JP6326196B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system.

  In the conventional fuel cell system, the other end of the atmospheric pressure setting pipe having one end connected to the reservoir tank is connected between the thermostat and the suction port of the circulation pump. And the cap was provided in atmospheric pressure setting piping (refer patent document 1).

JP 2009-259467 A

  In the fuel cell system, since the cooling water flows in a portion close to the live part inside the fuel cell, it is necessary to make it easy to ensure insulation resistance even when the conductivity of the cooling water is relatively high. For this reason, it is desirable to connect the fuel cell and the cooling system parts with piping of an insulating material. Further, from the viewpoint of absorbing dimensional tolerances during assembly, the piping of this part is preferably an elastic body, and can be used only for a rubber hose which is an elastic body and is an insulator.

  At the start of the fuel cell system, it is desired to increase the temperature of the cooling water early by increasing the heat generated by the heater and to promote the warm-up of the fuel cell.

  However, when the amount of heat given to the cooling water by the heater is increased, there is a possibility of local boiling unless the circulating flow rate of the cooling water is increased. Therefore, when the system is warmed up, it is necessary to circulate cooling water having a flow rate large enough not to cause local boiling.

  By the way, the inventors have found that the following inconvenience may occur if the rotation speed of the circulation pump is increased at a stroke in order to make the flow rate considering local boiling from the state where the circulation pump is stopped. It was done.

  After warming up, circulation of the cooling water by the circulation pump is started, and even if the cooling water on the suction port side of the circulation pump is insufficient due to the circulation, the cooling water is insufficient due to the supply of the cooling water from the reservoir tank There is nothing. However, if starting from a low temperature, the viscosity of the cooling water may be high, the supply of cooling water from the reservoir tank is not in time, the cooling water circulation passage on the suction port side of the circulation pump becomes negative pressure, The durability of the cooling water circulation passage may be reduced. In particular, when the cooling water circulation passage on the suction port side of the circulation pump is formed of an elastic material such as a rubber hose, the amount of contraction and deformation of the cooling water circulation passage becomes large, and the durability may be greatly reduced.

  This invention is made paying attention to such a problem, and it aims at suppressing the durable fall of a cooling water circulation channel | path.

The present invention is a fuel cell system that supplies anode gas and cathode gas to a fuel cell to generate electric power, and is provided in a refrigerant circulation passage through which a refrigerant that cools the fuel cell circulates, and in the refrigerant circulation passage. A circulation pump for circulation, a reservoir tank that stores the refrigerant therein and maintained at atmospheric pressure, and the refrigerant circulation passage on the suction side of the circulation pump are provided, and the pressure in the refrigerant circulation passage is predetermined. An open / close valve that opens when the pressure becomes lower than the negative pressure, supplies the refrigerant in the reservoir tank into the refrigerant circulation passage, a communication passage that connects the reservoir tank and the open / close valve, and drives the circulation pump to when starting the circulation of the refrigerant, a circulation pump control means for gradually increasing the rotational speed of the circulating pump, the refrigerant circulating in the upstream side of the circulating pump A radiator that is provided in the passage and reduces the temperature of the refrigerant passing therethrough; the refrigerant circulation passage upstream of the radiator so as to bypass the radiator; and the refrigerant upstream of the circulation pump A flow path for adjusting a flow rate of the refrigerant flowing through the bypass passage, provided at a connection portion between the bypass passage connected to the circulation passage, the refrigerant circulation passage upstream of the circulation pump, and the bypass passage. The refrigerant circulation passage is connected to the adjustment valve and the reservoir tank, and is provided in the refrigerant circulation passage between the radiator and the flow rate adjustment valve, and opens and closes according to the pressure in the refrigerant circulation passage. A pressure regulating valve that regulates the internal pressure within a predetermined range, wherein the on-off valve is provided in the refrigerant circulation passage between the flow rate regulating valve and the circulation pump .

  According to the present invention, when the circulation pump is driven to start the circulation of the refrigerant, the rotation speed of the circulation pump is gradually increased, so that the negative pressure of the cooling water circulation passage can be suppressed from being excessive. . Therefore, it is possible to suppress a decrease in durability of the cooling water circulation passage.

1 is a schematic configuration diagram of a fuel cell system according to an embodiment of the present invention. It is a flowchart explaining the rotational speed control of the circulation pump by one Embodiment of this invention. It is a table which calculates the target rotational speed of a circulation pump based on outside temperature and a count timer. It is a time chart explaining the operation | movement of the rotational speed control of the circulation pump by one Embodiment of this invention.

  Hereinafter, an embodiment 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.

  In a fuel cell, an electrolyte membrane is sandwiched between an anode electrode (fuel electrode) and a cathode electrode (oxidant electrode), an anode gas containing hydrogen in the anode electrode (fuel gas), and a cathode gas containing oxygen in the cathode electrode (oxidant) Electricity is generated by supplying gas. The electrode reaction that proceeds in both the anode electrode and the cathode electrode is as follows.

Anode electrode: 2H ₂ → 4H ⁺ + 4e ⁻ (1)
Cathode electrode: 4H ⁺ + 4e ⁻ + O ₂ → 2H ₂ O (2)

  The fuel cell generates an electromotive force of about 1 volt by the electrode reactions (1) and (2).

  When such a fuel cell is used as a power source for automobiles, a large amount of electric power is required, so that it is used as a fuel cell stack in which several hundred fuel cells are stacked. Then, a fuel cell system that supplies anode gas and cathode gas to the fuel cell stack is configured, and electric power for driving the vehicle is taken out.

  FIG. 1 is a schematic configuration diagram of a fuel cell system 1 according to an embodiment of the present invention.

  The fuel cell system 1 includes a fuel cell stack 2, a cooling device 3 that cools the fuel cell stack 2, and a controller 4.

  The fuel cell stack 2 generates power by receiving supply of anode gas and cathode gas. The gas supply device that supplies each of the anode gas and the cathode gas to the fuel cell stack 2 is not the main part of the present invention, and thus is not shown for easy understanding of the invention.

  The cooling device 3 includes a cooling water circulation passage 31, a radiator 32, a bypass passage 33, a heater 34, a thermostat 35, a circulation pump 36, a reservoir tank 37, a first cap 38, a second cap 39, A temperature sensor 40, a first pressure sensor 41, and a second pressure sensor 42 are provided.

  The cooling water circulation passage 31 is a passage through which cooling water for cooling the fuel cell stack 2 flows. The cooling water circulation passage 31 is connected to the cooling water inlet hole 21 and the cooling water outlet hole 22 of the fuel cell stack 2. The cooling water circulation passage 31 is formed with a rubber hose at the connection with the fuel cell stack 2 in order to ensure insulation between the fuel cell interior and the cooling system components. In addition, rubber hoses are frequently used in other parts in order to easily absorb the dimensional tolerance when assembling the parts. Hereinafter, for convenience, the cooling water outlet hole 22 side of the fuel cell stack 2 is treated as upstream of the cooling water circulation passage 31, and the cooling water inlet hole 21 side of the fuel cell stack 2 is treated as downstream of the cooling water circulation passage 31.

  The radiator 32 is provided in the cooling water circulation passage 31. The radiator 32 lowers the temperature of the cooling water that passes therethrough.

  The bypass passage 33 has one end connected to the coolant circulation passage 31 and the other end connected to the thermostat 35 so that the coolant can be circulated by bypassing the radiator 32. Similarly to the cooling water circulation passage 31, the bypass passage 33 has a portion formed by a rubber hose.

  The heater 34 is provided in the bypass passage 33. The heater 34 is energized when the fuel cell stack 2 is warmed up to raise the temperature of the cooling water. In this embodiment, a PTC heater is used as the heater 34, but the present invention is not limited to this.

  The thermostat 35 is provided in the cooling water circulation passage 31 on the downstream side of the radiator 32. The thermostat 35 is an on-off valve that automatically opens and closes according to the temperature of the cooling water flowing inside. The thermostat 35 is in a closed state when the temperature of the cooling water flowing through it is lower than a predetermined thermo-opening temperature, and only the relatively high-temperature cooling water that has passed through the bypass passage 33 is supplied to the fuel cell stack. 1 is supplied. On the other hand, when the temperature of the cooling water flowing in the interior becomes equal to or higher than the thermo-opening temperature, it gradually opens, and the cooling water passing through the bypass passage 33 and the relatively low temperature cooling water passing through the radiator 32 are mixed inside. And supply it to the fuel cell stack. In the present embodiment, the wax material and the spring constituting the thermostat 35 are adjusted so that the thermo valve opening temperature is about 60 [° C.].

  The circulation pump 36 is an electric pump, and is provided in the cooling water circulation passage 31 on the downstream side of the thermostat 35. The circulation pump 36 circulates the cooling water in the cooling water circulation passage 31. The discharge flow rate of the circulation pump 36 continuously changes in accordance with the rotation speed of the circulation pump controlled by the controller 4.

  The reservoir tank 37 is a tank that stores cooling water. The reservoir tank 37 is provided with an air release port 371 communicating with the outside air, whereby the pressure in the reservoir tank 37 is maintained at atmospheric pressure.

  The first cap 38 is provided in the cooling water circulation passage 31 between the radiator 32 and the thermostat 35 and is connected to the reservoir tank 37 by the first sub-passage 381. Inside the first cap 38, a pressurizing valve and a negative pressure valve are provided. Each of the pressurization valve and the negative pressure valve is a pressure-sensitive on-off valve that opens and closes according to the pressure in the cooling water circulation passage 31. A so-called radiator cap can be used as the first cap 38.

  When the pressure in the cooling water circulation passage 31 between the radiator 32 and the thermostat 35 is a positive pressure equal to or lower than a predetermined first specified pressure, the pressurization valve and the negative pressure valve are closed. In this state, the cooling water circulation passage 31 is kept airtight by the first cap 38, and the pressure in the cooling water circulation passage 31 is increased by the thermal expansion of the cooling water. Thereby, the boiling point of the cooling water is increased from that under atmospheric pressure, and the cooling efficiency of the radiator 32 is increased.

  When the temperature of the cooling water rises and the pressure in the cooling water circulation passage 31 between the radiator 32 and the thermostat 35 becomes higher than the first specified pressure, the pressurizing valve is opened. In this state, a part of the expanded cooling water in the cooling water circulation passage 31 is returned to the reservoir tank 37 via the first sub-passage 381. Thereby, the pressure in the cooling water circulation passage 31 is adjusted to the first specified pressure.

On the other hand, when the temperature of the cooling water decreases, the pressure in the cooling water circulation passage 31 decreases due to thermal contraction of the cooling water. When the pressure in the cooling water circulation passage 31 becomes a negative pressure lower than a predetermined second specified pressure, the negative pressure valve is opened. In this state, a part of the cooling water stored in the reservoir tank 37 is sucked back into the cooling water circulation passage 31 via the first sub passage 381. As a result, the pressure in the cooling water circulation passage 31 is adjusted to atmospheric pressure, and the amount of cooling water circulating through the cooling water circulation passage 31 is kept constant.

  The second cap 39 is provided in the cooling water circulation passage 31 between the thermostat 35 and the circulation pump 36 and is connected to the reservoir tank 37 by the second sub passage 391. The second cap 39 is a cap having the same structure as the first cap 38. The reason why the second cap 39 is provided in the cooling water circulation passage 31 between the thermostat 35 and the circulation pump 36 will be described later.

  The temperature sensor 40 is provided in the cooling water circulation passage 31 in the vicinity of the cooling water outlet hole 22 of the fuel cell stack 2 and detects the temperature of the cooling water discharged from the fuel cell stack 2 (hereinafter referred to as “stack temperature”) Ts. To do.

  The first pressure sensor 41 is provided in the cooling water circulation passage 31 between the second cap 39 and the circulation pump, and the pressure in the cooling water circulation passage 31 in the vicinity of the suction port of the circulation pump (hereinafter referred to as “pump inlet pressure”). Is detected.

  The second pressure sensor 42 is provided in the cooling water circulation passage 31 between the circulation pump and the fuel cell stack, and the pressure in the cooling water circulation passage 31 in the vicinity of the discharge port of the circulation pump (hereinafter referred to as “pump outlet pressure”). To detect.

  The controller 4 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). In addition to the temperature sensor 40, the first pressure sensor 41, and the second pressure sensor 42 described above, the controller 4 includes a current sensor 43 that detects the output current of the fuel cell stack 2 and a rotation that detects the rotational speed of the circulation pump. Signals from various sensors necessary for controlling the fuel cell system 1 such as the speed sensor 44 and the outside air temperature sensor 45 that detects the outside air temperature are input. In the present embodiment, the outside air temperature detected by the outside air temperature sensor 45 is used as the temperature of the cooling water in the reservoir tank 37.

  Hereinafter, the reason why the second cap 39 is provided in the cooling water circulation passage 31 between the thermostat 35 and the circulation pump 36 will be described.

  When the fuel cell system 1 is activated and the circulation pump 36 is driven, the discharge port side of the circulation pump 36, that is, the fuel cell stack 2, or the cooling water circulation passage 31 that connects the circulation pump 36 and the fuel cell stack 2. Pressure increases. As a result, the portion formed of the elastic material expands by pressurization, and the flow path volume as the cooling system increases. On the other hand, since the cooling water is an incompressible fluid and its volume does not change due to the pressure, the inside of the cooling water circulation passage 31 on the suction port side of the circulation pump 36, that is, the upstream side of the circulation pump 36 temporarily becomes a negative pressure. . Since a part of the cooling water circulation passage 31 between the thermostat 35 and the circulation pump 36 is formed by a rubber hose, the rubber hose contracts and deforms when the pressure inside the cooling water circulation passage 31 on the upstream side of the circulation pump 36 becomes negative.

  If the amount of shrinkage deformation of the rubber hose is large, the durability of the rubber hose itself is lowered, and the flow rate of the cooling water flowing through the shrinkage-deformed rubber hose portion is lowered, so the circulation flow rate of the cooling water circulating through the cooling water circulation passage 31 is also lowered. . When the fuel cell system 1 is activated, the heater 34 is activated to promote warm-up of the fuel cell stack. However, if the circulating flow rate of the cooling water decreases, the flow rate of the cooling water passing through the heater 34 decreases accordingly. As a result, the warm-up performance decreases.

  Therefore, when the fuel cell system 1 is started, the pressure in the cooling water circulation passage 31 on the upstream side of the circulation pump 36 is increased to the vicinity of the atmospheric pressure at an early stage while suppressing the amount of deformation of the rubber hose to a predetermined amount. I want to drive the heater 34 after securing the circulation flow rate.

  Therefore, in the present embodiment, in order to increase the pressure in the cooling water circulation passage 31 on the upstream side of the circulation pump 36 to the vicinity of the atmospheric pressure at an early stage, the cooling water circulation passage 31 between the thermostat 35 and the circulation pump 36 is first connected. Two caps 39 are provided.

  By providing the second cap 39 in the cooling water circulation passage 31 between the thermostat 35 and the circulation pump 36, the circulation pump 36 is driven, and the pressure in the cooling water circulation passage 31 on the upstream side of the circulation pump 36 becomes the second specified pressure. If it becomes lower than that, the negative pressure valve of the second cap 39 is opened. Accordingly, a part of the cooling water stored in the reservoir tank 37 can be sucked back into the cooling water circulation passage 31 directly upstream of the circulation pump 36 via the second sub passage 391. The pressure in the cooling water circulation passage 31 on the upstream side can be increased to near atmospheric pressure at an early stage.

  As described above, when the cooling water in the reservoir tank 37 is sucked back into the cooling water circulation passage 31 on the upstream side of the circulation pump 36, the pressure in the cooling water circulation passage 31 increases by the amount of the sucked cooling water. .

  However, if the rotation speed of the circulation pump 36 is increased too much, the pressure increase margin near the discharge port of the circulation pump 36 increases, and the expansion allowance of the flow path increases. Then, the flow rate sucked from the reserve tank 37 must be increased, the pump inlet pressure decreases excessively, and the amount of shrinkage deformation of the rubber hose exceeds a predetermined amount.

  On the other hand, in order to suck the cooling water in the reservoir tank 37 back into the cooling water circulation passage 31 upstream of the circulation pump 36, at least the pump inlet pressure is set so that the pump inlet pressure becomes lower than the second specified pressure. It is necessary to control the rotation speed.

  Therefore, in this embodiment, in order to suppress the amount of shrinkage deformation of the rubber hose to a predetermined amount, the rotational speed of the circulation pump 36 is set to a predetermined value so that the pump inlet pressure is maintained at a predetermined allowable negative pressure lower than the second specified pressure. The rate of change was gradually increased. The allowable negative pressure is a pressure at which the shrinkage deformation amount of the rubber hose becomes a predetermined amount.

  Hereinafter, the rotational speed control of the circulation pump 36 according to this embodiment will be described.

  FIG. 2 is a flowchart for explaining the rotational speed control of the circulation pump 36 according to the present embodiment. When the fuel cell system 1 is activated, the controller 4 executes this routine at a predetermined calculation cycle Δt (for example, 10 [ms]).

  In step S1, the controller 4 reads the detection values of the various sensors described above.

  In step S2, the controller 4 determines whether or not the warm-up end flag is set to 1. The warm-up end flag is a flag that is set to 1 when it is determined that the warm-up of the fuel cell stack 2 has ended, and the initial value is set to 0. If the warm-up end flag is 0, the controller 4 performs step S3. On the other hand, if the warm-up end flag is 1, the process of step S15 is performed.

  In step S3, the controller 4 determines whether or not the warm-up preparation end flag is set to 1. The warm-up preparation completion flag is a flag that is set to 1 when the rotation speed N of the circulation pump 36 is equal to or higher than the maximum rotation speed Nmax and preparation for driving the heater 34 is completed. The initial value of the warm-up preparation end flag is set to zero. If the warm-up preparation end flag is 0, the controller performs the process of step S4. On the other hand, if the warm-up preparation end flag is 1, the process of step S10 is performed.

  In step S4, the controller 4 refers to a table of FIG. 3 to be described later, and based on the outside air temperature Ta and the count timer t that counts the elapsed time since the fuel cell system 1 is started, the circulation pump 36. Target rotation speed Nt is calculated.

  In step S5, the controller 4 performs feedback control according to the rotation speed N of the circulation pump 36 and the target rotation speed Nt, and controls the rotation speed N of the circulation pump 36 to the target rotation speed Nt.

  In step S <b> 6, the controller 4 determines whether or not the rotational speed N of the circulation pump 36 is equal to or higher than the maximum rotational speed Nmax of the circulation pump 36. If the rotational speed N of the circulation pump 36 is less than the maximum rotational speed Nmax, the controller 4 performs the process of step S7. On the other hand, if the rotational speed N of the circulation pump 36 is equal to or higher than the maximum rotational speed Nmax, the process of step S8 is performed.

  In step S7, the controller 4 adds the calculation cycle Δt to the current value of the count timer t and updates the value of the count timer t. The initial value of the count timer t is set to 0.

  In step S8, the controller 4 updates the value of the count timer t to 0.

  In step S9, the controller 4 sets a warm-up preparation end flag to 1.

  In step S10, the controller 4 sets the target rotation speed Nt of the circulation pump 36 to the maximum rotation speed Nmax, and maintains the rotation speed N of the circulation pump 36 at the maximum rotation speed Nmax.

  In step S <b> 11, the controller 4 drives the heater 34.

  In step S12, the controller 4 determines whether or not the stack temperature Ts is 60 ° C. or higher. If the stack temperature Ts is less than 60 ° C., the controller 4 ends the current process. On the other hand, if the stack temperature Ts is 60 ° C. or higher, the process of step S13 is performed.

  In step S13, the controller 4 sets a warm-up end flag to 1. The warm-up end flag is returned to 0 when the fuel cell system is stopped.

  In step S14, the controller 4 sets the warm-up preparation end flag to 0.

  In step S <b> 15, the controller 4 performs normal control of the circulation pump 36. Specifically, for example, the fuel cell stack 2 is configured so that the water content (wetness) of the electrolyte membrane of each fuel cell constituting the fuel cell stack 2 is an appropriate amount according to the operation state of the fuel cell system 1. The rotational speed N of the circulation pump 36 is controlled based on the internal high frequency resistance (HFR). The internal high frequency resistance of the fuel cell stack 2 can be detected by a known AC impedance method.

  FIG. 3 is a table for calculating the target rotational speed Nt of the circulation pump 36 based on the outside air temperature Ta and the count timer t.

  As shown in FIG. 3, the target rotational speed Nt of the circulation pump 36 is set so as to increase as the elapsed time (count timer t) from the start of the fuel cell system 1 increases. In this way, by gradually increasing the rotation speed of the circulation pump 36 at a predetermined rate of change, the flow rate of the cooling water sucked back from the reservoir tank 37 into the cooling water circulation passage 31 and the components on the discharge side of the circulation pump 36 are reduced. The pump inlet pressure can be maintained at an allowable negative pressure in balance with the volume change amount.

  In the present embodiment, the lower the outside air temperature is, the slower the rotational speed of the circulation pump 36 increases. Hereinafter, this reason will be described.

  The flow rate of the cooling water sucked back into the cooling water circulation passage 31 upstream of the circulation pump 36 from the reservoir tank 37 via the second sub passage 391 depends on the viscosity of the cooling water, the passage cross-sectional area of the second sub passage 391, and the like. It changes according to the pressure loss characteristic of the determined second sub-passage 391. Specifically, the lower the temperature of the cooling water in the reservoir tank 37 and the higher the viscosity of the cooling water, the lower the flow rate of the cooling water sucked back into the cooling water circulation passage 31 on the upstream side of the circulation pump 36.

  Here, the temperature of the cooling water in the reservoir tank 37 at the start of the fuel cell system 1 can be considered to be equivalent to the outside air temperature. Therefore, the pump inlet pressure can be reliably maintained at the allowable negative pressure by making the increase speed of the rotational speed of the circulation pump 36 slower as the outside air temperature is lower.

  FIG. 4 is a time chart for explaining the operation of the rotational speed control of the circulation pump 36 according to the present embodiment.

  When the fuel cell system 1 is started at time t1, the target rotational speed Nt of the circulation pump 36 is calculated based on the outside air temperature Ta and the count timer t, and the rotational speed N of the circulation pump 36 is calculated as the target rotational speed Nt. Thus, the circulation pump 36 is feedback-controlled.

  As a result, the circulation pump 36 is gradually raised at a predetermined rate of change (FIG. 4A), and the pump inlet pressure is maintained at the allowable negative pressure (FIG. 4B).

  When the rotation speed N of the circulation pump 36 reaches the maximum rotation speed Nmax at time t2, the heater 34 is driven while the rotation speed N of the circulation pump 36 is maintained at the maximum rotation speed Nmax, and the fuel cell stack 2 is warmed up. Is done. Further, the pump inlet pressure gradually increases from the allowable negative pressure to the atmospheric pressure.

  According to the present embodiment described above, the second cap 39 is provided in the cooling water circulation passage 31 connected to the suction port of the circulation pump 36, and the circulation is performed when the circulation pump 36 is driven to start the circulation of the cooling water. The rotational speed of the pump 36 is gradually increased at a predetermined change rate.

  Thus, when the circulation pump 36 is driven to start the circulation of the cooling water, it is possible to suppress the pressure in the cooling water circulation passage 31 on the upstream side of the circulation pump 36 from being excessively reduced. A decrease in durability can be suppressed.

  In the present embodiment, since the rate of change of the rotational speed of the circulation pump 36 is set so that the pump inlet pressure is maintained at an allowable negative pressure, the cooling water circulation passage on the upstream side of the circulation pump 36 is made elastic such as a rubber hose. When formed of a material, the amount of shrinkage deformation of the rubber hose can be suppressed to a predetermined amount.

  Thereby, while being able to suppress the fall of durability of a rubber hose, since the fall of the flow of cooling water which flows through a rubber hose part can be controlled, the fall of the circulation flow of the cooling water which circulates through cooling water circulation passage 31 can be controlled. Therefore, since the flow rate of the cooling water passing through the heater 34 can be suppressed at the time of starting the fuel cell system, the deterioration of the warm-up performance can be suppressed.

  In this embodiment, the rate of change in the rotational speed of the circulation pump 36 is set in consideration of the pressure loss characteristics of the second sub-passage 391. Specifically, the rate of change was set such that the lower the cooling water temperature (outside air temperature) in the reservoir tank 37, the slower the increase in the rotational speed of the circulation pump 36.

  The flow rate of the cooling water sucked back from the reservoir tank 37 to the cooling water circulation passage 31 via the second sub passage 391 changes according to the pressure loss characteristics of the second sub passage 391. By setting the rate of change in the rotational speed, the pump inlet pressure can be more reliably held at the allowable negative pressure.

  In the present embodiment, the first cap 38 is provided in the cooling water circulation passage 31 between the radiator 32 and the thermostat 35, and the second cap 39 is provided in the cooling water circulation passage 31 between the thermostat 35 and the circulation pump 36. Was provided. Thereby, the following effects can be acquired.

  When the fuel cell system 1 is started and the circulation pump 36 is driven, the suction port side of the circulation pump 36, that is, the inside of the cooling water circulation passage 31 on the upstream side of the circulation pump 36 temporarily becomes negative pressure. When the fuel cell system 1 is started up, the temperature of the cooling water in the cooling water circulation passage 31 is usually lower than the thermo valve opening temperature, so that the flow path on the radiator 32 side of the thermostat 35 is closed.

  Therefore, the pressure of the first cap 38 part is lower than the suction port part pressure of the circulation pump 36. Specifically, the pressure of the suction port portion of the circulation pump 36 is reduced by the pressure loss of the bypass flow path 33 and the heater 34 and the thermostat 35 installed in the flow path. As a result, even if the cooling water is supplied into the system until the negative pressure valve of the first cap 38 opens and returns to the atmospheric pressure, the suction port portion of the circulation pump 36 is in a negative pressure due to the pressure loss described above. Thus, the pump inlet pressure cannot be maintained at the allowable negative pressure.

  Therefore, in the present embodiment, the second cap 39 is provided in the cooling water circulation passage 31 between the thermostat 35 and the circulation pump 36.

  Thereby, when the circulation pump 36 is driven and the pressure in the cooling water circulation passage 31 on the upstream side of the circulation pump 36 becomes lower than the second specified pressure, the negative pressure valve of the second cap 39 is opened, so that it is stored in the reservoir tank 37. A part of the cooled water is sucked back into the cooling water circulation passage 31 directly upstream of the circulation pump 36 via the second sub-passage 391, and the pump inlet pressure can be maintained at an allowable negative pressure.

  As a result, the amount of shrinkage deformation of the rubber hose can be suppressed to a predetermined amount, and a decrease in the durability of the rubber hose can be suppressed, and a decrease in the flow rate of the cooling water flowing through the rubber hose portion can be suppressed. A decrease in the circulating flow rate of the cooling water can be suppressed.

  Note that the present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

1 Fuel cell system 2 Fuel cell stack (fuel cell)
31 Cooling water circulation passage (refrigerant circulation passage)
32 Radiator
33 Bypass passage 35 Thermostat (Flow control valve)
36 Circulation pump 37 Reservoir tank 38 First cap (pressure regulating valve)
39 Second cap (open / close valve)
391 Second sub-passage (communication passage)
S5 Circulation pump control means

Claims (5)

A fuel cell system for generating power by supplying anode gas and cathode gas to a fuel cell,
A refrigerant circulation passage through which a refrigerant for cooling the fuel cell circulates;
A circulation pump provided in the refrigerant circulation passage for circulating the refrigerant;
A reservoir tank that stores refrigerant therein and is maintained at atmospheric pressure;
Provided in the refrigerant circulation passage on the suction side of the circulation pump, and opens when the pressure in the refrigerant circulation passage becomes a predetermined negative pressure or less, and supplies the refrigerant in the reservoir tank into the refrigerant circulation passage. An on-off valve;
A communication path connecting the reservoir tank and the on-off valve;
A circulation pump control means for gradually increasing the rotation speed of the circulation pump when the circulation pump is driven to start circulation of the refrigerant;
A radiator that is provided in the refrigerant circulation passage upstream of the circulation pump and reduces the temperature of the refrigerant passing therethrough;
A bypass passage connected to the refrigerant circulation passage upstream of the radiator and the refrigerant circulation passage upstream of the circulation pump so as to bypass the radiator;
A flow rate adjusting valve that is provided at a connection portion between the refrigerant circulation passage upstream of the circulation pump and the bypass passage, and adjusts the flow rate of the refrigerant flowing through the bypass passage;
The refrigerant tank is connected to the reservoir tank, and is provided in the refrigerant circulation passage between the radiator and the flow rate adjusting valve. A pressure adjusting valve that adjusts within a predetermined range;
With
The on-off valve is provided in the refrigerant circulation passage between the flow rate adjustment valve and the circulation pump.
A fuel cell system. The circulation pump control means includes
Considering the supply flow rate of the refrigerant that changes according to the pressure loss characteristics of the communication passage, gradually increasing the rotational speed of the circulation pump,
The fuel cell system according to claim 1. The circulation pump control means includes
The lower the temperature of the refrigerant in the reservoir tank, the slower the increase rate of the rotational speed of the circulation pump;
The fuel cell system according to claim 1. The circulation pump control means includes
Gradually increasing the rotational speed of the circulation pump so that the pressure in the refrigerant circulation passage on the suction side of the circulation pump does not fall below a predetermined allowable negative pressure lower than the predetermined negative pressure;
The fuel cell system according to any one of claims 1 to 3, characterized in that:   The fuel cell system according to any one of claims 1 to 4, wherein the refrigerant circulation passage on the suction side of the circulation pump is formed of an elastic material.

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