JPS5836999Y2 - Pirani vacuum gauge with coaxial vacuum terminal - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a Pirani vacuum gauge for measuring the degree of vacuum within a vacuum container, and particularly relates to a Pirani vacuum gauge that can be heated and can withstand ultra-high vacuum.

There is a conventional Pirani vacuum gauge as shown in Figure 1, in which one end of the glass body containing the filament A is connected to a stainless steel flange via a pipe C made of Kovar (trade name). At the same time, lead wires e made of soft metal are drawn out from the other end of the main body, and these lead wires e are connected with alligator clips.

However, with such conventional Pirani vacuum gauges, the main body is made of glass, so there is a risk of damage, and the lead wires e are sealed in glass, so the spacing between the two lead wires e is not constant. In addition, there is considerable variation, and as mentioned above, the soft metal lead wire e is connected by sandwiching the alligator clip, so the alligator clips may come into contact with each other and cause a short circuit, or the alligator clip may be damaged due to vibration. There is a problem that a normal signal cannot be sent due to falling off or contact deterioration, etc., and the connection of the lead wire e becomes unstable.

Furthermore, there is a conventional Pirani vacuum gauge as shown in Fig. 2. In the Pirani vacuum gauge shown in Fig. 2, the end of the body f made of metal such as brass has a
Glass-sealed hermetic seal g outer cylinder [This outer cylinder is made of Kovar (trade name) or stainless steel.

] are usually attached by soldering, and stems h and i are soldered to different pins of this hermetic seal g, respectively, and a filament a is attached to each stem h and i.

The reason why the outer cylinder of the hermetic seal g and the main body f are attached by soldering is as follows.

In other words, in general, Kovar (trade name) and stainless steel can be joined by TIG welding (tungsten inert gas welding) and can withstand long-term heating and degassing at 300 to 400°C, which is essential for achieving ultra-high vacuum. In this case, the effective dimension of the outer cylinder is extremely short, for example, about 3 mm, so if TIG welding is attempted, the glass will break due to the heat generated at that time.

Therefore, soldering is used for attachment.

However, when the outer cylinder of the hermetic seal g is attached to the main body f by soldering in this way, there is a problem that vacuum leakage occurs when used for a long time, and it also requires heat treatment called baking. The problem is that it cannot be done.

There is also a Pirani vacuum gauge that has a glass seal or epoxy hermetic seal attached to an aluminum body using epoxy adhesive. Similar to a vacuum gauge, there are problems in that vacuum leaks occur and baking cannot be performed.

This invention attempts to solve these problems.
To provide a Pirani vacuum gauge with a coaxial vacuum terminal that is durable, does not cause vacuum leakage even after long use, and can be heated by baking.

For this reason, the Pirani vacuum gauge with a coaxial vacuum terminal of the present invention is provided with an ultrafine wire filament and a pair of thin wire support members supporting both ends of the filament in a cylindrical body, and the cylindrical body A coaxial vacuum terminal consisting of a metal round bar pin, a ceramic cylindrical body fitted around the outer periphery of the pin, and a metal cylindrical body fitted around the outer periphery of the ceramic cylindrical body at one end. The ceramic cylindrical body is hermetically fixed to the pin at a first fixing point, which is one end that should be located inside the cylindrical body, and the other end that should be located on the atmosphere side. The pin is provided with an escape groove, and is airtightly fixed to the metal cylindrical body at a second fixed point offset in the axial direction from the first fixed point, and the filament is fixed via the support member. One of the pair of thin wire-shaped supporting members is connected to one end of the metal round bar pin, and the other of the pair of thin wire-shaped supporting members is connected to one end of the metal cylindrical body in order to supply current to the metal cylinder. It is characterized by being connected.

Hereinafter, a Pirani vacuum gauge with a coaxial vacuum terminal as an embodiment of the present invention will be explained with reference to the drawings. Fig. 3 is a longitudinal sectional view thereof, Fig. 4 is a longitudinal sectional view showing the coaxial vacuum terminal, and Fig. 5 is a longitudinal sectional view. It is a longitudinal cross-sectional view showing a modification of the coaxial vacuum terminal.

As shown in FIG. 3, inside a stainless steel cylindrical body 1 with a wall thickness of 1 mm and an outer diameter of 18 mm, a platinum filament 2 in the form of an extremely thin wire with a diameter of 25 μm is inserted at both ends through small nickel plates 3 and 4. are arranged so as to be supported by a pair of thin wire-shaped support members 5 and 6.

Here, each nickel platelet 3, 4 used has a thickness Q,
It is formed as a small piece of 1 mm in diameter, 1 mm in length, and 2 mm in width, and the supporting members 5 and 6 are rods made of thin wire Kovar (a trade name for an alloy of iron, nickel, cobalt, etc.) or stainless steel with a diameter of 1 mm. It is constructed as a member.

And the filament 2 has nickel platelets 3 on both ends.
, 4 are attached to supporting members 5 and 6 by electric spot welding.

Further, the outer diameter of the cylindrical main body 1 is dimensioned so that it can be attached to a gauge port (not shown) via an O-ring.

Further, an insulated coaxial vacuum terminal 7 is provided at one end of the cylindrical body 1.
is attached via a flange member 8 made of metal such as stainless steel, and the other end of the cylindrical body 1 is attached to a flange 9 made of stainless steel by argon arc welding to communicate with a vacuum vessel (not shown). There is.

Note that argon arc welding is used as a means for attaching the flange member 8 to the cylindrical body 1.

By the way, one end 5 of the pair of thin wire support members 5 and 6 is erected at right angles to one end 10 a of the metal round bar pin 10 of the coaxial vacuum terminal 7 on the inside of the cylindrical body 1 . The other end 6 of the pair of thin wire support members 5 and 6 is connected to one end 11a of the first metal cylindrical body 11 of the coaxial vacuum terminal 7, which is closer to the inside of the cylindrical body 1. Current can be supplied to the filament 2 from a power source (not shown) via the terminal 7 and the support members 5 and 6.

Note that the current supply to filament 2 is 1V from the power supply.
The filament 2 is heated to a temperature of several tens of degrees.

Here, a filament 2 is attached to one end of the cylindrical body 1.
The insulated coaxial vacuum terminal 7, which serves as a terminal for supplying current, will be explained in detail with reference to FIG. As mentioned above, the support member 5 is erected and supported at the end 10a on the side of the cylindrical body 1, and the end 10b on the atmosphere side has a hole in the center and a spring. It is cut into quarters to give it more power.

Further, on the outer periphery of the pin 10, a first ceramic cylindrical body 12 made of alumina porcelain is hermetically attached to the pin 10 at a first fixing point 13 at one end 12a that should be located on the vacuum side. The pin 10 is firmly fitted, and the other end 12b, which should be located on the atmosphere side, is fitted with an escape groove 12C having a required depth on the inner periphery of the pin 10.

The first ceramic cylindrical body 12 is provided with an escape groove 12d having a required depth on its outer periphery on the atmosphere side, and has a second fixing point deviated in the axial direction from the first fixing point 13. At 14, it is fixedly fitted to the first metal cylindrical body 11 in an airtight manner.

The first metal cylindrical body 11 is also made of a material such as the aforementioned Kovar (trade name), and the support member 6 is attached to the end 11 a on the cylindrical body 1 side as described above. In addition to being connected, two bosses 11C are provided at the end 11b on the atmosphere side so that it can be connected to a BNC plug.

Further, on the outer periphery of the first metal cylindrical body 11, a second ceramic cylindrical body 15 made of alumina porcelain is arranged so that the first metal cylindrical body 11 has a first and second A third fastening point 16, which is axially offset from both fastening points 13, 14, is fitted in an air-tight manner.

Before and after this third fixing point 16, relief grooves 1 are provided on the inner periphery of the second ceramic cylindrical body 15, respectively.
5 a and 15 b are formed.

Further, a second metal cylindrical body 17 made of Kovar (trade name) or the like is fitted onto the outer periphery of the second ceramic cylindrical body 15, and each of the first, second and third fixing points 13 ,14.
At a fourth fastening point 18 axially offset from 16, the two tubular bodies 15,17 are fastened to each other in a gas-tight manner.

Further, the second ceramic cylindrical body 15 has an outer circumferential surface 15C exposed in the cylindrical body 1 adjacent to the fourth fixing point 18.

The outermost second metal cylindrical body 17 has an end that protrudes further toward the atmosphere than the second ceramic cylindrical body 15 and is to be airtightly fixed to the cylindrical body 1 via the flange member 8. It has edges.

Note that the fixation between the metal (Kovar) pin 10 and the first ceramic cylindrical body 12 and the first ceramic cylindrical body 12
and the first metal (Kovar) cylindrical body 11, the first metal (Kovar) cylindrical body 11 and the second ceramic cylindrical body 15, or the second ceramic cylindrical body 15. The body 15 and the second metal (Kovar) cylindrical body 17 are fixed together as follows.

That is, after applying nickel (Ni) plating to the molybutton manganese (MoMn) metallized layer on the ceramic surface, this and Kovar (trade name) are combined with silver solder (an alloy of silver and copper) in a hydrogen reduction furnace. By using and brazing the parts, they are fixed to each other, and as a result, the above-mentioned members can be fixed in an airtight manner.

Further, the second metal (Kovar) cylindrical body 17 and the cylindrical body 8 of the Pirani gauge are fixed to each other without soldering.
This is done by IG welding, which allows the two members to be airtightly fixed.

Furthermore, relief grooves 12C, 12d, 15a, 15
The reasons for providing the fixing portions 13, 14, 16, and 18 with offsets in the axial direction are as follows.

In other words, this is to release distortion due to the difference in thermal expansion coefficient between ceramic and Kovar (trade name) due to repeated cycles of room temperature and high temperature, so as not to impair the high degree of airtightness.

Since the Pirani vacuum gauge with a coaxial vacuum terminal of the present invention is constructed as described above, baking can be performed at a high temperature of 300° C. when the inside of the cylindrical body 1 is evacuated.

This is because a coaxial vacuum terminal using silver-brazed ceramic and Kovar (trade name) is used, and the coaxial vacuum terminal and the Pirani gauge outer cylinder are joined by TIG welding.

Furthermore, it can be used even at extremely low temperatures and does not cause vacuum leakage even when used for long periods of time, making it possible to measure the degree of vacuum with high reliability.

In addition, in this embodiment, since the first metal cylindrical body 11 and the cylindrical body 1 are insulated, the influence of noise on the ground loop current is sufficiently removed, thereby making it possible to measure the degree of vacuum. This has the advantage of significantly improving reliability.

In addition, if the influence of noise due to ground loop current can be ignored, use the coaxial vacuum terminal 7 as shown in Figure 5.
' may be attached to one end of the cylindrical body 1.

This coaxial vacuum terminal 7' is obtained by removing the second ceramic cylindrical body 15 and the second metal cylindrical body 17 from the above-mentioned insulated coaxial vacuum terminal 7, and is shown in FIGS. The same reference numerals indicate similar parts.

Even if the coaxial vacuum terminal 7' is attached to one end of the cylindrical body 1 in this way, baking can be performed at a high temperature and vacuum leakage does not occur even when used for a long time. , it is possible to measure the degree of vacuum with high reliability.

[Brief explanation of drawings]

Figures 1 and 2 are both vertical cross-sectional views showing a conventional Pirani vacuum gauge, and Figures 3 to 5 show a Pirani vacuum gauge with a coaxial vacuum terminal as an embodiment of the present invention.
4 is a longitudinal sectional view showing the coaxial vacuum terminal, and FIG. 5 is a longitudinal sectional view showing a modification of the coaxial vacuum terminal. 1... Tubular body, 2... Filament, 3, 4... Nickel plate, 5, 6...
・Support member, 7...Insulated coaxial vacuum terminal, 7'
...Coaxial vacuum terminal, 8...Flange member, 9...Flange, 10...Metal round bar pin, 10a... End of the pin 10 on the cylindrical body 1 side, 10 b...End of the pin 10 on the atmosphere side, 11... First metal cylindrical body, 11 a
. . . End of the first metal cylindrical body 11 on the cylindrical body 1 side, 11 b . . . End of the first metal cylindrical body 11 on the atmosphere side, 11 C...Boss, 12...
...First ceramic cylindrical body, 12a...
- The end of the first ceramic cylindrical body 12 on the cylindrical main body 1 side, 12b... The other end of the first ceramic cylindrical body 12 on the atmosphere side, 12C... ... Relief groove 12d formed on the inner periphery of the first ceramic cylindrical body 12...
...Escape groove formed on the outer periphery of the first ceramic cylindrical body 12, 13...First fixing point, 14.
...Second fixing point, 15...Second ceramic cylindrical body, 15a, 15b...
Relief groove formed on the inner periphery of the second ceramic cylindrical body 15, 15C... Second ceramic cylindrical body 1
Outer peripheral surface of 5, 16...Third fixing point, 17.
...Second metal cylindrical body, 18...Fourth fixing point.

Claims (1)

[Scope of utility model registration request] The cylindrical body is provided with an ultra-fine wire filament and a pair of thin wire support members that support both ends of the filament, and a metal round bar pin is provided at one end of the cylindrical body, and a metal round bar pin is provided on the outer periphery of the pin. A fitted ceramic cylindrical body,
A coaxial vacuum terminal consisting of a metal cylindrical body fitted on the outer periphery of the ceramic cylindrical body is provided, and the ceramic cylindrical body has a first end portion as one end located within the cylindrical body. is airtightly fixed to the pin at the fixing point, and has an escape groove for the pin at its other end, which should be located on the atmosphere side, and is connected to the metal cylindrical body from the first fixing point. One of the pair of thin wire-shaped support members is attached to one end of the metal round rod-shaped pin to be airtightly fixed at a second fixation point offset in the axial direction, and to supply current to the filament via the support member. A Pirani vacuum gauge with a coaxial vacuum terminal, characterized in that the other of the pair of thin wire support members is connected to one end of the metal cylindrical body.