Model based enrichment for exhaust temperature protection

• US 6,286,305 B1
• Filed: 02/23/2000
• Issued: 09/11/2001
• Est. Priority Date: 02/23/2000
• Status: Expired due to Term

• Current Assignee: FCA US LLC (Stellantis NV)
• Original Assignee: Daimler Chrysler Corporation (Mercedes-Benz Group AG)
• Inventors: Poublon, Mark J, Wolfe, Kathryn A
• Primary Examiner(s): Denion, Thomas
• Assistant Examiner(s): TRAN, BINH Q
• Application Number:
  US09/511,229
• Time in Patent Office: 566 Days
• Field of Search: 602/74, 602/77, 603/00, 602/78, 602/85, 731/181
• US Class Current: 60/285
• CPC Class Codes: F02D 2200/0804 Estimation of the temperature of the exhaust gas treatment apparatus
• CPC Class Codes: F02D 41/0047 Controlling exhaust gas recirculation [EGR] temperature control with cooler in recirculation circuit F02M26/33
• CPC Class Codes: F02D 41/0087 Selective cylinder activation, i.e. partial cylinder operation deceleration cut-off F02D41/123
• CPC Class Codes: F02D 41/0235 in relation with the state of the exhaust gas treating apparatus control of exhaust gas treating apparatus per se F01N
• CPC Class Codes: F02M 26/13 Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories

Abstract

A method for controlling the temperature of a catalyst in a catalytic converter. The method includes the steps of calculating a stabilized catalyst temperature limit, determining a stabilized catalyst temperature without enrichment, comparing the stabilized catalyst temperature limit with the stabilized catalyst temperature without enrichment and enriching a fuel/air ratio to maintain a stabilized catalyst temperature at the stabilized catalyst temperature limit if the stabilized catalyst temperature without enrichment is greater than the stabilized catalyst temperature limit. A vehicle having a controller for controlling the enrichment of an air/fuel ratio to control the temperature of a catalyst in a catalytic converter is also provided.

Claims

1. A method for controlling a temperature of a catalyst in a catalytic converter, the method comprising the steps of:

calculating a stabilized catalyst temperature limit;

determining a stabilized catalyst temperature without enrichment;

comparing the stabilized catalyst temperature limit with the stabilized catalyst temperature without enrichment; and

modifying a fuel/air ratio to maintain a stabilized catalyst temperature at the stabilized catalyst temperature limit if the stabilized catalyst temperature without enrichment is greater than the stabilized catalyst temperature limit.

2. The method of claim 1, wherein the step of modifying a fuel/air ratio includes the steps of:

providing a fuel/air correction gain; and

calculating a fuel/air change amount by which to enrich the fuel/air ratio based on the stabilized catalyst temperature without enrichment, the stabilized catalyst temperature limit and the fuel/air correction gain.

3. The method of claim 2, wherein the step of calculating the fuel/air change amount includes the steps of:

calculating a difference between the stabilized catalyst temperature without enrichment and the stabilized catalyst temperature limit; and

dividing the difference by the fuel/air correction gain.

4. The method of claim 2, further comprising the steps of:

calculating an enrichment change rate based on the fuel/air change amount;

comparing the enrichment change rate to a predetermined change rate limit; and

if the enrichment change rate is less than the predetermined change rate limit, modifying the fuel/air ratio by the enrichment change amount.

5. The method of claim 4, further comprising the step of modifying the fuel/air ratio by the change rate limit if the enrichment change rate is not less than the change rate limit.

6. The method of claim 1, wherein the step of calculating a stabilized catalyst temperature limit includes the steps of:

determining a first catalyst temperature;

determining an update fraction;

providing a predetermined catalyst temperature limit; and

calculating the stabilized catalyst temperature limit based on the first catalyst temperature, the update fraction and the catalyst temperature limit.

7. The method of claim 6, wherein the step of calculating the stabilized catalyst temperature limit includes the steps of:

calculating a first intermediate term by subtracting the update fraction from a quantity of one (1);

calculating a second intermediate term by multiplying the first intermediate term by the first catalyst temperature;

calculating a third intermediate term by subtracting the second intermediate term from the temperature limit; and

calculating the stabilized catalyst temperature limit by dividing the third intermediate term by the update fraction.

8. A vehicle comprising:

an internal combustion engine;

an exhaust system coupled to the internal combustion engine and receiving a supply of exhaust gas discharged therefrom, the exhaust system including a catalytic converter having a catalyst;

fuel/air delivery means for controlling the delivery of fuel and air to the engine at a selectively controllable ratio;

a plurality of first sensors sensing various vehicle dynamics and generating a plurality of first sensor signals in response thereto;

a plurality of second sensors sensing various engine dynamics and generating a plurality of second sensor signals in response thereto;

a plurality of third sensors sensing various characteristics of air input to the engine and exhaust gas discharged from the engine and generating a plurality of third sensor signals in response thereto; and

a controller coupled to the fuel/air delivery means and the plurality of first, second and third sensors, the controller receiving the plurality of first, second and third sensor signals and calculating a stabilized catalyst temperature limit and a stabilized catalyst temperature without enrichment, the controller comparing the stabilized catalyst temperature limit with the stabilized catalyst temperature without enrichment and modifying the fuel/air ratio to maintain a stabilized catalyst temperature at the stabilized catalyst temperature limit if the stabilized catalyst temperature without enrichment is greater than the stabilized catalyst temperature limit.

9. The vehicle of claim 8, wherein the controller calculates the fuel/air change amount by which to enrich the fuel/air ratio by calculating a difference between the stabilized catalyst temperature without enrichment and the stabilized catalyst temperature limit and dividing the difference by a fuel/air correction gain.

10. The vehicle of claim 8, wherein the controller limits a rate with which the fuel/air ratio is enriched to an amount which does not exceed a predetermined change rate limit.

11. A method for controlling a temperature of a catalyst in a catalytic converter, the method comprising the steps of:

determining a first catalyst temperature;

determining an update fraction;

providing a predetermined catalyst temperature limit;

calculating the stabilized catalyst temperature limit based on the first catalyst temperature, the update fraction and the catalyst temperature limit;

determining a stabilized catalyst temperature without enrichment;

comparing the stabilized catalyst temperature limit with the stabilized catalyst temperature without enrichment;

providing a fuel/air correction gain;

calculating a fuel/air change amount by which to enrich the fuel/air ratio based on the stabilized catalyst temperature without enrichment, the stabilized catalyst temperature limit and the fuel/air correction gain; and

modifying a fuel/air ratio to maintain a stabilized catalyst temperature at the stabilized catalyst temperature limit if the stabilized catalyst temperature without enrichment is greater than the stabilized catalyst temperature limit.

12. The method of claim 11, wherein the step of calculating an fuel/air change amount includes the steps of:

calculating a difference between the stabilized catalyst temperature without enrichment and the stabilized catalyst temperature limit; and

dividing the difference by the fuel/air correction gain.

13. The method of claim 11, further comprising the steps of:

calculating an enrichment change rate based on the fuel/air change amount by which to enrich the fuel/air ratio;

comparing the enrichment change rate to a predetermined change rate limit; and

modifying the fuel/air ratio by the fuel/air change amount if the enrichment change rate is less than the change rate limit.

14. The method of claim 13, further comprising the step of modifing the fuel/air ratio by the change rate limit if the enrichment change rate in not less than the change rate limit.

15. The method of claim 11, wherein the step of calculating the stabilized catalyst temperature limit includes the steps of:

calculating a first intermediate term by subtracting the update fraction from a quantity of one (1);

calculating a second intermediate term by multiplying the first intermediate term by the first catalyst temperature;

calculating a third intermediate term by subtracting the second intermediate term from the temperature limit; and

calculating the stabilized catalyst temperature limit by dividing the third intermediate term by the update fraction.