In a hybrid vehicle with fuel cells and an engine mounted thereon as energy output
sources, the technique of the present invention adequately changes a working energy
output source according to a driving state of the hybrid vehicle. The hybrid vehicle
has the engine and a motor, both enabling power to be output to an axle. The hybrid
vehicle also has fuel cells as a main electric power supply for driving the motor.
The technique of the present invention changes the working energy output source
between the fuel cells and the engine, in order to reduce the output of the fuel
cells with consumption of a fuel for the fuel cells. With a decrease in remaining
quantity of the fuel, the technique narrows a specific driving range, in which
the motor is used as the power source. The technique also causes the engine to
drive the motor as a generator and charges a battery not with electric power of
the fuel cells but with electric power generated by the motor. This arrangement
effectively prevents the fuel for the fuel cells from being excessively consumed
in one driving mode. The fuel cells can thus be used preferentially in a specific
driving state of the hybrid vehicle where the fuel cells have a high efficiency.