Plastic article or earthenware shaping or treating: apparatus – Means for molding powdered metal
Reexamination Certificate
1999-09-03
2004-07-20
Jenkins, Daniel (Department: 1742)
Plastic article or earthenware shaping or treating: apparatus
Means for molding powdered metal
Reexamination Certificate
active
06764289
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a fixture for manufacturing magnets. More specifically, the present invention relates to a fixture and method for pressing and orientating magnets for voice coil actuator motors.
BACKGROUND
Disk drives are widely used in computers and data processing systems for storing information in digital form. Disk drives typically utilize one or more rotating, storage disks and a plurality of data transducers to interact with each storage disk. An E-block having a plurality of spaced apart actuator arms retains the data transducers proximate each storage disk. An actuator motor moves the E-block and the data transducers relative to the storage disks.
The need to rapidly access information has led to disk drives having storage disks which are rotated at ever increasing speeds and an actuator motor which moves the E-block at ever increasing rates. Unfortunately, this typically results in increased heat, noise and power consumption of the disk drive.
FIG. 1A
illustrates a rear perspective view of a portion of a prior art, rotary, voice coil actuator motor
10
P. In this embodiment, a flat, trapezoidal shaped coil
12
P is positioned between two permanent magnets
14
P and two flux return plates
16
P. The coil
12
P is secured to the E-block (not shown in FIG.
1
A). Current passing through the coil
12
P causes the coil
12
P to move relative to the permanent magnets
14
P to move the E-block.
One factor which effects efficiency of the actuator motor
10
P is the strength of the magnets
14
P. In the prior art actuator motor
10
P illustrated in
FIG. 1A
, the magnets
14
P include magnetization lines
18
P (illustrated as arrows) which are oriented substantially perpendicular to the coil
12
P. In this embodiment, the magnets
14
P are made of a magnetic powder which is also oriented substantially perpendicular to the coil
12
P.
FIG. 1B
illustrates a cross-sectional view of a prior art fixture
22
P which can be used to manufacture the magnet
14
P. The prior art fixture
22
P includes a fixture body
24
P, an upper punch
26
P, and a lower punch
28
P. This fixture body
24
P defines a cavity for receiving magnet powder to form the magnet
14
P. An orientating coil
30
P creates a magnet field
32
P having flux lines which orient the magnet powder in the magnet
14
P.
Unfortunately, the strength of the magnets
14
P illustrated in
FIG. 1A
vary approximately 14-20 percent across the stroke of the coil
12
P. More specifically, the strength of the magnets
14
P is high, near the center and drops near the sides of the magnets
14
P. This non-linearity causes difficulty in precisely moving the coil
12
P. Inaccurate positioning of the coil
12
P leads to data transfer errors between the data transducers and the storage disks.
In light of the above, it is an object of the present invention to provide an improved magnet and a fixture for making the improved magnet. It is another object to provide a fixture for manufacturing a magnet which is relatively easy to use. Yet another object is to provide a method for manufacturing a magnet which significantly improves the strength and performance of the magnet.
SUMMARY
A manufacturing fixture which satisfies these needs is provided herein. The manufacturing fixture is useful for manufacturing a magnet from a magnet powder for a motor. The manufacturing fixture includes a fixture body and an orientating device. The fixture body includes a fixture cavity for receiving the magnetic powder. The orientating device aligns the magnetic powder in the fixture cavity.
The fixture cavity includes a cavity axis, a first cavity segment, second cavity segment, and a cavity transition between the first cavity segment and the second cavity segment. Uniquely, the orientating device creates a magnetic field having flux lines which extend (1) substantially transverse to the cavity axis near the cavity transition, (2) highly angled relative to the cavity axis near a perimeter of the fixture cavity and, (3) substantially parallel to the cavity axis intermediate the perimeter and the cavity transition.
The flux lines orient the magnet powder into a unique powder pattern which includes first region powder lines in a first region of the magnet which are substantially parallel with a first region axis and second region powder lines in a second region of the magnet which are angled relative to the first region axis.
This powder pattern subsequenuy facilitates a unique magnetization pattern in the magnet. This magnetization pattern results in higher magnetic flux densities throughout the magnet, higher magnetic flux densities at the parts of the magnet which interact with a coil of the motor, and higher average magnetic flux densities in the magnet.
Additionally, the higher magnetic flux densities at the sides of the magnet body, i.e. a greater radius, results in higher torques on the coil of the motor. This enables the magnet to generate more force from a given amount of current in the coil and increases the efficiency of the motor. This also reduces the amount of power consumed by the motor, reduces the amount of heat and noise generated by the motor during operation and increases operational time of the motor for a given battery charge. Further, the size of the magnet can be reduced for a given force requirement. These considerations are particularly important for computer disk drives, which often operate in heat and noise sensitive environments, or on battery power.
The present invention is also a method for manufacturing a magnet. The method includes the steps of positioning a magnet powder in the fixture cavity of the manufacturing fixture and aligning a portion of the magnet powder in the fixture cavity with a magnetic field to form the powder pattern outlined above. The method can also include the step of magnetizing the magnet to include the magnetization pattern outlined above.
Importantly, the manufacturing fixture is used to make a magnet having a unique powder pattern. This powder pattern allows the magnet to accept a unique magnetization pattern which increases the amount of force generated for a given amount of current in the coil. This increases the efficiency, accuracy and performance of the actuator motor, thereby reducing data seek times and amount of power consumed by the actuator motor.
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Hitachi Rare-Earth Magnet Brochure, Hitachi Metal, Ltd., Front cover, p. 42 and Rear cover, date of publication unknown.
Hartman Albert
Lorimer Wendy
Broder James P.
Jenkins Daniel
Maxtor Corporation
Roeder Steven G.
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