JPH08306517A - R-fe-b permanent magnet excellent in electric insulation, heat resistance, and corrosion resistance, and its manufacture - Google Patents

Abstract

PURPOSE: To enhance the electric insulation, heat resistance, and corrosion resistance by covering the surface of an R-Fe-B permanent magnet with a polyimide resin layer through a carbon layer with a specified thickness by vapor polymerization method. CONSTITUTION: This is an R-Fe-B permanent magnet which has a polyimide layer 2.0μm-10μm thick on the surface of its main body whose main phase consists of tetragonal crystal through a carbon layer 0.005μm-0.1μm thick. And, for the manufacture, a polyimide layer 2.0μm-10μm thick is made by vapor polymerization after formation of carbon layer 0.005μm-0.1μm thick on the surface of a magnet by the PVD film formation method of vapor deposition, sputtering, and ion plating, after cleaning the surface of the R-Fe-B permanent magnet. The vapor polymerization is one which imide processing is performed at 280 deg.C-380 deg.C under normal pressure after formation of a polyamic acid film by heating and deposing two kinds of monomers at 200 deg.C-250 deg.C in a vacuum enclosure where the pressure is 1-10<-3> Pa.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an R-Fe-B system permanent magnet and a method for manufacturing the same, and vapor deposition is performed on the surface of an R-Fe-B system permanent magnet through a carbon film layer having a predetermined film thickness. The present invention relates to an R-Fe-B based permanent magnet which is coated with a polyimide resin layer by a polymerization method and achieves the electric insulation, heat resistance and corrosion resistance required for permanent magnets for automobile motors and the like, and a method for producing the same.

[0002]

2. Description of the Related Art R-Fe-B permanent magnets have the best magnetic properties among the practically used magnets, but in order to use them as permanent magnets for multi-pole type motors for automobiles. First, in order to prevent the generation of eddy currents generated in the permanent magnets, it is necessary to wear a coating having excellent electrical insulation properties, and an automobile has an engine room temperature of 200 when the motor is installed while traveling. More than ℃
The magnet used is required to have a coating that has both heat resistance and corrosion resistance.

R-Fe-B system permanent magnets have the drawback of poor corrosion resistance and temperature characteristics of magnetic properties. Therefore, it is proposed to coat the magnet surface with a resin in order to improve the corrosion resistance (Japanese Patent Laid-Open No. 60-63902). However, even if the corrosion resistance is improved by the above method, there is a problem that the heat resistance is not sufficient and the electric insulation is poor, and an R-Fe-B permanent magnet having excellent magnetic characteristics is used in automobiles. It is the cause that cannot be used for the motor.

[0004]

Recently, in order to improve wear resistance, a polyimide resin as a high wear resistant coating is formed on the Ni plating layer on the magnetic pole surface of the iron core and the magnetic pole surface of the actuator by vapor deposition polymerization method. Proposed wearing
No. 276532), the abrasion resistance of the opposing magnetic pole surface of the relay can be improved and improved, but the coating strength required for the R-Fe-B permanent magnet of the multi-pole type automobile motor is excellent. In addition, it does not satisfy electrical insulation, heat resistance, and corrosion resistance.

In particular, the present invention provides an R-Fe-B system permanent magnet excellent in electrical insulation and heat resistance required for a permanent magnet of a multi-pole type motor for an automobile and excellent in corrosion resistance, and a method for producing the same. It is intended to be provided.

[0006]

The inventors of the present invention use R-Fe-B based permanent magnets having excellent magnetic properties in motors for automobiles, and therefore improve and improve not only corrosion resistance but also electric insulation and heat resistance. Therefore, as a result of various studies, it was found that by covering the surface of the magnet with a polyimide resin, excellent magnetic properties are provided, and in addition to corrosion resistance, electric insulation and heat resistance are greatly improved.

However, when a polyimide resin is directly deposited on the surface of the magnet by vapor deposition polymerization, water is generated on the surface of the magnet during the polymerization reaction and the imidization treatment, and the water reacts with the surface of the magnet to cause the surface of the magnet to react. It was found that there is a problem that the adhesion of the polyimide resin to the above is impaired, and as a result of further study, after cleaning the magnet surface by an ion sputtering method or the like, a vacuum deposition method or a plasma sputtering method was applied to the magnet surface. When the carbon film layer is formed by a PVD thin film forming method such as ion plating, carbon is diffused on the surface of the R-Fe-B permanent magnet by heating during vapor deposition polymerization or imidization treatment of the polyimide resin, and particularly, , R-
It is considered that a part of B on the surface of the Fe-B based permanent magnet is replaced with carbon, and the carbon film layer and the polyimide resin cause a C-C reaction, and the adhesion of the polyimide resin film is greatly improved. As a result, the desired electrical insulation
It was found that an R-Fe-B based permanent magnet excellent in heat resistance and corrosion resistance can be obtained, and the present invention was completed.

That is, according to the present invention, a film thickness of 0.005 is formed on the surface of the R-Fe-B system permanent magnet body having a tetragonal main phase.
A film thickness of 2.0 μ through a carbon film layer of μm to 0.1 μm
R-Fe-B excellent in electrical insulation, heat resistance, and corrosion resistance, characterized by having a polyimide film layer of m to 10 μm
It is a permanent magnet.

Further, according to the present invention, as a method of manufacturing the above-mentioned R-Fe-B system permanent magnet, R- whose main phase is a tetragonal crystal is used.
After cleaning the surface of the Fe-B based permanent magnet, vacuum deposition,
After forming a carbon film having a film thickness of 0.005 μm to 0.1 μm on the surface of the magnet body by a PVD thin film forming method such as sputtering or ion plating, the magnet body is formed by a vapor deposition polymerization method to form a polyimide film layer having a film thickness of 2.0 μm to 10 μm. The present invention proposes a method for producing an R-Fe-B based permanent magnet excellent in electrical insulation, heat resistance, and corrosion resistance, which is characterized by forming

Further, in the invention, in the above-mentioned manufacturing method, the vapor deposition polymerization method comprises using a vacuum container having a degree of vacuum of 1 Pa to 10 ^-3 Pa to prepare two kinds of monomers which are raw materials for a polyimide film.
After forming a polyamic acid film by heat vapor deposition at 00 ° C to 250 ° C, it is subjected to imidization at 280 ° C to 380 ° C under normal pressure to form a polyimide film. R- which has excellent electrical insulation, heat resistance and corrosion resistance. Fe-B permanent magnet manufacturing method, and the two kinds of raw material monomers used in the vapor deposition polymerization method are aromatic carboxylic dianhydride and aromatic diamine, which have excellent electrical insulation, heat resistance, and corrosion resistance. A method of manufacturing an R-Fe-B based permanent magnet is also proposed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the thickness of the carbon film provided on the cleaned magnet surface is 0.005 μm to
The reason for limiting the thickness to 0.1 μm is that if it is less than 0.005 μm, the adhesion to the magnet surface is not sufficient, and if it exceeds 0.1 μm, there is no effective problem. Since it is not desirable and not preferable, the carbon film thickness is set to 0.005 μm to 0.1 μm. Further, the PVD thin film forming method such as vacuum deposition, sputtering, and ion plating is preferable as the method for forming the underlying metal film.

The reason why the thickness of the polyimide resin is limited to 2.0 μm to 10 μm in the present invention is that if the thickness is less than 2.0 μm, the coating is not sufficient and a coating excellent in electrical insulation, heat resistance and corrosion resistance cannot be obtained. If it exceeds 10 μm, there is no problem in terms of effect, but it is not preferable because it causes an increase in manufacturing cost and is not practical.

In the present invention, the reason why the vacuum degree of the vacuum vessel for vapor deposition polymerization is limited to 1 Pa to 10 ^-3 Pa is 1 P.
If it exceeds a, the polymerization reaction becomes non-uniform and the film quality deteriorates. If it is less than 10 ^-3 Pa, the evaporation of the monomer is extremely small and a stable polymerization reaction does not occur, which is not preferable.

The temperature of the substrate magnet during vapor deposition polymerization is 1
It is preferable to set the temperature to 50 ° C to 200 ° C. If the temperature is lower than 150 ° C, the adhesion to the magnet substrate is not sufficient, and if the temperature exceeds 200 ° C, the vapor deposition polymerization reaction on the magnet substrate does not proceed promptly. Is preferably set to 150 to 200 ° C.

In the present invention, the two kinds of raw material monomers used for vapor deposition polymerization are aromatic carboxylic acid dianhydrides and aromatic diamines, and aromatic carboxylic acid dianhydrides include pyromellitic dianhydride. As the aromatic diamine, diaminodiphenyl ether, p-phenylenediamine and the like are used.

The reason for accelerating vapor deposition of two kinds of raw material monomers at 200 ° C. to 250 ° C. in a vacuum container is 200 ° C.
If it is less than 250 ° C, the amount of evaporation is not sufficient, and if it exceeds 250 ° C, the evaporation rate is too high to control the film thickness, which is not preferable.

Further, in the present invention, if the imidization temperature for forming the polyimide resin is less than 280 ° C., the imidization reaction does not proceed sufficiently, the adhesion to the base film is not sufficient, and if it exceeds 380 ° C. 280 ° C. to 38 because resin deteriorates and becomes brittle, cracks and the like occur and peeling occurs
Set to 0 ° C.

Rare earth element R used in the permanent magnet of the present invention
Occupies 10 atomic% to 30 atomic% of the composition, but Nd,
At least one of Pr, Dy, Ho, Tb, or further La, Ce, Sm, Gd, Er, Eu, T
Those containing at least one of m, Yb, Lu and Y are preferable.

Although one of R is usually sufficient, a mixture of two or more kinds (Misch metal, didymium, etc.) can be practically used for the convenience of availability. It should be noted that this R does not have to be a pure rare earth element, and may contain an impurity that is unavoidable in manufacturing within the industrially available range.

[0020] R is an essential element in the R-Fe-B system permanent magnet, and if it is less than 10 atomic%, the crystal structure becomes a cubic crystal structure of α-iron with the same structure, so that high magnetic properties, especially high coercive force are obtained. If it exceeds 30 atomic%, the R-rich non-magnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet having excellent characteristics cannot be obtained. Therefore, R is l
The range of 0 atom% to 30 atom% is desirable.

B is an essential element in the above-mentioned permanent magnet. If it is less than 2 atomic%, a rhombohedral structure is the main phase and a high coercive force (iHc) cannot be obtained.
Since the rich non-magnetic phase increases and the residual magnetic flux density (Br) decreases, an excellent permanent magnet cannot be obtained. Therefore, B is preferably in the range of 2 atom% to 28 atom%.

Fe is an essential element in the above-mentioned permanent magnet, and the residual magnetic flux density (Br) decreases if it is less than 65 atom%, and a high coercive force cannot be obtained if it exceeds 80 atom%. % To 80 atomic% is desirable.

Further, substituting a part of Fe with Co can improve the temperature characteristics without deteriorating the magnetic characteristics of the obtained magnet, but the Co substitution amount is 20% of that of Fe.
On the other hand, if it exceeds, the magnetic characteristics are deteriorated, which is not preferable. The substitution amount of Co is 5 atomic% to 1 in the total amount of Fe and Co.
In the case of 5 atom%, (Br) is increased as compared with the case of not substituting, which is preferable for obtaining a high magnetic flux density.

In addition to R, B and Fe, the presence of impurities that are unavoidable in industrial production can be tolerated. For example, part of B is 4.0 wt% or less of C, 2.0 wt% or less of P, 2 .0
By substituting at least one of S of 2.0 wt% or less and Cu of 2.0 wt% or less with a total amount of 2.0 wt% or less, it is possible to improve the manufacturability of the permanent magnet and reduce the cost.

Further, Al, Ti, V, Cr, Mn, B
i, Nb, Ta, Mo, W, Sb, Ge, Sn, Zr,
At least one of Ni, Si, Zn, and Hf is R
It can be added to the -Fe-B based permanent magnet because it is effective in improving the coercive force, squareness of demagnetization curve, improving manufacturability, and lowering the cost. The upper limit of the addition amount is such that (Br) needs to be at least 9 kG or more in order to set the (BH) max of the magnet material to 20 MGOe or more.

The permanent magnet of the present invention comprises a compound having a tetragonal crystal structure having an average crystal grain size in the range of 1 to 80 μm as a main phase, and a volume ratio of 1% to 50% of a nonmagnetic phase ( (Excluding an oxide phase). The permanent magnet according to the present invention exhibits a coercive force iHc ≧ 1 kOe, a residual magnetic flux density Br> 4 kG, and a maximum energy product (BH).
max indicates (BH) max ≧ 10 MGOe, and the maximum value reaches 25 MGOe or more.

According to the present invention, the surface of the magnet is cleaned by an ion sputtering method or the like, and then the surface of the magnet is vacuum-deposited,
After forming a carbon film having a specific film thickness with good adhesion to the R-Fe-B permanent magnet and good adhesion to the polyimide resin by a PVD thin film forming method such as sputtering or ion plating, a polyimide resin is formed on the carbon film. By forming by vapor deposition polymerization, it has excellent electrical insulation, heat resistance, and corrosion resistance, and it is a high-performance R-type that can be used especially for motors for automobiles.
A Fe-B based permanent magnet is obtained.

[0028]

EXAMPLE A cast ingot having a composition of 15Nd-77Fe-8B (at%) was pulverized, finely pulverized, molded, sintered and heat-treated to obtain a magnet test piece having a diameter of 12 mm × 2 mm.
The magnet characteristics are shown in Table 1. 1 × 10 ^-3 P inside the vacuum container
Vacuum exhaust to a or less, Ar gas pressure 10Pa, -500V
After cleaning the surface of the magnet body by performing surface sputtering for 15 minutes, the inside of the vacuum vessel is evacuated again to 1 × 10 ⁻³ Pa or less, and the carbon rod is heated at 100 V and 40 A to evaporate the magnet. A carbon film having a thickness of 0.02 μm was formed on the surface.

The inside of the vacuum vessel was set to a vacuum degree of 1 × 10 ^-2 Pa, and two pyromellitic dianhydrides were used as one evaporation source.
While heating at 20 ° C., diaminodiphenyl ether as another evaporation source is heated at 210 ° C., the magnet substrate is further heated to 170 ° C., and treatment is performed for 1 hour.
A raw material monomer is vapor-deposited and polymerized on the surface of the magnet to form a polyamic acid film.

Next, the polyimide resin film was formed to a thickness of 5 μm by heating at 300 ° C. for 1 hour in a nitrogen atmosphere under normal pressure for imidization to form a polyimide resin film.

Thereafter, the permanent magnet test piece having the obtained polyimide resin film on the surface was placed at a temperature of 80 ° C. and a relative humidity of 90.
%, The magnetic properties, volume resistivity and heat distortion temperature were measured. The measurement results are shown in Table 2. The volume resistivity is used to evaluate the electrical insulation property, and the electrode resistance is measured, and the resistance between the coating surface and the magnet is measured and calculated from the following equation (1).

Ρ = R · S / l (1) where ρ: volume resistivity Ω · cm, R: resistance Ω, S: electrode area cm ² , l: polyimide film thickness cm. The heat resistance was evaluated, and the temperature was set to the temperature at which the film was discolored, cracked, and the like by leaving it at that temperature for 20 hours.

Comparative Example 1 A magnet body test piece having the same composition as in Example 1 was surface-cleaned under the same conditions as in Example 1, and then a polyimide resin film having a thickness of 5 μm was directly formed on the magnet surface under the same conditions as in Example 1. Formed. After that, the magnetic properties and the volume resistivity after standing for 500 hours under the same temperature of 80 ° C. and relative humidity of 90% as in Example 1,
The heat distortion temperature was measured, and the results are shown in Table 3.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

The R-Fe-B system permanent magnet according to the present invention is formed by depositing a polyimide resin layer on the surface of the system permanent magnet through a carbon layer having a specific predetermined film thickness by a vapor deposition polymerization method. As shown in the examples, excellent electrical insulation, heat resistance and sufficient corrosion resistance are achieved.
Fe-B system permanent magnet has the excellent magnetic properties originally possessed by
It can be provided for severe applications such as permanent magnets for multi-pole type automobile motors, and can contribute to downsizing and weight reduction of motors.

Claims (4)

[Claims] 1. A polyimide film having a film thickness of 2.0 μm to 10 μm on the surface of an R—Fe—B system permanent magnet body having a tetragonal main phase with a carbon film layer having a film thickness of 0.005 μm to 0.1 μm interposed therebetween. An R-Fe-B based permanent magnet excellent in electrical insulation, heat resistance, and corrosion resistance, which is characterized by having a layer. 2. After cleaning the surface of an R—Fe—B based permanent magnet body having a tetragonal main phase, a film thickness of 0.1 μm is formed on the surface of the magnet body by a PVD thin film forming method such as vacuum deposition, sputtering and ion plating. After forming a carbon film layer having a thickness of 005 μm to 0.1 μm, the magnet body is formed into a film having a thickness of 2.0 μm by a vapor deposition polymerization method.
The method for producing an R-Fe-B based permanent magnet excellent in electrical insulation, heat resistance, and corrosion resistance according to claim 1, wherein a polyimide film layer having a thickness of m to 10 m is formed. 3. A vacuum degree of 1 Pa to 10 ⁻³ P is used in the vapor deposition polymerization method.
In the vacuum container of a, two kinds of monomers that are raw materials of the polyimide film are heated and vapor-deposited at 200 ° C. to 250 ° C. to form a polyamic acid film, and then an imidization treatment is performed at 280 ° C. to 380 ° C. under normal pressure to perform the polyimide film The method for producing an R-Fe-B based permanent magnet excellent in electrical insulation, heat resistance and corrosion resistance according to claim 2, wherein a layer is formed. 4. The electrical insulation, heat resistance and corrosion resistance according to claim 3, wherein the two kinds of raw material monomers used in the vapor deposition polymerization method are an aromatic carboxylic acid dianhydride and an aromatic diamine. An excellent method for producing an R-Fe-B based permanent magnet.