JPH04105980U - cryopump - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a cryopump that minimizes heat radiation received from the normal temperature part of a container to be evacuated, has low refrigeration loss, and has a high pumping speed. [Structure] The inclination angle θ of the plurality of baffle members 12 of the frustoconical baffle 11 provided at the opening of the first stage cold panel 2 is set to the innermost baffle member 12.
The inclination angles θ _{2 ,} θ ₃ , θ ₄ , .

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

The present invention relates to a cryopump, and particularly to the structure of its baffle.

0002

[Conventional technology]

An example of a conventional cryopump, as shown in Fig. It has an exhaust pipe 9 whose end is connected to a roughing vacuum pump (not shown). A casing 1 is provided on the bottom of the casing 1, and a Gifford McMaho Utilizing the adiabatic expansion of high-pressure helium using the Stirling cycle, Stirling cycle, etc. The refrigerator 6 used and the cold head of the refrigerator 6 provided in the casing 1 The first stage cork is an upwardly facing cylindrical core attached to the first freezing stage 7a of the refrigerating stage 7a. the cold panel 2, and the first stage cold panel 2 at the tip of the cold head 7. A downward-facing bottomed cylindrical second stage cord is concentrically attached to the second freezing stage 7b. a cold panel 3, activated carbon 4 adhered to the surface of this second stage cold panel 3, It is provided at the opening on the upper surface of the first stage cold panel 2, and is arranged at a constant angle of inclination. A baffle composed of a plurality of annular baffle members 10 in the shape of a truncated cone arranged in the form of a core. It consists of a full 5.

0003 In the cryopump having such a structure, the first stage cold pump is operated by the refrigerator 6. The panel 2 and baffle 5 are cooled to about 70K, and the second stage cold panel 3 is cooled to about 15K. It is cooled to K.

[0004]The operation of the cryopump configured in this way is to guide the residual gas molecules in the evacuated container into the casing 1 through the opening of the baffle 5, and then to the first stage cold panel 2 which is cooled to about 70K. Gases with low vapor pressure such as water vapor are condensed and frozen in the baffle 5, and the gas molecules from which the water vapor has been removed are cooled to about 15K.The second stage cold panel 3 cools the gases such as N ₂ , O ₂ and Ar. Ne, H 2 and He, which cannot be condensed and frozen, are condensed and frozen in the first and second cold panels 2 and 3. Ne, H ₂ and He, which cannot be condensed and frozen, are cooled to a low temperature by the activated carbon 4, which is cooled to about 15K along with the second cold panel 3. It is adsorbed.

[0005] A perspective view of a conventional baffle used in such a cryopump is shown in FIG. This is shown in the longitudinal cross-sectional view of FIG. This baffle 5 has a plurality of truncated conical annular diameters different from each other. The baffle members 10 are arranged concentrically, and the inclination angle θ of each baffle member 10 is constant.

[0006]

[Problem that the idea aims to solve]

When gas molecules pass between the baffles 5 having the above-mentioned structure, some of the baffles are The time it takes to collide with the member 10, repeat reflection, and pass through the baffle 5 increases. Sometimes I put it away. In order to avoid this, the inclination angle θ of the baffle member 10 should be increased. (make it close to a cylindrical shape).

[0007] Increasing the inclination angle θ of the baffle member 10 in this way increases the visibility from inside the evacuated container. The upper area of the second stage cold panel 3 is large, and the cold panel 3 has a large upper area, which allows the cooling to be carried out from the normal temperature part inside the evacuated container. Heat radiation to the cold panel increases, especially in the second stage cold panel, which has a small refrigerating capacity. Heat radiation to panel 3 increases.

[0008] On the other hand, if the inclination angle θ of each baffle member 10 is made small, the second stage can be seen from the normal temperature section. The upper area of cold panel 3 becomes smaller, and the heat radiation to the cold panel becomes smaller. However, the pumping speed of the cryopump decreases.

[0009] The present invention has a high exhaust speed and reduces heat radiation, especially heat radiation to the second stage cold panel 3. The objective is to provide a cryopump with low radiation.

0010

[Means to solve the problem]

In order to solve the above-mentioned problem, the small cryogenic refrigerator 6 is used as a cold generation source, and the opening of the first stage cold panel 2 attached to the first freezing stage 7a provided in the cold head 7 of this refrigerator 6 is used. In a cryopump having a baffle 11 configured by a plurality of baffle members 12 having a truncated conical ring shape and having different diameters arranged concentrically, the baffle member formed by the inner surface of the baffle member 12 and the bottom surface thereof. The inclination angles θ ₁ , θ _{2 ,} θ ₃ , . The numbers are increased by about 12.

[0011]

【Example】

FIG. 1 is a sectional view of a cryopump according to the present invention. This cryopump is The parts other than the buffer 11 are the same as the conventional cryopump shown in Fig. 2, so the same parts are used. The explanation for this will be omitted.

The baffle 11 has a truncated conical shape, and a plurality of annular baffle members 12 having different diameters are arranged concentrically. Based on the inclination angle θ ₁ of the innermost baffle member 12 in this concentric arrangement, the inclination angle of the outer baffle member 12 is θ ₂ , and the inclination angle of the outermost baffle member 12 is θ ₃ , and in the following order. The inclination angles of the baffle members 12 located on the outside are θ ₄ and θ ₅ , and the angles θ ₁ to θ ₅ are set as θ ₁ <θ ₂ <θ ₃ <θ ₄ <θ ₅ .

As an example, θ ₁ =45°, θ ₂ =50°, θ ₃ =55°, θ ₄ =59°, and θ ₅ =70°. The pumping speed of a cryopump using a baffle 11 with such an inclination angle is approximately equal to the pumping speed of a cryopump using a conventional baffle 5 with a uniform inclination angle θ=55° as shown in FIG. .

[0014] However, when baffle 11 is used, the baffle part near the center of the concentric arrangement Since the inclination angle of the material 12 is smaller than the inclination angle θ=55° of the conventional baffle member 10, The upper surface of the second stage cold panel 3 which mainly receives heat radiation from the normal temperature part inside the evacuated container The heat radiation receiving area of the second stage cold panel through the baffle 11 becomes smaller. The view factor between the top surface of No. 3 and the inner surface of the evacuated container becomes small.

[0015] Therefore, the cryopump using the baffle 11 of the present invention has a uniform inclination angle. Compared to cryopumps using conventional baffle 5, the second stage cold panel Heat radiation to 3 is reduced.

[0016]

[Effect of the idea]

As mentioned above, the second stage cold of the cryopump using the conventional baffle 5 Heat radiation to the panel 3 is reduced by a cryopump using the baffle 11 according to the present invention. In order to equalize the heat radiation to the second stage cold panel 3, the baffle 5 must be uniformly The angle of inclination must be less than 55°, and such a baffle 5 is used. The pumping speed of the cryopump using the baffle 11 of the present invention is The pumping speed will be smaller than the pumping speed of

[0017] Also, when manufacturing a cryopump with equal heat radiation to the second stage cold panel 3, In this case, the cryopump can be made smaller.

[0018] Furthermore, because the heat radiation is small, the refrigeration loss of the refrigerator is reduced, and the cryopump The performance can be improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a cryopump of the present invention.

FIG. 2 is a sectional view of a conventional cryopump.

FIG. 3 is a perspective view of the baffle.

FIG. 4 is a longitudinal cross-sectional view of a conventional baffle.

[Explanation of symbols]

1 Casing 2 First stage cold panel 3 Second stage cold panel 4 Activated carbon 6 Freezer 7 cold head 7a First freezing stage 7b Second freezing stage 8 Exhaust port 9 Exhaust pipe 11 Baffle 12 Baffle member

Claims (1)

[Scope of utility model registration request] Claim 1: A cryogenic compact refrigerator is used as a cold generation source, and a truncated cone-shaped refrigerator is provided at an opening of a first stage cold panel attached to a first freezing stage provided in a cold head of the refrigerator. In a cryopump having a baffle configured by concentrically disposing a plurality of annular baffle members with different diameters, the angle of inclination of the inner surface of the baffle member between the inner surface of the baffle member and the bottom surface of the baffle member is defined as A cryopump characterized in that, based on the inclination angle of the innermost baffle member, the outer baffle members in the concentric arrangement are sequentially larger.