Cryogenic pumps and baffles for cryogenic pumps

Abstract

Provided are a cryogenic pump and a baffle for a cryogenic pump capable of improving exhaust performance. The baffle (14) includes: a first portion (14A), including a center (14C) of the baffle (14), having a first hole (14AH) formed therethrough; and a second portion (14B), including an edge (14E) of the baffle (14), having a second hole (14BH) formed therethrough. The electrical conductivity of the second portion (14B) is greater than that of the first portion (14A).

Description

Technical Field

[0001] The present invention relates to a cryogenic pump and a baffle for the cryogenic pump. Background Art

[0002] The cryopump includes a pump housing, a heat shield located within the pump housing, a plurality of cryogenic panels located within the heat shield, and a baffle located at an opening of the heat shield. The heat shield includes a first heat shield and a second heat shield. The first heat shield and the second heat shield each have a cylindrical shape. Each heat shield is located within the pump housing with its central axis aligned. The second heat shield is located further outward than the first heat shield, and the first heat shield is located closer to the opening of the pump housing than the second heat shield. The base end of the first heat shield is surrounded by the top end of the second heat shield. As a result, a fluid passage is formed between the base end of the first heat shield and the top end of the second heat shield (for example, see Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2010-48132 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] In the aforementioned cryopump, in addition to the gas flowing into the heat shield from the baffle, the gas flowing into the second heat shield through the flow path formed between the base end of the first heat shield and the top end of the second heat shield is also exhausted through the cryo-face plate. This improves the exhaust performance of the cryopump. On the other hand, compared to a case where the heat shield is formed from a single cylindrical member, the heat input through the flow path formed by the base end of the first heat shield and the top end of the second heat shield is greater. This also reduces the exhaust performance of the cryopump. Therefore, other methods for improving the exhaust performance of the cryopump are required.

[0008] An object of the present invention is to provide a cryopump and a baffle for a cryopump that can improve exhaust performance.

[0009] Solutions to Problems

[0010] A cryopump according to one embodiment includes a cryo-panel connected to a refrigerator; a main body housing the cryo-panel; and a baffle located at a gas inlet of the main body. The baffle includes a first portion, which includes the center of the baffle and has a first hole formed therethrough; and a second portion, which includes an edge of the baffle and has a second hole formed therethrough. The second portion has a greater electrical conductance than the first portion.

[0011] A cryopump baffle according to one embodiment includes a first portion including a center of the baffle and having a first hole formed therethrough; and a second portion including an edge of the baffle and having a second hole formed therethrough. The second portion has a greater electrical conductance than the first portion.

[0012] According to the aforementioned cryopump and cryopump baffle, the conductance of the second portion is greater than that of the first portion, allowing gas to flow easily from the second portion of the baffle into the main body. This facilitates the accumulation of condensed gas even in the peripheral portion (including the edges) of the cryopanel when viewed from above, preventing the preferential accumulation of condensed gas in the central portion (including the center) of the cryopanel. Consequently, uneven accumulation of condensed gas within the cryopanel can be suppressed. Consequently, the exhaust performance of the cryopump is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a cross-sectional view showing the structure of a cryopump in one embodiment.

[0014] Figure 2 It is a plan view showing the shape of the baffle in a plan view.

[0015] Figure 3 It is a plan view showing the structure of the cryopump when viewed from above. DETAILED DESCRIPTION

[0016] Reference Figures 1 to 3 An embodiment of a cryopump and a baffle for a cryopump will be described.

[0017] [Cryogenic pump]

[0018] like Figure 1 As shown in FIG. 1 , the cryopump 10 includes a refrigerator 11, a cryogenic panel 12, a main body 13, and a baffle 14. Figure 1 1 shows the cross-sectional structure of the main body 13 and the baffle 14 of the cryopump 10 and the side structure of the refrigerator 11 and the cryogenic panel 12. Figure 1 In FIG, for convenience of illustration, only a portion of the refrigerator 11 is shown.

[0019] The low-temperature panel 12 is connected to the refrigerator 11. The main body 13 houses the low-temperature panel 12. The main body 13 has a gas inlet 13A. The baffle 14 is located at the gas inlet 13A of the main body 13.

[0020] The main body 13 includes a pump housing 13B and a heat shield 13C. The pump housing 13B is a vacuum container that isolates the interior of the cryopump 10 from the exterior. The pump housing 13B includes a first housing portion 13B1 for housing the heat shield 13C and a second housing portion 13B2 for housing the refrigerator 11. The first housing portion 13B1 has a cylindrical shape. One end of the first housing portion 13B1 is closed by a bottom, and an opening 13BA is located at the other end.

[0021] Heat shield 13C protects cryogenic panel 12 from radiant heat from pump housing 13B. Heat shield 13C is located between pump housing 13B and cryogenic panel 12. Heat shield 13C has a cylindrical shape. One end of heat shield 13C is closed by a bottom, and an opening 13CA is located at the other end. Heat shield 13C houses cryogenic panel 12. Opening 13CA of heat shield 13C is surrounded by opening 13BA of pump housing 13B. Opening 13CA of heat shield 13C and opening 13BA of pump housing 13B form gas inlet 13A.

[0022] The refrigerator 11 is, for example, a Gifford-McMahon refrigerator. It includes a first cylinder 11A1, a first stage 11A2, a second cylinder 11B1, and a second stage 11B2. The first cylinder 11A1 and the second cylinder 11B1 are connected in series. A first displacer (not shown) is located within the first cylinder 11A1, and a second displacer (not shown) is located within the second cylinder 11B1.

[0023] The first cylinder 11A1 is located within the second housing portion 13B2 of the pump housing 13B. The first stage 11A2 is fixed to the end of the first cylinder 11A1, connected to the end of the second cylinder 11B1. The first stage 11A2 is in contact with the heat shield 13C, thereby thermally connecting the first stage 11A2 and the heat shield 13C.

[0024] Second cylinder 11B1 is located within a space defined by heat shield 13C. A second base 11B2 is secured to the end of second cylinder 11B1 opposite the end connected to first cylinder 11A1. Mounting member 11C, which connects low-temperature panel 12 to refrigerator 11, is connected to second base 11B2.

[0025] A plurality of low-temperature panels 12 are located in a space defined by a heat shield 13C. Each low-temperature panel 12 is assembled to an assembly member 11C. Thus, each low-temperature panel 12 is thermally connected to the second stage 11B2. Each low-temperature panel 12 is formed by a plate member. Each low-temperature panel 12 is formed into a truncated cone shape. Each low-temperature panel 12 is assembled to the assembly member 11C in such a way that the center of each low-temperature panel 12 is located on the same central axis when viewed from above. In addition, the term "viewed from above" used in this disclosure refers to the view from a position opposite to the plane in which the baffle 14 is unfolded (in the Figure 1In other words, the component is viewed from a direction perpendicular to the plane in which the baffle 14 is located. In this regard, the "planar structure" used in this disclosure refers to the structure of the component when viewed from above.

[0026] Refrigerator 11 cools first stage 11A2 to a predetermined first temperature within the range of, for example, 80K to 100K, and cools second stage 11B2 to a predetermined second temperature within the range of, for example, 10K to 20K. As described above, since heat shield 13C is thermally connected to first stage 11A2, heat shield 13C is cooled to the same temperature as first stage 11A2. Since low-temperature panel 12 is connected to second stage 11B2 via mounting member 11C, low-temperature panel 12 is cooled to the same temperature as second stage 11B2.

[0027] In the cryopump 10, gas condensed at the first temperature and having a relatively low vapor pressure is captured by the baffle 14 and the heat shield 13C, thereby discharging the gas from the vacuum chamber connected to the cryopump 10. Furthermore, gas condensed at the second temperature and having a relatively high vapor pressure is captured by the cryopanel 12, thereby discharging the gas from the vacuum chamber connected to the cryopump 10.

[0028] Figure 2 The planar structure of the baffle 14 is shown.

[0029] like Figure 2 As shown, baffle 14 includes a first portion 14A and a second portion 14B. First portion 14A includes center 14C of baffle 14. A first hole 14AH is formed in first portion 14A, penetrating baffle 14. First hole 14AH penetrates baffle 14 in the thickness direction of baffle 14. Second portion 14B includes edge 14E of baffle 14. Second hole 14BH is formed in second portion 14B, penetrating baffle 14. The electrical conductance of second portion 14B is greater than that of first portion 14A.

[0030] Because the electrical conductivity of the second portion 14B is greater than that of the first portion 14A, gas easily flows from the second portion 14B of the baffle 14 into the main body 13. As a result, when viewed from above, condensed gas is also more likely to accumulate in the outer peripheral portion (including the edge portion) of the cryogenic panel 12, and the accumulation of condensed gas in the central portion (including the center portion surrounded by the outer peripheral portion) of the cryogenic panel 12 can be suppressed. Consequently, uneven accumulation of condensed gas in the cryogenic panel 12 can be suppressed. As a result, the area where condensed gas accumulates can be expanded within the area defined by the main body 13, thereby improving the exhaust performance of the cryopump 10.

[0031] Conductance is an indicator of the flowability of gas in a flow channel. Given the same pressure difference between two spaces connected by a flow channel, the greater the flow channel's conductance, the greater the flow rate of gas flowing through it. Conductance depends on factors such as the channel's thickness and length, the type of gas flowing through it, and the temperature.

[0032] The aperture ratio of the second portion 14B based on the second hole 14BH can also be greater than the aperture ratio of the first portion 14A based on the first hole 14AH. Consequently, the electrical conductance of the second portion 14B can also be greater than the electrical conductance of the first portion 14A. This cryopump 10 makes it easier to increase the electrical conductance of the second portion 14B relative to the electrical conductance of the first portion 14A, compared to a case where the thickness of the baffle 14 is different from that of the second portion 14B. Furthermore, since the thickness of the baffle 14 can be suppressed, the volume of the main body 13 can be prevented from being reduced due to the thickness of the baffle 14.

[0033] The first hole 14AH and the second hole 14BH may be circular holes, that is, circular in plan view. In each of the first hole 14AH and the second hole 14BH, the circular hole also penetrates the baffle 14 in the thickness direction. The diameter of the second hole 14BH may be larger than the diameter of the first hole 14AH.

[0034] This allows the number of second holes 14BH to be reduced to less than the number of first holes 14AH, and also allows the conductance of second portion 14B to be greater than the conductance of first portion 14A. Therefore, processing of baffle 14 is facilitated.

[0035] The second hole 14BH can include a large hole 14BH1 and an intermediate hole 14BH2. In addition, the large hole 14BH1 is an example of a third hole, and the intermediate hole 14BH2 is an example of a fourth hole. The intermediate hole 14BH2 (fourth hole) is smaller than the large hole 14BH1 (third hole). The second portion 14B can include an outer peripheral portion 14B1 and an intermediate portion 14B2. Figure 2 and Figure 3 In the example, the outer portion 14B1 includes the edge 14E of the baffle 14 and is formed with a large hole 14BH1. The middle portion 14B2 is located between the outer portion 14B1 and the first portion 14A and is formed with a middle hole 14BH2.

[0036] exist Figure 2 and Figure 3In the example, first portion 14A is circular. First portion 14A may include only first hole 14AH. Middle portion B2 may also be referred to as a first annular portion surrounding first portion 14A. Middle portion B2 (first annular portion) may include only middle hole 14BH2 (fourth hole). Peripheral portion 14B1 may also be referred to as a second annular portion surrounding middle portion B2 (first annular portion). Peripheral portion 14B1 (second annular portion) may include only large holes 14BH1 (third hole). The number of large holes 14BH1 (third hole) may be greater than the number of middle holes 14BH2 (fourth hole).

[0037] Thus, the electrical conductance of baffle 14 can be increased in the order of first portion 14A, middle portion 14B2, and outer peripheral portion 14B1. Therefore, compared to a case where baffle 14 has uniform electrical conductance throughout second portion 14B, it is possible to suppress differences in the amount of condensed gas accumulated in the radial direction of low-temperature panel 12.

[0038] like Figure 2 As shown in the example, when the first hole 14AH and the second hole 14BH are circular holes, the diameter of the middle hole 14BH2 is smaller than the diameter of the large hole 14BH1. The diameter of the second hole 14BH may be larger than 1 times and less than 3 times the diameter of the first hole 14AH. Figure 2 In the example, all the second holes 14BH formed in the outer peripheral portion 14B1 are large holes 14BH1 , and all the second holes 14BH formed in the middle portion 14B2 are middle holes 14BH2 .

[0039] In the baffle 14, all through holes including the first holes 14AH and the second holes 14BH are arranged in a grid pattern, for example. Figure 2 In the example shown, the through holes are located one by one at the lattice points of the square lattice.

[0040] Figure 3 The planar structure of the cryopump 10 is shown.

[0041] like Figure 3 As shown, the low-temperature panel 12 is located within the area formed by the first portion 14A and the middle portion 14B2 when viewed from above. Therefore, the outer peripheral portion 14B1 is not opposed to the low-temperature panel 12, thereby suppressing heat input to the low-temperature panel 12 due to the large holes 14BH1 in the outer peripheral portion 14B1, and suppressing uneven distribution of condensed gas.

[0042] Hereinafter, the cryogenic panel 12 closest to the baffle 14 among the plurality of cryogenic panels 12 is referred to as the "first cryogenic panel," and the other cryogenic panels 12 are referred to as the "second cryogenic panel." Figure 1In the example shown, the diameter of the first cryogenic panel is smaller than the diameter of the second cryogenic panel. Each cryogenic panel 12 has a truncated cone shape when viewed from above. When viewed from above, the inclined surface of the second cryogenic panel protrudes from the first cryogenic panel. When viewed from above, a portion of the plurality of intermediate holes 14BH2 overlaps with the inclined surface of the second cryogenic panel.

[0043] [Test Example]

[0044] A plurality of through holes arranged in a grid pattern are formed on a circular plate having a diameter of 183 mm to 189 mm and a thickness of 2 mm. Thus, the baffles of Test Examples 1 to 5 are obtained. In addition, as described in Tables 1 and 2 below, the number and size of the through holes are set in the baffles of each test example. With respect to the cryopumps to which the baffles of each test example are applied, the volume of the condensed Ar gas stacked on the upper part of the first cryogenic panel in the area defined by the heat shield and the thickness of the condensed Ar gas stacked on the side of the cryogenic panel group are calculated through simulation experiments. In addition, with respect to the cryopumps to which the baffles of each test example are applied, the distribution of the condensed Ar gas stacked on the upper part of the first cryogenic panel is also calculated through simulation experiments. In addition, in the second part of the baffles of Test Examples 1, 4, and 5, only one type of hole larger than the first hole is provided as the second hole. In addition, an annular gap is formed in the second part (near the edge of the outer peripheral part) of the baffles of Test Examples 1 and 5.

[0045]

Table 1

[0046]

[0047]

Table 2

[0048]

[0049] As shown in Tables 1 and 2, it was confirmed that the volume of condensed Ar gas was greater than 1800 L, and that condensed Ar gas accumulated in more than 70% of the space above the first low-temperature panel. Furthermore, it was confirmed that the thickness of condensed Ar gas accumulated on the side surfaces of the low-temperature panel assembly was greater than 8.33 mm.

[0050] Furthermore, it was confirmed that the uniformity of the condensed Ar gas accumulated on the upper portion of the first low-temperature panel was improved in Test Examples 5 and 1 compared to the baffle of Test Example 4. Therefore, it can be said that the diameter of the second hole is preferably larger than 1 times and less than 3 times the diameter of the first hole. Furthermore, it was confirmed that the condensed Ar gas accumulated on the upper portion of the first low-temperature panel in the baffles of Test Examples 2 and 3 was substantially uniform.

[0051] According to an exemplary structure of the cryopump 10 and the baffle 14 for the cryopump 10 , the following effects can be obtained.

[0052] (1) The baffle 14 includes: a first portion 14A including the center of the baffle 14 and including the first hole 14AH; and a second portion 14B including the edge of the baffle 14 and including the second hole 14BH. The electrical conductance of the second portion 14B is greater than the electrical conductance of the first portion 14A. In this structure, gas easily flows from the second portion 14B of the baffle 14 into the main body 13. As a result, when viewed from above, condensed gas easily accumulates even in the outer peripheral portion (including the edge portion) of the cryogenic panel 12, and the accumulation of condensed gas in the central portion (including the center portion) of the cryogenic panel 12 can be suppressed. Therefore, the uneven accumulation of condensed gas in the cryogenic panel 12 can be suppressed. As a result, the area where condensed gas accumulates can be expanded within the area defined by the main body 13, so the exhaust performance of the cryopump 10 can be improved.

[0053] (2) In baffle 14, the aperture ratio of second portion 14B including second hole 14BH is larger than the aperture ratio of first portion 14A including first hole 14AH. In this case, even if the thickness of first portion 14A and the thickness of second portion 14B are the same, the electrical conductance of second portion 14B can be easily increased compared to the electrical conductance of first portion 14A.

[0054] (3) The diameter of the second hole 14BH is larger than the diameter of the first hole 14AH. With this structure, the number of second holes 14BH can be reduced to less than the number of first holes 14AH, and the electrical conductance of the second portion 14B can be increased compared to the electrical conductance of the first portion 14A. Therefore, the baffle 14 can be easily processed.

[0055] (4) The second hole 14BH includes a large hole 14BH1 (third hole) disposed in the outer peripheral portion 14B1 of the second portion 14B and an intermediate hole 14BH2 (fourth hole) disposed in the intermediate portion 14B2 of the second portion 14B. The intermediate hole 14BH2 is smaller than the large hole 14BH1 and larger than the first hole 14AH. In this structure, the electrical conductance of the baffle 14 can be easily increased in the order of the first portion 14A, the intermediate portion 14B2, and the outer peripheral portion 14B1. Therefore, compared to a case where the baffle 14 has the same electrical conductance throughout the entire second portion 14B, it is possible to suppress differences in the amount of accumulated condensed gas in the radial direction of the low-temperature panel 12.

[0056] (5) The outer peripheral portion 14B1 of the baffle 14 does not face the low-temperature panel 12 in a plan view. This structure can suppress heat input to the low-temperature panel 12 due to the large holes 14BH1 of the outer peripheral portion 14B1 and suppress uneven distribution of condensed gas.

[0057] The above-mentioned embodiment can be implemented with the following modifications. The above-mentioned embodiment and the following modifications can be implemented in combination with each other within the scope of no technical contradiction.

[0058] [Low temperature panel]

[0059] The outer peripheral portion 14B1 of the baffle 14 may overlap the low-temperature panel 12 in a plan view. Even in this case, the effect similar to the above-mentioned (1) can be obtained by making the conductance of the second portion 14B greater than that of the first portion 14A.

[0060] The first portion 14A of the baffle 14 and the low-temperature panel 12 may overlap in a plan view, while the second portion 14B of the baffle 14 and the low-temperature panel 12 may not overlap in a plan view. In this case, the following effects can be obtained.

[0061] (6) Since the second portion 14B and the cryogenic panel 12 do not overlap when viewed from above, the second portion 14B increases the flow rate of gas supplied to the main body 13 in the area outside the edge of the cryogenic panel 12. Therefore, the accumulation of condensed gas in the peripheral portion (including the edge) of the cryogenic panel 12 is suppressed to be smaller than the accumulation of condensed gas in the central portion (including the center) of the cryogenic panel 12.

[0062] [Baffle]

[0063] The second portion 14B may not have the outer portion 14B1 and the intermediate portion 14B2. Specifically, only one type of hole having the same size may be formed in the second portion 14B as the plurality of second holes 14BH. For example, the plurality of second holes 14BH having the same diameter may be formed throughout the entire second portion 14B. Even in this case, the effect similar to (1) above can be achieved by increasing the electrical conductance of the second portion 14B compared to the electrical conductance of the first portion 14A.

[0064] At least one of the first hole 14AH and the second hole 14BH may not be a circular hole, but may be a polygonal hole in a plan view. Even in this case, the effect similar to the above-mentioned (1) can be obtained by making the conductance of the second portion 14B greater than that of the first portion 14A.

[0065] When first holes 14AH and second holes 14BH are circular holes, the diameter of second holes 14BH can be smaller than the diameter of first holes 14AH. In this case, for example, by increasing the density of second holes 14BH in second portion 14B compared to the density of first holes 14AH in first portion 14A, the aperture ratio of second portion 14B can be increased compared to the aperture ratio of first portion 14A. In other words, the electrical conductance of second portion 14B can be increased compared to the electrical conductance of first portion 14A.

[0066] The aperture ratio of the second portion 14B may be less than or equal to the aperture ratio of the first portion 14A. In this case, for example, by making the thickness of the second portion 14B thinner than that of the first portion 14A, the conductance of the second portion 14B can be increased compared to the conductance of the first portion 14A.

[0067] In baffle plate 14, the through-holes, including first holes 14AH and second holes 14BH, do not need to be arranged in a grid pattern. In this case, for example, the through-holes may be arranged in a plurality of concentric rings defined in baffle plate 14. Alternatively, the through-holes may be randomly arranged in baffle plate 14.

[0068] Description of Reference Numerals

[0069] 10: Cryogenic pump

[0070] 11: Freezer

[0071] 12: Low temperature panel

[0072] 13: Main body

[0073] 14: Baffle

[0074] 14A: Part 1

[0075] 14AH: Hole 1

[0076] 14B: Part 2

[0077] 14B1: Peripheral part

[0078] 14B2: Middle part

[0079] 14BH: Hole 2

[0080] 14BH1: Large hole (hole 3)

[0081] 14BH2: Middle hole (4th hole)

Claims

1. A cryopump comprising: a low-temperature panel connected to the freezer; a main body, which houses the low-temperature panel; as well as a baffle located at the gas inlet of the main body, The baffle comprises: a first portion including the center of the baffle and having a first hole formed therein and passing through the baffle; and The second part includes the edge of the baffle and is formed with a second hole penetrating the baffle, The second hole includes a third hole and a fourth hole smaller than the third hole. The second part has: a peripheral portion including the edge and having the third hole formed therein; and a middle portion located between the peripheral portion and the first portion and having the fourth hole formed therein, The conductance of the second portion is greater than the conductance of the first portion.

2. The cryopump according to claim 1, wherein The aperture ratio of the second portion based on the second hole is greater than the aperture ratio of the first portion based on the first hole.

3. The cryopump according to claim 1, wherein The first hole and the second hole are circular holes, The diameter of the second hole is larger than the diameter of the first hole.

4. The cryopump according to any one of claims 1 to 3, wherein When the baffle is viewed from above, the low-temperature panel is located in a region overlapping the first portion and the middle portion.

5. The cryopump according to any one of claims 1 to 3, wherein When the baffle is viewed from above, the first portion overlaps with the low-temperature panel, and the second portion does not overlap with the low-temperature panel.

6. A baffle for a cryogenic pump, comprising: a first portion including the center of the baffle and having a first hole formed therein and passing through the baffle; and The second part includes the edge of the baffle and is formed with a second hole penetrating the baffle, The second hole includes a third hole and a fourth hole smaller than the third hole. The second part has: an outer peripheral portion including the edge and having the third hole formed therein; and a middle portion, which is located between the outer peripheral portion and the first portion and is formed with the fourth hole, The conductance of the second portion is greater than the conductance of the first portion.

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