JP5988485B2 - Electrochemical gas sensor - Google Patents

Description

  The present invention relates to an air vent structure of an electrochemical sensor in which a working electrode is in contact with an electrolyte solution on a gas permeable membrane to detect gas.

  Since the electrochemical gas sensor employs a structure in which an electrolytic solution is sealed in a container, there is a problem that the internal pressure of the container fluctuates due to a change in temperature or the like.

In order to solve such a problem, as shown in Patent Document 1, the electrolyte and the electrode constituting the sensor are connected by a hydrophobic porous material, and the fluid pressure in the sensor is passed through the hydrophobic porous material. It has also been proposed to escape from the electrode.
However, there is a problem that the electrode functions only in a posture positioned on the upper side of the sensor.

Canadian Patent No. 2255472

  The present invention has been made in view of such problems, and an object of the present invention is to provide an electrochemical gas sensor capable of maintaining the pressure of the cell container at atmospheric pressure regardless of the attitude of the cell container.

In order to achieve such a problem, the present invention provides an electrochemical gas sensor in which a working electrode is disposed in a liquid-tight manner in a window communicating with the outside air of a cell container that contains an electrolytic solution. An electrode layer made of an electrode forming material is formed so as to leave a peripheral portion on the porous membrane, and a region in contact with the peripheral region where the electrode layer of the hydrophobic porous membrane of the working electrode does not exist and a belt-shaped region crossing the electrolyte solution And an air bleeding piece made of a hydrophobic porous material having a wide portion facing the substantially entire surface of the bottom portion of the cell container.

  Since the air vent piece connected to the opposite surfaces of the container by the belt-like region is located in the region located almost at the periphery, the space in the cell container is connected to the outside air through the air vent piece, Regardless of the posture, the pressure in the cell container can be maintained at atmospheric pressure.

It is sectional drawing which shows one Example of the electrochemical gas sensor of this invention. It is a front view which shows one Example of an air bleeding piece, and a perspective view which shows the form at the time of use. Drawing (a)-(c) is a figure showing one example of an air bleeding piece, and a figure which looked at one example of a working electrode from the electrode layer side, respectively. It is a figure which shows the other Example of the air bleeding piece suitable for this invention.

Therefore, details of the present invention will be described below based on the illustrated embodiment.
One embodiment of the present invention is shown by taking a constant potential electrolytic gas detector as an example, and a cell container 1 has a protrusion 1b that engages with a positioning hole 2a of an air bleeding piece 2 to be described later on a bottom 1a. A space 4 for storing the electrolyte solution by the legs 3a, a surface 3b for accommodating the counter electrode 5 and the reference electrode 6 on the upper surface, and the electrolyte solution in the space 4 for storing the electrolyte solution in the water-containing paper 7 An electrode receiving member 3 having a through-hole 3c for replenishing it is accommodated.

  On the upper surface of the counter electrode 5 and the reference electrode 6, a water-containing paper 7 that absorbs and holds the electrolyte solution, a ring-shaped portion 2 b of the air bleeding piece 2 via an O-ring 8, and a working electrode 9 are laminated and disposed. An upper lid 11 is fitted through the adhesive plate 10.

The upper lid 11 is provided with an air intake port 11a, and a filter material 12 is disposed here.
In the figure, reference numeral 13 denotes a lead assembly that conducts to the counter electrode 5 and the reference electrode 6, and is arranged and fixed to the bottom 1 a of the cell container 1 via an adhesive 14.

  As is well known, the working electrode 9 is an electrode suitable for oxidizing and reducing the test gas so as to leave the peripheral edge 92 on the electrolyte side of the hydrophobic porous membrane 91 as shown in FIG. Forming material, for example, a mixture of fine metal powder such as platinum oxide (PtO) or ruthelium oxide (RuO2) and fluororesin powder is applied, sintered, or electrode layer 93 is formed by reactive sputtering or the like. Configured.

  FIG. 3A shows an embodiment of the air bleeding piece 2, and an annular portion 2 b having a size in contact with the peripheral edge portion 92 where the electrode layer 93 of the working electrode 9 is not formed, and a continuous belt-like shape. The region 2c and a wide region 2d covering the largest possible area, preferably the entire surface, of the bottom 1a of the cell container 1 are configured.

  Then, as shown in FIG. 2 (b), the positioning hole 2a of the wide region 2d is bent at the boundary between the annular region 2b and the wide region 2d so that the wide region 2d faces each other, and the protrusion of the bottom portion 1a of the cell container 1 is formed. The annular portion 2b is set so as to face the peripheral portion 92 where the electrode layer 93 of the working electrode 9 is not formed.

Thereby, the annular part 2b and the wide area | region 2d located in the top and bottom of the cell container 1 are connected via the strip | belt-shaped area | region 2c in electrolyte solution.
Further, by forming the air bleed piece 2 on the side of the opening 1b of the cell container 1 as an annular part 2b, the peripheral part 92 of the working electrode 9 is uniformly pressed by the upper lid 11 and the O-ring 8 of the cell container 1 to perform electrolysis Liquid leakage can be reliably prevented.

  In this embodiment, when the test gas reaches the working electrode 9, a current flows between the counter electrode 5 according to the gas concentration through the electrolytic solution of the water-containing paper 7 and is detected as a concentration signal.

  On the other hand, when the internal pressure of the cell container 1 rises due to a change in the outside air temperature, the air in the cell container 1 moves to the ring-shaped part 2b through the pores of the hydrophobic porous membrane constituting the air vent piece 2, and It moves to the region where the electrode layer 93 of the hydrophobic porous membrane 91 of the working electrode 7 in pressure contact is not formed, that is, the peripheral edge portion 92, and comes out of the cell container 1.

On the contrary, when the internal pressure of the cell container 1 decreases, the air in the peripheral portion 92 where the electrode layer 93 of the hydrophobic porous membrane 91 is not formed moves to the ring-shaped portion 2 b of the air bleeding piece 2 and enters the cell container 1. .
By such an action, the air in the cell container 1 and the outside air move to each other, and the pressure inside and outside the cell container 1 becomes equal.

  Needless to say, since the annular portion 2b and the wide region 2d of the air bleeding piece 2 are positioned on the top and the peripheral edge of the top of the cell container 1, either portion is in contact with the air in the cell container 1. . Therefore, even if the bottom portion 1a of the cell container 1 is the upper portion, the wide region 2d comes into contact with air, moves to the working electrode side through the strip-shaped portion 2c, and comes out from the peripheral portion 92 of the working electrode 9 to the outside. Thereby, the pressure of the cell container 1 is adjusted uniformly with the outside air regardless of the posture.

  In the above-described embodiment, the air bleeding piece 2 is configured separately from the working electrode 9, but as shown in FIG. The hydrophobic porous material is cut out so as to form a wide portion 2d 'having a width opposite to the bottom of the cell container at the other end, and the peripheral portion 92' is left in the circular portion. It is clear that the same effect can be obtained even if the electrode layer 93 'is formed on

DESCRIPTION OF SYMBOLS 1 Cell container 2 Air bleeding piece 8 Packing 6 Holding lid 7 Water-containing paper 9 Working electrode 91 Hydrophobic porous material 92 Peripheral part 93 Electrode layer

Claims (2)

  In an electrochemical gas sensor in which a working electrode is disposed in a liquid-tight manner in a window communicating with the outside air of a cell container that stores an electrolyte solution, the working electrode has an electrode-forming material so that a peripheral portion is left in the hydrophobic porous membrane. The electrode layer of the hydrophobic porous membrane of the working electrode is in contact with the peripheral region where the electrode layer does not exist, the belt-like region across the electrolyte solution, and the substantially entire bottom of the cell container. An electrochemical gas sensor in which an air bleeding piece made of a hydrophobic porous material having a wide portion is arranged.   The side of the air bleeding piece facing the electrode layer of the working electrode is formed in an annular shape so as to correspond to a region where the electrode layer of the hydrophobic porous film constituting the working electrode does not exist. The electrochemical gas sensor according to 1.

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