Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1998-01-20
1999-07-06
Miller, Carl S.
Internal-combustion engines
Charge forming device
Fuel injection system
123514, 123479, F02M 3704
Patent
active
059185783
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a fuel feeding system for an internal combustion engine, which can perform an injection of fuel at a relatively high fuel pressure and is suited for use in an in-cylinder injection internal combustion engine.
BACKGROUND ART
As internal combustion engines of the system whereby fuel is injected inside a cylinder--such engines generally called, for example, in-cylinder injection internal combustion engines or direct-injection internal combustion engines (DI internal combustion engines)--diesel engines are widely known. In spark ignition engines (hereinafter called "gasoline engines", as they are gasoline engines in general), those of the in-cylinder injection type have been proposed in recent years.
In such in-cylinder injection internal combustion engines, with a view to improving performance of the engines and reducing exhaust gas, there is a tendency toward increasing a fuel injection pressure to make fuel mist finer and hence to shorten a fuel injecting duration. Further, for engines equipped with supercharging systems, a high fuel injection pressure corresponding to a supercharging pressure is required during supercharging.
A fuel feeding system in an in-cylinder injection internal combustion engine is therefore constructed to feed fuel to a fuel injection valve by further pressurizing fuel through a high-pressure fuel pump subsequent to its pressurization through a low-pressure fuel pump so that such a sufficiently-high fuel injection pressure (for example, of several tens of atmospheres) can be obtained.
As a high-pressure fuel pump, however, a fuel pump of the engine-driven type is generally adopted. Its delivery pressure therefore corresponds to an engine speed (the number of revolutions of an engine). At the time of start-up of an engine, the number of revolutions of the engine is hence small so that the high-pressure fuel pump has an extremely low delivery pressure. The high-pressure fuel pump between a low-pressure fuel pump and a fuel injection valve conversely interferes with a flow of fuel, and a fuel pressure at the fuel injection valve fails to reach even a delivery pressure level of the low-pressure fuel pump.
Further, after the initiation of a start-up operation of the engine, the number of revolutions of the engine is generally low and the delivery pressure of the high-pressure fuel pump is low. The fuel is therefore at a low pressure level. A controller accordingly actuates the fuel injection valve in a low pressure mode. Upon elapse of a predetermined time after the initiation of a start-up operation of the engine, the number of revolutions of the engine generally increases, the delivery pressure of the high-pressure fuel pump becomes higher, and the fuel is brought to a high pressure level. The controller therefore actuates the fuel injection valve in a high pressure mode.
However, depending on the state or environment of the engine, for example, upon attempting a start-up at an extremely low temperature, the number of revolutions of the engine may not increase even when the predetermined time has elapsed. In contrast, the number of revolutions of the engine may increase even before the predetermined time elapses. A disharmony therefore arises between a fuel pressure and a control mode (low pressure mode or high pressure mode) of the fuel injection valve by the controller. As a result, an adequate fuel injection cannot be performed, thereby making it difficult to maintain stable combustion.
With a view to making it possible to obtain a predetermined fuel pressure even when the delivery pressure of a high-pressure fuel pump is not sufficient as in a start-up of an internal combustion engine and, further, to enable good combustion performance in the engine in accordance with a fuel pressure, a fuel feeding system for an internal combustion engine such as that shown in FIG. 5 has therefore been proposed, for example, in Japanese Patent Application Laid-Open (Kokai) No. HEI 7-83134 or the like.
In FIG. 5, there are shown fuel injection valves (i
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Miller Carl S.
Mitsubishi Jidosha Kogyo Kabushiki Kaisha
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