JPS58135317A - Combustion chamber of auxiliary combustion chamber type engine - Google Patents

Abstract

PURPOSE:To reduce the loss due to restriction of area in the nozzle for an auxiliary combustion chamber of an engine and reduce fuel consumption by an arrangement wherein the piston crown surface opposite to the open end face of the auxiliary combustion chamber nozzle facing a main combustion chamber is formed in parallel with the open end face and the angle defined between a plane including the piston crown and the center line of the piston is 90 deg. or less. CONSTITUTION:This engine has an auxiliary combustion chamber 4 formed in a cylinder head 5 and whose upper part is, for example, semi-spherical and whose lower part is, for example, of truncated cone shape. The auxiliary combustion chamber 4 communicates through an auxiliary combustion chamber nozzle 1 with a main combustion chamber defined by the crown of piston 2, a cylinder 8 and the lower surface of the cylinder head 5. The crown surface 2a of the piston 2 opposite to the open end of the auxiliary combustion chamber 1 on the side of the main combustion chamber 3 is formed in parallel with the open end face 1a of the auxiliary combustion chamber nozzle 1 and at a minimum angle theta between the piston crown surface 2a and the center-line A-A of the piston which is less than 90 deg.. This enables the nozzle 1 when the piston 2 is located near its top dead center to be restricted more than that in case of the prior art arrangement and the area of the auxiliary combustion chamber nozzle 1 to be increased with downward movement of the piston 2.

Description

[Detailed description of the invention] The present invention relates to improvements in the combustion chamber of pre-chamber engines.

Figure 1 shows the combustion chamber of a conventional pre-chamber engine. In the figure, the sub-combustion chamber 4 is recessed within the cylinder head 5.

The structure of the sub-combustion chamber 4 has a hemispherical upper part.

The lower part can be truncated conical or cylindrical, but 1
Fig. 1 shows the lower part having a truncated cone. A fuel injection valve 6 and a glow plug 7 for preheating the inside of the auxiliary combustion chamber 4 at the time of starting the engine are installed in the auxiliary combustion chamber 4 as necessary. The auxiliary combustion chamber 4 is connected to the top surface of the piston 2, the cylinder 8. The cylinder communicates with the main combustion chamber formed from the lower surface of the rad 5. The top surface of the piston 2 at the open end of the sub-chamber nozzle 1 on the main combustion chamber 3 side is parallel to the opening end surface of the sub-chamber nozzle 1, and forms an angle of 90' with the piston center line A-A.

During the compression stroke during engine operation, the main combustion chamber 3 is
The air inside is compressed and flows into the sub-combustion chamber 4 through the sub-chamber nozzle 1. The air flowing into the sub-combustion chamber 4 and the fuel injected from the fuel injection valve 6 mix.

Ignite and burn. Burnt and unburned gas in the sub-combustion chamber 4 is ejected into the main combustion chamber 3 through the sub-chamber nozzle 1.

While doing work to the piston, it mixes with the air in the main combustion chamber 3 and burns.

However, the above method has the following drawbacks.

In order to maintain the compression ratio, especially in small engines, piston 2
Since the gap between the top surface of the cylinder head 5 and the bottom surface of the cylinder head 5 becomes small, when gas is ejected from the auxiliary combustion chamber 4 to the main combustion chamber near the top dead center of the piston 2, the jet flow passes through the small gap at high speed. It flows. For this reason.

Penetration of the jet deteriorates due to increased flow resistance (poor mixture formation in the main combustion chamber 3), combustion deteriorates due to flame cooling by the wall of the main combustion chamber 3, and heat loss also increases.

As a countermeasure for this, near the top dead center where the gap is small,
In order to suppress gas ejection from the sub-combustion chamber 4 to the main combustion chamber 3, it is preferable to enlarge the sub-chamber nozzle 1 at a time when the throttle gap becomes large. Fig. 2 shows the minimum nozzle area f of the subchamber nozzle 1.
It shows the crank angle change mIn, but near the top dead center, the pre-chamber injection d: The peripheral area fc formed by the open end on the main combustion chamber 3 side and the top surface of the piston 20 becomes the minimum, and after that the main chamber gap becomes When increased, the subchamber nozzle 1 becomes the passage area itself.

When the passage area of the subchamber nozzle 1 is reduced from fl to f2,
” - peripheral area near the dead center fc + i.e. minimum nozzle area fr
mn also becomes smaller, and gas ejection from the sub-combustion chamber 4 to the main combustion chamber 3 can be suppressed (as shown by the broken line f2 in FIG. 2(b)).
When the main chamber gap is large and the minimum injection area is the passage area of the sub-chamber nozzle 1, this passage area is small, so the throttling loss of the sub-chamber nozzle 1 increases and fuel efficiency deteriorates.

The purpose of the present invention is to focus on the above-mentioned points, and to improve combustion in the main combustion chamber 3 where the gap between the top surface of the piston 20 and the bottom surface of the cylinder radiator 5 must be small. In order to suppress gas ejection from the sub-combustion chamber 4 to the main combustion chamber 3, the present invention is to provide a combustion chamber structure in which the sub-chamber nozzle 1 is throttled and expands when the gap between the sub-combustion chambers 1 and 1 becomes large. The top surface of the piston, which faces the opening end surface of the auxiliary chamber nozzle on the main combustion chamber side, is parallel to the opening end surface, and the minimum angle θ formed with the piston center line is θ<90°.

In this case, the cross-sectional area of the subchamber nozzle 1 was made the same as the conventional one! , t, the diaphragm is substantially applied near the top dead center.

- An embodiment according to the present invention will be described below with reference to the drawings. Fig. 3 is a sectional view showing a combustion chamber of an embodiment according to the present invention.

In the figure, the upper structure of the sub-combustion chamber 4 is hemispherical.

The lower part is a truncated cone, and the top surface 2a of the piston 2 facing the opening end of the sub-chamber nozzle 1 on the main combustion chamber 3 side is parallel to the opening end surface 1a of the sub-chamber nozzle 1, and is aligned with the piston center line A-A. The minimum angle θ formed by θ<90°.

Furthermore, 5 is the cylinder head and 6 is the fuel injection valve.

7 is a Gronolag, and 8 is a cylinder.

The functions and effects of the above configuration will be described.

Figures 4 and 5 show the distance from the opening end surface of the sub-chamber nozzle 1 on the main combustion chamber side to the top surface of the piston with respect to the crank angle when the angle θ = 90° and θ (900°, respectively. ) 1 (42) and the minimum area fmm of the pre-chamber nozzle. In Fig. 4, arrow C indicates the movement direction of the piston, and S indicates the main combustion chamber side opening of the pre-chamber nozzle in the direction of the piston center line A-A. Indicates the distance between the end surface and the top surface of the piston.

When the subchamber nozzle 1 and the top surface of the piston 2 are configured according to the present invention, that is, when θ is 90°, the angle is + compared to θ-90°.
hci becomes smaller (solid line in FIG. 5(a)).

Therefore, near top dead center, where the peripheral area fc formed by the main combustion chamber 3 side open end and the top surface of the piston 20 is the minimum area of the subchamber nozzle, the subchamber nozzle is narrowed more than before. Since gas outflow from the auxiliary combustion chamber 4 to the main combustion chamber 3 is suppressed, flame cooling and heat loss due to the walls of the main combustion chamber 3 are reduced, and the rate of pressure rise of the gas within the main combustion chamber 3 is also reduced. after that.

When the main combustion chamber 3 gap increases and the minimum area of the pre-chamber nozzle becomes the pre-chamber daily passage area, the pre-chamber nozzle area expands later than before, resulting in increased jet netration due to decreased flow resistance. , mixture formation and combustion within the main combustion chamber 3 are promoted.

Therefore, near the top dead center, the area of the passageway around the subchamber and the gap distance formed by the top surface of the giston are the same. Even if i is the same as before, the pre-chamber nozzle is narrower than before, and the minimum area of the pre-chamber nozzle is enlarged later than in the conventional case, making it more convenient for combustion.

As a result of the above, reductions in engine fuel consumption, smoke exhaust, noise, and heat loss can be achieved.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the combustion chamber of a conventional pre-chamber engine;
Figure (a) is an explanatory diagram showing the eyebrow area of the subchamber orifice in Figure 1;
FIG. 2(1)) is a diagram showing the change in the minimum nozzle area of the pre-chamber nozzle shown in FIG. 1 with respect to the crank angle. FIG. 3 is a cross-sectional view showing the combustion chamber of a pre-chamber type engine according to one embodiment of the present invention, and FIG. Distance at piston top surface deflection. An explanatory diagram showing 1, Fig. 4 (l) shows the above distance when the angle θ is <90°. An explanatory diagram showing 2, Fig. 4
Figure (c) is an enlarged view of the x part of Figure 4 (b), Figure 5 (a)
is the distance from the opening end surface of the sub-chamber injection port on the main combustion chamber side to the top surface of the piston with respect to the crank angle when the angle is θ-900 and θ<900. 1 or so. 2. Diagram showing 2. FIG. 5(b) is a diagram showing the minimum area fmjn of the pre-chamber nozzle port with respect to the crank angle when the angle θ=90° and θ<90°. ■... Sub-chamber nozzle, 1a... Main combustion chamber side inlet end face of sub-chamber nozzle, 2... Piston, 2a... Top surface of the piston. 3...Main combustion chamber, 4...Sub-combustion chamber, 5...Cylinder head, 8...Cylinder.

Claims (1)

[Claims] 1. In a sub-chamber engine having a sub-combustion chamber in the cylinder head and a sub-chamber nozzle that communicates the sub-combustion chamber with the main combustion chamber on the piston side, the sub-chamber nozzle faces the opening end surface of the sub-chamber nozzle on the main combustion chamber side. A combustion chamber for a subchamber type engine, characterized in that a top surface of the piston is parallel to the opening end surface, and a minimum angle θ with the piston center line is θ<90°.