JP2007100665A - Exhaust gas passage structure for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas passage structure for an engine capable of improving warming-up performance of the engine by efficiently rising cooling water temperature and oil temperature with effectively using waste heat of exhaust gas in a re-circulation passage when the engine is cold. <P>SOLUTION: The re-circulation passage 15 re-circulating part of exhaust gas discharged to the exhaust gas passage 13 from a combustion chamber of the engine 1 to an intake air passage 14 is provided. The part of the exhaust gas flowing in the re-circulation passage is cooled by a cooling device 4. A bypass passage 16 is provided between a downstream side of the cooler device of the re-circulation passage and the exhaust gas passage in a downstream of the re-circulation passage. An open and close valve 17 opening when the engine is cold is provided in the bypass passage. The part of the exhaust gas discharged to the exhaust gas passage from the combustion chamber when the engine is cold is positively circulated in the bypass passage from the re-circulation passage to heat oil and cooling water flowing ion the cooler device. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust passage structure of an internal combustion engine in which a part of exhaust gas discharged from a combustion chamber of the internal combustion engine to an exhaust passage is cooled by a water-cooled EGR cooler. It relates to measures to efficiently raise the temperature of water.

  Conventionally, a recirculation passage for taking out a part of exhaust gas discharged from the combustion chamber of the internal combustion engine into the exhaust passage and recirculating it to the intake passage of the internal combustion engine is provided, and a part of the exhaust gas flowing through the recirculation passage is The engine is cooled by a water-cooled EGR (exhaust gas recirculation) cooler, taken out, cooled by a water-cooled EGR cooler, and a part of the cooled exhaust gas is recirculated to the intake passage of the internal combustion engine. There is known one that suppresses the generation of NOx by lowering the combustion temperature in (see, for example, Patent Document 1).

In this case, a part of the exhaust gas flowing through the recirculation passage is determined by the EGR valve that opens the downstream end of the recirculation passage to the intake passage, and the exhaust amount for which the circulation amount is determined. Only a part of the gas is heat exchanged with the cooling water flowing through the water-cooled EGR cooler.
Japanese Patent Laid-Open No. 11-173219

  Incidentally, there is a demand for improving the warming-up performance of the internal combustion engine by rapidly raising the cooling water temperature when the internal combustion engine is at a low temperature. In that case, a part of the exhaust gas discharged from the combustion chamber of the internal combustion engine to the exhaust passage, that is, a part of the exhaust gas flowing through the recirculation passage is effectively used, and the part of the exhaust gas and the inside of the water-cooled EGR cooler are used. It is conceivable to raise the temperature of the cooling water using the waste heat of the exhaust gas in the recirculation passage by exchanging heat with the circulating cooling water.

  However, the flow rate of the exhaust gas flowing through the recirculation passage is determined by the EGR valve that opens the downstream end of the recirculation passage to the intake passage, and therefore becomes small when the internal combustion engine is at a low temperature. For this reason, the warm-up performance of the internal combustion engine cannot be improved by effectively increasing the cooling water temperature by effectively using the waste heat of the exhaust gas in the recirculation passage when the internal combustion engine is at a low temperature.

  The present invention has been made in view of such a point, and an object of the present invention is to efficiently raise the cooling water temperature by effectively utilizing waste heat of exhaust gas in the recirculation passage at a low temperature of the internal combustion engine. An object of the present invention is to provide an exhaust passage structure for an internal combustion engine that can improve the warm-up performance of the internal combustion engine.

  In order to achieve the above object, the present invention includes a recirculation passage for recirculating a part of the exhaust gas discharged from the combustion chamber of the internal combustion engine to the exhaust passage to the intake passage of the internal combustion engine, and flows through the recirculation passage. An exhaust passage structure of an internal combustion engine in which part of the exhaust gas is cooled by a water-cooled EGR cooler is assumed. A part of the exhaust gas is recirculated to the intake passage between the recirculation passage downstream of the water-cooled EGR cooler and the exhaust passage downstream of the recirculation passage. A bypass passage that leads to the exhaust passage without being made is provided. Further, an open / close valve that opens at a low temperature of the internal combustion engine is provided in the bypass passage so that a part of the exhaust gas discharged from the combustion chamber to the exhaust passage at the low temperature of the internal combustion engine is positively transferred from the recirculation passage to the bypass passage. The cooling water flowing in the water-cooled EGR cooler is heated and heated.

  Due to this specific matter, a part of the exhaust gas discharged from the combustion chamber to the exhaust passage at a low temperature of the internal combustion engine is recirculated from the recirculation passage to the intake passage through the water-cooled EGR cooler regardless of whether the EGR valve is opened or closed. Therefore, the air is actively guided from the bypass passage to the exhaust passage. For this reason, a part of the exhaust gas discharged from the combustion chamber to the exhaust passage at a low temperature of the internal combustion engine is actively guided from the recirculation passage to the bypass passage, and heat exchange is performed with the cooling water flowing in the water-cooled EGR cooler. It will be. As a result, it is possible to improve the warming-up performance of the internal combustion engine by effectively using the waste heat of the exhaust gas that is actively guided to the recirculation passage at a low temperature of the internal combustion engine and efficiently raising the cooling water temperature. Become.

  In particular, the following configurations are listed as specifying the operation of the on-off valve when an exhaust turbocharger is provided in the exhaust passage.

  In other words, an exhaust turbo that requires a turbine wheel of an exhaust turbocharger in the exhaust passage downstream of the recirculation passage and upstream of the bypass passage and requires the flow rate of exhaust gas to the turbine wheel. The on-off valve is closed when the turbocharger is supercharged.

  Due to this particular matter, the on / off valve is closed when the exhaust turbocharger is provided with a turbine wheel in the exhaust passage downstream of the recirculation passage and upstream of the bypass passage. When the machine is supercharged, part of the exhaust gas in the recirculation passage is shut off without being led to the bypass passage, and most of the exhaust gas except for part of the exhaust gas into the recirculation passage is the turbine wheel of the exhaust passage Thus, it is possible to smoothly perform supercharging by the exhaust turbocharger.

  Furthermore, a water-cooled oil cooler is integrally attached to the water-cooled EGR cooler so that a part of the exhaust gas discharged from the combustion chamber to the exhaust passage at the low temperature of the internal combustion engine is actively circulated from the recirculation passage to the bypass passage. When the cooling water flowing through the water-cooled oil cooler is also heated, a part of the exhaust gas discharged from the combustion chamber to the exhaust passage at the low temperature of the internal combustion engine is transferred from the recirculation passage to the bypass passage. Heat is exchanged with the cooling water that is actively guided and flows through the water-cooled EGR cooler and the oil that flows through the water-cooled oil cooler. As a result, the exhaust water waste heat that is actively guided to the recirculation passage at the low temperature of the internal combustion engine is effectively used to efficiently raise the cooling water temperature and the oil temperature, thereby further improving the warming performance of the internal combustion engine. It becomes possible.

  In short, in short, an on-off valve that opens at a low temperature of the internal combustion engine is connected to a bypass passage that connects a downstream side of the water-cooled EGR cooler in the recirculation passage and an exhaust passage downstream of the upstream end of the recirculation passage. By installing, when the temperature of the internal combustion engine is low, a part of the exhaust gas in the exhaust passage is actively led to the bypass passage without being recirculated from the recirculation passage to the intake passage via the water-cooled EGR cooler. Heat exchange performance of the internal combustion engine by efficiently exchanging heat with the cooling water flowing in the EGR cooler and effectively using the waste heat of the exhaust gas that is actively guided to the recirculation passage at low temperatures of the internal combustion engine Can be improved.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 shows a circulation path of cooling water circulated with respect to an engine as an internal combustion engine, 1 is an engine, 2 is an air-cooled radiator, and a water jacket and a radiator 2 in a cylinder head 11 of the engine 1 are cooled. A water inlet is connected via a first cooling water pipe 31. The cooling water outlet of the radiator 2 and the water jacket in the cylinder block 12 of the engine 1 are connected via a second cooling water pipe 32. The second cooling water pipe 32 is provided with a thermostat 21 and a water pump 33 in order from the upstream side. Further, the middle of the first cooling water pipe 31 and the thermostat 21 and the water pump 33 of the second cooling water pipe 32 are connected by a third cooling water pipe 34. The third cooling water pipe 34 is provided with an in-vehicle heater device 35.

  Further, the first cooling water pipe 31 is located upstream from the upstream end of the third cooling water pipe 34 (between the water jacket in the cylinder head 11 and the third cooling water pipe 34 upstream end), and the second cooling water pipe. The 32 thermostats 21 and the water pump 33 are connected by a fourth cooling water pipe 36. The fourth cooling water pipe 36 is provided with a cooler device 4 having a substantially rectangular cross section.

  As shown in FIG. 2, in the exhaust passage 13 of the engine 1, recirculation that recirculates a part of the exhaust gas discharged from the combustion chamber of the cylinder head 11 to the exhaust passage 13 to the intake passage 14 of the engine 1. A passage 15 is provided. The recirculation passage 15 has an upstream end connected to an exhaust passage 13 immediately downstream of the combustion chamber of the cylinder head 11 and a downstream end connected to an intake passage 14 via an EGR valve. It is installed. As shown in FIG. 3, an EGR gas introduction port 40a for introducing EGR gas from the recirculation passage 15 is provided on the upstream side (right side in FIG. 3) of the recirculation passage 15 of the cooler device 4. An EGR gas discharge port 40b for discharging the EGR gas heat-exchanged with the cooling water in the cooler device 4 to the recirculation passage 15 is provided on the downstream side of the recirculation passage 15 of the cooler device 4 (left side in FIG. 3). ing. Further, on the upper surface of the cooler device 4, an upstream end of a cooling water introduction pipe 4 a that introduces cooling water into an EGR cooler section 41 described later and a downstream end of a cooling water discharge pipe 4 b that discharges cooling water from the EGR cooler section 41. Are opened, and an upstream end of an oil introduction pipe 4c for introducing oil into an oil cooler section 42, which will be described later, and a downstream end of an oil discharge pipe 4d for discharging oil from the oil cooler section 42 are opened. .

  As shown in FIGS. 4 and 5, the cooler device 4 includes an EGR cooler unit 41 as a water-cooled EGR cooler that cools EGR gas by heat exchange with the cooling water introduced from the fourth cooling water pipe 36. And an oil cooler 42 as a water-cooled oil cooler that is integrally attached to the EGR cooler 41 and cools oil by heat exchange with the cooling water introduced from the fourth cooling water pipe 36. Yes. The EGR cooler portion 41 is arranged so that heat can be exchanged with the three layers of flat cooling water tubes 41a, 41a, 41a that allow the cooling water to flow, and the cooling water that flows in the cooling water tubes 41a. Two layers of flat EGR gas tubes 41b and 41b that allow EGR gas to flow are provided. On the other hand, the oil cooler portion 42 is provided with two layers of flat oil tubes 42a and 42a that are arranged so as to be able to exchange heat with the cooling water flowing through the cooling water tubes 41a and that allow oil to circulate. Yes. And the cooler apparatus 4 is a seven-layer laminated | stacked from the top in order of the cooling water tube 41a, the oil tube 42a, the EGR gas tube 41b, the cooling water tube 41a, the EGR gas tube 41b, the oil tube 42a, and the cooling water tube 41a. It consists of a tube structure and is in contact with each other so as to allow heat exchange between adjacent layers. Further, projections or fin-like plates are provided in these tubes 41a, 41b, and 42a so as to promote heat exchange between adjacent layers. In this case, the cooling water in each cooling water tube 41a and the oil in each oil tube 42a are opposed to the EGR gas flowing in each EGR gas tube 41b from the upstream side to the downstream side of the recirculation passage 15. That is, it flows from the downstream side of the recirculation passage 15 toward the upstream side.

  An EGR gas inlet is provided at the upstream end (the right end in FIGS. 3 to 5) and the downstream end (the left end in FIGS. 3 to 5) of the recirculation passage 15 of each tube 41a, 41b, 42a in the cooler device 4. An upstream side expansion chamber 41c that communicates with 40a and a downstream side expansion chamber 41d that communicates with the EGR gas discharge port 40b are provided. Each of the expansion chambers 41c and 41d communicates with each of the EGR gas tubes 41b, and the EGR gas introduced from the upstream side of the recirculation passage 15 into the upstream side expansion chamber 41c is supplied to each EGR gas tube 41b. Then, heat is exchanged between the oil in the oil tube 42a adjacent to the upper and lower sides and the cooling water in the cooling water tube 41a so as to be discharged from the downstream expansion chamber 41d to the downstream side of the recirculation passage 15. The cooling water tubes 41a open to the cooling water introduction pipe 4a and the cooling water discharge pipe 4b, while the oil tubes 42a open to the oil introduction pipe 4c and the oil discharge port 4d. Yes.

  As shown in FIG. 2, the recirculation passage 15 is provided between the recirculation passage 15 downstream of the cooler device 4 and the exhaust passage 13 downstream of the upstream end of the recirculation passage 15. A bypass passage 16 is provided for guiding the exhaust gas through the exhaust passage 13 to the exhaust passage 13 without recirculation. The bypass passage 16 is provided with an open / close valve 17 that opens when the engine 1 is at a low temperature, and a part of the exhaust gas discharged from the combustion chamber to the exhaust passage 13 when the engine 1 is at a low temperature is passed through the recirculation passage 15. The coolant is actively circulated through the bypass passage 16 to exchange heat with the cooling water and oil in the cooler device 4, and the cooling water and oil are heated. A turbine wheel 51 of the exhaust turbocharger 5 is disposed in the exhaust passage 13 located downstream of the recirculation passage 15 and upstream of the bypass passage 16. The turbine wheel 51 is connected to a compressor wheel 52 disposed in the intake passage 14 through a shaft 53 so as to rotate together. The compressor wheel 52 is rotated along with the rotation of the turbine wheel 51 rotated by exhaust gas flowing through the exhaust passage 13. Is rotated so that the intake air in the intake passage 14 is supercharged. Further, the bypass passage 16 is configured to bypass the downstream side of the turbine wheel 51 without introducing most of the exhaust gas to the turbine wheel 51 of the exhaust turbocharger 5 when the on-off valve 17 is opened. The on-off valve 17 is closed when the exhaust turbocharger 5 that requires the flow rate of the exhaust gas to the turbine wheel 51, such as when accelerating, is exhausted via the bypass passage 16. The bypass of the exhaust gas to the passage 13 is blocked, and the flow rate of the exhaust gas to the turbine wheel 51 is ensured. In FIG. 2, 18 is a catalyst device for purifying exhaust gas.

  Therefore, in the above embodiment, a part of the exhaust gas discharged from the combustion chamber of the engine 1 to the exhaust passage 13 is released from the recirculation passage 15 by the on-off valve that is opened when the engine is cold regardless of whether the EGR valve is opened or closed. The air is positively guided from the bypass passage 16 to the exhaust passage 13 without being recirculated through the cooler device 4 to the intake passage 14. For this reason, when the engine 1 is at a low temperature, a part of the exhaust gas discharged from the combustion chamber to the exhaust passage 13 is actively guided to the bypass passage 16 from the recirculation passage 15 and passes through the cooling water tube 41 a of the cooler device 4. Heat exchange is performed with the flowing coolant and the oil flowing in the oil tube 42a. Thereby, the warm air performance of the engine 1 is improved by effectively increasing the cooling water temperature and the oil temperature by effectively using the waste heat of the exhaust gas that is actively guided to the recirculation passage 15 when the engine 1 is at a low temperature. be able to.

  The on-off valve 17 is closed when the exhaust turbocharger 5 provided with the turbine wheel 51 in the exhaust passage 13 downstream of the upstream end of the recirculation passage 15 and upstream of the downstream end of the bypass passage is supercharged. Therefore, when the exhaust turbocharger 5 is supercharged, the exhaust gas in the recirculation passage 15 is shut off without being guided to the bypass passage 16, and the exhaust gas excluding a part of the exhaust gas into the recirculation passage 15 is blocked. Most of the gas is guided to the turbine wheel 51 in the exhaust passage 13 and can be smoothly supercharged by the exhaust turbocharger 5.

  In addition, this invention is not limited to the said embodiment, The other various modifications are included. For example, in the above embodiment, the oil cooler portion 42 is integrally attached to the EGR cooler portion 41 to configure the cooler device 4, but the cooler device may be configured only by the EGR cooler portion.

  Moreover, in the said embodiment, although the cooler apparatus 4 was comprised by the seven-layer tube structure which laminates | stacks the three-layer cooling water tube 41a, the two-layer oil tube 42a, and the EGR gas tube 41b in order, it adjoins mutually. The cooler device may be constituted by a tube structure having any number of layers as long as the layers are in contact with each other so that heat exchange is possible.

  Furthermore, the cooling water in each cooling water tube 41a and the oil in each oil tube 42a are caused to flow in the direction opposite to the EGR gas flowing in each EGR gas tube 41b. Of course, the cooling water and the oil in each oil tube may flow in the same direction as the EGR gas flowing in each EGR gas tube.

It is a cooling water path | route figure which shows the circulation path | route of the cooling water circulated with respect to the engine provided with the exhaust passage structure concerning embodiment of this invention. FIG. 3 is an exhaust path diagram showing an exhaust path of exhaust gas discharged from an engine. It is the top view which looked at the cooler apparatus from the upper part. It is sectional drawing of the cooler apparatus cut | disconnected in the AA of FIG. It is sectional drawing of the cooler apparatus cut | disconnected in the BB line of FIG.

Explanation of symbols

1 engine (internal combustion engine)
13 Exhaust passage 14 Intake passage 15 Recirculation passage 16 Bypass passage 17 On-off valve 41 EGR cooler (water-cooled EGR cooler)
42 Oil cooler (water-cooled oil cooler)
5 Exhaust turbocharger 51 Turbine wheel

Claims (3)

A recirculation passage is provided for recirculating a part of the exhaust gas discharged from the combustion chamber of the internal combustion engine to the exhaust passage to the intake passage of the internal combustion engine, and a part of the exhaust gas flowing through the recirculation passage is cooled by a water-cooled EGR cooler. An exhaust passage structure for an internal combustion engine that is cooled,
A part of the exhaust gas through the recirculation passage is recirculated to the intake passage between the recirculation passage downstream of the water-cooled EGR cooler and the exhaust passage downstream of the recirculation passage. There is a bypass passage that leads to the exhaust passage without any
The bypass passage is provided with an open / close valve that opens at a low temperature of the internal combustion engine,
A part of the exhaust gas discharged from the combustion chamber to the exhaust passage at a low temperature of the internal combustion engine is actively circulated from the recirculation passage to the bypass passage to heat the cooling water flowing in the water-cooled EGR cooler. An exhaust passage structure for an internal combustion engine. In the exhaust passage structure of the internal combustion engine according to claim 1,
A turbine wheel of an exhaust turbocharger is disposed in the exhaust passage downstream of the recirculation passage and upstream of the bypass passage.
An exhaust passage structure for an internal combustion engine, wherein the on-off valve is closed when supercharging an exhaust turbocharger that requires a flow rate of exhaust gas to the turbine wheel. In the exhaust passage structure of the internal combustion engine according to claim 1 or 2,
The water-cooled EGR cooler is integrally provided with a water-cooled oil cooler,
A part of the exhaust gas discharged from the combustion chamber to the exhaust passage at the low temperature of the internal combustion engine is actively circulated from the recirculation passage to the bypass passage so that the cooling water flowing in the water-cooled oil cooler is also heated. An exhaust passage structure for an internal combustion engine.

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