Linear motor

Abstract

To provide a linear motor capable of efficiently cooling a coil of a stator while improving thrust density of the motor.SOLUTION: A linear motor that drives a movable body in a pressure vessel includes a mover that is disposed inside the pressure vessel, is connected to the movable body, and is movable in a vessel axial direction of the pressure vessel, and a stator that is disposed outside the pressure vessel so as to face the mover across the pressure vessel. The stator includes a stator main body including a plurality of coils and an iron core, and a housing that houses the stator main body and supports the stator main body on both sides in a container axial direction. The iron core includes a salient pole portion protruding toward the movable element, and a yoke portion extending in the container axial direction and having a plurality of salient pole portions formed at predetermined intervals in the container radial direction of the pressure container. The coil forms a magnetic flux that drives the movable element, and is wound around the yoke portion so as to form an annular shape with respect to the container axial direction. The housing includes a cooling unit that cools the coils via a gap formed between the coils adjacent to each other in the container axial direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a linear motor that drives a movable body inside a pressure vessel. [Background technology]

[0002] Conventionally, as one of the driving means for relatively moving a movable body in a linear direction, a linear motor is known which drives a movable element in a linear direction by the magnetic force of a linearly arranged permanent magnet and an electromagnet (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-186244 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-143398 Summary of the Invention [Problem to be solved by the invention]

[0004] The application of a linear motor has been considered as a driving means for driving a movable body arranged inside a pressure vessel in the axial direction of the vessel. For example, a linear motor in which a stator having a coil is arranged outside the vessel and a movable part having a permanent magnet is arranged inside the vessel makes it possible to drive a movable body connected to the movable part from outside the vessel without laying out coil wiring or the like inside the vessel, and is therefore preferable as a driving means for a movable body inside the pressure vessel.

[0005] In the linear motor described above, a relatively large gap is created between the partition walls, and therefore a higher thrust density of the motor is required to drive the mover. Furthermore, since the maximum output and continuous operating time of a linear motor are greatly affected by the cooling performance of the stator coil, efficient cooling of the stator coil is also required to improve the performance of a linear motor.

[0006] The present invention has been made in view of the above circumstances, and has an object to provide a linear motor that can efficiently cool the stator coils while improving the thrust density of the motor. [Means for solving the problem]

[0007] A linear motor according to one embodiment drives a movable body within a pressure vessel. The linear motor includes a movable body disposed inside the pressure vessel, connected to the movable body, and movable in the vessel axial direction of the pressure vessel; and a stator disposed outside the pressure vessel, facing the movable body across the pressure vessel. The stator has a stator body including multiple coils and an iron core, and a housing that houses the stator body and supports the stator body on both sides in the vessel axial direction. The iron core includes salient pole portions that protrude toward the movable body and a yoke portion that extends in the vessel axial direction and has multiple salient pole portions formed at predetermined intervals in the vessel radial direction of the pressure vessel. The coils generate magnetic flux that drives the movable body, and are wound around the yoke portions in a ring shape relative to the vessel axial direction. The housing has a cooling portion that cools the coils through gaps formed between adjacent coils in the vessel axial direction.

[0008] In the above aspect, the cooling unit may cool the coils by supplying cooling air to gaps between the coils. In the above aspect, the cooling unit may cool the coils by supplying cooling oil to gaps between the coils. In the above aspect, the housing may have protrusions on its inner surface that are inserted into gaps between the coils, and the cooling unit may have cooling pipes that are thermally connected to the protrusions and circulate a refrigerant. The cooling unit may also cool the coils with the refrigerant via the protrusions. [Effects of the Invention]

[0009] According to one aspect, it is possible to provide a linear motor that can efficiently cool the stator coil while improving the thrust density of the motor. [Brief explanation of the drawings]

[0010] [Figure 1]FIG. 2 is a schematic diagram showing the overall configuration of a pressure vessel and a linear motor. [Figure 2] 1 is a longitudinal sectional view of a linear motor according to a first embodiment. [Figure 3] FIG. 2 is a diagram showing the structure of a stator body. [Figure 4] 3A and 3B are diagrams illustrating a configuration example of a housing of a stator in the first embodiment. [Figure 5] 10A and 10B are diagrams illustrating a configuration example of a housing of a stator in a second embodiment. [Figure 6] 10A and 10B are diagrams illustrating a configuration example of a housing of a stator in a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the embodiments, in order to make the explanation easier to understand, the structures and elements other than the main parts of the present invention will be explained in a simplified or omitted manner. Furthermore, the same elements will be given the same reference numerals in the drawings. Note that the shapes, dimensions, etc. of the elements shown in the drawings are shown schematically and do not represent the actual shapes, dimensions, etc.

[0012] (First embodiment) Figure 1 is a schematic diagram showing the overall configuration of a pressure vessel and a linear motor. The pressure vessel 1 of this embodiment has a sealed cylindrical shape, and the interior of the pressure vessel 1 is isolated from the environment outside the vessel. The interior of the pressure vessel 1 is set under pressure conditions (e.g., a vacuum environment) different from those outside the vessel. The material of the pressure vessel 1 can be one that has sufficiently high rigidity (pressure resistance) as well as relatively low magnetic permeability and allows magnetic flux to pass through easily.

[0013] A linear motor 2 is arranged along the axial direction (left-right direction in Figure 1) of the pressure vessel 1 at a part of the circumferential direction of the pressure vessel 1. A movable body 3 and a movable element 4 of the linear motor 2 are housed inside the pressure vessel 1, and a stator 5 of the linear motor 2 is arranged outside the pressure vessel 1.

[0014] The movable body 3 is a disk-shaped body with an outer diameter smaller than the inner diameter of the pressure vessel 1, and is supported within the vessel so as to be movable in the axial direction of the vessel. A mover 4 of the linear motor 2 is connected to one surface of the movable body 3 (the surface on the left side in FIG. 1).

[0015] The mover 4 is arranged to extend in the vessel axial direction and has a magnetic pole section 7 in which permanent magnets 6 of opposite polarity (south pole permanent magnets and north pole permanent magnets) are arranged alternately in a straight line. The magnetic pole section 7 of the mover 4 faces the cylindrical inner peripheral surface of the pressure vessel 1 via a small gap.

[0016] The stator 5 is disposed on the outer periphery of the pressure vessel 1, facing the mover 4 across the partition wall of the pressure vessel 1. The stator 5 has multiple coils (not shown in FIG. 1) arranged linearly in the vessel axial direction. In the linear motor 2, an alternating magnetic field is generated in the stator 5 by passing a current through the coils of the stator 5, which generates a magnetic attraction force or a repulsion force between the stator 5 and the permanent magnet 6 of the mover 4. This enables the linear motor 2 to drive the mover 4 and the mover 3 inside the pressure vessel 1 in the vessel axial direction.

[0017] As an example, the pressure vessel 1 and linear motor 2 described above can be applied to adjusting the position of a movable electrode within the pressure vessel 1 of a variable capacitance vacuum capacitor. In the above application, the movable electrode (not shown) of the vacuum capacitor is arranged on the other side (the right side in Figure 1) of the movable body 3 connected to the mover 4. The movable electrode is also arranged to face a fixed electrode (not shown) within the pressure vessel 1 of the vacuum capacitor. The movable electrode and fixed electrode are arranged to extend in the axial direction of the vessel with a gap in the radial direction of the vessel. By moving the movable body 3 in the axial direction of the vessel with the linear motor 2, the opposing area between the movable electrode and fixed electrode within the pressure vessel 1 changes, allowing the vacuum capacitor to obtain any desired capacitance.

[0018] Next, a configuration example of the linear motor of the first embodiment will be described with reference to Figs. 2 to 4. Fig. 2 is a longitudinal cross-sectional view of the linear motor 2 of the first embodiment. Fig. 3 is a diagram showing the structure of the stator body 10. Fig. 4 is a diagram showing a configuration example of the housing 13 of the stator 5 in the first embodiment. Note that the movable body is not shown in Fig. 2 for simplicity.

[0019] 2, the mover 4 has a flat mover yoke 8 extending in the axial direction of the container, and a magnetic pole section 7 made up of a plurality of permanent magnets 6. The magnetic pole section 7 is formed by arranging permanent magnets 6 with different polarities alternately on the mover yoke 8.

[0020] Although not particularly limited, the permanent magnet 6 of the mover 4 may be formed so that the surface facing the pressure vessel 1 in a plane perpendicular to the vessel axial direction forms an arcuate surface concentric with the inner circumferential surface of the pressure vessel 1 and convex toward the pressure vessel 1. With the above configuration, the amount of magnet occupying the space between the mover yoke 8 and the pressure vessel 1 increases, and the opposing area between the magnetic pole portion 7 and the inner circumferential surface of the pressure vessel 1 can also be increased. In addition, the gap between the surface of the magnetic pole portion 7 of the mover 4 and the inner circumferential surface of the pressure vessel 1 can be made uniform in the circumferential direction of the pressure vessel 1.

[0021] As shown in FIGS. 2 and 4, the stator 5 has a stator body 10 having a stator core 11 (iron core) and a plurality of coils 12, and a housing 13 that houses the stator body 10.

[0022] 3, the stator core 11 has a yoke portion 11a extending linearly in the axial direction of the container, and multiple teeth 11b branching from the yoke portion 11a and extending radially of the container. The teeth 11b are an example of salient poles of the stator core 11.

[0023] The multiple teeth 11b all have the same shape and are arranged in a comb-like shape at regular intervals in the vessel axial direction. As shown in Fig. 2, the tips of the teeth 11b are arranged to face the outer circumferential surface of the pressure vessel 1. In the stator core 11, spaces (slots) for winding the coils 12 are formed between adjacent teeth 11b and yoke portions 11a.

[0024] Although not particularly limited, in a plane perpendicular to the container axial direction, the width of the teeth 11b of the stator core 11 (the length in the direction perpendicular to both the container axial direction and the container radial direction) may be equal to or greater than the width of the magnetic pole portion 7 of the mover 4. If the width of the teeth 11b is made longer than the width of the magnetic pole portion 7, the interlinkage magnetic flux between the stator body 10 and the mover 4 increases and leakage magnetic flux is suppressed, thereby further improving the electromagnetic force of the linear motor 2.

[0025] Furthermore, the tips of the teeth 11b of the stator core 11 may be concentric with the outer peripheral surface of the pressure vessel 1 in a plane perpendicular to the vessel axial direction, and may have a shape that is concave toward the pressure vessel 1. By forming a concave portion at the tips of the teeth 11b, the opposing area between the tips of the teeth 11b and the outer peripheral surface of the pressure vessel 1 can be increased, and the gap between the tips of the teeth 11b and the outer peripheral surface of the pressure vessel 1 can also be made uniform in the circumferential direction of the pressure vessel 1.

[0026] In addition, insulators 14 made of an insulating material such as resin are disposed in the slots of the stator core 11 to insulate the stator core 11 from the coils 12. The insulators 13 have a cylindrical portion that covers the yoke portion 11a of the slot from the outside and a pair of flange portions formed on both ends of the cylindrical portion. Each flange portion protrudes annularly from the outer periphery of the cylindrical portion and is disposed in the slot so as to abut against the teeth portion 11b. The insulators 14 may be attached to the stator core 11 by joining half-pieces separated along the container axial direction, or may be provided integrally with the stator core 11 by insert molding.

[0027] Each coil 12 of the stator 5 is wound around a yoke portion 11a of the stator core 11 via an insulator 14 so as to form a ring shape in the axial direction of the container. The stator core 11, the insulator 14, and the coil 12 form a stator body 10.

[0028] Here, focusing on the surface of the stator body 10 facing the mover 4, in the stator body 10 of this embodiment, the coil 12 is wound around the stator core 11, also using the space on the surface opposite to the surface facing the mover 4. Therefore, compared to a configuration in which the coil is wound around the teeth portion 11b, the stator body 10 of this embodiment allows the same amount of coil 12 to be wound with half the slot cross-sectional area in the container axial direction. In other words, in this embodiment, the coil pitch in the container axial direction of the stator body 10 can be reduced, and the magnetic pole pitch of the opposing mover 4 can also be reduced to match the stator body 10, thereby reducing the size of the mover 4 in the container axial direction. When the size of the mover 4 in the container axial direction is reduced, the weight of the mover 4 can be reduced by reducing the number of magnets and yokes, thereby further improving the thrust density of the motor.

[0029] 2, the housing 13 is formed in a box shape with a space inside that can accommodate the stator body 10, and is attached to the outer periphery of the pressure vessel 1. The housing 13 has a top surface 21 that extends in the vessel axial direction and the housing width direction (directions perpendicular to both the vessel axial direction and the vessel radial direction), and peripheral wall portions 22a and 22b that extend from the top surface 21 toward the pressure vessel 1.

[0030] A pair of first peripheral wall portions 22a facing each other in the axial direction of the housing 13 are disposed at an interval corresponding to the axial length of the stator body 10. Grooves 23 each having a shape corresponding to the tooth portion 11b are formed along the radial direction of the housing on the inner surface of the housing of the first peripheral wall portions 22a.

[0031] The stator body 10 is inserted into the housing 13 along the grooves in the first circumferential wall 22a, and the teeth 11b located at the ends of the stator body 10 are fitted into the grooves 23 in the first circumferential wall 22a to be fixed. The teeth 11b of the stator body 10 may also be fixed to the first circumferential wall 22a by screws or the like. As a result, the stator body 10, which is sandwiched between the first circumferential wall 22a, is positioned in the container axial direction and supported within the housing 13. The first circumferential wall 22a that supports the stator body 10 has the function of receiving, from the stator body 10, a reaction force of an electromagnetic force acting in the container axial direction.

[0032] In the housing 13, a pair of second peripheral wall portions 22b facing each other in the housing width direction are disposed at a distance greater than the width direction of the stator body 10. An opening 24 that communicates with the outside of the housing 13 is formed in each of the second peripheral wall portions 22b. In the housing 13, a fan 25 that generates an air flow within the housing 13 is disposed in the opening 24 of one of the second peripheral wall portions 22b. The opening 24 and the fan 25 are an example of a cooling portion.

[0033] When the fan 25 in the stator 5 rotates, an air flow is generated inside the housing 13 from the opening 24 in one second peripheral wall portion 22b toward the opening 24 in the other second peripheral wall portion 22b. The air flow passes through the gaps between the coils 12 adjacent in the container axial direction and around the outer periphery of the coils 12, causing heat exchange between the coils 12 and the air inside the housing 13, thereby air-cooling the coils 12. Note that the fan 25 may be omitted if air flow can be ensured inside the housing 13.

[0034] In the stator body 10 of this embodiment, the coils 12 are wound around the yoke portion 11a in a ring shape in the axial direction of the container, and the coils 12 are arranged at regular intervals in the axial direction of the container. Therefore, in the stator body 10 of this embodiment, a large surface area in the housing 13 can be secured for the coils 12 to come into contact with the air.

[0035] As described above, in the stator body 10 of the first embodiment, the coil 12 is wound around the yoke portion 11a in a ring shape in the axial direction of the container, and the coil 12 is wound around the stator core 11 using the space on the surface opposite to the opposing surface of the mover 4. Therefore, by reducing the coil pitch in the axial direction of the container and reducing the weight of the mover 4, it is possible to further improve the thrust density of the motor. Furthermore, in the stator body 10 of the first embodiment, the gaps between adjacent coils 12 in the container axial direction are utilized to ensure a large surface area for heat exchange with the coils 12, thereby enabling the coils 12 to be cooled efficiently.

[0036] (Second embodiment) 5 is a diagram showing a configuration example of a housing 13A of a stator 5 in the second embodiment. In the following description of each embodiment, elements common to the first embodiment are denoted by the same reference numerals, and duplicated description will be omitted as appropriate.

[0037] The second embodiment is a modified example of the first embodiment, and is a configuration example in which the coil 12 of the stator body 10 is oil-cooled without providing the opening 24 and the fan 25 in the second peripheral wall portion 22b. The configurations of the pressure vessel 1, the mover 4, and the stator body 10 in the second embodiment are the same as those in the first embodiment.

[0038] The housing 13A is formed in a box shape with a space inside that can accommodate the stator body 10, and is attached to the outer periphery of the pressure vessel 1. The housing 13A has a top surface 21 (not shown in FIG. 5) that extends in the vessel axial direction and the housing width direction, and peripheral wall portions 22a, 22b that extend from the top surface 21 toward the pressure vessel. The bottom surface of the housing 13A that faces the pressure vessel 1 is liquid-tightly sealed over the entire surface by an oil sealing plate (not shown). Note that the housing 13A may be sealed by the partition wall of the pressure vessel 1, and the oil sealing plate may be omitted.

[0039] In the housing 13A, a pair of first peripheral wall portions 22a facing each other in the container axial direction are the same as those in the first embodiment. The peripheral wall portions of the housing 13A are also formed with an inlet port 31 for introducing cooling oil into the housing and an outlet port 32 for discharging the cooling oil from the housing 13A. The inlet port 31 and the outlet port 32 are each connected to an oil pump (not shown) that circulates the cooling oil via an oil cooler (not shown). The cooling oil circulation mechanism including the inlet port 31 and the outlet port 32 is an example of a cooling unit.

[0040] In the above-described casing 13A, cooling oil is supplied into the casing from inlet port 31 by driving an oil pump. The cooling oil passes through the gaps between coils 12 adjacent to each other in the axial direction of the container and around the outer periphery of coil 12 to remove heat from coil 12, and the cooling oil that has absorbed the heat from coil 12 is discharged from outlet port 32. In this way, coil 12 in casing 13A is oil-cooled. As in the first embodiment, the stator body 10 of the second embodiment has a shape that ensures a large surface area within casing 13A where coil 12 comes into contact with cooling oil, and therefore coil 12 can be efficiently oil-cooled.

[0041] 5, an inlet port 31 is formed in one of the second peripheral wall portions 22b, and an outlet port 32 is formed in the other of the second peripheral wall portions 22b. By arranging the inlet port 31 and the outlet port 32 across the stator body 10, a flow of cooling oil passes through the stator body 10 in the width direction of the casing 13A, facilitating heat exchange between the coil 12 and the cooling oil. Note that the positions of the inlet port 31 and the outlet port 32 in the casing 13A are not limited to the arrangement shown in FIG. 5 and can be changed as appropriate. As described above, the configuration of the second embodiment can also provide the same effects as the first embodiment.

[0042] (Third embodiment) 6 is a diagram showing a configuration example of the housing 13B of the stator 5 in the third embodiment. The third embodiment is a modification of the first embodiment, and is a configuration example in which the coil 12 of the stator body 10 is water-cooled via the housing 13B. The configurations of the pressure vessel 1, the mover 4, and the stator body 10 in the third embodiment are the same as those in the first embodiment.

[0043] The housing 13B is formed in a box shape with a space inside that can accommodate the stator body 10, and is attached to the outer periphery of the pressure vessel 1. The housing 13A has a top surface 21 that extends in the vessel axial direction and the housing width direction, and peripheral wall portions 22a and 22b that extend from the top surface 21 toward the pressure vessel 1.

[0044] In the housing 13B, a pair of first peripheral wall portions 22a facing each other in the axial direction of the housing are the same as those in the first embodiment. Furthermore, a plurality of protrusions 41 protruding toward the inner surface of the housing are formed on the top surface 21 of the housing 13B. Each of the protrusions 41 extends in the width direction of the housing (the depth direction of the paper in FIG. 6 ) and is arranged in a comb-like pattern at regular intervals in the axial direction of the housing. The length of the protrusions 41 in the axial direction of the housing corresponds to the gap between adjacent coils 12 in the stator body 10, and the gap between adjacent protrusions 41 corresponds to the length of the coils 12 in the axial direction of the housing. This allows the protrusions 41 of the housing 13B to be inserted into the gaps between the coils 12 of the stator body 10 when the stator body 10 is placed in the housing 13B.

[0045] Additionally, cooling pipes 42 that are thermally connected to the top surface 21 and the protrusions 42 and that circulate cooling water (refrigerant) are arranged on the top surface 21 of the housing 13B. The top surface 21 and the protrusions 41 of the housing 13B that face the coils 12 of the stator body 10 are cooled by the cooling water flowing through the cooling pipes 42. Therefore, the coils 12 are cooled by the cooling water in the cooling pipes 42 via the protrusions 41 of the housing 13B. The stator body 10 of the third embodiment has a large surface area for heat exchange between the coils 12 and the protrusions 41, and therefore can efficiently cool the coils 12. As described above, the configuration of the third embodiment can also provide the same effects as those of the first embodiment.

[0046] The present invention is not limited to the above-described embodiment, and various improvements and design changes may be made without departing from the spirit of the present invention.

[0047] For example, in the above embodiment, a variable capacitance vacuum capacitor has been described as an example of the application of the pressure vessel and linear motor. However, the pressure vessel and linear motor of the above embodiment are not limited to the application of a variable capacitance vacuum capacitor, and may be implemented in other devices configured to move a movable body within a pressure vessel. Furthermore, the shape of the movable body and the attachment position of the mover relative to the movable body may be changed as appropriate depending on the type of device, etc.

[0048] In the stator 5 of the above embodiment, an example has been described in which the teeth 11b are fitted into the grooves 23 of the housing. However, the stator body 10 may be fixed to the housing by, for example, shrink fitting, or may be fixed by interference fitting without providing a groove in the housing.

[0049] Furthermore, the embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0050] DESCRIPTION OF SYMBOLS 1...pressure vessel, 2...linear motor, 3...moving body, 4...moving piece, 5...stator, 6...permanent magnet, 7...magnetic pole portion, 8...moving piece yoke, 10...stator body, 11...stator core, 11a...yoke portion, 11b...teeth portion, 12...coil, 13, 13A, 13B...housing, 14...insulator, 21...top surface portion, 22a...first peripheral wall portion, 22b...second peripheral wall portion, 23...groove, 24...opening, 25...fan, 31...inlet port, 32...exhaust port, 41...projection portion, 42...cooling pipe

Claims

1. A linear motor that drives a movable body in a pressure vessel, a movable element disposed inside the pressure vessel, connected to the movable body, and movable in the vessel axial direction of the pressure vessel; a stator disposed outside the pressure vessel and facing the mover across the pressure vessel, the stator includes a stator body including a plurality of coils and an iron core, and a housing that accommodates the stator body and supports the stator body on both sides in the container axial direction, the iron core includes a salient pole portion that protrudes toward the mover, and a yoke portion that extends in the vessel axial direction and has a plurality of the salient pole portions formed at predetermined intervals in the vessel radial direction of the pressure vessel, the coils generate magnetic flux that drives the mover, and are wound around the yoke portions so as to form an annular shape in the axial direction of the container; The housing has a cooling section that cools the coils through a gap formed between the coils adjacent to each other in the axial direction of the container. Linear motor.

2. The cooling unit supplies cooling air to the gap between the coils to cool the coils.

2. The linear motor according to claim 1.

3. The cooling unit supplies cooling oil to the gap between the coils to cool the coils.

2. The linear motor according to claim 1.

4. the housing has a protrusion on an inner surface thereof that is inserted into the gap between the coils, the cooling unit is thermally connected to the protrusion and has a cooling pipe for circulating a refrigerant; The cooling unit cools the coil with the refrigerant via the protrusion.

2. The linear motor according to claim 1.

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