HK1069006B - Superconducting magnet apparatus - Google Patents

Description

Superconducting magnet device

Technical Field

The present invention relates to a superconducting magnet apparatus, and more particularly, to a superconducting magnet apparatus for switching itself into a persistent current mode using a detachable current wire.

Background

With the improvement in superconducting wire performance and the advance in coil manufacturing technology using such wire, and the technological advances in related technologies such as heat-insulating containers and refrigerators, various types of superconducting magnets and application devices employing various magnets have been created. One of them is operating in a continuous current mode. Superconducting magnet arrangements for magnetic resonance imaging systems (MRI) and for magnetic levitation vehicles (Maglev) are examples of the type that have been put into practical use. These superconducting magnet devices supply current from an external excitation power source to a coil cooled to extremely low temperatures. The starting and final winding sections of the coil are short-circuited by means of the superconducting switch while the necessary magnetic field is generated, and this allows the device to operate in a continuous current mode, in which current continues to flow into the coil without power. After the device is switched into the persistent current mode, power from the external excitation power source is cut off and the device acts independent of the power source. The superconducting magnet device requires a current wire as a component when current is supplied to this coil. The current lead is a current path that couples an external excitation power supply terminal connected to the outside of the superconducting magnet to the internal coil. From a thermal point of view, the current lead is also a heat leak path from the terminal at room temperature to the coil at very low temperatures, and especially when it is not electrically conductive, the lead is simply a thermally conductive member. It is important to minimize heat leakage into the superconducting magnet in order to reduce the refrigeration cost of the coil. Accordingly, it has been considered to use a releasable current lead in a superconducting magnet apparatus operating in a persistent current mode such that the amount of thermal leakage is reduced by releasing the current lead when it is not conducting.

In general, there are two types of systems for debonding a debondable current conductor. One system in which the attaching/detaching portion of the current lead is pulled away from the superconducting magnet (see, for example, documents 1 and 4), and another system in which a gap is formed at the contact portion between the attaching/detaching portion and the fixed portion (lead contact portion) (see, for example, document 2). Fig. 7A and 7B illustrate examples of the principle of the construction of the pull-away system and the gap formation system, respectively.

In the pull-away system shown in fig. 7A, the first current lead 111 is disposed in the vacuum vessel 110, and the second current lead 112 is designed such that it can be detached from the first current lead. The first current lead 111 is connected at one end to a coil, not shown, inside the vacuum vessel 110, and has a lead contact portion 111a at the other end exposed outside the vacuum vessel 110. The second current lead 112 has an attaching/detaching portion 112a on one end for detachably connecting itself to the lead contact portion 111a, and an electrode terminal 112b on the other end for connecting a lead wire leading to an external excitation power source.

The second current lead 112 is inserted into the first current lead 111 for connection when an external excitation power supply supplies current to the coil, and the second current lead 112 is pulled away from the first current lead 111 when the power supply is completed.

The pull-away system is simple and therefore a similar construction has been used in superconducting magnet devices for MRI. However, the device employing the pull-off system requires professional skills in handling and maintaining the superconducting magnet, such as ensuring contact pressure at a contact site required for each attaching/detaching coil at the time of exciting/demagnetizing the magnet, removing frost, removing an insulation coating due to oxidation and damage, or taking measures to prevent the above phenomenon. Superconducting magnet devices that conform to pull-away systems are not easily manageable. Thus, the superconducting magnet assemblies to which such a system can be applied are limited to those such as those used for MRI, where excitation/demagnetization occurs only once a year or so, and where the handling of the current leads may be by a professional dispatched for this purpose. Therefore, in the case where there are many superconducting magnet devices whose excitation/demagnetization is performed when needed or every few days, that is, as in the case of the superconducting magnet device for Maglev, if excitation/demagnetization is repeated in a range from every day to every two weeks while many superconducting magnets installed in a train are continuously excited/demagnetized one by one, manual operation of each releasable current lead generates a large amount of work. Secondly, there are also security risks. A strong magnetic force acts on the magnet as if ironware is used. In the case where the operator is often working in the vicinity of the strong magnetic field of the superconducting magnet, there is a fear that the operator may be attracted due to the magnet being carried by accident.

On the other hand, in the gap forming system shown in fig. 2B, the first current lead 121 is disposed inside the vacuum vessel 120, and the second current lead 122 is designed to be attachable to and detachable from the first current lead 121. The first current wire 121 is connected to a coil, not shown, inside the vacuum vessel 120 on one end, and has a wire connection portion 121a on the other end. The second current lead 122 has an attaching/detaching portion 122a on one end, is movable back and forth inside the vacuum vessel 120 to detachably connect itself to the lead contact portion 121a, and has an electrode terminal 122b on the other end for connection to a lead wire leading to an external excitation power source outside the vacuum vessel 120. The airtightness of the inside of the vacuum vessel 120 is maintained by an airtight cover 125 constituted by a bellows or the like disposed in close contact with the attaching/detaching portion 122a to cover the through-hole 120 through which the second current lead 122 passes.

When a current is supplied from an external excitation power source to the coil, the attaching/detaching portion 122a of the second current wire 122 is connected to the wire contact portion 121a of the first current wire 121. After the supply of the electric current is completed, the second current wire 122 is pushed away from the first current wire 121, forming a gap between the attaching/detaching portion 122a and the wire contact portion 121a to cause a non-contact state.

Such a gap forming system can prevent frost formation and insulation coating by providing a contact site between the attaching/detaching portion 122a and the wire contact portion 121a in the airtight space inside the superconducting magnet. Therefore, the operation and maintenance of the superconducting magnet become easy. In the case of applying a demagnetized current lead to a superconducting magnet in which excitation/demagnetization of the magnet is relatively frequent, it is essential to use such a gap forming system.

In the gap forming system, it is important that the airtightness at the portion where the vacuum vessel is penetrated is highly reliable. In particular, in the case of a superconducting magnet used in a dynamic environment subjected to vibration, a supporting device for ensuring high vibration resistance of the airtight cover is necessary. Usually, only releasable current leads have been implemented which are simple in design, pull-away systems. As for the gap forming system, a manually operated detachable current lead wire which does not take such a vibration environment into consideration has been proposed (see, for example, document 3).

However, such a manually operated wire has the same working and safety risks as the above mentioned wire in line with a pull-away system. In addition, it is absolutely necessary to apply a required pressing force so as to set the contact resistance at the contact portion to be equal to or lower than a set value. However, if the operator handles many detachable current leads by hand very frequently, a shortage of pushing force may be caused by human error.

Therefore, when the releasable current wire is used in the superconducting magnet of the superconducting magnet device, not only is a system of forming a gap at the contact portion between the attaching/detaching portion and the wire contact portion employed, but also automation of the operation by the operator is required. Heretofore, there has been a drive force generated by an electric motor for automation. In addition, as a sample having only a single releasable current lead portion, there is a disclosure article (see, for example, document 5) that employs a pneumatic drive system for automation.

Document 1

Unexamined Japanese patent publication No. 61-222209

Document 2

Unexamined Japanese patent publication No. 60-32374

Document 3

Unexamined Japanese patent publication No. 3-232205

Document 4

Shunji YAMAMOTO et al, "improvement of reliability of disconnectable power line", report on 42-year conference between autumn cryogenic engineering and superconductivity in 1989, C1-4, P44 (11 months in 1989) ("improvement in reliability of a reliable power lead", feature briefs at the 42 th^ndmeeting on cryogenic engineering and superconductivity for 1989 Autumn，C1-4，P44(November，1989))。

Document 5

Tsukasa WADA, Akio SATO, "Low Heat leakage Detachable Power line", summary of the deep Cooling engineering conference, B3-7, P136 (5. 1987) ("Low heat-leaving replaceable Power lead", resources for the meeting on nutritional engineering B3-7, P138(May, 1987).

However, if a driving means such as the above-mentioned electric motor is provided in the vacuum vessel and the driving force is generated directly by the interaction between the current and the magnetic field, the control is lost or the driving force is reduced due to the strong magnetic field generated by the superconducting magnet. In this case, by providing the magnetic shield, it is possible to generate a driving force in principle. However, such a magnetic shielding against a strong magnetic field may increase the weight of the device and require a large space. Depending on the design, this drive may also be arranged in a vacuum. At this time, the air cannot be cooled, and the current cannot be supplied in a sufficient amount in order to limit heat generation. Thus, the driving force becomes small and a contact pressure of a sufficient magnitude cannot be applied to the attaching/detaching portion. In other words, the electric motor for general use, which flows a large current for power generation, emits a large amount of heat, thereby causing a problem of temperature rise.

In the above pneumatic driving system, it is necessary to connect a compression and vacuum (decompression) pump, a surge tank, an expansion/contraction portion (bellows) for driving, and the like to the pipes and valves so that the attaching/detaching portion reciprocates. The numerous components required complicate the design of the device and also increase the size and number. Further, if the pneumatic drive system is used in the ultrasonic magnet device for Maglev, gas leakage occurs in the respective lines and the like, which are susceptible to vibrations because of traveling vibrations while the vehicle is traveling.

Disclosure of Invention

An object of the present invention, which has been made in view of the above problems, is to provide a superconducting magnet apparatus that enables efficient, accurate, and robust connection of superconducting magnet current leads.

In order to achieve the above object, a superconducting magnet device according to claim 1 comprises a superconducting coil cooled in a vacuum vessel; a first current lead fixed inside the vacuum container, one end of the first current lead being connected to the superconducting coil and the other end having a lead contact portion; and a second current lead passing through the through hole provided on the upper vacuum vessel in an airtight manner, one end of the second current lead being connected to a lead wire leading to an external excitation power source and the other end thereof having an attaching/detaching portion disposed on the lead wire contact portion in a releasable manner. The superconducting magnet device is switched to a continuous current mode by a current supplied from an external excitation power source in a state where the detachable portion is in contact with the wire contact portion. Then, the attaching/detaching portion is separated from the wire contact portion and is maintained in a continuous state.

In other words, the above constitution corresponds to the aforementioned "gap forming system". When a current is supplied to the superconducting coil, the attaching/detaching portion of the second current wire comes into contact with the wire contact portion of the first current wire to pass a current from the external excitation power source. After the device is switched into the persistent current mode, the current supply from the external excitation power supply is terminated and the power supply is cut off. The attaching/detaching portion is separated from the lead contact portion to form a gap therebetween, and the device operates by itself. The second current lead penetrates into the vacuum vessel in a gastight manner. Therefore, air outside the vacuum vessel can be prevented from leaking into the interior thereof.

Specifically, the superconducting magnet device includes a driving mechanism disposed inside the above vacuum vessel. The drive mechanism is made of a non-magnetic insulating device for automatically moving the attaching/detaching portion back and forth in the attaching/detaching direction with respect to the wire contact portion in response to a voltage applied by an external drive power source.

In the "gap forming system" as above, the attaching/detaching portion is not driven to and fro to a predetermined position manually but automatically. Therefore, no professional skills for operation and maintenance are required, and it is easy to take care of. This also eliminates the usual safety risks for the operator. Secondly, even if many superconducting magnets have to be excited/demagnetized one after another, no manpower is required and thus efficient operation is possible. Further, a required contact pressure for setting the contact resistance at the contact site between the wire contact portion and the attaching/detaching portion, which is necessary for each attaching/detaching, is equal to or lower than a certain set value, can be accurately obtained without human error.

In addition, the driving mechanism made of the non-magnetic insulating means can prevent or restrict the operation of the driving mechanism from being affected by the strong magnetic force of the superconducting magnet. Therefore, it is possible to precisely control the back-and-forth movement of the attaching/detaching portion.

Specifically, as described in claim 2, the above second current lead may be movably supported like a long shaft by a driving mechanism provided on the outer end face of the vacuum vessel in the attaching/detaching direction and partially held in contact with a contractible flexible member provided to cover the above through hole between the outer end face of the vacuum vessel and the driving mechanism.

In such a configuration, the second current lead and the flexible member (such as a bellows) are always partially in contact with each other. Therefore, even if the second current lead is moved, airtightness of the inside of the vacuum vessel can be ensured.

In this respect, there is a particular concern that gas inside the vacuum vessel leaks to the outside, as in the case where the superconducting magnet device is disposed in a vibrating environment, and it is preferable that an airtight chamber is provided in the vacuum vessel for constituting a double leak prevention device, as recited in claim 3.

The airtight chamber is formed of a tubular device, one end of which is continuously formed around the above through hole and extends into the vacuum vessel, and the other end of which movably supports and fixes the first current lead at a position spaced apart from the superconducting coil. A sealed space is formed via a through hole between the tubular device and the flexible member, and both the wire contact portion and the attaching/detaching portion are housed inside the sealed space.

According to the above configuration, the leakage of gas into the vacuum vessel is prevented at least doubly by the outer wall of the airtight chamber provided in the vacuum vessel and the flexible member, and therefore, the performance of the superconducting magnet device can be maintained.

Alternatively, the drive mechanism may be disposed inside the vacuum vessel, rather than being disposed outside as described above.

Specifically, as recited in claim 4, the second current lead may include a shaft-like terminal portion fitted to penetrate through a rigid airtight cap fitted to cover the above through hole of the vacuum vessel and connected to the above lead on an end exposed outside the vacuum vessel; a shaft-like detachable portion slidably supported by a driving mechanism inside the vacuum vessel in an attaching/detaching direction; and a flexible portion composed of a lead wire connecting the shaft-like terminal portion and a detachable portion inside the vacuum vessel.

With such a configuration, since the second current lead is fixed to the rigid airtight cover at the axial terminal portion, even if the superconducting magnet device is disposed in a vibration environment, deformation of the airtight cover is prevented or restricted. Thus, the vibration resistance of the device can be improved. Therefore, airtightness between the shaft-shaped terminal portion and the airtight cover becomes high, and this effectively prevents leakage of air. The attaching/detaching portion of the second current lead may be attached to and detached from the lead contact portion by a sliding means inside the vacuum vessel. Since the second current lead and the shaft-like terminal portion are in a conductive state via the flexible portion, the second current lead can suitably function as the second current lead.

An example of the above drive mechanism, as recited in claim 5, specifically comprises a housing disposed within the vacuum vessel; and a longitudinal piezoelectric device, as the above non-magnetic insulating means, extending parallel to the axis of the second current lead. One end of the piezoelectric device is connected to the case, and the other end thereof is directly or indirectly connected to the above second current lead. The piezoelectric device expands/contracts in response to a voltage applied from an external driving power source, and the attaching/detaching portion moves back and forth in accordance with this expansion/contraction.

In the above constitution, the piezoelectric device is directly or indirectly connected to the second current lead via the intermediate means. The piezoelectric device is extended/contracted in parallel to the second current lead (releasable portion) in accordance with the applied voltage. Such a piezoelectric device is not affected by a magnetic field. Therefore, it is possible to move the attaching/detaching portion back and forth to the proper position with a small heat load. Secondly, the drive mechanism needs to substantially secure only a space for the piezoelectric device, and thus a simple and lightweight construction can be obtained.

Alternatively, as recited in claim 6, the driving mechanism may include a case disposed inside the vacuum vessel; the ultrasonic motor is made of the non-magnetic insulating device fixed on the box body; and a sliding mechanism directly or indirectly connected to the second current lead and driven in a sliding manner parallel to the axis of the second current lead by rotation of the ultrasonic motor. The attaching/detaching portion is moved back and forth by rotating the ultrasonic motor via the external driving power source and driving the slide mechanism in a sliding manner.

Such a configuration can be realized using a rolling screw as a slide mechanism, and a circulation screw will be described in, for example, later embodiments. Also in this case, since the ultrasonic motor is not affected by the magnetic field, the attaching/detaching portion can be moved back and forth to the proper position with a small heat load. Secondly, there is great flexibility in the moving distance of the attaching/detaching portion as compared with the extension/contraction using the aforementioned piezoelectric device. Since the displacement distance can be made longer, it is possible, for example, to lengthen the contact between the first current conductor and the second current conductor in order to reduce the connection resistance.

The aforementioned superconducting magnet arrangement can be used for a variety of purposes, such as for MRI and for Maglev ultrasonic magnet arrangements. In particular, such superconducting magnet arrangement may show significant effects when used in a Maglev train, as indicated in claim 7. Maglev trains are equipped with a number of superconducting magnet assemblies whose excitation/demagnetization can be performed as needed or every few days. Therefore, in operation, it is very important to improve the efficiency of the aforementioned automation, maintain accuracy and operator safety, etc.

Drawings

Fig. 1 is an explanatory view showing a schematic configuration of a superconducting magnet apparatus according to a first embodiment of the present invention;

fig. 2 is an explanatory view showing a schematic configuration of a driving mechanism constituting a superconducting magnet apparatus of the first embodiment;

fig. 3 is an explanatory view showing a modification of the support structure in the drive mechanism of the first embodiment;

fig. 4 is an explanatory view showing a schematic configuration of a driving mechanism constituting a superconducting magnet apparatus of a second embodiment;

fig. 5 is an explanatory view showing a schematic configuration of a superconducting magnet apparatus according to a third embodiment of the present invention;

fig. 6 is an explanatory view showing a schematic configuration of a superconducting magnet device according to a fourth embodiment of the present invention;

fig. 7A and 7B are explanatory views each showing a schematic configuration of a conventional superconducting magnet device.

Detailed Description

Preferred embodiments of the present invention will now be described for further clarity with reference to the accompanying drawings.

First embodiment

This example illustrates a superconducting magnet arrangement for Maglev according to the present invention. Fig. 1 is an explanatory view (a partial cross-sectional view) showing a schematic configuration of a superconducting magnet device. Fig. 2 is an explanatory diagram showing a specific configuration of the drive mechanism indicated within a portion a (a chain line) of fig. 1.

As shown in fig. 1, the superconducting magnet device of the present invention includes a vacuum vessel 10, a superconducting coil (not shown) cooled in the vacuum vessel 10, a detachable current lead 20 for supplying a current from an external excitation power source 51 to the superconducting coil, and a driving mechanism 30 for attachment/detachment of the detachable current lead 20. Inside the vacuum vessel 10, there is an inner tank which houses liquid helium and liquid nitrogen for cooling the superconducting coil at an extremely low temperature; a radiation shield as an insulating layer covering the inner vessel, etc. However, the explanation and illustration of these components are omitted, since the superconducting magnet device of the present embodiment is characterized by the attaching/detaching mechanism of the releasable current lead 20.

The detachable current lead 20 includes a first current lead 21 disposed inside the vacuum vessel 20, and a second current lead 22 detachably connected to the first current lead 21.

The first current conductor 21 has an elongated shape. The first current wire 21 is connected to the superconducting coil (lower in the drawing) on one end thereof and has a wire contact portion 21a recessed on the other end. The first current lead 21 is fixed to and supported by the heat insulating support 11, and the support 11 is disposed inside the vacuum vessel 10 at a position spaced apart from the superconducting coils.

The second current conductor 22 is shaped like a long shaft. The second current lead 22 has an attaching/detaching portion 22a on one end thereof, which passes through a through-hole 10a provided on the vacuum vessel and is detachably connected to the lead contact portion 21 a; and a terminal connection portion 22b on the other end exposed outside the vacuum vessel 10 to be connected to a lead wire leading to an external excitation power source 51. The second current lead 22 is movably supported by a drive mechanism 30 provided on the outer end face of the vacuum vessel 10 in the attaching/detaching direction with respect to the first current lead 21. The second current lead 22 is partially held in close contact with each retractable bellows 12 (flexible member) provided between the outer end face of the vacuum vessel 10 and the drive mechanism 30 to cover the above through-hole 10 a.

The driving mechanism 30 extends/shortens a piezoelectric device (to be described later) housed inside the case 31 by applying a predetermined voltage from an external driving power source 52. The drive mechanism 30 automatically moves the attaching/detaching portion 22a back and forth in the attaching/detaching direction.

In other words, as shown in fig. 2, which is a schematic configuration of the drive mechanism 30 without the case 31, the second current lead 22 is supported by the support mechanism 40 provided inside the case 31 so that it can be moved back and forth in the axial direction. The support mechanism 40 includes a pair of upper and lower supports 41, 41 extending from the inner wall of the case 31 toward the second current lead 22. Each support member 41 includes a shaft-like portion 42 protruding from the inner wall of case body 31, and a square ring-like support portion 43 continuously formed from the tip of shaft-like portion 42 and surrounding second current lead 22. Each side of the support part 43 is provided with a roller element 45, which can rotate on this side. Roller element 45 supports second current conductor 22 so that it can be moved back and forth in a non-abrasive manner.

An outwardly projecting power transmission member 22c is provided on an axially intermediate portion of the second current lead 22. In addition, one end of the longitudinal piezoelectric ceramics 50 (piezoelectric device) is connected to and supported on the support member 32 provided in a protruding manner on the inner wall of the case body 31, and the other end thereof is connected to the tip portion of the power transmitting body 22 c. The piezoelectric ceramic 50 is arranged in such a way that it can extend parallel to the axial direction of the second current lead 21. Therefore, it elongates/shortens by applying a predetermined voltage and moves the second current lead in the upward direction (attachment/detachment direction). The voltage applied at this time is determined in advance in consideration of how much the piezoelectric ceramics 50 is elongated, so that the attaching/detaching portion 22a can be brought into contact with the wire contact portion 21a with a necessary contact pressure.

When the superconducting magnet device of the present embodiment is switched to the persistent current mode, first, a voltage is applied from the external drive power source 52 to the drive mechanism 30, and the piezoelectric ceramics 50 are elongated by the applied voltage. In response, the second current wire 22 is moved toward the first current wire 21 and the attaching/detaching portion 22a comes into contact with the wire contact portion 21 a. Then, a current is supplied from the external excitation power source 51 to the superconducting coils via the second current wire 22 and the first current wire 21.

After the switching to the persistent current mode is completed, the supply of current from the external excitation power source 51 is stopped, and then the supply of voltage from the external drive power source 52 is stopped. For the above reason, the piezoelectric ceramics 50 contracts to separate the attaching/detaching portion 22a from the wire contact portion 21a and form a gap between the first current wire 21 and the second current wire 22. The magnitude and timing of the power supply from the above external excitation power source 51 and external drive power source 52 are controlled by a not-shown supply power control device.

As described above, in the superconducting magnet device of the present embodiment conforming to the "gap generating system", the first current lead 22 constituting the releasable current lead 20 is driven back and forth to a predetermined position to make contact with the first current lead 21, not manually but automatically. Thus, the device is easily attended without requiring professional skills for operation and maintenance. It is also possible to eliminate the usual safety risks for the operator. Second, even if many superconducting magnets are excited/demagnetized one after another, no manpower is required to achieve efficient operation of the apparatus. Further, the contact pressure, in order to set the contact resistance necessary for each attachment/detachment at the contact portion between the wire contact portion 21a and the attachment/detachment portion 22a to be equal to or lower than the set value, can be accurately obtained without human error.

In addition, since the driving mechanism is constituted by the piezoelectric ceramics 50 of a non-magnetic insulating substance, it is possible to prevent the operation of the driving mechanism 30 from being affected by the strong magnetic force of the superconducting magnet. Also, the reciprocation and the attaching/detaching action of the attaching/detaching portion 22a can be accurately controlled. Furthermore, by using the longitudinal piezoelectric ceramics 50, not only the drive mechanism 30 but also the superconducting magnet device can be made simple and lightweight.

Modifications of the type

The above embodiment shows the support mechanism 40 supporting the second current wire 22 with a pair of upper and lower support members 41, as shown in fig. 2. However, other modes of the support mechanism are possible.

For example, as shown in fig. 3 showing a modified drive mechanism 30', it is also possible to employ a support structure including a projecting portion 61 projecting from the inner wall of the case body and a support portion 62 having a tubular shape of a predetermined length in the axial direction of the second current lead 22 so as to insert the second current lead therein, and continuously formed from the end of the projecting portion 61. Or, conversely, the supporting mechanism may be designed such that the second current lead 22 is supported axially by at least three supporting elements, and/or a number of supporting elements may each be designed differently.

Second embodiment

In the above first embodiment, the piezoelectric ceramics itself is used as the drive mechanism. This embodiment shows a superconducting magnet device employing, as a drive mechanism, a slide mechanism including an ultrasonic motor using piezoelectric ceramics. Fig. 4 is a schematic diagram of a relevant part, corresponding to fig. 2 in the first embodiment. The basic configuration, the manner of supplying electric power, and the like of the present superconducting magnet device are basically the same as those of the first embodiment. Accordingly, equivalent components may be numbered the same and will not be described repeatedly.

As shown in fig. 4, the second current lead 22 is supported by a slide mechanism 240 provided inside the case of the drive mechanism L30, and is driven back and forth in the axial direction.

This sliding mechanism 240 includes a plate-like member 241 bonded to the second current lead 22 in the axial direction; an ultrasonic motor 242 provided on a base member 232 mounted on an inner wall of the case; a roll screw 243 connected to a rotation axis of the ultrasonic motor 242 and extending in an axial direction; and a guide 244 for guiding the plate 241 in parallel to the second current wire.

The plate 241 is provided with a guide hole 241a and a screw hole 241 b. The guide hole 241a and the screw hole 241b are through holes and arranged parallel to the axial direction of the second current lead 22. The guide hole 241a has a substantially identical cross section to the guide 244. A nut that engages the threads of the roll screw 243 is formed in the screw bore 241 b. The guide 244 passes through the guide hole 241a and is fixed to the base member 232 or to the case at both ends thereof (the fixed state of the guide 244 is not shown in the drawings for convenience). The roll screw 243 is screwed into the screw hole 241b and thus slidably supports the plate 241.

When the superconducting magnet device of the present embodiment is switched to the continuous current mode, a voltage is first supplied from the external drive power source 52 to the drive mechanism 230 to drive the ultrasonic motor 242 to rotate the tumble screw 243. As a result, the plate 241 is slid by being guided by the guide 244, and therefore, the second current wire 22 moves toward the first current wire 21 and the attaching/detaching portion 22a comes into contact with the wire contact portion 21a, stopping the supply of the voltage from the external driving power source 52 and stopping the movement of the second current wire 22. Then, a current is supplied from the external excitation power source 51 to the superconducting coil via the second current wire 22 and the first current wire 21.

After the switching to the persistent current mode is completed, the supply of the current from the external excitation power source 51 is stopped, and then, in contrast to the above, the voltage supply from the external driving power source 52 is started again to drive the ultrasonic motor 242. For this reason, the roll screw is rotated to the opposite direction to the above. This separates the attaching/detaching portion 22a from the wire contact portion 21a and forms a gap between the first current wire 21 and the second current wire 22. The magnitude and timing of the power supply from the above external excitation power source 51 and external drive power source 52, the direction of the power supply, and the like are controlled by a not-shown supply power control device.

As described above, also in the superconducting magnet device of the present invention conforming to the "gap generating system", the attaching/detaching portion 22a is driven to and fro to a predetermined position not manually but automatically. Therefore, substantially the same effects as those in the first embodiment described above can be obtained. Secondly, the slide mechanism 240 using the ultrasonic motor 242 is employed, which has great flexibility in the moving distance of the attaching/detaching portion as compared with the case of using the extension/contraction of the piezoelectric ceramics in the above first embodiment. Since the moving distance can be made longer so that the contact portion between the first current lead 21 and the second current lead 22 is longer, it is possible to reduce the contact resistance.

Third embodiment

The present embodiment has a configuration substantially equivalent to that of the above first embodiment or second embodiment, and further exhibits excellent performance of preventing air from leaking into the vacuum vessel. Fig. 5 is a schematic view (partial cross-sectional view) of a superconducting magnet according to the present invention. Since the drive mechanism is employed in the above first embodiment or second embodiment, the description of the drive mechanism will not be repeated. Similarly, the basic constitution, the manner of supplying electric power, and the like of the present superconducting magnet device are basically the same as those in the first embodiment. Accordingly, each equivalent component may be numbered the same and its description is not repeated.

As shown in fig. 5, the hermetic chamber 310 of the superconducting magnet apparatus of the present embodiment is constituted by a tubular means 312 disposed to project inward (downward in the drawing) from the periphery of the through hole 10a into the vacuum vessel 10 and having the first current lead 21 inserted therein.

The tube-like means 312 includes a tube member 313 having a free end continuously formed around the through hole 10a on the inner end surface of the vacuum vessel 10 and extending axially along the first current wire 21 inside the vacuum vessel 10, and a cap 314 provided on the other end of the tube member 313. The pipe 312 is fixed to and supported by the heat insulating support means 311 inside the vacuum vessel 10 at the other end of the pipe 313. A through-hole 314a is provided at the center of the cap 314, and the first current lead 21 passes through the through-hole 314a in an airtight manner. The tubular means 312 and the bellows 12 constitute a gas-tight chamber 310 which forms a sealed space via the through-hole 10 a. The wire contact portion 21a and the attaching/detaching portion 22a are housed inside the airtight chamber 310.

As described above, the superconducting magnet device of the present embodiment is provided with the airtight chamber 310 in the vacuum vessel 10 and includes the double leakage prevention means, in addition to the configuration of the first embodiment or the second embodiment. Therefore, not only the same effects as in the first embodiment or the second embodiment can be obtained, but also double prevention of air leakage can be achieved by the outer wall of the tubular device provided inside the vacuum vessel 10 and the bellows 12. As a result, a temperature rise due to air leakage inside the superconducting magnet device for Maglev, and the like, particularly disposed in a vibration environment, can be avoided, and the function of the superconducting magnet device can be maintained.

In the present embodiment, an airtight chamber 310 is provided to form a double leakage prevention structure. However, more than one airtight chamber may be provided to form a triple or more leakage prevention structure.

Fourth embodiment

The present embodiment includes a driving mechanism equivalent to the above first embodiment or second embodiment, but this driving mechanism is not provided outside the vacuum vessel 10 but inside. Fig. 6 is a schematic view (partially sectional view) of the driving mechanism of the present embodiment. Accordingly, detailed description of the driving mechanism will not be repeated. The basic constitution, the manner of supplying electric power, and the like of the present superconducting magnet device are basically the same as those of the first embodiment. Accordingly, equivalent components may be numbered the same and description thereof will not be repeated.

As shown in fig. 6, the superconducting magnet apparatus of the present embodiment has a driving mechanism 430 similar to that in the foregoing first embodiment or second embodiment inside the vacuum vessel 10. The voltage is supplied from the external driving power source 52 via a lead wire connected to the driving mechanism 430, which is passed through a minute hole (not shown) drilled at a portion on the vacuum vessel 10 where the driving mechanism 430 is disposed.

The second current lead 420 includes a shaft-like terminal portion 421 fixed in an airtight manner and penetrating through a rigid airtight cover 412 fixed to cover the through-hole 10a on the outer end surface of the vacuum vessel 10; a shaft-like releasable portion 422 slidably supported by the drive mechanism 430 in the attaching/releasing direction toward the first current lead 21; and a flexible portion 423 made of a lead wire electrically connected to the shaft-like terminal portion 421 and the attaching/detaching portion 422.

The attaching/detaching portion 422 and the shaft-like terminal portion 421 of the second current lead 420 are in a conductive state via the flexible portion 423. The attaching/detaching portion 422 is movably supported by the driving mechanism 430 and driven back and forth so that it can be moved inside the vacuum vessel 10 and attached to and detached from the wire contacting portion 21 a.

Such a structure allows the second current lead 420 to be fixed to the rigid airtight cover 412 at the shaft-like terminal portion 421. Therefore, even if the superconducting magnet device itself is disposed in a vibration environment, deformation of the airtight cover 412 can be prevented or suppressed, and the vibration resistance can be improved. In other words, it is basically difficult to control the natural frequency of the flexible airtight cover, and if the natural frequency is included in the vibration environment, the flexible airtight cover resonates to have a large deformation. However, the natural frequency of the rigid hermetic cover 412 can be set substantially higher than the frequency accepted during the operating period of the superconducting magnet apparatus for Maglev due to the rigidity of the material. Therefore, it is easy to avoid resonance and minimize deformation. If the deformation due to the vibration is small, the distortion of the cover also becomes small, and the fatigue failure as a cause of the air leakage can be prevented and suppressed. Thus, high airtightness between the shaft-like terminal portion 421 and the airtight cover 412 is achieved, and air leakage can be effectively prevented. Thus, a high reliability of the superconducting magnet arrangement can be obtained and withdrawal of magnetic levitation vehicles (Maglev) due to failure and maintenance loss can be effectively reduced.

Various embodiments of the present invention have been described above. However, the embodiments of the present invention should not be limited to the above embodiments, and other modifications are possible without departing from the technical scope of the present invention.

In the above embodiments, for example, piezoelectric ceramics is used as the piezoelectric device. However, piezoelectric single crystals and piezoelectric organic substances other than piezoelectric devices can be used.

The invention makes it possible to effectively, accurately and reliably connect superconducting magnet current wires. It can be used for superconducting magnet devices for a variety of purposes, such as for MRI and for Maglev. In particular, if employed in Maglev trains, the present invention can significantly improve efficiency, maintain accuracy, improve operational safety, etc. through automation.

Claims (9)

1. A superconducting magnet apparatus comprising:

a superconducting coil cooled in the vacuum vessel;

a first current lead fixed within the vacuum vessel, one end of the first current lead being connected to the superconducting coil and the other end having a lead contact portion; and

a second current lead passing through a through hole provided on the vacuum vessel in an airtight manner, one end of the second current lead being connected to a lead leading to an external excitation power source and the other end having an attaching/detaching portion provided in a detachable manner with respect to the lead contact portion;

the superconducting magnet device is switched into a persistent current mode by a current supplied from an external excitation power source under the condition that the attachment/detachment portion is in contact with the wire contact portion, and the attachment/detachment portion is then separated from the wire contact portion while the device maintains the persistent current mode, wherein

The superconducting magnet device further includes a driving mechanism made of a non-magnetic insulating device disposed in the vacuum vessel for automatically moving the attaching/detaching portion back and forth in the attaching/detaching direction with respect to the wire contact portion in response to a voltage applied by an external driving power source.

2. The superconducting magnet assembly of claim 1 wherein

The second current lead is shaped like a long shaft, is movably supported in the attaching/detaching direction by a driving mechanism provided on the outer end surface of the vacuum vessel, and is held in partial contact with a retractable flexible member disposed between the outer end surface of the vacuum vessel and the driving mechanism so as to cover the through-hole.

3. The superconducting magnet device as claimed in claim 2, further comprising a hermetic chamber having a tubular shape, one end of which is continuously formed around said through hole and extends inwardly inside the vacuum vessel, and the other end of which movably supports and fixes the first current lead at a position spaced apart from the superconducting coil; a sealed space is formed between the airtight chamber and the flexible member through the through hole; and the wire contact portion and the attaching/detaching portion are accommodated within the sealed space.

4. The superconducting magnet assembly of claim 1 wherein the drive mechanism is disposed on an inner end face of the vacuum vessel, and

the second current lead includes:

a shaft-like terminal portion fixed to penetrate a rigid airtight cap fixed to cover the through-hole of the vacuum vessel and connected to the lead wire at an end exposed to the outside of the vacuum vessel;

an attaching/detaching portion having a shaft shape, slidably supported by the driving mechanism in an attaching/detaching direction inside the vacuum container; and

a flexible portion composed of a lead wire connecting the shaft-like terminal portion and the detachable portion inside the vacuum vessel.

5. The superconducting magnet assembly of any one of claims 1 to 4 wherein the drive mechanism comprises:

a case disposed in the vacuum container;

a longitudinal piezoelectric device as a non-magnetic insulating means extending parallel to the axis of the second current lead, one end of the piezoelectric device being connected to the case and the other end being connected directly or indirectly to the second current lead, wherein

The attaching/detaching portion is moved back and forth by the piezoelectric device in response to expansion/contraction of a voltage applied by an external driving power source.

6. The superconducting magnet assembly of any one of claims 1 to 4 wherein the drive mechanism comprises:

a box body arranged in the vacuum container;

the ultrasonic motor is made of a non-magnetic insulating device fixed on the box body; and

a sliding mechanism directly or indirectly connected to the second current lead and driven in a sliding manner parallel to the axis of the second current lead by the rotation of the ultrasonic motor, wherein

The drive mechanism moves the attaching/detaching portion back and forth by rotating the ultrasonic motor via the external drive power source and driving the slide mechanism in a sliding manner.

7. Superconducting magnet arrangement according to any of claims 1-4, wherein the superconducting magnet arrangement is used in a magnetic levitation vehicle.

8. The superconducting magnet assembly of claim 5 wherein the superconducting magnet assembly is used in a magnetic levitation vehicle.

9. The superconducting magnet assembly of claim 6 wherein the superconducting magnet assembly is used in a magnetic levitation vehicle.