JP2009262403A - Method for manufacturing magnet roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that filling with a molten resin magnetic material having a cavity fill amount exceeding 98 wt.% under a primary pressure (injection pressure) in a conventional molding method may cause a lot of voids to occur in the inside of the molded article, consequently to increase a variation or ripple in axial magnetic flux density, and deteriorate the strength of a body part with creases occasionally occurring during transport or during use. <P>SOLUTION: The ratio of a fill amount due to the primary pressure (injection pressure) and pressure keeping when an outside diameter of a magnet roller body part is less than ϕ12 mm is set to be (a primary pressure):(a hold pressure)=85-98 wt.%:15-2 wt.%, and the ratio of the fill amount due to the primary pressure and the pressure keeping when the outside diameter of the magnet roller body part is ϕ12 mm to ϕ18 mm is set to be (the primary pressure):(the hold pressure)=92-98 wt.%:8-2 wt.%. The axial magnetic flux density becomes uniform and the strength of the body part are improved by molding a shaft part integrated magnet roller. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a magnet roller incorporated in an image forming apparatus such as a copying machine, a printer, or a facsimile.

  Conventionally, a magnet roller incorporated in an image forming apparatus using powder toner in a copying machine, a printer, a facsimile machine, etc., injects a molten mixture containing a ferromagnetic powder and a resin binder into a cavity and applies a magnetic field to the magnet roller. Manufactured by injection molding.

  However, in the conventional injection molding method, air in the cavity is entrained when molten resin magnet material is injected, and voids occur frequently inside the molded product, causing variations in magnetic flux density and ripples in the axial direction, and lowering the body strength. There was a case.

In recent years, attempts to improve these problems have been proposed. That is, (1) in accordance with the injection speed of the molten resin magnet material, the slide mold is retracted while injecting the molten resin magnet material, the molding space is enlarged to a predetermined size, and the magnet roller is formed, thereby forming the magnet A method in which magnetic characteristics in the length direction of the roller are uniform (Patent Document 1), (2) A magnet is formed by centripetally injecting molten resin magnet material from two or more locations toward the central axis of the magnet roller. For example, there is a method (Patent Document 2) in which fluctuations in magnetic flux density on the surface of the roller portion are reduced.
JP-A-10-67030 JP-A 63-30875

  However, in Patent Documents 1 and 2, although the magnetic flux density in the longitudinal direction is uniform to a certain extent, the magnet main body has a large variation in strength and the strength is low. May be broken, and development may not be possible.

  The present invention relates to the ratio of the filling amount due to the primary pressure and the holding pressure when the outer diameter of the magnet roller main body is less than φ12 mm in the molding of a shaft-integrated magnet roller using a mixture mainly composed of ferromagnetic powder and resin binder. Is the primary pressure: holding pressure = 85 to 98 wt%: 15 to 2 wt%, and the ratio between the primary pressure and the filling amount by holding pressure when the outer diameter of the magnet roller main body is 12 mm or more and 18 mm or less. Primary pressure: holding pressure = 92 to 98 wt%: 8 to 2 wt% of the magnet roller manufacturing method.

  Further, the present invention provides a magnet roller formed by expanding the molding space to a predetermined size by retreating the slide mold while injecting the molten resin magnet material in accordance with the injection speed of the molten resin magnet material. It is a manufacturing method.

  According to the present invention, the magnetic flux density in the longitudinal direction becomes uniform, particularly ripple performance (local change in magnetic flux density) is improved, and the strength of the main body is improved, during transportation, assembling into the sleeve and during use. Breaking can be prevented.

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

  In a conventional injection molding method in which a molten mixture containing a ferromagnetic powder and a resin binder is injected into a cavity and a magnetic roller is molded by applying a magnetic field, a filling amount (cavity) corresponding to the cavity space is formed by primary pressure (injection pressure). The holding pressure was positioned as a pressure for preventing the backflow of the molten resin magnet material filled in the cavity after filling with the primary pressure.

  However, in order to improve the strength of the main body, the present inventors have conventionally responded by adjusting the additive amount of the additive and the molecular weight of the resin binder, but only by adjusting the resin magnet material composition, In order to reduce the entrainment of air, etc. in the cavity when injecting the molten resin magnet material, which has been a problem in the past, we focused on the relationship between the primary pressure and the holding pressure, which is the molding condition. As a result, when the filling amount at the primary pressure was reduced until now, there was a problem that the magnetic characteristics were disturbed by the flow mark, but the ratio of the filling amount by the primary pressure and the holding pressure should be controlled within a specific range. Thus, it has been found that air entrainment is reduced, and conventional problems such as variations in magnetic flux density in the axial direction, generation of ripples, or reduction in strength of the main body can be solved.

  That is, the present invention provides a filling amount by primary pressure and holding pressure when the outer diameter of the magnet roller main body is less than φ12 mm in molding of a shaft-integrated magnet roller using a mixture mainly composed of ferromagnetic powder and resin binder. The ratio of the primary pressure: the holding pressure = 85 to 98 wt%: 15 to 2 wt%, and the ratio between the primary pressure and the filling amount by the holding pressure when the outer diameter of the magnet roller main body is φ12 mm to φ18 mm is the primary pressure: This is a magnet roller manufacturing method in which holding pressure = 92 to 98 wt%: 8 to 2 wt%.

  For example, the resin binder is 5 to 50% by weight of a polyamide resin (including a lubricant, a stabilizer, etc.), and the ferromagnetic powder is an anisotropic ferrite magnetic powder of 95 to 50% by weight. As a surface treatment agent for the ferromagnetic powder, a coupling agent such as silane or titanate, a polystyrene or fluorine lubricant for improving fluidity, a stabilizer, a plasticizer, or a flame retardant is added, and mixed and dispersed. And then melt-kneaded and formed into pellets.

  The pellet is melted and injection molded using a molding apparatus (mold) as shown in FIG. 1 while applying a magnetic field of 150 K · A / m to 2400 K · A / m, and the main body as shown in FIG. A shaft-integrated magnet roller having an outer diameter of less than φ12 mm (eg, φ9.6 mm) or φ12 mm to φ18 mm (eg, φ13.6 mm) is obtained. The orientation magnetization magnetic field applied to each magnetic pole applied at the time of molding may be appropriately selected according to the magnetic flux density specification required for each magnetic pole. Further, depending on the required magnetic properties, the orientation magnetization magnetic field may not be applied at the time of molding, and may be magnetized after molding.

  When the outer diameter of the magnet body is less than φ12 mm, the amount of molten resin magnet material filled at the primary pressure in the above-mentioned injection molding is 85 to 98 wt% of the whole, and the remaining molten resin magnet material (15 to 2 wt%) is maintained. Fill with pressure.

  If the filling amount at the primary pressure is less than 85 wt%, burrs, excessive dimensions, mold release defects may occur, and wear of the mold may increase. Moreover, when the filling amount at the primary pressure exceeds 98 wt%, short shots, sink marks, and shrinkage distortion occur, and the strength of the main body decreases, and ripples (local changes in axial magnetic flux density) increase. There is a case.

  Similarly, when the outer diameter of the magnet main body is φ12 mm or more and φ18 mm or less, the amount of the molten resin magnet material filled at the primary pressure in the injection molding is 92 to 98 wt% of the whole, and the remaining molten resin magnet material (8 to 2 wt%) is filled with holding pressure.

  If the filling amount at the primary pressure is less than 92 wt%, burrs, excessive dimensions, mold release defects may occur, and mold wear may increase. Moreover, when the filling amount at the primary pressure exceeds 98 wt%, short shots, sink marks, and shrinkage distortion occur, and the strength of the main body decreases, and ripples (local changes in axial magnetic flux density) increase. There is a case.

  In the conventional injection molding method, when molten resin magnet material is injected, air or the like in the cavity is involved, and voids occur frequently inside the molded product, causing variations in the magnetic flux density in the axial direction, ripples, or a decrease in body strength However, in the present invention, by controlling the amount filled in the cavity with the primary pressure, the voids in the molded product are reduced, and the variation and ripple of the magnetic flux density in the axial direction are improved. Strength is also improved.

  In the present invention, the reason is not clear, but when the magnet main body diameter is less than φ12 mm, the sink of the main body (the outer diameter is slightly smaller) is relatively small, and the cavity volume is small. Although the amount of entrainment is reduced, by setting the filling amount at the primary pressure to 85 to 98 wt%, and when the magnet body diameter is φ12 mm or more and φ18 mm or less, the sink of the main body is relatively large, and the cavity volume is relatively large. However, when the filling amount at the primary pressure is set to 92 to 98 wt%, the problem can be solved as described above.

  Preferably, according to the present invention, in the molding described above, in accordance with the injection speed of the molten resin magnet material, the slide mold is moved backward while injecting the molten resin magnet material, and the molding space is enlarged to a predetermined size. It is a manufacturing method of a magnet roller.

By molding the magnet roller with a molding device (mold) as shown in FIG.
Since molten resin magnet material is gradually injected into the cavity from the gate side, entrainment of air, etc. is drastically reduced, resulting in drastic reduction of voids inside the molded product, resulting in small variations in magnetic flux density and ripples in the axial direction. In addition, the strength of the main body is improved.

  Here, the ferrite magnetic powder may be isotropic, anisotropic, or a mixed powder thereof, but anisotropic ferrite magnetic powder is more preferable in view of contribution to magnetic properties.

Examples of the ferrite magnetic powder include 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 or more of Sr, Ba, lead and the like 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 ferromagnetic powder shown above is preferably in the range of 50 to 95% by weight. If the content of the ferromagnetic powder is less than 50% by weight, the magnetic properties of the magnet piece are deteriorated due to insufficient magnetic powder, making it difficult to obtain a desired magnetic force, and the content of the ferromagnetic powder exceeds 95% by weight. If the binder is insufficient, 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. .

  Further, in this specification, a magnet roll having a five-pole configuration is illustrated, but the present invention is not limited to a five-pole magnet roll. That is, the number of magnetic poles and the magnetic pole position may be set as appropriate according to the desired magnetic flux density and magnetic field distribution.

  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 material for the magnet roller in FIG. 2, 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. Using the molding apparatus shown in FIG. 1, a magnetic material (240 K · A / m to 2400 K · A / 2) generated from an excitation source (5 locations) by injecting and injecting a resin magnet material in which the pellets are melted from the gate port is used. According to m), the molten resin magnet material was oriented and magnetized and cooled and solidified to form a shaft-integrated magnet roller as shown in FIG. In this case, a molten resin magnet material corresponding to 90 wt% of the cavity filling amount was injected at the primary pressure (injection pressure), and a molten resin magnet material corresponding to 10 wt% of the cavity filling amount was injected at the holding pressure. The injection speed of the molten resin magnet material having the primary pressure was 100 mm / sec, the pressure was 200 MPa, the injection speed by holding pressure was 3 mm / sec, and the pressure was 200 MPa.

  The outer diameter of the magnet roller main body was φ9.6 mm, the outer diameter of both end shaft portions was φ5, the axial length of the magnet roller main body portion was 220 mm, and the axial length of the magnet roller including both end shaft portions was 260 mm.

The obtained magnet roller is supported by the shafts at both ends of the magnet roller, separated from the center of the magnet roller by 6 mm in the radial direction, and the tip of the gauss meter probe (Bell magnetic flux density sensor) is installed at the center of the magnet roller. 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 measurement results are shown in Table 1.

  Here, the main pole magnetic flux density is preferably 75 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.

  In addition, with the apparatus shown in FIG. 4, 10 mm of both ends of the main body of the magnet roller are fixed and supported, the central portion in the axial direction of the magnet roller is pressed with a pressurizing jig, and the maximum strength until the main body is broken is It was. The pressure device was AGS-H (5 kN) manufactured by Shimadzu Corporation, the pressure rate was 50 mm / min, and the tip shape of the pressure jig was R3 mm. The measurement results are shown in Table 1.

  Here, the main body strength is preferably 120 N or more.

(Example 2)
The same procedure as in Example 1 was performed except that the filling amount by primary pressure was 85 wt% and the filling amount by holding pressure was 15 wt%.

(Example 3)
The same procedure as in Example 1 was performed except that the filling amount by primary pressure was 98 wt% and the filling amount by holding pressure was 2 wt%.

Example 4
The same procedure as in Example 1 was performed except that the outer diameter of the magnet roller main body was 13.6 mm, the filling amount by the primary pressure was 92 wt%, and the filling amount by the holding pressure was 8 wt%.
The main pole magnetic flux density is preferably 85 mT or more, and the main body strength is preferably 400 N or more.

(Example 5)
The same procedure as in Example 1 was performed except that the outer diameter of the magnet roller main body was 13.6 mm, the filling amount by primary pressure was 98 wt%, and the filling amount by holding pressure was 2 wt%.
The main pole magnetic flux density is preferably 85 mT or more, and the main body strength is preferably 400 N or more.

(Example 6)
The same procedure as in Example 1 was performed except that the outer diameter of the magnet roller main body was 18.0 mm, the filling amount by the primary pressure was 92 wt%, and the filling amount by the holding pressure was 8 wt%.
The main pole magnetic flux density is preferably 100 mT or more, and the main body strength is preferably 600 N or more.

(Example 7)
The same procedure as in Example 1 was performed except that the outer diameter of the magnet roller main body was 18.0 mm, the filling amount by primary pressure was 98 wt%, and the filling amount by holding pressure was 2 wt%.
The main pole magnetic flux density is preferably 100 mT or more, and the main body strength is preferably 600 N or more.

(Example 8)
Using the molding apparatus (mold) shown in FIG. 3, the slide mold is retracted while injecting the molten resin magnet material, and the molding space is enlarged to a predetermined size in accordance with the injection speed of the molten resin magnet material. Except that the roller was molded, the same procedure as in Example 1 was performed.

Example 9
Using the molding apparatus (mold) shown in FIG. 3, the slide mold is retracted while injecting the molten resin magnet material, and the molding space is enlarged to a predetermined size in accordance with the injection speed of the molten resin magnet material. Except that the roller was molded, everything was performed in the same manner as in Example 2.

(Example 10)
Using the molding apparatus (mold) shown in FIG. 3, the slide mold is retracted while injecting the molten resin magnet material, and the molding space is enlarged to a predetermined size in accordance with the injection speed of the molten resin magnet material. Except that the roller was molded, the same procedure as in Example 3 was performed.

Example 11
Using the molding apparatus (mold) shown in FIG. 3, the slide mold is retracted while injecting the molten resin magnet material, and the molding space is enlarged to a predetermined size in accordance with the injection speed of the molten resin magnet material. Except that the roller was molded, the same procedure as in Example 4 was performed.

Example 12
Using the molding apparatus (mold) shown in FIG. 3, the slide mold is retracted while injecting the molten resin magnet material, and the molding space is enlarged to a predetermined size in accordance with the injection speed of the molten resin magnet material. Except that the roller was molded, the same procedure as in Example 5 was performed.

(Comparative Example 1)
The same procedure as in Example 1 was performed except that the filling amount by the primary pressure was 100 wt% and the filling amount by the holding pressure was 0 wt%, that is, the holding pressure served to prevent the backflow of the molten resin magnet material.

(Comparative Example 2)
The same procedure as in Example 1 was performed except that the filling amount by primary pressure was 80 wt% and the filling amount by holding pressure was 20 wt%.

(Comparative Example 3)
The outer diameter of the magnet roller main body is 13.6 mm, the filling amount by the primary pressure is 100 wt%, the filling amount by the holding pressure is 0 wt%, that is, the holding pressure serves to prevent the backflow of the molten resin magnet material. Were all carried out in the same manner as in Example 1.

(Comparative Example 4)
The same procedure as in Example 1 was performed except that the outer diameter of the magnet roller main body was 13.6 mm, the filling amount by primary pressure was 90 wt%, and the filling amount by holding pressure was 10 wt%.

(Comparative Example 5)
Using the molding apparatus (mold) shown in FIG. 3, the slide mold is retracted while injecting the molten resin magnet material, and the molding space is enlarged to a predetermined size in accordance with the injection speed of the molten resin magnet material. The same as in Example 1 except that the roller is molded and the filling amount by the primary pressure is 100 wt% and the filling amount by the holding pressure is 0 wt%, that is, the holding pressure serves to prevent the backflow of the molten resin magnet material. went.

(Comparative Example 6)
Using the molding apparatus (mold) shown in FIG. 3, the slide mold is retracted while injecting the molten resin magnet material, and the molding space is enlarged to a predetermined size in accordance with the injection speed of the molten resin magnet material. The same procedure as in Example 1 was performed except that the roller was molded, the filling amount by primary pressure was 80 wt%, and the filling amount by holding pressure was 20 wt%.

  Comparing Examples 1 to 12 with Comparative Examples 1 to 6, it can be seen that in this example, variation in axial magnetic flux density and ripple are reduced, and the strength of the main body is improved.

  When Examples 1-3 are compared with Comparative Examples 1-2, the ratio of the primary pressure (injection pressure) and the filling amount by holding pressure when the outer diameter of the magnet roller main body is less than φ12 mm is expressed as primary pressure: holding pressure = 85. It can be seen that by setting it to ˜98 wt%: 15 to 2 wt%, the axial magnetic flux density variation and ripple are reduced, and the main body strength is improved.

  Comparing Examples 4 to 7 and Comparative Examples 3 to 4, the ratio of the primary pressure and the filling amount by holding pressure when the outer diameter of the magnet roller main body is φ12 mm or more and φ18 mm or less, the primary pressure: holding pressure = 92 to 98 wt. %: It can be seen that by setting the content to 8 to 2 wt%, variation in axial magnetic flux density and ripple are reduced, and the strength of the main body is improved.

  When Examples 8-10 are compared with Comparative Examples 5-6, the primary pressure (injection) when the outer diameter of the magnet roller body is less than φ12 mm, as in the comparison between Examples 1-3 and Comparative Examples 1-2. Pressure) and the filling amount ratio by holding pressure are set to primary pressure: holding pressure = 85 to 98 wt%: 15 to 2 wt%, the axial magnetic flux density variation and ripple are reduced, and the body strength is improved. You can see that

  Further, when Examples 1 to 7 are compared with Examples 8 to 12, while using the molding apparatus (mold) shown in FIG. 3, while injecting the molten resin magnet material according to the injection speed of the molten resin magnet material, In Examples 8 to 12, which are molding methods of a magnet roller in which the molding die is retreated and the molding space is expanded to a predetermined size, the axial magnetic flux density variation and ripple are further reduced, and the body strength is improved. You can see that

Magnet roller molding device (mold) Perspective view of magnet roller Another magnet roller molding device (mold) Magnet roller body strength measuring device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Molding space 2 Excitation source 3 Inlet 4 Fixed metal mold 5 Movable metal mold 6 Magnet roller main-body part 7 Magnet roller axial part 8 Slide metal mold | die 9 Pressurizing jig 10 Magnet roller main-body part fixing jig 11 Main-body part intensity | strength measuring apparatus Base stand

Claims (2)

  In a method for forming a shaft-integrated magnet roller using a mixture mainly composed of ferromagnetic powder and resin binder, the filling amount by primary pressure (injection pressure) and holding pressure when the outer diameter of the magnet roller body is less than φ12 mm The ratio of the primary pressure: the holding pressure = 85 to 98 wt%: 15 to 2 wt%, and the ratio between the primary pressure and the filling amount by the holding pressure when the outer diameter of the magnet roller main body is φ12 mm to φ18 mm is the primary pressure: Holding pressure = 92 to 98 wt%: 8 to 2 wt%   In the above molding, the magnet roller is molded by reversing the slide mold while injecting the molten resin magnet material and expanding the molding space to a predetermined size in accordance with the injection speed of the molten resin magnet material. Item 2. A method for manufacturing a magnet roller according to Item 1.

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