JP5545089B2 - COOLING SYSTEM AND COOLING SYSTEM CONTROL METHOD - Google Patents

Description

  The present invention relates to a cooling system and a cooling system control method.

  2. Description of the Related Art Conventionally, in a vehicle equipped with a fuel cell, a technique for using waste heat of the fuel cell as a heat source for temperature adjustment in the passenger compartment is known. For example, there is a technology in which cooling water flowing through a cooling circuit (cooling water circulation supply flow path) in which a fuel cell is disposed is supplied to a flow path in which a heater core for air conditioning is disposed, and the cooling water is used as a heat source for air conditioning. Known (for example, Patent Document 1).

JP 2009-113539 A JP 2005-263200 A Japanese Patent Laid-Open No. 62-198058

  When the temperature of the cooling water flowing through the cooling circuit is low, it is necessary to raise the temperature of the cooling water to a temperature that can be used as a heat source for air conditioning. In the technique of Patent Document 1, when the temperature of the cooling water is equal to or lower than a predetermined threshold, the temperature of the cooling water is increased by increasing the heat released from the fuel cell. More specifically, by switching from normal operation with relatively high power generation efficiency to low efficiency operation with relatively low power generation efficiency, the power loss is increased and the temperature of the fuel cell is raised.

  However, the technology that raises the temperature of the cooling water by changing the power generation efficiency of the fuel cell to use the waste heat of the fuel cell as a heat source for air conditioning may affect the output of the vehicle. It was. Such a problem is not limited to vehicles, but is a problem common to various systems that use waste heat of a fuel cell for indoor air conditioning.

  Therefore, the present invention has been made in view of such problems, and it is possible to efficiently increase the cooling water flowing through the cooling circuit in which the fuel cell is disposed while maintaining the power generation efficiency of the fuel cell stably. The purpose is to provide technology that can be used.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

Application Example 1 A cooling system, which is a fuel cell, a cooling circuit for circulating a refrigerant passing through the fuel cell, and an air conditioning circuit for circulating the refrigerant, and blows air into the refrigerant and the room An air conditioning circuit having a heat exchanger that exchanges heat with air, a first temperature detection unit for detecting an outlet temperature that is a temperature of a refrigerant at the fuel cell outlet, and the fuel cell Switching between a connected state in which the refrigerant flows into the air conditioning circuit, passes through the heat exchanger and flows into the cooling circuit, and a disconnected state in which the refrigerant flows between the cooling circuit and the air conditioning circuit is switched. A possible switching unit, and a flow rate control unit that controls a first flow rate that is a flow rate of the refrigerant circulating in the cooling circuit,
Furthermore, as a control mode of the flow rate control unit, a first flow rate control mode for controlling the first flow rate according to the power generation state of the fuel cell, and the first flow rate according to the power generation state of the fuel cell. A second flow rate control mode for controlling the flow rate, wherein the first flow rate in a predetermined power generation state is smaller than the first flow rate control mode, and
When there is a connection request for switching from a non-connected state to a connected state, if the outlet temperature is lower than a predetermined value, the cooling system causes the flow rate control unit to perform an operation in the second flow rate control mode.

  According to the cooling system of Application Example 1, when the outlet temperature is lower than the predetermined value, the operation is performed in the second flow rate control mode in which the flow rate is reduced. Therefore, the cooling circuit is maintained while maintaining the power generation efficiency of the fuel cell stably. The temperature of the refrigerant can be increased efficiently. Here, the predetermined value is set to a minimum value or more that can use the refrigerant in the cooling circuit as a heat source for air conditioning in response to a heating request on the air conditioning side. For example, the predetermined value can be set in a range of 40 ° C to 60 ° C.

[Application Example 2] The cooling system according to Application Example 1, wherein the power generation state is a power generation amount determined based on a current value and a voltage value of the fuel cell.
According to the cooling system of the application example 2, the operation of the cooling circuit is performed by performing the operation in the second flow rate control mode in which the first flow rate is controlled to be smaller than the first flow rate control mode at a certain predetermined power generation amount. The temperature of the refrigerant can be increased efficiently.

[Application Example 3] The cooling system according to Application Example 1 or Application Example 2, further including a second temperature detection unit for detecting an inlet temperature which is a temperature of the refrigerant at the fuel cell inlet, The first flow rate control mode is a control mode in which a temperature difference that is a difference between the inlet temperature and the outlet temperature is set to a first target value, and the second flow rate control mode Is a cooling system that is a control mode in which the temperature difference is controlled to be a second target value that is larger than the first target value.
According to the cooling system of Application Example 3, the flow rate control in the first and second flow rate control modes can be easily performed by setting a predetermined temperature difference. Specifically, for example, the flow rate can be controlled based on the following formula (1).
Q = C × m × ΔT (1)
Where Q is the calorific value (kW) of the fuel cell, m is the first flow rate (kg / s), C is the specific heat of the refrigerant passing through the fuel cell (kJ / g · ° C.), and ΔT is the fuel cell The temperature difference (° C) between the cooling water flowing in and the cooling water flowing out from the fuel cell.

  The target temperature difference in each flow rate control mode, the specific heat of the existing refrigerant, and the calorific value calculated from the power generation amount are substituted into the above formula (1). Thereby, the first flow rate m in each flow rate control mode can be easily determined. Here, the first target value is preferably set within a temperature range in which the fuel cell can be cooled by the refrigerant and the durability of the fuel cell can be more reliably maintained. For example, the first target value can be set in the range of 10 ° C to 15 ° C. The second target value is preferably set in a temperature range that is larger than the first target value and that can maintain the durability of the fuel cell. For example, the second target value can be set in the range of 20 ° C to 25 ° C.

[Application Example 4] The cooling system according to any one of Application Examples 1 to 3, wherein the outlet temperature is a first greater than the predetermined value as a control mode of the flow rate control unit. The first flow rate controlled by the third flow rate control mode at a predetermined power generation amount of the fuel cell, having a third flow rate control mode for controlling the first flow rate so as to maintain a reference value. Is larger than the first flow rate controlled by the second flow rate control mode and smaller than the first flow rate controlled by the first flow rate control mode, After the operation in the flow rate control mode 2 is performed, when the outlet temperature reaches the first reference value, the operation is performed by switching from the second flow rate control mode to the third flow rate control mode. Cooling system Beam.
According to the cooling system of the application example 4, it is possible to suppress an unnecessary increase in the outlet temperature. The outlet temperature can generally be considered as the internal temperature of the fuel cell. By maintaining the internal temperature of the fuel cell constant, the power generation state can be stably maintained as compared with the case where the internal temperature is not maintained constant.

Application Example 5 In the cooling system according to Application Example 4 subordinate to Application Example 3, after causing the flow rate control unit to perform an operation in the third flow rate control mode, the temperature difference is When the target value of 1 is reached, the cooling system is configured to execute the operation by switching from the third flow rate control mode to the first flow rate control mode.
According to the cooling system of the application example 5, it is possible to reduce problems caused in the fuel cell by performing an operation in which the temperature difference is further reduced. For example, the variation in temperature distribution inside the fuel cell can be reduced by making the temperature difference smaller. Thereby, the distortion which arises in each member which comprises a fuel cell is reduced, and possibility that the gas (fuel gas and oxidant gas) and refrigerant which pass through the inside of a fuel cell will leak outside can be reduced.

[Application Example 6] The cooling system according to Application Example 4 or Application Example 5, wherein the first reference value is equal to or lower than an upper limit temperature at which the fuel cell can be stably operated.
According to the cooling system of Application Example 6, the temperature of the refrigerant in the cooling circuit can be increased efficiently, and the fuel cell can be stably operated. Here, the state in which the fuel cell can be stably operated means a state in which at least one cell voltage of the fuel cell does not become 0 V or less. For example, when the fuel cell is a polymer electrolyte fuel cell, the upper limit temperature is about 80 ° C to 95 ° C.

[Application Example 7] The cooling system according to Application Example 3, wherein the second target value is determined by a fluid flowing through the inside of the fuel cell because each member constituting the fuel cell is distorted by thermal stress. A cooling system that is defined within a range that prevents leakage to the outside.
According to the cooling system of the application example 7, even when the temperature of the refrigerant in the cooling circuit is efficiently increased, problems occurring in the fuel cell can be reduced.

Application Example 8 A cooling system control method, which includes a fuel cell, a cooling circuit for circulating the refrigerant passing through the fuel cell, and an air conditioning circuit for circulating the refrigerant. And an air conditioning circuit having a heat exchanger for exchanging heat between the refrigerant and the air blown into the room, and a first temperature detector for detecting an outlet temperature which is a temperature of the refrigerant at the fuel cell outlet The refrigerant flowing out of the fuel cell flows into the air conditioning circuit, passes through the heat exchanger and flows into the cooling circuit, and the refrigerant flows between the cooling circuit and the air conditioning circuit. A switching unit capable of switching between a disconnected state and a disconnected state, and a flow rate control unit that controls a first flow rate that is a flow rate of the refrigerant circulating in the cooling circuit,
A receiving step of receiving a connection request for switching from a non-connected state to a connected state, a determination step of determining whether or not the outlet temperature is lower than a predetermined value after receiving the connection request, and the outlet temperature being lower than a predetermined value When it is determined that the temperature is lower, the temperature of the refrigerant flowing through the cooling circuit is increased by reducing the first flow rate in a predetermined power generation state of the fuel cell than when the outlet temperature is equal to or higher than a predetermined value. And a control method.
According to the control method of Application Example 8, when the outlet temperature is lower than the predetermined value, the flow rate is reduced, so that the temperature of the refrigerant in the cooling circuit can be increased efficiently while maintaining the power generation efficiency of the fuel cell stably. Can do.

It is a figure which shows the structure of the cooling system 1 as an Example of this invention. It is the figure which showed the flow of the cooling water of a connection state and a non-connection state. It is a figure for demonstrating the flow control mode. 3 is a flowchart for explaining flow rate control of the cooling system 1. It is a figure which shows the time change of the various states of the cooling system.

Next, embodiments of the present invention will be described in the following order.
A. Example:
B. Variations:

A. Example:
A-1: System configuration:
FIG. 1 is a diagram showing a configuration of a cooling system 1 as an embodiment of the present invention. In this embodiment, the cooling system 1 is mounted on a vehicle.

  As shown in FIG. 1, the cooling system 1 of the present embodiment includes a fuel cell stack 100 (also simply referred to as “FC100”), a cooling circuit 10 for circulating cooling water passing through the fuel cell stack 100, An air conditioning circuit 20 for circulating cooling water used for air conditioning of the passenger compartment 40, first and second communication channels 216, 218, a valve V3, and an ECU for controlling the operation of the cooling system 1 ( An electronic control unit (electronic control unit) 30 is mainly provided. In addition, although illustration is abbreviate | omitted, the cooling system 1 is provided with the hydrogen supply / discharge system which supplies / discharges hydrogen as fuel gas, and the air supply / discharge system which supplies / discharges air as oxidant gas. The hydrogen supply / discharge system supplies hydrogen to the anode of the fuel cell stack 100 and discharges the anode exhaust gas discharged from the fuel cell stack 100 to the outside of the system 1. The air supply / discharge system supplies air to the cathode of the fuel cell stack 100 and discharges the cathode exhaust gas discharged from the fuel cell stack 100 to the outside of the system 1.

  The fuel cell stack 100 is a polymer electrolyte fuel cell that is relatively small and excellent in power generation efficiency. Pure hydrogen as a fuel gas and oxygen contained in air as an oxidant gas cause an electrochemical reaction at each electrode. It is what happens. The fuel cell stack 100 has a stack structure in which a plurality of single cells (not shown) are stacked with a separator (not shown) interposed, and the number of stacks is arbitrarily determined according to the output required for the fuel cell stack 100 It can be set.

  A load 140 is electrically connected to the fuel cell stack 100, and electric power generated by an electrochemical reaction of the fuel cell stack 100 is supplied to the load 140. A current sensor 142 and a voltage sensor 144 are arranged between the fuel cell stack 100 and the load 140. The load 140 includes, for example, a vehicle driving motor and various actuators (water pumps WP1 and WP2, valves V1 and V2, a fan 112, a blower 220, and an electric heater 202) described later.

  The cooling circuit 10 includes a first cooling channel 120, a second cooling channel 126, and a third cooling channel 128. The cooling circuit 10 controls the opening and closing of the valve V1, thereby circulating the first cooling channel 120 and the second cooling channel 126, or the first cooling channel 120 and the third cooling channel 126. A circulation channel by the cooling channel 128 is formed. Specifically, the valve V1 is connected to three cooling channels 120, 126, and 128. The valve V1 adjusts the opening degree of the valve so that the cooling water flowing into the second cooling channel 126 from the outlet channel 124 of the first cooling channel 120 and the third from the outlet channel 124 The flow rate ratio with the cooling water flowing into the cooling flow path 128 is adjusted. Thus, the cooling circuit 10 is a circulation flow path for circulating the refrigerant passing through the fuel cell stack 100.

  The first cooling flow path 120 has the fuel cell stack 100 disposed in the middle. Further, the first cooling flow path 120 includes an inlet side flow path 122 through which cooling water flowing into the fuel cell stack 100 flows and an outlet side flow path 124 through which cooling water flowing out from the fuel cell stack 100 flows. In the inlet-side flow path 122, a water pump WP1 (hereinafter also simply referred to as “pump WP1”) for circulating the cooling water in the cooling circuit 10 and a temperature sensor 130 are arranged. The temperature sensor 130 is disposed in the vicinity of the cooling water inlet of the fuel cell stack 100 in the inlet-side flow path 122. A temperature sensor 132 is disposed in the vicinity of the coolant outlet of the fuel cell stack 100 in the outlet-side flow path 124. The temperature sensor 130 is mainly used to detect the cooling water temperature at the cooling water inlet of the fuel cell stack 100 (also referred to as “cooling water inlet temperature Tin”). The temperature sensor 132 is mainly used to detect the cooling water temperature at the cooling water outlet of the fuel cell stack 100 (also referred to as “cooling water outlet temperature Tout”). That is, the temperature sensor 130 is mainly used for detecting the temperature of the cooling water flowing into the fuel cell stack 100, and the temperature sensor 132 is mainly used for detecting the temperature of the cooling water flowing out from the fuel cell stack 100 (details). Is used to detect the temperature of the cooling water that flows out of the fuel cell stack 100 and flows into the air conditioning circuit 20 in the connected state described later. The arrangement position of the temperature sensor 130 is not limited to this. For example, the temperature sensor 130 can be disposed in any part of the inlet-side flow path 122. Further, the arrangement position of the temperature sensor 132 is not limited to this. For example, the temperature sensor 132 is arranged between a point where the fuel cell stack 100 is arranged in a part of the outlet side channel 124 and a point where the first communication channel 216 is connected to the outlet side channel 124. can do. Here, the temperature sensor 132 corresponds to the “first temperature detection unit” described in the means for solving the problem, and the “second temperature detection unit described in the means for the temperature sensor 130 solving the problem”. Is equivalent to.

  The second cooling channel 126 is connected to both ends of the first cooling channel 120. The second cooling flow path 126 includes a radiator 110 for cooling the cooling water and a temperature sensor 134. The ECU 30 controls the temperature of the cooling water flowing into the fuel cell stack 100 by controlling the operation of the fan 112 based on the detection value of the temperature sensor 134.

  The third cooling channel 128 is a bypass channel for allowing the cooling water flowing through the outlet side channel 124 to flow into the inlet side channel 122 without passing through the second cooling channel 126.

  The pump WP1 varies the flow rate of the cooling water circulating in the cooling circuit 10 (also referred to as “first flow rate m”) in accordance with the amount of power generated by the fuel cell stack 100. This specific aspect will be described later.

  The air conditioning circuit 20 includes a first air conditioning channel 210 and a second air conditioning channel 214 connected to both ends of the first air conditioning channel 210. The first air conditioning flow path 210 and the second air conditioning flow path 214 can form a cooling water circulation flow path.

  The first air conditioning channel 210 includes an electric heater 202, a heater core 200 as a heat exchanger, a water pump WP2 (hereinafter also simply referred to as “pump WP2”), and two temperature sensors 230 and 232. It is arranged. The first air conditioning channel 210 has an inlet side air conditioning channel 212 through which the cooling water flowing into the heater core 200 flows, and an outlet side air conditioning channel 213 through which the cooling water flowing through the heater core 200 flows out.

  In the cooling system 1, the cooling water in the cooling circuit 10 flows into the air conditioning circuit 20 through the two communication channels 216, 218, the flowing cooling water flows through the air conditioning circuit 20, and flows into the cooling circuit 10 again. It is possible. That is, in the cooling system 1, the cooling water flowing through the cooling circuit 10 flows into the air conditioning circuit 20, the inflowing cooling water flows through the air conditioning circuit 20, and flows into the cooling circuit 10 again, and the cooling circuit 10. And a non-connected state that blocks the flow of the cooling water between the air conditioning circuit 20. The switching between the two states is performed by the valve V3 provided at the connection point of the three flow paths, that is, the second communication flow path 216, the first air conditioning flow path 210, and the second air conditioning flow path 214. This is done by switching between opening and closing. Here, the valve V3 corresponds to the “switching unit” described in the means for solving the problem.

  FIG. 2 is a diagram showing the flow of cooling water in a connected state and a non-connected state. FIG. 2A is a diagram showing a flow of cooling water in a connected state, and FIG. 2B is a diagram showing a flow of cooling water in a non-connected state. In addition, FIG. 2 extracts and shows the structure required for description among the cooling systems 1. As shown in FIG. 2A, in the connected state, common cooling water circulates between the cooling circuit 10 and the air conditioning circuit 20 through the first and second communication channels 216 and 218. On the other hand, as shown in FIG. 2B, in the disconnected state, the cooling water of the cooling circuit 10 circulates only through the cooling circuit 10, and the cooling water of the air conditioning circuit 20 circulates only through the air conditioning circuit 20. Thus, the connected state is a state in which the waste heat of the fuel cell stack 100 can be used as a heat source for adjusting the temperature in the vehicle interior, and the non-connected state is the waste heat of the fuel cell stack 100 in the vehicle interior 40. It cannot be used as a heat source for temperature control.

  As shown in FIG. 1, the heater core 200 is installed in the ventilation duct 24, and heats the air blown from the blower 220 as a blower installed on the upstream side of the ventilation duct 24. Specifically, heat exchange is performed between the cooling water flowing inside the heater core 200 and the air blown from the blower 220 toward the heater core 200. The heat-exchanged air is sent from the ventilation duct 24 to the vehicle interior 40 that is inside the moving body. The ECU 30 determines the rotational speed (also referred to as “rotational speed”) of the pump WP2 and the rotational speed of the blower 220 (also referred to as “rotational speed”) according to the target vehicle interior temperature, the current vehicle interior temperature, the current vehicle exterior temperature, and the like set by the user. The amount of heat released from the heater core 200 is adjusted by controlling “rotational speed”. That is, the ECU 30 executes the operation of the cooling system 1 in response to the heating request on the air conditioning side.

  A temperature setting device 401 is disposed in the vehicle interior 40, and the user sets a target vehicle interior temperature in the temperature setting device 401. The temperature setter 401 is provided with a heating switch (not shown) that enables a heating mode for heating the vehicle interior 40. When the heating switch is turned on by the user, the ECU 30 receives a switch ON signal. Then, the heating operation using the air conditioning circuit 20 is performed. Moreover, the vehicle interior temperature set by the user using the temperature setting device 401 is sent to the ECU 30 as an output signal and used for controlling various actuators during the heating operation.

  The electric heater 202 is used to heat the cooling water flowing into the heater core 200 when the amount of heat of the cooling water exchanged by the heater core 200 is insufficient. For example, when the cooling system 1 is in a disconnected state, the waste heat of the fuel cell stack 100 cannot be used, so the cooling water flowing into the heater core 200 is heated in response to a heating request.

  The temperature sensor 230 detects the temperature of the cooling water flowing into the heater core 200. The temperature sensor 232 detects the temperature of the cooling water that has passed through the heater core 200. The temperatures detected by the two temperature sensors 230 and 232 are transmitted to the ECU 30 as output signals and used for controlling the cooling system 1.

  The ECU 30 mainly includes a CPU 310, a memory 320, and an input / output port 330. The input / output port 330 connects various actuators and various sensors to the ECU 30 via a control signal line. Here, as various actuators, for example, there are a fan 112, pumps WP1 and WP2, an electric heater 202, a blower 220, and valves V1 and V3. Examples of various sensors include temperature sensors 130, 132, 134, 230, and 232, a temperature setter 401, a current sensor 142, and a voltage sensor 144.

  In the memory 320, various programs executed by the CPU 310 and a heat generation amount map 322 are recorded. The calorific value map 322 includes a power generation amount of the fuel cell stack 100 (also simply referred to as “FC power generation amount”) and a heat generation amount of the fuel cell stack 100 that varies in proportion to the FC power generation amount (simply “FC heat generation amount Q”). It is also a map that associates. The CPU 310 controls the operation of the cooling system 1 using various programs and the heat generation amount map 322 recorded in the memory 320. For example, the flow rate control unit 312 controls the number of rotations (also referred to as “rotational speed”) of the pumps WP1 and WP2, and controls the flow rate of cooling water flowing through the cooling circuit 10 and the air conditioning circuit 20.

A-2. Flow control mode:
FIG. 3 is a diagram for explaining the flow rate control mode. The cooling system 1 has a first flow rate control mode, a second flow rate control mode, and a third flow rate control mode. In each flow rate control mode, the first flow rate m is different when the FC heat generation amount Q is the same. In the cooling system 1, the flow rate control is normally performed in the first flow rate control mode.

  In the first flow rate control mode, the temperature difference ΔT between the cooling water inlet temperature Tin of the fuel cell stack 100 and the cooling water outlet temperature Tout is controlled to the first target value Δ by controlling the rotational speed of the pump WP1. The first flow rate m is controlled according to the FC calorific value Q so as to be T1. In this embodiment, the first target value ΔT1 is set to 10 ° C. Note that the first target value ΔT1 is not limited to 10 ° C., but is within a range that can reliably prevent problems (leakage of gas and cooling water to the outside) caused by variations in the temperature distribution of the fuel cell stack 100. It can be set. For example, the first target value ΔT1 is preferably set in the range of 10 ° C. to 15 ° C.

The CPU 310 calculates the first flow rate m based on the following equation (2), and controls the rotation speed of the pump WP1 so as to satisfy the calculated flow rate.
Q = C × m × (Tout−Tin) (2)
Here, Q is the calorific value (kW) of the fuel cell stack 100, m is the first flow rate (kg / s), and C is the specific heat (kJ / g · ° C.) of the cooling water passing through the fuel cell stack.

  Specifically, CPU 310 calculates FC power generation amount E based on voltage value V and current value I of fuel cell stack 100 detected by current sensor 142 and voltage sensor 144. The CPU 310 refers to the heat generation amount map 322 based on the calculated FC power generation amount E, and calculates the current FC heat generation amount Q. Then, the CPU 310 calculates the first flow rate m according to the equation (2) based on the calculated FC calorific value Q, the known specific heat C, and the first target value ΔT1 (10 ° C.).

  In the second flow rate control mode, the FC heat generation amount Q is controlled so that the temperature difference ΔT becomes a second target value ΔT2 larger than the first target value ΔT1 by controlling the rotational speed of the pump WP1. The first flow rate is controlled accordingly. In this embodiment, the second target value ΔT2 is set to 20 ° C. That is, as shown in FIG. 3, when the FC calorific value Q is the same value, the first flow rate m controlled in the second flow rate control mode is controlled in the first flow rate control mode. The relationship is smaller than the first flow rate m. For example, when the FC heat generation amount Q is the heat generation amount Q1, the first flow rate m that flows through the cooling circuit 10 in the first flow rate control mode is the flow rate L1, whereas the cooling circuit 10 in the second flow rate control mode. The first flow rate m to be circulated is a flow rate L2 smaller than the flow rate L1. Note that the second target value ΔT2 is not limited to 20 ° C., and may be any value that is larger than the first target value ΔT1. In order to ensure the durability of the fuel cell stack 100, it is preferable to set the temperature within a range of 25 ° C. or lower (for example, 20 ° C. to 25 ° C.).

  In the third flow rate control mode, by controlling the number of revolutions of the pump WP1, the FC heat generation amount is maintained so that the cooling water outlet temperature Tout is maintained at the first reference value Ta regardless of the temperature rise of the cooling water inlet temperature Tin. The first flow rate m is controlled according to Q. In this embodiment, the first reference value Ta is set to 90 ° C. The first reference value Ta is not limited to 90 ° C., and can be set in a range that is greater than a predetermined value Tw described later and is equal to or lower than the heat resistant temperature of the fuel cell stack 100. The first reference value Ta is preferably set within a range (for example, 80 ° C. to 95 ° C.) in which the power generation state of the fuel cell stack 100 can be stably maintained. Specifically, at least one cell voltage of the fuel cell stack 100 can be set in a range that does not become 0 V or less.

  In the third flow rate control mode, the coolant inlet temperature Tin rises, and in the second flow rate control mode in which the second target value ΔT2 is maintained, the coolant outlet temperature Tout exceeds the first reference value Ta. This is a flow control mode executed in the case. In the third flow rate control mode, the cooling water outlet temperature Tout of the above equation (2) is set to 90 ° C., and the first flow rate m is calculated based on the calculated FC heat generation amount Q and the detected cooling water inlet temperature Tin. As shown in FIG. 3, the first flow rate m calculated in this way is smaller than the first flow rate m controlled in the first flow rate control mode when the FC calorific value Q is the same value, and The relationship is larger than the first flow rate m controlled in the second flow rate control mode.

  While the first flow rate m is controlled in the first to third flow rate control modes, the power generation efficiency of the fuel cell stack 100 is maintained substantially constant. That is, the operation is performed without switching the mode of power generation efficiency of the fuel cell stack 100 (a mode in which the power generation efficiency is relatively high and a mode in which the power generation efficiency is relatively low). Specifically, the cooling system 1 is operated with the air stoichiometric ratio set to 1.5 to 2.0. Here, the “air stoichiometric ratio” is a ratio of the amount of oxidant gas supplied to the fuel cell stack 100 to the amount of oxidant gas consumed by the fuel cell stack 100 (amount of oxidant gas consumed / supplied Oxidant gas amount). When all the oxygen in the oxidant gas supplied to the fuel cell stack 100 is used for power generation, the air stoichiometric ratio is 1.0.

A-3. Control flow:
FIG. 4 is a flowchart for explaining the flow rate control of the cooling system 1. FIG. 5 is a diagram illustrating temporal changes in various states of the cooling system 1. FIG. 5A is a diagram showing a time change of the cooling water inlet temperature Tin and the cooling water outlet temperature Tout, and FIG. 5B is a diagram showing a time change of the first flow rate m. 5 (c) shows the time change of the FC calorific value Q. Each diagram in FIG. 5 is a diagram created to facilitate understanding of the flow rate control mode, and does not represent various state changes of the cooling system 1 in the actual flow rate control mode. In this embodiment, the operation is performed in the second and third flow rate control modes and in the first flow rate control mode under the condition that the coolant outlet temperature Tout does not reach the first reference value Ta. In this case, the cooling water of the cooling circuit 10 flows through the third cooling flow path 128 and does not flow through the second cooling flow path 126 where the radiator 110 is disposed.

  As shown in FIG. 4, the ECU 30 determines whether or not there is a request for switching from the unconnected state to the connected state (also referred to as “connection request”) (step S <b> 10). In this embodiment, the ECU 30 determines whether the heating switch is turned on by the user. If it is determined that there is no connection request, step S10 is repeatedly executed.

  If it is determined that there is a connection request, the ECU 30 detects the coolant outlet temperature Tout (step S12). Next, the ECU 30 determines whether or not the coolant outlet temperature Tout is smaller than a predetermined value Tw (step s30). For example, the predetermined value Tw is set to the lowest temperature at which the cooling water flowing out from the fuel cell stack 100 can be used as a heat source on the air conditioning side. For example, the predetermined value Tw can be set in the range of 40 ° C to 60 ° C. This is because if the predetermined value Tw is lower than 40 ° C., the heat of the cooling water flowing through the cooling circuit 10 cannot be used effectively, and there is a case where air cannot be blown into the vehicle interior 40 in response to the heating request. In this embodiment, the predetermined value Tw is set to 50 ° C.

  As shown in FIG. 4, when it is determined that the cooling water outlet temperature Tout is equal to or higher than the predetermined value Tw (step S14: NO), the ECU 30 controls the opening and closing of the valve V3 to connect the cooling system 1 from the unconnected state. The state is switched (step S22a). Thereby, the waste heat of the fuel cell stack 100 can be used as a heat source on the air conditioning side. In this case, the flow control unit 312 continues to operate in the first flow control mode. Even when the operation in the first flow rate control mode is continued, when the cooling water outlet temperature Tout reaches the first reference value Ta, the opening and closing of the valve V1 and the fan 112 are stopped. The temperature of the cooling water flowing into the fuel cell stack 100 is adjusted by controlling the rotation speed so that the cooling water outlet temperature Tout maintains the first reference value Ta.

  On the other hand, when it is determined that the coolant outlet temperature Tout is smaller than the predetermined value Tw (step S14: YES), the cooling system 1 switches the flow rate control unit 312 from the first flow rate control mode to the second flow rate control mode. The operation is executed (step S18). For example, in FIG. 5A, when there is a connection request at time t1, the coolant outlet temperature Tout is smaller than the predetermined value Tw at time t1. In this case, as shown in FIGS. 5B and 5C, the ratio of the first flow rate m in the FC heat generation amount Q is reduced. Thereby, the cooling water outlet temperature Tout can be raised to the predetermined value Tw in a shorter time, and the cooling water flowing out from the fuel cell stack 100 can be used as a heat source on the air conditioning side in a shorter time. it can.

  As shown in FIG. 4, after step S18, the ECU 30 determines whether or not the coolant outlet temperature Tout has reached a predetermined value Tw (step S20). If it is determined that the predetermined value Tw has not been reached (step S20: NO), the determination in step S20 is repeated. In addition, after the connection request is made and before the cooling water outlet temperature Tout reaches the predetermined value Tw, the electric heater 202 causes the inlet side air-conditioning flow path 212 to be changed according to the target vehicle interior temperature set by the user. The cooling water is heated, and the heated cooling water is used as a heat source on the air conditioning side.

  After the operation in the second flow rate control mode, when the ECU 30 determines that the cooling water outlet temperature Tout has reached the predetermined value Tw (step S20: YES), the cooling system 1 is changed from the unconnected state to the connected state. Switching (step S22). For example, as shown in FIG. 5A, since the coolant outlet temperature Tout has reached a predetermined value Tw at time t2, the state is switched from the unconnected state to the connected state at time t2. Even after the connection state is established, the cooling water in the inlet-side air conditioning channel 212 is heated using the electric heater 202 as necessary.

  As shown in FIG. 4, after executing the operation in the second flow rate control mode, the ECU 30 determines whether or not the coolant outlet temperature Tout has reached the first reference value Ta (90 ° C.) (step S24). ). If it is determined that the coolant outlet temperature Tout has not reached the first reference value Ta, the determination in step S24 is repeated.

  On the other hand, when it is determined that the cooling water outlet temperature Tout has reached the first reference value Ta (step S24: YES), the cooling system 1 causes the flow rate control unit 312 to switch from the second flow rate control mode to the third flow rate. The operation is switched to the control mode (step S26). For example, in FIG. 5A, since the coolant outlet temperature Tout has reached the first reference value Ta at time t3, the flow rate control mode is switched from the second flow rate control mode to the third flow rate control mode. More specifically, as shown in various state changes from time t3 to time t4 in FIG. 5, in order to maintain the cooling water outlet temperature Tout at the first reference value Ta, as the cooling water inlet temperature Tin increases, The ratio of the first flow rate m to the predetermined FC heat generation amount Q is increased. Thus, the heat source that can be used for the heating request on the air conditioning side by performing the operation in the second flow rate control mode until the cooling water outlet temperature Tout reaches the first reference value Ta larger than the predetermined value Tw. Can be sufficiently held in the cooling water circulating in the cooling circuit 10. Further, when the coolant outlet temperature Tout reaches the first reference value Ta, the operation is performed by switching from the second flow rate control mode to the third flow rate control mode, so that the temperature of the fuel cell stack 100 is increased. The power generation state of the fuel cell stack 100 can be kept stable by keeping it substantially constant.

  As shown in FIG. 4, after switching to the third flow rate control mode, the ECU 30 determines whether or not the temperature difference ΔT has become equal to or smaller than the first target value ΔT1 (step S28). Step S28 is repeated until the temperature difference ΔT becomes equal to or less than the first target value ΔT1. When it is determined that the temperature difference ΔT is equal to or smaller than the first target value ΔT1 (step S28: YES), the cooling system 1 switches the flow rate control unit 312 from the third flow rate control mode to the first flow rate control mode. The operation is executed (step S30). Thereby, it is possible to perform an operation in which the temperature difference ΔT is further reduced, reducing distortion of each member (separator, solid polymer electrolyte membrane, catalyst layer, gas diffusion layer) constituting the fuel cell stack 100, The possibility that the gas or cooling water passing through the fuel cell stack 100 leaks to the outside can be reduced. When the operation is performed in the first flow rate control mode after the cooling water outlet temperature Tout reaches the first reference value Ta, the second temperature is controlled in order to suppress the temperature rise of the cooling water inlet temperature Tin. 1st cooling water is distribute | circulated to the cooling flow path 126 of this, and control which cools cooling water to predetermined | prescribed temperature is performed using the radiator 110 and the fan 112 (FIG. 1).

  Thus, according to the cooling system 1 of the present embodiment, when there is a connection request, when the cooling water outlet temperature Tout is smaller than the predetermined value Tw, the first flow rate m at the predetermined FC heat generation amount Q is obtained. By executing the operation for reducing the amount of time (operation in the second flow rate control mode), the cooling water outlet temperature Tout can be raised to the predetermined value Tw in a shorter time while maintaining the power generation efficiency stable. Thereby, since the cooling water flowing out from the fuel cell stack 100 can be used as a heat source on the air conditioning side in a shorter time, the use of other heat sources such as the electric heater 202 can be reduced, and the heating performance can be improved. .

B. Variations:
In addition, elements other than the elements described in the independent claims of the claims in the constituent elements in the above-described embodiments are additional elements and can be omitted as appropriate. Further, the present invention is not limited to the above-described examples and embodiments, and can be implemented in various forms without departing from the gist thereof. For example, the following modifications are possible.

B-1. First modification:
In the above embodiment, in the first flow rate control mode and the second flow rate control mode, different temperature differences ΔT (first target value ΔT1 and second target value ΔT2) are set and controlled. However, it is not particularly limited to this. For example, in the second flow rate control mode, the target value of the temperature difference ΔT is not set, and the FC heat generation amount Q is the same value as the first flow rate m controlled by the normal operation of the fuel cell stack 100. The flow rate control in which the flow rate m of 1 is reduced may be performed. By reducing the first flow rate m, the coolant outlet temperature Tout can be increased to the predetermined value Tw in a shorter time than when the flow rate control is performed without reducing the first flow rate m.

B-2. Second modification:
In the above embodiment, the waste heat of the fuel cell stack 100, the electric heater 202, and the heater core 200 can be used as the heating heat source. However, the heat source that can be used as the heating heat source is not particularly limited thereto. . For example, a heat exchanger such as a heat pump or an air heater may be provided in the ventilation duct 24.

B-3. Third modification:
In the above embodiment, the ECU 30 is used to control both the cooling circuit 10 having the fuel cell stack 100 and the air conditioning circuit 20 used for blowing air in the vehicle interior 40. However, the ECU 30 controls the cooling circuit 10. An ECU and an ECU for controlling the air conditioning circuit 20 may be provided. In this case, necessary information (such as a detection value of the temperature sensor 132) is communicated between the ECUs.

B-4. Fourth modification:
In the above embodiment, the cooling water is used as the refrigerant, but the invention is not particularly limited to this, and various fluids can be used as the refrigerant. For example, an antifreeze obtained by adding ethylene glycol or the like to water may be used as a refrigerant, or a gas such as carbon dioxide may be used. Even if it does in this way, there exists an effect similar to the said Example.

B-5. Fifth modification:
In the said Example, although demonstrated taking the case where the cooling system 1 was mounted in a vehicle as an example, this invention is applicable to various mobile bodies. For example, the cooling system according to the present invention can be applied to various moving bodies such as trains, ships, and aircraft. Furthermore, the cooling system of the present invention can be applied not only to a moving body but also to a system that uses waste heat of the fuel cell stack 100 as a heat source for air conditioning in a house.

B-6. Sixth modification:
In the above embodiment, the polymer electrolyte fuel cell is used as the fuel cell stack 100. However, various fuel cells such as a phosphoric acid fuel cell, a molten carbonate fuel cell, and a solid oxide fuel cell may be used. it can.

DESCRIPTION OF SYMBOLS 1 ... Cooling system 10 ... Cooling circuit 20 ... Air conditioning circuit 24 ... Ventilation duct 30 ... ECU
DESCRIPTION OF SYMBOLS 40 ... Car interior 100 ... Fuel cell stack 110 ... Radiator 112 ... Fan 120 ... 1st cooling flow path 122 ... Inlet side flow path 124 ... Outlet side flow path 126 ... 2nd cooling flow path 128 ... 3rd cooling flow Path 130, 132, 134 ... Temperature sensor 140 ... Load 142 ... Current sensor 144 ... Voltage sensor 200 ... Heater core 202 ... Electric heater 210 ... First air conditioning channel 212 ... Inlet side air conditioning channel 213 ... Outlet side air conditioning channel 214 ... 2nd air-conditioning flow path 216 ... 1st communication flow path 218 ... 2nd communication flow path 220 ... Blower 230,232 ... Temperature sensor 310 ... CPU
312 ... Flow control unit 320 ... Memory 322 ... Heat generation amount map 330 ... I / O port 401 ... Temperature setter Tin ... Cooling water inlet temperature Tout ... Cooling water outlet temperature V1, V3 ... Valve Ta ... First reference value Tw ... Predetermined Value WP1, WP2 ... Water pump

Claims (8)

A cooling system,
A fuel cell;
A cooling circuit for circulating the refrigerant passing through the fuel cell;
An air conditioning circuit for circulating the refrigerant, the air conditioning circuit having a heat exchanger for exchanging heat between the refrigerant and the air blown into the room;
A first temperature detector for detecting an outlet temperature which is a temperature of the refrigerant at the fuel cell outlet;
The refrigerant flowing out of the fuel cell flows into the air conditioning circuit, passes through the heat exchanger and flows into the cooling circuit, and interrupts the refrigerant flow between the cooling circuit and the air conditioning circuit. A switching unit capable of switching between an unconnected state,
A flow rate control unit that controls a first flow rate that is a flow rate of the refrigerant circulating in the cooling circuit,
Furthermore, as a control mode of the flow rate control unit,
A first flow rate control mode for controlling the first flow rate according to a power generation state of the fuel cell;
A second flow rate control mode for controlling the first flow rate according to the power generation state of the fuel cell, wherein the first flow rate in a predetermined power generation state is smaller than the first flow rate control mode. And a flow rate control mode of
When there is a connection request for switching from a non-connected state to a connected state, if the outlet temperature is lower than a predetermined value, the cooling system causes the flow rate control unit to perform an operation in the second flow rate control mode. The cooling system according to claim 1,
The cooling system, wherein the power generation state is a power generation amount determined based on a current value and a voltage value of the fuel cell. The cooling system according to claim 1 or 2, further comprising:
A second temperature detecting unit for detecting an inlet temperature which is a temperature of the refrigerant at the fuel cell inlet;
The first flow rate control mode is a control mode in which a temperature difference that is a difference between the inlet temperature and the outlet temperature is controlled to be a first target value,
The cooling system, wherein the second flow rate control mode is a control mode in which the temperature difference is controlled to be a second target value that is larger than the first target value. The cooling system according to any one of claims 1 to 3,
As a control mode of the flow rate control unit, the flow rate control unit further includes a third flow rate control mode for controlling the first flow rate so that the outlet temperature maintains a first reference value larger than the predetermined value.
The first flow rate controlled by the third flow rate control mode at a predetermined power generation amount of the fuel cell is greater than the first flow rate controlled by the second flow rate control mode, and the first flow rate is controlled by the second flow rate control mode. Smaller than the first flow rate controlled by one flow rate control mode,
When the outlet temperature reaches the first reference value after causing the flow rate control unit to perform the operation in the second flow rate control mode, the third flow rate is changed from the second flow rate control mode to the third flow rate. Cooling system that switches to control mode and executes operation. A cooling system according to claim 4 dependent on claim 3, comprising:
If the temperature difference reaches the first target value after causing the flow rate control unit to perform the operation in the third flow rate control mode, the first flow rate is changed from the third flow rate control mode. Cooling system that switches to control mode and executes operation. A cooling system according to claim 4 or claim 5, wherein
The cooling system according to claim 1, wherein the first reference value is equal to or lower than an upper limit temperature at which the fuel cell can be stably operated. A cooling system according to claim 3,
The cooling system according to claim 1, wherein the second target value is determined within a range in which each member constituting the fuel cell can be prevented from leaking to the outside due to distortion of each member due to thermal stress. A control method for a cooling system,
The cooling system includes a fuel cell, a cooling circuit for circulating the refrigerant passing through the fuel cell, and an air conditioning circuit for circulating the refrigerant, and heat is generated between the refrigerant and the air blown into the room. An air conditioning circuit having a heat exchanger for exchanging, a first temperature detection unit for detecting an outlet temperature which is a temperature of the refrigerant at the fuel cell outlet, and the refrigerant flowing out of the fuel cell is the air conditioning circuit A switching unit capable of switching between a connected state that flows into the cooling circuit through the heat exchanger and a non-connected state that blocks the flow of refrigerant between the cooling circuit and the air conditioning circuit; A flow rate control unit that controls a first flow rate that is a flow rate of the refrigerant circulating in the cooling circuit,
An accepting step for accepting a connection request for switching from the unconnected state to the connected state;
A determination step of determining whether the outlet temperature is lower than a predetermined value after receiving the connection request;
When it is determined that the outlet temperature is lower than a predetermined value, the cooling circuit is configured to reduce the first flow rate in a predetermined power generation state of the fuel cell, compared to a case where the outlet temperature is equal to or higher than a predetermined value. Increasing the temperature of the flowing refrigerant.

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