Electrical generator or motor structure – Dynamoelectric – Linear
Reexamination Certificate
2001-01-23
2004-08-17
Mullins, Burton S. (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Linear
Reexamination Certificate
active
06777832
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high-thrust linear motor in which armature coils and field magnets are arranged linearly to convert electrical energy supplied by the armature coils directly into linear kinetic energy with high thrust through the field magnets.
2. Discussion of Related Art
There is a linear motor that converts electrical energy directly into linear kinetic energy by utilizing repulsive or attractive magnetic force. This linear motor, for example, has a moving part consisting essentially of an armature winding formed from wound coils (electromagnets) and a stationary part having field magnets (permanent magnets) arranged along a guide. The moving part is caused to travel linearly along the guide serving as a stationary-side member by utilizing repulsive or attractive magnetic forces acting between the armature coils and the field magnets, thereby converting electrical energy into linear kinetic energy.
Linear motors arranged as stated above include two different types, i.e. coreless linear motors having no core in the armature winding, and cored linear motors having a core in the armature winding.
The coreless armature winding consists only of wound coils and therefore causes minimal variations in travel (cogging) of the moving part due to variations in magnetic reluctance that occur during the travel of the moving part. Further, the coreless armature winding is light in weight because it has no core. Therefore, the coreless armature winding is generally used in small-sized linear motors.
The cored armature winding can be arranged to provide thrust 2 to 3 times as high as that of coreless linear motors simply by inserting a core (magnetic member) into the hollow portion of an air-core armature winding, which has no core. Therefore, the cored armature winding is usually used in high-thrust linear motors.
There is a linear motor in which a large number of coils are wound in a plurality of slots formed in a core to form an armature winding, and the effective conductor portions of the armature coils are opposed to field magnets. It is known that this type of linear motor provides increased thrust because an increased number of coils can be wound in the slots.
In other words, it is known that high thrust can be obtained with a linear motor by adopting an arrangement in which: (1) a cored armature is used; (2) slots are formed in the core of the armature; and (3) a large number of coils are wound in the slots.
Next, a conventional cored linear motor having coils wound in slots will be described.
FIGS. 1 and 2
are a front view and a longitudinal sectional view, respectively, showing the arrangement of the cored linear motor. This cored linear motor is a three-phase linear motor and has a moving part
1
and a stationary part
2
as shown in FIG.
1
.
As shown in
FIG. 2
, the moving part
1
includes a core
1
a
and a table
1
b
secured to the upper surface of the core
1
a
. The moving part
1
further includes coils C
1
, C
2
and C
3
. The core
1
a
is formed with slots S. The coils C
1
, C
2
and C
3
are prewound coils and each inserted into two slots S separated by other slots S. The core
1
a
and the coils C
1
, C
2
and C
3
constitute an armature winding.
It should be noted that the reason why the prewound coils C
1
, C
2
and C
3
are inserted into the slots S is to facilitate the assembly. The coils C
1
, C
2
and C
3
are inserted in the following sequence. First, a U-phase coil C
1
, a W-phase coil C
2
and a V-phase coil C
3
are inserted into respective pairs of slots S in the order mentioned so as to lie adjacent to the innermost parts of the slots S. Thereafter, a V-phase coil C
3
is inserted into two slots S in such a manner as to be superimposed on the U-phase coil C
1
and the W-phase coil C
2
so that the V-phase coil C
3
is different in electrical angle from the phases inserted into the innermost parts of the slots S. Similarly, a U-phase coil C
1
is inserted into two slots S in such a manner as to be superimposed on the W-phase coil C
2
and the V-phase coil C
3
so that the U-phase coil C
1
is different in electrical angle from the phases inserted into the innermost parts of the slots S.
Meanwhile, the stationary part
2
is, as shown in
FIGS. 1 and 2
, formed from a yoke
2
a
and field magnets (permanent magnets)
2
b
. The yoke
2
a
and the field magnets
2
b
are disposed to extend linearly so as to face the moving part
1
.
When the coils C
1
, C
2
and C
3
are energized, electric currents flow in the directions of the arrows in
FIG. 3
, thus producing magnetic flux. Consequently, repulsive or attractive forces act between the coils C
1
, C
2
and C
3
and the field magnets
2
b
opposed thereto. Thus, thrust is generated in the leftward or rightward direction as viewed in
FIGS. 2 and 3
, causing the moving part
1
to move.
With the prior art, however, a problem arises when it is intended to achieve a reduction in size of a linear motor with a cored armature winding having the above-described conventional structure. That is, because it is impossible to obtain a large amount of winding of coils in comparison to the weight of the core, the cored armature winding is inferior in the level of attainable thrust to a coreless armature winding having the same weight. This has heretofore been an obstacle to achievement of a compact cored linear motor.
In addition, the conventional cored linear motor having the above-described structure suffers from the problem that the relative movement of the magnetic field is not smooth because of the manner of winding the coils. That is, after a U-phase coil C
1
and a W-phase coil C
2
have been inserted, a V-phase coil C
3
is inserted so as to lie over the area between the U-phase coil C
1
and the W-phase coil C
2
. Therefore, there are overlaps between the coils, and this prevents smooth relative movement of the magnetic field.
On the other hand, when prewound coils C
1
, C
2
and C
3
are inserted with a phase (electrical angle) displacement, as shown in
FIG. 2
, there is a blank space where no coil is wound in a slot S at each end of the core
1
a
, and the amount of winding of coils on the core
1
a
is correspondingly reduced. Accordingly, a desired high thrust cannot be obtained.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a high-thrust linear motor in which the amount of winding of coils can be increased in comparison to the weight of the core to obtain increased thrust and the linear motion of the moving part is favorably smooth.
Another object of the present invention is to provide a method of producing a high-thrust linear motor that allows coils to be wound in such a manner that there is no blank space where no coil is wound in a slot at each end of the core.
To attain the above-described objects, the present invention provides a high-thrust linear motor including a magnetic member having a plurality of slots formed in series in an axial direction thereof. The slots extend from both sides of the magnetic member in opposite directions intersecting the axial direction in corresponding relation to each other. Coils are wound in respective pairs of slots on both sides of the magnetic member. Field magnets extend in the axial direction at both sides of the magnetic member so as to face an effective conductor portion (a portion contributing to the generation of thrust) of each of the coils. Each field magnet has a plurality of pairs of magnetic poles magnetized in the axial direction.
With the above-described arrangement, because the coils can be wound over both sides of the magnetic member through the slots formed on both sides of the magnetic member, the space efficiency (density) of the coils is increased, so that it is possible to obtain higher thrust than in the case of the conventional cored linear motor. Accordingly, it becomes possible to attain a compact cored linear motor.
The high-thrust linear motor according to the present invention has the above-described matters as essential constituent
Jones Judson H.
Mullins Burton S.
THK Co. Ltd.
Westerman Hattori Daniels & Adrian LLP
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