JP2010186702A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system wherein an internal temperature of a fuel cell can be obtained with high accuracy. <P>SOLUTION: The fuel cell system 1, in which a fuel gas and an oxidizing gas are supplied to a fuel cell 20 and electricity is generated by an electrochemical reaction between these fuel and oxidizing gases, includes a temperature measuring portion 81 that has a heat capacity and a heat loss coefficient which are equivalent to those of the fuel cell 20, temperature sensors 85 and 95 that measure a temperature of the temperature measuring portion 81, and a controller 50 that controls the operation of the fuel cell 20 based on the temperature of the temperature measuring portion 81. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell system including a fuel cell.

  In recent years, a fuel cell system that uses a fuel cell that generates electric power by an electrochemical reaction of reaction gases (fuel gas and oxidizing gas) as an energy source has attracted attention. The fuel cell system supplies high-pressure fuel gas from the fuel tank to the anode of the fuel cell, and also supplies air as the oxidizing gas to the cathode, and generates an electromotive force by electrochemically reacting these fuel gas and oxidizing gas. It is something to be made.

  This type of fuel cell system has a cooling means for cooling by circulating cooling water into the stack constituting the fuel cell. Since the temperature of the cooling water becomes equal to the temperature inside the fuel cell during the operation of the fuel cell, it may be used for grasping the internal temperature of the fuel cell and other uses.

  For example, in a fuel cell system provided with such a cooling means, there is a fuel cell system that corrects the power generation amount of the fuel cell and calculates a target SOC value by estimating an allowable upper limit temperature of the cooling water. Then, the coolant temperature of the fuel cell during traveling is predicted (see, for example, Patent Document 1).

  In addition, there is also known one that estimates the temperature of the fuel cell from the amount of gas supplied to the fuel cell and the pressure change (see, for example, Patent Document 2).

  Furthermore, there is a system that starts in a state where all unit cells show normal values. In this system, temperature sensors are attached to both ends of the fuel cell, and based on the detection results of these temperature sensors, the fuel cell The temperature is estimated (see, for example, Patent Document 3).

JP 2007-53051 A JP 2007-35563 A JP 2006-244926 A

  By the way, the system of Patent Document 1 estimates the temperature of the cooling water itself as the internal temperature of the fuel cell. However, when the operation is stopped such as before the cooling water is not flowing, It was difficult to accurately grasp the internal temperature of the fuel cell because the temperature at the inlet and outlet of the water was different.

  Further, in the system of Patent Document 2, since the temperature of the fuel cell is estimated from the amount of gas supplied to the fuel cell and the pressure change, it is necessary to maintain the pressure. Therefore, it is difficult to maintain the pressure, and thus the accuracy of the temperature estimation of the fuel cell is low. In addition, since this system requires a flow meter for measuring the flow rate of the supply gas, the configuration becomes complicated.

  Furthermore, the system of Patent Document 3 estimates the temperature of the fuel cell based on the detection results of the temperature sensors attached to both ends of the fuel cell, but the both ends of the fuel cell easily dissipate heat. From the detection results of these temperature sensors, it was difficult to accurately grasp the internal temperature of the fuel cell.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a fuel cell system capable of accurately grasping the internal temperature of the fuel cell.

  In order to achieve the above object, a fuel cell system of the present invention is a fuel cell system that supplies a fuel gas and an oxidizing gas to the fuel cell, and generates electricity by causing an electrochemical reaction between the fuel gas and the oxidizing gas. A temperature measuring unit having a heat capacity and a heat dissipation coefficient equivalent to the fuel cell; a temperature sensor for measuring the temperature of the temperature measuring unit; and a control unit for controlling the operation of the fuel cell based on the temperature of the temperature measuring unit; It is equipped with.

  According to such a configuration, since the temperature measurement unit has the same heat capacity and heat dissipation coefficient as the fuel cell, the temperature history of the temperature measurement unit matches the internal temperature history of the fuel cell. For this reason, even after the system is stopped, the internal temperature of the fuel cell can be accurately grasped from the temperature of the temperature measuring unit.

The temperature measurement unit may be an external module separate from the fuel cell, or a part of a pipe for circulating a cooling medium in the fuel cell may be covered with a heat insulating material. .
In the former case, it is possible to reduce layout restrictions when installing the temperature measurement unit. In the latter case, it is possible to use a configuration (piping) that originally exists as a part of the fuel cell system, and thus it is possible to suppress an increase in cost.

The control unit may control the operation of the fuel cell based on the temperature of the temperature measurement unit when the system is started.
For example, in the case of a system that estimates the internal temperature of a fuel cell from the cooling medium that cools the fuel cell, generally, the internal temperature of the fuel cell and the temperature of the cooling medium must be after a predetermined time has elapsed since the start of circulation of the cooling medium. Therefore, immediately after the system is started, the internal temperature of the fuel cell cannot be estimated with high accuracy. On the other hand, according to the above configuration, the temperature measurement unit and the temperature history inside the fuel cell match even after the system is stopped. It is possible to grasp (estimate) the accuracy.

  According to the fuel cell system of the present invention, the internal temperature of the fuel cell can be accurately grasped.

1 is a system configuration diagram schematically showing a fuel cell system according to an embodiment of the present invention. It is sectional drawing of the external module which comprises a temperature measurement part. It is a graph which shows the temperature change of the temperature in the temperature sensor provided in the exterior of the fuel cell, and the internal temperature of a fuel cell. It is a graph which shows the temperature change of the temperature of an external module, and the internal temperature of a fuel cell. It is a perspective view which shows other embodiment of a temperature measurement part. It is sectional drawing of the temperature measurement part shown in FIG.

  First, the overall configuration of the fuel cell system 1 according to an embodiment of the present invention will be described. The fuel cell system 1 is an in-vehicle power generation system for a fuel cell vehicle. In addition to the in-vehicle fuel cell system, a fuel cell system for any moving body such as a ship, an aircraft, a train, and a walking robot, for example, a fuel cell However, it can also be applied to stationary fuel cell systems used as power generation equipment for buildings (housing, buildings, etc.).

  As shown in FIG. 1, the air as the oxidizing gas (reactive gas) is supplied to the air supply port of the fuel cell 20 via the air supply path 71. The air supply path 71 is provided with an air filter A1 that removes particulates from the air, a compressor A3 that pressurizes the air, a pressure sensor P4 that detects the supply air pressure, and a humidifier A21 that adds required moisture to the air. The compressor A3 is driven by the motor M. The motor M is driven and controlled by the control unit 50.

  The air off gas discharged from the fuel cell 20 is discharged to the outside through the exhaust path 72. The exhaust path 72 is provided with a pressure sensor P1 for detecting the exhaust pressure and a pressure adjusting valve A4. The pressure sensor P <b> 1 is provided in the vicinity of the air exhaust port of the fuel cell 20. The pressure adjustment valve A4 functions as a pressure regulator that sets the supply air pressure to the fuel cell 20.

  Detection signals from the pressure sensors P4 and P1 are sent to the control unit 50. The control unit 50 sets the supply air pressure and the supply air flow rate to the fuel cell 20 by adjusting the motor rotation speed of the compressor A3 and the opening area of the pressure adjustment valve A4.

  Hydrogen gas as a fuel gas (reactive gas) is supplied from the hydrogen supply source 30 to the hydrogen supply port of the fuel cell 20 via the fuel supply path 74. The fuel supply path 74 includes a shutoff valve H100 that supplies or stops supplying hydrogen from the hydrogen supply source 30, a pressure sensor P6 that detects the supply pressure of hydrogen gas from the hydrogen supply source 30, and hydrogen gas to the fuel cell 20. The pressure regulating valve H9 for reducing and adjusting the supply pressure of the fuel, the pressure sensor P9 for detecting the hydrogen gas pressure downstream of the hydrogen pressure regulating valve H9, and the shutoff valve H21 for opening and closing between the hydrogen supply port of the fuel cell 20 and the fuel supply path 74. , And a pressure sensor P5 for detecting the inlet pressure of the hydrogen gas fuel cell 20 is provided. Detection signals from the pressure sensors P5, P6, and P9 are also supplied to the control unit 50.

  The hydrogen gas that has not been consumed in the fuel cell 20 is discharged to the hydrogen circulation path 75 as a hydrogen off-gas and returned to the downstream side of the hydrogen pressure regulating valve H9 in the fuel supply path 74. The hydrogen circulation path 75 includes a temperature sensor T31 that detects the temperature of the hydrogen off-gas, a shutoff valve H22 that communicates / blocks the fuel cell 20 and the hydrogen circulation path 75, a gas-liquid separator H42 that collects moisture from the hydrogen off-gas, and a hydrogen A drain valve H41 that collects the produced water in a tank (not shown) outside the hydrogen circulation path 75 and a hydrogen pump H50 that pressurizes the hydrogen off-gas are provided.

  The shutoff valves H21 and H22 close the anode side of the fuel cell 20. A detection signal (not shown) of the temperature sensor T31 is supplied to the control unit 50. The operation of the hydrogen pump H50 is controlled by the control unit 50.

  The hydrogen off gas merges with the hydrogen gas in the fuel supply path 74 and is supplied to the fuel cell 20 for reuse. The shutoff valves H100, H21, and H22 are driven by a signal from the control unit 50.

  The hydrogen circulation path 75 is connected to the exhaust path 72 by the purge flow path 76 via the discharge control valve H51. The discharge control valve H51 is an electromagnetic shut-off valve, and discharges (purges) hydrogen off-gas to the outside by operating according to a command from the control unit 50. By performing this purge operation intermittently, it is possible to prevent the cell voltage from decreasing due to repeated hydrogen off-gas circulation and increasing the impurity concentration of the hydrogen gas on the fuel electrode side.

  A cooling path 73 for circulating the cooling water is provided at the cooling water inlet / outlet of the fuel cell 20. In the cooling path 73, a temperature sensor T1 for detecting the temperature of the cooling water drained from the fuel cell 20, a radiator (heat exchanger) C2 for radiating the heat of the cooling water to the outside, and a pump for pressurizing and circulating the cooling water C1 and a temperature sensor T2 for detecting the temperature of the cooling water supplied to the fuel cell 20 are provided. The radiator C2 is provided with a cooling fan C13 that is rotationally driven by a motor.

  The fuel cell 20 is configured as a fuel cell stack in which a required number of unit cells that generate power upon receiving supply of fuel gas and oxidizing gas are stacked. The electric power generated by the fuel cell 20 is supplied to a power control unit (not shown). The power control unit includes an inverter that drives a drive motor of a vehicle, an inverter that drives various auxiliary devices such as a compressor motor and a motor for a hydrogen pump, and charging to and from a power storage means such as a secondary battery. DC-DC converter etc. which supply electric power to these motors are provided.

  The control unit 50 receives control information from a requested load such as an accelerator signal of a vehicle (not shown) and sensors (pressure sensor, temperature sensor, flow rate sensor, output ammeter, output voltmeter, etc.) of each part of the fuel cell system 1, Control the operation of valves and motors in each part.

  The fuel cell system 1 includes a temperature measurement unit 81, and the temperature measurement unit 81 is disposed at a position away from the fuel cell 20.

  As shown in FIG. 2, the temperature measuring unit 81 includes an external module 84 that is separate from the fuel cell 20 and includes a spherical core 82 and a heat insulating material 83 that covers the core 82. The external module 84 has a heat capacity and heat dissipation coefficient equivalent to those of the fuel cell 20 by adjusting the thermal resistance of the core 82 by surrounding the core 82 with the heat insulating material 83.

  Further, the external module 84 of the temperature measuring unit 81 is passed through a bypass path 73a branched from the cooling path 73 from which the cooling water of the fuel cell 20 is discharged, and is arranged so that the bypass path 73a is in contact with the core 82. It is installed. The piping that defines the bypass passage 73 a may have a smaller diameter than the piping of the cooling passage 73.

  Further, the external module 84 is provided with a temperature sensor 85 so as to be in contact with the core 82, and the temperature of the external module 84 can be detected by the temperature sensor 85. The temperature sensor 85 is also connected to the control unit 50, and the detection result of the temperature sensor 85 is transmitted to the control unit 50.

  Here, the heat insulating material 83 of the external module 84 is made of, for example, polyethylene resin, and the thickness T is expressed by the following equation.

  T = surface area of core 82 × thermal conductivity of heat insulating material 83 × thermal resistance of fuel cell 20

  Therefore, for example, when the radius of the core 82 is 0.1 m, the thermal conductivity of the heat insulating material 83 is 0.34 W / mK, and the thermal resistance of the fuel cell 20 is 0.1 K / W, the thickness T of the heat insulating material 83 is It becomes as follows.

  T = 0.1256 x 0.34 x 0.1 = 0.0043m = 0.43cm

  The control unit 50 of the fuel cell system 1 performs the warm-up operation of the fuel cell 20 at a low temperature start, for example, below freezing. Specifically, for example, the heat generation amount of the fuel cell 20 is increased by performing a low-efficiency operation in which the power generation efficiency of the fuel cell 20 is intentionally reduced, thereby promoting warming of the fuel cell 20. Then, when detecting that the temperature of the fuel cell 20 has risen to a predetermined temperature, the controller 50 ends the warm-up operation and starts a normal operation in which power generation efficiency is emphasized.

  The determination as to whether or not to perform the warm-up operation is performed when the fuel cell system 1 is started, that is, before the circulation of the coolant is started. However, the detection result of the temperature sensors T1 and T2 coincides with the internal temperature of the fuel cell 20 after a predetermined time has elapsed since the circulation of the cooling water. The internal temperature cannot be accurately grasped. For this reason, it has been difficult to accurately determine whether or not the warm-up operation is required at the time of starting from the coolant temperature.

  Therefore, in the fuel cell system 1 of the present embodiment, the determination as to whether or not the control unit 50 performs the warm-up operation and the determination as to when the warm-up operation once started are equivalent to the fuel cell 20 are the same. This is performed based on the detection result from the temperature sensor 85 that measures the temperature of the temperature measurement unit 81 including the external module 84 having the heat capacity and the heat dissipation coefficient. That is, the necessity determination and the end determination of the warm-up operation should be performed based on the internal temperature of the fuel cell 20, but in this embodiment, the temperature measurement unit in which the internal temperature of the fuel cell 20 matches the history of temperature change. These determinations are made using a measured temperature of 81.

Here, as described above, the fuel cell 20 has a structure in which a required number of single cells that generate power upon receipt of fuel gas and oxidizing gas are stacked, and end plates are fastened from both sides of the cells to form a stack. Therefore, it is difficult to provide a temperature sensor inside the fuel cell 20 having the stack structure.
As a countermeasure, it is conceivable that a temperature measuring device is provided outside the fuel cell 20 and the internal temperature of the fuel cell 20 is grasped by this temperature measuring device. Is different from the heat capacity and the heat dissipation coefficient of the fuel cell 20, the internal temperature tn of the fuel cell 20 and the temperature measured by the temperature measuring device gradually deviate after the operation is completed, as shown in FIG.

  Therefore, at the time of the above-described low temperature start, if it is determined whether or not to perform the warm-up operation and whether or not to end the warm-up operation based on the measured temperature ta of the temperature measuring device, the determination is inaccurate. Accordingly, it becomes difficult to perform good operation control of the fuel cell 20 at the time of low temperature start.

  On the other hand, according to this embodiment using the temperature measured by the temperature measuring unit 81 including the external module 84 having the same heat capacity and heat dissipation coefficient as the fuel cell 20, the cooling water passing through the bypass 73a during operation is used. As shown in FIG. 4, the temperature tm of the external module 84 in which the core 82 heated to the same temperature as the fuel cell 20 is covered with the heat insulating material 83 changes to be equal to the internal temperature tn of the fuel cell 20 even after the operation is completed. Will be.

  Accordingly, as a result of the natural cooling of the fuel cell 20 and the cooling water after a lapse of a predetermined time after the system stop, the internal temperature of the fuel cell 20 and the cooling water temperature in the cooling water pipe, which were the same temperature immediately after the system stop, are Even if there is a temperature difference between them, the temperature of the external module 84 having the same heat capacity and heat dissipation coefficient as the fuel cell 20 decreases in the same manner as the fuel cell 20, so the temperature tm of the external module 84 is measured. Thus, the internal temperature tn of the fuel cell 20 can be accurately grasped (estimated).

  That is, according to the fuel cell system 1 according to the present embodiment, the external module having the same heat capacity and heat dissipation coefficient as the fuel cell 20 determines whether to perform the warm-up operation and whether to end the warm-up operation. 84, based on the detected temperature from the temperature measuring unit 81 provided with 84, the determination accuracy can be improved and the fuel cell 20 can be appropriately started, and in particular, the startability at a low temperature such as below freezing point can be achieved. Can be improved.

  In addition, by covering the core 82 with the heat insulating material 83, the heat capacity and heat dissipation coefficient of the external module 84 can be made the same as those of the fuel cell 20 without causing an increase in size.

  Moreover, since the external module 84 is a separate body from the fuel cell 20, the degree of freedom in arrangement can be increased.

  In the above embodiment, the bypass 82a is disposed in contact with the core 82 of the temperature measuring unit 81 so that the core 82 is warmed to the same temperature as the fuel cell 20 by the cooling water sent from the fuel cell 20 during operation. However, for example, a heater for warming the core 82 may be provided, and the core 82 may be warmed to the same temperature as the fuel cell 20 by the heater during operation.

  Further, in the above embodiment, the temperature change between the temperature of the external module 84 of the temperature measurement unit 81 and the internal temperature of the fuel cell 20 is set to be the same, but the temperature of the external module 84 and the internal temperature of the fuel cell 20 are set. A certain correlation may be given to the temperature, and the internal temperature of the fuel cell 20 may be determined from the temperature of the external module 84.

Next, another embodiment of the present invention will be described.
5 and 6 show a temperature measurement unit having another structure.
As shown in FIGS. 5 and 6, the temperature measuring unit 91 is provided in a cooling path 73 between the fuel cell 20 and the radiator C <b> 2 where the cooling water is discharged from the fuel cell 20.

  The temperature measuring unit 91 is configured by a part of a pipe 92 (hereinafter, simply referred to as “pipe 92”) constituting the cooling path 73 and a heat insulating material 93 covering the pipe 92. The temperature measuring unit 91 has a heat capacity and heat dissipation coefficient equivalent to those of the fuel cell 20 by adjusting the thermal resistance of the pipe 92 surrounded by the heat insulating material 93.

  Further, the pipe 92 is provided with a temperature sensor 95 so that the temperature of the pipe 92 through which the cooling water flows can be detected. The temperature sensor 95 is also connected to the control unit 50, and the detection result of the temperature sensor 95 is transmitted to the control unit 50.

  Here, the heat insulating material 93 is made of, for example, polyethylene resin, and the following equation is established among the inner diameter r1, the outer diameter r2, the length L, the thermal conductivity k, and the thermal resistance.

  Thermal resistance of heat insulating material 93 = ln (r2 / r1) / (2 × 3.14 × L × k)

  Therefore, the thickness T (T = r2-r1) and the length L of the heat insulating material 93 are adjusted so that the heat resistance of the heat insulating material 93 and the heat resistance of the fuel cell 20 are equal.

  For example, when the thermal conductivity of the heat insulating material 93 is 0.34 W / mK and the thermal resistance of the fuel cell 20 is 0.1 K / W, the following equation is obtained.

  ln (0.04 / 0.0359) / (2 × 3.14 × 0.5 × 0.34) = 0.1

  From the above formula, the heat insulating material 93 may have a thickness T = 0.0041 m = 0.41 cm and a length L = 0.5 m = 50 cm.

  Even when the temperature measuring unit 91 as described above is provided, the temperature measuring unit 91 has a heat capacity and a heat radiation coefficient equivalent to those of the fuel cell 20, so that the temperature measuring unit 91 allows the cooling path 73 to pass through during operation. The passing cooling water warms the fuel cell 20 to the same temperature, and the temperature change (temperature decrease) after the end of the operation is equivalent to the temperature change of the internal temperature of the fuel cell 20.

  Therefore, the internal temperature of the fuel cell 20 can be accurately grasped (estimated) by measuring the temperature of the temperature measuring unit 91.

  That is, also in the present embodiment, whether or not to perform the warm-up operation and whether or not to end the warm-up operation are determined based on the detected temperature from the temperature measurement unit 91 having the same heat capacity and heat dissipation coefficient as the fuel cell 20. Therefore, the accuracy of the determination can be improved, and the fuel cell 20 can be started properly. In particular, the startability at a low temperature such as below freezing point can be improved.

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 20 ... Fuel cell, 50 ... Control part, 81, 91 ... Temperature measurement part, 84 ... External module, 85, 95 ... Temperature sensor, 92 ... Piping, 93 ... Insulation material.

Claims (4)

A fuel cell system for generating power by supplying a fuel gas and an oxidizing gas to a fuel cell and causing an electrochemical reaction between the fuel gas and the oxidizing gas,
A temperature measurement unit having a heat capacity and a heat dissipation coefficient equivalent to the fuel cell;
A temperature sensor for measuring the temperature of the temperature measuring unit;
A control unit for controlling the operation of the fuel cell based on the temperature of the temperature measuring unit;
A fuel cell system comprising: The fuel cell system according to claim 1,
The temperature measurement unit is a fuel cell system which is an external module separate from the fuel cell. The fuel cell system according to claim 1,
The temperature measurement unit is a fuel cell system in which a part of a pipe for circulating a cooling medium in the fuel cell is covered with a heat insulating material. The fuel cell system according to any one of claims 1 to 3,
The said control part is a fuel cell system which controls the driving | operation of the said fuel cell based on the temperature of the said temperature measurement part at the time of system start-up.

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