Motor including a seal covering a high reflectivity metallic surface of a rotor hub
This motor includes a stationary portion including a stator; and a rotating portion supported to be rotatable about a central axis extending in a vertical direction with respect to the stationary portion, and including a shaft arranged to extend along the central axis. The stationary portion includes a bearing arranged to rotatably support the shaft, and a base portion arranged to hold the stator. The rotating portion includes a rotor hub portion arranged to extend in an annular shape around the shaft; a magnet directly or indirectly fixed to the rotor hub portion, and arranged opposite to the stator; a flywheel arranged axially above the rotor hub portion; and a seal portion arranged to have a thickness smaller than the thickness of the magnet. At least a portion of an outer circumferential surface of the rotor hub portion is a metal surface. The metal surface has a reflectivity higher than the reflectivity of an outer circumferential surface of the flywheel and the reflectivity of a surface of the seal portion. The metal surface is covered with the seal portion.
1. A motor comprising:
a stationary portion including a stator; and
a rotating portion supported to be rotatable about a central axis extending in a vertical direction with respect to the stationary portion, and including a shaft arranged to extend along the central axis; wherein
the stationary portion includes:
a bearing arranged to rotatably support the shaft; and
a base portion arranged to hold the stator;
the rotating portion includes:
a rotor hub portion arranged to extend in an annular shape around the shaft;
a magnet directly or indirectly fixed to the rotor hub portion, and arranged opposite to the stator;
a flywheel arranged axially above the rotor hub portion; and
a seal portion arranged to have a thickness smaller than a thickness of the magnet;
at least a portion of an outer circumferential surface of the rotor hub portion is a metal surface;
the metal surface has a reflectivity higher than a reflectivity of an outer circumferential surface of the flywheel and a reflectivity of a surface of the seal portion; and
the metal surface is covered with the seal portion.
2. The motor according to claim 1 , wherein at least a portion of the metal surface of the rotor hub portion and at least a portion of the outer circumferential surface of the flywheel are arranged to axially overlap with each other.
3. The motor according to claim 1 , wherein
the rotor hub portion includes:
an inertia portion being annular, made of a metal, and arranged to have a specific gravity greater than a specific gravity of the flywheel; and
a hub;
the hub includes:
a joining portion arranged to extend in an annular shape from an upper portion of the shaft;
a cylindrical portion arranged to extend in an axial direction from an outer circumferential portion of the joining portion; and
a flange portion arranged to extend radially outward from a lower portion of the cylindrical portion; and
the inertia portion is fixed to the cylindrical portion or the flange portion.
4. The motor according to claim 1 , wherein the rotor hub portion is arranged to have a mass greater than a mass of the flywheel.
5. The motor according to claim 1 , wherein the flywheel is made of a resin, and at least a portion of the rotor hub portion is made of a stainless metal.
6. The motor according to claim 1 , wherein
the rotor hub portion includes a groove portion recessed radially inward in at least a portion of the outer circumferential surface thereof; and
the motor further comprises a balance correction member arranged in the groove portion.
7. The motor according to claim 6 , wherein, in the outer circumferential surface of the rotor hub portion, the groove portion is arranged to extend in a circumferential direction over an entire circumferential extent of the rotor hub portion.
8. The motor according to claim 1 , wherein at least a portion of the outer circumferential surface of the flywheel is covered with the seal portion.
9. The motor according to claim 1 , wherein
the magnet is arranged radially outside of the stator;
the rotating portion further includes a cylindrical yoke fixed to a radially outer side of the magnet;
the yoke is fixed to the rotor hub portion;
an upper end of the seal portion is fixed to the outer circumferential surface of the flywheel; and
a lower end of the seal portion is fixed to an outer circumferential surface of the yoke.
10. The motor according to claim 1 , wherein
the magnet is arranged radially outside of the stator;
the rotating portion further includes a cylindrical yoke fixed to a radially outer side of the magnet;
the yoke is fixed to the rotor hub portion; and
the seal portion is arranged to cover an area extending from at least a portion of the outer circumferential surface of the flywheel to a lower end of an outer circumferential surface of the yoke.
11. The motor according to claim 1 , further comprising a thrust bearing portion at which a portion of the stationary portion and a portion of the rotating portion are arranged axially opposite to each other with a gap therebetween, the gap having a lubricating oil arranged therein, wherein a fluid dynamic pressure is induced in the lubricating oil.
12. The motor according to claim 11 , wherein
the bearing includes a sleeve, and a disk-shaped cap arranged to close a lower end portion of the sleeve;
the rotating portion further includes a disk-shaped annular portion arranged to extend radially outward from a lower end of the shaft, and arranged axially opposite to the cap;
the gap includes:
a thrust gap defined between an upper surface or a lower surface of the annular portion and a surface of the sleeve or of the cap which is axially opposite to the annular portion; and
a radial gap defined between an outer circumferential surface of the shaft and a surface of the sleeve which is radially opposite to the shaft;
the thrust dynamic pressure bearing portion is defined in the thrust gap;
the lubricating oil is continuously arranged in the gap including the thrust gap and the radial gap; and
in a situation in which the lubricating oil has been fully arranged in the gap, a liquid surface of the lubricating oil is defined only at an upper end of the radial gap.
13. The motor according to claim 12 , wherein
the gap further includes a second thrust gap defined between an upper surface of the sleeve and a lower surface of the rotor hub portion; and
the second thrust gap has a second thrust bearing portion defined therein.
14. The motor according to claim 1 , wherein the rotating portion includes a mirror supported by the flywheel and arranged to reflect light coming toward the flywheel.
15. The motor according to claim 1 , wherein the flywheel is arranged to have an outside diameter equal to an outside diameter of the rotor hub portion.
16. The motor according to claim 1 , wherein the flywheel is arranged to have an axial dimension greater than an axial distance from a lower end surface of the stationary portion to an upper end surface of the rotor hub portion.
17. The motor according to claim 1 , wherein
the metal surface is covered by the seal portion over an entire circumferential extent thereof; and
both circumferential end portions of the seal portion are arranged to overlap with each other.
18. The motor according to claim 1 , wherein the seal portion is made of a resin, and the surface of the seal portion is black in color.
19. The motor according to claim 9 , wherein at least the outer circumferential surface of the yoke is roughened.
20. The motor according to claim 9 , wherein at least the outer circumferential surface of the yoke is black in color.