EP2456962A1

EP2456962A1 - Device for treating exhaust gas and monitoring method

Info

Publication number: EP2456962A1
Application number: EP10737985A
Authority: EP
Inventors: Olivier Boucher
Original assignee: Peugeot Citroen Automobiles SA
Current assignee: PSA Automobiles SA
Priority date: 2009-07-20
Filing date: 2010-06-10
Publication date: 2012-05-30
Also published as: FR2948147B1; WO2011010029A1; FR2948147A1

Abstract

The invention relates to a device (16) for treating exhaust gas, including a particle filter (20), characterized in that, at the outlet of the particle filter (20), the device (16) further includes a tapping point (22) for the recirculation of the exhaust gases, and an additional filter (24) between the particle filter (20) and the recirculation tapping point (22). The treatment device can be used in particular in a vehicle exhaust line. The invention also relates to a method for monitoring the device. The invention makes it possible to better protect the recirculating loop that is connected to the recirculation tapping point.

Description

DEVICE FOR TREATING EXHAUST GAS AND METHOD OF

CONTROL

The present invention claims the priority of the French application 0955013 filed July 20, 2009 whose content (text, drawings and claims) is here incorporated by reference.

The invention relates to the field of combustion engines, and more specifically to the field of recirculation of the engine gas intake (EGR), particularly in a so-called low pressure circuit, and the treatment of recycled gas. In a combustion engine, it is known to reintroduce a portion of the exhaust gas to the engine intake. This function, recycling or recirculation of the exhaust gas at the intake, is commonly called "EGR", according to the acronym for the English expression "Exhaust Gas Recirculation". The EGR function makes it possible, particularly on diesel engines, to reduce emissions into the atmosphere of nitrogen oxides (NOx), pollutants whose emissions are regulated.

[ooo4] For turbocharged turbocharged engines, there are two main categories of architectures that make it possible to perform the EGR function: "high pressure" architectures and so-called "low pressure" architectures. In high-pressure EGR systems, the exhaust gases intended for recycling are taken upstream of the turbine (the concepts of upstream and downstream are considered according to the direction of flow of the exhaust gases in the circuit engine exhaust) and are re-injected downstream of the compressor. It is currently the most commonly used architecture. In low pressure EGR systems, the exhaust gases for recycling are taken downstream of the turbine and the pollution control system (usually at the outlet of the particle filter) and are fed back upstream of the compressor.

[ooo5] Low-pressure exhaust gas recirculation allows for better energy recovery by the turbocharger, which is traversed by the entire exhaust flow, and ensures better filling of the exhaust gases. engine cylinders, because the exhaust gases reintroduced to the intake are naturally colder than in the context of the high-pressure EGR.

However, in a low-pressure EGR architecture, it is necessary to have a particle filter upstream (or on the low-pressure EGR loop) of the sampling of the gases to be recycled, to the extent that particles could damage or degrade the operation of the turbine upstream of which they would be reintroduced. If the particles are thus removed from the recycled gases during normal operation of the engine and its depollution means, failure of the particulate filter could lead to chain failures, particularly in the turbocharger. In particular, if the particle filter cracks, soot particles can escape and pass into the EGR circuit. In addition, with the aging of the filter, in particular because of the significant thermal stresses it undergoes, a number of debris, including silicon particles, may become detached. [0007] Solutions have been proposed to protect the recirculation loop.

[0008] Document FR-A-2 895 015 describes an exhaust gas treatment device of an internal combustion engine comprising at least one catalytic treatment unit and an exhaust gas recirculation tapping in a " EGR loop ". The gases are distributed at the entrance of this device between two parallel processing paths joining at the exit thereof to the exhaust, including a first path that always leads the gas to the exhaust and a second path that carries stitching and a valve selectively orienting the gas towards the loop or the exhaust.

[0009] Document WO-A-01 9271 1 describes a device in which a filter specific to the recirculation line is arranged upstream of a particle filter in the same envelope (or "canning" in English) as the latter . The gases are recirculated in the recirculation loop against the direction of flow in the particulate filter.

[ooio] However, these devices do not effectively protect the recirculation loop. [Ooi i] For this, the invention provides an exhaust gas treatment device comprising a particulate filter characterized in that at the outlet of the particulate filter the device further comprises a tailpipe recirculation of the exhaust gas. , and an additional filter between the particulate filter and the recirculation tapping.

In a variant, the additional filter has a section transverse to the flow direction of the gas which is smaller than the section of the particulate filter.

In a variant, the filter comprises a plurality of gas circulation paths at the outlet of the particulate filter, a first channel communicating only towards the output of the treatment device and a second channel communicating with the additional filter.

In a variant, the filter comprises a valve movable between several positions, including an open position in which the second channel communicates only to the first channel downstream of the additional filter and a closed position in which the second channel communicates only to the recirculation tapping downstream of the additional filter.

Advantageously, the filter is adapted to operate according to an exhaust filtration mode in which the valve is in the closed position. Furthermore, the filter may be further adapted to operate in a regeneration mode of the particulate filter and the additional filter in which the valve is in the open position, with then preferably, in the regeneration mode, the closed stitching and the valve in open position.

In a variant the valve is free or controlled by a return spring or controlled by a control unit. In a variant, the valve is made of metal.

In a variant, the device comprises an envelope containing the particulate filter and the additional filter.

The present also relates to an exhaust line characterized in that it comprises the device described above and a loop recirculation connected to the exhaust gas recirculation tapping, this loop being preferably a low pressure recirculation loop.

The present invention also relates to a vehicle comprising a motor and such an exhaust line, the recirculation loop being connected to the engine intake.

Finally, the present invention also relates to a method of controlling an exhaust gas treatment device as described above, this method comprising the control of the operation of the device in a gas recirculation mode. exhaust in which the exhaust gas recirculation tap is open and a portion of the exhaust gas is directed to the recirculation tap through the filters or

- In a filter regeneration mode in which the exhaust gas recirculation tap is closed and the exhaust gas is directed to the outlet of the exhaust gas treatment device through the filters.

In a variant, the method is implemented with a device comprising a valve positioned between several positions, and in that this valve is controlled in the open position during the regeneration mode in which the exhaust gases are conveyed only through the filters and in the closed position during the recirculation mode in which a part of the gases is recirculated through the additional filter and the recirculation tap.

Other features and advantages of the invention will appear on reading the following detailed description of the embodiments of the invention, given by way of example only and with reference to the drawings which show:

• Figure 1, an exhaust line at the output of an engine;

• Figures 2 and 3, an example of exhaust gas treatment device. The invention relates to an exhaust gas treatment device comprising a particle filter. At the outlet of the particulate filter, the device further comprises an exhaust gas recirculation tapping, and an additional filtration filter between the particulate filter and the recirculation tapping. The device makes it possible to filter the exhaust gases at the outlet of the particulate filter. In particular, the additional filter can filter particles resulting from poor filtration by the particulate filter (in the event of cracks in the particulate filter, for example). The additional filter can further filter particles from the natural erosion of the particulate filter. This allows better protection of the recirculation loop connected to the recirculation tapping. Finally, the device does not require any fundamental modification on the architectures of existing depollution elements.

Figure 1 shows an exhaust line 12 at the output of a motor 10. The engine is for example of the Diesel type. Line 12 is connected to the motor 10 via an exhaust manifold 14 of the engine. Line 12 comprises a device 16 for treating the exhaust gas circulating in the exhaust line 12. The line 12 may comprise other exhaust gas treatment members (upstream or downstream of the device 16) which are not shown in FIG. 1. The device 16 notably comprises a particulate filter which will be better described in FIG. FIG. 1 shows an exhaust gas recirculation loop 18 or EGR loop (for "Exhaust gas recirculation" in English). The loop 18 recirculates gases from the line 12 to the inlet of the engine 10. In particular, the recirculation loop 18 is a low pressure recirculation loop or low pressure EGR loop. The low pressure EGR loop increases the exhaust gas recirculation rate. This makes it possible to lower the emissions of nitrogen oxides. For this, the line 18 takes the exhaust gas at the outlet of the device 16, and in particular downstream of the particulate filter, and reinjects the gas upstream of a compressor.

Figures 2 and 3 show the device 16 for treating the exhaust gas. The device 16 comprises the particulate filter 20 which makes it possible to filter the soot resulting from the combustion of the fuel in the engine 10. The particulate filter 20 can be regenerated so as to burn the trapped soot by the particulate filter 20. At the outlet of the particulate filter 20, the device 16 comprises a stitching 22 for recirculating the exhaust gas. The loop 18 is connected at the output of the device 16 via the stitching 22. The device 16 further comprises an additional filter 24 between the particle filter 20 and the stitching 22. This protects the recirculation loop 18 ( and in particular a turbocharger at the intake of the engine). Indeed, taking the gas output of the particulate filter 20 can cause problems because during the lifetime of the particulate filter, various phenomena can occur. The particulate filter 20 may lose silicon particles (which constitute the particulate filter 20). The particulate filter 20 may also crack, and allow the combustion particles to pass. These two sources of pollution can be very damaging for the intake circuit (and the turbocharger in particular) if these pollutions are ingested. The additional filter 24 thus makes it possible to treat these sources of pollution. This filter 24 stores combustion particles and other particles. The device 16 may comprise an envelope 26 or "canning" in English in which are joined the filters 20 and 24. The envelope 26 may include an inlet 28 and an outlet 30 between which the gases flow as indicated by In addition, the device 16 may also include an oxidation catalyst 25 upstream of the particulate filter 20, in the envelope 26. This makes it possible to have a treatment device 16 which a unitary module and easier to install on line 12.

The filter 24 may be non-regenerable. The filter 24 then stores the particles of combustion and particulate filter. This can be the case if a crack detection strategy in the particle filter 20 is used, involving a replacement thereof of the filter 20. The filter 24 can then also be replaced, which does not require the treatment of the particles. of combustion therefore to regenerate.

Preferably, the additional filter 24 may be a regenerable filter. It is possible to regenerate the additional filter 24 to rid it of the retained particles. This makes it possible to prevent the filter from having a large storage capacity and makes it possible not to increase the pressure drop, otherwise the low-pressure EGR loop will be plugged. This type of regenerable filter is compatible with any low pressure EGR loop architecture. Similarly this concept is compatible with any particulate filter architecture: additive or not, particulate filter underbody or onboard engine, made of silicon or metal. The regenerable filter 24 being placed before the quilting 22 (and in particular, in the same envelope 26) makes it possible to take advantage of the regeneration strategy of the particulate filter 20 by also passing the regeneration flow through the additional filter 24, for regenerate it and so burn the soot.

The additional filter 24 preferably has a section transverse to the flow direction of the gas in the device which is smaller than the section of the particulate filter 20. In other words, the filter 24 integrated in the envelope 26 preferably covers only a portion of the section of the envelope 26. This reduces the loss of load caused by its presence at full load. In addition, this allows the processing device 16 to comprise several channels 32, 34 for the circulation of the gases at the outlet of the particulate filter 20. A first channel 32 communicates only towards the outlet 30 of the device 16. The gases passing through this channel 32 The output of the particle filter 20 is directly fed to the output of the device 26. A second channel 34 communicates to the additional filter 24. The gases passing through this channel 34 at the outlet of the particulate filter 20 are conveyed to the additional filter 24. Channel 34 makes it possible to route the exhaust gases to the recirculation tap 22.

The device 16 may comprise a valve 36 movable between several positions. The valve 36 makes it possible to partition the channels 32, 34 or to make them communicate. The valve 36 may be made of metal to withstand high temperatures, particularly those reached in the event of regeneration of the filters 20, 24 (1000 ° C or more).

The valve 36 can occupy an open position in which the second communication channel 34 communicates only to the first channel 32 of communication downstream of the additional filter 24. In this position, the stitching 22 is closed. This open position is shown in FIG. 3. At the outlet of the particulate filter 20, the exhaust gases are conveyed towards the filter 24 and then are conveyed towards the track 32 in the direction of the exit of the device 16. This makes it possible to place the device 16 in a regeneration mode of the filters 20, 24. In this mode, the flow of regeneration gas passes through the two filters 20, 24 to burn the particles trapped on the filters without engaging in the loop 18 recirculation. The valve 36 may occupy a closed position in which the second communication channel 34 communicates only to the recirculation tap 22 downstream of the additional filter 24. In this position, the stitching 22 is open. This open position is shown in Figure 2. At the outlet of the particulate filter 20, the exhaust gas is fed to the filter 24 and then routed to the stitching 22 and the loop 18 recirculation. This makes it possible to place the device 16 in a mode of recirculation of the exhaust gases. In this mode, the gas flow is filtered before being recirculated towards the engine intake. Regardless of the position of the valve 36, the channel 32 still makes it possible to evacuate gases towards the outlet 30 of the device 16.

The valve can be controlled by a control unit not shown. The unit then positions the valve 36 in the position corresponding to the operating mode of the device 16. The valve 36 may be a free flap which is not controlled. In the case of FIG. 2, there is a gas pressure which is slightly less important in the track 34 than in the track 32 because of the pressure drop experienced by the gases through the filter 24. The valve 36 is thus kept closed, especially since the gases are discharged to the loop 18 through the stitching 22. In the case of FIG. 3, there is a gas pressure which is slightly greater in the track 34 than in the track 32 because of the closure of the stitching 22. The valve 36 is thus maintained by the gases themselves taking the track 34. It is also possible to provide a return spring of the valve 36 to one of the positions, preferably the position closed.

The invention also relates to a control method of the device 16 for operating the device 16 in one of the previously described operating modes.

Claims

An exhaust treatment device (16) comprising a particulate filter (20) characterized in that at the outlet of the particulate filter (20) the device (16) further comprises a tapping (22) of exhaust gas recirculation, and an additional filter (24) between the particulate filter (20) and the recirculation tapping (22).

2. The device (16) according to claim 1, characterized in that the additional filter (24) has a section transverse to the flow direction of the gas which is smaller than the section of the particulate filter (20).

3. The device (16) according to one of claims 1 or 2, characterized in that it comprises a plurality of gas flow paths at the outlet of the particulate filter (20), a first channel (32) communicating only towards the output of the processing device (16) and a second channel (34) communicating with the additional filter (24).

4. The device (16) according to claim 3, characterized in that it comprises a valve (36) movable between several positions, including an open position in which the second channel (34) communicates only to the first channel (32) downstream of the additional filter (24) and a closed position in which the second channel (34) only communicates to the recirculation tap (22) downstream of the additional filter (24).

5. The device (16) according to claim 4, characterized in that it is adapted to operate according to an exhaust filtration mode in which the valve (36) is in the closed position.

6. The device (16) according to one of claims 4 and 5, characterized in that it is adapted to operate in a regeneration mode of the particle filter (20) and the additional filter (24) in which the valve (36) is in the open position.

7. An exhaust line (12) characterized in that it comprises the device (16) according to one of claims 1 to 6 and a loop (18) for recirculation connected to the stitching (22) for recirculation of the exhaust gases. exhaust, preferably low pressure recirculation loop type.

8. A vehicle characterized in that it comprises a motor (10) and an exhaust line (12) of the engine according to claim 7, the loop (18) of recirculation being connected to the intake of the engine.

9. A method of controlling an exhaust gas treatment device (16) according to one of claims 1 to 6, characterized in that it comprises controlling the operation of the device (16).

- in an exhaust gas recirculation mode in which the exhaust gas recirculation tap (22) is open and a portion of the gases

exhaust system is directed to the recirculation tapping (22) through the filters or

in a mode of regeneration of the filters in which the quilting (22) of

The exhaust gas recirculation is closed and the exhaust gas is directed to the outlet of the exhaust gas treatment device (16) through the filters.

10. The method according to claim 9, characterized in that it is implemented with a device comprising a valve (16) positioned between several positions, and in that this valve is controlled in the open position during the regeneration mode in which the exhaust gases are conveyed only through the filters (20, 24) and in the closed position during the recirculation mode in which a part of the gases is recirculated through the additional filter (24) and the recirculation tap (22). .