JP2020012449A - Recirculation mechanism of exhaust recirculation gas - Google Patents

Abstract

To provide a recirculation mechanism of exhaust recirculation gas capable of preventing condensed water.SOLUTION: The mechanism comprises: a suction passage 4 for feeding intake air to an engine 1; an exhaust passage 6 for feeding exhaust air from the engine 1; an exhaust recirculation passage 20 for returning one part of exhaust air from the exhaust passage 6 as recirculation gas to the suction passage 4; and a block wall 24 formed in an extension direction of the suction passage 4 and blocking a downstream side of the suction passage 4 near a connection part of the suction passage 4 and the exhaust recirculation passage 20 and than the connection part into a first passage 25 for flowing only intake air and a second passage 26 for flowing mixed gas of suction air and recirculation gas. A passage cross section area of the exhaust recirculation passage 20 at the connection part is larger than the passage cross section area of the second passage 26 at the connection part.SELECTED DRAWING: Figure 2

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation mechanism used in a vehicle engine.

  For the purpose of reducing nitrogen oxides contained in exhaust gas discharged from an engine, a recirculation mechanism that recirculates a part of the exhaust gas as a recirculated gas to a combustion chamber may be adopted. In this recirculation mechanism, when high-temperature recirculation gas containing water and low-temperature intake air are mixed, the water in the mixed gas may condense to form condensed water. The condensed water may adversely affect mechanisms such as sensors provided in the engine.

  For example, in a control device for an internal combustion engine according to Patent Literature 1 below, a tumble control valve that varies the cross-sectional area of the intake passage is provided in the intake passage so that the cross-sectional area of the passage is smaller when the internal combustion engine is cold than when it is warm. Is controlled as follows. By doing so, the flow velocity of the intake passage at the time of cold is increased to blow off the condensed water, thereby preventing troubles caused by freezing of the condensed water.

  Further, in an exhaust gas recirculation apparatus for an internal combustion engine according to Patent Document 2, a compressor (impeller) of a turbocharger is arranged coaxially with an intake passage, and recirculated gas is introduced from an exhaust circulation passage that opens coaxially with the intake passage. ing. By doing so, the condensed water in which the moisture in the reflux gas is condensed, and foreign matter such as frozen ice which is condensed water is allowed to collide with the central portion where the circumferential speed of the impeller is relatively small, This prevents problems such as damage to the impeller due to

JP 2010-163937 A JP 2009-24692 A

  In the configuration disclosed in Patent Literature 1, since the passage cross-sectional area of the intake passage differs between when the internal combustion engine is cold and when it is warm, a difference in intake air amount is likely to occur, and the combustion characteristics of the internal combustion engine may not be stabilized. . Further, since the condensed water is blown downstream, the condensed water may cause trouble in the mechanism of the internal combustion engine. Further, in the configuration shown in Patent Document 2, similarly to the configuration shown in Patent Document 1, foreign matter such as condensed water is sent to the downstream side of the intake passage. There is a possibility that a trouble occurs in the side mechanism. Both of these problems according to both patent documents are due to the inevitable generation of condensed water.

  Therefore, an object of the present invention is to prevent the generation of condensed water in the exhaust gas recirculation mechanism.

  In order to solve the above-described problems, in the present invention, an intake passage for sending intake air to an engine, an exhaust passage for sending exhaust from the engine, and a portion of exhaust gas from the exhaust passage are returned to the intake passage as recirculated gas. A first passage through which only the intake air flows, and a mixed gas of the intake gas and the recirculated gas flowing through the exhaust gas recirculation passage, the vicinity of the connection between the intake passage and the exhaust gas recirculation passage, and the downstream side of the intake passage from the connection. A partition wall formed along a direction in which the intake passage extends so as to be divided into a second passage and a passage cross-sectional area of the exhaust gas recirculation passage at the connection portion. A recirculation mechanism for the exhaust gas recirculation gas having a passage cross-sectional area larger than that of the above.

  In the above configuration, it is preferable that, in a region where the partition wall of the intake passage is formed, a passage cross-sectional area of the first passage is larger than a passage cross-sectional area of the second passage.

  In each of the above configurations, it is preferable that an upstream end of the intake wall of the partition wall extends to an upstream side of the connection portion.

  In each of the above configurations, it is preferable that the second passage is formed along an inner surface of the intake passage on the connection portion side.

  In each of the above configurations, a heating device for heating the intake air introduced into the second passage may be provided in the intake passage. In this case, it is preferable that the heating device is provided in the second passage and heats only the intake air introduced into the second passage.

  In each of the above configurations, it is preferable that the exhaust gas recirculation passage is a low-pressure exhaust gas recirculation passage that returns recirculated gas from a downstream side of an exhaust turbine of a supercharger to an upstream side of a compressor of the supercharger.

  In this configuration, it is preferable that a downstream end of the intake passage of the partition wall extends so as to face an impeller of the compressor.

  In each of the above configurations, the partition wall may have a heat insulating material.

  In the exhaust gas recirculation mechanism according to the present invention, the intake passage for introducing the intake air into the engine is divided by the partition wall into a first passage through which only intake air flows and a second passage through which a mixed gas of intake air and the recirculation gas flows. did. By doing so, it is possible to prevent the high-temperature reflux gas containing water from being greatly cooled by the low-temperature intake air and condensing the water contained in the reflux gas to generate condensed water. For this reason, it is possible to prevent engine troubles caused by the condensed water.

1 is an overall view of an engine provided with an exhaust gas recirculation mechanism according to the present invention. FIG. 2 is a diagram showing a recirculation mechanism (first example) of the exhaust gas recirculation gas shown in FIG. 1. It is a figure which shows the other example of the partition wall shown in FIG. FIG. 4 is a diagram illustrating another example (second example) of the exhaust gas recirculation mechanism illustrated in FIG. 1. FIG. 8 is a diagram illustrating another example (third example) of the exhaust gas recirculation mechanism illustrated in FIG. 1.

  FIG. 1 is an overall view of an engine 1 provided with an exhaust gas recirculation mechanism (hereinafter, simply referred to as a recirculation mechanism) according to the present invention, and FIG. 2 shows an exhaust gas recirculation mechanism (first example). This engine 1 is an engine 1 for an automobile, and an intake passage 4 for sending intake air to a cylinder (intake port 3) of the engine 1 containing a piston 2, and an exhaust passage for sending exhaust from a cylinder (exhaust port 5) of the engine. 6, a fuel injection device 7 and the like. The intake port 3 and the exhaust port 5 are respectively opened and closed by valves.

  In the intake passage 4, a first throttle valve 8 for adjusting the passage cross-sectional area of the intake passage 4 from the intake port 3 toward the upstream side, an intercooler 9 for cooling intake air flowing through the intake passage 4, and a supercharger 10. A compressor 11, a second throttle valve 12 for adjusting the cross-sectional area of the intake passage 4, a temperature / humidity sensor 13 for monitoring the temperature and humidity of intake air (outside air), and an air cleaner case 14 containing an air cleaner are provided.

  The exhaust passage 6 includes, from the exhaust port 5 toward the downstream side, a turbine 15 of the supercharger 10, an exhaust purification unit 16 including a catalyst for removing nitrogen oxides and the like in the exhaust gas, and an exhaust pipe 17. Is provided.

  An intermediate portion between the turbine 15 and the exhaust port 5 in the exhaust passage 6 and an intermediate portion between the intake port 3 and the first throttle valve 8 in the intake passage 4 are formed by a high-pressure exhaust gas recirculation passage 18 constituting a high-pressure exhaust gas recirculation device. Communicating. A part of the exhaust gas discharged from the engine 1 returns to the intake passage 4 as a high-pressure recirculated gas via the high-pressure exhaust recirculation passage 18.

  The high-pressure exhaust gas recirculation passage 18 is provided with a high-pressure exhaust gas recirculation valve 19. The high-pressure recirculated gas merges with the intake air in the intake passage 4 according to the opening and closing of the high-pressure exhaust recirculation valve 19 and the pressure state in the intake passage 4 due to the opening and closing of the first throttle valve 8.

  An exhaust pipe 17 located on the downstream side of the exhaust purification section 16 in the exhaust passage 6 and a halfway portion between the compressor 11 and the second throttle valve 12 in the intake passage 4 are provided with a low-pressure exhaust gas recirculation device. They are connected by a return passage 20. A part of the exhaust gas discharged from the engine 1 is recirculated to the intake passage 4 on the upstream side of the compressor 11 as low-pressure recirculated gas via the low-pressure exhaust recirculation passage 20.

  A low-pressure exhaust gas recirculation passage 20 of the low-pressure exhaust gas recirculation device includes a recirculation gas cooler 21 for cooling the low-pressure recirculation gas from a connection portion with the exhaust pipe 17 to the downstream side, A low-pressure exhaust recirculation valve 22 for controlling the flow and a temperature sensor 23 for monitoring the temperature of the low-pressure recirculation gas are provided.

  In this embodiment, a water-cooled cooling device using cooling water as a refrigerant is used as the recirculating gas cooler 21, but an air-cooled cooling device using air as a refrigerant can also be used. The low-pressure recirculated gas merges with the intake air in the intake passage 4 according to the pressure state in the intake passage 4 due to the opening and closing of the low-pressure exhaust recirculation valve 22 and the opening and closing of the second throttle valve 12.

  In the above high-pressure exhaust gas recirculation device, the intake pressure may be higher than the exhaust pressure in a part of the supercharging region, and the high-pressure recirculated gas may not be recirculated to the intake passage in the supercharging region. On the other hand, the low-pressure exhaust gas recirculation device can recirculate the low-pressure recirculated gas to the intake passage even in the supercharging region.

  As shown in FIG. 2, the exhaust gas recirculation mechanism is provided on the low-pressure exhaust gas recirculation passage 20 side. Hereinafter, the “low pressure” of the low-pressure recirculation gas and the low-pressure exhaust recirculation passage 20 is omitted, and is simply referred to as a recirculation gas and an exhaust recirculation passage 20. This recirculation mechanism has an intake passage 4, an exhaust passage 6, an exhaust recirculation passage 20, and a partition wall 24 as main components.

  The partition wall 24 is a wall that partitions the intake passage 4 into a first passage 25 through which only the intake air flows and a second passage 26 through which a mixed gas of the intake air and the recirculating gas flows. An upstream end of the intake passage 4 of the partition wall 24 extends to an upstream side of a connection portion between the intake passage 4 and the exhaust recirculation passage 20. In this way, the recirculated gas flowing from the exhaust gas recirculation passage 20 toward the intake passage 4 can be reliably guided to the second passage 26 side.

  The downstream end of the intake passage 4 of the partition wall 24 extends so as to face the impeller of the compressor 11. The gap between the downstream end of the partition wall 24 and the impeller is preferably as narrow as possible, as long as they do not contact each other. In this way, the intake air flowing through the first passage 25 and the mixed gas flowing through the second passage 26 do not mix until they are introduced into the compressor 11. For this reason, it is possible to suppress a decrease in the temperature of the mixed gas due to mixing with the intake air as much as possible, and to prevent generation of condensed water in the mixed gas.

  The partition wall 24 is formed along the extending direction of the intake passage 4 (the flow direction of the intake air in the intake passage 4). Therefore, there is no problem that the intake resistance increases with the formation of the partition wall 24.

  The second passage 26 is formed along the inner surface of the intake passage 4 on the connection portion side between the intake passage 4 and the exhaust recirculation passage 20. With this configuration, it is not necessary to separately form a conduit for guiding the recirculated gas flowing through the exhaust gas recirculation passage 20 to the second passage 26, so that the flow resistance of the intake air in the intake passage 4 can be minimized.

  In the recirculation mechanism shown in FIG. 2, the ratio of the cross-sectional area of the second passage 26 at the connection between the intake passage 4 and the exhaust recirculation passage 20 to the cross-sectional area of the exhaust recirculation passage 20 is 50%. I have. Thus, by defining the ratio of the cross-sectional areas of both passages, the generation of condensed water due to the recirculated gas is prevented. Here, the “passage cross-sectional area” refers to an inner peripheral surface of each of the passages 4 and 20 when the passages 4 and 20 are cut along a plane perpendicular to the gas flow direction of the intake passage 4 and the exhaust recirculation passage 20. Also refers to the inner area (the same applies to the cross-sectional area of the second passage 26 described later).

  Here, the effect of preventing the generation of condensed water by defining the ratio of the cross-sectional areas of both passages as described above will be described.

  When a high-temperature gas containing water is cooled, condensed water is generated when the temperature of the gas reaches the dew point. In the mixed gas obtained by mixing the recirculated gas and the intake air, condensed water is generated when the mixed gas becomes lower than the dew point temperature with respect to the total amount of moisture contained in the recirculated gas and the intake air (humidity of the mixed gas). .

  In a general exhaust gas recirculation device, the recirculation gas is often introduced into the intake passage 4 such that the concentration of the recirculation gas in the mixed gas of the recirculation gas and the intake air is about 10 to 15%. The temperature of the reflux gas is, for example, about 100 ° C., and the temperature of the intake air is, for example, about 0 ° C. in winter. When the recirculated gas and the intake air are mixed so that the recirculated gas concentration becomes the above concentration (10 to 15%), the temperature of the mixed gas becomes about 20 to 30 ° C. corresponding to the mixing ratio. Generally, the dew point temperature of the mixed gas is often about 50 ° C., and when the temperature of the mixed gas is 20 to 30 ° C., condensed water may be generated.

  Therefore, as described above, if the ratio of the cross-sectional area of the second passage 26 to the cross-sectional area of the exhaust gas recirculation passage 20 is 50%, the mixing ratio of the recirculated gas and the intake air is about 2: 1. Even if the reflux gas at 100 ° C. and the intake air at about 0 ° C. are mixed, the temperature of the mixed gas exceeds at least 50 ° C., and the generation of condensed water can be reliably prevented.

  The cross-sectional area of both the exhaust gas recirculation passage 20 and the second passage 26 is determined by the characteristics of the engine 1 (exhaust gas temperature, etc.), the gas flow rates of the exhaust gas recirculation passage 20 and the intake passage 4, and the environment in which the vehicle is used (whether or not it is a cold region). ) Can be appropriately changed in consideration of, for example, the passage cross-sectional area of the exhaust gas recirculation passage 20 at the connection portion between the intake passage 4 and the exhaust gas recirculation passage 20. In a region that is larger than the area and in which the partition wall 24 of the intake passage 4 is formed, the passage cross-sectional area of the first passage 25 is larger than the passage cross-sectional area of the second passage 26.

  Specifically, the ratio of the passage cross-sectional area of the second passage 26 to the passage cross-sectional area of the exhaust gas recirculation passage 20 is in the range of 10% or more and less than 100%, further in the range of 20% or more and 90% or less, and It is more preferable to set it in the range of 30% or more and 80% or less from the viewpoint of preventing generation of condensed water.

  In the recirculation mechanism shown in FIG. 2, the ratio of the cross-sectional area of the second passage 26 to the cross-sectional area of the intake passage 4 in the region where the partition wall 24 is formed is set to 20%, and the intake air flowing through the intake passage 4 is set. Only flows into the second passage 26. Therefore, it is possible to more reliably prevent the generation of condensed water due to the temperature of the mixed gas falling below the dew point temperature due to the mixing of the recirculated gas and the intake air.

  The ratio of the cross-sectional area of both the intake passage 4 and the second passage 26 can be appropriately changed in consideration of the characteristics of the engine 1 and the like, as described above, but is within a range of 10% or more and 40% or less. Further, it is more preferable to be within a range of 15% or more and 30% or less from the viewpoint of preventing generation of condensed water.

  In the recirculation mechanism shown in FIG. 2, the partition wall 24 is a fixed wall fixed to the inner wall of the intake passage 4. However, the partition wall 24 has a movable wall movable in a direction indicated by an arrow M in FIG. You can also. With this configuration, the mixing ratio of the recirculated gas and the intake air is appropriately changed in accordance with the temperature and the humidity of the recirculated gas and the intake air. More specifically, for example, the lower the intake air temperature, the smaller the cross-sectional area of the second passage 26 becomes. By reducing the temperature, it is possible to more reliably prevent the generation of condensed water due to the temperature of the mixed gas falling below the dew point.

  The material of the partition wall 24 can be appropriately selected, but may be a heat insulating wall using a heat insulating material. With this configuration, the mixed gas flowing through the second passage 26 is prevented from being cooled by the low-temperature intake air flowing through the first passage 25, and the generation of condensed water can be more reliably prevented.

  When a heat insulating material is used as the material of the partition wall 24, as shown in FIG. 3, the first passage 25 side of the partition wall 24 is used as a heat insulating layer 27, and the second passage 26 side is made of a heat conductive material such as metal. The heat transfer layer 28 can be made of a material having a high thermal conductivity. In this way, it is possible to more reliably prevent the temperature of the mixed gas flowing through the second passage 26 from becoming lower than or equal to the dew point temperature and the generation of condensed water by the low-temperature intake air flowing through the first passage 25. Further, a configuration in which a heating device (not shown) such as a heater is provided in addition to the heat transfer layer 28 may be employed.

  Another example (second example) of the exhaust gas recirculation mechanism shown in FIG. 1 is shown in FIG. This recirculation mechanism has the same basic configuration as the recirculation mechanism shown in FIG. 2, except that a heating device 29 for heating only the intake air introduced into the second passage 26 is provided in the second passage 26. Is different. In this embodiment, an electric heater is used as the heating device 29. As described above, by heating the intake air flowing through the second passage 26, it is possible to more reliably prevent the temperature of the mixed gas obtained by mixing the recirculated gas and the intake air from becoming equal to or lower than the dew point temperature and generating condensed water. .

  Although the amount of heating by the heating device 29 may be constant, the intake air temperature is low based on the monitoring results of the temperature and humidity sensor 13 provided in the intake passage 4 and the temperature sensor 23 provided in the exhaust recirculation passage 20. It is also possible to adopt a configuration in which the heating amount can be changed, such as increasing the heating amount. Further, the heating device 29 is not limited to the electric heater, and for example, a configuration may be adopted in which a cooling water pipe through which the cooling water heated by the engine 1 flows passes through the second passage 26.

  FIG. 5 shows another example (third example) of the exhaust gas recirculation mechanism shown in FIG. This reflux mechanism is different from the reflux mechanism shown in FIG. 4 in that a heating device 30 is further provided upstream of the intake passage 4. In this embodiment, each of the heating devices 29 and 30 employs an electric heater. As described above, by heating the intake air flowing through the intake passage 4, it is possible to more reliably prevent the temperature of the mixed gas obtained by mixing the recirculated gas and the intake air from becoming equal to or lower than the dew point temperature and generating condensed water.

  The amount of heating by the two heating devices 29 and 30 may be constant similarly to the configuration of the second example shown in FIG. 4, but the amount of heating can be changed, such as increasing the amount of heating as the intake air temperature decreases. A configuration can also be adopted. The same applies to the point that both the heating devices 29 and 30 are not limited to the electric heater.

  The configuration of the exhaust gas recirculation mechanism described above is merely an example for explaining the present invention, and solves the problem of the present invention of preventing generation of condensed water in the exhaust gas recirculation mechanism. Modifications can be made to the above components as far as possible.

  For example, in each of the above-described embodiments, the structure in which the exhaust gas recirculation mechanism is provided on the low-pressure exhaust gas recirculation passage 20 side has been described. This is because, when the high-pressure exhaust gas recirculation device includes a device such as a sensor that may cause a trouble due to adhesion of water, it is necessary to prevent generation of condensed water.

Reference Signs List 1 engine 2 piston 3 intake port 4 intake passage 5 exhaust port 6 exhaust passage 7 fuel injection device 8 first throttle valve 9 intercooler 10 supercharger 11 compressor 12 second throttle valve 13 temperature and humidity sensor 14 air cleaner case 15 turbine 16 exhaust Purifier 17 Exhaust pipe 18 High-pressure exhaust recirculation path 19 High-pressure exhaust recirculation valve 20 Low-pressure exhaust recirculation path (exhaust recirculation path)
21 Reflux gas cooler 22 Low-pressure exhaust gas recirculation valve 23 Temperature sensor 24 Partition wall 25 First passage 26 Second passage 27 Heat insulation layer 28 Heat transfer layers 29, 30 Heating device

Claims (9)

An intake passage that sends intake air to the engine,
An exhaust passage for sending exhaust from the engine;
An exhaust gas recirculation passage that returns part of exhaust gas from the exhaust passage to the intake passage as recirculated gas,
A portion near the connection between the intake passage and the exhaust gas recirculation passage and downstream of the connection from the connection portion to a first passage through which only intake air flows, and a second passage through which a mixed gas of intake air and recirculation gas flows. Partitioning a partition wall formed along an extending direction of the intake passage;
With
The exhaust gas recirculation mechanism according to claim 1, wherein a cross-sectional area of the exhaust gas recirculation passage at the connection portion is larger than a cross-sectional area of the second passage at the connection portion. 2. The exhaust gas recirculation gas recirculation mechanism according to claim 1, wherein, in a region where the partition wall of the intake passage is formed, a passage cross-sectional area of the first passage is larger than a passage cross-sectional area of the second passage. 3. The exhaust gas recirculation mechanism according to claim 1, wherein an upstream end of the intake passage of the partition wall extends to an upstream side of the connection portion. 4. 4. The exhaust gas recirculation mechanism according to claim 1, wherein the second passage is formed along an inner surface of the intake passage on the connection portion side. 5. The exhaust gas recirculation mechanism according to any one of claims 1 to 4, wherein a heating device that heats intake air introduced into the second passage is provided in the intake passage. The exhaust gas recirculation mechanism according to claim 5, wherein the heating device is provided in the second passage and heats only intake air introduced into the second passage. The exhaust gas according to any one of claims 1 to 6, wherein the exhaust gas recirculation passage is a low-pressure exhaust gas recirculation passage that returns recirculated gas from a downstream side of an exhaust turbine of a supercharger to an upstream side of a compressor of the supercharger. A reflux gas reflux mechanism. 8. The exhaust gas recirculation mechanism according to claim 7, wherein a downstream end of the intake passage of the partition wall extends so as to face an impeller of the compressor. 9. The exhaust gas recirculation mechanism according to any one of claims 1 to 8, wherein the partition wall has a heat insulating material.

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