JP5316834B2 - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively use up hydrogen gas in a hydrogen gas tank. <P>SOLUTION: Upon receiving an output current value of a fuel cell 2 from a current sensor A, a control part 5 derives a gas shortage decision threshold value corresponding to an output current value of the fuel cell 2 by referring to a gas shortage decision threshold value map and changes it. Upon receiving a pressure value of hydrogen gas in a hydrogen supply passage 41 from a pressure sensor P1, the control part 5 decides whether the pressure value received is equal to or lower than the gas shortage decision threshold value or not, and when the decision is YES, the control part 5 displays gas shortage and stops the output of the fuel cell 2. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a fuel cell system.

In recent years, a fuel cell system using a fuel cell that generates electric power by an electrochemical reaction between a fuel gas, which is a reactive gas, and an oxidizing gas as an energy source has been developed. In a vehicle equipped with such a fuel cell system, when the hydrogen gas in the hydrogen tank, which is a fuel supply source, reaches a predetermined gas shortage determination threshold, a gas shortage display is displayed to stop the fuel cell, and the vehicle travels. It will not be possible to continue. Conventionally, there has been a method for determining whether or not the hydrogen gas in the hydrogen tank has reached a gas shortage determination threshold based on the value of a pressure sensor that detects the pressure in the hydrogen tank (see Patent Document 1 below). However, since the pressure sensor provided in the hydrogen tank has a wide detection range and low detection accuracy, the fuel cell system described in Patent Document 2 below uses a pressure sensor in the fuel supply passage with higher detection accuracy. Judging the lack of gas.
JP 2005-325950 A JP 2006-140132 A

  By the way, the pressure inside the fuel supply passage is affected by the pressure loss in the pipe, so that it is lower than the supply pressure in the hydrogen tank that is the fuel supply source. Therefore, if the lack of gas is determined based on the pressure in the flow path, it is determined that the hydrogen gas stored in the hydrogen tank is out of gas even though there is still room in the hydrogen tank. Since the output is stopped, the hydrogen gas cannot be used up.

  The present invention has been made to solve the above-described problems caused by the prior art, and an object of the present invention is to provide a fuel cell system that can use up fuel from a fuel supply source without waste.

  In order to solve the above-described problems, a fuel cell system according to the present invention includes a fuel cell that receives supply of a reaction gas and generates electric power by an electrochemical reaction of the reaction gas, and the fuel gas in the reaction gas is a fuel cell. A pressure sensor for detecting the pressure of the fuel gas in the fuel supply passage for supplying to the fuel, a determination means for determining whether or not the pressure of the fuel gas detected by the pressure sensor is equal to or less than a gas shortage determination threshold, Changing means for changing a gas shortage determination threshold based on a pressure loss of fuel gas in the supply flow path.

  According to the present invention, the gas shortage determination threshold value, which is a criterion for determining whether or not there is a gas shortage, can be changed based on the pressure loss in the fuel supply flow path. It is possible to make a gas shortage determination using a pressure sensor that detects the pressure of the fuel gas and a gas shortage determination threshold that is changed in consideration of pressure loss. As a result, it is possible to obtain the same result as that in the case of performing the gas shortage determination using the pressure value of the fuel gas in the fuel supply source that does not need to consider the pressure loss with higher accuracy. It can be used up without waste.

  In the fuel cell system, the changing means changes the gas shortage determination threshold value to a value obtained by subtracting the pressure of the fuel gas that decreases due to pressure loss from the reference gas shortage determination threshold value when the output of the fuel cell is stopped. can do.

  By doing so, it is possible to perform the gas shortage determination using the gas shortage determination threshold obtained by subtracting the fuel gas pressure that decreases due to the pressure loss from the reference gas shortage determination threshold.

  The fuel cell system may further include a current sensor that detects an output current of the fuel cell, and the changing unit may change the gas shortage determination threshold according to the output current of the fuel cell detected by the current sensor. . In this way, the pressure loss can be easily calculated using the output current of the fuel cell.

  The fuel cell system further includes a flow rate sensor for detecting a flow rate of the fuel gas flowing through the fuel supply flow path, and the changing unit changes the gas shortage determination threshold according to the flow rate of the fuel gas detected by the flow rate sensor. can do. By doing in this way, it becomes possible to calculate a pressure loss easily using the flow volume of fuel gas.

  According to the present invention, the fuel from the fuel supply source can be used up without waste.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a fuel cell system according to the invention will be described with reference to the accompanying drawings. This embodiment demonstrates the case where the fuel cell system which concerns on this invention is used as a vehicle-mounted power generation system of a fuel cell vehicle (FCHV; Fuel Cell Hybrid Vehicle).

  The fuel cell system according to the present embodiment reduces the pressure loss corresponding to the output of the fuel cell when determining whether or not the gas is exhausted based on the pressure of the fuel gas detected by the pressure sensor of the fuel supply flow path. By changing the gas shortage determination threshold based on this, the fuel gas can be used up without waste.

  First, the configuration of the fuel cell system in the present embodiment will be described with reference to FIG. FIG. 1 is a configuration diagram schematically showing a fuel cell system in the present embodiment.

  As shown in FIG. 1, a fuel cell system 1 includes a fuel cell 2 that generates electric power by an electrochemical reaction between an oxidizing gas that is a reactive gas and the fuel gas, and an oxidizing gas that supplies air as the oxidizing gas to the fuel cell 2. It has a piping system 3, a hydrogen gas piping system 4 that supplies hydrogen as fuel gas to the fuel cell 2, and a control unit 5 that performs overall control of the entire system.

  The fuel cell 2 has a stack structure in which a plurality of single cells that generate power upon receiving a reaction gas are stacked. A part of the DC power generated by the fuel cell 2 is stepped down by a DC / DC converter (not shown) and charged to a secondary battery (not shown) which is a battery. The fuel cell 2 is provided with a current sensor A that detects a current during power generation.

  The oxidizing gas piping system 3 compresses air taken in through the filter 30 and sends out compressed air as oxidizing gas, and an air supply flow path 32 for supplying the oxidizing gas to the fuel cell 2. And an air discharge passage 33 for discharging the oxidizing off-gas discharged from the fuel cell 2. The air supply flow path 32 and the air discharge flow path 33 are provided with a humidifier 34 that humidifies the oxidizing gas pumped from the compressor 31 using the oxidizing off gas discharged from the fuel cell 2. The oxidizing off gas that has undergone moisture exchange or the like in the humidifier 34 is finally exhausted into the atmosphere outside the system as exhaust gas.

  The hydrogen gas piping system 4 includes a hydrogen tank 40 as a fuel supply source that stores high-pressure (for example, 70 MPa) hydrogen gas, and a fuel supply passage for supplying the hydrogen gas from the hydrogen tank 40 to the fuel cell 2. A hydrogen supply channel 41 and a circulation channel 42 for returning the hydrogen off-gas discharged from the fuel cell 2 to the hydrogen supply channel 41 are provided. The hydrogen gas piping system 4 is an embodiment of the fuel supply system in the present invention. Instead of the hydrogen tank 40 in the present embodiment, for example, a reformer that reforms a hydrocarbon-based fuel into a hydrogen-rich fuel gas using water vapor, and a fuel gas reformed in the reformer with a high pressure A high-pressure gas tank that accumulates pressure in a state can be employed as a fuel supply source. A tank having a hydrogen storage alloy can also be employed as a fuel supply source.

  The hydrogen supply channel 41 includes a main stop valve 43 that shuts off or allows the supply of hydrogen gas from the hydrogen tank 40, regulators 44 and 45 that adjust the hydrogen gas pressure to a preset secondary pressure, and hydrogen gas And an injector 46 for adjusting the flow rate and pressure. Further, on the downstream side of the regulator 45 and the downstream side of the regulator 44, a pressure sensor P1 and a pressure sensor P2 for detecting the pressure of the hydrogen gas in the hydrogen supply channel 41 are provided.

  The circulation channel 42 is provided with a hydrogen pump 47 that pressurizes the hydrogen off-gas in the circulation channel 42 and sends it to the hydrogen supply channel 41 side. Further, a discharge flow path 50 is connected to the circulation flow path 42 via a gas-liquid separator 48 and an exhaust drain valve 49. The gas-liquid separator 48 recovers moisture from the hydrogen off gas. The exhaust / drain valve 49 discharges (purges) the water collected by the gas-liquid separator 48 and the hydrogen off-gas containing impurities in the circulation flow path 42 in accordance with a command from the control unit 5. The hydrogen off-gas discharged from the exhaust / drain valve 49 is diluted by the diluter 51 and merges with the oxidizing off-gas in the air discharge passage 33.

  The control unit 5 detects an operation amount of an acceleration operation member (accelerator or the like) provided in the fuel cell vehicle, and provides control information such as an acceleration request value (for example, a required power generation amount from a power consumption device such as a traction motor). In response, the operation of various devices in the system is controlled. In addition to the traction motor, the power consuming device includes, for example, auxiliary equipment necessary for operating the fuel cell 2 (for example, the motor of the compressor 31 and the hydrogen pump 47), and various devices involved in traveling of the vehicle. These include actuators used in (transmissions, wheel control devices, steering devices, suspension devices, etc.), air conditioning devices (air conditioners) for passenger spaces, lighting, audio, and the like.

  The controller 5 determines whether or not the sensor value of the pressure sensor P1 is equal to or less than the gas shortage determination threshold value. The gas shortage determination threshold is a residual pressure value of hydrogen gas when it is determined that there is a gas shortage. Therefore, when the sensor value of the pressure sensor P1 is equal to or less than the gas shortage determination threshold, the control unit 5 determines that the gas is short, displays a gas shortage, and stops the output of the fuel cell 2.

  The control unit 5 changes the gas shortage determination threshold according to the output current of the fuel cell 2 detected by the current sensor A. Specifically, the gas shortage determination threshold value is changed to a value obtained by subtracting the pressure value that decreases due to pressure loss from the reference gas shortage determination threshold value when the output of the fuel cell 2 is stopped. Examples of when the output of the fuel cell 2 stops include when the vehicle is stopped, when driving at a low load, and during regenerative braking.

  As a method of changing the gas shortage determination threshold according to the output current of the fuel cell 2, for example, there is a method using a gas shortage determination threshold map shown in FIG. FIG. 2 is a diagram showing a gas shortage determination threshold map, where the horizontal axis indicates the output current [A] of the fuel cell 2 and the vertical axis indicates the gas shortage determination threshold [kPa]. In the gas shortage determination threshold map shown in FIG. 2, when the output of the fuel cell 2 is stopped, that is, when the output current of the fuel cell 2 is 0 A, the reference gas shortage determination threshold is set to PA. It is shown that the gas shortage determination threshold decreases as the output current of the battery 2 increases. That is, the pressure loss PL increases as the output current of the fuel cell 2 increases.

  The out-of-gassing determination threshold map shown in FIG. 2 can be created as follows. First, the pressure loss PL corresponding to the output current of the fuel cell 2 is calculated. Subsequently, a gas shortage determination threshold is calculated by subtracting the pressure loss PL from the reference gas shortage determination threshold PA. As described above, the gas shortage determination threshold map shown in FIG. 2 can be created by calculating and graphing the gas shortage determination threshold obtained for each output current of the fuel cell 2. Each value shown in the gas shortage determination threshold map is appropriately corrected according to the experimental result and the like.

  Here, the output current of the fuel cell 2 is proportional to the flow rate of the hydrogen gas that is the fuel, and the flow rate of the hydrogen gas increases as the output current of the fuel cell 2 increases. On the other hand, the flow rate of hydrogen gas and the pressure loss have a relationship that the pressure loss increases as the flow rate of hydrogen gas increases. Therefore, as the output current of the fuel cell increases, the pressure loss increases and the pressure of the hydrogen gas in the hydrogen supply channel 41 decreases.

  The control unit 5 refers to the gas shortage determination threshold map, derives the gas shortage determination threshold corresponding to the output current of the fuel cell 2 detected by the current sensor A, and the sensor value of the pressure sensor P1 is the gas shortage determination threshold. It is determined whether or not: In this determination, when it is determined that the sensor value of the pressure sensor P1 is equal to or less than the gas shortage determination threshold, the gas shortage display is performed and the output of the fuel cell is stopped. On the other hand, when it is determined that the sensor value of the pressure sensor P1 is not less than or equal to the gas shortage determination threshold, the output of the fuel cell is continued.

  Here, the control unit 5 physically includes, for example, a CPU, a ROM and an HDD that store control programs and control data processed by the CPU, and a RAM that is mainly used as various work areas for control processing. And an input / output interface. These elements are connected to each other via a bus. Various sensors such as pressure sensors P1, P2 and current sensor A are connected to the input / output interface, and various drivers for driving the compressor 31, the main stop valve 43, the hydrogen pump 47, the exhaust drain valve 49, and the like. Is connected.

  The CPU receives the detection results of the current sensor A and the pressure sensor P1 through the input / output interface according to the control program stored in the ROM, and processes them using various data in the RAM, thereby the fuel cell system. 1 is controlled. Further, the CPU controls the entire fuel cell system 1 by outputting control signals to various drivers via the input / output interface.

  Next, the gas shortage determination process of the fuel cell system in the present embodiment will be described using the flowchart shown in FIG. This out-of-gassing determination process is repeatedly performed from when the ignition key is turned on to when it is turned off.

  First, when the control unit 5 receives the output current value of the fuel cell 2 from the current sensor A (step S1), the control unit 5 refers to the out-of-gassing determination threshold map to obtain the output current value of the fuel cell 2. A corresponding gas shortage determination threshold is derived (step S2). The control unit 5 changes the gas shortage determination threshold used in the gas shortage determination process to the value derived in step S2 (step S3).

  Subsequently, when the control unit 5 receives the pressure value of the hydrogen gas in the hydrogen supply channel 41 from the pressure sensor P1 (step S4), the control unit 5 detects that the received pressure value has changed in step S3. It is determined whether or not the following is true (step S5).

  When this determination is YES (step S5; YES), the control unit 5 displays a gas shortage and stops the output of the fuel cell (step S6). On the other hand, when the determination in step S5 is NO (step S5; NO), the control unit 5 continues the output of the fuel cell 2 (step S7).

  As described above, according to the fuel cell system 1 of the present embodiment, the gas shortage determination threshold value, which is a determination criterion when determining whether or not the gas is exhausted, is reduced by the pressure loss from the reference gas shortage determination threshold value. Since it can be changed by the gas shortage determination threshold obtained by subtracting the pressure of hydrogen gas to be performed, the pressure sensor P1 is more accurate than the pressure sensor provided in the hydrogen tank 40, and the gas is changed in consideration of pressure loss. A gas shortage determination can be performed using the shortage determination threshold. As a result, it is possible to obtain a result equivalent to the case where the gas shortage determination is performed using the pressure value of the hydrogen gas in the hydrogen gas tank 40 that does not need to consider the pressure loss with higher accuracy. Can be used up.

  In the embodiment described above, the sensor value of the pressure sensor P1 is compared with the gas shortage determination threshold at the time of gas shortage determination, but the value to be compared with the gas shortage determination threshold is not limited to this. For example, the gas shortage determination may be performed by comparing the sensor value of the pressure sensor P2 with a gas shortage determination threshold. Here, since the pressure sensor P2 is provided on the upstream side of the pressure sensor P1, the pressure loss is smaller than that of the pressure sensor P1. Therefore, the gas shortage determination threshold map when the pressure sensor P2 is used is an amount by which the pressure loss PL is smaller than the gas shortage determination threshold graph of the gas shortage determination threshold map when the pressure sensor P1 shown in FIG. 2 is used. As a result, the inclination of the gas shortage determination threshold graph becomes gentler. That is, when the output current is the same, the gas shortage determination threshold when the pressure sensor P2 is used is closer to the reference gas shortage determination threshold PA than the gas shortage determination threshold when the pressure sensor P1 is used.

  Here, in general, the detection accuracy of the pressure sensor P1 is higher than the detection accuracy of the upstream pressure sensor P2, and therefore, the determination using the pressure sensor P1 can be performed with higher accuracy when the gas shortage is determined. Therefore, it is preferable to use the pressure sensor P2 preliminarily when an abnormality occurs in the pressure sensor P1. As an abnormality occurring in the pressure sensor P1, for example, a disconnection or a short circuit is applicable, and when the sensor value (voltage value) of the pressure sensor P1 deviates from a predetermined range, it can be determined that a disconnection or a short circuit has occurred. .

  In the embodiment described above, when the control unit 5 changes the gas shortage determination threshold according to the output current of the fuel cell 2, the gas shortage determination threshold map shown in FIG. The method for changing the determination threshold is not limited to this. For example, at the time of gas shortage determination, the pressure loss corresponding to the output current of the fuel cell 2 at that time is calculated, and the gas shortage determination threshold is calculated by subtracting the pressure loss from a predetermined reference gas shortage determination threshold, The out-of-gassing determination threshold for the out-of-gassing determination process may be changed with the calculated out-of-gassing determination threshold.

  In the above-described embodiment, the gas shortage determination threshold is calculated in correspondence with the output current of the fuel cell 2, but may be calculated in correspondence with the flow rate of hydrogen gas. FIG. 4 is a configuration diagram schematically showing the fuel cell system 1 in the present modification. The fuel cell system shown in FIG. 4 is different from the fuel cell system in the above-described embodiment in that a flow meter F is further provided on the upstream side of the injector 46. The control unit 5 in this modification changes the gas shortage determination threshold according to the flow rate of hydrogen gas detected by the flow meter F. Specifically, the gas shortage determination threshold value is changed to a value obtained by subtracting the pressure value that decreases due to pressure loss from the reference gas shortage determination threshold value when the output of the fuel cell 2 is stopped. As a method for changing the gas shortage determination threshold according to the flow rate of hydrogen gas, for example, there is a method using a gas shortage determination threshold map in which the horizontal axis of the gas shortage determination threshold map shown in FIG. . Here, since the flow rate of the hydrogen gas is proportional to the output current of the fuel cell 2, the same process as in the case of changing the gas shortage determination threshold according to the output current of the fuel cell 2 described in the above embodiment is performed. be able to.

  In the above-described embodiment, the case where the fuel cell system according to the present invention is mounted on a fuel cell vehicle has been described. However, the present invention is also applied to various mobile bodies (robots, ships, aircrafts, etc.) other than the fuel cell vehicle. The fuel cell system according to the invention can be applied. Moreover, the fuel cell system according to the present invention can also be applied to a stationary power generation system used as a power generation facility for buildings (houses, buildings, etc.).

It is a lineblock diagram showing typically the fuel cell system in an embodiment. It is a figure which shows a gas shortage determination threshold value map. 3 is a flowchart for explaining a gas cell depletion determination process in the fuel cell system shown in FIG. 1. It is a block diagram which shows typically the fuel cell system in a modification.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 2 ... Fuel cell, 3 ... Oxidation gas piping system, 4 ... Hydrogen gas piping system, 5 ... Control part, 30 ... Filter, 31 ... Compressor, 32 ... Air supply flow path, 33 ... Air exhaust flow 34, humidifier, 40 ... hydrogen tank, 41 ... hydrogen supply channel, 42 ... circulation channel, 43 ... main stop valve, 44, 45 ... regulator, 46 ... injector, 47 ... hydrogen pump, 48 ... gas-liquid Separator 49 ... exhaust drain valve, 50 ... discharge flow path, 51 ... diluent, A ... current sensor, P1, P2 ... pressure sensor, F ... flow meter.

Claims (3)

A fuel cell that receives supply of a reactive gas and generates electric power by an electrochemical reaction of the reactive gas;
A pressure sensor for detecting a pressure of the fuel gas in a fuel supply channel for supplying the fuel gas of the reaction gas to the fuel cell;
The pressure of the fuel gas detected by the pressure sensor is equal to or less than a gas shortage determination threshold that is a residual pressure value of the fuel gas when it is determined that the fuel gas stored in the fuel supply source is out of gas. Determination means for determining whether or not,
A value obtained by subtracting a pressure loss value, which is a pressure component of the fuel gas that decreases due to a pressure loss of the fuel gas in the fuel supply flow path, from a reference gas shortage determination threshold value when the output of the fuel cell is stopped. Changing means for changing the gas shortage determination threshold,
The pressure loss value increases as the output current of the fuel cell or the flow rate of the fuel gas flowing through the fuel supply passage increases.
The determination means determines that the gas is exhausted when the pressure of the fuel gas is equal to or less than the gas exhaustion determination threshold.
A fuel cell system. A current sensor for detecting an output current of the fuel cell;
2. The fuel according to claim 1, wherein the changing unit changes the out-of-gassing determination threshold using the pressure loss value calculated according to the output current of the fuel cell detected by the current sensor. Battery system. A flow rate sensor for detecting a flow rate of the fuel gas flowing in the fuel supply flow path;
2. The fuel cell according to claim 1, wherein the changing unit changes the gas shortage determination threshold by using the pressure loss value calculated according to the flow rate of the fuel gas detected by the flow sensor. system.

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