JPS6239665B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piston cavity for a whirlpool diesel engine, and in particular to a cloverleaf piston cavity shape, the present invention aims to improve the air utilization rate in the main chamber and prevent unburned fuel and smoke. This is an improvement aimed at suppressing the occurrence of.

A whirlpool diesel engine generates a powerful swirl during its compression stroke by allowing air to flow into the whirlpool chamber at the cylinder head.
Fuel is injected here to cause sufficient mixing and combustion within the chamber, and is then jetted into the main chamber for complete combustion. A cloverleaf-shaped cavity is installed in the chamber to diffuse and swirl the combustion gas ejected from the whirlpool chamber.
Some are designed to achieve complete combustion.

Figure 1 shows the combustion chamber in a conventional spiral chamber diesel engine (published by Nissan Motor Co., Ltd.).
The structure of the LD diesel engine (see 1980 maintenance manual) is shown here, where 1 is a whirlpool chamber provided in the cylinder head 2, and 3 is an injection nozzle that injects fuel into the whirlpool chamber. When the piston 4 moves up during the compression stroke, air is forced into the swirl chamber 1 from the main nozzle 5, creating a strong swirl of air. Then, when the piston 4 reaches approximately the top dead center and the temperature of the compressed air rises, fuel is injected from the injection nozzle 3, so that the sprayed fuel becomes a sufficient mixture with the air, and combustion occurs. Start.

Next, when the piston 4 begins to descend due to this combustion, the combustion gas and some unburned fuel in the swirl chamber 1 are ejected from the main nozzle 5 into the main chamber 6, and at this time, the piston 4 The ejected gas and unburned fuel are diffused by the function of the cavity 7 formed at the top. In FIG. 2, a region 8 surrounded by a two-dot chain line shows the diffusion tendency and range of such gas, and the ejected gas and unburned fuel reach the diffusion region 7B from the handle 7A of the cloverleaf-shaped cavity 7. Then, it rapidly diffuses and spreads to almost the entire main chamber 6, and is further mixed with the air in the main chamber 6, thereby promoting combustion of unburned fuel and oxidation of smoke. In FIG. 1, 9 is a valve precess provided on the cylinder head 2 side, 10 is a valve center line, and 11 is a cylinder center line.

However, in the case of the piston cavity 7 of such a conventional whirlpool diesel engine,
Since the diffusion portion 7B is formed at a position shifted from the positions of an intake valve and an exhaust valve (not shown) in the cylinder axial direction, the valve recess 9 is
It is necessary to provide it separately from B. For this reason, in a swirl chamber type diesel engine, although increasing the volume ratio of the swirl chamber to the main chamber is effective for reducing smoke, the volume of the main chamber 6 including the valve recess 9 increases. Therefore, it was difficult to increase the vortex chamber volume ratio while keeping the compression ratio at a predetermined value.

Therefore, as shown in FIG. 3, it is conceivable to form the diffusion portion 17B of the cavity 17 so as to match the positions of the intake valve and the exhaust valve. In this way, the valve recess 9 can be used in combination with the diffusion section 17B, and the above-mentioned problems can be solved, but as shown in FIG.
0 is biased toward the ejection direction, and in the main chamber 6,
Air is difficult to mix in a region 21 shown surrounded by a broken line.

The purpose of the present invention is to solve these conventional problems by forming the diffusion part of the piston cavity so as to match the position of the valve, and by providing an air intake groove in the handle of the piston cavity. , increasing the vortex chamber volume ratio and improving the air utilization efficiency,
An object of the present invention is to provide a piston cavity for a whirlpool type diesel engine, which improves combustion characteristics and reduces smoke.

The present invention will be explained in detail below based on the drawings.

In the following, the same reference numerals will be used for the same parts as used in FIG. 1. FIG. 4 shows an embodiment of the present invention, where 27 is a piston cavity, and in this example, the position where the diffusion part 27B of the piston cavity 27 is used also as a valve recess,
That is, they are formed opposite to the intake and exhaust valves 27C and 27D. 27A is a handle of the cavity 27, and air intake grooves 28 are provided on both sides of the handle 27A, as shown in FIG.
In addition to forming a tapered groove toward the bottom of the handle 27A,
The grooves 28 are formed by alternating the formation positions left and right.

With the piston cavity 27 configured in this way, not only can the vortex chamber volume ratio be set sufficiently large while maintaining the compression ratio, but also the jet is ejected from the nozzle 5 to the handle 27A at high speed. Due to the flow of gas, the air in the area 29 surrounded by the broken line in the main chamber 6 is attracted to the handle 27A through the air intake groove 28, which effectively reduces the air utilization rate in the main chamber 6. This can promote the oxidation of unburned fuel and suppress the generation of smoke.

As explained above, according to the present invention, in the cloverleaf type cavity, the diffusion part is arranged at a position where it is also used as a valve recess.
The vortex chamber volume ratio can be set to a large value while maintaining the compression ratio at a predetermined value.Furthermore, the handle of the cavity is provided with air intake grooves on both sides, which allows for the control of the tendency and range of the gas ejected from the nozzle. Since the air in the main chamber at the part that comes off is also taken into the handle, the air utilization rate in the main chamber is improved, and unburned fuel and smoke in the exhaust gas can be significantly reduced compared to the conventional method.

Moreover, in the present invention, since the grooves are formed alternately, the mixture of fuel and air can be made uniform, and combustion can be improved.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the configuration of the combustion chamber in a conventional whirlpool diesel engine, and Figure 2 is a line showing the tendency and range of gas ejected from the nozzle toward the piston cavity and main chamber. Fig. 3 is a line diagram showing the ejection tendency and range of gas ejected from the nozzle toward the cavity and the main chamber when the diffusion section in the piston cavity is formed in accordance with the valve position. Figure 4 is a diagram showing an example of the structure of the piston cavity of the spiral chamber type diesel engine of the present invention, and Figure 5 is a diagram showing its A--A.
It is a sectional view of a line staircase. 1... Swirl chamber, 2... Cylinder head, 3... Injection nozzle, 4... Piston, 5... Main injection port, 6... Main chamber, 7
...Cavity, 7A...Handle, 7B...Diffusion part, 8...
Part, 9... Valve recess, 10, 11... Center line,
17... Cavity, 17B... Diffusion part, 20... Diffusion range, 21... Site, 27... Cavity, 27A...
Handle portion, 27B...diffusion portion, 27C, 27D...intake/exhaust valve, 28...air intake groove, 29...part.

Claims (1)

[Claims] 1. In a cloverleaf piston cavity for a whirlpool diesel engine, which has a handle that guides the flow of gas in the whirlpool ejected from the nozzle, and a diffusion part that diffuses the gas guided by the handle into the main chamber, A piston gear for a whirlpool type diesel engine, characterized in that the diffusion part is provided opposite to an intake and exhaust valve, and a groove is provided in the handle part to take in surrounding air toward the handle part. Bitey.