Motor

Details Motor Motor

2000-03-28

2001-07-03

Nguyen, Tran (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S0400MM, C310S254100

Reexamination Certificate

active

06255749

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a motor formed in an ultra-compact shape.
2. Related Background Art
A motor formed as a compact motor is conventionally well known as, for example, a compact cylindrical step motor shown in
FIG. 7. A
stator
102
of the step motor is formed in such a manner that a stator coil
105
is coaxially wound around a bobbin
101
, the bobbin is stationarily sandwiched between two stator yokes
106
in the axial direction, stator teeth
106
a
and
106
b
are alternately placed on the stator yoke
106
in the circumferential direction of the bobbin along the inner surface thereof, and that the stator yoke
106
integrated to the stator tooth
106
a
or
106
b
is fixed to the case
103
.
A flange
115
and a bearing
108
are fixed to one of two cases
103
and another bearing is fixed to the other case. A rotor
109
is composed of a rotor magnet
111
fixed to a rotor shaft
110
. The rotor magnet is rotatably supported between two bearings
108
.
A mechanism has been proposed in which a leadscrew is formed on the rotor shaft
110
, and the leadscrew engages with a female thread (not shown) to move the female thread in the axial direction. The mechanism is used in, for example, an autofocus mechanism of a video camera.
However, since, in the above-mentioned conventional step motor, the case
3
, bobbin
101
, stator coil
105
, and the stator yoke
106
are coaxially placed on the outer periphery of the rotor, such a disadvantage that the outside dimension of motor becomes large arose. Further, since magnetic flux, which is generated by energization to the stator coil, is mainly passed through an end surface
106
a
1
of a stator tooth
106
a
and an end surface
106
b
1
of a stator tooth
106
b
as shown in
FIG. 8
, it does not effectively act on a rotor magnet
111
. Accordingly, the output of motor was not increased.
A motor that solved such problems is known in U.S. Pat. No. 5,831,356. The motor is formed in such a manner that a permanent magnet rotor divided into equal parts in the circumferential direction and alternately polarized into different poles is formed in a cylindrical shape, a first coil, the rotor and a second coil are placed in the axial direction of the rotor, a first outer magnetic pole and a first inner magnetic pole excited with the first coil are opposingly placed on the outer periphery and the inner periphery of the rotor, respectively, and a second outer magnetic pole and a second inner magnetic pole excited with the second coil are opposingly placed on the outer periphery and the inner periphery of the rotor, respectively. A rotary shaft that is a rotor shaft is extended from within the cylindrical permanent magnet.
Thus formed, the motor may have a high output and a small outside dimension. Nevertheless, if, by thinning the magnet in such configuration the distance between the first outer magnetic pole and the first inner magnetic pole and the distance between the second outer magnetic pole and the second inner magnetic pole are decreased, the magnetic resistance of a magnetic circuit, may be decreased. Accordingly, current which is passed through the first coil and the second coil enables the generation of increased magnetic flux in a reduced amount of current.
Further, when a conventional motor shown in
FIG. 7
is applied to such a mechanism that a leadscrew is formed in the output shaft, the leadscrew is allowed to engage with a female thread to move the female thread in the axial direction, pressurization of the output shaft or rotor shaft in the axial direction to bias the output shaft or the rotor shaft in the axial direction is needed so that a hysteresis difference is not generated. This pressurizing means is usually a plate-shaped spring and is placed on the rear end surface of the motor body. Therefore, a length the entire motor including the pressurizing means becomes longer and the compactness of motor is lost. Further, looseness between the rotor shaft and the bearing portion generates a larger working noise.
SUMMARY OF THE INVENTION
In consideration of the above-mentioned circumstances an object of the present invention is to provide a high power and ultra-compact motor formed by mounting a pressurizing means in the axial direction of the output shaft on an inner side of an inner yoke.
Another object of the present invention is to provide a pressurizing means in which a contact surface of the pressurizing means with the output shaft has a shape that enables generation of a smaller working noise.
Still another object of the present invention will become apparent from concrete examples described below.


REFERENCES:
patent: 3361947 (1968-01-01), Schlebusch
patent: 4806813 (1989-02-01), Sumi et al.
patent: 4958099 (1990-09-01), Chigira et al.
patent: 5384506 (1995-01-01), Aoshima
patent: 5486054 (1996-01-01), Nagata et al.
patent: 5831356 (1998-11-01), Aoshima
patent: 5886438 (1999-03-01), Kawanishi
patent: 5925945 (1999-07-01), Aoshima
patent: 5945753 (1999-08-01), Maegawa et al.
patent: 5969453 (1999-10-01), Aoshima
patent: 5973425 (1999-10-01), Aoshima
patent: 5977678 (1999-11-01), Miller et al.
patent: 6046517 (2000-04-01), Sasaki et al.

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