Electricity: motive power systems – Positional servo systems – Pulse-width modulated power input to motor
Reexamination Certificate
2001-10-26
2003-07-29
Dang, Khanh (Department: 2837)
Electricity: motive power systems
Positional servo systems
Pulse-width modulated power input to motor
C318S132000, C318S139000, C318S254100
Reexamination Certificate
active
06600287
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a disk drive apparatus including a motor, and to a motor which can be used in a disk drive apparatus.
BACKGROUND OF THE INVENTION
In recent years, a motor which electrically alters current paths by a plural transistors has been widely used as a drive motor in an office automation equipment and an audio-visual equipment. A disk drive apparatus such as an optical disk drive apparatus (DVD, CD, and the like) and a magnetic disk drive apparatus (HDD, FDD, and the like) includes such a motor.
FIG. 29
shows a prior art motor, which alters current paths to the windings by PNP-type bipolar power transistors and NPN-type bipolar power transistors. The operation of the prior art motor is described hereinbelow. A rotor
2011
has a field part formed by a permanent magnet. In a position detector
2041
, three position detecting elements (three position sensors) detect magnetic field of the field part of the rotor
2011
. The position detector
2041
produces two sets of three-phase voltage signals Kp
1
, Kp
2
, Kp
3
, and Kp
4
, Kp
5
, Kp
6
on the basis of the three-phase output signals of the three position detecting elements in response to the rotation of the rotor
2011
.
A first distributor
2042
produces three-phase lower-side signals Mp
1
, Mp
2
, and Mp
3
in response to the voltage signals Kp
1
, Kp
2
, and Kp
3
, thereby controlling the activation of lower-side NPN-type bipolar power transistors
2021
,
2022
, and
2023
.
A second distributor
2043
produces three-phase upper-side signals Mp
4
, Mp
5
, and Mp
6
in response to the voltage signals Kp
4
, Kp
5
, and Kp
6
, thereby controlling the activation of upper-side PNP-type bipolar power transistors
2025
,
2026
, and
2027
. Accordingly, three-phase drive voltage signals are provided to windings
2012
,
2013
, and
2014
.
In this prior art configuration, the position detector
2041
comprises three position detecting elements for detecting the rotational position of the rotor
2011
. This has caused the necessity of a substantial space for installing these position detecting elements and the complexity of the wiring, and hence an increase in the cost.
On the other hand, a motor without a position detecting element is disclosed in the specifications of the U.S. Pat. Nos. 5,130,620 and 5,473,232, and the motor detects back-electromotive forces of the windings so as to obtain a rotational position of the rotor. The motor without a position detecting element, however, can not detect correctly the rotational position at a low rotational speed of the motor, since the amplitudes of the back-electromotive forces become too small to detect at a low rotational speed of the motor. So, it is difficult to drive and control the motor at a low speed. In particular, in case that the rotational speed is controlled by using the pulse signal responding with the detected back-electromotive forces, a large fluctuation of the rotational speed of the motor occurs at a low speed because of inaccurate detection of the pulse signal.
A motor with a single position detecting element is disclosed in the specification of the U.S. Pat. No. 5,729,102. The motor estimates the rotational electrical angle from the output of the single position detecting element, and supplies sinusoidal currents to the windings on the basis of the estimated rotational electrical angle. But, in the configuration of the motor according to the U.S. Pat. No. 5,729,102, it is difficult to estimate the rotational electrical angle with a fine step resolution. In particular, the error in the estimated electrical angle becomes larger at a higher rotational speed. Accordingly, a precise rotation control of the motor has been difficult.
In addition, since a microprocessor is used in the calculation of the estimated electrical angle and the generation of the drive signal, an inexpensive microprocessor can not be sufficient in the processing performance at a high rotational speed. This has caused a difficulty in the high-speed operation of the motor.
In an optical disk drive apparatus for reproducing DVD-ROM, CD-ROM, and CD disks, a stable operation is required over a wide range of rotational speed from 10,000 rpm at high-speed reproduction to 200 rpm at CD reproduction. In a rewritable disk drive apparatus for recording an information signal to a high-density disk and/or reproducing an information signal from a high-density disk such as DVD-RAM/RW, CD-R/RW, and the like, a precise rotation of the disk is required. In a magnetic disk drive apparatus such as HDD and FDD, a stable and precise rotation of the disk is required.
It is therefore an object of the present invention to solve the above-mentioned problems, respectively and concurrently and provide a disk drive apparatus and/or a motor which has the configuration to overcome all or some or each of the above-mentioned problems.
BRIEF SUMMARY OF THE INVENTION
The disk drive apparatus in accordance with 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, having a field part which generates field fluxes, for driving said disk; Q-phase windings (Q is an integer of 3 or more); voltage supplying means, including two output terminals, for supplying a DC voltage; Q first power amplifying means, each of said Q first power amplifying means including a first power transistor for forming a current path between one output terminal side of said voltage supplying means and one of said Q-phase windings; Q second power amplifying means, each of said Q second power amplifying means including a second power transistor for forming a current path between the other output terminal side of said voltage supplying means and one of said Q-phase windings; position detecting means for producing a position signal which responds with a rotation of said rotor; and activation operation means for controlling active periods of said Q first power amplifying means and said Q second power amplifying means responding with said position signal of said position detecting means, each of said active periods being larger than the period of 360/Q electrical degrees; and that said activation operation means comprises: time measuring means for measuring a time interval T
0
which responds with an interval of said position signal; first timing means for changing the state of a first state signal at an interval of a first adjust time T
1
which responds with said time interval T
0
and is less than T
0
/
2
, and setting said first state signal substantially to a first predetermined state responding with the measuring operation of said time measuring means; second timing means for changing the state of a second state signal at an interval of a second adjust time T
2
which responds with said time interval T
0
and is less than T
1
/
2
, and setting said second state signal substantially to a second predetermined state responding with a changing operation of said first state signal; and signal producing means for producing at least an activation control signal which responds with said first state signal and said second state signal, thereby controlling an active period of at least one power amplifying means among said Q first power amplifying means and said Q second power amplifying means responding with said at least an activation control signal; and said signal producing means includes: slope means for producing a slope signal which responds with said second state signal; and shaping means for producing said at least an activation control signal which responds with said slope signal and said first state signal, said at least an activation control signal varying substantially smoothly in at least one of rising and falling slopes responding with said slope signal.
In this configuration, the activation to the Q-phase windings can be accurately controll
Akin Gump Strauss Hauer & Feld L.L.P.
Dang Khanh
Matsushita Electric - Industrial Co., Ltd.
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