JP3740821B2 - Hydrodynamic bearing motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dynamic pressure bearing motor, and more particularly to a dynamic pressure bearing motor used for an optical deflector incorporated in a digital laser beam printer, an electrophotographic copying machine, or the like.
[0002]
[Prior art]
In general, a digital image forming apparatus such as a laser beam printer or an electrophotographic copying machine scans an image to be read with a light beam and scans a recording medium with a modulated light beam. An image recording apparatus for forming an image on a recording medium is provided. The image reading apparatus and the image recording apparatus are provided with an optical deflector for scanning a light beam.
[0003]
As shown in FIG. 5, in the image recording apparatus 70, the laser light L from the laser light source 85 such as a semiconductor laser or a gas laser enters the optical deflector 80 via a collimator lens 86 that converts the laser light into a parallel light beam. . The optical deflector 80 is a rotary polygon mirror 48 having a plurality of reflecting surfaces 48A, 48B, 48C... Formed on its side surface, and a drive for rotating the rotary polygon mirror 48 around the fixed shaft 14 in the direction of arrow X at an equal angular velocity. And a motor 81. The light beam L incident on one of the reflecting surfaces of the rotating polygon mirror 48 is deflected at a constant angular velocity along with the deflection of the reflecting surface by the rotation of the rotating polygon mirror 48 by the drive motor 81. Therefore, the laser beam L incident on the reflecting surface is gradually changed in deflection angle and incident on the fθ lens 87, and is scanned on the recording medium 88 at a constant speed in the arrow Y direction.
[0004]
That is, the laser beam L scans the recording medium 88 in the direction of the arrow Y as the rotary polygon mirror 48 rotates (main scanning). Note that the recording medium 88 rotates in the arrow Z direction as the laser light L scans the recording medium 88 in the arrow Y direction, and the irradiation position of the laser light L is shifted in the rotation direction of the recording medium 88. Is performed (sub-scanning). By these movements, two-dimensional writing is performed on the recording medium 88.
[0005]
As a drive motor for the optical deflector used in such an image recording apparatus 70, a rotary sleeve fixed to the rotary polygon mirror and a ring-shaped rotary drive magnet fixed to the rotary sleeve (hereinafter referred to as a drive magnet). A fixed shaft inserted through the rotary sleeve, a housing that holds the fixed shaft, a coreless coil that is fixed to the housing and applies rotational torque to the drive magnet, and an inner periphery of the drive magnet that is fixed to the rotary sleeve A ring-shaped frequency power generation magnet (hereinafter referred to as FG magnet) arranged concentrically with the drive magnet on the side, and a comb-shaped frequency for rotational frequency detection fixed to the housing and arranged at a position facing the FG magnet A hydrodynamic bearing motor equipped with a power generation coil (hereinafter referred to as FG (Frequency generation) coil) is known. There.
[0006]
FIG. 6 shows the arrangement of the coreless coil 20, the drive magnet 22, the FG coil 61, and the like in the above-described dynamic pressure bearing motor. A magnetic circuit necessary for the rotation is formed by the drive magnet 22 provided on the rotary sleeve 40 side and the drive coil 20 provided on the fixed shaft 14 side. The rotational torque is obtained by detecting a plurality of magnetic poles of the drive magnet 22 with a magnetic pole detection element 21 such as a hall detection element and energizing the drive coil 20 with a predetermined timing logic.
[0007]
At this time, the rotation speed is controlled to be constant by using a fluctuation component of the frequency of the voltage induced in the FG coil 61 by the FG magnet 60 provided on the rotating sleeve 40 side as a detection signal. Such a rotation detection mechanism that obtains a detection signal by the FG magnet 60 and the FG coil 61 is disclosed in, for example, Japanese Patent Application Laid-Open No. 1-204211.
[0008]
[Problems to be solved by the invention]
However, the fluid dynamic bearing motor having such a configuration has many indispensable parts, and it is difficult to reduce the size of the fluid dynamic bearing motor by reducing the number of parts. Further, there is a limit to downsizing from the necessity of maintaining the thickness of components such as a drive coil and the arrangement relationship of components for forming a magnetic circuit. Therefore, an object of the present invention is to provide a dynamic pressure bearing motor that can solve such problems and can be made smaller than a conventional dynamic pressure bearing motor.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to a first aspect of the present invention, there is provided a first magnet provided with a driving magnet for generating a magnetic field for rotational driving by alternately arranging N and S poles around a rotation center. The member and the radial portion of the coil that contributes to the rotational torque are arranged only on the surface side facing the drive magnet, and the circumferential portion of the coil that is exposed to the surface without contributing to the rotational torque is the odd and even turns And a second member in which a driving coil for rotational driving arranged alternately on the front surface side and the back surface side not facing the driving magnet is arranged facing the driving magnet, and the driving coil A hydrodynamic bearing that is energized to rotate one of the first member and the second member relative to the other by rotational torque generated by a magnetic circuit formed by the drive magnet and the drive coil. It is a motor.
[0010]
In the first aspect of the invention, the radial portion of the coil that contributes to the rotational torque of the drive coil is disposed only on the surface side facing the drive magnet, and the circumferential portion of the coil that is exposed to the surface without contributing to the rotational torque is an odd number. The windings and even windings are alternately arranged on the front side and the back side not facing the drive magnet. The portion exposed to the surface without contributing to the rotational torque is arranged in the rotational direction and distributed to the front surface side and the back surface side of the second member. Is also small. Thereby, since the 2nd member can be made smaller than before, it can be set as a hydrodynamic bearing motor small in the diameter direction.
According to a second aspect of the present invention, in the hydrodynamic bearing motor according to the first aspect, the drive coil is formed by winding the odd-numbered winding portion in the radial direction and the circumferential direction portion in a substantially rectangular shape on the surface side, The even-numbered windings are formed in parallel at a predetermined distance away from the position of the radial-direction portion of the odd-numbered winding before the first winding on the front surface side, and the circumferential-direction portion is formed on the back surface side. The circumferential portion on the surface side formed in the odd number winding before the first winding and the radial distance from the fixed shaft fixed to the rotation center are arranged so as to be formed at the same distance. It is a feature.
In the invention of claim 2, not only the drive coils are alternately arranged in half on the front and back sides, but also the positions of the coils on the front and back sides in the circumferential direction are the same distance from the rotation center. By arranging so as to overlap with each other, the width required for winding in the circumferential direction can be reduced to about half.
[0011]
In order to achieve the above object, the invention according to claim 3 is the dynamic pressure bearing motor according to claim 1 or 2 , wherein the second member does not contribute to the rotational torque of the drive coil. The frequency generating coil for detecting the rotational frequency is arranged between the portions exposed on the back side of the.
[0012]
In the invention of claim 3 , the frequency generating coil for detecting the rotational frequency is arranged between the portions exposed on the back surface side of the second member without contributing to the rotational torque of the drive coil on the back surface side of the second member. Therefore, it is not necessary to provide a region where the frequency power generation coil for detecting the rotational frequency is provided other than the region where the drive coil is disposed, and the dynamic pressure bearing motor can be made small in the radial direction of rotation.
[0013]
Further, by configuring as described above, the frequency power generation coil for detecting the rotational frequency is disposed in the magnetic field of the drive magnet, and therefore generates power under the influence of the drive magnet. Since the rotational frequency can be detected by this power generation, the magnet for the frequency power generation coil that has been provided only for detecting the rotational frequency in the prior art becomes unnecessary, and the number of components can be reduced. Therefore, a small hydrodynamic bearing motor can be provided in the radial direction.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention when the present invention is applied to a drive mechanism for rotating a rotary polygon mirror of an optical deflector will be described with reference to FIGS. In the following embodiments, the first member is a rotor and the second member is a stator.
[0015]
(First embodiment)
As shown in FIG. 1, in this optical deflector 80, a ceramic fixed shaft 14 is fixed to the center portion of the housing 12 on the side of the stator 10, which is a second member, by press fitting or the like. A large number of herringbone grooves 24 having a depth of several μm are formed on the outer peripheral surface of the bearing.
[0016]
On the upper surface of the housing 12, a plate-like circuit board 18 having a disc portion is disposed. As shown in FIGS. 2 and 3, six drive coils 23 formed by an etching pattern are arranged on the circuit board 18 at equal intervals so as to draw an annular ring as a whole around the fixed shaft 14. The drive coil 23 is connected to a control circuit (not shown) that controls excitation switching of these drive coils 23.
[0017]
In each drive coil 23, the radial portions 23a and 23c that contribute to the rotational torque are all disposed at positions facing the drive magnet on the surface side of the circuit board 18, and the circumferential portions 23b and 23d that do not contribute to the rotational torque are The coils are alternately arranged on the front surface side and the back surface side that does not face the drive magnet, and the through portions of the coils penetrating the circuit board 18 are the front surface side circumferential portions 23b and 23d or the back surface side circumferential portions 23b and 23d and the front surface side. Are connected to the radial direction portions 23a and 23c. Therefore, the circumferential portions 23b and 23d of the drive coil 23 exposed on the surface are about half the width of the circumferential portions 23a and 23c of the drive coil 23, as shown in FIG. Further, as shown in FIG. 2B, only the circumferential portions 23 b and 23 d of the drive coil 23 are exposed on the back surface of the circuit board 18. The details of the drive coil 23 will be described later.
[0018]
As shown in FIGS. 1 and 2, a Hall element 21 as a position detecting element for detecting the position of the rotor 16 is fixed to the center of each drive coil 23 on the circuit board 18 (see FIG. 2). . These Hall elements 21 detect a plurality of magnetic poles of a drive magnet 22 (to be described later), and the rotating position of the rotor 16 is detected based on the detection result.
[0019]
A stator yoke 28 made of a silicon steel plate installed in a shallow groove 30 drilled on the housing 12 is disposed on the back side of the circuit board 18.
[0020]
In addition, a thrust magnet holder 32 formed integrally with the housing 12 is erected on the upper surface of the housing 12, and a vertical cross section is formed in a ring shape with a rectangular vertical section on the upper portion of the thrust magnet holder 32. The stator side thrust magnet 38 is attached by a method such as adhesion.
[0021]
On the other hand, on the rotor 16 side, a ceramic rotary sleeve 40 as a first member is inserted through the fixed shaft 14 with a gap of about 3 to 8 μm. For this reason, when the rotary sleeve 40 rotates at high speed around the fixed shaft 14, dynamic pressure is generated between the fixed shaft 14 and the rotary sleeve 40, and the dynamic pressure causes the opposing movement along the radial direction of the fixed shaft 14. A pressure bearing is constructed.
[0022]
An aluminum ring-shaped flange 42 is fixed to a predetermined position on the outer peripheral portion of the rotary sleeve 40 by a method such as shrink fitting or press fitting. An attachment surface 46 is formed on the upper surface of the flange 42, and an aluminum rotary polygon mirror 48 is fixed on the attachment surface 46 by a fixing spring 50. The rotary polygon mirror 48 is formed in a polygonal column shape, and each side surface 48A is processed into a mirror surface. The mounting surface 46 is processed with high accuracy so as to be perpendicular to the axis of the rotary sleeve 40.
[0023]
A cutout portion 42A is formed in a portion of the flange 42 corresponding to the drive coil 23, and a drive magnet 22 for rotational driving is attached to the cutout portion 42A by adhesion or the like. The entire drive magnet 22 is formed in a ring shape, and an opening step portion 52 having an opening whose inner diameter is expanded by one step is formed on the stator 10 side in the central hole portion. Further, the drive magnet 22 is magnetized with N poles and S poles so that the adjacent sections have different polarities in each of the sections divided into eight equal portions of 45 degrees each.
[0024]
An FG magnet 60 for generating a frequency signal corresponding to the number of rotations is attached to the notch 56 of the flange 42 by adhesion. The entire FG magnet 60 is formed in a ring shape, and an N pole and an S pole are magnetized so that adjacent sections have different polarities in each section with the central angle divided into 16 equal parts.
[0025]
A comb-like FG coil 61 (see also FIG. 3) is formed by etching or the like at a position facing the FG magnet 60 on the circuit board 18, and the rotor is based on the alternating current generated in the FG coil 61. Sixteen rotations are detected.
[0026]
On the upper surface of the flange 42, there is provided a groove portion 54 that is formed by cutting out a ring with a rectangular vertical cross section, and a balance weight 57A for balance adjustment is attached to the groove portion 54. Further, a balance weight 57B for adjusting the balance is attached to a step portion 59 formed by the flange 42 and the FG magnet 60. These counterweights 57A and 57B adjust the balance during rotation of the rotor 16.
[0027]
A rotor-side thrust magnet 58 formed in a ring shape is attached to the outer peripheral surface of the flange 42 by adhesion. The rotor-side thrust magnet 58 is disposed at a predetermined interval so as to face the stator-side thrust magnet 38, and an attractive force is generated between the outer peripheral surface portion of the rotor-side thrust magnet 58 and the inner peripheral surface portion of the stator-side thrust magnet 38. They are magnetized with different polarities to work. For this reason, the rotor side thrust magnet 58 and the stator side thrust magnet 38 constitute a thrust magnetic bearing.
[0028]
In this thrust magnetic bearing, the attractive force acting on the rotor-side thrust magnet 58 and the stator-side thrust magnet 38 is set to be larger than the load in the thrust direction (axial direction) on the rotating sleeve 40 of the rotor 16. The entire rotor 16 is lifted by the suction force. In addition, as a method for supporting the rotating sleeve 40 in the axial direction, a method using a permanent magnet and a magnetic material, a method of floating by a dynamic pressure action of air, or the like can be used.
[0029]
As described above, the rotor 16 is supported in the thrust direction by the thrust magnetic bearing and is also supported in the radial direction by the dynamic pressure bearing. As a result, the drive control circuit on the circuit board 18 controls the AC voltage to be applied to each drive coil 23, so that a current flows through each drive coil 23 and the magnetic field of the drive magnet 22 facing each drive coil 23. An electromagnetic induction action works with the current, and a rotational driving force is generated for the driving magnet 22. This rotational driving force causes the rotor 16 to rotate at a high speed while floating in the air.
[0030]
The drive coil 23 in the present embodiment will be described in detail. In the drive coil 23, the radial portions 23a and 23c are arranged only on the front surface side of the circuit board 18, and the circumferential portions 23b and 23d are the front surface side and the back surface side of the circuit board. And a coil in a through hole in which the circumferential portions 23b and 23d on the front side or the circumferential portions 23b and 23d on the back side and the radial portions 23a and 23c on the front side pass through the circuit board. It is a spiral coil which consists of the etching pattern of the structure connected by these.
[0031]
As schematically shown in FIG. 3, the first turn inside the drive coil 23 is substantially rectangular in the clockwise direction in the order of A1 position → B1 position → C1 position → D1 position → A2 position only on the surface of the circuit board. The structure is wound in a shape. The A2 position is a position away from the A1 position by a predetermined distance from the D position in the A position direction.
[0032]
In the second roll, the radial portion extending from the A2 position to the B2 position is formed in parallel at a predetermined distance away from the outer peripheral side of the radial portion extending from the A1 position of the first roll to the B1 position. The C2 position is also a position that is a predetermined distance away from the C1 position in the BC direction. Therefore, the radial portion extending from the C2 position to the D2 position is the same as the radial portion extending from the A2 position to the B2 position. They are formed in parallel at a predetermined distance apart on the outer peripheral side of the radial portion extending from the C1 position to the D1 position.
[0033]
The circumferential portion of the coil extending from the B2 position of the second winding to the C2 position is from the fixed portion 14 and the circumferential portion of the coil extending from the B1 position to the C1 position formed by the first winding coil portion on the back side of the circuit board. The coil is formed at a position where the radial distance is the same. Similarly, the circumferential portion of the coil extending from the D2 position to the A3 position is also formed from the fixed shaft 14 and the circumferential portion of the coil extending from the D1 position to the A2 position formed by the first winding coil portion on the back side of the circuit board. The coil is formed at a position where the radial distance is the same.
[0034]
In this case, the connection between the radial portion of the coil formed on the front surface and the circumferential portion of the coil formed on the back surface is performed by providing a through hole in the circuit board 18 at a position connecting the front and back coil portions. The coil is embedded into a through portion for connection, and the front side end of the through portion is joined to the end of the radial portion of the coil on the surface of the circuit board 18, and the back side end of the through portion is the back side of the circuit board 18 This is done by joining the end of the circumferential portion of the coil.
[0035]
In the third roll, the radial portion of the coil extending from the A3 position to the B3 position is formed in parallel with a predetermined distance away from the outer peripheral side of the radial portion of the coil extending from the A2 position to the B2 position of the second roll. ing. Similarly, the radial portion of the coil extending from the C3 position to the D3 position is formed in parallel to a predetermined distance away from the outer peripheral side of the radial portion of the coil extending from the second winding C2 position to the D2 position. Yes.
[0036]
The circumferential portion of the coil extending from the B3 position of the third winding to the C3 position is previously placed on the outer peripheral side of the circumferential portion of the coil extending from the B1 position to the C1 position formed by the first winding coil portion on the surface side of the circuit board 18. It is formed at a predetermined fixed distance. Similarly, the circumferential portion of the coil extending from the D3 position to the A4 position is also separated by a predetermined distance on the outer peripheral side of the circumferential portion of the coil extending from the first winding D1 position to the A2 position on the surface side of the circuit board 18. Is formed.
[0037]
As in the first to third turns, the radial part of the fourth coil is parallel to a predetermined distance away from the outer peripheral side of the radial part of the third coil formed on the surface side. Is formed. The circumferential direction portion of the coil is arranged on the back surface side like the second winding, and is arranged so as to be the same distance as the radial direction distance from the fixed shaft 14 of the third winding coil portion.
[0038]
Although the description has been made up to the fourth winding using the schematic diagram of FIG. 3, the odd number winding of the coil forms all the coil portions on the surface side in this way, and the even number winding of the coil is the radial portion that contributes to the rotational torque. 23a and 23c (see also FIG. 2) are formed on the surface side, and the circumferential portions 23b and 23d that do not contribute to the rotational torque are formed on the back side, thereby occupying in the radial direction from the fixed shaft 14 of the drive coil 23. The area can be reduced more than before. Accordingly, since the circuit board 18 on which the drive coil 23 is formed can be formed smaller than the conventional one, the entire optical deflector 80 can be downsized.
[0039]
In the coil configured as described above, since magnetic flux passes in the thickness direction of the circuit board 18, circumferential force (tangential direction of rotation) is generated in a portion arranged in the radial direction, and is arranged in the circumferential direction. A radial force is generated in the part, and no force is generated in the penetrating part. Therefore, the coil portion arranged in the radial direction becomes a portion that contributes to the rotational torque, and the coil portion and the penetrating portion arranged in the circumferential direction become portions that do not contribute to the rotational torque.
[0040]
In the first embodiment, the circumferential portion of the coil that does not contribute to the rotational torque is arranged alternately and sequentially on the front side and the back side of the circuit board. The front half and the back side of the circuit board of the circumferential part of the coil are arranged such that the first half of the winding in the circumferential part of the coil is continuously arranged on the front side and the second half of the winding is arranged on the back side. The arrangement with respect to can also be changed.
[0041]
In the optical deflector according to the first embodiment, the drive magnet 22 and the FG magnet 60 are provided on the rotor 16 side, and the drive coil 23 and the FG coil 61 are provided on the stator 10 side. With regard to these arrangements, it is only necessary that the drive magnet 22 and the drive coil 61 face each other and the FG magnet 60 and the FG coil 61 face each other. The drive magnet 22 and the FG magnet 60 are provided on the stator 10 side, and the rotor 16 is provided. The present invention can also be applied to an optical deflector provided with the drive coil 23 and the FG coil 61 on the side, and the same effect as described above can be obtained.
[0042]
(Second Embodiment)
In the second embodiment, in the optical deflector described in the first embodiment, as shown in FIG. 4A, an FG (Frequency) for detecting the number of rotations between the fixed shaft 14 and the drive coil 23 is used. generation) without providing the coil 61, as shown in FIG. 4B, the FG coil 61 is placed in a region sandwiched between the circumferential portions 23b and 23d of two substantially parallel coils exposed on the back surface of the circuit board 18. This is a configuration provided.
[0043]
That is, as shown in FIG. 4B, two circumferential portions 23 b and 23 d of the drive coil 23 are formed on the back surface of the circuit board 18. The circumferential portions 23b and 23d of these two coils are arranged substantially parallel to each other by the length of the radial portion of the coil formed on the surface of the circuit board 18.
[0044]
Since the radial portions 23a and 23c of the coil are not formed on the back surface side of the semiconductor substrate 18, in the second embodiment, the coil is sandwiched between the two circumferential portions 23b and 23d of all the drive coils 23. An FG coil 61 having a configuration connected in the circumferential direction is formed in the region. This eliminates the need for a region for forming the FG coil 61 between the fixed shaft 14 and the drive coil 23, so that the radial distance from the fixed shaft 14 of the circuit board 18 can be reduced. Can be downsized.
[0045]
Further, by arranging the FG coil 61 on the back surface side of the drive coil 23, the FG coil 61 is also affected by the magnetic field of the drive magnet 22, so that an alternating current is generated in the FG coil 61 by the rotating drive magnet 22. The frequency can be detected by an alternating current. Therefore, the FG magnet 60 provided only for frequency power generation becomes unnecessary, and the number of parts can be reduced correspondingly, and the entire apparatus can be downsized. Since a driving magnet larger than the FG magnet 60 provided only for frequency power generation is used for frequency detection, there is an advantage that the output voltage of the FG coil 61 is increased. In addition, since the other part of the optical deflector of the 2nd embodiment is the same as that of 1st Embodiment mentioned above, description is abbreviate | omitted.
[0046]
In the optical deflector of the second embodiment, the example in which the drive magnet 22 is provided on the rotor 16 side and the drive coil 23 and the FG coil 61 are provided on the stator 10 side has been described. As long as the drive coil 23 and the FG coil 61 are opposed to the drive magnet 22, an optical deflector in which the drive magnet 22 is provided on the stator 10 side and the drive coil 23 and the FG coil 61 are provided on the rotor 16 side. The present invention is applicable and can achieve the same effects as described above.
[0047]
In the first and second embodiments described above, the case where the present invention is applied to the drive mechanism of the optical deflector for rotating the polygonal mirror has been described as an example of the dynamic pressure bearing motor. However, the present invention is not limited to this. The present invention can be applied as a drive mechanism for rotating other members that require rotation.
[0048]
In the first and second embodiments, the present invention is applied to the sleeve rotation type optical deflector 80 having a structure in which the cylindrical rotation sleeve 40 pivotally supported by the dynamic pressure air bearing is rotated outside the fixed shaft 14. However, the present invention can also be applied to a shaft rotation type optical deflector having a structure in which the shaft rotates inside the cylindrical fixed shaft 14.
[0049]
【The invention's effect】
As described above, according to the first and second aspects of the invention, the effect that the hydrodynamic bearing motor can be reduced in size is achieved.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an optical deflector according to a first embodiment of the present invention.
2A is an explanatory diagram showing a configuration of the upper surface side of the circuit board of the optical deflector of FIG. 1, and FIG. 2B is an explanatory diagram showing a configuration of the lower surface side of the circuit board of the optical deflector of FIG. 1; FIG.
FIG. 3 is a schematic diagram of a drive coil according to the first embodiment of the present invention.
FIG. 4A is an explanatory view showing a configuration of an upper surface side of a circuit board of an optical deflector according to a second embodiment of the present invention, and FIG. 4B is an optical deflection according to the second embodiment of the present invention. It is explanatory drawing which shows the structure of the lower surface side of the circuit board of a container.
FIG. 5 is a schematic configuration diagram of an image recording apparatus including an optical deflector.
FIG. 6 is an explanatory diagram showing a configuration of an upper surface side of a circuit board of a conventional optical deflector.
[Explanation of symbols]
12 Housing 14 Fixed shaft 18 Circuit board 22 Drive magnet 23 Drive coil 48 Rotating polygon mirror 60 FG magnet 61 FG coil 80 Optical deflector

Claims (3)

A first member provided with a drive magnet for alternately generating N and S poles around a rotation center to generate a magnetic field for rotational drive;
The radial portion of the coil that contributes to the rotational torque is disposed only on the surface side facing the drive magnet, and the circumferential portion of the coil that is exposed to the surface without contributing to the rotational torque is an odd number winding and an even number winding. A second member in which a driving coil for rotational driving arranged alternately on the front surface side and the back surface side not facing the driving magnet is arranged facing the driving magnet;
With
One of the first member and the second member is rotated relative to the other by rotational torque generated by a magnetic circuit formed by the drive magnet and the drive coil by energizing the drive coil. Dynamic pressure bearing motor. The drive coil is
  The odd-numbered winding is formed by winding the radial portion and the circumferential portion in a substantially rectangular shape on the surface side, and the even-numbered winding is a radial portion of the odd-numbered winding of the odd-numbered winding one turn before the surface side. It is formed in parallel at a predetermined distance from the position to the outer peripheral side, and the circumferential portion is fixed to the rotational portion and the circumferential portion on the front surface formed in the odd-numbered winding before the first winding on the back surface side. Arranged so that the radial distance from the fixed shaft formed is the same distance,
  The hydrodynamic bearing motor according to claim 1. 3. The dynamic pressure according to claim 1, wherein a frequency power generation coil for detecting a rotational frequency is disposed between portions exposed to the back side of the second member without contributing to the rotational torque of the drive coil. Bearing motor.

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