Quadratic screw pitch double-screw rotor and vacuum pump

Abstract

The invention provides a quadratic screw pitch double-screw rotor and a vacuum pump, and belongs to the technical field of vacuum pumps, the quadratic screw pitch double-screw rotor comprises a male rotor and a female rotor which are meshed with each other, the male rotor and the female rotor are rotationally meshed in opposite directions, the screw pitch of the male rotor and the female rotor is reduced from a suction end to an exhaust end in the circumferential direction, and the screw pitch changes along with a rotation angle in a quadratic relation; and a quadratic screw pitch design is adopted, so that the screw pitch of the screw is allowed to be decreased in a quadratic manner in the axial direction, the suction volume is further increased, and energy consumption and gas leakage are effectively reduced. The method is suitable for application scenes of high compression ratio and deep vacuum, compression efficiency can be effectively improved, energy loss is reduced, reliability of equipment is improved, and the service life of the equipment is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of vacuum pumps, and in particular relates to a quadratic pitch twin-screw rotor and a vacuum pump. Background Art

[0002] With the rapid development of industrial technology, the demand for vacuum technology in all walks of life is increasing. Especially in high-tech fields such as semiconductor manufacturing, pharmaceuticals, chemicals and new energy, higher requirements are placed on efficient, stable and low-energy vacuum equipment. Twin-screw vacuum pumps are widely used in various vacuum environments due to their non-contact, low vibration, low noise and high reliability.

[0003] However, traditional twin-screw vacuum pumps usually adopt a segmented equal pitch design, which makes processing difficult and exhibits problems of low efficiency or poor adaptability when faced with different pressure differences or vacuum requirements, such as low compression efficiency, high energy consumption or unstable working conditions. Summary of the invention

[0004] In order to solve the above problems in the prior art, a quadratic pitch twin-screw rotor and a vacuum pump are provided.

[0005] The technical solution adopted by the present invention to solve its technical problem is:

[0006] The technical solution proposes a quadratic pitch twin-screw rotor, comprising a male rotor and a female rotor meshing with each other, wherein the male rotor and the female rotor mesh in opposite directions, and is characterized in that the pitch of the male rotor and the female rotor decreases from the suction end to the exhaust end along the circumferential direction, and the equation for the pitch changing with the rotation angle in a quadratic relationship is:

[0007]

[0008] Where L is the rotor length, P1 is the starting pitch, P2 is the ending pitch, and t is the rotation angle.

[0009] Preferably, the end profiles of the male rotor and the female rotor are completely identical, and are both formed by connecting 12 segments of curves connected end to end, wherein six segments of curves sequentially include a tooth top arc ab, a first segment of epicycloid bc, a second segment of epicycloid cd, a tooth bottom arc de, a third segment of epicycloid ef and a fourth segment of epicycloid fg, and the other six segments of curves are centrally symmetrically arranged with the above six segments of curves;

[0010] The cusp a of one rotor in the positive rotor meshes with the second segment of the epicycloid c'd' in the negative rotor, and the remaining segments mesh in sequence according to the respective rotation directions of the positive rotor and the negative rotor.

[0011] Preferably, the profile equations of the tooth top arc ab of the male rotor and the female rotor are:

[0012]

[0013] Preferably, the outer circle diameter of the first section of the outer cycloid bc of the male rotor and the female rotor is D, and the inner circle diameter is d, so A=(D+d) / 2, and the pitch circle diameter Dd=(D+d) / 2.

[0014] Preferably, the starting point of the first section of the outer cycloid bc of the male rotor and the female rotor is located on the tooth bottom circle, and the end point is located on the pitch circle, so the cycloid diameter is L bc =D / 2; the meshing angle equation of the cycloid is:

[0015]

[0016] The equations of the first epicycloid bc at the x and y coordinates are:

[0017]

[0018] Preferably, the starting point of the second section of the outer cycloid cd of the male rotor and the female rotor is located on the pitch circle, and the end point is located on the top circle, so the cycloid diameter is L cd =Dd / 2; the meshing angle equation of the cycloid is:

[0019]

[0020] The equations of the second epicycloid cd at the x and y coordinates are:

[0021]

[0022] Preferably, the equations of the inner circles of the male rotor and the female rotor are:

[0023]

[0024] Preferably, the male rotor and the female rotor are made of cast iron or steel; and the outer surface of the rotor is coated with a nickel-phosphorus alloy coating or a polytetrafluoroethylene coating.

[0025] The present invention also provides a vacuum pump, which adopts the quadratic pitch twin-screw rotor described in any one of the above items.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] The quadratic pitch design is adopted in the present invention, which allows the screw pitch to decrease quadratically in the axial direction to further increase the suction volume, effectively reducing energy consumption and gas leakage. It is suitable for high compression ratio and deep vacuum application scenarios, which can effectively improve compression efficiency and reduce energy loss, and improve the reliability and service life of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0029] Figure 1 It is an axonometric view of the linear pitch of the male and female rotors.

[0030] Figure 2 It is a top view of the linear pitch of the male and female rotors.

[0031] Figure 3 It is an axonometric diagram of the quadratic variable pitch of the positive rotor and the negative rotor in the present invention.

[0032] Figure 4 It is a top view of the quadratic variable pitch of the male rotor and the female rotor in the present invention.

[0033] Figure 5 It is a schematic diagram of the profiles of the male rotor and the female rotor in the present invention.

[0034] Figure 6 It is a schematic diagram of the meshing lines of the male rotor and the female rotor at different positions in the present invention.

[0035] Figure 7 It is the volume change curve of equal pitch and linear pitch rotor.

[0036] Figure 8 It is the volume change curve of linear pitch and quadratic pitch rotor.

[0037] Description of reference numerals:

[0038] 1-male rotor; 2-female rotor. DETAILED DESCRIPTION

[0039] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] In addition, terms such as "long", "short", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings and are only used to facilitate the description of the present invention. They do not indicate or imply that the device or component referred to must have this specific direction or operate with a specific direction structure, and should not be understood as a limitation of the present invention.

[0041] The present invention will be described in detail below with reference to the specific embodiments shown in the accompanying drawings.

[0042] like Figure 1-8 As shown, this embodiment proposes a quadratic pitch twin-screw rotor, which includes: a male rotor 1 and a female rotor 2 meshing with each other, the male rotor 1 and the female rotor 2 meshing in opposite directions, the pitch of the male rotor 1 and the female rotor 2 decreases axially from the suction end to the exhaust end, and the equation for the change of the pitch angle in a quadratic relationship is:

[0043]

[0044] Where L is the rotor length, P1 is the starting pitch, P2 is the ending pitch, and t is the rotation angle.

[0045] The quadratic pitch design allows the screw pitch to decrease quadratically in the circumferential direction, which is suitable for applications with high compression ratios and deep vacuum, and can effectively improve compression efficiency and reduce energy loss. Figures 7 and 8 The volume change curves of medium pitch, linear pitch and quadratic pitch show that linear pitch can increase the suction volume, and the quadratic pitch design can further increase the suction volume compared to the linear pitch, solving the problems of low efficiency of vacuum pumps in high compression ratio and deep vacuum applications, and significantly improving the performance of gas compression and the adaptability of equipment. By optimizing the pitch design, energy consumption and gas leakage are effectively reduced, adapting to a variety of industrial needs, and improving the reliability and service life of the equipment, it has broad application prospects in semiconductors, pharmaceuticals, chemicals, and new energy.

[0046] Furthermore, the end profiles of the male rotor 1 and the female rotor 2 are completely identical, and are both formed by connecting 12 segments of curves connected end to end, wherein six segments of curves sequentially include the tooth top arc ab, the first segment of the epicycloid bc, the second segment of the epicycloid cd, the tooth bottom arc de, the third segment of the epicycloid ef and the fourth segment of the epicycloid fg, and the other six segments of curves are symmetrically arranged with the above six segments of curves, which will not be described in detail here;

[0047] The tip of a rotor in the positive rotor 1 meshes with the second epicycloid c'd' in the negative rotor 2, the tooth top arc ab in the positive rotor 1 meshes with the tooth bottom arc d'e' in the negative rotor 2, and so on. The remaining curves mesh in sequence according to the respective rotation directions of the positive rotor 1 and the negative rotor 2; wherein the pitch of the positive rotor 1 and the negative rotor 2 decreases along the circumferential direction from the intake end to the exhaust end.

[0048] In the design of twin-screw vacuum pumps, a larger envelope angle and suction volume are crucial to improving the pumping speed and ultimate vacuum of the pump. The traditional asymmetric profile rotor shows limitations at high speeds and can usually only operate below 5,000 rpm. In order to further improve the operating efficiency, the present invention proposes this symmetrical tooth-shaped variable pitch twin-screw rotor design. By adopting a symmetrical profile design, the vacuum pump can operate at a higher speed, up to 20,000 rpm, significantly improving the working efficiency of the vacuum pump.

[0049] The variable pitch design further optimizes the performance of the vacuum pump. The larger pitch of the suction section increases the suction volume, thereby increasing the pumping speed of the pump; the pitch of the exhaust section gradually decreases, reducing the leakage area at the exhaust end, reducing gas reflux, and thus reducing power consumption.

[0050] Through the above design, the compression process becomes more uniform, which not only improves the pumping speed, but also effectively reduces the exhaust temperature. In short, the present invention improves the operating speed, pumping speed and efficiency of the vacuum pump through the double-tooth symmetry and variable pitch design, while also significantly improving its stability and service life, providing an optimized solution that meets the needs of modern industry.

[0051] The outer diameter of the first section of the epicycloid bc of the rotor and the female rotor 2 is D, and the inner diameter is d, so A=(D+d) / 2, and the pitch circle diameter Dd=(D+d) / 2.

[0052] The profile equations of the tooth tip arc ab of the male rotor 1 and the female rotor 2 are:

[0053]

[0054] The starting point of the first section of the outer cycloid bc of the male rotor 1 and the female rotor 2 is located on the tooth bottom circle, and the end point is located on the pitch circle, so the cycloid diameter is L bc =D / 2; the meshing angle equation of the cycloid is:

[0055]

[0056] The equations of the first epicycloid bc at the x and y coordinates are:

[0057]

[0058] The starting point of the second epicycloid cd of the male rotor 1 and the female rotor 2 is on the pitch circle, and the end point is on the top circle, so the cycloid diameter is L cd =Dd / 2; the meshing angle equation of the cycloid is:

[0059]

[0060] The equations of the second epicycloid cd at the x and y coordinates are:

[0061]

[0062] It is worth noting that the first epicycloid bc and the fourth epicycloid fg have the same definition equation, and the second epicycloid cd and the third epicycloid ef have the same definition equation. The fourth epicycloid fg and the third epicycloid ef can be obtained by symmetry of the first epicycloid bc and the second epicycloid cd.

[0063] refer to Figure 6 , which shows a schematic diagram of the male rotor 1 and the female rotor 2 meshing at different positions. The rotor starts at 0°, and after rotating 180°, the rotor returns to the starting position. The angle interval of each figure is 30°. In this design, not only are the male rotor 1 and the female rotor 2 symmetrically arranged, but the male rotor 1 and the female rotor 2 are also symmetrically contoured. This design allows the male rotor 1 and the female rotor 2 to be evenly stressed during operation, greatly reducing vibration and noise during operation, and improving the stability and suction efficiency of the pump.

[0064] Furthermore, the equations of the inner circles of the male rotor 1 and the female rotor 2 are:

[0065]

[0066] The symmetrical special profile combined with the variable pitch design in this design improves the speed and stability during operation, effectively reduces the vibration of the rotor when running at high speed, thereby reducing the bearing load and extending the service life of the vacuum pump.

[0067] The present invention also proposes a vacuum pump, including the above-mentioned quadratic pitch twin-screw rotor, which is directly connected to the motor through the male rotor 1. The male rotor 1 and the female rotor 2 are meshed with each other through synchronous gears and rotate in opposite directions to form a closed volume with the shell, thereby realizing the gas suction, compression and exhaust process.

[0068] It is worth noting that in this embodiment, the vacuum pump adopts an oil-free twin-screw vacuum pump, and the rotor does not need lubricating oil for lubrication and cooling. The two rotors rotate through synchronous gears. Since the operating pressure of the two rotors is low, the requirements for the material are not high. Both cast iron and steel materials can meet the requirements of high speed. Carbon steel and alloy steel are suitable for occasions with high pressure and temperature, but surface treatment or plating is required in corrosive environments; stainless steel (such as 304, 316, etc.) has good corrosion resistance and is suitable for handling wet gas or corrosive media; 316 stainless steel is better than 304 stainless steel in corrosion resistance, and is particularly suitable for industries such as chemistry and pharmaceuticals that have high requirements for corrosion resistance. Rotors of different materials can be selected according to the actual use environment.

[0069] The outer layers of the male rotor 1 and the female rotor 2 are made of nickel-phosphorus alloy plating (Ni-P) or polytetrafluoroethylene (PTFE) coating. The nickel-phosphorus alloy plating (Ni-P) has good corrosion resistance and wear resistance and is suitable for use in corrosive gas environments. The nickel-phosphorus plating can form a uniform and dense protective layer on the surface of the parts. The PTFE coating is suitable for environments with strong corrosion or chemical reactions. Since PTFE has good chemical resistance and low friction characteristics, it can be used in some occasions that require chemical corrosion resistance, but its wear resistance is not as good as that of metal coatings.

[0070] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings, or directly / indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A quadratic pitch twin-screw rotor, comprising a male rotor and a female rotor meshing with each other, wherein the male rotor and the female rotor mesh in opposite directions, characterized in that: The pitch of the male rotor and the female rotor decreases from the suction end to the exhaust end along the circumferential direction, and the equation for the pitch changing with the rotation angle in a quadratic relationship is: Where L is the rotor length, P1 is the starting pitch, P2 is the ending pitch, and t is the rotation angle.

2. A quadratic pitch twin-screw rotor according to claim 1, characterized in that: The end profiles of the male rotor and the female rotor are completely identical, and are both formed by connecting 12 segments of curves connected end to end, wherein six segments of curves sequentially include a tooth top arc ab, a first segment of epicycloid bc, a second segment of epicycloid cd, a tooth bottom arc de, a third segment of epicycloid ef and a fourth segment of epicycloid fg, and the other six segments of curves are centrally symmetrically arranged with the above six segments of curves; The cusp a of one rotor in the positive rotor meshes with the second segment of the epicycloid c'd' in the negative rotor, and the remaining segments mesh in sequence according to the respective rotation directions of the positive rotor and the negative rotor.

3. A quadratic pitch twin-screw rotor according to claim 2, characterized in that: The outer diameter of the first section of the epicycloid bc of the male rotor and the female rotor is D, and the inner diameter is d, so A=(D+d) / 2, and the pitch circle diameter Dd=(D+d) / 2.

4. A quadratic pitch twin-screw rotor according to claim 3, characterized in that: The profile equations of the tooth tip arc ab of the male rotor and the female rotor are:

5. A quadratic pitch twin-screw rotor according to claim 4, characterized in that: The starting point of the first section of the outer cycloid bc of the male rotor and the female rotor is located on the tooth bottom circle, and the end point is located on the pitch circle, so the cycloid diameter is L bc =D / 2; the meshing angle equation of the cycloid is: The equations of the first epicycloid bc at the x and y coordinates are:

6. A quadratic pitch twin-screw rotor according to claim 5, characterized in that: The starting point of the second section of the outer cycloid cd of the male rotor and the female rotor is located on the pitch circle, and the end point is located on the top circle, so the cycloid diameter is L cd =Dd / 2; the meshing angle equation of the cycloid is: The equations of the second epicycloid cd at the x and y coordinates are:

7. A quadratic pitch twin-screw rotor according to claim 6, characterized in that: The equations of the inner circles of the male and female rotors are:

8. The quadratic pitch twin-screw rotor according to claim 1, characterized in that: The male rotor and the female rotor are made of cast iron or steel; and the outer surface of the rotor is coated with a nickel-phosphorus alloy coating or a polytetrafluoroethylene coating.

9. A vacuum pump, characterized in that: A variable pitch twin screw rotor as claimed in any one of claims 1 to 8 is used.

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