JP2001267164A - Method and device for manufacturing resin magnet molded goods - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing resin magnet molded goods by which molding operation can be performed in a state where a uniform magnetic field is applied, without inducing an increase in cost and the resin magnet molded goods having a uniform magnetic force be manufactured surely and at a low cost, by molding a resin magnet composition while applying a magnetic field thereto. SOLUTION: A plurality of permanent magnets are continuously arranged and they are integrally adhered with each other to form an assembled magnet, then the assembled magnet is around a cavity for molding, and molding is performed while applying a magnetic field by the assembled magnet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a resin magnet composition such as a magnet roller used for developing an electrostatic latent image by molding a resin magnet composition in which magnetic powder is dispersed in a resin binder. .

[0002]

2. Description of the Related Art In an electrophotographic apparatus such as a copying machine or a printer, or an electrostatic recording apparatus, as a developing method for visualizing an electrostatic latent image on a latent image carrier such as a photosensitive drum, a resin magnet is provided in a rotating sleeve. Magnetic developer (toner) provided on the sleeve surface with a magnet roller formed by
There is known a developing method in which toner is supplied to the surface of the latent image holding member by a so-called jumping phenomenon in which the toner is caused to fly onto the latent image holding member by the magnetic force characteristics of the magnet roller to visualize the electrostatic latent image.

Conventionally, the above-mentioned magnet roller is formed by injecting a resin magnet composition in which a magnetic powder such as ferrite is mixed with a binder of a thermoplastic resin such as nylon or polypropylene using a mold or a die having a magnetic field formed around the resin magnet. By molding or extruding, while forming into a roller shape, the magnetic powder in the resin magnet composition is oriented to a state suitable for desired magnetic force characteristics, and magnetized to a desired magnetic force characteristic simultaneously with or after this molding. It is manufactured by doing. Further, when complicated magnetic force characteristics are required, by molding the resin magnet composition in a state where a magnetic field is similarly applied,
A magnet roller having more complicated magnetic force characteristics is also obtained by forming a plurality of magnet pieces and bonding the magnet pieces together.

When the above-mentioned magnet roller or magnet piece is formed, a rare-earth permanent magnet is arranged around a cavity (molding cavity) of an injection molding die or extrusion molding die, so that the inside of the cavity is formed. In general, a magnetic field is applied to the resin magnet composition to perform molding.

[0005]

Here, in an electrophotographic apparatus such as a copying machine or a printer, or an electrostatic recording apparatus, a developing mechanism for visualizing an electrostatic latent image on a latent image holding member such as a photosensitive drum is used. Since the magnet roller to be used is very elongated, the permanent magnet to which a magnetic field is applied during molding is also required to be elongated. However, rare-earth magnets manufactured industrially are mostly used for relatively small ones, such as motor stators and rotors, and the corresponding size is rarely manufactured industrially. The magnet for applying the magnetic field must be manufactured, which results in an increase in cost.

Further, as is well known, rare earth magnets are very brittle, and such elongated rare earth magnets are extremely fragile and very poor in handling. Also,
In the case of such an elongated rare earth magnet, it is extremely difficult to make the magnetic force in the longitudinal direction uniform, and the strength of the magnetic force in the longitudinal direction is not small. When a magnet roller is formed in a state in which a magnetic field is applied using such a magnet having a non-uniform magnetic force, the resulting magnetic roller also has a non-uniform magnetic force in its length direction. May cause poor development.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances. By molding a resin magnet composition while applying a magnetic field, a uniform magnetic field can be obtained without incurring high costs when obtaining a resin magnet molded product. It is an object of the present invention to provide a method of manufacturing a resin magnet molded product that can perform molding in a state where a voltage is applied and that can reliably and inexpensively produce a resin magnet molded product such as a magnet roller having a uniform magnetic force.

[0008]

Means for Solving the Problems and Embodiments of the Invention The present inventors have made intensive studies to achieve the above object, and as a result, injection molding or extrusion of a resin magnet composition in which a magnetic powder is dispersed in a resin binder. When molding to obtain a resin magnet molded product, a plurality of permanent magnets are continuously arranged and bonded to form a collective magnet in which a plurality of permanent magnets are integrally bonded, and the collective magnet is formed into an injection molding die or By arranging around the molding cavity of the extrusion die and performing molding while applying a magnetic field to the molding, even when molding a long and narrow resin magnet molded product such as a magnet roller, it can be placed around the molding cavity. The permanent magnet can be easily arranged, and the molding can be performed with a uniform magnetic field applied without increasing the cost and the size of the apparatus. It found that a magnet molded product can reliably and inexpensively manufactured.

In this case, if the plurality of permanent magnets are not adhered to each other but are simply arranged around the molding cavity to form a collective magnet having a predetermined length, the magnetic force is disturbed at the joint between the permanent magnets. A uniform magnetic field cannot always be formed. For example, as shown in FIG. 3A, when a set magnet is configured by arranging four permanent magnets m, the same poles of the permanent magnets are adjacent to each other, so that a repulsive magnetic field is generated between the permanent magnets. Occurs, and as shown in the graph in the same figure,
A partial decrease in magnetic force occurs at the joint between the permanent magnets. For example, when a magnet roller is formed in a state in which such a magnetic field is applied, a decrease in magnetic force at the joint is traced by the formed magnet roller, and a streak-like image defect may occur when subjected to development. . However, as described above, by assembling the permanent magnets with an adhesive or the like to form a collective magnet, as shown in FIG.
As shown in (B), it is possible to prevent a decrease in magnetic force generated at the joint between the permanent magnets as much as possible, to obtain a collective magnet having a uniform magnetic force, and to arrange and fix the magnets in a mold or a base. It has been found that workability can be improved in this case, and the present invention has been completed.

Accordingly, the present invention provides a method for molding a resin injection molding or a die for extrusion molding when obtaining a resin magnet molding by injection molding or extrusion molding of a resin magnet composition in which magnetic powder is dispersed in a resin binder. A method of manufacturing a resin magnet molded product, in which a collective magnet in which a plurality of permanent magnets are continuously arranged is arranged around a cavity for forming a molded product while applying a magnetic field to the molded product by using the collective magnet. Resin magnet molding, wherein a plurality of permanent magnets are continuously arranged and bonded to form a collective magnet in which a plurality of permanent magnets are integrally bonded in advance, and the collective magnet is arranged around the molding cavity. Provided is a method for manufacturing a product.

Hereinafter, the present invention will be described in more detail.
The method for producing a resin magnet molded product of the present invention, as described above,
A set magnet in which a plurality of permanent magnets are continuously arranged and adhered is arranged around a molding cavity of an injection mold or an extrusion die, and a resin magnet composition is injected while applying a magnetic field with the collective magnet. Molding or extrusion molding is used to obtain a molded resin magnet such as a magnet roller. For example, as shown in FIGS. 1A and 1B, a pair of half molds 1a and 1
b) a resin magnet composition by applying a magnetic field to a cavity (molding cavity) 2 of an injection molding die 1 made of a plurality of permanent magnets m continuously arranged around the cavity 2 Is molded to form a magnet roller.

More specifically, for example, as shown in FIG. 2 (A), a plurality (eight in the figure) of permanent magnets m are continuously arranged, and the permanent magnets m are bonded with an adhesive s. And Figure 2
As shown in FIG. 1B, a collective magnet sm having a desired length is formed, and this collective magnet sm is inserted into a magnet arrangement groove 3 provided in an injection molding die 1, and FIG. As shown in (A) and (B), the collective magnet sm is arranged around the cavity (molding cavity) 2 of the mold, and the cavity (molding cavity) is formed by the collective magnet sm. A magnetic field is applied to the molded article molded in the step 2.

Each of the permanent magnets m constituting the collective magnet sm
Represents the resin magnet composition filled in the cavity 2,
Any material may be used as long as it can apply a magnetic force sufficient to orient the magnetic powder dispersed in the composition. For example, Nd-Fe-B alloy, Sm-Co alloy, Ce-C
Rare earth magnets such as o alloys, ferrite magnets such as Sr ferrite and Ba ferrite, Alnico (registered trademark) magnets, and the like can be given.

The size and number of each permanent magnet m are
It is appropriately selected depending on the size of the molded product (the size of the molding cavity), and is not particularly limited.
It is preferable to form the collective magnet sm by using 4 to 10, especially about 6 to 8, permanent magnets m having a normal size of about 80 mm, particularly about 40 to 60 mm.

Here, it is preferable that all the permanent magnets m have the same magnetic force. In the present invention, however, even if there is some variation between the permanent magnets, the permanent magnets are integrated by bonding. By using one set of magnets sm, an almost uniform magnetic field can be applied to the cavity (molding cavity) 2. However, if there is a very large variation in magnetic force between the permanent magnets m, the variation in the magnetic force is reduced. In some cases, it appears in the collective magnet sm and it becomes difficult to give a uniform magnetic field. Therefore, although not particularly limited, the variation in the magnetic force between the permanent magnets m constituting the collective magnet sm is 7% or less, particularly 5% or less, and further 3% with respect to the average magnetic force of all the permanent magnets m. The following is preferred.

In the method for producing a resin magnet molded product of the present invention, a cavity (molding cavity) is formed by using the above-mentioned collective magnet sm.
In this case, the variation expressed by the difference between the maximum value and the minimum value of the surface magnetic force of the collective magnet sm is 5% of the average magnetic force of the collective magnet sm surface.
Hereinafter, it is particularly preferably 3% or less, and by adjusting the magnetic force variation among the permanent magnets m as described above, a collective magnet having such a uniform surface magnetic force can be reliably obtained.

For example, when forming a magnet roller used in a developing mechanism of an electrophotographic apparatus, the magnet roller is provided with a magnetic pole having a magnetic force of usually about 5 to 10 m. Is 20
It is necessary to form a magnetic field having a magnetic force of about 0 to 600 mТ. In this case, the average magnetic force on the surface of the collective magnet sm is 200 to 500 m５００, particularly 300 to 400 mТ, and the difference between the maximum value and the minimum value of the collective magnet sm is 10 mТ or less,
In particular, the collective magnet sm may be configured so as to be 5 mТ or less, whereby an almost uniform magnetic field can be given. The magnetic pole formed on the magnet roller thus obtained also has a substantially uniform magnetic force, and is a small change in magnetic force with no problem in performance even if some variation occurs. It does not affect the image.

The adhesive used for forming the collective magnet sm by bonding the permanent magnet m is not particularly limited, and an appropriate adhesive may be used according to the material of the permanent magnet m. Specifically, epoxy adhesive, U
V-curable adhesives are exemplified.

In the method for producing a resin magnet molded product of the present invention, the above-described collective magnet sm is placed around a molding cavity of an injection molding die or an extrusion die to perform molding. In the case, the collective magnet sm is, for example, as shown in FIG.
As shown in FIG. 2B, by being inserted into the magnet arrangement groove 3 provided in the mold 1, it is arranged and fixed around the cavity (molding cavity) of the mold 1. According to the collective magnet sm of the present invention, this arrangement fixing work can be performed extremely easily.

That is, when a plurality of permanent magnets are arranged in a line and arranged around the cavity of a mold as one collective magnet, for example, if the collective magnet is for forming an S-pole in a molded product, each permanent magnet Are arranged with their S poles facing the cavity side. Therefore, in each permanent magnet, adjacent permanent magnets whose S pole and S pole are adjacent and whose N pole and N pole are adjacent to each other repel each other. Although it is not always easy to arrange a plurality of permanent magnets in a line in a row due to force, in the present invention, the collective magnets to which the permanent magnets are bonded in advance are arranged in the mold. Can be arranged and fixed in the mold. Further, in the conventional method, a gap or a gap is easily generated between the permanent magnets due to the repulsive force, which causes a reduction in the uniformity of the applied magnetic field. There is no reduction in the uniformity of the magnetic field.

Here, in the collective magnet sm in which a plurality of permanent magnets m are arranged in a line, the magnetic force near both ends tends to be higher than that in the center, and therefore, as shown in FIG. ,
It is preferable that the collective magnet sm is formed to be longer than the cavity 2 of the mold and that both ends of the collective magnet sm are located outside the both ends of the cavity 2.
In this case, how much both ends of the collective magnet sm should be longer than the cavity 2 is appropriately set according to the magnetic force of the magnetic field to be formed, and is not particularly limited, but is usually limited. 1-20m from the end of cavity 2
It is preferable to set so as to extend about m. In addition,
The collective magnet sm can be fixed to a mold using screws or the like, as shown in FIG. In some cases, a yoke made of a magnetically permeable material such as iron, steel, stainless steel, or nickel may be provided on the magnetic field application surface of the collective magnet sm.

In the method of manufacturing a resin magnet molded product according to the present invention, as shown in FIG. 1, for example, the plurality of permanent magnets m are formed around a cavity (molding cavity) 2 of a mold 1. The resin magnet composition is formed while the bonded magnets sm are arranged and a magnetic field is applied to the cavity 2.

The resin magnet composition used in the present invention may be any one in which magnetic powder is dispersed in a resin binder.
It can be appropriately selected and used according to the desired resin magnet molded product. For example, a case in which a magnet roller used in a developing mechanism of an electrophotographic apparatus is obtained will be described below as an example.

Examples of the resin 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 coalescing resin (EVA), ethylene-ethyl acrylate resin (EEA), epoxy resin, ethylene-vinyl alcohol copolymer resin (EVOH), polypropylene resin, polyethylene and polyethylene copolymer, and the structure of these polyolefins Modified polyolefins into which reactive functional groups such as a maleic anhydride group, a carboxyl group, a hydroxyl group, and a glycidyl group have been introduced, and one or more of these can be used in combination. Although not particularly limited, polyamide resins, EVA and EEA are among these.
Is preferably used.

As the above-mentioned magnetic powder, a usual magnetic powder conventionally used for a magnet roller can be used. Specifically, ferrite powders such as Sr ferrite and Br ferrite, Sm-Co alloy, Nd- Rare earth alloy powders such as Fe-B alloy and Ce-Co alloy can be exemplified.

The mixing ratio of the magnetic powder is appropriately selected according to the required strength of the magnetic force, and is not particularly limited, but is usually about 80 to 94% by weight of the whole composition. (The density is about 2.5 to 4.5 g / cm ³ ).

To this resin magnet composition, in addition to the binder component and the magnetic powder, an appropriate amount of a filler having a large reinforcing effect such as mica, whisker or talc, carbon fiber, glass fiber or other known additives is added. be able to.

In the production method of the present invention, the resin magnet composition is molded by using the mold 1 in which a magnetic field is applied to the cavity 2 with the collective magnet sm to which the permanent magnet m is adhered. Injection molding is preferably employed as the molding method, but extrusion molding may be employed. In the case of extrusion molding, a collective magnet sm to which the permanent magnet m is adhered is arranged around a molding cavity of an extrusion die. do it. The molding conditions can be set to normal conditions according to the type of the resin magnet composition used and the intended resin magnet molded product.

The manufacturing method of the present invention is suitably used for manufacturing a magnet roller used in a developing mechanism of an electrophotographic apparatus. For example, FIGS. 1 (A) and 1 (B)
By molding the resin magnet composition using the mold shown in (1), a magnet roller having four magnetic poles displaced by 90 ° can be obtained, but the present invention is not limited to this. The number and the arrangement position of the collective magnets sm consisting of m may be changed as appropriate to form a magnet roller of 5 poles or more or 3 poles or less. Further, instead of directly forming a magnet roller, a magnet roller is formed. For example, a magnet piece may be formed, and the magnet pieces may be bonded together to manufacture a magnet roller.
Furthermore, according to the production method of the present invention, the orientation and magnetization of the magnetic powder are performed simultaneously with the molding by applying a magnetic field, but when it is desired to finely adjust the magnetic force or the peak position of the magnetic pole, for example, once the molding is performed, You may make it demagnetize and magnetize again. The manufacturing method of the present invention is suitably used for manufacturing resin magnet molded products such as a motor rotor, a stator and a sensor rotor in addition to the magnet roller and its magnet piece.

[0030]

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

[Embodiment] Eight rare earth magnets (25 mm ×
(3 mm × 40 mm) were linearly arranged, and the respective magnets were adhered to each other with an epoxy-based adhesive to prepare a long plate-shaped aggregate magnet having a length of 320 mm. In this case, the average magnetic force of all the rare earth magnets is 390 mT, and the variation is at most 20.
mT. The surface magnetic force of the obtained collective magnet was 3
It was 91 to 398 mT (average magnetic force: 395 mT), and the difference between the maximum value and the minimum value of the surface magnetic force was 7 mT.

This collective magnet was placed around the cavity of an injection mold, and a resin magnet composition in which ferrite was mixed and dispersed in nylon 6 was injection molded to have a length of 300 mm.
A magnet roller having a diameter of 18 mm was formed. When the magnetic force of the obtained magnet roller was measured along the length direction, it had a substantially uniform magnetic force of 2 mT from one end to the other end of the magnet roller. Further, when the obtained magnet roller was mounted on a known developing device and an image was printed, a good image without image defects was obtained.

[Comparative Example] A collective magnet was formed by simply arranging and fixing each permanent magnet in a mold without adhering them. When the surface magnetic force of this collective magnet was measured, the magnetic force showed a variation of more than 10 mT at 350 to 400 mT, which was larger than that of the collective magnet used in the examples.

A magnet roller was formed using this mold in the same manner as in the embodiment, and the magnetic force of the obtained magnet roller was measured along the length direction. Corresponding to the seam, a marked decrease in magnetic force was observed in part. Further, when the obtained magnet roller was mounted on a known developing device and an image was printed, a streak-like image defect occurred corresponding to the portion where the magnetic force was reduced.

[0035]

As described above, according to the method for producing a resin magnet molded product of the present invention, by molding the resin magnet composition while applying a magnetic field, the resin magnet molded product can be obtained in advance. By applying a magnetic field using a collective magnet in which a plurality of permanent magnets are arranged and adhered, molding can be performed with a uniform magnetic field applied without incurring high costs or increasing the size of the apparatus. In addition, a resin magnet molded product such as a magnet roller having a uniform magnetic force can be reliably and inexpensively manufactured.

[Brief description of the drawings]

FIG. 1 shows an example of a mold used in the method for producing a resin magnet molded product of the present invention, wherein (A) is a schematic sectional view,
(B) is a partial enlarged sectional view along the BB line of (A).

FIG. 2 is a perspective view for explaining a method of forming a mold used in the manufacturing method.

FIG. 3 is a graph showing the magnetic force of a magnetic field formed when a plurality of permanent magnets are linearly arranged. FIG. 3 (A) shows the case where the permanent magnets are arranged without bonding, and FIG. This is a case where a permanent magnet is bonded.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold 2 Cavity (cavity part for molding) 3 Groove for magnet arrangement m Permanent magnet sm Assembly magnet s Adhesive

Claims (6)

[Claims] When a resin magnet composition in which magnetic powder is dispersed in a resin binder is injection-molded or extruded to obtain a resin magnet molded product, an injection molding die or an extrusion molding die cavity is formed. Around the periphery, a collective magnet in which a plurality of permanent magnets are continuously arranged is arranged, and in the method of manufacturing a resin magnet molded product in which molding is performed while applying a magnetic field to the molded product by the collective magnet, the plurality of permanent magnets are Adhere continuously and glue,
A method of manufacturing a molded resin magnet, comprising: forming a collective magnet in which a plurality of permanent magnets are integrally bonded in advance; and disposing the collective magnet around the molding cavity. 2. A plurality of permanent magnets are continuously arranged and bonded to form a collective magnet in which a plurality of permanent magnets are integrally bonded in advance, and the collective magnets are arranged around a molding cavity to form the collective magnet. The method for producing a resin magnet molded product according to claim 1, wherein the resin magnet composition is obtained by injection molding the resin magnet composition using a mold in which a magnetic field is applied to a cavity for use. 3. The variation in magnetic force between the permanent magnets constituting the collective magnet is 7% of the average magnetic force of all the permanent magnets.
The method for producing a resin magnet molded product according to claim 1, wherein: 4. The method according to claim 1, wherein the variation represented by the difference between the maximum value and the minimum value of the surface magnetic force of the collective magnet is 5% or less with respect to the average magnetic force of the collective magnet surface. 1
13. The method for producing a resin magnet molded product according to the above item. 5. A surface magnetic force of the collective magnet is 200 to 50.
The method for producing a resin magnet molded product according to claim 4, wherein the temperature is 0 mT. 6. The resin according to claim 1, which is a method for manufacturing a magnet roller used in a developing device for developing an electrostatic latent image, or a method for manufacturing a magnet piece for forming the magnet roller. Manufacturing method of magnet molding.