JPS59145344A - Piston fitted with combustion chamber - Google Patents

Abstract

PURPOSE:To cool a thin wall part with low temperature oil and improve the durability of a piston ever so high, by installing a cooling oil leading hole opened to the offset direction side, in a cooling cavity inside the piston surround ing a combustion chamber being offset. CONSTITUTION:At the top of a piston 5, a combustion chamber 11 is being offset as far as the specified entent (e) toward the side of a fuel injection nozzle 6 to a piston center shaft O1. Inside the piston 5, an annular cooling cavity 12 surrounding the combustion chamber and being offset as far as the same extent, and at the underside of the piston 5, both of a cooling oil leading hole 13 leading cooling oil into the inside of the cooling cavity 12 and a cooling oil discharge hole 12 exhausting the cooling oil from the cooling cavity 12 are formed up. The cooling oil leading hole 13 is installed at the offset direction side where a sectional area of the cooling cavity 12 becomes the widest whereby the cooling oil is so designed as to be taken in from an oil jet pipe.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piston with a combustion chamber in which a combustion chamber is recessed in the top surface, and particularly to an improvement in the cooling structure for cooling the inside of the piston with engine oil. .

Conventionally, when cooling the screws 1 to 1 of a diesel engine, etc., for example, Utility Model Application No. 54-182707 and
4-165606 Tan, an annular cooling cavity is formed inside the piston when viewed from the direction of the piston center axis, and inside the annular cooling cavity, a A well-known structure is one in which a piston is efficiently cooled from inside by forcibly introducing and circulating engine oil ejected as an oil jet from a jet pipe.

By the way, a piston used in a direct injection diesel engine has a circular combustion chamber (
The combustion chamber volume is secured by recessing the combustion chamber (cavity). In that case, the intake and exhaust ports 1e-1~ in the cylinder head of the engine move closer to each other in order to increase their respective opening areas, and the fuel injection nozzles move closer together to avoid interference with the intake and exhaust boats that are closer to each other. When the piston is laid out so as to be offset by a predetermined amount from the cylinder center axis, the center of the combustion chamber on the top surface of the piston is connected to the cylinder at F, which ensures the distribution of the fuel injected from the fuel injection nozzle. The central axis of the piston is offset in the same direction as the offset direction of the fuel injection nozzle (1). Therefore, the thickness between the side wall of the combustion chamber, which corresponds to the side where the center of the combustion chamber is offset, and the outer periphery of the piston is smaller than other parts, and the heat load on the piston ring on the offset side increases, improving seal performance and durability. ze1 decreases, and due to the decrease in heat dissipation, the heat load on the piston in that area becomes greater than in other areas, causing an imbalance.
As a result, piston deformation and crack occurrence are reduced by 10 <
There was a problem.

In view of this, the present invention provides a high heat load portion in a piston with a combustion chamber in which the combustion chamber is formed on the top surface offset from the center axis of the cylinder, that is, the combustion chamber corresponds to the offset direction of the combustion chamber. By effectively cooling the portion between the chamber side wall and the outer periphery of the piston using the cooling cavity described above, the imbalance in heat load in a piston with a combustion chamber having an offset combustion chamber can be corrected. The purpose of this invention is to equalize the temperature of the piston and thereby improve the durability of the piston with a combustion chamber.

In order to achieve this object, the configuration of the present invention is to provide a piston with a combustion chamber in which a combustion chamber is recessed in the top surface to the right of the center which is offset from the center of the piston by a predetermined distance with respect to the piston center axis. An annular cooling cavity is formed to surround the combustion chamber when viewed from the axial direction, and the center of the annular cooling cavity is offset from the piston central axis in the same direction as the offset direction of the combustion chamber center relative to the piston central axis. A cooling oil introduction hole for introducing cooling oil into the cooling cavity is formed so as to open into the cooling cavity on the offset direction side relative to the piston central axis at the center of the cooling cavity.

As a result, the part of the piston between the side wall of the combustion chamber and the outer periphery of the piston, which corresponds to the side where the center of the combustion chamber is located, is effectively cooled by the low-temperature cooling oil immediately after being introduced into the cooling cavity. It is.

Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings.

1 and 2, 1 is a cylinder block of a direct injection diesel engine, 2 is a cylinder formed within the cylinder block 1, and 3 is a cylinder block 1.
The cylinder head is airtightly joined to the upper surface via a gasket 4, and a piston 5 with a combustion chamber according to the present invention is fitted into the cylinder 2 so as to be able to reciprocate. Further, a fuel injection nozzle 6 for injecting and supplying fuel F into a combustion chamber 11 of the piston 5, which will be described later, is attached to the cylinder head 3, and a fuel injection part 6 at the lower end of the fuel injection nozzle 6 is attached.
Due to the arrangement layout of the intake and exhaust boats (not shown) that visit the cylinder head 3, a is attached to the lower surface of the cylinder head 3 at a position offset by a predetermined amount from the central axis OI of the cylinder 2, that is, the piston 5. It protrudes into the cylinder 2 from the inside. In addition, 7 is a glow plug that heats the combustion chamber 11 of the piston 5 when the engine is cold and improves C startability, and 8 is a connecting rod that connects the piston 5 with the crank bin 1o in the rank chamber 9.

As shown in FIG. 3, the top surface of the piston 5 is recessed with a squish-lip type circular combustion chamber 11 whose diameter increases from the opening toward the back.
1 is located midway between the central axis 01 of the piston 5 and the fuel injection part 6a at the lower end of the fuel injection nozzle 6, that is, the center o2 of the piston 5 is located in the middle between the central axis 01 of the piston 5 and the fuel injection part 6a at the lower end of the fuel injection nozzle 6, that is, the center o2 is located at a distance of a predetermined distance le toward the fuel injection nozzle 6 side with respect to the piston central axis o1. I'm on OffSera 1.

Moreover, the center axis 0 of the piston 5 is located inside the piston 5.
An annular cooling cavity 12 is formed to surround the combustion chamber 11 when viewed from one direction (a direction perpendicular to the top of the piston 5), and the center o3 of the annular cooling cavity 12 is aligned with the central axis 01 of the piston 5. The above combustion chamber 11 with respect to the central axis ○I
center of. It is offset in the same direction as the offset direction of No. 2 (arrow X direction in the figure) (in this embodiment, so as to coincide with the center 02 of the combustion chamber 11). In addition, the cooling cavity 1
The cross-sectional area of 2 is the center of the cooling cavity. The variation is greatest in the portion on the X side in the offset direction with respect to the piston center axis 01 in No. 3, and the minimum in the portions A and A facing in the radial direction.

Further, as shown in FIG. 4, the lower surface of the screw I-in 5 includes a cooling oil introduction hole 13 for introducing cooling oil (1 engine oil) into the annular cooling cavity 12. Cooling oil discharge holes 14 and 14 for discharging the cooling oil introduced into the interior to the outside are formed, and the cooling oil introduction hole 13 is located on the X side portion of the cooling cavity center O3 in the offset direction with respect to the center axis 01 of the screws 1 to 1. (the part where the cross-sectional area of the cooling cavity 12 is the largest), and the cooling oil discharge hole 1/1.14 is located at a part which is almost diametrically opposite to the part of the cooling oil introduction hole 13 (the part where the cross-sectional area is the smallest). part)
The cooling cavities 12 are opened at the respective openings.

On the other hand, an oil jet machine W115 is provided on the wall portion of the rank chamber 9 at a portion corresponding above and below to the cooling oil introduction hole 13 of the cooling cavity 12 of the piston 5, as indicated by -. As shown in enlarged detail in FIG. 5, the oil jet mechanism 15 communicates a jet pipe 16 that jets cooling oil upward as an oil jet, and the inside of the jet pipe 16 and the inside of the oil gear rally 17 of the cylinder block 1. A communication member 18 is provided, and the oil in the oil gear gallery 17 is jetted from the jet pipe 16 toward the cooling oil introduction hole 13 on the lower surface of the piston 5 that moves up and down.

Therefore, in the above embodiment, the oil in the oil gear gallery 17 of the cylinder block 1 is jetted from the jet pipe 16 of the A oil jet mechanism 15 in the -L direction and passes through the cooling oil introduction hole 13 on the lower surface of the piston 5 which moves up and down. The oil is introduced into the cooling cavity 12, flows through the cooling cavity 12, and then falls into the crank chamber 9 through the cooling oil discharge holes 14,14. As a result, the piston 5 is cooled by heat exchange with the cooling oil flowing within the cooling cavity 12.

In that case, the center 03 of the cooling cavity 12 is the center 02 of the combustion chamber relative to the piston center axis 01.
The cooling air introduction hole 13 is opened in the direction of the piston central axis OI of the cooling air cavity center 03, and the cooling air introduction hole 13 is opened in the direction of the piston center axis OI of the cooling air cavity center 03. Therefore, the offset side portion between the side wall of the combustion chamber 11 and the center axis of the screws 1 to 5 corresponding to the offset direction X of the combustion chamber 11 with respect to the piston center axis 0+ The portion that is thinner than the other portions and has lower heat dissipation is effectively cooled by the relatively low temperature cooling oil immediately after being introduced into the cooling cavity 12. As a result, the cooling effect on the offset side portion increases, so that the offset side portion does not become abnormally high in thirst, and the heat load becomes almost equal to the heat load on other portions.
As a result, the heat load on the entire screws 1 to 5 becomes uniform, and the IFT 1' can be prevented from becoming distorted or cracked.

Further, the cross-sectional area of the cooling cavity 12 decreases as it goes from the portion corresponding to the cooling oil introduction hole 13 to the portion corresponding to the cooling oil discharge holes 14, 14, and becomes ``rj''. Since the cooling oil is constricted at the portion corresponding to the discharge hole 14.14, the flow velocity of the cooling oil at the portion corresponding to the discharge hole 14, 14 is higher than that at the portion corresponding to the introduction hole 13. As a result, even if the cooling oil becomes high in temperature due to heat exchange with the piston 5 while flowing through the cooling cavity 12, the cooling oil discharge hole 14°1 in the piston 5 can be removed.
The four side portions can be cooled well, and the cooling effect of the piston 5 as a whole can be stably ensured.

In the above embodiment, the combustion chamber 11 of the engine 5 is a squishy collip type, but the present invention can also be applied to engines having other types of combustion chambers. Needless to say.

As explained above, according to the present invention,
A combustion chamber with a center offset from the central axis is recessed in the top surface of the piston, and an annular cooling cavity is provided inside the piston, which is offset in the same direction as the combustion chamber so as to surround the combustion chamber. By forming the cooling oil into the cooling cavity on the offset direction side of the cooling cavity with respect to the piston center axis, the piston has a gap between the combustion chamber side wall corresponding to the offset direction of the combustion chamber and the piston outer periphery. Since the 39 flesh part of the piston is efficiently cooled by the low-temperature cooling air immediately after it is introduced into the cooling cavity, the heat load on the entire piston can be balanced. It is a material that can improve durability.

[Brief explanation of drawings]

The drawings show embodiments of the present invention; FIG. 1 is a longitudinal sectional view of a cylinder portion of a diesel engine equipped with the piston of the present invention, FIG. 2 is an enlarged sectional view of the same essential part, and FIG. 3 is a plan view of the piston. FIG. 4 is a bottom view of the same, and FIG. 5 is an enlarged view of the oil jet mechanism. 1... Cylinder block, 3... Cylinder head,
5... Piston, 6... Fuel injection nozzle, 11...
・Combustion chamber, 12... Cooling cavity, 13... Cooling oil introduction hole, 15... Oil jet mechanism, 01... Piston center axis, 02... Combustion chamber center, Q3... Cooling cavity center.

Claims (1)

[Claims] (1) In a piston with a combustion chamber in which a combustion chamber whose center is offset by a predetermined IJ with respect to the center axis of the screw 1 is recessed in the top surface, there is a combustion chamber inside the screw 1 that extends in the direction of the center axis of the screw 1. An annular cooling cavity is formed surrounding the combustion chamber, and the center of the annular cooling cavity is offset from the piston central axis in the same direction as the offset direction of the combustion chamber center with respect to the piston central axis, and A combustion chamber with a combustion chamber characterized in that a cooling oil introduction hole for introducing cooling oil into the cooling cavity is formed so as to open into the cooling cavity on the offset direction side opposite to the piston central axis at the center of the cooling cavity. piston.