Catalyst temperature model
First Claim
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1. A method for monitoring the temperature of a catalyst in a catalytic converter in an exhaust system, the method comprising the steps of:
- determining a first catalyst temperature;
determining a stabilized catalyst temperature which includes the steps of determining a quantity of unfueled engine cylinders, and calculating a term to account for a quantity of air pumped through an engine without a corresponding release of combustion energy based on the quantity of unfueled engine cylinders; and
determining an updated catalyst temperature based on the first catalyst temperature, the stabilized catalyst temperature and an update fraction.
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Abstract
A method for calculating the temperature of a catalyst in a catalytic converter. The method includes the steps of determining a first catalyst temperature; determining a stabilized catalyst temperature; and using the first catalyst temperature, the stabilized catalyst temperature and an update fraction to calculate an updated catalyst temperature.
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Citations
22 Claims
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1. A method for monitoring the temperature of a catalyst in a catalytic converter in an exhaust system, the method comprising the steps of:
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determining a first catalyst temperature;
determining a stabilized catalyst temperature which includes the steps of determining a quantity of unfueled engine cylinders, and calculating a term to account for a quantity of air pumped through an engine without a corresponding release of combustion energy based on the quantity of unfueled engine cylinders; and
determining an updated catalyst temperature based on the first catalyst temperature, the stabilized catalyst temperature and an update fraction. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
determining an ambient air temperature;
calculating a difference between a reference temperature and the ambient air temperature; and
calculating an ambient cooling correction term based on the difference between the reference temperature and the ambient air temperature.
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6. The method of claim 1, wherein the step of determining the stabilized catalyst temperature includes the step of determining a heat-sink term to account for an amount of heat retained by the exhaust system.
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7. The method of claim 1, wherein the step of determining the stabilized catalyst temperature includes the steps of:
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determining an actual fuel/air ratio;
calculating a difference between a stoichiometric fuel/air ratio and the actual fuel/air ratio; and
calculating an enrichment cooling correction term based on the difference between the stoichiometric fuel/air ratio and the actual fuel/air ratio.
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8. The method of claim 1, wherein the step of determining the stabilized catalyst temperature includes the steps of:
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determining a theoretical spark delivery angle that provides a maximum brake torque;
determining an actual spark delivery angle;
calculating a difference between the theoretical spark delivery angle and the actual spark delivery angle; and
calculating a spark angle heating rate correction term based on the difference between the theoretical spark delivery angle and the actual spark delivery angle.
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9. The method of claim 1, wherein the step of determining the stabilized catalyst temperature includes the steps of:
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determining a rate of misfire; and
calculating a misfire heating correction term based on the rate of misfire.
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10. The method of claim 1, wherein the step of determining the stabilized catalyst temperature includes the steps of:
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determining if the first catalyst temperature exceeds a predetermined catalyst light-off temperature; and
if the first catalyst temperature does not exceed the predetermined catalyst light-off temperature, excluding an exothermic heating rate correction term to compensate for a quantity of heat not produced by an exothermic reaction within the catalytic converter.
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11. The method of claim 1, wherein the step of determining a first catalyst temperature includes the steps of:
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determining if the catalytic converter has been continuously used;
if the catalytic converter has been continuously used, setting the first catalyst temperature equal to the updated catalyst temperature calculated in an iteration of the method immediately preceding the present iteration; and
otherwise, calculating the first catalyst temperature with a model that considers the updated catalyst temperature calculated in a last iteration of the method immediately prior to a time at which the catalytic converter was not being used, an ambient air temperature and an amount by which the catalyst has cooled.
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12. The method of claim 11, wherein the step of calculating the first catalyst temperature with the model includes the steps of:
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calculating a first intermediate quantity by subtracting the ambient air temperature from the updated catalyst temperature calculated in the iteration of the method immediately preceding the present iteration;
calculating a second intermediate quantity by multiplying the first intermediate quantity by a cool down fraction that approximates an amount by which the catalyst has cooled down based on a length of time for which the catalytic converter was not being used; and
calculating the first catalyst temperature by subtracting the second intermediate quantity from the updated catalyst temperature calculated in the iteration of the method immediately preceding the present iteration.
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13. A method for monitoring the temperature of a catalyst in a catalytic converter of an exhaust system, the method comprising the steps of:
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determining a first catalyst temperature;
determining a first portion of a stabilized catalyst temperature based on a quantity of fueled engine cylinders and a steady state base temperature of the catalyst, the steady state base temperature based on a manifold absolute pressure and an engine rotational speed;
determining a second portion of the stabilized catalyst temperature based on a quantity of unfueled engine cylinders; and
calculating an updated catalyst temperature based on the first catalyst temperature, the first and second portions of the stabilized catalyst temperature and an update fraction. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22)
determining a convection cooling correction term based on a vehicle speed; and
adding the convection cooling correction term to the steady state base temperature.
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15. The method of claim 13, wherein the step of determining the first portion of the stabilized catalyst temperature further includes the steps of:
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determining an ambient air temperature;
calculating a difference between a reference temperature and the ambient air temperature;
calculating an ambient cooling correction term based on the difference between the reference temperature and the ambient air temperature; and
adding the ambient cooling correction term to the steady state base temperature.
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16. The method of claim 13, wherein the step of determining the first portion of the stabilized catalyst temperature includes the steps of:
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determining a heat-sink term to account for an amount of heat retained by the exhaust system; and
adding the heat-sink term to the steady state base temperature.
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17. The method of claim 13, wherein the step of determining the first portion of the stabilized catalyst temperature includes the steps of:
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determining an actual fuel/air ratio;
calculating a difference between a stoichiometric fuel/air ratio and the actual fuel/air ratio;
calculating an enrichment cooling correction term based on the difference between the stoichiometric fuel/air ratio and the actual fuel/air ratio; and
adding the enrichment cooling correction term to the steady state base temperature.
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18. The method of claim 13, wherein the step of determining the first portion of the stabilized catalyst temperature includes the steps of:
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determining a theoretical spark delivery angle that provides a maximum brake torque;
determining an actual spark delivery angle;
calculating a difference between the theoretical spark delivery angle and the actual spark delivery angle;
calculating a spark angle heating rate correction term based on the difference between the theoretical spark delivery angle and the actual spark delivery angle; and
adding the spark angle heating rate correction term to the steady state base temperature.
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19. The method of claim 13, wherein the step of determining the first portion of the stabilized catalyst temperature includes the steps of:
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determining a rate of misfire;
calculating a misfire heating correction term based on the rate of misfire; and
adding the misfire heating correction term to the steady state base temperature.
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20. The method of claim 13, wherein the step of determining the first portion of the stabilized catalyst temperature includes the steps of:
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determining if the first catalyst temperature exceeds a predetermined catalyst light-off temperature; and
if the first catalyst temperature does not exceed the predetermined catalyst light-off temperature, subtracting an exothermic heating correction term from the steady state base temperature, the exothermic heating correction term compensating for a quantity of heat not produced by an exothermic reaction within the catalytic converter.
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21. The method of claim 13, wherein the step of determining a first catalyst temperature includes the steps of:
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determining if the catalytic converter has been continuously used;
if the catalytic converter has been continuously used, setting the first catalyst temperature equal to the updated catalyst temperature calculated in an iteration of the method immediately preceding the present iteration; and
otherwise, calculating the first catalyst temperature with a model that considers the updated catalyst temperature calculated in a last iteration of the method immediately prior to a time at which the catalytic converter was not being used, an ambient air temperature and an amount by which the catalyst has cooled.
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22. The method of claim 21, wherein the step of calculating the first catalyst temperature with the model includes the steps of:
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calculating a first intermediate quantity by subtracting the ambient air temperature from the updated catalyst temperature calculated in the iteration of the method immediately preceding the present iteration;
calculating a second intermediate quantity by multiplying the first intermediate quantity by a cool down fraction which approximates an amount by which the catalyst has cooled down based on a length of time for which the catalytic converter was not being used; and
calculating the first catalyst temperature by subtracting the second intermediate quantity from the updated catalyst temperature calculated in the iteration of the method immediately preceding the present iteration.
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Specification