Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-01-28
2001-07-10
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S06800R, C310S162000, C310S257000
Reexamination Certificate
active
06259176
ABSTRACT:
BACKGROUND OF TIE INVENTION
1. Field of the invention
The present invention relates to a multi-phase outer-type permanent magnet PM stepping motor suitable for OA apparatus such as a printer, a high-speed facsimile equipment, a copying machine for normal paper, etc.
2. Description of the Related Art
Description will be made about a related-art outer-type PM stepping motor with reference to
FIGS. 18A and 18B
and FIG.
19
.
FIG. 18A
is a vertically sectional side view illustrating a configuration of a single-phase outer-type PM stepping motor
20
which is a first related-art example, and
FIG. 18B
is a partially cutaway perspective view of the same.
As shown in
FIGS. 18A and 18B
, this single-phase outer-type PM stepping motor
20
of the first related-art example is provided with a rotor
21
and a stator
23
, and the rotor
21
has N (north) and S (south) magnetic poles formed alternately circumferentially on the inner circumferenitial surface.
Further, the stator
23
is disposed so that the outer circumferential surface of the stator
23
is opposite to the magnetic poles formed on the inner circumferential surface of the rotor
21
at a distance, and comb-like magnetic poles are formed in the stator
23
.
In
FIGS. 18A and 18E
, the reference numeral
22
represents a rotating shaft;
24
, a stator coil;
26
, a motor mounting plate; and
27
, a bearing.
FIG. 19
is a longitudinally sectional side view of a two-phase outer-type PM stepping motor
30
which is a second related-art example.
As shown in
FIG. 19
, this outer-type PM stepping motor
30
is also provided with a rotor
31
and a stator
33
, and the stator
33
is constituted by first and second stator portions
33
a
and
33
b
stacked one on another in the axial direction.
In
FIG. 19
, the reference numeral
32
represents a rotating shaft;
34
, a stator coil;
36
, a motor mounting plate; and
37
, a bearing.
The single-phase outer-type PM stepping motor of the first related-art example as mentioned above had only one stator. Therefore, in order to determine the rotating direction of the motor, magnetic permeance or phase between the pole teeth of the stator and the magnetic poles of the rotor was shifted, or a mechanical method was used. Accordingly, the related-art single-phase PM stepping motor was unsuitable for equipments while required high-speed rotation or high torque.
On tile other hand, according to the two-phase outer-type PM stepping motor of the second related-art example which was developed to solve these problems, torque and speed have been improved greatly, but the two-phase outer-type PM stepping motor has problems as follows.
(1) The number of lead wires for coils is large (i.e. at least four lead wires ), and it is necessary to use at least eight transistors in a driving circuit.
(2) A torque ripple is so large that vibration is large.
(3) When the step angle is made small, a large number of magnetic poles must be formed, causing a problem on machining.
(4) It is difficult to obtain high torque with a fine step angle.
It is an object of the present invention to provide a multi-pilase outer-type PM stepping motor in which tile foregoing problems can be solved.
SUMMARY OF THE INVENTION
In order to achieve the above object, according to a first aspect of the present invention, provided is a multi-phase outer-type PM stepping motor comprising: a rotor constituted by a cylindrical permanent magnet in which N (north) and S (south) poles are magnetized alternately on an inner circumferential surface of the rotor; stator cores respectively having pole teeth disposed in opposition to the N or S poles of the rotor through a predetermined gap; and excitation coils wound in the stator cores for magnetizing the stator cores to thereby rotate tile rotor; wherein when a number of the stator cores is 3 and a magnetization pitch of the permanent magnet is P, the pole teeth of the stator cores are arranged so that tile pole teeth of one stator core are shifted by an angle of 2P/3 from the pole teeth of an adjacent stator core.
According to a second aspect of the present invention, in tile above multi-phase outer-type PM stepping motor, three stator coils wound on the three stator cores respectively are connected to have three terminals, and two or three of the three stator coils are bipolar-driven simultaneously by a driving circuit constituted by six transistors.
According to a third aspect of tile present invention, in the above multi-phase outer-type PM stepping motor, three stator coils wound on the three stator cores respectively are connected to have six terminals, and two or three of the three stator coils are bipolar-driven simultaneously by a driving circuit constituted by twelve transistors.
According to a fourth aspect of the present invention, provided is a multi-phase outer-type PM stepping motor comprising: a rotor constituted by a cylindrical permanent magnet in which N (north) and S (south) poles are magnetized alternately on an inner circumferential surface of the rotor; stator cores respectively having pole teeth disposed in opposition to tile N or S poles of the rotor through a predetermined gap; and excitation coils wound in the stator cores for magnetizing the stator cores to thereby rotate the rotor; wherein when a number of the stator cores is n (n is an odd number not smaller than 3) and a magnetization pitch of the permanent magnet is P, the pole teeth of the stator cores are arranged so that the pole teeth of one stator core are shifted by an angle of 2P
from the pole teeth of another stator core.
According to a fifth aspect of the present invention, provided is a multi-phase outer-type PM stepping motor comprising: three pairs of rotors and stators, each pair including a rotor constituted by a cylindrical permanent magnet in which N (north) and S (south) poles are magnetized alternately on an inner circumferential surface of the rotor, a stator core having pole teeth disposed in opposition to tile N or S poles of the rotor through a predetermined gap, and an excitation coil wound on the stator core for magnetizing the stator core to thereby rotate the rotor; wherein the three stator cores are stacked one on another in a three-ganged state at the same pitch, while a rotors are arranged in a manner so that, when the magnetization pitch of the permanent magnet is P, magnetic poles of a second rotor are shifted by 2P/3 from magnetic poles of a first rotor, and magnetic poles of a third rotor are shifted by 2P/3 from magnetic poles of the second rotor in the same manner.
According to a sixth aspect of the present invention, in the above multi-phase outer-type PM stepping motor, three stator coils wound on tile three stator cores respectively are connected to have three terminals, and two or three of the three stator coils are bipolar-driven simultaneously by a driving circuit constituted by six transistors.
According to a seventh aspect of tile present invention, in the above multi-phase outer-type PM stepping motor, three stator coils wound on the three stator cores respectively are connected to have six terminals, and two or three of tile three stator coils are bipolar-driven simultaneously by a driving circuit constituted by twelve transistors.
According to a eighth aspect of the present invention, provided is a multi-phase outer-type PM stepping motor comprising: n pairs of rotors and stators, each pair including a rotor constituted by a cylindrical permanent magnet in which N (north) and S (south) poles are magnetized alternately on an inner circumferential surface of the rotor, a stator core having pole teeth disposed in opposition to the N or S poles of the rotor through a predetermined gap, and an excitation coil wound on the stator core for magnetizing the stator core to thereby rotate the rotor; wherein the n stator cores are stacked one on another in n-ganged state at the same pitch, while the rotors are arranged in a manner so that, when a magnetization pitch of tile permanent magnet is P, magnetic poles of a second rotor are shifted by 2P
from magnetic poles of
Isozaki Kouki
Rokunohe Junji
Sato Naotugu
Shimura Ayako
Tsuda Yuuichi
Japan Servo Co., LTD
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Perez Guillermo
Ramirez Nestor
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