Fuel-actuated fuel injector having cooling fuel circuit and method

A fuel injector comprising:

• an injector housing including an injector body having formed therein a high-pressure fuel passage, a drain opening, and a valve pin bore extending to an armature cavity, the injector housing further including a nozzle piece having formed therein a plurality of spray orifices, and a valve seat plate clamped between the injector body and the nozzle piece and having formed therein each of a valve seat and a check control passage fluidly connected to the valve seat;
• a nozzle check having a closing hydraulic surface exposed to a fluid pressure of a control chamber formed between the valve seat plate and the nozzle check and fluidly connected to each of the check control passage and the high-pressure fuel passage;
• a cooling circuit including the armature cavity, a low-pressure fuel passage formed at least in part by the injector body, and a flushing drain formed by the injector body and directly fluidly connected to at least one of the valve pin bore or the armature cavity and extending to the drain opening;
• and
• an injection control valve in contact with the valve seat and positioned fluidly between the check control passage and the low-pressure passage.

A method of operating a fuel system for an internal combustion engine:

• feeding a pressurized fuel from a pressurized fuel reservoir to a high-pressure inlet of a fuel injector in the fuel system;
• energizing an electrical actuator to open an injection control valve such that a fuel pressure in a check control chamber in the fuel injector is reduced;
• conveying spent actuating fuel expelled from the check control chamber through a low-pressure fuel passage extending to an armature cavity in the fuel injector;
• exchanging heat between the spent actuating fuel and components of the fuel injector exposed to the armature cavity;
• flushing spent actuating fuel from the armature cavity through a flushing drain fluidly connected between the armature cavity and a drain opening formed in an outer surface of the fuel injector;
• and
• the conveying spent actuating fuel includes conveying spent actuating fuel through a leakage clearance formed between the injection control valve and an injector housing of the fuel injector.