Piston, crank drive and reciprocating internal combustion engine

Abstract

The invention relates to a piston, in particular for an engine, having a top, a bottom, a circumferential surface extending along the periphery and an axis of movement extending substantially parallel to the contour of the circumferential surface and through the top and the bottom, the circumferential surface being designed to guide the piston in the cylinder bore of the cylinder along the axis of movement, the top being designed to absorb the compressive forces of the gases and the bottom having a connecting rod receiving part, the connecting rod receiving part having an undercut or a plurality of undercuts in the tensile and compressive directions, whereby the connecting rod receiving part is set to receive in a form-fitting manner a thickened part of a connecting rod corresponding to the connecting rod receiving part, whereby said part is pivotable about a pivot axis, the piston having any number of radially arranged substantially flat cross sections extending through the axis of movement. The invention further relates to a crank drive and an internal combustion engine.

Description

[Technical field]

[0001] The present invention relates to a piston, particularly for a prime mover, having a peripheral surface extending along the upper and lower sides and substantially parallel to the axis of movement of the piston. The peripheral surface extends from the upper side to the lower side of the piston, the peripheral surface is designed to guide the piston in the cylinder bore along the axis of movement and the upper side is designed to receive the gas pressure force. The lower side of the piston has a connecting rod holder, the connecting rod holder having one or more undercuts. The undercuts are positioned to engage the connecting rod head and prevent the connecting rod head from being pulled out of the piston when the connecting rod is pulling the piston, so that the connecting rod holder can be used to securely connect the connecting rod and the piston in a pivotable arrangement about a pivot axis. The piston has any number of substantially flat cross sections extending through the axis of movement and arranged radially, each of which has approximately the same cross-sectional area. The invention also relates to a crank drive having a piston, in particular a connecting rod, and to a reciprocating piston internal combustion engine. [Background technology]

[0002] Previous engines that function according to the reciprocating piston principle, such as diesel or gasoline engines and other engines, usually have a piston with a cylindrical outer periphery centered on a central axis aligned with the bore of the cylinder in which the piston reciprocates. The piston is pivotally connected to a connecting rod on a pivot axis. In prior art designs, the piston and the connecting rod are pivotally connected to each other with a so-called piston pin. The piston pin adds to the reciprocating mass of the engine, which has a negative effect on the efficiency of the engine and therefore also on the polluting emissions of the engine or in other words prevents the reduction of polluting emissions.

[0003] If the piston is provided with a connecting rod holder arranged below and the connecting rod is provided with a head that can be attached to the connecting rod holder, this results in a reduction in the reciprocating mass of the assembly (due to the absence of a piston pin) and in reduced friction losses. However, thermal management of such pistons is often difficult, especially with regard to the heat generated by the engine's combustion process. Furthermore, in any case, regardless of the piston design, changes in the geometry of the piston caused by thermal expansion must be addressed. When a piston is heated, it naturally expands. Prior art pistons, especially in diesel engines, must be manufactured with an elliptical periphery in order to assume a preferred round geometry in warm operating conditions. Summary of the Invention [Problem to be solved by the invention]

[0004] The object of the present invention is to improve upon the prior art. [Means for solving the problem]

[0005] This problem is solved by a piston, in particular for a prime mover, having an upper side, a lower side and a peripheral surface extending along the periphery. The piston moves along a reciprocating movement axis extending substantially parallel to the tangent of the peripheral surface. The peripheral surface generally guides the piston along the cylinder bore in which it operates. The upper side of the piston is designed to absorb the compressive forces of the gas and the lower side has a connecting rod receiving portion arranged to withstand the forces exerted by the attached connecting rod. The undercut or several undercuts are arranged so that the connecting rod holder receives and holds the connecting rod head by fitting and pivotally about a pivot axis, the piston having any desired shape. The piston is shaped such that any number of cross sections taken through the movement axis of the piston have a substantially uniform cross-sectional area. The difference in the cross sections taken through this movement axis is preferably less than 10% of the cross-sectional area.

[0006] This geometric design of the piston, in particular by providing a substantially uniform cross-sectional area for all cross sections taken through the axis of movement, results in a uniform thermal expansion behavior around the piston, so that, for example, the piston is geometrically adapted very accurately to the diameter of the cylinder bore it operates in. This improves the sealing behavior against the cylinder wall and greatly simplifies the manufacture of the piston, since, for example, a uniform peripheral geometry of the piston can be achieved (rather than the elliptical shapes found in the prior art).

[0007] The following terms are explained in this context:

[0008] A "piston" is a movable component, which, together with the surrounding housing, in the case of engines and related machines, includes a "cylinder". The volume of the cylinder changes due to the reciprocating movement of the piston within the cylinder. Such a central component, in the present case specifically a reciprocating piston that can move up and down within the cylinder, can be realized in various ways with different designs.

[0009] The "upper side" (top side) of such a piston is, for example, the area of ​​the piston known as the piston crown, which in an internal combustion engine is, for example, assigned to the combustion chamber volume. This upper side then, using the example of an internal combustion engine, absorbs the pressurizing force from the expanding ignited gas mixture, thereby transmitting the force required to operate the crankshaft drive to the connecting rod and from the connecting rod to the crankshaft.

[0010] "Underside" is the side of the piston facing the connecting rod, i.e. in particular the side of the piston having the connecting rod holder.

[0011] The "circumferential surface" is the surface of the piston, which, for example in the case of an internal combustion engine, faces the cylinder bore. The exemplary details given refer to the usual design of the piston having an approximately cylindrical shape. Likewise, correspondingly different shapes of the piston and different shapes of the cylinder bore can also be realised, if technically possible. The peripheral surface can also usually be used as the so-called piston skirt.

[0012] "Axis of movement" describes the axis along which the piston moves during rotation of the crankshaft, e.g., in particular, this axis of movement is parallel to the central axis of the cylinder bore, whereby in any case not a mathematically exact axis is intended, but rather a corresponding direction with reasonable technical deviations.

[0013] A "cylinder bore" may be, for example, a cast and / or drilled cavity in an engine block of an internal combustion engine, which is then further polished, for example by honing. However, such a cylinder bore may be a round or essentially round cavity in a steam engine, steam generator telescopic drive, or another form of prime mover. A piston closes the cylinder bore against the last open side so that a pressurized force in the cylinder bore can be transmitted to the piston. A force then acts on the piston inside the cylinder bore.

[0014] The "gas" exerting a compressive force may be a simple compressed gas, such as compressed air, or a gas resulting from a phase change, such as superheated steam, or even a gas mixture, for example of ambient air with gasoline or diesel or another fuel, which through ignition exerts a compressive force on engine parts, for example in a gasoline or diesel engine.

[0015] A "connecting rod holder" on the underside of the piston is used to tensilely and pivotally attach the connecting rod to the piston, so that the piston together with the connecting rod is connected with a so-called crank drive, e.g. the connecting rod connecting the piston to the crankshaft. The pivotal connection of the piston to the connecting rod is established in such a way that the piston is free to pivot relative to the connecting rod, but is otherwise fixed.

[0016] "Undercut" refers to a design of a mounting or part of a mounting such that a component or area or partial area in the direction of a force ensures that it does not pull out or allows the transmission of a force. Such an undercut may be used by a component that is suspended or mounted through the undercut to transmit a force.

[0017] A "thickened section" (e.g., head) of a connecting rod is an area that has a larger or wider cross section or has a larger or wider diameter than the portion of the connecting rod adjacent to the thickened section. In particular, such thickened sections, together with undercuts, and in particular the surfaces formed by the undercuts, may serve to create a mating tensile or torsional connection to form a load-bearing connection.

[0018] The corresponding "cross-sectional area" refers to an essentially flat plane, which results from an imaginary section of the piston with a cutting plane passing through the axis of movement of the piston. This cross-sectional area is specified as a measure of extent, and a desirable feature of the invention is that this cross-sectional area is the same or substantially the same for different cross sections rotated through a rotation angle about the axis of movement.

[0019] To allow for even more precise control of thermal expansion, the piston is shaped so that the cross-sectional areas of planes passing through the axis of movement preferably differ from each other by less than 7%, more preferably less than 5%, and even more preferably less than 2%.

[0020] In this connection, it should be noted that each of the first and second cross-sectional areas represents an arbitrary cross-sectional area, for example, in some cases the two cross-sectional areas in different reference axes, for example perpendicular to the first cross-sectional area, are of identical or similar design, so that, for example, the thermal deformation behavior of the piston is controlled in two main directions. The respective cross-sectional areas can also extend at any angle relative to each other, so that in particular a comparison of any cross-sectional area around the piston bears a substantial uniformity criterion.

[0021] In one embodiment, the circumferential surface is provided with a protective covering from top to bottom and / or across the bottom of the underside of the piston, such that the piston skirt has a radial thickness of less than 10%, less than 5% and / or less than 2% of the diameter of the piston.

[0022] Typically, the "piston skirt", which is the tubular extension of the piston in the downward direction, i.e., toward the crankshaft, is particularly thin-walled. Thermal expansion in this area is greatly reduced.

[0023] For example, an equalization volume and / or several equalization volumes are placed above and / or below by equalizing one or more volumes in order to balance the respective cross-sectional areas compared to the required surface area and / or required portion of the piston, e.g., the undercut portion.

[0024] Consequently, one or more corresponding compensation volumes can be applied such that piston material is added or removed at one point, provided that this is not technically necessary and the criterion of uniformity of the different cross-sectional areas relative to one another is met.

[0025] In one embodiment, the removal volume and / or the plurality of removal volumes may be further concave on the upper and / or lower sides, whereby compensation of the volume section of the piston arranged on the respective cross-sectional area is created by one or more reduced volumes.

[0026] This means that the removal volume can also be used to compensate for the corresponding range size in combination with the corresponding added volume (compensation volume).

[0027] "Compensation volume" describes the increased volume in a particular area, i.e. the additional material that has been added, whereas "removed volume" describes the material that is not present or that has been removed. For example, when casting a piston, an additional tool volume can be provided in the forming tool for the corresponding removed volume, whereby a corresponding volume is removed from the forming tool for the compensation volume. On the other hand, if the piston is made by a metal cutting process, it is possible to generate the corresponding compensation or removed volume in a CNC milling program.

[0028] To ensure that the thermal expansion behavior of the piston is uniform, several compensation volumes and / or several removal volumes are arranged symmetrically with respect to the axis of movement.

[0029] In one embodiment, the piston has a diameter defined by the average value of the circumference, and any number of radii passing through the central radius and the axis of movement and disposed radially relative to the circumference preferably exhibit radii that differ from the average radius by less than 1%, more preferably by less than 0.5%, and even more preferably by less than 1‰.

[0030] The result is a piston with a particularly high degree of roundness, whereby this roundness is defined, for example, by the corresponding radius. By designing the respective cross-sectional areas to be of similar or even the same size, elliptical manufacturing is no longer necessary for pistons such as conventional pistons manufactured with piston pins. Thermal expansion is therefore taken into account in advance. Such pistons, when manufactured according to the invention, can therefore be particularly round and therefore manufactured, for example, on a lathe, in a simple manufacturing process. Likewise, when piston rings are also used together, such particularly round pistons properly seal against the round cylinder bore, so that no further oil losses, blow-by losses or unintended oil leakage occur, especially during cold starts of the engine.

[0031] The "average value of the surface" describes, for example, the average value from all possible measurement points of the surface in the circumferential range or from all calculated points of the surface. From this definition, a "mean radius" can be determined, which can be, for example, the arithmetic mean of any number of radii. This mean radius is used as a reference for other radii, which can cause corresponding local deviations of the radii and thus of the piston from roundness.

[0032] In order to make it possible to manufacture the piston particularly simply and lightly and at the same time provide high strength, the piston is preferably made from aluminium, steel or a steel alloy, such as a cast aluminium alloy.

[0033] In a further aspect, the invention employs a crankshaft drive having a piston according to one of the previous aspects, in particular a connecting rod having a thickened portion (connecting rod head) corresponding to the connecting rod holder of the piston.

[0034] Such a crank mechanism can be preassembled and installed in an internal combustion engine with the advantages that the present invention provides.

[0035] In a further aspect the problem is solved by a reciprocating piston internal combustion engine having a piston according to one of the above mentioned embodiments and / or having a crank drive as described above.

[0036] Such a reciprocating piston internal combustion engine has all the advantages of the present invention, for example the piston according to the present invention can be used to improve the corresponding tolerances between the piston and the cylinder bore, thus improving wear, oil consumption during cold starts and emissions, which applies in particular in connection with pistons having connecting rods connected to the pistons via connecting rod holders.

[0037] The invention is explained in further detail below with reference to exemplary embodiments. [Brief description of the drawings]

[0038] [Figure 1] FIG. 2 is a perspective view including hidden lines showing the crank mechanism including the piston and the connecting rod. [Figure 2a] FIG. 2 is a side view of a piston from the assembly of FIG. 1. [Figure 2b] FIG. 2 is a bottom view of a piston from the assembly of FIG. 1. [Figure 2c] FIG. 2 is a side cross-sectional view of a piston from the assembly of FIG. 1. [Figure 2d] FIG. 2 is a bottom view of the piston from the assembly of FIG. 1 with cross-section callouts. [Figure 3a] FIG. 2 is a side view showing a connecting rod from the assembly of FIG. 1; [Figure 3b] FIG. 2 is a perspective view showing a connecting rod from the assembly of FIG. 1; [Figure 4] 1 is a side view, with partial cross-section, illustrating an embodiment of a crank drive made in accordance with the present invention; [Diagram 5] 1 is a perspective view, partially cut away, illustrating an internal combustion engine that utilizes a crank assembly provided by the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] The crank unit 101 comprises a piston 201 and a connecting rod 301. The crank unit 101 is part of a diesel engine (not shown), whereby a corresponding diesel engine can have, for example, four of these crank units, six of these crank units or even eight of these crank units, whereby each piston 201 is accommodated movably along a movement axis 281 in a corresponding cylinder. The connecting rod 301 can move about a crank axis 185 on a respective crank pin of the crankshaft corresponding to the number of cylinders. The diesel engine is designed, for example, as an in-line 4-cylinder, in-line 6-cylinder or V8 engine. In each case, it is a diesel engine with a high-pressure injection system for diesel fuel and turbo and / or supercharging, which results in high combustion temperatures in the respective cylinders. Naturally, other designs can also be realized using the crank unit 101. The piston 201 is in this example made of an aluminum alloy.

[0040] Each connecting rod 301 is forged from steel. The connecting rod is pivotally connected to the piston 201 about the pivot axis 183, so that when the crankshaft makes a full revolution (not shown), the crankshaft 185 is guided through a circular movement and the piston 201 moves up and down in the cylinder by the connecting rod 301. A full revolution of the crankshaft is thereby performed without mechanical interference. The gas pressure generated by the combustion of the injected diesel at the upper side 203 of the piston 201 drives the piston 201, for example, so that the engine works according to the diesel principle. Ignition of the injected diesel fuel is achieved by compressing the intake air in the cylinder. The compression temperature of the intake air reaches more than 700° C. and the resulting combustion temperature exceeds 1,200° C. The thermal effects on the piston 201 are correspondingly high.

[0041] In addition to the upper side (crown) 203, which faces towards the combustion chamber in the cylinder, the piston 201 has a peripheral surface 205 and a lower surface 207 (see FIG. 2a). A combustion cavity 241 (see FIG. 2c) with a conical dome 243 is arranged in the upper side concentric with the axis of movement 281. The conical dome 243 increases the surface area in the combustion cavity 241.

[0042] The main components of the circumferential surface 205 form a piston skirt 219 which descends in the direction of the lower side 207 (see FIG. 2c). The piston skirt is cylindrical and has thin walls. Starting from the upper side 203, the piston 201 has a narrow peripheral collar 221 which forms a distance from the upper side 203 to a first annular ring groove 223. A piston ring for sealing against the cylinder is arranged in this first annular groove 223. Furthermore, in the direction of the lower side 207, a second annular ring groove 225 and a third annular ring groove 227 are arranged, whereby in the annular groove 225 a piston ring is inserted as a sealing ring and in the annular groove 227 a piston ring in the function of an oil scraper ring is inserted (piston rings are not shown in either case). An additional bore 229 is arranged above the annular groove 227, which facilitates the drainage of the engine oil.

[0043] The peripheral collar 221 is known in the prior art for diesel engines as a so-called "firewall" and in these engines is designed in the prior art with a diameter significantly smaller than the circumferential surface 20 of the piston. However, the peripheral collar 221 of the embodiment of the invention in Figure 2a has a radius 282 which is identical to the radius 284 of the circumferential surface 205 within engineering tolerances. Thus, the piston 201 can be machined to its cylindrical shape in a single clamping operation and a single turning operation to a uniform diameter on a lathe.

[0044] The peripheral collar 221 can be designed in this configuration because the present invention provides additional cooling to limit thermal expansion. The collar 221 must be made with a reduced diameter because in the prior art it would be the primary cause of increased heating of the piston crown causing significant expansion in this area. The piston heat sink of the present invention eliminates this need.

[0045] On the underside 207, the piston 201 has a connecting rod holder 210 for engaging a connecting rod 301. The holder 210 is essentially contained in a formed undercut 211 (see FIG. 2c), which is concentric around the pivot axis 183 and is characterized by a respective edge 217 at the end of the material. To leave the undercut 211 accessible along the pivot axis 183 and to allow the undercut 211 to terminate on the inner surface 213 of the connecting rod holder, the piston skirt 219 has a cutout 220 on both sides along the pivot axis 183. This cutout 220 allows the connecting rod head 303 (see FIG. 3a) to slide laterally into the connecting rod holder and to pivotally engage the inner surface 213 (see FIG. 2a). Furthermore, the presence of cutout 220 allows for the insertion of a tool for fine machining of inner surface 213 .

[0046] As can be seen from the underside of the piston 201 (see also FIG. 2b), the piston 201 is not radially symmetrical. In addition to the direct technical volume of the piston 201, i.e. the volume for forming the connecting rod holder 210 together with the undercut 211, the volume of the piston skirt 219 as well as the corresponding volumes of other features vary. The piston 201 has an area of ​​thickened wall 231, 235. The piston also comprises a number of pockets 233. The thickened wall and the pockets are arranged symmetrically with respect to the pivot axis 183. The corresponding volumes of the thickened part 231, the pocket 233 and the thickened part 235 are selected so that both the pocket 233 and the thickened part 235 can be such cut surfaces formed along the intersecting planes through the movement axis 281, i.e. for example the cut surfaces 271, 273 or 275 (see also FIG. 2d), each having the same cross-sectional area with respect to the cut surface 271, for example within a tolerance of 2% relative to the smallest one in the respective comparable intersecting plane. This geometric design ensures that the thermal expansion behavior of the piston 201 is almost identical or even identical at different polar positions around the movement axis 281. For this purpose, material is added to the thickened part 231, material is taken away from the pocket 233 and material is added to the thickened part 235. In this way, the volumes technically required for example for the pickup 210, for example added at the respective cut surfaces, are balanced accordingly. Similarly, for example, each thickened portion 235 is provided to at least partially offset the reduction in cross-sectional area over the area of ​​cutout 220 and the missing material in piston skirt 219. Similarly, other components are compensated for by removing or adding corresponding volumes of material to piston 201 to keep the piston balanced.

[0047] Annular retaining ring grooves 215 are provided in the inner surface 213 of the undercut 211 symmetrically about the axis of movement 281 on either side along the pivot axis 183 (see FIG. 2b), and are formed as partial annular grooves 215 due to the shape of the undercut 211. Each annular retaining ring groove 215 has a cross-section that extends from a diameter 216 of the inner surface 213 to a diameter 218 of the inner surface 213 (see FIG. 2c).

[0048] The connecting rod 301 (see FIG. 3a) has a connecting rod head 303, an intermediate region 305 and a crankshaft connection 307. The connecting rod head is designed as a bulge with a cylindrical outer surface 311. The outer surface 311 is machined for a close sliding and pivoting fit in the inner surface 213 of the piston. Furthermore, a chamfer 312 is arranged in the end region of the head 303 in the direction of the pivot axis 183. Thus, the connecting rod head 303 can be inserted laterally into the piston along the pivot axis 183 such that a pivot joint is made between the connecting rod and the piston around the pivot axis 183.

[0049] The intermediate region 305 connects the connecting rod head 303 with the crankshaft connection 307 and has a neutral plane between the connecting rod head 303 and the crankshaft connection 307. The intermediate region 305 also has recesses 306 on both sides, so that, overall, the rigid cross section of the intermediate region 305 is formed as a double T-beam. Furthermore, webs 315 with recesses 316 formed oppositely with respect to the intermediate region 305 are arranged so that the intermediate region and the crankshaft connection 307 are rigid and yet as light as possible.

[0050] Approximately half of the crankshaft connection 307 consists of a portion of the connecting rod 301. The other half consists of the connecting rod cap 308, the two components being concentrically disposed about the crankshaft axis 185. A bearing shell 321 is provided on the inner surface of the crankshaft bore 309 to create a low friction, wear resistant and quickly operable connection to the crankshaft. The bearing shell is provided with features that rotationally fix its position relative to the connecting rod 301 and rod cap 308.

[0051] Furthermore, the connecting rod 301 has a valve groove 341 of smaller diameter on the outer surface area 311 of the connecting rod head 303 (see FIG. 3b). The valve groove 341 is connected to an outlet opening 343 (see FIG. 3a). The outlet opening 343 is part of an oil channel 345, which is located between the outlet opening 343 and an inlet opening 347 arranged inside the crankshaft bore 309. The oil channel 345 is located along the neutral plane of the intermediate region 305 (a plane in which the metal particles are neither compressed nor stretched in normal operation), so that the intermediate region 305 is only weakened as little as possible by the oil channel 345, especially against bending.

[0052] To fit the connecting rod 301 to the piston 201, the connecting rod head 303 is pressed laterally along the pivot axis 183 into the piston undercut 211 (see FIG. 2a). In the annular retaining ring groove 215, a resilient retaining ring (not shown) with a round wire cross section is inserted such that a portion of the retaining ring is inserted into the cross section of the undercut 211 formed by the inner surface 213. This retaining ring is then pressed back into the annular groove 215 by the chamfer 312 on the connecting rod head 303, whereby the cross section of the retaining ring is selected so that it can be positioned completely between the diameters 216 and 218.

[0053] Thus, the chamfer 312 facilitates insertion of the connecting rod head 303 into the piston 201. The use of a retaining ring in the retaining ring groove 215 secures the connecting rod head 303 against unintentional removal from the piston along the pivot axis 183.

[0054] The function of the crank unit 101 with regard to lubrication of the connection between the connecting rod head and the piston 201 at the undercut 211 is explained as follows.

[0055] Inside the crankshaft, not shown, there are oil channels that extend to lubricate the corresponding support points of the crankshaft. Crankshaft oil outlet holes are provided at the support points. The crankshaft also has corresponding outlet holes for pressurized engine oil on the crankpin journals that receive the respective connecting rods 301 around the crankshaft 185. The engine oil is then fed into a peripheral annular groove on the crankshaft and flows through the inlet opening 347 (see FIG. 3a) in the oil channel 345 to the outlet opening 343. At the outlet opening 343 and the valve groove 341 an oil reservoir is created in which the pressurized engine oil is collected for lubrication of the pivoting interface between the cylindrical surface 311 (on the connecting rod) and the cylindrical inner surface 213 (on the piston).

[0056] Furthermore, the valve groove 341 is used to control the oil flow depending on the position of the crankshaft and the resulting position of the connecting rod 301 relative to the piston 201. When the piston 201 reaches top or bottom dead center, the connecting rod 301 is essentially vertical in the cylinder bore along the axis of movement 281. In that state, the valve groove 341 is completely sealed against the inner surface 213 of the undercut 211 so that oil cannot escape through the valve groove 341. Reliable lubrication and ideal lubrication are then guaranteed, for example when ignition of the fuel in the cylinder occurs, and heat transfer between the piston 201 and the connecting rod 301 is ensured. Similarly, the oil cushion of the oil reservoir also prevents direct material contact.

[0057] During the power stroke, the piston 201 is heated by the combustion gases and pushed downwards. First, the crankshaft pivots about 90° from TDC and the connecting rod 301 pivots relative to the piston. The valve groove 341 is now dimensioned such that a portion of the valve groove 341 is free at the edge 217 of the undercut 211 (see FIG. 2c). At this time, oil supplied through the oil channel 345 under engine pressure is released from the open portion of the valve groove 341. This oil is also heated and its release transfers heat away from the connecting rod / piston connection. In this condition, the connection between the connecting rod head 303 and the undercut 211 is relatively lightly loaded, so that the engine oil outflow can now be used effectively, even though this means that less oil is available for lubrication.

[0058] Then, when the crankshaft approaches bottom dead center (180° from TDC), the undercut 211 closes the valve groove 341. At this time, the inertia of the crankshaft can therefore act. Further crankshaft rotation starts the exhaust stroke, which starts with maximum oil pressure in the closed valve groove 341. At this point, there is also further heat transfer to the engine oil. Then, at a crankshaft position of 270°, the valve groove 341 of the valve is opened by a part of the valve groove 341 pivoting past the edge 217, so that oil pressure is again used to transfer heat from the engine oil. Then, up to a crankshaft position of 360° (0° or the full angle corresponding to TDC), the valve groove 341 is again closed by the edge 217, so that maximum oil pressure is again present in the connection at top dead center and a new availability of heat transfer for oil dissipation is reached. This cycle is of course repeated with every revolution of the crankshaft, whereby the result is sufficient lubrication of the motion about the pivot 183 and optimized heat dissipation from the connecting rod 301 and piston 201.

[0059] 4 shows a partial cross-sectional side view of an example embodiment of a crank mechanism according to the invention, which comprises a piston 201 according to one of the above-mentioned example embodiments and a corresponding connecting rod 301 with a lubricant guide located inside the piston 201 according to one of the above-mentioned example embodiments, i.e. a crank unit 101, and a crankshaft 401. The connecting rod 301 is coupled to the crankshaft 401 in a conventional manner. The piston 201 is arranged in a cylinder arrangement 501 along which it is movable along an axis 281.

[0060] 5 shows a detailed perspective partial cross-sectional view of an example embodiment of a reciprocating piston internal combustion engine 601, with a cylinder arrangement 501 having four cylinders forming a cylinder bank of an in-line four-cylinder engine, as well as a piston 201 and a connecting rod 301 according to one of the above embodiments. In each case, the piston 201 and the connecting rod 301 form a crank unit 101. The connecting rod 301 is connected to a crankshaft 401.

[0061] In the design example shown in Figures 4 and 5, the "inner workings" of the piston 201 and connecting rod 301 are not shown for clarity.

[0062] In this connection, it is noted that in all embodiments, the geometric design of the piston 201, as explained above, also optimizes heat dissipation. The central connection of the connecting rod 301 to the receiving part 210 of the piston 201 allows for better heat transfer, so that the "grate bar" known from the prior art can also be dispensed with. Together with the simple geometry and uniform roundness of the piston 201, this makes it possible to result in a diesel engine that is easy to manufacture and yet very efficient.

[0063] As a result, the diesel engine can be operated at high combustion temperatures and therefore with efficient combustion with reduced emissions, and the geometry of the piston 201, the compact design and the centralized combustion chamber allow the engine to operate at high combustion temperatures. The excess heat is dissipated to the connecting rod 301 by the controlled oil flow through the rest of the engine. The circulating oil provides good thermal management. Overall, therefore, the combination of the piston 201 and connecting rod 301 according to the invention has reduced reciprocating mass. It should be noted that although this type of piston 201 and connecting rod 301 is shown in this embodiment for a diesel engine with high pressure injection and turbocharger, the same device is suitable for other types of engines and machines, including gasoline engines and compressors. [Explanation of symbols]

[0064] 101 Crank unit 183 Swivel Axis 185 Crankshaft (crankpin shaft) 201 Piston 203 Top side (piston crown) 205 Peripheral surface 207 Lower side (bottom side) 210 Connecting rod holder 211 Undercut 213 Inside 215 Retaining ring groove 216 diameter 217 Edge 218 diameter 219 Piston Skirt 220 Cutout 221 Outer circumference color (surrounding color) 223 Ring groove (top compression ring groove) 225 Ring Groove (Second Compression Ring Groove) 227 Ring groove (oil control ring groove) 229 Drill Hole 231 Thick part 233 Pocket 235 Thick part 241 Combustion Cavity 243 Conical Dome 261 Width 271 Cut surface 273 Cut surface 275 Cut surface 281 Moving axis 282 Radius 284 Radius 301 Connecting rod 303 Connecting rod head 305 Mid-range 306 Depth (recess) 307 Crankshaft connection 308 Connecting Rod Cap 309 Crankshaft hole 311 Exterior 312 Chamfered part 315 Bar (Web) 316 Recess 321 Bearing shell 341 Valve Groove 343 Exit opening 345 Oil Channel 347 Entrance opening 401 Crankshaft 501 Cylinder device 601 Reciprocating internal combustion engine

Claims

1. A piston (201), in particular for an engine, having an upper side (203), a lower side (207), a peripheral surface (205) extending along the periphery, and a movement axis (281) extending essentially parallel to a tangent to the peripheral surface (205) and through the upper side (203) and the lower side (207), the peripheral surface (205) being used to guide the piston (201) along the movement axis (281) in a cylinder bore of a cylinder, the upper side (203) being designed to absorb gas compression forces, and the lower side (207) having a connecting rod holder (210), the connecting rod holder (210) having an undercut (211) or multiple undercuts in the tensile and compressive directions, whereby the connecting rod holder (210) is adapted to accommodate a connecting rod corresponding to the connecting rod holder (210). a piston (201) configured to form-lockingly receive a head (303) of a connecting rod (301), the piston being pivotable relative to the connecting rod head about a pivot axis (183), the piston (201) having any number of substantially planar cross sections (271, 273, 275) disposed radially through the axis of movement (281), the substantially planar cross sections (271, 273, 275) extending radially through the axis of movement (281), the piston (201) being shaped such that a first radially disposed substantially planar cross section (271, 273, 275) extending through the axis of movement (281) and a second radially disposed substantially planar cross section (271, 273, 275) extending through the axis of movement (281) have cross-sectional areas that differ from each other by less than 10%.

2. 2. The piston of claim 1, wherein a first substantially planar cross-section (271, 273, 275) radially disposed extending through the axis of movement (281) and a second substantially planar cross-section (271, 273, 275) radially disposed through the axis of movement (281) are shaped to have cross-sectional areas that differ from each other by less than 7%, less than 5%, and / or less than 2%.

3. 2. The piston according to claim 1, characterized in that on the circumferential surface (205), an inner surface (205) extends from the upper side (203) and extends up to and / or beyond the lower side (207), and a piston skirt (219) has a radial thickness, in particular less than 10%, less than 5% and / or less than 2% of a radius (284) of the piston (201).

4. 2. A piston according to claim 1, characterized in that thickened sections (231, 235) are provided on the upper side (203) and / or on the lower side (207) and / or several thickened sections (231, 235) are arranged, and by means of thickened sections (231, 235) and / or compensation volumes (231, 235) compensation of volume sections of the piston that are concave in the respective cross-sectional areas (271, 273, 275) is realized.

5. 2. The piston according to claim 1, characterized in that the pocket (233) and / or the pockets (233) are concave on the top side (203) and / or on the bottom side (207), and the pocket (233) and / or the relief pocket (233) provide compensation for a volume section of the piston (201) arranged on the respective cross-sectional area (271, 273, 275).

6. 5. Piston according to claim 4, characterized in that the thicknesses (231) and / or the pockets (233) are arranged symmetrically with respect to the axis of movement (281).

7. 2. A piston according to claim 1, characterized in that it has a mean radius defined by the mean value of the peripheral surface and any number of further radii (284) extending through and arranged radially relative to the axis of movement (281), and is shaped such that radii extending laterally from the axis of movement (281) deviate from the mean radius by less than 1%, less than 0.5%, in particular less than 1%.

8. 2. The piston of claim 1, comprising aluminum, a cast aluminum alloy, steel, a cast steel alloy and / or metal.

9. A crank unit (101) comprising a piston (201) according to claim 1 and a connecting rod (301) having a head region (303) that corresponds in particular to the connecting rod holder (210) of the piston (201).

10. A reciprocating piston internal combustion engine comprising a piston (201) according to any one of claims 1 to 8 or a crank mechanism (101) according to claim 9.

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