JP5192919B2 - Gas sensor - Google Patents

Description

  The present invention relates to a gas sensor that detects a gas to be detected such as hydrogen having a low specific gravity.

  In general, a polymer electrolyte fuel cell forms an MEA (Membrane Electrode Assembly) by sandwiching both sides of a solid polymer membrane between an anode (fuel electrode) and a cathode (oxygen electrode). A single fuel cell stack is configured by stacking a plurality of single cells sandwiched between a pair of separators. Then, hydrogen (fuel gas) is supplied to the anode, and air (oxidant gas) is supplied to the cathode. An electrode reaction occurs at the anode and the cathode, and the fuel cell generates power.

  Since unconsumed hydrogen is discharged from such a fuel cell, a hydrogen sensor is provided in the flow path of the off gas discharged from the fuel cell, and the hydrogen concentration in the off gas is monitored by this hydrogen sensor ( Patent Document 1).

WO2003 / 042678

However, if water vapor in the off-gas is condensed on the gas detection elements constituting such a hydrogen sensor, and the condensed water adheres to the gas detection element, the detection accuracy is lowered.
Accordingly, an object of the present invention is to provide a gas sensor in which condensed water is unlikely to adhere to the gas detection element.

As means for solving the above-mentioned problems, the present invention provides a cylindrical housing having a gas detection chamber into which a gas to be detected is taken and having an inlet for the gas to be detected at the bottom, and a vertical upper side of the housing. A base that closes the opening of the base, a stay provided so as to protrude vertically downward from the base, a gas detection element that is connected to the stay and detects a gas to be detected, and a gas detection element on the peripheral wall of the housing A heater for heating the chamber , wherein the base is recessed vertically upward from the peripheral part toward the center part, and around each stay of the top wall surface of the base, The gas sensor is characterized in that a recess is formed that surrounds each stay and is recessed upward .

According to such a gas sensor, since the base is recessed vertically upward from the peripheral part toward the central part, even if condensed water is generated at the base, the condensed water flows toward the housing. Thereby, dew condensation water becomes difficult to adhere to a gas detection element.
Moreover, according to such a gas sensor, the dew condensation water that flows toward the periphery of the base, that is, toward the peripheral wall of the housing can be heated and vaporized by the heater. Thereby, vaporized dew condensation water, that is, water vapor is easily discharged to the outside.

  In the gas sensor, it is preferable that the top wall surface is uneven in a circumferential direction, and a portion of the top wall surface from which the stay protrudes is higher than a portion adjacent in the circumferential direction.

  As means for solving the above-mentioned problems, the present invention provides a cylindrical housing having a gas detection chamber into which a gas to be detected is taken and having an inlet for the gas to be detected at the bottom, and a vertical upper side of the housing. A base that closes the opening of the gas detector, a gas detection element that protrudes vertically downward from the base, and a heater that heats the gas detection chamber on the peripheral wall of the housing. In the gas sensor, the base is recessed vertically upward from the peripheral part toward the central part, and the heater includes a peripheral wall part disposed along an inner peripheral surface of the housing, and a lower end of the peripheral wall part A bottom wall portion extending radially inward from the portion and having a through hole that overlaps the introduction port, and the peripheral portion of the base is connected to the peripheral wall portion of the heater A gas sensor for the butterflies.

  According to the present invention, it is possible to provide a gas sensor in which condensed water hardly adheres to the gas detection element.

<< First Embodiment >>
First, a first embodiment of the present invention will be described with reference to FIGS.

≪Configuration of hydrogen sensor≫
As shown in FIGS. 1 to 5, the hydrogen sensor 1 (gas sensor) according to this embodiment is a sensor that detects hydrogen (detected gas) having a specific gravity smaller than that of nitrogen. Here, the case where the hydrogen sensor 1 detects the hydrogen concentration in the off-gas pipe 105 (see FIG. 2) through which off-gas discharged from the fuel cell constituting the fuel cell system flows is illustrated.

  The hydrogen sensor 1 includes a case 10, a housing 20 projecting from the lower surface of the case 10, a base 30 that closes the opening 26 above the housing 20, a gas detection element 41 that is housed in the housing 20 and detects hydrogen. 41, a laminated body 50 provided in the introduction port 24 at the lower part of the housing 20, and a heater 60 disposed in the housing 20.

<Case>
The case 10 has a rectangular parallelepiped shape, and is a container made of polyphenylene sulfide, for example, and accommodates the control board 11. Flange portions 12 and 12 are formed at both ends of the case 10 in the longitudinal direction, and a collar 13 is attached to each flange portion 12. Then, as shown in FIG. 2, the bolts 14 inserted into the respective collars 13 are fastened to a mounting seat 105 </ b> A formed on the offgas pipe 105 through which the offgas flows, whereby the hydrogen sensor 1 is fixed to the offgas pipe 105. It has become so.

  The control substrate 11 has a function of calculating the hydrogen concentration based on signals from the gas detection elements 41 and 41. Further, the control board 11 has a function of turning the heater 60 on and off appropriately.

<Housing>
The housing 20 is a substantially bottomed cylindrical body (see FIGS. 3 and 5), and is fitted in a mounting hole formed in the peripheral wall portion of the offgas pipe 105 (see FIG. 2). An O-ring 21 is interposed between the housing 20 and the off-gas pipe 105 to improve airtightness so that off-gas does not leak.

  Such a housing 20 has a cylindrical peripheral wall portion 22 and a bottom wall portion 23. A circular through hole is formed in the center of the bottom wall portion 23, and this through hole serves as an inlet 24 that functions as an off-gas inlet / outlet containing hydrogen (a gas to be detected). Further, the inside of the housing 20 is a gas detection chamber 25 into which off gas is taken.

  Furthermore, the housing 20 is made of a material having thermal conductivity, for example, a resin such as polyphenylene sulfide (PPS) or polybutylene terephthalate (PBT), or a metal. Thereby, the heat of the heater 60 is conducted to the gas detection element 41, the water repellent filter 51, and the explosion-proof filter 52 through the housing 20.

<Base>
The base 30 closes the opening 26 on the vertical upper side of the peripheral wall portion 22 constituting the housing 20 and constitutes the top wall portion of the gas detection chamber 25. The base 30 is formed so as to be recessed vertically upward from the peripheral part toward the central part. That is, the lower surface of the base 30, that is, the top wall surface 31 above the gas detection chamber 25 is a substantially hemispherical concave curved surface that is recessed vertically upward, its peripheral edge is the lowest, and gradually increases toward the center, It is formed to be the highest at the center.

Of the top wall surface 31 of the base 30, the periphery of a through hole through which a stay 42 to be described later penetrates is recessed vertically upward to form a recess 32 (see FIG. 4).
The base 30 is formed of a material having thermal conductivity, like the housing 20. Further, it is preferable that a water repellent layer is formed on the inner surfaces of the top wall 31 and the recess 32 in order to promote the flow of the dew condensation water.

<Gas detection element>
The gas detection element 41 is an element that detects the hydrogen concentration in the off-gas taken into the gas detection chamber 25, is provided so as to protrude vertically downward from the base 30, and is disposed in the gas detection chamber 25. .
More specifically, the upper ends of two stays 42, 42 are connected to the lower surface of the control board 11, each stay 42 penetrates the case 10 and the base 30, and the lower end of each stay 42 is in the gas detection chamber 25. It extends to. The intermediate portion of each stay 42 is fixed to the base 30 with an epoxy resin or the like.
The gas detection element 41 is connected to the lower ends of the stays 42 and 42 so that the control substrate 11 detects the resistance value and the like of the gas detection element 41 corresponding to the hydrogen concentration via the stays 42 and 42. It has become.

Note that the type, number, and arrangement of the gas detection elements 41 are appropriately changed according to the hydrogen concentration detection method.
For example, when the hydrogen detection method is a gas catalytic combustion method, the gas detection element 41 is configured by a pair of a detection element and a temperature compensation element. Then, the hydrogen concentration is detected based on the electric resistance difference between the detection element and the temperature compensation element by utilizing the heat generated when hydrogen contacts each element and burns.
In addition, when the hydrogen detection method is a semiconductor method, the gas detection element 41 is configured by a pair of a detection element and a detection element, and has a resistance value generated when hydrogen comes into contact with or leaves from oxygen on the surface of each element. Based on this, the hydrogen concentration is detected.

<Laminated body>
The laminated body 50 includes a water-repellent filter 51 and an explosion-proof filter 52, and is configured integrally by stacking the explosion-proof filter 52 and the water-repellent filter 51 in this order toward an off-gas pipe 105 that is away from the gas detection element 41. In addition, it is a thin disc body having a two-layer structure. And the laminated body 50 is attached to the housing 20 so that the inlet 24 may be covered.

The water repellent filter 51 is a filter that transmits gas but does not transmit liquid contained in the gas, and is made of, for example, a tetrafluoroethylene film. As a result, while the gaseous off-gas is taken into the gas detection chamber 25, the liquid water contained in the off-gas is repelled by the water repellent filter 51 and does not enter the gas detection chamber 25.
The explosion-proof filter 52 is a filter for ensuring explosion-proof properties, and is made of, for example, a metal mesh or a porous body that allows liquid water to pass through.
In addition to this, for example, a disk-shaped heater for heating the water-repellent filter 51 and the explosion-proof filter 52 may be provided between the water-repellent filter 51 and the explosion-proof filter 52.

<Heater>
The heater 60 is a substantially bottomed cylindrical (bowl type) electric heater disposed along the inner wall surface of the housing 20, and extends inward in the radial direction from the cylindrical peripheral wall portion 61 and the lower end portion of the peripheral wall portion 61. And a bottom wall portion 62 in which a through hole 63 substantially overlapping with the introduction port 24 is formed. Such a heater 60 is composed of, for example, a PTC heater or a ceramic heater, and the peripheral wall portion 61 and the bottom wall portion 62 are integrally formed so as to generate heat integrally.

  Further, the heater 60 is connected to the control board 11 via a wiring (not shown). Then, the control board 11 performs ON / OFF control of the heater 60 based on the temperature and humidity of the gas detection chamber 25 so that condensed water is not generated. The temperature / humidity of the gas detection chamber 25 is detected by a temperature / humidity sensor (not shown) provided in the gas detection chamber 25.

≪Operation and effect of hydrogen sensor≫
Next, the function and effect of the hydrogen sensor 1 will be described.

<When the hydrogen sensor is activated (when the heater 60 is turned on)>
First, the operation of the hydrogen sensor 1 in which the fuel cell (not shown) generates power and the hydrogen sensor 1 detects the hydrogen concentration in the off-gas discharged from the fuel cell will be described.
Off-gas containing hydrogen enters the gas detection chamber 25 through the water-repellent filter 51 and the explosion-proof filter 52. Then, the hydrogen in the off gas comes into contact with the gas detection element 41, and the hydrogen concentration is detected. Here, the off-gas passes through the water-repellent filter 51 and the explosion-proof filter 52, then proceeds vertically upward in the gas detection chamber 25, and is blown onto the top wall 31 of the base 30. Thereby, water vapor contained in the off-gas is condensed on the ceiling wall surface 31, and the condensed water adheres to the ceiling wall surface 31.

The condensed water is guided radially outward, that is, toward the peripheral wall portion 61 of the heater 60 along the ceiling wall 31 that is lowered radially outward (see arrow A1 in FIG. 5). At this time, since the recess 32 is formed around the stay 42, the dew condensation water bypasses the stay 42 (see arrow A <b> 2 in FIG. 5), and the dew condensation water does not adhere to the stay 42. Thereby, the condensed water does not flow vertically downward along the stay 42, and the condensed water is prevented from adhering to the gas detection element 41.
Also, the dew condensation water that has reached the peripheral wall 61 of the heater 60 is heated by the heater 60 that generates heat, vaporizes into water vapor, and can be discharged to the outside through the water repellent filter 51 and the explosion proof filter 52.

<When the hydrogen sensor is stopped (when the heater 60 is turned off)>
Next, a description will be given of the time when the fuel cell power generation is stopped, the heater 60 is turned off, and the hydrogen sensor 1 is stopped without detecting the hydrogen concentration.
When the heater 60 is turned off, the temperature of the housing 20 and the base 30 gradually decreases. At this time, the temperature of the central portion of the base 30 far from the heater 60 tends to decrease. When the temperature of the base 30 is thus lowered, water vapor remaining in the gas detection chamber 25 is condensed on the top wall surface 31 of the base 30, and the dew condensation water adheres to the top wall surface 31.

  This condensed water is guided toward the radially outer side, bypassing the stay 42, as in the case of the operation of the hydrogen sensor 1 (see arrow A1 in FIG. 5). As a result, the condensed water does not flow downward along the stay 42, and the condensed water is prevented from adhering to the gas detection element 41.

<< Second Embodiment >>
Next, a second embodiment of the present invention will be described with reference to FIGS.
Similarly to the top wall surface 31 of the base 30 according to the first embodiment, the top wall surface 71 of the base 70 according to the second embodiment is recessed vertically upward from the peripheral part toward the center part. A recess 72 is formed around. The ceiling wall surface 71 is uneven in the circumferential direction (see FIGS. 7 and 8), and the condensed water adhering to the ceiling wall surface 71 is flowing in the lower part of the ceiling wall surface 71 in the circumferential direction (FIG. 7, arrow). A3), and flows outward in the radial direction (see FIG. 7, arrow A4). The portion of the top wall 71 through which the stay 42 penetrates is higher than the other portions in the circumferential direction, and it is difficult for dew condensation water to adhere to the stay.

  As mentioned above, although one suitable embodiment of the present invention was described, the present invention is not limited to the above-mentioned embodiment, and can be changed as follows, for example, in the range which does not deviate from the meaning of the present invention.

In the above-described embodiment, the case where the gas to be detected is hydrogen is exemplified, but other gases may be used.
In the above-described embodiment, the case where the hydrogen sensor 1 is provided downstream of the fuel cell and the concentration of hydrogen in the off-gas discharged from the fuel cell is detected is exemplified. However, the mounting position of the hydrogen sensor 1 is not limited to this. For example, a vehicle compartment or a tank chamber in which a hydrogen tank is disposed may be used.

It is a top view of the hydrogen sensor concerning a 1st embodiment. It is a longitudinal cross-sectional view of the hydrogen sensor which concerns on 1st Embodiment. It is a longitudinal cross-sectional view of the principal part of the hydrogen sensor which concerns on 1st Embodiment, and respond | corresponds to the X2-X2 line cross section of FIG. It is an enlarged view of the base part of a hydrogen sensor. It is the X1-X1 sectional view taken on the line of the hydrogen sensor shown in FIG. It is a longitudinal cross-sectional view of the principal part of the hydrogen sensor which concerns on 2nd Embodiment, and corresponds to FIG. It is a plane sectional view of the hydrogen sensor concerning a 2nd embodiment. It is the X2-X2 sectional view taken on the line of the hydrogen sensor shown in FIG.

Explanation of symbols

1 Hydrogen sensor (gas sensor)
20 Housing 24 Introduction Port 25 Gas Detection Chamber 26 Opening 30 Base 31 Top Wall 41 Gas Detection Element 60 Heater

Claims (3)

A cylindrical housing having a gas detection chamber into which the gas to be detected is taken, and an inlet for the gas to be detected at the bottom;
A base that closes an opening on a vertical upper side of the housing;
A stay provided so as to protrude vertically downward from the base ;
A gas detection element connected to the stay for detecting a gas to be detected;
A heater for heating the gas detection chamber on the peripheral wall of the housing;
A gas sensor comprising:
The base is recessed vertically upward as it goes from the peripheral part to the central part ,
The gas sensor according to claim 1, wherein a recess that surrounds each stay and is recessed upward is formed around each stay in the top wall surface of the base .   The top wall is uneven in the circumferential direction,
  The portion of the top wall surface from which the stay protrudes is higher than the adjacent portion in the circumferential direction
  The gas sensor according to claim 1. A cylindrical housing having a gas detection chamber into which the gas to be detected is taken, and an inlet for the gas to be detected at the bottom;
A base that closes an opening on a vertical upper side of the housing;
A gas detecting element provided to protrude vertically downward from the base and detecting a gas to be detected;
A heater for heating the gas detection chamber on the peripheral wall of the housing;
A gas sensor comprising:
The base is recessed vertically upward as it goes from the peripheral part to the central part ,
The heater includes a peripheral wall portion disposed along an inner peripheral surface of the housing, and a bottom wall portion having a through hole extending radially inward from a lower end portion of the peripheral wall portion and overlapping the introduction port. Prepared,
The gas sensor according to claim 1 , wherein the peripheral portion of the base is connected to the peripheral wall portion of the heater .

Images