JP3244043B2 - Superconducting magnet cooling device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a superconducting magnet cooling device for cooling a superconducting magnet.

[0002]

2. Description of the Related Art A superconducting magnet used in an MRI (magnetic resonance imaging apparatus) or the like must be cooled to an extremely low temperature of 10 K or less in order to maintain a superconducting state.
Conventionally, there is a superconducting magnet cooling device for cooling a superconducting magnet to a very low temperature as shown in FIG.
This superconducting magnet cooling device is a cooling device of a refrigerant system, in which a superconducting magnet is immersed in a refrigerant such as liquid helium and the refrigerant is cooled to a very low temperature by a refrigerator.

In FIG. 3, reference numeral 1 denotes a container, and a cross section having a cylindrical space 2 in the center is formed in an annular cylindrical body. A first shield 3 having a similar shape to the container 1 is sealed in the container 1, and a first shield 3 is provided in the first shield 3.
A second shield 4 having a similar shape to the shield 3 is enclosed. Further, the second shield 4 is provided inside the second shield 4.
And a liquid helium container 5 having a supply / discharge port 6 is sealed therein. And the liquid helium container 5
Inside, a cylindrical superconducting magnet (hereinafter simply referred to as a magnet) 7 is sealed. Liquid helium container 5
The second shield 4 and the first shield 3
One end of a supply / discharge pipe 8 penetrating the container 1 and protruding to the outside is attached. On the other hand, a valve 9 is attached to the other end of the supply / discharge pipe 8. Thus, the magnet 7
Is immersed in the liquid helium introduced into the liquid helium container 5 via the valve 9 and the supply / discharge pipe 8.
The helium gas formed by evaporating the liquid helium is discharged to the outside via the supply / discharge pipe 8 and the valve 9.

A cryogenic refrigerator is provided on the outer peripheral wall of the container 1.
A first heat station 11 and a second heat station 12 (hereinafter simply referred to as a refrigerator) are mounted so as to protrude into the container 1. The outer peripheral wall of the first shield 3 is attached to the first heat station 11, and the second shield 4 is attached to the second heat station 12.
Outer peripheral wall is attached. Here, the container 1 is installed in a shield 13 maintained at a predetermined temperature.

On the other hand, a compressor unit 15 is
Is installed to supply the high-pressure refrigerant gas compressed by the compressor 19 to the refrigerator 10, and recover the low-pressure refrigerant gas discharged from the refrigerator 10 to the compressor 19. The control device 16 provided in the compressor unit 15 includes a protection device 17
In the case of abnormal cooling water temperature of the compressor 19, abnormal refrigerant gas pressure, abnormal refrigerant gas temperature or abnormal current of the compressor motor (not shown), the compressor 1
9 is stopped.

FIG. 4 is a flowchart of an abnormal stop processing operation performed by the control device 16. When the compressor unit 15 is energized, an abnormal stop processing operation starts. When the operation switch is turned on in step S1, the process proceeds to step S2. In step S2, based on the command signal from the protection device 17, the protection device 17
It is determined whether or not is operating. If the protection device 17 is in the operating state, the process proceeds to step S6; otherwise, the process proceeds to step S3. In step S3, an operation command is output to the compressor motor, the compressor 19 is started, and the operation of the refrigerator 10 is started. Step S4
Then, if it is determined that a power failure has occurred based on a drop in the power supply voltage or the like, the process proceeds to step S5. In step S5, a stop command is output to the compressor motor, and the operation of the refrigerator 10 is stopped. After that, the abnormal stop processing operation ends. Then, when the power failure is restored, the compressor unit 15 is energized and the abnormal stop processing operation is started again.

In step S6, a lamp 18 indicating that the operation is abnormal stop other than a power failure is turned on. Step S
At 7, a stop command is output to the compressor motor, and the operation of the refrigerator 10 is stopped. After that, step S
Return to 1 and wait for the operation switch to be turned on.

Thus, in the case of an abnormality in the cooling water temperature of the compressor 19, an abnormality in the refrigerant gas pressure, an abnormality in the refrigerant gas temperature, or an abnormality in the current of the compressor motor, so-called self-holding for keeping the stopped state of the refrigerator 10 is performed. Do it.

[0009]

As described above, in the above-described conventional superconducting magnet cooling apparatus, when the cooling water temperature of the compressor 19 is abnormal (including the abnormal water level), the refrigerator 10
The self-holding of the stop is made. This is because the conventional superconducting magnet cooling device employs a refrigerant system in which the magnet 7 is cooled with liquid helium. Therefore, even if the refrigerator 10 is stopped, the low-temperature state can be maintained only for the time that the liquid helium evaporates. This is because there is no problem even if it is held.

However, in recent years, with the improvement in the performance of superconducting magnets, a direct cooling type superconducting magnet cooling device that directly cools with a refrigerator has appeared. In that case,
Because the superconducting magnet is cooled directly by a refrigerator,
If the refrigerator is self-maintained when stopped due to a cooling water abnormality, there is a problem that the superconducting magnet cannot be maintained at a low temperature and a quench occurs in which the superconducting state is broken.

Therefore, when the compressor 19 is stopped due to an abnormality in the cooling water, the self-holding operation is stopped and the compressor 19 is automatically returned. In the case of a temporary abnormality such as when the cooling water circulation path is clogged with dirt, etc. If the refuse clogging is naturally corrected, normal operation can be performed thereafter. However, in a case where the circulation of the cooling water is completely stopped due to a failure of the cooling water pump (not shown) or a case where the water level becomes 1/2 or less, the compressor 19 is sufficiently cooled. This causes a problem that the compressor 19 will eventually break down.

Accordingly, an object of the present invention is to provide a superconducting magnet cooling apparatus which automatically recovers in the event of a temporary abnormality in the supply of cooling water, and stops and freezes the refrigerator in the case of a complete abnormality. It is in.

[0013]

In order to achieve the above object, the invention according to claim 1 is directed to a direct cooling type superconducting magnet cooling system in which a superconducting magnet is directly cooled by a refrigerator in contact with the superconducting magnet. A compressor for supplying high-pressure refrigerant gas to the refrigerator, and a cooling water for detecting that the temperature of the cooling water for cooling the compressor has reached a predetermined temperature or higher and outputting a cooling water temperature abnormality signal. Temperature monitoring means, counting means for counting the number of cooling water temperature abnormalities based on the cooling water temperature abnormality signal from the cooling water temperature monitoring means, and receiving a cooling water temperature abnormality signal from the cooling water temperature monitoring means. When the count value of the counting means is larger than a predetermined value, the compressor is stopped, and a control means for maintaining the state is provided.

According to the above arrangement, when the number of abnormalities of the cooling water temperature counted by the counting means is larger than the predetermined number, the abnormalities of the cooling water temperature are determined to be complete abnormalities which are not immediately recovered, and the compressor of the refrigerator is used. It is stopped and its state is maintained. In this way, the compressor is stopped and the state is maintained in spite of a temporary cooling water temperature abnormality such that there is no fear that the superconducting macnet will quench to recover immediately, and the state is maintained. This can be prevented.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 is a configuration diagram of a superconducting magnet cooling device according to the present embodiment. This superconducting magnet cooling device is of a direct cooling type, in which a superconducting magnet is directly cooled to a very low temperature by a refrigerator.

In FIG. 1, reference numeral 21 denotes a container, and a cross section having a cylindrical space 22 in the center is formed in an annular cylindrical body. A shield 23 having a similar shape to the container 21 is sealed in the container 21, and a cylindrical superconducting magnet (hereinafter simply referred to as a magnet) 24 is sealed in the shield 23.

A cryogenic refrigerator is provided on the outer peripheral wall of the container 21.
A first heat station 26 and a second heat station 27 are attached to the container 21 so as to protrude into the container 21. An outer peripheral wall of the shield 23 is attached to the first heat station 26, and a magnet 24 is attached to the second heat station 27.
Is attached to the outer peripheral surface. Here, the container 21 is installed in a shield 28 maintained at a predetermined temperature.

On the other hand, a compressor unit 30
Is installed to supply the high-pressure refrigerant gas compressed by the compressor 33 to the refrigerator 25, while collecting the low-pressure refrigerant gas discharged from the refrigerator 25 into the compressor 33. The protection device 32 provided in the compressor unit 30 has a function as the cooling water temperature monitoring means, and includes a cooling water temperature abnormality of the compressor 33, a refrigerant gas pressure abnormality, a refrigerant gas temperature abnormality, or a compressor motor (FIG. (Not shown), and outputs a compressor stop command signal corresponding to the detected abnormality. Control device 31
Stops the compressor 33 as necessary based on a compressor stop command signal functioning as the above-mentioned cooling water temperature abnormality signal from the protection device 32.

FIG. 2 is a flowchart of the abnormal stop processing operation performed by the control device 31. When the compressor unit 30 is energized, the abnormal stop processing operation starts. When the operation switch is turned on in step S11, the process proceeds to step S12. In step S12, it is determined whether or not the protection device 32 is operating based on the command signal from the protection device 32. And the protection device 3
If 2 is in the operating state, the process proceeds to step S16; otherwise, the process proceeds to step S13.

In step S13, an operation command is output to the compressor motor, the compressor 33 is started, and the operation of the refrigerator 25 is started. If it is determined in step S14 that a power failure has occurred based on a decrease in the power supply voltage or the like, step S14 is performed.
Proceed to 15. In step S15, a stop command is output to the compressor motor, and the operation of the refrigerator 25 is stopped. After that, the abnormal stop processing operation ends. Then, when the power failure is restored, the compressor unit 30 is energized and the abnormal stop processing operation is started again.

In step S16, the compressor stop command signal from the protection device 32 is analyzed, and it is determined whether or not the operation of the protection device 32 is caused by an abnormal cooling water temperature. As a result, if the cooling water temperature is abnormal, the process proceeds to step S19, and if not, the process proceeds to step S17. In step S17, the lamp 34 for indicating that the cooling water temperature is abnormal and that the power is stopped due to a cause other than a power failure is turned on. In step S18, a stop command is output to the compressor motor to stop the operation of the refrigerator 25, and the operation stop state is maintained by itself. After that, the process returns to step S11 to wait for the operation switch to be turned on.

In step S19, a lamp 35 indicating that the temperature of the cooling water is abnormal is turned on. Step S20
Then, the built-in counter 36 determines the number of cooling water abnormalities n
Is counted. In step S21, the cooling water abnormality frequency n
Is smaller than or equal to a predetermined value N. as a result,
If n ≦ N, the process proceeds to step S22, while if n> N, the process proceeds to step S23. In step S22, when a predetermined time (for example, 2 minutes) elapses, the process returns to step S12 to automatically return. In step S23, a stop command is output to the compressor motor to stop the operation of the refrigerator 25, and the operation stop state is self-held. After that, the process returns to step S11 to wait for the operation switch to be turned on.

As described above, in the case of the refrigerant gas pressure abnormality, the refrigerant gas temperature abnormality of the compressor 33, or the compressor motor current abnormality, the lamp 34 for indicating the abnormal stop due to the abnormality other than the cooling water temperature and the power failure. Is turned on, and the refrigerator 25 is stopped to hold itself. If the cooling water temperature of the compressor 33 is abnormal, the lamp 35 for indicating that the cooling water temperature is abnormal is turned on. If the number of cooling water abnormalities n ≦ predetermined value N, the abnormality is caused by a temporary change in water level due to, for example, clogging of dust, so that the compressor 33 is automatically reset without stopping the compressor 33 so as not to be quenched. I do. On the other hand, if the cooling water abnormality frequency n> predetermined value N, it is not a temporary abnormality but a complete abnormality due to, for example, a failure of the cooling water pump.
Is stopped and self-holding is performed.

Therefore, the user can select the lamp 34,
By examining the lighting state of 35 and the operating state of the compressor 33, the measures for the superconducting magnet cooling device can be determined as follows. That is, if the lamp 34 is off, the lamp 35 is off, and the compressor 33 is on, it can be determined that the operation is normal. On the other hand, if the lamp 34 is off, the lamp 35 is on, and the compressor 33 is on, it can be determined that the cooling water abnormality has occurred N times or less (currently recovered). Therefore, the user needs to check the cooling water circulation system. If the lamp 34 is off, the lamp 35 is on, and the compressor 33 is off,
It can be determined that the compressor 33 has been stopped due to (N + 1) or more cooling water abnormalities. Therefore, the user needs to check the cooling water pump, the cooling water circulation path, the compressor 33, and the like, and repair the failed part. Also, the lamp 34 is turned on,
If the lamp 35 is off and the compressor 33 is off, it can be determined that the compressor 33 has been stopped due to an abnormal refrigerant gas pressure, an abnormal refrigerant gas temperature, or an abnormal electric current of the compressor motor. Therefore, the user needs to check and repair the compressor 33 and the compressor motor.

As described above, in the present embodiment,
In a direct cooling type superconducting macnet cooling device that directly cools the macnet 24 with the refrigerator 25, the control device 31 includes:
Based on the compressor stop command signal from the protection device 32 of the compressor 33, the compressor 33 in the case of abnormal cooling water temperature, abnormal refrigerant gas pressure, abnormal refrigerant gas temperature, or abnormal current in the compressor motor. To stop. In this case, whether the cooling water temperature abnormality is a temporary abnormality that recovers immediately or a complete abnormality that does not recover immediately is distinguished based on the number n of cooling water temperature abnormalities. In the former case, the refrigerator 24 is automatically returned without stopping so that the magnet 24 does not quench, while in the latter case, the refrigerator 25 is stopped to hold the state by itself. Therefore, it is possible to prevent the chiller 25 from stopping and self-holding even if the refrigeration machine 25 is temporarily abnormal and there is no concern about the quench of the McNet 24, thereby leading to the quench.

When the superconducting magnet cooling device is operated unattended at night, the user can use the lamps 34 and 35.
By checking the lighting state of and the operating state of the compressor 33, the operating state at night can be known, and the inspection and repair can be performed promptly and accurately.

As described above, according to the present embodiment,
It is possible to operate the superconducting McNet cooling device with high reliability at night.

If the value of the cooling water temperature abnormality frequency n by the counter 36 is displayed on the compressor unit 30, the user can grasp the state of the temporary abnormality of the cooling water temperature more minutely. Further, in the above embodiment, a two-stage Gifford McMahon refrigerator is used as the refrigerator 25, but it is needless to say that the present invention is not limited to this.

[0029]

As is apparent from the above description, the superconducting magnet cooling apparatus according to the first aspect of the present invention cools the superconducting magnet directly with a refrigerator and sets the cooling water temperature of the compressor of the refrigerator to a predetermined temperature. Then, the number of times of cooling water temperature abnormality is counted by the counter means based on the cooling water temperature abnormality signal output from the cooling water temperature monitoring means, and if the counted value is larger than a predetermined value, the cooling means The compressor is stopped because the water temperature abnormality is a complete abnormality that does not recover immediately, and this state is maintained, so that the temporary cooling water that does not have to worry about the quench of the superconducting macnet to recover immediately. Even if the temperature is abnormal, it is possible to prevent the compressor from stopping and maintaining the state, leading to the quench.

Therefore, according to the present invention, it is possible to enhance the reliability of the direct cooling type superconducting Macnet cooling device during unattended operation.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a superconducting Macnet cooling device of the present invention.

FIG. 2 is a flowchart of an abnormal stop processing operation performed by the control device in FIG. 1;

FIG. 3 is a configuration diagram of a conventional superconducting Macnet cooling device using a refrigerant system.

FIG. 4 is a flowchart of an abnormal stop processing operation performed by the control device in FIG. 3;

[Explanation of symbols]

21 ... container, 23 ... shield,
24: superconducting McNet, 25: refrigerator, 3
0: compressor unit, 31: control device, 3
2 ... Protector, 33 ... Compressor, 3
4, 35: lamp, 36: counter.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F25B 9/00 H01F 6/04

Claims (1)

(57) [Claims] 1. A direct cooling type superconducting magnet cooling device for cooling a superconducting magnet (24) with a refrigerator (25) in contact with the superconducting magnet (24), wherein a high pressure is applied to the refrigerator (25). Compressor that supplies refrigerant gas (3
3) a cooling water temperature monitoring means (32) for detecting that the temperature of the cooling water for cooling the compressor (33) has exceeded a predetermined temperature and outputting a cooling water temperature abnormality signal; Based on a cooling water temperature abnormality signal from the water temperature monitoring means (32), a counting means (36) for counting the number of cooling water temperature abnormalities, and a cooling water temperature abnormality signal from the cooling water temperature monitoring means (32). A superconducting means provided with a control means (31) for stopping the compressor (33) when the count value of the counting means (36) is larger than a predetermined value and maintaining the state; Magnet cooling device.