JPH0524050Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an improvement in an oxygen electrode for measuring oxygen concentration in, for example, a liquid or a gas.

[Conventional technology]

FIG. 3 shows a conventional oxygen electrode. In the same figure, 1 is a body made of, for example, synthetic resin, and a flange portion 2 is formed approximately in the middle of the body, and one side (lower side) of this flange portion 2 is formed. A cylindrical body 4 having a male threaded portion 3 on its outer periphery is connected to the cylindrical body 4 .

Reference numeral 5 denotes a bottomed cylindrical housing made of, for example, synthetic resin, which is open at the top, and a female threaded portion 6 that is screwed into the male threaded portion 3 is provided on the inner periphery of the opening. The lower bottom portion of the housing 5 is formed into a circular arc shape with a convex outer surface as a diaphragm holding portion 7, and a hole 8 is provided approximately in the center thereof.
Further, a groove 10 for a seal member is provided around the side wall portion 9 of the housing 5.

Reference numeral 11 denotes an oxygen permeable diaphragm provided so as to be in contact with the outer surface of the diaphragm holding portion 7, and is made of, for example, tetrafluoroethylene resin with a thickness of 25 μm. The end portion of the diaphragm 11 is fixed and held by a cylindrical body 12 made of, for example, synthetic resin and fitted onto the housing 5. 13 is a sealing member such as an O-ring.

14 is a cathode made of Ag, for example, and this cathode 1
4 is fixed so that its upper end 14A penetrates the flange portion 2 and bites into the body 1, and
The end surface 14b of the lower end portion 14B is inserted through a hole 8 provided in the diaphragm holding portion 7 and is provided in close contact with the inner surface of the diaphragm 11.

Reference numeral 15 denotes an insulating layer made of, for example, synthetic resin, and is provided to cover the periphery of the cathode 14 except for the lower end surface 14b.

Reference numeral 16 denotes a cylindrical anode made of, for example, Pb, which is provided around the cathode 14 with an insulating layer 15 in between, and its upper end 16A is connected to the flange portion 2 like the cathode 14.
It is fixedly installed so that it penetrates and bites into the body 1.

Reference numeral 17 denotes an internal liquid sealed within the housing 5 so as to be in contact with the diaphragm 11 and the anode 16, for example.
It is a KOH solution.

18 is a connector screwed onto the upper side of the body 1, and 19 and 20 are plugs serving as signal extraction sections connected to the cathode 14 and anode 16 via lead wires 21 and 22, respectively. Note that 23 is an electrically insulating adhesive that fixes the lead wires 21 and 22.

In addition, in order to seal the internal liquid 17 in the housing 5, there are two methods: filling the internal liquid 17 into the housing 5 and immediately tensioning the diaphragm 11; There were cases where the diaphragm 11 was stretched after the treatment.

[Problem that the invention attempts to solve]

However, when measuring the oxygen concentration in a liquid or gas using an oxygen electrode with the above configuration,
Test liquid (or test gas, hereinafter referred to as test liquid, etc.)
When the temperature rose to exceed 35°C, an output proportional to the oxygen concentration could not be obtained, as shown by the imaginary line A in FIG.

As a result of detailed investigation by the inventors of the present application, it was found that in the case where the internal liquid 17 was filled as described above,
It was found that about 30% of the products were defective because the oxygen concentration and output were not proportional, and that more than 90% of the products filled with the internal liquid 17 as described above were defective.

This is because the internal liquid 17 inside the housing 5 expands in volume as the temperature of the test liquid rises, and as shown in FIG.
This is considered to be because the particles enter between the diaphragm 11 and the cathode 14, making the degree of close contact between the diaphragm 11 and the cathode 14 unstable.

As mentioned above, there is a method shown in Japanese Utility Model Publication No. 13432/1983 that solves the problems caused by the volumetric expansion of the internal liquid due to heat, but the structure for absorbing the physical expansion of the internal liquid is complicated. It has the disadvantage of being.

The present invention was developed with the above-mentioned considerations in mind, and its purpose is to absorb the volumetric expansion of the internal liquid by extremely simple means and to stably maintain the adhesion between the diaphragm and the cathode. The purpose of the present invention is to provide an oxygen electrode with a high temperature.

[Means for solving problems]

In order to achieve the above-mentioned object, the oxygen electrode according to the present invention has a through hole in the diaphragm holder remote from the cathode between the position where the cathode of the diaphragm holder contacts the diaphragm and the side end of the diaphragm holder. It is formed.

[Effect]

According to the above configuration, even if the internal liquid expands in volume due to heat, the volume increase due to this volume expansion is
Since the diaphragm is pressed through the through hole provided in the diaphragm holder that is apart from the cathode between the position where the cathode contacts the diaphragm and the side end of the diaphragm holder, the cathode of the diaphragm holder comes into contact with the diaphragm. The effect of volume expansion of the internal liquid at the contact position is alleviated.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 shows an example of an oxygen electrode according to the present invention,
In the same figure, the same reference numerals as those in FIG. 3 indicate the same or equivalent parts.

The oxygen electrode shown in FIG. 1 is significantly different from the one shown in FIG. For example, a diameter of 1.5 mm is placed at a position as far away as possible (in the illustrated example, approximately midway between the side end 7A of the diaphragm holding part 7 and the contact position P).
This is because the through hole 30 is provided.

When filling the internal liquid 17 into the housing 5, the housing 5 is turned upside down from the one shown in FIG. , e.g. 50 μl
After removing some of the internal liquid 17, the diaphragm 11 is immediately stretched along the diaphragm holding part 7.

By doing this, as a result, about 50 μl of gas was mixed into the housing 5, but the amount of this gas mixed in (i.e., the amount of internal liquid 17 extracted) depends on the material of the housing 5, the diaphragm Needless to say, it may be set as appropriate depending on the type of 11 and the fixing method.

In the oxygen electrode configured as described above, even if the internal liquid 17 is warmed by the temperature of the test liquid and causes volumetric expansion, the through hole 30 is provided at a position quite far from the contact position P. Therefore, as shown in FIG. 2, a part of the internal liquid 17 that has expanded in volume is
Pressing the inner surface of the diaphragm 11 through this through hole 30,
Therefore, the diaphragm 11 and the cathode 14 at the contact position P
The adhesion between the two is maintained well.

As a result, as shown by the solid line B in FIG. 5, an output proportional to the oxygen concentration can be obtained even when the test liquid etc. is in a state of 35° C. or higher. According to experiments conducted by the inventors, good results were obtained even when the test liquid etc. was at a temperature of 45°C or higher.

The present invention is not limited to the above-described embodiments, and the position of the through hole 30 formed in the diaphragm holding part 7 may, in principle, be located away from the abutment position P, but preferably , a position approximately midway between the side end portion 7A of the diaphragm holding portion 7 and the contact position P is optimal.

Also, a diaphragm 11, a cathode 14, an anode 16, an internal liquid 1
7 etc. may be composed of other materials than those mentioned above.

[Effect of idea]

As explained above, according to the present invention, a very simple means is employed in which a through hole is formed in the diaphragm holder remote from the cathode between the position where the cathode contacts the diaphragm and the side end of the diaphragm holder. This makes it possible to effectively absorb the volume expansion of the internal liquid and maintain stable adhesion between the diaphragm and the cathode.
An oxygen electrode that can accurately measure oxygen without being affected by the temperature of the test liquid, etc. has been obtained.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view of an oxygen electrode according to the present invention;
FIG. 2 is a sectional view taken along the line X--X in FIG. 1, and FIG. 3 is a partial sectional view showing the essential parts of the enzyme electrode. FIGS. 4 and 5 are partial sectional views for explaining the prior art. FIG. 6 is a characteristic diagram showing the correlation between temperature and output. 7... Diaphragm holding part, 8... Hole, 11... Diaphragm,
14... cathode, 15... insulating layer, 16... anode,
17... Internal liquid, 30... Through hole, P... Contact position between diaphragm and cathode.

Claims (1)

[Scope of utility model registration request] an oxygen-permeable diaphragm provided so as to be in contact with the outer surface of the diaphragm holding part of the housing; and an oxygen permeable diaphragm provided in the housing so as to be inserted into a hole formed in the diaphragm holding part so that its tip is in close contact with the diaphragm. In an oxygen electrode comprising a cathode, an anode disposed around the cathode via an insulating layer, and an internal liquid sealed in the housing, the position where the cathode contacts the diaphragm and the diaphragm 1. An oxygen electrode characterized in that a through hole is formed in a diaphragm holding part separated from a cathode between the holding part and a side end part of the holding part.