Power plants – Internal combustion engine with treatment or handling of... – Exhaust gas or exhaust system element heated – cooled – or...
Reexamination Certificate
1998-10-09
2001-07-03
Chapman, Jeanette (Department: 3711)
Power plants
Internal combustion engine with treatment or handling of...
Exhaust gas or exhaust system element heated, cooled, or...
C060S298000
Reexamination Certificate
active
06253548
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an exhaust system with a catalytic converter for the exhaust gases from an internal combustion engine of a motor vehicle.
BACKGROUND OF THE INVENTION
Exhaust systems for motor vehicles are increasingly of the “catalytic converter” type. The function of the catalytic converter is to reduce the quantity of polluting gases emitted by the engine.
Catalytic converters contain a support material, generally alumina, onto which the noble metals which function as catalysts are deposited. In order to function correctly, the operating temperature of the catalytic converter must be sufficiently high. Motor vehicle manufacturers therefore tend to locate the catalytic converter as close as possible to the exhaust manifold so that the catalytic converter warms up as quickly as possible when the engine is started from cold.
On the other hand, excessively high operating temperatures reduce the service life of a catalytic converter by irreversible transformation of the support material. Such temperatures can also damage the entire exhaust system and necessitate the use of stronger and therefore more costly materials for each component of the exhaust system (muffler, exhaust pipes, etc). Such temperatures can be reached when the engine is working hard, for example on a freeway.
What is more, the improved thermal efficiency of internal combustion engines, in particular fuel injected diesel or petrol engines, reduces heat losses to the cooling circuit. The heat required to heat the passenger compartment is taken from the cooling circuit. Improved efficiency can therefore lead to insufficient heating.
Finally, the necessity to reduce polluting emissions from internal combustion engines has led to the use of new types of catalytic converter, one feature of which is that they operate within a narrow range of temperatures.
The present invention aims to mitigate these drawbacks. More precisely, the invention aims to limit or to regulate the temperature of the gases entering the catalytic converter whilst enabling the catalytic conventer to warm up quickly. The invention also aims to improve the heating of the passenger compartment of the vehicle and the conversion rate of the catalytic converter.
SUMMARY OF THE INVENTION
The invention provides an exhaust system with a catalytic converter for the exhaust gases from an internal combustion engine of a motor vehicle characterized in that it comprises at least one heat exchanger incorporating cooling fluid therein, selector means for selectively directing the exhaust gases, wholly or partly, into said heat exchanger for effecting cooling thereof, and means for using the heat of the cooling fluid from said exchanger to heat the passenger compartment of the vehicle.
Thus the exhaust system of the invention firstly reduces the temperature of the exhaust gases entering the catalytic converter because they are passed through the heat exchanger to cool them before they enter it. However, the exchanger does not compromise the warming up of the catalytic converter since the selector means enable the gases to bypass the exchanger until they have reached a sufficiently high temperature. Furthermore, the heat recovered in this way from the exhaust gases can be used to heat the passenger compartment of the vehicle. To this end the engine cooling fluid preferably passes through the heat exchanger because the heat from that fluid is already used to heat the passenger compartment.
Finally, the exhaust system of the invention regulates the temperature of the exhaust gases entering the catalytic converter by causing a certain flow of exhaust gas through the exchanger.
In a first embodiment of the invention the heat exchanger is located upstream of the catalytic converter in the direction of flow of the exhaust gases, and a pipe is provided for bypassing the heat exchanger, and the selector means comprise at least one valve upstream of the exchanger for selectively directing the exhaust gases, wholly or partly, into said exchanger or into said pipe.
The said valve can have one inlet and one outlet or one inlet and two outlets. In the latter variant either of the two outlets can be fed from the inlet, or both outlets can be fed simultaneously from said inlet.
In this case, the selector means comprise a second valve disposed between the heat exchanger and the catalytic converter at the discharge point of the pipe. The second valve connects the inlet of the catalytic converter either to the outlet of the heat exchanger or to the bypass pipe.
In another embodiment of the invention, the heat exchanger is located downstream of the catalytic converter in the direction of flow of the exhaust gases, a pipe being provided for bypassing the heat exchanger, and the selector means comprising at least one valve between the catalytic converter and the heat exchanger for selectively directing the exhaust gases, wholly or partly, into said heat exchanger or into said pipe.
In this second embodiment the device of the invention can also comprise a second pipe for bypassing the catalytic converter, the selector means comprising at least one valve for selectively directing the exhaust gases, wholly or partly, into the catalytic converter or into said second pipe, a third pipe being provided for conveying the exhaust gases from the outlet of the heat exchanger to the inlet of the catalytic converter.
Alternatively, in the second embodiment, the device of the invention can comprise a cooling loop upstream of the catalytic converter, the selector means comprising a valve for selectively directing the exhaust gases, wholly or partly, into said loop or directly into the catalytic converter.
Consequently, the heat exchanger is located upstream of the catalytic converter in the first embodiment, and downstream of it in the second embodiment. In the first embodiment the exhaust gases coming directly from the exhaust manifold therefore flow through the heat exchanger, which therefore benefits from a high operating temperature. Thus in this case priority is given to heating the passenger compartment.
In the second embodiment, on the other hand, priority is given to preventing pollution. In normal operation the heat exchanger is downstream of the catalytic converter. The catalytic converter therefore operates at a higher temperature, and so under more effective conditions, but the exhaust gases begin to cool in the converter. Their temperature is therefore lower when they enter the heat exchanger which therefore recovers less heat.
Particular embodiments of the invention will now be described by way of non-limiting example and with reference to the accompanying drawings.
REFERENCES:
patent: 3050935 (1962-08-01), Eastwood
patent: 5184462 (1993-02-01), Schatz
patent: 5603215 (1997-02-01), Sung et al.
patent: 195 00 476 (1996-07-01), None
patent: 195 00 472 (1996-07-01), None
patent: 197 006 626 (1997-09-01), None
patent: 47-20659 (1970-06-01), None
patent: 81-09822 (1994-11-01), None
French Search Report dated Jun. 11, 1998.
Ap Ngy Srun
Perset Denis
Chapman Jeanette
Morgan&Finnegan, LLP.
Valeo Thermique Moteur
Varma Sneh
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