JPS5855328B2 - diesel engine piston - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piston structure for a diesel engine that improves smoke and fuel efficiency.

Direct injection diesel engines have a cavity at the top of the piston, into which fuel is injected.

However, in the conventional piston structure, the air utilization rate near the outer circumferential top surface of the piston top surface is low, so that the amount of smoke or HC generated in this portion is extremely large.

Diesel engines are also required to take measures against exhaust gases, and the timing of fuel injection is being delayed.

In such cases, the above drawbacks become even more serious.

Exhaust gas countermeasures are usually improved comprehensively by accumulating various improvements.

An object of the present invention is to reduce smoke and HC generated near the outer circumferential top surface of the piston top surface.

This will be explained in detail below using figures.

FIG. 1 is a sectional view showing the structure of a conventional piston.

A conventional piston 1 has a cavity 2 formed on its top surface.

A recess 4 for valve escape is formed in the top surface 3 other than the cavity 2.

The conventional piston action described above is as shown in Figure 2 (A) below.

First, during the compression stroke of the piston, as shown in A, air in the space A1 sandwiched between the top surface portion 3 and the cylinder head 5 is expelled into the cavity 2 as shown by the arrow P1.

This squish P1 promotes the mixing of fuel and air within the cavity 2.

Further, during the expansion stroke of the piston 1, the combustion gas in the cavity 2 is blown out into the space A2 surrounded by the top surface portion 3 and the cylinder head 5 as shown by the arrow P2.

This reverse squish P2 expands the diffusion combustion region to A2.

However, in the conventional piston 1, there is no recess 4 for valve relief.
are not used effectively.

The present invention effectively utilizes the valve escape recess to improve the fuel mixing effect by squish, and further expands the diffusion combustion area by reverse squish. Explain the configuration.

A cavity 12 is formed on the top surface of the piston 11,
A recess 14 for valve escape is formed in the top surface 13 other than the cavity 12.

The recess 14 consists of an edge 15 facing the cavity 12, and a recess 16 which is recessed deeper than the edge 15.

Here, the width T of the edge 15 is 3 to 6 m, and the recess 1
The depth H of 6 is preferably about 1 to 3 degrees.

Note that the depth of the edge portion 15 from the top surface portion 13 is the valve relief depth.

Next, the above invention will be explained in detail.

Referring to FIG. 5A, near the end of the compression stroke of the piston 11, the air in the space B1 surrounded by the top surface portion 13 and the cylinder head 17 flows into the cavity 12 as indicated by the arrow Q1 in the figure. .

This Q is the same as the conventional squish style.

The air in the concave portion 16 is squeezed by the edge 15 as indicated by R1 in the figure and enters the cavity 12.

Since this R1 is constricted at the edge 15, it promotes mixing of fuel and air within the cavity 12.

Next, referring to the opening in FIG. 5, when the piston 11 is near the start of its expansion stroke, the combustion gas in the cavity 12 flows into the space surrounded by the top surface part 13 and the cylinder head 17 as shown in Q2 in the figure. Enter B2.

This Q2 is the same as the conventional reverse squish. The combustion gas within the cavity 12 is further throttled by the edge 15 and enters the recess 16 as indicated by arrow R2 in the figure.

This R2 becomes a turbulent flow within the concave portion 16, and the concave portion 1
Burns within 6.

The inside of the concave portion 16 has a sufficient volume, unlike the area B2, so that the combustion occurs.

The combustion within this concave portion 16 further expands to the region B2.

As described above, according to the present invention, not only the disturbance effect due to squish during the compression stroke is improved, but also the diffusion combustion area due to reverse squish during the expansion stroke is significantly increased.
It is distantly related to the reduction of smoke and HC in the exhaust gas, and contributes to the reduction of fuel consumption by improving the air utilization rate.

Furthermore, as mentioned above, in a diesel engine, a relatively large amount of smoke and HC are generated near the outer periphery of the piston top surface, but in the present invention, the diffusion combustion region is expanded to near the outer periphery to improve air utilization efficiency, so that the exhaust gas The effect of reducing smoke and HC is particularly remarkable.

[Brief explanation of drawings]

Figure 1 is a sectional view for explaining the conventional piston structure.
Fig. 2 is a sectional view for explaining the action of Fig. 1, Fig. 3 is a sectional view showing an embodiment of the present invention, and Fig. 4 is a view taken along the line X-X in Fig. 3. , No. 19 in FIG. 5 is a sectional view showing the operation of the present invention. 11: Piston, 12: Cavity-14: Recess, 15
: Edge, 16: Concave part.

Claims (1)

[Claims] 1. In a diesel engine piston in which a cavity is formed on the top surface of the piston and a recess for valve escape is formed in the top surface other than the cavity, the piston is deeper, leaving the edge facing the cavity of the recess. A diesel engine piston characterized by forming a concave portion.