JPH0321484Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a galvanic cell type oxygen sensor.

Conventional technology A galvanic cell type oxygen sensor generally consists of a positive electrode consisting of a catalytic electrode that controls the electrolytic reduction reaction of oxygen, a negative electrode consisting of a lead electrode, and an aqueous solution of alkali hydroxide or a mixed aqueous solution of an organic acid and an organic acid salt. It consists of an electrolytic solution, a fluororesin diaphragm for suppressing oxygen diffusion and preventing leakage of the electrolytic solution, and a plastic tank for housing these sensor components.

The problem that the invention aims to solve Plastic tanks vary depending on their material and wall thickness, but because they are more or less permeable to water vapor, water in the electrolyte may evaporate or vice versa. When the electrolyte absorbs moisture from the atmospheric gas, the internal pressure of the sensor decreases or increases. In particular, when the amount of electrolyte decreases, the contact between the electrode and the electrolyte is cut off, which causes the sensor's lifespan to end quickly.

Means to Solve the Problems The present invention adheres a laminated film of aluminum foil and plastic film to the surface of a plastic tank, and then covers it with a heat-shrinkable plastic sheet. This prevents the permeation of water vapor and solves the above-mentioned problems.

Function When ABS resin is used as the material for the plastic tank of a galvanic cell type oxygen sensor, the water permeability coefficient at 60°C is approximately 2 x 10 ^-2 g.
mm/cm ²・day・atm. On the other hand, the water permeability coefficient of a laminated film of aluminum foil and plastic film is almost zero. The adhesion of this laminated film to the plastic bath therefore almost completely prevents evaporation and absorption of water vapor.

On the other hand, the lifespan of a conventional galvanic cell oxygen sensor that uses an aqueous alkali hydroxide solution as an electrolyte is approximately 1.
It was a year ago. Therefore, when intended for use for such a relatively short period of time, the purpose of sufficiently preventing water from entering and exiting has been achieved simply by adhering the laminated film as described above. However, by using an aqueous mixed solution of an organic acid and an organic acid salt with a pH in the range of 4 to 7 as the electrolyte, the present inventors have found that the lifespan of the galvanic cell type oxygen sensor can be extended to 10 years or more. (Japanese Patent Application Laid-open No. 187846/1983). If a galvanic oxygen sensor is used for such a long period of time,
Alternatively, when used at relatively high temperatures, the life of the adhesive of the laminated film of aluminum foil and plastic film described above is insufficient, and as a result, the laminated film may peel off from the plastic tank during long-term use. It was hot. On the contrary,
By gluing this laminated film and covering it with a heat-shrinkable plastic sheet and binding it, the problem is solved because even if the adhesive loses its adhesive ability, this binding sheet will hold the laminated film. .

Example Examples of the present invention will be described in detail below.

The figure shows a cross-sectional structure of a galvanic cell type oxygen sensor according to an embodiment of the present invention. In a tank 1 made of ABS resin, a diaphragm 2 made of tetrafluoroethylene-hexafluoropropylene copolymer, a positive electrode 3 made of gold integrally joined to this diaphragm 2, carbon paper 4 as a current collector, Also housed are a titanium wire 5 as a current collector, a negative electrode 6 made of lead, and an electrolyte 7 made of a mixed aqueous solution of acetic acid, potassium acetate, and lead acetate. It is contacted via a thermistor 9. Laminated films 10, 10' of aluminum foil and polypropylene film are adhered to the surface of the tank 1, and heat-shrinkable binding sheets 11, 11' made of polyvinyl chloride are further covered thereon.

This galvanic oxygen sensor has a temperature of 60
When tested in a harsh atmosphere at ℃ and relative humidity of 10%, the water content in the electrolyte decreased by only 7% after 150 days, and no abnormalities were observed in the output characteristics of the oxygen sensor.

For comparison, a conventional galvanic cell type oxygen sensor having a structure in which the laminated films 10, 10' and heat-shrinkable binding sheets 11, 11' in the above-mentioned embodiment of the present invention were removed was subjected to similar conditions. When tested, the water content in the electrolyte decreased by 65% after 150 days, and the sensor output also decreased significantly, reaching the end of its life.

Effects of the invention As described above, according to the invention, in a galvanic cell type oxygen sensor using a plastic tank, it is possible to prevent the electrolyte from decreasing over a long period of time and maintain good oxygen sensor output characteristics. It can provide excellent advantages such as:

[Brief explanation of drawings]

The figure is a cross-sectional structural diagram of a galvanic cell type oxygen sensor according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Tank, 2... Diaphragm, 3... Positive electrode, 6... Negative electrode, 7... Electrolyte, 10, 10'... Laminated film, 11, 11' Heat-shrinkable binding sheet.

Claims (1)

[Scope of utility model registration request] A galvanic cell type oxygen sensor using a plastic tank, characterized in that a laminated film of aluminum foil and plastic film is adhered to the surface of the plastic tank, and further covered with a heat-shrinkable plastic sheet. Battery operated oxygen sensor.