Motor

Details Motor Motor

2001-03-29

2002-07-23

Nappi, Robert E. (Department: 2837)

Electricity: motive power systems

Switched reluctance motor commutation control

C318S132000, C318S434000

Reexamination Certificate

active

06424106

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a motor wherein current paths to windings are altered with a plurality of transistors without using position detecting elements.
PRIOR ART
In recent years, motors wherein current paths are altered electronically with a plurality of 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 altered with PNP-type bipolar power transistors and NPN-type bipolar power transistors is available as an example of the above-mentioned motors.
FIG. 28
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 Lp
1
, Lp
2
and Lp
3
responding with the voltage signals Kp
1
, Kp
2
and Kp
3
respectively to control the activation of low-side NPN-type bipolar 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
respectively to control the activation of high-side PNP-type bipolar power transistors
2025
,
2026
and
2027
. As a result, three-phase drive voltages are supplied to windings
2012
,
2013
and
2014
.
In this conventional configuration, it is a problem that power losses of the power transistors are large. This is because that the NPN-type bipolar power transistors
2021
,
2022
and
2023
and the PNP-type bipolar power transistors
2025
,
2026
and
2027
supply drive voltages having necessary amplitudes to the windings
2012
,
2013
and
2014
by controlling the voltage drop across the emitter and the collector in an analog manner. When the drive voltages are supplied, a voltage drop in each bipolar power transistor is large. As a result, a large power loss produced by the product value of the voltage drop and the drive current to the winding is caused, resulting in a large heat generation. To reduce this power loss, it is known to perform PWM drive (pulse drive voltages are supplied to the windings). For example, U.S. Pat. No. 5,982,118 discloses an example wherein a method of PWM-controlling power transistors by using two sensor outputs is used to reduce power losses.
However, the above-mentioned conventional example and U.S. Pat. No. 5,982,118 include three or two position detecting elements for detecting the rotational position of the rotor. For this reason, the spaces, connecting wires, etc. for the position detecting elements are required and become complicated, resulting in a high cost.
On the other hand, it is known that sensorless drive is performed to eliminate position detecting elements. U.S. Pat. No. 5,122,715 and U.S. Pat. No. 5,473,232 disclose a motor wherein the terminal voltages of windings are detected and current paths to the windings are altered in response to the timing of the detection. In U.S. Pat. No. 5,122,715, the width of activation has an electrical angle of 120 degrees, thereby having disadvantages of a large vibration and a large acoustic noise. The patent also discloses a complicated configuration having a switching regulator. In U.S. Pat. No. 5,473,232, power losses are reduced by making PWM switching of power transistors. However, the width of the activation for each power transistor has an electrical angle of120 degrees, thereby having disadvantages of a large vibration and a large acoustic noise.
It is therefore an object of the present invention to provide a motor capable of solving one or all of the above-mentioned problems.
BRIEF SUMMARY OF THE INVENTION
The motor in accordance with the main aspect of 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 FET power transistors and Q second FET power transistors for supplying a power to said Q-phase windings, each of said Q first FET 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 FET 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 in response to terminal voltages of said Q-phase windings;
state shifting means for shift-holding a holding state from one state to at least one other state in sequence in response to the detected pulse signal of said voltage detecting means;
activation control means for controlling active periods of said Q first FET power transistors and said Q second FET power transistors in response to said holding state;
commanding means for producing a command signal in response to an output pulse signal of said voltage detecting means; and
switching operation means for causing at least one of said Q first FET power transistors and said Q second FET power transistors to perform high-frequency switching in response to said command signal;
and that
said activation control means produces Q-phase first activation control signals and Q-phase second activation control signals in response to said holding state of said state shifting means for controlling said active periods of said Q first FET power transistors and said Q second FET power transistors, each of said active periods being an electrical angle which is larger than 360/Q degrees,
said switching operation means produces a switching pulse signal in response to said command signal, and makes high-frequency switching operation of at least one FET power transistor among said Q first FET power transistors and said Q second FET power transistors in response to said switching pulse signal, and
said state shifting means includes:
adjusting means for producing a timing signal after an adjust time from detection of said detected pulse signal,
shift hold means for shift-holding said holding state in response to said timing signal, and
adjust changing means for changing said adjust time of said adjusting means smaller in case that said command signal is larger than a predetermined value, thereby making the product value of said adjust time and said rotational speed of said rotor smaller in said case.
With this configuration, the switching operation means causes at least one of the FET power transistors of the power supplying means to perform high-frequency switching operation in response to the command signal. Therefore, power losses at the FET power transistors of the power supplying means can be reduced significantly, whereby the power efficiency of the motor can be improved greatly.
The voltage detecting means produces the detected pulse signal in response to the terminal voltages of the windings, the state shifting means shifts the phases of the activation to the windings in response to the detected pulse signal, and the activation control means control the active periods of the FET power transistors so as to rotate the rotor in a predetermined direction. Therefore, no position detecting element is required, and the configuration of the motor becomes simplified.
When the command signal of the commanding means becomes larger than a predetermined value, the adjust time to the output of the timing signal from the detected pulse

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