Electricity: motive power systems – Switched reluctance motor commutation control
Reexamination Certificate
2002-02-28
2004-01-20
Nappi, Robert (Department: 2837)
Electricity: motive power systems
Switched reluctance motor commutation control
C318S132000
Reexamination Certificate
active
06680593
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a motor and a disk drive apparatus including the motor.
In recent years, a motor in which current paths are altered electronically by using a number of transistors has been used widely in office automation apparatuses and audio-visual apparatuses. In other words, optical disk drive apparatuses (such as DVD apparatuses, CD apparatuses, etc.), magnetic disk drive apparatuses (such as HDD apparatuses, FDD apparatuses, etc.) and the like, include this kind of motor.
FIG. 35
shows a conventional motor, and the operation of the motor will be described below. A rotor
2011
has a field part formed by a permanent magnet. In a position detector
2041
, three position sensors detect the 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
and Kp
3
, and Kp
4
, Kp
5
and Kp
6
, from the three-phase output signals of the three position sensors responding with the rotation of the rotor
2011
. A first distributor
2042
produces three-phase low-side signals Mp
1
, Mp
2
and Mp
3
responding with the voltage signals Kp
1
, Kp
2
and Kp
3
, and controls the activation of the low-side NPN-type bipolar power transistors
2021
,
2022
and
2023
. A second distributor
2043
produces three-phase high-side signals Mp
4
, Mp
5
and Mp
6
responding with the voltage signals Kp
4
, Kp
5
and Kp
6
, and controls the activation of the high-side PNP-type bipolar power transistors
2025
,
2026
and
2027
. Hence, three-phase drive voltages are supplied to windings
2012
,
2013
and
2014
.
In this conventional configuration, power losses at the power transistors are large, whereby the power efficiency of the motor is significantly low. The NPN-type bipolar power transistors
2021
,
2022
and
2023
and the PNP-type bipolar power transistors
2025
,
2026
and
2027
supply drive voltages to the windings
2012
,
2013
and
2014
by controlling voltage drops between the emitters and the collectors thereof in an analogue manner responding with the output signals of the three position sensors. A residual voltage in each power transistor is large, and a large power loss and heat generation are caused by the product of the residual voltage and the drive current supplied to each winding. As a result, the power efficiency of the motor is low, and the power consumption of the disk drive apparatus including the motor is large. In addition, the power loss increases the disk temperature at the disk drive apparatus, thereby increasing bit errors during recording and reproduction of information on a disk.
The specification of U.S. Pat. No. 5,982,118 discloses a motor wherein power transistors are subjected to PWM operation (PWM: Pulse Width Modulation) by using the outputs of two sensor to reduce power consumption. However, in the motor configurations in accordance with the above-mentioned conventional example shown in FIG.
35
and the specification of U.S. Pat. No. 5,982,118, two or three position sensors are included to detect the rotational position of the rotor. Hence, space, wiring, etc. are required for the installation of the position sensors, thereby making the configurations complicated and raising the cost thereof.
The specifications of U.S. Pat. No. 5,122,715 and U.S. Pat. No. 5,473,232 disclose motors wherein the terminal voltages of the windings are detected and the current paths to the windings are altered responding with the timing of the detection. In the motor configuration described in the specification of U.S. Pat. No. 5,122,715, the width of activation is 120 degrees, whereby vibration and acoustic noise are significant. In addition, the motor configuration is complicated due to use of a switching regulator. In the motor configuration described in the specification of U.S. Pat. No. 5,473,232, power transistors are subjected to PWM operation to reduce power losses. However, the width of activation for each power transistor is 120 degrees, whereby vibration and acoustic noise are significant. Furthermore, in the motor configuration described in the specification of U.S. Pat. No. 5,473,232, the detection timing of the terminal voltages of the windings is apt to fluctuate because of the PWM operation. Hence, when the rotational speed of the rotor is controlled by a detected pulse signal responding with the terminal voltages of the windings, fluctuation of the rotational speed of the rotor occurs owing to the timing fluctuation of the detected pulse signal.
In magnetic disk drive apparatuses, such as HDD apparatuses, and optical disk drive apparatuses, such as DVD apparatuses, speed fluctuation (jitter) must be minimized to stably carry out recording and/or reproduction on a high-density disk. However, when power transistors are subjected to PWM operation, very large high-frequency switching noise occurs, thereby causing a large timing fluctuation of the detected pulse signal. Hence, the reliability of the recording and/or reproduction of the disk drive apparatus lowers significantly. It is thus difficult to subject the power transistors to PWM operation.
BRIEF SUMMARY OF THE INVENTION
The object of the present invention is to provide a motor and a disk drive apparatus including the motor wherein the above-mentioned problems have been solved individually or concurrently.
A motor in accordance with one aspect of the present invention comprises:
a rotor having 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 first 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 second output terminal side of said voltage supplying means and one of said Q-phase windings;
voltage detecting means for producing a detected pulse signal which responds with terminal voltages of said Q-phase windings;
phase detecting means for producing a phase pulse signal which responds with terminal voltages of said Q-phase windings;
state shifting means for shifting a holding state from one state to at least one other state in sequence responding with said detected pulse signal of said voltage detecting means;
activation control means for controlling active periods of said Q first power transistors and said Q second power transistors responding with said holding state of said state shifting means;
commanding means for producing a command signal which responds with said phase pulse signal of said phase detecting means; and
switching operation means for 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 command signal;
and that
said activation control means causes each of said active periods of said Q first power transistors and said Q second power transistors to become larger than the period of 360/Q electrical degrees,
said switching operation means produces a high-frequency switching pulse signal which responds with said command signal and switches said at least one power transistor responding with said switching pulse signal,
and
said phase detecting means includes:
slant producing means for producing a slant voltage signal at a terminal of a capacitor, said slant voltage signal responding intermittently with a voltage difference between one of the power supplying terminal voltages and the common terminal voltage of said Q-phase windings during sampling periods and having substantially a voltage slant during at least one of the rest periods except said sampling periods, and
phase pulse producing means for producing said phase pulse signal by comparing said slant voltage signal with a reference voltage.
With this configuration, the switching operation means cause the power tr
Akin Gump Strauss Hauer & Feld L.L.P.
Matsushita Electric - Industrial Co., Ltd.
McCloud Renata
Nappi Robert
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