GAS FUEL SUPPLY DEVICE, HIGH-PRESSURE GAS INJECTION DIESEL ENGINE, AND LIQUEFIED GAS FUEL SUPPLY METHOD FOR HIGH-PRESSURE GAS INJECTION DIESEL ENGINE

A gas fuel supply device (10) is equipped with: a reciprocating pump (20) that is driven by a hydraulic motor (50) and raises to a prescribed pressure the pressure of a liquefied gas that has been introduced, after which it is discharged; a hydraulic pump unit (53) that supplies hydraulic pressure for driving the hydraulic motor (50) from a variable-capacity hydraulic pump (51) driven by an electric motor; a heating device (30) that heats and gasifies the liquefied gas which is supplied from the reciprocating pump (20) and the pressure of which has been increased; a control unit (80) that adjusts the rotational velocity of the hydraulic motor (50) and maintains a constant gas fuel outlet pressure for the heating device (30); and an engine inlet gas decompression valve (40) that adjusts the pressure of the gas fuel injected into the combustion chamber.