1. Field of the Invention
The present invention relates to a magnetic disk drive and more particularly, to a low-profile magnetic disk drive that provides large storage capacity with a compact or thin body and that operates at high reliability.
2. Description of the Related Art
Conventionally, 3.5-inch and 2.5-inch magnetic disk drives typically comprise a disk enclosure (i.e., case) and an electronic circuit section (i.e., package) fixed to the back of the enclosure. The electronic circuit section or package, which performs the driving mechanism control and signal processing, includes circuit boards such as printed wiring boards (PWBs), in which necessary electronic circuits are formed and on which necessary electronic parts or components are mounted.
The disk enclosure includes a base which is usually made of aluminum (Al) material. On the base, a spindle motor and an actuator are mounted or fixed. The motor supports the magnetic disks and rotates the same around a specific axis. The actuator moves and positions the magnetic heads at desired positions over the disks. The actuator is driven by a rotary voice-coil motor. A flexible printed circuit (FPC) is connected to the actuator and the electronic circuit section (i.e., the package). The information to be written into the magnetic disks and the information to be read from the disks is transmitted as necessity by way of the FPC between the section and the heads.
The base on which the electronic components or parts are mounted is covered with a cover so as to form a sealed space therein, constituting the disk enclosure. The cover is usually made of stainless steel or Al material. The package or electronic circuit section, which is formed to have approximately the same footprint as the enclosure, is fixed to the back of the enclosure with screws.
An example of the conventional magnetic disk drives of this type is disclosed in the Japanese Non-Examined Patent Publication No. 9-115279 publishes in 1997. FIG. 1 shows schematically the configuration of the drive disclosed therein.
In FIG. 1, the conventional magnetic disk drive 301 comprises a body or disk enclosure 303 and a circuit board (i.e., package) 304. Electronic components or parts such as an Integrated Circuit (IC) chip 305 are mounted on the board 304. The body or enclosure 303 is fixed to a specific wall 309 of the casing of an apparatus or system. A thermally conducting sheet 306 is provided between one of the IC chip 305 and the enclosure 303 to contact therewith, thereby dissipating the heat generated in the board or package 304 and the enclosure 303 into the atmosphere due to heat conduction. A label 302, which indicates the product name, specification, and so forth, is attached to the surface of the enclosure 303.
A thermally conducting sheet may be provided between the enclosure 303 and the wall 309.
The basic configuration of the magnetic disk drive comprising the disk enclosure and the package has already been standardized. Also, the position of mounting screws for mounting the drive itself to an apparatus or system (e.g., personal computers and server computers), and the position of connectors for electrical connection to the apparatus or system have been defined. This is to ensure the disk drive to be mounted in a specified place of the apparatus or system with high compatibility.
With the conventional magnetic disc drives of this type, there are the following problems.
The first problem is that the height or profile of the drive is difficult to be lowered. This is because the disk enclosure and the electronic component package are formed to have approximately the same footprint and then, they are stacked and coupled together.
In recent years, there is the tendency that semiconductor elements or components designed for the magnetic disk drives, such as hard disc controllers (HDCs) and channel ICs, have been integrated and downsized more than ever. However, these elements or components have still occupied a considerably large space. Also, some of the components, for example, electrically programmable read-only memories (EPROMs), regulators, and capacitors, may be as high as 3 mm to 5 mm. Thus, if all these components are arranged in approximately the same footprint as the disk enclosure, it is obvious that the overall height of the magnetic disk drive itself will be considerably large.
As described above, the outline or contour of the magnetic disc drives have been standardized. Also, there has ever been no strong demand to make the drives thinner. Thus, it may be said that the existing height of the drives has never caused any disadvantage or inconvenience.
However, recently, it is anticipated that the magnetic disk drives will be built in various home appliances in the near future to satisfy the specific consumer""s needs, such as recording of the video data (i.e., image files) in many households. If so, the standardized profile of the drives induces inconvenience for mounting or setting-up of the drives. For example, if magnetic disk drives are incorporated into low-profile home appliances, such as wall-hung television (TV) sets, the dedicated space for the drives is difficult to be provided.
The thinner the magnetic disk drives, the more advantageous they are in mounting or setting-up. Therefore, if 2.5-inch magnetic disks are used for this purpose instead of 3.5-inch ones, the profile of the drives will be lower. In this case, however, there arises a problem that 2.5-inch magnetic disks provide insufficient storage capacity, in other words, desired storage capacity for video data recording is unable to be ensured.
Here, it is supposed that the 2.5-inch disk has a storage capacity as much as 10 gigabytes (GB). In this case, if the disk is used to record a digital broadcast program which has been planned to start in the year 2001 in Japan, the recordable time is as short as about 3 hours for standard TV (STV) and as short as about 40 minutes for high-definition TV (HDTV). As a result, it is difficult or unable to propose as attractive products with the 2.5-inch disk. This means that the 3.5-inch disk must to be used for this purpose because it enables larger storage capacity.
The second problem is that the rigidity of the hard disk drive degrades as its height is decreased, thereby degrading the reliability against the compression or pressing force to the disk enclosure.
Usually, because of the standard, the disk thickness of 0.8 mm, the head slider thickness of 0.3 mm, and the inter-disk gap of about 0.2 mm are unable to be changed. Also, various restrictions are present to decrease the motor height from the viewpoint of high-speed disk rotation. Accordingly, the base thickness may be decreased. In this case, however, there arises a problem that the rigidity of the disk drive itself is lowered according to the decreasing thickness of the base, because the base plays an important role to support or provide the desired rigidity. The lowered rigidity will cause vibrational disturbance, resulting in reliability degradation.
Accordingly, an object of the present invention is to provide a magnetic disk drive that decreases the profile or height of the drive itself without rigidity degradation.
Another object of the present invention is to provide a magnetic disk drive that decreases the profile or height of the drive itself without reliability degradation.
Still another object of the present invention is to provide a magnetic disk drive that realizes large capacity with a lower profile or height.
The above objects together with others not specifically mentioned will become clear to those skilled in the art from the following description.
A magnetic disc drive according to the present invention comprises:
(a) a rotatable magnetic disk around an axis;
(b) a spindle motor for rotating the disk;
(c) a magnetic head for writing information into the disk and for reading information from the disk;
(d) an actuator for positioning the head at a desired position over the disk;
(e) a disk enclosure for enclosing the disk, the motor, the head, and the actuator;
(f) a circuit board fixed to the enclosure;
the board having necessary circuits and necessary electronic elements for controlling operation of the drive;
the board having a projecting part located outside a footprint of the enclosure;
at least part of the elements being mounted on the projecting part.
With the magnetic disk drive according to the present invention, the circuit board has the projecting part located outside the footprint of the disk enclosure and at the same time, at least a part of the electronic elements are mounted on the projecting part. Thus, if the tall (i.e., high-profile) components are mounted on the projecting part of the circuit board while the short (i.e., low-profile) components are mounted on the remaining part, the height of the disk enclosure can be decreased. This means that the height of the magnetic disk drive itself can be decreased.
On the other hand, since it is unnecessary to decrease the height of the disk enclosure, the rigidity of the enclosure is not lowered. Thus, reliability degradation does not occur.
As a result, the profile or height of the magnetic disk drive itself can be decreased without reliability degradation. Also, a low-profile and large-capacity magnetic disk drive can be realized.
In a preferred embodiment of the drive according to the invention, the board has an overlapping part located in the footprint of the enclosure. The components mounted on the projecting part of the board are higher in average than the components mounted on the overlapping part thereof.
In another preferred embodiment of the drive according to the invention, the board has an overlapping part located in the footprint of the enclosure. The components equal to or lower than a specific reference height are mounted on the overlapping of the board. The components higher than the specific reference height are mounted on the projecting part of the board.
In still another preferred embodiment of the drive according to the invention, an additional circuit board is provided over the projecting part of the enclosure located outside the footprint of the enclosure. In this embodiment, it is preferred that the additional circuit board is electrically connected to the board having the projecting part by way of a connector.
In a further preferred embodiment of the drive according to the invention, the enclosure and the circuit board form a shape approximately a same as a CD-ROM case.
In a still further preferred embodiment of the drive according to the invention, the magnetic disk is 2.5 inch, 3.5 inch, or 5 inch in diameter.