CROSS REFERENCE TO RELATED APPLICATION

This application is a U.S. national stage application of International Patent Application No. PCT/JP2017/017134 filed on May 1, 2017, the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a permanent magnet-embedded rotor, and relates to a motor, a compressor and an air conditioner including the rotor.

BACKGROUND

In a permanent magnet-embedded rotor, a permanent magnet is disposed inside a magnet insertion hole formed in a rotor core. In some rotors, the magnet insertion hole is divided by a bridge into two or more in a circumferential direction in order to enhance strength of the rotor core.

On the other hand, in the case where the bridge is provided in the magnet insertion hole, magnetic flux caused by magnetic field (diamagnetic field) from a stator flows into the bridge, and an end part of the permanent magnet facing the bridge is likely to be demagnetized.

Patent Reference 1 discloses a rotor in which electromagnetic steel sheets each having magnet insertion holes provided with bridges and magnet insertion holes provided with no bridges are stacked while rotating each electromagnetic steel sheet by 90 degrees.

Patent Reference 2 discloses a rotor in which first electromagnetic steel sheets each having magnet insertion holes provided with positioning projections instead of bridges and second electromagnetic steel sheets each having magnet insertion holes provided with bridges are alternately stacked.

Patent Reference 3 discloses a rotor in which a magnet insertion hole is provided with a bridge and a relief part for reducing stress concentration is formed in a part of a rotor core corresponding to a root of the bridge.

PATENT REFERENCE

Patent Reference 1: Japanese Patent Application Publication No. 2009-153365 (see FIG. 3)

Patent Reference 2: Japanese Patent Application Publication No. 2001-157396 (see FIGS. 1, 10, and 11)

Patent Reference 3: Japanese Patent Application Publication No. 2002-136008 (see FIG. 2)

However, in the rotors disclosed in Patent References 1 and 2, the bridge is constituted by one electromagnetic steel sheet, and thus it is difficult to obtain sufficient strength of the rotor core. In the rotor disclosed in Patent Reference 3, demagnetization of a permanent magnet may be caused by magnetic flux flowing from the stator to the bridge.

SUMMARY

The present invention is made to solve the problems described above, and an object of the present invention is to enhance strength of a rotor core and suppress demagnetization of a permanent magnet.

A rotor according to the present invention includes a rotor core formed of a stacked body in which two or more first electromagnetic steel sheets and a second electromagnetic steel sheet are stacked in a direction of an axis, the rotor core having a magnet insertion hole passing through the stacked body in the direction of the axis, and a first permanent magnet and a second permanent magnet disposed in the magnet insertion hole. The magnet insertion hole has a first region in which the first permanent magnet is inserted, and a second region in which the second permanent magnet is inserted, the first region and the second region being arranged in a circumferential direction about the axis. The two or more first electromagnetic steel sheets are disposed on at least one end of the rotor core in the direction of the axis. Each of the two or more first electromagnetic steel sheets has a bridge dividing the magnet insertion hole into the first region and the second region. The second electromagnetic steel sheet has the magnet insertion hole in which the first region and the second region are formed continuously with each other.

According to the present invention, strength of the rotor core can be enhanced since each of the first electromagnetic steel sheets constituting the rotor core has the bridge, and demagnetization of the permanent magnets can be suppressed since the second electromagnetic steel sheet includes no bridge. In addition, when the permanent magnets are inserted into the magnet insertion hole, the bridge of each first electromagnetic steel sheet serves as a guide, and thus insertion of the permanent magnets is facilitated. Furthermore, since the bridge is constituted by the two or more first electromagnetic steel sheets, deformation or the like of the bridge during the insertion of the permanent magnets can be suppressed.

