WO2008092294A1 - A piston of an internal combustion engine - Google Patents

Abstract

A piston of an internal combustion engine is provided in the application, it particularly relates to a piston of an internal combustion engine made of carbon and the combination of the carbon piston and the cylinder made of various materials. The piston has a piston crown(1), a top land(2) axially adjoining the piston crown, a ring portion(3) and a piston skirt(4) in which boss bores(5) for receiving a piston pin are provided, bosses(51) are oppositely provided each other on the inside of the piston skirt(42) to form the boss bores(5) and extend smoothly into the underside(12) of the piston crown with a rounded configuration, and a dome surface(12) is formed between the bosses(51) of the underside of the piston crown and extends into the bosses at least in the upper region of the boss bores(5), the carbon base material is permeated with a light metal or a light alloy.

Description

 Carbon piston for internal combustion engine

 BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a piston for an internal combustion engine, and more particularly to a piston pair of an internal combustion engine made of carbon and a different pair of the above-described carbon pistons and cylinders made of different materials. Background technique

 As the demand for modern automotive engines (gasoline engines) and diesel engines increases, pistons with smaller masses and smaller structural volumes are required. A carbon piston consisting of modified carbon (Kohlenstoff) has been developed for this purpose, for example, or by hard-pressed coal (Hartbrandkohle) with a defined minimum bending strength (Pressgraphit) (EP- 258330A1), or a piston of this type consisting of graphite, graphite is made of a binderless carbon, a so-called mesophase. The mesophase is a raw material which is used as a liquid phase-pyrolysis intermediate of hydrocarbons, preferably derived from carbon-based and petroleum-derived pitches, and is composed of polyaramid. Mesophase spherules having a particle size in the micrometer range produced by carbonization and graphitization of such a polyaramid, that is, raw material particles.

 The carbon piston has a lower coefficient of thermal expansion than the piston material aluminum, which greatly reduces the gap between the piston and the cylinder running surface. In addition, due to the oil absorption of carbon, and it is not easy to get stuck (see EP258330A1), carbon has good self-lubricating properties and cold running characteristics as a piston material.

 EP 1 406 601 B1 discloses a carbon piston for an internal combustion engine which is characterized by a material-matching construction in which the piston top-bottom side forms an arched surface in the region between the pin seats.

 Despite this, however, there are no series of carbon pistons that can meet the service life requirements of PKW (cars), LKW (trucks), two-wheeled vehicles and equipment. In addition, since carbon is less thermally conductive than material aluminum, the temperature field generated in the carbon piston during operation may be significantly different from that in the aluminum piston. There are also the following problems: Carbon and aluminum have different coefficients of thermal expansion; traditional carbon materials have much lower bending fracture strength than aluminum. Summary of the invention

 SUMMARY OF THE INVENTION It is an object of the present invention to provide a carbon piston for an internal combustion engine which has a relatively long service life and can replace a series of aluminum pistons, particularly for passenger cars and trucks, and at the same time has the advantages of a carbon piston and The advantages of light metal pistons.

 The technical solution for achieving the object of the present invention is:

- Carbonaceous, for internal combustion engines, especially for PKW, LKW, two-wheeled vehicles and equipment a piston having a piston crown, a fire shore axially connected on the top of the piston, a ring bank and a piston skirt provided with a pin hole for receiving the piston pin, wherein the skirt wall is placed on the inner side of the skirt a pin seat opposite to each other for constituting the pin hole, and is smoothly connected to the top-bottom side of the piston in a rounded shape, and the top-bottom side of the piston forms an arch in a region between the pin seats And the arcuate surface is connected to the pin seat at least in the upper region of the pin bore, wherein the carbon matrix is permeable to a light metal or light metal alloy.

 The carbon substrate is infiltrated by a light metal or light metal alloy to make the carbon piston of the present invention a composite material, thereby having the advantages of both a carbon piston and a light metal piston. The method is to infiltrate a carbon piston by a gas permeation or die casting infiltration method. In both of the above methods, the carbon piston is heated above the melting temperature of the light metal, and then the liquid light metal is pressed under pressure into the pores of the carbon substrate.

 In a preferred embodiment, the carbon matrix is fine graphite. The fine-grained graphite composed of a mixture of mesophase and asphalt binder preferably has a particle size of 1-5 μm, which is particularly suitable as a high-performance material for a piston of a stroke type piston engine. Therefore, the carbon piston of the present invention is a carbon piston composed of an intermediate phase modified by a light metal infiltration treatment. By using a light metal infiltration treatment, the bending rupture strength of fine graphite can be increased by 120%. The flexural breaking strength of the plug blank is preferably increased to 170-220 MPa after the infiltration treatment to withstand the higher peak pressures that may occur in diesel engines.

 In another preferred embodiment, the light metal or light metal alloy in the piston has a volume percentage of from 5% to 50%. Material parameters such as bending fracture strength, thermal expansion coefficient, heat transfer coefficient, etc. can be adjusted by changing the volume percentage content of the light metal or light metal alloy.

 In another preferred embodiment, the light metal or light metal alloy in the piston has a volume percentage of from 5% to 30%.

 Furthermore, it can be provided that the light metal or light metal alloy is aluminum or an aluminum alloy. Very good compatibility with aluminum engine cylinders is achieved by the use of aluminum or an aluminum alloy.

 Furthermore, it can be provided that the light metal or light metal alloy is magnesium or a magnesium alloy. Very good compatibility with aluminum engine cylinders is achieved by the use of aluminum or an aluminum alloy, which has a very good unit weight.

 In a further preferred embodiment, the carbon matrix can be specified as follows - it can be provided that the pore size of the opening in the carbon matrix is at least 68% 0.6 μιη - 1.0 μιη, wherein the smallest pore size is 0.3 μ ηι .

 In another preferred embodiment, the majority of the pores in the carbon matrix have pore sizes between 0.4 μm and 0.8 μm.

It can be specified that the elastic modulus of the piston material is 12 GPa to 30 GPa and the bending rupture strength is 120 MPa to 220 MPa. The piston material having the above material parameters enables the application of the carbon piston or fine graphite piston of the present invention to a long-lasting operation with high reliability and highest heat resistance. Conventional aluminum pistons lose bending fracture strength at thermal loads equal to or greater than 50%, while permeated pistons made of fine graphite maintain a constant level of strength over the entire operating temperature range.

Furthermore, it can be provided that the density of the piston is from 1.8 g/cm ^{3 to} 2.4 g/cm ³ .

 The piston has a heat transfer coefficient of 30 W/m.K to 200 W/m.K. The heat transfer coefficient of the piston material is well matched to the heat transfer coefficient of the cylinder and/or the heat transfer coefficient of the crankcase and can be optimally set.

 It can be provided that the arched surface formed on the top-bottom side of the piston is independent of the surface shape of the top-upper side of the piston. The top-bottom side of the piston forms a dome surface in the form of a partial spherical surface.

 In another preferred embodiment, the structural shape of the top-bottom side of the piston can be defined as follows:

 The top-bottom side of the piston constitutes a ring curved surface whose axis is parallel to the extension of the axis of the pin hole. The piston top-bottom side approximately constitutes a cylindrical surface whose axis is parallel to the extension of the axis of the pin bore.

 The piston top-bottom side forms part of the surface of a cylinder having an elliptical cross-section, the cylinder axis being at a right angle to the piston axis and parallel to the axis of the pin bore. .

 The axis of the cylinder coincides with the axis of the pin bore and the major axis of the elliptical cross section is at a right angle to the axis of the piston and the pin bore.

 The top-bottom side of the piston constitutes a partial surface of a spheroid, the major axis of the spheroid is at a right angle to the axis of the piston and its axis of revolution coincides with the axis of the piston.

 The large major axis of the slewing ellipsoid passes through the intersection M of the axis of the piston and the axis of the pin bore.

 The top-bottom side of the piston constitutes a partial surface of a slewing ellipsoid, and the major axis of the spheroid is at a right angle to the axis of the piston and the axis of the pin bore and constitutes a rotary shaft.

 The rotary shaft passes through an intersection M of the axis of the piston and the axis of the pin bore.

 The surface of the piston top-bottom side is tangentially passed into the flat end faces of the pin seats facing each other.

 The flat top surface of the piston top-bottom side and the pin seat facing each other constitute a rounded corner. The outer surface of the fire shore is a cylindrical surface.

 The outer surface of the fire shore is a conical surface.

 The envelope surface of the outer surface of the bank is a cylindrical surface when the diameter of the piston is greater than or equal to 150 mm.

The outer peripheral surface of the piston skirt to the bank is an upwardly converging cone surface having a nearly straight contour. The cross section of the surface of the cone is an ellipse having a diameter 0.04 to 0.09% larger in the direction transverse to the axis of the pin hole than in the direction of the axis of the pin hole. a groove side wall of a lower side of the groove for receiving the scraper ring at least one discharge port on one side of the pin hole opposite to each other, the discharge port opening into a piston In the oil pocket in the outer peripheral surface of the skirt.

 A discharge port and an oil bag are provided near both sides of each pin hole.

 The oil pocket extends in a curved shape around the pin hole (5) or as a straight surface extending vertically downward or obliquely downward.

 The carbon piston of the present invention can also be configured in combination with different cylinder operating surfaces. The loading clearance of the piston at normal temperature depends on the material of the cylinder running surface. This gap is small when applying a ceramic cylinder running surface, but is larger in a metal cylinder running surface made of aluminum, gray cast iron or steel. However, it can be partially balanced by different coefficients of thermal expansion of the cylinder running surface.

 As a raw material for a carbon matrix of a carbon piston, it may have a modified carbon or a carbon composed of a mesophase as described above, and has a bending rupture strength of 65 MPa to 160 MPa, for example, a fine particle. Made of graphite, which is made of a binder-free carbon, a so-called mesophase and contains a matching asphalt binder. The mesophase is a raw material that acts as a liquid phase-heat of hydrocarbons. The intermediate product of the solution is preferably derived from a carbon-based and petroleum-derived pitch and composed of a polyaramid. A mesophase sphere having a particle size in the micrometer range produced by carbonization and graphitization of the polyaramid The granules, that is, the raw material granules, are prepared by mixing the mesophase with the asphalt binder to form a fine-grained graphite having a particle size of 1-10 μm, the final state of which is open porosity. The positive effects are as follows: (1) The piston of the internal combustion engine of the present invention is made of a carbon material, so that the thermal expansion is small, and the gap between the piston and the cylinder surface is greatly reduced during use of the piston, thereby The performance of the piston, and due to the oil absorption, self-lubricating properties and cold running characteristics of the carbon, the friction of the carbon piston with the cylinder during use is less, and it is not easy to get stuck. (2) The piston of the internal combustion engine of the present invention has a high bending fracture strength of the carbon piston of the present invention due to the infiltration of a metal material, particularly a light metal material, into the carbon material, and can adjust the metal content of the carbon piston of the present invention. Therefore, material parameters such as thermal expansion coefficient and heat transfer coefficient can be obtained to match the cylinders of different materials. Therefore, the piston of the internal combustion engine of the present invention has both the advantages of the carbon piston and the advantages of the metal piston, and has high performance and enthalpy. Service life. (3) The structural design of the piston of the internal combustion engine of the present invention and the pairing with different cylinders make the piston of the present invention meet the requirements of internal combustion engines, especially cars, trucks, two-wheeled vehicles and other similar equipment. Description

Figure 1 is a partial cross-sectional view of the piston of the present invention taken along line Ι-Ι in Figure 3 and a partial view with the outer surface of the piston, Figure 2 is the piston of the present invention along the 图 in Figure 3! ! A partial cross-sectional view of the Π-Π and a partial view with the outer surface of the piston, FIG. 3 is a cross-sectional view of the piston of the present invention taken along line ΙΠ-ΠΙ in FIG.

 Figure 4 is an axial cross-sectional view of another embodiment of the piston of the present invention,

 Figure 5 is a cross-sectional view corresponding to Figure 2 of another embodiment of the piston of the present invention,

 Figure 6 is an axial cross-sectional view similar to Figure 4 of another embodiment of the piston of the present invention,

 Figure 7 is a partial view of the piston shown in Figure 6 taken along the direction of arrow VII in Figure 6;

 Figure 8 is a graphical representation of the profile of the carbon piston of the present invention and its clearance relative to the cylinder running surface. BEST MODE FOR CARRYING OUT THE INVENTION

 The present invention will be further described below in conjunction with the drawings and embodiments, but is not limited thereto.

 As shown in Figures 1-3, the piston for a diesel engine includes a piston crown 1, a piston ring fire shore 2, a bank 3 and a piston skirt 4. A basin recess (groove) 11 is provided on the upper side of the piston crown 1. A pin hole 5 for diametrically oppositely disposed piston pins (not shown) is provided on the outer peripheral surface 41 of the piston skirt 4, and the pin hole 5 is provided at a pin seat of the inner wall 42 of the piston skirt 4. 51. At the outer end of the pin hole 5 is provided a groove 52 for providing a safety ring (not shown) for locking the piston pin. The pin hole 5 has a laterally extending axis 53 that coincides with the axis of the piston pin.

 The piston consists of a carbon matrix that is infiltrated with aluminum in its pores. In the present embodiment, the carbon is fine-grained graphite. The piston is infiltrated into a porous carbon piston by die casting infiltration. To this end, the carbon piston is heated to a temperature higher than the melting point of aluminum and then placed in the mold of the die casting apparatus. The mold is closed, liquid aluminum is charged into the casting cavity, and is extruded into a small hole of the carbon piston through a pressing piston. Of course, it can also be achieved by a gas pressure infiltration method in which the aluminum is placed under vacuum and then extruded into a small hole of the carbon piston by a high pressure gas such as nitrogen.

 The above-mentioned carbon piston infiltrated with aluminum has the following parameters, wherein the material used for fine-grain graphite is FU4617 (Fa, Schunk):

 - the volume percentage of aluminum in the piston: 19%;

- average pore size of the carbon matrix (before infiltration): 0.35 m _;

- the elastic modulus of the piston (Youngs modulus): 22 GPa _;

 - bending fracture strength: 182 MPa;

- the density of the piston: 2.2g/cm ³ ;

- Thermal conductivity of the piston: 92W/mK _;

- expansion coefficient: 8.8X 10_ ⁶ /K; The fine graphite for infiltrating aluminum as a preferred embodiment should have the following preferred physical parameters -

- bending fracture strength: 180-220 MPa;

 - Young's modulus: 18-24GPa;

- density: 2.0-2.25g/cm ³ ;

 - Thermal conductivity: 90-140 W/mK:.

 In the land 3, three annular grooves 31 for providing a piston ring (not shown) are provided, wherein the lowermost ring groove is for accommodating a scraper ring. The groove bottoms of the grooves are respectively arranged in a rounded structure to avoid stress concentration. On the side wall of the groove for the lower side of the ring groove 31 of the scraper ring, a discharge port 32 is provided beside the pin hole 5 in the circumferential direction of the piston, and the discharge port 32 opens into the outer peripheral surface of the piston skirt 4. A shallow flat oil bag 33. The oil bag 33 has an arcuate thickening 54 surrounding the pin hole 5 in the vicinity of the oil discharge port 32, the arc thickening 54 has a depth of 3 mm, and its depth gradually decreases at the lower end portion until The outer peripheral surface 41 disappears. The oil bag can also be configured as a vertical surface structure.

 As shown in Fig. 2, the bottom side 12 of the piston crown 1 has an arcuate surface, which in this embodiment is similar to a cylindrical surface, the cylinder axis (not shown) intersecting perpendicularly to the piston axis. That is, the bottom surface 12 of the piston crown 1 is constituted by a straight line perpendicular to the plane of the drawing of Fig. 2, and is excessively rounded to the opposite end faces 55 of the pin seats 51 (Fig. 1). Between the two oppositely opposed pin seats 51, the piston top-bottom surface 12 extends in the radial direction of the cylinder and is connected to the inner wall 42 of the piston skirt 4 by a rounded circle having a smaller radius. The above-mentioned excessive structure extends beyond the end of the lower side of the land 3 and is connected to the piston skirt 4 on the land 3.

The diameter of the piston crown 1, that is, the piston diameter D, is 86.835 mm in this embodiment _; the thickness of the piston crown 1 is 22 mm from the upper edge of the fire shore 2 at the apex of the bottom surface 12 of the piston crown (regardless of the basin) Concave 11). The entire twist of the piston from the upper edge of the fire shore 2 to the lower skirt edge 44 is 76.3 mm, wherein the piston skirt 4 has a shell thickness of 7.5 mm. This results in a piston crown thickness of 0.25 D, that is to say a ratio which is significantly greater for a diesel engine piston of this size than for an aluminum piston or grey cast iron piston.

4 is a longitudinal cross-sectional view of a carbon piston for a direct injection diesel engine having a combustion chamber basin recess 11. As shown, the bottom surface 12' of the piston crown assumes an arcuate surface. The difference between this embodiment and the embodiment shown in Figures 1-3 is that the bottom surface 12' of the piston crown is not one to the inner wall of the piston. It is a continuous cylindrical surface, but consists of a combination of three cylindrical surfaces in the lateral direction with respect to the axis of the piston pin. Thus most of the a of this surface has a radius Ra with its center point A on the piston axis 14. The two oppositely facing surface segments b are symmetrical with respect to this central plane of the piston on the axis of the piston pin and have a radius Rb with a center point B on a transverse axis intersecting the axis of the piston pin. It can be understood that the surface segments b are respectively shorter in the direction perpendicular to the plane of the drawing of FIG. 4 than the central surface segment a because they must extend to an excessive radius to In the inner wall of the piston skirt.

 In the area of the fire shore 2', the piston of Figure 4 has a diameter of 68.87 mm. Radius Ra and Rb are 41 and 12 respectively

 The piston according to the embodiment shown in Fig. 5 is similar in size and construction to the piston shown in Fig. 4. They differ from the embodiment shown in Figs. 1-3 in that a plurality of discharge holes 35 guided to the inside of the piston are provided in addition to the discharge ports 32' in the side walls of the lower groove 31'. The venting holes facilitate drainage through the outer oil pocket 33'.

 The pistons shown in Figures 6 and 7 are similar to the pistons shown in Figure 4, with a combustion chamber pocket on the upper side of the piston crown, also for a direct injection diesel engine. However, the following description is independent of the upper side structure of the piston crown, so the following explanation also applies to the case where the upper side is flat. The difference from the embodiment shown in Fig. 4 is that the piston top-bottom surface 112 forms part of the surface of a slewing ellipsoid whose axis of revolution 113 coincides with the piston axis 114. The large main axis 115 of the slewing ellipsoid extends at right angles to the piston shaft 114 and also extends at right angles to the axis 153 of the pin bore 105 (Fig. 7), which is the piston pin at the same time. Pin axis not shown). Further, the large main shaft 115 in this embodiment simultaneously intersects the axis 153 of the pin hole 5 with the piston axis 114. Therefore, the center point M of the slewing ellipsoid coincides with the intersection of the piston axis 114 and the axis 153, and the partial surface constituting the piston top-bottom surface 112 is largely identical to the half spherical surface of the spheroid of.

 For the actual situation, a part of the surface of the above-mentioned spheroid may be approximated as a ball arch having a radius R'a, and a hemisphere having a radius R'b is connected to both ends of the ball arch and the major spindle 115, respectively. Arch surface. The center point A of the radius R'a is located on the piston axis 114; the center point B' of the radius R'b is located on the large main axis 115, respectively. The radius R'a basically determines the surface curve of the top-bottom side 112 of the piston, which can be expressed according to the formula:

 R'a=rimin+d/2 is calculated.

 Ri represents the distance from the midpoint M to the top-bottom side 112 of the piston, so rimin is the minimum distance from the center point M to the top-bottom side of the piston and needs to be measured along the piston axis 114. d represents the twist of the inner wall 142 of the piston skirt 104 at the major spindle line 115, which is equivalent to the diameter at the height of the axis 153 of the pin bore 105.

According to the above-mentioned size range of determining the thickness of the piston crown by 0.12D to 0.30D (D-piston rated diameter) and determining the size range of the skirt wall thickness S by 0.05D-0.075D, the center point A can be determined separately. 'Position on piston axis 114 and center point B, position on main shaft 115. In determining the size of the piston top thickness, it must be noted that the lowermost ring groove of the land 103 above the top-bottom side of the arch piston is sufficiently large from the top-bottom side of the arch piston to avoid The cross section at the location is reduced to affect the force and heat flow. The excess between the partial spherical surfaces described above must be rounded, in the embodiment by an excessive surface to the surface of a spheroid. In this embodiment, the piston top-bottom surface 112 extends a distance in the direction of the axis 153 of the pin bore 105 to be less than the extent of the extension in the direction perpendicular to the axis 153, as must be taken into account in the region of the pin seat 151, Still Set enough free passages for the connecting rod holes. The above excess to the pin holder 151 needs to be rounded. The radius of the arcuate surface used to determine the top-bottom side 112 of the piston can also be estimated or determined by R'a = D, where K-0.5-0.75.

 Therefore, the internal profile of the piston of the present invention is significantly different from the internal profile of a conventional aluminum piston. In a conventional aluminum piston, the piston top is substantially flat and only in the excessive position to the fire shore. The excess where the piston ring is wound is rounded. Therefore, in calculating the piston piston top strength of the carbon of the present invention with a higher carrying capacity (for example, the piston according to Fig. 6), the torsional strength of the piston crown can be approximated by the torsional strength of the hollow ellipsoid whose constant hollow ratio is constant. Ground calculation, the formula is:

 W= π /32-CD ( 1- 4),

 Where α = c / C = d / D = ri / ra = constant.

 In the present embodiment, ramax = D/2. As shown in Fig. 6, the elliptical hollow body which is the basis of this calculation is indicated by a cross-hatched line.

 The piston of the present invention, when used for relatively small loads, such as for a passenger car engine, can select the lower boundary of the above-described size range for both the piston crown thickness and the skirt wall thickness S. In this case, a simplified formula for the torsional strength of a hollow ellipsoid with a constant wall thickness can be used for the calculation of the torsional strength of the piston top:

 W (approximate equal sign) 0.2sD (D+3C).

 The above calculation of the surface curve of the piston top-bottom side 112 and the calculation of its torsional strength can be applied to the piston top-bottom surface of a part of the surface of the cylinder having an elliptical cross section. The axis of the cylinder is at a right angle to the piston axis 114 and coincides with the axis 153 of the pin bore 105, i.e., the busbar of the cylinder is perpendicular to the plane of the drawing of Figure 6. The large (long) major axis 115 of the elliptical cross section of the cylinder is perpendicular to the piston axis 114 and is also perpendicular to the axis 153 (compare Figure 6). In this case, in the end region of the main shaft 115, the excessive surface is required to extend as far as possible into the cylindrical inner wall 142 when the (piston) skirt 104 is excessive.

 In Fig. 7, the contours are only qualitatively represented by contour lines 116 created by a cross section transverse to the piston axis 114.

In other embodiments, when the top-bottom side of the piston is formed by a partial surface of a spheroid, the axial section produces the same pattern as the spheroid shown in Figure 6, but the ellipsoid is The rotary axis is a large spindle 115. Also in this case, the center point of the spheroid is at the intersection M of the piston axis 114 and the pin hole 105 axis 153. The above-described structural shape creates an arched surface between the pin seats 151 which simply transitions into the pin seat by a slight rounding, but provides a larger area in the region of both ends of the large spindle 115. The skirt wall thickness is 104. In carbon pistons, the eccentric configuration often used in aluminum pistons (the piston pin axis has a displacement configuration relative to the piston axis) should be avoided.伹 Even if it indicates that the application is an eccentric configuration, the degree of eccentricity is better than that of the aluminum piston. The situation is small. The above embodiments shown in Figures 4, 5 and 6 are not eccentric. Therefore, in the embodiment of Fig. 6, the piston top-bottom side is constituted by a partial surface of a spheroidal ellipsoid, so that the center point M thereof is also located on the axis of the pin hole. However, if the piston is provided with an eccentric structure, the center point M is only located in the axis of the pin bore in the piston axis, 'the pin bore axis intersects the piston axis.

 In all of the above embodiments, an intersecting edge is theoretically created between the cylindrical inner wall of the piston and the arcuate surface forming the top-bottom side of the piston, which in practice is generally avoided by excessive rounding or excessive radius.

 Figure 8 is a graph showing the structural shape of a carbon piston having a diameter D = 100 mm of the present invention, wherein the profile of the fire shore 2, the bank 3 and the piston skirt 4 and the opposite one of the gray cast iron are shown. The partial clearance of the cylinder running surface. In the piston of the above-mentioned parameter size, it is also possible to provide an ellipticity in the embodiment made of carbon, which can produce a larger gap in the region of the pin hole 5 and laterally on the opposite pin hole axis 53. A smaller gap is created in the area where it is placed. However, the above values can be obtained, and the gap and the ellipticity can be approximately 0.3 times the corresponding values of the aluminum piston.

 The meaning in the figure is that the piston skirt profile, indicated by the dashed line, starts from the lower edge of the bank 3 and extends straight into the skirt edge 44 of the lower side, that is, not the drum shape required by the aluminum piston, but a Cone surface. Furthermore, it can be seen that in the carbon piston, the fire shore 2 is not cylindrical but has a tapered outer surface due to a high thermal load, and no ellipticity is set in its area.

 When paired with a piston/cylinder of a carbon piston, the above values are in principle lower than when paired with an aluminum piston. In spite of this, the above values will vary depending on whether the cylinder running surface is made of gray cast iron or of another material. Thus, a light metal running surface made of aluminum, magnesium and similar materials can be provided and carries a nickel coating with a high proportion of silicon carbide under the trade names Mkasil and Elnisil. It is also possible to provide a pure ceramic coating. Finally, it is also conceivable that the cylinder liner or cylinder running surface is made of a composite material, such as the metal/ceramic of the trade name Alusil, Lokasil, Silitec. When the cylinder-operating surface is provided by the material different from the gray cast iron described above, the loading gap of the piston in the cold state is 0.010-0.035% of the diameter of the piston, and the above value refers to the piston transverse to the piston when it has an ellipticity. The value determined in the direction of the pin axis. It is apparent that the above-described embodiments of the present invention are merely illustrative of the present invention and are not intended to limit the embodiments of the present invention. Other variations or modifications of the various forms may be made by those skilled in the art in light of the above description. There is no need and no way to exhaust all of the implementations. It is to be understood that the obvious changes or modifications which come within the spirit of the invention are still within the scope of the invention.

Claims

Claim  1. A carbon piston for an internal combustion engine, in particular for passenger cars, trucks, two-wheeled vehicles and equipment, comprising a piston crown (1), a fire shore (2) axially connected on the top of the piston, a ring skirt (3) and a piston skirt (4) provided with a pin hole (5) for receiving the piston pin, wherein the skirt wall (42) is placed on the inner side of the skirt to constitute the pin hole (5) The pin seats (51) opposite to each other are connected to the top-bottom side (12) of the piston in a rounded smooth connection, while the top-bottom side of the piston is formed in the region between the pin seats (51) An arched surface (12), and the arched surface (12) is connected to the pin seat at least in an upper region of the pin hole (5), characterized in that: the carbon matrix passes through a Light metal or light metal alloy infiltration treatment.  2. A carbon piston according to claim 1, wherein: said carbon matrix is fine-grain graphite. 3. A carbon piston according to claim 1 or 2, characterized in that the light metal or light metal alloy in the piston has a volume percentage of from 5% to 50%.  A carbon piston according to claim 3, wherein said light metal or light metal alloy in said piston has a volume percentage of 5% to 30%.  5. Carbon piston according to one of the preceding claims, characterized in that the light metal or light metal alloy is aluminium or an aluminium alloy.  6. A carbon piston according to any one of claims 1 to 4, wherein the light metal or light metal alloy is magnesium or a magnesium alloy.  7. A carbon piston according to any of the preceding claims, characterized in that the pore size of the opening in the carbon matrix is at least 68% 0.6 μπι - 1.0 μιη, wherein the smallest pore size is 0.3 μπι .  A carbon piston according to any one of the preceding claims, wherein: said piston material has an elastic modulus of 12 GPa to 30 GPa and a bending rupture strength of 120 MPa to 220 MPa. 9. Carbon piston according to one of the preceding claims, characterized in that the piston has a density of from 1.8 g/cm ^{3 to} 2.4 g/cm ³ .  10. Carbon piston according to one of the preceding claims, characterized in that the piston has a heat transfer coefficient of 30 W/m.K - 200 W/m.K.  A carbon piston according to any of the preceding claims, characterized in that said arched surface formed on the top-bottom side of the piston is independent of the surface shape of the top surface of the piston.  12. Carbon piston according to one of the preceding claims, characterized in that the top-bottom side of the piston forms a vaulted surface in the form of a partial sphere. 13. A carbon piston according to any one of claims 1-12, wherein: said piston top-bottom side forms a ring curved surface, the axis of said ring curved surface being parallel to the axis of the pin hole (5) (53) ) The extension line. 14. A carbon piston according to any of claims 1-12, characterized in that said piston top-bottom side approximately forms a cylindrical surface (12) whose axis is parallel to the pin The extension of the axis (53) of the hole (5).  A carbon piston according to any one of claims 1 to 12, wherein said piston top-bottom side (112) constitutes a partial surface of a cylinder having an elliptical cross section, said cylinder The axis is at a right angle to the piston axis (114) and is parallel to the axis (153) of the pin bore (105).  16. A carbon piston according to claim 15 wherein: the axis of the cylinder coincides with the axis (153) of the pin bore (105) and the major axis (115) of the elliptical cross section is A position at right angles to the axis of the piston (114) and the axis (153) of the pin bore.  17. A carbon piston according to any of claims 1-12, characterized in that said piston top-bottom side (112) forms part of the surface of a spheroid, the major axis of said spheroid (115) is at a right angle to the piston axis (114) and its axis of rotation coincides with the piston axis (114).  18. A carbon piston according to claim 17, wherein the major axis (115) of the slewing ellipsoid passes through the intersection M of the axis of the piston (114) and the axis (153) of the pin bore (105).  The carbon piston according to any one of claims 1 to 12, characterized in that: the top-bottom side of the piston constitutes a partial surface of a spheroid, and the major axis of the spheroid (115) It is at a right angle to the axis (153) of the piston axis (114) and the pin hole (105) and constitutes a rotary shaft.  20. A carbon piston according to claim 19, wherein said rotary shaft passes through an intersection M of the axis of the piston (114) and the axis (153) of the pin bore (105).  A carbon piston according to any one of the preceding claims, characterized in that the surface of the top-bottom side of the piston passes through a tangential passage into a flat end surface (55) of the pin seat (51) facing each other.  A carbon piston according to any of the preceding claims, characterized in that the surface of the top-bottom side of the piston and the flat end faces (55) of the pin seats (51) facing each other form a rounded corner.  A carbon piston according to any of the preceding claims, characterized in that the outer surface of the fire shore (2) is a cylindrical surface.  24. Carbon piston according to one of the preceding claims, characterized in that the outer surface of the fire shore (2) is a conical surface.  A carbon piston according to any of the preceding claims, characterized in that the envelope surface of the outer surface of the land (3) is a cylindrical surface when the diameter of the piston is greater than or equal to 150 mm. A carbon piston according to any of the preceding claims, characterized in that the outer peripheral surface (41) of the piston skirt (4) to the bank is an upwardly converging cone surface having a nearly straight contour. The carbon piston according to claim 26, wherein: the cross section of the surface of the cone is an ellipse, and the diameter of the ellipse in a direction transverse to the axis of the pin hole (53) is smaller than that in the pin hole. It is 0.04-0.09% larger in the axial direction.  28. A carbon piston according to any of the preceding claims, characterized in that in the bank (3) a groove side wall of the lower side of the groove (31) for receiving the scraper ring is at least opposite to each other One side of the pin hole (5) has a discharge opening (32) which opens into an oil pocket (33) located in the outer peripheral surface of the piston skirt (4).  A carbon piston according to claim 26, wherein: a discharge port and an oil bag are provided near both sides of each pin hole.  The carbon piston according to claim 28 or 29, wherein the oil bag extends in a curved shape around the pin hole (5), or extends vertically downward or obliquely downward as a straight surface.  31. A piston/cylinder-pair comprising a carbon piston according to any one of claims 1 to 30, wherein: said cylinder has an operating surface composed of gray cast iron, and said piston is in a cold state. The loading gap is 0.015-0.065% of the diameter of the piston.  32. A piston/cylinder-pair comprising a carbon piston according to any one of claims 1 to 30, wherein: said cylinder has an operating surface composed of a light metal, and said piston is mounted in a cold state. The gap is 0.010-0.035% of the diameter of the piston.  33. A piston/cylinder-pair comprising a carbon piston according to any one of claims 1 to 30, wherein: said cylinder has a ceramic running surface and said piston is placed in a gap in a cold state. It is 0.010-0.035% of the diameter of the piston.  34. A piston/cylinder-pair according to any one of claims 31-33, wherein in a piston having an ellipticity, the loading gap is a gap transverse to the axis of the piston pin.  35. A piston/cylinder-pair according to claim 32, wherein: said light metal running surface has a nickel coating containing bismuth of silicon carbide or has a ceramic coating.  36. The piston/cylinder-pair of claim 32, wherein: said light metal running surface comprises a cylinder liner comprised of a light metal/ceramic composite.  37. A piston/cylinder-pair according to claim 32, wherein: said running surface comprises a cylinder liner made of grey cast iron or of a gray iron alloy.  38. A piston/cylinder-pair according to claim 32, wherein said cylinder liner is constructed of steel or a steel alloy.