JP2020150615A - Motor and apparatus having the same - Google Patents

Abstract

To propose a new permanent magnet shape in a multipole (a small area per pole) motor.SOLUTION: A motor includes: a stator; a rotor iron core that is arranged in a gap of the stator and provided with a rotor shaft; and a sintered magnet arranged in the rotor iron core. When viewed from an axial direction, the sintered magnet includes: a substantially arc-shaped stator side circular arc portion with a curvature radius R1 centered on a first point on a more stator side than the sintered magnet; and an approximately arc-shaped axial side arc-shaped portion of a curvature radius R2 centered on a second point on a more stator side than the sintered magnet. R2 is equal to or larger than 95% of a length L2 of a perpendicular line downward from the second point to a q-axis.SELECTED DRAWING: Figure 4

Description

The present invention relates to an electric motor and a device including the electric motor.

The electric motor used in the closed compressor is required to be miniaturized. In a closed compressor mounted on a refrigerator or a heat pump type water heater, for example, the outer diameter of the rotor of the electric motor is often designed to be 55 to 65 mm. The number of permanent magnets embedded in the rotor core is preferably large from the viewpoint of efficiency, but it is difficult to arrange a large number of permanent magnets in a small rotor core, and in many cases, the rotor poles. The number is 4 or 6.

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

In order to increase the number of slots while avoiding the increase in size of the rotor, it is necessary to devise the shape of the permanent magnet. As for the permanent magnet, a sintered magnet is preferable to a bond magnet having a large degree of freedom in molding from the viewpoint of the amount of magnetic flux. However, it is relatively difficult to mold the sintered magnet into a small size. For example, from the viewpoint of moldability and durability, there are restrictions that the maximum arc angle and the radius of curvature when forming an arc shape cannot be freely designed, or the thickness must be made uniform. For this reason, it is known that two or more sintered magnets are arranged in order to arrange sintered magnets having a shape desired by the designer in one slot, but an increase in the number of permanent magnets causes an increase in cost. Not preferable.

Further, as the arrangement of the permanent magnets per pole, for example, one in which the magnetic pole surface of the permanent magnets is opposed to the magnetic pole center point on the outer circumference of the rotor is known. For example, it is known that one or more permanent magnets are arranged in an arc type, a bathtub type, a U shape, a V shape, or the like. In any case, increase the area of the permanent magnet on the magnetic pole center point side to secure the magnetic flux amount, and the sine wave distribution (or a distribution close to this) in which the magnetic flux amount gradually decreases from the magnetic pole center side toward both ends. ) Is desired to be obtained. From this point of view, it is preferable that the shape of the magnetic pole surface is not a straight line but an arc shape.

As a related technique, it is not clear whether a small product is assumed as the applied product, but Patent Document 1 is an example of a rotor that realizes ten-polarization. In Patent Document 1, linear sintered magnets 61 and 62 and a curved bond magnet 63 having a high degree of freedom in shape are arranged in one slot (0004,0008-0009, FIG. 1-4).

Japanese Unexamined Patent Publication No. 2015-133839

Patent Document 1 attempts to secure magnetic flux with a linear sintered magnet and connect the sintered magnet with a curved bonded magnet. The magnetic flux generated by the linear sintered magnet has a shape that is a little far from giving a sinusoidal distribution, and it is difficult to mold with the sintered magnet because the region where the bond magnet is arranged has a small radius of curvature. it is conceivable that. Bonded magnets have a high degree of freedom in molding but a small amount of magnetic flux. However, while the sintered magnet has a large amount of magnetic flux, it is difficult to mold it with a large curvature, a shape having a non-uniform thickness, and a large arc angle.

The present invention made in view of the above circumstances
Stator and
A rotor core, which is arranged in the gap of the stator and has a rotating shaft,
It has a sintered magnet arranged on the rotor core and
In axial view, the sintered magnet is
A substantially arc-shaped stator-side arc portion having a radius of curvature R1 centered on a first point located on the stator side and on the stator side of the sintered magnet.
It has a substantially arcuate axial side arc portion having a radius of curvature R2 centered on a second point located on the rotating shaft side and on the stator side of the sintered magnet.
The R2 is an electric motor having a length L2 of a perpendicular line drawn from the second point to the q-axis, which is 95% or more.

Perspective view of the electric motor of the embodiment Sectional view perpendicular to the axial direction of FIG. (A) Cross-sectional view of the permanent magnet in the axial direction and (b) perspective view of the embodiment. Top view of the entire one pole of the rotor magnetic pole of the embodiment and a part of the rotor magnetic poles adjacent thereto. Longitudinal sectional view of a closed compressor equipped with the electric motor of the embodiment Vertical cross-sectional view of a refrigerator as an example of a device equipped with the sealed compressor of the embodiment.

An embodiment of the present invention will be described with reference to the accompanying drawings.
The electric motor 1 of the present embodiment is a type of 10 poles and 12 slots, 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 the present 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 plates, and has a plurality of stator cores 4 having a circular gap on the center side in the top view (axial view) as shown in FIG. 2 and a plurality of stator cores 4 in the circumferential direction (the stator core 4). (12 in this embodiment) There are a plurality of (12 in this embodiment) slots 41 that are arranged and have an inner peripheral end facing each other in a circular gap, and a gap between the teeth 42 in a top view. are doing. In each of the slots 41, coils 5 of each phase are wound around a total of 12 places via an insulating material 6. The electric motor 1 may be a single-phase drive or a three-phase drive.

(Rotor)
The rotors are arranged in the circular voids of the stator core 4, and have a rotor core 7 formed by laminating electromagnetic steel sheets. The outer circumference 73 of the rotor core 7 faces the inner peripheral end of the teeth 42. A central hole 72 through which a rotating shaft (for example, a crankshaft of a compressor) is inserted and fixed is arranged at the center of the top view. A plurality of magnet insertion holes 71 (10 in the present embodiment) are arranged between the outer peripheral 73 and the central hole 72 in a top view, and permanent magnets 8 are provided in each of them. With reference to the center O of the central hole 72, which is the center of rotation, the direction toward the center of the permanent magnet 8 is the d-axis direction, and the direction toward the center (between the magnetic poles) between the two permanent magnets 8 is the q-axis direction. To do. In the following, 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. In the following, the dimensions of the permanent magnet 8 and the like are described, but 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, with respect to the relational expression satisfied by the dimensions, etc. listed in the present specification according to the context, the ratio of the dimensions, etc. is calculated again, and the reference value (upper and lower limit of the relational expression) to be less than, less than, more than, or more than this ratio is calculated. You can ask.

(Permanent magnet 8)
FIG. 3 is (a) a cross-sectional view of one permanent magnet in the axial direction and (b) a perspective view. FIG. 4 is a top view of the entire rotor magnetic pole 1 pole and a part of the rotor magnetic poles adjacent thereto.
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 stator side surface, a stator side arc portion 81 formed in a substantially arc shape centered on a point 85 (first point) located on the stator side of the permanent magnet 8, preferably the rotor core 4, is used. Have. The radius of curvature R1 of the stator-side arc portion 81 is shorter than the length L1 of the perpendicular line 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. Therefore, it is preferable that the side surface of the stator has a long circumference in the axial direction. Since it is difficult to form a V-shape, for example, which is drawn by two line segments with one sintered magnet, it is conceivable to form a curved shape. Then, it is preferable that at least the inside in the circumferential direction (d-axis side) has a substantially arc shape.

In the present embodiment, the entire side surface of the stator is formed into an arc shape to form the stator side arc portion 81, and three points from the first point 85 to both ends of the stator side arc portion 81 are connected by a virtual line segment. The angle θ made in the case, that is, the central angle (arc angle) is set to 140 ° or more and 150 ° or less. The circumference can be secured by setting the temperature to 140 ° or more. However, molding with a large arc angle is difficult, and by setting the angle to 150 ° or less, moldability with one sintered magnet can be ensured.

Further, when the first point 85 is on the shaft side, the side surface of the shaft is inevitably shifted to the shaft side. The area where one pole should be stored (the area from the rotation axis O (360 / (number of poles)) ° as illustrated in FIGS. 3 and 4) has a shape in which the shaft side is narrow and the stator side is wide, so that the permanent magnet is used. It becomes difficult to secure or make the thickness of 8 uniform. Therefore, in order to set the stator side surface to the stator side, the first point 85 is preferably located on the outer circumference of the rotor core 4 or closer to the stator side.

Therefore, from the viewpoint of securing the peripheral length and the thickness of the permanent magnet 8, the first point 85 is preferably on the outer periphery of the rotor core 4 or on the stator side of the rotor core 4. exist.

Further, from the viewpoint of moldability of the sintered magnet, the lower limit is the angle Φ formed when both ends of the stator side arc portion 81 are connected by a virtual line segment from the bending depth of the magnet, that is, the point where it intersects the d-axis. It is preferable to provide, for example, 105 ° or more.

At this time, the "end of the stator-side arc portion 81" is a virtual extension line of the stator-side arc portion 81, which will be described later, when the permanent magnet 8 is chamfered or otherwise rounded. It can be an intersection with a virtual extension line of the connection portion 84.

The side surface of the stator may be provided with a portion extending linearly from both ends of the arc portion 81 on the stator side toward the stator side, but the first point is from the viewpoint of moldability of the sintered magnet. The angle formed when connecting each of the two points at both ends of the straight line portion from 85 is subject to substantially the same limitation as when the entire shape is arcuate. Since it is easier to secure the peripheral length when the entire circumference is arcuate than when a part is linear, it is most preferable to make the entire arcuate as in the present embodiment. However, 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 making the magnetic flux distribution close to a sinusoidal shape, it is preferable to make substantially the entire arc shape.

The side surface of the shaft has a shaft-side arc portion 82 formed in a substantially arc shape centered on a point 86 (second point) located on the stator side of the permanent magnet 8. The radius of curvature R2 of the axial 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 line drawn from the second point 86 to the q-axis. You may. However, even when the value is 100% or more, the side surface of the shaft is separated from the q-axis without intersecting or touching the q-axis by having the portion 83 along the q-axis described later.

By the way, a sintered magnet is usually formed by pressing a magnetic powder as a material while applying a magnetic field in the direction of magnetic pole formation. In order to obtain excellent magnetic characteristics, the die is generally designed so that the pressing direction substantially coincides with the magnetic field direction, and in the present embodiment, the pressing is performed from the direction perpendicular to the axial direction.

Then, in order to apply the press pressure uniformly, it is preferable that the thickness in the shape in the axial direction as shown in FIG. 3A is substantially uniform. That is, it is preferable that the difference between the minimum value X of the thickness on the q-axis side where the thickness is small and the maximum value Y of the thickness on the d-axis side where the thickness is large is small. Therefore, in the present embodiment, the thickness is made uniform by substantially matching the first point 85 and the second point 86 and making the stator-side arc portion 81 and the shaft-side arc portion 82 substantially concentric circles. ..

The two points 85 and 86 do not necessarily have to match, but if they do not match, the second point 86 should be on the stator side of the first point 85. As a result, it is possible to reduce the possibility that X becomes too thin even if the q-axis portion 83 described later is provided.

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 used as in this embodiment, 1.0 <X / Y ≦ 1.2 may be used as Y <X.

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

The axis side of the q-axis portion 83, preferably the entire q-axis portion 83, is located on the d-axis side from an extension line that is a virtual extension of the axis-side arc portion 82. Another way of looking at the q-axis portion 83 is that the axis side of the q-axis portion 83, preferably the entire q-axis portion 83, is inside a virtual circle having a radius R2 centered on the second point 86 (boundary). Includes.).
The first point 85 may be the same as the second point 86 as in the present embodiment, or may be on the axial side of the second point 86.

Further, as a portion connecting the side surface of the stator and the side surface of the shaft, there is a connecting portion 84 connecting both ends of the arc portion 81 on the stator side and each side of the stator along the q-axis portion 83.

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

Further, since the amount of magnetic flux on the center side is large and the amount of magnetic flux on both ends is small, and the magnetic flux distribution can be brought close to a suitable one, permanent magnets can be effectively spread for the realization of multiple poles.

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

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

The electric motor 1 causes the rotor to rotate together with the shaft 35 by the electromagnetic force generated in the stator by passing an electric current through the coil 5.

1 Motor 4 Stator core 41 Slot 42 Teeth 5 Coil 6 Insulation material 7 Rotor core 71 Magnet insertion hole 72 Center hole 73 Outer circumference 8 Permanent magnet 81 Stator side arc part 82 Axis side arc part 83 q Axis along part 84 Connection part 85 Center point of the arc on the stator side (first point)
86 Center point of the arc on the axis side (second point)
50 Sealed compressor 100 Refrigerator

Claims (6)

Stator and
A rotor core, which is arranged in the gap of the stator and has a rotating shaft,
It has a sintered magnet arranged on the rotor core and
In axial view, the sintered magnet is
A substantially arc-shaped stator-side arc portion having a radius of curvature R1 centered on a first point located on the stator side and on the stator side of the sintered magnet.
It has a substantially arcuate axial side arc portion having a radius of curvature R2 centered on a second point located on the rotating shaft side and on the stator side of the sintered magnet.
The R2 is an electric motor having 95% or more of the length L2 of the perpendicular line drawn from the second point to the q-axis. The sintered magnet is
It has a q-axis portion along the q-axis of the sintered magnet and does not coincide with the q-axis.
The electric motor according to claim 1, wherein the rotation axis side along the q-axis is located inside or on a boundary of a virtual circle having a radius R2 centered on the second point. The electric motor according to claim 1 or 2, wherein the first point is on the outer periphery of the rotor core or on the stator side of the rotor core. The electric motor according to any one of claims 1 to 3, wherein the second point coincides with the first point or is on the stator side of the first point. Any of claims 1 to 4 in which the minimum value X of the thickness on the q-axis side of the sintered magnet and the maximum value Y of the thickness on the d-axis side satisfy the inequality 1.0 ≦ Y / X ≦ 1.2. The electric motor described in item 1. A device including the electric motor according to any one of claims 1 to 5.

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