Exhaust structure for internal combustion engine
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- NISSAN MOTOR CO LTD
- Filing Date
- 2025-02-03
- Publication Date
- 2026-08-06
Smart Images
Figure JP2025003413_06082026_PF_FP_ABST
Abstract
Description
Exhaust Structure of Internal Combustion Engine
[0001] The present invention relates to an exhaust structure of an internal combustion engine.
[0002] As a conventional exhaust structure of an internal combustion engine, for example, the one described in Patent Document 1 below is known.
[0003] In the exhaust structure of a conventional internal combustion engine, a first collecting portion that collects exhaust discharged from the first and third combustion chambers arranged in the cylinder arrangement direction, a first port that communicates from the first combustion chamber to the first collecting portion, and a third port that communicates from the third combustion chamber to the first collecting portion, in the exhaust structure of an engine in which an exhaust port mechanism including these is integrally formed in a cylinder head, the extension lines of the first and third ports are formed so as to intersect at an obtuse angle in a plan view, the extension line of the first port is connected to the upper half portion of the first collecting portion, and the extension line of the third port is connected to the lower half portion of the first collecting portion.
[0004] However, in the exhaust structure of the conventional internal combustion engine, a stepped portion curved toward the center of the first collecting portion is formed at the lower end portion of the connecting portion between the first port and the first collecting portion, and a stepped portion curved toward the center of the first collecting portion is formed at the upper end portion of the connecting portion between the third port and the first collecting portion. That is, in the exhaust structure of the conventional internal combustion engine, in the first collecting portion, the configuration is such that the passage cross-sectional area is narrowed in the height direction to cause a constriction flow. As a result, there is still room for improvement in that the ventilation resistance may increase in the first collecting portion.
[0005] Also, in order to obtain a good swirling flow in the exhaust port, the cross-sectional shapes of the first port and the third port upstream of the first collecting portion are important. That is, it is desirable that each of the first port and the third port before merging at the first collecting portion also has a cross-sectional shape capable of obtaining a good swirling flow. However, in the exhaust structure of the conventional internal combustion engine, there is still room for improvement in that the cross-sectional shapes and the generation modes of the swirling flows of the ports upstream of the first collecting portion are not considered at all.
[0006] Japanese Unexamined Patent Application Publication No. 2020 - 016189
[0007] In one aspect, the present invention provides an exhaust structure for an internal combustion engine, comprising at least a plurality of exhaust valves, namely a first exhaust valve and a second exhaust valve, for each cylinder, a first exhaust port and a second exhaust port having the first exhaust valve and the second exhaust valve as inlets, the first exhaust port and the second exhaust port being formed to be of unequal length, and an exhaust port merging section provided where the first exhaust port and the second exhaust port merge in the section leading to the outlet of the cylinder head, wherein the exhaust port merging section has a first aspect ratio approximation section in which the dimensional ratio of the width direction to the height direction is approximate.
[0008] According to the present invention, the ratio of dimensions in the width direction to the height direction (aspect ratio) is approximate at the exhaust port confluence. This makes it possible to reduce the airflow resistance of the swirling flow formed by the first exhaust flow guided from the first exhaust port and the second exhaust flow guided from the second exhaust port at the exhaust port confluence, thereby improving engine output.
[0009] This is a plan view of the exhaust port mechanism according to the present invention. This is a side view of the exhaust port mechanism shown in Figure 1. This is a cross-sectional view taken along line A-A in Figure 1. This is a cross-sectional view taken along line B-B in Figure 1. This is a cross-sectional view taken along line C-C in Figure 1. This is a cross-sectional view taken along line D-D in Figure 1.
[0010] The following describes in detail an embodiment of the exhaust structure for an internal combustion engine according to the present invention, based on the drawings. In this embodiment, as with conventional examples, the exhaust structure for an internal combustion engine is illustrated in which it is applied to the cylinder head of an automobile engine (spark-ignition internal combustion engine).
[0011] Figure 1 shows a plan view of the exhaust port mechanism EP, which is formed inside the cylinder head, illustrating its contour. Figure 2 shows a side view of the exhaust port mechanism EP shown in Figure 1, viewed from the side. Figure 3 shows a cross-sectional view of the exhaust port mechanism EP cut along line A-A in Figure 1. Figure 4 shows a cross-sectional view of the exhaust port mechanism EP cut along line B-B in Figure 1. Figure 5 shows a cross-sectional view of the exhaust port mechanism EP cut along line C-C in Figure 1. Figure 6 shows a cross-sectional view of the exhaust port mechanism EP cut along line D-D in Figure 1. In the descriptions of each figure, "width direction" refers to the direction perpendicular to the longitudinal direction of each port and perpendicular to the cylinder axis of the cylinder, and "height direction" refers to the direction of the cylinder axis of each cylinder.
[0012] For example, as shown in Figure 1, the internal combustion engine according to this embodiment is a three-cylinder in-line engine, and an exhaust port mechanism EP is formed inside the cylinder head of the engine that collects the exhaust gases from the combustion chambers of the first to third cylinders C1 to C3 and guides them to an exhaust pipe connected to the side of the cylinder head. This exhaust port mechanism EP has a first exhaust valve and a second exhaust valve (not shown) that open and close for each of the combustion chambers C1 to C3 as inlets, and a terminal section ED, which is a collection section connected to the exhaust pipe, as an outlet.
[0013] Specifically, the exhaust port mechanism EP integrally includes a first exhaust port 11 and a second exhaust port 12 that guide exhaust gas discharged from the combustion chamber of the first cylinder C1, a first exhaust port 21 and a second exhaust port 22 that guide exhaust gas discharged from the combustion chamber of the second cylinder C2, and a first exhaust port 31 and a second exhaust port 32 that guide exhaust gas discharged from the combustion chamber of the third cylinder C3.
[0014] Furthermore, in the exhaust port mechanism EP, the first exhaust port 11 and the second exhaust port 12 of the first cylinder C1 merge at the first exhaust port junction 1 on the upstream side of the exhaust. Similarly, in the exhaust port mechanism EP, the first exhaust port 31 and the second exhaust port 32 of the third cylinder C3 merge at the third exhaust port junction 3 on the upstream side of the exhaust.
[0015] In the exhaust port mechanism EP, the first exhaust port 11 and second exhaust port 12 of the first cylinder C1 merge at the first exhaust port merging section 1, and the first exhaust port 21 of the second cylinder C2 merge at the cylinder merging section 4. Then, just before the outlet of the exhaust port mechanism EP on the upstream side of the exhaust, the cylinder merging section 4, the second exhaust port 22 of the second cylinder C2, and the third exhaust port merging section 3 of the third cylinder C3 merge.
[0016] The first exhaust port 11 of the first cylinder C1 curves toward the second exhaust port 12 of the first cylinder C1 toward the first exhaust port confluence 1, and the first exhaust port 11 and the second exhaust port 12 of the first cylinder C1 are configured to be of unequal length with different port lengths. In other words, due to this unequal length configuration, when the first exhaust port 11 and the second exhaust port 12 merge at the first exhaust port confluence 1, a swirling flow is generated due to the pressure difference between the first exhaust port 11 and the second exhaust port 12.
[0017] As shown in Figure 3, the first exhaust port junction 1 has a relatively flattened shape at the first position P1, which is the point where the first exhaust port 11, which is the downstream end of the exhaust system, and the second exhaust port 12 merge, with the height Y1 being relatively smaller than the width X1.
[0018] Furthermore, at the second position P2, which is located upstream of the exhaust from the first position P1 and relatively close to the first exhaust port 11 and the second exhaust port 12, as shown in Figure 4, the width dimension X is reduced compared to the first position P1, but the height dimension Y2 is relatively smaller than the width dimension X2.
[0019] Furthermore, at the third position P3, which is upstream of the exhaust and relatively far from the first exhaust port 11 and the second exhaust port 12, a first aspect ratio approximation section 10 is formed, as shown in Figure 5, which approximates the aspect ratio of the dimension X3 in the width direction X and the dimension Y3 in the height direction Y. That is, the first aspect ratio approximation section 10 has a cross-sectional shape close to a circle C, as shown by the dashed line in Figure 5, because the aspect ratio of the dimension X3 in the width direction X and the dimension Y3 in the height direction Y are approximated.
[0020] In this embodiment, the first aspect ratio approximation section 10 shows a configuration corresponding to the circle C as an example of approximating the dimensional ratio (aspect ratio) of the dimension X3 in the width direction X and the dimension Y3 in the height direction Y. However, as another configuration of approximating the dimensional ratio (aspect ratio) of the dimension X3 in the width direction X and the dimension Y3 in the height direction Y, although specific illustrations are omitted, a cross-sectional shape close to a square may be used.
[0021] Here, at the third position P3 on the exhaust upstream side of the first exhaust port confluence 1, as shown in Figure 2, a bulge 13 is formed by expanding the dimension Y3 in the height direction Y vertically, and this bulge 13 constitutes the first aspect ratio approximation section 10. That is, the first aspect ratio approximation section 10 is formed by expanding the dimension Y2 in the height direction Y while generally maintaining the dimension X2 in the width direction X at the second position P2, and the flow path cross-sectional area is expanded by the amount of this expansion of the dimension Y2 in the height direction Y compared to the second position P2. In other words, the first aspect ratio approximation section 10 is not formed by decreasing the dimension X2 in the width direction X at the second position P2 to approximate the ratio (aspect ratio) of the dimension X3 in the width direction X and the dimension Y3 in the height direction Y.
[0022] Furthermore, in this embodiment, as shown in Figure 2, the bulge 13 is formed such that the dimension Y2 in the height direction Y of the second position P2 gradually expands toward the third position P3, with the maximum being approximately near the fourth position P4, and the dimension Y4 in the height direction Y of the fourth position P4 gradually shrinks toward the end portion ED. Note that in this bulge 13, it is sufficient to expand the dimension in the height direction Y from the second position P2 toward the third position P3 or the fourth position P4, and it is not necessary to shrink toward the end portion ED.
[0023] Furthermore, in the cylinder confluence section 4, which is upstream of the third position P3 and where the first exhaust port confluence section 1 and the first exhaust port 21 of the second cylinder C2 merge, a second aspect ratio approximation section 40 is formed, as shown in Figure 6, which approximates the aspect ratio of the dimension X4 in the width direction X and the dimension Y4 in the height direction Y. In the second aspect ratio approximation section 40, the dimension X4 in the width direction X and the dimension Y4 in the height direction Y are set to be larger than the dimension X3 in the width direction X and the dimension Y3 in the height direction Y of the first aspect ratio approximation section 10.
[0024] In other words, the second aspect ratio approximation section 40 is formed by expanding the dimensions X3 in the width direction X and Y3 in the height direction Y while generally maintaining the aspect ratio of the dimensions X3 in the width direction X and Y3 in the height direction Y at the third position P3. As a result, the flow path cross-sectional area is expanded compared to the third position P3 by the amount of this expansion of the dimensions X3 in the width direction X and Y3 in the height direction Y. In other words, the flow path cross-sectional area of the cylinder confluence section 4 is expanded by the amount of the flow rate of the first exhaust port 21 as the first exhaust port 21 of the second cylinder C2 merges.
[0025] (Effects of this embodiment) According to the present invention, in the first exhaust port confluence section 1, the dimensional ratio (aspect ratio) of the dimension X3 in the width direction X and the dimension Y3 in the height direction Y are approximate. As a result, in the first exhaust port confluence section 1, based on the pressure difference between the first exhaust port 11 and the second exhaust port 12, it is possible to reduce the airflow resistance of the swirling flow formed by the first exhaust flow led from the first exhaust port 11 and the second exhaust flow led from the second exhaust port 12, thereby improving the output of the engine.
[0026] Furthermore, in this embodiment, a second aspect ratio approximation section 40 is formed in the cylinder confluence section 4, where the aspect ratio (length-to-width ratio) of the dimension X4 in the width direction X and the dimension Y4 in the height direction Y are approximated. This makes it possible to more effectively reduce the airflow resistance of the swirling flow generated in the cylinder confluence section 4 based on the exhaust flow guided from each cylinder.
[0027] Furthermore, in this embodiment, the first aspect ratio approximation section 10 is formed as a bulge section 13, which is created by expanding the dimension Y2 in the height direction Y while maintaining (or expanding) the dimension X2 in the width direction X of the second position P2, rather than reducing the dimension X2 in the width direction X. This makes it possible to configure an appropriate first aspect ratio approximation section 10 in the bulge section 13. As a result, a good swirling flow can be generated at the first exhaust port confluence section 1 by the exhaust gases introduced from the first exhaust port 11 and the second exhaust port 12.
[0028] Furthermore, in this embodiment, the first aspect ratio approximation section 10 is configured such that, instead of decreasing the dimension X2 in the width direction X as the dimension Y2 in the height direction Y of the second position P2 increases, the flow path cross-sectional area increases by the amount of the increase in the dimension Y2 in the height direction Y. This makes it possible to configure an appropriate first aspect ratio approximation section 10 in the bulging section 13. As a result, a good swirling flow can be generated in the first exhaust port confluence section 1 by the exhaust gases introduced from the first exhaust port 11 and the second exhaust port 12.
[0029] The present invention is not limited to the configurations illustrated in the above embodiments, and can be freely modified according to the specifications of the cylinder head to which the exhaust structure of the internal combustion engine according to the present invention is applied, such as the number of cylinders and the number of exhaust valves (exhaust ports) for each cylinder.
Claims
1. An exhaust structure for an internal combustion engine, comprising at least a plurality of exhaust valves, namely a first exhaust valve and a second exhaust valve, for each cylinder, having a first exhaust port and a second exhaust port with the first exhaust valve and the second exhaust valve as inlets, wherein the first exhaust port and the second exhaust port are formed to be of unequal length, and an exhaust port merging section is provided where the first exhaust port and the second exhaust port merge in the section up to the outlet of the cylinder head, wherein the exhaust port merging section has a first aspect ratio approximation section in which the dimensional ratio of the width direction to the height direction is approximate.
2. An exhaust structure for an internal combustion engine according to claim 1, wherein, in the section up to the outlet of the cylinder head, there is a cylinder confluence section downstream of the exhaust port confluence section where the exhaust ports of each cylinder merge, and the cylinder confluence section has a second aspect ratio approximation section in which the dimensional ratio of the width direction and the height direction are approximate.
3. An exhaust structure for an internal combustion engine according to claim 1 or 2, wherein the exhaust port confluence portion has a bulge portion on the exhaust downstream side, farther from the first exhaust port and the second exhaust port, in which the height dimension is increased compared to the exhaust upstream side, which is closer to the first exhaust port and the second exhaust port, and the first aspect ratio approximation portion is formed in the bulge portion.
4. An exhaust structure for an internal combustion engine according to claim 3, wherein the bulging portion has an enlarged cross-sectional area of the flow path compared to the upstream side of the exhaust, due to an enlargement of the height dimension of the bulging portion.