Efficient cylindrical linear motor

Details Efficient cylindrical linear motor Efficient cylindrical linear motor

2001-06-27

2003-12-02

Ramirez, Nestor (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Linear

C310S014000

Reexamination Certificate

active

06657326

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a movable magnet type linear motor with the purpose of improving motor efficiency and of simplifying the manufacture of the motor.
BACKGROUND OF THE INVENTION
In recent years, fervent efforts have been made on the development of linear motor.
Japanese Patent Application 10-118358 describes a conventional type linear motor.
Description will be given below on the conventional type linear motor as described above referring to the drawings.
FIG. 14
is a cross-sectional plan view of a conventional type linear motor, and
FIG. 15
is a cross-sectional view along the line A—A in FIG.
14
.
An inner yoke
1
is designed in form of quadratic prism by laminating a multiple of thin plates
2
, each of which is in approximately rectangular shape and has high magnetic permeability. An outer yoke
3
is designed in form of quadratic prism by laminating a multiple of thin plates
4
, each of which is in approximately rectangular shape and has high magnetic permeability. Slots
6
and
7
are cut out in axial direction
5
, and three magnetic poles
8
,
9
and
10
are formed. The surface of the outer yoke
3
having the magnetic poles
8
,
9
and
10
is directed toward the inner yoke
1
and a yoke block
12
is formed with a given gap
11
between them. A set of yoke blocks is retained on a base
13
so that the inner yokes are arranged at positions opposite to each other with a given spacing.
Coils
14
are wound around the central magnetic pole
9
so that different magnetic poles are alternately formed at three magnetic poles
8
,
9
and
10
of outer yoke
3
. The coils
14
are independently wound on two outer yokes
3
, and the coils
14
are connected in parallel.
A movable unit
15
comprises a pair of planar permanent magnets
16
and
17
magnetized in opposed directions of the inner yoke
1
and the outer yoke
3
, a permanent magnet holder
18
, and a shaft
19
. The permanent magnets
16
and
17
are fixed by a permanent magnet holder
18
with a given spacing in axial direction so that directions of magnetization are opposite to each other, and these magnets are disposed in the gap
11
between the inner yoke
1
and the outer yoke
3
.
Description will be given now on operation of the linear motor with the above arrangement.
A magnetic flux generated from the permanent magnet
16
passes through the gap
11
, the inner yoke
1
, the gap
11
, the permanent magnet
17
, the outer yoke
3
, and the gap
11
and returns to the permanent magnet
16
, and a static magnetic field is generated in the gap
11
. In the inner yoke
1
and the outer yoke
3
, the magnetic flux circulates in the planes of the thin plates
2
and
4
.
When AC current is supplied to the coil
14
, different magnetic poles are alternately generated in axial direction at the magnetic poles
8
,
9
, and
10
. By magnetically attracting and repelling action of the permanent magnets
16
and
17
of the movable unit
15
, thrust force is generated, which is proportional to the magnitude of electric current flowing through the coil
14
and to magnetic flux density of the permanent magnets
16
and
17
. Then, the shaft
19
is reciprocally moved together with the movable unit
15
in synchronization with the frequency of AC current.
The conventional arrangement as described above is advantageous in that the inner yoke
1
and the outer yoke
3
can be manufactured in easier manner. However, planar permanent magnets
16
and
17
are arranged in parallel in the gap
11
between the inner yoke
1
and the outer yoke
3
each designed in form of quadratic prism. When the shaft
19
is disposed at axially rotated position during manufacture, balance is lost in the distance between the permanent magnets
16
and
17
and the inner yoke
1
or the distance between the permanent magnets
16
and
17
and the outer yoke
3
. This leads to instability of the thrust force of the linear motor.
BRIEF DESCRIPTION OF THE INVENTION
To solve the above problems of the conventional example, it is an object of the present invention to provide a linear motor, in which the thrust force of the linear motor is not turned to unstable even when the shaft
19
is disposed at axially rotated position during manufacture and motor efficiency can be improved and yokes can be manufactured in easier manner.
Also, when the permanent magnets
16
and
17
are disposed at deviated positions closer to the inner yoke
1
or to the outer yoke
3
during manufacture, balance is lost in the distance between the permanent magnets
16
and
17
and the inner yoke
1
or in the distance between the permanent magnets
16
and
17
and the other yoke
3
. Thus, the force to directly attract the permanent magnets
16
and
17
toward the inner yoke
1
or the outer yoke
3
is increased. As a result, sliding loss is increased on the bearings
20
via the movable unit
15
and the shaft
19
.
It is another object of the present invention to provide a linear motor, in which, even when permanent magnets are disposed at deviated positions closer to the inner yoke or the outer yoke during manufacture, the force to directly attract the permanent magnets toward the inner yoke or the outer yoke is not increased, and the motor efficiency is improved, and the yokes can be manufactured in easier manner.
To solve these problems, the linear motor according to the present invention comprises a movable unit in cylindrical shape and having the central axis at the intersection of X-axis and Y-axis, an inner yoke arranged on inner side of the movable unit with a given spacing in radial direction of the movable unit and being formed by laminating a multiple of thin plates each in approximately rectangular shape and having high magnetic permeability arranged in parallel to one of X-axis or Y-axis, an outer yoke arranged on outer side of the movable unit with a given spacing in radial direction of the movable unit and being formed by laminating a multiple of thin plates each in approximately rectangular shape and having high magnetic permeability arranged in the same direction as the thin plates of the inner yoke, and a pair of permanent magnets magnetized in a direction to connect the inner yoke with the outer yoke and mounted on the movable unit to be retained in a gap between the inner yoke and the outer yoke.
As a result, even when the shaft is disposed at axially rotated position during the manufacture, the thrust force of the linear motor is not turned to unstable. Iron loss of the inner yoke and the outer yoke is reduced. Motor efficiency is improved, and this facilitates the manufacture of the linear motor.
Also, the present invention provides the linear motor as described above, wherein a pair of permanent magnets magnetized in radial direction around the central axis are arranged with a given spacing in parallel to the central axis so that directions of magnetization are opposite to each other, and the magnets being retained in a gap between the inner yoke and the outer yoke.
With such an arrangement, even when the permanent magnets are disposed at deviated positions closer to the inner yoke or the outer yoke, the force to directly attract the permanent magnets toward the inner yoke or the outer yoke is not increased.
Further, the present invention provides the linear motor as described above, wherein the inner yoke is formed by laminating a multiple of thin plates of the same shape and the same dimension, and the outer yoke is formed by laminating a multiple of thin plates of the same shape and the same dimension.
As a result, it is possible to manufacture the linear motor in easier manner.
Also, the present invention provides the linear motor as described above, wherein radius of curvature of inner periphery of the outer yoke is equal to radius of curvature of inner periphery of the slot, and radius of curvature of outer periphery of the outer yoke is equal to radius of curvature of outer periphery of the slot, and radius of curvature of outer periphery of the outer yoke or the slot is greater than the

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