Patent Application
20080246572
The present invention relates to magnet rollers incorporated in, for example, image forming devices such as copiers, printers and facsimiles.
The magnet rollers incorporated in the image forming devices using powder toner in the copiers, the printers and the facsimiles or the like are generally configured as follows.
That is,
(1) a plurality of magnet pieces obtained by orientating a magnetization easy axis in a specific direction simultaneously with extrusion molding are fixed to a shaft to form a magnet roller (Patent Reference 1).
(2) After a magnet piece having a sectoral section shape and magnetized by orientating the magnetization easy axis of ferrite powder to the other three sides from a center part of a circular arc is injection molded, a plurality of magnet pieces are bonded on a shaft to form a magnet roller (Patent Reference 2).
However, as shown in the Patent Reference 1, the magnetic particles of each of the magnet pieces corresponding to magnetic pole positions are orientated in a parallel direction with respect to the center line of the radial direction. The magnetic particles of the magnet piece between the magnetic poles are orientated in a perpendicular direction with the respect to the center line of the radial direction (The center line of the radial direction is a line extended to the circumferential direction from the center point of the magnet roller, and the line passes a point for equally dividing the circular arc of the outer circumference of the magnet piece into two). That is, the orientation direction of the magnetic particles of the magnet piece is orientated parallel to the center line of the radial direction, or perpendicular to the center line of the radial direction (That is, the magnetic particles are orientated parallel to the perpendicular direction of a bonded surface when viewed from the bonded surface with adjoining magnet piece). Since the orientation of the magnetic particles is not inclined with respect to the above parallel line and perpendicular line, only a simple magnetic flux density pattern may be able to be formed, which is not shown in the Patent reference 1. Also, in the patent, eight magnet pieces are used in order to obtain four magnetic poles, and the use of the eight magnet pieces may become costly expensive.
Also, as shown in Patent Reference 2, after the magnet piece having the sectoral section shape and magnetized by orientating the magnetization easy axis of ferrite powder to the other three sides from the center part of the circular arc is injection molded, the plurality of magnet pieces are bonded on the shaft to form the magnet roller. Therefore, it is difficult to form the complicated magnetic flux density pattern, and only the simple magnetic flux density pattern may be able to be formed, which is not shown in the Patent reference 2.
A magnet roller of the present invention is obtained by combining a magnet piece formed by injection molding while performing pole-anisotropic orientation of magnetic particles and a magnet piece formed by extrusion molding while orientating magnetic particles in a certain direction inclined by 5 degrees or more with respect to a center line of a radial direction of the magnet piece. Thereby, the degree of freedom of a magnetic flux density pattern of each of the magnet pieces can be enhanced, and a complicated magnetic flux density pattern can be formed.
In the magnet roller of the present invention, an ethylene ethyl acrylate resin is used as a binder resin for the magnet piece formed by the extrusion molding, thereby providing the magnet piece having excellent dimension accuracy and moderate flexibility without having fear of warpage. Also, the magnet piece has enhanced degree of freedom of the magnetic flux density pattern, and can form a complicated magnetic flux density pattern.
In the magnet roller of the present invention, a polyamide resin is used as a binder resin of the magnet piece formed by the injection molding, thereby providing the magnet piece having excellent dimension accuracy. Also, the magnet piece has enhanced magnetic flux density strength and can form a magnetic pole having a high magnetic flux density.
In the magnet roller of the present invention, an ethylene ethyl acrylate resin is used as a binder resin of the magnet piece formed by the injection molding, thereby providing the magnet piece having excellent dimension accuracy and moderate flexibility without having fear of warpage. Also, the magnet piece has enhanced magnetic flux density strength and can form a magnetic pole having a high magnetic flux density
According to the present invention (claim 1), the magnet piece formed by the injection molding has the high magnetic flux density, and each of the magnet pieces formed by the extrusion molding has the enhanced degree of freedom of the magnetic flux density pattern. The magnet roller obtained by combining and bonding the magnet piece formed by the injection molding and the magnet pieces formed by the extrusion molding can correspond to the complicated magnetic flux density pattern.
According to the present invention (claim 2), the magnet piece formed by the extrusion molding has the excellent dimension accuracy, and even when the magnet pieces are bonded, the magnet piece has excellent accuracy of a magnetic pole position. Also, the magnet piece has enhanced and stabilized adhesive strength.
According to the present invention (claim 3), the magnet piece formed by the injection molding has the high magnetic flux density and excellent developer fogging.
According to the present invention (claim 4), the magnet piece formed by the injection molding has the high magnetic flux density, moderate flexibility without having fear of warpage. Also, the magnet piece has enhanced and stabilized adhesive strength.
A magnet roller of the present invention is configured by combining a magnet piece formed by injection molding while performing pole-anisotropic orientation of magnetic particles and a magnet piece formed by extrusion molding while orientating magnetic particles in a certain direction inclined by 5 degrees or more with respect to a center line of a radial direction of the magnet piece.
As shown in the Patent Reference 1, the conventional magnet roller is obtained by bonding a plurality of magnet pieces formed by the extrusion molding on the periphery of a shaft. The orientation direction of the magnetic particles of the magnet piece is parallel to the center line of the radial direction. The magnet piece between the magnetic poles is orientated in a direction perpendicular to the center line of the radial direction.
In the present invention, for example, as shown in
Herein, when the θ1 and the θ2 are less than 5 degrees, the θ1 and the θ2 are almost the same as 0 degree, and an effect of the inclination of the magnetic particles is not exhibited. Also, when the θ1 and the θ2 exceed 90 degrees, the polarity is turned into reverse polarity (for example, an N pole is turned into an S pole), and the target magnetic flux density pattern is not obtained.
The magnet piece 1 of the N1 pole is obtained by the following method using a mold having a magnetic circuit as shown in
The above magnet piece mainly contains a mixture of 50% by weight to 95% by weight of an anisotropic ferrite magnetic powder and 5% by weight to 50% by weight of a resin binder. If needed, silane and titanate coupling agents as a finishing agent, a polystyrene and fluoride lubricating agents for enhancing flow property, a stabilizer, a plasticizer or a fire retardant or the like are added, and are dispersively mixed. The resultant mixture is melted and kneaded, and molded into pellets before injection molding.
The orientation magnetization magnetic field applied in the formation needs only to be suitably selected according to magnetic flux density specification required for each of the magnetic poles. Also, the orientation magnetization magnetic field may not be applied in the formation but be subjected to magnetization after the formation depending on the required magnetic property.
Herein, Examples of the magnetic powders include an anisotropic ferrite magnetic powder having a chemical formula represented by MO-nFe2O3 wherein n is a natural number. In the formula, one or more of Sr, Ba and Pb are suitably used as the “M”. Also, examples of the resin binders include thermoplastic resins such as vinyl chloride-vinyl acetate copolymer, ethylene-ethyl acrylate resin, polyamide resin, polystyrene resin, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), ethylene-vinyl acetate copolymer (EVA), ethylene-vinyl alcohol copolymer (EVOH), chlorinated polyethylene (CPE) and polyvinyl chloride (PVC), and thermosetting resins such as epoxy resin, phenol resin, urea resin, unsaturated polyester resin, melamine resin, furan resin and polyimide resin. These may be used alone or combination thereof.
Also, an anisotropic ferrite magnetic powder, an isotropic ferrite magnetic powder, an anisotropic rare earth magnetic powder (for example, SmFeN) and an isotropic rare earth magnetic powder (for example, NeFeB) may be used alone or combination thereof as the magnetic powder according to the required magnetic flux density. If the content of the single magnetic powder or mixed magnetic powder described above is less than 50% by weight, the insufficiency of magnetic powder may cause the magnetic properties of the magnet piece to be impaired so that a desired magnetic force is not obtained, and if the content is more than 95% by weight, insufficiency of binder may cause the molding properties of the magnet pieces to be impaired.
Also, in the present invention, the magnet pieces of the N2 pole and N3 pole are obtained by the following method using an extrusion mold (die) having a magnetic circuit as shown in a, b of
Although the extrusion molding orientates the magnetic particles of the melted resin magnet passing through the inside of the mold by applying an unidirectional magnetic field (in a certain direction) using a mold (die) as shown in
Herein, Examples of the magnetic powders include an anisotropic ferrite magnetic powder having a chemical formula represented by MO.nFe2O3 wherein n is a natural number. In the formula, one or more of Sr, Ba and Pb are suitably used as the “M”.
Also, examples of the resin binders include thermoplastic resins such as vinyl chloride-vinyl acetate copolymer, ethylene-ethyl acrylate resin, polyamide resin, polystyrene resin, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), ethylene-vinyl acetate copolymer (EVA), ethylene-vinyl alcohol copolymer (EVOH), chlorinated polyethylene (CPE) and polyvinyl chloride (PVC), and thermosetting resins such as epoxy resin, phenol resin, urea resin, unsaturated polyester resin, melamine resin, furan resin and polyimide resin. These may be used alone or combination thereof. Also, an anisotropic ferrite magnetic powder, an isotropic ferrite magnetic powder, an anisotropic rare earth magnetic powder (for example, SmFeN) and an isotropic rare earth magnetic powder (for example, NeFeB) may be used alone or combination thereof as the magnetic powder according to the required magnetic flux density. If the content of the single magnetic powder or mixed magnetic powder described above is less than 50% by weight, the insufficiency of magnetic powder may cause the magnetic properties of the magnet piece to be impaired so that a desired magnetic force is not obtained, and if the content is more than 95% by weight, insufficiency of binder may cause the molding properties of the magnet pieces to be impaired.
Since the orientation magnetizing direction of the magnetic particles of the S1 pole and S2 pole of
An extrusion mold (die) having a magnetic circuit as shown in a, b of
Although the extrusion molding orientates the magnetic particles of the melted resin magnet passing through the inside of the mold by applying an unidirectional magnetic field (in a certain direction) using a mold (die) as shown in
The above magnet piece of the extrusion-molded article has moderate flexibility without having fear of warpage as compared with the magnet piece as the injection-molded article, and is easily bonded onto the shaft. The blend prescription of the material of the magnet pieces of the S1 pole and S2 pole is completely the same as the N2 pole and N3 pole of the extrusion-molded article.
The N1 pole having high magnetic force of 105 mT is attained by bonding each of the magnet pieces obtained by the above forming process on the outer circumferential face of the shaft as shown in
Furthermore, the magnetic properties are enhanced and the dimension accuracy of the injection-molded article is enhanced by using the ethylene ethyl acrylate resin for the binder resin of the resin magnetic material of the injection molding magnet piece. Also, the magnet piece has semihard hardness, and the injection-molded article is easily bonded onto the shaft without having fear of warpage. The fogging of the developer may be able to be decreased and prevented by obtaining the high magnetic flux density. Since it is unnecessary that all the magnet pieces used for the present invention are made of the same material (a binder and a magnetic powder or the like), any combination of the magnet pieces of different kind, the integration of magnetic properties and the reduction of cost may be attained.
Also, herein, although the constitution of the magnet roller of five poles is illustrated, the present invention is not limited to only the magnet roller of five poles. That is, the quantity of the magnet pieces needs only to be selected by a desired magnetic flux density and magnetic field distribution, and the number of the magnetic poles and magnetic pole positions need only to be also set suitably. Furthermore, when the magnetic field is applied simultaneously with the formation, the magnet piece may be once demagnetized in the mold or outside of the mold after the formation, and may be then magnetized for the enhancement in the formwork removal property of a molded product, the adhesion prevention of garbage such as residue of the molded product, and easy handling property of the magnet piece.
The present invention will be specifically described by means of the following Examples and Comparative Examples. It is to be understood that the present invention is not limited to the Examples.
Referring to a magnet piece material for an N1 pole of
Referring to a magnet piece material for poles (S1 pole, N2 pole, N3 pole and S2 pole) other than the N1 pole of
Five poles of the magnet pieces formed as described above were bonded on the outer circumferential face of the shaft to obtain a magnet roller as shown in
The results of the measurement are shown in Tables 1 to 3. Herein, as shown in
Referring to a magnet material for extrusion molding (S1 pole, N2 pole, N3 pole and S2 pole), there used 10% by weight (containing a lubricating agent and a stabilizer) of ethylene-ethyl acrylate (PES-210, manufactured by Nippon Unicar Company Limited) as a resin binder, and 90% by weight of an anisotropic strontium ferrite magnetic powder (SrO.6Fe2O3) as a magnetic powder. These were mixed, melted and kneaded and molded into pellets. The pellet was melted to a melted state. The same manner as in the Example 1 was performed except that the magnetic particles of the melted resin magnet were unidirectionally subjected to orientation magnetization per each of the pieces while applying a magnetic field of 240 K-A/m to 2400 K-A/m using molds (dies) of a, b of
The same manner as in the Example 1 was performed except that, referring to a magnet material for injection molding (N1 pole), there were used 10% by weight (containing a lubricating agent, a plasticizer and stabilizer) of nylon 12 (P3012U, manufactured by Ube Industries, Ltd.) as a resin binder, and 90% by weight of an anisotropic strontium ferrite magnetic powder (SrO.6Fe2O3) as a magnetic powder. The results of the measurement are shown in Tables 1 to 4.
The same manner as in the Example 1 was performed except that, referring to a magnet material for injection molding (N1 pole), there were used 10% by weight (containing a lubricating agent and a stabilizer) of ethylene-ethyl acrylate (DPDJ-9169, manufactured by Nippon Unicar Company Limited) as a resin binder, and 90% by weight of an anisotropic strontium ferrite magnetic powder (SrO.6Fe2O3) as a magnetic powder, and referring to a magnet material for extrusion molding (S1 pole, N2 pole, N3 pole and S2 pole), there were used 10% by weight (containing a lubricating agent and a stabilizer) of ethylene-ethyl acrylate (PES-210, manufactured by Nippon Unicar Company Limited) as a resin binder, and 90% by weight of an anisotropic strontium ferrite magnetic powder (SrO.6Fe2O3) as a magnetic powder. The results of the measurement are shown in Tables 1 to 4.
For an N1 pole, a magnet piece pole-anisotropically subjected to orientation magnetization by the completely same material and forming process as the Example 1 was formed. For poles other than the N1 pole (S1 pole, N2 pole, N3 pole and S2 pole), the same material as the N1 pole of the Example 1 was used as a magnet piece material. The magnetic particles of the melted resin magnet were unidirectionally subjected to orientation magnetization per each of the pieces while applying a magnetic field of 240 K-A/m to 2400 K-A/m using a mold having a magnetic circuit as shown in
Referring to a magnet piece material for all the poles (N1 pole, S1 pole, N2 pole, N3 pole and S2 pole) of
The process and measurement after forming the magnet piece were performed in the same manner as in the Example 1. The results of the measurement are shown in Tables 1 to 4.
As is observed from Table 1, when the Examples 1, 2, 3, 4 are compared with the Comparative Example 1, 2, the magnetic flux density patterns of the N2 pole and N3 pole of the Example 1, 2, 3, 4 are an asymmetric pattern with respect to the magnetic flux density peak. However, the magnetic flux density patterns of the N2 pole and N3 pole of the Comparative Examples 1, 2 are a symmetric pattern with respect to the magnetic flux density peak. It is turned out that the orientation magnetizing direction of the magnetic particles of the magnet pieces of the N2 pole and N3 pole of the Example 1 can be realized by inclining the magnetic particles with respect to the center line of the radial direction of the magnet piece. That is, it is turned out that an asymmetric magnetic flux density pattern with respect to the magnetic flux density peak is obtained by inclining and orientating the magnetic particles of the magnet piece like the above N2 pole and N3 pole, and a complicated magnetic flux density pattern can be formed. The asymmetric magnetic flux density pattern may enhance the carrying property of a developer, the passing performance of a developer regulation blade, the peel property of the developer or the like, and provide excellent image quality. As is observed from Table 2, when the Examples 2, 4 are compared with the Comparative Example 2, the distortion amount of the magnetic flux density peak position of each of the poles of the Examples 2, 4 is 1 degree or less. However, the distortion amount of the magnetic flux density peak position of each of the poles of the Comparative Example 2 is a maximum of 3 degrees. Since as the magnet piece material other than the N1 pole (for extrusion), the dimension accuracy of the magnet piece is enhanced by using the ethylene ethyl acrylate resin for the resin binder. As a result, the accuracy of magnetic pole position when the magnet pieces are bonded is enhanced. Also, since the dimension accuracy of an adhesion face with adjoining magnet piece and adhesion face with the shaft is enhanced, the adhesive strength is enhanced. The less distortion amount of the magnetic flux density peak position (the enhancement of the accuracy of magnetic pole position) may equalize the carrying property of the developer and provide excellent image quality.
As is observed from Table 3, when the Example 3 is compared with the Comparative Example 2, the strength the magnetic flux density of the N1 pole (development pole) of the Example 3 is 106 mT. By contrast, the strength of the magnetic flux density of the Comparative Example 2 is 95 mT. Since the magnetic particles of the magnet piece are pole-anisotropically orientated by using the polyamide resin as the resin binder, referring to the magnet piece material of the N1 pole (for injection), and as a result, the magnetic path becomes long, it is turned out that the strength of the magnetic flux density is enhanced. The fogging of the developer may be able to be decreased and prevented by the high magnetic flux density.
As is observed from Table 3, when the Example 4 is compared with the Comparative Example 1, the N1 pole of the Example 4 has the high magnetic flux density (104 mT). Also, as is observed from Table 4, each of the pieces of the Example 4 has no warpage and crack. By contrast, the N1 pole of the Comparative Example 1 has the high magnetic flux density (104 mT). However, each of the pieces has warpage of 0.18 mm to 0.23 mm, and the crack occurs on the N1 pole, the S1 pole and the N3 pole. It is turned out that the use of the ethylene ethyl alcohol resin binder for the magnet piece as in the Example 4 expresses flexibility, and has no warpage and crack. Furthermore, since the magnet piece has flexibility and excellent dimension accuracy, the adhesiveness with the shaft or adjoining magnet piece is enhanced, and the adhesive strength is enhanced. The fogging of the developer may be able to decreased and prevented by the high magnetic flux density. The crack may cause the locally rapid reduction of the magnetic flux density, and generate white line or the like on the image. The prevention of the crack may provide excellent image quality.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-167000 | Jun 2004 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2005/009321 | 5/23/2005 | WO | 00 | 1/11/2008 |
