JP2007315276A - Multi-hole type injector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly disperse fuel density of a spray injected from a main nozzle port, while securing spray achieving force of the main nozzle port, for enhancing stability of ignition and combustion in a low speed-low load area, in a spark ignition type cylinder direct injection engine having a spark plug arranged in a combustion chamber and a multi-hole injector for injecting fuel into the combustion chamber. <P>SOLUTION: This multi-hole type injector 1 has the main nozzle port 10 having the injection center pointing to the spark plug 2, and a sub-nozzle port having the injection center pointing in the direction different from the injection center of the main nozzle port. While setting spray achieving force of the sub-nozzle port so as to reduce more than the spray achieving force of the main nozzle port 10, in the cross-sectional area of the main nozzle port 10, an inner diameter of an outlet part 12 is set larger than an inner diameter of an inlet part 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a multi-hole injector suitable for a spark ignition in-cylinder direct injection engine.

  Conventionally, in order to improve fuel efficiency, a spark ignition type cylinder having an ignition plug disposed in a combustion chamber and a multi-hole type injector for injecting fuel into the combustion chamber and stratifying fuel around the ignition plug An internal direct injection engine is known.

  In such an engine, a multi-hole type injector having a main injection hole whose injection center is directed to the ignition plug and a sub injection hole whose injection center is directed in a direction different from the injection center of the main injection hole is used. In the low-speed and low-load region, fuel is injected near the compression top dead center in order to burn the air-fuel mixture in a layered manner around the spark plug. In the middle of the intake stroke, fuel is injected to generate and burn.

Japanese Patent Application Laid-Open No. 2004-228561 discloses a technique in which the fuel injection direction from the same nozzle hole can be changed by changing the flow velocity of the fuel flowing through the nozzle hole.
JP 2005-023846 A

  In a spark-ignition in-cylinder direct injection engine, when the bore diameter is large, the distance between the spark plug and the injector is long, and it is required to increase the spray penetration force of the main injection hole. However, when the fuel injection force is increased, not only the spray penetration force of the main injection hole, but also the spray penetration force of the sub injection hole is strengthened, so that the injection fuel from the sub injection hole is near the compression top dead center in the low speed and low load range. It tends to adhere to the piston crown surface and bore wall, and causes smoke and HC. Therefore, the spray penetration force of the sub nozzle hole is set smaller than the spray penetration force of the main nozzle hole. In other words, it is conceivable that only the spray penetration force of the main nozzle hole is set large, but the spray injected from the main nozzle hole stays around the spark plug, the fuel density of the spray becomes high, and the air-fuel ratio around the spark plug Becomes overrich, the stability of ignition and combustion is impaired, and HC tends to increase.

  The present invention has been made paying attention to such a problem, and in a spark-ignition in-cylinder direct injection engine, in order to improve the stability of ignition and combustion in a low-speed and low-load region, the spray penetration force of the main injection hole It is an object of the present invention to provide a multi-hole type injector capable of appropriately dispersing the fuel density of the spray injected from the main injection hole while ensuring the above.

  The present invention relates to a spark ignition type in-cylinder direct injection engine having an ignition plug disposed in a combustion chamber and a multi-hole injector for injecting fuel into the combustion chamber. The multi-hole injector has an injection center at the injection center. And a secondary injection hole whose injection center is oriented in a direction different from that of the main injection hole, and the cross-sectional area of the main injection hole is the inner diameter of the outlet part. It is characterized by being set larger than the above.

  In this invention, the jet of fuel flowing through the main nozzle hole flows along the inner surface of the main nozzle hole in the low speed and low load region, the inner diameter is larger than the inlet part, and the sectional area of the jet is expanded by the outlet part. Increases the injection angle. For this reason, for the main nozzle hole, if the inner diameter of the outlet part is set large without changing the inner diameter of the inlet part (the diameter of the nozzle hole), the injection amount remains constant, so without changing the overall air-fuel ratio, By widening the injection angle, the fuel density of the spray is moderately dispersed, and an air-fuel ratio air-fuel mixture suitable for ignition can be generated around the spark plug.

  Embodiments of the present invention will be described with reference to the accompanying drawings.

  In FIG. 1, reference numeral 3 denotes an engine combustion chamber, which is defined by a cylinder block 21, a cylinder head 22, and a piston 30. 41 is an intake valve that opens and closes the opening on the combustion chamber 3 side of the intake port 31 in conjunction with the piston 30, and 42 is an exhaust that opens and closes the opening on the combustion chamber 3 side of the exhaust port 32 in conjunction with the piston 30. 1 is a multi-hole type injector disposed at the side of the combustion chamber 3.

  In the illustrated case, the injector 1 is assembled to the cylinder head 22 with its tip end facing the peripheral edge of the combustion chamber 3, and a main injection hole and a plurality of sub injection holes are provided at the front end part 1a. In FIG. 1, F <b> 1 is spray sprayed from the main nozzle hole, F <b> 2 to F <b> 4 are spray sprayed from each sub nozzle hole, and the axis of the main nozzle hole is directed to the electrode of the spark plug 2. The axis of each sub nozzle hole is set so as to be directed in a direction different from the axis of the main nozzle hole. In the illustrated case, the axis of each sub injection hole is directed downward (piston side) in different angular directions with respect to the axis of the main injection hole.

  In the low-speed and low-load region, the injector 1 injects fuel from each injection hole of the tip 1a in the vicinity of the compression top dead center so that the air-fuel mixture is burnt in a layered manner around the spark plug 2. When the rotation and load increase, fuel is injected from each nozzle hole in the tip portion 1a in the middle of the intake stroke so as to generate a uniform air-fuel mixture in the fuel chamber 3 and burn it.

  In the vicinity of the compression top dead center in the low speed and low load region shown in FIG. 1, the spray F1 injected from the main injection hole has a length A1 that reaches the spark plug 3, and is supplied from the sub injection hole F2. ˜F4 are directed downward in different angular directions with respect to the spray F1 from the main nozzle hole, but all are suppressed to a length (A2, A3, A4) that does not reach the crown surface of the piston 30. Since the spray lengths A1 to A4 (spray penetration force) sprayed from the nozzle holes are substantially proportional to the effective length of each nozzle hole when the diameter of the nozzle hole is constant, the effective length of each nozzle hole is also A1> A2> A3> A4 is set to the same relationship.

  As a result, the spray penetration force of the sub injection hole is set to be smaller than the spray penetration force of the main injection hole, so that the fuel injected from the sub injection hole is near the compression top dead center in the low speed and low load region. It is possible to ensure the spray penetration force necessary for the main nozzle hole while preventing the piston 30 from adhering to the crown surface and the bore wall. When the spray penetration force increases, the fuel density of the spray tends to increase. For this reason, the main injection hole is configured so that the fuel density of the spray can be appropriately dispersed while ensuring the necessary spray penetration force.

  In the case of FIG. 2, the main injection hole 10 includes an inlet portion 11 and an outlet portion 12, and the inner diameter d1 of the outlet portion 12 is set larger than the inner diameter D of the inlet portion 11. The inlet portion 11 and the outlet portion 12 are coaxially formed in a flow path having constant inner diameters D and d1, and a step (difference in inner diameter) is set at the boundary between them.

  Since D <d1, the jet of fuel flowing through the main nozzle hole 10 flows along the inner surface of the main nozzle hole 10 in the low-speed and low-load region, and the inner diameter d1 is larger than the inner diameter D of the inlet portion 11 due to the outlet portion 12. The cross-sectional area of the jet is expanded, and the fuel injection angle is expanded. For this reason, if the inner diameter d1 of the outlet portion 12 is set larger than the inner diameter D of the inlet portion 11 without changing the inner diameter D of the inlet portion for the main injection hole 10, the injection amount remains constant, so By expanding the injection angle without changing the fuel ratio, the fuel density of the spray is moderately dispersed, and an air-fuel ratio air mass suitable for ignition and fuel can be generated around the spark plug 3.

  In the case of FIG. 3, the main injection hole 10 includes an inlet portion 11 and an outlet portion 12, and the inner diameter d <b> 2 of the outlet portion 12 is set larger than the inner diameter D of the inlet portion 11. The inlet portion 11 is formed in a flow path having a constant inner diameter D, and the outlet portion 12 is formed in a flow path whose inner diameter d2 is reduced in diameter toward the boundary (inner diameter D) with the inlet portion 11 with a taper angle a.

  The jet of fuel flowing through the main nozzle hole 10 flows along the inner surface of the main nozzle hole 10 in the low speed and low load region, and the outlet part 12 expands the inner diameter D from the inlet part 11 to the inner diameter d2 with a taper angle a. The cross-sectional area of the jet spreads smoothly, and the taper angle a makes the injection angle larger than in the case of FIG. 2, and the dispersion of the fuel density of the spray is also accelerated.

  In the case of FIG. 4, the main injection hole 10 includes an inlet portion 11 and an outlet portion 12, and the inner diameter d <b> 3 of the outlet portion 12 is set larger than the inner diameter D of the inlet portion 11. The inlet portion 11 is formed in a flow path having a constant inner diameter D, and the outlet portion 12 is formed in a flow path whose inner diameter d3 is reduced in diameter toward the boundary (inner diameter D) with the inlet portion 11 with a curvature R.

  The fuel jet flowing through the main nozzle hole 10 flows along the inner surface of the main nozzle hole 10 in the low speed and low load region, and the outlet part 12 expands the inner diameter D from the inlet part 11 to the inner diameter d3 with a curvature R. Compared with the case 3, the jet spreads smoothly and the injection angle becomes larger, and the fuel density dispersion of the spray can be accelerated.

  2 to 4, d <b> 1 to d <b> 3 are the inner diameters of the outlet portion located at a distance L from the inlet portion 11 with the inner diameter D, and the conventional spray angle (inner diameter D is a constant injection hole from the inlet to the outlet). If α and the spray angles in FIGS. 2 to 3 are α1, α2, and α3, respectively, there is a relationship of D <d1 <d2 <d3 and α <α1 <α2 <α3.

  5-8 represents another modification concerning the main injection hole 10, and the cross-sectional area of the outlet portion 12 is expanded in multiple stages toward the outside (outlet). The inlet 11 has a constant inner diameter D.

  In the case of FIG. 5, the outlet portion 12 is formed of a flow path portion 12a having a constant inner diameter ds and a flow path portion 12b that expands the inner diameter ds to the inner diameter dt of the outlet with a predetermined taper angle. In the case of FIG. 6, the outlet portion 12 is formed of a flow path portion 12 a having a constant inner diameter ds and a flow path portion 12 b that expands the inner diameter ds to the inner diameter dt of the outlet with a curvature R.

  In the case of FIG. 7, the outlet portion 12 is formed of a flow passage portion 12a that expands the inner diameter D of the inlet portion 11 to the outlet with a taper angle a1, and a flow passage portion 12b that further expands the inner diameter D with a taper angle a2. . In the case of FIG. 8, it is formed of a flow path portion 12 a that expands the inner diameter D of the inlet portion 11 to the outlet with a taper angle a, and a flow path portion 12 b that further expands the inner diameter D with a predetermined curvature R.

  5 to 8, since the cross-sectional area of the outlet portion 12 is expanded in a multistage manner toward the outside (outlet), the jet of fuel flowing through the outlet portion 12 is smoothly expanded without resistance, and the spray angle is efficiently increased. Can be enlarged.

  9 to 11 show another modification example related to the main injection hole 10, and the cross-sectional area of the outlet portion 12 is enlarged to a flat shape. The inlet portion 11 is set to have a circular cross section with a constant inner diameter D.

  9A is a vertical (vertical) cross section of the main nozzle hole 10, FIG. 9B is a horizontal (horizontal) cross section of the main nozzle hole 10, and the outlet 12 has a constant cross-sectional area. The cross-sectional shape (the cross-sectional shape orthogonal to the axis of the injection hole 10) is an elliptical shape having a long axis dh and a short axis dr.

  10, (a) is a vertical (vertical) cross section of the main nozzle hole 10, (b) is a horizontal (horizontal) cross section of the main nozzle hole 10, and the outlet portion 12 has a cross-sectional area extending vertically and horizontally outward. By enlarging with different angles av and ah, an elliptical cross-sectional shape is formed.

  In FIG. 11, (a) is a view of the main nozzle hole as viewed from the outside in the axial direction, (b) is an xx sectional view in (a), and (c) is also a yy sectional view. FIG. The exit part 12 is expanded to the exit with a taper angle ah in the cross-sectional area only in the lateral direction. That is, the outlet portion 12 is set to have an elliptical cross-sectional shape that extends flat in the lateral direction.

  9 to 11, by setting the cross-sectional area of the outlet portion 12 to a shape that flattenes in the horizontal direction, the cross-sectional area of the jet flowing through the main nozzle hole 10 is expanded from a circular shape to an elliptical shape, and the spray is also horizontal. Since it expands flatly, it leads to improved robustness when the injector 1 is attached, and the fuel density of the spray is moderately dispersed, so that it is possible to effectively prevent the fuel from adhering to the electrode of the spark plug 2 is there.

  About the nozzle hole shape of illustration (FIGS. 2-11), the application to a sub nozzle hole is also considered from not only the main nozzle hole but aiming at expansion of a spray angle.

It is a schematic block diagram of a spark ignition direct injection engine. It is sectional drawing which illustrates the structure of a main nozzle hole. It is sectional drawing which illustrates the structure of a main nozzle hole. It is sectional drawing which illustrates the structure of a main nozzle hole. It is sectional drawing which illustrates the structure of a main nozzle hole. It is sectional drawing which illustrates the structure of a main nozzle hole. It is sectional drawing which illustrates the structure of a main nozzle hole. It is sectional drawing which illustrates the structure of a main nozzle hole. It is sectional drawing which illustrates the structure of a main nozzle hole. It is sectional drawing which illustrates the structure of a main nozzle hole. It is explanatory drawing which illustrates the structure of a main nozzle hole.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Multi-hole type injector 2 Spark plug 3 Combustion chamber 10 Main injection hole 11 Entrance part of main injection hole 12 Outlet part of main injection hole 20 Engine F1 Spray from main injection hole F2-F4 Spray from sub injection hole

Claims (6)

  In a spark ignition in-cylinder direct injection engine having an ignition plug disposed in a combustion chamber and a multi-hole injector for injecting fuel into the combustion chamber, the multi-hole injector has a main injection hole whose injection center is directed to the ignition plug And a secondary injection hole whose injection center is oriented in a direction different from the injection center of the main injection hole, and the cross-sectional area of the main injection hole is set such that the inner diameter of the outlet part is larger than the inner diameter of the inlet part A multi-hole injector characterized by   2. The multi-hole injector according to claim 1, wherein a cross-sectional area of the main injection hole is set so as to expand to a flat shape toward the outside.   The multi-hole injector according to claim 1, wherein a cross-sectional area of the main injection hole is set to expand in a multistage manner toward the outside.   2. The multi-hole injector according to claim 1, wherein a cross-sectional area of the main injection hole is set so as to expand in a tapered shape toward the outside.   The multi-hole injector according to claim 1, wherein a cross-sectional area of the main injection hole is set so as to expand in a curved shape toward the outside.   2. The multi-hole injector according to claim 1, wherein a cross-sectional area of the main injection hole is set so as to expand stepwise toward the outside.

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