Stepping motor, timepiece movement, timepiece, and manufacturing method of stepping motor
A stepping motor includes a one-piece stator integrally molded by using a Fe—Ni alloy plate through machining, a rotor accommodating through-hole, and in which a magnetic path is disposed around the rotor accommodating through-hole. A rotor is rotatably arranged inside the rotor accommodating through-hole. A magnetic core is connected to the stator, and a coil is wound on the magnetic core. A Cr-diffusion region having a molten-solidified portion of Cr is diffused in the Fe—Ni alloy stator in a portion of the magnetic path.
1. A stepping motor comprising:
a one-piece stator comprised of Fe—Ni alloy, the stator having a rotor accommodating through-hole and defining a magnetic path around the rotor accommodating through-hole;
a rotor rotatably arranged inside the rotor accommodating through-hole;
a magnetic core connected to the stator; and
a coil wound on the magnetic core,
wherein a Cr-diffusion region having a molten-solidified portion of Cr is diffused in the Fe—Ni alloy stator in a portion of the magnetic path.
2. The stepping motor according to claim 1 ,
wherein the stator has a narrow portion where a cross-sectional area of the magnetic path is narrower than that of other portions, and the Cr-diffusion region is diffused in at least a portion of the narrow portion.
3. The stepping motor according to claim 2 ,
wherein the molten-solidified portion includes the narrow portion, and is disposed in a section which does not interfere with a cut-out portion disposed in the rotor accommodating through-hole in order to secure a stable position of the rotor.
4. The stepping motor according to claim 1 ,
wherein the Cr-diffusion region contains 15 mass % to 80 mass % of Cr.
5. The stepping motor according to claim 4 ,
wherein the Cr-diffusion region contains 18 mass % to 55 mass % of Cr.
6. A timepiece movement comprising:
the stepping motor according to claim 1 ; and
a hand that is rotated by the stepping motor so as to indicate time.
7. A timepiece comprising:
the timepiece movement according to claim 6 .
8. A manufacturing method of a stepping motor according to claim 1 comprising:
machining a Fe—Ni alloy plate to form a stator having a rotor accommodating through-hole and a magnetic path arranged around the rotor accommodating through-hole;
arranging a Cr-material for diffusion in at least a portion of the stator; and
emitting a laser beam to the Cr-material, melting and solidifying the Cr-material into the magnetic path, and forming a Cr-diffusion region having a molten-solidified portion of Cr.
9. The manufacturing method of the stepping motor according to claim 8 ,
wherein the arranging of the Cr-material comprises coating at least a portion of the magnetic path with a paste containing powdered metallic chromium.
10. The manufacturing method of the stepping motor according to claim 8 ,
wherein the arranging of the Cr-material comprises forming a chromium plating layer on a surface of the stator, and
wherein in the melting of the Cr-material, the Cr-material is melted by emitting the laser beam to the chromium plating layer formed in at least a portion of the magnetic path, within the chromium plating layer formed on the surface of the stator.
11. The manufacturing method of the stepping motor according to claim 8 ,
wherein in the forming of the stator, a narrow portion in which a cross-sectional area of the magnetic path is narrower than that of other portions is disposed in the stator, and
wherein in the arranging of the Cr-material, the Cr-material is arranged in a region including at least the narrow portion.