Apparatus and method for exhaust gas recirculation

Abstract

An internal combustion engine has an exhaust gas recirculation system for recirculating exhaust gases from the internal combustion engine into an intake region of the internal combustion engine. The exhaust gas recirculation system includes the following components: at least one exhaust gas cooler through which a first flow path for recirculating exhaust gas extends, having at least one first cooling stage and at least one additional cooling stage, at least one flap arrangement by which the at least one additional cooling stage can be connected, a bypass line through which a second flow path for recirculating exhaust gas extends and by which the exhaust gas cooler can be bypassed during the recirculation of exhaust gas, and an EGR valve having at least three possible positions.

Claims

1. An internal combustion engine, comprising: an exhaust-gas recirculation device that recirculates exhaust gases of the internal combustion engine into an intake region of the internal combustion engine, wherein the exhaust-gas recirculation device comprises: (a) at least one exhaust-gas cooler through which a first flow path for recirculation of exhaust gas runs and which has at least one first cooling stage and at least one additional cooling stage; (b) at least one flap arrangement by which the at least one additional cooling stage is activatable; (c) a bypass line through which a second flow path for the recirculation of exhaust gas runs and by which the exhaust-gas cooler can be bypassed during the recirculation of exhaust gas; and (d) an EGR valve having at least three possible positions: (1) a rest position, in which the exhaust-gas recirculation device is closed, (2) a first position, in which the first flow path through the exhaust-gas cooler is open, and (3) a second position, in which the second flow path through the bypass line is open.

2. The internal combustion engine as claimed in claim 1, wherein the at least one first cooling stage, the at least one additional cooling stage, the bypass line, the EGR valve and the flap arrangement are integrated in a housing of the exhaust-gas recirculation device.

3. The internal combustion engine as claimed in claim 2, wherein the EGR valve and the flap arrangement are arranged such that an anchoring of the flap is provided on an outer wall of the EGR valve, and the outer wall of the EGR valve simultaneously constitutes an inner wall of the at least one first cooling stage and of the at least one second cooling stage.

4. The internal combustion engine as claimed in claim 1, wherein the bypass line is thermally insulated.

5. The internal combustion engine as claimed in claim 1, wherein the EGR valve is a disk valve which has an inlet, a first outlet and a second outlet, the first and second outlets are arranged opposite one another, a first closure element is provided at the first outlet and a second closure element is provided at the second outlet, the first and second closure elements are braced relative to one another by a spring in order to close the first and second outlets in a rest position, and a slide is provided which is actuatable by an actuator in order to selectively open the first closure element at the first outlet or the second closure element at the second outlet.

6. The internal combustion engine as claimed in claim 5, wherein the actuator is configured such that opening widths of the first outlet and of the second outlet are adjustable in a continuously variable manner by the slide.

7. The internal combustion engine as claimed in claim 1, wherein the at least one first cooling stage and the at least one additional cooling stage are arranged in parallel with respect to one another.

8. A method of operating an internal combustion engine, equipped with an exhaust-gas recirculation device that recirculates exhaust gases of the internal combustion engine into an intake region of the internal combustion engine, wherein the exhaust-gas recirculation device comprises: (a) at least one exhaust-gas cooler through which a first flow path for recirculation of exhaust gas runs and which has at least one first cooling stage and at least one additional cooling stage; (b) at least one flap arrangement by which the at least one additional cooling stage is activatable; (c) a bypass line through which a second flow path for the recirculation of exhaust gas runs and by which the exhaust-gas cooler can be bypassed during the recirculation of exhaust gas; and (d) an EGR valve having at least three possible positions: (1) a rest position, in which the exhaust-gas recirculation device is closed, (2) a first position, in which the first flow path through the exhaust-gas cooler is open, and (3) a second position, in which the second flow path through the bypass line is open, the method comprising the acts of: a) operating the internal combustion engine without exhaust-gas recirculation by shutting off the exhaust-gas recirculation device, with the EGR valve set in the rest position; b) exhaust-gas recirculation during a low-load phase, wherein the exhaust-gas recirculation takes place through the bypass line, with the EGR valve set in the second position, wherein no cooling of the recirculated exhaust gas takes place; c) exhaust-gas recirculation during load operation, wherein the exhaust-gas recirculation takes place through the exhaust-gas cooler, with the EGR valve set in the second position; and d) enabling at least one additional cooling stage by the at least one flap arrangement if high-load operation is present.

9. A motor vehicle having an internal combustion engine as claimed in claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic illustration of a motor vehicle having an internal combustion engine with exhaust-gas recirculation device according to an embodiment of the invention.

(2) FIG. 2 is a schematic illustration of an exhaust-gas recirculation device for an internal combustion engine.

(3) FIG. 3 is a schematic illustration of the exhaust-gas recirculation device in FIG. 2, in which the second flow path has been opened up.

(4) FIG. 4 is a schematic illustration of the exhaust-gas recirculation device in FIG. 2, in which the first flow path has been opened up.

(5) FIG. 5 is a schematic illustration of the exhaust-gas recirculation device from FIG. 2, in which the first flow path has been opened up, and in which an additional cooling stage has been activated.

DETAILED DESCRIPTION OF THE DRAWINGS

(6) FIG. 1 shows a motor vehicle 1 in which an internal combustion engine 2 is integrated. Clean air from the surroundings can be drawn into an intake region 4.2 of the internal combustion engine 2 through a clean-air conduit 22. Fuel can be burned with the clean air in one or more combustion chambers of the internal combustion engine, whereby the motor vehicle 1 can be driven. Exhaust gas that is formed in the process can be discharged from the internal combustion engine 2 through an exhaust-gas outlet 4.1 and through an exhaust-gas line 23. Here, the exhaust gas passes through an exhaust-gas aftertreatment apparatus 25, which includes a catalytic converter 26. Exhaust gas from the exhaust-gas line 23 can be recirculated into the clean-air conduit 22 through an exhaust-gas recirculation line 24. Here, said exhaust gas can be cooled in an exhaust-gas cooler 5. The flow direction of the clean air and of the exhaust gas is indicated in each case by arrows.

(7) FIG. 2 is a schematic illustration of an exhaust-gas recirculation device 3 with an exhaust-gas cooler 5. In the illustration shown, a first cooling stage 8 is arranged in parallel with respect to an additional cooling stage 9. A bypass line 11 is arranged so as to be separated from the cooling stages 8 and 9 by way of thermal insulation 20. The bypass line 11 is preferably also insulated with respect to the surroundings. Furthermore, an EGR valve 12 is shown. The EGR valve 12 has an inlet 15, through which exhaust gas can enter the exhaust-gas cooler 5, a first outlet 16.1 at the bypass line 11 and a second outlet 16.2 at the first cooling stage 8. The EGR valve 12 is of cylindrical design. It has an outer wall 14. A first closure element 17.1 and a second closure element 17.2 are arranged in the interior of the EGR valve 12 such that the first outlet 16.1 and the second outlet 16.2 can be respectively closed by way of these closure elements. Owing to the oppositely situated arrangement of the first outlet 16.1 and of the second outlet 16.2, both the first outlet 16.1 and the second outlet 16.2 can be closed by the closure elements 17.1 and 17.2 by way of a spring 21. A slide 18 permits a continuously variable adjustment of the two closure elements 17.1 and 17.2. The slide 18 is operated via an actuator 19. The actuator 19 is preferably electronically controllable. The first cooling stage 8 and the additional cooling stage 9 are connectable by a flap arrangement 10. Here, the flap arrangement 10 is arranged on the outer wall 14 of the EGR valve 12, whereby exhaust gas that passes via the second outlet 16.2 of the EGR valve 12 into the first cooling stage 8 can pass via the flap arrangement 10 into the second cooling stage 9, such that the additional cooling stage 9 can be passed through over its full length. A first flow path runs through the second outlet 16.2 and the exhaust-gas cooler 5. A second flow path runs through the first outlet 16.1 and the bypass line 11.

(8) FIG. 3 shows all of the elements and the same detail of the exhaust-gas cooler 5 from FIG. 2. For the sake of clarity, not all of the reference designations have been repeated in FIG. 3 (reference should be made to FIG. 2). The illustration shows that the second flow path 7 through the bypass line 11 has been opened up. For this purpose, the first closure element 17.1 of the EGR valve 12 is in a position which opens up the first outlet 16.1 of the EGR valve 12. Thus, exhaust gas can flow through the bypass line 11, as indicated by the arrows. The first cooling stage 8 and the additional cooling stage 9 are not accessible to exhaust gas.

(9) FIG. 4 likewise shows the same detail of the exhaust-gas cooler 5 from FIG. 2. Therefore, in this case too, reference is made to FIG. 2. A situation is illustrated in which the first flow path 6 has been opened up. Exhaust gas can flow through the EGR valve 12 and through the first cooling stage 8, as indicated by arrows. Here, said exhaust gas is cooled in the first cooling stage 8. The second closure element 17.2 is in a position which opens up the second outlet 16.2 of the EGR valve. The flap arrangement 10 is closed, as a result of which the additional cooling stage 9 is not accessible to exhaust gas. The bypass line 11 is also not accessible.

(10) FIG. 5 differs from FIG. 4 merely in that the flap arrangement 10 is open in this case. Thus, the additional cooling stage 9 has been activated. As illustrated by arrows, exhaust gas can flow not only through the first cooling stage 8 but also through the additional cooling stage 9. Here, the exhaust gas is also cooled in the additional cooling stage 9, and for this purpose, the first flow path 6 has been expanded such that it also runs through the additional cooling stage 9. Altogether, therefore, the cooling power of the situation illustrated in FIG. 5 is greater than the cooling power of the situation illustrated in FIG. 4.

LIST OF REFERENCE DESIGNATIONS

(11) 1 Motor vehicle 2 Internal combustion engine 3 Exhaust-gas recirculation device 4 Exhaust-gas outlet 4.2 Intake region 5 Exhaust-gas cooler 6 First flow path 7 Second flow path 8 First cooling stage 9 Additional cooling stage 10 Flap arrangement 11 Bypass line 12 EGR valve 13 Housing 14 Outer wall 15 Inlet 16.1 First outlet 16.2 Second outlet 17.1 First closure element 17.2 Second closure element 18 Slide 19 Actuator 20 Thermal insulation 21 Spring 22 Clean-air conduit 23 Exhaust-gas line 24 Exhaust-gas recirculation line 25 Exhaust-gas aftertreatment apparatus 26 Catalytic converter

(12) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.