JP4695441B2 - Gas sensor - Google Patents

Description

  The present invention relates to a gas sensor placed in a high humidity environment.

  In general, a solid polymer membrane fuel cell is formed by sandwiching both sides of a solid polymer electrolyte membrane between a fuel electrode and an oxygen electrode to form a single cell, and a plurality of single cells are stacked to form one fuel cell stack. Yes. The fuel electrode is supplied with hydrogen as a fuel, the oxygen electrode is supplied with air as an oxidant, and hydrogen ions generated by a catalytic reaction at the fuel electrode pass through the solid polymer electrolyte membrane and pass through the oxygen electrode. The hydrogen ions and oxygen cause an electrochemical reaction to generate electricity.

  In such a solid polymer membrane fuel cell, conventionally, a hydrogen detector (gas sensor) is provided in the discharge system on the oxygen electrode side of the fuel cell, and the hydrogen on the fuel electrode side is removed from the solid polymer electrolyte membrane by this hydrogen detector. There is known a technique for detecting leakage to the oxygen electrode side through (see Patent Document 1). Specifically, in this technology, the hydrogen inlet (gas flow part) of the hydrogen detector is directed downward in the vertical direction, and the hydrogen detector is provided on the upper wall of the exhaust pipe. The structure is such that light hydrogen can be taken into the hydrogen detector well. In addition, in such a technology, by providing a water repellent filter at the hydrogen intake port, water droplets in the gas are removed by the water repellent filter before high-humidity gas enters the hydrogen detector to detect hydrogen. It is also considered to prevent water droplets from adhering to the detection element in the vessel.

JP2003-294675A (paragraphs 0008 to 0010, FIG. 4)

  However, in the above-described technique, in a state where the water vapor contained in the high-humidity gas has not yet become water droplets, the water vapor passes through the water-repellent filter, and thus the water vapor enters the hydrogen detector. When the internal temperature drops after entering, there is a problem that water vapor is liquefied and the liquefied water accumulates on the water repellent filter. If water accumulates on the water-repellent filter in this way, the water-repellent filter is clogged, so that it is difficult for gas to be taken into the hydrogen detector thereafter, which may affect sensing.

  Accordingly, an object of the present invention is to provide a gas sensor capable of suppressing clogging of a gas flow part configured to actively take in only gas while suppressing water ingress by a water repellent filter or the like. And

The invention according to claim 1 of the present invention that solves the above problems includes a gas detection element that detects a gas to be detected contained in a gas, an element storage portion that stores the gas detection element, and the element storage portion. A gas sensor provided on a wall of the flow path with the gas flow part facing the inside of the flow path through which the gas flows. The gas sensor comprises a hydrogen sensor for detecting hydrogen in the air off-gas discharged from the fuel cell, and the element housing portion is provided so as to protrude from the inner surface of the flow path, and the gas flow Is provided on the peripheral wall of the element housing portion so as to face the substantially horizontal direction , a water repellent filter is provided in the opening of the gas flow portion, and the gas flow portion is provided in the element housing portion. Air introduced toward the opening of The gas detection element in a portion which does not overlap with the direction of introduction Fugasu characterized is Rukoto is disposed.

  Here, “substantially horizontal direction” simply means a direction excluding the vertical direction. Specifically, the direction in which the horizontal component is minimized when the direction of the gas flow portion is displayed as a vector. It means to include.

According to the first aspect of the present invention, even if a gas (air off-gas) is taken into the element housing part from the gas flow part and then the internal temperature is lowered and a part of the substrate is liquefied, the gas flow part since part is oriented substantially horizontally, the opening of the gas passage flow section be provided with a water repellent filter, the liquefied liquid without accumulating in gas passage portion (on water repellent filter), eye Clogging can be suppressed. In addition, by suppressing the clogging of the gas flow part in this way, it is possible to improve the detection accuracy of the gas to be detected (hydrogen) , and at the same time, to improve the life of the gas sensor (hydrogen sensor) at a low cost. be able to.
Further, in the element housing portion, a gas detection element is disposed at a portion that does not overlap with the introduction direction of the air off-gas introduced toward the opening of the gas flow portion, and is introduced from the opening of the gas flow portion. Since air off gas containing a large amount of water vapor is prevented from directly hitting the gas detection element, the detection performance of the gas detection element can be prevented from deteriorating and the life of the gas sensor can be improved.

  A second aspect of the present invention is the gas sensor according to the first aspect, wherein the gas flow portion is provided on a side back portion of a peripheral wall of the element accommodating portion.

  Here, the “side back portion” means a portion corresponding to a side surface and a back surface when a portion directly exposed to gas is a front surface, in other words, a portion that becomes a shadow when light is applied from the direction in which the gas flows. Say. In addition, “providing the gas flow passage portion on the side back portion” does not mean that the gas flow passage portion is completely within the region of the side back portion, but more than half of the gas flow passage portion is in the region of the side back portion. It means that it needs to be within.

  According to the second aspect of the present invention, since the gas flow part is provided on the side back part of the peripheral wall of the element housing part, the gas flowing through the flow path does not enter the gas flow part directly but enters the gas flow part. It will be. Therefore, it is possible to prevent the inside of the element housing portion from becoming a high pressure, and it is possible to perform better sensing.

  According to a third aspect of the present invention, in the gas sensor according to the second aspect of the present invention, at least the element housing portion is arranged so that a cross-sectional area of the element housing portion in a plane orthogonal to the gas flow direction is reduced. It is characterized by tilting the side.

  Here, the “side portion” refers to a portion including the boundary between the front surface and the side back portion of the element housing portion.

According to the invention described in claim 3, by tilting the side portion of the element accommodating portion, the cross-sectional area of the element accommodating portion in the plane orthogonal to the gas flow direction (the surface on which the gas directly hits) is reduced. It is possible to suppress as much as possible that the gas sensor protruding from the inner surface of the flow path becomes a resistance to the gas flow. In particular, when the gas sensor is used as a hydrogen sensor for detecting hydrogen in the air off-gas discharged from the fuel cell, the resistance of the exhaust system during air supply is minimized and the energy consumption of the air supply is suppressed. It becomes possible.
According to the fourth aspect of the present invention, the air off gas introduced into the element housing portion is diffused by hitting the wall surface of the peripheral wall facing the opening, so that hydrogen in the air off gas discharged from the fuel cell is detected. This improves the detection accuracy of the gas detection element.
According to the fifth aspect of the present invention, the gas flow portion is provided in the tapered portion, so that the gas sensor is suppressed from becoming resistant to the flow of gas (air off gas) flowing through the flow path. The gas sensor can be downsized.
According to invention of Claim 6, the dew condensation water collected on the top part of the taper part can be smoothly discharged | emitted outside from a drain hole.

According to the first aspect of the present invention, since the gas flow portion is provided at a position facing the substantially horizontal direction, the condensed water liquefied in the element housing portion does not accumulate in the gas flow portion. Clogging of the flow part can be suppressed. In addition, since the air off gas containing a large amount of water vapor introduced from the opening of the gas flow passage is prevented from directly hitting the gas detection element, the gas detection element is prevented from deteriorating in detection performance. Improved lifespan can be achieved.

  According to the second aspect of the present invention, since the gas flow portion is provided on the side back portion of the peripheral wall of the element housing portion, the gas flowing through the flow path wraps around and enters the gas flow portion. It is possible to prevent the inside of the housing portion from becoming a high pressure, and it is possible to perform better sensing.

According to the third aspect of the present invention, since the cross-sectional area of the element accommodating portion is reduced by inclining the side portion of the element accommodating portion, the gas sensor protruding from the inner surface of the flow path has resistance to the gas flow. Can be suppressed as much as possible.
According to the fourth aspect of the present invention, the air off gas introduced into the element housing portion is diffused by hitting the wall surface of the peripheral wall facing the opening, so that hydrogen in the air off gas discharged from the fuel cell is detected. It is possible to improve the detection accuracy of the gas detection element.
According to the fifth aspect of the present invention, the gas flow portion is provided in the tapered portion, so that the gas sensor is suppressed from becoming resistant to the flow of gas (air off gas) flowing through the flow path. The gas sensor can be downsized.
According to invention of Claim 6, the dew condensation water collected on the top part of the taper part can be smoothly discharged | emitted outside from a drain hole.

[First Embodiment]
Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In the drawings to be referred to, FIG. 1 is a schematic configuration diagram showing a fuel cell system provided with a hydrogen sensor according to the first embodiment.

  As shown in FIG. 1, a hydrogen sensor (gas sensor) 1 according to the first embodiment is incorporated in a fuel cell system S in order to detect hydrogen in air off-gas discharged from the fuel cell 2. . Hereinafter, the fuel cell system S will be briefly described, and then the details of the hydrogen sensor 1 will be described.

The fuel cell system S mainly includes a fuel cell 2, an inlet side pipe 3 and an outlet side pipe 5 on the fuel electrode (anode) side, and an inlet side pipe 4 and an outlet side pipe 6 on the oxygen electrode (cathode) side. Yes.
The fuel cell 2 includes a single cell (not shown) in which an electrolyte membrane electrode structure in which a solid polymer electrolyte membrane made of, for example, a cation exchange membrane is sandwiched between a fuel electrode and an oxygen electrode is further sandwiched between a pair of separators. It consists of a stack composed of a large number of sets.

In this fuel cell 2, for example, hydrogen is supplied to the fuel electrode as a fuel via a fuel supply side inlet side pipe 3 from a hydrogen supply device (not shown) including a high-pressure hydrogen tank or the like, and an oxygen electrode is supplied by a compressor 21. Air is supplied to the oxygen electrode as an oxidant through the side inlet side pipe 4. On the catalyst electrode of the fuel electrode, hydrogen is ionized by the catalytic reaction, and the generated hydrogen ion passes through the appropriately polymerized solid polymer electrolyte membrane and moves to the oxygen electrode. Then, electrons generated during this period are taken out to an external circuit and used as direct current electric energy. Since oxygen-containing air is supplied to the oxygen electrode, hydrogen ions, electrons, and oxygen react electrochemically by the action of the catalyst of the oxygen electrode to generate water. .
Then, so-called off-gas containing unreacted reaction gas (for example, hydrogen or air) is discharged from the outlet side pipe 5 on the fuel electrode side and the outlet side pipe (flow channel) 6 on the oxygen electrode side.

Here, the hydrogen off-gas (anode off-gas) containing unreacted hydrogen is discharged from the outlet side pipe 5 on the fuel electrode side of the fuel cell 2 to the hydrogen circulation path 22, and the inlet side pipe on the fuel electrode side via the ejector 23. 3 is supplied to the fuel electrode of the fuel cell 2 again.
On the other hand, the air off gas (cathode off gas) containing a large amount of moisture in the reacted air is discharged to the atmosphere through the diluter 26 and the outlet side pipe 6.

Further, a hydrogen discharge path 25 is connected to the outlet side pipe 5 on the fuel electrode side of the fuel cell 2 via a purge valve 24, and a diluter 26 is connected to the hydrogen discharge path 25. The hydrogen off-gas can be discharged to the hydrogen discharge path 25 via the purge valve 24 and can be introduced to the diluter 26 through the hydrogen discharge path 25.
The diluter 26 is configured to dilute the hydrogen off gas taken from the hydrogen discharge passage 25 with an appropriate magnification by the air off gas discharged from the fuel cell 2 and discharge it as a diluted gas.
A gas catalytic combustion type hydrogen sensor 1 is disposed downstream of the diluter 26, and the hydrogen concentration of the diluted gas is monitored by this. Here, the hydrogen sensor 1 is arranged at the upper part in the vertical direction of the outlet side pipe 6 arranged so that the flow direction of the air off gas is the horizontal direction.

  Next, details of the hydrogen sensor 1 will be described with reference to FIGS. 2 and 3. In the drawings to be referred to, FIG. 2 is a cross-sectional view showing the inside of the hydrogen sensor according to the first embodiment, and FIG. 3 is a cross-sectional view along line AA in FIG. It is B sectional drawing (b).

  As shown in FIG. 2, the hydrogen sensor 1 includes a rectangular parallelepiped case 30 containing a control board (not shown). The case 30 is made of, for example, polyphenylene sulfide, and includes flange portions 31 at both ends in the longitudinal direction. A collar 32 is attached to the flange portion 31, and a bolt 33 is inserted into the collar 32, so that the flange portion 31 is attached to an outlet seat (flow path) 6 on the oxygen electrode side. (Wall) It is fastened and fixed to 6a.

  The lower end surface of the case 30 is provided with a gas detection element 50 and a heater 60 connected to the control board, and a bottomed cylindrical element receiving portion 34 for receiving these protrudes downward. It is provided as follows.

  The gas detection element 50 detects hydrogen (detected gas) contained in the dilution gas (gas). Specifically, as shown in FIG. 3A, the detection element 51 and the temperature compensation element 52 and a pair. The detection element 51 is a well-known element, and is formed by coating a coil of metal wire containing platinum or the like having a high temperature coefficient with respect to electric resistance with a carrier such as alumina carrying a catalyst. The catalyst is made of a noble metal active against hydrogen. The temperature compensation element 52 is inactive with respect to hydrogen, and is formed, for example, by coating the surface of a coil equivalent to the detection element 51 with a carrier such as alumina.

  When the detection element 51 becomes hot due to the reaction heat generated when hydrogen comes into contact with the catalyst, a difference occurs in the resistance value between the detection element 51 and the temperature compensation element 52, so that the hydrogen concentration can be detected from this difference. It can be done. Note that the change in electrical resistance value due to the ambient temperature is offset by using the temperature compensation element 52.

  The heater 60 heats the inside of the element accommodating portion 34 (hereinafter, this internal space is also referred to as “gas detection chamber R”), and thereby, the occurrence of condensation in the gas detection element 50 is suppressed.

  As shown in FIG. 2, the element accommodating portion 34 is adapted to fit into a through hole 6 c formed in the outlet side pipe 6, and a part of the element accommodating part 34 protrudes from the inner surface 6 b of the outlet side pipe 6. It is comprised so that it may expose in the side piping 6 (henceforth, the exposed part is called "lower half part"). And the gas flow part 70 is provided in the surrounding wall 34a of the lower half part of the element accommodating part 34 exposed in the outlet side piping 6 in this way so that it may face a horizontal direction, and, thereby, the outlet side piping 6 The dilution gas is taken into the gas detection chamber R from the gas flow part 70 that is in an inward state.

  Specifically, as shown in FIG. 3B, the gas flow portion 70 is provided on the side back portion SB of the peripheral wall 34 a of the element housing portion 34. Here, the “side back portion SB” means portions corresponding to the side surface and the back surface when the portion directly exposed to the dilution gas is the front surface FF, in other words, when the light is applied from the direction in which the dilution gas flows. The part which becomes. Further, “providing the gas flow portion 70 in the side back portion SB” does not mean that the gas flow portion 70 is completely within the region of the side back portion SB, but more than half of the gas flow portion 70. Means that it should be within the region of the back portion SB. In the present embodiment, the gas flow part 70 is provided so that only half of the gas flow part 70 is accommodated in the side back part SB, so that the gas flow part 70 is orthogonal to the flow direction of the dilution gas, and It is oriented in the direction along the horizontal plane.

  The gas flow part 70 includes an opening 71 formed on the peripheral wall 34 a of the element housing part 34, a water repellent filter 72 provided on the opening 71, and an explosion-proof filter provided on the water repellent filter 72. 73. Thereby, water contained in the wet dilution gas is repelled by the water repellent filter 72 so as not to enter the gas detection chamber R, and explosion-proof property is also ensured.

  As shown in FIG. 3A, a predetermined groove 34b along the circumferential direction is formed in the peripheral wall 34a of the upper half of the element housing portion 34, and a seal member 35 is provided in the groove 34b. Yes. Thereby, when the hydrogen sensor 1 is attached to the outlet side pipe 6, the seal member 35 is brought into close contact with the inner peripheral surface of the through hole 6 c of the outlet side pipe 6 and the groove 34 b of the element accommodating portion 34. Ensuring airtightness between.

  Further, as shown in FIG. 2, a drain hole 34d for discharging the water liquefied in the gas detection chamber R to the outside is provided at an appropriate position on the bottom wall 34c of the element accommodating portion 34. 34d is provided with an explosion-proof filter 73 similar to the above which is formed of a mesh capable of passing water. Furthermore, a drainage channel 36 is provided in the lower part of the drainage hole 34d, and the drainage hole 36 is formed so that the lower part of the drainage channel 36 is bent toward the downstream side in the flow direction of the dilution gas. The dilution gas is prevented from entering the gas detection chamber R from 34d. Incidentally, since the element housing part 34 protrudes from the inner surface 6b of the outlet side pipe 6, the cross-sectional area of the outlet side pipe 6 at that portion is reduced, so the flow rate of the dilution gas flowing below the element housing part 34 Therefore, the discharge of water from the drain hole 34d is promoted by the action of the negative pressure.

Next, the operation of the hydrogen sensor 1 will be described.
As shown in FIG. 2, the dilution gas flowing in the outlet side pipe 6 wraps around the lateral side (the back side in the figure) of the element housing part 34 and enters the gas detection chamber R from the gas flow part 70. . Then, after the dilution gas is taken into the gas detection chamber R from the gas flow part 70 in this way, when the internal temperature is lowered and a part of the water vapor of the dilution gas is liquefied, FIG. As shown, the water droplets W are attached to the inner surface of the element housing portion 34.

  At this time, the water droplet W attached to the inner surface of the peripheral wall 34a of the element accommodating portion 34 flows downward due to the influence of gravity and accumulates on the bottom wall 34c. Thereby, water does not collect in the gas flow part 70 provided in the peripheral wall 34a of the element accommodating part 34, and clogging of the water repellent filter 72 is suppressed. Further, the water accumulated in the bottom wall 34c is discharged into the outlet side pipe 6 through the drain hole 34d (see FIG. 2) and the drainage channel 36.

According to the above, the following effects can be obtained in the first embodiment.
Since the gas flow part 70 is provided at a position facing the horizontal direction, the water liquefied in the gas detection chamber R is suppressed from collecting in the gas flow part 70. Therefore, clogging of the gas flow part 70 (water repellent filter 72) can be suppressed. In addition, since the clogging of the gas flow part 70 is suppressed in this way, the hydrogen detection accuracy can be improved, and the life of the hydrogen sensor 1 can be improved at low cost.

Since the gas flow portion 70 is provided on the side back portion SB of the peripheral wall 34a of the element housing portion 34, the diluted gas flowing in the outlet side pipe 6 wraps around the gas flow portion 70 and enters the gas detection chamber. It is possible to prevent the inside of R from becoming a high pressure and perform better sensing.
Since the element accommodating portion 34 is provided with the drain hole 34d and the drainage channel 36 bent to the downstream side, the water accumulated inside can be drained well.

The present invention is not limited to the first embodiment, and can be implemented in various forms.
In the first embodiment, the gas flow portion 70 is provided at a position corresponding to the side of the peripheral wall 34a of the element accommodating portion 34 when the flow direction of the dilution gas is the front-rear direction. However, the present invention is not limited to this. It is not something. For example, as shown in FIGS. 4A and 4B, the gas flow portion 70 is provided on the back portion of the peripheral wall 34a of the element accommodating portion 34 (the portion located on the most downstream side in the flow direction of the dilution gas). May be.
In the first embodiment, the outer peripheral shape of the cross section of the element accommodating portion 34 is circular. However, the present invention is not limited to this, and may be any shape such as an elliptical shape or a polygonal shape. .

[Second Embodiment]
The second embodiment of the present invention will be described below. Since this embodiment is obtained by changing the shape of the element housing portion of the first embodiment, the same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. In the drawings to be referred to, FIG. 5 is a cross-sectional view showing the inside of the hydrogen sensor according to the second embodiment, and FIG. 6 is a cross-sectional view taken along the line DD in FIG. It is E sectional drawing (b).

As shown in FIG. 5, the hydrogen sensor 1 ′ according to the second embodiment includes an element housing portion 37 having a shape different from that of the first embodiment.
The element housing portion 37 has the same shape and structure as the upper half portion of the element housing portion 34 of the first embodiment, while the element housing portion 37 is inner as the peripheral wall 37a of the lower half portion moves downward. It is formed in a tapered shape that is inclined toward the surface. Thereby, as shown to Fig.6 (a), the cross-sectional area of the element accommodating part 37 in the surface orthogonal to the flow direction of dilution gas is set to the cross-sectional area of 1st Embodiment (refer Fig.3 (a)). Therefore, the element accommodating portion 37 according to the present embodiment is less resistant to the flow of dilution gas than the element accommodating portion 34 according to the first embodiment. Further, the inclined peripheral wall 37a of the lower half portion of the element accommodating portion 37 is, as shown in FIG. 6 (b), on its side portion (a position that lies directly against the flow of dilution gas) in the first implementation. The gas flow part 70 similar to the form is provided.

  Further, a drain hole 34d, an explosion-proof filter 73, and a drainage channel 36 similar to those in the first embodiment are provided in the bottom wall 37c of the element housing portion 37. Here, since the peripheral wall 37a around the bottom wall 37c has a mortar shape as apparent from the above, the water droplets W liquefied in the gas detection chamber R are well collected in the drain hole 34d. It is designed to be discharged.

According to the above, the following effects can be obtained in the second embodiment.
By tilting the peripheral wall 37a of the lower half of the element accommodating portion 37, the cross-sectional area of the element accommodating portion 37 in the plane orthogonal to the flow of the dilution gas (the surface directly exposed to the dilution gas) is reduced. It can suppress as much as possible that 1 'becomes resistance with respect to the flow of dilution gas. In addition, as a result, the air off-gas discharged from the fuel cell 2 flows out smoothly, so that it is possible to suppress the energy consumption of the air supply.

The present invention is not limited to the second embodiment, and can be implemented in various forms.
In the second embodiment, the gas flow portion 70 is provided at a position corresponding to the side of the peripheral wall 37a of the element housing portion 37 when the flow direction of the dilution gas is the front-rear direction. However, the present invention is not limited to this. It is not something. For example, as shown in FIGS. 7A and 7B, the gas flow portion 70 is provided on the back portion of the peripheral wall 37a of the element accommodating portion 37 (the portion located on the most downstream side in the flow direction of the dilution gas). May be.

  In the second embodiment, the entire lower half (side back portion SB and front surface FF) of the element accommodating portion 37 is formed in a tapered shape (conical frustum shape). However, the present invention is not limited to this, and the element accommodating portion 37 is formed. It is sufficient that at least the side part (the part where the gas flow part 70 is provided) is inclined.

Further, the present invention is not limited to the above-described two embodiments (first and second embodiments), and can be implemented in various forms.
In the above embodiment, the gas to be detected is hydrogen, but the present invention is not limited to this, and may be another gas such as carbon monoxide or hydrogen sulfide. Furthermore, in the above-described embodiment, the contact combustion type gas sensor is adopted as the gas sensor. However, the present invention may be any gas sensor provided with a gas detection chamber. For example, other types such as a semiconductor type gas sensor may be used. It may be a gas sensor.

  In the above embodiment, the gas flow part 70 is provided in the side back part SB of the element accommodating parts 34 and 37. However, the present invention is not limited to this and may be provided in the front surface FF. However, in the case where the gas flow part 70 is provided in the side back part SB, the dilution gas enters the gas flow part 70 so that the inside of the gas detection chamber R can be prevented from becoming a high pressure. It is desirable to be provided on the side back portion SB.

It is a schematic structure figure showing a fuel cell system provided with a hydrogen sensor concerning a 1st embodiment. It is sectional drawing which shows the inside of the hydrogen sensor which concerns on 1st Embodiment. FIG. 3 is a cross-sectional view taken along line AA in FIG. 2 and a cross-sectional view taken along line BB in FIG. They are sectional drawing (a) which shows the modification of 1st Embodiment, and CC sectional drawing (b) of Fig.4 (a). It is sectional drawing which shows the inside of the hydrogen sensor which concerns on 2nd Embodiment. It is DD sectional drawing (a) of FIG. 5, and EE sectional drawing (b) of FIG. 6 (a). It is sectional drawing (a) which shows the modification of 2nd Embodiment, and FF sectional drawing (b) of Fig.7 (a).

Explanation of symbols

1 Hydrogen sensor (gas sensor)
34 element housing part 34a peripheral wall 34b groove 34c bottom wall 34d drain hole 35 seal member 36 drainage channel 50 gas detection element 51 detection element 52 temperature compensation element 60 heater 70 gas flow part 71 opening 72 water repellent filter 73 explosion proof filter FF Front R Gas detection chamber SB side back 2 Fuel cell 6 Outlet side piping (flow path)
6a Mounting seat (wall)
6b Inner surface 1 'Hydrogen sensor (gas sensor)
37 Element receiving portion 37a Perimeter wall 37c Bottom wall

Claims (6)

A gas detection element for detecting a gas to be detected contained in the gas;
An element accommodating portion for accommodating the gas detecting element;
A gas flow part for flowing the gas into and out of the element housing part,
A gas sensor provided on a wall of the flow path with the gas flow portion facing the flow path through which the gas flows,
The gas sensor comprises a hydrogen sensor for detecting hydrogen in the air off-gas discharged from the fuel cell,
The element accommodating portion is provided so as to protrude from the inner surface of the flow path,
The gas flow part is provided on the peripheral wall of the element housing part so as to face a substantially horizontal direction ,
A water repellent filter is provided at the opening of the gas flow part,
Wherein the element receiving portion, the gas sensor the gas detection element in a portion which does not overlap with the direction of introduction of the air off-gas is introduced toward the opening of the gas through portions, characterized in Rukoto arranged therein.   The gas sensor according to claim 1, wherein the gas flow part is provided on a side back part of a peripheral wall of the element housing part.   The gas sensor according to claim 2, wherein at least a side portion of the element accommodating portion is inclined so that a cross-sectional area of the element accommodating portion in a plane orthogonal to the gas flow direction is reduced. 4. The gas sensor according to claim 1, wherein a portion of the peripheral wall of the element housing portion that faces the opening of the gas flow portion is configured by a wall surface of the peripheral wall. 5. The gas sensor according to claim 1, wherein the gas flow part is provided in a tapered part in which a diameter of the element housing part is gradually reduced. The gas sensor according to claim 5, wherein a drain hole for discharging water liquefied in the element accommodating portion to the outside is provided at a top portion of the tapered portion forming a bottom wall of the element accommodating portion.

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