JP2020084955A - Internal combustion engine - Google Patents

Abstract

To provide an exhaust port capable of enhancing a purification rate of unburned HC in the exhaust port.SOLUTION: An internal combustion engine comprising an exhaust port 12 communicating with a combustion chamber, comprises a deflecting part 51 formed on an inner surface of the exhaust port. The exhaust port comprises an inside communication part 12a that communicates with the inside of the combustion chamber in a radial direction and extends in an exhaust downstream direction, and an outside communication part 12b that communicates with the outside of the combustion chamber in the radial direction and extends in the exhaust downstream direction. The deflecting part is configured to redirect flow of exhaust gas so that the exhaust gas flowing along the outside communication part is directed to the inside communication part, or so that the exhaust gas flowing along the inside communication part is directed to the outside communication portion.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to an internal combustion engine that includes an exhaust port that communicates with a combustion chamber.

Various shapes of exhaust ports of internal combustion engines have been studied from various viewpoints. For example, in the exhaust port described in Patent Document 1, the inner surface of the exhaust port in the vicinity of the seating portion of the exhaust valve is formed in a smooth arc shape for the purpose of reducing exhaust resistance to exhaust gas discharged from the combustion chamber. ing.

Further, in the exhaust port described in Patent Document 2, a plurality of grooves extending in the circumferential direction are formed on the inner peripheral surface of the exhaust port at intervals in the exhaust flow direction, and the interval between each groove and another adjacent groove. Are formed to be smaller than twice the width of each groove. As a result, vortices are generated in each groove, the boundary layer becomes thicker, and this boundary layer functions as a heat insulating layer, so that the heat insulating property of the exhaust port can be improved.

JP-A-9-14047 JP, 2009-236110, A

By the way, the exhaust gas discharged from the combustion chamber contains unburned HC that remains unburned in the combustion chamber. Such unburned HC is purified by a purification device such as a three-way catalyst arranged in the exhaust passage of the internal combustion engine. However, in order to increase the purification rate of such unburned HC, or to be able to sufficiently purify such unburned HC even if the three-way catalyst has a low purification performance, the unburned HC in the exhaust port is not cleaned. It is preferable that the fuel HC can be purified to some extent. However, the exhaust ports having the structures described in Patent Documents 1 and 2 cannot necessarily be said to be able to sufficiently purify unburned HC in the exhaust ports.

In view of the above problems, an object of the present disclosure is to provide an exhaust port that can increase the purification rate of unburned HC in the exhaust port.

The summary of the present disclosure is as follows.

(1) An internal combustion engine having an exhaust port communicating with a combustion chamber, comprising a deflecting portion formed on an inner surface of the exhaust port, the exhaust port communicating with a radially inner side of the combustion chamber and exhausting gas. An inner communicating portion extending in the downstream direction and an outer communicating portion communicating in the radial outside of the combustion chamber and extending in the exhaust downstream direction are provided, and the deflection portion is configured such that exhaust gas flowing along the outer communicating portion is exhausted. An internal combustion engine configured to change a flow direction of exhaust gas so as to be directed toward the inner communication portion or exhaust gas flowing along the inner communication portion toward the outer communication portion.

According to the present disclosure, an exhaust port capable of increasing the purification rate of unburned HC in the exhaust port is provided.

FIG. 1 is a partial cross-sectional view schematically showing an internal combustion engine according to the first embodiment. FIG. 2 is an enlarged cross-sectional view showing the vicinity of the exhaust opening of FIG. 1 in an enlarged manner. FIG. 3 is a cross-sectional view of the exhaust port taken along line III-III in FIG. FIG. 4 is a sectional view of the convex portion taken along line IV-IV in FIG. FIG. 5 is a diagram showing a concentration distribution of unburned HC and a temperature distribution of exhaust gas in the exhaust port when the convex portion is not provided on the inner surface of the exhaust port. FIG. 6 is a partial sectional view similar to FIG. 1, schematically showing an internal combustion engine according to the second embodiment. FIG. 7 is an enlarged cross-sectional view similar to FIG. 2 in which the vicinity of the exhaust opening of FIG. 6 is enlarged and shown. FIG. 8 is a cross-sectional view of the exhaust port taken along line VIII-VIII in FIG. 7.

Hereinafter, embodiments will be described in detail with reference to the drawings. In addition, in the following description, the same components are designated by the same reference numerals.

<First embodiment>
<<Structure of internal combustion engine>>
The configuration of the internal combustion engine 1 according to the first embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a partial cross-sectional view schematically showing an internal combustion engine 1 according to the first embodiment. FIG. 2 is an enlarged cross-sectional view showing the vicinity of the exhaust opening of FIG. 1 in an enlarged manner. As shown in FIG. 1, the internal combustion engine 1 includes a cylinder block 2, a cylinder head 3, a piston 4, and a connecting rod 5.

The cylinder block 2 includes a plurality of cylinders 6 arranged side by side. The cylinder head 3 is arranged so as to abut the cylinder block 2 on the surface where the cylinder 6 is open, and is arranged so as to close one end of the cylinder 6 formed in the cylinder block 2.

The piston 4 is arranged so as to reciprocate in a cylinder 6 formed in the cylinder block 2. The piston 4 is connected to the connecting rod 5 via a piston pin. The connecting rod 5 is connected to a crankshaft (not shown) via a crankpin, and acts so as to convert the reciprocating motion of the piston 4 into the rotational mobility of the crankshaft. Further, the wall surface of the cylinder 6 of the cylinder block 2, the cylinder head 3 and the piston 4 form a combustion chamber 7 in which the air-fuel mixture burns.

As shown in FIG. 1, an intake port 11 and an exhaust port 12 are formed in the cylinder head 3. The intake port 11 faces the combustion chamber 7 and communicates with the combustion chamber 7 via an intake opening 13 formed in the cylinder head 3. Similarly, the exhaust port 12 faces the combustion chamber 7 and communicates with the combustion chamber 7 through an exhaust opening 14 formed in the cylinder head 3.

In this embodiment, two intake openings 13 and two exhaust openings 14 are provided for each combustion chamber 7. The two intake openings 13 are arranged side by side in the same direction as the direction in which the plurality of cylinders 6 are arranged side by side (hereinafter also referred to as “cylinder alignment direction”). Similarly, the two exhaust openings 14 are arranged side by side in the same direction as the cylinder alignment direction. Two intake openings 13 are arranged on one side and two exhaust openings 14 are arranged on the other side with respect to a central plane extending through the central axis of each cylinder 6 in the cylinder alignment direction.

In addition, an intake seat portion (not shown) is provided around the edge of each intake opening 13 over the entire circumference thereof so that an intake valve 21 described later abuts when the valve is closed. Similarly, around the edge of the exhaust opening 14, an exhaust seat portion 15 with which an exhaust valve 31 described later abuts when the valve is closed is provided over the entire circumference. As shown in FIG. 2, the exhaust seat portion 15 may be formed as a valve seat separate from the cylinder head 3, or may be a seat formed directly on the cylinder head 3.

Further, the cylinder head 3 is provided with an intake valve 21 that opens and closes the intake opening 13, an exhaust valve 31 that opens and closes the exhaust opening 14, and an ignition plug 41 that ignites the air-fuel mixture in the combustion chamber 7. Further, the cylinder head 3 is provided with a fuel injection valve (not shown) for injecting fuel into the intake port 11.

The intake valve 21 includes a valve stem 22 and a valve body 23 fixed to one end of the valve stem 22. The intake valve 21 is arranged in the cylinder head 3 so as to be slidable in the direction in which the valve stem 22 extends, that is, in the axial direction of the intake valve 21. The intake valve 21 is lifted in the axial direction by an intake valve operating mechanism (not shown). The intake valve operating mechanism may be a variable valve operating mechanism capable of changing at least one of the working angle, the phase angle and the maximum lift amount of the intake valve 21, or may be a valve operating mechanism incapable of changing these. Good.

Similarly, the exhaust valve 31 includes a valve stem 32 and a valve body 33 fixed to one end of the valve stem 32. The exhaust valve 31 is arranged in the cylinder head 3 so as to be slidable in the direction in which the valve stem 32 extends, that is, in the axial direction of the exhaust valve 31. The exhaust valve 31 is lifted in the axial direction by an exhaust valve mechanism (not shown). The exhaust valve operating mechanism may be a variable valve operating mechanism capable of changing at least one of the operating angle, the phase angle and the maximum lift amount of the exhaust valve 31, or may be a valve operating mechanism incapable of changing these. Good.

The spark plug 41 is attached to the cylinder head 3 so as to be located on the upper surface of the combustion chamber 7 in the approximate center of the combustion chamber 7.

In this embodiment, a fuel injection valve for injecting fuel is provided in the intake port 11, but instead of this fuel injection valve or in addition to this fuel injection valve, fuel is directly injected into the combustion chamber 7. A fuel injection valve that operates may be provided in the cylinder head 3. In this case, the fuel injection valve is arranged such that its injection hole is located close to the spark plug 41 and between the two intake openings 13.

Further, in the present embodiment, the spark plug 41 is provided so as to be exposed to the combustion chamber 7, but the spark plug 41 may not be provided. In this case, fuel injection from the fuel injection valve that directly injects fuel into the combustion chamber 7 is controlled so that the air-fuel mixture self-ignites in the combustion chamber 7.

In the present specification, in the axial direction of the cylinder 6, the cylinder head 3 side is relatively referred to as the upper side, and the cylinder block 2 side is relatively referred to as the lower side. However, the internal combustion engine 1 does not necessarily have to be arranged so that the axis of the cylinder 6 extends in the vertical direction, and may be arranged in various directions. Therefore, the internal combustion engine 1 may be arranged, for example, such that the axis of the cylinder 6 extends in the horizontal direction.

<<Exhaust port configuration>>
Next, the configuration of the exhaust port 12 will be described with reference to FIGS. 3 and 4. 3 is a cross-sectional view of the exhaust port 12 taken along line III-III of FIG. 2, and FIG. 4 is a cross-sectional view of the convex portion 51 taken along line IV-IV of FIG.

In this specification, a portion of the wall surface defining the exhaust port 12 that communicates with the inner side of the combustion chamber 7 in the radial direction and extends in the exhaust downstream direction is referred to as an inner communicating portion 12a. Further, in this specification, a portion of the wall surface defining the exhaust port 12 that communicates with the combustion chamber 7 in the radial direction and extends in the exhaust downstream direction is referred to as an outer communication portion 12b. Therefore, the inner communication portion 12 a defines the upper surface of the exhaust port 12, and the outer communication portion 12 b defines the lower surface of the exhaust port 12.

In the present embodiment, as shown in FIG. 3, the convex portion 51 is formed on the outer communication portion 12b of the exhaust port 12. As shown in FIG. 3, the convex portion 51 is arranged immediately downstream of the exhaust sheet portion 15 in the exhaust flow direction. That is, the convex portion 51 is arranged immediately downstream of the portion of the cylinder head 3 with which the exhaust valve 31 contacts in the exhaust flow direction. The convex portion 51 may be arranged so that the upstream end thereof is in contact with the downstream end of the exhaust sheet portion 15.

Further, as shown in FIG. 4, the convex portion 51 has an upstream surface 51a extending from the outer communicating portion 12b on the upstream side of the convex portion 51 toward the downstream side at an angle α with respect to the outer communicating portion 12b. .. In addition, the convex portion 51 has a downstream surface 51b extending from the outer communicating portion 12b on the downstream side of the convex portion 51 toward the upstream side at an angle β with respect to the outer communicating portion 12b. In addition, the upstream surface 51a and the downstream surface 51b are configured to have an angle γ with respect to each other.

The angle γ is, for example, 80° to 120°, preferably 85° to 110°, more preferably 90° to 100°. In this embodiment, the angle γ is 90°. Further, in the present embodiment, the angle α is smaller than the angle β. The angle α is, for example, 20° to 45°, preferably 25° to 40°, more preferably 30° to 35°. In addition, the angle β is, for example, 45° to 70°, preferably 50° to 65°, more preferably 55° to 60°.

Further, one convex portion 51 communicates with the outside of the exhaust port 12 over, for example, 5° to 70° in the circumferential direction, preferably 10° to 55°, and more preferably 15° to 40°. It is provided on the portion 12b. In the example shown in FIG. 3, the convex portion 51 is provided on the outer communication portion 12b of the exhaust port 12 over approximately 50°. In particular, in the example shown in FIG. 3, the convex portion 51 is formed so that its apex extends linearly in a direction perpendicular to the vertical direction. However, the convex portion 51 may be formed so that its apex extends in an arc shape.

In addition, the height of the convex portion 51 from the surface of the outer communication portion 12b to the apex thereof is 0.5 to 10% of the diameter of the exhaust port 12 at the highest point, preferably 1 to 7. %, more preferably 1.5 to 5%. In the example shown in FIG. 3, the height to the apex of the convex portion 51 is about 4% at the highest point.

In the above embodiment, only one convex portion 51 is provided on the surface of the outer communication portion 12b. However, the convex portion 51 may be provided on the surface of the inner communication portion 12a. Further, the plurality of convex portions 51 may be provided on the inner surface of the exhaust port 12. In this case, one convex portion 51 is provided on each of the outer communication portion 12b and the inner communication portion 12a. In this case, the convex portion 51 on the inner communication portion 12a and the convex portion 51 on the outer communication portion 12b may be provided on the same cross section with respect to a cross section perpendicular to the exhaust flow direction. May be offset in the downstream direction and provided on different cross sections,

≪Action and effect≫
Next, with reference to FIG. 5, the operation and effect produced by the internal combustion engine 1 having the above-described configuration will be described.

FIG. 5A is a diagram showing the concentration distribution of unburned HC in the exhaust port 12 when the convex portion 51 is not provided on the inner surface of the exhaust port 12. In particular, the region represented by a dark dot in FIG. 5A represents a region where the concentration of unburned HC is high. Further, FIG. 5B is a diagram showing the temperature distribution of the exhaust gas in the exhaust port 12 when the convex portion 51 is not provided on the inner surface of the exhaust port 12. In particular, a region shown by a dark dot in FIG. 5B represents a region where the temperature of exhaust gas is high.

As can be seen from FIG. 5(A), in the exhaust port 12, the concentration of unburned HC in the exhaust gas flowing through the outer communicating portion 12b is higher than the concentration of unburned HC in the exhaust gas flowing through the inner communicating portion 12a. It becomes higher than the fuel HC concentration. On the other hand, in the exhaust port 12, the temperature of the exhaust gas flowing through the inner communication portion 12a side is higher than the temperature of the exhaust gas flowing through the outer communication portion 12b side. It is considered that the distribution of the unburned HC concentration and the temperature of the exhaust gas in the exhaust port 12 is as follows.

That is, the air-fuel mixture in the outer peripheral portion of the combustion chamber 7 is cooled by the wall surface of the cylinder 6, and therefore has a lower temperature than the air-fuel mixture in the central portion of the combustion chamber 7. As a result, even if combustion of the air-fuel mixture occurs in the combustion chamber 7, the flame does not sufficiently reach the vicinity of the wall surface of the cylinder 6. As a result, a part of the HC in the air-fuel mixture near the wall surface of the cylinder 6 remains without being burned. In addition, since the air-fuel mixture is cooled by the wall surface of the cylinder 6 in the vicinity of the wall surface of the cylinder 6 and the air-fuel mixture does not burn sufficiently, the temperature of the combustion gas tends to be low near the wall surface of the cylinder 6.

Further, exhaust gas mainly flows out from the central portion of the combustion chamber 7 to the inner communication portion 12a side of the exhaust port 12. As a result, high-temperature exhaust gas having a low HC concentration flows on the inner communication portion 12a side. On the other hand, the exhaust gas mainly flows from the outer peripheral portion of the combustion chamber 7 to the outer communication portion 12b side of the exhaust port 12. As a result, low temperature exhaust gas having a high HC concentration flows to the outer communication portion 12b side.

On the other hand, in the internal combustion engine 1 according to the above embodiment, the convex portion 51 is provided on the outer communication portion 12b of the exhaust port 12. Therefore, the exhaust gas flowing into the exhaust port 12 along the outer communication portion 12b flows on the upstream surface 51a of the convex portion 51. Here, since the apex of the convex portion 51 has a relatively steep angle of 120° or less, the exhaust gas flowing on the upstream surface 51a is separated at the apex of the convex portion 51. As a result, the exhaust gas on the outer communication portion 12b is disturbed on the downstream side of the convex portion 51, and a part of the exhaust gas flowing along the outer communication portion 12b flows toward the inner communication portion 12a. , The direction of the flow is changed. As a result, the exhaust gas flowing along the outer communicating portion 12b and the exhaust gas flowing along the inner communicating portion 12a are mixed. When the exhaust gas is mixed in this way, the temperature of the exhaust gas flowing along the inner communication portion 12a is high as described above, so that the exhaust gas flowing from the outer communication portion 12b toward the inner communication portion 12a. Unburned HC inside is oxidized and purified. Therefore, according to the internal combustion engine 1 according to the above embodiment, the purification rate of unburned HC in the exhaust port 12 can be increased.

In addition, although the convex portion 51 is provided on the outer communicating portion 12b in the above embodiment, the convex portion 51 may be provided on the inner communicating portion 12a as described above. In this case, the direction of the flow is changed so that part of the exhaust gas flowing along the inner communication portion 12a is separated at the apex of the convex portion 51 and flows toward the outer communication portion 12b. To be done. As a result, the exhaust gas flowing along the inner communication portion 12a and the exhaust gas flowing along the outer communication portion 12b are mixed, and unburned HC in the exhaust gas is oxidized and removed. Therefore, even if the convex portion 51 is provided on the inner communication portion 12a, the purification rate of unburned HC in the exhaust port 12 can be increased.

<Second embodiment>
Next, an internal combustion engine 1 according to the second embodiment will be described with reference to FIGS. 6 to 8. In particular, in the following, the description will focus on the parts that are different from the internal combustion engine according to the first embodiment.

<<Exhaust port configuration>>
FIG. 6 is a partial sectional view similar to FIG. 1, schematically showing the internal combustion engine 1 according to the second embodiment. FIG. 7 is an enlarged cross-sectional view similar to FIG. 2 in which the vicinity of the exhaust opening of FIG. 6 is enlarged and shown. 8 is a sectional view of the exhaust port 12 taken along the line VIII-VIII in FIG. 7.

In the present embodiment, as shown in FIGS. 6 to 8, a plurality of recesses 61 are formed on the inner surface of the exhaust port 12. As shown in FIGS. 6 and 7, the recess 61 is arranged immediately downstream of the exhaust seat portion 15 in the exhaust flow direction. That is, the recess 61 is arranged immediately downstream of the portion of the cylinder head 3 with which the exhaust valve 31 comes into contact in the exhaust flow direction. The recess 61 may be arranged so that its upstream end contacts the downstream end of the exhaust sheet portion 15.

Further, as can be seen from FIGS. 7 and 8, in the present embodiment, a plurality of recesses 61 are arranged at equal intervals in the circumferential direction of the exhaust port 12. That is, the plurality of recesses 61 are arranged at equal intervals on the inner surface of the exhaust port 12 on one cross section perpendicular to the exhaust flow direction. As shown in FIG. 8, in this embodiment, twelve concave portions are arranged at equal intervals in the circumferential direction.

In the present embodiment, each recess 61 is formed in a spherical shape. In addition, each recess 61 is formed so that its opening diameter X is 2 to 15%, preferably 5 to 10% of the diameter of the valve body 23 of the exhaust valve 31. Further, each recess 61 is formed such that the depth thereof is 0.5 to 8%, preferably 2 to 5% of the diameter of the valve body 23 of the exhaust valve 31.

In the present embodiment, the recesses 61 are provided at equal intervals in the circumferential direction. However, the recesses 61 do not necessarily have to be provided at equal intervals in the circumferential direction. For example, the recess 61 may be provided in only one of the inner communication portion 12a and the outer communication portion 12b. Alternatively, the recess 61 is provided in the vicinity of the center of the inner communication portion 12a and the outer communication portion 12b, and is located on the side (that is, the direction perpendicular to the exhaust flow direction and the vertical direction (cylinder alignment direction) side). It may not be provided on the side surface of the exhaust port 12.

However, even in this case, the plurality of recesses 61 are arranged on one cross section perpendicular to the exhaust flow direction. Therefore, the plurality of recesses 61 are arranged so as not to be offset (not offset) between the upstream side and the downstream side in the exhaust flow direction.

≪Action and effect≫
In the internal combustion engine 1 according to the present embodiment, the recess 61 is provided on the inner surface of the exhaust port 12. Therefore, the exhaust gas flowing into the exhaust port 12 along the wall surface of the exhaust port 12 flows into the recess 61, and vortices are generated in the recess 61. As a result, a turbulent boundary layer is generated on the wall surface of the exhaust port 12 on the downstream side of the recess 61.

The thickness of the turbulent boundary layer gradually increases from the recess 61 toward the downstream side, and eventually the turbulent boundary layer on the inner communicating portion 12a of the exhaust port 12 and the turbulent boundary layer on the outer communicating portion 12b intersect. Become. Due to such turbulence of the air flow, the direction of the flow is changed so that a part of the exhaust gas flowing along the outer communication portion 12b flows toward the inner communication portion 12a. Similarly, the direction of the flow of the exhaust gas flowing along the inner communication portion 12a is changed so as to flow toward the outer communication portion 12b. As a result, the exhaust gas having a high temperature flowing along the inner communication portion 12a and the exhaust gas having a large amount of unburned HC flowing along the outer communication portion 12b are mixed, and the unburned HC in the exhaust gas is oxidized. , Purified. Therefore, according to the internal combustion engine 1 according to the second embodiment, the purification rate of unburned HC in the exhaust port 12 can be increased.

Further, unlike the present embodiment, when the plurality of recesses 61 are arranged side by side in the exhaust gas flow direction, the turbulent flow boundary layer is maintained relatively thin from the recess on the upstream side to the recess on the downstream side. As a result, the exhaust gas flowing along the inner communication portion 12a and the exhaust gas flowing along the outer communication portion 12b are less likely to mix with each other. On the other hand, in the present embodiment, the plurality of recesses 61 are arranged on one cross section perpendicular to the exhaust flow direction. Therefore, the turbulent boundary layer is prevented from being kept relatively thin, and thus the exhaust gas flowing along the inner communication portion 12a and the exhaust gas flowing along the outer communication portion 12b are easily mixed with each other. .. As a result, the purification rate of unburned HC in the exhaust port 12 can be increased.

<Other>
Although the preferred embodiments according to the present disclosure have been described above, the present disclosure is not limited to these embodiments, and various modifications and changes can be made within the scope of the claims.

In the above embodiment, the convex portion 51 and the concave portion 61 are provided on the inner surface of the exhaust port 12. However, a deflecting portion different from the convex portion 51 and the concave portion 61 may be provided on the inner surface of the exhaust port 12. However, in this case, in the deflecting portion, the exhaust gas flowing along the outer communicating portion 12b is directed toward the inner communicating portion 12a, or the exhaust gas flowing along the inner communicating portion 12a is outside the communicating portion 12b. It is necessary to be configured to redirect the flow of exhaust gas towards the. As an example of such a deflecting unit, for example, a plate-shaped member extending so as to traverse the inside of the exhaust port 12 may be considered.

1 Internal Combustion Engine 2 Cylinder Block 3 Cylinder Head 4 Piston 11 Intake Port 12 Exhaust Port 13 Intake Opening 14 Exhaust Opening 21 Intake Valve 31 Exhaust Valve 51 Convex 61 Concave

Claims (1)

An internal combustion engine having an exhaust port communicating with a combustion chamber,
A deflection portion formed on the inner surface of the exhaust port,
The exhaust port includes an inner communication portion that communicates with a radially inner side of the combustion chamber and extends in an exhaust downstream direction, and an outer communication portion that communicates with a radially outer side of the combustion chamber and extends in an exhaust downstream direction,
The deflecting portion is such that the exhaust gas flowing along the outer communicating portion is directed toward the inner communicating portion, or the exhaust gas flowing along the inner communicating portion is directed toward the outer communicating portion, An internal combustion engine configured to redirect the flow of exhaust gas.

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