JP6214255B2 - Injector - Google Patents

Description

  The present invention relates to a porous (multi-hole) injector provided in a spark-ignition direct injection engine, and particularly relates to a fuel injector that suppresses fuel cylinder wall surface adhesion and ensures combustion stability during stratified combustion with a simple configuration.

In recent years, direct-injection (in-cylinder injection) engines that inject fuel directly into a combustion chamber (inside a cylinder cylinder) have become widespread also in spark ignition engines such as gasoline engines.
By direct injection in this way, the knocking resistance is improved by cooling fresh air with the latent heat of vaporization of the fuel, the output is improved by improving the charging efficiency, and the spark plug is at the time of fast idling after cold start. There is an advantage that combustion stability can be improved by forming a rich air-fuel mixture around the stratified charge and performing stratified charge combustion.

As a conventional technique related to such an injector, for example, Patent Documents 1 and 2 disclose a multi-hole including a main injection hole directed to a spark plug and a sub injection hole that is injected around the spray injected from the main injection hole. In the injector, it is described that the diameter and shape of the injection hole are set so that the penetration (penetration force) of the spray injected from the sub injection hole becomes smaller than the penetration of the spray injected from the main injection hole. .
Further, Patent Document 3 describes that a single spray lump is formed by causing a plurality of sprays sprayed from nozzle holes other than those directed to the spark plug to interfere with each other.
Patent Document 4 describes that the penetration force is set to increase as the opening angle between adjacent spray axes of spray sprayed diffused radially from the nozzle hole is smaller.

JP 2007-291934 A JP 2007-315276 A JP 2007-278233 A JP 2007-292035 A

In a multi-hole injector for a direct-injection gasoline engine, if the piston is injected at a time near the bottom dead center after warming up to produce a substantially uniform mixture, the occurrence of smoke A spray arrangement that avoids the piston crown and combustion chamber with high sensitivity is set.
However, in this case, since the axis of each spray is directed toward the inner surface of the cylinder sleeve, fuel adhesion to the cylinder increases, and dilution of lubricating oil due to inflow of fuel into the crank chamber side is a problem. Become.
In order to suppress such fuel adhesion to the cylinder wall surface, it is effective to reduce the penetration of the spray. However, if all the penetrations of the spray are reduced, immediately after the engine cold start, It becomes difficult to form a rich air-fuel mixture for stratified combustion.
Also, as a technique for varying the penetration of the spray, for example, as described in Patent Documents 1 and 2, when the diameter and the shape are different between the nozzle holes, the processing at the time of manufacturing the nozzle becomes complicated.
In view of the above-described problems, an object of the present invention is to provide an injector that suppresses fuel cylinder wall surface adhesion and ensures combustion stability during stratified combustion with a simple configuration.

The present invention solves the above-described problems by the following means.
The invention according to claim 1 is an injector for injecting fuel into a combustion chamber of a spark ignition engine, and the spark ignition engine has a cavity for performing stratified combustion on a crown surface of a piston, The injector includes a first spray including a plurality of sprays including the injector and a spark plug and injected along a plane along a central axis direction of the cylinder and injected toward the cavity during the stratified combustion. Forming a second spray group to be sprayed in a region separated from the first spray group, and the Coanda effect generated between a plurality of sprays constituting the second spray group. The penetration of the second spray group is changed to the penetration of the first spray group by strengthening against the Coanda effect occurring between the plurality of sprays constituting the group. A injector, characterized in that reduced by.
In the invention according to claim 2, the first spray group includes a first spray and a second spray that is injected toward the bottom dead center side of the piston from the first spray. The injector according to claim 1.
The Coanda effect is an effect in which adjacent jets interfere with each other due to the property of the jets encircling the surrounding fluid and entrain each other.
According to this, by strengthening the Coanda effect acting between the sprays constituting the second spray group, the penetration of the second spray group is reduced and the fuel reaching the cylinder wall surface is reduced, thereby forming a uniform mixture The cylinder wall surface adhesion of the fuel at the time can be suppressed.
In addition, it has been found that the particle size of the fuel spray is also refined by such a Coanda effect, which has an effect of improving combustion and suppressing the generation of smoke.
On the other hand, the first spray group has a stronger penetration than the second spray group, so that the performance of generating a locally rich mixture around the spark plug immediately after the warm-up is not affected and is stable. Stratified combustion can be performed.

  As described above, according to the present invention, it is possible to provide an injector that suppresses the adhesion of fuel to the cylinder wall surface and ensures the combustion stability during stratified combustion with a simple configuration.

It is a figure which shows typically an example of the fuel spray state after the warming-up in the engine which has the Example of the injector to which this invention is applied. It is a figure which shows typically an example of the fuel spray state immediately after the cold start in the engine which has the injector of an Example. It is a figure which shows typically an example of the fuel spray state after warming-up in the engine which has the injector of the comparative example of this invention.

  The present invention aims to provide an injector that suppresses fuel cylinder wall surface adhesion and ensures combustion stability during stratified combustion with a simple configuration, with respect to the first spray group for performing stratified combustion during fast idle. Then, in the second spray group around it, the axis line between the sprays was brought close to each other, and the penetration was lowered by the Coanda effect.

Embodiments of an injector to which the present invention is applied will be described below.
The injector according to the embodiment injects fuel into a combustion chamber (inside a cylinder cylinder) of a gasoline direct injection reciprocating engine mounted as a driving power source in an automobile such as a passenger car.
The injector injects gasoline pressurized by a fuel pump (not shown) and stored in an accumulator chamber at a predetermined timing over a predetermined injection time by a needle valve driven by an actuator such as a piezo type.
The injector is a multi-hole (porous) injector in which a plurality of (for example, six) nozzle holes each forming a beam-like spray are formed.

In the embodiment, after completion of warming up of the engine (when warm), the injector injects fuel when the piston is near the suction bottom dead center, and forms a substantially uniform mixture throughout the combustion chamber. To do.
FIG. 1 is a diagram schematically illustrating an example of a fuel spray state after warming-up in an engine having an injector according to an embodiment.
1A is a cross-sectional view taken along a plane that includes an injector and a spark plug and is parallel to the cylinder center axis, and FIG. 1B is a view taken along the line bb in FIG. 1A. It is sectional drawing (same in FIG. 2, FIG. 3).

The engine includes a cylinder 10, a piston 20, a combustion chamber 30, a spark plug 40, an injector 50, and the like.
The cylinder 10 has a sleeve formed in a cylindrical shape.
The piston 20 is inserted on the inner diameter side of the cylinder 10 and reciprocates in the direction of the central axis of the cylinder 10 in conjunction with rotation of a crankshaft (not shown) via a connecting rod.
A cavity 22 is formed in the crown surface 21 where the piston 20 faces the combustion chamber 30.
The cavity 22 is a dish-shaped recess formed offset to the injector 50 side with respect to the center of the crown surface 21.
The cavity 22 has the effect of collecting the rich air-fuel mixture in the vicinity of the spark plug 40 by inverting the fuel injected from the injector 50 toward the combustion chamber 30 during fast idle (warm-up operation after cold start).

The combustion chamber 30 is a recess formed in the cylinder head that substantially closes one end opening of the cylinder 10, and is disposed facing the crown surface 21 of the piston 20.
As an example, the combustion chamber 30 is formed in a pent roof type, and is connected to an intake port and an exhaust port (not shown). Each port is provided with an intake valve and an exhaust valve that open and close them at a predetermined valve timing.

The spark plug 40 ignites the air-fuel mixture at a predetermined ignition timing by generating a spark.
The spark plug 40 has an electrode portion for generating sparks disposed at the center of the combustion chamber 30 (the top of the pent roof).

The injector 50 is inserted and fixed through a mounting hole formed in the cylinder head so that the nozzle portion is exposed in the combustion chamber 30.
The nozzle portion of the injector 50 is disposed close to one end portion (a portion adjacent to the end portion of the cylinder 10) of the combustion chamber 30, and from here, the fuel of the cylinder 10 is injected so as to inject the fuel toward the center portion side of the cylinder 10. They are arranged so as to be inclined with respect to the central axis direction and the radial direction, respectively.

As shown in FIG. 1, the injector 50 forms a first spray group 100 and a second spray group 200.
The first spray group 100 is injected along a plane (substantially the same as the paper surface of FIG. 1A) that includes the electrode portion of the spark plug 40 and the nozzle portion of the injector 50 and includes the central axis of the cylinder 10. Sprays 110, 120.
The spray 110 is spray sprayed in a direction that opens toward the cylinder head (upward in FIG. 1) with respect to the spray 120 in accordance with the separation from the nozzle after injection.
The spray 110 is injected in the vicinity of the end of the cylinder 10 on the combustion chamber 30 side.
The spray 120 is injected toward the inner surface of the cylinder 10 on the combustion chamber 30 side slightly from the crown surface 21 of the piston 20 when it is in the vicinity of the bottom dead center.

The second spray group 200 has sprays 210 and 220 that are sprayed in a direction separated from the first spray group 100 in the normal direction of the plane described above.
A pair of the second spray group 200 is formed substantially symmetrically with the first spray group 100 interposed therebetween.
The spray 210 is injected toward the vicinity of the outer peripheral edge of the crown surface 21 of the piston 20 when it is in the vicinity of the bottom dead center.
The spray 220 is sprayed between the spray 210 and the spray 110 of the first spray group 100 and with the spray axis closer to the spray 210 side than the middle thereof.
In the present specification, claims, etc., the “injection axis” refers to the central axis of the spray along the spray traveling direction.
Such an arrangement of the injection axes is such that the relative angle in the injection direction of the injection holes forming the sprays 210 and 220 in the injector 50 is made relatively close (opening is made small), and the positions of the injection holes are made close. Or both.

  Here, among the above-described sprays 110, 120, 210, and 220, the spray 210 and the spray 220 are close to the injection axis and the relative angle formed by the injection axis is small with respect to any other combination of sprays. It is arranged to be.

In addition, the injector 50 according to the embodiment has a crown surface 21 of the piston 20 at a later stage of the compression stroke (for example, about 40 ° before top dead center as a crank angle) during warm-up operation (fast idle) immediately after the cold start of the engine. In this way, a locally rich mixture is formed around the spark plug 40.
FIG. 2 is a diagram schematically illustrating an example of a fuel spray state immediately after a cold start in an engine having the injector of the embodiment.
At the time of fast idle shown in FIG. 2, the sprays 110 and 120 of the first spray group 100 are injected toward the area around the cavity 22 in the crown surface 21 of the piston 20, and the sprays 110 and 120 are injected into the cavity 22 and the like. , And is wound up toward the combustion chamber 30 to form a locally rich air-fuel mixture around the spark plug 40.
Thus, even when it is cold, the air-fuel mixture can be reliably ignited to stabilize the combustion.

Next, the effect of the above-described embodiment will be described in comparison with a comparative example of the present invention described below.
In the description of the comparative example, portions that are substantially the same as those in the above-described embodiment are denoted by the same reference numerals, description thereof is omitted, and differences are mainly described.
FIG. 3 is a diagram schematically illustrating an example of a fuel spray state after warm-up in an engine having an injector of a comparative example.
In the comparative example, the spray 220 is disposed at a substantially intermediate position between the spray 210 and the spray 110.
As a result, the spray 210 and the spray 220 are arranged such that the spray axes are relatively spaced from each other as compared with the case of the embodiment.

In the comparative example, the sprays 210 and 220 of the second spray group 200 have a relatively strong penetration (penetration force) because the influence of the Coanda effect is small, and cross the inside of the cylinder 10 on the side opposite to the injector 50. It reaches the inner surface of the cylinder 10.
As a result, liquid fuel adheres to the wall surface of the cylinder 10 and a part of the fuel flows out to the crank chamber side, causing dilution of the lubricating oil.
Moreover, the control accuracy of the air-fuel ratio also decreases due to such fuel wall adhesion.

On the other hand, according to the embodiment, by arranging the spray axes of the sprays 210 and 220 included in the second spray group 200 close to each other, adjacent jets interfere with each other between the sprays 210 and 220. As a result, a kind of Coanda effect is generated.
Accordingly, the penetration of the sprays 210 and 220 of the second spray group 200 is reduced, the fuel reaching the wall surface of the cylinder 10 is reduced, and the fuel wall surface adhesion is suppressed.
Further, at this time, due to the mutual interference between the sprays, the particle size of the fuel droplets contained in the sprays 210 and 220 is reduced, so that the combustion can be improved and the occurrence of smoke can be suppressed.
On the other hand, since the first spray group 100 has substantially the same penetration as that of the comparative example, the mixture formation performance at the time of stratified combustion at the time of fast idle as shown in FIG. 2 is affected. Absent.
As described above, according to the present embodiment, it is possible to provide an injector that suppresses fuel cylinder wall surface adhesion and ensures combustion stability during stratified combustion with a simple configuration.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and changes are possible, and these are also within the technical scope of the present invention.
(1) The shape, structure, arrangement, and the like of each component constituting the injector and the engine are not limited to the above-described embodiments, and can be changed as appropriate. Further, the arrangement and number of sprays formed by the injector are not particularly limited.
(2) Although the engine of the embodiment was a gasoline engine as an example, the present invention is applicable to an engine using other fuels as long as it is a reciprocating engine that forms a mixture using liquid fuel and sparks ignition. Is possible.

DESCRIPTION OF SYMBOLS 10 Cylinder 20 Piston 21 Crown surface 22 Cavity 30 Combustion chamber 40 Spark plug 50 Injector 100 1st spray group 110,120 Spray 200 2nd spray group 210,220 Spray

Claims (2)

An injector for injecting fuel into a combustion chamber of a spark ignition engine,
The spark-ignition engine has a cavity for stratified combustion at the crown of the piston,
The injector includes a first spray including a plurality of sprays including the injector and a spark plug and injected along a plane along a central axis direction of the cylinder and injected toward the cavity during the stratified combustion. Forming a group and a second spray group injected into a region spaced from the first spray group;
Penetration of the second spray group by strengthening the Coanda effect occurring between the plurality of sprays constituting the second spray group against the Coanda effect occurring between the plurality of sprays constituting the first spray group. The injector is reduced with respect to the penetration of the first spray group.   The first spray group includes a first spray and a second spray that is injected toward the bottom dead center side of the piston with respect to the first spray.
  The injector according to claim 1.

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