Sleeve metered unit pump and fuel injection system using the same
Pressurized injector actuation fluid, such as oil or fuel, is supplied to high pressure common rail by a fixed displacement fluid pump. Variable delivery from the pump is achieved by an improved sleeve metering approach. The sleeve surrounds the reciprocating piston and is manipulated to control venting of pumped fluid through vent ports in the piston. The sleeve is moved by preferably being the armature of a solenoid assembly. The varying of current to the solenoid coil alters the axial position of the sleeve relative to the piston to vary the effective pumping stroke of the piston.
1. A fuel injection system comprising:
a common rail;
a plurality of fuel injectors fluidly connected to said common rail;
a source of fluid;
a sleeve metered pump with an outlet fluidly connected to said common rail and an inlet fluidly connected to said source of fluid;
an inlet check valve fluidly positioned between said source of fluid and a pump chamber of said sleeve metered pump;
said sleeve metered pump including a solenoid assembly, at least one plunger that defines a vent and is positioned to reciprocate a stroke distance in a pump housing;
said solenoid assembly includes a coil disposed around said at least one plunger and a metering sleeve slidably mounted on each said at least one plunger; and
a camshaft operably coupled to said pump and being rotatable with respect to said at least one plunger.
2. The fuel injection system of claim 1 wherein a position of said metering sleeve is a function of current supplied to said solenoid assembly.
3. The fuel injection system of claim 1 wherein said metering sleeve has a first position in which said at least one vent is uncovered throughout said stroke distance; and
said metering sleeve has a second position in which said at least one vent is covered throughout said stroke distance.
4. The fuel injection system of claim 3 including a spring operably positioned in said pump housing to bias said metering sleeve toward said first position.
5. The fuel injection system of claim 1 wherein said solenoid assembly includes an armature; and
said armature is either a portion of said metering sleeve or operably positioned to move with said metering sleeve.
6. The fuel injection system of claim 1 wherein said at least one plunger is a single plunger.
7. The fuel injection system of claim 1 wherein said position of said metering sleeve is a function of current supplied to said solenoid assembly;
said metering sleeve has a first position in which said at least one vent is uncovered throughout said stroke distance, and a second position in which said at least one vent is covered throughout said stroke distance;
a spring operably positioned in said pump housing to bias said metering sleeve toward said first position;
said solenoid assembly includes an armature that is a portion of said metering sleeve;
said at least one plunger is a single plunger.
8. A method of controlling output from a sleeve metered pump in a common rail fuel injection system, comprising the steps of:
providing a sleeve metered pump that includes at least one plunger positioned to reciprocate a stroke distance in a pump housing and defining at least one vent, and further includes a solenoid assembly with a coil disposed around said at least one plunger and a metering sleeve slidably mounted on each said at least one plunger;
determining a desired effective pumping stroke for said sleeve metered pump;
determining a solenoid current magnitude that corresponds to said desired effective pumping stroke;
adjusting a position of said metering sleeve by supplying current to said solenoid assembly at a level corresponding to said solenoid current magnitude;
pumping fluid at least in part by rotating a camshaft, which is operably coupled to said sleeve metered pump, with respect to said at least one plunger; and
refilling a pump chamber at least in part by opening an inlet check valve fluidly positioned between the pump chamber and a source of fluid.
9. The method of claim 8 wherein said adjusting step is accomplished by applying a magnetic force to said metering sleeve via said coil.
10. The method of claim 8 wherein, if said desired effective pumping stroke is determined to be zero, then setting said solenoid current magnitude to zero.
11. The method of claim 8 wherein, if said desired effective pumping stroke corresponds to a maximum fluid delivery, then said adjusting step includes supplying a current that is sufficient to move said metering sleeve into contact with a stop surface.
12. The method of claim 8 wherein said determining steps are accomplished with an electronic control module.