JP2008099368A - Motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a disc driving motor capable of preventing thermal deformation of a disc placing surface while stably fixing a yoke on a rotor hub with good balance. <P>SOLUTION: The motor is provided with a rotor hub 7 having a flange portion 72 for placing a disc D, a yoke 8 fixed on the bottom surface of the flange portion 72, and a magnet 9 for a revolving field to be held by the yoke 8. A circular groove 73 is formed on the outer circumferential surface of the flange portion 72, and the flange portion 72 is segmented into a first flange 72a for supporting the disc D and a second flange 72b for supporting the yoke 8 by the circular groove 73. The yoke 8 has a cylindrical yoke body 81 and an inner flange 82 bent inward from one end of the yoke body, the outer plane of the inner flange 82 is brought into close contact with the bottom surface of the second flange 72b, and a protrusion 74 for fitting the inner flange 82 of the yoke 8 into the outer circumferential side continuously to the second flange 72b is formed on the rotor hub 7. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a motor for rotating a disk such as a hard disk, a CD, a CD-ROM, or a DVD.

  2. Description of the Related Art In recent years, spindle motors equipped with dynamic pressure type fluid bearings are frequently used for rotationally driving a disk as an information recording medium.

  Such a motor has, for example, a structure in which a cylindrical bearing member is fixed to a motor base that constitutes a stator, and lubricating oil is filled between the bearing member and the rotor shaft. For example, it has excellent performance.

  An example of the configuration will be described with reference to FIG. 6. Mb is a motor base constituting a stator, and a stator core Sc is fixed to the motor base Mb, and a stator coil Co is wound around the stator core. .

  On the other hand, a cylindrical bearing member Be is fixed to the motor base Mb, and the rotor shaft Rs is rotatably supported by the bearing member Be. A rotor hub Rh having a flange portion f is fixed to the rotor shaft Rs. The flange portion f is for placing the disk D, and the yoke Yk is fixed to the bottom surface side of the flange portion f by plastically deforming the ridge m formed on the rotor hub Rh. A field magnet Ma that generates a magnetic flux necessary for generating a rotational force is attached to the yoke Yk.

  The rotor hub Rh is made of a lightweight soft metal such as aluminum, while the yoke Yk is made of a hard magnetic material such as iron. The yoke Yk is in close contact with the flange portion f of the rotor hub Rh. If it is fixed in a state, when the flange portion f of the rotor hub and the yoke Yk portion are heated by the drive of the motor, the flange portion f is deformed by thermal stress, and the disk D placed on this fluctuates. This makes it impossible to read and write information accurately.

  Therefore, conventionally, as shown in FIG. 6, a protrusion n is formed on the rotor hub Rh adjacent to the protrusion m for fixing the yoke Yk, and the protrusion n causes a gap between the flange portion f of the rotor hub and the yoke Yk. Is formed (for example, Patent Document 1).

  According to Patent Document 1, even if a thermal stress is generated between the flange portion f (disk mounting portion) and the yoke Yk, the thermal stress is caused by the elastic deformation of the projection n, and the flange portion f and the yoke Yk. As a result of being absorbed by the gap, it is possible to prevent thermal deformation of the flange portion f.

Japanese Patent Laid-Open No. 10-4665

  However, in Patent Document 1, when the protrusion Y is plastically deformed by caulking and the yoke Yk is fixed to the rotor hub Rh, the receiving surface that supports the yoke Yk becomes small due to the presence of the projection n, and thus the fixing accuracy of the yoke Yk is reduced. Is easy to go crazy. For this reason, the rotational balance of the rotor hub Rh becomes unstable, and in particular, there is a problem that large vibrations occur during high-speed rotation and information cannot be read from or written to the disk D.

  Further, the projection n may be crushed by the pressure when fixing the yoke Yk, and there is a possibility that a gap sufficient to absorb thermal stress is not formed between the flange portion f and the yoke Yk.

  The present invention has been made in view of the circumstances as described above, and an object of the present invention is to provide a disk drive motor capable of preventing thermal deformation of a disk mounting surface while fixing a yoke to a rotor hub in a balanced and highly accurate manner. Is to provide.

In order to achieve the above object, the present invention
In a motor provided with a rotor hub 7 having a flange portion 72 for placing the disk D, a yoke 8 fixed to the bottom surface of the flange portion 72, and a field magnet 9 held by the yoke 8.
The flange portion 72 has an annular groove 73 on the outer peripheral surface, and the flange portion 72 is divided into a first flange 72a for supporting the disk D and a second flange 72b to which the yoke 8 is fixed via the annular groove 73. It is characterized by.

In addition, the yoke 8 has a cylindrical yoke body 81 and an inner flange 82 that is bent inward from one end of the yoke body, and the outer flat surface of the inner flange 82 is in close contact with the bottom surface of the second flange 72b. With
The rotor hub 7 is characterized in that a ridge 74 is formed to be connected to the second flange 72b and to fit the inner flange 82 of the yoke 8 to the outer peripheral side.

  According to the motor of the present invention, the flange portion is divided into the first flange that supports the disk and the second flange that fixes the yoke through the annular groove formed on the outer peripheral surface of the flange portion of the rotor hub. Therefore, even if thermal stress is generated between the flange portion of the rotor hub and the yoke, the thermal stress is absorbed by the annular groove. For this reason, the first flange is not thermally deformed, and the disk supported thereby can be rotated well without surface vibration.

  The yoke has a cylindrical yoke body and an inner flange that is bent inward from one end of the yoke body. The outer flat surface of the inner flange is in close contact with the bottom surface of the second flange. Since the ridge is formed so as to be connected to the flange and the inner flange of the yoke is fitted to the outer peripheral side, the yoke can be fixed to the rotor hub with high accuracy.

  For this reason, there is no rotational imbalance caused by poor fixing of the yoke, and the yoke is fixed to the bottom surface of the flange portion of the rotor hub. Therefore, after fixing the yoke, an annular groove is formed on the outer peripheral surface of the flange portion. Further, it is possible to prevent the flange portion from being deformed by the pressure when the yoke is fixed.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a motor (electric motor) according to the present invention. In this example, the motor is incorporated in a disk drive device (not shown) as a disk drive spindle motor for rotating a hard disk or the like.

  In FIG. 1, reference numeral 1 denotes a motor base constituting the stator. The motor base 1 is made of aluminum or the like, and a cylindrical tubular portion 1a is integrally formed at the central portion thereof.

  A stator core 2 is fixed to the outer periphery of the cylindrical portion 1 a of the motor base 1, and a stator coil 3 (armature winding) is wound around the stator core 2.

  Reference numeral 4 denotes a cylindrical bearing member fitted into the cylindrical portion 1a of the motor base 1, and this bearing member 4 is fixed to the motor base 1 by an adhesive applied between the cylindrical portion 1a. . In particular, the bearing member 4 is a radial bearing constituting a dynamic pressure type fluid bearing, and one end thereof is sealed by a seal plate 5.

  Further, a rotor shaft 6 is inserted into the bearing member 4, and the rotor shaft 6 is rotatably supported by the bearing member 4 through lubricating oil filled in the bearing member 4. In particular, a radial bearing portion 4 a that supports a radial load is formed on the inner peripheral surface of the bearing member 4.

  The radial bearing portion 4 a generates dynamic pressure that supports the radial load of the rotor shaft 6 by increasing the pressure of the lubricating oil in the bearing member 4 during rotation of the rotor shaft 6, and this is the inner peripheral surface of the bearing member 4. It is formed by forming a herringbone shaped groove.

  Further, a flange 6 a is formed on the outer periphery of one end of the rotor shaft 6 so as to face the seal plate 5. Thrust bearing portions 4 b that support the thrust load of the rotor shaft 6 are formed between the flange portion 6 a and the bearing member 4 and between the end surface of the rotor shaft 6 and the seal plate 5. The thrust bearing portion 4b is also formed by forming a groove in the bearing member 4 for increasing the pressure of the lubricating oil in the bearing member 4.

  On the other hand, a rotor hub 7 for holding the disk D is fixed to the tip of the rotor shaft 6 protruding from the bearing member 4 in a press-fitted state. The rotor hub 7 is formed by integrally forming a boss portion 71 fixed to the rotor shaft 6 and a flange portion 72 extending on the outer peripheral side thereof from a lightweight material such as aluminum, and the disk D is placed on the surface of the flange portion 72. The center portion of the disk D is pressed against the surface of the flange portion 72 by a clamp member (not shown) attached to the rotor hub 7, and the yoke 8 is fixed to the bottom surface of the flange portion 72.

  In particular, an annular groove 73 having a U-shaped cross-section for absorbing thermal stress is formed on the outer peripheral surface of the flange portion 72, and the two flanges are opposed to each other in the axial direction through the annular groove 73. (First flange 72a and second flange 72b). The disk D is supported by one first flange 72a, and the yoke 8 made of iron or other magnetic material is fixed to the bottom surface of the other second flange 72b.

  The yoke 8 is a structure having a cylindrical yoke body 81 having substantially the same diameter as the rotor hub 7 and an inner flange 82 bent at a right angle from one end of the yoke body 81 to the inner periphery of the yoke body 81. A field magnet 9 (permanent magnet) is mounted on the surface so as to face the stator core 2. The rotor hub 7 is rotated by the magnetic flux of the field magnet 9 acting on the rotating magnetic field generated by passing a drive current through the stator coil 3.

  The yoke 8 is fixed so that the outer flat surface of the inner flange 82 is in close contact with the bottom surface of the second flange 72b of the rotor hub 7. The rotor hub 7 is connected to the second flange 72b to fix the yoke 8. An annular ridge 74 is formed. Then, the inner flange 82 of the yoke 8 is fitted on the outer peripheral side of the ridge 74, and the tip of the ridge 74 is plastically deformed by caulking in this state, so that the yoke 8 causes the inner peripheral surface of the inner flange 82 to protrude onto the ridge. The rotor hub 7 is fastened in close contact with the outer peripheral surface of 74.

  According to the motor of the present application configured as described above, even if heat generated by energization of the stator coil 3 is transmitted to the rotor hub 7 and the yoke 8 and thermal stress is generated between the two, Therefore, the deformation force is not transmitted to the first flange 72a. Therefore, it is possible to prevent the first flange 72a from being thermally deformed and to rotate the disk D supported by the first flange 72a satisfactorily without surface vibration.

Here, as shown in FIG. 2, the thickness of the flange portion 72 is t1, the radial width of the flange portion 72 is L1, the opening width of the annular groove 73 is t2, and the depth of the annular groove 73 is L2. Then, t2 = 2.5 mm and L2 = 2.0 mm, but in order to prevent thermal deformation of the first flange 72a,
It is desirable to set t2 ≧ t1 / 3 and L2 ≧ L1 / 3.

  Next, a method for manufacturing the motor will be described with reference to FIGS. 3 and 4. In FIG. 3, J is a cup-shaped jig having a concave cross section, and the annular groove 73 is formed on the jig J. The unprocessed rotor hub 7 is arranged with the ridges 74 facing upward.

  Thus, with the flange portion 72 supported by the opening edge of the jig J, the inner flange 82 of the yoke 8 is fitted on the outer peripheral side of the convex strip 74, and in this state, the tip of the convex strip 74 is crimped. Is plastically deformed. Thus, the yoke 8 is fixed to the rotor hub 7 with the entire outer flat surface of the inner flange 82 being in close contact with the bottom surface of the flange portion 72 and the inner peripheral surface of the inner flange 82 being in close contact with the outer peripheral surface of the ridge 74. .

  The rotor hub 7 to which the yoke 8 is fixed as described above is rotatably supported by a chuck C of a machine tool (NC lathe or the like) as shown in FIG. An annular groove 73 is formed on the outer peripheral surface of the portion 72.

  As described above, according to the motor of the present application, the yoke 8 is fixed in a state where the inner flange 82 thereof is in close contact with the bottom surface of the flange portion 72 of the rotor hub 7 and the outer peripheral surface of the ridge 74, so that the fixing accuracy is high. In addition, since the annular groove 73 is formed after the yoke 8 is fixed to the rotor hub 7, the flange portion 72 is deformed by the pressure applied when the yoke 8 is fixed (the first flange 72 a and the second flange 72 b change the annular groove 73. It is possible to prevent the approach).

  The preferred example of the motor according to the present invention has been described above, but the annular groove 73 is not limited to a U-shaped cross section, and may be a V-shaped form as shown in FIG. Even when the annular groove 73 is V-shaped, it is desirable that the mouth width and depth have the same relationship with the flange portion 72 as in the above example. The motor shown in FIGS. 1 and 5 has the same configuration except that the shape of the annular groove 73 is different.

  Furthermore, in the present invention, the bearing member 4 is not limited to the dynamic pressure type, and a rolling bearing may be used for this.

1 is a longitudinal sectional view showing a configuration example of a motor according to the present invention. Partial enlarged sectional view showing the main part of the motor Explanatory drawing which shows the state which fixes a yoke to a rotor hub Explanatory drawing showing an example of forming an annular groove The longitudinal cross-sectional view which shows other embodiment of the motor based on this invention Longitudinal section showing a conventional motor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor base 2 Stator core 3 Stator coil 4 Bearing member 6 Rotor shaft 7 Rotor hub 71 Boss part 72 Flange part 72a 1st flange 72b 2nd flange 73 Annular groove 74 Projection 8 Yoke 81 Yoke body 82 Inner flange 9 Field magnet

Claims (2)

In a motor comprising a rotor hub having a flange part for placing a disk, a yoke fixed to the bottom surface of the flange part, and a field magnet held by the yoke,
The flange portion has an annular groove on an outer peripheral surface, and the flange portion is divided through the annular groove into a first flange that supports the disk and a second flange to which the yoke is fixed. Characteristic motor. The yoke has a cylindrical yoke body and an inner flange bent inward from one end of the yoke body, and an outer flat surface of the inner flange is in close contact with the bottom surface of the second flange.
The motor according to claim 1, wherein the rotor hub is formed with a ridge that is connected to the second flange to fit the inner flange of the yoke to the outer peripheral side.

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