KR20000051598A - A spindle motor - Google Patents

Abstract

PURPOSE: A spindle motor is provided to minimize non-periodically generated non-repeatable runout of a motor and increase a magnetic track density of a disc by inserting a damping element for absorbing vibrations generated from a position where a deformation energy is most generated in the motor. CONSTITUTION: A spindle motor includes a shaft(20) as a rotation shaft and a stator(30) formed of a coil(32) wound on cores(31) for generating electric fields by an input power supply. A rotor(40) is surrounding the stator with a predetermined air gap and has a rotor housing and a permanent magnet(42) attached on an inner periphery facing the stator. A ball bearing unit(50) has upper and lower ball bearings(51,52) mounted between an inner periphery and an outer periphery of the shaft and disposed with a plurality of balls(53) between inner and outer wheels(51a,52a,51b,52b). Damping elements(70) are closely contacted between outer wheels of the upper and lower bearings as a spacer for separating the upper and lower bearings with a predetermined distance for absorbing impact transmitted between the upper and lower bearings.

Description

Spindle Motor

The present invention inserts a damping means for absorbing vibration at the position where the deformation energy is generated the greatest in the motor, thereby minimizing the non-repeatable runout that occurs in the aperiodic, especially in the motor, thereby reducing the magnetism in the disc. It relates to a spindle motor that allows for increased magnetic track density.

The driving means mainly used in small devices such as hard disk drivers or floppy disk drivers are spindle motors.

Spindle motors known to date vary greatly depending on the type of use or the manufacturer, and the performance and speed of the spindle motors are improving very rapidly.

1 illustrates an example of a general spindle motor, in which the spindle motor is driven by an electromagnetic force generated by an interaction between an electric field formed by a current flowing in a coil 112 and a magnetic field formed by a permanent magnet 131. It is common to be.

In other words, when a current flows through the coil 112 that is a fixing member, the electromagnetic force is generated between the permanent magnets 132 formed to face the coil 112 and the rotational force is generated in the permanent magnets 132. By rotating the rotor 130 to which the permanent magnet 132 is attached.

Meanwhile, the spindle motor is largely divided into an outer ring rotation method and an inner ring rotation method according to the structure to which the ball bearing 140 is applied.

Outer ring rotation type inserts the bearing between the shaft and the rotor so that the rotor rotates simultaneously with the outer ring of the bearing.Inner ring rotation type inserts the bearing between the support housing of the shaft and the base plate and integrates it with the inner ring of the bearing. It is a type that the combined shaft and rotor rotate simultaneously.

That is, in the outer ring rotation method, the shaft is fixed to the base plate, and the bearing is inserted between the fixed shaft and the support housing of the rotor, thereby rotating the rotor together with the outer ring of the bearing by the electromagnetic force between the coil and the permanent magnet.

In the inner ring rotation method, as shown in FIG. 1, the shaft 120 is integrally coupled to the rotor casing 131, and the inner ring 141 of the ball bearing 140 is forcibly fitted to the shaft 120, and the ball bearing ( The inner circumferential surface of the support housing 101 of the base plate 100 is forcibly fitted to the outer ring 142 of the base plate 100, so that the inner ring 142 of the bearing 140 is caused by electromagnetic force between the coil 112 and the permanent magnet 132. Along with the shaft 120 and the rotor 130 is configured to rotate at the same time.

On the other hand, in the spindle motor to which the ball bearing is applied, vibration is generated finely in the axial direction and the radial direction of the shaft when the motor is driven, and the vibration displacement at this time is commonly referred to as runout.

As such, the runout generated in the bearing may be directly transmitted to the disk through the hub, depending on the structure of the motor, and may be transferred to the disk via the hub via the shaft.

When measuring and analyzing the frequency component of such a runout, in particular, there are components that occur randomly regardless of frequency components among certain frequency components.

Frequency components that occur periodically and repeatedly are generally referred to as repeatable runout, and frequency components other than such repeatable runout are referred to as non-repeatable runout.

Repeated runouts are generated periodically every time the motor is driven, so it is possible to predict when they will occur through repeated experiments. Therefore, at present, it is possible to compensate for the vibration displacement by providing a separate servo control system, such as changing the position of the head at the point of repeated runout.

However, non-recurring runouts cannot be predicted at all, which makes them practically out of control.

In particular, since the amount of non-repetitive runout determines the size of the distorted rotational trajectory of the disk, it causes the magnetic recording density of the disk according to the positional difference from the head. Therefore, the industry currently limits the amount of non-repetitive runout in manufacturing a motor to a certain level in advance. For example, in the case of a hard disk driver, non-repetitive runout is regulated to about 5% of the track pitch. In the 3.5-inch hard disk driver, the track pitch is 3.6 µm when the magnetic recording density of the disk is 7000TPI. Non-repetitive runout is regulated as 0.18 mu m.

However, in the recent trend of increasing the capacity and density of disks, simply regulating non-repetitive runout cannot satisfy this problem.

In other words, in order to increase the density of the disc, the track pitch must be made smaller, but the head cannot read or write the information of the disc without directly improving the non-repetitive runout of the motor, which limits the magnetic recording density of the disc.

Therefore, in order to enable higher density of magnetic recording density in the disk, it is necessary to further reduce the non-repetitive runout of the motor.

On the other hand, in order to reduce vibration in the motor, as shown in FIG. 2, a clamp 1, which covers the disk at the upper end of the shaft 4 and prevents the flow of the disk, is provided with the shaft 4 and the bolt 5. In addition, a structure was introduced in which a vibration damping structure having a soft tape 2 attached to a mass 3 was inserted between the shaft 4 and the clamp 1 while being fastened.

However, the above structure reduces only the runout transmitted through the shaft 4 and the clamp 1 by the soft tape 2 and the mass 3, thereby indirectly controlling the runout on the disc.

In particular, since the clamp 1 is provided on the outside of the motor, it is easy to apply, but there is no control over the direct runout through the rotor, which is the seating portion of the disk directly connected to the shaft 4 in the motor. Reduction has a problem that is difficult to expect.

As described above, the control of non-repetitive runout in the spindle motor is almost impossible, and thus, it is the main cause of the failure to realize the high density of the disk.

The present invention has been made to correct the above problems, and the present invention allows the damping means to be inserted at the site where strain energy is most concentrated, so that the runout on the disc, in particular, the non-repetitive runout, can be greatly reduced. The main purpose is to provide a spindle motor.

In addition, another object of the present invention is to enable high-density disc production by minimizing the frequency response function of the disc to increase the magnetic recording density of the disc.

Another object of the present invention is to provide a spindle motor that can be applied simultaneously to an inner ring and an outer ring driving method.

1 is a vertical cross-sectional view showing a conventional spindle motor,

2 is an exemplary diagram applying a vibration reduction structure in a conventional motor;

3 and 4 are vertical cross-sectional view of the spindle motor showing a first embodiment according to the present invention,

5 and 6 are half cross-sectional view of the spindle motor showing a state in which the reinforcing plate is coupled to the damping means in the first embodiment of the present invention,

7 and 8 are vertical cross-sectional view of the spindle motor showing a second embodiment according to the present invention,

9 and 10 are half cross-sectional views of a spindle motor showing a state in which a reinforcing plate is coupled to a damping means in a second embodiment of the present invention;

11 and 12 are vertical cross-sectional view of the spindle motor showing a third embodiment of the present invention,

13 and 14 are half cross-sectional views of a spindle motor showing a state in which a reinforcing plate is coupled to a damping means in a third embodiment of the present invention;

15 is a vertical sectional view of the spindle motor showing the fourth embodiment of the present invention;

16 and 17 are half cross-sectional views of a spindle motor showing a state in which a reinforcing plate is coupled to a damping means in a fourth embodiment of the present invention;

18 is a vertical sectional view of the spindle motor showing the fifth embodiment of the present invention;

19 and 20 are half cross-sectional views of a spindle motor showing a state in which a reinforcing plate is coupled to a damping means in a fifth embodiment of the present invention;

21 and 22 are output waveform diagrams showing the time- and frequency-domain runout of the diskless spindle motor;

FIG. 23 is a histogram of non-repeatable runouts according to FIGS. 21 and 22,

24 and 25 are output waveform diagrams showing the time-domain and frequency-domain runout of the spindle motor with the disc mounted;

FIG. 26 is a histogram of non-repeatable runouts according to FIGS. 24 and 25;

27 and 28 are output waveform diagrams showing the time domain and the frequency domain runout according to the presence or absence of damping means when the diskless spindle motor rotates at the rated speed.

29 and 30 are output waveform diagrams showing run-out for each time domain and frequency domain according to the presence or absence of damping means when the spindle motor is rotated at the rated speed while the disk is mounted;

31 is an output waveform diagram of a disk frequency response function depending on whether damping means is configured.

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

10 base plate 11 support housing

20: shaft 30: stator

40: rotor 50: ball bearing unit

60: bearing spacer unit 70: damping means

80: reinforcement plate

The present invention to achieve the above object

In the structure of the spindle motor which supports the shaft by the ball bearing, the damping means is inserted into the portion where the strain energy exerted by the ball bearing is most concentrated, thereby reducing the repetitive runout with the repetitive runout in the rotor. There is a characteristic to make it possible.

Hereinafter, described in detail with reference to the accompanying drawings a preferred embodiment of the present invention.

First, when the strain energy is measured by finite element analysis along the transmission path of the strain energy generated from the motor, the strain energy is measured between the contact surface (0.00857 ~ 1.353) with the upper bearing of the rotor and the upper end of the outer ring (0.0112 ~ 0.381) of the upper bearing. It can be seen that the upper and lower ends of the upper and lower bearings have the greatest inner ring (0.00489 to 1.604) and the spacer (0.00837 to 0.612).

Each strain energy at this time represents the magnitude of the output energy per unit input energy, and the actual value is multiplied by 10 ⁻³ .

Based on these results, the damping members 70 as in the present embodiment are respectively inserted in the areas where the deformation energy generated in the motor is the largest, so that non-repetitive runout in the disk can be significantly reduced.

3 and 4 are vertical cross-sectional views showing an example of a spindle motor showing a first embodiment according to the present invention. FIG. 3 is an inner ring driving method, FIG. 4 is an outer ring driving method, and 10 is a base plate. , 20 is a shaft, 30 is a stator, and 40 is a rotor.

In this embodiment, the shaft 20 may be a rotating shaft as shown in FIG. 3, or may be a fixed shaft fixed to the base plate 10 as shown in FIG. 4.

The stator 30 is composed of a core 31 and a winding coil 32 wound around the core 31, and as shown in FIG. 3, the support housing 11 or 4 which is integrally formed on the base plate 10. As is to be fixed directly to the base plate 10 directly.

In particular, the stator 30 is a part for forming an electric field by the power input from the outside.

Meanwhile, the upper part of the stator 30 includes a rotor 40 which surrounds the stator 30 and has an air gap formed at a predetermined interval from the stator 30.

The rotor 40 is composed of a permanent magnet 42 attached to the inner circumferential surface facing the stator 30 with the rotor housing 41 again with the air gap therebetween.

The base plate 10 and the rotor 40 each have a support housing 11, 43 having an inner diameter larger than the outer circumferential surface of the shaft 20, and protrude, and the outer circumferential surface of the shaft 20 and the support housing 11, 43. Between the inner circumferential surface of the) is provided with a ball bearing unit 50 consisting of an upper bearing 51 and a lower bearing 52, respectively.

The upper bearing 51 and the lower bearing 52 of the ball bearing unit 50 each have an inner ring 51a, 52a, an outer ring 51b, 52b, and an inner ring 51a, 52a and an outer ring 51b ( The plurality of balls 53 are arranged side by side between 52b).

The configuration as described above is the same as the conventional spindle motor, which is an inner ring driving method and an outer ring driving method.

However, in the present embodiment, the upper bearing 51 and the lower bearing 52 provided between the shaft 20 and the support housings 11 and 43 are spaced at a predetermined interval, and the upper bearing 51 and The damping means 70 is characterized in that the close contact between the outer ring of the lower bearing 52.

In other words, the upper bearing 51 and the lower bearing 52 are spaced at a predetermined interval, and the spaced apart between the outer ring 51b and 52b facing each other of the spaced upper bearing 51 and the lower bearing 52. The damping means 70 is inserted into the space to make close contact with each of the outer ring 51b, 52b.

At this time, since the damping means 70 functions as a spacer between the upper bearing 51 and the lower bearing 52 at the same time, the material is harder, and in particular, the surface in contact with the outer ring of the upper and lower bearings 51 and 52. More preferably, the upper and lower bearings 51 and 52 are formed as a material capable of absorbing the shock transmitted from the upper and lower bearings 51 and 52.

In particular, in the present embodiment, the damping means 70 is a harder material than the damping means 70 into the spaces spaced apart from the outer ring 51b, 52b of the bearing at least on one side as shown in FIGS. The reinforcement plate 80 provided may be inserted.

When the damping means 70 is inserted according to the embodiment as described above, the vibration generated between the upper and lower bearings 51 and 52 can be smoothly absorbed, thereby greatly reducing runout in the rotor 40. You can do it.

7 and 8 are vertical cross-sectional views showing an example of a spindle motor showing a second embodiment according to the present invention. FIG. 7 is an inner ring driving method, and FIG. 8 is an outer ring driving method.

The base plate 10, the shaft 20, the stator 30, the rotor 40, and the ball bearing unit 50 in this embodiment are the same as the first embodiment.

That is, the stator 30 is fixed to the base plate 10, the shaft 20 is a rotating shaft in the inner ring driving method, and is provided as a fixed shaft in the outer ring driving method, and the shaft 20 and the support housings 11 and 43 are provided. The ball bearing unit 50, which is provided with a pair of upper and lower bearings 51 and 52, is forcibly fitted.

In this embodiment, however, the bearing spacer 60 is inserted between the upper bearing 51 of the ball bearing unit 50 and the outer ring 51b, 52b of the lower bearing 52 so that they are always maintained at appropriate intervals. The most prominent feature is that the damping means 70 is provided between the outer races 51b and 52b of the upper and lower bearings 51 and 52 and the bearing spacer 60.

In other words, in the present embodiment, the bearing spacer 60 is inserted between the outer races 51b and 52b of the upper and lower bearings 51 and 52, but the spacer 60 and the upper and lower bearings 51 and 52 are The damping means 70 is also inserted between the outer ring 51b and 52b so as to absorb vibrations generated from the upper and lower bearings 51 and 52 from each other.

When the damping means 70 is formed to the upper and lower bearings 51 and 52, respectively, the vibration force generated by the bearing can be dispersed and absorbed, thereby further reducing the vibration force.

In addition, as shown in FIGS. 9 and 10, the reinforcing plate 80 made of a harder material than the damping means 70 is fixed to at least one side of the damping means 70 so as to securely hold the damping means 70.

That is, the rigid reinforcement plate 80 may be provided on the outer ring 51b, 52b side of the upper and lower bearings 51, 52 of the damping means 70, depending on the fixing portion, or on the bearing spacer 60 side. It may be provided.

11 and 12 are vertical cross-sectional views showing an example of a spindle motor showing a third embodiment according to the present invention. FIG. 11 is an inner ring driving method, and FIG. 12 is an outer ring driving method.

As shown in the drawings, the configuration in which the base plate 10, the shaft 20, the stator 30, the rotor 40, and the ball bearing unit 50 are provided is the same as the above-described embodiments.

That is, the stator 30 is fixed to the base plate 10, the shaft 20 is a rotating shaft in the inner ring driving method, and is provided as a fixed shaft in the outer ring driving method, and the shaft 20 and the support housings 11 and 43 are provided. The ball bearing unit 50, which is provided with a pair of upper and lower bearings 51 and 52, is forcibly fitted.

Therefore, in the inner ring driving method, the rotor 40 rotates together with the shaft 10. In the outer ring driving method, only the rotor 40 rotates to rotate the disk.

The present invention is a bearing spacer unit consisting of a first bearing spacer 61 and a second bearing spacer 62 between the outer ring 51b (52b) of the pair of upper and lower bearings 51 and 52 in the above configuration ( The most prominent feature is the configuration in which 60 is inserted and the damping means 70 is inserted between the first bearing spacer 61 and the second bearing spacer 62.

That is, the upper and lower bearings 51 and 52 are directly spaced apart from the outer ring 51b and 52b between the outer ring 51b and 52b of the upper and lower bearings 51 and 52 while being spaced apart from each other. The first bearing spacer 61 is provided on the upper bearing 51 side and the second bearing spacer 62 is provided on the lower bearing 52 side so as to be in surface contact.

In this case, a gap is formed between the first bearing spacer 61 and the second bearing spacer 62, and the damping means 70 is inserted into the gap.

In such an embodiment, the vibration generated from the upper and lower bearings 51 and 52 is also absorbed while being transmitted to the damping means 70 through the first and second bearing spacers 61 and 62, thereby vibrating shock through the bearing. Can be minimized.

13 and 14, at least one side of the damping means 70 inserted between the first and second bearing spacers 61 and 62 is connected to the first and second bearing spacers 61 and 62. It is more preferable to provide a reinforcement plate 80 made of a hard material than the damping means 70 in between.

Accordingly, the reinforcing plate 80 may be provided toward the first bearing spacer 61 side of the damping means 70 as shown in FIG. 13, and the second bearing spacer 62 of the damping means 70 as shown in FIG. 14. It may be provided on the side, it may be provided on both sides of the damping means 70 so as to contact each of the first and second bearing spacers (61, 62).

Such a reinforcement plate 80 can be inserted firmly even in the inserted state while allowing the damping means 70, which is a softer material, to be smoothly inserted between the first and second bearing spacers 61 and 62. Make sure

Thus, the vibration force transmitted to the rotor 40 by the damping means 70 supported and supported by the reinforcement plate 80 can be reduced as much as possible, thereby minimizing non-repetitive runout on the disc.

FIG. 15 is a vertical sectional view showing an example of a spindle motor showing the fourth embodiment according to the present invention, and is particularly applicable only to an inner ring drive motor.

As shown in the drawings, the stator 30 is fixed to the outer circumferential surface of the support housing 11 on the base plate 10, the shaft 20 is integrally connected to the rotor 40, and the support housing 11. ) And the ball bearing unit 50 provided with a pair of upper and lower bearings 51 and 52 are forcibly fitted between the shaft and the shaft 20.

Therefore, when an electromagnetic force is generated between the winding coil 32 of the stator 30 and the permanent magnet 42 of the rotor 40, the inner rings 51a and 52a of the upper and lower bearings 51 and 52 become the shaft 10. And rotate with the rotor 40.

In this structure, the present embodiment is most prominent in that the damping means 70 is provided between the inner ring 51a of the upper bearing 51 and the rotor casing 41 opposite thereto.

Thus, the embodiment of the present invention to absorb the vibration transmitted between the shaft 20 and the rotor 40 and the inner ring 51a of the upper bearing 51 which is a component that rotates in the motor by the damping means 70 Configuration.

In addition, in the fourth embodiment, one side of the damping means 70 may be provided with a reinforcing plate 80 made of a harder material than the damping means 70. FIG. 16 shows that the reinforcing plate 80 is damped. The upper bearing 51 side of the 70 is provided, and FIG. 17 shows that the reinforcing plate 80 is provided on the rotor case 41 side of the damping means 70.

When the reinforcing plate 80 is provided on one side of the damping means 70, the damping means 70 is easily inserted between the rotor case 41 and the inner ring 51a of the upper bearing 51. It is to maintain a steady even in the made state to continuously reduce the vibration force transmission to the rotor 40.

18 shows an example of a spindle motor showing the fifth embodiment according to the present invention, which is particularly applicable only to the outer ring driving method.

As shown in the drawing, the shaft 20 is fixed to the base plate 10, the stator 30 consisting of the core 31 and the winding coil 32 is fixed to the base plate 10, the stator 30 Rotor 40 having a rotor casing 41 having an air gap between the stator 30 and the permanent magnet 42 fixed to the inner wall of the rotor casing 41 while surrounding the stator 30 at an upper portion thereof. Is provided.

And a pair of a plurality of balls are arranged between the inner ring and the outer ring and the inner ring and the outer ring between the outer circumferential surface of the shaft 20 and the inner circumferential surface of the support housing 43 formed integrally protruding downward from the center of the rotor 40, respectively. The ball bearing unit 50 consisting of the upper bearing 51 and the lower bearing 52 is forcibly fitted.

This configuration is very similar to the conventional motor structure of the outer ring driving method, but in this embodiment, the damping means 70 is most prominently provided between the base plate 10 and the inner ring 52a of the lower bearing 52. It is characteristic.

That is, the inner ring 52a of the base plate 10 and the lower bearing 52 is a fixed member which is fixedly connected to the shaft 20 and is always in a stationary state, such that the base plate 10 and the lower bearing 52 which are the fixed members are fixed. By providing a damping means (70) between the inner ring (52a) of the is to achieve a vibration reduction in a more stable state.

In other words, if the damping means 70 is provided between the rotating rotating members, the damping means 70 itself also rotates, so that it is very difficult to properly control the rotational vibration, but the ball bearing unit 50 is fixed as in this embodiment. Controlling rotational vibration at the site makes it possible to stably absorb the vibrational force, thus reducing vibrational force more efficiently.

Meanwhile, one side of the damping member 70 between the base plate 10 and the inner ring 52a of the lower bearing 52 is provided with a reinforcing plate 80 that firmly supports the damping member 70.

At this time, the reinforcement plate 80 is made of a harder material than the damping member (70).

The reinforcement plate 80 provided as described above may be provided toward the lower bearing 52 side of the damping member 70 as shown in FIG. 19, and toward the base plate 10 side of the damping member 70 as shown in FIG. 20. It may be provided.

As described in the above embodiments, the present invention has the greatest feature in that it can block transmission of the vibration generated by the ball bearing to the rotor 40 when the motor is driven.

In other words, if the runout of the spindle motor is measured by using a separate experimental device, the total and exclusive runout, repetitive runout, and non-repetitive runout of the spindle motor only in the time domain and the frequency domain without the disk installed Divided measurement is as shown in Figure 21 and 22. In summary, the statistical characteristics of the measured runout are as shown in Table 1 below.

Deviation between max. And min. Standard deviation (㎛) TIR 3.1280 1.1927 RRO 3.0907 1.1927 NRRO 0.0521 0.0072

In the table, TIR is full run out, RRO is repetitive run out, and NRRO is non-repetitive run out.

23 shows the measured non-repetitive runout as a histogram. The solid line in the graph is a normal distribution having the same mean and standard deviation as the measured non-repetitive runout, and it is understood that the non-repetitive runout is a normal distribution.

However, when two discs are mounted on the spindle motor as described above and the axial runout of the disc is divided into the time domain and the frequency domain, the measurement is performed as shown in FIGS. 24 and 25. The statistical characteristics of the runout measured in this way are as shown in Table 2 below.

Deviation between max. And min. Standard deviation (㎛) TIR 22.2520 7.7800 RRO 22.0214 7.7798 NRRO 0.3113 0.0451

Compared with FIG. 18, it can be seen that the size of the TIR, the repetitive runout (RRO), and the non-repetitive runout (NRRO) are increased by about 7 times.

This is because the excitation of the ball bearing is amplified in addition to the motion of the disk in the process of transmission.

Based on the above measurement results, as shown in FIG. 26, the histogram of the spindle motor shows that the distribution of non-repetitive runout is a normal distribution having an average of 0. FIG.

On the other hand, when the spindle motor is equipped with the existing mass-produced product and the damping means according to the present invention without the disk mounted, the results of the dynamic characteristics analysis of the product were changed as the bearings were first replaced. same.

normal Upper bearing damping Damping between upper and lower bearing First mode 994 yen 986 yen 990 yen

As shown in the table above, when it is normal and when the damping means 70 is provided in the upper bearing 51 (UBD) and when the damping means 70 is provided between the bearings 51 and 52 (BSD). Divided.

When the non-repetitive runout according to the provision of the damping means 70 and the mounting position thereof is measured for each of the time domain and the frequency domain, as shown in FIGS. 27 and 28.

In addition, the dynamic characteristics of the existing mass-produced product in the state where the disk is mounted and the damping means 70 of the present invention can be seen to be changed as shown in Table 4 below.

First mode 2nd mode 3rd mode normal 554 yen 700㎐ 1043㎐ Upper bearing damping 533 yen 685 yen 1073㎐ Damping between upper and lower bearing

In addition, non-repetitive runout when rotating at the rated speed of 70 Hz with the disk mounted is measured for each of the time domain and the frequency domain, as shown in FIGS. 29 and 30.

As a result of analyzing the measurement results described above, it can be seen that non-repetitive runout is greatly reduced compared to the structure without the damping means provided in the bearing, and the damping means is provided as in the fourth embodiment of the present invention. When the damping means is provided on the upper bearing side, all the non-repetitive runouts due to the ball defects of the ball bearings in the spindle motor are reduced.

On the other hand, although some non-repetitive runout components appeared larger immediately after the disk was mounted on the spindle motor, most of the non-repetitive runout components disappeared.

In the case where the damping means 70 is damped between the upper ball bearing 51 and the lower ball bearing 52 as in the first to third embodiments of the present invention, the ball of the ball bearing in the spindle motor Non-repetitive runouts due to defects were all reduced as in the fourth embodiment, but it can be seen that non-repetitive runouts due to inner ring defects were larger. This may be due to the influence of the insertion position of the damping means, and a similar tendency appears after the disk is mounted, and as a result, the overall non-repetitive runout is most reduced.

In particular, when the damping means 70 is inserted as in the present invention, the standard deviation of non-repetitive runout was 16 nm, but when the damping member 70 was inserted between the upper bearing 51 and the rotor 40, the deviation was 11.9 nm. As a result, the reduction rate of the non-repetitive runout reaches about 26% as compared to the past, and when the damping means 70 is inserted between the upper bearing 51 and the lower bearing 52, the deviation becomes It can be seen that the damping between the upper bearing 51 and the lower bearing 52 is more effective since it can be seen that the reduction rate of non-repetitive runout reaches about 34% while being greatly reduced to 10.5 nm.

That is, in the case of damping between the rotor casing 41 and the upper bearing 51, only the energy transmitted from the inner ring 51a of the upper bearing 51 to the rotor casing 41 is absorbed, whereas the upper bearing 51 and the lower bearing The damping structure between 52 and 52 absorbs the vibration transmitted between the upper and lower bearings at the same time, so the reduction effect is increased because the energy absorbed is larger.

In addition, the effect of reducing the non-repetitive runout is greater than when the disc is not mounted because the inertia is increased by mounting the disc, thereby increasing the amount of strain energy consumed by the damping means 70. It seems to be.

Therefore, as in the present invention, the damping means 70 is formed at the site where the deformation energy is the greatest, thereby greatly reducing the deviation of the runout control.

On the other hand, by applying the damping means 70 as in the present invention, the improvement effect of the frequency response function transmitted to the disk is as shown in FIG.

In particular, when the reinforcing plate 80 is attached to the damping means 70, the assembling of the damping means 70 becomes very simple, and the reinforcing plate 80 can disperse various frequency components at high amplitude frequencies. As a result, it is possible to double the reduction in non-repetitive runout by promoting the equalization of the amplitude as a whole.

As described above, the present invention can be drastically reduced by simply inserting the non-repetitive runout, which is difficult to control among the components of the runout generated in the motor, into the portion where the deformation energy of the motor is generated the most simply by the damping means 70. To ensure that

That is, the vibration trajectory is blocked and absorbed at the place where the strain energy is greatest, so that the rotational trajectory of the disk can be approached to the source.

In addition, by minimizing non-repetitive runout components that limit the magnetic recording density of the disk, the magnetic recording density of the disk can be further increased.

This makes it possible to increase the magnetic recording density of the disk to about 25000TPI in the future and has a very useful effect of promoting the manufacture of high density disk drivers.

Claims (10)

A shaft; A stator having a core and a winding coil; A rotor having a rotor casing and a permanent magnet fixed to an inner wall of the rotor casing, the rotor having an air gap between the stator and surrounding the stator; A ball bearing unit provided between an outer circumferential surface of the shaft and an inner circumferential surface of the support housing, the pair of upper and lower bearings each having a plurality of balls arranged between the inner and outer rings and the inner and outer rings; And Damping means provided between the outer ring of the upper bearing and the lower bearing to substantially reduce the vibration of the motor; Spindle motor. The spindle motor of claim 1, wherein a reinforcing plate made of a harder material is attached to at least one side of the damping means. A shaft; A stator having a core and a winding coil; A rotor having a rotor casing and a permanent magnet fixed to an inner wall of the rotor casing, the rotor having an air gap between the stator and surrounding the stator; A ball bearing unit provided between an outer circumferential surface of the shaft and an inner circumferential surface of the support housing, the ball bearing unit comprising a pair of upper and lower bearings in which a plurality of balls are arranged between the inner and outer rings and the inner and outer rings, respectively; A bearing spacer provided between the outer ring of the upper bearing and the lower bearing and having a fine gap with at least one outer ring; And Damping means inserted in a gap between the bearing spacer and outer rings of the upper and lower bearings to substantially reduce vibration of the motor; Spindle motor. 4. The spindle motor of claim 3, wherein a reinforcing plate made of a harder material is attached to at least one side of the damping means. A shaft; A stator having a core and a winding coil; A rotor having a rotor casing and a permanent magnet fixed to an inner wall of the rotor casing, the rotor having an air gap between the stator and surrounding the stator; A ball bearing unit which is supplied between an outer circumferential surface of the shaft and an inner circumferential surface of the support housing, the pair of upper and lower bearings each having a plurality of balls arranged between the inner and outer rings and the inner and outer rings; A bearing spacer unit having a first bearing spacer in close contact with the outer ring of the upper bearing and a second bearing spacer in close contact with the outer ring of the lower bearing having a fine gap with the first bearing spacer; And Damping means inserted in a gap between the first bearing spacer and the second bearing space to substantially reduce vibration of the motor; Spindle motor. The spindle motor of claim 5, wherein a reinforcing plate made of a harder material is attached to at least one side of the damping means. A shaft; A stator having a core and a winding coil; A rotor having a rotor casing fixed to one end of the shaft and a permanent magnet fixed to an inner wall of the rotor casing, the rotor having an air gap between the stator and surrounding the stator; A ball bearing unit interposed between the outer circumferential surface of the shaft and the inner circumferential surface of the support housing, the pair of upper and lower bearings each having a plurality of balls arranged between the inner and outer rings and the inner and outer rings; Damping means inserted between the inner ring of the upper bearing and the rotor casing so that vibration of the motor can be substantially reduced; Spindle motor. 8. The spindle motor of claim 7, wherein at least one side of the damping means is attached to a reinforcing plate made of a harder material than the damping means. A base plate; A shaft fixed to the base plate; A stator having a core and a winding coil; A rotor having a rotor casing fixed to one end of the shaft and a permanent magnet fixed to an inner wall of the rotor casing, the rotor having an air gap between the stator and surrounding the stator; A ball bearing unit which is supplied between an outer circumferential surface of the shaft and an inner circumferential surface of the support housing, the pair of upper and lower bearings each having a plurality of balls arranged between the inner and outer rings and the inner and outer rings; Damping means inserted between the base plate and the inner ring of the lower bearing to substantially reduce vibration of the motor; Spindle motor. 10. The spindle motor of claim 9, wherein at least one side of the damping means is provided with a reinforcing plate made of a harder material than the damping means.