RU2257484C1 - Piston-cylinder tribomating of internal combustion engine - Google Patents

Abstract

FIELD: mechanical engineering.

SUBSTANCE: invention can be used in manufacture of pistons for internal combustion engines. Proposed piston has head and skirt with hole for piston pin. Length of skirt on loaded side is greater than length of skirt on unloaded side of piston, thickness of skirt on loaded side of piston exceeds thickness of skirt on unloaded side according to definite relationships. Carrying surfaces of skirt form X-like areas on opposite sides of skirt asymmetrical relative to longitudinal axis of piston and limited by curves. Opposite side generating surfaces of piston skirt form asymmetrical figure. Geometric parameters of piston are as follows: length of piston L=(0.65-0.9)D, height of sealing belt H=(0.48-0.60)D, maximum length of piston skirt B(I)=(0.25-0.45)D where D is nominal diameter of piston.

EFFECT: reduced to minimum friction losses without decreasing carrying capacity of piston.

5 dwg

Description

The invention relates to mechanical engineering, namely to engine building, and can be used for the manufacture of pistons of internal combustion engines (ICE).

A known design of the piston [1] of an internal combustion engine. The piston has an oval cross-section with greater ovality and a smaller wall thickness on the unloaded side, and also has a slot on the unloaded side in the groove of the oil scraper ring. This design makes it possible to reduce the gap between the loaded side of the piston and the cylinder wall and, therefore, to reduce the consumption of lubricant. The large length of the skirt on the loaded side reduces the angle of inclination of the piston and the noise it creates when shifted around the top dead center.

An analysis of the invention shows that for rectangular bearing surfaces, the described asymmetric profile of the skirt cannot create the same bearing capacity with angular shifting of the piston on the compression and stroke strokes. The reduction of friction losses is not enough.

A known piston design [2] of an internal combustion engine, in which the axial section of the piston skirt is an asymmetric figure described by parabolic curves, the parameters of which are selected taking into account the action of lateral forces in the combustion process, thermal deformations and the principles of the hydrodynamic theory of lubrication. The bearing surfaces of the skirt are made in the form of X-shaped areas, which are described by the radii of circles with an arc length θ determined by the corresponding ratio. Such an asymmetric profile of the skirt can create the same bearing capacity under different operating conditions on the “Compression” and “Travel” strokes, which is typical for internal combustion engines, since the gas pressure in the cylinder and, accordingly, the lateral force in the “Travel” stroke from -for the explosive nature of the combustion of the working mixture is several times higher than in the "Compression" cycle. The bearing surfaces are described by the radii of circles with the arc length θ, which varies depending on the radial clearance, profile and axial coordinate by expression

- осевая координата вершины боковой образующей профиля (осевая координата наиболее узкой части несущей Х-образной зоны), i=1, 2 - соответствуют нагруженной и ненагруженной стороне поршня; R - радиус юбки поршня;where h ₀ is the radial clearance between the cylinder and the piston skirt; Z is the axial coordinate with the beginning in the center of the axis of the hole for the piston pin;

- the axial coordinate of the top of the side generatrix of the profile (axial coordinate of the narrowest part of the bearing X-shaped zone), i = 1, 2 - correspond to the loaded and unloaded side of the piston; R is the radius of the piston skirt;

, - зазоры между цилиндром и юбкой поршня в верхней и нижней ее части; В⁽ⁱ⁾ - длина юбки на нагруженной и ненагруженной стороне поршня;

, - gaps between the cylinder and the piston skirt in its upper and lower parts; In ⁽ⁱ⁾ - the length of the skirt on the loaded and unloaded side of the piston;

Opposite lateral forming piston skirts form an asymmetric figure, the shape of which depends on the size of the skirt, radial clearance, the location of the axis of the piston pin and is determined by the expression

where h ⁽ⁱ⁾ is the deviation of the profile from the inner walls of the cylinder i, and

Surfaces perpendicular to the axis of the bore under the piston pin and lying outside the X-shaped areas are located in the areas of the so-called refrigerators and are not specially profiled.

The configuration of the profile and the location of its vertices are selected in such a way that they provide maximum hydrodynamic lifting force on the loaded side, that is, the liquid friction mode, reduce the likelihood of scoring.

Analysis of the design shows that the asymmetric profile solves the problem of accounting for angular shifting, however, the design does not fully take into account the different operating conditions at the “Compression” and “Travel” strokes and in the process of transverse shifting does not fully reduce the tribological losses in the piston pairing - cylinder, since the area of the piston bearing surface on the loaded and unloaded sides differs slightly.

Tribological losses are understood as losses on resistance to the movement of the piston on the lubricating layer in the cylinder and losses of the lubricant “on waste” due to its flow through the upper edge of the piston skirt.

The specified design is aimed at reducing friction losses in the piston-sleeve interface.

The basis of the invention is the technical problem - the creation of tribo-conjugation piston - cylinder of an internal combustion engine of such a design that would minimize tribological losses without reducing its bearing capacity.

This problem is solved in that in the tribo-coupling, the piston is a cylinder of an internal combustion engine containing a cylinder and a piston with an opening for a piston pin, consisting of a head and a guide part (skirt) in the form of a barrel-shaped asymmetric figure, the bearing surfaces are made in the form of X-shaped areas, which are bounded above and below the edges of the skirt and are described by the radii of circles, and having a piston - cylinder in tribo-conjugation, the deviation of the profile of the generating bearing surfaces of the loaded and unloaded sides of the piston skirt from the morning wall of the cylinder in a plane perpendicular to the axis of the hole, determined by the expression

, где

- зазоры между цилиндром и юбкой поршня в верхней и нижней ее части, согласно изобретению длина юбки на нагруженной стороне больше длины юбки на ненагруженной стороне поршня в соответствии с соотношением В⁽¹⁾/В⁽²⁾=1,1...1,3, а толщина юбки на нагруженной стороне больше толщины юбки на ненагруженной стороне поршня в соответствии с соотношением t⁽¹⁾/t⁽²⁾=1,2...1,5, при этом геометрические параметры поршня выполнены следующими: длина поршня L=(0,65...0,9)D, высота уплотняющего пояса H=(0,48...0,60)D, длина юбки поршня максимальная B⁽¹⁾=(0,25...0,45)D, где D - номинальный диаметр поршня.where h ⁽ⁱ⁾ is the deviation of the profile from the inner walls of the cylinder, h ₀ is the radial clearance between the cylinder and the piston skirt; Z is the axial coordinate with the beginning in the center of the axis of the hole for the piston pin; k ⁽ⁱ⁾ , m ⁽ⁱ⁾ , l ⁽ⁱ⁾ are the profile curve parameters, i = 1, 2 - correspond to the loaded and unloaded side of the piston, and

where

- gaps between the cylinder and the piston skirt in its upper and lower parts, according to the invention, the length of the skirt on the loaded side is greater than the length of the skirt on the unloaded side of the piston in accordance with the ratio B ⁽¹⁾ / B ⁽²⁾ = 1.1 ... 1, 3, and the thickness of the skirt on the loaded side is greater than the thickness of the skirt on the unloaded side of the piston in accordance with the ratio t ⁽¹⁾ / t ⁽²⁾ = 1.2 ... 1.5, while the geometric parameters of the piston are as follows: piston length L = (0.65 ... 0.9) D, the height of the sealing belt H = (0.48 ... 0.60) D, the maximum length of the piston skirt B ⁽¹⁾ = (0.25 ... 0, 45) D, where D is the nominal diameter tr piston.

The proposed design differs from the design [1] by the geometry of the bearing surfaces of the piston skirt, which corresponds to the loaded areas and, to a greater extent, takes into account the angular and lateral changes of the piston during the working cycle, and the piston has different proportions of its elements and does not have a cut on the unloaded side.

The proposed design differs from the design [2] in that it has a different length of the skirt on the loaded and unloaded sides and, moreover, takes into account the lateral shifting of the piston and the change in the load on the piston during the working cycle, as well as the smaller thickness of the skirt on the loaded side, which increases an elastic effect that prevents direct contact, thereby reducing friction losses in conjugation.

The invention is based on an analysis of the nature of the movement of the piston in the cylinder of an internal combustion engine when, when the crank is rotated, the piston is pressed with an inclination to one or the other during the movement from the top dead center (BDC) to the bottom dead center (BDC) and back side of the cylinder (the so-called transverse and angular shift of the piston in the cylinder occur). Since the unloaded side of the piston carries less loads, with the same specific load as on the loaded side, the skirt on this side can be made shorter, which will reduce the friction power loss in the lubricant layer between the piston skirt and the cylinder mirror, and this will make it possible to reduce the clearance in the interface to reduce oil consumption for waste. Existing designs do not take into account angular shifts when the bearing zones are located either above or below the piston skirt, depending on the angle of inclination.

The invention is illustrated by drawings, where figure 1 shows a General view of the tribological conjugation of the piston-cylinder; figure 2 is a side view of the pairing; figure 3 is a cross section of the piston in the plane of the axis of the piston pin; figure 4 - the nature of the movement of the piston in the cylinder: a - intake stroke; b - compression stroke; c - expansion stroke; g is the beat of the release; figure 5 is an external view of the piston (with a cutout).

Based on the formulated tasks, analysis of known structures and the nature of the natars of the working pistons, the following tribo-conjugation piston-cylinder is proposed. Tribological conjugation (figure 1, 2) consists of a cylinder 1 and a piston 2 containing a head 3 and a skirt 4 with a hole 5 under the piston pin. The length of the skirt on the loaded side 6 is greater than the length of the skirt on the unloaded side 7 of the piston: B ⁽¹⁾ > B ⁽²⁾ . The thickness of the skirt on the unloaded side is less than the thickness of the skirt on the loaded side of the piston t ⁽¹⁾ > t ⁽²⁾ (Fig. 3). The bearing surfaces of the skirt form on the opposite sides of the skirt X-shaped asymmetrical with respect to the longitudinal axis of the piston of area 8 and 9, bounded respectively by curves 10 and 11. Opposite side generators 12, 13 of the piston skirt (figure 2) form an asymmetric figure. The piston design is carried out in the following proportions:

Piston diameter D Necessary Piston length L (0.65 ... 0.9) D Sealing Belt Height N (0.48 ... 0.63) D Max piston skirt length B ⁽¹⁾ (0.25 ... 0.45) D Skirt length ratio B ⁽¹⁾ / B ⁽²⁾ 1.1 ... 1.3 Skirt thickness ratio t ⁽¹⁾ / t ⁽²⁾ 1,2 ... 1,5

The piston works as follows. When the piston moves in the cylinder, the lateral forces press it against one or the other side of the cylinder (Fig. 4), and the piston side 6, which is subjected to the greatest lateral force during the working cycle, is loaded.

Between the skirt 4 and the cylinder 1, when the piston 2 moves, hydrodynamic pressure arises in the lubricating layer. The bearing capacity of the lubricant layer is determined by the area of the friction bearing surfaces, however, an increase in the area contributes to an increase in friction power losses and lubricant consumption for waste. Depending on the direction of movement of the piston, the profile of the skirt, the inclination of the piston in the cylinder and the transverse crossings of the piston, hydrodynamic pressure (carrier layer) is generated either at the top or bottom of the piston skirt in the areas of X-shaped areas 8 and 9 on the side of the skirt that is pressed against the cylinder . At the same time, on the compression stroke (4b), the piston 2 is pressed against the cylinder 1 by side 7 with a shorter skirt length, on the expansion stroke, when the lateral load is maximum (4c) - side 6 with a longer skirt length. The large length and thickness of the skirt also contribute to a decrease in the deformation of the skirt and the correspondence of the friction mode to the calculated one. The shorter length and thickness of the skirt on the unloaded side 7 increases the elastic deformation, which prevents direct contact of the bearing surfaces of the piston 2 and cylinder 1, while reducing friction losses in the interface.

Thus, the different length and thickness of the skirt on the loaded 6 and unloaded 7 sides in combination with bearing friction surfaces in the form of X-shaped asymmetric areas 8 and 9, in contrast to the existing rectangular or trapezoidal ones, is most consistent with the actual distribution of hydrodynamic pressures when the pistons work, reduces the surface friction skirt, reduces friction power loss. The constant thickness of the lubricant layer between the piston skirt and the cylinder in the radial direction for each section is provided by a profile description along the radius.

The manufacture of the piston with the proposed profile will not cause great difficulties when processing it on a copy or on machines with numerical control. The proposed design can be used for internal combustion engines, reciprocating compressors.

Literature

1. US patent 5158008, MKI F 16 J 1/00 / Emil Ripberger; Mahle GmbH. - No. 688583. Publ. 10.27.92.

2. Patent of the Russian Federation 2095603, MKI 6 F 02 F 3/00 Publ. 11/10/97.

Claims (1)

Tribo-coupling piston - cylinder of an internal combustion engine, containing a cylinder and a piston with an opening for a piston pin, consisting of a head and a guide part (skirt) in the form of a barrel-shaped asymmetric figure, bearing surfaces are made in the form of X-shaped areas, which are limited by the edges of the skirt from above and below and are described by the radii of the circles, and having a piston-cylinder tribo-conjugation, the deviation of the profile of the generatrix of the bearing surfaces of the loaded and unloaded sides of the piston skirt from the inner wall of the cylinder in a plane perpendicular to the axis of the hole, determined by the expression: h ⁽ⁱ⁾ = h ₀ k ⁽ⁱ⁾ (Zm ⁽ⁱ⁾ ) 1 ⁽ⁱ⁾ , where h ⁽ⁱ⁾ is the deviation of the profile from the inner walls of the cylinder, h ₀ is the radial clearance between the cylinder and the piston skirt; Z is the axial coordinate with the beginning in the center of the axis of the hole for the piston pin; k ⁽ⁱ⁾ , m ⁽ⁱ⁾ , 1 ⁽ⁱ⁾ - profile curve parameters, i = 1, 2 - correspond to the loaded and unloaded side of the piston, and h ₂ ⁽²⁾ > h ₁ ⁽²⁾ > h ₂ ^(l) > h ₁ ⁽ⁱ⁾ , where h ₁ ⁽ⁱ⁾ , h ₂ ⁽ⁱ⁾ are the gaps between the cylinder and the piston skirt in its upper and lower parts, characterized in that the length of the skirt on the loaded side is greater than the length of the skirt on the unloaded side of the piston in in accordance with the ratio B ⁽¹⁾ / B ⁽²⁾ = 1.1 ÷ 1.3, and the thickness of the skirt on the loaded side is greater than the thickness of the skirt on the unloaded side of the piston in accordance with the ratio t ⁽¹⁾ / t ⁽²⁾ = 1, 2 ÷ 1,5, while the geometric parameters of the piston They are not as follows: piston length L = (0.65 ÷ 0.9) D, height of the sealing belt H = (0.48 ÷ 0.60) D, maximum length of the piston skirt B ⁽¹⁾ = (0.25 ÷ 0, 45) D, where D is the nominal diameter of the piston.

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