JP3399625B2 - Method of manufacturing roll-shaped magnet for development - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for a magnet roll used in an electrophotographic developing device such as a PPC copying machine, a laser beam printer (hereinafter referred to as LBP), a facsimile, and the like. The present invention relates to a method for producing a developing roll-shaped magnet. 2. Description of the Related Art Generally, a magnet roll for magnetic brush development mainly comprises a cylindrical non-magnetic sleeve and a roll-shaped magnet having a plurality of magnetic poles on its surface within the sleeve. A bearing for rotating at least one of the nonmagnetic sleeve and the roll-shaped magnet,
Alternatively, flanges with integrated bearings are fixed to both ends of the sleeve so as to hold the shaft portions at both ends of the roll-shaped magnet. In a developing device such as an electrophotographic apparatus or a facsimile receiver, at least one of the non-magnetic sleeve and the roll-shaped magnet is rotated to adsorb a developer made of magnetic powder on the non-magnetic sleeve. The above-described magnetic brush developing method in which the toner is conveyed, charged, and transferred to an electrostatic latent image formed on the surface of the photoreceptor to visualize the image is employed. [0005] The conventional magnet roll will be described with reference to FIG. 5. At both ends, bearings 7 a are provided at both ends of the non-magnetic sleeve 5 in order to relatively rotate the roll-shaped magnet 6 within the non-magnetic sleeve 5. , 7b and this bearing 7
A bearing portion is formed by flanges 8a and 8b for holding a and 7b and preventing foreign matter from entering the non-magnetic sleeve 5 from both ends. Reference numeral 6a denotes a shaft for rotating or fixing the roll-shaped magnet 6, which is drawn out of one flange 8b. The non-magnetic sleeve 5 and the flange 8b are connected to the outer peripheral surface of the shaft 6a and the flange 8b.
b, a minimum gap 9 is provided so that the rotational load does not become large, and is usually fixed with an adhesive. The roll-shaped magnet material 6b fixed to the outside of the shaft 6a has conventionally been formed using a rod-shaped or cylindrical sintered ferrite.
6, 11, 12), a composite resin magnet material using a thermoplastic resin such as polypropylene, polyethylene, chlorinated polyethylene, or vinyl acetate as a binder. Conventionally, the roll-shaped magnet 6 is manufactured by a method of orienting the easy axis of ferrite, which is a ferromagnetic powder, in a fixed direction by mechanical means, and a method of orienting by a magnetic field. As shown in FIG. 6A, a method of orienting the easy axis of ferrite in a certain direction by using mechanical means is to roll the resin magnet material 10 with a rolling roller 11 or the like as shown in FIG. A sheet-like magnet 13 in which the easy axis 12 is oriented in a direction perpendicular to the sheet surface is formed, and the sheet-like magnet 13 is wound around a shaft 6a to form a roll as shown in FIG. The magnet is formed into a roll magnet 6. As another method, as shown in FIG. 6C, in order to increase the orientation efficiency, a sheet-like magnet 13 is used.
FIG. 6 shows a piece 6e formed by stacking several pieces and pressing them into a fan shape.
As shown in (d), a method of forming a bonded roll adjacent to the center of the shaft 6a and forming the roll-shaped magnet 6 by attaching is also devised. [0009] The method of orienting by the action of a magnetic field is called magnetic field injection molding. During injection molding, a strong magnetic field is applied to the plastic composite magnet material in the mold, and the axis of easy magnetization of the ferrite becomes magnetic flux. As shown in FIG. 7, a plastic resin composite magnet material in a plastic state is disposed around a cavity 15 in a mold 14 during injection molding as shown in FIG. 7.
Under the action of a magnetic field from the orienting magnet 16 comprising the yoke 16a and the yoke 16b, the axis of easy magnetization 12 of the ferrite is oriented in the direction of the magnetic flux lines. In general, an electrophotographic developing apparatus using a dry developer causes an electrostatic attraction effect on image information such as a latent image formed by charging and exposing a photoreceptor to a latent image. A roll-shaped magnet 6 which has a high magnetic force in order to stir and charge and attract and transport the developer,
Received by flanges 8a, 8b via bearings 7a, 7b,
It is configured to be incorporated in the non-magnetic sleeve 5.
Then, the magnet portion is fixed, the flange is driven to rotate the non-magnetic sleeve, and the developer is transferred along the magnetic field distribution on the sleeve surface. For this reason, the function of each magnetic pole of the developing magnet roll composed of a plurality of poles is determined according to the configuration of the developing unit and the relationship with the photoreceptor, and an optimal magnetic field line distribution is required for the function. Is done. In other words, the magnetic field line distribution generated from the roll-shaped magnet has an important role in determining the image characteristics, and it is necessary to design a plurality of configured magnetic poles individually to realize a complicated magnetization pattern in an easy process. Is required. In particular, the developing pole facing the photoreceptor is also called a main pole, and migrates differently before and after the developer comes into contact with the photoreceptor. It is required to move quickly after development, and for that purpose, it is important to have a magnetized pattern with an asymmetric magnetic flux density distribution before and after the magnetic pole peak serving as a contact point. As described above, in the winding method shown in FIGS. 6A and 6B, the easy magnetization axis 12 of the ferrite is radially oriented from the shaft 6a as shown in FIG. Does not concentrate on the magnetic poles on the circumference, so that a high magnetic force cannot be obtained. On the other hand, FIG.
In the methods (c) and (d), a high magnetic force is obtained because the easy magnetization axis 12 of the ferrite is oriented in the direction of the magnetic flux lines. Although the characteristics can be independently designed and a complicated magnetized pattern can be obtained, the process is complicated and the productivity is inferior. In the magnetic field injection molding shown in FIG.
Are arranged in the same number as the number of magnetic poles corresponding to the magnetic pole positions of the developing magnet roll to be obtained.
Since the magnetic flux lines from 6 are concentrated in the direction of the magnetic poles, the orientation is efficiently performed and a magnet with a high magnetic force can be obtained, and the process is simpler. The magnetizing characteristics are determined collectively, and the magnetizing characteristics of the specific magnetic pole cannot be individually designed, so that there is a problem that a complicated magnetizing pattern cannot be obtained. SUMMARY OF THE INVENTION An object of the present invention is to solve the above contradictory problems and to easily change the magnetization pattern of a developing roll-shaped magnet used for a magnetic brush magnet roll having a complicated magnetization pattern. It is. [0016] In order to solve the above-mentioned problems, the present invention is to generate a magnetic field for alignment after heating and melting a mixture mainly composed of a ferromagnetic powder material and a polymer compound material. a plurality of injection molded into the main mold and the alignment magnet disposed of, the production method of the developing low <br/> Le shaped magnets forming a plurality of magnetic poles on the outer peripheral surface of the molded body, asymmetric magnetic flux density distribution of
The same orientation magnetic field as that of one main orientation magnet is provided between adjacent main orientation magnets that generate different orientation magnetic fields among the plurality of main orientation magnets to form a magnetization pattern. This is provided with a permanent magnet made of permanent magnet which generates the following. According to the above, the characteristics of the specific magnetic pole can be individually controlled, and a roll-shaped magnet having a complicated magnetization pattern can be manufactured with good productivity and at low cost. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a magnet roll and a manufacturing method according to the present invention will be described below with reference to FIGS. First, an embodiment of an alignment mold used in the present invention will be described with reference to FIG. That is, main orientation magnets 3 are arranged around the cavity 2 in the nonmagnetic base 1 made of stainless steel in accordance with the number and positions of the magnetic rolls to be obtained. The main oriented magnet 3 is a permanent magnet 3a.
Are integrated by a front yoke 3b and a base yoke 3c made of a soft magnetic material. The intervals between the adjacent main oriented magnets 3, that is, the so-called pole angles θ1, θ2, θ3, and θ4 are determined according to the product specifications, and the magnetic strength and size of the permanent magnet 3a and the tip size of the front yoke 3b. Is designed according to the product specifications, in particular, the magnetic force and the half-value width.
Rare earth cobalt magnets with 700G and 1700 Oe in 700G and 1HC are used, and are magnetized in the diameter direction. An auxiliary orientation magnet 4 having the same configuration as the main orientation magnet 3 is disposed between the S1 pole serving as a development pole and the N2 pole serving as a recovery pole, and has the same polarity as the N2 pole. Has become. The auxiliary orientation magnet 4 is installed in the non-magnetic base 1 in a state where the non-magnetic spacers 4d and 4e can be rearranged at the front ends of the front yoke 4b and the base yoke 4c integrated at both ends of the permanent magnet 4a. The distance between the auxiliary orientation magnet 4 and the cavity 2 can be adjusted. FIG. 1 is a sectional view showing a main part of a mold of the present invention. A shaft part is formed at both ends of a cavity part having an inner diameter of 17.4 mm, and a spool connected to a nozzle port at one end.
The connection of the runner is equivalent to a general injection mold. First, without using the nonmagnetic spacer 4d,
The molding was performed in a state where the auxiliary orientation magnet 4 was close to the cavity 2. In the injection molding, a shaft portion was integrally molded using a mixture containing 87% by weight of barium ferrite subjected to titanium coupling treatment using nylon 6 as a base material resin. The surface magnetic flux density of the obtained magnet roll was measured with a Gauss meter. The measurement was carried out by assembling it in a sleeve having an outer diameter of 20 mm and bringing a Hall element of a Gauss meter into contact with the surface of the sleeve in order to use it as a magnet roll. The magnetic flux density waveform of this magnet roll is shown by a solid line in FIG. As a comparative example, a magnet roll was prepared in the same manner as in the example except that the entire auxiliary orientation magnet 4 was removed, and the characteristics were measured. Figure 2 shows the resulting magnetic properties.
Only the differences from the embodiment are shown by dotted lines. As apparent from FIG. 2, the developing pole S1 has a magnetic flux density distribution in which the N1 pole side, which is a blade pole, swells and the N2 pole side, which is a recovery pole, abruptly attenuates.
Further, it was confirmed that the S1 pole side, which is the development pole of the N2 pole serving as the recovery pole, swelled to obtain a desirable magnetization pattern. Next, a front yoke 4b and a base yoke 4 integrated with both ends of the auxiliary orientation magnet 4 at both ends of the permanent magnet 4a.
Non-magnetic spacers 4d, 4e
FIG. 3 shows the results when the distances between the auxiliary orientation magnet 4 and the cavity 2 were adjusted by changing the positions of the magnets. Here, α1-α2 is a numerical value shown in FIG. 4 and is different at the developing pole facing the photoconductor before and after the developer comes into contact with the photoconductor. This value represents the magnetization pattern of asymmetric magnetic flux density distribution before and after the magnetic pole peak, which is the point of contact, because it moves slowly after development and away from the photoreceptor because it moves quickly after development. However, it is important that the angle is 6 degrees or more. This value can be further increased by adding an auxiliary orientation magnet having the same polarity as the S1 pole between the S1 pole and the N1 pole, but its use is appropriately determined in consideration of the influence on the N1 pole. Is done. The magnet roll formed as described above has optimum characteristics for each individual magnetic pole, and can reproduce a good electrophotographic developed image. The magnetic strength of the auxiliary orientation magnet 4 and the positional relationship with the orientation magnet are appropriately designed according to the magnetization pattern required for each product. Each of the main oriented magnet 3 and the auxiliary oriented magnet 4 is an electromagnet in which a coil made of a copper wire is arranged around a soft magnetic yoke, or a soft magnetic yoke is integrated at the tip of the molding space. Although it is possible to use a rare earth permanent magnet described above, it is effective to use a rare earth permanent magnet in which a soft magnetic yoke is integrated at the tip of at least the auxiliary orientation magnet 3 due to the space in the mold. It is. The mixture mainly composed of a ferromagnetic powder material and a high-molecular compound material used for molding uses a thermoplastic resin such as polyamide, polypropylene, polyethylene, ethylene-ethyl-acrylate copolymer as a base material. Hard ferrite powders such as barium ferrite and strontium ferrite or rare earth magnetic powders are surface-treated with a coupling agent such as titanium or silane and kneaded at a content of 80 to 95% by weight. Used. The roll magnet 6 may be formed by insert molding the shaft 6a as a metal material made of iron or stainless steel, even if the shaft 6a and the roll magnet material 6b are integrally formed of the same resin magnet material. It is a good thing. As described above, according to the present invention, a plurality of main oriented magnets which generate a magnetic field for orientation after heating and melting a mixture mainly composed of a ferromagnetic powder material and a polymer compound material Injection molding in a mold in which is disposed, in a method of manufacturing a developing roll-shaped magnet for forming a plurality of magnetic poles on the outer peripheral surface of the molded body,
In order to form a magnetized pattern having an asymmetrical magnetic flux density distribution, one of the plurality of main orientation magnets, in which main orientation magnets that generate different orientation magnetic fields are provided adjacent to each other, Since the auxiliary orientation magnet that generates the same orientation magnetic field as the main orientation magnet is provided, it is possible to provide a developing roll-shaped magnet that can obtain good image characteristics. Since the auxiliary orientation magnet is made of a permanent magnet, the space in the mold can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a mold for manufacturing a magnet roll according to one embodiment of the present invention. FIG. 2 is a pattern diagram of the same magnetic characteristics. FIG. FIG. 4 is a magnetic flux density distribution diagram showing the degree of asymmetry when the distance to the distance is adjusted. FIG. 4 is an explanatory diagram of α1-α2, which is a value representing a magnetization pattern of an asymmetric magnetic flux density distribution. FIG. 6 (a) is a perspective view for explaining a manufacturing state of a sheet-shaped magnet which is one of the manufacturing steps of a conventional magnet roll, and FIG. 6 (b) is a perspective view for explaining a manufacturing state of the roll-shaped magnet. c) A perspective view for explaining a state in which a sheet-shaped magnet is one of the manufacturing processes of the other prior art, which is pressure-formed into a fan shape. (d) A perspective view for explaining a manufacturing state of the other rolled magnet. FIG. 7 illustrates another related art. Conceptual view of the mold of the order EXPLANATION OF REFERENCE NUMERALS 3 main orientation magnet 4 auxiliary oriented magnets

Continuation of front page    (72) Inventor Katsunori Minaga               1006 Kadoma Kadoma, Kadoma City, Osaka Matsushita Electric               Kiki Sangyo Co., Ltd. (72) Inventor Takayuki Miyoshi               1006 Kadoma Kadoma, Kadoma City, Osaka Matsushita Electric               Kiki Sangyo Co., Ltd.                (56) References JP-A-63-5371 (JP, A)                 JP-A-64-66683 (JP, A)

Claims (1)

(57) [Claims 1] A plurality of main orientation magnets for generating a magnetic field for orientation after heating and melting a mixture mainly composed of a ferromagnetic powder material and a polymer compound material. In a method of manufacturing a developing roll-shaped magnet in which a plurality of magnetic poles are formed on an outer peripheral surface of a molded body, an asymmetric magnetic flux density distribution is formed.
The same orientation magnetic field as that of one main orientation magnet is provided between adjacent main orientation magnets that generate different orientation magnetic fields among the plurality of main orientation magnets to form a magnetization pattern. A method for producing a developing roll-shaped magnet provided with a permanent magnet-made auxiliary orientation magnet which generates a magnetic field.