JPH031887Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a gas control device for a fuel cell, and in particular, to a gas control device for a fuel cell that controls the differential pressure between reactant gases.

Conventionally, there has been a gas control device for a fuel cell as shown in FIG. In the figure, fuel electrode 1a,
A fuel cell main body 1 having an air electrode 1b is housed in a sealed casing 2. Nitrogen is supplied to the casing 2 through a flow rate adjustment valve 3, and fuel and air are supplied through flow rate adjustment valves 4 and 5, respectively. It is fed to the fuel electrode 1a and the air electrode 1b. Pressure regulating valves 6, 7, and 8 are provided downstream of the housing 2, the fuel electrode 1a, and the air electrode 1b, respectively. Converters 9, 10, and 11 convert the nitrogen pressure, nitrogen-fuel differential pressure, and nitrogen-air differential pressure within the housing 2 into electrical signals, respectively. These converters 9,1
Signals 0 and 11 are sent to controllers 12 and 1, respectively.
3 and 14, and the pressure regulating valves 6, 7, and 8 are operated.

In the above-described fuel cell composed of the fuel electrode 1a and the air electrode 1b, in order to improve the output characteristics of the cell, the operating pressure of each of the reactant gases, for example, fuel and air, is approximately 3 to 6 kg/cm ² g. The pressure is maintained at . However, due to problems with rail pressure resistance of each reaction gas manifold (not shown) attached to the fuel cell main body 1, the fuel cell main body 1 is normally housed in a casing 2 pressurized with nitrogen, and the nitrogen pressure is The pressure is maintained at a value slightly higher than the pressure of each of the reactant gases. The reason for making the nitrogen pressure higher than the reaction gas pressure in this manner is to ensure safety against leakage.

On the other hand, between the fuel electrode 1a and the air electrode 1b of the fuel cell, there is an electrolyte matrix (not shown) containing an electrolytic solution.
The reactant gases are separated from each other, but if a large pressure difference occurs between the reactant gases, a phenomenon occurs in which one reactant gas enters the other electrode, i.e., a crossover occurs, which deteriorates the characteristics of the fuel cell. let For this reason, it is necessary to suppress the differential pressure between each reaction gas to a sufficiently low value. The allowable differential pressure of the reaction gas is, for example, several hundred mmAg, and therefore strict control of the gas pressure is required.

A conventional technique related to pressure control of reactant gas in a fuel cell will be explained with reference to FIG. flow control valve 3,
The pressure of the nitrogen, fuel, and air exiting from the outlets 4 and 5 is controlled by pressure regulating valves 6, 7, and 8 on the outlet side, respectively. That is, the nitrogen pressure in the housing 2 is detected by the pressure converter 9, compared with a set value by the controller 12, and the nitrogen pressure is controlled by sending an operating signal to the pressure regulating valve 6. The pressure of fuel and air is determined by converting the differential pressure between the nitrogen pressure in the housing 2, the fuel supply pressure, and the air supply pressure into differential pressure converters 10 and 1.
1, and are controlled by controllers 13, 14 and pressure regulating valves 7, 8 so that the respective differential pressures become predetermined values. Normally, this differential pressure is set to about several tens of millimeters of Ag.

Therefore, the operating pressure of the fuel cell is set by controlling the nitrogen pressure inside the housing 2 using the above control device, and the fuel pressure and air pressure are kept slightly lower than the nitrogen pressure at any operating pressure. Can be set to a low value. That is, by accurately controlling the differential pressures between nitrogen and fuel and between nitrogen and air, the differential pressure between fuel and air can be kept sufficiently low, and the aforementioned crossover phenomenon can be prevented.

However, the conventional devices described above cannot perform the above functions when the fuel cell is in steady operation, or when the fuel cell load fluctuations are slow and the operating pressure or flow rate fluctuations are slow. However, when sudden load fluctuations occur, the pressure balance is transiently disrupted, causing damage to the fuel electrode and
The disadvantage was that an undesirably large differential pressure was created between the air electrodes.

This idea was made in order to eliminate the drawbacks of the conventional ones as described above, and by providing a differential pressure buffer between the fuel and air lines of the fuel cell, the fuel and air can be maintained even during sudden load changes. It is an object of the present invention to provide a gas control device for a fuel cell that prevents abnormal pressure differentials from occurring between the two.

An embodiment of this invention will be described below with reference to FIGS. 2 and 3. In the figure, parts indicated by numerals 1 to 14 are the same as the conventional one in FIG. 1, but this device can directly absorb differential pressure into the bypass pipe between the fuel supply line and the air supply line. A mechanical differential pressure buffer 15 is provided. FIG. 3 shows a shock absorber 15 with coil springs 16 on both sides.
A piston 17 with pistons a and 16b stretched is housed in a cylinder 19 via an O-ring 18, and a fuel side line and an air side line are connected to both sides of the piston 17, respectively, and the displacement of the piston 17,
The expansion and contraction of the coil springs 16a and 16b absorbs and alleviates differential pressure fluctuations.

Next, the action and effect will be explained. The differential pressure buffer device 15 is provided between the fuel supply line and the air supply line, and has a differential pressure buffer function. During steady operation, the differential pressure between fuel and air is kept constant by controlling the nitrogen-fuel differential pressure and the nitrogen-air differential pressure, as described above, and the piston 17 of the shock absorber 15 is moved by the amount corresponding to this differential pressure. It is balanced by producing a displacement of .

Here, when a sudden load change occurs in the fuel cell, the opening degree of the flow rate control valves 4 and 5 changes by the operation of a load control system (not shown) of the fuel cell in accordance with the increase or decrease in load. At the same time, the pressure control system consisting of pressure control valves 6 to 8, converters 9 to 11, and controllers 12 to 14 attempts to control the differential pressure between nitrogen and fuel and nitrogen and air at a constant level. The above differential pressure temporarily fluctuates due to the delay in response and the variation in response speed of 6 to 8. If this happens, the balance of the differential pressure between fuel and air will be disrupted, but the variation in this differential pressure is absorbed by the differential pressure buffer 15, thereby preventing sudden variations in the differential pressure. That is, if the differential pressure between fuel and air fluctuates from that during steady operation, the piston 17 is displaced by the amount of this fluctuation, thereby mitigating the fluctuation in the differential pressure. Differential pressure displacement is alleviated by
This is because the expansion and contraction of the coil springs 16a and 16b causes volume changes in both gases. The expansion/contraction volume and spring constant of the coil springs 16a, 16b are determined from the gas volume of each circuit, allowable differential pressure, etc.

In the above embodiment, the differential pressure buffer device 15 is installed in the upstream circuit of the fuel cell, but the differential pressure buffer device 15 may be installed in the downstream circuit of the fuel cell.

As described above, this invention has a simple structure that does not require differential pressure detection means, so that it is possible to prevent excessive pressure differentials from occurring between the gases at the fuel electrode and air electrode even during rapid load changes in the fuel cell. Therefore, crossover between the two electrodes is prevented, and the effect that stable operation of the fuel cell can be continued is obtained.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a conventional device, FIG. 2 is a system diagram of an embodiment of this invention, and FIG. 3 is a longitudinal cross-sectional view of the same main part. 1...Fuel cell main body, 1a...Fuel electrode, 1b...
...air electrode, 2...housing, 3-5...flow control valve,
6-8...Pressure control valve, 9...Pressure transducer, 1
0, 11...Differential pressure converter, 12-14...Controller, 15...Differential pressure buffer, 16a, 16b
...Coil spring, 17...Piston, 18...O
-Ring, 19... cylinder. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Scope of utility model registration request] a fuel cell body housed in a sealed housing and having a fuel electrode and an air electrode; a circuit for detecting and controlling the pressure of nitrogen within the housing; fuel and air supplied to the fuel electrode and the air electrode, respectively; In a gas control device for a fuel cell, which is a circuit that controls the differential pressure between the cylinder and nitrogen, and a differential pressure buffer device that directly absorbs the differential pressure is connected to a bypass pipe between the fuel and air lines. 1. A gas control device for a fuel cell, characterized in that the differential pressure buffer device is provided with the differential pressure buffer device, which is formed by connecting fuel and air lines to both sides of a piston housed in a piston and tensioned with coil springs.