Three-stage conical screw rotor and vacuum pump

Abstract

The utility model discloses a three -section type conical screw rotor, three -section type conical screw rotor is divided into suction section, compression section and exhaust section in proper order along screw axial direction, the suction section is equal cross section and equal pitch along screw axial direction, the compression section adopts and is variable cross section and variable pitch along screw axial direction, the exhaust section is equal cross section and equal pitch along screw axial direction, the cross section width of suction section along screw axial direction is greater than the cross section width of exhaust section along screw axial direction, the end face profile equation of each section is same, and all are by five curves of abutting together closed, and the five curves include involute section AB, addendum circle arc section BC, long amplitude outside cycloid section CD, dedendum circle arc section DE and point conjugate curve section EA. The utility model also provides a vacuum pump. The device of the utility model can effectively reduce the noise of vacuum pump, reduce the clearance backflow, thereby improve its reliable stability and practical life.

Description

Technical Field

[0001] This utility model belongs to the field of vacuum pump design technology, and in particular relates to a three-section conical screw rotor and a vacuum pump. Background Technology

[0002] Twin-screw vacuum pumps are highly efficient vacuum extraction devices widely used in industrial fields, particularly suitable for low-pressure, high-flow-rate vacuum applications. Traditional twin-screw vacuum pumps typically use a pair of meshing screws to compress and discharge gas within the pump chamber, utilizing the rotational motion of the screws and the sealing properties of the fluid. Their simple working principle, compact structure, high gas extraction capacity, and low operating noise make them widely applicable in many industrial processes requiring a stable vacuum environment, such as petrochemicals, semiconductor manufacturing, food processing, and laboratory research.

[0003] Patent document CN119435388A discloses a quadratic pitch twin-screw rotor and vacuum pump, which includes a male rotor and a female rotor that mesh with each other. The male rotor and the female rotor rotate in opposite directions and mesh. The pitch of the male rotor and the female rotor decreases circumferentially from the intake end to the exhaust end. The pitch changes with the rotation angle in a quadratic relationship. The quadratic pitch design allows the screw pitch to decrease quadratically in the axial direction, so as to further increase the intake volume and effectively reduce energy consumption and gas leakage.

[0004] Patent document CN 108071585 A discloses a two-stage screw vacuum pump rotor, characterized by an intake section and an exhaust section. The intake section has a variable pitch screw, while the exhaust section has a constant pitch screw. The pitch of the intake section gradually decreases non-linearly from the inlet face until it equals the pitch of the exhaust section. However, this screw rotor is a simple constant cross-section design, lacking the variable cross-section compression effect, and only exhibiting the variable pitch compression effect of the intake section. While relatively simple to manufacture, it results in lower compression within the fluid medium, lower efficiency, higher energy consumption, and a bulkier structure.

[0005] Furthermore, existing twin-screw vacuum pumps still face several technical challenges. First, the relatively simple screw profile meshing design easily leads to significant friction and wear, resulting in decreased pump efficiency, increased energy consumption, and shortened service life. Second, existing twin-screw designs are mostly traditional constant cross-section or simple variable cross-section designs, which cannot achieve optimal hydrodynamic performance under different operating conditions, affecting the overall efficiency and stability of the pump. Additionally, in high-vacuum applications, traditional twin-screw vacuum pumps often exhibit high noise, vibration, and backflow phenomena, further impacting their performance and operating environment.

[0006] Therefore, how to reduce frictional losses, optimize fluid dynamics, and reduce noise while ensuring efficient and stable operation has become an urgent problem to be solved in twin-screw vacuum pump technology. Utility Model Content

[0007] The purpose of this invention is to provide a three-section conical screw rotor and a vacuum pump. This three-section conical screw rotor can effectively reduce the noise of the vacuum pump and reduce backflow in the gap, thereby improving its reliability, stability and service life.

[0008] To achieve the first objective of this utility model, the following technical solution is provided: a three-section conical screw rotor, which is divided into an intake section, a compression section and an exhaust section along the screw axis;

[0009] The intake section has a uniform cross-section and a uniform pitch along the screw axis;

[0010] The compression section has a variable cross-section and variable pitch along the screw axis;

[0011] The exhaust section has a uniform cross-section and a uniform pitch along the screw axis;

[0012] The cross-sectional width of the intake section along the screw axis is greater than the cross-sectional width of the exhaust section along the screw axis.

[0013] Each segment has the same end face profile equation, which is closed by connecting the beginning and end of five curve segments. The five curve segments include the involute segment AB, the tooth tip arc segment BC, the long-amplitude outward curve segment CD, the tooth root arc segment DE, and the point conjugate curve segment EA.

[0014] Specifically, the intake section has a cylindrical cross-section along the screw axis and is designed with a single-stage helix to meet the following conditions:

[0015] 0≤τ≤ω1;

[0016] ω1 = 2π;

[0017] Where τ is the helix angle and ω1 is the end helix angle of the intake section.

[0018] Specifically, the compression section has a tapered cross-section along the screw axis and is designed with a multi-stage variable helix to meet the following conditions:

[0019] ω1≤τ≤ω2;

[0020] ω3-ω2≥4π;

[0021] Where τ is the helix angle, ω2 is the end helix angle of the compression section, and ω3 is the end helix angle of the exhaust section.

[0022] Specifically, the angle between the side of the inverted cone and the axial direction of the screw is 1 to 6°.

[0023] Specifically, the exhaust section has a cylindrical cross-section along the screw axis and is designed with a two-stage to four-stage helix to meet the following conditions:

[0024] ω2≤τ≤ω3;

[0025] ω3-ω2={4π,8π};

[0026] Where τ is the helix angle, ω2 is the end helix angle of the compression section, and ω3 is the end helix angle of the exhaust section.

[0027] Specifically, the expressions for the five curve segments are as follows:

[0028] The parametric equation of the involute segment AB is:

[0029]

[0030] The parametric equation for the tooth tip arc segment BC is:

[0031] The parametric equation of the long-amplitude epicycloid segment CD is:

[0032]

[0033] The parametric equation for the tooth root arc segment DE is:

[0034] The parametric equation of the conjugate curve segment EA is:

[0035]

[0036] In the formula, R1 represents the radius of the tooth tip arc BC; R3 represents the radius of the tooth root arc DE; R b α represents the base circle radius of the involute AB; α represents the initial angle of the involute AB; t represents the angular parameter; and β represents the preset angular offset.

[0037] To achieve the second objective of this utility model, the following technical solution is adopted: a vacuum pump, comprising a female screw rotor and a male screw rotor that mesh with each other, wherein both the female screw rotor and the male screw rotor are selected from the above-mentioned three-section conical screw rotor.

[0038] Specifically, the involute segment AB of the male screw rotor meshes with the involute segment B′A′ of the female screw rotor;

[0039] Point B of the male screw rotor meshes with the conjugate curve segment A′E′ of the female screw rotor.

[0040] The tooth tip arc segment BC of the male screw rotor and the tooth root arc segment E′D′ of the female screw rotor;

[0041] Point C of the male screw rotor meshes with the long-amplitude outward cycloidal segment D′C′ of the female screw rotor;

[0042] The long-amplitude outward cycloidal segment CD of the male screw rotor meshes with point C′ of the female screw rotor;

[0043] The tooth root arc segment DE of the male screw rotor meshes with the tooth tip arc segment C′B′ of the female screw rotor.

[0044] The point conjugate curve segment EA of the male screw rotor meshes with point B′ of the female screw rotor.

[0045] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0046] The compression section features dual compression with a large internal compression ratio and optimized multi-stage gradient volume, which can effectively adjust and optimize the multi-stage temperature field and flow field to adapt to harsh environments.

[0047] The exhaust section reduces pulsation and backflow losses, thereby effectively reducing noise, minimizing gap backflow, and ensuring stability and reliability. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the structure of the three-section conical screw rotor provided in this embodiment;

[0049] Figure 2 This is a schematic diagram of the five-segment end face profile provided in this embodiment;

[0050] Figure 3 This is a schematic diagram of the seven-segment end face profile provided in this embodiment;

[0051] Figure 4 A schematic diagram of the middle section of the three-section conical screw rotor provided in this embodiment;

[0052] Figure 5 This is a schematic diagram of the profile meshing under different axial cross sections provided in this embodiment. Detailed Implementation

[0053] To better illustrate the technical solution provided in this embodiment, the following explanation is provided:

[0054] Z1 is the axial distance of the intake section, Z2 is the axial distance of the intermediate compression section, Z3 is the axial distance of the exhaust section, A is the center distance, R1 is the radius of the tooth tip arc BC, R2 is the radius of the base circle, R3 is the radius of the tooth root arc DE, R4 is the radius of the BC fillet, and R5 is the radius of the DE fillet.

[0055] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this utility model provided in the accompanying drawings is not intended to limit the scope of the claimed utility model, but merely to illustrate selected embodiments of the utility model. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without inventive effort are within the scope of protection of this utility model.

[0056] like Figure 1 As shown, this embodiment provides a three-section conical screw rotor, which has a three-section structure including an intake section (Z1), a compression section (Z2), and an exhaust section (Z3).

[0057] The intake section (Z1) is designed with a constant cross-section and constant pitch. Because its pitch P (Z1) and the radius of the tooth tip circle R1 (Z1) are maximized, the intake section has the largest possible pitch and cross-section design, resulting in the maximum intake capacity. This increases the pumping speed of the entire vacuum pump, which is the most important performance parameter of a vacuum pump. It is usually designed as a single-stage helix, and its main function is to complete the intake process in the shortest possible axial structure. One rotation completes the intake process from the start to the end of intake, which is exactly one cycle of intake. This achieves the most compact structure and can effectively improve efficiency.

[0058] The compression section (Z2) features a variable cross-section and variable pitch design. The pitch P (Z2) gradually decreases from the maximum value in the intake section to the minimum value in the exhaust section. The radius of the tooth tip circle R1 (Z2) also gradually decreases from the maximum value in the intake section to the minimum value in the exhaust section. That is, it gradually transitions from a large pitch and large cross-section at the intake end to a small pitch and small cross-section at the exhaust end, forming a conical transition. The variable cross-section design effectively creates an internal compression effect due to the change in the effective area of ​​the cross-section, similar to 2D area compression. The variable pitch design also effectively creates an internal compression effect due to the change in axial width. The intermediate compression section of the three-section conical screw rotor adopts a variable cross-section and variable pitch design, which is equivalent to a double compression effect, similar to 3D volume compression. Therefore, under the same size conditions, the internal compression effect of the intermediate compression section designed in this invention is significantly improved, which can adapt to more demanding working conditions, effectively improve the ultimate vacuum degree of the vacuum pump, and has higher efficiency. Under the same design requirements, this invention can achieve the goal in a more compact structure, thus being more efficient and energy-saving.

[0059] Furthermore, the intermediate compression section typically employs a multi-stage variable cross-section and variable pitch design. This is achieved by optimizing the gradual change pattern of the intermediate compression section—that is, the gradual decrease in pitch P(Z1) and the radius of the tooth tip circle R1(Z1) from the maximum value in the intake section to the minimum value in the exhaust section—such as first-order gradual change, second-order gradual change, etc. Simultaneously, it requires smooth connection at the three-stage transition points to stabilize the flow field; that is, the first-order derivative values ​​at the three-stage transition points are the same. By optimizing the changes in multi-stage gradient volume and rationally designing the compression ratio of each stage, the structural design of the screw rotor can be precisely and efficiently adjusted. This optimizes the temperature and flow fields during operation to adapt to the working requirements of complex environments and media, thus giving this vacuum pump high performance.

[0060] The exhaust section (Z3) is designed with a constant cross-section and constant pitch. The pitch P (Z3) and the radius of the tooth tip circle R1 (Z3) are designed to be minimized, which minimizes the effective volume of the exhaust end and effectively improves the exhaust pressure. At the same time, the minimum design of the radius of the tooth tip circle R1 (Z3) ensures that the tooth tip width of the exhaust section is not too small, effectively reducing backflow in the tooth tip gap. Furthermore, it is usually designed with 2 to 4 stages of helix, which can effectively rectify the fluid medium, reduce pulsation, thereby effectively reducing vibration and noise, and improving the reliability, stability and long service life of the screw rotor.

[0061] like Figure 2 As shown, this embodiment provides five end face profiles, where the five curves, connected end to end, are, in sequence, an involute segment AB, a tooth tip arc segment BC, a long-amplitude outward curve segment CD, a tooth root arc segment DE, and a point conjugate curve segment EA. More specifically:

[0062] The parametric equation of the involute segment AB is:

[0063]

[0064] The parametric equation for the tooth tip arc segment BC is:

[0065] The parametric equation of the long-amplitude epicycloid segment CD is:

[0066]

[0067] The parametric equation for the tooth root arc segment DE is:

[0068] The parametric equation of the conjugate curve segment EA is:

[0069]

[0070] In the formula, R1 represents the radius of the tooth tip arc BC; R3 represents the radius of the tooth root arc DE; R bα represents the base circle radius of the involute AB; α represents the initial angle of the involute AB; t represents the angular parameter; and β represents the preset angular offset.

[0071] This embodiment also provides a seven-segment end face profile, such as Figure 3 As shown, it includes involute segment AB, circular arc segment BC, tooth tip circular arc segment CD, circular arc segment DE, cycloidal equidistant curve segment EF, tooth root circular arc segment FG, and circular arc conjugate curve segment GA.

[0072] That is, two circular arc segments are added to the five-segment end face profile: the radius of the circular arc segment BC is 4 and the radius of the circular arc segment DE is R5;

[0073] The parametric equation of the circular arc segment BC is:

[0074] The parametric equation of the circular arc segment DE is:

[0075] The corresponding two meshing curve segments, including the cycloidal equidistant curve segment EF and the circular arc conjugate curve segment GA, were optimized to ensure that they also meet the basic requirement of precise meshing of the male and female screw rotor profiles.

[0076] This embodiment also provides a vacuum pump, including a female screw rotor and a male screw rotor that mesh with each other, wherein both the female screw rotor and the male screw rotor adopt the three-section conical screw rotor provided in the above embodiment.

[0077] The assembly of its female screw rotor and male screw rotor is as follows: Figure 4 As shown, they mesh precisely with each other, and the profile structure and pitch variation law of the left-hand screw rotor and the right-hand screw rotor are exactly the same, with only the difference in the direction of rotation.

[0078] The intake section (Z1) is cylindrical. The pitch P(Z1) and cross-sectional profile design parameters (R1(Z1), R3(Z1), etc.) remain constant, and the tooth tip circle radius R1(Z1) = Rin. The corresponding inner wall of the vacuum pump cavity is also cylindrical. Its pitch P(Z1) = Pin, and it is typically designed as a single-stage helix, satisfying the following formula:

[0079] 0≤τ≤ω1;ω1=2π;

[0080] The intermediate compression section (Z2) is tapered. The pitch P(Z2) and the cross-sectional profile design parameters (R1(Z2), R3(Z2), etc.) gradually change along the axial direction. Among them, the tooth tip circle radius gradually decreases from Rin to Rout, that is: P(Z2)={R in →R out}; It is usually designed as a multi-stage variable spiral, generally with two or more stages, satisfying the following formula:

[0081] ω1≤τ≤ω2;ω3-ω2≥4π;

[0082] The exhaust section (Z3) is cylindrical with a constant pitch and cross-section. All profile design parameters remain unchanged, and the tooth tip circle radius R1(Z3) = Rout. The corresponding inner wall of the vacuum pump cavity is also cylindrical, with a pitch P(Z3) = Pout. It is typically designed with 2 to 4 stages of helix, satisfying the following formula:

[0083] ω2≤τ≤ω3;ω3-ω2={4π,8π};

[0084] In terms of cross-section: Rin is the largest, and the compression segment gradually transitions from Rin to Rout, with Rout being the smallest;

[0085] In terms of pitch: Pin is the largest, and the compression section gradually transitions from Pin to Pout, with Pout being the smallest.

[0086] The transitions between the three sections are smooth. As a preferred design, the cone angle of the middle compression section is between 1° and 6° to ensure that the entire three-section conical screw rotor structure is reasonably designed.

[0087] In the formula, τ is the helix angle; ω1 is the helix angle at the end of the intake section; ω2 is the helix angle at the end of the compression section; and ω3 is the helix angle at the end of the exhaust section.

[0088] More specifically, Figure 5 As shown, the profiles of the male and female screw rotors can achieve precise meshing during operation. Specifically, the involute segment AB of the male screw rotor meshes with the involute segment B′A′ of the female screw rotor; point B of the male screw rotor meshes with the point conjugate curve segment A′E′ of the female screw rotor; the tooth tip arc segment BC of the male screw rotor meshes with the tooth root arc segment E′D′ of the female screw rotor; point C of the male screw rotor meshes with the long-amplitude epicycloid segment D′C′ of the female screw rotor; the long-amplitude epicycloid segment CD of the male screw rotor meshes with point C′ of the female screw rotor; the tooth root arc segment DE of the male screw rotor meshes with the tooth tip arc segment C′B′ of the female screw rotor; and the point conjugate curve segment EA of the male screw rotor meshes with point B′ of the female screw rotor.

[0089] The same set of equations is used in different axial positions, such as five-segment or seven-segment curves, all of which include the tooth tip arc R1 and the tooth root arc R3. The characteristic is that the center distance A of the two screw rotors is always equal, and the rotation center axes are placed parallel, facilitating installation and stable operation. In the three segments, their center distance remains constant and satisfies the following equation:

[0090] A = R1 + R3

[0091] In the intake section, the tooth tip arc R1 and tooth root arc R3 remain unchanged, so the center distance A remains unchanged.

[0092] In the intermediate compression section, the tooth tip arc R1 gradually decreases and the tooth root arc R3 gradually increases, but the sum of the two remains unchanged, satisfying the above formula, and the center distance A remains unchanged.

[0093] At the exhaust end, both the tooth tip arc R1 and the tooth root arc R3 remain unchanged, therefore the center distance A remains unchanged;

[0094] The design method is as follows:

[0095] Generally, the internal compression ratio and intermediate cone angle are first determined based on actual design requirements, and then the intermediate compression section is designed.

[0096] In addition, the suction section was designed based on the required suction rate.

[0097] Based on this, a reasonable exhaust section is designed;

[0098] Finally, minor adjustments and optimizations were made to ensure a smooth transition between the three structural sections and a reasonable overall structural design.

[0099] The rotors of the dry twin-screw vacuum pump described herein consist of meshing male and female screw rotors, both of which are three-section conical screw rotors. Furthermore, the profiles and pitch variations of the two rotors are identical, differing only in their direction of rotation. This allows for precise meshing and operation, and the male and female screw rotors never directly contact each other, maintaining a very small gap. Similarly, the male and female screw rotors never directly contact the inner wall of the dry screw vacuum pump's cavity, also maintaining a very small gap. The absence of direct contact in the dry screw vacuum pump avoids frictional losses, significantly improving the pump's stability and lifespan.

[0100] Furthermore, the terms "upper," "lower," "inner," "outer," "front," and "rear" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Unless otherwise specifically stated, the relative steps, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of this invention.

[0101] Of course, the above description is only a specific embodiment of the present utility model and is not intended to limit the scope of the present utility model. All equivalent changes or modifications made to the structure, features and principles described in the claims of the present utility model should be included in the scope of the claims of the present utility model.

[0102] Finally, it should be noted that the above-described embodiments are merely specific implementations of this utility model, used to illustrate the technical solution of this utility model, and not to limit it. The protection scope of this utility model is not limited thereto. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features, within the technical scope disclosed in this utility model. These modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model, and should all be covered within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. A three-section conical screw rotor, characterized in that, The three-section conical screw rotor is divided into an intake section, a compression section, and an exhaust section along the screw axis. The intake section has a uniform cross-section and a uniform pitch along the screw axis; The compression section has a variable cross-section and variable pitch along the screw axis; The exhaust section has a uniform cross-section and a uniform pitch along the screw axis; The cross-sectional width of the intake section along the screw axis is greater than the cross-sectional width of the exhaust section along the screw axis. Each segment has the same end face profile equation, which is closed by connecting the beginning and end of five curve segments. The five curve segments include the involute segment AB, the tooth tip arc segment BC, the long-amplitude outward curve segment CD, the tooth root arc segment DE, and the point conjugate curve segment EA.

2. The three-section conical screw rotor according to claim 1, characterized in that, The intake section has a cylindrical cross-section along the screw axis and is designed with a single-stage helix to meet the following conditions: 0≤τ≤ω1; ω1 = 2π; Where τ is the helix angle and ω1 is the end helix angle of the intake section.

3. The three-section conical screw rotor according to claim 1, characterized in that, The compression section has a tapered cross-section along the screw axis and is designed with a multi-stage variable helix to meet the following conditions: ω1≤τ≤ω2; ω3-ω2≥4π; Where τ is the helix angle, ω2 is the end helix angle of the compression section, and ω3 is the end helix angle of the exhaust section.

4. The three-section conical screw rotor according to claim 3, characterized in that, The angle between the side of the inverted cone and the axial direction of the screw is 1 to 6°.

5. The three-section conical screw rotor according to claim 1, characterized in that, The exhaust section has a cylindrical cross-section along the screw axis and is designed with a two-stage to four-stage helix to meet the following conditions: ω2≤τ≤ω3; ω3-ω2={4π,8π}; Where τ is the helix angle, ω2 is the end helix angle of the compression section, and ω3 is the end helix angle of the exhaust section.

6. The three-section conical screw rotor according to claim 1, characterized in that, The expressions for the five curve segments are as follows: The parametric equation of the involute segment AB is: The parametric equation for the tooth tip arc segment BC is: The parametric equation of the long-amplitude epicycloid segment CD is: The parametric equation for the tooth root arc segment DE is: The parametric equation of the conjugate curve segment EA is: In the formula, R1 represents the radius of the tooth tip arc BC; R3 represents the radius of the tooth root arc DE; R b α represents the base circle radius of the involute AB; α represents the initial angle of the involute AB; t represents the angular parameter; and β represents the preset angular offset.

7. A vacuum pump comprising a female screw rotor and a male screw rotor meshing with each other, characterized in that, Both the female screw rotor and the male screw rotor are selected from the three-section conical screw rotors as described in any one of claims 1 to 6.

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