CN117869336A - Dry pump - Google Patents

Abstract

The invention relates to the technical field of vacuum obtaining equipment, in particular to a dry pump. A dry pump, comprising: the shell assembly is provided with an internal cavity, the side wall of the shell assembly is provided with an air inlet, and the shell assembly comprises a low vacuum side shell; the composite impeller is arranged in the inner cavity and is provided with a turbine stage, and the turbine stage is used for sucking gas entering from the air inlet; the main shaft is arranged in the inner cavity, the main shaft comprises a connecting section and a screw rod section, the composite impeller is sleeved on the peripheral wall of the connecting section, a first spiral groove is formed in the peripheral wall of the screw rod section, the low vacuum side shell is sleeved on the periphery of the screw rod section, an exhaust port is formed in the side wall of the low vacuum side shell corresponding to the first spiral groove, the main shaft rotates in a working state, the turbine stage firstly sucks in gas, the gas is compressed in the first spiral groove, and the gas is discharged out of the exhaust port along with the rotation of the first spiral groove. The invention solves the problem that the high vacuum pump needs to be matched with other types of pumps to discharge gas into the atmosphere when obtaining high vacuum.

Description

Dry pump

Technical Field

The invention relates to the technical field of vacuum obtaining equipment, in particular to a dry pump.

Background

For vacuum obtaining equipment, the compound turbomolecular pump has wide application in the industry of obtaining high vacuum, and has higher vacuum environment in the processing and manufacturing requirements of products in the industries of some semiconductor industries and the like.

In general, in order to obtain a high vacuum, one will typically use a high vacuum pump, such as a molecular pump, a diffusion pump, and a cold trap. However, these high vacuum pumps must be equipped with a backing pump when in use, and cannot be vented directly to the atmosphere. Otherwise, accidents such as motor burnout, rotor blade breaking, diffusion pump oil oxidation and the like can be caused. The compound turbo molecular pump as disclosed in CN116221151a is capable of pumping out most of the air in the enclosed space, but needs to be matched with other kinds of pumps to vent the gas into the atmosphere in order to bring the space to the required extreme vacuum environment.

Disclosure of Invention

Therefore, the technical problem to be solved by the invention is to overcome the defect that the high vacuum pump in the prior art needs to be matched with other types of pumps to discharge gas into the atmosphere when obtaining high vacuum, thereby providing a dry pump.

In order to solve the above problems, the present invention provides a dry pump comprising:

the shell assembly is provided with an inner cavity, the side wall of the shell assembly is provided with an air inlet, and the shell assembly comprises a low vacuum side shell;

the composite impeller is arranged in the inner cavity and is provided with a turbine stage, and the turbine stage is used for sucking gas entering from the air inlet;

the main shaft is arranged in the inner cavity, the main shaft comprises a connecting section and a screw rod section, the composite impeller is sleeved on the peripheral wall of the connecting section, a first spiral groove is formed in the peripheral wall of the screw rod section, the low vacuum side shell is sleeved on the periphery of the spiral section, an exhaust port is formed in the side wall of the low vacuum side shell corresponding to the first spiral groove, the main shaft rotates in a working state, the turbine stage firstly sucks gas, the gas is compressed in the first spiral groove, and the gas is discharged out of the exhaust port along with the rotation of the first spiral groove.

Optionally, the shell assembly further comprises a high vacuum side shell and an inner sleeve, the high vacuum side shell is sleeved on the periphery of the inner sleeve, the high vacuum side shell is connected with the low vacuum side shell, the low vacuum side shell is fixedly connected with the inner sleeve, the composite impeller further comprises a first traction section, the inner sleeve is sleeved on the periphery of the first traction section, and a second spiral groove is formed in the peripheral surface of the first traction section.

Optionally, the low vacuum side shell is provided with a second traction section, the outer circumferential surface of the second traction section is provided with a third spiral groove, and the first traction section is sleeved on the outer circumference of the second traction section.

Optionally, a first gap is left between the end face of the first traction section, which is away from the turbine stage, and the end face of the low vacuum side shell, and a second gap is left between the end face of the second traction section of the low vacuum side shell and the inner end face of the first traction section.

Optionally, the lead angle of the second spiral groove is larger than the lead angle of the third spiral groove, the spiral groove depth of the second spiral groove is equal to the spiral groove depth of the third spiral groove, and the spiral groove width of the second spiral groove is larger than the spiral groove width of the third spiral groove; the spiral angle of the third spiral groove is larger than that of the first spiral groove, the spiral groove depth of the third spiral groove is equal to that of the first spiral groove, and the spiral groove width of the third spiral groove is larger than that of the first spiral groove.

Optionally, the lead angle of the second spiral groove is greater than or equal to the lead angle of the third spiral groove.

Optionally, the housing assembly further comprises a high vacuum side bearing seat and a low vacuum side bearing cover, and the high vacuum side bearing seat and the low vacuum side bearing cover are respectively arranged at two ends of the main shaft.

Optionally, the device further comprises an airtight aviation plug-in unit and a power driving part, wherein the power driving part is arranged between the low vacuum side shell and the main shaft, the power driving part comprises a stator rotor and a movable rotor, the movable rotor is sleeved on the outer peripheral surface of the main shaft, the stator rotor is fixedly connected with the low vacuum side shell, and the airtight aviation plug-in unit is connected with a power driving part in a circuit manner.

Optionally, the device further comprises an air cooling assembly, wherein the air cooling assembly is fixedly connected with the low vacuum side bearing gland.

Optionally, the turbine stage includes a movable impeller and a stationary blade wheel, which are sequentially arranged at intervals.

The technical scheme of the invention has the following advantages:

1. the dry pump provided by the invention comprises: the shell assembly is provided with an internal cavity, the side wall of the shell assembly is provided with an air inlet, and the shell assembly comprises a low vacuum side shell; the composite impeller is arranged in the inner cavity and is provided with a turbine stage which is used for absorbing gas entering from the air inlet; the main shaft is arranged in the inner cavity and comprises a screw rod section and a connecting end section, the composite impeller is sleeved on the peripheral wall of the connecting section, a first spiral groove is formed in the peripheral wall of the screw rod section, the low vacuum side shell is sleeved on the periphery of the spiral section, and an exhaust port is formed in the side wall of the low vacuum side shell, corresponding to the first spiral groove.

Under the working condition, the main shaft rotates, the turbine stage firstly sucks in gas, the gas is compressed in the first spiral groove, and the gas is discharged to the outside of the exhaust port along with the rotation of the first spiral groove. Through the setting of turbine level and first spiral recess, rotate by the turbine level and make the gas that gets into from the air inlet carry out directional flow, produce the effect of bleeding, make gas get into in the first spiral recess again and receive the compression, discharge outside the gas vent. It should be noted that when the screw rod section rotates, the screw rod section is used as a rotor, the low vacuum side shell is used as a stator, so that the functions of air extraction and compression are realized in the same pump body, the composite impeller and the screw rod section rotate along with a main shaft, and the turbine stage and the screw rod section are matched, so that the functional requirement of directly exhausting air is realized.

2. The invention provides a dry pump, which comprises a shell assembly, a high-vacuum side shell and an inner sleeve, wherein the high-vacuum side shell is sleeved on the periphery of the inner sleeve, the high-vacuum side shell is connected with a low-vacuum side shell, the low-vacuum side shell is fixedly connected with the inner sleeve, the composite impeller further comprises a first traction section, the inner sleeve is arranged on the periphery of the first traction section, and a second spiral groove is formed in the periphery of the first traction section. The first traction section is used as a rotor and the inner sleeve is used as a stator, so that gas is discharged out of the exhaust port through the turbine stage, the second spiral groove and the first spiral groove in sequence. Because the gas pumped by the turbine stage has a larger pumping speed, the speed of the gas is buffered by the arrangement of the first traction section, and the speed of the gas discharged from the turbine stage is better matched to reduce the speed of the gas entering the first spiral groove.

3. The dry pump provided by the invention is characterized in that the low vacuum side shell is provided with the second traction section, the outer circumferential surface of the second traction section is provided with the third spiral groove, and the first traction section is sleeved on the outer circumference of the second traction section. The inner side wall of the first traction section is used as a rotor, the second traction section is used as a stator, gas enters the first spiral groove after passing through the first traction section and then passing through the second traction section, and the speed of the gas entering from the first traction section is further reduced by the second traction section.

4. According to the dry pump provided by the invention, a first gap is reserved between the end face of the first traction section, which is away from the turbine stage, and the end face of the low vacuum side shell, and a second gap is reserved between the end face of the second traction section of the low vacuum side shell and the inner end face of the first traction section. The first space plays the purpose of connecting third spiral groove and first spiral groove, and the second space plays the purpose of second spiral groove and first spiral groove, because the arrangement in first space and second space makes the screw rod section of main shaft, the second of low vacuum side casing pull section and compound impeller's first and pull the section and can arrange in proper order along the circumference of main shaft, makes overall structure compacter, reduces the volume of casing subassembly, and the effect of bleeding is better.

5. According to the dry pump provided by the invention, the helix angle of the second spiral groove is larger than that of the third spiral groove, the helix depth of the second spiral groove is equal to that of the third spiral groove, and the helix width of the second spiral groove is larger than that of the third spiral groove; the third spiral groove has a helix angle greater than the helix angle of the first spiral groove, a spiral groove depth equal to the spiral groove depth of the first spiral groove, and a spiral groove width greater than the spiral groove width of the first spiral groove, so that the second spiral groove accommodates a volume of gas greater than the third spiral groove, and the third spiral groove accommodates a volume of gas greater than the first spiral groove.

6. The spiral angle of the second spiral groove is larger than or equal to the spiral angle of the third spiral groove.

7. The dry pump provided by the invention further comprises a high-vacuum side bearing seat and a low-vacuum side bearing cover, wherein the high-vacuum side bearing seat and the low-vacuum side bearing cover are respectively arranged at two ends of the main shaft so as to fix and seal the main shaft.

8. The dry pump provided by the invention further comprises an airtight aviation plug-in unit and a power driving part, wherein the power driving part is arranged between the low vacuum side shell and the main shaft, the power driving part comprises a stator rotor and a movable rotor, the movable rotor is sleeved on the outer peripheral surface of the main shaft, the stator rotor is fixedly connected with the low vacuum side shell, and the airtight aviation plug-in unit is connected with a power driving part through a line. The power driving piece drives the main shaft to rotate, the airtight aviation plug provides electric energy, the stator rotor and the movable rotor are matched to convert the electric energy into kinetic energy, and finally the main shaft is driven to rotate.

9. The dry pump provided by the invention further comprises an air cooling assembly, wherein the air cooling assembly is fixedly connected with the low vacuum side bearing gland, and the air cooling assembly is used for cooling the whole structure.

10. The invention provides a dry pump, wherein a turbine stage comprises a movable impeller and a stationary impeller, the outer peripheral surface of the movable impeller is arranged corresponding to an air inlet, and the movable impeller and the stationary impeller are sequentially arranged at intervals.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic diagram of a dry pump provided in an embodiment of the present invention.

Reference numerals illustrate: 1. a main shaft; 2. a rotor; 3. a low vacuum side case; 4. a low vacuum side sleeve; 5. a stator and a rotor; 6. a bearing; 7. a locking block; 8. a low vacuum side bearing seat; 9. an elastic member; 10. a low vacuum side bearing gland; 11. an inner sleeve; 12. an exhaust port; 13. a composite impeller; 14. a locking member; 15. a stationary impeller; 16. a high vacuum side case; 17. a high vacuum side bearing seat; 18. a high vacuum side bearing gland; 19. a high vacuum side sleeve; 20. a first connection flange; 21. an airtight aviation plug; 22. an air cooling assembly; 23. a screw section; 24. a first helical groove; 25. a second void; 26. a first traction section; 27. a second traction section; 28. a first void; 29. an air inlet; 30. a moving impeller; 31. and a support end.

Detailed Description

The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

In addition, the technical features of the different embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.

One embodiment of a dry pump as shown in fig. 1 includes: a housing assembly having an internal chamber, a main shaft 1 and a compound impeller 13 provided in the housing assembly.

As shown in fig. 1, the spindle 1 comprises a connecting section and a screw section 23, wherein the screw section 23 is provided with a first helical groove 24 in the form of a helix.

As shown in fig. 1, the composite impeller 13 includes a turbine stage and a first traction section 26, the turbine stage of the composite impeller 13 is sleeved on the periphery of the connection section of the main shaft 1, the composite impeller 13 is fixedly connected with the main shaft 1 through a locking member 14, wherein the turbine stage is provided with five movable impellers 30 and five stationary impellers 15 which are alternately arranged, that is, the arrangement sequence of the movable impellers 30 and the stationary impellers 15 is '1 movable impeller 30-1 stationary impeller 15-1 movable impeller 30-1 stationary impeller 15 … …', and the outer peripheral surface of the first traction section 26 is provided with a second spiral groove. It should be noted that each stage of movable impeller 30 and each stage of stationary impeller 15 respectively comprise a plurality of blades, the inclination angles of the blades of the movable impeller 30 and the blades of the stationary impeller 15 are opposite, the pressure surface and the suction surface of each blade are curved surfaces, the thickness of the blade body of the blade is gradually reduced from the root to the top, and the angle of the blade body is also gradually reduced. It should be noted that the more the number of blades of the impeller 30 that are closer to the first traction segment 26, i.e., the most the number of blades of the impeller 30 that are closest to the first traction segment 26, the least the number of blades of the impeller 30 that are furthest from the first traction segment 26, the number of blades therebetween being presented in relation; meanwhile, the greater the number of blades, the smaller the blade body width of the blades, i.e., the smallest blade width of the movable sheave 30 closest to the first traction section 26, and the largest blade width of the movable sheave 30 farthest from the first traction section 26.

As shown in fig. 1, the housing assembly includes a high vacuum side housing 16, a low vacuum side housing 3 and an inner sleeve 11, wherein the high vacuum side housing 16 and the low vacuum side housing 3 are fixedly connected, the low vacuum side housing 3 is sleeved on the outer circumference of the screw section 23 of the main shaft 1, the low vacuum side housing 3 is provided with a second traction section 27, the outer circumference of the second traction section 27 is provided with a third spiral groove, the inner sleeve 11 is sleeved on the outer circumference of the first traction section 26 of the composite impeller 13, the high vacuum side housing 16 is sleeved on the outer circumference of the inner sleeve 11, and the low vacuum side housing 3 is fixedly connected with the inner sleeve 11, thereby forming the second traction section 27 of the low vacuum side housing 3 and the first traction section 26 of the composite impeller 13 which are sequentially arranged outwards from the screw section 23 of the main shaft 1 along the circumferential direction thereof as shown in fig. 1. It should be noted that the High Vacuum (High Vacuum-HV) side housing, the Low Vacuum (Low Vacuum-LV) side housing, the helix angle of the second helical groove is larger than the helix angle of the third helical groove, and the helical groove of the second helical groove is deeper than the helical groove of the third helical groove, and the helical groove width of the second helical groove is larger than the helical groove width of the third helical groove. In order to communicate the first traction section 26 with the second traction section 27, a first gap 28 is reserved between the end surface of the first traction section 26 facing away from the turbine stage and the end surface of the low vacuum side shell 3, so as to achieve the purpose of communicating the third spiral groove with the second spiral groove; in order to communicate the second traction section 27 with the screw section 23, a second gap 25 is left between the end surface of the second traction section 27 and the inner end surface of the first traction section 26 of the low vacuum side casing 3, so as to serve the purpose of the third spiral groove and the first spiral groove 24. As shown in fig. 1, the high vacuum side housing 16 is provided with a first connection flange 20, the first connection flange 20 is provided with an air inlet 29, the low vacuum side housing 3 is provided with a second connection flange, the second connection flange is provided with an air outlet 12, wherein the end of the screw section 23, which is arranged away from the connection section, is arranged corresponding to the air outlet 12. With the above arrangement, when the main shaft 1 rotates, the impeller 30 rotates to suck the gas entering from the gas inlet 29, so that the gas sequentially passes through the "turbine stage→the second spiral groove of the first traction section 26→the second gap 25→the third spiral groove of the second traction section 27→the first gap 28→the first spiral groove 24" of the screw section 23, and finally is discharged to the gas outlet 12 through the screw section 23. The lead angle, the helical groove depth and the helical groove width of the head and tail of the section in the second helical groove of the first traction section 26 are all equal; the lead angle, the screw groove depth and the screw groove width of the first and second screw grooves of the third traction section 27 are equal; the lead angle, the groove depth and the groove width of the first spiral groove located at the screw section 23 are gradually reduced from the head to the tail of the section, respectively, and the lead angle, the groove depth and the groove width of the second spiral groove are larger than those of the third spiral groove, the lead angle, the groove depth and the groove width of the third spiral groove are larger than those of the first spiral groove 24, and the start angle of the same first spiral groove 24 is larger than the end angle.

In order to enclose the housing assembly to form an internal chamber, the housing assembly further comprises a high vacuum side bearing housing 17, the high vacuum side bearing housing 17 being fixedly connected to the high vacuum side housing 16. As shown in fig. 1, the high vacuum side bearing seat 17 forms a spiral seal with the spindle 1, and the supporting end 31 of the low vacuum side housing 3 forms a simple beam structure with the spindle 1, so as to achieve the sealing purpose in a spiral effect, and ensure that gas does not enter into the internal cavity in the state of rotation of the spindle 1. Through the structural arrangement of the simply supported beams, each adjacent span is easy to be stressed independently and not easy to be influenced by deflection, and the convenience of manufacturing and installation is improved. In order to further connect the spindle 1, a bearing 6, a high vacuum side sleeve 19, an elastic member 9 and a high vacuum side bearing cover 18 are arranged between the high vacuum side bearing seat 17 and the spindle 1, the bearing 6 is sleeved on the outer peripheral surface of the spindle 1, the high vacuum side sleeve 19 is sleeved on the outer peripheral surface of the bearing 6, the high vacuum side bearing cover 18 is fixedly connected with the spindle 1 through a locking block 7, and the elastic member 9 is arranged between the high vacuum side bearing cover 18 and the high vacuum side sleeve 19. Specifically, the elastic member 9 is a wave spring.

For driving the main shaft 1 to rotate, as shown in fig. 1, the air-tight aviation plug-in unit further comprises an air-tight aviation plug-in unit 21 and a power driving part, wherein the power driving part is arranged between the low vacuum side shell 3 and the main shaft 1, the power driving part comprises a stator rotor 5 and a movable rotor 2, the movable rotor 2 is sleeved on the outer peripheral surface of the main shaft 1, the stator rotor 5 is fixedly connected with the low vacuum side shell 3, the air-tight aviation plug-in unit 21 is arranged outside the main shaft 1, the air-tight aviation plug-in unit 21 is connected with a power driving part line, and the air-tight aviation plug-in unit 21 provides electric energy to drive the movable rotor 2 to rotate. In order to further connect the main shaft 1, a low vacuum side bearing gland 10 is arranged at one end of the main shaft 1 near the air cooling assembly 22, and a bearing 6 and a low vacuum side shaft sleeve 4 are arranged between the low vacuum side bearing gland 10 and the main shaft 1. The bearing 6 is assembled with the low vacuum side shaft sleeve 4 in a hot-charging mode, the bearing 6 is sleeved on the outer peripheral surface of the main shaft 1, the outer side of the low vacuum side shaft sleeve 4 is assembled with the low vacuum side bearing seat 8 through shaft shoulder positioning, and the low vacuum side shaft sleeve 4 is axially locked with the bearing through the locking block 7. As shown in fig. 1, the low vacuum side bearing housing 8 is further included, the low vacuum side housing 3 and the low vacuum side bearing housing 8 are fixed by screws, and the low vacuum side bearing housing 8 is fixedly connected with the low vacuum side bearing gland 10. For cooling the overall structure, the air cooling assembly 22 is further included, and the air cooling assembly 22 is fixedly connected with the low vacuum side shell.

A method of installing a dry pump comprising the steps of:

1) The main shaft 1 and the movable rotor 2 are assembled in a hot-charging mode, glue is coated at the glue scraping groove, the main shaft 1 and the composite impeller 13 are assembled in a hot-charging mode, locking is carried out through the locking piece 14, and the completed movable rotor 2 is dynamically balanced, so that the design requirement is met;

2) The low vacuum side shell 3 and the inner sleeve 11 are subjected to hot fitting, the sealing ring of the low vacuum side shell 3 is assembled before hot fitting, the stator and rotor 5 and the low vacuum side shell 3 are assembled in a press fitting mode, the front end of the stator and rotor 5 is adhered with a heat-conducting silica gel pad, the stator and rotor 5 after the assembly is fixed through a jackscrew, finally, the low vacuum side bearing seat 8 and the low vacuum side shell 3 are assembled, the low vacuum side shell 3 and the low vacuum side bearing cover 10 are connected through screws, and the joint is provided with a fluororubber O ring for sealing;

3) The bearing 6 and the low vacuum side shaft sleeve 4 are subjected to hot mounting, and then the bearing 6 and the main shaft 1 are assembled in a press mounting mode, wherein an O-shaped ring is arranged on the low vacuum side shaft sleeve 4 to play a damping role, the bearing 6 and the main shaft 1 are fixed through a locking block 7 and an M6 screw after being mounted, and finally a low vacuum side bearing gland 10 is mounted;

4) The overturning tool is used for erecting the parts assembled in the earlier stage, then stationary blades are installed step by step, and the measurement of relevant sizes is carried out when no stage is installed;

5) Assembling the high-vacuum side shell 16 and assembled parts, wherein the high-vacuum side shell 16 is axially positioned through the static impeller 15, radially positioned through the outer ring of the low-vacuum side shell 3 and finally locked through M5 screws;

6) Assembling the high-vacuum side bearing seat 17 and the high-vacuum side shell 16, realizing locking through screws, and sealing the contact surface through an O-ring;

7) The bearing 6 and the high vacuum side shaft sleeve 19 are subjected to hot mounting, and then the bearing is subjected to press mounting with the main shaft 1, wherein an O-ring mainly plays a damping role on the contact surface of the high vacuum side bearing seat 17 and the high vacuum side bearing gland 18;

8) The elastic piece 9 is placed in a cavity of the bearing 6, and is pressed on the outer ring of the elastic piece 9 through the high vacuum side bearing gland 18, and finally is fixed through screws;

9) Mounting accessories such as a first connection flange 20, an airtight aviation plug 21, a purging component, a gas filtering component, a silencer, a plug, a gas release valve and other external accessories, and mounting an external sheet metal part and an electronic control module of an air cooling component 22.

When the main shaft 1 rotates, the movable impeller 30 rotates to suck the gas entering from the air inlet 29, so that the gas sequentially passes through the turbine stage, the first traction section 26, the second gap 25, the second traction section 27, the first gap 28, the screw section 23 and finally is discharged to the air outlet 12 through the screw section 23. In the initial stage, momentum is transferred to gas molecules at the gas inlet 29 through the high-speed rotation of the turbine stage, so that the gas molecules move on the surfaces of blades of the turbine stage to generate directional flow towards the first traction section 26, and the purpose of air extraction is achieved; after entering the first traction section 26, the gas is in a viscous flow state due to the action of the second spiral groove, and is pressurized step by the combined action of the first traction section 26, the second traction section 27 and the screw section 23 until reaching the exhaust port 12 and being discharged.

As an alternative embodiment, the helix angle of the second helical groove is equal to the helix angle of the third helical groove.

As an alternative embodiment, the helix angle, the helix depth and the helix width of the second helical groove may also be equal to the third helical groove.

It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present invention.

Claims (10)

1. A dry pump, comprising:

a housing assembly provided with an internal chamber, the side wall of the housing assembly being provided with an air inlet (29), the housing assembly comprising a low vacuum side housing (3);

a compound impeller (13) provided in the internal chamber, the compound impeller (13) being provided with a turbine stage for sucking in gas entering from an inlet (29);

the main shaft (1) is arranged in the inner cavity, the main shaft (1) comprises a connecting section and a screw rod section (23), the composite impeller (13) is sleeved on the peripheral wall of the connecting section, a first spiral groove (24) is formed in the peripheral wall of the screw rod section (23), the low vacuum side shell (3) is sleeved on the periphery of the spiral section, an exhaust port (12) is formed in the side wall of the low vacuum side shell (3) corresponding to the first spiral groove (24), the main shaft (1) rotates under the working state, the turbine stage firstly sucks gas, the gas is compressed in the first spiral groove (24), and the gas is discharged out of the exhaust port (12) along with the rotation of the first spiral groove (24).

2. Dry pump according to claim 1, characterized in that the housing assembly further comprises a high vacuum side housing (16) and an inner sleeve (11), the high vacuum side housing (16) is sleeved on the outer circumference of the inner sleeve (11), the high vacuum side housing (16) is connected with the low vacuum side housing (3), the low vacuum side housing (3) is fixedly connected with the inner sleeve (11), the composite impeller (13) further comprises a first traction section (26), the inner sleeve (11) is sleeved on the outer circumference of the first traction section (26), and the outer circumference of the first traction section (26) is provided with a second spiral groove.

3. Dry pump according to claim 2, characterized in that the low vacuum side housing (3) is provided with a second pull section (27), the outer circumferential surface of the second pull section (27) is provided with a third spiral groove, and the first pull section (26) is sleeved on the outer circumference of the second pull section (27).

4. A dry pump as claimed in claim 3, characterized in that a first gap (28) is left between the end face of the first pull-out section (26) facing away from the turbine stage and the end face of the low-vacuum side housing (3), and a second gap (25) is left between the end face of the second pull-out section (27) of the low-vacuum side housing (3) and the inner end face of the first pull-out section (26).

5. A dry pump as claimed in claim 3 wherein the helix angle of the second helical groove is greater than the helix angle of the third helical groove, the helix groove depth of the second helical groove is equal to the helix groove depth of the third helical groove, and the helix groove width of the second helical groove is greater than the helix groove width of the third helical groove; the helix angle of the third helix groove is larger than that of the first helix groove (24), the helix groove depth of the third helix groove is equal to that of the first helix groove (24), and the helix groove width of the third helix groove is larger than that of the first helix groove (24).

6. The dry pump of claim 5 wherein the helix angle of the second helical groove is greater than or equal to the helix angle of the third helical groove.

7. The dry pump of claim 4, wherein the housing assembly further comprises a high vacuum side bearing housing (17) and a low vacuum side bearing gland (10), the high vacuum side bearing housing (17) and the low vacuum side bearing gland (10) being provided separately at both ends of the main shaft (1).

8. The dry pump according to claim 7, further comprising an airtight aviation plug (21) and a power driving part, wherein the power driving part is arranged between the low vacuum side shell (3) and the main shaft (1), the power driving part comprises a stator rotor (5) and a movable rotor (2), the movable rotor (2) is sleeved on the outer peripheral surface of the main shaft (1), the stator rotor (5) is fixedly connected with the low vacuum side shell (3), and the airtight aviation plug (21) is connected with a power driving part line.

9. The dry pump of claim 8, further comprising an air cooling assembly (22), the air cooling assembly (22) being fixedly connected to the low vacuum side bearing gland (10).

10. The dry pump of claim 1, wherein the turbine stage comprises a movable impeller (30) and a stationary impeller (15), the movable impeller (30) and stationary impeller (15) being sequentially spaced apart.