Carbon dioxide self-cascade screw refrigeration unit

Abstract

The present invention discloses a carbon dioxide self-cascade screw refrigeration unit, which includes a screw compressor, a multi-stage regenerator and an oil-gas separation and collection tank. The reflux ends of the screw compressor and the multi-stage regenerator are fixedly connected through a U-shaped pipe. A pump body is installed on the top of the multi-stage regenerator, and the output end of the pump body is fixedly connected to the inner wall of the screw compressor through an oil outlet pipe. A vertical shaft is rotatably connected through the inner wall of the oil outlet pipe. An impeller is fixedly connected to the bottom side wall of the vertical shaft. A limiting block is slidably connected to the side wall of the vertical shaft. An arc-shaped plate is provided on the side wall of the limiting block. A balance plate is rotatably connected to the top wall of the multi-stage regenerator through a support plate. One end of the balance plate is fixedly connected to the arc-shaped plate, and a push rod is rotatably connected to one end of the balance plate. By setting structures such as a screw compressor and a multi-stage regenerator, the present invention constitutes a self-cascade screw refrigeration unit, which has a better refrigeration effect on carbon dioxide and improves the efficiency of carbon dioxide refrigeration.

Description

Technical Field

[0001] The invention relates to the technical field of refrigeration units, and in particular to a carbon dioxide self-cascading screw refrigeration unit. Background Art

[0002] The self-cascade refrigeration system uses the multi-stage cascade refrigeration principle and achieves refrigeration at -150℃ or even lower temperature in one system with one compressor, which greatly simplifies the multi-stage cascade refrigeration system. The volume and mass are significantly lower than the cascade refrigeration system. The screw refrigeration unit often uses a twin-screw air compressor to compress the gas. The two screws are continuously engaged to compress the introduced gas and discharge the high-pressure gas. During the continuous engagement of the two screws, the temperature of the compressed gas continues to rise. The hard friction between the screws and the hard friction between the screws and the compression chamber increase the vibration of the air compressor and make the gas output fluctuate greatly. Therefore, the existing screw refrigerator will introduce oil into the compression chamber of the twin-screw air compressor to mix the oil into the compressed gas, so that the screws adhere to the oil to form an oil film during the engagement process, thereby reducing hard friction and thermal damage. The working principle of the current carbon dioxide self-cascade screw refrigeration unit can be summarized as follows: the carbon dioxide gas is compressed by a screw compressor to form a high-temperature and high-pressure gas, and the gas-liquid separator separates the carbon dioxide gas and the oil body. The carbon dioxide is then cooled and dried and enters the multi-stage regenerator for heat exchange, and then returns to the multi-stage regenerator from the evaporator, and finally re-enters the screw compressor through the reflux end of the multi-stage regenerator to realize the refrigeration cycle.

[0003] At present, when the carbon dioxide self-cascade screw refrigeration unit is working, a constant speed and fixed quantity of oil is often directly introduced into the screw refrigerator to reduce hard friction and thermal damage. However, when the pressure flow rate of the carbon dioxide gas introduced into the screw refrigerator fluctuates, these constant speed and fixed quantity of oil will cause a certain amount of waste; and these oils will be separated in the oil-gas separator after circulating in the screw refrigerator, and then the user needs to recycle the oil in the oil-gas separator.

[0004] To this end, we proposed a carbon dioxide self-cascade screw refrigeration unit. Summary of the invention

[0005] The purpose of the present invention is to solve the problems existing in the prior art and to propose a carbon dioxide self-cascade screw refrigeration unit.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] Carbon dioxide self - cascading screw refrigeration unit, including a screw compressor, a multi - stage regenerator and an oil - gas separation and collection tank. The reflux ends of the screw compressor and the multi - stage regenerator are fixedly connected through a U - shaped pipe. A pump body is installed on the top of the multi - stage regenerator, and the output end of the pump body is fixedly connected to the inner wall of the screw compressor through an oil outlet pipe;

[0008] A vertical shaft is rotatably connected through the inner wall of the U - shaped pipe. An impeller is fixedly connected to the bottom side wall of the vertical shaft. A limiting block is slidably connected to the side wall of the vertical shaft. An arc - shaped plate is provided on the side wall of the limiting block. The top wall of the multi - stage regenerator is rotatably connected to a balance plate through a support plate. One end of the balance plate is fixedly connected to the arc - shaped plate. A push rod is rotatably connected to one end of the balance plate. A rotating rod is rotatably connected through the inner wall of the oil outlet pipe. A sealing plate is fixedly connected to one end of the rotating rod. A push plate is fixedly connected to the side wall of the other end of the rotating rod. The push rod and the push plate are rotatably connected;

[0009] A recycling mechanism for recycling the oil - gas separation and collection tank is provided on the vertical shaft.

[0010] Preferably, an annular groove is formed on the side wall of the limiting block. Sliders are symmetrically and fixedly connected to the inner wall of the arc - shaped plate. The sliders are in sliding contact with the annular groove. A circular ring block is fixedly connected to the bottom wall of the limiting block. Connecting plates are symmetrically and fixedly connected to the side wall of the circular ring block. A connecting rod is rotatably connected to the side wall of each connecting plate. Circular pins are symmetrically and rotatably connected to the side wall of the vertical shaft. A folding plate is fixedly connected to the side wall of each circular pin.

[0011] Preferably, one end of the folding plate is rotatably connected to the adjacent connecting rod, and a gravity ball is fixedly connected to the end of the folding plate away from the connecting rod.

[0012] Preferably, the recycling mechanism includes a circular plate fixedly connected to the vertical shaft. A circular shaft is fixedly connected to the top wall of the circular plate. The circular shaft is eccentrically arranged on the top of the circular plate. Slide rods are symmetrically and rotatably connected to the side wall of the circular shaft. Support rods are symmetrically and fixedly connected to the multi - stage regenerator. A box body is fixedly connected to the end of each support rod away from the multi - stage regenerator. A sliding plug is hermetically and slidably connected to the inner wall of the box body.

[0013] Preferably, one end of each slide rod away from the circular shaft is rotatably connected to the side wall of a sliding plug. A one - way inlet oil pipe and a one - way outlet oil pipe are fixedly connected through the inner wall of each box body. The end of the one - way inlet oil pipe away from the box body is fixedly connected to the inner wall of the oil - gas separation and collection tank.

[0014] Preferably, an oil storage bin is installed on the top of the multi - stage regenerator. A delivery oil pipe is fixedly connected through the inner wall of the oil storage bin. The end of the delivery oil pipe away from the oil storage bin is fixedly connected to the input end of the pump body. The end of the one - way outlet oil pipe away from the box body is fixedly connected to the inner wall of the oil storage bin.

[0015] Preferably, an oil outlet pipe is fixedly connected to the output end of the pump body. One end of the oil outlet pipe away from the pump body is fixedly communicated with the inner wall of the screw compressor, and the sealing plate is arranged inside the oil outlet pipe.

[0016] Preferably, a support plate is fixedly connected to the top wall of the multi-stage regenerator. A cylinder is rotatably connected to the inner wall of the support plate, and the middle position of the cylinder is rotatably connected to the support plate.

[0017] Compared with the existing technology, the advantages of the present invention are as follows:

[0018] 1. By setting structures such as a screw compressor and a multi-stage regenerator, a self-refrigerating screw compressor unit is formed, thereby achieving a better refrigeration effect on carbon dioxide and improving the efficiency of using carbon dioxide for refrigeration;

[0019] 2. By setting structures such as an impeller, a gravity ball and a folding plate, according to the carbon dioxide gas with different pressures flowing inside the U-shaped pipe, the gravity ball drives the folding plate to rotate at different angles, and the limiting block moves upward at different distances along the axial direction of the vertical axis. Then, through the downward rotation of the end of the balance plate away from the limiting block, the push rod drives the push plate to move downward, and the push rod will drive the rotating rod and the sealing plate to rotate a certain angle, so that the opening degree between the sealing plate and the oil outlet pipe gradually increases. Therefore, when the pressure of the carbon dioxide gas inside the U-shaped pipe is greater, the amount of oil automatically entering the screw compressor through the oil outlet pipe is more, which is beneficial to the operation of spraying, cooling and lubricating the carbon dioxide gas to be pressurized inside the screw compressor;

[0020] 3. During the rotation of the vertical axis, by setting structures such as a circular plate, a circular shaft and a box body, when one sliding rod drives the sliding plug rotatably connected thereto to squeeze the oil body inside the box body to the one-way oil outlet pipe and flow into the oil storage bin for collection, the other sliding rod drives the corresponding sliding plug to pump the oil body inside the oil-gas separation and collection box into the box body through the one-way oil inlet pipe, thereby ensuring the continuity of the recycling of the oil body inside the oil-gas separation and collection box, and there is no need for manual collection and utilization of the oil body generated by oil spraying during the refrigeration process of the screw refrigerator. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic structural diagram of the carbon dioxide self-refrigerating screw compressor unit proposed by the present invention Figure 1 ;

[0022] Figure 2 is Figure 1 an enlarged schematic diagram of part A structure in

[0023] Figure 3 is a schematic structural diagram of the carbon dioxide self-refrigerating screw compressor unit proposed by the present invention Figure 2 ;

[0024] Figure 4 This is a schematic diagram of the internal structure of the box body in the carbon dioxide self - cascading screw refrigeration unit proposed by the present invention;

[0025] Figure 5 This is a schematic diagram of the positional relationship of the one - way inlet oil pipe, one - way outlet oil pipe and oil delivery pipe in the carbon dioxide self - cascading screw refrigeration unit proposed by the present invention;

[0026] Figure 6 This is a schematic diagram of the positional relationship of the push rod, push plate and rotating rod in the carbon dioxide self - cascading screw refrigeration unit proposed by the present invention;

[0027] Figure 7 is Figure 6 an enlarged schematic diagram of part B structure in;

[0028] Figure 8 This is a schematic diagram of the internal structure of the outlet oil pipe in the carbon dioxide self - cascading screw refrigeration unit proposed by the present invention;

[0029] Fig. 9 is Figure 8 an enlarged schematic diagram of part C structure in.

[0030] In the figure: 1. Screw compressor; 2. Multi - stage regenerator; 3. Oil - gas separation and collection tank; 4. C - shaped pipe; 5. Vertical shaft; 6. Impeller; 7. Limit block; 8. Annular groove; 9. Ring block; 10. Connecting plate; 11. Connecting rod; 12. Folding plate; 13. Round pin; 14. Gravity ball; 15. Arc plate; 16. Balance plate; 17. Support plate; 18. Cylinder; 19. Push rod; 20. Push plate; 21. Rotating rod; 22. Sealing plate; 23. Outlet oil pipe; 24. Pump body; 25. Oil storage bin; 26. Round plate; 27. Round shaft; 28. Support rod; 29. Box body; 30. Slide plug; 31. Slide rod; 32. One - way inlet oil pipe; 33. One - way outlet oil pipe; 34. Oil delivery pipe; 35. Slide block. Specific embodiments

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0032] Refer to Figure 1 - Fig. 9, a carbon dioxide self - cascading screw refrigeration unit, including a screw compressor 1, a multi - stage recuperator 2 and an oil - gas separation and collection tank 3. The screw compressor 1, the multi - stage recuperator 2 and the oil - gas separation and collection tank 3 are all prior arts and will not be elaborated here. The oil - gas separation and collection tank 3 is shown in Figure 6 , the reflux ends of the screw compressor 1 and the multi - stage recuperator 2 are fixedly connected through a U - shaped pipe 4. A pump body 24 is installed at the top of the multi - stage recuperator 2, and the output end of the pump body 24 is fixedly connected to the inner wall of the screw compressor 1 through an oil outlet pipe 23;

[0033] A vertical shaft 5 is rotatably connected through the inner wall of the U - shaped pipe 4. An impeller 6 is fixedly connected to the bottom side wall of the vertical shaft 5. A limiting block 7 is slidably connected to the side wall of the vertical shaft 5. An arc - shaped plate 15 is provided on the side wall of the limiting block 7. The top wall of the multi - stage recuperator 2 is rotatably connected to a balance plate 16 through a support plate 17. One end of the balance plate 16 is fixedly connected to the arc - shaped plate 15. One end of the balance plate 16 is rotatably connected to a push rod 19. A rotating rod 21 (as shown in Fig. 9 ) is rotatably connected through the inner wall of the oil outlet pipe 23. One end of the rotating rod 21 is fixedly connected to a sealing plate 22. The sealing plate 22 can close and open the fluid flow inside the oil outlet pipe 23. A push plate 20 is fixedly connected to the other end side wall of the rotating rod 21. The push rod 19 and the push plate 20 are rotatably connected;

[0034] A circulation mechanism for recycling the oil - gas separation and collection tank 3 is provided on the vertical shaft 5.

[0035] An annular groove 8 is formed on the side wall of the limiting block 7. Slide blocks 35 are symmetrically and fixedly connected to the inner wall of the arc - shaped plate 15. The slide blocks 35 are in sliding contact with the annular groove 8. A circular ring block 9 is fixedly connected to the bottom wall of the limiting block 7. Connecting plates 10 are symmetrically and fixedly connected to the side wall of the circular ring block 9. A connecting rod 11 is rotatably connected to the side wall of each connecting plate 10. Circular pins 13 are symmetrically and rotatably connected to the side wall of the vertical shaft 5. A folding plate 12 is fixedly connected to the side wall of each circular pin 13.

[0036] One end of the folding plate 12 is rotatably connected to the adjacent connecting rod 11. The end of the folding plate 12 away from the connecting rod 11 is fixedly connected to a gravity ball 14. The folding plate 12 is in a V - shaped structure. When the vertical shaft 5 rotates and drives the folding plate 12 and the gravity ball 14 to rotate rapidly through the circular pin 13, the gravity ball 14 will move obliquely upward along an arc trajectory under the action of centrifugal force. The gravity ball 14 will drive the folding plate 12 fixedly connected to it to rotate upward by a certain angle with the circular pin 13 as the center. Then the end of the folding plate 12 away from the gravity ball 14 will drive the connecting rod 11 rotatably connected to it to move upward. Then each connecting rod 11 will drive the connecting plate 10 rotatably connected to it to move upward. Then the two connecting plates 10 will drive the limiting block 7 to move upward along the axial direction of the vertical shaft 5 by a certain distance through the circular ring block 9.

[0037] The circulation mechanism includes a circular plate 26 fixedly connected to the vertical shaft 5, a circular shaft 27 fixedly connected to the top wall of the circular plate 26, the circular shaft 27 is eccentrically arranged at the top of the circular plate 26, a sliding rod 31 is symmetrically rotatably connected to the side wall of the circular shaft 27, support rods 28 are symmetrically fixedly connected to the multi-stage heat regenerator 2, and each support rod 28 is fixedly connected to a box body 29 at one end away from the multi-stage heat regenerator 2, and a sliding plug 30 is sealingly and slidably connected to the inner wall of the box body 29. When the vertical shaft 5 rotates, the circular plate 26 is driven to rotate synchronously, and the circular plate 26 drives the circular shaft 27 fixedly connected to its top wall to rotate synchronously, and the circular shaft 27 will drive the two sliding rods 31 staggered on its side walls to move synchronously.

[0038] One end of each sliding rod 31 away from the circular shaft 27 is rotatably connected to the side wall of a sliding plug 30, so each sliding rod 31 will drive the sliding plug 30 rotatably connected to it to slide back and forth in a sealed manner inside the corresponding box body 29. A one-way oil inlet pipe 32 and a one-way oil outlet pipe 33 are fixedly connected through the inner wall of each box body 29. The end of the one-way oil inlet pipe 32 away from the box body 29 is fixedly connected to the inner wall of the oil-gas separation collection box 3. The one-way oil inlet pipe 32 only allows the oil inside the oil-gas separation collection box 3 to be drawn into the corresponding box body 29.

[0039] An oil storage tank 25 is installed on the top of the multi-stage heat regenerator 2, and an oil delivery pipe 34 is fixedly connected to the inner wall of the oil storage tank 25. The end of the oil delivery pipe 34 away from the oil storage tank 25 is fixedly connected to the input end of the pump body 24, and the end of the one-way oil outlet pipe 33 away from the box body 29 is fixedly connected to the inner wall of the oil storage tank 25. The one-way oil outlet pipe 33 only allows the oil inside the box body 29 to be squeezed into the oil storage tank 25 for collection and utilization.

[0040] The output end of the pump body 24 is fixedly connected to the oil outlet pipe 23. The end of the oil outlet pipe 23 away from the pump body 24 is fixedly connected to the inner wall of the screw compressor 1. The sealing plate 22 is arranged inside the oil outlet pipe 23. After the pump body 24 is turned on, the oil in the oil storage tank 25 is drawn into the oil delivery pipe 34 and pumped into the screw compressor 1 through the oil outlet pipe 23 to cool and lubricate the twin-screw pressurizing part inside the screw compressor 1.

[0041] A support plate 17 is fixedly connected to the top wall of the multi-stage heat regenerator 2, a cylinder 18 is rotatably connected to the inner wall of the support plate 17, and the cylinder 18 and the support plate 17 are rotatably connected at the middle position.

[0042] In the present invention, when the refluxed carbon dioxide gas in the multi-stage regenerator 2 enters the screw compressor 1 through the U-shaped pipe 4 for auto-cascade refrigeration, since this part of the carbon dioxide gas has a certain pressure, this part of the carbon dioxide gas will drive the impeller 6 to rotate inside the U-shaped pipe 4, causing the impeller 6 to drive the vertical shaft 5 fixedly connected thereto to rotate. The vertical shaft 5 drives two folding plates 12 to rotate synchronously through two symmetrically arranged round pins 13. Since a gravity ball 14 is fixedly connected to the bottom end of each folding plate 12, when the gravity ball 14 rotates rapidly with the folding plate 12 centered on the vertical shaft 5, the gravity ball 14 will move obliquely upward under the action of centrifugal force. Furthermore, the gravity ball 14 will drive the folding plate 12 fixedly connected thereto to rotate upward by a certain angle centered on the round pin 13. Then, the end of the folding plate 12 away from the gravity ball 14 will drive the connecting rod 11 rotatably connected thereto to move upward. Then, each connecting rod 11 will drive the connecting plate 10 rotatably connected thereto to move upward. Then, the two connecting plates 10 will drive the limiting block 7 to move upward along the axial direction of the vertical shaft 5 by a certain distance through the ring block 9.

[0043] Since an annular groove 8 is formed in the side wall of the limiting block 7 and the inner wall of the annular groove 8 abuts against and slides with the arc-shaped plate 15, the limiting block 7 will drive two sliders 35 in the arc-shaped plate 15 to move upward synchronously through the annular groove 8. Then, the two sliders 35 will drive the balance plate 16 to rotate by a certain angle centered on the cylinder 18 through the arc-shaped plate 15. Then, the end of the balance plate 16 away from the arc-shaped plate 15 will move downward along an arc by a certain distance. Then, the end of the balance plate 16 away from the arc-shaped plate 15 will drive the push rod 19 to move downward synchronously. The push rod 19 drives the push plate 20 rotatably connected thereto to move downward synchronously. Since the push plate 20 is fixedly connected to the side wall of the rotating rod 21, the push plate 20 will drive the rotating rod 21 to rotate by a certain angle, causing the rotating rod 21 to drive the sealing plate 22 to rotate by a certain angle. Furthermore, the opening degree between the sealing plate 22 and the oil outlet pipe 23 gradually increases. Furthermore, when the pressure of the carbon dioxide gas inside the U-shaped pipe 4 is greater, the amount of oil entering the screw compressor 1 through the oil outlet pipe 23 is automatically increased, which is beneficial to the oil injection and cooling operation of the carbon dioxide gas to be pressurized inside the screw compressor 1.

[0044] Refer to Figure 4During the rotation of the vertical shaft 5, the vertical shaft 5 will also drive the circular plate 26 to rotate synchronously, and the circular plate 26 will drive the circular shaft 27 fixedly connected to its top wall to rotate synchronously, then the circular shaft 27 will drive the two sliding rods 31 staggered on its side walls to move synchronously, and since one end of each sliding rod 31 away from the circular shaft 27 is rotatably connected to the side wall of a corresponding sliding plug 30, and the two sliding plugs 30 are respectively arranged on both sides of the vertical shaft 5, when one of the sliding rods 31 drives the sliding plug 30 rotatably connected to it to slide toward the deep inner cavity of the corresponding box body 29 in a sealed manner, When the oil inside the box body 29 is squeezed to the one-way oil outlet pipe 33 and flows to the oil storage tank 25 for collection, another sliding rod 31 drives the sliding plug 30 rotatably connected thereto to slide sealedly to the outside of the inner cavity of the corresponding box body 29, and then the sliding plug 30 can draw the oil inside the oil-gas separation collection box 3 into the box body 29 through the one-way oil inlet pipe 32, thereby ensuring the continuity of the recycling of the oil inside the oil-gas separation collection box 3, and there is no need to manually collect and utilize the oil generated by the oil injection of the screw compressor 1 during the refrigeration process.

[0045] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A carbon dioxide auto-cascade screw refrigeration unit, comprising a screw compressor (1), a multi-stage regenerator (2) and an oil-gas separation collection box (3), characterized in that: The return end of the screw compressor (1) and the multi-stage recuperator (2) is fixedly connected through a U-shaped pipe (4). A pump body (24) is installed on the top of the multi-stage recuperator (2), and the output end of the pump body (24) is fixedly connected to the inner wall of the screw compressor (1) through an oil outlet pipe (23). A vertical shaft (5) is rotatably connected through the inner wall of the U-shaped pipe (4). An impeller (6) is fixedly connected to the bottom side wall of the vertical shaft (5). A limiting block (7) is slidably connected to the side wall of the vertical shaft (5). An arc-shaped plate (15) is provided on the side wall of the limiting block (7). A balance plate (16) is rotatably connected to the top wall of the multi-stage recuperator (2) through a support plate (17). One end of the balance plate (16) is fixedly connected to the arc-shaped plate (15). One end of the balance plate (16) is rotatably connected to a push rod (19). A rotating rod (21) is rotatably connected through the inner wall of the oil outlet pipe (23). A sealing plate (22) is fixedly connected to one end of the rotating rod (21). A push plate (20) is fixedly connected to the side wall of the other end of the rotating rod (21). The push rod (19) is rotatably connected to the push plate (20). A circulating mechanism for recycling the oil-gas separation and collection tank (3) is provided on the vertical shaft (5). An annular groove (8) is formed in the side wall of the limiting block (7). Sliding blocks (35) are symmetrically and fixedly connected to the inner wall of the arc-shaped plate (15). The sliding blocks (35) are in sliding contact with the annular groove (8). A circular ring block (9) is fixedly connected to the bottom wall of the limiting block (7). Connecting plates (10) are symmetrically and fixedly connected to the side wall of the circular ring block (9). A connecting rod (11) is rotatably connected to the side wall of each connecting plate (10). Circular pins (13) are symmetrically and rotatably connected to the side wall of the vertical shaft (5). A folding plate (12) is fixedly connected to the side wall of each circular pin (13).

2. The carbon dioxide self-cascade screw refrigeration unit according to claim 1, characterized in that: One end of the folding plate (12) is rotatably connected to the adjacent connecting rod (11), and a gravity ball (14) is fixedly connected to the end of the folding plate (12) away from the connecting rod (11).

3. The carbon dioxide self-cascade screw refrigeration unit according to claim 2, characterized in that: The circulating mechanism includes a circular plate (26) fixedly connected to the vertical shaft (5). A circular shaft (27) is fixedly connected to the top wall of the circular plate (26). The circular shaft (27) is eccentrically arranged on the top of the circular plate (26). Slide rods (31) are symmetrically and rotatably connected to the side wall of the circular shaft (27). Support rods (28) are symmetrically and fixedly connected to the multi-stage recuperator (2). A box body (29) is fixedly connected to the end of each support rod (28) away from the multi-stage recuperator (2). A slide plug (30) is hermetically and slidably connected to the inner wall of the box body (29).

4. The carbon dioxide self-cascade screw refrigeration unit according to claim 3, characterized in that: One end of each slide rod (31) away from the circular shaft (27) is rotatably connected to the side wall of a slide plug (30). A one-way inlet oil pipe (32) and a one-way outlet oil pipe (33) are fixedly connected through the inner wall of each box body (29). The end of the one-way inlet oil pipe (32) away from the box body (29) is fixedly connected to the inner wall of the oil-gas separation and collection tank (3).

5. The carbon dioxide self-cascade screw refrigeration unit according to claim 4, characterized in that: An oil storage bin (25) is installed on the top of the multi-stage regenerator (2), and an oil delivery pipe (34) is fixedly connected to and penetrates the inner wall of the oil storage bin (25), one end of the oil delivery pipe (34) away from the oil storage bin (25) is fixedly connected to the input end of the pump body (24), and one end of the one-way oil outlet pipe (33) away from the box body (29) is fixedly connected to the inner wall of the oil storage bin (25).

6. The carbon dioxide auto-cascade screw refrigeration unit according to claim 1, characterized in that: The output end of the pump body (24) is fixedly connected to an oil outlet pipe (23); one end of the oil outlet pipe (23) away from the pump body (24) is fixedly connected to the inner wall of the screw compressor (1); and the sealing plate (22) is arranged inside the oil outlet pipe (23).

7. The carbon dioxide self-cascade screw refrigeration unit according to claim 1, characterized in that: The top wall of the multi-stage heat regenerator (2) is fixedly connected to a support plate (17), the inner wall of the support plate (17) is rotatably connected to a cylinder (18), and the cylinder (18) and the support plate (17) are rotatably connected at their middle positions.

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