JP2005133679A - Cylinder injection type spark ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To generate good homogeneous fuel/air mixture without diluting engine oil, in a cylinder injection type spark ignition internal combustion engine for performing homogeneous combustion. <P>SOLUTION: The cylinder injection type spark ignition internal combustion engine injects fuel with a fuel injection valve 2 arranged around the upper part of the cylinder to generate the homogeneous fuel/air mixture. The fuel injection valve injects fan-like fuel spray spreading mainly in the width direction W into the whole cylinder of last half of an intake process so that the center plane in the thickness direction of the fan-like fuel spray is substantially parallel with the center axis C of the cylinder, and a penetration force in the upper part of the fan-like fuel spray is weakened compared with the lower part of the fan-like fuel spray. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a direct injection spark ignition internal combustion engine.

  2. Description of the Related Art A cylinder injection spark ignition internal combustion engine that directly injects fuel into a cylinder in order to reliably supply a required amount of fuel into the cylinder is known.

  In such an in-cylinder injection spark ignition internal combustion engine, fuel is injected in the intake stroke to form a homogeneous mixture in the cylinder, and homogeneous combustion is performed in which this homogeneous mixture is ignited and combusted. In order to achieve good homogeneous combustion, it is necessary to form a sufficiently homogenized homogeneous mixture.

  In order to form a sufficiently homogenized homogeneous air-fuel mixture, fuel spray that spreads out is spread by a fuel injection valve arranged around the upper part of the cylinder so that the injected fuel spreads over the entire large cylinder space in the latter half of the intake stroke. It is necessary to inject with a relatively large penetration force. Since the penetration force is weak in the conical fuel spray, it is conceivable to use a fan-shaped fuel spray that spreads mainly in the width direction as the fuel spray that spreads forward.

  In-cylinder injection spark-ignition internal combustion that uses fan-shaped fuel spray in the vertical direction, for example, so that the width direction of fan-shaped fuel spray is parallel to a plane passing through the center of the injection hole of the fuel injection valve and the center axis of the cylinder An engine has been proposed (see, for example, Patent Document 1).

JP 2000-220460 A Japanese Patent Application Laid-Open No. 11-200086

  Using fan-shaped fuel spray in the vertical direction as described above, at the piston position in the latter half of the intake stroke, the upper part of the fan-shaped fuel spray faces the cylinder head in the cylinder space, and the lower part of the fan-shaped fuel spray faces the piston. In addition, by appropriately selecting the fan angle of the fan fuel spray, the injected fuel can be spread over the entire large cylinder space in the latter half of the intake stroke. This makes it possible to form a good homogeneous mixture in the subsequent compression stroke. However, when a fan-shaped fuel spray having a relatively high penetrating force is injected in this manner, the distance from the nozzle hole of the fuel injection valve to the cylinder bore is relatively short in the vicinity of the cylinder head. The fuel that collides and adheres to the cylinder bore at that time dilutes the engine oil.

  Accordingly, an object of the present invention is to enable the formation of a good homogeneous air-fuel mixture without diluting engine oil in an in-cylinder injection spark ignition internal combustion engine that performs homogeneous combustion.

  A direct injection spark ignition internal combustion engine according to claim 1 of the present invention is a direct injection spark ignition internal combustion engine in which fuel is injected by a fuel injection valve disposed around the upper part of the cylinder to form a homogeneous mixture. The fuel injection valve mainly injects fan-shaped fuel spray spreading in the width direction into the entire cylinder in the latter half of the intake stroke so that the center plane in the thickness direction of the fan-shaped fuel spray is substantially parallel to the cylinder center axis. The upper part of the fan-shaped fuel spray has a penetrating force weaker than that of the lower part of the fan-shaped fuel spray.

  According to a second aspect of the present invention, the direct injection spark ignition internal combustion engine according to the second aspect is the direct injection spark ignition internal combustion engine according to the first aspect, wherein the fuel injection valve injects the fan-shaped fuel spray. Therefore, a nozzle hole having an upper wall and a lower wall facing each other at a predetermined fan angle is provided. The nozzle hole communicates with a fuel reservoir in the fuel injection valve and is perpendicular to the thickness direction of the nozzle hole. In each cross section, the boundary between the fuel reservoir and the nozzle hole has an arc shape, and in each cross section, the intersection of the extension lines of the upper wall and the lower wall is the arc shape in each cross section. It is biased with respect to the center, and the extension line of the upper wall to the intersection point is longer than the extension line of the lower wall to the intersection point.

  According to a third aspect of the present invention, the direct injection spark ignition internal combustion engine according to the third aspect is the direct injection spark ignition internal combustion engine according to the first aspect, wherein the fuel injection valve injects the fan-shaped fuel spray. Therefore, it has a large number of small diameter nozzle holes arranged in the vertical direction, and the hole diameter of the upper small diameter hole group is smaller than the hole diameter of the lower small diameter hole group or the number of holes of the upper small diameter hole group Is smaller than the number of holes in the lower small-diameter nozzle hole group.

  According to the cylinder-injection spark ignition internal combustion engine according to claim 1, since the penetrating force is weakened in the upper part of the fan-shaped fuel spray as compared with the lower part of the fan-shaped fuel spray, the fan-shaped fuel spray in the latter half of the intake stroke. The lower part of the fan can fly long distances with a strong penetrating force, so that it can reach the vicinity of the piston reliably, and the upper part of the fan fuel spray can only fly a short distance with weak penetrating forces. However, although it reaches the vicinity of the cylinder bore, collision with the cylinder bore is suppressed. Thus, the injected fuel can be spread over the entire large cylinder space in the latter half of the intake stroke without diluting the engine oil, and a good homogeneous mixture can be formed.

  FIG. 1 is a schematic longitudinal sectional view in the latter half of an intake stroke of a cylinder injection type spark ignition internal combustion engine according to the present invention, and FIG. 2 is a plan view of the cylinder in FIG. In these drawings, reference numeral 1 denotes an ignition plug disposed substantially at the center of the upper part of the cylinder, and 2 denotes a fuel injection valve for injecting fuel directly from the periphery of the upper part of the cylinder into the cylinder. Reference numeral 3 denotes a piston. 4 is an intake port connected to the upper part of the cylinder, and 5 is an intake valve that opens and closes the opening of the intake port 4 in the cylinder. 6 is an exhaust port connected to the upper part of the cylinder. Reference numeral 7 denotes an exhaust valve that opens and closes the cylinder opening of the exhaust port 6. The fuel injection valve 2 is disposed on the intake port side where the temperature becomes relatively low due to the intake air flow in the cylinder in order to prevent fuel vapor.

  The fuel injection valve 2 has a slit-shaped injection hole, and mainly serves as a fan-shaped fuel spray extending in the width direction W. The center plane P in the thickness direction T of the fan-shaped fuel spray is substantially parallel to the cylinder center axis C. It is injected so that As shown in FIG. 2, the fan-shaped fuel spray may spread slightly in the thickness direction T. Further, as shown in FIG. 3, the fuel injection valve 2 is configured such that a plurality of (for example, two) fan-shaped fuel sprays have center planes (P1 and P2) in the thickness direction substantially parallel to the cylinder center axis C. You may make it inject so that it may become.

  Further, as shown in FIG. 1, the fan-shaped fuel spray injected from the fuel injection valve 2 has an upper portion of the fan-shaped fuel spray near the cylinder head in the cylinder space and a fan-shaped fuel spray at the piston position in the latter half of the intake stroke. The lower part of is directed to the vicinity of the piston.

  The fan-shaped fuel spray has a greater penetration force than the conical fuel spray, and each part of the fan-shaped fuel spray can fly over a relatively long distance. Thereby, in the latter half of the intake stroke, the lower part (piston side) of the fan-shaped fuel spray reliably reaches the vicinity of the piston, and the injected fuel can be spread over the entire large cylinder space in the latter half of the intake stroke. In the subsequent compression stroke, it is possible to form a homogeneous mixture that is sufficiently homogenized. However, when a normal fan fuel spray is used, the distance from the nozzle hole of the fuel injection valve to the cylinder bore is relatively short in the vicinity of the cylinder head. A disaster strikes the cylinder bore. At this time, if fuel adheres to the cylinder bore, a problem of dilution of engine oil occurs.

  In this embodiment, in order to solve this problem, the penetration force at the upper part of the fan-shaped fuel spray injected from the fuel injection valve 2 is weakened as compared with the lower part. Thereby, even if the upper part of the fan-shaped fuel spray reaches the vicinity of the cylinder bore, the collision with the cylinder bore is suppressed. Thereby, it is possible to form a good homogeneous mixture without diluting the engine oil.

  Thus, in order to weaken the penetration force of the upper part of fan-shaped fuel spray, in this embodiment, the slit-shaped injection hole 21 of the fuel injection valve 2 is formed as shown in FIG. FIG. 4 is an enlarged cross-sectional view perpendicular to the thickness direction of the injection hole 21 in the vicinity of the injection hole of the fuel injection valve 2. In the figure, reference numeral 22 denotes a fuel reservoir in the fuel injection valve, and the nozzle hole 21 communicates with the fuel reservoir 22. As a result, when the valve body (not shown) is opened and high pressure fuel is supplied to the fuel reservoir 22, the high pressure fuel in the fuel reservoir 22 is injected through the injection hole 21. On the other hand, when the valve body is closed and the supply of the high-pressure fuel to the fuel reservoir 22 is stopped, the fuel pressure in the fuel reservoir 22 decreases, and the fuel injection through the nozzle hole 21 is stopped.

  In the present embodiment, the fuel reservoir 22 has a hemispherical tip, and is an injection having an upper wall 21a and a lower wall 21b that communicate with the tip and face each other at a predetermined fan angle in order to inject a fan-shaped fuel spray. A hole 21 is formed. Thereby, in each cross section perpendicular | vertical to the thickness direction of the nozzle hole 21, the boundary of the fuel reservoir 22 and the nozzle hole 21 becomes circular arc shape.

  In each of these cross sections, unlike the present embodiment, the intersection R of the extension line of the upper wall 21a and the extension line of the lower wall 21b of the nozzle hole 21 is the center Q of the boundary arc shape (the center in the thickness direction). In the cross section, if the arc-shaped center Q coincides with the hemispherical center of the tip of the fuel reservoir 22, the fuel flowing from the fuel reservoir 22 into the inner opening of the injection hole 21 is radially divided. In this case, since the fuel pressure in the fuel reservoir 22 acts radially around the arc-shaped center Q, each fuel part spreads in the width direction equally in the nozzle hole 21 and from the outer opening of the nozzle hole 21. Be injected. Thus, each fuel part forming the fan-shaped fuel spray has a relatively high penetration force, and the upper part of the fan-shaped fuel spray collides with the cylinder bore.

  In the present embodiment, in each cross section described above, the intersection R of the extension line of the upper wall 21a and the extension line of the lower wall 21b of the nozzle hole 21 is deviated from the arcuate center Q of the boundary. The extension line of the wall 21a is made longer than the extension line of the lower wall 21b to the intersection. By doing so, the intersection R is below the straight line passing through the arcuate center Q and the center in the width direction of the outer opening of the nozzle hole 21.

  As a result, in the same way as described above, each part of the fuel that has flowed from the fuel reservoir 22 into the inner opening of the injection hole 21 is expanded in the width direction by the fuel pressure acting radially around the arc-shaped center Q in the injection hole 21. As shown in FIG. 4, due to the deviation of the intersection point R described above, the closer to the lower wall 21b, the less it spreads in the width direction, and the closer to the upper wall 21a of the nozzle hole 21, the more in the width direction. It spreads greatly and will be injected from the outer side opening of the nozzle hole 21. Thus, the penetration force of the fuel portion forming the upper part of the fan-shaped fuel spray is weakened, and only a short distance flight is possible, and the collision with the cylinder bore is suppressed. On the other hand, the penetrating force of the fuel portion forming the lower part of the fan-shaped fuel spray is strengthened, and it is possible to fly over a long distance and reliably reach the vicinity of the piston in the latter half of the intake stroke.

  In order to weaken the penetration force of the upper part of the fan-shaped fuel spray and to increase the penetration force of the lower part of the fan-shaped fuel spray with respect to the penetration force of each part of the fan-shaped fuel spray made uniform as in the prior art, the injection hole 21 An extension line of the upper wall intersects the straight line passing through the arc-shaped center Q and the center in the width direction of the outer opening of the nozzle hole 21 on the nozzle hole side with respect to the arc-shaped center Q. The extension line of the lower wall may intersect the straight line passing through the arc-shaped center Q and the center in the width direction of the outer opening of the injection hole 21 on the side opposite to the injection hole (valve element side) from the arc-shaped center Q. . Of course, also in this case, the extension line of the upper wall 21a to the mutual intersection becomes longer than the extension line of the lower wall 21b to the mutual intersection.

  By the way, it is possible to form the above-mentioned fan-shaped fuel spray not by the slit-shaped nozzle holes but by a large number of small-diameter nozzle holes arranged in the vertical direction as shown in FIGS. 5 and 6, the large number of small-diameter injection holes are preferably formed radially from the center of the hemispherical tip of the fuel reservoir. Even in this case, it is necessary to weaken the penetrating force in the upper part of the fan-shaped fuel spray.

  In the fuel injection valve 2 'shown in FIG. 5, the hole diameter of the upper first small-diameter nozzle hole group A forming the upper part of the fan-shaped fuel spray is set to the lower second small-diameter nozzle hole group B forming the lower part of the fan-shaped fuel spray. It is smaller than the hole diameter. Thereby, the flow rate of the fuel injected from the entire first small-diameter nozzle hole group A becomes smaller than the flow rate of the fuel injected from the entire second small-diameter nozzle hole group B, and the penetration force in the upper part of the fan-shaped fuel spray can be weakened. it can.

  In addition, in the fuel injection valve 2 ″ shown in FIG. 6, the number of holes in the upper first small-diameter nozzle hole group C forming the upper part of the fan-shaped fuel spray is set to the lower second small-diameter nozzle hole forming the lower part of the fan-shaped fuel spray. The number of holes is smaller than that of the group D. Thereby, the flow rate of the fuel injected from the entire first small-diameter nozzle hole group C is smaller than the flow rate of the fuel injected from the entire second small-diameter nozzle hole group D. The penetration force in the upper part of the fuel spray can be weakened, and the injection holes of the second small diameter injection hole group D are formed more densely than the injection holes of the first small diameter injection hole group C. Each fuel spray injected from each nozzle hole of the second small-diameter nozzle hole group D is likely to interfere with each other and easily form a lump. When the lump becomes a lump, the penetration force increases. It is possible to reliably reach the vicinity.

  The in-cylinder injection spark ignition internal combustion engine of the present embodiment performs homogeneous combustion by intake stroke fuel injection, but injects fuel in the latter half of the compression stroke when the engine has a low fuel injection amount and a low load. Stratified combustion in which a combustible air-fuel mixture is formed only near the spark plug is also possible.

It is a schematic longitudinal cross-sectional view in the second half of the intake stroke showing an embodiment of a direct injection spark ignition internal combustion engine according to the present invention. FIG. 2 is a plan view in a cylinder of the cylinder injection type spark ignition internal combustion engine of FIG. 1. FIG. 2 is another in-cylinder plan view of the in-cylinder injection spark ignition internal combustion engine of FIG. 1. It is an expanded sectional view perpendicular to the thickness direction of the nozzle hole in the vicinity of the nozzle hole of the fuel injection valve. It is a front view of another fuel injection valve. It is a front view of another fuel injection valve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Spark plug 2, 2 ', 2 "... Fuel injection valve 3 ... Piston 21 ... Injection hole 22 ... Fuel reservoir

Claims (3)

  In a cylinder injection spark ignition internal combustion engine in which fuel is injected by a fuel injection valve arranged around the upper part of the cylinder to form a homogeneous mixture, the fuel injection valve mainly produces a fan-shaped fuel spray spreading in the width direction. The fan-shaped fuel spray is injected into the entire cylinder in the latter half of the intake stroke so that the thickness-direction center plane is substantially parallel to the cylinder center axis, and the upper portion of the fan-shaped fuel spray is lower than the lower portion of the fan-shaped fuel spray. An in-cylinder injection spark ignition internal combustion engine characterized in that the penetration force is weakened.   The fuel injection valve includes a slit-shaped injection hole having an upper wall and a lower wall facing each other at a predetermined fan angle for injecting the fan-shaped fuel spray, and the injection hole is a fuel reservoir in the fuel injection valve. In each cross section perpendicular to the thickness direction of the nozzle hole, the boundary between the fuel reservoir and the nozzle hole has an arc shape, and the upper wall and the lower wall are extended in each cross section. The intersection of the lines is biased with respect to the center of the arc shape in each cross section, and the extension line of the upper wall to the intersection is longer than the extension line of the lower wall to the intersection. The in-cylinder injection spark ignition internal combustion engine according to claim 1.   The fuel injection valve includes a large number of small diameter nozzle holes arranged in the vertical direction to inject the fan-shaped fuel spray, and the hole diameter of the upper small diameter nozzle hole group is smaller than the hole diameter of the lower small diameter nozzle hole group. The in-cylinder injection spark ignition internal combustion engine according to claim 1, wherein the number of holes in the upper small-diameter hole group is smaller than the number of holes in the lower small-diameter hole group.

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