JPH0560067A - Hydrogen discharging method by cryopump and device thereof - Google Patents

Abstract

PURPOSE:To reduce invasion of heat in a first step cold panel by high heat conductivity of hydrogen gas molecule, in the case where a lot of hydrogen is discharged by a cryopump. CONSTITUTION:An annular throttle mechanism 11 is provided on the upper end of a casing 1, in a double torus part 12 provided between the casing 1 of a cryopump and a first stemp cold panel 2, and a hydrogen storage alloy cylinder 13 is provided in the double torus part 12 from the inner circumference side of the throttle mechanism 11. A hydrogen storage alloy throttle mechanism in which the throttle mechanism 11 and the hydrogen storage alloy cylinder 13 are unified together, may be provided on the upper end of the casing 1. Also, the hydrogen storage alloy cylinder 13 may be formed by such constitution that the inner circumference surface of the hydrogen storage alloy cylinder 13 is composed of a bright surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a cryopump,
In particular, it relates to a method and apparatus for exhausting hydrogen.

[0002]

2. Description of the Related Art As shown in FIG. 4, an example of a conventional cryopump has a casing 1 having an exhaust pipe 9 having one end connected to an exhaust port 8 of an exhaust chamber and connected to a roughing exhaust device (not shown). And a refrigerator 6 provided on the bottom surface of the casing 1 and utilizing adiabatic expansion of high-pressure helium using a Gifford McMahon cycle, Stirling cycle, etc., and a cold of the refrigerator 6 provided in the casing 1. An upward-facing, bottomed cylindrical first-stage cold panel 2 attached to the first freezing stage 7a of the head 7.
And a downward facing bottomed cylindrical second stage cold panel 3 attached to the second freezing stage 7b concentrically with the first stage cold panel 2 at the tip of the cold head 7, and this second stage cold panel Activated carbon 4 adhered to the surface of 3
And a baffle 5 provided in an opening on the upper surface of the first-stage cold panel 2.

The cryopump having such a structure uses the refrigerator 6 to cool the first cold panel 2 and the baffle 5.
Are cooled to about 70K, and the second cold panel 3 is cooled to about 15K.

The operation of the cryopump having the above-described structure is that the residual gas molecules in the exhaust chamber are introduced into the casing 1 through the opening of the baffle 5 and the first-stage cold panel 2 cooled to about 70K. Gas molecules having a low vapor pressure such as water vapor are condensed and frozen by the baffle 5, and the gas molecules from which the water vapor is removed are cooled to about 15K. The second cold panel 3 is used to remove gases such as N ₂ , O ₂ and Ar. Condensed and frozen, and Ne, H ₂ and He that cannot be condensed and frozen in the first and second cold panels 2 and 3 are the second cold panel 3
At the same time, it is adsorbed at a low temperature by the activated carbon 4 cooled to about 15K.

However, 10^-3-10^{- Four}Torr water
When the element is exhausted by a cryopump, casing 1
10 in the space between the first cold panel 2 and^-3~
10 ^{- Four}Torr hydrogen is present.

Since the molecular thermal conductivity of hydrogen is several times higher than the molecular thermal conductivity of nitrogen, oxygen, argon, etc., the thermal conduction from the casing 1 side through the hydrogen gas molecules to the first cold panel 2 side is achieved. growing. In particular, 10 <sup>- 3-10
- 4</sup> heat conduction through the hydrogen gas molecules in Torr drastically reduces refrigeration performance of the first refrigeration stage 7a of the refrigerator 6 to cool the first stage cold panel 2.

Further, as a result of this, the second freezing stage 7b of the refrigerator 6 cooling the second cold panel 3
Cause a decrease in the cooling performance, the temperature of the second cold panel 3 rises, the ability of the activated carbon 4 adhesively applied to the second cold panel 3 to adsorb hydrogen decreases, and the hydrogen exhaust capacity decreases. ..

[0008]

In order to prevent the above-mentioned phenomenon, (1) the outer periphery of the casing 1 of the cryopump is cooled with liquid nitrogen or the like (2) the casing 1 and the first stage cold panel. Widen the space between the two
(3) A method such as providing a throttle mechanism at the exhaust port 8 between the exhaust chamber and the cryopump is adopted.

In the method (1), by cooling the outer periphery of the casing 1 with a cryogen such as liquid nitrogen and lowering the temperature of the casing 1 on the high temperature side, the temperature on the high temperature side and the temperature on the low temperature side, which are the driving force for heat conduction, are increased. The temperature difference between and can be made small, and heat conduction can be made small.

However, the cryopump supply device and the like increase the size of the cryopump as a whole, and the operating cost for replenishing the cryogen also increases.

In the method (2), by widening the space between the casing 1 and the first-stage cold panel 2,
The heat transfer path involved in heat conduction becomes longer, and heat conduction can be reduced.

However, if the inner diameter of the casing 1 is made large, the cryopump becomes large, and if the outer diameter of the first stage cold panel 2 is made small, the exhaust speed is reduced.

In the method (3), the chamber to be evacuated has a volume of 10 ^-3 .
10 ^- 10 the internal cryo pump while keeping to ⁴ Torr
^Since it can be kept below -4 Torr, the pressure inside the cryopump, which is a proportional factor of the amount of heat conduction by gas molecules under vacuum, can be made small, and the heat conduction can be made small.

However, since the throttle mechanism is provided between the chamber to be evacuated and the cryopump, the evacuation speed is reduced.

It is an object of the present invention to solve the above problems and provide a cryopump that does not increase the size of the cryopump, does not reduce the exhaust speed, and does not increase operating costs.

[0016]

In order to solve the above problems, the residual hydrogen gas molecules between the casing 1 of the cryopump for exhausting a large amount of hydrogen gas in the exhaust chamber and the first cold panel 2 are In order to prevent deterioration of the refrigerating performance of the first cold panel 2 and the second cold panel 3 that are cooled by the refrigerator 6, the first cold panel 2 is heated by the external temperature by heat conduction, and thus the casing 1 And a hydrogen absorbing alloy provided between the first cold panel 2 and the first cold panel 2 reduce the pressure of the hydrogen gas molecules between the casing 1 and the first cold panel 2 to reduce the heat conduction of the hydrogen gas molecules. This is to prevent the deterioration of the refrigerating performance of the first and second cold panels 2 and 3 by reducing the temperature.

As a cryopump for this purpose, an annular throttle mechanism 11 provided at the end of the casing 1 on the exhausted chamber side, and below the throttle mechanism 11, the casing 1 and the first-stage cold panel 2 are provided. A hydrogen storage alloy cylinder 13 is provided in the double annular portion 12 between the two.

There is also one in which the throttle mechanism 11 and the hydrogen storage alloy cylinder 13 are integrated and an annular hydrogen storage alloy throttle mechanism 14 is provided at the end of the casing 1 on the exhaust chamber side.

Further, there is also a hydrogen storage alloy cylinder 15 in which the cylindrical surface of the hydrogen storage alloy cylinder 13 on the first cold panel 2 side is formed of a bright surface 15a.

[0020]

FIG. 1 is a sectional view of an embodiment of the cryopump of the present invention. Since the entire configuration is the same as that of the conventional cryopump of FIG. 4, description of common parts will be omitted.

An annular throttle mechanism 11 is provided along the entire circumference of the upper end portion of the casing 1 which is in contact with the exhaust port 8 of the exhaust chamber. A hydrogen storage alloy cylinder 13 is provided at the lower end of the double annular portion 12 in the double annular portion 12 formed by the casing 1 and the first-stage cold panel 2 from the inner circumference of the annular throttle mechanism 11. It is provided up to.

[0022] The pressure of the exhaust chamber in the thus constructed cryopump 10 ^{- 3-10 - 4} when evacuating the hydrogen while keeping the Torr, the diaphragm mechanism is provided in the cryopump inlet side of the casing 1 11 Is narrowed between the inner peripheral side and the upper end of the first-stage cold panel 2 to form the double annular portion 12
Internal probability passage of hydrogen gas molecules to become small, and so enters the hydrogen gas molecules are occluded in the hydrogen storage alloy cylinder 13, the pressure of the hydrogen gas molecules in the double annular portion 12 is 10 ^{- 5} Torr It can be:

As a result, the heat conduction by the hydrogen gas molecules is reduced in the double annular portion 12, and the first cold panel 2 is less susceptible to the temperature of the casing 1 due to the outside air temperature. Therefore, the refrigerating performance of the first refrigerating stage 7a of the refrigerator 6 cooling the first cold panel 2 is not deteriorated, and as a result, the refrigerator 6 cooling the second cold panel 3 is reduced. Since the cooling performance of the second freezing stage 7b does not decrease rapidly, the hydrogen exhaust capacity does not decrease.

FIG. 2 shows another embodiment of the diaphragm mechanism 11 of FIG.
The hydrogen storage alloy cylinder 13 is integrated with the hydrogen storage alloy drawing mechanism 14.

Since the operation in this case is the same as the operation in the case of FIG. 1, description thereof will be omitted.

FIG. 3 shows still another embodiment, in which the inner surface of the hydrogen storage alloy cylinder 13 shown in FIG. 1 (the surface facing the first cold panel 2) is a bright surface 15a of the hydrogen storage alloy cylinder 15.
It is what

The bright surface 15a may be a thin metal cylinder having a bright surface inserted therein.

The operation in this case is the same as that in each of the above-mentioned embodiments, except that the hydrogen storage function prevents heat conduction by hydrogen gas molecules and also prevents heat transfer by radiation.

In general, the heat radiation rate of the bright surface has a small value, so that the heat radiation from the casing 1 and the hydrogen storage alloy surface to the first cold panel 2 can be reduced by the bright surface 15a.

[0030]

As described above, the pressure of the hydrogen gas molecules in the double annular portion 12 is controlled by the throttle mechanism 11 and the hydrogen storage alloy cylinders 13 and 15 or the hydrogen storage alloy throttle mechanism 14 so that the hydrogen in the exhaust chamber is changed. By lowering the pressure of the gas molecules by one digit or more, the heat conduction by the hydrogen gas molecules from the casing 1 to the first-stage cold panel 2 can be reduced, thus increasing the operating cost without increasing the size of the cryopump. Without
The first and second cold panels 2 and 3 by the refrigerator 6.
It is possible to prevent the deterioration of the refrigeration capacity of.

Further, by making the inner surface of the hydrogen storage alloy cylinder 15 a bright surface 15a, it is possible to prevent the transfer of heat from the casing 1 due to heat radiation, and further prevent the refrigerating capacity of the refrigerator 6 from decreasing. is there.

Since no throttling mechanism or the like is provided between the cryopump and the chamber to be evacuated, it has nothing to do with the decrease in the exhaust speed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an embodiment of a cryopump having an improved hydrogen exhaust function of the hydrogen storage alloy of the present invention.

FIG. 2 is a sectional view of another example of the cryopump.

FIG. 3 is a sectional view of still another embodiment of the cryopump.

FIG. 4 is a cross-sectional view showing an example of a conventional cryopump.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Casing 2 1st stage cold panel 3 2nd stage cold panel 4 Activated carbon 5 Baffle 6 Refrigerator 7 Cold head 7a 1st freezing stage 7b 2nd freezing stage 8 Exhaust port 11 Throttling mechanism 12 Double torus 13 Hydrogen storage alloy Cylinder 14 Hydrogen storage alloy drawing mechanism 15 Hydrogen storage alloy cylinder 15a Bright surface

Claims (4)

[Claims] 1. A first-stage cold panel is heated by an external temperature by heat conduction of residual hydrogen gas molecules between a casing of a cryopump that exhausts a large amount of hydrogen gas in an exhaust chamber and a first-stage cold panel, In order to prevent deterioration of the refrigerating performance of the first-stage cold panel and the second-stage cold panel cooled by a refrigerator, the throttling mechanism and the hydrogen storage alloy provided between the casing and the first-stage cold panel The pressure of hydrogen gas molecules between the casing and the first cold panel is reduced to reduce the heat conduction of the hydrogen gas molecules to prevent the deterioration of the refrigeration performance of the first and second cold panels. A method for exhausting hydrogen by a cryopump, which is characterized in that 2. In a hydrogen exhaust device using a cryopump for exhausting a large amount of hydrogen gas in an exhaust chamber, an annular throttle mechanism provided at an end of the casing on the exhaust chamber side,
A hydrogen exhaust device by a cryopump, characterized in that a hydrogen storage alloy cylinder is provided in a double annular portion between the casing and the first-stage cold panel below the throttle mechanism. 3. The hydrogen storage alloy throttle mechanism is provided in an annular shape at the end of the casing on the exhausted chamber side by integrating the throttle mechanism and the hydrogen storage alloy cylinder.
Hydrogen pump with a cryopump. 4. The hydrogen pumping device for a cryopump according to claim 2, wherein the cylindrical surface of the hydrogen storage alloy cylinder on the first-stage cold panel side is a bright surface.