JP2009122485A - Method for manufacturing magnet roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that in a conventional magnet roller with a built-in shaft, a magnetic field is applied at the vicinity of a counter-gate side for a long time and it is easily cooled, so that the axial magnetic flux density in the vicinity of the counter-gate side is increased, thereby increasing variations of axial magnetic flux density and increasing ripple value on the counter-gate side, resulting in degradation in the image quality on the counter-gate side. <P>SOLUTION: A method for manufacturing a magnet roller includes a step of injecting a melted mixture containing ferromagnetic powder and resin binder into a cavity to mold the magnet roller by applying a magnetic field. A molding die having a magnetic body disposed at an counter-gate side end forming part of the magnet roller is used. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a magnet roller used as a developing roller incorporated in an image forming apparatus such as a copying machine, a printer, or a facsimile. More specifically, the present invention relates to a method of manufacturing a shaft-integrated magnet roller that has improved variations in magnetic flux density in the axial direction.

  As the magnet roller, a magnet roller in which a magnet piece is arranged on the outer periphery of a metal shaft, a shaft unit integrated magnet roller in which a shaft unit and a main body unit are integrated, or the like is known. In particular, the shaft-integrated magnet roller is widely used as a developing roller incorporated in an image forming apparatus, taking advantage of low cost.

As a method of forming the shaft-integrated magnet roller, before injecting the molten resin magnet material into the cavity, the injection of the molten resin magnet material is started with the volume in the cavity being minimized, and the molten resin magnet is A method of forming a magnet roller by retreating the slide mold in accordance with the material injection to increase the cavity volume (Patent Document 1), and injecting a molten resin magnet adjusted to a melt viscosity of 30 poise to 1000 poise into the cavity Then, a method of forming a magnet roller (Patent Document 2) has been proposed.
JP-A-11-138562. JP-A-63-61274.

  However, Patent Document 1 gradually injects the molten resin magnet while retracting the slide mold, but the molten resin magnet material injected from the gate gradually moves to the opposite gate side together with the slide mold. When the magnetic field application time to the molten resin magnet material near the anti-gate side becomes long and the molten resin magnet material near the anti-gate side is cooled, the magnetic flux density near the anti-gate side becomes high. There is.

  Patent Document 2 does not have a slide mold like Patent Document 1, but the molten resin magnet material injected and injected from the gate side is filled from the opposite gate side, so that the magnetic field application time on the opposite gate side is also used. Becomes longer, and cooling from the vicinity of the counter-gate side may result in an increase in the magnetic flux density near the counter-gate side.

  In the process of injecting a molten mixture containing a ferromagnetic powder and a resin binder into a cavity and molding a magnet roller by applying a magnetic field, the present invention arranges a magnetic body at an end forming portion on the side opposite to the gate of the magnet roller. The manufacturing method of the magnet roller using the molding die which was made.

  Moreover, this invention is a manufacturing method of the magnet roller by which the said magnetic body is arrange | positioned at the movable metal mold | die.

  Moreover, this invention is a manufacturing method of the magnet roller by which the said magnetic body is arrange | positioned at the slide metal mold | die.

  Furthermore, the present invention is a method for manufacturing a magnet roller using a molding die in which the magnetic material has an axial length of 0.5 mm to 8 mm.

  According to the magnet roller manufacturing method of the present invention, the magnetic field applied to the vicinity of the opposite side of the molded magnet roller can be reduced. Thereby, it is possible to prevent the magnetic flux density on the side opposite to the gate of the magnet roller from increasing, and to improve the variation in the magnetic flux density in the axial direction.

  Next, the magnet roller manufacturing method of the present invention will be described in detail with an example.

  The present invention is a method of manufacturing a magnet roller using a molding die in which a magnetic material is disposed at an end forming portion on the side opposite to the gate of the magnet roller.

  A shaft-integrated magnet roller is formed using a forming apparatus as shown in FIG. The molten resin magnet material is injected and injected from the gate port (2), and the molten resin magnet material is generated by the magnetic field (240K · A / m to 2400K · A / m) generated from the excitation source (3) (5 locations). Is magnetized by orientation and cooled and solidified to form a shaft-integrated magnet roller as shown in FIG. In this case, as shown in FIG. 1, a movable mold is used in which a magnetic body (6) is disposed at the end forming portion on the opposite side of the magnet roller.

  On the other hand, conventionally, as shown in FIG. 3, for example, the end forming portion on the side opposite to the gate of the magnet roller is made of a non-magnetic material. The magnetic flux almost flowed to the magnet roller side. Therefore, in the conventional manufacturing method, the magnetic field application time to the molten resin magnet existing in the vicinity of the non-gate side is long and the cooling time is short (it is immediately cooled). FIG. 4 shows a shaft-integrated magnet roller formed by the conventional manufacturing method. Near the anti-gate side of the formed magnet roller, as shown in the axial magnetic flux density graph shown in FIG. 5, the magnetic flux density near the anti-gate side becomes high, and the variation (10) in the axial magnetic flux density increases. In addition, the ripple value (magnetic flux density change amount (12) / axial distance (11)) near the non-gate side may increase, causing problems such as a decrease in density at the edge of the image and developer spillage. there were.

  However, in the present invention, the magnetic flux generated from the excitation source (3) in the vicinity of the anti-gate side also flows in the direction of the end surface on the anti-gate side formed of a magnetic material, and the magnetic flux flows in the molten resin magnet material. Since the magnetic field is not concentrated, the magnetic field applied to the vicinity of the magnet roller on the side opposite to the gate side is appropriately reduced, and it is possible to prevent the magnetic flux density on the side opposite to the magnet roller from increasing.

  Furthermore, the present invention can also be applied to a method of manufacturing a magnet roller in which a molten mixture containing a ferromagnetic powder and a resin binder is gradually injected into a cavity while a slide mold is retracted to apply a magnetic field.

  A shaft-integrated magnet roller is formed using a forming apparatus as shown in FIG. First, the molten resin magnet material is injected while moving the slide mold A (13) in which the magnetic body (6) is arranged at the end forming portion on the opposite side of the magnet roller in the direction in which the cavity volume increases. The molten resin magnet material is oriented and magnetized by a magnetic field (240 K · A / m to 2400 K · A / m) generated from an excitation source (3) (5 locations), and the slide mold A is placed at a predetermined position. The movement of (13) is stopped and cooled and solidified to form a shaft-integrated magnet roller as shown in FIG.

  Alternatively, as shown in FIG. 8, the cavity volume of the slide mold B (14) (either a magnetic body or a non-magnetic body may be arranged at the end forming portion on the opposite side of the magnet roller) is increased. The molten resin magnet material is poured while moving in the direction to stop, the movement of the slide mold B (14) is stopped at a predetermined position, and the magnet roller radial center (shaft) is formed, and then While moving the slide mold C (15) in which the end forming part on the opposite side of the magnet roller with the magnetic body (6) is moved in the direction of increasing the cavity volume, the molten resin magnet material is injected, The molten resin magnet material is oriented and magnetized by a magnetic field (240 K · A / m to 2400 K · A / m) generated from an excitation source (3) (5 locations), and a slide mold C (15) is placed at a predetermined position. Stop moving and Roller radially outer peripheral portion (body portion) is formed, solidified by cooling to form a shaft-integrated magnet roller as shown in FIG. In the above process, when the magnet roller radial center (shaft) is formed, the magnetic field from the excitation source may be applied. When forming a high magnetic flux density magnet roller, it is desirable to apply a magnetic field. To improve the strength of the shaft, a low magnetic field is applied or no magnetic field is applied, and the flow in the cavity of the molten resin magnet is performed. It is desirable to improve the property.

  On the other hand, as shown in FIG. 10, for example, while a non-magnetic slide mold D (19) is moved in a direction in which the cavity volume increases, a molten resin magnet material is injected, and at a predetermined position. The movement of the slide mold D (19) was stopped, and the shaft portion and main body portion of the shaft-integrated magnet roller as shown in FIG. 11 were formed. Therefore, in the conventional manufacturing method, the magnetic field application time to the molten resin magnet existing in the vicinity of the non-gate side is long and the cooling time is short. For this reason, the magnetic flux density in the vicinity of the anti-gate of the formed magnet roller becomes high, the variation in the axial magnetic flux density becomes large, and the ripple value in the vicinity of the anti-gate side becomes large. In some cases, problems such as density reduction and developer spillage occurred.

  However, in the present invention, the magnetic flux generated from the excitation source near the opposite gate side also flows in the direction of the slide mold (tip on the cavity side) formed of a magnetic material, and the molten resin magnet material Since the flow of magnetic flux is not concentrated, the magnetic field applied to the vicinity of the magnet roller on the side opposite to the gate side is appropriately reduced, and it is possible to prevent the magnetic flux density on the side opposite to the magnet roller from increasing.

  In the present invention, the length of the magnetic body in the axial direction is preferably 0.5 mm to 8 mm, and more preferably 1 mm to 6 mm. If the length of the magnetic body in the axial direction is less than 0.5 mm, the force attracting the magnetic flux may be weakened and the desired effect may not be exhibited. If the length exceeds 8 mm, the magnetic flux is excessively concentrated on the magnetic body. In some cases, the magnetic flux density on the opposite side of the magnet roller is further lowered from a desired value.

  Although there is no restriction | limiting in particular as said magnetic body, SUM system (SUM22, SUM24, etc.), SC system (S50C, S55C, etc.), SCM system (SCM435, 440, etc.), SKD11, SKD61, and high-speed steel are preferable. Moreover, in order to improve durability, you may perform a hardening process and surface treatment.

  In the above invention, the following ferromagnetic powder and resin binder can be used as the magnet roller material.

Examples of the ferromagnetic powder include anisotropic ferrite magnetic powder having a chemical formula represented by MO.nFe ₂ O ₃ (n is a natural number). As M in the formula, one type or two or more types such as Sr, Ba or lead are appropriately selected and used.

  Further, as the ferromagnetic powder, anisotropic ferrite magnetic powder, isotropic ferrite magnetic powder, anisotropic rare earth magnetic powder (for example, SmFeN-based), and isotropic rare earth magnetic powder (for example, NdFeB-based) are used alone or in two types. You may mix and use the above. What is necessary is just to select suitably by the required magnetic flux density.

  Resin binders include polyamide resin, ethylene ethyl acrylate resin, polystyrene resin, PET (polyethylene terephthalate), PBT (polybutylene terephthalate), PPS (polyphenylene sulfide), EVA (ethylene-vinyl acetate copolymer), EVOH (ethylene-ethylene). 1 type or 2 or more types such as vinyl alcohol copolymer) and PVC (polyvinyl chloride), or thermosetting properties such as epoxy resin, phenol resin, urea resin, melamine resin, furan resin, unsaturated polyester resin and polyimide resin. One kind or two or more kinds of resins can be mixed and used.

  The content of the single magnetic powder or mixed magnetic powder shown above is preferably in the range of 50 to 95% by weight. If the content of the single magnetic powder or the mixed magnetic powder is less than 50% by weight, the magnetic properties of the magnet roller are lowered due to the lack of magnetic powder, making it difficult to obtain a desired magnetic force, and the content is 95% by weight. If it exceeds 1, the resin binder becomes insufficient and the moldability may be impaired.

  Additives include silane and titanate coupling agents as surface treatment agents for magnetic powders, polystyrene and fluorine lubricants that improve fluidity, stabilizers, plasticizers, or flame retardants. .

  Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1
As a magnet roller material of Figure 2, Nylon 6 resin in the resin binder (manufactured by Unitika A1015P) 10 wt% (lubricant, including the stabilizer), ferromagnetic powder anisotropic strontium ferrite (SrO · _6Fe 2 _{O 3} ) 90% by weight of powder (NF-350 manufactured by Nippon Valve Industry Co., Ltd.), these are mixed, melt-kneaded and formed into a pellet. Using the molding apparatus shown in FIG. 1, a resin magnet material in which the pellets are melted is injected and injected from the gate port (2), and a magnetic field (240 K · A / A) generated from the excitation source (3) (5 locations) is injected. m-2400 K · A / m), the molten resin magnet material is oriented and magnetized and cooled and solidified to form a shaft-integrated magnet roller as shown in FIG. In this case, a movable mold in which the SUM 22 (magnetic material) (6) is arranged at the end forming portion on the side opposite to the gate of the magnet roller is used, and the axial length of the SUM 22 is set to 4 mm.

The outer diameter of the magnet roller main body is 13.6 mm, the outer diameter of both end shafts is 5 mm, the axial length of the magnet roller main body is 320 mm, and the axial length of the magnet roller including both end shafts is 355 mm. .
The obtained magnet roller is supported at both ends of the magnet roller by 8 mm in the radial direction from the center of the magnet roller, and the tip of a Gauss meter probe (Bell magnetic flux density sensor) is installed at the center of the magnet roller axis. The magnet roller is rotated, the magnetic flux density in the circumferential direction of the magnet roller is measured, the magnetic flux density peak position of the main pole is detected, the axial magnetic flux density of the main pole is measured at that position, and the magnet roller body In the region excluding 10 mm in both axial directions, the difference between the maximum magnetic flux density and the minimum magnetic flux density was taken as the axial magnetic flux density variation, and the local magnetic flux density change rate (mT / mm: ripple) was measured. The ripple value is (local magnetic flux density variation mT) / (axial distance mm). The measurement results are shown in Table 1.

ここで、主極磁束密度ピーク値は８０ｍＴ以上が好ましい。また、軸方向磁束密度バラツキは６ｍＴ以下が好ましく、軸方向の局所的な磁束密度低下率（リップル）は０．５ｍＴ／ｍｍ以下が好ましい
（実施例２）
図７のマグネットローラ用材料として、樹脂バインダーにナイロン６樹脂（ユニチカ製Ａ１０１５Ｐ）を１０重量％（滑剤、安定剤を含む）、強磁性体粉末に異方性ストロンチウムフェライト（ＳｒＯ・６Ｆｅ_２Ｏ_３）粉末（日本弁柄工業製ＮＦ−３５０）を９０重量％とし、これらを混合して溶融混練し、ペレット状に成形する。図６の（ａ）のようにキャビティ容積が最小の状態で、ゲート口（２）から上記ペレットを溶融状態にしたものを注入し、該溶融樹脂磁石材料の注入とともにスライド金型Ａ（１３）を後退させてキャビティ容積を増大させ、２４０Ｋ・Ａ／ｍ〜２４００Ｋ・Ａ／ｍの磁場を印加（５箇所）しながら配向着磁して、該スライド金型Ａ（１３）を所定の位置まで後退させ、冷却固化させて図５のような軸一体型のマグネットローラを形成する。この場合、マグネットローラの反ゲート側の端部形成部にＳＵＭ２２（磁性体）（６）を配置したスライド金型Ａ（１３）を用い、該ＳＵＭ２２の軸方向長さを４ｍｍとする以外はすべて実施例１と同様に行った。測定結果を表１に示す。

Here, the main pole magnetic flux density peak value is preferably 80 mT or more. Moreover, the axial magnetic flux density variation is preferably 6 mT or less, and the local magnetic flux density reduction rate (ripple) in the axial direction is preferably 0.5 mT / mm or less (Example 2).
As a material for the magnet roller in FIG. 7, 10% by weight of nylon 6 resin (A1015P manufactured by Unitika) is used as a resin binder, and anisotropic strontium ferrite (SrO.6Fe ₂ O ₃ ) is used as a ferromagnetic powder. ) 90% by weight of powder (NF-350 manufactured by Nippon Valve Industry Co., Ltd.), these are mixed, melt-kneaded and formed into a pellet. As shown in FIG. 6 (a), in a state where the cavity volume is at a minimum, a molten state of the pellet is injected from the gate port (2), and slide mold A (13) is injected together with the injection of the molten resin magnet material. The cavity volume is increased by retreating, and orientation and magnetization is performed while applying a magnetic field of 240K · A / m to 2400K · A / m (5 locations), and the slide mold A (13) is moved to a predetermined position. It is made to retreat and solidify by cooling to form a shaft-integrated magnet roller as shown in FIG. In this case, all except for using the slide mold A (13) in which the SUM22 (magnetic material) (6) is arranged at the end forming portion on the opposite side of the magnet roller, and the axial length of the SUM22 is 4 mm. The same operation as in Example 1 was performed. The measurement results are shown in Table 1.

(Example 3)
The same procedure as in Example 1 was performed except that the axial length of the SUM22 (magnetic material) disposed in the end forming portion on the side opposite to the gate of the magnet roller was 0.5 mm. The measurement results are shown in Table 1.

Example 4
The same procedure as in Example 1 was performed except that the axial length of the SUM 22 (magnetic material) disposed in the end forming portion on the opposite side of the magnet roller was 8 mm. The measurement results are shown in Table 1.

(Example 5)
As shown in FIG. 8, using a molding device in which a magnetic body (6) is arranged on a slide mold C (15), a magnet roller radial center (shaft) is first molded, and then a magnet roller radial outer periphery is formed. All the processes were performed in the same manner as in Example 2 except that the magnet roller was formed in two steps of forming the part (main body part). The measurement results are shown in Table 1.

(Comparative Example 1)
The same procedure as in Example 1 was performed except that the material of the end forming portion on the opposite side of the magnet roller was SUS303 (non-magnetic material). The measurement results are shown in Table 1.

(Comparative Example 2)
In the slide mold A (13), everything was performed in the same manner as in Example 1 except that the material of the end forming portion on the opposite side of the magnet roller was SUS303 (non-magnetic material). The measurement results are shown in Table 1.

(Comparative Example 3)
In the molding apparatus shown in FIG. 8, everything was performed in the same manner as in Example 5 except that the material of the end forming portion on the side opposite to the gate of the magnet roller was SUS303 (non-magnetic material). The measurement results are shown in Table 1.

  Comparing main pole axial direction magnetic flux density variation and ripple value of Examples 1 to 5 and Comparative Examples 1 to 3 (non-magnetic material), Examples 1 to 5 have smaller main pole axial direction magnetic flux density variation and ripple value. You can see that The main pole axial direction magnetic flux density variation and ripple value of Comparative Examples 1 to 3 are generally in the upper limit of the preferable range, but when higher image quality is required, the variation and ripple value are further increased. Smaller is desirable.

Apparatus for molding magnet roller of the present invention (mold) Magnetic roller perspective view of the present invention Conventional magnet roller molding equipment (mold) Conventional magnet roller perspective view Axial magnetic flux density (figure explaining variation and ripple) (Magnet) (a) is a state before injection of molten resin magnet material (b) is a state of completion of injection of molten resin magnet material into the shaft portion (c) is to the main body Of molten resin magnet material injection completed Another magnet roller perspective view of the present invention Apparatus (mold) for molding another magnet roller of the present invention Another magnet roller perspective view of the present invention Equipment for forming another conventional magnet roller (mold) Another conventional magnet roller perspective view

Explanation of symbols

1 Molding space 2 Gate port 3 Excitation source 4 Fixed mold (non-magnetic material)
5 Movable mold (non-magnetic material)
6 Magnetic body 7 Magnet roller body 8 Magnet roller shaft 9 Axial magnetic flux density pattern 10 Magnetic flux density variation 11 Axial distance (1 mm)
12 Magnetic flux density change (mT)
13 Slide mold A
14 Slide mold B
15 Slide mold C
16 Molding Space 17 Magnet Roller Body 18 Magnet Roller Shaft 19 Slide Die D

Claims (4)

  In a process of injecting a molten mixture containing a ferromagnetic powder and a resin binder into a cavity and molding a magnetic roller by applying a magnetic field, a molding metal in which a magnetic material is disposed at an end forming portion on the side opposite to the gate of the magnet roller. A method of manufacturing a magnet roller, wherein a mold is used.     The method of manufacturing a magnet roller according to claim 1, wherein the magnetic body is arranged in a movable mold.   2. The method of manufacturing a magnet roller according to claim 1, wherein the magnetic body is disposed in a slide mold.     The method for manufacturing a magnet roller according to any one of claims 1 to 3, wherein the axial length of the magnetic body is 0.5 mm to 8 mm.

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