JPH0623540B2 - Pentorf type direct injection internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pentroof type direct injection internal combustion engine for directly injecting fuel into a pentroof-shaped combustion chamber, and more particularly to a pit roof-shaped combustion chamber which is recessed in the crown surface of the piston. The present invention relates to a pent roof type direct injection internal combustion engine capable of generating a uniform air-fuel mixture in a cavity to be formed.

[Prior Art] Generally, in an internal combustion engine, the diameter of intake / exhaust valves is increased, or the number of intake / exhaust valves per cylinder is increased to increase the cross-sectional area of the intake / exhaust ports. The intake / exhaust efficiency can be improved by increasing.

However, when the flow passage cross-sectional area of the intake / exhaust port is increased in this way, the intake / exhaust valves are forced to incline their valve shafts in a V-shape in order to avoid their interference. Then, due to the arrangement of the valve mechanism, the combustion chamber formed on the lower surface of the cylinder head has a central portion that is recessed upward along the axis of the crankshaft and is gradually inclined on both sides to be substantially perpendicular to the valve axis. It becomes necessary to make a pent roof shape (roof shape) that is formed so that when a pent roof type combustion chamber is adopted for a direct injection internal combustion engine such as a direct injection diesel engine, a high compression ratio of 18 to 20 is obtained. In order to ensure the above, as shown in "Combustion chamber structure of diesel engine" proposed in Japanese Utility Model Application No. 60-143456, the crown of the piston is inevitably upwards corresponding to the shape of the lower surface of the cylinder head. You will have to make it into a pent roof shape that protrudes to the outside.

[Problems to be Solved by the Invention] In the case of a direct-injection internal combustion engine, a cavity for forming a substantial combustion chamber is provided in the center of the piston crown surface. As shown in FIG. 11, the cavity b has a circular cross section and its circumferential wall surface c.
The bottom portion d of the lower end of the is parallel to the piston ring groove e (t
= Constant). Therefore, when the inner peripheral wall surface c of the cavity b is developed, it is as shown in FIG. 12, and the upper end edge f of the opening of the cavity b is continuously raised along the circumferential direction with respect to the flat bottom level. Hb is changing. Therefore, two vertical planes a and b forming θ = 45 ° with respect to the vertical plane c along the ridge direction (axial direction of the piston pin hole g) of the pent roof are used to form A, B, and
When divided into four areas C and D, the volume V of these is V _A =
V _C > V _B = V _D , which were different from each other. On the other hand, from the injection nozzle e disposed above the center position of the cavity b, the inner peripheral wall surface c in each of the areas A, B, C, D
The same amount of fuel was injected into the F _A , F _B , F _C , and F _D positions at 90 ° phase angles in the horizontal plane. Therefore, the fuel spray F injected from the injection nozzle e
Is swirled by the swirl S and swirls in the cavity b,
A rich air-fuel mixture is generated in the areas B and D where the height of the inner wall surface c of the cavity is low and the volume is small, while a lean air-fuel mixture is generated in areas A and C of which the inner wall surface c of the cavity is high and the volume is large. Was generated, and a partially nonuniform air-fuel mixture was generated in the entire cavity b. As a result, sufficient air utilization could not be measured, a large amount of smoke was generated, and sufficient output could not be obtained.

The present invention has been made in view of the above problems, and an object thereof is to be able to generate a uniform air-fuel mixture in the entire cavity, thereby increasing the air utilization rate and reducing the amount of smoke generated. An object of the present invention is to provide a pent roof type direct injection internal combustion engine that can obtain a sufficient output.

[Means for Solving the Problems] In order to achieve the above object, the present invention is configured such that a cavity is formed by denting a crown surface of a pentroof type piston in a central portion thereof in a cylindrical shape having a bottom along the axial direction of the piston. In the pent roof type direct injection internal combustion engine in which the inside of the cavity is
It is divided into four areas in the circumferential direction by two imaginary vertical planes that pass through the axial center line of the cavity and along the ridge direction of the piston crown surface, and two imaginary vertical planes each forming 45 °, and above the approximate center of the cavity. An injection nozzle having a plurality of injection ports facing each area and injecting an amount of fuel corresponding to the volume of each area is arranged.

[Operation] With the above configuration, the air-fuel mixture having a substantially uniform concentration is dispersed and distributed throughout the cavity. Therefore, the air utilization rate will increase, and the HC and smoke emissions will decrease,
The output increases.

[Embodiment] A preferred embodiment of a pentroof type direct injection internal combustion engine according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a side sectional view showing an essential part of a pentroof type piston used in a pentroof type direct injection internal combustion engine of the present invention, FIG. 2 is a plan view of the piston crown surface, and FIG. 3 is a pent roof of the present invention. It is a partial side sectional view of a direct injection type internal combustion engine.

As shown in FIG. 3, a pent roof type direct injection internal combustion engine 1
Is arranged such that the intake valve 2 and the exhaust valve 3 have their valve axes inclined in a V shape with respect to each other, and the combustion chamber on the cylinder head side formed on the lower surface of the cylinder head 4 is the axial line of the crankshaft. The central portion is recessed to the uppermost side along (that is, the axis of the piston pin 5), and both side portions thereof are gradually inclined and formed in a pent roof shape so as to be substantially perpendicular to the valve axis.

Further, as shown in FIG. 3 and FIG. 1, the piston 6 corresponds to the shape of the combustion chamber on the cylinder head 4 side, and the piston crown surface 7 immediately above the piston pin 5 has an axial direction of the piston pin 5. Along with the cylinder head 4 at the end of the compression stroke (that is, at the top dead center position) at the center of the piston crown 7 at the end of the compression stroke. The cavity 8 which forms a substantial combustion chamber by means of and is recessed. In the present embodiment, the cavity 8 has a circular cross section like the conventional one and its bottom portion 8a is formed in parallel (t = constant) to the piston ring groove 10, and the upper edge portion 9 of the opening of the cavity 8 is formed. The height h ₉ is continuously changing on the circumferential side with respect to the piston ring groove 10. In other words, the level at the position directly above the piston pin 5 is the highest, and the level at the 90 ° positions on both sides is the lowest.

By the way, according to the present invention, the inside of the cavity 8 is divided into a plurality of areas along the circumferential side thereof, and the injection nozzle 11 attached to the cylinder head 4 is disposed above the substantially central portion of the cavity 8 and the injection nozzle 11 is provided. A plurality of nozzles 12 are formed at the tip of the nozzle 11 so as to face the above areas and spray a quantity of fuel corresponding to the volume of each area.

That is, in the illustrated example, as shown in FIG. 2, the inside of the cavity 8 is a vertical plane along the ridge direction of the pent roof type piston crown surface 7, that is, a vertical plane (virtual vertical plane) c passing through the axis of the piston pin 5. Are divided into four areas A, B, C, and D by two vertical planes (virtual vertical planes) a and b forming θ = 45 °. The volume is V _A = V _C > V _B = V _D. On the other hand, as shown in the bottom view of the injection nozzle in FIG. 4 and the development view of the cavity inner peripheral wall surface in FIG. 5, the injection port 12 opened at the tip of the injection nozzle 11 is in each of the above areas A, B, C, D. Toward the inner wall surface 13 of the inner cavity,
Phases of a predetermined angle α (α <45 ° as shown in FIG. 4) are provided in the horizontal direction in the downstream direction from b to the swirl S, and circular openings are formed at an angle of 90 ° to each other. At the same time, the fuel spray F from each injection port 12 is directed so as to be injected obliquely downward, and each area A,
Each of the nozzles 12a, 12b, 12 facing B, C, D
The cross-sectional areas S _A , S _B , S _C and S _D of c and 12d are formed corresponding to the volumes V _A , V _B , V _C and V _D of their respective areas A, B, C and D, and _A = S _C > S _B = S _D. Note that F _A , F _B , F _C , and F _D shown in FIG. 5 represent the collision positions of the fuel spray from the injection ports 12a, 12b, 12c, and 12d.

In other words, a large amount of fuel sprays F _a and F _c are injected to areas A and C where the height h ₉ of the opening upper edge portion 9 of the cavity inner peripheral wall surface 13 is high and the volume is large, in accordance with the volumes V _A and V _C. A small amount of fuel spray F _b , F _d is supplied to the areas B, D having a small height and a small height h ₉ of the opening upper edge portion 9 of the inner peripheral wall surface 13 in accordance with the volumes V _B , V _D. It is designed to be supplied by injection.

Therefore, as shown in FIG. 2, the fuel spray F _a ... D injected from each of the injection ports 12a, 12b, 12c, 12d is swirled in the swirl S and swirls in the cavity 8. The amount of fuel injected from the nozzles 12a, 12b, 12c, 12d is determined by the respective nozzles 12a, 12b, 12c,
Area A in the cavity 8 in which 12d is received,
Since the volumes of B, C, and D correspond to the volumes V _A , V _B , V _C , and V _D , it is necessary to generate and exist a substantially uniform air-fuel mixture in the cavity 8 as a whole. Will be able to. As a result, the air utilization rate is improved, the HC and smoke emissions are reduced as much as possible, and at the same time, the output is increased.

Further, since the fuel is injected in the range of the angle α <45 ° in the downstream direction from the swirl upstream virtual vertical plane of each area, the spray flowed in the swirl S in the areas A and C having a large volume is the inner wall surface 13 of the cavity. Since the height h9 of the cavity is large, even if a large amount of fuel is injected, it will not be spilled from the cavity 8. On the contrary, since the amount of injected fuel is small in areas B and D having a small volume, the height of the cavity inner peripheral wall surface 13 is high. Even if h9 is small, spillage does not occur.

In addition, the nozzle holes 12a, 1 facing the areas A, C having a large volume
2c is a nozzle 12b facing the areas B and D having a small volume,
As compared with 12d, as shown in FIG. 6 and FIG. 7, the diameter thereof is expanded in the depth (inner peripheral wall surface height) direction of the cavity to form an elliptical or elliptical shape. Nozzles 12a, 12
The cross-sectional area S _A , S _C of _c may be increased, or as shown in FIGS.
C has two nozzles 12a and 12c divided into upper and lower tiers.
Cross section S _A ,
S _C may be increased.

The swirl S in the cavity 8 is generated by the intake air from the intake port 14 as shown in FIG.

[Effects of the Invention] In short, according to the present invention, it is possible to generate / exist a substantially uniform air-fuel mixture throughout the cavity, and as a result, the air utilization rate is increased and smoke and HC The amount of emission can be reduced and the output can be increased at the same time.

[Brief description of drawings]

FIG. 1 is a side sectional view of a main part of a pentroof type piston used in a pentroof type direct injection internal combustion engine according to the present invention, FIG. 2 is a plan view of a crown surface of the piston, and FIG. 4 is a partial side sectional view of an injection type internal combustion engine, FIG.
FIG. 5 is a bottom view of the injection nozzle used in the present invention, FIG. 5 is a development view of the inner peripheral wall surface of the cavity shown in FIG. 2, and the collision position of the fuel spray when the injection nozzle of FIG. 4 is adopted will be described. FIG. 6 is a bottom view showing a modified example of the injection port of the injection nozzle, FIG. 7 is a development view of the inner wall surface of the cavity showing the collision position of the fuel spray when the injection nozzle of FIG. 6 is adopted, and FIG. FIG. 9 is a bottom view showing another modified example of the injection port of the injection nozzle, FIG. 9 is a development view of the inner wall surface of the cavity showing the collision position of the fuel spray when the injection nozzle of FIG. 8 is adopted, and FIGS. FIG. 12 is a diagram for explaining a conventional pent roof type direct injection internal combustion engine. In the figure, 6 is a pent roof type piston, 7 is a piston crown surface, 8 is a cavity, 9 is an upper edge portion of an opening, 11 is an injection nozzle, and 12, 12a, 12b, 12c and 12d are injection holes.

Claims (2)

[Claims] 1. A pentroof type direct injection internal combustion engine in which a cavity is formed in a central portion of a crown surface of a pentroof type piston by denting in a cylindrical shape having a bottom along the axial direction of the piston to form a cavity in the cavity. It is divided into four areas in the circumferential direction by two virtual vertical planes that pass through the axial center line of the piston and the virtual vertical planes that are 45 degrees each along the ridge direction of the piston crown surface, and above the center of the cavity. An injection nozzle having a plurality of injection ports for injecting fuel in an amount corresponding to the volume of each area facing the above areas in a range of an angle α <45 ° in the downstream direction from the virtual vertical surface on the upstream side of the swirl is provided. A pent roof type direct injection internal combustion engine characterized by being provided. 2. The injection nozzle is formed such that a cross-sectional area of the injection port facing an area having a high opening and a large volume of the cavity is large in accordance with the volume, and the height of the opening upper edge is low. The pent roof type direct injection internal combustion engine according to claim 1, wherein the injection port facing a small volume area has a small cross-sectional area.