JPH03164580A - Cryopump - Google Patents

Abstract

PURPOSE:To easily determine a normal/abnormal state of working cycles in a cryopump so as to generate a warning in an early stage by counting cycles of compression and expansion in a freezer by a sensor. CONSTITUTION:In a freezer of a cryopump, its very low temperature panel 1 is constantly cooled during operation by opening/closing of high and low pressure valves 2, 3 and reciprocating motion of an internal piston 4. When impurities 10 are condensed on an inner wall of a cold head cylinder 9, a slide occurs inside a cold head motor 5 and its rotating motion is not completely converted to reciprocating motion of a cam follower 6. In this case one cycle of the reciprocating motion in the internal piston 4 which is interlocked with the cam follower 6 is sensed by a sensor 7 and one cycle is counted by a pulse counter 8. By comparing pulse count numbers during a normal state and during operation, the state of working cycles is determined.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cryopump, and particularly to a cryopump equipped with means for monitoring the state of the cryopump.

[Conventional technology]

Conventionally, this type of cryopump has been equipped with a means of measuring the temperature of the condensation surface as a means of monitoring the state of the cryopump.

[Problem to be solved by the invention]

In the conventional cryopump described above, whether or not the cryopump is normal is determined based on the temperature rise of the condensation surface. However, if impurities are mixed into the refrigerant gas, the impurities will condense inside the refrigerator, and the increased load due to condensation will cause slipping inside the refrigerator motor, gradually reducing the normal operating cycle. Sometimes it happens.

In this way, the refrigeration capacity decreases as the operating cycle decreases, and by the time the refrigeration capacity falls below the exhaust load of the cryopump, the temperature of the condensation surface has already risen, so the original The disadvantage is that the desired ultimate vacuum cannot be obtained, resulting in unexpected maintenance.

The present invention differs from the conventional cryopump described above in that it can be determined whether the operating cycle is normal or not by monitoring the number of compression-expansion cycles within the refrigerator.

[Means to avoid solving problems]

The cryopump of the present invention has a sensor for counting cycles of compression and expansion inside the refrigerator, and it is possible to judge whether the operating cycle inside the refrigerator is clean or not based on the cycle detected by this sensor. There is.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a longitudinal sectional view of a cryopump refrigerator according to a first embodiment of the present invention.

The cryogenic panel 1 has a high pressure valve 2. Cooling is constantly maintained during operation by opening and closing the low pressure valve 3 and reciprocating the internal piston 4.

At this time, the rotation of the cold head motor 5 is converted into a reciprocating motion of the internal piston 4 by the cam follower 6, and one reciprocating motion is detected by the sensor 7 and counted as one by the pulse counter 8.

If impurities are mixed into the refrigerant gas, condensed impurities 1 will be present on the inner wall of the cold head cylinder 9 at extremely low temperatures.
0 grows, and depending on the degree of growth, slipping occurs inside the cold head motor 5, and the rotational motion is not completely converted into the reciprocating motion of the cam follower 6.

Since the number of pulse counts of the pulse counter 8 within a certain period of time during normal operation is determined by the rotation speed of the cold head motor 5, it is necessary to monitor the number of pulse counts during operation with respect to the number of pulse counts during normal operation. According to
It is possible to determine whether the operating cycle inside the refrigerator is normal or not.

FIG. 2 is a longitudinal sectional view of Example 2 of the present invention.

High pressure valve2. Low pressure valve 3. One cycle of compression and expansion consisting of the reciprocating motion of the internal piston 4 and the low pressure valve 3
The pulse counter 8 counts the pressure fluctuations detected by the pressure sensor 11 installed in front of the pulse counter 8.

In this embodiment, the reciprocating motion of the internal piston 4 is detected by pressure fluctuations, so by setting the range of fluctuations in the detected pressure, it is possible to reduce the filling pressure of the refrigerant gas or the small amount of the high-pressure valve 2 or low-pressure valve 3. It has the advantage of being able to detect seal leaks as well.

〔Effect of the invention〕

As explained above, by counting the number of cycles of compression and expansion of refrigerant gas, the present invention makes it easy to determine whether the operating cycle of the cryopump during operation is normal compared to the normal operating cycle of the cryopump. This has the effect that it is possible to warn of an abnormality in the cryopump before a situation occurs in which the ultimate vacuum value cannot be obtained due to a rise in the temperature of the condensation surface.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing a cryopump refrigerator according to a first embodiment of the present invention, and FIG. 2 is a vertical cross-sectional view of a cryopump refrigerator according to a second embodiment of the present invention.

Claims (1)

[Claims] A cryopump characterized by having a sensor for counting cycles of compression and expansion within a refrigerator.