JP3668940B2 - Linear motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is used for a linear motor that relatively moves a coil and a permanent magnet that are energized with a coil by using Lorentz force, particularly for precise positioning of various precision processing machines, semiconductor exposure apparatuses, and the like. It relates to linear motors.
[0002]
[Prior art]
In order to perform precise positioning in a conventional linear motor, it is necessary to measure the movement amount and movement position of the linear motor with high accuracy. Many of the measuring devices are affected by temperature. Joule heat is generated by passing an electric current through a coil in a linear motor, and the measurement of the position and movement amount of the linear motor may be affected based on this heat generation. From this point, the coil is accommodated in a jacket, and a gas or liquid refrigerant is allowed to flow into and out of the jacket to cool the coil. At this time, in order to increase the cooling effect, it is necessary to increase the pressure of the refrigerant in the jacket. On the other hand, in order to operate the linear motor with a small and relatively strong propulsive force, that is, to operate efficiently, it is better to bring the permanent magnet and the coil as close as possible. From such a point, a linear motor in which a reinforcing member is provided in a jacket is proposed in Japanese Patent Laid-Open No. 10-309071.
[0003]
The proposed linear motor will be described with reference to FIG. A coil 12 wound in a substantially rectangular shape is accommodated in a thin rectangular parallelepiped jacket 11. The jacket 11 includes a rectangular frame-like portion 11A and sheet-like portions 11B and 11C that close open surfaces on both sides thereof. The coil 12 is attached to the frame-shaped portion 11A by a support portion 13 while maintaining a distance from the inner peripheral surface of the jacket, and a reinforcing member that connects the opposing portions of the jacket 11 in the substantially central portion of the air core portion 14 of the coil 12. 15 is fixed. Although not shown in the drawing, an inflow port through which the refrigerant flows into the jacket 11 and an exhaust port through which the refrigerant is discharged from the jacket 11 are provided.
[0004]
Permanent magnets 16 and 17 are arranged in close proximity to and opposite to the outer surfaces of the sheet-like portions 11B and 11C of the jacket 11, and the surfaces of the permanent magnets opposite to the jacket 11 are connected by a magnetic yoke 18. The magnetic flux between the permanent magnets 16 and 17 passes substantially at right angles to the coil 12, and the magnetic flux is directed in the opposite direction at the opposite portion of the coil 12. Therefore, Lorentz force acts between the magnetic flux of the permanent magnet and the current flowing through the coil 12, and the permanent magnets 16 and 17 and the coil 12 move relatively in a direction parallel to the surface of the sheet-like portion of the jacket.
According to this configuration, the sheet-like portions 11B and 11C are hardly deformed due to the presence of the reinforcing member 15 and can be made thin, and the permanent magnets 16 and 17 and the coil 12 can be brought closer to each other. Therefore, a small and efficient linear motor can be obtained.
[0005]
[Problems to be solved by the invention]
In this conventional linear motor, since the relative movement direction of the coil and the permanent magnet is a plane parallel to the sheet-like portion of the jacket, there is a problem that the shape in the movement direction becomes large.
[0006]
[Means for Solving the Problems]
According to the present invention, an annular coil having at least two linear portions that are substantially parallel to each other is accommodated in a jacket configured to wrap the entire circumferential surface substantially along the annular coil. Permanent magnets are disposed on both the inner and outer peripheral walls of the jacket so as to sandwich both linear portions of the coil, and each pair of permanent magnets is connected to a magnetic yoke on the outer side of the jacket.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
As shown in the center of FIG. 1, the coil 21 has a racetrack shape in this example, and is an annular coil having two substantially parallel linear portions 21A and 21B. The linear portions 21A and 21B are provided side by side. The jacket 22 that accommodates the coil 21 is shaped so as to wrap the coil 21 substantially along the entire circumferential surface of the coil 21. That is, the jacket 22 has an outer wall portion 22A having a shape along the outer peripheral surface of the coil 21, an inner wall portion 22B having a shape along the inner peripheral surface of the coil 21, and one open surface between the outer wall portion 22A and the inner wall portion 22B. A plate ring-shaped portion 22C for closing and a plate ring-shaped portion 22D for closing the other open surface are provided. In this example, an outer wall portion 22A, an inner wall portion 22B, and a plate ring-shaped portion 22D are integrally formed to form a coil housing portion 23, which is covered with a plate ring-shaped portion 22C while the coil 21 is housed therein. The When the coil holding portion 24 is integrally formed inside the jacket 22, a step portion 24B is formed on the plate ring-shaped portion 22D side of the inner wall portion 22B, and the step is connected to the step portion to form a plate ring-shaped portion 22D. A portion 24A is formed, and the coil 21 is held by the step portions 24A and 24B. In this case, the coil 21 is in contact with the stepped portion 24A in a larger area than the contact with the stepped portion 24B. The distance between the facing surfaces of the coil 21 and the inner peripheral surface of the jacket is selected to be substantially the same depending on the height of the stepped portions 24A and 24B. In addition, when the plate ring-shaped portion 22C is covered, a part of the contact portions 25A and 25B is inserted and brought into contact between the outer wall portions 22A and 22B, and the contact portions 25A and 25B are sufficiently firmly fixed. Is selected. This connection and fixing is performed by an adhesive or screwing. The jacket 22 is preferably a non-magnetic material, for example, a polymer resin material such as PEEK or a ceramic material. An inlet 26 and an outlet 27 are formed in, for example, the outer wall portion 22A of the jacket 22, and the refrigerant is supplied into the jacket through the inlet 26, and the refrigerant is discharged from the outlet through the coil in the jacket. It is made like that.
[0008]
Permanent magnets 31, 32, 33, 34 are arranged outside the jacket 22 so as to be sandwiched between the linear portions 21A, 21B of the coil 21, respectively. These permanent magnets 31 to 34 have, for example, a strip shape, and are in close proximity to the outer wall portion and inner wall portion of the jacket so as to sandwich the linear portions 21A and 21B of the coil. Each permanent magnet is magnetized in the thickness direction so that the linear portions 21A and 21B are sandwiched with different polarities, and the directions of magnetic fluxes formed in the linear portions are opposite to each other. . Permanent magnets 31 and 32 and 33 and 34 are connected to a magnetic yoke, respectively. In this example, these magnetic yokes are made common, that is, a rectangular yoke portion 35A is provided facing one plate ring-shaped portion 22C of the jacket 22, and strip-shaped yoke portions 35B and 35C are connected to both ends of the yoke portion 35A. Permanent magnets 31 and 34 are fixed to each other on the inner surfaces of the strip-shaped yoke portions 35B and 35C. Further, in the middle of the yoke portions 35B and 35C of the yoke portion 35A, the central yoke portion 35D is erected integrally with the yoke portions 35B and 35C, and the permanent magnets 32 and 33 are in contact with both sides of the central yoke portion 35D. Fixed. A magnetic yoke 35 is configured by the yoke portions 35A to 35D. In this example, a concave portion 36 is formed on the surface of the yoke portion 35A facing the jacket 22 so that the relative movement between the permanent magnet and the coil can be increased, and a portion of the jacket 22 can enter the concave portion 36. Yes.
[0009]
A jacket holding portion 37 is provided in contact with the other plate ring-shaped portion 22D of the jacket 22, and the jacket 22 is held thereby.
In this configuration, when a current is passed through the coil 21, a Lorentz force is applied by the current, the magnetic flux generated between the permanent magnets 31 and 32, and the magnetic flux generated between 33 and 34, and the coil 21 and the permanent magnets 31 to 34 are connected to each other. It moves relatively in the direction parallel to the axis. Even if the outer wall portions 22A and 22B of the jacket 22 are made thin, they are fixed to the plate ring-like portions 22C and 22D at positions relatively close to the coil, so that they may be deformed even if the refrigerant pressure is increased. In addition, the distance between the permanent magnet and the coil can be made closer, the cooling efficiency can be increased, the thrust can be increased, and the size can be reduced. Moreover, in this case, the relative movement direction of the coil 21 and the permanent magnet is parallel to the axis of the coil, so that the linear motor dimension in this direction is considerably smaller than the conventional one shown in FIG. Can do. Further, the permanent magnets 32 and 33 and a part 35D of the magnetic yoke are arranged in the air core portion of the coil 21 so that the air core portion of the coil 21 is effectively used. Also in this respect, the overall shape of the linear motor is reduced. Can do.
[0010]
For example, as shown in FIG. 3, the jacket 22 may have a four-body configuration in which the outer wall portion 22A, the inner wall portion 22B, and the plate ring-shaped portions 22C and 22D are separated from each other. It will be easily understood that various other configuration methods can be used.
A jacket configuration that wraps substantially the entire circumference of the coil described above may be used, and the relative movement directions of the coil and the permanent magnet may be the same as in the conventional case. An example thereof is shown in FIG. 4 with the same reference numerals assigned to the portions corresponding to FIG. 2B. In this case, the plate ring-shaped portions 22C and 22D of the jacket 22 are made as thin as possible, and the strength of the thin plate ring-shaped portions 22C and 22D is maintained by the outer wall portion 22A and the inner wall portion 22B. For example, it is desirable that the coil holding portion 24 increase the contact area between the stepped portion 24B formed on the inner wall portion 22B and the coil, and reduce the contact between the stepped portion 24A on the plate ring-shaped portion 22D side. Permanent magnets 41, 42, 43, 44 are arranged on the outside of the plate ring-shaped portions 22 C, 22 D of the jacket so as to correspond to the linear portions 21 A, 21 B of the coil, and are opposed to the permanent magnets 41, 42, 43. , 44 is connected to a magnetic yoke 45 on the surface opposite to the jacket.
[0011]
【The invention's effect】
As described above, according to the present invention, the coil cooling efficiency can be increased, the thrust can be increased, and the dimensions of the coil and the permanent magnet in the relative movement direction can be reduced.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing an embodiment of the present invention.
2A is a side view of an embodiment of the present invention, and B is a cross-sectional view taken along the line ZZ of FIG. 2A.
FIG. 3 is a cross-sectional view showing a modified example of the jacket of the linear motor of the present invention.
FIG. 4 is a cross-sectional view showing another embodiment of the present invention.
FIG. 5 is a cross-sectional view showing a conventional linear motor.

Claims (1)

An annular coil having two aligned linear portions;
This annular coil is housed, envelops the entire circumferential surface along this annular coil, and an inlet and outlet for allowing refrigerant to flow into and out of the internal space, and a jacket having an outlet,
Two pairs of permanent magnets arranged so as to sandwich the linear portions of the coil in proximity to the outer peripheral wall and the inner peripheral wall of the jacket;
A linear motor comprising a magnetic yoke disposed on the outside of the jacket and connected to the pair of permanent magnets.

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