Hybrid stepping motor

Details Hybrid stepping motor Hybrid stepping motor

2001-12-31

2004-01-06

Nguyen, Tran (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S261100

Reexamination Certificate

active

06674187

ABSTRACT:

BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates to a construction of a rotating electric machine. Particularly, the present invention relates to an improvement of a high-resolution and high-accuracy hybrid stepping motor of an outer rotor type or an inner rotor type that is suitable for OA equipment, which requires accurate positioning during high speed operation, such as a printer, a high speed facsimile or a PPC copying machine.
2. Prior Art
The hybrid stepping motor that is a combination of a permanent magnet stepping motor and a variable reluctance stepping motor provides high accuracy, large torque and little step angle. For example, a conventional hybrid stepping motor of an inner rotor type (a motor for short in the following description) has the construction as shown in
FIGS. 35 and 36
.
FIG. 35
is a longitudinal sectional front view of one example of this kind of conventional motor, and
FIG. 36
is a sectional view of
FIG. 35
along XXXVI—XXXVI line.
In
FIGS. 35 and 36
, a symbol
21
represents a cylindrical casing and the casing
21
is integrally fixed to a stator iron-core
22
formed of magnetic material. A predetermined number of magnetic poles
23
corresponding to construction characteristic of this motor are centripetally formed around the inner circumference of the stator iron core
22
at equal pitches. A winding
24
to magnetize the magnetic pole
23
is wound around each of the magnetic poles
23
.
Further, pole teeth
23
a
whose number corresponds to the construction characteristic of this motor are formed on a tip of each magnetic pole
23
at equal pitches.
In general, the stator iron-core
22
and the magnetic pole
23
are manufactured by punching a magnetic material plate with a punch press. A predetermined number of the punched plates are stacked and the winding
24
is wound to shape a stator.
End plates
25
and
26
are integrally connected to both ends of the casing
21
.
A pair of bearings
27
a
and
27
b
are mounted on the center of the end plates
25
and
26
, which rotatably support a rotor axis
28
.
A permanent magnet
29
that is magnetized in the axial direction is engaged and fixed to the rotor axis
28
. The permanent magnet
29
is sandwiched between two rotor magnetic poles
30
A and
30
B having disc shapes. Around an outer circumference of each of the rotator magnetic poles
30
A and
30
B, pole teeth
30
a
are formed such that the shapes and the intervals thereof correspond to that of the pole teeth
23
a
formed on the magnetic pole
23
of the stator. The first and second rotor magnetic poles
30
A and
30
B are engaged such that the pole teeth
30
a
of the first rotor magnetic pole
30
A and the pole teeth
30
a
of the second rotor magnetic pole
30
B are deviated by ½ pitch.
In general, the magnetic pole of the rotor is manufactured by punching a magnetic material plate with a punch press. A predetermined number of the punched plates are stacked to shape a rotor.
In the motor having the above described configuration, when the windings
24
of the stator are sequentially energized in the predetermined order, each of the pole teeth
23
a
of the stator are magnetized in sequence. Accordingly, the rotor rotates and stops as the magnetic field caused by the magnetized pole teeth
23
a
of the stator varies according to the interaction between the respective pole teeth
23
a
of the stator and the respective pole teeth
30
a
of the rotor that are magnetized by the permanent magnet
29
.
Number of the magnetic poles
23
of the stator, number of the pole tooth
23
a
and number of the pole teeth
30
a
of the rotor vary depending on conditions such as number of phase of the motor.
FIG. 37
shows a connection example of a conventional 6-phase motor with monofier (unifier) windings and twelve lead lines drawn therefrom.
The numbers applied to the upper portion of the drawing represent the magnetic pole windings, assuming that the predetermined magnetic pole winding is referred to as
1
E and the next one is referred to as the next number in order until the number reaches
24
E.
The connection for each magnetic pole winding is shown in FIG.
37
. The magnetic pole windings
1
E,
7
E,
13
E and
19
E are connected in series between the lead lines A and A′ such that the magnetic pole windings
1
E,
13
E are in opposite phase to the magnetic pole windings
7
E,
19
E. The magnetic pole windings
2
E,
8
E,
14
E and
20
E are connected in series between the lead lines B and B′ such that the magnetic pole windings
2
E,
14
E are in opposite phase to the magnetic pole windings
8
E,
20
E. The magnetic pole windings
3
E,
9
E,
15
E and
21
E are connected in series between the lead lines C and C′ such that the magnetic pole windings
3
E,
15
E are in opposite phase to the magnetic pole windings
9
E,
21
E. The magnetic pole windings
4
E,
10
E,
16
E and
22
E are connected in series between the lead lines D and D′ such that the magnetic pole windings
4
E,
16
E are in opposite phase to the magnetic pole windings
10
E,
22
E. The magnetic pole windings
5
E,
11
E,
17
E and
23
E are connected in series between the lead lines E and E′ such that the magnetic pole windings
5
E,
17
E are in opposite phase to the magnetic pole windings
11
E,
23
E. The magnetic pole windings
6
E,
12
E,
18
E and
24
E are connected in series between the lead lines F and F′ such that the magnetic pole windings
6
E,
18
E are in opposite phase to the magnetic pole windings
12
E,
24
E.
An excitation electric current is sequentially applied to the respective lead lines.
FIG. 38
shows an example of an excitation sequence of one-phase excitation for the connection shown in FIG.
37
.
In
FIG. 38
, the symbols of the lead lines shown in
FIG. 37
to which an exciting current is applied are shown in the vertical direction and the excitation steps are shown at the upper portion in the horizontal direction. The rectangles above the respective lines in the horizontal direction represent that an electric current passes through the lead lines in the predetermined direction, and the rectangles below the respective lines represent that an electric current passes through the lead lines in the opposite direction.
In the drawing, an electric current passes from the lead line A shown in
FIG. 37
to the lead line A′ at step
1
, and, at the next step
2
, an electric current passes from the lead line B to the lead line B′. After that, an electric current flows step by step until step
6
, and an electric current passes in a direction from the lead line A′ to the lead line A at step
7
. Then, an electric current is applied to each lead line in the same manner to excite each magnetic pole of the stator in turn.
Accordingly, since magnetic polarity of each magnetic pole of the stator varies, the magnetic pole of the stator attracts the corresponding magnetic pole (pole teeth) of the rotor, which rotates the rotor axis
28
of the motor.
Further,
FIG. 39
shows an example of a connection of windings in a conventional 10-phase motor with a monofier (unifier) winding, and
FIG. 40
shows an example of an excitation sequence of one-phase excitation for the 10-phase motor with monofier winding shown in FIG.
39
. How to read is the same as
FIGS. 37 and 38
that are described above.
A step angle &thgr;
s
, which is a basic characteristic of the above described stepping motor, is determined by the following equation (1).
&thgr;
s
=180°/(
M×Z
)  (1)
Where M is phase number of the stator and Z is number of pole teeth of the rotor.
The above described inner rotor motor is constructed such that the rotor is located at the center of the motor and the stator is arranged around thereof. On the other hand, an outer rotor motor is constructed such that the stator is located at the center of the motor and the rotor is arranged around thereof. As a result, the structure of the rotating mechanism of the outer rotor motor is different from t

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