JP2017084665A - Control method for fuel battery system and fuel battery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of suppressing the pressure of cooling water in a circulation passage from decreasing to a tolerance limit negative pressure.SOLUTION: A fuel battery system 100 includes a fuel battery stack 1 for generating electric power upon reception of reaction gas, a circulation passage 41 connected to the fuel battery stack, a circulation pump 45 for circulating cooling water in the circulation passage 41, and a reserve tank 47 connected to the circulation passage 41 via a water amount adjustment valve 46. A controller 5 comprises a step of using a detection value of cooling water pressure measuring means (first pressure sensor) 56 in the circulation passage 41 to predict whether there occurs a state that the amount of cooling water in the circulation passage 41 becomes insufficient during operation of the circulation pump 45, and a step of executing inflow processing of causing the cooling water stored in a reserve tank 47 to flow into the circulation passage 41 through the water amount adjustment valve 46 when it is predicted that the water insufficient state will occur.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fuel cell system control method and a fuel cell system.

  Patent Document 1 discloses a circulation path connected to a fuel cell, a circulation pump that circulates cooling water in the circulation path, a radiator that radiates heat from the cooling water, and a reserve that is connected to the radiator via a radiator cap. A fuel cell system including a tank is disclosed.

JP 2005-190704 A

  In the fuel cell system as described above, the cooling water pressure and the amount of water in the circulation passage can be obtained by flowing the cooling water from the circulation passage to the reserve tank through the radiator cap or from the reserve tank to the circulation passage. Is adjusted.

  However, even in a fuel cell system equipped with such a reserve tank, depending on the operating state of the fuel cell system, the cooling water pressure on the inlet side of the circulation pump may exceed the allowable limit when the rotation speed of the circulation pump is increased. May drop to pressure. When the cooling water pressure on the inlet side of the circulation pump falls to the allowable limit negative pressure, cavitation occurs in the circulation pump, or the circulation passage formed by an elastic member such as rubber or resin is deformed and the flow of the cooling water is obstructed. Problem arises.

  The objective of this invention is providing the technique which can suppress that the cooling water pressure in a circulation channel falls to an allowable limit negative pressure.

  According to an aspect of the present invention, a fuel cell that generates power upon receiving a supply of a reaction gas, a circulation passage connected to the fuel cell, a circulation pump that circulates cooling water in the circulation passage, and a valve member in the circulation passage There is provided a control method for a fuel cell system including a reserve tank connected via a fuel tank. This control method is predicted to predict whether or not the amount of cooling water is insufficient in the circulation passage during driving of the circulation pump using the pressure of the cooling water in the circulation passage, and a water shortage state. And an execution step of executing an inflow process for causing the cooling water stored in the reserve tank to flow into the circulation passage through the valve member.

  According to this aspect, since the cooling water can be supplied from the reserve tank to the circulation passage before the inside of the circulation passage becomes in a water-deficient state, the cooling water pressure on the pump inlet side is increased during the subsequent driving of the circulation pump. It is possible to suppress a decrease to the allowable limit negative pressure.

FIG. 1 is a longitudinal sectional view of a fuel cell stack according to a first embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a fuel cell system including a fuel cell stack. FIG. 3A is a longitudinal sectional view of a water amount adjusting valve when the pressurizing valve is opened. FIG. 3B is a longitudinal sectional view of the water amount adjusting valve when the negative pressure valve is opened. FIG. 4 is a flowchart showing the circulation pump control executed by the controller of the fuel cell system. FIG. 5 is a map in which the output current of the fuel cell stack is associated with the target rotational speed of the circulation pump. FIG. 6 is a flowchart showing a forced cooling water inflow process executed by the controller. FIG. 7 is a time chart for explaining the behavior of the coolant pressure in the fuel cell system according to the first embodiment. FIG. 8 is a time chart for explaining the behavior of the cooling water pressure in the fuel cell system according to the comparative example. FIG. 9 is a flowchart illustrating a modification of the forced cooling water inflow process. FIG. 10 is a flowchart showing another modification of the cooling water forced inflow process. FIG. 11 is a flowchart showing a cooling water forced inflow process executed by the controller of the fuel cell system according to the second embodiment. FIG. 12 is a time chart for explaining the behavior of cooling water in the fuel cell system according to the second embodiment. FIG. 13 is a flowchart showing a cooling water forced inflow process executed by the controller of the fuel cell system according to the third embodiment. FIG. 14 is a time chart for explaining the behavior of cooling water in the fuel cell system according to the third embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, positive pressure means a pressure higher than atmospheric pressure, and negative pressure means a pressure lower than atmospheric pressure.

(First embodiment)
A fuel cell is configured by sandwiching an electrolyte membrane between an anode electrode and a cathode electrode. The fuel cell generates power by receiving supply of an anode gas (reaction gas) containing hydrogen and a cathode gas (reaction gas) containing oxygen. Electrode reactions that proceed at the anode and cathode electrodes of the fuel cell are as follows (1) and (2). The fuel cell generates an electromotive force of about 1 volt by the electrode reactions (1) and (2).

Anode electrode: 2H ₂ → 4H ⁺ + 4e ⁻ (1)
Cathode electrode: 4H ⁺ + 4e ⁻ + O ₂ → 2H ₂ O (2)
FIG. 1 is a longitudinal sectional view of a fuel cell stack 1 constituting the fuel cell system according to the first embodiment.

  A fuel cell stack 1 shown in FIG. 1 is a fuel cell stack used for a moving vehicle such as an electric vehicle or a hybrid vehicle. However, the fuel cell stack 1 is not limited to use in an automobile or the like, and may be used as a power source for various electric devices.

  The fuel cell stack 1 is a stacked battery configured by stacking a plurality of fuel cells 10 as unit cells.

  A fuel cell 10 constituting the fuel cell stack 1 is configured by arranging an anode separator 12 and a cathode separator 13 on both front and back surfaces of a membrane electrode assembly (MEA) 11.

  The MEA 11 includes an electrolyte membrane 11a, an anode electrode 11b, and a cathode electrode 11c. The MEA 11 has an anode electrode 11b on one surface of the electrolyte membrane 11a and a cathode electrode 11c on the other surface.

  The electrolyte membrane 11a is a proton-conductive ion exchange membrane formed of a fluorine-based resin. The anode electrode 11b includes a catalyst layer and a gas diffusion layer. The catalyst layer is formed from carbon black particles carrying platinum or platinum. The gas diffusion layer is formed of a member having sufficient gas diffusibility and conductivity, and is formed of, for example, a carbon cloth woven with yarns made of carbon fibers. Similarly to the anode electrode 11b, the cathode electrode 11c includes a catalyst layer and a gas diffusion layer.

  The anode separator 12 is disposed in contact with the anode electrode 11b. The anode separator 12 has a plurality of groove-like anode gas passages 121 for supplying anode gas to the anode electrode 11b on the side in contact with the anode electrode 11b. The anode separator 12 has a cooling water channel 122 through which cooling water for cooling the fuel cell 10 flows on the surface opposite to the surface 12a in contact with the anode electrode 11b.

  Similarly, the cathode separator 13 has a plurality of groove-like cathode gas flow paths 131 for supplying cathode gas to the cathode electrode 11c on the side in contact with the cathode electrode 11c. Further, the cathode separator 13 has a cooling water channel 132 on the surface opposite to the surface 13a in contact with the cathode electrode 11c.

  The cooling water flow paths 122 and 132 provided in the adjacent anode separator 12 and cathode separator 13 are formed so as to face each other, and the cooling water flow paths 122 and 132 form one cooling water flow path 14. The

  FIG. 2 is a schematic configuration diagram of the fuel cell system 100 according to the first embodiment.

  The fuel cell system 100 includes a fuel cell stack 1, an anode gas supply / discharge device 2, a cathode gas supply / discharge device 3, a stack cooling device 4, and a controller 5.

  The fuel cell stack 1 is formed by stacking a plurality of fuel cells 10, receives power from the anode gas and the cathode gas, generates electric power, and generates electric power necessary for driving the vehicle (for example, electric power necessary for driving the motor). ).

  The anode gas supply / discharge device 2 includes a high pressure tank 21, an anode gas supply passage 22, an anode pressure regulating valve 23, an anode pressure sensor 24, an anode gas discharge passage 25, a buffer tank 26, a purge passage 27, and a purge. And a valve 28. The anode gas supply / discharge device 2 supplies the anode gas to the fuel cell stack 1, temporarily stores the anode off-gas discharged from the fuel cell stack 1 in the buffer tank 26, and then discharges it from the purge passage 27 as necessary. .

  The high-pressure tank 21 stores the anode gas (hydrogen) supplied to the fuel cell stack 1 while maintaining the high-pressure state.

  The anode gas supply passage 22 is a passage for supplying the anode gas discharged from the high-pressure tank 21 to the fuel cell stack 1. One end of the anode gas supply passage 22 is connected to the high-pressure tank 21, and the other end is connected to the anode gas inlet hole 15 of the fuel cell stack 1.

  The anode pressure regulating valve 23 is provided in the anode gas supply passage 22. The anode pressure regulating valve 23 adjusts the anode gas discharged from the high-pressure tank 21 to a desired pressure and supplies it to the fuel cell stack 1. The anode pressure regulating valve 23 is an electromagnetic valve whose opening degree can be adjusted continuously or stepwise, and the opening degree is controlled by the controller 5.

  The anode pressure sensor 24 is provided in the anode gas supply passage 22 downstream of the anode pressure regulating valve 23. The anode pressure sensor 24 detects the pressure of the anode gas flowing through the anode gas supply passage 22 downstream of the anode pressure regulating valve 23. Hereinafter, the detected value of the anode pressure sensor 24 is referred to as an anode pressure, and this anode pressure is used as the pressure of the entire anode system including the anode gas passages 121 inside the fuel cell stack.

  One end of the anode gas discharge passage 25 is connected to the anode gas outlet hole 16 of the fuel cell stack 1, and the other end is connected to the buffer tank 26. A mixed gas (anode offgas) of excess anode gas that has not been used for the electrode reaction and impure gas such as nitrogen that has permeated from the cathode side to the anode gas flow path 121 is discharged to the anode gas discharge passage 25. Is done.

  The buffer tank 26 stores the anode off gas that has flowed through the anode gas discharge passage 25.

  One end of the purge passage 27 is connected to the anode gas discharge passage 25, and the other end is configured as an open end. The anode off gas stored in the buffer tank 26 once flows back through the anode gas discharge passage 25 and then is discharged from the open end to the outside of the system through the purge passage 27.

  The purge valve 28 is provided in the purge passage 27. The purge valve 28 is an electromagnetic valve whose opening / closing is controlled by the controller 5. By opening the purge valve 28, the anode off gas stored in the buffer tank 26 is discharged to the outside through the purge passage 27.

  The cathode gas supply / discharge device 3 includes a cathode gas supply passage 31, a cathode gas discharge passage 32, a filter 33, an air flow sensor 34, a cathode compressor 35, a cathode pressure sensor 36, and a water recovery device (Water Recovery Device; (Hereinafter referred to as “WRD”) 37 and a cathode pressure regulating valve 38. The cathode gas supply / discharge device 3 supplies the cathode gas to the fuel cell stack 1 and discharges the cathode off-gas discharged from the fuel cell stack 1 to the outside.

  The cathode gas supply passage 31 is a passage through which the cathode gas supplied to the fuel cell stack 1 flows. One end of the cathode gas supply passage 31 is connected to the filter 33, and the other end is connected to the cathode gas inlet hole 17 of the fuel cell stack 1.

  The cathode gas discharge passage 32 is a passage through which the cathode off gas discharged from the fuel cell stack 1 flows. One end of the cathode gas discharge passage 32 is connected to the cathode gas outlet hole 18 of the fuel cell stack 1, and the other end is configured as an open end. The cathode off gas is a mixed gas of the cathode gas and water vapor generated by the electrode reaction.

  The filter 33 removes foreign matters in the cathode gas taken into the cathode gas supply passage 31.

  The air flow sensor 34 is provided in the cathode gas supply passage 31 upstream of the cathode compressor 35. The air flow sensor 34 is supplied to the cathode compressor 35 and detects the flow rate of the cathode gas finally supplied to the fuel cell stack 1.

  The cathode compressor 35 is provided in the cathode gas supply passage 31. The cathode compressor 35 takes air (outside air) as cathode gas into the cathode gas supply passage 31 through the filter 33 and supplies the air to the fuel cell stack 1.

  The cathode pressure sensor 36 is provided in the cathode gas supply passage 31 between the cathode compressor 35 and the WRD 37. The cathode pressure sensor 36 detects the pressure of the cathode gas in the vicinity of the cathode gas inlet of the WRD 37. Hereinafter, the detection value of the cathode pressure sensor 36 is referred to as a cathode pressure.

  The WRD 37 is connected to each of the cathode gas supply passage 31 and the cathode gas discharge passage 32, collects moisture in the cathode off-gas flowing through the cathode gas discharge passage 32, and cathode that flows through the cathode gas supply passage 31 with the collected moisture. Humidify the gas.

  The cathode pressure regulating valve 38 is provided in the cathode gas discharge passage 32 downstream of the WRD 37. The cathode pressure regulating valve 38 is controlled to be opened and closed by the controller 5 and adjusts the pressure of the cathode gas supplied to the fuel cell stack 1 to a desired pressure.

  The stack cooling device 4 includes a circulation passage 41, a radiator 42, a bypass passage 43, a thermostat 44, a circulation pump 45, a water amount adjustment valve 46, a reserve tank 47, a water temperature sensor 55, and a first pressure sensor 56. And a second pressure sensor 57.

  The circulation passage 41 is a passage through which cooling water for cooling the fuel cell stack 1 flows. One end of the circulation passage 41 is connected to the cooling water inlet hole 19 of the fuel cell stack 1, and the other end is connected to the cooling water outlet hole 20. The cooling water introduced into the fuel cell stack 1 from the cooling water inlet hole 19 flows through the cooling water flow path 14 of each fuel cell 10 and is then discharged from the cooling water outlet hole 20.

  The circulation passage 41 is formed of an elastic member such as rubber or resin in order to prevent the elution of metal ions into the cooling water and ensure insulation. Hereinafter, the coolant outlet hole 20 side of the fuel cell stack 1 is treated as upstream of the circulation passage 41, and the coolant inlet hole 19 side of the fuel cell stack 1 is treated as downstream of the circulation passage 41.

  The radiator 42 is provided in the circulation passage 41 and radiates heat of the cooling water passing therethrough. Therefore, the temperature of the cooling water decreases as the cooling water passes through the radiator 42.

  The bypass passage 43 is a passage through which the coolant is circulated by bypassing the radiator 42. One end of the bypass passage 43 is connected to the circulation passage 41 on the upstream side of the radiator 42, and the other end is connected to a thermostat 44 disposed on the downstream side of the radiator 42. Similarly to the circulation passage 41, the bypass passage 43 is also formed of an elastic member such as rubber or resin.

  The thermostat 44 is provided in the circulation passage 41 on the downstream side of the radiator 42. The thermostat 44 is an on-off valve that opens and closes according to the temperature of the cooling water flowing inside. The thermostat 44 is closed when the coolant temperature is lower than a predetermined valve opening temperature, and supplies the coolant that has passed through the bypass passage 43 to the fuel cell stack 1. On the other hand, the thermostat 44 is opened when the cooling water temperature becomes equal to or higher than the valve opening temperature, and supplies the cooling water that has passed through the radiator 42 to the fuel cell stack 1.

  The thermostat 44 is configured such that the valve opening temperature is about 60 [° C.], for example. In the fuel cell system 100, the thermostat 44 is employed, but a three-way valve may be employed instead of the thermostat 44.

  The circulation pump 45 is an electric pump and is provided in the circulation passage 41 on the downstream side of the thermostat 44. The circulation pump 45 circulates the cooling water in the circulation passage 41. The discharge flow rate of the circulation pump 45 continuously changes according to the rotation speed of the circulation pump controlled by the controller 5.

  The water temperature sensor 55 is provided in the circulation passage 41 near the cooling water outlet hole 20 of the fuel cell stack 1 and detects the temperature of the cooling water discharged from the fuel cell stack 1.

  The first pressure sensor 56 is a pressure detection unit that is provided in the circulation passage 41 on the upstream side of the circulation pump 45 and detects the coolant pressure (pump inlet pressure) on the inlet side of the circulation pump 45. On the other hand, the second pressure sensor 57 is provided in the circulation passage 41 between the circulation pump 45 and the fuel cell stack 1, and detects the coolant pressure (pump outlet pressure) on the outlet side of the circulation pump 45. It is a detection unit.

  The water amount adjustment valve 46 is provided in the circulation passage 41 located between the thermostat 44 and the first pressure sensor 56. The water amount adjustment valve 46 is a valve member that adjusts the amount of cooling water in the circulation passage 41 according to the pressure of the cooling water in the circulation passage 41. The water amount adjusting valve 46 is connected to the reserve tank 47 through a connection passage. The reserve tank 47 is a container for storing cooling water.

  As shown in FIG. 3A, the water amount adjustment valve 46 includes a pressurization valve 46A, a first spring 46B that urges the pressurization valve 46A toward the valve seat, and a negative pressure valve 46C that is movable relative to the pressurization valve 46A. And a second spring 46D that urges the negative pressure valve 46C toward the pressurizing valve 46A.

  When the cooling water pressure on the inlet side of the circulation pump 45 becomes equal to or higher than the preset outflow pressure, the water amount adjusting valve 46 has the pressurizing valve 46A against the spring force of the first spring 46B with the negative pressure valve 46C closed. Are configured to open. When the pressurization valve 46A is thus opened, the circulation passage 41 and the reserve tank 47 communicate with each other, and the cooling water in the circulation passage 41 flows out to the reserve tank 47 as shown by the broken line arrow in FIG.

  Further, when the cooling water pressure on the inlet side of the circulation pump 45 becomes equal to or lower than a preset inflow pressure, the water amount adjusting valve 46 causes the negative pressure valve 46C to become the spring force of the second spring 46D while the pressurizing valve 46A is closed. It is configured to open against the valve. When the negative pressure valve 46C is thus opened, the circulation passage 41 and the reserve tank 47 communicate with each other, and the cooling water in the reserve tank 47 flows into the circulation passage 41 as shown by the broken line arrows in FIG.

  As described above, the water amount adjusting valve 46 allows the cooling water to flow out from the circulation passage 41 to the reserve tank 47 when the cooling water pressure on the inlet side of the circulation pump 45 becomes equal to or higher than a predetermined outflow pressure. When the cooling water pressure on the side becomes equal to or lower than a predetermined inflow pressure, the inflow of cooling water from the reserve tank 47 to the circulation passage 41 is allowed. Thus, in the stack cooling device 4, the amount and pressure of the cooling water in the circulation passage 41 are adjusted using the water amount adjustment valve 46 and the reserve tank 47.

  In the present embodiment, the outflow pressure of the water amount adjustment valve 46 is set to 140 kPa, which is higher than the standard atmospheric pressure, for example. The inflow pressure of the water amount adjusting valve 46 is set to 80 kPa, for example, higher than the allowable limit negative pressure and lower than the standard atmospheric pressure.

  Returning to FIG. 2, the controller 5 that comprehensively controls the fuel cell system 100 will be described.

  The controller 5 includes a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface).

  Detection signals from the anode pressure sensor 24, the air flow sensor 34, the cathode pressure sensor 36, the water temperature sensor 55, the first pressure sensor 56, and the second pressure sensor 57 are input to the controller 5. Further, the controller 5 includes a current sensor 51 for detecting the output current of the fuel cell stack 1 (load applied to the fuel cell stack 1), a voltage sensor 52 for detecting the output voltage of the fuel cell stack 1, and a large pressure for detecting atmospheric pressure. Various signals for detecting the operation state of the fuel cell system 100 such as the atmospheric pressure sensor 53 and the accelerator stroke sensor 54 for detecting the depression amount of the accelerator pedal are input.

  Based on the operating state of the fuel cell system 100, the controller 5 performs a pulsating operation that opens and closes the anode pressure regulating valve 23 and periodically raises and lowers the anode pressure. In the pulsation operation, the anode pressure is periodically raised and lowered within the range of the pulsation upper limit pressure and the pulsation lower limit pressure set according to the target output current of the fuel cell stack 1 to pulsate the anode pressure. By performing such pulsation operation, the liquid water inside the anode gas passage 121 can be discharged to the outside of the anode gas passage 121 when the anode pressure is increased, and the drainage performance and output performance of the fuel cell stack 1 can be discharged. Can be improved.

  Further, the controller 5 controls the rotational speed of the circulation pump 45 of the stack cooling device 4 according to the output current of the fuel cell stack 1. When the output current of the fuel cell stack 1 increases, the amount of heat generated in the fuel cell stack 1 increases. Therefore, the controller 5 increases the cooling water supplied to the fuel cell stack 1 as the output current of the fuel cell stack 1 increases. The rotational speed of the circulation pump 45 is increased so that the flow rate increases.

  Conventionally, in a fuel cell system, the cooling water in the circulation passage is cooled by flowing the cooling water from the circulation passage to the reserve tank or the cooling water from the reserve tank to the circulation passage through a water amount adjusting valve such as a radiator cap. Water pressure and volume are adjusted.

  However, even in a fuel cell system equipped with such a reserve tank, depending on the operating state of the fuel cell system, the cooling water pressure on the inlet side of the circulation pump may exceed the allowable limit when the rotation speed of the circulation pump is increased. May drop to pressure. The allowable limit negative pressure is a pressure lower than the inflow pressure of the water amount adjusting valve described above. When the cooling water pressure on the inlet side of the circulation pump falls to the allowable limit negative pressure, cavitation occurs in the circulation pump, or the circulation passage formed of an elastic material such as rubber or resin is deformed to obstruct the flow of the cooling water. Or

  The fuel cell system 100 according to the present embodiment is configured to execute a circulation pump control capable of suppressing the cooling water pressure on the inlet side of the circulation pump 45 of the stack cooling device 4 from being lowered to the allowable limit negative pressure. .

  FIG. 4 is a flowchart showing the circulation pump control executed by the controller 5 of the fuel cell system 100. The circulation pump control is repeatedly executed while the fuel cell system is activated. In the flowcharts of various controls described below, the order of each process can be changed or a specific process can be omitted as long as no contradiction occurs in the control.

  In S101, the controller 5 determines whether or not the pump inlet pressure Pi of the cooling water in the circulation passage 41 of the stack cooling device 4 is smaller than the first reference pressure P1. The controller 5 may be configured to execute the process of S101 when the circulation pump 45 is stopped or when the circulation pump 45 is operating at a low rotation speed close to zero.

The pump inlet pressure Pi is a pressure value calculated based on the detection value of the first pressure sensor 56. The first reference pressure P1 is preliminarily set to a value that can predict that the cooling water pressure on the inlet side of the circulation pump 45 may decrease to the allowable limit negative pressure when the rotation speed of the circulation pump 45 is increased. Is set. More specifically, the first reference pressure P1 is smaller than the outlet pressure P _H of the water amount adjusting valve 46 is set to a value greater than the inflow pressure P _L.

  The controller 5 compares the pump inlet pressure Pi with the first reference pressure P1 so that the cooling water pressure on the inlet side of the circulation pump 45 decreases to the allowable limit negative pressure while the circulation pump 45 is being driven. Whether or not, that is, whether or not the amount of cooling water in the circulation passage 41 is insufficient is predicted. In this way, S101 is a prediction step, and the controller 5 functions as a prediction unit that predicts whether or not the amount of cooling water in the circulation passage 41 will be insufficient while the circulation pump 45 is being driven.

  When the pump inlet pressure Pi is smaller than the first reference pressure P1, the controller 5 determines that the amount of cooling water in the circulation passage 41 is insufficient and the pump inlet pressure Pi may be reduced to the allowable limit negative pressure. And the cooling water forced inflow process of S105 is performed. The forced cooling water inflow process of S105 is a process for causing the cooling water stored in the reserve tank 47 to flow into the circulation passage 41. S105 is an execution step for executing the cooling water forced inflow process, and the controller 5 functions as an inflow process execution unit that causes the cooling water stored in the reserve tank 47 to flow into the circulation passage 41 when it is predicted that a water shortage state will occur. . The cooling water forced inflow process will be described later with reference to FIG.

  On the other hand, when the pump inlet pressure Pi is equal to or higher than the first reference pressure P1, the controller 5 has a sufficient amount of cooling water in the circulation passage 41 and the pump inlet pressure Pi decreases to the allowable limit negative pressure. It is determined that there is no fear, and the normal time circulation pump control of S102 to S104 is executed.

  In S <b> 102, the controller 5 detects the output current of the fuel cell stack 1 using the current sensor 51.

  In S103, the controller 5 calculates the target rotational speed of the circulation pump 45 based on the output current detected in S102.

  The target rotational speed of the circulation pump 45 is calculated by referring to a map in which the output current of the fuel cell stack 1 and the target rotational speed of the circulation pump 45 are associated as illustrated in FIG. As shown in FIG. 5, the target rotational speed of the circulation pump 45 increases as the output current of the fuel cell stack 1 increases. Thus, in the normal-time circulation pump control, when the output current of the fuel cell stack 1 increases and the amount of heat generated in the fuel cell stack 1 increases, the target rotational speed of the circulation pump 45 is increased to increase the fuel The flow rate of the cooling water supplied to the battery stack 1 is increased.

  After the process of S103 of FIG. 3, in S104, the controller 5 controls the circulation pump 45 so that the pump rotation speed becomes the target rotation speed determined in S103. Therefore, in the normal circulation pump control (S102 to S104), the circulation pump 45 is controlled according to the output current of the fuel cell stack 1, and the fuel cell stack 1 is cooled.

  Referring to FIG. 6, when it is predicted that the cooling water pressure on the inlet side of the circulation pump 45 may be reduced to the allowable limit negative pressure, that is, the amount of cooling water in the circulation passage 41 is predicted to be insufficient. The cooling water forced inflow process executed in this case will be described.

  When the cooling water forced inflow process is executed, the controller 5 sets the target rotational speed of the circulation pump to the forced inflow rotational speed in S201. The forced inflow rotation speed is a rotation speed set so that the cooling water pressure on the inlet side of the circulation pump 45 becomes the inflow pressure of the water amount adjustment valve 46.

  In S202, the controller 5 controls the circulation pump 45 so that the pump rotational speed becomes the target rotational speed determined in S201 (the rotational speed at forced inflow). Thus, the controller 5 functions as a pump control unit that controls the circulation pump 45 under various conditions.

  When the control of S202 is executed, the pump inlet pressure becomes the inflow pressure of the water amount adjusting valve 46, the negative pressure valve 46C (see FIG. 3B) of the water amount adjusting valve 46 is opened, and the cooling water in the reserve tank 47 is circulated. It flows into the passage 41. Thus, in the fuel cell system 100 of this embodiment, the pump inlet pressure is reduced to the inflow pressure of the water amount adjusting valve 46 using the circulation pump 45, and the cooling water is forcibly supplied into the circulation passage 41. The amount of cooling water in the circulation passage 41 can be increased.

  In S203, the controller 5 determines whether or not a predetermined time has elapsed since the start of the forced cooling water inflow process. The predetermined time is, for example, several seconds to several tens of seconds, and is determined according to the volume in the circulation passage 41 of the stack cooling device 4. S203 is an end process execution step for ending the cooling water forced inflow process, and the controller 5 functions as an end process execution unit for ending the cooling water forced inflow process.

  The controller 5 detects the time from the start of the forced cooling water inflow process using a timer, and repeatedly executes the processes after S201 when the detected time is smaller than the predetermined time. On the other hand, when the detected time is equal to or longer than the predetermined time, the controller 5 ends the cooling water forced inflow process. Thus, the cooling water forced inflow process is continued from the start of the process until a predetermined time elapses.

  As described above, in the fuel cell stack 1, the cooling water stored in the reserve tank 47 is forced to flow into the circulation passage 41 through the water amount adjustment valve 46 when it is predicted that the water shortage will occur in the circulation passage 41. Thereby, even when the rotational speed of the circulation pump 45 is rapidly increased thereafter, the cooling water pressure on the inlet side of the circulation pump 45 is reduced below the allowable limit negative pressure in the stack cooling device 4. Can be prevented.

  In S201 and S202, the controller 5 is configured to control the circulation pump 45 so that the pump rotational speed becomes the rotational speed at the forced inflow, but the pump inlet pressure is equal to the inflow pressure of the water amount adjusting valve 46. The circulation pump 45 may be feedback-controlled so as to be. In the forced cooling water inflow process, the circulation pump 45 may be controlled so that the pump inlet pressure is less than the inflow pressure of the water amount adjustment valve 46 within a range that does not fall below the allowable limit negative pressure.

  Next, the behavior of the cooling water pressure in the fuel cell system 100 according to the first embodiment and the behavior of the cooling water pressure in the fuel cell system according to the comparative example will be described with reference to FIGS.

  FIG. 7 is a time chart for explaining the behavior of the cooling water pressure in the fuel cell system 100 according to the present embodiment. FIG. 8 is a time chart for explaining the behavior of the cooling water pressure in the fuel cell system according to the comparative example. 7 and 8 exemplify a case of returning from the idle stop after the running idle stop is executed. Note that the fuel cell system according to the comparative example is a system configured to execute only the normal time circulation pump control without executing the forced cooling water inflow process.

  First, the behavior of the coolant pressure in the fuel cell system according to the comparative example will be described with reference to FIG.

In the stack cooling device of the fuel cell system according to the comparative example, the rotation speed of the circulation pump is adjusted according to the output current of the fuel cell stack, and the pump rotation speed increases as the output of the fuel cell stack increases until time t12. By cooling the fuel cell stack, the temperature of the cooling water rises, and the volume of cooling water (cooling water amount) in the circulation passage increases due to thermal expansion accompanying the temperature rise. Although until time t11 pump inlet pressure with an increase of the cooling water volume increases, the pump inlet pressure Pi reaches the outlet pressure P _H of the water amount adjustment valve, the water amount adjustment valve pressure valve is circulating passage open The cooling water flows out to the reserve tank, and the pressure and volume (water amount) of the cooling water are kept constant during the period of time t11 to t12.

  When the idling stop during running of the fuel cell system is executed at time t12, the output current of the fuel cell stack becomes zero, and accordingly, the pump rotation speed also becomes zero. Since the vehicle itself continues to travel during the idling stop during traveling, the cooling water in the radiator is cooled and the temperature of the cooling water in the circulation passage is lowered. As the cooling water temperature decreases, the cooling water volume in the circulation passage decreases, and the pump inlet pressure Pi also decreases as the cooling water volume decreases.

When the return processing from the idle stop is executed at time t13, the pump rotation speed increases with the output increase of the fuel cell stack. When the circulation pump is driven in a state where the pump inlet pressure and the cooling water volume in the circulation passage are reduced to some extent, the pump inlet pressure Pi decreases after the start of the return process. When the pump inlet pressure Pi decreases to the inflow pressure P _L of the water amount adjustment valve at time t14, the cooling water in the reserve tank starts to flow into the circulation passage. However, in such case the pump rotation speed increase rate is large, too late inflow of cooling water from the reserve tank, the pump inlet pressure Pi at time t15 decreases to acceptable limits negative pressure P _LM.

Thus, in the fuel cell system according to the comparative example, the cooling water pressure on the inlet side of the circulation pump may decrease to the allowable limit negative pressure _PLM depending on the system operation state. When the cooling water pressure on the inlet side of the circulation pump is reduced to the allowable limit negative pressure _PLM , cavitation occurs in the circulation pump, or the circulation passage formed of rubber or the like is deformed and the flow of the cooling water is obstructed. Therefore, the fail process is executed in the fuel cell system.

With reference to FIG. 7, the behavior of the cooling water pressure in the fuel cell system 100 according to the first embodiment will be described. The fuel cell system 100 differs from the fuel cell system of the comparative example in that the cooling water forced inflow process is executed to prevent the cooling water pressure on the inlet side of the circulation pump 45 from decreasing to the allowable limit negative pressure _PLM. ing.

In the stack cooling device 4 of the fuel cell system 100, the rotational speed of the circulation pump 45 is adjusted in accordance with the output current of the fuel cell stack 1 during normal times, and the pump rotational speed increases with the increase in the output of the fuel cell stack 1 until time t2. Increase. By cooling the fuel cell stack 1, the temperature of the cooling water rises, and the volume of the cooling water in the circulation passage 41 also increases due to thermal expansion accompanying the temperature rise. Although until time t1 pump inlet pressure Pi increases with increasing coolant volume, the pump inlet pressure Pi reaches the outlet pressure P _H of the water amount adjustment valve 46, pressure valve 46A of water adjustment valve 46 is opened The cooling water in the circulation passage 41 flows out to the reserve tank 47, and the pressure and volume (water amount) of the cooling water are kept constant during the period from time t1 to time t2.

  When the idling stop during running of the fuel cell system 100 is executed at time t2, the output current of the fuel cell stack 1 becomes zero, and accordingly, the pump rotation speed becomes zero. Since the vehicle itself continues to travel during the idling stop during traveling, the cooling water in the radiator 42 is cooled, and the temperature of the cooling water in the circulation passage 41 decreases. As the cooling water temperature decreases, the cooling water volume in the circulation passage 41 decreases, and the pump inlet pressure Pi decreases as the cooling water volume decreases.

When the pump inlet pressure Pi decreases to the first reference pressure P1, the controller 5 predicts that the amount of cooling water in the circulation passage 41 becomes insufficient, and the pump inlet pressure Pi is allowed depending on the driving state of the circulation pump 45 in the future. The cooling water forced inflow process is executed because it is determined that there is a risk of lowering to the limit negative pressure _PLM . Forced cooling water flowing processing at time t3 is started, the circulating pump 45 is controlled so that the pump inlet pressure Pi becomes inflow pressure P _L of water regulating valve 46. This control pump inlet pressure Pi is reduced to the inflow pressure P _L of water control valve 46, the coolant in the reserve tank 47 begins to flow into the circulation path 41 at time t4.

  At a time t5 when a predetermined time has elapsed from the start of the forced cooling water inflow process, the forced cooling water inflow process ends, and the circulation pump 45 stops. Since the cooling water in the reserve tank 47 is forcibly injected into the circulation passage 41, the pump inlet pressure Pi at the time t5 becomes higher than the pressure at the start of the cooling water forced inflow process (time t3).

In this way, when the return processing from the idle stop is executed with the coolant pressure on the pump inlet side and the coolant volume in the circulation passage 41 being high to some extent, the output of the fuel cell stack 1 increases at time t6. Accordingly, even if the pump speed increases, the pump inlet pressure Pi does not drop significantly. That is, in the stack cooling device 4 of the fuel cell system 100, the coolant pressure on the inlet side of the circulation pump 45 does not decrease to the allowable limit negative pressure _PLM .

  According to the fuel cell system 100 according to the first embodiment described above, the following effects can be obtained.

  The fuel cell system 100 includes a stack cooling device 4 that cools the fuel cell stack 1 and a controller 5 that controls a circulation pump 45 and the like of the stack cooling device 4. The controller 5 of the fuel cell system 100 is in a state where the amount of cooling water is insufficient in the circulation passage 41 during driving of the circulation pump 45 using the cooling water pressure (parameter regarding the amount of cooling water) on the pump inlet side in the circulation passage 41. If it is predicted that the water shortage state will occur, a cooling water forced inflow process is performed in which the cooling water stored in the reserve tank 47 flows into the circulation passage 41 through the water amount adjustment valve 46.

  Thus, by supplying the cooling water from the reserve tank 47 to the circulation passage 41 before the inside of the circulation passage 41 is in a water-deficient state, the cooling water pressure on the pump inlet side is allowed during the subsequent driving of the circulation pump 45. It can suppress that it falls to a limit negative pressure. Thereby, generation | occurrence | production of the cavitation in the circulation pump 45 and the deformation | transformation of the rubber-made circulation channel | path 41 can be suppressed, and execution of the fail control in the fuel cell system 100 can be avoided.

  Further, in the fuel cell system 100, the cooling water pressure on the pump inlet side is adopted as a parameter relating to the cooling water amount used for prediction of water shortage, and the cooling water pressure can be detected using an existing pressure sensor. Therefore, according to the fuel cell system 100, it is possible to predict the state of the cooling water amount in the circulation passage 41 with a simple configuration.

  Further, in the fuel cell system 100, the controller 5 controls the circulation pump 45 so that the cooling water pressure on the inlet side of the circulation pump 45 becomes equal to or lower than the inflow pressure of the water amount adjustment valve 46 during execution of the forced cooling water inflow process. . By controlling the circulation pump 45 in this manner, the negative pressure valve 46C of the water amount adjusting valve 46 can be opened, and the cooling water in the reserve tank 47 can be surely flowed into the circulation passage 41.

  Further, in the fuel cell system 100, the controller 5 ends the forced cooling water inflow process when a predetermined time has elapsed since the forced cooling water inflow process was started. Thereby, it is possible to avoid continuously executing the forced cooling water inflow process, and to realize efficient control of the fuel cell system 100.

  The controller 5 may execute the cooling water forced inflow process shown in FIG. 9 or 10 instead of executing the cooling water forced inflow process shown in FIG.

  In the cooling water forced inflow process shown in FIG. 9, the controller 5 (end process execution unit) executes the process of S203A instead of the process of S203 of FIG. The processes in S201 and S202 in FIG. 9 are the same as the processes in S201 and S202 in FIG.

  In S203A, the controller 5 determines whether or not the average cooling water pressure Pave in the circulation passage 41 is equal to or higher than the inflow processing stop pressure Ps. The inflow processing stop pressure Ps is set as a pressure higher than the inflow pressure of the water amount adjustment valve 46. The average cooling water pressure Pave is the cooling water pressure on the inlet side of the circulation pump 45 detected by the first pressure sensor 56 and the cooling water pressure on the outlet side of the circulation pump 45 detected by the second pressure sensor 57. It is calculated as an average value.

  During the forced cooling water inflow process, the cooling water is supplied from the reserve tank 47 to the circulation passage 41, and the flow rate of the cooling water in the circulation passage 41 increases. For this reason, even if the pump inlet pressure is kept constant, the pump outlet pressure increases, and the average cooling water pressure increases. Therefore, it is possible to determine whether or not a sufficient amount of cooling water has been supplied into the circulation passage 41 by monitoring the cooling water average pressure. When the average cooling water pressure Pave is equal to or higher than the inflow processing stop pressure Ps, the controller 5 determines that sufficient cooling water has flowed into the circulation passage 41 by the forced cooling water inflow processing, and ends the forced cooling water inflow processing. To do. On the other hand, the controller 5 continues the forced cooling water inflow process when the average cooling water pressure Pave is smaller than the inflow process stop pressure Ps.

  As described above, the controller 5 performs the process of S203A in FIG. 9, so that it is possible to avoid continuously executing the forced cooling water inflow process, and to realize efficient control of the fuel cell system 100. .

  Next, the case where the controller 5 executes the forced cooling water inflow process shown in FIG. In this case, the controller 5 (end process execution unit) executes the process of S203B instead of the process of S203 of FIG. The processes in S201 and S202 in FIG. 10 are the same as the processes in S201 and S202 in FIG.

  In S203B, the controller 5 determines whether or not the inflow amount V of the cooling water flowing into the circulation passage 41 from the reserve tank 47 during the forced cooling water inflow process is equal to or larger than the reference inflow amount V0. The reference inflow amount V0 is a threshold value for determining whether or not the amount of cooling water in the circulation passage 41 is sufficient, and has been previously tested in consideration of the volume of the circulation passage 41, the first reference pressure, and the like. It is a value set by

  Here, the cooling water inflow amount V is calculated by integrating the deviation between the atmospheric pressure Pamb and the pump inlet pressure Pi during the cooling water forced inflow processing by the following equation (1). The atmospheric pressure Pamb is detected by the atmospheric pressure sensor 53, and the pump inlet pressure Pi during the cooling water forced inflow process is detected by the first pressure sensor 56.

  When the cooling water inflow amount V is equal to or greater than the reference inflow amount V0, the controller 5 determines that sufficient cooling water has flowed into the circulation passage 41 by the cooling water forced inflow processing, and ends the cooling water forced inflow processing. On the other hand, the controller 5 continues the cooling water forced inflow process when the cooling water inflow amount V is smaller than the reference inflow amount V0.

  As described above, the controller 5 performs the process of S203B in FIG. 10, so that it is possible to avoid continuously performing the forced cooling water inflow process, and to realize efficient control of the fuel cell system 100. .

(Second Embodiment)
A fuel cell system 100 according to a second embodiment of the present invention will be described with reference to FIG. Note that in the following embodiments, the same reference numerals are used for configurations and the like that perform the same functions as those in the first embodiment, and repeated descriptions are omitted as appropriate.

  FIG. 11 is a flowchart showing a cooling water forced inflow process executed by the controller 5 of the fuel cell system 100 according to the second embodiment.

  When the forced cooling water inflow process is executed, in S301, the controller 5 determines whether or not it is necessary to increase the rotation speed of the circulation pump 45 in response to a request to increase the load (output current) to the fuel cell stack 1. To do. This determination is performed by comparing the rotational speed at forced inflow with the target rotational speed of the circulation pump 45 determined based on the required load on the fuel cell stack 1. The controller 5 determines that the rotational speed of the circulation pump 45 needs to be increased when the target rotational speed determined based on the required load on the fuel cell stack 1 is larger than the rotational speed at the time of forced inflow.

  When it is determined in S301 that it is not necessary to increase the pump rotation speed, the controller 5 executes the processing after S201. On the other hand, if it is determined in S301 that the pump rotational speed needs to be increased, the controller 5 executes the process of S302.

  In S <b> 302, the controller 5 controls the circulation pump 45 so that the pump rotational speed becomes a target rotational speed determined based on the required load on the fuel cell stack 1 in a state where the rate of increase of the pump rotational speed is limited. Then, the controller 5 executes the process of S203 after the process of S302. The rate of increase of the pump speed in the process of S302 is set lower than the rate of increase of the pump speed determined by the normal time pump control such as S103.

  During the forced cooling water inflow process, the pump inlet pressure is controlled to be equal to or lower than the inflow pressure of the water amount adjusting valve 46. Therefore, if the rotational speed of the circulation pump 45 suddenly increases with the output of the fuel cell stack 1 during this process, the pump inlet pressure may decrease to the allowable limit negative pressure. However, in the fuel cell system 100, even if the output of the fuel cell stack 1 increases rapidly during the forced cooling water inflow process, the circulation pump 45 is in a state where the rate of increase in the pump rotation speed is limited. Since it is controlled, it is possible to avoid a rapid increase in the pump speed. As a result, it is possible to suppress a decrease in the pump inlet pressure that accompanies a rapid increase in the pump speed.

  With reference to FIG. 12, the behavior of the cooling water pressure in the fuel cell system 100 according to the second embodiment will be described.

  Until time t21, the fuel cell stack 1 and the circulation pump 45 are operating in a low output state, and the cooling water of the stack cooling device 4 is cooled by outside air or the like. When the cooling water is cooled and the cooling water temperature decreases, the volume of the cooling water contracts, and the cooling water pressures Pi and Po on the inlet side and the outlet side of the circulation pump 45 decrease.

When the pump inlet pressure Pi decreases to the first reference pressure P1 at time t21, the controller 5 predicts that the water will be insufficient due to a decrease in the cooling water volume or the like, and executes the cooling water forced inflow process. When the circulation pump control based on the forced cooling water flowing processing is performed, the pump inlet pressure Pi at time t22 decreases to flow into the pressure P _L of water regulating valve 46. As a result, the cooling water flows from the reserve tank 47 into the circulation passage 41 through the water amount adjustment valve 46, and the amount of cooling water in the circulation passage 41 increases and the pump outlet pressure Po increases.

When the required load on the fuel cell stack 1 increases at time t23 and the output of the fuel cell stack 1 increases, the rotational speed of the circulation pump 45 increases according to the output of the fuel cell stack 1. When it is necessary for the controller 5 to increase the pump rotation speed due to a load increase request to the fuel cell stack 1 during the forced cooling water inflow process, the controller 5 increases the rate of increase in the pump rotation speed at the normal time (broken line) as shown by the solid line. The circulation pump 45 is controlled in a more restricted state. Therefore, to prevent the the rotational speed of the circulation pump 45 in the forced cooling water inflow process rapidly increases without the pump inlet pressure Pi at time t23 or later is reduced to acceptable limits negative pressure P _LM as shown by a broken line it can.

  According to the fuel cell system 100 according to the second embodiment described above, the following effects can be obtained.

When the controller 5 of the fuel cell system 100 increases the number of rotations of the circulation pump 45 due to a load increase request to the fuel cell stack during the forced cooling water inflow process, the controller 5 controls the circulation pump 45 based on the output of the fuel cell stack during normal time. The increase rate of the rotational speed of the circulation pump 45 is limited as compared with the above. As a result, the rotational speed of the circulation pump 45 does not rapidly increase during the forced cooling water inflow process, and the pump inlet pressure Pi is allowed even when the pump rotational speed is increased due to a load increase request to the fuel cell stack. It is possible to prevent the pressure from decreasing to the limit negative pressure _PLM .

(Third embodiment)
A fuel cell system 100 according to a third embodiment of the present invention will be described with reference to FIG. FIG. 13 is a flowchart showing a forced cooling water inflow process executed by the controller 5 of the fuel cell system 100 according to the third embodiment.

  When the cooling water forced inflow process is executed, in S301, the controller 5 determines whether or not it is necessary to increase the rotational speed of the circulation pump 45 due to a load (output current) increase request to the fuel cell stack 1. .

  If it is determined in S301 that it is not necessary to increase the rotational speed of the circulation pump 45, the controller 5 executes the processing from S201 onward. On the other hand, when it is determined in S301 that the rotation speed of the circulation pump 45 needs to be increased, the controller 5 executes the process of S302.

  In S <b> 302, the controller 5 controls the circulation pump 45 so that the pump rotational speed becomes a target rotational speed determined based on the required load on the fuel cell stack 1 in a state where the rate of increase of the pump rotational speed is limited. Thus, the controller 5 functions as a rotation speed limiter that limits the rate of increase of the pump rotation speed.

  In S303, the controller 5 determines whether or not the pump inlet pressure Pi detected by the first pressure sensor 56 is smaller than a preset second reference pressure P2. The second reference pressure P2 is set lower than the inflow pressure of the water amount adjustment valve 46 and higher than the allowable limit negative pressure.

  When the pump inlet pressure Pi is smaller than the second reference pressure P2, the controller 5 determines that there is a possibility that the pump inlet pressure Pi may decrease to the allowable limit negative pressure if the circulation pump 45 is continuously driven, and the process of S304 Execute. On the other hand, when the pump inlet pressure Pi is equal to or higher than the second reference pressure P2, the controller 5 does not have a possibility that the pump inlet pressure Pi decreases to the allowable limit negative pressure even if the driving of the circulation pump 45 is continued. And the process of S305 is executed.

  In S304, the controller 5 executes an anode pressure increasing process for increasing the pressure of the anode gas supplied to the fuel cell stack 1. As described above, the controller 5 functions as a gas pressure adjusting unit that adjusts the pressure of the anode gas and the cathode gas under various conditions. The controller 5 executes the process of S305 after executing the process of S304.

  When the anode pressure increasing process is executed, the anode pressure in the anode gas flow path 121 increases in the fuel cell stack 1 (see FIG. 1), and the anode separator 12 is deformed so as to be pushed toward the cathode separator. As a result, the volume of the cooling water passage 14 in the fuel cell stack 1 becomes smaller than that before the anode pressure increasing process, and the volume of the entire cooling system including the cooling water passage 14 and the circulation passage 41 is reduced. When the volume of the entire cooling system is thus reduced, the coolant pressure on the pump inlet side is increased as compared with the case where the volume of the entire cooling system is large even if the rotation speed of the circulation pump 45 is the same. Accordingly, when the pump inlet pressure Pi becomes smaller than the second reference pressure P2, the anode pressure increasing process is executed to reduce the volume of the entire cooling system, whereby the pump inlet pressure Pi is reduced to the allowable limit negative pressure. Can be prevented.

  In S <b> 305, the controller 5 determines whether or not it is necessary to reduce the rotational speed of the circulation pump 45 in response to a load (output current) reduction request for the fuel cell stack 1. This determination is made by comparing the current pump speed with the target speed of the circulation pump 45 determined based on the required load on the fuel cell stack 1. The controller 5 determines that the rotational speed of the circulation pump 45 needs to be reduced when the target rotational speed determined based on the required load on the fuel cell stack 1 is smaller than the current pump rotational speed.

  If it is determined in S305 that the pump rotation speed needs to be reduced, the controller 5 executes the processing from S306 onward. On the other hand, when it is determined in S305 that it is not necessary to reduce the rotational speed of the circulation pump 45, the controller 5 executes the process of S309.

  In S <b> 306, the controller 5 executes a process for reducing the pump speed of the circulation pump 45.

  In S307, the controller 5 determines whether or not an anode pressure increasing process is being executed. Whether or not the anode pressure increasing process is being performed can be determined, for example, by detecting the presence or absence of a flag related to the anode pressure increasing process.

  When the anode pressure increasing process is being executed, the controller 5 executes the process of S308 and then executes the process of S309. On the other hand, when the anode pressure increasing process is not executed, the controller 5 executes the process of S309 without executing the process of S308.

  In S308, the controller 5 executes a process for reducing the increased anode pressure. The controller 5 reduces the anode pressure, which has been increased by the anode pressure increasing process in S304, to a pressure corresponding to the output current of the fuel cell stack 1.

  As shown in S303 and S304, the anode pressure increasing process is executed when the pump inlet pressure Pi is close to the allowable limit negative pressure. Therefore, if the anode pressure is reduced before the pump rotational speed is reduced, the pump inlet pressure Pi may be reduced to the allowable negative pressure due to the increase in the volume of the cooling system accompanying the decrease in the anode pressure. . Therefore, when reducing the output of the fuel cell stack 1 during the execution of the anode pressure increasing process, the controller 5 first decreases the rotational speed of the circulation pump 45 and then decreases the anode pressure. As described above, by executing the pump rotation speed reduction process prior to the anode pressure reduction process, it is possible to prevent a significant decrease in the pump inlet pressure Pi.

  If it is determined in S305 that it is not necessary to decrease the pump rotation speed, if it is determined in S307 that the anode pressure increasing process is not executed, and if the process in S308 is executed, the controller 5 performs the process in S309. Execute. In S309, the controller 5 determines whether or not a predetermined time has elapsed since the forced cooling water inflow process was started.

  The controller 5 detects the time from the start of the forced cooling water inflow process using a timer, and repeatedly executes the processes after S303 when the detected time is smaller than the predetermined time. On the other hand, when the detected time is equal to or longer than the predetermined time, the controller 5 ends the cooling water forced inflow process.

  With reference to FIG. 14, the behavior of the cooling water pressure in the fuel cell system 100 according to the third embodiment will be described.

  Until time t31, the fuel cell stack 1 and the circulation pump 45 are operating in a low output state, and the cooling water of the stack cooling device 4 is cooled by outside air or the like. When the cooling water is cooled and the cooling water temperature decreases, the volume of the cooling water contracts, and the cooling water pressures Pi and Po on the inlet side and the outlet side of the circulation pump 45 decrease.

When the pump inlet pressure Pi decreases to the first reference pressure P1 at time t31, the controller 5 predicts that the water will be insufficient due to a decrease in the cooling water volume or the like, and executes the cooling water forced inflow process. Thereby, a circulation pump control based on the forced cooling water flowing processing is performed, the pump inlet pressure Pi is reduced to the inlet pressure P _L of water regulating valve 46. As a result, the cooling water flows from the reserve tank 47 into the circulation passage 41 through the water amount adjustment valve 46, and the amount of cooling water in the circulation passage 41 increases and the pump outlet pressure Po increases.

  When the required load on the fuel cell stack 1 increases at time t32 and the output of the fuel cell stack 1 increases, the rotational speed of the circulation pump 45 increases according to the output of the fuel cell stack 1. The controller 5 circulates in a state in which the rate of increase of the pump speed is limited from the normal time when it is necessary to increase the pump speed due to a request to increase the load on the fuel cell stack 1 during the forced cooling water inflow process. The pump 45 is controlled.

When the pump inlet pressure Pi decreases to the second reference pressure P2 set between the inflow pressure P _L of the water amount adjustment valve 46 and the allowable limit negative pressure P _{LM as} the rotational speed of the circulation pump 45 increases, the time t33 The controller 5 executes an anode pressure increasing process (S304 in FIG. 13) for increasing the anode pressure Pan supplied to the fuel cell stack 1. Since the volume of the entire cooling system including the cooling water passage 14 and the circulation passage 41 is reduced by the anode pressure increasing process, a decrease in the pump inlet pressure Pi is suppressed. As a result, even when continued rotation speed increase of the circulation pump 45, it is possible to prevent the pump inlet pressure Pi is reduced to acceptable limits negative pressure P _LM.

  When the required load on the fuel cell stack 1 decreases at time t34 and the output of the fuel cell stack 1 decreases, the controller 5 first decreases the rotational speed of the circulation pump 45 (S306 in FIG. 13), and thereafter time t35. In step S308, the anode pressure Pan is decreased (S308 in FIG. 13).

If the anode pressure Pan is reduced before the rotational speed of the circulation pump 45 is reduced when the output of the fuel cell stack 1 is decreased, the pump inlet pressure Pi is increased by a broken line due to the increase in the volume of the cooling system accompanying the decrease in the anode pressure. Thus, there is a possibility that the allowable negative pressure _PLM may be reduced. However, by reducing the rotational speed of the circulation pump 45 at time t34 and reducing the anode pressure Pan at time t35, the anode pressure Pan is lowered when the pump inlet pressure Pi rises to some extent, and the pump inlet pressure Pi Can be prevented from decreasing to the allowable limit negative pressure _PLM .

  The controller 5 is configured to reduce the anode pressure Pan when the anode pressure reduction condition is satisfied after the pump speed reduction process. For example, the controller 5 determines that the anode pressure reduction condition is satisfied when a predetermined time has elapsed since the start of the pump rotation speed reduction process. The controller 5 may be configured to determine that the anode pressure reduction condition is satisfied when the pump inlet pressure Pi rises to a predetermined pressure value after the pump rotation speed reduction process.

  According to the fuel cell system 100 according to the above-described third embodiment, the following effects can be obtained.

When the controller 5 of the fuel cell system 100 increases the rotational speed of the circulation pump 45 due to a load increase request to the fuel cell stack 1 during the forced cooling water inflow process, the pump inlet pressure Pi decreases to the second reference pressure P2. Then, an anode pressure increasing process for increasing the anode pressure Pan supplied to the fuel cell stack 1 is executed. Thereby, since the volume of the whole cooling system including the cooling water flow path 14 and the circulation path 41 is reduced, a decrease in the pump inlet pressure Pi is suppressed. As a result, even when continued rotation speed increase of the circulation pump 45, it is possible to prevent the pump inlet pressure Pi is reduced to acceptable limits negative pressure P _LM.

Further, when the controller 5 of the fuel cell system 100 decreases the rotation speed of the circulation pump 45 due to a load reduction request to the fuel cell stack during the forced cooling water inflow process, Reduce the pressure Pan. By reducing the pump rotational speed in this way, the pump inlet pressure Pi can be increased to some extent before the anode pressure Pan is decreased, and this is caused by a decrease in the anode pressure Pan (an increase in the cooling system volume). Thus, it is possible to prevent the pump inlet pressure Pi from being lowered to the allowable limit negative pressure _PLM .

  The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

  In the fuel cell system 100 of the first embodiment, the controller 5 is configured to execute the cooling water forced inflow process when the pump inlet pressure Pi is lower than the first reference pressure P1. The controller 5 calculates a decrease amount of the pump inlet pressure Pi in a predetermined period, and predicts a water shortage state in the circulation passage 41 based on whether or not the decrease amount of the pump inlet pressure Pi in the predetermined period is equal to or more than a reference decrease amount. It may be configured to. And the controller 5 performs a cooling water forced inflow process, when the fall amount of the pump inlet side pressure Pi in a predetermined period is more than a reference | standard fall amount.

  In the flowchart of FIG. 11 in the second embodiment and the flowchart of FIG. 13 in the third embodiment, the processing in S203 and S309 may be the same as the processing in S203A in FIG. 9 and S203B in FIG.

  As shown in S305 of FIG. 13, the controller 5 of the fuel cell system 100 according to the third embodiment is configured to increase the anode pressure and reduce the volume of the cooling system. The controller 5 may be configured to reduce the volume of the cooling system by increasing only the cathode pressure or by increasing both the anode pressure and the cathode pressure. When the output of the fuel cell stack 1 is reduced during the forced cooling water inflow process, the controller 5 reduces the pressures of the anode gas and the cathode gas after reducing the pump speed.

DESCRIPTION OF SYMBOLS 100 Fuel cell system 1 Fuel cell stack 2 Anode gas supply / exhaust device 3 Cathode gas supply / exhaust device 4 Stack cooling device 5 Controller 41 Circulation passage 42 Radiator 43 Bypass passage 44 Thermostat 45 Circulation pump 46 Water quantity adjustment valve 47 Reserve tank 51 Current sensor 56 First pressure sensor 57 Second pressure sensor

Claims (14)

A fuel cell that generates power by receiving a supply of a reactive gas; and
A circulation path connected to the fuel cell;
A circulation pump for circulating cooling water in the circulation passage;
A control method of a fuel cell system comprising a reserve tank connected to the circulation passage via a valve member,
A prediction step of predicting whether or not the amount of cooling water is insufficient in the circulation passage during driving of the circulation pump using the pressure of the cooling water in the circulation passage;
An execution step of executing an inflow process for causing cooling water stored in the reserve tank to flow into the circulation passage through the valve member when it is predicted that a water shortage state occurs;
A control method for a fuel cell system comprising: A control method for a fuel cell system according to claim 1,
The valve member is configured to allow inflow of cooling water from the reserve tank to the circulation passage when the cooling water pressure on the inlet side of the circulation pump becomes equal to or lower than the inflow pressure.
In the predicting step, when the cooling water pressure on the inlet side of the circulation pump is reduced to the first reference pressure set higher than the inflow pressure, it is predicted that the water shortage state occurs.
A control method for a fuel cell system. A control method for a fuel cell system according to claim 1,
The valve member is configured to allow inflow of cooling water from the reserve tank to the circulation passage when the cooling water pressure on the inlet side of the circulation pump becomes equal to or lower than the inflow pressure.
In the predicting step, when the amount of decrease in the cooling water pressure on the inlet side of the circulation pump in a predetermined period is equal to or greater than the reference decrease amount, it is predicted that the water shortage state occurs
A control method for a fuel cell system. A control method for a fuel cell system according to claim 2 or 3,
In the execution step, when it is predicted that a water shortage state occurs, the circulation pump is controlled so that the cooling water pressure on the inlet side of the circulation pump is equal to or lower than the inflow pressure, and the cooling water in the reserve tank is supplied to the valve member. Through the circulation passage through,
A control method for a fuel cell system. A control method for a fuel cell system according to any one of claims 2 to 4,
In the execution step, when increasing the rotation speed of the circulation pump due to a load increase request to the fuel cell during the inflow process, the rate of increase in the rotation speed of the circulation pump is limited.
A control method for a fuel cell system. A control method for a fuel cell system according to any one of claims 2 to 5,
In the execution step, when the rotation speed of the circulation pump is increased due to a load increase request to the fuel cell during the inflow process, the cooling water pressure on the inlet side of the circulation pump is set lower than the inflow pressure. To determine whether the pressure has decreased to the second reference pressure,
When the cooling water pressure on the inlet side of the circulation pump is reduced to the second reference pressure, the pressure of the reaction gas supplied to the fuel cell is increased.
A control method for a fuel cell system. A control method for a fuel cell system according to claim 6,
In the execution step, when the rotation speed of the circulation pump is decreased due to a load reduction request to the fuel cell during the inflow process, the pressure of the reaction gas is decreased after the rotation speed of the circulation pump is decreased. ,
A control method for a fuel cell system. A control method for a fuel cell system according to any one of claims 1 to 7,
In the execution step, when the predetermined time has elapsed after the execution of the inflow process, the inflow process is terminated.
A control method for a fuel cell system. A control method for a fuel cell system according to any one of claims 1 to 7,
In the execution step, after the execution of the inflow process, the inflow process is performed when an average value of the cooling water pressure on the inlet side and the outlet side of the circulation pump becomes equal to or higher than a set stop pressure higher than the inflow pressure. finish,
A control method for a fuel cell system. A control method for a fuel cell system according to any one of claims 1 to 7,
In the execution step, the cooling water inflow amount from the reserve tank to the circulation passage calculated based on a differential pressure between the atmospheric pressure and the cooling water pressure on the inlet side of the circulation pump after execution of the inflow processing is a reference. When the inflow amount is exceeded, the inflow process is terminated.
A control method for a fuel cell system. A fuel cell that generates power by receiving a supply of a reactive gas; and
A circulation path connected to the fuel cell;
A circulation pump for circulating cooling water in the circulation passage;
A radiator provided in the circulation passage and dissipating heat of the cooling water;
A reserve tank connected to the circulation passage via a valve member;
A prediction unit that predicts whether or not the amount of cooling water is insufficient in the circulation passage during driving of the circulation pump using the pressure of the cooling water in the circulation passage;
An inflow processing execution unit that causes cooling water stored in the reserve tank to flow into the circulation passage through the valve member when it is predicted that the water shortage state is caused by the prediction unit;
A fuel cell system comprising: The fuel cell system according to claim 11, wherein
A pressure detection unit for detecting the cooling water pressure on the inlet side of the circulation pump;
The valve member is configured to allow inflow of cooling water from the reserve tank to the circulation passage when the cooling water pressure on the inlet side of the circulation pump becomes equal to or lower than the inflow pressure.
The predicting unit predicts that a water shortage state occurs when the detected cooling water pressure on the inlet side of the circulation pump decreases to a first reference pressure set higher than the inflow pressure.
A fuel cell system. The fuel cell system according to claim 12, wherein
When the inflow processing execution unit is predicted to be in a water shortage state, the inflow processing execution unit controls the circulation pump so that the cooling water pressure on the inlet side of the circulation pump is equal to or lower than the inflow pressure, and the cooling water in the reserve tank is Flowing into the circulation passage through a valve member;
A fuel cell system. The fuel cell system according to any one of claims 11 to 13,
An end process execution unit for ending the inflow process when a predetermined time elapses after the inflow process is executed by the inflow process execution unit;
A fuel cell system.

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