JPS6315561Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas recirculation type diesel engine in which a portion of the exhaust gas of the diesel engine is recirculated to the intake system.

Diesel engines that inject fuel into compressed air generate particulates in high-load regions, but conventional diesel engines limit the maximum fuel injection amount and reduce the amount of particulates at the cost of slightly sacrificing output. The diesel engine was put into practical use by suppressing the
However, due to the recent demand for exhaust purification, _NO
Exhaust gas recirculation has also become necessary in diesel engines in order to reduce emissions. However, when exhaust gas recirculation is performed in a diesel engine, its combustion tends to be insufficient, and therefore a large amount of particulates are generated in the operating range where exhaust gas recirculation is performed. Diesel engine fuel contains a larger amount of sulfur than gasoline, and therefore the particulates produced by exhaust gas recirculation also contain a larger amount of sulfur. If such fine particles containing sulfur components enter the lubricating oil through the piston ring from the gap between the piston and liner of the engine, they cause deterioration of the lubricating oil, and furthermore, the lubricating oil mixed with fine particles enters the valve train. During this process, mechanical and chemical wear occurs.

In order to solve this problem, the applicant has
An annular groove is bored in the vicinity of the piston top between the top of the piston facing the combustion chamber and the piston ring fitting wall facing the piston liner on the circumferential surface of the piston of the diesel engine, and the particulate foreign matter generated in the combustion chamber is fitted into the piston ring. We have proposed an exhaust gas recirculation type diesel engine in which a foreign matter prevention ring is fitted into the annular groove to prevent foreign matter from being transferred to the wall. That is, as shown in FIG. 1, a piston liner 2 is fitted into a cylinder bore 1a formed in a cylinder block 1 of the engine, a cylinder head 3 is placed and fixed on the cylinder block 1, and a piston 5 is fitted into the piston liner 2. The piston liner 2, the cylinder head 3, and the top surface of the piston 5 form a combustion chamber 7 by being reciprocatably fitted in a sealed manner. In cylinder head 3,
An intake pipe 9 for sucking fresh air into the combustion chamber 7, an exhaust pipe 11 for discharging exhaust gas from the combustion chamber 7, and an oil injection valve 13 for injecting fuel into the combustion chamber 7 are provided. Further, an intake valve (not shown) is provided at the opening of the intake pipe 9 to the combustion chamber 7, and an exhaust valve 15 is provided at the opening of the exhaust pipe 11 to the combustion chamber 7, and these intake valves and exhaust valves are connected. Opening and closing are controlled in synchronization with the movement of an engine crankshaft (not shown) connected to the piston 5 via a rod 17. The exhaust pipe 11 and the intake pipe 9 are communicated with each other by an exhaust recirculation passage 19 and an appropriately structured exhaust recirculation control valve 21.
A part of the exhaust gas in the intake pipe 9 is recirculated into the intake pipe 9.

An annular ring groove 5a is formed on the peripheral surface of the piston 5, and first and second compression piston rings 23, 24 are fitted into the ring groove 5a. As a result, a circumferential gap 25 is formed between the piston 5 and the piston liner 2, and a gap 27 is formed between the compression piston rings 23, 24 and the ring groove 5a.
An oil ring 29 is attached below.

An annular groove 5c is bored in the vicinity of the top of the piston 5, and a blocking ring 31 is fitted into the annular groove 5c to prevent particulate foreign matter generated in the combustion chamber 7 from being transferred to the piston ring fitting wall surface. Here, the foreign matter prevention ring 31 preferably conforms to the Japanese Industrial Standard JIS.
It fits into the annular groove 5c of the piston 5 at a low tension of 0 to 0.7 kg as specified in B8130.
Therefore, during the expansion stroke of the engine, the fine particles in the combustion gas are blocked by the foreign matter prevention ring 31, and hardly enter the inner circumferential surface of the piston liner 2 and the outer circumferential sliding surface of the piston 5. is combusted together with the combustion gas in an operating range where the temperature of the combustion gas in the combustion chamber is high.

As shown in FIG.
d, and expands in the circumferential direction from the central axis of the piston 5, and the outer side of the upper surface 5e in the circumferential direction is connected to the vertical surface 5g. Note that the bottom surface 5d may be inclined in the opposite direction to the top surface 5e as appropriate. On the other hand, the foreign object prevention ring 31 includes a radial portion 31a extending in the radial direction and a circumferential portion 31b connected to the circumferential portion of the radial portion 31a and extending upward. The radius portion 31a is the bottom surface 5d of the annular groove 5c.
It has a bottom surface 31c and a top surface 31d corresponding to the top surface 5e, and is converged in the direction of the central axis of the piston 5. Therefore, the inclined upper surface 5e, 3
The foreign object prevention ring 31 is held concentrically with the piston 5 due to the alignment effect caused by the engagement of the piston 1d. The above-mentioned vertical surface 5g of the piston 5 and the vertical surface 31e of the circumferential portion 31b opposite to this vertical surface
When the pressure of the combustion chamber 7 (FIG. 1) acts during this period, the bottom surface 31c of the foreign matter prevention ring 31 is pressed against the bottom surface 5d of the annular groove 5c, and the foreign matter prevention ring 31
The outer circumferential surface 31f of the circumferential portion 31b is pressed against the piston liner 2, and the piston ring 23 of fine particles is formed.
24 (Figure 1). For this purpose, there must be sufficient space between the vertical surfaces 5g and 31e so that the foreign matter prevention ring 31 can sufficiently receive the pressure of the combustion chamber 7.

For this purpose, it is conceivable to make the wall thickness of the circumferential portion 31b of the foreign matter prevention ring 31 sufficiently thin as shown in FIG.
If the circumferential portion 31b is made thinner in order to increase the gap between e, the upper portion of the circumferential portion 31b will also be made thinner and there is a risk that it will be exposed to high-temperature gas and be melted or broken, which poses a problem in its durability.

Therefore, in the present invention, the thickness of the circumferential part of the foreign object prevention ring is gradually decreased from the joining part with the radius part toward the top of the piston, thereby making the area where the pressure of the combustion chamber acts sufficiently wide, and increasing the thickness of the circumferential part. It has sufficient durability without being excessively diluted.

In FIG. 4, instead of the vertical surface 31e shown in FIG. 2, an inclined surface 31e' forming an angle θ with the vertical line is formed, which allows the upper part of the circumferential portion 31b of the foreign object prevention ring 31 to be relatively large. The foreign matter prevention ring 31 can be pressed and sealed against the bottom surface 5d of the annular groove 5c and the piston liner 2 by the gas pressure within the combustion chamber 7 (FIG. 1) while preventing melting and breakage.

In the embodiment shown in FIG.
Instead of g, an inclined surface 5g' is formed which is inclined at an angle θ' in the direction opposite to the inclined surface 31e' with respect to the vertical line, thereby forming a large gap area between both the inclined surfaces 31e' and 5g'.

In the embodiment shown in FIG. 6, the foreign object preventing ring 31 having a T-shaped cross section is used instead of the foreign object preventing ring 31 having an L-shaped cross section shown in FIG.

This invention provides a highly durable foreign object prevention ring that prevents wear of pistons, piston liners, and piston rings caused by particulates in diesel engines with exhaust recirculation, as well as deterioration of the lubricating oil and wear of the valve train caused by particulate lubricating oil contamination. Subsidiary agencies will be provided.

Furthermore, in the present invention, the space between the vertical surface of the top of the piston and the vertical surface of the circumferential portion of the foreign object prevention ring increases as it approaches the top of the piston. The combustion chamber pressure acts as a sufficient back pressure on the foreign matter prevention ring without leaking, and the foreign matter prevention function can be maintained. Since this can be achieved without forming a dead space, it is possible to avoid a decrease in engine output due to a decrease in compression ratio.

[Brief explanation of drawings]

Figure 1 is a schematic cross-sectional front view of one cylinder of an exhaust recirculation diesel engine according to the present invention, Figures 2 and 3 are enlarged cross-sectional views of a foreign matter prevention ring that does not belong to the present invention, and Figure 4 FIG. 6 is an enlarged sectional view of the foreign object prevention ring of the present invention. 1... Cylinder block, 2... Piston liner, 7... Combustion chamber, 9... Intake pipe, 11... Exhaust pipe, 5... Piston, 5c... Annular groove, 31...
Foreign matter prevention ring, 31a...radius portion, 31b...
...circumferential part.

Claims (1)

[Scope of utility model registration request] The top of the piston on the circumferential surface of the piston of an exhaust gas recirculation diesel engine that recirculates a portion of the exhaust gas from the exhaust system to the intake system, between the top of the piston facing the combustion chamber and the piston ring fitting wall facing the piston liner. In the exhaust recirculation type diesel engine, an annular groove is bored in the vicinity thereof, and a foreign matter prevention ring is fitted into the annular groove to prevent particulate foreign matter generated in the combustion chamber from being transferred to the piston ring fitting wall surface. The foreign object prevention ring includes a circumferential portion extending circumferentially along the circumferential surface of the piston, one end coupled to the circumferential portion, and the other end extending radially from the circumferential portion toward the central axis of the piston. 1. An exhaust gas recirculation type diesel engine, characterized in that the circumferential portion has a wall thickness that gradually decreases from a joint with the radius portion toward the top of the piston.