Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-12-28
2001-03-27
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S254100
Reexamination Certificate
active
06208047
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of Invention
The present invention relates to a motor structured such that magnetization of the rotor thereof and layout of polar teeth of the stator thereof are devised to realize a high speed and large torque, and more particularly to a motor for use as a stepping motor.
2. Relate Art
Stepping motors are widely used in a variety of industrial fields. The stepping motor must realize high speed and large torque. To realize the high speed and large torque, efficient exertion of the magnetic flux generated in the polar teeth on the magnet in the rotor so as to raise the efficiency of use of the magnet is an important factor.
FIG. 14
shows the structure of a conventional stepping motor which is schematically constituted by a rotor
2
having a rotational shaft
1
; and a stator portion
3
disposed to surround the rotor
2
. The rotor
2
is constituted by a cylindrical boss
4
and a cylindrical magnet
5
disposed around the boss
4
.
The stator portion
3
incorporates cores
6
a
and
6
b
disposed to form two stages and arranged t serve as stator members; coils
7
a
and
7
b
wound around the cores
6
a
and
6
b
and arranged to serve as wound coils; and stator caps
8
a
and
8
b
which are stator members also serving as caps. The opposite surfaces of the cores
6
a
and
6
b
and the magnet
5
of the stator caps
8
a
and
8
b
are provided with polar teeth T
11
, T
12
, . . . , T
21
, T
22
, . . . , (refer to
FIG. 15
or
16
).
The rotor
2
and the stator portion
3
are held by a joining plate
9
and an upper cover
10
joined to the two ends (in the vertical direction in
FIG. 14
) of the rotor
2
. The joining plate
9
and the upper cover
10
are provide with bearings
11
a
and
11
b
. The foregoing rotational shaft
1
is rotatively supported by the bearings
11
a
and
11
b
. A disc spring
12
is sandwiched between the rotor
2
and the bearing
11
a
, while a washer
13
is sandwiched between the rotor
2
and the bearing
11
b.
FIG. 15
is a cross section l view taken along line indicated with arrows X—X shown in FIG.
1
and arranged to show the layout of polar teeth provided for the cores
6
a
and
6
b
of the stator portion
3
and the stator caps
8
a
and
8
b
. As can be understood from
FIG. 15
, the polar teeth T
11
and T
13
of the polar teeth T
11
, T
12
, T
13
and T
14
are provided for the core
6
a
of the stator portion
3
. The polar teeth T
12
and T
14
are provided for the stator cap
8
a
. That is, the polar teeth T
11
, T
12
, T
13
and T
14
are alternately provided for the core
6
a
and the stator cap
8
a
. Also the core
6
b
and the stator cap
8
b
are similarly structured.
FIG. 16
is a cross sectional view taken along a line indicated with arrows Y—Y shown in FIG.
14
. The relationship among the polar teeth of the core
6
b
and the stator cap
8
b
and the magnetized segments of the magnet
5
is schematically shown.
As shown in
FIG. 16
, the palar teeth T
21
, T
22
, T
23
, T
24
, . . . , are disposed apart from the outer surface of the magnet
5
for a predetermined distance to form a line such that the polar teeth are mutually engaged to one another in the circumferential direction of the magnet
5
. As described above, the polar teeth T
22
and T
24
are provided for the core (the core
6
b
in the foregoing case) and the polar teeth
21
a d T
23
are provided for the stator cap (the stator cap
8
b
in the foregoing case). That is, the polar teeth are alternately provided for the core
6
b
and the stator cap
8
b.
The foregoing polar teeth T
21
, T
22
, T
23
, T
24
, . . . , are magnetized in such a way that the adjacent polar teeth are magnetized to opposite polarities. For example, the polar tooth T
21
is magnetized to the south pole, the polar tooth T
22
is magnetized to the north pole, the polar tooth T
23
is magnetized to the south pole and the polar tooth T
24
is magnetized to the north pole. Thus, the magnet
5
is brought to a state in which attraction and repulsion forces are exerted on the magnetized segments of the surfaces opposite to the polar teeth T
21
, T
22
, T
23
, T
24
, . . . , so that the rotor
2
is rotated.
The conventional stepping motor having the above-mentioned structure, however, encounters a problem in that the efficiency of using the magnetic flux gene rated in the stator portion
3
is unsatisfactory. That is, as shown in
FIG. 17
, flows of the magnetic flux generated by the polar teeth T
21
, T
22
, T
23
, T
24
, . . . , include magnetic flux Hi which is exerted on the magnet
5
and a multiplicity of leaked magnetic flux portions, such as magnetic flux H
2
which flows along the reverse surface of the polar teeth T
21
, T
22
, T
23
, . . . , and magnetic flux H
3
which flows in between adjacent polar teeth.
Therefore, only a portion of the magnetic flux which is exerted on the magnet
5
is used. That is, the effective magnetic flux which is exerted on the magnet
5
to rotate the rotor
2
is only the magnetic flux H
1
in a case of the structure shown in FIG.
17
. The other flux is wasted. Therefore, only the magnetic flux Hi which is exerted on the mag et
5
is used as the output of the motor. As a result, a satisfactory efficiency cannot be realized.
The conventional structure incorporates the polar teeth T
11
, T
12
, . . . , T
21
, T
22
, . . . , arranged in a line such that the adjacent polar teeth have different polarities. Therefore, gap Gi (see
FIG. 15
) must be formed between polar teeth. Therefore, design of the polar teeth is considerably limited. The foregoing fact will now be described with reference to FIG.
15
. Each of the polar teeth T
11
, T
12
, . . . , T
21
, T
22
, . . . , has the trapezoidal shape. Both of the width W
1
of the leading end of the trapezoid and the width W
2
of the base of the same must be not larger than magnetizing pitch of the magnet
5
. Moreover, gap G
1
between the polar teeth having a size similar to the thickness (L
1
) of each of the stator caps
8
a
and
8
b
must be provided. To meet the foregoing requirements, the size, shape and the arrangement of the polar teeth are inevitably limited. Therefore, design of the stepping motor is considerably limited.
SUMMARY OF INVENTION
An object of the present invention is to provide a motor which is capable of efficiently exerting magnetic flux generated in the stator portion to the magnet of the rotor, therefore, realizing high speed and high torque and considerably relaxing limits of the shape and arrangement of the polar teeth to permit freedom to be given when the motor is designed.
According to an aspect of the present invention, there is provided a motor comprising: a rotor containing a cylindrical magnet having segments magnetized at predetermined pitches in a circumferential direction thereof, each of said magnetized segments being magnetized such that the inner portion and the outer portion are magnetized to different polarities and said magnetized segments disposed at adjacent pitches are magnetized to opposite polarities; and
a stator for imparting a rotating magnetic field to said magnet so as to rotate said rotor, said stator containing a first polar tooth row and a second polar tooth row each of which is constituted by polar teeth corresponding to the predetermined pitches of said magnetized segments such that said polar teeth disposed opposite to said magnetized segments across said magnet are magnetized to different polarities, and the polarities of said first polar tooth row and said second polar tooth row being switched so that a rotating magnetic field is imparted to said cylindrical magnet.
As described above, the claimed motor has the structure that the first polar tooth row and the second polar tooth row are disposed in the circumferential direction on the inside and outside of the magnet across the magnet. The opposite polar teeth of the first polar tooth row and the second polar tooth row are magnetized to different polarities. Moreover, the inside and outside of the magnet are magnetized to different polarities. Therefo
Agematsu Ikuo
Matsumoto Katsumi
Ogawa Yoshinori
Wakai Kiyoshi
Yumita Yukinobu
Kabushiki Kaisha Sanyo Seiki Seisakusho
Nguyen Tran
Sughrue Mion Zinn Macpeak & Seas, PLLC
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