Gas filling method

1. A gas filling method for filling a tank with gas from an accumulator of the gas in a gas filling system,

the gas filling system including:

the tank;

the accumulator; and

a pipe configured to connect the accumulator and the tank, and supply the gas from the accumulator to the tank,

the gas filling method comprising:

setting a target pressure rise rate which is a temporal change of a target tank pressure, when the tank is filled with the gas; and

adjusting, during filling of the tank with the gas, a flow rate of the gas supplied from the accumulator to the tank in a manner so that a dispenser pressure, which is a gas pressure in the accumulator, becomes a pressure that is higher than the target tank pressure and allows the target pressure rise rate to be maintained.

2. The gas filling method according to claim 1 , wherein

in the adjusting of the flow rate, the dispenser pressure that allows the target pressure rise rate to be maintained is calculated so as to match a sum of a pressure loss in the pipe and a tank pressure.

3. The gas filling method according to claim 2 , wherein

the pressure loss is calculated as a value obtained by dividing, by a gas density, a value obtained by multiplying a pressure loss coefficient by a square of a mass flow rate of the gas, and

the pressure loss coefficient is updated based on a detected pressure loss that is detected when supply of the gas from the accumulator is intentionally stopped during the supply of the gas.

4. The gas filling method according to claim 1 , wherein

the target pressure rise rate is set to a constant pressure rise rate.