Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2000-06-01
2002-06-04
Kwon, John (Department: 3754)
Internal-combustion engines
Charge forming device
Fuel injection system
C060S274000, C701S103000, C701S108000, C123S676000, C123S568160
Reexamination Certificate
active
06397820
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for controlling an internal combustion engine. In particular, the present invention is intended for use in connection with motor vehicles, for derivation of temperature values to be used in controlling the vehicle engine. The present invention also relates to apparatus for such control of an internal combustion engine.
BACKGROUND OF THE INVENTION
In connection with vehicles powered by an internal combustion engine, there is a general desire to reduce the vehicle fuel consumption as much as possible. This, in turn, is based upon environmental demands which are aimed at reducing the amount of detrimental discharges to the atmosphere, and upon demands for good fuel economy of the vehicle.
In today's motor vehicles, the supply of air and fuel to the engine is normally controlled by means of a computer-based engine control unit. This control unit is, in a known manner, arranged for detecting signals representing a number of different operating variables of the vehicle, e.g. engine speed, load, engine coolant temperature, vehicle speed, etc. From these signals, the amount of fuel to be supplied to the engine is continuously determined, and the supply is then effected by means of an injection device.
With the intention of limiting the fuel consumption of a vehicle, the control unit may be arranged, in a known way, so as to ensure that, during operation, a stoichiometric air/fuel mixture (i.e. a mixture where &lgr;=1) is fed to the engine. This guideline value cannot be achieved, however, for all points of operation, due to limitations regarding the maximum allowed thermal load on the components comprising the engine and the exhaust system. For example, the temperature of the engine cylinder head and exhaust system, and in any existing turbocharger unit, must be held within certain predetermined maximum limits. Should these limits be exceeded, there would be a risk of damaging the components.
The risk of a high thermal load on the engine system and its components is particularly marked at high loads and engine rotational speeds. For such operating conditions, the engine exhaust gas temperature must be limited, so as not to become so high that there will be a risk of damage to the engine and its associated components, as discussed above.
According to the known art, this cooling effect is obtained by supplying a certain excess amount of fuel to the engine during the above-mentioned operating conditions, such as when the vehicle driver applies full throttle. This will require that the fuel mixture will be controlled so as to deviate from the stoichiometric mixture. More precisely, this increase in fuel supply is controlled to reach a certain level, corresponding to the exhaust gas temperature remaining lower than a predetermined limit value. The magnitude of this limit value may be based on empirical criteria, which in turn would be determined by engine tests, and would include a limit above which there is a risk of damage to certain sensitive components in the engine and exhaust system.
A major drawback with this known procedure relates to the fact that it is not always necessary to supply the excess fuel as quickly as the change in engine load, since the engine and exhaust system temperatures do not increase as quickly as the load changes. This may be attributed to thermal inertia in the various parts of the engine system. This often entails supplying an excess amount of fuel to the engine at high loads and engine speeds, which is a drawback since it increases the vehicle fuel consumption.
Within the relevant technical area, a system for controlling the fuel supply to a combustion engine of a vehicle is previously known from U.S. Pat. No. 5,103,791. This system comprises means for detection of the engine load and the engine coolant temperature. Based on these values of load and temperature, a value of the temperature in the engine exhaust system is estimated. This temperature value is the basis for a correction of the amount of fuel fed to the engine. In this way, the exhaust system temperature can be limited, reducing the risk of damage.
Another system for controlling the fuel supply to a combustion engine is described in U.S. Pat. No. 5,158,063. This system comprises means for estimating the temperature of at least one component in the engine system as a function of the current engine operating conditions. The air/fuel mixture supplied to the engine may then be controlled as a function of this estimated component temperature.
A common feature of these two known systems is that they include relatively simple models for the engine system temperature, in particular providing a control that does not account for the thermal inertia of the respective temperature-sensitive component, e.g. during a sudden increase of the load.
Consequently, there is a demand for controlling the engine operation in a more effective manner based upon derived temperature values corresponding to critical material points, so that the engine system is cooled only when this is actually needed.
The object of the present invention is therefore to provide an improved method for controlling an internal combustion engine, in particular for a more optimized control of the thermal load acting upon the engine.
SUMMARY OF THE INVENTION
This and other objects have now been realized by the invention of a method for controlling an internal combustion engine in a vehicle comprising detecting the value of at least one predetermined variable associated with an operating condition of the internal combustion engine comprising the rotational speed and the load of the internal combustion engine, determining a temperature value of at least one temperature-critical component associated with the internal combustion engine in the vehicle, the temperature-critical component having an inherent thermal inertia, and controlling the thermal load of the internal combustion engine based upon the predetermined temperature value by adding surplus fuel to the internal combustion engine, the adding of the surplus fuel to the internal combustion engine comprising gradually increasing the supply of the surplus fuel based upon the value of the at least one predetermined variable derived from the inherent thermal inertia. In a preferred embodiment, the method includes providing a predetermined limit value for the at least one temperature-critical component, and wherein the controlling of the thermal load of the internal combustion engine comprises cooling the internal combustion engine, the cooling of the internal combustion engine comprising minimizing the cooling over time without the determined temperature value exceeding the predetermined limit temperature value for the at least one temperature-critical component.
In accordance with another embodiment of the method of the present invention, the method includes providing a predetermined limit value for the at least one temperature-critical component, and wherein the gradually increasing of the supply of the surplus fuel comprises controlling the supply of the surplus fuel whereby a substantially stoichiometric air/fuel mixture of the surplus fuel is supplied to the internal combustion engine, and including gradually enriching the air/fuel mixture based upon the difference between the determined temperature value and the predetermined limit temperature value.
In accordance with a preferred embodiment of the method of the present invention, controlling of the thermal load of the internal combustion engine comprises cooling at least one cylinder of the internal combustion engine by supplying an amount of a coolant to the at least one cylinder based on at least the determined temperature value.
In accordance with another embodiment of the method of the present invention, the internal combustion engine includes a thermostat for controlling the supply of coolant to the internal combustion engine, and the controlling of the thermal load of the internal combustion engine comprises controlling the thermostat.
In accordance with ano
Eriksson Sören
Novak Peter
Kwon John
Vo Hieu T.
Volvo Personvagnar AB
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