Disc driving motor and Information recording and reproducing apparatus

Abstract

The invention provides a motor which is mainly used in an HDD, maintains high accuracy without runout even upon rotation at high speed, and is excellent in resistance to external forces. A disc driving motor of the invention includes: a base; a hub having a ring-shaped disc receiving face on which a disc is placed; a hydrodynamic bearing rotatably supporting the hub; a motor unit mounted on the base, the motor unit having an outer diameter larger than that of the disc receiving face and giving a rotational force to the hub; and a magnetic shield plate provided on an axial clearance formed between the disc and the motor unit when the disc is placed on the disc receiving face. Herein, the magnetic shield plate is fixed while being inclined to the disc receiving face such that a pressure of an airflow in the axial clearance differs for each circumferential position upon rotation of the disc.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a sectional view showing a motor unit of an HDD in a first embodiment of the present invention, and FIGS. 1B and 1C are sectional views each showing the motor unit of the HDD in a modification of the first embodiment of the present invention;

FIG. 2A is a perspective view showing the first embodiment of the present invention, FIG. 2B schematically shows a pressure difference in the first embodiment of the present invention, and FIG. 2C is a plan view showing a disc driving motor according to the first embodiment of the present invention;

FIG. 3 schematically shows a rotor in the first embodiment of the present invention;

FIG. 4A is a plan view showing a second embodiment of the present invention, and FIG. 4B is a lateral sectional view showing a step of a magnetic shield plate in the second embodiment of the present invention;

FIG. 5A schematically shows a vortex generated at a step of the magnetic shield plate in a case that the step has a corner, FIG. 5B schematically shows a vortex generated at a step of the magnetic shield plate in a case that the step is tapered, and FIG. 5C schematically shows a vortex generated at a step of the magnetic shield plate in a case that the step has a corner radius;

FIG. 6 schematically shows a pressure in the second embodiment of the present invention;

FIG. 7A shows a moment about an X axis by a dynamic pressure in the second embodiment of the present invention, and FIG. 7B shows a relation between the moment about the X axis by the dynamic pressure in the second embodiment of the present invention and an opening angle θ;

FIG. 8A is a plan view showing a disc driving motor according to a third embodiment of the present invention, and FIG. 8B is a perspective view showing the third embodiment of the present invention;

FIG. 9A shows a moment about an X axis by a dynamic pressure in the third embodiment of the present invention, and FIG. 9B shows a relation between the moment about the X axis by the dynamic pressure in the third embodiment of the present invention and an opening angle θ;

FIG. 10A is a plan view showing a disc driving motor according to a fourth embodiment of the present invention, and FIG. 10B schematically shows a second axial clearance formed between a magnetic shield plate and a disc in the fourth embodiment of the present invention in a developed manner;

FIG. 11A shows a head pitch angle with respect to a disc, and FIG. 11B shows a head roll angle with respect to the disc;

FIGS. 12A to 12C are perspective views each showing a protrusion portion of the magnetic shield plate in a modification of the second embodiment of the present invention, FIGS. 12D and 12E are perspective views each showing a protrusion portion of a magnetic shield plate in a modification of the fourth embodiment of the present invention, and FIG. 12F is a perspective view showing a protrusion portion of a magnetic shield plate in a conventional configuration 1;

FIG. 13 is an exploded perspective view showing a motor unit of an HDD in the conventional configuration 1;

FIG. 14 is a sectional view showing the motor unit of the HDD in the conventional configuration 1;

FIG. 15A is a plan view showing an HDD in a conventional configuration 2, and FIG. 15B is a sectional view showing the HDD in the conventional configuration 2; and

FIG. 16 is a perspective view showing an HDD in a conventional configuration 3.

Claims

1. A disc driving motor comprising: a base;a hub having a ring-shaped disc receiving face on which a disc is placed;a hydrodynamic bearing rotatably supporting the hub;a motor unit mounted on the base, the motor unit having an outer diameter larger than that of the disc receiving face and giving a rotational force to the hub; anda magnetic shield plate provided on an axial clearance formed between the disc and the motor unit when the disc is placed on the disc receiving face, whereinthe magnetic shield plate is fixed while being inclined to the disc receiving face such that a pressure of an airflow in the axial clearance differs for each circumferential position upon rotation of the disc.

2. An information recording and reproducing apparatus comprising: the disc driving motor according to claim 1; anda head provided so as to oppose a disc, the head performing scanning on the disc to thereby record and reproduce information on/from the disc.

3. The information recording and reproducing apparatus according to claim 2, wherein the magnetic shield plate is inclined to the disc receiving face such that an axial distance between the magnetic shield plate and the disk over a region where the head performs no scanning is shorter than an axial distance between the magnetic shield plate and the disk over a region where the head performs scanning.

4. The information recording and reproducing apparatus according to claim 2, wherein the magnetic shield plate is inclined such that the axial distance becomes short toward a direction almost orthogonal to a tangent drawn from a rotational center of the disc with respect to a scanning locus arc of the head, in the axial clearance between the magnetic shield plate and the disc.

5. A disc driving motor comprising: a base;a hub having a ring-shaped disc receiving face on which a disc is placed;a hydrodynamic bearing rotatably supporting the hub;a motor unit mounted on the base, the motor unit having an outer diameter larger than that of the disc receiving face and giving a rotational force to the hub; anda magnetic shield plate provided on a first axial clearance formed between the disc and the motor unit when the disc is placed on the disc receiving face, whereinin a second axial clearance formed between the magnetic shield plate and the disc, the magnetic shield plate includes at least two planes, and the two planes are different from each other in one of axial height or inclining direction with respect to the disc receiving face and are smoothly connected to each other in a circumferential direction such that a pressure of an airflow generated between the magnetic shield plate and the disc differs for each circumferential position upon rotation of the motor unit.

6. The disc driving motor according to claim 5, wherein in the second axial clearance, the magnetic shield plate includes a step, and the step has different axial heights and is rounded in a circumferential direction so as to have corner radii.

7. The disc driving motor according to claim 6, wherein when a corner radius with a positive curvature located at a near side on the disc receiving face in the axial direction is R1 and a corner radius with a negative curvature located at a far side on the disc receiving face in the axial direction is R2 in the magnetic shield plate in the second axial clearance, a relation, R1>R2, is satisfied.

8. The disc driving motor according to claim 5, wherein the magnetic shield plate has an innermost circumference portion formed into a single ring-shaped plane.

9. The disc driving motor according to claim 5, wherein in the second axial clearance, a region where an axial thickness thereof is small is in a range between not less than 87° and not more than 248° in a direction of a circumference.

10. An information recording and reproducing apparatus comprising: the disc driving motor according to claim 5; anda head provided so as to oppose a disc, the head performing scanning on the disc to thereby record and reproduce information on/from the disc.

11. The information recording and reproducing apparatus according to claim 10, wherein an axial thickness of the second axial clearance over a region where the head performs no scanning is smaller than an axial thickness of the second axial clearance over a region where the head performs scanning.

12. The information recording and reproducing apparatus according to claim 10, wherein an axial thickness in a direction almost orthogonal to a tangent drawn from a rotational center of the disc with respect to a scanning locus arc of the head is smallest in the magnetic shield plate in the second axial clearance.

13. The information recording and reproducing apparatus according to claim 10, wherein an axial thickness of the second axial clearance over a portion corresponding to an arcuate scanning locus of the head is larger than an axial thickness of the second axial clearance over a portion located almost opposite to the portion when being seen from a rotational center of the disc.