High pressure fuel injection unit

Abstract

An accumulator type of fuel injection nozzle having an injection valve, a first electromagnet for initiating fuel injection, and a second electromagnet for controlling the lift amount of the injection valve is provided with an energizing arrangement which enables effective fuel injection control but which greatly reduces the risk of burning damage to the electromagnets. The amp-turn characteristics of the first electromagnet coil provide for a rapid start-up time wherein the peak magnetic flux is reached relatively quickly. In contrast, the amp-turn characteristics of the second electromagnet coil provide for a more gradual start-up time so that peak magnetic flux is reached more gradually. The second electromagnet coil is also adapted to achieve a relatively large magnetic flux without the need for large current supply. In operation, when the second electromagnet is energized, such energization is started before energization of the first electromagnet for a particular fuel injection cycle.

We claim: 
     
       1. An accumulator type of injection nozzle comprising an outer housing assembly defining a cavity partitioned into an accumulator chamber adapted to be supplied with high pressure fuel and a coil chamber, a nozzle port leading from said accumulator chamber, an injection valve moveable between a closed position and an open position for controlling the discharge of fuel from said accumulator chamber through said nozzle port, a control chamber for receiving pressurized fuel, an actuating member supported for movement within said control chamber and associated with said injection valve for retaining said injection valve in its closed position when said control chamber is pressurized and for movement of said injection valve to its open position when pressure is relieved in said control chamber, valve means moveable between a closed position for maintaining pressure in said control chamber and an open position for relieving pressure in said control chamber for effecting fuel discharge through said nozzle port, a first electromagnet within said outer housing assembly for moving said valve means to one of said positions when said first electromagnet is energized, and a second electromagnet within said outer housing assembly for controlling the lift amount of said injection valve by selectively energizing or de-energizing said second electromagnet, .Iadd.wherein said first and second electromagnets have first and second coils respectively, said first coil being wound with a lesser number of turns than said second coil and the wire of said first coil having a larger diameter than the wire of said second coil and .Iaddend.wherein when said second electromagnet is energized, energization of said second electromagnet is started before energization of said first electromagnet for a given fuel injection cycle. .[.2. An accumulator type of injection nozzle as recited in claim 1, wherein said first and second electromagnets have first and second coils respectively, the wire of said first coil having a larger diameter than the wire of said second coil and said first coil is wound 
     
     
        with a lesser number of turns than said second coil..]. 3. An accumulator type of injection nozzle as recited in claim .[.2.]..Iadd.1.Iaddend., wherein the amp-turn characteristics of said first coil is such that the current supplied to said first coil is greater than its number of turns so that, when energized, said first coil reaches peak magnetic flux more 
     
     
        quickly than said second coil when said second coil is energized. 4. An accumulator type of injection nozzle as recited in claim 3, wherein the amp-turn characteristics of said second coil is such that the current 
     
     
        supplied to said second coil is less than its number of turns. 5. An accumulator type of injection nozzle as recited in .[.2.]. .Iadd.1.Iaddend., wherein the amp-turn characteristics of said second coil is such that the current supplied to said second coil is less than its number of turns so that, when energized, said second coil reaches peak magnetic flux less quickly than said first coil when said first coil is 
     
     
        energized. 6. An accumulator type of injection nozzle as recited in claim 1, further comprising a regulating member moveable by said second electromagnet when energized such that when said second electromagnet is energized, movement of said regulating member is completed before energization of said first electromagnet for a given fuel injection cycle. 
     
     
        . An accumulator type of injection nozzle as recited in claim 1, wherein said first electromagnet is within said coil chamber and said second electromagnet is within said accumulator chamber. .Iadd.8. An accumulator type of injection nozzle as recited in claim 1, further comprising a holder member having an upper surface and a bore formed therein, and a regulating member movable by said second electromagnet and comprised of a guide portion having upper and lower ends and slidably supported within the bore and an armature having a lower surface facing the upper surface of said holder member and fixed on the upper end of the guide portion, wherein when electric current is supplied to said second coil, the upper surface of said holder member and the lower surface of said armature each have a portion in contact with each other and each have another portion apart from each other. .Iaddend.