A self-cascade refrigeration system and a low-temperature cabinet

Abstract

The present invention discloses a self-cascade refrigeration system and a low-temperature cabinet. The self-cascade refrigeration system includes: a self-cascade refrigeration circuit: formed by a compressor, an oil separator, a condenser, a multi-stage gas-liquid separator, a multi-stage heat exchanger, a regenerator, and an evaporator connected via a refrigerant liquid circuit and a refrigerant gas circuit; an expansion tank connected to the refrigerant gas circuit to relieve system pressure; an interface portion is formed at the bottom of the expansion tank and communicates with the internal space of the expansion tank; the compressor suction side is connected to the interface portion via a compressor suction channel. The present invention solves the problem of compressor oil return difficulty in the prior art self-cascade system.

Description

Technical Field

[0001] The present invention relates to the field of cryogenic technology, and in particular to an ultra-low temperature self-cascade refrigeration system and an improvement to the structure of a low-temperature cabinet having the self-cascade refrigeration system. Background Art

[0002] The existing ultra-low temperature low temperature self-cascade system structure is formed by connecting a compressor, an oil separator, a condenser, a multi-stage gas-liquid separator, a multi-stage heat exchanger, a regenerator and an evaporator.

[0003] The high-temperature and high-pressure gaseous refrigerant discharged from the compressor passes through the oil separator for gas-oil separation and then enters the condenser for condensation. The condensed refrigerant enters the first-stage gas-liquid separator for diversion. The diverted gaseous refrigerant directly flows into its corresponding heat exchanger through the refrigerant gas pipe configured in the gas-liquid separator.

[0004] The liquid refrigerant is mixed with the liquid refrigerant returned from the return air branch of the next stage heat exchanger and then enters the heat exchanger to exchange heat with the gaseous refrigerant. The refrigerant after heat exchange will enter the next stage gas-liquid separator.

[0005] Then it enters the next stage heat exchanger for heat exchange. The refrigerant is continuously cooled through the multi-stage heat exchanger. The refrigerant in the last stage heat exchanger enters the regenerator, and after passing through the regenerator, it enters the evaporator for evaporation, reaching the final required evaporation temperature to achieve ultra-low temperature refrigeration.

[0006] In order to achieve pressure relief, an expansion tank is usually connected to the refrigerant gas line of the entire system. During pressure relief, the gaseous refrigerant in the system can be discharged into the expansion tank to achieve pressure relief. After pressure relief, the lubricating oil brought into the expansion tank by the refrigerant is mainly concentrated at the bottom of the expansion tank.

[0007] When the existing expansion tank is set up, it is generally provided with an air intake port located at the top and an exhaust port located at the bottom. The compressor air intake channel is connected to the air intake port at the top. Since the lubricating oil is less and accumulates at the bottom of the expansion tank, it is difficult for the compressor to suck out the lubricating oil at the bottom of the expansion tank, resulting in the problem of oil return difficulty. Summary of the Invention

[0008] The present invention addresses the problem of oil return difficulty in the compressor of the auto-cascade system in the prior art;

[0009] The present invention proposes a novel low-temperature self-cascade system, which has an interface at the bottom of the expansion tank to communicate with the compressor suction channel, so that the lubricating oil can be smoothly sucked out by the compressor, solving the problem of difficult oil return of the compressor.

[0010] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0011] An auto-cascade refrigeration system, comprising:

[0012] Auto-cascade refrigeration circuit: It is formed by a compressor, oil separator, condenser, multi-stage gas-liquid separator, multi-stage heat exchanger, regenerator, and evaporator connected by a refrigerant liquid circuit and a refrigerant gas circuit;

[0013] The expansion tank is connected to the refrigerant gas line to relieve the pressure of the system;

[0014] An interface portion communicating with the internal space of the expansion tank is formed at the bottom of the expansion tank, and the suction side of the compressor is connected to the interface portion through a compressor suction channel.

[0015] In some embodiments of the present application, the interface portion is an interface pipe, which is inserted at the bottom position of the expansion tank. The expansion tank is connected to the refrigerant gas path through a pressure relief channel, and the pressure relief channel and the compressor suction channel are both connected to the interface pipe.

[0016] In some embodiments of the present application, the interface portion includes a first interface and a second interface, both of which are arranged at the bottom of the expansion tank, the first interface is connected to the pressure relief channel, and the second interface is connected to the compressor intake channel.

[0017] In some embodiments of the present application, a throttling component for achieving throttling and pressure reduction is provided on the compressor intake passage.

[0018] In some embodiments of the present application, the throttling component is a throttling capillary.

[0019] In some embodiments of the present application, the refrigerant gas circuit includes a refrigerant bronchial pipe configured with a gas-liquid separator and connected to its corresponding heat exchanger;

[0020] The pressure relief channel is connected to the expansion tank and the refrigerant gas pipe of one of the gas-liquid separators below the first-stage gas-liquid separator. A control component for controlling the on / off of the pressure relief channel is provided on the pressure relief channel.

[0021] Furthermore, a filter element is provided on the compressor intake passage.

[0022] A low-temperature cabinet includes a housing, the auto-cascade refrigeration system described in the above technical solution, and:

[0023] a first partition member, the first partition member being arranged in the box shell to divide the box shell into a first chamber and a second chamber;

[0024] The second partition component is arranged in the first chamber to divide the first chamber into a compressor compartment and an equipment compartment. The equipment compartment is arranged above the compressor compartment, and the expansion tank is arranged in the equipment compartment.

[0025] Furthermore, a clamping portion is provided on the second partition component, and the expansion tank is clamped in the clamping portion, with its interface portion facing the compressor compartment.

[0026] Furthermore, it also includes a clamping component for clamping and fixing the expansion tank, and the clamping component is arranged on the second partition component.

[0027] Compared with the prior art, the advantages and positive effects of the present invention are:

[0028] The present invention is provided with an interface portion at the bottom of the expansion tank. When the expansion tank is placed normally, the oil flowing back into the expansion tank will be concentrated at the bottom of the expansion tank due to gravity. The compressor suction channel is connected with the bottom space of the expansion tank through the interface portion. In this way, when the compressor absorbs oil, the oil droplets accumulated at the bottom of the expansion tank will be more easily sucked into the compressor suction channel and enter the interior of the compressor, thereby solving the problem of difficult oil return of the compressor.

[0029] Other features and advantages of the present invention will become more apparent after reading the detailed description of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are some embodiments of the present invention.

[0031] For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0032] Figure 1 This is a system principle diagram of a first implementation mode of the corresponding interface portion of the auto-cascade refrigeration system in an embodiment of the present invention;

[0033] Figure 2 This is a system principle diagram of a second implementation manner of the corresponding interface portion of the auto-cascade refrigeration system in an embodiment of the present invention.

[0034] Figure 3 The structure of the low temperature cabinet in the embodiment of the present invention is shown as follows: Figure 1 ;

[0035] Figure 4 The structure of the low temperature cabinet in the embodiment of the present invention is shown as follows: Figure 2 ;

[0036] Figure 5The structure of the low temperature cabinet in the embodiment of the present invention is shown as follows Figure 3 ;

[0037] Figure 6 This is a structural diagram of a first embodiment of the auto-cascade refrigeration system interface portion corresponding to the low-temperature cabinet in an embodiment of the present invention.

[0038] Among them, compressor - 110;

[0039] Oil separator-120;

[0040] Condenser - 130;

[0041] Regenerator-140;

[0042] Evaporator - 150;

[0043] Multi-stage gas-liquid separator-200;

[0044] First stage gas-liquid separator-210;

[0045] Final gas-liquid separator-220;

[0046] Multi-stage heat exchanger-300;

[0047] First stage heat exchanger-310;

[0048] Final stage heat exchanger-320;

[0049] Expansion tank - 400;

[0050] Interface unit-410;

[0051] First interface - 411;

[0052] Second interface - 412;

[0053] Compressor suction channel-500;

[0054] Pressure relief channel-600;

[0055] Throttle component - 700;

[0056] Filter element-800;

[0057] Box shell-910;

[0058] First chamber - 911;

[0059] Compressor compartment-9111;

[0060] Equipment warehouse-9112;

[0061] Second Chamber - 912

[0062] First partition member-920;

[0063] Second partition member-930;

[0064] Card installation department-931;

[0065] Clamping parts-940. DETAILED DESCRIPTION

[0066] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0067] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0068] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "install", "connect" and "connect" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection.

[0069] For those skilled in the art, the specific meanings of the above terms in the present invention can be understood in specific circumstances. In the description of the above embodiments, specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0070] The terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the quantity of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features.

[0071] In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0072] The present invention provides an embodiment of an auto-cascade refrigeration system, comprising:

[0073] The self-cascade refrigeration circuit is formed by a compressor 110, an oil separator 120, a condenser 130, a multi-stage gas-liquid separator 200, a multi-stage heat exchanger 300, a regenerator 140, and an evaporator 150 connected by a refrigerant gas path and a refrigerant liquid path.

[0074] During the specific connection, the exhaust side of the compressor 110 is connected to the oil separator 120 , and the air outlet of the oil separator 120 is connected to the condenser 130 . The oil separator 120 is mainly used to separate the refrigerant and oil flowing out of the compressor 110 into vapor and oil.

[0075] The refrigerant discharged from the compressor 110 passes through the oil separator 120 , and the separated gaseous refrigerant enters the condenser 130 .

[0076] The oil separator 120 is also connected to the return air side of the compressor 110 via a pipeline, so as to return the oil separated by the oil separator 120 to the compressor 110 .

[0077] The refrigerant enters the condenser 130 to be condensed, and the condensed refrigerant enters the multi-stage heat exchanger 300 to be cascaded.

[0078] Each stage of the heat exchanger is correspondingly configured with a gas-liquid separator, and the multi-stage heat exchanger 300 corresponds to the multi-stage gas-liquid separator 200 .

[0079] Each stage of the gas-liquid separator is equipped with a refrigerant branch liquid pipe and a refrigerant bronchial pipe 170 , and is connected to the corresponding heat exchanger via the refrigerant branch liquid pipe and the refrigerant bronchial pipe 170 .

[0080] The first-stage heat exchanger 310 is connected to the compressor 110 through the main return air path, and the first-stage gas-liquid separator 210 corresponding to the first-stage heat exchanger 310 is connected to the condenser 130 .

[0081] The remaining gas-liquid separators below the first stage are connected to the upper stage heat exchanger, and the refrigerant of the upper stage heat exchanger is introduced into the corresponding heat exchanger through the refrigerant branch liquid pipe and the refrigerant branch pipe 170 as liquid refrigerant and gaseous refrigerant respectively.

[0082] The remaining gas-liquid separators below the first stage include an intermediate gas-liquid separator and a final gas-liquid separator 220 .

[0083] The remaining stages of heat exchangers below the first stage heat exchanger 310 include an intermediate stage heat exchanger and a final stage heat exchanger 320 .

[0084] When the auto-cascade refrigeration system is a two-stage cascade refrigeration system, the multi-stage heat exchanger 300 correspondingly includes a first-stage heat exchanger 310 and a final-stage heat exchanger 320 , and the multi-stage gas-liquid separator 200 correspondingly includes a first-stage gas-liquid separator 210 and a final-stage gas-liquid separator 220 .

[0085] Each stage of heat exchanger is connected to the corresponding refrigerant branch pipe of the previous stage heat exchanger through the return air branch to merge the return refrigerant with the liquid refrigerant separated by the corresponding previous stage gas-liquid separator.

[0086] The regenerator 140 is connected to the final heat exchanger 320 and the evaporator 150 of the remaining heat exchangers to transfer the refrigerant flowing out of the final heat exchanger 320 to the evaporator 150 for further condensation and cooling.

[0087] The return air branch corresponding to the regenerator 140 is connected to the refrigerant branch pipe of the final stage heat exchanger 320 for refrigerant return.

[0088] The refrigerant discharged from the compressor 110 is separated by the oil separator 120 and enters the condenser 130 refrigerant, and then enters the first-stage gas-liquid separator 210 for gas-liquid separation.

[0089] After separation, the gaseous refrigerant is mixed with the liquid refrigerant and the diverted refrigerant that pass through the next-stage return air branch and enters the first-stage heat exchanger 310 for heat exchange. The refrigerant after heat exchange then enters the gas-liquid separator of the next stage for heat exchange. The cycle continues in sequence, and the multi-stage heat exchanger 300 is continuously overlapped to condense the refrigerant. Finally, it enters the regenerator 140 and the evaporator 150, and reaches the final temperature through the evaporator 150.

[0090] The pressure relief channel 600 is connected to the expansion tank 400 at one end and to the refrigerant gas path of the entire system at the other end for relieving the pressure of the system.

[0091] The refrigerant gas path is composed of all refrigerant flow paths through which the refrigerant flows when the entire system is running, and includes a plurality of refrigerant bronchial pipes 170 corresponding to the gas-liquid separators.

[0092] An interface portion 410 communicating with the internal space of the expansion tank 400 is formed at the bottom of the expansion tank 400 .

[0093] The bottom in this embodiment refers to the side of the expansion tank 400 facing the ground when the expansion tank 400 is in a normal placement state.

[0094] The compressor intake passage 500 is connected between the intake side of the compressor 110 and the interface portion 410 .

[0095] When the expansion tank 400 is placed normally, the lubricating oil flowing back into the expansion tank 400 through the pressure relief channel 600 will be concentrated and accumulated at the bottom of the expansion tank 400 due to gravity, and the amount of lubricating oil is large.

[0096] Since the interface portion 410 is arranged at the bottom of the expansion tank 400 and is connected to the compressor intake passage 500, when the compressor 110 absorbs oil, the lubricating oil in the expansion tank 400 can more easily enter the compressor intake passage 500, thereby solving the problem of oil return difficulty of the compressor 110.

[0097] In specific configuration, the compressor 110 in this embodiment can be disposed above or below the expansion tank 400 .

[0098] When the compressor 110 is disposed below the expansion tank 400 , during oil return, the oil at the bottom of the expansion tank 400 may be returned under the action of gravity and the suction force of the compressor 110 .

[0099] Of course, the compressor 110 may also be arranged above the expansion tank 400 . As long as the interface portion 410 is located at the bottom of the expansion tank 400 , it can be ensured that oil can be smoothly returned when the compressor 110 inhales air.

[0100] In some embodiments of the present application, Figure 1 、 Figure 6 As shown: the interface part 410 is an interface pipe, which is inserted at the bottom position of the expansion tank 400, and the pressure relief channel 600 and the compressor suction channel 500 are configured as a pressure relief pipe and a compressor suction pipe, which are both connected to the interface pipe.

[0101] That is, when connected, the pressure relief channel 600 is connected to the interface pipe, and the compressor suction channel 500 is also correspondingly connected to the interface pipe. The interface pipe, the compressor suction channel 500 and the pressure relief channel 600 form a three-way channel structure, which simplifies the connection structure.

[0102] When pressure relief is required, the pressure relief passage 600 is controlled to be open. At this time, the refrigerant and oil will flow through the pressure relief passage 600 and then back into the expansion tank 400 through the interface pipe to relieve pressure on the entire system.

[0103] When oil return is required, the compressor suction passage 500 is controlled to be open, and the compressor 110 is activated to suck the expanding lubricating oil and gaseous refrigerant into the interior through the interface pipe.

[0104] In some embodiments of the present application, Figure 2 As shown, the interface portion 410 includes a first interface 411 and a second interface 412 , and the first interface 411 and the second interface 412 are both located at the bottom of the expansion tank 400 .

[0105] The first interface 411 is connected to the pressure relief passage 600 , and the second interface 412 is connected to the compressor intake passage 500 .

[0106] The first interface 411 and the second interface 412 are arranged in parallel. The pressure relief channel 600 can be connected to the expansion tank 400 through the first interface 411 , and the compressor intake channel 500 can be connected to the expansion tank 400 through the second interface 412 .

[0107] Of course, in some embodiments, the interface portion 410 may also be configured as a first interface pipe and a second interface pipe, and both the first interface pipe and the second interface pipe may be connected to the bottom of the expansion tank 400 .

[0108] Alternatively, the first interface pipe and the second interface pipe are connected to each other, and at the same time, a connecting pipe is also led out from the bottom of the expansion tank 400. The first interface pipe, the second interface pipe and the connecting pipe can also form a three-way connecting pipe structure.

[0109] In some embodiments of the present application: the interface portion 410 is an opening, and is provided with one, which is opened at the bottom of the expansion tank 400, the pressure relief port is provided at the top of the expansion tank 400, the pressure relief channel 600 is connected to the pressure relief port, and the compressor intake channel 500 is connected to the opening located at the bottom of the expansion tank 400.

[0110] That is, arranging the pressure relief port at the top can also facilitate oil return of the compressor 110 .

[0111] In some embodiments of the present application, a throttling component 700 for achieving throttling and pressure reduction is provided on the compressor intake passage 500 .

[0112] By setting the throttling component 700, the gaseous refrigerant in the pressure relief channel 600 can be throttled and reduced in pressure when it flows back to the compressor 110 side. In this way, the gaseous refrigerant released into the expansion tank 400 will not enter the compressor 110 quickly, but will enter the compressor 110 slowly, allowing the compressor 110 to have enough time to establish a balance for the entire auto-cascade refrigeration system.

[0113] In addition, after the expansion tank 400 is depressurized, if the throttling component 700 is not set on the compressor intake channel 500, the gaseous refrigerant will quickly enter the compressor 110 through the compressor intake channel 500. The compressor 110 has just completed the pressure relief and is pressurized again. This will cause the compressor 110 to be directly stuck or the compressor 110 to frequently relieve pressure, making the entire system unable to refrigerate.

[0114] The throttling component 700 may correspond to an electronic expansion valve or a throttling capillary tube.

[0115] If the throttling component 700 is an electronic expansion valve, the throttling effect can be achieved by adjusting the opening of the electronic expansion valve during use.

[0116] Of course, in some embodiments, the opening and closing of the channel can be controlled by setting a control component on the compressor intake channel 500 to prevent the gaseous refrigerant in the expansion tank 400 from quickly entering the compressor 110. The control component can be a solenoid valve.

[0117] In some preferred embodiments of the present application, the throttling component 700 is a throttling capillary.

[0118] During pressure relief, the amount of oil flowing back into the expansion tank 400 through the pressure relief passage 600 is relatively small, and it is difficult to extract the oil back through the compressor suction passage 500 .

[0119] If a throttling capillary is provided on the compressor intake passage 500, the compressor 110 can more easily suck the oil in the expansion tank 400 into its interior, making oil return easier, mainly because the cross-sectional area corresponding to the throttling capillary is small, making it easier to form an oil seal when sucking oil.

[0120] In addition, if the throttling component 700 uses a throttling capillary tube, the entire compressor suction channel 500 can always be in a normally open state. In this way, there is no need to set up a separate control program to separately control the on and off of the compressor suction channel 500, which simplifies the entire system control.

[0121] In some embodiments of the present application, a filter element 800 is further provided on the compressor intake passage 500 .

[0122] The filter element 800 may be a filter for filtering impurities in the refrigerant flowing on the compressor suction channel 500 , thereby preventing the compressor suction channel 500 from being blocked.

[0123] In order to minimize the amount of lubricating oil in the entire low-temperature auto-cascade system flowing into the expansion tank 400 , the oil loss in the system is reduced, and the normal operation of the entire system is ensured.

[0124] During the setting, the pressure relief channel 600 is connected to the refrigerant bronchial pipe 170 corresponding to one of the gas-liquid separators below the first-stage gas-liquid separator 210 .

[0125] And to ensure that it can relieve pressure, it should be connected to the high-pressure end of the refrigerant bronchial pipe 170, that is, the end that is not throttled by the throttling element.

[0126] The refrigerant in the refrigerant duct 170 below the first-stage gas-liquid separator 210 has at least been separated by the oil separator 120 and the first-stage gas-liquid separator 210 .

[0127] After multiple oil separations, the corresponding lubricating oil content on the refrigerant bronchus 170 is particularly small. Therefore, when the pressure is released, the lubricating oil carried into the expansion tank 400 by the gaseous refrigerant is also less, thereby avoiding excessive lubricating oil from entering the system and affecting the normal operation of the system.

[0128] Example 2:

[0129] This application proposes an embodiment of a low-temperature cabinet, such as Figure 3-5 As shown, a box shell 910 is included, and a accommodating space is formed inside the box shell 910. In order to achieve the thermal insulation performance of the low-temperature cabinet, in some embodiments, a thermal insulation layer is also provided on the box shell 910. The thermal insulation layer can prevent the cold in the low-temperature cabinet from leaking out.

[0130] The present application also includes the self-cascade refrigeration system in Example 1, which is assembled in the accommodation space. The self-cascade refrigeration system arranged in the box shell 910 can be used to perform low-temperature refrigeration on items stored inside the box shell 910, thereby realizing the storage of low-temperature items.

[0131] In some embodiments of the present application, a first partition component 920 is further provided inside the box shell 910. The first partition component 920 divides the box shell 910 into a first chamber 911 and a second chamber 912. The first partition component 920 can be a partition plate, which is vertically arranged in the box shell 910. The first chamber 911 and the second chamber 912 divided by the first partition component 920 are arranged side by side.

[0132] In some embodiments of the present application, a second partition component 930 is further provided in the first chamber 911 , and the second partition component 930 divides the first chamber 911 into a compressor compartment 9111 and an equipment compartment 9112 .

[0133] The second partition part 930 can optionally use a second partition plate, which is arranged perpendicular to the first partition part 920 and the side wall of the first chamber 911 and is arranged horizontally to divide the first chamber 911. It can be fixedly connected to the first partition part 920 and the side wall of the first chamber 911 by welding or snapping.

[0134] The equipment compartment 9112 is arranged above the compressor compartment 9111 , and the expansion tank 400 is arranged in the equipment compartment 9112 .

[0135] The second partition component 930 enables the expansion tank 400 to be installed above the compressor compartment 9111. When the compressor 110 returns oil, the lubricating oil at the bottom of the expansion tank 400 can more easily flow back to the inside of the compressor 110 due to gravity.

[0136] In order to achieve fixed assembly of the expansion tank 400, in some embodiments of the present application, a clamping portion 931 is provided on the second partition component 930, and the expansion tank 400 is clamped in the clamping portion 931, with its interface portion 410 facing the compressor compartment 9111.

[0137] In some embodiments of the present application, the clamping portion 931 is a clamping slot provided on the second partition member 930 , the clamping slot passes through the second partition member 930 , and the expansion tank 400 is clamped on the clamping slot.

[0138] Its interface portion 410 is exposed from the bottom of the slot to facilitate connection and cooperation with the pressure relief channel 600 and the compressor intake channel 500 located in the compressor compartment 9111.

[0139] In order to further fix the expansion tank 400 , in some embodiments, a clamping component 940 for clamping and fixing the expansion tank 400 is further provided. The clamping component 940 is provided on the second partition component 930 .

[0140] The clamping component 940 can directly use a clamp or other clamping part in the existing technology, and it can be used to clamp and fix the expansion tank 400. No specific restrictions are made here. During assembly, the clamping component 940 can be installed on the second partition component 930 accordingly.

[0141] The clamping component 930 can be configured as a structure that adapts to the outer contour of the expansion tank 400 so that it can be clamped relatively tightly on the outer surface of the expansion tank 400 .

[0142] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for a person skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to replace some of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions claimed to be protected by the present invention.

Claims

1. An auto-cascade refrigeration system comprising: Auto-cascade refrigeration circuit: It is formed by a compressor, oil separator, condenser, multi-stage gas-liquid separator, multi-stage heat exchanger, regenerator, and evaporator connected by a refrigerant liquid circuit and a refrigerant gas circuit; The expansion tank is connected to the refrigerant gas line to relieve the pressure of the system. It is characterized by: An interface portion communicating with the internal space of the expansion tank is formed at the bottom of the expansion tank, and the suction side of the compressor is connected to the interface portion through a compressor suction channel, and a filter element is also provided on the compressor suction channel; The refrigerant gas circuit includes a refrigerant bronchial pipe equipped with a multi-stage gas-liquid separator, the pressure relief channel is connected to the refrigerant gas pipe equipped with one of the gas-liquid separators below the expansion tank and the first-stage gas-liquid separator, and a control component for controlling the opening and closing of the pressure relief channel is provided on the pressure relief channel.

2. The auto-cascade refrigeration system according to claim 1, characterized in that: The interface portion is an interface pipe, which is inserted at the bottom position of the expansion tank. The expansion tank is connected to the refrigerant gas path through a pressure relief channel. The pressure relief channel and the compressor suction channel are both connected to the interface pipe.

3. The auto-cascade refrigeration system according to claim 1, characterized in that: The interface portion includes a first interface and a second interface, wherein the first interface and the second interface are both arranged at the bottom of the expansion tank, the first interface is connected to the pressure relief channel, and the second interface is connected to the compressor suction channel.

4. The auto-cascade refrigeration system according to any one of claims 1 to 3, characterized in that: A throttling component for achieving throttling and pressure reduction is provided on the compressor intake passage.

5. The auto-cascade refrigeration system according to any one of claims 1 to 3, characterized in that: The throttling component is a throttling capillary.

6. A low temperature cabinet, comprising a box shell, characterized in that: Also includes the auto-cascade refrigeration system according to any one of claims 1 to 5 and: a first partition member, the first partition member being arranged in the box shell to divide the box shell into a first chamber and a second chamber; The second partition component is arranged in the first chamber to divide the first chamber into a compressor compartment and an equipment compartment. The equipment compartment is arranged above the compressor compartment, and the expansion tank is arranged in the equipment compartment.

7. The low-temperature cabinet according to claim 6, characterized in that: A clamping portion is provided on the second partition component, and the expansion tank is clamped in the clamping portion, with its interface portion facing the compressor compartment.

8. The low-temperature cabinet according to claim 7, characterized in that: It also includes a clamping component for clamping and fixing the expansion tank, and the clamping component is arranged on the second partition component.

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