Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2000-05-23
2001-10-09
Solis, Erick (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S490000, C701S104000, C701S105000
Reexamination Certificate
active
06298830
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method and apparatus for injecting pressurized high-pressure fuel directly into the cylinders of an internal combustion engine.
BACKGROUND ART
In recent years, high-pressure fuel injection apparatuses capable of injecting high-pressure fuel directly into the cylinders of an internal combustion engine have been employed practically. In conventional high-pressure fuel injection apparatuses of this type, high-pressure fuel obtained by use of a high-pressure pump is accumulated in a common rail and the required amount of high-pressure fuel is directly injected from the common rail into the cylinders. The valve-open period of each injector is controlled by adjusting the pulse width of a drive pulse for driving the injector in accordance with a target amount of fuel injection determined on the basis of the operation condition of the engine at each instant. Consequently, it follows that the amount of fuel injected into the cylinder through an injector when opened is affected by the pressure of the fuel at that time.
To overcome this disadvantage, JP A Hei 7-269394 teaches an arrangement in which the pulse width of the drive pulse signal (injection pulse width) for determining the actual injection period of the injector needed at each instant is corrected in accordance with the actual pressure of the fuel supplied to the injector so as to obtain the desired amount of fuel injection regardless of variation in the pressure of fuel supplied.
The functional relationship established between the injection period of the injector and the amount of fuel injected through fuel pressure as a parameter is utilized in the known apparatus disclosed in JP A Hei 7-269394. This conventional apparatus is arranged in such a way that the fuel pressure at that time is measured prior to the fuel injection and the injection period of the injector is corrected by use of the functional relationship and the measured result, whereby the desired amount of fuel injection can be obtained regardless of variation in the pressure of fuel supplied.
When the arrangement described above is employed, the target amount of fuel injection can be reliably obtained in the case where the fuel pressure stays at the previously measured level during the period of fuel injection. However, the pressure of fuel accumulated in the common rail of an actual apparatus decreases when the fuel is injected from the injector. Therefore, according to the foregoing conventional technology in which the injection period of the fuel from the injector is determined on the basis of only the fuel pressure detected previously, the actual amount of fuel injected becomes less than the target amount of fuel injection and accurate fuel injection operation cannot be achieved.
It is an object of the present invention to provide a method and apparatus for injecting high-pressure fuel which is capable of overcoming the disadvantages mentioned above.
It is another object of the present invention to provide a method and apparatus which is capable of precisely and economically controlling the amount of fuel injected with consideration to decrease in fuel pressure caused by fuel injection.
DISCLOSURE OF THE INVENTION
The present invention is characterized in that variation in fuel pressure over the period when fuel is being injected from an injector is estimated and the injection period of the fuel injected from the injector is adjusted on the basis of the estimated result, whereby the desired amount of fuel can be precisely injected from the injector.
According to the present invention, in a high-pressure fuel injection apparatus comprising a high-pressure pump for pressurizing fuel to supply high-pressure fuel, a fuel injection section having a common rail for accumulating the high-pressure fuel therein and an injector (s) for supplying and injecting the high-pressure fuel accumulated in the common rail to an internal combustion engine, and a control section for controlling an actual injection period of the injector (s);
said control section comprises
a first determining means responsive to at least one signal indicative of the operation condition of the internal combustion engine for determining a target amount of fuel injection per one period of fuel injection;
a second determining means for determining a reference injection period of the injector in correspondence to the target amount of fuel injection determined by the first determining means;
a calculating means responsive to the reference injection period and the rotational speed of the high-pressure pump for calculating a correction value for correcting the reference injection time so as to correct an error caused by decrease in fuel pressure during the period of fuel injection; and
a correcting means for correcting the reference injection period by the correction value, whereby the actual injection period is controlled in response to the output from the correcting means.
The high-pressure pump may be a pump driven by an electric motor. The calculating means may be arranged in such a way that the correction value for the reference injection period is calculated from the engine speed and the target amount of fuel injection, instead of the rotational speed of the high-pressure pump.
According to the present invention, in a method for injecting high-pressure fuel, in which high-pressure fuel pressurized by means of a high-pressure pump is accumulated in a common rail and the high-pressure fuel accumulated in the common rail is injected directly into a cylinder of an internal combustion engine by open/close controlling a solenoid valve of an associated injector, the method comprises a first determining step for determining a target amount of fuel injection per one period of fuel injection, the target amount being matched to the operation condition of the internal combustion engine;
a second determining step for determining a reference injection period indicating a valve-open-period of said solenoid valve for achieving the target amount of fuel injection;
a calculating step for calculating a correction value for correcting the reference injection period so as to correct an error caused by decrease in fuel pressure during the period of fuel injection in response to the reference injection period and the rotational speed of the high-pressure pump;
a step for correcting the reference injection period by the correction value to obtain an actual injection period during which the solenoid valve should be opened, whereby the solenoid valve is open/close controlled to open the solenoid valve for the actual injection time.
The correction value is calculated to become smaller as the rotational speed of the high-pressure pump increases. This calculation may be performed by map calculation based on map calculation data indicating the relationship between the reference injection period and the correction value using the rotational speed of the high-pressure pump as a parameter.
The present invention is advantageous in that the amount of fuel injected can be precisely controlled to enable the engine to operate as desired, because the actual injection period is determined with consideration to decrease in fuel pressure caused by fuel injection from the injector. That is, the target torque is obtained since the amount of fuel injected does not change even if the engine speed varies.
Furthermore, since the precise control can be achieved simply by detecting the rotational speed of the high-pressure pump, increase in cost is small, so that an inexpensive and high-performance high-pressure fuel injection apparatus can be obtained. In the case where the correction value is determined by the use of the engine speed and the amount of fuel injected per one period of fuel injection, instead of the rotational speed of the high-pressure pump, the cost advantage is still greater because no detection of the rotational speed of the high-pressure pump is necessary.
REFERENCES:
patent: 4603669 (1986-08-01), Takemoto et al.
patent: 5535621 (1996-07-01), Glidewell et al.
patent: 5617337
Connolly Bove & Lodge & Hutz LLP
Solis Erick
Zexel Corporation
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