Rotor core having bridges connection magnetic pole and method of manufacturing the same

1. A rotor for a rotating electrical machine comprising:

a rotor core made of a stack of a plurality of blanks of steel sheet including a yoke, a magnetic pole portion confronting the yoke, and a magnet insertion hole interposed between the yoke and the magnetic pole portion,

wherein the stack includes at least one blank having a bridge connecting the yoke and the magnetic pole portion and one or more blanks having the bridge blanked off, and

a magnet inserted to the magnet insertion hole,

wherein a projection is configured to project circumferentially beyond a width of the bridge and is formed at two circumferential sides of the magnetic pole portion and;

wherein a resin is molded between the magnetic pole portions and within a space of the stack of blanks defined by the blanked off bridge of the rotor core with the magnet being inserted to the magnet insertion hole.

2. The rotor of claim 1 , wherein the blank stacked at an uppermost layer and a lowermost layer include the bridge.

3. The rotor of claim 1 , wherein a length of projection of the projection ranges from 2 to 10% relative to a circumferential length of each magnetic pole portion.

4. A method of manufacturing a rotor of a rotating electrical machine including a rotor core made of a stack of a plurality of blanks including a yoke, a magnetic pole portion confronting the yoke, a magnet insertion hole interposed between the yoke and the magnetic pole portion, a magnet inserted into the magnet insertion hole, the method comprising:

forming a caulked portion in a magnetic pole corresponding portion that corresponds to the magnetic pole of a steel sheet for forming a core;

defining a magnet insertion hole by blanking a portion between a yoke corresponding portion that corresponds to the yoke and the magnetic pole corresponding portion of the steel sheet;

blanking the yoke corresponding portion, the magnetic pole corresponding portion, and a bridge corresponding portion that connects the yoke corresponding portion and the magnetic pole corresponding portion from the steel sheet to form blanks;

stacking the plurality of blanks to form the rotor core,

inserting the magnet into the magnet insertion hole of the rotor core; and

molding a resin between the magnetic pole portions and within a space of the stack of blanks defined by the blanked off bridge of the rotor core with the magnet being inserted to the magnet insertion hole,

wherein the blanking forms a projection projecting circumferentially beyond a width of the bridge at two circumferential sides of the magnetic pole portion by blanking the magnetic pole corresponding portion.

5. The method of claim 4 , wherein a length of projection of the projection ranges from 2 to 10% relative to a circumferential length of each magnetic pole portion.

6. A method of manufacturing a rotor of a rotating electrical machine including a rotor core made of a stack of a plurality of blanks including a yoke, a magnetic pole portion confronting the yoke, a magnet insertion hole that is interposed between the yoke and the magnetic pole portion, a magnet inserted into the magnet insertion hole, the method comprising:

cutting a bridge corresponding portion connecting a yoke corresponding portion that corresponds to the yoke and a magnetic pole corresponding portion that corresponds to the magnetic pole portion and forming a caulked portion in the magnetic pole corresponding portion of a steel sheet for forming a core;

defining a magnet insertion hole by blanking a portion between the yoke corresponding portion and the magnetic pole corresponding portion of the steel sheet;

blanking the yoke and the magnetic pole portion from the steel sheet to form a blank; and

stacking a plurality of blanks to form the rotor core;

inserting a magnet into the magnet insertion hole of the rotor core; and

molding a resin between the magnetic pole portions and within a space of the stack of blanks defined by the blanked off bridge of the rotor core with the magnet being inserted to the magnet insertion hole;

wherein the blanking forms a projection projecting circumferentially beyond a width of the bridge at two circumferential sides of the magnetic pole portion by blanking the magnetic pole portion and

wherein the stacked blanks include at least one blank having a bridge connecting the yoke and the magnetic pole portion.

7. The method of claim 6 , wherein the blanks stacked initially and lastly have a bridge connecting the yoke and the magnetic pole portion.

8. The method of claim 6 , wherein a length of the projection ranges from 2 to 10% relative to a circumferential length of each magnetic pole portion.