Internal-combustion engines – Combustion chamber means having fuel injection only – Using multiple injectors or injections
Reexamination Certificate
2000-09-18
2001-11-06
Kwon, John (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Using multiple injectors or injections
Reexamination Certificate
active
06311669
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a method for determining the injection time in a direct-injection internal combustion engine.
The diesel direct injection is controlled by a controller. it is known to split up the injection process into one or more pre-injections and into one or more main injections in order to optimize combustion characteristics with regard to exhaust gas emission and combustion noise. A drive time of the injectors that is required for a desired quantity to be injected into the cylinders is determined by a characteristic diagram. An important input variable for the characteristic diagram is an instantaneous pressure in a lead or in the pressure reservoir, frequently denoted as a common rail or simply as a rail, since this is detected by measurement. The pressure in the lead is assumed to be constant in known systems. That is to say, the drive time of the injectors is determined with the aid of the same pressure for the pre-injection and also for the main injection. However, the pressure between two sequential injections, for example between the pre-injection and the main injection, can be regarded as constant only as a coarse approximation, as measurements substantiate. Pressure fluctuations are produced in the injector and in the lead and give rise to a marked change in the injection quantity.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a is method for determining the injection time in a direct-injection internal combustion engine which overcomes the above-mentioned disadvantages of the prior art methods of this general type, in which the fuel quantity to be fed corresponds as exactly as possible to a desired value when the injection process is split up into a plurality of injections.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for determining an injection time in a direct-injection internal combustion engine having a high-pressure reservoir containing fuel and connected to an injector so that the fuel can be injected under control into a cylinder of the internal combustion engine as a function of at least a pressure in the high-pressure reservoir and a required fuel quantity. The method includes splitting up a total quantity of the fuel to be fed to the cylinder of the internal combustion engine into at least two injection processes per cylinder stroke; and taking into account pressure fluctuations in the injector occurring between the two injection processes, and in a line between the high-pressure reservoir and the injector when determining the injection time for a next injection process.
The pressure fluctuations occurring during two sequential injections (for example the pre-injection and the main injection) within the same working cycle of a cylinder in the lead to the injector are taken into account with the aid of a correction term. The drive time of the injectors is determined with the aid of the corrected pressure so that the desired fuel quantity is injected. The correction term is determined with the aid of a least-squares estimator that estimates the injection pressure at the nozzle of the injector as a function of the geometrical data of the system, in particular a length of the lead from the rail to the injector and the physical boundary conditions, for example the fuel temperature.
In accordance with an added feature of the invention, there is the step of feeding in the total quantity of the fuel in a pre-injection process and a main injection process, and taking into account the pressure fluctuations initiated by the pre-injection process when determining the injection time for the main injection process.
In accordance with an additional feature of the invention, there is the step of feeding in the total quantity of the fuel in a plurality of pre-injection processes and one main injection process, and taking into account the pressure fluctuations initiated by each of the pre-injection processes when determining the injection time for one of a respectively following pre-injection and the main injection process.
In accordance with another feature of the invention, there is the step of using the pressure fluctuations occurring between individual injection processes in each case to determine a correction term with an aid of which the pressure in the high-pressure reservoir is corrected, and determining the injection time with an aid of a corrected pressure value.
In accordance with another added feature of the invention, the corrected pressure value is an input variable of a characteristic map in which injection times are stored in dependence on the required fuel quantity.
In accordance with another addition feature of the invention, there is the step of determining the correction term with an aid of a least-squares estimator which, on a basis of an equation of a damped oscillation for the pressure fluctuations determines the injection pressure at a nozzle of the injector in dependence on geometrical data of an injection system and of physical boundary conditions.
In accordance with further added feature of the invention, there is the step of defining the equation of the damped oscillation for the pressure fluctuations as:
y(t)=A·e
−d·(t−t
0
)
·sin(2·&pgr;·f(t−t
0
)+&phgr;)·&sgr;(t−t
0
)
where
A
is an amplitude of an oscillation,
d
is a damping factor,
t
0
is a starting instant of the oscillation,
f
is a frequency,
&phgr;
is a phase, and
&sgr;(t − t
0
)
is a jump function at an instant t = 0.
In accordance with a concomitant feature of the invention, there is the step of using a further equation for determining an estimated pressure characteristic defined by:
p
(
t
)
=
b
^
2
cos
(
arctan
b
^
1
b
^
2
)
·
e
-
d
·
(
t
-
t
0
)
·
sin
(
ω
(
t
-
t
0
)
+
arctan
b
^
1
b
^
2
)
·
σ
(
t
-
t
0
)
,
where
b
1
=
A
·
sin
ϕ
b
2
=
A
·
cos
ϕ
.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for determining the injection time in a direct-injection internal combustion engine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made is therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
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patent: 5678521 (1997-10-01), Thompson et al.
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patent: 6073606 (2000-06-01), Shimizu et al.
patent: 6073608 (2000-06-01), Krieger et al.
patent: 6082331 (2000-07-01), Barnes et al.
patent: 6164264 (2000-12-01), Thomas
Patent Abstracts of Japan No. 62-186034 (Daisaku), dated Aug. 14, 1987.
Przymusinski Achim
Rader Thomas
Schernewski Ralf
Greenberg Laurence A.
Kwon John
Lerner Herbert L.
Siemens Aktiengesellschaft
Stemer Werner H.
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