JP2015063942A - Cylinder injection type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of soot and deterioration of an exhaust gas performance by restraining fuel from being adhered to a bottom face of a cavity even when the fuel is injected to the cavity at a piston top face.SOLUTION: A fuel injection valve 12 for injecting fuel to a cavity 13 on a top face of a piston 3 in a compression stroke is arranged on an outer side of a combustion chamber 6 than a suction port 8. Plural ribs 14 that have a pair of slope faces diagonally crossing with the bottom face of the cavity 13 on both sides of a ridge line and in which respective ridge lines extend in an expanding direction of the fuel injected from the fuel injection valve 12, are formed on the bottom face of the cavity 13. When air in the combustion chamber 6 is moved in a compressing direction, the air in the combustion chamber 6 is pressed by the slope faces of the ribs 14, and the air is turned in a direction away from the bottom face of the cavity 13 by the slope faces of the ribs 14 adjacent to each other or the slope faces of the ribs 14 adjacent to a peripheral edge of the cavity 13. The injected fuel is turned in a direction away from the bottom face of the cavity 13 by a flow of the air.

Description

  The present invention relates to an in-cylinder injection internal combustion engine that injects fuel into a cylinder, and is particularly suitable when a cavity is formed on the top surface of a piston and fuel is injected toward the cavity.

  For example, the following Patent Document 1 discloses a technique for forming a cavity on the top surface of a piston for fuel injection. In this cylinder injection internal combustion engine, a plurality of cavities are formed in the shape of a washing plate on the top surface of the piston along the fuel injection direction of the fuel injection valve. The angle formed between the bottom surface of each cavity and the plane orthogonal to the piston movement direction is increased toward the downstream side in the fuel injection direction. According to this configuration, it is possible to suppress the fuel that is not atomized after colliding with the piston from reaching the spark plug as droplets, thereby suppressing the spark plug from being swung. Yes.

JP 2006-52663 A

  By the way, there are various types of cavities formed on the top surface of the piston other than those described in Patent Document 1, but when fuel is injected from the fuel injection valve toward the cavity, the fuel is contained in the cavity. May stick to the bottom. If fuel adheres to the bottom surface of the cavity, soot may be generated or exhaust gas performance may be deteriorated.

  The present invention has been made paying attention to the above problems, and even when fuel is injected toward the cavity on the top surface of the piston, the adhesion of the fuel to the bottom surface of the cavity is suppressed, so that An object of the present invention is to provide an in-cylinder injection internal combustion engine that can prevent generation and deterioration of exhaust gas performance.

  In order to solve the above-described problems, an embodiment of the present invention provides a cylinder injection internal combustion engine that injects fuel into a cylinder, a combustion chamber formed between a cylinder block side surface of a cylinder head and a top surface of a piston. A spark plug disposed at an upper center portion of the combustion chamber, an intake port and an exhaust port opening at positions opposed to each other across the spark plug, a cavity formed in a top surface of the piston, and the intake port A fuel injection valve disposed outside the combustion chamber and injecting fuel into the cavity in a compression stroke; and a pair of slopes formed on the bottom surface of the cavity and obliquely intersecting the bottom surface of the cavity on both sides of the ridge line And a plurality of ribs each having a ridge line extending radially in the spreading direction of the fuel injected from the fuel injection valve. It is.

  The fuel injection valve includes a plurality of fuel injection ports for injecting fuel in a conical shape, and at least one of the ribs is disposed below a center line of fuel injected from the fuel injection port. did.

  Thus, according to an embodiment of the invention, a cavity is formed in the top surface of the piston, and a fuel injection valve that injects fuel into the cavity in the compression stroke is disposed outside the combustion chamber from the intake port. The bottom surface of the cavity has a plurality of ribs that have a pair of slopes obliquely intersecting the bottom surface of the cavity on both sides of the ridge line, and each ridge line extends radially in the direction of spreading of the fuel injected from the fuel injection valve. Form. Therefore, when moving in the direction in which the air in the combustion chamber is compressed, the air in the combustion chamber can be pushed by the inclined surfaces of the ribs. At that time, the air is swirled away from the bottom surface of the cavity or the top surface of the piston by the slopes of the ribs adjacent to each other and the slopes of the ribs adjacent to the peripheral edge of the cavity. By such an air flow, the injected fuel can be swung in a direction away from the bottom surface of the cavity or the top surface of the piston, and the fuel can be prevented from adhering to the bottom surface of the cavity. As a result, it is possible to prevent soot generation and deterioration of exhaust gas performance. In addition, the ridgeline of each rib extends radially in the fuel spreading direction, so that air flowing in the normal direction of the slope can be generated throughout the fuel reach range, and it is more reliable that the fuel adheres to the bottom surface of the cavity. Can be suppressed.

  The fuel injection valve has a plurality of fuel injection ports for injecting fuel in a conical shape, and the ridge line of the rib is arranged below the center line of the fuel injected from the fuel injection port. Therefore, the fuel can be turned symmetrically with respect to the ridgeline of the rib. As a result, it is possible to suppress the region where the concentration of the air-fuel mixture is extremely different from being generated in the combustion chamber while suppressing the fuel from adhering to the bottom surface of the cavity, thereby improving the combustion stability as an internal combustion engine. be able to.

1 is a longitudinal sectional view at the center of a port showing an embodiment of a direct injection internal combustion engine of the present invention. FIG. 2 is a longitudinal sectional view at the center of a combustion chamber of the direct injection internal combustion engine of FIG. 1. FIG. 2 is a perspective view of a fuel injection valve and a piston of the direct injection internal combustion engine of FIG. 1. FIG. 2 is a plan view of a fuel injection valve and a piston of the direct injection internal combustion engine of FIG. 1. FIG. 2 is a side view of a fuel injection valve and a piston of the direct injection internal combustion engine of FIG. 1. It is a top view of the piston of the cylinder injection type internal combustion engine of FIG. It is a longitudinal cross-sectional view of the piston of FIG. It is explanatory drawing which shows the flow of the fuel in the cavity of the piston of FIG. It is explanatory drawing which shows the flow of the fuel in the cavity of the conventional piston. It is a schematic diagram of the flow of the fuel of FIG. FIG. 10 is a schematic diagram of the fuel flow in FIG. 9. It is explanatory drawing of the fuel adhesion amount to the bottom face of a cavity. It is a top view of the piston which shows the other Example of the direct injection internal combustion engine of this invention.

  Next, an embodiment of a direct injection internal combustion engine of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view at the center of a port of the direct injection internal combustion engine of the present embodiment, and FIG. 2 is a longitudinal sectional view at the center of a combustion chamber of the direct injection internal combustion engine of FIG. In these drawings, the cylinder block is not shown, and only the sleeve (cylinder) 1 inserted and fixed in the cylinder block is shown in the cylinder block portion. A cylinder, a so-called cylinder bore, is formed inside the sleeve 1.

  A cylinder head 2 is mounted above the cylinder block that houses the sleeve 1. A cylinder head cover (not shown) is generally attached above the cylinder head 2. A crankcase is formed below the cylinder block, and generally an oil pan is attached below the crankcase. Although the internal combustion engine is mounted on the vehicle in various directions, the cylinder head is mounted so that the cylinder head is positioned above the cylinder block. It is defined as downward.

  A piston 3 is accommodated in the cylinder so as to be slidable in the axial direction of the sleeve 1, that is, in the vertical direction of the internal combustion engine. A crankshaft 4 is rotatably supported in the crankcase below the cylinder block. The axis of the crankshaft 4 passes on the axis of the sleeve 1 and is arranged in the direction perpendicular to the paper surface of FIGS. A crank pin is formed at a portion eccentric from the axis of the crank shaft 4, and the crank pin and the piston 3 are connected by a connecting rod (connecting rod) 5. Therefore, the reciprocating motion of the piston 3 in the vertical direction of the internal combustion engine is converted into the rotational motion of the crankshaft 4 and is taken out as the driving force of the vehicle. A cavity (recess) 13 is formed at the center of the top surface of the piston 3.

  In the internal combustion engine of the present embodiment, a combustion chamber 6 is formed between the cylinder block side surface of the cylinder head 2 and the top surface of the piston 3 as in the existing internal combustion engine. The combustion chamber 6 of the present embodiment is a so-called pent roof type combustion chamber, and a spark plug 7 is disposed at the upper center of the combustion chamber 6. Further, on the upper surface of the combustion chamber 6, an intake port 8 and an exhaust port 9 are opened at positions facing each other with the spark plug 7 interposed therebetween. In the present embodiment, two intake ports 8 and two exhaust ports 9 are arranged for each combustion chamber 6, so that each of the intake port 8 and the exhaust port 9 is in the crank axis direction with respect to the spark plug 7. It's off. The intake port 8 is opened and closed by an intake valve 10, the exhaust port 9 is opened and closed by an exhaust valve 11, the intake valve 10 is driven by an intake cam (not shown), and the exhaust valve 11 is driven by an exhaust cam (not shown).

  In the present embodiment, a fuel injection valve 12 is disposed outside the combustion chamber 6 from the intake port 8. The fuel injection valve 12 injects fuel toward the cavity 13 of the piston 3 in the compression stroke of each cylinder. Therefore, the internal combustion engine as in this embodiment is called a cylinder injection type internal combustion engine. It is out. Although there are various types of fuel injection valves 12, the fuel injection valve 12 of this embodiment includes a plurality of fuel injection ports for injecting fuel in a conical shape, that is, in a forwardly expanding manner, as will be described later. .

  3 is a perspective view of the fuel injection valve and piston of the direct injection internal combustion engine of FIG. 1, FIG. 4 is a plan view of the fuel injection valve and piston of FIG. 3, and FIG. 5 is the fuel injection valve of FIG. FIG. 6 is a side view of the piston, FIG. 6 is a plan view of the piston of the direct injection internal combustion engine of FIG. 1, and FIG. 7 is a longitudinal sectional view of the piston of FIG. As is apparent from these drawings, the piston 3 of the present embodiment has a plurality of radial ribs 14 formed on the bottom surface of the cavity 13. The ribs 14 are arranged such that each ridge line extends radially in the spreading direction of the fuel injected from the fuel injection valve 12, and a pair of diagonally intersecting the bottom surface of the cavity 13 is formed on both sides of each ridge line. A slope is formed. Further, as described above, the fuel injection valve 12 includes a plurality of fuel injection ports that inject fuel in a conical shape. Although this fuel injection port is difficult to recognize in the drawings, it is clear from the fact that there are a plurality of conical shapes of the fuel injected in FIGS. 3 and 4, for example. And in this embodiment, the ridgeline of each rib 14 is arrange | positioned under the centerline of the fuel injected from each fuel injection port. An intake recess (recess) 15 for avoiding interference with the intake valve 10 and an exhaust recess (recess) for avoiding interference with the exhaust valve 11 are provided around the cavity 13 in the top surface of the piston 3. ) 16 is formed.

  FIG. 8 is an explanatory diagram showing the flow of fuel in the cavity 13 of the piston 3 of the present embodiment. The small arrows in the figure indicate the fuel flow. On the other hand, FIG. 9 is an explanatory view showing the flow of fuel in the cavity 13 of the conventional piston 3. Here, the same reference numerals as in the present embodiment are used. This conventional piston 3 is flat without ribs on the bottom surface of the cavity 13. FIG. 10 is a schematic diagram of the fuel flow of FIG. 8, and FIG. 11 is a schematic diagram of the fuel flow of FIG.

  For example, as shown in FIG. 10, when the piston 3 moves in the direction in which the air in the combustion chamber 6 is compressed, the air in the combustion chamber 6 can be pushed by the inclined surfaces of the ribs 14. At that time, the air is swung in a direction away from the bottom surface of the cavity 13 or the top surface of the piston 3 by the peripheral edge of the cavity 13 and the slope of the rib 14 or the slope of the rib 14 adjacent to each other. By such an air flow, the injected fuel F can be swung in a direction away from the bottom surface of the cavity 13 or the top surface of the piston 3 to prevent the fuel F from adhering to the bottom surface of the cavity 13. As a result, it is possible to prevent soot generation and deterioration of exhaust gas performance. Further, since the ridges of the ribs 14 extend radially in the fuel spreading direction, air flowing in the normal direction of the slope can be generated throughout the fuel reach range, and the fuel adheres to the bottom surface of the cavity 13. It can suppress more reliably.

  On the other hand, in the conventional piston 3 in which no rib is formed on the bottom surface of the cavity 13, for example, as shown in FIG. 11, the air when the piston 3 moves in the direction of compressing the air in the combustion chamber 6 is pushed. The direction and the fuel F injection direction are simply opposite. At this time, since the moving speed of the upper surface of the piston 3 or the bottom surface of the cavity 13 is higher than the injection speed of the fuel F, the fuel F adheres to the bottom surface of the cavity 13. When the fuel F adheres to the bottom surface of the cavity 13 as a liquid, ideal combustion as an air-fuel mixture cannot be obtained, exhaust gas performance is lowered, and in some cases, carbon components in the fuel remain unburned. FIG. 12 is an explanatory diagram of the amount of fuel adhering to the bottom surface of the cavity 13. As is apparent from the figure, the amount of fuel adhering to the bottom surface of the cavity 13 before the compression top dead center is smaller for those with ribs than for those without ribs. Also from this, the rib 14 is formed on the bottom surface of the cavity 13, and a pair of slopes obliquely intersecting the bottom surface of the cavity 13 is formed on both sides of the ridge line of the rib 14, and the ridge line of the rib 14 is formed from the fuel injection valve 12. By setting the injection fuel radially in the spreading direction, it is possible to suppress the fuel from adhering to the bottom surface of the cavity 13.

  Furthermore, in this embodiment, the fuel injection valve 12 includes a plurality of fuel injection ports for injecting fuel in a conical shape, and the ridge line of the rib 14 is disposed below the center line of the fuel injected from the fuel injection port 12. Therefore, the fuel can be turned symmetrically with respect to the ridgeline of the rib 14. As a result, while suppressing the fuel from adhering to the bottom surface of the cavity 13, it is possible to suppress the region in which the concentration of the air-fuel mixture is extremely different from being generated in the combustion chamber 6. Can be improved.

  FIG. 13 is a plan view of the top surface of the piston 3 showing another embodiment of the direct injection internal combustion engine of the present invention. In this embodiment, a fuel injection valve 12 is disposed at the center upper portion of the combustion chamber 6, and fuel is injected from the fuel injection valve 12 in the axial direction of the sleeve (cylinder) 1. Therefore, in the piston 3 of the present embodiment, a projection 17 that gradually tapers is formed at the piston central portion of the cavity 13. In this way, when fuel is injected from the upper center of the combustion chamber 6 toward the center of the cylinder, a swirling flow of air is generated by the projection 17 provided at the piston central portion of the cavity 13, which is the same as in the above-described embodiment. Similarly, the adhesion of fuel to the bottom surface of the cavity 13 can be suppressed.

1 is a sleeve (cylinder)
2 is a cylinder head 3 is a piston 4 is a crankshaft 5 is a connecting rod 6 is a combustion chamber 7 is a spark plug 8 is an intake port 9 is an exhaust port 10 is an intake valve 11 is an exhaust valve 12 is a fuel injection valve 13 is a cavity 14 is a rib 15 Is the intake recess 16 is the exhaust recess 17 is the protrusion

Claims (2)

In a cylinder injection internal combustion engine that injects fuel into a cylinder,
A combustion chamber formed between the cylinder block side surface of the cylinder head and the top surface of the piston;
A spark plug disposed at the upper center of the combustion chamber;
An intake port and an exhaust port that open to positions facing each other across the spark plug;
A cavity formed in the top surface of the piston;
A fuel injection valve disposed outside the combustion chamber from the intake port and injecting fuel into the cavity in a compression stroke;
A plurality of slopes formed on the bottom surface of the cavity and obliquely intersecting the bottom surface of the cavity on both sides of the ridgeline, each ridgeline extending radially in the direction of spreading of the fuel injected from the fuel injection valve A cylinder injection internal combustion engine comprising a rib. The fuel injection valve includes a plurality of fuel injection ports for injecting fuel in a conical shape,
2. The direct injection internal combustion engine according to claim 1, wherein at least one of the ribs is disposed below a center line of fuel in which the ridge line is injected from the fuel injection port.

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