Chucking mechanism of center core of disk cartridge

Faulty engagement due to low surface precision of the engaging surfaces of a center core of a disk cartridge and a drive spindle is resolved. The center core 10 is positioned on the drive spindle 20 in a state where the center core 10 is in point contact with the drive spindle 20 at a minimum of three spots upon chucking. A minimum of three protrusions 10d are provided on the bottom surface of the center core 10, and lower ends P of the protrusions 10d are in point contact with the upper surface 21a of the drive spindle 20.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a chucking mechanism of a center core of a disk cartridge to receive a drive spindle, the center core being fixed to the center of a disk, which serves as a recording medium and is rotatably housed in a housing of the disk cartridge, which is of the type that is employed in a disk drive provided with the drive spindle.

2. Description of the Related Art

Recording media, e.g., a micro-magnetic disk cartridge called “clik! (registered trademark)” have been conventionally used for mobile equipment such as digital cameras.

FIGS. 4A to 4Care a plan view, a right side view and a bottom plan view of a magnetic disk cartridge1, respectively. As shown in these Figures, a flat housing of the magnetic disk cartridge1rotatably contains a magnetic disk5. The flat housing is constituted of a resin frame2which includes a pressing portion2a, and upper and lower shells3and4which are made of thin metal plates. The dimensions of the housing are 50 mm wide by 55 mm deep by 1.95 mm thick. The magnetic disk5has a storage capacity of 40 MB and a diameter of 1.8 inches (45.7 mm).

The magnetic disk cartridge1is constituted so as to be inserted and placed into a slot of a Type II PC card drive which has the dimensions of 53 mm wide by 85 mm deep by 5 mm thick. This disk drive is provided with a spindle motor and a magnetic head. The spindle motor includes a drive spindle which magnetically attracts a center core10of the magnetic disk5, and the magnetic head which accesses to the surface of the rotating magnetic disk5to record and reproduce information.

A V-shaped opening6is formed in the housing of the magnetic disk cartridge1for the magnetic head of the disk drive to access the surface of the magnetic disk5. A rotary shutter7, which is urged toward a closed position by a spring member, opens and closes the opening6. The rotary shutter7is locked at a closed position shown inFIGS. 4Aand C by a shutter locking member11provided in the housing.

A notch8is formed on the top portion of the left side of the housing to engage with an engaging member of the disk drive to ensure the positioning of the magnetic disk cartridge1in the disk drive. On the top portion of the right side surface, a small window9is formed so that the shutter locking member11faces outside. The shutter locking member11is constituted to be pressed by a lock releasing member provided in the disk drive to release the lock on the rotary shutter7when the magnetic disk cartridge1is inserted into the disk drive.

A circular opening4aand an arcuate groove4bare formed in the lower shell4of the housing. The opening4ais for the drive spindle of the disk drive to engage with the center core10of the magnetic disk5, and the arcuate groove4bis concentric with the rotary shutter7. A shutter knob7bis attached to the rotary shutter7. The shutter knob7bprotrudes from the arcuate groove4band moves along the arcuate groove4bto open and close the rotary shutter7.

FIG. 5is a sectional view showing the center core10as well as a drive spindle20. The center core10provided with a center aperture10ais formed from an iron based metal material. The magnetic disk5is affixed to a flat upper surface10b(adhesion surface) of the center core, and a bottom surface10c(engaging surface) engages with the drive spindle20.

Meanwhile, the drive spindle20is provided with the main body of a spindle21and a magnet22. The main body of the spindle21is the core, and the magnet22magnetically attracts the center core10. A flat upper surface21a(engaging surface) of the main body of the spindle21engages with the center core10. The drive spindle20is constituted as follows: when the magnetic disk cartridge1is placed in the disk drive, the magnet22attracts the center core10onto the main body of the spindle21; and the center core10engages with the drive spindle20in a state where the surfaces10cand21aare in contact with each other.

However, in the case where the center core10and the drive spindle20are engaged in a state where the surfaces10cand21aare in contact as described above, there were times when the center core10was engaged with the drive spindle20in a slanted state, when the surface precision of the engaging surface10cof the center core10is low. In this case, parallelism between the rotation surface of the drive spindle20and the rotation surface of the magnetic disk5is reduced. Accordingly, wobbling of the magnetic disk5surface increases when the drive spindle20rotates. Thus, there has been a problem that recording/reproducing characteristics are aversely affected.

Moreover, it is extremely difficult to maintain the surface precision of the engaging surface10cof the center core10. This has been reducing the material utilization rate for the center core10and increasing manufacturing costs of the center core10.

SUMMARY OF THE INVENTION

In consideration of the aforementioned circumstance, an object of the present invention is to provide a chucking mechanism in which faulty engagement due to low surface precision of the engaging surfaces of the conventional center core and the drive spindle is effectively resolved.

The present invention is a chucking mechanism of a center core in a disk cartridge for receiving a drive spindle. A housing of the disk cartridge rotatably contains a disk serving as a recording medium. The disk has a center core fixed to the center thereof. The disk cartridge is placed in a disk drive provided with the drive spindle.

The chucking mechanism is characterized by the center core being positioned on the drive spindle upon chucking in a state where the center core is in point contact with the drive spindle at a minimum of three locations.

Although the constitution can be achieved by providing a minimum of three protrusions on the bottom surface of the center core and causing these protrusions to be in point contact with the upper surface of the drive spindle, the protrusions can be provided on the drive spindle. The shape of the protrusions is preferably conical or hemispherical. In addition, to balance the attraction by the magnet, a minimum of three protrusions arranged in a circle about the axis at regular intervals are preferred. In other words, an angular interval of 120° is maintained when there are three protrusions. Furthermore, an angular interval of 90° is preferred to be maintained when there are four protrusions.

Additionally, the protrusions are most preferably cut to be formed integral with the center core. However, the protrusions can be provided separate from the center core and made of resin or rubber. Furthermore, dents can be provided on the upper surface of the drive spindle facing the protrusions of the center core to receive the lower ends of the protrusions at the bottom surfaces of the dents.

According to the present invention, the center core is positioned on the drive spindle in a state where the center core is in point contact with the drive spindle at a minimum of three spots. Thus, faulty engagement due to insufficient surface precision of the conventional center core is resolved. Therefore, the material utilization rate of the center core is improved, and manufacturing costs thereof can be reduced.

Moreover, the constitution has an effect that the parallelism is not reduced even when foreign matter is sandwiched between the center core and the drive spindle. In addition, a vibration suppression effect can be obtained by forming the protrusions from rubber.

Furthermore, the reception of the lower ends of the protrusions at the bottom surfaces of the dents can prevent positional displacement of the center core on the drive spindle.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention are described in detail below with reference to the drawings.

FIGS. 1A and 1Bare a sectional view and a bottom plan view of a center core used in a chucking mechanism of the present invention.

A center core10provided with a center aperture10ais formed from an iron based metal material. A magnetic disk5is affixed to a flat upper surface (adhesion surface10b) of the center core10, and four conical protrusions10dare protrusively provided on the center core10. These four protrusions10dare arranged in a circle about an axis at angular intervals of 90°.

FIG. 2is an enlarged sectional view of an essential part showing a state where the center core10ofFIG. 1is engaged with a drive spindle20.

The drive spindle20is provided with a main body of a spindle21and a magnet22. The main body of the spindle21is the core, and the magnet22magnetically attracts the center core10. Similar to the constitution shown inFIG. 5, a flat upper surface21a(engaging surface) of the main body of the spindle21engages with the center core10. However, in the present embodiment, the lower ends P of the conical protrusions10dof the center core10are in point contact with the upper surface21aof the main body of the spindle21. When the center core10is used in “clik! (registered trademark)”, the diameter of the portion of the protrusions10d, which are in contact with the bottom surface of the center core10, is preferably 0.5 to 2 mm. The height of the protrusions10dis preferably approximately 0.2 to 1 mm.

As described above, in the present embodiment, the lower ends P of the four protrusions10dformed on the bottom surface of the center core10are in point contact with the upper surface of the main body of the spindle21to be positioned on the drive spindle20. Thus, faulty engagement due to low surface precision of the conventional center core10is reduced. Therefore, the material utilization rate of the center core10is improved, and manufacturing costs thereof can be reduced.

Moreover, the chucking mechanism of the present invention has another effect that the parallelism is not reduced even when foreign matter is sandwiched between the center core10and the drive spindle20.

FIG. 3is an enlarged sectional view of an essential part showing another embodiment of the present invention in contrast withFIG. 2. In the present embodiment, a center core10has the same constitution as inFIGS. 1 and 2, except for the following: dents21bare provided on an upper surface21aof a main body of a spindle21of a drive spindle20to receive the protrusions10dof the center core10; and lower ends P of the protrusions10dare in point contact with the bottom surfaces of the dents21b.

According to the constitution shown inFIG. 3, it is possible to prevent positional displacement of the center core on the drive spindle20, in addition to the aforementioned effects of the constitution shown inFIG. 2.