System and methods for cold starting an internal combustion engine

Patent metadata

Field	Value
Publication number	US-9752521-B2
Application number	US-201514859018-A
Country	US
Kind code	B2
Filing date	Sep 18, 2015
Priority date	Sep 18, 2015
Publication date	Sep 5, 2017
Grant date	Sep 5, 2017

Abstract

Methods and systems are provided for regulating a flow of fuel vapors from a fuel tank to an engine during an engine start. In one example, a method may comprise prior to a cold start of an engine: sealing a fuel tank from an evaporative emissions control system and an air intake of the engine, operating a fuel pump of the fuel tank to generate vapors in the fuel tank, and in response to fuel vapor levels in the fuel tank reaching a threshold, initiating cylinder combustion and flowing fuel vapors from the fuel tank to an intake manifold of the engine. The method may further comprise providing liquid fuel to the engine to initiate cylinder combustion.

First claim

The invention claimed is:

1. A method comprising:
prior to an engine cold start:
sealing a fuel tank from an evaporative emissions control system and an air intake of an engine;
operating a fuel pump of the fuel tank to generate vapors in the fuel tank; and

in response to both fuel vapor levels in the fuel tank and an engine speed reaching respective thresholds:
initiating cylinder combustion and flowing fuel vapors from the fuel tank to an engine intake manifold.

2. The method of claim 1 , wherein the sealing the fuel tank comprises closing a fuel tank isolation valve positioned between the fuel tank and the intake manifold.

3. The method of claim 1 , wherein the initiating cylinder combustion comprises cranking the engine with a starter motor and injecting liquid fuel to the engine.

4. The method of claim 1 , wherein the fuel vapor levels are estimated based on a pressure in the fuel tank and a fuel level in the fuel tank, where the pressure is estimated based on outputs from a pressure sensor coupled to the fuel tank and the fuel level is estimated based on outputs from a fuel level sensor positioned within the fuel tank.

5. The method of claim 4 , further comprising prior to an exhaust oxygen sensor reaching a threshold temperature, delivering a desired starting amount of fuel to the engine, the desired starting amount of fuel including one or more of liquid fuel and fuel vapors, where an amount of liquid fuel injected to the engine is inversely proportional to an amount of fuel vapors flowing to the intake manifold.

6. The method of claim 5 , wherein the amount of fuel vapors flowing to the intake manifold is estimated based on the fuel vapor levels in the fuel tank and a vacuum level in the intake manifold is estimated based on outputs from a pressure sensor coupled to the intake manifold.

7. The method of claim 1 , further comprising after an exhaust oxygen sensor reaches a threshold temperature, adjusting one or more of a fuel injection amount via fuel injectors and an amount of fuel vapors flowing to the intake manifold by adjusting a position or duty cycle of a canister purge valve, to achieve a stoichiometric air to fuel ratio, where the amount of fuel vapors flowing to the intake manifold is estimated based on outputs from the exhaust oxygen sensor.

8. The method of claim 1 , wherein the flowing fuel vapors from the fuel tank to the intake manifold comprises opening a canister purge valve positioned in a purge line, the purge line providing fluidic communication between the fuel tank and the intake manifold.

9. The method of claim 1 , wherein the fuel vapors from the fuel tank are routed to the intake manifold during an engine start after one or more prior attempts to start the engine without the routing of the fuel vapors to the intake manifold.

10. The method of claim 1 , wherein the fuel vapors from the fuel tank continue to be delivered to the intake manifold after initiating cylinder combustion.

11. A method comprising:
prior to a cold start of an engine:
sealing a fuel tank from an evaporative emissions control system and an air intake of the engine; and
operating a fuel pump of the fuel tank to generate vapors in the fuel tank; and

cranking the engine with a starter motor, and in response to engine speed reaching a threshold, opening a canister purge valve (CPV) and flowing fuel vapors from the fuel tank and a fuel vapor storage canister to an intake manifold of the engine.

12. The method of claim 11 , further comprising during the cold start and prior to an exhaust oxygen sensor reaching a threshold temperature, providing a desired amount of fuel to the engine, the desired amount of fuel comprising one or more of liquid fuel injected from one or more fuel injectors and fuel vapors from the fuel tank and canister.

13. The method of claim 12 , further comprising prior to the engine speed reaching the threshold, injecting liquid fuel in an amount equivalent to the desired amount of fuel to one or more engine cylinders while cranking the engine to initiate cylinder combustion.

14. The method of claim 13 , further comprising reducing the amount of liquid fuel injected to the one or more engine cylinders from the desired amount in response to the opening of the canister purge valve, where the amount that the liquid fuel is reduced is proportional to an amount of fuel vapors flowing to the intake manifold, so that the desired amount of fuel continues to be provided to the engine prior to the exhaust oxygen sensor reaching the threshold temperature.

15. The method of claim 11 , further comprising not injecting liquid fuel to the engine prior to the engine speed reaching the threshold, and initiating cylinder combustion once the engine speed has reached the threshold by igniting the fuel vapors from the fuel tank and fuel vapor storage canister via a spark from a spark plug.

16. The method of claim 11 , further comprising turning off the fuel pump prior to the engine cold start in response to a state of charge of a vehicle battery decreasing below a threshold.

17. The method of claim 11 , further comprising opening a fuel tank isolation valve and a canister vent valve in response to the engine speed reaching the threshold.

18. The method of claim 11 , further comprising heating the fuel vapor storage canister with a heater coupled to the canister prior to opening of the CPV.

19. The method of claim 11 , wherein the threshold engine speed represents an engine speed at which a vacuum level in the intake manifold is sufficient to draw in fuel vapors from the fuel tank and canister.

20. An engine system comprising:
a fuel tank for storing liquid fuel;
fuel injectors for injecting the liquid fuel to one or more engine cylinders;
a fuel pump included in the fuel tank and configured to pump liquid fuel from the fuel tank to the fuel injectors; and
a controller with computer readable instructions for:
sealing the fuel tank and operating the fuel pump to generate fuel vapors in the fuel tank prior to a cold start of the engine system; and
routing fuel vapors in the fuel tank to the one or more engine cylinders during the cold start in response to an engine speed reaching a threshold.

Assignees

• Ford Global Tech Llc

Inventors

• Dudar Aed M

Classifications

• F02D41/1488

  Inhibiting the regulation · CPC title

• F02D41/1454

  the characteristics being an oxygen content or concentration or the air-fuel ratio · CPC title

• F02M25/0836

  Arrangement of valves controlling the admission of fuel vapour to an engine, e.g. valve being disposed between fuel tank or absorption canister and intake manifold · CPC title

• F02D41/0045

  Estimating, calculating or determining the purging rate, amount, flow or concentration · CPC title

• F02D41/064 Primary

  at cold start (F02D41/067 takes precedence) · CPC title