JP2014103064A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology for precisely detecting the residual amount of fuel gas while suppressing the cost.SOLUTION: A control part provided in a fuel cell system detects a signal outputted by a first pressure sensor as a first detection pressure value, calculates the pressure gradient of the first detection pressure value detected by the control part, and also calculates the residual amount of fuel gas in a tank by utilizing the rise gradient when the calculated pressure gradient is the rise gradient.

Description

  The present invention relates to a technology of a fuel cell system.

  2. Description of the Related Art A fuel cell system including a fuel cell that generates electric power by an electrochemical reaction between a fuel gas and an oxidant gas is known. The fuel cell system is used as a power source for automobiles, for example. The fuel cell system includes a tank that stores fuel gas at a pressure higher than normal pressure (atmospheric pressure). Conventionally, a technique that utilizes the state of pressure pulsation in order to detect the remaining amount of fuel gas in a tank is known (for example, Patent Document 1). The state of pressure pulsation is detected by a pressure sensor arranged on the downstream side of the flow rate adjustment valve.

JP 2006-156110 A JP 2009-123592 A JP 2007-051675 A

  However, when detecting the remaining amount of fuel gas in the tank based on the state of pressure pulsation, it is difficult to take measures to suppress pressure pulsation. For this reason, the power generation performance and durability of the fuel cell may decrease due to pressure pulsation. Further, since a relatively large pressure pulsation must be allowed, a member (for example, an electrolyte membrane) constituting the fuel cell needs to have a performance capable of withstanding the pressure pulsation. Although a mechanism for attenuating the pressure pulsation may be provided on the downstream side of the mechanism for detecting the pressure pulsation, there is a problem that the cost of the fuel cell system is increased by providing the mechanism for attenuating.

Further, a method in which a high-pressure sensor is disposed in a flow path located between the flow rate adjustment valve and the tank and the remaining amount of fuel gas in the tank is detected based on a detected pressure value of the high-pressure sensor can be considered. However, the detection range of the high pressure sensor is wide. Therefore, an expensive high-pressure sensor is required to increase the detection accuracy over a wide range, resulting in a problem that the cost of the fuel cell system increases.

  As described above, in the fuel cell system, a technique for accurately detecting the remaining amount of fuel gas while reducing cost is desired. Further, in a fuel cell system, improvement in power generation performance, improvement in durability, resource saving, ease of manufacture, improvement in usability, and the like are desired.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms.

(1) According to one aspect of the present invention, a fuel cell system is provided. In this fuel cell system, the fuel gas supplied from a tank in which fuel gas is stored at a pressure higher than normal pressure is adjusted to a pressure within a predetermined range by a pressure reducing valve, and then supplied to the fuel cell. In addition, the fuel cell system includes the pressure reducing valve, a gas flow path for allowing the fuel gas in the tank to flow to the fuel cell, and a downstream side of the pressure reducing valve in the gas flow path. A first pressure sensor and a control unit for controlling the fuel cell system. The control unit detects a signal output from the first pressure sensor as a first detected pressure value, calculates a pressure gradient of the detected first detected pressure value, and the calculated pressure gradient increases. In the case of a gradient, the remaining amount of the fuel gas in the tank is detected using the rising gradient. According to the fuel cell system of this embodiment, the remaining amount of the fuel gas can be detected using the ascending gradient calculated using the first pressure sensor arranged on the downstream side of the pressure reducing valve. That is, the fuel gas in the tank using the first pressure sensor having a measurement range relatively lower than the pressure sensor for detecting the pressure in the tank (hereinafter also referred to as “second pressure sensor”). The remaining amount can be detected.

(2) In the fuel cell system according to the above aspect, the controller may control the amount of the fuel gas in the tank based on the relationship that the remaining amount of the fuel gas in the tank increases as the rising gradient increases. A fuel cell system that detects the remaining amount.
The greater the remaining amount of fuel gas in the tank and the higher the pressure in the tank, the greater the slope of pressure increase downstream of the pressure reducing valve when the pressure reducing valve is open. For example, when the fuel gas is hydrogen, the pressure of the upstream portion (high pressure side) located upstream of the pressure reducing valve in the gas flow path is the pressure of the downstream portion (low pressure side) located downstream of the pressure reducing valve. It is known that the pressure on the high pressure side and the rising gradient on the low pressure side have a proportional relationship when the pressure is larger than twice the pressure.
That is, according to the fuel cell system of this embodiment, the control unit uses the relationship (hereinafter also referred to as “first relationship”) that the remaining amount of fuel gas increases as the ascending gradient increases. The remaining amount of fuel gas can be easily calculated based on the first detected pressure value detected by the pressure sensor.
Here, when the reaction gas which is a fluid flows through the gas flow path, a pressure loss is accompanied. Therefore, it is more preferable to adopt the following form in order to calculate the remaining amount of the fuel gas with higher accuracy. That is, a program such as a map and an arithmetic expression representing the first relationship created based on an experiment based on an actual machine is stored in the fuel cell system, and the control unit calculates the remaining amount of fuel gas using this program. To do.

(3) In the fuel cell system according to the above aspect, when the pressure gradient is a descending gradient, the control unit calculates a consumption amount of the fuel gas by the fuel cell using the descending gradient. Fuel cell system.
There is a fixed relationship between the volume of fuel gas remaining in the downstream portion and the pressure. That is, if the volume of the fuel gas staying in the downstream portion decreases, the pressure in the downstream portion also decreases. According to the fuel cell system of this aspect, the fuel gas consumption by the fuel cell can be calculated using the descending gradient calculated using the first pressure sensor disposed in the downstream portion.

(4) In the fuel cell system according to the above aspect, the control unit may reduce the consumption amount of the fuel gas based on a relationship that the consumption amount of the fuel gas by the fuel cell increases as the descending gradient increases. Calculate the fuel cell system. According to the fuel cell system of this form, the control unit uses this program by storing a program such as a map or an arithmetic expression representing the fixed relationship described in the above form (3) in the fuel cell system. Fuel gas consumption can be easily calculated.

(5) The fuel cell system according to the above aspect, comprising a current sensor for detecting a generated current value of the fuel cell, wherein the control unit detects a signal output by the current sensor as a generated current value. The fuel gas consumption by the fuel cell is calculated using the generated current value, and the fuel gas consumption calculated using the descending slope and the generated current value are used for calculation. A fuel cell system that calculates a difference value from the consumption amount of the fuel gas as a leakage gas amount that has not been used for power generation of the fuel cell. According to the fuel cell system of this embodiment, the leakage gas amount can be calculated by calculating the difference value. By calculating the amount of leaked gas, for example, it is possible to more appropriately control the operation of the fuel cell system, such as being able to notify whether or not an abnormality has occurred. Here, the cause of the generation of leakage gas that has not been used for power generation is, for example, a so-called crossover phenomenon in which the fuel gas passes through the electrolyte membrane without reacting at the anode, or a crack occurs when a crack occurs in the gas flow path, for example. There is a phenomenon in which the fuel gas supply pipe 70 and the like are purged with the fuel gas when the fuel cell system 5 is stopped or when the fuel cell system 5 is stopped.

(6) In the fuel cell system of the above aspect, the control unit calculates the leakage gas amount at every predetermined time interval, and based on the leakage gas amount calculated at the predetermined time interval, The corrected leaked gas amount is calculated, and the corrected leaked gas amount at the Nth time (N is an integer of 2 or more) is a moving average value of the leaked gas amount calculated every Nth time. The weighting factor to be used is larger in the first case when the generated current value is the first value and when the generated current value is the second value larger than the first value. Fuel cell system. According to the fuel cell system of this aspect, the weighting factor is used, and the weighting factor in the case of the first value smaller than the second value is increased as compared with the case where the generated current value is the second value. Thus, the amount of leaked gas can be calculated with high accuracy.

(7) In the fuel cell system according to the above aspect, the control unit corrects the consumption amount of the fuel gas calculated by using the generated current value by using the corrected leaked gas amount. A fuel cell system for calculating post fuel gas consumption. According to the fuel cell system of this embodiment, the consumption amount of the fuel gas in the tank can be detected with higher accuracy by taking the leakage gas amount into consideration.

(8) The fuel cell system according to the above aspect, further including a second pressure sensor that is disposed upstream of the pressure reducing valve in the gas flow path and can detect a pressure higher than the first pressure sensor. And the control unit detects a signal output by the second pressure sensor as a second detected pressure value, and detects the second detected pressure value by the first pressure sensor. A fuel cell system that performs correction processing using a detected pressure value of 1.
The second pressure sensor disposed on the high pressure side may be affected by the pressure of the fuel gas, and the detection accuracy may be lowered due to drift in the output characteristics. According to the fuel cell system of this embodiment, the pressure in the tank located on the high pressure side is corrected by correcting the second detected pressure value by the second pressure sensor using the pressure value by the first pressure sensor. It can be detected with high accuracy.

(9) The fuel cell system according to the above aspect, wherein the control unit executes the correction process when it is determined that the upward gradient is smaller than a predetermined value.
In a state where the ascending slope is smaller than a predetermined value, the fluctuation due to drift is large and affects the output signal of the second pressure sensor, so that the detection accuracy of the second pressure sensor is more significantly lowered. According to the fuel cell system of this embodiment, since the correction process is performed when the ascending gradient becomes smaller than a predetermined value, the pressure in the tank located on the high pressure side can be detected with high accuracy.

  It should be noted that the present invention can be realized in various forms, for example, in the form of a control method for a fuel cell system, a program for executing the control method, and the like.

It is a figure for demonstrating a fuel cell system. It is a conceptual diagram showing the pressure transition in a downstream supply piping. It is a figure for demonstrating the data memorize | stored in the control part. It is a figure for demonstrating the data memorize | stored in the control part. It is a figure for demonstrating the data memorize | stored in the control part. It is a figure for demonstrating the control routine which a control part performs. It is a figure for demonstrating the control routine which a control part performs. It is a figure for demonstrating the control routine which a control part performs. It is a figure for demonstrating the control routine which a control part performs. It is a figure for demonstrating the control routine which a control part performs.

Next, embodiments of the present invention will be described in the following order.
A. First embodiment:
B. Variations:

A. First embodiment:
A-1: Configuration of the fuel cell system:
FIG. 1 is a diagram for explaining the fuel cell system 5. The fuel cell system 5 can be used for an in-vehicle power generation system for a fuel cell vehicle and a power generation system for a moving body such as a ship, an aircraft, a train, and a walking robot. Further, the fuel cell system 5 can be used not only for moving objects but also for stationary power generation systems that are used as power generation systems for buildings (housing, buildings, etc.). Hereinafter, an embodiment will be described using an example in which the fuel cell system 5 is mounted on an automobile.

  The fuel cell system 5 includes a fuel cell 10, a fuel gas supply / discharge system 32, an oxidant gas supply / discharge system 85, a control unit 90, and a current sensor 20.

  The fuel cell 10 has a stack structure in which a plurality of unit cells that generate power upon receiving supply of reaction gases (fuel gas and oxidant gas) are stacked. The electric power generated by the fuel cell 10 is used as power for the automobile. In the present embodiment, the fuel cell 10 is a polymer electrolyte fuel cell. The generated current value of the fuel cell 10 is detected by the current sensor 20.

  The fuel gas supply / discharge system 32 supplies hydrogen as a fuel gas to the fuel cell 10 and discharges the fuel gas discharged from the fuel cell 10 to the outside as an anode off gas. The fuel gas supply / discharge system 32 mainly includes a tank 30, a fuel gas supply pipe 70 as a gas flow path, and a fuel gas discharge pipe 75. The tank 30 stores hydrogen as fuel gas. In an initial state before the supply of hydrogen from the tank 30 to the fuel cell 10 is started, hydrogen at a pressure higher than normal pressure (for example, 50 to 100 MPa_abs) is stored in the tank 30. The fuel gas supply pipe 70 allows the tank 30 and the fuel cell 10 to communicate with each other. Hydrogen in the tank 30 is supplied to the fuel cell 10 via the fuel gas supply pipe 70.

  In the fuel gas supply pipe 70, a first pressure sensor 40, a second pressure sensor 50, and a pressure reducing valve 60 as a pressure control valve are arranged. The pressure reducing valve 60 adjusts the upstream pressure (primary pressure) at which the tank 30 is disposed to a pressure within a predetermined range. Here, a portion of the fuel gas supply pipe 70 that is located on the fuel cell 10 side that is downstream of the pressure reducing valve 60 is referred to as a downstream supply pipe 72, and is located on the tank 30 side that is upstream of the pressure reducing valve 60. The portion that is positioned is referred to as an upstream supply pipe 71.

  The first pressure sensor 40 is disposed in the downstream supply pipe 72. The second pressure sensor 50 is disposed in the upstream supply pipe 71. The first pressure sensor 40 has a measurement range relatively lower than that of the second pressure sensor 50. That is, the second pressure sensor 50 can measure a higher pressure than the first pressure sensor 40. The measurement range of the first pressure sensor 40 is, for example, 0.1 MPa to 3 MPa. The measurement range of the second pressure sensor 50 is, for example, 1 to 100 MPa. Here, a value detected by the control unit 90 by the first pressure sensor 40 is referred to as a “first detected pressure value”, and a value detected by the control unit 90 by the second pressure sensor 50 is referred to as a “second detected pressure value”. Called “value”.

  The fuel gas discharge pipe 75 discharges hydrogen not used for power generation out of the hydrogen supplied to the fuel cell 10 to the outside as an anode off gas. Alternatively, the anode gas may be supplied to the fuel cell 10 again by connecting the fuel gas discharge pipe 75 to the fuel gas supply pipe 70.

  The oxidant gas supply / discharge system 85 supplies air as an oxidant gas to the fuel cell 10 and discharges the air discharged from the fuel cell 10 to the outside as a cathode off gas. The oxidant gas supply / discharge system 85 includes an oxidant gas supply pipe 80 and an oxidant gas discharge pipe 82. An air compressor 84 is disposed in the oxidant gas supply pipe 80. By operating the air compressor 84, air is supplied to the fuel cell 10 via the oxidant gas supply pipe 80. The oxidant gas discharge pipe 82 discharges the air that has not been used for the reaction out of the air supplied to the fuel cell 10 to the outside as a cathode off gas.

  Here, the fuel cell system 5 may include a refrigerant supply / discharge system for adjusting the temperature of the fuel cell 10. The refrigerant supply / discharge system supplies cooling water as a refrigerant to the fuel cell 10, cools the cooling water discharged from the fuel cell 10 with a radiator, and supplies the cooling water again to the fuel cell 10.

  The control unit 90 controls the operation of the fuel cell system 5. Various devices such as the first pressure sensor 40, the second pressure sensor 50, the pressure reducing valve 60, the current sensor 20, and the air compressor 84 are electrically connected to the control unit 90. The control unit 90 includes a storage unit 92. The storage unit 92 stores various data used for controlling the operation of the fuel cell system 5.

  FIG. 2 is a conceptual diagram showing the pressure transition in the downstream supply pipe 72. The vertical axis in FIG. 2 indicates the first detected pressure value PL, and the horizontal axis indicates time. A broken line described in the conceptual diagram indicates a change in the first detected pressure value PL due to opening and closing of the pressure reducing valve 60. The controller 90 controls the pressure reducing valve 60 to control the downstream supply pipe 72 to be in the range of pressures P1 and P2. Specifically, when the first detected pressure value PL reaches the pressure P1, the control unit 90 opens the pressure reducing valve 60 to supply hydrogen in the tank 30 to the downstream supply pipe 72 and the fuel cell 10. . On the other hand, when the first detected pressure value PL reaches the pressure P2, the supply of hydrogen from the tank 30 to the downstream supply pipe 72 and the fuel cell 10 is stopped by closing the pressure reducing valve 60.

  As shown in FIG. 2, when the pressure reducing valve 60 is in the open state, the pressure in the downstream supply pipe 72 increases, and when the pressure reducing valve 60 is in the closed state, the pressure in the downstream supply pipe 72 decreases. The pressure reducing valve 60 is open at times t1 to t2 and times t3 to t4, and the pressure reducing valve 60 is closed at times t2 to t3. Here, when the hydrogen in the tank 30 is consumed and the pressure in the tank 30 decreases, the amount of hydrogen per unit time supplied to the downstream supply pipe 72 also decreases. Therefore, the pressure gradient Gu (also referred to as “pressure increase gradient Gu”), which is the amount of change in the first detected pressure value PL when the pressure reducing valve 60 is open, and the pressure in the tank 30 can be expressed by a function. That is, when the pressure in the tank 30 decreases, the pressure increase gradient Gu also decreases. By obtaining the relationship between the pressure increase gradient Gu and the pressure in the tank 30 in advance, the pressure in the tank 30 can be calculated using the pressure increase gradient Gu calculated in the actual machine using the obtained relationship.

  As shown in FIG. 2, when the pressure reducing valve 60 is closed, hydrogen in the downstream supply pipe 72 is consumed by the fuel cell 10, so the pressure in the downstream supply pipe 72 gradually decreases. Therefore, the pressure gradient Gd (also referred to as “pressure decrease gradient Gd”), which is the amount of change in the first detected pressure value PL when the pressure reducing valve 60 is closed, and the hydrogen consumption per unit time (mol). / S) can be expressed by a function. That is, as the hydrogen consumption per unit time increases, the pressure decrease gradient Gd increases. By calculating the relationship between the pressure drop gradient Gd and the hydrogen consumption per unit time in advance, the hydrogen consumption per unit time is calculated using the pressure drop gradient Gd calculated in the actual machine using the obtained function. can do.

  The amount of hydrogen used for power generation of the fuel cell 10 (also referred to as “reaction consumption”) can be calculated using a known method based on the power generation current value detected by the current sensor 20. By calculating the difference between the reaction consumption amount and the hydrogen consumption amount calculated from the pressure decrease gradient Gd, the amount of hydrogen not used for power generation of the fuel cell 10 (also referred to as “leakage gas amount”) is acquired. can do.

  FIG. 3 is a diagram for explaining data (program) stored in the control unit 90. FIG. 3 is a graph that defines the relationship between the pressure increase gradient Gu and the pressure in the tank 30. 3 indicates the differential value DPL1 (pressure increase gradient Gu) calculated based on the first detected pressure value PL, and the vertical axis in FIG. 3 indicates the estimated pressure value PHI in the tank 30. The storage unit 92 stores a map representing the relationship between the pressure increase gradient Gu obtained in advance and the pressure in the tank 30.

  FIG. 4 is a diagram for explaining data (program) stored in the control unit 90. FIG. 4 is a graph that defines the relationship between the pressure decrease gradient Gd and the hydrogen consumption (also referred to as “estimated fuel consumption FCP”) estimated from the pressure decrease gradient Gd. 4 indicates the differential value DPL2 (pressure decrease gradient Gd) calculated based on the first detected pressure value PL, and the vertical axis in FIG. 4 indicates the estimated fuel consumption FCP. The storage unit 92 stores a map representing a relationship (second relationship) between the pressure decrease gradient Gd obtained in advance and the estimated fuel consumption amount FCP.

  FIG. 5 is a diagram for explaining the data (program) stored in the control unit 90. FIG. 5 shows the relationship between the generated current value and the coefficient J. This coefficient is the reciprocal of the weight coefficient used when calculating the corrected leak gas amount using the moving average. In other words, the smaller the generated current value, the larger the weight coefficient. In other words, in the case where the generated current value is the first value and the second value where the generated current value is smaller than the first value, the case of the first value is better than the case of the second value. The weighting factor is large. This relationship is based on the following findings. It is known that the reaction gas (hydrogen and air) supplied to the fuel cell 10 moves through the electrolyte membrane without reacting at each electrode and burns at the destination. As a result, regardless of the amount of the reaction gas supplied to the fuel cell 10, the amount of the reaction gas that has not been used for the reaction of the fuel cell 10 becomes substantially constant. For example, the lower limit value of the coefficient J is 128, and the upper limit value can be set to 1024.

A-2. Control routine:
6 and 7 are diagrams for explaining a control routine performed by the control unit 90. FIG. The control routine described in FIGS. 6 and 7 is executed at a cycle for ensuring the accuracy of the differential value calculated based on the first detected pressure value PL described later. For example, the control unit 90 executes a control routine every 10 ms.

  The controller 90 detects and stores the signal (voltage value) output by the second pressure sensor 50 as the second detected pressure value PH (step S102). Further, the control unit 90 detects and stores the signal (voltage value) output by the first pressure sensor 40 as the first detected pressure value PL (step S104). Next, it is determined whether or not the second detected pressure value PH is smaller than a predetermined value (step S106). This is a step provided to reduce the accuracy of the differential value DPL1 which is the pressure increase gradient Gu when the pressure in the tank 30 is high and the pressure increase gradient Gu of the downstream supply pipe 72 is large. That is, when the second detected pressure value PH is smaller than a predetermined value, the processes of steps S110 to S120 described below are performed. For example, the predetermined value may be set in a range of 1/2 to 1/30 of the pressure in the initial state in the tank 30. In the present embodiment, the predetermined value is 10 MPa_abs. Here, the predetermined value in step S106 is referred to as “collection availability determination pressure value”.

  When the control unit 90 determines that the second detected pressure value PH is smaller than the collection possibility determination pressure value (step S106: YES), the pressure reducing valve 60 is open in the current routine and in the previous routine. It is determined whether or not the open condition is satisfied (step S108). In step S <b> 108, the open state of the pressure reducing valve 60 may be determined by detecting that the pressure reducing valve 60 is actually open, or the control unit 90 is driven to open the pressure reducing valve 60. It may be determined that the pressure reducing valve 60 is in an open state by outputting a command value. When the condition defined in step S108 is satisfied (step S108: YES), the controller 90 calculates a differential value DPL1 representing the pressure increase gradient Gu based on the detected first detected pressure value PL (step S110). Specifically, the control unit 90 calculates the differential value DPL1 by subtracting the first detected pressure value PL detected in the previous routine from the first detected pressure value PL detected in the current routine.

  Next, the control unit 90 determines whether or not the differential value DPL1 is smaller than the predetermined value DPLs (step S112). The predetermined value DPLs is also called a lower limit value DPLs of the boost differential value. The lower limit value DPLs of the boost differential value can be determined, for example, in the range of 2 to 10 times the amount of hydrogen necessary for the maximum output of the fuel cell vehicle on which the fuel cell system 5 is mounted. In the present embodiment, the lower limit value DPLs is 0.5 Mpa / s.

  When the differential value DPL is smaller than the lower limit value DPLs (step S112: YES), it is determined whether or not step S112 is satisfied n times continuously (step S114). Here, n is an integer of 2 or more. In this embodiment, n is set to 100. By performing step S114, the occurrence of erroneous determination in step S112 can be suppressed. When step S112 is satisfied n times consecutively (step S114: YES), the control unit 90 determines that the remaining amount of fuel gas in the tank 30 is small (step S116). In this case, it is preferable that the control unit 90 limit the output of the fuel cell 10 or display an alarm for informing the user that the fuel gas remaining amount is low. For example, the output of the fuel cell 10 may be limited by limiting 1/2 of the output current value of the fuel cell 10 at the time point determined in step S116 as the maximum output value.

  Next, the control unit 90 calculates the estimated pressure value PHI in the tank 30 using the differential value DPL1 (step S118). Specifically, the control unit 90 calculates the estimated pressure value PHI based on a map (FIG. 3) that represents the relationship between the pressure increase gradient Gu stored in the storage unit 92 and the pressure in the tank 30. The estimated pressure value PHI in the tank 30 represents the remaining amount of hydrogen in the tank 30. Next, the control unit 90 stores the estimated pressure value PHI in the storage unit 92 and ends the routine (step S120).

  On the other hand, when the differential value DPL1 is greater than or equal to the lower limit value DPLs (step S112: NO), or when the step S112 is not satisfied continuously n times (step S114: NO), the control unit 90 sets the estimated pressure value PHI. The calculated estimated pressure value PHI is stored in the storage unit 92 (steps S118 and S120).

  On the other hand, if the control unit 90 determines that the second detected pressure value PH is greater than or equal to the collection possibility determination pressure value (step S106: NO), the pressure reducing valve 60 is in the closed state in the current routine and the previous time In step S122, it is determined whether or not the closed condition is satisfied. In step S122, as in step S108, the closed state of the pressure reducing valve 60 may be determined by detecting that the pressure reducing valve 60 is actually closed, or the control unit 90 is closed with respect to the pressure reducing valve 60. It may be determined that the pressure reducing valve 60 is in a closed state by outputting a drive command value for the control. When it is determined that the condition of step S122 is not satisfied (step S122: NO), the control unit 90 ends the routine. On the other hand, when it determines with satisfy | filling the conditions of step S122 (step S122: YES), the control part 90 calculates differential value DPL2 showing the pressure fall gradient Gd based on the detected 1st detected pressure value PL (step). S124). Specifically, the control unit 90 calculates the differential value DPL2 by subtracting the first detected pressure value PL detected in the current routine from the first detected pressure value PL detected in the previous routine.

  After calculating the differential value DPL2, the control unit 90 uses the differential value DPL2 to calculate the amount of hydrogen consumed by the fuel cell 10 as the estimated fuel consumption amount FCP (step S126). Specifically, the control unit 90 calculates the estimated fuel consumption amount FCP based on a map (FIG. 4) representing the relationship between the pressure decrease gradient Gd stored in the storage unit 92 and the estimated fuel consumption amount FCP. The control unit 90 stores the calculated estimated fuel consumption amount FCP in the storage unit 92 and ends the routine (step S120).

  If the condition defined in step S108 is not satisfied (step S108: NO), the control unit 90 executes steps S122 to S128 described above and ends the routine.

  FIG. 8 is a diagram for explaining a control routine performed by the control unit 90. The control unit 90 executes the control routine shown in FIG. 8 every 100 ms, for example. The execution period of the control routine may be set as appropriate within a range where the signal-to-noise ratio (S / N) does not become small.

  The controller 90 detects and stores the signal (voltage value) output by the current sensor 20 as the generated current value of the fuel cell 10 (step S200). After step S200, the fuel consumption amount FCI per unit time is calculated and stored based on the generated current value (steps S202 and S204). The fuel consumption amount FCI per unit time may be calculated based on a map stored in the storage unit 92. The fuel consumption amount FCI corresponds to the “consumption amount of fuel gas” described in the means for solving the problem.

  FIG. 9 is a diagram for explaining a control routine performed by the control unit 90. The control unit 90 executes the control routine shown in FIG. 9 every 100 ms, for example. The execution period of the control routine may be set as appropriate within a range where the signal-to-noise ratio (S / N) does not become small.

  The controller 90 determines whether or not the second detected pressure value PH is smaller than the calibration determination pressure value (step S302). As the second detected pressure value PH in step S302, the second detected pressure value PH (step S102) acquired in the routine of FIG. 6 is used. In this embodiment, the calibration determination pressure value in step S302 is 5 MPa_abs. If the control unit 90 determines that the detected pressure value PH is greater than or equal to the calibration determination pressure value (step S302: NO), the routine ends.

  On the other hand, when it is determined that the detected pressure value PH is smaller than the calibration determination pressure value (step S302: YES), the control unit 90 uses the first detected pressure value PL detected by the first pressure sensor 40. The moving average value of the difference value SB between the estimated pressure value PHI in the tank 30 calculated in step S118 (step S118 in FIG. 7) and the second detected pressure value PH detected by the second pressure sensor 50 (step S102). MA is calculated (step S304). This is because the accuracy of calibration of the second detected pressure value PH, which will be described later, is improved by calculating the moving average value MA.

  Next, the control unit 90 calibrates the second detected pressure value PH by correcting the second detected pressure value PH by adding the moving average value MA to the second detected pressure value PH, and calculates the corrected detected pressure value PHC1. (Step S308). Further, the control unit 90 stores the calculated detected pressure value PHC1 in the storage unit 92 (step S310). Note that the difference value SB is calculated in step S304, and the difference value SB is added to the second detected pressure value PH to correct the second detected pressure value PH, thereby calculating the detected pressure value PHC1. .

  FIG. 10 is a diagram for explaining a control routine performed by the control unit 90. The control unit 90 executes the control routine shown in FIG. 10 every 500 ms, for example. The controller 90 calculates a leakage gas amount QH1, which is the amount of hydrogen per unit time that does not contribute to power generation, among the hydrogen supplied to the fuel cell 10 (step S402). Specifically, the leakage gas amount QH1 is obtained by subtracting the moving average value of the fuel consumption amount FCI (step 204) from the moving average value of the estimated fuel consumption amount FCP (step S128) accumulated during the routine execution cycle. calculate. Next, the control unit 90 determines a coefficient J used in a process described later based on the generated current value detected by the current sensor 20 (step S404). The coefficient J is determined using a map representing the relationship between the generated current value stored in the storage unit 92 and the coefficient J (FIG. 5).

Next, the control unit 90 calculates the leakage gas amount QH1 calculated in step S402 in this routine (also referred to as “first leakage gas amount QH1a”) and the leakage gas amount QH1 calculated in step S402 in the previous routine ( The moving average value Va with “second leakage gas amount QH1b” is calculated (step S406). The moving average value Va is calculated using the following equation (1).
Va = (1 / J) × QH1a + {(J−1) / J} × QH1b (1)
Here, Va is a moving average value (mol / s), QH1a is a first leakage gas amount (mol / s), QH1b is a second leakage gas amount (mol / s), and J is a coefficient.

  In the above formula (1), since the coefficient J has a relationship that increases as the generated current value increases (FIG. 5), the weight coefficient 1 / J increases as the generated current value decreases. The calculated moving average value Va is stored in the storage unit 92 (step S408).

  Next, the control unit 90 determines whether or not the moving average value Va that is the corrected leaked gas amount is larger than a predetermined threshold (step S410). When the moving average value Va is larger than the predetermined threshold (step S410: YES), it is determined whether or not step S410 is continuously satisfied m times (step S412). Here, m is an integer of 2 or more. In the present embodiment, m is set to 12. By performing step S412, the occurrence of erroneous determination in step S410 can be suppressed.

  When step S410 is satisfied m times continuously (step S412: YES), the control unit 90 displays an alarm for informing the user that hydrogen is leaking (step S414). The alarm can be displayed by displaying it on a monitor or generating a warning sound.

  Next, the control unit 90 corrects the corrected fuel gas consumption amount QHC by correcting the fuel consumption amount FCI calculated based on the generated current value using the moving average value Va as the corrected leakage gas amount (step S202). Calculate (step S416). Specifically, the corrected fuel gas consumption amount QHC is calculated by adding the moving average value Va as the corrected leakage gas amount to the fuel consumption amount FCI. The calculated corrected fuel gas consumption amount QHC is stored in the storage unit 92. On the other hand, step no. If the determination is “NO” in 410 or step S412, steps S416 and S418 are executed without displaying an alarm.

A-3. effect:
According to the above embodiment, the fuel cell system 5 sets the pressure reducing valve 60 to the open state, and the pressure gradient calculated based on the first detected pressure value PL detected by the first pressure sensor 40 is the rising gradient. In the case of (pressure increase gradient Gu), the remaining amount of fuel gas in the tank 30 (internal pressure of the tank 30) is calculated using the increase gradient (step S118 in FIG. 7). Thereby, the remaining amount of fuel gas in the tank 30 can be calculated using the pressure increase gradient Gu. The second pressure sensor 50 disposed on the high pressure side may be affected by the pressure of the fuel gas and drift in the output characteristics. Detection accuracy decreases due to the occurrence of drift. On the other hand, the first pressure sensor 40 arranged on the low pressure side is not easily affected by the pressure of the fuel gas. Thereby, in the 1st pressure sensor 40, possibility that a drift will generate | occur | produce is low. Therefore, the remaining amount of fuel gas in the tank 30 is accurately measured by using the first pressure sensor 40 having a measurement range that is relatively lower than the second pressure sensor 50 for detecting the pressure in the tank 30. It can be detected well. Specifically, in the present embodiment, the second detected pressure value PH is corrected by adding the moving average value MA to the second detected pressure value PH (step S308 in FIG. 9).

  In the second pressure sensor 50, the output fluctuation range due to drift generally increases with the passage of time, and after a certain period of time, the output fluctuation range due to drift becomes substantially constant thereafter. That is, in the second pressure sensor 50, only the accuracy of the detected value on the high pressure side (for example, a pressure of 5 MPa_abs or higher) that is not easily affected by drift is ensured, and the detection accuracy on the low pressure side (for example, less than 5 MPa_abs) is the first. This can be ensured by correcting the detection value of the second pressure sensor 50 by the pressure sensor 40 (step S302 in FIG. 9). Thereby, since it is not necessary to use the sensor which ensures a wide pressure range with high precision as the 2nd pressure sensor 50, the cost of the 2nd pressure sensor 50 can be reduced. Therefore, the cost of the entire fuel cell system 5 can also be reduced.

  Further, based on the relationship (first relationship) in which the remaining amount of fuel gas in the tank 30 increases as the pressure increase gradient Gu representing the change in the first detected pressure value PL of the first pressure sensor 40 increases. The fuel cell system 5 detects the remaining amount of fuel gas in the tank 30 (FIG. 3). Therefore, the remaining amount of the fuel gas in the tank 30 can be easily detected based on the first relationship.

  Further, when the pressure gradient calculated based on the second detected pressure value PH detected by the second pressure sensor 50 is a downward gradient (pressure downward gradient Gd), the fuel cell system 5 uses the pressure downward gradient Gd. The fuel gas consumption amount of the fuel cell 10 is calculated as the estimated fuel consumption amount FCP using a certain differential value DPL2 (step S126 in FIG. 6). Thereby, the consumption amount of the fuel gas by the fuel cell 10 is computable using the pressure fall gradient Gd.

  Further, based on the relationship (second relationship) in which the amount of fuel gas consumed by the fuel cell 10 increases as the pressure decrease gradient Gd representing the change in the detected pressure value PH of the second pressure sensor 50 increases. The system 5 calculates the fuel gas consumption (estimated fuel consumption FCP) by the fuel cell 10 (FIG. 4). Therefore, the consumption amount of the fuel gas can be easily calculated based on the second relationship.

  Further, the fuel cell system 5 calculates a difference value between the estimated fuel consumption amount FCP and the fuel consumption amount FCI calculated using the generated current value as the leakage gas amount QH1 (step S402 to step S402 in FIG. 10). S406). Thereby, the leakage gas amount QH1 can be easily calculated by using the difference value. Further, by calculating the leakage gas amount QH1, it is possible to more appropriately control the operation of the fuel cell system 5 such as reporting whether or not an abnormality has occurred in the fuel cell system 5.

  The corrected leaked gas amount is calculated as a moving average value (step S408 in FIG. 10). The weighting factor is set to be larger as the generated current value is smaller. Here, regardless of the amount of fuel gas supplied to the fuel cell 10, the leakage gas amount QH1 is substantially constant. Therefore, the ratio of the leakage gas amount QH1 to the amount of fuel gas supplied to the fuel cell 10 increases as the generated current value decreases. Therefore, the leakage gas amount QH1 can be accurately calculated by increasing the weighting factor J used when calculating the moving average value as the generated current value is small.

  Further, the fuel cell system 5 calculates the corrected fuel gas consumption amount QHC by correcting the fuel consumption amount FCI calculated based on the generated current value by using the moving average value Va representing the corrected leakage gas amount. (Step S416 in FIG. 10). As a result, the fuel cell system 5 can more accurately detect the consumption amount of the fuel gas in the tank 30 in consideration of the leakage gas amount QHI (specifically, the corrected leakage gas amount).

B. Variations:
In addition, elements other than the elements described in the independent claims of the claims in the constituent elements in the embodiment are additional elements and can be omitted as appropriate. Further, the present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the gist thereof. For example, the following modifications are possible.

B-1. First modification:
In the above embodiment, the control unit 90 has the storage unit 92 and stores the maps representing the relationships shown in FIGS. 3 to 5 in the storage unit 92. For example, an external server that can communicate with the control unit 90 You may memorize.

DESCRIPTION OF SYMBOLS 5 ... Fuel cell system 10 ... Fuel cell 20 ... Current sensor 30 ... Tank 32 ... Fuel gas supply / discharge system 40 ... 1st pressure sensor 50 ... 2nd pressure sensor 60 ... Pressure reducing valve 70 ... Fuel gas supply piping 71 ... Upstream Side supply pipe 72 ... Downstream side supply pipe 75 ... Fuel gas discharge pipe 80 ... Oxidant gas supply pipe 82 ... Oxidant gas discharge pipe 84 ... Air compressor 85 ... Oxidant gas supply / discharge system 90 ... Control unit 92 ... Storage unit

Claims (9)

A fuel cell system that adjusts the fuel gas supplied from a tank in which fuel gas is stored at a pressure higher than normal pressure to a predetermined range of pressure by a pressure reducing valve and supplies the fuel gas to a fuel cell,
A gas flow path in which the pressure reducing valve is disposed, and the fuel gas in the tank is circulated to the fuel cell;
A first pressure sensor disposed downstream of the pressure reducing valve in the gas flow path;
A control unit for controlling the fuel cell system,
The controller is
Detecting a signal output by the first pressure sensor as a first detected pressure value;
Calculating a pressure gradient of the detected first detected pressure value;
A fuel cell system that detects the remaining amount of the fuel gas in the tank using the rising gradient when the calculated pressure gradient is an rising gradient. The fuel cell system according to claim 1,
The controller is
A fuel cell system that detects the remaining amount of the fuel gas in the tank based on the relationship that the remaining amount of the fuel gas in the tank increases as the upward gradient increases. The fuel cell system according to claim 1 or 2, wherein
The controller is
A fuel cell system that calculates a consumption amount of the fuel gas by the fuel cell using the descending gradient when the pressure gradient is a descending gradient. The fuel cell system according to claim 3,
The controller is
A fuel cell system that calculates a consumption amount of the fuel gas based on a relationship that the consumption amount of the fuel gas by the fuel cell increases as the descending gradient increases. The fuel cell system according to claim 3 or 4, further comprising:
A current sensor for detecting a generated current value of the fuel cell;
The controller is
Detecting a signal output by the current sensor as a generated current value,
Calculate the consumption amount of the fuel gas by the fuel cell using the generated current value,
The difference between the fuel gas consumption calculated using the descending slope and the fuel gas consumption calculated using the power generation current value is a leakage that was not used for power generation of the fuel cell. A fuel cell system that calculates the amount of gas. The fuel cell system according to claim 5, wherein
The controller is
Calculate the amount of leaked gas at predetermined time intervals,
Based on the leaked gas amount calculated at each predetermined time interval, a corrected leaked gas amount is calculated,
The corrected leaked gas amount at the Nth time (N is an integer of 2 or more) is a moving average value of the leaked gas amount calculated every Nth time,
The weighting factor used in the moving average value is the first case when the generated current value is a first value and when the generated current value is a second value larger than the first value. The fuel cell system is bigger. The fuel cell system according to claim 6,
The controller is
A fuel cell system that calculates a corrected fuel gas consumption amount by correcting a consumption amount of the fuel gas calculated using the generated current value by using the corrected leakage gas amount. The fuel cell system according to any one of claims 1 to 7, further comprising:
A second pressure sensor disposed on the upstream side of the pressure reducing valve in the gas flow path and capable of detecting a pressure higher than the first pressure sensor;
The controller is
Detecting a signal output by the second pressure sensor as a second detected pressure value;
A fuel cell system, wherein the second detected pressure value is corrected using the first detected pressure value detected by the first pressure sensor. The fuel cell system according to claim 8, wherein
The controller is
A fuel cell system that executes the correction process when it is determined that the ascending slope is smaller than a predetermined value.

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