WO2006005862A1 - System for assisting regeneration of pollution management means associated with catalyst forming means - Google Patents

Abstract

The invention concerns a system for assisting regeneration of pollution management means (1) associated with oxidation catalyst forming means (2) and integrated in an exhaust line (3) of a motor vehicle diesel engine (4), wherein the engine is associated with common ramp means (7, 8) supplying fuel to the engine cylinders, adapted, through modification of engine operation control parameters and use of fuel post-injections into the cylinders thereof, to shift the engine among three depolluting means regeneration strategies, the first called level 1 strategy, the second called level 2 strategy and the third called over-calibrated level 2 strategy, enabling different thermal levels to be achieved in the exhaust line (3).

Description

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

More particularly, the invention relates to such a system in which the engine is associated with common roll fuel supply means thereof, in at least one post injection.

Such a post-injection is, in a conventional manner, an injection of carbu¬ rant after top dead center of the cylinder considered.

These supply means are adapted to implement, by iso-torque, by modifying engine operating control parameters, different regeneration strategies for obtaining different thermal levels in the exhaust line.

Thus, for example, feed means implementing a first regeneration strategy according to a so-called level 1 strategy and a second regeneration strategy according to a so-called level 2 strategy and / or an overcalibrated level 2 strategy have already been implemented. proposed.

It is known that in order to ensure the regeneration of depol¬ lution means such as a particulate filter, the soot trapped in it is burned thanks to the heat supplied by the engine and to the exotherm produced by the conversion. HC and CO on oxidation catalyst means placed for example upstream of the particulate filter.

This combustion can be assisted by a catalyst element melan¬ with soot, resulting for example from a regeneration aid additive, mixed with the engine feed fuel or by a catalyst deposited directly on the walls of the filter to particles (catalyzed particle filter).

The higher the thermal levels in the exhaust line at the inlet of the particulate filter, the shorter the regeneration time of the filter.

However, in critical driving conditions, such as in the city or in traffic jams, the levels achieved through the conventional regeneration assistance strategies of the particulate filter may be insufficient to ensure the correct regeneration of the filter. which can result in very long generations and therefore very fuel-consuming, or even incomplete. Any strategy of elevation of thermal levels during these critical rollings then makes it possible to ensure complete regenerations, to reduce the over consumption due to this regeneration of the particulate filter, and especially to increase the margin of safety with respect to the cracking or breakage of these filters.

The object of the invention is to propose such a strategy. For this purpose, the subject of the invention is a system for assisting the regeneration of depollution means associated with oxidation catalyst means and integrated into an exhaust line of a motor vehicle diesel engine. wherein the engine is associated with common rail fuel supply means of the engine cylinders, adapted by modifying engine operation control parameters and implementing fuel post-injections into the cylinders of the engine. in order to switch the engine between three strategies for regeneration of the means of decontamination, the first so-called level 1 strategy, the second called level 2 strategy and the third one called the supercalibrated level 2 strategy, making it possible to to obtain different thermal levels in the exhaust line, the thermal level obtained by applying the supercalibrated level 2 strategy being higher than that obtained by application of the level 2 strategy, which itself is greater than that obtained by application of the level 1 strategy, characterized in that the supply means are connected to means for detecting a request for regeneration of the means depollution device for controlling the supply means in order to initiate an operation of the engine according to the level 1 strategy, means for monitoring the starting state of the catalyst means to trigger the overcalibrated level 2 strategy, thermal level acquisition means in the exhaust line for engaging the engine level 2 strategy when said thermal level exceeds a predetermined target temperature for a first predetermined period of time or for cutting the regeneration if said temperature has not been reached before the expiry of a second predetermined maximum period of time, and the level 2 operation of the engine to control a supercalibrated level 2 engine operation if the thermal level in the exhaust line drops below a predetermined low temperature threshold for a third period of time, and with looping strategies, until detection of a request to stop regeneration by the detection means. According to other characteristics:

- The objective and low temperatures are calibrated; - time periods are calibrated;

it comprises means for transmitting the request for regeneration and for stopping it;

the means for monitoring the starting state of the catalyst means and for acquiring a thermal level in the exhaust line comprise temperature sensors;

the depollution means comprise a particulate filter;

the particulate filter is catalyzed;

the depollution means comprise a NOx trap;

the fuel comprises an additive intended to be deposited with particles to which it is mixed, on the depollution means to facilitate their regeneration;

the fuel comprises an additive forming a NOx trap,

the depollution means are impregnated with a SCR formulation providing a CO / HC oxidation function; and the engine is associated with a turbocharger.

The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the appended drawings, in which:

FIG. 1 represents a block diagram illustrating the structure of a help system according to the invention; and

- Fig.2 shows a flowchart illustrating the operation thereof.

FIG. 1 has in fact illustrated a system for assisting the regeneration of depollution means designated by the general reference 1, associated with oxidation catalyst means, designated by the general reference 2 and placed in an exhaust line 3 of a heat engine such as a diesel engine of a motor vehicle.

This engine is designated by the general reference 4 and can be associated for example with a turbocharger whose turbine portion 5 is associated with the exhaust line and the compressor portion 6 is placed upstream of the engine.

The engine is associated with common rail fuel supply means of the cylinders thereof, designated by the general reference 7, the operation of which is controlled by a supervisor 8.

These means are then adapted to control the operation of the engine and in particular, by modifying the control parameters of the function of the engine, to switch it between three regeneration strategies of the depollution means, designated by the general reference 9 in this figure, a first so-called level 1 strategy, 11, a second so-called level 2 strategy, 12, and a third said supercalibrated level 2 strategy, 13, to obtain different thermal levels in the exhaust line.

Thus, the thermal level obtained by applying the third supercalibrated level 2 strategy is higher than that obtained by applying the second level 2 strategy, which itself is greater than that obtained by application. of the first level 1 strategy.

The supervisor 8 is also connected to means for transmitting a request for regeneration of the depollution or stopping means thereof, designated by the general reference 15 in this FIG. 1 and to different temperature sensors. for example 16, 17 and 18, distributed in the exhaust line to acquire thermal levels therein, as will be described in more detail later.

The temperature sensor 16 is adapted to acquire, for example, the thermal level in the exhaust line, whereas the sensors 17 and 18, placed on either side of the catalyst means, make it possible to determine, for example, the boot state thereof, conventionally.

The operation of this system is illustrated in FIG. 2 and begins with the reception by the supervisor 8 of a request for regeneration of the depollution means.

On detection of this regeneration request, the supply means 7, 8 are then adapted to engage a motor operation according to the first level 1 strategy, at 21. These means then ensure a monitoring of the priming state of the catalyst forming means 22, to switch on as soon as the catalyst means are activated, the third level 2 strategy overscaled 23.

The thermal level in the exhaust line is then acquired and analyzed to initiate the level 2 engine strategy when the thermal level exceeds a predetermined target temperature for a first predetermined period of time or to cut the regeneration if this temperature has not been reached before the expiry of a second predetermined maximum time period. These different tests are designated by the general reference 24 in this figure, the end of the regeneration being designated by the general reference 25, while the engagement of the level 2 strategy is designated by the general reference 26.

The operation of the engine in level 2 is then monitored to trigger an operation of this supercalibrated level 2 engine if the thermal level in the exhaust line falls below a predetermined low temperature threshold during a third period. time and this, with looping strategies, until the detection of a re¬ generation stop request by the detection means. These various tests are designated by the general reference 27 in this figure, which, as long as the thermal level in the exhaust line has not fallen below the predetermined low temperature, loops back to step 26 of level 2 strategy and in the case where the thermal level in the exhaust line drops below the predetermined low temperature, switches the engine on a level 2 operation sur¬ calibrated at 28, which loops on the test step 24 described above.

This then makes it possible to maximize the chances of success of the regeneration especially in critical driving conditions, such as in the city or in traffic jams. It goes without saying that the objective and low temperatures determined are calibrated, as well as the periods of time mentioned above.

By way of example, the following criteria can be passed for a conventional calibration of aid for the regeneration of a level 2 particulate filter: - maximum temperature exhaust manifold = 800 ° C

maximum catalyst exotherm = 15O ⁰ C

maximum catalyst outlet temperature = 71O ⁰ C

maximum internal catalyst temperature = 76O ⁰ C

- minimum oxygen content of the catalyst exit gas = 3%

the following criteria for an over-calibrated level 2 strategy:

- maximum temperature exhaust manifold = 830 ° C

- exotherm maximum catalyst = 200 ⁰ C

maximum catalyst outlet temperature = 73O ⁰ C

- maximum internal catalyst temperature = no maximum value

minimum oxygen content of the catalyst output gases = 2%;

With the following results:

Of course, it goes without saying that different embodiments of this system can be envisaged and that the means of decontamination can carry a particulate filter, such as a catalyzed particulate filter or a NOx trap.

In addition, the fuel may also comprise an additive intended to be deposited with the particles to which it is mixed, on the depollution means to facilitate their regeneration.

These depollution means may also be impregnated with a SCR formulation providing a CO / HC oxidation function in a conventional manner.

Other oxidation catalyst means may be envisaged and the depollution means and the oxidation catalyst means may be integrated into one and the same element, in particular on the same substrate.

By way of example, a particulate filter incorporating the oxidation function can be envisaged. Similarly, a NOx trap incorporating such an oxidation function can also be envisaged, whether or not it is additive.

This oxidation function and / or NOx trap can be filled, for example by an additive mixed with the fuel.

Claims

1. System for assisting the regeneration of depollution means (1) associated with means forming an oxidation catalyst (2) and integrated in an exhaust line (3) of a diesel engine (4) ) of a motor vehicle, in which the engine (4) is associated with means (7, 8) with a common fuel supply ramp of the engine cylinders, adapted by modifying engine operation control parameters ( 4) and by implementing post-injections of fuel in the cylinders thereof, to switch the engine between three regeneration strategies of the pollution control means (1), the first so-called level 1 strategy (11), the second so-called level 2 strategy (12) and the third said overcalibrated level 2 strategy (13), making it possible to obtain different thermal levels in the exhaust line (3), the thermal level obtained by applying the strategy supercalibrated level 2 (13) being greater than that obtained by applying the level 2 strategy (12), which itself is higher than that obtained by applying the level 1 strategy (11), characterized in that the supply means (7) are connected to means (8) for detecting a request for regeneration of the depollution means (1) for controlling the supply means (7) in order to trigger a function of the engine according to the level 1 strategy (11). ), means (8, 17, 18) for monitoring the starting state of the catalyst means (2) for triggering the overcalibrated level 2 strategy (13), means (8, 16) of acquiring the thermal level in the exhaust line (3) to engage the engine level 2 strategy (12) when said thermal level exceeds a predetermined target temperature, during a first predetermined period of time or to cut the regeneration if this temperature has not been reached before the ex a second predetermined maximum period of time, and means (8) for monitoring the operation of the level 2 (12) of the engine to control an operation of the supercalibrated level 2 motor (13) if the thermal level in the line d escapement (3) falls below a predetermined low temperature threshold for a third period of time, and this, with looping strategies, until the detection of a request for stopping the regeneration by means of detection. 2. System according to claim 1, characterized in that the objective and low temperatures are calibrated. 3. System according to claim 1 or 2, characterized in that the time periods are calibrated. 4. System according to any one of the preceding claims, characterized in that it comprises means (15) for transmitting the request for regeneration and stopping thereof. 5. System according to any one of the preceding claims, characterized in that the means for monitoring the priming state of the catalyst means (2) and thermal level acquisition in the exhaust line (3). , include temperature sensors (16, 17, 18). 6. System according to any one of the preceding claims, characterized in that the pollution control means (1) comprise a particulate filter. 7. System according to claim 6, characterized in that the particulate filter is catalyzed. 8. System according to any one of the preceding claims, characterized in that the pollution control means (1) comprise a NOx trap. 9. System according to any one of the preceding claims, characterized in that the fuel comprises an additive intended to be deposited with particles to which it is mixed on the depollution means (1) to facilitate their regeneration. 10. System according to any one of the preceding claims, characterized in that the fuel comprises an additive forming a NOx trap. 11. System according to any one of the preceding claims, characterized in that the pollution control means (1) are impregnated with a formulation SCR ensuring a CO / HC oxidation function. 12. System according to any one of the preceding claims, characterized in that the engine (4) is associated with a turbocharger (5,6).