JP2011208575A - Exhaust gas recirculation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide exhaust gas recirculation devices in a simple construction which prevents condensed water from being sucked into an engine, and prevents excessive heating of air intake parts.SOLUTION: Exhaust gas recirculation devices 50 and 60 respectively include a first exhaust gas circulation passage 51 for introducing exhaust gas of the engine 10 into an air intake duct 31 located upstream from a supercharger 20, and a second exhaust gas circulation passage 61 for introducing high-temperature and high-pressure exhaust gas into an air intake duct located downstream from the supercharger with respect to the first exhaust gas circulation passage. In the exhaust gas recirculation devices, a storage section S disposed along the second exhaust gas circulation passage is installed at the junction between the air intake duct and the second exhaust gas circulation passage. The condensed water W in the air intake duct flows into the storage section and is stored therein.

Description

  The present invention relates to an exhaust gas recirculation (EGR) device that recirculates exhaust gas of an engine to an intake side, and particularly relates to an apparatus that prevents intrusion of condensed water generated by cooling of the exhaust gas into the engine side.

For example, in automobile engines, part of the exhaust gas is extracted and introduced into the intake pipe and mixed with the combustion air (fresh air) to control the combustion temperature and reduce pump loss. .
In addition, in the case of an engine having a supercharger such as a turbocharger, in addition to high-pressure EGR that introduces exhaust gas into fresh air after supercharging, low-pressure EGR that introduces exhaust gas into fresh air before supercharging It may be done.

The exhaust gas is usually cooled by an EGR cooler and then introduced into fresh air. Further, in the case of low pressure EGR in which exhaust gas is introduced upstream of the supercharger, it is pressurized by a compressor while being mixed with fresh air, and then cooled again by an intercooler.
In some cases, the water vapor contained in the exhaust gas returned as EGR is condensed by receiving the cooling, and becomes condensed liquid in the intake pipe. When such condensed water is inhaled into the engine body, engine durability such as corrosion due to strong acidity of condensed water in which components in the exhaust gas are dissolved, water hammer phenomenon when the amount increases, etc. Concerns arise.

  As a prior art regarding countermeasures against condensed water caused by EGR, for example, in Patent Document 1, the EGR gas passage is bent in a V shape in a side view, and a condensed water tank is formed at a lower end portion thereof. It is described that the drain valve is opened and discharged to the outside when the water level becomes.

JP-A-7-269417

  However, in the above-described prior art, it is necessary to provide a sensor, an actuator, and the like for detecting the water level in the condensed water tank and opening / closing the drain valve, which complicates the configuration of the EGR device. Further, since the EGR pipe is bent into a V shape, the flow path resistance increases and there is a concern that the response of the EGR control will deteriorate.

On the other hand, in recent years, the use of resin for intake system parts has been promoted for the purpose of weight reduction and the like. In particular, if the intake system part where the exhaust gas is introduced by EGR can be formed of resin, it is advantageous because the acid resistance is high and there is no concern about corrosion. However, in the high-pressure EGR as described above, high-temperature exhaust gas is introduced, so that it is necessary to maintain an appropriate temperature range in order to prevent damage due to heat.
An object of the present invention is to provide an exhaust gas recirculation device which prevents condensed water from being sucked into an engine and prevents overheating of intake system parts with a simple configuration.

The present invention solves the above-described problems by the following means.
The first aspect of the present invention is a first exhaust gas circulation passage for introducing exhaust gas of an engine into an intake pipe upstream of a supercharger, and high-temperature and high-pressure exhaust gas from the first exhaust gas circulation passage. An exhaust gas recirculation device comprising a second exhaust gas circulation passage that is introduced into the intake pipe downstream from the supercharger, and is provided at a junction of the intake pipe and the second exhaust gas circulation passage. The exhaust gas recirculation device is provided with a storage portion that is provided along the second exhaust gas circulation passage and in which condensed water in the intake pipe flows and is stored.
According to this, the condensed water stored in the storage part cools the vicinity of the connection part between the second exhaust gas circulation flow path and the intake pipe line by the sensible heat and the latent heat of vaporization, thereby preventing overheating of these intake system components. can do. This makes it possible to expand the use of resin parts that are lightweight and have excellent corrosion resistance, and at the same time can reduce costs.
In addition, since the condensed water flows into the storage part by its own weight and is then evaporated or outflowed before being processed, it is not necessary to detect the water level or to discharge by the drain valve, and the configuration of the apparatus can be simplified.

According to a second aspect of the present invention, the inner peripheral surface of the reservoir is the same as the outer peripheral surface of the second exhaust gas circulation flow path, and the outer peripheral surface of the reservoir is formed in a cylindrical shape surrounding the inner peripheral surface. The exhaust gas recirculation device according to claim 1.
According to this, the storage part and the second exhaust gas circulation channel have a double pipe structure, and the periphery of the second exhaust gas circulation channel can be directly cooled over the entire circumference by the condensed water in the storage part.

The invention according to claim 3 is characterized in that the condensed water stored when the storage section reaches a predetermined water level or more flows out into the second exhaust gas circulation passage. It is an exhaust gas recirculation apparatus as described in above.
According to this, the condensed water overflowing from the storage part is allowed to flow into the second exhaust gas circulation channel, so that the condensed water is directly converted into a high-temperature high-pressure EGR gas while cooling the second exhaust gas circulation channel. Can be evaporated by exposure.

According to a fourth aspect of the present invention, there is provided scattering prevention means for preventing scattering of condensed water on the upstream side of the storage section in the intake pipe. The exhaust gas recirculation device according to item.
According to this, condensed water contained as splash in fresh air can be captured and guided to the reservoir via the inner wall of the intake pipe, preventing the condensed water from being sucked into the engine. it can.

  As described above, according to the present invention, it is possible to provide an exhaust gas recirculation device that prevents the condensed water from being sucked into the engine and prevents overheating of the intake system components with a simple configuration.

1 is a schematic diagram showing a configuration of an engine including an embodiment of an exhaust gas recirculation device to which the present invention is applied. FIG. 2 is a schematic enlarged cross-sectional view of a II part in FIG. 1. It is typical sectional drawing which shows the use condition of the storage part (condensate reservoir) shown in FIG.

  The present invention provides a problem of providing an exhaust gas recirculation device that prevents the condensed water generated by cooling the exhaust gas from being sucked into the engine and prevents overheating of the high pressure exhaust gas circulation piping, on the intake duct side of the high pressure EGR piping. This problem has been solved by providing a double pipe structure at the end and providing a reservoir where condensed water flows in by its own weight between the inner pipe and the outer pipe.

Hereinafter, an embodiment of an exhaust gas recirculation (EGR) device to which the present invention is applied and an engine including the same will be described.
As shown in FIG. 1, the engine 10 is provided with a turbocharger 20, an intake system 30, an exhaust system 40, a low pressure EGR device 50, a high pressure EGR device 60, and the like.
The low pressure EGR device 50 and the high pressure EGR device 60 cooperate to constitute the exhaust gas recirculation device of the present invention.
Also, in the figure, the flow of relatively high temperature exhaust gas and EGR gas is indicated by black arrows, and the flow of fresh air at normal temperature and the cooled EGR gas is indicated by white arrows.
The engine 10 is, for example, a horizontally opposed, in-line, V-type diesel engine, and is mounted on a vehicle such as a passenger car as a driving power source.

The turbocharger 20 is a supercharger including a compressor 21, a turbine 22, and the like.
The compressor 21 is a centrifugal compressor that compresses combustion air (fresh air) taken in by the engine 10.
The turbine 22 drives the compressor 21 using the exhaust energy of the engine 10.

The intake system 30 includes an intake duct 31 that is a conduit for introducing fresh air into the engine 10. An intake manifold (not shown), which is a branch pipe that distributes fresh air to the intake ports of the cylinders, is provided at the end of the intake duct 31 on the engine 10 side.
The intake duct 31 is provided with an air cleaner 32, an air flow meter 33, a compressor 21, an intercooler 34, and a throttle 35 in order from the upstream side (the side away from the engine 10).

The air cleaner 32 filters the outside air drawn into the intake duct 31 and removes dust and the like.
The air flow meter 33 detects the flow rate of fresh air passing therethrough and transmits it to an engine control unit (ECU) (not shown).
The intercooler 34 cools the fresh air that has been pressurized by the compressor 21 and has reached a high temperature, for example, by heat exchange with traveling wind.
The throttle 35 includes a throttle valve that is a butterfly valve that restricts the cross-sectional area of the intake duct 31.

The exhaust system 40 includes an exhaust pipe 41 that exhausts the burned gas (exhaust gas) exhausted from the engine 10. At the end of the exhaust pipe 41 on the engine 10 side, there is provided an exhaust manifold (not shown) that is a collecting pipe that joins exhaust from the exhaust ports of the cylinders.
The exhaust pipe 41 includes a turbine 22, an exhaust gas aftertreatment device 42, a back pressure adjustment valve 43, a muffler 44, and the like in order from the upstream side (engine 10 side).

The exhaust gas aftertreatment device 42 includes an oxidation catalyst converter, a diesel particulate filter (DPF), a selective reduction catalyst (SCR) converter, and the like, and reduces NOx, PM, hydrocarbon, and the like in the exhaust gas.
The back pressure adjusting valve 43 adjusts the exhaust pressure (back pressure) in the exhaust pipe 41 on the upstream side by restricting the flow path of the exhaust pipe 41.
The muffler 44 includes a silencer that reduces exhaust noise.

  The low-pressure EGR device 50 extracts a part of the exhaust gas as a low-pressure EGR gas from between the exhaust gas after-treatment device 42 and the back pressure adjustment valve 43 in the exhaust pipe 41, and connects the air flow meter 33 and the compressor 21 in the intake duct 31. A low-pressure EGR pipe 51 introduced between them is provided.

The low-pressure EGR pipe 51 is provided with an EGR cooler 52 and an EGR valve 53 in order from the upstream side (exhaust pipe 41 side).
The EGR cooler 52 is a heat exchanger that cools the low-pressure EGR gas.
The EGR valve 53 controls the flow rate of the low pressure EGR gas.

The high-pressure EGR device 60 extracts a part of the exhaust gas as a high-pressure EGR gas from between the engine 10 and the turbine 22 in the exhaust pipe 41 and introduces it between the throttle 35 in the intake duct 31 and the engine 10. 61 is provided.
The high-pressure EGR gas has a higher pressure and a higher temperature than the above-described low-pressure EGR gas.

The high-pressure EGR pipe 61 is provided with an EGR cooler 62 and an EGR valve 63 in order from the upstream side (exhaust pipe 41 side).
The EGR cooler 62 is a heat exchanger that cools the high-pressure EGR gas.
The EGR valve 63 controls the flow rate of the high pressure EGR gas.

FIG. 2A is an enlarged schematic cross-sectional view of the II part in FIG. FIG. 2B is a cross-sectional view taken along the line bb in FIG.
At the junction between the intake duct 31 and the high-pressure EGR pipe 61, the intake duct 31 is disposed substantially along the horizontal direction, and the end of the high-pressure EGR pipe 61 is disposed substantially along the vertical direction. It is connected to the lower part of 31 and communicates.

The end of the high-pressure EGR pipe 61 has a double pipe structure including a cylindrical inner pipe 64 and an outer pipe 65 arranged concentrically. The lower end portion of the double tube structure is closed by a bottom surface portion 66 provided between the inner tube 64 and the outer tube 65. The bottom surface portion 66 is disposed in the vicinity of the upper end portion of the EGR valve 63.
The high pressure EGR gas that has flowed through the high pressure EGR pipe 61 is introduced from the inner pipe 64 into the intake duct 31.
The upper end portion of the outer tube 65 is joined to the outer peripheral surface of the intake duct 31 over the entire circumference.
An upper end portion of the storage portion S that is a space portion constituted by the inner tube 64, the outer tube 65, and the bottom surface portion 66 communicates with the intake duct 31 at the lower portion of the intake duct 31. The storage section S functions as a condensed water reservoir in which condensed water generated by condensation of water vapor contained therein flows in by its own weight when the low-pressure EGR gas is cooled in the EGR cooler 52 and the intercooler 34. .
The upper end portion of the inner pipe 64 is disposed at a position lower than the lower surface of the intake duct 31 in order to prevent leakage of condensed water to the engine 10 side.

  Further, a mesh M such as a wire mesh is provided at the outlet portion of the throttle 35 in the intake duct 31 so as to cross the cross section of the flow path. This mesh M captures splashes of condensed water in fresh air and prevents scattering.

Condensed water captured by the mesh M and flowing along the inner peripheral surface of the intake duct 31 gathers under the intake duct 31 due to its own weight and flows to the engine 10 side along with the flow of fresh air.
When the condensed water flowing in the lower part of the intake duct 31 reaches the opening in the upper part of the storage part S, it flows into the storage part S from here.

As shown in FIG. 3, when the water level reaches the upper end of the inner pipe 64, a part of the condensed water W stored in the storage section S overflows beyond the upper end of the inner pipe 64, It descends by its own weight into the high-pressure EGR pipe 61 along the inner peripheral surface. The condensed water flowing down into the high-pressure EGR pipe 61 is heated and evaporated by being directly exposed to a high-temperature high-pressure EGR gas.
Moreover, a part of the condensed water W evaporates in the storage part S by being heated by the high pressure EGR gas.

According to the embodiment described above, the condensed water generated by cooling the low-pressure EGR gas is stored in the storage part S and then processed by flowing into the inner pipe 64 or evaporating. The configuration of the EGR device can be simplified with respect to the prior art that opens and closes the drain valve according to the water level.
Further, the condensed water stored in the storage portion S and the condensed water flowing into the inner pipe 64 from here reach the vicinity of the end portion on the intake duct 31 side of the high-pressure EGR pipe 61 by the sensible heat and the latent heat of vaporization. It cools and the temperature of the surrounding intake duct 31, an intake manifold, the high pressure EGR piping 61, etc. is reduced.
Thereby, even when the intake duct 31 and the intake manifold are formed of a resin material such as PP or PA having heat resistance of 160 ° C. or less, for example, the heat resistance temperature can be maintained and durability can be ensured. As a result, the intake manifold and the like can be made into a resin-integrated molded product, and weight reduction and cost reduction can be achieved.
If the sulfur content in the EGR gas is dissolved in the condensed water, the condensed water becomes strongly acidic. If such an intake system component can be resinized, it is advantageous from the viewpoint of corrosion resistance. .
Furthermore, by providing the mesh M at the outlet portion of the throttle 35, it is possible to prevent the splash of condensed water from being sucked into the engine 10.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and changes are possible, and these are also within the technical scope of the present invention.
For example, detailed configurations of the engine, the intake / exhaust system, the EGR device, and the like are not limited to the above-described embodiments, and can be changed as appropriate.
For example, the storage part in which the condensed water is stored is not limited to the double pipe structure as in the embodiment, but may have other forms.

DESCRIPTION OF SYMBOLS 10 Engine 20 Turbocharger 21 Compressor 22 Turbine 30 Intake system 31 Intake duct 32 Air cleaner 33 Air flow meter 34 Intercooler 35 Throttle M Mesh 40 Exhaust system 41 Exhaust pipe 42 Exhaust gas aftertreatment device 43 Back pressure adjustment valve 44 Muffler 50 Low pressure EGR device 51 Low pressure EGR piping 52 EGR cooler 53 EGR valve 60 High pressure EGR device 61 High pressure EGR piping 62 EGR cooler 63 EGR valve 64 Inner pipe 65 Outer pipe 66 Bottom surface S Reservoir W Condensed water

Claims (4)

A first exhaust gas circulation passage for introducing engine exhaust gas into an intake pipe upstream of the supercharger;
An exhaust gas recirculation device comprising: a second exhaust gas circulation channel that introduces high-temperature and high-pressure exhaust gas into the intake pipe downstream from the supercharger with respect to the first exhaust gas circulation channel,
A reservoir that is provided along the second exhaust gas circulation flow path at a junction between the intake pipe and the second exhaust gas circulation flow path and stores the condensed water flowing in the intake pipe. An exhaust gas recirculation device characterized by being provided. The inner peripheral surface of the storage part is common to the outer peripheral surface of the second exhaust gas circulation flow path, and the outer peripheral surface of the storage part is formed in a cylindrical shape surrounding the inner peripheral surface. Item 2. An exhaust gas recirculation device according to Item 1. 3. The exhaust gas recirculation device according to claim 1, wherein the storage unit causes the condensed water stored when the water level reaches a predetermined level or more to flow into the second exhaust gas circulation passage. . The exhaust gas recirculation according to any one of claims 1 to 3, wherein scattering prevention means for preventing scattering of condensed water is provided upstream of the storage portion in the intake pipe. apparatus.

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