Electricity: motive power systems – Switched reluctance motor commutation control
Reexamination Certificate
2000-12-06
2002-06-11
Dang, Khanh (Department: 2837)
Electricity: motive power systems
Switched reluctance motor commutation control
C388S804000
Reexamination Certificate
active
06404153
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a motor and a disk drive apparatus including the motor.
In recent years, motors wherein current paths are alternated electronically with plural transistors have been used widely as drive motors for office automation apparatuses and audio-visual apparatuses. These motors are included in disk drive apparatuses, such as optical disk drive apparatuses (DVD apparatuses, CD apparatuses, etc.) and magnetic disk drive apparatuses (HDD apparatuses, FDD apparatuses, etc.). A motor wherein current paths to windings are alternated with PNP power transistors and NPN power transistors is available as an example of the above-mentioned motors.
FIG. 26
shows a conventional motor, 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 Mp
1
, Mp
2
and Mp
3
responding with the voltage signals Kp
1
, Kp
2
and Kp
3
respectively to control the activation of the low-side NPN power transistors
2021
,
2022
and
2023
shown in
FIG. 26. A
second distributor
2043
generates three-phase high-side signals Mp
4
, Mp
5
and Mp
6
responding with the voltage signals Kp
4
, Kp
5
and Kp
6
respectively to control the activation of the high-side PNP power transistors
2025
,
2026
and
2027
shown in FIG.
26
. As a result, three-phase drive voltages are supplied to windings
2012
,
2013
and
2014
.
In the conventional configuration, power loses of the power transistors are large, and heat generation at the motor and the disk drive apparatus causes problems. The NPN power transistors
2021
,
2022
and
2023
and the PNP power transistors
2025
,
2026
and
2027
supply drive voltages having desired amplitudes to the windings
2012
,
2013
and
2014
by controlling the voltage across the emitter and the collector in an analogue manner. Each of the NPN power transistors
2021
,
2022
and
2023
and the PNP power transistors
2025
,
2026
and
2027
changes the voltage across the emitter and the collector depending on the change in the resistance value across the emitter and the collector. Therefore, a remaining voltage in each power transistor is large, and a large power loss produced by the product of the large remaining voltage and the conducted current is generated, resulting in heat generation at each power transistor. Since a recordable disk (a RAM disk, a rewritable disk, etc.) is susceptible to heat, the heat generation at the power transistors, i.e., the main heat sources of the disk drive apparatus, is desired to be reduced as low as possible in order to improve the reliability of recording and/or-reproducing on/from the recordable disk.
In addition, since the position detector
2041
includes three position detecting elements for detecting the rotational position of the rotor
2011
so as to distribute drive currents to the windings, it is necessary to provide spaces for the position detecting elements. Furthermore, wire connection and the like for the elements become complicated, thereby raising the cost of the motor and the apparatus. By eliminating the position detecting elements, the motor can be made smaller, and the disk drive apparatus can be made thinner.
Furthermore, in the case of rewritable disk drive apparatuses, such as DVD-RAM/RW apparatuses, information is recorded and/or reproduced on/from a high-density disk. Therefore, it is desired to rotate the disk with reduced vibration during recording and/or reproducing on/from the disk. Moreover, it is necessary to rotate the disk at high speed with reduced acoustic noise in the case of reproducing from a DVD-ROM/CD-ROM disk. However, in a configuration without a position detecting element, it is very difficult to rotate the rotor and the disk with a low vibration and a low acoustic noise while reducing heat generation.
It has been strongly desired to develop a motor and/or a disk drive apparatus in which each of or all of these problems are solved. It is therefore an object of the present invention to solve the above-mentioned problems, respectively or concurrently and provide a motor and/or a disk drive apparatus that has the configuration suitable for reducing the power consumption and the acoustic noise.
BRIEF SUMMARY OF THE INVENTION
A motor in accordance with the present invention comprises:
a rotor which has a field part generating field fluxes;
Q-phase windings (Q is an integer of 3 or more);
voltage supplying means which includes two output terminals for supplying a DC voltage;
power supplying means having Q first power transistors and Q second power transistors for supplying a power to the Q-phase windings, each of the Q first power transistors forming a current path between one output terminal side of the voltage supplying means and one of the Q-phase windings, and each of the Q second power transistors forming a current path between the other output terminal side of the voltage supplying means and one of the Q-phase windings;
voltage detecting means for producing a detected pulse signal;
state shifting means for shifting a holding state from one state to at least one other state in sequence responding with the detected pulse signal of the voltage detecting means;
activation control means for controlling active periods of the Q first power transistors and the Q second power transistors responding with the holding state; and
switching operation means for causing at least one of the Q first power transistors and the Q second power transistors to perform high-frequency switching corresponding to a command signal;
and that
the activation control means produces Q-phase first activation control signals and Q-phase second activation control signals responding with said holding state of said state shifting means for controlling the active periods of the Q first power transistors and the Q second power transistors, each of the active periods being an electrical angle larger than 360/Q degrees,
the switching operation means produces a switching pulse signal responding with the command signal, and makes high-frequency switching operation of at least one power transistor among the Q first power transistors and the Q second power transistors responding with the switching pulse signal, and
the voltage detecting means stops detecting of the detected pulse signal during at least one of a first stop period including a changing timing from OFF to ON of the at least one power transistor and a second stop period including another changing timing from ON to OFF of the at least one power transistor, and executes detecting of the detected pulse signal during at least ON period of the at least one power transistor excluding the at least one of the first stop period and the second stop period, thereby producing the detected pulse signal responding with terminal voltages of the Q-phase windings. With this configuration, the switching operation means subjects the power transistors of the power supplying means to high-frequency switching. Therefore, power loses at the power transistors of the power supplying means can be reduced significantly, and heat generation at the motor can also be reduced greatly. In addition, the voltage detecting means produces the detected pulse signal responding with the terminal voltages of the windings, and the state shifting means shifts the phases of the activation to the windings in response to the detected pulse signal. Furthermore, the activation control means activates the power transistors responding with the holding state so as to rotate the rotor in a predetermined direction. Therefore, no position detecting element is required, and the configurati
Akin Gump Strauss Hauer & Feld L.L.P.
Dang Khanh
Matsushita Electric - Industrial Co., Ltd.
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