ROTATING DEVICE HAVING ROTOR, STATOR, AND DRIVING MECHANISM
A rotating device includes: a rotor on which a recording disk is to be mounted; a stator rotatably supporting the rotor; and a driving mechanism configured to rotate the rotor with respect to the stator. The relationship between (a) the magnitude of a gap between the rotor and the stator and (b) a viscosity of a lubricant introduced in the gap is defined such that a Q-value of a peak of mechanical resonance in a translation mode of the rotating device is 3 or less when the peak of mechanical resonance and a peak of torque ripple in the driving mechanism are in the range of 1 kHz-5 kHz in a frequency spectrum.
1 . A rotating device comprising:
a rotor on which a recording disk is to be mounted;
a stator rotatably supporting the rotor; and
a driving mechanism configured to rotate the rotor with respect to the stator,
wherein the relationship between (a) the magnitude of a gap between the rotor and the stator and (b) a viscosity of a lubricant introduced in the gap is defined such that a Q-value of a peak of mechanical resonance in a translation mode of the rotating device is 3 or less when the peak of mechanical resonance and a peak of the torque ripple in the driving mechanism are in the ranges of 1 kHz-5 kHz in a frequency spectrum.
2 . The rotating device according to claim 1 ,
wherein the relationship is given by
R≧k (η) 0.34
where R μm denotes the magnitude of the gap, η P denotes an absolute viscosity of the lubricant at 40° C., and k denotes a variable that depends on the Q-value and that does not depend on the magnitude R of the gap or the absolute viscosity of the lubricant, and where k is defined such that the larger the Q-value, the smaller the variable k.
3 . The rotating device according to claim 1 ,
wherein the gap is formed such that the magnitude thereof is in a range between 5 μm and 7 μm.
4 . The rotating device according to claim 1 ,
wherein the stator has a cylindrical sleeve around a rotational axis of the rotor,
the rotor is formed with a shaft accommodated in the sleeve,
a surface of the sleeve facing the shaft is formed with a dynamic pressure generation part provided with a radial dynamic pressure groove, and is formed with a circumferential contact part provided to extend from the dynamic pressure generation part, and
the circumferential contact part comes into contact with the shaft prior to the dynamic pressure generation part, when the shaft is inclined with respect to the rotational axis to come into contact with the surface of the sleeve facing the shaft.
5 . The rotating device according to claim 4 ,
the circumferential contact part is formed such that a diameter of a portion of the circumferential contact part that comes into contact with the shaft when the shaft is inclined with respect to the rotational axis to come into contact with the surface of the sleeve facing the shaft becomes progressively larger as it goes away from the dynamic pressure generation part in a direction of the rotational axis.
6 . The rotating device according to claim 4 ,
wherein a surface of the shaft facing the sleeve is formed such that a portion of the surface facing the circumferential contact part is larger than the diameter of a portion of the surface facing the dynamic pressure generation part.
7 . The rotating device according to claim 4 ,
wherein a portion of the shaft facing the sleeve and facing, in particular, the circumferential contact part has a shape conforming to a shape of the circumferential contact part.
8 . The rotating device according to claim 4 ,
wherein the circumferential contact part is formed such that the width thereof in a direction of the rotational axis is in a range between 1/10 and ⅓ the width of the dynamic pressure generation part in the direction of the rotational axis.
9 . The rotating device according to claim 4 ,
wherein the circumferential contact part is formed such that the width thereof in a direction of the rotational axis is in a range between 0.5 mm and 2 mm.
10 . The rotating device according to claim 4 ,
wherein the surface of the sleeve facing the shaft is formed with an enlarged-diameter part provided to extend from the circumferential contact part in a direction opposite to the dynamic pressure generation part and have a larger diameter than the circumferential contact part.
11 . A rotating device comprising:
a rotor on which a recording disk is to be mounted;
a stator rotatably supporting the rotor; and
a driving mechanism configured to rotate the rotor with respect to the stator,
wherein a peak of mechanical resonance in a translation mode of the rotating device and a peak of torque ripple in the driving mechanism are in the ranges of 1 kHz-5 kHz in a frequency spectrum,
the stator has a cylindrical sleeve around a rotational axis of the rotor,
the rotor is formed with a shaft accommodated in the sleeve,
a surface of the sleeve facing the shaft is formed with a dynamic pressure generation part provided with a radial dynamic pressure groove, and is formed with a circumferential contact part provided to extend from the dynamic pressure generation part, and
the circumferential contact part comes into contact with the shaft prior to the dynamic pressure generation part, when the shaft is inclined with respect to the rotational axis to come into contact with the surface of the sleeve facing the shaft.
12 . The rotating device according to claim 11 ,
wherein the circumferential contact part is formed such that a diameter of a portion of the circumferential contact part that comes into contact with the shaft when the shaft is inclined with respect to the rotational axis to come into contact with the surface of the sleeve facing the shaft becomes progressively larger as it goes away from the dynamic pressure generation part in a direction of the rotational axis.
13 . The rotating device according to claim 11 ,
wherein a surface of the shaft facing the sleeve is formed such that a portion of the surface facing the circumferential contact part is larger than the diameter of a portion of the surface facing the dynamic pressure generation part.
14 . The rotating device according to claim 11 ,
wherein a portion of the shaft facing the sleeve and facing, in particular, the circumferential contact part has a shape conforming to a shape of the circumferential contact part.
15 . The rotating device according to claim 11 ,
wherein the surface of the sleeve facing the shaft is formed with an enlarged-diameter part provided to extend from the circumferential contact part in a direction opposite to the dynamic pressure generation part and have a larger diameter than the circumferential contact part.
16 . The rotating device according to claim 11 ,
wherein the surface of the sleeve facing the shaft is formed with another circumferential contact part provided to extend from the dynamic pressure generation part in a direction opposite to said circumferential contact part, and
one of the circumferential contact part and the other circumferential contact part comes into contact with the shaft prior to the dynamic pressure generation part, when the shaft is inclined with respect to the rotational axis to come into contact with the surface of the sleeve facing the shaft.
17 . The rotating device according to claim 11 ,
the circumferential contact part is formed such that a surface roughness thereof is smaller than that of a bottom of the radial dynamic pressure groove.
18 . The rotating device according to claim 11 ,
wherein the circumferential contact part is formed with a discharge groove aligned with a direction of the rotational axis.
19 . The rotating device according to claim 18 ,
wherein the discharge groove is formed to be continuous with the radial dynamic pressure groove.
20 . The rotating device according to claim 18 ,
wherein the discharge groove is formed with the same depth as the radial dynamic pressure groove.