KR102283425B1 - Permanent magnet, method for manufacturing the magnet, and motor including the magnet - Google Patents

Abstract

The permanent magnet of the embodiment includes a base magnet denoted by abc (a includes a rare earth element, b includes a transition element, and c includes boron (B)) and a coating layer coated on the surface of the base magnet. Including, the coating layer includes a compound containing a metal having a magnetic, the compound is phosphorus (P); and metals belonging to period 4 of the periodic table.

Description

Permanent magnet, method for manufacturing the magnet, and motor including the magnet

The embodiment relates to a permanent magnet, a method for manufacturing the same, and a motor including the same.

Recently. Nd-Fe-B type permanent magnets are used in motors such as motors for automobiles and motors for elevators. Such a permanent magnet may be exposed to high temperature or a humid environment, in particular, moisture containing salt, depending on its use. Accordingly, there is a demand for a permanent magnet that can be manufactured at a low manufacturing cost while having high corrosion resistance.

In addition, the permanent magnet can be heated to 200°C to 300°C or higher for a short time in a manufacturing process or operating environment of motors, so that high heat resistance is also required. The Curie temperature at which the Nd-Fe-B type permanent magnet loses its magnetic force is around 300°C. Accordingly, in order to maintain the magnetic force of the permanent magnet even in a high-temperature environment, recently heavy rare earth elements such as dysprosium (Dy) or terbium (Tb) are used, but heavy rare earth elements are expensive.

Therefore, in order to reduce the amount of expensive heavy rare earth elements used, research on improving grain boundaries through diffusion heat treatment after coating the surface of permanent magnets with heavy rare earth elements is being conducted.

In addition, since the Nd-Fe-B-based permanent magnet is easily oxidized when it comes into contact with air, the magnetic force may be reduced, and a protective layer may be formed on the surface of the permanent magnet by plating and coating the surface of the permanent magnet. For example, the protective layer may include a phosphate coating, epoxy, or electrolytic/electroless Ni and Al. However, since the conventional protective layer formed on the surface of the permanent magnet is made of a non-magnetic material, the performance of the permanent magnet may be deteriorated.

In addition, when the protective layer is formed with a phosphate film on the surface of the permanent magnet, since there are relatively many pinholes, the permanent magnet exposed to moisture containing salt may rust. In addition, when the protective layer is formed on the surface of the permanent magnet by resin coating, corrosion resistance and heat resistance may be insufficient.

The embodiment provides a permanent magnet having excellent corrosion resistance, heat resistance, oxidation prevention and improved magnetic properties, a manufacturing method thereof, and a motor including the same.

A permanent magnet according to an embodiment includes a base magnet denoted by a-b-c (a includes a rare earth element, b includes a transition element, and c includes boron (B)); and a coating layer coated on the surface of the base magnet, wherein the coating layer includes a compound including a metal having a magnetism, and the compound is phosphorus (P); and a metal belonging to period 4 of the periodic table.

For example, a may be neodymium (Nd), and b may be iron (Fe).

For example, a surface of the base magnet may include a void, and at least a portion of the coating layer may be buried in the void of the base magnet.

For example, the metal belonging to period 4 of the periodic table may include one selected from iron (Fe), cobalt (Co), and nickel (Ni). The metal belonging to the fourth period of the periodic table may be cobalt (Co). The content of the phosphorus (P) may be 1% to 12%.

For example, the size of the particles constituting the coating layer may be smaller than the size of the void.

For example, the thickness of the coating layer may be greater than the depth of the void. The thickness of the coating layer may be 1 μm to 20 μm.

For example, the coating layer may include a first surface facing the base magnet; and a second surface opposite to the first surface, wherein a roughness of the outer surface of the base magnet may be greater than that of the second surface of the coating layer.

For example, when the ambient temperature of the permanent magnet is 120° C., the permanent magnet may have a residual magnetic flux density greater than 11.71 kG.

For example, when the ambient temperature of the permanent magnet is 120° C., the permanent magnet may have a coercive force greater than 7 kOe.

For example, when the ambient temperature of the permanent magnet is 120° C., the permanent magnet may have a maximum magnetic energy product greater than 32 MGOe.

For example, when the ambient temperature of the permanent magnet is 120° C. or higher, the permanent magnet may have an angular formation index greater than 100%.

For example, when the ambient temperature of the permanent magnet is 120°C, the absolute value of the temperature coefficient expressed as follows may be 0.6%/°C or less.

Here, ß represents the absolute value of the temperature coefficient, Hc(Tr) represents the coercive force at room temperature Tr, Hc(Tp) represents the coercive force at the ambient temperature Tp, and ΔT represents the ambient temperature Tp ) and the temperature difference between room temperature (Tr).

A method of manufacturing a permanent magnet according to another embodiment includes preparing a base magnet denoted by a-b-c (a includes a rare earth element, b includes a transition element, and c includes boron (B)); and forming a coating layer on the surface of the base magnet, wherein the coating layer includes a magnetic compound, the compound being phosphorus (P); and a metal belonging to period 4 of the periodic table.

For example, the coating layer may be formed on the surface of the base magnet using an electroless plating method or an electrolytic plating method.

A motor according to another embodiment includes a stator having a cylindrical through-groove; a plurality of stator winding slots disposed on an inner circumferential surface of the stator; a rotor disposed in the through groove of the stator; A plurality of permanent magnets coupled to the rotor are included, and the permanent magnets are denoted by abc (a includes rare earth elements, b includes transition elements, and c includes boron (B)). becoming a base magnet; and a coating layer coated on the surface of the base magnet, wherein the coating layer includes a compound including a metal having a magnetism, and the compound is phosphorus (P); and a metal belonging to period 4 of the periodic table.

For example, a is neodymium (Nd), b is iron (Fe), the coating layer includes phosphorus (P) and cobalt (Co), and the phosphorus (P) content is 1% to 12 It can be %.

A permanent magnet, a method for manufacturing the same, and a motor including the same according to the embodiment have oxidation prevention, excellent heat resistance, and improved magnetic properties, and have excellent price competitiveness and productivity.

1 shows a cross-sectional view of a permanent magnet according to an embodiment.
2A to 2D are locally enlarged photographs of the surface of the coating layer different according to the phosphorus content when the coating layer is implemented with CoP.
FIG. 3 shows an enlarged photograph of a portion 'A' of the permanent magnet according to the embodiment shown in FIG. 1 .
4 is a graph showing the residual magnetic flux density of the permanent magnet according to the embodiment for each thickness of the coating layer.
5 is a flowchart for explaining a method of manufacturing a permanent magnet according to an embodiment of manufacturing the permanent magnet shown in FIG. 1 .
6A and 6B are process cross-sectional views for explaining the method illustrated in FIG. 5 .
7 is a diagram illustrating a schematic structure of an electrolytic plating apparatus according to an exemplary embodiment.
8 is a graph showing a change in magnetic flux density with respect to the strength of an externally applied magnetic field at room temperature in Comparative Examples and Examples 1 and 2;
9 is a graph illustrating a change in magnetic flux density with respect to the strength of an externally applied magnetic field according to temperature in Comparative Example and First Example.
10 is a graph showing a change in magnetic flux density with respect to the strength of an externally applied magnetic field according to temperature in Comparative Example and Second Example.
11A is a cross-sectional view of an SPM motor, FIG. 11B is a cross-sectional view of an IPM motor, and FIG. 11C is a cross-sectional view of a spoke type motor.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings to help the understanding of the present invention by giving examples, and to explain the present invention in detail. However, the embodiments according to the present invention may be modified in various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described in detail below. The embodiments of the present invention are provided to more completely explain the present invention to those of ordinary skill in the art.

In the description of this embodiment, in the case where it is described as being formed on "on or under" of each element, above (above) or below (below) ( on or under includes both elements in which two elements are in direct contact with each other or in which one or more other elements are disposed between the two elements indirectly.

In addition, when expressed as "up (up)" or "down (on or under)", a meaning of not only an upward direction but also a downward direction may be included based on one element.

Also, as used hereinafter, relational terms such as "first" and "second," "upper/upper/above" and "lower/lower/below" refer to any physical or logical relationship or It may be used to distinguish one entity or element from another, without requiring or implying an order.

1 shows a cross-sectional view of a permanent magnet 100 according to an embodiment.

The permanent magnet 100 shown in FIG. 1 may include a base magnet 110 and a coating layer 120 .

The base magnet 110 may be denoted by a-b-c. Here, a may include a rare earth element, b may include a transition element, and c may include boron (B).

a may be at least one of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, which are rare earth elements. For example, a may be neodymium (Nd) or samarium (Sm), but the embodiment is not limited thereto.

In addition, b may be any one of transition elements, for example, may be iron (Fe), but the embodiment is not limited thereto.

Accordingly, the base magnet 110 denoted by a-b-c may be, for example, NdFeB.

In addition, the surface of the base magnet 110 may include a void (VOID).

Continuingly, referring to FIG. 1 , the coating layer 120 may be disposed in a coated form on the surface of the base magnet 110 . The coating layer 120 may include a compound including a magnetic metal. The compound included in the coating layer 120 may include phosphorus (P) and a metal belonging to period 4 of the periodic table, for example, iron (Fe), cobalt (Co), nickel (Ni), and the like.

When the compound included in the coating layer 120 is CoP, that is, when the metal belonging to the fourth period of the periodic table is cobalt (Co), CoP can perform a function of preventing oxidation of the base magnet 110 and have magnetism can

Accordingly, the coating layer 120 may include phosphorus (P) and cobalt (Co), but the embodiment is not limited thereto.

2A to 2D are locally enlarged photographs of the surface of the coating layer 120 that is different for each phosphorus (P) content when the coating layer 120 is implemented with CoP.

FIG. 2a is a case in which the phosphorus (P) content is less than 1%, FIG. 2b is a case in which the phosphorus (P) content is 1% to 6%, and FIG. 2c is a case in which the phosphorus (P) content is 7% to 12%. , and FIG. 2D is a case in which the content of phosphorus (P) exceeds 12%. Reference numeral 120A denotes fine nanocrystalline CoP.

If the content of phosphorus (P) included in the coating layer 120 is less than 1%, referring to FIG. 2A , oversized grains having a size of 10 μm to 20 μm are generated and voids present on the surface of the base magnet 110 . It may be difficult to fill (VOID) with particles of the coating layer 120 .

Alternatively, when the content of phosphorus (P) included in the coating layer 120 exceeds 12%, referring to FIG. 2d , the degree of amorphization is rapidly increased to form needles, and the surface of the base magnet 110 and the coating layer 120 . The adhesion may be lowered, and a phenomenon in which the 110 and 120 may be peeled off may occur. Accordingly, the content of phosphorus (P) included in the coating layer 120 may be 1% to 12%, but the embodiment is not limited thereto.

As described above, by adjusting the content of phosphorus (P) included in the coating layer 120 within the range of 1% to 12%, the particle size of the coating layer 120 buried in the voids (VOID) can be adjusted.

Referring to FIG. 1 , at least a portion of the coating layer 120 may be buried in a void existing on the surface of the base magnet 110 . To this end, the size of the particles constituting the coating layer 120 may be smaller than the size of the void. For example, the width Φ of the void may be 10 μm to 40 μm, and the size of the particles constituting the coating layer 120 may be smaller than the width Φ of the void, but the embodiment is not limited thereto.

FIG. 3 shows an enlarged photograph of a portion 'A' of the permanent magnet 100 according to the embodiment shown in FIG. 1 .

1 and 3 , it can be seen that the thickness T of the coating layer 120 is greater than the depth D of the void VOID.

In addition, the thickness T of the coating layer 120 shown in FIG. 1 may be 0.1 μm to 1.0 mm, but the embodiment is not limited thereto.

Hereinafter, the residual magnetic flux density (Br) of the permanent magnets according to Comparative Examples and Examples will be described with reference to the accompanying drawings. In the permanent magnet according to the comparative example, the surface of the base magnet 110 is phosphated instead of forming the coating layer 120 on the surface of the base magnet 110 shown in FIG. 1 . In the case of phosphate treatment, the surface of the base magnet 110 is artificially oxidized.

4 is a graph showing the residual magnetic flux density (Br) of the permanent magnet according to the embodiment for each thickness (T) of the coating layer 120, and the ordinate indicates the residual magnetic flux density (Br).

4 is a graph obtained when the base magnet 110 shown in FIG. 1 according to the embodiment is implemented with NdFeB and the coating layer 120 is implemented with CoF, according to the thickness T of the coating layer 120 It can be seen that the residual magnetic flux density Br of the permanent magnet 100 varies.

Referring to FIG. 4 , the thickness T of the coating layer 120 is 5 μm (T=T1), 10 μm (T=T2), 15 μm (T=T3), or 20 μm (T=T4). It can be seen that in both cases, the residual magnetic flux density (Br) is larger than that of the comparative examples.

As illustrated in FIG. 4 , as the thickness T of the CoP, which is the coating layer 120 , in the permanent magnet 100 according to the embodiment increases by 20 μm, it can be seen that the residual magnetic flux density (Br) decreases. there is. This is because the interaction between NdFeB, which is the base magnet 110 , and Co included in the coating layer 120 is reduced. In addition, as the thickness T of the CoP plating, which is the coating layer 120 , is reduced by 1 μm, the possibility that the surface of the NdFeB, which is the base magnet 110 , and oxygen meet increases, and thus rust may occur.

Accordingly, the thickness T of the coating layer 120 shown in FIG. 1 may be 1 μm to 20 μm, but the embodiment is not limited thereto.

Also, the coating layer 120 may include first and second surfaces S1 and S2. The first surface S1 is a surface facing the base magnet 110 , and the second surface S2 is a surface opposite to the first surface S1 .

The roughness of the outer surface of the base magnet 110 facing the first surface S1 of the coating layer 120 may be greater than the roughness of the second surface S2 of the coating layer 120 . That is, since the existing permanent magnet includes only the base magnet 110 and does not include the coating layer 120 , the roughness of the outermost surface thereof is large.

On the other hand, in the permanent magnet 100 according to the embodiment, since the coating layer 120 is formed on the surface of the base magnet 110 , the roughness of the outermost surface of the permanent magnet 100 can be reduced compared to that of the conventional permanent magnet. This is because the coating layer 120 may be buried in the void VOID of the base magnet 110 .

Hereinafter, a method of manufacturing the permanent magnet 100 according to the above-described embodiment will be described with reference to the accompanying drawings.

FIG. 5 is a flowchart for explaining a method 200 for manufacturing a permanent magnet according to an embodiment of manufacturing the permanent magnet 100 shown in FIG. 1 .

6A and 6B are process cross-sectional views for explaining the method 200 shown in FIG. 5 .

Hereinafter, the permanent magnet 100 shown in FIG. 1 will be described as being manufactured by the method 200 shown in FIG. 5 , but the embodiment is not limited thereto. That is, the permanent magnet 100 shown in FIG. 1 may be manufactured by a method different from the method 200 shown in FIG. 5 . Also, the method 200 shown in FIG. 5 may produce a permanent magnet 100 other than that shown in FIG. 1 .

As shown in Figure 6a, according to the permanent magnet manufacturing method 200 according to the embodiment, first, the base magnet 110 is prepared (step 210). The base magnet 110 may be denoted as a-b-c, as described above. Here, a, b, and c are the same as described above, and thus overlapping descriptions will be omitted.

If the base magnet 110 is NdFeB, step 210 may be performed as follows.

The base magnet 110 may be formed by molding, sintering/heating, cutting, and grinding magnetic powder having a size of several tens of micrometers. As described above, since the method of generating the base magnet 110 made of NdFeB is general, a detailed description thereof is omitted here.

Meanwhile, after performing step 210, the coating layer 120 is formed on the surface of the base magnet 110 (step 220). The coating layer 120 includes a compound containing a metal having a magnetism, and the compound includes phosphorus (P) and a metal belonging to period 4 of the periodic table, for example, iron (Fe), cobalt (Co), nickel (Ni), etc. can do. Since the compound included in the coating layer 120 is the same as described above, the overlapping description will be omitted. For example, when the coating layer 120 is formed by CoP, as shown in FIG. 6b , CoP particles 120A are plated on the surface of the base magnet 110 to fill the voids VOID, and the coating layer 120 ) can be formed as

According to an embodiment, step 220 may be performed using an electroless plating method or an electrolytic plating method. That is, the coating layer 120 may be formed on the surface of the base magnet 110 by using an electroless plating method or an electrolytic plating method.

Hereinafter, the 220 step of forming the coating layer 120 by the electrolytic plating method will be described as follows.

7 is a diagram illustrating a schematic structure of an electrolytic plating apparatus 300 according to an exemplary embodiment.

The electrolytic plating apparatus 300 shown in FIG. 7 may include a water bath 302 , an electrolytic solution 304 , an anode 305 , a cathode 306 , and a power supply 308 .

Step 220 illustrated in FIG. 5 may be performed in the electrolytic plating apparatus 300 illustrated in FIG. 7 , but the embodiment is not limited thereto. That is, step 220 illustrated in FIG. 5 may be performed in an electrolytic plating apparatus having a configuration different from that of the electrolytic plating apparatus 300 illustrated in FIG. 7 .

First, an electrolyte solution 304 containing cobalt (Co) metal and phosphorus (P), that is, a plating solution is placed in a water tank 302 . At this time, the anode 305 and the cathode 306 are put in the water tank 302 and a current flows between the two electrodes 305 and 306 from the power supply 308 . In order for current to flow continuously, charge transfer must occur at the interface between the electrodes 305 and 306 and the aqueous electrolyte solution 304 . At this time, the cobalt metal ions of the aqueous electrolyte solution 304 are reduced at the interface of the cathode 306 and the anions are oxidized at the anode 305 . As described above, as the cobalt metal ions 310 are reduced and precipitated in the cathode 306 , a thin film of CoP, which is the coating layer 120 , may be formed on the surface of the base magnet 110 placed on the cathode 306 .

Hereinafter, the permanent magnet 100 according to the above-described embodiment and the permanent magnet according to the comparative example will be compared and described as follows. In the case of the permanent magnet of the comparative example, as described above, the coating layer 120 is not formed on the surface of the base magnet 110 , and the surface of the base magnet 110 is phosphated. In the case of the permanent magnet according to the embodiment, it will be described that the coating layer 120 made of CoP is formed on the surface of the base magnet 110 made of NdFeB.

In general, as an index indicating the magnetic properties of a permanent magnet, residual magnetic flux density (Br), coercive force (Hc), knee point (Hk), maximum magnetic energy product (maximum magnetic energy product) ( (BH)max), each formation index (Hk/Hc), and the like. The coercive force (Hc) corresponds to a magnetic field in which the magnetic flux density (B) becomes '0' in a hysteresis loop. In addition, the maximum magnetic energy product corresponds to the maximum area of the B-H rectangle in the second quadrant of the hysteresis curve, and may be used as a relative index of the magnetic strength of the permanent magnet.

Comparing the magnetic properties and the temperature coefficient of the permanent magnet according to the comparative example and the permanent magnet 100 according to the embodiment may be shown in Table 1 below.

Here, in the first embodiment, the content of phosphorus (P) included in the coating layer 120 is 1% to 6%, and in the second embodiment, the content of phosphorus (P) included in the coating layer 120 is 7 % to 12%. In each of the first and second embodiments, the thickness of the coating layer 120 was tested to be 6 μm, and it was assumed that the current density was 2.0 (A/dm 2 ).

In addition, one of the temperature coefficients, the first temperature coefficient α, may be calculated as shown in Equation 1, and the second temperature coefficient β, which is the other temperature coefficient, may be calculated as shown in Equation 2 below.

In Equation 1, Br(Tr) represents the residual magnetic flux density at room temperature (Tr), Br(Tp) represents the residual magnetic flux density at ambient temperature (Tp), and in Equation 2, Hc(Tr) represents room temperature ( Tr) represents the coercive force and Hc(Tp) represents the coercive force at ambient temperature (Tp). In addition, in Equations 1 and 2, ΔT represents the temperature difference between the ambient temperature (Tp) and the room temperature (Tr). For convenience of explanation, in Table 1, the temperature coefficients (α, β) are expressed as absolute values.

Although not indicated in Table 1, Br(Tr) when calculating the first temperature coefficient (α) of each of the first and second examples is 13.44 KG, the Br(Tr) value of the comparative example is a measured value at room temperature , and 18.88 kOe, which is a comparative example Hc(Tr) value at room temperature, was substituted for Hc(Tr) when calculating the second temperature coefficient β of each of the first and second examples.

Referring to Table 1 described above, it can be seen that the permanent magnet 100 according to the embodiment has excellent magnetic properties at the same temperature as compared to the comparative example. That is, in contrast to the comparative example, the permanent magnet 100 according to the embodiment has the coating layer 120 disposed on the surface of the base magnet 110, thereby having improved magnetic properties and an excellent temperature coefficient. A detailed look at this is as follows.

The permanent magnet 100 according to the embodiment may have a residual magnetic flux density (Br) greater than 11.71 kG when its ambient temperature is 120 °C, and a residual magnetic flux density (Br) greater than 11.07 kG when its ambient temperature is 150 °C. ) can have

In addition, the permanent magnet 100 according to the embodiment may have a coercive force (Hc) greater than 7 kOe when its ambient temperature is 120 °C, and has a coercive force (Hc) greater than 6 kOe when its ambient temperature is 150 °C. can

In addition, the permanent magnet 100 according to the embodiment may have a maximum magnetic energy product greater than 32 MGOe when its ambient temperature is 120° C., and may have a maximum magnetic energy product greater than 28 MGOe when its ambient temperature is 150° C. .

In addition, the permanent magnet 100 according to the embodiment may have an angular formation index greater than 94.6%, for example greater than 100%, when its ambient temperature is 120° C. or higher.

In addition, in the permanent magnet 100 according to the embodiment, when its ambient temperature is 120°C, the absolute value of the second temperature coefficient (β) may be 0.6%/°C or less, and when its ambient temperature is 150°C, the first 2 The absolute value of the temperature coefficient β may be 0.55%/°C or less. The small absolute value of the second temperature coefficient β means that the amount of change in the coercive force Hc is small despite the change in the temperature Tp around the permanent magnet 100 . Therefore, considering that the second temperature coefficient (β) of the permanent magnet 100 according to the embodiment is 0.6%/°C or less, the amount of change in the coercive force (Hc) according to the change in the temperature (Tp) around the permanent magnet 100 It can be seen that this is small.

As described above, the permanent magnet 100 according to the embodiment has superior angular formation index and improved temperature coefficients (α, β) than the permanent magnet according to the comparative example at the same temperature.

Therefore, when the permanent magnet 100 according to the embodiment is mounted on motors, etc., since the torque of the motor is proportional to the residual magnetic flux density (Br), it is possible to provide a higher magnetic flux density in terms of the operating point, so that the output of the motor It can also contribute to improvement.

In general, the characteristics of a magnet can be easily identified through the size and shape of a hysteresis curve. For example, a soft magnetic material is relatively easily magnetized by an externally applied magnetic field. These soft magnetic materials exhibit a small hysteresis loop. For example, soft magnetic materials have high initial permeability and low coercive force. On the other hand, it is difficult to initially magnetize a hard magnetic material by a magnetic field applied from the outside. Hard magnetic materials show a large hysteresis loop. For example, hard magnetic materials have high residual magnetism and high saturation flux density.

8 to 10 are graphs showing the change in magnetic flux density (J: Magnetic flux density) with respect to the strength (H) of the externally applied magnetic field according to the temperature in the comparative example and the first and second examples shown in Table 1; As a graph, the horizontal axis represents the strength (H) of an externally applied magnetic field, and the vertical axis represents the magnetic flux density (J) induced in the magnetic material when the magnetic material is placed in the magnetic field.

In the case of FIG. 8, the magnetic flux density change of the comparative example and the first and second examples at room temperature is compared and shown. In the case of FIG. 9 , as the temperature increases from room temperature to high temperature, the change in magnetic flux density of the comparative example and the first example is compared and shown. In the case of FIG. 10, as the temperature increases from room temperature to high temperature, the change in magnetic flux density of the comparative example and the second example is compared and shown.

8 to 10 , it can be seen that the first and second examples have better magnetism than the comparative examples. The reason for this is as follows.

There are many defects such as voids (VOID) on the surface of the base magnet 110 . Nuclei start to be generated from defects on the surface of the base magnet 110 , and magnetic domains move throughout the magnet, thereby demagnetization may occur. In the case of the permanent magnet according to the comparative example, oxidation of the base magnet 110 can be prevented by phosphate treatment of the surface of the base magnet 110, but since VOIDs still exist on the surface of the base magnet 110, demagnetization is difficult. This may result in deterioration of magnetic properties.

On the other hand, in the case of the permanent magnet 100 according to the embodiment, the void (VOID), which is the main cause of the reverse magnetic domain generation on the surface of the base magnet 110, is filled with the coating layer 120 having fine nanocrystal particles to densify. In addition, since the coating layer 120 has excellent magnetic performance, it can interact with the base magnet 110 to improve the demagnetization performance of the permanent magnet 100 .

In addition, in the case of the permanent magnet according to the comparative example, the base magnet 110 by phosphating the surface of the base magnet 110 or forming a protective layer using a non-magnetic element (eg, Cu, Sn, Zn, Al). oxidation can be prevented. As such, the main purpose of the protective layer formed on the surface of the base magnet 110 is to prevent oxidation.

On the other hand, in the case of the permanent magnet 100 according to the embodiment, by forming the coating layer 120 having a magnetism on the surface of the base magnet 110, it is possible to have excellent magnetic properties while improving the heat resistance as well as oxidation prevention.

In addition, unlike the conventional method of using expensive heavy rare earth elements (eg, Dy, Tb) to improve the heat resistance of the permanent magnet, according to the embodiment, a magnetic material having a lower price than the heavy rare earth element, for example, CoP is used. Thus, since the coating layer 120 is formed on the base magnet 110 by an electroless plating method or an electrolytic plating method, the cost of the permanent magnet 100 can be reduced, thereby increasing price competitiveness and increasing productivity.

The permanent magnet 100 according to the embodiment may be applied to, for example, a motor, a generator, or a battery in various fields such as automobiles, elevators, or clean energy.

Hereinafter, an embodiment of a motor including a permanent magnet 100 according to an embodiment will be described with reference to the accompanying drawings as follows.

11A is a cross-sectional view of a Surface Permanent Magnet (SPM) motor, FIG. 11B is a cross-sectional view of an IPM (Interior Permanent Magnet) motor, and FIG. 11C is a cross-sectional view of a spoke type motor inserted into the side of the rotor. indicates.

As an energy-efficient motor, there is a permanent magnet (PM) motor. The permanent magnet motor may be divided into the SPM motor shown in FIG. 11A , the IPM motor shown in FIG. 11B , and the spoke type motor shown in FIG. 11C . Here, the spoke type motor shown in FIG. 11C is a modified embodiment of the IPM motor shown in FIG. 11B .

The SPM motor, the IPM motor, and the spoke type motor shown in FIGS. 11A, 11B and 11C each include a stator 402, 412, 422, a stator winding slot 404, 414, 424, a permanent magnets 406 , 416 , 426 and rotors 408 , 418 , 428 .

The stators 402 , 412 , 422 have a ring-shaped cross section through which the inside is cylindrically penetrated. A plurality of stator winding slots 404 , 414 , 424 extending in a direction penetrating the stators 402 , 412 , 422 are formed on inner peripheral surfaces of the stators 402 , 412 , and 422 . A coil may be wound along the winding slots 404 , 414 , 424 in the direction of their extension. The number of winding slots 404, 414, 424 may vary depending on the design of the motor, for example, 27 winding slots 404, 414, 424 may be arranged at regular intervals, but the embodiment is limited thereto. doesn't happen

In addition, as shown in FIGS. 11A to 11C , rotors 408 , 418 , and 428 may be disposed inside the stators 402 , 412 , 422 . At this time, as shown in FIGS. 11A and 11B , the stators 402 and 412 may be penetrated in a cylindrical shape. At this time, the rotors 408 , 418 , and 428 are members installed in the space through which the stators 402 , 412 , 422 pass, and electromagnetic force generated as a current flows in the coil wound around the stators 402 , 412 , 422 . It may be configured to include a plurality of permanent magnets (406, 416, 426) to be rotated by receiving. A rotating shaft (not shown) may be connected to the rotors 408 , 418 , and 428 to transmit rotational force to a compression unit provided in the compressor. To this end, a plurality of insertion holes that are formed through the rotor (404, 418, 428) in parallel with the rotation shaft of the rotor (408, 418, 428) so that the permanent magnet (406, 416, 426) can be inserted is formed. can Permanent magnets 406, 416, and 426, respectively, may be inserted into the insertion holes in a direction parallel to or in the direction of the rotation axis of the rotors 408, 418, 428, in this case, permanent magnets having different poles in adjacent insertion holes Magnets 406 , 416 , 426 may be inserted.

As the permanent magnets 406 , 416 , and 426 shown in FIGS. 11A to 11C , the permanent magnet 100 according to the above-described embodiment may be used. At this time, since the permanent magnet 100 according to the embodiment has a large coercive force (Hc), it is applied to the motor shown in FIGS. 11A, 11B or 11C, and a large current is applied to the coil of the stator (402, 412, 422). It can be designed to send , improving the performance of the motor. That is, the direction of the reverse magnetic field generated when the permanent magnet 100 according to the embodiment is mounted on the motor is mostly in the opposite direction to the out-of-plane direction, and the greater the coercive force Hc in this direction, the better the performance. Considering this, a reverse magnetic field (external magnetic field) is formed in the magnet as current flows through the stator coil. If the coercive force (Hc) is large, the ability to withstand this reverse magnetic field is improved, thereby improving the performance of the motor.

In the above, the embodiment has been mainly described, but this is only an example and does not limit the present invention, and those of ordinary skill in the art to which the present invention pertains are not exemplified above in the range that does not depart from the essential characteristics of the present embodiment. It will be appreciated that various modifications and applications are possible. For example, each component specifically shown in the embodiment can be implemented by modification. And differences related to such modifications and applications should be construed as being included in the scope of the present invention defined in the appended claims.

100: permanent magnet 110: base magnet
120: coating layer 300: electrolytic plating device
302: water bath 304: electrolytic solution
305: positive 306: negative
308: power supply 402, 412, 422: stator
404, 414, 424: stator winding slots
406, 416, 426: permanent magnets 408, 418, 428: rotor

Claims (21)

a base magnet denoted by abc (a includes rare earth elements, b includes transition elements, and c includes boron (B)); and
A coating layer coated on the surface of the base magnet,
The coating layer includes a compound containing a metal having a magnetic property,
The compound is
phosphorus (P); and
contains metals belonging to period 4 of the periodic table,
When the ambient temperature of the permanent magnet is 120℃, the absolute value of the temperature coefficient expressed as below is 0.6%/℃ or less.

(Where ß represents the absolute value of the temperature coefficient, Hc(Tr) represents the coercive force at room temperature (Tr), Hc(Tp) represents the coercive force at the ambient temperature (Tp), and ΔT is the ambient temperature ( It represents the temperature difference between Tp) and room temperature (Tr).) The permanent magnet of claim 1, wherein a is neodymium (Nd) and b is iron (Fe). The method of claim 1, wherein the surface of the base magnet comprises a void,
At least a portion of the coating layer is embedded in the void of the base magnet permanent magnet. The permanent magnet of claim 1 , wherein the metal belonging to period 4 of the periodic table includes one selected from iron (Fe), cobalt (Co), and nickel (Ni). 5. The permanent magnet according to claim 4, wherein the metal belonging to period 4 of the periodic table is cobalt (Co). The permanent magnet according to claim 1, wherein the phosphorus (P) content is 1% to 12%. The permanent magnet according to claim 3, wherein the size of the particles constituting the coating layer is smaller than the size of the void. The permanent magnet according to claim 3, wherein a thickness of the coating layer is greater than a depth of the void. The permanent magnet according to claim 1, wherein the coating layer has a thickness of 1 µm to 20 µm. According to claim 1, wherein the coating layer
a first surface facing the base magnet; and
a second surface opposite to the first surface;
a roughness of the outer surface of the base magnet is greater than that of the second surface of the coating layer. The permanent magnet according to claim 1, wherein the permanent magnet has a residual magnetic flux density greater than 11.71 kG when the ambient temperature of the permanent magnet is 120°C. The permanent magnet according to claim 1, wherein the permanent magnet has a coercive force greater than 7 kOe when the ambient temperature of the permanent magnet is 120°C. The permanent magnet according to claim 1, wherein the permanent magnet has a maximum magnetic energy product greater than 32 MGOe when the ambient temperature of the permanent magnet is 120°C. The permanent magnet according to claim 1, wherein the permanent magnet has an angular formation index greater than 100% when the ambient temperature of the permanent magnet is 120 DEG C or higher. delete preparing a base magnet denoted by abc (a includes rare earth elements, b includes transition elements, and c includes boron (B)); and
Comprising the step of forming a coating layer on the surface of the base magnet,
The coating layer contains a magnetic compound,
The compound is
phosphorus (P); and
contains metals belonging to period 4 of the periodic table,
When the ambient temperature of the permanent magnet is 120°C, the absolute value of the temperature coefficient of the permanent magnet expressed as follows is 0.6%/°C or less.

(Where ß represents the absolute value of the temperature coefficient, Hc(Tr) represents the coercive force at room temperature (Tr), Hc(Tp) represents the coercive force at the ambient temperature (Tp), and ΔT is the ambient temperature ( It represents the temperature difference between Tp) and room temperature (Tr).) The method of claim 16, wherein the coating layer is formed on the surface of the base magnet by using an electroless plating method or an electrolytic plating method. a stator having a cylindrical through-groove;
a plurality of stator winding slots disposed on an inner circumferential surface of the stator;
a rotor disposed in the through groove of the stator;
It includes a plurality of permanent magnets coupled to the rotor,
The permanent magnet includes a base magnet denoted by abc (a includes a rare earth element, b includes a transition element, and c includes boron (B)); and
A coating layer coated on the surface of the base magnet,
The coating layer includes a compound containing a metal having a magnetic property,
The compound is
phosphorus (P); and
contains metals belonging to period 4 of the periodic table,
When the ambient temperature of the permanent magnet is 120°C, the absolute value of the temperature coefficient of the permanent magnet expressed as follows is 0.6%/°C or less.

(Where ß represents the absolute value of the temperature coefficient, Hc(Tr) represents the coercive force at room temperature (Tr), Hc(Tp) represents the coercive force at the ambient temperature (Tp), and ΔT is the ambient temperature ( It represents the temperature difference between Tp) and room temperature (Tr).) The motor of claim 18, wherein a is neodymium (Nd) and b is iron (Fe). The motor of claim 18 , wherein the coating layer includes phosphorus (P) and cobalt (Co). The motor according to claim 18, wherein the phosphorus (P) content is 1% to 12%.

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