JPH03236206A - Manufacture of multiple anisotropic resin magnet - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multipolar anisotropic resin magnet used in small, high-performance motors, etc., and a method for manufacturing the same.

[Prior Art] Resin magnets, which are made by molding resin containing magnetic powder into a ring shape or the like and providing a large number of anisotropic magnetic poles on the outer circumferential surface, can be used in parts composed of magnetic members such as motors. Since it is easy to reduce the size and weight of motors, etc., they are used or are being considered for use in various fields.

In response to the expansion of the range of applications of resin magnets, various attempts have been made to obtain high-performance resin magnets with high magnetic energy and sharp magnetic poles.

For example, 80% by weight to 9% by weight, etc.
By injection molding a thermoplastic resin containing magnetic powder at a high density of 0% by weight in a magnetic field for orientation (anisotropy) of the magnetic powder, and magnetizing the resulting molded product. A method of manufacturing a multipolar anisotropic magnet is disclosed.

[Problems to be Solved by the Invention] The magnetic force in a resin magnet obtained using a resin material containing magnetic powder is mainly determined by the amount of magnetic powder forming the magnetically effective region and the magnetic strength. Note that the magnetically effective region is a region in which magnetic powder is oriented by magnetic field treatment that has the same magnetic direction as the magnetic circuit generated by magnetization.

However, in the resin magnet described in the above-mentioned Japanese Patent Publication No. 56-5045, etc., since the content of magnetic powder is high, there is a high content of magnetic powder even in the part that is not the magnetically effective area as shown in 1' in Fig. 6. It will be included in quantity. This is because if the magnetic powder content is high, the interference between the magnetic particles such as agglomeration of magnetic particles becomes large, which hinders their mutual movement. I can't bring it to you. This tendency becomes worse as the number of poles of the magnet increases because the polar orientation magnetic field shifts toward the surface of the magnet. In other words, magnetic powder that does not contribute to the magnetic strength of the resin magnet is contained in a high concentration in the non-magnetic force effective region, and the resin magnet obtained by this method still has problems that need to be improved from the viewpoint of effective use of magnetic powder. It had a

In particular, rare earth magnet powder is often used as magnetic powder to obtain higher performance resin magnets, but rare earth magnet powder is very expensive compared to ferrite magnet powder, etc., so these rare earth magnet powders are used. In some cases, effective use of magnetic powder in resin magnets is important in reducing the cost of high-performance resin magnets.

Furthermore, if the magnetic powder can be used more effectively and the magnetic powder content can be reduced, the weight of the resin magnet itself can be reduced.

In addition, as in the above-mentioned conventional technology, if the thermoplastic resin is contained in a high concentration of 80 to 90% by weight, the fluidity will be extremely deteriorated, so in injection molding, high mold temperature, high resin temperature, high injection pressure , high injection speed is required. Therefore, it is necessary to add special configurations that are costly to the mold and the molding machine, and the mold and molding machine also become larger, which also causes an increase in manufacturing costs. Furthermore, molds made of commonly used mold materials have limited capacity to accommodate high-pressure molding, and it is difficult to obtain molds with high durability when molding at high pressures and high temperatures. There are also many.

As mentioned above, a non-magnetic effective area is formed in the central part of a resin magnet that contains magnetic powder but does not contribute to magnetic force, that is, a non-magnetic effective area is formed, and the magnetic powder is not effectively used. A method of manufacturing a resin magnet by inserting or outsert a block made of, for example, a thermosetting resin into a region is known.

However, according to this type of insert or outsert molding method, although it is improved in terms of effective use of magnetic powder to insert or outsert blocks etc. into areas that do not contribute to the magnetic force of the magnet, it is still difficult to use magnetic powder. 80wt! Because the resin containing ~90 wt% is injected into the mold, problems remain with the molding machine, mold capacity, durability, etc. Furthermore, insert or outsert molding results in drawbacks such as a complicated mold and an increased number of steps.

On the other hand, JP-A-53-2814, JP-A-53-14
] No. 499 discloses a method for obtaining a high-performance multipolar anisotropic resin magnet by increasing the content of magnetic powder in the magnetized magnetic pole part compared to other parts using a multipolar orienting magnetic field.

However, the methods disclosed in these publications are expected to be effective in terms of effective use of magnetic powder in the production of resin magnets with a small number of poles, such as 2-pole or 4-pole (outer diameter φ30). In the production of small diameter resin magnets with six or more poles, which are normally used in small, high-performance stepping rotors, etc., it is practically impossible to expect the above-mentioned effects. As the number of poles increases from 4 poles, it becomes the magnetic circuit which is the principle of polar anisotropic orientation between adjacent magnetic pairs, and the part where the strongest magnetic field is applied is between the magnetic pole gaps, which are the strings that connect them over the shortest distance. The problem is that as the number of poles increases relative to the center of the cavity, it moves toward the outer surface. For this reason, magnetic field lines leak directly between the magnetic poles around the cavity, for example, as shown by the arrows in Figure 3, and in the center, only due to a very weak leakage flux defined by the permeance between the magnetic pole gaps. It is not possible to draw the magnetic powder close to each other, and therefore it is not possible to sufficiently converge the magnetic powder near the magnetic pole portion.

An object of the present invention is to provide a multipolar anisotropic resin magnet having a structure in which magnetic powder is efficiently used for generating magnetic force, and a method for manufacturing the same.

Another object of the present invention is to provide a multipolar anisotropic resin magnet that has a structure that can effectively utilize magnetic powder, thereby reducing the content of magnetic powder and thereby reducing size, weight, and cost. The purpose is to provide a method.

Another object of the present invention is to provide a manufacturing method that makes it possible to reduce the size, weight, and cost of a high-performance multipolar anisotropic resin magnet.

Another object of the present invention is to provide a method for manufacturing high-performance multipole anisotropic resin magnets at low cost using a molding machine that does not have expensive special configurations required for molding under high temperature and high pressure. It's about doing.

[Means for Solving the Problems] The method for producing a multipolar anisotropic resin magnet of the present invention includes: (1) injecting a liquid reaction-curing resin containing magnetic powder into a mold for molding;
A method for manufacturing a multipolar anisotropic resin magnet by applying a multipolar orientation magnetic field, the method comprising: (a) a large number of magnetic poles arranged at predetermined intervals including Mi poles that can freely convert magnetic properties; Injecting the reactive hardening resin into a molding cavity provided between the opposing back yokes, and (b) flowing magnetic flux in one direction to the back yoke with each magnetic pole having the same polarity, and holding the uncured resin injected into the resin, and unevenly distributing and orienting the magnetic powder in the resin according to the magnetic flux; (C) after completing step (b), making the magnetic poles have the desired magnetism; Completing the reaction hardening of the resin while applying a magnetic field obtained by converting it in accordance with the multipolar anisotropy of the resin magnet, and unevenly distributing and orienting the magnetic powder in the resin in accordance with the magnetic field. It is characterized by

As the reaction-curable resin used in the present invention, a composition containing one or more selected from polymers, oligomers, and polymers and a curing agent as required can be used, such as urethane, nylon, acrylic resin, etc. Examples include those in which a curing agent is mixed with a resin component, and those having a curing time (reaction time from mixing of necessary components to curing) sufficient to carry out the above steps (b) and (C) are used. .

As the magnetic powder to be contained in the resin, various materials such as Sr ferrite, neodymium iron, ferrite magnet powder, rare earth magnet powder, etc. can be used. In addition, according to the method of the present invention, it is possible to effectively utilize magnetic powder, so even when expensive rare earth magnet powder is used, an increase in manufacturing costs can be suppressed to a minimum.

The content of magnetic powder in the raw resin may be selected appropriately depending on the magnetic strength of the desired resin magnet, etc.; In consideration of movement and orientation, the amount is 70% by weight or less, preferably 50 to 70% by weight.

In the present invention, for example, by using a reactive hardening resin containing 50 to 70% by weight of magnetic powder, it is possible to obtain a magnetically effective region containing magnetic powder at a high concentration of 80 to 95% by weight.

An example of the method of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view schematically showing the main parts of a molding die that can be used in the present invention.

This mold includes a cavity 6 for obtaining a ring-shaped molded product, magnetic poles 4 arranged around the cavity 6 along its outer peripheral wall at predetermined intervals, and magnetic poles 4 made of a high permeability magnetic material. An electromagnetic coil 3 that magnetizes the magnet, and a cavity 6
A back yoke 5 made of a high magnetic permeability magnetic material that faces the magnetic pole 4 via the electromagnetic coil 2 that excites the back yoke 5.
and has.

In the present invention, first, when a current is applied to the electromagnetic coil 2 and the hack yoke 5 is excited with the same polarity, lines of magnetic force flow from the magnetic pole 4 through the cavity 6 to the back yoke 5 in one direction. In this state, when a resin containing magnetic powder is injected into the cavity 6, the magnetic powder 8 is unevenly distributed and oriented in the uncured resin, as shown in the cross-sectional view of FIG.

The lines of magnetic force 7 generated at this time once concentrate on the magnetic pole 4 and then gradually disperse in the cavity 6 toward the hack yoke 5, resulting in convergence toward the magnetic pole 4 as shown in FIG. The magnetic powder is unevenly distributed and oriented to That is, a distribution of magnetic powder is obtained in which the magnetic powder is present at a high concentration in the magnetic force effective region 1 and at a low concentration in the non-magnetic force effective region 1'.

Next, when the magnetic powder is sufficiently unevenly distributed in the magnetic force effective area, the excitation by the electromagnetic coil 2 is stopped and the i! ! A current is passed so that the poles have different magnetisms, and this state is maintained until the resin in the cavity 6 is cured.

At this time, the lines of magnetic force draw a loop between the magnetic poles 4 and flow into the cavity 6, and the magnetic powder 8, which was unevenly distributed as shown in FIG. 2, is further oriented according to the flow of the lines of magnetic force 9 shown in FIG. 3. At this time, due to the presence of the back yoke 5 made of a high permeability magnetic material, the magnetic lines of force 9 flowing from the magnetic pole 4 into the cavity 6 are pulled in the direction of the back yoke 5 as shown in FIG. 'The lines of magnetic force 9 can be sent to a deeper place in the direction of the inner circumferential wall of the cavity 6 than the lines of magnetic force 11 in the case where the yoke 5 is not provided, and leakage 10 between the magnetic poles can be effectively prevented.

Once the desired uneven distribution and orientation of the magnetic powder has been established and the shape of the molded product has hardened and stabilized, the molded product is removed from the mold.
For example, a ring-shaped multipolar anisotropic resin magnet having the structure shown in FIG. 6 can be obtained.

This resin magnet contains magnetic powder 8 at a high concentration in the magnetic force effective region 1 and at a low concentration in the non-magnetic force effective region 1'', and has extremely high magnetic powder utilization efficiency.

Unlike thermoplastic resins, which begin cooling and solidifying as soon as they are injected into the mold, the curing state can be optimized by adjusting the combination of resin and curing agent, their mixing ratio, the heating conditions of the mold, etc. Because of the sufficient uneven distribution of magnetic powder,
An oriented state can be obtained before solidification.

The magnetic field may be applied at least until the desired uneven distribution and orientation of the magnetic powder in the resin in the cavity becomes stable as the resin hardens, and the desired magnetic force is obtained.

Further, the magnetic force of each magnetic pole 4 is determined depending on the design of a desired product, and may be the same or different.

[Example] Example 1 Samarium cobalt (SmCos) powder (particle size: 1 to 3
Reactive curable epoxy resin containing 67% by weight of
Curing time: 1 minute), and injected and filled into the cavity 6 of the mold shown in FIG. 1 with current flowing through the electromagnetic coil 2, and held in that state for 3 seconds.

The cavity 6 has an outer diameter of 6 mm and an inner diameter of 4 mm.

The structure was such that a ring-shaped molded product with a height of 7 mm could be formed, and the magnetic strength of the back yoke 5 was 20 KG on the cavity surface. Further, the timing for starting excitation may be during injection or at the time of injection filling.

Next, the excitation by the electromagnetic coil 2 is stopped and the electromagnetic coil 3 is stopped.
A current was passed through the tube to excite the magnetic poles 4 so that adjacent magnetic poles had different magnetic properties, and this state was maintained for 1 minute.

In order to obtain this molded product, a main material (first liquid) and a hardening agent (second liquid) containing magnetic powder were placed in two feed tanks of a reaction injection molding machine, and kept at approximately 40°C while being circulated. Ta. Next, the first liquid and the second liquid are passed through a mixing nozzle at 90°C.
After the mixture was injected into a mold and held for about 1 minute, the mold was opened and released using an extrusion bottle. In order to reduce mold release resistance, excitation by the electromagnetic coil was not performed when the mold was opened.

The formation state of the magnetic poles in the plane perpendicular to the axis of the resulting ring-shaped resin magnet, the uneven distribution and orientation of the magnetic powder were determined by lapping the cross section of the magnet and observing the cross section with a metallurgical microscope. When a small piece was extracted and fired, it was found that six anisotropic magnetic poles were formed around the periphery, as shown in Figure 6, and most of the magnetic powder was located in the effective magnetic field along the lines of magnetic force passing through each magnetic pole. It was confirmed that the particles were unevenly distributed and oriented within 1. The content of magnetic powder in effective magnetic force region 1 was 92% by weight, and the content of magnetic powder in non-magnetic effective region 1 was 8% by weight.

Furthermore, when a ring-shaped resin magnet obtained by a conventionally known magnetization method was magnetized and its surface magnetic flux density and weight were measured, the surface magnetic flux density was 730G and the weight was 0.3g.

Comparative example samarium cobalt powder (particle size: about 1 to 3 scales) was
Thermoplastic 6-nylon resin containing % by weight, resin temperature 280
℃, an injection pressure of 1500 g/cm 2 and a mold temperature of 110° C., injection molding was carried out using a conventionally known hexagonal orientation method.

The surface magnetic flux density of the obtained ring-shaped resin magnet after magnetization is 7
20G, and its weight was 0.6g.

Furthermore, when the state of magnetic pole formation in a plane perpendicular to the axis of this ring-shaped resin magnet was examined, it was confirmed that six anisotropic magnetic poles were formed around the ring-shaped resin magnet. Also,
When we investigated the distribution of magnetic powder in a plane perpendicular to the axis, we found that the magnetic powder content in the magnetically effective area was 86% by weight, and it contributed to the magnetic force equivalent to the non-magnetically effective area 1゛ in Figure 6. The magnetic powder content in the non-containing part is also as high as 94% by weight.

As can be seen from the above results, the multipolar anisotropic resin magnet according to the present invention has a larger surface magnetic flux ring and is lighter in weight, so it is very useful for high-speed torque rotors and the like.

In particular, one of the requirements for obtaining good rotational performance in a rotor is that the moment of inertia is low. The moment of inertia of a rotor is proportional to the square of the radial distance from the center of the rotor and the specific gravity at that point. Therefore,
When a ring-shaped resin magnet having the configuration shown in FIG. 6 is used as a rotor, the moment of inertia is can be lowered, and good rotational performance can be obtained from the rotor.

[Effects of the Invention] According to the present invention, since the magnetic powder can be effectively unevenly distributed in the magnetic force effective region, the magnetic powder can be efficiently utilized for magnetic force. As a result, even if the magnetic powder content is small, a magnetically effective region containing magnetic powder at a high concentration can be formed, sufficient magnetic strength can be obtained, and significant cost and weight reductions can be achieved.

In addition, in the present invention, since the resin magnet is obtained by low-pressure molding, the molding machine does not require any configuration necessary for high-pressure molding, for example, and it is possible to use an inexpensive molding machine with a simpler configuration. From this point of view, it is also possible to reduce manufacturing costs.

Further, according to the present invention, there is no need for complicated processes such as inserts or actoserts of blocks made of thermosetting resin, etc., and the multipolar anisotropic resin magnet is efficient and labor-saving due to integral molding. It is possible to manufacture

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view showing the main parts of a mold that can be used in the present invention, and Figs. 2 and 3 are cross-sectional views taken along the line A-A in Fig. 1, showing the state inside the mold during molding. Figure 4 is a flow chart showing the manufacturing process of the resin magnet material used in the present invention, Figure 5 is a diagram explaining the effect of the back yoke of the present invention, and Figure 6 is a flowchart showing the manufacturing process of the resin magnet material used in the present invention. FIG. 2 is a cross-sectional view of a six-pole anisotropically oriented product. 1... Magnetic energy effective region, t' -... Region that does not contribute to magnetic energy, 2.
3... Electromagnetic coil, 4... Magnetic pole for polar anisotropic orientation, 5... Back yoke, 6... Cavity 7°9... Lines of magnetic force, 8... Magnetic powder.

Claims (1)

[Claims] 1) A method for manufacturing a multipolar anisotropic resin magnet by injecting a liquid reaction-curing resin containing magnetic powder into a mold and applying a multipolar orienting magnetic field. (a) The reaction-curing resin is placed in a molding cavity provided between a large number of magnetic poles arranged at predetermined intervals, including magnetic poles that can freely convert magnetic properties, and a back yoke facing these magnetic poles. (b) A magnetic flux is flowed in one direction to the back yoke with each magnetic pole having the same polarity, the injected uncured resin is held in the magnetic flux, and the magnetism in the resin is adjusted according to the magnetic flux. (c) After the completion of step (b), the magnetic field obtained by converting the magnetism of the magnetic poles in accordance with the desired multipolar anisotropy of the resin magnet is applied to the resin. 1. A method for manufacturing a multipolar anisotropic resin magnet, comprising the steps of: completing the reaction curing of the above step, and unevenly distributing and orienting magnetic powder within the resin according to the magnetic field. 2) A multipolar anisotropic resin magnet obtained by the method of claim 1. 3) The multipolar anisotropic resin magnet according to claim 2, wherein the magnetic powder content within the magnetically effective region is 80% by weight or more.