Fuel cell system including coolant de-airing passage

1. A fuel cell, comprising:

multiple unit cells stacked upright in a vertical direction or stacked in a vertically inclined orientation;

an insulating plate arranged on a vertically upper-side end of the stacked multiple unit cells;

a cooling medium supply manifold arranged to distribute a supply flow of a cooling medium into the multiple unit cells and a cooling medium discharge manifold arranged to join together discharged flows of the cooling medium from the multiple unit cells; and

a de-airing passage formed to release a gas accumulated in either the cooling medium supply manifold or the cooling medium discharge manifold,

wherein the cooling medium supply manifold and the cooling medium discharge manifold are respectively connected to a cooling medium supply piping and a cooling medium discharge piping on a vertically lower-side end of the fuel cell, and

the de-airing passage includes a lower end section, an upper end section, and an electric resistance-generating portion, the de-airing passage is formed such that the electric resistance-generating portion is located in the insulating plate, includes a tubular section, and extends in a direction perpendicular to a stacking direction of the unit cells, and the de-airing passage is connected to either the cooling medium discharge manifold or the cooling medium supply manifold on a vertically upper end side of the cooling medium discharge manifold or the cooling medium supply manifold.

2. The fuel cell in accordance with claim 1 , wherein one end of the de-airing passage is connected to either the cooling medium discharge manifold or the cooling medium supply manifold, and

the other end of the de-airing passage is connected to a joint for releasing the air at a position proximal to a middle of an outer circumferential side of the insulating plate.

3. The fuel cell in accordance with claim 2 , further comprising:

an end plate arranged adjacent to the insulating plate,

wherein the joint is received in the end plate such that the joint has no protrusion from a parallelepiped defined by an outer circumference of the end plate.

4. The fuel cell in accordance with claim 1 ,

wherein the multiple unit cells are arranged to form two parallel cell stacks,

the two cell stacks are stacked to generate voltages in opposite directions and are electrically connected by a common collector provided on a vertically lower side of the fuel cell, and

each of the two cell stacks has:

the insulating plate arranged on a vertically upper-side end of the cell stack of the unit cells;

the cooling medium supply manifold arranged to distribute a supply flow of the cooling medium into the cell stack of the multiple unit cells and a cooling medium discharge manifold arranged to join together discharged flows of the cooling medium from the cell stack of the multiple unit cells; and

the de-airing passage formed to release the gas accumulated in either the cooling medium supply manifold or the cooling medium discharge manifold.

5. The fuel cell in accordance with claim 4 , wherein one common insulating plate is provided across and over the two cell stacks as the insulating plate arranged on the vertically upper-side ends of the two cell stacks, and

the two de-airing passages are arranged to communicate with each other in the common insulating plate.