Equal-diameter variable-pitch multistage roots vacuum pump

Abstract

A left rotor and a right rotor are the same in structure, a rotating shaft is installed at the output end of a driving motor, branch rotors are installed on the rotating shaft, each branch rotor is provided with three teeth, and the branch rotors are multi-stage branch rotors different in shape and size; the addendum circle radius and the dedendum circle radius of each section of sub-rotor are equal, the addendum circle radiuses of all stages of sub-rotors are sequentially reduced, the dedendum circle radiuses corresponding to the sub-rotors are sequentially increased, and the section contour of the whole sub-rotors in the shell forms a trapezoid, so that the air suction volumes of all the sections of sub-rotors are different; according to the air compressor, sucked air can be compressed again in the vacuum pump, so that the compression ratio is increased, from the air suction side to the air exhaust side, the addendum circle radiuses of all stages of the sub-rotors are sequentially reduced, the root circle radiuses corresponding to the sub-rotors are sequentially increased, it can be ensured that the air suction volumes of the sub-rotors from the air suction side to the air exhaust side are sequentially reduced, and the larger air compression ratio can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of vacuum pumps, in particular to a multi-stage Roots vacuum pump with equal diameter and variable pitch. Background Art

[0002] Roots vacuum pump is a rotary positive displacement vacuum pump, which uses the rotation of the rotor to suck gas into the pump body, and compresses the air and discharges it through the rotation of the rotor. Roots vacuum pump can work in a wide pressure range. There is no oil in the pump chamber of Roots vacuum pump. It has been widely used in vacuum systems in semiconductor, electronics, petroleum, chemical and other industries.

[0003] The multi-stage Roots vacuum pump is a type of dry Roots vacuum pump. Compared with the traditional single-stage Roots vacuum pump, the multi-stage Roots vacuum pump is different in structure. Its "multi-stage" is mainly reflected in the fact that multiple rotors are connected in series, and multiple relatively independent pump chambers are formed by the intermediate wall. Each pump chamber is connected to the exhaust port through the air inlet of each stage to form an air flow channel. A notable feature of the multi-stage Roots vacuum pump is its high compression ratio. The pumped gas enters the pump chamber from the first stage air inlet, and after multi-stage compression, it is finally discharged from the last stage to achieve multi-stage compression.

[0004] The traditional multi-stage Roots vacuum pump has the same sub-rotor tooth shape, and the sub-rotor diameter is large and the tooth height is large on the exhaust side. The thermal deformation of the shell end plate is large, and the end plate and rotor are prone to scratching. The traditional multi-stage Roots vacuum pump has the same sub-rotor diameter, the thickness of the sub-rotor on the exhaust side is reduced, the rotor rigidity is reduced, the high-speed operation stability is worse, and a larger gap is required. In addition, the rotor shaft diameter is limited by the root diameter of the tooth and cannot be enlarged. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the present invention provides an equal-diameter and variable-pitch multi-stage Roots vacuum pump, in which the cross-sectional profile of the sub-rotor as a whole in the shell forms a trapezoid, which can make the suction volume of each sub-rotor different. By changing the suction volume, the sucked gas can be compressed again in the vacuum pump, thereby improving the compression ratio. From the suction side to the exhaust side, the radius of the tooth top circle of each stage of the sub-rotor decreases successively, and the radius of the tooth root circle corresponding to the sub-rotor increases successively, which can ensure that the suction volume of the sub-rotor from the suction side to the exhaust side decreases successively, and a larger air compression ratio can be achieved.

[0006] To solve the above technical problems, the present invention provides the following technical solutions: a multi-stage Roots vacuum pump with equal diameter and variable pitch, comprising a driving motor, a rotor being installed at the output end of the driving motor, the rotor being installed in a housing, a front end cover and a rear end cover being installed at both ends of the housing by screws respectively, a sealing gasket being arranged between the front end cover and the rear end cover and the housing, the driving motor being arranged on the front end cover by a bracket, the rotor comprising a left rotor and a right rotor, the left rotor and the right rotor having the same structure, the left rotor comprising a rotating shaft, the rotating shaft being installed at the output end of the driving motor, a sub-rotor being installed on the rotating shaft, the sub-rotor being provided with three teeth, the sub-rotor being a multi-stage sub-rotor with different shapes and sizes, the sub-rotors being evenly distributed on the rotating shaft, the tooth top circle radius of each section of the sub-rotor being equal to the tooth root circle radius, the tooth top circle radius of each stage of the sub-rotor being successively reduced, and the tooth root circle radius corresponding to the sub-rotor being successively increased.

[0007] Furthermore, the diameter of the rotor hole of the housing where each stage of the sub-rotor is located decreases successively from the intake side to the exhaust side.

[0008] Furthermore, the thickness of the sub-rotors at each stage is consistent, and the radius of the tooth top circles of the sub-rotors are different.

[0009] Furthermore, a sealing ring is provided between the rotating shaft and the housing.

[0010] Furthermore, gears are installed at one end of the left rotor and the right rotor close to the rear end cover, and the gear installed on the left rotor is meshed with the gear installed on the right rotor through teeth.

[0011] Furthermore, a bearing is arranged between the rotating shaft and the housing.

[0012] Furthermore, there are gaps between the left rotor, the right rotor and the casing.

[0013] Furthermore, the drive motor is a water-cooled motor or an air-cooled motor.

[0014] Furthermore, a cooling channel is provided in the rotor, the cooling channel flows through each tooth of the sub-rotor, an injection port of the cooling channel is coaxially arranged with the rotating shaft and extends outside the transmission shaft, and the injection port is connected to an external pump body through a connecting nozzle.

[0015] Furthermore, the connecting nozzle includes a first connecting buckle mounted on the injection port, a second connecting buckle installed on the output end of the external pump body, and a connecting tube for connecting the first connecting buckle and the second connecting buckle. Both the first connecting buckle and the second connecting buckle can rotate freely on the connecting tube, and the inner diameter of the connecting tube is the same as the inner diameter of the injection port.

[0016] Compared with the prior art, the present invention can achieve the following beneficial effects: 1. The conventional multi-stage Roots rotors have the same tooth shape, while the cross-sectional profile of the rotors of this device as a whole in the shell forms a trapezoid, so that the suction volume of each rotor is different. By changing the suction volume, the inhaled gas can be compressed again in the vacuum pump, thereby improving the compression ratio; 2. From the suction side to the exhaust side, the radius of the tooth top circle of each level of the sub-rotor decreases successively, and the radius of the tooth root circle corresponding to the sub-rotor increases successively, which can ensure that the suction volume of the sub-rotor from the suction side to the exhaust side decreases successively, and a larger air compression ratio can be achieved; 3. The device adopts equal-diameter variable-pitch multi-stage Roots, which has smaller deformation after being subjected to force and heat, and can reduce the risk of end plate scratching. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall cross-sectional structure of an equal-diameter variable-pitch multi-stage Roots vacuum pump of the present invention; Figure 2 It is a structural schematic diagram of a rotor of a multi-stage Roots vacuum pump with equal diameter and variable pitch according to the present invention; Figure 3 It is a schematic diagram of the cross-sectional structure of a rotor of an equal-diameter and variable-pitch multi-stage Roots vacuum pump of the present invention; Figure 4 The present invention is a schematic diagram of the cross-sectional structure of a connecting nozzle of an equal-diameter and variable-pitch multi-stage Roots vacuum pump.

[0018] Among them: drive motor 1; front end cover 2; shell 3; rear end cover 4; left rotor 5; rotating shaft 51; sub-rotor 52; cooling flow channel 53; connecting nozzle 54; first connecting buckle 541; connecting pipe 542; second connecting buckle 543; right rotor 6; bearing 7; gear 8; sealing ring 9. DETAILED DESCRIPTION

[0019] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments, but the following embodiments are only preferred embodiments of the present invention, not all. Based on the embodiments in the implementation mode, other embodiments obtained by those skilled in the art without creative work all belong to the protection scope of the present invention. The experimental methods in the following embodiments, unless otherwise specified, are conventional methods, and the materials, reagents, etc. used in the following embodiments, unless otherwise specified, can all be obtained from commercial channels.

[0020] Embodiment: Combination Figure 1 and Figure 2As shown, the present invention provides an equal-diameter variable-pitch multi-stage Roots vacuum pump, including a drive motor 1, wherein a rotor is installed at the output end of the drive motor 1, and the material of the rotor can be selected from aluminum alloy, stainless steel, titanium alloy and special corrosion-resistant alloy according to specific operating conditions.

[0021] Aluminum alloy: Aluminum alloy is a widely used rotor material with the characteristics of light weight, high strength and corrosion resistance. It is suitable for handling some corrosive gases. It is relatively cheap and suitable for the production and use of small and medium-sized Roots pumps. ‌Stainless steel‌: Stainless steel rotors have the advantages of corrosion resistance and easy processing, and are widely used in food industry, pharmaceutical industry and other occasions that require high hygiene standards. Stainless steel rotors have a high cost-effectiveness and are suitable for industries that require high hygiene standards‌; ‌Titanium alloy‌: Titanium alloy rotors have high strength, corrosion resistance and high temperature resistance, and are suitable for processing high-purity, high-temperature gases. The strength and corrosion resistance of titanium alloys make them perform well in specific applications. They are high in strength, corrosion resistance and high temperature resistance, and are suitable for processing high-purity, high-temperature gases‌; Special corrosion-resistant alloys: such as Hastelloy, etc. These alloys are rich in corrosion-resistant elements such as nickel, molybdenum, and chromium. They can form a dense and stable passivation film in a corrosive environment, effectively blocking the invasion of corrosive gases and liquids. They are suitable for highly corrosive environments and ensure the stable operation of equipment in corrosive environments.

[0022] The rotor is installed in the shell 3, and the rotor can rotate freely in the shell 3. The shell 3 is the main body of the vacuum pump. The material of the shell 3 can be cast iron or stainless steel. Cast iron and stainless steel have good thermal conductivity. Cast iron is a commonly used material for the shell of a Roots vacuum pump. Cast iron has good casting performance and high strength, which can ensure that the structure of the pump body is firm and stable. Stainless steel has the characteristics of corrosion resistance, wear resistance, acid and alkali resistance, and is suitable for various complex working environments. The two ends of the shell 3 are respectively installed with a front cover 2 and a rear cover 4 by screws. A sealing gasket is arranged between the front cover 2 and the rear cover 4 and the shell 3. The sealing gasket can ensure the sealing between the front cover 2 and the rear cover 4 and the shell 3, so that they form a closed space to avoid air leakage during the operation of the vacuum pump, resulting in gas loss. The drive The motor 1 is mounted on the front end cover 2 through a bracket, and is characterized in that: the rotor includes a left rotor 5 and a right rotor 6, and the left rotor 5 and the right rotor 6 have the same structure. The left rotor 5 includes a rotating shaft 51, and the rotating shaft 51 is mounted on the output end of the driving motor 1. A sub-rotor 52 is mounted on the rotating shaft 51, and the sub-rotor 52 is provided with three teeth. The sub-rotor 52 is a multi-stage sub-rotor 52 with different shapes and sizes. The sub-rotors 52 are evenly distributed on the rotating shaft 51, and the cross-sectional profile of the sub-rotor 52 as a whole in the shell 3 forms a trapezoid, so that the suction volume of each section of the sub-rotor 52 is different. By changing the suction volume, the inhaled gas can be compressed again in the vacuum pump, thereby improving the compression ratio. The radius of the tooth top circle and the root circle radius of each section of the sub-rotor 52 are equal to ensure that the corresponding meshing center distances of all sub-rotors are equal. From the intake side to the exhaust side, the radius of the tooth top circle of each stage of the sub-rotor 52 decreases successively, and the radius of the tooth root circle corresponding to the sub-rotor 52 increases successively. This arrangement can ensure that the intake volume of the sub-rotor 52 from the intake side to the exhaust side decreases successively, and a larger air compression ratio can be achieved.

[0023] The diameter of the rotor hole of the shell 3 where the sub-rotors 52 of each level are located decreases successively from the intake side to the exhaust side. With this arrangement, the rotor cavity end plate is stronger, and the deformation after being subjected to force and heat is smaller, which can reduce the risk of end plate scratching.

[0024] The thickness of the sub-rotors 52 at each level is consistent, and the radius of the tooth top circle of the sub-rotors 52 is different. By changing the radius of the tooth top circle of the sub-rotors 52, the change of the suction volume is achieved, so that the rotor rigidity is stronger.

[0025] A sealing ring 9 is provided between the rotating shaft 51 and the housing 3. The sealing ring 9 has the function of sealing and supporting the rotating shaft 51. The sealing ring 9 effectively isolates the cooling lubricating oil from entering the housing 3, seals the housing 3, and ensures that the rotor cavity of the housing 3 is dry. The sealing ring 9 is a labyrinth seal or a dynamic and static combined seal.

[0026] The labyrinth seal is a seal with many tortuous chambers between the rotating part (rotating shaft 51) and (fixed part housing 3) to reduce leakage. The labyrinth seal is a seal with a number of annular sealing teeth arranged in sequence around the rotating shaft, and a series of interception gaps and expansion cavities are formed between the teeth. When the sealed medium passes through the gaps of the tortuous labyrinth, a throttling effect is generated to achieve the purpose of leakage prevention. Since there is a gap between the rotor and the casing of the labyrinth seal, there is no solid contact, no lubrication is required, and thermal expansion is allowed, which is suitable for high temperature, high pressure, high speed and frequency occasions. This type of seal is widely used in the shaft ends and sealing between stages of steam turbines, gas turbines, compressors, blowers, and the front seals of other dynamic seals.

[0027] A dynamic-static combined seal refers to a sealing structure that combines the dynamic ring on the rotating shaft with the bearing seat, housing, and uniform static ring in a special geometric shape. When axial movement occurs on the shaft, the dynamic ring protrudes outward and presses the corresponding contact parts with the inside and outside of the static ring, making these contact parts tight and forming a complete sealing structure.

[0028] The left rotor 5 and the right rotor 6 are provided with gears 8 at one end close to the rear end cover 4. The gears 8 installed on the left rotor 5 are meshed with the gears 8 installed on the right rotor 6 through teeth. With such arrangement, one of the gears 8 can be driven to rotate by the driving motor 1. Since the two gears 8 are meshed through teeth, the two rotating shafts 51 can be driven to rotate in opposite directions, thereby realizing the function of air intake by utilizing the sub-rotor 52.

[0029] A bearing 7 is provided between the rotating shaft 51 and the housing 3 , and the bearing 7 supports the rotating shaft 51 and ensures that the rotating shaft can rotate stably at high speed.

[0030] There is a gap between the left rotor 5, the right rotor 6 and the housing 3, and the gap is 0.1mm to 0.3mm. The size of the gap directly affects the vacuum pumping efficiency, sealing performance and service life of the vacuum pump. If the gap is too large, it will lead to a decrease in the vacuum pumping efficiency, increased energy consumption and possible leakage problems; if the gap is too small, it may cause the friction between the rotor and the pump housing to increase, thereby accelerating wear and shortening the service life of the vacuum pump.

[0031] The drive motor 1 is a water-cooled motor or an air-cooled motor. In the present application, the drive motor 1 is preferably a water-cooled direct-drive motor. Since the specific heat capacity of water is greater than that of air, the heat dissipation effect is usually better than that of an air-cooled motor, and the motor temperature can be better kept stable under high temperature conditions. The water-cooled direct-drive motor is directly connected to the drive shaft 51 for operation, has a simple structure, high transmission efficiency, and is easy to use. The water-cooled direct-drive motor can be used in harsh environments such as large temperature fluctuations, high heat dissipation requirements, high temperature, and high humidity.

[0032] Combination Figure 3As shown, a cooling channel 53 is provided in the rotor, and the cooling channel 53 flows through each tooth of the sub-rotor 52. The injection port of the cooling channel 53 is coaxially arranged with the rotating shaft 51 and extends to the outside of the transmission shaft 51. The injection port is connected to an external pump body through a connecting nozzle 54. Since the energy generated by air compression is relatively large, it is impossible to achieve an ideal cooling effect by relying on the shell 3, and excessive temperature will cause thermal deformation of the rotor, causing the rotor to directly contact with the shell 3, generating large noise, causing energy loss, and even causing the rotor to be unable to rotate. The coolant is injected into the injection port through the external pump body, and the coolant flows through the rotating shaft 51 and the sub-rotor 52, thereby realizing the function of cooling the rotor, so as to reduce the thermal deformation of the rotor and enable the rotor to rotate stably.

[0033] Combination Figure 4 As shown, in order to avoid twisting of the injection port when the rotor rotates and interfering with the rotation of the rotor, the connecting nozzle 54 includes a first connecting buckle 541 mounted on the injection port, a second connecting buckle 543 installed at the output end of the external pump body, and a connecting tube 542 for connecting the first connecting buckle 541 and the second connecting buckle 543. The first connecting buckle 541 and the second connecting buckle 543 can both rotate freely on the connecting tube 542. In this way, when the rotor rotates, the rotation between the first connecting buckle 541, the second connecting buckle 543 and the connecting tube 542 can be used to avoid transmitting the torque of the rotor rotation to the external pump body, thereby avoiding In order to avoid twisting of the injection port position when the rotor rotates, the inner diameter of the connecting pipe 542 is the same as the inner diameter of the injection port, which can reduce energy loss when the coolant flows. It should be noted that during operation, the external pump body should be started first, and the drive motor 1 should be started after confirming that the coolant has completed a cycle in the rotor. When the drive motor 1 is running, the left rotor 5 and the right rotor 6 are driven to rotate at high speed through the coupling and gear 8, and the medium is sucked in from the air inlet, passes through the large-pitch suction end of the rotor, and is compressed in the equal-diameter variable-pitch compression part of the rotor, and is discharged from the exhaust port through the small-pitch exhaust end of the rotor.

[0034] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A multi-stage Roots vacuum pump with equal diameter and variable pitch, comprising a drive motor (1), wherein a rotor is mounted at the output end of the drive motor (1), wherein the rotor is mounted in a housing (3), wherein a front end cover (2) and a rear end cover (4) are respectively mounted at both ends of the housing (3) by screws, wherein a sealing gasket is arranged between the front end cover (2) and the rear end cover (4) and the housing (3), wherein the drive motor (1) is mounted on the front end cover (2) by a bracket, wherein: The rotor comprises a left rotor (5) and a right rotor (6). The left rotor (5) and the right rotor (6) have the same structure. The left rotor (5) comprises a rotating shaft (51). The rotating shaft (51) is mounted on the output end of the driving motor (1). A sub-rotor (52) is mounted on the rotating shaft (51). The sub-rotor (52) is provided with three teeth. The sub-rotors (52) are multi-stage sub-rotors (52) with different shapes and sizes. The sub-rotors (52) are evenly distributed on the rotating shaft (51). The tooth tip circle radius and tooth root circle radius of each stage of the sub-rotor (52) are equal. The tooth tip circle radius of each stage of the sub-rotor (52) decreases in sequence, and the tooth root circle radius corresponding to the sub-rotor (52) increases in sequence.

2. The equal-diameter variable-pitch multi-stage Roots vacuum pump according to claim 1, characterized in that: The diameter of the rotor hole of the housing (3) where each stage of the sub-rotor (52) is located decreases sequentially from the intake side to the exhaust side.

3. The equal-diameter variable-pitch multi-stage Roots vacuum pump according to claim 2, characterized in that: The thickness of the sub-rotors (52) at each level is consistent, and the radius of the tooth top circles of the sub-rotors (52) are different.

4. The equal-diameter variable-pitch multi-stage Roots vacuum pump according to claim 1, characterized in that: A sealing ring (9) is provided between the rotating shaft (51) and the housing (3).

5. The equal-diameter variable-pitch multi-stage Roots vacuum pump according to claim 1, characterized in that: Gears (8) are installed at one end of the left rotor (5) and the right rotor (6) close to the rear end cover (4), and the gear (8) installed on the left rotor (5) and the gear (8) installed on the right rotor (6) are meshed through teeth.

6. The equal-diameter variable-pitch multi-stage Roots vacuum pump according to claim 1, characterized in that: A bearing (7) is provided between the rotating shaft (51) and the housing (3).

7. The equal-diameter variable-pitch multi-stage Roots vacuum pump according to claim 1, characterized in that: Gaps are left between the left rotor (5), the right rotor (6) and the housing (3).

8. The equal-diameter variable-pitch multi-stage Roots vacuum pump according to claim 1, characterized in that: The drive motor (1) is a water-cooled motor or an air-cooled motor.

9. The equal-diameter variable-pitch multi-stage Roots vacuum pump according to claim 1, characterized in that: A cooling channel (53) is provided in the rotor, the cooling channel (53) flows through each tooth of the sub-rotor (52), an injection port of the cooling channel (53) is coaxially arranged with the rotating shaft (51) and extends outside the transmission shaft (51), and the injection port is connected to an external pump body via a connecting nozzle (54).

10. The equal-diameter variable-pitch multi-stage Roots vacuum pump according to claim 9, characterized in that: The connecting nozzle (54) comprises a first connecting buckle (541) sleeved on the injection port, a second connecting buckle (543) installed on the output end of the external pump body, and a connecting tube (542) used to connect the first connecting buckle (541) and the second connecting buckle (543), the first connecting buckle (541) and the second connecting buckle (543) can both rotate freely on the connecting tube (542), and the inner diameter of the connecting tube (542) is the same as the inner diameter of the injection port.

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