JPS5938533B2 - Vacuum reference pressure chamber sealing structure of absolute pressure detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sealing structure for vacuum-sealing a vacuum reference pressure chamber provided in an absolute pressure detector that detects absolute pressure based on vacuum.

In absolute pressure detectors, a vacuum reference pressure chamber is provided,
Absolute pressure is detected by detecting the pressure difference between the vacuum in this vacuum reference pressure chamber and the pressure to be measured.

Unless a degree of vacuum of about 10'' Torr is ensured in the vacuum reference pressure chamber, the reference value will change due to changes in ambient temperature, making it impossible to perform highly accurate measurements.

In the past, the vacuum reference pressure chamber of an absolute pressure detector was vacuum sealed in the following manner.

A small hole is made in the cover that makes up the vacuum reference pressure chamber, the absolute pressure detector is placed in the vacuum container, the vacuum container is evacuated, the reference pressure chamber is evacuated, and then the hole in the cover is evacuated. It was closed by welding and crushing it.

That is, as shown in FIG. 1, an absolute pressure detector 12 is disposed within a vacuum container 11, and the absolute pressure detector 12 has a cylindrical body 13, for example, whose both ends are closed with diaphragms 14 and 15, and which faces the diaphragm 14. A cover 16 is attached to the body 13 at its peripheral edge on the outside thereof, and a vacuum reference pressure chamber 17 is formed between the cover 16 and the diaphragm 14.

A flange 18 is connected to the body 13 on the outside of the diaphragm 15.
A hole 19 for introducing pressure is formed in the center of the flange 18, and the pressure to be measured is applied to the diaphragm 15 through this hole 19.

Although not shown in the figure, between the diaphragm 14 and the diaphragm 15 of the vacuum reference pressure chamber 17, there is a detection section inside the body 13 that converts the displacement corresponding to the difference between the vacuum and the measured pressure into a signal and extracts it. It is provided.

A small hole 21 for evacuation is opened in the cover 16, and the vacuum chamber 11 is evacuated and the inside of the vacuum reference pressure chamber 17 is also opened using the small hole 21.
Similarly, a vacuum is drawn through the

After completing the evacuation, the small evacuation hole 21 was welded inside the vacuum container 11 and the hole 21 was crushed.

In order to make the vacuum reference pressure chamber 17 a vacuum of about 1O-3 Torr, the small hole 21 for evacuation must be made quite large so that the air inside the vacuum reference pressure chamber 17 can be easily exhausted. The degree of vacuum in the vacuum container 11 cannot be made comparable.

However, as described above, the small vacuum holes 21 are made by melting the peripheral edges by welding and collapsing the small holes 21 so that they are connected to each other, so there is a limit to how large the holes 21 can be made to be.

Since this welding is performed by electron beam welding inside the vacuum vessel 11, for example, a plate that can be used to close the hole is brought in,
In practice, it was difficult to weld the periphery of the hole to close the hole.

From this point of view, conventionally it has been difficult to create a vacuum reference pressure chamber having a degree of vacuum comparable to the degree of vacuum within the vacuum container 11 in a short period of time.

The purpose of this invention is to construct a large exhaust hole that can make the vacuum reference pressure chamber of an absolute pressure detector to the same degree of vacuum as the vacuum inside the vacuum container in a short time. It is an object of the present invention to provide a vacuum reference pressure chamber sealing structure capable of sealing an exhaust hole within a vacuum container.

According to the present invention, a cut and raised piece is formed on the cover constituting the vacuum reference pressure chamber of the pressure detector, and an exhaust hole is formed in the cover based on the cut and raised piece.

In this way, the exhaust hole can be made relatively large, and even if the height of the cut and raised piece is not made very high, the hole is considerably larger than the conventional exhaust hole. It is possible to do so.

Therefore, when a pressure detector is placed in a vacuum container, the degree of vacuum in the vacuum reference pressure chamber can be matched with the degree of vacuum in the vacuum container in a short time.

Moreover, after creating a vacuum, the vacuum reference pressure chamber is sealed by welding the peripheral edge of the cut and raised piece to the peripheral edge of the exhaust hole formed in the cut and raised piece.

For example, FIG. 2 shows a sealing structure for a vacuum reference pressure chamber according to the present invention, with the same reference numerals attached to parts corresponding to those in FIG.
In this invention, a part of the cover 16 has a cut-and-raised piece 22, for example, in the center.

The cut-and-raised piece 22 is, for example, circular, and a portion thereof is connected to the cover 16 by a connecting portion 23, as shown in enlarged form in FIGS. 3 and 4.

That is, the cut-and-raised piece 22 is cut and raised, leaving the connecting portion 23.

By forming this cut and raised piece 22, the exhaust hole 2 is formed in the cover 16.
4 is formed.

In this case, the cut and raised piece 22 may not be cut and raised so much, that is, the angle of inclination with respect to the surface of the cover 12 may be made small.

In this way, the exhaust hole 24 can be made relatively large.

If the pressure detector configured as described above is evacuated in the vacuum container 11 as shown in FIG. The degree of vacuum inside becomes the same in a short time.

After the evacuation is completed, the edges of the cut and raised piece 22 and the exhaust hole 24 are welded to each other within the vacuum vessel 11 using an electron beam.

In this case, the cut and raised pieces 22 are laid down so as to substantially coincide with the plate surface of the cover 16, and their peripheral edges are connected to each other by welding 25 as shown in FIGS. 5 and 6.

In this way, this welding can be easily performed without requiring any special jig.

As described above, according to the vacuum side stop structure according to the present invention, the exhaust flow cross-sectional area of the exhaust hole can be made sufficiently large when the vacuum reference pressure chamber is evacuated, and therefore the degree of vacuum in the vacuum reference pressure chamber can be increased. The degree of vacuum in the vacuum container can be reached in a short time, and the work to achieve that vacuum can be done in a short time.

Moreover, even if the exhaust hole is relatively large, it can be easily welded by electron beam welding.

In other words, instead of bringing another small piece to cover the exhaust hole and welding it, since the cut and raised piece 22 is attached to the cover 16, the cut and raised piece 22 can be slightly removed as needed. Welding can be easily performed by pressing it to make it flush with the cover 16 and then welding it.

Note that the shape of the cut and raised piece 22 does not necessarily have to be circular and can be any shape.

[Brief explanation of drawings]

Fig. 1 is a sectional view for explaining the work to evacuate the vacuum reference pressure chamber of a conventional absolute pressure detector, and Fig. 2 is an absolute pressure sensor with a sealing structure for the vacuum reference pressure chamber according to the present invention. 3 is a sectional view showing an example of the detector, FIG. 3 is a sectional view of the exhaust hole before sealing, FIG. 4 is a plan view thereof, FIG. 5 is a sectional view showing the exhaust hole in a sealed state, and FIG. The figure is a plan view thereof. 12...Absolute pressure detector, 13...Body, 14.15...Diaphragm, 16...
...Cover, 17...Vacuum reference pressure chamber, 2
2... Cut and raised piece, 24... Exhaust hole, 2
3...Connecting part, 25...Welding part.

Claims (1)

[Claims] 1 The periphery of the cut-and-raised piece formed on the cover constituting the vacuum reference pressure chamber of the absolute pressure detector and the periphery of the hole created by the formation of the raised piece are welded to A sealed structure of an absolute pressure detector in which the reference pressure chamber is sealed.