JPH01178781A - Cryopump - Google Patents

Abstract

PURPOSE:To prevent a load of heat of condensation from being unnecessarily increased by changing the flow rate of a gas forming a condensed layer by the pressure of a gas being exhausted near an inlet port of a cryopump. CONSTITUTION:When the pressure of a gas being exhausted introduced from an inlet port 1 into the inside is raised, a pressure-rise is detected by a pressure gage 26 installed in a pressure detecting pipe 25, and a detection signal of the pressure-rise is sent to a pressure-opening corresponding device 27. The pressure-opening corresponding device 27 gives a signal for regulating the opening of a flow control valve 22 to a drive mechanism control device 24 in response to the detection signal value from the pressure gage 26, and controls the flow rate of argon-gas flowing in an introducing pipe 20 so as to increase in proportion to the pressure-rise in the gas being exhausted. Accordingly, the volume of the condensed layer 13 formed is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a cryopump in which the amount of formation of a condensation layer acting as an adsorbent cooled to an extremely low temperature is controlled.

(Prior art) This type of cryopump uses argon to form a gas condensation layer that acts as an adsorbent on a surface cooled to an extremely low temperature, and the adsorption or cryotrapping effect of the gas condensation layer formed with argon. There are known devices in which helium is exhausted from the gas phase.

As shown in FIG. 12, the cryopump of the above type has a liquid nitrogen reservoir 5 which has a radiation shield 3 and a chevron-shaped baffle 4 inside a vacuum vessel 2 equipped with an inlet.
A chevron-shaped baffle 4 is provided so as to face the intake port 1, and inside the liquid nitrogen reservoir 5 there is a liquid helium reservoir 7 having a chevron-shaped baffle 6 at the lower part and a liquid helium reservoir having a gas-liquid separator 8 at the upper part. A blow-off pipe 11 having a blow-off hole 10 is provided to face the liquid helium reservoir 9, and the blow-off pipe 1] is connected to an argon supply device (not shown) via a manifold 12. Argon is blown out from the blow-off hole of the blow-off pipe 11 to form a condensation layer 3 acting as an adsorbent on the outer surface of the liquid helium reservoir. The condensation layer 3 is cooled by the liquid helium in the liquid helium reservoir and constitutes an exhaust surface for exhausting gas to be exhausted such as helium.

The gas to be evacuated is guided inside from the inlet of the vacuum container 2 through a chevron-shaped baffle 4 cooled by liquid nitrogen in a liquid nitrogen reservoir 5 and a chevron-shaped baffle cooled by liquid helium in a liquid helium reservoir 7. 6 and reaches the condensation layer 13 that acts as an adsorbent formed on the outer surface of the liquid helium reservoir 9. In this process, components such as hydrogen other than the helium and other gases in the gas to be exhausted mainly form a chevron shape. The baffle 6 condenses and exhausts the gas, and the gas to be exhausted, such as helium, is mainly exhausted onto the exhaust surface 13 by adsorption or cryotrapping.

(Problem to be solved by the invention) However, in the above-mentioned type of cryopump, the amount of adsorbent forming gas such as argon introduced is set in advance to a constant amount corresponding to the gas to be evacuated such as helium. If we know the exhaust flow rate of the gas to be exhausted such as helium and its increase/decrease in advance, is it possible to form an appropriate adsorbent-forming gas condensation layer? When exhausting, the exhaust flow rate value of the gas to be exhausted and its increase/decrease value are not necessarily known, and if the exhaust flow rate value of the gas to be exhausted is lower than expected, it may be necessary to form an adsorbent and form a gas condensation layer. The amount becomes larger than necessary, and as a result, the heat load on the exhaust surface becomes larger than necessary due to the heat of condensation.
The problem is that the consumption of liquid helium increases unnecessarily, and the thickness of the adsorbent-forming gas condensation layer on the exhaust surface unnecessarily increases, resulting in a decrease in the exhaust capacity for the target gas such as helium. There is.

On the other hand, if the exhaust flow rate value of the gas to be pumped is higher than expected, the amount of adsorbent forming gas condensation layer formed is relatively insufficient, and the gas to be pumped such as helium is not sufficiently pumped out. The problem is that when the pressure rises by 1, the cryopump exhibits unstable operation, such as re-releasing the gas that had been evacuated up to that point.

The present invention has been made in view of the above points, and it forms an adsorbent-forming gas condensation layer necessary for obtaining a stable exhaust effect, and also forms an adsorbent-forming gas condensation layer on the exhaust surface cooled to an extremely low temperature. It is an object of the present invention to provide a cryopump that appropriately controls the displacement amount due to the increase in the thickness of the adsorbent forming gas condensation layer so as to prevent the condensation heat load accompanying the formation.

[Structure of the invention]

(Means for Solving the Problems) The cryopump of the present invention condenses a first gas acting as a condensation layer or an adsorption medium on a surface cooled to an extremely low temperature in a vacuum, and condenses the first gas. In a cryopump that exhausts a second gas to be exhausted into a layer or onto a condensation layer from a gas phase in a vacuum by adsorption or cryotrapping, the pressure of the second gas near the cryopump inlet The control device is provided with a control device for changing the amount of the first gas condensed layer formed in response to the amount of the first gas condensed layer.

(Function) In the cryopump of the present invention, the condensation layer of the first gas, which acts as a second gas adsorption medium, changes in the pressure of the second gas to be evacuated near the cryopump inlet. By varying the amount of formation, the condensation layer necessary to obtain a stable exhaust effect is formed, and the heat load on the exhaust surface is not increased more than necessary.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, the same members as in FIG. 12 are given the same reference numerals.

In FIG.
2 and an argon supply device (not shown), and a flow rate control valve 22 is disposed in the introduction pipe 20 at a position outside the lid 21 of the vacuum container 2. The drive mechanism 23 attached to the flow rate control valve 22 is moved by a drive mechanism control device 24 that controls the drive mechanism 23, and adjusts the opening degree of the flow rate control valve 22.

On the other hand, a pressure detection tube 25 is attached to a portion of the vacuum container 2 near the inlet. A pressure gauge 26 is connected to the pressure detection tube 25 to detect the pressure of a gas to be evacuated, such as helium, passing through the inlet 1 of the vacuum container 2.

A detection signal from the pressure gauge 26 is sent to a pressure opening correspondence device 27. This pressure opening adjustment device 27 outputs a signal for adjusting the opening of the flow rate control valve 22 to the drive mechanism control device 24 in response to the detected signal value of the pressure gauge 26, and
Control the flow rate of argon gas flowing through the argon gas.

Thus, the opening degree of the flow rate control valve 22 is set to a predetermined setting value, and a predetermined flow rate of argon gas flows through the inlet pipe 20 through the manifold [2] and the blowout hole [0] of the blowout pipe 11. A condensed layer 13 is formed on the outer surface of the liquid helium reservoir 9, which acts as an adsorbent.

- The gas to be exhausted led into the interior from the intake port 1 of the empty cutting tool container 2 is passed through the chevron-shaped baffle 4 cooled by liquid nitrogen in the liquid nitrogen reservoir 5 and the chevron-shaped baffle cooled by liquid helium in the liquid helium reservoir 7. 6 and reaches the condensation layer 13 that acts as an adsorbent formed on the outer surface of the liquid helium reservoir 9. In this process, components such as hydrogen other than the helium and other gases in the gas to be exhausted mainly form a chevron shape. The baffle 6 condenses and exhausts the gas, and the gas to be exhausted, such as helium, is mainly exhausted onto the exhaust surface 13 by adsorption or cryotrapping.

In a steady state, each member operates according to the set conditions, but when the pressure of the gas to be exhausted that is led inside from the intake port 1 increases, this pressure increase is detected by the pressure gauge 26 provided in the pressure detection tube 25. The detection signal is sent to the pressure opening correspondence device 27.

This pressure opening adjustment device 27 outputs a signal to the drive mechanism control device 24 to adjust the opening degree of the flow rate control valve 22 in response to the detected signal value of the pressure gauge 26, and the flow rate of the argon gas flowing through the introduction pipe 20 is output to the drive mechanism control device 24. is controlled so that it increases in proportion to the rise in pressure of the gas to be exhausted.

Further, when the pressure of the gas to be exhausted guided inside from the intake port 1 decreases, the drive mechanism control device 2 sends an opening adjustment signal in response to a detection signal output from the pressure gauge 26 that detects this pressure decrease.
4 and controls the flow rate of argon gas flowing through the introduction pipe 20 so as to decrease in proportion to the rise in pressure of the gas to be exhausted.

FIGS. 2 to 7 show other embodiments of the present invention. In the embodiment shown in FIG. In addition to connecting the heavy pole mass spectrometer 31, a pulse motor 32 and an encoder 33 are provided to the flow rate control valve 22, and a drive mechanism control device 34 of the pulse motor 32 and a reading device 35 of the encoder 33 are connected to the pressure opening corresponding device 27. are doing. and the gas to be exhausted passing through the intake port 1 of the vacuum container 2,
For example, the pressure of helium is detected by a quadrupole mass spectrometer 31 provided in the analysis tube 30, and the detection signal of this quadrupole mass spectrometer 31 is sent to the pressure opening degree corresponding device 27. In this case, the drive mechanism control device 34 controls the flow rate control valve 22 in response to the detection signal value of the quadrupole mass spectrometer 31.
The flow rate of argon gas flowing through the introduction pipe 20 is outputted, and the opening degree of the flow rate control valve 22 is read by the reading device 35 of the encoder 33, and this signal is sent to the pressure opening corresponding device 27. In this step, the detection signal of the quadrupole mass spectrometer 31 is compared, and an appropriate opening degree of the flow rate control valve 22 is set.

In the embodiment shown in FIG.
A flowmeter sensor 36 is provided further downstream, and a signal from the flowmeter sensor 36 is sent to the pressure opening correspondence device 27 via a flowmeter output device 37. In this case, the signal that is compared with the value of the pressure gauge 31 to determine the opening/closing direction and degree of opening/closing of the flow rate control valve 22 is the flow rate of argon gas flowing through the introduction pipe 20, and even if the pressure of the argon gas fluctuates, this pressure The argon gas flow rate can be controlled in response to fluctuations.

In the embodiment shown in FIG. 4, the flow rate control valve 22 provided in the introduction pipe 20 has a structure including a valve having a mechanism for adjusting conductance using a piezoelectric element, and the piezoelectric element is incorporated into the flow rate control valve 22. A pressure opening adjustment device 27 compares the pressure value output from the pressure gauge 26 with the voltage applied to the piezoelectric element, and generates a piezoelectric element corresponding to the pressure value output from the pressure gauge 26. The voltage applied to the element is determined. In this case, the flow rate of argon gas flowing through the introduction pipe 20 can be adjusted with a fast response speed.

In the embodiment shown in FIG.
is connected, and the drive mechanism control device 24 is instructed to open and close the flow control valve 22 based on the pressure value output from the total pressure gauge 39. In this case, the gas to be exhausted is limited to cases where the gas to be exhausted contains a large proportion of the gas to be exhausted, such as helium, and the total pressure can be regarded as the partial pressure of the gas to be exhausted, such as helium. Become.

In the embodiment shown in FIG. 6, an analysis tube 40 is attached to a portion of the vacuum container 2 near the inlet 1, and a magnetic field deflection type partial pressure π14] is connected to the analysis tube 40.

In the embodiment shown in FIG. 7, a connecting pipe 42 is attached to a portion of the vacuum container 2 near the intake port 1, and a helium leak detector 43 is connected to this connecting pipe 42. If the gas to be exhausted is helium, there is no problem in measurement even if a helium leak detector is used as an a+U constant device for helium partial pressure.

8 to 11 show an embodiment in which the present invention is applied to a cryopump of a different type from the above-mentioned cryopump, and the cryobomb in the embodiment of FIG. 8 is different from the cryopump shown in FIG. In this case, helium, hydrogen, and other gases to be exhausted are simultaneously exhausted to the exhaust surface 13, so it is necessary to distinguish the helium exhaust surface from the exhaust surface other than helium. It is effective when there is no.
The cryopump in the embodiment shown in FIG. 9 uses a helium refrigerator 51 to cool the gas exhaust surface 50, and this helium refrigerator 51 is roughly connected to a first stage cooling section 52 that is cooled to the boiling point temperature of liquid nitrogen. It is equipped with a second stage cooling section 53 that is cooled to 20K and a third stage cooling section 54 that is cooled to approximately the boiling point temperature of liquid helium. is formed. Also the first
A chevron-shaped baffle 57 is disposed on the radiation shield 56 provided in the stage cooling section 52, and a chevron-shaped baffle 59 is disposed on the radiation shield 58 provided in the third stage cooling section 54, respectively.

The cryopump in the embodiment shown in FIG. 10 differs from the cryopump shown in FIG. 9 in that the radiation mold 58 and the chevron-shaped baffle 59 provided in the third stage cooling section 54 are omitted. In this case, since there is no radiation shield 58 and chevron-shaped baffle 59 cooled to approximately the boiling point temperature of liquid helium, helium, hydrogen, and other gases are simultaneously exhausted at the exhaust surface 50.

In the cryopump in the embodiment shown in FIG. 11, the exhaust surface 60 cooled with liquid helium is located on the inner surface of an annular liquid helium reservoir 62 whose inlet plane of the central opening is located approximately parallel to the cryopump intake port 61. It is formed. An annular louver blind baffle 63 located inside the liquid helium reservoir 62 is cooled by a liquid helium reservoir 64 . Furthermore, the fins 67 of the annular louver blind baffle 66 cooled by the liquid nitrogen reservoir 65 are arranged at an angle so as to prevent radiation from the exhaust surface 60 from the cryopump intake port 61 . In this case, the probability that the incident gas will pass through the annular louver blind baffle 63 and the exhaust surface 60 increases, resulting in a cryopor tube with a high exhaust speed.

[Effects of the Invention] As described above, according to the present invention, there is provided a control device for changing the flow rate of a gas forming a condensed layer acting as an adsorbent depending on the pressure of the gas to be exhausted near the cryopump intake port. Since this is provided, it is possible to form a condensation layer that acts as an adsorbent necessary to obtain a stable exhaust action without unnecessarily increasing the condensing heat load or reducing the exhaust capacity.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a cryopump according to the present invention, FIGS. 2 to 11 are views showing other embodiments of the cryopump according to the present invention, and FIG. 12 is a cross-sectional view of a conventional cryopump. DESCRIPTION OF SYMBOLS 1...Intake port, 2...Vacuum container, 10...Blowout hole, 11...Blowout pipe, 13...Exhaust surface, 20...Introduction pipe, 22...Flow control valve, 23... Drive mechanism, 2
4... Drive mechanism control device, 26... Pressure gauge, 27.
...Pressure opening ratio control device. Applicant's agent Mr. Sato - Figure 4 Figure 1/ Figure 8 Figure 12

Claims (1)

[Claims] 1. A condensation layer condenses a first gas acting as an adsorbent on a surface cooled to an extremely low temperature in a vacuum, and an exhaust target is placed in or on the condensation layer of the first gas. In a cryopump that exhausts a second gas from a vacuum gas phase by adsorption or cryotrapping, the first gas is evacuated in response to the pressure of the second gas near the cryopump inlet. A cryopump characterized by being equipped with a control device for changing the amount of condensation layer formed. 2. The cryopump according to claim 1, wherein the first gas is argon or nitrogen, and the second gas is helium. 3. The control device includes a flow control valve disposed in the first gas introduction pipe path, a control mechanism for the flow control valve, a second gas pressure measurement device, and a measurement value of the pressure measurement device. 2. The cryopump according to claim 1, further comprising a flow rate adjustment device that adjusts the opening degree of the flow rate adjustment valve by moving a control mechanism of the flow rate adjustment valve accordingly.