CN1032574A - Radial Molecular Pump - Google Patents

Abstract

The invention belongs to a high-rotating-speed mechanical vacuum pump of molecular pumps, which is structurally characterized in that: each moving and static impeller is provided with a plurality of rows of blades distributed at equal intervals, and the single end of each blade is connected with the plane of the impeller; the impeller is provided with one or two air-extracting blade grooves with dragging surfaces, the different impeller structures can be coaxially arranged, and the impeller structures or the impeller structures and a common pump can be combined into a radial flow type molecular pump which is connected in parallel, in series or in series-parallel; the pump has simple structure and convenient processing, improves the pumping speed and the working pressure intensity, and reduces the cost.

Description

The invention belongs to the category of high-speed mechanical vacuum pumps and molecular pumps. The pumps are mainly used in the fields of thin film, plasma, surface analysis, accelerators, and the manufacture of vacuum devices and microelectronic devices.

Existing molecular pumps, referred to as ordinary molecular pumps, all adopt turbo-axial flow type, have low working pressure, complex structure, high price, and low pumping speed, which limit the further popularization and application of molecular pumps.

U.S. Patent US 3322334 (1967) proposed a radial flow molecular pump structure, the pumping speed of the pump has been significantly improved, however, due to the long blade structure, when the rotor rotates at high speed, the axial direction installed on the rotor bracket The blade bears a lot of stress, and several reinforcement devices need to be installed on the blade, so that the structure is more complicated than that of ordinary molecular pumps. In addition, this structure usually has four rows of turbine blades, and the compression ratio is very low. Therefore, it has not been used so far. Product molecular pump.

The purpose of the present invention is to provide a novel radial flow molecular pump with high pumping speed and high working pressure, simple structure and convenient processing.

The present invention is achieved like this:

The basic structure of the invention is a single-stage radial flow molecular pump impeller group composed of a moving impeller, a rotating shaft, a stationary impeller and a pump casing. The moving impeller is fixed on the rotating shaft, and the stationary impeller is fixed on the pump casing. Among the moving and static impellers, at least one side is provided with inclined blades or vane slots connected to the plane of the impeller at one end, and the blades or vane slots form an integral structure with the impeller, so that the impellers are easy to assemble, and several stages of impellers can be combined at the same time. The shaft is installed to form a series, parallel or a combination of multi-stage radial flow molecular pumps.

Basic structure of the present invention is divided into three kinds:

The first structure is a radial turbomolecular pump.

In this structure, there is at least one row of blade rows concentric with the rotating shaft on one side of the moving impeller. Each blade row is composed of several uniformly distributed blades. The blades are perpendicular to the plane of the impeller. The included angle between the radii of the impellers is 50°～75°. The blades of the same blade row have the same inclination angle, and the blades of different blade rows can have different inclination angles. However, the blades on the side of the same impeller should have the same inclination direction. In the same blade row, The ratio of the gap t of the blade in the circumferential direction of the blade row to the blade width b, that is, the optimal value of the blade's hollow chord ratio t/b is 0.8 to 1.2, and the number of blades in each blade row is usually between 15 and 80. between.

One side of the stationary impeller also has at least one row of blade rows concentric with the rotating shaft. The structure and optimal value of the blades in the blade rows are the same as those of the moving impeller blades, but the direction of inclination of the blades is opposite, and the thickness of the blades is also thinner. The radial position of the vane row on the stationary impeller should diverge from the position of the vane row of the moving impeller.

After the moving and static impellers are assembled, the blade rows are inserted alternately, and there is a certain working gap in the radial direction and the shaft. Among them, the gaps between the outer side of the moving impeller and the pump casing, and the inner side of the static impeller and the rotating shaft are large and serve as a barrier for gas flow. aisle. The blades on the assembled dynamic and static impellers alternately change their inclination directions.

When the moving impeller rotates at high speed, the pair of impellers form a radial turbomolecular pump.

If a pair of radial turbomolecular pump impellers are radially arranged with n rows of blades, then the compression ratio of the pair of impellers will be roughly equal to that of n ordinary molecular pump impellers working in series. The value of n is usually up to 10 or more. It can be seen that the compression ratio of the radial turbomolecular pump is very high.

The pumping speed of a radial turbomolecular pump is directly proportional to the blade length. Due to the high-speed rotation of the moving impeller, the root of the blade on the moving impeller bears a lot of stress. The magnitude of the stress is proportional to the radius of the blade, the square of the rotational speed and the square of the length of the blade, and inversely proportional to the thickness of the blade. Appropriately increasing the thickness of the blade root can make the rotating blade work in a state of equal stress, and the blade length can be increased by more than 40%. The pumping speed of a pair of radial turbomolecular pump impellers is usually equivalent to 1/3 to 1/2 of the pumping speed of ordinary molecular pumps.

Changing the direction of rotation of the moving impeller, or changing the inclination direction of the blades of the moving and stationary impellers can change the direction of radial air extraction.

In the radial flow turbomolecular pump described above, the pitch t of the vanes is substantially equal. If the blades are processed into unequal thickness shapes, or similar to the gradually curved blades in turbomachinery, so that the vertical distance between adjacent blades in the blade row is smaller near the inlet side and larger near the outlet side, it can be Further improve the compression ratio of the radial flow turbomolecular pump when working under high pressure conditions. This structure can also be used for gas compressors.

When the moving impeller or the stationary impeller has blade rows on both sides and constitutes a radial turbomolecular pump with the corresponding static and moving impellers, it shall be regarded as a two-stage pump.

The second structure is a disc drag molecular pump, referred to as a disc pump.

In this structure, the stationary impeller is in the shape of a flat disk, and there is at least one helical suction groove on one side of the stationary impeller, and the shape of the groove is approximately a logarithmic spiral. The optimum value of the ratio of groove depth to blade radius is 0.03-0.06. The thickness of the groove wall is about 1 mm. The optimum angle between the spiral groove and the radius of the impeller is 50°-75°. The optimal value of the number of slots is 10 to 30.

The moving impeller is made of a flat disc, or a dial-shaped disc that is thin on the outside and thick on the inside.

When the dynamic and static impellers are assembled, there are certain working clearances in the axial and radial directions respectively. Since the air suction groove adopts a logarithmic helix, the axial gap between the dynamic and static impellers can be increased. The gap between the outer side of the moving impeller and the pump casing and between the inner side of the stationary impeller and the rotating shaft should be large, which also serves as a channel for gas flow. When the moving impeller rotates at a high speed, the impeller constitutes a first-stage radial flow molecular pump.

The compression ratio of the single-stage disc pump is similar to the compression ratio when the impellers of 3-4 stages of ordinary molecular pumps are pumped in series, and the pumping speed is 1/20-1/10 of that of ordinary molecular pumps.

Changing the direction of inclination of the spiral groove or changing the direction of rotation of the moving impeller can change the direction of radial air extraction.

The moving impeller of the disc pump has a simple structure and is easy to process and assemble, so the manufacturing cost is relatively low.

There are spiral suction grooves on both sides of the static impeller, and when they are respectively combined with the disc-shaped moving impeller to form a suction unit, it should be regarded as a secondary pump.

The third structure is a double-drag surface disc molecular pump, referred to as a double-drag pump.

In this structure, the moving impeller is composed of two flat discs, or two setback-shaped discs that are thin on the outside and thick on the inside. Among the two discs, at least one of the discs is provided with a plurality of evenly distributed air holes near the rotating shaft to form air inlet and outlet passages.

The static impeller is in the shape of a disc, consisting of inner and outer rings, and several spiral blades are fixed between the two rings. Sometimes the inner ring can be used, depending on the strength of the blades. The shape of the blade is approximately a logarithmic spiral, and the optimal value of the angle between the blade and the radius of the impeller is 50°-75°. The thickness of the blade is about 1mm. The optimal value of the ratio of the blade width (in the axial direction) to the impeller radius is 0.03 to 0.08. The optimal number of leaves is 8-25.

The static impeller is installed in the middle of the two moving impeller discs, and the moving and static impellers have working gaps in the axial and radial directions respectively. The gaps between the outer side of the moving impeller and the pump casing, and the inner side of the static impeller and the rotating shaft are also used as gas flow channels.

When the moving impeller rotates at a high speed, the impeller constitutes a first-stage radial flow molecular pump.

In this structure, the air suction groove is composed of two adjacent stationary impeller blades and two moving impeller disks. In each air suction groove, there are two high-speed moving surfaces, that is, the surfaces of the two moving impeller disks. The inner surface. Therefore, we call it a double drag surface disc molecular pump.

The pumping speed of the double-drag pump is twice that of the disc pump, and the compression ratio is square times that of the disc pump.

Changing the inclination direction of the vanes of the stationary impeller or the rotation direction of the moving impeller can change the suction direction of the double drag pump.

Due to structural reasons, there is an inherent short-circuit channel between the air inlet and outlet of the double-drag pump. Therefore, a dynamic sealing device should be added outside the moving impeller with air holes, for example, a disc pump.

The above three basic structures can independently form a molecular pump with practical value. However, a radial flow molecular pump with better performance, or a radial flow and axial flow hybrid molecular pump can be formed by combining them in series and parallel with each other and with ordinary molecular pumps.

Several single-stage radial flow molecular pumps are installed coaxially, and the blades on the adjacent dynamic and stationary impellers, or the inclination directions of the vane grooves are respectively opposite, so that the radial pumping direction of the adjacent two-stage pumps changes alternately. A multi-stage radial flow molecular pump pumped in series. In principle, the number of stages of series impeller groups can be increased arbitrarily, and its compression ratio is approximately the product of the compression ratios of impeller groups at all stages.

Install several single-stage radial flow molecular pumps coaxially, and the blades on the adjacent moving and stationary impellers, or the inclination directions of the blade grooves are respectively the same, so that the pumping directions of the impellers at all levels are the same; at the same time, at the position where the moving impeller is close to the shaft A number of evenly distributed communicating air holes are set at the place where the gases meet; if there is no ready-made gas communicating channel on the outside of the stationary impeller, gas communicating air holes should also be provided at the place where the stationary impeller is close to the pump casing, but they do not have to be evenly distributed; a parallel pump can be formed. Working multistage radial flow molecular pump.

When there are not many impeller groups for parallel pumping, for example, less than 10 stages, the total pumping speed is similar to the sum of the pumping speeds of the impellers of all stages.

In the double-drag pump with parallel pumping, the dynamic seal between adjacent two stages can be removed.

The series and parallel multistage radial flow molecular pumps can be installed coaxially to form a series and parallel multistage radial flow molecular pump. In order to obtain the best air extraction performance, generally, the impellers near the air inlet adopt parallel air extraction, and the impellers near the air outlet use serial air extraction.

Install the basic structures of the impellers of the three radial flow molecular pumps, or their series and parallel combinations, coaxially with the ordinary axial flow turbomolecular pump, and leave a large axial gap between the axial flow impeller and the radial flow impeller , such as about 5 mm, to form a channel for the airflow to flow from the axial direction to the radial direction, and a radial flow and axial flow hybrid molecular pump can be formed.

The above-mentioned single-stage or multi-stage radial flow molecular pump connected in parallel, in series or in series and in parallel is coaxially installed with a single-stage or two-stage rotary mechanical vacuum pump, and the air outlet of the molecular pump is directly connected with the air inlet of the mechanical pump. A novel composite vacuum pump can be formed.

Advantages of the present invention:

1. The impellers of the three radial flow molecular pumps proposed by the present invention are simple in structure, and it is convenient to install the multistage impellers coaxially to form a multistage radial flow molecular pump in series, parallel or a combination of series and parallel.

2. The multi-stage radial flow molecular pump composed of three basic structures connected in series and in parallel and the composite molecular pump composed of them and ordinary molecular pumps have a simple structure, and the number of impeller stages is at least 40% lower than that of ordinary molecular pumps, and the cost is correspondingly reduced , the pumping speed can also be increased.

3. The impeller of the radial flow molecular pump proposed by the present invention adopts a shorter blade length, or adopts a vane groove structure of a drag molecular pump, so the working pressure is relatively high. Usually, the air inlet pressure can reach more than 0.1 Torr, and the air outlet pressure can reach several Torr, which are more than 10 times higher than ordinary molecular pumps.

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Fig. 1 is a single-stage radial turbomolecular pump of the present invention.

Fig. 2 is a front view of the moving impeller 1 of the present invention.

Fig. 3 is a left side view of the moving impeller 1 of the present invention.

Fig. 4 is a front view of the stationary impeller 3 of the present invention.

Fig. 5 is a left side view of the stationary impeller 3 of the present invention.

Fig. 6 is a schematic structural diagram of a single-stage radial flow disc-shaped drag molecular pump of the present invention.

Fig. 7 is a front view of the stationary impeller 6 of the disc drag molecular pump of the present invention.

Fig. 8 is a left side view of the stationary impeller 6 of the disc drag molecular pump of the present invention.

Fig. 9 is a schematic diagram of a single-stage radial-flow double drag surface disc molecular pump of the present invention.

Fig. 10 is a front view of the stationary impeller 8 of the double drag surface molecular disc pump of the present invention.

Fig. 11 is a left side view of the stationary impeller 8 of the double drag surface molecular disc pump of the present invention.

Fig. 12 is a schematic structural diagram of the serial radial flow molecular pump of the present invention.

Fig. 13 is a schematic structural diagram of a parallel radial flow molecular pump of the present invention.

Fig. 14 is a structural schematic diagram of series and parallel radial flow molecular pumps of the present invention.

Fig. 15 is a schematic structural view of a horizontal radial flow turbomolecular pump of the present invention.

Fig. 16 is a structural schematic diagram of the vertical radial flow and axial flow hybrid molecular pump of the present invention.

In the accompanying drawings: 1-moving impeller, 2-rotating shaft, 3-stationary impeller, 4-housing, 5-moving impeller, 6-stationary impeller, 7-moving impeller, 8-stationary impeller, 9-blade, 10-intake Mouth, 11-air outlet, 12-motor, 13-blade groove, 14-moving impeller, 15-stationary impeller, 16-impeller, 17-pre-stage pipe, 18-blade, 19-cooling water tank, 20-air vent, 21-dynamic seal 22-groove wall, 23-inner ring sleeve, 24-outer ring sleeve.

Embodiment 1: single-stage radial flow turbomolecular pump

A single-stage radial flow turbomolecular pump is shown in Figure 1 and consists of a moving impeller 1, a rotating shaft 2, a stationary impeller 3, and a pump casing 4.

The moving impeller 1 is shown in Figures 2 and 3. The moving impeller 1 is provided with 5 rows of blade rows concentric with the rotating shaft, and only 2 rows are shown in the figure. The stationary impeller 3 is also provided with 5 rows of blade rows concentric with the rotating shaft, and only 1 row is shown in the figure. The moving and stationary impeller blades 9 are perpendicular to the plane of the impeller and form an integral structure with the impeller. The angle between the blade and the radius is about 60°, and the air-chord ratio is about 1. The length and thickness of the blade 9 are determined by the rotating speed, the radius of the impeller, and the strength of the impeller material.

The moving impeller 1 is installed on the rotating shaft 2 , and the stationary impeller 3 is installed on the pump casing 4 . After assembly, the inclination directions of the blades on the dynamic and static impellers should be opposite. The axial and radial working gaps between the dynamic and static impellers are 0.5 to 1 mm. The larger the radius of the impeller, the larger the working gap. The gap between the outside of the moving impeller and the pump casing is about 5 mm, and the gap between the inside of the stationary impeller and the shaft is about 20 mm.

Embodiment 2: single-stage radial flow disc drag molecular pump

The single-stage disc pump is shown in Figure 6 and consists of a moving impeller 5, a rotating shaft 2, a stationary impeller 6, and a pump casing 4.

Moving impeller 5 is a flat disc. The static impeller 6 is disc-shaped, as shown in FIGS. 7 and 8 . One side of the stationary impeller has at least 1 to 5 helical air suction grooves 13, two of which are shown in the figure. The angle between the suction groove and the radius is about 60°, the ratio of the groove depth to the radius is about 0.05, and the thickness of the groove wall 22 is about 1 mm.

The moving impeller 5 is installed on the rotating shaft 2 , and the stationary impeller 6 is installed on the pump casing 4 . The axial working gap between the dynamic and static impellers is about 0.3-0.75 mm. If the size of the impeller is larger, take the larger value, and the remaining gaps are the same as in Embodiment 1.

Embodiment 3: Single-stage radial-flow double-drag disc-shaped molecular pump

The single-stage double-drag pump is shown in Figure 9 and consists of a moving impeller 7, a stationary impeller 8, a rotating shaft 2, a dynamic seal 21, and a pump casing 4.

The moving impeller 7 is composed of two flat disks, the flat disk on the left is provided with evenly distributed communicating air holes 20, and the static impeller 8 is disk-shaped, as shown in Figures 10 and 11, there are 12 air holes on the static impeller. Spiral blade 18, shows 3 among the figure, and the included angle between blade 18 and radius is approximately 60 °, and the thickness of blade 18 is about 1 millimeter, and the ratio of width and impeller is about 0.08.

The movable impeller 7 is fixed on the rotating shaft 2, and a dynamic seal 21 is installed on the outside of the left movable impeller. The dynamic seal 21 is composed of the static impeller 6 of the disc pump, and the static impeller 8 and the dynamic seal 21 are fixed on the pump casing 4. When installing , The static impeller is inserted in the middle of two moving impeller discs, the axial gap between the moving impeller 7 and the static impeller 8, and the dynamic seal 21 is 0.5 to 1 mm, and other gaps are the same as in embodiment 1.

Embodiment 4: Multi-stage radial flow molecular pumps connected in series, in parallel and in series and in parallel

The serial, parallel and combined multi-stage radial molecular pumps are shown in Figures 12, 13 and 14, and are composed of a moving impeller 14, a rotating shaft 2, a stationary impeller 15, and a pump casing 4. The dynamic and static impellers 14, 15 can be any one of the basic structures of the three radial molecular pumps, and the dynamic seal 21 of the double-drag pump is not shown. The working clearance between the moving and stationary impellers is the same as in Embodiment 1.

The series multi-stage radial flow molecular pump is shown in Figure 12. In Figure 12, a three-stage radial flow molecular pump is installed coaxially. , the vanes on the stationary impeller, or the directions of the vane grooves are respectively opposite. The flow path of the pumped gas is shown by the dotted line in FIG. 12 .

Parallel multi-stage radial flow molecular pumps are shown in Figure 13, and three-stage radial flow molecular pumps are also coaxially installed in Figure 13. The inclination directions of blades or blade slots on the dynamic and static impellers at all stages are respectively the same. The moving impeller of the left secondary pump is provided with evenly distributed air holes 20 . The flow path of the pumped gas is shown by the dotted line in FIG. 13 .

The combination of series and parallel multi-stage radial flow molecular pumps is shown in Figure 14. Four-stage radial flow molecular pumps are coaxially installed in Fig. 14 . The blades on the moving and stationary impellers of the third-stage pump on the right, or the inclination directions of the vane grooves are the same respectively, and the blades on the moving and stationary impellers of the left-side one-stage pump, or the inclination directions of the vanes and grooves are opposite to those of the three-stage pump on the right, respectively. The movable impeller of the intermediate secondary pump is provided with evenly distributed air holes 20 . The flow path of the pumped gas is shown by the dotted line in Figure 14, that is, the three-stage pump on the right is pumped in parallel and then pumped in series with the one-stage pump on the left.

Embodiment 5: Horizontal Radial Flow Turbomolecular Pump

The invention consists of several stages of radial flow turbomolecular pumps. The specific structure is shown in Figure 15, consisting of a moving impeller 1, a stationary impeller 3, a rotating shaft 2, a pump casing 4, inlet and outlet ports 10, 11, a motor 12, a front-stage pipeline 17, and a cooling water tank 19.

There are 10 moving impellers 1 fixed on the rotating shaft 2, only four of which are shown in Fig. 15 . Static impeller 3 has one more than moving impeller, is fixed on the pump casing 4, only shows five among Fig. 15. Except that the two stationary impellers 3 on both sides only have blade rows on one side, the rest of the moving and static impellers 1 and 3 have blade rows on both sides.

The dynamic and stationary impellers 1 and 3 form a total of 20 radial flow turbomolecular pumps. Among them, except for the 2nd and 19th stages (counting from the left), the inclination directions of the blades 9 on all the moving and stationary impellers 1 and 3 are respectively the same, and the rotation direction of the impellers makes the 2nd and 19th stages from inside to outside Air is pumped, and the remaining stages are pumped from the outside to the inside. The moving impellers of the 3rd to 18th stage pumps are provided with evenly distributed air holes 20 . Thereby, the 16-stage pumps in the middle form suction stages that are connected in parallel to pump air from the outside to the inside, and there are two compression stages that are pumped in series with each of them on both sides.

The pumped gas is inhaled by the air inlet 10 of the pump through the suction stage composed of 16 parallel impellers in the middle, and then divided into left and right two paths, respectively passing through the compression stage and the front stage pipeline composed of two serial radial flow impellers on both sides 17, collected at the air outlet 11, and finally pumped away by the backing pump.

Embodiment 6: vertical radial flow, axial flow hybrid molecular pump

The invention consists of two-stage radial-flow turbomolecular pump and nine-stage common axial-flow turbomolecular pump impellers coaxially installed. The specific structure is shown in Figure 16, consisting of radial flow turbomolecular pump dynamic and stationary impellers 1, 3, rotating shaft 2, common molecular pump impeller 16, pump housing 4, motor 12, air inlet and outlet ports 10, 11 and cooling water tank 19.

The structures and installation dimensions of the dynamic and static impellers 1 and 3 of the radial flow turbomolecular pump are the same as those in Embodiment 1. The upper stage of the radial flow pump draws air from the inside to the outside, and the lower stage of the radial flow pump pumps air from the outside to the inside, and the second stage of the pump works in series to form a compressor The impeller size of the 9-stage ordinary molecular pump is the same as that of the suction stage impeller of the ordinary molecular pump. There should be an axial gap of about 5 mm between the impeller of the axial flow molecular pump and the impeller of the radial flow molecular pump, forming a channel for gas flow.

The pumped gas is sucked into the pump body through the air inlet, passes through the 9-stage ordinary molecular pump impeller in the axial direction, and then passes through the two-stage radial flow turbomolecular pump working in series, and collects at the air outlet 11, and finally, is pumped away by the backing pump.

Claims (9)

1. A radial flow molecular pump is composed of a moving impeller 1, a rotating shaft 2, a stationary impeller 3 and a pump casing 4, and is characterized in that: a) The moving and stationary impellers 1 and 3 are disk-shaped, and there is at least one row of blade rows concentric with the rotating shaft 2 on one side, and each row of blade rows consists of several uniformly distributed, equal-thickness, single-ended blades connected to the impeller plane 9 , the blade 9 is perpendicular to the plane of the impeller, and the angle between the blade 9 and the radius of the impeller is 50°~75°, the inclination angle of the blades on the same blade row is equal, and the inclination direction of the blades on the same impeller side is the same, the best value of the air-chord ratio of the blade 9 0.8 to 1.2, the radial position of the upper blade row of the dynamic and static impellers 1 and 3 should be divergent; b) The length of the blade 9 is relatively short, and forms an integral structure with the moving and stationary impellers 1 and 3, and does not require additional support devices, and the blades on the stationary impeller 3 are relatively thin; c) The moving impeller 1 is fixed on the rotating shaft 2, the stationary impeller 3 is fixed on the pump casing 4, the blade rows on the moving and stationary impellers 1 and 3 are alternately inserted, leaving 0.5 to 1 mm working distance in the axial and radial directions Clearance, wherein the radial clearance between the outer side of the moving impeller 1 and the pump casing 4, and the inner side of the stationary impeller 3 and the rotating shaft 2 is about 5 to 20 mm. After assembly, the blades on the moving and stationary impellers 1 and 3 have opposite inclination directions . 2. A radial flow molecular pump consisting of a moving impeller 5, a rotating shaft 2, a stationary impeller 6 and a pump casing 4, characterized in that: a) The moving impeller 5 is in the shape of a flat disk, or a backed-up disk with a thin outer layer and a thicker inner layer; b) The static impeller 6 is in the shape of a disc, with at least one helical suction groove on one side, the groove shape is approximately a logarithmic spiral, the angle between the suction groove and the radius is 50°～75°, the groove depth and the impeller radius The optimal value of the ratio is 0.03 to 0.06, the optimal value of the number of slots is 10 to 30, and the number of outer slots of the stationary impeller 6 can be higher than the number of inner slots; c) The moving impeller 5 is fixed on the rotating shaft 2, and the static impeller 6 is fixed on the pump casing 4. The moving and static impellers 5 and 6 are installed close to each other, leaving a working gap of 0.5-1mm in the axial direction. There is a large radial gap between the outside of the moving impeller 5 and the pump casing 4, and between the inside of the stationary impeller 6 and the rotating shaft 2, about 5 to 20 millimeters. 3. A radial flow molecular pump is composed of a moving impeller 7, a rotating shaft 2, a stationary impeller 8, a casing 4 and a dynamic seal 21, and is characterized in that: a) The movable impeller 7 is composed of two flat disks, or two dial-shaped disks that are thin on the outside and thick on the inside. At least one of the two disks is provided with uniform air holes 20 near the rotating shaft 2, and The outside of the disk is actuated with a seal 21 . b) The stationary impeller 8 is in the shape of a disk, and the stationary impeller is composed of inner and outer rings 23 and 24 (the inner rings can be omitted), and several spiral blades 18 are fixed between the two rings, and the shape of the blades 18 is approximately logarithmic The spiral, the angle between the blade 18 and the radius of the impeller is 50°-75°, and the optimum value of the ratio of the width of the blade to the radius of the impeller is 0.03-0.08. The optimal number of blades is 8 to 25, and the number of blades on the outer side of the impeller can be more than that on the inner side; c) The moving impeller 7 is fixed on the rotating shaft 2, the stationary impeller 8 and the dynamic seal 21 are fixed on the casing 4, and there is a working gap of 0.5-1mm in the axial direction between the moving and stationary impellers 7, 8 and the dynamic seal 21, There is a gap of about 5-20 mm between the outer side of the movable impeller 7 and the casing 4, and the inner side of the stationary impeller 8 and the rotating shaft 2; d) The dynamic seal 21 device can also adopt the structure of the static impeller 6 . 4. The radial flow molecular pump according to claim 1, characterized in that the blades 9 on the moving impeller 1 are thicker as they get closer to the plane of the impeller. 5. The radial flow molecular pump according to claim 1, characterized in that the blades 9 adopt unequal thickness or gradually curved blades, so that the vertical distance between adjacent blades is smaller near the inlet side and closer to the outlet side. larger. 6. The radial flow molecular pump according to claims 1-5, characterized in that the impeller groups at all levels are coaxially installed, and the blades 9, 18 on the dynamic and static impellers 14, 15 of two adjacent stages, or the blade grooves 13 The directions of inclination are opposite. 7. The radial flow molecular pump according to claims 1-5, characterized in that the impeller groups at all levels are coaxially installed, and the blades 9, 18 on the moving and stationary impellers 14, 15 of the adjacent second stage, or the blade grooves 13 The inclination directions are the same respectively, and the movable impeller 14 is provided with several evenly distributed air holes 20 near the rotating shaft 2, and when there is no ready-made gas channel outside the stationary impeller 15, a number of communicating air holes 20 are also provided near the pump casing 4, but it is not necessary Evenly distributed. 8. The radial flow molecular pump according to claims 1-7, characterized in that the impeller groups at all levels are coaxially installed to form a series and parallel combination of multistage radial flow molecular pumps. 9. The radial flow molecular pump according to claims 1-8, characterized in that the radial flow molecular pump impeller sets 14, 15 are installed coaxially with the ordinary axial flow turbomolecular pump impeller 16, and there is a gap between the radial flow and axial flow impellers. Large axial clearance, for example 5-10mm.

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