JP2000329138A - Bearing device and motor using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a rotation stability of a rotating body and an enhancement of reliability by enhancing a rigidity of a dynamic pressure bearing portion and preventing a staying of an abrasion powder without requiring a processing which is complex and requires a labor and an increase in the number of components. SOLUTION: A thrust bearing 8 using a magnetic force applied to a space between a stator 40 side and a rotor 20 side and a radial bearing 7 using a dynamic pressure generated between an outer periphery 440 of a fixed shaft 44 and an inner periphery of a center hole 21 of the rotor 20 are formed between the rotor 20 and the stator 40 in a motor 5. A dynamic pressure- generating groove 441 for generating an air stream downwardly directed is formed on the outer periphery 440 of the fixed shaft 44. Since a pressure-rising portion 450 in which the dynamic pressure-generating groove 441 is not formed is formed at a lower end side of the fixed shaft 44, a rigidity of the radial bearing 7 is large. An air is drawn from the outside to an annular space 70 for generating a dynamic pressure by an annular air chamber 92 for an air damper and an annular space 91 for an air damper communicating the air chamber with the outside.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing device using dynamic pressure and a motor using the bearing device. More specifically, the present invention relates to a structure of a bearing device.

[0002]

2. Description of the Related Art Among various motors, for example,
In the motor disclosed in JP-A-31188, a spiral dynamic pressure generating groove is formed on the outer peripheral surface of a fixed shaft or the inner peripheral surface of a rotating body (sleeve) into which the fixed shaft is inserted. A motor using a dynamic pressure bearing that allows air to flow downwards as a radial bearing is disclosed. Further, in the dynamic pressure bearing disclosed therein, a dynamic pressure generating groove is formed in the entire area in the motor axis direction with respect to the outer peripheral surface of the fixed shaft or the inner peripheral surface of the rotating body. In addition, as the dynamic pressure bearing, among those between the fixed shaft and the rotating body, those configured to generate airflow from both sides in the motor axis direction toward the center, or from the center in the motor axis direction to both ends. There is a configuration that generates a heading airflow. Further, there may be a case where a groove penetrating in the axial direction of the motor is formed in order to impart a pressure gradient to the air pressure generated between the outer peripheral surface of the fixed shaft and the inner peripheral surface of the rotating body. When any of these dynamic pressure bearings is used, the rotating body rotates without contact with the fixed shaft. Therefore, wear of the rotating body and the fixed shaft does not occur, so that the life of the motor can be extended.

As a method of fixing a fixed shaft in an upright posture with respect to a motor frame or the like, conventionally, a hole for inserting the fixed shaft into a frame and a shaft end of the fixed shaft is press-fitted into the hole, Alternatively, there is a method of performing crimping after inserting the shaft end of the fixed shaft into the hole.

[0004]

However, in the conventional dynamic pressure bearing, there is a problem that rigidity is low and rotation stability is low because the rotating body rotates in a non-contact state with respect to the fixed shaft. . In addition, even in the case of a dynamic pressure bearing, when the stationary shaft and the rotating body are in contact with each other at the time of stopping, abrasion powder is generated at the time of startup or at the time of stopping. In the configuration in which the airflow generated between the upper and lower portions in the motor axial direction is directed upward, the configuration is directed from both sides to the center in the motor axial direction, or the configuration is such that the airflow is generated from the center to both ends in the motor axis direction, Wear powder may accumulate between the body and the body, causing a burn-in between the fixed shaft and the rotating body.

Further, as in the motor disclosed in Japanese Patent Application Laid-Open No. 64-3318, an air dynamic pressure bearing is used as a radial bearing, and a magnetic force generated between magnets disposed on the rotor side and the stator side is utilized. Then, in a motor in which the rotor is lifted in the thrust direction, the rotor is completely in a non-contact state during rotation, so that high-speed rotation is possible. However, in such a motor, the rotor easily moves up and down. Therefore,
A configuration has been considered in which an annular air chamber for an air damper is formed between a fixed shaft and a rotor, and the air chamber communicates with the outside through a small hole (orifice). With this configuration, an air damper can be added to the motor by the small hole and the annular air chamber for the air damper, so that the vertical movement of the rotor can be suppressed by resistance when air passes through the small hole. . However, to construct such an air damper, small holes or grooves functioning as orifices are required. However, when such holes are formed by drilling, no matter how small the holes are to be formed. , Φ0.4 mm and a hole with a length of about 5 mm are the limits. Further, when such a perforated member is fastened to another member with a screw or the like to form an air damper annular air chamber, the air damper annular air chamber communicates with the outside through the joint surface. It may not function as a damper. In addition, as the size of the motor increases, the air damper needs to increase the flow resistance at the orifice, so a thin and long hole is required as the orifice. It is difficult with the processing method.

Further, when the fixed shaft is fixed to the motor frame, as in the prior art, when the motor is used for high-speed rotation driving of the polygon mirror, the centrifugal force is generated when the motor is used for driving the polygon mirror at high speed. The resulting stress acts on the joint between the fixed shaft and the frame, and loosening and rattling are likely to occur. As a result, the verticality of the fixed axis is reduced, and the polygon mirror may be tilted.

[0007] In view of the above problems, an object of the present invention is to provide:
Improving the rotational stability and reliability of the rotating body by increasing the rigidity of the hydrodynamic bearing part and preventing the accumulation of abrasion powder without the need for complicated and time-consuming processing and an increase in the number of parts. An object of the present invention is to provide a bearing device that can be achieved and a motor using the bearing device.

Another object of the present invention is to provide a bearing device provided with an air damper having a high degree of freedom in setting a damping rate with a small number of parts without performing complicated and laborious processing, and to use this bearing device. To provide a suitable motor.

Further, an object of the present invention is to prevent the joint between the fixed shaft and the frame from becoming loose even when the rotating body rotates at a high speed, and to maintain the verticality of the fixed shaft. It is to provide a motor.

[0010]

According to the present invention, in order to solve the above-mentioned problems, the present invention provides the above-mentioned structure in which the fixed shaft is provided between an outer peripheral surface of the fixed shaft and an inner peripheral surface of a center hole of a rotating body into which the fixed shaft is inserted. At least one side of a communication passage through which air can flow in from the outside, an inner peripheral surface of the center hole of the rotating body, and an outer peripheral surface of the fixed shaft from above to below along the axial direction of the fixed shaft. A dynamic pressure generating portion for generating a downward airflow by a dynamic pressure generating groove formed in the above, and the dynamic pressure generating groove is not formed in order to increase the air pressure of the airflow supplied from the dynamic pressure generating portion The booster is formed in this order. Here, the length of the booster in the motor axis direction is a dimension corresponding to about １ ／ of the entire length of the fixed shaft.

In the bearing device configured as described above,
During the rotation of the rotating body, the air flow (dynamic pressure) generated by the dynamic pressure generating section is between the outer peripheral surface of the fixed shaft and the inner peripheral surface of the rotating body.
Keeps the rotating body and the fixed shaft in a non-contact state, so that high-speed rotation is possible. Further, since the rotating body and the fixed shaft are not in contact with each other, the rotating body and the fixed shaft do not wear. Further, the air pressure generated in the dynamic pressure generating section is increased in the pressure increasing section in which the dynamic pressure generating groove is not formed, so that the rigidity of the dynamic pressure bearing is high. Therefore, the rotation stability of the rotating body is high. Furthermore, even in the case of a dynamic pressure bearing, the rotating body and the fixed shaft come into contact with each other at the time of stop, so that there is a possibility that abrasion powder may be generated at the time of start and at the time of stop. The airflow is generated only toward the airflow, and the air is supplied from the outside to the dynamic pressure generation unit via the communication unit, so that the downward airflow can be generated smoothly. As a result, the abrasion powder moves smoothly downward by the airflow and the gravity, and is discharged from between the rotating body and the fixed shaft. Therefore, the reliability of the bearing device can be improved, for example, seizure does not occur between the rotating body and the fixed shaft.

[0012] In the present invention, there is further provided a thrust bearing for holding the rotating body at a predetermined position in the axial direction of the fixed shaft by a magnetic force acting between the rotating body side and the fixed shaft side, and the communication passage. It is preferable that an annular air chamber for the air damper communicating with the dynamic pressure generating portion and an annular gap for the air damper for communicating the annular air chamber for the air damper with the outside are formed. With this configuration, when the rotating body starts rotating, the rotating body is held at a magnetically balanced position in the thrust bearing. In this state, the rotating body and the fixed shaft are completely out of contact with each other, so that the rotating body can rotate at high speed. Further, since the fixed shaft and the rotating body are completely out of contact with each other, there is no wear and the like, and the life of the bearing device can be extended. However, a thrust bearing using magnetic force has a small rigidity, so that the rotating body vibrates in a vertical direction due to an external force or the like. However, in the present invention, when the rotating body vibrates up and down due to disturbance in the motor axial direction, the air in the air damper annular air chamber is discharged from the air chamber through the narrow air damper annular gap, or Air is sucked into the annular air chamber from the outside through the annular gap for the air damper. At this time, intake and exhaust in the annular air chamber for the air damper through the annular gap for the air damper generates friction of the air, and the friction absorbs vertical vibration energy of the rotating body. Vibration can be suppressed. Further, in the case of the air damper according to the present invention, depending on the shape of the outer peripheral surface of the fixed shaft and the inner peripheral surface of the rotating body, the gap size and the axial length of the annular gap for the air damper are determined. Can be arbitrarily designed. Therefore, it is possible to configure a bearing device with a built-in air damper that can freely set the damping rate in the vertical vibration of the rotating body without performing complicated and troublesome processing and with a small number of parts.

In the present invention, a small diameter portion and a large diameter portion for forming the annular gap for the air damper and the dynamic pressure generating portion are provided on an outer peripheral surface of the fixed shaft and an inner peripheral surface of the center hole of the rotating body. Portion is formed, a step portion between the small diameter portion and the large diameter portion formed on the outer peripheral surface of the fixed shaft, and the small diameter portion and the large diameter portion formed on the inner peripheral surface of the center hole. Preferably, the annular air chamber for the air damper is formed by a portion facing the stepped portion.

Such a bearing device is suitable for a motor, especially a motor for rotating a polygon mirror at high speed. Here, when the bearing device is used for a motor,
The stator includes a stator core around which a drive coil is wound, the fixed shaft, and a frame that holds a lower end of the fixed shaft, while the rotating body includes a rotor magnet facing the stator core as a rotor. Configuration.

In the present invention, the frame includes a fixed shaft insertion hole through which a lower end of the fixed shaft is inserted, and the fixed shaft is in contact with an upper surface side of the frame and the fixed shaft insertion hole of the fixed shaft. A step portion that defines an insertion depth with respect to, and a shaft end portion that penetrates through the fixed shaft insertion hole and protrudes downward from the frame, and the shaft end portion of the fixed shaft has a lower surface side of the frame. It is preferable to attach a fastener for fixing the fixed shaft upright with respect to the frame by fixing the fixed shaft to the frame by fixing the fixed shaft to the shaft end so as to sandwich the spring in a compressed state. With this configuration, even if the rotor rotates at high speed and the stress caused by the centrifugal force is transmitted to the joint between the fixed shaft and the frame, the spring absorbs such stress. Therefore, the verticality of the fixed axis does not decrease.

In the present invention, the fastener is, for example, a push nut attached to a shaft end of the fixed shaft such that a leaf spring as the spring is sandwiched between the frame and the frame.

[0017]

Embodiments of the present invention will be described with reference to the drawings.

1 and 2 are a plan view and a sectional view, respectively, of a polygon mirror driving device using a motor to which the present invention is applied. FIG. 3 is an enlarged half sectional view showing a bearing device and a motor used in the polygon mirror driving device.

(Overall Configuration) In FIGS. 1 and 2, a polygon mirror driving device 1 according to the present embodiment generally includes a motor 5 configured on an iron substrate 10 (plate-shaped frame).
And a polygon mirror 30 mounted on the rotor 20 of the motor 5 and a case 2 covering the entire motor 5 and the polygon mirror 30. The case 2 is a dustproof and soundproof cover. A connector 1 for outputting a drive signal to the drive coil 41 is provided on the substrate 10.
4 is mounted by soldering or the like.

In FIG. 3, a motor 5 includes a stator 40 having a stator core 42 around which a drive coil 41 is wound and a fixed shaft 44, a center hole 21 into which the fixed shaft 44 is inserted, and a rotor magnet 22 facing the stator core 42. And a rotor 20 (rotating body) including the above.

(Structure of Stator) In this embodiment, in the stator 40, the base end side of the fixed shaft 44 is fitted into the fixed shaft insertion hole 11 formed in the iron substrate 10, and the fixed shaft insertion hole 11 A push nut 12 (fastener) is attached to the protruding shaft end 443 on the lower surface of the substrate 10 so as to compress the disc spring 134 between the shaft end 443 and the lower surface of the substrate 10. This push nut 12
The lower end 12a is engaged with the shaft end 443 by being pushed into the shaft end 443 of the fixed shaft 44, and the return is regulated. In this state, the fixed shaft 44
Is vertically fixed to the substrate 10 by a push nut 12 (fastener) and a disc spring 13.

In the stator 40, a core holder 43 is fixed on the substrate 10, and a thin stator core 42 is fixed on the outer peripheral surface of the core holder 43 in a laminated state. The drive coil 41 is wound around the pole. Here, as for the core holder 43, the core holder 43 is installed on the substrate 10 with the outer peripheral surface serving as a mounting portion of the stator core 42 and the lower end surface of the cylindrical portion 431 as a contact surface on the substrate 10. Sometimes the fixed step portion 4 of the fixed shaft 44
An annular fixing portion 432 sandwiched between the substrate 42 and the substrate 10 is provided. Therefore, the fixing step portion 44 of the fixed shaft 44
2 is pressed against the upper surface of the substrate 10 via the annular fixing portion 432 of the core holder 43 so that the fixed shaft insertion hole 11 of the fixed shaft 44 is formed.
After determining the insertion depth with respect to the
0, and when fixed via the push nut 12 and the disc spring 13 which is pressed and compressed by the push nut 12, the annular fixing portion 43 of the core holder 43.
2 is sandwiched between the fixing step portion 442 of the fixed shaft 44 and the substrate 10 so that the core holder 43
Fixed on top.

(Structure of Rotor) In this embodiment, the rotor 20 has a rotor main body 25 having a center hole 21 and a rotor main body 2 extending from the rotor main body 25 to the outer peripheral side.
5, a yoke 27 fixed to the lower surface side of the
And a rotor magnet 22 fixed to the inner peripheral surface of the rotor. The rotor magnet 22 is adhesively fixed to the yoke 6 and then caulked and fixed to an annular projection 251 formed on the lower end surface of the rotor body 25. Here, the rotor body 25 is provided for the purpose of improving its wear resistance and corrosion resistance.
Surface treatment such as alumite treatment or plating treatment may be applied. Further, in this embodiment, when the unbalance amount is too large at the time when the rotor 20 is formed, the balance performance of the rotor 20 may be improved by giving a weight or the like to the annular protrusion 251.

A pedestal portion 26 on which a polygon mirror 30 is mounted is formed on the outer peripheral side of the rotor body 25. The polygon mirror 30 mounted on the pedestal portion 26 is supported by a ring-shaped mirror pressing member 50. It is pressed and fixed to the part 26. This mirror pressing member 50 is
The cylindrical portion 250 of the rotor body 25 is passed through the central hole 501, and in this state, the plurality of claw portions 502 projecting inside the central hole 501 are elastically deformed, and the engagement grooves formed on the outer peripheral surface of the cylindrical portion 250. By engaging with 255, the mirror pressing member 50 is fixed to the rotor main body 25. Here, the polygon mirror 30 has its center hole 3
00, the cylindrical portion 256 of the rotor main body 25 is passed through, and when the cylindrical portion 256 of the rotor main body 25 passes through the central hole 300 of the polygon mirror 30, an excessive force is applied to the polygon mirror 30 to cause the polygon mirror 30 to move. The center hole 300 and the cylindrical portion 25 of the rotor body 25 are not deformed.
6, a predetermined clearance is secured. Therefore, the mirror pressing member 50 elastically presses and fixes the polygon mirror 30 toward the pedestal portion 26 by a spring 505 formed on itself (or a spring 505 separately mounted between the polygon mirror 30). I have. Therefore, the polygon mirror 30 is positioned and fixed by the frictional force with the upper surface of the base 26.

For this reason, when the rotor 20 rotates, the centrifugal force received by the rotor 20 and the centrifugal force received by the polygon mirror 30 due to the difference between the outer diameter of the rotor 20 and the outer diameter of the polygon mirror 30 are different. Since there is a difference between them, these members swell independently of each other due to centrifugal force, and the degree differs. As a result, the polygon mirror 30 may be displaced on the pedestal portion 26 of the rotor 20 while the motor 5 repeatedly starts and stops. On the other hand, the mirror pressing member 50 is completely fixed to the fixed shaft 44 and does not deform due to centrifugal force. Therefore, in this embodiment, the mirror pressing member 50
The friction force generated between the polygon mirror 30 and the polygon mirror 30 is made larger than the friction force generated between the polygon mirror 30 and the pedestal portion 26 of the rotor 20. For example, an alumite process, a plating process, a nitriding process, and a coating process are performed on at least the pedestal portion 26 of the rotor 20 on the surface of the rotor 20, and the polygon mirror 30 is formed.
The frictional force generated between the rotor 20 and the pedestal 26 of the rotor 20 is reduced. On the other hand, the mirror pressing member 50
As with the polygon mirror 30, the mirror pressing member 50 and the polygon mirror 3 are made of aluminum.
The frictional force generated between 0 and 0 is increased. Therefore,
Even if the motor 5 is repeatedly started and stopped, the polygon mirror 30 is always positioned by the mirror pressing member 50, so that the polygon mirror 30 is displaced on the pedestal portion 26 of the rotor 20 and the polygon mirror 30 vibrates. Does not occur. Even if the mirror pressing member 50 and the polygon mirror 30 are fixed with an adhesive, the displacement of the polygon mirror 30 on the pedestal portion 26 of the rotor 20 can be prevented.

In this embodiment, the mirror pressing member 50
Has a ring shape having a predetermined width as shown in FIG. The mirror pressing member 50 is generally annular, but has a central hole 50 through which the cylindrical portion 250 passes.
The two points symmetrical with respect to 1 have a shape in which the outer peripheral side is linearly cut, and this part is a cut scheduled part 506 whose width dimension is about 程度 narrower than other parts. . That is, after the polygon mirror 30 is pressed and fixed on the rotor 20 by the mirror pressing member 50, the mirror pressing member 50 is fitted in the engagement groove 255 of the rotor main body 25 even when the polygon mirror 30 is desired to be removed. Therefore, in the present embodiment, a narrow cutting portion 506 is formed in advance on the mirror pressing member 50, and the mirror pressing member 50 has a spring 505 between the mirror pressing member 50 and the polygon mirror 30. The part to be cut 5
If a nipper (not shown) is inserted into 06, the mirror pressing member 50 can be easily cut.
Therefore, since the mirror pressing member 50 can be easily removed from the rotor body 25, the polygon mirror 30 can be removed without damaging it.

(Structure of Thrust Bearing of Bearing Device) In the motor 5 thus configured, the rotor 20 is supported on the fixed shaft 44 by a bearing device including a thrust bearing 8, a radial bearing 7 and an air damper 9 described below. Have been.

First, between the rotor 20 and the stator 40, the magnetic force acting between the magnet 81 disposed at the upper end of the fixed shaft 44 and the magnet 82 disposed at the upper end of the rotor 20, and the stator core 42 and rotor magnet 2
A thrust bearing 8 in which the stator 40 supports the rotor 20 in the thrust direction by using a magnetic force acting between the thrust bearing 8 and the thrust bearing 8. That is, the rotor magnet 22 magnetically attracts the stator core 42 and the rotor 20
And a pair of magnets 81 fixed to the side of the stator 40,
82 are opposed to each other with different poles, and the fixed shaft 44 is
An attempt is made to hold the rotor 20 at a predetermined position in the direction of the motor axis L. As described above, the thrust bearing 8 is configured by using the magnetic force acting at these two locations.
High positioning accuracy in the motor axis L direction. Also,
Since the resonance point in the direction of the motor axis L is high, more stable high-speed rotation is possible.

(Structure of the dynamic pressure bearing / radial bearing of the bearing device) Further, a gap formed between the outer peripheral surface 440 of the fixed shaft 44 and the inner peripheral surface of the rotor 20 between the rotor 20 and the stator 40. Using the dynamic pressure generated in the stator 40
Radial bearing 7 for supporting the rotor 20 in the radial direction
Is configured. Here, on the outer peripheral surface of the fixed shaft 44,
A surface treatment is applied to improve abrasion resistance and seizure resistance.
No. 9966, and a resin coating of polyamideimide.

On the fixed shaft 44, the surface of the polyamide-imide resin coating layer is provided with a counterclockwise direction (a direction indicated by an arrow CCW in FIG. 1) when viewed from the tip of the shaft.
In addition, a dynamic pressure generating groove 441 such as a herringbone or a spiral groove is formed by a method such as cutting. Accordingly, when the rotor 20 rotates counterclockwise as viewed from above, the dynamic pressure generating portion 71 in which the dynamic pressure generating groove 441 is formed is moved by the outer peripheral surface 440 of the fixed shaft 44 and the inner peripheral portion of the center hole 21 of the rotor main body 25. Only a downward airflow is generated between the surfaces. Therefore, when the motor 5 is stopped, the rotor 20 that has been slightly floating due to the thrust bearing 8 becomes slightly sinked when it starts rotating, and is held at a magnetically balanced position in the thrust bearing 8. Is done. In this state, since the stator 40 and the rotor 20 are not in contact with each other, the rotor 20 can rotate at a high speed.

In this embodiment, the center hole 2
1 of the outer peripheral surface 440 of the fixed shaft 44, the lower end corresponding to the downstream of the airflow is about 1% of the entire length of the fixed shaft 44.
As shown in FIG. 2, the portion corresponding to / 4 does not have the dynamic pressure generation groove 441 as the pressure increasing portion 450 for increasing the air pressure of the air flow supplied from the dynamic pressure generating portion 71. Therefore, in the radial bearing 7 as the dynamic pressure bearing, the dynamic pressure rigidity (dynamic pressure) is high.

(Configuration of the Air Damper of the Bearing Device) In the motor 5 configured as described above, the fixed shaft 44 has a large diameter portion 446 at the center in the axial direction, and the upper end of the large diameter portion 446. A small diameter portion 447 is formed on the side. For this reason, the outer peripheral surface 440 of the fixed shaft 44
In, a step portion 448 is formed between the large diameter portion 446 and the small diameter portion 447. Here, a boundary portion 449 between the large-diameter portion 446 and the small-diameter portion 447 is further deeply cut and dented. Therefore, even if the rotor 20 shifts downward, the boundary portion 449 between the large diameter portion 446 and the small diameter portion 447.
Is not hit by the rotor 20. Such a shape
Since the outer peripheral surface 440 of the fixed shaft 44 can be formed by processing with the same processing machine,
The coaxiality is high in any of the parts.

On the other hand, the inner peripheral surface of the center hole 21 of the rotor 20 also has a large diameter portion 2 at a central portion in the axial direction.
A small diameter portion 217 is formed on the upper end side of the large diameter portion 216. Therefore, on the inner peripheral surface of the center hole 21 of the rotor 20, the large diameter portion 216 and the small diameter portion 2
A step part 218 is formed between the step part 218 and the step 17. Here, a boundary portion 219 between the large diameter portion 216 and the small diameter portion 217
Is cut further to the bottom and dented. In addition, fixed shaft 4
At 4, the corner 444 of the large diameter portion 216 is chamfered. Therefore, even if the rotor 20 is displaced downward, the fixed shaft 44 is attached to the boundary portion 219 between the large diameter portion 216 and the small diameter portion 217.
Corner 444 does not hit. Such a shape can also be formed by processing the inner peripheral surface of the center hole 21 with the same processing machine, so that the coaxiality is high in any part of the center hole 21.

Here, the large-diameter portion 216 and the small-diameter portion 217 formed on the inner peripheral surface of the center hole 21 of the rotor 20
The large-diameter portion 446 and the small-diameter portion 447 formed on the outer peripheral surface of the fixed shaft 44 are formed to be slightly larger by about 20 μm. Therefore, when the fixed shaft 44 is inserted into the center hole 21 of the rotor 20, the large-diameter portion 44 is formed between the outer peripheral surface of the fixed shaft 44 and the inner peripheral surface of the center hole 21 of the rotor 20.
An annular gap 70 for generating dynamic pressure is formed in a region where the gaps 6 and 216 overlap in the radial direction and the gap dimension is slightly wider than 10 μm. Further, a small diameter portion 44 is formed between the outer peripheral surface 440 of the fixed shaft 44 and the inner peripheral surface of the center hole 21 of the rotor 20.
In a region where the elements 7 and 217 overlap each other in the radial direction, a gap dimension of an air damper 9 described later is about 10 μm.
Is formed in the annular gap 91 (communication portion) for the air damper. Furthermore, in this embodiment, the small diameter portion 447 of the outer peripheral surface 440 of the fixed shaft 44 and the large diameter portion 447 of the inner peripheral surface of the center hole 21 of the rotor 20 partially overlap in the radial direction. Step portion 448 and rotor 20
The annular air chamber 9 for the air damper is formed by a slightly larger annular space defined by the stepped portion 218 of the center hole 21 of the air damper.
2 (communication part) is formed.

Therefore, in this embodiment, the motor axis L is provided between the outer peripheral surface 440 of the fixed shaft 44 and the inner peripheral surface of the center hole 21.
Along the direction, the outer peripheral surface 440 of the fixed shaft 44 and the center hole 21
An annular gap 70 (dynamic pressure generating section 71) for generating dynamic pressure between the inner peripheral surfaces of the air gap, an annular air chamber 92 for an air damper communicating with the annular gap 70, and an annular air for the air damper An annular gap 91 for the air damper for communicating the chamber 92 with the outside is formed in this order, and the annular air chamber 92 for the air damper and the annular gap 91 for the air damper constitute the air damper 9 for the rotor 20.

(Operation and Effect of the Present Embodiment) In the motor 5 configured as described above, when the rotor 20 rotates counterclockwise as viewed from above, the outer peripheral surface 440 of the fixed shaft 44 and the rotor 2
In the annular gap 70 for generating dynamic pressure between the inner peripheral surface of the outer ring 0 and the dynamic pressure generating section 71 in which the dynamic pressure generating groove 441 is formed, the annular gap 91 for the air damper and the annular air chamber 92 for the air damper are externally mounted. And a downward airflow while drawing in air from the outside. The dynamic pressure generated by this air flow is generated between the stator 40 and the rotor 20.
And in a non-contact state in the radial direction. At this time, a dynamic pressure generating groove 441 is formed at the lower end of the outer peripheral surface 440 of the fixed shaft 44.
Is formed, the air pressure of the airflow supplied from the dynamic pressure generating unit is increased by the boosting unit 450. Therefore, in the motor of this embodiment, dynamic pressure rigidity (dynamic pressure) is high instead of using a dynamic pressure bearing as the radial bearing 7. Therefore, the rotation stability of the rotor 2 is high.

Further, while the motor 5 is stopped, the rotor 20 which has slightly floated upward when it starts rotating, sinks slightly downward and is held at a position where the thrust bearing 8 is magnetically balanced. In this state, the stator 40
And the rotor 20 are in a completely non-contact state, so that the rotor 20 can rotate at a high speed. Further, since the stator 40 and the rotor 20 are completely out of contact with each other, there is no wear and the like, and the life of the motor 5 can be extended.

However, the thrust bearing 8 utilizing magnetic force is
Since the rigidity is relatively small, the rotor 20 vibrates in the vertical direction due to an external force or the like. However, in the motor 5 of the present embodiment, even when the motor 5 vibrates up and down due to disturbance in the direction of the motor axis L in the air damper 9 including the annular air chamber 92 for air damper and the annular gap 91 for air damper, The air in the annular air chamber 92 is discharged to the outside through the narrow gap 91 for the air damper, or the air gap 92 for the air damper is discharged.
Air from outside passes through the annular air chamber 92 for the air damper.
Get inside. When such exhaust and intake occur, the annular gap 91 for the air damper generates friction with air. As a result, the vibration energy in the vertical direction of the rotor 20 is absorbed, so that the vibration is suppressed.

In the case of the air damper 9 configured in the motor 5 of the present embodiment, the air damper 9 depends on the shape of the outer peripheral surface 440 of the fixed shaft 44 and the inner peripheral surface of the center hole 21 of the rotor 20. The gap size of the annular gap 91 for the damper and the length dimension in the axial direction of the motor 5 can be arbitrarily designed. Therefore, the motor 5 with the built-in air damper 8 that can freely set the damping rate in the vertical vibration of the rotor 20 can be configured with a small number of parts without performing complicated and troublesome processing.

Further, when a dynamic pressure bearing is used as the radial bearing 7, abrasion powder tends to be generated at the time of starting or stopping, but in the present embodiment, the abrasion powder is promoted to fall by gravity. The air flow generated by the dynamic pressure generating section 71 is set so as to be supplied downward, so that such abrasion powder is removed from the fixed shaft 44 and the rotor body 25.
Is forcibly pumped downward from between the center hole 21 of
Released outside. Therefore, the fixed shaft 44 and the rotor body 2
The problem that abrasion powder stays with the center hole 21 of 5 and causes seizure can be avoided.

Further, since the fixed shaft 44 is vertically fixed to the substrate 10 via the push nut 12 and the disc spring 13 while being inserted into the fixed shaft insertion hole of the substrate 10, the rotor 2 rotates at a high speed. Even if a stress due to the centrifugal force at this time is applied to the joint between the fixed shaft 44 and the substrate 10, such a stress is absorbed by the disc spring 13.
Therefore, since the push nut 12 is not loosened, the verticality of the fixed shaft 44 can always be maintained.

(Other Embodiments) In the above embodiment, the large-diameter portions 446, 2, and 2 for forming the dynamic pressure generating portion 71 are provided on the outer peripheral surface 440 of the fixed shaft 44 and the inner peripheral surface of the center hole 21.
16 and small-diameter portions 447 and 217 for forming the annular gap 91 for the air damper, respectively. Contrary to such a configuration, the outer peripheral surface 440 of the fixed shaft 44 and the center hole are formed. A small diameter portion for forming a dynamic pressure generating portion and a large diameter portion for forming an annular gap for an air damper may be formed on the inner peripheral surface of the inner portion 21. Even in such a configuration, the fixed shaft 4
The stepped portion between the small-diameter portion and the large-diameter portion formed on the outer peripheral surface 440 and the stepped portion between the small-diameter portion and the large-diameter portion formed on the inner peripheral surface of the center hole face each other. In this portion, an annular air chamber for an air damper can be formed.

[0043]

As described above, in the bearing device and the motor according to the present invention, the air flow (dynamic pressure) generated in the dynamic pressure generating section keeps the rotating body and the fixed shaft in a non-contact state.
High speed rotation is possible. Further, since the rotating body and the fixed shaft are not in contact with each other, the rotating body and the fixed shaft do not wear. Further, the air pressure generated in the dynamic pressure generating section is increased in the pressure increasing section in which the dynamic pressure generating groove is not formed, so that the rigidity of the dynamic pressure bearing is high. Therefore, the rotation stability of the rotating body is high. Furthermore, the dynamic pressure generation section generates airflow only downward, and air is supplied from outside to the dynamic pressure generation section via the communication section, so that the downward airflow can be smoothly generated. Can be. Therefore, the abrasion powder generated between the rotating body and the fixed shaft moves smoothly downward due to the airflow and the gravity, and is discharged from between the rotating body and the fixed shaft. Therefore, the reliability of the bearing device can be improved, for example, seizure does not occur between the rotating body and the fixed shaft.

[Brief description of the drawings]

FIG. 1 is a plan view of a polygon mirror driving device using a motor to which the present invention is applied.

FIG. 2 is a sectional view of the polygon mirror driving device shown in FIG.

FIG. 3 is an enlarged half sectional view showing a structure of a fixed shaft and a rotor in the polygon mirror driving device shown in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polygon mirror drive device 2 Case 5 Motor 8 Thrust bearing 9 Air damper 10 Substrate 11 Fixed shaft insertion hole 12 Push nut (fastener) 13 Disc spring 14 Connector 20 Rotor (rotating body) 21 Center hole of rotor 22 Rotor magnet 25 Rotor Main body 26 Pedestal part 30 Polygon mirror 40 Stator 41 Drive coil 42 Stator core 44 Fixed shaft 43 Core holder 50 Mirror pressing member 70 Dynamic gap for generating dynamic pressure 71 Dynamic pressure generating section 81, 82 Magnet 91 Ring gap for air damper 92 Air damper Annular air chamber 216 Large-diameter portion of center hole of rotor 217 Small-diameter portion of center hole of rotor 218 Step portion of center hole of rotor 440 Outer peripheral surface of fixed shaft 441 Dynamic pressure generating groove 442 Step portion for fixing 443 Axis of fixed shaft End 446 of fixed shaft Diameter portion 447 cut portion of the spring 506 mirror pressing member of the stepped portion 450 booster 505 a polygon mirror for fixing the small-diameter portion 448 fixed axis of the fixed shaft

Claims (7)

[Claims] 1. Between the outer peripheral surface of a fixed shaft and the inner peripheral surface of a center hole of a rotating body into which the fixed shaft is inserted, from above to below along the axial direction of the fixed shaft. A downwardly flowing air flow is formed by a dynamic pressure generating groove formed on at least one of an inner peripheral surface of the center hole of the rotating body and an outer peripheral surface of the fixed shaft. A bearing comprising: a dynamic pressure generating section to be generated; and a boosting section in which the dynamic pressure generating groove is not formed in order to increase the pressure of the air flow supplied from the dynamic pressure generating section. apparatus. 2. The motor according to claim 1, wherein a length of the booster in the motor axis direction is about 約 of a total length of the fixed shaft.
A bearing device having a size corresponding to (1). 3. The thrust bearing according to claim 1, further comprising: a thrust bearing that holds the rotating body at a predetermined position in an axial direction of the fixed shaft by a magnetic force acting between the rotating body side and the fixed shaft side. Along with the communication passage, an annular air chamber for an air damper communicating with the dynamic pressure generating portion, and an annular gap for an air damper for communicating the annular air chamber for the air damper with the outside are formed. And bearing device. 4. The small diameter portion for forming the air damper annular gap and the dynamic pressure generating portion on an outer peripheral surface of the fixed shaft and an inner peripheral surface of the center hole of the rotating body. And a large-diameter portion, a stepped portion between the small-diameter portion and the large-diameter portion formed on the outer peripheral surface of the fixed shaft, and a small-diameter portion formed on the inner peripheral surface of the center hole. A bearing device, wherein the annular air chamber for the air damper is formed by a portion facing a step portion with a diameter portion. 5. A motor using the bearing device defined in any one of claims 1 to 4, wherein the stator includes a stator core around which a drive coil is wound, the fixed shaft, and a lower end of the fixed shaft. A motor comprising: a holding frame; and the rotating body includes, as a rotor, a rotor magnet facing the stator core. 6. The frame according to claim 5, wherein the frame includes a fixed shaft insertion hole through which a lower end of the fixed shaft is inserted, and the fixed shaft contacts an upper surface of the frame to fix the fixed shaft. A step portion that defines an insertion depth with respect to the shaft insertion hole, and a shaft end portion that penetrates through the fixed shaft insertion hole and protrudes downward from the frame, wherein the shaft end portion has a lower surface side of the frame. A motor which is fixed to the end of the shaft so as to sandwich the spring in a compressed state, thereby fixing the fixed shaft in an upright state with respect to the frame. 7. The fixing device according to claim 6, wherein the fastener is a push nut attached to the shaft end of the fixed shaft such that a leaf spring as the spring is sandwiched between the frame and the frame. Motor to do.