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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a linear stepping motor, especially for a
new-type secondary structure of a linear stepping motor and its
manufacturing method.
2. Description of the Prior Art
Linear stepping motors are applied in industry widely. For example, some
equipment such as a wafer clamper and a high-speed wafer scanner, is
equipped with linear stepping motors and act due to excitation between the
primary and secondary of linear stepping motors. Commonly used secondary
structure of the linear stepping motor is usually manufactured by milling
or etching teeth. Teeth milling and etching have the following
disadvantages, respectively:
1. Disadvantages of milling teeth
(1) It is uneasy to manufacture: For the sake of shortening the
displacement of each step to improve the resolution of the stepping
motors, tooth grooves are usually thin and deep so that the
special-purpose cutting tool is not easy to be manufactured and is
expensive in cost while short in life. Besides, processing rate is slow,
and process cost is high;
(2) It is uneasy to measure: After milling teeth, products are not easy to
be measured, so expensive apparatus are essential to examine and the
quality is not easy to be controlled;
(3) The weight is heavy: The whole solid block of metal is used to be
processed, so the product is heavy in weight;
(4) Eddy current: For the sake of using a whole metal block, which is a
good conductor, eddy current is produced, while the motor is excited, such
that energy is wasted;
(5) Restriction of length and area: The length and area of the secondary
structure of the motor are restricted by the working area of the
milling-machining frame.
2. Disadvantages of etching teeth:
(1) Process is complicate: Several steps such as washing, photograph
development and exposure, and etching, etc, are complicate. Besides, if
deeper etching depth is required, longer etching time and higher
manufacturing cost are caused;
(2) High pollution: Chemical reactant used for etching accompanies with
high pollution, therefore it easily results in environmental problems;
(3) The same situation of heavy weight, restricted area and producing eddy
current as in the aforementioned teeth milling occurs for the same reason,
using a whole metal block.
SUMMARY OF THE INVENTION
The purpose of the present invention is to provide a new-type secondary
structure of a linear stepping motor and its manufacturing method. By the
design of the present invention, the manufacture of the secondary
structure of a linear stepping motor is simpler and cheaper. Besides, both
weight and eddy current of the secondary of the linear stepping motor are
reduced. Quality control is easier and more efficient. The structure of
the new-type secondary structure of the linear stepping motor mainly
comprises several permeance sheets and insulating sheets arranged in
stagger one by one. The permeance sheets are made of permeance material,
which usually is (pure) iron or silicon steel, and so on. The insulating
sheets are made of material with poor permeance. Among many common
materials with poor permeance, ones still having characteristics of light
mass, good combination, sufficient strength and good machinability are
resin, glass and glass fiber compound material, carbon fiber compound
material. Especially glass fiber compound material, because it's
relatively cheaper in price and better in strength, it is a very ideal
material for insulating sheets.
After the permeance sheets and insulating sheets are shaped, and before
they are assembled, the secondary structure can be easily measured so that
the thickness of the aforementioned sheets can be got and the precision of
the tooth shape can be controlled. When the structure is manufactured, the
process just comprises arranging the permeance sheets and insulating
sheets in stagger one by one and then combining these sheets. Therefore,
the manufacture process is very simple. There are many methods of
combining the permeance sheets and insulating sheets, for example,
pressurizing and shaping, arranging regularly and locking via screws or
gluing, etc. For the surface of combined permeance sheets and insulating
sheets, colloid is filled into the clearance of the permeance teeth and
then the top surface of combined permeance sheets and insulating sheets
are ground to get a flat plane to make the slide between the primary and
the secondary structure more smooth.
Because the secondary structure of the linear stepping motor can be piled
successively, the restriction of length or area of milling or etching
teeth of traditional manufacturing methods can be overcome. Besides, the
use of the insulating sheets with specific gravity less than metal, the
total weight of secondary structure can be lowered to reduce the inertial
while the secondary structure serves as a rotor, the lighter weight or
smaller inertial yields larger acceleration. In addition, because of the
isolation effect of the insulating sheets, less eddy current is produced
so that efficiency of the motor is increased and temperature rise is
decreased.
BRIEF DESCRIPTION OF THE DRAWINGS
The drawings disclose an illustrative embodiment of the present invention
which serves to exemplify the various advantages and objects hereof, and
are as follows:
FIG. 1 is the diagram of the appearance of the present invention, the
secondary structure of a linear stepping motor;
FIG. 2 is the schematic diagram of the case of applying FIG. 1 in the
one-axis linear stepping motor;
FIG. 3 is the schematic diagram of the case of applying FIG. 1 in the
thin-plate-type linear stepping motor;
FIG. 4 is the schematic diagram showing the planar linear stepping motor
applying the present invention before the present invention is assembled;
and
FIG. 5 is the diagram of the appearance of that FIG. 4 is finished
assembling and gluing.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Please refer to FIG. 1, which is the diagram of the appearance of the
present invention, the secondary structure of a linear stepping motor, the
secondary structure 10 mainly comprises permeance sheets 11 (which can be
a silicon steel plate or thin iron plate structure) and insulating sheets
12 (which can be a glass fiber structure), and both permeance sheets 11
and insulating sheets 12 are thin sheets and arranged in stagger. The
manufacturing method of the secondary structure 10 is to first make the
permeance sheets 11, which are made of good permeance material such as
silicon steel or iron and shaped as a sheet in advance, and the insulating
sheets 12, which are made of poor permeance material such as glass fiber
and shaped as a sheet in advance, arranged in stagger, and secondly, to
shape the ordered sheets by using the jig to pressurize and then to glue,
and next, the surface is ground to be a flat plane such that the slide
between the new-type secondary structure and the primary of the linear
stepping motor provided from the present invention is smooth.
FIG. 2 is the schematic diagram of the case of applying FIG. 1 in the
one-axis linear stepping motor. The secondary structure of the linear
stepping motor 10 is arranged in pair with the primary structure 20. The
secondary structure of the linear stepping motor 10 comprises permeance
sheets 11 and insulating sheets 12. The primary structure 20 is composed
of an iron core 21, coils 22 and a permanent magnet 23. In addition to the
magnetic flux caused by permanent magnet 23, the varying current flowing
through coil 22 mounted on the iron coil 21 generates corresponding amount
of magnet flux in the primary structure 20. In the mean while, reluctance
is different according to the relative position of the primary structure
20 and the secondary one 10. The combined effect of these two mechanism
forms the electromagnetic force to move the linear stepping motor.
FIG. 3 is the schematic diagram of the application of the thin-plate-type
linear stepping motor. The linear stepping motor is similarly composed of
a secondary structure 10 arranged in pair with the primary structure 20.
The secondary structure of the linear stepping motor 10 comprises
permeance sheets 11 and insulating sheets 12. The primary structure 20 is
usually a mover while the secondary structure 10 is a stator. While the
secondary structure is used as a mover, the acceleration of the linear
stepping motor of the present invention is larger than that of the
traditional secondary structure, because the insulating sheets 12 of the
new-type secondary structure has a smaller specific gravity, i.e., the
inertia of the new-type secondary structure is smaller.
Furthermore, the present invention is mode in view of practicability, and
devised from the electromagnetism and mechanics, so except for the
one-axis linear motor shown in FIG. 2 and FIG. 3, the present invention
can be applied to dual-direction planar linear motor in practice. The
manufacturing method of the secondary structure of the planar linear motor
consists of two methods as follows:
1. Please refer to FIG. 4 and FIG. 5, first, the permeance sheets 41 and
insulating sheets 42 are manufactured and shaped first, especially that
permeance teeth 411 are set on the permeance sheets 41, and shaped by
finishing or punching such that the manufacturing method is relatively
simple. Besides, because the permeance sheets are in the sheet shape, the
thickness is easy to be measured and controlled. Because of the permeance
sheets 41 are in the sheet shape, the permeance teeth 411 can be measured
by projection method so that the shape is easier to be controlled, while
the teeth shape is hard to measure in traditional methods. After the
permeance sheets 41 and the insulating sheets 42 are combined together,
the colloid 43, such as epoxy resin, is filled into the clearance of the
permeance teeth 411, then the top surface is ground to a flat plane, as in
the secondary structure of the planar linear motor. The method is very
convenient in manufacturing, and has the effect of reducing the inertia of
the secondary structure of the linear stepping motor.
2. Please refer to the secondary structure of the linear stepping motor in
FIG. 1 again, the shape of the permeance teeth 411 in FIG. 5 is cut or
finished to the dash line 30 of the secondary structure of the linear
stepping motor in FIG. 1. The method similarly has the effect of reducing
the inertia of the secondary structure of the linear stepping motor
because the insulating sheets are made of material having specific gravity
smaller than metal.
The secondary structure of the linear stepping motor of the present
invention is made by arranging the permeance sheets and insulating sheets
in stagger and then pressurizing to shape. In this patent several
secondary structures can be combined. Similarly, so there will be no
restriction in length, width or volume, and the disadvantage of shaping a
whole metal block and being unable to lengthen the secondary. Also,
because the secondary structure is not manufactured from a whole metal
block, eddy current can be effectively reduced. In addition, the
manufacturing process is easy. In particular, arranging insulating sheets
with lighter weight among permeance sheets in stagger decreases the weight
of secondary structure. Summing up every advantage of the present
invention, no traditional technology can be compared with.
Many changes and modifications in the aforementioned embodiment of the
invention can, of course, be carried out without departing from the scope
thereof. Accordingly, to promote the progress in science and the useful
arts, the invention is disclosed and intended to be limited only by the
scope of the appended claims.
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