JP2003308866A - Gas leakage detecting method and device for fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive detecting device for detecting the leakage of fuel gas from a fuel gas circulating supply system during operating a vehicular fuel cell system. <P>SOLUTION: When a value for an output current i in a fuel cell is smaller than a threshold during regenerating decelerating energy (S1), the output current i is shut off by an output current circuit breaker to stop the generation of a fuel cell (S4) and, in turn, a purge valve for discharging water together with the fuel gas from a circulation system and a pressure reducing control valve for controlling the supply of the fuel gas from a fuel supply source are forcibly closed (S2, S3). At this point pressure in a closed space of the fuel gas circulating supply system is detected by a pressure gage, and when the detection result of the pressure gage shows pressure drop at a reference speed or faster, the leakage of the fuel gas is determined (S5-S7). <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas leak detection method and apparatus for a fuel cell system, and more particularly to a method and apparatus for detecting a fuel gas leak inside a fuel cell system.

[0002]

2. Description of the Related Art Conventionally, as a method for detecting a leak of hydrogen-containing fuel gas in a fuel cell system, Japanese Patent Application Laid-Open No. HEI11-1999 has been proposed.
There is a method disclosed in Japanese Patent Laid-Open No. 2246811 and Japanese Patent Laid-Open No. 8-329965. JP-A-11-2246
The method disclosed in Japanese Patent No. 81 calculates the amount of fuel gas used in the fuel cell based on the output current value of the fuel cell, and calculates the fuel gas pressure in the fuel gas cylinder from the amount of fuel gas used. By comparing the calculated pressure with the pressure value actually detected by the pressure sensor, the leakage of the fuel gas is judged.

Further, the method disclosed in Japanese Unexamined Patent Publication No. 8-329965 has a valve provided at each of an upstream portion and a downstream portion of a fuel cell, and the fuel gas is sealed by closing the valve before a power generation operation, The pressure change is detected by the pressure detecting means, and the leakage of the fuel gas is detected based on the decrease in the enclosed pressure.

[0004]

However, the method disclosed in Japanese Patent Laid-Open No. 11-224681 has a problem that the consumption of the fuel gas by the purge control may be erroneously detected as a leak. In the fuel cell system, the water vapor contained in the humidified hydrogen-containing fuel gas supplied to the fuel cell becomes water around the fuel electrode, and when the exhaust path is filled with water, a flooding phenomenon that causes a decrease in the output of the fuel cell occurs. .

As a countermeasure against the above-mentioned flooding phenomenon, for example, when the filling of water is judged based on the output reduction of the fuel cell, the water is purged using the fuel gas. Here, the fuel gas used for purging hardly contributes to the output of the fuel cell, so the fuel gas used for purging is calculated as the leak amount, and the leak is detected with high accuracy. If this is attempted, a problem will occur in which the occurrence of leakage is erroneously detected when the purge is executed.

Further, the method disclosed in Japanese Patent Application Laid-Open No. 8-329965 is an inexpensive detection method because it is possible to determine the presence or absence of fuel gas leakage by monitoring the value of a pressure gauge, but leakage is detected before starting. Since this is a method of detecting, there is a drawback that the occurrence of leakage after the start of operation is not detected until it is restarted. In particular, in fuel cell systems for vehicles, the possibility of leakage, such as mechanical vibrations and shocks input during driving, thermal deformation due to large thermal changes, etc. There are many.

Therefore, the leak detection method that can detect only before starting as in the conventional example has a problem that the detection performance required for the fuel cell system for a vehicle cannot be secured. The present invention has been made in view of the above problems, and an object of the present invention is to provide a gas leak detection method and device for a fuel cell system, which can detect a fuel gas leak even during operation and which is inexpensive.

[0008]

Therefore, the first and fourth aspects are as follows.
In the detection method and apparatus according to the described invention, the output current of the fuel cell is interrupted when the electric load of the fuel cell is smaller than a threshold value, and the pressure state in the closed space of the fuel gas circulation supply system including the fuel cell at this time The fuel gas leakage in the closed space is detected based on the above.

According to the above construction, when the electric load of the fuel cell is smaller than the threshold and the power generation of the fuel cell can be stopped, the output current of the fuel cell is cut off to stop the power generation of the fuel cell. When the power generation is stopped, the fuel gas is not consumed in the fuel cell, and the pressure condition in the closed space of the fuel gas circulation supply system including the fuel cell is affected only by the leakage. Detects the presence of leaks.

In the detection method and apparatus according to the second and fifth aspects of the invention, when the electric load of the fuel cell is smaller than a threshold value, the output current of the fuel cell is cut off, and the fuel supply source to the closed space is operated. The fuel gas supply is forcibly cut off and the fuel gas leakage is detected based on the pressure drop rate in the closed space at this time. According to the above configuration, in the closed space where the supply of the fuel gas from the fuel supply source is cut off, when the fuel gas flows out due to the leakage, the pressure in the closed space is drastically reduced as compared with when there is no leakage. Therefore, the occurrence of leakage is detected based on whether the pressure drop rate is large enough to indicate the occurrence of leakage.

In the detection method and apparatus according to the third and ninth aspects of the present invention, the differential pressure across the pressure loss portion in the closed space is detected, and fuel gas leakage is detected based on this differential pressure. did. According to the above configuration, when leakage occurs from the closed space, a flow of fuel gas is generated in the closed space, and the flow causes a differential pressure before and after the pressure loss portion. The occurrence of the flow of fuel gas is detected based on the pressure, and thus the presence or absence of fuel gas leakage is detected.

In the detection device according to the invention of claim 6,
In the configuration for detecting a fuel gas leak based on the pressure drop rate in the closed space, when the leak is detected by shutting off the output current, the closed space of the fuel gas circulation supply system including the fuel cell is closed by a plurality of closed spaces. It is configured to shut off the space and detect the pressure of each of the plurality of closed spaces, and determine the presence or absence of fuel gas leakage and the location of fuel gas leakage based on the pressure drop rate of each of the plurality of closed spaces. It was configured to do.

According to the above structure, the closed space in which the supply of the fuel gas from the fuel supply source is cut off is cut into a plurality of spaces, and the pressure is detected in each of the closed spaces, whereby the location where the fuel gas leaks occurs. Is specified as one of the plurality of closed spaces. In the detection device according to the invention of claim 7, in the configuration for detecting the fuel gas leakage based on the pressure drop rate in the closed space, the pressure between the pressure loss parts in the closed space is set at a plurality of points respectively. The configuration is such that the presence or absence of fuel gas leakage and the location where fuel gas leakage has occurred are detected based on the pressure drop rate at each detection site.

According to the above structure, a plurality of pseudo closed spaces having the pressure loss portion as a boundary are set, and the location of the fuel gas leakage is determined by the pressure drop rate for each pseudo closed space. Specify the crab. In the detection device according to the invention described in claim 8, in the configuration of claim 7, when the largest pressure drop rate of the pressure drop rates at the respective detection sites is larger than the threshold value, the largest drop rate is exhibited. The configuration is such that the occurrence of fuel gas leakage at the detection site is determined.

According to the above structure, the fuel gas leakage at one location affects the other detected pressure via the pressure loss portion, but the pressure drop at the location where the fuel gas leakage occurs becomes the largest. , The detection site that shows the largest descent rate is identified as the location of the fuel gas leakage. Claim 1
In the detection device according to the invention described in 0, in the configuration for detecting the fuel gas leakage based on the differential pressure across the pressure loss portion in the closed space, the differential pressures across the plurality of pressure loss portions in the closed space are respectively detected. To detect the occurrence of fuel gas leakage when the differential pressure across the front is greater than a threshold value,
The configuration is such that the location where the fuel gas leak has occurred is determined based on the direction of the differential pressure between the adjacent detection units.

According to the above construction, the flow direction of the fuel gas can be identified from the direction of the differential pressure across the pressure loss portion, and the location of the fuel gas leakage is identified based on this. Claim 11
In the detector according to the invention described above, when the presence or absence of the fuel gas leakage is judged, the purge from the circulation system by the purge means is forcibly interrupted to form the closed space.

According to the above arrangement, the fuel gas circulation supply system can be used as a closed space for leak detection.
Forcibly shut off the purge.

[0018]

According to the present invention, the output current of the fuel cell is interrupted when the electric load of the fuel cell is smaller than the threshold value to form a closed space in which fuel gas is not consumed. For example, in a vehicle fuel cell system,
Fuel leakage can be detected when the output current of the fuel cell is small or when the output current is not needed, such as when the deceleration energy is regenerated, and a relatively inexpensive pressure gauge is used during operation. There is an effect that the fuel gas leakage can be detected.

According to the second and fifth aspects of the present invention, the leakage is detected based on the pressure drop in the closed space where the supply of the fuel gas from the fuel supply source is cut off. Moreover, there is an effect that the fuel gas leakage can be detected. According to the third and ninth aspects of the invention, the flow of the fuel gas caused by the fuel gas leakage is detected based on the differential pressure across the pressure loss portion in the closed space, so that it is affected by the absolute pressure in the closed space. There is an effect that the occurrence of the fuel gas leakage can be detected with high accuracy.

According to the sixth aspect of the invention, there is an effect that the location where the fuel gas leak has occurred can be accurately specified based on the pressure drop in each of the closed spaces that are blocked. According to the invention described in claim 7, it is possible to specify the location of the fuel gas leakage without dividing the fuel gas circulation supply system into a plurality of areas using a valve or the like, and to easily identify the location of the leakage. There is an effect that it can be done in.

According to the eighth aspect of the present invention, even if the influence of the fuel gas leakage affects other pressure detection portions via the pressure loss portion, the location of the fuel gas leakage can be accurately determined from the pressure drop rate. The effect is that it can be specified.
According to the invention of claim 10, there is an effect that the generation direction of the fuel gas leakage can be accurately specified by specifying the flow direction of the fuel gas accompanying the fuel gas leakage from the differential pressure across the pressure loss portion. is there.

According to the eleventh aspect of the present invention, the closed space required for detecting the fuel gas leakage is surely formed, and the fuel gas leakage can be detected surely when the electric load of the fuel cell is smaller than the threshold value. The effect is that it can be done.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a vehicle fuel cell system according to a first embodiment. In FIG. 1, the fuel gas from the hydrogen gas supply source 1 (fuel supply source) is passed through a fuel gas supply line 2, a pressure reducing control valve 3, a fuel gas supply line 4, an ejector 5, and a fuel gas supply line 6. Introduced into the fuel electrode (not shown) of the fuel cell 10,
The fuel gas not consumed in the fuel cell 10 passes through the fuel gas discharge line 11 and the fuel gas circulation line 12,
The fuel gas is recirculated to the fuel gas supply line 6 by the ejector 5.

The fuel gas supply line 2 and the pressure reducing control valve 3
(Supply source cutoff means), fuel gas supply line 4, ejector 5, fuel gas supply line 6, fuel gas discharge line 11
The fuel gas circulation line 12 constitutes a fuel gas circulation supply system. In the fuel gas discharge line 11,
A purge line 14 in which a purge valve 13 is interposed is connected.

The purge valve 13 and the purge line 14 constitute a purge means. The purge valve 13 is
The opening control is performed when the water accumulated in the fuel gas discharge line 11 is discharged together with the fuel gas. On the other hand, the air electrode (not shown) of the fuel cell 10 is supplied with the oxidizing gas (air) from the oxidizing gas supply source 20 through the gas supply line 21, and the oxidizing gas not consumed in the fuel cell 10 is , Is discharged through the discharge line 22.

The output wiring 32 for outputting the output current i of the fuel cell 10 has an ammeter 31 for detecting the output current i, and an output current breaker 30 for interrupting the output current i (output current cutoff). Means). Further, a pressure gauge 7 (pressure state detecting means, pressure detecting means) for detecting the pressure in the fuel gas supply line 6 is provided.

The signal processing device 40 to which the detection outputs of the ammeter 31 and the pressure gauge 7 are input controls the opening / closing operations of the purge valve 13 and the output current circuit breaker 30, and forcibly operates the pressure reducing adjustment valve 3. It has the function of shutting off. In the above structure, the fuel gas flow rate Q0 from the hydrogen gas supply source 1
Is supplied, and the flow rate Q1 (= Q0 + Q2) obtained by adding the reflux gas flow rate Q2 is guided to the fuel electrode of the fuel cell 10 by the ejector 5.

In the fuel cell 10, a flow rate of ΔQ commensurate with the output current i is consumed, and the remaining fuel gas Q2 circulates,
The fuel gas is fed back to the fuel gas supply line 6.
That is, the flow rate of the fuel gas supplied to the fuel electrode of the fuel cell 10 has a relationship of ΔQ = Q1-Q2 = Q0, and the pressure reducing control valve 3 causes the fuel consumption amount of the fuel cell 10 (fuel gas circulation supply line Supply the fuel gas commensurate with the pressure drop).

Here, the electric load required for the vehicle, that is, the output current i is a value that can fluctuate significantly,
For example, when the vehicle is equipped with a regenerative braking device that converts the inertial energy of the vehicle into electric energy during braking (at the time of deceleration), electric energy can be supplied by regenerative braking, and thus the output current i from the fuel cell 10 is unnecessary. Or
It becomes an extremely small value, and at this time, the pressure reducing control valve 3 shuts off the flow of the fuel gas or minutely reduces the supply amount Q0.

When the regenerative braking is completed, the condition for making the output current zero (or a small value) is released, so that the fuel gas consumption flow rate corresponding to the required current i corresponding to the electric load of the vehicle is reproduced, The fuel supply flow rate Q0 also starts to flow. As described above, in the fuel cell system for a vehicle, the power generation of the fuel cell 10 is not always required, and a state in which the power generation of the fuel cell 10 can be stopped occurs during operation.

When the power generation of the fuel cell 10 is stopped, the fuel gas is not consumed in the fuel cell 10. Therefore, if the purge valve 13 is closed and a closed space is formed,
Since the fuel gas is confined in the closed space, a large pressure change does not occur. Here, if the supply of the fuel gas from the hydrogen gas supply source 1 is cut off, when the fuel gas leaks from the closed space, the pressure in the closed space will drop. The occurrence of fuel gas leakage can be estimated based on

Therefore, the signal processing device 40 detects the presence / absence of fuel gas leakage according to the procedure shown in the flowchart of FIG. The signal processing device 40 is shown in FIG.
As shown in the flow chart of FIG. 3, it has functions as an electric load discriminating means, a shutoff control means, a fuel gas leak determining means, and a purge shutoff means.

First, in step S1, it is determined whether or not the output current i (electrical load) is smaller than the threshold value i0. When the output current i (electrical load) is smaller than the threshold value i0, the process proceeds to step S2, the purge valve 13 is forcibly held in the closed state, and the pressure reducing adjustment valve 3 is forcibly closed in the next step S3. Keep it in the state.

A shutoff valve may be provided on the upstream side or the downstream side of the decompression adjustment valve 3 to forcibly shut off the supply of fuel gas from the hydrogen gas supply source 1. Further, in step S4, the output of the output current i is cut off by the output current breaker 30 to stop the power generation (fuel gas consumption) of the fuel cell 10. By the above process, the closed space including the fuel cell 10 in which the supply of the fuel gas from the hydrogen gas supply source 1 is cut off is mechanically formed, while the consumption of the fuel gas in the fuel cell 10 becomes 0, and If there is no fuel gas leakage from the space, the pressure detected by the pressure gauge 7 does not show a large change.

In step S5, a change amount ΔP / Δt per unit time Δt of the pressure P detected by the pressure gauge 7, which indicates a pressure drop rate in the closed space, is calculated.
The change amount ΔP / Δt is calculated as a positive value with respect to the decrease change of the pressure P. Then, in step S6, it is determined whether or not the change amount ΔP / Δt is larger than the threshold value A.

When it is determined that the amount of change ΔP / Δt exceeds the threshold value A and the rate of decrease of the pressure P exceeds the reference value, the fuel gas leaks from the closed space and the pressure drops at a rate higher than a predetermined rate. If so, the process proceeds to step S7 to output a leak detection signal and output a leak detection display. The leak detection display output is, for example, a control signal for lighting a warning light provided near the driver's seat of the vehicle.

In the fuel gas leak detection according to the above-described embodiment, it is possible to judge the presence or absence of fuel gas leak every time the output current i (electrical load) becomes smaller than the threshold value i0 during operation (for example, every deceleration operation). Therefore, the occurrence of fuel gas leakage can be detected with good response, and the pressure gauge 7 is relatively inexpensive.
Therefore, the leak detection device can be configured at low cost.
By the way, in the above-described embodiment, the pressure reducing valve 3, the fuel gas supply line 4, the ejector 5, the fuel gas supply line 6,
Since one pressure gauge 7 is provided in the closed space of the fuel gas circulation supply system including the fuel cell 10, the fuel gas discharge line 11 and the fuel gas circulation line 12, the fuel is not provided in any of the closed spaces. Although it is possible to detect the occurrence of gas leakage, it is not possible to limit the location of leakage.

Therefore, as shown in the second embodiment shown in FIG. 3, shut-off valves 8 and 15 (closed space dividing means) for further dividing and shutting off the closed space of the fuel gas circulation supply system into two closed spaces.
And the pressure gauges 7 and 9 are provided for each closed space that is shut off by the shutoff valves 8 and 15, depending on which pressure detection value indicates a pressure drop rate higher than a predetermined value, fuel gas leakage Can be specified as one of the two closed spaces.

Specifically, the first cutoff valve 8 is provided in the middle of the fuel gas supply line 6 and the fuel gas discharge line 1 is provided.
The second shutoff valve 15 is provided in the middle of 1, while the pressure gauge 7 is provided to detect the pressure in the fuel gas supply line 6 between the first shutoff valve 8 and the ejector 5, and the second shutoff valve 15 is provided. A pressure gauge 9 is provided to detect the pressure in the fuel gas discharge line 11 between the fuel cell 15 and the fuel cell 10.

In the second embodiment, leak detection is performed as shown in the flowchart of FIG. In the flowchart of FIG. 4, step S11 to step S1
In 3, similar to steps S1 to S3, the process of forcibly holding the purge valve 13 and the pressure reducing adjustment valve 3 in the closed state is performed on condition that the output current i of the fuel cell 10 is smaller than the threshold value i0. To do.

Further, by closing the shutoff valves 8 and 15 in the next step S14, the closed space of the fuel gas circulation supply system is divided and shut into two. Then, in step S15,
The output current breaker 30 shuts off the output of the output current i, and stops the power generation (fuel gas consumption) of the fuel cell 10. By the above process, two closed spaces are formed in which the pressure does not suddenly decrease when the fuel gas does not leak.

In step S16, the amount of change ΔP1 / Δt (pressure decrease rate) is determined based on the pressure P1 detected by the pressure gauge 7.
Is calculated, and in step S17, the detected pressure P of the pressure gauge 9 is calculated.
Based on 2, the change amount ΔP2 / Δt (pressure decrease rate) is calculated. In step S18, steps S16 and S17
The larger one (the one with the faster descending speed) of the changes ΔP1 / Δt and ΔP2 / Δt calculated in step S1 is selected, and step S1
In 9, it is determined whether or not the change amount ΔP / Δt selected in step S18 is larger than the threshold value A.

When the change amount ΔP / Δt is larger than the threshold value A, the routine proceeds to step S20, where the leak detection signal is output and the leak detection display is output, and at the same time, step S
Proceed to step 21 and, for example, pressure gauges 7 and 9 that have detected the occurrence of leakage.
Is stored, the fuel gas leakage occurrence site is stored. By storing the leak occurrence location, for example, even if the leak occurs temporarily and then the leak section is closed and the alarm is not output, the history of the leak and the leak occurrence location can be known later.

The location of the leak may be stored in the memory or the like in the signal processing device 40 or may be stored in a storage device provided separately. In the present embodiment, the closed space is divided into two by the shutoff valves 8 and 15, and therefore, for example, in the case where the rate of decrease in the pressure detected by the pressure gauge 7 is larger than the other and the value exceeds the threshold A. Means that fuel gas leakage has occurred in any of the closed spaces from the shutoff valve 15 to the shutoff valve 8 via the fuel gas circulation line 12 and the ejector 5, and conversely, the detection by the pressure gauge 9 is detected. When the rate of pressure drop is higher than the other and exceeds the threshold value A, any of the closed spaces from the shutoff valve 8 to the shutoff valve 15 via the fuel cell 10 and the fuel gas discharge line 11 This means that a fuel gas leak has occurred.

In the above embodiment, the closed space is divided into two blocks, and a pressure gauge is provided for each block, so that the leak occurrence point can be specified in one of the two closed spaces. If the number of closed spaces to be shut off is three or more and each is equipped with a pressure gauge, it is possible to specify the fuel gas leak location more finely. However, in practice, the required number may be determined according to the scale of the fuel gas supply system, the piping structure, and the like.

In the second embodiment, the shutoff valve 8,
Although the closed space is mechanically cut off by 15 to form two closed spaces independent of each other, the ejector 5 and the fuel cell 10 which are interposed in the fuel gas circulation supply line form a pressure loss portion. Although the pressure drop at the location of fuel leakage affects the entire closed space, the degree of the influence is limited by the pressure loss portion.

In other words, the pressure drop rate in the fuel gas supply line 6 and the pressure drop rate in the fuel gas discharge line 11 and the fuel gas circulation line 12 are such that the pressure drop rate at which fuel leakage is occurring is greater. growing. Therefore, it is possible to identify the location where the fuel gas leak has occurred without providing the shutoff valves 8 and 15. A third embodiment having such a configuration will be described below.

FIG. 5 shows a fuel cell system according to the third embodiment. In contrast to the system configuration diagram of FIG. 1 showing the first embodiment, a pressure gauge 9 is provided in a fuel gas discharge line 11.
In addition, the pressure is detected by the pressure gauge 9 and the pressure gauge 7 provided in the fuel gas supply line 6, respectively. The fuel gas leak detection using the pressure gauges 7 and 9 is performed according to the procedure shown in the flowchart of FIG.

In step S31 to step S33 in the flow chart of FIG. 6, the output current i of the fuel cell 10 is equal to the threshold value i as in step S1 to step S3.
On condition that the value is smaller than 0, the purge valve 13 and the pressure reducing adjustment valve 3 are forcibly held in the closed state. Here, since the ejector 5 and the fuel cell 10 provided in the closed space of the fuel gas circulation supply system serve as a pressure loss portion, the fuel gas supply line 6 and the fuel gas discharge line 11 are simulated.
And the fuel gas circulation line 12 are divided into two closed spaces.

In step S34, the output of the output current i is cut off by the output current breaker 30, and the fuel cell 10
Stop power generation (fuel gas consumption). By the above processing,
If there is no fuel gas leakage, two closed spaces that do not show a sudden drop in pressure are pseudo-formed. In step S35, the amount of change ΔP1 / Δt (pressure decrease rate) is calculated based on the pressure P1 detected by the pressure gauge 7, and in step S36, the amount of change ΔP2 / Δt (based on the pressure P2 detected by the pressure gauge 9 is calculated. Calculate the pressure drop rate).

In step S37, steps S35, 3
The larger one of the change amounts ΔP1 / Δt and ΔP2 / Δt calculated in step 6 (the one with the faster descending speed) is selected, and step S
At 38, the change amount ΔP / Δt selected at step S37.
Is larger than the threshold value A. Then, when the change amount ΔP / Δt is larger than the threshold value A, the process proceeds to step S39, where the leak detection signal is output and the leak detection display is output, and the process proceeds to step S40 where, for example, the pressure gauge 7, which has detected the leak occurrence, By storing 9, the fuel gas leakage occurrence site is stored.

In the above first to third embodiments, the fuel cell 10 in which the supply of fuel gas is shut off and the power generation is stopped
Although the fuel gas leakage is detected based on the pressure drop in the closed space of the fuel gas circulation supply system including the above, when the fuel gas leakage occurs, the fuel cell 10 consumes no fuel. Instead, a flow of fuel gas is generated in the closed space, which causes a differential pressure across the pressure loss parts such as the ejector 5, the fuel cell 10, and the pressure reducing valve 3.

Therefore, in the fourth embodiment described below,
Fuel gas leakage is detected based on the differential pressure across the fuel cell. FIG. 7 shows a fuel cell system according to a fourth embodiment, in which a first differential pressure gauge 16 for detecting a differential pressure between a fuel gas supply line 2 and a fuel gas supply line 4 before and after a pressure reducing valve 3, an ejector 5 is shown. A second differential pressure gauge 17 for detecting the differential pressure between the front and rear fuel gas supply lines 4 and 6, and a third differential pressure gauge 17 for detecting the differential pressure between the fuel gas circulation line 12 before and after the ejector 5 and the fuel gas supply line 6. Differential pressure gauge 18, fuel cell 10
Front and rear fuel gas supply line 6 and fuel gas discharge line 11
A fourth differential pressure gauge 19 for detecting the differential pressure with respect to is provided.

Here, the differential pressure output values of the differential pressure gauges 16 to 19 (pressure state detecting means, differential pressure detecting means) are represented by ΔP1 and ΔP.
2, ΔP3, ΔP4, and the pressure sensing polarities of the differential pressure gauges 16 to 19 are the differential pressure output values ΔP1, ΔP2, ΔP when the pressure on the side indicated by the plus sign in FIG. 7 is relatively high.
It is assumed that a positive value is output as 3, ΔP4.
Then, the detection of the fuel gas leak using the differential pressure gauges 16 to 19 is performed by the procedure shown in the flowchart of FIG.

First, in step S51, the output current i
It is determined whether (electrical load) is smaller than the threshold i0. When the output current i (electrical load) is smaller than the threshold value i0, the process proceeds to step S52 and the purge valve 13
Is forcibly held in the closed state, and in the next step S53,
The output current breaker 30 shuts off the output of the output current i, and stops the power generation (fuel gas consumption) of the fuel cell 10.

At step S54, each differential pressure gauge 16-19
The output values ΔP1, ΔP2, ΔP3 and ΔP4 of are read.
In step S55, the read output values ΔP1, ΔP
2, ΔP3, ΔP4 is an electric signal noise, or whether or not it is larger than a minute pressure fluctuation value within the design value of the fuel cell system, the absolute value of each output value ΔP1, ΔP2, ΔP3, ΔP4 and a predetermined threshold value. It judges by comparing with A.

Here, all output values ΔP1, ΔP2, Δ
When P3 and ΔP4 are equal to or less than the threshold value A, step S
Proceeding to 56, the detected differential pressures of all the differential pressure gauges 16 to 19 are regarded as 0, and in the next step S57, it is determined that there is no fuel gas leakage. When all the detected differential pressures are 0, it means that the flow of the fuel gas in the fuel gas circulation supply lines 4, 6, 11 and 12 is stopped, which means that the fuel gas is stopped because the power generation of the fuel cell 10 is stopped. Therefore, it is judged that no fuel gas leakage has occurred because it matches the state where the fuel gas is not consumed and remains in the pipe.

On the other hand, in step S55, the output value ΔP1,
If it is determined that the threshold value A is exceeded among ΔP2, ΔP3, and ΔP4, the process proceeds to step S58. Step S
At 58, if the absolute value of the output values of the differential pressure gauges 16 to 19 is less than or equal to the threshold value A, it is regarded as 0, and if the absolute value exceeds the threshold value A, only the differential pressure direction is stored as plus or minus.

Then, in step S59, the location of the fuel gas leakage is identified based on the comparison between the determination map as shown in FIG. 9 and the actual differential pressure detection pattern. For example, when the detection result of the first differential pressure gauge 16 is positive, but the detection result of the second differential pressure gauge 17 is 0 or negative, the fuel gas is leaking in the fuel gas supply line 4 (Q0 pipe). Judge as something.

That is, the fact that the detection result of the first differential pressure gauge 16 is positive means that the pressure on the downstream side of the pressure reducing adjustment valve 3 is lower than that on the upstream side, and the fuel gas flowing toward the fuel cell 10 side in the pressure reducing adjustment valve 3 is low. However, when the detection result of the second differential pressure gauge 17 is 0 or negative, there is no flow in the ejector 5, or there is no flow from the fuel gas supply line 6 side to the fuel gas supply line 4 side. There will be an on-going flow, which will indicate the occurrence of a fuel gas leak in the fuel gas supply line 4.

In addition, the third differential pressure gauge 18 and the fourth differential pressure gauge 19
If both of the detected differential pressures are negative, the pressure of the fuel gas supply line 6 is lower than that of the fuel gas discharge line 11 and the fuel gas circulation line 12, which means that A flow flowing into the fuel gas supply line 6 side via the cell 10 is generated, and at the same time, a flow flowing into the fuel gas supply line 6 side from the fuel gas circulation line 12 via the ejector 5 is generated. Indicates the occurrence of fuel gas leakage in the fuel gas supply line 6 (Q1 pipe).

On the contrary, the third differential pressure gauge 18 and the fourth differential pressure gauge 19
If both of the detected differential pressures are positive, the pressures of the fuel gas discharge line 11 and the fuel gas circulation line 12 are lower than those of the fuel gas supply line 6, which means that A flow flowing into the fuel gas discharge line 11 side via the cell 10 is generated, and at the same time, a flow flowing into the fuel gas circulation line 12 side from the fuel gas supply line 6 via the ejector 5 is generated. Indicates the occurrence of fuel gas leakage in the fuel gas discharge line 11 and the fuel gas circulation line 12 (Q2 pipe).

The shaded display in FIG. 9 shows the minimum combination required for the determination of the leaked portion, and the leaked portion can be specified only by the combination of the shaded portions. However, it is also possible to make a determination from all the differential pressure outputs. At that time, if a condition not shown in FIG. 9 is detected, it is determined that the entire fuel cell system has some trouble, and an emergency stop is performed. An important alarm may be output.

When the location where the leak has occurred is identified in step S59, the determination result is stored as history information in preparation for the subsequent repair work in step S60, and the next step S6.
In No. 1, the driver is informed of the occurrence of leakage by an alarm or display, and the driver is prompted to perform an operation for ensuring safety. As described above, if the configuration is such that the generation of the flow of the fuel gas due to the fuel leakage is detected based on the differential pressure, it is possible to obtain a high detection sensitivity without being influenced by the absolute pressure in the pipe. It is possible to detect various fuel gas leaks and reduce the cost.

[Brief description of drawings]

FIG. 1 is a block diagram of a fuel cell system according to a first embodiment.

FIG. 2 is a flowchart showing a procedure of leak detection according to the first embodiment.

FIG. 3 is a block diagram of a fuel cell system according to a second embodiment.

FIG. 4 is a flowchart showing a leak detection procedure in the second embodiment.

FIG. 5 is a block diagram of a fuel cell system according to a third embodiment.

FIG. 6 is a flowchart showing a procedure of leak detection according to the third embodiment.

FIG. 7 is a block diagram of a fuel cell system according to a fourth embodiment.

FIG. 8 is a flowchart showing a procedure of leak detection in the fourth embodiment.

FIG. 9 is a diagram showing a determination map used for determining a leaked portion in the fourth embodiment.

[Explanation of symbols]

1 ... Hydrogen gas supply source 2 ... Fuel gas supply line 3 Decompression control valve 4 ... Fuel gas supply line 5 ... Ejector 6 ... Fuel gas supply line 7, 9 ... Pressure gauge 8, 15 ... Shut-off valve 10 ... Fuel cell 11 ... Fuel gas discharge line 12 ... Fuel gas circulation line 13 ... Purge valve 14 ... Purge line 16 to 19 ... Differential pressure gauge 20 ... Oxidant gas supply source 21 ... Gas supply line 22 ... Discharge line 30 ... Output current breaker 31 ... Ammeter 32 ... Output wiring 40 ... Signal processing device

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shuji Torii             Nissan, Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan             Inside the automobile corporation F term (reference) 5H027 AA02 BA19 KK05 KK11 KK56                       MM08 MM26

Claims (11)

[Claims] 1. When the electric load of the fuel cell is smaller than a threshold value, the output current of the fuel cell is cut off, and based on the pressure state in the closed space of the fuel gas circulation supply system including the fuel cell at this time. A method for detecting gas leakage in a fuel cell system, comprising detecting fuel gas leakage in the closed space. 2. The fuel gas supply from a fuel supply source to the closed space is forcibly cut off, and the fuel gas leakage is detected based on the pressure drop rate in the closed space. A method for detecting gas leakage in a fuel cell system as described. 3. The gas leak detection method for a fuel cell system according to claim 1, wherein the fuel gas leak is detected based on the differential pressure across the pressure loss portion in the closed space. 4. A fuel cell system including a fuel cell, a fuel supply source, and a fuel gas circulation supply system, and an output current interruption means for interrupting an output current of the fuel cell, and a fuel gas including the fuel cell. Pressure state detection means for detecting a pressure state in the closed space of the circulation supply system, electric load determination means for determining a state where the electric load of the fuel cell is smaller than a threshold value, and electric power of the fuel cell by the electric load determination means When it is determined that the load is smaller than a threshold value, the cutoff control means that cuts off the output current of the fuel cell by the output current cutoff means, and the cutoff control means cuts off the output current, And a fuel gas leakage judging means for judging the presence or absence of fuel gas leakage from the closed space based on the pressure state detected by the pressure state detecting means. Gas leak detection apparatus for a fuel cell system. 5. A fuel cell system comprising a fuel cell, a fuel supply source, and a fuel gas circulation supply system, wherein an output current interruption means for interrupting an output current of the fuel cell, and a fuel gas circulation supply system. A supply source cutoff means for forcibly shutting off the supply of fuel gas from the fuel supply source, a pressure detection means for detecting the pressure in the closed space of the fuel gas circulation supply system including the fuel cell, and the fuel cell An electric load discriminating means for discriminating a state in which the electric load is smaller than a threshold value; and when the electric load discriminating means discriminates that the electric load of the fuel cell is smaller than the threshold value, the output current interruption means outputs the fuel cell A cutoff control means for cutting off the current and forcibly cutting off the supply of the fuel gas from the fuel supply source by the supply source cutoff means, and a cutoff control of the output current by the cutoff control means. When the supply of fuel gas from the fuel supply source is forcibly cut off,
A fuel cell system comprising: a fuel gas leakage determining means for determining whether or not there is a fuel gas leakage from the closed space based on a pressure drop rate detected by the pressure detecting means. Gas leak detector. 6. A closed space dividing means for shutting off a closed space of a fuel gas circulation supply system including the fuel cell into a plurality of closed spaces, and the pressure detecting means detects the pressure of each of the plurality of closed spaces. 6. The fuel gas leakage determination means is configured as described above, and determines the presence or absence of the fuel gas leakage and the location of the fuel gas leakage based on the pressure drop rates of the plurality of closed spaces. Gas leak detection device for fuel cell system in Japan. 7. The pressure detection means detects the pressure between the pressure loss portions in the closed space at a plurality of points, and the fuel gas leakage determination means determines the pressure drop rate at each detection portion. The gas leak detection device for a fuel cell system according to claim 5, wherein the presence or absence of the fuel gas leak and the location where the fuel gas leak has occurred are determined. 8. The fuel gas leakage determining means, when the largest pressure drop speed among the pressure drop speeds at the respective detection parts is larger than a threshold value, the fuel at the detection part showing the largest drop speed. The gas leakage detection device for a fuel cell system according to claim 7, wherein the occurrence of gas leakage is determined. 9. A fuel cell system including a fuel cell, a fuel supply source, and a fuel gas circulation supply system, and an output current interruption means for interrupting an output current of the fuel cell, and a fuel gas including the fuel cell. Differential pressure detection means for detecting a differential pressure across at least one pressure loss portion in a closed space of the circulation supply system, electrical load determination means for determining a state in which the electrical load of the fuel cell is smaller than a threshold value, and the electrical load When the determination means determines that the electric load of the fuel cell is smaller than the threshold value, the output current cutoff means cuts off the output current of the fuel cell, and the cutoff control means cuts off the output current. When the differential pressure is detected, based on the differential pressure detected by the differential pressure detecting means,
A fuel leak detecting device for a fuel cell system, comprising: a fuel gas leak judging means for judging whether or not a fuel gas leaks from the closed space. 10. The differential pressure detecting means respectively detects differential pressures across a plurality of pressure loss portions in the closed space,
The fuel gas leakage determination means determines the occurrence of fuel gas leakage when the front-back differential pressure is greater than a threshold value, and determines the location of the fuel gas leakage based on the direction of the differential pressure at each of the adjacent detection units. 10. The gas leak detection device for a fuel cell system according to claim 9, wherein 11. The fuel cell system comprises a purge means for controlling purge from the circulation system of the fuel gas circulation supply system, and when the fuel gas leakage determination means determines the fuel gas leakage. The gas leak detection of the fuel cell system according to any one of claims 4 to 10, further comprising: a purge shutoff means for forcibly shutting off the purge by the purge means to form the closed space. apparatus.