SE528644C2 - Device for recirculating exhaust gases of an internal combustion engine - Google Patents

Abstract

The present invention relates to a device for recirculation of exhaust gases of a combustion engine (1). The recirculating exhaust gases are intended to be led from an exhaust line (3) of the combustion engine (1) via a return line (9) to an inlet line (7) which is intended to lead air to the combustion engine (1). The device (11) can be fitted close to a connection between the return line (9) and the inlet line (7). The device (11) comprises means (13, 15, 19) for controlling the flow of exhaust gases from the return line (9) to the inlet line (7) and for mixing the exhaust gases with the air in the return line (7).

Description

25 30 35 528 644 internally permeated by air. Returning exhaust gases are led substantially uniformly into the periphery of the cylindrical body by means of a worm-shaped exhaust duct extending around the cylindrical body.

US 6,425.3 82 discloses a mixing device which comprises a stationary tubular element. The returning exhaust gases are supplied radially outside the tubular element and the lu fi is led radially internally through the tubular element. The tubular member has a star-shaped end portion which causes the exhaust gases and air to provide a mixture substantially immediately downstream of said end portion.

SUMMARY OF THE INVENTION The object of the present invention is to provide a device in an exhaust gas recirculation system, which device provides a control of the recirculating exhaust gas flow while providing an efficient mixture of exhaust gases and air.

This object is achieved with the device of the kind mentioned in the introduction, which is characterized by the features stated in the characterizing part of claim 1. Conventional EGR valves are usually mounted at the beginning of the return line in a position upstream of an EGR cooler intended to cool the exhaust gases. However, it is possible to mount such an EGR valve in a substantially arbitrary position in the return line to control the flow of exhaust gases to the inlet line. However, a mixing device that provides a mixture of exhaust gases and air must be applied in connection with a connection between the return line and the inlet line. A device according to the invention which both controls the flow of exhaust gases from the return line to the inlet line and mixes the exhaust gases with the air must thus also be mounted in connection with the connection between the return line and the inlet line. An exhaust gas recirculation system which includes such a device which functions both as an EGR valve and a mixing device thus provides a reduced number of components compared to a conventional system. A system for recirculation of exhaust gases with such a device thus becomes less space-consuming and cheaper to manufacture than a conventional system which comprises a separate EGR valve and a separate mixing device.

In addition, the pressure drop in the return line is considerably lower with the device according to the invention than when a conventional EGR valve and mixing device are used. According to a preferred embodiment of the invention, said means comprise a movable control element which is adjustable in a first position when a passage is formed which allows a desolation of exhaust gases from the return line to the inlet line and in a second position when it is not such a passage is formed so that a fate of the exhaust gases from the return line to the inlet line is prevented. By means of such a movable control element, it is possible to control in a simple and efficient manner the recirculating fl fate of exhaust gases from the return line to the inlet line. Advantageously, the control element is adjustable in at least a third position, whereby a reduced flow of exhaust gases from the return line to the inlet line is obtained in the third position via a passage having a reduced cross-sectional area relative to the cross-sectional area of the passage in the first position. Thus, at least two different fl fates of exhaust gases can be led from the return line to the inlet line. Preferably, the control element is adjustable in a large number of positions which are located between said first position and said second position. Thus, a corresponding number of different sizes of passage can be obtained and a corresponding number of varying fl fates of exhaust gases are led from the return line to the inlet line. The exhaust gas flow to the inlet line can thus be controlled so that a desired fate with good precision can always be led to the inlet line depending on the operating condition of the internal combustion engine. The control element can be slidably arranged in a reciprocating direction between the first position and the second position. Thus, the control element obtains an uncomplicated movement and it is possible to place the control element in a substantially arbitrary position between the approximate first and second end positions. The exhaust gas to the inlet line can thus be controlled in a simple way and with very good precision.

According to another preferred embodiment of the invention, said means comprises a housing having an exhaust duct with an inlet opening for receiving exhaust gases from the return line and an outlet opening which is connected to said passage. The housing is mounted in the dry connection between the return line and the inlet line. the inlet line has a circumferential radial opening and the outlet opening of the exhaust duct extends outside the circumferential radial opening. With such an outlet opening, the exhaust gases can be dispersed and supplied substantially homogeneously to the inlet line via the circumferential radial opening. Such a scattered supply of the exhaust gases to the inlet line facilitates the mixing of the exhaust gases with the air in the inlet line.

According to another preferred embodiment of the invention, the housing comprises a surface adjacent to the outlet opening which is arranged to co-operate with a surface of the control element, said surfaces being arranged to extend said passage for supply of returning exhaust gases. to the inlet line. The housing is arranged stationary in connection with the connection between the return line and the inlet line, while the control element is arranged movably. It is thus suitable to form the passage for supplying exhaust gases to the inlet line by means of a stationary surface in the housing and a movably arranged surface of the control element. By displacing the control element in relation to the housing, said surfaces are displaced in relation to each other, whereby the dimensions of the passage can be varied and thus also the exhaust fl fate which is led through the passage to the inlet line.

According to another preferred embodiment of the invention, the control element is tubular and that said passage for supply of returning exhaust gases is located radially outside the tubular control element and that the lug in the inlet line is arranged to flow internally through the tubular control element. The exhaust gases are advantageously supplied here in an annular passage which is formed radially outside the tubular guide element before they are mixed with the air which has flowed internally through the tubular guide element. The guide element comprises at a downstream end with respect to the flow directions of the exhaust gases and the air portions which are located at different radial distances from a central axis extending through the tubular guide element. Such portions result in the exhaust gases outside the control element and the air inside the control element being at different radial distances from the central axis as it leaves the control element. As a result, the exhaust gases and the air provide an immediately good mixture substantially immediately after leaving the control element. Thus, a very short distance is required to mix the exhaust gases with the air in the inlet line. The part of the inlet line that extends between the return line for the exhaust gases and the combustion engine can thus be made very short.

According to another preferred embodiment of the invention, said means comprise a power device, which is connected to the control element, by means of which means it is possible to displace the control element to at least the first position and the second position. Such a power tool can be of a substantially arbitrary type and is activated electrically, hydraulically or pneumatically. The control element advantageously has a portion which is located outside the inlet line which is in contact with the power device. BRIEF DESCRIPTION OF THE DRAWING In the following, by way of example, a preferred embodiment of the invention is described with reference to the accompanying drawing, in which: Fig. 1 shows an exhaust gas recirculation system of a supercharged dry combustion chamber. motor with a device according to the invention, Fig. Fig. 2 shows the device in more detail in a fully open position, Fig. 3 shows a section along the plane AA in Fig. 2, Fig. 4 shows the device in Fig. 2 in a partially open position and Fig. 5 shows the device in Fig. 2 in a completely closed position.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION Fig. 1 shows a system for recirculating the exhaust gases of a supercharged internal combustion engine. Such recirculation is usually called EGR (Exhaust Gas Recirculation). By mixing exhaust gases in the compressed air that is led to the engine's cylinders, the dry burning temperature is lowered and thus also the content of nitrogen oxides (N OX) that is formed during the combustion engine's combustion processes.

The internal combustion engine 1 is advantageously a drive motor for a heavier vehicle. The exhaust gases from the cylinders of the combustion engine 1 are led, via an exhaust gas collector 2, to an exhaust line 3.

The exhaust gases in the exhaust line 3, which have an overpressure, are led to a turbine 4. The turbine 4 thereby provides a driving force, which is transmitted, via a connection, to a compressor 5. The compressor 5 sucks, via a lamp 6, ambient air into an inlet line 7.

The air is compressed by the compressor 5 so that it obtains an overpressure. After compression, the air obtains a relatively high temperature. A charge air cooler 8 is arranged in the inlet line 7 to cool the compressed air before it is led to the internal combustion engine 1.

A system for providing a recirculation of a part of the exhaust gases in the exhaust line 3 comprises a return line 9 which extends between the exhaust line 3 and the inlet line 7. The return line 9 comprises an EGR cooler 10, in which the exhaust gases are cooled. The return line 9 comprises a device 11 which has the task of controlling the flow of exhaust gases from the return line 9 to the inlet line 7 and mixing exhaust gases from the return line 9 with the air in the inlet line 7. The device 11 is mounted in connection 10 15 20 25 30 35 528 644 to a connection between the return line 9 and the inlet line 7. Such a device 11 can replace a conventional EGR valve, which has the task of controlling the flow of exhaust gases from the return line 9 to the inlet line 7, and a mixing device, which has the task of mixing exhaust gases from the return line 9 with the air in the inlet line 7. The number of components in the system that enables recirculation of exhaust gases can thus be reduced. A control unit 12 is arranged to activate a crate 13 for controlling the device 11 with information about the current operating condition of the internal combustion engine 1 so that a desired amount of exhaust gases is recirculated to the internal combustion engine. The control unit 12 may be a computer unit provided with a suitable software. The power unit 13 can be electrically, hydraulically or pneuranically driven.

If the combustion engine is an overcharged Otto engine, the exhaust gases in the return line 9 can be led directly into the inlet line 7 as the exhaust gases in the exhaust line 3 of an Otto engine under substantially all operating conditions have a higher pressure than the compressed air in the inlet line 7. If the combustion engine is operating condition the exhaust gas pressure in the exhaust line 3 is lower than the compressed air pressure in the inlet line 7. The device 11 can be used to stop the exhaust gas flow in the return line 9 during the standstill då when the exhaust pressure is lower than the air pressure in the inlet line 7. 9 is mixed with the compressed air in the inlet line 7, the mixture is led, via a branch 14, to the respective cylinders of the combustion engine 1.

Fig. 2 shows the device 11 described above in more detail. In connection with the connection to the return line 9, the inlet line 7 comprises a first line portion 7a and a second line portion 7b. The adjacent ends of the conduit portions 7a, b are arranged at a distance from each other so that a circumferential radial opening 7c is formed between the conduit portions 7a, b. 7c between the conduit portions 7a, b. The housing 15 is axially attached to an end portion of the second conduit portion 7b. The housing 15 comprises an inlet opening 16 for an exhaust duct 17 which extends substantially one turn outside the radial opening 7c. The exhaust duct 17 is intended to receive exhaust gases from the return line 9. The exhaust duct 17 comprises a radially internally located outlet opening 18 which extends substantially around the entire radial opening 7c. The dimensions of the exhaust duct 17 substantially decrease gradually in the direction of flow of the exhaust gases. The device 11 comprises a tubular guide element 19 which is arranged inside the housing 15 in connection with the radial opening 7c between the conduit portions 7a, b. The tubular guide element 19 has a first part 19a which has a substantially constant cross-section. section area and a second part l9b which has a varying cross-sectional area. The first part 19a of the guide element has an inner surface 19c with a substantially corresponding shape and size as an outer surface 7d of the first conduit portion 7a. The first part 19a of the guide element thus comprises a portion which is slidably arranged outside the first conduit portion 7a. The first part 19a of the guide element has an outer surface 19d with a substantially corresponding shape and size as an inner surface 15a of the housing. The first part 19a of the guide element thus comprises a portion which is slidably arranged inside the housing 15. The first part 19a of the guide element is slidably arranged in a radial gap between the housing 15 and the first conduit portion 7a. The power supply 13 is fixed on an outlet. facing surface of the first conduit portion 7a. The power device has projecting means 13a which can be given a variable projecting length. The outer end of the projecting member 13a is here connected to an outer surface of the first part 19a of the guide element. It is thus possible, by means of the projecting member 13a, to displace the guide element 19 to different positions in relation to the housing 15 along a substantially rectilinear reciprocating path. Optionally, the contact area between the outer surface 19d of the control element and the surface 15a of the housing can be provided with a suitable sealing means to ensure that no exhaust gases leak to an environment. Correspondingly, the contact area between the inner surface 19c of the guide element and the outer surface 7d of the first conduit portion 7a can also be provided with a suitable sealing means to ensure that compressed air does not leak to the environment via this contact area.

The second part 19b of the control element comprises an inclined surface 19e which is intended to together with an inclined surface 15b of the housing 15 form an annular outlet passage 20 for the exhaust gases. The outlet passage 20 is connected to the outlet opening 18 of the exhaust duct 17. part l9b thus has a varying cross-sectional area. At a downstream end in the flow direction of the exhaust gases, the cross-sectional area is substantially star-shaped, which can be seen in Fig. 3. The guide element 19 here has alternating radially outer portions 19f and radially inner portions 19g with respect to a central axis 21 extending through the guide element 19. Thus the exhaust gases are led into the second conduit portion 7b at different radial distances from the central axis 21. The air in the inlet conduit 7 flows internally through the tubular 10 15 20 25 30 35 528 644 1 In the guide element 19. the alternating radially outer portions 19f and the radially inner portion 19g also results in the air being at different radial distances from the central axis 21 as it leaves the control element 19. Since both the exhaust gases and the compressed air are at alternating radial distances from the central axis 21 when they leave the control element 19, they provide a substantially good mixture in the second part of the line pa. rtíet 7b.

Fig. 2 shows the guide element 19 when it is in a first end position, in which the inclined surface 19e of the guide element is located at a maximum distance from the inclined surface 15b of the housing. When the control element is in this end position the passage 20 has a maximum width so that a maximum fate of exhaust gases can be led from the return line 9 to the inlet line 7. During some of the operating conditions of the internal combustion engine it is suitable to reduce the amount of returning exhaust gases to the internal combustion engine 1. 12 receives such information, the force means 13 is activated so that it displaces the outer end of the projecting means 13a outwards to a desired position. The force means 13 thereby displaces the control element 19 from the first end position to the position shown in Figs. 4. The inclined surface l9e of the guide element here is located much closer to the inclined surface 15b of the housing. The width of the outlet passage 20 has been reduced here. When the control element 19 is in this position, a reduced fl fate of exhaust gases is led from the return line 9 to the inlet line 7.

During some of the operating conditions of the internal combustion engine, it is suitable that no returning exhaust gases are led to the internal combustion engine 1. If the control unit 12 receives such information, the collar 13 is activated so that the outer end of the projecting member 13a obtains a maximum extended position. The force means 13 thus displaces the control element 19 to a second end position. The guide element 19 is shown in the second end position in Fig. 5. The inclined surface l9e of the guide element here finds itself in contact with the inclined surface l5b of the housing. The width of the outlet passage 20 has thus been completely reduced. When the control element 19 is in this position, no exhaust gases can be led from the return line 9 to the inlet line 7. If necessary, the control element 19 can be placed in a substantially arbitrary position between the first end position corresponding to a fully open position and the second end position corresponding to a completely closed position. Thus, the outlet passage 20 can be given a substantially continuously variable width and a desired flow of retracting exhaust gases can with good precision be led into the inlet line 7 during the different operating conditions of the combustion engine.

The description is in no way limited to the embodiments described in the drawings but can be varied freely within the scope of the claims.

Claims (7)

10 15 20 25 30 35 528 64-4- f? Patent claims An exhaust gas recirculation device of an internal combustion engine (1), wherein the recirculating exhaust gases are intended to be led from an exhaust line (3) of the internal combustion engine (1), via a return line (9), to an inlet line (7). is intended to direct air to the internal combustion engine (1), the device (11) comprising means for controlling the flow of exhaust gases in the return line (9) to the inlet line (7), which means comprises a movably arranged tubular control element (19) mounted in connection to a connection between the return line (9) and the inlet line (7), which control element (19) a: stanbm in a farce aa it burns a passage (20) which allows a fl fate of exhaust gases from the return line (9) to the inlet line (7) and in a second position when such a passage is not formed so that a desolation of exhaust gases from the return line (9) to the inlet line (7) is prevented, and said passage (20) for supplying returning exhaust gases is located radially outside of the tubular control element (19) and that the air in the inlet line (7) is arranged to flow internally through the tubular control element (19), characterized in that the device comprises means for mixing the exhaust gases with the air in the inlet line (7), which means comprise that the control element (19), at a downstream end with respect to the flow directions of the exhaust gases and the air, is provided with portions (19f, 19g) which are located on. different radial distances from a central axis (21) extending through the tubular guide member (19). Device according to claim 1, characterized in that the control element (19) is adjustable in stone a third position, wherein a reduced fl fate of exhaust gases å- from the return line (9) to the inlet line (7) is obtained in the third position via a passage (20 ) having a reduced cross-sectional area relative to the cross-sectional area of the passage (20) in the first position. _... Device according to claim 1 or 2, characterized in that the control element (19) is displaceably arranged in a direction and reciprocating direction between the first position and the second position. Device according to claim 2 or 3, characterized in that the device comprises a housing (15) 50111 has an exhaust duct (17) with an inlet opening (16) for receiving exhaust fumes from the return line (9) and a drain opening (18) which are connected to said passage (20). 10 15 528 / O 644 Device according to claim 4, characterized in that the inlet conduit ß ß fifl (7) has a circumferential radial opening (7c) and in that the exhaust duct (17) has an extension outside the radial opening (70) - Device according to claim 4 or 5, characterized in that the housing (15) comprises a surface (15b) in connection with the outlet opening (18) which is arranged to cooperate with a surface (19e) of the guide element (19), wherein said surfaces (1517, 199) 51 'mfâttade at? the said passage (20) for supplying returning exhaust gases to the inlet line (7) - Device according to any one of the preceding claims, characterized in that said means comprise an electric device (13), which is connected to the control elements fl fef (19) = by means of Which device (13) they: a; possible aa mfskjum sfyrelementer (19) to å flfl i fl s fl me d * first position and the second position.