JPS63501585A - Rapid adsorption cryopump - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Rapid adsorption cryopump The present invention relates to a cryopump that is cooled by a two-stage closed cycle cooler. This applies to cryopumps.

Background technology Currently available cryopumps are either open-type refrigeration cycle cases or closed-type refrigeration cycle cases. generally follow the same design concept, even if cooled by T'L .

A cold second stage array, typically operating in the 4-25° range, is located at the primary pump surface. this The surface is usually surrounded by a high temperature cylinder working in the temperature range from 40 to 130°; This provides radiation shielding for the cold column. Radiation shields are generally used for primary pumps. A housing that is closed except for the front row, which is located between the top surface and the chamber to be evacuated. Contains. This high temperature, first stage, front row is for high boiling point gases such as water vapor. Acts as a pump site.

In operation, high boiling gases such as water vapor condense in the front row. low boiling point Gas passes from the front row into a chamber in the radiation shield and condenses on the second row.

These inner surfaces absorb cold, non-condensable gases such as hydrogen, neon or helium. coated with an adsorbent such as charcoal or zeolite for adhesion. Adsorption is gas K is physically captured by materials held at cold temperatures and is therefore removed from the environment. This is a process in which it is removed. When gas is condensed or adsorbed on the pump surface in this way, it creates an odor. Tsunomi remains in the work room.

In systems that are cooled by closed cycle chillers, the chillers are usually radiant sealed. It is a two-tier frozen rock with cold fingers extending into the bay. The second part of the refrigerator The cold end of the stage that is also cooled is at the end of the cold fin. Primary pump surface reed In Liopanel, the cold fins are heat sinks at the coldest end of the second stage. connected to the network. This cryopanel is, for example, US Pat. No. 4,494,3 placed around and connected to the second stage heat sink, as in No. 81. It can be a simple metal plate, a tip or a cylindrical row of metal baffles.

This second stage cryopanel also uses a low-carbon material such as charcoal or zeolite as described above. Can support hot condensate gas adsorbents.

The radiation shield is installed at the coldest end of the first stage of the refrigerator by a heat sink or is connected to the heat station. This shield protects it from radiant heat. Surround the first stage cryopanel with C to protect it. Forward closing radiation shield 4,356.701 through the shield or as described in U.S. Pat. It is cooled by the first stage heat sink via the heat transfer struts as described above.

In an ordinary cryopump, the cryo-cooling finger of the cryocooler is a cup-shaped radiation shield. It extends concentrically with the shield through the base of the shield. In other methods, low temperature The fingers extend through the sides of the radiation shield.

Such geometries are often dictated by the space available for installing the cryopump. Fits well.

Cryopumps occasionally need to be regenerated after collecting large amounts of gas; If they do, they will no longer be valid. The regeneration was previously [adsorbed by the C cryopump]. This is a process in which gas is released. Regeneration usually occurs when the cryopump returns to ambient temperature. This is achieved by allowing the gas to be cryopumped by a secondary pumping device. removed. Following this release and removal of gas, the cryopump is restarted. After recooling, large amounts of gas can be removed from the working chamber again.

Prior art practice uses adsorbent material placed on the second stage cryopanel, e.g. Protecting, condensing, for example by surrounding the second impregnated material with a chevron plate to prevent gas from condensing and thus to seal off the layer of adsorbent material. . In this way, the layer absorbs non-condensable gases such as hydrogen, neon or helium. protected for wear. This reduces the frequency of regeneration cycles. however , the chevron plates reduce the possibility of access of non-condensable gases to the adsorbent.

Summary of the invention The present invention increases the rate of non-condensable gas delivery and limits the frequency of system regeneration. limit This allows the second stage cryopanel to be opened and hydrogen, neon or helical A suction system installed on the inner surface of a secondary cryopanel disk for non-condensing gases such as This is achieved by providing greater accessibility to the dressing material. this child This allows non-condensable gases to be adsorbed more quickly, and the delivery of non-condensable gases Increase speed. At simultaneous C, the second row is first filled with all gas molecules by the adsorbent material. It is not designed to collide with the uncoated cryopanel surface. Ru.

Cryopumps related to the theory of the present invention are multi-stage refrigerators and cryopumps with low temperature heating on the refrigerator. It contains a cryopanel attached to a sink. Extremely low temperature cryo The panel is a second stage cryopanel. It's a coma axis to the front cryopanel It includes a row of discs extending along it. Furthermore, the second stage cryopanel is equipped with a second stage heat shield. in thermal contact with the tank. Each disk in the row has a forward cryopanel at the outer edge of the disk. Each day the plate is flattened radially inward from the fold.

The surface of the disk that is radially inward from the bend and away from the front cryopanel is covered with adsorbent. It's been overturned.

In a preferred embodiment, the disc of the second stage cryopanel is connected to the front cryopanel. It is bent at 45 degrees. The outermost end of each disk is the front cryopanel (r (near It is at the same height as the flat part of the next disk. The disc is located in front of the cryopath. The diameter shall gradually become smaller as it approaches the flannel. I can do it.

Brief description of the drawing The foregoing and other objects, features and advantages of the present invention are illustrated below, particularly in the drawings. , as will be apparent from the description of preferred embodiments of the invention, in which: The same reference numerals may indicate similar parts throughout the different drawings. The drawing is reduced in size , which does not necessarily need to be extended, but instead evaluates and explains the theory. It is.

FIG. 1 is a sectional view of one embodiment of the present invention.

FIG. 2 is a longitudinal cross-sectional view of another embodiment of the invention.

FIG. 3 is a composite view of the second row of the embodiment shown in FIG. 2;

Description of the preferred embodiment FIG. 1 is a sectional view of a cryopump related to the theory of the present invention.

The cryopump 80 in FIG. including a main cryopump housing 83 that can be attached to the intermediate date pulp between There is. The two-stage low-temperature fin 85 of the low-temperature refrigerator passes through the opening 66 into the Ussing. It stands out. In this case, the refrigerator is a Gifford-MacMahon cycle. Although this is a refrigerator, other refrigerators may also be used.

The refrigerator has a displacer in a cold finger 85 driven by a motor 48. including. Helium gas is introduced into the cold finger via tubes 38 and 36 and discharged. .

The helium gas entering the cold finger is expanded by the displacer and becomes extremely low. It is cooled to produce a temperature. Such refrigerators use Cbθ1118 and other US special No. 3,218.815.

The first stage pump surface 90 is connected to the first stage 96 of the refrigerator 85 through the radiation shield 82'ft. It is attached to the cold end heat sink 94.

The cup-type radiation shield attached to the first stage heat sink 74 operates at an angle of approximately 77°. Ku. A radiation shield surrounds the second stage cryopump area for direct radiation or high condensation. Prevent heating of the area by hot steam. The first stage pump surface is a row of front chevron plates. 90, it is a radiation shield for the second stage pump area as well as a water vapor Acts as a cryopump surface for high-temperature condensed gas. forward shown here The row of chevron plates 90 is of normal construction, but the front row can be constructed in several different ways. It is effective in collecting high temperature condensed gas. This row of chevron plates has low stiffness. Allows the passage of condensing temperature gas to the second stage pump area.

The second stage cryopanel 84 includes a row of disks attached to a rod 89. 9 extends parallel to the second stage 98 of the refrigerator and is attached to the second stage heat sink 92. There is. Spacers 81 are also used to support and separate adjacent discs from each other. be able to. The rods are typically spaced about 90° apart from each other around the circumference of the disk.

Each disc has a single peripheral bend 91f, whereby the rim of the disc is directed towards the front row. Directed. For best results, the bend should be approximately 45°.

The adsorbent 93, typically charcoal or zeolite, is applied in a radial direction from the bend in the disk a1. It is attached to the flat side of the disc away from the inner front cryopanel. If one If a large amount of adsorbent is required, the adsorbent can be placed in a flat area as well as in a frusto-conical rim 8. 4 can be glued to the top surface of both sides with epoxy resin, but such adsorbent Similarly, it is not protected from contamination.

The outermost end 102 of each disc of the second stage cryopanel is close to 90 of the front cryopanel. Preferably, it is at the same height as the flat surface 91 of the next disk. 2nd cryopanel The rows of disks become progressively smaller as they approach the front cryopanel. The diameter changes.

The disk array of the secondary cryopanel is not covered with adsorbent material for condensable gases. It is designed to have a sufficient chance of condensation on the surface. At the same time, the disk is inside the radiation block. to promote rapid condensation of non-condensable gases onto the adsorbent material. Ru.

Gas molecules in a low pressure atmosphere move along straight paths and they collide with surfaces When, it is probably reflected from a surface according to the law of cosines. The second stage Kushiio panel is these It is designed to take advantage of the phenomenon of Condensation impinging on one cold side of the disk The gas molecules condense on the surface after only one collision. However, if the non-condensed If a gas molecule impinges on a part of the surface of the disk that is not covered with adsorbent material, then the circular The array of plates has non-condensable gas molecules adsorbed on the uncoated surface of the disk. It is designed so that there is no repulsion at a 90° angle to the surface. non-condensable gas impinges on a surface covered by an adsorbent material where it is absorbed with maximum probability Before it hits the non-adsorbent coated surface. The minimum amount of gas that hits a non-adsorbent surface reduces the molecular path length to the adsorbent and increases the rate of non-condensable gas adsorption. increase in strength. This is associated with increasing the rate at which the system feeds. these Features include:

■ A 45° bend at the 91 end of each disk directs non-condensable gas toward the adsorbent. guide you.

■ In Figure 1, the outermost edge of each disc 102 is located near the front panel, on the flat surface of the next disc. It is approximately at the same height as portion 91. Therefore, the column is optically transparent to the adsorbent. There, the adsorbent is low 11. W is qualitatively protected by the condensing surface. On the other hand, each circle The outer rim of the plate creates a long path in which non-condensable gases are trapped from time to time by multiple reflections. It does not extend to the extent that

■ In order to minimize the length of the path for the adsorbent, the outer bent part of the disc flat radially inward from

■ The row of disks gradually becomes smaller as they approach the cryopanel in front. the As a result, the bent rims of some of the discs are clearly visible from the front row and Molecules migrating from the columns are quickly captured by their rims or directed toward the adsorbent. It's biased.

All the above design features of the disk array are directed towards the adsorbent coated surface inside the cryopanel. Facilitates reflection of non-condensable gas molecules. The design of the column also means that the gas molecules first Virtually impossible to hit the protected adsorbent coated surface of the disc before impacting the part make it possible. As long as each molecule hits an uncovered part, almost all of it hits the uncovered part of the disk. All a-condensing properties promote the condensation of gas and reduce the frequency of regeneration.

The cryopump variant shown in Figure 2 is attached to the wall of the working room along the flange 14ic. It includes a wet vacuum container 12. The front opening 16 of the container 12 is connected to the circular opening of the working chamber. It's communicating. The two-stage cold finger 18 of the refrigerator passes through the cylindrical portion 20 of the container 12. protrudes into the container 12. A two-stage displacer with 18 cold fins has a motor 22. 1st stage heat sink, straddling heat station 2 8 is attached to the low temperature end of the first stage refrigerator 29. At the same time, heat sink 30 is attached to the cold end of the second stage 32.

The primary pump surface is a row of discs 34 attached to the second stage heat station 30. Ru. This column is angled at 20° to condense low condensing temperature gases and adsorb non-condensable gases. It is preferable to maintain the temperature at the following temperature. The Kotop type radiation shield 36 is the first stage heat It is attached to the sink 28. The second stage 32 of the cold finger opens the radiation shield. It extends through the mouth. This shield minimizes heating of the array due to radiation. It surrounds the second row 34 to the rear and side blades of the second row. Preferably, The temperature of this radiation shield is kept below about 100'.

The front row 38 serves as a radiation shield for the primary cryopanel 34 and as a water vapor shield. Acts as a cryopump surface for high boiling point gases such as air. This row has radial support. It includes a shutter joined by a retaining rod 42.

The support rod is attached to the radiation shield. The shield supports the front row. Both act as a heat transfer path from the array to the heat sink.

As shown in FIG. 3, the disk array of the secondary cryopanel of the embodiment shown in FIG. semicircular disk portions 48 and 50 attached to brackets 52 and 54, respectively; Brackets 52 and 54 are formed from two separate groups and are connected to heat station 30. It is attached to the flat surface 46 of. Those brackets are flat L-shaped rods. Ru. They have cold fins on both sides of the heat station 30 that extend laterally of the heat station 32. are doing. The discs differ from the embodiment shown in FIG. 1 and are of the same diameter. . To better understand these characteristics, Bart. See U.S. Patent Application No. 611.683 to Lett. The disk is in front of Figure 2. It is bent at an angle of 45° toward the cryopanel 38.

While the invention has been described and illustrated in terms of its preferred embodiment, C. To those skilled in the art, various changes in type and details may be limited to the scope of the appended claims. It will be appreciated that other changes may be made without departing from the spirit and scope of the invention as described. cormorant.

F/θ/ ANNEX To’i’FE Engineering NTERNATTONAL 5EARCH EPORT 0NCH-A-65280429/11/85 None

Claims (13)

[Claims] 1. A cryopump: a refrigerator having a first and a second stage; A second stage cryocooler that condenses low-temperature condensable gas in thermal contact with a second stage heat sink. panel; and surrounds the second stage cryopanel and connects well with the first stage heat sink. It can also be used as a radiation shield that touches the ground, and as a radiation shield for the second stage cryopanel. Before crossing the opening in the radiation shield, which acts as the cryopump surface for the condensing temperature gas. includes a front cryopanel; the second stage cryopanel is perpendicular to the front cryopanel; including an array of disks spaced along the axis and in intimate thermal contact with the second stage heat sink. each disk in the row bends toward the front cryopanel at the outer edge of the disk; flat radially inward from the bend, and flat radially inward from the bend in the disk; The cryopanel is covered with adsorbent material on the side facing away from the front cryopanel. Lyopump. 2. The disk array of the second stage cryopanel is attached to a support element. The cryopump described in item 1. 3. A cryopump according to claim 2, wherein the support element is a rod. 4. A cryopump according to claim 2, wherein the support element is a bracket. 5. The disc of the second stage cryopanel faces the front cryopanel at a 45° angle. The cryopump according to claim 1, wherein the cryopump is bent. 6. The outermost edge of each disc is approximately the same as the flat part of the next disc near the front cryopanel. The cryopump according to claim 5, which is at the same height. 7. The disc becomes progressively smaller as it approaches the front cryopanel. 7. A cryopump according to claim 6, which is of varying diameter. 8. The outermost edge of each disc of the second stage cryopanel is located at the next closest to the front cryopanel. The cryopump according to claim 1, wherein the cryopump is located at approximately the same height as the flat surface of the disk. 9. so that the disc becomes progressively smaller as it approaches the anterior cryopanel 9. A cryopump according to claim 8, which is of varying diameter. 10. The disk gradually becomes smaller as it approaches the front cryopanel. A cryopump according to claim 1, having a diameter varying in diameter. 11. Each disc includes two parts that are separately attached to the bracket. The cryopump according to claim 1, wherein the cryopump is attached to the second stage of the refrigerator. . 12. A cryopump: a refrigerator having a first and a second stage; The second stage cryocondenses the low temperature condensable gas in thermal contact with the second stage heat sink. and the second stage cryopanel and thermally connected to the first stage heat sink. It can also be used as a contact radiation shield and as a radiation shield for the primary cryopanel. Before crossing the opening in the radiation shield, which acts as the cryopump surface for the condensing temperature gas. a second stage cryopanel; the second stage cryopanel includes a disk row; and the second stage cryopanel includes a disk row; mounted on a support element, the discs being spaced along an axis perpendicular to the anterior cryopanel; and in intimate thermal contact with the second stage heat sink, with each disk in the row at the outer edge of the disk. Then bend it toward the front cryopanel at a 45° angle, and also make a radius from the bend. The inward direction is flat, and the outermost edge of each disk is close to the next disk near the front cryopanel. is approximately at the same height as the flat part of the disc, and the disc extends radially inward from the bend. Cryopump coated with adsorbent material on the side away from the front cryopanel . 13. The disk gradually becomes smaller as it approaches the front cryopanel. 13. A cryopump according to claim 12, which has a diameter varying in diameter.