JP2006017619A - Gas concentration detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance explosion-proofness, and to accurately detect a gas concentration even when a large amount of moisture is contained in a measured gas such as that in a fuel cell system. <P>SOLUTION: The first explosion-proof body 10 (sensor protection tube 7 and metal wire gauze 9) is provided to cover a heater built-in type gas concentration sensor element 4, and the second explosion-proof body (capillary) 11 is provided in a passage for introducing the measured gas flowing in a main tube 50 into a gas concentration sensor element 4 side. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a gas concentration detection device that detects an oxygen concentration or a hydrogen concentration, and more particularly to a device applicable to a fuel cell system or the like.

Conventionally, as a method for detecting an oxygen concentration or a hydrogen concentration, it is known to use an oxygen ion conductive solid electrolyte as described in Patent Document 1. This method utilizes the property that an oxygen ion conductive solid electrolyte operates optimally at a high temperature of 600 ° C to 900 ° C.
However, this method has a safety problem when applied to a fuel cell system using hydrogen as a fuel. In other words, when the proton exchange membrane of the solid electrolyte breaks down in the fuel cell system, an abnormal situation occurs where oxygen (air) flows into the hydrogen line, and the hydrogen detector attached to the hydrogen line ignites as an ignition source. There is a fear. On the other hand, when hydrogen flows into the oxygen (air) line, there is a possibility that the oxygen detector may cause an explosion as an ignition source.

As an example for solving these problems, an explosion-proof sensor described in Patent Document 2 is disclosed. This explosion-proof sensor has an explosion-proof structure in which a wire mesh or a sintered metal is provided so as to cover a high-temperature solid electrolyte body. This explosion-proof structure has a flame arrester effect (effect as a flame prevention device) that prevents flame propagation, and prevents explosion propagation of the entire system because flame propagation to the outside of the detector is prevented.
Japanese Unexamined Patent Publication No. 2000-9985 JP 2000-65783 A

However, Patent Document 2 also relies only on the explosion-proof function of the explosion-proof structure, and if the explosion-proof function fails, safety cannot be maintained. Factors that cause the explosion-proof structure to lose its explosion-proof function include damage to the explosion-proof structure, corrosion, deterioration, or damage caused by contact with foreign matter.
Furthermore, in the case of a fuel cell system, not only is there a safety problem, but the gas to be measured has a relatively large amount of water and the temperature of the gas is 100 ° C. or less, so that the moisture in the gas to be measured undergoes a phase change. May occur, and the moisture concentration of the gas phase may change greatly. When such a phase change occurs, other gas component concentrations (oxygen concentration or hydrogen concentration) are affected, which causes a gas concentration detection error.

  The present invention has been made paying attention to such a problem. In addition to improving the explosion-proof property, the gas concentration is accurately adjusted even when the gas to be measured contains a large amount of moisture as in a fuel cell system or the like. It is an object of the present invention to provide a device capable of detecting the above.

  Therefore, according to the present invention, in a gas concentration detection device having a gas introduction pipe and a heating type gas concentration sensor element, a first explosion-proof body provided so as to cover the gas concentration sensor element, and a first explosion-proof body disposed in the gas introduction pipe And 2 explosion-proof bodies.

  According to the present invention, the explosion-proof property can be improved by the first explosion-proof body and the second explosion-proof body, so that the safety of the gas concentration detection device can be further improved. And even when a large amount of moisture is contained in the gas to be measured, the gas concentration can be accurately detected, and there is an effect that measurement error and reliability can be ensured.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a configuration of a gas concentration detection apparatus 1 according to the first embodiment. FIG. 2 is a view showing a cross section taken along line AA of FIG. The gas concentration detection device 1 detects an oxygen concentration or a hydrogen concentration as an object of the gas concentration to be detected, and these concentration detections can be detected in the same manner, or a measurement target composed of oxygen and hydrogen gas. Since the remaining hydrogen concentration can be detected by measuring the oxygen concentration in the gas, only an apparatus for detecting the oxygen concentration will be described here.

The gas concentration detection apparatus 1 is roughly composed of a sensor body 2 and a gas introduction pipe 3, and is inserted into a through hole 50a formed in a main pipe 50 through which a gas to be measured flows.
The sensor main body 2 includes a gas concentration sensor element 4, a sensor element support 5, a connector 6, and a sensor protective tube 7. The gas concentration sensor element 4 is supported by a sensor element support 5 on the base side, and a connector 6 is disposed on the outer periphery of the support 5, while the connector 6 covers the gas concentration sensor element 4. A sensor protection tube 7 is provided.

The gas concentration sensor element 4 is a heating type incorporating a heater (not shown), and detects the gas concentration (here, oxygen concentration). The gas concentration sensor element 4 has one end (the lower side in FIG. 1) protruding below the lower ends of the sensor element support 5 and the connector 6 and the other end (the upper side in FIG. 1) for electrical connection. Lead wire 8 is connected.
The sensor element support 5 serves as a gas seal, heat insulation and electrical insulation. The lead wire 8 transmits electricity for transmitting an electric signal from the gas concentration sensor element 4 or for heating a heater (not shown).

  The gas concentration sensor element 4 is integrally held by the connector 6 by the sensor element support 5. A sensor protective tube 7 is connected to the lower end (lower side of the figure) of the connector 6 so as to cover the gas concentration sensor element 4. The sensor protection tube 7 has a bottomed cylindrical shape with one end (lower side in the figure) closed, and the other end (upper side in the figure) is connected to the lower end of the connector 6. The sensor protective tube 7 is formed with windows (through holes) having a predetermined shape at predetermined intervals in the circumferential direction, and a metal mesh 9 is attached to the window (or has a metal mesh structure). As a result, gas can pass through the gas concentration sensor element 4.

  The sensor protective tube 7 and the wire mesh 9 are configured as a first explosion-proof body 10 having a flame propagation preventing function. Particularly in a fuel cell system or the like, since the gas to be measured is hydrogen gas, the first explosion-proof body 10 prevents flame propagation even when hydrogen gas is burned by the heat of the heater in the gas concentration sensor element 4. To do. The explosion-proof body 10 may be constituted by a wire mesh 9 as a whole of the sensor protection tube 7. If the gas to be measured can pass through the gas concentration sensor element 4 through the gas concentration sensor element 4, the explosion-proof body 10 may be configured as a mesh. The size doesn't matter.

  The gas introduction pipe 3 is inserted into the through hole 50a of the main pipe 50, and introduces the gas to be measured flowing in the main pipe 50 into the gas concentration sensor element 4 (in the first explosion-proof body 10) of the sensor body 2. . The gas introduction tube 3 has a hollow cylindrical shape, and a large number of thin tubes 11 having the same length as the gas introduction tube 3 are arranged inside the gas introduction tube 3 without a gap (see FIGS. 1 and 2). The thin tube 11 has a thin wall thickness of, for example, 0.1 mm or less, and the inner diameter of the thin tube 11 is sufficiently smaller than the inner diameter of the gas introduction tube 3, which is about 0.1 to 0.3 mm here. This thin tube 11 has a function as a second explosion-proof body and prevents flame propagation even when hydrogen gas is burned by the heat of the heater in the gas concentration sensor element 4.

Note that the second explosion-proof body provided in the gas introduction pipe 3 may have a honeycomb structure (see FIG. 2). That is, an object of the present invention is to provide an explosion-proof function in the passage that guides the gas to be measured flowing in the main pipe 50 to the sensor body 2. For this reason, it is sufficient for the second explosion-proof body to have a strength capable of passing the gas to be measured and preventing flame propagation.
The gas introduction pipe 3 is designed to protrude outward from the main pipe 50 by a predetermined length. Thereby, the outer periphery of the gas introduction pipe 3 can be cooled (air cooled) by the outside air. In addition, the moisture concentration in the gas to be measured can be reduced and stabilized, and the gas concentration detection accuracy is improved.

The gas introduction pipe 3 is held by a sensor holder 12 disposed between the sensor main body 2 (connector 6). The sensor holder 12 has a substantially hollow cylindrical shape, and holds the upper end portion of the gas introduction pipe 3 by a heat insulator 13 disposed at the lower end portion.
A female screw 12a is formed on the upper inner peripheral surface of the sensor holder 12, and a male screw 6a formed on the outer periphery of the boss portion of the connector 6 is screwed into this part 12a. Between the upper end surface 12b of the sensor holder 12 and the shoulder 6b of the connector 6, a gasket 14 is disposed in a compressed state.

The operation of the above configuration will be described.
As a first action, the narrow tube 11 (second explosion-proof body) disposed in the gas introduction tube 3 has an effect of preventing the propagation of flame due to its small inner diameter. Although the sensor body 2 having a high temperature portion of 500 ° C. or more includes the first explosion-proof body 10, even if the first explosion-proof body 10 fails in function, the flame generated in the sensor body 2 by the thin tube 11 is Propagation to the tube 50 side can be prevented, and the explosion-proof property is further enhanced.

  As a second action, the gas introduction pipe 3 is provided to protrude outward from the main pipe 50 by a predetermined length, so that the outer periphery of the gas introduction pipe 3 is cooled (air-cooled) by outside air, so that the gas to be measured The water vapor is condensed to reduce the water vapor concentration and stabilize the water vapor concentration. This effect will be described in more detail. The concentration of each component in the gas to be measured is directly affected by the change in the water vapor concentration.

  For example, in the case of a fuel cell system, when the amount of water generated is large and the water state (water vapor state or liquid water state) changes greatly depending on the operating state, the concentration of gas (oxygen or hydrogen) also changes greatly due to the influence. . Moisture is very troublesome because it undergoes a phase change (gas-liquid). For this reason, the water vapor concentration (gas temperature) is lowered by the thin tube 11 arranged in the gas introduction tube 3, and the gas concentration is detected by reducing the influence of moisture change.

Here, the heat insulator 13 makes it difficult to transfer the heat of the sensor holder 12 to the gas introduction pipe 3 side. That is, in order to lower the temperature of the gas to be measured that reaches the sensor body 2 (reducing water vapor), the heat insulator 13 also works effectively.
The length of the gas introduction pipe 3 is a predetermined length that can ensure the required accuracy of gas concentration detection, and is preferably shorter considering the responsiveness, but in the case of the present invention (the multi-tube structure has a large cooling surface area). In the case of ()), it is possible to condense the water vapor efficiently, so that there is an effect that it can be shortened.

  According to the present embodiment, the gas introduction pipe 3 for introducing the measurement gas from the main pipe 50 through which the measurement gas flows, and the heating type gas concentration sensor element 4 for detecting the concentration of the introduced measurement gas are provided. The gas concentration detection apparatus has a first explosion-proof body 10 provided so as to cover the gas concentration sensor element 4 and a second explosion-proof body arranged in the gas introduction pipe 3. For this reason, since the explosion-proof property can be improved by the first explosion-proof body 10 and the second explosion-proof body, the safety of the gas concentration detection device 1 can be further improved.

According to this embodiment, the second explosion-proof body is configured by bundling a plurality of thin tubes 11 in the gas introduction tube 3. For this reason, it is possible to sufficiently secure a passage for introducing the gas to be measured from the main pipe 50, and to prevent the gas concentration detection response from being impaired.
According to this embodiment, the second explosion-proof body has a honeycomb structure in the gas introduction pipe 3 (FIG. 2). For this reason, it is possible to sufficiently secure a passage for introducing the gas to be measured from the main pipe 50, and to prevent the gas concentration detection response from being impaired.

Further, according to the present embodiment, the gas introduction pipe 3 is formed to protrude outward from the main pipe 50 by a predetermined length. For this reason, even when the gas to be measured contains a large amount of water, the gas introduction pipe 3 is cooled by the outside air, and the water vapor concentration in the gas to be measured can be stabilized. As a result, the gas concentration can be accurately detected, and measurement errors and reliability can be ensured.
Next, a second embodiment will be described with reference to FIGS. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  In this embodiment, as shown in FIG. 3, the length of the several thin tube 11 which functions as a 2nd explosion-proof body is each changed. Thereby, as for the 2nd explosion-proof body, the front-end | tip parts (11a, 11c) which protrude from the main pipe 50 side (lower side of FIG. 3) of the gas introduction pipe 3 become a mountain shape. Further, the second explosion-proof body has a rear end portion (11b) on the gas concentration sensor element 4 side at a position higher than a front end portion on the main pipe 50 side, and a downstream side of the measured gas flow in the main pipe 50 (FIG. 3). It is formed so that it becomes lower in the direction in which gravity acts.

Here, the “mountain shape” at the tip of the second explosion-proof body (narrow tube 11) is not only formed in a conical shape on the lower side, but also the lowest end point of the narrow tube 11 perpendicular to the gas flow direction to be measured. It shall contain the shape which makes the formed ridgeline.
Since the tip of the second explosion-proof body has a mountain shape, first, the gas to be measured flows into the sensor main body 2 side at the inlet opening 11a opposite to the flow of the gas to be measured under dynamic pressure. At this time, the water vapor contained in the gas to be measured is condensed to generate condensed water.

  Condensed water has a part that falls below the narrow pipe 11 (in the main pipe 50) and a part that is carried to the gas concentration sensor element 4 side by the gas flow, but here, the second that opens to the gas concentration sensor element 4 side. Since the rear end portion of the explosion-proof body is shaped to be lower in the direction in which gravity acts on the downstream side, moisture carried to the gas concentration sensor element 4 side is easily carried to the downstream side (dashed arrow in the sensor side opening 11b). See), and is discharged into the main pipe 50 through the outlet opening 11c of the second explosion-proof body.

  The inlet opening 11a is formed to be inclined so that the inclined surface faces the upstream side of the gas to be measured, while the outlet opening 11c has an inclined surface that faces the downstream side of the gas to be measured. It is formed so as to be inclined (see FIG. 3). Therefore, the pressure at the outlet opening 11c is lower than that at the inlet opening 11a, and the gas to be measured (including condensed water) is, as indicated by the broken arrow, the inlet opening 11a → the sensor side opening 11b → the outlet opening 11c. It flows smoothly in the order. As a result, the gas to be measured detected by the gas concentration detection device 1 can be replaced quickly, and the detection response of the detection device 1 is improved.

In addition, as shown in FIG. 4, while increasing the inclination of the inlet opening 11a of the gas introduction pipe 3 (narrow tube 11), while reducing the inclination of the outlet opening 11c (L1 <L2), there is much condensed water. Even in this case, a smooth gas flow may be obtained.
According to the present embodiment, the second explosion-proof body (narrow tube 11) has a mountain-like shape at the tip portions (inlet opening portion 11a, outlet opening portion 11c) protruding from the tip of the gas introduction tube 3 on the main tube 50 side. is there. For this reason, after introduce | transducing to-be-measured gas into the sensor main body 2 side from the inlet opening part 11a in a 2nd explosion-proof body, it can flow smoothly from the outlet opening part 11. FIG.

  Further, according to the present embodiment, the second explosion-proof body has a rear end portion (sensor side opening portion 11b) on the gas concentration sensor element 4 side and a front end portion (inlet opening portion 11a, outlet opening portion 11c) on the main tube 50 side. It is formed so that it is in a higher position and becomes lower in the direction in which gravity acts on the downstream side of the gas flow to be measured in the main pipe 50. For this reason, the condensed water generated by compression of the gas to be measured when introduced into the gas concentration sensor element 4 side can be efficiently discharged.

Next, a third embodiment will be described with reference to FIG. In the present embodiment, the same components as those in the second embodiment are denoted by the same reference numerals and description thereof is omitted.
In the present embodiment, the sampling tube portion 3 a for introducing the measurement gas from the main pipe 50 is formed at the tip of the gas introduction pipe 3 in parallel with the flow direction of the measurement gas in the main pipe 50. The sampling part 3b of the sample sampling pipe part 3a is opened on the upstream side of the main pipe 50, and the gas to be measured is introduced from the inlet opening part 11a. For this reason, as shown by the dashed arrow, the gas to be measured (including condensed water) is introduced from the inlet opening 11a to the sensor body 2 side, and the inlet opening 11a → the sensor side opening 11b → the outlet opening 11c in this order. Flows smoothly. Then, the gas to be measured and the condensed water are discharged by the discharge portion 3c of the sampling tube portion 3a.

Also here, as shown in FIG. 4, while increasing the inclination of the inlet opening 11a of the gas introduction pipe 3 (narrow pipe 11), while reducing the inclination of the outlet opening 11c (L1 <L2), condensed water Even when there is a large amount of gas, a smooth gas flow may be obtained.
Further, the tip of the second explosion-proof body (inlet opening 11a, outlet opening 11c) does not need to reach the bottom of the sampling tube portion 3a. For example, the length is the same as that of the gas introduction tube 3 as in the first embodiment. It may be.

  According to the present embodiment, the gas introduction pipe 3 is arranged at the tip thereof in parallel with the flow direction of the gas to be measured in the main pipe 50, and the sampling pipe part 3 a for introducing the gas to be measured from the main pipe 50. Have Therefore, the gas to be measured can be easily introduced to the sensor body 2 side through the sampling portion 3b and the inlet opening portion 11a of the sample sampling tube portion 3a, and the sensor side opening portion 11b, the outlet opening portion 11c and the discharge portion 3c are provided. Gas to be measured (including condensed water) can be discharged.

Sectional drawing which shows 1st Embodiment Sectional drawing in the AA line of FIG. Sectional drawing which shows 2nd Embodiment Sectional drawing which shows the lower end part of the gas introduction pipe 3 Sectional drawing which shows 3rd Embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas concentration detection apparatus 2 Sensor main body 3 Gas introduction pipe 4 Gas concentration sensor element 5 Sensor element support body 10 1st explosion-proof body 11 Narrow tube (2nd explosion-proof body)
11a Inlet opening (tip)
11b Sensor opening (rear end)
11c Exit opening (tip)
50 Main pipe 50a Through hole

Claims (7)

In a gas concentration detection apparatus having a gas introduction pipe for introducing a measurement gas from a main pipe through which the measurement gas flows, and a heating type gas concentration sensor element for detecting the concentration of the introduced measurement gas,
A first explosion-proof body provided to cover the gas concentration sensor element;
A second explosion-proof body disposed in the gas introduction pipe;
A gas concentration detection device comprising:   The gas concentration detection device according to claim 1, wherein the second explosion-proof body is configured by bundling a plurality of thin tubes in the gas introduction tube.   The gas concentration detection device according to claim 1, wherein the second explosion-proof body has a honeycomb structure in the gas introduction pipe.   The gas according to any one of claims 1 to 3, wherein the second explosion-proof body has a chevron-shaped tip portion protruding from a tip on the main pipe side of the gas introduction pipe. Concentration detector.   In the second explosion-proof body, the rear end portion on the gas concentration sensor element side is located higher than the front end portion on the main pipe side, and the downstream side of the gas flow to be measured in the main pipe becomes lower in the direction in which gravity acts. The gas concentration detection device according to any one of claims 1 to 4, wherein the gas concentration detection device is formed as described above.   The gas introduction pipe has a sampling pipe section that is arranged at a tip portion thereof in parallel with a flow direction of the gas to be measured in the main pipe and introduces the gas to be measured from the main pipe. The gas concentration detection apparatus according to any one of claims 1 to 5.   The gas concentration detection device according to any one of claims 1 to 6, wherein the gas introduction pipe is formed to protrude outward from the main pipe by a predetermined length.

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