Trapped volume split check assembly in fuel injector

A fuel injector comprising:

• an injector housing defining a longitudinal axis, and having formed therein a high pressure inlet, a fuel cavity fluidly connected to the high pressure inlet, a low pressure drain, and a check control chamber, and the injector housing further including a nozzle having formed therein a plurality of spray outlets;
• an injection control valve assembly including a control valve movable from a closed position, where the control valve blocks the check control chamber from the low pressure drain, to an open position;
• a split check assembly within the injector housing and including a control piece having a check top surface exposed to the check control chamber, and an outlet piece coaxially arranged with the control piece and having a tip in contact with the injector housing to block the spray outlets from the fuel cavity;
• the split check assembly further including a check sleeve receiving the control piece and the outlet piece therein and, together with the control piece and the outlet piece, forming a trapped volume;
• the trapped volume hydraulically couples movement of the control piece and the outlet piece from advanced positions to retracted positions, to open the spray outlets to the fuel cavity, based on the moving of the control valve from the closed position to the open position;
• and
• a starting rate shape clearance is formed between the check sleeve and at least one of the control piece or the outlet piece and fluidly connects the trapped volume to the fuel cavity.

A method of operating a fuel system comprising:

• moving a control piece in a split check assembly in a fuel injector from an advanced position toward a retracted position;
• opening an outlet piece of the split check assembly hydraulically coupled to the control piece based on the moving of the control piece toward a retracted position;
• leaking fuel, through a starting rate shape clearance formed between a check sleeve and at least one of the control piece or the outlet piece, between a fuel cavity in the fuel injector and a trapped volume formed between the control piece and the outlet piece, during the opening of the outlet piece;
• and
• shaping a rate of fuel injection through spray outlets in the fuel injector opened by the opening of the outlet piece, based on the leaking of fuel between the trapped volume and the fuel cavity.