RU2095603C1 - Friction joining between piston and cylinder of internal combustion engine - Google Patents

Abstract

FIELD: mechanical engineering. SUBSTANCE: piston 2 has head 3 and skirt 4 (guide portion) provided with opening 5 for the piston pin. The bearing surfaces of the skirt are bounded with curves 6 and 7 and define X-shaped convex areas on the opposite sides of the skirt asymmetrical with respect to the longitudinal axis. The shape and profile of the areas are defined by relationships presented in the invention description. EFFECT: enhanced reliability. 3 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).

 Known piston for internal combustion engines, containing a head and a skirt, in the center of which there is a hole for the finger [1] The axial section of the piston skirt is a centrally symmetrical figure with a second-order axis of symmetry coinciding with the axis of the hole for the piston pin. Such a profile of the side surfaces should create, according to the authors, an equally high bearing capacity on the most loaded strokes of the internal combustion engine - “Compression” and “Working stroke” and help to reduce mechanical friction losses and thereby reduce dangerous wear and scuff of the friction surfaces of the piston skirt and cylinder liners. The radial section profile of the piston skirt is not mentioned in the description of the invention.

 Analysis of the invention shows that the centrally-symmetrical profile of the skirt can create the same bearing capacity only under the same operating conditions on the compression and working strokes, which is impossible for internal combustion engines, since the gas pressure in the cylinder and, accordingly, the lateral force in the cycle The “stroke” due to the explosive nature of the combustion of the working mixture is several times higher than in the “Compression” cycle. At the same time, the reduction of friction losses is small.

 A known piston design, devoid of this drawback, since the piston skirt profile in the axial direction is an asymmetric figure described by parabolic curves, taking into account the action of lateral forces in the combustion process, thermal deformations and the principles of the hydrodynamic theory of lubrication [2] The lengths of the arcs of the bearing part of the skirt are determined in radial sections of the piston, and the angle θ bounding the bearing surface, linearly depends on the axial coordinate of the skirt, increasing with increasing distance from the top of the skirt. Thus, the projection of the lateral bearing surface onto a plane parallel to the longitudinal axis of the piston is a trapezoid with a base coinciding with the bottom edge of the skirt. The profile of radial sections is not specified.

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

 An analysis of the piston design shows that the profile of the skirt in the axial direction described by the proposed parabolic functions does not depend on the radial clearance and the coordinates of the axis of the piston pin, which significantly limits the scope of the invention to the frames of one type of piston and engine. In the radial direction, the length of the arc of the bearing part is connected only with the axial coordinate of the piston, increasing uniformly from the top of the skirt down. The length of the arc does not depend on the radial clearance, the position of the piston pin and the longitudinal profile of the skirt, which also limits the application of the invention to the engines of the same type and does not reduce tribological losses in the piston-cylinder interface.

 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 lubricating fluid “on waste” due to its flow through the upper edge of the piston skirt.

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

где h₀ радиальный зазор между цилиндром и юбкой поршня;
Z осевая координата с началом в центре оси отверстия для поршневого пальца;
m⁽ⁱ⁾ Zc⁽ⁱ⁾/R; Zc⁽ⁱ⁾ осевая координата наиболее узкой несущей Х-образной зоны (осевая координата вершины боковой образующей профиля), i 1, 2 соответствуют нагруженности и ненагруженной стороне поршня; R -радиус юбки поршня;

зазоры между цилиндром и юбкой поршня в верхней и нижней ее части; B - длина юбки поршня;
k⁽ⁱ⁾=h $\genfrac{}{}{0ex}{}{\text{(i)}}{\text{1}}$ (B-2Zc⁽ⁱ⁾)/(2h_oR),
при этом в трибосопряжении цилиндр поршень отклонение профиля образующих несущих поверхностей юбки поршня от внутренней стенки цилиндра в плоскости, перпендикулярной оси отверстия, от головки к нижней части юбки определено по выражению:

причем h $\genfrac{}{}{0ex}{}{\text{(2)}}{\text{2}}$ > h $\genfrac{}{}{0ex}{}{\text{(2)}}{\text{1}}$ > h $\genfrac{}{}{0ex}{}{\text{(1)}}{\text{2}}$ > h $\genfrac{}{}{0ex}{}{\text{(1)}}{\text{i}}$ ..This problem is solved by the fact 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, according to the invention, the bearing surfaces of the skirt 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 with arc length q in accordance with the ratio:

where h _{0 is the} radial clearance between the cylinder and the piston skirt;
Z is the axial coordinate with the origin in the center of the axis of the piston pin bore;
m ⁽ⁱ⁾ Zc ⁽ⁱ⁾ / R; Zc ^{(i) the} axial coordinate of the narrowest bearing X-shaped zone (the axial coordinate of the top of the lateral forming profile), i 1, 2 correspond to the loaded and unloaded side of the piston; R is the radius of the piston skirt;

gaps between the cylinder and the piston skirt in its upper and lower parts; B is the length of the piston skirt;
k ⁽ⁱ⁾ = h $\genfrac{}{}{0ex}{}{\text{(i)}}{\text{one}}$ (B-2Zc ⁽ⁱ⁾ ) / (2h _o R),
moreover, in the tribo-coupling cylinder piston, the deviation of the profile of the generating bearing surfaces of the piston skirt from the inner wall of the cylinder in a plane perpendicular to the axis of the hole from the head to the bottom of the skirt is determined by the expression:

where h $\genfrac{}{}{0ex}{}{\text{(2)}}{\text{2}}$ > h $\genfrac{}{}{0ex}{}{\text{(2)}}{\text{one}}$ > h $\genfrac{}{}{0ex}{}{\text{(one)}}{\text{2}}$ > h $\genfrac{}{}{0ex}{}{\text{(one)}}{\text{i}}$ ..

 Reducing tribological losses without reducing the bearing capacity of the tribological conjugation is provided.

 The invention is based on the analysis of the nature of the movement of the piston in the cylinder of an internal combustion engine, when during rotation of the crank the piston is pressed with an inclination to one or the other under the action of lateral forces when moving from top dead center (TDC) to bottom dead center (BDC) and back side of the cylinder (the so-called transverse and angular shift of the piston in the cylinder). 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. At the same time, analysis of the natirates on the lateral surface of the working pistons showed that in most cases they form an X-shaped illuminated area on the piston skirt. This indicates that this area is the bearing for the piston.

 In FIG. 1 shows a general view of the tribo-mating piston cylinder; in FIG. 2 type of pairing on the side; in FIG. 3 nature of the movement of the piston in the cylinder.

где h₀ радиальный зазор между цилиндром и юбкой поршня;
Z осевая координата с началом в центре оси отверстия для поршневого пальца;
m⁽ⁱ⁾=Z $\genfrac{}{}{0ex}{}{\text{(i)}}{\text{o}}$ /R; Z $\genfrac{}{}{0ex}{}{\text{(i)}}{\text{o}}$
осевая координата вершины боковой образующей профиля (осевая координата наиболее узкой части несущей Х-образной зоны); i 1, 2 соответствует нагруженной и ненагруженной стороне поршня; R радиус юбки поршня;

зазоры между цилиндром и юбкой поршня в верхней и нижней ее части; B - длина юбки поршня;
k⁽ⁱ⁾=h $\genfrac{}{}{0ex}{}{\text{(i)}}{\text{1}}$ (B-2Zc⁽ⁱ⁾)/(2h_oR).
Противолежащие боковые образующие 8,9 юбки поршня (фиг. 2) образуют несимметричную фигуру, форма которой зависит от размеров юбки, радиального зазора, расположения оси поршневого пальца и определяется по выражению

где h⁽ⁱ⁾ отклонение профиля от внутренних стенок цилиндра i, причем
h $\genfrac{}{}{0ex}{}{\text{(2)}}{\text{2}}$ > h $\genfrac{}{}{0ex}{}{\text{(2)}}{\text{1}}$ > h $\genfrac{}{}{0ex}{}{\text{(1)}}{\text{2}}$ > h $\genfrac{}{}{0ex}{}{\text{(1)}}{\text{1}}$ .
Поверхности, перпендикулярные оси отверстия под поршневой палец и ограниченные кривыми 6, 7, находятся в зонах так называемых холодильников и специально не профилируются.Based on the formulated tasks, analysis of known structures and the nature of the natars of the working pistons, the following tribo-conjugation cylinder piston is proposed. The tribological conjugation (Fig. 1) consists of a cylinder 1 and a piston 2 containing a head 3 and a skirt 4 with an opening 5 for a piston pin. The bearing surfaces of the skirt are bounded by curves 6 and 7 and form on the opposite sides of the skirt X-shaped convex areas asymmetrical with respect to the longitudinal axis. 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

where h _{0 is the} radial clearance between the cylinder and the piston skirt;
Z is the axial coordinate with the origin in the center of the axis of the piston pin bore;
m ⁽ⁱ⁾ = Z $\genfrac{}{}{0ex}{}{\text{(i)}}{\text{o}}$ / R; Z $\genfrac{}{}{0ex}{}{\text{(i)}}{\text{o}}$
the axial coordinate of the top of the side generatrix of the profile (the axial coordinate of the narrowest part of the bearing X-shaped zone); i 1, 2 corresponds to the loaded and unloaded side of the piston; R is the radius of the piston skirt;

gaps between the cylinder and the piston skirt in its upper and lower parts; B is the length of the piston skirt;
k ⁽ⁱ⁾ = h $\genfrac{}{}{0ex}{}{\text{(i)}}{\text{one}}$ (B-2Zc ⁽ⁱ⁾ ) / (2h _o R).
Opposite lateral forming 8.9 piston skirts (Fig. 2) 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
h $\genfrac{}{}{0ex}{}{\text{(2)}}{\text{2}}$ > h $\genfrac{}{}{0ex}{}{\text{(2)}}{\text{one}}$ > h $\genfrac{}{}{0ex}{}{\text{(one)}}{\text{2}}$ > h $\genfrac{}{}{0ex}{}{\text{(one)}}{\text{one}}$ .
Surfaces perpendicular to the axis of the bore under the piston pin and bounded by curves 6, 7 are in the zones of the so-called refrigerators and are not specially profiled.

 The piston works as follows. When the piston moves in the cylinder, the lateral forces press it to one side, the current to the other side (Fig. 3), and the side on which the greatest lateral side acts during the duty cycle is loaded.

 Between the skirt and the cylinder, when the piston moves, hydrodynamic pressure in the lubricating layer occurs. 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 and the inclination of the piston in the cylinder, hydrodynamic pressure (carrier layer) is generated either at the top or bottom of the piston skirt in areas of X-shaped areas. The region of the top of the profile is not bearing, its angular dimensions affect the consumption of lubricant for waste, so the length of the arc of the radius of the skirt in this place is minimal.

 Thus, the X-shaped asymmetric friction area on the side surface of the piston, unlike the existing rectangular or trapezoidal ones, is most consistent with the actual distribution of hydrodynamic pressures during piston operation, reduces the friction surface of the skirt, and reduces the friction power loss. The constant thickness of the lubricating 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 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.

 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.

References:
1. USSR author's certificate N 1249183, cl. F 02 F 3/00, 1986.

 2. USSR author's certificate N 1590596, cl. F 02 F 3/00, 1990.

Claims (1)

Tribo-coupling piston is a cylinder of an internal combustion engine, comprising a cylinder and a piston with a hole for a piston pin, consisting of a head and a guide part (skirt) in the form of a barrel-shaped asymmetric figure, characterized in that the bearing surfaces are made in the form of X-shaped areas, which are limited from above and below the edges of the skirt and are described by the radii of circles with the arc length θ in accordance with the ratio

where h _{o 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,
m ⁽ⁱ⁾

the 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,

where h $\genfrac{}{}{0ex}{}{\text{(i)}}{\text{one}}$ h $\genfrac{}{}{0ex}{}{\text{(i)}}{\text{2}}$ - gaps between the cylinder and the piston skirt in its upper and lower parts; B the length of the skirt and piston;
K ⁽ⁱ⁾ = h $\genfrac{}{}{0ex}{}{\text{(i)}}{\text{one}}$ (B-2Zc ⁽ⁱ⁾ ) / (2h _o R),
in the tribo-conjugation, the piston cylinder, the deviation of the profile of the generatrix of the bearing surfaces of the piston skirt from the inner wall of the cylinder in a plane perpendicular to the axis of the hole from the head to the bottom of the skirt is determined by the expression

moreover
h $\genfrac{}{}{0ex}{}{\text{(2)}}{\text{2}}$ > h $\genfrac{}{}{0ex}{}{\text{(2)}}{\text{one}}$ > h $\genfrac{}{}{0ex}{}{\text{(one)}}{\text{2}}$ > h $\genfrac{}{}{0ex}{}{\text{(one).}}{\text{i}}$ one

Images