JP7485588B2 - Injection Unit - Google Patents

Description

The present invention relates to an injection device.

At the International Space Station, activities are being carried out to release small satellites with various functions (Non-Patent Document 1). In these activities, the small artificial satellite is transported from the ground by a supply ship to the experimental module "Kibo" installed on the International Space Station, where it is grasped by a robotic arm and moved into space through the airlock. The small artificial satellite is then released into space by a spring mechanism installed on the robotic arm.

However, the spring mechanism limits the speed at which the object can be ejected, and one possible method to overcome this limitation is to use a coil gun (Non-Patent Documents 2-4).

"JEM Payload Accommodation Handbook -Vol.8- Microsatellite Release Interface Management Specification Rev.C", December 2017, Japan Aerospace Exploration Agency, retrieved December 5, 2018, URL: http://iss.jaxa.jp/kiboexp/equipment/ef/jssod/images/jx-espc-110132-c.pdf Zou Bengu, et. al., “Magnetic-Structural Coupling Analysis of Armature in Induction Coilgun”, January 2011, IEEE Transaction on Plasma Science, Volume 39, Issue 1, pp.65-70 Tao Zhang, et.al., “Design and Evaluation of the Driving Coil on Induction Coilgun”, May 2015, IEEE Transaction on Plasma Science, Volume 43, Issue 5, pp.1203-1207 Polzin, Kurt A., et.al., “Coilgun Acceleration Model Containing Multiple Interacting Coils”, January 2019, NASA Technical Reports, M18-7139

A coilgun accelerates conductive objects by passing a time-varying current through a coil to generate a magnetic field. For this reason, it is desirable to generate a magnetic field that is as strong as possible. However, there are restrictions on the current that can be passed through the coil, which limits the magnetic field that can be generated by the coil, making it difficult to efficiently accelerate objects by increasing the amount of current.

As shown in Non-Patent Documents 2 to 4, the speed of an object can be increased by arranging multiple coils in the direction of the object's emission and accelerating the object in multiple stages. However, since the object passes through coils located close to the emission port at high speed, it is necessary to make the current rise as fast as possible. This requires that the inductance of the coils be made small, which results in a smaller acceleration being applied to the object.

The present invention was made in consideration of the above circumstances, and aims to provide an ejection device that can efficiently accelerate an object to be ejected.

Other objects and novel features will become apparent from the description of this specification and the accompanying drawings.

The injection device according to one embodiment has an outer coil having an annular shape with the injection direction of the object as its central axis, in which a current flows in a first circumferential direction, and an inner short-circuit coil having an outer surface and an inner surface surrounding the central axis, and accelerating the object with a magnetic field generated by an induced current flowing through the inner surface due to a magnetic field generated by the current flowing through the outer coil, a gap is provided around the circumference of the annular shape of the inner short-circuit coil, the outer surface and the inner surface of the inner short-circuit coil are connected by two ends of the annular shape separated by the gap, and the induced current flows from the outer surface through one of the ends into the inner surface, flows through the inner surface in a second circumferential direction, and flows from the inner surface to the outer surface through the other end.

The present invention provides an ejection device that can efficiently accelerate an object to be ejected.

1 is a diagram illustrating a schematic configuration of an injection system including an injection device according to a first embodiment. FIG. FIG. 1 is a diagram showing an example in which the launch system is mounted on a satellite. FIG. 1 is a diagram illustrating a basic configuration of an injection device according to a first embodiment. FIG. 1 is a diagram showing a schematic diagram of acceleration of an object in a repulsive coilgun. FIG. 2 is a diagram showing a schematic diagram of acceleration of an object in a suction-type coilgun. FIG. 2 is a diagram showing a schematic diagram of acceleration of an object in a suction-type coilgun. FIG. 2 is a perspective view of a coil according to the first embodiment; 2 is a front view of the coil according to the first embodiment as viewed from the +Z side. FIG. 2 is a diagram showing a schematic YZ cross-sectional configuration of the coil according to the first embodiment; FIG. FIG. 11 is a perspective view of a coil according to a second embodiment. FIG. 11 is a front view of the coil according to the second embodiment as viewed from the +Z side. FIG. 11 is a diagram showing a schematic YZ cross-sectional configuration of a coil according to a second embodiment. FIG. 13 is a diagram showing a schematic YZ cross-sectional configuration of a coil according to a third embodiment. FIG. 13 is a perspective view of a coil according to a third embodiment. FIG. 11 is a front view of the coil according to the third embodiment as viewed from the +Z side. FIG. 13 is a diagram showing a schematic YZ cross-sectional configuration of a coil according to a third embodiment. FIG. 13 is a diagram showing a schematic XY cross-sectional configuration of a coil according to a third embodiment.

Specific embodiments will be described in detail below with reference to the drawings. However, the present invention is not limited to the following embodiments. In addition, the following description and drawings have been simplified as appropriate to clarify the explanation. In addition, the same elements are given the same reference numerals, and duplicate explanations will be omitted.

First embodiment
An object injection device according to the embodiment 1 will be described. Fig. 1 shows a schematic configuration of an injection system 1000 including an injection device 100 according to the embodiment 1. The injection system 1000 has the injection device 100, a power supply device 110, and a control device 120.

The ejection system 1000 supplies current to the ejection device 100, which is configured as a so-called coil gun, and accelerates and ejects the ejection target by the force generated at that time. The operating principle of the coil gun is described in, for example, Non-Patent Documents 2 to 4. The power supply device 110 is connected to the ejection device 100 and is configured to be able to supply current to the ejection device 100.

The control device 120 is composed of, for example, a computer, and can control the operation of the power supply device 110 by providing a control signal CON. For example, the control device 120 can control the timing and waveform of the current that the power supply device 110 supplies to the injection device 100, the current value of the current, etc. This allows the control device 120 to control the timing at which the injection device 100 ejects the injection object and the injection speed of the injection object.

The launch system 1000 can be mounted on, for example, a satellite. FIG. 2 shows an example of the launch system being mounted on a satellite. In this example, as shown in FIG. 2, a launch system 1001 in which a shock absorbing device 140 is added to the launch system 1000 is mounted on the satellite SAT. The power supply device 110 may be a power source for the satellite SAT. The power supply device 110 may also be coupled to a power supply system of the satellite SAT and may be charged by a solar cell 130 or the like provided on the satellite SAT. The control device 120 may be included in a control device for the satellite SAT, or may be provided as a control device separate from the control device for the satellite SAT.

The shock absorbing device 140 is a device that reduces the shock when the object 1 is ejected from the ejection device 100. The shock absorbing device 140 may be a mechanism that combines shock absorbers, or may be a device that ejects gas in the opposite direction to the ejection direction of the object 1.

The launch system 1001 can launch an object stored in the artificial satellite SAT into space. For example, multiple small artificial satellites can be stored in the artificial satellite SAT in advance, and the artificial satellite (object 1) can be launched in a specified direction at a specified speed as needed.

Next, the basic configuration and operation of the injection device 100 will be described. Figure 3 shows a schematic diagram of the basic configuration of the injection device 100 according to the first embodiment. In Figure 3, the positive direction of the Z axis parallel to the horizontal direction of the paper (to the right of the paper, also referred to as the first direction) is the injection direction D of the object. The direction perpendicular to the Z direction on the paper is the Y direction (also referred to as the third direction), and the direction perpendicular to the Y and Z directions is the X direction (also referred to as the second direction).

The object injection device 100 has a configuration in which multiple coils are arranged in the object injection direction D. In this example, three coils 10 are arranged side by side at equal intervals of pitch P, with the injection direction D as the central axis. An accelerated object 2 is inserted into an acceleration space 3 that passes through the hollow parts of the three coils 10 in the injection direction D. The accelerated object 2 is made of a magnetic material and functions as a striker that pushes out the object 1, which is the object to be injected.

Although not shown, the coil 10 may be placed inside a cylindrical member with a central axis in the Z direction, for example. The cylindrical member may have various shapes, such as a circle, an ellipse, or a polygon including a rectangle, as long as it can hold the coil 10. The end of the cylindrical member on the side of the emission direction D may be open or closed. The cylindrical member may also be provided with holes or the like to reduce weight. The coil 10 may also be held by a member of any shape other than a cylindrical member.

The accelerated body 2, which is made of a magnetic material, is accelerated in the ejection direction D in response to the magnetic field that is generated when a current is passed through the coil 10. The ejection device 100 is configured as an attraction-type coil gun that accelerates the accelerated body 2 by the electromagnetic force that acts on the accelerated body 2 when a current is passed through the coil 10, and ejects the object 1 held by the accelerated body 2.

Next, the principle of object ejection in a coilgun will be explained. It is generally known that coilguns can be configured as repulsive coilguns that eject objects using the repulsive force of electromagnetic force, or as suction coilguns that eject objects using the suction force of electromagnetic force.

The principle of ejection of a repulsive coilgun is explained. Figure 4 shows the acceleration of an object in a repulsive coilgun. As shown in Figure 4, when the accelerated object 2 is located on the side of the coil C in the ejection direction D (Z direction), a magnetic field B is generated along the ejection direction D when a current (e.g., a pulse current) Ip is passed through the coil C. Figure 4 shows an example in which the current Ip flows counterclockwise through the coil when viewed from the +Z side. As a result, an eddy current EC that flows clockwise is generated on the bottom surface (-Z side surface) of the accelerated object 2, and a repulsive force F due to the eddy current EC acts on the accelerated object 2 made of a conductor, and the accelerated object 2 moves toward the ejection direction D. With the action of the repulsive force in this way, the object 1 attached to the accelerated object 2 is ejected in the ejection direction D.

Next, the principle of ejection of the attraction type coil gun will be explained. Figure 5 shows the acceleration of an object in an attraction type coil gun. When the accelerated object 2 is located on the opposite side of the ejection direction D (+Z direction) with respect to the coil C (the -Z side in Figure 5, i.e. the left side), and a current (for example, a pulse current) Ip is passed through the coil C, a magnetic field B is generated along the ejection direction D. As a result, as shown in Figure 5, a magnetic force F acts on the accelerated object 2, and the accelerated object 2 made of a magnetic material is accelerated by being attracted toward the coil C. Then, as shown in Figure 6, when the energization of the coil C is stopped at the point when the accelerated object 2 reaches the coil C, the magnetic field B disappears, and the magnetic force F acting on the accelerated object 2 also disappears. Therefore, as shown in Figure 6, the object 1 attached to the accelerated object 2 continues to move in the ejection direction D (Z direction) by inertia and is ejected.

As explained above, in a coilgun, an object is accelerated using the force generated by electromagnetic force, so in order to rapidly accelerate an object, it is desirable to generate a magnetic field B that is as strong as possible. Therefore, the coil in this embodiment has a configuration that can strengthen the magnetic field generated by passing a current through it.

The configuration of the coil 10 according to this embodiment will be described below. Fig. 7 is a perspective view of the coil 10 according to the first embodiment, Fig. 8 is a front view of the coil 10 according to the first embodiment as viewed from the +Z side, and Fig. 9 is a schematic diagram showing the Y-Z cross-sectional configuration of the coil 10 taken along line IX-IX in Fig. 8. The coil 10 is composed of an outer coil 11 and an inner short-circuited coil 12.

The outer coil 11 is configured as a cylindrical coil in the shape of a closed ring with a central axis in the direction of injection (Z direction) and with current flowing in one direction. In this example, current I1 flows clockwise in the outer coil 11 when viewed from the +Z side. It is preferable that the outer coil 11 be configured as a coil with multiple turns in order to strengthen the induced magnetic field generated by the flowing current I1.

The inner short-circuit coil 12 is configured as a single-turn cylindrical coil having an open ring cross-sectional shape with the injection direction (Z direction) as the central axis. In this example, the inner short-circuit coil 12 has a gap 12A that penetrates from the central axis to the outer periphery on the +X side of the inner short-circuit coil 12, and this gap 12A gives the inner short-circuit coil 12 an open ring shape, in other words a shape that resembles the letter C.

The outer coil 11 and the inner short-circuit coil 12 are arranged so as to be electrically insulated. In other words, the outer coil 11 and the inner short-circuit coil 12 are arranged so as to be spatially separated. In addition, an insulating material that insulates the outer coil 11 and the inner short-circuit coil 12 from each other may be inserted or filled between them.

Next, the current flowing through the coil 10 and the induced magnetic field will be described. If the number of turns of the outer coil 11 is N (N is an integer equal to or greater than 2) and the current supplied to the outer coil 11 is I, then a clockwise current I1=N×I flows through the outer coil 11, and a counterclockwise current I2, which is the opposite direction to the current I1, flows through the cylindrical outer surface 12B of the inner short-circuited coil 12 due to electromagnetic induction. In this configuration, by making the outer coil 11 an N-turn coil, the inductance of the inner short-circuited coil 12 as viewed from the power source side that supplies current to the outer coil 11 becomes ^N2 times, and it becomes possible to more efficiently inject energy supplied from the power source side into the inner short-circuited coil 12.

The current I2 flowing through the outer surface 12B of the inner short-circuit coil 12 flows through the lower surface 12D (also called the first end) of the gap 12A into the cylindrical inner surface 12C of the inner short-circuit coil 12 and flows clockwise around the inner surface 12C. Then, the current I2 reaches the outer surface 12B of the inner short-circuit coil 12 through the upper surface 12E (also called the second end) of the gap 12A and flows counterclockwise around the outer surface 12B.

In this configuration, the inner short-circuit coil 12 with one turn is inserted inside the outer coil 11 with multiple turns, so that the induced magnetic field generated by the outer coil 11 is suitably coupled to the inner short-circuit coil 12. Therefore, the amount of current I2 flowing through the inner short-circuit coil 12 by electromagnetic induction can be increased.

In order to efficiently accelerate the accelerated body 2, it is preferable that the induced magnetic field caused by the current I1 flowing through the outer coil 11 couples as efficiently as possible with the inner short-circuited coil 12. Therefore, it is preferable that the inner surface 11A of the outer coil 11 and the outer surface 12B of the inner short-circuited coil 12 are as close as possible to each other. In addition, it is preferable that the dimension of the inner short-circuited coil 12 in the emission direction (Z direction) is the same as or as close as possible to the dimension of the outer coil 11 in the emission direction (Z direction), as shown in FIG. 9.

The current I2 flows in a circular manner in the small-diameter acceleration space 3 surrounded by the inner surface 12C of the inner short-circuited coil 12. If the inner diameter of the outer coil 11 is a and the inner diameter of the inner short-circuited coil 12 is b (i.e., b<a), it is possible to make the strength of the magnetic field generated in the acceleration space 3 ^twice as strong (a/b) as in the case where the inner short-circuited coil 12 is not provided.

Therefore, with this configuration, a strong magnetic field can be induced in the acceleration space 3, thereby efficiently accelerating the accelerated object 2.

Embodiment 2
A description will be given of an injection device according to embodiment 2. The injection device according to embodiment 2 has a configuration in which the coil 10 of the injection device 100 according to embodiment 1 is replaced with a coil 20.

The coil 20 will be described below. Fig. 10 is a perspective view of the coil 20 according to the second embodiment, Fig. 11 is a front view of the coil 20 according to the second embodiment as viewed from the +Z side, and Fig. 12 shows a schematic Y-Z cross-sectional configuration of the coil 20 taken along line XII-XII in Fig. 11. The coil 20 is composed of an outer coil 21 and an inner short-circuited coil 22.

The outer coil 21 is similar to the outer coil 11, so its description is omitted.

The inner short-circuit coil 22 is configured as a single-turn cylindrical coil having an open ring cross-sectional shape with the emission direction (Z direction) as the central axis, similar to the inner short-circuit coil 12 according to the first embodiment. In this example, the inner short-circuit coil 22 has a gap 22A that penetrates from the central axis to the outer periphery on the +X side of the inner short-circuit coil 22, and this gap 22A gives the inner short-circuit coil 22 an open ring shape. Also, similar to the inner short-circuit coil 12, the outer surface 22B and the inner surface 22C of the inner short-circuit coil 22 are connected by surfaces 22D and 22E (i.e., the first end and the second end) that face each other across the gap 22A.

Unlike the inner short-circuit coil 12, the inner short-circuit coil 22 is configured so that the dimension in the emission direction (Z direction) becomes smaller near the central axis. As shown in FIG. 12, the inner short-circuit coil 22 has a tapered shape in which the dimension in the emission direction (Z direction) becomes continuously smaller from the outer surface 22B to the inner surface 22C in the Y-Z cross section. In this example, the dimension in the emission direction (Z direction) of the inner short-circuit coil 22 at the outer surface 22B is d, and the dimension in the emission direction (Z direction) of the inner short-circuit coil 22 at the inner surface 22C is c (c<d).

As described above, according to this configuration, the dimension of the center of the inner short-circuit coil 22 in the emission direction (Z direction) is made smaller than the dimension at the outer surface, so that the density of the current I2 flowing at the inner surface of the center can be increased. This increases the strength of the electric field generated by the inner short-circuit coil 22, and accelerates the accelerated body 2 more efficiently.

Embodiment 3
A description will be given of an injection device according to embodiment 3. The injection device according to embodiment 3 has a configuration in which the coil 20 of the injection device according to embodiment 2 is replaced with a coil 30.

The coil 30 will now be described. Figure 13 shows a schematic Y-Z cross-sectional configuration of the coil 30 according to the third embodiment. The coil 30 is composed of an outer coil 31 and an inner short-circuit coil 32.

The inner short-circuit coil 32 of the coil 30 is similar to the inner short-circuit coil 22 of the coil 20, so a description thereof will be omitted. In other words, the outer surface 32B and the inner surface 32C of the inner short-circuit coil 32 are connected by two opposing surfaces (i.e., a first end and a second end) that are spaced apart.

The outer coil 31 of the coil 30 is constructed by winding an insulating material, such as a resin-coated electric wire 31B, N times around the inner short-circuit coil 32 as a winding frame. In FIG. 13, the outer coil 31 is shown as a single-layer coil wound so that the electric wire 31B is aligned in the injection direction (Z direction), but it may be constructed as a multi-layer coil.

As described above, according to this configuration, the outer coil 31 can be brought into close contact with the inner short-circuit coil 32, so that the induced magnetic field by the outer coil 31 can be more efficiently coupled to the inner short-circuit coil 32, and if the current flowing through the outer coil 31 is I3, a current of N x I3 can be induced in the inner short-circuit coil 32. In addition, the coating material of the electric wire 31B that constitutes the outer coil 31 makes it possible to easily insulate the outer coil 31 from the inner short-circuit coil 32.

In addition, by inducing a strong magnetic field in the acceleration space 3, the accelerated body 2 can be accelerated efficiently, and an injection device that can be manufactured relatively easily can be realized.

Fourth embodiment
A description will be given of an injection device according to embodiment 4. The injection device according to embodiment 3 has a configuration in which the coil 20 of the injection device according to embodiment 2 is replaced with a coil 40.

The coil 40 will be described below. Fig. 14 is a perspective view of the inner short-circuited coil 42 of the coil 40 according to the fourth embodiment, Fig. 15 is a front view of the coil 40 according to the fourth embodiment as viewed from the +Z side, Fig. 16 is a schematic diagram showing the Y-Z cross-sectional configuration of the coil 40 taken along line XVI-XVI in Fig. 15, and Fig. 17 is a schematic diagram showing the Y-Z cross-sectional configuration of the coil 40 taken along line XVII-XVII in Fig. 15. The coil 40 is a modified example of the coil 20, and is composed of an outer coil 41 and an inner short-circuited coil 42.

The outer coil 41 is similar to the outer coil 21, so its description is omitted.

The inner short-circuit coil 42, like the inner short-circuit coil 22, is configured as a single-turn cylindrical coil having an open ring cross-sectional shape with the injection direction (Z direction) as the central axis. In this example, the inner short-circuit coil 42 has a gap 42A that penetrates from the central axis to the outer periphery on the X+ side of the inner short-circuit coil 42, and this gap 42A gives the inner short-circuit coil 42 an open ring shape.

However, unlike the inner short-circuit coil 22, the inner short-circuit coil 42 has an inner annular portion 421 surrounding the acceleration space 3 and an outer annular portion 422 surrounding the inner annular portion 421, and a hollow portion 425 exists between the inner annular portion 421 and the outer annular portion 422. Therefore, the outer surface of the outer annular portion 422 becomes the outer surface 42B of the inner short-circuit coil 42, and the inner surface of the inner annular portion 421 becomes the inner surface 42C of the inner short-circuit coil 42. The inner annular portion 421 (inner surface 42C) and the outer annular portion 422 (outer surface 42B) are connected by a bridge portion 423 provided below the gap 42A and a bridge portion 424 provided above it.

Next, the current flowing through the coil 40 and the induced magnetic field will be described. If the number of turns of the outer coil 41 is N (N is an integer equal to or greater than 2) and the current supplied to the outer coil 41 is I, then a clockwise current I1=N×I flows through the outer coil 41, and a counterclockwise current I2, which is opposite to the current I1, flows through the outer annular portion 422 due to electromagnetic induction. In this configuration, as with the outer coil 11 according to the first embodiment, the outer coil 41 is an N-turn coil, so that the inductance of the inner short-circuited coil 42 as viewed from the power supply side that supplies current to the outer coil 41 becomes ^N2 times, and it becomes possible to more efficiently inject energy supplied from the power supply side into the inner short-circuited coil 42.

The current I2 flowing in the outer annular portion 422 of the inner short-circuited coil 42 flows into the inner annular portion 421 through the lower surface 42D (i.e., the first end) of the gap 42A and flows in a clockwise direction through the outer annular portion 422. The current I2 then reaches the outer annular portion 422 through the upper surface 42E (i.e., the second end) of the gap 42A and flows in a counterclockwise direction through the outer annular portion 422.

As described above, with this configuration, it is possible to pass a current in the same manner as the coil 20 according to the second embodiment. In addition, by providing a hollow portion 425 in the inner short-circuit coil 42, it is possible to make the inner short-circuit coil 42 lighter than the inner short-circuit coil 22.

Other embodiments The present invention is not limited to the above-mentioned embodiments, and can be modified as appropriate without departing from the spirit of the present invention. For example, in the above-mentioned embodiments, the outer coil and the inner short-circuited coil are described as being cylindrical coils, but as long as they can accelerate an object, they may be coils of any cylindrical shape other than a cylinder.

Although the inner short-circuit coil has been described as having one gap, the inner short-circuit coil may have two or more gaps as long as current can flow in the same direction on the outer and inner surfaces of the inner short-circuit coil.

In FIG. 3, an example in which three coils are arranged in the injection device is described, but this is merely an example. Only one coil may be arranged in the injection device, or two or four or more coils may be arranged.

In the injection devices according to the first and fourth embodiments, the outer coil may be configured similarly to the outer coil 31 according to the third embodiment.

REFERENCE SIGNS LIST 1 object 2 accelerated body 3 acceleration space 10, 20, 30, 40 coil 11, 21, 31, 41 outer coil 11A inner surface 12, 22, 32, 42 inner short-circuited coil 12A, 22A, 42A gap 12B, 22B, 32B, 42B outer surface 12C, 22C, 32C, 42C inner surface 31B electric wire 12D, 12E, 22D, 22E, 42D, 42E surface 100 ejection device 110 power supply device 120 control device 130 solar cell 140 shock absorbing device 421 inner annular portion 422 outer annular portion 423, 424 bridge portion 425 hollow portion 1000 ejection system 1001 ejection system C coil CON control signal SAT artificial satellite

Claims (4)

an outer coil having an annular shape with a central axis in the direction in which the object is emitted, in which a current flows in a first rotational direction around the central axis;
an inner short-circuited coil having an annular shape with an outer surface facing the outer coil and an inner surface surrounding the central axis, the inner short-circuited coil accelerating the object by a magnetic field generated when an induced current flows through the inner surface in response to a magnetic field generated by the current flowing through the outer coil;
a gap is provided on a circumference of the annular shape of the inner short-circuited coil, and the outer surface and the inner surface of the inner short-circuited coil are connected by a first end and a second end of the annular shape that are spaced apart by the gap,
the induced current flows from the outer surface through the first end to the inner surface, flows around the inner surface in a second orbital direction opposite to the first orbital direction, and flows from the inner surface through the second end to the outer surface;
The inner short-circuit coil has a C-shape,
an outer annular portion having the outer surface;
an inner annular portion having the inner surface and disposed closer to the central axis than the outer annular portion;
a first bridge portion connecting the outer surface and the inner surface, the first end of the first bridge portion being a surface facing the gap;
a second bridge portion connecting the outer surface and the inner surface, the second bridge portion having a surface facing the gap as the second end portion;
Injection device. a dimension of the inner short-circuited coil in the direction of the central axis at the inner surface is smaller than a dimension of the inner short-circuited coil in the direction of the central axis at the outer surface;
The injection device according to claim 1 . a dimension of the inner short-circuited coil in a direction of the central axis becomes continuously smaller from the outer surface to the inner surface;
3. The injection device according to claim 2 . The outer coil is configured by winding an electric wire covered with an insulating material around the outer periphery of the inner short-circuit coil.
An injection device according to any one of claims 1 to 3 .

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