Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2000-06-23
2002-03-05
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S568210, C073S118040, C701S108000
Reexamination Certificate
active
06352065
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and a device for determining a gas charge of an internal combustion engine. The invention is applicable in particular to the field of automotive engineering, for example, in an internal combustion engine in a passenger car.
BACKGROUND INFORMATION
Customary internal combustion engines have an intake manifold in which a gas mixture made up of a fresh air/fuel mixture and an exhaust gas is located. During the operation of the internal combustion engine, this gas mixture is drawn into the cylinder volume of the internal combustion engine and subsequently compressed and burned. The volume of the gas flowing into the cylinder, in particular the fresh air/fuel mixture component of this volume, must be determined to meter the quantity of fuel to be made available for combustion.
German Patent No. 32 38 190 concerns an electronic system to control or regulate the operating characteristics of an internal combustion engine. In doing so, the pressure in the intake manifold is determined based on speed and air throughput in the intake manifold and/or the air throughput is determined based on speed and pressure.
German Paten Application No. 1 97 13 379 concerns a device for determining the air entering the cylinders of an internal combustion engine having a supercharger. This system also takes into account the physical circumstances additionally occurring due to the supercharging. In particular, the physical events occurring in the intake manifold of an internal combustion engine with a supercharger can be readily detected by including physical and fluid engineering relationships.
At least some methods and devices treat the gas mixture present in the intake manifold uniformly with regard to the determination of the gas charge of the internal combustion engine. In particular, no distinction is made between a fresh air/fuel mixture component and an exhaust gas component in the gas mixture. As a result of this, the determined gas charge volumes contain errors. The non-linear relationship between the measured quantities and the target variable of charge per stroke as well as the influence of exhaust gas recirculation are corrected directly in an empirical manner. Such a correction is only precise in a steady-state condition. Moreover, the variable relationship between the gas charge and the intake manifold pressure such as occurs, for example, with active tank ventilation or cam adjustment is not taken into account.
SUMMARY OF THE INVENTION
An object of the invention is therefore to provide a method and a device for determining a gas charge of an internal combustion engine which overcomes the disadvantages described above. In particular, the object may be achieved by determining the fresh air/fuel mixture component in the charged gas volume. Moreover, the invention should be very flexible with regard to the input variables used. In addition, the method according to the invention should be robust and reliable in operation and the associated device should be economical to produce, operate and maintain invention are described in the sub-claims.
A listing of the abbreviations used in the following description can be found at the end of the description.
The aforementioned objects may be achieved by a method for determining a gas charge of an internal combustion engine having an intake manifold, a gas mixture made up of a fresh air/fuel mixture and an exhaust gas being present in the intake manifold, a gas mass flow mp_ab flowing out of the intake manifold and an intake manifold pressure (ps) being present in the intake manifold, including by the steps: determining of a partial pressure of fresh air/fuel mixture component ps_fg in gas mass flow mp_ab by setting up a mass balance for a fresh air/fuel mixture mass flow mp_fg and determining of a partial pressure of exhaust gas component ps_ag in gas mass flow mp_ab by setting up a mass balance for an exhaust gas mass flow mp_ag. In setting up the mass balance, the time derivation of the general gas equation
m×R×T=p×V
is to be understood in particular. Accordingly, the mass balance for the fresh air/fuel mixture component is as follows:
mp_fg
=
mp_fg
_zu
_
-
mp_fg
_ab
=
ⅆ
ⅆ
t
(
m_fg
)
=
ⅆ
ⅆ
t
(
ps_fg
×
VS
×
1
R
×
TS
)
Correspondingly, the following applies to the mass balance for the exhaust gas component:
mp_ag
=
mp_ag
_zu
-
mp_ag
_ab
=
ⅆ
ⅆ
t
(
m_ag
)
=
ⅆ
ⅆ
t
(
ps_ag
×
VS
×
1
R
×
TS
)
This separate balancing of fresh air/fuel mixture and exhaust gas offers the advantage that the charged fresh air/fuel mixture volume can be calculated precisely. This advantageously makes an exact and reliable determination of the quantity of fuel to be supplied possible. It makes environmentally acceptable and energy-saving operation of the internal combustion engine possible. As a result, the operating costs of the internal combustion engine are reduced and its life expectancy is increased. Moreover, it is advantageous that a precise determination of the quantity of fuel to be supplied is made possible even with various configurations of the internal combustion engine, for example, with or without exhaust gas recirculation, with or without supercharging, etc.
In an exemplary particular embodiment of the invention, the method calculates intake manifold pressure ps from the sum of the partial pressure of fresh air/fuel mixture component ps_fg and of the partial pressure of exhaust gas component ps_ag. This calculation is made via the addition:
Ps=Ps_fg+ps_ag
This calculation of intake manifold pressure ps offers the advantage that a possibly additionally measured value for the intake manifold pressure can be checked using the calculated value. Moreover, it is an advantage that the intake manifold pressure can be determined in this manner without the additional expense of a pressure measuring sensor. In addition, it is advantageous that the intake manifold pressure can be determined in this manner even in the event of failure of an existing pressure measuring sensor.
An exemplary embodiment of the invention determines intake manifold pressure ps using a corresponding measuring sensor. Any commercially available pressure measuring sensors may be used as measuring sensors, wire strain gauges, diaphragm pressure sensors or resonant pressure sensors, in particular. The pressure may be determined directly or indirectly via an intermediate medium. The signal supplied by the pressure measuring sensor may be additionally processed by appropriate circuitry; for example, a temperature compensation or an offset balancing may be provided. The determination of intake manifold pressure ps using a measuring sensor offers the advantage that intake manifold pressure ps can be determined very precisely with it. Moreover, it is an advantage that the intake manifold pressure calculated via the partial pressures can be checked and corrected if necessary and the calculation can be calibrated via the measured intake manifold pressure.
An exemplary embodiment of the invention determines gas mass flow mp_ab from the intake manifold pressure. This determination is made with the consideration of speed n of the internal combustion engine as well as a camshaft adjustment NWS that may be present in the internal combustion engine from which a correction value p_iagr of the internal exhaust gas recirculation is taken into account. In particular, this makes it possible to determine gas mass flow mp_ab flowing out of the intake manifold according to the equation:
mp_ab=(ps−p_iagr)×K.
The value K in this connection is a calculation constant in which the pump equation is included and possible pulsation effects that were determined empirically are included. The advantage of this calculation of the gas mass flow mp_ab is that it is possible even without the provision of a measured intake manifold pressure, solely on the basis of the calc
Benninger Nikolaus
Hess Werner
Koerner Hendrik
Mallebrein Georg
Reuschenbach Lutz
Castro Arnold
Yuen Henry C.
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