Stator for electric rotating machine

1. A stator for an electric rotating machine, the stator comprising:

an annular stator core comprised of a plurality of stator core segments that are arranged in a circumferential direction of the stator core so as to adjoin one another in the circumferential direction;

an outer cylinder fitted on a radially outer surface of the stator core; and

a stator coil mounted on the stator core,

wherein

the stator coil is fixed to the stator core by a thermosetting resin that is set by induction-heating the stator core,

each of the stator core segments is formed by laminating a plurality of steel sheets in an axial direction of the stator core and fixing at least some of the steel sheets by staking,

for each of the stator core segments, the plurality of steel sheets forming the stator core segment comprise a plurality of first steel sheets and a plurality of second steel sheets,

the number of staking portions formed in each of the first steel sheets is larger than the number of staking portions formed in each of the second steel sheets,

in the axial direction of the stator core, the first steel sheets are arranged in a first range where it is desired for the thermosetting resin to be more quickly set than in a second range, and the second steel sheets are arranged in the second range where it is allowed for the thermosetting resin to be set more slowly than in the first range,

the stator core has a plurality of slots formed therein;

the stator coil has a plurality of in-slot portions each of which is received in a corresponding one of the slots of the stator core;

the thermosetting resin is applied to the in-slot portions of the stator coil;

the stator core also has an annular back core portion and a plurality of stator teeth;

the stator teeth each extend from the back core portion radially inward and are spaced from one another in the circumferential direction of the stator core at predetermined intervals;

each of the slots is formed between one circumferentially-adjacent pair of the stator teeth so as to open on a radially inner periphery of the stator core; and

each of the second steel sheets has only one staking portion formed in the back core portion and circumferentially centered in the second steel sheet.

2. The stator as set forth in claim 1 , wherein

the first range where the first steel sheets are arranged comprises both end parts of the stator core segment in the axial direction of the stator core, and the second range where the second steel sheets are arranged comprises a central part of the stator core segment in the axial direction.

3. The stator as set forth in claim 2 , wherein the second steel sheets are fixed by at least one fixing means selected from staking, welding and adhesive bonding.

4. The stator as set forth in claim 1 , wherein

the first range where the first steel sheets are arranged comprises a central part of the stator core segment in the axial direction of the stator core, and the second range where the second steel sheets are arranged comprises both end parts of the stator core segment in the axial direction.

5. The stator as set forth in claim 4 , wherein the second steel sheets are fixed by at least one fixing means selected from staking, welding and adhesive bonding.

6. A stator for an electric rotating machine, the stator comprising:

an annular stator core comprised of a plurality of stator core segments that are arranged in a circumferential direction of the stator core so as to adjoin one another in the circumferential direction;

an outer cylinder fitted on a radially outer surface of the stator core; and

a stator coil mounted on the stator core,

wherein

the stator coil is fixed to the stator core by a thermosetting resin that is set by induction-heating the stator core,

each of the stator core segments is formed by laminating a plurality of steel sheets in an axial direction of the stator core and fixing at least some of the steel sheets by staking,

for each of the stator core segments, the plurality of steel sheets forming the stator core segment comprise a plurality of first steel sheets and a plurality of second steel sheets,

the number of staking portions formed in each of the first steel sheets is larger than the number of staking portions formed in each of the second steel sheets,

in the axial direction of the stator core, the first steel sheets are arranged in a first range where it is desired for the thermosetting resin to be more quickly set than in a second range, and the second steel sheets are arranged in the second range where it is allowed for the thermosetting resin to be set more slowly than in the first range,

the stator core has a plurality of slots formed therein;

the stator coil has a plurality of in-slot portions each of which is received in a corresponding one of the slots of the stator core;

the thermosetting resin is applied to the in-slot portions of the stator coil;

the stator core also has an annular back core portion and a plurality of stator teeth;

the stator teeth each extend from the back core portion radially inward and are spaced from one another in the circumferential direction of the stator core at predetermined intervals;

each of the slots is formed between one circumferentially-adjacent pair of the stator teeth so as to open on a radially inner periphery of the stator core; and

all of the staking portions of the first and second staking portions are formed in the back core portion.

7. The stator as set forth in claim 6 , wherein

the first range where the first steel sheets are arranged comprises both end parts of the stator core segment in the axial direction of the stator core, and the second range where the second steel sheets are arranged comprises a central part of the stator core segment in the axial direction.

8. The stator as set forth in claim 6 , wherein

the second steel sheets are fixed by at least one fixing means selected from staking, welding and adhesive bonding.

9. The stator as set forth in claim 6 , wherein

the first range where the first steel sheets are arranged comprises a central part of the stator core segment in the axial direction of the stator core, and the second range where the second steel sheets are arranged comprises both end parts of the stator core segment in the axial direction.

10. The stator as set forth in claim 6 , wherein

the second steel sheets are fixed by at least one fixing means selected from staking, welding and adhesive bonding.

11. The stator as set forth in claim 6 , wherein

each of the second steel sheets has only one staking portion formed in the back core portion and circumferentially centered in the second steel sheet; and

each of the first steel sheets has a first staking portion, a second staking portion and a third staking portion that are respectively formed at three different positions in the back core portion, the first staking portion being circumferentially centered in the first steel sheet and radially extending between a radially inner end and a radial center of the back core portion, the second and third staking portions being located respectively on opposite circumferential sides of the first staking portion and both radially outward of the first staking portion, each of the second and third staking portions extending perpendicular to the radial direction in which the first staking portion extends.