A fuel injection device is used in an internal combustion engine having a combustion chamber partitioned by a cylinder head, a cylinder, and a piston crown surface so that at least one of the amount of NOx, Pmax, and a thermal efficiency is maintained at a predetermined value. The fuel injection device includes a fuel injection change unit. The fuel injection change unit virtually divides the combustion chamber into N number of combustion zones where N is a natural number of 2 or more, and can change a fuel injection method according to the respective combustion zones. The fuel injection change unit divides the combustion chamber into the N number of combustion zones, thereby being capable of eliminating a difference of heat in the respective combustion zones, and precisely controlling an in-cylinder pressure P in the combustion chamber. As a result, the amount of NOx and the thermal efficiency can be optimized. Therefore, both of a reduction in the amount of NOx and the high thermal efficiency can be achieved.

A method for operating an internal combustion engine system using gaseous fuel is disclosed. The method includes injecting, by activating a fuel injector to generate a first injection in association with a compression stroke, a first amount of gaseous fuel into a pre-combustion chamber, wherein the first injection and the first amount of gaseous fuel are adapted so that an ignitable fuel-air mix is formed in the pre-combustion chamber but not in a main combustion chamber; igniting, by activating an igniter, the ignitable fuel-air mix in the pre-combustion chamber formed by the first injection; and injecting, by activating the fuel injector to generate a second injection after ignition of the first amount of fuel, a second amount of gaseous fuel into the pre-combustion chamber, wherein the second injection and the second amount of gaseous fuel are adapted so that fuel is forced through the orifices into the main combustion chamber.

A method for operating an internal combustion engine system using gaseous fuel is disclosed. The method includes injecting, by activating a fuel injector to generate a first injection in association with a compression stroke, a first amount of gaseous fuel into a pre-combustion chamber, wherein the first injection and the first amount of gaseous fuel are adapted so that an ignitable fuel-air mix is formed in the pre-combustion chamber but not in a main combustion chamber; igniting, by activating an igniter, the ignitable fuel-air mix in the pre-combustion chamber formed by the first injection; and injecting, by activating the fuel injector to generate a second injection after ignition of the first amount of fuel, a second amount of gaseous fuel into the pre-combustion chamber, wherein the second injection and the second amount of gaseous fuel are adapted so that fuel is forced through the orifices into the main combustion chamber.

A fuel injection control device is a control device controlling an injection of fuel by a fuel injector and includes: a setting part that sets a request injection quantity of an injection quantity requested of the fuel injector; a dividing part that divides the request injection quantity set by the setting part into a specified injection quantity and an adjusting injection quantity other than the specified injection quantity; an injection performing part that performs a dividing injection of an adjusting injection and a partial lift injection by the fuel injector, the adjusting injection injecting the adjusting injection quantity of fuel, the partial lift injection finishing a lift of a valve body of the fuel injector in a partial lift state before the valve body reaching a full lift position and injecting the specified injection quantity of fuel; and a learning part that learns an injection characteristic of the fuel injector at the time of the partial lift injection.