WO1997015751A1

WO1997015751A1 - Testing of catalyst in the exhaust system of an internal combustion engine

Info

Publication number: WO1997015751A1
Application number: PCT/SE1996/001356
Authority: WO
Inventors: Amir Baranzai; Ingemar LUNDSTRÖM; Anita Lloyd Spetz
Original assignee: Forskarpatent I Linköping Ab
Priority date: 1995-10-25
Filing date: 1996-10-23
Publication date: 1997-05-01
Also published as: SE9503762L; SE505910C2; SE9503762D0; AU7355996A

Abstract

Method for the testing of catalysers of combustion engines, where a gas sensor is placed in the exhausts after the catalyser which is sensitive to some substances normally burnable for the catalyser, for instance a thin oil. While the engine runs, momentarily a suitable amount of this substance is fed to the inlet of the engine, so that the gas sensor indicates the presence of the substance in the exhaust gases and so indicates the correct functioning of the catalyser system.

Description

TESTING OF CATALYST IN THE EXHAUST SYSTEM OF AN INTERNAL COMBUSTION ENGINE

In order to reduce the degree in which cars pollute the air it is known to provide these with a catalyser in the exhaust systems, where a possible surplus of unburnt fuel can be burnt catalytically in the presence of the platinum of the catalyser. Since however the platinum coating of the catalyser can be polluted with unburnable materials or be poisoned by a coating of lead the catalyser in reality has a limited length of life. Due to the required technique for fabrication in order to achieve the large area in the catalyser and not least the use of platinum the catalysers are expensive to fabricate. Consequently one does not wish to exchange them unnecessarily. Since furthermore the lifetime of catalysers is difficult to predict exchange after a certain time has not been prescribed. The result is that some cars are travelling around without catalytic purification of the exhaust. At controls the rate of carbon monoxide is measured in the exhaust gases, this measurement takes however place at idling, that is with very little load for the catalyser, that may cope with this but not more. Alternatively the catalyser may be used up but the car's own control of the fuel feed may be so precise, at idling, that no indication is obtained when measuring.

In view of the above problem there is a need of a practical way. for instance at the annual control of cars, to be able to test the capacity of the catalyser as regards its ability to clean the exhaust gases.

In accordance with the invention this object is solved by placing, in the exhaust pipe, a gas sensor, for instance of the type that is described in the Swedish patent application xx. While the engine is running, preferably idling, a suitable substance that can normally be burnt in the catalyser is injected into the inlet of the engine. If the gas sensor registers a pulse like pollution the catalyser is defect. The injected amount is preferably adapted to the size of the engine and therewith to the capacity of the catalyser.

In order to achieve repeatability in the injection a spring actuated piston/cylinder device may be used that is pre-tensioned to different extents for different engines. The substance that is injected into the engine, passes the engine in a few piston strokes and does therefore not influence the running of the engine in any significant way, if the engine's own fuel is injected as test substance. The only result is that the engine misses a few ignitions. In order to make it unnecessary for the test personnel to handle so volatile substances as petrol instead a thin oil may be used, for instance vegetal. This also has the advantage that the influence on the running of the engine will be less since the oil will not take part actively in the combustion in the engine.

It has turned out that for instance the suggested sensor very well has time to react on the short pulse that is given by the additionally injected amount of burnable substance. If so is desired of course the test may be repeated to improve the precision.

The method in accordance with the invention may when needed be varied according to the motor type that is to be tested and it may in some instances be appropriate to provide the burnable additional amount of the suitable substance to the exhaust system behind the engine but in front of the catalyser. At this one may also provide additional air to secure that sufficient oxygen is present in the exhaust gases or the catalyser to take care of the test burning. In many cars there is already a connection for this and it is not more difficult to carry out this test of the catalyser than to test the function of the ERG valves.

Claims

1. Method for the testing of catalysers of combustion engines, characterised in that in the exhaust gases behind the catalyser a gas sensor is placed sensitive to some for the catalyser normally burnable substance and that during the running of the engine momentarily a suitable amount of this substance is fed to the inlet of the engine, so that the gas sensor indicates the presence of the substance in the exhaust gases and thereby the function of the catalyser system.

2 Method according to claim 1 , characterised in that the substance that is added is a thin oil.

3. Method according to claim 1 or 2, characterised in that the sensor that is used is of the type that includes a catalytic surface layer with a thereunder arranged semiconductor component reacting on the changes in the electrical field that is obtained at catalytic burning on the surface.

4. Injector for the use in the method in accordance with claim 1 for the testing of catalysers, characterised in that it includes a spring pre-tensioned piston, moveable in a cylinder and releasably lockable in its tensioned position.

5. Injector according to claim 4, characterised in that the injector is lockable in different positions corresponding to different feed volumes.

6. Injector according to claim 4 or 5, characterised in that it further includes additional means for the injection of further air or oxygen simultaneously for instance in the form of an additional piston/cylinder device or valve to a system for pressurized air.