JPH09219952A - Motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To give the same electric potential to a stator and a motor base, to reduce vibration during rotation and restricts the movement in the axial direction. SOLUTION: Grooves 19 and 19 are formed at a rotating shaft 18 of a spindle hub 17, and a dynamic fluid bearing means 20 is constituted by a bearing cylinder 16, a groove 19 and 19 and lubricating oil. A thrust receiving member 23 is provided on the upper surface of a lower block plate 22 of a motor base 11. This thrust receiving member 23 is constituted by baking graphite with paint on the top surface of the main body 23a made of sapphire and a conductive film 23b is coated.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a magnetic disk,
The present invention relates to a small and precise motor mounted in an information storage device such as an optical disk device.

[0002]

For example, a small precision spindle motor used in a hard disk drive device has a structure as shown in FIG. That is, the bearing sleeve 2 is formed on the motor base 1,
On the outer peripheral surface of the bearing sleeve 2, a stator 5 formed by winding a winding 4 on a stator core 3 is arranged.

A rotary shaft 7 of a spindle hub 6 which is a rotor is rotatably supported by an inner peripheral surface of the bearing sleeve 2 via a ball bearing 8. Further, the outer peripheral portion 6a of the spindle hub 6 is shaped so as to fall to the outer periphery of the stator 5, and the permanent magnet 9 is attached to the inner peripheral surface of the outer peripheral portion 6a.

As is well known, the hard disk drive device having the above spindle motor is a device for storing magnetic information on a magnetic disk with a certain track width. In this case, it is required to improve the storage capacity with the same size, and for that purpose, it is necessary to narrow the track width. At that time, if the spindle motor, which is the center of rotation, has vibration that is indicated as asynchronous shaft run-out, it will be off the track when reading / writing information from / to the disk.
There is a problem that the stored information becomes inaccurate. Therefore, there is a problem that the track width cannot be narrowed and the storage capacity cannot be increased.

The cause of the vibration of the spindle motor is often the assembling accuracy of the bearing portion and the accuracy of the parts of the bearing. Especially, in the case of a ball bearing which rotates with a contact portion, the vibration is inevitable. Is likely to occur. That is, as is well known, the ball bearing is configured by arranging a large number of balls in the inner and outer rings, and each of these balls is made with high accuracy, but again, there are variations in accuracy, There is a possibility that vibrations may be generated by the balls when the ball rotates.

As a countermeasure against this, as shown in Japanese Utility Model Laid-Open No. 3-10359, for example, a herringbone-shaped groove is provided on either the rotary shaft or a bearing cylinder fitted with the rotary shaft, and the rotary shaft and the bearing cylinder are connected to each other. There is a configuration in which a fluid, for example, oil is filled between the two so that the rotating shaft can be stably rotated in a non-contact manner by the dynamic pressure of the oil generated during rotation.

However, since the rotating shaft does not come into contact with the bearing tube, there is a problem that the magnetic disk, which is in an electrically floating state and is rotated above the rotor, is susceptible to noise and the like. In addition, since the rotary shaft is not regulated in the axial direction, the rotor may move in the axial direction, which may damage the magnetic head that reads from and writes to the disk.

The present invention has been made in view of the above circumstances, and an object thereof is to reduce vibration during rotation of a motor and to reduce movement in the axial direction, and further to reduce a rotor and a motor base. An object is to provide a motor that can have the same potential.

[0009]

According to the present invention, there is provided a stator, which is provided on a motor base and is formed by winding a stator core, a rotating shaft made of a conductive material, and a permanent magnet which rotates integrally with the rotating shaft. A rotor that is configured to have a rotatably mounted hydrodynamic bearing means, and a rotor that is made of a conductive material and is electrically connected to the motor base, and has an end of the rotary shaft. And a thrust receiving member that receives an axial load applied to the portion.

According to this construction, when the rotor rotates, it is rotatably supported by the hydrodynamic bearing means. In this case, the rotary shaft of the rotor is supported by the dynamic pressure of the fluid in a non-contact state, so that the occurrence of vibration is reduced. Further, the axial load applied to the end of the rotary shaft is received by the thrust receiving member. In this case, the rotary shaft is not in contact with the motor base side, but since the thrust receiving member has conductivity, it can be set to the same potential as the motor base.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows the overall structure of a small precision spindle motor used in a hard disk drive device. In the figure,
The metal motor base 11 has a cylindrical bearing sleeve 1
2 are formed. On the outer peripheral surface of the bearing sleeve 12, a stator 15 constituted by winding a winding wire 14 on a stator core 13 is arranged. A bearing sleeve 16 is fitted on the inner peripheral surface of the bearing sleeve 12.

In the spindle hub 17 which is a rotor, the rotating shaft 18 is made of a conductive material,
Herringbone-shaped grooves 19, 19 are formed in the upper and lower portions of the outer peripheral surface of the rotary shaft 18. Also,
The rotating shaft 18 on the inner peripheral surface of the bearing tube 16 that supports the rotating shaft 18.
The inner diameter of the portion corresponding to the groove 19 of the groove 19 is
Since the inner diameters of the portions corresponding to 9 and 19 are formed slightly larger, the rotation resistance can be reduced, and when the fluid is lubricating oil, this portion functions as an oil sump.

Further, since the lower end side of the rotary shaft 18 in the drawing is formed in a substantially spherical shape with the shaft center as the apex, the contact with the thrust receiving member 23 described later becomes a point, which also reduces the rotational resistance. In addition, since the contact is made at the center of the shaft, stable rotation can be obtained.

The rotary shaft 18 and the bearing cylinder 16
A fluid, for example, a lubricating oil (not shown) is filled between the and. The grooves 19, 19 and the bearing sleeve 16 and the lubricating oil constitute a hydrodynamic bearing means 20. The spindle hub 17 is rotatably provided by the hydrodynamic bearing means 20. Further, the outer peripheral portion 17a of the spindle hub 17 is shaped so as to fall to the outer periphery of the stator 15, and the permanent magnet 21 is attached to the inner peripheral surface of the outer peripheral portion 17a.

On the other hand, a closing plate 22 made of a metal plate for closing the lower surface of the bearing sleeve 12 is provided under the motor base 11, and the upper surface of the closing plate 22, that is, the lower end of the rotary shaft 18 is provided. A thrust receiving member 23 is arranged at the facing portion. As shown in FIG. 2, the thrust receiving member 23 is formed by coating and baking a conductive material such as graphite on the surface (upper surface) of a main body member 23a made of, for example, sapphire. Then, the membrane 23b and the closing plate 2
Conductor 24 is electrically connected to 2. The body member 23a may be ruby or ceramics other than sapphire, and the film 23b may be silver, platinum or titanium other than graphite.

In the above structure, the winding 14 of the stator 15
Is controlled by a motor drive circuit (not shown),
The spindle hub 17 having the magnetic desk attached thereto is rotated. In this case, the rotary shaft 18 is supported by the hydrodynamic bearing means 20 in a non-contact state. That is, the rotary shaft 18
When is rotated, dynamic pressure is generated by the inner peripheral surface of the bearing cylinder 16, the groove 19 and the lubricating oil, and the rotating shaft 18 smoothly rotates in a non-contact state with the bearing cylinder 16. This can reduce the occurrence of vibration. As a result, the track width of the magnetic disk can be reduced, which can contribute to an increase in storage capacity.

Further, the axial load (downward load) applied to the end of the rotary shaft 18 is received by the thrust receiving member 23, so that the spindle hub 17 as the rotor can be prevented from moving in the axial direction, Therefore, the magnetic head is not damaged. In this case, the rotary shaft 18 is not in contact with the motor base 11 side, but the thrust receiving member 2
Since 3 has conductivity, it can be made to have the same potential as the motor base 11, and noise can be prevented from entering the magnetic disk or the like by dropping it to ground.

Particularly, in this embodiment, since the main body member 23a of the thrust receiving member 23 is made of sapphire,
The hardness is high, and the surface roughness can be 0.1 μm or less (the surface accuracy can be extremely high). Therefore, the surface accuracy of the film 23b coated on the surface of the main body member 23a is also high, and the electrical The axial movement of the spindle hub 17 can be suppressed extremely well while achieving electrical continuity.

FIG. 3 shows a second embodiment of the present invention, in which the thrust receiving member 31 has a first structure.
Is different from the embodiment. That is, this thrust receiving member 31
Is obtained by injecting metal ions 31b into the surface of the main body member 31a made of ruby, for example, and processing the surface of the main body member 31a with a conductive material. That is, the main body member 31a
The metal ions 31b are diffused in the ruby single crystal lattice with high energy to change the physical properties of the ruby itself, thereby increasing the hardness and wear resistance of the ruby itself. The metal ions 31b are conducted to the closing plate 22 by the conductor 32.

According to the second embodiment, the surface accuracy and hardness can be further increased while ensuring the conductivity of the thrust receiving member 31, and the axial movement of the spindle hub 17 can be further restricted. It also has a long service life. The material of the main body member 31a may be sapphire or ceramics.

FIG. 4 shows a third embodiment of the present invention, in which the structure of the hydrodynamic bearing means 41 is different from that of the first embodiment. That is, in the hydrodynamic bearing means 41, instead of the bearing tube 16 of the first embodiment,
It differs from the first embodiment in that a jewel bearing 42 is provided and air is used as a fluid without using lubricating oil. The jewel bearing 42 is made of ruby or sapphire, has high bearing hardness, high surface accuracy (surface roughness of 0.1 μm or less), low friction, and excellent wear resistance. As a result, there is no problem even if air is used as the fluid, and it is possible to prevent the occurrence of oil mist.
Although the present invention is applied to the spindle motor in each of the above-described embodiments, it is needless to say that the present invention can be applied to other motors.

[0022]

As apparent from the above description, the present invention has the following effects. According to the invention of claim 1, since the rotary shaft of the rotor is rotatably supported via the hydrodynamic bearing means, the rotary shaft can be supported in a non-contact state by the dynamic pressure of the fluid. Therefore, it is possible to reduce the occurrence of vibration, and since the axial load applied to the end portion of the rotary shaft is received by the thrust receiving member, it is possible to regulate the axial movement, and further, this thrust receiving member can be regulated. Since the member is configured to have conductivity, it can have the same potential as the motor base.

According to the second aspect of the present invention, since the inner diameter of the bearing cylinder portion corresponding to the groove for generating the dynamic pressure is formed larger than the inner diameter dimension of the bearing portion corresponding to the groove, the rotation between the grooves can be prevented. The resistance can be reduced. According to the invention of claim 3, since the end of the rotary shaft on the thrust receiving member side is formed into a curved surface having the center of the rotary shaft as an apex, the rotation resistance can be reduced and stable rotation can be obtained. You can

According to the invention of claim 4, the thrust receiving member is formed by coating the surface of the main body member made of ruby, sapphire, or ceramics with a film made of a conductive material. The axial movement of the can be regulated extremely well. According to the fifth aspect of the invention, since the film is made of graphite, silver, platinum or titanium, it is possible to ensure good conductivity of the thrust receiving member.

According to the invention of claim 6, the thrust receiving member is configured such that metal ions are injected into the surface of the main body member made of ruby, sapphire or ceramics, and the surface of the main body member is processed into a conductive material. While ensuring the conductivity of the thrust receiving member, the surface accuracy and hardness can be further enhanced, the axial movement of the rotor can be further restricted, and the service life can be extended.

According to the invention of claim 7, since the hydrodynamic bearing means comprises the hydrodynamic groove formed on the rotary shaft and the jewel bearing corresponding to the outer peripheral surface of the rotary shaft, the friction is improved. It has less wear resistance and is excellent in wear resistance. Therefore, even if air is used as the fluid, there is no problem and it is possible to prevent the generation of oil mist.

[Brief description of drawings]

FIG. 1 is an overall vertical sectional side view showing a first embodiment of the present invention.

FIG. 2 is a vertical sectional side view of a thrust receiving member portion.

FIG. 3 is a vertical sectional side view of a thrust receiving member portion showing a second embodiment of the present invention.

FIG. 4 is an overall vertical sectional side view showing a third embodiment of the present invention.

FIG. 5 is an overall vertical sectional side view showing a conventional example.

[Explanation of symbols]

11 is a motor base, 13 is a stator core, 14 is a winding wire,
Reference numeral 15 is a stator, 16 is a bearing tube, 17 is a spindle hub (rotor), 18 is a rotary shaft, 19 is a groove, 20 is a hydrodynamic bearing means, 21 is a permanent magnet, 22 is a closing plate, and 23 is a thrust bearing. Reference numeral 23a is a main body member, 23b is a film, 31 is a thrust receiving member, 31a is a main body member, 31b is metal ions, 41 is a hydrodynamic bearing means, and 42 is a jewel bearing.

Claims (7)

[Claims] 1. A hydrodynamic bearing having a stator provided on a motor base, the stator core having windings, a rotating shaft made of a conductive material, and a permanent magnet rotating integrally with the rotating shaft. A rotor that is rotatably provided via a means, and a thrust receiver that is electrically conductive and electrically connected to the motor base and that receives an axial load applied to the end of the rotary shaft. A motor including a member. 2. The hydrodynamic bearing means comprises a plurality of grooves for dynamic pressure generation formed on the rotary shaft and a bearing cylinder corresponding to the outer peripheral surface of the rotary shaft, and the inter-grooves for dynamic pressure generation are provided. 2. The motor according to claim 1, wherein the inner diameter dimension of the bearing tube portion corresponding to is larger than the inner diameter dimension of the bearing tube portion corresponding to the groove. 3. The motor according to claim 1, wherein an end portion of the rotary shaft on the thrust receiving member side is formed into a curved surface having a central portion of the rotary shaft as an apex. 4. The motor according to claim 1, wherein the thrust receiving member is formed by coating a surface of a main body member made of ruby, sapphire or ceramics with a film made of a conductive material. 5. The motor according to claim 4, wherein the film is graphite, silver, platinum or titanium. 6. The thrust receiving member is characterized in that metal ions are injected into the surface of a main body member made of ruby, sapphire or ceramics, and the surface of the main body member is processed into a conductive material. The motor according to any one of 1 to 3. 7. The hydrodynamic bearing means comprises a hydrodynamic groove formed on the rotary shaft and a jewel bearing corresponding to the outer peripheral surface of the rotary shaft. Motor described.