Methods and systems for boost control based on exhaust pressure greater than a threshold

Patent metadata

Field	Value
Publication number	US-10119479-B2
Application number	US-201514820409-A
Country	US
Kind code	B2
Filing date	Aug 6, 2015
Priority date	Aug 6, 2015
Publication date	Nov 6, 2018
Grant date	Nov 6, 2018

Abstract

Methods and systems are provided for mitigating excessive exhaust pressures in an engine. In one example, a method may include adjusting an intake throttle responsive to exhaust pressure upstream of an exhaust turbine being higher than a threshold without reducing boost level. In this way, boost pressures may be maintained while reducing exhaust pressures.

First claim

The invention claimed is:

1. A method for an engine, comprising:
adjusting an intake throttle responsive to pre-turbine exhaust pressure greater than a threshold without reducing boost level and while maintaining valve timing,
wherein the threshold is based on a pressure required to force open a closed exhaust valve.

2. The method of claim 1 , wherein the pre-turbine exhaust pressure is a predicted pressure.

3. The method of claim 2 , wherein the pre-turbine exhaust pressure is modeled based on a post-turbine exhaust manifold pressure.

4. The method of claim 3 , wherein the engine includes a soot filter coupled downstream of a turbocharger turbine, and wherein the pre-turbine exhaust pressure is further modeled based on soot load of the soot filter and the boost level.

5. The method of claim 4 , wherein the pre-turbine exhaust pressure is further modeled based on one or more of engine air flow, exhaust flow, spark timing, air-fuel ratio, cam timing, manifold temperature, vehicle speed, and manifold pressure.

6. The method of claim 3 , wherein the post-turbine exhaust manifold pressure is estimated by an exhaust pressure sensor.

7. The method of claim 1 , wherein the adjusting includes reducing an opening of the intake throttle until the pre-turbine exhaust pressure is below the threshold.

8. The method of claim 7 , wherein the adjusting includes reducing the opening of the intake throttle for a threshold duration, and responsive to the pre-turbine exhaust pressure remaining greater than the threshold after the threshold duration, reducing boost level by adjusting an exhaust wastegate.

9. The method of claim 8 , wherein the adjusting further includes reducing the opening of the intake throttle while closing the exhaust wastegate.

10. The method of claim 8 , wherein the engine is coupled in a vehicle and wherein the threshold duration includes one of a threshold number of engine combustion events, a threshold duration of vehicle travel, and a time taken for a threshold distance of vehicle travel.

11. The method of claim 10 , wherein reducing the boost level by adjusting the exhaust wastegate includes increasing an opening of the exhaust wastegate to reduce the boost level until the pre-turbine exhaust pressure is lower than the threshold.

12. A method for an engine, comprising:
treating engine exhaust gas with a particulate filter, the particulate filter positioned downstream of a turbocharger turbine;
estimating exhaust pressure upstream of the turbocharger turbine based on soot loading of the particulate filter; and
reducing intake airflow if the estimated exhaust pressure is greater than a threshold,
wherein the threshold is based on a pressure that will force open an exhaust valve when the exhaust valve would otherwise be closed.

13. The method of claim 12 , wherein the threshold is further based on a spring wear of the exhaust valve over a life of the engine.

14. The method of claim 12 , wherein the threshold is further based on one or more of engine speed and intake manifold pressure.

15. The method of claim 12 , wherein the threshold is further based on cam timing.

16. The method of claim 15 , wherein reducing intake airflow includes, during a first condition, reducing intake airflow via adjustments to an intake throttle opening, and during a second condition, reducing intake airflow via adjustments to an intake valve and/or intake cam timing.

17. An engine system, comprising:
an engine including an intake and an exhaust;
an engine cylinder including an intake valve and an exhaust valve;
a turbocharger for providing a boosted intake airflow, the turbocharger including an exhaust turbine;
an intake throttle;
an exhaust wastegate;
an intake cam for adjusting an intake valve timing;
a particulate filter coupled downstream of the exhaust turbine;
a pressure sensor coupled downstream of the exhaust turbine; and
a controller with computer readable instructions stored on non-transitory memory for:
operating the engine with boost enabled and with positive valve overlap to blow-through an amount of boosted air from the intake to the exhaust via the engine cylinder;
estimating exhaust pressure upstream of the exhaust turbine based on soot loading of the particulate filter; and
if the estimated exhaust pressure is greater than a threshold, reducing one or more of intake airflow via the intake throttle and the amount of blow-through boosted air,
wherein reducing the amount of blow-through boosted air includes adjusting a timing of the intake cam to reduce the positive valve overlap between an intake valve and an exhaust valve.

18. The engine system of claim 17 , wherein the reducing includes: only reducing intake airflow via the intake throttle when engine speed is higher than a first speed threshold, only reducing the amount of blow-through boosted air when the engine speed is lower than a second speed threshold and engine load is higher than a load threshold, and reducing each of intake airflow via the intake throttle and the amount of blow-through boosted air when the engine speed is between the first speed threshold and the second speed threshold and the engine load is higher than the load threshold.

Assignees

• Ford Global Tech Llc

Inventors

• Fabien Philip Andrew
• Russ Stephen George
• Mancini Michael A
• Cherry Jonathan

Classifications

• F01N2560/07

  the means being an exhaust gas flow rate or velocity meter or sensor, intake flow meters only when exclusively used to determine exhaust gas parameters · CPC title

• F01N2560/06

  the means being a temperature sensor · CPC title

• F02D2041/001

  for engines with variable valve actuation · CPC title

• F02D2200/0406

  Intake manifold pressure · CPC title

• F02D2200/0414

  Air temperature · CPC title