Engine catalyst temperature estimating device and catalyst diagnostic device
First Claim
1. A temperature estimating device for a catalyst which purifies exhaust of an engine, comprising:
- means for determining whether said engine has been given a hot start or a cold start,means for setting a reference heat amount depending on a condensation produced in said catalyst when said engine has been given a cold start, and a reference heat amount corresponding to a state without condensation when said engine has been given a hot start,means for detecting a running condition of said engine,means for computing a catalyst temperature in a steady state engine running condition according to the detected running condition,means for detecting an intake air volume of said engine,means for integrating a heat amount given by the exhaust to the catalyst, from the catalyst temperature and engine intake air volume during the steady state engine running condition,means for setting a catalyst temperature estimated value to a preset value when the total heat amount given by the exhaust to the catalyst after engine startup is equal to or less than said reference heat amount, andmeans for computing said catalyst temperature estimated value from a first order delay equation having the catalyst temperature during said steady state engine running condition as a parameter, when said total heat amount is greater than said reference heat amount.
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Abstract
The suitability of diagnosing deterioration of a catalyst which purifies engine exhaust is determined based on estimated catalyst temperature. A value depending on condensation in the catalyst, and a value corresponding to a state without condensation, are respectively set as a reference heat amount for a cold start and a hot start. A catalyst temperature during steady state running condition of the engine is also computed based on the engine running conditions. The heat amount given by the exhaust to the catalyst is computed from this catalyst temperature and the engine intake air volume. When the total heat amount given to the catalyst after engine startup is equal to or less than the reference heat amount, a catalyst temperature estimated value is set to a fixed value. In all other cases, the catalyst temperature estimated value is calculated by a first order delay equation having catalyst temperature during steady running conditions as a parameter. In this way, the catalyst temperature is estimated with high precision.
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Citations
6 Claims
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1. A temperature estimating device for a catalyst which purifies exhaust of an engine, comprising:
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means for determining whether said engine has been given a hot start or a cold start, means for setting a reference heat amount depending on a condensation produced in said catalyst when said engine has been given a cold start, and a reference heat amount corresponding to a state without condensation when said engine has been given a hot start, means for detecting a running condition of said engine, means for computing a catalyst temperature in a steady state engine running condition according to the detected running condition, means for detecting an intake air volume of said engine, means for integrating a heat amount given by the exhaust to the catalyst, from the catalyst temperature and engine intake air volume during the steady state engine running condition, means for setting a catalyst temperature estimated value to a preset value when the total heat amount given by the exhaust to the catalyst after engine startup is equal to or less than said reference heat amount, and means for computing said catalyst temperature estimated value from a first order delay equation having the catalyst temperature during said steady state engine running condition as a parameter, when said total heat amount is greater than said reference heat amount. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification