JP2009193921A - Fuel cell stack and fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of simplifying a structure thereof. <P>SOLUTION: A fuel cell stack 5 generating power by electrochemical reaction with fuel gas and oxidization gas includes: a laminate 14 with a plurality of fuel cells laminated; and a refrigerant flow channel fitted inside the latter 14, flowing cooling medium for cooling each fuel cell 13 of the laminate 14, and having a main flowing part flowing a cooling medium which is distributed to each of laminated fuel cells 13 or a cooling medium which is made to join from each fuel cell 13. The main flow part is arranged so that heat can be exchanged between a cooling medium flowing in the main flow part and a cooled apparatus at a position in the vicinity of the cooled apparatus arranged on a surface of the laminate 14. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell stack and a fuel cell system.

  In recent years, a fuel cell has attracted attention as a power source excellent in operating efficiency and environmental performance. A fuel cell generates power by an electrochemical reaction between a fuel gas and an oxidizing gas. The electrochemical reaction between the fuel gas and the oxidizing gas is performed in a fuel battery cell that supports a catalyst.

In supplying electric power from a fuel cell to a load, there is a technique of adjusting a voltage via a DC / DC converter (see, for example, Patent Document 1). Moreover, there exists a technique which arrange | positions electrical components, such as a relay, in the vicinity of the end plate of a fuel cell (for example, refer patent documents 2-4). Further, there is a technique for dissipating power loss by disposing a diode at a cooler part in a fuel cell stack (see, for example, Patent Document 5). In addition, there is a technique for performing heat exchange between an electronic component and a fuel cell (see, for example, Patent Document 6). Moreover, there exists a technique which integrates semiconductor elements, such as a voltage converter, with the laminated body of a fuel cell stack (for example, refer patent documents 7-9). In addition, there is a technique for boosting the output voltage of a warm-up fuel cell and stabilizing the operation of auxiliary equipment driven at a high voltage (see, for example, Patent Document 10).
JP 2000-36308 A JP 2004-55384 A JP 2002-362165 A JP 2007-128752 A JP 2001-357866 A Japanese Patent No. 3910553 JP 2006-302629 A Special Table 2003-065487 JP 2006-332025 A JP 2007-184243 A

  Since the fuel cell generates power by an electrochemical reaction between the fuel gas and the oxidizing gas, it is necessary to appropriately control the reaction heat. For example, it is necessary to raise the temperature of the fuel cell so that an electrochemical reaction occurs, or to cool the fuel cell that generates heat due to the electrochemical reaction. Here, in view of simplifying the configuration of the system, it is preferable to reduce the number of devices that perform heat exchange between the inside and outside of the system.

  This invention is made | formed in view of the problem which concerns, and makes it a subject to simplify the structure of a fuel cell system.

  In order to solve the above-mentioned problems, the present invention simplifies the configuration of the fuel cell system by arranging the devices in consideration of heat exchange between the fuel cell stack and other devices.

Specifically, a fuel cell stack that generates electric power by an electrochemical reaction between a fuel gas and an oxidizing gas, wherein a stacked body in which a plurality of fuel cells that electrochemically react the fuel gas and the oxidizing gas are stacked, and the stack A refrigerant flow path that is provided inside the body and flows a refrigerant that cools each fuel battery cell of the stack, and is divided from each of the stacked fuel battery cells or joined from each fuel battery cell. A refrigerant flow path having a main flow portion through which the refrigerant flows, wherein the main flow portion is positioned close to a device to be cooled disposed on a surface of the stacked body and the refrigerant flowing through the main flow portion and the covered flow passage. It arrange | positions so that heat exchange with a cooling device is possible.

  Each cell of the stacked body in which a plurality of fuel battery cells are stacked causes an electrochemical reaction by being supplied with a fuel gas and an oxidizing gas, respectively. Here, the laminated body includes a refrigerant flow path for flowing a refrigerant for cooling each cell that generates heat by an electrochemical reaction. The refrigerant flow path is based on the premise that the refrigerant is divided into each cell in order to cool each cell substantially uniformly, and the main flow part is a flow path provided inside the laminate. The flow paths provided in each cell are connected to each other. Therefore, the total amount of refrigerant flows through the main flow portion by combining the refrigerant flowing through each cell. The main flow part is a part of the refrigerant flow path provided in the laminated body, and is a flow through which the refrigerant diverted to each stacked fuel cell or the refrigerant merged from each fuel cell flows. For example, it is a so-called manifold in which one flow path is divided into a plurality of flow paths or a plurality of flow paths are combined into one flow path. The main flow portion can transport a large amount of heat because a total amount of the refrigerant flowing through the fuel cells flows. In addition, the main flow part may be only a part through which the refrigerant before being diverted to each fuel cell flows, or may be only a part through which the refrigerant flows after merging from each fuel battery cell. It may include both parts.

  Here, it is assumed that the fuel cell stack is provided with a device to be cooled that requires cooling on the surface of the stack. A device to be cooled is a device that requires cold heat during operation, and examples thereof include an electronic device that constitutes a part of a fuel cell system. In the fuel cell stack, a main flow portion provided in the laminated body is provided at a position close to the device to be cooled, and heat exchange is performed between the refrigerant flowing through the fuel cell stack and the device to be cooled. As a result, the heat exchangeable region of the surface of the stack of fuel cell stacks is effectively utilized, and the configuration of the fuel cell system can be simplified by reducing the number of equipment that cools the equipment to be cooled.

  Further, the main flow part is a flow path that penetrates the inside of the laminated body in the lamination direction of the laminated body, and is disposed on the surface of the laminated body that is lateral to the lamination direction. You may arrange | position in the position close | similar to an apparatus. This is because it is structurally rational that the main flow portion provided in the laminated body is a flow path penetrating in the laminating direction of the laminated body in order to flow a refrigerant that is divided or merged with each of the laminated cells. Thereby, the side surface with respect to the stacking direction of the surface of the stacked body is effectively utilized, and the configuration of the fuel cell system can be simplified.

  In addition, the main flow part may be disposed at a position inside the stacked body in the vicinity of the device to be cooled and at a position where the amount of cold heat required by the device to be cooled can be heat exchanged. From the viewpoint of simplifying the configuration of the fuel cell system, if the cooling of the cooling target device depends only on the refrigerant flowing through the refrigerant flow path, the cooling target apparatus is not capable of sufficiently exchanging heat with the refrigerant flowing through the refrigerant flow path. Can overheat. Therefore, by determining the position of the main stream portion from the viewpoint of the amount of heat exchange, it becomes possible to compensate for cooling of the apparatus to be cooled.

  Further, the present invention is a fuel cell system that generates electricity by an electrochemical reaction between a fuel gas and an oxidizing gas, and has a stacked body in which a plurality of fuel cell cells that electrochemically react the fuel gas and the oxidizing gas are stacked. A fuel cell stack, and a booster device that boosts the output voltage of the fuel cell stack, the booster device capable of transferring heat generated in itself to the fuel cell stack as the output voltage is boosted, The boosting device may raise the temperature of the stacked body with heat generated by boosting the output voltage by boosting the output voltage of the fuel cell stack.

In the fuel cell system, reducing the amount of heat balance between the inside and outside of the system and effectively using heat between devices constituting the system leads to an improvement in power generation efficiency of the entire system. Here, in the fuel cell system, the heat balance between the devices varies depending on the state during power generation. For example, it may be desirable to heat the fuel cell stack to promote an electrochemical reaction in the fuel cell stack, or it may be desirable to cool the fuel cell stack to protect the fuel cell stack.

  By the way, the fuel cell stack generates power by an electrochemical reaction between the fuel gas and the oxidizing gas. To cause such an electrochemical reaction, the temperature of the fuel cell stack is maintained at a temperature suitable for the electrochemical reaction. Need to be. For example, in the case of a polymer electrolyte membrane fuel cell stack using hydrogen and oxygen, the fuel cell stack must be heated to a temperature above the freezing point of water so as not to inhibit proton movement in the electrolyte membrane. Is desirable. In general, it is known that the reaction rate of an electrochemical reaction greatly depends on temperature, and the reaction rate usually increases as the temperature increases. In other words, in a fuel cell that generates electricity by an electrochemical reaction, when the temperature decreases, the reaction rate decreases and the electrical output decreases. However, since the voltage required on the load side is usually constant, it is necessary to maintain the voltage on the fuel cell side higher than that on the load side in order to continue power generation. Therefore, the fuel cell system includes a boosting device that boosts the output voltage of the fuel cell stack.

  Here, in the fuel cell system, as described above, when the fuel cell stack is at a low temperature, the booster device operates. In addition, a conversion device such as a booster device generates heat due to conversion loss. Therefore, this heat is used to raise the temperature of the fuel cell stack in a low temperature state. As a result, the device for cooling the booster device can be omitted, and the configuration of the fuel cell system can be simplified.

  Further, the boosting device is configured so that the temperature of the fuel cell stack is lower than the temperature in the rated operation state and the output voltage of the fuel cell stack is lower than the voltage required by the load. By raising the output voltage, the laminated body may be heated with heat generated by raising the output voltage. As a result, it is possible to raise the temperature of the fuel cell stack that is in a lower temperature state than the temperature in the rated operation state as quickly as possible while simplifying the configuration of the fuel electronic system.

  The boosting device includes a switch and a coil, and the boosting device boosts the output voltage of the fuel cell stack with a counter electromotive force of the coil generated by the switch performing a switching operation on the coil. Thus, heat may be generated due to the switching loss of the switch. In the case of a switching type boosting device including a coil, the boosting ratio depends on the switching frequency. Here, the amount of heat generated by the switching loss depends on the magnitude of the switching frequency. In other words, the amount of heat generated increases or decreases according to the magnitude of the step-up ratio. Therefore, according to the fuel cell system, it is possible to adjust the increase / decrease in the boost ratio and the increase / decrease in the required heating amount by increasing / decreasing the switching frequency.

  Further, the booster device may be disposed adjacent to an end portion in the stacking direction of the stacked body and capable of transferring heat to the fuel cell at the end portion. In the case of a stacked body in which fuel cells are stacked, the fuel cells located at the end in the stacking direction are less likely to be heated because there is little reaction heat transmitted from adjacent fuel cells. Therefore, in the case of a fuel cell system in which a booster device is disposed in such a portion, the temperature of the fuel cell in the end portion that particularly needs heating is increased as quickly as possible among the fuel cells constituting the laminate. It is possible.

The fuel cell stack is a refrigerant flow path for flowing a refrigerant that cools each fuel battery cell of the stack, and the refrigerant that is diverted to each of the stacked fuel battery cells or joined from each fuel battery cell. A refrigerant flow path having a main flow part through which the refrigerant flows, and the switch may be disposed at a position close to the main flow part on the surface of the laminate. According to this, it is possible to raise the temperature of each cell with the heat generated by the switching loss, and it is possible to raise the temperature of each fuel cell constituting the stacked body substantially evenly.

  In addition, the main flow part is a flow path that penetrates the inside of the stacked body in the stacking direction of the stacked body, and the boosting device includes a plurality of boosting circuits including the switch and the coil. The plurality of switches may be arranged so as to be aligned in the stacking direction of the stacked body at a position close to the mainstream portion on the surface of the stacked body. In the case of a multi-phase type boosting device, it is desirable to prevent variation in the electrical characteristics of each phase. Therefore, by arranging the switches of each phase along the main stream part, it is possible to cool the switches constituting the booster circuit of each phase substantially uniformly and make the electrical characteristics of each phase substantially the same.

  The configuration of the fuel cell system can be simplified.

  Hereinafter, a fuel cell stack and a fuel cell system according to an embodiment of the present invention will be described.

<Configuration of Embodiment>
FIG. 1 is an overall configuration diagram of a fuel cell system 1 according to an embodiment of the present invention. The fuel cell system 1 is a system to which a fuel cell stack according to an embodiment of the present invention is applied. The fuel cell system 1 is assumed to be mounted on a vehicle 2 using an electric motor as a drive source, and to supply power to a drive motor (hereinafter simply referred to as “motor 3”) of the vehicle 2. The vehicle 2 is self-propelled and movable when the driving wheel is driven by the motor 3. The motor 3 is a so-called three-phase AC motor, and operates by receiving AC power from the inverter 4. The inverter 4 converts DC power supplied from a fuel cell 5 as a main power source of the fuel cell system 1 and a battery 6 as a secondary battery into AC power and supplies the AC power to the motor 3.

  The fuel cell system 1 is mounted on a vehicle 2 that is a moving body and supplies power to the motor 3 of the vehicle 2. However, the fuel cell system 1 is used for a moving body such as a ship or a robot or a power consuming device that does not move. Is applicable.

  Here, the fuel cell 5 generates power by an electrochemical reaction between hydrogen gas stored in the hydrogen tank 7 and oxygen in the air that is pumped by the compressor 8. An FC boost converter 9 which is a boost DC-DC converter is electrically connected between the fuel cell 5 and the inverter 4. As a result, the voltage of the electric power output from the fuel cell 5 is boosted to an arbitrary voltage by the FC boost converter 9 and applied to the inverter 4. The detailed configuration of the FC boost converter 9 will be described later. The battery 6 is a chargeable / dischargeable power storage device, and is a boost type battery booster so that the inverter 4 is in parallel with the FC boost converter 9 between the battery 6 and the inverter 4. Converter 10 is electrically connected. Thereby, the voltage of the power output from the battery 6 is boosted to an arbitrary voltage by the battery boost converter 10 and applied to the inverter 4. As shown in FIG. 1, in the fuel cell system 1, a step-up / step-down converter capable of a step-up operation and a step-down operation can be employed instead of the step-up type battery step-up converter 10. In the following embodiments, the description will be given mainly assuming that the battery boost converter 10 is a boost converter. However, there is no intention to limit the use of the step-up / step-down converter, and appropriate adjustments are made in the adoption. .

The fuel cell 5 includes a cooling device 2 for removing reaction heat generated by the electrochemical reaction.
2 is provided. The cooling device 22 has a cooler that cools the refrigerant with air, and is provided with a refrigerant pipe that circulates water (LLC) that is the refrigerant between the cooler and the fuel cell 5. The refrigerant pipe is provided with a pump for circulating the refrigerant, and the cooler is provided with a cooling fan that starts and stops according to the temperature of the LLC. The cooling device 22 cools the fuel cell 5 by constantly circulating the refrigerant while the fuel cell system 1 is operating. The water that is a refrigerant is a so-called antifreeze.

  The vehicle 2 includes an electronic control unit (hereinafter referred to as “ECU11”). ECU11 is electrically connected with each control object mentioned above, and controls each apparatus which comprises a system. For example, the vehicle 2 is provided with an accelerator pedal that receives an acceleration request from the user, the opening degree thereof is detected by the accelerator pedal sensor 12, and the detection signal is electrically transmitted to the ECU 11. The ECU 11 is also electrically connected to an encoder that detects the number of rotations of the motor 3, whereby the number of rotations of the motor 3 is detected by the ECU 11. The ECU 11 can perform various controls based on these detected values.

  In the fuel cell system 1 configured as described above, the accelerator pedal opening degree that the user of the vehicle 2 has stepped on is detected by the accelerator pedal sensor 12, and the ECU 11 is based on the accelerator opening degree, the rotation speed of the motor 3, and the like. The power generation amount of the fuel cell 5 and the charge / discharge amount from the battery 6 are appropriately controlled. Here, in order to improve the fuel consumption of the vehicle 2 that is a moving body, the motor 3 is a PM motor of high voltage and low current specifications. Therefore, since the motor 3 can exhibit a high torque at a low current, it is possible to reduce heat generation in the windings and other wirings inside the motor, and to reduce the rated output of the inverter 4. It becomes possible. Specifically, in the motor 3, the counter electromotive voltage is set to be relatively high in order to enable a relatively large torque output at a low current, while the motor 3 has a high rotational speed against the high counter electromotive voltage. The supply voltage from the fuel cell system 1 is set high so that it can be driven. At this time, the FC boost converter 9 is provided between the fuel cell 5 and the inverter 4, and the battery boost converter 10 is also provided between the battery 6 and the inverter 4, thereby increasing the supply voltage to the inverter 4. It is done.

  As described above, the fuel cell system 1 includes the FC boost converter 9 so that the motor 3 is driven by the boost operation of the FC boost converter 9 even when the output voltage (inter-terminal voltage) of the fuel cell 5 itself is low. It becomes possible to do. Accordingly, it is possible to reduce the size of the fuel cell 5 by reducing the number of stacked cells. As a result, the weight of the vehicle 2 can be reduced, and the fuel efficiency improvement can be further promoted.

  Here, the characteristics of the electric circuit of the FC boost converter 9 will be briefly described. FIG. 2 is a circuit diagram of the FC boost converter 9. FIG. 2 shows the electrical configuration of the fuel cell system 1 with the FC boost converter 9 as the center, but the description of the battery 6 and the battery boost converter 10 is omitted for ease of explanation.

  The FC boost converter 9 boosts the output voltage of the fuel cell 5 by releasing the energy stored in the coil L1 to the motor 3 side (inverter 4 side) via the diode D5 by the switching operation of the switch element S1. Specifically, one end of the coil L1 is connected to the terminal on the high potential side of the fuel cell 5. The pole at one end of the switch element S1 is connected to the other end of the coil L1, and the pole at the other end of the switch element S1 is connected to a terminal on the low potential side of the fuel cell. The cathode terminal of the diode D5 is connected to the other end of the coil L1, and the capacitor C3 is connected between the anode terminal of the diode D5 and the other end of the switch element S1.

Here, the switch element S1 is an insulated gate bipolar transistor, so-called IGBT (Insulated Gate Bipolar Transistor), and is a semiconductor element capable of switching large power at high speed. The switch element S1 changes in heat generation in proportion to the switching frequency and needs to be cooled, but has a heat resistant temperature higher than that of the coil L1. The capacitor C3 functions as a smoothing capacitor that suppresses voltage fluctuations of the boosted power. The diode D5 is a SIC diode (SIC: Silicon Carbide) and has a heat resistant temperature higher than that of the switch element S1 and the coil L1.

  The FC boost converter 9 configured as described above adjusts the switching duty ratio of the switch element S1, thereby increasing the boost ratio by the FC boost converter 9, that is, the output voltage of the fuel cell 5 input to the FC boost converter 9. The ratio of the output voltage of the FC boost converter 9 applied to the inverter 4 is controlled.

  Next, the fuel cell 5 will be described. FIG. 3 is a top view of the fuel cell 5, and FIG. 4 is a perspective view of the fuel cell 5. As shown in FIGS. 3 and 4, the fuel cell 5 is a polymer electrolyte fuel cell stack suitable for a moving medium, and includes a stack 14 in which a plurality of fuel cells 13 are stacked. The laminated body 14 is configured such that end cells 15 at both ends thereof are sandwiched by tension plates (not shown) and a fastening force in the stacking direction is applied to each cell. The end cell 15 on one end side of the stacked body 14 is provided with a pipe connection port for supplying refrigerant, fuel gas, and oxidizing gas into the stacked body 14. A hydrogen tank 7 is connected to the upstream side of the connection port that receives the fuel gas, and a compressor 8 is connected to the upstream side of the connection port that receives the oxidizing gas. The refrigerant circulation pipe of the cooling device 22 is connected to the connection port of the refrigerant pipe.

  FIG. 5 is an exploded perspective view of the fuel cell 5. As shown in FIG. 5, the fuel cell 5 is configured to stack a plurality of fuel cells 13. The fuel battery cell 13 includes a membrane electrode assembly (hereinafter referred to as MEA 16) in which a polymer electrolyte membrane is sandwiched between a catalyst electrode layer and a gas diffusion layer membrane, and a separator 17. The polymer electrolyte membrane is composed of a conductive material having ion exchange ability with a solid polymer such as polyfluorocarbon as a main chain and a side chain such as a sulfone group or a carboxylic acid group attached to carry a charge. . The catalyst electrode film is made of carbon black or the like carrying platinum (Pt). The MEA 16 causes an electrochemical reaction by supplying a fuel gas and an oxidizing gas to the gas diffusion layer film, and generates a potential difference between both electrodes. The separator 17 of the fuel cell 13 is composed of three types, a first separator 17A having a recess for flowing a refrigerant on the cathode side surface and a recess 18H for flowing a fuel gas on the anode side surface, the cathode side A second separator 17B having a recess 18H for flowing an oxidizing gas on the surface and a recess 18H for flowing a fuel gas on the surface on the anode side, and a recess for flowing an oxidizing gas on the surface on the cathode side and on the surface on the anode side. The third separator 17C has a recess 18L through which the refrigerant flows. The fuel cell 13 constitutes a single cell by stacking the first separator 17A, the MEA 16, the second separator 17B, the MEA 16, and the third separator 17C. The separators 17A, B, and C are provided with holes 19H, O, and L, respectively, for flowing fuel gas, oxidizing gas, and refrigerant by communicating with the piping of the end cell 15 on the anode side. A large number of MEAs 16 are stacked so that the holes 19L of the separators 17A, 17B, and 17C coincide with each other, thereby forming a refrigerant flow path corresponding to the main flow portion in the present invention. Hereinafter, of the main flow portion of the refrigerant flow path constituted by the holes 19L, the upstream main flow portion constituted by the holes 19L (H) is divided into the upstream manifold 20 (stacked fuel cells). This is a diverting part through which the refrigerant flows and corresponds to a part or all of the main flow part in the present invention). The downstream main flow part constituted by the holes 19L (L) is connected to the downstream manifold 21 (each laminated layer). It is a merged portion for flowing the refrigerant merged from the fuel cells, and corresponds to a part or all of the main flow portion in the present invention. In the upstream manifold 20, the refrigerant flowing from the connection pipe is distributed to the recesses 18 </ b> L of each separator 17, and in the downstream manifold 21, the refrigerant distributed to the recesses 18 </ b> L of each separator 17 merges.

6 is a transparent top view of the fuel cell 5 showing the flow of the refrigerant flowing through the upstream manifold 20, the recess 18L, and the downstream manifold 21, and FIG. 7 is a transparent perspective view. As shown in FIGS. 6 and 7, the refrigerant is divided into the recesses 18 </ b> L of the separators 17 while passing near the surface of the stacked body 14, and joins again near the surface of the stacked body 14. Therefore, the vicinity of the upstream manifold 20 among the surfaces of the stacked body 14 is most easily cooled, and the vicinity of the downstream manifold 21 is most hardly cooled.

  Here, as described above, in the electronic element constituting the FC boost converter 9, the coil L1 requires the most cold, and then the switch element S1 and the diode D5 require the cool heat in this order. As described above, the heat generation amount of the switch element S1 changes in proportion to the switching frequency. Therefore, in the fuel cell 5 according to this embodiment, the coil L1 is disposed at a position close to the upstream manifold 20 (cooling position A in FIG. 3) on the surface of the stacked body 14, and the switch element S1 is connected to the end cell ( The cooling positions B, B ′) in FIG. 3 and the diode D5 are disposed at positions close to the downstream side manifold 21 (cooling position C in FIG. 3). The coil L1, the switch element S1, and the diode D5 are joined to the laminate 14 by a material having thermal conductivity and electrical insulation, and the laminate 14 in all the operation regions of the FC boost converter 9 is connected. It is configured to be cooled to a heat resistant temperature or lower by a refrigerant flowing inside. The coil L1, the switch element S1, and the diode D5, which are to-be-cooled devices, are each disposed in such an appropriate position in accordance with the temperature distribution on the surface of the stacked body, thereby efficiently receiving the cooling heat of the refrigerant. It becomes possible.

<Operation Flow of Embodiment>
Next, control of the fuel cell 5 will be described. FIG. 8 is a control flow diagram of the fuel cell 5. Hereinafter, the control flow of the fuel cell 5 will be described with reference to the control flow diagram of FIG.

  (Step S101: Power Generation Mode Determination) When the fuel cell system 1 is activated, the ECU 11 determines whether or not the fuel cell 5 needs to be heated by a temperature sensor (not shown) attached to the fuel cell 5. Specifically, the ECU 11 generates power in the normal power generation mode if the temperature of the fuel cell 5 is equal to or higher than a predetermined temperature (hereinafter referred to as Tc) preset in a memory or the like (executes the process of S102). If the temperature of the fuel cell 5 is lower than Tc, power generation is performed in the low-efficiency power generation mode (the process of S103 is executed). Here, the predetermined temperature (Tc) is determined by whether or not the fuel cell 5 can generate power at the rated output immediately after the start of power generation when the fuel gas and the oxidizing gas are supplied to the fuel cell 5. The temperature of the fuel cell 5 is, for example, the temperature at which the produced water remaining in the fuel cell 5 is frozen (temperature of 0 ° C. or lower). The ECU 11 may determine the power generation mode with a temperature sensor attached to the fuel cell 5, but may determine with the outside air temperature, the refrigerant temperature, or the like. Further, during the operation of the fuel cell system 1, the ECU 11 repeatedly executes the determination process of step S101. If the temperature of the fuel cell 5 during power generation rises to a temperature equal to or higher than Tc (for example, 10 ° C.), power generation is performed. The mode is switched from step S103 to step S102.

  (Step S102: Normal Power Generation Mode) The ECU 11 that has selected the normal power generation mode in step S101 executes the following processing. That is, the ECU 11 controls the hydrogen tank 7 and the compressor 8 to supply hydrogen, which is a fuel gas, and oxygen, which is an oxidizing gas, to the fuel cell 5. The flow rates of the fuel gas and the oxidizing gas supplied to the fuel cell 5 are the required power generation amount calculated based on the required torque detected by the accelerator pedal sensor 12, the input / output current of the battery 6, the consumption current of the motor 3, and the like. It is decided according to. That is, the amount of hydrogen consumed and the amount of oxygen consumed with respect to the required power generation amount are determined from the operation model of the fuel cell 5 stored in advance in the ECU 11, and the hydrogen tank is supplied so that the determined amount of hydrogen and oxygen is supplied to the fuel cell 5. The opening degree of the outlet valve 7 and the rotation speed of the compressor 8 are controlled. Thereby, the electrochemical reaction of hydrogen and oxygen starts in the fuel cell 5, and power generation is started.

(Step S103: Low-Efficiency Power Generation Mode) The ECU 11 that has selected the low-efficiency power generation mode in step S101 executes the following processing. That is, the ECU 11 controls the hydrogen tank 7 and the compressor 8 to supply hydrogen as a fuel gas and oxygen as an oxidant gas to the fuel cell 5. By changing the ratio of both gases supplied at this time, the fuel cell 5. To reduce the power generation efficiency. That is, the ECU 11 determines the amount of hydrogen consumption and the amount of oxygen consumption with respect to the required power generation amount from the operation model of the fuel cell 5, corrects the determined parameters, and sets the ratio of the fuel gas to the oxidizing gas in the normal power generation mode of step S102 described above Lower than the time of. As a result, the fuel cell 5 is in a state where the fuel gas is insufficient with respect to the oxidizing gas, the power generation efficiency of the entire system is lowered, and the residual heat of the fuel cell 5 and auxiliary equipment that increases due to low-efficiency power generation causes the fuel cell 5 Heating is promoted and the temperature of the fuel cell 5 is quickly raised.

  As described above, when the fuel cell system 1 is activated, the processing from step S101 to step S103 is repeatedly executed, and power generation is continued.

  Next, control of the FC boost converter 9 of the fuel cell system 1 will be described. FIG. 9 is a control flow diagram of the FC boost converter 9. Hereinafter, the operation of the fuel cell system 1 will be described along the control flow of FIG. The control flow of the FC boost converter 9 is executed in parallel with the control of the fuel cell 5 described above.

  (Step S201) The ECU 11 calculates the maximum torque that the motor 3 can output at maximum, corresponding to the actual rotational speed of the motor 3 detected by the encoder. Specifically, the ECU 11 has a map in which the rotation speed of the motor 3 is associated with the maximum torque corresponding thereto, and the maximum torque of the motor 3 is obtained by accessing the map according to the detected rotation speed. Calculated. When the ECU 11 finishes the process of step S201, the ECU 11 executes the process of S202.

(Step S <b> 202) The ECU 11 calculates the required torque requested to be output from the motor 3 based on the accelerator pedal opening detected by the accelerator pedal sensor 21. If the full opening of the accelerator pedal is defined as requiring the maximum torque at the current rotational speed of the motor 3, the required torque is calculated according to the following formula, assuming that the coefficient when fully opened is 100% and the coefficient when fully closed is 0%. Is calculated. When the ECU 11 finishes the process of step S202, it executes the process of S203.
(Required torque) = (Maximum torque) x (Coefficient according to accelerator pedal opening)

(Step S203) The ECU 11 calculates a required output, which is an output required for the motor 3, based on the calculation results in S201 and S202, according to the following equation. When the ECU 11 finishes the process of step S203, it executes the process of S204.
(Request output) = (Request torque) x (Motor speed)

  (Step S <b> 204) The ECU 11 requires a motor required voltage (voltage to be applied to the inverter 4) so that necessary power is supplied to the motor 3 based on the required output calculated in S <b> 203 and the rotation speed of the motor 3. Vmot) is calculated. Specifically, the ECU 11 has a motor required voltage map in which a function F formed by the rotation speed (rpm) of the motor 3 and the required output (P) and a motor required voltage are associated with each other. The required voltage of the motor is calculated by accessing this map according to the motor speed and the required output. The required motor voltage map can be determined in advance by experiments or the like. As an example, the required voltage value should be increased because the counter electromotive voltage increases as the rotational speed of the motor 3 increases. Since the required voltage value should be increased in order to achieve its output with less current as the value of becomes higher, these points are reflected in the correlation between the function F and the required motor voltage. When the ECU 11 ends the process of S204, the ECU 11 executes the process of S205.

  (Step S <b> 205) The ECU 11 detects the output voltage (Vfc) of the fuel cell 5 in which power generation is performed according to the accelerator pedal opening detected by the accelerator pedal sensor 21. This detection is performed via a voltage sensor (not shown).

  (Step S206) When the process of step S205 is completed, the ECU 11 calculates the boost ratio Rt (= Vmot / Vfc) by dividing the required motor voltage calculated in S204 by the output voltage of the fuel cell 5 detected in S205. .

  (Step S207) The ECU 11 determines whether or not the operation of the FC boost converter 9 is necessary. That is, the ECU 11 determines that the output power of the fuel cell 5 needs to be boosted if the boost ratio Rt calculated in the process of S206 is 1 or more, and executes the process of S208. On the other hand, if the boosting cost Rt calculated in the process of S206 is less than 1, the ECU 11 determines that there is no need to boost the output voltage of the fuel cell 5, and executes the process of S209.

  Here, the determination process in step S207 will be described in detail. FIG. 10A is a correlation diagram showing the required motor voltage (Vmot) and the output voltage (Vfc) of the fuel cell 5 according to the speed of the vehicle. As indicated by Vmot in FIG. 10A, the counter electromotive voltage of the motor 3 increases as the speed of the vehicle 2 increases, so that the required motor voltage also increases as the vehicle speed increases. Here, in the correlation between the output voltage Vfc of the fuel cell 5 and the required motor voltage Vmot, it is conceivable that the system is configured such that Vfc is higher than Vmot in all speed regions of the vehicle 2. In this embodiment, the FC boost converter 9 is provided to adjust the output voltage of the fuel cell 5 and the required voltage of the motor 3 in order to increase the size of the fuel cell 5. That is, in the fuel cell system 1 designed in this way, the output voltage from the fuel cell 5 is higher than the motor required voltage for driving the motor 3 until the speed of the vehicle 2 reaches VS0. Even without the boost operation of the FC boost converter 9, the motor 3 can be driven by the direct output voltage from the fuel cell 5. In other words, under this condition, driving of the motor 3 can be secured by stopping the switching operation by the FC boost converter 9 and applying the output voltage from the fuel cell 5 to the inverter 4. On the other hand, when the vehicle speed of the vehicle 2 is equal to or higher than VS0, the required motor voltage for driving the motor 3 is higher than the output voltage from the fuel cell 5, so that the boost operation by the FC boost converter 9 is necessary. Become. In FIG. 10A, the region where the boost operation by the FC boost converter 9 is necessary is indicated by hatching. The above is the content of the determination process in step S207.

  (Step S208) When the ECU 11 makes an affirmative determination in S207, the FC boost converter 9 is operated to boost the output power of the fuel cell 5, and the boosted power is applied to the inverter 4. As a result, current flows through the switch element S1, the coil L1, and the diode D5 of the FC boost converter 9, and heat is generated due to switching loss and the like.

  By the way, although the speed region in which this step S208 is executed is shown in the correlation diagram of FIG. 10A, the correlation diagram of FIG. 10A shows the correlation when the fuel cell 5 is generating power at the rated output. In an operating state where 5 is less than the rated output, the correlation between the output voltage of the fuel cell 5 and the required motor voltage changes. For example, when the vehicle 2 is in an extremely cold region or the like, the output voltage of the fuel cell 5 decreases due to freezing of the fuel cell of the fuel cell 5 immediately after startup, and the relationship shown in the correlation diagram of FIG. 10B. It may become. When the temperature of the fuel cell 5 is low, the temperature increase of the fuel cell 5 is promoted by being controlled in the low efficiency power generation mode (S103) as described above. As shown, the state where the output voltage of the fuel cell 5 is low continues.

  Here, in the fuel cell system 1 according to the present embodiment, the switch element S1, the diode D5, and the coil L1 of the FC boost converter 9 are attached to the surface of the stacked body 14 of the fuel cell 5 so that heat exchange is possible. Therefore, the stacked body 14 of the fuel cell 5 is heated by the operation of the FC boost converter 9. FIG. 11 is a diagram showing a heat generation state of the fuel cell 5. As shown in FIG. 11, the stack 14 of the fuel cell 5 in a low temperature state is heated by the heat of the FC boost converter 9. In particular, the vicinity of the end cell with little heat input from the adjacent cell is efficiently heated by the heat generated by the switching loss of the switch element S1. Further, each fuel cell 13 is heated by the heat generated by the coil L1 disposed in the vicinity of the upstream manifold 20, and the stacked body 14 of the fuel cell 5 is entirely heated as shown in FIG. Thereby, the temperature rise of the fuel cell 5 is promoted, and the transition to the rated output operation is completed quickly. The power generation mode changing process from the low efficiency power generation mode to the normal power generation mode is appropriately performed in the conditional branch of S101 in the process flow of FIG. 8 executed in parallel with the process flow shown in FIG.

  (Step S209) On the other hand, when the ECU 11 makes a negative determination in S207, the ECU 11 stops the FC boost converter 9 and directly applies the output voltage from the fuel cell 5 to the inverter 4. Thereby, heat generation of the switch element S1, the coil L1, and the diode D5 of the FC boost converter 9 is stopped. Due to the stop of the FC boost converter 9, the heat generating region of the fuel cell 5 is only the laminate 14 as shown in FIG.

  In the description of the processing from S201 to S209, for the sake of simplicity, the description has been given focusing only on the correlation between the fuel cell 5 and the motor 3. However, the present fuel cell system 1 Power supply from the battery 6 is also possible. When power is supplied from the battery 6, the output voltage from the battery 6 is boosted by the battery boost converter 10 and then applied to the inverter 4. Here, since the battery boost converter 10 is a so-called boost converter, in order to supply power from the battery 6 to the inverter 4, the outlet voltage of the battery boost converter 10 (the voltage on the inverter 4 side, the FC boost converter 9 Is equal to or higher than the inlet voltage (voltage on the battery 6 side).

<Effect of embodiment>
As described above, according to the present embodiment, the heat of the heat generating device such as the FC boost converter is cooled by the refrigerant flowing in the fuel cell. Therefore, a dedicated cooling device such as a cooling fin or a cooling fan is provided on these heat generating devices. There is no need to provide it, and the system can be simplified. In addition, when the temperature of the fuel cell is low and the output power needs to be boosted, the heat of the FC boost converter is used to combine the temperature rising and boosting to achieve extremely efficient heat. Energy can be used, and fuel efficiency can be improved by effectively using heat energy.

<Modification>
In the above-described embodiment, the output power of the fuel cell 5 is boosted by the boost converter. However, it goes without saying that a step-up / step-down converter that can perform both the boost operation and the buck operation can be adopted. Moreover, in the said embodiment, although switch element S1 is arrange | positioned at cooling position B, B ', these apparatuses are not limited to such a layout, According to the heat-resistant temperature etc. of an element. It is possible to layout appropriately. For example, the switch S1 of the FC boost converter 9 may be disposed at the cooling position A or the like. If the switch S1 is arranged, each fuel cell 13 of the fuel cell 5 in a low temperature state can be heated evenly. Moreover, in the said embodiment, although the boost converter is illustrated as a to-be-cooled apparatus arrange | positioned in the laminated body 14 of the fuel cell 5, this invention is not limited to this, To-be-cooled other than a boost converter It may be a device. The laminated body 14 of the fuel cell 5 is sandwiched between tension plates as shown in FIG.
When the cooled device is attached to B ′, the cooled device is arranged between the end cell and the tension plate so that heat can be exchanged with the laminate 14.

  In the above embodiment, a single-phase boost converter is illustrated, but the present invention is not limited to this, and a multi-phase boost converter is used depending on the output power of the fuel cell, the required power of the motor, the required frequency, and the like. It is also possible to adopt a converter as appropriate and apply it to the above embodiment. FIG. 15 shows a perspective view when a three-phase boost converter is employed and attached to the laminate 14 of the fuel cell 5. As shown in FIG. 15, a highly heat-resistant component such as a diode D5 is attached to the bus bar electrically connected to the anode of the fuel cell 5, and the coil L1 or the like is connected to the bus bar electrically connected to the cathode of the fuel cell 5. A part having low heat resistance such as the switch element S1 is attached. A downstream manifold 21 is disposed in the vicinity of the bus bar connected to the anode, and an upstream manifold 20 is disposed in the vicinity of the bus bar connected to the cathode. In addition, in order to simplify drawing, although the modification shown in FIG. 15 has changed the position of the connection port of refrigerant | coolant piping with the thing of the said embodiment, this position can be changed suitably. By arranging the switching elements of each phase and the like so that the relative distances from the stacked body 14 of the fuel cell 5 are substantially the same, the temperature of the elements does not vary for each phase, and the fuel cell Compared with the case where the switching elements are arranged at positions away from 5, the distance of the electrical path between the fuel cell 5 and the FC boost converter 9 can be shortened. Since the electric power before boosting is larger than the electric power after boosting, it is possible to minimize the loss due to the electric resistance of the electric circuit by shortening the electric circuit connecting the fuel cell 5 and the FC boost converter 9. . Further, since the switching elements of the respective phases are arranged in parallel at extremely close positions, the switching deviation of the boosting circuit of each phase is reduced, and it becomes possible to supply boosted power having a favorable waveform.

The block diagram of a fuel cell system. The circuit diagram of FC boost converter. The top view of a fuel cell. The perspective view of a fuel cell. The disassembled perspective view of a fuel cell. The permeation | transmission top view which shows the flow of the refrigerant | coolant of a fuel cell. The permeation | transmission perspective view which shows the flow of the refrigerant | coolant of a fuel cell. FIG. 4 is a control flow diagram in a power generation mode. FIG. 3 is a control flow diagram of the FC boost converter. The graph explaining operation | movement of FC boost converter. The graph explaining operation | movement of FC boost converter. The figure which shows the heat_generation | fever state of a fuel cell. The figure which shows the heat_generation | fever state of a fuel cell. The figure which shows the heat_generation | fever state of a fuel cell. The top view of the fuel cell which concerns on a modification. The external appearance perspective view of the fuel cell which concerns on a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system 2 ... Vehicle 3 ... Motor 4 ... Inverter 5 ... Fuel cell 6 ... Battery 7 ... Hydrogen tank 8 ... Compressor 9 ... FC pressure | voltage rise Converter 10 ... Battery boost converter 11 ... ECU
12 ... Accelerator pedal sensor 13 ... Fuel cell 14 ... Stack 15 ... End cell 16 ... MEA
17 ... Separator 18 ... Recess 19 ... Hole 20 ... Upstream manifold 21 ... Downstream manifold 22 ... Cooling device

Claims (9)

A fuel cell stack that generates electricity by an electrochemical reaction between a fuel gas and an oxidizing gas,
A laminated body in which a plurality of fuel cells that electrochemically react the fuel gas and the oxidizing gas are stacked;
A refrigerant flow path that is provided inside the laminated body and flows a refrigerant that cools each fuel battery cell of the laminated body, and is divided from each of the stacked fuel battery cells or from each fuel battery cell. A refrigerant flow path having a main flow part for flowing the merged refrigerant,
The main flow portion is disposed at a position close to the cooled device disposed on the surface of the laminate so that heat can be exchanged between the refrigerant flowing through the main flow portion and the cooled device. The
Fuel cell stack. The main flow part is a flow path that penetrates the inside of the laminated body in the lamination direction of the laminated body, and is provided on the cooled device disposed on a side surface of the laminated body in the lamination direction. Placed in close proximity,
The fuel cell stack according to claim 1. The main flow part is disposed at a position inside the laminated body adjacent to the cooled device, and at a position where the amount of cold heat required by the cooled device can be heat-exchanged.
The fuel cell stack according to claim 1 or 2. A fuel cell system that generates electricity by an electrochemical reaction between a fuel gas and an oxidizing gas,
A fuel cell stack having a laminate in which a plurality of fuel cells that electrochemically react the fuel gas and the oxidizing gas are stacked;
A boosting device that boosts the output voltage of the fuel cell stack, the boosting device capable of transferring heat generated by itself to the fuel cell stack as the output voltage is boosted;
The boosting device boosts the output voltage of the fuel cell stack, thereby raising the temperature of the laminate with heat generated by boosting the output voltage.
Fuel cell system. The boosting device has an output voltage of the fuel cell stack in a state where the temperature of the fuel cell stack is lower than the temperature in the rated operation state and the output voltage of the fuel cell stack is lower than the voltage required by the load. To increase the temperature of the laminate with the heat generated by boosting the output voltage,
The fuel cell system according to claim 4. The boosting device includes a switch and a coil, and the boosting device boosts the output voltage of the fuel cell stack with a back electromotive force of the coil generated when the switch performs a switching operation on the coil. , Heat is generated by the switching loss of the switch,
The fuel cell system according to claim 4 or 5. The booster device is disposed adjacent to an end in the stacking direction of the stacked body and capable of transferring heat to the fuel cell at the end.
The fuel cell system according to any one of claims 4 to 6. The fuel cell stack is a refrigerant flow path for flowing a refrigerant for cooling each fuel battery cell of the stacked body, and is divided from each of the stacked fuel battery cells or joined from each fuel battery cell Having a refrigerant flow path having a main flow part for flowing refrigerant;
The switch is disposed at a position close to the main stream portion of the surface of the laminate.
The fuel cell system according to claim 6. The main flow part is a flow path that penetrates the inside of the laminate in the lamination direction of the laminate,
The booster device is a multiphase booster device having a plurality of booster circuits having the switch and the coil,
The plurality of switches are arranged at positions close to the mainstream portion of the surface of the stacked body and aligned along the stacking direction of the stacked body.
The fuel cell system according to claim 8.

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