JP2003061305A - Motor and disc device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain idling operation of a rotor during a standstill without degradation of the rotating performance thereof in a motor comprising a fluid dynamic pressure bearing mechanism. SOLUTION: In the motor 1, a magnetic body 14 is provided on a stator 12 side so as to face a magnet 31 of the rotor 11. The central position 31C of the magnet 31 is located on a stator 12 side for the central position 32C of an electromagnet 32. During a standstill, magnetic attraction between the magnet 31 and the magnetic body 41 causes a force facing the stator 12 side to act on the rotor 11, and a thrust plate 211 and a counter plate 23 of a shaft 21 are brought into contact with each other. Consequently, disturbance restrains the rotor 11 from idling in the thrust direction. During the rotation of the rotor 11, a deviation of the central position 31C from the central position 32C causes a force in the direction separating from the stator 12 to act on the rotor 11, thus permitting the rotation of the rotor 11 without degradation of the rotating performance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric motor having a fluid dynamic pressure bearing mechanism and a disk device using this motor.

[0002]

2. Description of the Related Art In an electric motor utilizing a fluid dynamic pressure bearing mechanism, conventionally, the center of a magnet on the rotor side and the center of an electromagnet on the stator are substantially aligned with each other in the direction of the rotation axis so that cogging torque, etc. Had improved the motor characteristics. On the other hand, in motors that use ball bearings and pivot bearings, the center of the magnet on the rotor side is displaced toward the stator side with respect to the center of the electromagnet, and the ferromagnetic body is placed on the stator side to maintain the preload of the bearing. By doing so, there is one in which a force in the thrust direction is always applied to the shaft.

[0003]

By the way, in many motors having a fluid dynamic bearing mechanism, the end of the shaft is a fluid dynamic pressure mechanism that receives a thrust load, and such a motor receives a radial load. The gap between members that generate dynamic pressure is set to be larger in the fluid dynamic pressure mechanism that receives a thrust load than in the fluid dynamic pressure mechanism. Further, as described above, in the motor having the fluid dynamic pressure mechanism, the thrust force is hardly applied to the shaft. Therefore, when a disturbance such as impact or vibration is applied when the motor is not rotating, the rotor is allowed to move in the thrust direction.

From the above, if the fluid dynamic pressure mechanism that receives the thrust load is improperly designed or processed, the rotor may move freely to cause product troubles when the motor is not rotating. For example, if an improper motor is used in a hard disk, the head may come into contact with the disk during transportation of the hard disk.

Further, in a motor having a fluid dynamic pressure bearing mechanism using oil, when the shaft abruptly moves in the thrust direction due to impact, bubbles are generated due to the squeeze effect in the fluid dynamic pressure mechanism that receives the thrust load, and May flow out from the seal portion, or a seizure phenomenon may occur due to rotation with bubbles.

[0006] On the other hand, it is conceivable to apply a force in the thrust direction to the shaft at all times by a method similar to that of a motor using a ball bearing or a pivot bearing to prevent the rotor from moving in the thrust direction during non-rotation. However, in such a method, a force acts on the shaft even during rotation, and a large force in the thrust direction needs to act on the rotor to prevent the shaft from moving. May be damaged. That is, when such a method is adopted, unless the number of rotations is increased, the dynamic pressure effect in the thrust direction may not be obtained, or the wear and damage may be severe. In some cases, the rotation itself may become difficult.

The present invention has been made in view of the above problems, and an object of the present invention is to suppress, in a motor having a fluid dynamic pressure bearing mechanism, the rotor's floating motion at rest without deteriorating the rotational performance.

[0008]

According to a first aspect of the present invention, there is provided an electric motor, comprising: a first member to which a magnet is arranged around a predetermined central axis; and the magnet. By a second member, which is arranged to face each other and provided with an electromagnet that generates a rotational force around the central axis, and one bearing element rotates relative to the other bearing element,
A fluid dynamic bearing mechanism for rotatably supporting the first member relative to the second member about the central axis; and a magnetic body provided on the second member, In the state where the first member is stationary with respect to the second member, the one bearing element is brought into contact with the other bearing element by the magnetic action generated between the magnet and the magnetic body. The relative movement of the first member and the second member in contact with each other is suppressed, and when the first member rotates with respect to the second member, the first action is caused by the magnetic action. The component of the force acting on the member in the central axis direction is canceled by the force generated between the magnet and the electromagnet.

According to a second aspect of the present invention, there is provided an electric motor, wherein a first member to which a magnet arranged around a predetermined central axis is attached, and a first member arranged so as to face the magnet are provided. A second member provided with an electromagnet that generates a rotational force around the central axis and one bearing element relatively rotate with respect to the other bearing element, so that the first element is centered around the central axis. Between the magnet and the magnetic body, a fluid dynamic pressure bearing mechanism that rotatably supports the member of FIG. 2 relative to the second member, a magnetic body provided on the second member. An auxiliary coil capable of canceling a magnetic action, and a magnetic action generated between the magnet and the magnetic body in a state where the first member is stationary with respect to the second member. Causes the one bearing element to abut the other bearing element. Relative movement between the first member and the second member is suppressed, and when the first member rotates with respect to the second member, the auxiliary coil cancels the magnetic action. To be done.

A third aspect of the present invention is the motor according to the first or second aspect, wherein the magnetic body has an annular shape centered on the central axis.

A fourth aspect of the present invention is the motor according to the first or second aspect, wherein the magnetic body comprises a plurality of magnetic bodies arranged at equal intervals in a circumferential direction of the central axis. Composed.

According to a fifth aspect of the present invention, there is provided the motor according to any one of the first to fourth aspects, wherein the one bearing element is a shaft, and an end portion of the shaft is a fluid dynamic body that receives a thrust load. The shaft is a thrust plate that is a part of a pressure mechanism, and in a state where the first member is stationary with respect to the second member, the shaft is generated by a magnetic action generated between the magnet and the magnetic body. A force having a component toward the thrust plate acts on the thrust plate.

According to a sixth aspect of the present invention, in the motor according to the fifth aspect, a convex portion is formed on a surface facing the thrust plate in the fluid dynamic pressure mechanism that receives the thrust load.

According to a seventh aspect of the present invention, in the motor according to the first aspect, the magnetic action causes a magnetic field between the one bearing element and the other bearing element to be perpendicular to the central axis. A force with components acts.

According to an eighth aspect of the present invention, there is provided a disk device in which a disc-shaped recording medium capable of recording information is mounted, the housing containing the recording medium and the recording fixed to the inside of the housing. The motor according to any one of claims 1 to 7 for rotating a medium, and access means for writing or reading information to or from the recording medium.

[0016]

1 is a diagram showing the internal structure of a general disk device 70 to which an electric motor 1 according to a first embodiment of the present invention is attached. A housing 71 provides a clean space inside the disk device 70 with extremely little dust. The housing 71 includes a plurality of disc plates 72 and disc plates 7 which are disc-shaped recording media.
An access unit 73 for writing and / or reading information to and from the disk 2, and a motor 1 for rotating the disk plate 72 are housed.

The access unit 73 is a head 731 that magnetically writes and reads information in and from the disk plate 72, an arm 732 that supports the head 731, and a head 731 by moving the arm 732.
And a head moving mechanism 733 for changing the relative position of the disk plate 72. With such a configuration, the head 7
Reference numeral 31 accesses a desired position on the disk plate 72 in a state of being close to the rotating disk plate 72, and writes and reads information.

FIG. 2 is a vertical sectional view showing the structure of the motor 1 according to the first embodiment. The motor 1 includes a rotor 11 that rotates around a central axis 11J and a stator 12 that is a mounting side.
The rotor 11 is rotatably supported with respect to the stator 12 by the fluid dynamic pressure bearing mechanism 2 using oil. The following description will be given with reference to the vertical direction of FIG. 2 as necessary.

The rotor 11 has a rotor body 111, a shaft 21 attached to the rotor body 111 at the position of the central axis 11J, and an annular magnet 31 attached inside the outer periphery of the rotor body 111. The ring-shaped magnet 31 is magnetized in the circumferential direction in multiple poles. The stator 12 includes a bracket 121, a hollow holder 122 attached to the center of the bracket 121, and a plurality of electromagnets 32 arranged around the holder 122. Further, in the stator 12, the sleeve 2 into which the shaft 21 is inserted
2, and the counter plate 23 facing the lower end of the shaft 21 is arranged in the holder 122.

The lower end of the shaft 21 is a disk-shaped thrust plate 211 sandwiched between the lower surface of the sleeve 22 and the upper surface of the counter plate 23, and spiral grooves are formed on the upper and lower surfaces of the thrust plate 211. It The thrust plate 211 is filled with oil, and when the shaft 21 rotates, the thrust plate 2
A fluid dynamic pressure effect is generated on the upper and lower surfaces of 11, and the upper and lower surfaces are in a non-contact state. That is, the upper and lower surfaces of the thrust plate 211, the lower surface of the sleeve 22 and the upper surface of the counter plate 23 constitute a fluid dynamic pressure mechanism that receives a thrust load directed toward the central axis 11J.

Oil is also filled between the outer surface of the shaft 21 around the axis and the inner surface of the sleeve 22, and a herringbone groove is formed on the outer surface of the shaft 21.
Therefore, when the shaft 21 rotates, the shaft 21
The fluid dynamic pressure effect is generated between the outer surface of the shaft 22 and the inner surface of the sleeve 22, and the outer surface of the shaft 21 and the inner surface of the sleeve 22 are not in contact with each other. That is, the outer surface of the shaft 21 and the inner surface of the sleeve 22 constitute a fluid dynamic pressure mechanism that receives a radial load.

As described above, the fluid dynamic pressure bearing mechanism 2 of the motor 1 is a combination of the fluid dynamic pressure mechanism which receives the radial load and the thrust load by the shaft 21, the sleeve 22 and the counter plate 23. . In addition, the sleeve 22 and the holder 122 are formed with a vent hole 22a for removing air bubbles generated in the oil of the fluid dynamic bearing mechanism 2.

The multi-pole magnetized annular magnet 31 and the plurality of electromagnets 32 are arranged around the central axis 11J so as to face each other, and by controlling the current applied to the plurality of electromagnets 32, the magnets 31 and A rotational force around the central axis 11J is generated between the plurality of electromagnets 32. As a result, the rotor 11 rotates with respect to the stator 12. At this time, the space between the shaft 21 and the sleeve 22 and the shaft 21
A fluid dynamic pressure is generated between the counter plate 23 and the counter plate 23, and the shaft 21 smoothly rotates in a non-contact state.

In the motor 1, two magnetic bodies 41 are further provided at a position on the stator 12 facing the magnet 31 on the rotor 11 with the central shaft 11J interposed therebetween. Also, the central axis 1
The center position 31C of the magnet 31 in the direction of 1J (hereinafter, referred to as "center position 31C") is lower than the center position 32C of the electromagnet 32 in the direction of the central axis 11J (hereinafter, referred to as "center position 32C"). It is arranged on the side (that is, on the magnetic body 41 side).

The magnetic body 41 is a ferromagnetic body such as iron. By disposing the magnetic body 41, the magnetic body 41 has an annular shape when the motor 1 is not rotating, that is, when the rotor 11 is stationary with respect to the stator 12. Magnetic attraction force is generated between the magnet 31 and the magnetic body 41 of the thrust plate 2
The force directed to the 11 side (downward in FIG. 2) acts. As a result, when the motor 1 is not rotating, the thrust plate 2
11 abuts on the counter plate 23. Since the two magnetic bodies 41 are symmetrically arranged with the central axis 11J in between, the radial force does not act on the shaft 21 via the rotor body 111. It should be noted that applying a force to the rotor 11 is equivalent to applying a similar force to the shaft 21.

The magnetic attractive force generated between the magnet 31 and the magnetic body 41 causes the rotor 11 to move upward (the shaft 21 moves away from the counter plate 23) due to the acceleration α received by the motor 1 during transportation. It is set to a size that does not move. That is, when the mass of the rotor 11 is m, the magnetic body 41 is arranged so that the magnetic attraction force is sufficiently larger than mα. As a result, it is possible to suppress the free movement of the rotor 11 using the thrust plate 211.

As shown in FIG. 2, since the center position 32C is located higher than the center position 31C, the magnet 31 is slightly attracted to the iron core of the electromagnet 32 even at rest. Therefore, the magnetic attraction force between the magnet 31 and the magnetic body 41 is F1, and the magnet 31 and the electromagnet 3 are at rest.
The central axis 11J direction component of the force generated between the second iron core and F is F
If it is 2, the size of F1 needs to be set so that (F1−F2) exceeds mα.

A convex portion 231 is formed at the center of the counter plate 23. As a result, the rotor 11 stands still and the thrust plate 211 and the counter plate 23
It is possible to reduce the amount of oil that moves from between these plates when and are brought into contact with each other, so that the thrust plate 211 and the counter plate 23 can be brought into immediate contact with each other. In the actual design, the diameter of the shaft 21 (the diameter of the portion supported by the sleeve 22) is determined based on the output characteristics of the motor 1, and the shaft 21 rotates against the contact between the thrust plate 211 and the convex portion 231. In consideration of the necessity of starting the process, the protrusion 231 is formed in the vicinity of the central axis 11J with a diameter equal to or smaller than the diameter of the shaft 21. This allows
At the time of rotation, the thrust plate 211 and the counter plate 23 can be brought into contact with each other at a portion where the relative speed is small, so that the torque required at the time of startup can be reduced and the wear damage at startup can be reduced.

When the electromagnet 32 is energized and the rotor 11 starts to rotate, the center position 31C of the magnet 31 is located below the center position 32C of the electromagnet 32, so that an upward force is applied to the magnet 31. To work. Since the magnet 31 and the electromagnet 32 are arranged around the central axis 11J, a force that faces upward (that is, a force in the opposite direction to the thrust plate 211 side) acts on the rotor 11 when the rotor 11 starts rotating.

The magnitude of the upward force is such that it cancels the action on the rotor 11 and the shaft 21 due to the magnetic attraction force between the magnet 31 and the magnetic body 41. That is, the magnetic attraction force between the magnet 31 and the magnetic body 41 is F1.
When the force generated between the magnet 31 and the electromagnet 32 during rotation is F3, the center position 31C of the magnet 31 and the center position 32 of the electromagnet 32 are set so that (F1-F3) becomes substantially zero.
The positional relationship with C is set. Therefore, the rotor 11
Thrust plate 21 even when the vehicle rotates at low speed
1 and the counter plate 23, a fluid dynamic pressure effect can be appropriately generated, and the rotation characteristics of the motor 1 are not impaired.

As described above, in the motor 1 according to the first embodiment, by disposing the magnetic body 41 on the stator 12 side, the thrust plate 21 is attached to the rotor 11 when stationary.
The force acting toward the first side (that is, the bracket 121 side) acts, and the shaft 21 is opposite to the thrust plate 211 (that is, the rotor 11 is the stator 1
It is suppressed that it floats in the direction away from 2. As a result, it is possible to reliably prevent the head 731 from coming into contact with the disk plate 72 even if the disk device 70 using the motor 1 shown in FIG. 1 receives a disturbance such as vibration.

On the other hand, when rotating, the magnet 31 and the electromagnet 3
Since the force acting on the rotor 11 (that is, the force acting on the shaft 21) is canceled by using the force generated between the rotor 2 and the rotor 11, the rotation performance is not deteriorated.

In the first embodiment, as shown in FIG. 2, the two magnetic bodies 41 are symmetrically arranged with the central axis 11J therebetween. As a result, the magnetic attraction between the magnet 31 and the magnetic body 41 is utilized to exert a force only on the rotor 11 in the thrust direction parallel to the central axis 11J. FIG. 3 shows a magnetic body 41 as a motor according to the second embodiment.
It is a top view which shows a mode that only one is arrange | positioned typically. The configuration of the motor is the same as that of the first embodiment except that only one magnetic body 41 is arranged, and the reference numerals in FIG. 2 are referred to as appropriate.

As shown in FIG. 3, when the arrangement of the magnetic body 41 is asymmetric with respect to the central axis 11J, the magnetic body 41 causes the shaft 21 to pass through the rotor body 111 and the component in the thrust direction and the radial direction (central axis). And a component in the direction perpendicular to 11J) acts. Therefore, when the rotor 11 is stationary with respect to the stator 12, the thrust plate
1 and the counter plate 23 are in contact with each other, and the shaft 21 is inclined by the component in the radial direction and is in contact with the inner surface of the sleeve 22.

In the motor according to the second embodiment, not only the thrust direction component of the magnetic attraction force between the magnet 31 and the magnetic body 41 but also the contact between the shaft 21 and the inner surface of the sleeve 22 is utilized. As a result, the rotor 11 is prevented from idling in the thrust direction when it is not rotating. In this way, the shaft 21 may be prevented from moving when it is stationary by contact between the shaft 21 and the sleeve 22. When only one magnetic body 41 is provided as shown in FIG.
Shaft 2 when stationary compared to motor 1 according to the embodiment of
The force of the component in the thrust direction acting on 1 can be reduced.

The radial component of the force acting on the shaft 21 does not affect the fluid dynamic pressure generated between the outer surface of the shaft 21 and the inner surface of the sleeve 22 when the rotor 11 rotates. Further, similarly to the first embodiment, the center position 31C of the magnet 31 is located below the center position 32C of the electromagnet 32, and the magnetism generated between the magnet 31 and the magnetic body 41 when the rotor 11 rotates. The thrust-direction component of the attractive force is canceled by the force generated between the magnet 31 and the electromagnet 32. As a result, when the motor 1 is operating, the rotor 11 is smoothly rotated by the fluid dynamic pressure bearing mechanism 2.

As shown in FIG. 4, the distance between the magnetic body 41 and the central axis 11J is changed to change the magnet 31 and the magnetic body 41.
By adjusting the relative positional relationship with
The magnitude of the radial component of the force acting on 1 may be appropriately adjusted.

FIG. 5 is a sectional view showing a state in the vicinity of the magnetic body 41 of the motor according to the third embodiment. Magnetic body 41
Are provided symmetrically with respect to the central axis 11J.
An auxiliary coil 42 is provided so as to cover the periphery of 1. Further, unlike the first embodiment shown in FIG. 2, the magnet 31 and the electromagnet 32 are arranged so that the center position 31C of the magnet 31 and the center position 32C of the center position 32C of the electromagnet 32 coincide with each other. The configuration other than these is the same as that of the first embodiment, and the same reference numerals as those of the first embodiment will be given to the description.

When the motor is stationary, no current is passed through the auxiliary coil 42. Therefore, as in the first embodiment, a force toward the thrust plate 211 acts on the rotor 11 by the magnetic attraction force generated between the magnet 31 and the magnetic body 41. As a result, the shaft 21 is prevented from moving in the thrust direction.

On the other hand, when the motor is operating, a predetermined circuit controls the energization of the auxiliary coil 42. A current corresponding to the motor rotation speed is applied to the auxiliary coil 42 so as to cancel the magnetization of the magnetic body 41 by the magnet 31. As a result, the magnetic attractive force generated between the magnet 31 and the magnetic body 41 is released, and the thrust force due to the influence of the magnetic body 41 does not act on the shaft 21. As a result, the magnetic substance 4
As in the case where 1 does not exist, the rotor 11 can rotate smoothly.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments and various modifications can be made.

The motor according to the above embodiment is an electric motor having a fluid dynamic pressure bearing mechanism, and can be used for any application as long as it is necessary to suppress the rotor from moving in the thrust direction. It is possible. The contact between the shaft and the sleeve also suppresses rotational movement of the rotor due to disturbance such as vibration.

Further, the location where the groove is formed in the fluid dynamic bearing mechanism 2 may be changed as appropriate. For example, the groove may be formed on the inner surface of the sleeve 22 instead of the outer surface of the shaft 21, and the groove may be formed on the upper surface of the counter plate 23 instead of forming the groove on the thrust plate 211.

In the above embodiment, the shaft 21 rotates in the sleeve 22, but the shaft may be fixed and the sleeve may rotate. Further, the stator may be provided with a magnet, and the rotor may be provided with an electromagnet. That is, in the fluid dynamic pressure bearing mechanism, one of the bearing elements constituting the bearing mechanism rotates relatively to the other bearing element, so that the stator supports the rotor relatively rotatable about the central axis. Anything can be used. Then, when stationary, one bearing element comes into contact with the other bearing element, so that relative play between the rotor and the stator is suppressed.

In the first and second embodiments, the magnetic body 41 may be a magnet (that is, a magnetized magnetic body). In this case, the magnetic action between the magnet and the magnetic body may be a magnetic repulsive force, and the repulsive force may be designed so that a force toward the stator side acts on the rotor.

The number of the magnetic bodies 41 is not limited to one or two, but three or more magnetic bodies 41 have a central axis 11J.
It may be arranged around. When the plurality of magnetic bodies 41 are arranged, as shown in FIG. 6, it is preferable that the plurality of magnetic bodies 41 are arranged at equal intervals in the circumferential direction of the central axis 11J. This prevents the radial force from acting on the rotor 11.

FIG. 7 is a diagram schematically showing a state in which the magnetic body 41 has an annular shape centered on the central axis 11J. In this case, even if the magnetic body 41 is a single member, it continuously exists around the central axis 11J, so that it is possible to prevent the rotor 11 from being subjected to a radial force. That is, when only one magnetic body 41 is provided, the magnetic body 41
Most preferably, is an annular shape.

The magnetic members 41 are preferably arranged at equal intervals in the circumferential direction of the central axis 11J, but may be arranged at arbitrary intervals or discontinuously with respect to the circumferential direction of the central axis 11J within a range that does not affect the rotation. May exist. In this case, the rotor 11
A force having a radial component perpendicular to the central axis 11J acts on, but the magnetic component is arranged so that the radial component is limited to a size that does not affect rotation.
Further, the current flowing through the electromagnet 32 may be controlled to cancel the radial component during rotation.

Furthermore, a force having only a radial component may be applied to the rotor 11 by the magnetic body 41. Even in this case, the outer surface of the shaft 21 and the inner surface of the sleeve 22 are in contact with each other, so that the shaft 21 can be prevented from moving in the thrust direction.

In the case of the third embodiment, since the magnetic attraction between the magnet 31 and the magnetic body 41 is released by the auxiliary coil 42, the magnetic body 41 is arranged at an arbitrary position on the stator 12 side. can do.

The auxiliary coil 42 may be arranged in any manner as long as it can release the magnetic attraction force generated between the magnet 31 and the magnetic body 41. For example, the auxiliary coil 42 does not include the magnetic body 41, but the auxiliary coil 42 may be arranged in the vicinity of the magnetic body 41.

In the above description, it was explained that a radial force perpendicular to the central axis 11J may be applied to the rotor 11 (shaft 21). However, the radial force may be a couple force (the shaft 21 to the central axis 11J). Force to rotate about an axis perpendicular to) is included.

In the motor 1 according to the above-mentioned embodiment, the annular multi-pole magnetized magnet 31 is used, but the magnet 31 may of course be composed of a plurality of magnets. On the contrary, the electromagnet 32 is not limited to the form that can be regarded as a plurality of electromagnets, and may be one electromagnet capable of generating a plurality of magnetic poles.

In the above embodiment, the motor having the fluid dynamic pressure bearing mechanism 2 using oil has been described. However, it is a fluid dynamic pressure bearing mechanism using a fluid other than oil such as air and magnetic fluid. However, the present invention can be applied.

Further, in the disc device 70 shown in FIG. 1, the disc plate 72 is fixed to the motor 1, but the disc plate 72 may be detachable from the motor 1. The head 731 is also used for writing or reading information to or from the disc plate 72
It is not limited to the magnetic method using. For example, a method using light or light and magnetism may be used.

[0056]

According to the invention of claims 1 to 7, it is possible to suppress the relative play between the first member and the second member at rest without deteriorating the rotational performance.

Further, in the invention of claim 5, the thrust plate can be used to suppress the floating motion, and in the invention of claim 6, the thrust plate can be brought into immediate contact with the facing surface.

In the eighth aspect of the invention, the disk device using the motor according to the first to seventh aspects prevents the recording medium and the access means from coming into contact with each other when subjected to vibration or the like. be able to.

[Brief description of drawings]

FIG. 1 is a diagram showing a general internal configuration of a disk device.

FIG. 2 is a vertical cross-sectional view of the motor according to the first embodiment.

FIG. 3 is a schematic diagram showing an arrangement relationship between a central axis and a magnetic body in the second embodiment.

FIG. 4 is a vertical cross-sectional view showing another example of arrangement of magnets and magnetic bodies.

FIG. 5 is a vertical cross-sectional view showing a state in the vicinity of a magnetic body of a motor according to a third embodiment.

FIG. 6 is a schematic view showing still another example of arrangement of magnets and magnetic bodies.

FIG. 7 is a schematic view showing an annular magnetic body.

[Explanation of symbols]

1 motor 2 Fluid dynamic bearing mechanism 11 rotor 11J central axis 12 stator 21 shaft 22 Sleeve 23 plates 31 magnets 32 electromagnet 41 Magnetic 42 Auxiliary coil 70 disk unit 72 disk plate 73 Access 211 Thrust plate 231 convex

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H02K 5/16 H02K 5/16 Z 21/22 21/22 MF term (reference) 3J011 AA11 BA04 CA02 JA02 KA02 KA03 LA05 MA21 5D109 BA01 BA14 BA16 BA17 BB12 BB18 BB21 BB22 5H605 AA00 AA02 BB05 BB19 CC02 CC04 CC05 DD03 DD16 EB01 EB03 EB21 EB28 EB35 5H607 AA00 AA05 AA05 A01050103 HH01 JK17 JK19

Claims (8)

[Claims] 1. An electric motor, comprising: a first member to which a magnet arranged around a predetermined central axis is attached; and a rotational force around the central axis, which is arranged so as to face the magnet. And a second member provided with an electromagnet that generates the electric field, and one of the bearing elements rotates relative to the other bearing element, so that the first member moves the first member about the central axis. A fluid dynamic bearing mechanism that rotatably supports the member, and a magnetic body provided on the second member, wherein the first member is stationary with respect to the second member. In this state, the one bearing element is brought into contact with the other bearing element by the magnetic action generated between the magnet and the magnetic body, and the first member and the second member Relative movement is suppressed, and the first member with respect to the second member A motor characterized in that, when rotating, a component of a force acting on the first member due to the magnetic action in the central axis direction is canceled by a force generated between the magnet and the electromagnet. 2. An electric motor, comprising: a first member to which a magnet arranged around a predetermined central axis is attached; and a rotational force around the central axis, which is arranged so as to face the magnet. And a second member provided with an electromagnet that generates the electric field, and one of the bearing elements rotates relative to the other bearing element, so that the first member moves the first member about the central axis. A fluid dynamic pressure bearing mechanism that rotatably supports the member, a magnetic body provided on the second member, and a magnetic action generated between the magnet and the magnetic body are released. An auxiliary coil that enables the one of the bearings by a magnetic action generated between the magnet and the magnetic body in a state where the first member is stationary with respect to the second member. An element abuts the other bearing element and the first part Relative movement between the second member and the second member is suppressed, and the magnetic action is canceled by the auxiliary coil when the first member rotates with respect to the second member. The motor to drive. 3. The motor according to claim 1, wherein the magnetic body has an annular shape centered on the central axis. 4. The motor according to claim 1, wherein the magnetic body is composed of a plurality of magnetic bodies arranged at equal intervals in a circumferential direction of the central axis. The motor to drive. 5. The motor according to claim 1, wherein the one bearing element is a shaft, and an end portion of the shaft is a part of a fluid dynamic pressure mechanism that receives a thrust load. A component that is a thrust plate and causes the shaft to move toward the thrust plate due to a magnetic action generated between the magnet and the magnetic body in a state where the first member is stationary with respect to the second member. A motor having a force acting on it. 6. The motor according to claim 5, wherein in the fluid dynamic pressure mechanism that receives the thrust load, a convex portion is formed on a surface facing the thrust plate. 7. The motor according to claim 1, wherein a force having a component perpendicular to the central axis acts between the one bearing element and the other bearing element by the magnetic action. A motor characterized by the following. 8. A disk device in which a disc-shaped recording medium capable of recording information is mounted, wherein the housing accommodates the recording medium, and the recording medium is fixed inside the housing to rotate the recording medium. 8. A disk device comprising: the motor according to any one of 1 to 7; and an access unit that writes or reads information on the recording medium.