Electricity: motive power systems – Positional servo systems
Reexamination Certificate
2001-07-25
2003-07-01
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Positional servo systems
C318S132000, C318S139000, C318S254100, C318S434000, C318S599000, C318S811000
Reexamination Certificate
active
06586902
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a disk drive apparatus and a motor.
In recent years, a motor which alters current paths to plural-phase windings electronically with plural transistors has been used widely as a drive motor for an office automation apparatus and an audio-visual apparatus. A disk drive apparatuses, such as an optical disk drive apparatus (DVD drive apparatus, CD drive apparatus, for example) and a magnetic disk drive apparatus (HDD drive apparatus, FDD drive apparatus, for example), includes such a motor.
FIG. 23
shows a conventional motor which alters current paths to windings with PNP power transistors and NPN power transistors, and its operation will be described below. A rotor
2011
has a field part formed by a permanent magnet. Three position detecting elements of a position detector
2041
detect the magnetic field of the field part of the rotor
2011
. In other words, the position detector
2041
generates two sets of voltage signals, Kp
1
, Kp
2
and Kp
3
, and, Kp
4
, Kp
5
and Kp
6
, from the three-phase output signals of the three position detecting elements in response to the rotation of the rotor
2011
. A first distributor
2042
generates three-phase low-side signals Lp
1
, Lp
2
and Lp
3
responding with the voltage signals Kp
1
, Kp
2
and Kp
3
to control the activation of the low-side NPN power transistors
2021
,
2022
and
2023
. A second distributor
2043
generates three-phase high-side signals Mp
1
, Mp
2
and Mp
3
responding with the voltage signals Kp
4
, Kp
5
and Kp
6
to control the activation of the high-side PNP power transistors
2025
,
2026
and
2027
. As a result, three-phase drive voltages are supplied to windings
2012
,
2013
and
2014
.
Though the conventional motor may be used in a disk drive apparatus, it has a disadvantage of large power losses of the power transistors. The NPN power transistors
2021
,
2022
and
2023
and the PNP power transistors
2025
,
2026
and
2027
supply drive voltages to the windings
2012
,
2013
and
2014
by controlling the voltage drop across the emitter and the collector of each bipolar power transistor in an analogue manner. Since the voltage drop in each bipolar power transistor is large, each power transistor produces a large power loss by the product value of the voltage drop and the drive current to the winding. The power loss makes a large heat generation.
U.S. Pat. No. 5,982,118 discloses a motor which reduces the power losses of the power transistors by supplying PWM drive voltages to windings responding with output signals of two position detecting elements. However, the conventional motor such as one in
FIG. 23
or one in U.S. Pat. No. 5,982,118 includes three or two position detecting elements for detecting the rotational position of the rotor. For this reason, the spaces, connecting wires, etc. of the position detecting elements are required, which makes the motor complicated and expensive.
U.S. Pat. No. 5,473,232 discloses a motor which detects terminal voltages of the windings and alters current paths to the windings in response to the timing of the detection. However, the speed fluctuation of the motor of U.S. Pat. No. 5,473,232 may be large, because it detects only one terminal voltage of the windings.
In a disk drive apparatus such as a HDD drive apparatus or a DVD drive apparatus, a motor with reduced speed fluctuation (jitter) as well as reduced heat generation has been demanded so as to achieve a good reproduction and/or a good recording on a high-density disk. Since a large jitter of the rotational speed of the disk causes frequent bit errors in a reproduced digital signal, the disk drive apparatus is required to reduce the jitter of the rotational disk speed. Furthermore, the large jitter of the rotational speed of the disk causes positional displacements of the recording signal on the disk in recording a signal.
It is therefore an object of the present invention to provide a disk drive apparatus and a motor capable of solving one or all of the above-mentioned problems.
BRIEF SUMMARY OF THE INVENTION
The disk drive apparatus in accordance with the main aspect of the present invention comprises:
head means for at least reproducing a signal from a disk or recording a signal on said disk;
processing means for at least processing an output signal from said head means and outputting a reproduced signal, or processing a signal and outputting a recording signal into said head means;
a rotor for driving said disk, provided with a field part which generates field fluxes;
Q-phase windings (Q is an integer of 3 or more);
voltage supplying means, including two output terminals, for supplying a DC voltage;
power supplying means having Q first power transistors and Q second power transistors, each of said Q first power transistors forming a current path between one output terminal side of said voltage supplying means and one of said Q-phase windings, and each of said Q second power transistors forming a current path between the other output terminal side of said voltage supplying means and one of said Q-phase windings;
voltage detecting means for producing a detected pulse signal responding with terminal voltages of said Q-phase windings;
activation operation means for controlling active periods of said Q first power transistors and said Q second power transistors responding with said detected pulse signal of said voltage detecting means, each of said active periods being an electrical angle which is larger than 360/Q degrees;
commanding means for producing a command signal corresponding to a rotational speed of said disk; and
switching operation means for producing a switching pulse signal corresponding to said command signal, causing at least one power transistor among said Q first power transistors and said Q second power transistors to perform high-frequency switching responding with said switching pulse signal, and changing a timing of said switching pulse signal responding with detection of said detected pulse signal from said voltage detecting means.
With this configuration, the switching operation means causes at least one of the power transistors of the power supplying means to perform high-frequency switching operation. Therefore, the power losses and heat generation of the power transistors of the power supplying means can be reduced significantly. Furthermore, the voltage detecting means and the activation operation means control the alteration of current paths to the windings responding with the detected pulse signal which is obtained by detecting the terminal voltages of the windings, thereby rotating the disk in a predetermined direction. Hence, no position detecting element is required, and thus the configuration of the disk drive apparatus is simplified. Furthermore, the switching operation means changes the timing of the high-frequency switching operation of the power transistors responding with the occurrence of the detected pulse signal of the voltage detecting means. This prevents the switching operation of the power transistors from occurring near a point of time when it is expected that the voltage detecting means obtains the next generation of the detected pulse signal responding with the terminal voltages of the windings. Therefore, the voltage detecting means can accurately detect the terminal voltages of the windings and produce an accurate and precise detected pulse signal without an influence of the switching noises by the high-frequency switching operation of the power transistors. As a result, the disk drive apparatus can alter current paths to the windings accurately responding with the detected pulse signal of the voltage detecting means, thereby rotating the disk stably. Moreover, the disk drive apparatus can achieve an accurate speed control with reduced jitter without providing a speed detector by controlling the disk speed responding with the detected signal, for example. In other words, the disk drive apparatus can achieve stable and precise disk rotation without a position detecting element and a speed d
Gotou Makoto
Mori Hideaki
Ochi Masaaki
Akin Gump Strauss Hauer & Feld L.L.P.
Matsushita Electric - Industrial Co., Ltd.
Nappi Robert E.
Smith Tyrone
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