Electricity: motive power systems – Positional servo systems – With particular motor control system responsive to the...
Reexamination Certificate
2002-05-22
2003-12-16
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Positional servo systems
With particular motor control system responsive to the...
C318S696000
Reexamination Certificate
active
06664753
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus of controlling to rotate a step motor for driving to rotate a step motor and detecting presence or absence of rotation of the step motor.
2. Description of the Prior Art
Conventionally, there has bee used a step motor as a motor for driving to rotate a time hand or the like in an electronic timepiece.
FIG. 2
is a constitution view of a step motor conventionally used in an electronic timepiece. In
FIG. 2
, a step motor is provided with a stator
401
, a coil
307
wound around the stator
401
and a rotor
402
of two poles arranged at inside of the stator
401
. The stator
401
is formed with saturable portions
403
and
404
.
When a drive pulse of a rectangular wave is supplied to the coil
307
and current i is made to flow in an arrow mark direction of
FIG. 2
, magnetic flux is generated in an arrow mark direction in the stator
401
. Thereby, the saturable portions
403
and
404
are firstly saturated, thereafter, by interactive operation of a magnetic pole produced at the stator
401
and a magnetic pole of the rotor
402
, the rotor
402
is rotated by 180 degrees in the counterclockwise direction. Thereafter, by making current having different polarities flow alternately to the coil
307
, the above-described similar operation is carried out and the rotor
402
is rotated in the counterclockwise direction by 180 degrees respectively.
FIG.
3
and
FIG. 4
are circuit diagrams showing an apparatus of controlling to rotate a step motor conventionally used in an electronic timepiece, constituting a circuit integrally constituted with a rotation drive circuit and a rotation detection circuit.
FIG. 3
is an explanatory view of operation when the step motor is controlled to rotate by the rotation drive circuit and
FIG. 4
is an explanatory view when rotation of the step motor is detected by the rotation detection circuit. Further,
FIG. 5A
shows a drive pulse used in driving to rotate the step motor and
FIG. 5B
shows a control pulse for detecting rotation used in detecting rotation of the step motor.
In FIG.
3
and
FIG. 4
, P-channel MOS transistors
301
and
302
and N-channel MOS transistors
303
and
304
are constituent elements of a motor drive circuit and a coil
307
of a step motor is connected between a point of connecting sources of the transistor
301
and the transistor
303
and a point of connecting sources of the transistor
302
and the transistor
304
.
Meanwhile, N-channel MOS transistors
303
through
306
, a resistor
308
for detection connected in series with the transistor
305
and a resistor
309
for detection connected in series with the transistor
306
and a comparator
310
are constituent elements of the rotation detection circuit.
Gates of the respective transistors
301
through
306
are connected in a control circuit
312
.
A point OUT
2
for connecting the resistor
308
for detection and the coil
307
and a point OUT
1
for connecting the resistor
309
for detection and the coil
307
are connected to an input portion of the comparator
310
. Further, the input portion of the comparator
310
is inputted with threshold voltage Vss.
In the above-described constitution, when a drive pulse P
1
of
FIG. 5A
is supplied to an input portion Vi of a control circuit
312
, by control of the control circuit
312
, as shown by
FIG. 3
, the transistors
302
and
303
are brought into an ON state. Thereby, current is made to flow to the coil
307
in an arrow mark direction and as shown by
FIG. 2
, the rotor
402
is rotated in the counterclockwise direction.
Meanwhile, there is provided a rotation detection period for detecting whether the step motor is rotated, immediately after a motor drive period.
During the rotation detection period, the input portion Vi of the control circuit
312
is supplied with rotation detection control pulse SP
1
of FIG.
5
B. In response to the rotation detection control pulse SP
1
, as shown by
FIG. 4
, the control circuit
312
controls to make the transistor
304
to ON/OFF in a state of making the transistors
303
and
306
ON.
At this occasion, detection voltage is outputted from the connection point OUT
1
of the resistor
309
for rotation detection and the coil
307
. As the detection voltage, there is provided a signal having a waveform as shown by FIG.
7
(
a
). In FIG.
7
(
a
), there is generated detection voltage on a lower side of VDD when the rotor
42
is oscillated in the counterclockwise direction and there is generated detection voltage on an upper side of VDD when the rotor
42
is oscillated in the clockwise direction.
When the rotor
402
is rotated, there is provided detection voltage equal to or lower than predetermined threshold voltage (Vss according to the conventional example) and a rotation detection signal Vs at a high level is outputted from the comparator
310
. When the rotor
402
is not rotated, the detection voltage is not equal to or lower than the threshold voltage and therefore, the rotation detection signal Vs at a low level is outputted from the comparator
310
. Whether the step motor is rotated, can be detected from the rotation detection signal Vs. After detection of rotation has been finished, the transistors
303
and
304
are maintained in an ON state to thereby brake the step motor.
At a successive motor drive period, the following normal drive pulse P
1
is supplied to the input portion Vi of the control circuit
312
. The control circuit
312
controls the transistors
301
and
304
to an ON state and drive current in a direction reverse to that of the drive current (direction reverse to the arrow mark of
FIG. 3
) is made to flow at the coil
307
and the rotor
402
is rotated in the counterclockwise direction.
During the rotation detection period at this occasion, when the rotation detection control pulse SP
1
is supplied to the input portion Vi of the control circuit
312
, the transistors
304
and
305
are controlled to ON and the transistor
303
is controlled to ON/OFF. At this occasion, detection voltage is outputted from the connection point OUT
2
of the resistor
308
and the coil
307
and a level thereof is determined by the comparator
310
. Similar to the above-described,when the rotor
402
is rotated, the rotation detection signal Vs at the high level is outputted from the comparator
310
and when the rotor
402
is not rotated, the rotation detection signal Vs at the low level is outputted from the comparator
310
. Whether the motor is rotated, can be detected from the rotation detection signal Vs. When detection of rotation has been finished, the transistors
303
and
304
are brought into an ON state to thereby brake the step motor.
According to the step motor having the above-described constitution, after the rotor
402
is driven by the drive pulse P
1
, the rotor
402
is freely oscillated centering on a position at which the rotor
402
is to be stopped. Immediately after finishing the drive pulse P
1
, free oscillation of the rotor
402
is considerable, further, by inertia, the rotor
402
is oscillated in a direction the same as a regular rotational direction (counterclockwise direction in the above-described conventional example). When the rotor
402
is oscillated in the counterclockwise direction, in
FIG. 4
, current is made to flow in the arrow mark direction.
Meanwhile, as shown by
FIG. 6
, an equivalent circuit of the respective transistors
303
through
306
is constituted by a series circuit of a switch
501
and a resistor
502
and a diode
503
and a capacitor
504
respectively connected in parallel with the series circuit and the respective transistors
303
through
306
are equivalently regarded as an element having a diode in one direction.
Therefore, even when the step motor is not rotated, within a predetermined period IT immediately after finishing the drive pulse P
1
, oscillation of the rotor
42
in the counter direction is considerable and therefore, as shown by FIG.
7
(
a
), there is a
Adams & Wilks
Miller Patrick
Nappi Robert E.
LandOfFree
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