Electricity: motive power systems – Synchronous motor systems
Reexamination Certificate
2000-03-23
2002-08-13
Masih, Karen (Department: 2837)
Electricity: motive power systems
Synchronous motor systems
C318S711000, C318S717000, C318S721000, C318S724000, C318S280000, C318S647000, C318S652000
Reexamination Certificate
active
06433503
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to synchronous motors and synchronous motor control circuits for controlling the electric signals supplied to the motor to drive the rotor. More particularly, the present invention relates to synchronous motor control circuits capable of generating phase timing signals that are supplied to the respective stator coils, which signals are generated based upon output signals of a rotor position detector.
2. Description of the Related Art
FIG. 5
shows a known switched reluctance motor (“SR motor”) or commutator-less motor. This SR motor is a 6-4-pole three-phase SR motor having a stator and a rotor. The stator includes a stator core with six stator poles
51
-
56
that are physically spaced at 60° intervals, which corresponds to electrical angles of 120°. Coils are wound around the respective stator poles
51
-
56
. Coils wound around two opposing stator poles are electrically connected in series to provide an opposing pair of stator coils that will be energized by the same control signal. For example, the coils wound around stator poles
51
and
54
are connected with each other in series. The three sets of electrically coupled coils are respectively energized in each of the respective three phases, i.e., U-phase, V-phase and W-phase.
The rotor
64
has a rotor core
65
with a rotating axis and magnetic rotor poles
57
projecting from the outer periphery of the rotor core
65
. The magnets in the rotor
64
create eight magnetic regions
58
, which each cover 45° intervals of the rotor
64
.
A control circuit (not shown) controls the timing of the rotor drive (control) signals that are supplied to the stator coils for each of the respective three phases. The timing signals are generated based upon output signals from rotor position detectors. The control circuit generates rotor driving signals that cause the rotor to rotate either in a forward direction or a reverse direction. The known control circuit uses Hall ICs
63
u,
63
v
and
63
w
as the rotor position detectors, which Hall ICs contain Hall elements for detecting the magnetic field of the rotor magnetic regions
58
. A Hall IC (
63
u,
63
v
and
63
w
) is located at a central position of each stator pole (U-phase stator pole
51
, V-phase stator pole
56
and W-phase stator pole
52
, respectively).
FIG. 6
shows a timing chart with timing signals of a type suitable for driving a typical SR motor. This timing chart shows the relationship between rotor position signals output from the Hall ICs for each of the respective phases and rotor driving signals supplied to the stator coils for each of the respective phases. At the top, the inductance of each stator coil is shown in relation to the rotor position for each of the respective phases. In the second timing chart, the outputs of the Hall ICs (
63
u
-
63
w
) are shown for each of the respective phases according to the rotor position. If the rotor driving signals are supplied to the respective stator coils while the inductance of the respective stator coils is increasing, a torque (positive torque) is generated that causes the rotor to rotate in a first direction. On the other band, if the rotor driving signals are supplied to the respective stator coils while the inductance of the respective stator coils is decreasing, an opposite torque (negative torque) is generated that causes the rotor to rotate in a direction that is opposite to the direction that the rotor rotates when the positive torque is applied to the rotor.
In order to cause the rotor to rotate in the forward direction, the SR motor control circuit uses a forward rotation logic to control the timing of the rotor driving signals, which signals are supplied to the stator coils for each of the respective phases. The rotor driving signals are generated based upon the output signals of the Hall ICs
63
u
-
63
w
for each of respective phases. For example, the rotor driving signals may be supplied to the U-phase coil, V-phase coil and W-phase coil in this order.
FIG. 6
also shows a timing chart for specific set of rotor driving signals to control the known SR motor. The rotor driving signal for the U-phase stator coil is initiated when Hall IC
63
u
detects the U-phase trailing edge signal. This U-phase rotor driving signal is terminated when Hall IC
63
v
detects the trailing edge signal of the V-phase. Similarly, the rotor driving signal for the V-phase stator coil is initiated when Hall IC
63
v
detects the V-phase trailing edge signal. This V-phase rotor driving signal is terminated when Hall IC
63
w
detects the trailing edge signal of the W-phase. Finally, the rotor driving signal for the W-phase stator coil is initiated when Hall IC
63
w
detects the W-phase trailing edge signal. This W-phase rotor driving signal is terminated when Hall IC
63
u
detects the trailing edge signal of the U-phase. In
FIG. 6
, when the rotor is rotating in the forward direction, the electrical angle is 0° with respect to the forward rotating direction (clockwise direction in
FIG. 5
, right direction in FIG.
6
).
In order to cause the rotor to rotate in the reverse direction, the SR motor control circuit uses a reverse rotation logic to control the timing of the rotor driving signals, which signals are supplied to the stator coils for each of the respective phases. The rotor driving signals are generated based upon the output signals of the Hall ICs
63
u
-
63
w
for each of the respective phases. For example, the rotor driving signals may be supplied to the U-phase coil, W-phase coil and V-phase coil in this order.
The rotor driving signal for the U-phase stator coil is initiated when Hall IC
63
u
detects the U-phase leading edge signal. This U-phase rotor driving signal is terminated when Hall IC
63
w
detects the leading edge signal of the W-phase. Similarly, the rotor driving signal for the W-phase stator coil is initiated when Hall IC
63
w
detects the W-phase leading edge signal. This W-phase rotor driving signal is terminated when Hall IC
63
v
detects the leading edge signal of the V-phase. Finally, the rotor driving signal for the V-phase stator coil is initiated when Hall IC
63
v
detects the V-phase leading edge signal. This V-phase rotor driving signal is terminated when Hall IC
63
u
detects the leading edge signal of the U-phase. In
FIG. 6
, when the rotor is rotating in the reverse direction, the electrical angle is 0° with respect to the reverse rotating direction (counterclockwise direction in
FIG. 5
, left direction in FIG.
6
).
The start timing of the rotor driving signals supplied to the stator coils of respective phases (coil energizing start timing) may be advanced in order to improve motor operating efficiency. One method for advancing the start timing of the rotor driving signals includes providing the rotor position detectors in a position that is offset from the central position of a magnetic pole. Japanese Laid-Open Patent Publication No. 6-165464, for example, shows that this can be accomplished by advancing the position detectors by 30 electrical degrees. However, if only one offset rotor position detector is provided for each stator pole, the prior art has taught that the motor operating properties are different when the rotor is rotating in the forward direction as opposed to the reverse direction. Therefore, in these prior art systems it would be necessary to provide two rotor position detectors for each stator pole of a bi-directional motor, i.e., in both the forward rotating direction and reverse rotating direction of the rotor, each position detector being offset or shifted from the central position of the stator pole.
SUMMARY OF THE INVENTION
It is, accordingly, an object of the present invention to teach an improved synchronous motor and an improved control circuit for generating rotor driving signals that are supplied to the synchronous motor. By positioning the rotor position detectors appropriately, the number of rotor position detectors can be reduced as compared to the known relucta
Minoshima Norimoto
Uematsu Tatsuya
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Masih Karen
Morgan & Finnegan , LLP
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