WO2018083263A1

WO2018083263A1 - Connecting rod having a stepped piston

Info

Publication number: WO2018083263A1
Application number: PCT/EP2017/078225
Authority: WO
Inventors: Zoltán Riba; Martin Bodensteiner; Kai Arens; Steffen Latz; Malte Heller; Norbert Mayrhofer
Original assignee: Iwis Motorsysteme Gmbh & Co. Kg; Avl List Gmbh
Priority date: 2016-11-03
Filing date: 2017-11-03
Publication date: 2018-05-11
Also published as: AT519303A3; AT519303B1; AT519303A2; DE102016120942A1

Abstract

The invention relates to a length-adjustable connecting rod for an internal combustion engine, in particular a spark-ignition engine, comprising a first connecting rod part and a second connecting rod part, wherein the first connecting rod part can be moved relative to the second connecting rod part, and comprising at least one cylinder-piston unit in order to adjust the first connecting rod part relative to the second connecting rod part. The cylinder-piston unit comprises at least one cylinder bore, an adjustment piston arranged for longitudinal movement in the cylinder bore, a piston rod, and at least one first pressure chamber provided in the cylinder bore for holding engine oil, which pressure chamber is bounded on one side by an end face of the movable adjustment piston. The problem addressed by the invention is that of providing a length-adjustable connecting rod that can be used in the greatly limited installation space and that has the required long service life. For this purpose, according to the invention, the adjustment piston is stepped and has at least two further end surfaces such that at least two further pressure chambers are formed. The invention further relates to the use of such a connecting rod in an internal combustion engine and to an internal combustion engine having such a length-adjustable connecting rod.

Description

Connecting rod with stepped piston

The present invention relates to a length-adjustable connecting rod for an internal combustion engine, in particular a gasoline engine, with a first Pleuelteil and a second Pleuelteil, wherein the first Pleuelteil is movable relative to the second Pleuelteil, and at least one cylinder-piston unit, relative to the first Pleuelteil To adjust the second Pleuelteil, the cylinder-piston unit comprises at least one cylinder bore, a longitudinally movably arranged in the cylinder bore adjusting piston, a piston rod and at least one provided in the cylinder bore first pressure chamber for receiving engine oil on one side of a front side of the movable adjusting piston is limited. Furthermore, the invention relates to an internal combustion engine with such a connecting rod, the use of such a connecting rod in an internal combustion engine and a method for mounting the length-adjustable connecting rod.

The thermal efficiency of an internal combustion engine, especially in gasoline engines, is dependent on the compression ratio between the stroke volume and the compression volume in the combustion chamber. As the compression ratio increases, the thermal efficiency increases. The increase in the thermal efficiency via the compression ratio is degressive, but still relatively strong in the range of today's usual values.

In practice, the compression ratio can not be increased arbitrarily, since too high a compression ratio leads to an unintentional spontaneous combustion of the combustion mixture due to pressure and temperature increase. This early combustion not only leads to a troubled run and the so-called knocking in gasoline engines, but can also lead to component damage to the engine. In the partial load range, the risk of spontaneous combustion, which depends not only on the influence of ambient temperature and pressure but also on the operating point of the engine, is lower. Accordingly, a higher compression ratio is possible in the partial load range. In the development of modern internal combustion engines, there are therefore efforts to adjust the compression ratio to the respective operating point of the engine.

For the realization of a variable compression ratio (VCR), there are different solutions with which the position of the crank pin or the piston pin of the engine piston changed or the effective length of the connecting rod is varied. There are always solutions for a continuous and discontinuous adjustment of the components. Continuous adjustment allows optimum reduction of C0 ₂ emissions and consumption due to a compression ratio that can be set for each operating point. ses. In contrast, a discontinuous adjustment with two trained as end stops the adjustment stages design and operational advantages and still allows compared to a conventional crank mechanism significant savings in consumption and C0 ₂ emissions.

Already the document US 2,217,721 describes an internal combustion engine with a length-adjustable connecting rod with two telescopically movable rod parts, which together form a high-pressure chamber. For filling and emptying of the high-pressure chamber with engine oil and thus to change the length of the connecting rod, a control valve is provided with a spring-biased closure element which is displaceable by the pressure of the engine oil in an open position.

A discontinuous adjustment of the compression ratio for an internal combustion engine is shown in EP 1 426 584 A1, in which an eccentric connected to the piston pin makes it possible to adjust the compression ratio. In this case, a fixation of the eccentric in one or the other end position of the pivoting area by means of a mechanical locking.

DE 10 2005 055 199 A1 likewise discloses the mode of operation of a length-variable connecting rod with which different compression ratios are made possible. The realization is also done here via an eccentric in the small connecting rod, which is fixed in position by two hydraulic cylinders with variable resistance.

WO 2013/092364 A1 describes a length-adjustable connecting rod for an internal combustion engine with two telescopically movable rod parts, wherein a rod part forms a cylinder and the second rod part forms a longitudinally displaceable piston element. Between the adjusting piston of the first rod part and the cylinder of the second rod part, a high-pressure space is formed, which is supplied via an oil passage and an oil pressure-dependent valve with engine oil.

A similar length-adjustable connecting rod for an internal combustion engine with telescopically displaceable rod parts is shown in WO 2015/055582 A2. According to WO 2015/055582 A2, the compression ratio in the internal combustion engine should be adjusted by the connecting rod length. The connecting rod length affects the compression volume in the combustion chamber, wherein the stroke volume is determined by the position of the crankshaft journal and the cylinder bore. Therefore, a short connecting rod leads to a lower compression ratio than a long connecting rod with otherwise the same geometric dimensions, such as piston, cylinder head, crankshaft, valve timing, etc. The connecting rod length is hydraulically between two positions varies. The entire connecting rod is made of several parts, wherein the change in length is effected by a telescopic mechanism with a double-acting hydraulic cylinder. The small connecting rod eye, usually for receiving the piston pin, is connected to a piston rod (telescopic rod part). The associated adjusting piston is axially displaceably guided in a cylinder which is arranged in the connecting rod part with the large connecting rod eye, usually for receiving the crankshaft journal. The adjusting piston separates the cylinder into two pressure chambers, an upper and a lower pressure chamber. These two pressure chambers are supplied with engine oil via check valves, whereby the supply of engine oil takes place via the lubrication of the connecting rod bearing. For this purpose, an oil passage from the crankshaft journal over the connecting rod bearing to the connecting rod and there via the check valves in the pressure chambers is required. If the connecting rod is in the long position, there is no engine oil in the upper pressure chamber. The lower pressure chamber, however, is completely filled with engine oil. During operation, the connecting rod is loaded alternately due to the gas and inertial forces on train and pressure. In the long position of the connecting rod, a tensile force is absorbed by the mechanical contact with an upper stop of the adjusting piston. The connecting rod length does not change as a result. An applied compressive force is transmitted via the piston surface to the oil-filled lower pressure chamber. Since the check valve of this pressure chamber prevents the oil return, the oil pressure rises, whereby pressures of more than 2,000 bar can occur in the lower pressure chamber. The connecting rod length does not change. The connecting rod is hydraulically locked in this direction. In the short position of the connecting rod, the conditions turn around. The lower pressure chamber is empty, the upper pressure chamber is filled with engine oil. A tensile force causes a pressure increase in the upper pressure chamber. A compressive force is absorbed by a mechanical stop. The connecting rod length can be adjusted in two stages by emptying one of the two pressure chambers. Here, one of the two inlet check valves is bridged by an associated return channel. Engine oil can flow through these return passages independently of the pressure difference between the pressure chamber and the supply device. The respective check valve loses its effect accordingly. The two return channels are opened and closed by a control valve, always exactly one return channel open, the other is closed. The actuator for switching the two return channels is hydraulically controlled by the supply pressure, for example.

The space for such a length-adjustable connecting rod is limited both axially and radially. In the crankshaft direction of the space is limited by the bearing width and the distance of the counterweights. Axial is anyway only the space between the small connecting rod eye for the storage of the piston pin and the large connecting rod for the storage of the crankshaft journal and a possible Verstellhub the connecting rod available.

The forces to be transmitted by a connecting rod in an internal combustion engine are considerable, which is why the pressures in the pressure chamber of the adjusting mechanism can be considerable. In view of the high internal pressures in such an adjustment mechanism, the fatigue strength of the materials used is problematic, but also the construction of the adjustment mechanism in view of the small installation space. In addition, particles can enter the connecting rod and the adjusting mechanism via the engine oil, which is why the adjusting mechanism must also have a high tolerance to contamination.

It is therefore the object of the present invention to provide a length-adjustable connecting rod, which allows easy production and ensures a long service life despite existing impurities in the engine oil.

For this purpose, the invention provides that the adjusting piston is discontinued and has at least two further end faces, so that at least two further pressure chambers are formed. Usually, the adjusting piston and the cylinder bore of the cylinder-piston unit are rotationally symmetrical, but not limited to such a geometric shape. A length-adjustable connecting rod according to the present invention also includes oval, polygonal or other cross-sectional shapes of the adjusting piston and the cylinder bore of the cylinder-piston unit.

The adjusting piston is designed as a stepped piston and has a plurality of end faces. As a result, the effective area of the adjusting piston is larger and the pressure generated by the forces acting on the connecting rod is lower. Due to this lower system pressure and the load on the hydraulic components are lower, whereby a long life of the connecting rod is made possible.

A simple embodiment is possible if the adjusting piston comprises at least two adjusting piston components arranged one behind the other in the axial direction. The adjusting piston components are arranged spaced from one another.

In a further variant it can be provided that the cylinder-piston unit comprises a further cylinder bore and each adjusting piston component is arranged in a cylinder bore. As a result, a simple design of the adjusting and thus the cylinder-piston unit is possible. In order to enable simple manufacture and assembly, it can be provided that the piston rod comprises at least two piston rod components arranged one behind the other in the axial direction.

Good guidance of the piston rod of the cylinder-piston unit is made possible when the lower end of the piston rod is received in a recess in the second connecting rod part.

In yet another variant, it can be provided that each cylinder bore has an integrated upper stop for the adjusting piston component arranged therein. Due to the design of the cylinder bore and the upper stop as a component, the upper stop is very robust. Since the upper stop is integrally formed with the cylinder bore, the cylinder bore, the upper stop and a rod guide for the piston rod can be made good coaxially by the upper stop.

It can also be provided that the first and the second cylinder bore are formed with the integrated stops each in a first and a second cylinder housing and the cylinder housing oil grooves for oil supply of the respective pressure chambers. This allows a massive design of the cylinder bore and a simple oil supply of the cylinder-piston unit.

In addition, the cylinder-piston unit may have an anti-rotation, by means of which a relative rotation between the at least one cylinder bore and the adjusting piston is prevented. As a result, no unnecessary torsional forces are introduced into the connection points of the connecting rod on the engine piston and the crankshaft.

Furthermore, the invention also relates to a method for mounting the length-adjustable connecting rod described above. A method is to be provided that allows for easy manufacture of a length adjustable connecting rod with tight tolerances and good guidance and which results in a stable connecting rod with a long service life. For this purpose, it is provided according to the invention that the assembly method comprises the following steps in the order given:

Assembly of at least one piston rod seal and optionally at least one piston rod scraper in the region of the first piston rod component and at least one piston seal in the region of the first adjusting piston component;

Inserting the first variable displacement piston member and the first piston rod component into the first cylinder bore in the first cylinder housing; Assembly of at least one piston rod seal and possibly at least one piston rod scraper in the region of the second piston rod component and at least one piston seal in the region of the second adjusting piston component;

Inserting the two cylinder housings into each other;

Inserting the second variable displacement piston member and the second piston rod component into the second cylinder bore in the second cylinder housing;

Connecting the piston rod components with each other or with the adjusting piston components;

Connecting the second cylinder bore with the second Pleuelteil.

Characterized in that the adjusting piston has a plurality of end faces, its effective area is larger and thereby lower the pressure occurring during operation. The production of the cylinder-piston unit is facilitated by the fact that two adjusting piston components, two piston rod components and two cylinder bores or two cylinder housings are provided, each with a cylinder bore. As a result, firstly a first and a second pressure chamber can be constructed, which are formed by the respective cylinder bore and the adjusting piston component arranged therein, and thereafter a third and a fourth pressure chamber, which are formed by the respective other cylinder bore and the adjusting piston component arranged therein. This is particularly important because the individual components are relatively small due to the small space and therefore mounting is difficult.

The method may include a further step in which an anti-rotation device is mounted between the adjusting piston and the cylinder bore. This ensures that the adjusting piston always runs in the correct position in the cylinder bore.

In a further variant, it can be provided that a functional test of the cylinder-piston unit is performed before connecting the second cylinder bore and thus the cylinder-piston unit with the second connecting rod. Any existing errors can still be easily remedied at this time.

The invention further relates to the use of the above-described length-adjustable connecting rod in an internal combustion engine with at least one reciprocating piston. As a result, an internal combustion engine with an adjustable compression ratio is provided, which can be very easily manufactured and controlled, and has a long service life. In a further aspect, the invention also relates to an internal combustion engine having at least one reciprocating piston and having at least one adjustable compression ratio in a cylinder and a length-adjustable connecting rod connected to the reciprocating piston according to the embodiments described above. Preferably, all the reciprocating piston of an internal combustion engine are equipped with such a length-adjustable connecting rod, but this is not required. The fuel savings of such an internal combustion engine can be considerable and u. U. up to 20%, if, depending on the operating condition, the compression ratio is set accordingly.

According to a variant of the internal combustion engine, a control drive can be provided with at least one timing chain, a tensioning and / or guide rail, and / or a chain tensioner which connects the crankshaft to the at least one camshaft of the internal combustion engine. The timing drive is important because it can have a significant influence on the dynamic load of the engine and thus also on the length-adjustable connecting rod. This is preferably designed so that no excessive dynamic forces are introduced via the control drive.

In the following the invention will be explained in more detail by means of non-limiting exemplary embodiments, which are illustrated in the drawings. Show it:

FIG. 1 shows a schematic cross section through an internal combustion engine,

2 shows a cylinder-piston unit for length adjustment of a connecting rod of the internal combustion engine from FIG. 1, FIG.

3a shows a variant of the cylinder-piston unit in a first switching position, and

Figure 3b, the variant of Fig. 3a in a second switching position.

For reasons of clarity identical parts are provided with the same reference numerals in the figures and the following description.

In Fig. 1, a combustion engine (gasoline engine) 1 is shown in a schematic representation. The internal combustion engine 1 has three cylinders 2.1, 2.2 and 2.3, in each of which a reciprocating piston 3.1, 3.2, 3.3 moves up and down. Furthermore, the internal combustion engine 1 comprises a crankshaft 4, which is rotatably mounted by means of crankshaft bearings 5.1 - 5.4. The crankshaft 4 is connected by means of connecting rods 6.1, 6.2 and 6.3 each with associated reciprocating 3.1, 3.2 and 3.3. For each connecting rod 6.1, 6.2 and 6.3, the crankshaft 4 has an eccentrically arranged crankshaft journals 7.1, 7.2 and 7.3. The large connecting rod eye 8.1, 8.2, and 8.3 is because stored on the associated crankshaft journal 7.1, 7.2 and 7.3. The small connecting rod 9.1, 9.2 and 9.3 are each mounted on a piston pin 10.1, 10.2 and 10.3 and so pivotally connected to the associated reciprocating 3.1, 3.2 and 3.3.

The crankshaft 4 is provided with a crankshaft sprocket 1 1 and coupled by means of a timing chain 12 with a Nockenwellenkettenrad 13. The camshaft sprocket 13 drives a camshaft 14 with its associated cams for actuating the intake and exhaust valves (not shown in detail) of each cylinder 2.1, 2.2 and 2.3. The slack side of the timing chain 12 is tensioned by means of a pivotally mounted clamping rail 15 which is pressed by means of a chain tensioner 16 to this. The Zugtrum the timing chain 12 can slide along a guide rail. The essential operation of this control drive including the fuel injection and ignition by spark plug is not explained in detail and assumed to be known.

The eccentricity of the crankshaft journals 7.1, 7.2 and 7.3 are mainly the stroke H _K , especially if, as in the present case, the crankshaft 4 is arranged exactly centric below the cylinders 2.1, 2.2 and 2.3. In Fig. 1, the reciprocating piston 3.1 is shown in its lowermost position, while the reciprocating piston 3.2 is shown in its uppermost position. The difference results in the present case, the stroke H _K. The remaining height H _c (see cylinder 2.2) gives the remaining compression height in the cylinder 2.2. In conjunction with the diameter of the reciprocating piston 3.1, 3.2 or 3.3 or the associated cylinder 2.1, 2.2 and 2.3 results from the stroke H _K, the stroke volume V _h and from the remaining compression height H _{c is} calculated, the compression volume V _c . Of course, the compression volume V _c significantly depends on the design of the cylinder cover. From these volumes V _h and V _c , the compression ratio ε is calculated. ε is calculated from the sum of the stroke volume V _h and the compression volume V _c divided by the compression volume V _c . Today's values for gasoline engines are between 10 and 14 for e.

Thus, depending on the operating point (n, T, throttle position) of the internal combustion engine 1, the compression ratio ε can be adjusted, the connecting rods 6.1, 6.2 and 6.3 according to the invention designed to be adjustable in length. As a result, e.g. be operated in the partial load range with a higher compression ratio than in the full load range.

Each of the connecting rods 6.1, 6.2, 6.3 comprises a first connecting rod part 17.1, 17.2, 17.3 and a second connecting rod part 18.1, 18.2, 18.3. In the first Pleuelteil 17.1, 17.2, 17.3, the said small connecting rod 9.1, 9.2, 9.3 is formed. The second connecting rod 18.1, 18.2, 18.3 surrounds together with a lower bearing shell 19.1, 19.2, 19.3, the said large connecting rod 8.1, 8.2, 8.3. The lower bearing shells 19.1, 19.2, 19.3 are connected to the respective second connecting rod 18.1, 18.2, 18.3 in the usual way by means of fasteners. In the exemplary embodiment according to FIG. 1, between each first connecting rod part 17.1, 17.2, 17.3 and the associated second connecting rod part 18.1, 18.2, 18.3, a cylinder-piston unit 20.1, 20.2, 20.3 is arranged for length adjustment of the connecting rods 6.1, 6.2, 6.3. In variants not shown, such a cylinder-piston unit can be provided only in some connecting rods 6.1, 6.2, 6.3 of the internal combustion engine 1.

In Fig. 2, a cylinder-piston unit 20.1 is shown, which is, however, identical to the other cylinder-piston units 20.2, 20.3 configured. The following description applies accordingly to all cylinder-piston units. The cylinder-piston unit 20.1 comprises an adjusting piston 21.1. The adjusting piston 21.1 is discontinued and thus has a taper on the center. In the illustrated embodiment, the adjusting piston 21.1 is formed by a first adjusting piston component 22.1 and a second adjusting piston component 23.1, which are connected to one another by means of a short stub shaft, which is part of a second piston rod component 30.1. The two adjusting piston components 22.1 and 23.1 are arranged axially one behind the other and objected to one another. The first adjusting piston component 22.1 comprises a first end face 24.1 and a second end face 25.1. The second adjusting piston component 23.1 likewise comprises a first end side 26.1 and a second end side 27.1.

The adjusting piston 21 .1 is connected to a piston rod 28.1. The piston rod 28.1 is likewise designed in two parts and comprises a first piston rod component 29.1 and the second piston rod component 30.1 already mentioned. The first piston rod component 29.1 and the second piston rod component 30.1 are arranged one behind the other in the axial direction and at a distance from one another. The first piston rod component 29.1 is connected to the first adjusting piston component 22.1, the second piston rod component 30.1 is connected to the second adjusting piston component 23.1. The lower end 31.1 of the piston rod 28.1 is received in a recess 32.1 in the second connecting rod part 18.1.

The first adjusting piston component 22.1 is guided in a first cylinder bore 33.1, which is formed in a first cylinder housing 35.1. The second adjusting piston component 23.1 is guided in a second cylinder bore 34.1, which is formed in a second cylinder housing 36.1. The first cylinder housing 35.1 comprises a first upper stop 37.1, which is formed integrally with the first cylinder bore 33.1. The second cylinder housing 36.1 comprises a second upper stop 38.1, which is formed integrally with the second cylinder bore 34.1. The two end faces 24.1, 25.1 of the first adjusting piston component 22.1 and the associated first cylinder bore 33.1 form a first pressure chamber 40.1 and a second pressure chamber 41.1. The two end faces 26.1, 27.1 of the second adjusting piston component 23.1 and the associated second cylinder bore 34.1 form a third pressure chamber 42.1 and a fourth pressure chamber 43.1. All end faces 24.1, 25.1, 26.1, 27.1 are preferably circular. In the first cylinder housing 35.1 and the second cylinder housing 36.1 oil grooves 39.1 are formed, via which the pressure chambers 40.1, 41 .1, 42.1 43.1 are supplied with engine oil. For this purpose, the oil grooves 39.1 are preferably in communication with the oil lubrication of the large connecting rod eye 8.1.

The cylinder-piston unit 20.1 with the adjusting piston 21.1 and the cylinder bores 33.1, 34.1 is part of an adjusting mechanism for changing the length of the connecting rod 6.1. The adjusting mechanism also includes a hydraulic circuit which is responsible for the flow of hydraulic fluid, i. of the engine oil, in or out of the pressure chambers 40.1, 41.1, 42.1, 43.1 and thus provides for a movement of the adjusting piston 21.1 or locked. This circuit will not be described in detail in connection with the embodiment of FIG. Only their function is briefly outlined.

If the connecting rod 6.1 is in its long position, the first end face 24.1 of the first adjusting piston component 22.1 bears against the first upper stop 37.1 of the first cylinder bore 33.1. The first end face 26.1 of the second adjusting piston component 23.1 bears against the second upper stop 38.1 of the second cylinder bore 34.1. The first pressure chamber 40.1 and the third pressure chamber 42.1 are accordingly empty. The second pressure chamber 41 .1 and the fourth pressure chamber 43. 1 are filled with engine oil. By appropriate devices, such as a shut-off valve, it is ensured that the engine oil can not escape from the second pressure chamber 41.1 and the fourth pressure chamber 43.1. The connecting rod 6.1 is thereby hydraulically locked in its long position.

If a signal given by an unspecified control to transfer the connecting rod 6.1 from the long position or position in their short position or position, the second pressure chamber 41.1 and the fourth pressure chamber 43.1 are released, so that the engine oil from these Pressure chambers can drain. At the same time, engine oil flows into the first pressure chamber 40.1 and the third pressure chamber 42.1, so that these pressure chambers 40.1, 42.1 are filled with engine oil. As a result, the connecting rod 6.1 is transferred to its short position. The short position is reached when the second end face 25.1 of the first adjusting piston component 22.1 bears against the first lower stop 44.1 and the second end face 27.1 of the second adjusting piston component 23.1 bears against the second lower stop 45.1 of the second cylinder bore 34.1 is present. Accordingly, the second pressure chamber 41 .1 and the fourth pressure chamber 43. 1 are empty, the first pressure chamber 40. 1 and the third pressure chamber 42. 1 are filled with engine oil. The short position of the connecting rod 6.1 is hydraulically locked, in which the outflow of engine oil from the first pressure chamber 40.1 and the third pressure chamber 42.1, for example, by a shut-off valve (not shown) is prevented.

The short position of the connecting rod 6.1 is advantageous at full load, whereas long position of the connecting rod 6.1 is advantageous for the partial and low load operation.

A variant of a cylinder-piston unit 20.1 is shown schematically in FIGS. 3a and 3b. Therein, a likewise offset adjusting piston 21.1 is guided in a first cylinder bore 33.1 within a first cylinder housing 35.1. The adjusting piston 21 .1 is connected to a piston rod 28.1, which has a first piston rod component 29.1. Via the piston rod 28.1, a connection is made to the first connecting rod part 17.1 (not shown in FIGS. 3a and 3b, see FIG. 1), in which the small connecting rod eye 9.1 is formed.

In the illustrated embodiment, a third adjusting piston component 55.1 is provided in addition to the first 22.1 and second adjusting piston component 23.1. The adjusting piston components 22.1, 23.1, 55.1 are arranged one behind the other in the axial direction and at a distance from one another and connected to the first piston rod component 29.1. The axial direction here is a direction along a longitudinal axis of a connecting rod 6.1, which is represented in FIG. 3a and FIG. 3b by a dot-dash line.

The first adjusting piston component 22.1 comprises a first end face 24.1 and a second end face 25.1; The second adjusting piston component 23.1 likewise comprises a first end side 26.1 and a second end side 27.1. The third adjusting piston component 55.1 also has a first front side 48.1 and a second front side 49.1. The first end faces 24.1, 26.1, 48.1 are arranged on the second end faces 25.1, 27.1, 49.1 on axially opposite sides of the adjusting piston components 22.1, 23.1, 55.1. As already described above, the end faces 24.1, 25.1, 26.1, 27.1, 48.1, 49.1 are preferably circular.

In contrast to the separate cylinder housings 35.1 and 36.1 of the embodiment of Fig. 2 is in the variant of FIGS. 3a and 3b only a first cylinder housing 35.1 provided and the pressure chambers are separated by stop members 63.1, 63.2, 63.3. The stop members 63.1, 62.2, 63.3 are designed as annular elements which are arranged within the cylinder bore 33.1, for example, welded, are. At the stop members 63.1, 63.2, 63.3 corresponding stops are provided to the respective end faces, which - depending on the switching position of a hydraulic switching element 57.1, which is described in more detail below - together span the pressure chambers.

At the first stop member 63.1, a first upper stop 37.1 is provided which forms a first pressure chamber 40.1 together with the first end face 24.1 of the first adjusting piston component 22.1.

A second pressure chamber 41 .1 is formed by the second end face 25.1 of the first adjusting piston component 22.1 and a first lower stop 44.1 of a second stop component 63.2.

The two end faces 26.1, 27.1 of the second adjusting piston component 23.1 together with a second upper stop 38.1 of the second stop member 63.2 and a second lower stop 45.1 of a third stop member 63.3 form a third pressure chamber 42.1 (second upper stop 38.1 and first end face 26.1 of the second adjusting piston component 23.1). and a fourth pressure chamber 43.1 (second lower stop 45.1 and second end face 27.1 of the second adjusting piston component 23.1).

In addition, the end faces 48.1, 49.1 of the third adjusting piston component 55.1 together with a third upper stop 51.1 of the third stop member 63.3 and a third lower stop 50.1, which is designed as part of the first cylinder housing 35.1 at the bottom of the first cylinder bore 33.1, form a fifth pressure chamber 53.1 (FIG. third upper stop 51.1 and first end face 48.1 of the third adjusting piston component 55.1) and a sixth pressure chamber 54.1 (third lower stop 50.1 and second end face 49.1 of the third adjusting piston component 55.1).

Another seventh pressure chamber 52.1 is formed by a piston rod end face 46.1 designed as part of the first piston rod component 29.1 and a fourth lower stop 47.1, which is designed on the side of the first stop component 63.1 facing the small connecting rod 9.1 in the installed state.

The filling and draining of the pressure chambers 40.1, 41.1, 42.1, 43.1, 53.1, 54.1, 52.1 takes place via oil bores 62.1, 62.2, which are embodied in the first cylinder housing 35.1. As already described in connection with the exemplary embodiment of FIG. 2, the oil bores 62. 1, 62. 2 are connected to a hydraulic medium source, for which purpose preferably the oil lubrication of the large connecting rod 8.1 is used. The drainage can also be done in the oil lubrication or other, not shown channels in the crankcase. The hydraulic switching element 57.1 required for this purpose is briefly described below. The hydraulic switching element 57.1 has two switch positions and can connect the pressure chambers 40.1, 41.1, 42.1, 43.1, 53.1, 54.1, 52.1 alternately with an oil feed bore 58.1 and an oil drainage bore 59.1.

In a first switching position, which is shown in FIG. 3a and corresponds to a long connecting rod 6.1, the second pressure chamber 41.1, the fourth pressure chamber 43.1, the sixth pressure chamber 54.1 and the seventh pressure chamber 52.1 are connected to the oil supply bore 58.1 via the second oil bore 62.2. Thus, the said pressure chambers hydraulic medium is supplied.

At the same time, the first 40.1, third 42.1 and fifth 53.1 pressure chambers are connected to the oil drainage hole 59.1 via the first oil hole 62.1, thereby draining hydraulic medium in them.

Fig. 3b shows the second switching position, which corresponds to a short connecting rod 6.1. The connections are reversed to those in Fig. 3a, so that the filled therein pressure chambers 41 .1, 43.1, 54.1, 52.1 are now connected to the Ölableitungsbohrung 59.1 and the emptied in Fig. 3a pressure chambers 40.1, 42.1, 53.1 with the Ölzuführbohrung 58.1 are connected.

The switching of the hydraulic switching element 57.1 can take place in various ways, for example hydraulically via variable oil pressures, mechanically by controls inside or outside the connecting rod 6.1 or e.g. by magnetic actuation. These switching variants will not be described further here.

The filling and draining of the pressure chambers is promoted by the mass forces occurring during operation of the internal combustion engine 1, which positively causes a "sucking" of the hydraulic medium into the pressure chambers connected to the oil supply bore 58.1 and squeezes the hydraulic medium out of the pressure chambers to be drained.

In order to prevent pressure chambers to be filled from filling too slowly because inertia forces the hydraulic medium back into the oil supply bore 58.1, the hydraulic switching element 57.1 in the channel leading to the oil supply bore 58.1 has a check valve 60.1 which closes in the direction of the oil feed bore 58.1.

To further pressure peaks in the direction of the pressure chambers 40.1, 41 .1, 42.1, 43.1, 53.1, 54.1, 52.1, but in particular also from the pressure chambers in the hydraulic medium source - it may indeed be the regular oil system of the internal combustion engine 1 - to prevent , are provided in the oil holes 62.1, 62.2 throttle elements 56.1, 56.2, 56.3, 56.4, 56.5. In the following, the assembly of the connecting rod 6.1 will be briefly described according to the embodiment shown in FIG. The procedure is as follows: First, at least one piston rod seal and at least one piston rod scraper in the region of the first piston rod component 29.1 and at least one piston seal in the region of the first adjusting piston component 22.1 are fastened. Subsequently, the first adjusting piston component 22.1 and the first piston rod component 29.1 are inserted into the first cylinder housing 35.1 with the first cylinder bore 33.1. Following this, at least one piston rod seal and at least one piston rod scraper are mounted in the region of the second piston rod component 30.1 and at least one piston rod seal is fastened in the region of the second adjusting piston component 23.1. Now the two cylinder housings 35.1, 36.1 are interlocked. Subsequently, the second adjusting piston component 23.1 and the second piston rod component 30.1 are inserted into the second cylinder housing 36.1 with the second cylinder bore 34.1. The piston rod components 29.1, 30.1 are now connected to one another or to the adjusting piston components 22.1, 23.1. Following this, an anti-twist device, for example a pin, is mounted between the adjusting piston 21 .1 and the cylinder bores 33.1, 34.1. The preassembled cylinder and piston unit 20.1 fastened to the first connecting rod part 17.1 can then be subjected to a functional test before it is connected to the second connecting rod part 19.1.

The illustrated variants of the adjusting piston 21.1 have the advantage that occurring during operation of such length-adjustable connecting rods pressures that can be well over 1000 bar, can be better distributed and managed. This is particularly advantageous in large engines, in commercial vehicles and more generally in the increasingly increasing peak pressures in modern combustion engines.

The construction of the adjusting piston 21 .1 also allows the saving of seals in the cylinder-piston unit 21.1 and thus a faster and more cost-effective production and higher durability by wear resistance.

By compared to conventional solutions enlarged surfaces of faces and attacks also results in larger hydraulic active surfaces that allow in particular a more stable hydraulic locking the connecting rods. In contrast to known solutions, leaks occurring during operation have significantly less influence on the function and a "compression" caused thereby, ie small changes in length of the connecting rod, can be reduced. LIST OF REFERENCE NUMBERS

I combustion engine

2.1, 2.2.2.3 cylinders

3.1, 3.2.3.3 reciprocating piston

4 crankshaft

5.1, 5.2.5.3.5.4 crankshaft bearing 6.1, 6.2.6.3 connecting rod

7.1, 7.2.7.3 crankshaft journals 8.1, 8.2,8.3 large connecting rod 9.1, 9.2,9.3 small connecting rod eye 10.1, 10.2, 10.3 piston pin

I I crankshaft sprocket

12 timing chain

13 camshaft sprocket

14 camshaft

15 tensioning rail

16 chain tensioners

17.1, 17.2, 17.3 first connecting rod part 18.1, 18.2, 18.3 second connecting rod part 19.1, 19.2, 19.3 bearing shell

20.1, 20.2, 20.3cylinder-piston unit 21.1 adjusting piston 22.1 first adjusting piston component

23.1 second adjusting piston component

24.1 first end face

25.1 second end face

26.1 first end face

27.1 second end face

28.1 piston rod

29.1 first piston rod component

30.1 second piston rod component

31.1 lower end piston rod

32.1 deepening

33.1 first cylinder bore

34.1 second cylinder bore

35.1 first cylinder housing

36.1 second cylinder housing

37.1 first upper stop

38.1 second upper stop

39.1 Oil grooves

40.1 first pressure chamber

41.1 second pressure chamber

42.1 third pressure chamber

43.1 fourth pressure chamber 44.1 first stop

45.1 second lower stop

46.1 Piston rod end face

47.1 fourth lower stroke

48.1 first end face

49.1 second end face

50.1 third bottom stop

51.1 third upper stop

52.1 seventh pressure chamber

53.1 fifth pressure chamber

54.1 sixth pressure chamber

55.1 third adjusting piston component

56.1 throttle element

56.2 throttle element

56.3 throttle element

56.4 Throttling element

56.5 throttle element

57.1 hydraulic switching element

58.1 Oil supply hole

59.1 Oil drainage hole

60.1 Check valve

62.1 Oil hole 62.2 Oil hole

63.1 stop component

63.2 stop component

63.3 Stop component V _h Stroke volume

V _c compression volume

H _c compression height

H _K stroke

ε compression ratio n speed

T temperature

Claims

claims

1. Length-adjustable connecting rod (6.1, 6.2, 6.3) for an internal combustion engine (1), in particular a gasoline engine, with a first connecting rod part (17.1, 17.2, 17.3) and a second connecting rod part (18.1, 18.2, 18.3), wherein the first connecting rod part ( 17.1, 17.2, 17.3) relative to the second connecting rod part (18.1, 18.2, 18.3) is movable, and with at least one cylinder-piston unit (20.1, 20.2, 20.3) to the first connecting rod part (17.1, 17.2, 17.3) relative to second connecting rod (18.1, 18.2, 18.3) to adjust, the cylinder-piston unit (20.1, 20.2, 20.3) comprises at least one cylinder bore (33.1), in the cylinder bore (33.1 34.1) long movably arranged adjusting piston (21.1), a Piston rod (28.1) and at least one in the cylinder bore (33.1) provided first pressure chamber (40.1) for receiving engine oil, which is bounded on one side by an end face (24.1) of the movable adjusting piston (21.1), characterized in that the adjusting piston (21.1) is discontinued and mi At least two further end faces (25.1, 26.1, 27.1), so that at least two further pressure chambers (41.1, 42.1, 43.1) are formed.

2. Length-adjustable connecting rod (6.1, 6.2, 6.3) according to claim 1, characterized in that the adjusting piston (21.1) comprises at least two in the axial direction successively arranged adjusting piston components (22.1, 23.1).

3. Length-adjustable connecting rod (6.1, 6.2, 6.3) according to claim 1 or 2, characterized in that the cylinder-piston unit (20.1, 20.2, 20.3) comprises a further cylinder bore (34.1) and each adjusting piston component (22.1, 23.1) in a cylinder bore (33.1, 34.1) is arranged.

4. Length-adjustable connecting rod (6.1, 6.2, 6.3) according to one of claims 1 - 3, characterized in that the piston rod (28.1) comprises at least two in the axial direction one behind the other arranged piston rod components (29.1, 30.1).

5. Length-adjustable connecting rod (6.1, 6.2, 6.3) according to any one of claims 1-4, characterized in that the lower end (31.1) of the piston rod (28.1) is received in a recess (32.1) in the second connecting rod part (18.1).

6. Length-adjustable connecting rod (6.1, 6.2, 6.3) according to one of claims 1-5, characterized in that each cylinder bore (33.1, 34.1) has an integrated upper stop (37.1, 38.1) for the adjusting piston component (22.1, 23.1) arranged therein ,

7. Length-adjustable connecting rod (6.1, 6.2, 6.3) according to any one of claims 1-6, characterized in that the first and the second cylinder bore (33.1, 34.1) with the integrated stops (37.1, 38.1) each in a first and a second Cylinder housing (35.1, 36.1) are formed and the cylinder housing (35.1, 36.1) oil grooves (39.1) for oil supply to the respective pressure chambers (40.1, 41.1, 42.1, 43.1).

8. length-adjustable connecting rod (6.1, 6.2, 6.3) according to one of claims 1-7, characterized in that the cylinder-piston unit (20.1 20.2, 20.3) has a rotation, by means of a relative rotation between the at least one cylinder bore ( 33.1) and the adjusting piston (21.1) is prevented.

9. A method for assembling a length-adjustable connecting rod (6.1, 6.2, 6.3) according to any one of claims 1-8, characterized by the following steps in the order given:

Assembly of at least one piston rod seal and possibly at least one piston rod wiper in the region of the first piston rod component (29.1) and at least one piston seal in the region of the first adjusting piston component (22.1);

Inserting the first adjusting piston component (22.1) and the first piston rod component (29.1) into the first cylinder bore (33.1) in the first cylinder housing (35.1);

Assembly of at least one piston rod seal and possibly at least one piston rod wiper in the region of the second piston rod component (30.1) and at least one piston seal in the region of the second adjusting piston component (23.1);

Inserting the two cylinder housings (35.1, 36.1) into one another;

Inserting the second adjusting piston component (23.1) and the second piston rod component (30.1) into the second cylinder bore (34.1) in the second cylinder housing (36.1);

Connecting the piston rod components (29.1, 30.1) with each other or with the adjusting piston components (22.1, 23.1). Connecting the second cylinder bore (34.1) with the second connecting rod part (18.1, 18.2, 18.3).

10. The method according to claim 9, characterized in that between the adjusting piston (21.1) and the cylinder bores (33.1, 34.1) an anti-rotation device is mounted.

1 1. A method according to any one of claims 9 or 10, characterized in that before connecting the cylinder-piston unit (20.1, 20.2, 20.3) with the second connecting rod part (18.1, 18.2, 18.3) is a functional test of the cylinder-piston Unit (20.1, 20.2, 20.3) is performed.

12. Use of a length-adjustable connecting rod (6.1, 6.2, 6.3) according to one of claims 1-8 in an internal combustion engine (1) with at least one reciprocating piston (3.1, 3.2, 3.3).

13. Internal combustion engine (1) with at least one reciprocating piston (3.1, 3.2, 3.3) and with at least one adjustable compression ratio in a cylinder (2.1, 2.2, 2.3) and connected to the reciprocating piston (3.1, 3.2, 3.3) connecting rod (6.1, 6.2, 6.3) according to any one of claims 1-8.

14. internal combustion engine (1) according to claim 13, characterized in that a timing drive with at least one timing chain (12), a tensioning and / or guide rail (15) and / or a chain tensioner (16) is provided or are the crankshaft (4) connects with at least one camshaft (14).