Evaporative emissions of fuel vapor from a vehicle having an internal combustion engine occur principally due to venting of the fuel tank of the vehicle. When the vehicle is parked, diurnal changes in temperature or pressure of the ambient atmosphere cause air to waft into and out of the fuel tank. Some of the fuel inevitably evaporates into the air within the tank and thus takes the form of a vapor. If the air emitted from the fuel tank were allowed to flow untreated into the atmosphere, it would inevitably carry with it this fuel vapor. The fuel vapor, however, is a pollutant. For that reason, federal and state governments have imposed increasingly strict regulations over the years governing how much fuel vapor may be emitted from the fuel system of a vehicle.
One approach that automobile manufacturers have long employed to reduce the amount of fuel vapor that a vehicle emits to the atmosphere involves the use of a storage canister. In this approach, a tube, often referred to as a “tank tube,” is used to connect the air space in the fuel tank to the storage canister. Inside the storage canister is contained a sorbent material, typically activated carbon, whose properties enable it to adsorb the fuel vapor. Consequently, when air flows out of the tank, the tank tube carries it to the storage canister wherein the fuel vapor is adsorbed into the sorbent material There the fuel vapors are temporarily stored so that they can be burned later in the engine rather than being vented to the atmosphere when the engine is not operating. Due to increasingly stringent air quality standards, improvements are always sought in the art.
In a first aspect of the invention, an evaporative emissions control system for reducing the amount of fuel vapor emitted from a vehicle is presented, where the vehicle has an engine with an air intake passage and a fuel system. The control system includes a canister having a purge port, a tank port, and a vent port in communication with a sorbent material disposed within the canister. The purge port communicates with the intake passage via a purge valve. The tank port communicates with the fuel system and allows a mixture of air and the fuel vapor it carries to be conveyed between the fuel system and the canister. The vent port connects to one end of a vent valve whose other end communicates to atmosphere. The canister has a substantially cylindrical cartridge heater disposed within it such that the heater is disposed in direct physical contact with the sorbent material so as to allow heat conduction from the heater to the sorbent material. During at least one predetermined time interval electrical power is supplied to the heater through electrical terminals located exterior to the canister to heat the sorbent material when the control system is operated in a regenerative phase of operation. During a storage phase of operation, the control system allows of the mixture of air and fuel vapor to flow from the fuel system through the tank port and into the canister. As the mixture flows through the canister, the sorbent material adsorbs a percentage of the fuel vapor. The mixture of air and any unadsorbed fuel vapor then flows through the vent port and through the vent valve to atmosphere. During the regenerative phase, the control system allows air drawn in from atmosphere to flow through the vent valve and the vent port into the canister. As the mixture flows through the canister, fuel vapor is desorbed from the sorbent material. The mixture of air and desorbed fuel vapor is drawn out through the purge port into the intake passage by the engine for combustion within the engine.
In a related aspect, the invention provides a method of manufacturing an evaporative emissions control system. The method includes receiving a canister having a hole defined in an exterior wall of the canister. The method further includes receiving a substantially cylindrical cartridge heater having electrical terminals disposed at or near one end of the heater. The method further includes disposing a heat sink in contact with the cartridge heater and disposing the cartridge heater through the hole in the canister, so that the heat sink is internal to the canister and the electrical terminals are external to the canister.
The above-mentioned and other features and advantages of this invention will become apparent and be better understood by reference to the following description of embodiments of the invention in conjunction with the accompanying drawings, in which:
The storage canister 10 has a tank port 12 and a purge port 14, both of which communicate with the first compartment 20. The tank port 12 connects to the tank tube 7, and thereby allows the air space in the fuel tank 8 to communicate with the first compartment 20. To the left of the tank port 12 as viewed from the perspective of
The storage canister 10 also features a vent port 16 that communicates with the second compartment 22. The vent port 16 connects to a vent line 6. The vent line 6 communicates with the ambient atmosphere through a vent valve 17. Typically controlled via a solenoid, the vent valve 17 is normally held open. When opened, the vent valve 17 allows the storage canister 10 via the second compartment 22, vent port 16 and vent line 6 to communicate with the atmosphere. The vent valve 17 is closed when the storage canister 10 is being tested for leaks.
Evaporative emission control systems of this type essentially have two phases of operation. During the storage phase when the engine is off, the system operates with the purge valve 15 closed and the vent valve 17 opened. When the pressure in the fuel tank 8 is high relative to atmospheric pressure, air from the tank and the fuel vapor it carries flows into tank tube 7 and through tank port 12 into storage canister 10. Inside the storage canister 10, the fuel vapor is adsorbed by the sorbent material 28 as the air that carried it flows not only through the first compartment 20 but also through the second compartment 22 via intercompartmental flow passage 26. Although a high percentage of the fuel vapor is adsorbed into the sorbent material 28, the air as it exits the canister 10 via vent port 16 carries with it some unadsorbed fuel vapor to atmosphere.
During the regenerative phase of operation when the engine 90 is running, the system operates with both the purge valve 15 and the vent valve 17 opened. A vacuum is developed within the intake manifold as a result of the combustion occurring within the cylinders of the engine 90. This vacuum ultimately causes fresh air from the atmosphere to be drawn through vent valve 17 and into the storage canister 10. Specifically, the air is pulled by vacuum through vent port 16, second compartment 22, flow passage 26, first compartment 20 and out purge port 14. Inside the storage canister 10, as the fresh air flows through the sorbent material 28, it strips it of the fuel vapor that it had adsorbed during the previous storage cycle. The sorbent material 28 is thus regenerated for the next storage phase. The purged fuel vapors are carried by the air stream through purge line 19, purge valve 15, air intake passage 9 and to the cylinders where they are consumed as fuel during combustion.
During the storage phase, the fuel vapors previously adsorbed by the sorbent material 28 may also return to the fuel tank 8 when the pressure in the tank lowers relative to atmospheric pressure. This occurs when the temperature inside the fuel tank 8 drops and the fuel vapors condense. Being normally open, the vent valve 17 under such conditions allows air into the storage canister 10 and relieves any vacuum.
The regeneration process may be aided by providing heat to the sorbent material in the canister, thereby enabling the sorbent material to more readily release the adsorbed fuel vapor. Systems that heat the air entering the vent port of a canister and/or the sorbent material in a canister have been described, for example in U.S. Pat. No. 6,230,693, the entire disclosure of which is hereby incorporated by reference.
Referring to
As depicted in the exploded view of
The cartridge heater 140 shown in the Figures includes a flange 132 to facilitate mounting the cartridge heater 140 to the mounting boss 134 on the canister 110 and sealing the interface between the cartridge heater 140 and the canister 110. The flange 132 is shown being affixed to the mounting boss 134 by fasteners 136, but it will be appreciated that other means of affixing the cartridge heater 140 to the canister 110 may be employed, including but not limited to snap fit, bayonet mount, or adhesives. Sealing the interface between the cartridge heater 140 and the canister 110 may be accomplished by any of a number of known means including but not limited to an O-ring seal, a separate gasket, a form-in-place gasket, and the like. As shown in
With continued reference to
In an embodiment of the invention as shown in
The heat sink 144 may also be provided with a second opening 152, the purpose of which will be recognized with reference to
In a related aspect of the invention, a method is provided to manufacture an evaporative emissions control system. The method may be understood with reference to the exploded view in
In an aspect of the method, the step of disposing at least one heat sink 144 in contact with the cartridge heater 140 includes inserting the cartridge heater 140 through a first opening 146 defined in the heat sink 144. In an advantageous embodiment of the method, the heater 140 and the heat sink 144 are configured so as to result in a press fit between the heater 140 and the heat sink 144.
In a further aspect of the invention, one or more heat sinks 144 may be located in a fixture that is configured to support the one or more heat sinks 144 in a desired position while the heater 140 is inserted through openings 146 defined in the one or more heat sinks 144.
In a further aspect of the invention, the method may include locating a second opening 152 defined in the heat sink 144 so as to substantially surround a feature 156 defined internal to the canister 110. A portion of the feature 156 may subsequently be deformed to prevent relative movement between the heat sink 144 and the canister 110.
While the invention has been described in terms of specific embodiments, the present invention can be further modified within the spirit and scope of this disclosure. This application is intended to cover any variations, uses, or adaptations of the present invention using the general principles disclosed herein. Further, this application is intended to cover such departures from the present disclosure as come within the known or customary practice in the art to which this invention pertains and which fall within the limits of the claims which follow.
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Number | Date | Country | |
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20140158094 A1 | Jun 2014 | US |