JP2010210302A - Vacuum gauge for low-temperature apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum gauge for low-temperature apparatus which is capable of performing measurement even when its measuring range is a region other than a molecular flow region, has improved the vibration-proof property and durability of the conventional vacuum gauge, is suitable for measuring, monitoring, etc., the degree of vacuum of a low-temperature apparatus to which impulses and vibration are applied, is hard to fail even if the pressure of a measuring object increases, and has a wide measuring range. <P>SOLUTION: This vacuum gauge for low-temperature apparatus includes: a low temperature heat source 1 arranged inside a vacuum heat-insulating section, a plurality of heat receiving plates 2, 3, and 4 arranged so as to face this low-temperature source 1 with separations s, m, and L between them; a temperature sensor 5 for measuring the temperature of the low-temperature source 1, a plurality of thermometer sensors 6, 7, and 8 for measuring the respective temperatures of the plurality of heat receiving plates 2, 3, and 4; and a temperature sensor 10 for measuring the temperature of a thermal shield plate or partitions 9. A pressure range inside the vacuum heat-insulating section is detected from the temperature of the low-temperature source 1, the temperature of the shield plate or partitions 9, and respective temperature distributions of the heat receiving plates 2, 3, and 4. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vacuum gauge capable of monitoring the pressure of a place requiring a vacuum such as a heat insulation place in a cryogenic device, and in particular, the measurement range can be measured in a region other than the molecular flow region, and the impact and vibration can be measured. The present invention relates to a vacuum gauge that can withstand use in a certain environment and has improved durability.

  Conventionally, Pirani vacuum gauges, thermocouple vacuum gauges, and the like that are generally used have a problem that they are likely to fail when subjected to impact or vibration or measured at a pressure higher than the measurement range. Among these, since the heat conduction vacuum measuring device (see Patent Document 1 below) does not use a thin filament, it is considered that durability against vibration / impact and unexpected high pressure measurement can be secured. However, this heat conduction vacuum measuring device is limited to measurement only in a low pressure region (molecular flow region) in which the mean free path of gas molecules is more than a distance.

  In addition, there is a case in which a quartz friction type vacuum gauge with high vibration resistance that does not use heat transfer characteristics is under development (see Non-Patent Document 1 below).

Japanese Patent Publication No. 6-040046 Japanese Patent Application No. 2008-115173

Junichi Kurihara, Isao Murata, Kei Sato, Yoshihiro Kajikawa, Tomomi Abe, “Performance Test of Quartz Barometer”, Japan Aerospace Exploration Agency 2007 Air Ball Symposium Geophysics, 4

  As described above, the conventional vacuum gauge cannot measure in a region other than the molecular flow region, and has various problems to be solved in terms of vibration resistance and durability.

  In view of the above situation, the present invention is capable of measuring in a region other than the molecular flow region, and improves the vibration resistance and durability of a conventional vacuum gauge, and the degree of vacuum of a low-temperature device to which impact or vibration is applied. An object of the present invention is to provide a vacuum gauge for low-temperature equipment that is suitable for measurement and monitoring, and that does not easily fail even when the pressure rises above the measurement range.

In order to achieve the above object, the present invention provides
[1] In a vacuum gauge for low-temperature equipment, a low-temperature source disposed in the vacuum heat insulating portion, a plurality of heat receiving plates disposed to be opposed to each other at different distances from the low-temperature source, and the temperature of the low-temperature source A temperature sensor for measuring, a plurality of temperature sensors for measuring the temperature of each of the plurality of heat receiving plates, and a temperature sensor for measuring the temperature of the heat shield plate or the partition wall, and the temperature of the low temperature source and the heat shield The pressure region in the vacuum heat insulating part is detected from the temperature of the plate or partition and the temperature distribution of each of the plurality of heat receiving plates.

  [2] In the vacuum gauge for low temperature equipment according to [1] above, from the relationship between the temperature of the low temperature source, the temperature of the heat shield plate or the partition, and the temperature distribution with respect to the separation of the plurality of heat receiving plates from the low temperature source. A molecular flow region that occurs when the separation between the low-temperature source and the plurality of heat receiving plates is smaller than the gas molecule mean free path, a viscous flow region that occurs when the separation is greater than the gas molecule mean free path, and their transition It is characterized by determining which one of the characteristics of the intermediate flow region, which is a region, and detecting the pressure region in the vacuum heat insulating portion according to the combination thereof.

  [3] The vacuum gauge for low-temperature equipment according to [1] above, the separation between the low-temperature source and the plurality of heat receiving plates, the area of the surface where the low-temperature source and the plurality of heat receiving plates are opposed, the specific heat of the heat receiving plate And the mass, the amount of heat penetration from the partition wall of the vacuum heat insulating portion into the plurality of heat receiving plates in the vacuum heat insulating portion, and the heat transfer coefficient between the low temperature source and the plurality of heat receiving plates, and the low temperature source and the plurality of heat receiving plates The amount of heat transfer or heat transfer coefficient between the heat receiving plates is obtained, and from the relationship between the heat transfer amount or heat transfer coefficient between the low temperature source and the plurality of heat receiving plates, the molecular flow region and the viscosity are determined according to the separation between the low temperature source and the plurality of heat receiving plates. It is characterized by determining which of the characteristics of the flow region and the intermediate flow region the heat transfer is based on, and detecting the pressure region in the vacuum heat insulating portion according to the combination thereof.

  That is, on the premise of application to low-temperature equipment, the low-temperature equipment has a low-temperature source as a heat source, and the pressure is measured without using a filament that was easily broken by the conventional technology. The low-temperature source uses a liquid helium system, a refrigerator cold head, or the like whose temperature is fixed. The heat transfer coefficient from the heat receiving plate to the low temperature source differs depending on the distance by arranging a plurality of heat receiving plates with different separations facing each other in the low temperature source, but each heat transfer characteristic depends on the pressure Change. By utilizing the difference in these characteristics, the temperature of each heat receiving plate is measured, and the pressure is converted from each relationship.

  According to the present invention, it is possible to provide a vacuum gauge that has improved vibration resistance and durability, is not easily damaged even by pressure outside the measurement range, and has an expanded measurement range for low-temperature equipment having a low-temperature source. It is possible to measure, monitor and control the degree of vacuum of low-temperature equipment subjected to shock and vibration.

It is a schematic diagram of the vacuum gauge for low temperature equipment which shows the principle of this invention. It is a figure which shows the change of the heat transfer characteristic with the heat transfer distance which shows the principle of this invention. It is a schematic diagram of the vacuum gauge for low temperature equipment which shows the Example of this invention. It is a figure which shows the relationship between the heat transfer distance and the amount of heat transfers in the Example of this invention.

  The vacuum gauge for low-temperature equipment according to the present invention includes a low-temperature source disposed in the vacuum heat insulating portion, a plurality of heat receiving plates disposed to face each other at different distances from the low-temperature source, and the temperature of the low-temperature source. A temperature sensor for measuring, a plurality of temperature sensors for measuring the temperature of each of the plurality of heat receiving plates, and a temperature sensor for measuring the temperature of the heat shield plate or the partition wall, and the temperature of the low temperature source and the heat shield The pressure region in the vacuum heat insulating part is detected from the temperature of the plate or partition and the temperature distribution of each of the plurality of heat receiving plates.

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 1 is a schematic diagram of a vacuum gauge for low-temperature equipment showing the principle of the present invention, and FIG. 2 is a diagram showing changes in heat transfer characteristics with the heat transfer distance.

  In these drawings, 1 is a low temperature source, 2, 3 and 4 are a plurality of heat receiving plates which are at different distances (separations) from the low temperature source 1, and 5 is a first temperature sensor for measuring the temperature of the low temperature source 1. , 6 is a second temperature sensor for measuring the temperature of the heat receiving plate 2, 7 is a third temperature sensor for measuring the temperature of the heat receiving plate 3, 8 is a fourth temperature sensor for measuring the temperature of the heat receiving plate 4, 9 Is a fifth temperature sensor for measuring the temperature of the partition wall or the heat shield plate 9, and 11, 12, and 13 are a plurality of heat receiving plates 2, 3, and 4, respectively. A heat receiving plate fixing member for fixing.

  As shown in FIG. 1, the heat receiving plates 2, 3, 4 having a different distance from the low temperature source 1 are installed facing each other. The low temperature source 1 is the first temperature sensor 5, the heat receiving plates 2, 3, 4 are the second temperature sensor 6, the third temperature sensor 7 and the fourth temperature sensor 8, and the partition wall or the heat shield plate 9 is the first temperature sensor 5. The temperature is measured by each of the five temperature sensors 10. Distances (separations) s, m, L between the low temperature source 1 and the heat receiving plates 2, 3, 4, the area of the surface where the low temperature source 1 and the heat receiving plates 2, 3, 4 face each other, the heat receiving plate 2 , 3 and 4, the amount of heat penetration from the partition wall or heat shield plate 9 to the heat receiving plates 2, 3, 4, and between the low temperature source 1 and each heat receiving source 2, 3, 4 which changes according to the pressure From the heat transfer coefficient, the amount of heat transfer between the low temperature source 1 and each of the heat receiving plates 2, 3, 4 can be obtained. For this reason, the equilibrium temperature of the low-temperature source 1, the heat receiving plates 2, 3, 4 and the partition wall or the heat shield plate 9 can be measured and converted into the pressure to be measured from this measurement result and their relationship.

  The relationship between the heat transfer amount and the distance according to the pressure in a rare gas (vacuum) generally has the characteristics shown in FIG. The heat transfer characteristics include the characteristics of the molecular flow region that occurs when the heat transfer distance (separation) is smaller than the gas molecule mean free path, the viscous flow region that occurs when the heat transfer distance is greater than the gas molecule mean free path, and these There is a characteristic of the intermediate flow region, which is the transition region. As for these characteristics, when the pressure is constant and the heat transfer distance is short, the heat transfer coefficient decreases as the heat transfer distance increases according to the characteristics of the molecular flow region. Transition to the characteristics of the decreasing intermediate flow region. When the heat transfer distance is further increased, the characteristics of the viscous flow region where the rate of decrease in the heat transfer coefficient is large again are transferred. The transition of the region characteristics in the heat transfer characteristics varies depending on the pressure. The higher the pressure, the shorter the heat transfer distance, and the longer the heat transfer distance, the lower the pressure.

  In the present invention, based on the measurement results of the temperatures of the heat receiving plates 2, 3, 4 separated from the low temperature source 1 by different distances, the heat transfer regions corresponding to the separation of the heat receiving plates 2, 3, 4 and the low temperature source 1 are used. The characteristics can be collated, and the pressure range can be specified stepwise according to the combination of these. The relationship between the combination of heat transfer characteristics from the low-temperature source to each heat receiving plate and the pressure range is as shown in Table 1 when the structure includes three heat receiving plates, for example.

Since the heat transfer coefficients in the molecular flow region, the intermediate flow region, and the viscous flow region shown in FIG. 2 and Table 1 are greatly different, the equilibrium temperature of the heat receiving plate in each region is greatly different. For this reason, it is possible to easily determine in which region characteristics the respective heat receiving plates are transferring heat from the equilibrium temperature of each heat receiving plate, and by grasping the combination of the heat transfer region characteristics of each heat receiving plate. The pressure of the measurement object can be obtained.

  FIG. 3 is a schematic diagram of a vacuum gauge for low-temperature equipment showing an embodiment of the present invention, and FIG. 4 is a diagram showing a relationship between a heat transfer distance and a heat transfer amount in this embodiment.

  In FIG. 3, reference numeral 21 denotes a low-temperature source, reference numerals 22, 23, and 24 denote a plurality of heat receiving plates arranged at different distances (separations) from the low-temperature source 21, and reference numeral 25 denotes a first temperature for measuring the temperature of the low-temperature source 21. The temperature sensor 26 is a second temperature sensor that measures the temperature of the heat receiving plate 22, 27 is a third temperature sensor that measures the temperature of the heat receiving plate 23, and 28 is a fourth temperature sensor that measures the temperature of the heat receiving plate 24. , 29 is a heat shield plate, 30, 31 and 32 are heat receiving plate fixing members, 33 is a fifth temperature sensor for measuring the temperature of the heat shield plate 29, 34 is a vacuum heat insulation container, and 35 is a heat insulation plate with the vacuum heat insulation container 34. A heat insulating member 36 disposed between the plates 29 is a refrigerator that cools the low temperature source 21.

The vacuum gauge using the low temperature source 21 cooled by the refrigerator 36 is configured as shown in FIG. In the low temperature apparatus having the low temperature source 21 of about 40 [K], the inside of the vacuum heat insulating container 34 is an atmosphere of dilute helium gas, and the internal pressure of about 1 [Pa] is measured and monitored. Under this condition, the three heat receiving plates 22, 23, and 24 are arranged facing the low temperature source 21 with a separation of 3 mm, 10 mm, and 30 mm. Each of the heat receiving plates 22, 23, and 24 is a square of 0.01 [m ² ], and is fixed to a heat shield plate 29 of 77 [K] via the heat receiving plate fixing members 30, 31, and 32.

  The relationship between the heat transfer distance between the low-temperature source 21 and the heat receiving plates 22, 23, 24 and the amount of heat transferred at that time is based on the theory described in Patent Document 2 [Equations (1) to (4)] and experimental results. Analyzed. As a result of the analysis, the relationship between the amount of heat transfer at each pressure and the distance between the low temperature source and the heat receiving plate is as shown in FIG. The conditions when this characteristic is analyzed are as shown in Table 2.

Based on the relationship between the amount of heat transfer and the pressure in FIG. 4, the equilibrium temperature of the three heat receiving plates in the embodiment shown in FIG. 3 was analytically determined as follows.

  The amount of heat transferred from the heat receiving plate to the low temperature source is expressed by the following formula (1).

Q ₁ = ηA (T−40) (1)
Here, T is determined by the heat receiving plate temperature, η is determined by the heat receiving plate area, the heat transfer distance and pressure, the gas type, and the like.

  The amount of heat transfer from the heat shield plate to the heat receiving plate is represented by the following formula (2).

Q ₂ = (k ₀ A ₀ / l) · (77−T) (2)
(K ₀ : heat transfer coefficient of heat receiving plate fixing member, A ₀ : cross sectional area of heat receiving plate fixing member, l: length of heat receiving plate fixing member)
The amount of heat necessary for temperature change of the heat receiving plate is represented by the following formula (3).

Q = Cm (dT / dt) (3)
(C: heat receiving plate specific heat, m: heat receiving plate mass, T: heat receiving plate temperature)
The temperature change of the heat receiving plate in a short time is represented by the following formula (4).

By solving this equation (4), each heat receiving plate equilibrium temperature under the conditions of the present embodiment can be calculated, and since η changes according to the pressure, the equilibrium temperature according to the pressure can be calculated. . Of the various conditions of the examples, those other than those shown in Table 2 are shown in Table 3.

Further, Table 4 shows the obtained equilibrium temperature of each heat receiving plate.

When the pressure is extremely low, the three heat receiving plates equilibrate at a low temperature, and the equilibrium temperature hardly rises as the pressure increases, but when the pressure increases further, the equilibrium temperature rises from the heat receiving plate with a large separation, The equilibrium temperature of the heat receiving plate with a small separation also starts to rise sequentially. Further, when the pressure is further increased, the heat receiving plate having a large separation is equilibrated at a high temperature, and the heat receiving plates having a small separation are also sequentially balanced at a high temperature. Thereafter, even if the pressure increases, the equilibrium temperature of the heat receiving plate hardly increases. Therefore, the pressure of the measurement object can be grasped by comparing and comparing the temperature measurement result of each heat receiving plate with the characteristics shown in Table 4.

  In addition, this invention is not limited to the said Example, Based on the meaning of this invention, a various deformation | transformation is possible and these are not excluded from the scope of the present invention.

  The vacuum gauge for low-temperature equipment of the present invention can be measured in a region other than the molecular flow region, can measure the degree of vacuum of a low-temperature device even in an environment where impact and vibration are applied, and has a wide measurement range. It can be used as a vacuum gauge.

1,21 Low temperature source 2,3,4,22,23,24 Heat receiving plate 5,25 First temperature sensor 6,26 Second temperature sensor 7,27 Third temperature sensor 8,28 Fourth temperature sensor 9 Bulkhead or heat shield plate 10, 33 Fifth temperature sensor 11, 12, 13, 30, 31, 32 Heat receiving plate fixing member 29 Heat shield plate 34 Vacuum heat insulating container 35 Heat insulating member 36 Refrigerator

Claims (3)

  A low-temperature source disposed in the vacuum heat insulating section, a plurality of heat receiving plates disposed to face each other at different distances from the low-temperature source, a temperature sensor for measuring the temperature of the low-temperature source, and the plurality of heat receiving units A plurality of temperature sensors for measuring the temperature of each of the plates, and a temperature sensor for measuring the temperature of the heat shield plate or the partition wall, and the temperature of the low temperature source, the temperature of the heat shield plate or the partition wall, and the plurality of heat receiving units. A vacuum gauge for low-temperature equipment, wherein a pressure region in the vacuum heat insulating portion is detected from a temperature distribution of each plate.   2. The vacuum gauge for low temperature equipment according to claim 1, wherein the low temperature source is calculated from the relationship between the temperature of the low temperature source, the temperature of the heat shield plate or the partition wall, and the temperature distribution of each of the plurality of heat receiving plates from the low temperature source. A molecular flow region that occurs when the separation between the plurality of heat receiving plates is smaller than the gas molecule mean free path, a viscous flow region that occurs when the separation is greater than the gas molecule mean free path, and an intermediate between these transition regions A vacuum gauge for low-temperature equipment, characterized by determining which one of the characteristics of the flow region is a region and detecting the pressure region in the vacuum heat insulating portion according to a combination thereof.   The vacuum gauge for low temperature equipment according to claim 1, wherein the low temperature source and the plurality of heat receiving plates are separated, the area of the surface where the low temperature source and the plurality of heat receiving plates are opposed, the specific heat and mass of the heat receiving plate, Transfer of heat between the low temperature source and the plurality of heat receiving plates based on the amount of heat penetration from the partition of the vacuum heat insulating unit to the plurality of heat receiving plates in the vacuum heat insulating unit and the heat transfer coefficient between the low temperature source and the plurality of heat receiving plates. The amount of heat or heat transfer coefficient is obtained, and from the relationship between the heat transfer amount or heat transfer coefficient between the low temperature source and the plurality of heat receiving plates, the molecular flow region, the viscous flow region, and the intermediate according to the separation of the low temperature source and the plurality of heat receiving plates, respectively. A vacuum gauge for low-temperature equipment, characterized by determining which of the characteristics of the flow region is responsible for heat transfer, and detecting the pressure region in the vacuum heat insulating portion according to a combination thereof.