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What is claimed is:
1. A stage device having a moving part on which an object is loaded, and a stationary part, wherein:
a pole unit is included in one of the moving part and the stationary part, the pole unit having a plurality of magnets in which same poles of adjacent ones of the magnets are opposed and a plurality of yokes are interposed between the plurality
of magnets; and
a thrust generator is included in the other of the moving part and the stationary part, the thrust generator having a plurality of armature coils opposed to and spaced from the pole unit and a magnetic core that anchors the plurality of armature
coils.
2. The stage device of claim 1, wherein the plurality of magnets are aligned in one direction with a specified pitch P, and the yokes are aligned with the specified pitch P; and
the plurality of armature coils are relatively shifted by 1/n of the pitch P, n being an integer of at least 2 or more, and are arranged on the magnetic cores.
3. The stage device of claim 1, wherein the armature coils have hollow centers.
4. The stage device of claim 1, wherein the plurality of magnets are a plurality of permanent magnets.
5. An exposure device that exposes a pattern image on a mask onto a substrate, comprising the stage device of claim 1 for loading the substrate.
6. The stage device of claim 1, wherein the moving part is moved by a Lorentz force.
7. An electromagnetic motor comprising:
a pole unit having a plurality of magnets in which same poles of adjacent ones of the magnets are opposed and are aligned in X and Y directions with a specified pitch P, the X and Y directions being orthogonal, and a plurality of yokes interposed
in the X and Y directions between the plurality of magnets; and
a thrust generator having a plurality of armature coils opposed to and spaced from the pole unit, and surrounded by a space equal to the pitch P, and a magnetic core that anchors the plurality of armature coils in the X and Y directions.
8. The electromagnetic motor of claim 7, wherein the plurality of magnets are arranged so that a magnetic axis of each magnet is inclined at approximately 45.degree. with respect to the X and Y directions.
9. The electromagnetic motor of claim 7, wherein a non-magnetic, non-conductive member is interposed in an area that is surrounded by the plurality of yokes.
10. The electromagnetic motor of claim 7, further comprising second magnets provided on back surfaces of the plurality of yokes opposite a surface of the yokes that oppose the armature coil, the second magnets having magnetic axes extending in a
Z direction, which is orthogonal to the X and Y directions, with the poles facing the yokes that are magnetized by the first magnets.
11. The electromagnetic motor of claim 7, wherein the thrust generator has a plurality of the armature coils for X direction driving arranged so as to be relatively shifted by 1/n, n being an integer of 2 or more, of the pitch P in the X
direction, and a plurality of the armature coils for Y direction driving arranged so as to be relatively shifted by 1/n of the pitch P in the Y direction.
12. The electromagnetic motor of claim 11, wherein the armature coils for the X direction driving and the armature coils for the Y direction driving cross each other and are arranged in an X-Y plane.
13. The electromagnetic motor of claim 12, wherein the armature coils have hollow centers.
14. The electromagnetic motor of claim 7, wherein the plurality of magnets are a plurality of permanent magnets.
15. A stage device having a moving part on which an object is loaded, and a stationary part, wherein the pole unit of claim 7 is included in one of the moving part and the stationary part, and the thrust generator of claim 7 is included in the
other of the moving part and the stationary part.
16. An exposure device that exposes a pattern image on a mask onto a substrate, comprising the stage device of claim 15 loading the substrate.
17. The electromagnetic motor of claim 7, wherein the electromagnetic motor generates a Lorentz force.
18. An electromagnetic motor comprising:
a pole unit having a plurality of pairs of magnets, each pair of magnets having a first magnet and a second magnet, the first magnet having poles that are opposed to same poles of the second magnet, the poles of each pair of magnets being opposed
to same poles of the adjacent pair of magnets, the pairs of magnets being aligned in X and Y directions with a pitch P, the X and Y directions being orthogonal, and a plurality of yokes that are interposed in the X and Y directions between the plurality
of pairs of magnets; and
a thrust generator having a plurality of armature coils opposed in parallel to and spaced from the pole unit, and surrounded by a space equal to the pitch P, and a magnetic core that anchors the plurality of armature coils in the X and Y
directions.
19. The electromagnetic motor of claim 18, wherein the first and second magnets are permanent magnets.
20. The electromagnetic motor of claim 18, wherein the electromagnetic motor generates a Lorentz force.
21. A method of making a stage device that incorporates an electromagnetic motor made by forming a pole unit by providing a plurality of magnets in which same poles of adjacent magnets are opposed, and interposing a plurality of yokes between
the plurality of magnets; and spacing a thrust generator from the pole unit, the thrust generator having a plurality of armature coils opposed to and spaced from the pole unit and a magnetic core that anchors the plurality of armature coils, the method
including the steps of:
providing a moving part on which an object is loaded; and
providing a stationary part;
wherein the pole unit is included in one of the moving part and the stationary part, and the thrust generator is included in the other of the moving part and the stationary part.
22. The method of claim 21, further comprising aligning the plurality of magnets in one direction with a specified pitch P, and aligning the yokes with the specified pitch P; and
relatively shifting the plurality of armature coils by 1/n of the pitch P, n being an integer of at least 2 or more, and arranging the plurality of armature coils on the magnetic cores.
23. The method of claim 21, wherein the electromagnetic motor generates a Lorentz force.
24. A method of making an exposure device that exposes a pattern image on a mask onto a substrate, the exposure device including a stage device for loading the substrate, the stage device incorporating an electromagnetic motor made by forming a
pole unit by providing a plurality of magnets in which same poles of adjacent magnets are opposed, and interposing a plurality of yokes between the plurality of magnets; and spacing a thrust generator from the pole unit, the thrust generator having a
plurality of armature coils opposed to and spaced from the pole unit and a magnetic core that anchors the plurality of armature coils, the method including the steps of:
providing a projection system that projects the pattern image on the mask onto the substrate;
providing a moving part on which the substrate is loaded; and
providing a stationary part;
wherein the pole unit is included in one of the moving part and the stationary part, and the thrust generator is included in the other of the moving part and the stationary part.
25. The method of claim 24, wherein the electromagnetic motor generates a Lorentz force.
26. A method of making an electromagnetic motor comprising:
forming a pole unit by providing a plurality of magnets in which same poles of adjacent ones of the magnets are opposed and are aligned in X and Y directions with a specified pitch P, the X and Y directions being orthogonal, and interposing a
plurality of yokes between the plurality of magnets in the X and Y directions; and
spacing a thrust generator having a plurality of armature coils opposed to and spaced from the pole unit, and surrounded by a space equal to the pitch P, and a magnetic core that anchors the plurality of armature coils in the X and Y directions.
27. The method of claim 26, further comprising arranging the plurality of magnets so that a magnetic axis of each magnet is inclined at approximately 45.degree. with respect to the X and Y directions.
28. The method of claim 26, further comprising interposing a non-magnetic, non-conductive member in an area that is surrounded by the plurality of yokes.
29. The method of claim 26, further comprising providing second magnets on back surfaces of the plurality of yokes opposite a surface of the yokes that oppose the armature coil, the second magnets having magnetic axes extending in a Z direction,
which is orthogonal to the X and Y directions, with the poles facing the yokes that are magnetized by the first magnets.
30. The method of claim 26, wherein the thrust generator has a plurality of the armature coils for X direction driving arranged so as to be relatively shifted by 1/n, n being an integer of 2 or more, of the pitch P in the X direction, and a
plurality of the armature coils for Y direction driving arranged so as to be relatively shifted by 1/n of the pitch P in the Y direction.
31. The method of claim 20, wherein the armature coils for the X direction driving and the armature coils for the Y direction driving cross each other and are arranged in an X-Y plane.
32. The method of claim 26, wherein the electromagnetic motor generates a Lorentz force.
33. A method of making an electromagnetic motor comprising:
forming a pole unit by providing a plurality of pairs of magnets, each pair of magnets having a first magnet and a second magnet, opposing poles of the first magnet to same poles of the second magnet, opposing the poles of each pair of magnets to
same poles of the adjacent pair of magnets, aligning the pairs of magnets in X and Y directions with a pitch P, the X and Y directions being orthogonal, and interposing a plurality of yokes in the X and Y directions between the plurality of pairs of
magnets; and
providing a thrust generator having a plurality of armature coils opposed in parallel to and spaced from the pole unit, and surrounded by a space equal to the pitch P, and a magnetic core that anchors the plurality of armature coils in the X and
Y directions.
34. The method of claim 33, wherein the electromagnetic motor generates a Lorentz force. |
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Claims |
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Description |
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INCORPORATION BY REFERENCE
The disclosures of the following priority applications are herein incorporated by reference: Japanese Patent Application No. 9-278171, filed Sep. 25, 1997; and Japanese Patent Application No. 10-229739, filed Aug. 14, 1998.
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an electromagnetic motor that generates thrust from a magnetic flux using Lorenz's forces generated by flowing current in a coil. In particular, this electromagnetic motor is especially suitable for use with a
stage used in an Electron Beam (EB) exposure device or in a projection exposure device used to manufacture, for example, integrated circuits (ICs), liquid crystal displays (LCDs) and other thin film devices.
2. Description of Related Art
A conventional linear type electromagnetic force motor is explained referring FIGS. 9A and 9B. FIG. 9A is a plan view of a linear type electromagnetic motor. FIG. 9B is a cross sectional view of FIG. 9A, which is cut along the line B--B. The
electromagnetic motor is schematically composed of a pole unit 400 and a thrust generating unit 300. The pole unit 400 is composed of, for example, low carbon steel as a magnetic member and a rectangular parallelepiped shaped yoke 208 that extends in
the X direction in the figure. A plurality of permanent magnets 204 and 210 that are alternately aligned (i.e., the N and S poles of adjacent magnets are alternately arranged) with a predetermined pitch P in the X direction are provided on the +Y
direction side surface of the yoke 208. The permanent magnets 204 and 210 have magnetic axes that approximately match in the Y direction. The S poles of the permanent magnets 204 are polarized on the surface facing in the +Y direction, and the N poles
are polarized on the surface facing in the -Y direction. On the other hand, the N poles of the permanent magnets 210 are polarized on the surface facing in the +Y direction, and the S poles are polarized on the surface facing in the -Y direction.
Additionally, both magnetic pole ends of each of the permanent magnets 204 and 210 have a width of P/2 in the X direction.
The thrust generating unit 300 sandwiches the pole unit 400 from the +Y direction and the -Y direction, and has two cores 200 and 216 that are composed of, for example, low carbon steel as a magnetic member. An armature coil 202, which opposes
the end surfaces of the plurality of permanent magnets 204 and 210 with a specified spacing, is provided on the +Y direction surface side of the yoke 208. The armature coil 202 has an opening in the X-Z surface (i.e, the surface contained in the XZ
plane), and the coil is wound so that the aforementioned opening extends in the Y direction. The two surfaces of the armature coil 202 that are opposed to the permanent magnets 204 and 210 have a width of P/2 in the X direction, respectively, and have a
longer width than the length of the permanent magnets 204 and 210 in the Z direction as shown in FIG. 9B. Additionally, the distance between centers of the two surfaces of the armature coil 202 equals the pitch P in the X direction.
Regarding the yoke 208 of the pole unit 400 and the core 216 that opposes it from the -Y direction, an armature coil 214 is provided on core 216 and is opposed to the end surfaces of a plurality of permanent magnets 206 and 212 that are provided
on the -Y direction side surface of the yoke 208 with a predetermined spacing therebetween. The armature coil 214 has an opening in its X-Z surface, and the coil is wound so that the aforementioned opening extends in the Y direction. The two surfaces
of the armature coil 214 that are opposed to the end surfaces of the permanent magnets 206 and 212 have a width of P/2 in the X direction, and have a longer width than the length of the permanent magnets 206 and 212 in the Z direction. Additionally, the
distance between the centers of these two surfaces is equal to the length of the pitch P in the X direction.
A specified current is supplied from a power device, which is not shown in the figure, to the armature coils 202 and 214. Additionally, the pole unit 400 is supported so as to be movable in the X direction relative to the thrust generating unit
300 by a supporting mechanism, which is not shown in the figure.
In the electromagnetic motor having the above-mentioned structure, when the thrust generating unit 300 and the pole unit 400 are in the relative position shown in FIGS. 9A and 9B, a magnetic flux loop 218 of one cycle is formed as shown in the
figure. The magnetic flux of this magnetic flux loop 218, for example, starting at the permanent magnet 204, comprises a closed magnetic path that goes through the yoke 208 of the magnetic body, the permanent magnet 206, passes through the surface of
the armature coil 214 that extends in the Z direction, goes through the magnetic core 216 and passes through the other side surface of the armature coil 214 that extends in the Z direction, reaches the permanent magnet 212, passes through the yoke 208
and the permanent magnet 210, passes through a surface of the armature coil 202 that extends in the Z direction, passes through the magnetic core 200, and passes through the other side surface of the armature coil 202 that extends to the Z direction, and
returns to the permanent magnet 204.
The current flows in the direction shown in FIG. 9A with respect to the armature coils 202 and 214 from a power device, not shown in the figure. In FIG. 9A, the ".cndot." symbol indicates that the current flows outward from the paper surface,
and the "x" symbol indicates that current flows into the paper surface. Hereafter, the ".cndot." and "x" directions are called the axis directions of the coil.
As shown in the figure, by supplying current in the Z direction through the armature coils 202 and 214, a Lorentz's force is generated in the X direction in accordance with Fleming's left hand rule in the areas where magnetic flux passes out of
the armature coils 202 and 214 and into the permanent magnets 204, 206, 210 and 212. When the thrust generating unit 300 is anchored at a specified position, the pole unit 400, which is movably held in the X direction by a supporting member (not shown
in the figure) shifts in the +X direction by using the reaction of the Lorentz's force. By doing this, an electromagnetic motor can be structured with the thrust generating unit 300 as the stationary part and the pole unit 400 as the moving part.
Further, a planar motor can be structured by developing this linear type electromagnetic motor in two-dimensions.
However, with the conventional electromagnetic motor explained above, the following problems occur.
(1) Problems with high thrust force and high efficiency
The permanent magnet surfaces of the magnets 204, 206, 210 and 212 that are used in the conventional electromagnetic motor are directly arranged so that magnetic flux passes parallel to the winding axes of the armature coils 202 and 214 of the
thrust generating unit 300, as is clear from FIG. 9A. Accordingly, in order to improve the thrust, a permanent magnet having a high energy must be used, and accordingly the magnetic path cross-sectional area of the magnetic circuit has to be enlarged.
However, with this method, there are problems in that the total cost of the permanent magnet is large and the efficiency becomes poor since the weight of the pole unit 400 when it is used as the moving part becomes large.
(2) Problems of preventing the failure of the magnets
In the conventional electromagnetic motor, there are problems in that the
permanent magnets 204, 206, 210 and 212 are arranged in order to have a magnetic axis (magnetic direction) parallel to the winding axes of the armature coils 202 and 214. In this case, the magnetic field produced by excitation of the armature
coils 202 and 214 (due to the corkscrew rule) also operates as a demagnetization field with respect to the permanent magnets 204, 206, 210 and 212. Therefore, the permanent magnets 204, 206, 210 and 212 become demagnetized or degaussed. Another problem
is that the magnet surface burns due to the eddy currents generated in the permanent magnets 204, 206, 210 and 212.
(3) Problems of high thrust density
In a planar electromagnetic motor in which the conventional linear electromagnetic motor is two dimensionally developed, there are problems in that a large surface area is necessary since armature coils must be separately provided for the coil
for X axis driving and the coil for Y axis driving. These drive coils for each axis are anchored and arranged on independent areas on the thrust generating unit, and the driving force per unit has to be small.
Another problem is that since the X axis driving force and the Y axis driving force operate in different positions, unnecessary rotation force is generated in the moving part, the control of which becomes difficult.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the technical problems of the above-mentioned conventional electromagnetic motor. Thus, it is an object of the present invention to provide an electromagnetic motor that can achieve high thrust and
high efficiency by generating high magnetic flux density without making the permanent magnets large.
Another object of the present invention is to avoid causing a demagnetization field to the permanent magnets by the armature coil, and to provide an electromagnetic motor that prevents the burning of the permanent magnets.
Another object of the present invention is to make the driving force per area unit large, and to provide a planar electromagnetic motor that does not cause unnecessary rotating force to be applied to the moving part.
According to one embodiment of the present invention, the above-mentioned objects are achieved by providing an electromagnetic motor having a pole unit that has a plurality of magnets (e.g., permanent magnets) in which same poles of adjacent
magnets oppose each other and are aligned in one direction with a specified pitch P, and a plurality of yokes that are interposed between the plurality of magnets and aligned in one direction having the pitch P. A thrust generating unit has a plurality
of armature coils opposed to the pole unit via a predetermined space, and surrounded by a space equal to the pitch P, and a magnetic core that anchors the plurality of armature coils so as to align the plurality of armature coils in one direction.
Preferably, the plurality of armature coils are relatively shifted by 1/n (n is an integer of 2 or more) of the pitch P, and are arranged on the cores. Additionally, the armature coils can have hollow centers.
According to another embodiment, an electromagnetic motor has a pole unit having a plurality of magnets (e.g., permanent magnets) in which same poles of adjacent magnets oppose each other and are aligned in X and Y directions with a specified
pitch P, and a plurality of yokes interposed between the plurality of magnets in the X and Y directions. A thrust generating unit has a plurality of armature coils are that opposed to the pole unit in parallel via a specified space, and are surrounded
by a space equal to the pitch P, and a magnetic core that anchors the plurality of armature coils in the X and Y directions.
In this electromagnetic motor, the plurality of magnets are arranged such that a direction of each magnetic axis is inclined by approximately 45.degree. with respect to the X and Y directions. Additionally, a non-magnetic, non-conductive member
preferably is interposed in an area that is surrounded by the plurality of yokes. Additionally, on a back surface of the plurality of yokes, opposite the surface that opposes the armature coils, magnets are provided with their magnetic axis in the Z
direction, with same poles facing the poles of the yokes that are magnetized by the magnets. Additionally, the thrust generating unit can have a plurality of the armature coils for X driving that are arranged relatively shifted by 1/n (n is an integer
of 2 and more) of the pitch P in the X direction and, a plurality of the armature coils for Y driving that are arranged relatively shifted by 1/n (n is an integer of 2 and more) of the pitch P in the Y direction. Additionally, the armature coils can
have hollow centers.
According to another embodiment, an electromagnetic motor has a pole unit having a plurality of pairs of magnets, each pair of magnets having a first magnet and a second magnet, the first magnet having poles that are opposed to same poles of the
second magnets, the poles of each pair of magnets being opposed to same poles of an adjacent pair, the pairs of magnets being aligned in X and Y orthogonal directions with a pitch P. The pole unit also has a plurality of yokes interposed between the
plurality of pairs of magnets in the X and Y directions. A thrust generating unit has a plurality of armature coils opposed in parallel with the pole unit via a specified space, and surrounded by a space equal to the pitch P, and a magnetic core that
anchors the plurality of armature coils in the X and Y directions.
According to the present invention, the conventional technical problems can be solved by the following effects.
(1) Problems of high thrust and high efficiency
Since the permanent magnets are arranged so that the magnetic polarization directions are opposed, front and rear and left and right on the X-Y plane, and the magnetic yoke that comprises the magnetic circuit is arranged therebetween, a high
magnetic flux can be generated in the magnetic circuit structured between the pole unit and the thrust generating unit.
At this time, the magnetizing direction of the permanent magnet of a planar motor is inclined with respect to each of the X-axis and the Y-axis of the X-Y plane. For example, they are polarized in a direction of 45.degree.. By doing this, since
the yokes adjacent at the front, rear, left and right of the permanent magnets are each magnetized so as to have poles, the magnetic flux of the magnets can be effectively used for generating electromagnetic force.
(2) Problems of preventing magnet failure
Since permanent magnets that have a magnetic direction are arranged at a right angle with respect to the axis of the armature coil, and since magnetic yokes are arranged between the permanent magnets and the magnetic circuit that supply the
magnetic flux from the yokes to the armature coil, the demagnetizing field from the armature coil does not directly affect the permanent magnets. Additionally, burning of the permanent magnets can be prevented.
(3) Problems of high thrust density
Since each X driving coil and each Y driving coil are alternately arranged, the driving force per unit surface area can be improved. Additionally, since the X driving force and the Y driving force function at the same point, rotating force does
not occur, and it is easy to control.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in conjunction with the following drawings in which like reference numerals designate like elements and wherein:
FIGS. 1A and 1B show the schematic structure of a linear type electromagnetic motor of a first embodiment of the present invention;
FIGS. 2A-2D show the operation of a planar motor that is the basic form of electromagnetic motor of a second embodiment of the present invention;
FIGS. 3A and 3B show a schematic structure of the planar electromagnetic motor of the second embodiment of the present invention;
FIGS. 4A and 4B show a structure of the moving part of the planar electromagnetic motor of the second embodiment of the present invention;
FIGS. 5A-5C show the generation of a magnetic flux loop in the planar electromagnetic motor of the second embodiment of the present invention;
FIGS. 6A and 6B show the operation of the planar electromagnetic motor of the second embodiment of the present invention;
FIGS. 7A-7C show another structure of a planar electromagnetic motor of the second embodiment of the present invention;
FIG. 8 shows the structure in which the planar electromagnetic motor of the second embodiment of the present invention is adopted in an exposure device; and
FIGS. 9A-9B show a conventional linear type electromagnetic motor.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
An electromagnetic motor according to a first embodiment of the present invention is explained referring to FIGS. 1A and 1B. FIG. 1A shows the schematic structure of the electromagnetic motor of the first embodiment. The electromagnetic motor
of the first embodiment is a linear motor in which a movable body shifts in one axial direction.
FIG. 1A is a plan view of the linear type electromagnetic motor of the present embodiment. FIG. 1B is a cross section cut along line B--B. The electromagnetic motor is schematically composed of the pole unit 2 and the thrust generating unit
(thrust generator) 4. The pole unit 2 has a plurality of permanent magnets 10 that are aligned at a specified pitch P in the X direction, and with the poles aligned in the X direction so that same poles of adjacent magnets oppose each other. A
plurality of yokes 12 made of magnetic bodies of, for example, low carbon steel are interposed between the plurality of permanent magnets 10, and aligned at the pitch P in the X direction. The width in the X direction of the permanent magnets 10 and
yokes 12 is P/2. The entire pole unit 2 has a rectangular shape, which is elongated in the X direction. Additionally, for the permanent magnets 10 of the first embodiment, material such as, for example, Neomax42 (made by Sumitomo Special Metal
Industries), which has a residual magnetic flux density Br=1.33 [T], and relative permeability .mu.=1.0667, Hc=947000 [A/m] can be used.
The thrust generating unit 4 has two cores 6 and 16 that sandwich the pole unit 2 from the +Y direction and the -Y direction and are made of a magnetic body, for example, a low carbon steel magnet. An armature coil 8, which is opposed to the
pole unit 2 via a specified space in the +Y direction, is provided on the core 6, which is opposed to the pole unit 2 from the +Y direction. The armature coil 8 is hollow and has an opening in its X-Z surface, and the coil is wound so that the
aforementioned opening extends in the Y direction. The two surfaces of the armature coil 8 that oppose the side surface of the pole unit 2 have widths of P/2 in the X direction, and have a longer width in the Z direction than the length of the pole unit
2 as shown in FIG. 1B. Additionally, the distance between the centers of these two surfaces is equal to the pitch P in the X direction.
The armature coil 14 that opposes from the -Y direction of the pole unit 2 via a specified space is provided on the core 16 that opposes pole unit 2 from the -Y direction. The armature coil 14 is hollow and has an opening in its X-Z surface, and
the coil is wound so that the aforementioned opening extends in the -Y direction. The two surfaces of the armature coil 14 that oppose the side surface of the pole unit 2 have a width of P/2 in the X direction, and have a longer width in the Z direction
than the length of the pole unit 2 as shown in FIG. 1B.
These armature coils 8 and 14 have a winding wire diameter d of the coil=0.5 [mm]. The current value I supplied to the coil=1.0 [A], and for the current density, with 49 as the number of coils in the cross section d1.times.d2, shown in FIG. 1A,
=4.times.4 (mm.sup.2) of the coil in the X-Y plane, the current density .alpha.=(49.times.1.0)/(4.times.4)=3.06 [A/mm.sup.2 ]=3.06.times.10.sup.6 [A/m.sup.2 ].
A specified current from a power device (not shown) is supplied to the armature coils 8 and 14. Additionally, the pole unit 2 is supported by a support mechanism, which is not shown in the figure, so as to be movable in the X direction relative
to the thrust generating unit 4.
In the linear type electromagnetic motor of the first embodiment, when the thrust generating unit 4 and the pole unit 2 are in the relative position shown in FIG. 1A, two magnetic flux loops 22 and 24 (shown in the figure) are formed. The
magnetic flux of the magnetic flux loop 22 forms a closed magnetic circuit that passes from the pole of the permanent magnet 10 positioned at the center of FIG. 1A, and of which the N pole faces the -X direction and the S pole faces the +X direction,
goes through the yoke 12 which contacts the aforementioned N pole (the left side of the aforementioned permanent magnet 10 in FIG. 1A), passes from the +Y direction side surface of the yoke 12 through one coil, among the coils of the armature coil 8,
that extends in the Z direction, goes through the magnetic core 6 and through another coil, among the coils of the armature coil 8, that extends in the Z direction, and reaches the S pole of the aforementioned permanent magnet 10 via the yoke 12 at the
right of the aforementioned permanent magnet 10.
Additionally, the magnetic flux of the other magnetic flux loop 24 forms a closed magnetic circuit that passes from the N pole of the permanent magnet 10 that is positioned in the center of FIG. 1A, and of which the N pole faces the -X direction
and the S pole faces the +X direction, goes through the yoke 12 that contacts the aforementioned N pole (the left side of the aforementioned permanent magnet 10 in FIG. 1A), passes from the -Y direction side surface of the yoke 12 through one coil among
the coils of the coil 14, that extends in the Z direction, goes through the magnetic core 16 and through another coil among the coils of armature coil 14 that extends in the Z direction, and reaches the S pole of the aforementioned permanent magnet 10
via the yoke 12 at the right of the aforementioned permanent magnet 10.
At this time, the current flows in the direction shown in FIG. 1A to the armature coils 8 and 14 from the power device, which is not shown in the figure. In FIG. 1A, a ".cndot." symbol indicates that the current flows in a direction out of the
paper surface, and an "x" symbol indicates that current flows in a direction into the paper surface.
By supplying current to the armature coils 8 and 14, a Lorentz's force is generated in the +X direction in accordance with Fleming's left hand rule due to the magnetic flux that passes out of the surfaces of the armature coils 8 and 14 and the
magnetic flux of the permanent magnets 10. When the thrust generating unit 4 is anchored at a specified position, the pole unit 2 which is mounted to move in the X direction by a supporting member (not shown) shifts in the +X direction as a reaction to
the Lorentz's force. When the direction of the current that flows to the armature coils 8 and 14 is reversed, it is possible to reverse the direction of movement of the pole unit 2. Thus, the electromagnetic motor is structured with the thrust
generating unit 4 as the stationary part and the pole unit 2 as the moving part. Further, the thrust generating unit 4 can function as the moving part, and the pole unit 2 can function as the stationary part by fixedly mounting the pole unit 2 and
movably mounting the generating unit 4.
Additionally, in the electromagnetic motor of the first embodiment, if a plurality of the armature coils 8 and 14 are arranged relatively shifted by 1/n (n is an integer of 2 or above) of the pitch P, the electromagnetic motor can be realized in
which irregularities in the thrust are decreased. In other words, smooth movement is possible.
Here, if the magnetic flux density Bg of the magnetic flux that passes through the areas of the armature coils 8 and 14 in which the current flows in the Z direction in the condition of FIG. 1A is obtained by simulation, Bg=0.223-0.591 [T], and
the average magnetic flux density Bga=0.407 [T]. Additionally, when the current value I that flows in the armature coils 8 and 14 is I=1.0 [A], and when the length of the armature coil in the magnetic flux is the length a=0.03 [m] of the coil of the Z
direction shown in FIG. 1B, 1=49 [coils].times.0.03 [m].times.4 [places]. Accordingly, the thrust (Lorentz's force) F generated by the electromagnetic motor of the present embodiment becomes F=Bga.times.I.times.1=0.407 [T].times.1.0 [A].times.49
[coils].times.0.03
[m].times.4 [places]=2.39 [N].
The generated thrust obtained for a conventional electromagnetic motor explained using FIGS. 9A-B is now used as a comparative example. First of all, the magnetic flux density Bg of the magnetic flux that passes through the areas among the
armature coils 202 and 214 in the condition of FIG. 9A, in which the current flows in the Z direction is obtained by simulation, Bg=0.03297-0.32417 [T], and the average magnetic flux density Bga=0.1786 [T]. When other conditions are the same as used
above for the electromagnetic motor of the first embodiment, the thrust (Lorentz's force) F which is generated becomes F=Bga.times.I.times.1=0.1786 [T].times.1.0 [A].times.49 [coils].times.0.03 [m].times.4 [places]=1.05 [N].
As stated above, with the electromagnetic motor of the first embodiment, an improved thrust of 2.3 times better than a conventional electromagnetic motor can be obtained.
According to the first embodiment, since the pole unit 2 is composed of a plurality of permanent magnets 10 with same poles of adjacent magnets opposed to each other and aligned at a specified pitch P in the X direction with their poles aligned
in the X direction, and a plurality of yokes 12 that are composed of a magnetic body that are interposed between the plurality of permanent magnets 10 and are aligned at the pitch P in the X direction, a high magnetic flux density can be generated in a
magnetic circuit composed by the pole unit 2 and the magnetic body of the thrust generating unit 4, and a high thrust and the high efficiency are achieved.
Additionally, according to the electromagnetic motor of the first embodiment, since there are no poles of the permanent magnets 10 that are close to the armature coils 8 and 14, the electromagnetic motor does not receive the influence of the
magnetic field generated in the armature coils 8 and 14. In other words, the magnetic fields generated in the armature coils 8 and 14 only pass therethrough, and burning of the permanent magnets 10 can be prevented.
Next, an electromagnetic motor of a second embodiment of the present invention is explained by using FIGS. 2A-D and 6A-B. The electromagnetic motor of the second embodiment is a planar type motor that is movable in two axial (perpendicular)
directions. The planar motor that is the basic form of the electromagnetic motor of the second embodiment is explained. FIG. 2A is a perspective plan diagram in which a part of the planar motor is viewed through the back side. FIG. 2B is a cross
section diagram cut along the line B--B of FIG. 2A. As shown, the main structural elements of this planar motor are the thrust generating unit 28, which is as the fixed element, and the pole unit 40, which is the movable element.
The pole unit 40 has magnetic yokes 48, a plurality of permanent magnets 46 interposed between a plurality of the magnetic yokes 48 and having same poles of adjacent magnets opposed to each other, and a flat magnetic yoke 44 that anchors the
magnetic yokes 48 and the permanent magnets 46 to each other. The permanent magnets 46 are alternately arranged being shifted by the pitch P in a plane, and the width of each is P/2. Additionally, the magnetic axes of the magnets 46 are facing in the X
direction, and are arranged so that the poles of the magnetic yokes 48 become N poles and S poles.
The main structural elements of the thrust generating unit 28 are a plurality of armature coil 36a, 36b, . . . , and the like, and a flat magnetic core 38 that anchors a plurality of the armature coils 36a, 36b . . . to each other. On one
surface of the core 38, the armature coils 36a, 36b . . . that oppose the end surfaces of the permanent magnets 46 of the pole unit 40 are anchored. Each armature coil 36a, 36b . . . is hollow and has an opening in its X-Y surface. The coils are
wound so that the aforementioned opening extends in the Z direction. The openings of the armature coils 36a, 36b . . . have a rectangular (in this case square) shape that has a width of P/2 in both the X and Y directions. The coil which is wound
around the opening has a width of P/2 in the X-Y plane. Accordingly, the distance between the centers of adjacent coils is 3P/2, and they are arranged to be relatively shifted by P/2 in the X and Y directions.
The pole unit 40 is supported so as to be two dimensionally movable in the X-Y plane with respect to the thrust generating unit 28 by a support mechanism (for example, an air bearing or the like), which is not shown in the figure, via a specified
space.
The operation of the planar motor having the above structure is now explained. FIG. 2A shows the direction of the current that flows in the armature coil of the thrust generating unit 28 and the direction in which the magnetic flux operates.
Additionally, FIGS. 2A and 2B show the generation of a thrust by a Lorentz's force based on Fleming's left hand rule. As shown in FIGS. 2A and 2B, magnetic yokes 48 are positioned on the area of coils that faces the Y direction of the armature coil 36a,
36b . . . , and magnetic flux from the magnetic yokes 48 has the magnetic flux density B, and passes through the coils that face the Y direction of the armature coil 36a. When a specified current I flows clockwise in the figure from the power device,
which is not shown in the figure, and to the armature coil 36a, a Lorentz's force is generated which tries to shift the coils that are aligned in the Y direction of the armature coil 36a to the left direction (-X direction) in the figure.
The thrust generating unit 28 is anchored in a specified position, and the pole unit 40, which is movably supported by the support mechanism (by an air bearing or the like), shifts in the +X direction by reacting to the Lorentz's force. When the
direction of the current that flows in the armature coil 36a is reversed, it is possible to reverse the direction of movement of the pole unit 40. Thus, an electromagnetic motor is structured with the thrust generating unit 28 as the stationary part,
and the pole unit 40 as the moving part. Further, the pole unit 40 can function as the stationary part and the thrust generating unit 28 can function as the movable part by fixedly mounting the pole unit 40 and movably mounting the thrust generating
unit 28.
Next, the fact that the thrust is smoothed by using the armature coil 36b in addition to the armature coil 36a is explained referring to FIGS. 2C and 2D. FIG. 2C shows the characteristics of the current that flows in the armature coil 36a and
the thrust that is generated. Additionally, FIG. 2D shows the characteristics of the current that flows in the armature coil 36b and the thrust that is generated. As explained by using FIGS. 2A and 2B, since the armature coil 36a and the armature coil
36b are arranged so as to be relatively shifted by P/2, in the condition in which the permanent magnets 46 of the pole unit 40 are opposed on (or over) the armature coil 36b, the magnetic flux that passes through the coils of the armature coil 36b is
virtually non-existent, and the armature coil 36b does not contribute to the thrust generation. However, when the pole unit 40 starts shifting with the thrust generated by the armature coil 36a, and the magnetic yoke 48 is shifted, the magnetic flux
that passes through the coil in the Y direction of the armature coil 36a is gradually decreased, and the thrust obtained from the armature coil 36a is gradually decreased. Meanwhile, the magnetic yoke 48 becomes closer to the position opposed to the
armature coil 36b along with the shifting of the pole unit 40, and the magnetic flux that passes through the coil in the Y direction of the armature coil 36b increases. Therefore, when a specified current is supplied to the armature coil 36b at a
specified energizing schedule, a thrust can be generated by the armature coil 36b. The armature coil 36b is in the position shifted by P/2 with respect to the armature coil 36a, and the thrust characteristic becomes as shown in FIGS. 2C and 2D. An
overall smooth thrust characteristic can be obtained by driving to compose the waveforms of FIGS. 2C and 2D.
FIG. 3A is a perspective plan view in which the entire electromagnetic motor is viewed through the back surface. FIG. 3B is a cross sectional view along line B--B of FIG. 3A. As shown, the main structural elements of the planar electromagnetic
motor of the present embodiment are the thrust generating unit 42, which is the stationary part, and the pole unit 40, which is the movable body. The pole unit 40 is composed of a plurality of the permanent magnets 46 that have cubical shapes, yokes 48
made of a plurality of magnetic bodies and a flat non-magnetic, non-conductive member 44 that aligns and fixes a plurality of non-magnetic, non-conductive members 50 in a matrix shape in the X-Y plane. The detailed structure of the pole unit 40 is later
explained referring to FIGS. 4A and 4B.
The main structural elements of the thrust generating unit 42 are a plurality of armature coils 52 and 54 and a flat core 62 which is made of a magnetic body that anchors the plurality of the armature coils 52 and 54. On one surface of the core
62, a plurality of the armature coils 52 and 54 are affixed opposing the flat end surface formed by the permanent magnets 46 the yoke 48 and the non-magnetic, non-conductive members 50. The armature coils 52 and 54 are hollow and have openings in the
X-Y plane, and the coils are wound so that the aforementioned openings extend in the Z direction.
The openings of the armature coils 52 have a rectangular shape having a width of P/2 in the X direction, and 5P/2 in the Y direction. The coils that are wound around the opening have a width of P/2 in the X-Y direction. Additionally, on the
core 62, the armature coils 52 and 54 are crossed in the X-Y plane and arranged forming the units 60a and 60b as best seen in FIG. 3A. The armature coils 52 are used as the armature coils for X direction driving, and the armature coils 54 are used as
the armature coils for the Y direction driving. Additionally, the units 60a and the units 60b of the adjacent armature coils 52 and 54 are arranged so as to be relatively shifted by P/2 in each of the X and Y directions.
The pole unit 40 is supported by a supporting mechanism, which is not shown in the figure, so as to be two dimensionally movable in the X-Y plane relative to the thrust generating unit 42, via a specified space.
Next, the structure of the pole unit 40 is explained in detail referring to FIGS. 4A and 4B. FIG. 4A is a plan view of the pole unit 40, and FIG. 4B is a cross-sectional view along line B--B of FIG. 4A. The pole unit 40 has pluralities of four
differently oriented cube-shaped permanent magnets 46a, 46b, 46c and 46d, same poles of adjacent magnets being opposed to each other. The permanent magnets are provided at a specified pitch P in the X-Y direction, the poles being parallel to the
aforementioned X-Y plane. A plurality of the permanent magnets 46a, 46b, 46c and 46d are arranged so that the directions of the magnetic axes are inclined with respect to the X and Y directions. The inclination amount in the present embodiment is
45.degree. with respect to each of the X and Y axes. A plurality of the permanent magnets 46a, 46b, 46c | | |
