Internal-combustion engines – Charge forming device – Having fuel vapor recovery and storage system
Reexamination Certificate
2003-03-17
2003-12-09
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Having fuel vapor recovery and storage system
C123S357000, C123S494000, C073S196000, C073S861040
Reexamination Certificate
active
06659087
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to systems and methods connected with vapor storage canisters. In particular, the present invention concerns drawing adsorbed hydrocarbon vapor from a storage canister for use in an internal combustion engine.
BACKGROUND OF THE INVENTION
The automotive industry has actively sought improved emissions reduction, including reduction in emissions due to gasoline evaporation. Gasoline includes a mixture of hydrocarbons ranging from higher volatility butanes (C
4
) to lower volatility C
8
to C
10
hydrocarbons. When vapor pressure increases in the fuel tank due to conditions such as higher ambient temperature or displacement of vapor during filling of the tank, fuel vapor flows through openings in the fuel tank. To prevent fuel vapor loss into the atmosphere, the fuel tank is vented into a canister that contains an adsorbent material such as activated carbon granules.
As the fuel vapor enters an inlet of the canister, the fuel vapor diffuses into the carbon granules and is temporarily adsorbed. The size of the canister and the volume of the adsorbent material are selected to accommodate the expected fuel vapor evaporation. After the engine is started, the control system uses engine intake vacuum to draw air through the adsorbent to desorb the fuel. An engine control system may use an engine control module (ECM), a powertrain control module (PCM), or other such controller to optimize fuel efficiency and minimize emissions. The desorbed fuel vapor is directed into an air induction system of the engine as a secondary air/fuel mixture to consume the desorbed fuel vapor. One exemplary evaporative control system is described in U.S. Pat. No. 6,279,548 to Reddy, which is hereby incorporated by reference.
The amount of adsorbed fuel vapor in the canister will vary, so the amount of fuel vapor available to be drawn from the canister cannot be predicted. Further, the rate at which fuel vapor is drawn from the canister will decrease as more and more is removed until finally all of the fuel will have been desorbed from the canister. It would be desirable to enable the engine or powertrain control module to take into account the amount of fuel vapor drawn from the storage container in optimizing fuel efficiency and minimizing emissions and to be able to adjust for the decrease in fuel vapor from the storage canister as the adsorbed fuel is depleted.
One way to provide to the controller the information of fuel vapor drawn from the storage container might be to control the flow of vapors from the canister into the engine during purging based on information from an exhaust gas oxygen sensor. But a more direct, and possibly more accurate, approach would be to measure directly the amount of hydrocarbon being drawn from the storage canister during purging so that the engine controller can reduce the fuel from the fuel tank injected into the engine accordingly.
It would thus be useful to have a sensor that could measure the amount of hydrocarbon in the air drawn through the canister into the engine for better engine fuel control. The fuel vapor/air mixture exiting the canister will in general have a concentration of fuel (referred to herein also as “hydrocarbon”) vapor that will initially vary depending upon the degree of adsorbent saturation and will decrease as more hydrocarbon vapor is drawn from the canister. Such a sensor could also be used to allow purging of the canister only while there is vapor to be withdrawn from the canister by detecting when the concentration of hydrocarbon vapor becomes zero. Presently, however, no cost-effective hydrocarbon sensors suitable for use in automotive vehicle vapor control systems have been developed. Thus, it would be desirable to be able to monitor the amount of hydrocarbon in the purge air using presently available sensors.
SUMMARY OF THE INVENTION
The present invention provides a method and an apparatus for detecting the concentration of hydrocarbon vapor in purge air drawn from a fuel vapor adsorbent canister or other fuel vapor storage canister, such as would be useful for preventing release of fuel vapors during fueling or for engine cold start with vapor, into the engine of an automotive vehicle. The canister contains adsorbent material capable of adsorbing fuel vapor from a fuel tank storing a volatile fuel. The canister includes a vapor inlet coupled to the fuel tank or a canister that generates fuel vapor, a purge outlet coupled to an air induction system of an engine, and an air inlet having a purge valve. The air induction system draws air from the canister at a given flow rate. Desorbed hydrocarbon vapor enters the air as it is drawn through the canister. The flow rate of the vapor/air mixture drawn into the engine, or “maximum flow rate,” may be governed by a valve with a given maximum flow rate that is located between the vapor canister and the engine. Alternatively, the maximum flow rate may be governed by a pump with a given pump capacity located between the canister and the engine or by a known maximum flow rate due to manifold vacuum generated by the engine. The air inlet further includes a mass flow sensor that measures the air flow rate through the air inlet. The sensor provides the measured value for the air flow rate through the air inlet to an electronic engine controller. The controller approximates the flow rate of hydrocarbon in the air drawn from the canister according to the formula:
hydrocarbon flow rate leaving canister=maximum flow rate−air flow rate through air inlet
The controller can then use the value for the approximate hydrocarbon flow rate calculated from the air flow detected by the mass air flow sensor to make adjustments for engine fuel control or to end purging of the canister when no further vapor (or essentially no vapor) is being drawn from the canister.
The invention further provides a method for purging a vapor storage canister having adsorbed fuel (or hydrocarbon) coupled with an engine having a system for controlling the amount of fuel provided to the engine, e.g. an electronic engine control module. In the method, the amount of fuel vapor in the purge is determined by drawing with a pump or intake manifold vacuum a known total flow rate of air and vapor from the canister; using a mass air flow sensor at the air inlet to determine the flow rate of air into the canister; and subtracting the flow rate of air from the total flow rate to obtain the flow rate of fuel vapor in the fuel/air mixture the pump or manifold vacuum draws from the canister. The known total flow rate of air and vapor drawn from the canister may be obtained, for example, by either using a known manifold vacuum or a pump at a given flow rate capacity to draw the air and vapor through the canister or by using a valve having a given flow rate that limits the flow rate at which the intake manifold vacuum or pump would otherwise draw the air and vapor mixture through the canister. An ECM or PCM can use the information of fuel vapor flow from the canister obtained in this way to improve fuel efficiency. The amount of fuel drawn from the fuel tank can be reduced by the known amount of fuel vapor in the purge.
In another embodiment, the amount of fuel vapor determined to be in the purge gas is monitored so that when the amount drops to a desired amount (for example, when essentially no more hydrocarbon vapor is in the purge), the purge is ended.
In still a further embodiment, the purge gasoline vapor is used for engine cold start and the controller determines the amount of fuel vapor in the purge to use in controlling engine conditions. This process uses a vapor cold start system having a canister containing activated carbon, which adsorbs hydrocarbon vapor to become a charged canister, a system for generating the hydrocarbon vapor to charge the canister, the canister being connected between an air inlet and the intake manifold. A mass air flow sensor is located between the canister and the intake manifold. The mass air flow sensor provides input to an ECM or PCM, which use
General Motors Corporation
Marra Kathryn A.
Miller Carl S.
LandOfFree
Detection of EVAP purge hydrocarbon concentration does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Detection of EVAP purge hydrocarbon concentration, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Detection of EVAP purge hydrocarbon concentration will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3163433