JPH0321483Y2 - - 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 present invention relates to a galvanic cell type oxygen sensor comprising a positive electrode made of a catalytic electrode effective for electrolytic reduction of oxygen, a negative electrode made of lead, an electrolytic solution, a diaphragm, and a container.

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 ship holds 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 for detection.

BACKGROUND OF THE INVENTION A galvanic cell type oxygen sensor is usually composed of a positive electrode made of a catalytic electrode, a negative electrode made of lead, an electrolyte, a diaphragm, and a container.

Conventionally, the sensor container is usually filled with electrolyte, but in this case, if the temperature of the atmospheric gas in which the oxygen sensor is placed is high and the relative humidity is low, the electrolyte Water evaporates through the diaphragm and the sensor internal pressure decreases. Conversely, when the temperature of the atmospheric gas is low and the relative humidity is high, moisture in the atmospheric gas is absorbed by the electrolyte, increasing the sensor internal pressure.

In order to suppress such fluctuations in the internal pressure of the sensor, the inventors of the present application have already proposed a method in which a sensor container is not filled with electrolyte, but instead leaves some space.

Problems that the invention aims to solve: If some space is left inside the container, there will be problems such as movement of the zero point due to dissolved oxygen and fluctuations in the sensor output that occur when vibration is applied to the sensor. .

Means for Solving the Problems The present invention attempts to solve the above-mentioned problems by insulatingly covering the portion of the positive electrode current collector located inside the container with synthetic resin or natural resin. It is something.

Effect If some space is left in the sensor container, oxygen in the air in the space will dissolve. The amount of dissolved oxygen also changes when vibration is applied to the sensor. However, in the past, the positive electrode current collector made of metal was in direct contact with the electrolyte and the air in the space inside the sensor container, but in many cases, this positive electrode current collector caused electrolytic reduction of oxygen, albeit to a small extent. Since it has catalytic ability, dissolved oxygen near this positive electrode current collector affects the sensor output. For example, if the oxygen concentration of the atmospheric gas in which the oxygen sensor is placed is 0%, the sensor output should be 0V, but in reality, due to the above-mentioned reaction of dissolved oxygen on the positive electrode current collector, several mV output comes out and the zero point moves. Furthermore, if the amount of dissolved oxygen changes when vibration is applied, the sensor output will also change.
On the other hand, when the positive electrode current collector is insulated, direct contact between the positive electrode current collector and the electrolyte is avoided, so the electrolytic reduction reaction of oxygen on the positive electrode current collector also does not occur, and the sensor output The effect of dissolved oxygen on

As the insulating coating material, it is effective to apply a synthetic resin or natural resin, or to wrap a tube of synthetic resin around it.

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, there is a presser plate 3, O
a ring 4, a diaphragm 5 made of a film of tetrafluoroethylene-hexafluoropropylene copolymer, a positive electrode 6 made of gold, an intermediate current collector 7 made of carbon paper,
A positive electrode current collector 8 made of a titanium wire is housed and screwed together. A positive electrode 6 is vacuum deposited on the diaphragm 5 . The container 1 contains an electrolytic solution 9 made of a mixed aqueous solution of acetic acid, potassium acetate, and lead acetate, and a negative electrode 10 made of lead. Furthermore, a space 11 is provided within the container. The positive electrode current collector 8 is covered with a heat-shrinkable insulating tube 12 made of polyvinyl chloride.

A thermistor 13 and a resistor 14 for temperature compensation are connected between the positive electrode and the negative electrode.

Effect of the invention The galvanic cell type oxygen sensor obtained in the example is referred to as A, and in the example, the heat-shrinkable tube 1
The conventional sensor without coating 2 is designated as B,
When the oxygen concentration-output characteristics of each were compared, the results were as shown in FIG. In other words, while the zero point has moved in the case of conventional product B,
In the case of product A of the present invention, it passes through the zero point. On the other hand, when the oxygen sensor was kept stationary and the output over time was compared when the oxygen sensor was struck at some point, the results shown in FIG. 3 were obtained. That is, it can be seen that in the case of the conventional product B, the output fluctuates, whereas in the case of the product A of the present invention, the output does not fluctuate at all.

[Brief explanation of the drawing]

Fig. 1 shows the cross-sectional structure of a galvanic cell type oxygen sensor according to an embodiment of the present invention, and Fig. 2 shows the oxygen concentration-output characteristics of the galvanic cell type oxygen sensor A of the present invention compared to that of the conventional product B. FIG. 3 is a diagram showing the change over time of the galvanic cell type oxygen sensor A of the present invention in comparison with that of the conventional product B. 1... Container body, 2... Container lid, 5... Diaphragm,
6... Positive electrode, 8... Positive electrode current collector, 9... Electrolyte,
10...Negative electrode, 11...Space, 12...Heat-shrinkable insulating tube.

Claims (1)

[Scope of utility model registration request] In a galvanic cell type oxygen sensor, which is composed of a positive electrode consisting of a catalytic electrode for electrolytic reduction of oxygen, a negative electrode consisting of lead, an electrolytic solution, a diaphragm, and a container, and which has a partial space inside the container, the container of the positive electrode current collector A galvanic cell type oxygen sensor characterized by having an insulating coating on the inner part with synthetic resin or natural resin.