FR2859238A1 - Exhaust gas thermal adjustment device for motor vehicle, has heat exchanger with openings and cover situated at surfaces of gas intake flange, cylindrical wall and outlet box that receives valve and central by-pass tube - Google Patents

Abstract

The device has a heat exchanger with openings (4) and a cover (18). Exhaust gas is transmitted through a central by-pass tube (2) or the heat exchanger by a valve (26). The openings and the cover of the heat exchanger are situated at the surfaces of a gas intake flange (3), a cylindrical wall (19) and an outlet box (24). The box receives the valve and the tube. An independent claim is also included for an installation for circulating exhaust gas for a thermal engine.

Description

2859238 Exhaust gas thermal regulation device

  The invention relates to thermal regulation devices for gas flowing along an exhaust line at the output of thermal engines of motor vehicles.

  Environmental standards impose a significant reduction in the emission levels of internal combustion engines of motor vehicles.

  To reduce the formation of nitrogen oxides, there are known thermal exhaust gas control devices that exit a heat engine and go to a catalytic element of the type known under the designation "DENOX" and able to reduce the temperature. nitrogen oxide content. These devices include a heat exchanger with an external bypass that allows the gas to reach the correct temperature in the catalyst. The gases pass either in the exchanger to be cooled, or in the bypass to not be cooled.

  The main disadvantage of an external bypass is its bulk.

  The invention relates to a device for thermal control of vehicle engine exhaust gas that overcomes this disadvantage through the presence of an internal bypass heat exchanger.

  This object is achieved, according to the invention, by the fact that the device for thermal regulation of gas flowing along an exhaust line of a heat engine comprises: a heat exchanger having an inlet and an outlet for gases; a branch capable of being traversed by said gases; distribution means for transmitting the gases, either via the bypass, or via the heat exchanger, or in a way shared between these two directions, said device comprising a housing accommodating at least said means distribution and said bypass, the inlet and / or outlet of said heat exchanger being located on the surface of said housing.

  Thus for the exhaust gas, the catalytic element can be used in a wide range of temperatures, or whatever the temperature of the exhaust gas, which makes it possible to operate the lean-burn engine more often, or even whenever this is desirable to reduce fuel consumption.

  Preferably, the heat exchanger and the bypass have at least one communication orifice allowing the introduction of the exhaust gases into said heat exchanger from said bypass.

  In a preferred embodiment of the invention, the bypass is in the form of a central bypass tube coupled by a first end to the input of the regulating device to be fed by the engine exhaust gases. , a transfer tube surrounding the central bypass tube over at least a part of its length to transfer the exhaust gas flowing in the vicinity of a second end of the central tube into the heat exchanger disposed around the transfer tube.

  Thanks to these characteristics, the heat exchanger makes it possible to cool the exhaust gases that pass through it efficiently, without significantly lowering the temperature of the exhaust gases circulating inside the bypass that is located. separated from the exchanger cooling circuit.

  It should also be noted that such a device may, according to the invention, be applied to the thermal regulation of any type of gas, in particular recirculated exhaust gas at the intake of the engine.

  The bypass means are then coupled between the second end of the central bypass tube and an outlet of the exhaust gas of the regulating device for transmitting the gases leaving the second end of the central bypass tube, or directly to the exhaust outlet of the regulating device when the diverting means are in an open position, or indirectly to the outlet of the exhaust gas of the regulating device via the heat exchanger connected to the transfer tube, when the branching means are in a closed position, or shared between these two directions when the branching means are in an intermediate position between the open position and the closed position.

  According to another important characteristic of the invention, the central bypass tube is traversed in the vicinity of its second end by openings which put the interior of the central bypass tube into communication with the transfer tube.

  This arrangement prevents the gases from entering the heat exchanger when the bypass means (usually a valve) are in a fully open position. To do this, the openings of the central tube are located very close to the second end of the central tube, which allows the pressure of the exhaust gas to drop before and after the passage of the distribution means (usually a valve body) , and make negligible gas leaks to the heat exchanger.

  According to yet another characteristic of the invention, the heat exchanger comprises a beam formed of a multiplicity of parallel tubes arranged all around the transfer tube and assembled with the transfer tube, between a first and a second collecting box with Which they communicate, the assembly formed by the transfer tube, the bundle of tubes and the manifolds being traversed by the exhaust gas passing through the openings of the central bypass tube located near its second end, while the bundle of tubes is cooled by a coolant circulating in the space left free between the tubes of the bundle.

  When the valve is completely closed, the exhaust gas passes through the openings at the second end of the central bypass tube and flows between the walls of the central bypass tube and the transfer tube towards the first manifold of the heat exchanger where they penetrate to distribute through tubes of the tube bundle. During their passage through the tubes of the bundle, the exhaust gases are cooled by the coolant which bathes the bundle of tubes before being directed towards the output of the regulating device.

  According to another characteristic of the invention, the first manifold consists of an annular flange on which a cylindrical wall depends, while the first manifold is closed by a cover into which the ends of the tubes of the bundle and a first end transfer tube.

  Advantageously, the second collecting box is formed projecting around a first end of a sleeve in which is engaged the second end of the central bypass tube and comprises a bottom delimited by a cylindrical wall of the sleeve in which the second end is engaged. of the central tube, and a second cylindrical wall surrounding the cylindrical wall of the sleeve, while the second header is closed by a cover in which the ends of the tubes of the bundle open.

  The bottom of the second header preferably has an annular opening centered on the longitudinal axis 2859238 of the central bypass tube which communicates the interior of the second manifold with an exhaust outlet box (24). in the form of a truncated cone, connected by its largest base to the second header, the smaller base having an outlet through which exhaust gas exiting the regulating device.

  In a preferred embodiment, the dispensing means comprise a valve body having an inlet port coupled to the sleeve and an outlet port, opposite the inlet port, opening into the gas outlet box. exhaust.

  The distribution means advantageously comprise a valve coupled between the heat exchanger and the bypass for transmitting the exhaust gas, either directly from the inlet to the outlet when the valve is in the open position, or indirectly to the outlet via the intermediate of the heat exchanger when the valve is in the closed position, is shared between these two directions when the valve is in an intermediate position between the open position and the closed position.

  In the invention, the heat exchanger is advantageously cooled by a mixture of water and glycol.

  It is furthermore advantageous that the sections of the exhaust gas flows in the central tube and in the circuit formed by the transfer tube and the heat exchanger are approximately constant.

  In another embodiment of the invention, the bypass is in the form of a straight tube extending between an inlet and an outlet of the regulating device, while the heat exchanger is made in the form of a U-tube communicating with the bypass tube, respectively with an upstream intersection on the inlet side and a downstream intersection on the outlet side, the bypass means being coupled between the bypass tube and the exhaust pipe. heat exchange.

  In this second embodiment of the invention, the derivation means advantageously comprise a butterfly type valve housed in the branch tube between the upstream intersection and the downstream intersection.

  Of course, other embodiments are possible, from the moment when the device comprises an internal bypass associated with a heat exchanger, the internal bypass and the heat exchanger being mounted between the inlet and the outlet of the device. .

  In another aspect, the invention relates to an exhaust gas circulation system for a heat engine, this installation comprising a thermal exhaust gas control device as defined above.

  The regulating device is advantageously interposed between a three-way catalyst and a catalytic element, in particular of the "Denox" type.

  Other features and advantages of the invention will become apparent upon reading the description which follows with reference to the appended figures. In these figures: - Figure 1 is a schematic sectional view of an embodiment of a thermal exhaust gas control device according to the invention - Figure 2 is an external front view of the control device thermal of Figure 1; - Figure 3 is a diagram of an installation comprising a control device according to the invention interposed between a three-way catalyst and a catalytic element; and FIG. 4 is a sectional view of a thermal control device according to a second embodiment of the invention interposed between a three-way catalyst and a catalytic element.

  The thermal exhaust gas control device, which is designated by the reference 1 in Figure 1, is more particularly intended to operate in connection with a motor vehicle engine.

  The regulating device 1 comprises a central bypass tube 2 with a longitudinal axis XX 'whose first end is engaged in a gas inlet flange 3. The wall of the central bypass tube 2 is traversed in the vicinity of the second end of the tube through openings 4 which connect the interior of the central bypass tube 2 with a heat exchanger 5 via a transfer tube 6 surrounding the central branch tube 2 over part of its length. The openings 4 thus constitute the inlet of the heat exchanger 5.

  The heat exchanger 5 is formed in known manner by a beam formed of a multiplicity of parallel tubes 7 arranged all around the transfer tube 6 in a direction parallel to the axis XX 'and assembled with the transfer tube 6, between a first manifold 8 and a second manifold 9 with which they communicate so that the assembly formed by the transfer tube 6, the bundle of tubes 7 and the manifolds 8 and 9 can be traversed by the gases of exhaust.

  The first manifold 8 consists of an annular flange 10 on which a cylindrical wall 11 depends. The first manifold 8 is closed by a cover 12, forming a collector, into which the ends of the tubes 7 of the bundle and a first end of the transfer tube 6. The first manifold 8 is fixed by screws 13 against the gas inlet flange 3.

  The second manifold 9 is formed protruding around a first end of a sleeve 14 in which is engaged the second end of the central bypass tube 2. It consists of a bottom 15 delimited by a cylindrical wall 16. the sleeve 14 in which is engaged the end of the central bypass tube 2, and a second cylindrical wall 17 surrounding the cylindrical wall 16 of the sleeve. The second manifold 9 is closed by a cover 18 forming a collector into which the ends of the tubes 7 of the bundle open. The lid 18 thus forms the outlet of the heat exchanger.

  The bundle of parallel tubes 7 is disposed inside a cylindrical wall 19 closed at its ends by the covers 12 and 18 of the manifolds 8 and 9 and is cooled by a coolant such as, for example, a mixture of water and glycol, from the engine cooling circuit, not shown. The coolant enters the space left free between the tubes 7 of the bundle and the space defined by the cylindrical wall 19 and the covers 12 and 18 of the manifolds 8 and 9, by an intake manifold 20 and a manifold 21 (Figure 2) connected to the engine cooling circuit. The lid 18 thus constitutes the outlet of the heat exchanger 5.

  The bottom 15 of the second header 9 has an annular opening 22 defined by two circular edges centered on the longitudinal axis XX 'of the central bypass tube 2. The annular opening 22 communicates the interior of the second header 9 with an exhaust outlet box 24, which has a flange 23 for attachment to the manifold 9. The outlet box 24 has the shape of a truncated cone and is connected by its larger base to the manifold 9, the smallest base having an outlet 25 through which the exhaust gas exiting the regulating device 1 escapes.

  The sleeve 14 also communicates the central bypass tube 2 with the outlet box 24 of the exhaust gas via a valve 26 provided with a valve 27 and whose body has a port of FIG. inlet 28 coupled to the sleeve 14 and an outlet port 29, opposite the inlet port 28, opening opposite the outlet port 25. The body of the valve has the shape of a cylinder centered on the XX 'axis and is connected to the outlet box 24 by a diametrical spacer 30.

  The valve 27 is rotated by an actuator 31, for example a pneumatic valve, shown in FIG. 2, and makes it possible to control the temperature of the exhaust gases leaving through the orifice 25 of the outlet box 24.

  The regulating device comprises a housing, formed here by the gas inlet flange 3, the cylindrical wall 19 and the outlet box 24. This housing accommodates at least the distribution means, ie here the valve 26 , and the bypass 2. The inlet 4 and / or the outlet 18 of the heat exchanger are located on the surface of said housing.

  Optimum operation of the device which has just been described can be obtained by paying particular attention to the fact that the sections of the exhaust gas flows in the central tube 2 and in the circuit formed by the transfer tube 6 and the heat exchanger. heat 5 are approximately constant, this in order to minimize the pressure losses in the circuits and heat losses in the central tube 2.

  In order to prevent the gases from entering the heat exchanger when the valve 26 is fully open, the openings 4 of the central tube 2 are placed very close to the second end of the central tube, which allows the pressure of the gases exhaust before and after passing through the valve body, and greatly limit gas leakage to the heat exchanger 5. In this way, when the valve 27 is fully open, the exhaust gases that arrive by the inlet flange 3 are directed through the central bypass duct 2 and the valve body 26 directly to the outlet manifold 24.

  When the valve 27 is completely closed, the exhaust gas passes through the openings 4 situated at the second end of the central bypass tube 2 and circulates between the wall of the central bypass tube 2 and that of the transfer tube 6 in the direction of the first manifold 8 of the heat exchanger 5 where they penetrate to be distributed through the tubes 7 of the bundle of tubes. During their journey in the tubes 7 of the bundle, the exhaust gases are cooled by the cooling liquid which bathes the bundle of tubes 7, then they are directed towards the outlet box 24.

  When the valve 27 is in an intermediate open position, it can be controlled so as to control the flow of the exhaust gas leaving the valve body 26 and the flow of gas flowing in the heat exchanger 5 to obtain a precise temperature value determined at the outlet in the outlet orifice 25 of the outlet box 24.

  Referring now to Figure 3 which schematically illustrates the integration of a control device 1 according to the invention between a catalyst 32 of the three-way type and a catalyst element 33 of the "Denox" type. The catalyst 32 is connected to the manifold 34 of a heat engine 35 and is thus fed by the exhaust gas of the latter. At the outlet of the catalyst 32, the exhaust gas is cooled to the right temperature by the regulating device of the invention and then sent to the catalytic element 33 which reduces the nitrogen oxide content of the exhaust gases. 'exhaust. These are then evacuated to the outside by a duct 36.

  In the diagram of FIG. 3, the regulating device 1 may be constituted by a regulating device such as shown in FIGS. 1 and 2, or by another internal bypass regulating device corresponding to the characteristics of the invention. .

  FIG. 4 schematically illustrates another thermal regulation device 1 according to the invention. This device 1 comprises an inlet 37 and an inlet 38 respectively connected to the outlet of a catalyst 32 similar to that of FIG. 3, and to the inlet of a catalytic element 33 similar to that of FIG. FIG. 4 also shows the exhaust gas manifold 34 and the pipe 36 which exhaust the exhaust gases to the outside.

  In the embodiment of FIG. 4, the shunt here is in the form of a straight tube 39 extending between the inlet 37 and the outlet 38 of the thermal control device.

  The device further comprises a heat exchanger 40 made here in the form of a U-shaped tube 40 communicating with the bypass tube 39, respectively with an upstream intersection 41 on the input 37 side and with a downstream intersection. 42 on the outlet side 38. The heat exchanger 40 defines two circulation branches 43 and 44 connected by a U-shaped bend 45. An intermediate partition 46 defines the inlet and the outlet of the branches 43 and 44.

  The device 1 of FIG. 4 further comprises a butterfly valve 47 housed in the bypass tube 39 between the upstream intersection and the downstream intersection so as to be coupled between the bypass tube and the exchange tube. heat. This bypass valve is pivotally mounted about an axis 48.

  When the valve is in the open position, the exhaust gases are transmitted directly from the inlet 37 to the outlet 38. When the valve is in the closed position, the exhaust gases are transmitted by the heat exchanger 40. when the valve is in an intermediate position, the exhaust gases are shared between the tube 39 and the heat exchanger 40.

  The regulating device comprises a housing 39 'which, as in the previous embodiment, accommodates at least the distribution means, ie the valve 47 and the bypass 39. The inlet (upstream intersection 41) and / or the outlet (downstream intersection 42) of the heat exchanger are located on the surface of said housing.

  As indicated above, the thermal control device 1 according to the invention can be used in other applications.

Claims (2)

13 Claims   A device for thermal regulation of gas flowing along an exhaust line of a heat engine, comprising: - a heat exchanger (5; 40) having an inlet (4; 41) and an outlet (18; 42) for gases; - a bypass (2; 39) adapted to be traversed by said gases; distribution means (26; 47) for transmitting the gases, either via the bypass (2; 39), or via the heat exchanger (5; 40), or in a shared manner between these two directions, characterized in that said device comprises a housing (3, 19, 24; 39 ') accommodating at least said distribution means (26; 47) and said bypass (2; 39), the inputs (4; 41) and / or outlet (18; 42) of said heat exchanger being located on the surface of said housing.   2. Device according to claim 1, characterized in that said heat exchanger (5; 40) and said bypass (2; 39) have at least one communication port (4; 41) allowing the introduction of the exhaust gas. in said heat exchanger from said bypass.   3. Device according to one of claims 1 and 2, characterized in that the bypass is formed as a central bypass tube (2), coupled by a first end to the input of the device to be powered by the exhaust gases of the heat engine, in that a transfer tube (6) surrounds the central bypass tube (2) over at least a part of its length to transfer the exhaust gas circulating in the vicinity of a second end of the central tube in the heat exchanger (5) disposed around the transfer tube (6), and in that the distribution means (26) are coupled between the second end of the central bypass tube (2) and an outlet (25) of the exhaust gas of the regulating device (1) for transmitting the gases leaving the second end of the central bypass tube (2), either directly to the outlet orifice (25) exhaust gas from the regulating device ulation when the dispensing means (26) are in an open position, or indirectly to the outlet (25) of the exhaust gas of the regulating device (1) via the heat exchanger (5). ) connected to the transfer tube (6) when the dispensing means (26) are in a closed position, or shared between these two directions when the dispensing means (26) are in an intermediate position between the open position and the closed position.   4. Device according to claim 3, characterized in that the central bypass tube (2) is traversed in the vicinity of its second end by openings (4) which put in communication the inside of the central bypass tube (2) with the transfer tube (6).   5. Device according to one of claims 3 and 4, characterized in that the heat exchanger (5) comprises a beam formed of a plurality of parallel tubes (7) arranged around the transfer tube (6) and assembled with the transfer tube (6), between a first manifold (8) and a second manifold (9) with which they communicate, the assembly formed by the transfer tube (6), the bundle of tubes (7) ) and the manifolds 8, 9) being traversed by the exhaust gases passing through the openings (4) of the central bypass tube (2) situated in the vicinity of its second end, and in that the bundle of tubes (7) is refrigerated by a coolant circulating in the space left free between the tubes (7) of the beam.   6. Device according to claim 5, characterized in that the first manifold (8) consists of an annular flange (10) on which a cylindrical wall (11) depends, and in that the first manifold (8) is closed by a cover (12) into which the ends of the tubes (7) of the bundle and a first end of the transfer tube (6).   7. Device according to one of claims 5 and 6, characterized in that the second manifold (9) is formed protruding about a first end of a sleeve (14) in which is engaged the second end of the tube central bypass (2) and comprises a bottom (15) delimited by a cylindrical wall (16) of the sleeve (14) in which is engaged the second end of the central tube (2), and a second cylindrical wall (17) surrounding the cylindrical wall (16) of the sleeve (14), and in that the second header (9) is closed by a cover (18) in which the ends of the tubes (7) of the bundle open.   8. Device according to claim 7, characterized in that the bottom (15) of the second manifold (9) comprises an annular opening (22) centered on the longitudinal axis of the central bypass tube (2) which puts in communication inside the second manifold (9) with a truncated cone-shaped exhaust outlet (24), connected by its larger base to the second manifold (9), the smaller base having an outlet (25) through which the exhaust gases exiting the regulating device (1) escape.   9. Device according to one of claims 7 and 8, characterized in that the dispensing means comprise a valve body (26) having an inlet port (28) coupled to the sleeve (16) and an outlet port ( 29), opposite. at the inlet port, opening into the exhaust outlet box (24).   10. Device according to one of claims 1 to 9, characterized in that the distribution means comprise a valve (26; 47) coupled between the heat exchanger (5; 40) and the bypass (2; 39) for transmit the exhaust gas either directly from the inlet to the outlet when the valve is in the open position or indirectly to the outlet via the heat exchanger (5; 40) when the valve is in the closed position, or in a shared position between these two directions when the valve (26; 47) is in an intermediate position between the open position and the closed position.   11. Device according to one of claims 1 to 10, characterized in that the heat exchanger (5) is cooled by a mixture of water and glycol.   12. Device according to one of claims 9 to 11, characterized in that the sections of the exhaust gas flows in the central tube (2) and in the circuit formed by the transfer tube (6) and the exchanger of heat (5) are approximately constant.   Device according to claim 1, characterized in that the bypass is in the form of a straight tube (39) extending between an inlet (37) and an outlet (38) of the device, in that the heat exchanger (40) is formed as a U-tube communicating with the bypass tube (39), respectively with an upstream intersection (41) on the inlet side (37) and a downstream intersection (42). ) on the outlet side (38), and in that the distribution means (47) are coupled between the bypass tube and the heat exchange tube.   14. Device according to claim 13, characterized in that the distribution means comprise a valve (47) of the butterfly type housed in the bypass tube (39) between the upstream intersection (41) and the downstream intersection (42). .   15. Installation for circulating exhaust gas for a heat engine, characterized in that it comprises a thermal exhaust gas control device according to one of claims 1 to 14.   16. Installation according to claim 15, characterized in that the regulating device (1) is interposed between a catalyst (32) with three channels and a catalytic element (33).