Open-loop method and system for controlling the storage and release cycles of an emission control device

• US 6,490,860 B1
• Filed: 06/19/2001
• Issued: 12/10/2002
• Est. Priority Date: 06/19/2001
• Status: Expired due to Fees

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Farmer, David George, Surnilla, Gopichandra, Cullen, Michael John
• Primary Examiner(s): Denion, Thomas
• Assistant Examiner(s): TRAN, BINH Q
• Application Number:
  US09/884,331
• Publication Number:
  US 20020189241A1
• Time in Patent Office: 539 Days
• Field of Search: 602/74, 602/85, 602/76, 602/95, 602/97, 602/86
• US Class Current: 60/285
• CPC Class Codes: F01N 13/009 having two or more separate purifying devices arranged in series
• CPC Class Codes: F01N 13/0093 the purifying devices are of the same type
• CPC Class Codes: F01N 2570/04 Sulfur or sulfur oxides
• CPC Class Codes: F01N 2570/14 Nitrogen oxides
• CPC Class Codes: F01N 3/0807 by using absorbents or adsorbents
• CPC Class Codes: F01N 3/0842 Nitrogen oxides
• CPC Class Codes: F02D 2041/389 for injecting directly into the cylinder
• CPC Class Codes: F02D 2200/0808 NOx storage capacity, i.e. maximum amount of NOx that can be stored on NOx trap
• CPC Class Codes: F02D 2200/0818 SOx storage amount, e.g. for SOx trap or NOx trap
• CPC Class Codes: F02D 41/028 Desulfurisation of NOx traps or adsorbent
• CPC Class Codes: F02D 41/1441 Plural sensors
• CPC Class Codes: F02D 41/1446 the characteristics being exhaust temperatures
• CPC Class Codes: F02D 41/1462 with determination means using an estimation
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

Abstract

A method and system for controlling the operation of an internal combustion engine, wherein exhaust gas generated by the engine is directed through an emission control device, includes determining instantaneous rates of storage for a constituent of the exhaust gas, such as NO_x, as well as the capacity reduction of the device to store the exhaust gas constituent as a function of a calculated value representing an amount of SO_x which has accumulated in the device since a prior device-regeneration (desulfation) event. The calculated accumulated SO_x value is also preferably used to schedule a device-regeneration event, as when the calculated accumulated SO_x value exceeds a predetermined threshold value.

Claims

1. In a method for controlling an engine, wherein the engine is operative at a plurality of engine operating conditions, including a desulfating engine operating condition, characterized by combustion of air-fuel mixtures lean and rich of a stoichiometric air-fuel mixture, and wherein exhaust gas generated by such combustion is directed through an emission control device that stores a selected exhaust gas constituent when the exhaust gas is lean and releases the stored selected constituent when the exhaust gas is rich, the method comprising:

determining a first value representing an amount of SO_x accumulated in the device;

determining a second value representing an amount of the selected constituent currently stored in the device as a function of the first value; and

selecting an engine operating condition as a function of the second value, wherein determining the first value includes accumulating an instantaneous value representative of an incremental amount of accumulated SO_x during an engine operating condition characterized by an air-fuel mixture that is not richer than a stoichiometric air-fuel mixture.

2. The method of claim 1, wherein the instantaneous value is adjusted based on at least one of an instantaneous air-fuel ratio and an instantaneous device temperature.

3. The method of claim 1, including resetting the first value to zero when selecting the desulfating engine operating condition.

4. In a method for controlling an engine, wherein the engine is operative at a plurality of engine operating conditions, including a desulfating engine operating condition, characterized by combustion of air-fuel mixtures lean and rich of a stoichiometric air-fuel mixture, and wherein exhaust gas generated by such combustion is directed through an emission control device that stores a selected exhaust gas constituent when the exhaust gas is lean and releases the stored selected constituent when the exhaust gas is rich, the method comprising:

determining a first value representing an amount of SO_x accumulated in the device;

determining a second value representing an amount of the selected constituent currently stored in the device as a function of the first value; and

selecting an engine operating condition as a function of the second value, wherein the first value is determined as a function of the instantaneous fuel flow rate during engine operating conditions no richer than a stoichiometric engine operating condition.

5. In a method for controlling an engine, wherein the engine is operative at a plurality of engine operating conditions, including a desulfating engine operating condition, characterized by combustion of air-fuel mixtures lean and rich of a stoichiometric air-fuel mixture, and wherein exhaust gas generated by such combustion is directed through an emission control device that stores a selected exhaust gas constituent when the exhaust gas is lean and releases the stored selected constituent when the exhaust gas is rich, the method comprising:

determining a first value representing an amount of SO_x accumulated in the device;

determining a second value representing an amount of the selected constituent currently stored in the device as a function of the first value; and

selecting an engine operating condition as a function of the second value, further including determining a third value representing a current capacity of the device to store the selected constituent as a function of the first value; and

wherein selecting includes comparing the second value to the third value.

6. In a method for controlling an engine, wherein the engine is operative at a plurality of engine operating conditions, including a desulfating engine operating condition, characterized by combustion of air-fuel mixtures lean and rich of a stoichiometric air-fuel mixture, and wherein exhaust gas generated by such combustion is directed through an emission control device that stores a selected exhaust gas constituent when the exhaust gas is lean and releases the stored selected constituent when the exhaust gas is rich, the method comprising:

determining a first value representing an amount of SO_x accumulated in the device;

determining a second value representing an amount of the selected constituent currently stored in the device as a function of the first value; and

selecting an engine operating condition as a function of the second value, wherein selecting further includes comparing the first value with a predetermined threshold value.

7. The method of claim 6, wherein the desulfating engine operating condition is selected when the first value exceeds the predetermined threshold value.

8. A system for controlling an engine, wherein the engine is operative at a plurality of engine operating conditions, including a desulfating engine operating condition, characterized by combustion of air-fuel mixtures lean and rich of a stoichiometric air-fuel mixture, and wherein exhaust gas generated by such combustion is received by an emission control device that stores a selected exhaust gas constituent when the exhaust gas is lean and releases the stored selected constituent when the exhaust gas is rich, the system comprising:

a controller including a microprocessor arranged to determine a first value representing an amount of SO_x accumulated in the device, and to determine a second value representing an amount of the selected constituent currently stored in the device as a function of the first value,

the controller being further arranged to select an engine operating condition as a function of the second value, wherein the controller is further arranged to accumulate an instantaneous value representative of an incremental amount of accumulated SO_x during an engine operating condition characterized by an air-fuel mixture that is not richer than a stoichiometric air-fuel mixture.

9. The system of claim 8, wherein the controller is further arranged to adjust the instantaneous value based on at least one of an instantaneous air-fuel ratio and an instantaneous device temperature.

10. The system of claim 8, wherein the controller is further arranged to reset the first value to zero when selecting the desulfating engine operating condition.

11. A system for controlling an engine, wherein the engine is operative at a plurality of engine operating conditions, including a desulfating engine operating condition, characterized by combustion of air-fuel mixtures lean and rich of a stoichiometric air-fuel mixture, and wherein exhaust gas generated by such combustion is received by an emission control device that stores a selected exhaust gas constituent when the exhaust gas is lean and releases the stored selected constituent when the exhaust gas is rich, the system comprising:

a controller including a microprocessor arranged to determine a first value representing an amount of SO_x accumulated in the device, and to determine a second value representing an amount of the selected constituent currently stored in the device as a function of the first value,

the controller being further arranged to select an engine operating condition as a function of the second value, wherein the controller is further arranged to determine the first value as a function of the instantaneous fuel flow rate during engine operating conditions no richer than a stoichiometric engine operating condition.

12. A system for controlling an engine, wherein the engine is operative at a plurality of engine operating conditions, including a desulfating engine operating condition, characterized by combustion of air-fuel mixtures lean and rich of a stoichiometric air-fuel mixture, and wherein exhaust gas generated by such combustion is received by an emission control device that stores a selected exhaust gas constituent when the exhaust gas is lean and releases the stored selected constituent when the exhaust gas is rich, the system comprising:

a controller including a microprocessor arranged to determine a first value representing an amount of SO_x accumulated in the device, and to determine a second value representing an amount of the selected constituent currently stored in the device as a function of the first value,

the controller being further arranged to select an engine operating condition as a function of the second value, wherein the controller is further arranged to determine a third value representing a current capacity of the device to store the selected constituent as a function of the first value, and wherein the controller is further arranged to compare the second value to the third value.

13. A system for controlling an engine, wherein the engine is operative at a plurality of engine operating conditions, including a desulfating engine operating condition, characterized by combustion of air-fuel mixtures lean and rich of a stoichiometric air-fuel mixture, and wherein exhaust gas generated by such combustion is received by an emission control device that stores a selected exhaust gas constituent when the exhaust gas is lean and releases the stored selected constituent when the exhaust gas is rich, the system comprising:

a controller including a microprocessor arranged to determine a first value representing an amount of SO_x accumulated in the device, and to determine a second value representing an amount of the selected constituent currently stored in the device as a function of the first value,

the controller being further arranged to select an engine operating condition as a function of the second value, wherein the controller is further arranged to compare the first value with a predetermined threshold value.

14. The system of claim 13, wherein the controller is further arranged to select the desulfating engine operating condition when the first value exceeds the predetermined threshold value.