JP2006215148A - Magnet roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnet roller having a developing area where developer is attracted to the surface of a sleeve and conveyed to a developing position and a developer peeling area where developer passed through the developing area is peeled from the sleeve, the magnet roller in which unsatisfactory ability to peel developer in the developer peeling area, resulting in ghost and nonuniform screw pitch, etc. in an image is prevented. <P>SOLUTION: The range of the developer peeling area is set to 25° or more, the developing area having a magnetic flux density of 8 mT or below and being sandwiched between the same magnetic poles each of which has a magnetic flux density of 8 mT or above. The developing material peeling area is also set so as to have one maximal value of the magnetic flux density. A difference between the maximum value and the minimum value within the range is set to 0.5 mT to 5mT. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  Generally, a magnet roller incorporated in an image forming apparatus using powder toner in a copying machine, a printer, a facsimile machine, or the like is configured as follows.

That is, (1) the area of the magnet roller corresponding to the part from which the developer is peeled is substantially 0 gauss. (Patent Document 1) (2) An angle range in which the amount of change in magnetic flux density in the developer peeling area is approximately 1.1 mT / degree is set to 45 degrees or more, and the minimum value is set to approximately 10 mT or less. is there. (Patent Document 2)
JP 08-15589 JP 2001-142302 A

  However, in Patent Document 1, there is a case where the developer is not completely peeled off, the developer is swung around, and a ghost is generated in the image or a screw pitch unevenness is generated. is there.

  Also, in Patent Document 2, as in Patent Document 1, the developer may not be completely peeled off, causing the developer to hang around, causing ghosting in the image, screw pitch unevenness, and the like. May occur.

  The present invention provides a magnetic flux density of 8 mT in a magnet roller having a developing area that adsorbs developer to the sleeve surface and conveys it to the developing position, and a developer peeling area that peels the developer that has passed through the developing area from the sleeve surface. The region where the magnetic flux density of 8 mT or less sandwiched between the magnetic poles exceeding 25 degrees or more is defined as a developer separation region, and within the developer separation region, the magnetic flux density has one maximum value, The difference between the minimum value and the maximum value is set to be 0.5 mT to 5 mT.

  According to the present invention, in the magnet roller formed by bonding a plurality of magnet pieces, the magnet pieces are arranged in the developer peeling region.

  According to the present invention (Claim 1), the release of the developer is improved, the developer can be prevented from being swung around, ghosts and screw pitch unevenness can be prevented from being generated in the image, and a good image can be obtained.

  According to the present invention (Claim 2), in a magnet piece bonded type magnet roller, it becomes easy to form a low magnetic flux density pattern in the developer stripping region of the present invention, and the developer stripping becomes good. Contouring can be prevented, and ghosts and screw pitch unevenness can be prevented from occurring in the image, and a good image can be obtained.

  The present invention provides a magnetic flux density of 8 mT in a magnet roller having a developing area that adsorbs developer to the sleeve surface and conveys it to the developing position, and a developer peeling area that peels the developer that has passed through the developing area from the sleeve surface. The region where the magnetic flux density of 8 mT or less sandwiched between the magnetic poles exceeding 25 degrees or more is defined as a developer separation region, and within the developer separation region, the magnetic flux density has one maximum value, The magnet roller is characterized in that the difference between the minimum value and the maximum value is set to 0.5 mT to 5 mT.

  The low magnetic flux density pattern in the developer peeling area of the conventional magnet roller does not have the maximum value (convex part) of the magnetic flux density in the low magnetic flux density area, as in Patent Documents 1 and 2, and the magnetic flux density gradually decreases. The magnetic flux density pattern has a shape in which the magnetic flux density gradually rises from the minimum value.

  In the present invention, for example, magnetic particles of a molten resin magnet are applied by a mold (magnetic circuit) as shown in FIG. 1 and a magnetic field of 240 K · A / m to 2400 K · A / m is applied by an electromagnet or a permanent magnet. A magnet piece is formed by extrusion while being magnetized, and the magnetic particles of the molten resin magnet are converted into 240K · A / m to 2400K · by an electromagnet or permanent magnet in a mold (magnetic circuit) as shown in FIG. A magnetic field of A / m is applied and injection molding is performed while orientation magnetization is performed to form a magnet piece, and a plurality of magnet pieces thus molded are bonded to the outer peripheral surface of the shaft to form a magnet roller as shown in FIG. Constitute.

  Various methods of forming the low magnetic flux density pattern in the developer peeling region of the present invention can be considered. For example, as shown in FIG. 4, the shoulder portions of the two magnetic pole patterns adjacent to the developer peeling region can be demagnetized, As shown in FIG. 5, a notch may be provided in two magnet pieces adjacent to the developer peeling area.

  In this way, the low magnetic flux density pattern of the present invention can be obtained easily and at low cost, the developer can be peeled well, the developer can be prevented from swirling, and in the image quality, ghost and screw pitch unevenness can be prevented, A good image is obtained.

  Here, the magnet piece is mainly composed of a mixture composed of 50 wt% to 95 wt% of anisotropic ferrite magnetic powder and 5 wt% to 50 wt% of a resin binder (ethylene ethyl acrylate resin). Depending on the surface treatment agent of magnetic powder, coupling agents such as silane and titanate, polystyrene and fluorine lubricants that improve fluidity, stabilizers, plasticizers, or flame retardants are added and mixed. After being dispersed, melt-kneaded and formed into a pellet, extrusion molding or injection molding is performed.

  The orientation magnetization magnetic field 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.

  Moreover, a complex magnetic flux density pattern can be obtained by orienting and magnetizing magnetic particles of a magnet piece using the resin magnet material in various directions and bonding the magnet pieces together to form a magnet roller.

  According to another aspect of the present invention, there is provided a magnet roller in which a magnet piece is disposed in a developer peeling region in a magnet roller formed by bonding a plurality of magnet pieces.

  One or more magnet pieces for forming a low magnetic flux density pattern are disposed in the developer peeling area. The magnet piece may be a normal magnet piece molding method (extrusion molding or injection molding), and a magnetic field is applied at the same time as the molding to orient and magnetize the magnetic particles. It may be magnetized.

  As shown in FIG. 6, the magnet piece is magnetized by bringing a magnetizing yoke into contact with the outer peripheral surface of the magnet piece and applying a magnetic field to form a magnet roller as shown in FIG. The width of the magnetized yoke and the strength of the magnetic field to be applied are appropriately selected according to the magnetic potential of the magnet piece and the magnetic characteristics of both adjacent poles, and the magnetic flux density of 8 mT or less sandwiched between the same magnetic poles exceeding the magnetic flux density of 8 mT. An area where the range of 25 ° C. or more is defined as a developer peeling area, and the developer peeling area has one maximum magnetic flux density, and the difference between the minimum value and the maximum value in the area is 0.5 mT. What is necessary is just to be set to -5mT.

  In this case, when the range of the magnetic flux density of 8 mT or less sandwiched between the same magnetic poles exceeding the magnetic flux density of 8 mT is less than 25 degrees, the peeled state of the developer is deteriorated and the spinning occurs. On the other hand, when the difference between the minimum value and the maximum value is less than 0.5 mT, or when it exceeds 5 mT, the peeled state of the developer is deteriorated, and spinning occurs.

  Further, when the difference between the minimum value and the maximum value is 0.5 mT to 3 mT, the peeling of the developer is further improved.

  Further, by setting the range of the magnetic flux density of 8 mT or less sandwiched between the same magnetic poles exceeding the magnetic flux density of 8 mT to 35 degrees or more, the peelability of the developer is further improved.

  At this time, the width of the magnetized yoke is not particularly limited with respect to the width of the outer peripheral surface of the magnet, but a good pattern can be obtained when the width is 20% to 100%.

Here, examples of the magnetic 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 or more of Sr, Ba, lead and the like are appropriately selected and used.

  As the resin binder, one or more of ethylene-ethyl acrylate resin, polyamide resin, polystyrene resin, PET, PBT, PPS, EVA, EVOH, PVC, etc., or epoxy resin, phenol resin, urea resin, melamine resin In addition, one kind or two or more kinds of thermosetting resins such as furan resin, unsaturated polyester resin, and polyimide resin can be mixed and used.

  Further, depending on the required magnetic flux density, as magnetic powder, anisotropic ferrite magnetic powder, isotropic ferrite magnetic powder, anisotropic rare earth magnetic powder (for example, SmFeN system), isotropic rare earth magnetic powder (for example, NeFeB system) May be used alone or in admixture of two or more.

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

  In each magnet piece constituting the magnet roller, it is not necessary for all the magnet pieces to use the same resin magnet material, and the magnet roller may be constituted by appropriately combining.

  That is, the magnet pieces used in the present invention need not all be made of the same material (binder, magnetic powder, etc.), so even if different kinds of magnet pieces are arbitrarily combined, the magnetic characteristics can be adjusted, and the cost can be reduced. Good.

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 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, when a magnetic field is applied simultaneously with molding, in order to improve the demoldability of the molded product, to prevent the adhesion of dust such as magcus of the molded product, and to facilitate the handling of the magnet piece, It may be demagnetized once outside the mold and then magnetized.

  Furthermore, in the above description, the magnet piece is bonded to the shaft. However, a mixture mainly composed of ferromagnetic powder and resin binder is used as an injection molded magnet roller with the same material or shaft inserted in the shaft. As described above, a low magnetic flux density pattern in the developer peeling area may be formed. In this case, since the process of bonding the magnet pieces can be omitted, the cost is reduced.

  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 magnet piece material, 10% by weight of ethylene ethyl acrylate resin (PES220 made by Nihon Unicar) as resin binder (including lubricant, plasticizer and stabilizer) and anisotropic strontium ferrite magnetic powder (SrO.6Fe ₂ O as magnetic powder) ₃ ) 90% by weight, these are mixed, melt-kneaded, formed into pellets, the pellets are melted, and using an extrusion die as shown in FIG. 1, N1 pole, N2 pole, S2 Magnet pieces for the pole, the S3 pole, and the developer peeling pole were extruded while applying a magnetic field of 800 to 1200 K · A / m while orientationally magnetizing the magnetic particles of the molten resin magnet. In addition, as magnet piece material, ethylene ethyl acrylate resin (DPDJ-9169 manufactured by Nihon Unicar) as resin binder is 10% by weight (including lubricant, plasticizer and stabilizer), and anisotropic strontium ferrite magnetic powder (SrO) as magnetic powder.・ 6Fe ₂ O ₃ ) 90% by weight, these are mixed, melt-kneaded, formed into pellets, the pellets are melted, and an injection mold as shown in FIG. The magnet piece was injection molded while applying a magnetic field of 1500 K · A / m while magnetically orienting and magnetizing magnetic particles of the molten resin magnet.

  Only in the developer peeling magnet piece, the magnetized yoke (the width of the magnetized yoke is 20% of the width of the magnet piece outer peripheral surface) is brought into contact with the outer peripheral surface of the magnet piece as shown in FIG. Magnetization was performed at 120 K · A / m.

  The magnet piece of 6 poles molded as described above was bonded to the outer peripheral surface of the shaft to obtain a magnet roller as shown in FIG.

The outer diameter of the magnet roller main body was 13.6, the length of the magnet main body was 320 mm, and the outer diameter of the shaft was φ6 (material SUM22). (Fig. 8)
The probe (magnetic flux density sensor) is set at a position 8 mm away from the center of the magnet roller (on the sleeve) while supporting the shafts on both ends of the obtained magnet roller and rotating the magnet roller. The circumferential magnetic flux density pattern was measured.

  The low magnetic flux density range with a magnetic flux density of 8 mT or less is the range shown in a of FIG. 9, and the difference between the minimum value and the maximum value is the amount shown in b of FIG. Also, the developer peelability was evaluated with ◎, ○, △, ×, ◎ very good (developer was peeled off from the sleeve in the developer release region, and no developer entanglement was observed) ○ is good (sometimes a small amount of developer is mixed, but there is no problem in practical use), △ is slightly rotated (developer slightly affects the image), × is rotated (development) The agent almost peeled off from the sleeve and greatly affected the image).

  The measurement results are shown in Table 1.

(Example 2)
All operations were performed in the same manner as in Example 1 except that the magnetizing magnetic field of the developer peeling magnet piece was 280 K · A / m.

(Example 3)
The same procedure as in Example 1 was performed except that the magnetizing magnetic field of the developer peeling magnet piece was 120 K · A / m and the width of the magnetizing yoke was 50% of the width of the outer peripheral surface of the magnet piece.

Example 4
The same procedure as in Example 1 was performed except that the magnetizing magnetic field of the developer peeling magnet piece was 280 K · A / m, and the width of the magnetizing yoke was 50% of the width of the outer peripheral surface of the magnet piece.

(Example 5)
The same procedure as in Example 1 was performed except that the magnetizing magnetic field of the developer peeling magnet piece was 200 K · A / m and the width of the magnetizing yoke was 50% of the width of the outer peripheral surface of the magnet piece.

(Example 6)
The same procedure as in Example 1 was performed except that the magnetizing magnetic field of the developer peeling magnet piece was 200 K · A / m, and the width of the magnetizing yoke was 100% of the width of the outer peripheral surface of the magnet piece.

(Comparative Example 1)
The same procedure as in Example 1 was performed except that the magnetizing magnetic field of the developer peeling magnet piece was 120 K · A / m and the width of the magnetizing yoke was 15% of the width of the outer peripheral surface of the magnet piece.

(Comparative Example 2)
All operations were performed in the same manner as in Example 1 except that the magnetizing magnetic field of the developer peeling magnet piece was 100 K · A / m.

(Comparative Example 3)
The same procedure as in Example 1 was performed except that the magnetizing magnetic field of the developer peeling magnet piece was set to 300 K · A / m.

(Comparative Example 4)
The same procedure as in Example 1 was performed except that the magnetizing magnetic field of the developer peeling magnet piece was 100 K · A / m and the width of the magnetizing yoke was 50% of the width of the outer peripheral surface of the magnet piece.

(Comparative Example 5)
The same procedure as in Example 1 was performed except that the magnetizing magnetic field of the developer peeling magnet piece was 300 K · A / m and the width of the magnetizing yoke was 50% of the width of the outer peripheral surface of the magnet piece.

  When Example 1 and Comparative Example 1 are compared, the developer peelability of Example 1 is ○, but the developer peelability of Comparative Example 1 is ×, so the low magnetic flux density range is suitably 25 degrees or more. It can be seen that it is.

  Comparing Example 1 and Comparative Example 2, the developer peelability of Example 1 is ○, but the developer peelability of Comparative Example 2 is Δ and a little screw pitch unevenness occurs. 2 and Comparative Example 3 were compared, the developer peelability of Example 2 was ○, but the developer peelability of Comparative Example 3 was Δ, and a little ghost and screw pitch unevenness occurred. It can be seen that 0.5 mT to 5 mT is appropriate as the difference between the maximum value and the maximum value.

When Examples 3, 4, 5, and 6 are compared with Comparative Examples 4 and 5, the developer peelability is reduced by setting the low magnetic flux density range to 35 degrees or more and the difference between the minimum value and the maximum value to 0.5 mT to 3 mT. It can be seen that the image quality is further improved and a good image can be obtained.

Magnetic circuit part of mold for extrusion of magnet piece Magnetic circuit part of injection mold for magnet piece injection Cross section of a conventional magnet roller The figure explaining the demagnetization method of the magnet piece adjacent to a developer peeling area | region Sectional view of the magnet roller of the present invention The figure explaining the method of magnetizing the magnet piece arrange | positioned in a developer peeling area | region Diagram of magnet pieces placed in the developer peeling area Perspective view of magnet roller The figure explaining the low magnetic flux density pattern of a developer peeling area

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electromagnet or permanent magnet 2 Orientation magnetization yoke (magnetic body)
3 Extrusion mold (non-magnetic)
4 Magnet piece 5 Magnetic particle orientation magnetization direction 6 Shaft 7 Notch 8 Magnet piece placed in developer peeling area 9 Shaft 10 Low magnetic flux density pattern in developer peeling area

Claims (2)

  In a magnet roller having a developing area for adsorbing the developer to the sleeve surface and transporting it to the developing position, and a developer peeling area for peeling the developer that has passed through the developing area from the sleeve surface, with the same magnetic pole exceeding a magnetic flux density of 8 mT A region where the sandwiched magnetic flux density of 8 mT or less is 25 degrees or more is defined as a developer separation region, and the developer separation region has one maximum magnetic flux density, and the minimum and maximum values in the region. A magnet roller having a value difference of 0.5 mT to 5 mT.   The magnet roller according to claim 1, wherein the magnet roller is formed by bonding a plurality of magnet pieces, wherein the magnet piece is disposed in the developer peeling region.

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