Fuel injector method and apparatus

A method of fuel injection with a fuel injector comprising a nozzle body with an elongated valve bore, an annular valve seat and longitudinally spaced, coaxial, upper valve guide and lower valve ring above the valve seat;

• an elongated needle valve in the valve bore having longitudinally spaced, coaxial, upper guide and lower ring which cooperate with the upper valve guide and lower valve ring respectively of the nozzle body to provide axial movement of the needle valve within the valve bore between a lower dosed position in engagement with the valve seat and an upper fully open position having a predetermined maximum lift;
• the nozzle body having hole means connected to the valve bore below the valve seat for injection of fuel;
• the nozzle body providing an upper fuel chamber surrounding the needle valve between the upper valve guide and lower valve ring and a lower fuel chamber surrounding the needle valve between the lower valve ring and valve seat;
• closure spring means biasing the needle valve downwardly into engagement with the valve seat, including first stage spring means holding the needle valve in its closed position and biasing the needle valve downwardly as it is lifted upwardly from its closed to its fully open position and second stage spring means biasing the needle valve downwardly as it is lifted upwardly from a predetermined intermediate position with a predetermined intermediate lift to its fully open position;
• the upper guide of the needle valve having a greater diameter than the valve seat to provide a differential area for hydraulically opening the needle valve against the bias of the valve closure spring means;
• the upper fuel chamber being connected to receive high pressure pulses of fuel for opening the needle valve against the bias of the spring means and for supplying fuel for fuel injection tiaough the hole means;
• the method comprising the steps of providing a predetermined fuel metering passage between the lower rings of the nozzle body and needle valve for metering fuel between the upper and lower fuel chambers during only an initial increment of upward movement of the needle valve from its closed position substantially less than said predetermined maximum lift and slightly greater than said predetermined intermediate lift, and a corresponding last increment of downward movement of the needle valve, thereby to regulate the rate of fuel injection during said initial increment of upward movement and the pressure in the lower fuel chamber during said last increment of downward movement.

A fuel injector comprising a nozzle body with an elongated valve bore, an annular valve seat and longitudinally spaced, coaxial, upper valve guide and lower outer valve ring above the valve seat;

• an elongated nozzle needle valve in the valve bore having longitudinally spaced, coaxial, upper guide and lower inner ring which cooperate with the valve guide and outer ring respectively of the nozzle body to provide axial movement of the needle valve within the valve bore between a lower closed position in engagement with the valve seat and an upper fully open position with a predetermined maximum lift;
• the nozzle body having hole means connected to the valve bore below the valve seat for injection of fuel;
• the nozzle body providing an upper fuel chamber surrounding the needle valve between the upper valve guide and outer ring and a lower fuel chamber surrounding the needle valve between the outer ring and valve seat;
• two stage valve closure spring means biasing the needle valve downwardly into engagement with the valve seat, including first stage spring means holding the needle valve in its closed position and biasing the needle valve downwardly as it is lifted upwardly from its closed to its fully open position and second stage spring means biasing the needle valve downwardly as it is lifted upwardly from a predetermined intermediate position with a predetermined intermediate lift to its fully open position;
• the upper guide of the needle valve having a diameter greater than both the inner ring and valve seat and the inner ring having a diameter greater than the valve seat to provide two differential areas for hydraulically opening the needle valve against the bias of the spring means;
• the upper fuel chamber being connected to receive periodic high pressure pulses of fuel for opening the needle valve against the bias of the spring means and for supplying fuel for fuel injection through the hole means;
• the outer rinq forming an outer metering ring with an internal, annular metering surface;
• the inner ring forming an inner metering ring with an external annular, metering surface;
• the inner metering ring, with the needle valve in its closed position, being received within the outer metering ring with a predetermined axial overlap greater than said predetermined intermediate lift and with a predetermined clearance between the inner and outer metering surfaces providing a metering passageway to regulate fuel flow between the upper and lower fuel chambers during predetermined opening movement of the needle valve from its closed position greater than said intermediate lift and to regulate the pressure in the lower fuel chamber durinq the last part of the closing movement of the needle valve.

A method of fuel injection with a fuel injector comprising a nozzle body with an elongated valve bore, an annular valve seat and longitudinally spaced, coaxial, upper valve guide and lower outer valve ring above the valve seat;

• an elongated needle valve in the valve bore having longitudinally spaced, coaxial, upper guide and lower inner ring which cooperate with the valve guide and outer ring respectively of the nozzle body to provide axial movement of the needle valve within the valve bore between a lower closed position in engagement with the valve seat and an upper fully open position having a predetermined maximum lift;
• the nozzle body having hole means connected to the valve bore below the valve seat for injection of fuel;
• the nozzle body providing an upper fuel chamber surrounding the needle valve between the Upper valve guide and outer ring and a lower fuel chamber surrounding the needle valve between the outer ring and valve seat;
• closure spring means biasing the needle valve downwardly into engagement with the valve seat, including first stage spring means holding the needle valve in its closed position and biasing the needle valve downwardly as it is lifted upwardly from its closed to its fully open position and second stage spring means biasing the needle valve downwardly as it is lifted upwardly from a predetermined intermediate position with a predetermined intermediate lift to its fully open position;
• the upper guide of the needle valve having a diameter greater than both the inner ring and valve seat and the inner ring having a diameter greater than the valve seat to provide two differential areas for hydraulically opening the needle valve against the bias of the spring means;
• the upper fuel chamber being connected to receive high pressure pulses of fuel for opening the needle valve against the bias of the spring means and for supplying fuel for fuel injection through the hole means;
• the method comprising the steps of providing predetermined fuel metering.passage between the outer and inner rings of the nozzle body and needle valve for metering fuel between the upper and lower fuel chambers during predetermined.opening movement of the needle valve from its closed position greater than said predetermined intermediate lift and during the last part of the closing movement of the needle valve, thereby to regulate the rate of fuel injection during said predetermined opening movement and the pressure in the lower fuel chamber during said last part of closing movement.