WO2013114541A1

WO2013114541A1 - Embedded permanent magnet electric motor and compressor

Info

Publication number: WO2013114541A1
Application number: PCT/JP2012/052027
Authority: WO
Inventors: 馬場　和彦; 昌弘仁吾; 浩二矢部; 和慶土田
Original assignee: 三菱電機株式会社
Priority date: 2012-01-30
Filing date: 2012-01-30
Publication date: 2013-08-08

Abstract

An embedded permanent magnet electric motor obtained by arranging within a stator a rotor core (7) obtained by layering a plurality of electromagnetic steel sheets, wherein magnets constituting a magnetic pole of the rotor core (7) comprise: ferrite magnets (4) arranged in the circumferential direction of the rotor core (7) in a number equivalent to the number of poles, the ferrite magnets (4) being provided to the outer peripheral side of the rotor core (7); and rare earth magnets (3) arranged between the ferrite magnets (4); the cumulative thickness of the rotor core (7) is formed to be greater than the cumulative thickness of a stator core (24); the axial length (Lf) of the ferrite magnets (4) is formed to be greater than the axial length (Ln) of the rare earth magnets (3); the axial length (Ln) of the rare earth magnets (3) is formed to be substantially equivalent to the cumulative thickness of the stator core (24); the axial length (Lf) of the ferrite magnets (4) is formed to be substantially equivalent to the cumulative thickness of the rotor core (7) and the rare earth magnets (3) are provided to a position corresponding to an inner peripheral section of the stator core (24) with respect to the cumulative thickness direction of the rotor core (7).

Description

Permanent magnet embedded electric motor and compressor

The present invention relates to a permanent magnet embedded motor and a compressor equipped with this motor.

Demand for improving motor efficiency is increasing due to increased environmental awareness. As high-efficiency electric motors, permanent magnet embedded electric motors in which permanent magnets are embedded in the iron core of a rotor are spreading mainly in compressor motors such as air conditioners. An embedded permanent magnet electric motor employs one of a ferrite magnet and a rare earth magnet as a permanent magnet constituting the magnetic pole of the rotor. When a ferrite magnet is used, although it is inexpensive, since the magnetic flux density is small, the current flowing through the electric motor increases and it is difficult to achieve high efficiency. For this reason, rare earth magnets having a higher magnetic flux density than ferrite magnets are often used in electric motors used in compressors such as air conditioners that require high efficiency. However, since the rare earth magnet contains expensive rare earth elements such as neodymium (Nd) and dysprosium (Dy), there is a problem that the cost of the electric motor increases.

In addition, as a refrigerant used in the compressor, low GWP (GWP: global warming potential when CO2 = 1) and high safety R32 refrigerant, or R32 exceeds 50%, and the discharge temperature is higher than R22. When a high R32 rich mixed refrigerant is used, the compressor discharge temperature is about 20 ° C. higher than when R22, R410A, and R407C are used, and the rare-earth magnet is demagnetized during high-temperature operation of the compressor. There was a problem that efficiency decreased.

In order to solve such a problem, in the permanent magnet motor shown in Patent Document 1 below, the magnet constituting the field magnetic pole corresponds to the number of poles in the rotation direction of the rotor along the circumference of the rotor core inner diameter. The number of rare earth magnets and the number of ferrite magnets arranged along the boundary between the magnetic poles of the rare earth magnets are included. Each of the magnetic poles is composed of at least three permanent magnets using the ferrite magnet as a shared adjacent magnetic pole. . An effect of reducing the cost is shown by using an expensive rare earth magnet and an inexpensive ferrite magnet in combination.

Moreover, the compressor shown by the following patent document 2 uses the brushless DC motor which has the rare earth magnet as a drive source using the R32 refrigerant | coolant or R32 rich mixed refrigerant | coolant mentioned above as a refrigerant | coolant used for a compressor, and the said rare earth magnet is used as a refrigerant | coolant. By making the thickness larger than the thickness of the permanent magnet in the compressor employing R22, R410A, or R407C, high efficiency and suppression of increase in compressor discharge temperature are achieved.

Japanese Patent No. 3832530 (FIG. 1 etc.) Japanese Patent Laid-Open No. 2001-115963 (FIG. 1 etc.)

However, in the permanent magnet motor shown in Patent Document 1, rare earth magnets are arranged around the inner diameter of the rotor core in order to obtain reluctance torque. That is, the rare earth magnet is disposed closer to the rotor shaft (shaft) center hole than the ferrite magnet. For this reason, the iron core area between the rare earth magnet and the outer peripheral surface of the rotor is larger than when the rare earth magnet and the ferrite magnet are arranged on the same circumference, and the circumferential width of the rare earth magnet is greatly increased. It was necessary to make it smaller. Therefore, even when a ferrite magnet is arranged to supplement the magnetic flux density, a sufficient magnetic flux density cannot be obtained compared to a rotor composed only of rare earth magnets, resulting in a decrease in efficiency.

Further, since the permanent magnet motor shown in Patent Document 1 has a structure in which reluctance torque is actively used, there is a problem that electromagnetic excitation force such as torque ripple increases, and sound and vibration increase. In particular, when this electric motor is built into a compressor, the electromagnetic excitation force causes the compressor casing and piping to vibrate, so measures such as increasing the rigidity of the compressor casing and increasing the strength of the piping can be taken. There was a problem that the cost increased.

Moreover, in the compressor shown by the said patent document 2, in order to suppress the thermal demagnetization of the permanent magnet accompanying the temperature rise inside a compressor becoming large, the thickness of a permanent magnet is thickened or coercive force of Measures such as using a high permanent magnet (rare earth magnet) are being taken. Therefore, there has been a problem that the amount of rare earth magnet used increases or the amount of rare earth elements contained in the rare earth magnet increases, resulting in an increase in the cost of the electric motor.

The present invention has been made in view of the above, and an object thereof is to obtain a permanent magnet embedded type electric motor and a compressor that can reduce sound and vibration with high efficiency.

In order to solve the above-described problems and achieve the object, the present invention is a permanent magnet embedded electric motor in which a rotor core formed by laminating a plurality of electromagnetic steel plates is disposed in a stator, Magnets constituting the magnetic poles of the rotor core are provided between the ferrite magnets and ferrite magnets provided on the outer peripheral side of the rotor core and arranged in a number corresponding to the number of poles in the circumferential direction of the rotor core. The rotor core has a thickness greater than that of the stator core, and the axial length of the ferrite magnet is greater than the axial length of the rare earth magnet. The axial length of the rare earth magnet is formed substantially equal to the stack thickness of the stator core, and the axial length of the ferrite magnet is formed approximately equal to the stack thickness of the rotor core, The rare earth magnet Characterized in that it is provided at a position opposed to the inner peripheral portion of the stator core with respect to the lamination thickness direction of the child core.

According to the present invention, there is an effect that sound and vibration can be reduced with high efficiency.

FIG. 1 is a cross-sectional view of a permanent magnet embedded electric motor according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the structure of the rotor shown in FIG. FIG. 3 is a cross-sectional view centering on the magnet insertion hole. FIG. 4 is a cross-sectional view of a rotor using a ferrite magnet whose magnetization direction is radial. FIG. 5 is a cross-sectional view for explaining the relationship between the magnetic circuit of the ferrite magnet and the magnetic circuit of the rare earth magnet shown in FIG. FIG. 6 is a cross-sectional view of a rotor using a ferrite magnet in which the magnetization direction of the magnet is parallel. FIG. 7 is a sectional view of a rotor using a ferrite magnet in which the magnetization direction of the magnet is polar. FIG. 8 is a cross-sectional view of a conventional permanent magnet embedded electric motor using only rare earth magnets. FIG. 9 is a diagram for explaining the relationship between the thickness and width of the ferrite magnet. FIG. 10 is a diagram for explaining the relationship between the magnetic pole opening of the rare earth magnet and the tooth width. FIG. 11 is a perspective view of an embedded permanent magnet electric motor. FIG. 12 is a side view of the permanent magnet embedded electric motor. FIG. 13 is a perspective view of the rotor core and the permanent magnet. FIG. 14 is a longitudinal sectional view of the rotary compressor.

Hereinafter, embodiments of an embedded permanent magnet electric motor and a compressor according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment.
FIG. 1 is a cross-sectional view of a permanent magnet embedded electric motor (hereinafter referred to as “electric motor”) 100 according to an embodiment of the present invention, and FIG. 2 shows the structure of the rotor 1 shown in FIG. It is sectional drawing. FIG. 3 is a cross-sectional view centering on the magnet insertion hole, FIG. 4 is a cross-sectional view of the rotor 1 using the ferrite magnet 4 having a radial magnetization direction, and FIG. 5 is shown in FIG. FIG. 6 is a cross-sectional view for explaining the relationship between the magnetic circuit of the ferrite magnet 4 and the magnetic circuit of the rare-earth magnet 3, and FIG. 6 is a cross-sectional view of the rotor 1 using the ferrite magnet 4 in which the magnet magnetization directions are parallel. FIG. 7 is a cross-sectional view of the rotor 1 using the ferrite magnet 4 in which the magnetization direction of the magnet is polar.

In FIG. 1, an electric motor 100 according to an embodiment of the present invention includes a stator 2 and a rotor 1. A plurality of teeth are formed on the inner peripheral portion of the stator 2 at an equiangular pitch in the circumferential direction.

In FIG. 2, the rotor 1 includes a rotor core 7 embedded with a magnet, a rare earth magnet 3, and a ferrite magnet 4 as main components. In FIG. 2, as an example, the shaft hole side surface 4 a of the ferrite magnet 4 is arranged on the same circumference as the shaft hole side surface 3 a of the rare earth magnet 3.

The rotor iron core 7 is manufactured by laminating electromagnetic steel plates, and the outer peripheral surface of the rotor 1 (hereinafter simply referred to as “rotor outer peripheral surface”) is formed in a cylindrical shape. The magnetic pole 21 is composed of one Nd—Fe—B rare earth magnet 3 and one side of two ferrite magnets 4.

The ferrite magnet 4 has a plate shape in which the shaft hole side surface 4a is formed in a substantially arc shape. The rare earth magnet 3 has a flat plate shape magnetized in parallel in the thickness direction (radial direction of the rotor 1). The residual magnetic flux density of the Nd—Fe—B rare earth magnet 3 is about three times the residual magnetic flux density of the wet ferrite magnet 4. The rare earth magnet 3 is formed to be thinner than the ferrite magnet 4. In the rotor 1 of the present embodiment, for example, the rare earth magnet 3 has a thickness of about 2 mm and the ferrite magnet 4 has a thickness of about 4 mm. is there.

A shaft hole 8 for connecting a shaft (not shown) for transmitting rotational energy and the rotor core 7 is provided at the center of the rotor 1. The rotor core 7 and the shaft are connected by shrink fitting, press fitting or the like. Between the shaft hole 8 and the magnets (3, 4), there are provided an air hole 9a for allowing refrigerant and refrigeration oil to pass therethrough and a rivet hole 9b for bundling the laminated rotor cores 7. Further, in the rotor 1 of the present embodiment, the air hole 9a is disposed on the inner diameter side of the rare earth magnet 3 and the rivet hole 9b is disposed on the inner diameter side of the ferrite magnet 4, but this may be reversed. Moreover, the rotor 1 of this Embodiment can improve the performance by increasing the flow path of the refrigerant when driven in the compressor by increasing the cross-sectional area of the air hole 9a within a range in which the torque does not decrease.

In FIG. 3, between the shaft hole 8 and the rotor outer peripheral surface, ferrite magnet insertion holes 22 formed in a number corresponding to the number of poles in the rotation direction of the rotor 1 on the rotor outer peripheral surface side, and ferrite A rare earth magnet insertion hole 23 formed on the same circumference as the ferrite magnet insertion hole 22 is provided between the magnet insertion holes 22. The rare earth magnet 3 is accommodated in the rare earth magnet insertion hole 23, and the ferrite magnet 4 is accommodated in the ferrite magnet insertion hole 22. In the following description, the ferrite magnet insertion hole 22 is referred to as the insertion hole 22, and the rare earth magnet insertion hole 23 is referred to as the insertion hole 23.

Between the insertion hole 22 and the insertion hole 23, an inter-magnet thin portion 14 is provided, and between the insertion hole 22 and the rotor outer peripheral surface, a ferrite magnet outer peripheral thin portion 15 is provided. The thicknesses of the inter-magnet thin portion 14 and the ferrite magnet outer peripheral thin portion 15 are, for example, 0.35 mm, which is about the same as the thickness of the electromagnetic steel plate (not shown) forming the rotor core 7. In the following description, the inter-magnet thin portion 14 is referred to as a thin portion 14, and the ferrite magnet outer peripheral thin portion 15 is referred to as a thin portion 15.

An air hole 19 is formed between the ferrite magnet 4 and the thin portion 15 shown in FIG. This air hole 19 is formed by cutting the rotor outer peripheral surface side of the insertion hole 22, for example.

On the rotor outer peripheral surface side of the rare earth magnet 3, there is an iron core portion 7 a formed thicker than the thickness of the thin portion 15. That is, in the rotor 1 of the present embodiment, the iron core area (thickness of the iron core portion 7a) between the rare earth magnet 3 and the rotor outer peripheral surface is the same as the iron core area (thin wall thickness) between the insertion hole 22 and the rotor outer peripheral surface. The thickness of the portion 15 is larger than the thickness.

The iron core portion 7a is provided with slits 6 in the radial direction for relaxing magnetic flux density imbalance and magnetic saliency.

2 represents a boundary line where adjacent magnetic poles 21 (N pole and S pole) are switched. The rare earth magnet 3 is disposed at the center of the magnetic pole 21, and the ferrite magnet 4 is disposed between the poles 20. It arrange | positions so that the center of the ferrite magnet 4 may be located. The ferrite magnet 4 disposed between the poles 20 is composed of at least one, and is magnetized so that the magnetization direction is reversed with respect to the poles 20. Hereinafter, the magnetization direction will be described.

In FIG. 4, the magnetization direction of the rare earth magnet 3 is parallel, and the magnetization direction of the ferrite magnet 4 is radial orientation. The magnetization direction of the ferrite magnet 4 is magnetized so as to be reversed between the poles 20. FIG. 4 shows a focal point 17 having a radial orientation as a position where the magnetization direction is reversed. The magnetization direction of the ferrite magnet 4 is substantially the same as the direction of the rare earth magnet 3 with the inter-electrode 20 as a boundary.

Here, in the case where the rare earth magnet 3 and the ferrite magnet 4 are used in combination, the effective magnetic flux amount linked to the stator 2 when both magnets are arranged to have a magnetic resistance on the magnetic circuit of the other magnet. Is not preferable. For example, when the magnetization direction of the ferrite magnet 4 is perpendicular to the gap 20, the rare earth magnet 3 exists in the magnetization direction of the ferrite magnet 4. Therefore, the rare earth magnet 3 becomes a magnetic resistance when viewed from the ferrite magnet 4, and the magnetic flux of the ferrite magnet 4 cannot be used effectively. In the above prior art, the rare earth magnet 3 is arranged on the inner peripheral side (the shaft hole 8 side) of the ferrite magnet 4 in order to effectively use the magnetic flux of the ferrite magnet 4.

On the other hand, when the magnetization direction of the ferrite magnet 4 is parallel, radial, or polar, the rare earth magnet 3 and the ferrite magnet 4 are unlikely to have a magnetic resistance on each other's magnetic circuit. FIG. 5 schematically shows a magnetic circuit (flow of magnetic flux) by the rare earth magnet 3 disposed on the rotor 1 and a magnetic circuit by the ferrite magnet 4. The magnetic flux generated from each magnet constitutes a magnetic circuit as indicated by a broken line through the stator 2 shown in FIG. The rotor 1 according to the present embodiment is a parallel circuit in which both magnetic circuits do not interfere with each other. Therefore, the rotor 1 can make maximum use of the magnetic flux of the rare earth magnet 3 and the ferrite magnet 4.

Further, when compared with a conventional electric motor using only the rare earth magnet 3 with the same rotor magnetic flux, the rotor 1 of the present embodiment reduces the amount of the rare earth magnet 3 for the magnetic flux supplement by the ferrite magnet 4. be able to.

The magnetic flux of the ferrite magnet 4 is easily short-circuited because the magnetization direction is switched between the poles 20. However, in order to reduce the short-circuit magnetic flux, the magnetization direction of the ferrite magnet 4 is nearly perpendicular to the gap 20 ( It is preferably oriented in a direction that is not completely vertical.

Therefore, the rotor 1 according to the present embodiment is effective in interlinking with the stator 2 by setting the magnetization direction of the ferrite magnet 4 to the radial orientation as shown in FIG. 4 or the polar orientation as shown in FIG. The amount of magnetic flux is increased. The magnetization direction of the ferrite magnet 4 is not limited to the radial orientation and the polar orientation, and may be a parallel orientation as shown in FIG. In this case, although the effective magnetic flux amount interlinking with the stator 2 is lower than that in the case of radial orientation or polar orientation, it is possible to avoid the above-described configuration of the magnetic resistance.

FIG. 8 is a cross-sectional view of a conventional permanent magnet embedded electric motor 110 using only the rare earth magnet 3. The conventional permanent magnet embedded motor 110 has a problem that the short-circuit magnetic flux between the adjacent rare earth magnets 3 (adjacent N pole and S pole) is large. Specifically, for example, when the magnetic flux emitted from the magnetic pole 21 shown in FIG. 2 is linked to the coil of the stator 2 shown in FIG. 1, this magnetic flux is effectively used as the magnet torque. However, when the magnetic flux emitted from the magnetic pole 21 is short-circuited without passing through the coil of the stator 2, this magnetic flux cannot be used as magnet torque.

As shown in FIG. 2, the rotor 1 according to the present embodiment includes a ferrite magnet 4 having a large magnetic resistance between adjacent rare earth magnets 3. Therefore, the magnetic flux of the rare earth magnet 3 is not easily short-circuited. Yes. As a result, the effective magnetic flux amount interlinking with the stator 2 can be increased.

The short circuit of the magnetic flux between the adjacent rare earth magnets 3 tries to pass through the thin portion 15 shown in FIG. In the rotor 1 of the present embodiment, since the ferrite magnet 4 is arranged on the outer peripheral surface side of the rotor, the thin portion 15 is thinned, and the magnet of the permanent magnet embedded electric motor 110 of the rare earth magnet 3 alone. The magnetic resistance can be made larger than that of the outer peripheral thin portion 15a. Moreover, since the thin part 15 of this Embodiment is magnetically saturated with the magnetic flux of the ferrite magnet 4, it becomes difficult to produce a short circuit magnetic flux. As a result, the effective magnetic flux amount interlinking with the stator 2 can be increased.

Further, when the rare earth magnet 3 and the ferrite magnet 4 are used in combination, a thin portion 14 as shown in FIG. 2 is required, but this thin portion 14 creates a short-circuit path of magnetic flux from the front to the back of the magnet, thereby fixing the thin portion. The effective magnetic flux amount interlinking with the child 2 is reduced. In the rotor 1 of the present embodiment, the rare earth magnet 3 and the ferrite magnet 4 are arranged on the same circumference, and the thin portion 14 is further thinned. And short-circuit the thin-walled portion 14 (short-circuit from the front to the back of the magnet), so that the thin-walled portion 14 is likely to be magnetically saturated. Accordingly, the amount of short-circuit magnetic flux can be reduced as compared with the case where the rare earth magnet 3 alone or the ferrite magnet 4 alone is configured. As a result, the effective magnetic flux amount interlinking with the stator 2 can be increased.

Further, in the electric motor 100, the iron core on the surface of the magnetic pole 21 causes an increase in sound and vibration due to an increase in torque ripple due to reluctance torque and a magnetic attraction force when the rotor 1 is eccentric. Therefore, a design that reduces the iron core area on the surface of the magnetic pole 21 is preferable. In the rotor 1 of the present embodiment, the rare earth magnet 3 and the ferrite magnet 4 are arranged on the same circumference, so that the area of the iron core portion 7a existing on the rotor outer peripheral surface side of the rare earth magnet 3 is reduced. Can do. Therefore, it is possible to reduce the sound and vibration described above.

Further, the residual magnetic flux density of the rare earth magnet 3 is about three times that of the ferrite magnet 4. Therefore, when the rare earth magnet 3 and the ferrite magnet 4 are used in combination, the energy change amount of the magnetic flux density at the boundary surface between the rare earth magnet 3 and the ferrite magnet 4 on the outer peripheral surface of the rotor is large, and this energy change increases sound and vibration. Cause it. In the rotor 1 of the present embodiment, the iron core portion 7 a existing on the rotor outer peripheral surface side of the rare earth magnet 3 is larger than the iron core (thin wall portion 15) existing on the rotor outer peripheral surface side of the ferrite magnet 4. It is configured. Therefore, the concentration of the magnetic flux density on the surface of the rare earth magnet 3 having a high magnetic flux density is alleviated, and the amount of energy change of the magnetic flux density described above becomes small. As a result, the electric motor 100 with low sound and vibration can be realized.

In addition, when the slit 6 is provided in the iron core part 7a on the surface of the rare earth magnet 3, the magnetic attraction force can be reduced while relaxing the energy change of the magnetic flux density described above by adjusting the width and position of the slit 6, and sound and It is effective in reducing vibration.

Further, by arranging the rare earth magnet 3 and the ferrite magnet 4 on the same circumference, it is possible to secure a wide space in the inner circumference of the rotor 1 having a small influence on the magnetic characteristics. Therefore, caulking, air holes 9a, and rivet holes 9b can be easily provided in this space, and the manufacturability, cooling performance, and strength of the rotor 1 can be improved. In the case of a compressor in which the refrigerant passes through the electric motor, the circulation amount of the refrigerant is increased by opening the air holes 9a, and the effect of improving the performance is great.

In the rotor 1 of the present embodiment, an air hole 19 is formed between the ferrite magnet 4 and the thin portion 15. By providing the air holes 19, the following effects can be obtained. When a current having a demagnetization phase is passed through the stator 2, a magnetic field (demagnetizing field) in a direction opposite to the magnetization direction of the magnet is generated. The demagnetizing field with respect to the rare earth magnet 3 escapes through the thin portion 14 because the rare earth magnet 3 is somewhat embedded in the shaft hole 8 side. However, the demagnetizing field with respect to the ferrite magnet 4 is easy to demagnetize the ferrite magnet 4 because the ferrite magnet 4 is disposed in the vicinity of the outer peripheral surface of the rotor. Therefore, in the rotor 1 of the present embodiment, by providing the air holes 19 on the rotor outer peripheral surface side of the ferrite magnet 4, the ferrite magnet 4 is difficult to demagnetize, and the reliability of the rotor 1 against demagnetization is increased. Can be improved.

FIG. 9 is a diagram for explaining the relationship between the thickness and the width of the ferrite magnet 4. The ferrite magnet 4 shown in FIG. 9 is such that W> T, where T is the thickness in the magnetization direction (length in the radial direction) and W is the width (length in the rotation direction) of the ferrite magnet 4. It is configured.

In the electric motor 100 of the present embodiment, since the ferrite magnet 4 having a large magnetic resistance exists between the adjacent rare earth magnets 3, the magnetic flux of the rare earth magnet 3 becomes difficult to be short-circuited, and the effective magnetic flux amount interlinked with the stator 2. Can be increased. And since the magnetic resistance between the adjacent rare earth magnets 3 can be increased as the width W of the ferrite magnet 4 is increased, the effect of reducing the short-circuit magnetic flux can be enhanced by configuring W> T. Is possible. Moreover, since the rare earth magnet 3 can be brought closer to the rotor outer peripheral surface as the thickness T is smaller, the iron core area (thickness of the iron core portion 7a) between the rare earth magnet 3 and the rotor outer peripheral surface can be reduced. And vibration can be further reduced.

FIG. 10 is a diagram for explaining the relationship between the magnetic pole opening A and the teeth width B of the rare earth magnet 3. In the electric motor 100 shown in FIG. 10, the width of the magnetic pole opening (the length between adjacent ferrite magnets 4) on the surface of the rare earth magnet 3 is A, and the teeth width of the teeth 18 (the teeth 18 facing the rotor outer peripheral surface). When B is defined as (end face width), B> A.

In the rotor 120 of the rare earth magnet 3 alone as shown in FIG. 8, the rare earth magnet 3 is widely arranged on the rotor surface to effectively use the magnet space of the rotor 120, and the rare earth magnet 3 is larger than the teeth width B. In many cases, the width of the magnetic pole opening on the surface (corresponding to the width A) is wide. In that case, the magnetic flux of the rare earth magnet 3 is easily short-circuited to the adjacent magnet through the teeth 18.

The electric motor 100 of the present embodiment can be configured to reduce the width A of the magnetic pole opening on the surface of the rare earth magnet 3 by using the rare earth magnet 3 and the ferrite magnet 4 in combination. Therefore, the width A is smaller than the teeth width B, the magnetic flux of the rare earth magnet 3 having a high magnetic flux density can be prevented from being short-circuited to the adjacent rare earth magnet 3 through the teeth 18, and the electric motor 100 having a high magnetic flux utilization rate of the magnet can be obtained. It is possible to obtain. In particular, in the electric motor 100 of the present embodiment, since the rare earth magnet 3 is surrounded by the ferrite magnet 4 having a large magnetic resistance, by configuring the width A to be smaller than the teeth width B, the magnetic flux of the rare earth magnet 3 is It becomes easy to flow to the teeth 18 having a small magnetic resistance.

In the present embodiment, the configuration example in which the shaft hole side surface 4a of the ferrite magnet 4 and the shaft hole side surface 3a of the rare earth magnet 3 are arranged on the same circumference has been described. For example, the rare earth magnet 3 is replaced with the ferrite magnet 4 Alternatively, the rare earth magnet 3 may be disposed closer to the slit 6 than the shaft hole 8.

FIG. 11 is a perspective view of the electric motor 100. 12 is a side view of the electric motor 100, and FIG. 13 is a perspective view of the rotor core 7 and permanent magnets (rare earth magnet 3 and ferrite magnet 4). 12 and 13 show the thickness of the stator core 5 (thickness of the stacked electromagnetic steel plates) formed by laminating electromagnetic steel sheets, the thickness of the rotor core 7, the axial length of the rare earth magnet 3, and the ferrite. The relationship with the axial length of the magnet 4 is shown.

Here, when the stack thickness of the stator core 5 is Ls, the stack thickness of the rotor core 7 is Lr, the axial length of the rare earth magnet 3 is Ln, and the axial length of the ferrite magnet 4 is Lf. Is configured to satisfy the following relational expression.
Ls <Lr, Ln <Lf, Ls≈Ln, and Lf≈Lr
That is, in the electric motor 100 of the present embodiment, the rotor core 7 is configured such that the stack thickness Lr is larger than the stack thickness Ls of the stator core 5, and the axial length Lf of the ferrite magnet 4 is the rare earth magnet 3. The axial length Ln of the rare earth magnet 3 is configured to be substantially equal to the stacking thickness Ls of the stator core 5, and the axial length of the ferrite magnet 4 is configured to be larger than the axial length Ln. Lf is configured to be approximately equal to the thickness Lr of the rotor core 7. Here, “substantially equal” refers to a range of about ± 2 mm.

As shown in FIG. 13, the rare earth magnet 3 is inserted into the insertion hole 23, and the rare earth magnet 3 inserted into the insertion hole 23 has an inner circumference of the stator core 5 with respect to the stacking direction of the rotor core 7. It is provided at a position (predetermined position) facing the part. More specifically, a stopper (not shown) is provided in the insertion hole 23 so that the rare earth magnet 3 is disposed at a predetermined position. The rare earth magnet 3 inserted into the insertion hole 23 is provided at a predetermined position by the axial end surface 3b of the rare earth magnet 3 coming into contact with the stopper, and the rare earth magnet 3 is arranged in a lower direction of the rotary compressor 200 described later. The magnet 3 is also prevented from falling.

As described above, from the relationship of Ln <Lf and Lf≈Lr, the axial length (≈Lr) of the insertion hole 23 is formed to be larger than the axial length Ln of the rare earth magnet 3. Yes. Accordingly, a leakage of the same shape as the insertion hole 23 is formed on the outer side (between the axial end face 3b and the axial end face 7b of the rotor core 7) of the rare earth magnet 3 inserted into the insertion hole 23. A magnetic flux suppression unit 10 (see FIG. 11) is formed. In the present embodiment, as an example, the leakage flux suppressing portion 10 and the insertion hole 23 have the same shape, but the shape of the leakage flux suppressing portion 10 is not limited to this, and the rotor core 7 is not limited thereto. As long as the thin-walled portion 14 is formed and provided outside the axial end surface 3 b of the rare earth magnet 3, the shape may be different from that of the insertion hole 23.

As described above, in the electric motor 100 according to the present embodiment, the leakage flux suppression unit 10 is provided outside the end surface 3b in the axial direction of the rare earth magnet 3, so that the magnetic flux of the rare earth magnet 3 is outside the end surface 3b in the axial direction. Leakage can be suppressed. Further, in the rotor core 7, a portion of the intermagnet thin portion 14 is formed between the leakage flux suppressing portion 10 and the insertion hole 22, so that the leakage flux of the ferrite magnet 4 can be suppressed.

In addition, the electric motor 100 according to the present embodiment is configured such that the axial length Lf of the ferrite magnet 4 is larger than the axial length Ln of the rare earth magnet 3, thereby using an inexpensive ferrite magnet 4. Thus, it is possible to achieve both high efficiency and low cost of the electric motor 100.

Here, the configuration when the electric motor 100 is mounted on a rotary compressor 200 (an example of a compressor) will be described. FIG. 14 is a longitudinal sectional view of the rotary compressor 200, and the rotary compressor 200 shown in FIG. 14 is a one-cylinder rotary compressor.

A rotary compressor (hereinafter simply referred to as “compressor”) 200 includes an electric motor 100 (electric element) and a compression element 31 in an airtight container 30. Although not shown, refrigerating machine oil that lubricates each sliding portion of the compression element 31 is stored at the bottom of the sealed container 30.

The compression element 31 includes the following elements.
(1) A cylinder 32 for storing refrigerant gas therein.
(2) A rotating shaft 34 having an eccentric shaft 33 that is rotated by the electric motor 100.
(3) A piston 35 fitted into the eccentric shaft 33 of the rotating shaft 34.
(4) A vane (not shown) that divides the inside of the cylinder 32 into a suction side and a compression side.
(5) A pair of upper and lower upper frames 36a and 36b in which the rotating shaft 34 is rotatably inserted and closes the axial end surface of the cylinder 32.
(6) An upper discharge muffler 37a and a lower discharge muffler 37b mounted on the upper frame 36a and the lower frame 36b, respectively.

Next, the operation will be described. The refrigerant gas passes through the suction muffler 38 and is sucked into the cylinder 32 through a suction pipe 39 fixed to the sealed container 30. When the electric motor 100 is rotated by an inverter (not shown), the piston 35 fitted to the eccentric shaft 33 of the rotating shaft 34 rotates in the cylinder 32. Thereby, the refrigerant gas is compressed in the cylinder 32. The compressed high-temperature refrigerant gas is discharged into the sealed container 30 through the upper discharge muffler 37a and the lower discharge muffler 37b, and is supplied to the high-pressure side of the refrigeration cycle through the discharge pipe 41 provided in the sealed container 30. The

The stator 2 of the electric motor 100 is directly attached and held in the sealed container 30 by a method such as shrink fitting or welding. Electric power from the glass terminal 40 fixed to the hermetic container 30 is supplied to the winding 11 wound around the stator 2.

The rotor 1 is arranged via a gap provided on the inner peripheral side of the stator 2, and the compression element 31 provided at the lower part of the compressor 200 via the rotation shaft 34 at the center of the rotor 1. The bearings (the upper frame 36a and the lower frame 36b) are held in a rotatable state.

In addition, although R410A, R407C, R22, etc. are conventionally used as the refrigerant of the compressor 200, any refrigerant such as a low GWP (global warming potential) refrigerant can be applied. From the viewpoint of preventing global warming, a low GWP refrigerant is desired. As typical examples of the low GWP refrigerant, there are the following refrigerants.

(1) A halogenated hydrocarbon having a carbon double bond in the composition, for example, HFO-1234yf (CF3CF = CH2). HFO is an abbreviation for Hydro-Fluoro-Olefin, which is an unsaturated hydrocarbon having one double bond. The GFO of HFO-1234yf is 4.
(2) A hydrocarbon having a carbon double bond in the composition, for example, R1270 (propylene). GWP is 3, which is smaller than HFO-1234yf, but flammability is larger than HFO-1234yf.
(3) a mixture containing at least one of a halogenated hydrocarbon having a carbon double bond in the composition or a hydrocarbon having a carbon double bond in the composition, for example, a mixture of HFO-1234yf and R32, etc. is there. Since HFO-1234yf is a low-pressure refrigerant, its pressure loss is large, and the performance of the refrigeration cycle (especially in an evaporator) tends to deteriorate. Therefore, a mixture with R32 or R41, which is a high-pressure refrigerant, is more effective than HFO-1234yf in practical use.

Of the low GWP refrigerants, R32 refrigerant is notable for toxicity and is not highly flammable, and thus has received particular attention. Moreover, when R32 refrigerant | coolant is used for the compressor 200, it has the characteristic that the internal temperature of the compressor 200 becomes about 20 degreeC high compared with R410A, R407C, R22 etc. which are used conventionally.

The temperature inside the compressor 200 varies depending on the compression load state (rotation speed, compression load torque, refrigerant), and is particularly dependent on the rotation speed. When the rotational speed of the electric motor 100 becomes the highest, the temperature inside the compressor 200 becomes maximum, and in the case of the R410A refrigerant, it is about 90 to 110 ° C. When the R32 refrigerant is used, the temperature in the compressor 200 further increases by about 20 ° C. to 110 to 130 ° C. with respect to the R410A refrigerant.

Under the above environment, the refrigerant sucked from the suction port (suction pipe 39) is compressed and passes through the sealed container 30 and flows from the discharge pipe 41 to the external refrigerant circuit. Therefore, the temperature inside the compressor 200 is It depends on the temperature of the refrigerant rather than the heat generated by the electric motor 100 itself.

As the temperature inside the compressor 200 rises, the temperature of the rare earth magnet 3 arranged inside the rotor 1 also rises. The rare earth magnet 3 has a negative coercivity temperature coefficient in which the coercive force decreases as the temperature increases.

Here, the coercive force is an index of the demagnetization resistance of the permanent magnet. The larger the value, the higher the demagnetization resistance against reverse magnetic field and heat. For example, a typical rare earth magnet 3 used in the compressor 200 is the temperature coefficient of -0.55 [% / ℃] about by coercive force _{H CJ} more than 20kOe at room temperature (20 ° C.). The coercive force temperature coefficient indicates the degree to which the coercive force characteristic changes with temperature. In the case of the Nd / Fe / B rare earth magnet 3, the coercive force decreases as the temperature of the permanent magnet increases. For example, it means that when the magnet temperature is increased by 100 ° C., the coercive force is reduced by 55%.

Therefore, when the R32 refrigerant whose temperature inside the compressor 200 is higher is used, the radial thickness of the rare earth magnet 3 is increased or the Dy is increased in order to avoid demagnetization of the rare earth magnet 3. Measures such as the use of the rare earth magnet 3 having a large coercive force are necessary, and all of them increase the cost of the electric motor.

By using the electric motor 100 according to the present embodiment for the compressor 200, even when the R32 refrigerant is used, the amount of the rare earth magnet 3 used can be reduced and the cost can be reduced as compared with the case where only the rare earth magnet 3 is used. A high-efficiency electric motor with suppressed increase can be obtained.

In the present embodiment, a one-cylinder rotary compressor has been described as an example. However, the present invention is not limited to this. If the electric motor 100 is incorporated in the compressor 200, the gist of the present invention is deviated. It goes without saying that the structure of the compressor 200 can be changed within a range not to be changed.

As described above, the electric motor 100 according to the present embodiment is an embedded permanent magnet electric motor in which the rotor core 7 formed by laminating a plurality of electromagnetic steel plates is disposed in the stator 2. Magnets constituting the magnetic poles 21 of the rotor core 7 are provided on the outer peripheral side of the rotor core 7 and are arranged in a number corresponding to the number of poles in the circumferential direction of the rotor core 7, and the ferrite magnet 4 The rotor core 7 has a stack thickness Lr larger than the stack thickness Ls of the stator core 5, and the ferrite magnet 4 has an axial length Lf of rare earth magnet 3. The axial length Ln of the rare earth magnet 3 is formed to be substantially equal to the stack thickness Ls of the stator core 5, and the axial length Lf of the ferrite magnet 4 is formed to be larger than the axial length Ln of the magnet 3. Formed approximately equal to the thickness Lr of the rotor core 7 Since the rare earth magnet 3 is provided at a position facing the inner peripheral portion of the stator core 5 with respect to the stacking direction of the rotor core 7, the amount of effective magnetic flux is increased by using an inexpensive ferrite magnet 4. Thus, both high efficiency and low cost of the electric motor 100 can be achieved.

Further, the rotor core 7 according to the present embodiment is formed with an insertion hole 23 provided on the outer peripheral side of the rotor core 7 for inserting the rare earth magnet 3, and the rare earth magnet 3 inserted into the insertion hole 23. Since the leakage flux suppressing part 10 is formed between the axial end surface 3b and the axial end surface 7b of the rotor core 7, the magnetic flux of the rare earth magnet 3 is prevented from leaking outside the axial end surface 3b. can do. Further, in the rotor core 7, a portion of the intermagnet thin portion 14 is formed between the leakage flux suppressing portion 10 and the insertion hole 22, so that the leakage flux of the ferrite magnet 4 can be suppressed.

Further, the ferrite magnet 4 according to the present embodiment is arranged so that the center of the ferrite magnet 4 is located between the poles 20 of the magnetic pole 21, and is magnetized so that the magnetization direction is reversed with respect to the poles 20. Therefore, the magnetic circuit of both the rare earth magnet 3 and the ferrite magnet 4 is a parallel circuit that does not interfere with each other, and the magnetic flux of the rare earth magnet 3 and the ferrite magnet 4 can be utilized to the maximum. Further, when compared with a conventional electric motor using only the rare earth magnet 3 with the same rotor magnetic flux, the rotor 1 of the present embodiment reduces the amount of the rare earth magnet 3 for the magnetic flux supplement by the ferrite magnet 4. can do. As a result, the area of the iron core portion 7a existing on the rotor outer peripheral surface side of the rare earth magnet 3 can be reduced, and cost reduction, high efficiency, low noise, and low vibration can be realized.

Further, in the electric motor 100 according to the present embodiment, since the ferrite magnet 4 having a large magnetic resistance exists between the rare earth magnets 3, the magnetic flux between the adjacent rare earth magnets 3 is difficult to be short-circuited, and the front and back of the magnets are reversed. Short-circuit magnetic flux is hardly generated. Therefore, when the rare earth magnet 3 per unit volume is considered, the effective magnetic flux amount linked to the stator 2 is increased, the magnet torque is increased, the applied current can be reduced, and the output can be increased. Alternatively, the increase in the amount of magnetic flux can be directed to reducing the amount of rare earth magnet 3 used.

In addition, since the ferrite magnet 4 according to the present embodiment is configured such that the magnetization direction is parallel orientation, radial orientation, or polar orientation, the rare earth magnet 3 does not become magnetoresistive when viewed from the ferrite magnet 4, In particular, in the case of radial orientation or polar orientation, the magnetization direction of the ferrite magnet 4 is oriented in a direction nearly perpendicular to the gap 20, so that the amount of effective magnetic flux linked to the stator 2 can be increased. Therefore, when compared with a conventional electric motor using only the rare earth magnet 3 with the same rotor magnetic flux, the amount of the rare earth magnet 3 for the magnetic flux supplement by the ferrite magnet 4 can be reduced, and the cost can be further reduced. And high efficiency can be achieved.

Further, since the rare earth magnet 3 according to the present embodiment is arranged on the same circumference as the ferrite magnet 4, the iron core is a cause of increasing the sound and vibration associated with the magnetic attractive force when the rotor 1 is eccentric. The area of the part 7a can be reduced. Therefore, compared with the case where the rare earth magnet 3 is not arranged on the same circumference as the ferrite magnet 4, it is possible to reduce noise and vibration.

Further, the rotor core 7 according to the present embodiment is formed with an insertion hole 22 provided on the outer peripheral side of the rotor core 7 and into which the ferrite magnet 4 is inserted. Since a gap (air hole 19) is formed between them, it is possible to eliminate a part that is easily demagnetized at the design stage, prevent a change in the amount of magnetic flux due to demagnetization, and improve reliability. It is possible to improve the quality of a product equipped with the electric motor 100.

Further, in the ferrite magnet 4 according to the present embodiment, when the thickness in the radial direction of the rotor core 7 is T and the length in the rotation direction of the rotor core 7 is W, W> T. Since it is comprised, the magnetic resistance between the rare earth magnets 3 is increased as W is increased, and the effect of reducing the short-circuit magnetic flux can be enhanced. Further, as T is smaller, the shaft hole side surface 4a can be brought closer to the vicinity of the outer peripheral surface of the rotor 1, and the shaft hole side surface 3a can be brought closer to the outer peripheral surface of the rotor 1 accordingly. It is possible to reduce the iron core area between the rotor outer peripheral surfaces (thickness of the iron core portion 7a), and to further reduce sound and vibration.

A plurality of teeth 18 formed at intervals in the circumferential direction are formed on the inner peripheral side of the stator 2 according to the present embodiment, and the width of the magnetic pole opening on the surface of the rare earth magnet 3 is increased. As A, when the width of the tooth 18 is B, since B> A, the magnetic flux of the rare earth magnet 3 can be prevented from being short-circuited to the adjacent rare earth magnet 3 through the tooth 18. It is possible to obtain the electric motor 100 having a high magnetic flux utilization rate of the magnet.

Note that the permanent magnet embedded electric motor and the compressor according to the embodiment of the present invention show an example of the content of the present invention, and can be combined with another known technique. Of course, it is possible to change and configure such as omitting a part without departing from the gist of the present invention.

As described above, the present invention can be applied to an interior permanent magnet electric motor and a compressor, and is particularly useful as an invention capable of reducing sound and vibration with high efficiency.

DESCRIPTION OF SYMBOLS 1,120 Rotor 2 Stator 3

Rare earth magnet

3a, 4a Shaft

hole side surface

3b, 7b Axial end face 4

Ferrite magnet

5, 24 Stator iron core 6 Slit 7 Rotor iron core 7a Iron core part 8 Shaft hole

9a Air hole

9b Rivet hole 10 Leakage magnetic flux suppression part 11 Winding 14 Thin part between magnets 15 Ferrite magnet outer peripheral thin part 15a Magnet outer peripheral thin part 17 Focal point of radial orientation 18 Teeth 19 Air hole (gap)
20 Pole 21 Magnetic pole 22 Ferrite magnet insertion hole 23 Rare earth magnet insertion hole 30 Sealed container 31 Compression element 32 Cylinder 33 Eccentric shaft 34 Rotating shaft 35 Piston 36a Upper frame 36b Lower frame 37a Upper discharge muffler 37b Lower discharge muffler 38 Suction muffler 39 Suction Pipe 40 Glass terminal 41

Discharge pipe

100, 110 Embedded permanent magnet electric motor 200 Rotary compressor Lf, Ln Axial length Lr, Ls Stack thickness

Claims

A permanent magnet embedded electric motor in which a rotor core formed by laminating a plurality of electromagnetic steel sheets is arranged in a stator,
The magnet constituting the magnetic pole of the rotor core is
A ferrite magnet provided on the outer peripheral side of the rotor core and disposed in a number corresponding to the number of poles in the circumferential direction of the rotor core, and a rare earth magnet disposed between the ferrite magnets,
The rotor core stack is formed larger than the stator core stack,
The axial length of the ferrite magnet is formed larger than the axial length of the rare earth magnet,
The axial length of the rare earth magnet is formed approximately equal to the thickness of the stator core,
The axial length of the ferrite magnet is formed approximately equal to the thickness of the rotor core,
The permanent magnet embedded electric motor, wherein the rare earth magnet is provided at a position facing an inner peripheral portion of the stator core with respect to a stacking direction of the rotor core.
The rotor core is provided with an insertion hole for inserting the rare earth magnet provided on the outer peripheral side of the rotor core,
2. The permanent magnet embedding according to claim 1, wherein a leakage flux suppressing portion is formed between an axial end face of the rare earth magnet inserted into the insertion hole and an axial end face of the rotor core. Built-in electric motor.
2. The ferrite magnet is disposed so that a center of the ferrite magnet is located between poles of the magnetic pole, and is magnetized so that a magnetization direction is reversed with respect to the gap between the poles. The permanent magnet embedded type electric motor described in 1.
2. The embedded permanent magnet motor according to claim 1, wherein the rare earth magnet is disposed on the same circumference as the ferrite magnet.
The rotor core is provided with an insertion hole for inserting the ferrite magnet provided on the outer peripheral side of the rotor core,
The permanent magnet embedded electric motor according to claim 1, wherein a gap is formed between the outer peripheral surface of the ferrite magnet and the insertion hole.
The ferrite magnet is configured such that W> T, where T is the thickness in the radial direction of the rotor core and W is the length in the rotational direction of the rotor core. The embedded permanent magnet electric motor according to claim 1.
A plurality of teeth formed at intervals in the circumferential direction are formed on the inner peripheral side of the stator,
2. The permanent magnet embedding according to claim 1, wherein B is greater than A when the width of the magnetic pole opening on the surface of the rare earth magnet is A and the width of the teeth is B. 3. Type electric motor.
A compressor equipped with the permanent magnet embedded motor according to any one of claims 1 to 7.
The compressor according to claim 8, wherein R32 refrigerant is used as the refrigerant.