Double-screw pressurizing vacuum pump and screw rotor thereof

Abstract

The screw rotor comprises a rod body, the rod body sequentially comprises a first rod body section, a middle section and a second rod body section in the axial direction, and the first rod body section, the middle section and the second rod body section are arranged on the rod body. The first rod body section is provided with three first-class spiral grooves extending in the axial direction, and the second rod body section is provided with three second-class spiral grooves extending in the axial direction. The first spiral groove axially penetrates through the first rod body section; and the second spiral groove axially penetrates through the second rod body section. According to the design of the screw rotor, a gas dead zone is eliminated through the through type grooves so as to improve the conveying efficiency, and the two sections are symmetrically arranged to balance bidirectional compression force and offset axial loads.

Description

TECHNICAL FIELD

[0001] The utility model relates to a vacuum pump technical field especially relates to a double screw rod booster vacuum pump and screw rod rotor thereof. BACKGROUND

[0002] Vacuum pump plays a key role in the industrial gas processing field, and the traditional screw pump design often causes turbulent flow stagnation due to the interruption of gas flow path, reduces the conveying efficiency; at the same time, the rotor dynamic imbalance leads to vibration aggravation, and the imperfect sealing interface affects the vacuum degree maintenance. SUMMARY

[0003] In order to solve the technical problems in the background art, the utility model provides a double screw rod booster vacuum pump and screw rod rotor thereof.

[0004] The utility model provides a screw rod rotor, include: the pole body, the pole body includes first pole body section, intermediate section and second pole body section in sequence along the axial direction, first type helical groove is set up on the first pole body section three along the axial extension, first type helical groove is set up on the second pole body section three along the axial extension, first type helical groove penetrates first pole body section in the axial direction, second type helical groove penetrates second pole body section in the axial direction.

[0005] Further, three first type helical grooves are distributed in 120 degree equiangular angle in the circumferential direction of the first pole body section, and three second type helical grooves are distributed in 120 degree equiangular angle in the circumferential direction of the second pole body section, the helix angle of each helical groove Satisfies: 15 DEG <= <= 25 DEG, the surface roughness of the transition area of groove side wall and groove bottom , and the profile tolerance is less than or equal to 0.02 .

[0006] Further, in the axial direction of the pole body away from the intermediate section, the cross-sectional area of each first type helical groove and second type helical groove is in a decreasing trend, wherein the decreasing trend allows the existence of a local cross-sectional area constant transition section.

[0007] Further, the transition section satisfies the following geometric conditions: located in the axial distance L1 to L2 interval from the intermediate section end face; the length Satisfies: , wherein, is the length of the pole body section; in the interval, the curvature radius of the groove side wall generatrix , wherein, is the groove opening width.

[0008] Further, the first type of spiral groove and the second type of spiral groove are mirror symmetric about the axial midpoint of the middle section; and satisfy: three first type of spiral grooves and three second type of spiral grooves correspond to each other in axial position; in any cross section perpendicular to the screw shaft, the cross-sectional area of the first type of spiral groove and the second type of spiral groove at the symmetric position are equal; in the axial direction of the screw, the decreasing gradient of the cross-sectional area of the first type of spiral groove is the same as the decreasing gradient of the cross-sectional area of the second type of spiral groove.

[0009] The application also provides a double-screw pressurized vacuum pump, which comprises a shell, a front end cover, a rear end cover, a driving mechanism and a pair of intermeshing screw rotors.

[0010] The front end cover, the shell and the rear end cover are sequentially fixedly connected to enclose a sealed inner cavity; the two rotors are arranged in parallel in the sealed inner cavity; and the two ends of the shaft of each rotor are supported on the front end cover and the rear end cover through bearings.

[0011] The shell is provided with an air inlet at the middle section, and the shell is provided with a first air outlet and a second air outlet; one end of all the first type of spiral grooves is communicated with the air inlet adjacent to the middle section, and the other end is communicated with the first air outlet; one end of all the second type of spiral grooves is communicated with the air inlet adjacent to the middle section, and the other end is communicated with the second air outlet.

[0012] Further, the air inlet is used for sucking gas into the sealed inner cavity when the pair of rotors rotate synchronously in opposite directions.

[0013] The first type of spiral groove is used for compressing and guiding the gas along the first rod body section to the first air outlet through the axial decreasing trend of the cross-sectional area when the rotor rotates.

[0014] The second type of spiral groove is used for compressing and guiding the gas along the second rod body section to the second air outlet through the axial decreasing trend of the cross-sectional area when the rotor rotates.

[0015] Further, the mirror symmetric configuration of the first type of spiral groove and the second type of spiral groove is used for keeping the dynamic balance of the compression process on both sides when the rotor rotates; wherein the compression gradient is independently controlled by the decreasing gradient of the cross-sectional area of the groove, and the compression forces on both sides offset each other to reduce the axial load.

[0016] The screw rotor design of the utility model eliminates the gas dead zone through the through groove to improve the conveying efficiency, the double-section symmetric configuration balances the bidirectional compression force and offsets the axial load; the axial flow rate of the gas is regulated through the spiral lift angle to optimize the compression efficiency, or a nanoscale sealing interface is constructed by precise machining of the surface, and the dynamic balance mechanism and the labyrinth sealing path are combined, so that the vacuum stability is significantly enhanced and the service life of the equipment is prolonged, and the decreasing gradient control of the groove and the sealing technology implementation mode are not limited in the scheme. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The structural schematic diagram of the screw rotor in an embodiment of the utility model.

[0018] Figure 2 The structural schematic diagram of the screw rotor in an embodiment of the utility model Figure One .

[0019] Figure 3 The structural schematic diagram of the screw rotor in an embodiment of the utility model Figure Two .

[0020] Figure 4 The structural schematic diagram of the double-screw pressurization vacuum pump in an embodiment of the utility model.

[0021] Figure 5 The structural schematic diagram of the double-screw pressurization vacuum pump in an embodiment of the utility model. DETAILED DESCRIPTION

[0022] It should be noted that the embodiments in the utility model and the features in the embodiments can be combined with each other without conflict.The utility model will be described in detail below with reference to the drawings and in combination with the embodiments.

[0023] With reference to Figures 1-5 , the utility model discloses a screw rotor, which comprises a rod body 1, the rod body 1 comprises a first rod body section 11, an intermediate section 12 and a second rod body section 13 in sequence along the axial direction, three first type helical grooves 14 extending along the axial direction are formed on the first rod body section 11, and three second type helical grooves 15 extending along the axial direction are formed on the second rod body section 13, the first type helical groove 14 penetrates the first rod body section 11 along the axial direction, and the second type helical groove 15 penetrates the second rod body section 13 along the axial direction.

[0024] Specifically, the rod body 1 is the main structure of the screw rotor and is a cylindrical long shaft to bear the rotating load and the gas compression force; the rod body 1 comprises the first rod body section 11, the intermediate section 12 and the second rod body section 13 arranged symmetrically in sequence along the axial direction, wherein the first rod body section 11 is provided with three first type helical grooves 14 penetrating the axial direction, and the second rod body section 13 is provided with three second type helical grooves 15 penetrating the axial direction. Both the two types of grooves are continuous helical grooves and are used for capturing and guiding the gas flow, when the rotor is installed in the vacuum pump cavity and rotates, the gas is sucked into the groove near the intermediate section 12 and flows along the uninterrupted through-type path, and the design can eliminate the flow dead zone and improve the conveying efficiency; the double-section symmetric layout lays a structural foundation for bidirectional compression and significantly reduces the risk of rotor dynamic imbalance.

[0025] Three first type helical grooves 14 are distributed at an equal angle of 120° in the circumferential direction of the first rod section 11, and three second type helical grooves 15 are distributed at an equal angle of 120° in the circumferential direction of the second rod section 13. The helix angle of each helical groove is satisfies: 15°≤ ≤25°; the surface roughness of the transition region between the groove side wall and the groove bottom satisfies: , and the profile tolerance is ≤0.02 .

[0026] Specifically, the circumferential equal angle distribution requires that the three grooves are strictly spaced at an angle of 120° in the circumferential direction, and the helix angle, which is defined as the angle between the tangent of the groove and the vertical plane of the rotor axis, directly determines the axial flow velocity of the gas. The surface roughness quantifies the microscopic unevenness of the groove, and the profile tolerance restricts the geometric deviation.

[0027] In the axial direction of the rod 1 away from the intermediate section 12, the cross-sectional area of each of the first type helical groove 14 and the second type helical groove 15 gradually decreases, wherein the gradual decrease allows for a transition section with a constant cross-sectional area.

[0028] Specifically, the gradual decrease in cross-sectional area is manifested as a gradual reduction in the cross-sectional area of the groove from the intermediate section 12 to the end of the rod 1. The transition section refers to the axial interval that maintains a constant area during the gradual decrease. The compression process is implemented in three stages: the initial section immediately adjacent to the intermediate section 12, the area decreases exponentially; the intermediate section 12 is a transition zone with limited axial length, the area remains constant; the terminal section linearly decreases to the minimum value at the free end. This structure forms a progressive compression chamber, where the transition section alleviates the pressure jump to avoid airflow shock, and the exponential decrease mode significantly optimizes the compression efficiency.

[0029] In specific embodiments, the gradient function of the gradual decrease in cross-sectional area satisfies: , wherein, A is the cross-sectional area; x is the axial coordinate with the origin at the end face of the intermediate section 12; is the decreasing coefficient, with a value range of 0.02~0.05 ; is the attenuation factor, with a value range of 0.15~0.25 ; is the initial cross-sectional area of the groove at the end face of the intermediate section 12.

[0030] ​Specifically, the mirror symmetry refers to taking the axial midpoint of the middle section 12 as the symmetry plane, so that the first rod body section 11 and the second rod body section 13 grooves are in a spatial mirror image relationship, and the decreasing gradient is defined as the change amount of the groove cross-sectional area per unit length in the axial direction. In the design stage, the three-dimensional modeling is used to realize the geometric symmetry of the two side grooves, to ensure that the axial positions of the three grooves are one-to-one corresponding, and the cross-sectional areas of the symmetric grooves in any cross section are equal and the decreasing gradients are consistent. This configuration balances the gas compression force in both directions to offset the axial load, while ensuring that the gas flow pressures of the two outlets are balanced.

[0031] The transition section satisfies the following geometric conditions: located in the axial distance L1 to L2 interval from the end face of the middle section 12; the length Satisfies: , is the length of the rod body 1 section; in the interval, the groove side wall generatrix curvature radius , is the groove opening width.

[0032] Specifically, the sealing inner cavity 22 is composed of the shell 2 and the front end cover 3 and the rear end cover 4, the gas inlet 21 is arranged in the middle section 12 of the shell 2, the first gas outlet and the second gas outlet are arranged at both ends of the shell 2, and when the two rotors are reversely and synchronously rotated through the gear set: in the suction stage, the gas is synchronously introduced into the two side grooves from the gas inlet 21 of the middle section 12; in the compression stage, the gas is axially pushed and compressed along with the decreasing cross-sectional area of the groove; in the exhaust stage, the compressed gas is discharged into the first gas outlet through the first type of groove and into the second gas outlet through the second type of groove, and the double-outlet design improves the exhaust efficiency, the intermediate gas inlet reduces the airflow disturbance, and the precise gap control realizes oil-free sealing.

[0033] The first type of spiral groove 14 and the second type of spiral groove 15 are mirror symmetric about the axial midpoint of the middle section 12; and satisfy: the axial positions of the three first type of spiral grooves 14 and the three second type of spiral grooves 15 are one-to-one corresponding; in any cross section perpendicular to the screw shaft, the cross-sectional areas of the first type of spiral groove 14 and the second type of spiral groove 15 at the symmetric positions are equal; in the axial direction of the screw, the decreasing gradient of the cross-sectional area of the first type of spiral groove 14 is the same as that of the second type of spiral groove 15.

[0034] Specifically, the reverse synchronous rotation is realized by the precise gear set to rotate the two rotors at the same speed in the opposite directions, and the compression guiding function relies on the synergistic effect of the decreasing groove area and the spiral structure. The specific working process is as follows: the motor drives the driving shaft to drive the driven shaft through the helical gear, and the gas sucked by the negative pressure of the air inlet 21 is divided into independent chambers by the rotating groove; the chamber volume decreases with the decrease of the area, and the spiral angle generates an axial thrust to push the gas to the gas outlet; when the chamber is connected to the gas outlet, the compressed gas is discharged in the form of pulsation, and the rotor rotation completes a complete cycle once every ninety degrees. The synergistic effect of the spiral angle and the decreasing area realizes efficient compression, and the phase difference design of the double rotors eliminates the exhaust pulsation.

[0035] The application also provides a double-screw supercharged vacuum pump, which comprises a shell 2, a front end cover 3, a rear end cover 4, a driving mechanism 5 and a pair of rotors as described in any one of the preceding embodiments; the front end cover 3, the shell 2 and the rear end cover 4 are sequentially fixedly connected to enclose a sealed inner cavity 22; the two rotors are arranged in parallel in the sealed inner cavity 22; the shafts of the rotors are supported by bearings at the two ends of the shafts on the front end cover 3 and the rear end cover 4; the middle section 12 of the shell 2 is provided with an air inlet 21, the shell 2 is provided with a first gas outlet and a second gas outlet, all the first spiral grooves 14 are in communication with the air inlet 21 adjacent to the middle section 12 at one end and in communication with the first gas outlet at the other end, and all the second spiral grooves 15 on the rotors are in communication with the air inlet 21 adjacent to the middle section 12 at one end and in communication with the second gas outlet at the other end.

[0036] Specifically, the dynamic balance requires that the amplitudes of the gas compression forces on the two sides are equal and the directions are opposite, and the resultant force tends to be zero; the axial load refers to the axial thrust generated by the gas compression. When the rotors rotate, the first type of groove on the left side generates a rightward axial force, and the second type of groove on the right side generates a leftward axial force, and the mirror symmetry makes the difference between the compression forces at the corresponding positions less than 5%, the axial resultant force is reduced to less than 10% of the single-side force, and the residual force is borne by the angular contact bearing. By adjusting the decreasing gradient of the groove, the single-side compression ratio can be independently controlled, which significantly prolongs the service life of the bearing and suppresses the axial movement of the rotor.

[0037] The air inlet 21 is used to suck gas into the sealed inner cavity 22 when the pair of rotors rotate in the opposite directions; the first type of spiral groove 14 is used to compress and guide the gas along the first rod body section 11 to the first gas outlet through the axial decreasing trend of the cross-sectional area of the groove when the rotor rotates; the second type of spiral groove 15 is used to compress and guide the gas along the second rod body section 13 to the second gas outlet through the axial decreasing trend of the cross-sectional area of the groove when the rotor rotates.

[0038] Specifically, the airflow equalization means that the gas at the gas inlet 21 is evenly distributed to the three grooves; the compression ratio means the absolute pressure ratio of the gas outlet to the gas inlet 21. The helix angle effect is that the axial flow rate of the gas is 0.5-2 m / s in the range of 15-20 degrees and the compression efficiency reaches the peak value; if the angle is less than 15 degrees, the flow rate is less than 0.3 m / s, which will cause the gas retention rate to exceed 10%; if the angle is greater than 25 degrees, the flow rate is more than 3 m / s, which will cause the turbulent leakage to reach 8% of the total flow. By precisely controlling the angle, the compression ratio is stabilized in the range of 3-4, the airflow is evenly distributed to eliminate the rotor eccentric wear, and the angle is optimized to balance the compression efficiency and leakage control.

[0039] The mirror image symmetry configuration of the first type of helical groove 14 and the second type of helical groove 15 is used to dynamically balance the compression process of the gas on both sides when the rotor rotates; wherein the compression gradient is independently controlled by the decreasing gradient of the cross-sectional area of the groove, and the compression forces on both sides offset each other to reduce the axial load.

[0040] Specifically, the sealing interface refers to the micro-sealing band formed by the groove surface and the paired rotor; the backflow rate refers to the ratio of the reverse leakage volume of the compressed gas to the exhaust volume. The surface roughness of 0.8 microns and the profile tolerance of 0.02 mm constitute a triple sealing mechanism: the molecular adsorption effect uses a smooth surface to adsorb a layer of gas molecules to fill the micro-unevenness; the labyrinth seal forms a tortuous leakage path in the meshing gap through precise profile; the dynamic seal relies on the oil film in rotation to fill the residual gap. When the axial load is balanced, the backflow rate is reduced to less than 0.5%, the vacuum degree is improved to the order of magnitude of 0.001 Pa, and the nanometer-level sealing and mechanical balance are cooperated to realize high-vacuum stable operation.

[0041] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any skilled person in the art can make equivalent replacement or change according to the technical scheme and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A screw rotor, characterized in that Comprising: a rod body (1) comprising in sequence along the axial direction a first rod body segment (11), an intermediate segment (12) and a second rod body segment (13); three first type helical grooves (14) extending along the axial direction are formed on the first rod body segment (11), and three second type helical grooves (15) extending along the axial direction are formed on the second rod body segment (13); the first type helical grooves (14) axially penetrate the first rod body segment (11); the second type helical grooves (15) axially penetrate the second rod body segment (13).

2. The screw rotor of claim 1 wherein, Three first type helical grooves (14) are distributed at 120° equiangularly in the circumference of the first rod body section (11), and three second type helical grooves (15) are distributed at 120° equiangularly in the circumference of the second rod body section (13); the helical pitch angle of each helical groove satisfies: 15°≤ ≤25°; the surface roughness of the transition region between the groove side wall and the groove bottom is 0.02 .

3. The screw rotor of claim 1 wherein, In the axial direction of the rod body (1) away from the intermediate segment (12), the cross-sectional area of each of the first type helical grooves (14) and the second type helical grooves (15) presents a decreasing trend, wherein the decreasing trend allows the existence of a transition segment with constant cross-sectional area.

4. The screw rotor of claim 3 wherein, The transition section satisfies the following geometric conditions: located at an axial distance L1 to L2 from the end face of the intermediate section (12); length satisfies: wherein, is the length of the rod body (1) section; in the interval, the groove side wall generatrix radius of curvature wherein, is the groove opening width.

5. The screw rotor of claim 3 wherein, The first type helical grooves (14) and the second type helical grooves (15) are mirror-symmetric about the axial midpoint of the intermediate segment (12); and satisfy: the three first type helical grooves (14) and the three second type helical grooves (15) correspond to each other in axial position; in any cross section perpendicular to the screw shaft, the cross-sectional area of the first type helical groove (14) at the symmetric position is equal to that of the second type helical groove (15); in the axial direction of the screw, the decreasing gradient of the cross-sectional area of the first type helical groove (14) is the same as that of the second type helical groove (15).

6. A twin screw booster vacuum pump characterized in that, Comprising: a housing (2), a front end cover (3), a rear end cover (4), a driving mechanism (5) and a pair of mutually meshing screw rotors as claimed in any one of claims 1-5; the front end cover (3), the housing (2) and the rear end cover (4) are fixedly connected in sequence to enclose a sealed inner cavity (22); the two rotors are arranged in parallel in the sealed inner cavity (22); the shafts of each rotor are supported by bearings at both ends on the front end cover (3) and the rear end cover (4); an air inlet (21) is arranged on the housing (2) at the intermediate segment (12), and a first air outlet and a second air outlet are arranged on the housing (2); one end of each first type helical groove (14) is in communication with the air inlet (21) adjacent to the intermediate segment (12), and the other end is in communication with the first air outlet; one end of each second type helical groove (15) on the rotor is in communication with the air inlet (21) adjacent to the intermediate segment (12), and the other end is in communication with the second air outlet.

7. A twin screw booster vacuum pump according to claim 6, characterised in that, The air inlet (21) is used to suck gas into the sealed inner cavity (22) when the pair of rotors rotate synchronously in opposite directions; The first type helical grooves (14) are used to compress and guide the gas along the first rod body segment (11) through the axial decreasing trend of the cross-sectional area when the rotors rotate; The second type helical grooves (15) are used to compress and guide the gas along the second rod body segment (13) through the axial decreasing trend of the cross-sectional area when the rotors rotate.

8. A twin screw booster vacuum pump according to claim 6, characterised in that, The mirror-symmetric configuration of the first type helical grooves (14) and the second type helical grooves (15) is used to maintain dynamic balance in the compression process on both sides when the rotors rotate; wherein the compression gradient is independently controlled by the decreasing gradient of the cross-sectional area of the grooves, and the compression forces on both sides cancel each other out to reduce the axial load.

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