JP6040641B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine.

In a spark ignition type reciprocating engine, a technique for improving flame propagation in a combustion chamber has been proposed (see Patent Document 1).
In this technique, the combustion chamber is defined when the piston is at the top dead center among the volume V1 of the combustion chamber when the piston is at the top dead center and the virtual sphere of radius r centering on the ignition point of the spark plug. The combustion chamber is formed so that the volume V2 of the non-interference portion that does not interfere with the combustion chamber wall that is in contact and the area S of the interference surface where the virtual sphere interferes with the combustion chamber wall when the piston is at top dead center And the recessed part is provided in the top surface of the piston.
And by satisfy | filling said conditions and forming a recessed part, the flame propagation property is accelerated | stimulated by making the degree of interference with the flame accompanying a flame propagation and a combustion chamber wall gentle.

JP 2009-162153 A

However, in the above-described conventional technology, the degree of interference between the flame and the combustion chamber wall is moderated, and no particular consideration is given to promoting combustion of the air-fuel mixture, thereby improving fuel consumption. There is room for improvement above.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an internal combustion engine that is advantageous in improving fuel efficiency by promoting combustion of an air-fuel mixture.

In order to achieve the above object, the invention according to claim 1 is directed to a combustion chamber formed by a cylinder formed in a cylinder block, a lower surface of the cylinder head, and a piston top surface, and an intake port provided in the cylinder head. An internal combustion engine comprising an exhaust port and a spark plug, wherein the top surface of the piston surrounds the ignition point of the spark plug in a state where the piston is positioned near top dead center. An intake side for creating a squish airflow, which is formed in a concave portion formed in the center and a portion including the outer peripheral portion of the top surface closer to the intake port than the concave portion and extends on a plane perpendicular to the axis of the piston and a squish portion, said cylinder head, said in cooperation with the formed where the cylinder head that faces the intake side squish portion the intake side squish portion liked A lower surface of a cylinder head that generates a gas flow, and the top surface of the piston includes, on the intake port side and the exhaust gas, an edge portion that forms a boundary between the recess and the top surface located around the recess. A first flat portion is formed along an edge portion extending along a direction connecting the port side, and an edge portion that forms a boundary between the concave portion and the top surface portion located around the concave portion When the portion located on the intake port side is an intake side edge and the portion located on the exhaust port side is an exhaust side edge, the intake side edge is formed lower than the exhaust side edge. It is characterized by being.
According to a second aspect of the present invention, the cylinder head includes an intake valve disposed in the intake port and an exhaust valve disposed in the exhaust port, and a top surface of the piston corresponds to the intake valve. An intake valve recess provided in correspondence with the exhaust valve and an exhaust valve recess provided corresponding to the exhaust valve, and the first flat portion is provided between the intake valve recess and the exhaust valve recess. Features.
According to a third aspect of the present invention, a third flat portion is formed along the outer periphery of the piston top surface, and the first flat portion and the third flat portion are connected by a curved surface portion. It is characterized by that.
Fourth aspect of the present invention, the portion of the top surface located at the exhaust port side of the exhaust side edges, two of said exhaust valve recesses to avoid interference with the exhaust valve is formed, the two exhaust In the axial direction of the piston, a protrusion that protrudes further toward the cylinder head than the exhaust valve recess is formed between the valve recesses.
According to a fifth aspect of the present invention, when the top surface of the piston is viewed in plan, the edge of the concave portion is closer to the intake port side than the dimension in the direction connecting the intake port side and the exhaust port side. It is formed in a long shape having a large dimension in a direction orthogonal to a straight line connecting the exhaust port side.

According to the first to third aspects of the present invention, in the compression stroke, the air-fuel mixture between the intake-side squish part and the lower surface of the cylinder head easily flows into the recess through the intake-side edge by the squish airflow. This is advantageous for reliably collecting the air around the ignition point. Further, since the exhaust side edge is higher than the intake side edge, the air-fuel mixture collected in the recess is unlikely to flow out of the exhaust side edge, which is advantageous in maintaining the air-fuel mixture around the ignition point. Therefore, the air-fuel mixture is easily ignited at the ignition point, which is advantageous in promoting combustion of the air-fuel mixture and improving fuel consumption.
According to the fourth aspect of the present invention, the protrusion can suppress the outflow of the air-fuel mixture from the recess to the exhaust port side, and the protrusion can reduce the volume of the combustion chamber on the exhaust port side. More air-fuel mixture in the combustion chamber can flow into the recess, which is more advantageous for collecting the air-fuel mixture around the ignition point.
According to the fifth aspect of the present invention, since the intake side edge portion, which is the portion where the air-fuel mixture flows into the recess, can be largely secured, the flow of the air-fuel mixture flowing into the recess through the intake side edge portion is promoted. This is more advantageous for reliably collecting the air-fuel mixture around the ignition point.

1 is a cross-sectional view showing a structure in the vicinity of a combustion chamber 20 of an engine 10 according to the present embodiment. It is a principal part expanded sectional view of FIG. It is the perspective view which looked at piston 18 of engine 10 concerning this embodiment from one direction. It is the perspective view which looked at piston 18 of engine 10 concerning this embodiment from other directions. FIG. 4 is a view taken in the direction of arrow X1 in FIG. 3. FIG. 4 is a view taken in the direction of arrow X2 in FIG. 3. FIG. 5 is a view taken in the direction of arrow X3 in FIG. 4. FIG. 5 is a view taken along arrow X4 in FIG. 4. It is a top view of piston 18 of engine 10 concerning this embodiment. FIG. 10 is a sectional view taken along line AA in FIG. 9. FIG. 10 is a sectional view taken along line BB in FIG. 9. It is CC sectional view taken on the line of FIG. FIG. 10 is a sectional view taken along the line DD in FIG. 9. It is the EE sectional view taken on the line of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, an internal combustion engine (hereinafter referred to as an engine) 10 includes a cylinder block 14 in which a cylinder 12 is formed, a cylinder head 16 provided on an upper portion of the cylinder block 14, and a piston disposed in the cylinder 12. 18.
The combustion chamber 20 is constituted by the inner peripheral surface 12A of the cylinder 12, the lower surface 16A of the cylinder head 16, and the top surface 18A of the piston 18 in the vicinity of the top dead center of the piston 18.

  The cylinder head 16 is provided with an intake port 22, an intake valve 24, an exhaust port 26, an exhaust valve 28, and a spark plug PL.

Two intake ports 22 are provided and connected to an intake passage (not shown). The intake air introduced into the intake passage is mixed with fuel injected from a fuel injection valve (not shown) provided in the intake passage to become an air-fuel mixture, and is supplied to the intake port 22. Therefore, in the present embodiment, engine 10 is an intake pipe injection type engine.
Two intake valves 24 are provided and arranged in each intake port 22. When the intake valve 24 is opened, the intake port 22 and the combustion chamber 20 communicate with each other, and the air-fuel mixture flows into the combustion chamber 20 from the intake port 22.

Two exhaust ports 26 are provided and connected to an exhaust passage (not shown).
Two exhaust valves 28 are provided and disposed in each exhaust port 26. When the exhaust valve 28 is opened, the exhaust port 26 and the combustion chamber 20 communicate with each other, and the exhaust from the combustion chamber 20 is discharged from the exhaust port 26 to the exhaust passage.

  The spark plug PL is provided in the cylinder head 16 so that the ignition point P1 is located substantially at the center of the combustion chamber 20.

As shown in FIGS. 1, 3, and 4, the piston 18 includes a piston head portion 1802, a pair of skirt portions 1804, and a pair of sidewall portions 1806.
The piston head portion 1802 has a cylindrical outer peripheral surface 18B that faces the inner peripheral surface 12A of the cylinder 12, and a top surface 18A that connects the entire upper end of the outer peripheral surface 18B.
As shown in FIGS. 1 and 5, the outer peripheral surface 18 </ b> B is formed with a plurality of ring grooves 1810 at intervals in the central axis Op direction of the piston 18. In the present embodiment, three ring grooves 1810 are formed, and piston rings (not shown) are fitted into these ring grooves 1810.

  The skirt portion 1804 is suspended downward from a lower portion of the piston head portion 1802 facing the piston head portion 1802 in the diameter direction.

The sidewall portions 1806 are opposed to each other in the direction perpendicular to the direction in which the pair of skirt portions 1804 face each other, and are suspended downward from the lower portion of the piston head portion 1802 to connect the pair of skirt portions 1804.
The sidewall portion 1806 is located at a location displaced radially inward from the outer peripheral surface 18B, and each sidewall portion 1806 is provided with a pin hole 1812 for supporting a piston pin.

  As shown in FIGS. 2 to 14, the top surface 18 </ b> A of the piston 18 includes a concave portion 29, an intake side squish portion 30, two intake valve recesses 32, two exhaust valve recesses 34, and a protrusion 36. It is configured.

As shown in FIG. 2, the recess 29 is formed in an open shape at the center of the top surface 18A so as to surround the ignition point P1 of the ignition plug PL in a state where the piston 18 is located near the top dead center. 29 extends on a spherical surface centered on a point located in the vicinity of the central axis Op of the piston 18.
As shown in FIG. 9, when the top surface 18A of the piston 18 is viewed in plan, the edge portion 38 of the recess 29 is closer to the intake port 22 side than the dimension in the direction connecting the intake port 22 side and the exhaust port 26 side. And is formed in a long shape having a large dimension in a direction perpendicular to a straight line connecting the exhaust port 26 side. In the present embodiment, the recess 29 has an oval shape or an elliptical shape.

As shown in FIG. 2, the bottom surface of the recessed portion 29 is formed higher than the intake side squish portion 30.
As shown in FIG. 9, the portion located on the intake port 22 side of the edge portion 38 that forms the boundary between the concave portion 29 and the top surface 18 </ b> A of the piston 18 located around the concave portion 29 is referred to as an intake side edge portion 38 </ b> A. When the portion located on the exhaust port 26 side is the exhaust side edge 38B, the intake side edge 38A is formed lower than the exhaust side edge 38B as shown in FIG.

As shown in FIGS. 3, 4, and 9, the intake valve recess 32 is a place that avoids interference with the intake valve 24 when the intake valve 24 is opened, and two intake valve recesses 32 are provided corresponding to the intake valve 24. Yes.
The intake valve recess 32 is formed by cutting out a portion of the top surface 18A corresponding to the intake valve 24, and is provided at a location adjacent to the intake side edge portion 38A.
As shown in FIG. 9, the end portion of the two intake valve recesses 32 on the outer peripheral surface 18B side is an arc portion 3202 that extends in an arc shape, and the two arc portions 3202 are adjacent to each other in a straight line portion. 3204 is connected.
As shown in FIGS. 9 to 11, the space between the straight portion 3204 and the intake side edge 38 </ b> A and the two intake valve recesses 32 are formed by a single plane 40, which is the center of the top surface 18 </ b> A. Is inclined higher than the outer peripheral portion of the top surface 18A.
2 and 9, the two intake valve recesses 32 and the plane 40 between the straight portion and the intake side edge 38A cooperate with the lower surface 16A of the cylinder head 16 in the compression stroke. Thus, it functions as a guiding portion that guides the squish airflow S to the recess 29.

As shown in FIG. 2, the intake side squish part 30 has a smaller volume between the intake side squish part 30 and the lower surface 16A of the cylinder head 16 facing the intake side squish part 30 in the compression stroke. A squish airflow S is generated in which the air-fuel mixture therebetween flows toward the recess 29.
The squish portion for creating the squish airflow is only the intake side squish portion 30.
As shown by oblique lines in FIGS. 3, 4, and 9, the intake side squish portion 30 is formed in a portion including the outer peripheral portion of the top surface 18 </ b> A closer to the intake port 22 than the recess 29. More specifically, the intake side squish part 30 is formed from the outer peripheral edge part to the two arc parts 3202 and the straight part 3204.
The intake side squish portion 30 is formed of a plane orthogonal to the central axis Op of the piston 18 (the axis of the piston 18).

As shown in FIGS. 3, 4, and 9, the exhaust valve recess 34 is a portion that avoids interference with the exhaust valve 28 when the exhaust valve 28 is opened, and two exhaust valve recesses 34 are provided corresponding to the exhaust valve 28. Yes.
The exhaust valve recess 34 is formed by cutting out a portion of the top surface 18A corresponding to the exhaust valve 28, and is provided at a location adjacent to the exhaust side edge 38B.

As shown in FIG. 9, a first flat portion 42 is provided along the edge 38 of the recess 29 between the intake valve recess 32 and the two exhaust valve recesses 34, and the recess 29 between the two exhaust valve recesses 34 is provided. A second flat portion 44 is provided along the edge portion 38.
The flat portions 42 and 44 are formed by a plane orthogonal to the central axis Op of the piston 18, and the flat portions 42 and 44 extend on the same plane.

As shown in FIGS. 2 to 4 and 9, the protrusion 36 extends toward the outer peripheral surface 18 </ b> B between the two exhaust valve recesses 34 adjacent to the second flat portion 44.
The protrusion 36 protrudes further toward the cylinder head 16 than the exhaust valve recess 34 in the axial direction of the piston 18 and is inclined so that the height gradually decreases from the exhaust side edge 38B toward the outer peripheral surface 18B.

As shown in FIGS. 3, 4, and 9, a third flat portion 46 is provided along the outer periphery of the top surface 18 </ b> A, and two intake valve recesses 32 are provided at both ends in the extending direction of the third flat portion 46. Located at the end of the.
The third flat portion 46 is formed by a plane orthogonal to the central axis Op of the piston 18, and extends on the same plane as the intake side squish portion 30.

  As shown in FIGS. 3, 4, and 9, the first flat portion 42 and the third flat portion 46 are connected by a first curved surface portion 48, respectively, and the protrusion 36 and the third flat portion 46 are connected to each other. The flat surface 46 is connected by a second curved surface portion 50, and the first curved surface portion 48 and the second curved surface portion 50 extend on a single conical surface.

Next, the function and effect will be described.
In a state where the piston 18 is located near the top dead center, the recess 29 is formed so as to surround the ignition point P1 of the spark plug PL, and the bottom surface of the recess 29 is formed higher than the intake side squish part 30. The intake side edge 38A of 29 is formed lower than the exhaust side edge 38B.
Therefore, as shown in FIG. 2, in the compression stroke, the air-fuel mixture between the intake side squish portion 30 and the lower surface 16A of the cylinder head 16 easily flows into the recess 29 through the intake side edge portion 38A by the squish air flow S. This is advantageous in reliably collecting the air-fuel mixture around the ignition point P1.
Further, since the exhaust side edge 38B is higher than the intake side edge 38A, as shown by the arrow A, the air-fuel mixture collected in the recess 29 is unlikely to flow out from the exhaust side edge 38B. It is also advantageous for holding around.
Therefore, the air-fuel mixture is easily ignited at the ignition point P1, which is advantageous in promoting combustion of the air-fuel mixture and improving fuel consumption.

  Further, since the squish portion for creating the squish airflow is only the intake-side squish portion 30, the air-fuel mixture collected in the recess 29 by the squish airflow by the intake-side squish portion 30 during the compression stroke is squished by other squish portions Since the air-fuel mixture is not affected by the airflow, it is more advantageous for reliably collecting the air-fuel mixture around the ignition point P1.

In addition, a protrusion 36 that protrudes above the exhaust valve recess 34 is formed between the two exhaust valve recesses 34.
Therefore, in addition to suppressing the outflow of the air-fuel mixture from the concave portion 29 to the exhaust port 26 side, the projection portion 36 is formed at a location on the exhaust port 26 side of the top surface 18A. Since the volume of the combustion chamber 20 on the exhaust port 26 side can be reduced, a larger amount of air-fuel mixture in the combustion chamber 20 can flow into the recess 29, which is more advantageous for collecting the air-fuel mixture around the ignition point P1. It becomes.

  Further, when the top surface 18A of the piston 18 is viewed in plan, the edge portion 38 of the recess 29 is closer to the intake port 22 side and the exhaust port 26 side than the dimension in the direction connecting the intake port 22 side and the exhaust port 26 side. Is formed in a long shape having a large dimension in a direction perpendicular to the straight line connecting the two, the intake side edge 38A, which is the portion where the air-fuel mixture flows into the recess 29, can be secured large. By promoting the flow of the air-fuel mixture flowing into the concave portion 29, it is more advantageous for reliably collecting the air-fuel mixture around the ignition point P1.

  In the present embodiment, the case where the internal combustion engine is an intake pipe injection type engine in which an injector is provided in the intake pipe has been described, but the present invention is naturally applicable to a naturally aspirated type engine or a direct injection type engine. .

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine (engine), 12 ... Cylinder, 12A ... Inner peripheral surface, 14 ... Cylinder block, 16 ... Cylinder head, 16A ... Lower surface, 18 ... Piston, 18A ... Top surface, 20 ...... Combustion chamber, 22 ...... Intake port, 24 ...... Intake valve, 26 ...... Exhaust port, 28 ...... Exhaust valve, 29 ...... Recess, 30 ...... Intake side squish part, 32 ...... Intake valve recess, 34. ... exhaust valve recess, 36 ... projection, 38 ... edge, 38A ... intake side edge, 38B ... exhaust side edge, PL ... ignition plug, Op ... center axis, P1 ... ignition point, S: Squish airflow.

Claims (5)

A combustion chamber formed by a cylinder formed in the cylinder block, a lower surface of the cylinder head, and a piston top surface;
An intake port, an exhaust port, a spark plug provided in the cylinder head;
An internal combustion engine comprising:
The top surface of the piston has a recess formed in the center of the top surface so as to surround the ignition point of the spark plug in a state where the piston is positioned near the top dead center, and the intake port side from the recess. An intake side squish part for creating a squish airflow that is formed in a part including the outer peripheral part of the top surface and extends on a plane perpendicular to the axis of the piston,
The cylinder head includes a lower surface of the cylinder head that is formed at a position of the cylinder head facing the intake side squish portion and generates the squish airflow in cooperation with the intake side squish portion.
The top surface of the piston extends along a direction connecting the intake port side and the exhaust port side of an edge portion that forms a boundary between the concave portion and the top surface portion located around the concave portion. A first flat portion is formed along the edge to be
Of the edge portion that borders the concave portion and the top surface portion located around the concave portion, the portion located on the intake port side is defined as the intake side edge portion, and the portion located on the exhaust port side is exhausted. When it is a side edge, the intake side edge is formed lower than the exhaust side edge,
An internal combustion engine characterized by that.   The cylinder head includes an intake valve disposed in the intake port and an exhaust valve disposed in the exhaust port,
  An intake valve recess provided corresponding to the intake valve and an exhaust valve recess provided corresponding to the exhaust valve are formed on the top surface of the piston,
  The first flat portion is provided between the intake valve recess and the exhaust valve recess.
  The internal combustion engine according to claim 1.   A third flat portion is formed on the piston top surface along the outer periphery, and the first flat portion and the third flat portion are connected by a curved surface portion.
  The internal combustion engine according to claim 2, wherein: Two exhaust valve recesses for avoiding interference with the exhaust valve are formed in the top surface portion located on the exhaust port side with respect to the exhaust side edge,
4. The internal combustion engine according to claim 2 , wherein a protrusion is formed between the two exhaust valve recesses so as to protrude toward the cylinder head from the exhaust valve recess in the axial direction of the piston. When the top surface of the piston is viewed in plan, the edge of the recess is a straight line connecting the intake port side and the exhaust port side rather than the dimension in the direction connecting the intake port side and the exhaust port side. Is formed in a long shape with a large dimension in the direction orthogonal to
The internal combustion engine according to any one of claims 1 to 4, wherein

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