CS201727B1 - Piston for combustion engines with modification for control of the heat expansion - Google Patents

Description

The present invention relates to a piston for internal combustion engines and to an arrangement for controlling thermal expansion.

The used pistons of internal combustion engines are highly stressed both thermally and mechanically. For today's internal combustion engines and pistons, they are manufactured from light alloys whose mechanical properties are temperature-dependent. Due to the shape and nature of the thermal load, the temperature of the piston varies considerably at various locations and the maximum difference reaches a normal temperature of 200 ° C. In high-speed engines, the piston is stressed not only by the gas pressure in the axis, but also by considerable lateral pressures at the piston stroke / connecting rod length ratios used. These force ratios are particularly pronounced in diesel engines and direct injection. Lateral pressure when the piston rod swings against the piston requires proper bearing surface and lubrication of the piston. The guide in the piston connecting rod is provided by a guide surface having a temperature so low during the operating cycle that it does not cause lubrication. Appropriate pressure distribution over the guide surfaces, however, requires a very precise alignment of the stiffness and shape accuracy of the connecting rod part of the piston, since inaccuracies lead to seizures, deformations and, above all, difficulties in oil consumption. A drawback of this embodiment of the piston is the relieving of the head part, which in the compression space permits the penetration of high temperature gases up to the upper piston ring. The gas pressure increases the pressure of the upper piston ring both on the cylinder wall and on the lower groove surface of the piston ring, which increases the wear of this part of the cylinder under increased temperature and conditions resulting from impaired lubrication and flue gas chemical action. The gradual coking of the lubricating oil onto the piston, penetrated by the non-ring part, forms the corresponding

201 727

201 727 of the cylinder height, an insulating layer that impairs heat transfer and immobilizes the upper piston ring, thus disabling it. Another drawback is the play on the piston head, allowing various hard contaminants to penetrate into the gap formed, and when the piston is lifted, the functional working surface of the cylinder is sagging. The impurities form carbon or coarser unfiltered particles.

The above-mentioned drawbacks are eliminated by a piston for internal combustion engines with a heat expansion control arrangement consisting of a head part, a ring part and a connecting rod part. The piston has a guide surface and two abutment surfaces. The basis is a support surface formed on the head part, in which the circumferential grooves are formed, and on the lower part of the connecting rod part. The remaining parts of the connecting rod part form the guide surface. The circumferential grooves have a parallelogram or trapezoid door open towards the cylinder. The circumferential groove has a depth to width ratio of at least 2.0.

An advantage of the piston arrangement according to the invention is to provide a support surface on the head portion, whereby the forces from the tipping moment are reduced and the load is distributed over a larger surface. Reduced clearance will reduce gas penetration to the upper piston ring, thereby removing increased wear, especially at the top dead center, and eliminating the breaking of the upper piston ring groove on the lower surface. By contacting the warmer piston head portion with the cylinder, a considerable amount of heat is dissipated and heat relieves the upper piston ring. A longer advantage is the formation of circumferential grooves on the piston head, fulfilling the function of a labyrinth seal, which reduces the pressure, temperature and the amount of gases penetrating the upper piston ring several times. The reduced load on this piston ring will create conditions for the transition to a smaller number of piston rings, which will positively affect production and operating costs. The circumferential grooves of the trapezoidal profile, open to the cylinder wall, ensure their automatic cleaning from the penetrating oil by inertial forces, and further lubricate the piston head portion. However, the circumferential grooving of the piston will increase the volume of the compression space, which will impair starting of a particularly cold engine. In order to maintain good engine start-up properties, the groove should be allowed to deteriorate by a maximum of four times the allowable tolerance.

An example of a piston according to the invention is shown in the accompanying drawing, in which Fig. 1 is a front view of the felt, Fig. 2 shows the direction of printing on the upper piston ring, Figs. trapezoid.

The piston 1 consists of a head portion 8, an annular portion J and a connecting rod portion 6 which is divided into a guide surface 1 and a support surface 8. The head section 6 is provided as a support surface 8 on which circumferential grooves χ are formed. The circumferential groove 2 is formed by a parallelogram or trapezoidal profile open towards the wall of the cylinder 10. The upper piston ring 8 is pressed radially on the cylinder χθ and axially on the lower surface IX by the compression pressure ·.

Claims (3)

SUBJECT MATTER A piston for internal combustion engines, adapted to control thermal expansion, comprising a head portion, an annular portion and a connecting rod portion on which a guide surface and two support surfaces are formed, characterized in that the support surface (6) is formed on the a part (2) in which circumferential grooves (7) are formed and on the bottom part of the connecting rod part (4), the remaining parts of the connecting rod part (4) forming a guide surface (5); Piston for internal combustion engines according to claim 1, characterized in that the circumferential groove (7) has a parallelogram or trapezoidal profile open towards the cylinder (10). Piston for internal combustion engines according to claim 1, characterized in that the circumferential groove (7) has a depth to width ratio of at least 2.0.