Symmetrical molded line variable pitch twin-screw rotor and vacuum pump

Abstract

The invention provides a symmetric molded line variable-pitch twin-screw rotor and a vacuum pump, and belongs to the technical field of vacuum pumps, the symmetric molded line variable-pitch twin-screw rotor comprises a driving rotor and a driven rotor which are meshed with each other, the pitch of the driving rotor and the driven rotor is reduced from the suction end to the exhaust end in the circumferential direction, and the end face molded lines of the driving rotor and the driven rotor are completely the same. Each of the four sections of curves sequentially comprises a tooth crest arc ab, a first section of epicycloid bc, a tooth bottom arc cd and a second section of epicycloid de, and the other four sections of curves and the four sections of curves are arranged in a central symmetry manner. By means of the design, it is ensured that the rotor is evenly stressed in the rotating process, vibration and noise generated by unbalanced stress are reduced, and the stability of the vacuum pump is remarkably improved; and meanwhile, a leakage triangle is omitted, so that the leakage triangle does not exist in the meshing process, the sealing performance is further improved, and gas leakage and energy loss are remarkably reduced.

Description

Technical Field

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

[0002] With the rapid development of industrial technology, the demand for vacuum technology in various industries is increasing, especially in high-tech fields such as semiconductor manufacturing, pharmaceuticals, chemicals and new energy, which puts forward higher requirements for efficient, stable and low-energy vacuum equipment. Twin-screw vacuum pumps are widely used in various vacuum environments due to their characteristics of non-contact, low vibration, low noise and high reliability. However, traditional twin-screw vacuum pumps usually adopt segmented equal pitch design, which makes processing difficult. When faced with different pressure differences or vacuum requirements, they show problems of low efficiency or poor adaptability, such as low compression efficiency, high energy consumption or unstable working state. Summary of the invention

[0003] In order to solve the above problems in the prior art, a symmetrical variable pitch twin-screw rotor and a vacuum pump are provided.

[0004] The technical solution adopted by the present invention to solve its technical problem is:

[0005] The technical scheme proposes a symmetrical profile variable pitch twin-screw rotor, comprising a driving rotor and a driven rotor meshing with each other, wherein the pitch of the driving rotor and the driven rotor decreases from the suction end to the exhaust end along the circumferential direction, wherein the end profiles of the driving rotor and the driven rotor are completely identical, and are both formed by connecting eight segments of curves connected end to end, wherein four segments of the curves sequentially include a tooth top arc ab, a first segment of an outer cycloid bc, a tooth bottom arc cd, and a second segment of an outer cycloid de, and the other four segments of the curves are centrally symmetrically arranged with the above four segments of the curves; wherein the first segment of the cycloid bc extends from the end point of the tooth top circle to the tooth bottom circle, and the second segment of the cycloid bc is symmetrical with the first segment of the cycloid bc; during the meshing process, the tip a of a rotor in the driving rotor meshes with the intersection of the first segment of the cycloid bc and the tooth bottom arc df in the driven rotor, and the remaining segments mesh in sequence according to the respective rotation directions of the driving rotor and the driven rotor.

[0006] Preferably, the outer diameter of the driving rotor and the driven rotor is D, and the inner diameter is d. The center distance A of the driving rotor and the driven rotor can be obtained by the equation A=(D+d) / 2.

[0007] Preferably, the equations for the outer circles of the active rotor and the driven rotor are:

[0008]

[0009] Preferably, the starting point of the first cycloid bc is located on the tooth bottom circle, and the focus is located on the tooth top circle. The cycloid diameter L of the first cycloid bc can be determined by the outer diameter of the rotor, and its equation is: L = D / 2. The meshing angle equation of the cycloid is:

[0010]

[0011] The equations of the first cycloid bc at the x and y coordinates are:

[0012]

[0013] Preferably, the inner circle equations of the active rotor and the driven rotor are:

[0014]

[0015] Preferably, the relationship equation between the length of the active rotor and the driven rotor and the rotation angle is:

[0016]

[0017] Where L is the rotor length, P1 is the starting pitch, P2 is the ending pitch, and t is the rotation angle.

[0018] Preferably, the equation for the pitch of the active rotor and the driven rotor to change with the rotation angle in a quadratic relationship is:

[0019]

[0020] Where L is the rotor length, P1 is the starting pitch, P2 is the ending pitch, and t is the rotation angle.

[0021] Preferably, the active rotor and the driven 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.

[0022] The present invention also provides a vacuum pump, which adopts the symmetrical tooth-shaped variable pitch twin-screw rotor described in any one of the above items.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1. The present invention adopts a rotor with a symmetrical profile. The profiles of the active rotor and the driven rotor are completely symmetrical in geometric structure. This symmetrical design ensures that the rotor is subjected to uniform force during rotation, reduces vibration and noise caused by unbalanced force, significantly improves the stability of the vacuum pump, and extends the service life of the equipment.

[0025] 2. The present invention adopts a circumferential variation design of the pitch. The larger pitch design at the suction end can increase the suction volume, improve the pumping speed of the vacuum pump, and effectively increase the probability of gas suction; the pitch component at the exhaust end is reduced, which reduces the leakage area of ​​the exhaust end and reduces the impact of gas reflux on the pump efficiency, thereby reducing energy loss.

[0026] 3. The special profile of the present invention also eliminates the leakage triangle. When the profile meshing point of the active rotor and the driven rotor can coincide with the sharp point of the casing, the leakage triangle can be eliminated, so that there is no leakage triangle during the meshing process, which further improves the sealing performance and significantly reduces gas leakage and energy loss. This improvement plays a key role in improving the overall efficiency of the pump, especially in applications under high-precision vacuum environments, and can ensure the stability and efficiency of gas compression. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] 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.

[0028] Figure 1 It is a three-dimensional structural schematic diagram of the active rotor and the driven rotor in the present invention.

[0029] Figure 2 It is a top view (quadratic pitch) of the driving rotor and the driven rotor in the present invention.

[0030] Figure 3 It is a schematic diagram of the profiles of the active rotor and the driven rotor in the present invention.

[0031] Figure 4 It is a schematic diagram of the profile of the active rotor and the driven rotor meshing at different positions in the present invention.

[0032] Figure 5 It is a schematic diagram of the structure of eliminating the leakage triangle in the present invention.

[0033] 1. Driving rotor; 2-driven rotor. DETAILED DESCRIPTION

[0034] 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.

[0035] 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.

[0036] The present invention will be described in detail below with reference to the specific embodiments shown in the accompanying drawings.

[0037] like Figure 1-5 As shown, this embodiment proposes a variable pitch twin-screw rotor, which includes: a driving rotor 1 and a driven rotor 2 that mesh with each other, the driving rotor 1 and the driven rotor 2 rotate in opposite directions, and the pitches of the driving rotor 1 and the driven rotor 2 decrease from the suction end to the exhaust end along the circumferential direction, wherein the end surface profiles of the driving rotor 1 and the driven rotor 2 are exactly the same, and are both formed by eight segments of curves connected end to end, wherein four segments of the curves include a tooth top arc ab, a first segment of the epicycloid bc, a tooth bottom arc cd, and a second segment of the epicycloid de in sequence, and the other four segments of the curves are centrally symmetrically arranged with the above four segments of the curves, which will not be described in detail here.

[0038] Among them, the tooth top arc ab is an arc curve related to the tooth top, which is used to connect the highest point part of the rotor profile; the first cycloid bc extends from the end point of the tooth top circle to the tooth bottom circle. This part of the curve is the external contour of the tooth shape. Through the geometric characteristics of the cycloid, the main working curve of the rotor tooth shape when it is meshing with the driven rotor 2 is defined; the tooth bottom arc cd forms the lowest point of the rotor when compressing gas, ensuring a smooth transition in the flow area, and the second cycloid bc echoes the first cycloid bc and presents a symmetrical structure; during the meshing process, the tip a of a rotor in the active rotor 1 meshes with the intersection of the first cycloid bc and the tooth bottom arc df in the driven rotor 2, and the remaining line segments mesh in sequence according to the respective rotation directions of the active rotor 1 and the driven rotor 2.

[0039] The rotor adopts a symmetrical tooth design. The active rotor 1 and the driven rotor 2 are completely symmetrical in geometry. This design ensures that the rotor is evenly stressed during rotation and reduces the noise caused by unbalanced stress. Compared with the traditional asymmetric linear rotor, the symmetrical tooth rotor significantly improves the operating stability of the vacuum pump, enabling it to run smoothly at a higher speed, up to 20,000 rpm. This design not only improves the working efficiency of the pump, but also extends the service life of the equipment, and is suitable for industrial applications that require high performance and high stability.

[0040] Further, such as Figure 5 As shown in FIG. 1 , the design eliminates the leakage triangle in the profile. The thick line portion in the upper half of the figure is the leakage triangle in the traditional rotor structure, which is easy to cause gas leakage and reduce the pumping efficiency of the pump. Figure 5 After the rotor profile is optimized in the lower half, when the meshing point of the active rotor 1 and the driven rotor 2 can coincide with the sharp point of the casing, the leakage triangle can be eliminated, so that there is no leakage triangle during the meshing process, which further improves the sealing performance and significantly reduces gas leakage and energy loss. This improvement plays a key role in improving the overall efficiency of the pump, especially in applications under high-precision vacuum environments, and can ensure the stability and efficiency of gas compression.

[0041] Among them, the outer circle line equations of the active rotor 1 and the driven rotor 2 are:

[0042]

[0043] The outer diameter of the active rotor 1 and the driven rotor 2 is D, and the inner diameter is d. The center distance A of the active rotor 1 and the driven rotor 2 can be obtained by the equation A=(D+d) / 2.

[0044] The starting point of the first cycloid bc is located on the tooth bottom circle, and the midpoint is located on the tooth top circle. The cycloid diameter L of the first cycloid bc can be determined by the outer diameter of the rotor, and its equation is: L = D / 2. The meshing angle equation of the cycloid is:

[0045]

[0046] The equations of the first cycloid bc at the x and y coordinates are:

[0047]

[0048] The inner circle equations of the active rotor 1 and the driven rotor 2 are:

[0049]

[0050] It is worth noting that the definition equations of the first epicycloid bc and the second epicycloid de are the same. The geometric shape of the fourth epicycloid de can be obtained by symmetric processing of the first epicycloid bc. Half of the rotor profile is composed of the tooth top arc ab, the first epicycloid bc, the tooth bottom arc cd and the second epicycloid de. These curves are accurately calculated and matched to achieve the integrity and smooth transition of the rotor geometry. By rotating the above profile 180°, the other half of the rotor can be generated, thus forming a complete rotor shape.

[0051] Figure 4 The meshing process of the active rotor 1 and the driven rotor 2 at different positions. The starting position of the rotor is set to 0°, and the meshing state of the active rotor 1 and the driven rotor 2 at different angles is displayed every time the rotor rotates 30°. When the rotor rotates 180°, the active rotor 1 and the driven rotor 2 return to the starting position, so that the meshing relationship of the rotors at different angles can be clearly observed, ensuring the synchronization of the two rotors and the stability of gas compression during the entire operation.

[0052] refer to Figure 2 In some embodiments, the pitch of the rotor gradually decreases from the intake end to the exhaust end along the circumferential direction, and the relationship equation between the length of the active rotor 1 and the driven rotor 2 and the rotation angle is:

[0053]

[0054] Where L is the rotor length, P1 is the starting pitch, P2 is the ending pitch, and t is the rotation angle.

[0055] In some embodiments, another pitch variation method is proposed, in which the pitch of the active rotor 1 and the driven rotor 2 varies with the rotation angle in a quadratic relationship as follows:

[0056]

[0057] Where L is the rotor length, P1 is the starting pitch, P2 is the ending pitch, and t is the rotation angle.

[0058] The screw pitch changes in a quadratic relationship, and the screw pitch gradually decreases from the suction end to the exhaust end, forming a change pattern with a large pitch in the suction section and a small pitch in the exhaust section. The larger pitch design in the suction section can increase the suction volume, improve the pumping speed of the vacuum pump, and effectively improve the gas suction efficiency; the pitch at the exhaust end gradually decreases, reducing the leakage area at the exhaust end, reducing the impact of gas reflux on the pump efficiency, and thus reducing energy loss. At the same time, the variable pitch design also effectively reduces the exhaust temperature, avoids equipment loss caused by excessive temperature, and further improves the overall stability and operating efficiency of the equipment.

[0059] The combination of the symmetrical tooth profile and the variable pitch design of the present invention makes the gas flow more stable during the compression process, avoids the common air flow fluctuation problem in traditional pumps, and makes the compression process more uniform and stable. By optimizing the flow path of the gas, the leakage and energy loss in the compression chamber are reduced, which not only improves the pumping speed of the pump, but also improves the overall working efficiency of the equipment. This design ensures that the gas is evenly stressed during the entire compression process, reduces the loss of mechanical components, and prolongs the service life of the equipment.

[0060] In order to further improve the operation effect of the vacuum pump, the present invention cancels the exhaust port in the traditional design. By canceling the exhaust port design, the heat accumulation at the exhaust end is reduced, and the aging problem of the equipment caused by high temperature is effectively prevented. This design not only reduces the temperature of the exhaust end, but also reduces the maintenance cost, so that the vacuum pump can continue to operate stably under high speed conditions, and extend the service life of the equipment.

[0061] The present invention also proposes a vacuum pump, including the above-mentioned symmetrical tooth shape variable pitch twin-screw rotor, which is directly connected to the motor through the active rotor 1. The active rotor 1 and the driven 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.

[0062] 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.

[0063] Among them, the outer layer of the active rotor 1 and the driven rotor 2 is made of nickel-phosphorus alloy plating (Ni-P) or polytetrafluoroethylene (PTFE) coating. Nickel-phosphorus alloy plating (Ni-P) has good corrosion resistance and wear resistance, and is suitable for use in corrosive gas environments. Nickel-phosphorus plating can form a uniform and dense protective layer on the surface of the parts. PTFE coating is suitable for environments with strong corrosion or chemical reactions. Because 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.

[0064] Through the above innovative design, the vacuum pump using symmetrical tooth-shaped variable pitch twin-screw rotors has shown significant advantages in improving air extraction efficiency, reducing energy consumption, and extending service life. Compared with the prior art, the present invention can provide stable and efficient working performance at higher speeds and more complex working conditions, and is particularly suitable for industrial application fields such as semiconductor manufacturing, pharmaceuticals, and chemicals that have high requirements for vacuum environments, and has broad market application prospects.

[0065] 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 symmetrical variable pitch twin-screw rotor, comprising a driving rotor and a driven rotor meshing with each other, wherein the pitch of the driving rotor and the driven rotor decreases from the suction end to the discharge end along the circumferential direction, characterized in that: The end profiles of the active rotor and the driven rotor are completely identical, and are both formed by connecting eight segments of curves connected end to end, wherein four segments of curves sequentially include a tooth top arc ab, a first segment of epicycloid bc, a tooth bottom arc cd, and a second segment of epicycloid de, and the other four segments of curves are centrally symmetrically arranged with the above four segments of curves; Among them, the first cycloid bc extends from the end point of the tooth top circle to the tooth bottom circle, and the second cycloid bc is symmetrical with the first cycloid bc. During the meshing process, the tip a of a rotor in the active rotor meshes with the intersection of the first cycloid b'c' and the tooth bottom arc c'd' in the driven rotor, and the remaining line segments mesh in sequence according to the respective rotation directions of the active rotor and the driven rotor.

2. A symmetrical tooth-profile variable pitch twin-screw rotor according to claim 2, characterized in that: The outer diameter of the driving rotor and the driven rotor is D, and the inner diameter is d. The center distance A between the driving rotor and the driven rotor can be obtained by the equation A=(D+d) / 2.

3. The symmetrical tooth-profile variable pitch twin-screw rotor according to claim 1, characterized in that: The equations for the outer circles of the active rotor and the driven rotor are:

4. A symmetrical tooth-profile variable pitch twin-screw rotor according to claim 3, characterized in that: The starting point of the first cycloid bc is located on the tooth bottom circle, and the midpoint is located on the tooth top circle. The cycloid diameter L of the first cycloid bc can be determined by the outer diameter of the rotor, and its equation is: L = D / 2. The meshing angle equation of the cycloid is: The equations of the first cycloid bc at the x and y coordinates are:

5. A symmetrical tooth-profile variable pitch twin-screw rotor according to claim 4, characterized in that: The inner circle equations of the active rotor and the driven rotor are:

6. A symmetrical tooth-profile variable pitch twin-screw rotor according to claim 5, characterized in that: The relationship equation between the length of the active rotor and the driven rotor and the rotation angle is: Where L is the rotor length, P1 is the starting pitch, P2 is the ending pitch, and t is the rotation angle.

7. The symmetrical tooth-profile variable pitch twin-screw rotor according to claim 5, characterized in that: The equation for the pitch of the active rotor and the driven rotor 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.

8. The symmetrical tooth-profile variable pitch twin-screw rotor according to claim 1, characterized in that: The active rotor and the driven 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 symmetrical tooth-shaped variable pitch twin-screw rotor as claimed in any one of claims 1 to 8 is used.

Images