Internal-combustion engines – Charge forming device – Fuel injection system
Utility Patent
1997-11-03
2001-01-02
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S467000, C123S506000, C137S628000, C251S129210
Utility Patent
active
06167869
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to fuel injection apparatus, and more particularly to a fuel injector utilizing a solenoid as a control device.
BACKGROUND ART
Fuel injected engines employ fuel injectors, each of which delivers a metered quantity of fuel to an associated engine cylinder during each engine cycle. Prior fuel injectors were of the mechanically or hydraulically actuated type with either mechanical or hydraulic control of fuel delivery. More recently, electronically controlled fuel injectors have been developed. In the case of an electronic unit injector, fuel is supplied to the injector by a transfer pump. The injector includes a plunger which is movable by a cam-driven rocker arm to compress the fuel delivered by the transfer pump to a high pressure. An electrically operated mechanism either carried outside the injector body or disposed within the injector proper is then actuated to cause the fuel delivery to the associated engine cylinder.
The injector may include a valving mechanism comprising a spill valve and a direct operated check (DOC) valve wherein the former is operated to circulate fuel through the injector for cooling, to control injection pressure and to reduce the back pressure exerted by the injector plunger on the cam following injection. However, the need to separately control two valves leads to the requirement for two separate solenoids to control the valves. Besides adding to the overall cost of the injector, the need for two solenoids undesirably increases component count and undesirably increases the overall size of the injector and/or decreases the space available inside the injector for other components.
SUMMARY OF THE INVENTION
A fuel injector includes a single solenoid which is capable of operating a plurality of moveable elements, such as valves.
More particularly, in accordance with one aspect of the present invention, a fuel injector includes first and second valves, a solenoid including a solenoid coil and an armature assembly wherein the first and second valves are coupled to the armature assembly and a solenoid drive circuit coupled to the solenoid coil. The solenoid drive circuit delivers a first current waveform portion to the solenoid coil at a first time to cause the armature assembly to operate the first valve without operating the second valve. The drive circuit further delivers a second current waveform portion different from the first current waveform portion to the solenoid coil at a second time later than the first time to operate the second valve. Preferably, each of the first and second current waveform portions includes a pull-in current level and a holding current level. Also preferably, the first valve comprises a spill valve, and the second valve may comprise either a two-way valve or a three-way valve which controls fluid pressure delivered to a check.
Still further in accordance with the preferred embodiment, the armature assembly comprises a single armature member coupled to the first and second valves. Also, the armature assembly preferably comprises first and second armature members coupled to the first and second valves, respectively.
Still further in accordance with the preferred embodiment, the first and second valves are biased by first and second springs, respectively, wherein the first and second springs exert first and second biasing forces, respectively.
In accordance with a further aspect of the present invention, a fuel injector includes a solenoid having a single movable armature member and a solenoid coil and a solenoid driver circuit coupled to the solenoid coil. The driver circuit delivers a first current waveform portion to the solenoid coil at a first time to move the armature member to a first position and further delivers a second current waveform portion which may be different than the first current waveform portion to the solenoid coil at a second time later than the first time to move the armature member to a second position different than the first position.
In accordance with yet another aspect of the present invention, a method of controlling a fuel injector having first and second valves and a solenoid including a solenoid coil and an armature assembly wherein the first and second valves are coupled to the armature assembly comprises the steps of delivering a first current waveform portion to the solenoid coil at a first time to cause the armature assembly to close the first valve without closing the second valve and delivering a second current waveform portion which may be different from the first current waveform portion to the solenoid coil at a second time later than the first time to cause the armature assembly to close the second valve.
In accordance with a still further aspect of the present invention, a method of controlling a fuel injector having first and second moveable armatures controlled by a solenoid coil comprises the steps of delivering a first current waveform portion to the solenoid coil at a first time to move the first armature without substantially moving the second armature and delivering a second current waveform portion different than the first current waveform portion to the solenoid coil at a second time later than the first time to move the second armature.
The present invention utilizes a single solenoid to control a plurality of movable elements, leading to a desirable decrease in component count as well as other possible advantages.
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Coldren Dana R.
Forck Glen F.
Martin David E.
Ramalingam Prabhakar
Schneider Marvin P.
Caterpillar Inc.
Marshall O'Toole Gerstein Murray & Borun
Miller Carl S.
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