JP2008171623A - Fuel cell system - Google Patents

Abstract

A fuel cell system capable of detecting leakage of a reaction gas upstream of a reaction gas supply means.
SOLUTION: A fuel cell 10, a reaction gas supply system 3 for supplying a reaction gas to the fuel cell 10, and a reaction gas supply for adjusting the gas state on the upstream side of the reaction gas supply system 3 and supplying the reaction gas to the downstream side Means 35, a control means 4 for driving and controlling the reaction gas supply means 35, and a leak detection means 4 for detecting a reaction gas leak upstream of the reaction gas supply means 35. The reaction gas supply means 35 is provided on the downstream side. The gas supply flow rate per unit time is predetermined, and the leak detection means 4 has the gas supply flow rate per unit time downstream of the reaction gas supply means 35 and the gas supplied by the reaction gas supply means 35. A gas leak upstream of the reaction gas supply means 35 is detected from the change in the gas state quantity upstream of the reaction gas supply means 35.
[Selection] Figure 1

Description

  The present invention relates to a fuel cell system provided with a reaction gas supply means having a predetermined gas supply flow rate per unit time to the downstream side.

Currently, a fuel cell system including a fuel cell that receives a supply of reaction gas (fuel gas and oxidizing gas) and generates electric power has been proposed and put into practical use. Such a fuel cell system is provided with a fuel supply channel for flowing fuel gas supplied from a fuel supply source such as a hydrogen tank to the fuel cell, and an upstream gas state is provided in the fuel supply channel. As a fuel supply means that adjusts the pressure and supplies the fuel gas downstream, a technique has been proposed in which an injector capable of appropriately controlling the supply of fuel gas with high responsiveness is provided (see, for example, Patent Document 1).
JP 2005-302563 A

  By the way, in the fuel cell system, it is necessary to detect the leakage of the fuel gas, and in particular, it is necessary to detect the leakage of the fuel gas upstream of the fuel supply means having a high fuel gas pressure. Although the above-described technology discloses disclosure of response control in the event of an injector failure, there has been no disclosure regarding detection of leakage of fuel gas upstream from such fuel supply means.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a fuel cell system capable of detecting leakage of a reaction gas (particularly, fuel gas) upstream of the reaction gas supply means. To do.

  To achieve the above object, a fuel cell system according to the present invention includes a fuel cell, a reaction gas supply system for supplying a reaction gas to the fuel cell, and a gas state upstream of the reaction gas supply system. A reaction gas supply means for supplying the reaction gas to the downstream side, a control means for controlling the operation of the reaction gas supply means, and a leak detection means for detecting a reaction gas leak upstream of the reaction gas supply means. In the fuel cell system, the reaction gas supply means has a predetermined gas supply flow rate per unit time to the downstream side, and the leak detection means is a gas per unit time to the downstream side in the reaction gas supply means. Based on the supply flow rate and the change in the gas state quantity upstream of the reaction gas supply means accompanying the gas supply of the reaction gas supply means, the reaction gas leakage upstream of the reaction gas supply means is detected. It is intended.

  According to such a configuration, when the reaction gas supply means supplies the reaction gas downstream, the gas state quantity upstream of the reaction gas supply means changes according to the gas supply flow rate. By using a predetermined gas supply flow rate per unit time to the downstream side as a means, the gas supply flow rate to the downstream side by the reactive gas supply means is determined, and the upstream gas state quantity associated therewith is determined. Based on the change, the reaction gas leakage upstream of the reaction gas supply means can be detected.

  The leak detection means determines that the reaction gas leak is present when a reaction gas leakage amount obtained by subtracting the gas state change from the gas supply flow rate per unit time is greater than a predetermined reference value. Also good.

  The reaction gas is, for example, a fuel gas. The reactive gas supply means may be an electromagnetically driven on-off valve, such as an injector, which can adjust the gas flow rate and gas pressure by driving the valve body with an electromagnetic driving force at a predetermined driving cycle and separating it from the valve seat. Good.

  According to the present invention, it is possible to detect leakage of a reactive gas (for example, fuel gas) upstream of the reactive gas supply means.

  Hereinafter, a fuel cell system 1 according to an embodiment of the present invention will be described with reference to the drawings. In the present embodiment, an example in which the present invention is applied to an on-vehicle power generation system of a fuel cell vehicle (moving body) will be described. First, the configuration of the fuel cell system 1 according to the embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 1, the fuel cell system 1 according to the present embodiment includes a fuel cell 10 that generates electric power upon receiving a supply of reaction gas (oxidation gas and fuel gas), and the fuel cell 10 has an oxidant gas. An oxidizing gas piping system 2 for supplying the air, a hydrogen gas piping system 3 for supplying hydrogen gas as a fuel gas to the fuel cell 10, a control device 4 for integrated control of the entire system, and the like.

  The fuel cell 10 has a stack structure in which a required number of unit cells that generate power upon receiving a reaction gas are stacked. The electric power generated by the fuel cell 10 is supplied to a PCU (Power Control Unit) 11. The PCU 11 includes an inverter, a DC-DC converter, and the like that are disposed between the fuel cell 10 and the traction motor 12. Further, the fuel cell 10 is provided with a current sensor 13 for detecting a current during power generation.

  The oxidant gas piping system 2 includes an air supply passage 21 that supplies the oxidant gas (air) humidified by the humidifier 20 to the fuel cell 10, and an air exhaust that guides the oxidant off-gas discharged from the fuel cell 10 to the humidifier 20. A flow path 22 and an exhaust flow path 23 for guiding the oxidizing off gas from the humidifier 20 to the outside are provided. The air supply passage 21 is provided with a compressor 24 that takes in the oxidizing gas in the atmosphere and pumps it to the humidifier 20.

  The hydrogen gas piping system 3 includes a hydrogen tank 30 as a fuel supply source storing high-pressure (for example, 70 MPa) hydrogen gas, and hydrogen as a fuel supply passage for supplying the hydrogen gas from the hydrogen tank 30 to the fuel cell 10. A supply flow path 31 and a circulation flow path 32 for returning the hydrogen off-gas discharged from the fuel cell 10 to the hydrogen supply flow path 31 are provided. The hydrogen gas piping system 3 is an embodiment of the reaction gas supply system in the present invention.

  Instead of the hydrogen tank 30, a reformer that generates a hydrogen-rich reformed gas from a hydrocarbon-based fuel, a high-pressure gas tank that stores the reformed gas generated by the reformer in a high-pressure state, and Can also be employed as a fuel supply source. A tank having a hydrogen storage alloy may be employed as a fuel supply source.

  The hydrogen supply flow path 31 is provided with a shutoff valve 33 that shuts off or allows the supply of hydrogen gas from the hydrogen tank 30, a regulator 34 that adjusts the pressure of the hydrogen gas, and an injector 35. A primary pressure sensor 41 and a temperature sensor 42 that detect the pressure and temperature of the hydrogen gas in the hydrogen supply flow path 31 are provided on the upstream side of the injector 35. Further, on the downstream side of the injector 35 and upstream of the junction between the hydrogen supply flow path 31 and the circulation flow path 32, a secondary side pressure sensor 43 that detects the pressure of the hydrogen gas in the hydrogen supply flow path 31. Is provided.

  The regulator 34 is a device that regulates the upstream pressure (primary pressure) to a preset secondary pressure. In the present embodiment, a mechanical pressure reducing valve that reduces the primary pressure is employed as the regulator 34. The mechanical pressure reducing valve has a structure in which a back pressure chamber and a pressure adjusting chamber are formed with a diaphragm therebetween, and the primary pressure is reduced to a predetermined pressure in the pressure adjusting chamber by the back pressure in the back pressure chamber. Thus, a publicly known configuration for the secondary pressure can be employed.

  The injector 35 is an electromagnetically driven on-off valve capable of adjusting the gas flow rate and gas pressure by driving the valve body directly with a predetermined driving cycle with an electromagnetic driving force and separating it from the valve seat. The injector 35 includes a valve seat having an injection hole for injecting gaseous fuel such as hydrogen gas, a nozzle body for supplying and guiding the gaseous fuel to the injection hole, and an axial direction (gas flow direction) with respect to the nozzle body. And a valve body that is movably accommodated and opens and closes the injection hole.

  In the present embodiment, the valve body of the injector 35 is driven by a solenoid that is an electromagnetic drive device, and the opening area (opening state) of the injection hole is set in two stages by turning on and off the pulsed excitation current supplied to the solenoid. The above-described multistage or stepless switching can be performed. The gas injection time and gas injection timing of the injector 35 are controlled by a control signal output from the control device 4, whereby the flow rate and pressure of hydrogen gas are controlled with high accuracy.

  Injector 35 changes the opening area (opening) and the opening time of the valve body provided in the gas flow path of injector 35 in order to supply the required gas flow rate downstream thereof, thereby reducing the downstream flow rate. The gas flow rate (or hydrogen molar concentration) supplied to the side (fuel cell 10 side) is adjusted.

  Since the gas flow rate is adjusted by opening and closing the valve body of the injector 35 and the gas pressure supplied downstream of the injector 35 is reduced from the gas pressure upstream of the injector 35, the injector 35 is controlled by a pressure regulating valve (pressure reducing valve, regulator). ). Further, in the present embodiment, a variable pressure control valve capable of changing the pressure adjustment amount (pressure reduction amount) of the upstream gas pressure of the injector 35 so as to match the required pressure within a predetermined pressure range in accordance with the gas requirement. Can also be interpreted.

  A discharge flow path 38 is connected to the circulation flow path 32 via a gas-liquid separator 36 and an exhaust drain valve 37. The gas-liquid separator 36 collects moisture from the hydrogen off gas. The exhaust / drain valve 37 is operated according to a command from the control device 4 to discharge (purge) moisture collected by the gas-liquid separator 36 and hydrogen off-gas containing impurities in the circulation flow path 32 to the outside. Is.

  In addition, the circulation channel 32 is provided with a hydrogen pump 39 that pressurizes the hydrogen off gas in the circulation channel 32 and sends it to the hydrogen supply channel 31 side. The hydrogen off-gas discharged through the exhaust / drain valve 37 and the discharge passage 38 is diluted by the diluter 40 and merges with the oxidizing off-gas in the exhaust passage 23.

  The control device 4 detects an operation amount of an acceleration operation device (accelerator or the like) provided in the vehicle, receives control information such as an acceleration request value (for example, a required power generation amount from a load device such as the traction motor 12), In addition to functioning as control means for controlling the operation of various devices in the system, the present embodiment further functions as leakage detection means for detecting fuel gas leakage upstream of the injector 35.

  In addition to the traction motor 12, the load device is an auxiliary device (for example, a compressor 24, a hydrogen pump 39, a cooling pump motor, or the like) necessary for operating the fuel cell 10, and various types of vehicles involved in traveling of the vehicle. It is a collective term for power consumption devices including actuators used in devices (transmissions, wheel control devices, steering devices, suspension devices, etc.), occupant space air conditioners (air conditioners), lighting, audio, and the like.

  The control device 4 is configured by a computer system (not shown). Such a computer system includes a CPU, ROM, RAM, HDD, input / output interface, display, and the like, and various control operations are realized by the CPU reading and executing various control programs recorded in the ROM. It is like that.

  Specifically, as shown in FIG. 2, the control device 4 is consumed by the fuel cell 10 based on the operating state of the fuel cell 10 (current value during power generation of the fuel cell 10 detected by the current sensor 13). The amount of hydrogen gas (hereinafter referred to as “hydrogen consumption”) is calculated (fuel consumption calculation function: B1). In the present embodiment, the hydrogen consumption is calculated and updated for each calculation cycle of the control device 4 using a specific calculation formula representing the relationship between the current value of the fuel cell 10 and the hydrogen consumption.

  Further, the control device 4 determines the target pressure value of hydrogen gas (to the fuel cell 10) at the downstream position of the injector 35 based on the operating state of the fuel cell 10 (current value at the time of power generation of the fuel cell 10 detected by the current sensor 13). Target gas supply pressure) (target pressure value calculation function: B2). In the present embodiment, a position (pressure) where the secondary pressure sensor 43 is arranged for each calculation cycle of the control device 4 using a specific map representing the relationship between the current value of the fuel cell 10 and the target pressure value. The target pressure value at the pressure adjustment position where adjustment is required is calculated and updated.

  Further, the control device 4 calculates the feedback correction flow rate based on the deviation between the calculated target pressure value and the detected pressure value at the downstream position (pressure adjustment position) of the injector 35 detected by the secondary pressure sensor 43 ( Feedback correction flow rate calculation function: B3). The feedback correction flow rate is a hydrogen gas flow rate (pressure difference reduction correction flow rate) added to the hydrogen consumption in order to reduce the deviation between the target pressure value and the detected pressure value. In the present embodiment, the feedback correction flow rate is calculated and updated every calculation cycle of the control device 4 using a target tracking control law such as PI control.

  Moreover, the control apparatus 4 calculates the feedforward correction | amendment flow volume corresponding to the deviation of the target pressure value calculated last time and the target pressure value calculated this time (feedforward correction | amendment flow volume calculation function: B4). The feedforward correction flow rate is a change in the hydrogen gas flow rate due to the change in the target pressure value (correction flow corresponding to the pressure difference). In the present embodiment, the feedforward correction flow rate is calculated and updated every calculation cycle of the control device 4 using a specific calculation formula representing the relationship between the deviation of the target pressure value and the feedforward correction flow rate. .

  Further, the control device 4 determines the static flow rate upstream of the injector 35 based on the gas state upstream of the injector 35 (hydrogen gas pressure detected by the primary pressure sensor 41 and hydrogen gas temperature detected by the temperature sensor 42). (Static flow rate calculation function: B5). In the present embodiment, the static flow rate is calculated for each calculation cycle of the control device 4 using a specific calculation formula representing the relationship between the pressure and temperature of the hydrogen gas upstream of the injector 35 and the static flow rate. We are going to update.

  Further, the control device 4 calculates the invalid injection time of the injector 35 based on the gas state upstream of the injector 35 (pressure and temperature of hydrogen gas) and the applied voltage (invalid injection time calculation function: B6). Here, the invalid injection time means the time required from when the injector 35 receives the control signal from the control device 4 until the actual injection is started. In the present embodiment, the invalid injection time is calculated for each calculation cycle of the control device 4 using a specific map representing the relationship between the pressure and temperature of the hydrogen gas upstream of the injector 35, the applied voltage, and the invalid injection time. I am going to update it.

  Further, the control device 4 calculates the injection flow rate of the injector 35 by adding the hydrogen consumption amount, the feedback correction flow rate, and the feedforward correction flow rate (injection flow rate calculation function: B7). Then, the control device 4 calculates the basic injection time of the injector 35 by multiplying the value obtained by dividing the injection flow rate of the injector 35 by the static flow rate by the drive cycle of the injector 35, and the basic injection time and the invalid injection time. Are added to calculate the total injection time of the injector 35 (total injection time calculation function: B8).

  Here, the drive cycle means a stepped (on / off) waveform cycle representing the open / close state of the injection hole of the injector 35. In the present embodiment, the drive period is set to a constant value by the control device 4.

  And the control apparatus 4 controls the gas injection time and gas injection timing of the injector 35 by outputting the control signal for implement | achieving the total injection time of the injector 35 computed through the above procedure, and fuel cell The flow rate and pressure of the hydrogen gas supplied to 10 are adjusted. That is, the injector 35 is a reaction gas supply means having a predetermined gas supply flow rate per unit time downstream of the injector 35.

  During normal operation of the fuel cell system 1, hydrogen gas is supplied from the hydrogen tank 30 to the fuel electrode of the fuel cell 10 through the hydrogen supply channel 31, and the air that has been subjected to humidification adjustment passes through the air supply channel 21. Is supplied to the oxidation electrode of the fuel cell 10 to generate power. At this time, the power (required power) to be drawn from the fuel cell 10 is calculated by the control device 4, and hydrogen gas and air in an amount corresponding to the amount of power generation are supplied into the fuel cell 10.

  Next, detection of leakage of hydrogen gas (fuel gas) upstream of the injector (fuel supply means) 35 by the control device 4 of the fuel cell system 1 will be described.

Since the injector 35 has a predetermined injection amount per unit time at the time of opening operation, that is, a gas supply flow rate, the control device 4 ends the predetermined detection from a predetermined detection start timing t1 as shown in FIG. The gas supply flow rate ΔQ _inj [NL] to the downstream side by the injector 35 from the time point t1 to the time point t2 is integrated by integrating the gas supply flow rate due to each opening operation of the injector 35 until the time point t2. calculate.

On the other hand, with the injection from the time point t1 to the time point t2 of the injector 35 described above, the state quantity Q _t1 at the time point t1 upstream of the injector 35 changes to the state quantity Q _t2 at the time point _t2. State quantity change ΔQ _t2−t1 = Q _t2 −Q _t1 [NL] is obtained as follows.

Since the volume V upstream of the injector 35 is predetermined, the pressure P _t1 and the temperature T _t1 of the hydrogen gas at the time t1 detected by this and the primary pressure sensor 41 and temperature sensor 42 upstream of the injector 35 From this, the gas state quantity Q _t1 at time _t1 is calculated by the following equation based on the gas state equation.

Q _t1 = Z (P _t1 V) / (RT _t1 )

Here, R is a gas constant. Z is a compression coefficient, and Z determined by the pressure P _t1 and temperature T _t1 at time t1 is obtained from the map from a map showing the relationship between the compression coefficient Z, pressure P, and temperature T set in advance by experiments or the like. And assign.

Similarly, from the pressure P _t2 and temperature T _t2 of the hydrogen gas at time t2, the gas state quantity Q _t2 at time _t2 is _calculated from the map, and Z determined by the pressure P _t2 and temperature T _t2 at time _t2 from the map is Substitute and calculate.

Q _t2 = Z (P _t2 V) / (RT _t2 )

Next, the gas state quantity change (substance quantity change) ΔQ _t2−t1 upstream of the injector 35 accompanying the gas supply of the injector 35 from the time t1 to the time t2 is calculated by the following equation.

ΔQ _t2-t1 = Q _t2 -Q _t1 [NL]

Subsequently, the control device 4 determines the gas supply flow rate ΔQ _inj from the time point t1 to the time point t2 by the injection of the injector 35 obtained as described above, and the injector accompanying the gas injection to the downstream side of the injector 35. From the gas state quantity change ΔQ _t2-t1 upstream of 35, the hydrogen gas leakage quantity ΔQ _Leak upstream of the injector 35 is calculated by the following equation.

ΔQ _Leak = ΔQ _t2−t1 −ΔQ _inj [NL]

If there is no hydrogen gas leak upstream of the injector 35, ΔQ _t2−t1 = ΔQ _inj and ΔQ _Leak = 0. _Therefore , the control device 4 considers measurement errors and the like as hydrogen gas leak. From the comparison between the reference value ΔQ _jdg [NL] set as an allowable amount and the hydrogen gas leakage amount ΔQ _Leak, it is determined whether there is hydrogen gas leakage upstream of the injector 35.

That is, if ΔQ _Leak > ΔQ _jdg , the control device 4 determines that hydrogen gas leaks upstream from the injector 35. On the other hand, if ΔQ _Leak > ΔQ _{jdg is} not _satisfied , the control device 4 determines that there is no leakage of hydrogen gas upstream of the injector 35.

Alternatively, the leak rate per unit time ΔQ _Leak / (t 2 −t 1) [NL / sec] is calculated, and this leak rate should be larger than the reference rate that is acceptable as the hydrogen gas leak rate in consideration of measurement errors and the like. For example, it may be determined that there is a hydrogen gas leak upstream of the injector 35, and if it is not larger, it may be determined that there is no hydrogen gas leak upstream of the injector 35.

  When it is determined that there is hydrogen gas leakage, the control device 4 performs processing such as closing the shutoff valve 33 of the hydrogen tank 30 to stop the supply of hydrogen gas and generating an alarm.

  According to the fuel cell system 1 according to the embodiment described above, when the injector 35 supplies gas to the downstream side, the gas state quantity upstream of the injector 35 changes according to the gas supply flow rate. By utilizing the fact that the predetermined gas supply flow rate per unit time to the downstream side is used, the gas supply flow rate to the downstream side by the injector 35 is determined, and this is accompanied by the upstream gas associated therewith. Based on the change in the state quantity, hydrogen gas leakage upstream of the injector 35 can be detected.

  Even if the reaction gas (fuel gas) supply means other than the injector 35 is used, if the gas supply flow rate per unit time to the downstream side is a predetermined one, the above-described hydrogen gas leak detection method is applied. Thus, it is possible to detect a gas leak upstream of the reaction gas supply means.

1 is a configuration diagram of a fuel cell system according to an embodiment of the present invention. It is a control block diagram for demonstrating the control aspect of the control apparatus of the fuel cell system shown in FIG. FIG. 2 is a timing chart for explaining a hydrogen gas leak detection operation upstream of an injector by a control device of the fuel cell system shown in FIG. 1.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 3 ... Hydrogen gas piping system (reaction gas supply system), 4 ... Control apparatus (control means, leak detection means), 10 ... Fuel cell, 35 ... Injector (reaction gas supply means).

Claims (4)

A fuel cell, a reaction gas supply system for supplying a reaction gas to the fuel cell, a reaction gas supply means for adjusting a gas state on the upstream side of the reaction gas supply system and supplying the gas to the downstream side, and the reaction gas A fuel cell system comprising: control means for controlling the operation of the supply means; and leak detection means for detecting a reaction gas leak upstream of the reaction gas supply means,
The reaction gas supply means has a predetermined gas supply flow rate per unit time to the downstream side,
The leak detection means includes a gas supply flow rate per unit time to the downstream side in the reaction gas supply means, and a gas state quantity change upstream of the reaction gas supply means accompanying the gas supply of the reaction gas supply means. Based on the above, a fuel cell system that detects a reaction gas leak upstream of the reaction gas supply means. The fuel cell system according to claim 1, wherein
The leak detection means determines that the reaction gas leak is present when a reaction gas leak amount obtained by subtracting the gas state change from the gas supply flow rate per unit time is greater than a predetermined reference value. Battery system. The fuel cell system according to claim 1 or 2,
The fuel cell system, wherein the reaction gas is a fuel gas. The fuel cell system according to any one of claims 1 to 3,
The reaction gas supply means is a fuel cell system that is an injector capable of adjusting a gas flow rate and a gas pressure by driving a valve body with an electromagnetic driving force at a predetermined driving cycle and separating the valve body from a valve seat.

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