JPH0231214B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a combustion chamber of a subchamber type engine.

Figure 1 shows the subchamber nozzle of a conventional swirl chamber engine. In the figure, the auxiliary combustion chamber 2 is connected to the cylinder head 4.
It is recessed inside. The structure of the auxiliary combustion chamber 2 includes a hemispherical upper part and a truncated conical or cylindrical lower part, and FIG. 1 shows a truncated conical lower part. A fuel injection valve 5 and a glow plug 6 for preheating the inside of the auxiliary combustion chamber 2 at the time of starting the engine are installed in the auxiliary combustion chamber 2 as necessary. The auxiliary combustion chamber 2 is the auxiliary chamber nozzle 3
It communicates with the main combustion chamber 1, which is made up of the top surface of the piston 7, the cylinder 8, and the bottom surface of the cylinder head 4, through the piston 7. The ridge lines of the sub-chamber nozzle 3 at a cut plane of the sub-chamber nozzle 3 taken by a plane including the sub-combustion chamber center line AA and the cylinder center line BB are parallel (θ _L =θ _R ).

During the compression stroke during engine operation, air in the main combustion chamber 1 is compressed by the piston 7 and flows into the auxiliary combustion chamber 2 through the auxiliary chamber nozzle 3 to generate a vortex S. When fuel is injected from the fuel injection valve 5 along the direction of the vortex S, the fuel swirls in the sub-combustion chamber 2 along with the vortex S.
Fuel and air are mixed, ignited, and burned. Combustion gas and unburned fuel in the auxiliary combustion chamber 2 are ejected into the main combustion chamber 1 through the auxiliary chamber nozzle 3, work on the piston, and mix with the air in the main combustion chamber 1 to perform mixed combustion. That is, the jet flow flowing out from the sub-combustion chamber 2 reaches the cylinder wall 8 on the opposite side of the sub-combustion chamber 2 with respect to the cylinder center line BB, and collides with the wall surface. After the collision, the particles disperse along the wall surface of the cylinder wall 8.

However, the above method has the following drawbacks.

In order to reduce exhaust gas _NO
When combustion starts, the piston 7 is in its downward stroke, so the gas in the sub-combustion chamber 2 flows out into the main combustion chamber 1 through the sub-chamber nozzle 8, so the fuel in the sub-combustion chamber 2 remains unburned. It flows out into the main combustion chamber 1 with a large amount of water remaining. In this case, when the load is low, that is, in an operating range where the amount of fuel injection is small, there is too much air in the main combustion chamber 1, and the temperature level of the ejected gas is low, so incomplete combustion occurs even within the main combustion chamber 1. , emissions of unburned hydrocarbons, HC, etc. will increase. In addition, when the load is high, that is, when the fuel injection amount is large, there is a lack of air in the main combustion chamber 1, causing incomplete combustion.
Smoke, etc. worsens.

As a method of suppressing gas outflow from the auxiliary combustion chamber 2 to the main combustion chamber 1 at the time of ignition in the auxiliary combustion chamber 2,
Possible solutions include (1) reducing the passage area of the subchamber nozzle, and (2) reducing the subchamber nozzle angle θ _L (=θ _R ).

To suppress the above gas outflow, it is necessary to take measures to compensate for the combustion delay in the main combustion chamber 1 during high loads, that is, to promote the mixing and combustion of fuel and air in the main combustion chamber 1. For this purpose, in the case of (1), the passage area of the sub-chamber nozzle 3 must be made considerably smaller, and in this case, the vortex S in the sub-combustion chamber 2 during the compression stroke becomes stronger.
Combustion spray disperses too much at low loads, making it difficult to ignite and burn. In the case of (2), the sub-chamber nozzle 3 protrudes from the sub-chamber mouthpiece 9 and cannot be constructed, or the structure becomes complicated, resulting in high costs (see FIG. 2).

The purpose of the present invention is to focus on the above points and provide a pre-chamber nozzle that can prevent incomplete combustion that occurs when reducing _NOx by delaying fuel injection timing. Among the ridge lines of the sub-chamber nozzle on the cut plane of the sub-chamber nozzle by a plane including the combustion chamber center line and the cylinder center line, the minimum angle between the ridge line located on the cylinder center line side and a plane perpendicular to the cylinder center line. is expressed by θ _L , and the minimum angle between the ridge line located away from the cylinder center line and a plane perpendicular to the cylinder center line is expressed by θ _R , then θ _L
<θ _R of the main combustion chamber side of the nozzle passage wall located away from the cylinder centerline in the cross section of the subchamber nozzle passage taken by a plane including the auxiliary combustion chamber centerline and the cylinder centerline of the tapered auxiliary chamber nozzle. By providing a protrusion in the opening, if the minimum angle between the ridgeline of the nozzle passage of the opening and a plane perpendicular to the cylinder centerline is θ _R ', then θ _R '<θ _R is satisfied.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a sectional view showing the combustion chamber of the first embodiment of the present invention, and FIG. 4 is an enlarged sectional view showing the subchamber nozzle in FIG. 3.

The structure of the auxiliary combustion chamber 2 includes a hemispherical upper part and a truncated conical or cylindrical lower part, and the lower part is shown as a truncated conical one.

Center line A-A and cylinder center line B-
The inclinations θ _L and θ _R of the ridge lines in the cross section of the nozzle passage when the pre-chamber nozzle 3 is cut by a plane including B have a relationship of θ _L <θ _R. The opening end area of the sub-chamber nozzle 3 is made smaller on the sub-combustion chamber side compared to the main combustion chamber side.

Of the cross section of the nozzle passage above, the cylinder center line B-
The minimum angle θ _{R '} between the ridgeline of the nozzle passage at the opening end and a plane perpendicular to the cylinder center line B-B is θ _R A protrusion consisting of a combination of a circular arc with radius R and a straight line is provided so that '<θ _R (see Fig. 4).

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

With the above-mentioned pre-chamber nozzle, even if the fuel injection timing is delayed to reduce NO _x and ignition occurs in the sub-combustion chamber 2 when the piston 7 is on its downward stroke, the opening area of the pre-chamber nozzle 3 on the sub-combustion chamber side will be reduced. is small and the angle θ _L is small, so gas outflow from the sub-combustion chamber 2 to the main combustion chamber 1 is suppressed (both effects make it unnecessary to reduce the opening area on the sub-chamber side). Combustion within the combustion chamber 2 is promoted and becomes stable.
After that, gas flows out into the main combustion chamber 1 due to the pressure increase in the auxiliary combustion chamber 2, but the angles θ _R ′ and θ _L
Since this is small, the penetration of the ejected gas toward the center of the cylinder is improved, and the formation and combustion of a mixture of unburned fuel and air in the main combustion chamber 1 is promoted.

With the above, it is possible to reduce NO _x , HC, and smoke from the engine, and also to reduce noise.

FIG. 5 is a sectional view showing a subchamber nozzle of a combustion chamber in a second embodiment of the present invention.

In the first embodiment, the protrusion on the cross section of the subchamber nozzle 3 is configured in a straight line. The operation and effect are almost the same as in the first embodiment.

FIG. 6 is a sectional view showing the subchamber nozzle of the combustion chamber of the third embodiment of the present invention.

In the first embodiment, the protrusion on the cross section of the sub-chamber nozzle 3 is configured as a circular arc with a radius R. action,
The effect is almost the same as in the first embodiment.

FIG. 7 is a sectional view showing a subchamber nozzle of a combustion chamber in a fourth embodiment of the present invention.

In the first embodiment, the tip of the protrusion on the cross section of the subchamber nozzle 3 is rounded (radius r) or shaved off, and FIG. 7 shows the former case. The operation and effect are almost the same as those of the first embodiment, but the tip of the protrusion can be prevented from melting, cracking, etc., and is excellent in durability. The same can be said of the second and third embodiments.

FIG. 8 is a sectional view showing a combustion chamber of a fifth embodiment according to the present invention.

In the first embodiment, the sub-combustion chamber centerline A-A is inclined at an angle θ _C with respect to the cylinder centerline B-B.

The action and effect are almost the same as in the first embodiment, but
Since the angle between the ridge line of the sub-chamber nozzle 3 and the bottom surface of the sub-combustion chamber 2 increases by θ _C , the effect of suppressing gas outflow from the sub-combustion chamber 2 to the main combustion chamber 1 due to the angle of the sub-chamber nozzle 3 is reduced. Become.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing a combustion chamber having a conventional sub-chamber nozzle, Fig. 2 is an explanatory diagram showing a gas outflow state from the sub-combustion chamber to the main combustion chamber, and Fig. 3 is a first embodiment according to the present invention. 4 is an enlarged sectional view showing the pre-chamber nozzle of FIG. 3; FIG. 5 is a sectional view showing the pre-chamber nozzle of the combustion chamber of the second embodiment of the present invention; FIG. 6 is a cross-sectional view showing the pre-chamber nozzle of the combustion chamber according to the third embodiment of the present invention, FIG. 7 is a cross-sectional view showing the pre-chamber nozzle of the combustion chamber of the fourth embodiment according to the present invention, and FIG. It is a sectional view showing a combustion chamber of a fifth example according to the present invention. 1...Main combustion chamber, 2...Sub-combustion chamber, 3...Sub-chamber nozzle, A-A...Sub-combustion chamber center line, B-B...Cylinder center line.

Claims (1)

[Claims] 1. Among the ridgelines of the sub-chamber nozzle on the cut plane of the sub-chamber nozzle by a plane including the sub-combustion chamber center line and the cylinder center line, the ridge line located on the cylinder center line side and the plane perpendicular to the cylinder center line. A tapered pre-chamber nozzle with θ _L < θ _R , where the minimum angle is expressed as θ _L , and the minimum angle between a ridge line located away from the cylinder center line and a plane perpendicular to the cylinder center line is expressed as θ _R. By providing a protrusion at the main combustion chamber side opening of the nozzle passage wall located away from the cylinder centerline in the cross section of the subchamber nozzle passage taken by a plane including the auxiliary combustion chamber centerline and the cylinder centerline, A combustion chamber for a pre-chamber engine characterized in that θ _R ′<θ _R , where θ _R ′ is the minimum angle between the ridgeline of the nozzle passage of the opening and a plane perpendicular to the cylinder centerline.