Fuel cell system

1. A fuel cell system comprising:

a fuel cell that generates electricity through an electrochemical reaction between a fuel gas and an oxidant gas;

an oxidant gas supply piping that supplies the oxidant gas to the fuel cell;

an oxidant gas discharge piping that discharges the oxidant gas from the fuel cell;

an air compressor disposed on the oxidant gas supply piping;

a turbine disposed on the oxidant gas discharge piping and provided on the same shaft as the air compressor;

a pressure regulating valve disposed on the oxidant gas discharge piping between the fuel cell and the turbine;

a check valve that is provided between the turbine and the pressure regulating valve and that communicates with outside air so as to introduce an external air to the turbine; and

an air filter disposed at an outside air side of the check valve,

wherein a housing that constitutes the turbine has an air suction port of the turbine which is provided integrally with the housing or provided separately from the housing, and

wherein a wall of the air suction port is provided with the check valve that provides communication between an inside and an outside of the air suction port and the air filter is attached to the wall so as to cover the check valve.

2. The fuel cell system according to claim 1 , wherein the check valve is disposed below a position of a central horizontal line of the air suction port of the turbine.

3. The fuel cell system according to claim 1 , further comprising a cooling medium circulation piping that circulates a cooling medium in the fuel cell,

wherein a portion of the cooling medium circulation piping is provided directly on the check valve or near the check valve.

4. A fuel cell system comprising:

a fuel cell to generate electric power through an electrochemical reaction between a fuel gas and an oxidant gas;

an oxidant gas supply piping which is connected to the fuel cell and through which the oxidant gas is to flow to the fuel cell;

an oxidant gas discharge piping which is connected to the fuel cell and via which the oxidant gas is to be discharged from the fuel cell;

an air compressor connected to the oxidant gas supply piping and being rotatable around a rotational shaft;

a turbine connected to the oxidant gas discharge piping and being rotatable around the rotational shaft;

a pressure regulating valve disposed in the oxidant gas discharge piping between the fuel cell and the turbine;

a check valve connected to the oxidant gas discharge piping between the turbine and the pressure regulating valve to introduce an external air to the turbine; and

an air filter disposed at an outside air side of the check valve,

wherein a housing that constitutes the turbine has an air suction port of the turbine which is provided integrally with the housing or provided separately from the housing, and

wherein a wall of the air suction port is provided with the check valve that provides communication between an inside and an outside of the air suction port and the air filter is attached to the wall so as to cover the check valve.

5. The fuel cell system according to claim 4 , wherein the check valve is disposed below a position of a central horizontal line of the air suction port of the turbine.

6. The fuel cell system according to claim 4 , further comprising a cooling medium circulation piping that circulates a cooling medium in the fuel cell,

wherein a portion of the cooling medium circulation piping is provided directly on the check valve or near the check valve.