A screw vacuum pump

Abstract

This invention provides a screw vacuum pump, belonging to the field of pump body technology. It solves the problem that existing screw vacuum pumps require increased screw length to achieve higher pumping efficiency. This screw vacuum pump includes a pump body with two rotors inside. The rotors have K helical turns, a total length of L, and helix pitches P1 to Pi from the inlet to the outlet. One rotor is left-handed, and the other is right-handed, and the two rotors mesh with each other. One rotor's end face profile rotates around its rotation center by a central angle θ. The rotor has a helical coordinate equation, and its outer circumference is formed by curves along the helix on the end face profile. This screw vacuum pump allows for adjustment of the rotor pitch according to specific requirements, achieving an optimal pitch that ensures high pumping efficiency while reducing rotor length.

Description

Technical Field

[0001] This invention belongs to the field of pump technology and relates to a screw vacuum pump. Background Technology

[0002] A screw vacuum pump is a pumping device that uses a pair of screws rotating synchronously at high speed in opposite directions within a pump casing to generate suction and exhaust. Currently, most screw rotors in screw vacuum pumps are of two types: constant pitch screws and variable pitch screws.

[0003] For constant pitch screws, machining is more convenient. However, when compressing gas, the compression ratio between each pitch must be the same. Since the volume of gas decreases as it approaches the outlet, a higher compression ratio is required. Therefore, setting the same compression ratio means that the screw needs to be longer to achieve gas compression. Variable pitch screws, on the other hand, achieve rapid compression by using a sudden change in pitch. They are formed by splicing multiple segments of equal pitch. This not only facilitates machining but also reduces the pitch of the screw near the outlet to obtain a larger compression ratio, thus achieving rapid compression of gas near the outlet.

[0004] The two types of screws mentioned above are composed of one or more equal-pitch screw sections. In actual production, gas can only be compressed in one section. During the production process, the vacuum at the pump inlet is high, and the inlet needs a large intake volume to accommodate enough gas for rapid compression. As the pressure difference near the outlet increases, the required compression ratio of the gas increases continuously rather than linearly. Therefore, using a screw with abrupt pitch means that the compression ratio cannot change continuously with the demand for gas. If the above structure is to achieve high pumping efficiency, the length of the screw still needs to be designed to be relatively long, resulting in a large overall axial length and volume of the pump body. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems in existing technologies by proposing a screw vacuum pump. The technical problem to be solved by this invention is: how to solve the problem that existing screw vacuum pumps require increasing the length of the screw to achieve higher pumping efficiency.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A screw vacuum pump includes a pump body containing two rotors. The rotors have K helical turns, a total length of L, and helical pitches from the inlet to the outlet of the rotors ranging from P1 to Pi. One rotor is left-handed, and the other is right-handed, and the two rotors mesh with each other. The profile of one rotor end face rotates about its rotation center by a central angle θ.

[0008] The equation for calculating the central angle θ is:

[0009] θ = 2Ωkt;

[0010] In the formula, t∈[0~1];

[0011] The coordinate equation of the rotor's helix is:

[0012] X(θ) = R sin θ;

[0013] Y(θ) = R cos θ;

[0014] Z(θ)=P(θ)=LA(1-t)-B(sin(90(1-t) m )) n ;

[0015] In the formula, R is the distance from any point on the end face profile to the center of rotation, L = A + B, A = KPi, where Pi is the minimum pitch of the rotor exhaust end, A ranges from 0.5L to 0.7L, taking a smaller value when the rotor compression ratio needs to be increased and a larger value when the rotor compression ratio needs to be decreased; n ranges from 20 to 80, taking a larger value when the rotor compression ratio needs to be increased and a smaller value when the rotor compression ratio needs to be decreased; m ranges from 0.3 to 0.9, when the compression ratio needs to be further adjusted, a larger value of m increases the compression ratio, and a smaller value of m decreases the compression ratio. The outer circumferential surface of the rotor is formed by rotating each segment of the curve on the end face profile along the helix.

[0016] The central angle is formed by rotating the rotor around its own axis (Z-axis) at a point on the rotor end face profile. Before the rotor is formed, the rotor end face profile and the rotor helix need to be determined. Then, the outer circumference of the rotor is formed by rotating the curves of each segment on the rotor end face profile along the helix. In order to achieve a larger suction volume at the screw inlet, the Z-axis formula of the helix allows the central angle θ to be within 180 degrees, resulting in a shorter rotor pitch. The rotor is always connected to the inlet in the first half of the rotation, which acts as a seal to ensure that the rotor pitch can obtain a larger suction volume at the inlet, effectively increasing the suction space. Therefore, the screw rotor can close the compression exhaust as early as possible, thus allowing the screw rotor of the same length to obtain a greater suction speed and effectively improve the suction efficiency. In the helix coordinate equation... The central angle θ is obtained by varying the value of the ratio variable t and the number of spiral turns k on the rotor. The overall shape and direction of the spiral are determined by the X, Y, and Z axes. The direction of the Z-axis needs to be determined based on the different screw pitches of the rotor. Therefore, the spiral algorithm on the Z-axis requires the selection of multiple fixed values ​​A, B, and n. In the Z-axis equation of this spiral, the larger the value of n, the larger the compression ratio, and the smaller the value of n, the smaller the compression ratio. When the value of n changes, it will change the screw pitches near the intake end, while the screw pitches near the exhaust end remain basically unchanged. This characteristic allows for maximizing the pumping volume while ensuring that the subsequent screw can quickly compress the gas. By adjusting the rotor screw pitch according to specific needs, the optimal screw pitch can be achieved, which ensures both high pumping efficiency and reduced rotor length.

[0017] The value of m needs to be adjusted only when further adjustment of the compression ratio of the screw rotor is required. Specifically, the compression ratio of the screw rotor increases as the value of m increases and decreases as the value of m decreases.

[0018] The aforementioned rotor outer circumference has the following advantages: 1. Reduced energy consumption of the screw pump, specifically reducing energy consumption per liter of pumped air; 2. Uniform and stable temperature rise, ensuring the thermal stability of the entire machine and improving its operational reliability; 3. Reduced noise, with a gradual increase in exhaust pressure on a flat surface, reducing the pressure difference between the screw outlet and the exhaust port, and reducing airflow pulse noise; 4. The same pumping speed can be achieved with a shorter rotor length, saving materials and space.

[0019] In the aforementioned variable pitch screw vacuum pump, when the central angle θ rotates in the opposite direction, the rotors are obtained with opposite helices, and the rotors formed by the rotation of the two helices mesh with each other.

[0020] By rotating in the opposite direction at angle θ, opposite helices can be obtained, thus allowing the rotors derived from the two opposing helices within the variable pitch screw vacuum pump to mesh with each other.

[0021] In the above-mentioned screw vacuum pump, the compression ratio of the screw rotor gradually decreases. When the number of rotor helical coils K = 5, and the sealed cavity formed by the two rotors and the pump body is isolated and closed from the air inlet, the compression ratio of each stage is: V1:V2:V3:V4.

[0022] In the aforementioned screw vacuum pump, the formula for calculating the compression power of the screw vacuum pump is: P w =S1ΔP1+……+S i ΔP i ,

[0023] In the formula, i = K-1, and K is the number of spiral turns mentioned above;

[0024] S1……S i Let ΔP1 be the geometric pumping speed of each stage of the rotor, ..., ΔP2 be the speed of each stage of the rotor. i This represents the pressure difference between each stage of the rotor.

[0025] ΔP is the pressure difference over a certain period of time. By calculating the power of the vacuum pump, the pumping speed decreases when the pressure difference is small, and the pumping speed decreases when the pressure difference near the outlet increases. This allows the screw vacuum pump to achieve high energy efficiency.

[0026] In the aforementioned screw vacuum pump, the volume of each sealed cavity formed by the rotor and the pump body when the screw vacuum pump rotates is:

[0027]

[0028] In the formula, S(θ) is the area of ​​the extraction space formed by the meshing of the two rotors at different central angles, and dθ is a variable, θ∈[a~a+4π].

[0029] The above equation is formed by integrating the volume of each sealed cavity segment after taking the area of ​​the air extraction space created by the meshing of the two existing rotors at different central angles, the derivative of the helical coordinate function and the variable dθ. The volume of the sealed cavity formed by the rotor and pump body can be quickly measured when the central angle is constantly changing.

[0030] In the aforementioned screw vacuum pump, the end face profiles and outer peripheral surfaces of the two rotors are identical, and the rotating helixes are either left-handed or right-handed.

[0031] This design makes the machining of screw vacuum pumps easier and reduces manufacturing costs.

[0032] In the screw vacuum pump described above, the value of m is 0.5.

[0033] Compared with existing technologies, this screw vacuum pump has the following advantages:

[0034] 1. The Z-axis formula of the helix allows the central angle θ to be within 180 degrees, resulting in a shorter rotor pitch. The rotor is always connected to the air inlet in the first half of the turn, which acts as a seal to ensure that the rotor pitch can obtain a larger air volume at the air inlet end, effectively increasing the air extraction space. Therefore, the screw rotor can close and enter the compression exhaust as early as possible, thus allowing the screw rotor of the same length to obtain a greater air extraction speed and improve the air extraction efficiency.

[0035] 2. Reduce the energy consumption of the screw pump, specifically by reducing the energy consumption per liter of pumped air.

[0036] 3. The temperature rise is uniform and stable, ensuring the thermal stability of the whole machine and improving the reliability of the whole machine.

[0037] 4. Reduce noise by gradually increasing exhaust pressure on flat surfaces, reducing the pressure difference between the screw outlet and the exhaust port, and reducing airflow pulse noise. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the rotor in this invention, showing a spiral line.

[0039] Figure 2 This is a front view of the rotor in this invention.

[0040] Figure 3 This is a partial structural diagram of the assembly of two rotors in this invention.

[0041] Figure 4 This is a schematic diagram of the rotor pitch varying with the central angle in this invention, taking multiple n values ​​and m being 0.5.

[0042] Figure 5 This is a schematic diagram showing the relationship between compression ratio and pitch at each stage as the central angle changes when K is 5 in this invention.

[0043] Figure 6 This is a schematic diagram of the different meshing states of the two rotors rotating from 0° to 330° in this invention.

[0044] Figure 7 This is a schematic diagram of the different meshing states of the two rotors rotating from 360° to 720° in this invention.

[0045] Figure 8 This is a schematic diagram of the rotor pitch varying with the central angle in this invention, where K is 5, A is 0.6L, n is 30, and m is 0.5.

[0046] Figure 9 This is a schematic diagram of the rotor pitch varying with the central angle in this invention, where K is 5, A is 0.6L, n is 40, and m is 0.5.

[0047] Figure 10This is a schematic diagram of the rotor pitch varying with the central angle in this invention, where K is 5, A is 0.6L, n is 50, and m is 0.5.

[0048] Figure 11 This is a schematic diagram of the rotor pitch varying with the central angle in this invention, where n is 50 and multiple m values ​​are taken.

[0049] In the diagram, 1 is the rotor; 2 is the end face profile; 3 is the helix; and 4 is the air inlet. Detailed Implementation

[0050] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0051] like Figure 1 As shown, this screw vacuum pump includes a pump body, within which two rotors 1 are mounted. The pump body structure and how to connect it to the pump body can be described using existing technology, therefore, this will not be elaborated upon further, and the accompanying drawings do not provide a schematic representation.

[0052] Specifically, such as Figure 1-11 As shown, rotor 1 has K helical turns, and the total length of rotor 1 is L. The pitch of rotor 1 from the intake end to the exhaust end is P1 to Pi respectively. The two rotors 1 are one left-handed and one right-handed, and the two rotors 1 mesh with each other. The angle of rotation of the end face profile 2 of one of the rotors 1 around the center of rotation is the central angle θ.

[0053] The equation for calculating the central angle θ is:

[0054] θ = 2Ωkt;

[0055] In the formula, t∈[0~1];

[0056] The coordinate equation of the helix 3 of rotor 1 is:

[0057] X(θ) = R sin θ;

[0058] Y(θ) = R cos θ;

[0059] Z(θ)=P(θ)=LA(1-t)-B(sin(90(1-t) m )) n ;

[0060] In the formula, R is the distance from any point on the end face profile 2 to the center of rotation, L = A + B, A = KPi, where Pi is the minimum pitch at the exhaust end of rotor 1, A ranges from 0.5L to 0.7L, taking the smaller value when increasing the compression ratio of rotor 1 and the larger value when decreasing the compression ratio of rotor 1; n ranges from 20 to 80, taking the larger value when increasing the compression ratio of rotor 1 and the smaller value when decreasing the compression ratio of rotor 1; m ranges from 0.3 to 0.9, generally taking 0.5, and when further adjustment of the compression ratio is needed, m is taken as... When the value of m is large, the compression ratio increases; when the value of m is small, the compression ratio decreases. The outer circumference of rotor 1 is formed by rotating the curves of each segment on the end face profile 2 along the spiral line 3. When the central angle θ rotates in the opposite direction, the spiral line 3 of rotor 1 is obtained in the opposite direction. The rotor 1 formed by the rotation of the two spiral lines 3 gradually decreases in compression ratio due to the meshing of the screw rotor 1. For example, when the spiral ring K of rotor 1 is 5, when the sealed cavity formed by the two spiral rotors and the pump body is isolated and closed from the air inlet 4, the compression ratio of each stage is: V1:V2:V3:V4.

[0061] The central angle is formed by rotating the rotor 1 around its own axis Z-axis at a point on the end face profile 2 of the rotor 1. Before the rotor 1 is formed, the end face profile 2 and the helix 3 of the rotor 1 need to be determined first. Then, the outer circumference of the rotor 1 is formed by rotating the curves on the end face profile 2 of the rotor 1 along the helix 3. In order to achieve a larger suction volume at the intake end of the screw, the Z-axis formula of the helix 3 can make the pitch of the rotor 1 shorter when the central angle θ is within 180 degrees. The rotor 1 is always connected to the intake port 4 in the first half of the turn, and the first half of the turn of the rotor 1 plays a sealing role to ensure that the rotor 1 pitch can obtain a larger suction volume at the intake end, effectively increasing the suction space. Therefore, the screw rotor 1 can close and enter the compression exhaust as early as possible, so that the screw rotor 1 of the same length can obtain a larger suction speed and improve the suction efficiency. In the coordinate equation, the central angle θ is obtained by the value of the ratio variable t and the change of the number of spiral turns k on rotor 1. The entire shape and direction of the spiral 3 are determined by the X-axis, Y-axis, and Z-axis. The direction of the Z-axis needs to be determined for different pitches of rotor 1. Therefore, in the Z-axis spiral 3 algorithm, multiple fixed values ​​A, B, and n need to be selected. In the Z-axis equation of this spiral 3, the larger the value of n, the larger the compression ratio, and the smaller the value of n, the smaller the compression ratio. When the value of n changes, it will change the pitches near the air inlet, while the pitches near the air outlet remain basically unchanged. This characteristic allows for maximizing the pumping volume while ensuring that the subsequent screw can quickly compress the gas. By adjusting the pitch of rotor 1 according to specific needs, the optimal pitch can be achieved, which can ensure high pumping efficiency while reducing the length of rotor 1.

[0062] The value of m is generally 0.5. The value of m needs to be adjusted only when the compression ratio of the screw rotor 1 needs to be further adjusted. Specifically, the compression ratio of the screw rotor 1 increases as the value of m increases and decreases as the value of m decreases.

[0063] The outer circumference of the rotor 1 described above has the following advantages: 1. Reduced energy consumption of the screw pump, specifically reduced energy consumption per liter of pumped air; 2. Uniform and stable temperature rise, ensuring the thermal stability of the whole machine and improving the reliability of the whole machine; 3. Reduced noise, gradually increasing exhaust pressure on a flat surface, reducing the pressure difference between the screw outlet and the exhaust port, and reducing airflow pulse noise; 4. The same pumping speed can be achieved with a shorter rotor length, saving materials and space.

[0064] The formula for calculating the compression power of a screw vacuum pump is: P w =S1ΔP1+……+S i ΔP i ,

[0065] In the formula, i = K-1, and K is the number of spiral turns mentioned above;

[0066] S1……S i Let ΔP1 be the geometric pumping speed of each stage of rotor 1, ..., ΔP i This represents the pressure difference between each stage of rotor 1.

[0067] When the rotor 1 of the vacuum pump rotates, the volume of each sealed cavity formed by the rotor and the pump body is:

[0068]

[0069] In the formula, S(θ) is the area of ​​the air extraction space formed by the meshing of the two rotors 1 at different central angles, and dθ is a variable, θ∈[0~4π].

[0070] The end face profiles 2 and outer peripheral surfaces of the two rotors 1 are identical, and the rotating helix 3 is divided into left-handed and right-handed.

[0071] like Figure 8-10 The figure shown is the coordinate diagram of a variable pitch rotor designed with K=5, A=0.6L, m=0.5, and n=30, 40, and 50 respectively in P(θ).

[0072] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A screw vacuum pump, comprising a pump body, wherein the pump body is provided with two rotors (1), characterized in that, The rotor (1) has K spiral turns, the total length of the rotor (1) is L, the pitch of the rotor (1) from the intake end to the exhaust end is P1 to Pi, the two rotors (1) are one left-handed and one right-handed respectively, and the two rotors (1) mesh with each other, the end face profile (2) of one of the rotors (1) rotates around the rotation center by a central angle θ. The equation for calculating the central angle θ is: θ = 2Ωkt; In the formula, t∈[0~1]; The coordinate equation of the helix (3) of the rotor (1) is: X(θ) = R sinθ; Y(θ) = R cosθ; Z(θ)=P(θ)=LA(1-t)-B(sin(90(1-t m )) n ; In the formula, R is the distance from any point on the end face profile (2) to the center of rotation, L = A + B, A = KPi, where Pi is the minimum pitch of the exhaust end of the rotor (1), the range of A is 0.5L to 0.7L, a smaller value is taken when the compression ratio of the rotor (1) needs to be increased, and a larger value is taken when the compression ratio of the rotor (1) needs to be decreased; the range of n is 20 to 80, a larger value is taken when the compression ratio of the rotor (1) needs to be increased, and a smaller value is taken when the compression ratio of the rotor (1) needs to be decreased; the range of m is 0.3 to 0.9, when the compression ratio needs to be further adjusted, the compression ratio increases when m is larger, and the compression ratio decreases when m is smaller. The outer circumferential surface of the rotor (1) is formed by rotating along the spiral line (3) through the curves on the end face profile (2).

2. The screw vacuum pump according to claim 1, characterized in that, When the central angle θ rotates in the opposite direction, a helix (3) opposite to that of the rotor (1) is obtained, and the rotor (1) formed by the rotation of the two helixes (3) meshes with each other.

3. The screw vacuum pump according to claim 1 or 2, characterized in that, The compression ratio of the screw rotor (1) gradually decreases. When the number of helical turns K of the rotor (1) is 5, the compression ratio of each stage is: V1:V2:V3:V4 when the sealed cavity formed by the two rotors (1) and the pump body is isolated and closed from the air inlet (4).

4. The screw vacuum pump according to claim 1 or 2, characterized in that, The formula for calculating the compression power of the screw vacuum pump is: P w =S1ΔP1+……+S i ΔP i , In the formula, i = K-1, and K is the number of spiral turns mentioned above; S1……S i Let ΔP1……ΔP be the geometric pumping speed of each stage of rotor (1). i The pressure difference is the pressure difference of each stage of the rotor (1).

5. The screw vacuum pump according to claim 1 or 2, characterized in that, When the rotor (1) of the screw vacuum pump rotates, the volume of each sealed cavity formed by the rotor (1) and the pump body is: In the formula, S(θ) is the area of ​​the air extraction space formed by the meshing of the two rotors (1) at different central angles, and dθ is a variable, θ∈[0~4π].

6. The screw vacuum pump according to claim 1 or 2, characterized in that, The end face profiles (2) and outer circumferences of the two rotors (1) are the same, and the rotating helixes (3) are divided into left-handed and right-handed.

7. The screw vacuum pump according to claim 1 or 2, characterized in that, The value of m is 0.5.

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