JPH11299171A - Spindle motor having dynamic air pressure bearing and rotary mechanism using the spindle motor as driving source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make radial dynamic pressure and thrust dynamic pressure higher, to remove fear of occurrence of precession, and besides to prevent unfavorable upward movement of a protrusion-side bearing member, in a dynamic air pressure bearing having conical dynamic pressure bearings. SOLUTION: The first conical dynamic pressure bearing of this spindle motor is composed of a protrusion-side bearing member 20 having a first conical protrusion 21a and a second conical protrusion 21b facing each other with a column section 22 between and having a cylinder 23 formed along a central axis, and a first recession-side bearing member 30 having a first conical recession 31 to be fitted to a second conical protrusion 21b without touching, and its radial dynamic pressure bearing is composed of a thin and long shaft 50 arranged piercing the cylinder 23 and a protrusion-side bearing member 20. Besides, its second conical dynamic pressure bearing is composed of a second recession-side bearing member 40 having a second conical recession 41 to be fitted to a second conical protrusion 21b without touching, and the protrusion- side bearing member 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor in which a rotor is supported on a stator by an air dynamic pressure bearing having a conical dynamic pressure bearing and a radial dynamic pressure bearing, and a magnetic disk, an optical disk, and a polygon. The present invention relates to a rotator device serving as a drive source for a rotator such as a mirror.

[0002]

2. Description of the Related Art Air bearings having a radial dynamic pressure bearing portion and a thrust dynamic pressure bearing portion at the same time have been widely used in recent years as spindle motor bearings. Has also been various. FIG. 5 shows an example of a conventional spindle motor in which a rotor is supported on a stator by an air dynamic pressure bearing having a conical dynamic pressure bearing portion and a radial dynamic pressure bearing portion, and the air dynamic pressure bearing is provided at a lower end. A conical dynamic pressure bearing includes a cylindrical bearing member 2 having a conical convex portion 2a in the middle and a cylindrical portion 2b formed in the middle, and a cylindrical bearing member 3 in the bottom having a conical concave portion 3a in the middle formed with the cylindrical portion 3b. Part and a radial dynamic pressure bearing part. The conical dynamic pressure bearing portion includes a conical convex portion 2a and a conical concave portion 3a, and the dynamic pressure grooves G are formed on the surface of the conical convex portion 2a in two upper and lower stages. Also,
The radial dynamic pressure bearing is composed of a cylindrical portion 2b and a cylindrical portion 3b, and the dynamic pressure grooves G are formed at the upper end of the cylindrical portion 2b at two upper and lower stages and at the lower end thereof at two upper and lower stages. The rotor,
It includes a rotor member 4 having a substantially cup-shaped hub structure to which a rotor magnet 6 is attached, and a mounting hole of the rotor member 4 is fitted to a cylindrical end 2c of the cylindrical bearing member 2 to be attached to the air dynamic pressure bearing. ing. The stator includes a base plate 1 and a stator coil 5. Cylindrical bearing member 3
Are erected on the base plate 1, and the stator coil 5 is attached to the outer peripheral surface of the cylindrical bearing member 3.

[0003] In this conventional air dynamic pressure bearing, a conical dynamic pressure bearing portion and a radial dynamic pressure bearing portion are arranged vertically on a rotating shaft, that is, in a so-called thrust direction.
The whole bearing becomes longer. Further, as shown in FIG. 6, the pressure distribution of the bearing in this conventional pneumatic dynamic pressure bearing has a vertical axis as a position and a horizontal axis as a pressure P, as shown in FIG.
It has one peak. This is a necessary constraint to ensure that the center of gravity of the rotating body provided with the air dynamic pressure bearing does not deviate from the center of the pressure distribution of the bearing to ensure rotation stability. Due to such structural restrictions, the conventional pneumatic dynamic bearing shown in FIG. 5 has a problem that it is difficult to reduce the size. Further, there is a problem that precession movement is easily generated.

Accordingly, the applicant of the present application is an air dynamic pressure bearing having a conical dynamic pressure bearing portion and a radial dynamic pressure bearing portion,
An air dynamic bearing that solves these problems was developed, and a patent application (Japanese Patent Application No. 10-67666) was filed earlier. An air dynamic pressure bearing according to this patent application includes a convex-side bearing member having a conical convex portion and having a cylinder formed along a central axis, and a bearing member erected on a stator of a motor, wherein the conical convex portion is provided. And a concave bearing member having a conical concave portion which is fitted in a non-contact manner, and wherein a dynamic pressure groove is formed on one of the surface of the conical convex portion and the surface of the conical concave portion. A bearing portion, a bearing member disposed through the cylinder, the lower end portion comprising an elongated shaft fixed to the stator and the convex bearing member, and an outer peripheral surface of the elongated shaft and the cylinder And a radial dynamic pressure bearing portion in which a dynamic pressure groove is formed on one of the inner peripheral surfaces. In other words, this air dynamic pressure bearing is one in which a radial dynamic pressure bearing portion and a conical dynamic pressure bearing portion are arranged on the inner side and the outer side so as to be coaxial with the rotating shaft, that is, arranged in a radial direction, so that it can be miniaturized. Although it has the feature that precession is unlikely to occur, there are still some problems.

[0005]

An object of the present invention is to provide an air dynamic pressure bearing in which a radial dynamic pressure bearing portion and a conical dynamic pressure bearing portion are arranged on the inner side and the outer side so as to be coaxial with the rotating shaft. A spindle motor equipped with the motor or a rotating device using the motor as a driving source of a rotating body, in which radial dynamic pressure and thrust dynamic pressure of the air dynamic pressure bearing are increased so as to be able to adapt to a large load; The object is to improve the stability of rotation by eliminating the possibility of occurrence and preventing undesired movement of the convex bearing member upward. Another problem to be solved is to be able to easily adapt as necessary to both thrust and radial load capacities.

[0006]

According to the present invention, there is provided a spindle motor comprising a rotor including a rotor magnet, a stator including a stator coil, and an air dynamic bearing for supporting the rotor on the stator. The air dynamic pressure bearing was composed of a first conical dynamic pressure bearing portion, a radial dynamic pressure bearing portion, and a second conical dynamic pressure bearing portion.

[0007] The first conical dynamic pressure bearing portion has a first conical convex portion and a second conical convex portion opposed to each other with a cylindrical portion interposed therebetween, and has a cylinder formed along a central axis. A bearing member fixed to the stator and a first concave side bearing member having a first conical concave portion in which the first conical convex portion is fitted in a non-contact manner. Was formed on one of the surface of the first conical convex portion and the surface of the first conical concave portion. The radial dynamic pressure bearing portion is a bearing member disposed through the cylinder, the lower end portion of which is composed of an elongated shaft fixed to a stator and the convex side bearing member, and the dynamic pressure groove is formed by the dynamic pressure groove. It was formed on one of the outer peripheral surface of the elongated shaft and the inner peripheral surface of the cylinder. Further, a second conical hydrodynamic bearing portion is a bearing member fixed to an upper end portion of the elongated shaft, the second conical hydrodynamic bearing portion having a second conical concave portion in which the second conical convex portion is fitted in a non-contact manner.
It is composed of a concave bearing member and the convex bearing member, and the dynamic pressure groove is formed on one of the surface of the second conical concave portion and the surface of the second conical convex portion.

The first conical dynamic pressure bearing and the second conical dynamic pressure bearing have a symmetrical structure to improve the stability of the bearing. The respective dynamic pressure grooves of the first conical dynamic pressure bearing portion, the second conical dynamic pressure bearing portion, and the radial dynamic pressure bearing portion are oriented so that the centers of the dynamic pressure distribution in the rotation axis direction substantially coincide with each other. Formed, eliminating the risk of precession, and increasing the stability of rotation. The rotor member to which the rotor magnet is attached has a substantially cup-shaped hub structure, and a mounting hole formed in the center of the rotor member is fitted to the cylindrical portion and fixed to the convex bearing member, and the magnetic circuit of the motor is provided. Was made to constitute a part. The convex-side bearing member, the first concave-side bearing member, and the second concave-side bearing member were formed of stainless steel or aluminum, and diamond-like carbon (DLC) was formed with a predetermined thickness on their sliding surfaces. . Further, at least the first conical dynamic pressure bearing portion of the first conical dynamic pressure bearing portion and the second conical dynamic pressure bearing portion has a protrusion for supporting a load in a thrust direction, and The protrusion is provided at one of the tip of the first conical convex portion and the bottom of the first conical concave portion.

An air dynamic pressure having a first conical dynamic pressure bearing portion and a second conical dynamic pressure bearing portion suitable for a spindle motor which has a cone apex angle of 30 to 40 degrees and focuses on a radial load capacity. The bearing was realized. Also, the cone apex angle should be 50-70.
An air dynamic pressure bearing having a first conical dynamic pressure bearing portion and a second conical dynamic pressure bearing portion suitable for a spindle motor emphasizing load capacity in the thrust direction is realized. Further, no matter what the cone apex angle is, the groove angle of the hydrodynamic groove of the first conical dynamic pressure bearing portion and the second conical dynamic pressure bearing portion is 15
The angle was set to ２０20 degrees to effectively generate the air dynamic pressure.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention, in which a polygon mirror 7 is a spindle motor provided with an air dynamic pressure bearing.
0 shows a polygon mirror device for driving a zero. 1, the spindle motor includes a rotor 60 including a rotor magnet 62, a stator 10 including a stator coil 12, and an air dynamic bearing for supporting the rotor 60 on the stator 10. The rotor 60 includes a rotor member 61 attached to an air dynamic pressure bearing. The rotor member 61 has a substantially cup-shaped hub structure, and a rotor magnet 62 is attached to an end of a vertical portion 61b. Polygon mirror 70
The fitting hole 70a is fitted into an annular mounting portion 61c, which is a horizontal portion of the rotor member 61, and further pressed against the receiving portion 61d of the rotor member 61 by a pressing spring 64 to be tightly attached to the rotor 60. ing.
63 is a screw for fixing the fixing portion of the holding spring 64 to the rotor member 61. The stator 10 includes a substantially cup-shaped stator member 11, and the stator coil 12 includes a stator member 1.
It is attached to 1.

The air dynamic pressure bearing includes a first conical dynamic pressure bearing portion,
It has three dynamic pressure bearings, a radial dynamic pressure bearing and a second conical dynamic pressure bearing. The first conical dynamic pressure bearing portion has a first conical convex portion 21a and a second conical convex portion 21b opposed to each other with the cylindrical portion 22 interposed therebetween, and a convex-side bearing in which a cylinder 23 is formed along a central axis. A member 20 and a bearing member fixed to the stator member 11,
a having a first conical recess 31 into which a is fitted without contact
And a concave bearing member 30. The dynamic pressure groove G1
Is formed on one of the surface of the first conical convex portion 21a and the surface of the first conical concave portion 30. Here, it is formed on the surface of the first conical convex portion 21a.

The radial dynamic pressure bearing portion is a bearing member disposed through the cylinder 23, and includes an elongated shaft 50 having a lower end 52 fixed to the stator member 11, and a convex bearing member 20. I have. The dynamic pressure groove G2 is
It is formed on one of the outer peripheral surface of the elongated cylindrical portion 51 of the elongated shaft 50 and the inner peripheral surface of the cylinder 23. Here, it is formed on the outer peripheral surface of the cylindrical portion 51.

The second conical dynamic pressure bearing portion is a bearing member fixed to the upper end portion 53 of the elongated shaft 50, and has a second conical concave portion 41 into which the second conical convex portion 21b is fitted without contact. It comprises a second concave bearing member 40 and a convex bearing member 20. The dynamic pressure groove G is formed on one of the surface of the second conical concave portion 41 and the surface of the second conical convex portion 21b. Here, it is formed on the surface of the second conical convex portion 21b.

The second concave bearing member 40 is provided with a mounting hole 43 at the center thereof. The mounting hole is pressed or screwed into the upper end 53 of the elongated shaft 50,
The second concave bearing member 40 is attached to the elongated shaft 50. The lower end 52 of the elongated shaft 50 is
Mounting hole 33 provided at the center of concave bearing member 30
And mounting hole 1 formed in the center of stator member 11
3 and is fixed to the stator member 11 by a nut 54.

The respective dynamic pressure grooves G of the first and second conical dynamic pressure bearing portions are formed so as to be oriented so that the centers of the dynamic pressure distribution in the direction of the rotation axis substantially coincide with each other. There is no fear of occurrence, and the rotation stability is improved. As described above, the rotor member 61 having a substantially cup-shaped hub structure in which the rotor magnet 62 is attached to the vertical portion 61b fits the mounting hole 61a formed in the center portion of the rotor member 61 into the columnar portion 22 so as to be convex. Since the magnetic flux is fixed to the bearing member 20 and forms a part of the magnetic circuit of the motor, the magnetic flux passes substantially the center of gravity of the rotating body driven by the spindle motor, so that the structure is stable.

Convex side bearing member 20, first concave side bearing member 30
The second concave bearing member 40 is formed of stainless steel or aluminum, and diamond-like carbon (DLC) is formed on a sliding surface thereof at a predetermined thickness. Even if it occurs, there is no fear of wear.

In the first conical dynamic pressure bearing portion and the second conical dynamic pressure bearing portion, the conical convex portions 21a and 21b and the conical concave portion 3
The conical apex angles of 1, 41 are 45 degrees or less if emphasis is placed on the radial load capacity, but are preferably 30 to 40 degrees. If the emphasis is placed on the load capacity in the thrust direction, it is 45 degrees or more, but preferably 50 to 70 degrees. The groove angle of the dynamic pressure groove G1 is 15 to 18 degrees regardless of the size of the cone apex angle. The groove width ratio of the dynamic pressure groove G1, that is, the ratio between the groove width and the groove wavelength is from 0.4 to 0.7, but preferably 0.6. The groove depth of the dynamic pressure groove G1 is 2 to 10 μm, preferably 5 μm. Further, although the groove pattern of the dynamic pressure groove G1 is a herringbone or a spiral, a herringbone groove is preferable.

In the radial dynamic pressure bearing portion, a dynamic pressure groove G2
Has a groove angle of 12 to 20 degrees, preferably 15 to 18 degrees. The groove width ratio of the dynamic pressure groove G2 is 0.4 to 0.7, preferably 0.6. The groove depth of the dynamic pressure groove G2 is 2 to 10 μm, preferably 5 μm. Further, the groove pattern of the dynamic pressure groove G2 is a herringbone, spiral or parallel groove, but a herringbone groove is preferable.

In order to enhance the stability of the bearing, the first conical dynamic pressure bearing and the second conical dynamic pressure bearing have a symmetric structure. That is, in the convex-side bearing member 20, the first conical convex portion 21a and the second conical convex portion 21b opposed to each other with the cylindrical portion 22 interposed therebetween are vertically symmetrical, and the first conical convex portion 21a is in non-contact. First conical concave portion 31 and second conical convex portion 21b to be fitted
The second conical concave portion 41 to which is fitted in a non-contact manner is formed to have the same apex angle and depth. For the same purpose, radial dynamic pressure grooves are formed in the radial dynamic pressure portion in a vertically symmetric manner.

[0020]

FIG. 2 shows another embodiment of the present invention, which shows a polygon mirror device in which a polygon mirror 70 is driven by a spindle motor having an air dynamic pressure bearing. The apparatus shown in FIG. 2 is configured by adding a motor cover and a laser emission window 71 to the apparatus shown in FIG. The motor cover is formed integrally with the second concave bearing member 40 in FIG. 2, but may be formed separately. In any case, the elongated shaft 50
The upper end portion 53 is fixed to the motor cover and the lower end portion 52 is fixed to the stator member 11, respectively. The air dynamic pressure bearing has a structure resistant to vibration and impact.

Further, at least one of the first conical dynamic pressure bearing portion and the second conical dynamic pressure bearing portion, and in the example of FIG. 3, the first conical dynamic pressure bearing portion supports a load in the thrust direction. Of the first conical convex portion 21a and the bottom portion 32 of the first conical concave portion 31 at rest.
And the contact area with the substrate could be reduced. The protrusion S
In the case of the first conical dynamic pressure bearing portion, as shown in FIG. When it is provided on the second conical dynamic pressure bearing portion, it is provided on one of the tip portion 24b of the second conical convex portion 21b or the bottom portion 42 of the second conical concave portion 41.

1 and 2, that is, a radial bearing in which an air dynamic bearing in which a radial dynamic pressure bearing portion and a conical dynamic pressure bearing portion are arranged on the inner side and the outer side so as to be coaxial with the rotating shaft, respectively. The dynamic pressure is the radial dynamic pressure of the radial dynamic pressure bearing, the radial dynamic pressure component of the first conical dynamic pressure bearing, and the second dynamic pressure.
The radial dynamic pressure component of the conical dynamic pressure bearing portion is added. The thrust dynamic pressure is obtained by adding the thrust dynamic pressure component of the second conical dynamic pressure bearing to the thrust dynamic pressure component of the first conical dynamic pressure bearing. Each of the dynamic pressures is obtained from an air dynamic pressure bearing in which the radial dynamic pressure bearing portion and the conical dynamic pressure bearing portion disclosed in Japanese Patent Application No. 10-67666 filed earlier are coaxially arranged with the rotating shaft and are respectively disposed inside and outside. Became even bigger.

[0023]

The present invention is basically an air dynamic pressure bearing in which a radial dynamic pressure bearing portion and a conical dynamic pressure bearing portion are arranged on the inner side and the outer side so as to be coaxial with the rotating shaft, respectively. The first and second conical dynamic pressure bearings are provided symmetrically in the vertical direction, and the upper and lower concave bearing members, which are these components, are used as components of the radial dynamic pressure bearing. A spindle motor provided with air dynamic pressure bearings fixed to both ends of an elongated shaft or a rotating body device using the spindle motor as a drive source. And in addition to such a unique structure,
The respective dynamic pressure grooves of the first conical dynamic pressure bearing portion, the second conical dynamic pressure bearing portion, and the radial dynamic pressure bearing portion are formed so as to be oriented such that the centers of the dynamic pressure distribution in the direction of the rotation axis substantially coincide with each other. The air dynamic pressure bearing has a feature that a large radial dynamic pressure and a thrust dynamic pressure are generated, and there is no precession movement or undesired upward movement of the bearing member. Furthermore, it is possible to easily adapt to both radial and thrust load capacities only by changing the conical apex angles of the constituent members of the first conical dynamic pressure bearing portion and the second conical dynamic pressure bearing portion. It also has the feature. Therefore, the spindle motor according to the present invention having the air dynamic pressure bearing having various features as described above or the rotating body device using the spindle motor as a driving source can be applied to a larger load, and its rotation stability and smoothness can be improved. Was able to enhance the character.

[Brief description of the drawings]

FIG. 1 shows a polygon mirror device which drives a polygon mirror by a spindle motor having an air dynamic pressure bearing according to an embodiment of the present invention.

FIG. 2 shows a polygon mirror device which drives a polygon mirror with a spindle motor having an air dynamic pressure bearing according to another embodiment of the present invention.

FIG. 3 is a partially enlarged sectional view of the air dynamic pressure bearing.

FIG. 4 shows an example of a conventional air dynamic pressure bearing having a conical dynamic pressure bearing portion and a radial dynamic pressure bearing portion.

FIG. 5 shows a pressure distribution of the conventional air dynamic pressure bearing of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base plate 2 Cylindrical bearing member 2a Conical convex part 2b Cylindrical part 3 Cylindrical bearing member 3a Conical concave part 3b Cylindrical part 4 Rotor member 5 Stator coil 10 Stator 11 Stator member 12 Stator coil 13 Mounting hole 20 Convex bearing member 21a 1st Conical convex portion 21b Second conical convex portion 22 Column portion 23 Cylinder 24a First distal end portion 24b Second distal end portion 30 First concave side bearing member 31 First conical concave portion 32 First bottom portion 33 First mounting hole 40 Second concave side Bearing member 41 Second conical concave portion 42 Second bottom portion 43 Second mounting hole 50 Slender shaft member 51 Column portion 52 Lower end portion 53 Upper end portion 54 Nut 60 Rotor 61 Rotor member 61a Mounting hole 61b Vertical portion 61c Annular mounting portion 61d Receiving portion 62 Rotor magnet 63 Screw 64 Holding spring 70 Poly Gon mirror 70a Mounting hole 71 Laser emission window M Mirror surface G Dynamic pressure groove G1 Dynamic pressure groove G2 Dynamic pressure groove

Claims (10)

[Claims] 1. A spindle motor comprising: a rotor including a rotor magnet; a stator including a stator coil; and an air dynamic bearing that supports the rotor on the stator. A convex bearing member having a conical convex portion and a second conical convex portion and having a cylinder formed along a central axis, and a bearing member erected on a stator, wherein the first conical convex portion is in non-contact. First to be fitted
A first conical dynamic pressure formed by a first concave bearing member having a conical concave portion, wherein a dynamic pressure groove is formed on one of a surface of the first conical convex portion and a surface of the first conical concave portion A bearing portion, a bearing member disposed through the cylinder, the lower end portion of which is constituted by an elongated shaft fixed to a stator and the convex-side bearing member, and an outer peripheral surface of the elongated shaft and an inner portion of the cylinder. A radial dynamic pressure bearing portion having a dynamic pressure groove formed on one of its peripheral surfaces; and a bearing member fixed to an upper end portion of the elongated shaft, wherein the second conical convex portion is fitted in a non-contact manner. It is composed of a second concave bearing member having a second conical concave portion and the convex bearing member, and a dynamic pressure groove is formed on one of the surface of the second conical concave portion and the surface of the second conical convex portion. And the second conical dynamic pressure bearing part The spindle motor according to claim Rukoto. 2. The structure according to claim 1, wherein the first conical dynamic pressure bearing portion and the second conical dynamic pressure bearing portion have a symmetric structure.
Spindle motor. 3. The dynamic pressure grooves of the first conical dynamic pressure bearing portion, the second conical dynamic pressure bearing portion, and the radial dynamic pressure bearing portion have substantially the same center of dynamic pressure distribution in the direction of the rotation axis. 2. The spindle motor according to claim 1, wherein the spindle motor is formed so as to be oriented. 4. The rotor member to which the rotor magnet is attached has a substantially cup-shaped hub structure, and a mounting hole formed at the center thereof is fitted to the cylindrical portion and fixed to the convex-side bearing member. 2. The spindle motor according to claim 1, wherein said spindle motor constitutes a part of a magnetic circuit of the motor. 5. The convex bearing member, the first concave bearing member,
2. The spindle motor according to claim 1, wherein the second concave bearing member is formed of stainless steel or aluminum, and diamond-like carbon (DLC) is formed on a sliding surface thereof with a predetermined thickness. 6. At least the first conical dynamic pressure bearing portion of the first conical dynamic pressure bearing portion and the second conical dynamic pressure bearing portion has a projection for supporting a load in a thrust direction. 2. The spindle motor according to claim 1, wherein the protrusion is provided at one of a tip of the first conical convex portion and a bottom of the first conical concave portion. 7. The spindle motor according to claim 1, wherein the first conical dynamic pressure bearing portion and the second conical dynamic pressure bearing portion have a cone apex angle of 30 to 40 degrees. 8. The spindle motor according to claim 1, wherein the first conical dynamic pressure bearing portion and the second conical dynamic pressure bearing portion have a cone apex angle of 50 to 70 degrees. 9. The spindle motor according to claim 1, wherein the groove angles of the dynamic pressure grooves of the first conical dynamic pressure bearing portion and the second conical dynamic pressure bearing portion are 15 to 20 degrees. 10. A rotating body device using the spindle motor according to claim 1 as a driving source for the rotating body.