JPH0614031Y2 - Vortex chamber type diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to improvement of a sub chamber structure of a swirl chamber type diesel engine.

(Prior Art) As a type of a combustion chamber suitable for a diesel engine, there is known a type including a subchamber of an air swirling type in communication with a main chamber (see Japanese Utility Model Laid-Open No. 54-124808).

This will be described with reference to FIG.
And a hot plug 3 fitted from the lower surface of the injection port 5 are formed in a substantially spherical shape, and the injection port 5 has an opening 5A on the side of the sub chamber 4 thereof.
In the tangential direction of the spherical auxiliary chamber 4, the opening 5B on the main chamber 8 side is formed so as to face the cavity 9 on the top surface of the piston 2.

In the figure, 6 is a fuel injection valve and 7 is a glow plug.

Based on such a configuration, the pushing flow that flows into the sub chamber 4 through the injection port 5 during the compression stroke flows in from the tangential direction of the spherical sub chamber 4 to generate a vortex and the piston 2 reaches the vicinity of top dead center. When this is done, the fuel injected from the fuel injection valve 6 is atomized and mixed with air. When the air-fuel mixture is ignited by the pressure increase in the sub chamber 4, the fuel gas in the sub chamber 4 is ejected into the main chamber 8 through the injection port 5, and then the combustion is completed in the main chamber 8 to perform the work of the piston 2. It is designed to be taken out.

(Problems to be solved by the invention) By the way, since the upper half of the inner wall surface 14 that directs the vortex has a single spherical curved surface, the vortex is forced by the inflow and the side of the sub-chamber 4 opposite the injection port 5 side. Will be pushed by. That is, during the compression stroke of 20 ° before the piston top dead center, a strong inflow flows from the injection port 5 as shown by the arrow in FIG. 3, and the flow velocity of the auxiliary chamber 4 on the injection port 5 side (right direction in the drawing) is increased. The center of swirling of the vortex flow becomes eccentric on the side opposite to the injection port 5 (leftward in the figure).
As shown in FIG. 4, at the piston top dead center, the swirling flow weakens and the swirling center of the vortex flow slightly shifts to the center side of the sub chamber 4, but is still eccentric to the side opposite to the injection port 5. For this reason,
The fuel injected from the fuel injection valve 6 passes through the swirl center portion of the vortex flow having a small flow velocity, and the atomization of the fuel and the mixing with air are not sufficiently performed, and as a result, the smoke emission increases, There was a problem that the output was reduced.

The present invention aims to solve the above problems.

(Means for Solving the Problems) The present invention provides a sub-chamber formed in a cylinder head, an injection port for communicating the sub-chamber with the main chamber along a tangential direction of a wall surface of the sub-chamber, and a sub-chamber. In a swirl chamber type diesel engine having a fuel injection valve for supplying fuel toward the upstream side inner wall part and a downstream side inner wall part for the swirl flow generated in the sub chamber on the inner wall surface defining the upper half part of the sub chamber. The center of curvature of the downstream side inner wall portion is separated from the center of curvature of the upstream side inner wall portion in the direction perpendicular to the piston axis of the engine by an amount corresponding to the sectional thickness of the injection port, and the sectional shape of the sub chamber is the above-mentioned. The fuel injection valve is formed in a substantially elliptical shape including the upstream side inner wall portion and the downstream side inner wall portion and is long in the separating direction, and the fuel injection valve supplies fuel toward a substantially swirling direction of the vortex flow generated in the downstream side inner wall portion. It is arranged as follows.

(Operation) Based on the above configuration, by making the vertical cross-sectional shape of the sub-chamber substantially elliptical, a spatial margin that can be held near the central portion of the sub-chamber of the swirl center of the vortex flow generated in the sub-chamber. Is secured immediately downstream of the opening of the injection port, that is, the swirl center of the vortex flow is held near the central portion of the sub-chamber with the influence of the pushing flow being alleviated. As a result, the swirl center of the vortex moves away from the inner wall of the downstream side, and a vortex with strong uniform flow is generated throughout the sub-chamber, and a large vortex flow velocity is secured even in the vicinity of the inner wall of the downstream side. .

Then, the fuel injection valve is arranged so as to supply the fuel toward the high speed region of the vortex flow secured by eliminating the influence of the pushing flow, that is, the position away from the swirl center of the vortex flow,
Moreover, since the fuel supply direction is substantially along the swirling direction of the vortex flow, atomization of the injected fuel is promoted, thereby reducing the smoke emission amount and improving the engine output.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.
The same components as those of the conventional example are designated by the same reference numerals.

As shown in FIG. 1, a sub chamber 4 is formed between the cylinder head 1 and the hot plug 3, and an injection port 5 is opened in the sub chamber 4 with a sectional thickness T in a tangential direction.

The cross-sectional shape of the upper half of the sub chamber 4 is an ellipse. That is, in the upper half portion of the inner wall surface 14, the upstream inner wall portion 14a that is upstream with respect to the vortex flow generated by the indentation flow is formed by a curved surface of a ¼ sphere having the curvature radius R with the point Qa as the center of curvature. At the same time, the downstream side inner wall portion 14b is formed by a curved surface of a quarter sphere having a radius of curvature R with the curvature center at the point Qb, and the curvature center Qb of the downstream side inner wall portion 14b is different from the curvature center Qa of the upstream side inner wall portion 14a. Is separated by an amount corresponding to the cross-sectional thickness of the injection port 5, that is, an amount substantially equal to the cross-sectional thickness T of the injection port 5, and the vertical cross-sectional shape in the upper half of the sub chamber 4 is in the separation direction (horizontal direction in the figure). It has a long oval shape.

A continuous surface 1 that connects the upstream and downstream inner wall portions 14a and 14b with a step
4c is formed with a width L.

The lower half of the inner wall surface 14 is formed by sloping an inclined portion 14d continuous from the downstream inner wall portion 14b at a predetermined angle in a substantially linear cross section, and a bottom portion 14 continuous from the inclined portion 14d.
e is formed to have a substantially horizontal cross section, and the bottom portion 14e and the upstream side inner wall portion 14a are formed by forming a continuous surface 14f into a curved surface of a 4/1 sphere.
The injection port 5 opens in the tangential direction of the continuous surface 14f.

The fuel injection valve 6 is arranged on the upstream side inner wall portion 14a in the upper half of the sub chamber 4 and is arranged so as to be oriented substantially in the swirling direction of the vortex generated in the downstream side inner wall portion 14b. In addition, 7 in the figure
Is a glow plug.

Based on such a configuration, during the compression process, the inflow flows into the sub chamber 4 with a width T through the injection port 5 as shown by the white arrow in the figure, and in the sub chamber 4, the continuous surface 14f and the upstream inner wall portion. 14a, the continuous surface 14c, the downstream side inner wall portion 14b, the inclined portion 14d and the bottom portion 14e, and turns as shown by the solid line arrow in the figure.

Since the sub-chamber 4 has a horizontal width of 2R + T and has a substantially oval vertical cross-section, the swirl center of the vortex flow generated in the sub-chamber 4 is located immediately downstream of the opening of the injection port 5 in the sub-chamber 4. There is a spatial allowance that can be retained near the central portion. Therefore, the swirling center of the vortex flow is shown by the point 5 in the figure.
It is located on the line 1 that divides the horizontal line, which is obtained by subtracting the width T from the side, into two approximately equal parts.

Further, since a spatial allowance for holding the swirl center O of the vortex flow in the substantially central portion of the sub chamber 4 is secured immediately downstream of the opening of the injection port 5, the vortex flow and the sub chamber 4 continue to flow. The center O of the swirling flow is located slightly below the center position of the sub chamber 4 in the up-down direction.

In this way, the influence of the inflow flow from the injection port 5 is mitigated, and the swirl center O of the vortex flow generated in the sub chamber 4 is retained near the central portion of the sub chamber 4 without being largely biased to the side opposite to the injection port 5. Therefore, the fuel injected from the fuel injection valve 6 when the piston 1 reaches the vicinity of the top dead center is not supplied to the vicinity of the swirl center O of the swirl flow but is injected and supplied to the outer part of the swirl flow having a high flow velocity, Moreover, the injection direction is substantially along the vortex flow. Further, since the swirl center O of the vortex is held near the substantially central portion of the sub-chamber 4, a vortex having a strong and uniform flow is generated throughout the sub-chamber, and the spray flame spreads uniformly throughout the sub-chamber. It will be.

As a result, the atomization of the atomized fuel is promoted, the mixing with air proceeds, and a uniform air-fuel mixture is formed in the sub-chamber 4 without producing a fuel rich region. As a result, the amount of smoke produced can be reduced and the output can be improved.

(Effect of the Invention) As described above, according to the present invention, there is a spatial margin just downstream of the nozzle opening so that the swirl center of the vortex generated in the sub-chamber can be held near the substantially central portion of the sub-chamber. Therefore, the swirl center of the vortex flow is moved away from the inner wall portion on the downstream side, and a vortex flow having a uniform strong flow is generated throughout the sub chamber. As a result, a portion where the flow velocity of the vortex is large is secured even in the vicinity of the inner wall of the downstream side, and the fuel is supplied toward the portion where the flow velocity of the vortex is secured near the inner wall of the downstream side. Can promote mixing with air,
It is possible to reduce smoke output and improve engine output.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a conventional example, and FIGS. 3 and 4 are explanatory views showing vortices generated in the sub chamber. 1 ... Cylinder head, 2 ... Piston, 3 ... Hot plug, 4 ... Sub chamber, 5 ... Injection port, 6 ... Fuel injection valve,
7 ... glow plug, 8 ... main room, 14 ... inner wall surface, 1
4a ... upstream inner wall portion, 14b ... downstream inner wall portion, T ...
... Cross section thickness, Qa, Qb ... Center of curvature

Claims (1)

[Scope of utility model registration request] 1. A sub-chamber formed in a cylinder head, an injection port communicating the sub-chamber with the main chamber along a substantially tangential direction of a wall surface of the sub-chamber, and a fuel injection valve for supplying fuel into the sub-chamber. In a swirl chamber type diesel engine having: an inner wall surface that defines an upper half of the sub chamber, the inner wall portion has an upstream side inner wall portion and a downstream side inner wall portion with respect to a vortex flow generated in the sub chamber, and a curvature of the inner wall portion downstream side. The center is separated from the center of curvature of the upstream side inner wall portion in a direction perpendicular to the piston axis of the engine by an amount corresponding to the sectional thickness of the injection port, and the sectional shapes of the sub chambers are the upstream side inner wall portion and the downstream side inner wall portion. And the fuel injection valve is arranged so as to supply the fuel in the substantially swirl direction of the vortex flow generated in the inner wall portion on the downstream side. A swirl chamber type diesel engine.