JPH0122903Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piston for an internal combustion engine, and more particularly to a piston having a concave combustion chamber formed at the top thereof to promote mixing of fuel and air.

Conventionally, direct injection internal combustion engines have a concave combustion chamber at the top of the piston, and the inner diameter of the combustion chamber is generally equal or larger from the bottom to the top. It's summery.

However, in such a combustion chamber,
A portion of the fuel injected from the injection nozzle toward the side wall of the combustion chamber is blown up to the top surface of the piston, and as a result, this blown up fuel causes incomplete combustion, increasing black smoke in the engine. This results in a decrease in combustion efficiency.

Therefore, in order to improve this, an annular shelf was provided around the inlet of the concave combustion chamber to suppress combustion from blowing up to the top of the piston, and to promote mixing of fuel and air during squishing and reverse squishing. A ski-lip type combustion chamber has been proposed.

By the way, in such a skid lip type combustion chamber, the thickness of the shelf portion is uniform over the entire circumference to maintain a good mixing distribution of fuel and air over the entire circumference.

However, in a piston with such a combustion chamber in which a valve relief is formed, the thickness of the shelf portion becomes thinner by the thickness of the valve relief, which causes an imbalance in the air-fuel mixture with other parts. There are problems such as thermal cracks due to an imbalance in temperature distribution due to the thinning of the shelf.
Further, when the valve relief portion is deep, the end portion of the valve relief portion cannot be chamfered which is necessary for durability, which further exacerbates the above-mentioned problem.

Therefore, there is an idea in Japanese Utility Model Application Laid-open No. 54-82209, in which the shelf at the boundary between the thinner part and the regular thick part is removed to make it discontinuous. However, although the prior art disclosed in this publication can prevent the occurrence of thermal strain by separating the shelf portions having different thicknesses from each other, there is a problem in that the imbalance in the air-fuel mixture due to the difference in thickness cannot be corrected.

The present invention has been developed by focusing on the above-mentioned problems, and when providing a valve relief part and a concave ski-lipped combustion chamber, it is possible to promote the mixing of fuel and air, and moreover, it is possible to promote the mixing of fuel and air. The object of the present invention is to provide a piston for an internal combustion engine that prevents the occurrence of thermal cracks.

The structure of the piston of the internal combustion engine of the present invention to achieve the above object is such that the top of the piston has a concave combustion chamber, a concave intake valve that partially overlaps the combustion chamber, and is shallower than the combustion chamber, and an exhaust valve. A valve relief portion of the valve is provided, and the combustion chamber extends into the combustion chamber over the entire circumference through a portion opening to the top portion and a portion opening to the valve relief portion at an upper end portion of the side wall of the forward combustion chamber. It is characterized by having shelf parts of the same width.

The shelf with the above structure has a stepped shape in the valve relief part and other parts, but since the shelf part has the same thickness, that is, the width, it is possible to prevent cracks from occurring due to uneven temperature distribution. In addition, the configuration in which the widths are the same acts to sufficiently mix air and fuel, and the generation of smoke can be significantly improved.

The details of the present invention will be explained below with reference to the drawings. Figure 1 is a perspective view of the upper part of a piston 1 of an internal combustion engine in an embodiment of the present invention, and the top of the piston 1 has a concave combustion chamber 2. In addition, valve relief portions 3 corresponding to valve umbrellas of intake and exhaust valves (not shown) are formed.

Therefore, in the present invention, as shown in the longitudinal cross-sectional view of FIG. A shelf 4 having approximately the same width H is formed around the upper end of the side wall 2a, and the end of the shelf 4 is appropriately chamfered as indicated by arrow R.

Even if fuel is injected against the inner wall of the combustion chamber 2 of the piston 1 configured as described above,
Due to the function of the shelf portion 4 continuously formed with a uniform width around the upper end of the combustion chamber 2, fuel and air are effectively mixed in the vertical direction over the entire circumference.

In addition, since the width of the shelf 4 is the same in the valve relief part 3 as in other parts, the edge of the shelf 4 is chamfered around the entire circumference, which prevents the occurrence of thermal cracks at this corner. do not have.

As explained above, the piston of the internal combustion engine of the present invention has a concave combustion chamber at the top of the piston, and a concave valve relief part of the intake valve and exhaust valve that partially overlaps with the combustion chamber and is shallower than the combustion chamber. and a shelf part of the same width extending into the combustion chamber and extending over the entire circumference through the part where the combustion chamber opens to the top and the part which opens to the valve relief part, at the upper end of the side wall of the combustion chamber. With this configuration, the following effects can be obtained.

That is, due to the effect of the shelf provided at the upper end of the side wall of the combustion chamber, fuel and air are sufficiently mixed and combustion is promoted, so that the combustion efficiency of the internal combustion engine can be improved.

Further, since the shelf portion is formed with approximately the same width all around the circumference, there is no fear of cracking due to high temperatures, and this is effective in improving the durability of the piston.

[Brief explanation of the drawing]

FIG. 1 is a top perspective view of the main parts of a piston according to an embodiment of the present invention, and FIG. 2 is a longitudinal cross-sectional view of the main parts developed in the direction AB of FIG. 1. 1...Piston, 2...Combustion chamber, 2a...Side wall, 3...Valve relief part, 4...Shelf part, H...
width.

Claims (1)

[Scope of utility model registration request] A concave combustion chamber is provided at the top of the piston, and concave valve relief portions of the intake and exhaust valves are provided that partially overlap the combustion chamber and are shallower than the combustion chamber, and the upper end of the side wall of the combustion chamber is provided with a concave valve escape portion of the intake valve and the exhaust valve. A piston for an internal combustion engine, wherein the combustion chamber extends over the entire circumference through a portion opening to the top and a portion opening to the valve relief portion, and forms a shelf portion having the same width and projecting into the combustion chamber.