JPH10308308A - Magnet roller and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnet roller in which the height and position of the peak of the magnetic force can be adjusted after forming a roller and which can cope easily with the demand for complicated magnetic patterns without incurring higher cost. SOLUTION: At least two kinds of a first magnet piece 6 in which an anisotropic magnetic powder is oriented to be focused from both sides and rear side to the specified position on a front side, and a second magnetic piece 7 which is made of anisotropic magnetic powder having no orientation property, are used in combination, and the first and the second magnet pieces 6 and 7 are arranged and fixed on to the outer circumference of a shaft 8, so as to form a magnet roller provided with a magnet layer 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001]

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic process for a copying machine, a facsimile, a printer, or the like, in which a developer is supplied to a latent image holding member such as a photosensitive drum, and an electrostatic latent image on the latent image holding member is supplied. The present invention relates to a magnet roller suitably used in a developing mechanism for developing a toner image, and a method of manufacturing the same.

[0003]

[0002]

[0004]

2. Description of the Related Art Conventionally, an electrostatic latent image on a latent image holding member such as a photosensitive drum has been visualized in an electronic pager such as a copying machine or a printer or an electrostatic recording device. As a developing roller, a magnet roller formed of a resin magnet or a rubber magnet is provided in a rotating sleeve, and a magnetic developer (toner) carried on the surface of the sleeve is applied to the latent image holding member by the magnetic force characteristics of the magnet roller. A developing method is known in which a toner is supplied to the surface of a latent image holding member by a so-called jumping phenomenon that causes the electrostatic latent image to be visualized.

[0005]

Conventionally, the above-mentioned magnet roller has a pellet-shaped resin magnet composition or rubber magnet composition in which a magnetic powder such as ferrite is mixed with a thermoplastic resin such as nylon or polypropylene or a rubber binder, and a magnetic field is applied to the surroundings. It is manufactured by injection molding or extrusion molding using a formed mold, forming into a roller shape, and magnetizing to a desired magnetic force characteristic.

[0006]

However, with the recent development of electrophotographic apparatuses and the like, there is a tendency that a more complicated magnetic force pattern is required for a magnet roller, but there is a limit to a magnetic force pattern that can be designed with a conventional magnet roller. , Can not fully meet this demand.

[0007]

Therefore, conventionally, in order to increase the degree of freedom of the magnetic force pattern of the magnet roller, a plurality of magnet pieces magnetized with magnetic poles corresponding to the target magnetic force pattern are formed by the above resin magnet or rubber magnet, and these are formed. 2. Description of the Related Art A desired magnetic force pattern is formed by laminating around a shaft.

[0008]

In this case, it has been proposed to form each magnet piece by using the mold shown in FIG. 1 in order to obtain the above-mentioned magnet piece having a high magnetic force peak (Japanese Patent Laid-Open Publication No. H10-209,837).
No. 512025). That is, as shown in FIG. 1, the magnet pieces are provided with magnetic metal materials 3a and 3b such as iron, respectively, disposed above and below the non-magnetic metal material 2, and a cabinet is provided between the magnetic metal materials 3a and 3b. It is formed by injection molding or extrusion molding of the resin magnet or rubber magnet in a state where a coil 4 is energized and a magnetic field is formed around the cavity 1 using a mold having the tee 1 formed therein. The two side surfaces and the back surface (the surface opposite to the front surface side) of the cavity 1 are formed of the magnetic metal material 3b, and the protrusions 5 are provided on the upper magnetic metal material 3a by projecting. It has been proposed to mold the magnet piece by using a mold in which a magnet is disposed near a desired position on the surface side of the cavity 1. The magnet piece molded using this mold is oriented so that the magnetic powder converges from both sides and the back side to a predetermined position on the front side, as indicated by arrows in FIG. , A high magnetic force peak can be obtained.

[0009]

However, in a magnet roller in which a plurality of magnet pieces are formed using the mold shown in FIG. 1 and fixed on the outer periphery of the shaft, the magnetic force peak of each magnetic pole increases due to the orientation described above. On the other hand, when a low magnetic force is required, it is necessary to reduce the outer diameter of the magnet piece or to move the magnetic force peak to a position shifted from the center of the magnet piece, as shown in FIG. As described above, various types of molds are required in accordance with the magnetic force pattern, such as forming the convex portion 5 provided on the upper magnetic metal material 3a at a position shifted from the center of the cavity 1 and performing molding. This causes an increase in the manufacturing cost of the magnet roller.

[0010]

In this case, a conventional method of manufacturing a magnet roller has been to demagnetize a magnet roller formed by a mold in which a magnetic field is formed around a cavity and then magnetize the magnet roller again to a desired magnetic force pattern. Has been
In the magnet roller formed by the magnet pieces formed using the molds shown in FIGS. 1 and 2 described above, the position of the magnetic force peak is extremely limited due to the orientation described above,
Attempting to move the position of the magnetic force peak after forming the roller by arranging and fixing each magnet piece around the shaft causes a problem such as a significant decrease in the magnetic force, and actually moves the magnetic force peak after molding. It is impossible.

[0011]

The present invention has been made in view of the above circumstances, and can cope with a case where a partially low magnetic peak is required without changing the dimensions of the magnet piece. The peak position can be easily moved without the need for various types of molds even if you want to move the position, and even for complicated magnetic force patterns, it is easy without significant cost increase. It is an object of the present invention to provide a magnet roller capable of coping with the above, and a method of manufacturing the same.

[0012]

[0010]

[0013]

Means for Solving the Problems and Embodiments of the Invention As a result of diligent studies to achieve the above object, the present inventor has found that a plurality of magnet pieces obtained by dispersing magnetic powder in a resin or rubber binder. Is fixed on the outer circumference of the shaft,
In a magnet roller having a magnet layer formed on the outer periphery of a shaft, a first magnet as the plurality of magnet pieces, wherein the anisotropic magnetic powder is oriented such that the anisotropic magnetic powder converges from a side surface and a back surface to a predetermined position on the front surface. The first magnet piece is used in a portion where a high magnetic force peak is required by using a combination of at least two types of magnet pieces of a piece and a second magnet piece having no orientation characteristics using isotropic magnetic powder. By using the second magnet piece in a portion where a relatively low magnetic force peak is required or where the peak position needs to be moved and fine adjustment is required, a sufficient magnetic force peak can be obtained and a low magnetic force peak can be obtained. For the parts that need to be adjusted for peaks and delicate peak positions, they can be easily adjusted by the magnetizing operation after roller formation. The demand for such magnetic patterns, found that it is possible to inexpensively corresponding without requiring many types of molds.

[0014]

That is, the first magnet piece formed by using the mold shown in FIG. 1 and oriented such that the anisotropic magnetic powder is converged from the both side surfaces and the back side to a predetermined position on the front side. Is used for a portion where a relatively high magnetic force peak is required, and a second magnet piece having no orientation characteristics and formed by using a normal mold using isotropic magnetic powder is required to have a relatively low magnetic force peak. Before and after fixing the first magnet piece and the second magnet piece around the shaft or after forming and fixing the roller, it is necessary to use the first magnet piece and the second magnet piece around the shaft. The height of the magnetic force peak of the second magnet piece portion can be adjusted and the position of the peak can be relatively freely moved by demagnetizing the formed roller and magnetizing the formed roller to a desired magnetic force pattern according to Let Bets can be, it found that may correspond to the requirements of complex magnetic patterns without the need for many types of molds, and completed the present invention.

[0015]

Accordingly, the present invention relates to a magnet roller having a plurality of magnet pieces formed by dispersing magnetic powder in a resin or rubber binder, arranged and fixed on the outer periphery of the shaft, and forming a magnet layer on the outer periphery of the shaft. A first magnet piece in which anisotropic magnetic powder is oriented so as to converge at a predetermined position on the front side from both side surfaces and a back surface, and orientation characteristics using isotropic magnetic powder as the plurality of magnet pieces; Roller, characterized by using at least two types of magnet pieces in combination with a second magnet piece having no magnet, and a resin magnet composition or rubber magnet composition in which magnetic powder is dispersed in a resin or rubber binder Are molded in a mold to form a plurality of magnet pieces. In the method for manufacturing a magnet roller for magnetizing a desired magnetic force pattern after obtaining a roller having a magnetic layer formed thereon, anisotropic magnetic powder is used as the plurality of magnet pieces as described above on both sides and a back side to a predetermined surface side. At least two types of magnet pieces are formed: a first magnet piece oriented so as to converge to a position, and a second magnet piece having no orientation characteristics using isotropic magnetic powder, and these are combined to form the magnet layer. And a method for manufacturing a magnet roller characterized by forming

[0016]

Hereinafter, the present invention will be described in more detail.

As described above, the magnet roller of the present invention comprises: a first magnet piece oriented so that the anisotropic magnetic powder converges from both sides and the back side to a predetermined position on the front side;
At least two types of magnet pieces are used in combination with a second magnet piece having no orientation characteristics using isotropic magnetic powder, and these first and second magnet pieces are arranged and fixed on the outer periphery of the shaft. It is formed in a roller shape.

[0018]

Each of the first magnet piece and the second magnet piece is a molded product obtained by dispersing magnetic powder in a resin or rubber binder.

[0019]

Examples of the binder include polyamide resins such as nylon 6 and nylon 12, polystyrene resins, polyethylene terephthalate resin (PET), polybutylene terephthalate resin (PBT), polyphenylene sulfide resin (PPS), and ethylene-vinyl acetate copolymer. Polyolefins such as resin (EVA), ethylene-ethyl acrylate resin (EEA), epoxy resin, ethylene-vinyl alcohol copolymer resin (EVOH), polypropylene resin, polyethylene, polyethylene copolymer, and the like. Thermoplastic resins such as modified polyolefins into which reactive functional groups such as maleic acid groups, carboxyl groups, hydroxyl groups, and glycidyl groups have been introduced, may be used alone or in combination of two or more. Can. It should be noted that, although not particularly limited, polyamide resin, EV
A and EEA are preferably used. Rubber can also be used as the binder, for example, nitrile rubber (NBR), chloroprene rubber (CR), chlorosulfonated polyethylene (CSM), silicone rubber, and the like can be used.

[0020]

The magnetic powder may be ordinary magnetic powder conventionally used for magnet rollers. In the present invention, anisotropic magnetic powder is used for the first magnet piece. The second magnet piece uses isotropic magnetic powder. The anisotropic magnetic powder used for the first magnet piece is not particularly limited, but ferrite powders such as anisotropic Sr ferrite and anisotropic Ba ferrite, and anisotropic Nd-F-B Rare earth alloy powders such as alloys are exemplified. On the other hand, the isotropic magnetic powder used for the second magnet piece is not particularly limited, but isotropic Sr ferrite and isotropic Ba.
Examples thereof include ferrite powder such as ferrite and rare earth alloy powder such as isotropic Nd-FB alloy, Sm-Co alloy, and Ce-Co alloy.

[0021]

The mixing ratio of the magnetic powder is appropriately selected according to the required strength of the magnetic force, and is not particularly limited. % By weight (density is 2.5 to 4.5 g / cm
^{About 2} ).

[0022]

[0018] In addition to the binder component and the magnetic powder, a filler having a large reinforcing effect such as mica, whisker or talc, carbon fiber or glass fiber may be added to the first and second magnet pieces as required. Can be. That is,
When the magnetic force required for the molded product is relatively low and the filling amount of the magnetic powder is small, the rigidity of the molded product tends to be low. In such a case, filling of mica, whisker, etc. A molded article can be reinforced by adding a material. In this case, the filler preferably used in the present invention is preferably mica or whisker. Examples of the whisker include non-oxide whiskers made of silicon carbide, silicon nitride, etc., ZnO, MgO, TiO ₂ , SnO ₂ , and Al _2. Examples thereof include metal oxide whiskers made of O _{3 and the} like, and double oxide whiskers made of potassium titanate, aluminum borate, basic magnesium sulfate, and the like. In particular, when a thermoplastic resin is used as a binder, a double oxide whisker is particularly preferably used because it can be easily compounded with a plastic.

[0023]

The mixing ratio when using these fillers is not particularly limited, but is usually about 2 to 32% by weight, especially about 5 to 20% by weight of the whole resin magnet. In addition, additives other than the filler may be added to the resin magnet or the rubber magnet forming the first and second magnet pieces as long as the object of the present invention is not deviated.

[0024]

The first and second magnet pieces are formed into a resin magnet composition or a rubber magnet composition in which the binder, magnetic powder, and, if necessary, the filler and other additives are mixed. Although it is obtained by that, in this case is not particularly limited, the above components are mixed according to a usual method, melt-kneaded, molded into pellets, to obtain a pellet-shaped molding material, It is preferable to form each magnet piece by subjecting it to injection molding or extrusion molding. In this case, the melt-kneading can be performed by using a twin-screw kneading extruder, a KCK kneading extruder, or the like under ordinary methods and conditions.

[0025]

Here, the first magnet piece is arranged from both sides and the back side (the center side of the roller, that is, the shaft side) of the magnet piece to the front side (the surface forming the surface of the roller).
The anisotropic magnetic powder is oriented so as to converge to a predetermined position, and the orientation of such magnetic powder is determined by injection molding or extrusion molding using the mold of FIG. 1 described above. Obtainable. The first magnet piece can be easily obtained by using the mold of FIG. 1 described above, but may be obtained by another method, in other words, the orientation of the magnetic powder is adjusted. The magnetic powder may be obtained by any method as long as the magnetic powder is oriented so as to converge from both side surfaces and the back surface to a predetermined position on the front surface.

[0026]

On the other hand, the second magnet piece has no orientation characteristics using the above-mentioned isotropic magnetic powder as the magnetic powder. The second magnet piece can be easily formed by injection molding or extrusion molding without applying a magnetic field during molding using a normal mold.

[0027]

Further, in the first magnet piece, the predetermined position on the surface side where the orientation direction of the magnetic powder converges can be appropriately set according to a target magnetic force pattern and the like.
For example, the convergence position in the alignment direction may be shifted from the center using the mold shown in FIG. 2, but it is usually preferable to set the center of the surface to obtain a higher magnetic force peak.

[0028]

In the magnet roller of the present invention, for example, as shown in FIG. 3, the magnetic powder forms the surface (the surface of the roller) from both side surfaces and the back surface (the center side of the roller, that is, the surface on the shaft side). (See arrow in FIG. 3).
The second magnet piece 7 having no orientation characteristics using isotropic magnetic powder is arranged and fixed on the outer periphery of the shaft 8, and the magnet layer 9 is formed on the outer periphery of the shaft 8.

[0029]

In this case, FIG. 3 shows an example in which the magnet layer 9 is formed by the five-piece magnet pieces 6 and 7, but the number of the magnet pieces 6 and 7 constituting the magnet layer 9 is particularly limited. However, it is appropriately selected according to the required magnetic force pattern and the like, and is usually preferably 2 to 10 pieces, particularly preferably 3 to 8 pieces according to the number of magnetic poles and the size of the roller. In addition, the first
The number of each of the magnet pieces 6 and the second magnet pieces 7 is appropriately selected according to the number of magnetic poles, the strength of the magnetic force required for each magnet piece, and is not particularly limited. The magnet piece has 1 to 4 pieces, and the second magnet piece has 1 to 4 pieces. Further, in the magnet roller of FIG. 3, three first magnet pieces 6 form a half circumference of the magnet layer 9, and the remaining half circumference is formed by the two second magnet pieces 7. The arrangement of 6 and 7 is not limited to this. For example, the first magnet pieces 6 and the second magnet pieces 7 may be alternately arranged, and may be appropriately determined according to a required magnetic force pattern or the like. They can be arranged in combination.
Furthermore, as shown in FIG. 3, the first magnet piece 6 and the second magnet piece 7 are usually formed in a sector shape in cross section, but the shape is not limited to this sector shape. In other words, the magnet layer 9 can be formed on the outer periphery of the shaft 8 by combining and fixing the first and second magnet pieces 6 and 7 on the outer periphery of the shaft 8. Anything can be obtained.
The shaft 8 may be a normal shaft such as a solid or hollow shaft made of metal or a shaft made of various resins. In this case, a shaft having a polygonal cross section may be used. The magnet roller of the present invention can be obtained by arranging and fixing the first magnet piece 6 and the second magnet piece 7 using an adhesive.

[0030]

Here, in the magnet roller of the present invention, although not particularly limited, the first magnet piece 6 is used in a portion where a relatively high magnetic force peak is required, and the second magnet piece 7 is used. It is preferably used for a part where a relatively low magnetic force peak is required or a part where the position of the magnetic force peak needs to be moved. Thus, the magnet pieces 6, 7 are temporarily demagnetized and re-magnetized after molding or roller formation, so that the height of the magnetic force peak of the portion formed by the second magnet pieces 7 becomes a desired height. The magnetic force pattern can be adjusted to a desired pattern by adjusting and moving the position of the peak to a desired position. In this case, the demagnetization operation and the magnetization operation can be performed by a usual method, and can be performed by a known method using a known device according to a target magnetic force pattern. As shown in FIG. 5, an example of the magnetizing device and the magnetizing method is as shown in FIG. Polar magnetization).

[0031]

The magnet roller of the present invention is suitably used as a magnet roller constituting a developing roller or a cleaning roller of an electrophotographic apparatus such as a copying machine or a printer, or an electrostatic recording apparatus. In addition, the cleaning roller is a device that scrapes toner remaining on a latent image holding member such as a photosensitive drum with a cleaning blade and then collects the toner by a magnetic force, and arranges a magnet roller in a place suitable for collection. The toner is attracted to the magnet roller by a magnetic force, the toner is peeled off from the magnet roller by a blade at a predetermined position, and the toner is collected in a predetermined collection section.

[0032]

[0028]

[0033]

As described above, according to the magnet roller of the present invention, it is possible to cope with a case where a partially low magnetic force peak is required without changing the dimensions of the magnet piece. Even when moving the position of the magnetic force peak of one piece, the peak position can be easily moved without the need for various types of molds, and a significant cost increase is required even for complicated magnetic force pattern requirements. It can be easily handled without inviting,
According to the method of manufacturing the magnet roller of the present invention, the height and position of the magnetic force peak can be easily adjusted by demagnetization and magnetization after forming the roller, and by combining several types of magnet pieces. In addition, a plurality of types of magnet rollers having a complicated magnetic force pattern can be easily manufactured without incurring a large cost.

[0034]

[0029]

[0035]

The present invention will now be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[Embodiment] Three first magnet pieces 6 and 2
The second magnet pieces 7 are injection-molded under the following conditions, and they are bonded to the outer periphery of the metal shaft 8 to form a magnet layer 9 on the outer periphery of the shaft 8 to obtain the magnet roller shown in FIG. Was. Note that the arrow in FIG. 3 indicates the orientation direction of the magnetic powder in the first magnet piece 6.

[0037]

Shape and size (1) First magnet piece 6 Shape: Sector-shaped magnet piece with a central angle of 60 ° Diameter of outer arc of fan shape: 16 mm Diameter of inner arc of fan shape: 6 mm Length: 310 mm (2) Second magnet piece 7 Shape: Sector-shaped magnet piece with a central angle of 90 ° Cross section Diameter of outer arc of fan shape: 16 mm Diameter of inner arc of fan shape: 6 mm Length: 310 mm Molding material (bonded magnet composition ) 1 magnet piece 6 Binder: 10% by weight of ethylene-ethyl acrylate (EEA) Magnetic powder: 90% by weight of anisotropic Sr ferrite (2) Second magnet piece 7 Binder: 10% by weight of ethylene-ethyl acrylate (EEA) Magnetic powder: isotropic Ba ferrite 90 wt% using a mold (1) first magnet piece 6 mold of FIG. 1 (2) second magnet piece 7 Field generator device no regular mold injection molding conditions (both magnet piece common) cylinder temperature: 245 ° C. Mold temperature: 65 ° C. Injection pressure: 700 [kg / cm ^2] orientation state (1) of the magnetic powder the 1 Magnet piece 6 Oriented so as to converge from both sides and the back side to the center part on the front side (see arrow in FIG. 3) (2) Second magnet piece 7 No orientation characteristics

[0038]

After the obtained magnet roller was once demagnetized, it was magnetized using the magnetizing device shown in FIG. 5 under various conditions to obtain three types of magnet rollers. The surface magnetic force of each roller was measured along the circumferential direction, and the magnetization pattern of each roller was graphed. FIG. 6 shows the results. As shown in FIG. 6, according to this magnet roller, the height and position of the magnetic force peak can be easily changed and adjusted by forming the magnet roller and then demagnetizing and magnetizing again. It was confirmed that a plurality of types of magnet rollers having a complicated magnetic force pattern could be easily obtained.

[0039]

[Comparative Example] Three first magnet pieces 12 and two second magnet pieces 13 were injection-molded under the following conditions, and these were bonded to the outer periphery of the metal shaft 8.
The magnet layer 14 was formed on the outer periphery of the shaft 8 to obtain the magnet roller shown in FIG. The arrow in FIG. 4 indicates the orientation direction of the magnetic powder in each of the magnet pieces 12 and 13.

[0040]

Shape and size (1) First magnet piece 12 Shape: Sector-shaped magnet piece with central angle of 60 ° Diameter of outer arc of fan shape: 16 mm Diameter of inner arc of fan shape: 6 mm Length: 310 mm (2) Second magnet piece 13 Shape: Cross-section fan-shaped magnet piece with a central angle of 90 ° Diameter of fan-shaped outer arc: 16 mm Diameter of fan-shaped inner arc: 6 mm Length: 310 mm Molding material (bonded magnet composition) (both magnet pieces) Common) binder: ethylene-ethyl acrylate (EEA) 10% by weight Magnetic powder: mold using 90% by weight of anisotropic Sr ferrite (1) First magnet piece 12 Mold of FIG. 1 (2) Second magnet piece 13 mold injection molding conditions of FIG. 2 (both magnet piece common) cylinder temperature: 245 ° C. mold temperature: 65 ° C. injection pressure: 700 [kg / cm ^2] magnetic Orientation from the orientation state (1) the first magnet piece 12 opposite side surfaces and the rear surface side so as to converge to the central portion of the front side (see an arrow in FIG. 4) (2) opposite side surfaces and the rear surface side second magnet piece 13 Orientation so that it converges to a part of one circumferential end on the front side (see the arrow in FIG. 4).

[0041]

The magnet roller obtained was once demagnetized and magnetized again to adjust the magnetization pattern in the same manner as in the embodiment. As a result, the magnetic force pattern shown in FIG. 7 could be obtained. Try to move the magnetic peak,
A significant decrease in magnetic force occurred, and it was not possible to obtain a magnet roller that could withstand practical use. Therefore, it is difficult to obtain a complicated magnetic force pattern by adjusting the height and position of the magnetic force peak after forming the magnet roller, and to obtain a plurality of types of magnetic rollers having different magnetic force patterns, It has been found that even if the difference is slight, many types of molds are required according to the respective magnetic force patterns.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a mold for forming a first magnet piece constituting a magnet roller of the present invention.

FIG. 2 is a schematic sectional view showing a mold used in a comparative example.

FIG. 3 is a schematic cross-sectional view showing a magnet roller according to one embodiment of the present invention, in which an orientation direction of magnetic powder is indicated by an arrow.

FIG. 4 is a schematic cross-sectional view showing a magnet roller obtained in a comparative example, in which an orientation direction of magnetic powder is indicated by an arrow.

FIG. 5 is a schematic view showing an example of a magnetizing device used in the manufacturing method of the present invention.

FIG. 6 is a graph showing a magnetic force pattern of a magnet roller obtained in an example.

FIG. 7 is a graph showing a magnetic force pattern of a magnet roller obtained in a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cavity 2 Non-magnetic metal material 3a, 3b Magnetic metal material 4 Coil 5 Convex part 6 First magnet piece 7 Second magnet piece 8 Shaft 9 Resin magnet layer

Claims (4)

[Claims] 1. A magnet roller comprising a plurality of magnet pieces formed by dispersing magnetic powder in a resin or rubber binder and fixed on the outer periphery of a shaft to form a magnet layer on the outer periphery of the shaft. As the magnet piece, a first magnet piece in which anisotropic magnetic powder is oriented so as to converge from both side surfaces and a back surface to a predetermined position on a front surface side, and a first magnet piece having no orientation characteristics using isotropic magnetic powder. A magnet roller comprising at least two types of magnet pieces combined with two magnet pieces. 2. The magnet roller according to claim 1, wherein a relatively high magnetic force peak is formed in said first magnet piece portion, and a relatively low magnetic force peak is formed in said second magnet piece portion. 3. A plurality of magnet pieces are formed by molding a resin magnet composition or a rubber magnet composition in which magnetic powder is dispersed in a resin or rubber binder with a mold, and each of the obtained magnet pieces is placed on the outside of a shaft. After obtaining a roller having a magnet layer formed on the outer periphery of the shaft by disposing and fixing it on the shaft, in the method of manufacturing a magnet roller for magnetizing a desired magnetic force pattern, anisotropic magnetic powder is used as the plurality of magnet pieces on both sides. Forming at least two types of magnet pieces: a first magnet piece oriented so as to converge to a predetermined position on the front side from the front and back sides, and a second magnet piece having no orientation characteristics using isotropic magnetic powder. And a method for manufacturing the magnet roller, wherein the magnet layer is formed by combining them. 4. A magnetic metal material is disposed above and below a non-magnetic metal material, and both side surfaces and a back surface of the cavity are formed of a lower magnetic metal material, and a protrusion is formed on the upper magnetic metal material. Using a mold in which the tip of the projection is disposed near a desired position on the front surface side of the cavity, the anisotropic magnetic powder is converged from both side surfaces and the back surface to a predetermined position on the front surface side. 4. An oriented first magnet piece is formed.
A manufacturing method of the magnet roller described in the above.