JP5075415B2 - Magnet roller - Google Patents

Description

  The present invention relates to a method of manufacturing a magnet roller used in an electrophotographic copying machine, a facsimile, a laser printer, and the like, and a magnet roller.

  A high magnetic flux density can be obtained by configuring at least one specific magnetic pole by a plurality of magnet pieces and arranging the magnet pieces so as to repel each other magnetically (Patent Document 1).

A resin injection gate port is provided on the end surface of the short side or near the short side and the magnet piece is injection-molded, and a plurality of magnet pieces are bonded onto the shaft to form a magnet roller. It can be improved (Patent Document 2).
JP-A-11-65283 JP 02-165176

  However, in Patent Document 1, a high magnetic flux density can be obtained by arranging the magnet pieces so as to be magnetically repelled, and the magnetic attraction force can be strengthened as a whole. In some cases, the magnetic attractive force cannot be selectively increased at the position, and as a result, developer fogging may occur.

  Moreover, in patent document 2, since one specific magnetic pole is not comprised by several magnet pieces, and this magnet piece is not arrange | positioned so that it may mutually repel magnetically, it cannot obtain a high magnetic flux density. There is a case.

The present invention is a magnet roller formed by laminating a plurality of magnet pieces formed of a mixture mainly composed of a ferromagnetic powder and a resin binder, wherein at least one specific magnetic pole is constituted by a plurality of magnet pieces, and the magnetic properties of the magnet pieces constituting the specific magnetic pole in the different ones, by Rukoto to form a single magnetic flux density peak by the plurality of magnets Peace, selectively magnetically attracted to a position deviated from the magnetic flux density peak position This is a magnet roller with increased strength.
The difference in the residual magnetic flux density value (Br value) of the magnet pieces constituting the specific magnetic pole is preferably 20 mT or more, more preferably 50 mT or more.
The angle between the magnetic flux density peak position and the magnetic attractive force peak position is preferably 3 ° or more, more preferably 5 ° or more and 15 ° or less. As a result, the magnetic attractive force peak value can be positioned on the downstream side of the development by simply increasing the magnetic flux density peak value of the developing magnetic pole.

  According to the present invention, it is possible to provide a magnetic attraction force peak at a position different from the magnetic flux density peak position in the vicinity of the specific magnetic pole, and the developer fog phenomenon can be prevented by using the magnet roller having this configuration.

The present invention is a magnet roller formed by laminating a plurality of magnet pieces formed of a mixture mainly composed of a ferromagnetic powder and a resin binder, wherein at least one specific magnetic pole is constituted by a plurality of magnet pieces, and A magnet roller in which the magnetic characteristics of the magnet pieces constituting the specific magnetic pole are different from each other.
Magnet pieces with different magnetic properties can be manufactured by applying a mixture of ferromagnetic powder and resin binder mainly with different magnetic fields, or by using different ferromagnetic powders and resins. There is a method in which a mixture mainly composed of a binder is applied with a magnetic field having the same strength.

  The present invention relates to a magnet roller formed by laminating a plurality of magnet pieces formed of a mixture mainly composed of a ferromagnetic powder and a resin binder. In one embodiment, the material of the magnet piece is 5 resin binders. From 50% by weight to 50% by weight (including lubricants, stabilizers, etc.) and ferromagnetic powder at 95% to 50% by weight, these are mixed and melt-kneaded to form pellets. The pellets are melted, and a molten resin magnet material is injected and injected from the injection port using the molding apparatus (mold) shown in FIG. 1, and orientation and magnetization is performed while applying a magnetic field to obtain each magnet piece. As a method of applying a magnetic field, a magnetic field is generally generated in a mold using a permanent magnet or an electromagnet as an excitation source. The applied magnetic field is generally 200 K · A / m to 2400 K · A / m.

  Even in the same resin magnet material, magnet pieces having different magnetic characteristics can be obtained by applying different magnetic fields.

  The magnet piece formed as described above is bonded onto the shaft to form a magnet roller as shown in FIG. 2 (perspective view) and FIG. 3 (cross-sectional view).

  The axial length of the magnet piece, the outer diameter of the magnet roller main body, the axial length of the shaft, and the outer diameter of the shaft may be appropriately designed to the desired dimensions. The shaft material may be either a magnetic material or a non-magnetic material. A SUM material or the like is used for the magnetic material, and a SUS material or the like is used for the non-magnetic material.

  The magnetic flux density in the circumferential direction of the obtained magnet roller is such that a probe (magnetic flux density sensor) is placed at a position (on the sleeve) 8 mm away from the center of the magnet roller while rotating the magnet roller while supporting the shafts at both ends of the magnet roller. The magnetic flux density value in the circumferential direction was measured with a Gauss meter. In addition, the circumferential magnetic attraction force of the obtained magnet roller is supported at a position 8 mm away from the center of the magnet roller while rotating the magnet roller while supporting the shafts on both ends of the magnet roller with an apparatus as shown in FIG. A SUM22 square bar (1 mm × 1 mm × 30 mm) was set, and the circumferential magnetic attractive force was measured with an electronic balance.

  In addition, even in the same applied magnetic field, magnet pieces having different magnetic characteristics can be obtained by changing the resin magnet material.

  The difference in the residual magnetic flux density value (Br value) of the magnet pieces constituting the specific magnetic pole is preferably 20 mT or more, more preferably 50 mT or more. If it is less than 20 mT, the effect of making the magnetic properties of the magnet pieces different may not appear.

The angle between the magnetic flux density peak position and the magnetic attraction force peak position is preferably 3 ° or more, more preferably 5 ° or more. If it is less than 3 °, the effect of providing an angle difference does not appear,
When the angle exceeds 15 °, the gap between the developing roller and the photosensitive member becomes wide, and it may be difficult to attract excess developer adhering to the photosensitive member to the developing roller side.

  Examples of the resin binder include ethylene ethyl acrylate resin, polyamide resin, polystyrene resin, PET (polyethylene terephthalate), PBT (polybutylene terephthalate), PPS (polyphenylene sulfide), EVA (ethylene-vinyl acetate copolymer), EVOH (ethylene- Vinyl alcohol copolymer) and PVC (polyvinyl chloride). These may be used alone or in combination. Alternatively, one kind or two or more kinds of thermosetting resins such as epoxy resin, phenol resin, urea resin, melamine resin, furan resin, unsaturated polyester resin, and polyimide resin can be mixed and used.

  Here, as the ferromagnetic powder, anisotropic ferrite magnetic powder having a chemical formula represented by MO.nFe2O3 (n is a natural number) can be used. As M in the formula, one type or two or more types such as Sr, Ba or lead are appropriately selected and used.

  In addition to anisotropic ferrite magnetic powder, isotropic ferrite magnetic powder, anisotropic rare earth magnetic powder (for example, SmFeN series), and isotropic rare earth magnetic powder (for example, NdFeB series) are used alone as the ferromagnetic powder. Alternatively, two or more types may be mixed and used. What is necessary is just to select suitably by the required magnetic flux density.

The content of the ferromagnetic powder (single magnetic powder or mixed magnetic powder) shown above is usually 50 to 95%. If its content is less than 50% by weight, due to the lack of magnetic powder, the magnetic properties of the magnet piece will be reduced, making it difficult to obtain the desired magnetic force,
Moreover, when those content rates exceed 95 weight%, there exists a possibility that a resin binder may become insufficient and a moldability may be impaired.

  Additives include magnetic powder surface treatment agents such as silane and titanate coupling agents, polystyrene and fluorine lubricants that improve fluidity, stabilizers, plasticizers, or flame retardants. It can be appropriately selected depending on the case.

  In the present invention, a typical magnet piece material has been described using an ethylene ethyl acrylate resin as a resin binder and anisotropic strontium ferrite or rare earth magnetic powder (SmFeN system) as a ferromagnetic powder, but is not limited thereto. It is not something.

  In the present specification, a magnet roller composed of five magnetic poles is mainly described. However, the present invention is not limited to a five-pole magnet roller. That is, the number of magnet pieces may be selected according to the desired magnetic flux density and magnetic field distribution, and the number of magnetic poles and the magnetic pole position may be set as appropriate.

  Furthermore, in the present invention, it is mainly explained that the magnet piece is formed by injection molding, but the molding of the magnet piece may be extrusion molding, compression molding or the like, and the molding method is changed for each magnet piece. May be.

Example 1
As a material for the magnet piece, 10% by weight (including lubricant and stabilizer) of ethylene ethyl acrylate resin (Nihon Unicar PES210) as a resin binder and anisotropic strontium ferrite (SrO.6Fe ₂ O ₃ ) as a ferromagnetic powder The powder (NF-350 manufactured by Nippon Valve Industry Co., Ltd.) was 90% by weight, and these were mixed, melted and kneaded into pellets. The pellet was melted and molded by injection-injecting a molten resin magnet material from the inlet using the molding apparatus (mold) shown in FIG. Orientation magnetization was performed by applying a magnetic field of 2400 K · A / m when forming the N1A piece, and applying a magnetic field of 1200 K · A / m when forming the N1B piece. Further, when molding pieces other than N1A and N1B, a magnetic field of 240 K · A / m to 2400 K · A / m was applied to perform orientation magnetization.

  When the magnetic properties of the two magnet pieces were measured with a vibration magnetometer manufactured by Riken Electronics, the residual magnetic flux density (Br value) of the N1A piece was 280 mT, and the residual magnetic flux density (Br value) of the N1B piece was 260 mT. It was.

  The other magnetic poles were one magnet piece for each magnetic pole, and the magnet pieces were formed while applying a magnetic field of 240 K · A / m to 2400 K · A / m.

  The magnet piece formed as described above is bonded onto the shaft to form a magnet roller as shown in FIG. 2 (perspective view) and FIG. 3 (cross-sectional view). The N1 pole that is the specific magnetic pole was formed of two magnet pieces, an N1A piece and an N1B piece.

  The axial length of the magnet piece was 320 mm, the shaft material was SUM22, the shaft outer diameter was 6 mm, and the total shaft length was 370 mm. Moreover, the outer diameter of the main part (portion where the magnet piece was bonded) of the magnet roller formed by bonding the magnet piece on the shaft was 13.6 mm.

  Here, the N1A piece side is on the downstream side of the development with respect to the line (angle reference 0 °) connecting the magnet roller center and the photoreceptor center.

  As for the magnetic flux density in the circumferential direction of the obtained magnet roller, set a probe (magnetic flux density sensor) at a position 8 mm away from the center of the magnet roller (on the sleeve), support both end shafts of the magnet roller, and rotate the magnet roller Then, the circumferential magnetic flux density value was measured with a gauss meter, and the circumferential magnetic flux density peak value and the position of the N1 pole as the specific magnetic pole are shown in Table 1.

Further, the circumferential magnetic attraction force of the obtained magnet roller is set at a position 8 mm away from the center of the magnet roller while rotating the magnet roller while supporting the shafts of both ends of the magnet roller using the apparatus of FIG. A SUM22 square bar (attraction force sensor: 1 mm × 1 mm × 30 mm) was set, and the force with which the SUM22 square bar was attracted to the magnet roller was measured with an electronic balance to obtain a circumferential magnetic attraction force. Table 1 shows the circumferential magnetic attractive force peak value and its position of the N1 pole that is the specific magnetic pole.
FIG. 5 shows the circumferential magnetic flux density pattern and the circumferential magnetic attractive force pattern measured as described above.

  Further, the obtained magnet roller was incorporated into a cartridge of Canon LBP5900, and the developer fog (carrier fog) was visually observed. The fog state was evaluated as ◎: no fogging problem, ◯: practically no fogging problem, Δ: slight fogging, ×: fogging, and listed in Table 1.

(Example 2)
In the two magnet pieces (N1A piece and N1B piece) that make up the N1 pole, which is the specific magnetic pole, N1A piece material is a mixture of ethylene ethyl acrylate resin and rare earth (SmFeN) magnetic powder as N1A piece material. the ethylene-ethyl acrylate resin and an anisotropic strontium (SrO · _6Fe 2 _{O 3)} is used a mixture of magnetic powder. In forming the N1A piece and the N1B piece, the magnetic field to be applied is 2400 K · A / m, and the magnetic characteristics of the two magnet pieces are different. When the magnetic properties of the two magnet pieces were measured with a vibration magnetometer manufactured by Riken Electronics, the residual magnetic flux density (Br value) of the N1A piece was 650 mT, and the residual magnetic flux density (Br value) of the N1B piece was 280 mT. It was.

  Except for the above, the same procedure as in Example 1 was performed.

  The obtained magnet roller measures the circumferential magnetic flux density and the circumferential magnetic attractive force in the same manner as described above, and shows the measured circumferential magnetic flux density pattern and circumferential magnetic attractive force pattern in FIG.

(Example 3)
The same procedure as in Example 2 was performed except that the residual magnetic flux density (Br value) of the N1A piece was 330 mT and the residual magnetic flux density (Br value) of the N1B piece was 280 mT.

Example 4
The same procedure as in Example 2 was performed except that the residual magnetic flux density (Br value) of the N1A piece was 450 mT and the residual magnetic flux density (Br value) of the N1B piece was 280 mT.

(Comparative Example 1)
The same procedure as in Example 1 was performed except that the residual magnetic flux density (Br value) of the N1A piece was 280 mT and the residual magnetic flux density (Br value) of the N1B piece was 280 mT.

(Comparative Example 2)
In the two magnet pieces (N1A piece and N1B piece) constituting the N1 pole which is the specific magnetic pole, a mixture of ethylene ethyl acrylate resin and rare earth (SmFeN-based) magnetic powder is used as the material for the N1A piece and the N1B piece. Further, the magnetic field applied when forming the N1A piece and the N1B piece was 240 K · A / m, and the magnetic characteristics of the two magnet pieces were the same. When the magnetic properties of the two magnet pieces were measured with a vibration magnetometer manufactured by Riken Denshi Co., the residual magnetic flux density (Br value) of the N1A piece and the N1B piece was 450 mT.

  Except for the above, the same procedure as in Example 1 was performed.

実施例１と比較例１を比べると、実施例１のＮ１極の磁束密度や磁気吸引力は、比較例１よりもやや小さくなっているが、Ｎ１極の磁気吸引力ピークが現像下流側に位置するため、該磁気吸引力により現像剤カブリを防止していることがわかる。

Comparing Example 1 and Comparative Example 1, the magnetic flux density and magnetic attractive force of the N1 pole of Example 1 are slightly smaller than those of Comparative Example 1, but the magnetic attractive force peak of the N1 pole is on the development downstream side. Therefore, it can be seen that the developer fog is prevented by the magnetic attractive force.

  Also in the comparison between Example 4 and Comparative Example 2, it can be seen that the same as described above.

  As can be seen from Examples 1 to 4, the developer fog disappears as the magnetic attractive force peak value increases.

Magnet piece molding machine (mold) Magnet roller of the present invention (perspective view) Magnet roller of the present invention (cross-sectional view) Magnetic attractive force measuring device Circumferential magnetic flux density pattern and magnetic attractive force pattern Another circumferential magnetic flux density pattern and magnetic attraction pattern

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnet piece 2 Orientation magnetization direction of magnetic particle 3 Excitation source 4 Yoke 5 Shaft 6 Magnet roller main-body part 7 Attraction force sensor 8 Sensor support jig 9 Electronic balance 10 Magnet roller support jig 11 Magnetic attraction force measuring device base 12 Sleeve 13 Circumferential magnetic flux density pattern 14 Circumferential magnetic attractive force pattern 15 Line connecting the center of the magnet roller and the center of the photosensitive member (angle reference 0 °)

Claims (4)

In the magnet roller formed by bonding a plurality of molded magnet pieces in a mixture composed mainly of a ferromagnetic powder and a resin binder, and constitute at least a developing pole in a plurality of magnet pieces and constituting the developing magnetic pole Of the magnet pieces, the residual magnetic flux density value (Br value) of the magnet piece located on the downstream side of the development is set larger than the residual magnetic flux density value (Br value) of the magnet piece located on the upstream side of the development , and the plurality of magnet pieces Rutotomoni to form a single magnetic flux density peak, the flux magnetic attractive force peak development downstream of density peaks is provided, characterized in that the angle between the magnetic flux density peak position and the magnetic attraction force peak position is less than 3 ° Magnet roller. 2. The magnet roller according to claim 1, wherein a difference in residual magnetic flux density (Br value) between magnet pieces constituting the developing magnetic pole is 20 mT or more. 2. The magnet roller according to claim 1, wherein a difference in residual magnetic flux density (Br value) between magnet pieces constituting the developing magnetic pole is 50 mT or more. The magnet roller according to claim 1 the angle between the front Ki磁 flux density peak position and the magnetic attraction force peak position is 15 ° or less.

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