FR2900195A3 - Internal combustion engine`s exhaust gas treating assembly for motor vehicle, has flap movable between positions in which flap permits/does not permit gas flow in by-pass pipe, respectively, and injector associated with air injection - Google Patents

Abstract

The assembly has a particle filter placed in the downstream of an exhaust gas treating catalyst along a direction of flow of an exhaust gas (G). An exhaust pipe (2) connects an exhaust line of an internal combustion engine to an inlet of the catalyst. A by-pass pipe (7) is placed in upstream of the catalyst. A low pressure fuel injector (8) is placed on the pipe (7), where an air injection is associated with the injector. The pipe (7) has a by-pass flap (9) that is movable between positions in which the flap permits and does not permit the flow of the exhaust gas in the pipe (7), respectively. An independent claim is also included for a method of treating an exhaust gas of an internal combustion engine of a motor vehicle.

Description

EXHAUST INJECTOR PROTECTION BY-PASS CONDUIT

  The present invention relates to the field of engine exhaust gas treatment of a motor vehicle. Ble more particularly relates to devices for optimally using particulate filters inserted in the exhaust line, downstream of a catalyst for treating these gases. Such filters have the role of trapping the soot and particles contained in the combustion gases in the engine to reduce their emission to the atmosphere. Their performances are directly related to the temperature of the gases at their entry, and several solutions are known to increase it, in particular during the regeneration phases of these filters, during which the particles and trapped soot are thermally destroyed so that their accumulation does not disturb the flow of the exhaust gas. The main injection can thus be delayed and associated with one or more late post-injections, or a low pressure injector can be inserted into the exhaust line, upstream of the catalyst, in order to increase the amount of hydrocarbons within of this: these hydrocarbons, by burning in the already initiated catalyst, make it possible to increase the temperature of the gases upstream of the particulate filter. Such an injector, implanted in the exhaust duct, is, however, exposed to all temperature variations in the exhaust line. It is, moreover, exposed to fouling by the particles and soot resulting from combustion in the engine, which can lead to a degradation of its performance. It is known, for example from document US4615173, to insert, upstream of the particulate filter, a fuel injector, associated with an air injection and a priming device, in a duct opening into the air line. 'exhaust. This injector makes it possible to initiate a second combustion, and thus to increase the temperature of the gases at the inlet of the particulate filter. Such an injector, placed slightly behind the flow of gas flowing in the exhaust line, is here less exposed to fouling and temperature variations. Such a device, however, is not suitable for the use of a low pressure injector. It has, moreover, a relatively large size. The present invention aims to protect an injector under the best conditions.

For this purpose, it proposes to place a bypass duct upstream of the catalyst. Advantageously, a fuel injector is placed in the bypass duct. According to a preferred embodiment of the invention, the bypass duct is equipped with a bypass flap, movable between a position in which it allows the passage of exhaust gases in the bypass duct. , and a position in which it prevents the passage of exhaust gases in the bypass duct. According to various embodiments, the fuel injector may also be associated with an auxiliary device for injecting air. The subject of the invention is also a method of treatment, by an assembly as described above, of the gases resulting from combustion in the engine of a motor vehicle, in which: during the regeneration phases of the particulate filter, said gases 20 are conveyed into the particulate filter via the bypass duct, during the other operating phases, said gases are conveyed into the particulate filter without passing through said bypass duct. Finally, the invention relates to a motor vehicle engine whose exhaust line is equipped with such a treatment unit. Other characteristics and advantages of the invention will emerge on reading the description which follows, with reference to the appended figures in which: FIG. 1 is a schematic overview of an exhaust line provided with a 2 is a schematic view of the invention, according to a first position of the bypass flap, FIG. 3 is a schematic view of the invention, according to FIG. a second position of the bypass flap. Figure 1 schematically shows an exhaust gas treatment assembly G of the internal combustion engine 1 of a motor vehicle. G gases from combustion in the engine 1 are conveyed, via an exhaust pipe 2, to a catalyst 3 in which they undergo a first treatment, then through a pipe 4, to a particulate filter Wherein the particles and soot present in the gases G are trapped. The gases G are then conveyed via a suitable conduit 6 to the atmosphere. The exhaust duct 2, the catalyst 3, the duct 4, the particulate filter 5 and the duct 6 constitute the exhaust line E of the engine 1. According to the invention, a bypass duct 7 is implanted, on the exhaust duct 2, upstream of the catalyst 3, and a fuel injector 8 (preferably the fuel injector 8 is a low pressure injector) is placed on the bypass duct 7. Preferentially As shown in FIGS. 2 and 3, the bypass duct 7 comprises a bypass flap 9. The bypass flap 9 is movable between a first position, represented by FIG. 2, in which it authorizes the passage of the exhaust gases G in the bypass duct 7, and a second position, represented by FIG. 3, in which it does not allow the passage of the exhaust gases G into the duct By-pass 7. When the particle filter 5 is to be regenerated, the bypass flap 9 is placed in its front. 1st position (see Figure 2): the exhaust gases G 25 then circulate in the bypass duct 7 to the catalyst 3 and the particulate filter 5, and the fuel injected by the injector 8 allows an increase in the temperature at the inlet of the particle filter 5, ensuring efficient regeneration thereof. Conversely, during operating phases of the treatment unit according to the invention in which there is no regeneration of the particle filter 5, the bypass flap 9 is placed in its second position (see FIG. 3): the exhaust gases G are then conventionally conveyed to the catalyst 3 and the particulate filter 5 via the exhaust pipes 2 and 4, without being put in contact with the injector 8. In this configuration the injector 8 is thus protected from the particles and soot conveyed by the exhaust gas G. The invention thus makes it possible to produce a simple and inexpensive device 5 for protecting the injector 8. It should be noted that, according to various embodiments of the invention, an air injection can be associated with the injector 8 to improve performance, without the invention being questioned.

Claims (7)

  1. Exhaust gas treatment unit (G) of a motor vehicle, in which the gases (G) resulting from the combustion in the engine (1) of the vehicle are conveyed by an exhaust line (E) to the atmosphere, comprising at least: an exhaust gas treatment catalyst (3), a duct (2) connecting the exhaust of the engine (1) to the inlet of the catalyst (3), a particulate filter (5), placed downstream of the catalyst (3) in the direction of flow of the exhaust gases (G), and a conduit (4) connecting the catalyst (3) to the particulate filter (5) , characterized in that it comprises a bypass duct (7) is placed upstream of the catalyst (3).   2. An assembly according to claim 1, characterized in that a fuel injector (8) is placed on the bypass duct (7).   3. An assembly according to either of claims 1 or 2, characterized in that the bypass duct (7) comprises a bypass flap (9).   4. An assembly according to claim 3, characterized in that the bypass flap (9) is movable between a first position, in which it allows the passage of the exhaust gases (G) in the bypass duct ( 7), and a second position, in which it does not allow this passage.   5. An assembly according to any one of claims 2 to 4, characterized in that an air injection is associated with the fuel injector (8).   6. A method of treatment, by an assembly according to any one of claims 1 to 5, gases (G) from combustion in the engine (1) of a motor vehicle, wherein: during the regeneration phases of the particle filter (5), the bypass flap (9) is in its first position and the injector (8) delivers fuel, during the other operating phases, the bypass flap (9) is in his second position.-6-   7. Motor (1) of a motor vehicle characterized in that its exhaust line (E) is equipped with a treatment unit according to any one of claims 1 to 5.