Onboard misfire, partial-burn detection and spark-retard control using cylinder pressure sensing
First Claim
1. A method of estimating the unburned fuel rate to the exhaust from at least one cylinder of a multi-cylinder engine in an automotive vehicle,said engine comprising a plurality of cylinders, each cylinder containing a reciprocatable piston and having a known volume at each position of said piston, said pistons being connected to a crank shaft for rotation through a top dead center position in their respective cylinders;
- said engine further comprising means for introducing air and fuel into said cylinders to form a combustible mixture, means for ignition of said combustible mixtures, means for exhausting combustion gases from said cylinders, a crank shaft position sensor to determine the position of said pistons with respect to their top dead center positions, a sensor for providing signals indicative of the pressure in said cylinder at predetermined crankshaft positions;
said vehicle comprising a programmed computer for controlling fuel delivery and optional exhaust gas recycle flow to said cylinders and ignition timing therein, and for detecting and recording possible engine operating conditions adverse to an exhaust gas treatment system of said vehicle, said computer being adapted to receive pressure indicative signals and crank shaft position signals from said sensors, said method being performed by said computer immediately following predetermined combustion events with respect to each cylinder in which said condition is to be detected and comprising, computing values indicative of motored pressure for a plurality of crankshaft angles based on values of the pressure indicative signals at crank angles before the top dead center position of the compression stroke of a said piston, determining a pressure indicative value for said cylinder at a predetermined crank angle after top dead center of the expansion stroke of said piston, calculating a pressure ratio of said pressure indicative value at said predetermined crank angle to the computed value of motored pressure at the same crank angle and subtracting a value of one from said pressure ratio to determine a modified pressure ratio at said crank angle, calculating the quotient of said modified pressure ratio and a predetermined reference value for complete burning at the current operating condition, using said quotient subtracted from one as a measure of the fraction of fuel unburned during said combustion event, and multiplying said value by the fuel delivered to the cylinder to estimate the amount of unburned fuel leaving the cylinder and storing said value in the engine control computer.
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Accused Products
Abstract
A method is disclosed for detecting misfire or partial burn and for controlling spark retard in the cylinders of an internal combustion engine operated under the control of a microprocessor and utilizing signals indicative of the pressure in said cylinder at crank angle positions before and after initiation of combustion. A ratio of the actual pressure to the motored pressure in the cylinder at one or more predetermined crank angles is used to estimate the fraction of fuel burned which, in turn, enables a determination of combustion failure in said cylinder cycle. Confirmation of said misfire or unacceptable partial burn leads to correction of engine operation by said controller and/or to a diagnosis of possible damage to the vehicle'"'"'s catalytic converter. This method also permits better engine operation under conditions of high spark retard.
67 Citations
19 Claims
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1. A method of estimating the unburned fuel rate to the exhaust from at least one cylinder of a multi-cylinder engine in an automotive vehicle,
said engine comprising a plurality of cylinders, each cylinder containing a reciprocatable piston and having a known volume at each position of said piston, said pistons being connected to a crank shaft for rotation through a top dead center position in their respective cylinders; - said engine further comprising means for introducing air and fuel into said cylinders to form a combustible mixture, means for ignition of said combustible mixtures, means for exhausting combustion gases from said cylinders, a crank shaft position sensor to determine the position of said pistons with respect to their top dead center positions, a sensor for providing signals indicative of the pressure in said cylinder at predetermined crankshaft positions;
said vehicle comprising a programmed computer for controlling fuel delivery and optional exhaust gas recycle flow to said cylinders and ignition timing therein, and for detecting and recording possible engine operating conditions adverse to an exhaust gas treatment system of said vehicle, said computer being adapted to receive pressure indicative signals and crank shaft position signals from said sensors, said method being performed by said computer immediately following predetermined combustion events with respect to each cylinder in which said condition is to be detected and comprising,computing values indicative of motored pressure for a plurality of crankshaft angles based on values of the pressure indicative signals at crank angles before the top dead center position of the compression stroke of a said piston, determining a pressure indicative value for said cylinder at a predetermined crank angle after top dead center of the expansion stroke of said piston, calculating a pressure ratio of said pressure indicative value at said predetermined crank angle to the computed value of motored pressure at the same crank angle and subtracting a value of one from said pressure ratio to determine a modified pressure ratio at said crank angle, calculating the quotient of said modified pressure ratio and a predetermined reference value for complete burning at the current operating condition, using said quotient subtracted from one as a measure of the fraction of fuel unburned during said combustion event, and multiplying said value by the fuel delivered to the cylinder to estimate the amount of unburned fuel leaving the cylinder and storing said value in the engine control computer. - View Dependent Claims (2, 3, 4)
- said engine further comprising means for introducing air and fuel into said cylinders to form a combustible mixture, means for ignition of said combustible mixtures, means for exhausting combustion gases from said cylinders, a crank shaft position sensor to determine the position of said pistons with respect to their top dead center positions, a sensor for providing signals indicative of the pressure in said cylinder at predetermined crankshaft positions;
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5. A method of detecting the relative completeness of combustion or for classifying a misfire condition in at least one cylinder of a multi-cylinder internal combustion engine in an automotive vehicle,
said engine comprising a plurality of cylinders, each cylinder containing a reciprocatable piston and having a known volume at each position of said piston, said pistons being connected to a crank shaft for rotation through a top dead center position in their respective cylinders; - said engine further comprising means for introducing air and fuel into said cylinders to form a combustible mixture, means for ignition of said combustible mixtures, means for exhausting combustion gases from said cylinders, a crank shaft position sensor to determine the position of said pistons with respect to their top dead center positions, a sensor for providing signals indicative of the pressure in said cylinder at predetermined crankshaft positions;
said vehicle comprising a programmed computer for controlling fuel delivery and optional exhaust gas recycle flow to said cylinders and ignition timing therein, and for detecting and recording possible engine operating conditions adverse to an exhaust gas treatment system of said vehicle, said computer being adapted to receive pressure indicative and crank shaft position signals from said sensors, said method being performed by said computer immediately following predetermined combustion events with respect to each cylinder in which said condition is to be detected and comprising,computing values indicative of motored pressure for a plurality of crankshaft angles based on values of the pressure indicative signals at crank angles before the top dead center position of the compression stroke of a said piston, determining a value indicative of the actual pressure in said cylinder at a predetermined crank angle after top dead center and after combustion in said cylinder is expected to have occurred in the current operating mode of said engine, calculating a pressure ratio of said value indicative of actual pressure at said predetermined crank angle to the value indicative of motored pressure at the same crank angle and subtracting a value of one from said pressure ratio to determine a modified pressure ratio at said crank angle, and storing said modified pressure ratio in said computer as indicating a measure of the completeness of combustion or a misfire condition in said cylinder if said modified pressure ratio is a predetermined value in the range of zero to about two. - View Dependent Claims (6, 7, 8, 9, 10, 11)
- said engine further comprising means for introducing air and fuel into said cylinders to form a combustible mixture, means for ignition of said combustible mixtures, means for exhausting combustion gases from said cylinders, a crank shaft position sensor to determine the position of said pistons with respect to their top dead center positions, a sensor for providing signals indicative of the pressure in said cylinder at predetermined crankshaft positions;
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12. A method of controlling the operation of a multi-cylinder internal combustion engine in an automotive vehicle where the ignition timing of said engine is to be significantly retarded from best efficiency timing,
said engine comprising a plurality of cylinders, each cylinder containing a reciprocatable piston and having a known volume at each position of said piston, said pistons being connected to a crank shaft for rotation through a top dead center position in their respective cylinders; - said engine further comprising means for introducing air and fuel into said cylinders to form a combustible mixture, means for ignition of said combustible mixtures, means for exhausting combustion gases from said cylinders, a crank shaft position sensor to determine the position of said pistons with respect to their top dead center positions, sensors for providing signals indicative of the pressure in said cylinders at predetermined crankshaft positions;
said vehicle comprising a programmed computer for controlling fuel delivery and optional exhaust gas recycle flow to said cylinders and ignition timing therein, said computer being adapted to receive pressure indicative signals and crank shaft position signals from said sensors, said method being performed by said computer during predetermined ignition events with respect to each cylinder in which said condition is to be detected and comprising,computing values indicative of motored pressure for a plurality of crankshaft angles based on values of the pressure indicative signals at crank angles before the top dead center position of the compression stroke of a said piston, determining a value indicative of the actual pressure in each of said cylinders at a predetermined crank angle of twenty five degrees or more after top dead center, calculating a pressure ratio value indicative of the ratio of actual pressure at said predetermined crank angle to the value indicative of motored pressure at the same crank angle, and adjusting the ignition timing in each cylinder to maintain a predetermined pressure ratio value for said cylinder. - View Dependent Claims (13, 14, 15)
- said engine further comprising means for introducing air and fuel into said cylinders to form a combustible mixture, means for ignition of said combustible mixtures, means for exhausting combustion gases from said cylinders, a crank shaft position sensor to determine the position of said pistons with respect to their top dead center positions, sensors for providing signals indicative of the pressure in said cylinders at predetermined crankshaft positions;
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16. A method of controlling the operation of a multi-cylinder internal combustion engine in an automotive vehicle where the ignition timing of said engine is to be significantly retarded from best efficiency timing
said engine comprising a plurality of cylinders, each cylinder containing a reciprocatable piston and having a known volume at each position of said piston, said pistons being connected to a crank shaft for rotation through a top dead center position in their respective cylinders; - said engine further comprising means for introducing air and fuel into said cylinders to form a combustible mixture, means for ignition of said combustible mixtures, means for exhausting combustion gases from said cylinders, a crank shaft position sensor to determine the position of said pistons with respect to their top dead center positions, sensors for providing signals indicative of the pressure in said cylinders at predetermined crankshaft positions;
said vehicle comprising a programmed computer for controlling fuel delivery and optional exhaust gas recycle flow to said cylinders and ignition timing therein, said computer being adapted to receive pressure indicative signals and crank shaft position signals from said sensors, said method being performed by said computer during predetermined ignition events with respect to each cylinder in which said condition is to be detected and comprising,computing values indicative of motored pressure for a plurality of crankshaft angles based on values of the pressure indicative signals at crank angles before the top dead center position of the compression stroke of a said piston, determining a value indicative of the actual pressure in each of said cylinders at a predetermined crank angle of twenty five degrees or more after top dead center and at a later predetermined crank angle for which combustion should be complete (complete burn), calculating a pressure ratio values indicative of the ratio of actual pressure at said predetermined crank angles to the values indicative of motored pressures at the same crank angles and subtracting a value of one from each said pressure ratio to determine a modified pressure ratio for each, calculating the quotient of said modified pressure ratios corresponding to the twenty five degree or later crank angle to the said modified pressure ratio (complete burn), and adjusting the spark timing in each said cylinder to yield a value of said quotient equal to a predetermined optimum value for the engine operating condition. - View Dependent Claims (17, 18, 19)
- said engine further comprising means for introducing air and fuel into said cylinders to form a combustible mixture, means for ignition of said combustible mixtures, means for exhausting combustion gases from said cylinders, a crank shaft position sensor to determine the position of said pistons with respect to their top dead center positions, sensors for providing signals indicative of the pressure in said cylinders at predetermined crankshaft positions;
Specification