JP2007309908A - Hydrogen sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the detection precision by reducing the amount of attachment of water to the hydrogen sensor to be used in the fuel cell system, etc. <P>SOLUTION: A detection head 13, with built in detection element 24 and the reference element 23 arranged in the detection gas flow flowing in the piping 2, is protruded into the piping from the wall part of the piping 2, while being supported by the support arm 12 which is made of a heat insulating material. The detection head 13 is provided with a gas guide in port 25 for guiding the detection gas to the detection element 24, in a direction reverse to the gas flow direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydrogen sensor used for detecting a hydrogen concentration in a fuel cell system or the like.

As a conventional hydrogen sensor, there is one as described in Patent Document 1.
This is to detect the hydrogen concentration of the gas to be detected based on the difference in electrical resistance between the detection element that responds to the hydrogen concentration of the gas to be detected and the reference element (temperature compensation element), and the pipe through which the gas to be detected flows. Is installed with the gas inlet facing downward on the wall (ceiling) on the upper side in the gravity direction.
In addition, in a fuel cell such as a solid polymer membrane fuel cell, a reactive gas (hydrogen or air) supplied to the fuel cell is actively humidified in order to maintain the ionic conductivity of the solid polymer electrolyte membrane. Furthermore, water is generated together with heat of reaction by an electrochemical reaction during power generation of the fuel cell. Therefore, the reaction gas is hot and humid, and the hydrogen sensor used in the fuel cell system is exposed to these hot and humid gases.

However, when humidified water, generated water, or the like adheres to the detection element of the hydrogen sensor, local temperature distribution is uneven on the surface of the detection element, and there is a risk of sensitivity reduction or element destruction.
Therefore, in Patent Document 1, a heater is incorporated in the hydrogen sensor, the temperature of the sensing element storage space is controlled to be higher than the gas temperature on the upstream side of the hydrogen sensor, and the relative humidity of the gas guided to the sensing element is set to the upstream gas. The relative humidity is surely lowered.
JP 2003-294675 A

  The conventional hydrogen sensor is installed on the ceiling of the pipe where the gas to be detected flows with the gas inlet facing downward, so once a high concentration of hydrogen gas is introduced, the specific gravity is low, so it is detected High concentration hydrogen stays in the element storage space, and even if the hydrogen concentration of the gas to be detected decreases, the high concentration hydrogen that has stayed for a while will be mistakenly detected as the hydrogen concentration of the gas to be detected. There is a problem of poor responsiveness.

In addition, because the heater is used to heat the surroundings of the sensing element above the dew point temperature or the boiling point of water, the power consumption is large, and in addition, the warm-up time until the sensing element operates effectively at startup However, there is a problem that the system using this for control is slow to start.
In view of such a problem, the present invention aims to improve responsiveness, power consumption, and the like while minimizing the adhesion of water to the sensing element.

  For this reason, in the present invention, the detection unit including the detection element and the reference element is supported by a support made of a heat insulating material protruding from the wall portion of the pipe through which the gas to be detected flows into the pipe, A gas introduction port that is arranged in the flow and guides the gas to be detected to the detection element is opened to the detection unit in a direction opposite to the flow of the gas to be detected.

According to the present invention, the detection unit is separated from the inner wall of the pipe toward the center of the pipe and thermally insulated, so that condensation occurs when the pipe temperature is low, or even if the detected gas is cooled and condensed after the operation stops, Since the dew condensation of the detection element can be prevented, the detection accuracy can be improved without using a heater.
Further, since the gas introduction port is opened in the direction opposite to the flow of the gas to be detected, even if the gas to be detected contains liquid droplets (splash water), the liquid droplets do not hit the detection element. For this reason, it is possible to prevent temporary detection failure due to droplet adhesion and deterioration / damage of the detection element due to thermal shock.

  In addition, since the detection unit is arranged in the high flow velocity space of the gas to be detected, the gas in the detection element storage space can be quickly replaced, and the response of hydrogen concentration detection can be improved.

Embodiments of the present invention will be described below with reference to the drawings.
First, a first embodiment of the present invention will be described with reference to FIG.
The hydrogen sensor 10 of the present invention is attached to the pipe 2 through which the gas to be detected flows, and detects the hydrogen concentration of the gas to be detected.
The hydrogen sensor 10 includes a body 11 attached to an outer wall surrounding the sensor attachment hole of the pipe 2, a support arm (support) 12 extending from the body 11 through the sensor attachment hole of the pipe 2 to the center of the pipe 2, It comprises a detection head (detection unit) 13 supported at the tip of the support arm 12.

The body 11 forms a case of the signal adjustment circuit 14, has a fixing flange to the outer wall of the pipe 2, and is attached by a bolt 15. Further, a sealing material 16 such as an O-ring is interposed on the joint surface between the pipe 2 and the body 11 so as to surround the sensor mounting hole, thereby preventing gas leakage. An external wiring 17 is led out of the body 11 from the signal adjustment circuit 14.
The support arm 12 supports the detection head 13 and is disposed in the flow of the gas to be detected in the pipe 2 (support), and heat of the detection head 13 is radiated to the pipe 2 through the body 11. In order to reduce this, it is made of heat insulating material such as industrial plastic. In addition, a through-hole through which the wiring 18 that connects the signal adjustment circuit 14 in the body 11 and the detection element in the detection head 13 and the like is provided is provided in the support arm 12 so that a gas leakage path is not formed after the wiring is assembled. Is filled.

  The detection head 13 includes a detection element and a reference element (detection unit). Here, the outer wall of the detection head 13 is substantially hemispherical and protrudes toward the upstream side in the flow direction of the gas to be detected in the pipe 2. The cross-sectional area increases toward the downstream side, and is constituted by a shell body 19 having an open downstream end portion having a maximum cross-sectional area A (the cross-sectional area in the radial direction D of the pipe is maximum). The shell 19 is made of a material (for example, SUS316L) that has a high thermal conductivity so as to immediately equilibrate to the temperature of the test gas and that does not deteriorate with the detection gas.

Then, the inside of the shell 19 is partitioned by a partition wall 20 at an intermediate portion in the flow direction, and a reference element storage space 21 sealed by a front end side outer wall of the shell body 19 is formed on the upstream side of the partition wall 20. In addition, a sensing element storage space 22 opened at the rear end of the shell 19 is formed.
A reference element 23 is stored in the reference element storage space 21, and a detection element 24 is stored in the detection element storage space 22.

Since the reference element 23 is mainly used for temperature compensation (detection error reduction due to Cf temperature), the reference element 23 and the detection element 24 are thermally coupled to each other through the partition wall 20. For this reason, as a material of the partition 20, for example, alumina ceramics or SUS316L is used.
For example, a gas heat conduction type gas detection element is used as both the detection element 24 and the reference element 23. The gas heat conduction type gas detection element uses two elements having the same electrical characteristics, one is exposed to the gas to be detected as a detection element, the other is exposed to the reference gas as a reference element, and both elements are energized. Sometimes, a change in resistance proportional to the difference in thermal conductivity between the gas to be detected and the reference gas occurs, so that the hydrogen concentration of the gas to be detected can be detected by detecting the difference in electrical resistance. is there.

In order to use this principle, the reference element storage space 21 is a sealed space and encloses a reference gas. As the reference gas, air can be used at a low cost, but an inert gas such as nitrogen gas is more preferable in terms of stability.
On the other hand, in the detection element storage space 22, the rear end portion of the shell 19 is opened as a gas inlet 25 in the direction opposite to the flow of the gas to be detected, and is always exposed to the gas to be detected. .

  A protective mesh 26 is attached to the opening surface (gas introduction port 25) at the rear end of the shell 19 so that mechanical external force is not applied to the detection element 24. Since the mesh 26 is mainly used to prevent the detection element 24 from being accidentally damaged when the hydrogen sensor 10 is attached / detached, the mesh 26 may be a coarse mesh, so that the gas to be detected is free in the detection element storage space 22 without resistance. Can enter and exit (B in the figure).

  According to the present embodiment, a support body made of a heat insulating material in which a detection unit (detection head 13) incorporating the detection element 24 and the reference element 23 is protruded into the pipe from the wall part of the pipe 2 through which the gas to be detected flows ( The gas introduction port 25 that is supported by the support arm 12) and arranged in the flow in the pipe 2 and leads the detection gas to the detection element 24 to the detection unit (detection head 13) is opposite to the flow of the detection gas. Due to the opening, the following effects can be obtained.

Since the detector (detection head 13) is placed away from the inner wall of the pipe toward the center of the pipe and insulated, it is possible to detect dew condensation when the pipe temperature is low or even if the gas to be detected cools down after operation is stopped. Since dew condensation of the element 24 can be prevented, detection accuracy can be improved without using a heater.
Further, since the gas introduction port 25 is opened in the direction opposite to the flow of the gas to be detected, the liquid droplet (splash water) hits the detection element 24 even if the gas to be detected contains liquid droplets (splash water). There is no. For this reason, it is possible to prevent temporary detection failure due to droplet adhesion and deterioration / damage of the detection element 24 due to thermal shock or the like.

In addition, since the detection unit is arranged in the high flow velocity space of the gas to be detected, the gas in the detection element storage space 22 can be replaced quickly, and the response of hydrogen concentration detection can be improved.
Moreover, since the suction effect of the detection element storage space 22 according to the gas flow rate can be obtained by the downstream negative pressure of the detection unit, the gas replacement is promoted and the dew point rises at the time of low temperature startup or pressurization of the gas to be detected. Even if droplets are generated in the sensing element storage space 22, they are quickly drained. Therefore, it is possible to improve the responsiveness following the gas flow rate, and to prevent a detection failure due to droplets.

Moreover, since there is no adhesion of water droplets as a secondary effect, the freeze resistance can be improved.
Furthermore, it is possible to detect the hydrogen concentration even in gas pipes mixed with splashed water at high humidity, such as a fuel cell anode electrode, which could not be applied due to dew condensation, and a hydrogen production facility by reforming.
In addition, according to the present embodiment, the detection unit (detection head 13) includes the storage space 22 of the detection element 24 and the storage space 21 of the reference element 23 via the partition wall 20, and the storage space 21 of the reference element 23. Is sealed with the outer wall (shell 19) and the partition wall (20) of the detection unit, and the reference gas is sealed inside, thereby obtaining the following effects.

Since the reference element storage space 21 and the outer wall of the detection unit are combined, the reference element storage space 21 is sealed by the partition wall 20 and the detection element storage space 22 is further divided, so that the number of parts is reduced and the heat capacity is reduced. Is done.
Further, the heat of the gas to be detected is received by the outer wall (shell 19) of the detection unit, the reference element 23 and the detection element 24 are adjusted to the temperature of the detection gas, and the detection unit is maintained at the dew point (boiling point) or higher. Therefore, a heater for heating is unnecessary or simplified, and power saving and low cost can be achieved. Moreover, since the heat capacity is small, the response of hydrogen concentration output can be improved.

Further, according to the present embodiment, the storage space 21 of the reference element 23 is arranged on the upstream side and the storage space 22 of the detection element 24 is arranged on the downstream side in the flow direction in the pipe 2. The following effects can be obtained.
Even if the gas to be detected includes liquid droplets (splash water), the reference element storage space 21 becomes a partition and the liquid droplets (splash water) are not sprayed on the detection element 24. For this reason, it is possible to prevent temporary detection failure due to droplet adhesion and deterioration / damage due to thermal shock.

In addition, the reference element storage space 21 whose heat capacity has become higher (relative to the detection element storage space 22) due to the inclusion of the reference gas can be actively controlled by the detected gas, and in particular the temperature of the detected gas. When a sudden change occurs, the temperature difference between the reference element storage space 21 and the detection element storage space 22 having different heat capacities can be quickly brought into an equilibrium state, and the transient response is improved.
Further, according to the present embodiment, the outer wall (shell 19) of the detection unit (detection head 13) is formed so that the cross-sectional area increases toward the downstream side in the flow direction in the pipe 2, and the downstream having the maximum cross-sectional area is formed. By using the gas inlet 25 as the side end, the following effects can be obtained.

Even if the gas to be detected includes a droplet (splash water), the droplet (splash water) is not sprayed on the detection element 24. As a result, it is possible to prevent temporary detection failure due to droplet adhesion and deterioration / damage due to thermal shock.
In addition, since the flow velocity of the gas to be detected flowing along the outer wall of the detection unit is maximized, a vortex (separation) generated on the downstream side is generated from a low flow rate, and this vortex promotes gas replacement in the detection element storage space 22. . As a result, the gas concentration detection response can be improved over a wide flow range.

Further, according to the present embodiment, by providing the mesh 26 at the gas inlet 25, it is possible to protect the sensing element 24 from being applied with mechanical external force. 24 can be prevented from being damaged.
Next, a second embodiment of the present invention will be described with reference to FIG. In the second and subsequent embodiments, the description of the same parts as those already described will be omitted, and only different parts will be described.

  In the present embodiment, the mesh 27 attached to the opening surface of the rear end portion of the shell 19 swells downstream in the flow direction of the gas to be detected, and has a spindle shape as a whole together with the outer wall (shell 19) of the detection head 13. It is shaped into a shape. In other words, the outer wall of the detection head 13 is formed in a spindle shape along the flow direction of the pipe 2, and the downstream side of the maximum cross-sectional area A is configured by the mesh 27 to form the gas inlet 25. Note that the shell 19 and the mesh 27 are joined at the maximum cross-sectional area A without a step. As a result, a vortex flow (C in the drawing) is generated from the pressure gradient accompanying the flow velocity change at the mesh 27 portion.

  In the present embodiment, a heater 28 is provided between the reference element 23 and the partition wall 20 in the reference element storage space 21. The heater 28 generates heat only at a low temperature start-up as will be described later in the application example. For example, a ceramic heater or a platinum resistance wire heater can be used. In this case, it is desirable that the reference gas sealed in the reference element storage space 21 is an inert gas such as nitrogen.

In particular, according to the present embodiment, the outer wall of the detection unit (detection head 13) is formed in a spindle shape along the flow direction in the pipe 2, and at least a part of the downstream side from the maximum cross-sectional area A is configured by the mesh 27. Thus, the gas inlet 25 provides the following effects.
By adopting the spindle shape, an increase in the flow resistance of the gas to be detected can be suppressed, and the insertion pressure loss of the hydrogen sensor can be reduced.

Further, since the downstream side of the position where the detected gas flowing along the outer wall of the detection unit reaches the maximum flow velocity is configured by the mesh 27, the detected gas has a rectifying action and the pressure difference for gas replacement. Due to the eddy, gas replacement in the sensing element storage space 22 can be promoted.
In addition, according to the present embodiment, the heater 28 is used in the detection unit (detection head 13), particularly in the storage space 21 of the reference element 23, and generates heat only at low temperature startup, so that the heater 28 is used at a low temperature. By using it only at the time of start-up, power saving can be achieved and the life of the heater can be extended, so that the durability of the hydrogen sensor can be improved.

Further, according to the present embodiment, by using an inert gas as a reference gas, stability as reference point compensation can be improved, and various electrical components including a heater 28 built in the reference element storage space 22 can be obtained. The characteristics can be stabilized over a long period of time.
Next, a third embodiment of the present invention will be described with reference to FIG.
In the present embodiment, the signal adjustment circuit 29 is integrated on silicon using a semiconductor process and provided between the reference element 23 and the partition wall 20. At this time, the signal adjustment circuit 29 has a signal adjustment function and also has a heater function by operating heat.

Further, the mesh 27 is formed with a drain port 30 for the droplet F by using the lower part E in the direction of gravity as a rough mesh or opening. Further, the mesh 27 is made of fluorine, tetrafluoroethylene (Teflon) or the like, and has water repellency. As another method for imparting water repellency, a stainless steel substrate may be coated with fluorine or the like.
In addition, by attaching a hydrophilic material such as glass to a portion (surface G of the partition wall 20) that is close to the detection element 24 in the detection element storage space 22, the contact angle of the droplet is lowered and the droplet is separated from the partition wall 20. Cross-linking to the sensing element 24 is prevented. As another method for imparting hydrophilicity, a hydrophilic coating such as titanium oxide may be applied.

In particular, according to the present embodiment, the lower portion of the mesh 27 in the direction of gravity is a rough mesh or opening, and the drain port 30 is formed, so that the sensing element storage space can be prevented from dew point rise due to low temperature startup or gas pressurization. Even if a liquid droplet is generated in 22, it is quickly drained. Thereby, the detection failure by a droplet can be prevented.
Further, according to the present embodiment, the mesh 27 is made of a water repellent material, or is produced by applying a water repellent coating to the mesh base material, so that the mesh 27 has water repellency. While the gas to be detected including water vapor is passed through the space 22, it is possible to reduce the ingress of droplets and the formation of a water film that become obstacles to detection. Thereby, since the composition of the gas to be detected guided to the detection element storage space 22 does not change, the accuracy of detecting the hydrogen concentration can be increased.

  In addition, according to the present embodiment, the portion adjacent to the detection element 24 in the storage space 22 of the detection element 24 is made hydrophilic. Specifically, the corresponding portion is made of a hydrophilic material. Alternatively, by applying a hydrophilic coating to the corresponding part, the liquid droplet does not stay between the detection element 24 and the part adjacent to the detection element 24. For this reason, it is possible to prevent temporary detection failure due to droplet adhesion and deterioration / damage due to thermal shock.

Next, a fourth embodiment of the present invention will be described with reference to FIG.
FIG. 4 is a view from the body 11 side of FIGS.
In the present embodiment, the tip of the support arm 12 having a spindle shape in the flow direction of the gas to be detected is used as the detection head 13 ′, and the inside thereof is partitioned by the partition wall 20 ′ along the flow direction. In parallel, a reference element storage space 21 (reference element 23) and a detection element storage space 22 (detection element 24) are arranged.

A portion corresponding to the sensing element storage space 22 is formed on the downstream side of the maximum cross-sectional area portion with a mesh 27 ′, which serves as the gas inlet 25.
In particular, according to the present embodiment, the storage space 21 of the reference element 23 and the storage space 22 of the detection element 24 are arranged in parallel to the flow direction in the pipe 2, so that the temperature of the gas to be detected is increased. The temperature is uniformly transmitted to the reference element storage space 21 and the detection element storage space 22, and the temperature compensation performance can be improved.

Although not shown, in the first to fourth embodiments, a humidity detection element (not shown) is provided in the detection element storage space 22, and based on the humidity of the gas to be detected detected by the humidity detection element. Temperature compensation should be performed.
As the humidity detection element, an electrostatic capacitance type relative humidity detection element or the like can be used. In the vicinity of the detection element 24 in the detection element storage space 22, the outer wall (shell 19) of the detection head 13 is thermally excellent. Install in combination.

By performing humidity compensation, it is possible to accurately detect the hydrogen concentration because the water vapor concentration can be corrected even if a hydrogen sensor having sensitivity to water vapor, such as a gas heat conduction type hydrogen sensor, is used. Moreover, since the dew condensation resistance of the humidity sensor (humidity detection element) is ensured as well as the hydrogen sensor, the humidity detection information can be used for humidification control of the gas to be detected.
Next, usage examples of the hydrogen sensor according to the present invention will be described.

FIG. 5 is a configuration diagram of the fuel cell system.
The fuel cell stack 1 is configured by laminating a large number of fuel cell units in which an electrolyte electrode structure in which a solid polymer electrolyte membrane is sandwiched between an anode side electrode and a cathode side electrode is sandwiched between a pair of separators. Yes.
The anode side electrode is supplied with hydrogen gas (fuel gas) from the hydrogen supply source through the hydrogen supply valve 3 and through the inlet pipe 2a, and hydrogen is ionized on the electrode, and the cathode is passed through the solid polymer electrolyte membrane. Move to the side electrode. Electrons generated in the meantime are taken out to an external circuit and used as direct current electric energy. Since air (oxidant gas) is supplied to the cathode side electrode through the inlet pipe 2b, water is generated. The anode side outlet pipe 2c is connected to the inlet pipe 2a via a circulation pump (circulation pipe) 4 in order to reuse the hydrogen gas, and off-gas is appropriately supplied via a purge valve (not shown). Discharge out of the system. The cathode side outlet pipe 2d discharges off-gas outside the system.

Signals are input to the operation control module 5 from a temperature sensor 6 and a pressure sensor 7 provided on the inlet pipe 2a on the anode side. In addition, a signal is input from the hydrogen sensor 10a (and a temperature sensor (not shown)) provided in the anode side outlet pipe 2c and / or the hydrogen sensor 10b provided in the cathode side outlet pipe 2d.
Here, the operation control module 5 performs operation control according to the flowcharts of FIGS. 6 and 7 and controls the operations of the hydrogen supply valve 3 and the circulation pump 4. In FIG. 5, 8 is a memory for storing various information, and 9 is an alarm device.

FIG. 6 is a flowchart of operation control when the hydrogen sensor 10a is installed in the outlet pipe 2c on the anode side of the fuel cell.
When the operation start switch of the fuel cell is pressed (S100), the operation control module first reads the gas temperature Tg in the anode outlet pipe and compares it with the pre-stored detection head dew condensation temperature Th at system startup ( S110) If the temperature is equal to or lower than the dew condensation temperature Th, the heater provided in the reference element storage space is energized to generate heat (S111). As a result, the warm-up time of the cooled detection head is shortened, but since the output of the hydrogen sensor is not stable until the warm-up is completed, the determination for hydrogen concentration control is waited for a certain time (S112).

  When the warm-up is finished, the output (detected concentration) Cg of the hydrogen sensor is read and compared with the low value Chm of the hydrogen concentration control width (S113). At this time, if the value is lower than the low value Chm, the hydrogen concentration is insufficient, so a command is issued to open the hydrogen supply valve (S114). On the other hand, if it is equal to or higher than the low value Chm, then it is compared with the high value ChL of the hydrogen concentration control width (S115). At this time, if the value is higher than the high value ChL, the hydrogen concentration is excessive, so a command is issued to close the hydrogen supply valve (S116). As a result of this repeated treatment, the hydrogen concentration at the anode outlet is maintained at a predetermined concentration. The predetermined concentration is set in advance so that the fuel cell can be operated efficiently and does not deteriorate, so that the fuel cell is optimally controlled.

  In addition, the system shown in FIG. 5 includes a circulation pump for reusing the anode outlet hydrogen. However, nitrogen is accumulated in the circulation system due to nitrogen leakage from the cathode electrode of the fuel cell stack, and the hydrogen concentration is adjusted to a predetermined concentration. Since it cannot be maintained, it is necessary to discharge the anode outlet gas to the outside when the predetermined nitrogen concentration is reached. In order to determine this timing, it is compared whether or not the hydrogen concentration Cg detected by the hydrogen sensor is continuously lower than the purge concentration Cp stored in advance for a predetermined period in the result of the hydrogen concentration control. Determination is made (S117). As a result, if it is continuously lower, the nitrogen concentration has reached a predetermined concentration, so a command is issued to the purge valve to open the purge valve and discharge the anode outlet gas (S118).

Next, the hydrogen concentration Cg is compared with an abnormal concentration Cf corresponding to the time of failure stored in advance (S119). If the result is an abnormal value (Cg> Cf), a command to issue an alarm is output to the alarm device to alert the driver (S910), and a predetermined process is executed and stopped so that the failure does not expand. (S911, S912).
On the other hand, when it is not abnormal, another operation control routine (S130) is executed, and the operation control is completed. Subsequently, the next operation control is started. At this time, it is determined whether or not the gas temperature Tg is equal to or higher than the dew condensation temperature Th of the detection head (S120). If the dew condensation temperature Th is still below, the energization of the heater is continued.

As described above, the hydrogen sensor 10a is installed in the anode side pipe (in addition to the outlet pipe 2c, the inlet pipe 2a or the circulation pipe 4) of the fuel cell system, and according to the detected hydrogen concentration, the fuel cell stack By implementing at least one of control of gas supply to 1, control of impurity purge, operation stop of the fuel cell system, and alarm, the following effects can be obtained.
By performing gas supply control and impurity purge control, the operation of the fuel cell system is optimized, and the fuel cell system can be improved in fuel consumption, stack durability, and reliability.

In addition, when the concentration is out of the specified concentration range, it is determined that the system is abnormal, and an alarm is output and the operation of the fuel cell system is stopped. Can be prevented.
FIG. 7 is a flowchart of a gas leak monitoring routine when the hydrogen sensor 10b is installed in the outlet pipe 2d on the cathode side of the fuel cell.

When the fuel cell stack failure diagnosis routine is executed in the control of the operation control module (S200), the output (detection concentration) Cg of the hydrogen sensor is read, and the gas leak determination concentration Ce stored in advance is stored. A comparison is made (S210).
At this time, if the gas leakage determination concentration Ce is equal to or higher than that, hydrogen gas at the anode electrode has leaked to the cathode electrode due to a failure, so an instruction to issue an alarm is output to the alarm device to warn the driver ( Along with S920), predetermined processing is executed and stopped so that the failure does not expand (S921, S922).

On the other hand, if the gas leakage determination concentration Ce is equal to or lower than the threshold value, the process proceeds to another operation control routine (S211).
As described above, when the hydrogen sensor 10b is installed in the outlet pipe 2d on the cathode side of the fuel cell system and a hydrogen concentration of a predetermined value or more is detected, at least one of the shutdown and alarm of the fuel cell system is detected. By implementing one, abnormality of the fuel cell stack can be detected quickly, and the expansion of the failure location can be prevented.

The figure which shows 1st Embodiment of this invention The figure which shows 2nd Embodiment of this invention. The figure which shows 3rd Embodiment of this invention. The figure which shows 4th Embodiment of this invention. Diagram showing an installation example in a fuel cell system Flow chart of control example 1 in fuel cell system Flow chart of control example 2 in fuel cell system

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell stack 2 Piping 2a Inlet piping on the anode side 2b Inlet piping on the cathode side 2c Outlet piping on the anode side 2d Outlet piping on the cathode side 3 Hydrogen supply valve 4 Circulation pump 5 Operation control module 10 (10a, 10b) Hydrogen sensor 11 Body 12 Support arm (support)
13 Detection head (detection unit)
14 Signal Conditioning Circuit 15 Bolt 16 Sealing Material 17 External Wiring 18 Wiring 19 Outer Shell 20 Bulkhead 21 Reference Element Storage Space 22 Detection Element Storage Space 23 Reference Element 24 Detection Element 25 Gas Inlet 26 Mesh 27 Mesh 28 Heater 29 Integrated as a Heater Mold signal conditioning circuit 30 Drain port

Claims (15)

A hydrogen sensor that detects a hydrogen concentration of a gas to be detected based on a difference in electrical resistance between a detection element that responds to the hydrogen concentration of the gas to be detected and a reference element,
The detection unit incorporating the detection element and the reference element is supported by a support made of a heat insulating material protruding into the pipe from the pipe wall through which the gas to be detected flows, and is arranged in the flow in the pipe.
A hydrogen sensor, wherein a gas introduction port for introducing a gas to be detected to the detection element is opened in the detection unit in a direction opposite to the flow of the gas to be detected.   The detection unit includes a storage space for the detection element and a storage space for the reference element via a partition wall. The storage space for the reference element is sealed by the outer wall of the detection unit and the partition wall, and the reference gas is sealed inside. The hydrogen sensor according to claim 1.   3. The hydrogen sensor according to claim 2, wherein a storage space for the reference element is disposed upstream and a storage space for the detection element is disposed downstream of the flow direction in the pipe.   The hydrogen sensor according to claim 2, wherein a storage space for the reference element and a storage space for the detection element are arranged in parallel to the flow direction in the pipe.   The hydrogen sensor according to any one of claims 2 to 4, wherein an inert gas is used as the reference gas.   The outer wall of the detection part is formed so that the cross-sectional area increases toward the downstream side in the flow direction in the pipe, and the downstream end part having the maximum cross-sectional area is used as the gas introduction port. The hydrogen sensor according to claim 5.   The hydrogen sensor according to any one of claims 1 to 6, wherein a mesh is provided at the gas inlet.   The outer wall of the detection part is formed in a spindle shape along the flow direction in the pipe, and at least a part of the downstream side from the maximum cross-sectional area part is constituted by a mesh to serve as the gas inlet. The hydrogen sensor according to any one of claims 1 to 5.   The hydrogen sensor according to claim 7 or 8, wherein a drain port is formed by using a lower part of the mesh in a gravitational direction as a rough mesh or an opening.   The hydrogen sensor according to claim 7, wherein the mesh has water repellency.   The hydrogen sensor according to any one of claims 1 to 10, wherein a portion that is close to the detection element in the storage space of the detection element is made hydrophilic.   The hydrogen sensor according to any one of claims 1 to 11, wherein a heater is provided in the detection unit to generate heat only at low temperature startup.   The hydrogen sensor according to claim 1, wherein a humidity detection element is provided in a storage space of the detection element, and humidity compensation is performed based on humidity detected by the humidity detection element.   At least one of control of gas supply to the fuel cell stack, control of impurity purging, shutdown of the fuel cell system, and alarm according to the detected hydrogen concentration, installed in the anode side pipe of the fuel cell system The hydrogen sensor according to claim 1, wherein the hydrogen sensor is implemented.   It is installed in the outlet pipe on the cathode side of the fuel cell system, and when a hydrogen concentration of a predetermined value or more is detected, at least one of operation stop and alarm of the fuel cell system is performed. The hydrogen sensor according to any one of claims 1 to 13.

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