RU2725297C1 - Cylinder-piston group of piston engines - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention relates to machine building, in particular to engine building. Piston engines cylinder-piston group consists of cylinder, piston and piston rings. Between upper piston compression ring and piston bottom throttling ring is installed out of heat-resistant alloy with radial clearances between cylinder and piston, sum of which is smaller than radial clearance between upper piston compression ring and piston.

EFFECT: technical result consists in reduction of heat load on compression rings and intensity of wear of cylinders, pistons and rings.

1 cl, 1 dwg

Description

The invention relates to the field of mechanical engineering, in particular engine manufacturing, and in particular to the design of a cylinder-piston group of piston engines and can be used both in the design of new engine models and in the improvement of existing ones.

The closest to the claimed technical solution, the prototype is a cylinder-piston group [1], containing a piston with compression rings and a cylinder, on the working surface of which grooves are made in the form of closed rings filled with non-ferrous metal.

The disadvantage of [1] is the impossibility of reducing gas pressure in the gaps in the labyrinths of the compression ring seals, and as a result, the inability to affect the wear rate of the parts of the cylinder-piston group and the loss of engine power to overcome friction forces.

The aim of the invention is to increase the reliability of the cylinder-piston group of piston engines and reduce mechanical energy losses.

The goal is achieved by the fact that in the proposed design of the cylinder-piston group of piston engines, the pressure is reduced in the gaps of the labyrinth of seals of the compression piston rings by installing an additional throttle ring located between the piston bottom and the upper compression piston ring with radial clearances between the cylinder and the piston. Thus, the technical result is achieved by a cylinder-piston group of piston engines consisting of a cylinder, a piston and piston rings, while between the upper piston compression ring and the piston bottom a throttle ring made of heat-resistant alloy with radial clearances between the cylinder and the piston, the sum of which is less than the radial the gap between the upper piston compression ring and the piston.

The reliability of most modern piston engines is limited by the wear of parts of the cylinder-piston group. The performance of this unit is limited by the service life of the upper compression piston ring, piston and cylinder, and the upper compression piston ring wears out 2-3 times faster than the piston and cylinder.

The reason for the insufficient wear resistance of the upper compression rings and the parts mating with them lies not only in the tribotechnical properties of the friction pairs, but also in the level of mechanical stresses from the working gas pressure, in conditions of insufficient lubrication.

The high wear rate of the parts of the cylinder-piston group, due to the high pressure of the working gases in the gaps in the labyrinth of seals with the piston, does not allow creating an equally strong and equally wear-resistant engine that could work reliably until overhaul without replacing the cylinder-piston group.

Creating an equally robust engine with equally wear parts is a complex and as yet unsolved problem.

To create equally wear-resistant friction pairs of the cylinder-piston group, to reduce the wear rate of the upper compression piston ring, cylinder and piston, it is necessary to reduce the mechanical loads acting in the mates of these parts.

The maximum pressure of the compression rings in the working cycle on the cylinder and the lower plane of the annular piston groove is created by three main forces:

- the elastic forces of the rings;

- radial pressure forces of the working gases in the gaps of the labyrinth of the piston seal (back pressure)

- axial pressure forces of the working gases in the end gap between the rings and the upper planes of the piston grooves.

The radial pressure of the compression rings on the cylinder wall from the elastic forces of the rings in modern automotive engines is selected in the range of 0.15-0.4 MPa (1.5-4 kgf / cm ² ) from the condition of providing seal over-piston space in all cycles of the duty cycle.

The maximum radial "ring" pressure of the working gases in the upper compression piston ring during the expansion process is reached 0.75 Pz,

where Pz is the maximum pressure in the above-piston space (combustion chamber) of the working stroke.

At high engine speeds, the radial pressure in the gaps between the upper compression piston ring and the piston remains approximately constant throughout the process of expansion of the working gas and is completely transmitted to the cylinder walls. This pressure in modern diesel engines reaches 10-11 MPa (100-110 kgf / cm ² ), which is 20-25 times more than the radial pressure from the elastic forces of the ring.

The maximum axial pressure of the working gases above the upper compression piston ring is equal to their pressure in the cylinder and top dead center (TDC) of diesel engines reaches 12-14 MPa (120-140 kgf / cm ² ).

The axial pressure of the gases above the upper compression piston ring, as a result of the piston shifting to the TDC and the friction forces in conjugation, the upper compression piston ring — the end surface of the piston groove — is transmitted to half the ring-cylinder interface, which leads to wear of the cylinder and the ring in the direction of piston shifting (ovalization of the cylinder).

The main factor determining the wear rate of the cylinder-piston group is the high pressure of the working gases in the gaps of the seal labyrinth between the upper compression ring and the piston.

Analysis of known technical solutions in this technical field showed that the proposed cylinder-piston group of piston engines has distinctive features that are not in the prototype. In aggregate, the listed distinctive essential features make it possible to obtain a new technical result: to increase the reliability of engines and reduce mechanical power losses to overcome friction forces.

In FIG. 1 shows the proposed design of the cylinder-piston group,

Where:

1 - throttle ring,

2 - insert

3 - piston

4- upper compression piston ring,

5 - cylinder

Δ ₁ is the radial clearance between the ring and the cylinder,

Δ ₂ is the radial clearance between the ring and the piston,

Δ ₃ is the radial clearance between the upper compression piston ring and the wall of the groove.

The proposed cylinder-piston group of piston engines contains a throttle ring 1 of heat-resistant alloy, which is installed in an additional groove of the piston 3 with a radial clearance Δ ₁ between the ring and cylinder 5 and a radial clearance Δ ₂ between the ring and the piston. The piston can be made with insert 2 or without insert.

The outer diameter of the throttle ring is less than the diameter of the cylinder by 2 Δ ₁ , and the inner diameter is larger than the diameter of the piston groove under the throttle ring by 2 Δ ₂ . The dimensions of the outer and inner diameters of the throttle ring are selected from the condition that the sum of the gaps Δ ₁ and Δ _{2 is} less than the radial clearance Δ ₃ between the upper compression piston ring 4 and the groove wall:

Δ ₁ + Δ ₂ <Δ ₃

The flow of gases through the gaps Δ ₁ and Δ _{2 of the} throttle ring into the gap of the upper compression piston ring is accompanied by throttling and pressure reduction in the gaps of the upper compression piston ring. The decrease in gas pressure in the gaps of the upper compression piston ring occurs under the influence of two factors: throttling and a smaller passage area of the sum of the gaps Δ ₁ and Δ ₂ compared with the gap Δ ₃ . By changing the sum of the gaps Δ ₁ and Δ _2, you can get the necessary pressure in the gaps of the upper compression piston ring and other compression rings.

The proposed design of the cylinder-piston group allows to reduce the pressure of the working gases in the labyrinths of the compression ring seals to the required values, to reduce the heat load on these rings and the wear rate of the cylinders, pistons and rings.

Limiting the pressure in the joints of the compression rings between the cylinder and the piston can significantly reduce the mechanical energy loss of the engine. According to estimates, the mechanical efficiency of the engine can be increased by 3-4%.

The proposed design of the cylinder-piston group allows to reduce the number of compression rings for both high-speed and low-speed engines. In high-speed engines, the number of compression rings can be reduced to one, with reliable compaction of the over-piston space.

Limiting the gas pressure in the gaps between the upper compression piston ring and the piston is an effective means of reducing the wear rate of the piston rings, cylinder and piston.

Thus, the technical problem has been completely solved to increase the reliability of the cylinder - piston group of piston engines and reduce mechanical energy losses.

The proposed cylinder-piston group of piston engines meets the condition of industrial applicability and can be used both in the design of new models of piston engines and in the improvement of existing ones.

Used sources

1. RF patent No. 2440503, IPC F02F 1/18. Priority from 10.01.2010. Published on July 20, 2011. Patent Description

Claims (1)

A cylinder-piston group of piston engines consisting of a cylinder, a piston and piston rings, characterized in that between the upper piston compression ring and the piston bottom there is a throttle ring made of heat-resistant alloy with radial clearances between the cylinder and the piston, the sum of which is less than the radial clearance between the upper piston compression ring and piston.

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