JP2008259373A - Linear motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linear motor capable of efficiently improving thrust performance of the motor. <P>SOLUTION: The linear motor is provided with a stator equipped with an electromagnetic coil 10 in which a plurality of bobbins 14 having a winding wire wound therearound are continuously arranged, and a center core 11 piercing through the bobbins; and a mover 20 equipped with a permanent magnet 21 imposed by an action of a magnetic flux of the stator and arranged so as to linearly move along the stator. In the linear motor, a space 16a for allowing a fluid for cooling the electromagnetic coil 10 to pass is formed between the bobbins 14 and the center core 11. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a moving magnet type linear motor, and more particularly, to a cylindrical field type linear motor including a cylindrical field structure and an armature associated therewith.

  Conventionally, as a drive mechanism for linearly moving a drive system of a precision positioning device, a mechanism that converts the rotation of a rotary motor into a linear motion to move an object to be driven, or a direct linear motor, a so-called linear motor, is used. A moving object is used.

  Linear motors have the advantages of simple structure, small number of parts, low frictional resistance in driving, high operation accuracy, and direct movement of linear motors for quick movement. ing.

  For this reason, linear motors are becoming mainstream in drive mechanisms that perform linear motion in fields that require precise positioning.

For example, in an exposure apparatus used in a photolithography process when manufacturing a semiconductor device, a liquid crystal display device, a thin film magnetic head, etc., a linear motor is used as a drive mechanism for moving a stage on which a reticle, a wafer, etc. are mounted. Yes.
JP-A-01-188241 Japanese Patent Laid-Open No. 08-005767

  The motor thrust is theoretically determined by Fleming's law, the magnetic flux density in the space between the opposing field magnets (hereinafter referred to as field gap), and the coil present in the field gap that is useful for generating the force. The product of the length of the wire (hereinafter referred to as the effective wire length) and the value of the current flowing through the coil wire in the field gap.

  The thrust constant obtained by dividing the motor thrust by the current value is determined by the structure of the motor and is used in motor design as an important factor that affects the thrust performance of the motor. In order to improve the thrust performance of the motor, it is important to increase the thrust constant, and it is necessary to increase the effective wire length or increase the magnetic flux density.

  A linear motor is a kind of electromechanical converter, which supplies electric energy to linearly move the secondary side mover by current force or magnetic force. Therefore, in order to obtain thrust, it is necessary to pass a current through the armature coil. As a result of the current flowing through the coil, the coil generates heat due to the Joule heat generated by the resistance of the coil wire, and the generated eddy current The surrounding members generate heat.

  Although there are differences depending on the type of linear motor, it is necessary to increase the current flowing through the coil in order to increase the thrust of linear motion. Therefore, if the output of the linear motor is high, the energy loss due to heat generation increases accordingly. Become. In addition, the coil and peripheral members may be damaged due to heat generation. Therefore, in general, the rated thrust of a linear motor is determined by an allowable temperature at which a covering material such as enamel that insulates the coil and a molded resin material that molds the coil are not deformed.

  Incidentally, for example, a stage of an exposure apparatus that places and moves a wafer is required to position a predetermined area of the wafer at a predetermined position in as short a time as possible in order to improve throughput. For this reason, the stage needs to be able to move stably at a high speed and to have high rigidity so as not to be deformed or vibrated even during rapid acceleration / deceleration. As a result, the mass of the stage must be increased. Therefore, the linear motor used in the stage drive system is required to have a thrust performance that can drive a heavy stage with a large acceleration.

  As a method of improving the thrust performance of the conventional linear motor, it is conceivable to increase the number of turns of the coil wire so that the effective wire length becomes long. However, if the number of turns of the coil is increased, the direction of the field magnet of the coil is increased. Since the thickness is increased, the gap between the field magnets must be widened, so that the magnetic flux density in the field gap is lowered and the propulsion performance of the linear motor cannot be improved so much. Arise. Further, if it is attempted not to reduce the magnetic flux density in the field gap, the field magnet must be large and heavy, resulting in a problem that the linear motor becomes large.

  Increasing the effective wire length of the coil also increases the amount of heat generated by the coil, and in the conventional linear motor configuration, the generated heat is radiated from the coil surface to gas in the surrounding atmosphere. There is a problem that the fluctuation of the refractive index is caused by the fluctuation, and the thermal expansion of the stage is caused.

  Accordingly, the present invention has been made in view of the above-described problems, and an object thereof is to provide a linear motor that can effectively improve the propulsion performance of the motor.

  Furthermore, another object of the present invention is to provide a linear motor capable of efficiently cooling the heat generated in the coil without adversely affecting the surrounding environment.

  In order to solve the above-described problems and achieve the object, a linear motor according to the present invention includes an electromagnetic coil in which a plurality of bobbins wound with windings are continuously arranged, and a center core that passes through the bobbin. A stator having a permanent magnet that receives the action of magnetic flux from the stator, and a mover arranged so as to be linearly movable along the stator, between the bobbin and the center core. Further, a space for allowing a fluid for cooling the electromagnetic coil to pass therethrough is formed.

  In the linear motor according to the present invention, the space formed between the bobbin and the center core includes a recess formed on the outer periphery of the center core and a protrusion formed on the bobbin so as to face the recess. It is formed by the part.

  Further, in the linear motor according to the present invention, the convex portion formed on the bobbin is partially fitted into the concave portion formed on the outer periphery of the center core, and also serves as a rotation stopper for the bobbin with respect to the center core. Features.

  In the linear motor according to the present invention, the convex portion formed on the bobbin is provided with a space for storing the lead wire from the electromagnetic coil.

  In the linear motor according to the present invention, a fluid for cooling the electromagnetic coil is allowed to pass through a space for wiring the lead wire from the electromagnetic coil.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the linear motor which can improve the propulsion performance of a motor effectively.

  It is also possible to provide a linear motor that can efficiently cool the heat generated in the coil without adversely affecting the surrounding environment.

  Hereinafter, a linear motor according to an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of a stage apparatus using a linear motor, which is common to each embodiment of the present invention.

  In FIG. 1, a linear motor is composed of a shaft body (hereinafter referred to as a stator) 10 containing a plurality of electromagnetic coils (hereinafter referred to as coils) continuously arranged, and a magnetic flux from these coils. A movable magnet body (hereinafter referred to as a movable element) 20 that can travel in the same direction as the extending direction of the stator 10 by the interaction (can be linearly moved) is configured. The stator 10 is bridged between two brackets 33A and 33B fixed on the base 31 with an interval.

  Two guide blocks 35 are assembled to the mover 20 via a table 32, and these two guide blocks 35 are slid and guided by guide rails 34 arranged on the base 31 along the traveling direction of the mover 20. Then, it moves with the gap maintained with respect to the outer periphery of the stator 10.

  The thrust is the same even if there is a variation in the gap between the outer surface of the stator 10 and the inner surface of the mover 20, and the mover 20 and the stator 10 require strict mounting accuracy and processing accuracy. Not.

  A linear sensor scale 43 and a linear sensor head 42 provided along the traveling direction of the mover 20 are attached on the base 31. The detection signal from the linear sensor head 42 is used for positioning control of the mover 20. Further, a power cable for three-phase driving is connected to each coil in the stator 10 from a control driver 44 through a bracket 33A. A controller 45 is connected to the control driver 44, and positioning control of the mover 20 is performed based on control data given from the controller 45.

  On the base 31, a limit sensor 41 for detecting the mover 20 is provided. The detection signal of the limit sensor 41 is sent to the control driver 44 and used for positioning the origin of the mover 20 or preventing runaway.

  The linear motor shown in FIG. 1 can reciprocate the mover 20 in a specified region.

  Hereinafter, specific embodiments showing the structure of the linear motor portion of the stage apparatus shown in FIG. 1 will be described in more detail, but these do not limit the present invention and depart from the spirit of the present invention. Variations are possible within the range not to be.

(First embodiment)
The structure of the linear motor according to the first embodiment will be described below.

  2 is a transverse sectional view showing a schematic configuration of the linear motor according to the first embodiment, FIG. 3 is a longitudinal sectional view of the linear motor, and FIG. 4 is a configuration of a stator of the linear motor according to the first embodiment. FIG.

  The mover 20 includes a plurality of annular permanent magnets 21 that can surround the coil 12, and a magnet case 22 that houses the plurality of permanent magnets 21. The plurality of permanent magnets 21 have the same length dimension, are combined in series so that adjacent magnetic poles are opposite to each other, and the magnetic pole axes are parallel to the axis of the center core 11, thereby forming a magnet case 22. Is housed in.

  The stator 10 is configured by penetrating a center core 11 made of a magnetic material such as iron through a bobbin 14 in which a coil 12 is formed by wrapping wires coated with an insulating film in multiple layers. Since the linear motor in the present embodiment is a three-phase drive type, a coil set including three coils of a U-phase coil 12a, a V-phase coil 12c, and a W-phase coil 12b is used as one unit (see FIG. 4). The current flowing through the V-phase coil 12c has a phase difference of 120 ° with respect to the current flowing through the U-phase coil 12a, and the current flowing through the W-phase coil 12b has a phase difference of 120 ° with respect to the current flowing through the V-phase coil 12c. To drive. A plurality of coil sets are mounted around the center core 11 along the axial direction, and these coil sets are covered with a pipe 13 made of a nonmagnetic material (stainless steel or the like) indicated by a virtual line.

  As shown in FIG. 3, the center core 11 is formed with a U-shaped notch (recess) 16. On the inner periphery of the bobbin 14, a U-shaped convex portion 14 a is formed in accordance with the notch portion 16 of the center core 11. This convex portion 14a (a part of the bobbin) is partially fitted into the entrance portion of the concave portion 16 of the center core 11 and also serves as a rotation stopper for the bobbin 14 relative to the center core 11. In the present embodiment, a fluid for cooling the stator 10 is caused to flow in a space 16 a surrounded by the notch portion 16 of the center core 11 and the convex portion 14 a of the bobbin 14. Thereby, formation of the space 16a through which the fluid for cooling is formed and positioning of the coil 12 in the rotational direction can be performed simultaneously, and the shape of the center core 11 can be simplified.

  In the U-shaped convex portion 14 a formed on the bobbin 14, a wiring portion 15 for storing the lead wire 17 of the three-phase coil is formed. As described above, the refrigerant circulates in the space 16a formed by the U-shaped notch 16 of the center core 11 and the U-shaped convex portion 14a of the bobbin 14. As a result, the vicinity of the coil 12 that generates heat and the lead wire 17 of the coil can be directly cooled, and efficient cooling becomes possible.

  The brackets 33A and 33B are provided with a tube 39A and a joint 38A through which a refrigerant having a predetermined temperature by a cooling system (not shown) flows into the stator 10, and a joint 38B and a tube 39B for returning the refrigerant to the cooling system. The O-rings 37A and 37B and the sealing material 36 prevent the refrigerant from leaking to the outside. As a result, the refrigerant flows from the cooling system through the tube 39A and the joint 38A to the inside of the stator 10, absorbs heat from the coil 12 through the vicinity of the coil 12, and then returns to the cooling system through the joint 38B and the tube 39B. Circulate like so.

  The pipe 13 is made of a nonmagnetic metal material such as stainless steel, but may be a resin material or the like.

  The center core 11 is made of a magnetic material such as iron in order to have a function as a yoke, and has a U-shaped notch so as to have a shape suitable for cooling while maintaining mechanical strength. For the permanent magnet 21, for example, a neodymium magnet having high performance as a magnet is used. In particular, the dimensions of the permanent magnet 21 in the magnetic pole axis direction must all be the same. As the magnet case 22, a nonmagnetic material such as an aluminum alloy is used.

  The coil 12 has an outer diameter of 0.3 mm, for example, and the outside of a copper conductor part is covered with an extremely thin coating layer such as enamel or polyurethane.

(Second Embodiment)
FIG. 5 is a transverse sectional view showing a schematic configuration of the linear motor according to the second embodiment of the present invention, and FIG. 6 is a longitudinal sectional view of the linear motor. Similar to the first embodiment, the linear motor of the second embodiment is a three-phase drive type linear motor.

  The center core 51 is formed with a U-shaped cutout 56 as in the first embodiment. On the inner periphery of the bobbin 54, a U-shaped convex portion 54a is formed so as to follow the outer periphery shape of the center core 51. In the U-shaped convex portion 54a formed on the bobbin 54, a wiring portion 55 for wiring the lead wire of the three-phase coil is formed. The refrigerant circulates through a space 56 a formed by the U-shaped notch 56 of the center core 51 and the U-shaped convex portion 54 a of the bobbin 54, and is further formed on the bobbin 54. The refrigerant also circulates in the space of the lead wire wiring portion 55. Thereby, the lead wire 57 from the coil 52 can be directly cooled by distributing and introducing the refrigerant into the space 56a formed in the center core 51 and the space 55 formed in the bobbin 54, and the vicinity of the coil 52 that generates heat. Alternatively, since the refrigerant can be passed through the coil 52, efficient cooling is possible.

  As described above, according to the above-described embodiment, by passing a fluid such as liquid or gas through the space formed by the bobbin and the center core, the inside of the motor body is cooled to reduce the volume or weight per thrust. The propulsion performance of the motor can be effectively improved by minimizing. Furthermore, the heat generated in the coil can be efficiently discharged without adversely affecting the surrounding environment.

  The linear motor of the present invention is not limited to the three-phase drive type. A two-phase or four-phase or more linear motor may be used. You may comprise so that a needle | mover may move on a circular arc instead of a linear motion. Further, the shape of the notch portion formed in the center core is not limited to the U-shape, and a bobbin shape and a wiring portion corresponding to the shape may be formed.

It is the figure which showed schematic structure of the stage apparatus using a linear motor common to each embodiment of this invention. 1 is a cross-sectional view showing a schematic configuration of a linear motor according to a first embodiment of the present invention. 1 is a longitudinal sectional view showing a schematic configuration of a linear motor according to a first embodiment of the present invention. It is a block diagram of the stator of the linear motor concerning the 1st Embodiment of this invention. It is a cross-sectional view which shows schematic structure of the linear motor concerning the 2nd Embodiment of this invention. It is a longitudinal cross-sectional view which shows schematic structure of the linear motor concerning the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Stator 11 Center core 12 Coil 13 Pipe 14 Bobbin 20 Mover 21 Permanent magnet 22 Magnet case

Claims (5)

A stator including an electromagnetic coil in which a plurality of bobbins wound with windings are continuously arranged, and a center core penetrating the bobbin;
A permanent magnet that receives the action of magnetic flux from the stator, and a mover arranged so as to be linearly movable along the stator;
A linear motor in which a space for allowing a fluid for cooling the electromagnetic coil to pass is formed between the bobbin and the center core.   The space formed between the bobbin and the center core is formed by a concave portion formed on the outer periphery of the center core and a convex portion formed on the bobbin so as to face the concave portion. The linear motor according to claim 1.   3. The linear portion according to claim 2, wherein a convex portion formed on the bobbin is partially fitted into a concave portion formed on an outer periphery of the center core, and serves also as a rotation stopper for the bobbin with respect to the center core. motor.   The linear motor according to claim 2, wherein a space for wiring and storing a lead wire from the electromagnetic coil is formed in the convex portion formed on the bobbin.   The linear motor according to claim 4, wherein a fluid for cooling the electromagnetic coil is allowed to pass through a space for wiring the lead wire from the electromagnetic coil.

Images