Electricity: motive power systems – Switched reluctance motor commutation control
Reexamination Certificate
2002-01-25
2003-01-28
Leykin, Rita (Department: 2837)
Electricity: motive power systems
Switched reluctance motor commutation control
C318S132000, C318S434000, C318S061000, C318S090000, C388S847000
Reexamination Certificate
active
06512342
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a brushless motor driving device of the sensorless type so configured to detect a rotor position fry use of an induced voltage generated across an armature coil.
In the brushless motor driving device of the sensorless type, when a rotor is in a stationary condition, since no induced voltage generates across an armature coil, it is not possible to detect a rotor position. Therefore, when the motor is started, it becomes necessary to forcibly give a rotating magnetic field from the outside at the time of starting the motor. A brushless motor driving device having a means for this purpose is proposed in for example Japanese Patent Application Pre examination Publication No. JP-A-57-173385.
Now, the brushless motor driving device disclosed in JP-A-57-173385 will be described with reference to FIG.
14
. In the drawing, a power supply
1
is connected through a power switch
2
to each of a U-phase coil, a V-phase coil and a W-phase coil of armature coils
3
of a three-phase brushless motor and to a fixed timer circuit
4
. The armature coils
3
are located to surround a rotor
10
. The U-phase coil, the V-phase coil and the W-phase coil of the armature coils
3
are connected to a collector of transistors TR
1
, TR
2
and TR
3
, respectively, which are included in a driver circuit
9
. An emitter of these transistors TR
1
, TR
2
and TR
3
are connected to ground. An output S
1
of the fixed timer circuit
4
is connected to a switching timer circuit
5
and a rotating magnetic field generating circuit
6
, and an output S
2
of the switching timer circuit
5
is connected to a switch circuit
7
for controlling the switch circuit
7
. An induced voltage detecting circuit
8
has inputs connected to the U-phase coil, the V-phase coil and the W-phase coil of the armature coils
3
, respectively, for detecting an induced voltage generated on the respective phase coils of the armature coils
3
. This switch circuit
7
receives, from the rotating magnetic field generating circuit
6
, currents S
3
, S
4
and S
5
for driving the driver circuit
9
. The switch circuit
7
also receives, from the induced voltage detecting circuit
8
, a drive current based on the induced voltage detected from the respective phase coils of the armature coils
3
. The switch circuit
7
is controlled by the switching timer circuit
5
to select one of the received drive currents so as to supply the selected drive current to the driver circuit
9
. Three output terminals of the switch circuit
7
are connected to a base of the transistors TR
1
, TR
2
and TR
3
, respectively.
With this arrangement, when the power switch
2
is turned on, one end of each of the U-phase coil, the V-phase coil and the W-phase coil of the armature coils
3
, is connected the power supply
1
. Simultaneously, the fixed timer circuit
4
operates to generate the control signal S
1
having a constant time width shown at (a) in
FIG. 15
for exciting one phase coil of the armature coils
3
, for example, the W-phase coil. This control signal S
1
is supplied to the rotating field generating circuit
6
, and at the same time, to the switching timer circuit
5
. When a constant time elapses after the control signal S
1
is outputted from the fixed timer circuit
4
, the fixed timer circuit
4
is brought into an off condition. Thus, the rotating magnetic field venerating circuit
6
generates the drive signals S
3
, S
4
and S
5
as shown at (c), (d) and (e) in
FIG. 15
, respectively, for exciting the U-phase coil, the V-phase coil and the W-phase coil of the armature coils
3
. The drive signals S
3
, S
4
and S
5
are supplied through the switch circuit
7
S to the base of the transistors TR
1
, TR
2
and TR
3
, respectively. The switch circuit
7
is controlled by the switching signal S
2
at (b) in
FIG. 15
outputted from the switching timer circuit
5
, so that switches in the switch circuit
7
are putted in a connection condition shown in FIG.
14
. This connection condition is maintained until the switching signal S
2
is brought into a low level.
The drive signals S
3
, S
4
and S
5
generated in the rotating magnetic field generating circuit
6
are sequentially supplied to the base of the transistors TR
1
, TR
2
and TR
3
, respectively, so that an electric current supplied from the power supply
1
sequentially flows in the U-phase coil, the V-phase coil and the W-phase coil of the armature coils
3
, respectively, with the result that a rotating magnetic field is generated in the armature coils
3
so that the rotator starts to rotate. Thus, if use motor is started and if the predetermined time has elapsed, the switching signal S
2
outputted from the switching timer circuit
5
is brought into the low level, so that the connection condition of the switch circuit
7
is changed from a condition opposite to the connection condition shown in FIG.
14
. As a result, the drive signals outputted from the induced voltage detecting circuit
8
by detecting an induced voltage generated an the respective phase coils of the armature coils
3
, are supplied through the switch circuit
7
to the drive circuit
9
so as to sequentially drive the transistors TR
1
, TR
2
and TR
3
, whereby rotation of the three-phase brushless motor is maintained.
However, since the drive signals generated by the rotating magnetic field generating circuit
6
have a constant pulse width, when the motor is started, a phase exciting time becomes constant, so that a time required for starting becomes long, or alternatively, the motor cannot he started smoothly. Furthermore, the phase exciting time and the operating time of the fixed timer circuit 4 are fixed and therefore, cannot be changed arbitrarily.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide to brushless motor driving device which has overcome the above mentioned problems of the prior art.
Another object of the present invention is to provide a brushless motor driving device capable of shortening the starting time and also of smoothly starting the motor.
Still another object of the present invention is to provide a brushless motor driving device capable of arbitrarily setting the exciting time at the time of starting the motor.
The above and other objects of the present invention are achieved in accordance with the present invention by a brushless motor driving device so configured to control excitation of each phase armature coil on the basis of starting patterns supplied from a start circuit in a starting operation and a rotator position signal obtained from an induced voltage generated between opposite ends of each phase armature coil after completion of the starting operation, thereby to rotate a rotator, wherein the start circuit includes a main counter generates a pulse at each time the main counter counts a clock signal to a variable full count value, a sub counter counts the pulse generated by the main counter, the variable full count value being subtracted by a count value of the sub counter, and a start pattern generating circuit generating starting pattern in response to the pulse generated by the main counter.
In an embodiment of the brushless motor driving device, the sub counter is of m bits and the main counter is of n bits where m<n, and only m MSB bits of the full count value in the main counter is variable.
Specifically, the main counter includes n flipflops connected to constitute a counter of n bits, a plurality of AND circuits each receiving an output of different flipflops of the n flipflops, and a plurality of selector circuits connected between an output of selected flipflops of the n flipflops and the AND circuits, and the sub counter includes m flipflops connected to constitute a counter of m bits. Each of the selector circuits receives a corresponding one bit of the m MSB bit, of the main counter and a fixed logical level and is controlled by a corresponding one of the m bits of the sub counter to output the corresponding one bit of the in MSB bits o
Choate Hall & Stewart
Leykin Rita
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