Combined turbomolecular vacuum pump

Abstract

The utility model relates to vacuum technology, to means for generating vacuum, and to turbomolecular vacuum pumps. The combined turbomolecular vacuum pump consists of a shaft mounted in bearing assemblies located in a composite housing consisting of upper and lower housings on which a rotor is fixed, the shaft is driven by an electric motor, the flow part of the pump includes successively arranged stages one after another: one turbomolecular, made in the form of alternating rotor and stator bladed impellers, and seven disk molecular stages, while the turbomolecular stage consists of 19 impellers, including 10 rotor and 9 stator, divided into 5 packages, while the first package contains 3 impellers, the second, third, fourth and fifth packages contain 4 impellers each, and the angle of inclination of the blades to the plane of the wheel is 35° for the wheels of the first package, 30° for the wheels of the second package, 25° for the third,15° for the wheels of the fourth and fifth packages, and one molecular disk stage is formed by a smooth rotor disk and a mating stator disk with spiral grooves. The technical result of the claimed utility model is a reduction in the ultimate residual pressure generated by the turbomolecular pump while simultaneously increasing the pump's compression ratio. 2 figs.

Description

[0001] Technical field

[0002] The utility model relates to vacuum technology, to means for producing vacuum, to turbomolecular vacuum pumps.

[0003] Turbomolecular vacuum pumps are a type of mechanical vacuum pump. This combination turbomolecular vacuum pump can be used in various industrial installations to create and maintain vacuum, such as in the aerospace, petrochemical, food, optical, and electronics industries, as well as in various scientific, research, and laboratory installations that operate in vacuum conditions, such as particle accelerators.

[0004] State of the art

[0005] A prior art analogue of the combined turbomolecular vacuum pump is a high-vacuum hybrid pump (RU 2561514, August 27, 2015). It is a combined high-speed axial turbine with an active viscous stage, designed as a four-start rectangular threaded groove with a variable cross-section, located on the inner surface of the rotor. The pump has a three-part cylindrical body, within which is located the flow path. The flow path consists of a turbomolecular stage and a viscous stage, designed as a four-start rectangular threaded groove with a variable cross-section.

[0006] The main disadvantages of the considered analogue are the high ultimate residual pressure (about 10 -6 Pa) and low pump compression ratio.

[0007] The closest analogue of the claimed combined turbomolecular vacuum pump is also known from the prior art - a single-flow four-stage turbomolecular pump (RU 2560133, 20.08.2015). The flow path of the turbomolecular vacuum pump includes four sequentially following stages: one turbomolecular, one transition end molecular and two, the first and second, concentrically located cylindrical molecular stages opposite each other. The flat end surface of the stator is made with grooves formed by arcs of circles with centers uniformly spaced on the central circumference and with an angle of inclination counter to the rotation of the rotor and facing with an axial working gap towards the end surface of the last rotor disk of the turbomolecular stage with blades located on the periphery at an angle of inclination in the direction of rotation of the shaft.The interblade channels of the blades are optically closed and form a transitional end molecular stage. Concentrically located, equidistant cylindrical sections opposite each other between the inner surface with multi-start helical grooves of the stator and the outer surface of the hollow cylinder of the rotor, as well as between the inner surface of the hollow cylinder of the rotor and the outer surface with multi-start grooves of the cylindrical projection of the middle housing, form the first and second cylindrical molecular stages of the pump's flow path, respectively.

[0008] The disadvantage of the considered design is the high ultimate residual pressure.

[0009] Disclosure of Utility Model

[0010] The technical result of the claimed utility model is a decrease in the maximum residual pressure created by a turbomolecular pump while simultaneously increasing the compression ratio of the pump.

[0011] The above technical result is achieved by a combined turbomolecular vacuum pump consisting of a shaft mounted in bearing assemblies located in a composite housing consisting of upper and lower housings on which a rotor is fixed, the shaft is driven by an electric motor, the flow part of the pump includes sequentially arranged stages one after another: one turbomolecular, made in the form of alternating rotor and stator bladed impellers, and seven disk molecular stages, while the turbomolecular stage consists of 19 impellers, including 10 rotor and 9 stator, divided into 5 packages, while the first package contains 3 impellers, the second, third, fourth and fifth packages contain 4 impellers, and the angle of inclination of the blades to the plane of the wheel is 35 ° for the wheels of the first package, 30 ° for the wheels of the second package, 25 ° for the third, 15 ° for wheels of the fourth and fifth packages,and one disk molecular stage is formed by a smooth rotor disk and a mating stator disk with spiral grooves.

[0012] Brief description of drawings

[0013] The essence of the utility model is explained by drawings, where:

[0014] Fig. 1 shows a longitudinal section of a combined turbomolecular vacuum pump;

[0015] in Fig.2 – profile of the stator disk of the molecular stage.

[0016] Implementation of a utility model

[0017] The combined turbomolecular vacuum pump consists of a shaft 1 rotating at an angular velocity ω, installed in bearing assemblies 2 and 3, located in housings 4 and 5, on which a rotor 6 is fixed.

[0018] The shaft is driven by an electric motor 7. The rotor of the pump 6 with the impellers of the turbomolecular stage and the smooth disks of the molecular stage 8, 9, 10 is made of one piece, for example, solidly milled and has a cavity in its lower part, the shape and size of which allow for the placement of a bearing assembly and / or an electric motor. The pump casing is made of a composite, consisting of an upper casing 4 and a lower casing 5. The flat end surface of the lower casing 5 is made with spiral grooves 11 and, together with the last smooth rotor disk 10, forms the last molecular stage.

[0019] Such design of the component parts and their relative position ensures the compactness of the pump and allows to reduce its weight and dimensions.

[0020] The stator impellers are split. Spacer rings are positioned between them. The stator impeller and spacer ring assembly is pressed together by adjusting rings, which ensure the correct axial clearance between the rotor and stator impellers.

[0021] The molecular stage set is a structure consisting of alternating stator 12, 13, 14 and rotor 8, 9, 10 disks, at least one of each. The rotor disks are made smooth, on the mating stator parts, spiral grooves are cut on both sides. On one side of the stator wheel, the pumped gas moves along the spiral groove from the center to the periphery, on the opposite side - from the periphery to the center. The molecular disk spiral stage consists of a smooth rotor disk 8 and a mating stator part 12 having at least one spiral groove, at least on the surface facing the said rotor disk; spiral grooves 17-24 (Fig. 2) on the stator surface are separated from each other and operate in parallel. The positioning of the stator disks 12, 13, 14 in the pump housing is performed in accordance with the direction of rotation of the shaft 1, as shown in Fig. 2.

[0022] The mating stator parts are made in the form of a disk, on both sides of which channels are cut, or the role of the mating stator part of the stage is performed by the end surface of the housing with cut spiral grooves 11, which, together with the disk 10, forms the seventh molecular stage. The disk molecular stages are connected in series. Centripetal and centrifugal molecular stages alternate, and the first molecular stage, following the turbomolecular stage, is always centripetal. The first molecular stage is formed by the end surface of the last impeller 15 of the turbomolecular stage and the stator molecular disk 12 with spiral grooves. Disk 12 is installed with an axial clearance relative to the wheel 15, with all pairs of smooth rotor and mating parts of the stator disks installed with a clearance of the same value, i.e. the value of all axial gaps in the molecular step is constant and lies within the range of 10 -5 m to 2 mm.

[0023] The preferred axial clearance in the molecular stage is 0.4 mm or less. Further increasing the clearance increases the backflow, leading to a significant drop in compression ratio.

[0024] It is preferable that the turbomolecular stage consists of at least one rotor disk and at least one stator disk with a mirror-image arrangement of blades.

[0025] It is also preferable that the outer surface of the cases be equipped with air cooling fins.

[0026] The operating principle of the combined turbomolecular vacuum pump is that gas molecules enter the pump's suction port and then the interblade channels of the turbomolecular stage. Upon collision with the moving surface of the channels, the gas molecules are imparted with additional momentum in the pumping direction, and are drawn into motion through the interblade channels of the turbomolecular stage and the spiral grooves of the molecular stages, after which they are removed from the discharge cavity through the discharge port 16 by the forevacuum pump.

[0027] The flow part of the pump includes at least one spiral disk molecular stage, wherein the number of molecular stages is determined based on the required degree of compression and pumping speed.

[0028] The use of disk molecular stages in the flow section of a turbomolecular pump allows the pump's compression ratio to be increased by several orders of magnitude, subject to high requirements for manufacturing and assembly accuracy.

[0029] The speed of the molecular stage depends on the geometric parameters of the grooves (axial size of the groove, working length of the groove, the size of the axial gap between the rotor and stator disks, i.e. between disks 8 and 12, 8 and 13, 9 and 13, 9 and 14, 10 and 14), the rotation speed of the disks, and the area of ​​the input surface.

[0030] As the speed of rotation of the wheels increases, the probability of gas molecules passing through the grooves in the pumping direction increases, which leads to an increase in the speed of the pump, however, the speed of rotation of the wheels is limited by the strength properties of the material used for manufacturing, taking into account its geometric shape.

[0031] The compression ratio and operating speed of the molecular section of the pump depend on the number of molecular stages. Designing flow sections for different operating speeds and compression ratios is achieved by selecting the required number of disks to achieve a given compression ratio and pump operating speed.

[0032] The increase in the compression ratio is achieved by increasing the compression ratio of the molecular stage by installing a disk-type molecular stage, which has a theoretical compression ratio that is hundreds of times higher than that of cylindrical-type molecular stages.

[0033] The reduction of the ultimate residual pressure is achieved due to the selected composition of the flow part of the pump, which includes 5 packages of turbomolecular wheels, the above geometry and 7 disk molecular stages.

[0034] Increased pump performance is also achieved by increasing the rotor speed relative to analogs from 24-36,000 rpm to 60,000 rpm.

[0035] The difference between the flow part of a combined turbomolecular vacuum pump and the flow parts of analogs lies in the composition and design of the flow part.

[0036] Unlike the given analogs, in the designs of which cylindrical molecular stages are used, in the flow part of the combined turbomolecular vacuum pump only disk molecular stages are used (at least one disk stage) with alternating smooth rotor disks and stator disks, on which at least one spiral groove is cut, the profile of which is shown in Fig. 2.

[0037] Unlike its analogs, the turbomolecular stage consists of 19 impellers, including 10 rotor and 9 stator wheels, divided into 5 packages, each consisting of wheels of different geometries. Each package contains at least 2 impellers. The impeller thickness at the blade root, the number of blades, the blade length, and the angle of the blade relative to the impeller plane vary across the impeller packages. The blades on the stator wheels differ from those on the corresponding rotor wheels in both the number and length of the blades and the angle of the blade relative to the impeller plane.

[0038] The angle of inclination of the blades to the plane of the wheel is 35° for the wheels of the first package, 30° for the wheels of the second package, 25° for the third, 15° for the wheels of the fourth and fifth packages.

[0039] This composition of the turbomolecular stage allows to reduce the ultimate residual pressure it creates and increase the compression ratio accordingly.

[0040] To solve the problem and achieve the technical result, a combined turbomolecular vacuum pump is proposed, the flow part of which includes stages arranged sequentially one after the other: one turbomolecular stage, made in the form of alternating rotor and stator blade impellers, and at least one disk molecular stage.

Claims

A combined turbomolecular vacuum pump consisting of a shaft mounted in bearing assemblies located in a composite housing consisting of upper and lower housings on which a rotor is fixed, the shaft is driven by an electric motor, the flow part of the pump includes successively arranged stages one after another: one turbomolecular stage, made in the form of alternating rotor and stator bladed impellers, and seven disk molecular stages, characterized in that the turbomolecular stage consists of 19 impellers, including 10 rotor and 9 stator, divided into 5 packages, wherein the first package contains 3 impellers, the second, third, fourth and fifth packages contain 4 impellers each, and the angle of inclination of the blades to the plane of the wheel is 35° for the wheels of the first package, 30° for the wheels of the second package, 25° for the third, 15° for the wheels of the fourth and fifth packages,and one disk molecular stage is formed by a smooth rotor disk and a mating stator disk with spiral grooves.

Images