Disk drive with airflow control and fins at a transition surface between base surfaces

Embodiments of the invention suppress the occurrence of turbulence in a disk drive. In one embodiment, an HDD includes a spindle motor for rotating a magnetic disk, and a base for housing the spindle motor therein. The base includes a first bottom surface opposed to the magnetic disk, and a second bottom surface that is opposed to the magnetic disk and that is larger in distance to the magnetic disk than the first surface. A step is formed between the first bottom surface and the second bottom surface, where rotation of the magnetic disk produces an airflow running from the first surface toward the second surface. The step is provided with upright fins extending from the first surface toward the second surface which are stood upright.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority from Japanese Patent Application No. JP2004-373078, filed Dec. 24, 2004, the entire disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a disk drive, and more particularly, to control of an airflow generated by rotation of a recording disk in a disk drive.

Data storage devices using various types of media such as optical disks and magnetic tapes are known in the art. Among them, hard disk drives (hereinafter referred to as HDDs) have become popular as storage devices for computers to such an extent that they are one type of the storage devices indispensable for today's computers. Further, not limited to computer systems, HDDs are expanding more and more in application because of their excellent characteristics. For example, HDDs are used for moving picture recording/reproducing devices, car navigation systems, cellular phones, and removable memories for use in digital cameras.

Each magnetic disk used in an HDD has a plurality of tracks formed concentrically and each track is divided into a plurality of sectors. Servo data and user data are stored in each of the sectors. A spindle motor rotates the magnetic disk and a head element as a thin film element makes access to a desired address position in accordance with the servo data stored in a sector, whereby it is possible to effect write or read of data to or from the magnetic disk.

Head element portions are fixed to a slider and constitute a head. The slider flies above a rotating magnetic disk to thereby enable positioning of the head or head element portions to a desired position on the magnetic disk. In data read processing, a signal read from the magnetic disk by a head element portion is subjected to predetermined signal processing such as waveform shaping or decoding processing by a signal processing circuit and is transmitted to a host. The data transferred from the host is subjected to predetermined processing by the signal processing circuit, after which it is written in the magnetic disk.

The HDD has a problem with an airflow generated by rotation of the magnetic disk. For example, the airflow causes an actuator to flutter, which obstructs accurate positioning of a head. In order to suppress the vibration of the head caused by turbulence of an airflow, for example, Patent Reference 1 (Japanese Patent Laid-open No. 2004-171674) discloses a magnetic disk device in which a straightening plate is provided on a ramp in order to suppress the vibration of the head caused by turbulence of an airflow.

The HDD has another problem of vibration of a magnetic disk (disk flutter) caused by the turbulence of an airflow generated by rotation of the magnetic disk. The disk flutter obstructs accurate positioning of the head to the track, similar to the vibration of the head itself. In particular, an increase in recording density of the magnetic disk raises TPI (Track Per Inch), which requires more accurate positioning of the head. Thus, slight disk flutter poses a great problem.

BRIEF SUMMARY OF THE INVENTION

One approach to reduce the flutter of the magnetic disk is to make a gap between the bottom surface of the base and the magnetic disk small to suppress a flow of gas between the magnetic disk and the base bottom surface. However, as the base bottom surface is made closer to the magnetic disk to increase air resistance is increased, thereby increasing the current of the spindle motor.

The present invention has been accomplished on the basis of the circumstances as described above, and a feature of the invention is to suppress the flutter of a magnetic disk to reduce the amount of motor current.

Here, a base bottom surface is formed with some steps. For example, since it is necessary to ensure the turning space of an actuator, part of the base bottom surface cannot be made closer to the magnetic disk. Therefore, a step is produced between a base bottom surface near the recording surface of the magnetic disk and another base bottom surface away from the recording surface of the magnetic disk. The inventors have studied earnestly, and then found that the shape of the step between the base bottom surfaces greatly contributes to the turbulence of an airflow caused by rotation of the magnetic disk, or to the current amount of the spindle motor.

A disk drive according to a first aspect of the present invention comprises: a motor for rotating a recording disk; a base adapted to house the motor therein, and having a first bottom surface opposite to the recording disk and a second bottom surface opposite to the recording disk, a distance between the second bottom surface and the recording disk being greater than that between the first bottom surface and the recording disk; and an upright fin extending from the first bottom surface to the second bottom surface, at a step between the first bottom surface and the second bottom surface, where rotation of the recording disk produces an airflow running from the first bottom surface toward the second bottom surface. With provision of the fin, it is possible to suppress the turbulence of an airflow.

In some embodiments, the step is formed by a slope extending from the first bottom surface toward the second bottom surface.

In some embodiments, the step is formed with a plurality of fins. Further, preferably, the plurality of fins are spaced apart from each other at substantially equal intervals in the radial direction of the recording disk. Thus, it is possible to suppress the turbulence of an airflow more effectively.

Preferably, the plurality of fins each have a circular arc sidewall which is convex toward the outer circumference of the recording disk.

Preferably, an inclined angle of the step is substantially 5° to 15°. Thus, it is possible to suppress the turbulence of an airflow more effectively.

The disk drive further includes an actuator which is turned to thereby move a head above the recording disk, wherein the second bottom surface is formed at a level lower than the first bottom surface so as to form a turning range of the actuator. In the disk drive with such a configuration, the present invention is particularly effective.

A disk drive according to another aspect of the present invention comprises: a motor for rotating a recording disk; a base for housing the motor, and having a first bottom surface opposite to the recording disk and a second bottom surface, a distance between the second bottom surface and the recording disk being greater than that between the first bottom surface and the recording disk; a first step located between the first bottom surface and the second bottom surface, where rotation of the recording disk produces an airflow running from the first bottom surface toward the second bottom surface; and a second step located between the first bottom surface and the second bottom surface, where the rotation of the recording disk produces an airflow running from the second bottom surface toward the first bottom surface, the second step having an inclined angle larger than that of the first step. Since the inclined angle of the second step is larger than that of the first step, it is possible to suppress the turbulence of an airflow to reduce the amount of current of the motor.

In specific embodiments, an inclined angle of the step is substantially 5° to 15° in order to suppress the turbulence of an airflow more effectively. Further, an inclined angle of the second step is substantially 45° or more in terms of reduction in the current amount of the motor. Furthermore, the first step is provided with a plurality of fins stood upright from the base bottom and extending from the first surface toward the second surface; and the plurality of fins each have an inner circumferential surface and an outer circumferential surface that are curved in the inner circumferential direction of the recording disk, and are spaced apart from each other at substantially equal intervals in the radial direction of the recording disk. With the provision of fins, it is possible to suppress the turbulence of an airflow.

Preferably, the first step is provided a fin stood upright from the base bottom and extending from the first surface toward the second surface. With the provision of fins, it is possible to suppress the turbulence of an airflow.

According to the present invention, it is possible to suppress flutter of a recording disk to reduce the amount of current of the motor.

DETAILED DESCRIPTION OF THE INVENTION

The specific embodiments to which the present invention is applied will be hereinafter described. For clarification of explanation, the following description and drawings are suitably omitted and simplified. Further, in the drawings, the same elements are indicated by the same reference numerals, and to clarify explanation, duplicate explanation or the reference numerals of the drawings are omitted.

Specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. The disk drive in the present embodiment is characterized by the structure of the base thereof. For better understanding of the present invention, first, the whole structure of a hard disk drive (hereinafter referred to as HDD) as one example of the disk drive will be described.FIG. 1is an exploded perspective view schematically showing the structure of a HDD100according to the present embodiment. InFIG. 1, numeral101denotes a recording medium for storing data, which is a magnetic disk, a non-volatile recording disk, for storing data by magnetizing a magnetic layer. Numeral102denotes a base for housing structural elements of the HDD100. The base102is fixed to a top cover103closing an upper opening of the base102through a gasket104to constitute a disk enclosure, which is able to house the structural elements of the HDD100in a closed state. Incidentally, the structure of the base102will be mentioned later in detail.

The magnetic disk101is placed on a hub of a spindle motor105, held between a screwed top clamp106and a hub, and thereby fixed to the spindle motor105. The spindle motor105is fixed to the bottom surface of the base102to rotate the magnetic disk101at a predetermined speed.

An actuator107is held by a turning shaft108for turning, and driven by a VCM (Voice Coil Motor)109. The actuator107holds a head (not shown) at an extreme end thereof, and turns to position the head to a desired position on the magnetic disk101. The head comprises a slider, and a head element as a conversion element fixed to the surface of the slider. The head element writes and/or reads to and/or from the magnetic disk101data input and output between the head element and a host (not shown). The head element portion has a recording element for converting an electrical signal into a magnetic field according to data stored in the magnetic disk101and/or a reproducing element for converting the magnetic field from the magnetic disk101into an electrical signal.

The actuator107includes structural members, that is, a suspension110, an arm111, a coil support112, and a flat coil113, which are connected to one another in that order from the extreme end where the head is disposed. Numeral114denotes an upper stator magnet holding plate, numeral115adenotes a lower stator magnet, and numeral115bdenotes a lower stator magnet holding plate. These are arranged so as to put the flat coil113between an upper stator magnet (not shown) fixed to the upper stator magnet holding plate114and the lower stator magnet115b. The VCM109is composed of the flat coil113, the upper stator magnet and the lower stator magnet115a.

Numeral116denotes a ramp adapted to rest the head unloaded from the magnetic disk101when rotation of the magnetic disk101stops. The present embodiment illustrates the load/unload system HDD with the ramp116, but the present invention can be also applied to a CSS (Contact Start and Stop) system in which when data write/read processing is not carried out, the head is unloaded to a zone arranged in the inner periphery of the magnetic disk101.

Further, the present embodiment illustrates the HDD provided with a single magnetic disk, but the present invention can be applied to a HDD provided with a plurality of stacked magnetic disks. If a plurality of magnetic disks are provided, the spindle motor integrally holds the plurality of magnetic disks spaced from one another at fixed intervals in the direction of a rotary axis thereof. Further, typically, data are stored in both surfaces of the magnetic disk as shown in the present embodiment, but the structure for recording data on only one surface of the magnetic disk is enabled.

For read/write of data from the magnetic disk101, the actuator107moves the head above the data region of the surface of the rotating magnetic disk101. The actuator107turns about the rotary shaft108whereby the head moves in the radial direction of the surface of the magnetic disk101. Thus, the head (head element portion) is able to get access to a desired track. Pressure caused by viscosity of air between an ABS (Air Bearing Surface) opposite to the magnetic disk101and the rotating magnetic disk becomes balanced with pressure applied in the direction of the magnetic disk101by the suspension110whereby the head flies at a fixed gap above the magnetic disk101.

When rotation of the magnetic disk101stops, the actuator107withdraws the head from the data region to the ramp116. The actuator107turns in the direction of the ramp116, and the tab at the extreme end of the actuator slidably moves on the slope of the ramp116to ride on the parking surface of the ramp116, whereby the head is unloaded. At the time of loading, the actuator107supported on the parking surface is disengaged from the ramp116, and moves above the surface of the magnetic disk101.

A circuit board (not shown) is mounted on the outer surface (lower surface) of the base102. The circuit board is typically a rectangle of the size that covers the outer half surface of the base102. Electric power and signals for driving the motor are input and output between the circuit board and the spindle motor105. Power to a coil for the VCM109, electric power and signals for read of the head is input and output between the circuit board and the actuator107. Input/output between the circuit board and the head is carried out through a FPC117afixed to a FPC (Flexible Printed Circuit) support117b.

The base102in the present embodiment will be described in detail hereinafter. As shown inFIG. 1, the base102is provided with a bottom portion210to which the structural parts of the HDD100are fixed, and a wall portion220formed so as to surround the outer periphery of the bottom portion210. The bottom portion210is provided with a plurality of areas (bottom surfaces). One of them is a first bottom surface211opposed to the magnetic disk101and located at a level higher than other bottom surfaces. Another one is a second bottom surface212that is formed adjacent to the first bottom surface and on the side of the actuator107in the first bottom surface. The second bottom surface212is lower than the first bottom surface211and corresponds to the turning range of the actuator107. Furthermore, the bottom portion210is provided with a third bottom surface213which is lower than the second bottom surface212and to which the structural parts of the VCM109are fixed.

FIG. 2is a perspective view showing a partial structure of the HDD100in the present embodiment. InFIG. 2, the magnetic disk101is omitted. The first bottom surface211opposed to the magnetic disk101is formed at a level higher than the second bottom surface212, and is small in distance from the recording surface of the magnetic disk101. The first bottom surface211occupies a major surface facing the magnetic disk101in the bottom portion210. A gap between the first bottom surface211and the magnetic disk101is made small to thereby suppress an airflow between the magnetic disk101and the first bottom surface211, thereby reducing the flutter of the magnetic disk101.

To suppress the flutter of the magnetic disk101, preferably, the whole bottom surface opposed to the magnetic disk101is made closer to the magnetic disk101. However, it is necessary to define a space adapted to turn the actuator107between the bottom portion210and the recording surface of the magnetic disk101. As mentioned above, the second bottom surface212corresponds to the turning range of the actuator107, a part thereof is opposed to the magnetic disk101, and the other part thereof is opposed to the actuator107in an unloaded state. The second bottom surface212is formed at a level lower than the first bottom surface211whereby the space adapted to turn the actuator107can be secured between the magnetic disk101and the second bottom surface212.

As described above, the distance between the surface of the second bottom surface212, opposed to the magnetic disk101and the recording surface of the magnetic disk101is larger than that between the surface of the first bottom surface211, opposed to the magnetic disk101and the recording surface of the magnetic disk101. Thus, two steps215,216or differences in level are present between the first bottom surface211and the second bottom surface212. The first step215is present on the rear end side of the actuator107, that is, on the side of the VCM109. The second step216is present on the extreme end side of the actuator107, that is, on the side of the head or ramp116.

The first step215is formed with a slope251extending from the first bottom surface211toward the second bottom surface212. Further, the step215is formed with a plurality of fins extending from the first bottom surface211toward the second bottom surface212. In an example ofFIG. 2, the first step215is formed with three fins252a,252b, and252cillustratively.

FIG. 3is a top plan view showing the internal structure of the HDD100according to the present embodiment. InFIG. 3, only the outline of the magnetic disk101is shown, and the base bottom portion210to which the magnetic disk101is opposed is shown. As shown inFIG. 3, the magnetic disk101rotates toward the suspension110from the VCM107. In other words, the magnetic disk101rotates counterclockwise as viewed from the top cover103(the side opposite to the base102).

Rotation of the magnetic disk101produces an airflow between the magnetic disk101and the base bottom portion210. The airflow runs in the rotational direction of the magnetic disk101. Thus, in the first step215, the airflow runs from the first bottom surface211toward the second bottom surface212according to the rotation of the magnetic disk101. On the other hand, in the second step216, the airflow runs from the second bottom surface212toward the first bottom surface211according to the rotation of the magnetic disk101.

Returning toFIG. 2, the step215is formed with the slope251as mentioned above. This suppresses the turbulence of the airflow running from the first bottom surface211toward the second bottom surface212, and leads to reduction in flutter of the magnetic disk101, or reduction in the current amount of the spindle motor105. The slope251is formed such that its height becomes progressively smaller from the first bottom surface211toward the second bottom surface212. Accordingly, the distance between the slope251and the magnetic disk101become progressively larger as the second bottom surface212is approached. As described above, the space between the base bottom210and the magnetic disk101is gradually widened from the narrow space between the first bottom surface211and the magnetic disk101to the wide space between the second bottom surface212and the magnetic disk101. This makes it possible to effectively suppress the turbulence of airflow (generation of turbulent flow) at the first step215.

Here, it is preferred that to suppress the turbulence of airflow, a slope in which the distance relative to the magnetic disk101changes continuously is formed, but the first step215may be formed with a slope having another shape. For example, it is possible to form a plurality of sub-steps in the first step215. Further, the slope may be formed to be a convex or concave circular arc relative to the magnetic disk101.FIG. 4shows an example of a sectional shape of the first step215.FIG. 4(a) shows the linear slope shown inFIG. 2,FIG. 4(b) shows a slope with a concave circular arc relative to the magnetic disk101, andFIG. 4(c) shows a multi-step slope.

To effectively suppress an airflow running from the first step215toward the second step216, an inclined angle of the slope of the first step215is preferably substantially 5° to 15°, more preferably, about 7° to 13°. Here, the inclined angle is an angle defined between a line joining an end of the first bottom surface211and the end of the second bottom surface212of the first step215and the second bottom surface212as shown inFIG. 4.

Further, a plurality of fins252are present in the first step215. In the present example, each fin252is provided on the slope251, and stand upright substantially vertical to the first and second bottom surfaces211,212. The upper surface of each fin252(surface opposed to the magnetic disk101) is substantially flush with the first bottom surface211. The distance between the upper surface of each fin252and the magnetic disk101is substantially the same as that between the first bottom surface211and the upper surface of each fin252. The side face of each fin252on the side of the second bottom surface212is substantially vertical to the second bottom surface212. In the present embodiment, the fin252is formed integral with the base101, that is, the fin252and the base101are the same member. Therefore, the fin252can be formed merely by processing the base102without increasing the number of components. It is to be noted that the fin252may be formed with a slope on the upper surface thereof or on the side face thereof on the side of the bottom surface212.

Referring toFIG. 3, a plurality of fins252are spaced apart from each other in the radial direction of the magnetic disk101. The fins252are spaced apart from each other at equal intervals. Alternatively, the fins252are spaced apart from each other at unequal intervals. Where the fins252are spaced apart from each other at unequal intervals, they can be spaced at intervals that become progressively larger from the inner peripheral side toward the outer peripheral side of the magnetic disk101. Alternatively, they can be spaced at intervals that become progressively smaller from the inner peripheral side toward the outer peripheral side. The spacing between each fin252is set to a preferable value in terms of reduction in disk flutter or motor current. To suppress the turbulence of airflow produced by the rotating magnetic disk101, preferably, each fin252is provided with a circular arc-like sidewall that is convex toward the outside of the magnetic disk101. Further, preferably, the sidewall substantially coincides with, and is curved along, the circumference of the magnetic disk101. The circular-arc-like sidewall can be formed merely on the inner peripheral side or outer peripheral side of each fin252, but as shown inFIG. 5, preferably, the sidewalls on both sides of each fin252are circular arc-like as mentioned above.

In the first step215, the plurality of fins252control the airflow in the radial direction of the magnetic disk101so as to run along the circumferential direction thereof. As shown inFIG. 5, the airflow runs along the plurality of fins252, and the fins252suppress the turbulence of the airflow running in the radial direction of the magnetic disk101in the first step215. Thus, it is possible to reduce the amount of current used by the spindle motor105for rotating the magnetic disk101.

The effect of the fins252in the present embodiment was measured. Current amounts of the spindle motor were measured for a HDD in which the base having a fin is mounted on the first step portion, and a HDD in which the base not provided with a fin is mounted on the first difference in level portion.FIG. 6shows the measurements. In the graph ofFIG. 6, the X-axis indicates a position of an actuator, and the Y-axis indicates the current amount of a spindle motor. In the X-axis, “unload” means a state where the actuator107is withdrawn to the ramp116, “OD” an outer peripheral side, “MD” a center, and “ID” an inner peripheral side. The structures of the two HDDs were the same except for the presence or absence of the fins. As shown in the graph ofFIG. 6, in the state where the actuator is unloaded, a great reduction in the current amount of the spindle motor of the HDD with the fins is found.

In the above-mentioned base102, the first step215is provided with the slope251and the fins252, but only one of them may be also employed in alternative embodiments. For example, in the first step215, the first bottom surface211and the second bottom surface212are joined together through the sidewall vertical thereto, and the sidewall is formed with a fin extending therefrom toward the second bottom surface212. Further, it is preferable that a plurality of fins be formed in terms of suppressing a turbulent flow, but even a single fin can exhibit the straightening effect.

Referring toFIGS. 2 and 3, a flow passage is formed which extends from the first bottom surface211toward the third bottom surface213having the VCM109thereon. The flow passage is formed with a slope231(FIG. 5). The slope231is formed so that the height thereof becomes progressively smaller from the first bottom surface211toward the third bottom surface213. That is, the distance between the magnetic disk101and the slope increases progressively. As described, a section (space) expands progressively from the narrow space between the first bottom surface211and the magnetic disk101toward a wide space defined between the third bottom surface213having the VCM109thereon and the magnetic disk. Thus, the turbulence of an airflow under the magnetic disk101can be suppressed effectively. It is to be noted that the slope231can be replaced with an inclined surface of another shape similar to the first step215.

Now, the second step216will be described hereinafter. In the HDD100of the present embodiment, the steps215,216are formed such that an inclined angle of the second step216is larger than that of the first step215. In the present embodiment, as shown inFIG. 7, the second step216is not formed with a slope, but a wall261is formed substantially vertical to the second bottom surface212.

Preferably, the first difference in level portion215is formed at a predetermined inclined angle in terms of turbulent suppression. Preferably, in the second step216, however, an inclined angle is made larger in terms of reduction in current amount of the spindle motor. The inclined angles of the two steps215,216are made to differ from each other, and the slopes are formed unsymmetrical, whereby reduction in turbulence of airflow and consumption power can be achieved. An inclined angle of the second step216from the second bottom surface212toward he first bottom surface211is preferably substantially not less than 45°, preferably not more than 90°. The slope shape of the second step216can be formed, for example, as in the aforementioned first step portion215. However, preferably, the second step216is formed with the substantially vertical wall261(an inclined angle 90°), as shown inFIG. 7.

FIG. 8is a diagram showing the effect of the second step216in the present embodiment. The current amounts of the spindle motor were measured for a HDD having the base in which the second step216is not inclined is mounted thereon, and a HDD having the base in which the slope and fins similar to those of the first step215are provided on the second step216mounted thereon. The first step215was provided with the slope251and the plurality of fins252, as shown inFIG. 2. The structures of the two HDDs were the same except the shape of the second step.FIG. 8shows the measurements. In the graph ofFIG. 8, the X-axis indicates a position of an actuator, and the Y-axis indicates the current amount of a spindle motor. In the HDD having the second step216without a slope, a reduction in the current amount of the spindle motor in the positions of the actuator is found as shown in the graph ofFIG. 8.

As described above, an inclined angle of the second step216that generates an airflow running from the second bottom surface212toward the first bottom surface211is made larger than that of the first step215that generates an airflow running from the first bottom surface211close to the magnetic disk101toward the second bottom surface212away from the magnetic disk101. This achieves suppression of turbulence generation and reduction in consumption power. It is to be noted that in the above-described embodiment, the first step215is provided with the fins252, but the first step215may not be provided with fins in other embodiments.

The foregoing description explains the embodiments of the present invention, and the present invention is not limited thereto. It is possible for those skilled in art to easily change, add or convert the elements of the aforementioned embodiments within the scope of the present invention. For example, the present invention can be applied to a device provided with a recording disk other than the magnetic disk of the present invention. Alternatively, the present invention can be applied to a data storage device for carrying out only reproduction in addition to a data storage device for carrying out recording and reproduction.