JP2013155690A - Cylinder head of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure a function of an exhaust emission control device by controlling temperature drop of exhaust emission in an internal combustion engine having a catalytic type exhaust emission control device in an exhaust passage.SOLUTION: An assembly exhaust port part 9 communicated with a plurality of individual exhaust ports 7 is formed inside a cylinder head 1. Exhaust gas is emitted from one assembly exhaust port part 9 to an exhaust passage 10. Upper and lower projecting bars 21 are formed on the assembly exhaust port part 9, and an outer end of the projecting bar 21 forms an expansion part 22 having an increased cross sectional area of the passage. When the exhaust gas flow velocity is dropped by the expansion part 22, abrupt collision of the exhaust gas against an upper inner surface 10c' of the exhaust passage 10 is controlled, and the temperature drop of the exhaust gas can be controlled thereby. As a result, the function of an exhaust emission control device can be ensured.

Description

  The present invention relates to a cylinder head of an internal combustion engine.

  An intake port and an exhaust port are opened in the cylinder head, and exhaust gas is discharged to the exhaust passage through the exhaust port. In the case of a multi-cylinder internal combustion engine, generally, exhaust ports corresponding to the respective cylinders are opened on the side surfaces of the cylinder head, and each exhaust port is connected to one exhaust passage by connecting an exhaust manifold to the cylinder head. However, as in Patent Document 1 related to the application of the present applicant, for example, a collective exhaust port portion in which each exhaust port communicates with the cylinder head is formed, and one exhaust is provided at the outlet of the collective exhaust port portion. It has also been proposed to connect passages.

JP 2011-157827 A

  In general, a catalyst type exhaust gas purification device is interposed in the exhaust passage. However, the catalyst has a property that the function is not exhibited efficiently unless the exhaust gas is at a high temperature of a certain level or more. Therefore, it is preferable that the exhaust gas discharged from the combustion chamber reaches the exhaust gas purification device in a high temperature state without taking heat as much as possible.

  The present invention has been made on the basis of such knowledge, and an object of the present invention is to provide a cylinder head that can suppress the temperature drop of exhaust gas passing through the exhaust passage as much as possible.

  The inventor of the present application has observed the behavior of the exhaust gas in the exhaust port and the exhaust passage, studied to reduce the rate of heat exchange from the exhaust gas to the exhaust passage, and completed the present invention. That is, the present invention relates to a cylinder head having an exhaust port to which an exhaust passage having a catalytic exhaust gas purification device interposed is connected in the middle, wherein an end on the outlet side of the exhaust port is defined as an end on the outlet side. It is characterized by forming an enlarged portion having an opening area larger than that of the inside.

  Now, the starting end of the exhaust passage connected to the exhaust port is bent or constricted, so that the exhaust gas discharged from the exhaust port tends to collide with the wall surface of the starting end of the exhaust passage. ing. Conventionally, the exhaust gas often collides strongly with the start end of the exhaust passage, so that it can be said that a large amount of heat of the exhaust gas has been taken away by the exhaust passage.

  On the other hand, in the present invention, by providing the enlarged portion at the outlet end portion of the exhaust port, the exhaust gas discharged from the exhaust port has a lower flow velocity, so the exhaust gas is strongly against the inner surface of the start end portion of the exhaust passage. The collision is prevented or remarkably suppressed, and as a result, the exhaust gas can be guided to the catalytic exhaust gas purification device in a state in which the temperature decrease is suppressed, thereby contributing to ensuring the function of the exhaust gas purification device. Moreover, since the temperature rise of the exhaust passage can be suppressed, it can contribute to the improvement of the durability of the exhaust passage.

  The cylinder head is generally a cast product made of a metal such as aluminum. Therefore, in order to secure adhesion to the exhaust passage, the surface where the exhaust port is opened is cut by milling. In many cases, it is a flat surface. For example, if the exhaust port has a simple taper shape, the width of the opening changes as the cutting depth changes. There may be a step between the starting end face of the passage. If a step is generated between the opening end face of the exhaust port and the start end face of the exhaust passage, there is a possibility that the flow of the exhaust gas is hindered or the stepped portion becomes abnormally high in temperature.

  On the other hand, in the present invention, since the inner peripheral surface of the enlarged portion is formed in a straight shape perpendicular to the opening end surface, the width of the opening can be kept constant regardless of the cutting amount of the cylinder head. By preventing a step between the opening end face of the port and the start end face of the exhaust passage, a smooth flow of the exhaust gas can be secured and an abnormally high temperature can be prevented.

  The present invention can be applied to a cylinder head to which an external exhaust manifold is connected. However, it is more preferable that the invention is applied to a cylinder head in which a collective exhaust port portion is integrally provided as in Patent Document 1. In other words, because the cylinder head is often hotter than the exhaust passage due to the heat of the combustion gas, the rate at which the exhaust gas touches the exhaust port of the cylinder head and the temperature decreases is lower than that of the external manifold type. When the present invention is applied, the exhaust gas maintained at as high a temperature as possible can be guided to the exhaust passage in a state in which the temperature drop is suppressed and reach the exhaust gas purification device. The function can be secured more accurately.

It is a plane sectional view of the cylinder head concerning an embodiment. It is the II-II front view of FIG. (A) is a sectional view taken along the line IIIA-IIIA in FIG. 2, and (B) to (D) are diagrams showing comparative examples. FIG. 4 is a sectional view taken along line IV-IV in FIG. 1. FIG. 5 is a cross-sectional view taken along the line V-V in FIG. 1.

  Next, an embodiment of the present invention will be described with reference to the drawings. The internal combustion engine of the present embodiment has three cylinders. Therefore, as shown in FIG. 1, three combustion chambers 2 are formed in a state where the cylinder head 1 is arranged in series on the lower surface of the cylinder head 1, and the cylinder block S1 includes Has three cylinder bores S2 arranged in series. A piston P is slidably fitted in the cylinder bore S2.

  In each combustion chamber 2, two first to third intake ports 3, 4, 5 are opened, and two first to third individual exhaust ports 6, 7, 8 are provided. It is open. The individual exhaust ports 6, 7, 8 are gathered in a collective exhaust port portion 9, and an exhaust passage (exhaust pipe) 10 is connected to the collective exhaust port portion 9. A catalytic exhaust gas purification device (not shown) is inserted in the middle of the exhaust passage 10.

  Needless to say, the intake ports 3, 4, 5 and the individual exhaust ports 6, 7, 8 are arranged on both sides of the cylinder row center line 11 extending in the direction in which the combustion chambers 2 are arranged. The groups 3, 4, and 5 and the groups of the individual exhaust ports 6, 7, and 8 are arranged along the cylinder row center line 11. The end 12 of the intake ports 3, 4, 5 is opened / closed by an intake valve 13, and the start ends 14 of the individual exhaust ports 6, 7, 8 are opened / closed by an exhaust valve 15. A spark plug 16 is attached to a portion of the cylinder head 1 located at the center of each combustion chamber 2.

  As shown in FIG. 1, the second individual exhaust port 7 located in the center among the individual exhaust ports 6, 7, 8 is in a collective exhaust port portion 9 in a posture close to a straight line in a plan view as viewed from the axial direction of the cylinder bore. On the other hand, the first and third individual exhaust ports 6 and 8 are connected to the collective exhaust port portion 9 in a curved posture in plan view. As shown in FIG. 2, the collective exhaust port portion 9 has an elongated shape in the direction in which the individual exhaust ports 6, 7, 8 are arranged. The opening end surface 18 of the collective exhaust port portion 9 is a flat surface having a certain width, and a boss portion 19 for fixing the exhaust passage 10 is provided outside the opening end surface 18. A tapped hole is formed. The opening end surface 18 of the collective exhaust port portion 9 and the end surface of the boss portion 19 are flush with each other.

  As shown by a one-dot chain line in FIG. 2, an enlarged portion 10a having the same inner diameter as that of the terminal end 9a of the collective exhaust port portion 9 is formed at the start end portion of the exhaust passage 10, and the enlarged portion 10a is gradually constricted. It has converged into a substantially circular shape. The enlarged portion 10a forms a flange 10b that overlaps the opening end face 18 of the collective exhaust port portion 9, and a fastening portion 10c that overlaps the boss portion 19 of the cylinder head 1 is integrally projected on the flange 10b. It is fixed to the boss portion 19 with a bolt 20. The exhaust passage 10 extends downward from the cylinder head 1. Therefore, as shown in FIGS. 4 and 5, the start end of the exhaust passage 10 is curved downward.

  Then, by providing the upper and lower surfaces of the collective exhaust port portion 9 with a loose chevron-shaped projecting ridge 21 projecting in the central direction of the collective exhaust port portion 9, an exit-side portion outside the ridge 21 is provided. It is formed with the enlarged portion 22. The protrusion 21 and the enlarged portion 22 extend long along the circumferential direction of the collective exhaust port portion 9. Further, the protrusion 21 is formed in an extension portion of the two second individual exhaust ports 7 and is not formed in a portion between the extension portions of the two second individual exhaust ports 7, but extends in a series. It can also take the form. Moreover, although the protrusion 21 and the enlarged portion 22 are formed on the upper surface and the lower surface of the collective exhaust port portion 9, they are formed on either one of the upper and lower surfaces or in a loop shape extending over the entire circumference. It is also possible to do.

  For example, as can be understood from FIG. 4, in the present embodiment, the individual exhaust ports 6, 7, 8 are directed toward the collective exhaust port portion 9 while slightly increasing the cross-sectional area. After the cross-sectional area is once narrowed at the position 21, the cross-sectional area is drastically increased at the enlarged portion 22. Of course, it is also possible to form each individual exhaust port 6, 7, 8 and the collective exhaust port portion 9 in a substantially straight shape so that the sectional area of only the end portion of the collective exhaust port portion 9 is abruptly enlarged. is there.

  Since the present embodiment is a three-cylinder four-cycle internal combustion engine, in each cylinder, the fuel explodes in a state where the phase is shifted by 240 ° with respect to the rotation angle of the crankshaft. Accordingly, the exhaust gas is not simultaneously discharged from the three individual exhaust ports 6, 7, and 8, but is sequentially discharged at intervals of 240 °.

  For example, taking the second individual exhaust port 7 as an example, the exhaust gas flows into the exhaust passage 10 from the collective exhaust port portion 9 in a state of substantially straight traveling in a plan view. Therefore, if no countermeasure is taken, FIG. As can be understood from the figure, the exhaust gas collides with the inner surface of the enlarged portion 10a in the exhaust passage 10, and therefore the heat of the exhaust gas is taken away by the enlarged portion 10a of the exhaust passage 10 and the temperature drop of the exhaust gas becomes severe. .

  Further, as shown in FIG. 4, the exhaust passage 10 is curved downward so that the exhaust gas flowing out from the second individual exhaust port 7 tends to collide with the upper inner surface 10 c ′ of the start end portion of the exhaust passage 10. For this reason, unless any countermeasure is taken, the temperature of the exhaust gas rapidly decreases even when it collides with the upper inner surface 10c ′ of the start end portion of the exhaust passage 10.

  On the other hand, in the present embodiment, the exhaust gas discharged from the second individual exhaust port 7 is subjected to the action of being spread laterally at the location of the protrusion 21 when passing through the collective exhaust port portion 9, and then expanded. When it moves to the part 22, the flow velocity decreases rapidly.

  That is, the exhaust gas is subjected to a diffusing action that spreads in the enlarged portion 10a of the exhaust passage 10, and the flow velocity is rapidly reduced by shifting to the enlarged portion 10a in that state. It is possible to prevent or remarkably prevent a collision with the inner surface of 10a or a collision of the exhaust gas with the upper inner surface 10c 'of the start end portion of the exhaust passage 10. Therefore, heat exchange from the exhaust gas to the exhaust passage 10 can be remarkably suppressed, and as a result, the exhaust gas can reach a catalytic exhaust gas purification device (not shown) while keeping the exhaust gas as high as possible. .

  Due to the presence of the protrusion 21, the exhaust gas receives a guide action that approaches the central portion of the exhaust passage 10, and this also suppresses the exhaust gas from colliding violently with the upper inner surface 10 c ′ of the exhaust passage 10. ing. That is, the protrusion 21 has a rectifying action for diffusing the exhaust gas in the longitudinal direction of the enlarged portion 10a of the exhaust passage 10 and a rectifying action for collecting the gas at the upper and lower intermediate portions.

  Since the exhaust gas discharged from the first individual exhaust port 6 and the third individual exhaust port 8 also moves to the exhaust passage 10 through the collective exhaust port portion 9, the diffusion action by the protrusion 21 and the flow velocity reduction action by the enlarged portion 22. Therefore, the temperature drop of the exhaust gas discharged from the first individual exhaust port 6 and the third individual exhaust port 8 is also suppressed.

  Now, the cylinder head 1 is a cast product made of a light alloy such as aluminum. If the exhaust passage 10 is fixed as cast, the exhaust gas may leak or the mounting accuracy of the exhaust passage 10 may deteriorate. There is. Thus, the opening end face 18 and the boss part 19 are machined into a highly accurate flat surface by milling, but the inner surface of the collective exhaust port part 9 is tapered as shown in FIG. If so, the distance e from the arbitrarily set reference position to the opening end changes due to the difference in the cutting amount E.

  Then, when the exhaust passage 10 is fixed, the start end of the exhaust passage 10 is located outside the end of the collective exhaust port portion 9 as shown in (C), or the start end of the exhaust passage 10 is gathered as shown in (D). There may be a step between the end of the exhaust port portion 9 and the end of the collective exhaust port portion 9 and the start end of the exhaust passage 10. As a result, the smooth flow of the exhaust gas may be hindered, or the joint portion between the collective exhaust port portion 9 and the exhaust passage 10 may be abnormally heated.

  On the other hand, in the present embodiment, as shown in FIG. 2A, a portion close to the opening end surface 18 in the inner peripheral surface of the enlarged portion 22 is formed as a straight portion 22 a perpendicular to the opening end surface 18. Accordingly, the distance from the axis to the opening edge can be kept constant regardless of the cutting amount E. For this reason, the collective exhaust port portion 9 and the exhaust passage 10 can be connected so that their inner surfaces are the same regardless of the cutting amount E. Thereby, it is possible to prevent the smooth flow of the exhaust gas from being hindered or partial abnormal heating from occurring.

  The present invention can be embodied in various ways other than the above-described embodiment. For example, the application target is not limited to a cylinder head for three cylinders, and can be widely applied to a single-cylinder or multi-cylinder internal combustion engine. The cylinder head is not necessarily provided with a collective exhaust port portion, and can be applied to an exhaust manifold externally attached cylinder head in which an individual exhaust port is opened on the side surface of the cylinder head (in this case, An enlarged portion may be formed at the end of each individual exhaust port.)

  The present invention is actually applicable to a cylinder head of an internal combustion engine such as a gasoline engine or a diesel engine. Therefore, it can be used industrially.

DESCRIPTION OF SYMBOLS 1 Cylinder head 2 Combustion chamber 3, 4, 5 Intake port 6, 7, 8 Individual exhaust port 9 Collective exhaust port part 10 Exhaust passage 10a The expansion part which comprises the start end part of an exhaust passage 13 Exhaust valve 18 Open end surface 19 Boss part 21 Projection 22 Expanded part of the collective exhaust port

Claims (1)

It has an exhaust port to which an exhaust passage through which a catalytic exhaust gas purification device is inserted is connected in the middle, and the end on the outlet side of the exhaust port is opened more than the inside of the end on the outlet side It consists of an enlarged part with an enlarged area,
Cylinder head of internal combustion engine.

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