Structure of exhaust gas recirculation passage

Abstract

A structure of an exhaust gas recirculation passage that makes a part of exhaust gas generated by combustion recirculate to a cylinder in which the combustion is generated, includes: an introduction pipe (2) that introduces the exhaust gas to the cylinder side; first branch pipes (3A, 3B) that branch at a front end of the introduction pipe (2) into a plurality; second branch pipes (4A, 4B, 4C, 4D) that branch at a front end of the first branch pipes (3A, 3B) into a plurality; a connection passage (5) that connects any one of the second branch pipes (4B) branched from any one of the first branch pipes (3A) with any one of the second branch pipes (4C) branched from the other first branch pipes (3B); and a flow resistance portion (6) that resists condensate water flowing along an inner surface of the connection passage (5). With the structure of the present disclosure, it is possible to achieve both suppression of condensate water concentration and suppression of EGR gas amount deviation.

Description

Technical Field

[0001] The present invention relates to the structure of a passage for exhaust gas recirculation (EGR) that incorporates a portion of the exhaust gas generated from the combustion of a fuel-air mixture into the mixture. Background Technology

[0002] Japanese Patent Application Publication No. 2021-107696 discloses a passage structure having an inlet passage for introducing exhaust gas from the engine's exhaust system. This inlet passage splits into two branches at its front end, forming a first gas passage section and a second gas passage section. These gas passage sections communicate with a gas chamber. Multiple gas distribution passages are provided within the gas chamber for distributing and supplying recirculated gas (EGR gas) to the engine cylinders. The walls (i.e., partition walls) of the openings of each gas distribution passage are separated from each other by raised ribs. Therefore, each gas distribution passage communicates with the gas chamber as a so-called manifold, but the raised ribs protrude into the gas chamber, thus preventing or inhibiting the flow of condensate between the openings on the gas chamber side of the gas distribution passages. As a result, it is possible to prevent condensate from flowing relative to specific combustion cylinders in the engine.

[0003] In the structure of the EGR gas passage relative to the combustion cylinder described in Japanese Patent Application Publication No. 2021-107696, although EGR gas is distributed from the gas inlet path to the first and second gas passages, the distributed EGR gas is caused to merge in the gas chamber. Then, EGR gas is distributed from the gas chamber to the gas distribution passage and delivered to the combustion cylinder. Therefore, condensate contained in the EGR gas, or condensate generated during its journey to the gas chamber, will merge in the gas chamber. Since the gas chamber is internally a cavity, when centrifugal force is applied due to vehicle turning, condensate will concentrate in a specific gas distribution passage. Although a raised rib is provided in the structure described in this document, the raised rib does not divide the interior of the gas chamber into multiple cavity sections, and therefore may not be able to adequately prevent the concentration of condensate relative to a specific combustion cylinder.

[0004] To avoid condensate buildup, it's considered to separate and independent the gas distribution path and the pathways leading to it. For example, the inlet path could be divided into two branches, and each branch could be further divided into two branches before guiding the EGR gas to each combustion cylinder. With this structure, the pathways are separated and independent just before entering the combustion cylinder, so condensate guided to the designated combustion cylinder won't move to other combustion cylinders. However, in such a structure with multiple branches, the amount of EGR gas can sometimes deviate between combustion cylinders. For example, if combustion occurs continuously in two adjacent combustion cylinders, while combustion in two other cylinders is time-interval, the EGR gas continuously flows through one branch from the inlet path and then to another branch. EGR gas has inertia, so there's a delay when switching the flow path from one branch to another, causing a deviation in the amount of EGR gas between combustion cylinders. Increasing the amount of EGR gas introduced increases this deviation between combustion cylinders. Utility Model Content

[0005] The purpose of this disclosure is to provide a structure for an exhaust gas recirculation path that can simultaneously suppress the concentration of condensate and the deviation of EGR gas volume.

[0006] To achieve the above objectives, this disclosure provides a structure for an exhaust gas recirculation passage that allows a portion of the exhaust gas generated during combustion to flow back to the cylinder where the combustion occurred. The passage comprises: an inlet pipe that guides the exhaust gas to the cylinder side; a first branch pipe that branches into multiple branches at its front end; a second branch pipe that branches into multiple branches at its front end; a connecting passage that connects any second branch pipe branching from any first branch pipe to other second branch pipes branching from other first branch pipes; and a flow obstruction portion that prevents condensate from flowing along the inner surface of the connecting passage.

[0007] In the structure of the exhaust gas recirculation passage disclosed herein, the pipelines guiding the exhaust gas to the cylinders branch off from the inlet pipeline and ultimately become independent of each other. Therefore, the movement of condensate between cylinders is prevented at each branching point. Furthermore, the deviation in exhaust gas volume between the first branch pipelines caused by the inertia of the exhaust gas is eliminated or suppressed by the connecting passage. Moreover, since a flow obstruction is provided in the connecting passage, the concentration of condensate in specific cylinders can be prevented or suppressed. As a result, this disclosure can simultaneously prevent or suppress deviations in exhaust gas volume and the concentration of condensate. Attached Figure Description

[0008] Figure 1 This is a schematic diagram illustrating one embodiment of the present disclosure. Detailed Implementation

[0009] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, the embodiments described below are merely examples for implementing this disclosure and are not intended to limit the scope of this disclosure.

[0010] The exhaust gas recirculation passage disclosed herein is arranged between the engine's exhaust system and the intake system, such as the intake manifold, to allow a portion of the exhaust gas generated by the combustion of the fuel-air mixture in the engine cylinder to flow back into the cylinder. Figure 1 An example is schematically shown. The structure 1 of the exhaust gas recirculation passage shown here has an inlet pipe 2, which connects to the engine's exhaust system (not shown separately) and guides the exhaust gas G to the intake side. At the front end of this inlet pipe 2, there are multiple branches (in... Figure 1 In the example, there are two first branch pipes 3A and 3B. The first branch pipes 3A and 3B can be a structure where two pipes are joined into a bifurcated shape and connected to the front end of the inlet pipe 2. Alternatively, it can be a structure where two pipes branch and connect to a manifold pipe, and this manifold pipe is then connected to the inlet pipe 2. Furthermore, the exhaust gas (i.e., EGR gas) G flowing inside the inlet pipe 2 is split in two and flows to the first branch pipes 3A and 3B; therefore, the diameter of each first branch pipe 3A, 3B can be approximately half that of the inlet pipe 2.

[0011] A branch pipeline is provided to supply exhaust gas G from each of the first branch pipelines 3A and 3B to multiple cylinders (not shown). That is, each of the multiple (two in this example) first branch pipelines 3A and 3B has a branch at its front end, which branches into multiple cylinders (in...) Figure 1 In the example, there are two second branch pipes (4A, 4B, 4C, and 4D). Figure 1 In the example shown, a pair of second branch pipes 4A and 4B are connected to a first branch pipe 3A, and another pair of second branch pipes 4C and 4D are connected to another first branch pipe 3B. These pairs of second branch pipes 4A and 4B (or 4C and 4D) can be structures that join two pipes into a bifurcated shape and connect them to the front end of the first branch pipe 3A (or 3B). Alternatively, they can be structures where two pipes branch and connect to a manifold pipe, and this manifold pipe is then connected to the first branch pipe 3A (or 3B). Furthermore, the exhaust gas G flowing inside each of the first branch pipes 3A and 3B is further divided in two and flows to each of the second branch pipes 4A, 4B, 4C, and 4D; therefore, the diameter of each of the second branch pipes 4A, 4B, 4C, and 4D can be approximately half that of the first branch pipes 3A and 3B.

[0012] exist Figure 1 In the example shown, the second branch pipes 4A, 4B, 4C, and 4D originate from... Figure 1Starting from the left, it is sequentially connected to cylinder #1, cylinder #2, cylinder #3, and cylinder #4. Furthermore, the ignition sequence is cylinder #1, cylinder #3, cylinder #4, and cylinder #2. Therefore, after continuously supplying exhaust gas G to cylinder #3 and cylinder #4, exhaust gas G is then supplied to cylinder #2 and cylinder #1. Regarding the piping through which exhaust gas G flows, during the two ignition cycles, exhaust gas G flows through a first branch pipe 3B, and then flows through another first branch pipe 3A. In other words, the supply of exhaust gas G switches from cylinder #1 to cylinder #3, and from cylinder #4 to cylinder #2.

[0013] exist Figure 1 In the example shown, a connecting passage 5 is also provided, which connects the second branch pipe 4B on the side of one first branch pipe 3A to the second branch pipe 4C on the side of another first branch pipe 3B. This connecting passage 5 is a passage connecting one first branch pipe 3A to another first branch pipe 3B on the sides of the second branch pipes 4A, 4B, 4C, and 4D. Therefore, the connecting passage 5 may not be located between the second branch pipe 4B connected to the second cylinder #2 and the second branch pipe 4C connected to the third cylinder #3, but rather between the second branch pipe 4A connected to the first cylinder #1 and the second branch pipe 4D connected to the fourth cylinder #4.

[0014] The connecting passage 5 functions to allow the pipes or exhaust gas G separated by the first branch pipes 3A and 3B to merge. Therefore, a flow obstruction is provided to prevent or inhibit the movement and merging of condensate water along with the exhaust gas G. Examples of such flow obstructions include bends, protrusions, etc., inside the connecting passage 5. Figure 1 In the example shown, the inclined portion 6 provided in the connecting passage 5 is the flow obstruction portion. The inclined portion 6 is the part of the passage that is inclined at a predetermined angle relative to a straight line, which connects the connection points (or open ends) of the second branch pipes 4B and 4C at both ends of the connecting passage 5. Figure 1 In the example shown, inclined portions 6 are provided at both ends of the connecting passage 5. This angle is preferably greater than 4 degrees, for example.

[0015] exist Figure 1 In the structure 1 of the exhaust gas recirculation passage shown, the exhaust gas G flowing inside the inlet pipe 2 is split into two at the front end of the inlet pipe 2 and flows to the first branch pipes 3A and 3B. These first branch pipes 3A and 3B are independent of each other, so even if condensate is generated inside each of them, the condensate will not be concentrated on either the first branch pipe 3A or 3B side due to centrifugal force or the like.

[0016] The exhaust gas G is further split in two at the front ends of each of the first branch pipes 3A and 3B, and then flows to each of the second branch pipes 4A, 4B, 4C and 4D. It is then delivered to the first cylinder #1 to the fourth cylinder #4, which are connected to the second branch pipes 4A, 4B, 4C and 4D respectively. In this configuration, each of the second branch pipes 4A, 4B, 4C and 4D is independent of the others. Therefore, even if condensation occurs within each of them, it is possible to avoid or suppress the concentration of condensation in any one of the second branch pipes 4A, 4B, 4C and 4D or any one of the cylinders #1 to #4 due to centrifugal force or other factors.

[0017] As mentioned above, in Figure 1 In the example shown, exhaust gas G is delivered to a first branch pipe 3A (or 3B) during the two ignition cycles, and then to another first branch pipe 3B (or 3A). With this switching of exhaust gas G flow, the exhaust gas volume can sometimes deviate due to the inertia of the exhaust gas G. In this case, a difference in gas flow rate or pressure occurs at the outlet sides of each first branch pipe 3A, 3B, i.e., between one second branch pipe 4B and another second branch pipe 4C. Accompanying this, exhaust gas G flows through connecting passage 5, thus correcting any imbalance or deviation in the gas volume of each cylinder #1 to cylinder #4.

[0018] Furthermore, when centrifugal force exerts a strong effect on condensate due to vehicle turning, the flow of condensate is blocked or suppressed by the inclined portion 6 in the connecting passage 5. As a result, even if the outlet sides of each first branch pipe 3A and 3B, i.e., one second branch pipe 4B and another second branch pipe 4C, are connected through the connecting passage 5, it is possible to prevent or suppress the flow and accumulation of condensate in the direction of centrifugal force, or the accumulation of condensate in specific cylinders #1 to #4. According to the structure of the exhaust gas recirculation passage described above, it is possible to both suppress the accumulation of condensate and suppress deviations in the EGR gas volume.

[0019] Furthermore, while the above embodiments illustrate an example using a four-cylinder engine, this disclosure can be implemented for engines with a number of cylinders other than four. Therefore, the number of the first branch line and the second branch line is not limited to the numbers shown in the above embodiments.

[0020] Explanation of reference numerals in the attached figures 1: Structure of the exhaust gas recirculation path 2: Inlet tubing 3A, 3B: First branch pipeline 4A, 4B, 4C, 4D: Second branch pipes 5: Connecting Paths 6: Inclined section (flow obstruction section) G: Exhaust gas (EGR gas) #1, #2, #3, #4: Cylinders

Claims

1. A structure for an exhaust gas recirculation passage, wherein a portion of the exhaust gas generated during combustion is recirculated back to the cylinder from which the combustion occurred, characterized in that, have: The exhaust gas is guided to the cylinder side via an inlet pipe. The first branch pipe branches into multiple branches at the front end of the inlet pipe; The second branch pipeline branches into multiple branches at the front end of the first branch pipeline; Connecting pathways, linking any second branch pipe branching from any of the first branch pipes to other second branch pipes branching from other first branch pipes; and The flow obstruction prevents condensate from flowing along the inner surface of the connecting passage.

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