JP2014055540A - Exhaust gas recirculation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance mixing of intake air and a recirculated gas even in a short distance, in recirculating a part of exhaust gas of an internal combustion engine to an intake system as the recirculated gas.SOLUTION: An exhaust gas recirculation device includes a recirculation passage 51 communicating between an exhaust system and an intake system of an internal combustion engine 1 to recirculate exhaust gas circulated in the exhaust system to the intake system as recirculated gas, and a recirculated gas inlet 15 formed on the intake system. The recirculation passage 51 has a connecting portion 54 for allowing an exhaust gas to flow toward a direction intersecting a flowing direction of the intake air in the intake system connected with the inlet 15, and a passage portion 55 communicated with the connecting portion 54 and allowing the exhaust gas to flow toward a direction intersecting the exhaust gas flowing direction of the connecting portion 54. The connecting portion 54 has a flat opposite face 54B facing an opening face 54A provided with an opening 54h communicated with the passage portion 55, and extending to the inlet 15, and both side wall faces 54D, 54E between the opening face 54A and the opposite face 54B are oriented so that a circulation cross-section of the recirculated gas is gradually expanded from the passage portion 55 side toward the inlet 15.

Description

  The present invention relates to an exhaust gas recirculation device that recirculates a part of exhaust gas of an internal combustion engine as a recirculation gas to an intake system.

  Conventionally, a part of the exhaust discharged from the combustion chamber of the internal combustion engine to the exhaust passage is recirculated to the intake passage, and the combustion temperature of the air-fuel mixture is lowered to suppress the emission amount of nitrogen oxides (NOx). Techniques for improving are known. In such an exhaust gas recirculation device, the fresh air (air) that has circulated through the intake passage and the exhaust gas that has been recirculated (exhaust gas recirculation, hereinafter referred to as EGR gas) must be sufficiently mixed before flowing into each intake port. There is. If intake is introduced into each intake port with insufficient mixing, combustion variation between the cylinders may occur during engine operation, which may increase fluctuations in engine speed.

  Therefore, various techniques for promoting the mixing of fresh air and EGR gas have been proposed. For example, in the technique disclosed in Patent Document 1, in a multi-cylinder engine, an EGR gas introduction port that guides EGR gas is provided in a throttle body upstream of a collector portion that distributes intake air to each cylinder of the engine. A plate having guide vanes is sandwiched between the collector portion and the throttle body, and a swirl speed component is imparted to the intake air that passes through the plate and travels toward the collector portion. Thereby, even with a short passage length, the EGR gas and the intake air are sufficiently mixed, and the amount of EGR gas distributed to each cylinder can be made uniform.

  For example, in the technique disclosed in Patent Document 2, a curved portion formed in a curved shape is provided in the intake passage, and an EGR gas inlet is provided in the curved portion. And it is supposed that mixing of intake air and EGR gas can be promoted by flowing EGR gas into a curved portion where the flow of intake air is deflected.

JP 2000-8967 A JP 2010-222975 A

  However, when the distance from the inlet of the EGR gas to each intake port is short as in Patent Document 1 described above, or when there is not enough space for providing a curved portion in the intake passage, it is described in Patent Document 2 described above. The technology cannot be adopted. Recently, in order to reduce the weight of components, reduce costs, improve responsiveness, etc., the distance from the EGR gas inlet to the intake port has been made more compact. A structure that can mix well is awaited.

  In addition, if it is the technique of above-mentioned patent document 1, even if it is a case where the mixing space of EGR gas and fresh air cannot fully be ensured, it can be employ | adopted. However, since it is necessary to sandwich a plate having guide vanes, the number of parts increases, and the weight increases accordingly, which may lead to an increase in cost.

  Incidentally, the exhaust gas recirculation devices described in Patent Documents 1 and 2 above recirculate the exhaust gas flowing from the exhaust manifold to the exhaust passage to the vicinity of the intake manifold (so-called high pressure EGR system). In addition, an exhaust gas recirculation device having a recirculation passage (so-called low pressure EGR system) for recirculating exhaust gas from an exhaust passage downstream of the catalyst device to an intake passage upstream of the supercharger is also known.

  An exhaust gas recirculation apparatus including such a high pressure EGR system and a low pressure EGR system is also called a dual loop EGR system, and is considered to be very effective in reducing NOx in the exhaust gas. In such an exhaust gas recirculation device, the fresh air mixed with the EGR gas in the vicinity of the intake manifold already includes exhaust gas recirculated by the low pressure EGR system. For this reason, an air-fuel ratio sensor may be provided to accurately detect the air-fuel ratio of the intake air introduced into each intake port.

  This air-fuel ratio sensor is provided at a position (at least at the collector portion of the intake manifold) downstream from the position where the high-pressure EGR gas is introduced and before branching to each intake port. As a result, the air-fuel ratio detected at one location can be assumed to be the air-fuel ratio of the intake air flowing into all intake ports, and an accurate air-fuel ratio can be obtained while realizing cost reduction and weight reduction. Is possible.

  However, if the position where the high-pressure EGR gas is introduced and the detection position of the air-fuel ratio sensor are close and not sufficiently mixed, the value detected by the air-fuel ratio sensor is the actual intake air that is introduced into each intake port. There is a high possibility that the air-fuel ratio will be different from the value. Therefore, even if an air-fuel ratio sensor is provided, it is necessary to mix intake air and EGR gas at an early stage.

This case has been devised in view of such a problem. When a part of the exhaust gas of the internal combustion engine is recirculated to the intake system as a recirculation gas, the intake air and the recirculation gas can be reduced over a short distance without increasing the number of parts. An object of the present invention is to provide an exhaust gas recirculation apparatus that can promote mixing of the exhaust gas.
The present invention is not limited to this purpose, and is a function and effect derived from each configuration shown in the embodiments for carrying out the invention described later, and other effects of the present invention are to obtain a function and effect that cannot be obtained by conventional techniques. Can be positioned.

  (1) An exhaust gas recirculation apparatus disclosed herein communicates an exhaust system of an internal combustion engine with an intake system to recirculate exhaust gas flowing through the exhaust system to the intake system as a recirculation gas, and to the intake system. An exhaust gas recirculation apparatus including the formed recirculation gas inlet. The recirculation passage is connected to the inlet and connected to the exhaust port in a direction intersecting the flow direction of the intake air in the intake system, and the exhaust flow direction of the connection portion communicates with the connection portion. And a passage portion through which exhaust gas flows in a direction intersecting with respect to.

  Further, the connection portion is opposed to an opening surface in which an opening communicating with the passage portion is formed, and an opposing surface extending to the introduction port is formed in a flat shape, and the flow cross-sectional area of the exhaust is on the passage portion side. Both side wall surfaces between the opening surface and the facing surface are oriented so as to gradually expand toward the introduction port. “Intake” here means fresh air (air) if it does not have a low-pressure EGR system upstream, and low-pressure EGR gas mixed with fresh air if it has a low-pressure EGR system upstream. It is a mixture.

  (2) The connection portion is connected in a direction orthogonal to the flow direction of the intake air flowing through the intake system, and the passage portion is set in a direction orthogonal to the flow direction of the exhaust gas flowing through the connection portion. It is preferable to be connected.

  (3) The intake system includes an intake manifold having a collector portion that distributes intake air to a plurality of cylinders of the internal combustion engine, and an intake passage connected to an upstream side of the intake manifold, It is preferable to have a bent portion formed by bending. At this time, it is preferable that the connecting portion is connected to an upstream side of the intake flow with respect to the bent portion. The “bent portion” here includes not only a portion bent in a corner shape but also a portion bent with a curved portion.

  (4) Further, the collector portion has a plurality of communication ports formed in a line communicating with the plurality of cylinders, respectively, and the connection portion takes intake air from the intake passage toward the plurality of communication ports. It is more preferable that the flow cross-sectional area is formed so as to expand so that the reflux gas spreads in a direction in which the plurality of communication ports are arranged while being connected to the upstream side of the flow.

  (5) An air-fuel ratio sensor that detects an air-fuel ratio of intake air is provided outside the flow path of the bent portion, and the connection portion protrudes from the facing surface toward the opening surface, and It is preferable to have a protrusion formed in the approximate center of the area.

(6) At this time, it is preferable that the said protrusion has a side wall surface which opposes the said both side wall surface of the said connection part in parallel or substantially parallel.
(7) Moreover, it is preferable that the edge part by the side of the said inlet of the said protrusion is provided so that the inner peripheral surface of the said intake manifold or the said intake passage to which the said connection part is connected may be provided.

  In the disclosed exhaust gas recirculation device, the recirculation gas flowing through the recirculation passage flows through the passage portion and flows into the connection portion from the opening. At this time, since the facing surface facing the opening surface in which the opening is formed is formed in a flat shape, the reflux gas can collide with the facing surface and be dispersed. Moreover, since this planar opposing surface is extended to the inlet, the dispersion | distribution tendency of the recirculation | reflux gas which was made to collide with the opposing surface and was disperse | distributed can be maintained.

  Furthermore, the connecting portion is oriented toward the inlet because both side wall surfaces between the opening surface and the facing surface are oriented so that the flow cross-sectional area of the reflux gas gradually expands from the passage portion toward the inlet. Dispersion can be promoted. In addition, since the cross-sectional area of the flow path is increased, the flow rate of the reflux gas can be reduced. Thereby, it is possible to ensure a long time for the reflux gas to mix with the intake air, and to promote the mixing of the intake gas and the reflux gas. Further, it is not necessary to add a new part for promoting mixing, and the number of parts is not increased.

  For example, in a multi-cylinder engine, when the intake air is distributed to a plurality of cylinders, even if an inlet is provided near the position that becomes the branch point, the exhaust gas recirculation device can quickly mix the intake ports. Therefore, the concentration of the reflux gas introduced into each cylinder can be made uniform. Thereby, even if recirculation | reflux gas is introduce | transduced at the time of operation | movement of an internal combustion engine, the combustion variation between each cylinder can be suppressed. If the way of capturing is changed, the inlet can be provided near the position that becomes the branch point of the intake air, so that the configuration of the intake system can be made compact.

It is a block diagram which shows the intake / exhaust system of the engine for motor vehicles equipped with the exhaust gas recirculation apparatus which concerns on each embodiment. It is a schematic diagram which shows the exhaust gas recirculation apparatus which concerns on 1st embodiment, (a) is longitudinal cross-sectional views, such as an intake passage, Comprising: AA arrow sectional drawing of FIG.2 (b), (b) is a figure. 2A is a cross-sectional view taken along the line B-B of FIG. 2A, and FIG. 2C is a view when the introduction port of FIG. It is a schematic diagram which shows the degree of EGR gas concentration in the exhaust gas recirculation apparatus of FIG. 2, (a) is a figure corresponding to FIG. 2 (a), (b) is a figure corresponding to FIG.2 (b). It is a schematic diagram which shows the exhaust gas recirculation apparatus which concerns on 2nd embodiment, (a) is a longitudinal cross-sectional view of an intake passage etc., (b) is CC sectional view taken on the line of FIG. 4 (a). FIG. 5B is a schematic diagram corresponding to FIG. 4B showing the flow of intake air in the exhaust gas recirculation apparatus of FIG. 4, where FIG. 5A is when the intake valve of the fourth cylinder is opened, and FIG. , (C) is when the intake valve of the third cylinder is open. It is a schematic diagram which shows the degree of EGR gas concentration in the exhaust gas recirculation apparatus of FIG. 4, (a) is a figure corresponding to FIG. 4 (a), (b) is a figure corresponding to FIG.4 (b).

Hereinafter, embodiments will be described with reference to the drawings. Note that the embodiment described below is merely an example, and there is no intention to exclude various modifications and technical applications that are not explicitly described in the following embodiment.
1 to 6 illustrate an embodiment of the invention. FIG. 1 is a diagram illustrating matters common to the first and second embodiments. FIGS. 2 and 3 illustrate the first embodiment. FIG. 4 to FIG. 6 are diagrams for explaining the second embodiment.

[1. First embodiment]
[1-1. overall structure]
First, an automotive engine (internal combustion engine) to which the exhaust gas recirculation apparatus according to the present embodiment is applied and an intake / exhaust system thereof will be described. In this embodiment, an engine and an intake / exhaust system including a dual loop EGR system including a low pressure EGR system and a high pressure EGR system will be described.

  As shown in FIG. 1, the engine 1 according to the present embodiment is a common rail diesel engine. The engine 1 is a multi-cylinder direct injection type (only one cylinder is shown in FIG. 1). A plurality of cylinders (cylinders) 2 are formed in a cylinder block 1B of the engine 1, and pistons 3 that reciprocate in the vertical direction in the drawing are provided in each cylinder 2. The piston 3 is connected to the crankshaft via a connecting rod. The piston 3 is formed with a cavity 3a serving as a combustion chamber on the top surface. The plurality of cylinders 2 are provided side by side in a direction orthogonal to the paper surface of FIG. 1, and all the cylinders 2 have the same configuration. Here, a case where four cylinders 2 (first cylinder 2a, second cylinder 2b, third cylinder 2c, and fourth cylinder 2d) are provided is illustrated.

  The cylinder head 1H above the cylinder 2 is equipped with an injector 4. The injector 4 has a tip projecting from the in-cylinder space of the cylinder 2 and directly injects fuel into the cylinder 2. The injection direction of the fuel injected from the injector 4 is set to a direction toward the cavity 3 a of the piston 3. A fuel pipe (not shown) is connected to the base end portion of the injector 4, and pressurized fuel is supplied to the injector 4 from the fuel pipe.

  The cylinder head 1H is provided with an intake port 6 and an exhaust port 7 communicating with the in-cylinder space of the cylinder 2, and an intake valve 8 and an exhaust valve 9 for opening and closing these ports 6 and 7 are provided. An intake manifold (hereinafter referred to as intake manifold) 10 is connected upstream of the intake port 6 in the intake flow. The intake manifold 10 includes a surge tank (collector portion) 11 for temporarily storing air flowing toward the intake port 6, and branch pipes 13 a to 13 d communicating with the intake ports 6.

  The surge tank 11 functions to alleviate intake pulsation and intake interference generated in each cylinder 2, and also functions as a collector unit that distributes intake air to the four cylinders 2a to 2d. The branch pipes 13a to 13d are pipes that are connected to the downstream side of the intake flow of the surge tank 11 and branch toward the four cylinders 2a to 2d. The surge tank 11 is located at a branch point before branching to the branch pipes 13a to 13d. An intake passage 21 provided with various devices is connected to the upstream end of the intake manifold 10 (that is, the upstream end of the surge tank 11).

  Further, an exhaust manifold (hereinafter referred to as an exhaust manifold) 30 is connected downstream of the exhaust port 7 in the exhaust flow. The exhaust manifold 30 is formed such that exhaust ends are joined from the four cylinders 2a to 2d with each upstream end connected to the exhaust port 7. A collecting portion at the downstream end of the exhaust manifold 30 is connected to an exhaust passage 31 provided with various devices.

  The engine 1 is equipped with a turbocharger 40, a low pressure EGR device 60, and a high pressure EGR device (exhaust gas recirculation device) 50 provided across the intake and exhaust systems. The low-pressure EGR device 60 and the high-pressure EGR device 50 are devices that recirculate a part of the exhaust gas to the intake system as EGR gas (reflux gas). In the low-pressure EGR device 60 and the high-pressure EGR device 50, an EGR cooler 69 and an EGR cooler 59 are interposed in the intermediate portions of the low-pressure EGR passage 61 and the high-pressure EGR passage 51, respectively.

  From the upstream side of the intake air flow to the intake passage 21, the air cleaner 22, the first intake throttle valve (throttle valve) 23, the outlet 63 of the low pressure EGR passage 61 of the low pressure EGR device 60, the compressor 41 of the turbocharger 40, the intercooler 24. , A second intake throttle valve (throttle valve) 25 is provided in order. Further, the surge tank 11 is provided with an outlet 53 of a high pressure EGR passage (reflux passage) 51 of the high pressure EGR device 50. A low pressure EGR valve 67 is provided at the outlet 63 of the low pressure EGR passage 61. A high pressure EGR valve 57 is provided between the EGR cooler 59 and the outlet 53 of the high pressure EGR passage 51.

The flow rate of EGR gas (hereinafter referred to as first EGR gas) flowing through the low pressure EGR passage 61 is the value of both the first intake throttle valve 23 and the low pressure EGR valve 67 that adjust the flow rate of fresh air (air) that has passed through the air cleaner 22. It is adjusted by the valve opening. The flow rate of the EGR gas (hereinafter referred to as second EGR gas) flowing through the high pressure EGR passage 51 is a second intake throttle valve that adjusts the flow rate of the mixture of fresh air that has passed through the intercooler 24 and the first EGR gas. 25 and the high-pressure EGR valve 57.
Hereinafter, when distinguishing between a mixture of fresh air and first EGR gas and a mixture of this mixture with the second EGR gas, the former is referred to as the first mixture and the latter is referred to as the second mixture. That's it. If these are not particularly distinguished, they are simply referred to as intake.

  On the other hand, in the exhaust passage 31, from the upstream side of the exhaust flow, the inlet 52 of the high pressure EGR passage 51 of the high pressure EGR device 50, the turbine 42 of the turbocharger 40, the exhaust purification device 32, and the low pressure EGR passage 61 of the low pressure EGR device 60. An inlet 62 is provided in order. The exhaust purification device 32 is a catalyst device interposed on the exhaust passage 31, and includes hydrocarbon (HC) components, carbon monoxide (CO), nitrogen oxide (NOx), particulate matter contained in the exhaust gas. It has the function of purifying and collecting (PM), etc., and includes, for example, an oxidation catalyst and DPF (filter). HC, PM, etc. in the exhaust discharged from the combustion chamber of the engine 1 are removed by the action of the catalyst of the exhaust purification device 22.

  Such an intake / exhaust system of the engine 1 is equipped with various sensors for acquiring information such as for controlling the engine 1. For example, an air flow sensor and an intake air temperature sensor 26 are provided near the outlet of the air cleaner 22, an intake system pressure sensor and a temperature sensor 27 are provided in the intake passage 21 near the surge tank 11, and the surge tank 11 is empty. A fuel ratio sensor 28 is provided. The exhaust purification device 32 in the exhaust passage 31 is equipped with an exhaust system pressure sensor 33, a temperature sensor 34, an air-fuel ratio sensor 35, and the like.

[1-2. EGR gas mixing promotion structure]
Next, the structure of the connecting portion between the high-pressure EGR device 50 as the exhaust gas recirculation device and the intake system will be described with reference to FIG. In this embodiment, the case where the high pressure EGR passage 51 is connected to the surge tank 11 as the collector part of the intake manifold 10 as described above is exemplified.

  As shown in FIGS. 2A and 2B, the surge tank 11 is provided with four communication ports 12a to 12d, which are openings communicating with the four cylinders 2a to 2d, in a line. Branch pipes 13a to 13d connected to the cylinders 2a to 2d are connected to the communication ports 12a to 12d. Thereby, the intake air in the surge tank 11 is distributed from the communication ports 12a to 12d to the cylinders 2a to 2d through the branch pipes 13a to 13d. Hereinafter, when the four communication ports 12a to 12d are not particularly distinguished, they are simply referred to as the communication ports 12.

  The surge tank 11 is provided with an inlet 14 that is an opening through which intake air flows into the surge tank 11, and the downstream end 21 a of the intake passage 21 is connected to the inlet 14. The inflow port 14 is formed such that intake air flows in a direction intersecting with the flow of intake air from the surge tank 11 toward the communication ports 12a to 12d. Here, the communication ports 12a to 12d and the communication ports 12a to 12d and the flow direction of the intake air flowing into the surge tank 11 from the flow inlet 14 and the flow direction of the intake air from the surge tank 11 toward the communication ports 12a to 12d are orthogonal to each other. An inlet 14 is provided. The inlet 14 is provided closest to the third communication port 12c communicating with the third cylinder 2c.

  That is, the intake air introduced into the surge tank 11 through the intake passage 21 is sent to the intake port 6 through the branch pipes 13a to 13d with the flow direction being bent by approximately 90 degrees. In other words, the surge tank 11 is provided with a bent portion 11 </ b> L that is bent at approximately 90 degrees on the way from the inlet 14 to the communication port 12. In FIG. 2A, the outer corner of the bent portion 11L is shown as being chamfered and formed flat, but in reality, the surge tank 11 is formed in a smooth curve or curved surface. The surge tank 11 shown in FIGS. 2A and 2B is a schematic view.

  The surge tank 11 is formed with an inlet 15 communicating with the outlet 53 of the high pressure EGR passage 51. The introduction port 15 is an opening for introducing the second EGR gas that has flowed through the high-pressure EGR passage 51 into the intake system. The introduction port 15 is upstream of the intake flow from the intake passage 21 toward the four communication ports 12a to 12d, and is upstream of the chamfered portion of the bent portion 11L (hereinafter referred to as the chamfered portion 11M). Is provided. In this case, the four communication ports 12a to 12d are closest to the third communication port 12c. The introduction port 15 has a substantially rectangular shape formed by rounding corners as shown in FIG.

  The high-pressure EGR passage 51 includes a connection portion 54 having an outlet 53 on one end side and an opening 54 h on the other end side, and a passage portion 55 connected to the opening 54 h of the connection portion 54. The connection portion 54 is an end portion on the outlet side of the high-pressure EGR passage 51 and is a portion connected to the introduction port 15. The passage portion 55 is a portion where the upstream end is connected to the exhaust system and the second EGR gas flows.

  The second EGR gas that has circulated through the passage portion 55 flows into the intake system (surge tank 11) from the inlet 15 via the connection portion 54. The connecting portion 54 is connected in a direction orthogonal to the flow direction of the intake air flowing into the surge tank 11 from the inlet 14. The passage portion 55 is connected in a direction orthogonal to the flow direction of the second EGR gas flowing through the connection portion 54.

  The connecting portion 54 and the passage portion 55 may be formed by bending one tube, or may be formed integrally by connecting two members. Moreover, the shape of the channel | path part 55 is not specifically limited, The cross section orthogonal to the distribution direction of high pressure EGR gas may be circular or a rectangle. However, the flow cross-sectional area of the passage portion 55 is smaller than the flow cross-sectional area of the intake passage 21.

  The connecting portion 54 has a flat facing surface 54B that faces a surface 54A (hereinafter referred to as an opening surface 54A) where the opening 54h is provided. Here, four surfaces other than the facing surface 54B (the opening surface 54A, the end surface 54C facing the introduction port 15 and the opposite side wall surfaces 54D and 54E between the opening surface 54A and the facing surface 54B) are also formed in a flat shape. Yes. One end sides of the planar opening surface 54A, the opposing surface 54B, and the opposite side wall surfaces 54D and 54E on the introduction port 15 side are connected to the rectangular introduction port 15. That is, each surface formed in a planar shape of the connecting portion 54 extends to the introduction port 15 while remaining planar.

  Further, the connection portion 54 has both side wall surfaces 54D and 54E oriented so that the flow cross-sectional area of the second EGR gas gradually expands from the passage portion 55 side (end surface 54C side) toward the introduction port 15. The distribution cross-sectional area here means the area of a cross section orthogonal to the direction in which the second EGR gas flows. That is, the connecting portion 54 is provided such that the opposing side wall surfaces 54 </ b> D and 54 </ b> E are not parallel, and the distance from each other increases as the inlet 15 is approached. Furthermore, the connection part 54 is formed by expanding the flow cross-sectional area so that the second EGR gas spreads in the direction in which the four communication ports 12a to 12d are arranged in a line.

[1-3. Action / Effect]
Next, the mixing of the first gas mixture flowing through the intake passage 21 and the second EGR gas flowing through the high-pressure EGR passage 51 will be described with reference to FIGS. FIGS. 3A and 3B show the EGR gas concentration distribution when the intake valve of the fourth cylinder 2d is opened, and the intake air in the surge tank 11 is directed to the communication port 12d following the intake port 6 of the fourth cylinder 2d. be introduced. The first air-fuel mixture is in a sufficiently uniform state in the process of flowing through the intake passage 21.

  As shown in FIG. 3A, when the second EGR gas that has flowed through the passage portion 55 of the high-pressure EGR passage 51 flows into the connection portion 54 from the opening 54h, it collides with the opposing surface 54B formed in a planar shape. And disperse. Since the opposing surface 54B extends to the introduction port 54 in a flat shape, the second EGR gas once dispersed flows toward the introduction port 15 while maintaining the dispersion tendency. This is very different from the EGR gas that circulates in a general circular cross-section reflux passage. That is, when the cross section orthogonal to the flow direction of the reflux passage is circular, the surface corresponding to the facing surface 54B is a concave curved surface, and the outlet corresponding to the introduction port 15 is also circular. For this reason, even if the EGR gas collides with the concave curved surface, it tends to gather in the middle, and the EGR gas cannot be dispersed efficiently.

  On the other hand, in the present exhaust gas recirculation device 50, since the planar opposing surface 54B extends to the introduction port 15, the second EGR gas once dispersed does not collect and remains dispersed. . Further, in the exhaust gas recirculation device 50, the both side wall surfaces 54D and 54E are oriented so that the connection portion 54 gradually expands the flow cross-sectional area of the second EGR gas from the passage portion 55 side toward the introduction port 15. The second EGR gas toward the inlet 15 is further dispersed and the flow rate of the second EGR gas is reduced.

  In the intake passage 21 and the high-pressure EGR passage 51, the passage section 55 of the high-pressure EGR passage 51 has a smaller flow cross-sectional area than the intake passage 21, so that the second EGR gas is mixed with the first EGR gas depending on the engine operating state. The flow rate may be faster than Qi. For this reason, when the flow rate of the second EGR gas flowing through the passage portion 55 is introduced into the intake passage 21, the faster-flowing second EGR gas is likely to reach the communication port 12 first, and mixing is sufficiently performed. There are times when it becomes impossible to break. Therefore, the flow rate of the second EGR gas is reduced by the connecting portion 54 so that the mixing is sufficiently performed.

  The second EGR gas introduced into the surge tank 11 from the introduction port 15 collides and mixes substantially perpendicularly to the flow direction of the first gas mixture flowing into the surge tank 11 through the intake passage 21. . In this way, the first air-fuel mixture and the second EGR gas are mixed at the upstream portion in the surge tank 11. The concentration of EGR gas gradually increases from the inlet 14 of the intake passage 21 toward the chamfered portion 11M of the bent portion 11L. However, when the flow direction changes at the bent portion 11L, mixing is further promoted, and FIG. ), The EGR gas concentration is substantially uniform in the vicinity of the outlet of the surge tank 11 (that is, in the vicinity of the communication port 12). That is, mixing is completed at the stage of flowing into the communication ports 12a to 12d.

  Therefore, according to the present exhaust gas recirculation apparatus 50, since the opposed surface 54B facing the opening surface 54A in which the opening 54h is formed is formed in a flat shape, the second EGR gas is collided with the facing surface 54B and dispersed. Can be made. Further, since the planar opposing surface 54B extends to the inlet 15 formed in the intake system, the dispersion tendency of the second EGR gas dispersed by colliding with the opposing surface 54B is maintained.

  Further, since both side wall surfaces 54D and 54E are oriented so that the flow cross-sectional area of the second EGR gas gradually expands from the passage portion 55 side toward the introduction port 15, the connection portion 54 faces the introduction port 15. Dispersion can be promoted. Moreover, since the cross-sectional area of the flow path is increased, the flow rate of the second EGR gas can be reduced. Thereby, it is possible to ensure a long time for mixing the second EGR gas with the gas flowing through the intake passage 21, and to promote the mixing of the second EGR gas. Further, it is not necessary to add a new part for promoting mixing, and the number of parts is not increased.

  Further, in the multi-cylinder engine 1 as in the present embodiment, when the intake air is distributed to the plurality of cylinders 2, the inlet 15 is provided near the position (that is, the collector portion) that becomes the branch point. However, since the second EGR gas can be quickly mixed, the concentration of the EGR gas introduced into each cylinder 2 can be made uniform. Thereby, the combustion variation between each cylinder at the time of the driving | operation of the engine 1 can be suppressed. In other words, since the introduction port 15 can be provided near a position that becomes a branch point of intake air, the configuration of the intake system can be made compact.

  Further, the connecting portion 54 of the high pressure EGR passage 51 is connected so as to be orthogonal to the flow of intake air flowing through the intake system, and the passage portion 55 is orthogonal to the flow direction of the second EGR gas flowing through the connecting portion 54. Therefore, mixing of the intake air flowing through the intake system and the second EGR gas can be further promoted while promoting the dispersion of the second EGR gas.

  Further, since the connecting portion 54 of the high pressure EGR passage 51 is connected to the upstream side of the bent portion 11L provided in the surge tank 11 of the intake manifold 10, the flow direction of the intake air after the second EGR gas flows in is bent. Since it changes in part 11L, mixing can be promoted more.

  The connecting portion 54 is connected to the upstream side of the intake flow from the intake passage 21 toward the plurality of communication ports 12a to 12d, and the second EGR gas spreads and disperses in the direction in which the plurality of communication ports 12a to 12d are arranged. Therefore, the second EGR gas can be uniformly fed into the plurality of cylinders 2 while mixing is promoted. In other words, the concentration of EGR gas can be made uniform before flowing into the communication port 12, and combustion stability can be ensured.

[2. Second embodiment]
[2-1. Constitution]
Next, the exhaust gas recirculation apparatus according to the second embodiment will be described with reference to FIGS. This exhaust gas recirculation device is provided with an air-fuel ratio sensor (A / F sensor) 28 for detecting the air-fuel ratio (A / F) of the intake air in the intake manifold 10 in the surge tank 11 and a part of the connection portion 54. The structure is the same as that of the first embodiment except that the configuration is different. Hereinafter, parts and structures similar to those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and redundant description is omitted.

  As shown in FIGS. 4A and 4B, the air-fuel ratio sensor 28 is provided outside the flow path of the bent portion 11 </ b> L of the surge tank 11. Specifically, the chamfered portion 11M is provided on an extension line of the axial center of the intake passage 21. The air-fuel ratio sensor 28 is disposed around the sensor element to protect the sensor element, a rod-shaped sensor element (not shown), a heater (not shown) that heats the sensor element so as to increase the temperature to the activation temperature. And a protective cover 28a. The protective cover 28a has a plurality of small holes formed at positions close to the wall of the surge tank 11, from which gas is taken into the protective cover 28a.

  The air-fuel ratio sensor 28 detects the air-fuel ratio of the second mixture by detecting the oxygen concentration of the second mixture in which the second EGR gas is mixed with the first mixture by the sensor element. The air-fuel ratio information detected here is transmitted as information on the air-fuel ratio of the intake air introduced into each cylinder 2 to a controller (not shown) that controls the automobile.

  That is, the air-fuel ratio detected on the upstream side (that is, the surge tank 11) before being distributed to each intake port 6 is regarded as the air-fuel ratio of the intake air introduced into each cylinder 2 and used for various controls. As a result, only one air-fuel ratio sensor 28 needs to be provided, which is effective for cost reduction and weight reduction. However, if the oxygen concentration of the portion where the oxygen concentration is detected by the air-fuel ratio sensor 28 (hereinafter referred to as the detection unit 29) and the oxygen concentration of the intake air introduced into each intake port 6 are different, the sensor value and the actual An error will occur between the value and the control accuracy will be reduced.

  Therefore, in the present embodiment, the connection portion 54 is provided with a protrusion 56 that protrudes from the facing surface 54B toward the opening surface 54A. The protrusion 56 is provided substantially at the center of the flow cross-sectional area, and disperses the second EGR gas that has flowed through the high-pressure EGR passage 51 in two hands. The protrusion 56 extends from the end surface 54C side toward the introduction port 15 side, one end portion 56a on the end surface 54C side is provided apart from the end surface 54C, and the other end portion 56b on the introduction port 15 side is the intake passage. 21 along the inner peripheral surface.

  Further, the protrusion 56 does not completely divide the connection portion 54 into two, and a gap is provided between the upper surface 56C of the protrusion 56 and the opening surface 54A. Further, the protrusion 56 has side wall surfaces 56D and 56E that face the side wall surfaces 54D and 54E of the connecting portion 54 in parallel or substantially in parallel. That is, the width 56 of the protrusion 56 (the length from the side wall surface 56D to the side wall surface 56E) is formed so as to gradually increase from the passage portion 55 side toward the introduction port 15. Thereby, the projection 56 guides the second EGR gas so as to be divided in two directions along the connecting portion 54 without impeding the flow of the second EGR gas dispersed by colliding with the facing surface 54B of the connecting portion 54. Function as.

[2-2. Action / Effect]
Next, with reference to FIGS. 5A to 5C and FIGS. 6A and 6B, the first mixture gas that has circulated through the intake passage 21 and the second EGR gas that has circulated through the high-pressure EGR passage 51 are used. The mixing with will be described. 5 (a) to 5 (c) are views showing the flow of intake air, (a) is when the intake valve of the fourth cylinder 2d is opened, and (b) is the intake valve open of the first cylinder 2a or the second cylinder 2b. (C) shows when the intake valve of the third cylinder 2c is open.

  As shown in FIG. 5A, when the intake valve 8 of the fourth cylinder 2d is opened, the intake air in the surge tank 11 is introduced into the communication port 12d following the intake port 6 of the fourth cylinder 2d. At this time, the second EGR gas that has flowed through the high-pressure EGR passage 51 collides with the facing surface 54 </ b> B at the connection portion 54 and is dispersed, and then is dispersed into two flows by the protrusion 56. At this time, the EGR main flow that flows closer to the communication port 12d of the introduction destination out of the two EGR main flows indicated by the thick broken lines flows directly to the communication port 12d without passing through the detection unit 29. On the other hand, the EGR main flow that flows farther from the communication port 12d as the introduction destination passes through the vicinity of the detection unit 29 while generating an EGR subflow indicated by a thin broken line around it.

  In addition, the first air-fuel mixture flowing through the intake passage 21 is dispersed into the main flow indicated by the thick solid line and the subflow surrounding the main flow indicated by the thin solid line while being distributed between the two divided EGR main flows. It flows toward. The substream of the first air-fuel mixture mixes with the EGR substream near the detection unit 29, and the EGR gas concentration is made uniform in the region 16 indicated by the dots in the drawing. This region 16 is a mixing part in which the first gas mixture and the second EGR gas are mixed, and the detection part 29 is included in this mixing part 16. Other substreams and mainstreams are mixed on the way to the communication port 12d, and are uniformly mixed when introduced into the intake port 6.

  FIGS. 6A and 6B show the EGR gas concentration distribution when the intake valve of the fourth cylinder 2d is opened. As shown in FIGS. 6A and 6B, the concentration of the EGR gas in the surge tank 11 is uniform in the detection portion 29 and the communication port 12d communicating with the fourth cylinder 2d. This is because the first air-fuel mixture flows toward the wall portion of the chamfered portion 11M between the second EGR gases divided into two by the projection 56, and therefore, on the extension line of the axial center of the intake passage 21, This is because the air-fuel mixture and the second EGR gas mix quickly.

  When the intake valve of the second cylinder 2b is opened, the flow when the intake valve of the fourth cylinder 2d is opened is reversed as shown in FIG. 5B. That is, the second EGR gas is dispersed into two flows by the projection 56, and the EGR main flow that flows closer to the communication port 12 b following the intake port 6 of the second cylinder 2 b out of the two EGR main flows passes through the detection unit 29. Without going directly to the communication port 12b. On the other hand, the EGR main flow that flows farther from the communication port 12b of the introduction destination passes in the vicinity of the detection unit 29 while generating an EGR subflow around it.

  Further, the first air-fuel mixture flowing through the intake passage 21 flows toward the communication port 12b while being divided into a main flow and a sub-flow surrounding the main flow between the two EGR main flows. The substream of the first air-fuel mixture is mixed with the EGR substream around the detection unit 29, the EGR gas concentration is made uniform in the mixing unit 16 including the detection unit 29, and the other substreams and the main flow enter the communication port 12b. It mixes on the way, and when it is introduced into the intake port 6, it is in a uniformly mixed state. When the intake valve of the first cylinder 2a is opened, the flow is the same as when the intake valve of the second cylinder 2b is opened.

  Further, when the intake valve of the third cylinder 2c is opened, as shown in FIG. 5C, the second EGR gas is dispersed into two flows by the projection 56, bypasses around the detection unit 29, and the third cylinder It flows toward the communication port 12c following the intake port 6 of 2c. The two EGR mainstreams indicated by the thick broken lines pass through the vicinity of the detection unit 29 while generating an EGR subflow indicated by the thin broken line around them. In addition, the first air-fuel mixture flowing through the intake passage 21 flows toward the communication port 12c while being divided into a main flow and a substream surrounding the main flow between the two EGR main flows. The substream of the first air-fuel mixture mixes with the EGR substream around the detection unit 29, and the EGR gas concentration is made uniform in the mixing unit 16 including the detection unit 29.

  Therefore, according to the exhaust gas recirculation device 50 including the air-fuel ratio sensor 28, in addition to the effects obtained by the configuration according to the first embodiment, the EGR gas concentration in the detection unit 29 of the air-fuel ratio sensor 28 can be made uniform. it can. That is, the second projecting from the facing surface 54B of the connecting portion 54 toward the upper opening 54A, and colliding with the facing surface 54B of the connecting portion 54 by the projection 56 formed substantially at the center of the flow cross-sectional area. EGR gas can be dispersed in two hands. Then, since the first air-fuel mixture flows between the flow of the second EGR gas dispersed in two hands, the second EGR gas can be mixed while being entrained in the first air-fuel mixture. As a result, the air-fuel ratio detected at one upstream position before the intake air is distributed can be made the air-fuel ratio of the intake air introduced into each cylinder 2, thereby realizing cost reduction and weight reduction. it can.

  Further, since the projection 56 is provided with side wall surfaces 56D and 56E facing the both side wall surfaces 54D and 54E of the connecting portion 54 in parallel or substantially parallel to each other, the second EGR gas dispersed by colliding with the facing surface 54B , And can flow along the connection portion 54 formed to expand. Further, the gas once divided into two tends to collect thereafter, but since the projection 56 is formed to spread toward the introduction port 15, the position where the second EGR gas collects is sucked more than the detection unit 29. It can be downstream of the flow. Thereby, the EGR gas concentration in the detection part 29 can be equalized.

  Further, since the end 56 b on the inlet 15 side of the protrusion 56 is provided along the inner peripheral surface of the intake passage 21, the protrusion 56 serves as a flow resistance of the first air-fuel mixture flowing through the intake passage 21. Can be prevented.

[3. Others]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.
In the above embodiments, the dual loop EGR system in which the low pressure EGR device 60 is provided in addition to the high pressure EGR device 50 has been described, but the low pressure EGR device 60 may not be equipped. In this case, the fresh air (air) is introduced into the surge tank 11 through the intake passage 21, and the fresh air and the EGR gas are mixed in the surge tank 11.

  Further, in each of the above embodiments, the connecting portion 54 is connected in a direction orthogonal to the flow direction of the intake air flowing through the intake passage 21, but in a direction intersecting the flow direction of the intake air in the intake system. It only has to be connected so that the exhaust flows in. Further, the passage portion 55 only needs to communicate with the connection portion 54 so that the exhaust gas flows in a direction intersecting the exhaust flow direction of the connection portion 54.

Moreover, the structure of the above-described surge tank 11 is an example, and is not limited to the above-described structure. For example, the chamfered portion 11M may not be provided in the bent portion 11L, and the air-fuel ratio sensor 28 only needs to be attached to the outside in the flow path of the bent portion 11L. Further, the bent portion 11L may have a curved portion as well as a cornered shape. That is, the shape may be a curve that is greatly curved on the way from the inflow port 14 to the communication port 12.
Further, the four communication ports 12a to 12d may not be formed in a line in the surge tank 11, and the second EGR gas spreads in the connecting portion 54 in the direction in which the four communication ports 12a to 12d are arranged in a line. Thus, it is not restricted to what the distribution cross-sectional area is expanded and formed.

The position and shape of the introduction port 15 described above are examples, and are not limited to those described above. For example, the inlet 15 may be formed not in the surge tank 11 but in the intake passage 21 immediately upstream of the surge tank 11. That is, the first air-fuel mixture and the second EGR gas may be mixed in the intake passage 21, and the connection portion 54 of the high-pressure EGR passage 51 is connected to the connection portion between the intake passage 21 and the surge tank 11. It may be a configuration.
Further, the shape of the introduction port 15 is not limited to the above, and for example, only the side to which the facing surface 54B is connected may be linear. Four surfaces other than the facing surface 54B of the connecting portion 54 may not be formed in a flat shape.

  Further, the configuration of the engine 1 is not limited to that shown in FIG. 1 and is not limited to a four-cylinder engine. Furthermore, the present exhaust gas recirculation device is not limited to an automobile equipped with the above-described multi-cylinder direct injection type diesel engine, but can also be applied to an automobile equipped with a gasoline engine, a hybrid electric vehicle, or a vehicle other than an automobile.

1 engine (internal combustion engine)
2 cylinders
10 Intake manifold (intake manifold)
11 Surge tank (collector part)
11L Bent part 12, 12a-12d Communication port 15 Inlet port 21 Intake passage 28 Air-fuel ratio sensor 50 High-pressure EGR device (exhaust gas recirculation device)
51 High pressure EGR passage (reflux passage)
54 connecting portion 54h opening 54A opening surface 54B facing surface 54D, 54E side wall surface 55 passage portion 56 projection 56D, 56E side wall surface

Claims (7)

A recirculation passage for communicating a part of the exhaust gas flowing through the exhaust system through the exhaust system of the internal combustion engine and recirculating to the intake system as a recirculation gas, and an inlet for the recirculation gas formed in the intake system An exhaust gas recirculation device comprising:
The recirculation passage is connected to the inlet and connected to the exhaust port in a direction intersecting the flow direction of the intake air in the intake system, and the exhaust flow direction of the connection portion communicates with the connection portion. And a passage portion for allowing exhaust to flow in a direction intersecting with
The connection portion is opposed to an opening surface in which an opening communicating with the passage portion is formed, and an opposite surface extending to the introduction port is formed in a flat shape, and an exhaust cross-sectional area is from the passage portion side to the passage portion. The exhaust gas recirculation apparatus, wherein both side wall surfaces between the opening surface and the facing surface are oriented so as to gradually expand toward the introduction port. The connecting portion is connected in a direction orthogonal to a flow direction of the intake air flowing through the intake system;
The exhaust gas recirculation apparatus according to claim 1, wherein the passage portion is connected in a direction orthogonal to a flow direction of the exhaust gas flowing through the connection portion. The intake system includes an intake manifold having a collector portion that distributes intake air to a plurality of cylinders of the internal combustion engine, and an intake passage connected to the upstream side of the intake manifold,
The intake manifold has a bent portion formed by bending,
3. The exhaust gas recirculation apparatus according to claim 1, wherein the connection portion is connected to an upstream side of the intake flow with respect to the bent portion. The collector section has a plurality of communication ports formed in a row communicating with the plurality of cylinders, respectively.
The connection portion is connected to an upstream side of an intake flow from the intake passage toward the plurality of communication ports, and the flow cross-sectional area is expanded so that the reflux gas spreads in a direction in which the plurality of communication ports are arranged. The exhaust gas recirculation apparatus according to claim 3, wherein the exhaust gas recirculation apparatus is formed as follows. An air-fuel ratio sensor that is provided outside the flow path of the bent portion and detects an air-fuel ratio of intake air;
5. The exhaust gas recirculation apparatus according to claim 3, wherein the connection portion has a protrusion that protrudes from the facing surface toward the opening surface and is formed at a substantially center of the flow cross-sectional area. The exhaust gas recirculation apparatus according to claim 5, wherein the protrusion has a side wall surface facing the both side wall surfaces of the connection portion in parallel or substantially in parallel. The exhaust according to claim 5 or 6, wherein an end of the protrusion on the introduction port side is provided so as to be along an inner peripheral surface of the intake manifold or the intake passage to which the connection portion is connected. Reflux apparatus.

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