JP2016160927A - Exhaust passage structure of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance discharge efficiency of exhaust gas to improve output of an engine.SOLUTION: In an exhaust passage structure of an engine 100, an exhaust port 6 has a curved part 63. In the exhaust port 6, on the downstream side of a portion on the side where the curvature of the curved part 63 is large, formed is a rectification unit 64 swollen to the inward of the exhaust port 6 and configured to rectify exhaust gas flow. In the exhaust port 6, on the downstream side of the rectification unit 64, formed is a venturi unit 65 of which a flow passage area is narrowed.SELECTED DRAWING: Figure 4

Description

  The technology disclosed herein relates to an engine exhaust passage structure.

  2. Description of the Related Art Conventionally, a technique for increasing a flow rate of exhaust gas by providing a throttle portion in an exhaust passage of an engine is known. For example, in the engine according to Patent Document 1, an ejector nozzle having a reduced flow path area is provided at the outlet of the exhaust port, and a secondary air supply port is provided around the ejector nozzle. According to this configuration, the secondary air is introduced into the exhaust gas by the ejector effect.

JP 58-55324 A

  By the way, in the exhaust passage structure of an engine, it is desired to improve the exhaust gas exhaust efficiency and thus improve the engine output. In order to improve the exhaust gas exhaust efficiency, it is conceivable to increase the flow rate of the exhaust gas. One technique for increasing the flow rate of exhaust gas is to throttle the exhaust passage like an ejector nozzle. However, simply narrowing the exhaust passage is not sufficient for improving exhaust gas exhaust efficiency, and there is room for further improvement.

  The technology disclosed herein has been made in view of such a point, and an object thereof is to improve exhaust gas exhaust efficiency and improve engine output.

  The technology disclosed herein is an engine exhaust passage structure including a cylinder head in which an exhaust port for discharging exhaust gas from a combustion chamber is formed, the exhaust port having a curved portion, and the exhaust port A rectifying unit that swells inward of the exhaust port and rectifies the flow of the exhaust gas is formed on the downstream side of the curved portion of the port where the curvature is large, and the rectifying unit in the exhaust port It is assumed that a venturi portion with a narrowed flow path area is formed on the downstream side of the.

  According to this configuration, the exhaust gas flowing through the exhaust port is first rectified by the rectification unit. As described above, in an exhaust port having a curved portion, there may be a case where separation occurs in the flow of exhaust gas on the downstream side of a portion having a large curvature in the curved portion (hereinafter referred to as “inner portion of the curved portion”). . When flow separation occurs, the flow rate of the exhaust gas decreases, and the exhaust gas exhaust efficiency deteriorates. On the other hand, the exhaust gas is rectified by providing the rectification portion on the downstream side of the inner portion of the curved portion, and flow separation is suppressed. As a result, the exhaust gas flow rate increases. Subsequently, the exhaust gas passes through the venturi section, thereby further increasing the flow velocity.

  As described above, the flow rate of the exhaust gas is not increased only by the venturi part, but the flow rate of the exhaust gas is increased by suppressing the separation of the exhaust gas in the previous stage of flowing into the venturi part. Thereby, the flow rate of the exhaust gas can be increased more effectively by the venturi section. Thus, by increasing the exhaust gas flow rate, exhaust gas exhaust efficiency can be improved and engine output can be improved. Further, if the exhaust gas exhaust efficiency can be improved, the residual gas in the cylinder can be reduced, so that the knocking limit can be improved.

  Furthermore, since the separation of the exhaust gas is suppressed by providing the rectifying unit, the contact of the exhaust gas with the inner peripheral surface of the exhaust port is promoted. Thereby, cooling of exhaust gas is promoted. For example, in an operation region where the engine speed is high and the engine load is high, the engine may be operated at an air-fuel ratio richer than the stoichiometric air-fuel ratio in order to prevent catalyst overheating. As described above, if the cooling of the exhaust gas can be promoted, the air-fuel ratio can be brought close to the stoichiometric air-fuel ratio while preventing the catalyst from overheating, so that the fuel consumption can be improved. In particular, according to the above configuration, the rectifying unit is not provided in the exhaust pipe, but is provided in the exhaust port formed in the cylinder head. Therefore, the contact between the exhaust gas and the cylinder head can be promoted. Since the cylinder head is cooled by cooling water or the like, the exhaust gas can be cooled more efficiently by promoting the contact between the exhaust gas and the cylinder head.

  Further, two exhaust ports are provided for each combustion chamber, the two exhaust ports merge into one on the downstream side, and the venturi section joins one of the exhaust ports. You may form in the part used as the book.

  According to this configuration, the rectification unit is provided in each of the two exhaust ports, and the venturi unit is provided in a portion after the two exhaust ports merge into one.

  Further, the cylinder head is provided with a support portion that supports a swing arm that is driven by a cam portion of a camshaft to open and close the exhaust valve, and the support portion is a hydraulic type that stops the opening and closing operation of the exhaust valve. It has a valve stop mechanism and may be arranged corresponding to a portion of the cylinder head that bulges inward of the exhaust port by forming the venturi portion.

  According to this configuration, a portion of the cylinder head that bulges inward of the exhaust port is formed by forming the venturi portion. A support portion having a valve stop mechanism is arranged using this portion. Thereby, the support part which has a valve stop mechanism in a cylinder head can be arrange | positioned compactly.

  According to the exhaust passage structure of the engine, exhaust gas exhaust efficiency can be increased and engine output can be improved.

1 is a schematic cross-sectional view of an engine cut along a plane including an axis of a cylinder. It is sectional drawing of the cylinder head in the II-II line | wire of FIG. It is sectional drawing of the cylinder head in the III-III line of FIG. It is sectional drawing of the exhaust port in the IV-IV line of FIG. The cross-sectional view around the rectification part of the exhaust port is shown, (A) is a cross-sectional view taken along line AA in FIG. 4, (B) is a cross-sectional view taken along line BB in FIG. 4C is a cross-sectional view taken along line CC in FIG. 4, FIG. 4D is a cross-sectional view taken along line DD in FIG. 4, and FIG. 4E is a cross-sectional view taken along line EE in FIG. It is. The cross-sectional view around the venturi portion of the exhaust port is shown, (A) is a cross-sectional view taken along line FF in FIG. 4, (B) is a cross-sectional view taken along line GG in FIG. (C) is a cross-sectional view taken along the line HH in FIG. 4, and (D) is a cross-sectional view taken along the line II in FIG. It is a graph which shows the cross-sectional area change of the downstream end part of an exhaust port.

  Hereinafter, exemplary embodiments will be described in detail with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view of engine 100 cut along a plane including the axis of the cylinder. In the present specification, for convenience of explanation, the axial direction of the cylinder is referred to as the vertical direction, and the cylinder row direction is referred to as the front-rear direction. Further, in the cylinder row direction, the non-transmission side of engine 100 is referred to as a front side, and the transmission side is referred to as a rear side.

  The engine 100 is an in-line four-cylinder engine in which four cylinders are arranged in a predetermined cylinder row direction. The engine 100 includes a cylinder head 1, a cylinder block 2 attached to the cylinder head 1, and an oil pan (not shown) attached to the cylinder block 2.

  In the cylinder block 2, four cylinders 23 are formed side by side in the cylinder row direction (only one cylinder 23 is shown in FIG. 1). A piston is inserted into the cylinder 23. A combustion chamber 27 is defined by the cylinder 23, the piston, and the cylinder head 1. The combustion chamber 27 has a pent roof shape. The four cylinders 23 correspond to the first cylinder, the second cylinder, the third cylinder, and the fourth cylinder in order from the front side, and when distinguishing them, the first cylinder 23A, the second cylinder 23B, the third cylinder These are referred to as cylinder 23C and fourth cylinder 23D.

  The cylinder head 1 is provided with an intake port 5 and an exhaust port 6 that open to the combustion chamber 27, and the intake port 5 is provided with an intake valve 13 that opens and closes the intake port 5. The exhaust port 6 is provided with an exhaust valve 14 that opens and closes the exhaust port 6. The intake valve 13 and the exhaust valve 14 are driven by cam portions 41a and 42a provided on the cam shafts 41 and 42, respectively.

  Specifically, the intake valve 13 and the exhaust valve 14 are urged in the closing direction (upward in FIG. 1) by the valve springs 15 and 16. Swing arms 43 and 44 are interposed between the intake valve 13 and the exhaust valve 14 and the cam portions 41a and 42a, respectively. One end portions of the swing arms 43 and 44 are supported by hydraulic lash adjusters (hereinafter referred to as “HLA”) 45 and 46, respectively. The swing arms 43 and 44 swing around the one end portions supported by the HLA 45 and 46 as the cam followers 43a and 44a provided at substantially central portions thereof are pushed by the cam portions 41a and 42a, respectively. By swinging in this way, the swing arms 43 and 44 move the intake valve 13 and the exhaust valve 14 at the other end in the opening direction (downward in FIG. 1) against the urging force of the valve springs 15 and 16, respectively. Let The HLA 45 and 46 automatically adjust the valve clearance to zero by hydraulic pressure. FIG. 1 shows the HLA 45 and 46 of the first cylinder 23A. The HLA 45 and 46 provided in the first cylinder 23A and the fourth cylinder 23D stop the operation of the intake valve 13 and the exhaust valve 14, respectively. There are provided valve stop mechanisms 45a and 46a. The HLA 45, 46 provided with the valve stop mechanisms 45a, 46a has a longer dimension in the longitudinal direction than the HLA 45, 46 provided with no valve stop mechanism. The HLA 46 is an example of a support part.

  The cylinder head 1 is formed with a water jacket 11 through which cooling water flows. The cylinder head 1 is cooled by the cooling water flowing through the water jacket 11.

  A cam cap 47 is attached to the upper part of the cylinder head 1. The cam shafts 41 and 42 are rotatably supported by the cylinder head 1 and the cam cap 47.

  Next, the configuration of the exhaust port 6 will be described in detail. FIG. 2 is a sectional view of the cylinder head 1 taken along the line II-II in FIG. FIG. 3 is a sectional view of the cylinder head 1 taken along the line III-III in FIG. In FIG. 3, a line parallel to the axis of the exhaust port 6 and a line extending in the circumferential direction around the axis are arranged in a lattice pattern on the inner surface so that the undulation of the inner surface of the exhaust port 6 can be seen. I'm drawing.

  As shown in FIGS. 2 and 3, two exhaust ports 6 are provided for each cylinder 23. The upstream ends of the two exhaust ports 6 open to one of the two inclined surfaces that form the pent roof of the combustion chamber 27. The two exhaust ports 6 merge at the downstream side and become one. The downstream end of the exhaust port 6 is open to the side surface of the cylinder head 1. Hereinafter, the portion of the exhaust port 6 that is divided into two is referred to as a branch pipe 61, and the portion that is joined to one is referred to as a collecting pipe 62.

  As shown in FIG. 1, the exhaust port 6 extends in the normal direction of the inclined surface and then curves toward the side surface of the cylinder head 1. More specifically, the branch pipe 61 has a curved portion 63. As described above, the bending portion 63 is bent from the normal direction of the inclined surface of the pent roof toward the side surface of the cylinder head 1. Further, as shown in FIG. 2, the upstream ends of the two branch pipes 61 are arranged at intervals in the cylinder row direction, whereas the downstream ends of the two branch pipes 61 are connected to the collecting pipe 62. Therefore, the two branch pipes 61 are curved so as to approach each other from the upstream side toward the downstream side. That is, the bending portion 63 is not only bent from the normal direction of the inclined surface of the pent roof toward the side surface of the cylinder head 1 but also bent in the direction in which the two branch pipes 61 approach each other.

  The exhaust port 6 configured in this way is formed with a rectifying unit 64 that swells inward of the exhaust port 6 and rectifies the flow of the exhaust gas, and a venturi unit 65 with a reduced flow path area. . 4 shows a cross-sectional view of the exhaust port 6 along line IV-IV in FIG. 2, FIG. 5 shows a cross-sectional view around the rectifying unit 64 of the exhaust port 6, and FIG. It is sectional drawing in the A line, (B) is sectional drawing in the BB line in FIG. 4, (C) is sectional drawing in the CC line in FIG. 4, (D) is a figure. 4 is a cross-sectional view taken along a line D-D in FIG. 4, and (E) is a cross-sectional view taken along a line EE in FIG.

  Specifically, the rectifying unit 64 suppresses separation of the flow of exhaust gas flowing through the exhaust port 6. In a curved flow path, flow separation tends to occur in a portion immediately after bending. In the exhaust port 6, a curved portion 63 is provided in the branch pipe 61, and an inner portion of the curved portion 63 in the branch pipe 61 (that is, a portion on the side where the curvature of the curved portion 63 is large (or the curvature radius is small)). Separation of the flow tends to occur on the downstream side. Further, the two branch pipes 61 are bent so as to approach each other and merge with the collecting pipe 62. Therefore, the separation of the flow in the branch pipe 61 is more likely to occur in a portion biased toward the other branch pipe 61 in the circumferential direction of the branch pipe 61 than in a portion immediately below the center of the branch pipe 61.

  Therefore, a rectifying portion 64 is formed on the downstream side of the inner portion of the bending portion 63 in the branch pipe 61. In the circumferential direction of the branch pipe 61, the rectifying unit 64 is closer to the other branch pipe 61 of the pair of branch pipes 61 than just below the center of the branch pipe 61 as shown in FIGS. It is arranged at the position. The rectifying unit 64 bulges inwardly from the exhaust port 6. More specifically, the rectifying unit 64 bulges inwardly toward the exhaust port 6 in comparison with at least the front and rear portions in the axial direction of the exhaust port 6 (FIGS. 5A and 5E). As shown in FIGS. 5B to 5D, the bulging amount of the rectifying unit 64 gradually increases from the upstream side of the branch pipe 61 toward the downstream side, and then gradually decreases. . The surface of the rectifying unit 64 is formed with a curved surface in order to reduce the flow resistance of the branch pipe 61 and is not angular. Moreover, the part which is not the rectification | straightening part 64 among the internal peripheral surfaces of the rectification | straightening part 64 and the branch pipe 61 is smoothly connected via the curved surface.

  Since the rectifying unit 64 bulges from the inner peripheral surface of the branch pipe 61, flow separation is suppressed so that the exhaust gas flows while contacting the surface of the rectifying unit 64. Thereby, the flow rate of exhaust gas increases. At this time, since the rectification unit 64 is smoothly connected to the inner peripheral surface of the branch pipe 61 and is formed by a curved surface on the surface of the rectification unit 64, an increase in the exhaust gas flow resistance is suppressed. This point also contributes to an increase in the exhaust gas flow velocity.

  The venturi unit 65 increases the flow rate of the exhaust gas by reducing the flow path area. The venturi unit 65 is provided on the downstream side of the rectification unit 64 in the exhaust port 6. 6 shows a cross-sectional view around the venturi portion 65 of the exhaust port 6, (A) is a cross-sectional view taken along line FF in FIG. 4, and (B) is taken along line GG in FIG. 4. 5 is a cross-sectional view, (C) is a cross-sectional view taken along the line H-H in FIG. 4, and (D) is a cross-sectional view taken along the line II in FIG. 4. FIG. 7 is a graph showing changes in the cross-sectional area at the downstream end of the exhaust port.

  The venturi 65 is provided at the downstream end of the collecting pipe 62. After the two branch pipes 61 gather, the collecting pipe 62 gradually decreases in the lateral direction (cylinder row direction) toward the downstream end that opens to the side surface of the cylinder head 1. On the other hand, the vertical dimension of the collecting pipe 62 decreases once and then expands toward the downstream end. As a result, in the venturi section 65, the cross-sectional area of the collecting pipe 62 is once reduced toward the downstream end and then expanded as shown in FIG.

  Thus, the flow area of the exhaust gas passing through the venturi section 65 is increased by reducing the flow path area in the venturi section 65. Combined with the effect of the rectifying unit 64 described above, the flow rate of the exhaust gas passing through the exhaust port 6 is increased, so that the exhaust gas discharge efficiency is improved and the engine output can be improved.

  As described above, in the exhaust passage structure of the engine 100, the exhaust port 6 has the curved portion 63, and the exhaust port 6 has a curved portion 63 on the downstream side of the portion with the larger curvature of the curved portion 63. A rectifying section 64 that swells inward and rectifies the flow of exhaust gas is formed, and a venturi section 65 with a reduced flow passage area is formed on the exhaust port 6 downstream of the rectifying section 64.

  According to this configuration, in the curved exhaust port 6, flow separation tends to occur on the downstream side of the curved portion 63 on the side with a large curvature. On the other hand, a rectifying portion 64 that bulges inward of the exhaust port 6 is formed in this portion. Thereby, flow separation is suppressed, and the flow rate of the exhaust gas can be increased. In addition, a venturi portion 65 is formed on the downstream side of the rectifying portion 64. Therefore, the exhaust gas whose flow velocity is increased by the rectifying unit 64 can be further increased by the venturi unit 65. Thus, by increasing the flow rate of the exhaust gas by the rectifying unit 64 and the venturi unit 65, the exhaust gas exhaust efficiency can be improved and the engine output can be improved. Further, if the exhaust gas exhaust efficiency can be improved, the residual gas in the cylinder 23 can be reduced, so that the knocking limit can be improved.

  Furthermore, since the separation of the exhaust gas is suppressed by providing the rectifying unit 64, the contact of the exhaust gas with the inner peripheral surface of the exhaust port 6 is promoted. Thereby, cooling of exhaust gas is promoted. In engine 100, in an operating region where the engine speed is high and the engine load is high, the engine is operated at an air-fuel ratio richer than the stoichiometric air-fuel ratio in order to prevent catalyst overheating. If cooling of the exhaust gas can be promoted, overheating of the catalyst can be prevented even if the air-fuel ratio is brought close to the stoichiometric air-fuel ratio. And if an air fuel ratio can be brought close to a theoretical air fuel ratio, a fuel consumption can be improved. In particular, in the engine 100, the rectifying unit 64 is not provided in the exhaust pipe downstream of the exhaust port 6 but is provided in the exhaust port 6. Therefore, contact between the exhaust gas and the cylinder head 1 can be promoted. Since the cylinder head 1 is cooled by the cooling water flowing through the water jacket 11, the exhaust gas can be cooled more efficiently by promoting the contact between the exhaust gas and the cylinder head 1.

  Further, in the venturi portion 65, the upper wall surface of the exhaust port 6 bulges inward of the exhaust port 6 so that the flow path area is reduced. Thereby, in the cylinder head 1, a space is secured in a portion above the exhaust port 6 and corresponding to the venturi portion 65. The exhaust-side HLA 46 is disposed using this space. In particular, the HLA 46 of the first cylinder 23A and the fourth cylinder 23D includes a valve stop mechanism 46a, and its longitudinal dimension is large. By disposing the HLA 46 with the valve stop mechanism 46a using the space above the venturi section 65, the vertical dimension of the cylinder head 1 can be suppressed.

  As described above, the embodiment has been described as an example of the technique disclosed in the present application. However, the technology in the present disclosure is not limited to this, and can also be applied to an embodiment in which changes, replacements, additions, omissions, and the like are appropriately performed. Moreover, it is also possible to combine each component demonstrated by the said embodiment and it can also be set as new embodiment. In addition, among the components described in the accompanying drawings and detailed description, not only the components essential for solving the problem, but also the components not essential for solving the problem in order to exemplify the above technique. May also be included. Therefore, it should not be immediately recognized that these non-essential components are essential as those non-essential components are described in the accompanying drawings and detailed description.

  For example, in the above-described embodiment, the exhaust ports provided for each cylinder are two upstream and one downstream, but are not limited thereto. There may be one exhaust port from the upstream end to the downstream end, or two exhaust ports from the upstream end to the downstream end.

  Further, although the rectifying unit 64 is provided in the branch pipe 61 of the exhaust port 6, the rectifying unit 64 may be provided in the collecting pipe 62 depending on the position of the bending part 63. Further, the venturi unit 65 may be provided in the branch pipe 61 as long as it is downstream of the rectification unit 64.

  As described above, the technique disclosed herein is useful for the engine exhaust passage structure.

DESCRIPTION OF SYMBOLS 100 Engine 1 Cylinder head 14 Exhaust valve 42 Cam shaft 42a Cam part 44 Swing arm 46 HLA (support part)
46a Valve stop mechanism 6 Exhaust port 63 Bending part 64 Rectifying part 65 Venturi part 27 Combustion chamber

Claims (3)

An engine exhaust passage structure including a cylinder head formed with an exhaust port for discharging exhaust gas from a combustion chamber,
The exhaust port has a curved portion,
In the exhaust port, on the downstream side of the portion of the curved portion where the curvature is large, a rectifying portion that swells inward of the exhaust port and rectifies the flow of the exhaust gas is formed,
An exhaust passage structure for an engine, wherein a venturi portion having a reduced flow path area is formed in the exhaust port downstream of the rectifying portion. The engine exhaust passage structure according to claim 1,
Two exhaust ports are provided for each combustion chamber,
The two exhaust ports merge into one on the downstream side,
An exhaust passage structure for an engine, wherein the venturi portion is formed in a portion of the exhaust ports that merges into one. The engine exhaust passage structure according to claim 1 or 2,
The cylinder head is provided with a support portion that supports a swing arm that is driven by a cam portion of a camshaft to open and close an exhaust valve,
The support portion has a hydraulic valve stop mechanism that stops the opening / closing operation of the exhaust valve, and corresponds to a portion of the cylinder head that bulges inward of the exhaust port due to the formation of the venturi portion. An exhaust passage structure for an engine characterized by being arranged.

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