KR101068264B1 - Spindle motor with hydrodynamic pressure bearing - Google Patents

Abstract

A spindle motor having a hydrodynamic bearing is disclosed. A holder having a core fixed to the outer circumferential surface protrudes upward, a cylindrical shaft integrally coupled to the center of the base and having a dynamic pressure generating groove formed on the upper and outer circumferential surfaces, respectively, the upper end surface of the shaft and the outer circumferential surface of the shaft One side of the hollow cylinder-shaped sleeve portion is inserted into the protruding in the center, the edge portion is extended downwards, the inner side of the downwardly extending portion is formed with a hub that is opposed to the core and spaced from the core, coupled to the lower end of the sleeve portion By providing a spindle motor having a hydrodynamic bearing including a ring-shaped cap that shields the coupled portion of the shaft of the base, the effective contact of the hydrodynamic bearing is reduced without increasing the number of parts constituting the spindle motor. To ensure sufficient area, and to It does not form a through-hole the locking mode is improved fixing part gajyeoseo sufficient rigidity.

Hydrodynamic Bearings, Spindle Motors, Disc Drives

Description

SPINDLE MOTOR WITH HYDRODYNAMIC PRESSURE BEARING}

The present invention relates to a spindle motor having a hydrodynamic bearing.

In a hard disk drive or an optical disk drive used as a storage device such as a computer, a spindle motor for rotating a disk-shaped storage medium is used. While the storage capacity of such a disk drive is increased, its size is not increased, so that the recording density of a hard disk or an optical disk is increased.

As the recording density of a hard disk or an optical disk increases, a hard disk drive or an optical disk drive becomes very sensitive to vibration, but a higher speed is required. Accordingly, continuous research and development have been conducted to achieve low noise and low non-repeatable runout (NRRO) of the spindle motor for driving the hard disk drive or the optical disk drive.

In order to achieve low noise and low NRRO of the spindle motor, a fluid dynamic bearing with less driving friction than a ball bearing is applied to the spindle motor.

The conventional hydrodynamic bearing of a spindle motor is integrally coupled with a sleeve to the base supporting the entire spindle motor, and the shaft integrally fixed to the hub rotating relative to the base is provided with a gap in the hole formed in the center of the sleeve. Formed and combined.

A groove is formed on the outer circumferential surface and the upper end of the shaft to generate a dynamic pressure by concentrating fluid, and a journal bearing is formed by using a gap formed between the outer circumferential surface of the shaft and the inner circumferential surface of the sleeve. A groove is formed and a thrust bearing is formed using the gap between the top surface of the shaft and a thrust plate disposed at one end of the sleeve. And, the other end of the sleeve is provided with a cap for shielding the fluid outflow.

In the hydrodynamic bearing of the conventional spindle motor as described above, since the height of the sleeve is reduced by the space occupied by the thrust plate and the cap, the effective contact area of the journal bearing is reduced, and the space occupied by the sleeve As the diameter is reduced, the effective contact area of the thrust bearing is reduced. And, because the through hole is formed in the center of the sleeve to engage the shaft did not have sufficient rigidity.

Therefore, the conventional hydrodynamic bearing of the spindle motor has a disadvantage in that noise and NRRO are induced due to a rocking mode that appears due to the rigidity and ductility of the base in the natural vibration mode.

The present invention has been made to solve the above-mentioned disadvantages, the present invention is a spindle motor having a hydrodynamic bearing that can secure the effective contact area and improve the locking mode without increasing the size of the spindle motor To provide.

In order to achieve the above object, according to an aspect of the present invention, the holder is fixed to the outer peripheral surface of the base protruding upward, the base integrally coupled to the center of the base grooves for generating dynamic pressure on the upper surface and the outer peripheral surface Cylindrical shafts each formed with a hollow cylinder-shaped sleeve portion in which one end of the shaft is inserted into the top surface of the shaft and the outer peripheral surface of the shaft is formed to protrude in the center, and the edge portion extends downwards and forms a gap with the core inside the downwardly extended portion. And a hydrodynamic bearing having a hub having opposite magnets disposed thereon, and a ring-shaped cap coupled to the lower end of the sleeve and shielding the coupled portion of the shaft of the base.

A gap may be formed between the upper surface of the shaft, the inner central portion of the sleeve portion, and the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve portion.

The spindle motor having the hydrodynamic bearing as described above may further include a pulling plate disposed in a portion adjacent to the magnet of the base and made of a magnetic material.

Spindle motor having a hydrodynamic bearing according to the present invention, by reducing the number of parts constituting the spindle motor can ensure sufficient effective contact area of the hydrodynamic bearing without increasing its size, and to connect the shaft to the sleeve The locking mode is improved because the fixing part has sufficient rigidity since it does not form a through hole for the same.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all transformations, equivalents, and substitutes included in the spirit and scope of the present invention. In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a longitudinal sectional view of a spindle motor having a hydrodynamic bearing according to an embodiment of the present invention.

Referring to FIG. 1, a spindle motor 100 having a hydrodynamic bearing according to an embodiment of the present invention includes a fixing part 101 and a rotating part 102.

The fixing part 101 includes a base 110 supporting the entire spindle motor 100 having a hydrodynamic bearing, a coil 120 having a coil for selectively forming a magnetic field when power is applied, and a base 110. It includes a shaft 140 integrally coupled to the center of the).

The holder part 111 protrudes upward from the base 110, and the core 120 is fixed to the outer circumferential surface of the holder part 111. Here, the holder 111 is formed to be spaced apart from the center of the shaft 140 is coupled.

Grooves 142 and 144 for generating hydrodynamic pressure of the fluid are formed on the top and outer circumferential surfaces of the shaft 140, respectively. The grooves 142 and 144 may be formed in a herringbone or spiral shape.

Rotator 102 includes hub 150 and magnet 160.

The central portion of the hub 150 is formed with a hollow hollow cylindrical sleeve portion 151 on one side. The sleeve 151 has an upper end surface and an outer circumferential surface of the shaft 140 inserted therein. At this time, the inner diameter of the sleeve portion 151 is slightly longer than the diameter of the shaft 140, a clearance 103 is formed between the inner peripheral surface of the sleeve portion 151 and the outer peripheral surface of the shaft 140. The gap 103 is filled with a fluid such as oil.

The edge portion of the hub 150 extends downward, and a magnet 160 is provided inside the downwardly extended portion.

When the sleeve 151 is coupled to the shaft 140, the magnet 160 is disposed to face the core 120 at a distance. The sleeve 151 covers all the outer circumferential surface of the shaft 140 in which the groove 142 is formed, and the lower end portion is formed to have a length close to the portion where the shaft 140 is coupled to the base 110. A ring-shaped cap 170 is coupled to the lower end of the sleeve 151 to shield the fluid filled in the gap 103 to a portion where the base 110 and the shaft 140 are coupled.

The base 110 is coupled to a pulling plate (pulling plate: 130) made of a magnetic material. The pulling plate 130 is disposed at a portion adjacent to the magnet 160, and the attraction force by the magnetic force acts between the pulling plate 130 and the magnet 160.

When power is applied to the coil of the core 120, the hub 150 rotates by an electromagnetic force generated between the core 120 and the magnet 160. Therefore, since the sleeve 151 rotates with respect to the shaft 140, the fluid filled in the gap 103 is concentrated by the groove 142 to generate dynamic pressure. In addition, the fluid is concentrated in the groove 144 formed on the top surface of the shaft 140 so that dynamic pressure is generated between the inner center of the sleeve portion 151 and the top surface of the shaft 140.

Therefore, the upper end surface and the outer peripheral surface of the shaft 140 are in non-contact state with the inner central portion and the inner peripheral surface of the sleeve portion 151, thereby reducing the frictional load. In other words, the outer circumferential surface of the shaft 140 and the inner circumferential surface of the sleeve portion 151 form the journal bearing portion 141, and are perpendicular to the central axis of the shaft 140 in the spindle motor 100 having the hydrodynamic bearing. Support the force applied. In addition, the upper end surface of the shaft 140 and the inner center of the sleeve portion 151 form a thrust bearing portion 143, which is applied to the spindle motor 100 having the hydrodynamic bearing in the direction of the central axis of the shaft 140. I support losing power.

However, the force acts upward on the hub 150 by the dynamic pressure generated between the upper end surface of the shaft 140 and the inner central portion of the sleeve portion 151. This force is canceled by the attractive force between the pulling plate 130 and the magnet 160, so that the thrust bearing portion 143, in which the upper surface of the shaft 140 and the inner central portion of the sleeve portion 151 are formed, is maintained.

Here, the gap between the pooling plate 130 and the magnet 160 and the size and shape of the pooling plate 130 are appropriately adjusted, so that the hub 150 is moved to the direction of moving away from the base 110. Forces and the attraction force by the magnetic force acting in the direction to bring the hub 150 close to the base 110 to balance. In addition, the inner circumferential surface of the holder portion 111 is formed so as not to contact the outer circumferential surface of the sleeve portion 151, so that the sleeve portion 151 can be smoothly rotated with respect to the shaft 140.

Spindle motor 100 having a hydrodynamic bearing according to an embodiment of the present invention is composed of only the components as described above. That is, since the number of parts constituting the spindle motor 100 having a hydrodynamic bearing is reduced, it is possible to sufficiently secure the diameter and height of the shaft 140 without increasing the overall size.

Since the area and the length of the inner central portion of the sleeve portion 151 can be sufficiently secured, the journal bearing portion 141 and the thrust bearing portion 143 formed between the shaft 140 and the sleeve portion 151 can be secured. The effective contact area can also be sufficiently secured. Accordingly, the dynamic pressure characteristics of the journal bearing portion 141 and the thrust bearing portion 143 are excellent, which will be described with reference to FIG. 2.

Figure 2 shows the results of experiments of the stiffness of the journal bearing portion applied to the spindle motor having a hydrodynamic bearing in accordance with an embodiment of the present invention. It will be described with reference to Figure 1 together.

2, a journal bearing portion (141, hereinafter referred to as a 'journal bearing portion') applied to the spindle motor 100 having a hydrodynamic bearing according to an embodiment of the present invention and having a conventional hydrodynamic bearing The results of experiments comparing the stiffness of the journal bearings (hereinafter referred to as 'traditional journal bearings') applied to the spindle motor are shown graphically.

The line A indicated by the solid line in the graph is the change in the stiffness of the journal bearing portion 141 according to the change in the gap, and the line B indicated by the dotted line is the stiffness of the conventional journal bearing when the gap is 2 m.

According to the experimental results, the journal bearing portion 141 has a stiffness six times higher than that of the conventional journal bearing when the gap is 2 占 퐉, and has a stiffness similar to that of the conventional journal bearing when the gap is increased to 4 占 퐉. Have

Accordingly, since the journal bearing portion 141 exhibits sufficient dynamic pressure characteristics even when the gap increases, the tolerance between the outer circumferential surface of the shaft 140 forming the journal bearing portion 141 and the inner circumferential surface of the sleeve portion 151 also increases. . That is, in the process of manufacturing the shaft 140 and the sleeve portion 151, it is possible to save the time and effort required for the management of the processing precision, the production cost of the spindle motor 100 having a hydrodynamic bearing is saved.

For reference, the locking mode described above is generated at a frequency of 1000 Hz or less. Since the locking mode is generated by being coupled with the fixing part 101, when the rigidity of the fixing part 101 is increased, the frequency of the locking mode is increased. However, since the spindle motor 100 having the hydrodynamic bearing according to the exemplary embodiment of the present invention has a small number of components and can secure a sufficient diameter and height of the shaft 140, the rigidity of the fixing part 101 is increased. Is increased.

That is, the spindle motor 100 having a hydrodynamic bearing according to an embodiment of the present invention has an improved vibration mode because the locking mode is improved.

Although the spindle motor having the hydrodynamic bearing according to the exemplary embodiment of the present invention has been described above, the spirit of the present invention is not limited to the embodiments presented herein, and those skilled in the art to understand the spirit of the present invention are the same. Within the scope of the present invention, other embodiments may be easily proposed by adding, changing, deleting, or adding components, but this will also fall within the scope of the present invention.

1 is a longitudinal sectional view of a spindle motor having a hydrodynamic bearing according to an embodiment of the present invention.

Figure 2 is a graph showing the results of experiments of the stiffness of the journal bearing portion applied to the spindle motor having a hydrodynamic bearing according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

100: spindle motor with hydrodynamic bearing

101: fixing part 102: rotating part

103: gap 110: base

111: holder portion 120: core

130: pulling plate 140: shaft

141: journal bearing portions 142, 144: groove

143: thrust bearing portion 150: hub

151: sleeve portion 160: magnet

170: cap

Claims (3)

A base having a holder portion fixed to the core on an outer circumferential surface thereof and protruding upward; A cylindrical shaft integrally coupled to the central portion of the base and having grooves for generating dynamic pressure on upper and outer circumferential surfaces, respectively; The hollow cylinder-shaped sleeve portion of which the upper end surface of the shaft and the outer circumferential surface of the shaft is inserted is formed to protrude in the center, the edge portion extends downward, and the inner side of the downward extension portion forms a gap with the core. A hub having a magnet disposed therein; And Spindle motor having a hydrodynamic bearing coupled to the lower end of the sleeve portion, comprising a ring-shaped cap for shielding the portion of the base coupled to the shaft. The method of claim 1, And a gap is formed between an upper end surface of the shaft, an inner center portion of the sleeve portion, and an outer circumferential surface of the shaft and an inner circumferential surface of the sleeve portion, respectively. The method of claim 2, Spindle motor having a hydrodynamic bearing further comprising a pull plate made of a magnetic material and disposed in a portion adjacent to the magnet of the base.

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