JPH0342366Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a galvanic cell type oxygen sensor. More specifically, the galvanic cell type consists of a positive electrode made of a catalytic electrode effective for electrolytic reduction of oxygen, a diaphragm made of a polymer membrane integrally joined to the positive electrode, a negative electrode made of lead, an electrolytic solution, and a container. It concerns oxygen sensors.

Galvanic cell-type oxygen sensors are small, lightweight, operate at room temperature, and are inexpensive, so they can be used to check oxygen deficiency conditions in ships and manholes, and to check oxygen concentration in medical equipment such as anesthesia machines and artificial respirators. It is used in a wide range of fields such as monitoring.

BACKGROUND OF THE INVENTION A galvanic cell type oxygen sensor typically comprises a positive electrode consisting of a catalytic electrode effective in the electrolytic reduction of oxygen, a negative electrode consisting of lead, an electrolyte, a diaphragm, and a container.

Conventionally, the diaphragm and the positive electrode are of a type in which they are simply in contact (for example, Japanese Patent Application Laid-open No. 187846/1982), and in others they are integrally joined (for example, British Patent No. 1200595). The present invention relates to the latter type.

In order to fix the diaphragm-positive electrode integral assembly to the sensor container, conventionally, between the container body and the container lid,
A method is adopted in which a diaphragm-positive electrode integral assembly, an O-ring, and a presser plate are provided, and the container body and container lid are screwed together. At that time, the O-ring is fitted into a groove provided in the holding plate, and the O-ring is only in contact with the holding plate and the diaphragm surface of the diaphragm-positive electrode integral assembly.

Problems to be solved by the invention When the method of fixing the diaphragm-positive electrode assembly as described above is adopted, the gap between the threaded part of the container body and the container lid, the gap between the container lid and the presser plate, and the gap between the container body and the presser plate is Oxygen passes through the gap with the plate and directly reaches the positive electrode without passing through the diaphragm, and further dissolves into the electrolyte that is in contact with the positive electrode.

Although the galvanic cell type oxygen sensor is originally designed so that only the oxygen that has passed through the perforations and diaphragm provided in the holding plate and reached the positive electrode participates in the sensor reaction, the above phenomenon occurs. When this occurs, the oxygen dissolved in the electrolyte also participates in electrolytic reduction at the positive electrode, causing the sensor output to become unstable and the zero point to shift (even though the oxygen concentration in the detected gas is 0%). The output voltage is
(The voltage does not go to 0V).

Means for Solving the Problems The present invention prevents oxygen from directly reaching the positive electrode by bringing the O-ring into close contact not only with the diaphragm and the holding plate but also with the inner wall of the container body. This is an attempt to solve such problems.

Effect If the structure described above is adopted, even if oxygen enters the threaded part of the container body and the container lid, or the gap between the container lid and the holding plate, it will be blocked by the O-ring and will not reach the positive electrode. As a result, since no oxygen is dissolved in the electrolyte, problems such as instability of the sensor output or shift of the zero point due to dissolved oxygen are eliminated.

Embodiment FIG. 1 shows a cross-sectional structure of a galvanic cell type oxygen sensor according to an embodiment of the present invention.

Between the container body 1 and the container lid 2, a presser plate 3 with perforations, O-rings 4, 4', and tetrafluoroethylene
A diaphragm 5 made of a film of propylene hexafluoride copolymer, a positive electrode 6 made of gold, a carbon paper 7 having functions as an electrolyte holder and a current collector, and a positive electrode current collector 8 made of a titanium wire. installed and screwed down. A positive electrode 6 is integrally joined to the diaphragm 5 by sputtering.

Inside the container body 1, there is an electrolytic solution 9 consisting of a mixed aqueous solution of propionic acid, potassium propionate, and lead oxide;
A negative electrode 10 made of lead is housed therein. A thermistor 11 and a resistor 12 are connected between the positive electrode and the negative electrode. The voltage between the positive and negative electrodes is the output of this galvanic cell type oxygen sensor, which has linearity with the oxygen concentration. The structure of this galvanic cell type oxygen sensor is characterized by O-rings 4 and 4'.
This is because they are in close contact with the inner wall of the container body 1, the perforated holding plate 3, and the diaphragm 5, respectively.

Effects of the invention The galvanic cell type oxygen sensor obtained in the example is designated as A, the O-ring is fitted into the groove of the perforated holding plate provided with a groove, and the conventional sensor that is not in close contact with the container body is designated as B, respectively. When the output voltage was measured in the air with a digital voltmeter, in the case of A, it showed a stable value of 37 mV, whereas in the case of B, it fluctuated in the range of 35 to 40 mV and was extremely unstable. It was hot. This is because A is not affected by dissolved oxygen, whereas B
In this case, this is because oxygen is dissolved in the electrolyte.

[Brief explanation of the drawing]

FIG. 1 shows a cross-sectional structure of a galvanic cell type oxygen sensor according to an embodiment of the present invention. 1...Container body, 2...Container lid, 3...Press plate, 4, 4'...O-ring, 5...Diaphragm, 6...
...Positive electrode, 9... Electrolyte, 10... Negative electrode.

Claims (1)

[Claims for Utility Model Registration] A utility model consisting of a positive electrode made of a catalytic electrode effective for electrolytic reduction of oxygen, a diaphragm made of a polymer membrane integrally joined to the positive electrode, a negative electrode made of lead, an electrolytic solution, and a container. , a galvanic cell type oxygen sensor with a structure in which the diaphragm-positive electrode integral assembly is fixed to the container body with an O-ring using a holding plate, the holding plate is provided with a protrusion that is the same as or slightly larger than the inner diameter of the O-ring. A galvanic cell type oxygen sensor characterized in that the deformation of the ring is directed outward, and the outer periphery of the O-ring is in close contact with the inner wall of the container body.