JPH01104914A - Piston for swirl-chamber type diesel engine - Google Patents

Abstract

PURPOSE:To aim at improvement in an air utilization factor, etc., by forming a specified-form recess, guiding a combustion air flow to be sprayed at a main combustion chamber from a swirl chamber via a nozzle hole, on a top face of a piston, and also forming a projection, deflecting this combustion air flow, in a part of this recess. CONSTITUTION:A main combustion chamber 1 of an engine E is partioned by a cylinder liner 3, a cylinder head 4 and a piston 5. In this cylinder head 4, a swirl chamber 6 is formed in a position to be decentered from an axial center of the main combustion chamber 1 to the peripheral edge, and this swirl chamber 6 and the main combustion chamber 1 are interconnected to each other by a nozzle hole 7. In this constitution aforesaid, a recess 11, guiding a combustion air flow to be sprayed out of this nozzle hole 7, is formed on a top face 10 of the piston 5. Then, the recess 11 is formed into a sector form as unfolded at both sides of the combustion air flow with a guide starting end 14 to the nozzle hole 7 as the center. In addition, a projection 16, deflecting the combustion air flow to the side of the cylinder head 4, is formed in an space between the guide starting end 14 and its tip part 15 of the recess 11.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is characterized in that the combustion air flow injected from the vortex chamber into the main combustion chamber through the nozzle is aligned with the axis of the main combustion chamber on the cylinder head side end surface of the main combustion chamber. It is ejected from the nozzle opening at an eccentric position on the piston side in an inclined direction approaching the cylinder axis direction,
In particular, with regard to the piston of the vortex chamber type diesel engine used in the vortex chamber type diesel engine, which is configured so that the jet is ejected in a laterally expanding shape when viewed from the axis of the main combustion chamber, the air utilization rate can be increased. This invention relates to a piston for a swirl chamber diesel engine that increases combustion efficiency and output and prevents the generation of carbon and blue-white smoke.

<Prior Art> As shown in FIG. 1, in many swirl chamber type diesel engines, a swirl chamber 6 is provided in a cylinder head 4 at a position 7 eccentric from the cylinder axis. Combustion chamber 1
The nozzle 7 that communicates with the cylinder of the main combustion chamber 1 is opened at a position eccentric from the cylinder axis on the end face on the rad 4 side, and the center line of this nozzle 7 normally extends as the cylinder progresses from the rad 4 side to the piston 5 side. It is inclined so as to approach the cylinder axis direction. Further, the top surface 8 of the piston 5 is generally formed into a flat surface. Furthermore, in a swirl chamber type diesel engine, the top surface 8 of the piston is usually formed flat in order to set the volume of the main combustion chamber 1 as small as possible relative to the volume of the vortex chamber 6 and to enhance the vortex effect in the vortex chamber 6. ,Also,
The distance between the top surface 8 of the piston 5 and the end surface of the main combustion chamber 1 on the side of the cylinder head 4 at the top dead center is made as small as possible.

By the way, when the nozzle 7 has a simple circular cross-sectional shape, the spread of the combustion air injected from the nozzle 7 into the main combustion chamber 1 is relatively narrow, resulting in a problem that the air utilization rate is low. be.

Therefore, as a method of increasing the air utilization rate in a swirl chamber type diesel engine, for example, as shown in Japanese Patent Publication No. 57-59410, the left and right sides of the jet nozzle 7 have a taper that expands from the swirl chamber 6 side toward the main combustion chamber 1 side. It has been proposed to form it into a shape. By configuring the shape of the nozzle 7 in this manner, the combustion airflow injected into the main combustion chamber 1 from the nozzle 7 spreads widely on both left and right sides of the main combustion chamber 1, thereby increasing the air utilization rate.

<Problems to be Solved by the Invention> However, according to the conventional piston in which the top surface 8 is formed flat as described above, the top surface 8 of the piston 5 and the cylinder head of the main combustion chamber 1 at the top dead center If the distance between the nozzle 4 and the end face of the nozzle 4 is made small, the nozzle 7 will come very close to the top surface 8 of the piston 5 when the piston 5 is at or near the top dead center, and the resistance to the combustion air jetting out from the nozzle 7 will be extremely high. becomes larger, making it difficult for the combustion airflow to eject forcefully into the main combustion chamber 1, and the resistance becomes approximately equal over the entire circumference of the nozzle 7, causing the combustion airflow to have the same directionality as a simple cylindrical nozzle. While the air utilization rate decreases on the opposite side of the main combustion chamber from the nozzle, unburned fuel is injected excessively on the nozzle side of the main combustion chamber, resulting in incomplete combustion, carbon generation, and blue-white smoke. This may lead to problems such as outbreaks.

Also, among the fuel airflows ejected from the nozzle 7, the fuel airflow that is injected while spreading diagonally laterally is recirculated from the opposite side of the main combustion chamber 1 to the nozzle 7 along the circumferential surface of the main combustion chamber 1. However, as engines become faster or more compressible, this recirculation becomes insufficient and the main combustion chamber 1
A problem arises in that the air utilization rate along the circumferential surface of the main combustion chamber 1 from the opposite side of the nozzle port 7 to the nozzle port 7 side decreases.

The present invention has been made in consideration of the above-mentioned circumstances. For example, as shown in FIG. Centering on the inclination direction approaching the main combustion chamber axis direction on the piston 5 side from the nozzle opening 7 opened at a position eccentric from the cylinder axis center on the end surface of the cylinder head 4 side of No. 1, and from the main combustion chamber axis direction In the piston of the vortex chamber diesel engine used in the vortex chamber diesel engine, which is configured so that the jet is ejected in a horizontally expanding manner, the piston of the vortex chamber diesel engine is designed to increase the air utilization rate, increase the combustion efficiency and output, and also reduce the amount of carbon and blue-white smoke. The object of the present invention is to provide a piston for a vortex chamber type diesel engine that can prevent the occurrence of such problems.

<Means for solving the problems> The piston of the swirl chamber diesel engine according to the present invention has the following features:
In order to achieve the above purpose, for example,
As shown in the figure, a recess 11 for injection guidance is formed in the top surface 10 of the piston 5, and this recess 11 allows the combustion air to flow when viewed from the axial direction of the piston 5 with the guide starting end 14 facing the nozzle 7 as the center. The cylinder head 4 is formed into a fan shape that spreads outward on both sides of the center line of the cylinder head 4, and the combustion air flow is directed between the guide start end 14 and the tip end 15 of the recess 11.
It is characterized in that a convex portion 16 is formed to deflect it to the side.

According to the present invention, while the piston is located at or near top dead center, the combustion air flow injected from the nozzle is injected to the guide starting end of the recess, and is guided by the recess and spreads in a fan shape within the recess. while proceeding to the opposite side of the main combustion chamber from the nozzle. In other words,
The injection direction of the combustion airflow is restricted by the recess, and the majority of the combustion airflow is on the opposite side of the main combustion chamber from the nozzle, and moreover, it flows so as to spread appropriately on both sides of the center line of the combustion airflow, so it is opposite to the nozzle inside the main combustion chamber. This makes it possible to effectively utilize a large amount of air on the side for combustion, and also to reduce the amount of combustion air injected to the nozzle side of the main combustion chamber, thereby preventing the generation of carbon and blue-white smoke. The combustion airflow is deflected toward the cylinder head by the convex part while it travels inside the recess from the guide starting end to the tip, and a part of the combustion airflow is regulated by the recess by exiting from the recess to the cylinder head side. It spreads laterally wider than the main combustion chamber, forming a flow that flows back from the middle of the main combustion chamber along its circumferential surface toward the nozzle port. In this way, while the piston is at or near top dead center, a flow is created that flows from the middle of the main combustion chamber to the nozzle side along its circumference, thereby achieving higher speeds or higher compression ratios. The air in the main combustion chamber, which is sometimes difficult to utilize, can be sufficiently mixed with the fuel, thereby increasing the -layer air utilization rate and output.

<Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a vertical cross-sectional view of the main parts of a swirl chamber type diesel engine equipped with a piston according to an embodiment of the present invention, and FIG.
FIG. 3 is a plan view of the piston, FIG. 3 is a schematic diagram showing the fuel air flow in the main combustion chamber formed by the piston, and FIG. 4 is a schematic diagram of the nozzle of the engine.

The main combustion chamber 1 of the swirl chamber type diesel engine E shown in FIG. The piston 5 is slidably fitted into the piston 5. cylinder head 4
A vortex chamber 6 is formed inside the main combustion chamber 1 at an eccentric position from the axis of the main combustion chamber 1 to the vicinity of its periphery, and the vortex chamber 6 and the main combustion chamber 1 are communicated through a nozzle 7.

The shape of the nozzle 7 is such that it connects from the vortex chamber 6 to the main combustion chamber 1 via the nozzle 7.
The combustion air flow injected into the cylinder head 4 side of the main combustion chamber 1 approaches the main combustion chamber axis direction from the nozzle 7 opened at a position eccentric from the main combustion chamber axis center on the piston 5 side. There is no particular limitation as long as the jet is formed so as to spread out laterally when viewed from the cylinder axis direction, but for example, the jets shown in FIGS. 1 and 4, FIGS. It may be formed into a shape as shown in FIG. 7 or 8.

That is, the nozzle 7 shown in FIGS. 1 and 4 has a main hole 8 which is a circular hole that is inclined so that the central axis approaches the axis of the main combustion chamber 1 as it goes from the cylinder head 4 side to the piston 5 side. and a sub-hole 9 consisting of a pair of tapered holes formed on both sides thereof so as to communicate with the sub-hole. The tapered hole 9 gradually expands from the vortex chamber 6 side toward the main combustion chamber 1 side, and the boundary between the circular hole 8 and the tapered hole 9 is formed in a peak shape. According to the nozzle 7 shown in FIGS. 1 and 4, the combustion air flow jetted into the main combustion chamber 1 is directed toward the cylinder of the main combustion chamber 1 at a position eccentric from the axis of the main combustion chamber on the side end surface of the rad 4. Centering on the inclination direction approaching the main combustion chamber axis direction from the opened nozzle port 7 on the piston 5 side, and in the left and right direction (up and down direction in Fig. 1) as seen from the cylinder axis direction, the width is approximately 60@ It is designed to eject in a spreading shape at the end.

Further, the nozzle 7 shown in FIG. 5 has a main hole 8 which is an elliptical hole that gradually expands from the vortex chamber 6 side toward the main combustion chamber 1 side,
A pair of auxiliary holes 9 are formed on both sides of this so as to communicate with this, and are circular holes that gradually enlarge from the vortex chamber 6 side toward the main combustion chamber 1 side.

The nozzle 7 shown in FIG. 6 is composed of an elliptical hole that gradually expands from the vortex chamber 6 side toward the main combustion chamber 1 side, and the nozzle 7 shown in FIG. It is formed into a circular shape at the side end of the main combustion chamber 1. Spout 7 shown in Figure 8
is formed in an oval shape long in the front and back at the end on the side of the vortex chamber 7, and is formed in an oval shape long in the left and right at the end on the side of the main combustion chamber 1.

The top surface 10 of the piston 5 is formed with a recess 11 for guiding the combustion air flow injected from the nozzle 7, an intake valve pulp recess 12, and an exhaust valve pulp recess 13.

As shown in FIG. 2, the recessed portion 11 is formed in a fan shape that spreads outward on both sides of the center line of the combustion air flow, with the guide starting end 14 facing the jet nozzle 7 as the center.

The fan-shaped included angle of this recess 11 is not particularly limited as long as it is an acute angle greater than the spread angle of the combustion air flow, but here it is about 60'', which is the same as the spread angle of the combustion air flow. It is sufficient that the structure is formed so that the combustion airflow can be received almost without leakage when the piston 5 is located at or near the top dead center. For example, as shown in FIGS. When located in the vicinity, it can be placed in a position facing the nozzle 7 in the axial direction of the nozzle 7, and although not shown, it can also be placed in a position facing the nozzle 7 in the axial direction of the main combustion chamber. .

A protrusion 16 is formed between the guide starting end 14 and the tip 15 of the recess 11, as shown in FIGS. 1 and 3, for deflecting the combustion air flow toward the cylinder 4. This convex part 1
6 may be formed in a circular arc shape centered on the guide starting end 14 in a plan view, or may be formed in a straight line that traverses the recessed portion 11 . Moreover, it may be formed entirely between both side edges of the recessed portion 11, or may be formed in a portion thereof. Here, in order to mix the combustion air flow with as much air as possible in the main combustion chamber 1, the convex part 16 is formed in an arc shape centered on the guide start end 14 in plan view, and the entire area between both side edges of the concave part 11 is It is formed over a period of time. Incidentally, the one-dot chain line in FIG. 2 indicates the center line of the convex portion 16.

According to the piston 5 configured as described above, the combustion air flow injected from the nozzle 7 while the piston 5 is located at or near the top dead center is injected toward the guide start end 14 of the recess 11, 11 and inside the recess 11.
The main combustion chamber 1 expands in a fan shape as shown by arrow a in the figure.
It moves toward the opposite side from the spout 7. That is, while the piston 5 is located at or near the top dead center, the injection direction of the combustion airflow is restricted by the recess 11, and the combustion airflow is spread to the opposite side of the main combustion chamber 1 from the nozzle 7, and also in an appropriate lateral direction. As a result, the combustion airflow is efficiently mixed with a large amount of air on the opposite side of the nozzle 7 in the main combustion chamber 1, increasing the air utilization rate and output, and the combustion toward the nozzle 7 side of the main combustion chamber 1 is efficiently mixed. This makes it possible to reduce the amount of airflow and prevent the generation of carbon and blue-white smoke. While the combustion air flow travels inside the recess 11 from the guide starting end 14 to the tip 15, it is deflected toward the cylinder head 4 by the convex part 16, and a part of it is directed toward the opposite side of the main combustion chamber 1 from the nozzle 7. As shown by the arrow in FIG. 2, the flame spreads laterally beyond the area limited by the recess 11 and reaches the circumferential surface of the main combustion chamber 1, and from there reaches the circumferential surface of the main combustion chamber 1. It flows back to the nozzle 7 side along the line. This makes it difficult for fuel air to reach the main combustion chamber 1 when increasing speed or compression ratio.
Sufficient fuel is supplied to the inner parts of the engine, increasing air utilization and further increasing power output.

Note that a portion of the combustion air injected when the piston 5 is at or near the top dead center flows through the nozzle 7 while the piston 5 is descending from the top dead center, as shown by arrow C in FIG. 3, for example.
The subsequent combustion airflow (indicated by arrow d) injected from the main combustion chamber 1 causes the direction to be changed to the side of the piston 5, so that it somersaults within the main combustion chamber 1 and moves to the opposite side of the main combustion chamber 1 from the nozzle 7. Since the combustion airflow reaches the peripheral edge, the combustion airflow is mixed with a large amount of air in the main combustion chamber 1 more efficiently, and the air utilization rate and output can be further increased. Furthermore, if the piston 5 descends beyond a certain level, the combustion airflow is injected in a direction regulated by the jet nozzle 7 in a divergent manner, reaches the peripheral edge on the opposite side, and then continues along the circumferential surface of the main combustion chamber 1 toward the jet nozzle 7 side. The air flows into the main combustion chamber 1 and is mixed with the air on the injection port 7 side of the main combustion chamber 1. As a result, the combustion airflow is mixed with a large amount of air throughout the main combustion chamber 1, further increasing air utilization and power output.

FIG. 9 is a plan view of a piston of a swirl chamber type diesel engine according to another embodiment of the present invention, and FIG. 10 is a longitudinal sectional view of a peripheral guide groove thereof.

In this embodiment, in addition to the structure of the above embodiment, a peripheral guide groove 17 is formed which extends in an arc shape from both valve recesses 12 and 13 along the peripheral edge of the piston 5.

According to this embodiment, the combustion airflow flowing into both valve recesses 12, 13 through the recess 11 is guided by the peripheral guide groove 17 and flows forcefully toward the injection port 7 side of the main combustion chamber 1, so that the combustion air flowing through the recess 11 Both side edges of the airflow and this peripheral guide groove 1
The air utilization rate can be further increased by involving a large amount of surrounding air into the combustion airflow flowing through the main combustion chamber 1.
It is possible to further increase the air utilization efficiency in the area along the circumferential surface. In addition, combustion can proceed evenly throughout the main combustion chamber 1, and pressure is evenly applied to each part of the piston 5, making it extremely difficult for the piston to oscillate, thereby reducing operational noise. be able to.

In each of the above embodiments, the valve recess 12.13 is formed in the top surface 10, but the present invention can also be applied to a piston that does not have a pulp recess 12.13.

<Effects of the Invention> As described above, the piston of the present invention receives the combustion air flow injected from the nozzle when the piston is located at or near top dead center on the top surface, and directs the combustion air in the axial direction of the main combustion chamber. It has a concave part that guides the combustion airflow so that it gradually spreads laterally toward the side opposite to the nozzle when viewed from above, so most of the fuel injected from the nozzle is transferred to a large volume extending from the nozzle to the opposite side of the main combustion chamber. While increasing the air utilization rate by mixing with air, it reduces the amount of fuel injected into the small volume main combustion chamber that extends from the main combustion chamber axis toward the nozzle in a direction further eccentric from the nozzle, resulting in incomplete combustion. Since this can be prevented, output can be increased. In addition, by reducing the amount of fuel injected into the main combustion chamber, which has a small volume and spreads further toward the periphery from the nozzle, to prevent incomplete combustion, carbon generation due to incomplete combustion and burning of piston rings due to carbon are avoided. It is possible to prevent the occurrence of blue-white smoke, etc. Furthermore, by deflecting the combustion airflow toward the cylinder head side by the convex part, the combustion airflow is spread laterally from the middle of the main combustion chamber beyond the area restricted by the concave part, and directed toward the circumferential surface of the main combustion chamber. Since the combustion airflow is directed to the nozzle side along the main combustion chamber, sufficient combustion airflow is generated along the circumference of the main combustion chamber near the nozzle, which is difficult for the combustion airflow to reach when increasing the speed or compression ratio. can be supplied, further increasing the air utilization rate and further increasing the output.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of the essential parts of a swirl chamber diesel engine equipped with a piston according to an embodiment of the present invention, FIG. 2 is a plan view of the piston, and FIG. FIG. 4 is a schematic diagram of the nozzle of the engine, FIGS. 5 to 8 are schematic diagrams showing modified examples of the nozzle, and FIG. FIG. 10 is a plan view of the piston of the swirl chamber type diesel engine according to the embodiment, and FIG. 10 is a longitudinal sectional view of the peripheral guide groove thereof. E... Vortex chamber type diesel engine, 1... Main combustion chamber, 4... Cylinder head, 5... Piston, 6...
・Vortex chamber, 7... Nozzle, 10... Top surface, 11...
- Concave portion, 14... Guide starting end, 15... Tip, 1
6...Protrusion.

Claims (1)

[Claims] 1. The combustion air flow injected from the vortex chamber 6 into the main combustion chamber 1 via the nozzle 7 is transmitted from the nozzle 7 opened at a position eccentric from the axis of the main combustion chamber on the end face of the cylinder head 4 of the main combustion chamber 1 to the piston 5. Used in a swirl chamber type diesel engine E that is configured to eject air in an inclined direction approaching the axial direction of the main combustion chamber at the side, and eject air in a shape that widens laterally when viewed from the axial direction of the main combustion chamber. In the piston of a swirl chamber type diesel engine, a recess 11 for injection guidance is formed in the top surface 10 of the piston 5, and the recess 11 extends in the axial direction of the piston 5 with the guide start end 14 facing the jet nozzle 7 as the center. When viewed from above, it is formed into a fan shape that spreads outward on both sides of the center line of the combustion air flow, and the guide starting end 1 of this recess 11
A piston for a swirl chamber type diesel engine, characterized in that a convex portion 16 is formed between a tip portion 15 and a convex portion 16 for deflecting a combustion air flow toward a cylinder head 4 side.