JP2008187844A - Spindle motor and recording/reproducing device therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spindle motor and a recording/reproducing device therewith, capable of effectively reducing leakage of a magnetic flux forming a magnetic field formed around a rotor magnet to the outside, even if the device is made thin. <P>SOLUTION: This spindle motor 20 includes a shaft 1; a rotor hub 6 fixed to the axial upper end portion of the shaft 1; a plurality of salient poles 28, wounded by a stator coil 9 for applying the magnetic flux to a roughly annular magnet 7 fixed to the rotor hub 6. An axial projected rim 6a, extending to the stator coil 9 side along the axial direction, is formed on the radial outermost circumferential portion of the rotor hub 6. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a spindle motor mounted on a hard disk device, a magneto-optical disk device, an optical disk device, a floppy (registered trademark) disk or the like, and a recording / reproducing apparatus including the same.

In recent years, along with the reduction in size and weight of devices equipped with hard disk devices, magneto-optical disk devices, optical disk devices, floppy disk devices, etc., demands for smaller, thinner, larger capacity, cost reduction, etc. of these devices have increased. It is coming.
For this reason, the spindle motor mounted on the apparatus is required to satisfy not only the demand for thinning, but also the other demand to prevent leakage of magnetic flux to the outside of the apparatus even when the thickness is reduced. .
For example, in Patent Document 1, as a countermeasure against leakage of magnetic flux that forms a magnetic field formed around a rotor magnet (rotating magnet) to the outside, the hub side shield surface is axially arranged on the outer side in the radial direction than the rotor magnet. A spindle motor provided with a rim portion that is gently bent (about 30 to 45 degrees) is disclosed.
JP 2006-121802 A (published May 11, 2006) JP 2004-324681 A (published on November 18, 2004) JP 2005-160202 A (released on June 16, 2005)

However, the conventional spindle motor has the following problems.
That is, in the spindle motor disclosed in the above publication, a rim portion formed by bending the hub-side shield surface is formed with a surface inclined with respect to the radial direction on the shield side of the hub. For this reason, the distance between the inclined surface of the rim portion where the hub-side shield surface is bent and the rotor magnet becomes too close, and the magnetic flux from the magnet is short-circuited to the inclined surface and linked, and the rim portion of the hub and the shield plate There is a risk that magnetic noise leaking from the gaps between the two will increase.
An object of the present invention is to provide a spindle motor capable of effectively reducing leakage of a magnetic flux forming a magnetic field formed around a rotor magnet to the outside even when the apparatus is thinned, and a recording provided with the same. To provide a playback device.

A spindle motor according to a first invention includes a shaft, a salient pole part, a rotating magnet, and a rotor hub. The salient pole portion is wound with a stator coil, and a plurality of salient pole portions are arranged along a radial direction centering on the axis. The rotating magnet has a substantially annular shape, and is disposed radially inward with respect to the salient pole portion. The rotor hub is attached with a rotating magnet and rotates around an axis. Further, the rotor hub has a protruding portion that protrudes substantially parallel to the shaft on one side in the axial direction on the surface facing the rotating magnet on the radially outer side than the mounting position of the rotating magnet. And the front-end | tip of a protrusion part is extended | stretched to the position exceeding the height position of the surface of the other side of an axial direction in a rotating magnet.
Here, in a spindle motor that rotationally drives a rotor hub to which a rotating magnet is attached by a magnetic field generated by flowing a current through a stator coil wound around a salient pole part, the surface of the rotor hub opposite to the rotating magnet is opposed to the rotating magnet. A projecting portion that projects substantially parallel to the axial direction is provided at a radially outer position. And this protrusion part is formed so that it may extend | stretch to the position exceeding the height position of the surface of the opposing rotating magnet in an axial direction.

Here, the rotor hub generally has a disk mounting portion on which a disk is mounted, and rotates about a rotation axis by a magnetic flux applied to the attached rotating magnet. And the protrusion part formed in the rotor hub is an annular part formed in the radial direction outer side in the rotor hub, Comprising: It forms so that a rotary magnet may be arrange | positioned at radial direction inner side. The projecting portion may be any projecting so long as it has an inclination angle of 20 degrees or less, more preferably 5 degrees or less with respect to the axial direction.
Thereby, since the protrusion part formed in the rotor hub is extended substantially straight toward the axial direction, the distance of a protrusion part and a rotating magnet can be ensured more than predetermined amount. Therefore, it is possible to avoid the occurrence of a short circuit of the magnetic flux in the portion where the distance is too close due to the distance to the part of the rotor hub arranged so as to cover the rotating magnet. As a result, for example, when viewed from the magnetic head mounted on the magnetic recording / reproducing apparatus, the rotating magnet is completely covered by the rotor hub including the protrusion, and the leakage of magnetic flux to the outside can be effectively prevented. Therefore, it is possible to avoid the leakage magnetic flux from adversely affecting external parts such as a magnetic head.

A spindle motor according to a second invention includes a shaft, a salient pole part, a rotating magnet, and a rotor hub. A plurality of salient pole portions are arranged along the radial direction centered on the axis, and a winding portion around which the stator coil is wound, and a winding portion formed at a tip portion on the radially inner side of the winding portion And a wide portion wider than the width. The rotating magnet has a substantially annular shape, and is disposed radially inward with respect to the salient pole portion. The rotor hub is attached with a rotating magnet and rotates around an axis. Further, the rotor hub has a protruding portion that protrudes to the one side in the axial direction on the surface facing the rotating magnet on the radially outer side than the mounting position of the rotating magnet. And the protrusion part has the axial direction front-end | tip part arrange | positioned in the radial direction outer side rather than the wide part.
Here, in the spindle motor having a salient pole portion having a wide portion wider than the winding portion of the stator coil at the tip portion, the rotating magnet is positioned radially outside the mounting position of the annular rotating magnet in the rotor hub. A protruding portion extending in the axial direction is provided on the opposing surface. And the axial direction front-end | tip part of this protrusion part is comprised so that it may be located in the radial direction outer side with respect to the wide part in the said salient pole part by which the stator coil was wound.

Here, the rotor hub generally has a disk mounting portion on which a disk is mounted, and rotates about a rotation axis by a magnetic flux applied to the attached rotating magnet. And the protrusion part formed in the rotor hub is an annular part formed in the radial direction outer side in the rotor hub, Comprising: It forms so that a rotary magnet may be arrange | positioned at radial direction inner side.
Usually, the winding portion of the stator coil in the salient pole portion has a large magnetic resistance, and the wide portion at the tip thereof has a small magnetic resistance. For this reason, when the protrusion part formed in the rotor hub is arranged opposite to the wide part in the salient pole part, the magnetic flux linked to the salient pole part from the rotating magnet may flow to the protrusion part. .
In the spindle motor of the present invention, the protruding portion formed on the rotor hub is disposed opposite to the winding portion around which the stator coil having strong magnetic resistance is wound, not the wide portion at the tip of the salient pole portion.

Thereby, the leakage of the magnetic flux from the salient pole part to the protruding part can be effectively suppressed, and the leakage of the magnetic flux to the outside of the apparatus can be effectively suppressed. The projecting portion may be any projecting so long as it has an inclination angle of 20 degrees or less, more preferably 5 degrees or less with respect to the axial direction.
A spindle motor according to a third aspect of the present invention includes a shaft, a salient pole portion, a rotating magnet, and a rotor hub. The salient pole portion is wound with a stator coil, and a plurality of salient pole portions are arranged along a radial direction centering on the axis. The rotating magnet has a substantially annular shape and is arranged at a position facing the salient pole part. The rotor hub is attached with a rotating magnet and rotates around an axis. Further, the rotor hub has a protruding portion that protrudes to the one side in the axial direction on the surface facing the rotating magnet on the radially outer side than the mounting position of the rotating magnet. The salient pole portion has a bent portion that is bent in a direction away from the projecting portion at least at a portion facing the tip portion in the axial direction of the projecting portion.

Here, in a spindle motor that rotationally drives a rotor hub to which a rotating magnet is attached by a magnetic field generated by flowing a current through a stator coil wound around a salient pole part, the surface of the rotor hub opposite to the rotating magnet is opposed to the rotating magnet. A protruding portion that protrudes in the axial direction is provided at a radially outer position. And in the salient pole part which opposes the axial direction front-end | tip part of this protrusion part, it is bent in the direction away from a protrusion part.
Here, the rotor hub generally has a disk mounting portion on which a disk is mounted, and rotates about a rotation axis by a magnetic flux applied to the attached rotating magnet. And the protrusion part formed in the rotor hub is an annular part formed in the radial direction outer side in the rotor hub, Comprising: It forms so that a rotary magnet may be arrange | positioned at radial direction inner side.
Thereby, even when a protrusion is provided in a part of the rotor hub, the distance between the protrusion and the rotating magnet can be secured by a predetermined amount or more. Therefore, it is possible to avoid the occurrence of a short circuit of the magnetic flux in the portion where the distance is too close due to the distance to the part of the rotor hub arranged so as to cover the rotating magnet. As a result, for example, when viewed from the magnetic head mounted on the magnetic recording / reproducing apparatus, the rotating magnet is completely covered by the rotor hub including the protrusion, and the leakage of magnetic flux to the outside can be effectively prevented. Therefore, it is possible to avoid the leakage magnetic flux from adversely affecting external parts such as a magnetic head.

In addition, it is more preferable that this protrusion extends | stretches within 20 degrees of parallelism with respect to an axis | shaft, More preferably, within 5 degrees.
A spindle motor according to a fourth aspect of the invention is the spindle motor according to the first aspect of the invention, wherein the salient pole portions are provided at a winding portion around which the stator coil is wound and a tip portion on the radially inner side of the winding portion. And a wide portion wider than the formed winding portion. And the axial direction front-end | tip part of the protrusion part is arrange | positioned in the outer side in radial direction rather than the wide part.
Here, in addition to the positional relationship in the axial direction between the protruding portion of the rotor hub and the opposed surface of the rotor magnet, the positional relationship in the radial direction between the protruding portion and the wide portion of the salient pole portion is also specified.
Thereby, the protrusion part formed in the rotor hub is opposingly arranged by the wide part in a salient pole part, and it can prevent that the magnetic flux linked to the salient pole part from a rotating magnet flows with respect to a protrusion part. As a result, the leakage of magnetic flux from the salient pole part to the protruding part can be further effectively suppressed, and the leakage of magnetic flux to the outside of the apparatus can be effectively suppressed.

A spindle motor according to a fifth invention is the spindle motor according to the first or second invention, wherein the salient pole part is located on the outer peripheral side of the part facing the front end in the axial direction of the projecting part from the projecting part. It is bent in the direction of separating in the axial direction.
Here, in addition to the positional relationship in the axial direction between the protruding portion of the rotor hub and the facing surface of the rotor magnet described above, or the positional relationship in the radial direction between the protruding portion and the wide portion of the salient pole portion, the protruding portion that faces the protruding portion is used. The shape of the pole portion is specified.
Thereby, even when a protrusion is provided on a part of the rotor hub, the distance between the protrusion and the rotating magnet can be more reliably ensured by a predetermined amount or more. Therefore, it is possible to avoid the occurrence of a short circuit of the magnetic flux in the portion where the distance is too close due to the distance to the part of the rotor hub arranged so as to cover the rotating magnet. As a result, for example, when viewed from the magnetic head mounted on the magnetic recording / reproducing apparatus, the rotating magnet is completely covered by the rotor hub including the protrusion, and the leakage of magnetic flux to the outside can be effectively prevented. Therefore, it is possible to avoid the leakage magnetic flux from adversely affecting external parts such as a magnetic head.

A spindle motor according to a sixth aspect of the present invention is the spindle motor according to any one of the first to fifth aspects, wherein the protrusion is a protrusion of the stator coil wound around the salient pole portion in the axial direction. It extends to a position that does not reach the height position of the surface facing the part.
Here, the protruding portion that protrudes in the axial direction on the outer side in the radial direction than the rotating magnet in the rotor hub is formed with a length that does not reach the axial height position of the stator coil wound around the salient pole portion.
Thereby, a magnetic flux can be reliably linked to the salient pole part around which the stator coil is wound. As a result, it is possible to more effectively prevent a reduction in motor performance while preventing leakage of magnetic flux to the outside.
A spindle motor according to a seventh aspect of the present invention is the spindle motor according to any one of the first to sixth aspects, wherein a rotating magnet is attached to the rotor hub with a gap in the axial direction. .

Here, the rotating magnet is attached to the rotor hub with a gap in the axial direction.
Thereby, since it can avoid that the magnetic flux formed by a rotating magnet leaks inside a rotor hub, it can prevent that a magnetic flux leaks from the surface of the axial direction opposite side in a rotor hub. Further, by preventing magnetic flux leakage from the surface of the rotor hub, magnetic flux can flow to the salient pole portion around which the stator coil is wound, so that the torque constant of the spindle motor can be improved.
A recording / reproducing apparatus according to an eighth aspect includes the spindle motor according to any one of the first to seventh aspects.
As a result, it is possible to obtain a recording / reproducing apparatus that can effectively prevent leakage of magnetic flux to the outside and prevent the leakage magnetic flux from adversely affecting external components such as a magnetic head.

  The spindle motor according to the present invention can effectively reduce the amount of magnetic flux leaked to the outside of the magnetic flux forming the magnetic field formed by the rotating magnet even when the apparatus is thinned.

A hard disk device (recording / reproducing device) (hereinafter, referred to as HDD) 40 equipped with a spindle motor 20 according to an embodiment of the present invention will be described with reference to FIGS.
[Configuration of HDD 40 as a whole]
As shown in FIGS. 1 and 2, the HDD 40 according to this embodiment includes a head unit 12 including a plurality of recording / reproducing heads 12 a and 12 b and a spindle motor 20. Then, information is written to or reproduced from the disk (recording medium) 13 by the respective recording / reproducing heads 12a and 12b included in the head unit 12.
The head unit 12 includes two recording / reproducing heads 12 a and 12 b and is disposed so as to be close to the front and back surfaces of the disk 13.

The disk 13 is a disk-shaped recording medium having a diameter attached to the HDD 40 of, for example, 0.85 inch, 1.0 inch, or 1.8 inch.
The spindle motor 20 is a device that serves as a rotational drive source for rotationally driving the disk 13, and as shown in FIGS. 1 and 2, a magnet (rotary magnet) 7, a stator core 8, a stator coil 9, and a magnetic shield plate. 14 and a bearing portion (fluid bearing device) 30 and the like.
[Description of each member constituting the spindle motor 20]
The magnet 7 is composed of an Nd—Fe—Bo resin magnet or the like, and is attached to a magnet holding portion 6b (see FIG. 2 and the like) of the rotor hub 6 described later. The magnet 7 is fixed to the surface of the magnet holding portion 6b along the axial direction of the rotor hub 6, and is attached so as to be separated from the surface along the radial direction of the rotor hub 6. That is, the rotor hub 6 and the magnet 7 are fixed to each other in a state of being separated in the axial direction. Thereby, it is possible to prevent the magnetic flux from flowing from the magnet 7 to the lower surface of the rotor hub 6.

  The stator core 8 has a plurality of salient pole portions 28 (see FIG. 3) arranged at substantially equal angular intervals along the radial direction, and the stator coils 9 are wound around the salient pole portions 28, respectively. The Further, the stator core 8 has an inclined portion (bending portion) 8a inclined downward inward in the radial direction at a position facing an axially protruding rim (protruding portion) 6a formed on a part of the rotor hub 6 described later. is doing. Thereby, the stator core 8 prevents a magnetic flux leakage from the salient pole portion 28 of the stator core 8 to the axially projecting rim 6a by ensuring a predetermined distance or more from the axially projecting rim 6a and increasing the magnetic resistance. can do. The salient pole portion 28 includes a coil winding portion 28a around which the stator coil 9 is wound, and a wide portion 28b that is wider than the coil winding portion 28a and formed at the radially innermost side. . The wide portion 28b is formed in a radial direction with respect to the axially protruding rim 6a formed in a part of the rotor hub 6 as shown in FIG. 4 in order to constitute one of the magnetic flux leakage prevention structures 10 described later. It is comprised so that it may be arrange | positioned inside. The magnetic flux leakage prevention structure 10 will be described in detail later.

The magnetic shield plate 14 is attached so as to cover the upper portion of the stator core 8 and is a magnetic stainless steel material having a thickness of about 0.1 mm for preventing magnetic leakage to the outside.
The bearing portion 30 is a hydrodynamic bearing device included in the spindle motor 20, and is configured to include a shaft (shaft) 1, a sleeve 2, a thrust flange 4, a base 5, and a rotor hub 6.
[Description of each member constituting the bearing portion 30]
The shaft 1 is a member that becomes a rotating shaft of the bearing portion 30 and is made of stainless steel.
The sleeve 2 is fitted in a state in which the sleeve 2 can rotate relative to the shaft 1 and the thrust flange 4. A thrust dynamic pressure generating groove (not shown) for generating dynamic pressure is formed on a surface of the thrust flange 4 facing the sleeve 2 in the axial direction, and between the thrust flange 4 and the sleeve 2 is formed. A thrust dynamic pressure generating portion is formed. Similarly, a radial dynamic pressure generating groove (not shown) for generating dynamic pressure is formed between the radially opposing surfaces of the shaft 1 and the sleeve 4, and the radial is formed between the shaft 1 and the sleeve 2. A dynamic pressure generating part is formed. The sleeve 2 is made of a copper alloy such as brass, and the surface is plated with electroless nickel.

The thrust flange 4 is fixed to the shaft 1 by integral processing, press-fitting or adhesion, and is formed of stainless steel.
The base 5 is made of a stainless steel material having magnetism, and may be formed by plating an iron-based material. A disk having a large disk size is formed of an aluminum alloy, which is a nonmagnetic material, and constitutes a stationary part of the spindle motor 20. The base 5 constitutes a sealed housing of the HDD 40. In addition, the base 5 has a bearing portion 30 fixed in the vicinity of the central portion thereof.
The rotor hub 6 has good machinability, excellent outgas resistance, is formed of stainless steel made of a magnetic material, is fixed so as to be fitted to the outer peripheral side of the sleeve 2, and rotates together with the sleeve 2. . The rotor hub 6 includes an axially protruding rim 6a, a magnet holding portion 6b, and a disk mounting surface 6c.

  The axially protruding rim 6a is a substantially annular protruding portion that protrudes toward the lower side in the axial direction provided on the outermost peripheral side in the radial direction of the rotor hub 6, and the magnetic flux generated by the magnet 7 leaks to the outside of the apparatus. It is provided to prevent this. Specifically, as shown in FIG. 2, the axially protruding rim 6a extends below the height position of the upper surface of the magnet 7 disposed on the inner peripheral side (the surface facing the rotor hub 6). At the same time, it extends to a position where it does not reach the height of the stator coil 9 wound around the coil winding portion 28a of the stator core 8. The axially projecting rim 6 a is disposed on the radially outer side than the wide portion 28 b formed at the tip of the salient pole portion 28 of the stator core 8. Further, the axially protruding rim 6 a is disposed at a position facing the inclined portion 8 a in the stator core 8. The magnetic flux leakage prevention structure 10 using the axially protruding rim 6a and the like will be described in detail later.

The magnet holding portion 6 b holds the magnet 7 on the outer peripheral surface side in the extending portion formed on the radially outer side of the sleeve 2 and extending downward in the axial direction.
The disk mounting surface 6c is formed in a step portion formed above the magnet 7 held by the magnet holding portion 6b, and the disk 13 is mounted on the step portion.
<Description of magnetic flux leakage prevention structure 10>
In the spindle motor 20 of the present embodiment, the magnetic flux leakage prevention structure 10 is configured by the positional relationship of the rotor hub 6, the magnet 7, the stator core 8, etc., among the above configurations, and the magnetic flux generated by the magnet 7 leaks to the outside of the apparatus. To prevent it.
Specifically, the magnetic flux leakage prevention structure 10 has a positional relationship in the axial direction between the axially protruding rim 6 a and the upper surface of the magnet 7, and a diameter between the axially protruding rim 6 a and the wide portion 28 b of the salient pole portion 28 of the stator core 8. 3 leakage prevention structures including the positional relationship in the direction and the separation distance between the axially protruding rim 6a and the inclined portion 8a of the stator core 8 are included. Hereinafter, the magnetic flux leakage prevention structure 10 will be described in detail.

(1) Axial positional relationship between the axially protruding rim 6a and the upper surface of the magnet 7 In this embodiment, as shown in FIG. 2, the axially protruding rim is a part of the rotor hub 6 and extends downward in the axial direction. About 6a, the upper surface in the magnet 7 axial direction is extended to a height position exceeding the distance X (X is a positive value). In other words, the axially protruding rim 6 a is formed so as to cover the side surface side of the magnet 7 with respect to the rotor hub 6 disposed so as to cover the upper surface of the magnet 7. Further, the axially protruding rim 6a protrudes from the outermost peripheral side of the rotor hub 6 downward in the axial direction substantially perpendicularly to the lower surface of the rotor hub 6 (substantially parallel to the axial direction).
Thus, the magnetic flux leaking from between the radially outer portion of the rotor hub 6 and the magnetic shield plate 14 provided on the upper surface of the stator core 8 by providing the axially protruding rim 6a so as to cover the side of the magnet 7. Can be effectively reduced. As a result, it is possible to reduce the adverse effect of the leakage magnetic flux on the recording / reproducing heads 12a, 12b, etc., and to avoid problems such as the generation of magnetic noise.

Further, as described above, the axial protruding rim 6 a that reduces the leakage magnetic flux protrudes substantially parallel to the axial direction on the radially outermost side of the rotor hub 6. For this reason, by providing such a protrusion on the rotor hub 6, the axially protruding rim 6a is too close to the magnet 7, so that the magnetic flux from the magnet 7 is short-circuited to a part of the axially protruding rim 6a. There is no end to it. Therefore, even when the axially protruding rim 6a is provided for the rotor hub 6, a sufficient distance between the axially protruding rim 6a and the magnet 7 is ensured to short-circuit the magnetic flux from the magnet 7 to the axially protruding rim 6a. It can be effectively prevented.
The axially protruding rim 6a does not need to protrude strictly vertically, and may be inclined by 70 degrees or more (parallelism within 20 degrees with respect to the rotation axis). Even in this case, it is possible to have both the magnetic leakage prevention effect and the magnetic flux short circuit prevention. Furthermore, the parallelism is more preferably within 5 degrees.

(2) Radial positional relationship between the axially protruding rim 6a and the wide portion 28b of the salient pole portion 28 of the stator core 8 In this embodiment, as shown in FIGS. 3 and 4, the radial direction of the axially protruding rim 6a With respect to the position at, the outer end of the salient pole part 28 constituting the stator core 8 is arranged outside the wide part 28b. In other words, the axial front end portion of the axially protruding rim 6a is disposed at a position facing the coil winding portion 28a on the radially outer side than the wide portion 28b in the opposed stator core 8.
Normally, in the salient pole portion 28 constituting the stator core, the coil winding portion 28a around which the stator coil 9 is wound has a larger magnetic resistance than the position of the wide portion 28b at the tip.
In this embodiment, the axial direction front-end | tip part of the axial direction protrusion rim 6a formed in a part of the rotor hub 6 mentioned above is arrange | positioned in the position facing the coil winding part 28a by the side with a large magnetic resistance.

This increases the magnetic resistance between the axially protruding rim 6a and the coil winding portion 28a, and prevents the magnetic flux linked from the magnet 7 to the stator core 8 from flowing toward the axially protruding rim 6a. By doing so, a reduction in the torque constant of the motor can be suppressed.
The axially protruding rim 6a may be inclined by 70 degrees or more (parallelism within 20 degrees with respect to the rotation axis). Even in this case, it is possible to have both the magnetic leakage prevention effect and the magnetic flux short circuit prevention. Furthermore, the parallelism is more preferably within 5 degrees.
(3) Distance between the axially protruding rim 6a and the inclined portion 8a of the stator core 8 In this embodiment, as shown in FIG. 2, the axially protruding rim 6a is formed on the upper surface of the stator core 8 facing the axially protruding rim 6a. An inclined portion 8a that is inclined downward in a direction away from the center is provided. The inclined portion 8a is bent so as to be inclined downward from the near side facing the axial tip of the axially protruding rim 6a toward the radially outer side.

Thereby, even when the axially protruding rim 6 a extending toward the stator core 8 is provided in a part of the rotor hub 6, a minimum distance between the rotor hub 6 and the stator core 8 is ensured, and the space between the rotor hub 6 and the stator core 8 is ensured. The magnetic coupling in can be reduced. As a result, it is possible to prevent the magnetic flux flowing from the magnet 7 to the stator core 8 from flowing from the stator core 8 to the rotor hub 6 side via the axially protruding rim 6a, and to suppress the decrease in the torque constant of the motor. it can.
The axially protruding rim 6a may be inclined by 70 degrees or more (parallelism within 20 degrees with respect to the rotation axis). Even in this case, it is possible to have both the magnetic leakage prevention effect and the magnetic flux short circuit prevention. Furthermore, the parallelism is more preferably within 5 degrees.

In the present embodiment, the results of performance comparison of the spindle motor 20 employing the above-described magnetic flux leakage prevention structure 10 with a conventional spindle motor will be described with reference to FIGS. Street.
Specifically, a spindle motor (hereinafter referred to as axial direction) having a rotor hub 6 (see FIG. 5A, α≈0 degrees, 5 degrees, 20 degrees) including the axially protruding rim 6a employed in the above embodiment. A spindle motor having a conventional rotor hub 56 (see FIG. 5 (b)) including a protruding portion 56a whose axial protruding portion has an inclined surface of α≈40 degrees or 60 degrees. Hereinafter, it is indicated as an inclined rim), and a spindle motor (hereinafter, referred to as flat) provided with a conventional rotor hub 66 (see FIG. 5C) having no protrusion on the outer peripheral portion 66a. The results of comparing the relationship between the size of the core step, the torque constant (Kt), the attraction ripple, the attraction force, and the leakage magnetic flux density are shown in FIGS.

First, regarding the torque constant (Kt), as shown in FIG. 6, the axially protruding rim (α≈0, α≈5, α≈20) according to the present invention has a smaller torque constant than the conventional flat, It was slightly larger than the conventional inclined rim (α≈40, 60). From this result, it can be seen that the axially projecting rim according to the present invention shows a decrease in torque constant as compared with a conventional flat, but a decrease in torque constant is small compared with a conventional inclined rim.
Next, with respect to the suction ripple, as shown in FIG. 7, the axial protruding rim (α≈0, α≈5, α≈20) according to the present invention is the same as the conventional inclined rim (α≈40, 60). Compared with the results, the suction ripple was reduced, which was almost the same as the conventional flat. From this result, in the axially protruding rim according to the present invention, even when the protruding portion is provided on a part of the rotor hub, it is possible to suppress the rise of the suction ripple as compared with the conventional case having a gentle inclination. Generation of vibrations in the spindle motor can be suppressed.

As shown in FIG. 8, the axially projecting rim according to the present invention, the conventional inclined rim, and the flat were substantially the same as the suction force. As a result, it can be seen that even if the protrusion is provided on a part of the rotor hub, the suction force is not particularly adversely affected.
Finally, with respect to the leakage magnetic flux density (max), as shown in FIG. 9, the axially protruding rim according to the present invention significantly reduces the leakage magnetic flux as compared with the conventional flat rim, similar to the conventional inclined rim. The amount could be reduced. From this result, it was found that the amount of magnetic flux leaking to the outside can be surely reduced by providing a protruding portion (axially protruding rim 6a) extending in the axial direction on a part of the rotor hub.
From the above experimental results, according to the configuration of the present invention, by providing the axially protruding rim 6a in a part of the rotor hub, the leakage magnetic flux to the outside of the device is reduced, the torque constant of the motor is reduced, and the suction ripple is reduced. As a result, a spindle motor with less vibration can be obtained.

[Features of the present spindle motor 20]
(1)
In the spindle motor 20 of the present embodiment, as shown in FIG. 2, the shaft 1, the rotor hub 6 fixed to the axial upper end of the shaft 1, and the substantially annular magnet 7 fixed to the rotor hub 6. And a plurality of salient pole portions 28 around which a stator coil 9 for applying magnetic flux is wound. An axially protruding rim 6 a extending toward the stator coil 9 along the axial direction is formed at the radially outermost peripheral portion of the rotor hub 6.
As a result, by providing the axially protruding rim 6a so as to cover the magnet 7 from the upper surface to the side surface, it is effective that the magnetic flux generated from the magnet 7 leaks from the gap between the rotor hub 6 and the magnetic shield plate 14. Can be prevented. Further, since the axially protruding rim 6a is protruded along the axial direction, the occurrence of harmful effects such as a decrease in torque constant and an increase in suction ripple due to the provision of the protruding portion from the rotor hub 6 can be suppressed and vibration can be prevented. Thus, the spindle motor 20 with a small number of the like can be obtained.

(2)
In the spindle motor 20 of this embodiment, as shown in FIGS. 2 and 4, the shaft 1, the rotor hub 6 fixed to the upper end in the axial direction of the shaft 1, and the substantially annular magnet 7 fixed to the rotor hub 6. There are provided a plurality of salient pole portions 28 having a coil winding portion 28a around which a stator coil 9 for applying magnetic flux is wound and a wide portion 28b formed at the tip portion thereof. The axially protruding rim 6a formed on the outermost peripheral portion in the radial direction of the rotor hub 6 so as to extend toward the stator coil 9 along the axial direction is disposed radially outward with respect to the wide portion 28b. .
Thereby, the axially protruding rim 6a is provided so as to face the wide portion 28b side by providing the axially protruding rim 6a so as to face the side of the stator core 8 where the magnetic resistance is large (coil winding portion 28a side). Compared with the case where it provides, the movement of the magnetic flux with respect to the axial direction protrusion rim 6a from the stator core 8 can be prevented effectively. As a result, leakage of the magnetic flux is prevented by the axially protruding rim 6a, and leakage of the magnetic flux linked from the magnet 7 to the stator core 8 to the axially protruding rim 6a side is prevented to suppress a decrease in the torque constant of the motor. be able to.

In addition, since it has an inclined surface substantially parallel to the axis, the magnetic coupling between the inclined portion of the wide portion 28b and the axially protruding rim 6a can be reduced, and as a result, an increase in attractive force ripple can be suppressed. There is also an effect.
Furthermore, the leakage of magnetic flux to the outside can be more effectively prevented by combining the above-described height position in the axial direction of the axially protruding rim 6a with the configuration specified for the relationship with the upper surface of the magnet 7. .
(3)
In the spindle motor 20 of the present embodiment, as shown in FIG. 2, the shaft 1, the rotor hub 6 fixed to the axial upper end of the shaft 1, and the substantially annular magnet 7 fixed to the rotor hub 6. And a plurality of salient pole portions 28 around which a stator coil 9 for applying magnetic flux is wound. An axially protruding rim 6a extending toward the stator coil 9 along the axial direction is formed at the radially outermost peripheral portion of the rotor hub 6, and a surface on the side of the stator core 8 facing the axially protruding rim 6a. Is formed with an inclined portion 8a.

Thereby, the separation distance between the axially projecting rim 6a and the stator core 8 is secured to the minimum by the inclined portion 8a, thereby preventing leakage of magnetic flux interlinked from the magnet 7 to the stator core 8 to the axially projecting rim 6a. be able to. As a result, it is possible to suppress a decrease in the torque constant of the motor while preventing leakage of magnetic flux to the outside of the apparatus.
Further, since a predetermined gap amount can be opened between the protruding portion and the inclined portion 8a of the stator core 8, the magnetic coupling between the wide portion 28b and the axial protruding rim 6a can be reduced, and as a result, the attractive force There is also an effect that an increase in ripple can be suppressed.
Further, the above-described configuration in which the height position in the axial direction of the axially protruding rim 6a is specified with respect to the upper surface of the magnet 7, and the position of the salient pole portion 28 in the radial direction of the axially protruding rim 6a. By combining with the configuration specified for the relationship, leakage of magnetic flux to the outside can be more effectively prevented.

(4)
In the spindle motor 20 of this embodiment, as shown in FIG. 2, the axially protruding rim 6a reaches the height position of the stator coil 9 wound around the coil winding portion 28a of the salient pole portion 28 in the axial direction. It is formed so as not to.
Thereby, a magnetic flux can be reliably linked to the inside of the stator core 8 around which the stator coil 9 is wound. As a result, a decrease in torque constant can be reduced and a reduction in motor performance can be prevented.
(5)
In the spindle motor 20 of this embodiment, as shown in FIG. 2, the rotor hub 6 to which the magnet 7 is attached and the magnet 7 are fixed to each other with a gap in the axial direction.

As a result, compared to the conventional configuration in which the upper surface of the magnet and the lower surface of the rotor hub are in contact, the magnetic flux generated from the magnet 7 is transmitted from the lower surface of the rotor hub 6 and the magnetic flux leaks from the upper surface of the rotor hub 6. Can be prevented. As a result, the magnetic flux generated from the magnet 7 can be efficiently directed to the stator core 8 to effectively prevent the torque constant from being lowered.
(6)
In the spindle motor 20 of the present embodiment, as shown in FIG. 2, an inclined portion 8a is provided as a bent portion formed on the upper surface of the stator core 8 facing the axially protruding rim 6a formed on a part of the rotor hub 6. ing.
Thereby, since the separation distance between the axially protruding rim 6a and the upper surface of the stator core 8 can be increased, the magnetic flux linked from the magnet 7 to the stator core 8 flows toward the axially protruding rim 6a. Can be prevented. As a result, it is possible to maintain the motor performance by keeping the magnetic flux interlinked in the stator core 8 and preventing a decrease in the torque constant of the motor.

[Other Embodiments]
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the summary of invention.
(A)
In the above embodiment, the magnetic flux leakage prevention structure 10 includes three structures (the positional relationship between the axially protruding rim 6a and the upper surface of the magnet 7, the axially protruding rim 6a and the wide portion 28b of the salient pole portion 28 of the stator core 8). The positional relationship and the positional relationship between the axially protruding rim 6a and the inclined portion 8a of the stator core 8) have been described as examples. However, the present invention is not limited to this.
For example, the spindle motor of the present invention can be configured using a rotor hub, a stator core, or the like that employs only one of the above three configurations. Or you may comprise the spindle motor of this invention using the rotor hub, stator core, etc. which combined two of the said three structures.

Even in these cases, the respective effects of the magnetic flux leakage prevention structure 10 can reduce the amount of magnetic flux leaking to the outside of the apparatus and prevent the decrease in the torque constant of the motor. .
(B)
In the above embodiment, an example in which the spindle motor 20 according to the present invention is mounted on the HDD 40 on which only one disk 13 is mounted has been described. However, the present invention is not limited to this.
For example, as shown in FIG. 10, the spindle motor 120 according to the present invention may be adopted for an HDD (recording / reproducing apparatus) 140 on which two or more disks 13 are mounted via a spacer 112.

In this case, the bearing portion 130 including the shaft (shaft) 101, the sleeve 102, and the like, and the spindle motor 120 including the rotor hub 106 may be used, and an axially protruding rim may be provided on a part of the rotor hub 106 as described above. .
Thus, the present invention can be applied to a recording / reproducing apparatus such as the HDD 140 mounted with a plurality of disks.
(C)
In the embodiment described above, an example in which a projecting portion having a substantially square cross section is used as the axial projecting rim 6a formed on the outer peripheral portion of the rotor hub 6 in order to reduce leakage magnetic flux to the outside has been described. However, the present invention is not limited to this.
For example, for the radially inner stretched portion, it is preferably a surface along the axial direction since the distance from the magnet is reduced by having an inclined surface, but the radially outer stretched portion As for the axially protruding rim 6a of the above-described embodiment, the surface does not have to be a surface along the axial direction, and may be a surface oblique to the axial direction or a protruding surface.

(D)
In the above embodiment, the spindle motor 20 according to the present invention has been described as an example applied to the HDD 40. However, the present invention is not limited to this.
For example, the present invention can naturally be applied to a spindle motor mounted on a magneto-optical disk device, an optical disk device, a floppy (registered trademark) disk, or the like.

  The spindle motor of the present invention has the effect of effectively reducing the amount of magnetic flux leakage to the outside of the magnetic flux that forms the magnetic field formed by the rotating magnet even when the device is thinned. The present invention can be widely applied as a spindle motor mounted on various recording / reproducing apparatuses such as an HDD, a magneto-optical disk apparatus, an optical disk apparatus, and a floppy (registered trademark) disk.

1 is a cross-sectional view showing a configuration of an entire HDD equipped with a spindle motor according to an embodiment of the present invention. FIG. 2 is an enlarged view in which a part of the HDD of FIG. 1 is enlarged. The top view which shows the structure of the stator core which comprises HDD of FIG. (A), (b) is an enlarged view which shows the positional relationship in the radial direction of the wide part of a stator core and axial direction protrusion rim in the internal structure of HDD of FIG. (A) is the rotor hub employ | adopted for the spindle motor which concerns on a present Example, (b), (c) is sectional drawing which each shows the structure of the rotor hub mounted in the conventional spindle motor. FIG. 6 is a graph showing the relationship between the magnitude of the magnet-core step and the torque constant of the motor for the spindle motor according to the embodiment of FIGS. 5 (a) to 5 (c). FIG. 6 is a graph showing the relationship between the size of the magnet-core step and the suction ripple of the motor for the spindle motor according to the embodiment of FIGS. 5 (a) to 5 (c). The graph which shows the relationship between the magnitude | size of a magnet-core level | step difference, and attractive force about the spindle motor which concerns on the Example of Fig.5 (a)-FIG.5 (c). The graph which shows the leakage magnetic flux density according to each direction about the spindle motor which concerns on the Example of Fig.5 (a)-FIG.5 (c). Sectional drawing which shows the structure of the whole HDD carrying the spindle motor which concerns on other embodiment of this invention.

Explanation of symbols

1 Shaft
2 Sleeve 4 Thrust flange 5 Base 6 Rotor hub 6a Axial protruding rim (protruding portion)
6b Magnet holding part 6c Disk mounting surface 7 Magnet (rotating magnet)
8 Stator core 8a Inclined part (bent part)
9 Stator coil 10 Magnetic flux leakage prevention structure 12 Head portion 12a, 12b Recording / reproducing head 13 Disc (recording medium)
14 Magnetic shield plate 20 Spindle motor 28 Salient pole part 28a Coil winding part 28b Wide part 30 Bearing part (fluid bearing device)
40 HDD (recording and playback device)
56 Rotor hub 56a Protruding portion 66 Rotor hub 66a Outer peripheral portion 101 Shaft (axis)
102 Sleeve 106 Rotor hub 112 Spacer 120 Spindle motor 130 Bearing portion 140 HDD (recording / reproducing apparatus)

Claims (8)

The axis,
A stator coil is wound, and a plurality of salient pole portions arranged along a radial direction centered on the axis;
A substantially annular rotating magnet disposed on the radially inner side with respect to the salient pole part;
The rotor magnet is mounted, and a rotor hub that rotates about the axis;
With
The rotor hub has a protruding portion that protrudes substantially parallel to the shaft on one side in the axial direction on a surface facing the rotating magnet on a radially outer side than a mounting position of the rotating magnet,
The tip of the protruding portion extends to a position that exceeds the height position of the surface on the other axial side of the rotating magnet.
Spindle motor. The axis,
A plurality of windings are arranged along the radial direction centering on the shaft, and a winding part around which the stator coil is wound, and the winding part formed at the radially inner tip part of the winding part A salient pole portion having a wide width portion,
A substantially annular rotating magnet disposed on the radially inner side with respect to the salient pole part;
The rotor magnet is mounted, and a rotor hub that rotates about the axis;
With
The rotor hub has a protruding portion that protrudes to the one side in the axial direction on a surface facing the rotating magnet on the radially outer side than the mounting position of the rotating magnet,
The projecting portion has an axial tip portion arranged outside the wide portion in the radial direction,
Spindle motor. The axis,
A stator coil is wound, and a plurality of salient pole portions arranged along a radial direction centered on the axis;
A substantially annular rotating magnet disposed at a position facing the salient pole portion;
The rotor magnet is mounted, and a rotor hub that rotates about the axis;
With
The rotor hub has a protruding portion that protrudes to the one side in the axial direction on a surface facing the rotating magnet on the radially outer side than the mounting position of the rotating magnet,
The salient pole portion has a bent portion that is bent in a direction away from the protruding portion at a portion facing the tip end portion in the axial direction of the protruding portion.
Spindle motor. The salient pole part has a winding part around which a stator coil is wound, and a wide part wider than the winding part formed at the distal end portion on the radially inner side of the winding part. And
The axial tip portion of the projecting portion is disposed on the outer side in the radial direction than the wide portion.
The spindle motor according to claim 1. The salient pole part is bent in a direction away from the projecting part in the axial direction at a part on the outer peripheral side from a part facing the tip end part in the axial direction of the projecting part.
The spindle motor according to claim 1 or 2. The protrusion extends in the axial direction to a position that does not reach a height position of a surface facing the protrusion of the stator coil wound around the salient pole part.
The spindle motor according to any one of claims 1 to 5. The rotating magnet is attached to the rotor hub with a gap provided in the axial direction.
The spindle motor according to any one of claims 1 to 6. A spindle motor according to any one of claims 1 to 7,
A head unit that performs recording and reproduction on a disk mounted on a disk mounting surface formed on the rotor hub;
A recording / reproducing apparatus.

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