JP4005209B2 - Piston of internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piston for an internal combustion engine.
[0002]
[Prior art]
Generally, in a direct injection type cast iron piston, a combustion chamber that is recessed in a concave shape is formed at the top, and a plurality of ring grooves for mounting a piston ring are formed on the outer periphery. In addition, an oil sump (hereinafter referred to as “oil gallery”) for introducing cooling oil for cooling the combustion chamber and the ring groove that becomes high temperature when the piston is operated is formed inside.
[0003]
There are various types of oil galleries of this type, and examples thereof include those shown in FIGS. 9 to 11. The oil gallery (1) is formed in a substantially annular shape along the circumferential direction of the piston body (3) on the upper side of the piston pin boss (2), and the top ring groove ( The upper cavity (6) formed inside the top land (5) up to 4) and the lower cavity (6) formed below the upper cavity (6) and inside the ring grooves (4) (4). 7) are substantially saddle-shaped in cross section and communicate with each other in a state of being displaced inward and outward.
[0004]
FIG. 12 shows the flow of the cooling oil (8) in the ascending process of the piston provided with the oil gallery (1), and FIG. 13 shows the flow of the cooling oil (8) in the descending process of the piston. . In this way, the cooling oil (8) in the oil gallery (1) is shaken by the vertical movement of the piston, thereby agitating the cooling oil (8) to promote heat conduction and the peripheral portion of the combustion chamber (9). Further, the temperature rise of the groove bottom portions of the ring grooves (4), (4), ... is reduced.
[0005]
In particular, when the shape of the oil gallery (1) has a substantially bowl shape as described above, the cooling oil (8) is inclined upward at the boundary between the upper cavity (6) and the lower cavity (7) during the piston ascending process. The top ring groove (4) collides with the surface (10), thereby destroying a kind of coating layer on which the oil on the inclined surface (10) adheres and heat conduction becomes very bad, further promoting heat transfer. ) Has the effect of lowering the groove bottom temperature. In the figure, (11) is an oil supply port for supplying the cooling oil (8) into the oil gallery (1), and (12) is for discharging the cooling oil (8) in the oil gallery (1). The oil discharge port (13) is a sand removal hole which is closed during use, and (14) is a piston skirt.
[0006]
[Problems to be solved by the invention]
However, as the engine increases in output, the conventional cooling structure cannot sufficiently cope with it, and especially the top ring groove among the peripheral portion of the combustion chamber (9) and the ring grooves (4) (4). (4) The temperature at the bottom of the groove becomes high, which adversely affects the thermal strength of the piston itself, or the lubricant oil scraped off by the piston ring is solidified and the piston ring is stuck, thereby generating blow-by gas. There was a malfunction.
[0007]
Japanese Utility Model Laid-Open No. 3-1242 discloses that a high heat conductive member is embedded in the oil gallery to reduce the groove bottom temperature of the top ring groove. In this case, a separate member from the piston is used. Since a high heat conductive member is required, the number of parts increases, the structure becomes complicated, and the manufacturing cost increases.
[0008]
In view of the above, an object of the present invention is to provide a piston for an internal combustion engine that has a simple structure and can sufficiently suppress a temperature rise in a peripheral portion of a combustion chamber and a groove bottom portion of a ring groove and has excellent cooling capacity.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides an oil sump for introducing cooling oil having a substantially bowl-shaped cross-section in which an upper cavity and a lower cavity are communicated with each other while being displaced from each other. In the piston of the internal combustion engine formed in an annular shape along the circumferential direction of the oil reservoir, the piston body moves up and down from the portion corresponding to the inner side of the ring groove on the wall surface on the land side of the oil sump toward the piston center side. A protrusion that collides with the cooling oil that moves along with the protrusion is integrally formed, and the protrusion is positioned below the upward inclined surface at the boundary between the upper cavity and the lower cavity . In addition, it is desirable that the protrusion be formed corresponding to the top ring groove located at the uppermost part of the ring groove.
[0010]
As a result, in the process of raising and lowering the piston, the cooling oil collides violently with the upper and lower surfaces of the protrusion, so that the stirring efficiency of the cooling oil can be remarkably increased, and the coating layer around the protrusion, that is, the inner side of the ring groove The coating layer is surely destroyed, and the cooling oil scattered by hitting the protrusion is likely to collide with the inner wall surface of the oil reservoir, which has been difficult to reach, and the coating layer inside the combustion chamber is also destroyed. As a result, heat transfer can be promoted more than before, and the temperature of the peripheral portion of the combustion chamber and the groove bottom portion of the ring groove can be sufficiently lowered.
[0011]
The protrusions are formed only on the exhaust valve side of the oil sump so as to equalize the temperature on the intake valve side and on the exhaust valve side where the temperature is higher than that . Further, the protrusion is formed so as to avoid the oil supply port for supplying the cooling oil into the oil reservoir, so that the supply of the cooling oil into the oil reservoir is not obstructed by the protrusion. Yes.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described in detail with reference to the drawings. First, a reference example as a premise thereof will be described. 1 and 2 are longitudinal sectional views of a piston according to a reference example, and FIG . 3 is a transverse sectional view of the same. The cast iron piston according to this reference example integrally has a projection (20) in the oil gallery (1) that collides with cooling oil (8) that moves as the piston body (3) moves up and down. Thus, the stirring efficiency of the cooling oil (8) is increased to improve the cooling capacity.
[0013]
The oil gallery (1) has a substantially bowl-shaped cross section in which the upper cavity (6) and the lower cavity (7) communicate with each other in a shifted state, as in the prior art, and a combustion chamber ( 9) having a downwardly inclined surface (22) projecting outward along the land, and having an upwardly inclined surface (10) projecting outward so as to surround the top ring groove (4) on the wall surface on the land side. Yes.
[0014]
The protrusion (20) is located near the portion corresponding to the inner side of the ring groove (4) (4) on the land-side wall of the oil gallery (1), particularly among the plurality of ring grooves (4) (4). It protrudes inward from the vicinity of the portion corresponding to the inside of the top ring groove (4) where cooling is highly necessary, and is positioned below the upward inclined surface (10).
[0015]
Further, as shown in FIG. 3, the protrusion (20) prevents the oil supply port (11) from blocking the space immediately above the oil supply port (11) formed in the bottom wall of the oil gallery (1). Avoiding it, it is formed in a substantially annular shape as a whole. Thereby, the cooling oil (8) is smoothly supplied from the oil supply port (11) into the oil gallery (1). Other structures are the same as those of the conventional structure shown in FIGS. 9 to 11, and members having the same functions as those of the conventional structure are denoted by the same reference numerals.
[0016]
Here, the flow of the cooling oil (8) in the oil gallery (1) accompanying the vertical movement of the piston will be described. FIG. 4 shows the flow of the cooling oil (8) in the upward movement process of the piston, and FIG. 5 shows the flow of the cooling oil (8) in the downward movement process of the piston. First, in the ascending process of the piston, the cooling oil (8) not only hits the inclined portion (10) at the boundary between the upper cavity (6) and the lower cavity (7), but also along the upward inclined surface (10). The upper surface of the projection (20) protruding so as to block the flow also violently collides, so that the coating layer around the inclined surface (10) and the projection (20), that is, the coating layer inside the top ring groove (4) is surely provided. The cooling oil (8) that has broken and splashed on the upper surface of the protrusion (20) is likely to collide with the downward inclined surface (22) near the oil gallery (1), which was difficult to reach in the past, and the combustion chamber (9) The inner coating layer can also be destroyed.
[0017]
Also, during the piston descending process, the cooling oil (8), which flowed relatively smoothly in the conventional structure, collides with the lower surface of the protrusion (20) and is disturbed, so the coating around the lower side of the protrusion (20) The coating layer in the vicinity of the downward inclined surface (22) of the oil gallery (1) can also be destroyed by the cooling oil (8) that breaks down the layer and splatters against the lower surface of the protrusion (20).
[0018]
As described above, the cooling oil (20) collides with the protrusion (20) formed in the oil gallery (1), so that the stirring efficiency of the cooling oil (8) can be remarkably increased, and the top ring groove (4 In addition, the coating layer on the inner side of the combustion chamber (9) can be destroyed in a wide range and reliably, and the coating layer on the inner side of the combustion chamber (9), which was difficult with the conventional structure, can also be destroyed. Even if the output of the engine increases, the temperature at the periphery of the combustion chamber (9) in the piston and the groove bottom temperature of the top ring groove (4) can be sufficiently lowered.
[0019]
6 to 8 show the structure of a piston according to an embodiment of the present invention based on the above reference example . In this piston, the exhaust valve in the diametrical direction of the annular oil gallery (1) is shown. A protrusion (30) is formed on about half of the side. In general, the temperature of the piston is higher on the exhaust valve side than on the intake valve side. Therefore, if the protrusion (20) is uniformly formed over the entire circumference in the oil gallery (1), Although the temperature of the peripheral part of the combustion chamber (9) and the bottom part of the top ring groove (4) varies between the intake valve side and the exhaust valve side, a protrusion (30) is formed only on the exhaust valve side as described above. By doing so, it is possible to reliably suppress the temperature rise on the exhaust valve side, which is particularly high, and to make the temperature of the peripheral portion of the combustion chamber (9) and the groove bottom portion of the top ring groove (4) uniform.
[0020]
【The invention's effect】
As is clear from the above description, according to the present invention, the stirring efficiency of the cooling oil in the oil reservoir can be remarkably increased by an extremely simple structure that only forms protrusions in the oil reservoir. In addition to reliably destroying the inner coating layer, it is also possible to destroy the inner coating layer of the combustion chamber, which was difficult with the conventional structure. The groove bottom temperature of the ring groove can be lowered sufficiently.
[0021]
Therefore, even if the engine output increases, it is possible to reduce the thermal strength fatigue of the piston itself, to prevent the piston ring from sticking due to the solidification of the lubricating oil, and to suppress the generation of blow-by gas, Thereby, the durability of the piston can be improved.
[0022]
In addition, by forming a protrusion only on the exhaust valve side of the oil reservoir, it is possible to reliably suppress the temperature rise on the exhaust valve side, which becomes a high temperature, and the peripheral portion of the combustion chamber on the intake valve side and the exhaust valve side of the piston The temperature of the groove bottom portion of the ring groove can be made uniform, and problems such as variations in accuracy between the intake valve side and the exhaust valve side of the piston due to long-term use can be prevented.
[0023]
Further, by forming the protrusion while avoiding the oil supply port, the cooling oil can be smoothly supplied from the oil supply port into the oil reservoir without being obstructed by the protrusion. Cooling capacity can be further improved by quickly introducing uncooled low-temperature cooling oil into the oil reservoir.
[Brief description of the drawings]
FIG. 1 is a front sectional view of a piston of a reference example as a premise of the present invention.
FIG. 2 is a side sectional view of the same.
FIG. 3 is a plan sectional view of the same.
FIG. 4 is a diagram showing the flow of cooling oil in the ascending process of the piston.
FIG. 5 is a diagram showing the flow of cooling oil in the descending process of a piston.
FIG. 6 is a front sectional view of a piston according to an embodiment of the present invention .
FIG. 7 is a side sectional view of the same.
FIG. 8 is a plan sectional view of the same.
FIG. 9 is a front sectional view of a conventional piston.
FIG. 10 is a side sectional view of the same.
FIG. 11 is a plan sectional view of the same.
FIG. 12 is a diagram showing the flow of cooling oil in the ascending process of the piston.
FIG. 13 is a diagram showing the flow of cooling oil during the downward movement of the piston.
[Explanation of symbols]
(1) Oil sump
(3) Piston body
(4) Ring groove
(8) Cooling oil
(9) Combustion chamber
(11) Oil supply port
(30) Protrusion

Claims (2)

An oil reservoir for introducing cooling oil having a substantially bowl-shaped cross section in which the upper cavity and the lower cavity communicate with each other in a state of being shifted from each other is formed in an annular shape along the circumferential direction of the piston body. In the piston of the internal combustion engine, a protrusion that collides with the cooling oil that moves as the piston body moves up and down from the vicinity of the portion corresponding to the inside of the ring groove on the wall surface on the land side of the oil reservoir toward the center of the piston. The protrusion is located below the upward inclined surface at the boundary between the upper cavity and the lower cavity and formed only on the exhaust valve side in the diametrical direction in the oil reservoir. A piston for an internal combustion engine. The piston of the internal combustion engine according to claim 1 , wherein the protrusion is formed avoiding an oil supply port for supplying the cooling oil into the oil reservoir.

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