Method of manufacturing core product

1. A method of manufacturing a core product comprising:

pre-heating a solid resin pellet, after being previously refrigerated, at a temperature of 28° C. to 32° C. for 24 hours to 120 hours, the solid resin pellet being formed of a thermosetting resin composition including an epoxy resin, a curing agent, an accelerator, and a release agent, wherein said pre-heating causes the solid resin pellet to undergo a cross-linking reaction of the epoxy resin without melting;

holding a core body, having a resin formation region, between a pair of holding members;

disposing the solid resin pellet, after being previously pre-heated at the temperature of 28° C. to 32° C., in a resin pot formed in at least one of the pair of holding members;

melting the solid resin pellet in the resin pot at a temperature of 150° C. or higher to form a melted resin, wherein the release agent is preferentially expelled to an outside surface of the melted resin due, at least in part, to the cross-linking reaction of the epoxy resin that occurred during said pre-heating of the solid resin pellet at the temperature of 28° C. to 32° C.;

injecting the melted resin into the resin formation region through a resin channel extending from the resin pot in communication with the resin formation region; and

curing the melted resin injected into the resin formation region to form a cured resin of the core product.

2. The method according to claim 1 , wherein said pre-heating the solid resin pellet includes:

removing the solid resin pellet from a refrigerator; and

leaving the solid resin pellet in a heat treatment chamber regulated to the temperature of 28° C. to 32° C. for 24 hours to 120 hours.

3. The method according to claim 1 , wherein said pre-heating the solid resin pellet includes:

removing a bag containing a plurality of solid resin pellets from a refrigerator; and

pre-heating the bag including the plurality of solid resin pellets at the temperature of 28° C. to 32° C. for 24 hours to 120 hours.

4. The method according to claim 1 , wherein the pair of holding members includes a lower mold and an upper mold.

5. The method according to claim 4 , wherein a resin guide member is interposed between the upper mold and the core body, and wherein the resin guide member is configured to guide the melted resin into the resin formation region, the resin formation region including a magnet insertion hole of the core body.

6. The method according to claim 5 , wherein the resin guide member includes a plurality of resin channels, and a plurality of runner grooves.

7. The method according to claim 6 , wherein each of the resin channels at least partially overlaps a corresponding magnet insertion hole of the core body.

8. The method according to claim 6 , wherein the plurality of runner grooves extend along a surface of the resin guide member, and wherein each runner groove is in communication with a corresponding resin channel.

9. The method according to claim 4 , wherein the lower mold or the upper mold is configured to guide the melted resin into the resin formation region, the resin formation region including a magnet insertion hole of the core body.

10. The method according to claim 9 , wherein the lower mold or the upper mold includes a plurality of resin channels, and a plurality of runner grooves.

11. The method according to claim 10 , wherein each of the resin channels at least partially overlaps a corresponding magnet insertion hole of the core body.

12. The method according to claim 10 , wherein the plurality of runner grooves extend along a surface of the lower mold or the upper mold, and wherein each runner groove is in communication with a corresponding resin channel.

13. The method according to claim 1 , wherein said curing the melted resin comprises solidifying the melted resin in the resin formation region to fix a permanent magnet that is inserted in a magnet insertion hole of the resin formation region.

14. The method according to claim 1 , wherein a content of the epoxy resin is equal to or less than 20% by mass, a content of the curing agent is equal to or less than 10% by mass, a content of the accelerator is equal to or less than 1% by mass, and a content of the release agent is equal to or less than 1% by mass, with respect to 100% by mass of a total amount of the thermosetting resin composition.

15. The method according to claim 1 , wherein the thermosetting resin composition contains 55% by weight to 65% by weight of silica, 10% by weight to 20% by weight of epoxy resin, and 5% by weight to 10% by weight of phenolic resin.

16. The method according to claim 1 , wherein the thermosetting resin composition contains 70% by weight to 80% by weight of silica, 10% by weight to 20% by weight of epoxy resin, and 5% by weight to 10% by weight of phenolic resin.

17. A method of manufacturing a core product comprising: refrigerating a solid resin pellet;

pre-heating the solid resin pellet, after said refrigerating, at a temperature of 28° C. to 32° C. for 24 hours to 120 hours, the solid resin pellet being formed of a thermosetting resin composition including an epoxy resin, a curing agent, an accelerator, and a release agent, wherein said pre-heating causes the solid resin pellet to undergo a cross-linking reaction of the epoxy resin without melting;

melting the solid resin pellet, after said pre-heating, at a temperature of 150° C. or higher to form a melted resin, wherein the release agent is preferentially expelled to an outside surface of the melted resin due, at least in part, to the cross-linking reaction of the epoxy resin that occurred during said pre-heating of the solid resin pellet at the temperature of 28° C. to 32° C.;

injecting the melted resin into a resin formation region; and

curing the melted resin in the resin formation region, after said injecting, to form a cured resin of the core product.

18. The method according to claim 17 , wherein:

the resin formation region is located on a core body,

the core body is held between two holding members,

a resin pot is formed in at least one of the two holding members, and

the melted resin is injected into the resin formation region through a resin channel extending from the resin pot.

19. The method according to claim 17 , wherein said refrigerating comprises refrigerating the solid resin pellet at a temperature of about 4° C. or less before pre-heating the solid resin pellet at the temperature of 28° C. to 32° C.