JPH0544548Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a cryopump for vacuum evacuation, and particularly to a buffer and a shield for the cryopump.

[Conventional technology]

FIG. 6 shows a cross-sectional view of a conventional cryopump.

1 is a reciprocating refrigerator using a piston or a displacer such as a Stirling cycle, Gifford-McMahon cycle, or Solvay cycle;
2 is a gas compressor that makes the helium gas supplied to the refrigerator 1 high pressure; 3 is a high-pressure gas pipe for supplying high-pressure helium gas to the refrigerator 1; and 4 is a gas compressor for supplying low-pressure helium gas returned from the refrigerator 1. 5 is the first-stage cylinder of the refrigerator 1, 6 is the second-stage cylinder, 7 is the first-stage heat station where the refrigerator 1 generates cold, 8 is the second-stage heat station, and 9 is the second-stage heat station. A shield attached to the first-stage heat station 7, 10 a cryopanel provided on the second-stage heat station 8, 11 a battleship attached to the top of the cryopanel 10,
12 is a pump case; 13 is a vacuum container that is evacuated by a cryopump; 14 is a flange for connecting the pump case 12 and the vacuum container 13;
15 is a seal for maintaining a vacuum, and 16 is a connection between the refrigerator 1 and the pump case 12, which are connected by welding or the like. 17 is a support part for supporting the buttful, 19 is a screw hole for connecting the shield 9 and the support part 17 with screws, etc., and 18 is a vacuum container 1.
This is the vacuum section of No. 3.

The helium gas made high pressure by the gas compressor 2 is sent to the first stage cylinder 5 and second stage cylinder 6 of the refrigerator 1.
The piston or displacer built into the
By reciprocating about 120 times per minute and adiabatically expanding the high-pressure helium gas, cold is intermittently generated in the first-stage heat station 7 and the second-stage heat station 8. The shield 9 is thermally connected to the first stage heat station 7 to be cooled, and the temperature is around 80K. The temperature of the second stage heat station 8 and cryopanel 10 is cooled to about 20K. The buffer 11 is cooled by the cold of the shield 9 via the support part 17, and the temperature is about 80K. The gas and water vapor inside the vacuum container 13 are transferred from the vacuum section 18 to the vacuum chamber 1
After colliding with 1 and being cooled down, it enters inside the shield 9. Gases with relatively high boiling points (e.g. gases with a boiling point of 80K or more such as oxygen gas) and water vapor are condensed in the shield 9, and gases with low boiling points (e.g. nitrogen gas,
Hydrogen gas and other gases with a boiling point of 80K or lower) are condensed in the cryopanel 10.

FIG. 7 shows the shape of a baffle 11 commonly used in cryopumps. FIG. 8 is a view of FIG. 7 viewed from above. A plurality of annular buffle members with different diameters are prepared, each having a diameter that gradually becomes smaller toward the top, and these are arranged concentrically with each other so as to provide overlapped portions with each other in the vertical direction.
The structure is such that the exhaust gas does not collide with the buffer 11 and directly enters the cryopanel 10 section. The support portion 17 has the function of holding the buffle member in a predetermined position and cooling the buffle member 11 to about 80K by heat conduction using the cold temperature of the shield 9.

[The problem that the idea aims to solve]

(1) As described above, the exhausted gas and water vapor collide with the buffer 11 before entering the inside of the shield 9, and their temperature is lowered. At this time, most of the water vapor condenses and solidifies on the buffer 11. FIG. 9 shows a numerical analysis of the amount of energy given to the baffle 11 by the gas and water vapor colliding with the buffle 11.

In FIG. 9, the amount of energy Q is shown by hatching on the surface of the buffed surface on the vacuum section 18 side. A similar energy distribution is obtained on the surface facing the cryopanel 10 (although not shown in FIG. 9, the distribution is symmetrical on both sides).

Therefore, a large amount of thermal energy enters the vacuum section 18 side (upper part of the butthole) on both sides of the butthole 11,
The temperature will rise locally. If the temperature rises locally, not only will the performance of the cryopump deteriorate, but the condensed and solidified water vapor will re-evaporate, causing pressure fluctuations and pressure instability in the vacuum section 18 due to repeated condensation and evaporation. Become.

(2) As mentioned above, the exhausted gas and water vapor enter inside the shield 9. The behavior of this gas and water vapor inside the shield 9 is analyzed by numerical calculation, and the amount of energy imparted to the inner wall of the shield 9 when the gas and water vapor collide with the inner wall is determined in FIG. 10. (i.e. gas and water vapor molecules impart energy to the inner wall by colliding with it, causing the molecules to cool down or condense and
solidify. ) In FIG. 10, the length of the horizontal line drawn on the inner wall of the shield indicates the amount of energy Q' obtained by the inner wall. That is, the amount of incident energy is large on the inner surface near the immediate lower part of the baffle 11 (that is, there is a large amount of gas colliding with the shield), and therefore, the largest amount of gas and water vapor condenses and solidifies on the inner surface in this vicinity. Concentration of gas collision, condensation, and solidification on a part of the inner surface of the shield not only causes deterioration of cryopump performance, but also causes the condensed and solidified gas to re-evaporate due to the energy of the newly incoming gas. Therefore, due to repeated condensation and evaporation, the pressure fluctuation inside the shield 9 is reduced to the pressure fluctuation in the vacuum section 18.
This will cause pressure instability.

[Means to solve the problem]

(1) In a baffle system in which a plurality of annular buffle members with different diameters whose diameters gradually become smaller toward the top are prepared, and these are arranged concentrically with each other, and overlapping parts are provided with each other in the vertical direction. , the supporting parts of the plurality of buttful members are above the buttful members (exhaust gas incidence side)
A thermally bonded structure (such as integral casting or welding, in which heat conduction occurs in the mutually contacting portions of a plurality of members in the same way as inside the same member) is considered as a buffer.

(2) In a cryopump whose cold generation source is a refrigerator using a refrigeration cycle such as a Stirling cycle, Gifford-McMahon cycle, or Solvay cycle, the shape of the shield attached to the first stage heat station of the refrigerator is It has a structure in which a plurality of fin-like plates are installed in the axial or circumferential direction on the inner surface of the shield opening (near the full width).

[Effect]

(1) Not only can cryopump performance deterioration be prevented, but also the re-evaporation of water vapor that has condensed and solidified can be prevented.
It does not occur on 8.

(2) It not only prevents deterioration of the exhaust performance of the cryopump (decreased pumping speed), but also prevents re-evaporation of gas and water vapor that have condensed and solidified on the inner surface of the shield 9 (prevents repeated condensation and re-evaporation of gas and water vapor);
Therefore, no pressure increase or pressure instability occurs in the vacuum section 18.

[First example] 1 and 2 show a first embodiment of the present invention.

FIGS. 1 and 2 show the full 21, the support part 22,
Only the mounting screw holes 23 in the shield 9 are shown, and the other overall structure is the same as that in FIG. 6. In such a device, the buttful 21 and the support part 2
2 are thermally coupled by welding or the like.

Next, the action of this Batsuful will be explained.

The support part 22 is located at the upper part of the buttful 21 (vacuum part 18
side), so it is thermally bonded to the
The temperature distribution is lower at the top and higher at the bottom. Therefore, as shown in FIG. 9, even if a large amount of heat energy enters the upper part of the buttful, the temperature of the buttful 21 can be lower than that of the conventional one, so the temperature rise can be suppressed to a low level, and water vapor can be regenerated. Evaporation can also be reduced. Therefore, pressure fluctuations and pressure instability in the vacuum section 18 due to re-evaporation can be prevented.

[Second example] 3 and 4 show a second embodiment of the present invention.

Figures 3 and 4 show Shield 9 and Batsuful 2.
Only 1 is shown, and the other overall structure is shown in 6th.
Same as the figure. Reference numeral 24 denotes a fin-like plate provided on the inner surface of the shield opening (near the full width), and is installed in the axial direction.

In such a device, gas and water vapor entering (exhausting) the inside of the shield 9 from the vacuum section 18 are transferred to the portion where the fin-like plate 24 is provided (the heat transfer area and the condensation/solidification area are large). Since most of the gas is incident on the cryopump, the temperature of the gas and water vapor decreases, and the condensation and solidification proceed rapidly, increasing the pumping speed of the cryopump. Furthermore, by increasing the condensation/solidification area, the amount of molecules condensed/solidified can be increased. Furthermore, since the amount of condensation and solidification can be made uniform, the thickness of the film of gas etc. solidified on the fin-like plate can be made thinner, and the temperature of the thin surface can be lowered, so that re-evaporation can be prevented. Therefore, repetition of condensation and evaporation can be prevented, and pressure fluctuations and pressure instability in the vacuum section 18 can be prevented.

FIG. 5 shows another embodiment in which the fin-like plates 25 are disposed in the circumferential direction, and the functions and effects are similar to those of the second embodiment described above.

[Effect of idea]

The present invention provides a cryopump whose cold generation source is a refrigerator using a refrigeration cycle such as a Stirling cycle, Gifford-McMahon cycle, Solvay cycle, etc. (1) A shield attached to the first stage heat station of the refrigerator. The buttle provided in the opening of the buttle is configured by concentrically arranging a plurality of buttle members having different annular diameters that gradually become smaller upwardly, and a supporting member of the buttle is thermally attached to the upper part of the buttle. (2) A plurality of fin-like members are installed in the axial or circumferential direction on the inner surface near the opening of the shield attached to the first stage heat station of the refrigerator. The installation produces the following effects.

The pumping capacity of the cryopump has been improved, the effects of re-evaporation of condensed and solidified water vapor (pressure fluctuations, pressure instability) can be prevented, and these effects can be obtained at a low cost.

[Brief explanation of the drawing]

Fig. 1 is a side view of the buff-full portion in the first embodiment of the cryopump of the present invention, Fig. 2 is a plan view of Fig. 1, and Fig. 3 is a side sectional view near the shield opening in the second embodiment. 4 is a sectional view taken along the line AA in FIG. 3, FIG. 5 is a drawing similar to FIG. 3 in another embodiment, FIG. 6 is an overall side sectional view of a conventional cryopump, and FIG. Fig. 8 is a plan view of Fig. 7, Fig. 9 is a diagram showing the amount of energy that gas and water vapor entering the buffle give to the buffal surface, and Fig. 10 is the inner wall of the shield. FIG. 3 is a diagram showing the amount of energy given to the inner wall by gas and water vapor incident on the inner wall. 9... Shield, 18... Vacuum space section, 21...
. . . Full, 22 . . . Support portion, 24 . . . Fin-like plate.

Claims (1)

[Claims for Utility Model Registration] 1. In a cryopump whose cold generation source is a refrigerator using a refrigeration cycle such as a Stirling cycle, a Gifford-McMahon cycle, or a Solvay cycle, the cryopump is attached to the first stage heat station of the refrigerator. A plurality of annular buttful members having different diameters are concentrically disposed so that the diameter gradually decreases upward, and a support member for the buttful is heated to the upper part of the buttful. A cryopump that is characterized by being attached to a double-sided pump. 2 In a cryopump whose cold generation source is a refrigerator using a refrigeration cycle such as a Stirling cycle, Gifford-McMahon cycle, Solvay cycle, etc., the inner surface near the opening of the shield attached to the first stage heat station of the refrigerator. A cryopump characterized in that a plurality of fin-like members are installed in the axial direction or the circumferential direction.