Internal-combustion engines – Charge forming device – Combined liquid and gaseous fuel
Reexamination Certificate
1999-10-11
2001-05-22
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Combined liquid and gaseous fuel
C123S531000, C123S520000
Reexamination Certificate
active
06234153
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention generally relates to fuel control systems for fuel-injected vehicles and, more particularly, to a fuel injector system using fuel vapors from the fuel tank to power an internal combustion engine during start-up and steady-state operation.
2. Discussion
Modern automotive vehicle engines commonly employ injected fuel for combustion. At start-up, when the engine is not fully warm, the injected fuel is commonly cold. Cold fuel is harder to vaporize than warm fuel. As such, some of the fuel remains in a liquid state when injected. The injected liquid fuel tends to lead to decreased combustibility at start-up. This may result in undesirable emission levels.
To improve emission levels, different techniques have been employed before and after combustion. One pre-combustion treatment has been to heat the fuel prior to its injection. By heating the fuel, it becomes more easily vaporized thereby improving its combustibility. While successful, such pre-combustion heating is complex and expensive to implement. A common post-combustion treatment involves the employment of a catalyst in the engine exhaust gas stream. The catalyst burns the undesirable exhaust gas constituents prior to their passage to the atmosphere. While also successful, such post-combustion burning is also expensive and complex to implement.
Modern automotive vehicles are commonly equipped with a fuel vapor purge control system. Such a system accommodates fuel within the fuel tank which tends to vaporize as temperatures increase. The vaporized fuel collects in the fuel tank and is periodically removed by the purge vapor control system. The fuel vapors from the tank are initially collected and stored in a vapor canister. When the engine operating conditions are conducive to purging, a purge valve is opened permitting the engine to draw the fuel vapors from the purge canister for combustion.
Even with such a purge fuel vapor control system installed, some fuel vapor is commonly present in the dome portion of the fuel tank at start-up. Advantageously, it has now been discovered that these fuel vapors can be supplied to the engine at start-up via the fuel injectors. This allows the engine to utile fuel vapors in place of some portion of the cold liquid fuel at start-up. Moreover, the fuel vapors can continue to be injected during the steady-state operation to take full advantage of the availability of the fuel vapor.
SUMMARY OF THE INVENTION
The present invention provides a purge assisted fuel injection system and a method of using the same. The system includes a fuel tank coupled to a purge vapor collection canister by a vapor line. The purge vapor collection canister is coupled to a fuel injector operatively associated with an internal combustion engine by a second vapor line. A purge vapor canister vent valve selectively seals the purge vapor canister from atmosphere such that the fuel tank, purge vapor canister, and fuel injectors form a closed system.
Upon engine start, a purge valve disposed between the purge vapor canister and the fuel injectors is opened such that the pressure differential between the fuel injectors and the remainder of the system causes fuel vapor collected within a dome portion of the fuel tank to be drawn through the purge vapor canister and toward the fuel injectors. Simultaneously therewith, the amount of liquid fuel injected by the fuel injectors to the engine is reduced such that a desired amount of total fuel delivery is established. As the pressure differential between the fuel injectors and the remainder of the closed system changes over time, the flow rate of purge vapors from the fuel tank decreases. Commensurate therewith, the amount of injected liquid fuel is increased. During this time the engine is warming such that the increased amount of injected liquid fuel is more easily vaporized thereby yielding better combustibility. When the engine reaches a fully warm operating condition, the purge valve may be closed with complete fuel delivery being provided by the fuel injectors. Alternatively and desirably, purge vapors, if in adequate supply, may continue to fuel the engine through the fuel injectors during steady-state engine operations to make the most efficient use of the fuel vapors.
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DeGroot Kenneth P.
Duty Mark J.
Reale Michael J.
Soltis Dennis A.
Sullivan Raymond J.
Berry Donna L.
DaimlerChrysler Corporation
Miller Carl S.
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