JP7169911B2 - Electric motors and equipment equipped with them - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electric motor and equipment provided with the same.

Electric motors used in hermetic compressors are required to be downsized. Hermetic compressors mounted on refrigerators and heat pump water heaters are often designed with a rotor having an outer diameter of, for example, 55 to 65 mm. From the viewpoint of efficiency, it is preferable that the number of permanent magnets embedded in the rotor core is as large as possible. The number is 4 or 6.

However, if a further increase in the number of poles such as 8 poles or 10 poles can be achieved, the required amount of magnetic flux per pole can be dispersed, and the magnetic path of the stator can be reduced, and further efficiency improvement can be expected. 12 slots can be considered as a suitable slot number combination for a rotor with 8 poles or 10 poles.

In order to increase the number of slots while avoiding an increase in the size of the rotor, it is necessary to devise the shape of the permanent magnets. Regarding permanent magnets, sintered magnets are preferable to bonded magnets, which have a large degree of freedom in forming, from the viewpoint of the amount of magnetic flux. However, it is relatively difficult to mold a sintered magnet into a small size. For example, from the standpoint of formability and durability, restrictions appear such as the inability to freely design the maximum arc angle and radius of curvature when forming into an arc shape, and the need to make the thickness uniform. For this reason, it is known to arrange two or more sintered magnets in one slot in order to arrange a sintered magnet having a shape desired by the designer. I don't like it.

As for the arrangement of the permanent magnets per pole, for example, it is conventionally known that the magnetic pole faces of the permanent magnets face the magnetic pole center point on the outer circumference of the rotor. For example, it is known to arrange one or more permanent magnets in arcs, bathtubs, U-shapes, V-shapes, and the like. In any case, the area of the permanent magnet on the side of the magnetic pole center point is increased to ensure the amount of magnetic flux, and a sine wave distribution (or a distribution close to this) in which the amount of magnetic flux gradually decreases from the magnetic pole center side toward both ends. ) is desired. From this point of view, it is preferable to make the magnetic pole face shape circular rather than linear.

As a related technology, although it is not clear whether a small product is assumed as a product to which the technology is applied, there is Patent Document 1 as an example of a rotor that realizes 10 poles. In Patent Document 1, linear sintered magnets 61 and 62 and a curved bonded magnet 63 with a high degree of freedom in shape are arranged in one slot (0004, 0008-0009, FIGS. 1-4).

JP 2015-133839 A

Patent Document 1 attempts to secure magnetic flux with a linear sintered magnet and connect the sintered magnets with a curved bond magnet. The magnetic flux from a linear sintered magnet has a shape that is a little far from giving a sinusoidal distribution. it is conceivable that. Bonded magnets have a high degree of freedom in forming, but have a small amount of magnetic flux. However, while the sintered magnet has a large amount of magnetic flux, it is difficult to mold with a large curvature, a shape with uneven thickness, and a large arc angle.

The present invention, which has been made in view of the above circumstances,
a stator;
a rotor core disposed in the gap of the stator and having a rotating shaft disposed thereon;
a sintered magnet arranged in the rotor core;
When viewed in the axial direction, the sintered magnet has
a substantially arc-shaped stator-side arc portion having a curvature radius R1 centered at a first point located on the stator side and closer to the stator than the sintered magnet;
a substantially arc-shaped shaft-side arc portion having a radius of curvature R2 centered at a second point located on the rotating shaft side and closer to the stator than the sintered magnet ;
along the q-axis of the sintered magnet and along the q-axis that does not coincide with the q-axis,
the second point is closer to the stator than the first point;
The maximum value Y of the thickness on the d-axis side of the sintered magnet is longer than the minimum value X of the thickness on the q-axis side,
Said R2 is a motor which is 95% or more of the length L2 of the perpendicular drawn from said second point to said q-axis.

1 is a perspective view of an electric motor according to an embodiment; Sectional view perpendicular to the axial direction of FIG. (a) Cross-sectional view of the permanent magnet viewed from the axial direction and (b) perspective view of the embodiment A top view of an entire magnetic pole of the rotor of the embodiment and a part of the adjacent rotor magnetic pole. FIG. 1 is a vertical cross-sectional view of a hermetic compressor equipped with an electric motor according to an embodiment; FIG. 1 is a vertical cross-sectional view of a refrigerator as an example of equipment equipped with the hermetic compressor of the embodiment.

Embodiments of the present invention will be described with reference to the accompanying drawings.
The electric motor 1 of this embodiment is of a 10-pole, 12-slot type, but the number of poles and the number of slots are not necessarily limited to this.

FIG. 1 is a perspective view of the electric motor 1 of this embodiment. FIG. 2 is a cross-sectional view perpendicular to the axial direction of FIG.
The electric motor 1 has a stator and a rotor.

(stator)
The stator is formed by laminating electromagnetic steel sheets, and has a stator core 4 provided with a circular gap in the center when viewed from above (in the axial direction) as shown in FIG. In this embodiment, 12 slots 42 are arranged, and the inner peripheral ends of the teeth 42 face each other in a circular gap. is doing. The coils 5 for each phase are wound around the slots 41 at a total of 12 locations via the insulating material 6 . The electric motor 1 may be single-phase drive or three-phase drive.

(rotor)
The rotor is arranged in a circular gap of the stator core 4 and has a rotor core 7 formed by laminating electromagnetic steel plates. The outer circumference 73 of the rotor core 7 faces the inner circumference ends of the teeth 42 . A center hole 72 through which a rotating shaft (for example, a crankshaft of a compressor) is inserted and fixed is arranged at the center in top view. A plurality of (10 in this embodiment) magnet insertion holes 71 are arranged between the outer circumference 73 and the center hole 72 in top view, and the permanent magnets 8 are provided in each of them. The direction toward the center of the permanent magnet 8 is defined as the d-axis direction, and the direction toward the center (between the magnetic poles) between the two permanent magnets 8 is defined as the q-axis direction. do. In the following description, the d-axis and the q-axis may be used as virtual half lines. The radius r of the rotor of this embodiment is 33.00 mm. Although the dimensions of the permanent magnet 8 and the like are described below, it is obvious that the ratio of the dimensions to r and the like can be obtained by referring to the value of r. In addition, regarding the relational expressions that the dimensions, etc. listed in this specification satisfy according to the context, the ratios of the dimensions, etc. are calculated again, and the reference values (upper and lower limits of the relational expressions) that should be less than or less than or more than or greater than this ratio can ask.

(Permanent magnet 8)
FIG. 3 is (a) a cross-sectional view of one permanent magnet viewed from the axial direction, and (b) a perspective view. FIG. 4 is a top view of an entire rotor pole and a portion of the adjacent rotor pole.
The permanent magnet 8 is a sintered magnet having a stator side surface on the stator side and a shaft side surface on the rotating shaft side.

As the side surface of the stator, the permanent magnet 8, preferably a stator-side arc portion 81 formed in a substantially arc shape around a point 85 (first point) located on the stator side of the rotor core 4 is provided. have. The radius of curvature R1 of the stator-side arc portion 81 is shorter than the length L1 of the perpendicular drawn from the point 85 to the q-axis.

From the viewpoint of increasing the amount of magnetic flux, it is required to increase the area of the side surface of the stator. For this reason, it is preferable that the side surface of the stator has a longer peripheral length when viewed in the axial direction. Since it is difficult to form a single sintered magnet into a V-shape, for example, as drawn by two line segments, it is conceivable to form a curved shape. Then, it is preferable that at least the inner side (d-axis side) in the circumferential direction is formed into a substantially arc shape.

In this embodiment, the stator-side arc portion 81 is formed by making the entire side surface of the stator arc-shaped, and three points from the first point 85 to both ends of the stator-side arc portion 81 are connected by imaginary line segments. The angle θ formed in the case, that is, the central angle (arc angle) is set to 140° or more and 150° or less. By setting the angle to 140° or more, the peripheral length can be secured. However, molding with a large arc angle is difficult, and by setting the arc angle to 150° or less, the formability of a single sintered magnet can be ensured.

Also, if the first point 85 is on the shaft side, the shaft side surface will inevitably shift toward the shaft side. The area where one pole should be accommodated (the area of (360/(number of poles))° from the rotation axis O as exemplified in FIGS. 3 and 4) has a narrow shape on the shaft side and a wide shape on the stator side. It becomes difficult to ensure the thickness of 8 and make it uniform. Therefore, the first point 85 is preferably located on the outer circumference of the rotor core 4 or closer to the stator than this in order to set the stator side to the stator side.

Therefore, from the viewpoint of ensuring the circumference length and the thickness of the permanent magnet 8, the first point 85 is preferably located on the outer circumference of the rotor core 4 or closer to the stator side than the rotor core 4. exist.

Also, from the viewpoint of formability of the sintered magnet, the lower limit is given to the angle Φ formed when each end of the stator-side circular arc portion 81 is connected by an imaginary line segment from the bending depth of the magnet, that is, the point at which it intersects the d-axis. is preferably provided, for example, 105° or more.

At this time, the "end portion of the stator-side arc portion 81" is an imaginary extension line of the stator-side arc portion 81 when the permanent magnet 8 is chamfered or otherwise rounded. The point of intersection with the imaginary extension of the connecting portion 84 can be used.

As the side surface of the stator, portions extending linearly from both ends of the stator-side arc portion 81 toward the stator side may be provided. The angle formed by connecting two points at both ends of the linear portion from 85 is subject to substantially the same restrictions as in the case where the entirety is arc-shaped. Since it is easier to secure the peripheral length by making the whole arcuate shape rather than making it partly straight, it is most preferable to make the whole arcuate shape as in the present embodiment. Of course, substantially the entire circumference, that is, 90% or more, 95% or more, or 98% or more of the circumference may be arcuate. Further, from the viewpoint of approximating the magnetic flux distribution to a sinusoidal shape, it is preferable to form substantially the entire arc shape.

The shaft side surface has a shaft-side arc portion 82 formed in a substantially arc shape centering on a point 86 (second point) on the stator side of the permanent magnet 8 . The radius of curvature R2 of the shaft-side arc portion 82 can be 95% or more, 98% or more, 99% or more, or 100% or more of the length L2 of the perpendicular drawn from the second point 86 to the q-axis. may However, even in the case of 100% or more, the axial side surface is spaced apart from the q-axis without intersecting or contacting the q-axis by having a portion 83 along the q-axis, which will be described later.

A sintered magnet is usually formed by pressing magnetic powder as a material while applying a magnetic field in the direction of magnetization. In order to obtain excellent magnetic properties, the mold is generally designed so that the direction of pressing substantially coincides with the direction of the magnetic field. In this embodiment, pressing is performed from a direction perpendicular to the axial direction.

Then, in order to uniformly apply the pressing pressure, it is preferable that the thickness in the axially viewed shape as shown in FIG. 3(a) is substantially uniform. That is, it is preferable that the difference between the minimum thickness X on the q-axis side where the thickness is small and the maximum thickness Y on the d-axis side where the thickness is large is small. For this reason, in the present embodiment, the first point 85 and the second point 86 are substantially aligned to make the stator-side arc portion 81 and the shaft-side arc portion 82 substantially concentric, thereby making the thickness uniform. .

The two points 85 and 86 do not necessarily have to match, but if they do not match, the second point 86 should be closer to the stator than the first point 85 is. As a result, even if a portion 83 along the q-axis, which will be described later, is provided, the risk of X becoming too thin can be reduced.

It is preferable that the difference between X and Y is within a discrepancy of 5.00 mm or less, or that the inequality of 1.0≦Y/X≦1.2 holds. Although X≦Y may be satisfied as in the present embodiment, Y<X may be 1.0<X/Y≦1.2.

Further, the shaft side surface further has q-axis portions 83 connected to both ends of the shaft-side arc portion 82 and extending toward the stator side along the q-axis, preferably parallel to the q-axis. Here, "to follow" does not include matching to the object to be followed. That is, the q-axis portion 83 is partly or wholly separated from the q-axis, and partly or wholly does not coincide with the q-axis.

The portion 83 along the q-axis is positioned on the d-axis side of the extension line of the axial-side arc portion 82, preferably the entire portion 83 along the q-axis. From another point of view, the q-axis portion 83, preferably the entire q-axis portion 83, is inside an imaginary circle of radius R2 centered at the second point 86 (the boundary is including.)
The first point 85 may be the same as the second point 86 in the same manner as in this embodiment, or may be on the shaft side of the second point 86 .

In addition, as a portion that connects the stator side surface and the shaft side surface, there are connecting portions 84 that connect both end sides of the stator side circular arc portion 81 and each of the q-axis portion 83 on the stator side.

By forming the permanent magnet in such a shape, while securing the area of the stator-side arc portion 81 that serves as the magnetic pole surface of the permanent magnet, a portion with a small radius of curvature appears and the thickness of the magnet becomes thin or uneven. Since this can be suppressed, the moldability and durability of the permanent magnet 8 can be improved.

In addition, since the magnetic flux amount on the center side is large and the magnetic flux amount on both end sides is small, the magnetic flux distribution can be approximated to a suitable one, so that the permanent magnets can be effectively laid out to realize multiple poles.

As a result, without increasing the size of the stator of hermetic compressors such as air conditioners and heat pump water heaters, it is possible to increase the number of poles, for example, 8 poles or 10 poles or more. type motor can be provided.

FIG. 5 is a vertical cross-sectional view of a hermetic compressor as an example of equipment equipped with an electric motor. FIG. 6 is a vertical cross-sectional view of a refrigerator as an example of a home appliance equipped with a hermetic compressor. Home appliances also include air conditioners and heat pump water heaters.
Inside the sealed container 50, there are the electric motor 1, a power transmission unit composed of a crankshaft 35 fastened to the rotor, a connecting rod 36 that converts the rotary motion of the crankshaft into a reciprocating motion of the piston 37, and a reciprocating motion of the piston 37. It is composed of a compressor mechanism section composed of a valve plate 19 that compresses the refrigerant gas in the cylinder 38 by motion and controls the intake and suction of the refrigerant gas.

The electric motor 1 rotates the rotor together with the shaft 35 by the electromagnetic force generated in the stator by applying current to the coil 5 .

1 Electric motor 4 Stator iron core 41 Slot 42 Teeth 5 Coil 6 Insulating material 7 Rotor iron core 71 Magnet insertion hole 72 Center hole 73 Outer circumference 8 Permanent magnet 81 Stator-side arc portion 82 Shaft-side arc portion 83 Along q-axis 84 Connecting portion 85 Center point of stator-side arc (first point)
86 Center point of shaft-side arc (second point)
50 hermetic compressor 100 refrigerator

Claims (6)

a stator;
a rotor core disposed in the gap of the stator and having a rotating shaft disposed thereon;
a sintered magnet arranged in the rotor core;
When viewed in the axial direction, the sintered magnet has
a substantially arc-shaped stator-side arc portion having a curvature radius R1 centered at a first point located on the stator side and closer to the stator than the sintered magnet;
a substantially arc-shaped shaft-side arc portion having a radius of curvature R2 centered at a second point located on the rotating shaft side and closer to the stator than the sintered magnet ;
along the q-axis of the sintered magnet and along the q-axis that does not coincide with the q-axis,
the second point is closer to the stator than the first point;
The maximum value Y of the thickness on the d-axis side of the sintered magnet is longer than the minimum value X of the thickness on the q-axis side,
The electric motor, wherein the R2 is 95% or more of the length L2 of the perpendicular drawn from the second point to the q-axis. 2. The electric motor according to claim 1, wherein the rotation axis side along the q-axis is located inside or on the boundary of an imaginary circle having a radius R2 centered at the second point. 3. The electric motor according to claim 1, wherein the first point is on the outer circumference of the rotor core or closer to the stator than the rotor core. 4. The electric motor according to claim 1 , wherein said minimum value X and said maximum value Y satisfy an inequality 1.0≤Y/X≤1.2. 5. The electric motor according to claim 4, wherein the difference between said minimum value X and said maximum value Y is 5.00 mm or less. A device comprising the electric motor according to any one of claims 1 to 5.

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