KR100749028B1 - Spindle motor with fluid dynamic bearing - Google Patents

Abstract

A spindle motor supported by a fluid dynamic journal bearing is provided to increase an eccentric ratio of a rotor caused by a magnetic force by arranging a permanent magnet to face a shaft and a hub with a gap in an inner part or upper and lower parts of a sleeve. A spindle motor supported by a fluid dynamic journal bearing includes a base(110), a sleeve(112), a fixing sleeve(116), a shaft(120), an upper journal bearing(131), a lower journal bearing(132), and a permanent magnet(118). The sleeve(112) is vertically installed on a center of the base(110). The fixed sleeve(116) is coupled to be contacted with an outer plane of the sleeve(112). The shaft(120) is supported by the sleeve(112) and the fixing sleeve(116), and is rotatably installed on a hollow unit of a central part. The upper and lower journal bearings(131,132) are formed on an upper part and a lower part of the shaft(120). The permanent magnet(118) is installed inside the fluid dynamic journal bearing to generate a magnetic force of a radius direction to the fluid dynamic journal bearing.

Description

Spindle motor with fluid dynamic bearing

1 is a longitudinal sectional view showing a spindle motor supported by a hydrodynamic journal bearing according to the present invention;

2 is a cross-sectional view showing a shaft and a sleeve and a permanent magnet forming an upper journal bearing of a spindle motor supported by a hydrodynamic journal bearing according to the present invention;

FIG. 3 is an exploded view showing the groove pattern (groove pattern) formed on the outer peripheral surface of the shaft of FIG.

4 is a cross-sectional view showing a shaft and a sleeve and a multipole magnetized permanent magnet forming an upper journal bearing of a spindle motor supported by a hydrodynamic journal bearing according to the present invention;

5 is a view showing the groove pattern of the thrust bearing formed on the upper surface of the fixed sleeve according to the present invention,

6 is a cross-sectional view showing a shaft and a sleeve and a fan-shaped permanent magnet forming an upper journal bearing of a spindle motor supported by a hydrodynamic journal bearing according to the present invention;

7 is a cross-sectional view showing a shaft and a sleeve and a rod-shaped permanent magnet forming an upper journal bearing of a spindle motor supported by a hydrodynamic journal bearing according to the present invention;

8 is a longitudinal sectional view showing a spindle motor supported by a conventional hydrodynamic journal bearing;

9 is a sectional view showing a shaft and a sleeve forming the upper journal bearing of the spindle motor shown in FIG. 8;

FIG. 10 is an exploded view showing the groove pattern formed on the outer circumferential surface of the shaft illustrated in FIG. 9.

<Explanation of symbols for main parts of the drawings>

110: base 112: sleeve

114: coil 116: fixed sleeve

118,218,318,418: permanent magnet 120: shaft

121,122 Groove 124 Herb

126: magnet 131: upper journal bearing

132: lower journal bearing 141: upper thrust bearing

142: lower thrust bearing

The present invention relates to a spindle motor supported by a hydrodynamic journal bearing, and more particularly, to improve the radial and axial stiffness and damping performance of the bearing, thereby improving rotation accuracy. The present invention relates to a spindle motor supported by a hydrodynamic journal bearing.

In general, the spindle motor is widely used as a laser beam scanner motor for a laser printer, a motor for a hard disk drive (HDD), a motor for an optical disk drive such as a CD or a DVD.

Since the spindle motor used in the hard disk drive requires high rotational precision, a fluid dynamic bearing having high rotational precision is generally used.

8 shows a spindle motor for a hard disk drive to which a conventional hydrodynamic bearing is applied. Referring to the accompanying drawings, the spindle motor for a conventional hard disk drive includes a base 10 and a sleeve 12. And a fixed sleeve 16, a shaft 20, and a hub 24.

Coils 14 are provided at both sides of the base 10, and the fixing sleeve 16 is fixedly installed at the base 10, a hollow part is formed at a central part thereof, and the sleeve 12 is inside the hollow part. ) Is fixed.

A hollow portion is formed at the center of the sleeve 12, and the shaft 20 is rotatably installed inside the hollow portion.

A bearing clearance is formed between the shaft 20 and the sleeve 12 to prevent contact with the sleeve 12 when the shaft 20 rotates, and the bearing gap is filled with a lubricating fluid. .

The upper portion of the shaft 20 is coupled to the hub 24 on which the disk is seated.

In addition, magnets 26 corresponding to the coil 14 are provided at both lower portions of the hub 24.

The coil 14 and the magnet 26 configured as described above rotate the shaft 20 by generating an electromagnetic force by interaction with each other.

On the other hand, a stopper 40 is provided under the shaft 20 so that the shaft 20 does not escape from the sleeve 12.

Here, a bearing gap is formed between the stopper 40 and the hub 24 and the sleeve 12, and the bearing gap is filled with lubricating fluid.

The rotating part of the spindle motor as described above is radially supported by the upper and lower journal bearings 21 and 22 formed on the upper and lower parts of the shaft 20, and the upper part formed under the sleeve 12 and the upper part of the fixed sleeve 16. And axially supported by the lower thrust bearings 41 and 42.

9 is a cross-sectional view of the shaft 20 and the sleeve 12 forming the upper journal bearing 31 of the spindle motor, and FIG. 10 is a groove formed on the outer circumferential surface of the shaft 20 shown in FIG. It is an expanded view showing the pattern unfolded.

9 and 10, a plurality of grooves 21 are formed in the shape of a herringbone on the outer circumferential surface of the shaft 20 forming the upper journal bearing 31. The grooves 21 are formed at a constant interval therebetween.

Meanwhile, as shown in FIG. 8, a plurality of grooves 21 having a comb-tooth shape are formed at regular intervals under the outer circumferential surface of the shaft 20 forming the lower journal bearing 32.

In addition, a plurality of grooves are formed at regular intervals on the upper surface of the fixed sleeve 16 and the lower surface of the sleeve 12 forming upper and lower thrust bearings (not shown).

On the other hand, the hydrodynamic bearing increases rigidity and attenuation performance as the eccentricity rate of the rotating body increases.

When the static load in the radial direction acts on the shaft 20, the eccentricity is increased to improve the rigidity and attenuation performance in the radial direction.

In addition, when the static load in the axial direction acts on the thrust bearing, the floating height is reduced to improve the stiffness and the damping performance in the axial direction.

However, in the conventional spindle motor for a hard disk drive which has a small mass unbalance of the rotating body and no external force applied to the rotating body, the groove 21 is distributed on the outer circumferential surface of the shaft 20 as described above. When the upper and lower journal bearings 31 and 32 are used, the eccentricity of the rotating body is very small, which makes it difficult to increase the rigidity of the upper and lower journal bearings 31 and 32.

If the conventional upper and lower journal bearings (31,32) are used to design a bearing with high rigidity at the same rotational speed, there is a method of increasing the size of the bearing, but in this case, the friction torque increases. There arises a problem that the efficiency is greatly reduced at the time of starting and driving the motor.

In addition, when the static load in the axial direction acts on the thrust bearing, the floating height is reduced to improve the stiffness and the damping performance in the axial direction.

However, in the conventional spindle motor for hard disk drives in which the mass of the rotating body is minute and the direction of the axial load due to its own weight varies depending on the mounting state, grooves are distributed in the thrust bearing (not shown) as described above. If a conventional thrust bearing is used, it is difficult to reduce the height of the thrust bearing determined by the shape, the rotational speed, and the weight of the thrust bearing, which makes it difficult to increase the rigidity and attenuation of the thrust bearing.

Therefore, although a mechanism for applying a static load using permanent magnets has been invented as a solution, it is possible to increase only axial rigidity and attenuation by generating only static load in the axial direction.

Accordingly, the present invention has been invented to solve the above problems, in the spindle motor for a hard disk drive, the permanent magnet facing the shaft and the hub or thrust bearing to form a gap, the top, bottom, top and bottom of the sleeve By arranging in the shape of annular, fan-shaped, rod, etc. inside, it increases the eccentricity of the rotating body due to magnetic force and self-weight so that the bearing's radial and axial stiffness and damping performance can be improved without affecting friction torque. It is an object of the present invention to provide a spindle motor supported by a hydrodynamic journal bearing which can be improved, thereby improving the rotational accuracy.

Hereinafter, the features of the present invention for achieving the above object are as follows.

Spindle motor supported by the hydrodynamic journal bearing according to the present invention,

A base;

A sleeve installed perpendicular to the center of the base and a fixed sleeve coupled to an outer edge of the sleeve;

A shaft installed so as to be rotatable in a hollow portion at the center thereof, using the sleeve and the fixed sleeve as support means;

In the spindle motor supported by the hydrodynamic journal bearing configured to include upper and lower journal bearings respectively formed on the upper and lower portions of the shaft,

Permanent magnets are installed inside the hydrodynamic journal bearing so as to generate a radial magnetic force in the hydrodynamic journal bearing.

Hereinafter, the configuration of the present invention with reference to the accompanying drawings in detail.

1 is a longitudinal sectional view showing a spindle motor supported by a hydrodynamic journal bearing according to the present invention.

As shown in FIG. 1, the spindle motor supported by the hydrodynamic journal bearing according to the present invention includes a base 110 and a cylindrical sleeve 112 perpendicular to the center thereof, wherein the base and the sleeve are installed. The fixed sleeve 116 coupled to the outside of the fixed is installed.

In addition, the sleeve 112 and the fixed sleeve 116 as a support means in the central hollow portion is installed so that the shaft 120 is rotatable.

Here, the shaft 120 is supported by two hydrodynamic journal bearings (131, 132) installed in the upper and lower portions between the sleeve 112 and.

At this time, the two journal bearings (131, 132) are positioned at a predetermined interval while generating a radial bearing force when the motor rotates.

 In addition, a bearing clearance is formed between the shaft 120 and the sleeve 112 to prevent contact with the sleeve 112 when the shaft 120 rotates, and the bearing gap is filled with a lubricating fluid.

Since the lubricating fluid separates the shaft 120 and the sleeve 112, the shaft 120 rotates without contacting the sleeve 112.

In this case, since the lubricating fluid is air available, when air having a low viscosity is used as the lubricating fluid, not only the friction loss can be reduced but also the bearing characteristic change due to the frictional heat can be minimized.

In addition, an upper portion of the sleeve 112 is provided with an annular permanent magnet 118, and the eccentricity increases because a static load in the radial and axial directions is applied by the magnetic force and the magnetic weight of the permanent magnet 118. As a result, stiffness and attenuation increase.

Therefore, non-repeatable runout (NRRO) and repeatable runout (RRO) that adversely affect recording / reproducing of the hard disk can be reduced.

On the other hand, the shaft 120 is preferably made of a magnetic material in order to smooth the flux flow of the permanent magnet 118 and the shaft 120, wear resistance and resistance to ensure the wear resistance and impact resistance required for the spindle motor It is preferable to use a material excellent in impact properties.

On the other hand, the sleeve 112 is also preferably made of a magnetic material in the same way as the shaft 120.

On the other hand, the upper portion of the shaft 120 is coupled to the hub (hub, 124) is seated on the disc, the magnet (magnet, 126) corresponding to the coil 114 is provided on the lower side of both sides of the hub (124) have.

The coil 114 and the magnet 126 rotate the shaft 120 by generating electromagnetic force by interaction with each other.

Meanwhile, a stopper 140 having an outer diameter larger than that of the shaft 120 is coupled to the lower portion of the shaft 120 so that the shaft 120 does not escape from the sleeve 112.

In addition, a bearing gap is formed between the stopper 140, the hub 124, the fixed sleeve 116, and the sleeve 112, and the bearing gap is filled with a lubricating fluid.

In the spindle motor supported by the fluid hydrodynamic journal bearing of the above structure, between the shaft 120, the sleeve 112, the annular permanent magnet 118 and the first bearing means for radially supporting the rotating body and the radial direction A second bearing means for supporting the rotating body in the axial direction is formed between the permanent magnet 118, the stopper 140, the sleeve 112, the hub 124, the fixed sleeve 116 is formed a mechanism capable of applying a static load And a mechanism capable of applying an axial static load.

The first bearing means includes upper and lower journal bearings 131 and 132 formed at upper and lower portions of the shaft 120, respectively, and a permanent magnet 118 capable of generating a magnetic force in a radial direction.

2 is a cross-sectional view showing a shaft, a sleeve, and an annular permanent magnet forming an upper journal bearing of a spindle motor supported by a hydrodynamic journal bearing according to the present invention, and FIG. 3 is a groove pattern formed on an outer circumferential surface of the shaft of FIG. It is an expanded view showing the groove pattern) unfolded.

2 and 3, a plurality of grooves 121 are formed on the outer circumferential surface of the shaft 120 to generate fluid dynamic pressure in the radial direction of the shaft 120 to form the upper journal bearing 131. It is formed in the shape of a herringbone.

As such, when the groove 121 is formed in the shape of a comb, a large load capacity and stiffness in the radial direction of the shaft 120 may be obtained by the pumping effect of the fluid. Also, rotational stability can be secured.

In addition, the permanent magnet 118 is disposed while maintaining a gap with the outer peripheral surface of the shaft 120 in the sleeve (112).

When the permanent magnet 118 is disposed as described above, the bearing bearing force, the inertial force and the magnetic force of the fluid bearing are balanced by the magnetic force between the shaft 120 made of the magnetic material and the permanent magnet 118. It moves to the point forming the eccentric rotation, thereby increasing the rigidity and attenuation of the upper and lower journal bearings (131, 132).

4 is a cross-sectional view showing a shaft, a sleeve, and a multipole magnetized permanent magnet forming an upper journal bearing of a spindle motor supported by a hydrodynamic journal bearing according to the present invention. The magnetization structure is shown.

In the above description, the first bearing means has been described as having two journal bearings 131 and 132 and one permanent magnet. However, the first bearing means is not limited thereto, and one journal bearing and one permanent magnet are provided. Magnets or two or more journal bearings and two or more permanent magnets may be provided.

In addition, the position of the permanent magnet 118 has been described in the case where the upper portion of the sleeve 112, but not limited to the spindle motor according to the embodiment of the present invention, can be located anywhere, regardless of the top or bottom of the sleeve. Do.

The second bearing means includes thrust bearings 141 and 142 and permanent magnets 118 formed on an upper surface of the fixed sleeve 116 and a lower surface of the sleeve 112.

5 is a view illustrating a groove pattern of a thrust bearing formed on an upper surface of the fixed sleeve according to the present invention. Referring to the accompanying drawings, in order to form an upper thrust bearing 141 on an upper surface of the fixed sleeve 116. A plurality of grooves 141 for generating fluid dynamic pressure in the axial direction of the shaft 120 are formed in the shape of a herringbone.

As such, when the grooves 141 are formed on the upper and lower surfaces of the flange 140 in the form of comb teeth, a large load capacity and rigidity can be obtained in the axial direction of the shaft 120.

In addition, the magnetic force in the axial direction is generated by the magnetic force between the flange 140 and the permanent magnet 118 made of a magnetic material, thereby reducing the gap between the thrust bearings (141, 142).

Accordingly, the stiffness and attenuation of the thrust bearings 141 and 142 are further increased.

6 is a cross-sectional view showing a shaft and a sleeve and a fan-shaped permanent magnet forming an upper journal bearing of a spindle motor supported by a hydrodynamic journal bearing according to the present invention, in which a permanent magnet is disposed in a preferred embodiment of the present invention. Unlike the above-described embodiment, the fan-shaped permanent magnet 318 is disposed by inserting the fan-shaped cavity into the processed sleeve 112.

At this time, the sealed magnetic pattern of the permanent magnet 318 is capable of single-pole or multi-pole magnetization in the radial direction.

On the outer circumferential surface of the shaft 120, a plurality of grooves 121 generating fluid dynamic pressure in the radial direction of the shaft 120 to form the upper journal bearing 131 are formed in the shape of a herringbone.

As such, when the groove 121 is formed in the shape of a comb, it is possible to obtain a large load capacity and stiffness in the radial direction of the shaft 120 by the pumping effect of the fluid. Rotational stability can also be secured.

In addition, the permanent magnet 318 is disposed while maintaining a gap with the outer peripheral surface of the shaft 120 in the sleeve (112).

 In addition, a bearing clearance is formed between the shaft 120 and the sleeve 112 to prevent contact with the sleeve 112 when the shaft 120 rotates. In this case, the fan-shaped permanent magnet ( Since 318 is disposed to be inserted into the sleeve 112, the magnetic material of the sleeve 112 is also located between the shaft 120 and the sleeve 112.

As such, when the permanent magnet 318 is disposed, bearing bearing force, inertial force and magnetic force of the fluid bearing due to the magnetic force between the shaft 120 and the permanent magnet 318 made of a magnetic material ) Rotates to the point of equilibrium and rotates eccentrically, thereby increasing the rigidity and attenuation of the upper and lower journal bearings (131, 132).

Upper and lower thrust bearings supporting the shaft 120 in the axial direction as the shaft 120 rotates on the outer circumferential surfaces of the hub 124, the stopper 140, the fixed sleeve 116, and the sleeve 112, respectively. Grooves (not shown) for forming 141 and 142 are formed.

Here, the groove is formed in the shape of a comb as described above, it is arranged at regular intervals.

As such, when the groove is formed in the shape of a comb pattern, a large load capacity and rigidity can be obtained in the axial direction of the shaft 120, and a gap is reduced due to the magnetic force between the flange 140 and the permanent magnet 318. The stiffness and attenuation of the second bearing means is further increased.

7 is a cross sectional view showing a shaft and a sleeve and a rod-shaped permanent magnet forming an upper journal bearing of a spindle motor supported by a hydrodynamic journal bearing according to the present invention, in which a permanent magnet is disposed in a preferred embodiment of the present invention. Unlike the embodiment described above, the rod-shaped permanent magnet 418 is inserted into and fixed to the radially processed insertion hole 418a of the sleeve 112.

At this time, the magnetization pattern of the permanent magnet 418 is preferably a single pole magnet in the radial direction.

On the outer circumferential surface of the shaft 120, a plurality of grooves 121 generating fluid dynamic pressure in the radial direction of the shaft 120 to form the upper journal bearing 121 is formed in the shape of a herringbone.

As such, when the groove 121 is formed in the shape of a comb, it is possible to obtain a large load capacity and stiffness in the radial direction of the shaft 120 by the pumping effect of the fluid. Rotational stability can also be secured.

In addition, the permanent magnet 418 is disposed while maintaining a gap with the outer peripheral surface of the shaft 120 in the sleeve (112).

As such, when the permanent magnet 418 is disposed, bearing bearing force, inertial force and magnetic force of the fluid bearing due to the magnetic force between the shaft 112 and the permanent magnet 418 made of a magnetic material ) Rotates to the point of equilibrium and rotates eccentrically, thereby increasing the rigidity and attenuation of the upper and lower journal bearings (131, 132).

On the other hand, Table 1 is a result of comparing the static characteristics of the upper and lower journal bearings of the conventional spindle motor for a hard disk drive and the spindle motor for a hard disk drive according to the present invention.

Referring to Table 1, it can be seen that the eccentricity of the spindle motor according to the present invention is larger than the eccentricity of the conventional spindle motor.

On the other hand, the friction torque of the upper and lower journal bearings of the spindle motor according to the present invention is hardly increased compared to the upper and lower journal bearings of the conventional spindle motor, but it can be seen that the load capacity is increased by four times.

Table 2 shows the results of calculating the stiffness and attenuation coefficients of the upper and lower journal bearings of the conventional spindle motor and the spindle motor according to the present invention using the finite element method.

In Table 2, K _xx , K _xy , K _yy , K _θxθx , K _θxθy , K _θyθy represent the stiffness components, and C _xx , C _xy , C _yy , C _θxθx , C _θxθy , C _θyθy , respectively The aromatic component of the attenuation coefficient is shown.

Referring to Table 2, it can be seen that the rigidity of the upper and lower journal bearings of the spindle motor according to the present invention is increased by about 0.6 to 7% than that of the upper and lower journal bearings of the conventional spindle motor.

In addition, it can be seen that the damping coefficients of the upper and lower journal bearings of the spindle motor according to the present invention are increased by about 3 to 150% than the damping coefficients of the upper and lower journal bearings of the conventional spindle motor.

As such, the spindle motor supported by the hydrodynamic journal bearing according to the present invention has an increased rigidity and attenuation coefficient than the conventional spindle motor.

Therefore, the spindle motor supported by the hydrodynamic journal bearing according to the present invention has higher rigidity and attenuation than the conventional spindle motor, thereby achieving high rotational accuracy.

As described above, according to the spindle motor supported by the hydrodynamic journal bearing according to the present invention, by placing a permanent magnet facing the shaft and the hub and facing the inside or in the upper and lower parts of the sleeve, the rotation of the rotating body due to the magnetic force Increasing the eccentricity can improve the rigidity and damping performance of the bearing, thereby improving the rotational accuracy.

Claims (10)

A base; A sleeve installed perpendicular to the center of the base and a fixed sleeve coupled to an outer edge of the sleeve; A shaft installed so as to be rotatable in a hollow portion at the center thereof, using the sleeve and the fixed sleeve as support means; In the spindle motor supported by the hydrodynamic journal bearing configured to include upper and lower journal bearings respectively formed on the upper and lower portions of the shaft, A spindle motor supported by a hydrodynamic journal bearing, characterized in that a permanent magnet is installed inside the hydrodynamic journal bearing so as to generate a radial magnetic force in the hydrodynamic journal bearing. The method according to claim 1, The permanent magnet is a spindle motor supported by a hydrodynamic journal bearing, characterized in that simultaneously generating a magnetic force in the radial and axial direction to the hydrodynamic journal bearing. The method according to claim 1 or 2, The permanent magnet is supported by a hydrodynamic journal bearing, characterized in that located in any one of the upper, lower, upper and lower, the inside of the sleeve. The method according to claim 1, The shaft and the sleeve is a spindle motor supported by a hydrodynamic journal bearing, characterized in that the magnetic material. The method according to claim 1 or 2, The permanent magnet is a spindle motor supported by a hydrodynamic journal bearing, characterized in that formed in an annular shape. The method according to claim 1 or 2, The permanent magnet is a spindle motor supported by a hydrodynamic journal bearing, characterized in that the fan-shaped shape is inserted into the cavity of the sleeve. The method according to claim 1 or 2, The permanent magnet is inserted into the insertion hole formed in the radial direction of the sleeve and the spindle motor supported by a hydrodynamic journal bearing, characterized in that the rod shape. The method according to claim 1 or 2, The permanent magnet is a spindle motor supported by a hydrodynamic journal bearing, characterized in that consisting of a radial magnetization pattern. The method according to claim 1, A spindle motor supported by a hydrodynamic journal bearing, characterized in that a bearing gap is formed between the outer circumferential surface of the shaft and the inner circumferential surface of the permanent magnet. The method according to claim 1, And a bearing clearance and a magnetic material are disposed between the outer circumferential surface of the shaft and the inner circumferential surface of the permanent magnet.

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