Internal-combustion engines – Charge forming device – Having fuel vapor recovery and storage system
Reexamination Certificate
1999-07-01
2001-06-19
Dolinar, Andrew M. (Department: 3747)
Internal-combustion engines
Charge forming device
Having fuel vapor recovery and storage system
C123S568140, C123S568210, C073S117020, C701S108000
Reexamination Certificate
active
06247457
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method for operating an internal combustion engine such as the engine of a motor vehicle. In the engine, air is conducted to an intake manifold via a throttle flap and exhaust gas is fed back from the exhaust-gas pipe to the intake pipe via an exhaust-gas return. The invention also relates to an internal combustion engine and especially an engine for a motor vehicle having a throttle flap via which air can be supplied to an intake manifold. The engine also includes an exhaust-gas return via which the exhaust gas can be returned from an exhaust-gas pipe to the intake pipe and a control apparatus for open-loop or closed-loop control of the engine.
BACKGROUND OF THE INVENTION
The requirements imposed on a modern internal combustion engine become ever greater with the view of reducing the consumed fuel and the discharged exhaust gases and the toxic substances contained therein. This is the same as the objective of improving the combustion in the combustion chamber of the engine and especially to obtain the most complete combustion possible. To reduce the nitrogen oxide, the exhaust gas discharged from the combustion chamber is fed back into the intake manifold and therefore into the combustion chamber for further or renewed combustion.
This can be carried out by means of an external exhaust-gas return wherein a controllable exhaust-gas feedback valve is introduced into an exhaust-gas return line. With this feedback valve, the quantity of the exhaust gas to be fed back can be adjusted. Alternatively, or in addition, it is possible to provide an internal exhaust-gas return wherein an inlet valve of the engine is controlled in such a manner that it is opened at least for a short time duration during the discharge phase of the engine. During this time duration, the exhaust gas from the combustion chamber can reach the intake manifold and this defines an exhaust-gas feedback.
A further measure for improving the operation of the engine comprises precisely detecting the sequence of the combustion, which takes place in the combustion chamber of the engine, in order to be then able to consider the sequence especially as to the metering of fuel into the combustion chamber. One possibility to achieve this comprises forming a model of the engine and especially of the sequence of the combustion in the combustion chamber. As to a model, a type of engine observer is understood in this case. In this way, it can be achieved that the conditions present in the combustion chamber can be taken or derived from the model at each time point. The operating variables of the engine such as the fuel mass to be metered can be optimally determined and adjusted in dependence upon these conditions.
SUMMARY OF THE INVENTION
It is an object of the invention to improve the above-described method for operating an engine with the aid of a model.
The method of the invention is for operating an internal combustion engine such as an internal combustion engine for a motor vehicle, the engine having an intake manifold wherein an air/fuel mixture is formed and an exhaust-gas pipe. The method includes the steps of: supplying air via a throttle flap to the intake manifold; recirculating exhaust gas from the exhaust-gas pipe also to the intake manifold via an exhaust-gas return; and, splitting the air/fuel mixture in the intake manifold into a fresh-gas component (rffgabg), an inert-gas component (rfigabg) and a fuel-gas component (rfhcabg).
The invention is based on the recognition that the gas mixture, which is supplied to the combustion chamber, does not only comprise air but that this gas mixture has a fresh gas component, an inert gas component and a fuel gas component. The fresh gas is understood to be a gas which is necessary for a combustion, that is, oxygen for example. An inert gas is understood to be a gas which is not combustible such as carbon monoxide or carbon dioxide. A fuel gas is a gas such as fuel vapor.
The subdivision into the components of the gas mixture is applied for the gas mixture supplied to the intake manifold in the determination of a model of the engine. Accordingly, the gas mixture supplied to the intake manifold is subdivided into the above-mentioned fresh gas component, inert gas component and fuel gas component. The model of the combustion in the combustion chamber of the engine is then formed on the basis of this subdivision.
It is possible to provide a precise model of the charge in the intake manifold because of the subdivision of the gas mixture, which is supplied to the intake manifold, into the above-mentioned components. Inaccuracies in the formation of the model are thereby avoided. Likewise, it is possible to separately further process the individual components of the exhaust gas. In this way too, the precision is further increased. For example, the fresh gas component in the exhaust gas can be separately coupled with the fresh gas component of the air supplied via the throttle flap. In this way, inaccuracies are avoided which arise with a coupling of the supplied air with the total fed back exhaust gas.
With the aid of the model and especially with the aid of the model charge in the intake manifold of the engine, a conclusion can, inter alia, be drawn as to the sequence of the combustion in the combustion chamber. This opens the possibility to more precisely determine than heretofore the following: the fuel to be injected and/or the air flowing in via the throttle flap and/or the return rate of the exhaust gas. This, inter alia, has the consequence of a reduction of the generated exhaust gas and therefore of the discharged toxic substances.
In an advantageous further embodiment of the invention, the exhaust gas is fed back from the exhaust-gas pipe to the intake manifold via an external exhaust-gas return and the external exhaust-gas return is considered via a first dead time operating on each of the fresh gas component, the inert gas component and the fuel gas component. In an alternative or supplementary advantageous further embodiment of the invention, the exhaust gas from the exhaust-gas pipe is returned to the intake manifold via an internal exhaust-gas return and the internal exhaust-gas return is considered via a second dead time operating on each of the fresh gas component, the inert gas component and the fuel gas component. In this simple manner, it is possible to consider in the determined model the time duration, which the exhaust gas discharged by the combustion chamber needs to reach the intake manifold from the exhaust-gas pipe or from the combustion chamber.
In a further advantageous embodiment of the invention, the quantity of the exhaust gas, which is fed back via the external exhaust-gas return, is determined in dependence upon the control of an exhaust-gas return valve and/or the quantity of the exhaust gas, which is returned via the internal exhaust-gas return, is determined in dependence upon the control of an inlet valve. In this way, it is possible to compute for the model the quantity of the exhaust gas, which is returned via the external exhaust-gas return, from the control of the exhaust-gas return valve. Correspondingly, it is possible to draw a conclusion as to the quantity of the exhaust gas, which is fed back via the internal exhaust-gas return, from the control of the inlet valve.
In an advantageous embodiment of the invention, the regeneration gas from a tank-venting system is supplied to the intake manifold and the regeneration gas is broken down into a fresh gas component and a fuel gas component. The tank-venting system defines still another measure with which less toxic substances are outputted to the air while at the same time fuel should be saved. The fuel which vaporizes in the fuel tank at least to a certain extent is no longer outputted to the ambient; instead, it is trapped and supplied to the intake manifold and therefore to the combustion. According to the invention, this regeneration gas, which originates in the fuel tank, is subdivided into the above-mentioned components. As a differenc
Castro Arnold
Dolinar Andrew M.
Ottesen Walter
Robert & Bosch GmbH
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