IT202100014207A1 - AN EXHAUST GAS AFTER-TREATMENT SYSTEM FOR A WASTE GAS EXHAUST SYSTEM OF AN INTERNAL COMBUSTION ENGINE AND ITS TEST METHOD - Google Patents

Description

DESCRIPTION

of the patent for industrial invention entitled:

?AN EXHAUST GAS AFTER-TREATMENT SYSTEM FOR AN INTERNAL COMBUSTION ENGINE EXHAUST GAS SYSTEM AND METHOD OF CHECKING IT?

TECHNICAL SECTOR

The present invention ? relating to an exhaust gas aftertreatment system for an exhaust gas exhaust system of an internal combustion engine and to a control method of said exhaust gas aftertreatment system.

EARLIER ART

As known, an internal combustion engine? typically equipped with a number of cylinders, each of which ? connected to an intake manifold and an exhaust manifold, to which ? an exhaust duct is connected which feeds the exhaust gases produced by combustion to an exhaust system, which emits the gases produced by combustion into the atmosphere.

An exhaust gas post-treatment system usually includes a pre-catalyst arranged along the exhaust duct; a particulate filter also arranged along the exhaust duct, downstream of the pre-catalyst; and a catalytic converter arranged along the exhaust duct, upstream of the particulate filter.

Finally, the exhaust gas post-treatment system also includes a burner intended to introduce exhaust gases (and consequently heat) into the exhaust duct in order to speed up the heating of the catalytic converter and in order to facilitate regeneration of the filter particulate matter. Inside the burner ? a combustion chamber is defined which receives fresh air from an air supply circuit and which receives fuel from an injector, arranged to inject the fuel into the combustion chamber. Also, a candle ? coupled to the burner to determine the ignition of the mixture present inside the combustion chamber itself.

The exhaust gases produced by the burner have a concentration of pollutants which is particularly high during an initial start-up phase of the burner. During this initial phase, the temperature of the catalytic converter ? lower than the activation temperature and, therefore, the catalytic converter has an extremely low conversion efficiency of the pollutants produced by the burner.

It is therefore of fundamental importance to be able to contain the pollutants produced by the burner and released into the atmosphere, in particular during the start-up phase of the burner itself.

DESCRIPTION OF THE INVENTION

Purpose of the present invention? to provide a method of controlling a burner for an exhaust system of an internal combustion engine which is free from the drawbacks described above and, in particular, which is easy and economical to implement.

According to the present invention there is provided a method of controlling a burner for an exhaust system of an internal combustion engine according to what is claimed in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention will come now described with reference to the attached drawings, which illustrate a non-limiting embodiment thereof, in which:

figure 1 schematically shows an internal combustion engine provided with an exhaust gas post-treatment system made in accordance with the present invention;

- figures 2 to 4 schematically illustrate a first variant of the exhaust gas post-treatment system of figure 1 in different ways? of operation; And

- figure 5 schematically illustrates a second variant of the exhaust gas post-treatment system of figure 1.

PREFERRED EMBODIMENTS OF THE INVENTION

In figure 1, with the number 1 ? indicated as a whole a supercharged internal combustion engine, provided with an exhaust gas exhaust system 2 in a motor vehicle (not shown) and having a number of cylinders 3, each of which ? connected to an intake manifold 4 and to an exhaust manifold 5 via at least one respective exhaust valve (not shown).

The intake manifold 4 receives a gas mixture which includes both exhaust gas and fresh air, i.e.? air coming from the external environment through an intake duct 6, which ? equipped with an air filter for the flow of fresh air and ? regulated by a butterfly valve 8. Along the intake duct 6 downstream of the air filter 7, ? a flow meter 9 (better known as the Air Flow Meter) is also available.

To the exhaust manifold 5? an exhaust duct 10 is connected which feeds the exhaust gases produced by the combustion to the exhaust system 2, which emits the gases produced by the combustion into the atmosphere.

The supercharged internal combustion engine 1 comprises a supercharging system of the internal combustion engine 1, made by means of a turbocharger 11 provided with a turbine 12, which ? arranged along the exhaust duct 10 to rotate at high speed? under the action of the exhaust gases expelled from the cylinders 3, and a compressor 13, which ? disposed along the suction duct 6 and ? mechanically connected to the turbine 12 to be driven into rotation by the turbine 12 itself so? to increase the pressure of the air present in the supply duct 6.

The gas discharge system 2? provided with an exhaust gas post-treatment system 14 comprising a pre-catalyst 15 arranged along the exhaust duct 10, downstream of the turbocharger 11 and a particulate filter 16 (also known as Gasoline Particulate Filter) also arranged along the duct 7, downstream of the pre-catalyst 15. According to a preferred variant, the exhaust gas post-treatment system 14 is? provided with a catalytic converter 17 arranged along the exhaust pipe 7, upstream of the anti-particulate filter 16. According to a preferred embodiment, the catalytic converter 17 and the particle filter 16 are arranged one after the other inside a common tubular container.

According to a first variant, the internal combustion engine 1 ? also provided with a linear oxygen probe 18 of the UHEGO or UEGO type housed along the exhaust duct 10 and interposed between the turbocharger 11 and the pre-catalyst 15 to detect the air/fuel ratio (or title) of the exhaust gases (providing an linear which indicates the oxygen content in the exhaust gases) downstream of the turbocharger 11 and upstream of the pre-catalyst 15.

The internal combustion engine? furthermore provided with a lambda probe 19 designed to supply a binary output of the on/off type which indicates whether the title of the exhaust gases ? above or below the stoichiometric value, housed along the exhaust duct 10 and interposed between the pre-catalyst 15 and the assembly defined by the catalytic converter 17 and the anti-particulate filter 16 to detect the oxygen concentration inside the exhaust gases downstream of the pre-catalyst 15; and finally a lambda probe 20 destined to supply an on/off type binary output which indicates whether the title of the exhaust gases ? above or below the stoichiometric value, housed along the exhaust duct 10 and arranged downstream of the assembly defined by the catalytic converter 17 and the anti-particulate filter 16 to detect the oxygen concentration inside the exhaust gases downstream of the defined assembly by the catalytic converter 17 and by the particulate filter 16.

The exhaust gas post-treatment system 14 then comprises a burner 21 intended to introduce exhaust gases (and consequently heat) into the exhaust duct 10 so as to speed up the heating of the pre-catalyst 15 and/or of the catalytic converter 17 and so as to facilitate the regeneration of the anti-particulate filter 16. The 21 burner? arranged so as to introduce the exhaust gases into the exhaust duct 10 upstream of the pre-catalyst 15 or upstream of the catalytic converter 17.

According to what is better illustrated in figures 2 to 5, inside the burner 21? a combustion chamber 22 is defined which receives fresh air (i.e. air coming from the external environment) via an air supply circuit 23 provided with a pumping device 24 which draws from the external environment and feeds the air via a duct 25. Preferably, between the intake manifold 4 and the pumping device 24 ? interposed an element 39 for filtering the air. The combustion chamber 22 also receives the fuel from an injector 27, arranged to inject the fuel into the combustion chamber 22. Also, a 28 candle ? coupled to the burner 21 to determine the ignition of the mixture present inside the combustion chamber 22. The internal combustion engine 1 also comprises a fuel supply circuit 29 provided with a pumping device 30 which supplies the fuel via a duct 31.

The burner exhaust gas post-treatment system 14 comprises a three-way valve 40 housed along the duct 25, downstream of the pumping device 24. Finally, the exhaust gas post-treatment system 14 comprises a three-way valve 41 housed along an outlet duct 35 intended to pour the exhaust gases leaving the burner 21 into the exhaust duct 10.

Finally, the exhaust gas post-treatment system 14 comprises a duct 42 which originates from the outlet duct 35 (in particular, in correspondence with the three-way valve 41) and along which ? housed a tank 43 for collecting the exhaust gases leaving the burner 21. In particular, the duct 42 connects the three-way valve 41 to the three-way valve 40.

The three-way valve 41 ? made to selectively convey the exhaust gases produced by the burner 21 in the exhaust duct 10 or in the duct 42 towards the collection tank 43 or, alternatively, to convey the exhaust gases collected in the collection tank 43 towards the exhaust duct 10.

The 40 three-way valve ? instead it is made to selectively convey the flow of air towards the burner 21 or in the duct 42 towards the collection tank 43.

Finally, the internal combustion engine 1 comprises a control system 32 which ? suitable for supervising the operation of the internal combustion engine 1 itself. The control system 32 comprises at least one unit? electronic control unit (normally called ?ECU? ? ?Electronic Control Unit?), which supervises the operation of the various components of the internal combustion engine 1.

The spark plug 28 is driven by the unit? Electronic control ECU to make a spark strike between its own electrodes and therefore determine the ignition of the air/petrol mixture inside the combustion chamber 22. The control system 32 further comprises a plurality of of sensors connected to the unit? Electronic control ECU. Also the two three-way valves, indicated respectively by 40 and 41, are connected to the unit? Electronic control ECU that oversees their operation.

The sensors comprise, in particular, a temperature and pressure sensor 33 of the flow of air fed to the burner 21 preferably housed along the duct 25, preferably upstream of the three-way valve 40; a sensor 34 for the temperature and pressure of the exhaust gases leaving the burner 21 housed along the outlet duct 35, preferably upstream of the three-way valve 41; a fuel pressure sensor 36 supplied to the burner 21 housed along the duct 31. The unit? Electronic control ECU ? furthermore connected to the linear oxygen probe 18 of the UHEGO or UEGO type and to the lambda probes 19, 20 from which it receives signals indicative of the air/fuel ratio (or title) of the exhaust gases.

In use, during normal operation of the exhaust gas post-treatment system 14, the working conditions described in the following discussion are envisaged.

For an initial interval of time at the start-up of the burner 21, the temperature of the pre-catalyst 15 and/or of the catalytic converter 17 ? lower than the activation temperature and the concentration of pollutants produced by the burner 21 ? higher than a limit value; the flow of air coming from the intake manifold 4 is directed to the burner 21 while the three-way valve 41 ? driven by the unit? Electronic control ECU so that the exhaust gases leaving the burner 21 are not directed into the exhaust duct 10 but rather in the collection tank 43 (condition illustrated in Figure 2 ).

When the concentration of pollutants produced by the burner 21 has reached a value lower than or equal to the limit value a few instants after the start-up of the burner 21, the flow of air coming from the intake manifold 4 is directed to the burner 21 while the valve 41 vie is driven by the unit? Electronic control ECU so that the exhaust gases leaving the burner 21 are directed into the exhaust duct 10 (condition illustrated in figure 3) in order to be able to exert the heating action on the pre-catalyst 15 and/or catalytic converter 17.

Finally, when is the temperature of the pre-catalyst 15 and/or of the catalytic converter 17 ? above the activation temperature and the internal combustion engine 1 ? in engine cut-off conditions - i.e. when the fuel delivery to the injectors is interrupted during the release phase with the accelerator pedal fully lifted and the internal combustion engine 1 driven by the wheels - a cleaning phase is carried out collection tank 43. Is the three-way valve 40 driven by the unit? electronic control ECU so that the flow of air coming from the intake manifold 4 is not directed to the burner 21 but rather? to the collection tank 43, while the three-way valve 41 is piloted by the unit? Electronic control ECU so that the exhaust gases leaving the collection tank 43 are directed into the exhaust duct 10 (condition illustrated in Figure 4).

According to a second embodiment illustrated in Figure 5, the exhaust gas post-treatment system 14 comprises the three-way valve 41 housed along the outlet duct 35 intended to pour the exhaust gases leaving the burner 21 into the duct 10 exhaust but ? without the three-way valve 40 downstream of the pumping device 24. Furthermore, the flow of air along the duct 25 is regulated by a shut-off valve 26, preferably of the on/off type.

The exhaust gas post-treatment system 14 comprises a duct 44 which originates from the tank 43 for collecting the exhaust gases leaving the burner 21 and flows into the intake manifold 4. The flow of exhaust gas leaving the collection tank 43 through the conduit 44 is regulated by a shut-off valve 45, piloted by the unit? Electronic control ECU.

Also in this case, during normal operation of the exhaust gas post-treatment system 14, the working conditions described in the following discussion are envisaged.

For an initial interval of time at the start-up of the burner 21, the temperature of the pre-catalyst 15 and/or of the catalytic converter 17 ? lower than the activation temperature and the concentration of pollutants produced by the burner 21 ? higher than a limit value; the flow of air coming from the external environment is directed to the burner 21 while the three-way valve 41 ? driven by the unit? Electronic control ECU so that the exhaust gases leaving the burner 21 are not directed into the exhaust duct 10 but rather in the collection tank 43.

When the concentration of pollutants produced by the burner 21 has reached a value lower than or equal to the limit value a few instants after the start-up of the burner 21, the air flow coming from the external environment continues to be directed to the burner 21, while the valve 41 three-way is driven by the unit? Electronic control ECU so that the exhaust gases leaving the burner 21 are directed into the exhaust duct 10 in order to be able to exert the heating action on the pre-catalyst 15 and/or catalytic converter 17.

Finally, when is the temperature of the pre-catalyst 15 and/or of the catalytic converter 17 ? above the activation temperature and the engine conditions permit it (the internal combustion engine 1 is in engine cut-off conditions - i.e. when the fuel delivery to the injectors during the release phase is interrupted with the accelerator fully raised and the internal combustion engine 1 driven by the wheels 2 or the combustion of the engine can tolerate a certain percentage of recirculated exhaust gases) a cleaning phase of the collection tank 43 is performed. Is the shut-off valve 45 driven by the unit? Fully open electronic control ECU so that the exhaust gases leaving the collection tank 43 are sucked into the intake manifold 4.

The exhaust gas post-treatment system 14 and the method described up to now have some advantages; in particular they allow to contain the pollutants which are released into the atmosphere produced by the burner 21 during the start-up phase of the burner 21 itself.

LIST OF REFERENCE NUMBERS

1 internal combustion engine

2 exhaust system

3 cylinders

4 intake manifold

5 exhaust manifold

6 intake duct

7 air filter

8 butterfly valve

9 flow meter

10 exhaust duct

11 turbocharger

12 turbine

13 compressor

14 after treatment system 15 pre-catalyst

16 particle filter

17 catalytic converter

18 linear probe

19 lambda probe

20 lambda probe

21 burner

22 combustion chamber

23 air supply circuit 24 pumping device

25 conducted

26 shut-off valve 27 injector

28 candle

29 fuel supply circuit 30 pumping device

31 conducted

32 control system

33 P, T sensor

34 P, T sensor

35 outlet duct

36 P, T sensor

39 air filter element

40 three-way valve

41 three-way valve

42 conducted

43 collection tank

44 conducted

45 valve

ECU unit? of electronic control

Claims (11)

1.- An exhaust gas after-treatment system (14) for an exhaust gas exhaust system (2) of an internal combustion engine (1) having an exhaust duct (10); the system (14) comprises at least one catalyst (15, 17) arranged along the exhaust duct (10) and a burner (21) intended to introduce exhaust gases into the exhaust duct (10) so as to speed up the heating of the said at least one catalyst (15, 17) by means of an outlet duct (35), in which inside the burner (21) is? a combustion chamber (22) is defined which receives fresh air via an air supply circuit (23) equipped with a pumping device (24) and the fuel from an injector (27), arranged to inject the fuel into the chamber (22) and a spark plug (28) coupled to the burner (21) to determine the ignition of the mixture present inside the combustion chamber (22); the system (14) ? characterized in that it comprises a first three-way valve (41) housed along the outlet duct (35) and a first duct (42) which originates from the outlet duct (35) and along which ? housed a tank (43) for collecting the exhaust gases leaving the burner (21); the first three-way valve (41) ? made to selectively convey the exhaust gases produced by the burner (21) in the exhaust duct (10) or in the first duct (42) towards the collection tank (43) or alternatively to convey the exhaust gases collected in the chamber (43) towards the discharge duct (10). 2.- A system according to Claim 1, in which the air supply circuit (23) comprises a second duct (25) along which housed the pumping device (24); the system (14) comprises a second three-way valve (40) housed along the second conduit (25) downstream of the pumping device (24), wherein the first conduit (42) connects the first valve (41) to three ways to the second three-way valve (40). 3.- A system according to claim 2, wherein the second three-way valve (40) is made to selectively convey the air flow towards the burner (21) or in the first duct (42) towards the collection tank (43). 4. A system according to Claim 1 and comprising a third duct (44) which originates from the exhaust gas collection tank (43) and preferably regulated by means of a first shut-off valve (45). 5.- System according to Claim 4, in which the third duct (44) flows into an intake manifold (4) of the internal combustion engine (1). 6.- System according to claim 4 or 5, in which the air supply circuit (23) comprises a second duct (25) along which the pumping device (24) is housed and regulated by a second shut-off valve (26) arranged downstream of the pumping device (24). 7.- Method for controlling an exhaust gas aftertreatment system (14) for an exhaust gas exhaust system (2) of an internal combustion engine (1) made in accordance with any one of claims 1 to 6; the method provides: a start-up phase of the burner (21) in which the first three-way valve (41) ? piloted so that the exhaust gases leaving the burner (21) are directed into the collection tank (43); And a phase of steady state operation, subsequent to the start-up phase, in which the concentration of pollutants produced by the burner (21) has reached a limit value and in which the first three-way valve (41) ? piloted so that the exhaust gases leaving the burner (21) are directed into the exhaust duct (10). 8.- Method according to claim 7 and comprising a cleaning step of the collection tank (43) in which the second three-way valve (40) is piloted so that the air flow is directed into the collection tank (43) , and the first three-way valve (41) is piloted so that the exhaust gases leaving the collection tank (43) are directed into the exhaust duct (10). 9.- Method according to Claim 7 and comprising a cleaning step of the collection tank (43) in which the first shut-off valve (45) is piloted so that the exhaust gases leaving the collection tank (43) are aspirated inside an intake manifold (4) of the internal combustion engine (1). 10.- Method according to claim 8 or 9, wherein the step of cleaning the collection tank (43)? made when the internal combustion engine (1) ? under engine cut-off conditions. 11. A method according to claim 9, wherein the step of cleaning the collection tank (43) is built the combustion engine (1) ? switched on and in conditions which allow the recirculation of exhaust gases to be tolerated.