JP2001227832A - Starling refrigerating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent low-temperature generation efficiency from decreasing by suppressing the decrease in the pressure of a helium gas in a pressure container. SOLUTION: When a piston 16 and a displacer 18 reciprocate in first and second cylinders that are arranged in first and second pressure containers 11 and 12 that are filled with helium, the helium in the first and second pressure containers 11 and 12 repeats compression and inflation at a fixed period. The inside of the first pressure container 11 communicates with an auxiliary container 25 via a connecting path 26, and the helium that is sealed into the auxiliary container 25 is filled into the first pressure container 11 through the connecting path 26. The filling of the helium is controlled by a control valve 27 that is provided in the connecting path 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a Stirling refrigerator used for generating a low temperature.

[0002]

2. Description of the Related Art A reciprocating Stirling refrigerator for generating a low temperature is also called an inverted Stirling cycle engine in terms of heat cycle.

FIG. 8 is a sectional view showing a schematic structure of a conventional Stirling refrigerator. This Stirling refrigerator is
It has a first pressure vessel 11 and a second pressure vessel 12 coaxially connected to the first pressure vessel 11. The first pressure vessel 11 and the second pressure vessel 12 have one end face 11
a and 12a abut each other and are concentrically connected to each other, and the insides thereof communicate with each other by through holes 13 provided in the end faces 11a and 12a.

A first cylinder 14 is provided inside the first pressure vessel 11 so as to be concentric with the through-hole 13. A second cylinder 15 is also provided inside the second pressure vessel 12.
Are provided concentrically with the through holes 13. The first cylinder 14 provided in the first pressure vessel 11 is fixed to an end face 11 a of the first pressure vessel 11, and the second cylinder 15 is connected to each end face 12 a and 12 b of the second pressure vessel 12.
Are arranged at appropriate intervals.

[0005] A piston 16 is slidably disposed inside the first cylinder 14. Piston 16
The end face 11 b of the first pressure vessel 11 facing the piston 16 is connected by a piston spring 17.

A displacer body 18a of the displacer 18 is slidably disposed inside a second cylinder 15 disposed in the second pressure vessel 12. A rod portion 18 b that passes through the axial portion of the piston 16 disposed in the first cylinder 14 is inserted into the axial portion of the displacer 18.
Is provided. The distal end of the rod 18 b and the end surface 11 b of the first pressure vessel 11 to which the piston spring 17 is attached are connected by a displacer spring 19.

The working space 2 is provided inside the second pressure vessel 12.
1 is formed. The working space includes a displacer main body 18a that slides in the second cylinder 15 and the first cylinder 1
Compression space 21a between the piston 15 and the piston 15
And an expansion space 21b between the displacer body 18a and the cold head 12c provided on the end surface 12b of the second pressure vessel 12.

[0008] The compression space 21a and the expansion space 21b are connected by a regenerator 22 provided between the peripheral surface of the second pressure vessel 12 and the second cylinder. The regenerator 22
It is composed of a mesh-shaped copper material or the like.

First pressure vessel 11 and second pressure vessel 12
Are sealed by a sealing member such as an O-ring or by a method such as welding so that the filled helium does not leak outside.

The operation of the above-structured Stirling refrigerator will be described. When the piston 16 to which the piston spring 19 is connected is reciprocated in the first cylinder 14 at a constant cycle by a piston driving device (not shown) such as a linear motor, the working medium in the compression space 21a is used. A certain helium gas repeats compression and expansion at a constant cycle. Thereby, the displacer 18
Is the first pressure vessel 1 linked to the reciprocating motion of the piston 16.
Due to the pressure fluctuation of the helium gas in the first and second pressure vessels 12, the second cylinder 15 is reciprocated in a constant cycle.

The cycle of the reciprocating movement of the displacer 18 is
The shape, gas pressure, etc. of each component are designed to be the same as the cycle of the reciprocating motion of the piston 16 and to have a predetermined phase difference (usually 90 degrees). As described above, when the displacer 18 reciprocates, the helium gas expands in the expansion space 21b, whereby the cold head 12
c is cooled and a low temperature is generated.

Helium, which is the working medium of the Stirling refrigerator, has an optimum thermodynamic and kinetic value as the operating pressure. This optimum operating pressure is important for operating the refrigerator with high efficiency, and proper operating performance cannot be obtained with operation at an arbitrary pressure.

FIG. 9 shows the helium pressure and the COP value (Coefficie) indicating the refrigerating capacity of the Stirling refrigerator.
9 is a graph showing a relationship with the nt of the performance. By setting an appropriate upper limit value (filling reference pressure) Pb2 and a lower limit value (stable boundary lower limit value) Pb1 with respect to the gas pressure C1 at which the COP value becomes maximum, and setting the helium pressure within the range, Operated with high efficiency. Therefore, in order to operate the Stirling refrigerator efficiently for a long time, it is desirable that the pressure of helium in the pressure vessel is always kept within the range between the upper limit value Pb1 and the lower limit value Pb2.

[0014]

Helium filled as a working medium in the first and second pressure vessels 11 and 12 has a large specific heat and is inactive. In order to increase the refrigerating capacity of the Stirling refrigerator, Usually, it is used in a high-pressure gas state of 20 atm or more. Helium is an environmentally suitable substance, as it does not cause global warming, ozone layer depletion, etc., which have become problems in recent years. Hydrogen, which has a smaller molecular diameter than helium, has a very high specific heat, but has a high risk of explosion, and is hardly used as a working medium of a Stirling refrigerator. As described above, helium is considered to be further used as a working medium of the Stirling refrigerator.

However, since helium has the second smallest molecular diameter after hydrogen, there is a problem that helium easily leaks from the inside of the pressure vessel to the outside. As a method for sealing the pressure vessel, a method such as use of a sealing member such as an O-ring or welding of the pressure vessel is used. However, gas leakage from the pressure vessel often results from poor sealing of these seal portions. Even when gas tightness is obtained with respect to gases other than helium, when helium is used, since helium has a small molecular diameter, it leaks directly to the outside from a seal portion or a pinhole in a pressure vessel wall. Sometimes. As described above, helium is a material having a high risk of leakage, while being very advantageous in terms of thermal characteristics and environment as a working medium of the Stirling refrigerator.

As described above, in the operation of the Stirling refrigerator, it is desirable to keep the pressure of helium in the pressure vessel within a predetermined range. However, since helium is a substance that easily leaks from the pressure vessel, When the refrigerator is operated for a long period of time, helium leaks to the outside of the pressure vessel, and the pressure of helium in the pressure vessel may fall below the lower limit Pb1 of the pressure suitable for operation. It may not be possible to operate at efficiency.

The present invention has been made to solve such a problem, and its object is to solve the problem even when driving for a long time.
An object of the present invention is to provide a Stirling refrigerator capable of stably maintaining a working medium pressure in a pressure vessel and generating a low temperature with high efficiency.

[0018]

According to the Stirling refrigerator of the present invention, a piston and a displacer reciprocate in a cylinder arranged in a pressure vessel filled with a working medium, whereby the operation in the pressure vessel is performed. A Stirling refrigerator in which the medium repeats compression and expansion at a constant cycle, thereby generating a low temperature, and an auxiliary container in which the working medium is sealed at a higher pressure than the pressure container,
A connection path communicating between the inside of the pressure vessel and the inside of the auxiliary vessel, and a control valve provided in the communication path to control the flow of the working medium from the auxiliary vessel to the pressure vessel. It is characterized by the following.

When the difference between the pressure in the pressure vessel and the pressure in the auxiliary vessel is smaller than a set value, the flow of the working medium from the auxiliary vessel to the pressure vessel is shut off by the control valve.

Preferably, a predetermined signal is output when a difference between the pressure in the pressure vessel and the pressure in the auxiliary vessel is smaller than a set value.

Preferably, a predetermined signal is output when a pressure change amount of the working medium in the auxiliary container at a preset reference time is larger than a set value.

Preferably, a predetermined signal is output when the flow rate of the working medium from the auxiliary container to the pressure container at a preset reference time is larger than a set value.

[0023]

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

(Embodiment 1) FIG. 1 is a schematic configuration diagram showing an example of an embodiment of a Stirling refrigerator of the present invention. This Stirling refrigerator has a first pressure vessel 11,
A second pressure vessel 12 is coaxially connected to the first pressure vessel 11. First pressure vessel 11 and second pressure vessel 11
The pressure vessel 12 has one end faces 11a and 12a abutted on each other and is connected concentrically, and the insides of the pressure vessels 12 communicate with each other by through holes 13 provided in each end face 11a and 12a.

A first cylinder 14 is provided inside the first pressure vessel 11 so as to be concentric with the through hole 13, and a second cylinder 15 is provided inside the second pressure vessel 12.
Are provided concentrically with the through holes 13. The first cylinder 14 provided in the first pressure vessel 11 is fixed to an end face 11 a of the first pressure vessel 11, and the second cylinder 15 is connected to each end face 12 a and 12 b of the second pressure vessel 12.
Are arranged at appropriate intervals.

A piston 16 is slidably disposed inside the first cylinder 14. Piston 16
The end face 11 b of the first pressure vessel 11 facing the piston 16 is connected by a piston spring 17.

A displacer body 18a of a displacer 18 is slidably disposed inside a second cylinder 15 disposed in the second pressure vessel 12. A rod portion 18 b that passes through the axial portion of the piston 16 disposed in the first cylinder 14 is inserted into the axial portion of the displacer 18.
Are slidably provided. And the rod part 18b
And the end face 11 b of the first pressure vessel 11 to which the piston spring 17 is attached, is connected by a displacer spring 19.

The working space 2 is provided inside the second pressure vessel 12.
1 is formed. The working space 21 includes the second cylinder 1
The compression space 21 between the displacer main body 18a sliding in the inside 5 and the piston 16 sliding in the first cylinder 14
a and an expansion space 21b between the displacer body 18a and the cold head 12c provided on the end face 12b of the second pressure vessel 12.

The compression space 21a and the expansion space 21b are connected by a regenerator 22 provided between the peripheral surface of the second pressure vessel 12 and the second cylinder. The regenerator 22
It is composed of a mesh-shaped copper material or the like.

The inside of the first pressure vessel 11 forms a back space 23 with respect to the piston 16 sliding in the first cylinder 14, and the pressure in the back space 23 is detected in the first pressure vessel 11. A first pressure gauge 24 is provided.

In the following description, the gas pressure in the first pressure vessel 11 is the same as the gas pressure in the back space.

An auxiliary container 25 is provided on the outer peripheral surface of the first pressure container 11. The inside of the auxiliary container 25 is communicated with the inside of the first pressure vessel 11 by a connection passage 26. The connection passage 26 has a control valve for adjusting the flow rate of the working medium flowing through the connection passage 26. 27 are provided. The auxiliary container 25 is provided with a second pressure gauge 28 for measuring the internal pressure.

First pressure vessel 11 and second pressure vessel 12
Inside, helium of about 20 to 30 atm is filled in a gaseous state as a working medium. In addition, the auxiliary container 25
Is higher than the helium gas filled in the first and second pressure vessels 11 and 12 (for example, 35 to 5).
(0 atm) of helium in a gaseous state. Then, the first pressure vessel 11, the second pressure vessel 12, the auxiliary vessel 2
5 is a sealing member such as an O-ring or the like so that the filled helium does not leak outside.
Each is sealed by a method such as welding.

In this construction, the first cylinder 14 and the second cylinder 15 constitute a cylinder. However, the cylinder is an integral cylinder which forms a gas flow path between the compression space 21a and the regenerator 22. Is also possible.

The operation of the above-structured Stirling refrigerator will be described. When the piston 16 to which the piston spring 19 is connected is reciprocated in the first cylinder 14 at a constant cycle by a piston driving device (not shown) such as a linear motor, the working medium in the compression space 21a is used. A certain helium gas repeats compression and expansion at a constant cycle. Thereby, the displacer 18
Is the first pressure vessel 1 linked to the reciprocating motion of the piston 16.
Due to the pressure fluctuation of the helium gas in the first and second pressure vessels 12, the second cylinder 15 reciprocates at a constant cycle.

The cycle of the reciprocating movement of the displacer 18 is
The shape, gas pressure, etc. of each component are designed to be the same as the cycle of the reciprocating motion of the piston 16 and to have a predetermined phase difference (usually 90 degrees). In this manner, when the displacer 18 reciprocates, the helium gas expands in the expansion space 21b, thereby causing the cold head 12 to expand.
c is cooled and a low temperature is generated.

The helium gas repeatedly compresses and expands in the working space 21 at a constant cycle due to the reciprocating motion of the piston 16 and the displacer 18, so that the pressure in the working space 21 fluctuates at a constant cycle. In this case, the helium gas in the back space 23 also slightly compresses and expands in conjunction with the reciprocating motion of the piston 16, and the pressure in the back space 23 also fluctuates at a constant cycle. It is detected by a first pressure gauge 24 provided in the pressure vessel 11.

FIG. 2 shows how the pressure of the helium gas in the back space 23 in the first pressure vessel 11 fluctuates. The amplitude Pd of the pressure fluctuation inside the first pressure vessel 11 follows the amplitude change of the reciprocating piston 16, but the first pressure vessel 11
If the temperature condition inside is constant, the center value of the amplitude is
It depends only on the gas pressure of the helium filled in the first pressure vessel 11. The pressure at the center of the amplitude of the pressure inside the first pressure vessel 11, that is, the amplitude center pressure is Pave.

The amplitude center pressure Pave is constant when the gas pressure (average) of the entire helium filled in the first pressure vessel 11 is constant, and is equal to the total gas pressure in the first pressure vessel 11. Increases or decreases with increase or decrease. When the temperature condition in the first pressure vessel 11 is constant, the first pressure vessel 11
The total gas pressure is proportional to the mass of the gas present in the first pressure vessel 11. Therefore, when the helium in the first pressure vessel 11 is leaking outside, the first pressure vessel 1
Because the mass of helium present in 1 decreases,
If the temperature condition is constant, the gas pressure in the first pressure vessel 11 decreases, and the amplitude average pressure Pave also decreases. as a result,
During operation of the Stirling refrigerator, the first pressure gauge 2
By monitoring the fluctuating center gas pressure Pave of helium in the first pressure vessel 11 based on the measurement value of 4, the leakage of helium can be detected.

FIG. 3 is a flowchart showing a procedure for controlling the pressure in the first pressure vessel 11 of the Stirling refrigerator according to the present invention. In this case, as an initial condition, the first pressure vessel 1
The gas pressure of helium in the whole 1 (in the back space 24) is
A stable boundary lower limit value Pb1 of the amplitude center gas pressure Pave and a filling reference pressure Pb2 are set in advance. Then, in order to operate the Stirling refrigerator with high efficiency, the first pressure vessel 1
1, so that the set filling reference pressure Pb2 is obtained.
Helium is initially filled.

In this control, first, the gas pressure Pa of helium in the first pressure vessel 11 is measured by the first pressure gauge 11 provided in the first pressure vessel 11 (step S in FIG. 3).
1, the same applies hereinafter). In this case, the gas pressure of helium in the first pressure vessel 11 fluctuates at a constant cycle due to the reciprocation of the piston 16, and the average value of the gas pressure Pa measured by the first pressure gauge 11 is equal to the amplitude center gas. Pressure Pave
(Step S2).

When the amplitude center gas pressure Pave is calculated,
The calculated amplitude center gas pressure Pave is compared with a preset stable boundary lower limit value Pb1 of the amplitude center gas pressure (step S3). Then, when the calculated amplitude center gas pressure Pave is larger than the stable boundary lower limit value Pb1 (Pave> Pb1), the process returns to step S1. On the other hand, the calculated amplitude center gas pressure Pave
Is lower than the stable boundary lower limit value Pb1 (Pave ≦ Pb1), the control valve 27 is opened (step S4). Thereby, the helium in the auxiliary container 12 flows into the first pressure container 11 through the connection path 26, and the pressure in the back space 23 increases. Therefore, the amplitude center gas pressure Pave calculated based on the measurement value of the first pressure gauge 24 also increases.

As the pressure in the first pressure vessel 11 increases in this manner, the calculated amplitude center gas pressure Pave increases, and the amplitude center gas pressure Pave becomes equal to a predetermined amplitude center gas pressure. (Step S5). And the amplitude center gas pressure P
When ave becomes equal to the filling reference pressure Pb2 (Pav
e = Pb2), and the control valve 14 is closed (step S)
6).

When such control is repeated, the helium in the first pressure vessel 11 leaks to the outside for some reason and the amplitude center gas pressure Pave decreases. Helium is replenished in the pressure vessel 11 to prevent the pressure in the first pressure vessel 11 from dropping. As a result, the amplitude center pressure Pave in the back space 23 in the first pressure vessel 11 is controlled between a preset filling reference pressure Pb2 and a stable boundary lower limit value Pb1. When the center pressure Pave reaches the stable boundary lower limit value Pb1, the control valve 27 is opened. When the amplitude center pressure Pave reaches the filling reference pressure Pb2, the control valve 2 opens.
7 is closed, and the flow of helium from the auxiliary container 25 to the inside of the first pressure container 11 is controlled to be on-off. However, the amplitude center pressure Pave is reduced by the operating efficiency of the Stirling refrigerator. The opening degree of the control valve 27 may be variably controlled so that is always maintained at the optimal pressure value Pb at which the maximum pressure Pb becomes maximum.

(Embodiment 2) In the present embodiment 2, in the Stirling refrigerator shown in FIG.
When the pressure difference between the pressure in the first container 1 and the pressure in the auxiliary container 25 is smaller than the set pressure difference, the control valve 27 controls the auxiliary container 2
5 to the first pressure vessel 11 is controlled so as to block the flow of helium, and the control procedure is shown as a flowchart in FIG.

In this case, the internal pressure of the auxiliary container 25 and the first pressure container 1 are set so that helium can smoothly flow from the auxiliary container 25 through the control valve 27 into the first pressure container 11.
1. The reference value of the pressure difference from the internal pressure is the reference pressure difference ΔPc
1 is set in advance.

In this embodiment, first, the pressure Pc in the auxiliary container 25 is measured by the second pressure gauge 2 provided in the auxiliary container 25.
8 (see step S11 in FIG. 4, the same applies hereinafter). Further, the gas pressure Pa of helium in the first pressure vessel 11 is measured by the first pressure gauge 11 provided in the first pressure vessel 11 (step S12), and the average value is calculated as the amplitude center gas pressure Pave. (Step S1
3).

Then, the difference between the measured internal pressure Pc of the auxiliary container 25 and the calculated amplitude center gas pressure Pave is calculated as a pressure difference ΔPc (step S14).
The calculated pressure difference ΔPc is compared with a preset reference pressure difference ΔPc1 (step S15). in this case,
When the pressure difference △ Pc is equal to or larger than the reference pressure difference △ Pc1 (△ Pc ≧ △ Pc1), the calculated amplitude center gas pressure Pave becomes the stable boundary lower limit value Pb of the amplitude center gas pressure.
1 (step S16).

Then, the calculated amplitude center gas pressure Pav
When e is the stable boundary lower limit value Pb1 (Pave ≦ Pb1)
Then, the control valve 27 is opened (step S17), and the helium in the auxiliary container 12 flows into the first pressure container 11 through the connection path 26. Thereafter, the amplitude center gas pressure Pave calculated based on the measurement value of the first pressure gauge 24 is compared with a preset filling reference pressure Pb2 of the amplitude center gas pressure (Step S18), and the amplitude center gas pressure Pave is determined. ,
When it becomes equal to the filling reference pressure Pb2 (Pave = Pb
2), the control valve 27 is closed (step S19).

As described above, helium is replenished from the inside of the auxiliary container 25 into the first pressure container 11 due to the leakage of helium from the first pressure container 11, whereby the amount of helium in the auxiliary container 25 decreases. Thus, the pressure in the auxiliary container 12 decreases. When helium leaks from the first pressure vessel 11 continuously, the amount of helium in the auxiliary vessel 25 continues to decrease, so that the pressure in the auxiliary vessel 12 also decreases, and finally, the auxiliary vessel 25 The pressure in 25 becomes equal to or lower than the filling reference pressure Pb2 of the amplitude center gas pressure Pave.
As a result, even within the first pressure vessel 11, the amplitude center gas pressure Pave does not exceed the filling reference pressure Pb2.

In this case, the pressure difference ΔPc between the pressure in the first pressure vessel 11 and the pressure in the auxiliary vessel 25 continues to decrease,
When the pressure difference ΔPc becomes smaller than the set pressure difference ΔPc1,
The control valve 27 is shut off. Therefore, the control valve 27 is always opened, so that the inside of the first pressure vessel 11 communicates with the inside of the auxiliary container 25, and the volume of the back space 23 increases by the volume of the auxiliary container 25. There is no fear of doing it. In a Stirling refrigerator,
Since the volume of the rear space 23 is designed in consideration of the refrigeration capacity and the operation efficiency, the refrigeration capacity of the Stirling refrigerator is reduced by avoiding the increase in the volume of the rear space 23 in this manner. A decrease in operating efficiency can be prevented.

(Embodiment 3) In the Stirling refrigerator according to Embodiment 3, pressure control is performed based on a flowchart shown in FIG. As shown in FIG. 5, the internal pressure of the auxiliary container 25 and the first pressure container 11
When the pressure difference ΔPc from the internal pressure of the Stirling refrigerator is smaller than the reference pressure difference ΔPc1 (step S15), the internal pressure of the auxiliary container 25 and the internal pressure of the first pressure container 11 Pressure difference {Pc is the reference pressure difference}
A signal indicating that the control valve 27 is closed by dropping below Pc1 is sent (step S20), and the control valve 27 is closed (step S19).

When the signal indicating that the control valve 27 has been closed is output, the fact that the control valve 27 has been closed is notified by, for example, lighting of an alarm lamp. As a result, helium is replenished into the auxiliary container 25 and the like.

(Embodiment 4) FIG. 6 shows Embodiment 4 of the present invention.
4 is a flowchart showing a control procedure in the embodiment. In the present embodiment, when the change amount of the gas pressure of helium in the auxiliary container 25 is larger than the set reference change amount, abnormal leakage of helium occurs in the first pressure container 11 to the outside of the Stirling refrigerator. To emit a signal.

In this case, the amount of decrease in the pressure of helium in the auxiliary container 25 per reference time is preset as ΔXd. The reference pressure decrease amount ΔXd is set based on the inevitable leakage amount of helium from the first pressure vessel 11 to the outside which is assumed at the time of design.

In the fourth embodiment, first, the auxiliary container 25
The pressure Pc of helium inside is measured by the second pressure gauge 28 provided in the auxiliary container 25 (step S2 in FIG. 6).
1, the same applies hereinafter), and the amount of decrease ΔXc in the pressure of helium in the auxiliary container 12 per reference time is calculated (step S22). Then, the reduction amount △ Xc of the working medium pressure in the auxiliary container 25 is compared with a preset reference pressure reduction amount △ Xd (step S23), and the reduction amount △ Xc of the helium pressure in the auxiliary container 25 is If the reference pressure drop amount is equal to or more than △ Xd (△ Xc ≧ △ Xd), a signal indicating this is output to the outside (step S24). When the decrease amount △ Xc of the helium pressure in the auxiliary container 25 is smaller than the reference pressure decrease amount △ Xd, the pressure in the first pressure container 11 is detected as in the third embodiment. Since the control is performed in the same procedure as in the flowchart shown in FIG. 5 (step S12), the same reference numerals as in the steps in the flowchart shown in FIG.

The decrease amount △ Xc of the helium pressure in the auxiliary container 25 is larger than the reference pressure decrease amount △ Xd. If the helium pressure is left as it is, the helium pressure in the first pressure container 11 continues to decrease. Specifically, the amplitude center gas pressure becomes equal to or lower than the stable boundary lower limit value Pb1. In the present embodiment, the first
It can be quickly recognized that the pressure of helium in the pressure vessel 11 becomes equal to or lower than the lower limit Pb1 of the stable boundary of the amplitude center gas pressure. Therefore, the operating efficiency of the Stirling refrigerator is significantly reduced, and the refrigeration capacity is insufficient. In the worst case, it is possible to more reliably prevent serious problems such as breakage of the internal structure of the Stirling refrigerator such as the piston and the displacer.

Further, from the recognition that the amount of leakage from the first pressure vessel 11 is large, early inspection and repair of the seal and the like of the first pressure vessel 11 can be performed.

(Embodiment 5) FIG. 7 is a flowchart showing a control procedure according to Embodiment 5 of the present invention.

In the fifth embodiment, a flow meter (not shown) is provided in the connection path 26 to reduce the amount of leakage of helium in the first pressure vessel 11 of the Stirling refrigerator when it is inevitable. Design the volume of the auxiliary container so that it can be sufficiently refilled. In this case, the first pressure vessel 11
The helium replenishment flow rate ΔXd per reference time is preset. This ΔXd is the first value assumed at the time of design.
It is set based on the amount of inevitable leakage from the pressure vessel 11 to the outside.

In this embodiment, first, the pressure Pc in the auxiliary container 25 is measured by the second pressure gauge 2 provided in the auxiliary container 25.
8 (see step S11 in FIG. 7, the same applies hereinafter). Further, the gas pressure Pa of helium in the first pressure vessel 11 is measured by the first pressure gauge 11 provided in the first pressure vessel 11 (step S12), and the average value is calculated as the amplitude center gas pressure Pave. (Step S1
3).

Then, the difference between the measured internal pressure Pc of the auxiliary container 25 and the calculated amplitude center gas pressure Pave is calculated as the pressure difference ΔPc (step S14).
The calculated pressure difference ΔPc is compared with a preset reference pressure difference ΔPc1 (step S15).

When the pressure difference ΔPc is smaller than the reference pressure difference ΔPc1 (△ Pc <△ Pc1), the internal pressure of the auxiliary container 25 and the first pressure container 11 And outputs a signal indicating that the control valve 27 is closed when the pressure difference ΔPc from the internal pressure falls below the reference pressure difference ΔPc1 (step S2).
0), the control valve 27 is closed (step S19).

On the other hand, when the pressure difference に Pc is equal to or larger than the reference pressure difference △ Pc1 (ｃPc ≧ △ Pc
In 1), the calculated amplitude center gas pressure Pave is compared with the stable boundary lower limit value Pb1 of the amplitude center gas pressure (step S16).

If the calculated amplitude center gas pressure Pave is the lower limit Pb1 of the stable boundary (Pave ≦ Pb1), the control valve 27 is opened (step S17), and the helium in the auxiliary container 12 is connected to the connection path 26. Through the first pressure vessel 11.

Thereafter, the flow rate of helium replenished in the first pressure vessel 11 is measured based on the flow meter provided in the auxiliary vessel 25 (step S31), and based on the measured helium replenishment amount, The flow rate ΔXa of the replenished helium per reference time is calculated (step S32). The calculated replenishment helium flow rate per reference time ΔXa is equal to a preset reference flow rate of helium per reference time ΔXb.
Helium flow rate per reference time ΔXa
Is greater than or equal to the reference flow rate ヘ Xb of helium per reference time (△ Xa ≧ △ Xb), a signal indicating this is output to the outside (step S34).

On the other hand, the replenishment helium flow rate per reference time {Xa is the helium reference flow rate per reference time}
If it is smaller than Xb (△ Xa <△ Xb), the amplitude center gas pressure Pave calculated based on the measurement value of the first pressure gauge 24 is set to a predetermined filling reference of the amplitude center gas pressure. Compared with the pressure Pb2 (step S18), when the amplitude center gas pressure Pave becomes equal to the filling reference pressure Pb2 (Pave = Pb2), the control valve 27 is closed (step S19).

As described above, when the flow rate △ Xa of the helium gas to be replenished is larger than the reference helium gas flow rate △ Xb, a signal indicating the fact is output, so that the operating efficiency of the Stirling refrigerator significantly decreases. Then, it is possible to more reliably avoid the occurrence of a serious problem such as damage to the internal structure of a Stirling refrigerator such as a piston, a displacer, or the like, in the worst case of insufficient refrigeration capacity.

Further, from the recognition that the amount of leakage from the first pressure vessel 11 is large, early inspection and repair of the seal and the like of the first pressure vessel 11 can be performed.

[0070]

According to the Stirling refrigerator of the present invention, since the working medium sealed in the auxiliary container is made to flow through the pressure container by the control valve,
A decrease in the pressure of the working medium in the pressure vessel can be prevented, and a decrease in low-temperature generation efficiency can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of an embodiment of a Stirling refrigerator of the present invention.

FIG. 2 is a graph showing a change in gas pressure in a pressure chamber for explaining an operation of the Stirling refrigerator.

FIG. 3 is a flowchart showing an example of the operation of the Stirling refrigerator.

FIG. 4 is a flowchart showing another example of the operation of the Stirling refrigerator.

FIG. 5 is a flowchart showing still another example of the operation of the Stirling refrigerator.

FIG. 6 is a flowchart showing still another example of the operation of the Stirling refrigerator.

FIG. 7 is a flowchart showing still another example of the operation of the Stirling refrigerator.

FIG. 8 is a sectional view showing a schematic configuration of a conventional Stirling refrigerator.

FIG. 9 is a graph showing a relationship between a gas pressure of a working medium in a pressure vessel and a COP in a Stirling refrigerator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 1st pressure vessel 12 2nd pressure vessel 14 1st cylinder 15 2nd cylinder 16 piston 17 piston spring 18 displacer 19 displacer spring 24 1st pressure gauge 25 auxiliary vessel 26 connection path 27 control valve 28 2nd pressure gauge

Claims (6)

[Claims] A piston and a displacer reciprocate in a cylinder disposed in a pressure vessel filled with a working medium, whereby the working medium in the pressure vessel repeatedly compresses and expands at a constant cycle. A Stirling refrigerator in which a low temperature is generated by an auxiliary container in which a working medium is sealed at a pressure higher than that of a pressure container; and a connection path that communicates the inside of the pressure container with the inside of the auxiliary container. A control valve provided in the communication path to control the flow of the working medium from the auxiliary container to the pressure container. 2. When the difference between the pressure in the pressure vessel and the pressure in the auxiliary vessel is smaller than a set value, the control valve shuts off the flow of the working medium from the auxiliary vessel to the pressure vessel. The Stirling refrigerator according to claim 1. 3. The Stirling refrigerator according to claim 1, wherein a predetermined signal is output when a difference between the pressure in the pressure vessel and the pressure in the auxiliary vessel is smaller than a set value. 4. The Stirling refrigerator according to claim 1, wherein a predetermined signal is output when a pressure change amount of the working medium in the auxiliary container at a preset reference time is larger than a set value. 5. The Stirling refrigerator according to claim 1, wherein a predetermined signal is output when a flow rate of the working medium from the auxiliary container to the pressure container at a preset reference time is larger than a set value. 6. The Stirling refrigerator according to claim 1, wherein a predetermined signal is output when a pressure change of the working medium in the pressure vessel at a preset reference time is greater than a set value.