JP2000275563A - Dynamic pressure air bearing motor and polygon scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower the cost by using components forming a radial dynamic pressure air bearing in common and to prolong the life by suppressing the wear of the surface of the radial dynamic pressure air bearing. SOLUTION: A hollow rotary shaft 41 as a component of the radial dynamic pressure air bearing 40 is formed in a simple shape having uniform outward sizes and then used in common for dynamic air bearing motors of respective types. Further, an axial bearing 49 which supports a rotary body 38 axially is an attraction type magnetic bearing 49 forming a radial magnetic gap between a fixed part 47 and a rotary part 48 arranged inside the hollow rotary shaft 41 and more than a half of the attraction type magnetic bearing 49 axially overlap with the radial dynamic pressure air bearing surface 45, so when the rotary body 38 stops rotating, the radial dynamic pressure air bearing surface 45 of the radial dynamic pressure air bearing 40 comes into linear contact state the wear quantity of the radial dynamic pressure air bearing surface 45 decreases, thereby prolonging the life of the dynamic pressure air bearing motor 33.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure air bearing motor using a radial dynamic pressure air bearing and a polygon scanner using the dynamic pressure air bearing motor.

[0002]

2. Description of the Related Art Conventionally, in a motor for rotating a polygon mirror at a high speed, a motor for a hard disk drive, and a motor for an optical disk drive used in a laser writing apparatus, a dynamic pressure air bearing motor using a radial dynamic pressure air bearing is used. It is used. The radial dynamic pressure air bearing is a ring-shaped minute gap formed between the fixed member and the rotating member. When the rotating member is rotationally driven, the rotating member and the fixed member are generated by dynamic pressure air generated in the minute gap. Are maintained in a non-contact state.

An example of a polygon scanner using such a dynamic pressure air bearing motor will be described with reference to FIGS. 10 and 11. The polygon scanner 1 includes a housing 2 and
A dynamic pressure air bearing motor 3 housed in a housing 2,
It is formed by a polygon mirror 4 driven to rotate by a dynamic pressure air bearing motor 3. The housing 2 is formed by fixing a cover 6 to a case 5, and a mounting reference surface 5 a for mounting the polygon scanner 1 to a predetermined position of the optical housing is formed in a flange shape on an outer peripheral portion of the case 5.

The dynamic pressure air bearing motor 3 has a lower end fixed to the case 5 by press-fitting or shrink-fitting, a rotating body 8 rotatable about the fixed shaft 7, and a rotating body 8 rotatably driven. It is formed by the motor unit 9 and the like.

The rotary body 8 is fitted around the fixed shaft 7 and forms a radial dynamic pressure air bearing 10 with the fixed shaft 7. The cylindrical hollow rotary shaft 11 has an outer peripheral portion. The polygon mirror 4 is formed by a rotor magnet 12 fixed to the polygon mirror 4 and a flange 11a screwed to the upper end of the hollow rotary shaft 11 and formed on the outer peripheral portion of the hollow rotary shaft 11.
Is formed by a mirror presser 13 and the like for pressing and fixing the pressure. Radial dynamic air bearing 1 on the outer peripheral surface of fixed shaft 7
A groove 14 for enhancing the dynamic pressure effect is formed on the radial dynamic pressure air bearing surface forming 0. Hollow rotating shaft 11
A screw hole 16 into which a screw 15 for screwing the mirror retainer 13 is screwed is formed on the end face on the upper end side.

[0006] Permanent magnets 17, 18 and 19 are fixed to the upper end of the fixed shaft 7, the mirror retainer 13 and the cover 6, respectively. These permanent magnets 17 to 19 are arranged with the same poles facing each other. The permanent magnets 17 to 19 are rotated by fine holes (not shown) formed in the mirror retainer 13 for damping vertical vibrations. Vertical repulsion type magnetic bearing 20 as an axial bearing for supporting the body 8 in the axial direction.
Are formed.

A printed circuit board 21 is fixed in the case 5 by bonding or screwing. Printed circuit board 21
Is opposed to the end face of the rotor magnet 12, and the winding coil 22 and the Hall element 2 are
3 are attached and are pattern-wired to the connector 24. One end of a harness 25 is connected to the connector 24, and the other end of the harness 25 is connected to a drive circuit 26 attached to a lower part of the housing 4. Then, the rotor magnet 12, the printed circuit board 21, the winding coil 2
2. A motor unit 9 for rotating and driving the rotating body 8 is formed by the Hall element 23, the connector 24, the harness 25, the drive circuit 26, and the like. The motor unit 9 includes a Hall element 23
The rotation of the rotating body 8 is controlled at a constant speed by sequentially switching the energization to the winding coil 22 in accordance with the position detection signal.

[0008]

In the vertical repulsion type magnetic bearing 20 used as an axial bearing in the above-described dynamic air bearing motor 3, three permanent magnets 17-1 are used.
9, the dynamic pressure air bearing motor 3 is increased in size and the product cost is increased. In addition, it is necessary to bond each of the three permanent magnets 17 to 19, which increases the number of working steps and increases the product cost. Further, due to the temperature difference between when the hydrodynamic air bearing motor 3 is driven and when it is not driven, a shear stress is applied to the adhesive layer cured by bonding the permanent magnets 17 to 19, and the adhesive layer is sheared and broken. There is a problem. When the adhesive layer is shear-ruptured and the permanent magnets 17 to 19 are displaced in the radial direction with respect to the rotation center of the rotating body 8, the rotational balance of the rotating body 8 is disrupted, generating vibration and noise, and the quality of the written image is reduced. There is a problem.

Further, a screw hole 16 is formed by cutting to press and fix the polygon mirror 4, and if the cutting oil is not sufficiently washed after forming the screw hole 16, the remaining cutting oil is rotated. When the body 8 rotates, it scatters and adheres to the optical components such as the polygon mirror 4 and the window glass, and the quality of the written image is reduced. Therefore, it takes time to process the screw hole 16 and clean the screw hole 16, which increases the product cost.

Further, since the vertical repulsion type magnetic bearing 20 is provided at the distal end of the radial dynamic pressure air bearing 10,
Due to the repulsive force generated by the magnetic bearing 20, a point contact state occurs at the tip of the radial dynamic pressure air bearing surface (the outer peripheral surface of the fixed shaft 7 and the inner peripheral surface of the hollow rotary shaft 11) of the radial dynamic pressure air bearing 10, When the rotation stops, the amount of contact wear on the radial dynamic pressure air bearing surface increases, and the life of the radial dynamic pressure air bearing 10 decreases.

The point contact state generated at the tip of the radial dynamic pressure air bearing surface will be described with reference to FIG. In FIG. 11, the gap (the radial dynamic pressure air bearing 10) formed between the fixed shaft 7 and the hollow rotary shaft 11 is exaggerated. A repulsive force (Fm) is applied to the permanent magnet 18 (point of force) located at the upper end of the rotating body 8 due to a slight axial displacement of the rotating body 8.
Acts, the hollow rotary shaft 11 moves in the direction in which the repulsive force (Fm) works, and the outer peripheral surface of the fixed shaft 7 and the inner peripheral surface of the hollow rotary shaft 11 come into line contact. However, in this state, there is no force that balances the repulsive force (Fm) acting on the power point, so that the hollow rotary shaft 11 has the upper end of the radial dynamic pressure air bearing surface of the fixed shaft 7 as a fulcrum.
Leans. However, the hollow rotary shaft 11 is not always tilted infinitely, but is limited by the clearance with the fixed shaft 7,
The inner peripheral surface (radial dynamic pressure air bearing surface) of the hollow rotary shaft 11 comes to rest in a state where it contacts the upper and lower ends of the radial dynamic pressure air bearing surface of the fixed shaft 7.

The point at which the repulsive force (Fm) acts is the point of force, the point of contact between the upper end of the radial dynamic pressure bearing surface of the fixed shaft 7 and the radial dynamic pressure air bearing surface of the hollow rotary shaft 11 is the fulcrum, and the point of The force acting at each point is considered with the contact point between the lower end of the radial dynamic pressure air bearing surface and the radial dynamic pressure air bearing surface of the hollow rotary shaft 11 as an action point. At the point of action, a force (Ffa) that balances with the repulsive force (Fm) acting at the force point acts on the fixed shaft 7, and a force (Fra) acts on the hollow rotary shaft 11 as a reaction. At the fulcrum, a force (Ffs) having a magnitude balanced with the sum of (Fm) and (Fra) acts on the fixed shaft 7, and (Frs) acts on the hollow rotary shaft 11 as a reaction. That is, when the rotation is stopped, the fixed shaft 7 is repelled by the repulsive force (Fm) of the permanent magnet 18.
The maximum force is applied to the contact point at the upper end of the radial dynamic pressure air bearing surface. When the rotating body 8 is driven to rotate from the state shown in FIG. 11, the upper end of the radial dynamic pressure air bearing surface of the fixed shaft 7 is most likely to be worn.

Further, since a flange 11a for mounting the polygon mirror 4 is formed on the outer peripheral surface of the hollow rotary shaft 11, when the dimensions of the polygon mirror 4 change,
It is necessary to change the dimensions of the flange portion 11a accordingly. Therefore, the hollow rotary shaft 11, which is a component forming the radial dynamic pressure air bearing 10, cannot be shared by different types of dynamic pressure air bearing motors, and the product cost of the dynamic pressure air bearing motor is increased.

Further, as a structure of a rotating body used in the hydrodynamic air bearing motor, a ring-shaped member is shrink-fitted and fixed to the outer peripheral portion of the hollow rotary shaft, and after the shrink-fitting fixation, the ring-shaped member is formed in a required shape. (For example, a polygon mirror) is described in JP-A-7-190047. By shrink-fitting or press-fitting the two members in this manner, the two members are firmly fixed, and stable high-speed rotation can be performed. However, when the ring-shaped member is fixed to the outer peripheral portion of the hollow rotary shaft by shrink fitting and press-fitting, the inner peripheral surface of the hollow rotary shaft is deformed in a zigzag manner, and the outer peripheral surface of the fixed shaft disposed inside the hollow rotary shaft is fixed. The dimension of the gap (radial dynamic pressure air bearing) between them becomes uneven, and the dynamic pressure bearing function is impaired.

For this reason, the ring-shaped member is fixed by shrink fitting.
After press-fitting and fixing, the inner peripheral surface of the hollow rotary shaft must be ground, which increases the processing cost.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a dynamic pressure air bearing motor and a polygon scanner which can share the components forming the radial dynamic pressure air bearing and can reduce the cost.

Further, according to the present invention, a flange for mounting a motor component (for example, a rotor magnet), a polygon mirror, or the like is shrink-fitted to the outer periphery of the hollow rotating shaft or fixed by press-fitting to fix the inner periphery of the hollow rotating shaft. It is an object of the present invention to provide a hydrodynamic air bearing motor and a polygon scanner that do not require processing for correcting the deformation even when the surface is deformed.

Another object of the present invention is to provide a dynamic pressure air bearing motor and a polygon scanner which can suppress the wear of the radial dynamic pressure air bearing surface of the radial dynamic pressure air bearing and extend the life.

Another object of the present invention is to provide a hydrodynamic air bearing motor and a polygon scanner which can be reduced in size.

[0020]

According to the first aspect of the present invention,
In a hydrodynamic air bearing motor in which a rotating body is supported by a radial dynamic pressure air bearing and an axial bearing in a radial direction and an axial direction, respectively, and a motor unit for driving the rotating body is provided, the rotating body has an outer peripheral surface. A cylindrical hollow rotary shaft having a radial dynamic pressure air bearing surface formed thereon and an outer diameter dimension uniformly formed thereon, and an outer peripheral surface on one end side of the hollow rotary shaft other than the radial dynamic pressure air bearing surface A flange fixed by shrink-fitting or press-fitting, and a motor part component part fixed to the flange and constituting a part of the motor part, wherein the axial bearing is disposed inside the hollow rotary shaft. A radial magnetic gap between the fixed portion and the rotating portion, wherein at least half of the axial direction of the magnetic attraction portion of the magnetic attraction portion of the magnetic attraction is formed between the radial dynamic pressure air bearing surface and the shaft. One Overlap each other in and are located.

Accordingly, the hollow rotary shaft, which is a component forming the radial dynamic pressure air bearing, is formed into a simple shape having uniform outer dimensions, and this hollow rotary shaft is shared by all types of dynamic pressure air bearing motors. As a result, the cost of the dynamic pressure air bearing motor can be reduced.

Further, since the flange is fixed by shrink-fitting or press-fitting to a portion other than the radial dynamic pressure air bearing surface on one end side outer peripheral surface of the hollow rotary shaft, fixing the flange causes the hollow rotary shaft to be fixed. Even if the inner peripheral surface of the hollow rotary shaft is deformed in a zigzag manner, the radial dynamic pressure air bearing surface of the hollow rotary shaft does not deform, and post-processing for correcting the deformation of the hollow rotary shaft after fixing the flange is unnecessary.

Also, since the radial dynamic pressure air bearing surface is formed on the outer peripheral surface of the hollow rotary shaft, the diameter of the radial dynamic pressure air bearing and the outer diameter of the hollow rotary shaft become the same, and a certain diameter is obtained. In the case where a radial dynamic pressure air bearing is to be obtained, the radial dynamic pressure air bearing surface is formed between the hollow rotary shaft formed on the inner peripheral surface and the hollow rotary shaft formed on the outer peripheral surface. The outer diameter of the hollow rotary shaft formed on the outer peripheral surface is smaller, and the inner diameter of the flange fixed to the outer circumference of the hollow rotary shaft can be reduced.
Accordingly, even if the flange expands due to a rise in temperature, the expansion amount is small, and the flange is prevented from being loosened or dropped from the hollow rotary shaft.

The axial bearing that supports the rotating body in the axial direction is a suction-type magnetic bearing that forms a radial magnetic gap between a fixed portion and a rotating portion disposed inside a hollow rotating shaft. Since more than half of the suction type magnetic bearing overlaps the radial dynamic pressure air bearing surface of the hollow rotating shaft in the axial direction, the radial dynamic pressure air bearing surface of the hollow rotating shaft is stopped when the rotating body stops rotating. The fixed member which forms the radial dynamic pressure air bearing facing the rotating shaft is in line contact with the radial dynamic pressure air bearing surface of the fixed member. For this reason, the amount of wear on the radial dynamic pressure air bearing surface is reduced, and the life of the radial dynamic pressure air bearing and the dynamic pressure air bearing motor is extended.

Further, a radial dynamic pressure air bearing surface is formed on the outer peripheral surface of the hollow rotary shaft, and a suction type magnetic bearing is formed inside the hollow rotary shaft. The generated dust does not enter the radial dynamic pressure air bearing, and the occurrence of rotation abnormality of the dynamic pressure air bearing motor due to the entry of dust generated from the attraction type magnetic bearing is prevented.

According to a second aspect of the present invention, in the dynamic air bearing motor according to the first aspect, the hollow rotary shaft is formed of ceramics, and the flange has a larger coefficient of thermal expansion than the ceramics forming the hollow rotary shaft. Made of material.

Therefore, the flange can be securely fixed to the hollow rotary shaft by shrink fitting, and the seizure resistance and wear resistance of the radial dynamic pressure air bearing are improved.

According to a third aspect of the present invention, in the hydrodynamic air bearing motor according to the first or second aspect, the attraction type magnetic bearing is a ring-shaped permanent magnet having an outer peripheral portion fixed to an inner peripheral portion of the hollow rotary shaft. A fixed portion having a magnet and an outer cylindrical surface which is disposed opposite to the inner peripheral surface of the ring-shaped permanent magnet and forms a magnetic gap with the ring-shaped permanent magnet;

Therefore, in this attraction type magnetic bearing, it is sufficient to use one ring-shaped permanent magnet, and the size and cost of the hydrodynamic air bearing motor can be reduced.

According to a fourth aspect of the present invention, in the dynamic pressure air bearing motor according to the first or second aspect, the attraction type magnetic bearing comprises a ring-shaped permanent magnet magnetized to two poles in the axial direction and the ring-shaped permanent magnet. And two yoke plates made of a ferromagnetic material having a central circle formed with a diameter smaller than the inner diameter of the permanent magnet,
Both ends of the ring-shaped permanent magnet are sandwiched by two yoke plates arranged so that the center circle is located concentrically, and an outer peripheral portion of the yoke plate is fixed to an inner peripheral portion of the hollow rotary shaft. The rotating portion and the fixed portion, which is disposed to face the center circle of the two yoke plates and has an outer cylindrical surface that forms a magnetic gap between these yoke plates.

Therefore, in this attraction type magnetic bearing, only one ring-shaped permanent magnet may be used, and the size and cost of the hydrodynamic air bearing motor can be reduced. Furthermore, by providing a yoke plate that is easier to process than a ring-shaped permanent magnet, the magnetic gap between the fixed portion and the outer cylinder surface can be reduced, and the ring-shaped permanent magnet can be formed by reducing the magnetic gap. The magnetic force of the magnet can be used effectively.

According to a fifth aspect of the present invention, in the dynamic pressure air bearing motor according to the third or fourth aspect, the outer cylindrical surface of the fixed portion is eccentric with respect to the rotation center of the rotating portion.

Therefore, by using this hydrodynamic air bearing motor with the axial direction oriented horizontally and the side with the large eccentricity on the upper side, the radial dynamic pressure air bearing surface of the hollow rotary shaft when the rotation of the rotating body is stopped. The contact pressure when the fixed member forming the radial dynamic pressure air bearing faces the hollow rotary shaft in line contact with the radial dynamic pressure air bearing surface is reduced, and the wear amount of the radial dynamic pressure air bearing surface is reduced. Therefore, the life of the radial dynamic pressure air bearing and the dynamic pressure air bearing motor is prolonged.

[0034] The invention according to claim 6 is the invention according to claims 1 to 5.
In the dynamic pressure air bearing motor according to any one of the above, a cap member having a fine hole for attenuating axial vibration of the rotating body is fixed to an inner peripheral portion of the hollow rotating shaft.

Therefore, when the rotating body rotates, the vibration of the rotating body in the axial direction is reduced, and stable rotation is performed.

A polygon scanner according to a seventh aspect of the present invention includes the dynamic pressure air bearing motor according to any one of the first to sixth aspects, and a polygon mirror fixed to the flange of the dynamic pressure air bearing motor. .

Therefore, this polygon scanner can obtain the respective effects when the dynamic pressure air bearing motor according to any one of claims 1 to 6 is used.

According to an eighth aspect of the present invention, in the polygon scanner according to the seventh aspect, the polygon mirror is pressed and fixed by a mirror retainer press-fitted and fixed to an end of the cylindrical hollow rotary shaft.

Therefore, the polygon mirror can be fixed with a simple and inexpensive structure.

[0040]

FIG. 1 shows a first embodiment of the present invention.
This will be described with reference to FIG. The polygon scanner 31 of the present embodiment includes a housing 32 and a housing 32.
A dynamic pressure air bearing motor 33 housed therein, and a polygon mirror 34 rotationally driven by the dynamic pressure air bearing motor 33
Are formed. The housing 32 is the case 3
A fixing reference surface 35 a for mounting the polygon scanner 31 to a predetermined position of the optical housing is formed in a flange shape on the outer peripheral portion of the case 35. The cover 36 has an opening 36 a through which laser light from a semiconductor laser (not shown) enters and exits.
Is formed, and the opening 36a is formed by a transparent glass plate 36b.
It is closed by.

The hydrodynamic air bearing motor 33 includes a fixed sleeve 37 fixed to a substantially central portion of the case 35, a rotating body 38 rotatable around the center line of the fixed sleeve 37, and a rotating body 38.
Is formed by a motor unit 39 for rotating the motor.

The rotating body 38 has a cylindrical hollow rotary shaft 41 which is fitted into the fixed sleeve 37 and forms a radial dynamic pressure air bearing 40 with the fixed sleeve 37, and an upper outer peripheral surface of the hollow rotary shaft 41. A flange 42 fixed by shrink fit or press fitting, a motor component constituting part of the motor section 39, a rotor magnet 43 press fitted and fixed to the flange 42, and a press fitting fixed to the upper end of the hollow rotary shaft 41. Polygon mirror 34 mounted on flange 42
Is formed by a mirror retainer 44 for pressing and fixing the mirror. The hollow rotary shaft 41 is formed of ceramics, which is a non-magnetic material, and the flange 42 is formed of an aluminum alloy, steel, or the like having a higher coefficient of thermal expansion than the ceramics forming the hollow rotary shaft 41. In addition, the hollow rotary shaft 4
The fixed sleeve 37 into which 1 is fitted is also made of ceramics.

The hollow rotary shaft 41 has a uniform outer diameter, and a portion of the outer circumferential surface of the hollow rotary shaft 41 which faces the inner circumferential surface of the fixed sleeve 37 is a radial dynamic pressure air bearing surface 45. I have. A flange 42 is fixed to a portion other than the radial dynamic pressure air bearing surface 45 on the upper side of the outer peripheral surface of the hollow rotary shaft 41 by shrink fitting or press fitting. A groove 46 for enhancing the dynamic pressure effect is formed on the radial dynamic pressure air bearing surface 45.

Inside the hollow rotary shaft 41, a fixed portion 47 fixed to the case 35 and a rotary portion 4 fixed to the inner peripheral portion of the hollow rotary shaft 41 and rotating integrally with the hollow rotary shaft 41.
8 is an attractive magnetic bearing which is an axial bearing composed of
Is provided. In the attraction type magnetic bearing 49, a radial magnetic gap is formed between the fixed part 47 and the rotating part 48.

The rotating part 48 includes a ring-shaped permanent magnet 50 magnetized to two poles in the axial direction of the attraction type magnetic bearing 49, and a pair of ring-shaped yokes sandwiching the ring-shaped permanent magnet 50 at both ends in the axial direction. Plates 51 and 52 are formed. The yoke plates 51, 52 are formed of a ferromagnetic material, and the diameters of the center circles 51a, 52a are formed smaller than the inner diameter of the ring-shaped permanent magnet 50, and the two center circles 51a, 52.
a are arranged concentrically.

The fixing portion 47 is formed of a ferromagnetic material of iron and steel. The fixing portion 47 is disposed opposite to the inner peripheral surfaces of the center circles 51a and 52a of the yoke plates 51 and 52 so as to face these yoke plates 51 and 52a. An outer cylindrical surface 47a which forms a magnetic gap between the outer cylindrical surface 47a and the outer cylindrical surface 52a is formed. The magnetic gap is preferably 0.1 to 0.5 mm as shown in FIG. Further, in the present embodiment, the outer cylinder surface 4 for forming the magnetic gap is formed.
Although 7a is divided into upper and lower parts as an example, it may have a continuous cylindrical shape.

Further, inside the hollow rotary shaft 41, a cap member 53 having a fine hole 53a for attenuating the vertical vibration of the rotary body 38 by utilizing the viscous resistance when air passes therethrough, and a rotary section 48. And a stopper 54 for preventing the falling off are press-fitted and fixed.

In the case 35, a printed board 55 screwed and a stator core 56 are fixed, and a winding coil 57 wound around the stator core 56 is mounted on the printed board 55.
It is connected to the. A Hall element 58 is mounted on the printed circuit board 55, and is patterned and wired. The stator core 56 around which the winding coil 57 is wound and the rotor magnet 43 face each other in a direction perpendicular to the axial direction, and the printed board 55, the stator core 56, and the winding coil 5
7, the Hall element 58, the rotor magnet 43, etc.
A motor section 39 for driving the rotating body 38 to rotate is formed. The motor unit 39 controls the rotation of the rotating body 38 at a constant speed by sequentially switching the energization of the winding coil 57 in accordance with the position detection signal of the Hall element 58.

In such a configuration, when the polygon scanner 31 is driven, the rotating body 38 and the polygon mirror 34
Means that the bearing is supported by a radial dynamic pressure air bearing 40 in the radial direction and is supported by a suction-type magnetic bearing 49 in the axial direction and rotates at high speed.

As shown in FIG. 5, in the attraction type magnetic bearing 49, the N-pole passes through the ring-shaped permanent magnet 50, the yoke plates 51 and 52, and the fixed portion 47, which are magnetized into two poles in the axial direction. The lines of magnetic force directed toward the south pole are closed to form a loop.

Next, the state of the radial dynamic pressure air bearing 40 when the rotation of the dynamic pressure air bearing motor 33 is stopped will be described with reference to FIG. The center circle 5 of the yoke plates 51 and 52 depends on the dimensional variation of each part such as the rotating part 48 and the fixed part 47.
1a, 52a and the outer cylindrical surface 47a of the fixing portion 47 are eccentric, and a radial suction force (Fm) acts. At this time, the radial dynamic pressure air bearing surface 45 is moved from either one of its upper end or lower end to the inner peripheral surface of the fixed sleeve 37 (the radial dynamic pressure air bearing 40 which faces the radial dynamic pressure air bearing surface 45 to form the radial dynamic pressure air bearing 40). Contact with the compressed air bearing surface) starts, and finally comes to rest in a line contact state where the forces can be balanced as shown in FIG. When the radial dynamic pressure air bearing surface 45 of the hollow rotary shaft 41 and the inner peripheral surface of the fixed sleeve 37 come into line contact with each other, the suction force (Fm) due to the eccentricity of the suction type magnetic bearing 49 is reduced by the hollow rotary shaft 41. When working with the fixed sleeve 37, Fr1, Fr2, F
, Fs1, Fs2, Fs3,..., the contact pressure acting on the radial dynamic pressure air bearing surface 45 decreases. When the contact pressure acting on the radial dynamic pressure air bearing surface 45 decreases, the radial dynamic pressure air bearing surface
5 and the amount of wear on the inner peripheral surface of the fixed sleeve 37 is reduced, and the life of the radial dynamic pressure air bearing 40 and the dynamic pressure air bearing motor 33 is extended. The dynamic air bearing motor 33
In order to bring the radial dynamic pressure air bearing surface 45 into a line contact state when the rotation is stopped, at least half of the attraction type magnetic bearing 49 is disposed so as to overlap the radial dynamic pressure air bearing surface 45 in the axial direction.

In the radial dynamic pressure air bearing 40, the hollow rotary shaft 41, which is a component forming the radial dynamic pressure air bearing 40, is formed in a simple cylindrical shape having uniform outer dimensions, and polygon mirrors having different dimensions are provided. When mounting 34, flanges 42 of different dimensions are used as needed. Therefore, the hollow rotary shaft 41 and the hollow rotary shaft 41
The fixed sleeve 37 into which the shaft is fitted can be shared by the dynamic pressure air bearing motors 33 of each type, and the cost of the dynamic pressure air bearing motor 33 can be reduced.

The fixing of the flange 42 to the hollow rotary shaft 41 is performed by shrink-fitting or press-fitting on the outer peripheral surface on one end side of the hollow rotary shaft 41 other than the radial dynamic pressure air bearing surface 45. By fixing the flange 42, the radial dynamic pressure air bearing surface 45 is not deformed even if the inner peripheral surface of the hollow rotary shaft 41 deforms in a stepped manner, and the deformation of the hollow rotary shaft 41 is fixed after the flange 42 is fixed. No need for post-processing to correct.

Further, since the hollow rotary shaft 41 is formed of ceramics and the flange 42 is formed of a material having a higher thermal expansion coefficient than the ceramics forming the hollow rotary shaft 41, the hollow rotary shaft 41 is formed by shrink fitting. Flange 4
2 can be securely fixed. In addition, since the hollow rotary shaft 41 and the fixed sleeve 37 are formed of ceramics, the wear resistance and seizure resistance of the radial dynamic pressure air bearing 40 are improved.

Further, since the radial dynamic pressure air bearing surface is formed on the outer peripheral surface of the hollow rotary shaft 41, the diameter of the radial dynamic pressure air bearing 40 and the outer diameter of the hollow rotary shaft 41 become the same. In order to obtain a radial dynamic pressure air bearing of a different diameter, the hollow rotary shaft 41 having a radial dynamic pressure air bearing surface 45 formed on the outer peripheral surface and the hollow rotary shaft 11 formed on the inner peripheral surface. (See FIG. 10), the outer diameter of the hollow rotary shaft 41 in which the radial dynamic pressure air bearing surface 45 is formed on the outer peripheral surface is smaller, and the inner diameter of the flange 42 fixed to the outer circumference of the hollow rotary shaft 41. The size can be reduced. Further, since the inner diameter of the flange 42 is reduced, even if the expansion of the flange 42 due to the temperature rise occurs, the expansion amount is small, and the loosening or falling off of the flange 42 with respect to the hollow rotary shaft 41 is prevented. .

As the attraction type magnetic bearing 49 for supporting the rotating body 38 in the axial direction, one ring-shaped permanent magnet 50 may be used, and the size and cost of the hydrodynamic air bearing motor 33 can be reduced. . Furthermore, by providing the yoke plates 51 and 52, which are easier to process than the ring-shaped permanent magnet 50, the magnetic gap between the fixed portion 47 and the outer cylindrical surface 47a can be reduced, and the magnetic gap can be reduced. By doing so, the magnetic force of the ring-shaped permanent magnet 50 can be effectively used, and the dynamic pressure air bearing motor 33 can be further reduced in size.

A radial dynamic pressure air bearing surface 45 is formed on the outer peripheral surface of the hollow rotary shaft 41, and a suction type magnetic bearing 49 is formed inside the hollow rotary shaft 41. Attraction or after assembling magnetic bearing 49
The dust generated from the motor does not enter the radial dynamic pressure air bearing 40, and the occurrence of rotation abnormality of the dynamic pressure air bearing motor 33 due to the entry of dust generated from the attraction type magnetic bearing 49 is prevented.

Next, a second embodiment of the present invention will be described with reference to FIG.
A description will be given based on FIG. 1 to 6 are denoted by the same reference numerals, and description thereof will be omitted (the same applies to the following embodiments). In the dynamic pressure air bearing motor 33 of the present embodiment, the outer cylindrical surface 47a of the fixed portion 47 is arranged eccentrically with respect to the rotation center of the rotating portion 48. Therefore, as shown in FIG. 7, the magnetic gap formed between the outer cylindrical surface 47a and the yoke plates 51 and 52 is deviated in one direction, and the rotating body 38 is moved in the direction in which the magnetic gap is narrowed. Suction force (F
m) occurs. The amount of bias of the magnetic gap is determined by the attractive force (F
m) and the magnitude of gravity (Fw) acting on the rotating body 38 are set to be substantially the same.

In such a configuration, the dynamic pressure air bearing motor 33 is used with the axial direction oriented in the horizontal direction and the side with the larger magnetic gap as the upper side (see FIG. 8).
Then, the suction force (Fm) and the gravity (Fw) are balanced,
At the time of rotation stop, the contact pressure when the radial dynamic pressure air bearing surface 45 of the hollow rotary shaft 41 comes into line contact with the inner peripheral surface (radial dynamic pressure air bearing surface) of the fixed sleeve 37 becomes small, and the radial motion at the time of rotation stop is reduced. The amount of wear of the compressed air bearing surface 45 and the inner peripheral surface (radial dynamic pressure air bearing surface) of the fixed sleeve 37 is reduced, and the life of the radial dynamic pressure air bearing 40 and the dynamic pressure air bearing motor 33 is extended.

Further, the attractive force (F
If the position where m) works and the position where the center of gravity (Fw) of the rotating body 38 works coincide with each other in the axial direction, the amount of wear of the radial dynamic pressure air bearing surface 45 and the inner peripheral surface of the fixed sleeve 37 when the rotation is stopped is reduced. It can be further suppressed.

Next, a third embodiment of the present invention will be described with reference to FIG.
It will be described based on. The dynamic pressure air bearing motor 60 of the present embodiment includes a fixed sleeve 37 fixed to a substantially central portion of a case 35, a rotating body 38a rotatable around a center line of the fixed sleeve 37, and a motor for driving the rotating body 38a to rotate. It is formed by the portion 39 and the like.

The rotating body 38 a is fitted into the fixed sleeve 37 and forms a radial dynamic pressure air bearing 40 with the fixed sleeve 37. The cylindrical hollow rotating shaft 41, the upper outer peripheral surface of the hollow rotating shaft 41. A flange 42 fixed by shrink-fit or press-fitting, a motor component constituting a part of the motor portion 39, a rotor magnet 62 press-fitted and fixed to the flange 61, and a press-fit fixed to the upper end of the hollow rotary shaft 41. Polygon mirror 3 placed on flange 61
4 is formed by a mirror presser 44 for pressing and fixing.

The housing 3 is provided on the outer peripheral side of the flange 61.
The stator core 63 fixed inside 2 is arranged.
A winding coil 64 is wound around the stator core 63.
And these stator core 63, winding coil 64,
The motor unit 3 for rotatingly driving the rotating body 38 by the rotor magnet 62, the printed board 55, the Hall element 58, and the like.
9 are formed.

Inside the hollow rotary shaft 41, a fixed portion 47 fixed to the case 35 and a ring that is fixed to the inner peripheral portion of the hollow rotary shaft 41 and is a rotary portion that rotates integrally with the hollow rotary shaft 41. An attraction type magnetic bearing 66 is provided as an axial bearing composed of the permanent magnet 65. In the attraction type magnetic bearing 66, a radial magnetic gap is formed between the fixed portion 47 and the ring-shaped permanent magnet 65.

In such a configuration, since the rotor magnet 62 is disposed inside the stator core 63, the size of the rotor magnet 62 can be reduced.
Thereby, the centrifugal force acting on the rotor magnet 62 can be reduced, the windage loss around the rotor magnet 62 can be reduced, and the dynamic pressure air bearing motor 60 suitable for high-speed rotation can be obtained.

In each of the above embodiments,
The case where the polygon mirror 34 is rotationally driven by the dynamic pressure air bearing motors 33 and 60 has been described as an example. However, the dynamic pressure air bearing motors 33 and 60 include information such as a hard disk drive motor and an optical disk drive motor. It can be used as a motor for equipment.

[0067]

According to the hydrodynamic air bearing motor of the first aspect of the present invention, the hollow rotary shaft, which is a component forming the radial hydrodynamic air bearing, is formed in a simple shape having uniform outer dimensions. The hollow rotary shaft can be shared by each type of dynamic pressure air bearing motor, and the cost of the dynamic pressure air bearing motor can be reduced. In addition, by forming a radial dynamic pressure air bearing surface on the outer peripheral surface of the hollow rotary shaft, when a radial dynamic pressure air bearing of a certain diameter is to be obtained, the radial dynamic pressure air bearing surface is formed on the inner peripheral surface. The outer dimensions of the hollow rotary shaft can be made smaller than the hollow rotary shaft, and the inner diameter of the flange fixed to the outer periphery of the hollow rotary shaft by shrink fitting or press fitting can be reduced. Thus, even if the flange expands due to a rise in temperature, the amount of expansion is small, so that the flange can be prevented from loosening or falling off with respect to the hollow rotary shaft. In addition, since the flange is fixed to a portion other than the radial dynamic pressure air bearing surface on one end side outer peripheral surface of the hollow rotary shaft by shrink fitting or press fitting, by fixing the flange, the inner peripheral surface of the hollow rotary shaft is fixed. The radial dynamic pressure air bearing surface of the hollow rotary shaft is not deformed even if the surface is deformed in a continuous manner, so that post-processing for correcting the deformation of the hollow rotary shaft after fixing the flange is unnecessary. The axial bearing that supports the rotating body in the axial direction is a suction-type magnetic bearing that forms a magnetic gap in the radial direction between the fixed portion and the rotating portion disposed inside the hollow rotating shaft. More than half of the radial magnetic pressure air bearing surface in the axial direction overlaps the radial dynamic pressure air bearing surface in the axial direction, so that when the rotating body stops rotating, the radial dynamic pressure air bearing surface Therefore, the wear amount of the radial dynamic pressure air bearing surface can be reduced, and the life of the radial dynamic pressure air bearing and the dynamic pressure air bearing motor can be extended. Further, since a radial dynamic pressure air bearing surface is formed on the outer peripheral surface of the hollow rotary shaft and a suction type magnetic bearing is formed inside the hollow rotary shaft, dust generated from the suction type magnetic bearing at the time of assembling or after assembling is obtained. Does not enter the radial dynamic pressure air bearing, and the occurrence of rotation abnormality of the dynamic pressure air bearing motor due to the entry of dust generated from the attraction type magnetic bearing can be prevented.

According to the hydrodynamic air bearing motor according to the second aspect of the present invention, the flange can be securely fixed to the hollow rotary shaft by shrink fitting, and the radial dynamic pressure air bearing has seizure resistance and wear resistance. Performance can be improved.

According to the dynamic air bearing motor of the third aspect of the present invention, one ring-shaped permanent magnet may be used in the attraction type magnetic bearing used in the dynamic air bearing motor. The size and cost can be reduced.

According to the dynamic air bearing motor of the fourth aspect of the present invention, one ring-shaped permanent magnet may be used in the attraction type magnetic bearing used in the dynamic air bearing motor. By providing a yoke plate that can be reduced in size and cost and is easier to process than a ring-shaped permanent magnet, the magnetic gap between the fixed portion and the outer cylinder surface can be reduced. The magnetic force of the ring-shaped permanent magnet can be effectively used by reducing the magnetic gap.

According to the dynamic pressure air bearing motor of the present invention, by using the dynamic pressure air bearing motor with the axial direction oriented horizontally and the side having the larger eccentricity as the upper side, the rotation of the rotating body is improved. When the rotation is stopped, the contact pressure when the radial dynamic pressure air bearing surface of the radial dynamic pressure air bearing makes linear contact can be reduced to reduce the amount of wear on the radial dynamic pressure air bearing surface. The life of the hydrodynamic air bearing motor can be extended.

According to the dynamic air bearing motor of the present invention, when the rotating body rotates, the axial vibration of the rotating body can be reduced, and the rotating body can be stably rotated.

According to the polygon scanner of the seventh aspect of the present invention, by using the hydrodynamic air bearing motor according to any one of the first to sixth aspects, it is possible to obtain the case where the hydrodynamic air bearing motor is used. The same effect as that obtained is obtained.

According to the polygon scanner of the present invention, the polygon mirror can be fixed with a simple and inexpensive structure.

[Brief description of the drawings]

FIG. 1 is a vertical sectional front view showing a polygon scanner according to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a polygon scanner.

FIG. 3 is an exploded perspective view showing a rotating body of the polygon scanner.

FIG. 4 is an exploded perspective view showing a suction type magnetic bearing of the polygon scanner.

FIG. 5 is a vertical sectional front view showing a suction type magnetic bearing of the polygon scanner.

FIG. 6 is a longitudinal sectional front view showing a state in which the radial dynamic pressure air bearing surface makes line contact when rotation is stopped.

FIG. 7 is a longitudinal sectional front view showing a suction type magnetic bearing of a polygon scanner according to a second embodiment of the present invention.

FIG. 8 is a vertical sectional front view showing a state in which the radial dynamic pressure air bearing surface makes line contact when rotation is stopped.

FIG. 9 is a vertical sectional front view showing a polygon scanner according to a third embodiment of the present invention.

FIG. 10 is a vertical sectional front view showing a conventional polygon scanner.

FIG. 11 is a longitudinal sectional front view showing a state in which the radial dynamic pressure air bearing surface makes point contact when rotation is stopped.

[Explanation of symbols]

 33,60 Dynamic pressure air bearing motor 34 Polygon mirror 38,38a Rotating body 39 Motor part 40 Radial dynamic pressure air bearing 41 Hollow rotary shaft 42,61 Flange 43,62 Motor part component 44 Mirror presser 45 Radial dynamic pressure air bearing surface 47 Fixed part 47a Outer cylinder surface 48 Rotating part 49, 66 Axial bearing, attracting magnetic bearing 50 Ring-shaped permanent magnet 51, 52 Yoke plate 51a, 52a Center circle 53 Cap member 53a Micro hole 65 Rotating part, ring-shaped permanent magnet

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H02K 7/08 H02K 7/08 A 5H607 H04N 1/113 H04N 1/04 104A F-term (reference) 2H045 AA13 AA24 AA28 DA41 3J011 CA02 DA02 SB02 SB04 SD01 3J102 AA01 BA04 CA21 DA03 DA10 GA02 5C072 AA03 BA02 BA13 DA21 HA13 HB15 5H605 AA04 AA05 AA07 BB05 BB19 CC04 CC05 EB06 5H607 AA04 AA11 BB09 BB17 CC01 DD08 DD14 FF12 GG01 GG12 GG01 GG12 HGG

Claims (8)

[Claims] 1. A dynamic pressure air bearing motor comprising: a rotating body supported by a radial dynamic pressure air bearing and an axial bearing in a radial direction and an axial direction, respectively; and a motor unit for rotating and driving the rotating body. The body has a cylindrical hollow rotating shaft having a radially-dynamic-pressure air bearing surface formed on the outer peripheral surface and an outer diameter dimension formed uniformly, and the radial-dynamic-pressure air on the outer peripheral surface on one end side of the hollow rotating shaft. A flange fixed to a portion other than the bearing surface by shrink fitting or press-fitting, and a motor part component fixed to the flange and forming a part of the motor part, wherein the axial bearing A suction-type magnetic bearing that forms a radial magnetic gap between a fixed portion and a rotating portion disposed inside a shaft, wherein at least half of the suction-type magnetic bearing has the radial dynamic pressure air bearing surface. Dynamic pressure air bearing motor, characterized by being arranged to overlap in the axial direction. 2. The dynamic pressure according to claim 1, wherein the hollow rotary shaft is formed of ceramics, and the flange is formed of a material having a higher coefficient of thermal expansion than the ceramics forming the hollow rotary shaft. Air bearing motor. 3. The attraction type magnetic bearing includes a ring-shaped permanent magnet having an outer peripheral portion fixed to an inner peripheral portion of the hollow rotary shaft, and a ring-shaped permanent magnet which is disposed opposite to an inner peripheral surface of the ring-shaped permanent magnet. 3. The hydrodynamic air bearing motor according to claim 1, further comprising: the fixed portion having an outer cylindrical surface forming a magnetic gap between the fixed portion and a permanent magnet. 4. The attraction type magnetic bearing is made of a ferromagnetic material having a ring-shaped permanent magnet magnetized to two poles in an axial direction and a center circle having a diameter smaller than the inner diameter of the ring-shaped permanent magnet. And two yoke plates, wherein both ends of the ring-shaped permanent magnet are sandwiched by the two yoke plates arranged so that the center circle is located concentrically, and the outer peripheral portion of the yoke plate is The rotating portion fixed to the inner peripheral portion of the hollow rotary shaft, and an outer cylindrical surface which is disposed opposite to the center circle of the two yoke plates and forms a magnetic gap between these yoke plates are formed. The dynamic pressure air bearing motor according to claim 1, further comprising the fixing portion. 5. The hydrodynamic air bearing motor according to claim 3, wherein the outer cylindrical surface of the fixed portion is eccentric with respect to a rotation center of the rotating portion. 6. The hollow member according to claim 1, wherein a cap member having a fine hole for attenuating an axial vibration of the rotating body is fixed to an inner peripheral portion of the hollow rotating shaft. A dynamic pressure air bearing motor according to any one of the preceding claims. 7. A polygon scanner comprising: the dynamic pressure air bearing motor according to claim 1; and a polygon mirror fixed to the flange of the dynamic pressure air bearing motor. 8. The polygon scanner according to claim 7, wherein said polygon mirror is pressed and fixed by a mirror presser pressed and fixed to an end of said cylindrical hollow rotary shaft.