초록

A homogeneous charge compression ignition engine is fueled within a warm-up region of engine temperatures using a minimally defined fuel mass schedule and injection timings and simple interpolative techniques.

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The invention claimed is: 1. A method of operating an internal combustion engine in a four-stroke combustion cycle, said engine including a direct-injection fuel system, a spark-ignition system, and a variable volume combustion chamber defined by a piston reciprocating within a cylinder between top

The invention claimed is: 1. A method of operating an internal combustion engine in a four-stroke combustion cycle, said engine including a direct-injection fuel system, a spark-ignition system, and a variable volume combustion chamber defined by a piston reciprocating within a cylinder between top-dead center and bottom-dead center points, intake and exhaust passages, and intake and exhaust valves controlled during repetitive, sequential exhaust, intake, compression and expansion strokes of said piston, said method comprising: determining engine temperature within a predefined warm-up temperature region of engine operation, said warm-up temperature region including predefined non-overlapping low, middle and high temperature regions of engine operation; controlling intake and exhaust valves within said warm-up temperature region of engine operation to effect a partial-lift, negative valve overlap of about 180 to about 200 crank angle degrees; and in said low temperature region of engine operation, injecting a low temperature region predetermined total fuel mass comprising a low temperature region first injection terminating at about 350 to about 360 crank angle degrees before top dead center combustion and a low temperature region second injection terminating at about 270 to about 300 crank angle degrees before top dead center combustion; in said middle temperature region of engine operation, injecting a middle temperature region predetermined total fuel mass comprising a middle temperature region first injection terminating at about 270 to about 300 crank angle degrees before top dead center combustion; and in said high temperature region of engine operation, injecting a high temperature region predetermined total fuel mass comprising a high temperature region first injection terminating at about 370 to about 440 crank angle degrees before top dead center combustion and a high temperature region second injection terminating at about 25 to about 50 crank angle degrees before top dead center combustion. 2. The method of claim 1, wherein injecting a middle temperature region predetermined total fuel mass consists of only the middle temperature region first injection. 3. The method of claim 1, wherein injecting a middle temperature region predetermined total fuel mass further comprises a middle temperature region second injection terminating at about 360 to about 370 crank angle degrees before top dead center combustion. 4. The method of claim 1, further comprising: in a temperature region between adjacent ones of the low, middle and high temperature regions, injecting a fuel mass based on the engine temperature and interpolated from the two respective fuel masses corresponding to said adjacent ones of the low, middle and high temperature regions. 5. The method of claim 2, further comprising: in a temperature region between adjacent ones of the low, middle and high temperature regions, injecting a fuel mass comprising a first injection terminating at a crank angle based on the engine temperature and interpolated from the two respective first injection termination crank angles corresponding to said adjacent ones of the low, middle and high temperature regions. 6. The method of claim 3, further comprising: in a temperature region between adjacent ones of the low, middle and high temperature regions, injecting a fuel mass comprising a first injection terminating at a crank angle based on the engine temperature and interpolated from the two respective first injection termination crank angles corresponding to said adjacent ones of the low, middle and high temperature regions. 7. The method of claim 3, further comprising: in a temperature region between said middle and high temperature regions, injecting a fuel mass comprising a second injection terminating at a crank angle based on the engine temperature and interpolated from the two respective second injection termination crank angles corresponding to said middle and high temperature regions. 8. The method of claim 3, wherein: said low temperature region predetermined total fuel mass comprises a respective ratio of said respective first to said respective second low temperature injections, said middle temperature region predetermined total fuel mass comprises a respective ratio of said respective first to said respective second low temperature injections, said high temperature region predetermined total fuel mass comprises a respective ratio of said respective first to said respective second low temperature injections, and further comprising in a temperature region between adjacent ones of the low, middle and high temperature regions, injecting a fuel mass comprising respective first and second injections at a respective ratio based on the engine temperature and interpolated from the two respective injection ratios corresponding to said adjacent ones of the low, middle and high temperature regions. 9. An apparatus for controlling a direct-injection, spark ignition, internal combustion engine within a spark-assisted homogeneous-charge, compression-ignition range during engine warm-up at idle conditions, comprising: a control system monitoring engine temperature and effecting control of an engine warm-up procedure comprising intake and exhaust valve control to effect a partial-lift, negative valve overlap of about 180 to about 200 crank angle degrees, fuel mass injection according to an idle warm-up stable combustion minimum fuel mass delivery schedule, said schedule comprising: a low temperature fuel mass value in a low temperature region; a middle temperature fuel mass value in a middle temperature region, a high temperature fuel mass value in a high temperature region, and interpolated minimum fuel mass delivery values, estimated across a range of engine temperatures between said low temperature and said high temperature by interpolation based on said low temperature fuel mass value, said middle temperature fuel mass value, and said high temperature fuel mass value; and fuel mass injection timing to effect split injection effective to sustain said spark-assisted homogeneous-charge, compression-ignition operation. 10. The apparatus of claim 9, wherein said fuel mass injection timing comprises: in said low temperature region, a first end of injection between about 350 and 360 degrees before top dead center combustion and a second end of injection between about 270 and 300 degrees before top dead center combustion; in said middle temperature region, said first end of injection between about 360 and 370 degrees before top dead center combustion and said second end of injection between about 270 and 300 degrees before top dead center combustion; and in said high temperature region, said first end of injection between about 370 and 440 degrees before top dead center combustion and said second end of injection between about 25 and 50 degrees before top dead center combustion. 11. The apparatus of claim 9, wherein said low temperature region, said middle temperature region, and said high temperature region are defined by said engine temperature, and wherein said low temperature region is less than about 30 degrees Celsius, wherein said middle temperature region is between about 50 and 60 degrees Celsius, and wherein said high temperature region is between about 80 and 90 degrees Celsius.