JPH05291028A - Multipole integrated magnet roll and manufacturing method thereof - Google Patents

Abstract

PURPOSE:To increase the magnetic force of a specified pole piece only by a method wherein a groove or cut out surface is provided on a part or the whole of a shaft in the longitudinal direction to be filled up or bonded with a magnet and then the shaft is inserted through a cylindrical main body magnet. CONSTITUTION:A cylindrical main body magnet 4 comprising a plastic raw material dispersedly mixed with the ferromagnetic body powder having a magnetic anisotropy with a groove 2 or cut out surface along a part or the whole of a shaft 1 in the longitudinal direction to be filled up or bonded with a magnet 3. Next, the title multipole integrated magnet roll comprising the cylindrical main body magnet 4 with the shaft 1 inserted therethrough is manufactured. Through these procedures, the magnetic force of a specific pole only is increased so that the slender multipole integrated magnet roll hardly affected by the magnetic force of the other pole pieces may be manufactured by the extruding step in high productivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnet roll used in a developing device or a cleaning device such as a copying machine, a facsimile and a laser beam printer (LBP) by electrophotography. More specifically, the present invention relates to a "multi-pole integrated magnet roll" in which a required number of magnetic poles are formed on the surface of one long plastic bond magnet by a polar anisotropic orientation method or a multi-pole magnetization, and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, electronic copying machines, facsimiles and L
With the miniaturization of BPs, small-diameter magnet rolls are required. Specifically, it is required that the length be 220 mm or more and the diameter be 13 mm or less, which is compatible with A4 size. There is also a demand for a diameter of 10 mm or less. When it becomes thin like this, problems such as "what kind of shaft is used" and "how to form the shaft" emerge. The reason is as follows.

The required value of the surface magnetic flux density (hereinafter simply referred to as magnetic force) of the main pole of an ordinary magnet roll is 700 to 100.
It is 0 gauss. In order to achieve this level, the wall thickness of the magnet part needs to be a certain size or more. The specific value depends on the magnet material used, but it is about 3 mm or more in a commonly used bond magnet using hexagonal ferrite. Therefore, in order to secure this thickness, it is unavoidable to use a considerably thin shaft in a magnet roll having a small diameter. For example, the magnet has a diameter of 10 mm and a length of 22.
In the case of a magnet roll of 0 mm, a shaft having a diameter of about 3 mm and a length of about 250 mm must be used.
However, when it gets thinner like this, the materials that are commonly used (soft iron,
A round bar made of aluminum alloy, stainless steel, etc.) has insufficient strength and often causes bending during the production process. Although it is considered to use a special material having high strength, the use of such a special material causes a large increase in cost and is not preferable. Although it is considered that the material is hardened, even the hardened material cannot be said to have sufficient strength, and there is a problem that bending often occurs during hardening. Further, although a certain degree of strength can be obtained by making the cross section square (almost square), such a shaft is expensive.

One method of solving the shaft problem is to perform injection molding in the magnetic field of the main body magnet part and the shaft part as an integral body made of the same magnet material (Japanese Patent Laid-Open No. 61-61).
-172305). By doing so, the magnet roll can be formed into a solid body (usually a cylinder), so that a magnet having a volume necessary for maintaining the surface magnetic flux density at a predetermined level can be secured.

[0005]

[Means for Solving the Problems] However, since injection molding has low productivity, there is a limit to cost reduction.
It is not easy to shape the elongated bonded magnet so that the magnetic characteristics are uniform over the entire length. In addition, since warpage is often generated in the molding process, a warp straightening process is usually required. On the other hand, in extrusion molding, such a problem does not occur in principle and the productivity is high, which is highly desirable. However, in the conventional manufacturing method in which the multi-pole cylindrical long magnet is extruded in the magnetic field and then the round bar shaft is pierced, if the magnetic force is prioritized, a thinner shaft will be used and the strength will be insufficient. If the shaft strength is prioritized, the body magnet becomes thin and the magnetic force is sacrificed.

In order to solve this problem, the inventors of the present invention have a structure in which a pipe is filled with a magnet material and a magnet main body is provided around the pipe (Japanese Patent Application No. 3-197).
No. 082, Japanese Patent Application No. 3-357864), and the entire shaft formed using a magnet body (March 12, 1992)
Japanese patent application) has already been proposed. However, although these are effective for increasing the magnetic force of a specific pole, the magnetic force of other poles may be too low to be used as a magnet roll. In particular, when a magnetic pole having the same polarity exists at or near the opposing position (the position rotated by about 180 °) of the magnetic pole for increasing the magnetic force, the magnetic force of this magnetic pole may become too low. The present invention solves this problem.

That is, the present invention relates to a magnet roll comprising a cylindrical main body magnet made of a material in which a ferromagnetic powder having magnetic anisotropy is dispersed and mixed in plastic, and a shaft. The gist of the present invention is to provide a groove or a cut surface over the entire surface, to fill or adhere a magnet to the groove or the cut surface, and to allow the shaft to penetrate the main body magnet.

[0008]

As described above, if the shaft is made thick enough to exhibit sufficient strength, it is unavoidable to reduce the wall thickness of the main body magnet of the magnet roll, resulting in a decrease in the magnetic field. However, since the present invention shaft has a magnet attached, the shaft itself generates a magnetic field,
It is possible to compensate for the decrease in the magnetic field of the main body magnet. Moreover, since the entire shaft is not a magnet, the magnetic forces of magnetic poles other than the magnetic poles for increasing the magnetic force do not cause a magnetic force reduction that makes it impossible to use. As described above, according to the present invention, it is possible to increase the magnetic force of a specific pole while using a shaft having a thickness capable of ensuring sufficient strength (further, a pole other than the specific pole that requires a high magnetic force (especially the opposing position). Or a pole near it)
It is possible to obtain a multi-pole integrated type long magnet roll which does not significantly reduce the magnetic force of.

[0009]

EXAMPLES Next, details of the present invention will be described based on examples. FIG. 1 shows a shaft main body portion, (a) is an axial sectional view, and (b) is a radial sectional view. 2 shows a state in which a groove formed in the shaft main body is filled with a magnetic material, (a) shows an axial sectional view, and (b) shows a radial sectional view. Further, FIGS. 3, 4 and 5 are sectional views in the radial direction of respective embodiments of a magnet roll formed by penetrating a shaft in a cylindrical main body magnet. In the example shown in the figure, the magnet material 3 is filled in the groove 2 of the shaft main body 1 provided with the groove 2 in a part or all of the longitudinal direction, and the shaft manufactured in this way is applied to the cylindrical main body magnet 4. This is the case when it is pierced. Other methods can be used to attach the magnet material 3 to the shaft body 1. For example, a cut surface may be provided on the shaft body and a long magnet body separately manufactured may be bonded to the cut surface. Further, in the illustrated example, the groove 2 is provided only in the portion where the cylindrical main body magnet 4 is arranged in the longitudinal direction of the shaft main body 1, but it may be provided over the entire length. Hereinafter, each of the body magnet 4, the shaft body 1, and the magnet material 3 attached to the shaft body will be specifically described.

(1) Main body magnet of magnet roll As the magnetic powder of the bond magnet material used for the main body magnet, hexagonal ferrite, SmCo type alloy, NdFeB type alloy, SmFeN type alloy and the like can be mentioned. Hexagonal ferrite is particularly preferable because it is inexpensive. It is the same as the usual bonded magnet manufacturing method that these magnetic powders are appropriately subjected to surface treatment for improving moldability and for rust prevention in the case of rare earth magnetic powders. Any plastic can be used as the binder as long as it can be extruded, and a typical binder is a mixture of polyvinyl chloride and polyvinyl acetate homo- or copolymer, chlorinated polyethylene, and a suitable plasticizer. The cross-sectional shape of the main body magnet is substantially cylindrical, but cut surfaces or grooves for positioning etc. may be formed alone or together on the outer peripheral surface and / or the inner peripheral surface. In order to give a predetermined magnetic pole to the outer side surface of the main body magnet, either of "polar anisotropic magnetic field oriented extrusion" and "method of magnetizing with multiple poles after extruding in a non-magnetic field" can be selected. The former is preferable because a magnet roll having high magnetic properties can be obtained. However, if the desired magnetic force can be secured, the latter which is easy to implement may be selected. Especially when thin magnet roll or thin magnet roll is required
It is recommended to apply the latter method by using magnetic powder having high saturation magnetization such as dFeB magnetic material.

(2) Shaft main body The material of the shaft main body is iron, aluminum, aluminum alloys, other metals, or the powders of which are sintered after molding, or molded in a mold after melting. Examples thereof include those molded of hard plastic (which may contain a reinforcing filler). The shape of the cross section may be any shape as long as the shaft magnet is attached, and examples thereof include a circle with a cut surface and a circle with a groove. Further, these cuts, grooves and the like do not necessarily have to be provided over the entire length, and may be the length of the main body magnet.

(3) Shaft Magnet As the magnetic material of the plastic bond magnet attached to the shaft body, the same magnetic material as that used for the body magnet can be used. The content is required magnetic characteristics, types of magnetic powder,
Although it is determined in consideration of strength and formability when attached to the shaft, 30 to 70% by volume is desirable. Any plastic can be used as the binder plastic as long as it can be used for plastic magnets, such as various polyamide resins (so-called nylon), polyethylene terephthalate, polyester, acrylic resin, polyphenylene sulfide (PPS), polyimide, liquid crystal polymer, phenol resin, epoxy. Resin etc. are mentioned. A filler may be filled to increase the strength. It goes without saying that other additives for improving moldability and stabilizers for preventing deterioration of the resin are appropriately added.

The following method can be used to attach the shaft magnet to the shaft body. A method for adhering a shaft magnet, which has been molded to a specified size by injection molding, extrusion molding, etc., to the shaft body. A method in which a plastic bond magnet molded by injection molding, extrusion molding, etc. is processed into the size and shape required for a shaft magnet, and then bonded or filled into the shaft body. A method of attaching an elongated magnet piece cut out from a calendered sheet magnet to the shaft body (filling the groove or adhering to a flat surface). A method of filling the groove for the shaft main body with the shaft magnet by coextrusion of the shaft main body and the molten resin magnet.

It is desirable that the magnetic particles in the magnet for the shaft have a high magnetic property if they are oriented by a magnetic field or mechanical shearing force during molding. The magnetic field oriented may be used as it is, but if magnetism is an obstacle to assembly, it may be demagnetized once, attached to the shaft body, and then re-magnetized. The magnetizing step is essential because the material that has gone through the mechanical orientation step is not magnetized. To magnetize the shaft magnet, a DC power supply, a capacitor type pulse power supply and a magnetizer having an appropriate magnetic circuit structure may be used.

The cross-sectional shape of the entire shaft can be appropriately selected from round shape, square shape, etc., but the round shape is preferable. However, if necessary, the cut surface, the groove, or the protrusion may be provided alone or together. Whatever shape you choose,
Both ends of the shaft must be constructed so that they can be attached to the rotation support (including the case where other parts are attached).

The present invention is mainly applied to a thin magnet roll, but the present invention increases not only the thin magnet roll but also the magnetic force of a specific pole of a thick magnet roll without reducing the magnetic force of the opposite pole. It can also be used for purposes. Next, specific examples carried out to confirm the effects of the present invention will be described. These do not limit the invention in any way.

Example 1 (1) Shaft main body A bar of aluminum-copper alloy (92Al, 8Cu) having a diameter of 6 mm and a length of 250 mm, having a length of 220 mm excluding 15 mm from both ends, having a depth of 2 mm and a width of 3 mm. It has a groove. This was used as the shaft. (2) Shaft magnet part

[Table 1] Kneading the formulations having the composition of Table 1 to make pellets,
A sheet having a thickness of 2 mm was produced by calendar molding. From this, a magnet piece having a length of 219.5 mm and a width of 2.95 mm was cut out and used as a shaft magnet portion. (3) Main body magnet A pellet having a composition shown in Table 1 is kneaded to prepare a pellet.
An outer diameter of 10φ, an inner diameter of 6.03 mm (partially with a cut surface, see FIG. 4), and a length of 220 mm, a 4-pole long magnet (each magnetic pole interval was 90 °) was formed by magnetic field orientation extrusion. (4) Assembly An adhesive was applied to the groove of the shaft body to embed the shaft magnet part. This was passed through the hollow portion of the main body magnet portion to obtain a magnet roll. Table 2 shows the results of measuring the magnetic force of each pole with a Gauss meter. As a comparative example, the table also shows the magnetic force of a magnet roll having a normal shaft (made of iron and no magnet) provided therethrough.

[Table 2] As shown in this table, in the magnet roll of the present invention, the magnetic force of the main pole (N1 pole) is improved. Moreover, the opposite pole (N
It can be seen that the decrease in magnetic force of the two poles) is small and favorable results are obtained.

Example 2 (1) Shaft main body and shaft magnet portion A soft iron (SS41) round bar having a diameter of 6φ and a length of 250 mm is provided with a U-shaped groove having a deepest depth of 2.5 mm and a width of 3 mm over the entire length. The shaft formed was used as the shaft body. Next, pellets of a bonded magnet compound for injection molding containing 90% by weight of strontium ferrite "OP71" manufactured by Nippon Benji Co., Ltd. and using nylon 12 as a binder were prepared. This was subjected to insert injection molding together with the shaft body to fill the U-shaped groove with the bond magnet. During the injection molding, a magnetic field was applied to magnetize the bonded magnet in a direction perpendicular to the longitudinal direction of the bonded magnet so that the magnet surface became the S pole. (2) Main body magnet Four-pole integrated type cylindrical long magnet having an angle between magnetic poles shown in Table 3 (outer diameter 10 mm, inner diameter 6.03 mm, length 22)
0 mm) was prepared by magnetic field oriented extrusion using the same formulation as in Example 1.

[Table 3] (3) Assembly The shaft made in (1) was inserted into the main body magnet in (2). At this time, set the magnet side of the shaft to S
Matched to one pole. (See Figure 5)

Comparative Example 2 The present inventors have filed Japanese Patent Application Nos. 3 197082 and 3-3.
A shaft was made by the method disclosed in No. 57864. That is, an aluminum pipe having an outer diameter of 6 mm, an inner diameter of 4 mm, and a length of 250 mm was filled with the composition shown in Table 1 and magnetized in the diameter direction to form a shaft, and this shaft was attached to the body magnet of (2) in Example 2 with S1 pole. It was inserted in such an arrangement that the magnetic force of was increased.

Magnetic Force Measurement Table 4 shows the results of measuring the surface magnetic force of each pole of the magnet rolls of Example 2 and Comparative Example 2 with a Gauss meter.

[Table 4] As shown in this table, there is no great difference in the magnetic force of the main pole (S1), but there is a great difference in the magnetic force of the S2 pole located 155 ° from the S1 pole by design. Of S
Much higher than the two-pole magnetic force. Further, the peak position of the S2 pole in Comparative Example 2 largely deviated from the design value, but did not significantly deviate in Example 2. The deviation of the peak position that occurs after inserting the shaft can be avoided by making it by shifting the magnetic force peak position of the main body magnet in advance and designing it so that it will be in a normal position when the shaft magnetic field is applied. Such a design is quite difficult when the width to be shifted in advance is large. According to the present invention, since the magnetic force peak position of the main body magnet does not shift so much,
The magnet roll is easy to design and preferable.

[0021]

As described above, by using the shaft whose part of the cross-section is a magnet, only the magnetic force of the desired pole is increased and the magnetic force of the other pole is not affected so much. It can be produced by extrusion molding with high properties. Therefore, electronic copiers, facsimiles and LBPs
It is possible to contribute to downsizing and thinning of devices using electrophotography.

[Brief description of drawings]

FIG. 1 shows an embodiment of a shaft main body used in the present invention, (a) is an axial sectional view, and (b) is a radial sectional view.

FIG. 2 shows a state in which a magnetic material is filled in the shaft main body of the embodiment, (a) is an axial sectional view, and (b) is a radial sectional view.

FIG. 3 is a sectional view of an embodiment of a multi-pole integrated magnet roll of the present invention.

FIG. 4 is a sectional view of an embodiment of a multi-pole integrated magnet roll of the present invention.

FIG. 5 is a sectional view of an embodiment of a multi-pole integrated magnet roll of the present invention.

[Explanation of symbols]

 1 Shaft body 2 Groove 3 Magnet material 4 Body magnet

Claims (6)

[Claims] 1. A magnet roll comprising a cylindrical main body magnet made of a material obtained by dispersing and mixing a ferromagnetic powder having magnetic anisotropy in a plastic, and a shaft,
A groove or a cut surface is provided over a part or the whole of the longitudinal direction of the shaft, a magnet is filled or adhered to the groove or the cut surface, and the shaft is penetrated through the cylindrical main body magnet. Multi-pole integrated type magnet roll. 2. A main body of the shaft is formed by sintering iron, aluminum, aluminum alloy, other metal, or powder thereof, and then, by melting and molding in a mold, or by molding hard plastic. The multi-pole integrated magnet roll according to claim 1, wherein the multi-pole magnet roll is a magnetic roll. 3. The multi-pole integrated magnet roll according to claim 1, wherein the cylindrical main body magnet is a long-sized multi-pole integrated plastic bond magnet extruded in a magnetic field. 4. A cylindrical main body magnet made of a material in which a ferromagnetic powder having magnetic anisotropy is dispersed and mixed in plastic, and a groove or a cut surface is provided over a part or the whole of the longitudinal direction, and the groove or the cut surface is formed. A method for producing a multi-pole integrated magnet roll, characterized in that a shaft having a cut surface filled with or adhered with a magnet is produced, and the shaft is provided through the main body magnet. 5. The shaft main body is formed by molding iron, aluminum, aluminum alloy, other metal, or powder thereof and then sintering, or by molding in a mold after melting, or by molding hard plastic. 5. The method for manufacturing a multi-pole integrated magnet roll according to claim 4, wherein 6. The method for producing a multi-pole integrated magnet roll according to claim 4, wherein the cylindrical main body magnet is a long multi-pole integrated plastic bond magnet extruded in a magnetic field. .