JPS6220686Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piston for an internal combustion engine, and more particularly to a piston for an internal combustion engine in which a recess for forming a combustion chamber is provided at an eccentric position of the piston head.

Conventionally, a piston for an internal combustion engine has been proposed in which a recess is provided at an eccentric position in the piston head, and a combustion chamber is formed by this recess and an opposite recess on the cylinder head side.

In such a piston for an internal combustion engine, a squish area is formed with a slight gap between the flat part of the piston head that is not formed with a recess and the flat part on the opposite cylinder head side. can be placed on the same plane as the ignition position of the ignition plug located in the combustion chamber.Therefore, since the air-fuel mixture is pushed from the squeezing area towards the ignition position of the ignition plug, there is no air inside the combustion chamber. An overflow state suitable for combustion is formed, and an internal combustion engine with a high compression ratio and good combustion efficiency can be constructed.

However, in an internal combustion engine equipped with such an internal combustion engine piston, the combustion temperature, which is high due to combustion based on a high compression ratio, is transmitted from the recessed part to the piston pin boss part, and the shape of the piston is changed to the piston pin boss part. The piston has an elliptical shape expanded in the axial direction, and there are problems in that the abnormal contact of the piston with the cylinder bore causes hammering noise and local wear, and it also abnormally increases oil consumption.

This idea was devised in view of the above-mentioned conventional problems, and the amount of heat conducted to the piston pin boss of an internal combustion engine piston is provided with a recess that forms a combustion chamber at an eccentric position of the piston head. An object of the present invention is to provide a piston for an internal combustion engine that can reduce the

In order to achieve the above object, this invention provides a piston for an internal combustion engine in which a recess is provided at an eccentric position of the piston head, and a combustion chamber is formed by a recess on the cylinder head side arranged opposite to this recess.
The center of the piston pin is arranged in a direction opposite to the recess with respect to the center of the piston and eccentrically relative to the center of the piston.

Hereinafter, embodiments of this invention will be described with reference to the drawings.

FIG. 1 is an explanatory diagram showing one embodiment of a piston for an internal combustion engine according to this invention. A cylinder bore 2 is formed in the cylinder block 1, and a cylinder head 4 is fixed to the upper part of the bore through a gasket 3. In a portion of the cylinder head 4 facing the cylinder bore 2, a recess 5 is arranged eccentrically with respect to the cylinder bore center Cb. In this recess 5, intake valves 6 and exhaust valves 6 are provided, as well as an ignition plug 7.

A piston 8 is housed inside the cylinder bore 2 of the cylinder block 1 so as to be able to reciprocate with its piston center aligned with the cylinder bore center Cb.A top ring 9, a second ring 10 and an oil ring 11
is equipped with. Further, a recess 12 is provided on the upper surface of the head of the piston 8 at an eccentric position opposite to the recess 5 on the side of the cylinder head 4.
2 is adapted to form a combustion chamber together with the recess 5.

Also, inside the skirt portion of the piston 8, a position eccentric from the piston center (Cb) in the direction opposite to the recess 12 by an eccentric amount E (preferably within 2.5 mm) is set as the piston pin center Cp. A piston pin boss portion 13 is disposed on the piston pin boss portion 13, and a piston pin 14 is connected to an end portion of a connecting rod (not shown).
is supported by inset.

Next, the operation of the above embodiment will be explained. When the air-fuel mixture sucked into the cylinder moves upward to the vicinity of the top dead center of the piston 8, the air-fuel mixture
5, it is pushed in a swirling state toward the ignition position of the ignition plug 7 in the combustion chamber formed by the recess 5 on the cylinder head 4 side and the recess 12 on the piston 8 side, and is ignited by the ignition plug 7. It burns and expands, causing the piston 8 to move downward. Since the flow of the air-fuel mixture in the combustion chamber is in a vortex state suitable for combustion, the compression ratio is high, and therefore the combustion temperature is particularly high, and the head of the piston 8 that defines the combustion chamber The temperature on the part side also becomes high. However,
Piston pin boss portion 13 in this piston 8
is arranged in the opposite direction to the recess 12 forming the combustion chamber with respect to the piston center (Cb), so the distance between them is large and the amount of heat conducted from the combustion chamber to the piston pin boss 13 is reduced.

According to the above embodiment, in the piston 8, the amount of heat conducted from the combustion chamber to the piston pin boss portion 13 is reduced, and therefore the piston 8 is prevented from becoming oval due to abnormal thermal expansion deformation, and It is possible to prevent an extreme increase in oil consumption, a banging sound of the piston 8, and abnormal wear between the piston 8 and the cylinder bore 2 under such conditions.

As described above, this invention provides a piston for an internal combustion engine in which a recess is provided at an eccentric position in the piston head, and a recess on the cylinder head side arranged opposite to this recess forms a combustion chamber. Since the center of the piston pin is arranged in the opposite direction and at a position eccentric to the center of the piston, the amount of heat conducted from the combustion chamber to the piston pin boss can be reduced. As a result, uneven expansion of the piston in the axial direction of the piston boss is suppressed, and various problems such as hammering noise, local wear, and abnormal increase in oil consumption due to abnormal contact between the piston and cylinder bore are eliminated. can get.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an internal combustion engine to which an embodiment of the piston for an internal combustion engine according to the present invention is applied. 4... Cylinder head, 5... Recess, 8...
Piston, 12... recess, 13... piston pin boss section, 14... piston pin.

Claims (1)

[Scope of utility model registration request] In a piston for an internal combustion engine in which a recess is provided at an eccentric position in the piston head, and a recess on the cylinder head side opposite to the recess forms a combustion chamber, the recess is located in the opposite direction to the center of the piston. A piston for an internal combustion engine, characterized in that the center of the piston pin is located at a position eccentric to the piston.