JP5282398B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system.

The fuel cell system uses, as an energy source, a fuel cell that generates electricity by an electrochemical reaction between a fuel gas that is a reaction gas and an oxidizing gas. The oxidizing gas supplied to the fuel cell is sent from a compressor that takes in and compresses air in the atmosphere (see Patent Documents 1 to 3 below).
JP 2006-139998 A JP 2006-185907 A JP 2007-073292 A

  By the way, when the outside air temperature is low, the temperature of the air taken into the compressor becomes low, so the temperature of the oxidizing gas supplied to the fuel cell also becomes low. Therefore, when the above-described conventional fuel cell system is started at a low temperature, not only the temperature of the fuel cell itself but also the temperature of the oxidizing gas supplied to the fuel cell is lowered. The time required for heating increases, and the power generation efficiency of the fuel cell decreases.

  The present invention has been made to solve the above-described problems caused by the prior art, and provides a fuel cell system capable of shortening the temperature rise time of the fuel cell when started at a low temperature. Objective.

  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 reactive gas and generates electric power by an electrochemical reaction of the reactive gas, and an oxidizing gas in the reactive gas. Are provided in the oxidizing gas supply channel, the compressor for supplying the oxidizing gas to the fuel cell, and the oxidizing gas supply channel on the downstream side of the compressor, and discharged from the compressor. An oxidizing gas circulation channel for circulating a part of the oxidizing gas to the oxidizing gas supply channel on the upstream side of the compressor, and an inflow of the oxidizing gas to the oxidizing gas circulation channel. And a control means for opening the valve when the temperature detected by a predetermined temperature sensor is equal to or lower than a predetermined low temperature threshold value.

  According to the present invention, when the temperature is low, the oxidizing gas is allowed to flow into the oxidizing gas circulation flow path, and a part of the oxidizing gas discharged after being compressed by the compressor is discharged to the upstream side of the compressor. Since it can be circulated through the supply flow path, the temperature of the oxidizing gas supplied to the fuel cell at a low temperature can be increased more quickly using a compressor, and the oxidation at a low temperature supplied to the fuel cell can be performed. The gas supply flow rate can be reduced. Therefore, the temperature rise (warming up) of the fuel cell can be performed in a shorter time.

  In the fuel cell system, the predetermined temperature sensor is a temperature sensor that detects a temperature of the fuel cell, and the control means is configured to control the valve when the temperature detected by the temperature sensor is equal to or lower than a predetermined low temperature threshold. Can be opened.

  As a result, when the temperature of the fuel cell is low, a part of the oxidizing gas discharged from the compressor can be circulated to the oxidizing gas supply channel on the upstream side of the compressor, so that the oxidizing gas supplied to the fuel cell The temperature can be increased more quickly.

  In the fuel cell system, the predetermined temperature sensor is an outside air temperature sensor that detects an outside air temperature, and the control means controls the valve when the temperature detected by the outside air temperature sensor is equal to or lower than a predetermined low temperature threshold. Can be opened.

  Accordingly, when the outside air temperature is low, a part of the oxidizing gas discharged from the compressor can be circulated to the oxidizing gas supply channel on the upstream side of the compressor, so that the temperature of the oxidizing gas supplied to the fuel cell is increased. Can be raised more quickly.

  The fuel cell system further includes a discharge temperature sensor for detecting the temperature of the oxidizing gas discharged from the compressor, and the control means is configured to detect a temperature detected by the discharge temperature sensor at or above a predetermined discharge temperature. The valve can be closed.

  Thereby, the situation where a fuel cell is damaged by the heat | fever of the oxidizing gas supplied to a fuel cell can be avoided beforehand.

  According to the present invention, it is possible to shorten the temperature rise time of the fuel cell when it is started at a low temperature.

  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).

  When the fuel cell system according to the present invention is started at a low temperature, an oxidizing gas supplied to the fuel cell is circulated by circulating a part of the oxidizing gas discharged after being compressed by the compressor to the upstream side of the compressor. The temperature is raised more quickly by using a compressor, and the supply flow rate of the low-temperature oxidizing gas supplied to the fuel cell is reduced. Hereinafter, the configuration and operation of the fuel cell system having such characteristics will be described in detail.

  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 the figure, a fuel cell system 1 includes a fuel cell 2 that generates electric power by an electrochemical reaction upon receiving supply of an oxidizing gas and a fuel gas as reaction gases, and air as an oxidizing gas to the fuel cell 2. An oxidizing gas piping system 3 to be supplied, a hydrogen gas piping system 4 to supply hydrogen as fuel gas to the fuel cell 2, a cooling system 5 to circulate and supply cooling water to the fuel cell 2, and a control for overall control of the entire system Part 6 (control means). The fuel cell system 1 also includes an outside air temperature sensor T3 for measuring the outside air temperature.

  The fuel cell 2 is, for example, a polymer electrolyte fuel cell, and has a stack structure in which a large number of single cells are stacked. The single cell has a cathode electrode (air electrode) on one surface of an electrolyte made of an ion exchange membrane, an anode electrode (fuel electrode) on the other surface, and further sandwiches the cathode electrode and anode electrode from both sides. It has the structure which has a pair of separator. In this case, hydrogen gas is supplied to the hydrogen gas flow path of one separator, oxidizing gas is supplied to the oxidizing gas flow path of the other separator, and electric power is generated by the chemical reaction of these reaction gases.

  The oxidizing gas piping system 3 includes a compressor 31 that takes in and compresses atmospheric oxidizing gas through a filter 30, and an air supply passage 32 (oxidizing gas supply) for supplying the oxidizing gas to the fuel cell 2. A flow path), an air discharge flow path 33 for discharging the oxidizing off-gas discharged from the fuel cell 2, and an air supply flow path 32 on the upstream side of the compressor 31 for a part of the oxidizing gas discharged from the compressor 31. And an air circulation channel 34 (oxidizing gas circulation channel) for returning to the above. The air supply channel 32 and the air discharge channel 33 are provided with a humidifier 35 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 35 is finally exhausted into the atmosphere outside the system as exhaust gas.

  The air circulation channel 34 branches from the air supply channel 32 on the downstream side of the compressor 31, and circulates part of the oxidizing gas discharged from the compressor 31 to the air supply channel 32 on the upstream side of the compressor 31. As a result, the supply amount of the oxidizing gas to the fuel cell 2 is reduced. The air circulation channel 34 is provided with a shut-off valve 36 (valve) that blocks or allows the inflow of oxidizing gas to the air circulation channel 34. The shut-off valve 36 is constituted by an electromagnetic valve, for example. On the downstream side of the compressor 31, a temperature sensor T1 (discharge temperature sensor) that detects the temperature of the oxidizing gas discharged from the compressor 31 (hereinafter referred to as discharge temperature) is provided.

  The hydrogen gas piping system 4 includes a hydrogen tank 40 as a fuel supply source storing high-pressure hydrogen gas, and a hydrogen supply channel 41 as a fuel supply channel for supplying the hydrogen gas in the hydrogen tank 40 to the fuel cell 2. And a hydrogen circulation channel 42 for returning the hydrogen off-gas discharged from the fuel cell 2 to the hydrogen supply channel 41.

  The hydrogen supply passage 41 is provided with a main stop valve 43 that shuts off or allows the supply of hydrogen gas from the hydrogen tank 40 and a regulator 44 that adjusts the pressure of the hydrogen gas to a preset secondary pressure. .

  The hydrogen circulation channel 42 is provided with a hydrogen pump 45 that pressurizes the hydrogen off-gas in the hydrogen circulation channel 42 and sends it to the hydrogen supply channel 41 side. In addition, a discharge flow path 48 is connected to the hydrogen circulation flow path 42 via a gas-liquid separator 46 and an exhaust drain valve 47. The gas-liquid separator 46 recovers moisture from the hydrogen off gas. The exhaust / drain valve 47 discharges (purges) the water recovered by the gas-liquid separator 46 and the hydrogen off-gas containing impurities in the hydrogen circulation passage 42 in accordance with a command from the control unit 6. The hydrogen off-gas discharged from the exhaust / drain valve 47 is diluted by the diluter 49 and merges with the oxidizing off-gas in the air discharge passage 33.

  The cooling system 5 includes a radiator 51 that cools the cooling water, a cooling water circulation passage 52 that circulates and supplies the cooling water to the fuel cell 2 and the radiator 51, and a cooling water circulation pump 53 that circulates the cooling water to the cooling water circulation passage 52. Have A temperature sensor T <b> 2 (temperature sensor) that detects the temperature of the cooling water is provided on the outlet side of the fuel cell 2 in the cooling water circulation passage 52.

  The control unit 6 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, an auxiliary device (for example, a motor for the compressor 31, the hydrogen pump 45, and the cooling water circulation pump 53) necessary for operating the fuel cell 2, traveling of the vehicle Actuators used in various devices involved in the transmission (transmission, wheel control device, steering device, suspension device, etc.), occupant space air conditioner (air conditioner), lighting, audio, and the like.

  When the fuel cell system 1 is started, the control unit 6 determines whether or not the temperature of the cooling water detected by the temperature sensor T2 is equal to or lower than a predetermined low temperature start start temperature (a predetermined low temperature threshold). The predetermined low temperature start start temperature corresponds to, for example, a temperature about 10 ° C. lower than the temperature of the cooling water during the standard operation of the fuel cell 2.

  When it is determined that the temperature of the cooling water is equal to or lower than the predetermined low-temperature start start temperature, the control unit 6 opens the shut-off valve 36 of the air circulation channel 34 to start the low-temperature start-up operation. The cold start operation is an operation mode when starting the fuel cell system 1 at a low temperature. Specifically, the shutoff valve 36 of the air circulation flow path 34 is opened, and a part of the oxidizing gas discharged from the compressor 31 is circulated to the air supply flow path 32 on the upstream side of the compressor 31, so that the fuel This is an operation mode in which the flow rate of the oxidizing gas supplied to the battery 2 is reduced.

  By performing the low temperature start-up operation, the supply flow rate of the low temperature oxidizing gas supplied to the fuel cell 2 that is not sufficiently warmed can be reduced. The temperature of the oxidizing gas discharged after being compressed by the compressor 31 is higher than the temperature of the air taken into the compressor 31. Therefore, since the heat of the oxidizing gas discharged from the compressor 31 can be applied to the cold air taken into the compressor 31 by performing the low temperature startup operation, the temperature of the oxidizing gas supplied to the fuel cell 2 is set. It can be raised more quickly.

  In addition, when starting the low temperature start-up operation, it is determined whether to start using the temperature of the cooling water detected by the temperature sensor T2, but the temperature used for the determination is not limited to the temperature of the cooling water. . For example, the temperature of the stack of fuel cells may be used, and any temperature may be used as long as the temperature can correspond to the temperature of the fuel cell 2 at that time.

  The controller 6 determines whether or not the temperature of the cooling water detected by the temperature sensor T2 is equal to or higher than a predetermined low-temperature start end temperature during the low-temperature start-up operation. As the predetermined low temperature startup end temperature, for example, the temperature of the cooling water during the standard operation of the fuel cell 2 is applicable.

  When it is determined that the temperature of the cooling water is equal to or higher than the predetermined low-temperature start end temperature, the control unit 6 closes the shutoff valve 36 of the air circulation channel 34 and shifts to normal operation. Thereby, all of the discharged oxidizing gas can be supplied to the fuel cell 2 without circulating the oxidizing gas discharged from the compressor 31.

  Here, the control unit 6 physically includes, for example, a CPU, a ROM that stores a control program and control data processed by the CPU, 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 temperature sensors T1 and T2 are connected to the input / output interface, and the compressor 31, the shutoff valve 36, the main stop valve 43, the hydrogen pump 45, the exhaust drain valve 47, the cooling water circulation pump 53, and the like are driven. Various drivers are connected.

  The CPU receives the detection results of the temperature sensors T1 and T2 via the input / output interface according to the control program stored in the ROM, and processes them using various data in the RAM, thereby starting the fuel cell system. Control time processing. Further, the CPU controls the entire fuel cell system 1 by outputting control signals to various drivers via the input / output interface.

  Next, the startup process of the fuel cell system according to this embodiment will be described with reference to the flowchart shown in FIG.

  First, when receiving an operation start command such as ignition ON (step S1), the control unit 6 determines whether or not the temperature of the cooling water detected by the temperature sensor T2 is equal to or lower than a predetermined low temperature start start temperature ( Step S2). If this determination is NO (step S2; NO), the process proceeds to step S6 described later.

  On the other hand, when it is determined in step S2 that the temperature of the cooling water is equal to or lower than the predetermined low-temperature start temperature (step S2; YES), the control unit 6 has the shutoff valve 36 in the air circulation channel 34. Is opened (step S3), and operation at low temperature start is started. Thereby, a part of the oxidizing gas discharged from the compressor can be circulated through the air supply flow path 32 on the upstream side of the compressor 31, so that the temperature of the oxidizing gas supplied to the fuel cell 2 can be controlled by the compressor 31. It can be used to increase the speed more quickly, and the flow rate of the oxidizing gas supplied to the fuel cell 2 can be reduced.

  Subsequently, the control unit 6 determines whether or not the temperature of the cooling water detected by the temperature sensor T2 is equal to or higher than a predetermined low temperature activation end temperature (step S4). If this determination is NO (step S4; NO), this determination process is repeated.

  On the other hand, when it is determined in step S4 that the temperature of the cooling water is equal to or higher than the predetermined low temperature start end temperature (step S4; YES), the control unit 6 closes the shutoff valve 36 (step S5). ) And shift to normal operation (step S6). Thereby, all of the oxidizing gas discharged from the compressor 31 can be supplied to the fuel cell 2 without being circulated.

  As described above, according to the fuel cell system 1 in the embodiment, when the temperature of the fuel cell 2 is equal to or lower than the predetermined low temperature start start temperature, the inflow of the oxidizing gas to the air circulation passage 34 is allowed. Thus, a part of the oxidizing gas discharged from the compressor 31 can be circulated in the air supply passage 32 upstream of the compressor 31, so that the temperature of the oxidizing gas supplied to the fuel cell 2 is changed using the compressor 31. As a result, the flow rate of the oxidizing gas having a low temperature supplied to the fuel cell 2 can be reduced. Therefore, the temperature rise (warming up) of the fuel cell 2 can be performed in a shorter time, and the power generation efficiency of the fuel cell 2 can be improved.

  In the above-described embodiment, when shifting to the low temperature startup operation, it is a condition that the temperature of the cooling water is equal to or lower than a predetermined low temperature startup start temperature. It is not limited to this. For example, the control unit 6 determines whether or not the temperature detected by the outside air temperature sensor T3 is equal to or lower than a predetermined outside air temperature (a predetermined low temperature threshold), and when this determination is satisfied (YES), the shut-off valve 36 may be opened to start the cold start operation. For example, about 0 ° C. corresponds to the predetermined outside air temperature. When the outside air temperature is low, the temperature of the oxidant gas discharged from the compressor 31 is also lowered. Therefore, by circulating a part of the oxidant gas discharged to the air supply flow path 32 on the upstream side of the compressor 31, The temperature of the oxidizing gas supplied to the fuel cell can be increased more quickly, and the temperature of the fuel cell 2 can be increased in a shorter time. Thereby, the power generation efficiency of the fuel cell 2 can be improved.

  Further, in the above-described embodiment, the condition that the temperature of the cooling water is equal to or higher than the predetermined low-temperature start-up temperature when shifting from the low-temperature start-up operation to the normal operation is provided. The condition for shifting to is not limited to this. For example, the control unit 6 determines whether or not the temperature detected by the temperature sensor T1 is equal to or higher than a predetermined discharge temperature during the low temperature startup operation, and when this determination is satisfied (YES), the shutoff valve 36 may be closed to shift to normal operation. The predetermined discharge temperature corresponds to a temperature at which the stack of the fuel cell 2 is not damaged by the heat of the oxidizing gas supplied to the fuel cell 2, for example. Thereby, the situation where the stack | stuck etc. of the fuel cell 2 are damaged with the heat | fever of the oxidizing gas supplied to the fuel cell 2 can be avoided beforehand.

  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 flowchart for demonstrating the process at the time of starting of a fuel cell system.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 2 ... Fuel cell, 3 ... Oxidation gas piping system, 4 ... Hydrogen gas piping system, 5 ... Cooling system, 6 ... Control part, 30 ... Filter, 31 ... Compressor, 32 ... Air supply flow path, 33 ... Air discharge flow path, 34 ... Air circulation flow path, 35 ... Humidifier, 36 ... Shut-off valve, T1, T2 ... Temperature sensor, T3 ... Outside air temperature sensor.

Claims (3)

A fuel cell that receives supply of a reactive gas and generates electric power by an electrochemical reaction of the reactive gas;
An oxidizing gas supply channel for supplying the oxidizing gas of the reaction gas to the fuel cell;
A compressor that is provided in the oxidizing gas supply flow path and supplies the oxidizing gas to the fuel cell;
An oxidizing gas circulation flow for branching from the oxidizing gas supply channel on the downstream side of the compressor and circulating a part of the oxidizing gas discharged from the compressor to the oxidizing gas supply channel on the upstream side of the compressor Road,
A valve provided in the oxidant gas circulation channel, for blocking or allowing the inflow of the oxidant gas to the oxidant gas circulation channel;
When the temperature detected by the temperature sensor for detecting the temperature of the fuel cell is equal to or lower than a predetermined low temperature threshold, the valve is opened , and a part of the oxidizing gas discharged from the compressor Control means for circulating an oxidizing gas through the oxidizing gas circulation flow path and supplying the remaining oxidizing gas to the fuel cell ;
A fuel cell system comprising: It further includes an outside air temperature sensor for detecting outside air temperature,
The fuel cell system according to claim 1, wherein the control means opens the valve when the temperature detected by the outside air temperature sensor is equal to or lower than a predetermined low temperature threshold. A discharge temperature sensor for detecting the temperature of the oxidizing gas discharged from the compressor;
The fuel cell system according to claim 1 or 2 , wherein the control means closes the valve when the temperature detected by the discharge temperature sensor is equal to or higher than a predetermined discharge temperature.

Images