JPS6010278A - Manufacture of anisotropic cylindrical magnet - Google Patents

Abstract

PURPOSE:To obtain a sufficiently anisotropic cylindrical resin magnet by using a die having a permanent magnet and a magnetic circuit including a yoke. CONSTITUTION:The die consists of rare earth cobalt magnets 31-34 magnetized radially around a cylindrical space 1 having a core 2 at the inside concentrically, magnetic field coils 41-44 and soft magnetic bodies 5, 6. A material made by adding polyamide resin to ferrite particles of average grain size 1mum and mixing at, for instance, 250 deg.C, is put in the die and cooled and solidified at a temperature of 270 deg.C and at a pressure of 70kg/cm<2>. This is formed, for instance, to 30mm.phi in outer diameter and 12mm.phi in inner diameter, and worked to the external form of 24mm.phi. Thus, a magnet having magnetic flux density distribution of an anisotropic cylindrical magnet can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an anisotropic cylindrical magnet, which includes a step of press-molding a mixed material containing a ferromagnetic powder and a polymer compound in a magnetic field.

In image reproducing devices (dry type) such as electrophotographic copying machines, facsimile machines, and printers, a means for transporting magnetic developer (two-component developer that is a mixed powder of magnetic carrier and toner, or one-component magnetic toner, etc.) A permanent magnet member having a plurality of magnetic poles is installed inside a non-magnetic sleeve as a developing roll or cleaning roll, etc.
A magnetic roll configured to rotate the two relative to each other is generally used.

The magnetic rolls mentioned above also have various structures5.
For example, as described in Utility Model Publication No. 57-9798, a permanent magnet is formed by fixing a long anisotropic block magnet obtained by press-molding ferrite powder in a magnetic field and then sintering it around a shaft. Those using a magnetic member, or those using a permanent magnet member formed by fixing a cylindrical permanent magnet made of hard ferrite to a shaft (for example,
907, and Japanese Patent Publication No. 55-47045). However, in the former case, there are problems such as a large number of assembly steps and low-temperature demagnetization.

On the other hand, in the latter case, the magnet material is also used in the part between the magnetic poles, and the density of the sintered body is as high as about 517 cd, so there is a problem in that it is heavy. In addition, ferrite magnets generally have a problem in that since the material itself is brittle, cracks are likely to occur during or after sintering, resulting in poor yield.

On the other hand, ferromagnetic powder (generally ferrite powder is used) and polymer compounds (
A magnet roll using a so-called resin magnet, which is made by integrally molding a mixed wire material (generally made of rubber or plastic material) into a cylindrical shape by extrusion molding or injection molding, and magnetizing it after cooling and solidifying it. is proposed,
Practical use.

It is being considered. (For example, JP-A-56-108207.

(Refer to publications such as No. 57-150407 and No. 57-164509) When manufacturing this cylindrical magnet, resin magnets have lower density than sintered magnets, so in order to obtain magnetic properties equivalent to ferrite magnets, The axis of easy magnetization of the ferromagnetic powder is made to coincide with the direction of the lines of magnetic force inside the magnet after magnetization until cooling and solidification are completed. It is well known that a so-called anisotropy process is necessary. (For example, see Japanese Utility Model Publication No. 51-62396) Various proposals have been made regarding the manufacturing method of cylindrical resin magnets having anisotropy (hereinafter simply referred to as anisotropic cylindrical magnets). Use a mold in which magnetic yokes and non-magnetic spacers are alternately combined surrounding the molding space and magnetized coils are installed on the outside, as described in Japanese Patent No. 170501, or alternatively, magnetized coils are installed around the outer periphery of the molding space. It is common to use a mold in which the

However, when using the former mold, in order to generate a magnetic field of a predetermined strength within the molding space.

The magnetomotive force is increased by using a high-voltage, low-current type power source and by increasing the number of turns of the magnetizing coil, but this method has disadvantages such as first order. In other words, the coil housing space becomes large and the equipment becomes larger.

Furthermore, in order to effectively converge the magnetic field excited by the magnetizing coil into the molding space using the yoke from the outside of the mold, the length of the magnetic path must be made longer, so a considerable portion of the magnetomotive force is lost as leakage magnetic flux. It gets consumed.

On the other hand, in the latter case, as described in Japanese Patent Publication No. 5B-8571, a low voltage, large current type or capacitor type power supply is used, and the number of turns of the coil is reduced, and a large current is passed to obtain a predetermined magnetomotive force. However, there are drawbacks such as the following. In other words, the magnetizing coil itself can be made relatively small, and since the magnetizing coil is inside the mold, it is possible to shorten the magnetic path and prevent magnetic flux leakage, but the coil requires a large current of several thousand amperes. If this happens, a large amount of heat will be generated due to Joule heat, so a large-scale cooling mechanism will be required.

Moreover, from the viewpoint of magnetic properties, it is necessary to keep the mold warm to increase the solidification time of the molded body in order to improve the orientation. Therefore, in this case, the magnetic properties must be ignored to some extent and the magnetizing coil must be sufficiently cooled, or the cycle time must be lengthened and the molding efficiency must be ignored to some extent. In addition, this type of coil can be used for 5 to 10 m using a capacitor type magnetizer.
There is also a method of orientation using an instantaneous magnetic field as described in No. 5, and with this method, it is possible to suppress heat generation due to Joule heat to some extent. However, in this method, usually 1
The magnetic field application time is 5 to 10 times for the molding time of ~2zgc.
Since the length is as short as m5, local variations in orientation are large and it is difficult to impart strong anisotropy.

SUMMARY OF THE INVENTION An object of the present invention is to provide an anisotropic cylindrical magnet that eliminates the drawbacks of the prior art described above and allows a permanent magnet having predetermined magnetic properties to be obtained with relatively simple equipment.

The method for producing an anisotropic cylindrical magnet of the present invention involves injection or extrusion molding of a mixture mainly consisting of ferromagnetic powder and a polymer compound in a mold having a cylindrical molding space in the presence of a magnetic field. In the method for manufacturing an anisotropic cylindrical magnet in which the outer peripheral surface of a cylindrical molded body is magnetized with even number of poles in the same direction as the anisotropy direction, yokes are provided at positions corresponding to magnetic pole portions around the molding space. and a rare earth cobalt magnet is installed on the outside of each yoke, and a magnetic field coil is installed between the yokes, and the magnetic field coil applies a pulsed magnetic field to the surface of the molding space, and the rare earth cobalt magnet It is characterized by the supplementary application of a static magnetic field.

The details of the present invention will be explained below with reference to the drawings.

FIG. 1 is a sectional view showing an example of a mold used in the present invention.

In the mold shown in FIG. 1, radially magnetized rare earth cobalt magnets 51 + 32 + 'Is and 54 are arranged around a cylindrical molding space 1 in which a core 2 is provided concentrically. 5. Between these magnets. -12.52-33.5. -5
4 and 34-5. Each has a magnetic field coil 411421
4s and 44 are installed, and these are surrounded by a yoke 5 made of a soft magnetic material, and a rare earth cobalt magnet 54 is installed.
．． 52, 53 and 34 are also provided with yokes 61, 62, 63 and 64 made of soft magnetic material, respectively.
has been completed.

The magnetic circuit of the above mold is explained as follows.

Rare earth cobalt magnet5. , 52.55. and 54 are
It is used to constantly generate a silent magnetic field necessary for anisotropy in the molding space 1, and is arranged so that the i-pole face faces the molding space 1. Next is York 6.

62, 6. and 64 are the magnets 5+ and 52*, respectively.
It is used to effectively converge the magnetic flux generated from 55 and 54 into the molding space 1.

In addition, rare earth cobalt magnet 3. ~52.52~53.5
3-54.5. The magnetic field coil buried between
For example, it is connected to an instantaneous DC power supply (not shown) that inputs a commercial AC power supply, boosts and rectifies it to a predetermined DC voltage, charges it with a group of capacitors, and discharges it through a thyristor.
A pulsed magnetic field is applied to the surface of the molding space 10.

The yoke 5 is used to increase the permeance of the magnetic circuit and to form a closed magnetic circuit.

According to the above-mentioned mold, the pulsed magnetic field instantly produces 100%
A magnetic field of 00 to 200,000 g is generated to saturate the kneaded material, and the mixture is cooled and solidified for 5 to 10 seconds; a magnetic field of about 6,000 to 80'OOG by a permanent magnet prevents the orientation from being disturbed during the solidification time. Is possible. In this case, the rare earth cobalt magnet has a Br of 8.000 G or more (preferably 9.000 G or more) and an IHC of 10.00001 or more (preferably 15
．． 0,000 g or more) (for example, Japanese Patent Application Laid-Open No. 55-50100, Japanese Patent Application No. 57-24505)
(see specification) is appropriate. In the above mold, the time for energizing the coil is as short as 5 to IQmy for a molding cycle of 10 to 60 seconds, and there is no problem in practical use even without using a special cooling mechanism.

In the present invention, an anisotropic cylindrical magnet is obtained using the above mold, for example, in the following manner.

First, as raw materials, ferromagnetic powder such as Ba-ferrite, 5r-tourite powder having a magnetic plumbite crystal structure, alnico magnet powder, Fg-Cr-Co magnet powder, or rare earth cobalt magnet powder, and styrene. - Prepare a hybrid of a polymer compound made of a thermoplastic resin such as butadiene copolymer, ethylene vinyl acetate copolymer, polyethylene, polyamide, or the like. In this case, the amount of ferromagnetic powder blended is preferably 60% by weight or more from the viewpoint of magnetic properties. In addition, to improve moldability, a small amount (bundle amount %) of a lubricant such as polyethylene or calcium stearate may be added, and an organosilicon compound may be added to improve the wettability between the ferromagnetic powder and the polymer compound. , organic titanate compounds, and other additives may be added.

Next, the above-mentioned kneaded material is put into an injection molding machine or an extrusion molding machine equipped with the mold shown in FIG. 1, molded in the mold while applying a magnetic field, and then taken out from the mold after being cooled and solidified.

The obtained compact is machined to a predetermined outer diameter as necessary, and after fixing the shaft, it is magnetized in the same direction as the anisotropic direction to form four poles as shown in Figure 2. A magnetized anisotropic cylindrical magnet is obtained.

In the above example, the production of an anisotropic cylindrical magnet with three pole magnetization was described, but by increasing the number of rare earth cobalt magnets, an anisotropic cylindrical magnet with six or more magnetic poles can be obtained. Of course. Further, the rare earth cobalt magnet constituting the magnetic circuit of the mold, the shape and dimensions of the yoke, etc. may be appropriately set according to the required magnetic properties using an analytical method such as the finite element method.

The present invention will be explained in detail below.

Ferrite particles with an average particle size of 1 μm (BtxO・6Fg2
0. 1.55) liters of polyamide resin (Nylon 61 trade name) was added to 1651f and kneaded in a kneader at 250°C.

This mixed material was put into an experimental injection molding machine equipped with the mold shown in FIG. 1, injected into the mold at a temperature of 270 υ and a pressure of 7011/-, and then cooled and solidified. In this case, the rare earth cobalt magnet has a Br of 9.000 G.

One with tHc of 10.0000g (Hitachi Metals H-22
, 4) and applying a pulsed magnetic field of 10.0000 -. The magnetic flux density distribution on the surface of the molding space is as shown in FIG.

The obtained molded body (outer diameter 50 mm, inner diameter 12 m5i1 + length 260 wn) was processed to have an outer diameter of 24 WRIll to produce an anisotropic cylindrical magnet as shown in FIG.

When the magnetic flux density distribution of the obtained anisotropic cylindrical magnet was measured, the waveform shown in FIG. 4 was obtained, and it was confirmed that the magnetic flux density distribution was approximately the same as that of the anisotropic cylindrical magnet produced by the rubber press method.

As described above, according to the present invention, a cylindrical resin magnet with sufficient anisotropy can be obtained by using a mold having a magnetic circuit including a permanent magnet and a yoke, and the equipment can be significantly reduced compared to the conventional method. Can be made smaller.

[Brief explanation of the drawing]

Fig. 1 is a schematic sectional view showing an example of a mold used in the present invention, Fig. 2 is a sectional view showing an example of an anisotropic cylindrical magnet according to the invention, and Fig. 3 is a schematic sectional view showing an example of an anisotropic cylindrical magnet according to the invention. It is a figure showing magnetic flux density distribution of a magnet. 11 molding spaces, 21 cores, 2+52+55+54'
Rare earth cobalt magnet, 44.42. j, magnetic field coil, 5°64.62165I64; yoke.

Claims (1)

[Claims] 1. A cylindrical molded product obtained by injection or extrusion molding of a mixture mainly consisting of ferromagnetic powder and a polymer compound in a mold having a cylindrical molding space in the presence of a magnetic field. Even-numbered pole magnetization in the same direction as the anisotropic direction is applied to the outer circumferential surface of the magnet. In a method of manufacturing an anisotropic cylindrical magnet. Each yoke is installed at a position corresponding to a magnetic pole portion around the molding space, and each yoke is provided on the outside of each yoke. A rare earth cobalt magnet is installed, and a magnetic field coil is installed between the yokes. A pulsed magnetic field is applied to the surface of the molding space. A method for producing an anisotropic cylindrical magnet, characterized in that a static magnetic field from the rare earth cobalt magnet is supplementarily applied.