JP3555270B2 - Manufacturing method of magnet roll - Google Patents

Description

【００３０】
そして、図１に示すように、鉄などからなるシャフト８の周囲に複数個の磁極ピース６を貼り合わせてロール状磁石を得る。
【００３１】
電子写真現像装置で重要な感光体と着磁パターンの位置関係を確保するために、現像装置に組み込む時に基準面となるシャフト端部のＤカット部８ａと現像極磁極ピース端部を設計寸法角度に固定する図４に示す磁極ピース端部の突状部６ａと対応する穴部７ａと、シャフト基準となるＤカット部８ａに対応した他の穴部７ｂを有する位置決め治具７を用いて、ＳＵＭ材からなるシャフト８の周囲に複数個の磁極ピース６を貼り合わせてロール状磁石を得る。
【００３２】
図１は本発明に於ける一ピース成形装置の主要部を示す断面図であるが、断面が扇形で円弧中央部から他の三辺へ配向した磁極ピース６のキャビティ部一端にはノズル口に連なるスプール、ランナーが連結されているのは一般の射出成形金型と同等である。
【００３３】
成形に使用した複合樹脂マグネットは６ナイロンを母材樹脂とし、チタニウムカップリング処理されたバリウムフェライトを８７重量％含有した混合物を用いて成形した。
【００３４】
得られたロール状磁石の表面磁束密度をガウスメーターにより測定した。測定はマグネットロールとして使用される状態とするために、外径３０ｍｍのスリーブ内に組み込み、ガウスメーターのホール素子をそのスリーブ表面に接触させて行った。
【００３５】
このマグネットロールの主極長手方向の磁束密度特性を（表１）の実施例１〜３および比較例について図５に示す。
【００３６】
本発明によれば端部を凸形状とし小とする程比較例Ｄと比べてエッジ効果が解消されることが図５により明らかであるが、小にし過ぎるといわゆる肩ダレ状態になりマイナス効果となるため、製品要求特性から定められた磁極ピース設計寸法とのバランスで端部凸形状寸法を最適設計すれば良い。又、実際のマグネットロールの着磁特性はそれぞれの極間角度、磁力は不均一であり、開き角度θは異なり、端部を小とした程度が異なる磁極ブロックを組み合わせるという事が設計ポイントとなってくる。
【００３７】
【発明の効果】
以上のように本発明のマグネットロールの製造方法によれば、良質な画像特性を実現するために端部まで平坦で高磁力かつ複雑な着磁パターンを高精度に形成する磁気ブラシ現像用ロールを、生産性に優れ、安価に生産でき、電子写真現像装置などに最適な磁気ブラシ現像用ロールを得ることができ、その実用価値は大きい。
【図面の簡単な説明】
【図１】本発明のマグネットロールの一実施例である薄型の断面が扇形で円弧中央部から他の三辺へ配向した磁極ピースをシャフトに接着固定した磁石ロールの斜視図
【図２】同マグネットロールの製造に用いられる製造装置の断面図
【図３】同要部である薄型の断面が扇形で円弧中央部から他の三辺へ配向し端部が小なる形状とした磁極ピースの斜視図
【図４】同磁極ピースをシャフト基準面に接着固定する時の位置決め治具の一実施例の斜視図
【図５】同特性図
【図６】従来のマグネットロールの断面図
【図７】同径方向の断面図
【図８】同他の従来技術におけるマグネットロールの径方向の断面図
【図９】従来の磁石ロールの製造方法の説明図
【図１０】従来の磁石ロールの他の製造方法の説明図
【図１１】従来の磁石ロールの他の製造方法の説明図
【符号の説明】
１ 縦型射出成形機
２ コイル
３ 磁性材
４ 非磁性材
５ 金型
６ 磁極ピース
７ 位置決め治具
８ シャフト[0001]
[Industrial applications]
The present invention relates to a method for manufacturing a magnet roll used in an electrophotographic developing device such as a PPC copier, an LBP printer, and a facsimile.
[0002]
[Prior art]
In general, a magnet roll for magnetic brush development is mainly composed of a cylindrical non-magnetic sleeve and a roll-shaped magnet having a plurality of magnetic poles on its surface within the non-magnetic sleeve. A bearing for rotating at least one of the magnetic sleeve and the roll-shaped magnet, or a flange integrated with the bearing is fixed to both ends of the non-magnetic sleeve so as to hold the shaft portions at both ends of the roll-shaped magnet. I have.
[0003]
In the electrophotographic developing device, at least one of the non-magnetic sleeve and the roll-shaped magnet is rotated, and the developer made of magnetic powder on the non-magnetic sleeve is conveyed by suction, charged, and formed on the surface of the photoreceptor. A magnetic brush development method is used in which a latent image is transferred to a developed electrostatic latent image and visualized.
[0004]
FIG. 6 is a sectional view of a general magnet roll, in which the roll-shaped magnet 10 is relatively rotated in the non-magnetic sleeve 11, but bearings 12a, 12b and the bearings 12a are provided at both ends of the non-magnetic sleeve 11. , 12b and a flange 13a, 13b for preventing foreign matter from entering the non-magnetic sleeve 11 from both ends is formed. The roll-shaped magnet 10 and the non-magnetic sleeve 11 The flanges 13a and 13b are fixed to the non-magnetic sleeve 11 with an adhesive with a minimum distance 9 and a dimensional relationship that does not increase the rotational load.
[0005]
The shaft 8 for rotating or fixing the roll-shaped magnet 10 is drawn out of one of the flanges 13b, but the method in which the roll-shaped magnet 10 is fixed and the non-magnetic sleeve 11 is rotated is mainly used, In order to regulate the positional relationship between the pattern and the photoconductor, a reference surface 8a such as a D-cut is provided at an end of the shaft 8.
[0006]
Conventionally, the roll-shaped magnet 10 fixed to the outside of the shaft 8 is configured using a plurality of rod-shaped sintered ferrites 14 as shown in FIG. 7 or a cylindrical sintered ferrite 15 as shown in FIG. However, in recent years, it is configured using a composite resin magnet material using a thermoplastic resin such as nylon (6, 66, 11, 12), polypropylene, polyethylene, chlorinated polyethylene, or vinyl acetate as a binder. .
[0007]
Conventionally, composite resin magnet rolls are manufactured by a method of orienting an easy axis of magnetization of ferrite powder, which is a ferromagnetic powder, in a fixed direction by mechanical means, and a method of orienting by the action of a magnetic field.
[0008]
As shown in FIG. 9A, a method for orienting the easy axis of ferrite powder in a certain direction using mechanical means is to roll the composite resin magnet material 16 with a rolling roller 17 or the like as shown in FIG. A sheet-like magnet 19 in which the easy axis 18 is oriented in a direction perpendicular to the sheet surface is formed, and then the sheet-like magnet 19 is wound around the shaft 8 into a roll as shown in FIG. Magnetization is performed to form the roll-shaped magnet 10.
[0009]
As another method, as shown in FIGS. 10 (a) to 10 (c), in order to increase the orientation efficiency, a piece 20 formed by stacking several sheet-like magnets 19 and pressure-forming in a fan shape is shown in FIG. As shown in FIG. 10 (d), there is a device in which the outer periphery of the lamination is cut into a roll shape adjacent to the shaft 8 as a center and magnetized to form the roll magnet 10. The method of orienting by the action of a magnetic field is called magnetic field injection molding.At the time of injection molding, a strong magnetic field is applied to the composite resin magnet material in a plastic state in a mold, and the easy axis of ferrite powder is changed to the magnetic flux line. As shown in FIG. 11, a composite resin magnet material in a plastic state is provided with a coil 23a and a yoke 23b arranged around a cavity 22 in a mold 21 during injection molding as shown in FIG. Under the action of a magnetic field from the orienting magnet 23 made of, the axis of easy magnetization 18 of the ferrite powder is oriented in the direction of the magnetic flux lines.
[0010]
In each case, the end of the roll-shaped magnet has the same shape as the center, and is configured in a planar state.
[0011]
[Problems to be solved by the invention]
Among the above-described conventional composite resin magnet rolls, in the winding method shown in FIGS. 9A and 9B, the easy magnetization axis 18 of the ferrite powder is separated from the shaft 8 as shown in FIG. Since the magnetic flux lines are radially oriented and the magnetic flux lines do not concentrate on the magnetic poles on the circumference, a high magnetic force cannot be obtained. On the other hand, in the method shown in FIGS. 10A to 10D in which pressure is formed into a sector shape, a high magnetic force is obtained because the axis of easy magnetization of the ferrite powder is oriented in the direction of the magnetic flux line, and the angle of the sector and the dimension of the magnetic pole portion are obtained. By combining the position and the positional relationship, the magnetization characteristics of the specific magnetic pole can be independently designed to obtain a complicated magnetization pattern, but the process becomes complicated and productivity is poor.
[0012]
Also, in the magnetic field injection molding of FIG. 11, the same number of magnetic poles as the number of magnetic poles are arranged corresponding to the magnetic pole positions of the developing magnet roll to be obtained. Since the orientation is concentrated, the orientation is performed efficiently and the process is simpler, but the entire magnetization pattern is determined collectively in relation to the adjacent orientation magnet, and the magnetization characteristics of the specific magnetic pole are individually determined. It cannot be designed and a complicated magnetization pattern cannot be obtained. Furthermore, a sufficient orientation magnetic field cannot be contributed to the center of the roll, and there is a limit in increasing the magnetic force.
[0013]
Generally, an electrophotographic developing device using a dry developer is a device in which a developing material acts on image information such as a latent image formed by charging and exposing a photoreceptor to a latent image by using a developing material with an electrostatic attraction effect to visualize the image. A roll-shaped magnet with a high magnetic force for the purpose of stirring and charging the suction agent to carry it by suction is received by a flange via a bearing, and is incorporated in a non-magnetic sleeve.
[0014]
Then, the roll-shaped magnet is fixed, the flange is driven to rotate the non-magnetic sleeve, and the developer is transferred along the magnetic field distribution on the surface of the non-magnetic sleeve.
[0015]
For this reason, the function of each magnetic pole of the developing magnet roll composed of a plurality of poles is determined in accordance with the configuration of the developing unit and the relationship with the photoreceptor, and an optimal magnetic force 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, a plurality of configured magnetic poles can be individually designed, and a complicated magnetization pattern can be realized in an easy process. Required.
[0016]
In particular, the developing pole facing the photoreceptor is also called the main pole, and migrates differently before and after the developer contacts the photoreceptor, contacts the photoreceptor slowly when developing, and after developing away from the photoreceptor Is required to move quickly, and for that purpose, it is important to have a magnetization pattern with an asymmetric magnetic flux density distribution before and after a magnetic pole peak serving as a contact point. Further, a strong magnetic flux density (magnetic force) is required for the purpose of reliably transporting the developer and realizing high-definition image quality, and it is important to assemble the positional relationship between the photoconductor and the magnetization pattern with high precision.
[0017]
In addition, in order to obtain uniform image quality over the entire surface, uniformity of magnetic force in the longitudinal direction is also important. Particularly in the case of a conventional product having a uniform overall shape, the edge of the developing material rises due to the edge effect, and the image contamination is prevented. Members are needed.
[0018]
An object of the present invention is to solve a contradictory problem that cannot be solved by the conventional technology as described above, and to provide a magnet roll for magnetic brush development that forms a flat, high magnetic force and a complicated magnetized pattern with high accuracy to the end. The manufacturing method is provided at low cost.
[0019]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention is to heat and melt a mixture mainly composed of a ferromagnetic powder material and a polymer compound material, and then use a magnetic field for orientation to form a fan-shaped cross-sectional shape and form another three-dimensional shape from the arc side. A magnetic pole piece formed by molding ferromagnetic powder on the side while orienting the magnetic pole piece so that both ends in the longitudinal direction have a protruding portion is formed, and then a plurality of these are combined and attached to a shaft .
[0020]
[Action]
According to the above configuration, it is possible to easily produce a developing magnet roll having a high magnetic force and excellent coaxial characteristics.
[0021]
【Example】
First, the outline of the magnet roll of the present invention will be described.
[0022]
The key point of the present invention is that a magnetic pole piece having a sector shape in which the orientation magnetic force can be utilized to the utmost in advance and oriented from the arc side to the other three sides is formed into a shape having a small width at both ends in the longitudinal direction. Then, these are combined with a plurality of shafts and bonded.
[0023]
In particular, by regulating the angle relationship between the narrow portion and the shaft reference portion by using a jig and bonding, the optimum positional relationship between the photoconductor and the magnet roll magnetized pattern can be easily obtained.
[0024]
The developing magnet roll produced in this way has uniform and optimal characteristics up to the end for each individual magnetic pole, and is capable of reproducing a good electrophotographic developed image. In other words, it is important that the number of magnetic pole pieces to be bonded, the fan opening angle of the magnetic pole pieces, and the position and width of the arc-side alignment pole are designed to be optimal according to the required magnet roll magnetization pattern.
[0025]
A mixture mainly composed of a ferromagnetic powder material and a polymer compound material used for molding is made of a rare earth magnetic powder, a barium ferrite, a strontium based on a thermoplastic resin such as polyamide, polypropylene, or polyethylene. Hard ferrite powder such as ferrite is subjected to a surface treatment with a coupling agent such as titanium or silane, and kneaded at a content of 80 to 95% by weight.
[0026]
Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. An embodiment of an apparatus for magnetic field injection molding of a piece of the present invention, which has a thin sector shape and has ferromagnetic powder oriented on the other three sides from the arc side, will be described with reference to FIG.
[0027]
That is, as shown in FIG. 2, a fan-shaped concave portion 3a is provided in a central portion provided in a coil 2 of a composite resin magnet material pellet made of a rare earth magnetic powder or a ferrite powder and a polymer material, as shown in FIG. The magnetic material 3 which forms a magnetic path from the center of the arc to the other three sides by the lower magnetic material 3b and the T-shaped upper magnetic material 3c, and the part excluding the upper part on both sides of the fan and the center of the arc surface. Injection molding is performed in a mold 5 which is formed of the surrounding non-magnetic material 4 and is processed so that both ends in the longitudinal direction are convex. The magnetic field generated by energizing the coil 2 orients the axis of easy magnetization of the rare-earth magnetic powder or ferrite particles in the direction of the line of magnetic force, so that the cross section shown in FIG. A magnetic pole piece 6 having a protruding portion 6a that is oriented and has a small width at both ends in the longitudinal direction is formed.
[0028]
The upper arc radius r1, the lower arc radius r2, the opening angle θ, and the orientation magnetic field formed from the center of the arc to the other three sides by the T-shaped upper magnetic material 3c correspond to the product specifications. The shape and dimensions are determined in an optimum state corresponding to these dimensions. Table 1 shows the dimensions of the developing pole pieces in the examples and comparative examples.
[0029]
[Table 1]

[0030]
Then, as shown in FIG. 1, a plurality of magnetic pole pieces 6 are bonded around a shaft 8 made of iron or the like to obtain a roll-shaped magnet.
[0031]
To ensure the important positional relationship between the photoreceptor and the magnetized pattern in the electrophotographic developing device, the D-cut portion 8a at the end of the shaft and the end of the developing magnetic pole piece, which serve as a reference surface when assembling into the developing device, are designed at a dimensional angle. Using a positioning jig 7 having a hole 7a corresponding to the protrusion 6a at the end of the magnetic pole piece shown in FIG. 4 and another hole 7b corresponding to the D cut 8a serving as a shaft reference, as shown in FIG. A plurality of magnetic pole pieces 6 are bonded around a shaft 8 made of a SUM material to obtain a roll-shaped magnet.
[0032]
FIG. 1 is a cross-sectional view showing a main part of a one-piece molding apparatus according to the present invention. The cross-section of the pole piece 6 is sector-shaped and oriented from the center of the arc to the other three sides. The connection of the continuous spool and runner is equivalent to that of a general injection mold.
[0033]
The composite resin magnet used in the molding was molded using a mixture containing 6% nylon as a base resin and containing 87% by weight of barium ferrite subjected to titanium coupling treatment.
[0034]
The surface magnetic flux density of the obtained roll-shaped magnet was measured with a Gauss meter. The measurement was carried out by assembling it in a sleeve having an outer diameter of 30 mm and bringing a Hall element of a Gauss meter into contact with the surface of the sleeve in order to be used as a magnet roll.
[0035]
FIG. 5 shows the magnetic flux density characteristics of the magnet roll in the main pole longitudinal direction with respect to Examples 1 to 3 in Table 1 and Comparative Example.
[0036]
According to the present invention, it is clear from FIG. 5 that the edge effect is eliminated as compared with Comparative Example D as the end portion is made convex and smaller, but if it is too small, a so-called shoulder sagging state occurs and a negative effect is obtained. Therefore, it is only necessary to optimally design the convex shape at the end portion in balance with the design dimension of the magnetic pole piece determined from the required characteristics of the product. In addition, the design points are that the magnetizing characteristics of the actual magnet roll are such that the pole angle and the magnetic force are non-uniform, the opening angle θ is different, and the magnetic pole blocks differ in the degree to which the ends are small. Come.
[0037]
【The invention's effect】
As described above, according to the method of manufacturing a magnet roll of the present invention, a magnetic brush developing roll that forms a high-magnetism and complex magnetized pattern with high accuracy and flatness to the end to achieve good image characteristics is provided. It is excellent in productivity, can be produced at low cost, and can obtain a magnetic brush developing roll most suitable for an electrophotographic developing device and the like, and its practical value is great.
[Brief description of the drawings]
FIG. 1 is a perspective view of a magnet roll according to one embodiment of the present invention, in which a magnetic pole piece having a fan-shaped cross section having a fan-shaped cross section and oriented from the center of a circular arc to other three sides is bonded and fixed to a shaft. FIG. 3 is a cross-sectional view of a manufacturing apparatus used for manufacturing a magnet roll. FIG. 3 is a perspective view of a magnetic pole piece in which a thin section, which is an essential part, has a sector shape and is oriented from the center of the arc to the other three sides and the ends are small. FIG. 4 is a perspective view of an embodiment of a positioning jig when the magnetic pole piece is bonded and fixed to a shaft reference surface. FIG. 5 is a characteristic diagram. FIG. 6 is a cross-sectional view of a conventional magnet roll. FIG. 8 is a sectional view in the radial direction of the magnet roll according to another related art. FIG. 9 is an explanatory view of a method of manufacturing a conventional magnet roll. FIG. 10 is another manufacturing method of a conventional magnet roll. FIG. 11 is an illustration of a method. Explanatory diagram of a method [DESCRIPTION OF SYMBOLS]
Reference Signs List 1 vertical injection molding machine 2 coil 3 magnetic material 4 non-magnetic material 5 mold 6 magnetic pole piece 7 positioning jig 8 shaft

Claims (1)

After heating and melting a mixture mainly composed of a ferromagnetic powder material and a polymer compound material, the magnetic field for orientation is used to shape the ferromagnetic powder while orienting the ferromagnetic powder from the arc side to the other three sides from the arc side. A method for manufacturing a magnet roll , comprising: forming a magnetic pole piece so that both ends in the longitudinal direction have a protruding projection, and combining and bonding a plurality of them to a shaft.

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