Electricity: motive power systems – Positional servo systems – With particular motor control system responsive to the...
Reexamination Certificate
1999-06-09
2001-06-12
Ip, Paul (Department: 2837)
Electricity: motive power systems
Positional servo systems
With particular motor control system responsive to the...
C318S696000, C318S687000, C318S254100
Reexamination Certificate
active
06246205
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a driving apparatus for a stepping motor.
2. Prior Art
Some vehicle air conditioners use a PM (permanent Magnet) type stepping motor in an actuator driving a door for switching blowing-out ports in a duct, or the like. To drive the stepping motor, a unipolar driving system (a first prior art) and a bipolar driving system (a second prior art) have been used.
(The First Prior Art)
As shown in
FIGS. 10A and 10B
, a stepping motor
10
of a unipolar driving system has a rotor
11
and first to fourth exciting coils L
1
-L
4
which apply a rotating magnetic field to the rotor
11
. The respective ends of the first to the fourth exciting coils L
1
-L
4
are connected to the plus terminal of a power supply V via an external terminal P
0
of the motor
10
. The respective other ends of the first to the fourth exciting coils L
1
-L
4
are connected to a driving circuit
12
via external terminals P
1
-P
4
, respectively.
The driving circuit
12
includes four npn-type bipolar transistors Tr
1
-Tr
4
and four flywheel diodes D
1
-D
4
. Each of the diodes D
1
-D
4
is connected between a collector and an emitter of one of the transistors Tr
1
-Tr
4
. The collectors of the transistors Tr
1
-Tr
4
are connected to the other ends of the first to the fourth exciting coils L
1
-L
4
via the external terminals P
1
-P
4
, respectively, and the emitters thereof are connected to the ground GND.
Control signals Ø
1
-Ø
4
from a control circuit
13
are input to the bases of the transistors Tr
1
-Tr
4
, respectively, and the transistors Tr
1
-Tr
4
are selectively turned on and off by the control signals Ø
1
-Ø
4
.
Thus, in the driving circuit
12
of the stepping motor
10
, the transistors Tr
1
-Tr
4
are sequentially turned on and off on the basis of the control signals Ø
1
-Ø
4
from the control circuit
13
and the first to the fourth exciting coils L
1
-L
4
are sequentially excited. The sequential excitations of the first to the fourth exciting coils L
1
-L
4
causes the rotating magnetic field to be generated and the rotor
11
to be rotated.
(The Second Prior Art)
As shown in
FIGS. 11A and 11B
, a stepping motor
20
of a bipolar driving system has a rotor
21
and first and second exciting coils L
11
and L
12
that apply a rotating magnetic field to the rotor
21
. Both ends of the first exciting coil L
11
are connected via external terminals P
11
and P
12
, respectively, to a first driving portion
22
a
of a driving circuit
22
. Both ends of the second exciting coil L
12
are connected via external terminals P
13
and P
14
, respectively, to a second driving portion
22
b
of the driving circuit
22
.
The first driving portion
22
a
includes a bridge circuit
23
a
including four npn-type bipolar transistors Tr
11
-Tr
14
, and four flywheel diodes D
11
-D
14
each connected between a collector and an emitter of each of the transistors Tr
11
-Tr
14
. A power supply V is supplied between nodes N
1
and N
2
, where the node N
1
is located between the collectors of the transistors Tr
11
and Tr
12
, and the node N
2
is located between the emitters of the transistors Tr
13
and Tr
14
. A node N
3
, between the emitter of the transistor Tr
11
and the collector of the transistor Tr
13
, is connected via the external terminal P
11
to the one end of the first exciting coil L
11
. A node N
4
existing between the emitter of the transistor Tr
12
and the collector of the transistor Tr
14
is connected via the external terminal P
12
to the other end of the first exciting coil L
11
.
The second driving portion
22
b
includes a bridge circuit
23
b
including four npn-type bipolar transistors Tr
15
-Tr
18
, and four flywheel diodes D
15
-D
18
each connected between a collector and an emitter of each of the transistors Tr
15
-Tr
18
. The power supply V is supplied between nodes N
5
and N
6
, where the node N
5
is located between the collectors of the transistors Tr
15
and Tr
16
, and the node N
6
is located between the emitters of the transistors Tr
17
and Tr
18
. A node N
7
existing between the emitter of the transistor Tr
15
and the collector of the transistor Tr
17
is connected via the external terminal P
13
to the one end of the second exciting coil L
12
. A node N
8
existing between the emitter of the transistor Tr
16
and the collector of the transistor Tr
18
is connected via the external terminal P
14
to the other end of the second exciting coil L
12
.
Control signals Ø
11
-Ø
18
from a control circuit
24
are input to the bases of the transistors Tr
11
-Tr
18
, respectively, and the transistors Tr
11
-Tr
18
are selectively turned on and off on the basis of the control signals Ø
11
-Ø
18
.
More specifically, as shown in
FIG. 12
, the control circuit
24
first turns on only the transistors Tr
11
and Tr
14
(Step 1). This causes an exciting current to flow through the first exciting coil L
11
in the direction of an arrow A
1
and a magnetic field is generated on the basis of the exciting current. Next, the control circuit
24
turns on only the transistors Tr
15
and Tr
18
(Step 2). This causes an exciting current to flow through the second exciting coil L
12
in the direction of an arrow A
2
and a magnetic field is generated on the basis of the exciting current. Subsequently, the control circuit
24
turns on only the transistors Tr
12
and Tr
13
(Step 3). This causes an exciting current to flow through the first exciting coil L
11
in the direction of an arrow A
3
and a magnetic field is generated on the basis of the exciting current. Next, the control circuit
24
turns on only the transistors Tr
16
and Tr
17
(Step 4). This causes an exciting current to flow through the second exciting coil L
12
in the direction of an arrow A
4
and a magnetic field is generated on the basis of the exciting current.
Thus, in the driving circuit
22
of the stepping motor
20
, the transistors Tr
11
-Tr
18
are turned on and off in the order of Step 1 to Step 4 on the basis of the control signals Ø
11
-Ø
18
from the control circuit
24
and the first and the second exciting coils L
11
and L
12
are excited in a predetermined timing and polarity. These excitations of the first and the second exciting coils L
11
and L
12
cause the rotating magnetic field to be generated and the rotor
21
to be rotated.
The first prior art motor
10
described above is more advantageous than the second prior art motor
20
in that the driving circuit
12
can easily be formed with fewer transistors. However, when the motor
10
has the same dimension as the motor
20
, the motor
10
requires much more exciting current than the motor
20
, when both of the motors
10
and
20
provide the same outputs. Therefore, the motor
10
generates a large amount of heat and is inefficient. Conversely, although the motor
20
generates less heat and is more efficient than the motor
10
, the motor
20
has a problem in that the driving circuit
22
must be formed with many transistors and is expensive.
There is a demand for a stepping motor having both features of a high efficiency and a low cost. Accordingly, the driving circuit
22
for the motor
20
(bipolar driving system) having a high efficiency should be simplified in circuit structure.
SUMMARY OF THE INVENTION
In light of the above, it is an object of the present invention to provide a driving apparatus for a stepping motor driven by a bipolar driving system and having a simplified circuit structure.
In order to achieve the above object, in accordance with a first aspect of the present invention, there is provided an apparatus for driving a stepping motor, the stepping motor having a plurality of exciting coils from a first exciting coil to a last exciting coil, each having a first terminal and a second terminal. The apparatus comprises a first and a second switching circuit connected between the first terminal of the first exciting coil and a power supply and between the first terminal and a ground, respectively. Also, the apparatus comprises a third a
Kujira Yukinobu
Tateishi Seiji
Asmo Co. Ltd.
Ip Paul
Nawrocki, Rooney & Sivertson P.A.
LandOfFree
Driving apparatus for stepping motor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Driving apparatus for stepping motor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Driving apparatus for stepping motor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2452438