CN112413918A

CN112413918A - Low-temperature refrigerator

Info

Publication number: CN112413918A
Application number: CN202011236205.1A
Authority: CN
Inventors: 王哲; 胡子珩; 章彬; 汪桢子; 汪伟; 李奥; 巢伟
Original assignee: Shenzhen Power Supply Co ltd
Current assignee: Shenzhen Power Supply Co ltd
Priority date: 2020-11-09
Filing date: 2020-11-09
Publication date: 2021-02-26
Anticipated expiration: 2040-11-09
Also published as: CN112413918B

Abstract

The invention discloses a cryogenic refrigerator, comprising: the gas distribution valve comprises a cylinder (13) and a piston (10) which axially reciprocates in the cylinder (13), a hot end and a cover body (2) form a hot cavity (8), a gas distribution valve (6) is installed in the cover body (2) and limited to rotate around the axis by a valve body positioning pin (16), a gas distribution valve air hole (63) in the gas distribution valve (6) is hermetically communicated with a cover body air hole (21) and the hot cavity (8) to form a communicating passage, a pressure difference control mechanism (100) is hermetically connected between an area formed by the cover body air hole (21) and the hot cavity (8) and a low-pressure passage (22), and the direction of pressure difference controlled by the pressure difference mechanism (100) is the direction of releasing gas pressure from the communicating passage to the low-pressure passage (22). The invention can discharge the gas with over-high pressure into the low-pressure passage, thereby avoiding the loss of refrigerant gas, and simultaneously adjusting the high-low pressure difference in the refrigerator, thereby avoiding the problem of over-high power consumption caused by the internal pressure difference.

Description

Low-temperature refrigerator

Technical Field

The invention relates to the technical field of low-temperature refrigerators, in particular to a low-temperature refrigerator.

Background

A cryogenic refrigerator, typified by a Gifford-McMahon (GM) refrigerator, has an expander and a compressor of a working gas (also referred to as a refrigerant gas). The refrigerator provides high pressure air flow from the compressor, and the high pressure air flow enters the pushing piston arranged in the cylinder via the air distributing mechanism and reciprocates up and down to exchange heat with the cold accumulating material, then the high pressure air flow enters the expansion cavity to do work expansion, and then the high pressure air flow flows out of the air distributing mechanism via the pushing piston and returns to the low pressure cavity of the compressor. Through the continuous circulation process, the refrigeration effect is formed.

The cryocooler is particularly directed at a 4K double-stage cryocooler, as shown in fig. 2, the density of helium in a 4K temperature region is more than ten times to more than one hundred times at high temperature, and when the internal pressure of the cryocooler rises sharply in an emergency (power failure), if the helium cannot be discharged, the air pressure in an air cylinder rises sharply, so that equipment damage and casualties are caused. The prior art typically releases the pressure through a safety mechanism to protect the cylinder. However, the safety valve is not communicated to the low-pressure passage, and once the safety valve is opened, the internal gas flow is discharged to the outside of the refrigerator, so that the refrigerant gas loss of the refrigerator is caused, and economic loss is caused.

Disclosure of Invention

The technical problem to be solved by the present invention is to provide a cryocooler to effectively control the pressure in the cylinder.

In order to solve the above-mentioned technical problem, the present invention provides a cryogenic refrigerator comprising: the gas distribution valve is arranged in the cover body and is limited to rotate around the self axis by a valve body positioning pin, gas distribution valve holes in the gas distribution valve are communicated with the cover body gas holes and the heat cavity in an airtight manner to form a communication passage, a pressure difference control mechanism is connected between an area formed by the cover body gas holes and the heat cavity and a low-pressure passage in an airtight manner, and the direction of pressure difference controlled by the pressure difference control mechanism is the direction of releasing gas pressure from the communication passage to the low-pressure passage.

Furthermore, the cold end of the piston and the cylinder form an expansion cavity, the piston is driven by the connecting rod, and the upper end and the lower end of the connecting rod are coaxially and tightly matched with guide sleeves.

Furthermore, the rotary valve is pressed on the air distribution valve along the axial line of the air distribution valve, a high-pressure air hole on the air distribution valve hermetically communicates high-pressure air flow discharged by the compressor with a high-pressure groove on the rotary valve, and a low-pressure hole on the rotary valve is hermetically communicated with a low-pressure passage.

Further, under the drive of a cam driven by a motor, the rotary valve rotates along the axis of the rotary valve, and a high-pressure groove is communicated with an air distribution valve air hole on the air distribution valve within a period for a part of time to form high-pressure airflow which flows into the hot cavity to the piston and finally enters the expansion cavity; the high-pressure groove is not communicated with the air hole of the air distribution valve in the remaining time, and is communicated with the air hole of the air distribution valve through the low-pressure hole to form low-pressure airflow which flows out from the expansion and flows out from the air hole of the air distribution valve through the piston to the hot cavity.

Further, the differential pressure control mechanism is a one-way valve, a safety valve or a pressure relief valve.

Further, when the pressure in the region formed by the cover air hole and the thermal chamber is Pa and the pressure in the low-pressure passage is PL, the following equation is satisfied:

Pa-PL≤23bar。

further, the low-temperature refrigerator is a single-stage refrigerator or a multi-stage refrigerator.

The embodiment of the invention has the beneficial effects that: according to the invention, the pressure difference control mechanism is hermetically arranged between the communicating area of the cover body air hole and the thermal cavity and the low-pressure passage, when the pressure in the thermal cavity is overhigh, the overhigh pressure gas can be discharged into the low-pressure passage, and the loss of refrigerant gas is avoided. Meanwhile, the internal high-low pressure difference of the refrigerator can be adjusted, and the problem of overlarge power consumption caused by the internal pressure difference is avoided.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a cryocooler according to an embodiment of the present invention.

FIG. 2 is a schematic of helium density as a function of temperature.

Fig. 3 is a schematic diagram of changes of high-pressure and low-pressure pressures inside the refrigerator during the cooling process of the refrigerator.

Description of reference numerals: 1-a compressor; 1 a-a high pressure exhaust duct; 1 b-a low pressure suction duct; 2, a cover body; 21-cover body air hole; 22 — a low pressure path; 3, a cam; 31-eccentric cam handle; 41. 42, a guide sleeve; 5, connecting rods; 6-distributing valve; 62-high pressure vent; 63-air hole of air distribution valve; 7-a rotary valve; 71-low pressure hole; 72-high pressure tank; 8-a thermal chamber; 9-an expansion chamber; 10-a piston; 10 a-front hole of piston; 10 b-piston rear bore; 10 c-cold storage material; 12-a motor; 13-a cylinder; 14-a bearing; 15-a spring; 16-valve body locating pin.

Detailed Description

The following description of the embodiments refers to the accompanying drawings, which are included to illustrate specific embodiments in which the invention may be practiced. The terms of direction and position of the present invention, such as "up", "down", "front", "back", "left", "right", "inside", "outside", "top", "bottom", "side", etc., refer to the direction and position of the attached drawings. Accordingly, the use of directional and positional terms is intended to illustrate and understand the present invention and is not intended to limit the scope of the present invention.

An embodiment of the present invention provides a cryogenic refrigerator, including: the gas distribution valve comprises a cylinder 13 and a piston 10 which axially reciprocates in the cylinder 13, a hot end and a cover body 2 form a hot cavity 8 with variable volume, a gas distribution valve 6 is arranged in the cover body 2, the rotary motion of the gas distribution valve around the self axis is limited by a valve body positioning pin 16, a gas distribution valve air hole 63 on the gas distribution valve 6 is hermetically communicated with a cover body air hole 21 and the hot cavity 8 to form a communication passage, a pressure difference control mechanism 100 is hermetically connected between an area formed by the cover body air hole 21 and the hot cavity 8 and a low-pressure passage 22, and the direction of the pressure difference controlled by the pressure difference mechanism 100 is the direction of releasing gas pressure from the communication passage to the low-pressure passage 22.

Specifically, as shown in fig. 1, the cryocooler includes a compressor 1, a cover 2, a cylinder 13, and a pushing piston 10, wherein a motor 12 and a driving cam 3 are installed in the cover 2; the eccentric cam handle 31 on the cam 3 drives the connecting rod 5 to convert the rotary motion into the up-and-down reciprocating motion, thereby driving the pushing piston to move up and down in the cylinder 13. The air distribution mechanism RV consists of an air distribution valve 6 and a rotary valve 7. The gas distribution valve 6 is mounted in the housing 2, fixed therein by a positioning pin 16, and arranged coaxially with the rotary valve 7. The cam shank 31 rotates the rotary valve 7 mounted on the bearing 14 along the rotation axis. The compressor 1 sucks and compresses a refrigerant gas to discharge the refrigerant gas as a high-pressure refrigerant gas. The high-pressure discharge pipe 1a supplies the high-pressure refrigerant gas to the cover 2, and passes through the high-pressure gas hole 62 in the gas distribution valve 6 to the high-pressure groove 72 in the rotary valve 7 to which the gas is hermetically attached. The rotary valve 7 is provided with a low pressure hole 71, and the low pressure hole 71 is communicated with the low pressure passage 22 in the cover body 2. According to the position shown in fig. 1, the low-pressure hole 71 is in overlapped communication with the air distribution valve air hole 63 on the air distribution valve 6; at the moment, the system is in a low-pressure exhaust stage, gas in the expansion cavity 9 changes from high pressure to low pressure, flows out through a piston rear hole 10b, a cold accumulation material 10c and a piston front hole 10a on the pushing piston in sequence, enters the thermal cavity 8, is led out through a gas distribution valve air hole 63, enters the low-pressure passage 22 and returns to the low-pressure suction pipeline 1b of the compressor 1. When the rotary valve 7 rotates a certain angle, at this time, the low pressure hole 71 is not communicated with the air distribution valve air hole 63 on the air distribution valve 6, and becomes a high pressure groove 72 on the rotary valve 7 to be communicated with the air distribution valve air hole 63 on the air distribution valve 6, and high pressure air discharged by the compressor 1 passes through the high pressure air hole 62 on the air distribution valve 6 and the high pressure groove 72 on the rotary valve 7 communicated with the same, passes through the cover body air hole 21, the hot chamber 8, enters the cylinder 13, and sequentially passes through the piston front hole 10a on the push piston, the cold storage material 10c and the piston rear hole 10b to enter the expansion chamber 9. In the above process, the high pressure air discharged from the compressor 1 acts on the back surface of the air distribution valve 6, and the air distribution valve 6 is tightly attached to the rotary valve 7 by the positive pressure on the back surface parallel to the area of the air distribution surface, so that the high-low pressure valve on the air distribution mechanism is separated to isolate the high-low pressure air flow.

According to the direction of the arrow shown in fig. 1, the direction of the differential pressure, i.e., the direction in which the pressure is released from the thermal chamber 8 to the low-pressure passage 22, is controlled by the differential pressure control mechanism 100. The differential pressure control mechanism 100 is typically selected to be a one-way valve, a safety valve, or a pressure relief valve.

When the high-pressure valve is opened, the pressure Pa in the thermal cavity 8 is generally between 28 and 22bar, and when the low-pressure valve is opened, the pressure Pa is consistent with the pressure in the low-pressure passage 22 and is generally between 3 and 6bar, and the internal pressure changes in the process that the refrigerating machine is lowered from the room temperature to the lowest temperature as shown in FIG. 3. The density of helium in this process will also vary from 1kg/m³Increased to 100 kg/m or more³。

When the refrigerator is stopped and does not work due to power failure and the temperature of the low-temperature helium gas rises sharply, the pressure Pa in the thermal chamber 8 rises sharply, and a large pressure difference with the pressure PL in the low-pressure passage 22 triggers the pressure difference control mechanism 100 to open, thereby discharging the excessive pressure in the cylinder 13 to the low-pressure passage 22. Because the low-pressure passage 22 is always communicated with the low-pressure side of the compressor 1 through the low-pressure suction pipeline 1b, a low-pressure buffer area with the volume far larger than the internal volume of the refrigerator is formed, namely, an internal bypass is formed, and the pressure in the cylinder 13 is always ensured to be smaller than the design pressure. The difference between the embodiment of the invention and the prior art is that the discharged refrigerant gas directly returns to the compressor system, is not leaked to the atmosphere, does not cause the loss of the refrigerant gas, and does not need to be added again.

Since the pressure PL of the low-pressure passage 22 is generally 6bar, the pressure Pa in the thermal chamber 8 and the cylinder 13 cannot generally exceed 29bar, otherwise the cylinder 13 is liable to cause problems. Since the pressure of Pa cannot be smaller than PL, Pa-PL.ltoreq.23 bar is set as the trigger pressure difference of the pressure difference control mechanism 100 at the time of designing the pressure difference, and therefore Pa-PL.ltoreq.20 bar is preferably designed, and Pa-PL.ltoreq.18 bar is more preferably designed.

In addition to the above advantages, the present invention has another advantage: that is, in the cooling process, as shown in fig. 3, the pressure of the high-pressure airflow entering the thermal cavity 8 and the cylinder 13 is relatively high at the beginning stage of the cooling process, and reaches 28bar, and the pressure of the low-pressure exhaust is generally only about 3 bar. The lowest temperature of the refrigerator is that the high-pressure air flow is only 22bar generally, and the low-pressure return air pressure is 6bar generally. The pressure difference provided by the compressor 1 will thus vary from 25bar to 16bar during the cooling down. The power consumption of the compressor 1 is in direct proportion to the pressure difference provided by the compressor, so that the electric power consumed by the compressor 1 in the starting process is far larger than that consumed by the refrigerator in the stable state, and the economic benefit is poor.

In the present embodiment, due to the existence of the differential pressure control mechanism 100, when the rotary valve mechanism RV is in the process of switching high and low pressures, the high and low pressures of the whole refrigerating machine system can be adjusted through the process of discharging the pressure from the low-pressure passage 22 at the top of the thermal cavity 8, so that the differential pressure between the high and low pressures is controlled within 23bar, and the power consumption of the compressor is reduced. More preferably, the pressure difference is set at 18bar, i.e. Pa-PL 18 b. In the cooling process, the pressure difference between the high pressure and the low pressure of the whole refrigerating machine system is not too large (less than the limit pressure difference of 25 bar), and the power consumption of the compressor 1 is in a reasonable range. When the temperature reduction process is finished and the refrigerator is in a stable state, the internal pressure difference is reduced to 16bar, the pressure difference control mechanism 100 cannot be triggered to be opened at the moment, the internal bypass path is closed, all air flow of the compressor passes through the piston 10 and enters the expansion cavity 9 for expansion refrigeration, and bypass loss cannot be caused.

As can be seen from the above description, the embodiments of the present invention have the following beneficial effects: according to the invention, the pressure difference control mechanism is hermetically arranged between the communicating area of the cover body air hole and the thermal cavity and the low-pressure passage, when the pressure in the thermal cavity is overhigh, the overhigh pressure gas can be discharged into the low-pressure passage, and the loss of refrigerant gas is avoided. Meanwhile, the internal high-low pressure difference of the refrigerator can be adjusted, and the problem of overlarge power consumption caused by the internal pressure difference is avoided.

The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention, and it is therefore to be understood that the invention is not limited by the scope of the appended claims.

Claims

1. A cryocooler, comprising: the gas distribution valve comprises a cylinder (13) and a piston (10) which axially reciprocates in the cylinder (13), a hot end and a cover body (2) form a hot cavity (8) with variable volume, a gas distribution valve (6) is installed in the cover body (2), the rotating motion of the gas distribution valve around the self axis is limited by a valve body positioning pin (16), a gas distribution valve air hole (63) in the gas distribution valve (6) is hermetically communicated with a cover body air hole (21) and the hot cavity (8) to form a communicating passage, a pressure difference control mechanism (100) is hermetically connected between an area formed by the cover body air hole (21) and the hot cavity (8) and a low pressure passage (22), and the direction of the pressure difference controlled by the pressure difference mechanism (100) is the direction of releasing gas pressure from the communicating passage to the low pressure passage (22).

2. The cryocooler according to claim 1, characterized in that the cold end of the piston (10) forms an expansion chamber (9) with the cylinder (13), the piston (10) being driven by the connecting rod (5) and being coaxially fitted with guide sleeves (41), (42) at the upper and lower ends of the connecting rod (5).

3. The cryocooler according to claim 1, characterized in that the rotary valve (7) is pressed against the gas distribution valve (6) along the axial direction of the gas distribution valve (6), the high-pressure gas port (62) of the gas distribution valve (6) connects the high-pressure gas flow discharged from the compressor (1) in a gas-tight manner to the high-pressure groove (72) of the rotary valve (7), and the low-pressure gas port (71) of the rotary valve (7) connects in a gas-tight manner to the low-pressure channel (22).

4. A cryogenic refrigerator according to claim 3, characterized in that the rotary valve (7) is rotated along its axis by the cam (3) driven by the motor (12), and the high pressure groove (72) is connected to the gas distribution valve air hole (63) of the gas distribution valve (6) for a part of the cycle, and forms a high pressure gas flow into the hot chamber (8) to the piston (10) and finally into the expansion chamber (9); the high-pressure groove is not communicated with the air distribution valve air hole (63) in the remaining time, and is communicated with the air distribution valve air hole (63) through a low-pressure hole (71), so that low-pressure air flows out from the expansion part (9), passes through the piston (10) to the hot cavity (8) and flows out from the air distribution valve air hole (63).

5. The cryocooler according to claim 1, wherein the differential pressure control mechanism (100) is a one-way valve, a safety valve or a pressure relief valve.

6. The cryocooler according to claim 1, wherein a pressure in a region defined by the cover air hole (21) and the thermal chamber (8) is Pa, and a pressure in the low-pressure passage (22) is PL, and the following equation is satisfied:

Pa-PL≤23bar。

7. a cryogenic refrigerator according to any one of claims 1 to 6, wherein the cryogenic refrigerator is a single stage refrigerator or a multi-stage refrigerator.