JP2010034522A - Permanent magnet, method of manufacturing the same, permanent magnet for motor, and permanent magnet motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an SmCo-based magnet having a low coercive force suitable for a magnet for a motor, and a high squareness ratio, and a method of manufacturing the same. <P>SOLUTION: The permanent magnet has a predetermined composition, wherein coercive force is 0.5-3.5 kOe, and a squareness ratio expressed by a ratio of remanent magnetization to magnetization in a magnetic field of 10 kOe is 80% or more. Average recoil magnetic permeability of second and third quadrants is 1.00-1.08. The permanent magnet preferably has three phases such as a CaCu<SB>5</SB>phase, a Th<SB>2</SB>Zn<SB>17</SB>phase and a Th<SB>2</SB>Co<SB>7</SB>phase as constituent phases. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a permanent magnet, particularly a permanent magnet having a low coercive force and a high squareness ratio suitable for a motor, and a method for manufacturing the same. Furthermore, the present invention relates to a permanent magnet motor using these magnets.

Conventionally, Alnico magnets, ferrite magnets, Sm-Co magnets, Nd-Fe-B magnets, and the like are known as permanent magnets, and these permanent magnets are classified into various motors such as VCM and spindle motor, measuring instruments, In addition to speakers, medical MRI, and the like, appropriate magnets are used as key parts of various electric devices.
Among these magnets, a large amount of Fe or Co and rare earth elements are contained. Fe and Co contribute to an increase in saturation magnetic flux density, while rare earth elements contribute to an increase in coercive force because they bring about a very large magnetic anisotropy derived from the behavior of 4f electrons in the crystal field. Realizes magnet characteristics.
In recent years, there is a growing demand for miniaturization and energy saving of various electrical devices, and the permanent magnets that are key component materials for these devices also have a higher maximum energy product [(BH) _max ], a large coercive force, and improved temperature characteristics of magnet properties. Has been demanded.
As an application field of permanent magnets, motors are especially attracting attention from the viewpoint of energy saving, and when used in this, the loss can be greatly reduced compared to conventional induction type, so as an energy saving technology for various applications such as in-vehicle and home appliance applications. It is spreading.

  Generally, permanent magnet motors are roughly divided into two types. These are a surface magnet type permanent magnet motor in which a permanent magnet is attached to the outer periphery of a rotor core and an embedded type permanent magnet motor in which a permanent magnet is embedded in the rotor core. An embedded permanent magnet motor is suitable for the variable speed drive motor.

The configuration of the rotor of the embedded permanent magnet motor will be described with reference to FIG. In FIG. 1, 11 is a rotor, 12 is a rotor core, and 14 is a high coercivity permanent magnet. A rectangular cavity is provided in the outer peripheral portion of the rotor core 12 by the same number as the number of poles. FIG. 1 shows a four-pole rotor 11 in which four cavities are provided and a permanent magnet 14 is inserted. The permanent magnet 14 is magnetized in the radial direction of the rotor or in the direction perpendicular to the side facing the air gap surface in the rectangle of the cross section of the permanent magnet 14. The permanent magnet 14 is mainly an NdFeB permanent magnet having a high coercive force so as not to be demagnetized by a load current. The rotor core 12 is formed by laminating electromagnetic steel plates punched out of cavities. An example of such a motor is a permanent magnet type reluctance type rotating electrical machine described in JP-A-11-136912 (Patent Document 1).
In the permanent magnet type rotating electrical machine, the interlinkage magnetic flux of the permanent magnet is always generated at a constant value, so that the induced voltage by the permanent magnet increases in proportion to the rotational speed. In variable speed operation from low speed to high speed, the induced voltage by the permanent magnet becomes extremely high at high speed rotation, and when the induced voltage by the permanent magnet is applied to the electronic components of the inverter and exceeds the withstand voltage of the electronic components, the components break down. To do. For this reason, it is conceivable to perform a design in which the amount of magnetic flux of the permanent magnet is reduced so as to be equal to or lower than the withstand voltage, but the output and efficiency in the low speed region of the permanent magnet type rotating electrical machine are reduced.

In the permanent magnet type rotating electrical machine, the interlinkage magnetic flux of the permanent magnet is always generated at a constant value, so that the induced voltage by the permanent magnet increases in proportion to the rotational speed. When operating while changing the magnetization from low speed to high speed, the induced voltage by the permanent magnet becomes extremely high at high speed rotation, and the induced voltage by the permanent magnet is applied to the electronic components of the inverter, and the component exceeds the withstand voltage of the electronic components. Breaks down. For this reason, it is conceivable to perform a design in which the amount of magnetic flux of the permanent magnet is reduced so as to be equal to or lower than the withstand voltage.

  When operation is performed while changing the magnetization close to constant output from low speed to high speed, the flux linkage of the permanent magnet is constant, so in the high-speed rotation range, the voltage of the rotating electrical machine reaches the upper limit of the power supply voltage and the current required for output No longer flows. As a result, the output is greatly reduced at high speeds, and further, it becomes impossible to drive over a wide range up to high speeds. Recently, flux-weakening control has begun to be applied as a method of expanding the operating range while changing the magnetization. In the flux weakening control, a demagnetizing field due to the d-axis current is applied to the high coercive force permanent magnet 4, and the magnetic operating point of the permanent magnet is moved within a reversible range to change the amount of magnetic flux. For this reason, a NdFeB magnet having a high coercive force is applied to the permanent magnet so that it is not irreversibly demagnetized by a demagnetizing field.

Since the interlinkage magnetic flux of the permanent magnet decreases due to the demagnetizing field of the d-axis current, the decrease of the interlinkage magnetic flux creates a voltage margin with respect to the voltage upper limit value. Since the current can be increased, the output in the high speed region increases. Further, the rotational speed can be increased by the voltage margin, and the range in which the operation can be performed while changing the magnetization is expanded.
However, it is necessary to continue to apply a demagnetizing field to the permanent magnet, and since the d-axis current that does not contribute to the output is continuously supplied, the copper loss increases and the efficiency deteriorates. Further, the demagnetizing field due to the d-axis current generates a harmonic magnetic flux, and the increase in voltage generated by the harmonic magnetic flux or the like is weakened, creating a limit of voltage reduction by the magnetic flux control. Therefore, even if the flux-weakening control is applied to the embedded permanent magnet type rotating electric machine, it is difficult to operate at a variable speed that is three times or more the base speed. Furthermore, the iron loss is increased by the harmonic magnetic flux, and vibration is generated by the electromagnetic force generated by the harmonic magnetic flux.

Further, when an embedded permanent magnet motor is applied to a drive motor for a hybrid vehicle, the motor is rotated in a state where it is driven only by an engine. At medium / high speed rotation, the induced voltage of the motor's permanent magnet exceeds the power supply voltage, and the d-axis current continues to flow under the flux-weakening control. In this state, since the motor generates only a loss, the overall operation efficiency is deteriorated.
For this reason, with respect to the problems of the prior art as described above, Japanese Patent Laid-Open No. 2006-280195 (Patent Document 2) enables operation while changing the magnetization in a wide range from low speed to high speed. Motors that can change the magnetization state of all or part of permanent magnets that can provide higher torque and higher output in the middle / high-speed rotation range, improved efficiency, and improved reliability (permanent magnet type) Rotating electric machines) have been proposed.

  That is, this permanent magnet type motor includes a stator provided with a stator winding as shown in FIG. 2 (FIG. 1 of Patent Document 2), and a magnetic field generated by a current of the stator winding in a rotor core. And a rotor in which a low coercivity permanent magnet having a coercive force that irreversibly changes the magnetic flux density and a high coercivity permanent magnet having a coercivity more than twice that of the low coercivity permanent magnet are provided. It is a thing. In other words, a permanent magnet rotating electrical machine that enables variable speed operation in a wide range from low speed to high speed, realizing high torque in the low-speed rotation range, high output in the medium / high-speed rotation range, improved efficiency, and improved reliability. Can provide. As the magnet used for the permanent magnet motor, a high coercive force magnet is an NdFeB magnet, and a low coercive force magnet is an alnico magnet or an FeCrCo magnet.

  Patent Document 2 shows an Alnico magnet (AlNiCo) or FeCrCo magnet as a low coercivity permanent magnet, and an NdFeB magnet as a high coercivity permanent magnet. The coercive force of the alnico magnet (magnetic field at which the magnetic flux density becomes 0) is 60 to 120 kA / m, which is 1/15 to 1/8 of the coercive force of 950 kA / m of the NdFeB magnet. The coercive force of the FeCrCo magnet is about 60 kA / m, which is 1/15 of the coercive force of the NdFeB magnet of 950 kA / m. Alnico magnets and FeCrCo magnets have considerably lower coercivity than NdFeB high coercivity magnets, and this low coercivity makes it possible to change the magnetization state of all or part of permanent magnets. Make it. In the embodiment, a high coercive force permanent magnet having a coercive force 8 to 15 times that of the low coercive force permanent magnet is applied, thereby obtaining a rotating electrical machine having excellent characteristics.

On the other hand, SmCo magnets aimed at developing a high coercive force have been disclosed.
Among RCo ₅ rare earth intermetallic compounds (R: rare earth elements) having a rare earth to cobalt ratio of 1: 5, SmCo ₅ exhibits particularly high uniaxial crystal magnetic anisotropy and a high coercive force. It has been known. For this reason, in this intermetallic compound, research has been conducted on each composition in which rare earth elements are changed, and basic physical properties such as anisotropic magnetic field and saturation magnetization have been reported.
In addition, in order to increase the coercive force, a composition richer in the rare earth than in the stoichiometric composition is selected and densification is achieved by liquid phase sintering. Further, a high coercive force is obtained by performing heat treatment at about 850 ° C. after sintering.
However, for example, the Co site of SmCo ₅ cannot be replaced in large quantities by Fe having a larger magnetic moment, so it is difficult to replace Co with another wire metal element to make a stronger magnet.
As described above, permanent magnets were aimed at improving the maximum energy product, that is, increasing the residual magnetic flux density and coercive force. Therefore, there are almost no magnets that have been put to practical use in R-Co based alloy systems with relatively low Co. It was.

JP-A-11-136912 JP 2006-280195 A

All patent documents aim at high coercive force. Therefore, the concept of the low coercivity magnet in the motor that can change the magnetization state of the whole or a part of the permanent magnets applied this time cannot be sufficiently exhibited. On the other hand, low coercivity magnets applied to motors that can change the magnetization state of all or part of permanent magnets are required to improve efficiency by controlling magnetic flux in a wider range than when using alnico magnets. It was.
To further increase the output, efficiency, and reliability of motors, especially motors that can change the magnetization state of all or part of permanent magnets, it is necessary to be able to set the optimum amount of magnetic flux under specified operating conditions. . An object of the present invention is to provide a permanent magnet suitable for such a setting and particularly suitable for a low coercive force magnet and a method for manufacturing the same. The present invention provides a permanent magnet that is extremely effective for increasing the efficiency of motors of various capacities, such as household appliances such as washing machines and air conditioners, in-vehicle applications, and train applications. Furthermore, it is providing the permanent magnet motor and permanent magnet for motors suitable for the above applications.

  The present invention sets an optimum amount of magnetic flux under a predetermined operating condition for further high output, improved efficiency, and improved reliability of a motor, particularly a motor capable of changing the magnetization state of the whole or a part of permanent magnets. An object of the present invention is to provide a permanent magnet suitable for this, particularly suitable for a low coercivity magnet, and a method of manufacturing the same. The present invention provides a permanent magnet that is extremely effective for increasing the efficiency of motors of various capacities, such as household appliances such as washing machines and air conditioners, in-vehicle applications, and train applications. Furthermore, it is providing the permanent magnet motor and permanent magnet for motors suitable for the above applications.

The permanent magnet of the present invention satisfies the following general formula and has a coercivity at room temperature of 0.5 kOe or more and 5 kOe or less, and a squareness ratio expressed by a ratio of residual magnetization to magnetization in a magnetic field of 10 kOe is 80% or more. It is characterized by being.
General _{formula: Sm 1-x R x (} Co 1-a-b-c-d Fe a Cu b M c T d) z
R: at least one selected from La, Ce, Pr, and Nd
M: at least one selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Ni, Mn
T: At least one selected from Si, B, Al, and Ga
Atomic ratio when R is 1
0 ≦ x ≦ 0.65
0 ≦ a ≦ 0.2
0.02 ≦ b ≦ 0.3
0 ≦ c ≦ 0.05
0 ≦ d ≦ 0.05
0.02 ≦ a + b + c + d ≦ 0.35
3.2 ≦ z ≦ 4.1

The coercive force at room temperature is preferably 0.5 kOe or more and 3.5 kOe or less. Moreover, it is preferable that the value of the general formula x is 0.02 ≦ x ≦ 0.6, the a value is 0.01 ≦ a ≦ 0.15, and the b value is 0.02 ≦ b ≦ 0.2. The average recoil permeability of the second and third quadrants is preferably 1.00 to 1.08. Moreover, it is preferable to comprise at least one of a Th ₂ Co ₇ phase and a CaCu ₅ phase or an RCo ₃ phase. The permanent magnet is preferably a sintered body. Moreover, it is suitable for the permanent magnet mounted on the motor. In particular, the coercive force at room temperature is 0.5 kOe or more and 5 kOe or less, the squareness ratio expressed by the ratio of the residual magnetization to the magnetization in the magnetic field of 10 kOe is 80% or more, and the average recoil permeability 1 in the second and third quadrants is 1 The permanent magnet having 0.001 to 1.08 is suitable for a motor that can change the magnetization state of the whole or part of the permanent magnet.
In addition, the method for producing a permanent magnet of the present invention includes a molding step of adjusting a molded body by molding an alloy powder satisfying the following general formula in a magnetic field, and a temperature of 1000 ° C. to 1200 ° C. of the molded body in an inert atmosphere. In the sintering step of obtaining a sintered body by sintering and forming a solution by sintering for 10 minutes to 20 hours, and heat-treating the sintered body at a temperature of 500 ° C. to 800 ° C. for 1 hour to 100 hours, An aging treatment step of cooling to room temperature after cooling to 450 ° C. or less at a cooling rate of 1 to 10 ° C./min is provided.

General _{formula: Sm 1-x R x (} Co 1-a-b-c-d Fe a Cu b M c T d) z
R: at least one selected from La, Ce, Pr, and Nd
M: at least one selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Ni, Mn
T: At least one selected from Si, B, Al, and Ga
Atomic ratio when R is 1
0 ≦ x ≦ 0.65
0 ≦ a ≦ 0.2
0.02 ≦ b ≦ 0.3
0 ≦ c ≦ 0.05
0 ≦ d ≦ 0.05
0.02 ≦ a + b + c + d ≦ 0.35
3.2 ≦ z ≦ 4.1

Further, the _Th 2 Co ₇ phase by aging treatment, it is preferable to comprise at least one CaCu ₅ phase or RCo ₃ phases. The coercive force at room temperature is preferably 0.5 kOe or more and 5 kOe or less, and the squareness ratio represented by the ratio of residual magnetization to magnetization in a magnetic field of 10 kOe is preferably 80% or more.
Moreover, it is preferable to cool to room temperature or the said heat processing temperature at the cooling rate of 1-100 degrees C / min after the said sintering process.
A permanent magnet for a motor according to the present invention is a permanent magnet for a motor used for a motor capable of changing the magnetization state of the whole or a part of the permanent magnet,
The coercive force at room temperature is 0.5 kOe or more and 5 kOe or less, the squareness ratio expressed by the ratio of the residual magnetization to the magnetization in a magnetic field of 10 kOe is 80% or more, and the average recoil permeability in the second and third quadrants is 1.00 or more. It is a rare earth magnet of 1.08 or less.
The permanent magnet motor according to the present invention has a coercive force at room temperature of not less than 0.5 kOe and not more than 5 kOe, a squareness ratio represented by a ratio of residual magnetization to magnetization in a magnetic field of 10 kOe, and 80% or more in the second and third quadrants. A first rare earth permanent magnet for changing the magnetization state, having an average recoil permeability of 1.00 to 1.08;
And a second rare earth permanent magnet having a higher coercive force at room temperature than the first rare earth permanent magnet.
Furthermore, according to the present invention, the following general formula is satisfied, and the squareness ratio expressed by the ratio of the remanent magnetization to the magnetization in a magnetic field of 10 kOe is not less than 80% and the coercive force is not less than 0.5 kOe and not more than 3.5 kOe. A permanent magnet is provided.

  According to the present invention, since a permanent magnet having a low coercive force and a high squareness ratio can be provided, it is suitable for a low coercivity side magnet of a motor, particularly a motor capable of changing the magnetization state of the whole or a part of the permanent magnet. It is. Moreover, if it is the manufacturing method of this invention, the low coercive force and the permanent magnet of a high squareness ratio can be manufactured efficiently.

The figure which shows an example of a permanent magnet motor. The figure which shows an example of the motor using the permanent magnet of this invention. Sectional drawing which shows the permanent magnet motor which concerns on embodiment. Sectional drawing which shows the permanent magnet motor which concerns on another embodiment.

The permanent magnet of the present invention satisfies the following general formula, has a coercive force at room temperature of 0.5 kOe or more and 5 kOe or less, and a squareness ratio expressed by a ratio of residual magnetization to magnetization in a magnetic field of 10 kOe is 80% or more. It is characterized by this.
General _{formula: Sm 1-x R x (} Co 1-a-b-c-d Fe a Cu b M c T d) z
R: at least one selected from La, Ce, Pr, and Nd
M: at least one selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Ni, Mn
T: At least one selected from Si, B, Al, and Ga
Atomic ratio when R is 1
0 ≦ x ≦ 0.65
0 ≦ a ≦ 0.2
0.02 ≦ b ≦ 0.3
0 ≦ c ≦ 0.05
0 ≦ d ≦ 0.05
0.02 ≦ a + b + c + d ≦ 0.35
3.2 ≦ z ≦ 4.1

  First, the coercive force at room temperature is 0.5 kOe or more and 5.0 kOe or less. If the coercive force is less than 0.5 kOe, the magnetic flux control range in the motor that can change the magnetization state of the whole or a part of the permanent magnet is narrowed, and if it exceeds 5.0 kOe, it is very large to reverse the magnetization of this magnet. Since electric energy is required, the energy saving effect is greatly reduced. Therefore, it is preferably 1 to 3.5 kOe, and more preferably 1 to 3.0 kOe. When the permanent magnet motor operates at a high temperature up to 150 ° C., a high-efficiency motor can be obtained with a coercive force of up to 5 kOe. In addition, the squareness ratio is 80% or more, and if it is less than 80%, the magnetic flux control range in the motor that can change the magnetization state of the whole or a part of the permanent magnets is narrow, so the range in which high-efficiency operation can be performed is narrow. Become. A preferable value of the squareness ratio is 90 to 100%. The squareness ratio of the present invention is a value expressed by the ratio of residual magnetization to magnetization in a magnetic field of 10 kOe. 10 kOe was selected because the permanent magnet of the present invention has a low coercive force of 5 kOe or less and is almost magnetically saturated in a magnetic field of 10 kOe, which is suitable for defining the squareness ratio. . In the case of a permanent magnet, the value obtained by dividing the square of the residual magnetization by 4 is usually the theoretical value of the maximum energy product, and the value obtained by dividing the actual maximum energy product value by this value is the square ratio. However, since the permanent magnet of the present invention controls the coercive force with a relatively small value, the squareness ratio applied to the soft magnetic material was used as a reference as a new index representing the squareness.

The average recoil permeability of the second and third quadrants is preferably 1.00 to 1.08. The recoil permeability is less than 1.00 in principle, and if it exceeds 1.08, the magnetic flux control amount of the motor that can change the magnetization state of the whole or a part of the permanent magnets is reduced. The range that can be operated efficiently is narrowed. A preferred recoil permeability is 1.07 or less.
The recoil permeability is obtained from a change of magnetization in the second and third quadrants by a magnetic field, for example, a change from 15 kOe to zero magnetic field using a sample vibration type magnetometer. Specifically, the magnetization measurement is performed by applying a magnetic field up to −15 kOe opposite to the direction of magnetizing the sample magnetized with a pulse magnetic field of 60 kOe and changing the strength of the magnetic field from there to 0. Thereafter, after applying a magnetic field up to −14 kOe, the magnetic field is similarly changed to zero and the magnetization is measured. This is repeated every 1 kOe and measured in the range from the third quadrant to the second quadrant. The recoil permeability approximates a straight line, and is a value obtained by dividing each magnetic field (−15 kOe, −14 kOe,...) And the difference in magnetization when the magnetic field is zero by the amount of change in the magnetic field. Magnetic susceptibility.
The coercive force and the squareness ratio can be obtained by ordinary measurement. The coercive force is a coercive force when a full loop measurement is performed with a maximum magnetic field of 10 kOe. The squareness ratio is the remanent magnetization relative to the magnetization at 10 kOe.

Next, each element shown in the general formula will be described.
Sm is an essential element which is the basis of the permanent magnet of the present invention together with Co. R is at least one selected from La, Ce, Pr, and Nd. R is an element capable of substituting the Sm site, maintains the crystal structure, and realizes the characteristics of the present invention. The amount x value is 0.65 or less, and if it exceeds that, the control of the coercive force becomes difficult. Among the rare earth elements of Sm and R, Sm is the element that preferably has the highest content. Preferred elements among R are Pr, La, and Nd. Note that R may be a rare earth element before separation such as misch metal or didymium. Further, when the rare earth element is composed of plural kinds, industrially stable magnetic characteristics can be obtained. Preferably, they are Pr, La, Nd and Sm, and may be three or more.

  Co constitutes three crystal phases to be described later in combination with rare earth elements (Sm and R), and is an essential element for improving the characteristics of the permanent magnet of the present invention. Fe is an element that contributes to an increase in saturation magnetization by substitution with Co. However, when the amount a is less than 0.01, the effect is small, and when it exceeds 0.2, a phase other than the above three phases is formed. This causes a decrease in squareness and an increase in recoil permeability. Preferably, the a value is 0.02 ≦ a ≦ 0.15. Cu is an essential element for controlling the coercive force, and is an element that promotes a pinning-type magnetization process by aging treatment. The amount b is 0.02 ≦ b ≦ 0.30. If it is less than 0.02, the effect is not exhibited. On the other hand, if it exceeds 0.30, the magnetization is excessively lowered. Preferably, 0.03 ≦ b ≦ 0.25.

The M element is at least one selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, and Ni, and is effective for coercive force control and squareness ratio control by suppressing crystal grain coarsening. The amount c value is 0.05 or less, and if it exceeds this, it will cause heterogeneous precipitation and lead to a decrease in the squareness ratio. Preferably, it is 0.04 or less. Moreover, it is preferable that a minimum is 0.001 or more.
The T element is at least one selected from Si, B, Al, and Ga, and is an element effective for controlling coercive force and squareness. The amount d value is 0.04 or less, and if it exceeds this, a heterogeneous phase is precipitated, and as a result, the squareness deteriorates. Preferably, it is 0.03 or less. Moreover, it is preferable that a minimum is 0.001 or more.

  The z value is the total atomic ratio of Co, Fe, and the like with respect to the rare earth element, and the coercive force is controlled by this value and the aging treatment. It becomes difficult and the amount of magnetic flux change when the motor is used becomes difficult. Preferably, 3.1 ≦ z ≦ 4.1, and more preferably 3.2 ≦ z ≦ 4.0.

For the Sm ₂ Co ₇ magnet of the above general formula, C as an inevitable impurity is 0.05 wt% or less, O: 0.5 wt% or less, Al, Si, and Ca are each 0.06 wt% or less, and Sn is 0 Even if 0.005 wt% or less is contained, the characteristics of the present invention are not disturbed.
In addition to the above composition, the magnet of the present invention may contain oxygen at 5000 wtppm, hydrogen at 2000 wtppm or less, and nitrogen at 1000 wtppm or less. In particular, when hydrogen is used in a process such as hydrogen pulverization, hydrogen may remain somewhat, but there is no problem in characteristics. Further, other components (including impurities) may be contained in a total amount of 0.1 wt% or less.

Although the manufacturing method of the permanent magnet of this invention is not specifically limited, The following are mentioned as a method obtained efficiently. The mother alloy is prepared to a predetermined ratio, then melted by a method such as high-frequency melting, and produced by casting or strip casting. In the case of a casting method, it is preferable to cast on a water-cooled mold or a water-cooled metal plate in order to obtain a sufficient cooling rate. In the case of strip casting, the thickness of the obtained flakes is preferably about 70 μm or more and 2 mm or less. More preferably, it is mainly 100 μm or more and 1 mm or less. As for the strip casting method, it is possible to shorten the homogeneity of the mother alloy and the heat treatment time.
Coarse grinding is performed using a jaw crusher, a stamp mill, or the like. In the case of a sample obtained by strip casting, coarse pulverization may be unnecessary. In addition, the sample produced by strip casting is effective in stabilizing the characteristics because the secondary phase is homogeneously dispersed.
For example, a jet mill may be used for fine pulverization, and the average particle size of the pulverized powder is preferably 1 to 15 μm. If it is 1 μm or less, it becomes difficult to obtain a sufficient sintered density, and it becomes easy to be oxidized. On the other hand, if it exceeds 15 μm, the squareness starts to deteriorate. Preferably it is 2-12 micrometers, More preferably, it is 3-10 micrometers. On the other hand, hydrogen pulverization using hydrogen may be used, but since this method may not reach a predetermined average particle diameter, hydrogen storage / release is repeated a plurality of times, or after hydrogen pulverization, a wet method such as a ball mill or Further pulverization may be performed by a dry method such as a jet mill.
Forming in a magnetic field may be a longitudinal magnetic field or a transverse magnetic field, and the magnetic field at that time is preferably stronger in order to orient, but may be 20 kOe that is normally used. The molding pressure is preferably higher, but it may be 100 kg / cm ² or more, which is usually used.

In the sintering and solution treatment, first, the temperature is raised from room temperature at a rate of 1 to 50 ° C./min. And degassed at 500 to 700 ° C. for 1 to 2 hours. By performing degassing, the content of gas components such as oxygen, hydrogen, and nitrogen can be reduced. Thereafter, the temperature is increased in the Ar atmosphere to a sintering temperature of 900 to 1200 ° C. at the same temperature increase rate, and sintering is performed for a total of 10 minutes to 20 hours in this temperature range. Thereafter, 1 to 100 ° C./min. Cool at the speed of. The aging may be carried out at a temperature of 500 ° C. or higher and 800 ° C. or lower for 1 hour to 100 hours following the sintering, and the subsequent cooling rate is 0.1 to 10 ° C./min. Cool with. Between the sintering treatment and the aging treatment, the treatment may be once cooled to room temperature or continuously. In addition, aging can control the coercive force by one-stage (one temperature condition) treatment, but it may be two-stage (two temperature conditions) or more treatment. In this case, it is preferable to go through a step from a higher temperature side to a lower temperature, and in this case, the cooling rate between the two temperatures is 1 to 5 ° C./min. To do. In the case of multiple stages, the entire aging time may be 100 hours or less.
The atmosphere in this process is preferably a non-oxidizing atmosphere, and treatment in Ar, nitrogen and vacuum is preferred. The sintered density is preferably 95% or more. The sintered density is determined by (actual measured value / theoretical density by Archimedes method) × 100%.

The magnet obtained by the above process preferably comprises at least one of a Th ₂ Co ₇ phase and a CaCu ₅ phase or an RCo ₃ phase by aging treatment. Therefore, it is important to make the Th ₂ Co ₇ phase into a single phase or a main phase by the sintering treatment, and thereby the coercive force can be controlled. The ratio of the Th ₂ Co ₇ phase is preferably 60% or less, more preferably 50% or less, by volume.
Since the coercive force is too large for Th ₂ Co ₇ phase single phase, and _Th 2 Co ₇ phase, it is preferable to comprise at least one CaCu ₅ phase or RCo ₃ phases. Further, a total of 10% by volume of the R ₅ Co ₁₉ phase, the RCo ₂ phase, and the rare earth oxide phase may be present. The presence or absence of these phases can be determined by XRD (X-ray diffraction method). In the present invention, it is not excluded that only each phase has a phase configuration other than three phases. The phase ratio can be determined by X-ray diffraction. In the case of a small amount of precipitation, it may be difficult to detect by X-ray diffraction, and similar results can be obtained by observation with SEM and EPMA.

On the other hand, when the Th ₂ Co ₇ phases are all separated into two phases, the application to a motor capable of changing the magnetization state of the whole or a part of permanent magnets, which is the object of the present invention, becomes a low Hc and low squareness ratio. It is difficult. Accordingly, the Th ₂ Co ₇ phase is preferably 10% or more, and more preferably 20% or more.
In order to satisfy all of the coercive force, squareness, recoil permeability, etc., the above aging conditions are preferable. However, if control can be performed in a shorter time, there is no problem with heat treatment on the high temperature side exceeding 800 ° C. In consideration of time control with time aging, 800 ° C. or lower is preferable. On the other hand, the lower limit is preferably 600 ° C. or more from the viewpoint of reducing variation in coercive force.
The obtained magnet has excellent oxidation resistance, but it can be used in a wide variety of environments by performing various surface treatments such as Ni plating, Cu plating, and Al plating in order to provide further oxidation resistance. I can do it.
Moreover, in order to obtain a magnetic flux suitable for the operation mode, the permanent magnet motor using the permanent magnet according to the present invention reverses the magnetization direction of some magnets and controls the amount of magnetic flux, thereby improving the efficiency. It is intended. That is, the permanent magnet motor has a coercive force at room temperature of 0.5 kOe or more and 5 kOe or less, a squareness ratio represented by a ratio of residual magnetization to magnetization in a magnetic field of 10 kOe, and an average recoil of the second and third quadrants. A first rare earth permanent magnet having a magnetic permeability of 1.00 or more and 1.08 or less and a second rare earth permanent magnet having a room temperature coercivity higher than that of the first rare earth permanent magnet; Is provided. The first rare earth permanent magnet is a low coercivity magnet that reverses the magnetization direction to control the magnetic flux. The first rare earth permanent magnet is preferably in the range of 5 to 70% of the total magnet volume. By setting it as such a range, the output of a motor, efficiency, and reliability can be improved. Preferably it is 10-67%, More preferably, it is 15-50%.
The coercive force at room temperature of the first rare earth permanent magnet is desirably 0.5 kOe or more and 3.5 kOe or less. The first rare earth permanent magnet preferably has a composition containing a rare earth element containing Sm and a transition metal element containing Co as a main component. A more preferable composition is a composition represented by the general formula described above.
An example of the second rare earth permanent magnet is an NdFeB magnet.
The permanent magnet motor of the present invention may be either an inner rotor type or an outer rotor type, and may have either a surface magnet type (SPM) or an embedded magnet type (IPM). As the surface magnet type (SPM), for example, a permanent magnet including a first rare earth permanent magnet and a second rare earth permanent magnet can be provided on the surface or inner peripheral surface of the rotor. An example of the embedded magnet type (IPM) is one in which a permanent magnet including a first rare earth permanent magnet and a second rare earth permanent magnet is embedded in a rotor.
As an example, an inner rotor type IPM type is shown in FIG. As shown in FIG. 2, the rotor 1 includes a rotor core 2, a plurality of first rare earth permanent magnets (low coercivity permanent magnets) 3, and a plurality of second rare earth permanent magnets (high coercivity permanent magnets) 4. It is configured. The first rare earth permanent magnet 3 and the second rare earth permanent magnet 4 are embedded in the rotor core 2 and arranged in the circumferential direction of the rotor 1. The first cavity 5 is provided at both ends of the first rare earth permanent magnet 3. The second cavity 6 is provided at both ends of the second rare earth permanent magnet 4. Reference numeral 7 denotes a magnetic pole portion of the rotor core 2.
3 and 4 show an embodiment of an outer rotor type IPM type permanent magnet motor. As shown in FIG. 3, the rotor 21 in the permanent magnet motor of this embodiment includes a rotor core 22, a first rare earth permanent magnet 23, and a second rare earth permanent magnet 24. The rotor core 22 is configured by stacking silicon steel plates, for example. Four first rare earth permanent magnets 23 and two second rare earth permanent magnets 24 are embedded in the radial cross section of the rotor core 22. The first rare earth permanent magnet 23 is disposed along the radial direction of the rotor 21 and has a trapezoidal cross section. The magnetization direction of the first rare earth permanent magnet 23 is substantially the circumferential direction. The second rare earth permanent magnet 24 is disposed substantially in the circumferential direction and has a rectangular cross section. The magnetization direction of the second rare earth permanent magnet 24 is substantially the radial direction.
A cavity 25 is provided at each end of each of the first rare earth permanent magnet 23 and the second rare earth permanent magnet 24. The bolt hole 26 is opened in the rotor core 22. The magnetic pole core 27 of the rotor core 22 is formed so as to be surrounded by the two first rare earth permanent magnets 23 and the one second rare earth permanent magnet 24. The central axis direction of the magnetic core part 27 of the rotor core 22 is the d axis, and the central axis direction between the magnetic poles is the q axis. Accordingly, the first rare earth permanent magnet 23 is arranged in the q-axis direction which is the central axis between the magnetic poles, and the magnetization direction of the first rare earth permanent magnet 23 is 90 ° or 90 ° with respect to the q axis. In the adjacent first rare earth permanent magnets 23, the magnetic pole faces facing each other are the same. The second rare earth permanent magnet 24 is disposed in a direction perpendicular to the d axis that is the central axis of the magnetic pole core 27, and the magnetization direction is 0 ° or 180 ° with respect to the d axis. In the adjacent second rare earth permanent magnet 24, the directions of the magnetic poles are opposite to each other.
Such a rotor 21 is housed inside the stator 28. The stator 28 is configured by housing the armature winding 29 in a slot formed inside the stator core 30. The inner peripheral surface of the stator 28 and the outer peripheral surface of the rotor 21 are opposed to each other through an air gap 31.
On the other hand, as shown in FIG. 4, the rotor 41 in the permanent magnet motor of the present embodiment has a first rare earth permanent magnet 43 and a second rare earth permanent magnet 44 embedded in a rotor core 42. It is a configuration. The rotor core 42 is configured by laminating silicon steel plates. Eight first rare earth permanent magnets 43 and two second rare earth permanent magnets 44 are embedded in the radial cross section of the rotor core 42. Each of the eight sets of the first rare earth permanent magnet 43 and the second rare earth permanent magnet 44 is installed in a convex shape on the inner diameter side of the rotor 41. The magnetization directions of the first rare earth permanent magnet 43 and the second rare earth permanent magnet 44 are both substantially smaller in magnet size. If necessary, both ends of the first rare earth permanent magnet 43 and the second rare earth permanent magnet 44 may be provided with a magnetic flux short circuit and a cavity 45 for stress relaxation. The magnetic core 46 of the rotor core 42 is formed so as to be surrounded by the first rare earth permanent magnet 43 and the second rare earth permanent magnet 44. Reference numeral 47 denotes a rotating shaft.
Such a rotor 41 is accommodated in the stator 48. The stator 48 is configured by accommodating the armature winding 49 in a slot formed inside the stator core 50. The inner peripheral surface of the stator 48 and the outer peripheral surface of the rotor 41 are opposed to each other through an air gap 51.
The permanent magnet motor used by this invention is not limited to the form shown in FIGS. The present invention is applicable to a permanent magnet motor in which a plurality of permanent magnets are regularly arranged. Permanent magnets are arranged in the circumferential direction of the rotor, and the number or size (thickness, cross-sectional area, etc.) of the high coercive force and the low coercive force magnets are alternately or within the above volume ratio range. It can be changed to a permanent magnet motor of optimum specification.
The effects of the invention will be shown below by examples.

(Example)
(Examples 1-30)
About the composition shown in Table 1, after preparing raw material powder, it melt | dissolved in the high frequency induction heating furnace, the odd number was cast on the water-cooled copper plate, and it was set as the mother alloy. Further, even-numbered flake samples of 50 to 500 μm were obtained by strip casting. The obtained sample was coarsely pulverized and then finely pulverized to an average particle size of 3 to 5 μm by a jet mill, and formed into a predetermined shape in a magnetic field under the conditions of a magnetic field of 20 kOe and a press pressure of 0.5 t / cm ² . After the obtained molded body was sintered at 1000 to 1200 ° C. for 4 hours and then cooled to room temperature at 20 ° C./min, the odd numbered samples were even numbered at 800 ° C. for 60 hours. The sample was heat-treated at 700 ° C. for 40 hours and cooled at a rate of 5 ° C./min. The rate of temperature increase up to the aging treatment temperature was 20 ° C./min. Unified. Further, the temperature rise until sintering is performed at 5 ° C./min in a vacuum, once kept at 600 ° C. for degassing, and thereafter all in an Ar atmosphere.
In any case, 100 samples were prepared, and the residual magnetic flux density (Br), the coercive force (Hc), the squareness ratio, the recoil permeability, and the Hc range were measured as evaluation of the magnet characteristics. The residual magnetic flux density (Br), the coercive force (Hc), the squareness ratio, and the recoil permeability were measured using the method described above, and the average value of 100 pieces was obtained. The Hc range shows the variation in coercive force, and was obtained from “maximum value−minimum value” of 100 coercive forces (Hc). The results are shown in Table 1.
Each sample was subjected to X-ray diffraction measurement (Cukα, tube voltage: 50 kV, tube current: 100 mA) to evaluate the phase configuration.

As can be seen from Table 1, the coercive force of the permanent magnet according to this example was not too high, not too small, the variation in coercive force was small, and the recoil permeability was small. Further, as a result of SEM and EPMA measurement of the constituent phases, the permanent magnets according to the examples each include at least one of a Th ₂ Co ₇ phase, a CaCu ₅ phase or an RCo ₃ phase, or 2 to 3 volumes. % R ₅ Co ₁₉ , RCo ₂ phase, Sm ₂ O _{3 and} other rare earth oxide phases. Moreover, all were 98% or more of sintered density.
(Comparative example)
Table 2 shows a comparative example.

(Comparative Examples 1-20)
The compositions of Comparative Examples 1 to 20 shown in Table 2 were dissolved at high frequency. The obtained ingot was roughly pulverized with a jaw crusher, finely pulverized to a particle size of 3 to 6 μm using a jet mill, and then molded in a magnetic field.
The conditions for forming in a magnetic field are a magnetic field of 20 kOe and a press pressure of 0.5 t / cm ² . The molded body was sintered at 1020 to 1180 ° C. for 4 hours in a vacuum, and then cooled to room temperature at 30 ° C./min.
The odd number is cooled to 200 ° C at a rate of 100 ° C / min after aging treatment at 900 ° C for 40 hours, and the even number is cooled to 200 ° C at a rate of 5 ° C / min after heat treatment at 400 ° C for 80 hours. did. In any case, 100 samples were prepared, and the average value of the evaluation results of the magnet characteristics is shown in Table 2.
As a result of evaluating the magnetic characteristics, as shown in Table 2, those having a high coercive force were obtained.

(Application to motor)
The characteristics when Examples 1 to 30 and Comparative Examples 1 to 20 were incorporated into a permanent magnet motor were evaluated. As an evaluation of the motor characteristics, the permanent magnets according to the respective examples and comparative examples are incorporated in the low coercive force magnet portion of the motor capable of changing the magnetization state of all or part of the permanent magnets shown in FIG. Using a NdFeB magnet (Hc = 21 kOe, Br = 12.4 kG) as a magnetic magnet, the efficiency of the motor was evaluated. Table 2 shows an alnico magnet as Comparative Example 21.
The permanent magnet motors used as the reference are based on the efficiency when using NdFeB magnets (Comparative Example 22: the same magnet as the low coercive force side is used for the low coercive force side) as the reference, and the efficiency of the example and the comparative example are relative. Shown as a value. The evaluation condition is an average value of efficiency at high speed rotation (3000 rpm), medium speed rotation (2000 rpm), and low speed rotation (1000 rpm) of the motor. These conditions are low torque, medium torque, and high torque when torque is used as an index, and the efficiency under each operating condition is reflected.
The results are also shown in Tables 1 and 2. When the permanent magnet according to this example is used, the efficiency is significantly improved as compared with the permanent magnet motor using only the NdFeB magnet, and an alnico magnet is used. It can be seen that the efficiency is higher than the case.
In addition, although applied to the motor which can change the magnetization state of the whole or a part of permanent magnet of the structure shown in FIG. 2 as an embodiment this time, a magnet having a high coercive force and a magnet having a relatively small coercive force. As long as the permanent magnet of the present embodiment is used as a permanent magnet motor magnet constituted by the combination, the motor structure is not particularly limited.

(Examples 31-35)
Next, raw material powders having the same composition as in Example 5 were prepared, and the production conditions were changed as shown in Table 3 for production. The obtained permanent magnet was subjected to measurement of the same magnetic properties as in Example 5. The results are shown in Table 3.

  As can be seen from Table 3, it can be seen that the permanent magnet of the present invention can be obtained by the manufacturing method of this example.

(Examples 37 to 46)
About the composition shown in Table 4, after preparing raw material powder, it melt | dissolved in the high frequency induction heating furnace, the odd number was cast on the water-cooled copper plate, and it was set as the mother alloy. Further, even-numbered flake samples of 50 to 500 μm were obtained by strip casting. The obtained sample was coarsely pulverized and then finely pulverized to an average particle size of 3 to 5 μm by a jet mill, and formed into a predetermined shape in a magnetic field under the conditions of a magnetic field of 20 kOe and a press pressure of 0.5 t / cm ² . After the obtained molded body was sintered at 1000 to 1200 ° C. for 4 hours and then cooled to room temperature at 20 ° C./min, the odd numbered samples were at 820 ° C. for 60 hours and even numbered samples. The sample was heat-treated at 750 ° C. for 40 hours and cooled at a rate of 5 ° C./min. The rate of temperature increase up to the aging treatment temperature was 20 ° C./min. Unified. Further, the temperature rise until sintering is performed at 5 ° C./min in a vacuum, once kept at 600 ° C. for degassing, and thereafter all in an Ar atmosphere.
In any case, 100 samples were prepared, and the residual magnetic flux density (Br), the coercive force (Hc), the squareness ratio, the recoil permeability, and the Hc range were measured as evaluation of the magnet characteristics. The residual magnetic flux density (Br), the coercive force (Hc), the squareness ratio, and the recoil permeability were measured using the method described above, and the average value of 100 pieces was obtained. The Hc range shows the variation in coercive force, and was obtained from “maximum value−minimum value” of 100 coercive forces (Hc). The results are shown in Table 1.
Each sample was subjected to X-ray diffraction measurement (Cukα, tube voltage: 50 kV, tube current: 100 mA) to evaluate the phase configuration.

Next, the characteristics when the permanent magnets of Examples 37 to 46 were incorporated in the same permanent magnet motor as in Example 1 were evaluated. The evaluation temperature is 100 ° C. As an evaluation of the motor characteristics, the permanent magnets according to the respective examples and comparative examples are incorporated in the low coercive force magnet portion of the motor capable of changing the magnetization state of all or part of the permanent magnets shown in FIG. Using a NdFeB magnet (Hc = 21 kOe, Br = 12.4 kG) as a magnetic magnet, the efficiency of the motor was evaluated. Table 4 shows an alnico magnet as Comparative Example 25.
The permanent magnet motors used as the reference are all based on the efficiency when using NdFeB magnets (Comparative Example 26: the same magnet as the low coercive force side is used for the low coercive force side) as the reference, and the relative efficiency of the example and the comparative example. Shown as a value. The evaluation condition is an average value of efficiency at high speed rotation (3000 rpm), medium speed rotation (2000 rpm), and low speed rotation (1000 rpm) of the motor. These conditions are low torque, medium torque, and high torque when torque is used as an index, and the efficiency under each operating condition is reflected.
The results are shown in Table 4. When the permanent magnet according to the present example is used, the efficiency is significantly improved compared to the permanent magnet motor using only the NdFeB magnet, and even when compared with the case using the alnico magnet. It turns out that efficiency is high.
In addition, although applied to the motor which can change the magnetization state of the whole or a part of permanent magnet of the structure shown in FIG. 2 as an embodiment this time, a magnet having a high coercive force and a magnet having a relatively small coercive force. As long as the permanent magnet of the present embodiment is used as a permanent magnet motor magnet constituted by the combination, the motor structure is not particularly limited.
In addition, the permanent magnet motor using the magnet of the present invention exhibits excellent efficiency even at an evaluation temperature of 100 ° C. or higher, for example, 120 ° C. or 150 ° C.

   1, 11, 21, 41 ... rotor, 2, 12, 22, 42 ... rotor core, 3, 23, 43 ... first rare earth permanent magnet (low coercive force permanent magnet), 4, 24, 44 ... 2nd rare earth permanent magnet (high coercive force permanent magnet), 5 ... 1st cavity, 6 ... 2nd cavity, 7, 27, 46 ... Magnetic pole part of an iron core, 14 ... Permanent magnet, 26 ... Bolt hole, 28, 48 ... Stator, 29, 49 ... Armature winding, 30, 50 ... Stator core, 31, 51 ... Air gap.

Claims (25)

Permanently characterized in that the following general formula is satisfied, the coercive force at room temperature is 0.5 kOe or more and 5 kOe or less, and the squareness ratio represented by the ratio of residual magnetization to magnetization in a magnetic field of 10 kOe is 80% or more. magnet.
General _{formula: Sm 1-x R x (} Co 1-a-b-c-d Fe a Cu b M c T d) z
R: at least one selected from La, Ce, Pr, and Nd
M: at least one selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Ni, Mn
T: At least one selected from Si, B, Al, and Ga
Atomic ratio when R is 1
0 ≦ x ≦ 0.65
0 ≦ a ≦ 0.2
0.02 ≦ b ≦ 0.3
0 ≦ c ≦ 0.05
0 ≦ d ≦ 0.05
0.02 ≦ a + b + c + d ≦ 0.35
3.2 ≦ z ≦ 4.1   The permanent magnet according to claim 1, wherein the permanent magnet satisfies the following general formula and has a coercive force of 0.5 kOe to 3.5 kOe.   The value of x is 0.02 ≦ x ≦ 0.6, the a value is 0.01 ≦ a ≦ 0.15, and the b value is 0.02 ≦ b ≦ 0.2. 2. The permanent magnet according to 2.   The permanent magnet according to any one of claims 1 to 3, wherein the permanent magnet has an average recoil permeability of 1.00 to 1.08 in the second and third quadrants. _5. The permanent magnet according to claim 1, comprising a Th ₂ Co ₇ phase and at least one of a CaCu ₅ phase or an RCo ₃ phase. 6.   The permanent magnet according to any one of claims 1 to 5, wherein the permanent magnet is a sintered body.   The permanent magnet according to claim 1, wherein the permanent magnet is mounted on a motor. The coercive force is 0.5 kOe or more and 5 kOe or less, the squareness ratio represented by the ratio of the residual magnetization to the magnetization in a magnetic field of 10 kOe is 80% or more, and the average recoil permeability of the second and third quadrants is 1.00 to 1. 0.08, and a motor capable of changing the magnetization state of the whole or a part of permanent magnets, characterized in that the main component is a rare earth element consisting of Th ₂ Co ₇ phase and CaCu ₅ phase or RCo ₃ and cobalt. For permanent magnets. A molding process for adjusting a molded body by molding an alloy powder satisfying the following general formula in a magnetic field, and sintering and solution forming the molded body at a temperature of 900 ° C. to 1200 ° C. for 10 minutes to 20 hours in an inert atmosphere. A sintering step for obtaining a sintered body by heat-treating the sintered body at a temperature of from 500 ° C. to 800 ° C. for from 1 hour to 100 hours, and at a cooling rate of from 0.1 to 10 ° C./min after the heat treatment at room temperature The manufacturing method of the permanent magnet characterized by comprising the aging treatment process cooled to to.
General _{formula: Sm 1-x R x (} Co 1-a-b-c-d Fe a Cu b M c T d) z
R: at least one selected from La, Ce, Pr, and Nd
M: at least one selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Ni, Mn
T: At least one selected from Si, B, Al, and Ga
Atomic ratio when R is 1
0 ≦ x ≦ 0.65
0 ≦ a ≦ 0.2
0.02 ≦ b ≦ 0.3
0 ≦ c ≦ 0.05
0 ≦ d ≦ 0.05
0.02 ≦ a + b + c + d ≦ 0.35
3.2 ≦ z ≦ 4.1   10. The permanent magnet according to claim 9, wherein the coercive force of the permanent magnet is 0.5 kOe or more and 5 kOe or less, and the squareness ratio expressed by the ratio of the residual magnetization to the magnetization in a magnetic field of 10 kOe is 80% or more. Manufacturing method.   The coercive force at room temperature is 0.5 kOe or more and 3.5 kOe or less, and the squareness ratio expressed by the ratio of the residual magnetization to the magnetization in a magnetic field of 10 kOe is 80% or more. A method for producing a permanent magnet according to claim 1.   The method for manufacturing a permanent magnet according to any one of claims 9 to 11, wherein after the sintering step, cooling to room temperature or the heat treatment temperature is performed at a cooling rate of 5 to 100 ° C / min. After the sintering step, the sintered body is heat-treated at a temperature of 500 ° C. or higher and 800 ° C. or lower for 1 hour or longer and 100 hours or shorter, and cooled to room temperature at a cooling rate of 0.1 to 10 ° C./min after the heat treatment 13. The method for manufacturing a permanent magnet according to claim 9, comprising: a Th ₂ Co ₇ phase and at least one of a CaCu ₅ phase or an RCo ₃ phase. A permanent magnet for a motor used in a motor capable of changing the magnetization state of all or part of permanent magnets,
The coercive force at room temperature is 0.5 kOe or more and 5 kOe or less, the squareness ratio expressed by the ratio of the residual magnetization to the magnetization in a magnetic field of 10 kOe is 80% or more, and the average recoil permeability in the second and third quadrants is 1.00 or more. A permanent magnet for a motor, which is a rare earth magnet of 1.08 or less.   The permanent magnet for motor according to claim 14, wherein the coercive force at room temperature is 0.5 kOe or more and 3.5 kOe or less.   The permanent magnet for motor according to claim 14 or 15, wherein the rare earth magnet contains a rare earth element containing Sm and a transition metal element containing Co as a main component. The coercive force at room temperature is 0.5 kOe or more and 5 kOe or less, the squareness ratio expressed by the ratio of the residual magnetization to the magnetization in a magnetic field of 10 kOe is 80% or more, and the average recoil permeability in the second and third quadrants is 1.00 or more. A first rare earth permanent magnet for changing a magnetization state, which is 1.08 or less;
A permanent magnet motor comprising: a second rare earth permanent magnet having a coercivity at room temperature higher than that of the first rare earth permanent magnet.   The permanent magnet motor according to claim 17, wherein the coercive force of the first rare earth permanent magnet is 0.5 kOe or more and 3.5 kOe or less. 19. The first rare earth permanent magnet includes a rare earth element containing Sm and a transition metal element containing Co as a main component, and has a CaCu ₅ type crystal structure as a main phase. The permanent magnet motor of any one of Claims.   20. The permanent magnet motor according to claim 17, wherein a ratio of the first rare earth permanent magnet to a total magnet volume is 5% or more and 70% or less.   21. The permanent magnet motor according to claim 17, wherein the permanent magnet motor is an inner rotor system or an outer rotor system.   The permanent magnet motor according to claim 17, further comprising a rotor in which the first rare earth permanent magnet and the second rare earth permanent magnet are arranged in a circumferential direction.   The permanent magnet motor according to claim 17, further comprising a rotor in which the first rare earth permanent magnet and the second rare earth permanent magnet are embedded.   The permanent magnet motor according to claim 17, further comprising a rotor on which the first rare earth permanent magnet and the second rare earth permanent magnet are installed.   The permanent magnet motor according to claim 17, further comprising a rotor on which the first rare earth permanent magnet and the second rare earth permanent magnet are installed on an inner peripheral surface.

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