FR2812687A1 - Regeneration system for integral exhaust catalyst for vehicle with diesel engine has controller initiating a regeneration phase when quantity of chemical species fixed on catalyst over preset value - Google Patents

Abstract

A regeneration system for an integral catalyst in a vehicle exhaust has a controller (17) initiating a regeneration phase when the quantity of chemical species fixed on the catalyst exceeds a preset value. The controller gathers information about operation of the vehicle engine and its fuel supply system to control the air and/or fuel supply (2,8) to the engine. The catalyst is an oxidation catalyst or a DENOx catalyst or NOx removal catalyst. The catalyst is upstream of a particle filter. The controller operates the fuel injectors to deliver 5-50 mm<3> per cylinder during the time when they are normally inactive, e.g between 10 deg after TDC and 180 deg after that. The regeneration phase is disabled when the engine is being electrically heated

Description

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The present invention relates to a system for assisting the regeneration of a catalyst integrated in an exhaust line of a motor vehicle engine.

We know that the reduction of polluting emissions linked to the operation of motor vehicle engines is a constant concern of manufacturers.

Various systems have already been developed in the state of the art to reduce the level of these polluting emissions, in particular by using a catalyst integrated in the exhaust line.

However, the management of the operation of the latter and in particular the management of its regeneration still generates difficulties.

The aim of the invention is therefore to solve them.

To this end, the invention relates to a system for assisting the regeneration of a catalyst integrated in an exhaust line of a motor vehicle engine, characterized in that the engine is associated with various components, among which - air intake means in the engine, - a system for supplying fuel to the cylinders of the engine, comprising electrically controlled injectors associated with these cylinders, - means for acquiring information relating to various operating parameters of the engine and of the components associated with it, and, - means for controlling the operation of the intake means and / or of the supply system, to control the operation of the engine, these control means being in furthermore adapted to determine the quantity of chemical species fixed on the catalyst in order to trigger a regeneration phase of the latter if this quantity exceeds a predetermined threshold.

The invention will be better understood on reading the description which will follow, given solely by way of example and made with reference to the appended drawing which represents a block diagram illustrating an example of the layout of a system according to the invention. to a diesel engine of a motor vehicle.

In fact, this figure shows a diesel engine for a motor vehicle which is designated by the general reference 1.

This diesel engine is associated with air intake means at the inlet thereof, which are designated by the general reference 2.

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At the output, this engine is associated with an exhaust line which is designated by the general reference 3.

Means for recycling exhaust gas from the engine at the inlet thereof are also provided and are designated by the general reference 4. These means are then interposed for example between the outlet of the engine and the intake means 2 of the engine. air in this one.

The exhaust line can also be associated with a turbocharger designated by the general reference 5 and more particularly with the turbine portion thereof, in a conventional manner.

Finally, the exhaust line comprises an oxidation catalyst, for example, designated by the general reference 6, arranged for example upstream of a particulate filter designated by the general reference 7, arranged in the exhaust line.

The engine is also associated with a system for supplying, for example, common fuel to the cylinders thereof. This system is designated by the general reference 8 in this figure and comprises, for example, electrically controlled high pressure injectors associated with these cylinders.

Of course, other high pressure supply systems such as for example pump injectors can be considered.

Conventionally, the fuel is injected for example into each cylinder in the form of at least one pilot injection and one main injection of fuel offset in the engine cycle.

In the exemplary embodiment shown, the engine is a four-cylinder engine and therefore comprises four electrically controlled injectors, respectively 9,10,11 and 12.

These different injectors are associated for example with a common fuel supply rail designated by the general reference 13 and connected to fuel supply means designated by the general reference 14, comprising for example a high pressure pump.

These supply means are connected to a fuel tank designated by the general reference 15 and for example to means for adding to this fuel an additive intended to be deposited on the particulate filter in order to lower the combustion temperature of the fuel. particles trapped in it.

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In fact, this additive can for example be contained in an auxiliary tank designated by the general reference 16 associated with the fuel tank 15 to allow the injection of a certain quantity of this additive into the fuel.

Other means for lowering this temperature can also be used, for example a catalyzed filter.

Finally, this engine and the various components which have just been described are also associated with means for controlling their operation designated by the general reference 17 in this figure, comprising for example any suitable computer 18 associated with storage means for information 19, and connected as input to various means of acquiring information relating to various operating parameters of this engine and of these components, this computer then being suitable for controlling the operation of the intake means, of the recycling means, of the turbocharger and / or of the supply system to control the operation of the engine and in particular the torque generated by the latter as a function of the running conditions of the vehicle in a conventional manner: This is how, for example, this computer is connected to a differential pressure sensor 20 at the terminals of the catalyst and the particulate filter, respectively 6 and 7, to temperature sensors 21, 22 and 23, r espectively upstream of the catalyst, between this catalyst and the particulate filter and downstream of this particulate filter in the exhaust line.

The pressure sensor 20 can also be connected to the terminals of the filter alone.

The computer can also receive information on the oxygen content of the exhaust gases from a Lambda probe #. designated by the general reference 24 in this figure, integrated into the exhaust line.

At the output, this computer is suitable for controlling the air intake means, the exhaust gas recycling means, the turbocharger, the means for adding the additive to the fuel, the fuel supply means. of the common rail and the various injectors associated with the engine cylinders.

In particular, this computer is suitable for triggering a catalyst regeneration phase, for example by triggering a phase

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multiple injections of fuel into the cylinders of the engine during their expansion phase.

During the use of the vehicle, the catalyst fixes different chemical species, solid (soot, ash), liquid (hydrocarbons, water) and gaseous (sulfur species, etc.), which degrade the performance of the catalyst in terms of efficiency. conversion (poisoning) and causing re-emissions of smoke, odors or other pollutants in certain operating phases.

The computer is then suitable for determining the quantity of chemical species fixed on the catalyst to trigger the regeneration phase of this catalyst, if this quantity exceeds a predetermined threshold.

Thus, for example, the computer can evaluate the quantity of chemical species entering the catalyst, for example by means of a map of the emissions of the engine and / or of one or more gas composition sensors as has been described and the capacity for fixing / adsorption and release / desorption of the catalyst, for example by means of temperature sensors arranged upstream and downstream thereof.

From this different information, the computer determines the quantity of chemical species fixed on the catalyst in order, when this exceeds the predetermined threshold, to control the regeneration phase of this catalyst.

In fact, if the catalyst is too loaded with chemical species, its efficiency decreases and re-emissions of fumes, odors or other pollutants can then occur.

These chemical species fixed on the catalyst can in fact be released or burned when the temperature within the catalyst exceeds a predetermined threshold which may depend on the chemical species considered, for example 100 C for H20, 150 to 250 C for HC and 500 at 600 C for soot.

Such an increase in temperature in the catalyst can be caused by increasing the temperature of the engine exhaust gases by initiating a phase of multiple injections of fuel into the cylinders of the engine during their expansion phase.

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Thus, for example, this phase of multiple injections can be triggered by the control means 17 to cause these multiple injections in a range of the operating cycle of the engine extending between +10 to +180 after the top dead center of the latter. Here, the quantity of fuel injected can vary from 5 mm 'per stroke to 50 mm' per stroke, per cylinder and per liter of unit displacement.

This system can find many applications to all types of catalysts placed in an exhaust line of a Diesel engine for example, this catalyst being an oxidation catalyst, a DENOx catalyst, a NOx trap, etc.

It goes without saying of course that the assistance system according to the invention is not limited to use with a Diesel engine whose exhaust line is equipped with a particulate filter, but can be applied to any other type of motor vehicle engine.

In addition, other means can be used to trigger the regeneration of the catalyst, such as for example means for electrically heating the latter, the energy supply of which is then controlled by the control means, to trigger its regeneration.

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Claims (1)

CLAIMS 1. System for assisting the regeneration of a catalyst integrated into an exhaust line of a motor vehicle engine, characterized in that the engine (1) is associated with various components, among which - means ( 2) air intake in the engine, - a system (8) for supplying fuel to the cylinders of the engine, comprising electrically controlled injectors (9,10,11,12) associated with these cylinders, - means (20,21,22,23,24) for acquiring information relating to various operating parameters of the engine and of the components associated with it, and - means (17) for controlling the operation of the means of 'intake and / or supply system, to control the operation of the engine, these control means (17) being further adapted to determine the amount of chemical species fixed on the catalyst (6) to trigger a regeneration phase of the latter if this quantity exceeds a predetermined threshold. 2. System according to claim 1, characterized in that the engine (1) of the vehicle is a diesel engine. 3. System according to claim 1 or 2, characterized in that the catalyst (6) is arranged upstream of a particulate filter (7) in the exhaust line. 4. System according to any one of the preceding claims, characterized in that the catalyst (6) is an oxidation catalyst. 5. System according to claim 1, 2 or 3, characterized in that the catalyst is a DENOx catalyst. 6. System according to claim 1, 2 or 3, characterized in that the catalyst is a NOx trap. 7. System according to any one of the preceding claims, characterized in that the catalyst regeneration phase is triggered by the control means (17) by initiating a phase of multiple injections of fuel into the cylinders of the engine during their phase. of relaxation. 8. System according to claim 7, characterized in that the multiple injections are caused in a range of the engine cycle extending between <Desc / Clms Page number 7> 10 after top dead center and 180 after this, the quantity of fuel injected during this phase of multiple injections being between 5 and 50 mm3 per stroke, per cylinder and per liter of unit displacement. 9. System according to any one of claims 1 to 6, characterized in that the catalyst regeneration phase is triggered by the control means (17) by causing the supply of energy to electrical heating means thereof. . 10. System according to any one of the preceding claims, characterized in that the supply system is a high pressure common rail supply system for the cylinders of the engine. 11. System according to any one of claims 1 to 9, characterized in that the supply system comprises pump injectors.