Dynamic magnetic information storage or retrieval – Record transport with head stationary during transducing – Disk record
Reexamination Certificate
2001-09-19
2004-02-10
Evans, Jefferson (Department: 2652)
Dynamic magnetic information storage or retrieval
Record transport with head stationary during transducing
Disk record
Reexamination Certificate
active
06690540
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a disk drive apparatus, which is typically a hard disk drive.
2. Background Art
A hard disk drive (hereinafter, to be referred to as the HDD), which is the most popular storage means for computer data, is structured so that a single or a plurality of magnetic disks are disposed on one and the same axis and driven rotationally by a spindle motor therein. A head provided so as to face each magnetic disk reads/writes data from/on the disk. The head is driven by an actuator, usually by a voice coil motor (hereinafter, to be described as the VCM). The magnetic disk, the head, and the actuator are all housed in housing referred to as a disk enclosure. The disk enclosure is configured by a thin-box-like base made of an aluminum alloy and a top cover used to seal the opening of the base. Improvement of the storage capacity per magnetic disk and improvement of the speed for reading/writing data from/on the magnetic disk have been main technical issues for improvement of the HDD.
The latter issue, that is, improvement of the speed for reading/writing data, can be achieved by reducing the seek time of the head that moves to a target track on the subject disk. This seek time can also be improved by improving the performance of the VCM, since the VCM drives the head as described above. And, in order to improve the performance of the VCM, it is only required to make the magnetic power of the permanent magnet of the VCM more stronger or increase the thickness of the permanent magnet, thereby increasing the magnetic field to be applied to the voice coil. The improvement of the magnetic power of the permanent magnet, however, has already reached its technical limit. In addition, the thickness of the permanent magnet cannot be increased any longer in such the HDD whose compaction is demanded more and more.
Furthermore, the speed for reading/writing data can also be improved by speeding up the rotation of the magnetic disk. As the rotation of the magnetic disk is speeded up such way, however, a problem arises from the sound or vibration properties of the subject HDD.
3. Problems to be Solved by the Invention
Conventionally, a damper has been stuck on the subject HDD so as to repress the HDD vibration. The damper is made of, for example, stainless steel.
FIG. 9
shows an example of such a damper having been used conventionally. The damper
50
shown in
FIG. 9
is formed by punching a flat plate into a predetermined shape. In this case, therefore, the HDD design parameters to be changed freely are the external dimension and the thickness of the HDD. And, the external dimension is limited by the size of the HDD. For example, the external dimension is just permitted to have such an additional portion as the damper
51
shown in
FIG. 10
at part thereof. An increase of the wall thickness of the HDD might also cause the life of the punching mold for punching the damper to be reduced and such an increase of the wall-thickness is limited by the size of the HDD.
The conventional HDD includes two problems to arise from sound or vibration.
One is existence of a sound frequency peak to be generated by the rotation of the spindle motor for driving the HDD. Although a damper is formed so as to reduce this sound frequency, the sound frequency is often amplified when the resonant frequency of the damper matches with the HDD sound frequency band in which a sound frequency peak is generated by the rotation of the spindle motor (hereinafter, to be referred to as an HDD sound peak frequency band). Especially, as the rotation speed of the spindle motor is increased, this sound frequency amplification becomes remarkable. In order to avoid this problem, therefore, much care must be taken for shifting the resonant frequency of the damper from the HDD sound peak frequency band when the damper
50
or
51
is formed in the HDD whose rotation speed is fast, concretely over 10,000 rpm. In spite of this, such the consideration for the damper
50
or
51
is also limited due to the HDD design.
The above HDD vibration problem occurs as a reaction to the seek operation of the actuator. This vibration is referred to as a rotational vibration (R.V.). In order to improve the HDD properties to reduce the R.V., therefore, a well-known method has been proposed so as to increase the mass of the damper
50
/
51
. In case the mass of the damper
50
/
51
is increased, however, the damper must also be increased in thickness or a plurality of dampers must be bonded together. The conventional method has not taken such the measure enough due to the limitation by the HDD design as described above.
There is also a well-known method for disposing a member that increases the mass at an outer periphery area of the HDD so as to increase the moment, which functions as a resistance to the above R.V. And, an attempt has been made to fix the member (mass) by screws at an outer periphery area of the HDD. In case the member (mass) is fixed by screws such way, an additional work must be added to the manufacturing process, thereby the manufacturing cost is increased. Under such circumstances, it is an object of the present invention to provide a damper that solves the above conventional problems, thereby providing a disk drive apparatus excellent in sound or vibration properties.
SUMMARY OF THE INVENTION
The inventor of the present invention has examined a method for increasing the wall thickness of a damper partially while examination has been done conventionally so as to change the shape of the damper whose wall thickness is premised to be fixed. As a result, the inventor has found that it is easy to shift the resonant frequency of the damper from the HDD sound peak frequency band. In other words, it is easy to avoid the matching between the resonant frequency of the damper and the HDD sound peak frequency band in case the wall thickness of the damper is increased partially. On the contrary, the inventor has also found that it is not easy to shift the resonant frequency of the damper from the peak band even when the wall thickness of the damper is increased in case the damper is fixed in thickness.
The present invention is based on such the knowledge and the damper of the present invention is attached to the subject disk drive apparatus and enabled to repress the HDD vibration. The damper comprises a flat portion having a jointing surface onto the disk drive apparatus and a wall-thickness portion that is thicker than the flat portion. The damper of the present invention has a three-dimensional shape while the conventional flat damper whose thickness is in uniform has a two-dimensional shape. Consequently, the damper can be varied more freely in shape, thereby it is possible to adjust the resonant frequency of the damper more freely. It is thus possible to shift the resonant frequency of the damper from the HDD sound peak frequency band more easily.
Basically, the damper of the present invention enables the wall-thickness portion to be formed at any position thereon. Preferably, however, it should be formed at an outer periphery area of the flat portion. For example, in case the damper of the present invention is to be attached to an HDD, a space for housing the wall-thickness portion will have to be provided on the housing of the HDD. This is because it would be easy to secure such a space at an outer periphery area of the HDD housing. As for the R.V. problem, the wall-thickness portion should preferably be formed at such an outer periphery area. And, when the mass is the same, disposing the wall-thickness portion at such an periphery area makes it possible to get a larger moment, which is effective for reducing the R.V.
The damper of the present invention also enables the wall-thickness portion as described above to be formed at a plurality of places thereon. This is because there is a case preferred to shift the resonant frequency of the damper from the HDD sound peak frequency band. This method is also effective when it is difficult to form a wall-thickness p
Hirasaka Yoshihiro
Matsuzaki Shin-ichi
Serizawa Kohji
Takahashi Kohji
Bracewell & Patterson L.L.P.
Evans Jefferson
Hitachi Global Storage Technologies - Netherlands B.V.
Martin Robert B.
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