Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-11-29
2003-01-07
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S216006, C310S261100
Reexamination Certificate
active
06504272
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multi-phase (referred to as a “P-phase” in this specification) electric rotating machine having toroidal coils such as a P-phase stepping motor having toroidal coils that is adequate for a driving motor of an ink-jet printer, a copier or the like.
2. Description of Prior Arts
Several types of stepping motors are known as prior arts in this kind of use.
FIG. 13
is perspective view showing a claw pole permanent magnet type (referred to as a “PM-type” in the following description) stepping motor as a first prior art.
In
FIG. 13
, a stator S consists of a first stator unit
101
and a second stator unit
102
that make up a two-phase construction. The first stator unit
101
consists of comb-shaped shaped stator teeth
101
a,
101
b
that arranged by turns along the inner circumference thereof, and a toroidal coil
101
c
that is housed in these stator teeth
101
a,
101
b.
In the same manner, the second stator unit
102
consists of comb-shaped stator teeth
102
a,
102
b
and a toroidal coil
102
c
that is housed in these stator teeth
102
a,
102
b.
Here, the stator teeth
101
a
and
102
a
are arranged with difference of 90 degrees in electric angle, for example.
The reference symbol R represents a rotor, which consists of a permanent magnet
103
whose outer circumference is magnetized such that N and S poles are alternatively arranged in the circumferential direction, a yoke
104
and a rotating shaft
105
. The rotating shaft
105
is supported by the stator S through a bearing.
In this case, the angular pitch of the stator teeth in each stator unit of the stator S and the angular pitch of the N and S poles of the rotor R are determined to be coincident with each other.
Since the coils of the claw pole PM type stepping motor are formed by winding wires on bobbins, a time needed for winding wire is relatively short and connection wires can be easily attached, which can reduce the manufacturing cost. Therefore, this type of stepping motor is widely used in office automation equipment or the like.
FIG. 14
is a partially sectional perspective view showing a principal portion of a hybrid type (referred to as a “HB-type ” in the following description) stepping motor as a second prior art.
In
FIG. 14
, the reference numeral
15
represents a rotating shaft,
17
represents a stator pole,
18
and
19
represent rotor teeth of a pair of rotor units.
Since the HB-type stepping motor allows the stator and the rotor to have a large number of pole teeth, step angle can be kept small, which gives advantages in positioning accuracy and in low-speed stability. Therefore, this type of stepping motor is also widely used in office automation equipment such as a printer or a copier.
In this construction, the coils of the stator are wound on the stator poles through slots formed at the inside portion of the stator, and therefore a two phase motor requires eight coils because the two-phase motor is provided with eight stator poles in general, as shown in FIG.
14
.
The above described conventional constructions have problems as follows.
The PM-type stepping motor, which is the first prior art shown in
FIG. 13
, is produced at low !price because of the bobbin winding construction, while it is difficult to increase a number of magnetic poles because the stator teeth of the stator are formed as the claw poles (i.e., the comb teeth) that are meshed by turns and the rotor is magnetized. In general, the PM-type stepping motor whose motor diameter is about 40 mm has twenty-four magnetic poles, and resolution (i.e., step angle) of the two-phase motor is about 7.5 degrees.
Further, in the claw pole stator, since a magnetic flux is concentrated at the root of the claw pole, a magnetic flux density becomes saturated at the root of the claw pole, which produces a reduction of torque.
Still further, when the claw pole stator is adapted, since the stator teeth are meshed by turns, a leakage flux between the claw poles becomes larger.
On the other hand, the HB-type stepping motor, which is the second prior art shown in
FIG. 14
, has high resolution, while it has disadvantages that a time needed for winding wire is relatively long and a setting of connection wires is complex and expensive, because it is difficult to wind the stator coil wire through the narrow slot formed at the inside portion of the stator.
Further, though a magnetic flux generated from a permanent magnet of the rotor flows to the stator tooth faced thereto, the ratio of effective magnetic flux interlinkage with the coil is about 50%, which requires an expensive permanent magnet having a strong magnetic flux in order to keep adequate torque. This phenomenon will be described with reference to FIG.
15
.
FIG. 15
is an enlarged view of the stator pole
17
, the rotor tooth
18
that is S pole and the rotor tooth
19
that is N pole, which are shown in FIG.
14
.
The rotor teeth
18
and
19
are arranged with difference of half-pitch.
A magnetic flux &phgr;
1
exited from the rotor tooth
18
is divided into a magnetic flux &phgr;
2
that returns to the adjacent rotor tooth
19
and a magnetic flux &phgr;
3
interlinkage with the coil. Since the returning magnetic flux &phgr;
2
is a half of the magnetic flux &phgr;
1
, the effective magnetic flux &phgr;
3
, which produces torque, becomes the remaining half of &phgr;
1
.
It is therefore an object of the present invention to provide a P-phase electric rotating machine having toroidal coils that solves the foregoing problems and using method thereof.
SUMMARY OF THE INVENTION
In order to achieve the above object, a P-phase electric rotating machine having toroidal coils of the present invention is constructed as follows.
According to a first aspect of the present invention, provided is a P-phase electric rotating machine comprising: a stator including the number P of stator units (P is integer satisfying P≧2) each of which is formed of a pair of stator iron cores made from magnetic material and a toroidal coil that concentrically gets caught between the pair of stator iron cores, each of the stator iron cores being provided with the number Ns of stator teeth formed around an inner circumference at equal pitch Ps, the pair of stator iron cores of the each stator unit being arranged such that the stat br teeth are shifted to each other by ½ of the pitch Ps, and the number P of stator units being concentrically connected to be arranged in a direction of a rotating shaft such that the stator teeth of the stator units are shifted to one another by ½ P of the pitch Ps; and a rotor that faces the stator with a predetermined air gap and is rotatable, the rotor consisting of at least one rotor unit that has a permanent magnet and rotor teeth of Nr in the total number made from magnetic material arranged around the permanent magnet in the rotating direction of the rotor, the rotor teeth consisting of k pair of N (north) and S (south) polar rotor teeth groups (k is integer satisfying k≧1) arranged in the rotating direction, the each N polar rotor teeth group consisting of the number (Nr/2k) if rotor teeth that are continuously arranged in the rotating direction, and the each S polar rotor teeth group consisting of the number (Nr/2k) of rotor teeth that are continuously arranged in the rotating direction.
According to a second aspect of the present invention, in the P-phase electric rotating machine according to the first aspect of the present invention, the rotor comprises the number P of independent rotor units that correspond to and face the stator units, respectively.
According to a third aspect of the present invention, in the P-phase electric rotating machine according to the second aspect of the present invention, the number P of stator units are arranged such that the stator teeth of the stator units are coincident with one another instead of shifting, and the number P of rotor units are arranged such that the rotor teeth of the rotor units are shifted to one another by &frac1
Japan Servo Co. Ltd.
Nguyen Tran
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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