CN208380871U - A kind of self-balanced multiple-stage cryogenic pump - Google Patents

Abstract

The utility model discloses a kind of self-balanced multiple-stage cryogenic pumps, belong to fluid delivery system field, it is excessive to solve the axial force that the connection structure of impeller assembly and cylinder part needs to bear, lead to the problem that connection structure is easy to damage, its key points of the technical solution are that including cylinder, guidance set is equipped in the cylinder, impeller assembly is rotatably connected in the cylinder, the cylinder upper end is equipped with inlet tube, the cylinder lower end is equipped with outlet tube, the impeller assembly rotate driving fluid is conveyed downwards by guidance set, the utility model is structurally reasonable, using fluid to the gravity of the thrust-balancing impeller itself of impeller assembly, to alleviate axial force between impeller assembly and the connection structure of cylinder part, keep the connection structure of impeller assembly and cylinder part more reliable and more stable.

Description

A kind of self-balanced multiple-stage cryogenic pump

Technical field

The utility model relates to a kind of fluid delivery systems, more specifically, it relates to a kind of self-balanced multiple-stage cryogenic pump.

Background technique

With the development of air separation technology, cancel the equipment such as oxygen compressor, nitrogen compressor in Internal-compression flow air separation unit, The conveying of product oxygen, nitrogen becomes liquid conveying from gaseous state conveying, to produce the demand to high pressure low temperature centrifugal pump.Motor band When impeller high speed rotation on moving axis, fluid in impeller is filled under the influence of centrifugal force, from impeller center along blade Between runner get rid of the surrounding to impeller, the effect due to liquid by blade makes pressure and speed while increasing, by leading shell Runner and the impeller for being led to time level-one, are exactly such principle, successively flow through all impellers and lead shell, further make fluid Pressure energy increase.

Current vertical multilevel low-temperature pump, including cylinder part and the electric machine support being assemblied at the top of cylinder part；Cylinder Components interior is provided with multilevel deflector component and impeller；Multilevel deflector component is made of guide vane and middle section component；Cylinder part Upper end is equipped with outlet tube, and the lower end of cylinder part is equipped with inlet tube.Liquid enters inside cylinder part from inlet tube, in impeller sets So that liquid is accelerated pressurization under the action of part, is then discharged from the outlet tube of upper end.

In above-mentioned technical proposal, upper end pressure is greater than the pressure of its lower end in cylinder part, so that impeller assembly is by liquid The pressure that the connection structure of the downward pressure of body pressure, impeller assembly and cylinder part needs the liquid born downward to impeller assembly The resultant force of power and impeller assembly self gravity, and then the axial direction for causing the connection structure of impeller assembly and cylinder part to need to bear Power is excessive, and connection structure is easy to damage.

Utility model content

In view of the deficienciess of the prior art, utilizing stream the utility model lies in that provide a kind of self-balanced multiple-stage cryogenic pump Body to the gravity of the thrust-balancing impeller itself of impeller assembly, thus alleviate impeller assembly and cylinder part connection structure it Between axial force, keep the connection structure of impeller assembly and cylinder part more reliable and more stable.

To achieve the above object, the utility model provides following technical solution: a kind of self-balanced multiple-stage cryogenic pump, including Cylinder, the cylinder is interior to be equipped with guidance set, impeller assembly is rotatably connected in the cylinder, the cylinder upper end is equipped with feed liquor Pipe, the cylinder lower end are equipped with outlet tube, and the impeller assembly rotate driving fluid is conveyed downwards by guidance set.

By using above-mentioned technical proposal, after impeller assembly rotation, fluid enters in cylinder from inlet tube, then in impeller Then fluid pressurized under the action of component is discharged in outlet tube from below；The pressure of lower end is greater than the pressure of upper end in cylinder, Fluid can apply upward thrust to impeller assembly under the action of the pressure difference, using fluid to the thrust-balancing of impeller assembly The gravity of impeller itself, to alleviate axial force between impeller assembly and the connection structure of cylinder part, make impeller assembly with The connection structure of cylinder part is more reliable and more stable.

The utility model is further arranged to: the guidance set includes cavity and guide vane, and the cavity has multiple in same Axis setting, the cylinder is interior to be equipped with connecting rod, and the cavity is placed on connecting rod.

By using above-mentioned technical proposal, cavity components are fixed using connecting rod after cavity components are stacked, facilitate guiding The installation and removal of component are replaced after also facilitating later period impeller assembly to damage.

The utility model is further arranged to: the guide vane is fixedly connected on cavity, is equipped between the guide vane and cavity The first runner and second flow channel of connection, the second flow channel are located at the lower section of guide vane, and the second flow channel sectional area is greater than the The sectional area of one runner.

By using above-mentioned technical proposal, when fluid flows to second flow channel from first runner, because of second flow channel section Product be greater than first runner sectional area, so as to cause the fluid in second flow channel flowing velocity than the flow velocity in first runner Slowly, so that the pressure in second flow channel increases, under the action of guidance set, the pressure of fluid increases step by step, thus Pressurization is achieved the purpose that.

The utility model is further arranged to: the guide vane includes upper end cover, lower cover and guide vane, the water conservancy diversion leaf Piece is fixedly connected between upper end cover and lower cover, and the area of the upper end cover is less than the area of lower cover.

By using above-mentioned technical proposal, the pressure of lower cover is greater than the pressure of upper end cover, and the area of lower cover is greater than upper The area of end cap, the pressure so as to cause lower cover by fluid is greater than pressure of the upper end cover by fluid, and then makes guiding group Part is upwarded pressure by fluid, using the gravity for the pressure balance guidance set itself that fluid applies guidance set, reduces Axial compressive force between guidance set and cylinder connection structure.

The utility model is further arranged to: the cavity lower end is equipped with communicating pipe, and the lower end of the communicating pipe is placed in out In liquid pipe, the linear expansion coefficient of the communicating pipe material is less than the linear expansion coefficient of outlet tube material.

It by using above-mentioned technical proposal, installs at normal temperature, communicating pipe is inserted into outlet tube, and the two is matched in gap Close, place low temperature in after by low temperature under the influence of, there is shrinkage phenomenon, the linear expansion coefficient of communicating pipe in communicating pipe and outlet tube Less than the linear expansion coefficient of outlet tube, so that outlet tube inner wall holds outlet tube outer wall tightly, it is interference fitted the two, and then reach The effect of sealing；When occurring shrinkage phenomenon at low temperature, the gap between communicating pipe and outlet tube is axial receipts between the two Contracting provides the space of relative movement, prevents communicating pipe and is interfered both when outlet tube shrinkage so as to cause communicating pipe or gone out Liquid pipe rupture.

The utility model is further arranged to: the impeller assembly includes main shaft and impeller, the impeller have it is multiple and It is fixedly and coaxially connected in main shaft, the main shaft is connect with barrel body rotation, and the main shaft upper end passes through cylinder and extends to outside cylinder.

By using above-mentioned technical proposal, pressure of the connection structure of main shaft and cylinder at inlet tube, inlet tube compared with It is small, so that the sealed pressure of the junction of main shaft and cylinder is smaller, it is not likely to produce leakage.

The utility model is further arranged to: the impeller offers balance hole.

By using above-mentioned technical proposal, the pressure of back shroud of impeller is reduced using balance hole, reduces fluid to impeller Axial force prevents fluid to be greater than the own wt of impeller assembly to the axial compressive force of impeller assembly, to alleviate impeller assembly The axial force between the connection structure of cylinder part.

The utility model is further arranged to: the main shaft upper end is coaxially arranged with connecting shaft, and the connecting shaft is non-gold Belong to material to be made.

By using above-mentioned technical proposal, using the low characteristic of the thermal conductivity of non-metallic material, reduces heat and connect from passing through Spindle is transferred on main shaft, and then is transferred to the intracorporal heat of cylinder by main shaft, further increases heat insulation.

The utility model is further arranged to: the collar bush is equipped with axle sleeve, and the axle sleeve is opened up there are three annular groove, The cylinder is fixedly connected with suction nozzle and outlet nozzle, and the outlet nozzle be connected to intermediate annular groove, the suction nozzle and The connection of other two annular groove.

By using above-mentioned technical proposal, gap location of the part sealed medium between main shaft and axle sleeve, which leaks into, to be leaned on Under annular groove in, sealed medium can vaporize in annular groove, the gas that blanket gas is mixed with the sealed medium of vaporization Body, the gap between main shaft and axle sleeve enter in intermediate annular groove, then arrange from intermediate annular groove from venthole Out, close to spindle motor end annular groove in blanket gas can the gap between main shaft and axle sleeve enter intermediate annular groove In, to be further reduced gas that blanket gas is mixed with the sealed medium of vaporization to the motor side of main shaft, prevent from being sealed Dielectric corrosion damages motor.

The utility model is further arranged to: the cylinder offers the link slot of annular, and the axle sleeve offers connection Annular groove is connected to by hole, the connecting hole with link slot, the suction nozzle and outlet nozzle be fixedly connected on cylinder and with even Access slot connection.

By using above-mentioned technical proposal, suction nozzle and outlet nozzle and cylinder connection type are more convenient, thus, and benefit Annular groove is connected to suction nozzle and outlet nozzle with link slot is more convenient.

In conclusion the utility model has the following beneficial effects:

First, cylinder upper end feed liquor, bringing out under cylinder makes fluid pressurized under the action of liquid impeller assembly, then from below It is discharged in outlet tube；The pressure of lower end is greater than the pressure of upper end in cylinder, and fluid can be to impeller sets under the action of the pressure difference Part applies upward thrust, using fluid to the gravity of the thrust-balancing impeller itself of impeller assembly, to alleviate impeller sets Axial force between part and the connection structure of cylinder part keeps the connection structure of impeller assembly and cylinder part more reliable and more stable；

Second, the sectional area of second flow channel is made to be greater than the sectional area of first runner, it is greater than the pressure of guide vane lower cover and leads The pressure of leaf upper end cover, and the area of lower cover is greater than the area of upper end cover, the pressure so as to cause guide vane lower cover by fluid Power is greater than pressure of the upper end cover by fluid, thus the pressure balance guidance set itself that guidance set is applied using fluid Gravity, to mitigate the pressure of connection structure between guidance set and cylinder；

Third, using multiple annular grooves are offered on axle sleeve, so that the pressure controlled in annular groove further subtracts The gas that few blanket gas is mixed with the sealed medium of vaporization prevents sealed medium corrosion and damage electric to the motor side of main shaft Machine；

Fourth, main shaft is connected to motor the connecting shaft using non-metallic material, reduces the external world and passed heat by main shaft It is handed in cylinder, to increase the heat insulation of cryogenic pump.

Detailed description of the invention

Fig. 1 is the sectional view of the present embodiment；

Fig. 2 is the sectional view that the present embodiment is used to show guidance set upper end formation；

Fig. 3 is the sectional view that the present embodiment is used to show guidance set lower end structure；

Fig. 4 is the sectional view that the present embodiment is used to show guide vane；

Fig. 5 is the sectional view that the present embodiment is used to show main shaft；

Fig. 6 is the portion the A enlarged drawing of Fig. 5.

Appended drawing reference: 1, cylinder；11, inlet tube；12, outlet tube；13, electric machine support；131, motor shaft；14, the second peace Fill ring；141, connecting hole；15, link slot；2, guidance set；21, cavity；211, the first mounting groove；212, the first mounting ring； 213, chamber；214, it is connected to runner；22, fixed frame；221, the second mounting groove；23, guide vane；231, upper end cover；232, lower cover； 233, guide vane；234, ring body；235, first runner；236, second flow channel；24, connecting rod；25, lower platen；251, communicating pipe； 3, impeller assembly；31, main shaft；311, connecting shaft；312, inducer；32, impeller；321, balance hole；322, wheel hub；4, axle sleeve； 41, the first annular groove；42, the second annular groove；43, third annular groove；44, suction nozzle；441, air inlet pipe；45, outlet nozzle；451, outlet Pipe.

Specific embodiment

The utility model is described in further detail below in conjunction with attached drawing.

The same or similar label correspond to the same or similar components in the attached drawing of the utility model embodiment；It is practical at this In novel description, it is to be understood that if the orientation or positional relationship for having the instructions such as term " on ", "lower", "left", "right" is It is based on the orientation or positional relationship shown in the drawings, is merely for convenience of describing the present invention and simplifying the description, rather than indicate Or imply that signified device or element must have a particular orientation, be constructed and operated in a specific orientation, therefore retouch in attached drawing The term for stating positional relationship only for illustration, should not be understood as the limitation to this patent, for the common skill of this field For art personnel, the concrete meaning of above-mentioned term can be understood as the case may be.

A kind of self-balanced multiple-stage cryogenic pump, as shown in Figure 1, including cylinder 1, impeller assembly 3 and guidance set 3.On cylinder 1 End side wall is fixedly connected with the inlet tube 11 being connected to its inside, and 1 lower end of cylinder has been fixedly and coaxially connected outlet tube 12, guiding group Part 3 is fixedly and coaxially connected in cylinder 1, and there are biggish spaces between 1 inner wall of 3 outer wall of guidance set and cylinder, thus Slow down the flowing of heat, improves heat insulation.Guidance set 3, which rotates coaxially, to be connected in guidance set 3.1 upper end of cylinder is equipped with Electric machine support 13,13 upper end of electric machine support are fixedly connected with driving motor (not shown), and driving motor drives impeller assembly 3 It rotates, the fluid at inlet tube 11 is pressurized under the action of impeller assembly 3, is then discharged in outlet tube 12 from below.

As depicted in figs. 1 and 2, guidance set 2 includes fixed frame 22, cavity 21, guide vane 23 and connecting rod 24, wherein cavity 21 Cylindrical, 21 lower end of cavity coaxially offers circular chamber 213, and the upper end of cavity 21 is offered to be connected to chamber 213 It is connected to runner 214.21 upper surface of cavity coaxially offers the first mounting groove 211 of annular, and 21 lower end of cavity is fixedly and coaxially connected There is the first mounting ring 212, the first mounting ring 212 is adapted to the first mounting groove 211.There are five cavitys 21 and is arranged coaxially, The first mounting ring 212 for being located above cavity 21 is adapted to the first mounting groove 211 for being located below cavity 21, the cavity of the top 21 contact on fixed frame 22.

As shown in figure 3, the lowermost cavity 21 contacts on lower platen 25, lower platen 25 has been fixedly and coaxially connected communicating pipe 251, it extends downwardly communicating pipe 251 and outlet tube 12 is connected to.The linear expansion coefficient that communicating pipe 251 uses is less than 12 material of outlet tube The linear expansion coefficient of matter, is installed at normal temperature, and communicating pipe 251 is inserted into outlet tube 12, and the two is in clearance fit, is placed low After middle benefit gas by low temperature under the influence of, there is shrinkage phenomenon, the linear expansion coefficient of communicating pipe 251 in communicating pipe 251 and outlet tube 12 Less than the linear expansion coefficient of outlet tube 12, so that 12 inner wall of outlet tube holds 251 outer wall of communicating pipe tightly, it is interference fitted the two, into And sealing is achieved the effect that；Both when occurring shrinkage phenomenon at low temperature, the gap between communicating pipe 251 and outlet tube 12 is Between axial shrinkage provide the space of relative movement, prevent communicating pipe 251 with 12 shrinkage of outlet tube when both interfere It is ruptured so as to cause communicating pipe or outlet tube 12.

As shown in Figures 2 and 3, connecting rod 24 is set to lower platen 25 there are four circumferential, and 24 lower end of connecting rod passes through lower platen 25, The threaded one end that connecting rod 24 passes through lower platen 25 is connected with nut, applies support force to lower platen 25 using nut.Connecting rod 24 Upper end is threadedly coupled with fixed frame 22, when the nut on connecting rod 24 is tightened, using lower platen 25 and fixed frame 22 to cavity 21 Apply pressure, all cavitys 21 are clamped.Fixed frame 22 coaxially offers the second mounting groove 221, inner wall of the cylinder 1 close to upper end Be fixedly connected with the second mounting ring 14 being adapted to the second mounting groove 221, using second mounting ring 14 to fixed frame 22 apply to On thrust, so that guidance set 2 is fixedly connected on cylinder 1.

As shown in figure 4, guide vane 23 includes upper end cover 231, lower cover 232 and guide vane 233, upper end cover 231 and lower end Ring body 234 is fixedly connected between lid 232, guide vane 233 is fixed to be connected in 234 side wall of ring body, and 233 upper end of guide vane contradicts Inside 213 upper end of chamber, 233 lower end of guide vane contacts at the upper surface of lower section cavity 21.234 side wall of ring body and chamber It is in multiple first runners 235 that gap between 213 side walls is separated by guide vane 233.Lower cover 232 and 21 upper surface of cavity it Between there are the formation second flow channels 236 in gap.Guide vane 233 is set to be inclined to set, to increase the length of first runner 235 The sectional area for spending and reducing first runner 235 makes the sectional area of first runner 235 be less than the sectional area of second flow channel 236. When flowing to second flow channel 236 from first runner 235 under the action of fluid is in impeller assembly 3, because of 236 section of second flow channel Product is greater than the sectional area of first runner 235, so as to cause the flowing velocity and first runner 235 of the fluid in second flow channel 236 The flowing velocity of interior fluid is slow, so that the pressure in second flow channel 236 increases, under the action of guidance set 2, stream The pressure of body increases step by step, to achieve the purpose that pressurization.The pressure of fluid is greater than the stream of upper end cover 231 at lower cover 232 The pressure of body is led so that fluid can apply upward thrust to guide vane 23 using the pressure balance that flowing applies guidance set 2 To the gravity of component 2 itself, the axial compressive force between guidance set 2 and 1 connection structure of cylinder is reduced.To be further reduced guiding Axial compressive force between 1 connection structure of component 2 and cylinder makes the area of upper end cover 231 be less than the area of lower cover 232, thus Further increase the pressure difference between upper end cover 231 and lower cover 232, further increase fluid guide vane 23 is applied it is upward Pressure, reach fluid and the gravity of stable steering component 2 itself of upwarding pressure applied to guidance set 2, make guidance set 2 with 1 connection structure of cylinder is more stable.

As shown in figure 4, impeller assembly 3 includes main shaft 31 and impeller 32.There are five be fixedly and coaxially connected in master impeller 32 On axis 31, five impellers 32 are respectively placed in the chamber 213 of five cavitys 21.The water inlet of impeller 32 connects with runner 214 is connected to Logical, impeller 32 generates biggish centrifugal force and goes out to suck from water inlet by fluid when rotating, and then throws away from edge into first In runner 235, is flowed into second flow channel 236 from first runner 235, then flow to next leaf from second flow channel 236 again In wheel 32, thus increase the pressure of fluid step by step, thus make the pressure of 32 rear end cap of impeller greater than the pressure of 32 drive end bearing bracket of impeller, Fluid can apply upward thrust to impeller assembly 3 under the action of the pressure difference, flat using thrust of the fluid to impeller assembly 3 The gravity of weighing apparatus impeller 32 itself makes impeller to alleviate axial force between the connection structure of 1 component of impeller assembly 3 and cylinder Component 3 and the connection structure of 1 component of cylinder are more reliable and more stable.

As shown in figure 4,32 rear end cap of impeller has been fixedly and coaxially connected wheel hub 322, the upper end cover of wheel hub 322 and guide vane 23 231 rotation connections, 32 rear end cap of impeller offer balance hole 321, and balance hole 321 is located at 322 inside of wheel hub, utilizes balance hole 321 reduce the pressure of 32 back shroud of impeller, reduce the axial force of fluid Multi-impeller 32, prevent fluid to the axial direction of impeller assembly 3 Pressure is greater than the own wt of impeller assembly 3, to alleviate axial between the connection structure of 1 component of impeller assembly 3 and cylinder Power.

As shown in figure 5, main shaft 31 is coaxially arranged in guidance set 2, the lower end of main shaft 31 and lower platen 25(are referring to Fig. 3) Rotation connection, the upper end of main shaft 31 pass through 1 upper end inner wall of cylinder and extend cylinder 1.31 upper end of main shaft is coaxially arranged with connecting shaft 311, the motor shaft 131 of 311 upper end of connecting shaft and driving motor is fixedly and coaxially connected by flange coupling.In order to reduce cylinder Heat outside 1 is transferred in cylinder 1 from main shaft 31, and connecting shaft 311 is that the low non-metallic material of thermal conductivity is made, it is preferable to use poly- Amide.It reduces inside the heat transfer to cylinder 1 on the motor shaft 131 of driving motor.It has been fixedly and coaxially connected and has lured on main shaft 31 Guide wheel 312, the rotation of main shaft 31 drive inducer 312 to rotate, the water in inlet tube 11 are delivered at impeller 32, increase impeller 32 Feed liquor pressure.

As shown in fig. 6, being equipped with axle sleeve 4 between main shaft 31 and cylinder 1, the inside of 4 outer wall of axle sleeve and cylinder 1 is interference fitted, The inner wall of axle sleeve 4 and the outer wall of main shaft 31 are in clearance fit.4 inner wall of axle sleeve is opened up there are three annular groove, from top to bottom successively It is third annular groove 43, the second annular groove 42 and the first annular groove 41.1 inner wall of cylinder is opened up there are three link slot 15, is offered on axle sleeve 4 Three annular grooves are connected to link slot 15 by three connecting holes 141, three connecting holes 141 respectively.Cylinder 1 is fixedly connected on two A suction nozzle 44 and an outlet nozzle 45, outlet nozzle 45 is connected to intermediate link slot 15, to make the second annular groove 42 and outlet Mouth 45 is connected to；Two suction nozzles 44 are connected to the link slot 15 of the top and the most link slot 15 that issues respectively, to make air inlet Mouth 44 is connected to the first annular groove 41 and third annular groove 43.Two suction nozzles 44 are connected to air inlet pipe 441, thus outlet nozzle 45 with go out Tracheae 451 is connected to.It is passed through blanket gas into the first annular groove 41, third annular groove 43 by air inlet pipe 441, makes the first annular groove 41 and Air pressure is greater than the air pressure in pump chambers 213 in three annular grooves 43, to reduce the leakage of sealed medium.Part sealed medium from Gap location between main shaft 31 and axle sleeve 4 leaks into the first annular groove 41, and sealed medium can vaporize in the first annular groove 41 In gas, blanket gas is mixed with the sealed medium of vaporization, and then the mixed gas in part can be between main shaft 31 and axle sleeve 4 Gap enter in the second annular groove 42, and pressure is greater than the pressure in the second annular groove 42 to mixed gas in third annular groove 43 Know from experience and be discharged by escape pipe 451, to be further reduced gas that blanket gas is mixed with the sealed medium of vaporization to main shaft 31 motor side prevents sealed medium corrosion and damage motor.The width of link slot 15 is greater than the width of annular groove, thus more Add to facilitate and is connected to suction nozzle 44 and outlet nozzle 45 with annular groove.

Specific working mode: driving motor drives main shaft 31 to rotate, and main shaft 31 rotates impeller 32 and rotates, and 32 turns of impeller Biggish centrifugal force is generated when dynamic and goes out to suck from water inlet by fluid, is then thrown away from edge into first runner 235, from First runner 235 flows into second flow channel 236, then again from being flowed in second flow channel 236 in next impeller 32, thus by Grade increases the pressure of fluid, is finally discharged from outlet tube 12.

This specific embodiment is only the explanation to the utility model, is not limitations of the present invention, ability Field technique personnel can according to need the modification that not creative contribution is made to the present embodiment after reading this specification, but As long as all by the protection of Patent Law in the scope of the claims of the utility model.

Claims (10)

1. a kind of self-balanced multiple-stage cryogenic pump, including cylinder (1), the cylinder (1) is interior to be equipped with guidance set (2), the cylinder (1) impeller assembly (3) are rotatably connected in, it is characterized in that: the cylinder (1) upper end is equipped with inlet tube (11), the cylinder (1) Lower end is equipped with outlet tube (12), and impeller assembly (3) the rotate driving fluid is conveyed downwards by guidance set (2).

2. a kind of self-balanced multiple-stage cryogenic pump according to claim 1, it is characterized in that: the guidance set (2) includes chamber Body (21) and guide vane (23), the cavity (21) have it is multiple be arranged coaxially, be equipped with connecting rod (24) in the cylinder (1), it is described Cavity (21) is placed on connecting rod (24).

3. a kind of self-balanced multiple-stage cryogenic pump according to claim 2, it is characterized in that: the guide vane (23) is fixedly connected on Cavity (21) is equipped with the first runner (235) being connected to and second flow channel (236), institute between the guide vane (23) and cavity (21) The lower section that second flow channel (236) is located at guide vane (23) is stated, second flow channel (236) sectional area is greater than first runner (235) Sectional area.

4. a kind of self-balanced multiple-stage cryogenic pump according to claim 3, it is characterized in that: the guide vane (23) includes upper end cover (231), lower cover (232) and guide vane (233), the guide vane (233) are fixedly connected with upper end cover (231) and lower end It covers between (232), the area of the upper end cover (231) is less than the area of lower cover (232).

5. a kind of self-balanced multiple-stage cryogenic pump according to claim 2 connects it is characterized in that: the cavity (21) lower end is equipped with The lower end of siphunculus (251), the communicating pipe (251) is placed in outlet tube (12), and the line of communicating pipe (251) material expands system Number is less than the linear expansion coefficient of outlet tube (12) material.

6. a kind of self-balanced multiple-stage cryogenic pump according to claim 1, it is characterized in that: the impeller assembly (3) includes master Axis (31) and impeller (32), the impeller (32) have multiple and are fixedly and coaxially connected in main shaft (31), the main shaft (31) It is rotatablely connected with cylinder (1), main shaft (31) upper end passes through cylinder (1) and extends to cylinder (1) outside.

7. a kind of self-balanced multiple-stage cryogenic pump according to claim 6, it is characterized in that: the impeller (32) offers balance Hole (321).

8. a kind of self-balanced multiple-stage cryogenic pump according to claim 7, it is characterized in that: the main shaft (31) upper end is coaxially set It is equipped with connecting shaft (311), the connecting shaft (311) is made of non-metallic material.

9. a kind of self-balanced multiple-stage cryogenic pump according to claim 8, it is characterized in that: the main shaft (31) is arranged with axle sleeve (4), the axle sleeve (4) opens up there are three annular groove, and the cylinder (1) is fixedly connected with suction nozzle (44) and outlet nozzle (45), the outlet nozzle (45) is connected to intermediate annular groove, and the suction nozzle (44) is connected to other two annular groove.

10. a kind of self-balanced multiple-stage cryogenic pump according to claim 9, it is characterized in that: the cylinder (1) offers annular Link slot (15), the axle sleeve (4) offers connecting hole (141), and the connecting hole (141) is by annular groove and link slot (15) it is connected to, the suction nozzle (44) and outlet nozzle (45) are fixedly connected on cylinder (1) and are connected to link slot (15).