Motor

1. A motor comprising:

a stator including a stator iron-core formed of a salient iron-core and a yoke, and a winding wound on the stator iron-core; and

a rotor facing an inner wall of the salient iron-core and held rotatably, the rotor including a rotor iron-core formed by laminating an iron sheet of high permeability,

wherein the rotor iron-core includes a plurality of holes in which permanent magnets are to be buried, and the permanent magnets buried in the holes,

wherein a magnetic pole centerline connecting a rotary center of the rotor to a magnetic pole center crosses an external shape of the rotor iron-core at end point X, and a magnetic-pole boundary line connecting the rotary center to a magnetic pole boundary point crosses the external shape of the rotor iron core at end point Z, and a straight line angled at a given angle “θa” from the magnetic pole centerline toward the magnetic boundary line and extending through the rotary center crosses the external shape of the rotor iron-core at end point A,

wherein a sectional view of the rotor iron-core shows an arc drawn between end points X and A, and a center of the arc is the rotary center, and the end points A and Z are connected by at least one straight line, and the at least one straight line exists inside a circle drawn by an extension line of the arc at the same curvature, and

wherein a minimum distance between an end of one of the plurality of holes and the external shape of the rotor iron-core is referred to as “Ln”, and a thickness of the iron sheet of high permeability is referred to as “d”, then a relation of d/2<Ln<2d is established.

2. The motor of claim 1 , wherein each one of the plurality of holes includes a projection at both ends along a circumferential direction.

3. The motor of claim 1 , wherein the given angle “θa” falls within a range of 15°<θa<75°, and the end point A is connected to the end point Z by a plurality of straight lines in series.

4. The motor of claim 3 , wherein an intersection point of the plurality of straight lines in series forms a protrusion.

5. The motor of claim 3 , wherein a minimum distance between an end of each one of the plurality of holes and the external shape of the rotor iron-core is referred to as “Ln”, and an intersection point of the plurality of straight lines in series is changed in response to a value of “Ln”.

6. The motor of claim 1 , wherein the given angle “θa” falls within a range of 30°<θa<75°, and the end point A is connected to end point Z by one straight line.

7. The motor of claim 1 , wherein the winding is wound in a concentrated manner.

8. A motor comprising:

a stator having an inner surface; and

a rotor having an outer surface facing the inner surface of the stator, the rotor including a rotor iron-core formed by laminating a plurality of iron sheets,

wherein the rotor iron-core includes a plurality of holes for receiving a plurality of permanent magnets, the permanent magnets forming magnetic poles,

wherein a first radial line across a center of one of the magnetic poles intersects the outer surface of the rotor at point X, a second radial line across a boundary of the one of the magnetic poles intersects the outer surface of the rotor at point Z, and a third radial line at a given angle “θa” from the first radial line intersects the outer surface of the rotor at point A,

wherein the outer surface of the rotor forms an arc between points X and A, and the outer surface of the rotor forms at least one straight line between points A and Z, and

wherein the plurality of iron sheets each have a thickness “d”, and a minimum distance between an outermost end of each one of the plurality of holes and the outer surface of the rotor is “Ln”, such that d/2<Ln<2d.