Intake flow diffusing mechanism for high vacuum pump down speed test

Abstract

The application relates to a high-vacuum pumping speed test air inlet flow distribution mechanism, which comprises a connecting flange, an air inlet pipe connected to one side of the connecting flange, and a planar flow distribution plate, a first connecting rod, a first conical flow distribution plate, a second connecting rod and a second conical flow distribution plate connected to the other side of the connecting flange in sequence. The flow distribution plate based on the double-stage conical flow distribution structure can ensure that the gas molecules collide at least twice when entering the back, realizes a good equilibrium state, has the advantage of small air release amount, avoids the beam effect caused by the traditional elbow air inlet, reduces the measurement uncertainty of the background vacuum, and can improve the test efficiency and the reliability of the test results.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high vacuum pump performance testing, and particularly relates to a gas inlet flow distribution mechanism for high vacuum pump pumping speed testing. BACKGROUND

[0002] In recent years, with the development and industrial upgrading of the fields of semiconductor, chemical pharmaceutical and high-energy physics research, the demand for vacuum pumps is increasingly widespread, and the requirements for the performance of vacuum pumps are increasingly stringent. Therefore, it is increasingly necessary to accurately and reliably test various performances of the vacuum pump. The performance test of the vacuum pump is mainly the test of the pumping speed performance. At present, most manufacturers and research institutions of vacuum pumps test the performance of the vacuum pump according to the provisions of the national standard by using the flow method and the flow guide method, for example, see [GB / T 40344.1-2021 Standard Method for Performance Measurement of Vacuum Pumps; GB / T 7774-2007 Measurement of Performance Parameters of Turbomolecular Pumps in Vacuum Technology; JB / T 11081-2011 Low Temperature Pumps in Vacuum Technology]. The flow method and the flow guide method both use a curved pipe gas inlet method, and the gas outlet of the gas inlet pipe is on the axis of the test cover, so that the gas enters the test cover from a direction away from the pump port. Generally, for a test cover with a diameter of D, the diameter of the gas inlet pipe is 0.1D, the total length is about D, and the distance between the gas outlet and the top of the test cover is 0.5D. Ignoring the wall thickness of the gas inlet pipe, the total surface area of the gas inlet pipe inside the test cover can be estimated to be about 0.2πD 2 . In theory, the gas entering the test cover should quickly reach a uniform distribution equilibrium state, which requires the gas entering the test cover to collide with the wall at least once. When testing the pumping speed performance of a vacuum pump with a larger diameter or a larger pumping speed, the size of the test cover required is larger, the distance between the gas inlet pipe interface and the top of the test cover is larger, and the diameter of the gas inlet pipe is relatively larger. As a result, two problems will arise: first, after the gas enters the test cover through the gas inlet pipe, the probability of collision with the wall will decrease, and the time for the gas to reach the equilibrium state will be longer, reducing the test efficiency; second, the increase in the diameter of the gas inlet pipe means an increase in the surface area, which will generate a large amount of outgassing during the evacuation of the test cover, adversely affecting the base vacuum, increasing the uncertainty of the test, and reducing the reliability of the test results. SUMMARY

[0003] Therefore, the present application aims to solve the problems of gas inlet pipe outgassing affecting the base vacuum and insufficient collision of gas in the test cover in the conventional high vacuum pump pumping speed test device, and proposes a gas inlet flow distribution mechanism for high vacuum pump pumping speed testing, which improves the test efficiency and the reliability of the test results of the performance of the vacuum pump.

[0004] The air inlet flow mechanism comprises a connecting flange in the middle, an air inlet pipe connected to one side of the connecting flange, and a planar flow plate, a first connecting rod, a first conical flow plate, a second connecting rod and a second conical flow plate connected to the other side of the connecting flange in sequence.

[0005] Further, the connecting flange, the planar flow plate, the first connecting rod, the first conical flow plate, the second connecting rod and the second conical flow plate are coaxially arranged.

[0006] Further, the center of the connecting flange has an air inlet hole, and the air inlet pipe is installed on the connecting flange through the air inlet hole.

[0007] Further, the planar flow plate is circular, the diameter of the planar flow plate is the same as the diameter of the air inlet hole on the connecting flange, and the planar flow plate has a plurality of first flow holes.

[0008] Further, the tips of the first conical flow plate and the second conical flow plate are arranged in a direction away from the connecting flange.

[0009] Further, the distance between the tips of the first conical flow plate and the second conical flow plate is half the height of the first conical flow plate or the second conical flow plate, and the length of the second connecting rod is also half the height of the first conical flow plate or the second conical flow plate.

[0010] Further, the radial dimension of the bottom circle of the first conical flow plate and the second conical flow plate is the same as the radial dimension of the planar flow plate.

[0011] Further, the taper angle of the first conical flow plate and the second conical flow plate is 60°, and a plurality of second flow holes are arranged on the first conical flow plate and the second conical flow plate.

[0012] Further, the angle between the center line of the nearest adjacent second flow holes on the first conical flow plate and the second conical flow plate and the normal line of the corresponding second flow hole is greater than or equal to 30°.

[0013] Further, the length of the first connecting rod is times the diameter of the planar flow plate.

[0014] The embodiment of the present application provides a high vacuum pump pumping speed test air inlet flow mechanism based on a double-stage conical structure, the top center of a test cover can be fixedly installed on a connecting flange, gas molecules pass into the test cover through an air inlet pipe and the connecting flange, collide with a planar flow plate and a double-stage series conical flow plate in sequence, and then diffuse in the test cover, and finally reach an equilibrium state.

[0015] The air inlet flow mechanism of the embodiment of the present application has a small air outlet area, can obtain a background vacuum more quickly, and reduces the influence of air outlet on test results, the planar flow plate and the double-stage series conical flow plate can ensure that the gas reaches an equilibrium state after colliding at least twice after entering the test cover, and the distribution uniformity of gas molecules in the test cover is improved. In addition, based on the above characteristics, the embodiment of the present application is especially suitable for a large-diameter test cover with a caliber greater than or equal to 200 mm, and can avoid the problems of the influence of air outlet of the air inlet pipe on the background vacuum and insufficient collision of gas in the test cover in the test process of the traditional large-diameter test cover. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0017] Figure 1 FIG. 1 is a structural schematic diagram of an air inlet flow mechanism of the embodiment of the present application;

[0018] Figure 2 FIG. 2 is a planar schematic diagram of a planar flow plate of the embodiment of the present application;

[0019] Figure 3 FIG. 3 is a structural schematic diagram of a first conical flow plate and a second conical flow plate of the embodiment of the present application.

[0020] Explanation of reference signs:

[0021] Air inlet pipe 1, connecting flange 2, planar flow plate 3, first connecting rod 4, first conical flow plate 5, second conical flow plate 6, and second connecting rod 7. DETAILED DESCRIPTION

[0022] The description of the embodiments of the present application should be combined with the corresponding drawings, and the drawings should be regarded as a part of the complete description. In the drawings, the shape or thickness of the embodiments can be enlarged, and the drawings can be simplified or facilitated. Furthermore, the parts of the structures in the drawings will be described respectively, and it should be noted that the elements not shown in the drawings or not described by words are forms known by those skilled in the art.

[0023] The description of the embodiments herein, any reference to direction or orientation is merely intended for convenience of description and is not construed to be limiting of the scope of the present application. The following description of the preferred embodiments will refer to a combination of features that can exist independently from each other or in combination. The present application is not particularly limited to the preferred embodiments. The scope of the present application is defined by the claims.

[0024] As shown in Figure 1 , the air inlet flow mechanism of the embodiments of the present application comprises a connecting flange 2, an air inlet pipe 1 connected to one side of the connecting flange 2, and a planar flow plate 3, a first connecting rod 4, a first conical flow plate 5, a second connecting rod 7 and a second conical flow plate 6 connected to the other side of the connecting flange 2 in sequence. When the air inlet flow mechanism of the embodiments of the present application is used for high vacuum pump speed test, the connecting flange 2 is fixed at the top center of the high vacuum pump speed test cover, one side is connected to the standard gas flow meter through the air inlet pipe 1, and the other side is welded with the planar flow plate 3 through the stainless steel pipe. In this way, it can be ensured that the gas reaches the equilibrium state after at least two collisions after entering the test cover, the uniformity of the distribution of gas molecules in the test cover is improved, the problems of the influence of the air inlet pipe on the background vacuum degree and the insufficient collision of the gas in the test cover during the test are avoided, and the test efficiency and the reliability of the test results can be effectively improved.

[0025] As shown in Figure 1 , in this embodiment, the center of the connecting flange 2 has an air inlet hole (not shown in the figure), the air inlet pipe 1 is installed on one side of the connecting flange 2 through the air inlet hole, and the connecting flange 2 can be a CF35 interface connecting flange. On the other side of the connecting flange 2, a sleeve (not shown in the figure) can be provided, one end of the sleeve is welded with the connecting flange 2 and the other end is welded with the planar flow plate 3, so as to connect the connecting flange 2 and the planar flow plate 3 together. The first connecting rod 4 is arranged at the center of the planar flow plate 3, the end of the first connecting rod 4 is connected with the first conical flow plate 5, the second connecting rod 7 is connected at the center of the other end of the first conical flow plate 5, and the end of the second connecting rod 7 is connected with the second conical flow plate 6. In addition, the connecting flange 2, the planar flow plate 3, the first connecting rod 4, the first conical flow plate 5, the second connecting rod 7 and the second conical flow plate 6 are coaxially arranged.

[0026] As shown in Figure 1 and Figure 2 , in this embodiment, the planar flow plate 3 is a circular sheet, and the diameter size of the planar flow plate 3 is basically the same as the diameter size of the air inlet hole on the connecting flange 2. Referring to Figure 2 , a plurality of first flow holes are uniformly distributed on the planar flow plate 3, and the first flow holes can be circular through holes. The length of the first connecting rod 4 is times.

[0027] As Figure 1 and Figure 3 shown, in this embodiment, the tips of the first and second conical flow diffusers 5 and 6 are arranged in a direction away from the connecting flange 2. The first and second conical flow diffusers 5 and 6 are identical in structure and size. The distance between the tips of the first and second conical flow diffusers 5 and 6 is half the height of the first or second conical flow diffuser 5 or 6, and the length of the second connecting rod 7 is also half the height of the first or second conical flow diffuser 5 or 6. The radial dimension of the conical base of the first and second conical flow diffusers 5 and 6 is the same as that of the planar flow diffuser 3. The conical angle of the first and second conical flow diffusers 5 and 6 is 60°, and a plurality of secondary flow holes are arranged on the first and second conical flow diffusers 5 and 7, which can be circular through holes.

[0028] As Figures 1-3 shown, in this embodiment, the inner diameter of the sleeve between the connecting flange 2 and the planar flow diffuser 3 is 30 mm, and the height is 3 mm, and the material can be stainless steel. The diameter of the planar flow diffuser 3 is 30 mm, and the thickness is 1 m, and the diameter of the primary flow holes distributed thereon is 2-4 mm, preferably 4 mm. The length of the first connecting rod 4 is 27 mm, and the length of the second connecting rod 7 is 14 mm. The conical angle of the first and second conical flow diffusers 5 and 6 is 60°, and the height is 27 mm, and the diameter of the secondary flow holes uniformly distributed thereon is 2-4 mm, preferably 4 mm. And the secondary flow holes on the first and second conical flow diffusers 5 and 7 are arranged in a staggered manner, and the angle between the center line of the nearest adjacent secondary flow holes and the normal line of the corresponding secondary flow hole is greater than or equal to 30°, preferably 30°.

[0029] In this embodiment, all components can be made of SUS316L stainless steel and subjected to high-temperature hydrogen removal process.

[0030] The gas inlet flow diffuser mechanism of this embodiment has the application condition that the gas in the test cover is in a molecular flow state, that is, the average free path of the gas molecules is much larger than the size of the test cover, and the gas in the test cover is mainly wall-molecule collision. Therefore, in order to make the gas quickly reach the equilibrium state when it first enters the test cover, this embodiment adopts a flow diffuser mechanism of planar flow diffuser, first conical flow diffuser and second conical flow diffuser, so that the gas can fully collide with the flow diffuser mechanism after entering the test cover, and then quickly reach the equilibrium state. According to the setting of the above structure and size, angle and other parameters, the gas discharge area can be much smaller than that of the traditional gas inlet mechanism.

[0031] In this embodiment, the wall thickness of all components is ignored, the outgassing of the first connecting rod 4 and the second connecting rod 7 is ignored, the outgassing area of the flow holes on the planar flow plate 3, the first conical flow plate 5 and the second conical flow plate 6 is calculated as the outgassing area of planar plate flow holes, and then according to the given parameters, the outgassing area of the intake flow mechanism of the high vacuum pump pumping speed test in this embodiment can be estimated as about:

[0032] (1) Calculate the outgassing area of the sleeve between the connecting flange 2 and the planar flow plate 3:

[0033] S1 = 2πr1h1 × 2

[0034] wherein r1 is the radius of the planar flow plate 3 (15 mm); h1 is the height of the sleeve (3 mm).

[0035] Then the value of S1 is 180πmm 2 .

[0036] (2) Calculate the outgassing area of the planar flow plate 3:

[0037] S2 = 2πr1 2 + 2πr1h2

[0038] wherein h2 is the thickness of the planar flow plate 3 (1 mm).

[0039] Then the value of S2 is 480πmm 2 .

[0040] (3) Calculate the outgassing area of the first conical flow plate 5 and the second conical flow plate 6:

[0041] S3 = 4 × πr2l

[0042] wherein r2 is the radius of the bottom surface of the conical flow plate; l is the length of the generatrix. r2 and l can be calculated according to the length of the first connecting rod 4 and the conical angle

[0043] Then the value of S3 is 1944πmm 2 .

[0044] (4) Total outgassing area

[0045] It can be obtained that the total outgassing area is about 2604πmm 2 .

[0046] The outgassing area of the traditional intake mechanism using a bent pipe intake is 0.2πD 2 mm 2 , and for a test cover with a caliber of 200 mm, the outgassing area of the intake pipe is about 8000πmm 2 , which is obviously higher than the 2604πmm of the embodiment.2 Therefore, the air exhaust area of the air inlet flow distribution mechanism based on the conical structure is significantly smaller than the air exhaust area of the conventional air inlet pipe, and the mechanism is particularly suitable for large-diameter test covers with a caliber of 200 mm or more.

[0047] In addition, it should be noted that the parameter settings regarding the size and angle in the present embodiment are only preferred conditions and should not be understood as being limited to the above settings. For example, the angle between the center line of the first-stage flow distribution hole and the normal line is 30°, so that the flow distribution holes between the two-stage conical flow distribution plates are spaced apart, ensuring that the gas molecules collide with the flow distribution mechanism sufficiently. It is known that when the angle is greater than 30° and is ensured to be not greater than a certain angle, the same effect of the total air exhaust area being significantly better than the conventional air inlet area can be achieved. For another example, the length of the first connecting rod 4 is 1.5 times the diameter of the planar flow distribution plate 3, which is a preferred condition calculated by the Pythagorean theorem, and the purpose is to ensure that the size of the bottom surface of the conical flow distribution plate is approximately the same as the area size of the planar flow distribution plate 3 when the bottom surface of the conical flow distribution plate is coplanar with the bottom surface of the planar flow distribution plate 3 and the conical angle of the conical flow distribution plate is 60°, so as to ensure that the gas molecules pass through the planar flow distribution plate and enter the conical flow distribution plate as much as possible. It is known that even if the length of the first connecting rod 4 varies within a certain range of 1.5 times, the total air exhaust area of the present embodiment is still significantly better than the conventional air inlet area. For another example, the length of the second connecting rod 7 is half the height of the conical flow distribution plate, which is also for the purpose of ensuring that the gas molecules collide with the flow distribution mechanism as much as possible. The length of the second connecting rod 7 can be slightly larger or smaller, and the total air exhaust area is still significantly better than the conventional air inlet area.

[0048] The present application relates to an air inlet flow distribution mechanism for high-vacuum pump pumping speed test, which adopts a planar flow distribution plate and a two-stage conical flow distribution plate as main parts. On the one hand, the air exhaust amount during the process of extracting the background vacuum of the test cover is reduced, and on the other hand, the gas in the test cover is ensured to reach the equilibrium state quickly. The uncertainty of the vacuum pump performance test is reduced, and the test efficiency is improved.

[0049] The above only describes the preferred embodiments of the present application and should not be used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.​​

Claims

1. An intake flow diffusing mechanism for high vacuum pumping speed test, characterized by, The air inlet pipe (1) is connected to one side of the connecting flange (2), and the planar flow distribution plate (3), the first connecting rod (4), the first conical flow distribution plate (5), the second connecting rod (7) and the second conical flow distribution plate (6) are sequentially connected to the other side of the connecting flange (2); The tips of the first conical flow distribution plate (5) and the second conical flow distribution plate (6) are arranged in a direction away from the connecting flange (2); A plurality of secondary flow distribution holes are arranged on the first conical flow distribution plate (5) and the second conical flow distribution plate (6); The angle between the center line of the nearest adjacent secondary flow distribution holes on the first conical flow distribution plate (5) and the second conical flow distribution plate (6) and the normal line of the corresponding secondary flow distribution hole is greater than or equal to 30°.

2. The air intake flow disperser of claim 1, wherein, The connecting flange (2), the planar flow distribution plate (3), the first connecting rod (4), the first conical flow distribution plate (5), the second connecting rod (7) and the second conical flow distribution plate (6) are coaxially arranged.

3. The air intake flow disperser of claim 1, wherein, The center of the connecting flange (2) has an air inlet hole, and the air inlet pipe (1) is installed on the connecting flange (2) through the air inlet hole.

4. The air intake flow disperser of claim 3, wherein, The planar flow distribution plate (3) is circular, the diameter of the planar flow distribution plate (3) is the same as the diameter of the air inlet hole on the connecting flange (2), and the planar flow distribution plate (3) has a plurality of primary flow distribution holes.

5. The air inlet flow disperser of claim 1, wherein, The distance between the tips of the first conical flow distribution plate (5) and the second conical flow distribution plate (6) is half of the height of the first conical flow distribution plate (5) or the second conical flow distribution plate (6), and the length of the second connecting rod (7) is also half of the height of the first conical flow distribution plate (5) or the second conical flow distribution plate (6).

6. The air intake flow disperser of claim 1, wherein, The radial dimension of the bottom circle of the cone of the first conical flow distribution plate (5) and the second conical flow distribution plate (6) is the same as the radial dimension of the planar flow distribution plate (3).

7. The air intake flow disperser of claim 1, wherein, The cone angle of the first conical flow distribution plate (5) and the second conical flow distribution plate (6) is 60°.

8. The air inlet flow distribution mechanism of claim 1, wherein, The length of the first connecting rod (4) is the diameter dimension of the planar flow distribution plate (3) / 2.

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