JPH0629553B2 - Whirlpool combustion chamber of diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a vortex chamber type combustion chamber of a diesel engine, by guiding combustion air flow in grooves provided along both left and right side surfaces of a recess of a piston head. Provided is one that can effectively improve the air utilization rate even during a period in which the piston passes near the top dead center and can prevent thermal distortion of the ring stick and the piston.

<Prior Art> As shown in FIG. 4, the basic structure of a vortex chamber combustion chamber of a diesel engine, which is the subject of the present invention, is a vortex chamber through an injection port 2 at an eccentric location of a main combustion chamber 1 of a diesel engine E. 3 and the axial center 4 of the injection port 2 extends from the vortex chamber 3 to the main combustion chamber 1
Is closer to the central portion of the main combustion chamber 1, and the combustion airflow is blown from the injection port 2 to the piston head 8 near the top dead center.

As a conventional technique of this type, the nozzle 2 is simply formed into a cylindrical shape, or the Japanese Patent Publication No. 57-594 is used to improve the dispersion performance of the combustion air flow in the main combustion chamber 1 and increase the air utilization rate.
As shown in Japanese Patent Publication No. 10, a pair of sideways is attached to both wing portions of a round hole to form a downwardly widening taper-shaped injection port 2, and from this injection port 2 to the left and right toward a flat piston head that is compressed and raised. There is a jet of combustion air with a divergence angle.

<Problems of Prior Art> Generally, in order to increase the swirl efficiency to the vortex chamber 3, it is necessary to make the volume of the vortex chamber 3 as large as possible and the main combustion chamber 1 as small as possible. The gap is very narrow.

Therefore, in the above-mentioned conventional technique, since the injection port 2 seems to be blocked by the flat piston head during the period in which the piston passes near the top dead center, not only when the injection port 2 is formed in a simple tubular shape, Even when formed in a downwardly widening tapered shape, the combustion airflow that expands in the vortex chamber 3 receives a large flow resistance at the outlet of the injection port 2 and causes a pressure loss.

In addition, since the combustion airflow is subject to flow resistance, flame propagation is delayed and combustion performance deteriorates.

Further, the combustion airflow that expands in the vortex chamber 3 cannot flow smoothly and correctly to the front of the main combustion chamber 1 because of the large flow resistance at the outlet of the injection port 2, and spreads too much to the left and right and fills in front of this. You cannot make good use of the air you are using.

Therefore, the combustion is accompanied by a shortage of air, and carbon is easily generated to easily generate ring stick.

By the way, since this carbon generation position is close to the sliding surface between the piston and the cylinder, carbon easily enters the sliding surface, further promoting the ring stick.

Moreover, since the combustion air flow does not reach the entire piston head, there is a risk that the heating may be biased and the piston may be thermally distorted.

<Prior Art> Therefore, in order to reduce the flow resistance of the combustion airflow even during the period in which the piston passes near the top dead center and to prevent the thermal distortion of the ring stick and the piston,
The invention shown in FIG. 3 was previously proposed.

That is, in the above-mentioned prior invention, a fan-shaped recess 7 is formed in the piston head 8 so that it becomes shallower as it goes to the left and right as it goes from the starting end 10 to the tip 12. It was made to face.

In the above-mentioned prior art, even when the piston 6 passes near the top dead center, the injection port 2 faces the starting end of the recess 7 formed in the piston head 8 and is opened, so that the injection port 2 is opened to the main combustion chamber. The combustion airflow jetted to the 1 enters the recess 7 without receiving the flow resistance, and smoothly flows into the tip 1 thereof.
Will be guided to.

Therefore, the flow resistance of the combustion airflow is significantly reduced, the pressure loss is reduced, and the delay of flame propagation is eliminated.

However, the combustion airflow entering the recess 7 spreads to the left and right according to the opening angle of the recess, but the air on the left and right sides of the recesses 7 on both left and right sides 7a and 7b is Side 7
There is a possibility that it will not be used promptly due to the constraints of a and 7b, and there is a risk that the mixing of the combustion air flow and air in the main combustion chamber 1 will be restricted.

The present invention aims to further improve the air utilization rate in the main combustion chamber.

<Means for Solving Problems> Means for achieving the above problems will be described below with reference to FIGS. 1 to 12 corresponding to the embodiment.

That is, according to the present invention, in the vortex chamber type combustion chamber of the diesel engine of the basic structure described above, when the piston 6 is near the top dead center, the combustion airflow ejected from the injection port 2 in the main combustion chamber 1 in the left-right direction. The piston head 8 has a recess 7 that guides forward with a divergence angle of 10 mm from the start end 10 to the tip 1.
As it goes to 2, it is formed in such a shape that it spreads to the left and right and becomes shallower so that the starting end portion 10 of the recess 7 faces the injection port 2, and the portions 30 and 31 along the left and right side surfaces of the recess 7 are formed in the middle portion 32 of the recess 7.
It is characterized in that it is formed in a deeper groove.

<Operation> The combustion airflow injected from the nozzle 2 to the starting end portion 10 of the recess 7 is
Although it advances toward the tip 12 of the recess 7 in a fan shape, a part of the combustion airflow is strongly directed and intensively guided in the grooves formed in the portions 30 and 31 along the left and right side surfaces of the recess 7. , I try to jet too fast by increasing the flow velocity.

Therefore, due to the flow of the combustion airflow traveling along the left and right side surfaces of the recess 7, the air outside the recess 7 is drawn into the recess 7 from the left and right side surfaces thereof and promotes the mixing with the combustion airflow. However, it spreads from the tip 12 to the entire main combustion chamber 1.

Further, the combustion airflow along both the left and right side surfaces of the depression 7 accelerates its flow velocity and is ejected from the tip 12 of the depression to the front thereof, so that the mixing performance of the combustion airflow and the air in the entire main combustion chamber 1 becomes higher. .

<Effects of the Invention> (1) First, in the present invention, by forming a recess in the piston head, the flow resistance of the combustion airflow is reduced, pressure loss is eliminated, and flame propagation can be speeded up.

In addition, by strongly guiding the combustion airflow to the grooves formed on both the left and right sides of the dent to accelerate its flow velocity, the air on the outside of the left and right sides of the dent is strongly drawn into the dent and the combustion airflow It is possible to improve the mixing performance with air by the injection force.

As a result, the mixing of the combustion air flow with the air is further promoted,
The air utilization rate can be effectively improved.

(2) Combustion airflow is uniformly mixed with air to eliminate partial air deficiency, which significantly reduces carbon generation,
It is possible to smoothly prevent carbon from being caught between sliding surfaces of the cylinder and the piston to form a ring stick.

(3) The combustion airflow spreads and spreads throughout the main combustion chamber, and this spread does not remain only around the injection port, so only a part of the piston is locally heated, and the piston heats up. It does not cause distortion.

<Examples> Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view of a piston head showing the first embodiment, FIG. 2 is a sectional view taken along line II-II of FIG. 1, FIG. 3 is a right side view of a vertical section around the piston head, and FIG. 4 is a vertical diesel engine. FIG. 10 is a schematic right side vertical cross-sectional view of the main part of the engine, and FIG. 10 is a schematic view of the injection port.
It is vertically slidably fitted inside.

The cylinder head 16 is assembled above the cylinder block 14, and the fuel injection space 19 is bored in the wall surface of the cylinder head 16 facing the main combustion chamber 1 in the latter half of the cylinder head 16, and the fuel injection space 19 is half opened from the lower opening edge. The split injection chamber member 20 is fitted to form the vortex chamber 3 by the upper hemisphere portion of the fuel injection space 19 and the lower hemisphere portion of the injection chamber member 20.

A nozzle fitting hole 21 is provided so as to extend from the upper end of the latter half of the cylinder head 16 to the fuel injection space 19, and a fuel injection nozzle 22 is fitted into the fitting hole 21, and the tip injection port portion 23 is inserted into the vortex chamber 3. To face.

The injection port 2 is provided in the injection chamber member 20 in a rearward upward slope shape, that is,
The axis 4 of the injection port 2 is oriented so as to approach the center of the main combustion chamber 1 as it approaches the main combustion chamber 1 from the vortex chamber 3.

As shown in FIG. 10, the injection port 2 has a round hole 24, which serves as a main ejection passage for the combustion air flow, formed in the center thereof, and a side passage 25 is formed over the left and right side surfaces 5 slightly forward. It is constructed by forming a boundary in a mine shape.

With respect to the axis of the round hole 24, the respective axes of the sideways 25 are inclined so as to expand to the left and right as they go downward (that is, the sideways 25
The cross-sectional area of the passage is increased in the left-right direction as it approaches the main combustion chamber 1) so that the combustion airflow ejected from the injection port 2 into the main combustion chamber 1 spreads to the left and right sides.

However, as the taper-shaped injection port 2 for spreading the combustion airflow to the left and right, for example, in addition to the above-described embodiment, for example, the eleventh
As shown in the drawing, both the upper and lower surfaces of the injection port may be elongated in the left and right directions, but in the present invention, the injection port 2 simply formed in a cylindrical shape as shown in FIG. 12 may be used.

On the other hand, the piston head 8 is provided with a fan-shaped recess 7 opened at approximately 60 degrees, and the recess 7 is formed such that the starting end 10 which is the key to the fan is deepest and becomes shallower as it goes to the tip 12 (first (See Figures and 3).

The recess 7 is arranged near the center of the piston head 8, and the starting end 10 thereof faces the opening end of the injection port 2 on the main combustion chamber side.

The portions 30 and 31 along the left and right sides 7a and 7b of the recess 7 are formed in a groove shape deeper than the intermediate portion 32 of the recess 7,
As shown in the figure, the groove portions 30 and 31 are on the left and right side surfaces 7a and 7b.
Is formed in a concave portion which is drawn by drawing a smooth curve, and the intermediate portion 32 is formed in a smooth surface having an appropriate lateral width.

In this case, when the contour line in the recess 7 is taken, it becomes an arc-shaped curve protruding toward the starting end portion 10 as shown in FIG.

However, as an aspect of the groove portions 30 and 31 and the intermediate portion 32 in the transverse direction, as shown in FIG. 9, the groove portion and the intermediate portion are continuous with a smooth curve, and the intermediate portion 32 is configured as a single curved surface instead of a smooth surface. You may.

On the other hand, the shape of the recess 7 in the longitudinal direction (to be exact, the groove 30.
31), the starting end 10 of the recess 7 to the leading end 12 are divided into three parts, and the starting end 10 is cut down into a front-down inclined smooth surface, and the middle part is horizontally smoothed at the same depth. It is formed on the surface, and from the midway portion to the tip end portion 12 is a smooth surface that is inclined forward and upward. In addition, the shape of the intermediate portion 32 is an upwardly sloped shape with a curve that is gently recessed downward.

In this case, the recess 7 may have a shape that becomes shallower as it goes from the starting end portion 10 to the leading end portion 12, and therefore the shape in the longitudinal direction is not limited to the above-described embodiment, and the following cases are also acceptable.

That is, FIG. 6 shows a first modification of the recess 7 in the longitudinal direction, which is a single curved surface that is recessed downward from the middle portion of the recess 7 to the tip portion 12, and the smooth surface of the middle portion is smoothed to this single curved surface. It is a continuous one.

FIG. 7 shows a second modification of the recess 7 in the longitudinal direction, showing the recess 7
Is unified with a smooth surface that slopes forward and the start end 1
The cut-down start portion of 0 is formed into a curved surface, and the recess 7 and the upper wall surface of the piston head 6 are connected to each other by a smooth continuous surface. It is possible to prevent the occurrence of heat points. FIG. 8 shows a third modification of the recess 7 in the longitudinal direction, in which the start end portion 10 of the second modification is cut down into a vertical smooth surface.

In this case, the intermediate portion 32 of the recess 7 constitutes a convex portion which is continuous to the tip portion 12 while forming a double curved surface from the portion where the starting end portion 10 is cut down and bulging.

[Brief description of drawings]

1 to 12 show an embodiment of the present invention, FIG. 1 is a plan view of a piston head showing the first embodiment, and FIG.
Fig. 3 is a sectional view taken along the line II-II in Fig. 3, Fig. 3 is a right side view in vertical section around the piston head, Fig. 4 is a right side view in vertical section of a main part of a vertical diesel engine, and Fig. 5 is a view showing contour lines of a recess. 6 to 8 are right side views of longitudinal sections of main parts of piston heads showing modified examples of the recess in the longitudinal direction, FIG. 9 is a view corresponding to FIG. 2 showing a modified example of the recess in the transverse direction, and FIG. FIG. 11 is a schematic view of the injection port, FIG. 11 and FIG. 12 are equivalent views of FIG. 10 showing another modification of the injection port, and FIG. 13 is an equivalent view of FIG. 1 showing the prior invention. 1 ... Main combustion chamber, 2 ... Injection port, 3 ... Vortex chamber, 4 ... Axial center, 6 ... Piston, 7 ... Recess, 8 ... Piston head, 10 ... 7 start end, 12 ... The end portion of 7 ..., the portion along the left side surface of 30 ... 7, the portion along the right side surface of 31 ... 7, and the intermediate portion of 32 ... 7.

Claims (1)

[Claims] 1. A vortex chamber 3 communicates with an eccentric portion of a main combustion chamber 1 of a diesel engine E via an injection port 2, and the axial center 4 of the injection port 2 becomes closer to the main combustion chamber 1 from the vortex chamber 3 to the main combustion chamber 1. In the vortex chamber combustion chamber of a diesel engine configured so that the combustion airflow is blown from the injection port 2 to the piston head 8 located near the top dead center, the piston 6 is located near the top dead center. In some cases, the piston head 8 is provided with a recess 7 for guiding the combustion airflow ejected from the injection port 2 forward in the main combustion chamber 1 with a divergence angle in the left-right direction.
In addition, it is formed in a shape that becomes shallower as it spreads left and right as it goes from the starting end portion 10 to the tip end portion 12, and the starting end portion 10 of the recess 7 is made to face the injection port 2, and a portion 30 along both left and right side surfaces of the recess 7 is formed.
A vortex chamber combustion chamber of a diesel engine, wherein 31 is formed in a groove shape deeper than the intermediate portion 32 of the recess 7.