JP2000114031A - Magnet roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a magnet roll in which the breakage, etc., during assembling are eliminated and problems such as spillage of developer due to edge effect are dissolved. SOLUTION: This magnet roll 11 comprises a columnar resin magnet 12 made mainly of magnet powder and binder resin, and a supporting part which is extended on its one end or both ends and is thinner than the columnar resin magnet 12. In the sectional external shape including the rotary central axis of the magnet roll 11, the supporting part is formed thinner than the columnar resin magnet 12 on its one end or both ends whose curvature radius is 2 mm or larger.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnet roll, and more particularly, to a magnet roll free from problems such as breakage during assembly and the like, and having improved problems such as developer spillage due to the so-called edge effect. The magnet roll of the present invention is used for a developing device and a cleaning device such as an electrophotographic copying machine, a printer, and a facsimile.

[0002]

2. Description of the Related Art Conventionally, this type of magnet roll generally has a structure in which a sintered magnet is mounted on a metal shaft, but the sintered magnet is brittle and easily broken, and has a dimensional accuracy. However, there was a problem that the productivity was low due to the necessity of cutting and polishing steps. Therefore, recently, a magnet roll using a resin magnet having excellent moldability, high impact strength, and being hardly damaged, and containing magnetic powder and a binder resin as main components has been frequently used.

As such a magnet roll, as shown in FIG. 8, for example, a shaft portion 3 is provided in a cylindrical hole of a cylindrical resin magnet 2.
, And a structure in which a cylindrical resin magnet 2 and a shaft portion 3 are integrally formed as shown in FIG.
Further, as shown in FIG. 10, there is a structure in which a shaft portion 3 is provided at both ends of a cylindrical resin magnet 2 through a cylindrical portion 4 having a smaller diameter than the resin magnet 2. In FIG. 10,
The D cut 5 is generally provided for the purpose of positioning in the circumferential (angular) direction.

Although not shown, the above-mentioned magnet roll is provided with a sleeve, a flange, and the like, and a shaft portion (support portion) protruding from both ends of the magnet (in FIG. 10, the column portion 4 and the shaft portion 3 constitute a support portion). ) Is used by attaching to a magnet roll support part of a cartridge of a copying machine, a printer, or the like.

[0005]

However, there is a problem that a magnet roll having a shaft portion made of the same material as a resin magnet is easily damaged. That is, as described above, the magnet roll is assembled together with the sleeve and the flange, and is assembled into a cartridge or a printer. In this case, the magnet roll has support portions projecting from both ends of the resin magnet and supports the magnet roll in the cartridge or the printer. Used in a state supported by the part. Thus, when the magnet roll is assembled with the sleeve or the flange, or when the magnet roll is assembled in the cartridge or the printer, it may be damaged by an impact or stress. Breakage is likely to occur at the boundary between the large diameter portion and the small diameter portion, that is, at the stepped portion (B in FIGS. 8 to 10).

On the other hand, in a conventional magnet roll, as shown in FIG. 11, the magnetic force at both ends of the magnet roll increases in the axial magnetic force distribution due to the so-called edge effect. The adsorbing power of the agent increases. For this reason, the transport amount of the developer at both ends of the magnet roll increases, and as a result, the pressure increases in the gap between the sleeve and the seal or the doctor blade, and troubles such as spilling of the developer cannot be avoided.

In order to solve this problem, for example, Japanese Patent No. 2512025 proposes a magnet roll in which a plurality of magnetic pole pieces each having a smaller thickness at both ends than at the center are combined and bonded. It is still not enough.

The present invention solves the above-mentioned problems of the prior art,
An object of the present invention is to provide a magnet roll which is free from troubles such as breakage at the time of assembling or the like and in which problems such as fusion of developer and spillage caused by an edge effect are improved.

[0009]

According to the present invention, there is provided a columnar resin magnet having magnetic powder and a binder resin as main components, and extending at one or both ends thereof,
A magnet roll comprising a support portion thinner than the columnar resin magnet, wherein a radius of curvature of one end or both ends of the columnar resin magnet is 2 mm in an outer shape of a cross section including a rotation center axis of the magnet roll. The magnet roll is characterized in that the support portion is formed so as to be thinner than the columnar resin magnet by the above curve (first example).
Section).

In a preferred embodiment, the ratio L / D of the length (L) to the diameter (D) of the cylindrical resin magnet is 15 or more (Second Item).

Further, in a preferred embodiment, the support portion is formed in multiple stages to be thinner than the columnar resin magnet (claim 3).

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, one end or both ends of a cylindrical resin magnet are curved with a radius of curvature of 2 mm or more in a cross-sectional shape including a rotation center axis of a magnet roll. It is characterized in that it is thinned to form a support portion. If the radius of curvature is too large, the length necessary to form the support portion becomes long, and as a result, the magnet roll becomes unnecessarily long, and it is difficult to achieve miniaturization of the device, which is not preferable. 2-30m
m, more preferably 2 to 15 mm.

One end or both ends of the columnar resin magnet is narrowed by a curve having a radius of curvature of 2 mm or more to form the support portion. However, it is not always necessary to make the support thinner in one step, but in multiple steps according to the shape of the sleeve. It may be thin. In order to improve the mechanical strength by shortening the minimum diameter portion as much as possible, it is desirable to make the diameter smaller in multiple steps. However, when the number of steps is excessively large, not only the production becomes difficult, but also the shape of the sleeve becomes complicated, so that two to three steps are preferable.

A straight portion may be interposed between curves having a radius of curvature of 2 mm or more. Further, when forming the support portion at both ends by a curve having a radius of curvature of 2 mm or more, the shape of both ends does not necessarily have to be the same,
It may be different. Further, there is no problem in providing an asymmetrical portion such as a D-cut at the tip of the support portion for the purpose of positioning.

Length (L) and diameter (D) of the cylindrical resin magnet
As the ratio L / D with the ratio increases, the stress due to its own weight applied to the holding portions at both ends increases, and the stress tends to cause breakage. Therefore, the present invention is particularly effective when L / D is 10 or more, especially 15 or more, and breakage can be effectively prevented.

In the present invention, the length (L) of the columnar resin magnet is a portion that substantially exhibits magnetic properties.
The radius of curvature refers to a large diameter portion that is not narrowed by a curve of 2 mm or more, and the diameter (D) of the cylindrical resin magnet refers to the diameter of the large diameter portion (see FIG. 1).

Examples of the magnetic powder constituting the resin magnet used in the present invention include strontium ferrite, barium ferrite, and rare earth alloy resins, and these may be used alone or in combination of two or more. The mixing ratio of the magnetic powder is usually preferably 80 to 92% by weight.
The surface treatment of the magnetic powder, mixing and kneading with the binder resin, and the like may be performed by conventional methods.

The binder resin constituting the resin magnet used in the present invention is a polyamide resin (nylon 6, nylon 6).
Nylon 12, nylon 610, etc.), polypropylene,
Polyethylene, polycarbonate, vinyl acetate, ethylene / vinyl acetate copolymer, ethylene / ethyl acrylate resin, polyethylene terephthalate resin, polybutylene terephthalate resin, thermoplastic polyester, polyphenylene sulfide, liquid crystal polyester, elastomer, etc. It is used in combination of two or more.

In addition to the magnetic powder and the binder resin, if necessary, additives such as generally used lubricants and stabilizers are added. Usually, the magnet roll of the present invention is preferably formed by injection molding at one time, but may be formed by post-processing such as cutting after forming.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view (hereinafter, simply referred to as a cross-sectional view) including an axis of rotation showing an embodiment of a magnet roll of the present invention. In the figure, in the magnet roll 11 of the present invention, one end of the cylindrical resin magnet 12 has a curved portion 13, 14 and 15 having a radius of curvature of 2 mm or more (13: 4 mm,
(14: 2 mm, 15: 2 mm), the diameter is gradually and smoothly reduced to form the support portion 16, and the other end of the cylindrical resin magnet 12 has the curved portions 17 and 18 with a radius of curvature of 2 mm or more ( (17: 2 mm, 18: 2 mm), the diameter of the support 19 is gradually and smoothly reduced. Further, D-cuts 20 and 21 are provided at the tip portions of the support portions 16 and 19, respectively.

FIG. 2 is a partial sectional view showing another embodiment of the magnet roll of the present invention.
One end of the cylindrical resin magnet 12 is gradually and smoothly reduced in diameter from curves 22 and 23 (22: 6 mm, 23: 2 mm) having a radius of curvature of 2 mm or more and a straight portion 24 between the curves 22 and 23. The support portion 25 is formed. The support 25
A D-cut 26 is provided at the tip of the.

FIG. 3 is a partial sectional view showing still another embodiment of the magnet roll of the present invention.
Is that one end of the cylindrical resin magnet 12 is smoothly reduced in diameter from curves 27 and 28 (27: 3 mm, 28: 2 mm) having a radius of curvature of 2 mm or more and a curved portion 29 between the curves 27 and 28. A support 30 is formed. A D-cut 31 is provided at the tip of the support portion 30.

FIG. 4 is a partial sectional view showing another embodiment of the magnet roll of the present invention. The magnet roll 11 has substantially the same configuration as that of FIG. The cut 32 is formed by a smooth curve.

In the embodiments shown in FIGS. 2 to 4, only one end is shown, and the other end may have the same configuration as that of the one end or may be different. ~ FIG.
May be arbitrary.

FIG. 5 is a sectional view showing still another embodiment of the magnet roll according to the present invention. In the magnet roll 11, one end of the cylindrical resin magnet 12 has curved portions 33 and 34 having a radius of curvature of 2 mm or more (33 , 34: 27 mm each) to form a supporting portion 35, and the other end of the cylindrical resin magnet 12 has a curved portion 36 and 37 having a radius of curvature of 2 mm or more (36, 37: respectively). 19 mm), and the diameter is smoothly reduced to form the support portion 38. Also, a D-cut 3 is provided at the tip of the support portions 35 and 38.
9 and 40 are provided respectively.

[0026]

The present invention will be described below in more detail with reference to Examples and Comparative Examples, which do not limit the scope of the present invention.

Examples 1 and 2 86% by weight of strontium ferrite magnetic powder surface-treated with aminosilane, 0.2% by weight of a lubricant (calcium stearate), and the remaining polyamide resin (PA
6) A mold in which powder is mixed, guided to a KCK kneader, kneaded and plasticized, and the melt is guided to an injection molding machine as it is, and a permanent magnet incorporated in the mold forms an orientation magnetic field in a cavity. Then, a magnet roll having a structure shown in FIG. 1 and dimensions (mm) shown in FIG. 6 was obtained. In FIG. 1, the curvature radius of the curved portions 13, 14, 15, 17 and 18 was 2 mm or 4 mm, and two types of magnet rolls having different curvature radii were obtained.

The two types of magnet rolls obtained were subjected to a bending strength test by the method shown in FIG. That is,
A portion near one end of the cylindrical resin magnet 12 of the magnet roll 11 is fixed with a fixing tool 41, and a D-cut 20 located 25.6 mm away from a base R of the support 16 and a base of the support 16 as well. Forces F ₁ and F ₂ were applied to portions 15.8 mm away from the portion R, respectively, and the force required to break the vicinity of the base R was measured. Table 1 shows the results.

Further, with respect to the obtained magnet roll, a magnetic field at a position 6 mm away from the center of the rotation axis of the magnet roll was measured along the length direction of the cylindrical resin magnet 12, and the magnetic force change at the end ( Edge effect) was measured. Table 2 shows the results.

Comparative Example In Examples 1 and 2, the radius of curvature was 0.1 to 0.3.
A magnet roll was obtained in the same manner except that mm was set. The obtained magnet roll was subjected to a bending strength test and a change in magnetic force at the end (edge effect) in the same manner as in Examples 1 and 2.
Was measured. The results are shown in Tables 1 and 2, respectively.

[0031]

[Table 1]

[0032]

[Table 2]

From the results shown in Table 1, it is understood that the strength of the magnet roll of the present invention is improved, and the magnet roll is not easily damaged by impact or stress. Further, from the results in Table 2, it is understood that the magnet roll of the present invention has improved edge effect.

[0034]

According to the magnet roll of the present invention, the mechanical strength is greatly increased by forming a smooth curve (surface) avoiding the corner portion where the impact and stress are concentrated, thereby greatly reducing the impact and stress. On the other hand, it is hard to be damaged, and both ends or one end of the magnetic characteristic manifesting portion of the magnet roll are smoothly thinned, so that the degree of orientation at the time of magnetic field injection molding of the magnet roll becomes lower as it becomes the tip. Together with the sleeve surface, the edge effect is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a magnet roll of the present invention.

FIG. 2 is a sectional view (part) showing another embodiment of the magnet roll of the present invention.

FIG. 3 is a cross-sectional view (part) showing still another embodiment of the magnet roll of the present invention.

FIG. 4 is a sectional view (part) showing another embodiment of the magnet roll of the present invention.

FIG. 5 is a sectional view (part) showing still another embodiment of the magnet roll of the present invention.

FIG. 6 is a sectional view of a magnet roll obtained in Examples 1 and 2.

FIG. 7 is an explanatory diagram of a bending strength test method for a magnet roll.

FIG. 8 is a sectional view showing an example of a conventional magnet roll.

FIG. 9 is a sectional view showing another example of a conventional magnet roll.

FIG. 10 is a sectional view showing still another example of a conventional magnet roll.

FIG. 11 is a schematic view showing an edge effect of a magnet roll.

[Description of Signs] 1 Magnet Roll 2 Resin Magnet 3 Shaft 4 Small Diameter Column 5 D Cut 11 Magnet Roll 12 Cylindrical Resin Magnet 13, 14, 15, 16, 17, 18, 22, 23, 2
7, 28, 33, 34, 36, 37 Curved portion 16, 19, 25, 30, 35, 40 Support portion 20, 21, 26, 31, 32, 39, 40 D cut 24 Linear portion 29 Curved portion 41 Fixture B Stepped portion R Root of support

Claims (3)

[Claims] 1. A magnet roll comprising: a columnar resin magnet mainly composed of magnetic powder and a binder resin; and a support portion extending at one end or both ends thereof and having a smaller thickness than the columnar resin magnet. In the outer shape of the cross section including the rotation center axis of the magnet roll, one end or both ends of the columnar resin magnet is formed to have a radius of curvature of 2 mm or more in a curve smaller than the columnar resin magnet to form a support portion. A magnet roll characterized by being made. 2. The magnet roll according to claim 1, wherein the ratio L / D of the length (L) to the diameter (D) of the cylindrical resin magnet is 15 or more. 3. The magnet roll according to claim 1, wherein the support portion is formed in multiple stages to be narrower than the cylindrical resin magnet.