CN111120324A - Screw vacuum pump with multiple suction cavities and exhaust ports - Google Patents

Screw vacuum pump with multiple suction cavities and exhaust ports Download PDF

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Publication number
CN111120324A
CN111120324A CN201911396874.2A CN201911396874A CN111120324A CN 111120324 A CN111120324 A CN 111120324A CN 201911396874 A CN201911396874 A CN 201911396874A CN 111120324 A CN111120324 A CN 111120324A
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China
Prior art keywords
suction
vacuum pump
cavity
screw vacuum
exhaust
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CN201911396874.2A
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Chinese (zh)
Inventor
李军
徐东旭
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Zhejiang Cisco Vacuum Technology Co Ltd
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Zhejiang Cisco Vacuum Technology Co Ltd
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Priority to CN201911396874.2A priority Critical patent/CN111120324A/en
Publication of CN111120324A publication Critical patent/CN111120324A/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C25/00—Adaptations of pumps for special use of pumps for elastic fluids
    • F04C25/02—Adaptations of pumps for special use of pumps for elastic fluids for producing high vacuum
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C18/00—Rotary-piston pumps specially adapted for elastic fluids
    • F04C18/08—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing
    • F04C18/12—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type
    • F04C18/14—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons
    • F04C18/16—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons with helical teeth, e.g. chevron-shaped, screw type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
    • F04C29/04—Heating; Cooling; Heat insulation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
    • F04C29/12—Arrangements for admission or discharge of the working fluid, e.g. constructional features of the inlet or outlet
    • F04C29/124—Arrangements for admission or discharge of the working fluid, e.g. constructional features of the inlet or outlet with inlet and outlet valves specially adapted for rotary or oscillating piston pumps
    • F04C29/126—Arrangements for admission or discharge of the working fluid, e.g. constructional features of the inlet or outlet with inlet and outlet valves specially adapted for rotary or oscillating piston pumps of the non-return type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2240/00—Components
    • F04C2240/20—Rotors

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Applications Or Details Of Rotary Compressors (AREA)

Abstract

The invention discloses a screw vacuum pump with a plurality of suction cavities and exhaust ports, which belongs to the technical field of screw vacuum pumps and is used for solving the following technical problems: the screw vacuum pump has the maximum air suction capacity in a low vacuum range through the design of the multi-section rotor, the plurality of air suction cavities and the air exhaust port, has the specific power value far lower than that of the screw vacuum pump in the prior art, and is more energy-saving. A screw vacuum pump with multiple suction cavities and exhaust ports features that the cavity of screw vacuum pump is divided into multiple suction cavities and exhaust ports, the exhaust position at the end of engaged rotor in each suction cavity is communicated with the suction inlet end of engaged rotor in the next suction cavity via a hollow space, and an exhaust port is arranged in the space for exhausting air. The invention realizes the approximately constant air exhaust performance in the full pressure range and has wider applicable working pressure range.

Description

Screw vacuum pump with multiple suction cavities and exhaust ports
Technical Field
The invention belongs to the technical field of screw vacuum pumps, and particularly relates to a screw vacuum pump with a plurality of suction cavities and exhaust ports.
Background
The known screw vacuum pump works according to the following principle: the screw rotors engaged with each other exhibit a volume expansion process, i.e., a suction process, on the suction end face of the rotors by rotation, and a lead gas volume is contained between the engaged rotors and the inner wall of the pump chamber at every rotation, and a meshed volume reduction process, i.e., a discharge process, is exhibited on the discharge end rotor face as the gas moves in the spiral angle direction with rotation until discharged.
In the prior known disclosure, the spiral line of the rotor of the screw vacuum pump is continuously spiral in the axial direction from the suction port to the exhaust port, that is, when the starting point of the spiral line is regarded as the suction end, the terminal point of the lead angle of the spiral line is regarded as the exhaust end. As described above, in the two screw rotors engaged with each other, the volume change phenomenon that the volume expansion and then the suction is generated is only provided at the starting point of the spiral line, and in the starting point and the end point of the engaged spiral line, the volume between each lead and the inner wall of the pump cavity is only the process of gas delivery as the rotors rotate, and until the gas moves to the end point, namely the exhaust end, along with the rising angle of the spiral line, the process of gas delivery of one volume is completed.
In this suction and exhaust process, when the lead on the spiral line changes in the axial direction from the suction port to the exhaust port, which is known as a variable pitch screw vacuum pump, in the prior known disclosure, the change in the lead of the variable pitch is divided into various types, but in general, the trend of the change in the lead in the direction from the suction port to the exhaust port is reduced.
It is known that, in a variable pitch screw vacuum pump, when a volume included in a leading stroke after meshing is rotated to a following stroke in a lead stroke adjacent to the front and back of a spiral line by rotation, if a ratio of the front and back volumes is larger than a ratio of a pressure in the following stroke volume to a pressure in the leading stroke volume, an excessive compression, abbreviated as an over-compression, is generated. In the prior art, the overcompression of the variable pitch screw vacuum pump is only present in the space formed between the engaged rotor and the pump cavity in the suction chamber, and when the screw vacuum pump is operated in a range from the initial vacuum pumping of the atmospheric pressure to a certain low pressure range, the overcompression phenomenon is generated in the space formed by the other lead between the lead at the suction end and the last lead at the discharge end in the suction chamber and the inner wall of the pump cavity if the ratio of the discharge pressure to the suction pressure of the screw vacuum pump is smaller than the ratio of the volume contained in one rotation between the lead at the suction end engaged in the suction chamber and the inner wall of the pump cavity and the volume contained in one rotation between the last lead at the discharge end engaged in the suction chamber and the inner wall of the pump cavity.
As is known, in a screw vacuum pump, the size of the lead of the suction end is decisive for the influence of the maximum pumping speed, and in the case of a variable pitch screw vacuum pump, in order to have a greater pumping speed and a lower specific power in the low-pressure operating region, in the prior known prior art, the ratio of the volume of the suction end after large lead internal meshing to the geometric volume of the exhaust end after lead internal meshing is generally designed to be greater than 2, and this design, based on the above-mentioned over-compression principle, leads to the following problems:
1. in any vacuum equipment, the suction pressure is gradually reduced until the required vacuum pressure is reached, especially for a screw vacuum pump capable of directly discharging to atmosphere, in this process, the exhaust pressure is usually a certain value in most cases, calculated according to the exhaust pressure being the standard atmospheric pressure of 101.325kpa.a, ideally, only when the suction pressure is less than 50kpa.a (101.325/2), the design that the ratio of the volume after the large lead internal engagement in the suction section of the screw vacuum pump and the geometric volume after the lead internal engagement at the tail end of the exhaust is designed to be more than 2 is met, however, the difference between the pressure at the exhaust port and the suction port is very small in the initial stage of the vacuum pumping, and in the stage of the suction pressure from one atmospheric pressure to 50kpa.a, because the compression ratio is less than 2, obviously, the geometrical volume after the inner meshing of the lead at the exhaust end needs to be larger to control the gas exhaust pressure to be 101.325kpa.a, but in the case that the compression ratio is fixed to be 2 or more, the problem of over-compression caused by the excessive reduction of the volume between the inner meshed lead and the inner wall of the pump cavity in the process of conveying the gas in the pump cavity is caused, so that the screw vacuum pump needs to consume more energy to perform useless gas compression.
2. The screw vacuum pump as described above is limited to the design of the fixed compression ratio of the screw rotor, and in the prior art, when the screw vacuum pump is operated in the process of pumping vacuum at the suction port pressure from one atmosphere to 50kpa, due to the excessive compression, one characteristic shown on the pumping performance curve is that the pumping speed is minimum but the consumed power is maximum at the initial stage of pumping vacuum, then the pumping speed is gradually increased along with the reduction of the suction port pressure, and the consumed power is gradually reduced until the pumping speed reaches the maximum value in a certain suction pressure interval, and the power consumption reaches the minimum value, which presents an opposite characteristic compared with the pumping performance curve of most volume-variable vacuum devices, which results in that in practical application, compared with other types of vacuum devices with the same nominal maximum pumping speed, screw vacuum pumps are more time consuming to evacuate to a certain low pressure from the initial stage.
3. The compression ratio design of the screw vacuum pump of the prior art and the characteristic curve of the air-extracting performance exhibited by the compression ratio design are great defects in some practical process applications, for example, in the evaporation process of the low-boiling-point solvent, because a large amount of solvent needs to be evaporated in the early stage, the saturated vapor pressure of the low-boiling-point solvent is limited to be high, and the screw vacuum pump needs to be operated under the condition of low vacuum for a long time, obviously, the screw vacuum pump of the design is very uneconomical and even cannot be suitable for the working conditions.
In order to solve the above problems, in the prior known disclosures, the following technical solutions are adopted by those skilled in the art to improve the defects:
1. the patent application with publication (publication) No. CN102395793A provides a solution, which opens a plurality of overpressure outlets on the side wall of the pump body that defines the suction chamber, and installs a spherical overpressure valve at the overpressure outlets, so that when the gas pressure in the suction chamber in the pump is compressed to a sufficient level, the spherical overpressure valve is pushed open and flows out, thereby avoiding the occurrence of overpressure. However, the patent application does not clearly specify the opening position of the overpressure outlet, which deteriorates the operability in guiding the actual design, and the technical method of the overpressure opening is limited by the speed of the lead screw angular rotation and the length of the single lead, the time for which each overpressure opening is connected to the overpressure outlet channel is too short, and the velocity of the gas passing through the overpressure openings must be much higher than the speed of the lead screw change in the lead screw angular rotation according to bernoulli fluid mechanics equation, otherwise, the overpressure gas is not discharged through the overpressure opening channel until it is shielded by the tooth crest face, and it is known that the technical method requires a larger pressure difference or a larger overpressure opening to discharge the overpressure gas in a short time, while the larger overpressure opening cannot be realized in the technical method, and the larger pressure difference aggravates the overpressure of the screw vacuum pump, the use of more rows of overpressure openings increases the amount of backflow, making these overpressure openings worthless — one of the main reasons that this technique has not been practically used to date; the patent application adopts the scheme that the spherical overpressure valve is directly installed at the overpressure outlet and is derived from exhaust valve structures of various oil seal type vacuum pumps, the spherical overpressure valve is repeatedly reset by means of self weight, but the fault that the overpressure valve is not tightly closed easily occurs under the oil-free condition, once the overpressure valve is not tightly closed, backflow leakage to the interior of the pump through the overpressure outlet in the subsequent air suction process is inevitably caused, and therefore the pumping speed and the ultimate vacuum degree of the pump are reduced; secondly, the spherical overpressure valve is accompanied by great noise in the opening working stage, and can bring adverse effects to field workers; thirdly, the multiple sections of overpressure outlets of the patent application are communicated with the inner cavity of the pump through the same independent connecting channel, and the faults of mutual air leakage caused by the simultaneous opening of the spherical overpressure valves easily occur among the holes of the front section and the rear section, so that the pumped body in the pump generates circular flow through the connecting channel; in addition, the connecting channel of the overpressure outlet of the patent application extends along the length direction of the whole pump body, the arrangement of a pump body cold water jacket is necessarily influenced, the cold water jacket is not well arranged, the cooling effect is inevitably reduced, the temperature of the pump body is inevitably increased, the overpressure openings are uniformly arranged on a path route corresponding to the tooth pitch of the screw rotor and are distributed along the longitudinal direction of a spiral line of the screw rotor, and when the screw rotor rotates for one circle, the tooth tops of the overpressure openings are always shielded, so that the opening of the overpressure valve is rapidly opened and closed in a pulse mode, and any valve is extremely easily damaged. In addition, according to the working principle of the screw vacuum pump, each overpressure opening can cause the gas backflow in the pump cavity to be intensified, so that the volumetric efficiency of the screw vacuum pump designed by the technical method is reduced and the ultimate pressure is increased.
2. The patent application with publication (announcement) No. CN109139471A provides another solution, in which, under the condition that the compression ratio of the screw vacuum pump is greater than 3, a set of pressure relief holes are formed in the pump body in a spiral distribution according to the lead angle of the screw rotor helix and the rotation direction of the screw rotor, and each screw rotor is correspondingly provided with a set of pressure relief holes, and a pressure relief cavity is arranged outside the pump body, so that the inner cavity of the pump body is communicated with the pressure relief cavity through the pressure relief holes, and then the pressure in the pressure relief holes is controlled by an automatically controlled vacuum stop valve or a manually controlled vacuum stop valve through arranging a channel outside the pressure relief cavity and communicating with the atmosphere, when the gas pressure at the pressure relief holes is higher than the exhaust pressure, the automatically controlled vacuum stop valve or the manually controlled vacuum stop valve is opened to discharge the compressed gas from the exhaust port of the pump body until the gas pressure at the pressure relief holes is no longer higher, the pressure relief valve is then closed. However, the disadvantage of this design is that the pressure relief holes are all arranged on the path route corresponding to the pitch of the screw rotor, and are distributed along the lead angle of the spiral line of the screw rotor and the rotation direction of the screw rotor, so that the pressure relief holes are always shielded by the tooth top surface when the screw rotor rotates for one circle, and the pressure in the communicated pressure relief cavity is suddenly high and suddenly low, and the pressure is difficult to be accurately measured when a sensor is used for detection; furthermore, the manner in which the manually controlled vacuum stop valve opens and closes to achieve pressure relief is impractical for those enterprises that use vacuum equipment in large quantities. In addition, according to the working principle of the screw vacuum pump, each overpressure opening causes the gas backflow in the pump cavity to be intensified, which causes the volumetric efficiency of the screw vacuum pump designed by the technical method to be reduced and the ultimate pressure to be increased, and the technical method of the overpressure opening is limited by the length of the single lead in the speed of the lead in the lead helix angle rotation, the time for connecting each overpressure opening and the overpressure outlet channel is too short, according to the bernoulli fluid mechanics equation, the gas flow rate of the overpressure gas passing through the overpressure openings must be much higher than the speed of the lead transformation in the lead helix angle rotation, otherwise, the overpressure gas is not discharged through the overpressure opening channel until being shielded by the tooth crest face, therefore, the technical method needs a larger pressure difference or a larger overpressure opening to discharge the overpressure gas in a short time, and the larger overpressure opening cannot be realized by the technical method, the greater pressure difference aggravates the over-compression of the screw vacuum pump, and the more rows of over-pressure openings increase the amount of backflow, so that the over-pressure openings are worthless.
3. In the prior art, a solution that a frequency converter is used for starting a screw vacuum pump is adopted in actual process application, and the rotating speed of the screw vacuum pump is reduced to a range that the output power of a motor can bear by reducing the frequency until the rotating speed is recovered to a normal rotating speed after the difference between the exhaust pressure and the suction inlet pressure is gradually increased. Obviously, this further greatly reduces the pumping rate of the initial pumping phase and increases the necessary electrical control system and unnecessary costs due to the need for a frequency converter.
Disclosure of Invention
The invention discloses a screw vacuum pump with a plurality of suction cavities and exhaust ports, aiming at the problems in the prior art, and the screw vacuum pump is used for solving the following technical problems:
the invention aims to provide a screw vacuum pump with a plurality of suction cavities and exhaust ports, which comprises a pump body and rotors meshed with each other, wherein the full-pressure working interval of the screw vacuum pump has approximately constant air exhaust performance through the design of a plurality of sections of rotors, a plurality of suction cavities and exhaust ports, and particularly has the maximum air exhaust capacity under low vacuum, and the air exhaust speed of the screw vacuum pump is gradually reduced only when the suction pressure is reduced to a certain interval and is limited by pressure difference, gas density and return flow.
In order to achieve the purpose, the invention is realized by the following technical scheme:
those skilled in the art should understand that: the gas contained in the volume between each lead of the meshed rotors and the inner wall of the pump cavity moves along with the rotation of the rotors and the ascending angle of the spiral line, in the process, the Bernoulli fluid mechanics equation shows that the gas generates dynamic pressure characteristic, the gas with dynamic pressure generates extension resistance in the delivered volume due to speed, dynamic viscosity and friction of the gas, the pressure gradient exists in each adjacent lead, the trend of the pressure gradient is necessarily gradually increased when seen from the direction from the suction port to the exhaust port, when the heat transfer factor between the delivered gas and the pump body is not considered, the gas volume is obviously gradually reduced when seen in an isothermal process, the pressure ratio of the gas contained in the adjacent leads is equal to the inverse proportion of the volume, and at the moment, if the change of the leads accords with the change of the gas volume, the screw vacuum pump rotor is limited by the characteristics of the rotor, the compression ratio of the rotor cannot be synchronized with the change, only a specific compression ratio design can be carried out aiming at a certain actual working pressure interval, the overlarge compression ratio design can generate over compression when the rotor is used for a low vacuum process condition, the energy consumption is higher, and the small compression ratio design cannot be economical when the rotor is used for a process condition with a higher vacuum requirement.
Thus, it will be further understood by those skilled in the art that, in accordance with the principles of operation of a screw vacuum pump, the suction process is derived from the volume expansion of the intermeshing rotor faces as they rotate, the pressure gradient existing in each adjacent lead results in a front-to-back pressure differential, the magnitude of which determines the rate at which gas in the lead will flow back through the gap into the previous lead, and so on, it will be further understood by those skilled in the art that, based on the principles of fluid mechanics equations and conservation of mass, the pressure differential achieved before and after each lead has a maximum value, and that the pressure differential is nearly constant, such that the mass of gas flowing back due to the front-to-back pressure differential in the lead has the same volume as the volume of gas contained in the intermeshing lead before it flows back into the lead, and conversely, when the pressure differential is reduced, the return flow rate decreases and the efficiency of the lead internal geometric volume utilization increases after meshing, and thus, it will be understood by those skilled in the art that the lower the pressure at the suction port due to the presence of the front-to-back pressure difference, the smaller the mass of the gas sucked by the suction port, and the greater the compression ratio due to the front-to-back pressure difference.
In this context, it will be understood by those skilled in the art that, at the exhaust outlet from the engaged rotor in the suction chamber to the end of the last exhaust lead of the screw vacuum pump, a cavity space is constructed for exhausting gas, and a pump chamber is extended in the axial direction of the rotor, or a plurality of pump bodies are axially combined into a pump cavity, so that the pump cavity is divided into a plurality of suction cavities and exhaust ports at intervals through the hollow cavity, in the same pump cavity, one or more sections of meshed rotors and one or more matched suction cavities are reconstructed along the coaxial axial direction of the rotor shaft, so that the rotors in the suction cavities at the suction inlet end of the screw vacuum pump adopt large lead, the rotors in the rear suction cavities adopt small lead, and the exhaust part at the tail end of the meshed rotors in each section of suction cavity is communicated with the suction inlet end of the meshed rotors in the rear section of suction cavity at intervals through cavities.
The volume of the suction end surface of the screw rotor meshed with the suction cavity at the previous section contained in each rotation is VaThe geometric volume utilization efficiency by the back flow due to the front-back pressure difference was ηaThe suction pressure is set to PaThe suction temperature is set to TaThe volume of the screw rotor engaged in the suction cavity at the later section is set to be V in every rotation of the suction end surface of the screw rotorbThe geometric volume utilization efficiency by the back flow due to the front-back pressure difference was ηbThe suction pressure is set to PbThe suction temperature is set to TbIn general, V must be seta×ηa×Pa/Ta＝Vb×ηb×Pb/TbHowever, in order to make the screw vacuum pump have larger pumping speed performance under low vacuum, V is useda/VbAt most 3, in the initial evacuation phase, Va×ηa×Pa/Ta≈3×Vb×ηb×Pb/TbAn air outlet is established with the outside in a cavity space between an air outlet end of a rotor meshed in a front section of suction cavity and an air inlet end of a rotor meshed in a rear section of suction cavity in a pump cavity, a valve with non-return function is arranged on an air outlet pipeline, so that air exhausted from the air outlet end of the rotor meshed in the front section of suction cavity is exhausted to the outside of a pump body through the air outlet and the valve with non-return function, and the air is prevented from returning to the cavity space from the outside, the pressure difference between the air outlet and the air inlet of the screw vacuum pump is gradually increased, according to the principle that the pressure difference is increased and the backflow is increased, until the quality of the air sucked by the rotors meshed in the suction cavity at the air inlet end of the screw vacuum pump is equal to the quality of the air suckeda×ηa×Pa/Ta＝Vb×ηb×Pb/TbThe non-return valve is closed to prevent the external air from flowing back to the inlet of the suction cavity in the next section through the air outlet in the interval. Thus, according to the invention, the high pumping speed in the full-pressure working interval of the screw vacuum pump can be ideally realized under the condition of not increasing the power consumption, and the pumping speed is limited by the pressure difference, the gas density and the return flow rate until the suction pressure is reduced to a certain interval, so that the pumping speed is gradually reduced.
Based on the above, it should be further understood by those skilled in the art that by installing a heat exchange device in the cavity space between the exhaust end of the engaged rotor in the previous suction cavity and the suction end of the engaged rotor in the next suction cavity of the screw vacuum pump of the present invention, or by dividing the cavity space into an exhaust port and an intake port by upper and lower partition plates (or called as guide plates), the exhaust port is connected to the inlet of the heat exchange device designed externally or integrally on the pump body, and the intake port is connected to the outlet of the heat exchange device designed externally or integrally on the pump body, the compression heat of the exhaust gas at the end of the engaged rotor in the previous suction cavity of the screw vacuum pump can be reduced to a certain extent by the heat exchange device, so that the exhaust volume is further reduced, and because of the temperature reduction, the temperature of the gas sucked by the engaged rotor in the next suction cavity and the gas temperature reduction at the exhaust port can be achieved These temperature reductions will allow the design of smaller clearances and more uniform temperature rise of the screw rotors, thereby further improving the efficiency of the screw vacuum pump of the present invention when operating.
As mentioned above, the number of the rotor guide path engaged in each suction chamber in the pump chamber is at least more than or equal to 1 lead, preferably, the number of the rotor guide path engaged in each section in each suction chamber of the screw vacuum pump is 1-3 leads, and the pump chamber is composed of 2-3 suction chambers.
As already mentioned, the preferred design of the nonreturn valve is preferably of the lifting type.
As described above, it is preferable that the exhaust port established with the outside in the cavity space is circular.
As described above, preferably, the state before the volume starts to be compressed after the lead meshing at the exhaust end face of the meshed rotors in the previous stage of the suction chamber in the pump chamber is meshed corresponds to the state after the lead meshing at the suction end face of the next stage of the suction chamber is meshed, that is, the exhaust end of the meshed rotors in the previous stage of the suction chamber starts to enter the exhaust stage and the suction end face of the meshed rotors in the next stage of the suction chamber starts to enter the suction stage synchronously.
In the context of the present invention meshing is used to express a very close relationship between the rotors on two shafts, where the rotor segment spacing, shape of the segments on one shaft is determined by the rotor segment spacing and shape of the segments on the other shaft, resulting in good sealing properties between the two rotors.
Compared with the prior art, the invention has the following advantages:
1. compared with the screw vacuum pump in the prior art, the screw vacuum pump with the plurality of suction cavities and the exhaust port in the invention has the advantages that the air suction speed can reach the maximum value in the initial vacuum-pumping stage under the atmospheric pressure, and the power consumption is approximately at the lowest point;
2. in the range of a full-pressure air-pumping performance curve, the air-pumping speed is approximately a constant value, and compared with the prior art that the screw vacuum pump can obtain the optimal air-pumping performance only under the pressure lower than 10kPa.a, the screw vacuum pump with a plurality of suction cavities and exhaust ports has the optimal air-pumping performance under the full-pressure working condition;
3. thanks to the design of a plurality of suction cavities and exhaust ports, the temperature rise of the screw rotor due to compression work can be kept at a lower degree through the interstage cooling function, and meanwhile, the temperature distribution of the screw rotor is more balanced, which lays a foundation for designing and manufacturing a larger screw vacuum pump far beyond the prior specification technology;
4. due to the design of a plurality of suction cavities and exhaust ports, the specific power value of the screw vacuum pump in the low vacuum range is far lower than that of the prior art, and the screw vacuum pump is more energy-saving.
Drawings
FIG. 1 is an isometric view of the configuration of a screw vacuum pump of the present invention having multiple suction and exhaust ports.
Fig. 2 is a schematic axial sectional view of fig. 1.
Fig. 3 is a top view of fig. 1.
Fig. 4 is a side view of fig. 1.
Fig. 5 is a cross-sectional view of the radial cross-section of fig. 1.
Fig. 6 is an isometric view of an external configuration of a screw vacuum pump having multiple suction chambers and exhaust ports incorporating a heat exchange device according to the present invention.
Fig. 7 is an axial sectional structural view of fig. 6.
Fig. 8 is a side view of fig. 6.
Fig. 9 is a cross-sectional view of the radial cross-section of fig. 6.
Fig. 10 is a schematic view of the rotor structure of the present invention.
Fig. 11 is a top view of fig. 10.
Detailed Description
While the preferred features of the present invention will be described in detail below by way of example with reference to the accompanying drawings, it is to be understood that the following description is of some embodiments of the invention and that other embodiments will become apparent to those skilled in the art from consideration of the specification and practice of the embodiments disclosed herein without departing from the inventive concepts.
Example one
As shown in fig. 1 to 5, the screw vacuum pump having a plurality of suction chambers and exhaust ports of the present invention includes a pump body 1, a suction port 10, an exhaust port 30, a check valve 31, an exhaust passage 32, and an exhaust port 50.
The meshed rotors are arranged in the pump cavity in the pump body 1, each complete rotor is composed of a suction end screw rotor section 101, a discharge end screw rotor section 102 and a rotor shaft 111, a suction cavity 11 and a suction cavity 21 are respectively formed between the meshed rotors and the pump cavity of each section, a cavity interval 40 is reserved between the rotors of the front section and the rear section, sucked gas enters the suction cavity 11 through a suction port 10, moves to the discharge end of the screw rotor section 101 along with the rotation of the lead angle of the screw rotor and then is discharged into the cavity interval 40, under the condition that the ratio of the pressure at a gas outlet 50 to the pressure at the gas inlet 10 is smaller than 3, a part of gas moves to a gas outlet 50 along with the rotation of the lead angle of the screw rotor section 102 through the suction cavity interval 21 of the rear section, and a part of gas is discharged to the outside from the gas outlet 30 through a gas discharge channel 32 and a check valve 31 of the.
Example two
As shown in fig. 6 to 11, the screw vacuum pump having a plurality of suction chambers and exhaust ports of the present invention includes a pump body 1, a suction port 10, an exhaust port 30, a check valve 31, an exhaust passage 32, and an exhaust port 50.
The meshed rotors are arranged in the pump cavity in the pump body 1, each complete rotor is composed of a suction end screw rotor 101 section, a discharge end screw rotor 102 section and a rotor shaft 111, a suction cavity 11 and a suction cavity 21 are respectively formed between the meshed rotors and pump cavities of the sections, a cavity interval 40 is left between the front and rear rotors, in the cavity interval 40, a heat exchange device 41 is divided into two parts through an upper partition plate 43 and a lower partition plate 44 respectively, the two parts are communicated through a channel 42 on the partition plate, sucked gas enters the suction cavity 11 through a suction inlet 10, moves to a discharge end of the screw rotor 101 section along with the rotation of the lead angle of the screw rotor, then is discharged into the cavity interval 40, under the condition that the ratio of the pressure at a gas outlet 50 to the pressure at the gas inlet 10 is less than 3, a part of the gas enters the suction cavity 21 at the next section through the heat exchange device 41 and the partition plate channel 42, and moves to a gas outlet 50 along with the rotation of the lead angle, a part of the gas is discharged from the gas discharge port 30 to the outside through the cavity space 40 and the external gas discharge passage 32 and the check valve 31.
As shown in fig. 10 and 11, each complete rotor is composed of a rotor segment 101, a rotor segment 102 and a rotor shaft 111 in the axial direction, and a space is left between the front and rear rotor segments.

Claims (6)

1. A screw vacuum pump with multiple suction chambers and exhaust ports comprises a pump body and rotors meshed with each other, wherein the rotors are positioned in an inner cavity of the pump body, and is characterized in that a cavity interval is constructed from the meshed rotors in the suction chambers of the screw vacuum pump to an exhaust outlet at the tail end of a final exhaust lead for exhausting gas, a pump cavity extends upwards along the axial direction of the rotors, or the multiple pump bodies are axially combined into a pump cavity, the pump cavity is divided into multiple suction chambers and exhaust ports by the cavity interval, the rotors in the suction chambers at the suction inlet ends of the screw vacuum pump adopt large leads, the rotors in the rear suction chambers adopt small leads, and the exhaust part at the tail ends of the meshed rotors in each suction chamber is communicated with the suction inlet ends of the meshed rotors in the suction chambers at the later stages by the cavity interval;
the method comprises the steps of establishing an exhaust port with the outside in a space interval in front of an exhaust part at the tail end of a rotor meshed in a suction cavity at the suction inlet end of the screw vacuum pump and an exhaust inlet end of a rotor meshed in a rear section suction cavity, exhausting gas exhausted from the exhaust tail end of the rotor meshed in the suction cavity at the suction inlet end of the screw vacuum pump, and then installing a valve with non-return effect on a pipeline communicated with the atmosphere outside the exhaust port at the space interval position to prevent the external gas from flowing back.
2. A screw vacuum pump having a plurality of suction chambers and discharge ports according to claim 1, wherein the screw vacuum pump is characterized in that the volume per revolution of the lead at the suction end face of the rotor engaged in the suction chamber at the suction inlet port of the screw vacuum pump is VaThe volume contained by the lead at the position of the air suction end face of the rotor meshed in the later section of the air suction cavity in each rotation is set as VbLet V bea/Vb≤3。
3. A screw vacuum pump having a plurality of suction chambers and discharge ports according to claim 2, wherein a discharge port is established with the outside in the cavity space between the discharge end of the rotor engaged in the front stage suction chamber and the suction end of the rotor engaged in the rear stage suction chamber in the pump chamber, and a check valve is installed in the discharge port pipe so that the gas discharged from the discharge end of the rotor engaged in the front stage suction chamber is discharged to the outside of the pump body through the passage and the check valve and the gas is prevented from returning from the outside to the cavity space.
4. A screw vacuum pump according to claim 3 having a plurality of suction chambers and discharge ports, wherein the state before the volume starts to be compressed after the lead meshing at the discharge end faces of the rotors meshing in the previous suction chamber in the pump chamber is in correspondence with the state after the volume starts to be expanded after the lead meshing at the suction end faces of the rotors meshing in the subsequent suction chamber, i.e. the discharge ends of the rotors meshing in the previous suction chamber start to enter the discharge stage and the suction end faces of the rotors meshing in the subsequent suction chamber start to enter the suction stage simultaneously.
5. A screw vacuum pump with multiple suction chambers and exhaust ports according to claim 4, wherein the number of rotor leads engaged in each suction chamber in the pump chamber is at least 1 lead, and the pump chamber is composed of 2 to 3 suction chambers.
6. A screw vacuum pump with multiple suction chambers and exhaust ports according to claim 5, wherein the heat exchanger is disposed in the cavity space between the exhaust end of the engaged rotor in the front suction chamber and the suction end of the engaged rotor in the rear suction chamber, or the cavity space is divided into an exhaust port and an intake port by upper and lower partition plates (or called guide plates), the exhaust port is connected to the inlet of the heat exchanger externally or integrally formed on the pump body, and the intake port is connected to the outlet of the heat exchanger externally or integrally formed on the pump body.
CN201911396874.2A 2019-12-30 2019-12-30 Screw vacuum pump with multiple suction cavities and exhaust ports Pending CN111120324A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114688021A (en) * 2020-12-25 2022-07-01 宁波市润桥工业设计有限公司 Screw pump with controllable filling and discharging

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3209990A (en) * 1962-01-18 1965-10-05 Atlas Copco Ab Two stage screw rotor machines
JPS6336086A (en) * 1986-07-30 1988-02-16 Taiko Kikai Kogyo Kk Multi-stage screw type vacuum pump
JPH02245493A (en) * 1989-03-20 1990-10-01 Hitachi Ltd Screw vacuum pump
CN106194734A (en) * 2014-09-05 2016-12-07 大卫·金 Twin-stage dry vacuum pump
CN106704179A (en) * 2017-03-09 2017-05-24 上海格什特螺杆科技有限公司 Novel direct-connected dual-screw compressor
CN109642574A (en) * 2016-08-30 2019-04-16 莱宝有限公司 Dry compression vacuum pump

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3209990A (en) * 1962-01-18 1965-10-05 Atlas Copco Ab Two stage screw rotor machines
JPS6336086A (en) * 1986-07-30 1988-02-16 Taiko Kikai Kogyo Kk Multi-stage screw type vacuum pump
JPH02245493A (en) * 1989-03-20 1990-10-01 Hitachi Ltd Screw vacuum pump
CN106194734A (en) * 2014-09-05 2016-12-07 大卫·金 Twin-stage dry vacuum pump
CN109642574A (en) * 2016-08-30 2019-04-16 莱宝有限公司 Dry compression vacuum pump
CN106704179A (en) * 2017-03-09 2017-05-24 上海格什特螺杆科技有限公司 Novel direct-connected dual-screw compressor

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114688021A (en) * 2020-12-25 2022-07-01 宁波市润桥工业设计有限公司 Screw pump with controllable filling and discharging

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Application publication date: 20200508