JP3948664B2 - Fuel cell cooling system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell cooling device that cools a fuel cell with cooling water cooled by a radiator.
[0002]
[Prior art]
A fuel cell vehicle is a kind of electric vehicle, and is supplied with electric power from a mounted fuel cell to drive a traveling motor. The fuel cell receives the supply of air as an oxidant gas from an air supply system, and also receives the supply of hydrogen as a fuel gas from a hydrogen supply system, and generates electricity by an electrochemical reaction between the oxygen and hydrogen. Is supplied to a power consumption system consisting of a traveling motor and other auxiliary equipment such as a compressor.
[0003]
By the way, in the fuel cell described above, the relative relationship between the pressure of fuel gas and oxidant gas (hereinafter referred to as “reactive gas”) flowing into the inside of the fuel cell and the pressure of cooling water flowing into the inside is also limited. Has been. In general, when the pressure of the cooling water is higher than the pressure of the reaction gas, for example, there is a possibility that the seal in the cooling path of the fuel cell deteriorates or the electrolyte membrane of the fuel cell may be damaged. In this case, the pressure of the cooling water is always kept lower than the pressure of the reaction gas.
[0004]
Conventionally, in order to maintain such a pressure difference between the cooling water and the reaction gas (differential pressure between the electrodes), when the pressure of the reaction gas supplied to the fuel cell changes in an increasing direction, the target pressure of the cooling water When the value change is slow and the pressure of the reaction gas changes in the decreasing direction, the pressure target value that is the reference for cooling water is compared with its control target value, and the smaller value is set as the target value. The technique made to do is disclosed (refer patent document 1).
[0005]
[Patent Document 1]
JP 2002-280036 A (page 4, FIG. 2)
[0006]
According to this prior art, the target value of the cooling water pressure rises later than the target value of the reaction gas when the pressure of the reaction gas and the cooling water is adjusted in the increasing direction as the power generation output of the fuel cell increases. In addition, while maintaining a sufficient flow rate for cooling, the pressure difference between the cooling water pressure and the reaction gas (differential pressure between the electrodes) is maintained.
[0007]
[Problems to be solved by the invention]
However, in the conventional technology, when the power generation output is reduced, it is not sufficiently considered, and when a sudden decrease command is output to the circulation pump that circulates the cooling water, the cooling water has a predetermined kinetic energy. Therefore, the pressure does not suddenly decrease, and there is a possibility that a phenomenon in which the pressure temporarily increases (for example, a water hammer phenomenon) may occur. Also, when this phenomenon occurs, the above-mentioned differential pressure between the electrodes is not maintained (for example, cooling water pressure> reactive gas pressure), which may cause deterioration in the sealing performance of the fuel cell stack and damage to the electrolytic membrane. there were.
[0008]
Therefore, an object of the present invention is to maintain the differential pressure between the cooling water and the reaction gas even if the power generation output of the fuel cell is drastically reduced, and to prevent deterioration of the seal of the fuel cell and damage to the electrolyte membrane. It is an object of the present invention to provide a fuel cell cooling device that can be used.
[0009]
[Means for Solving the Problems]
The invention according to claim 1 of the present invention that has solved the above problems is provided in a fuel cell that generates power by an electrochemical reaction by flowing a fuel gas and an oxidant gas as a reaction gas. In the cooling device for a fuel cell that circulates cooling water between the fuel cell and the radiator by controlling a circulation pump in accordance with the generated power generation current, the reaction occurs when the power generation current of the fuel cell changes in a decreasing direction. An electrode differential pressure control means is provided for reducing the cooling water inflow command value with a predetermined delay when the gas inflow command value changes in a decreasing direction.
[0010]
According to the first aspect of the present invention, the inter-electrode differential pressure control means sets the cooling water inflow command value when the generated current of the fuel cell decreases and the reaction gas inflow command value changes in the decreasing direction. By reducing with a predetermined delay, the predetermined kinetic energy of the cooling water can be gradually attenuated. Therefore, the pressure difference between the electrodes can be maintained without abruptly increasing the pressure of the cooling water due to the water hammer phenomenon or the like, so that the deterioration of the seal of the fuel cell and the breakage of the electrolyte membrane can be prevented.
[0011]
According to a second aspect of the present invention, in the configuration of the first aspect of the present invention, the inter-electrode differential pressure control means increases the cooling water inflow command value as the decrease in the generated current of the fuel cell increases. It is characterized by decreasing with a large delay.
[0012]
According to the second aspect of the present invention, in addition to the action of the first aspect of the invention, when the change in the power generation output of the fuel cell is large, there is a possibility that the pressure of the cooling water increases due to the water hammer phenomenon or the like. Therefore, the larger the decrease in the power generation output, the greater the delay in decreasing the cooling water command value. By doing so, the differential pressure between the cooling water and the reaction gas can be maintained, and the deterioration of the seal of the fuel cell and the breakage of the electrolyte membrane can be prevented.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a configuration diagram showing a fuel cell cooling apparatus according to the present invention. In FIG. 1, a fuel cell 1 is configured by stacking a plurality of cells formed by sandwiching a solid polymer electrolyte membrane between an anode and a cathode from both sides, and an oxidant gas from an air supply system 2. Is supplied to the cathode electrode, and hydrogen is supplied as fuel gas from the hydrogen supply system 3 (hydrogen tank H2) to the anode electrode, and power is generated by an electrochemical reaction between oxygen and hydrogen. The generated electric power includes auxiliary equipment such as a supercharger (S / C) 4 of the air supply system 2, a circulation pump (W / P) 5 of the cooling device 10, a radiator fan 7 that sends air to the radiator 6, and the like. The power is supplied to a power consumption system such as a traveling motor.
[0014]
The cooling device 10 of the fuel cell 1 is mainly composed of a circulation pump 5, a radiator 6, a radiator fan 7, and a cooling water flow path 10 a, and the circulation pump 5 is controlled by an ECU (interelectrode differential pressure control means) 9. It has come to be. The cooling device 10 cools the fuel cell 1 by circulating the cooling water cooled by the radiator 6 by the circulation pump 5 in the cooling water flow path 10a. A pressure balancer 8 is provided between the cooling device 10 and the air supply system 2. The pressure balancer 8 maintains the pressure difference between the air supply system 2 and the cooling water flow path 10a substantially constant, and the pressure in the cooling water flow path 10a is higher than the pressure in the air supply system 2. The pressure is lowered by a predetermined pressure. Further, a pressure balancer (not shown) having a function similar to that of the pressure balancer 8 is provided between the air supply system 2 and the hydrogen supply system 3 so that the pressure difference between the two is maintained substantially constant. Has been.
[0015]
The ECU 9 mainly controls the supercharger 4, the electromagnetic valve (not shown) of the hydrogen tank H2, and the like and the circulation pump 5. Specifically, the ECU 9 generates a reaction gas inflow command value (a control signal for designating the amount of reaction gas to be supplied to the fuel cell 1) based on the current value taken out from the fuel cell 1 and the electromagnetic of the supercharger 4 and the hydrogen tank H2. These are output to valves and controlled. Further, the ECU 9 outputs a cooling water inflow command value (a control signal designating a flow rate of the cooling water to be circulated in the cooling water flow path 10a) to the circulation pump 5 in accordance with the generated current generated from the fuel cell 1. By controlling this, an amount of cooling water suitable for the calorific value of the fuel cell 1 is circulated. Further, the ECU 9 decreases the inflow command value of the cooling water with a predetermined delay when the inflow command value of the reaction gas changes in the decrease direction due to a change in the generated current of the fuel cell 1. Yes.
[0016]
2 and 3 are drawings for explaining the operation of the cooling device 10 of the fuel cell 1, and are a flowchart (FIG. 2) showing a flow of processing by the ECU 9, and output states such as a generated current and a command value. Each of the sequence diagrams shown (FIG. 3) is shown. Hereinafter, the operation of the cooling device 10 shown in FIG. 1 will be described in detail with reference to FIGS. 2 and 3.
[0017]
As shown in FIG. 2, first, the ECU 9 calculates a cooling water inflow command value based on the generated current IFC extracted from the fuel cell 1 (or an output command value for extracting a desired current from the fuel cell 1). After that (step S21), it is determined whether or not the inter-electrode differential pressure (cooling water pressure-reactive gas pressure) exceeds a predetermined value (step S22). If it is determined in this step S22 that the pressure difference between the electrodes has exceeded a predetermined value (YES), the delay rate DR (from the change ΔIFC (A / sec) of the generated current is referred to the predetermined map M. sec / rpm) and the delay rate DR is applied to the inflow command value calculated in step S21 (step S23). In step S23, an inflow command value to which a predetermined delay rate DR is applied is determined as a W / P final command value, and this W / P final command value is output to the circulation pump 5 to control the circulation pump 5. (Step S24). If it is determined in step S22 that the pressure difference between the electrodes is equal to or less than the predetermined value (NO), the inflow command value calculated in step S21 is determined as it is as the W / P final command value, and this W / P final value is determined. The circulation pump 5 is controlled by the command value (step S24).
[0018]
Further, the control method by the ECU 3 will be described in more detail.
FIG. 3 to be referred to is a sequence diagram (a) showing the output state of the generated current of the fuel cell, a sequence diagram (b) showing the output state of the inflow command value of the reaction gas output to the supercharger, and the circulation pump 5. It is the sequence diagram (c) which shows the output state of the inflow command value of the cooling water to output, and the sequence diagram (d) which shows the state of an inter-electrode differential pressure. In FIG. 3, the horizontal axis is the time axis.
[0019]
First, a conventional control method will be described in order to clearly recognize the effect of the present invention.
As shown in FIGS. 3A to 3C, when the power generation current IFC of the fuel cell 1 rapidly decreases to 0 A, the reaction gas inflow command value and the cooling water inflow command value (see FIG. 3 (shown by a dotted line in FIG. 3C) also suddenly changes in the decreasing direction to 0 rpm and 0%, respectively. At this time, the actual pressure in the air supply system 2 or the hydrogen supply system 3 gradually decreases because the inertial force of the reaction gas is small as shown in FIG. On the other hand, the pressure in the cooling water flow path 10a rises temporarily due to a water hammer phenomenon or the like because the inertial force of the cooling water is large as shown by the dotted line in the figure. At this time, if the inter-electrode differential pressure exceeds a predetermined value (cooling water pressure−reactive gas pressure> predetermined value), the cooling water pressure becomes larger than the reactive gas pressure, and the cooling water and reactive gas There may be a problem that the pressure difference between the electrodes cannot be maintained.
[0020]
Next, the control method in this embodiment will be described.
As shown in FIGS. 3A to 3C, when the generated current IFC of the fuel cell 1 rapidly decreases, the reaction gas inflow command value also changes rapidly in the direction of decrease. When the pressure exceeds a predetermined value, the cooling water inflow command value gradually decreases based on the predetermined delay rate as shown by the solid line in FIG. And since the rotational speed of the circulation pump 5 controlled by such a cooling water inflow command value is gradually reduced, the pressure in the cooling water flow path 10a does not occur without causing a water hammer phenomenon or the like. As shown by the solid line in FIG. 3D, it gradually decreases.
[0021]
According to the above, the following effects can be obtained in the present embodiment.
When the reaction gas inflow command value changes in the decreasing direction, the cooling water inflow command value is decreased with a predetermined delay, so that even if the power generation current IFC of the fuel cell 1 rapidly decreases, the cooling water, the reaction gas, Thus, it is possible to prevent the deterioration of the seal of the fuel cell 1 and the breakage of the electrolyte membrane.
[0022]
As mentioned above, this invention is implemented in various forms, without being limited to the said embodiment.
In the present embodiment, the delay rate DR is determined from the change ΔIFC in the generated current. However, the present invention is not limited to this. For example, the delay rate DR may be determined from the change in the inter-electrode differential pressure.
In the present embodiment, a system based on the premise that the cooling water pressure is lower than the reaction gas pressure is disclosed. However, in the fuel cell system that needs to maintain the pressure difference between the cooling water and the reaction gas within a predetermined range. The present invention can be suitably implemented.
[0023]
【The invention's effect】
According to the first aspect of the present invention, when the inflow command value of the reaction gas changes in the decreasing direction, the inflow command value of the cooling water is decreased with a predetermined delay, so that the predetermined kinetic energy of the cooling water is reduced. It can be gradually attenuated, and even if the power generation output of the fuel cell decreases sharply, the pressure difference between the coolant and the reaction gas is maintained, and the deterioration of the fuel cell seal and the electrolyte can be prevented. .
[0024]
According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, the larger the decrease in the generated current is, the more the cooling water command value is decreased with a larger delay, so that a larger kinetic energy is obtained. Since it can be attenuated by a large delay and the increase in the pressure of the cooling water can be suppressed, the pressure difference between the cooling water and the reaction gas can be maintained.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a fuel cell cooling device according to the present invention.
FIG. 2 is a flowchart showing a flow of processing by an ECU.
FIG. 3 is a sequence diagram (a) showing an output state of a power generation current of a fuel cell, a sequence diagram (b) showing an output state of an inflow command value of a reaction gas output to a supercharger, and an output to a circulation pump 5 It is the sequence figure (c) which shows the output state of the inflow command value of cooling water, and the sequence figure (d) which shows the state of inter-electrode differential pressure.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fuel cell 2 Air supply system 3 Hydrogen supply system 4 Supercharger 5 Circulation pump 6 Radiator 7 Radiator fan 8 Pressure balancer 9 ECU (Differential pressure control means)
10 Cooling device 10a Cooling water flow path IFC Generated current

Claims (2)

Provided in a fuel cell that generates power by electrochemical reaction by flowing fuel gas and oxidant gas as reaction gas, and controlling the circulation pump according to the generated current generated from the fuel cell, In a fuel cell cooling device for circulating cooling water between radiators,
When the reaction current inflow command value changes in the decreasing direction due to the generation current of the fuel cell changing in the decreasing direction, the pressure difference between the electrodes gradually decreases the cooling water inflow command value with a predetermined inclination. A fuel cell cooling apparatus comprising control means. The inter-electrode differential pressure control means is
2. The fuel cell cooling apparatus according to claim 1, wherein the cooling water inflow command value is decreased with a larger inclination as the change in the generated current of the fuel cell is larger. 3.

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