetic toner of m negatively chargeable magnetic one component. Three
9 prevents the magnetic toner 38 from spilling from the developer reservoir 37
This is the developing device entrance seal.

Reference numeral 40 denotes a stainless steel electrode roller having a diameter of 16 mm and a wall thickness of 1 mm, which is installed at a distance of 200 μm from the photosensitive drum 31. Reference numeral 41 is an AC high-voltage power supply that supplies a rectangular wave AC voltage to the electrode roller 40. Reference numeral 42 denotes an electrode roller shaft made of stainless steel, having a diameter of 4 mm and coaxial with the electrode roller 40. Fixed magnets 43 and 44 are bonded to the electrode roller shaft 42. The fixed magnet 43 on the upstream side in the rotation direction of the electrode roller 40 is magnetized to the N pole, and the fixed magnet 44 on the downstream side is magnetized to the S pole. The shown θ ₃ and θ ₄ are 50 degrees and 30 degrees, respectively. Further, the fixed magnet 43 and the fixed magnet 44 are arranged at a distance of 0.5 mm from the back surface of the electrode roller 40. Reference numeral 45 denotes a toner scraping member made of a phosphor bronze plate for scraping the toner on the electrode roller 40.
Other than that, it is electrically insulated. Reference numeral 46 is a toner hopper that stores toner, and 47 is a rotary blade that supplies the magnetic toner 38 from the toner hopper 46 to the developer reservoir 37. A cleaning member 48 removes the magnetic toner 38 remaining on the photosensitive drum 31 after the transfer.

The photosensitive drum 31 has a peripheral speed of 32.5 m.
It was rotated at m / s. The electrode roller 40 was rotated at the same speed as the photoconductor drum 31 and in the opposite direction at the portion facing the photoconductor drum 31.

The operation of the electrophotographic apparatus configured as described above will be described below with reference to FIG. The photoconductor drum 31 was charged to −450V by the corona charger 35. The photosensitive drum 31 was irradiated with the signal light 36 to form an electrostatic latent image. At this time, the exposure potential of the photosensitive drum 31 was −70V. Toner was supplied from the toner hopper 46 onto the surface of the photoconductor drum 31 and adhered thereto. Next, the photosensitive drum 31 with the toner attached was passed in front of the electrode roller. At this time, the high voltage power supply 41 is applied to the electrode roller 40.
To a frequency of 2 kHz and an alternating voltage of 1.4 kVp-p.
A developing bias on which a DC voltage of 270 V was superimposed was applied. Due to the alternating electric field applied between the photoconductor drum 31 and the electrode roller 40, of the toner on the surface of the photoconductor drum 31, the toner attached to the non-image portion is collected on the electrode roller 40 side and attached to the image portion. Only the toner remained on the surface of the photosensitive drum 31. The toner collected on the side of the electrode roller 40 is collected by the toner scraping member 45.
0 removed from above.

The toner image obtained on the photosensitive drum 31 was transferred onto an image receiving paper (not shown) by a transfer device (not shown) and then fixed by a fixing device (not shown). On the other hand, the toner remaining on the photosensitive drum 31 after the transfer was removed from the surface of the photosensitive drum 31 by the cleaning member 48.

Using the electrophotographic apparatus having the above-described structure, the fixed magnet 33 distributes the magnetic flux of the S pole distributed along the outer peripheral direction of the photosensitive drum 31 to 1.5 × 10 ^{−3 to} 4.5 × 10 ^{−. 3} W
The image was output while being changed in the range of b / m. At this time, the fixed magnet 34 distributes the magnetic flux of the N pole distributed along the outer peripheral direction of the photoconductor drum 31 to 1.5 × 10 ⁻³ Wb / m.
Fixed to. Further, the photosensitive drum 31 and the electrode roller 4
It was installed so that the magnetic flux density peak of the fixed magnet 34 would be on the line connecting the center of rotation with 0 (hereinafter abbreviated as the axis center line). In addition, the fixed magnet 43 distributes the magnetic flux of the N pole distributed along the outer peripheral direction of the electrode roller 40 to 2.5 × 10 5.
^-3 Wb / m, the magnetic flux of the S pole generated by the fixed magnet 44 distributed in the outer peripheral direction of the electrode roller 40 is 1.5 × 10 ^-3 Wb / m.
Fixed to. Further, the photosensitive drum 31 and the electrode roller 4
It was installed so that the center between the magnetic flux density peaks of the fixed magnet 43 and the fixed magnet 44 would be on the axis center line of 0.

Table 1 shows the image quality evaluation results for each setting. As shown in Table 1, when the magnetic flux of the fixed magnet 33 was 1.5 × 10 ⁻³ Wb / m or less, the image density was lowered and the density unevenness became more noticeable. When the magnetic flux of the fixed magnet 33 was 4.5 × 10 ⁻³ Wb / m or more, characters and line drawings were crushed and fogging occurred in the non-image area immediately after the solid black image was output. In addition, uneven density has increased. In addition,
At 2.0 × 10 ^{−3 to} 2.5 × 10 ⁻³ Wb / m, there was no problem with the initial image, but when images were continuously output, the image density decreased.

[0023]

[Table 1]

As a result, the magnetic flux generated by the fixed magnet 33 on the surface of the photosensitive drum 31 is 2.0 × 10 ⁻³ Wb / m or more and 4.0 × 10 ⁻³ Wb / m or less, preferably 3.0 ×. 10
^An image of high quality was obtained when it was ⁻³ Wb / m or more and 4.0 × 10 ⁻³ Wb / m or less.

The consideration of the above results will be described below with reference to the drawings. 2 and 3, when the magnetic flux generated by the fixed magnet 33 is larger than the magnetic flux generated by the fixed magnet 34, that is, 3.0 × 10 ^{−3 to} 4.0 × 10 ⁻³ Wb in Table 1.
It is a figure which shows the magnetic field structure in the case equivalent to / m. Figure 2
Is when the photosensitive drum 31 and the electrode roller 40 are magnetically independent of each other, and FIG. 3 shows a magnetic field configuration in the developer reservoir 37 in the apparatus shown in FIG.

In FIG. 2, between the magnetic flux Φ _A penetrating the outer surface of the photosensitive drum 31 from the fixed magnet 33 and the magnetic flux Φ _B penetrating the outer surface of the photosensitive drum 31 from the fixed magnet 34, | Φ _A | − | Φ _B |> 0 (1) holds. As a result, a magnetic flux φ connecting the fixed magnet 33 and the fixed magnet 34 is formed on the outer surface of the photosensitive drum 31.
Two magnetic fluxes appear, _AB and a surplus magnetic flux φ _AA that does not contribute to the magnetic flux φ _AB and converges only by the fixed magnet 33. Since the fixed magnet 33 and the fixed magnet 34 are adjacent to each other, the magnetic flux Φ
Most of _B is connected to the magnetic flux φ _AB , and becomes | φ _AB | ≈ | Φ _B | (2). Therefore, the excess magnetic flux φ _AA is the difference between the magnetic fluxes emitted from the fixed magnets 33 and 34, that is, | φ _AA | ≈ | Φ _A |-| Φ _B | Appears. Due to this excess magnetic flux, the toner can be evenly attracted and attached to the surface of the photosensitive drum 31. As a result, an image with high density and no density unevenness can be obtained.

The magnetic flux Φ _C penetrating the outer surface of the electrode roller 40 from the fixed magnet 43 and the fixed magnet 44 to the electrode roller 40.
Between the magnetic flux Φ _D that penetrates the outer surface, | Φ _AA |> | Φ _C |-| Φ _D |> 0 (4). As a result, on the outer surface of the electrode roller 40, a magnetic flux φ _CD (≈, which connects the fixed magnet 43 and the fixed magnet 44).
| Φ _D |) and a surplus magnetic flux φ _CC (≈ | Φ _C | − | Φ _D |) that does not contribute to the magnetic flux φ _CD and is converged only by the fixed magnet 43.

Further, as shown in FIG. 3, when the photosensitive drum 31 and the electrode roller 40 are brought close to each other with a predetermined gap, part of the excess magnetic flux φ _AA of the fixed magnet 33 and the fixed magnet 43.
And the surplus magnetic flux φ _CC of is connected to form the magnetic flux φ _CA.
From the developing nip to the photoconductor drum 31 by the magnetic flux φ _CA ,
Since the magnetic field for restraining the magnetic toner is generated, the electrode roller 4
Transport of magnetic toner from 0 to the surface of photosensitive drum 31
The supply is stable.

At the same time as above, on the photosensitive drum 31, the magnetic flux is surplus by the amount of | φ _AA | − | φ _CA |. Due to this excess magnetic flux, the toner is attracted from the toner hopper 46 onto the photosensitive drum 31. Therefore, even if the toner is consumed, the toner can be surely replenished to the developer reservoir 37 by the action of the magnetic attraction force. Therefore, even if images are continuously output, the amount of toner circulating in the developer reservoir 37 Is kept constant.

As described above, by setting each fixed magnet so that the expression (4) is satisfied, (3.0 × in Table 1)
(Equivalent to 10 ^{−3 to} 4.0 × 10 ⁻³ Wb / m), the magnetic toner is conveyed and supplied from the electrode roller 40 to the surface of the photosensitive drum 31, and the circulating toner amount during continuous image output is stable. Therefore, it is possible to obtain an image without density reduction or density unevenness.

When the expression (1) is not satisfied (corresponding to 1.5 × 10 ⁻³ Wb / m in Table 1), the excess magnetic flux φ _AA is not formed, so that the toner supply to the photosensitive drum 31 is bad. As a result, the toner adhesion amount on the photoconductor 31 becomes sparse. For this reason, the image density becomes low and the density unevenness also increases.

Although equation (1) holds, (4)
When the formula is not satisfied (from 2.0 × 10 ^{−3 in} Table 1
2.5 × 10 ⁻³ Wb / m), the excess magnetic flux | φ _AA | − | φ _CA | formed at the upper end of the fixed magnet 33 is not formed, so that the toner supply from the toner hopper 46 becomes worse. Therefore, the image density decreases as the images are continuously output.

When the magnetic flux generated by the fixed magnet 33 is more than the magnetic flux generated by the fixed magnet 34 (4.5 in Table 1).
X10 ^-3 Wb / m), the excess magnetic flux | φ _AA |-|
Since the number of φ _CA | is too large, not only the toner conveyance amount to the developing nip becomes excessive, but also the toner acts as a magnetic binding force on the photosensitive drum 31. For this reason, fogging immediately after a solid black image and density unevenness such as toner being dragged on the photosensitive drum 31 occur.

(Embodiment 2) A second embodiment of the present invention will be described using the apparatus shown in FIG. In this embodiment, the fixed magnet 43
The magnetic flux of the N pole distributed along the outer peripheral surface of the electrode roller 40 and emitted is changed in the range of 1.0 × 10 ^{−3 to} 2.5 × 10 ⁻³ Wb / m and an image is output. At this time, the fixed magnet 33 distributes the magnetic flux of the S pole distributed and distributed along the outer peripheral direction of the photosensitive drum 31 to 3.5 × 10 ⁻³ Wb / m, and the fixed magnet 34 sets the fixed magnet 34 to the outer peripheral direction of the photosensitive drum 31. The magnetic fluxes of the N poles distributed and emitted along were fixed at 1.5 × 10 ⁻³ Wb / m. Further, the magnetic flux density peak of the fixed magnet 34 was placed on the axis center line between the photosensitive drum 31 and the electrode roller 40. Further, the magnetic flux of the S pole generated by the fixed magnet 44 distributed along the outer peripheral direction of the electrode roller 40 was fixed to 1.5 × 10 ⁻³ Wb / m. Further, the photoconductor drum 31 and the electrode roller 40 were installed so that the center of the magnetic flux density peaks of the fixed magnet 43 and the fixed magnet 44 would be on the axial centerline.

Table 2 shows the image quality evaluation results for each setting. As shown in Table 2, when the magnetic flux of the fixed magnet 43 was 1.0 × 10 ⁻³ Wb / m or less, characters and line drawings were crushed and fog occurred. 1.5-2.0 × 10 ^-3 Wb
With / m, there was no problem with the initial image, but when images were continuously output, the image density decreased. 2.5 x 1
A high quality image was obtained at 0 ^-3 Wb / m or more.

[0036]

[Table 2]

FIG. 4 shows that when the magnetic flux generated by the fixed magnet 34 is equal to or less than the number of magnetic fluxes of the fixed magnet 43, that is, when it corresponds to 1.5 to 2.5 × 10 ⁻³ Wb / m in Table 2, FIG. 6 is an enlarged view of a magnetic field configuration near the developing nip.
In FIG. 4, most of the magnetic flux Φ _B penetrating the outer surface of the photosensitive drum 31 from the fixed magnet 34 converges on the adjacent fixed magnet 33 side. Further, most of the magnetic flux Φ _C penetrating the outer surface of the electrode roller 40 from the fixed magnet 43 converges on the fixed magnet 44 and the fixed magnet 33 which are adjacent to each other.

The magnetic flux Φ _B converged by the fixed magnet 33 acts as a force for carrying and supplying the magnetic toner supplied onto the photosensitive drum 31 to the developing nip. Therefore, the toner supplied to the photosensitive drum 31 is conveyed to the developing nip along the magnetic flux Φ _B. Further, the magnetic flux Φ _C acts on the magnetic toner collected on the electrode roller 40 side in the developing nip as a force to move the magnetic toner along the outer peripheral surface of the electrode roller 40 and remove it from the developing nip. Therefore, the toner collected on the electrode roller 40 side is removed from the developing nip along the magnetic flux Φ _C. Therefore, if the number of magnetic fluxes Φ _C is greater than or equal to the number of magnetic fluxes Φ _B , the amount of toner removed from the developing nip is larger than the amount of toner supplied to the developing nip. Immediately after, fog disappears.

The magnetic flux generated by the fixed magnet 34 is generated by the fixed magnet 43.
When the magnetic flux is larger than the magnetic flux emitted by (1.0 × 10 ^{-3 in} Table 2
(Corresponding to Wb / m), a toner amount exceeding the toner collecting ability to the electrode roller is supplied to the developing nip, which causes toner collecting failure.

(Embodiment 3) A third embodiment of the present invention will be described using the apparatus shown in FIG. In this embodiment, the length of the developing device entrance seal 39 is changed within the range of 3 to 10 mm,
Output the image. As the developing device entrance seal 39 used in this embodiment, a PET sheet having a thickness of 38 μm was used.

At this time, the fixed magnet 33 moves the photosensitive drum 3
2. The magnetic flux of the S pole distributed and emitted along the outer peripheral direction of 1.
The magnetic flux of the N pole generated by the fixed magnet 34 distributed along the outer peripheral direction of the photosensitive drum 31 was fixed to 5 × 10 ⁻³ Wb / m and 1.5 × 10 ⁻³ Wb / m, respectively. Further, the magnetic flux density peak of the fixed magnet 34 was placed on the axis center line between the photosensitive drum 31 and the electrode roller 40. Further, the magnetic flux of the N pole generated by the fixed magnet 43 distributed along the outer peripheral surface of the electrode roller 40 is 2.4 × 10 ⁻³ Wb /
At m, the magnetic flux of the S pole generated by the fixed magnet 44 distributed along the outer peripheral direction of the electrode roller 40 is 1.5 × 10 ⁻³ Wb / m.
Fixed to. Further, the photosensitive drum 31 and the electrode roller 4
It was installed so that the center between the magnetic flux density peaks of the fixed magnet 43 and the fixed magnet 44 would be on the axis center line of 0.

Table 3 shows the image quality evaluation results for each setting. As shown in Table 3, the image density started to decrease when the length of the developing device inlet seal 39 was around 7 mm. Further, when the length was 9 mm, the density decrease became remarkable, and at the same time, the density unevenness became conspicuous. 6
When the length was at least mm, the tip of the developing device inlet seal 39 reached the magnetic pole surface of the fixed magnet 33 through the photosensitive drum 31. The tip of the developing device entrance seal 39 is 5 mm.
At a shorter time, the toner was spilled from the developer reservoir 37 when a shock was applied to the apparatus.

[0043]

[Table 3]

From the above results, the developing device entrance seal 39
When the length was less than 5 mm, a high density image was obtained.
Further, when it was 5 mm or more, toner spillage from the developer reservoir 37 was prevented.

The consideration of the relationship between the length of the developing device entrance seal 39 and the image density will be described below with reference to the drawings. FIG. 5 is a diagram showing a magnetic field configuration in the vicinity of the inlet of the developer reservoir 37 when the tip of the developer inlet seal 39 reaches the magnetic pole surface of the fixed magnet 33 via the photosensitive drum 31. As shown in FIG. 5, when the tip of the developer inlet seal 39 reaches the magnetic pole surface of the fixed magnet 33, the magnetic flux generated by the fixed magnet 33 penetrates the developer inlet seal 39 to form a magnetic field. The magnetic flux generated by the fixed magnet 33 contributes to the toner supply to the surface of the photosensitive drum 31. Therefore, the toner scraped by the toner scraping member and the toner replenished from the toner hopper are attached to the photosensitive drum 31 via the developing device inlet seal 39 as shown in FIG. However, only the magnetic flux that contributes to the supply to the photoconductor drum 31 passes through the toner supplied onto the developing device entrance seal 39, and the magnetic conveying force to the developing nip is not applied. Further, those toners are used as the photosensitive drum 3
Since it does not come into contact with the surface 1, it cannot be conveyed by the dispersing force on the surface of the photosensitive drum 31. Therefore, the developing device entrance seal 3
Since the toner supplied to the toner 9 is not subjected to the conveying force to the developing nip, it remains stationary. This allows
The area on the photosensitive drum 31 that receives the supplied toner is reduced. Therefore, the toner supply to the surface of the photosensitive drum 31 becomes poor. Further, in addition to the magnetic force, the dispersing force of the surface of the photoconductor drum 31 acts as a driving force for toner circulation, but the area to which this dispersing force is applied is also reduced, so that the toner in the developer reservoir 37 is The circulation speed also becomes slow. For this reason, the image density becomes low and the density unevenness also increases.

In the apparatus of this embodiment, ± 15 degrees from the axis center line between the photosensitive drum 31 and the electrode roller 40,
It is preferable to install the fixed magnet 34 so that the peak of the magnetic flux density is within a range of ± 10 degrees. If the magnetic flux density peak is located downstream of the axial center line in the moving direction of the photoconductor drum 31, the magnetic flux Φ _B that regulates toner conveyance reaches a region that cannot be completely recovered by the alternating electric field applied to the electrode roller 40. . As a result, the toner is transferred to the photosensitive drum 3
Fog remains on the surface and causes fog. Further, when the magnetic flux density peak is located on the upstream side in the moving direction of the photosensitive drum 31 with respect to the axial center line, the magnetic flux Φ that regulates the toner conveyance.
_B does not reach the developing nip. As a result, it becomes difficult for the toner to be conveyed to the developing nip, and the image density decreases.

Further, as seen in the outer peripheral direction of the photosensitive drum 31,
It is better to make the width of the fixed magnet 33 wider than that of the fixed magnet 34. Thereby, it is easy to make the number of magnetic fluxes Φ _A larger than the number of magnetic fluxes Φ _B. Further, it is possible to secure two areas on the fixed magnet 33, that is, an area in which the toner is replenished on the photosensitive drum 31 by the magnetic flux φ _AA and an area in which the toner is conveyed to the developing nip by the magnetic flux φ _AB .

Further, the photosensitive drum 31 and the electrode roller 40
It is preferable to set the center of the magnetic flux density between the fixed magnet 43 and the fixed magnet 44 to be within ± 15 degrees, preferably ± 10 degrees from the axis center line of. When the center between the magnetic flux density peaks is on the upstream side of the above range in the moving direction of the electrode roller 40, the magnetic flux Φ _C that regulates toner recovery is
The area that cannot be completely recovered by the alternating electric field applied to the electrode roller 40 is reached. As a result, the toner remains on the surface of the photosensitive drum 31 to cause fog. Further, the center between the magnetic flux density peaks is higher than the above range in the electrode roller 4
On the downstream side in the moving direction of 0, the magnetic flux Φ _B and the magnetic flux Φ _C become dense before the developing nip. As a result, it becomes difficult for the toner to be conveyed to the developing nip, and the image density decreases.

Also, when viewed in the moving direction of the electrode roller 40,
The width of the constant magnet 43 is equal to or wider than the width of the fixed magnet 44.
It is better to do above. As a result, the magnetic flux Φ_CThe number of
Bundle Φ _DIt is easy to make more than the number of.

In this embodiment, the fixed magnet 33 and the fixed magnet 44 are S poles and the fixed magnets 34 and 43 are N poles. However, the fixed magnets 33 and 44 are N poles and fixed magnets. Of course, 34 and the fixed magnet 43 may be S poles.

In addition to the organic photoconductor, the photoconductor 31 may be made of zinc oxide, selenium, cadmium sulfide, amorphous silicon, or the like. Needless to say, ordinary electrostatic recording paper may be used. The surface of the photoconductor may be roughened by sandblasting or the like in order to accelerate the conveyance of the toner.

The magnetic developer used in the present invention is preferably an insulating one-component toner. This is because the device configuration can be simplified by using the one-component toner. The one-component toner used in the present invention is obtained by dispersing magnetite or ferrite powder in a binder resin such as styrene resin or acrylic resin together with a charge control agent, pulverizing and classifying. The toner may be a powder obtained by spray drying or a powder chemically obtained by a pearl polymerization method or the like. The average particle diameter of the toner used is preferably 15 μm or less, but 12 μm
A sharper image can be obtained by the following.

In the present invention, a two-component developer composed of toner and a magnetic carrier can be used. The toner used in the present invention is obtained by dispersing a color pigment such as carbon black or phthalocyanine in a binder resin such as an acrylic resin or a polyester resin, pulverizing and classifying. This toner may be a powder obtained by spray drying, or may be a powder chemically obtained by a pearl polymerization method, an emulsion polymerization method, or the like. Further, the toner particles may be directly mixed with a carrier, or silica particles or fluororesin fine powder may be adhered to the surface of the toner. The average particle size of the toner used is preferably 15 μm or less, but 12 μm
If it is less than m, a sharper image can be obtained.

The carrier used in the present invention is a magnetic substance such as iron powder or ferrite powder, or a powder whose surface is coated with a resin, or a fine powder such as ferrite powder or magnetite in a proportion of about 30-80%. A magnetic powder that is dispersed and mixed in a resin, an epoxy resin, a styrene-acrylic resin, and pulverized and classified is used. The average particle size of the carrier is 3
The thickness is preferably 00 μm or less, but particularly 150 μm or less allows the toner to be uniformly charged.

The distance between the electrode roller 40 and the photoconductor 31 is
100 μm to 700 μm when a one-component toner is used
Degree: 400 μm to 2 m when using a two-component developer
It is preferable to install them at a distance of about m.

The material of the electrode roller 40 may be conductive. When the fluidity of the magnetic developer is poor, the electrode roller 4
When 0 is a magnetic material, the magnetic lines of force from the fixed magnet inside the photoconductor 31 reach the electrode roller 40, and as a result, the developer transportability is improved. Examples of such a material include soft iron, magnetic stainless steel, and nickel. The surface of the electrode roller 40 may be a polished one, or may be one having an irregular surface by sandblasting or a groove. However,
When the electrode roller 40 is a magnetic substance, the magnetic field that can be formed on the surface thereof becomes strong, but a magnetic attraction force acts between the fixed magnet and the electrode roller 40, and the driving torque of the electrode roller 40 increases. There is a point. Therefore, the electrode roller 40 may be a non-magnetic roller having a magnet fixed inside. For example, there is a configuration in which a magnet is inserted into a cylinder made of non-magnetic stainless steel or aluminum.

The AC voltage applied to the electrode roller 40 may be a pulse waveform or a triangular wave, as a matter of course.
It suffices if an alternating electric field is effectively applied between and. The frequency of this alternating voltage depends on the process speed of the image formation,
The range is approximately 50 Hz to 5000 Hz, and preferably 300 to 3000 Hz. The value of the AC voltage is a zero to peak value, which is preferably about 0.5 to 3 times the charging potential of the photoconductor 31, and further 0.5.
Therefore, a double value is preferable. In the case of reversal development, if the value of the DC voltage to be superimposed on the AC voltage is set equal to or lower than the charging potential of the photoconductor 31 by several tens of percent, a good negative-positive reversal image can be obtained. On the other hand, in the case of normal development, a good positive image can be obtained by setting the value to be equal to or higher than the background potential of the electrostatic latent image carrier by several tens of percent.

The toner scraping member 45 is the electrode roller 4
It is desirable to be electrically insulated so as not to affect 0. Therefore, plastic such as polyester film may be used.

The developing device entrance seal 39 is preferably one that does not affect the electrostatic characteristics and surface properties of the photoconductor 31. Therefore, a urethane film or a PPS film may be used.

[0060]

As described above, according to the present invention, since the magnetic flux generated by the fixed magnet A is made larger than the magnetic flux generated by the fixed magnet B, an excess magnetic flux is generated from the fixed magnet A and scraped from the electrode roller. The developer and the developer newly supplied from the developer storage unit can be magnetically attracted to the surface of the electrostatic latent image holding member, so that an image having high image density and no density unevenness can be obtained.

Further, the magnetic flux generated by the fixed magnet C is set to be larger than the magnetic flux generated by the fixed magnet B, so that the magnetic developer on the electrostatic latent image carrier is more magnetically conveyed to the developing nip than the electrode. Since the force for magnetically moving the magnetic developer on the roller from the developing nip can be increased, an image without density unevenness or fog can be obtained.

Further, the fixed magnet inside the electrostatic latent image holding member is arranged on the downstream side of the tip of the developing device entrance seal, so that all the magnetic developers supplied onto the electrostatic latent image holding member are exposed to the developing nip. A high-density image can be obtained because a conveyance force to the sheet can be applied.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an electrophotographic apparatus according to an embodiment of the present invention.

FIG. 2 is a magnetic field configuration diagram when the photosensitive drum and the electrode roller in one embodiment of the present invention are magnetically independent of each other.

FIG. 3 is a magnetic field configuration diagram in a developer reservoir according to an embodiment of the present invention.

FIG. 4 is a magnetic field configuration diagram in the vicinity of a developing nip according to an embodiment of the present invention.

FIG. 5 is a magnetic field configuration diagram in the vicinity of a developer reservoir entrance in an embodiment of the present invention.

[Explanation of symbols]

 31 photoconductor drum 32 photoconductor drum shaft 33 photoconductor internal fixed magnet (S pole) 34 photoconductor internal fixed magnet (N pole) 35 corona charger 36 signal light 37 developer reservoir 38 magnetic toner 39 developer inlet seal 40 electrode Roller 41 AC voltage power supply 42 Electrode roller shaft 43 Electrode roller internal fixed magnet (N pole) 44 Electrode roller internal fixed magnet (S pole) 45 Toner scraping member 46 Toner hopper-47 Rotating blade 48 Cleaning member

Front page continued (72) Inventor Hiroshi Komagine 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (8)

[Claims] 1. An electrostatic latent image holder that rotates, a magnetic developer, a developer reservoir, and the electrostatic latent image holder are contained in the electrostatic latent image holder to form a magnetic field on the outer surface of the electrostatic latent image holder. And a fixed magnet A that is included in the electrostatic latent image holder and is adjacent to the fixed magnet A on the downstream side in the moving direction of the electrostatic latent image holder when viewed from the fixed magnet A. A fixed magnet B having a polarity different from that of the electrode, an electrode roller installed with a gap between the electrostatic latent image holding member and the electrostatic latent image holding member, and an electrode roller rotatably moving in a direction opposite to the electrostatic latent image holding member. A fixed magnet C having a polarity different from that of the fixed magnet A, and a fixed magnet C which is included in the electrode roller and which is adjacent to the fixed magnet C on the downstream side of the fixed magnet C in the moving direction of the electrode roller. A fixed magnet D having the same polarity as the magnet A, and a non-image portion on the electrostatic latent image holder. An electric power source for applying a voltage for removing the magnetic developer to the electrode roller, wherein the magnetic flux generated by the fixed magnet A on the outer surface of the electrostatic latent image holding member is Φ _A , An electrophotographic apparatus, wherein when a magnetic flux generated by the fixed magnet B on the outer surface of the electrostatic latent image carrier is Φ _B , | Φ _A | − | Φ _B |> 0. 2. When the magnetic flux generated by the fixed magnet C on the outer surface of the electrode roller is Φ _C and the magnetic flux generated by the solid magnet D on the outer surface of the electrode roller is Φ _D , | Φ _A | − | Φ _B |> | The electrophotographic apparatus according to claim 1, wherein Φ _C | − | Φ _D |> 0 holds. 3. An electrostatic latent image holding member that rotates, a magnetic developer, a developer reservoir, and the electrostatic latent image holding member are included in the electrostatic latent image holding member to form a magnetic field on the outer surface of the electrostatic latent image holding member. And a fixed magnet A that is included in the electrostatic latent image holder and is adjacent to the fixed magnet A on the downstream side in the moving direction of the electrostatic latent image holder when viewed from the fixed magnet A. A fixed magnet B having a polarity different from that of the electrode, an electrode roller installed with a gap between the electrostatic latent image holding member and the electrostatic latent image holding member, and an electrode roller rotatably moving in a direction opposite to the electrostatic latent image holding member. A fixed magnet C having a polarity different from that of the fixed magnet A, and a fixed magnet C which is included in the electrode roller and which is adjacent to the fixed magnet C on the downstream side of the fixed magnet C in the moving direction of the electrode roller. A fixed magnet D having the same polarity as the magnet A, and a non-image portion on the electrostatic latent image holder. And a power supply for applying a voltage for removing the magnetic developer to the electrode roller, wherein the magnetic flux generated by the fixed magnet B on the outer surface of the electrostatic latent image holding member is Φ _B , An electrophotographic apparatus, wherein when the magnetic flux generated by the fixed magnet C on the outer surface of the electrode roller is Φ _C , | Φ _B | ≦ | Φ _C | 4. When the magnetic flux generated by the fixed magnet A on the outer surface of the electrostatic latent image carrier is Φ _A and the magnetic flux generated by the fixed magnet D on the outer surface of the electrode roller is Φ _D , | Φ _A | − 4. The electrophotographic apparatus according to claim 3, wherein | Φ _B |> | Φ _C | − | Φ _D |> 0 holds. 5. An electrostatic latent image carrier that rotates, a magnetic developer, a developer reservoir, and a developing device inlet seal that projects from the inlet of the developer reservoir and contacts the electrostatic latent image carrier. An outer surface of the electrostatic latent image holder, which is included in the electrostatic latent image holder and is located downstream of the tip of the developing device entrance seal when viewed in the moving direction of the electrostatic latent image holder. A fixed magnet that forms a magnetic field, an electrode roller that is installed via a gap with the electrostatic latent image holder, and rotates in the opposite direction to the electrostatic latent image holder, and the electrostatic latent image holder An electrophotographic apparatus, comprising: a power supply for applying a voltage for removing the magnetic developer in the non-image area to the electrode roller. 6. A fixed magnet A contained in the electrostatic latent image carrier and forming a magnetic field on the outer surface of the electrostatic latent image carrier; and a fixed magnet A contained in the electrostatic latent image carrier and The fixed magnet B is adjacent to the fixed magnet A on the downstream side in the moving direction of the electrostatic latent image holding member, has a polarity different from that of the fixed magnet A, and is included in the electrode roller and the fixed magnet A. Is a fixed magnet C having a different polarity, and is enclosed by the electrode roller, is adjacent to the fixed magnet C on the downstream side in the moving direction of the electrode roller when viewed from the fixed magnet C, and has the same polarity as the fixed magnet A. The magnetic flux generated by the fixed magnet A on the outer surface of the electrostatic latent image holding body is Φ _A, and the magnetic flux generated by the fixed magnet B on the outer surface of the electrostatic latent image holding body is Φ _B. Contraction characterized by the following: | Φ _A | − | Φ _B |> 0 The electrophotographic apparatus according to claim 5. 7. When the magnetic flux generated by the fixed magnet C on the outer surface of the electrode roller is Φ _C and the magnetic flux generated by the fixed magnet D on the outer surface of the electrode roller is Φ _D , | Φ _A | − | Φ _B |> | 7. The electrophotographic apparatus according to claim 6, wherein Φ _C | − | Φ _D |> 0 holds. 8. When the magnetic flux generated by the fixed magnet B on the outer surface of the electrostatic latent image carrier is Φ _B and the magnetic flux generated by the fixed magnet C on the outer surface of the electrode roller is Φ _C , | Φ _B The electrophotographic apparatus according to claim 6 or 7, wherein | ≤ | Φ _C | holds.