JPH082428Y2 - Combustion chamber of internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a combustion chamber of an internal combustion engine, and more particularly to a combustion chamber formed by appropriately recessing the top of a piston.

[Prior Art] Generally, a combustion chamber of a direct injection diesel engine or the like is formed in an appropriate shape so that high output and purification of exhaust emission can be achieved. Especially in the near future,
A combustion chamber with a lip (shelf) has been proposed in order to improve air flow, improve mixing with fuel, and the like.

As shown in FIG. 3 and FIG. 4, in the conventional combustion chamber of this type, the top portion of the piston 1 is recessed into a predetermined shape so as to be partitioned and formed, and along the opening edge 2 of the combustion chamber A lip 3 is formed so as to project inward. Further, the horizontal position of the combustion chamber is eccentric to the piston, and its center O is separated from the axial center P of the piston 1 by a predetermined distance S.

By forming in this way, a swirl swirling in the plane direction and a squish swirling in the vertical direction are appropriately formed as the air flow, and the mixture of the fuel to be ignited and the air in the combustion chamber is promoted. Become.

[Problems to be Solved by the Invention] By the way, the pressure of the combustion gas and the expansion force due to the combustion heat are applied to the opening edge 2 of the combustion chamber.

According to the simulation conducted by the present inventors, it was found that the distribution of the stress generated at the opening edge 2 is as shown in FIG. That is, based on the position of the piston pin (not shown) of the piston 1, a tensile stress F ₁ is generated in the same direction A as the pin, and a compressive stress F ₂ is generated in the direction B orthogonal thereto.

This is because the combustion in the cylinder causes the high temperature of the piston 1 to cause the combustion chamber opening formed on the top surface to
Compressive stress occurs. Further, since the piston 1 is held by way of the piston pin, the left and right semicircular portions centering on the piston pin pin direction and the longitudinal center line of the piston pin are pushed down by the gas pressure in the connecting rod direction, and the combustion occurs. Tensile stress F ₁ is generated in the direction of the pin of the chamber opening in the direction of eliminating the compressive stress. In addition to compressive stress due to heat, compressive stress due to gas pressure is superposed in the direction perpendicular to the opening pin direction,
Subject to large compressive stress F ₂ . Since the above-mentioned stress was repeatedly applied to the opening of the combustion chamber during engine operation, a crack was generated in the opening perpendicular to the pin.

Furthermore, as the background of recent combustion chamber technology, there are exhaust measures, high power output, rise in gas pressure due to turbocharging, and increase in heat load.Prevention of cracks has become an issue for this type of combustion chamber. It was

Therefore, in view of the above circumstances, the present invention was devised to provide a combustion chamber in which a lip does not crack.

[Means for Solving the Problems] The present invention, in a combustion chamber formed on the upper surface of a piston held by a piston pin and eccentric from the piston axis, projects radially inward at the opening edge of the combustion chamber. A protrusion restriction that forms a lip and increases the thickness of the lip shape in the piston axial direction in order to increase the strength of the lip in the direction passing through the piston axis and orthogonal to the piston pin, rather than the lip in the direction of the piston pin. It has a section. The protrusion limiting section is preferably provided only on the side opposite to the eccentricity.

[Operation] With the above configuration, the strength against the compressive stress generated at the opening edge of the combustion chamber is increased.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a combustion chamber of an internal combustion engine according to the present invention, which is applied to a combustion chamber having a substantially rectangular shape in plan view.

The center O _{1 of} this combustion chamber is separated from the axial center P ₁ of the piston 1 by a predetermined distance S ₁ and its opening edge is
A lip 12 is provided on the protrusion 11 so as to project inward in the radial direction. The lip 12 is provided with a protrusion limiting section 13 which is a feature of the present invention.

The protrusion limiting section 13 is a portion on the side opposite to the eccentric direction when viewed from the axis P ₁ , in other words, a straight line L connecting the axis P ₁ and the center O ₁ and extended, and one of the opening edge 11. It corresponds to the part centered on the intersection point X ₁ . This straight line L is in the direction B passing through the axis P ₁ and orthogonal to the piston pin. That is, the protrusion limiting section 13 is provided to increase the strength of the piston pin relative to the lip 12 in the direction A. In the present embodiment, the central angle of the fan shape seen from the center O is within the range of about 90 degrees.

As shown in FIG. 2, the protrusion limiting section 13 is provided with a wide lip 19 in which the thickness d in the piston axial direction is increased more than that of the lip 12 shown by the chain double-dashed line in the figure, Has a raised lip shape. Further, the projection limiting section 13 and the lip 12 in the other sections are configured so that their thickness d changes sequentially and are smoothly connected.

In addition, the combustion chamber of the present embodiment has a valve recess for avoiding interference between the piston 1 and the intake / exhaust valve (not shown).
17 are provided, and the protrusion limiting section 13 also serves as reinforcement of the corners 18 of these valve recesses 17.

 Next, the operation of this embodiment will be described.

When the fuel is ignited and burned in the combustion chamber while the internal combustion engine is operating, the tensile stress F in the pin direction A is applied to the opening edge 11 by the pressure and thermal expansion of the combustion gas.
₁ and a compressive stress F ₂ is generated in the direction B at right angles. However, in the part where the largest stress occurs, the protrusion limiting section
Since 13 is provided and its strength is substantially increased, it is not a detrimental stress on the opening edge 11.

As described above, since the lip 3 is not formed at the portion where the harmful compressive stress F ₂ is generated, the combustion chamber and the piston are prevented from being damaged, and the durability is improved.

[Effects of the Invention] In short, according to the present invention, the following excellent effects are exhibited.

A protrusion limit section is provided to increase the strength of the lip in the direction orthogonal to the piston pin, passing through the piston axis rather than the lip in the direction of the piston pin, so that the durability of the piston is secured and good combustion is maintained by the lip. it can.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a combustion chamber of an internal combustion engine according to the present invention, FIG. 2 is a sectional view taken along the line II--II in FIG. 1, and FIG. 3 is a conventional internal combustion engine. A plan view showing the combustion chamber,
FIG. 4 is a partially broken side view thereof, and FIG. 5 is a stress distribution diagram for explaining the problems of the conventional combustion chamber of an internal combustion engine. In the figure, 12 is a lip and 13 is a protrusion limiting section.

Claims (2)

[Scope of utility model registration request] 1. A combustion chamber formed on an upper surface of a piston held by a piston pin and eccentric from a piston axial center, wherein a lip projecting radially inward is formed at an opening edge of the combustion chamber, and In order to increase the strength of the lip in the direction orthogonal to the piston pin that passes through the piston axis rather than the lip in the direction of the piston pin, a protrusion limiting section with an increased thickness in the piston axial direction of the lip shape is provided. The combustion chamber of the internal combustion engine. 2. The combustion chamber of an internal combustion engine according to claim 1, wherein the protrusion limiting section is provided only on the side opposite to the eccentricity.