Engine Control Method and System

• US 20110209685A1
• Filed: 03/29/2011
• Published: 09/01/2011
• Est. Priority Date: 03/29/2011
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Shane, Michael Daniel, Pakko, James David, Laing, Paul M.
• Granted Patent: US 8,272,362 B2
• Time in Patent Office: Days
• US Class Current: 123/299
• CPC Class Codes: F02D 41/0002 Controlling intake air
• CPC Class Codes: F02D 41/0007 for control of turbo-charged or super-charged engines control of the pumps per se F02B37/12
• CPC Class Codes: F02D 41/025 by changing the composition of the exhaust gas, e.g. for exothermic reaction on exhaust gas treating apparatus
• CPC Class Codes: F02D 41/064 at cold start F02D41/067 takes precedence
• CPC Class Codes: F02D 41/402 Multiple injections
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

Methods and systems are provided for heating a catalyst during engine cold-start conditions. One example embodiment uses positive valve overlap to drive a boosted blow-through airflow through the cylinders of an engine. Fuel is injected with the blow-through airflow during the valve overlap, and also injected into engine cylinders outside the valve overlap. The catalyst is heated by the resulting exothermic reaction of the blow-through airflow with the combustion products and the injected fuel in the exhaust manifold.

Claims

1. A method of operating a boosted engine, comprising,

during an engine cold start,

operating the engine with positive intake to exhaust valve overlap to drive a boosted blow-through airflow into an engine exhaust through engine cylinders;

injecting a first amount of fuel during the valve overlap;

injecting a second amount of fuel outside of the valve overlap; and

exothermically reacting the blow-through airflow with fuel in the exhaust.

2. The method of claim 1, wherein the first injection amount and second injection amount are injected in the same engine cylinder.

3. The method of claim 1, wherein the first injection amount is injected in a first engine cylinder and the second injection amount is injected in a second engine cylinder, the first and second engine cylinders selected based on their firing order.

4. The method of claim 1, wherein the second amount of fuel is injected in an intake stroke of the same combustion cycle as the first injection amount.

5. The method of claim 1, wherein the second injection amount is injected in an intake stroke of a different combustion cycle as the first injection amount.

6. The method of claim 5, wherein the different combustion cycle is either a combustion cycle immediately preceding or immediately following the combustion cycle of the first injection amount.

7. The method of claim 1, wherein a sum of the first and second injection amounts is adjusted to maintain an overall air-fuel ratio in the exhaust at a desired air-to-fuel ratio, and wherein a ratio of the first injection amount relative to the second injection amount is adjusted based at least on an exhaust catalyst temperature.

8. The method of claim 7, wherein the first and second injection amounts are further adjusted based on air-to-fuel ratio feedback from an exhaust gas oxygen sensor.

9. The method of claim 1, wherein the engine cold-start condition includes at least one of a catalyst temperature being below a threshold temperature, and the engine being in an engine-off condition for greater than a threshold duration.

10. A method of operating an engine, comprising:

during a first engine cold-start condition, mixing a rich blow-through air-fuel mixture with a lean cylinder combustion air-fuel mixture in an exhaust manifold to generate more heat at an exhaust catalyst; and

during a second engine cold-start condition, mixing a lean blow-through air-fuel mixture with a rich cylinder combustion air-fuel mixture in the exhaust manifold to generate less heat at the exhaust catalyst.

11. The method of claim 10, wherein the first engine cold-start condition includes a temperature of the exhaust catalyst being lower than a threshold, and the second engine cold-start condition includes the temperature of the exhaust catalyst being higher than the threshold.

12. The method of claim 10, wherein during the first and second engine cold-start conditions, the blow-through air-fuel mixture is a boosted blow-through air-fuel mixture generated by operating a turbocharger during a positive intake to exhaust valve overlap period while injecting a first amount of fuel during the positive valve overlap period.

13. The method of claim 12, wherein during the first and second engine cold-start conditions, the cylinder combustion air-fuel mixture is generated by injecting a second amount of fuel outside of the positive valve overlap period but before an intake valve closes.

14. The method of claim 13, wherein the cylinder combustion air-fuel mixture and the boosted blow-through air-fuel mixture are generated in the same cylinder, in the same combustion cycle.

15. The method of claim 10, wherein during the first and second conditions, an exhaust gas mixture in the exhaust manifold is maintained substantially at stoichiometry.

16. The method of claim 15, wherein the maintaining includes adjusting the first and/or second injection amount based on feedback received from an exhaust air-to-fuel ratio sensor.

20. The system of claim 16, wherein the control system includes instructions for further adjusting the first and second injection amounts based on air-to-fuel ratio feedback from the exhaust gas oxygen sensor, the adjustment including,

during a first condition, adjusting the first injection amount but not the second injection amount responsive to the feedback;

during a second condition, adjusting the second injection amount but not the first injection amount responsive to the feedback; and

during a third condition, adjusting the first and the second injection amount responsive to the feedback.

17. An engine system, comprising:

a boosted engine;

a direct injector for direct injecting fuel into an engine cylinder;

an exhaust catalyst;

an exhaust gas oxygen sensor; and

a control system including instructions for;

injecting a first amount of fuel and driving an amount of boosted air through engine cylinders into an exhaust manifold, during a positive intake to exhaust valve overlap period, to generate a blow-through mixture;

injecting a second amount of fuel after the valve overlap but before the intake valve closes to generate a cylinder combustion mixture; and

exothermically reacting the blow-through mixture with the cylinder combustion mixture in the exhaust manifold.

18. The system of claim 17, wherein driving a first amount of boosted air through the engine includes operating a turbocharger coupled between the exhaust manifold and an engine intake to generate positive boost pressure.

19. The system of claim 17, wherein a sum of the first and second injection amounts are adjusted to maintain an air-to-fuel ratio of an exhaust gas mixture around stoichiometry while a ratio of the first injection amount relative to the second injection amount is adjusted based at least on exhaust catalyst temperature.