JPH08279407A - R-fe-b permanent magnet being excellent in electrical insulating properties, heat resistance and corrosion resistance and manufacture thereof - Google Patents

Abstract

PURPOSE: To obtain a permanent magnet for an automobile being excellent in electrical insulating properties, heat resistance and corrosion resistance by providing a polyimide film of a specified film thickness on the surface of an R-Fe-B permanent magnet body of which the main phase is constituted of tetragonal crystals, with a ground metal film of a specified film thickness interlaid. CONSTITUTION: A polyimide film of a film thickness 2.0-10μm is provided on the surface of an R-Fe-B permanent magnet body of which the main phase is constituted of tetragonal crystals, with a ground metal film of a film thickness 1.0-3.0μm interlaid. The reason why the thickness of a ground metal provided on the cleaned surface of a magnet is limited to 1.0-3.0μm is that the thickness less than 1.0μm and that exceeding 3.0μm are both undesirable since the former is insufficient for the adhesion to the surface of the magnet and the latter causes a rise in the cost as the ground film. The reason why the thickness of polyimide resin is limited to 2.0-10μm is that the thickness less than 2.0μm and that exceeding 10μm are both undesirable since the former makes it impossible to obtain a film being excellent in electrical insulating properties, heat resistance and corrosion resistance and the latters causes a rise in the cost of manufacture.

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 it is vapor-deposited on the surface of an R-Fe-B system permanent magnet through an underlying metal layer having a predetermined film thickness. R-Fe-B permanent magnet with excellent electrical insulation, heat resistance, and corrosion resistance that has been achieved by using a polyimide resin by the polymerization method and has achieved the electrical insulation, heat resistance, and corrosion resistance required for permanent magnets for automobile motors. And its manufacturing method.

[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 in the permanent magnets, it is necessary to wear a coating having excellent electrical insulation properties. Also, in an automobile, the temperature of the engine room in which the motor is placed during traveling is 200 As the temperature rises to ℃, it is required for the magnet to be used 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, it has been proposed to use a vapor deposition polymerization method to coat a polyimide resin as a highly wear-resistant coating on a Ni plating layer on the magnetic pole surface of an iron core and the magnetic pole surface of an actuator, respectively. No. 3-276532), the main purpose of the method is to improve the wear resistance of the opposing magnetic pole surfaces of the relay.

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, the magnet surface was cleaned by an ion sputtering method or the like, and then the magnet surface was plated or ion plated. By a vapor phase thin film forming method such as ion-sputtering method, vapor deposition, or the like, having a specific film thickness A with good adhesion to an R-Fe-B system permanent magnet and adhesion to a polyimide resin.
l, Ti, Ni, Zn, Sn, Fe and other metal or alloy coatings are used to form a base metal film, and then polyimide resin is formed on the base metal film by vapor deposition polymerization to achieve the desired electrical insulation, heat resistance and corrosion resistance. It was found that an excellent R-Fe-B based permanent magnet can be obtained, and the present invention was completed.

That is, according to the present invention, a film thickness of 1.0 μm is formed on the surface of the R—Fe—B system permanent magnet body having a tetragonal main phase.
~ 3.0 μm underlying metal film with a film thickness of 2.0 μm ~ 1
It is an R-Fe-B based permanent magnet excellent in electrical insulation, heat resistance and corrosion resistance, which is characterized by having a polyimide film of 0 μm. Further, according to the present invention, in the above-mentioned structure, the underlying metal layer is made of Al, Ti, Ni, Zn, Sn, Fe and alloys thereof, and is an R-Fe-B based permanent material excellent in electrical insulation, heat resistance and corrosion resistance. We also propose a 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 body, a film thickness of 1.0 μm is formed on the surface of the magnet body by a plating method or a vapor deposition method.
After forming a base metal film of ˜3.0 μm, the magnet body is housed in a vacuum container and a film thickness of 2.0 μm to 1 by a vapor deposition polymerization method.
We propose 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 a polyimide film layer of 0 μm.

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. The two kinds of raw material monomers used in the production method of the Fe-B permanent magnet and the vapor deposition polymerization method are aromatic carboxylic acid dianhydride and aromatic diamine. R-Fe- which has excellent electric insulation, heat resistance and corrosion resistance. A method for manufacturing a B-based permanent magnet is also proposed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the thickness of the underlying metal film provided on the cleaned magnet surface is 1.0 μm to 3.0 μm.
The reason for limiting the thickness to 1.0 μm is that if the thickness is less than 1.0 μm, the adhesion to the magnet surface is insufficient, and if it exceeds 3.0 μm, there is no problem in terms of effectiveness. Since it is not desirable, the underlying metal film thickness is 1.0 μ
m to 3.0 μm.

The underlying metal film may be formed by a plating method such as an electrolytic plating method or an electroless plating method, or a vapor phase thin film forming method such as an ion plating method, an ion sputtering method, or a vapor deposition method. In the present invention, the underlying metal film is formed of Al, Ti, Ni, Zn, S which has good adhesion to the R-Fe-B system permanent magnet and good adhesion to the polyimide resin.
N, Fe and their alloys are preferred.

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-phenyldiamine 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 large 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 underlying metal 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 reasons 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.

[0021] R is an essential element in the R-Fe-B system permanent magnet, and if it is less than 10 atom%, the crystal structure becomes a cubic crystal structure of α-iron having 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, and 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.

Further, 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 nonmagnetic phase of 1% to 50% by volume ( (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, after the magnet surface is cleaned by an ion sputtering method or the like, an R-Fe-B permanent magnet is formed on the magnet surface by a vapor phase thin film forming method such as a plating method or an ion plating method. Al, Ti, Ni of a specific film thickness with good adhesion to
By forming a base metal film of a metal such as Zn, Sn, Fe, or an alloy film, and then forming a polyimide resin by vapor deposition polymerization on it, the desired electrical insulation, heat resistance, and corrosion resistance are excellent, especially for automobiles. A feature is that a high-performance R-Fe-B based permanent magnet that can be used in a motor is obtained.

[0029]

EXAMPLE A cast ingot of 16Nd-77Fe-7B composition was crushed, finely crushed, formed, sintered, and heat-treated to obtain a diameter of 1
A magnet body test piece having a size of 2 mm × 2 mm was obtained. The magnet characteristics are shown in Table 1. The inside of the vacuum vessel was evacuated to 1 × 10 ⁻³ Pa or less, and surface sputtering was performed at Ar gas pressure of 10 Pa and −500 V for 15 minutes to clean the surface of the magnet body.
Under the ion plating conditions shown in Table 2, the base metal coating layer of Ti, Al, Zn, Sn, and Fe shown in Table 2 was formed on the surface of the magnet body. The Ni undercoat layer was formed by electroplating.

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, under normal pressure, it was heated in a nitrogen atmosphere at 300 ° C. for 1 hour for imidization to form a polyimide resin film, thereby forming a polyimide resin film with a thickness of 5 μm.

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 3.

The volume resistivity is used to evaluate the electrical insulation property, and the electrode resistance is measured, and the resistance between the surface of the coating 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. It was evaluated and was set to a temperature at which discoloration, cracks and the like of the coating film were left in the atmosphere 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.

Comparative Example 2 A magnet test piece having the same composition as in Example 1 was coated with an epoxy resin to a thickness of 10 μm by a spray method in the atmosphere. 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.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

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

Claims (5)

[Claims] 1. A polyimide film having a thickness of 2.0 μm to 10 μm on the surface of an R—Fe—B system permanent magnet body whose main phase is tetragonal with a base metal film having a thickness of 1.0 μm to 3.0 μm interposed. An R-Fe-B based permanent magnet excellent in electrical insulation, heat resistance and corrosion resistance, which is characterized by having 2. The base metal layer is made of Al, Ti, Ni, Z.
The R-Fe-B based permanent magnet excellent in electrical insulation, heat resistance, and corrosion resistance according to claim 1, which is n, Sn, Fe, or an alloy thereof. 3. A film having a thickness of 1.0 .mu.m to 3.0 .mu.m formed on the surface of the magnet body by a plating method or a vapor deposition method after cleaning the surface of the R--Fe--B system permanent magnet body having a tetragonal main phase.
3. After forming the base metal film of 1., the magnet body is housed in a vacuum container to form a polyimide film layer having a thickness of 2.0 μm to 10 μm by a vapor deposition polymerization method. A method for producing an R-Fe-B based permanent magnet having excellent electric insulation, heat resistance, and corrosion resistance as described. 4. 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 3, wherein 5. The electrical insulation, heat resistance and corrosion resistance according to claim 4, 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.