JP2018035721A - engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve suction charging efficiency, regarding an engine where an exhaust manifold is incorporated into a cylinder head.SOLUTION: This invention relates to an exhaust manifold built-in engine where a plurality of exhaust passages 1 are made confluent into one inside a cylinder head 11. In each of the exhaust passages 1, a bent part 2 is provided, thereby bending flow of exhaust gas, discharged from a cylinder 13, in an engine side surface direction. An expansion part 3 is formed on a downstream side of the exhaust passage 1 with respect to the bent part 2. The shape of the expansion part 3 has such a shape as to expand upward from an inner wall lower part of the exhaust passage 1 toward the inside of the exhaust passage 1.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an engine having a built-in exhaust manifold in which a plurality of exhaust passages are joined together in a cylinder head.

  Conventionally, an engine in which a passage structure corresponding to an exhaust manifold (exhaust manifold) is built in a cylinder head is known. In other words, the engine has a structure in which a plurality of exhaust passages connected to a cylinder (cylinder) of the engine are merged into one flow path inside the cylinder head. By adopting such a structure, the distance between the exhaust purification catalyst interposed in the exhaust system and the engine can be shortened, and the exhaust purification performance can be improved. Further, since the length of the exhaust system itself is shortened, pressure loss due to exhaust can be reduced, and the space saving of the engine is facilitated (see, for example, Patent Document 1).

JP 2004-052546 A

  In the engine as described above, the flow rate of the exhaust gas is reduced by setting the cross-sectional area of the exhaust passage to be large so that the heat transfer from the exhaust gas to the cylinder head does not become excessive. However, since the volume in the exhaust passage increases as the cross-sectional area of the exhaust passage increases, the charging efficiency of the intake air may decrease depending on the operating state of the engine. For example, in an operating state where the engine rotation speed is in the middle / low speed range, intake air is less likely to flow into the cylinder due to a decrease in exhaust pressure or interference with exhaust pulsation. As a result, the desired charging efficiency cannot be obtained, and the output torque of the engine may decrease. On the other hand, if the volume in the exhaust passage is reduced, it is easy to ensure the charging efficiency, but the amount of heat transfer from the exhaust gas to the cylinder head tends to increase.

  One of the purposes of this case was created in view of the above-mentioned problems, and provides an engine with a built-in exhaust manifold that can increase the charging efficiency while suppressing excessive temperature rise of the cylinder head. It is to be. It should be noted that the present invention is not limited to this purpose, and is an operational effect that is derived from each configuration shown in “Mode for Carrying Out the Invention” to be described later. Can be positioned as a purpose.

  (1) The engine of the present case is an engine with a built-in exhaust manifold in which a plurality of exhaust passages are joined together in a cylinder head. The engine is provided with a bent portion that is provided in each of the plurality of exhaust passages and that bends the flow of the exhaust gas discharged upward from the cylinder of the engine in the side direction of the engine. Further, the engine is provided with a bulging portion formed in a shape bulging upward from the bottom surface of the inner wall of the exhaust passage toward the center of the exhaust passage on the downstream side of the bent portion. It is done.

(2) It is preferable that the said bulging part is extended along the extension direction of the said exhaust passage. That is, it is preferable that the bulging portion is a protrusion.
(3) It is preferable that the bulging portion is formed in a branched shape corresponding to a shape obtained by joining the plurality of exhaust passages.
(4) It is preferable to provide a water jacket disposed below the exhaust passage inside the cylinder head. Moreover, it is preferable to provide the 2nd bulge part formed in the shape bulged upwards from the inner wall top surface of the said water jacket toward the outer side of the said water jacket below the said bulge part.

  Filling efficiency can be increased while suppressing excessive temperature rise of the cylinder head.

It is a disassembled perspective view which shows the structure of an engine. It is a perspective view which shows the side surface of a cylinder head. It is a horizontal sectional view showing the internal structure of a cylinder head. It is a longitudinal cross-sectional view (AA sectional drawing of FIG. 3) of an engine and a cylinder head. It is a longitudinal cross-sectional view (BB sectional drawing of FIG. 3) which shows the internal structure of a cylinder head.

  An engine 10 as an embodiment will be described with reference to the drawings. The embodiment described below is merely an example, and there is no intention of excluding various modifications and technical applications that are not explicitly described in the following embodiment. Each configuration of the present embodiment can be implemented with various modifications without departing from the spirit thereof. Further, they can be selected as necessary, or can be appropriately combined.

[1. Constitution]
An engine 10 shown in FIG. 1 is a water-cooled multi-cylinder engine and has a structure in which a cylinder head 11 is fastened and fixed to an upper surface of a cylinder block 12. Hereinafter, the structural features of the engine 10 will be described with reference to a posture in which the upper surface of the cylinder block 12 is horizontal and upward. The cylinder block 12 of the engine 10 is formed with a cylinder 13 (cylinder bore) formed by arranging a plurality of hollow cylinders whose cylinder axes are vertical. Around each cylinder 13 is provided a water jacket 4 (water chamber) through which engine coolant flows.

  The cylinder head 11 is fastened and fixed to the upper surface of the cylinder block 12 via a gasket. An intake valve hole and an exhaust valve hole 6 (see FIG. 4) are provided in a portion corresponding to the top surface of the cylinder 13 in the bottom surface of the cylinder head 11. The exhaust gas generated inside the cylinder 13 is discharged to the exhaust system through the exhaust valve hole 6. Two exhaust valve holes 6 of the present embodiment are provided for each cylinder 13 (see FIG. 3).

  The cylinder head 11 incorporates an exhaust manifold (exhaust manifold) structure in which a plurality of exhaust passages 1 are joined together. As shown in FIG. 3, one exhaust passage 1 is provided for each exhaust valve hole 6, and is integrated into one flow path for each cylinder 13 on the downstream side in the exhaust gas flow direction. Further, on the further downstream side, three flow paths corresponding to the three cylinders 13 are collected into one flow path. As described above, the overall shape of the exhaust passage 1 is merged as the six flow paths proceed to the downstream side, and finally merged into one (in other words, upstream of the exhaust gas flow direction). The shape is a branch shape (a tree diagram shape) in which the number of branches increases toward the upstream side. Such an exhaust passage is built in the cylinder head 11.

  Of the exhaust passage 1, the narrowest passage connected to the exhaust valve hole 6 (the branch pipe portion located on the most upstream side) is referred to as a small passage 21. Further, a passage in which a plurality of small passages 21 are aggregated for each cylinder is called a middle passage 22, and a passage in which a plurality of middle passages 22 are gathered is called a large passage 23. The cross-sectional area of the small passage 21 is set to a size corresponding to the opening area of one exhaust valve hole 6 (for example, approximately the same as the opening area of the exhaust valve hole 6). A pair of small passages 21 connected to the same cylinder 13 merge at a position relatively close to the exhaust valve hole 6 to form an intermediate passage 22. Further on the downstream side, a large passage 23 is provided in which three middle passages 22 are gathered into one. The cross-sectional shape of the small passage 21 is substantially circular. Further, the cross-sectional shapes of the middle passage 22 and the large passage 23 are formed in a long elliptical shape or a track shape in which two semicircles are connected by a rectangle.

  As shown in FIG. 2, an exhaust flange 7 having a flat fastening surface perpendicular to the flow direction of the exhaust gas is formed at the downstream end of the large passage 23 (the portion serving as the exhaust gas discharge port). The The exhaust flange 7 is a portion to which an exhaust pipe (including a pipe for connecting to a turbocharger or a catalyst device) on the downstream side is fastened and fixed. A boss hole for attaching a plurality of fasteners is provided around the exhaust flange 7.

  As shown in FIG. 4, in the middle of the small passage 21 in the exhaust passage 1, there is a bent portion 2 that bends the flow of the exhaust gas exhausted upward from the cylinder 13 of the engine 10 in the lateral direction of the engine 10. Provided. Moreover, the site | part downstream from the bending part 2 is extended in the substantially horizontal direction. The exhaust passage 1 on the downstream side of the bent portion 2 is provided with a bulging portion 3 having a shape bulging upward from the bottom of the inner wall of the exhaust passage 1 toward the center of the exhaust passage 1. The bulging portion 3 of the present embodiment is formed in a small passage 21, an intermediate passage 22, and a large passage 23 on the downstream side of the bent portion 2.

  The bulging portion 3 is a protruding portion provided to reduce the cross-sectional area of the exhaust passage 1 without increasing the flow rate of the exhaust gas flowing through the exhaust passage 1 as much as possible. The flow velocity distribution of the exhaust gas inside the exhaust passage 1 appears to be biased in the cross section of the flow path downstream of the bent portion 2, and the upper portion is faster than the lower portion. In addition, the flow velocity distribution in the width direction of the exhaust passage 1 is higher at both the left and right ends than at the center. That is, the vicinity of the bottom surface of the inner wall of the exhaust passage 1 is a portion of the exhaust passage 1 where the flow velocity of the exhaust gas is the lowest. In this way, by forming the bulging portion 3 at a portion where the flow velocity is the lowest, it becomes easy to suppress an increase in the flow velocity of the exhaust gas while reducing the volume in the exhaust passage 1.

  The bulging portion 3 is preferably formed only in a portion of the exhaust passage 1 where the flow rate of the exhaust gas is relatively low. The reason is that as the bulging portion 3 is enlarged, the flow rate of the exhaust gas increases and the temperature of the cylinder head 11 is easily increased. The protruding length of the bulging portion 3 from the bottom of the inner wall is preferably set, for example, with the upper limit of the length at which the upper end of the bulging portion 3 reaches the central portion of the exhaust passage 1.

  As shown in FIG. 2, the bulging portion 3 of the present embodiment is formed as a ridge extending along the extending direction of the exhaust passage 1. By extending the bulging portion 3 along the flow direction of the exhaust gas, the reduced volume in the exhaust passage 1 is increased, and the intake charging efficiency is improved. As shown in FIG. 3, the overall shape of the bulging portion 3 is formed in a branched shape corresponding to the overall shape of the exhaust passage 1. That is, the bulging portion 3 is formed not only in the small passage 21 downstream of the bent portion 2 but also in the middle passage 22 and the large passage 23. Thereby, not only the reduction volume in the exhaust passage 1 is further increased, but also the exhaust gas rectification effect is increased, and the intake charging efficiency is further improved.

  As shown in FIG. 5, a water jacket 4 through which engine cooling water circulates is provided above and below the exhaust passage 1 inside the cylinder head 11. As shown in FIG. 4, these water jackets 4 can be connected to the water jacket 4 of the cylinder block 12. The water jacket 4 provided below the exhaust passage 1 is provided with a second bulging portion 5 corresponding to the shape of the bulging portion 3.

  The second bulging portion 5 is formed in a shape bulging upward from the top surface of the inner wall of the water jacket 4 toward the outside of the water jacket 4. The thickness of the wall that separates the bulging portion 3 and the second bulging portion 5 is, for example, about several millimeters. As described above, by disposing the second bulging portion 5 directly below the bulging portion 3, the cooling performance of the exhaust gas is improved. That is, by improving the cooling performance, it becomes possible to cancel the influence of the increase in flow velocity accompanying the volume reduction of the exhaust passage 1.

[2. Action, effect]
(1) By providing the bulging portion 3 having a shape bulging from the lower inner wall of the exhaust passage 1, the volume of the portion where the flow rate of the exhaust gas is low can be reduced. Thereby, compared with the case where the bulging part 3 is not provided, a large volume reduction effect can be obtained with a small flow rate increase rate. That is, the capacity in the exhaust pipe can be reduced while suppressing an increase in the flow rate of the exhaust gas. Therefore, it is possible to improve the intake charging efficiency while suppressing the excessive temperature rise of the cylinder head 11.
(2) As shown in FIGS. 3 and 4, by extending the bulging portion 3 along the flow direction of the exhaust gas, the reduced volume in the exhaust passage 1 can be increased. As a result, the volume of the exhaust passage 1 can be reduced while enhancing the effect of suppressing the increase in the flow rate of the exhaust gas, and the intake charging efficiency can be improved.

(3) As shown in FIG. 3, by making the bulging portion 3 into a branched shape, it is possible to reduce the exhaust passage volume while enhancing the effect of suppressing the increase in flow velocity. Further, since the overall shape of the bulging portion 3 is a shape corresponding to the overall shape of the exhaust passage 1, the exhaust gas rectifying effect can be enhanced, and the intake charging efficiency can be further improved.
(4) As shown in FIG. 5, the exhaust gas can be efficiently cooled through the bulging portion 3 by providing the second bulging portion 5 of the water jacket 4 below the bulging portion 3. Moreover, it becomes possible to cancel the influence of the increase in the flow velocity accompanying the volume reduction of the exhaust passage 1, and the excessive temperature rise of the cylinder head 11 can be more reliably suppressed.

[3. Modified example]
In the above-described embodiment, the structure in which the bulging portion 3 is formed in the small passage 21, the middle passage 22 and the large passage 23 on the downstream side of the bent portion 2 of the exhaust passage 1 is illustrated. The layout is not limited to this. For example, the bulging portion 3 may be formed only in the small passage 21 downstream of the bent portion 2 of the exhaust passage 1, or the bulging portion 3 may be formed only in the large passage 23. By disposing the bulging portion 3 at least on the downstream side of the exhaust passage 1 with respect to the bent portion 2, the same effects as those of the above-described embodiment can be obtained.

DESCRIPTION OF SYMBOLS 1 Exhaust passage 2 Bending part 3 Expanding part 4 Water jacket 5 Second expanding part 6 Exhaust valve hole 7 Exhaust flange 10 Engine 11 Cylinder head 12 Cylinder block 13 Cylinder 21 Small path 22 Middle path 23 Large path

Claims (4)

An engine with a built-in exhaust manifold in which a plurality of exhaust passages are joined together in the cylinder head,
A bent portion that is provided in each of the plurality of exhaust passages and bends the flow of exhaust gas discharged upward from the cylinder of the engine toward the side surface of the engine;
A bulging portion formed in a shape bulging upward from the bottom surface of the inner wall of the exhaust passage toward the center of the exhaust passage on the downstream side of the exhaust passage from the bent portion. engine. The engine according to claim 1, wherein the bulging portion extends along an extending direction of the exhaust passage. The engine according to claim 1, wherein the bulging portion is formed in a branched shape corresponding to a shape obtained by joining the plurality of exhaust passages. A water jacket disposed below the exhaust passage inside the cylinder head;
A second bulging portion formed in a shape bulging upward from the top surface of the inner wall of the water jacket toward the outside of the water jacket is provided below the bulging portion. Item 4. The engine according to any one of Items 1 to 3.

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