Variable diameter variable pitch screw vacuum pump and its rotor

Abstract

The application relates to the technical field of vacuum pumps, in particular to a variable-diameter and variable-pitch screw vacuum pump and a rotor thereof. The rotor of the variable-diameter and variable-pitch screw vacuum pump has an air inlet section, a compression and transportation section and an air outlet section. The air outlet section satisfies that the product of the rotor tooth tip circle radius at a certain rotation angle and the pitch thereof is within the range of 95% to 105% of the product of the rotor tooth tip circle radius at the position of 4pi after the rotation angle and the pitch thereof. Thus, the compression volumes of adjacent periods in the air outlet section are approximately equal, so that the air outlet pressure of the air outlet section is relatively more stable, and the air outlet noise is reduced to a certain extent.

Description

Technical Field

[0001] This application relates to the field of vacuum pump technology, specifically to a variable diameter, variable pitch screw vacuum pump and its rotor. Background Technology

[0002] When achieving a high compression ratio, the rotor of a constant-diameter variable-pitch screw vacuum pump is relatively large, with thinner teeth in the exhaust section, making machining at the tooth root position more difficult, and resulting in poorer sealing between the tooth tip and the pump casing inner wall. Compared to a constant-diameter variable-pitch screw vacuum pump rotor, a variable-diameter variable-pitch screw vacuum pump rotor can achieve a larger compression ratio within the same volume, but the exhaust noise is also relatively higher. Summary of the Invention

[0003] This application provides a variable diameter, variable pitch screw vacuum pump and its rotor to solve the problem of excessive exhaust noise in variable diameter, variable pitch screw vacuum pumps.

[0004] According to one aspect of this application, one embodiment provides a variable diameter, variable pitch screw vacuum pump rotor, having an inlet section, a compression and transport section, and an exhaust section, wherein the exhaust section satisfies:

[0005] (1-5%)R a 2 (θ r +4π)P(θ r +4π)≤R a 2 (θ r )P(θ r )≤(1+5%)R a 2 (θ r +4π)P(θ r +4π),

[0006] Among them, R a (θ r ) represents the rotation angle θ r The rotor tooth tip circle radius at the angular position, P(θ) r ) represents the rotation angle θ r The rotor pitch at the location, R a (θ r +4π) is the rotation angle (θ) r The rotor tooth tip circle radius at position +4π, P(θ) r +4π) is the rotation angle (θ) r The rotor pitch at position +4π) and θ r This is one of the rotation angles within the exhaust section.

[0007] In an optional embodiment, the exhaust section further satisfies:

[0008] (1-3%)R a 2 (θ r +4π)P(θ r +4π)≤R a 2 (θ r )P(θ r )≤(1+3%)R a 2 (θ r +4π)P(θ r +4π).

[0009] In an optional embodiment, the exhaust section further satisfies:

[0010] (1-1%)R a 2 (θ r +4π)P(θ r +4π)≤R a 2 (θ r )P(θ r )≤(1+1%)R a 2 (θ r +4π)P(θ r +4π).

[0011] In an alternative embodiment, the θ r Satisfying θ r =2nπ, where n is an odd number greater than or equal to 3.

[0012] In an optional embodiment, the slopes of the pitch variation curve P(θ) of the variable diameter, variable pitch screw vacuum pump rotor at the starting point pitch P1 of the intake section, the starting point pitch P2 of the compression and transport section, and the starting point pitch P3 of the exhaust section are all 0, and the pitch variation curve P(θ) includes the pitch variation curve P of the intake section. a (θ), the pitch variation curve P of the compressed transport section b (θ) and the pitch variation curve P of the exhaust section c (θ);

[0013] The pitch variation curve P of the intake section a (θ) consists of two curves with radii of curvature r at both ends. a The intake section's pitch variation curve P is composed of a curve and a straight line tangent to the curves at the beginning and end. a The expression for (θ) is:

[0014]

[0015] Wherein, θ1 corresponds to the starting point of the intake section, and θ1=0; θ2 is the rotation angle corresponding to P2; Δθ1 is the rotation angle range corresponding to the first or last curve segment; Δθ2 is the rotation angle range corresponding to the straight line in the middle section; and ΔP1 is the pitch value of the first or last curve segment within the range of Δθ1. The slope angle is the angle when the middle section is in a straight upward state.

[0016] The pitch variation curve P of the compressed transport section b (θ) consists of two curves with radii of curvature r at both ends. b The pitch variation curve P of the compressed transport section is composed of a curve and a straight line tangent to the curves at the beginning and end. b The expression for (θ) is:

[0017]

[0018] Where θ3 is the rotation angle corresponding to P3, Δθ3 is the angle range corresponding to the first or last curve segment, Δθ4 is the angle range corresponding to the straight line in the middle segment, and ΔP3 is the pitch value of the first or last curve segment within the angle range of Δθ3. It represents the slope angle when the middle segment is in a straight downward state.

[0019] In an optional embodiment, the exhaust section pitch variation curve P c The expression for (θ) is:

[0020]

[0021] Where θ4 is the rotation angle corresponding to the end of the exhaust section. The slope angle is the curve angle of the exhaust section pitch change when it is in the rising state.

[0022] In one optional embodiment, the outer diameter of the variable diameter, variable pitch screw vacuum pump rotor changes linearly at an angle α from the inlet section to the exhaust section, and the rotor's tooth tip circle radius R is at a rotation angle θ. a (θ) is:

[0023] R a (θ)=R a (0)-L(θ)tan(α),

[0024] Among them, R a (0) is the initial tooth tip circle radius of the rotor in the intake section, and L(θ) is the axial position corresponding to the rotation angle θ. L(θ) is:

[0025]

[0026] in, This indicates that the rotor rotation angle is The corresponding pitch.

[0027] In one optional embodiment, the end face profile of the variable diameter and variable pitch screw vacuum pump rotor includes a tooth tip arc curve AB, an involute curve BC, a rounded curve CD, a tooth root arc curve DE, and a long-amplitude epicycloid curve EF.

[0028] The radius R of the rotor's tooth root circle when rotating at an angle θ b (θ) is:

[0029] R b (θ)=R b (0)+L(θ)tan(α),

[0030] Among them, R b (0) is the initial root circle radius of the rotor in the intake section; or,

[0031] The radius R of the rotor's tooth root circle when rotating at an angle θ b (θ) is:

[0032] R b (θ)=AR a (θ),

[0033] Where A is the center distance of the rotor of the variable diameter and variable pitch screw vacuum pump;

[0034] The equation of the tooth tip arc curve AB is:

[0035]

[0036] Where x(θ,t) and y(θ,t) are the coordinate values ​​of the tooth tip arc curve AB in the rectangular coordinate system, and t is the angle parameter variable in the rectangular coordinate system;

[0037] The equation of the involute curve BC is:

[0038]

[0039] Where x(θ,t) and y(θ,t) are the coordinate values ​​of the involute curve BC in the rectangular coordinate system, σ(θ) is the unfolding angle of the involute curve BC at a rotation angle θ, and the base circle radius R of the involute curve BC is... c (θ) satisfies the following relationship:

[0040] R c0 (θ)<R c (θ)≤R b (θ),

[0041] Among them, R c0(θ) is the minimum critical base circle radius of the involute curve BC, R c0 (θ) satisfies the following relationship:

[0042]

[0043] Where σ0(θ) is the base circle radius R. c0 The angle of development of the involute curve BC when (θ) is given;

[0044] The rounded curve CD is tangent to both the involute curve BC and the tooth root arc curve DE. The equation of the rounded curve CD is:

[0045]

[0046] Where x(θ,t) and y(θ,t) are the coordinate values ​​of the rounded curve CD in the rectangular coordinate system, and R P Let R be the pitch circle radius of the end face profile, and let R be the pitch circle radius. P Let A be half the center distance A of the variable diameter, variable pitch screw vacuum pump rotor, and let τ(θ) be the phase angle of the rounded curve CD at the rotation angle θ. The equation for τ(θ) is:

[0047]

[0048] The equation of the tooth root arc curve DE is:

[0049]

[0050] Where x(θ,t) and y(θ,t) are the coordinate values ​​of the tooth root arc curve DE in the rectangular coordinate system;

[0051] The equation for the long-amplitude epicycloid curve EF is:

[0052]

[0053] Where x(θ,t) and y(θ,t) are the coordinate values ​​of the long-amplitude epicycloid curve EF in the rectangular coordinate system.

[0054] In an optional embodiment, the base circle radius R of the involute curve BC c The aspect ratio σ(θ) and the aspect ratio σ(θ) corresponding to the involute curve BC at the rotor rotation angle θ are:

[0055] R c (θ)=R b (θ)-γ

[0056]

[0057] Where γ is a constant, and γ satisfies the following relationship:

[0058] 0 < γ < R b (θ)-R c0 (θ).

[0059] In an optional embodiment, the end face profile of the main rotor further includes a chamfer curve FA, the equation of which is:

[0060]

[0061] Where x(θ,t) and y(θ,t) are the coordinate values ​​of the chamfered curve FA in the rectangular coordinate system, and β is the phase angle of the chamfered curve FA.

[0062] According to one aspect of this application, one embodiment provides a variable diameter variable pitch screw vacuum pump, including a pump housing and a variable diameter variable pitch screw vacuum pump rotor as described in any of the above claims, wherein the variable diameter variable pitch screw vacuum pump rotor is rotatably mounted within the pump housing.

[0063] According to the variable diameter and variable pitch screw vacuum pump and its rotor in the above embodiment, the variable diameter and variable pitch screw vacuum pump rotor has an inlet section, a compression and transport section, and an exhaust section. The exhaust section satisfies the following: the product of the rotor tooth tip circle radius and its pitch at a certain rotation angle is within 95% to 105% of the product of the rotor tooth tip circle radius and its pitch at a position 4π after that rotation angle, so that the compression volume of adjacent cycles in the exhaust section is approximately equal, thereby making the exhaust pressure in the exhaust section relatively more stable, and thus reducing exhaust noise to a certain extent. Attached Figure Description

[0064] Figure 1 This is a partial structural schematic diagram of the rotor of a variable diameter, variable pitch screw vacuum pump in one embodiment.

[0065] Figure 2 This is a schematic diagram of the enclosed gas structure of the rotor of a variable diameter and variable pitch screw vacuum pump in a 4π segment, where the gray area in the figure represents the enclosed gas region.

[0066] Figure 3 This is a schematic diagram of the axial end face structure of the rotor of a variable diameter and variable pitch screw vacuum pump in one embodiment;

[0067] Figure 4 In one embodiment, the variable diameter, variable pitch screw vacuum pump rotor operates at intervals within one cycle. A schematic diagram of the gas distribution structure, with the cross-sectional areas in the diagram indicating the gas distribution regions;

[0068] Figure 5 This is a schematic diagram of the end face profile structure of a variable diameter, variable pitch screw vacuum pump rotor in one embodiment;

[0069] Figure 6 This is a schematic diagram of the end face profile structure of the variable diameter and variable pitch screw vacuum pump rotor when the value of γ is different in some embodiments.

[0070] Figure 7 This is a partial structural schematic diagram of the end face profile of the variable diameter and variable pitch screw vacuum pump rotor when the value of β is different in some embodiments;

[0071] Figure 8 This is a graph showing the pitch variation of the rotor of a variable diameter, variable pitch screw vacuum pump in the inlet section, as described in one embodiment.

[0072] Figure 9 This is a graph showing the pitch variation of the rotor of a variable diameter, variable pitch screw vacuum pump in one embodiment.

[0073] In the diagram: The dashed lines and dotted lines in the attached diagram are auxiliary lines for easy identification. Detailed Implementation

[0074] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments. In different embodiments, similar elements are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the present application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to the present application are not shown or described in the specification. This is to avoid obscuring the core parts of the present application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0075] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments, and the operational steps involved in each embodiment can also be rearranged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the specification and drawings are only for clearly describing a particular embodiment and do not imply that they represent the necessary components and / or order.

[0076] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages).

[0077] This application provides a variable diameter, variable pitch screw vacuum pump rotor, which is rotatably mounted in the pump casing of the variable diameter, variable pitch screw vacuum pump. The compression volumes of adjacent cycles in the exhaust section of the variable diameter, variable pitch screw vacuum pump rotor are approximately equal, thereby making the exhaust pressure in the exhaust section relatively more stable and thus reducing exhaust noise to a certain extent.

[0078] The variable diameter, variable pitch screw vacuum pump rotor (hereinafter referred to as the rotor) of this application is described in reference. Figures 1 to 4 The pump consists of a main rotor and a driven rotor that mesh with each other. The main rotor and the driven rotor have the same and conjugate end face profiles, and the pitch variation curves of the main rotor and the driven rotor are the same. The rotor is rotatably mounted in the pump casing. The gap between the rotor tooth tip and the pump casing is small and constant. The gap space between two adjacent teeth in the axial direction of the rotor and between the tooth root in the radial direction and the pump casing is the space in which the variable diameter and variable pitch screw vacuum pump rotor transports gas.

[0079] The rotor, from the intake side to the exhaust side, consists of an intake section, a compression and transport section, and an exhaust section. Please refer to [reference needed]. Figure 3 and Figure 4 The cross-section of the gas delivery space along the rotor axis is at least a portion of the area enclosed by the main rotor, the driven rotor, and the pump casing. This portion of the area extends axially along the rotor to form the gas delivery space. The rotation angle of the end face profiles of the main rotor and the driven rotor along the central axis of their respective screws is simply referred to as the rotor rotation angle. The cross-sectional area of ​​the gas delivery space is different at different rotor rotation angles, and the cross-sectional shape of the gas delivery space can change regularly with the rotor rotation angle. The gas delivery space within one cycle can form a sealed space. The rotor rotation angle of this cycle is 4π, that is, the rotor rotation angle in each cycle is 4π. The cross-sectional shape of the gas delivery space at the corresponding rotation angle in each cycle, that is, at the corresponding point with the same rotation angle between the starting point of each cycle and the starting point of each cycle, is the same. Alternatively, in other embodiments, it can be considered that the rotor rotation angle within one cycle can be less than 4π or greater than 4π, and the changing patterns of the gas delivery space in two adjacent cycles are different.

[0080] The variable diameter, variable pitch screw vacuum pump rotor of this application can be configured with an exhaust section that satisfies the following relationship:

[0081] (1-5%)R a 2 (θ r +4π)P(θ r +4π)≤R a 2 (θ r )P(θ r )≤(1+5%)R a 2 (θ r +4π)P(θr +4π),

[0082] Where, θ r R is one of the rotation angles of the exhaust section, which can be any rotation angle within the exhaust section. a (θ r ) represents the rotation angle θ r The rotor tooth tip circle radius at the angular position, and the rotation angle θ r The product of the square of the rotor tooth tip circle radius at the specified location and π can be approximated by the rotation angle θ. r The cross-sectional area of ​​the gas transport space at the location, P(θ) r ) represents the rotation angle θ r Rotor pitch at position, rotation angle θ r The product of the cross-sectional area of ​​the gas delivery space at the location and the pitch can be used as an approximation of the rotation angle θ. r The actual volume of gas delivered at the location.

[0083] Similarly, R a (θ r +4π) is the rotation angle (θ) r The rotor tooth tip circle radius at position +4π, P(θ) r +4π) is the rotation angle (θ) r The rotor pitch at position +4π, and the rotation angle (θ) r The product of the gas delivery space cross-sectional area and the pitch at the +4π position can be used as an approximation of the rotation angle (θ). r The actual volume of gas transported at the +4π position.

[0084] In some embodiments, the above formula can be understood as the rotation angle of one cycle being 4π, and the change pattern of the cross-sectional shape of the transport gas space in two adjacent cycles being the same. The volume of the transport gas space at the corresponding rotation angle in two adjacent cycles is approximately equal. The corresponding rotation angle can be understood as the position where the rotation angle between the gas transport direction and the starting point of each cycle is the same. The above formula can be approximately described as the product of the rotor tooth tip circle radius and its pitch at a certain rotation angle in the previous cycle being within 95% to 105% of the product of the rotor tooth tip circle radius and its pitch at the corresponding rotation angle in the next cycle. For example, the percentage between the product of the rotor tooth tip circle radius and its pitch at a certain rotation angle in the previous cycle and the product of the rotor tooth tip circle radius and its pitch at the corresponding rotation angle in the next cycle can be 95% or 105%.

[0085] In some embodiments, the exhaust section may also satisfy the following relationship:

[0086] (1-3%)R a 2 (θr +4π)P(θ r +4π)≤R a 2 (θ r )P(θ r )≤(1+3%)R a 2 (θ r +4π)P(θ r +4π);

[0087] This can be understood as a rotation angle of 4π in one cycle. Within the exhaust section, two adjacent cycles satisfy the condition that the product of the rotor tooth tip circle radius and its pitch at a certain rotation angle position in the previous cycle is within the range of 97% to 103% of the product of the rotor tooth tip circle radius and its pitch at the corresponding rotation angle in the next cycle. This range is a range that further and relatively better achieves the same volume of the exhaust section. For example, the percentage between the product of the rotor tooth tip circle radius and its pitch at a certain rotation angle in the previous cycle and the product of the rotor tooth tip circle radius and its pitch at the corresponding rotation angle in the next cycle can be 97% or 103%.

[0088] In other embodiments, the percentage between the product of the rotor tooth tip circle radius and its pitch at a certain rotation angle in the previous cycle and the product of the rotor tooth tip circle radius and its pitch at the corresponding rotation angle in the next cycle can be set to 96% or 104%.

[0089] In some embodiments, the following relationship can also be satisfied within the exhaust section:

[0090] (1-1%)R a 2 (θ r +4π)P(θ r +4π)≤R a 2 (θ r )P(θ r )≤(1+1%)R a 2 (θ r +4π)P(θ r +4π);

[0091] This can be understood as a rotation angle of 4π in one cycle. Within the exhaust section, two adjacent cycles satisfy the condition that the product of the rotor tooth tip circle radius and its pitch at a certain rotation angle position in the previous cycle is within 99% to 101% of the product of the rotor tooth tip circle radius and its pitch at the corresponding rotation angle in the next cycle. This range is a further step and relatively easier to achieve an equal volume range for the exhaust section. For example, the product of the rotor tooth tip circle radius and its pitch at a certain rotation angle in the previous cycle is set to be equal to the product of the rotor tooth tip circle radius and its pitch at the corresponding rotation angle in the next cycle.

[0092] In other embodiments, the percentage between the product of the rotor tooth tip circle radius and its pitch at a certain rotation angle in the previous cycle and the product of the rotor tooth tip circle radius and its pitch at the corresponding rotation angle in the next cycle can be set to 98% or 102%.

[0093] In the above-mentioned exhaust section, the rotation angle θ r The product of the square of the rotor tooth tip circle radius at the given location and π is approximately equal to the rotation angle θ. r The cross-sectional area of ​​the gas delivery space at the location is determined in order to reduce the rotation angle θ. r The product of the square of the rotor tooth tip circle radius at the location and π, and the rotation angle θ r For the difference between the cross-sectional areas of the gas delivery spaces at different locations, please refer to... Figure 4 The rotation angle for one cycle is 4π, and θ is set. r The rotation angle θ is set at the position with the largest cross-sectional area of ​​the gas delivery space in each cycle. r = 2nπ, where n is an odd number greater than or equal to 3, that is, within a period of rotation angle ranging from 4π to 8π, θ r The angle is between 4π and 8π, i.e., θ. r For 6π, within a period of rotation angle ranging from 8π to 12π, θ r The value is 10π, which further ensures that the exhaust section of the variable diameter, variable pitch screw vacuum pump has the same volume.

[0094] In some embodiments, please refer to Figure 1 and Figure 2 The outer diameters of both the main rotor and the driven rotor change linearly from the intake section to the exhaust section at a fixed angle α. The tooth tip circle radius R of the rotor is at the rotation angle θ. a (θ) is:

[0095] R a (θ)=R a (0)-L(θ)tan(α),

[0096] Among them, R a (0) is the initial tip circle radius of the rotor in the intake section, Ra (0) and α can both be measured directly or indirectly, or R a (0) and α can also be determined in advance during the design phase. To ensure that the rotor has a high compression capacity, α can be set to a value in the range of 2.5° to 5°. For example, in one embodiment, α can be 3.5°. L(θ) is the axial position corresponding to the rotation angle θ. This axial position is related to the pitch, and the relationship is as follows:

[0097]

[0098] in, This indicates that the rotor rotation angle is The corresponding pitch.

[0099] In some embodiments, please refer to Figure 1 , Figure 2 and Figure 8 , Figure 9 The rotor pitch variation curve P(θ) with rotation angle θ includes the pitch variation curve P of the intake section. a (θ), Pitch variation curve of the compressed transport section b (θ) and the pitch variation curve P of the exhaust section c (θ); The pitch variation curve P(θ) is set using an approximate N-shaped curve, and the pitch variation curve P in the intake section is... a (θ) Overall, the pitch variation curve of the compression transport section gradually increases with the rotation angle. b (θ) Overall, the pitch change curve of the exhaust section gradually decreases with the rotation angle. c (θ) generally increases gradually with the rotation angle.

[0100] In one embodiment, the rotor intake section starts with a rotation angle θ1 = 0 and a pitch P1; the compression and transport section starts with a rotation angle θ2 and a pitch P2; the exhaust section starts with a rotation angle θ3 and a pitch P3; and the exhaust section ends with a rotation angle θ4 and a pitch P4. Furthermore, the slopes of the pitch curves at rotation angles θ1, θ2, and θ3 in the corresponding pitch variation curves are all 0. Please refer to [reference needed]. Figure 8 P pitch variation curve of the intake section a (θ) consists of two curves with radii of curvature r at both ends. a The curve is composed of the curve and the straight line tangent to the first and last curves in the middle. O1 and O2 are the center points of the first and last curves, respectively. The pitch change curve P of the intake section is... a The expression for (θ) is:

[0101]

[0102] Wherein, Δθ1 is the rotation angle range corresponding to the first or last curve segment, Δθ2 is the rotation angle range corresponding to the straight line in the middle segment, and ΔP1 is the pitch value of the first or last curve segment varying within the range of Δθ1. The slope angle is the angle when the middle segment is in a straight upward state.

[0103] Please refer to Figure 9 The pitch variation curve P of the compressed transport section b (θ) consists of two curves with radii of curvature r at both ends. b The curve P, consisting of the curve and the straight line tangent to the curves at the beginning and end, represents the pitch variation curve of the compressed transport section. b The expression for (θ) is:

[0104]

[0105] Wherein, Δθ3 is the rotation angle range corresponding to the first or last curve segment, Δθ4 is the rotation angle range corresponding to the straight line in the middle segment, and ΔP3 is the pitch value of the first or last curve segment varying within the range of Δθ3. The slope angle is the angle of the middle section when it is in a straight downward state.

[0106] In some embodiments, the exhaust section pitch variation curve P c (θ) represents a structure similar to the intake section pitch variation curve, such as the exhaust section pitch variation curve P. c (θ) consists of two curves with constant radii of curvature and a straight line tangent to the first and last curves in the middle; or the exhaust pitch variation curve P can be simplified. c The setting of (θ) allows you to set the exhaust section pitch variation curve P. c (θ) represents a linear structure, such as the exhaust section pitch variation curve P. c The expression for (θ) is:

[0107]

[0108] in, The slope angle of the exhaust section pitch change curve during its upward phase.

[0109] The pitch variation curve adopts an N-shaped structure, which not only facilitates pitch setting at various rotation angle positions, but also helps to make the compression volume of adjacent cycles in the exhaust section approximately equal, thereby reducing exhaust noise to a certain extent.

[0110] In some embodiments, the pitch values ​​P1, P2, P3, and P4 mentioned above correspond to the rotation angles θ2, θ3, and θ4, and the radius of curvature r of the first and last curves in each pitch variation curve segment. a rb These are all preset values ​​initially defined at the beginning of the design, and can be defined as θ4-θ3≥2π, r a <r b To meet the requirement of low rotor power consumption, the above pitch value can be set to satisfy P3 < P1 ≤ P4 < P2.

[0111] Specifically, in one embodiment, α is initially defined as 3.5°, R a (0)=100mm, P1=70mm, P2=82mm, P3=38mm, P4=75mm, θ2=8π, θ3=40π, θ4=48π, r a =0.5π, r b =2.8π, the variable diameter and variable pitch screw vacuum pump rotor obtained by using the above defined parameters satisfies the condition that the product of the rotor tooth tip circle radius and its pitch at a certain rotation angle in the exhaust section is within 95% to 105% of the product of the rotor tooth tip circle radius and its pitch at 4π after that rotation angle; and the rotor pitch variation curve is parametrically designed, which not only achieves the same volume of the exhaust section, but also makes it easy to control the pressure and temperature of the gas in the exhaust section, reduce rotor exhaust noise, and through a suitable pump casing heat exchange scheme, it is also easier to control the gap of the exhaust section, thereby improving the overall performance of the variable diameter and variable pitch screw vacuum pump.

[0112] For the rotor end face profile, please refer to some embodiments. Figures 3 to 7 The rotor's end face profile includes the tooth tip arc curve AB, the involute curve BC, the fillet curve CD, the tooth root arc curve DE, and the long-amplitude epicycloid curve EF; the equation of the tooth tip arc curve AB is:

[0113]

[0114] Where x(θ,t) and y(θ,t) are the coordinate values ​​of the tooth tip arc curve AB in the rectangular coordinate system, the plane of which the rectangular coordinate system is located is parallel to the axial end face of the rotor, and t is the angle parameter variable in the rectangular coordinate system;

[0115] The equation of the involute curve BC is:

[0116]

[0117] Where x(θ,t) and y(θ,t) are the coordinate values ​​of the involute curve BC in the aforementioned rectangular coordinate system, and σ(θ) is the unfolding angle of the involute curve BC at a rotation angle θ, or it can be understood as the phase angle of the starting point of the involute curve BC in the aforementioned rectangular coordinate system; R c (θ) is the base circle radius of the involute curve BC. By changing R... c(θ) can change the area utilization rate of the rotor end face profile, thereby changing the volume of gas transported at the corresponding position, R c (θ) can be continuously varied, or it can be varied in segments within different rotation angle ranges as required. However, in order to ensure that the end face profile can close normally, R c (θ) satisfies the following relationship:

[0118] R c0 (θ)<R c (θ)≤R b (θ),

[0119] Among them, R c0 (θ) is the minimum critical base circle radius of the involute curve BC, R b (θ) is the radius of the tooth root circle when the rotor rotation angle is θ.

[0120] In some embodiments, R can be determined by the following relationship: c0 The values ​​of (θ):

[0121]

[0122] In the formula, σ0(θ) is the base circle radius R. c0 The angle of development of the involute curve BC when (θ) is given.

[0123] In some embodiments, the rotor's tooth root circle radius R is [value missing] when rotating by an angle θ. b (θ) is:

[0124] R b (θ)=R b (0)+L(θ)tan(α),

[0125] Among them, R b (0) is the initial root circle radius of the rotor in the intake section, R b (0) Can be measured directly or indirectly, or R b (0) It can also be determined in advance at the beginning of the design.

[0126] Or the rotor's tooth root circle radius R when rotating at angle θ. b (θ) can also be determined by the following formula:

[0127] R b (θ)=AR a (θ),

[0128] Where A is the center distance of the rotor, which can be measured directly or indirectly, or it can be determined in advance at the beginning of the design.

[0129] In one embodiment, A = 150 mm, R a(0) = 100mm, R b (0) = 50mm.

[0130] In some embodiments, the base circle radius R of the involute curve BC is... c (θ), please refer to Figure 6 The base circle radius R of the involute curve BC c The aspect ratio σ(θ) and the involute curve BC at a rotor rotation angle θ can also be:

[0131]

[0132] Among them, R P Let R be the pitch circle radius of the end face profile, and let R be the pitch circle radius. P The center distance A of the variable diameter, variable pitch screw vacuum pump rotor is half of the total distance, such as R. P It can be 75mm; γ is a constant, and γ satisfies the following relationship:

[0133] 0 < γ < R b (θ)-R c0 (θ)

[0134] Please continue to refer to this. Figure 6 γ can be 0, 10 mm, or even 20 mm. Figure 6 The image shows the different shapes of the end face profile corresponding to different values ​​of γ. Figure 6 As can be seen, different γ values ​​result in different areas formed by the rotor's closed end face profile, which in turn affects the gas volume inside the variable diameter, variable pitch screw vacuum pump.

[0135] In some embodiments, please continue to refer to Figures 3 to 7 The rounded curve CD is essentially a long-amplitude epicycloid. The rounded curve CD is tangent to both the involute curve BC and the tooth root arc curve DE. The equation of the rounded curve CD is:

[0136]

[0137] Where x(θ,t) and y(θ,t) are the coordinate values ​​of the rounded curve CD in the above rectangular coordinate system, and τ(θ) is the phase angle of the rounded curve CD at a rotation angle θ. The equation of τ(θ) is:

[0138]

[0139] The equation of the tooth root arc curve DE is:

[0140]

[0141] Where x(θ,t) and y(θ,t) are the coordinate values ​​of the tooth root arc curve DE in the above rectangular coordinate system;

[0142] The equation for the long-amplitude epicycloid curve EF is:

[0143]

[0144] Where x(θ,t) and y(θ,t) are the coordinate values ​​of the long-amplitude epicycloid curve EF in the above rectangular coordinate system.

[0145] The end face profile structure of the rotor can be determined by combining the equations of the tooth tip arc curve AB, involute curve BC, rounded curve CD, tooth root arc curve DE, and long-amplitude epicycloid curve EF in the above embodiments with the selected parameter values.

[0146] In some embodiments, the rotor end face profile may further include a chamfer curve FA. The chamfer curve FA is essentially a long-amplitude epicycloid, which can be obtained by rotating a long-amplitude epicycloid curve EF symmetrically around the rotor axis by a certain angle. The equation of the chamfer curve FA is:

[0147]

[0148] Where x(θ,t) and y(θ,t) are the coordinate values ​​of the chamfer curve FA in the aforementioned rectangular coordinate system, and β is the phase angle of the chamfer curve FA, which can be understood as the phase angle of the starting point of the chamfer curve FA in the rectangular coordinate system. By changing the value of β, the length of the chamfer curve FA can be changed; β can be 1°, 2°, or 5°. Figure 7 The chamfer curve FA has different directions and shapes when β takes different values. The larger the value of β, the longer the length of the chamfer curve FA, and the shorter the corresponding long-amplitude epicycloid curve EF. In order to meet the processing conditions, the length of the chamfer curve FA needs to be in the range of 0.4mm to 1.5mm. This can improve the rotor's ability to adapt to working environments containing large particulate impurities and enhance the ability of the process medium to prevent backflow.

[0149] This application also provides a variable diameter, variable pitch screw vacuum pump, which includes a pump housing and a variable diameter, variable pitch screw vacuum pump rotor as described in any of the above embodiments. The variable diameter, variable pitch screw vacuum pump rotor is rotatably mounted in the pump housing.

[0150] The above examples illustrate this application only to aid in understanding the solutions presented and are not intended to limit the scope of this application. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the ideas presented.

Claims

1. A variable diameter, variable pitch screw vacuum pump rotor, comprising an inlet section, a compression and conveying section, and an exhaust section, characterized in that, The pitch variation curve of the rotor of the variable diameter, variable pitch screw vacuum pump Including the pitch variation curve of the exhaust section The exhaust section pitch variation curve The expression is: ， in, The pitch at the starting point of the exhaust section is... for The corresponding rotation angle, This represents the rotation angle corresponding to the end of the exhaust section. The slope angle of the exhaust section pitch change curve during its upward state; The exhaust section satisfies: ， in, Rotation angle The rotor tooth tip circle radius at the location. Rotation angle The rotor pitch at the location, Rotation angle The rotor tooth tip circle radius at the location. Rotation angle The rotor pitch at the location, and This is one of the rotation angles within the exhaust section.

2. The variable diameter, variable pitch screw vacuum pump rotor as described in claim 1, characterized in that, The exhaust section also satisfies: 。 3. The variable diameter, variable pitch screw vacuum pump rotor as described in claim 1, characterized in that, The exhaust section also satisfies: 。 4. The variable diameter, variable pitch screw vacuum pump rotor as described in claim 1, characterized in that, The satisfy ,in It is an odd number greater than or equal to 3.

5. The variable diameter, variable pitch screw vacuum pump rotor as described in any one of claims 1 to 4, characterized in that, The pitch variation curve of the rotor of the variable diameter, variable pitch screw vacuum pump The starting pitch of the intake section described in the text The starting pitch of the compressed transport section The starting point pitch of the exhaust section The slope at each point is 0, and the pitch variation curve is... It also includes the pitch variation curve of the intake section. and the pitch variation curve of the compressed transport section ; The pitch variation curve of the intake section The first and last two radii of curvature are both The pitch variation curve of the intake section is composed of a curve and a straight line tangent to the curves at the beginning and end. The expression is: ， in, Corresponding to the starting point of the intake section, and ; for The corresponding rotation angle, This refers to the range of rotation angles corresponding to the first or last segment of the curve. This represents the range of rotation angles corresponding to the middle straight segment. For the first or last segment of the curve Pitch values ​​varying within a range The slope angle is the angle when the middle section is in a straight upward state. The pitch variation curve of the compressed transport section The first and last two radii of curvature are both The pitch variation curve of the compressed transport section is formed by the curve and the straight line tangent to the curve at the beginning and end. The expression is: ， in, for The corresponding rotation angle, This refers to the angle range corresponding to the first or last segment of the curve. This represents the range of angles corresponding to the middle straight segment. For the first or last segment of the curve Pitch values ​​varying within the angular range, It represents the slope angle when the middle segment is in a straight downward state.

6. The variable diameter, variable pitch screw vacuum pump rotor as described in any one of claims 1 to 4, characterized in that, The outer diameter of the variable diameter, variable pitch screw vacuum pump rotor changes from the inlet section to the exhaust section. Angle linear change, rotation angle The tooth tip circle radius of the rotor for: ， in, The initial tooth tip circle radius of the rotor in the intake section is [missing information]. Rotation angle The corresponding axial position at that time for: ， in, This indicates that the rotor rotation angle is The corresponding pitch.

7. The variable diameter, variable pitch screw vacuum pump rotor as described in claim 6, characterized in that, The end face profile of the variable diameter, variable pitch screw vacuum pump rotor includes the tooth tip arc curve. Involute curve , rounded curve Tooth root arc curve and long epicycloid curve ; Rotation angle The root circle radius of the rotor for: ， in, The initial root circle radius of the rotor in the intake section; or, Rotation angle The root circle radius of the rotor for: ， in, The center distance of the rotor of the variable diameter, variable pitch screw vacuum pump; The tooth tip arc curve The equation is: ， in, , The tooth tip arc curve Coordinates in a Cartesian coordinate system These are angular parameter variables in a Cartesian coordinate system. The involute curve The equation is: ， in, , The involute curve The coordinate values ​​in the Cartesian coordinate system The involute curve rotation angle The corresponding development angle; the involute curve base circle radius The following relationship must be satisfied: ， in, The involute curve The minimum critical base circle radius, The following relationship must be satisfied: ， in, For a base circle radius of The involute curve described above Corresponding angle; The rounded curve respectively with the involute curve and the tooth root arc curve Tangent, the rounded curve The equation is: ， in, , For the rounded curve The coordinate values ​​in the Cartesian coordinate system Let be the pitch circle radius of the end face profile, and let the pitch circle radius be... The center distance of the rotor of the variable diameter, variable pitch screw vacuum pump Half of For the rounded curve rotation angle Phase angle at time, The equation is: ； The tooth root arc curve The equation is: ， in, , The tooth root arc curve The coordinate values ​​in the Cartesian coordinate system; The long-amplitude epicycloid curve The equation is: ， in, , The long-amplitude epicycloid curve The coordinate values ​​in the Cartesian coordinate system.

8. The variable diameter, variable pitch screw vacuum pump rotor as described in claim 7, characterized in that, The involute curve base circle radius With the involute curve Rotor rotation angle The corresponding angle of time for: ， in, It is a constant. The following relationship must be satisfied: 。 9. The variable diameter, variable pitch screw vacuum pump rotor as described in claim 7, characterized in that, The end face profile of the variable diameter, variable pitch screw vacuum pump rotor also includes a chamfered curve. The chamfer curve The equation is: ， in, , The chamfer curve The coordinate values ​​in the Cartesian coordinate system The chamfer curve The phase angle.

10. A variable diameter, variable pitch screw vacuum pump, characterized in that, The pump includes a pump housing and a variable diameter, variable pitch screw vacuum pump rotor as described in any one of claims 1 to 9, wherein the variable diameter, variable pitch screw vacuum pump rotor is rotatably mounted within the pump housing.

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