Low-temperature gear pump structure

Abstract

The utility model discloses a low-temperature gear pump structure, which relates to the technical field of gear pumps and comprises a shell, a positioning protective sleeve, a driving gear component, a driven gear component, a coupler and a motor. The positioning protective sleeve is installed on one side of the shell, and the driving gear assembly and the driven gear assembly are installed in the shell in a meshed mode. The coupler is a magnetic coupler, one end of the magnetic coupler is fixed to an output shaft of the motor, and the other end of the magnetic coupler is fixed to the end of the driving gear assembly. The low-temperature gear pump is reasonable in design, the performance and the reliability of the gear pump in the low-temperature environment are remarkably improved, the potential leakage risk is reduced, and the safety and the efficiency of the whole system are improved through the innovative coupling design.

Description

TECHNICAL FIELD

[0001] The utility model relates to gear pump technical field more specifically is in low temperature gear pump structure technical field. BACKGROUND

[0002] Gear pump is the rotary pump that relies on the working volume variation and removal formed between pump cylinder and meshing gear to transport liquid or make it pressurized. Two closed spaces are formed by two gears, pump body and front and back covers, when the gear rotates, the volume of the space on the gear disengagement side changes from small to large, forming a vacuum, liquid is sucked in, the volume of the space on the gear meshing side changes from large to small, and liquid is squeezed into the pipeline. The prior art discloses the following technology:

[0003] The patent with publication number CN104329251A and the patent name "a miniature ultra-low temperature magnetic drive gear pump" discloses the following content: a miniature ultra-low temperature magnetic drive gear pump, the left end of the connecting frame is sequentially provided with a pump rear cover, a gear cavity and a pump front cover from left to right, the gear cavity is sequentially provided with a main gear, a driven gear, a sealing gasket on both sides of the gear cavity, a positioning pin hole and a bolt hole from inside to outside, the main gear and the driven gear are respectively installed on the transmission main shaft and the driven shaft; the pump rear cover is provided with a liquid sealing sleeve, and a liquid sealing sleeve gasket is arranged between the pump rear cover and the liquid sealing sleeve; a sealing seat is arranged in the middle of the right end of the pump rear cover, a shaped sealing ring is arranged in the sealing seat, and a sealing gland is arranged at the right end of the sealing seat; wear-resistant sliding bearings are arranged outside the transmission main shaft hole and the driven shaft hole of the pump rear cover. The present application has reasonable structure, can transport media with very low temperature, very small flow, relatively high operating pressure, flammability, explosiveness and easy vaporization, and is safe, stable and reliable in operation during use, 100% sealed without leakage, and can meet the requirements of laboratory equipment for the transportation of LNG low-temperature liquid.

[0004] The patent with publication number CN214196648U and the patent name "a gear pump for ultra-low temperature environment" discloses the following content: a gear pump for ultra-low temperature environment, comprising a front pump cover, a middle pump body, a rear pump body, a transmission shaft, a gear, a first bearing arranged on one side of the front pump cover and a second bearing arranged in the rear pump body; the middle pump body is provided with a through hole in the axial direction; the front pump cover, the middle pump body and the rear pump body form a gear cavity; one end of the transmission shaft passes through the rear pump body and the middle pump body in sequence and is inserted into the first bearing, and the transmission shaft is inserted into the second bearing; the gear is in transmission connection with the transmission shaft, and the gear is located in the gear cavity; the gear has a gear side gap between the gear and the inner wall of the gear cavity in the axial direction; the gear has a gear top gap between the gear and the inner wall of the gear cavity in the radial direction; the transmission shaft and the first bearing have a first bearing gap; the transmission shaft and the second bearing have a second bearing gap. The utility model expands the application range of the gear pump, and ensures the normal operation of the gear pump in the ultra-low temperature environment.

[0005] The above patent and existing low-temperature delivery gear pump are centrifugal pumps or plunger pumps, most of which need a vacuum structure, are large in size, and have strict maintenance requirements for the pump under low-temperature conditions, and any improper maintenance can affect the efficiency and service life of the pump, and professional personnel are required to operate and maintain the pump; the low-temperature delivery gear pump can reduce the overall efficiency of the pump under a relatively high-temperature condition due to the gasification phenomenon, because additional energy is required to maintain the low-temperature state of the pump body and its contents, and special materials are required to meet the low-temperature hardness requirement to reduce mechanical damage, and the low-temperature plunger pump cannot be easily converted for fluid transmission under a conventional temperature, thereby limiting the application flexibility. Utility model content

[0006] The utility model discloses a low-temperature gear pump structure, which has the advantages of low cost, stable operation, small size, easy maintenance, zero leakage and the like.

[0007] The utility model discloses a low-temperature gear pump structure, which has the advantages of low cost, stable operation, small size, easy maintenance, zero leakage and the like.

[0008] The utility model provides a low-temperature gear pump structure, including the casing, the positioning protection sleeve, the driving gear assembly, the driven gear assembly, the shaft coupling and the motor, the positioning protection sleeve installs at the one side of casing, and the driving gear assembly and the driven gear assembly are installed in the casing through the meshing form, the shaft coupling is the magnetic coupling, and one end of the magnetic coupling is fixed on the output shaft of motor, and the other end of the magnetic coupling is fixed in the end of driving gear assembly.

[0009] Specifically, the unique shaft coupling design: the inner sleeve and the outer sleeve of the shaft coupling are connected by magnetic force without bolt fixing, which not only realizes the zero leakage target of low-temperature liquid delivery, but also enhances the safety of the system. When the gear torque is too large, the slip design of the shaft coupling can effectively protect the motor from overload damage, reflecting the intelligent fault avoidance strategy.

[0010] The inner sleeve and the outer sleeve of the shaft coupling are connected without bolts, and the inner sleeve and the outer sleeve are driven by magnetic force. When the gear torque is greater than the maximum torque of the shaft coupling, the inner and outer shaft couplings will move relatively to protect the safety of the motor and ensure the safety of the delivery pipeline. When the load is greater than the magnetic force of the inner and outer sleeves, the inner and outer sleeves will slip to avoid motor overload.

[0011] In one embodiment, the driving gear assembly includes a driving spindle arranged in the casing through a low-temperature bearing and a driving gear sleeved outside the driving spindle; the driven gear assembly includes a driven shaft arranged in the casing through a low-temperature bearing and a driven gear sleeved outside the driven shaft.

[0012] The driving gear is engaged with the driven gear.

[0013] Specifically, the driving gear and the driven gear are respectively installed on the driving spindle and the driven spindle. The driving spindle and the driven spindle are supported at both ends by low-temperature bearings to ensure stable operation in the later period.

[0014] In one embodiment, the shell comprises a pump cavity with openings at both front and rear ends, a front cover plate and a rear cover plate arranged at the front and rear sides of the pump cavity, and the pump cavity, the front cover plate and the rear cover plate are connected by a stud bolt assembly to form a sealed cavity.

[0015] In one embodiment, metal winding gaskets are arranged at the connection between the pump cavity and the front cover plate and at the connection between the pump cavity and the rear cover plate for static sealing.

[0016] Specifically, the gears are installed in the pump cavity, and the front cover plate and the rear cover plate are connected by a stud bolt assembly to form a sealed volume. Metal winding gaskets are arranged on both end faces of the volume for static sealing.

[0017] In one embodiment, the end face of the pump cavity is provided with a concave-convex surface for mounting the metal winding gasket.

[0018] Specifically, the low-temperature liquid enters the pump cavity. After the pump cavity is cooled, the material will shrink. To ensure that the low-temperature liquid does not leak after shrinking, the general sealing material cannot withstand a low temperature of -196 degrees. Therefore, the end face of the pump cavity adopts a concave-convex surface structure for mounting the metal winding gasket to compensate for the shrinkage of the material due to the low temperature and ensure the normal operation of the gear pump.

[0019] In one embodiment, the driving spindle extends into the positioning protection sleeve through a pan seal on the side close to the positioning protection sleeve and is connected with the magnetic coupling.

[0020] Specifically, the driving spindle is installed in the bearing inner ring of the rear cover plate for rotation. There is a gap between the bearing inner ring and the driving spindle. To avoid the driving spindle shrinking after contacting the low-temperature liquid and the gap becoming larger, three pan seals are designed between the driving spindle and the bearing inner ring to ensure that the low-temperature liquid does not leak.

[0021] In one embodiment, an isolation sleeve is arranged at the connection between the shell and the positioning protection sleeve, and a bearing sleeve is arranged at the extension of the driving spindle out of the shell. A static sealing ring is arranged at the isolation sleeve and the bearing sleeve to ensure zero leakage of hazardous media.

[0022] In one embodiment, the magnetic coupling comprises an inner coupling sleeve and an outer coupling sleeve. The driving spindle is fixedly connected with the inner coupling sleeve, the inner coupling sleeve and the outer coupling sleeve are driven by magnetic force, and the outer coupling sleeve is connected with the output shaft of the motor.

[0023] Specifically, the transmission main shaft and the inner sleeve of the coupling are connected through a key, the inner sleeve of the coupling and the outer sleeve of the coupling are driven by magnetic force, the outer sleeve of the coupling is connected with the motor, the coupling is rotated by the motor, and the positioning protection sleeve is connected with the motor. The inner sleeve of the coupling and the outer sleeve of the coupling are not connected by bolts, and the inner sleeve and the outer sleeve are separated by a spacer sleeve for magnetic transmission, which can realize zero leakage of low-temperature liquid and ensure safety.

[0024] In addition, the inner sleeve of the coupling and the outer sleeve of the coupling are not connected by bolts, and the inner sleeve and the outer sleeve are driven by magnetic force, and the outer sleeve drives the inner sleeve to rotate. When the gear torque is greater than the maximum torque of the coupling, the inner and outer couplings will move relatively, protecting the safety of the motor and ensuring the safety of the conveying pipeline.

[0025] In addition, when the transmission main shaft contacts the low-temperature liquid, the material of the transmission main shaft will shrink under the action of low temperature, providing a release point for shrinkage stress. The transmission main shaft is connected to the cover plate as a fixed end, and the transmission main shaft and the inner sleeve of the coupling are used as movable ends for stress release when the transmission main shaft shrinks.

[0026] In one embodiment, the transmission main shaft and the inner sleeve of the coupling are connected through a key.

[0027] In one embodiment, the double-headed bolt assembly includes a bolt and a nut.

[0028] As shown in Figure 4 An innovative zero-leakage test method for a low-temperature gear pump is as follows: open the valve, low-temperature liquid enters the pipeline from the storage tank, start the low-temperature gear pump, the rear end of the low-temperature gear pump is provided with a flowmeter and a temperature transmitter, and the normal operation of the low-temperature gear pump under different working conditions is verified through testing. Through the test method of the test platform, test under the working conditions of low-temperature gas phase, low-temperature liquid phase and low-temperature gas-liquid mixing, measure the flow of the low-temperature gear pump under different powers through the temperature transmitter and the flowmeter, and detect whether the LNG leaks through the test.

[0029] When the valve is opened and the low-temperature gear pump is running, the low-temperature liquid will be sucked into the pipeline by the gear pump, the low-temperature liquid exchanges heat with the pipeline, the liquid becomes gas, the gas pressure increases, the low-temperature gear and the pipeline can be used as a supercharger, and the storage tank is pressurized without energy consumption.

[0030] The beneficial effects of the utility model are as follows:

[0031] 1. The patent design is reasonable, the method significantly improves the performance and reliability of the gear pump in a low-temperature environment, reduces the potential leakage risk, and improves the safety and efficiency of the overall system through the innovative coupling design.

[0032] 2, by using concave-convex surface and installing metal winding pad on the end face of pump cavity, effectively cope with the sealing challenge caused by material shrinkage at low temperature, prevent leakage. Low temperature liquid enters into the pump cavity, after the pump cavity is cooled, the material will shrink, in order to ensure that the low temperature liquid does not leak after shrinkage, the general sealing material cannot resist-196 degrees of low temperature, therefore, the end face of the pump cavity is provided with concave-convex surface and metal winding pad, which makes up for the shrinkage of the material due to low temperature, and ensures the normal operation of the gear pump;

[0033] 3, main shaft sealing optimization: set up the packing seal between the transmission main shaft and the rear cover plate shaft sleeve, ensure that the low temperature liquid does not leak, at the same time, reserve the gap and stress release mechanism for the main shaft due to low temperature shrinkage, improve the stability and durability of the pump.

[0034] 4, unique coupling design: the inner sleeve and the outer sleeve of the coupling are connected by magnetic force, without bolt fixing, which not only realizes the zero leakage target of low temperature liquid conveying, but also enhances the safety of the system. When the gear torque is too large, the slip design of the coupling can effectively protect the motor from overload damage, which embodies the intelligent fault avoidance strategy. The inner sleeve and the outer sleeve of the coupling are connected without bolt, the inner sleeve and the outer sleeve are driven by magnetic force, the outer sleeve drives the inner sleeve to rotate, when the gear torque is greater than the maximum torque of the coupling, the inner and outer coupling will move relatively, which protects the safety of the motor and ensures the safety of the conveying pipeline. When the load is greater than the magnetic force of the inner and outer sleeve, the inner and outer sleeve will slip, thereby avoiding the overload of the motor. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical scheme of the embodiment of the utility model, the following will be briefly introduced the drawings needed to be used in the embodiment, it should be understood, the following drawings only show some embodiments of the utility model, therefore, should not be regarded as the limitation to the scope, for those skilled in the art, under the premise of not paying the creative labor, still can obtain other related drawings according to these drawings.

[0036] Figure 1 It is the structure schematic diagram of the utility model;

[0037] Figure 2 It is the right view of Figure 1 ;

[0038] Figure 3 It is the partial enlarged view of Figure 1 ;

[0039] Figure 4 It is the structure schematic diagram of the innovative low temperature gear pump zero leakage test method;

[0040] Reference numerals: 1-bolt, 2-nut, 3-front cover plate, 4-driving gear, 5-low temperature bearing, 6-driven shaft, 7-driven gear, 8-metal winding pad, 9-pump cavity, 10-rear cover plate, 11-transmission main shaft, 12-packing seal, 13-key, 14-coupling inner sleeve, 15-coupling outer sleeve, 16-positioning protection sleeve, 17-motor, 18-isolation sleeve, 19-bearing sleeve. DETAILED DESCRIPTION

[0041] To make the technical problems, technical solutions and technical effects of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0042] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0043] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0044] In the description of the embodiments of the present application, it should be noted that the directions or position relationships indicated by the terms "inner", "outer", "upper", etc. are based on the directions or position relationships shown in the drawings, or the directions or position relationships in which the product of the present application is usually placed, which are only for the convenience of describing the present application and simplifying the description, and are not intended to indicate or imply that the indicated devices or elements must have a particular direction, be constructed and operated in a particular direction, and therefore cannot be understood as a limitation on the present application.

[0045] Example 1

[0046] As Figures 1 to 3As shown in the figure, the embodiment provides a low-temperature gear pump structure, which comprises a shell, a positioning protective sleeve 16, a driving gear assembly, a driven gear assembly, a shaft coupling and a motor 17; the positioning protective sleeve 16 is installed on one side of the shell, the driving gear assembly and the driven gear assembly are installed in the shell in the form of meshing; the shaft coupling is a magnetic coupling, one end of the magnetic coupling is fixed on the output shaft of the motor 17, and the other end of the magnetic coupling is fixed on the end of the driving gear assembly.

[0047] Specifically, the unique shaft coupling design: the inner sleeve 14 and the outer sleeve of the shaft coupling are connected by magnetic force, without the need for bolts 1 to be fixed, which not only achieves the zero leakage goal of low-temperature liquid delivery, but also enhances the safety of the system. When the gear torque is too large, the slip design of the shaft coupling can effectively protect the motor 17 from overload damage, embodying the intelligent fault avoidance strategy.

[0048] The inner sleeve 14 and the outer sleeve 15 of the shaft coupling are connected without bolts 1, the inner and outer sleeves are driven by magnetic force, the outer sleeve drives the inner sleeve to rotate, when the gear torque is greater than the maximum torque of the shaft coupling, the inner and outer shaft couplings will move relatively, protecting the safety of the motor 17, and also ensuring the safety of the delivery pipeline, when the load is greater than the magnetic force of the inner and outer sleeves, the inner and outer sleeves will slip, thereby avoiding the overload of the motor 17.

[0049] Embodiment 2

[0050] As Figures 1 to 3 shown, the embodiment provides a low-temperature gear pump structure, which comprises a shell, a positioning protective sleeve 16, a driving gear assembly, a driven gear assembly, a shaft coupling and a motor 17; the positioning protective sleeve 16 is installed on one side of the shell, the driving gear assembly and the driven gear assembly are installed in the shell in the form of meshing; the shaft coupling is a magnetic coupling, one end of the magnetic coupling is fixed on the output shaft of the motor 17, and the other end of the magnetic coupling is fixed on the end of the driving gear assembly.

[0051] The driving gear assembly comprises a transmission main shaft arranged in the shell through a low-temperature bearing 5 and a driving gear 4 sleeved outside the transmission main shaft; the driven gear assembly comprises a driven shaft 6 arranged in the shell through a low-temperature bearing 5 and a driven gear 7 sleeved outside the driven shaft 6;

[0052] The driving gear 4 meshes with the driven gear 7.

[0053] Specifically, the driving gear 4 and the driven gear 7 are respectively installed on the transmission main shaft 11 and the driven shaft 6. The transmission main shaft and the driven shaft 6 are supported at both ends by the low-temperature bearing 5, ensuring smooth operation in the later period.

[0054] Embodiment 3

[0055] This embodiment is further optimized on the basis of embodiment 2, specifically:

[0056] The shell comprises a pump cavity 9 with open ends, a front cover plate 3 and a rear cover plate 10 arranged on the front and rear sides of the pump cavity 9, and the pump cavity 9, the front cover plate 3 and the rear cover plate 10 are connected by a stud bolt assembly to form a closed cavity.

[0057] The connection between the pump cavity 9 and the front cover plate 3 and the connection between the pump cavity 9 and the rear cover plate 10 are provided with metal winding gaskets 8 for static sealing.

[0058] Specifically, the gear is installed in the pump cavity 9, and the front cover plate 3 and the rear cover plate 10 are connected by a stud bolt assembly to form a closed volume, and the metal winding gaskets 8 are arranged on the two end faces of the volume for static sealing.

[0059] Embodiment 4

[0060] This embodiment is further optimized on the basis of Embodiment 3, specifically:

[0061] The end face of the pump cavity 9 is provided with a concave-convex surface for installing the metal winding gasket 8.

[0062] Specifically, the low-temperature liquid enters the pump cavity 9, and after the pump cavity 9 is cooled, the material will shrink. In order to ensure that the low-temperature liquid does not leak after shrinking, the general sealing material cannot withstand a low temperature of-196 degrees, so the end face of the pump cavity 9 adopts a concave-convex surface structure for installing the metal winding gasket 8, which makes up for the shrinkage of the material due to the low temperature, and ensures the normal operation of the gear pump.

[0063] The transmission main shaft extends into the positioning protection sleeve 16 through the pan seal 12 on the side close to the positioning protection sleeve 16 and is connected with the magnetic coupling.

[0064] Specifically, the transmission main shaft is installed in the bearing inner ring of the rear cover plate 10 for rotation, and there is a gap between the bearing inner ring and the transmission main shaft. In order to avoid the transmission main shaft from shrinking after contacting the low-temperature liquid and the gap becoming larger, three pan seals 12 are designed between the transmission main shaft and the bearing inner ring to ensure that the low-temperature liquid does not leak.

[0065] The transmission main shaft and the inner sleeve 14 of the coupling are connected through the key 13.

[0066] The stud bolt assembly comprises a bolt 1 and a nut 2.

[0067] Embodiment 5

[0068] This embodiment is further optimized on the basis of Embodiment 3 or 4, specifically:

[0069] The connection between the shell and the positioning protection sleeve 16 is provided with an isolation sleeve 18, and the transmission main shaft extending out of the shell is provided with a bearing sleeve 19; a static sealing ring is arranged at the isolation sleeve 18 and the bearing sleeve 19 to ensure zero leakage of the hazardous medium.

[0070] The magnetic coupling includes an inner coupling sleeve 14 and an outer coupling sleeve 15. The transmission main shaft is fixedly connected to the inner coupling sleeve 14. The inner coupling sleeve 14 and the outer coupling sleeve 15 are driven by magnetism. The outer coupling sleeve 15 is connected to the output shaft of the motor 17.

[0071] Specifically, the transmission main shaft and the inner coupling sleeve 14 are connected by a key 13. The inner coupling sleeve 14 and the outer coupling sleeve 15 are driven by magnetism. The outer coupling sleeve 15 is connected to the motor 17. The motor 17 drives the coupling to rotate. The positioning protection sleeve 16 is connected to the motor 17. There is no bolt 1 connection between the inner coupling sleeve 14 and the outer coupling sleeve 15. The inner and outer sleeves are separated by an isolation sleeve 18 for magnetic drive, which can achieve zero leakage of cryogenic liquid and ensure safety.

[0072] In addition, there is no bolt 1 connection between the inner coupling sleeve 14 and the outer coupling sleeve 15. The inner and outer sleeves are driven by magnetism. The outer sleeve drives the inner sleeve to rotate. When the gear torque is greater than the maximum torque of the coupling, the inner and outer couplings will move relative to each other, protecting the safety of the motor 17 and also ensuring the safety of the pipeline.

[0073] Furthermore, when the transmission main shaft contacts the cryogenic liquid, under the action of low temperature, the material of the transmission main shaft will shrink. To provide a release point for the shrinkage stress, the transmission main shaft is connected to the cover plate as a fixed end, and the transmission main shaft and the inner coupling sleeve 14 are used as movable ends for stress release when the transmission main shaft shrinks.

[0074] Example 6

[0075] As Figure 4 shown, this embodiment provides an innovative zero-leakage test method for a cryogenic gear pump. The specific steps are as follows: Open the valve, and the cryogenic liquid enters the pipeline from the storage tank. Start the cryogenic gear pump. A flow meter and a temperature transmitter are provided at the rear end of the cryogenic gear pump. Through testing, verify the normal operation of zero leakage under different working conditions of the cryogenic gear pump. Through the test method of the test platform, conduct tests under the working conditions of cryogenic gas phase, cryogenic liquid phase, and cryogenic gas-liquid mixture. Measure the flow rate of the cryogenic gear pump at different powers through the temperature transmitter and the flow meter, and detect whether LNG leaks through the test.

[0076] When the valve is opened and the cryogenic gear pump is running, since the gear pump is a positive displacement pump, the cryogenic liquid will be sucked into the pipeline by the gear pump. The cryogenic liquid exchanges heat with the pipeline, and the liquid becomes gas, increasing the air pressure. The cryogenic gear and the pipeline can also be used as a booster to pressurize the storage tank without energy consumption.

Claims

1. A cryogenic gear pump structure, characterized by, It includes a shell, a positioning protective sleeve (16), a driving gear assembly, a driven gear assembly, a shaft coupling and a motor (17); the positioning protective sleeve (16) is installed on one side of the shell, the driving gear assembly and the driven gear assembly are installed in the shell in the form of meshing; the shaft coupling is a magnetic coupling, one end of the magnetic coupling is fixed on the output shaft of the motor (17), and the other end of the magnetic coupling is fixed on the end of the driving gear assembly; The shell includes a pump cavity (9) with openings at the front and rear ends, a front cover plate (3) and a rear cover plate (10) arranged on the front and rear sides of the pump cavity (9), and the pump cavity (9), the front cover plate (3) and the rear cover plate (10) are connected by a double-headed bolt assembly to form a closed cavity. Metal winding gaskets (8) for static sealing are arranged at the connection between the pump cavity (9) and the front cover plate (3) and the connection between the pump cavity (9) and the rear cover plate (10); the end face of the pump cavity (9) is provided with a concave-convex surface for mounting the metal winding gasket (8); the transmission main shaft extends into the positioning protective sleeve (16) and is connected with the magnetic coupling after passing through the pan seal (12) on the side close to the positioning protective sleeve (16).

2. A cryogenic gear pump structure according to claim 1, wherein The driving gear assembly includes a transmission main shaft arranged in the shell through a low-temperature bearing (5) and a driving gear (4) sleeved on the outside of the transmission main shaft; the driven gear assembly includes a driven shaft (6) arranged in the shell through a low-temperature bearing (5) and a driven gear (7) sleeved on the outside of the driven shaft (6); The driving gear (4) meshes with the driven gear (7).

3. A cryogenic gear pump structure according to claim 2, wherein An isolation sleeve (18) is arranged at the connection between the shell and the positioning protective sleeve (16), a bearing sleeve (19) is arranged at the position where the transmission main shaft extends out of the shell; a static sealing ring is arranged at the isolation sleeve (18) and the bearing sleeve (19).

4. A cryogenic gear pump structure according to claim 3, wherein The magnetic coupling includes an inner coupling sleeve (14) and an outer coupling sleeve (15), the transmission main shaft is fixedly connected with the inner coupling sleeve (14), the inner coupling sleeve (14) and the outer coupling sleeve (15) are driven by magnetic force, and the outer coupling sleeve (15) is connected with the output shaft of the motor (17).

5. A cryogenic gear pump structure according to claim 4, wherein The transmission main shaft and the inner coupling sleeve (14) are connected by a key (13).

6. A cryogenic gear pump structure according to claim 1, wherein The double-headed bolt assembly includes a bolt (1) and a nut (2).

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