Systems and methods for reducing vehicle evaporative emissions

• US 10,047,705 B2
• Filed: 03/14/2016
• Issued: 08/14/2018
• Est. Priority Date: 03/14/2016
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Dudar, Aed M., Yang, Dennis Seung-Man
• Primary Examiner(s): Huynh, Hai
• Assistant Examiner(s): Laguarda, Gonzalo
• Application Number:
  US15/068,839
• Publication Number:
  US 20170260914A1
• Time in Patent Office: 883 Days
• Field of Search: 123516, 123519, 123520, 123459, 7311439
• CPC Class Codes: F02D 41/0032 Controlling the purging of the canister as a function of the engine operating conditions
• CPC Class Codes: F02D 41/042 for stopping the engine
• CPC Class Codes: F02M 25/0836 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 Class Codes: F02M 25/0854 Details of the absorption canister
• CPC Class Codes: F02M 25/089 Layout of the fuel vapour installation
• CPC Class Codes: F02M 35/0218 acting by absorption or adsorption; trapping or removing vapours or liquids, e.g. originating from fuel

Abstract

Methods and systems are provided for managing fuel vapor in a vehicle evaporative emissions system configured with a fuel vapor canister for capturing and storing vapors from a vehicle fuel tank. In one example, a three-way valve is positioned between the fuel vapor canister and atmosphere, and may function during engine-off conditions to direct fuel tank vapors through the fuel vapor canister where they may be adsorbed, and then to an intake manifold of the engine where a second adsorbent for capturing and storing fuel vapors is positioned. In this way, fuel vapors that are not adsorbed by the fuel vapor canister, or fuel vapors that are freed from the canister during engine-off conditions may be routed to the second adsorbent prior to exiting to atmosphere, thus reducing undesired bleed emissions.

Claims

1. A method comprising:

operating an engine;

when an engine is operating, routing vapors from a fuel tank through a purge valve, and routing desorbed vapors from a vapor adsorbent through the purge valve, into the engine for combustion, the desorbed vapors desorbed from the vapor adsorbent via fresh air routed through a three-way vent valve positioned between the vapor adsorbent and atmosphere;

not operating the engine; and

when the engine is not operating, changing the routing so that fuel tank vapors are routed through the vapor adsorbent for adsorption and then to an intake manifold of the engine without being routed through the purge valve, the fuel tank vapors routed from the vapor adsorbent to the intake manifold via the three-way vent valve.

2. The method of claim 1, further comprising:

closing or maintaining closed the purge valve when the engine is not operating, and wherein changing the routing so that fuel vapors are routed through the vapor adsorbent for adsorption and then to the intake manifold without being routed through the purge valve comprises routing the fuel vapors through the vapor adsorbent, through the three-way vent valve, and from the three-way vent valve to the intake manifold via a vapor line that couples to the intake manifold downstream of an intake throttle, and further comprising, during a fuel tank refill event when the engine is not operating, opening the intake throttle.

3. The method of claim 1, wherein changing the routing so that fuel tank vapors are routed through the vapor adsorbent for adsorption and then to the intake manifold of the engine without being routed through the purge valve includes coupling a fuel tank that supplies fuel to the engine to the intake manifold, wherein not operating the engine includes one or more of not operating the engine following a key-off event or not operating the engine while a vehicle in which the engine is installed is powered solely by energy provided by an onboard energy storage device, wherein the vapor adsorbent is housed in a fuel vapor canister, and further comprising:

capturing and storing fuel tank vapors not adsorbed by the fuel vapor canister in the intake manifold of the engine when the engine is not operating.

4. The method of claim 3, wherein capturing and storing fuel tank vapors not adsorbed by the fuel vapor canister further comprises:

capturing and storing fuel tank vapors in a second vapor adsorbent, the second vapor adsorbent smaller than the adsorbent housed within the canister.

5. The method of claim 1, further comprising:

opening the purge valve when the engine is operating under a predetermined set of conditions so that the fuel tank vapors are inducted into the engine, and atmospheric air is inducted across the vapor adsorbent via the three-way vent valve being in a first position to desorb stored fuel vapors which are then inducted into the engine; and

sealing the vapor adsorbent from the engine under another set of predetermined conditions while the engine is operating so that fuel tank vapors are routed through the vapor adsorbent for adsorption prior to exiting to atmosphere, the sealing including closing the purge valve and maintaining the three-way vent valve in the first position, and wherein when the engine is not operating, the fuel tank vapors are routed from the vapor adsorbent to the intake manifold via the three-way vent valve in a second position.

6. A system for a vehicle, comprising:

a fuel vapor canister comprising;

an adsorbent bed and an adsorbent buffer, the adsorbent bed coupled to a canister vent port and the adsorbent buffer coupled to a canister load port and a canister purge port;

a fuel tank fluidly connected to the vapor canister adsorbent buffer at the canister load port;

a canister purge valve positioned in a first vapor line between the canister purge port and an engine intake manifold of the vehicle;

a three-way vent valve positioned in a vent line between the canister vent port and atmosphere, the three-way valve also connected to a second vapor line which in turn is coupled to the intake manifold downstream of the canister purge valve, the three-way vent valve having a first position which couples the canister vent port to atmosphere a second position which couples the canister vent port to the second vapor line and a third position which seals the canister vent port; and

a controller, holding executable instructions stored in non-transitory memory, that when executed, cause the controller to;

responsive to a first condition that includes an engine-off condition, direct fuel tank vapors from the fuel tank through the fuel vapor canister to the engine intake manifold by closing the canister purge valve and controlling the three-way vent valve to its second position; and

responsive to a second condition that includes an engine-on condition, direct fuel tank vapors from the fuel tank through the fuel vapor canister to atmosphere without being directed to the engine intake manifold by closing the canister purge valve and controlling the three-way vent valve to its first position.

7. The vehicle system of claim 6, wherein the controller further holds executable instructions stored in non-transitory memory, that when executed, cause the controller to:

responsive to the first condition, command or maintain the three-way valve in the second position such that the canister vent port is fluidly coupled to the engine intake manifold via a junction between the canister purge valve and the engine intake manifold; and

responsive to the second condition, command or maintain the three-way vent valve in the first position such that the canister vent port is fluidly coupled to atmosphere to direct fuel tank vapors through the fuel vapor canister to atmosphere.

8. The vehicle system of claim 7, further comprising:

an air intake throttle positioned between the engine intake manifold and atmosphere; and

wherein

the controller is further configured with instructions stored in non-transitory memory, that when executed cause the controller to;

responsive to the first condition, command open the air intake throttle.

9. The vehicle system of claim 8, wherein commanding open the air intake throttle comprises a request for refueling of the fuel tank;

and wherein

the controller is further configured with instructions stored in non-transitory memory, that when executed cause the controller to;

return the air intake throttle to a default condition subsequent to completion of refueling the fuel tank.

10. The vehicle system of claim 7, wherein the second condition includes engine operation under a predetermined set of conditions;

and wherein

the controller is further configured with instructions stored in non-transitory memory, that when executed cause the controller to;

responsive to another set of predetermined conditions during the second condition, open the canister purge valve and command the three-way vent valve in the first position to induct fuel tank vapors into the engine intake manifold, and to direct atmospheric air across the adsorbent bed to desorb stored fuel vapors which are then inducted into the engine intake manifold for combustion.

11. The vehicle system of claim 6, further comprising:

an air intake system hydrocarbon trap positioned in the engine intake manifold.

12. The vehicle system of claim 7, wherein the controller is further configured with instructions stored in non-transitory memory, that when executed cause the controller to:

seal the fuel vapor canister and fuel tank from the engine intake manifold and from atmosphere by commanding closed the canister purge valve and commanding the three-way vent valve to a third position.

13. The vehicle system of claim 12, further comprising:

a fuel tank pressure transducer positioned between the fuel tank and the fuel vapor canister; and

wherein

the controller is further configured with instructions stored in non-transitory memory, that when executed cause the controller to;

in the first condition, responsive to predetermined conditions being met,

seal the fuel vapor canister and fuel tank from the engine intake manifold and from atmosphere; and

indicate an absence of undesired evaporative emissions responsive to a pressure build greater than a predetermined threshold; and

in the second condition, responsive to predetermined conditions being met,

open the canister purge valve while maintaining the three-way vent vent valve in the third position to draw vacuum on the fuel vapor canister and fuel tank;

close the canister purge valve responsive to a vacuum build reaching a predetermined threshold;

monitor pressure bleed-up for a predetermined duration; and

indicate an absence of undesired emissions responsive to pressure bleed-up lower than a predetermined threshold pressure bleed-up.

14. The vehicle system of claim 13, wherein the controller is further configured with instructions stored in non-transitory memory, that when executed cause the controller to:

in the first condition, responsive to the pressure build lower than the predetermined threshold,

command the three-way vent valve to the second position to depressurize the fuel tank and fuel vapor canister;

command the three-way vent valve to the third position responsive to pressure reaching atmospheric pressure;

monitor vacuum build for a predetermined duration; and

indicate the absence of undesired emissions responsive to vacuum build greater than another threshold vacuum build.

15. A method for a vehicle comprising:

coupling a fuel tank that supplies fuel to an engine to an intake manifold of the engine during engine-off conditions, wherein an engine-off condition includes one or more of a key-off event or a condition wherein the vehicle is powered solely by energy provided by an onboard energy storage device, and wherein fuel tank is coupled to the engine via a three-way vent valve during engine-off conditions; and

coupling the fuel tank to the intake manifold of the engine via a purge valve during engine-on conditions, the three-way vent valve configured to additionally couple the fuel tank to atmosphere during the engine-on conditions.

16. The method of claim 15, further comprising:

selectively coupling the intake manifold to atmosphere via an air intake throttle; and

commanding open the air intake throttle, wherein the engine-off condition includes a refueling event where fuel is added to the fuel tank.

17. The method of claim 15, further comprising:

adsorbing fuel tank vapors in a fuel vapor canister positioned in an evaporative emissions system of the vehicle; and

wherein

coupling the fuel tank to the intake manifold during engine-off conditions routes fuel tank vapors to the fuel vapor canister to be adsorbed therein, prior to being routed to the intake manifold.

18. The method of claim 17, further comprising:

adsorbing fuel tank vapors in an adsorbent material positioned in the engine intake manifold; and

wherein

coupling the fuel tank to the intake manifold during engine-off conditions reduces bleed emissions from the fuel vapor canister.