JP2002276648A - Spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently supply air into a bearing clearance of a dynamic pressure gas bearing, to miniaturize a spindle motor, and to improve accuracy, speed, load in rotating of the spindle motor. SOLUTION: This spindle motor comprises a shaft 26 having a collar portion 26a; a bearing member 40 composed of a sleeve 34 sliding along an outer peripheral surface and upper and lower surfaces of the collar portion 26a, an upper thrust 36, and a lower thrust 38; a first dynamic pressure generating groove 50 provided on the outer peripheral surface of the collar portion 26a; second dynamic pressure generating grooves 52, 54 provided on the upper and lower surfaces of the collar portion 26a; and air inducing grooves 56, 58 provided on the upper thrust 36 and the lower thrust 38.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor, and more particularly, to a spindle motor that supports a shaft using a dynamic pressure gas bearing, and includes a magnetic recording device such as a magnetic disk and an optical disk, a grinding machine, and a precision machine. The present invention relates to a spindle motor used for rotating a rotating body provided in a high-precision measuring device such as a precision machine tool such as a grinder, a rotary table, and a linear guide with high accuracy and at a high speed.

[0002]

2. Description of the Related Art A spindle motor generally includes a stator, a rotor rotating around the stator, and bearings for rotatably supporting the rotor on the stator.
As bearings used for spindle motors, those having various structures are known, and gas bearings are generally used frequently in spindle motors used for precision machine tools, high-precision measuring instruments and the like.

A gas bearing is a bearing that raises the pressure of a gas in a gap between a shaft and a bearing by utilizing the viscosity of the gas, and causes the shaft to float by the pressure. Gas bearings are classified into various types according to the principle of pressure generation, and dynamic bearings or static pressure bearings are generally used as bearings for spindle motors. The dynamic pressure type is a bearing of a type in which gas is pushed into a wedge-shaped gap by relative movement of opposing surfaces, and the shaft is levitated by the pressure. The static pressure type is a bearing of a type in which a gas pressurized from the outside is introduced into a gap and the shaft is floated by the static pressure.

[0004] Gas bearings are characterized by much lower friction than bearings using lubricants, and the interior of the system is not contaminated with lubricants. Further, since the rotor rotates in a state where the shaft completely floats from the bearing, there is a feature that the rotation accuracy of the shaft is extremely high and the durability is high. However, since the gas filling the gap between the shaft and the bearing is compressible, there is a disadvantage that the rigidity of the bearing is extremely low. That is, when a load exceeding a specified level is applied to the shaft, the shaft and the bearing come into contact with each other, and seizure easily occurs.

[0005] In the field of spindle motors using gas bearings, various proposals have conventionally been made to solve this problem. For example, JP-A-11-1179
No. 39 discloses that high pressure air is supplied to the outer peripheral surface and upper and lower surfaces of a thrust plate fixed to a shaft in order to increase rigidity in both the radial direction and the thrust direction, and the outer peripheral surface and upper and lower surfaces of the thrust plate are An air spindle having a hydrostatic gas radial bearing and a hydrostatic gas thrust bearing is disclosed.

[0006] Japanese Patent Application Laid-Open No. 5-30720 discloses that
In order to reduce the gas flow supplied to the hydrostatic gas bearing,
A spindle motor is disclosed in which an outer peripheral surface and a lower surface of a rotor are a static pressure gas radial bearing and a static pressure gas thrust bearing, respectively, and an upper surface of the rotor is a dynamic pressure gas thrust bearing.

Japanese Patent Application Laid-Open No. H11-69711 discloses that a simple structure is used to enable forward and reverse rotation.
The outer peripheral surface and the upper and lower surfaces of the cylindrical bearing member fixed to the hollow shaft are a dynamic pressure gas radial bearing and a dynamic pressure gas thrust bearing, respectively. A forward / reverse rotating spindle motor is disclosed in which a conduction hole for connecting the shafts is provided inside a bearing member, and a self-valve provided at a lower end of a shaft is used to shut off or open / close the conduction hole.

Further, Japanese Patent Application Laid-Open No. 2000-74043 discloses that, in order to increase the load capacity without increasing the external dimensions, an inner ring is fixed to a bracket, and the outer peripheral surface and the upper surface of the inner ring are respectively subjected to a dynamic pressure gas radial. A spindle motor having a bearing and a dynamic pressure gas thrust bearing is disclosed.

[0009]

In particular, a spindle motor used in a magnetic recording device such as a hard disk drive has been required to have a small bearing in addition to a high bearing rigidity. However, since the static pressure gas bearing requires a means for generating high-pressure air, there is a limit to miniaturization.

On the other hand, a hydrodynamic gas bearing can be easily reduced in size as compared with a hydrostatic gas bearing, but cannot provide high bearing rigidity. In order to increase bearing rigidity without increasing the size of the spindle motor, in addition to optimizing the area and arrangement of the hydrodynamic gas radial bearing and hydrodynamic gas thrust bearing,
It is necessary to efficiently introduce air into the bearing clearance. However, there is no example in which a method of supplying air has been studied in order to increase the bearing rigidity of the dynamic pressure gas bearing.

The problem to be solved by the present invention is to efficiently supply air to the bearing clearance of a dynamic pressure gas bearing, and to achieve downsizing, high-precision rotation, high-speed rotation, and high-load rotation of a spindle motor. It is in.

[0012]

In order to solve the above problems, a spindle motor according to the present invention comprises a shaft having a flange, a bearing member sliding along the outer peripheral surface and upper and lower surfaces of the collar, A first bearing provided on one of an outer peripheral surface of the collar portion and a first bearing surface of the bearing member opposed thereto;
A dynamic pressure generating groove, a second dynamic pressure generating groove provided on one of the upper and lower surfaces of the collar portion or a second bearing surface of the bearing member facing the collar portion, and an inner peripheral end of the collar portion. The gist of the invention is to provide a second dynamic pressure generating groove and air introducing means for introducing air into the first dynamic pressure generating groove.

A first dynamic pressure generating groove is provided on an outer peripheral surface of a flange fixed to a shaft or a first bearing surface of a bearing member opposed thereto to form a dynamic pressure gas radial bearing. When a second dynamic pressure generating groove is provided on the second bearing surface of the opposed bearing member to form a dynamic pressure gas thrust bearing, the load is supported by both the dynamic pressure gas radial bearing and the dynamic pressure gas thrust bearing, so that the bearing is compact and compact. A highly rigid spindle motor can be obtained. Further, when the air introducing means is provided on the inner peripheral end side of the collar portion, air flows from the inner peripheral side to the outer peripheral side of the collar portion by centrifugal force. Therefore, a high pressure is generated in the bearing clearance, and the rigidity of the bearing is further improved.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a sectional view of a spindle motor according to one embodiment of the present invention. In FIG. 1, the spindle motor 10 includes a stator 20 and a rotor 30.

The stator 20 includes a base 22, a fixing bolt 24, a shaft 26, and a stator core 28. The fixing bolt 24 is provided upright at the center of the protrusion 22 a provided at the center of the base 22. The shaft 26 is fixed around the fixing bolt 24, and a cylindrical flange 26 a is provided at the center of the shaft 26. Further, a plurality of stator cores 2 are provided on the side surface of the convex portion 22a at positions facing each other.
8, 28... Are provided. Stator core 28 is an electromagnet for generating a rotational force.

The rotor 30 includes a hub 32 and a sleeve 3
4, a bearing member 40 including an upper thrust 36 and a lower thrust 38, a magnet 42, and a back yoke 44. The hub 32 is for holding the rotating body 46 (for example, a hard disk), and has a cylindrical shape. Inside the sleeve 34 and the upper thrust 3
6 and a bearing member 40 composed of the lower thrust 38 are fixed.

The sleeve 34 has a cylindrical shape, and upper and lower thrusts 36 and 38 are fixed to upper and lower ends thereof, respectively. The sleeve 34 has a flange 26a.
Is defined such that a predetermined bearing clearance is formed between the outer peripheral surface of the sleeve 34 and the inner peripheral surface (first bearing surface) of the sleeve 34. Further, the sleeve 34 is formed between the upper surface of the collar portion 26a and the lower surface (second bearing surface) of the upper thrust 36 and the lower surface of the collar portion 26a and the upper surface (second bearing surface) of the lower thrust 38, respectively. The height is determined so that a predetermined bearing clearance is formed therebetween. Further, the inner diameters of the upper thrust 36 and the lower thrust 38 are determined such that their inner peripheral surfaces are close to the outer peripheral surface of the shaft 26 adjacent to the flange 26a.

The lower end of the hub 32 is in the form of a skirt, and its inner peripheral surface is provided with a multipolar magnetized ring-shaped magnet 42.
Has been fixed. The magnet 42 cooperates with the stator core 28 to generate a rotational force, and is substantially on the same horizontal plane as the stator core 28 and
8 is provided in the vicinity. Also, the back yoke 44
The magnet 42 is used to increase the coercive force of the magnet 42.
Of the hub 32 and the inner peripheral surface of the lower end of the hub 32.

A first dynamic pressure generating groove 50 is formed on the outer peripheral surface of the collar 26a. First dynamic pressure generating groove 50
1B includes herringbone grooves 50a and 50b arranged in two rows along the axial direction of the shaft 26, as shown in FIG. Each herringbone groove 50a, 50b, respectively,
The linear groove has a V-shape meeting at one point. As the rotor 30 rotates around the stator 20, air is pushed into the meeting points 50c and 50d, and the meeting points 50c and 50d
The highest pressure is generated at 50d. That is, in the example shown in FIG. 1B, the rotor 30 is supported at two points at two meeting points 50c and 50d.

Further, second dynamic pressure generating grooves 52 and 54 are formed on the upper and lower surfaces of the flange 26a, respectively. Figure 1
(C) shows a top view of the second dynamic pressure generating groove 54 formed on the lower thrust 38 side. As shown in FIG. 1C, the second dynamic pressure generating groove 54 is a spiral groove formed in an arc shape from the center of the shaft 26 to the outside, and the second dynamic pressure generating groove 54 rotates around the stator 20 when the rotor 30 rotates around the stator 20. Accordingly, the air is pushed outward from the center of the shaft 26. The second dynamic pressure generating groove 52 formed on the upper thrust 36 side also
Although not shown, a structure similar to that of the second dynamic pressure generating groove 54 is provided.

Further, the inner peripheral surfaces of the upper thrust 36 and the lower thrust 38 are respectively provided with air introduction grooves 56 and 5
8 are formed. FIG. 1D shows the upper thrust 36.
5 shows an air introduction groove 56 formed on the inner peripheral surface of FIG. Figure 1
As shown in (d), the air introduction groove 56 is a straight groove formed obliquely on the inner peripheral surface of the upper thrust 36, and as the rotor 30 rotates around the stator 20, the outer peripheral surface of the shaft 26. From the gap between the inner peripheral surface of the upper thrust 36
Air is introduced into the dynamic pressure generating groove 52 and the first dynamic pressure generating groove 50. Although not shown, the air introduction groove 58 formed on the inner peripheral surface of the lower thrust 38 has the same structure as the air introduction groove 56.

The surface opposite to the surface on which the first dynamic pressure generating groove 50, the second dynamic pressure generating grooves 52, 54 and the air introduction grooves 56, 58 are formed, that is, the inner peripheral surface of the sleeve 34, the upper thrust It is preferable to perform blasting on the lower surface of the lower thrust 36, the upper surface of the lower thrust 38, and the outer peripheral surface of the shaft 26 adjacent to the flange 26a. When such blasting is performed on a surface facing the surface on which the dynamic pressure generating groove or the air introduction groove is formed, microscopic irregularities are formed on the surface by the blasting. Since the micro unevenness functions as an air reservoir when the rotor 30 rotates, there is an advantage that the bearing rigidity can be increased. It is more preferable to perform blasting on the surface on which the first dynamic pressure generating groove 50, the second dynamic pressure generating grooves 52 and 54, and the air introduction grooves 56 and 58 are formed.

Next, the operation of the spindle motor 10 according to this embodiment will be described. When the polarity of the current supplied to each stator core 28 is reversed at appropriate intervals, the stator core 28 fixed to the stator 20 and the rotor 3
Attraction and repulsion are repeated with the magnet 42 fixed to 0, and the rotor 30 starts rotating around the shaft 26.

When the rotor 30 rotates about the shaft 26, the relative movement between the outer peripheral surface of the shaft 26 and the inner peripheral surfaces of the upper thrust 36 and the lower thrust 38 introduces air into the air introduction grooves 56, 58. You. Next, the air introduction groove 5
The air introduced into the upper and lower thrusts 36 and 58 is supplied to the thrust bearing clearance formed between the upper surface of the collar 26a and the lower surface of the upper thrust 36, and the lower and lower thrusts 38 of the collar 26a.
Flows into the thrust bearing gap formed on the upper surface of the bearing.

When air flows into the thrust bearing clearance,
By the relative movement between the upper surface of the collar 26a and the lower surface of the upper thrust 36 and the lower surface of the collar 26a and the upper surface of the lower thrust 38, air is pushed into the second dynamic pressure generating grooves 52 and 54. Therefore, pressure is generated in the thrust bearing clearance, and the upper and lower surfaces of the flange portion 26 a float from the lower surface of the upper thrust 36 and the upper surface of the lower thrust 38.

Further, a part of the air pushed into the second dynamic pressure generating grooves 52 and 54 is caused by the pressure generated by the air introducing grooves 56 and 58 and the centrifugal force caused by the rotation of the rotor 30 to form the flange. It flows into a radial bearing clearance formed by the outer peripheral surface of 26 a and the inner peripheral surface of the sleeve 34. When the air flows into the radial bearing clearance, the air is pushed into the first dynamic pressure generating groove 50 by the relative movement between the outer peripheral surface of the collar 26a and the inner peripheral surface of the sleeve 34. As a result, pressure is generated in the radial bearing clearance, and the flange 26
Of the sleeve 34 floats from the inner peripheral surface of the sleeve 34.

The spindle motor 10 according to the present embodiment
Since the outer peripheral surface and the upper and lower surfaces of the flange 26a function as a radial bearing and a thrust bearing, respectively, the load can be supported in both the radial direction and the thrust direction. Further, since the thrust bearing is provided on the inner peripheral side of the radial bearing, the radial bearing diameter (that is, the outer diameter of the flange 26a) can be increased. Therefore, a small spindle motor having high bearing rigidity can be obtained.

Further, since the herringbone grooves 50a and 50b arranged in two rows are used as the first dynamic pressure generating grooves 50, the radial load can be supported at two points.
The load capacity of the radial bearing is improved.

Further, the air introduction grooves 56, 58 are provided on the inner peripheral surfaces of the upper thrust 36 and the lower thrust 38, respectively, so that the air introduced into the thrust bearing clearance can be provided with the air introduction grooves 56, 58. And a centrifugal force due to the rotation of the rotor 30 acts. Therefore, the flow of air from the inner peripheral end to the outer peripheral end of the collar portion 26a is accelerated, and the load capacity of the radial bearing is further improved. This also makes it possible to reduce the size, increase the precision of rotation, increase the speed of rotation, and increase the load of the spindle motor 10.

Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various modifications are possible without departing from the gist of the present invention. is there.

For example, in the above embodiment, the shaft 26
Is fixed to the stator 20, but a configuration in which the shaft is fixed to the rotor side and the bearing member including the sleeve, the upper thrust, and the lower thrust is fixed to the stator side is also possible.

In the above-described embodiment, the first dynamic pressure generating groove 50 is provided on the outer peripheral surface of the collar portion 26a, but the first dynamic pressure generating groove 50 is provided on the inner peripheral surface of the sleeve 34. It may be. Similarly, the second dynamic pressure generating grooves 52 and 54 are provided on the upper surface and the lower surface of the collar portion 26a, respectively, while the second dynamic pressure generating grooves 52 and 54 are respectively provided on the lower surface or the lower portion of the upper thrust 36. It may be provided on the upper surface of the thrust 38.

In the above embodiment, the air introduction grooves 56 and 58 are provided on the inner peripheral surface of the upper thrust 36 and the inner peripheral surface of the lower thrust 38, respectively.
The air introduction groove 56 or 58 may be provided on the outer peripheral surface of the shaft 26 close to the inner peripheral surface of the upper thrust 36 or the inner peripheral surface of the lower thrust 38.

Further, in the above-described embodiment, two herringbone grooves 50a and 50b arranged in two rows in the axial direction are used as the first dynamic pressure generating grooves 50.
The dynamic pressure generating grooves 50 may be a single row of herringbone grooves, or herringbone grooves arranged in three or more rows in the axial direction, or may be dynamic pressure generating grooves having another structure.

[0035]

The spindle motor according to the present invention has a first dynamic pressure generating groove provided on one of an outer peripheral surface of a flange provided on a shaft and a first bearing surface of a bearing member opposed thereto. And a second dynamic pressure generating groove provided on one of the upper and lower surfaces of the collar portion and the second bearing surface of the bearing member, so that a small-sized spindle motor having high bearing rigidity can be obtained. .

In addition, since air introducing means for introducing air from the inner peripheral end of the collar portion into the second dynamic pressure generating groove and the first dynamic pressure generating groove is provided, a high pressure is generated in the bearing clearance, and the bearing rigidity is increased. Is further improved. In addition, this allows the spindle motor to rotate with high precision, high speed,
In addition, there is an effect that high-load rotation can be performed.

[Brief description of the drawings]

1A is a cross-sectional view of a spindle motor according to an embodiment of the present invention, FIG. 1B is a side view of a collar, and FIG. 1C is a collar. FIG. 1D is a partial view showing a top view of a second dynamic pressure generating groove formed on the lower surface of FIG.
It is a partial view showing an inner peripheral surface of an upper thrust.

[Explanation of symbols]

 Reference Signs List 10 spindle motor 26 shaft 26a collar 40 bearing member 50 first dynamic pressure generating groove 52, 54 second dynamic pressure generating groove 56, 58 air introduction groove (air introduction means)

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 3J011 AA04 BA06 CA01 CA02 JA02 KA04 KA05 PA02 5D109 BB02 BB13 BB18 BB21 BB22 5H607 BB01 BB14 BB17 CC01 CC05 DD01 DD02 DD05 DD08 GG01 GG02 GG12 GG14 J

Claims (2)

[Claims] A shaft having a flange portion, a bearing member sliding along an outer peripheral surface and upper and lower surfaces of the collar portion, and an outer peripheral surface of the collar portion or a first bearing surface of the bearing member opposed thereto. A first dynamic pressure generating groove provided on any one of: a second dynamic pressure generating groove provided on one of the upper and lower surfaces of the collar portion or a second bearing surface of the bearing member opposed thereto; A spindle motor including air introduction means for introducing air from an inner peripheral end of the collar portion to the second dynamic pressure generating groove and the first dynamic pressure generating groove. 2. The air introducing means is an air introducing groove provided in one of an outer peripheral surface of the shaft, a portion adjacent to the flange portion and an inner peripheral surface of the bearing member adjacent thereto. The spindle motor according to claim 1.