The majority of compression-ignition and spark-ignition internal combustion engines utilize an oil delivery system via oil delivery tubes through piston flow nozzles. Excessive piston oiling occurs in large part because original equipment manufacturers design oiling systems for worst-case conditions and, in particular, have limited means to reduce oiling for a cylinder-deactivated state, a light engine load state and/or, idle periods.
A system to improve fuel economy and vehicle emissions has been developed, known as Cylinder Cutout (CCO) and more recently, a method introduced to improve cylinder pumping losses called Cylinder Deactivation (CDA), to shutoff cylinder injection during light load conditions. CDA is accomplished by turning off valve motion, fuel injectors, and spark ignition in a single or multiple cylinders. In contrast, CCO only turns off the fuel injectors to predetermined cylinders. In both CCO and CDA, a non-firing cylinder creates a lower cylinder gas pressure and may result in oil leakage past the top compression ring's end gap, and into the combustion chamber. The longer a cylinder remains in a “deactivated” state, the complete cylinder wall and piston assembly becomes cooler and promotes oil consumption issues. The tolerances increase as the parts cool down and, in particular, piston ring end-gaps open up with an absence of heat, wherein more oil is drawn upward into the combustion chamber. CCO technology is also present in “Jacob-brake” and “engine-brake” applications, having been used for years to assist heavily loaded trucks and heavy-duty vehicles in stopping. When Jacob-brake activation occurs, the deactivated cylinders will allow the engine to “self-brake” on a downhill slope by reducing engine pumping efficiency in the non-firing cylinder(s). CDA/CCO also occurs in diesel engines during particulate filter regeneration, to burn off accumulated particulate matter.
Zheng Ma PhD, of General Motors addresses this issue of oil leakage in SAE Technical Paper 2010-01-1098, “Oil Transport Analysis of a Cylinder Deactivation Engine”. Ma suggests a redesign of the piston lands and drain-holes and, in particular, limits the oil supply to the bottom of the piston. Takashi Inoue of Toyota Motor Corp authored an SAE Paper “Study of Oil Consumption of Automotive Engine” ISSN: 0148-7191, describes transient oil consumption during engine-brake conditions, wherein a higher intake manifold vacuum occurs, creating a transient reverse oil flow upward in the cylinder bore. Engine manufacturers design their piston ring packages primarily for the engine operating in an active “firing state” and not in a “deactivated state”, which may lead to an oil leakage issue.
One methodology to limit oil leakage is a re-design of ring sets and pistons that seal more effectively for both active and deactivated firing states. A number of years ago, GM experienced a growing issue with their version of cylinder deactivation, termed “Active Fuel Management”. Designers learned that deactivating cylinders on long highway drives definitely reduced fuel consumption, however, inactive pistons still reciprocate in the cylinder bores and generate heat from frictional forces. Lubrication over spraying led to “cooking” the oil on a hot piston, resulting in a buildup of burnt oil deposits on the piston rings, causing continuous oil consumption. GM introduced a shield to keep the oil from “slugging-up” the piston bore. Although the above prior art and research has improved the understanding of excessive lubrication during cycles of cylinder inactivity (no pulse width), idle conditions and, light load scenarios, the leakage of lubrication oil to the combustion chamber, continues to be a sizeable issue.
Another concept addressing this issue is publication US2020/0018197A1 to McCarthy, Jr. PhD et al. of Eaton Ltd., wherein the intake and exhaust valve sequencing is manipulated during cylinder deactivation. The motivation is to promote “increased in-cylinder pressure” to reduce oil accumulation in the cylinder.
U.S. Pat. No. 8,955,474 B1 to Derbin et al. generally describes a system for reducing soot in diesel engines; however, there is no method or system of addressing lubrication mitigation in deactivated cylinders, cylinder cutout, engine-braking and, in particular, for when deactivation is rotated to other active cylinders in a plurality of rotation sequences.
Two primary challenges are associated with current lubrication mitigation schemes. First, they may not effectively cover all ranges of load expectations of the engine and, secondly, cylinder deactivation lubrication ends up becoming complicated and cumbersome requiring expensive electro-mechanical infrastructure. Hence, there is a continuing need for a robust control methodology to lubricate the cylinder assembly throughout the operation of all engine conditions of load/speed and, in particular, during cylinder deactivation, to mitigate excessive reverse flow of oil to the combustion chamber (firedome).
It is therefore an object of the present invention to provide a mitigated means to lubricate the piston dome underside and cylinder wall for selected deactivated cylinders and, additionally, for all remaining active cylinders. The present invention comprises an oil sump, an oil pump, oil lubricating distribution tube (common-rail manifold), an electro-mechanical solenoid capable of being pulse-width-modulated (pwm) and a flow nozzle directed to the piston dome underside. In addition, an engine control module “ECM”, including a plurality of sensors and tables, including a throttle position sensor, rpm sensor, coolant temperature sensor, oil pressure sensor, map sensor, injector base fuel table, timing table and, a governor map is generally used. It is important to note that engine manufacturers incorporate various sensors to measure and manage their own specific fuel injection control systems, and may differ somewhat from manufacturer to manufacturer.
Operation of a modern electronically controlled fuel injected internal combustion engine, requires the operator to press on the vehicle pedal, wherein the ECM reads this pedal position as a requested throttle position and additionally, engine speed (RPM) is measured by a magnetic pickup from a single or multi-toothed gear. A (TORQUE-RPM) table incorporates a non-volatile memory array of desired injector pulse widths, commonly termed an (EFI BASE) table and, specifically, these pulse widths translate to a “duty cycle” value. A pulse-width-modulated (PWM) signal electronically modulates the fuel injector's plunger that is controllable with a duty cycle between (0 to 100%). The “ON” time of an electronic fuel injector, is the percentage “duration” of the duty cycle that the spring-loaded injector allows fuel delivery to the combustion chamber. The finalized fuel injection duty cycle dictates the desired engine brake torque to the vehicle drivetrain and represents the total horsepower demands placed on the engine pistons, engine components, and all vehicle drive train components. A typical ECM will provide a proportional-integral-derivative (PID) control in a closed-loop fashion, to each cylinder's fuel injection drive and feedback circuitry. The ECM controls each fuel injector independently, and follows the desired dictates of the fuel table, filled with “finalized” duty cycle values.
The present invention leverages the modern fuel injection base table data value(s), wherein a requested table value is evaluated by a software matching-filter and, specifically, adjusts the value to one of five specific duty cycle values that most closely matches the “requested” value. A lubrication module performs the filter and adjustment control, wherein, each requested injector fuel duty cycle value becomes a requested “oil jet” duty cycle, determined from five distinct choices (Cases). A summing junction and a proportional-integral (PI) stage, accept this modified duty cycle, wherein the signal drives the oil solenoid valve that delivers lubricating oil through its respective flow nozzle. In addition, the nozzle is preferably directed upward to the piston underside, wherein, more than one nozzle may exist per cylinder. A 100% duty cycle represents full flow and, in particular, allows full volumetric pump flow of oil through the nozzle to the piston dome underside, i.e. cylinder assembly. A majority of diesel engines and a percentage of high output powered gasoline engines incorporate oil-lubrication jet nozzles for piston lubrication and allow the pump to operate at full flow based on engine speed. In general, rated speed will yield full pump flow. The widely used fixed and volumetric pump flow designs accommodate lubrication needs for worst-case engine operating conditions and, specifically, may create an over-lubricating issue for lower imposed loads.
The present invention “smart firedome” accommodates lubrication for light loads and, in particular, detects cylinder deactivation as a (0% fuel injection duty cycle). This “injector shutoff state” dictates a substantially lowered quantity of oil delivered to the piston underside and, specifically, just enough to overcome the cylinder bore frictional forces. Again, when a cylinder is not firing (deactivated or inactive), the cylinder's combustion chamber temperature and pressure is lowered and the need for lubrication to the piston dome underside and cylinder wall is substantially reduced. It will be appreciated this present embodiment mitigates oil usage for the entire spectrum of the piston dome underside and cylinder wall with an improvement upon present lubrication methods and, in particular, does so by reducing costs with a minimal amount of hardware/software infrastructure modifications.
For a more complete understanding of this disclosure, reference is made to the following description, taken in conjunction with the accompanying drawings, in which:
The embodiment described in the present invention is by way of illustration only and should not be construed in any way, to limit the scope of the invention. Those skilled in the art will understand that the principles of the present invention may be implemented in any type of suitably arranged device or system. The drawings may not necessarily be to scale and certain features illustrated in a schematic form. As used in the specification and claims, for the purpose of describing and defining the disclosure, the term “substantially” is used herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue. “Comprise”, “include”, and/or plural forms of each are open-ended, include the listed parts, and can include additional parts that are not listed. For purposes of clarity, the same reference numbers apply to
ECM 50 comprises a CPU 52, System Clock 54, Memory 56 (includes RAM, EEPROM, FLASH), memory look-up tables, including BOI 58, DEMAND TORQUE 60, TORQUE/RPM/BOI 62, FUEL INJECTION MODULE 64, Fuel Injector Driver 66 and the fuel injector(s) 40, 42. The Oil Jet Lubrication Control 68, is in communication with both the ENGINE CONTROL ROUTINES 70 and the Oil Jet Solenoid Valve Driver 72. A programmable timer module (PTM) 74 is also in communication with the Oil Jet Solenoid Valve Driver 72 and, specifically, is responsible for creating the base frequency and duty cycle modulation for driving the solenoid valve(s) 20, 22. Electronic control signal lines 76, 78 interface the oil jet module 72 to solenoid valve(s) 20, 22. It will be appreciated that a “shunt current” circuit exists in Block 72 (not illustrated) for each oil jet solenoid 20, 22 as a method to sense feedback current. Each oil jet solenoid is controlled independently to maintain the “desired” oil jet duty cycle in a Proportional/Integral (PI) control-loop (not illustrated in
The SENSORS 84 block represents sensors commonly used on spark-ignition and compression-ignition engines 10 and may include but not limited to manifold absolute pressure (MAP), engine speed (RPM), vehicle throttle position, engine oil temperature, oil pressure, coolant temperature (individual sensors not illustrated). Note, the dashed boundary line (86) within ECM 50 and Engine 10, indicates the “smart firedome” system.
Turning to
The OIL JET Lubrication Control 68 receives a continuous updated “oil jet % duty cycle value” representing fuel injection (not illustrated). This value is evaluated through a set of software “lubricating/oiling rules” and, specifically, evaluated for equivalence by a set of five specific “Case” scenarios (discussed in
Turning now to
While this disclosure has described certain embodiments and generally associated methods, alterations and permutations of these embodiments and methods will be apparent to those skilled in the art. Accordingly, the above description of example embodiments does not define or constrain this disclosure. Other changes, substitutions, and alterations are also possible without departing from the scope of this disclosure, as defined by the following claims.