JP5930676B2 - Combustion chamber structure of internal combustion engine - Google Patents

Description

  The present invention relates to a combustion chamber structure of an internal combustion engine.

  In an internal combustion engine for automobiles, a combustion chamber wall surface, which is an upper portion of a combustion chamber, is recessed in the lower surface of a cylinder head, two intake ports, two exhaust ports, and an ignition plug insertion hole for inserting an ignition plug, Is opened on the wall of the combustion chamber. In such a combustion chamber, an ignition plug insertion hole is disposed at the center of the wall surface of the combustion chamber, and two intake ports are adjacent to each other and two exhaust ports are adjacent to each other around the ignition plug insertion hole. ing. In such a combustion chamber, in order to promote the generation of tumble flow in order to guide the combustible gas flowing in from the intake port to the vicinity of the spark plug, the peripheral portion of the opening end of the intake port to the combustion chamber is formed in a conical surface. Some have been formed (for example, Patent Document 1). By making the peripheral edge of the opening end of the intake port a conical surface, the flammable gas flowing into the combustion chamber from the gap between the intake port and the intake valve flows smoothly to the piston side along the conical surface. Promoted.

JP-A-2-215921

  Near the top dead center, combustible gas is compressed and the tumble flow collapses. In order to increase the ignitability and combustion efficiency of the combustible gas, it is preferable to increase the turbulence (turbulence intensity) of the combustible gas around the spark plug near the top dead center. That is, it is preferable to concentrate the combustible gas disturbance in the vicinity of the spark plug.

  The present invention has been made in view of the above background, and it is an object of the present invention to concentrate turbulence (vortex) of combustible gas in the vicinity of a spark plug near the top dead center in a combustion chamber structure of an internal combustion engine. .

In order to solve the above problems, the present invention has a combustion chamber wall surface (7) provided on the lower surface (4) of the cylinder head (3) to define the upper surface of the combustion chamber (8), A spark plug insertion hole (11) opened in the center of the combustion chamber wall surface, two intake ports (12, 13) and two exhaust ports (14, 15) arranged around the spark plug insertion hole The combustion chamber structure of the internal combustion engine (1) is provided with an ignition plug region (35) provided on the outer periphery of the ignition plug insertion hole on the combustion chamber wall surface and provided on the outer periphery of each port. The port areas (36, 37, 38, 39) are mutually separated by ridges (41 to 48) and form mutually independent concave surfaces, the ridges surrounding the spark plug area in an annular shape, and the ignition Between the open end of the plug insertion hole It said ignition spherical concave surface to form a plug region is present, the exhaust port region provided on each of the outer periphery of each of the exhaust ports and intake port areas (36, 37) provided on an outer periphery of the intake port ( 38, 39) is characterized in that the ridge is steeply formed with a radius of curvature of 3 mm or less at the tip thereof.

According to this configuration, since the spark plug region is disposed at the center of the combustion chamber wall surface and forms a concave surface, the combustible gas is concentrated in the spark plug region near the top dead center, and is compressed and swirled ( Disturbance) occurs. Therefore, ignitability and combustion efficiency are improved. In addition, the ridge between the intake port region and the exhaust port region becomes steep, and the gas flow is easily inhibited. Therefore, the blow-off of combustible gas from the intake port to the exhaust port is suppressed.

  Another aspect of the present invention is characterized in that each port region is formed as a concave surface having a conical surface having a cone angle of 120 ° or less at least in the vicinity of each port. Here, the cone angle refers to an angle formed by two generatrices of the cone appearing in the cross section when the cone is cut along a plane passing through its central axis.

  According to this configuration, since the spread of the peripheral edge portion of the opening end of each port is reduced, the gas flow corresponding to each port is suppressed from spreading and hardly interferes with each other. In addition, in the intake port, the direction of the gas flowing into the combustion chamber can be restricted to one direction, and the generation of the tumble flow can be promoted.

  According to the above configuration, in the combustion chamber structure of the internal combustion engine, the combustible gas disturbance can be concentrated in the vicinity of the spark plug near the top dead center.

Sectional view showing the combustion chamber of the cylinder head on an enlarged scale Perspective view of combustion chamber viewed from below Top view of combustion chamber viewed from below IV-IV sectional view of FIG. V-V cross section of Fig. 3

  Embodiments in which the present invention is applied to an automobile engine will be described below in detail with reference to the drawings. The engine 1 according to the present embodiment is a 4-valve DOHC type engine. As shown in FIG. 1, the engine 1 has a cylinder block 2 and a cylinder head 3 fastened to the cylinder block 2. In the following description, as shown in FIG. 1, the side on which the cylinder head 3 is provided with respect to the cylinder block 2 is the upper side.

  The cylinder head 3 has a flat lower end surface 4 joined to the upper end surface of the cylinder block 2 at the lower portion thereof. The cylinder block 2 is formed with a cylinder 5 that accommodates a piston (not shown) so as to be movable up and down. The cylinder 5 extends in the vertical direction and opens at the upper end surface of the cylinder block 2. A portion of the cylinder head 3 corresponding to the cylinder 5 is formed with a combustion chamber wall surface 7 that is recessed upward in a substantially hemispherical shape. The combustion chamber wall surface 7 defines a combustion chamber 8 in cooperation with the cylinder 5 and the piston. That is, the combustion chamber wall surface 7 constitutes the upper surface of the combustion chamber 8.

  As shown in FIGS. 2 and 3, an ignition plug for inserting an ignition plug (not shown) into the center of the combustion chamber wall surface 7, that is, the deepest portion (bottom portion) of the recess formed by the combustion chamber wall surface 7. An insertion hole 11 is formed. Around the spark plug insertion hole 11, a first intake port 12, a second intake port 13, a first exhaust port 14, and a second exhaust port 15 are ignited at approximately 90 ° intervals with the spark plug insertion hole 11 as the center. It is formed so as to surround the plug insertion hole 11. The first intake port 12 and the second intake port 13 are adjacent to each other, and the first exhaust port 14 and the second exhaust port 15 are adjacent to each other. Using the spark plug insertion hole 11 as a reference, the side on which the first and second intake ports 12 and 13 are arranged is referred to as the intake side, and the side on which the first and second exhaust ports 14 and 15 are arranged is referred to as the exhaust side.

  As shown in FIG. 1, annular valve seats 16 to 19 are embedded in the open ends of the ports 12 to 15 of the combustion chamber wall surface 7. The inner peripheral surfaces of the valve seats 16 to 19 are conical tapered surfaces 21 to 24 in which the combustion chamber 8 side is widened. An intake valve or an exhaust valve (not shown) that is a poppet valve is formed on the tapered surfaces 21 to 24. ) Is seated, and the ports 12 to 15 are opened and closed.

  Each intake port 12, 13 extends upward from the opening end to the combustion chamber wall surface 7, then bends and extends to the intake side, and opens on the side surface of the cylinder head 3. Each intake port 12, 13 is formed with an intake valve hole 27 into which an intake valve guide 26 through which the stem portion of the intake valve passes is fitted. In the engine 1 of this embodiment, a combustion injection device (not shown) is provided in the intake ports 12 and 13, and fuel is injected into the intake ports 12 and 13 and mixed with air. Each exhaust port 14, 15 extends upward from the opening end to the combustion chamber wall surface 7, then bends and extends to the exhaust side, and opens on the side surface of the cylinder head 3. Each exhaust port 14, 15 is formed with an exhaust valve hole 29 into which an exhaust valve guide 28 through which the stem portion of the exhaust valve passes is fitted. Cooling water passages 31 are formed at appropriate positions around the ports 12 to 15 of the cylinder head 3.

  As shown in FIGS. 2 and 3, the combustion chamber wall surface 7 includes an ignition plug region 35 formed around the opening end of the ignition plug insertion hole 11 and an opening end (valve seat 16) of the first intake port 12. The first intake port region 36 formed in the periphery, the second intake port region 37 formed around the open end (valve seat 17) of the second intake port 13, and the open end (valve) of the first exhaust port 14 The first exhaust port region 38 formed around the seat 18) and the second exhaust port region 39 formed around the open end (valve seat 19) of the second exhaust port 15 are partitioned into five regions. ing. Each of the regions 35 to 39 is formed as a concave surface that is independent of each other. Since the regions 35 to 39 are concave surfaces independent of each other, ridges 41 to 48 are formed along the boundaries of the regions 35 to 39, respectively.

  The spark plug region 35 has a first ridge 41 at the boundary with the first intake port region 36, a second ridge 42 at the boundary with the second intake port region 37, and a second exhaust port region 39. And a fourth ridge 44 at the boundary with the first exhaust port region 38. The first to fourth ridges 41 to 44 are continuously annular and surround the spark plug region 35.

  A fifth ridge 45 is formed at the boundary between the first intake port region 36 and the second intake port region 37. One end of the fifth ridge 45 is continuous to the intersection of the first ridge 41 and the second ridge 42, extends to the intake side, and the other end is continuous to the periphery of the combustion chamber wall surface 7.

  A sixth ridge 46 is formed at the boundary between the second intake port region 37 and the second exhaust port region 39. One end of the sixth ridge 46 is continuous with the intersection of the second ridge 42 and the third ridge 43, extends in a direction orthogonal to the intake-exhaust direction, and the other end is continuous with the periphery of the combustion chamber wall 7. doing.

  A seventh ridge 47 is formed at the boundary between the second exhaust port region 39 and the first exhaust port region 38. The seventh ridge 47 has one end continuous to the intersection of the third ridge 43 and the fourth ridge 44, extends to the exhaust side, and the other end continuous to the periphery of the combustion chamber wall 7.

  An eighth ridge 48 is formed at the boundary between the first exhaust port region 38 and the first intake port region 36. The eighth ridge 48 has one end continuous to the intersection of the fourth ridge 44 and the first ridge 41, extends in a direction orthogonal to the intake-exhaust direction, and the other end continuous to the periphery of the combustion chamber wall 7. doing.

  The spark plug region 35 is formed in one continuous spherical surface. A spark plug (not shown) having a spark plug (not shown) provided at the tip of the spark plug insertion hole 11 is inserted and fixed so that the opening end of the spark plug insertion hole protrudes. That is, the ground electrode is located in the combustion chamber 8.

  As shown in FIG. 1, in the first intake port region 36, the vicinity of the opening end (valve seat 16) of the first intake port 12 to the combustion chamber wall surface 7 is formed as a conical surface (conical frustum surface). The conical surface is arranged such that its central axis coincides with the axis A of the opening end (valve seat 16) of the first intake port 12 to the combustion chamber wall surface 7, and the conical angle θ1 is 120 ° or less. It is set to be. In other words, the angle (θ1 / 2) formed between the generatrix of the conical surface and the axis A is set to be 60 ° or less in the cross section taken along the plane including the axis A. A surface constituting the first intake port region 36 is a curved surface that is curved so that an angle formed with the axis A gradually decreases as viewed from a cross section when cut along a plane including the axis A as the distance from the valve seat 16 increases. ing.

  As shown in FIG. 4, in the second intake port region 37, similarly to the first intake port region 36, the vicinity of the opening end (valve seat 17) to the combustion chamber wall surface 7 of the second intake port 13 is formed in a conical surface. The cone angle θ2 is 120 ° or less. The surface constituting the second intake port region 37 is curved so that the angle formed with the axis B gradually decreases as the distance from the valve seat 17 is viewed in a cross section when cut along a plane including the axis B of the valve seat 17. It is a curved surface.

  As shown in FIG. 1, the first exhaust port region 38 has a conical surface in the vicinity of the opening end (valve seat 18) of the first exhaust port 14 to the combustion chamber wall surface 7, similar to the first intake port region 36. The cone angle θ3 is 120 ° or less. The surface constituting the first exhaust port region 38 is curved so that the angle formed with the axis C gradually decreases as the distance from the valve seat 18 is viewed in a cross section when cut along a plane including the axis C of the valve seat 18. It is a curved surface. Although not shown, the second exhaust port region 39 is symmetrical with the first exhaust port region 38.

  The fifth to eighth ridges 45 to 48 are set so that the radius of curvature of the protruding end is 3 mm or less.

  In the engine 1 configured as described above, the spark plug region 35 is formed in a spherical concave surface partitioned from the other regions 36 to 39 as shown in FIG. It becomes easy to concentrate on the spark plug region 35, and turbulent flow (vortex) of combustible gas generated by compression concentrates on the spark plug region 35 in the vicinity of the top dead center. Therefore, the ignitability is improved and the combustion efficiency is improved.

  In addition, since each intake port region 36, 37 is formed as a concave surface including a conical surface, combustible gas can be guided downward along the wall surface of each intake port region 36, 37, that is, to the piston side. Can be promoted.

  Further, the exhaust port regions 38 and 39 are formed in a concave surface, and the sixth ridge 46 and the eighth ridge 48 project downward toward the boundary between the intake port regions 36 and 37 and the exhaust port regions 38 and 39. Therefore, it is possible to suppress blow-through directly flowing from the intake ports 12 and 13 to the exhaust ports 14 and 15. In particular, since the tips of the ridges 46 and 48 are steep so that the curvature radii of the sixth ridge 46 and the eighth ridge 48 are 3 mm or less, the blow-through can be reliably suppressed. It is expected that the sharper the tips of the ridges 46 and 48, the greater the effect of suppressing blow-through. However, when the ridges 46 and 48 are steep, shape deterioration (blunting) is likely to occur due to metal wear, making it difficult to stabilize the shape. When the cylinder head 3 is formed by casting an aluminum alloy, the shapes of the ridges 46 and 48 may vary due to metal wear with the mold. Therefore, in this embodiment, the curvature radius is set to 3 mm or less, and the quality is homogenized while the blow-through is reliably suppressed.

  Since the first and second ridges 41 and 42 are disposed between the intake port regions 36 and 37 and the spark plug region 35 and the spark plug region 35 is concave, as shown in FIG. It arrange | positions in the part back | increased above the combustion chamber wall surface 7. FIG. Therefore, it becomes difficult for the fuel liquid adhering to the wall surfaces of both intake port regions 36 and 37 to reach the spark plug along the wall surfaces. Thereby, the ignition performance of the spark plug is stabilized.

  Although the description of the specific embodiment is finished as described above, the present invention is not limited to the above embodiment and can be widely modified. For example, each of the port regions 36 to 39 may be formed on a spherical surface. Further, the spark plug region 35 may be a conical surface. In addition, although it was set as the combustion chamber 8 of 4 valves in embodiment, you may make it 5 valves.

  DESCRIPTION OF SYMBOLS 1 ... Engine, 3 ... Cylinder head, 4 ... Lower end surface, 7 ... Combustion chamber wall surface, 8 ... Combustion chamber, 11 ... Spark plug insertion hole, 12 ... 1st intake port, 13 ... 2nd intake port, 14 ... 1st Exhaust port, 15 ... second exhaust port, 16-19 ... valve seat, 35 ... ignition plug region, 36 ... first intake port region, 37 ... second intake port region, 38 ... first exhaust port region, 39 ... first 2 exhaust port region, 41 ... first ridge, 42 ... second ridge, 43 ... third ridge, 44 ... fourth ridge, 45 ... fifth ridge, 46 ... sixth ridge, 47 ... first 7 ridges, 48 ... 8th ridge

Claims (2)

In order to define the upper surface of the combustion chamber, it has a combustion chamber wall surface provided on the lower surface of the cylinder head, an ignition plug insertion hole opened in the center of the combustion chamber wall surface, and a periphery of the ignition plug insertion hole A combustion chamber structure of an internal combustion engine provided with two intake ports and two exhaust ports arranged in
In the combustion chamber wall surface, the spark plug region provided on the outer periphery of the spark plug insertion hole and the port regions provided on the outer periphery of the ports have mutually independent concave surfaces that are partitioned by ridges, respectively.
There is a spherical concave surface that forms the spark plug region between the ridge that annularly surrounds the spark plug region and the open end of the spark plug insertion hole ,
The ridge portion between the intake port region provided on the outer periphery of each of the intake ports and the exhaust port region provided on the outer periphery of each of the exhaust ports is formed steeply with a radius of curvature of the tip of 3 mm or less. a combustion chamber structure for an internal combustion engine, characterized in that it is. 2. The combustion chamber structure for an internal combustion engine according to claim 1 , wherein each port region is formed as a concave surface having a conical surface having a cone angle of 120 ° or less at least in the vicinity of each port.

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