JP4558567B2 - Dissolved oxygen sensor - Google Patents

Description

  The present invention relates to a dissolved oxygen sensor that measures the amount of oxygen dissolved in a liquid such as water, and relates to a dissolved oxygen sensor that has an improved seal structure in a dissolved oxygen sensor that includes a diaphragm for permeating oxygen.

  Biosensors are configured using biofunctional materials such as enzymes and antibodies, and living organisms such as microorganisms and cells, as molecular identification elements that recognize chemical substances to be measured in sample water. That is, an immobilized membrane is provided in which these biological materials are chemically encapsulated or covalently bonded to a porous polymer membrane.

  In a biosensor, sample water is brought into contact with an immobilized membrane of biological material, and the concentration change of a substance generated or consumed by a biochemical reaction caused thereby is detected by an electrical output (hereinafter referred to as current or voltage) by a detector. , Measured as sensor output).

In the measurement using the biosensor, it is necessary to make the temperature and pH conditions constant so that the immobilized biological material functions stably. Therefore, the biosensor application measuring instrument is equipped with a heat exchanger that warms the sample water to a constant temperature and a constant temperature bath that keeps the sensor temperature constant in order to keep the temperature constant, and to maintain a constant pH condition. A buffer solution is used.

Here, a biosensor for detecting harmful substances in water as shown in Patent Document 1 has been developed.
In this technology, nitrifying bacteria, which are microorganisms that are extremely vulnerable to harmful substances, are used as biological materials, the nitrifying bacteria are fixed alive and sealed with a polymer porous membrane, and a dissolved oxygen electrode is used as a detector. A respiration activity detection type biosensor that is combined with a buffer solution containing a constant concentration of a substrate of nitrifying bacteria and a micronutrient and a sample water is mixed and flowed continuously at a predetermined ratio. Continuous monitoring of contamination with harmful substances.

The diaphragm type galvanic cell type dissolved oxygen sensor used in the above biosensor detects the amount of oxygen in the microbial membrane through the oxygen permeable membrane. In this method, only the end face of the cathode electrode in contact with the oxygen permeable membrane is used. Detect potential changes. For this reason, the electrolytic solution, the cathode electrode, and the attached lead wires are insulated and protected by the insulating glass in other portions.
Japanese Patent Publication No. 7-85072

The dissolved oxygen sensor is a galvanic cell, and deposits are generally generated by a chemical reaction during continuous operation for a long period of time. If these deposits enter the cathode electrode and the oxygen permeable membrane as precipitates, the sensor output decreases. Further, even when the dissolved oxygen sensor is not operated and stored for a long period of time, if the electrolytic solution is not removed, the chemical reaction proceeds in the same manner and precipitates are generated. If the storage period is long or the storage temperature is high, the sensor output may decrease at the time of storage, and a situation may occur that cannot be used.

  In the conventional dissolved oxygen sensor used in the biosensor disclosed in Patent Document 1, the electrode is fixed with an adhesive and the electrolytic solution is sealed. However, when an adhesive is used, if the fluidity is poor due to its viscosity, the adhesive does not flow to the end, resulting in poor adhesion or poor sealing. Further, in such a conventional dissolved oxygen sensor, since the adhesive layer is thick, when the storage temperature is high, adhesive peeling occurs due to thermal stress between the adhesive and the electrode or the housing, resulting in a poor seal and lowering the sensor output. Or the electrolytic solution corrodes or breaks a copper electric wire that is a sensor output wiring, and there is a problem that the sensor output does not come out.

  The present invention has been made in view of the above circumstances, and prevents a decrease in sensor output accompanying a penetration of a precipitate caused by a chemical reaction between the cathode electrode and the oxygen permeable membrane, and also reduces the thermal stress of the electrode portion. Then, it aims at providing the dissolved oxygen sensor by which the performance improvement was made | formed.

  In order to achieve the above object, a dissolved oxygen sensor according to the present invention is a dissolved oxygen sensor that measures the amount of oxygen dissolved in a liquid such as water, and includes an oxygen permeable membrane for permeating oxygen, and the oxygen permeable membrane. A cathode electrode formed by penetrating the outside of the electrode portion into the inside of the insulating protection portion, an anode electrode having the cathode electrode installed inside, the cathode electrode, and the cathode electrode An electrolyte solution facing the anode electrode is provided in the casing, and the casing is made of a material that reduces the difference between the linear expansion coefficient α1 and the linear expansion coefficient α2 of the cathode electrode. To do.

The dissolved oxygen sensor according to the present invention, the linear expansion coefficient α1 of the housing, the ratio of the linear expansion coefficient α2 of the cathode electrode, that make up a material such that within 2-fold. Furthermore, it is more preferable to use a material that is 1.6 times or less. That is, α1: α2 = 2: 1 to 1: 2, more preferably α1: α2 = 1.6: 1 to 1: 1.6, so that the difference between them does not exceed each other .

  In the dissolved oxygen sensor according to the present invention, it is preferable that the insulation protection portion of the cathode electrode is made of either a glass material, an insulating ceramic, or a resin material. Any material can be used as long as it is a solid having the property without any particular limitation on the material.

  Further, in the dissolved oxygen sensor according to the present invention, one end side of the cathode electrode and the anode electrode is fixed to a second casing provided at the upper part of the casing, and the other end side is substantially set. It is preferable that the free end is constructed.

  In another embodiment, the dissolved oxygen sensor according to the present invention is such that the second casing is screwed into the upper casing and the upper casing fixed to the upper section of the casing, or The cover member is fitted to the upper housing, the upper end portion of the anode electrode is sandwiched between the upper housing and the cover member and bonded with an adhesive, and the upper end portion of the cathode electrode is attached to the cover member. It is characterized in that it is formed by adhering to an adhesive.

  In another embodiment of the dissolved oxygen sensor according to the present invention, the second casing is screwed to the upper casing fixed to the upper section of the casing and the inner periphery of the upper casing. A cover member and an inner cover member threadedly engaged with the inner periphery of the cover member. The upper end portion of the cathode electrode is brought into contact with the lower surface of the inner cover member, and the screwing force of the inner cover member is used. A contact force is applied to the contact portion between the electrode portion of the cathode electrode and the inner surface of the oxygen permeable membrane.

  In another embodiment of the dissolved oxygen sensor according to the present invention, the second casing is screwed to the upper casing fixed to the upper section of the casing and the inner periphery of the upper casing. A contact portion between the electrode portion of the cathode electrode and the inner surface of the oxygen permeable membrane by the screwing force of the cover member. It is characterized in that a contact force is applied to.

  In another embodiment, the dissolved oxygen sensor according to the present invention fixes the upper end portion of the cathode electrode and the upper end portion of the anode electrode to the second casing through packing, and The lower end side of the electrode and the anode electrode is configured as a free end.

  In another embodiment, the dissolved oxygen sensor according to the present invention fixes the upper end portion and the lower end portion of the anode electrode to the second casing through packing, and the upper end portion of the cathode electrode. And an O-ring between the second casing and the two packings and the O-ring to perform electrolyte leakage sealing.

  In another embodiment, the dissolved oxygen sensor according to the present invention fixes the upper end of the anode electrode to the second casing via a packing, and the upper end of the cathode electrode and the first Between the two casings and between the inner periphery of the lower end portion of the anode electrode and the outer periphery of the intermediate portion of the cathode electrode, and the electrolyte solution leaks and seals by the packing and the two O rings. It is configured as described above.

According to the present invention, by combining the material on the cathode electrode side and the material on the housing side with a material having a linear expansion coefficient α of substantially the same level, the electrode portion fixed to the lower end portion of the cathode electrode; It can be avoided that the contact pressure between the oxygen permeable membrane and the inner surface of the oxygen permeable membrane decreases due to the difference in thermal expansion between the cathode electrode side and the housing side as in the prior art.
Thereby, the decrease in the contact pressure can be prevented, and the electrode part and the inner surface of the oxygen permeable film are always in contact with each other at a predetermined contact pressure. It is possible to avoid a decrease in the sensor output of the dissolved oxygen sensor due to intrusion into the gap, and the required sensor output can be maintained at all times. Such precipitates are generated regardless of whether the dissolved oxygen sensor is in operation or not. Especially when the dissolved oxygen sensor is stored at a high temperature, sufficient performance is obtained from the beginning regardless of whether it is not used. The inconvenience that it is not possible can be avoided.

  In addition, according to the present invention, the upper end of the anode electrode and the upper end of the cathode electrode can be fixed to the second casing by securely performing an electrolyte leakage seal using adhesion or an O-ring or packing, Since the lower end side of the anode electrode and the cathode electrode is configured as a free end, there is no restraint portion, so that a decrease in contact pressure between the electrode portion and the oxygen permeable membrane due to the difference in the amount of thermal expansion as described above is prevented. However, the thermal stress of the anode electrode and the cathode electrode can be suppressed.

  Embodiments of a dissolved oxygen sensor according to the present invention will be described below in more detail with reference to the drawings.

FIG. 1 is a block diagram showing a schematic structure of a biosensor equipped with a dissolved oxygen sensor according to the present invention. 4 is a flow cell, 5 is a sample passage formed inside the flow cell, and the inside of the sample passage 5 is shown in FIG. The sample water is flowing as shown by the arrow. Reference numeral 1 denotes a microbial membrane for adhering microorganisms in the sample water.
Reference numeral 2 denotes a dissolved oxygen sensor which is an object of the present invention. In this embodiment, a diaphragm type galvanic cell dissolved oxygen sensor is used. Reference numeral 3 denotes a lead wire from an anode electrode and a cathode electrode described later.

In this biosensor, biological functional materials such as enzymes and antibodies, and living organisms such as microorganisms and cells are used as molecular identification elements for recognizing chemical substances to be measured in sample water. A combination of the microbial membrane 1 immobilized by chemical inclusion or covalent bonding to the membrane and the dissolved oxygen sensor 2 is used to convert the molecular identification signal of the biological material into an electrical signal and to convert the chemical substance in the sample water. Measure.
That is, such a biosensor makes sample water contact the microbial membrane 1 which is an immobilization membrane of the biological material, and a dissolved oxygen which is a detector to detect a concentration change of a substance generated or consumed by a biochemical reaction caused thereby. The sensor 2 converts it into a change in electrical output such as current or voltage (hereinafter referred to as sensor output) and measures it.

2A is a schematic configuration diagram showing a schematic structure of a sensor portion of the dissolved oxygen sensor 2, and FIG. 2B is an enlarged view of a Z portion in FIG.
2 (A) and 2 (B), reference numeral 34 denotes a housing having a structure to be described later. Reference numeral 29 denotes an anode electrode attached to the inside of the housing 34. In this embodiment, a lead electrode is used. Reference numeral 30 denotes a cathode electrode provided inside the anode electrode 29, an electrode portion 30a made of a platinum electrode, a silver wire 30b coupled to the electrode portion 30a, and an insulating glass for insulating the electrode portion 30a and the silver wire 30b. 32 or the like.

31 is an oxygen permeable film, which is made of a thin film capable of blocking moisture such as Teflon FEP material and permeable to gas such as oxygen. The inner surface of the oxygen permeable membrane 31 and the electrode portion 30a of the cathode electrode 30 are brought into contact with each other with a predetermined pressure as shown in FIG. 31b is a contact part.
An electrolytic solution 33 is stored in the casing 34 so that the anode electrode 29 and the cathode electrode 30 face each other.

In the dissolved oxygen sensor 2 configured as described above, microorganisms in the sample water are attached to the microbial membrane 1, and when harmful substances are mixed in the sample water, the microorganisms attached to the microbial membrane 1 are Killed or weakened by harmful substances. When such microorganisms die or weaken, the oxygen consumption by the microorganisms decreases.
Therefore, if the dissolved oxygen sensor 2 detects the amount of oxygen that has passed through the oxygen permeable membrane 31 that is permeable to gas such as oxygen, the presence or absence and amount of harmful substances in the sample water is detected by the change in the amount of oxygen. it can.
<First Embodiment>

FIG. 3 is a longitudinal sectional view showing the structure of the main part of the diaphragm type galvanic cell dissolved oxygen sensor according to the first embodiment of the present invention.
In FIG. 3, 34 is a housing, 29 is a cylindrical anode electrode mounted inside the housing 34, and in this embodiment, a lead electrode is used.
Reference numeral 30 denotes a cathode electrode provided inside the anode electrode 29. The cathode electrode 30 has a silver wire 30b connected to a lead wire coupled to an upper portion of an electrode portion 30a made of a platinum electrode, and penetrates the electrode portion 30a and the silver wire 30b inside a cylindrical insulating glass 32. Configured. Reference numeral 30 c denotes a lead wire for the anode electrode 29.
In the electrode housing hole 34c formed in the housing 34, the electrolytic solution 33 is stored so that the anode electrode 29 and the cathode electrode 30 face each other.
Reference numeral 38 denotes an electrode pressing collar for pressing the lower portion of the cathode electrode 30.

  31 is an oxygen permeable film made of a thin film capable of blocking moisture such as Teflon FEP material and allowing gas such as oxygen to pass through. The inner surface of the central part of the cathode electrode 30 is the same as the contact part 31b in FIG. It is brought into contact with the electrode portion 30a with a predetermined pressure.

  Both end portions of the oxygen permeable membrane 31 are in contact with the retainer 36, and a lower cover 35 screwed into the lower portion of the housing 34 is screwed with a screw portion 35 a, whereby the housing 34 is interposed via the retainer 36. It is fixed at the bottom. The retainer 36 is prevented from rotating by a rotation stop pin 36b.

  Reference numeral 37 denotes an O-ring that is sealed between the lower surface of the housing 34 and the upper surface of the retainer 36 to avoid leakage of the electrolytic solution 33 on the lower side of the housing 34.

In this embodiment, the insulating glass 32 of the cathode electrode 30 is made of a lead glass material having a linear expansion coefficient (α) of about α = 8.5 × 10 ⁻⁶ / ° C., while the casing 34 is made of Polyphenyl sulfide (PPS) material added with glass having a linear expansion coefficient (α) of about α = 10 × 10 ⁻⁶ / ° C., which is a value close to the linear expansion coefficient of the insulating glass 32, or the linear expansion coefficient α = It is composed of a polyphenyl sulfide material having about 13.5 × 10 ⁻⁶ / ° C.
Such a combination of linear expansion coefficients is an example, and in the present invention, for example, the material of the cathode electrode insulation protection portion 32 and the housing 34 is an insulating solid, and the material of each other What is necessary is just to comprise so that ratio of a linear expansion coefficient may become less than 2 times. That is, α1: α2 = 2: 1 to 1: 2, more preferably α1: α2 = 1.6: 1 to 1: 1.6 is preferably set such that the difference between them does not exceed each other. .

  The hollow casing 11 is screwed into the upper part of the electrode accommodation hole 34c of the casing 34 (11a is a threaded portion). The hollow casing 11 is integrated with the upper lid 12 and the adhesive filling portion 13. The lower end of the lid 12 is in pressure contact with the upper surface 34 d of the housing 34. 41 is an O-ring inserted between the outer periphery of the hollow casing 11 and the upper inner periphery of the electrode housing hole 34c of the casing 34, and the electrolyte 33 leaks to the upper surface 34d side of the casing 34. Is sealed.

The anode electrode 29 is formed with a collar portion 29 a at the upper portion, and is in contact with the upper end of the hollow casing 11.
An adhesive 14 is interposed between the hollow casing 11 and the anode electrode 29 in the longitudinal direction, and an adhesive 15 is also interposed between the anode electrode 29 and the cylindrical insulating glass 32 in the longitudinal direction. This prevents leakage of the electrolyte.

In the first embodiment, as the temperature of the oxygen sensor 2 rises, the casing 34 is thermally expanded in the axial direction (longitudinal direction), and the insulating glass 32 of the cathode electrode 30 is thermally expanded.
However, the insulating glass 32 of the cathode electrode 30 is made of a lead glass material having a linear expansion coefficient (α) of about α = 8.5 × 10 ⁻⁶ / ° C., and the casing 34 is made of a linear expansion coefficient ( α) is a polyphenyl sulfide (PPS) material added with a glass having a value of about α = 10 × 10 ⁻⁶ / ° C., which is close to the linear expansion coefficient of the insulating glass 32, or the linear expansion coefficient α = 13.5 ×. Since it is made of a polyphenyl sulfide material having a temperature of about 10 ⁻⁶ / ° C., the insulating glass 32 on the cathode electrode 30 side and the thermal expansion amount on the housing 34 side are almost at the same level, and the insulation of the cathode electrode 30 is The difference in thermal expansion between the glass 32 side and the housing 34 side is extremely small or 0 (zero).

  Therefore, according to the first embodiment, the material on the insulating glass 32 side of the cathode electrode 30 and the material on the housing 34 side are combined with materials having substantially the same level of linear expansion coefficient α. The contact pressure between the electrode portion 30a fixed to the lower end portion of the insulating glass 32 and the inner surface of the central portion of the oxygen permeable membrane 31 made of the thin film is different from the insulating glass 32 side of the cathode electrode 30 as in the prior art. It is possible to avoid a decrease due to the difference in thermal expansion from the case 34 side.

Therefore, according to the first embodiment, the decrease in the contact pressure can be prevented, and the electrode portion 30a and the inner surface of the oxygen permeable membrane 31 are always in contact with each other at a predetermined contact pressure and stored for a long time at a high temperature. Alternatively, it can be avoided that precipitates generated by a chemical reaction during continuous operation enter the gap between the electrode portion 30a and the inner surface of the oxygen permeable membrane 31 and the sensor output of the oxygen sensor 2 decreases. The required sensor output can be maintained at all times.
<Second Embodiment>

  FIG. 4 is a longitudinal cross-sectional view showing the main structure of a diaphragm type galvanic cell dissolved oxygen sensor according to a second embodiment of the present invention. This second embodiment also has elements in common with the first embodiment. However, since there are considerable differences from the first embodiment, an overlapping description will be given.

In FIG. 4, 34 is a housing, 29 is a cylindrical anode electrode attached to the inside of the housing 34, and in this embodiment, a lead electrode is used.
Reference numeral 30 denotes a cathode electrode provided inside the anode electrode 29. The cathode electrode 30 has a silver wire 30b connected to a lead wire coupled to an upper portion of an electrode portion 30a made of a platinum electrode, and penetrates the electrode portion 30a and the silver wire 30b inside a cylindrical insulating glass 32. Configured. Reference numeral 30 c denotes a lead wire for the anode electrode 29.

In the electrode housing hole 34c formed in the housing 34, the electrolytic solution 33 is stored so that the anode electrode 29 and the cathode electrode 30 face each other.
Reference numeral 38 denotes an electrode pressing collar for pressing a shift of the lower portion of the cathode electrode 30.

  31 is an oxygen permeable film made of a thin film capable of blocking moisture such as Teflon FEP material and allowing gas such as oxygen to pass through. The inner surface of the central part of the cathode electrode 30 is the same as the contact part 31b in FIG. It is brought into contact with the electrode portion 30a with a predetermined pressure.

  Both end portions of the oxygen permeable membrane 31 are in contact with the retainer 36, and a lower cover 35 screwed into the lower portion of the housing 34 is screwed with a screw portion 35 a, whereby the housing 34 is interposed via the retainer 36. It is fixed at the bottom. In the second and subsequent embodiments, the rotation stopper 36a described in the first embodiment is omitted. Of course, the rotation stopper 36a may be provided in an embodiment other than the first embodiment.

  Reference numeral 37 denotes an O-ring that is sealed between the lower surface of the housing 34 and the upper surface of the retainer 36 to avoid leakage of the electrolytic solution 33 on the lower side of the housing 34.

In this embodiment, the insulating glass 32 of the cathode electrode 30 is made of a lead glass material having a linear expansion coefficient (α) of about α = 8.5 × 10 ⁻⁶ / ° C., while the casing 34 is made of Polyphenyl sulfide (PPS) material added with glass having a linear expansion coefficient (α) of about α = 10 × 10 ⁻⁶ / ° C., which is a value close to the linear expansion coefficient of the insulating glass 32, or the linear expansion coefficient α = It is composed of a polyphenyl sulfide material having about 13.5 × 10 ⁻⁶ / ° C.
As described above, in the present invention, it is generally preferable to use a material in which the ratio between the linear expansion coefficient α1 of the casing and the linear expansion coefficient α2 of the cathode electrode is within twice. That is, α1: α2 = 2: 1 to 1: 2, more preferably α1: α2 = 1.6: 1 to 1: 1.6 is preferably set such that the difference between them does not exceed each other. .

Reference numeral 39 denotes a hollow upper housing that is screwed into the upper portion of the electrode housing hole 34c of the housing 34 (39a is a threaded portion), thereby being pressed against the upper surface 34d of the housing 34. Reference numeral 41 denotes an O-ring fitted between the lower outer periphery of the upper casing 39 and the upper inner periphery of the electrode housing hole 34c of the casing 34, and the electrolyte 33 to the upper surface 34d side of the casing 34. Seals the leak.
A cover member 40 is screwed into the upper hole 39e of the upper casing 39 (40a is a screw portion).

  The anode electrode 29 has a flange portion 29 a formed on the upper portion thereof, and the cover member 40 is screwed into the upper housing 39 to sandwich the flange portion 29 a, and the upper surface of the flange portion 29 a is placed on the lower surface of the cover member 40. While being bonded by an adhesive, the lower surface of the collar portion 29a is bonded to the hole of the upper casing 39 by an adhesive. In addition, what was shown as S in the figure is an adhesion part.

  Further, the upper end surface of the cylindrical insulating glass 32 is adhered to the hole of the cover member 40 with an adhesive (S is an adhesive portion), and the inner periphery of the lower end portion of the anode electrode 29 and the outer periphery of the insulating glass 32 of the cathode electrode 30. Are bonded by an adhesive (S is an adhesive portion).

In the second embodiment, as the temperature of the oxygen sensor 2 rises, the casing 34 is thermally expanded in the axial direction (longitudinal direction), and the insulating glass 32 of the cathode electrode 30 is in contact with the hole of the cover member 40. The thermal expansion is performed downward from the adhesive portion S.
However, the insulating glass 32 of the cathode electrode 30 is made of a lead glass material having a linear expansion coefficient (α) of about α = 8.5 × 10 ⁻⁶ / ° C., and the casing 34 is made of a linear expansion coefficient ( α) is a polyphenyl sulfide (PPS) material added with a glass having a value of about α = 10 × 10 ⁻⁶ / ° C., which is close to the linear expansion coefficient of the insulating glass 32, or the linear expansion coefficient α = 13.5 ×. Since it is made of a polyphenyl sulfide material having a temperature of about 10 ⁻⁶ / ° C., the insulating glass 32 on the cathode electrode 30 side and the thermal expansion amount on the housing 34 side are almost at the same level, and the insulation of the cathode electrode 30 is The difference in thermal expansion between the glass 32 side and the housing 34 side is extremely small or 0 (zero).

  Therefore, according to the second embodiment, by combining the material on the insulating glass 32 side of the cathode electrode 30 and the material on the housing 34 side with a material having a linear expansion coefficient α of substantially the same level, The contact pressure between the electrode portion 30a fixed to the lower end portion of the insulating glass 32 and the inner surface of the central portion of the oxygen permeable membrane 31 made of the thin film is different from the insulating glass 32 side of the cathode electrode 30 as in the prior art. It is possible to avoid a decrease due to the difference in thermal expansion from the case 34 side.

  Therefore, according to the second embodiment, the decrease in the contact pressure can be prevented, and the electrode portion 30a and the inner surface of the oxygen permeable membrane 31 are always in contact with each other at a predetermined contact pressure and stored at a high temperature for a long time. It is possible to prevent the precipitates generated by the chemical reaction during the time of entering the gap between the electrode portion 30a and the inner surface of the oxygen permeable membrane 31 and the sensor output of the dissolved oxygen sensor 2 from being lowered. Sensor output can be maintained.

  Further, according to the second embodiment, the upper end portion of the anode electrode 29 is fixed to the upper casing 39 and the cover member 40, and the upper end portion of the cathode electrode 30 is fixed to the cover member 40. The lower part and the intermediate part of the cathode electrode 30 are limited to the adhesion S that is about the steady state, and the lower ends of the anode electrode 29 and the cathode electrode 30 are configured as free ends, and there is no restraint part due to the adhesive in the longitudinal direction. The thermal stress of the anode electrode 29 and the cathode electrode 30 can be suppressed while preventing a decrease in contact pressure between the electrode portion 30a and the oxygen permeable membrane 31 due to the difference in thermal expansion amount.

Further, according to the second embodiment, the collar portion 29a of the anode electrode 29 is sandwiched between the cover member 40 and the upper housing 39, and the upper surface of the collar portion 29a is bonded to the lower surface of the cover member 40 with the adhesive. The upper surface of the insulating glass 32 of the cathode electrode 30 and the cover member 40 are bonded to each other at the portion S, and the lower surface of the collar portion 29a is bonded to the upper housing 39 with an adhesive. Since the adhesive is bonded at the bonding portion S, the upper end portion of the anode electrode 29 and the upper end portion of the cathode electrode 30 can be surely fluid-sealed, and leakage of the electrolytic solution 33 from the electrode connection portion can be prevented. Can be prevented.
<Third Embodiment>

FIG. 5 shows the third embodiment of the present invention and corresponds to FIG. 4 describing the second embodiment.
In the third embodiment, 39 in the second embodiment is replaced with a structure in which the cover member 40 is screwed into the upper hole 39e of the hollow upper casing 39, and the upper hole 39e of the hollow upper casing 39 is replaced. The cover member 20 is fitted to the cover member 20, the collar portion 29 a of the anode electrode 29 is sandwiched between the lower surface of the cover member 20 and the hole of the upper housing 39, and the upper surface of the collar portion 29 a is held on the cover member 20. The lower surface of the flange portion 29a is bonded to the hole of the upper housing 39 with an adhesive (S is an adhesive portion).

Further, the upper end surface of the insulating glass 32 of the cathode electrode 30 is bonded to the hole of the cover member 20 with an adhesive (S is an adhesive portion).
In the case of the third embodiment, the cover member 20 is fitted into the upper hole 39e of the upper casing 39, and the anode electrode 29 and the cathode electrode 30 are bonded to the cover member 20. The structure is simpler and easier to assemble than the form.
Other configurations and operational effects are the same as those of the second embodiment, and the same members are denoted by the same reference numerals.
<Fourth embodiment>

FIG. 6 shows a fourth embodiment of the present invention and corresponds to FIG. 4 describing the second embodiment.
In the fourth embodiment, the cover member 20 is screwed into the upper casing 39 (20a is a threaded portion), and the collar portion 29a of the anode electrode 29 is connected to the cover member in the second embodiment. 20 and the upper housing 39, and a cylindrical inner cover member 50 is screwed onto the inner peripheral side of the cover member 20 (50a is a threaded portion).

  Further, the upper end portion of the insulating glass 32 is adhered to the lower surface of the cover member 20 with an adhesive (S is an adhesive portion), and the electrode portion is interposed by the inner cover member 50 via the insulating glass 32 of the cathode electrode 30. Contact force is applied to the contact portion between 30a and the inner surface of the oxygen permeable membrane 31.

  Further, the lower end portion of the upper casing 39 and the outer periphery of the anode electrode 29 are adhered by an adhesive (S is an adhesive portion), the inner periphery of the lower end portion of the cylindrical inner cover member 50 and the outer periphery of the insulating glass 32. Are bonded with an adhesive (S is an adhesive portion), and the lower end portion of the anode electrode 29 and the collar portion 50a of the inner cover member 50 are bonded with an adhesive (S is an adhesive portion). The leakage of the liquid 33 is sealed.

  In the case of the fourth embodiment, a contact force is applied to the contact portion between the electrode portion 30a and the inner surface of the oxygen permeable membrane 31 by the screwing force of the inner cover member 50 screwed into the inner periphery of the cover member 20. Therefore, it is possible to avoid the formation of a gap due to a decrease in the contact surface pressure of the contact portion and the intrusion of precipitates into the gap due to this.

Other configurations and operational effects are the same as those of the second embodiment, and the same members are denoted by the same reference numerals.
<Fifth Embodiment>

FIG. 7 shows a fifth embodiment of the present invention and corresponds to FIG. 4 describing the second embodiment.
In the fifth embodiment, in contrast to the fourth embodiment, the anode electrode 29 is formed in a cylindrical shape without the collar portion 29a, and the anode is formed on the lower surface of the cover member 20 screwed into the upper housing 39. The upper end portion of the electrode 29 is bonded by an adhesive (S is an adhesive portion), and the upper end portion of the insulating glass 32 of the cathode electrode 30 is bonded to the inner lower surface of the cover member 20 by an adhesive (S is an adhesive). Part).

  Further, the lower portion of the upper housing 39 is extended into the housing 34 and screwed into the housing 34 at the back (34a is a screw portion), and the lower end of the upper housing 39 and the anode electrode The lower end part of 29 is adhere | attached with the adhesive agent (S is an adhesion part).

In the case of this fifth embodiment, since the contact force is applied to the contact portion between the electrode portion 30a and the inner surface of the oxygen permeable membrane 31 by the screwing force of the cover member 20, the contact surface pressure of the contact portion It is possible to avoid the formation of a gap due to a decrease in the thickness and the intrusion of precipitates into the gap due to this.
Other configurations and operational effects are the same as those of the fourth embodiment, and the same members are denoted by the same reference numerals.
<Sixth Embodiment>

FIG. 8 shows the sixth embodiment of the present invention and corresponds to FIG. 4 describing the second embodiment.
In the sixth embodiment, in contrast to the second to fifth embodiments, the upper ends of the insulating glass 32 of the anode electrode 29 and the cathode electrode 30 are fixed to the upper housing 39 side through packing, Adhesion by the adhesive in the second to fifth embodiments is abolished.
Reference numeral 40 denotes a cover member (40a is a screw portion) screwed to the upper portion of the upper casing 39, and 22 is an inner cover member screwed to the upper inner periphery of the cover member 40 (22a is a screw portion).

Further, a collar portion 29a is formed at the upper end portion of the cylindrical anode electrode 29, and a packing 53 is sandwiched between the upper surface of the collar portion 29a and the lower surface of the cover member 40, and the lower surface of the collar portion 29a and the upper portion of the collar portion 29a. The packing 54 is sandwiched between the bottom surface of the hole of the casing 39 and the cover member 40 is fastened to the upper casing 39 to perform fluid sealing (leakage sealing of the electrolyte 33) by the packing 53 and the packing 54. Yes.

Further, a collar portion 32a is formed at the upper end portion of the insulating glass 32 of the cathode electrode 30, and a packing 51 is sandwiched between the upper surface of the collar portion 32a and the lower surface of the inner cover member 22, and the lower surface of the collar portion 32a and the above-mentioned The packing 52 is sandwiched between the bottom surface of the hole of the cover member 40 and the inner cover member 22 is fastened to the cover member 40, thereby performing fluid sealing (leakage sealing of the electrolyte 33) by the packing 51 and the packing 52. Yes.

In the case of the sixth embodiment, both sides of the collar portion 29a formed on the upper end portion of the anode electrode 29 and both sides of the collar portion 32a formed on the upper end portion of the cathode electrode 30 are connected to the packing 53, the packing 54, the packing 51, and the packing. Therefore, the leakage of the electrolyte solution 33 can be more reliably performed without bonding with an adhesive as in the first to fifth embodiments.

In addition, the upper end collar portion 29a of the anode electrode 29 and the upper end collar portion 32a of the cathode electrode 30 are configured as strong fixed ends with packings 51 to 54 interposed therebetween, so that the lower end side is completely free of any restraining portion. Since it can be configured at the end, the effect of suppressing the thermal stress of the anode electrode 29 and the cathode electrode 30 is increased.

Other configurations and operational effects are the same as those of the second embodiment, and the same members are denoted by the same reference numerals.
<Seventh embodiment>

FIG. 9 shows the seventh embodiment of the present invention and corresponds to FIG. 4 describing the second embodiment.
In the seventh embodiment, the upper ends of the insulating glass 32 of the anode electrode 29 and the cathode electrode 30 are used in combination with packing, an O-ring, and an adhesive means, as compared with the second to fifth embodiments. It is fixed to the upper casing 39 side.

That is, in FIG. 9, the upper casing 39 is formed with a collar portion 39b on the inner peripheral side of the lowermost threaded portion 34a in the cylinder housed in the casing 34, and the anode formed in the cylindrical body. The packing 24 is inserted between the lower end surface of the electrode 29 and the upper surface of the collar portion 39b.

On the other hand, a cover member 40 is screwed into the upper casing 39 (40a is a threaded portion), and a packing 53 is inserted between the lower surface of the cover member 40 and the upper surface of the anode electrode 29.
Therefore, by screwing the cover member 40 into the upper housing 39, the upper packing 53 is compressed and the lower packing 24 is compressed, so that the leakage seal of the electrolyte on the anode electrode 29 side can be ensured. It can be carried out.

  An O-ring 23 is interposed between the outer periphery of the upper end portion of the insulating glass 32 of the cathode electrode 30 and the inner periphery of the hole portion of the cover member 40, and the upper end surface of the insulating glass 32 of the cathode electrode 30. And the hole bottom surface of the cover member 40 are bonded by an adhesive (S is an adhesive portion).

  In the case of the seventh embodiment, the upper end and the lower end of the anode electrode 29 are sealed with electrolytes 53 and 24, and the upper end of the cathode electrode 30 is problematic because of the difference in thermal expansion from the casing 34. Since the part side has a structure in which the electrolyte solution leaks and seals by using the O-ring 23 and adhesive bonding together, the difference in thermal expansion between the cathode electrode 30 side and the housing 34 is suppressed, and the thermal stress is reduced. In addition, the electrolyte solution can be securely sealed.

Other configurations and operational effects are the same as those of the second embodiment, and the same members are denoted by the same reference numerals.
<Eighth Embodiment>

FIG. 10 shows an eighth embodiment of the present invention and is a view corresponding to FIG. 4 describing the second embodiment.
In the eighth embodiment, a collar portion 29a is formed at the upper end portion of the cylindrical anode electrode 29, and the upper surface of the collar portion 29a and the upper housing 39 are compared with the second to fifth embodiments. A packing 53 is sandwiched between the lower surface of the screwed cover member 40, a packing 54 is sandwiched between the lower surface of the collar portion 29a and the bottom surface of the hole of the upper housing 39, and the cover member 40 is disposed in the upper housing. By tightening to the body 39, leakage sealing of the electrolyte solution 33 by the packing 53 and the packing 54 is performed.

Further, an O-ring 55 is interposed between the outer periphery of the upper end portion of the insulating glass 32 of the cathode electrode 30 and the inner periphery of the hole portion of the cover member 40, and the outer periphery of the lower end portion of the insulating glass 32 and the anode An O-ring 56 is interposed between the inner periphery of the lower end of the electrode 29.
Therefore, in the eighth embodiment, the leakage of the electrolytic solution 33 on the cathode electrode 30 side is sealed by the upper and lower O-rings 55 and 56 without restraining thermal expansion on the cathode electrode 30 side and generating thermal stress. In addition, the anode electrode 29 can securely seal the leakage of the electrolyte solution 33 by firmly fastening the anode electrode 29 through the packings 53 and 54 at the upper end.

Other configurations and operational effects are the same as those of the second embodiment, and the same members are denoted by the same reference numerals.
Depending on the required performance of the dissolved oxygen sensor, only the seal structure described in the second to eighth embodiments can be implemented as an improved point regardless of the improved portion related to the linear expansion coefficient.

  The dissolved oxygen sensor according to the first embodiment (Examples 1 to 3), the dissolved oxygen sensor according to the eighth embodiment (Examples 4 to 6), and the dissolved oxygen sensor according to the conventional product (Comparative Examples 1 and 2) FIG. 11 shows the result of examining the decrease in output when left at a high temperature of 65 ° C. Moreover, what took each average of Examples 1-3, Examples 4-6, and Comparative Examples 1 and 2 and put together the tendency is shown in FIG.

  As can be understood from these results, the decrease in the initial output of the dissolved oxygen sensor is clearly suppressed even in Examples 1 to 3 in which only the improvement relating to the linear expansion coefficient is performed as compared with the conventional product. Furthermore, in Examples 4 to 6 according to the eighth embodiment in which structural improvements were made, 60% of the initial output was maintained even when a load of nearly 2000 hours was applied.

In Examples 1 to 6 according to the first and eighth embodiments, the insulating glass 32 of the cathode electrode 30 is a lead glass material having a linear expansion coefficient (α) of α = 8.5 × 10 ⁻⁶ / ° C. The casing 34 is made of a polyphenyl sulfide material added with glass having a coefficient of linear expansion (α) close to the coefficient of linear expansion of the insulating glass 32 and α = 10 × 10 ⁻⁶ / ° C.
In Comparative Examples 1 and 2, the insulating glass 32 of the cathode electrode 30 is made of a lead glass material having a linear expansion coefficient (α) of α = 8.5 × 10 ⁻⁶ / ° C. and the casing 34 is linearly expanded. The polyacetal material having a large coefficient (α) of α = 8.5 × 10 ⁻⁵ / ° C. was used.

  The dissolved oxygen sensor according to the first embodiment (Examples 1 to 3), the dissolved oxygen sensor according to the eighth embodiment (Examples 4 to 6), and the dissolved oxygen sensor according to the conventional product (Comparative Examples 1 and 2) Fig. 13 shows the results of examining the sensor output at room temperature with respect to oxygen-free water when left at a high temperature of 65 ° C.

  In Comparative Examples 1 and 2, even in the case of oxygen-free water, the gap between the electrode tip and the oxygen permeable membrane is widened, so that the electrolyte tends to flow, and oxygen tends to be held in the electrolyte above. Therefore, it is understood that oxygen is detected even in anoxic water. Examples 1-6 do not have such a thing. This is particularly effective for an application object that is required to respond sensitively to minute changes such as a biosensor.

  According to the present invention, it is possible to prevent a decrease in sensor output due to penetration of a precipitate due to a chemical reaction between the cathode electrode and the oxygen permeable membrane, and it is possible to reduce the thermal stress of the electrode portion, thereby improving the performance. A dissolved oxygen sensor can be provided.

It is a block diagram which shows schematic structure of the biosensor equipped with the dissolved oxygen sensor which concerns on this invention. (A) is a schematic block diagram which shows schematic structure of the sensor part of the said dissolved oxygen sensor, (B) is the Z section enlarged view in (A). It is a longitudinal cross-sectional view which shows the principal part structure of the diaphragm type | mold galvanic cell dissolved oxygen sensor which concerns on 1st Embodiment of this invention. It is a longitudinal cross-sectional view which shows the principal part structure of the diaphragm type | mold galvanic cell dissolved oxygen sensor which concerns on 2nd Embodiment of this invention. It is a longitudinal cross-sectional view corresponding to FIG. 4 used about 2nd Embodiment which shows 3rd Embodiment of this invention. It is a longitudinal cross-sectional view corresponding to FIG. 4 used about 2nd Embodiment which shows 4th Embodiment of this invention. FIG. 6 is a longitudinal sectional view corresponding to FIG. 4 used for the second embodiment, showing a fifth embodiment of the present invention. It is a longitudinal cross-sectional view corresponding to FIG. 4 used about 2nd Embodiment which shows 6th Embodiment of this invention. It is a longitudinal cross-sectional view corresponding to FIG. 4 used about 2nd Embodiment which shows 7th Embodiment of this invention. It is a longitudinal cross-sectional view corresponding to FIG. 4 used about 2nd Embodiment which shows 8th Embodiment of this invention. About the dissolved oxygen sensor (Examples 1-3) which concerns on 1st Embodiment, the dissolved oxygen sensor (Examples 4-6) which concerns on 8th Embodiment, and the dissolved oxygen sensor (Comparative Examples 1 and 2) which concern on a conventional product, It is a graph which shows the result of having investigated the output fall at the time of leaving at high temperature of 65 degreeC. It is a graph which shows the result of having taken each average of Examples 1-3, Examples 4-6, and Comparative Examples 1 and 2. FIG. About the dissolved oxygen sensor (Examples 1-3) which concerns on the said 1st Embodiment, the dissolved oxygen sensor (Examples 4-6) which concerns on the said 8th Embodiment, and a dissolved sensor (Comparative Examples 1 and 2) to a conventional product, It is a graph which shows the result of having investigated the sensor output at the room temperature with respect to anoxic water at the time of leaving to high temperature of 65 degreeC.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Microbial membrane 2 Dissolved oxygen sensor 3 Lead wire 4 Flow cell 5 Sample flow path 20 and 40 Cover members 23 and 41, O-ring 29 Anode electrode 30 Cathode electrode 30a Electrode part 31 Oxygen permeable film 32 Insulating glass 33 Electrolytic solution 34 Case 39 Upper casing 51 Packing S Bonding part

Claims (9)

A dissolved oxygen sensor for measuring the oxygen concentration of a gas and the amount of oxygen dissolved in a liquid such as water, comprising an oxygen permeable membrane for permeating oxygen, comprising an electrode portion in pressure contact with the inside of the oxygen permeable membrane, A cathode electrode configured by penetrating the outside of the insulating part into the inside of the insulating protection unit, an anode electrode having the cathode electrode installed therein, and an electrolyte solution facing the cathode electrode and the anode electrode are provided in the housing , the housing, the linear expansion coefficient Ri α1 and name in the difference between the linear expansion coefficient α2 of the cathode electrode is composed of a material smaller, the linear expansion coefficient α1 of the housing, the cathode electrode A dissolved oxygen sensor , characterized in that it is made of a material that has a ratio to the linear expansion coefficient α2 that is twice or less . 2. The dissolved oxygen sensor according to claim 1, wherein the insulation protection portion of the cathode electrode is made of either a glass material, an insulating ceramic, or a resin material. Claim, characterized by comprising the one end of the cathode electrode and the anode electrode is fixed to the second housing provided in the upper portion of the housing, constitutes the other side to a substantial free end 1 Or 2 dissolved oxygen sensors. The second casing includes an upper casing fixed to an upper portion of the casing and a cover member screwed into the upper casing or fitted to the upper casing. thereby adhering the sandwiched adhesive upper end portion of the anode electrode between the cover member, the upper end portion of the cathode electrode of claim 3, characterized by being configured bonded with adhesive to the cover member Dissolved oxygen sensor. The second casing includes an upper casing fixed to the upper section of the casing, a cover member screwed to the inner periphery of the upper casing, and an inner cover member screwed to the inner periphery of the cover member The upper end portion of the cathode electrode is brought into contact with the lower surface of the inner cover member, and the contact portion between the electrode portion of the cathode electrode and the inner surface of the oxygen permeable membrane is caused by the screwing force of the inner cover member. The dissolved oxygen sensor according to claim 3 , wherein the sensor is configured to apply a contact force. The second casing includes an upper casing fixed to an upper portion of the casing and a cover member screwed to an inner periphery of the upper casing, and the cathode electrode is formed on a lower surface of the cover member. is abutted against the upper end, claim 3, characterized by being configured to apply a contact force to the contact portion between the electrode portion and the inner surface of the oxygen permeable film of the cathode electrode by screwing force of the cover member Dissolved oxygen sensor. The upper end portion of the cathode electrode and the upper end portion of the anode electrode are fixed to the second casing through packing, and the lower end side of the cathode electrode and anode electrode is configured as a free end. The dissolved oxygen sensor according to claim 3 . The upper end and the lower end of the anode electrode are fixed to the second casing through packing, and an O-ring is interposed between the upper end of the cathode electrode and the second casing, 4. The dissolved oxygen sensor according to claim 3 , wherein said two packings and an O-ring are configured to perform leakage leakage sealing of the electrolyte. The upper end portion of the anode electrode is fixed to the second casing via a packing, and the upper end portion of the cathode electrode and the second casing, the inner periphery of the lower end portion of the anode electrode, and the cathode electrode 4. The dissolved oxygen sensor according to claim 3, wherein an O-ring is interposed between the outer periphery of each of the intermediate portions and the electrolyte and the two O-rings are sealed to leak electrolyte.

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