JP2012186936A - Linear motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a linear motor that can cool both a mover and a stator without using cooling means on a mover side.SOLUTION: The linear motor includes: a stator 10 comprising a series connection of a plurality of permanent magnets 11, and a mover 20 having cylindrical coils 21U, 21V, 21W combined around the stator for sliding motion along the stator. The plurality of permanent magnets 11 are housed in a pipe 16 having an inside diameter larger than an outside diameter of the permanent magnets and having an outside diameter smaller than an inside diameter of the coils. Refrigerant supply means can be connected to at least one end of the pipe 16 to introduce a refrigerant into a space between an outer circumference of the permanent magnets 11 and an inner circumference of the pipe 16, and the refrigerant can be jetted out of the pipe 16, that is, onto an inner surface of the coils being slid, via a plurality of holes 16a formed in predetermined positions in the pipe 16.

Description

  The present invention relates to a coreless type linear motor composed of a coil and a permanent magnet.

  A coreless cylindrical linear motor that obtains thrust by the action of a magnetic field generated from a plurality of cylindrical permanent magnets and an electric current that flows through a cylindrical coil is known (Patent Document 1). This linear motor is sometimes called a “shaft motor”.

  As shown in FIG. 5, this type of linear motor has a cylindrical shape in which a plurality of cylindrical permanent magnets 51 magnetized in the central axis direction are connected to each other, and a minute gap is formed around the cylindrical permanent magnet 51. 52 is slidably combined. The permanent magnet 51 is combined with the same magnetic poles facing each other so that N poles and S poles alternate, and becomes a stator. The coil 52 is composed of at least three coils in order to form a three-phase linear motor here, and a current having a phase difference of 120 ° is flowed through each of the coils to form a mover. That is, by switching energization to the coil 52, the mover is linearly moved along the stator.

Japanese Patent Laid-Open No. 10-313566 Japanese Patent Laid-Open No. 2003-209962

  By the way, in this type of linear motor, there is a heat generating action by energizing the coil 52, and this heat gives a demagnetizing action to the permanent magnet 51. Therefore, means for suppressing heat radiation from the coil 52 is required. The

  An example of cooling the mover side in order to suppress heat radiation from the coil on the mover side in the linear motor is shown in Patent Document 2.

  However, in the linear motor of Patent Document 2, a cooling medium passage is provided in the movable element to cool the movable element side, and the cooling medium is connected to a cooling medium supply (or circulation) means different from the movable element. Since it is configured to supply (or circulate), there is a problem that the size and weight on the side of the mover increase, and a problem that the thrust is reduced correspondingly.

  In the linear motor of Patent Document 2, the stator side permanent magnet is formed in a hollow cylindrical shape to cool the stator side by passing a cooling medium through the hollow portion, and the permanent magnet is accommodated in a pipe. The stator side is also cooled by passing a cooling medium through a gap between the pipe and the outer periphery of the permanent magnet.

  However, in the linear motor of Patent Document 2, a cooling circuit dedicated to the mover side is indispensable for cooling the mover side. When the stator side is to be cooled in addition to the mover side, the stator side is required. Requires a dedicated cooling circuit.

  Therefore, the present invention intends to provide a linear motor capable of cooling both the mover and the stator without providing a cooling means on the mover side.

  According to the aspect of the present invention, a mover having a stator in which a plurality of permanent magnets are connected in series and a cylindrical coil that is slidably combined along the stator on the outer peripheral side of the stator. The plurality of permanent magnets are housed in a pipe having an inner diameter larger than the outer diameter and smaller than the inner diameter of the coil, and a refrigerant supply means is provided on at least one end side of the pipe. It is connected so that the refrigerant can be introduced into a space between the outer periphery of the permanent magnet and the inner periphery of the pipe, and the refrigerant is jetted out of the pipe through a hole provided in a predetermined portion of the pipe. A linear motor is provided.

  In the linear motor according to the above aspect, the plurality of permanent magnets are held so as to be sandwiched by two holding portions from both sides thereof, and the pipe is bridged between the two holding portions, and at least one of the permanent magnets is held. It is preferable that the holding unit is connected to the refrigerant supply means and is provided with one or more inlets for introducing the refrigerant into a space between the outer periphery of the permanent magnet and the inner periphery of the pipe. .

  In the linear motor according to the aspect described above, the one or more introduction ports are provided in both the holding portions, and the holes are a plurality of locations spaced in the central axis direction of the pipe, and the pipe It is preferable that a plurality of portions spaced apart in the circumferential direction of the pipe and spaced apart in the central axis direction of the pipe are set in a region where the slide of the mover is large.

  In the linear motor according to the above aspect, it is preferable that a spacer having a conical surface facing the holding portion is interposed between the holding portion having the introduction port and the permanent magnet closest to the holding portion. .

  In the linear motor according to the above aspect, the total cross-sectional area of the one or more inlets is larger than the cross-sectional area of the space between the outer periphery of the permanent magnet and the inner periphery of the pipe, and the total area of the holes Is preferably smaller than the cross-sectional area of the space between the outer periphery of the permanent magnet and the inner periphery of the pipe.

  According to the present invention, not only can the overheating of the stator, that is, the permanent magnet be prevented, but also the mover can be cooled, so that the characteristic change of the linear motor due to temperature can be prevented.

It is the figure which showed the cross-section of the stator and the needle | mover in the linear motor by embodiment of this invention. It is the perspective view which showed the external appearance of the stator shown by FIG. It is the figure which showed the temperature measurement result of the pipe surface in the linear motor by embodiment of this invention, the U-phase coil surface, and the coil casing with room temperature. It is the figure which showed the relationship between the temperature of the U-phase coil surface and the energization current (effective value) of the U-phase coil in the linear motor according to the embodiment of the present invention with and without cooling. It is a figure for demonstrating the general example of a linear motor.

  The present invention has been made based on the following idea.

  In a linear motor in which a rod-shaped stator is constructed by connecting a plurality of cylindrical permanent magnets together and then housed in a pipe, and a movable coil is slidable around it, the coil is energized. Joule heat is generated when driven. This heat is released to the outside of the coil through the coil casing or is transferred to the outside air inside the coil. The heat transferred to the inside of the coil is transferred to the pipe that contains and protects the permanent magnet, reaches the permanent magnet inside, and raises the temperature of the permanent magnet.

  This phenomenon is particularly remarkable when the drive range (distance) of the mover is shorter than the entire length of the mover. This is because some permanent magnets constituting the rod-shaped stator are always exposed to heat generated from the coil. That is, since the coil is located on the outer periphery of the permanent magnet, the permanent magnet at this location is overheated due to the heat exhaustion. When the temperature of the permanent magnet rises, there arises a problem that the magnetic characteristics change. When the magnetic characteristics change, the characteristics of the linear motor change and precise control becomes impossible.

  The present invention is intended to solve such a problem, and cools the permanent magnet by flowing a fluid between the permanent magnet and a pipe disposed outside the permanent magnet. For this reason, it is set as the structure which can connect the supply source of the fluid to the edge part of a stator. In addition, by providing a through-hole at a predetermined location of the pipe, the permanent magnet is directly cooled from the outer peripheral side, and by ejecting fluid from the through-hole of the pipe, the mover, that is, the coil is cooled from the inside. . As a result, the coil can be cooled from the stator side without mounting extra parts for cooling on the mover side. The fluid is preferably compressed air, but may be liquid.

  Embodiments of the present invention will be described below with reference to FIGS.

  FIG. 1 shows a cross-sectional structure of a stator and a mover in a three-phase linear motor according to an embodiment of the present invention. FIG. 1 (a) is a cross-sectional view along the central axis of the stator, and FIG. FIG. 1C is a cross-sectional view perpendicular to the center axis of the child, and FIG. 1C is a view of the combination of the stator and the mover as viewed from the left side of FIG. In the following, the central axis means the central axis of the stator unless otherwise specified. In the following, the case where the stator is columnar and the mover is cylindrical will be described. However, it is only necessary that the cross-sectional shape of the stator corresponds to the opening surface of the mover. In addition to the columnar shape, any of a cylindrical shape, a rectangular tube shape, and a rectangular bar shape may be used, and the mover may be a cylindrical shape or a rectangular tube shape.

  The stator 10 is formed by connecting a plurality of ring-shaped or cylindrical permanent magnets 11 in series. In particular, the permanent magnet 11 is magnetized in the direction of its central axis, and is combined with the same magnetic poles facing each other so that N poles and S poles are alternated. An example of this combination technique is as follows.

  One end side of the center shaft 12 having a male screw cut over the entire length is screwed into a female screw 13a-1 provided at the center of one end side of the holding portion 13a. Next, the spacer 14 a is attached to the center shaft 12. The spacer 14a has a conical shape in which the surface facing the holding portion 13a is cut from the tip of a cone for the reason described later.

  Subsequently, the plurality of cylindrical permanent magnets 11 are mounted on the center shaft 12 with the same magnetic poles facing each other so that the N poles and the S poles are alternated. At that time, since a repulsive force acts between the adjacent permanent magnets 11, the permanent magnet 11 is mounted while being pressed in the direction of the central axis by a jig (not shown). Alternatively, a female screw that is screwed into the male screw of the center shaft 12 may be formed on the inner diameter side of the permanent magnet 11. The number of permanent magnets 11 is determined by the stroke of the mover 20.

  When the predetermined number of permanent magnets 11 are mounted, the nut 15-1 is mounted on the center shaft 12, and the predetermined number of permanent magnets 11 are tightened. This tightening is preferably performed with the double nuts 15-1 and 15-2 so as not to be loosened later.

  Next, after the spacer 14b is attached to the center shaft 12, the pipe 16 is attached, and the other end side of the center shaft 12 is screwed into a female screw 13b-1 provided at the center of one end side of the holding portion 13b. Like the spacer 14a, the spacer 14b has a conical shape in which the surface facing the holding portion 13b is cut at the tip of the cone, and a storage portion for the double nuts 15-1 and 15-2 is formed on the opposite side. Has been. Further, in order to bridge the pipe 16 between the holding part 13 a and the holding part 13 b, a part of the outer peripheral part of the holding parts 13 a and 13 b enters the pipe 16. In this case, the joint between the pipe 16 and the holding portions 13a and 13 is preferably sealed by a method such as an O (O) ring, a viscous fluid-like sealing material, or brazing in order to maintain airtightness.

  A cylindrical mover 20 in which three ring-shaped or cylindrical coils 21U, 21V, and 21W are accommodated in a coil casing 22 slides along the stator 10 on the stator 10 configured as described above. Can be combined. Each of the coils 21U, 21V, and 21W is formed by winding a winding around a bobbin, and the winding is star or delta-connected and connected to a three-phase power source (not shown) and a control device (not shown). Since the connection form with the three-phase power supply and the control form by the control device are not the gist of the present invention, the detailed description is omitted.

  Each of the holding portions 13a and 13b is provided with a plurality of through holes 13a-2 and 13b-2 that penetrate in the central axis direction at equal angular intervals, here, at an angular interval of 90 degrees. . A pipe 31 for supplying compressed air as a refrigerant from a blower 30 as a refrigerant supply source is connected to each of these inlets via a joint 32. As shown in FIG. 1C, the holding portion 13b is provided with a screw hole 13b-3 extending to the female screw 13b-1 in a direction perpendicular to the central axis, and the male screw is screwed into the center shaft. 12 is prevented from loosening. The same applies to the holding portion 13a side.

  Now, since the pipe 16 has an inner diameter larger than the outer diameter of the permanent magnet 11 and an outer diameter smaller than the inner diameter of the coils 21U, 21V, and 21W, there is a gap between the outer periphery of the permanent magnet 11 and the inner periphery of the pipe 16. An annular space G1 is formed, and a gap G2 space is formed between the outer periphery of the pipe 16 and the inner periphery of the mover 20.

  In the present embodiment, the pipe 16 is provided with a total of 16 through holes 16a at two places spaced in the central axis direction and at eight places spaced in the circumferential direction.

  With the above-described structure, the compressed air introduced from the inlets 13a-2 and 13b-2 in the holding portions 13a and 13b on both sides of the stator 10 passes through the space on the outer surface side of the conical shape of the spacers 14a and 14b, respectively. It is introduced into the annular space between the permanent magnet 11 and the pipe 16 and flows toward the center, and is ejected out of the pipe 16 through the through hole 16a. At this time, since there is a space formed by the conical spacer between the inlet and the annular space of the gap G1, the compressed air introduced from the three inlets easily flows uniformly into the annular space of the gap G1. . This is the reason why the surfaces of the spacers 14a and 14b facing the holding portions 13a and 13b are conical.

  The compressed air passing through the annular space of the gap G1 cools the stator 10, that is, the permanent magnet 11, from the outer peripheral side, and the compressed air ejected from the through hole 16a causes the mover 20, that is, the coils 21U, 21V, and 21W to be included therein. Cool from the circumferential side. In particular, the region in which the through hole 16a is provided is a region that tends to overlap in the stroke range of the mover 20, that is, a region where heat generation from the coil tends to be stagnant, for example, a central region with respect to the central axis direction. Thus, the cooling efficiency of the mover 20 can be improved.

  Furthermore, the total cross-sectional area of the three inlets in each holding portion is made larger than the cross-sectional area of the annular space of the gap G1 between the outer periphery of the permanent magnet 11 and the inner periphery of the pipe 16, and the total area of the through hole 16a Is made smaller than the cross-sectional area of the annular space of the gap G1, the flow rate of the compressed air and the ejection speed to the coil inner surface can be increased, and the cooling effect of the mover 20 can be enhanced.

  FIG. 3 is a view showing the temperature measurement results of the pipe 16 surface, the U-phase coil 21U surface, and the coil casing 22 together with the room temperature in the linear motor according to the present embodiment.

  As can be seen from FIG. 3, when compressed air is introduced into the stator 10, the temperature of the pipe 16 surface, the U-phase coil 21U surface, and the coil casing 22 are all quickly reduced and the cooling effect is high.

  FIG. 4 is a diagram showing the relationship between the temperature of the surface of the U-phase coil 21U and the energization current of the U-phase coil 21U in the linear motor according to the present embodiment, with and without cooling.

  FIG. 4 also shows that the energization current can be increased as compared to the case without cooling due to the improvement of the cooling effect by the cooling structure of the present embodiment. As a result, an increase in thrust as a linear motor can be realized.

  While the present invention has been described with reference to the preferred embodiments, the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the spirit and scope of the present invention described in the claims.

  The linear motor according to the present invention is suitable for a transport unit of precision equipment, for example, a transport system of a semiconductor manufacturing apparatus, but is not limited thereto.

DESCRIPTION OF SYMBOLS 10 Stator 11 Permanent magnet 12 Center shaft 13a, 13b Holding | maintenance part 14a, 14b Spacer 16 Pipe 20 Movable element 21U, 21V, 21W Coil 31 Piping 32 Joint

Claims (5)

In a linear motor including a stator formed by connecting a plurality of permanent magnets in series, and a mover having a cylindrical coil that is slidably combined along the stator on the outer peripheral side of the stator,
Storing the plurality of permanent magnets in a pipe having an inner diameter larger than an outer diameter thereof and an outer diameter smaller than an inner diameter of the coil;
A refrigerant supply means is connected to at least one end of the pipe so that the refrigerant can be introduced into a space between the outer periphery of the permanent magnet and the inner periphery of the pipe, and the hole is provided through a hole provided at a predetermined position of the pipe. A linear motor characterized in that a refrigerant is jetted out of the pipe.   The linear motor according to claim 1, wherein the plurality of permanent magnets are held so as to be sandwiched by two holding portions from both sides thereof, and the pipe is bridged between the two holding portions, and at least One of the holding portions is connected to the refrigerant supply means and is provided with one or more inlets for introducing the refrigerant into a space between the outer periphery of the permanent magnet and the inner periphery of the pipe. A linear motor characterized by   3. The linear motor according to claim 2, wherein the one or more introduction ports are provided in both of the holding portions, and the holes are a plurality of locations spaced in the central axis direction of the pipe, and A linear motor, wherein a plurality of pipes are provided at intervals in a circumferential direction of the pipe, and a plurality of places spaced in the central axis direction of the pipe are set in an area where the slide of the mover is large.   4. The linear motor according to claim 2, wherein a spacer having a conical surface facing the holding portion is interposed between the holding portion having the introduction port and the permanent magnet closest to the holding portion. A linear motor characterized by that.   5. The linear motor according to claim 2, wherein a total cross-sectional area of the one or more introduction ports is larger than a cross-sectional area of a space between an outer periphery of the permanent magnet and an inner periphery of the pipe. The total area of the holes is smaller than the cross-sectional area of the space between the outer periphery of the permanent magnet and the inner periphery of the pipe.

Images