AT17441U1 - Length-adjustable connecting rod with locking element for screw connection - Google Patents

Abstract

The present invention describes a length-adjustable connecting rod (1) for a reciprocating engine, in particular for an internal combustion engine, the connecting rod (1) having a first connecting rod part (2) and a second connecting rod part (3) and the two connecting rod parts (2, 3) pointing in the direction a longitudinal axis (1a) of the connecting rod (1), in particular telescopically, are designed to be movable towards and/or into one another and the second connecting rod part (3) has a guide cylinder (10) at its end facing the first connecting rod part (2) and the first connecting rod part (2) has a piston element (12) that can be displaced in the guide cylinder (10). The piston element (12) is connected to the first connecting rod part (2) by means of a screw connection (5). The length-adjustable connecting rod (1) has at least one preferably mechanical securing element (22), the piston element (12) and the first connecting rod part (2) being set up to interact with the securing element (22) in order to prevent the screw connection (5th ) to prevent. The invention also relates to an internal combustion engine with at least one such connecting rod (1).

Description

description

LENGTH-ADJUSTABLE CONNECTING ROD WITH SECURING ELEMENT FOR SCREW CONNECTION

The invention relates to a length-adjustable connecting rod for a reciprocating piston engine, in particular for an internal combustion engine, the connecting rod having a first connecting rod part and a second connecting rod part and the two connecting rod parts being designed to be movable towards and/or within one another in the direction of a longitudinal axis of the connecting rod, in particular telescopically and the second connecting rod part has a guide cylinder at its end facing the first connecting rod part, and the first connecting rod part has a piston element which can be displaced in the guide cylinder. The invention also relates to an internal combustion engine with at least one such connecting rod.

In order to increase the efficiency of reciprocating engines, it is known to equip them with variable compression ratios. For this purpose, length-adjustable connecting rods can be used, for example. The length-adjustable connecting rod preferably has a first connecting rod part, which is set up to be connected to a reciprocating piston. The length-adjustable connecting rod preferably has a second connecting rod part which is designed to be connected to a crankshaft. The length-adjustable connecting rod preferably has a length adjustment device which is set up to move the two connecting rod parts towards and/or into one another in the direction of a longitudinal axis of the connecting rod parts, in particular telescopically. The length adjustment device is preferably operated hydraulically, as is described, for example, in DE 10 2017 217 492 A1.

The document DE 10 2017 217 492 A1 relates to a connecting rod for a reciprocating engine, in particular for a reciprocating internal combustion engine. This has a first connecting rod part with at least one element of a connecting rod bearing, in particular a connecting rod eye, which is set up to connect the first connecting rod part to a reciprocating piston. Furthermore, the connecting rod has a second connecting rod part with a piston element that acts on both sides, preferably a stepped piston. Furthermore, the connecting rod has a third connecting rod part with a guide cylinder and a connecting rod eye, which is designed to accommodate the piston element. The first connecting rod part can be connected or is connected to the second connecting rod part via a shank by means of a connecting means to form a unit. A first hydraulic working chamber is defined between a side of the piston element facing the connecting rod eye and the bottom of the guide cylinder. A second hydraulic working chamber is defined between a side of the piston element facing the element of a connecting rod bearing and a boundary of the guide cylinder.

It is an object of the invention to provide an improved length-adjustable connecting rod for a reciprocating engine. In particular, it is an object of the invention to minimize the risk of damage to the components, in particular the connecting rod parts, the length adjustment device and the reciprocating piston.

This object is achieved by a connecting rod mentioned at the outset in that the piston element is connected to the first connecting rod part by means of a screw connection and the length-adjustable connecting rod has at least one mechanical securing element, the piston element and the first connecting rod part being set up to be connected to the securing element cooperate to prevent the screw connection from loosening by itself. Advantageous developments are claimed in the dependent claims. The teaching of the claims is hereby made a part of the specification.

[0006] Guide cylinder and piston element represent a cylinder-piston unit which makes it possible to change an effective length of a connecting rod. This can be done hydraulically, for example, directly by means of the guide cylinder functioning as a hydraulic cylinder. A mechanical adjustment of the length, for example by means of an eccentric that is actuated via the cylinder-piston unit, is also possible. A length adjustment takes place in particular in the direction of a longitudinal axis of the connecting rod.

A screw connection within the meaning of the invention is preferably a friction-locking connection

binding of two components by means of a thread. Preferably, one component has an external thread and the other component has a corresponding internal thread. By joining the components together and twisting them against each other, the external and internal threads engage and thus connect the components to one another.

A fuse element according to the invention is preferably at least one specially shaped body or several interacting bodies that are suitable due to their material properties to transmit forces. A mechanical securing element transmits the forces, in particular mechanically. Examples of mechanical securing elements are a securing ring, a securing pin, a securing wedge or a weld.

The invention is based in particular on the finding that a pulsation of a hydraulic fluid in the cylinder-piston unit, triggered by the intended use of a connecting rod, can lead to a loosening of the screw connection between the connecting rod part and the piston element. At higher loads, the frictional forces of the thread of the screw connection are not sufficient to compensate for the forces that arise in particular from the pulsation. Even if the screw connection is slightly loosened, this can lead to damage to the length-adjustable connecting rod, the reciprocating piston and the crankshaft. The piston element and the connecting rod part are therefore set up in such a way that they interact with the securing element and thus prevent the screw connection from loosening on its own, even under high forces, pressures and temperatures.

In other words, it was recognized that the normally practicable, simple and inexpensive means of thread bonding in the specific case of the length-adjustable connecting rod is not sufficient in such cases. Rather, due to the high mechanical and thermal loads on the connecting rod, it is necessary to insert at least one additional component, the securing element, in order to be able to ensure a secure screw connection.

The securing element and the special design of the piston element, the guide cylinder and the connecting rod part create a high-temperature-resistant connection that can withstand the high mechanical loads and accelerations of a connecting rod. This prevents the screw connection between the piston element and the connecting rod part from loosening and thus provides an improved length-adjustable connecting rod for a reciprocating piston engine. This minimizes the risk of damage to the components, in particular the connecting rod parts, the piston element and the reciprocating piston.

In an advantageous embodiment, the piston element has a first recess, and the first connecting rod part has a second recess, the recesses being set up to interact with the securing element as a positive connection.

A recess within the meaning of the invention is preferably a targeted recess on a component. The component preferably deviates from its usual shape in the area of the recess. The recess can arise, for example, during the shaping of the component or can arise subsequently by removing material. Examples of recesses are grooves, blind holes or through holes, which are made in particular by drilling.

A positive connection within the meaning of the invention is preferably a targeted coupling of components, in which at least two connection partners, due to their external shape, interact in order to transmit force. In other words, the components are preferably shaped in such a way and engage in one another in such a way that when one component moves, the other component is necessarily moved as well due to the direct material contact.

The shape and arrangement of the securing element, in conjunction with the shape and arrangement of the first and second recesses, thus represent a secure positive connection that remains stable even at high temperatures and pressures.

In an advantageous embodiment, the first recess, in particular designed as a blind hole, has a base which serves at least partially as a securing element, in that it is deformed and/or deformable in such a way that it communicates with the second recess, which in particular

which is designed as a cutout, interacts as a positive connection.

A bottom according to the invention is preferably an element that limits the extension of the recess in one direction, preferably in the direction of the depth of the recess, and is significantly larger in terms of width and / or length and / or diameter than in terms of its Thickness.

A blind hole according to the invention is preferably a recess with a round cross-section and linear extension, preferably produced by means of a drill, which is at least partially not, at least not completely, continuous at one end.

This configuration is advantageous because the bottom of the first recess serves as a securing element. In this case, the first recess is preferably produced in such a way that its base is thin enough to be formed into a securing element. After the piston element and connecting rod part have been connected by means of the screw connection, the base of the first recess is preferably deformed in the direction of the second recess. In other words, the bottom is deformed or can be deformed in such a way that it spatially extends into the second recess. In this way, a preferably form-fitting connection is produced between the connecting rod part and the piston element, which prevents the screw connection between the connecting rod part and the piston element from loosening.

In a further advantageous embodiment, the bottom of the first recess is essentially symmetrically deformed and/or deformable, in particular by stamping.

Symmetrically deformed within the meaning of the invention is preferably a bulge in the bottom of the first recess in the direction of the second recess, which is distributed symmetrically over its circumference, for example hemispherical or conical. A symmetrical bulge in the base is advantageous, since the fewest possible stress peaks then occur in the component under load. The flow of forces in the component is optimized by symmetrical bulging of the base. This reduces the risk of stress fractures in highly stressed areas of the component.

In a further advantageous embodiment, the bottom of the first recess is essentially asymmetrically deformed and/or deformable, in particular by punching, and as a result has in particular the shape of a nose.

Asymmetrically deformed within the meaning of the invention is preferably a bulge of the bottom of the first recess in the direction of the second recess, which preferably does not run continuously and has a kind of jump in its shape. This is advantageous since the area of the asymmetrical deformation creates a particularly strong blocking effect against loosening of the screw connection. In the case of a symmetrically deformed base, due to the more continuous course of the shape, there is a greater risk that the second recess will slide over the deformed base. An asymmetrical deformation, in particular in the form of a nose, forms a kind of stop that makes it difficult to loosen this connection.

In a further advantageous embodiment, the bottom is at least partially broken in the deformed state, in particular to form the shape of a nose.

[0025] A thread turn of an internal thread of the screw connection is preferably set up to serve as a targeted weak point for breaking through.

This configuration aims at the same effect as that described above. The area of the asymmetrical deformation creates a particularly strong blocking effect against loosening of the screw connection. If the bottom of the first recess is perforated, this blocking effect is particularly great, since the second recess can practically not or only with difficulty be pushed over the nose that has been formed. The targeted opening of the base thus represents a particularly effective security element. In order to produce this opening in the desired shape and at the desired location, it is particularly advantageous to provide a targeted weak point in the area of the base of the first recess. This weak point causes the floor to tear or break through in a targeted manner in this area

Weak spot. In this way, the shape and position of the nose can be specifically influenced. In particular, it is advantageous if a thread turn of an internal thread of the screw connection is set up to serve as a targeted weak point for breaking through. As a result, one work step can be saved in the production of the length-adjustable connecting rod, since the work step of internal thread cutting, which takes place anyway, is also used to produce the weak point.

In a further advantageous embodiment, a floor holding element is mounted in the first recess, which is set up to support the deformed floor. A floor holding element within the meaning of the invention is preferably a component which is designed in such a way that it can be fastened in the first recess in particular in a form-fitting and/or friction-fitting manner. The floor holding element can in particular be screwed or pressed into the first recess. The base holding element is in particular shaped in such a way that it supports the deformed base from the direction of the first recess, in particular since it is at least partially in form-fitting contact with the base. In other words, the base holding element supports the base in particular in such a way that it absorbs forces that act on the base and introduces them into the piston element. This prevents unwanted deformation of the floor and thus ensures a secure hold of the screw connection. In particular, in addition to the support function, the floor holding element can also be used for the targeted initial deformation of the floor during assembly. For example, a bolt with a semicircular head can be pressed into the first recess in order to reshape the bottom. This bolt then remains in the first recess and serves as a supporting floor holding element.

In a further advantageous embodiment, the first recess and the second recess are in particular designed in such a way that they extend essentially along a common recess axis, and the securing element is designed in such a way that it also extends along this recess axis, and thereby a form-fitting Connection between the piston element and the first connecting rod part is made. The first and second recesses are preferably designed in the form of a bore, the first recess in particular as a through bore, and the securing element as a pin or pin-shaped accumulation of material. The combination of bore and pin is particularly advantageous because it is simple and inexpensive to manufacture. At the same time, this combination represents a particularly safe solution, since a pin can transmit large forces and is held securely by the bore.

In a further advantageous embodiment, the first recess is at least partially cylindrical, in particular as a through hole through the piston element, and the second recess is at least partially spherical, in particular hemispherical, and the securing element is designed as a spherical element, with at least one retaining ring or a retaining sleeve is provided which is set up to hold the securing element in position, so that a positive connection is established between the piston element and the first connecting rod part. A substantially spherical securing element offers the particular advantage that it can equally absorb and release forces in all directions and is easy and error-free to assemble. In interaction with a second recess, which is in particular designed in the form of a hemisphere, the securing element, which is in particular designed in the shape of a sphere, can thus optimally transmit the forces. In order to mount the securing element, it is inserted through the first recess, which is in particular cylindrical in shape, until it is in particular in contact with the second recess. In order to prevent the at least partially spherical securing element from slipping out of the first recess, the holding element is mounted.

A retaining ring or a retaining sleeve within the meaning of the invention is preferably at least one component which is designed in such a way that it can at least partially close the first recess after insertion of the securing element. Retaining ring or sleeve are designed in such a way that the securing element is held in position in such a way that a positive connection is established between the connecting rod part and the piston element.

In a further advantageous embodiment, the first connecting rod part has a first

impact, and the piston element has a second stop, the first stop, the second stop and the screw connection being set up and coordinated with one another in such a way that a compressive force between the piston element and connecting rod part is transmitted by means of the stops, in particular predominantly via the stops. This is advantageous because it reduces the load on the screw connection. In reciprocating internal combustion engines, the length-adjustable connecting rod and thus also the screw connection are exposed to very high mechanical loads. If the force is transmitted at least partially via the stops, the load on the screw connection is minimized, which also reduces the risk of the screw connection loosening itself.

In a further advantageous embodiment, an anti-rotation element is provided, which is connected to the second connecting rod part and set up to interact with the piston element in such a way that a rotary movement of the piston element around a longitudinal axis of the connecting rod is prevented and a movement of the piston element along the Longitudinal axis of the connecting rod and is made possible relative to the second connecting rod part. This is particularly the case in the assembled state when there is a screw connection between the piston element and the first connecting rod part, or the piston element is connected to the first connecting rod part by means of an anti-twist device if there is a screw connection between the piston element and the second connecting rod part. In particular, the anti-twist device is set up such that it prevents rotation between the piston element and connecting rod part and enables translation, in particular by means of a groove in the piston element and a bolt arranged in the connecting rod part or guided or held by the connecting rod part.

The anti-rotation element therefore preferably prevents rotation of the piston element about a longitudinal axis of the piston element, preferably parallel to the longitudinal axis of the connecting rod, and/or rotation between the piston element and the connecting rod part, and enables translation, preferably in a direction along or parallel to the longitudinal axis of the piston element and/or the connecting rod longitudinal axis.

[0034]An anti-twist device within the meaning of the invention is preferably a mechanical coupling of two components, which prevents rotation between the components but enables translation. In addition to the securing element, the anti-rotation element is an additional measure to prevent the length-adjustable connecting rod or the reciprocating piston from twisting relative to the crankshaft. Depending on the construction of the length-adjustable connecting rod, the piston element is secured against twisting with respect to both connecting rod parts or the connecting rod part connected to the piston element against the other connecting rod part. The risk of damage to the components caused by undesired twisting is thus further reduced.

The object of the invention is also achieved by an internal combustion engine with at least one such connecting rod.

The invention is explained in more detail below with reference to non-limiting exemplary embodiments which are at least partially illustrated in the figures. Further features and advantages result from these exemplary embodiments in connection with the corresponding figures. They show at least partially schematically:

1 shows a schematic representation of a connecting rod according to the invention;

2 shows a sectional view of a first variant of a connecting rod from the prior art;

3 shows a sectional view of a second variant of a connecting rod from the prior art;

4 is a partial sectional view of a first embodiment of a length-adjustable connecting rod for a reciprocating engine according to the invention;

Figure ba is a perspective view of part of a piston element of the first

embodiment;

5b is a perspective view of a connecting rod part of the first embodiment; Fig. 5c is a partial sectional view of the assembled length-adjustable connecting rod

rod of the first embodiment;

[0044] FIG. 6 shows a second exemplary embodiment of a length-adjustable connecting rod according to the invention for a reciprocating piston engine in a sectional view;

[0045] FIG. 7a shows a first sectional view of a third exemplary embodiment of a length-adjustable connecting rod according to the invention for a reciprocating piston machine along the line VIIa-Vlila in FIG. 7b;

[0046] FIG. 7b shows a second sectional view of the length-adjustable connecting rod of the third exemplary embodiment, sectioned along the line VIlb-VIlb in FIG. 7a;

7c is a perspective view of the first connecting rod part of the third embodiment;

8a is a sectional view of a fourth embodiment of an inventive

dimensionally adjustable connecting rod for a reciprocating engine, sectioned along the Villa-Villa line in Figure 8b;

[0049] FIG. 8b shows a second sectional view of the length-adjustable connecting rod of the fourth exemplary embodiment, sectioned along the line VIllb-VIIlb in FIG. 8a;

9a shows a sectional view of a fifth exemplary embodiment of a length-adjustable connecting rod according to the invention for a reciprocating piston engine;

9b is a sectional view of the length-adjustable connecting rod of the fifth embodiment with an alternative configuration;

Fig. 10a is a partial sectional view of a sixth embodiment of a length-adjustable connecting rod for a reciprocating engine according to the invention, cut along the line Xa-Xa in Fig. 10b;

Fig. 10b is a second sectional view of the length-adjustable connecting rod of the sixth embodiment, cut along the line Xb-Xb in Fig. 10a;

Fig. 11a is a partial sectional view of a seventh embodiment of a length-adjustable connecting rod for a reciprocating engine according to the invention, sectioned along line Xla-Xla in Fig. 11b;

Fig. 11b is a second sectional view of the length-adjustable connecting rod of the seventh embodiment, cut along the line XIb-XIb in Fig. 11a;

12a shows a partial sectional view of an eighth exemplary embodiment of a length-adjustable connecting rod for a reciprocating engine according to the invention, sectioned along the line XIla-XIla in FIG. 12b;

[0057] FIG. 12b shows a second sectional view of the length-adjustable connecting rod of the eighth exemplary embodiment, sectioned along the line XIlb-XIlb in FIG. 12a;

Fig. 13a is a partial sectional view of a ninth embodiment of a length-adjustable connecting rod for a reciprocating engine according to the invention, sectioned along the line XIlla-XIlla in Fig. 13b;

[0059] FIG. 13b shows a second sectional view of the length-adjustable connecting rod of the ninth embodiment, sectioned along the line XIllb-XIllb in FIG. 13a;

Fig. 14 is a sectional view taken at a position, for example, along the line XIllb-XIllb in Fig.

13a another tenth variant of the length-adjustable connecting rod according to the invention;

Fig. 15a is a partial sectional view of an eleventh embodiment of a length-adjustable connecting rod for a reciprocating engine according to the invention, sectioned along the line XVa-XVa in Fig. 15b;

Fig. 15b is a second sectional view of the length-adjustable connecting rod of the eleventh embodiment, cut along the line XVb-XVb in Fig. 15a;

16a shows a partial sectional view of a twelfth embodiment of a length-adjustable connecting rod for a reciprocating engine according to the invention, sectioned along the line XVla-XVla in Fig. 16b;

Fig. 16b is a second sectional view of the length-adjustable connecting rod of the twelfth embodiment, cut along the line XVIb-XVIb in Fig. 16a;

Fig. 17 shows a sectional view at a position, for example along the line XIIIIb-XIIIIb in Fig. 13a, of another thirteenth variant of the length-adjustable connecting rod according to the invention; and

18 is a schematic view of an internal combustion engine according to the invention.

Fig. 1 shows a schematic view of an exemplary embodiment of a length-adjustable connecting rod 1 according to the invention with a first connecting rod part 2 and a second connecting rod part 3, the first connecting rod part 2 having a smaller connecting rod eye 2a on a first, piston-side end for connecting the connecting rod 1 to a Having reciprocating pistons of a reciprocating internal combustion engine. At the other end of the connecting rod 1, on the crankshaft side, the second connecting rod part 3 has a larger connecting rod eye 3a for connecting the connecting rod 1 to a crankshaft of the reciprocating piston engine. For this purpose, the second connecting rod part 3 is connected to a bearing shell 3b via connecting rod screws 4 and forms the larger connecting rod eye 3a with this. The first connecting rod part 2 can be adjusted relative to the second connecting rod part 3 between an extended position and a pushed-in position in the direction of the longitudinal axis 1a of the connecting rod 1 in order to vary the connecting rod length PL. The connecting rod length PL is defined as the distance between the axes of rotation of the smaller 2a and larger connecting rod eye 3a. For the adjustment, a length adjustment device 6 that can be charged with hydraulic medium, in particular oil or engine oil, is provided, which can be designed in various ways.

shows an example of a schematic internal combustion engine 100 with four cylinders 101, which are arranged in a cylinder block 102 and are delimited at the top by a cylinder head 103. A reciprocating piston 104 is movably arranged in each of the cylinders and is connected to a crankshaft 105 via connecting rods 1, it being possible for at least one or more of the connecting rods 1 to be designed as length-adjustable connecting rods according to the invention.

The feeding of the length adjustment device 6 with or draining of hydraulic medium takes place via hydraulic channels 7 , 7 ° and a hydraulic medium supply channel 8 , the flow rate of which is controlled by a control device 9 . The hydraulic medium supply channel 8 is connected to the hydraulic medium supply of a reciprocating internal combustion engine via the larger connecting rod eye 3a, for example. With regard to the design of the control device 9, reference is made to known systems in the prior art, in particular those of the applicants.

2 shows a sectional view of a connecting rod 1 with an embodiment variant of the length adjustment device 6 according to the prior art, the control device 9 not being shown for reasons of clarity. The second connecting rod part 3 has a section with a guide cylinder 10 at its end facing the first connecting rod part 2 . The first connecting rod part 2 has, at its end facing the second connecting rod part 3 , a piston rod 11 and a piston element 12 formed thereon or connected thereto and designed to correspond to the guide cylinder 10 . Guide cylinder 10 and piston element 12 or piston rod 11 have a circular cross-section, for example, but can also be oval

or be designed with a polygonal cross-section. The piston element 12 is shown in a middle position in Fig. 2 and divides the guide cylinder 10 into an upper pressure chamber 13 oriented in the direction of the small connecting rod eye 2a and a lower pressure chamber 14 oriented in the direction of the larger connecting rod eye 3a.

Piston seals 15 are provided on the piston element 12 and are held in their position on the piston element 12 by holding elements 16 . The piston seals 15 seal the piston element 12 in relation to the guide cylinder 10 and thus also the pressure chambers 13, 14 from one another.

The upper pressure chamber 13 is delimited at the top by a sleeve element 17 in which a piston rod seal 18 is arranged, which is also held in position by a holding element 16 . The sleeve element 17 acts as an axial guide for the piston rod 11 and prevents movements in the radial direction. To fix the sleeve element 17 in the second connecting rod part 3, the sleeve element 17 can have a threaded section (not shown) on its outside, which corresponds to a threaded section (not shown) in the upper area of the guide cylinder 10 facing the small connecting rod eye 2a.

The piston element 12 is at least partially accommodated by the guide cylinder 10 and can be displaced relative to the guide cylinder 10 along a longitudinal axis 1a of the connecting rod 1 relative to the guide cylinder 10 or the second connecting rod part 3 in order to adjust the effective connecting rod length PL. In particular, the piston element 12 can be pushed into the guide cylinder 10 or pulled out of it. Pushing the piston element 12 and guide cylinder 10 into one another causes the effective connecting rod length PL to be shortened, and pulling the piston element 12 apart or pulling it out of the guide cylinder 10 leads to an increase in the effective connecting rod length PL.

The piston element 12 is moved by alternately filling or draining the pressure chambers 13, 14 with hydraulic medium, which is controlled by the control device 9 shown in FIG.

The effective connecting rod length PL can be set between a minimum effective connecting rod length PL and a maximum effective connecting rod length PL. The effective connecting rod length PL is defined by the distance between the two axes of rotation of the connecting rod 1 about which the connecting rod 1 can rotate on the piston side and on the crankshaft side in a functional state of use. These axes of rotation are essentially the piston pin of the reciprocating piston and the crankshaft, which are guided in the connecting rod eye 2a, 3a.

When the maximum length PL is set, the upper pressure chamber 13 is drained and the lower pressure chamber 14 is filled with hydraulic medium. The piston element 12 rests on the sleeve element 17, which acts as an upper stop for the maximum achievable effective connecting rod length PL. When the minimum length PL is set, the upper pressure chamber 13 is filled with hydraulic medium and the lower pressure chamber 14 is emptied of hydraulic medium.

To explain the structure, FIG. 2 shows the piston rod 11 and the piston element 12 as one piece according to the prior art. In contrast, Fig. 3 shows another embodiment from the prior art, in which the piston rod 11 and the piston element 12 are designed as separate components, the piston element 12 connecting the piston rod 11 at its second connecting rod part 3 or the larger connecting rod eye 3a facing end embraces. At its end facing the first connecting rod part 2, the piston element 12 has a section with a cylinder bore 19, in which an internal thread 5a is preferably at least partially formed. At the end of the piston rod 11 facing the piston element 12, a corresponding external thread 5b is formed on the outer wall. Here, the piston rod 11 and the piston element 12 are designed to be screwed together.

In the figures described below are different embodiments of the

Securing the connection between the piston element 12 and the first connecting rod part 2 is described, the piston element 12 being predominantly connected to the piston rod 11 of the first connecting rod part 2 . FIG. 4 now shows a partial sectional view of a first exemplary embodiment of a length-adjustable connecting rod 1 according to the invention for a reciprocating piston engine. The first connecting rod part 2 is designed to be connected to a reciprocating piston (not shown) by means of a small connecting rod eye 2a. Furthermore, the second connecting rod part 3 is set up to be connected to a crankshaft (not shown) by means of the large connecting rod eye (not shown in FIG. 4). The length adjustment device 6 for moving the two connecting rod parts 2, 3 in the direction of a connecting rod longitudinal axis 1a of the connecting rod parts, in particular telescopically, towards and/or into one another, is in particular hydraulically actuated, as described above. For this purpose, the length adjustment device 6 has a piston element 12 , which is preferably designed as a stepped piston that acts on both sides and is connected to the first connecting rod part 2 , preferably by means of a screw connection 5 . For this purpose, an external thread 5b is provided on the piston rod 11 of the first connecting rod part 2 and interacts with an internal thread 5a provided on the inside of the piston element 12 .

The piston element 12 is connected to the first connecting rod part 2 and guided in a sliding manner in the guide cylinder 10 arranged on the second connecting rod part 3 . The lower hydraulic pressure or working chamber 14 is defined between a side of the piston element 12 facing the large connecting rod eye (not shown in FIG. 4) and a cylinder base 20 of the guide cylinder 10 . An upper hydraulic pressure or working space 13 is defined between a side of the piston element 12 facing the small connecting rod eye 2a and a sleeve element 17 mounted in the guide cylinder 10 . In Fig. 4 the connecting rod 1 is shown in a long position in which the lower pressure chamber 14 is filled with hydraulic medium and the upper end of the piston element 12 comes into contact with the sleeve element 17 - for this reason the upper pressure chamber 13 in Fig. 4 not visible or not shown.

By pressurizing the upper 13 or lower hydraulic pressure chamber 14 by supplying hydraulic medium, the piston element 12 in the guide cylinder 10 is moved back and forth. As a result, the distance between the first 2 and second connecting rod part 3 and thus also the length of the connecting rod can be changed, which corresponds to a length-adjustable connecting rod 1 .

The piston element 12 preferably has a first recess 21, in particular designed as a blind hole, as can be seen in particular in FIG. 5a. In the exemplary embodiment shown, the first recess 21 runs essentially normal to the longitudinal axis 1a of the connecting rod. According to the first exemplary embodiment, a base 21a of the first recess 21 serves as a securing element 22. For this purpose, the base 21a is deformed in such a way that it is connected to a second recess 23 (e.g. in the form of a milled cutout, see Fig. 5b) in the piston rod 11 of the first Connecting rod part 2 interacts as a positive connection. The first recess 21 is preferably produced in such a way that its bottom 21a is thin enough to be formed into the securing element 22 . After the piston element 12 and the first connecting rod part 2 have been connected by means of the screw connection 5, the bottom 21a of the first recess 21 is deformed in the direction of the second recess 23. In other words, the base 21a is deformed in such a way that it spatially extends into the second recess 23 . A form-fitting connection is thus produced between the first connecting rod part 2 and the length adjustment device 4 , which prevents the screw connection 5 between the piston rod 11 of the first connecting rod part 2 and the piston element 12 from loosening.

According to the first exemplary embodiment, the bottom 21a of the first recess 21 is preferably deformed or deformable essentially symmetrically, in particular by stamping. In the deformed state, the base 21a preferably has a hemispherical bulge in the direction of the second recess 23, as can be seen for example in FIG. 5c. The symmetrical bulging of the bottom 21a is advantageous because the fewest possible stress peaks occur under load, since the flow of forces is optimized. This reduces the risk of the bottom 21a deforming or breaking out under load.

Due to this special design of the bottom 21a as a securing element 22 and the special design of the piston element 12 and the first connecting rod part 2, a high-temperature

temperature-resistant connection made that withstands the high mechanical loads and accelerations of a length-adjustable connecting rod 1. The risk of damage to the components, in particular the connecting rod parts 2, 3 and the length adjustment device 6 with the piston element 12 and the guide cylinder 10, is minimized as a result.

5a shows a perspective sectional view of the piston element 12 as part of the length adjustment device 6 of the first exemplary embodiment. The first recess 21 is designed in particular as a blind hole and has a bottom 21a. The base 21a is the material remaining between the first recess 21 and the cylinder bore 19 formed in the piston element 12 and is not yet deformed in FIG. 5a. The bottom 21a can be produced by generating only a blind hole when forming the first recess 21, e.g. by drilling in the piston element 12 from the outside in the radial direction inwards, and leaving material so that the wall of the piston element 12 is not completely drilled through.

5b shows a perspective view of the piston rod 11 of the first connecting rod part 2 of the first exemplary embodiment. The piston rod 11 has an external thread 5b for the screw connection 5, which can interact with the internal thread 5a for the screw connection 5 on the piston element 12. The piston rod 11 of the first connecting rod part 2 has the second recess 23, which can be produced in particular by milling. The first connecting rod part 2 has, on its side facing the large connecting rod eye 3a in the assembled state, a first stop 24 which is in form-fitting contact, in particular, with a second stop 25 in the piston element 12 when the screw connection 5 between the first connecting rod part 2 and the piston element 12 is made. The screw connection 5 is relieved by force transmission via the stops 24, 25, and loosening of the screw connection 5 is made even more difficult.

Fig. 5c shows a part of a sectional view of the assembled length-adjustable connecting rod 1 of the first embodiment. The screw connection 5 is made. The stops 24, 25 are positively connected. The bottom 21a of the first recess 21 is deformed and is thus in contact with the second recess 23 in the piston rod 11 in a form-fitting manner. the deformed bottom 21a. The bottom holding element 21b was pressed in particular into the first recess 21 and has thus deformed the bottom 21a. In particular, a press fit between the floor holding element 21b and the first recess 21 ensures that the floor holding element 21b is held firmly in the first recess 21.

6 shows, in a cross-sectional view normal to the longitudinal axis 1a of the connecting rod, a second exemplary embodiment of a length-adjustable connecting rod 1 according to the invention for a reciprocating piston engine. The structure is essentially analogous to the first exemplary embodiment. The difference is the type of deformation of the base 21a of the first recess 21. According to the second exemplary embodiment, the base 21a is in particular asymmetrically deformed and in particular has at least one opening. This deformation is produced in particular by stamping and is therefore in particular in the shape of a nose. In other words, the bulging of the base 21a of the first recess 21 in the direction of the second recess 23 preferably does not run continuously in the second exemplary embodiment, but shows a kind of jump in its shape. This is advantageous since the area of the asymmetrical deformation creates a particularly strong blocking effect against loosening of the screw connection 5 . In the case of a symmetrically deformed bottom 21a, the second recess 23 can slide over the deformed bottom 21a due to the more continuous course of the shape. An asymmetrical deformation, in particular in the form of a nose, forms a kind of stop that makes it difficult to loosen this connection. If the bottom 21a of the first recess 21 is broken through, the blocking effect is particularly great, since the second recess 23 can only be pushed over the resulting nose with difficulty. The targeted breakthrough of the bottom 21a thus represents a particularly effective securing element 22.

Figs. 7a and 7b show two sectional views of a third embodiment of a length-adjustable connecting rod 1 for a reciprocating engine, in which a bolt 26 on the side

a thread start of a screw connection 5 on the first connecting rod part 2 acts as a securing element 22 . The start of the thread on the first connecting rod part 2 is preferably that side of the external thread 5b with which the first connecting rod part 2 or the piston rod 11 is screwed into the piston element 12 . A thread end is preferably the opposite side of the same external thread 5b. In the third exemplary embodiment, a first recess 21 and a second recess 23 are designed in particular in such a way that they essentially extend along a common recess axis 21°, in particular in the form of a continuous bore. The first recess 21 is designed as a borehole leading along the recess axis 21 ′ through the piston element 12 and its interior space, which results in two aligned openings in the piston element 12 . The recess axis 21' runs essentially normal to a longitudinal axis 1a of the connecting rod. The second recess 23 is preferably also designed as a cutout, as can be seen in FIG. 7c. The securing element 22 is thus designed in such a way that it also extends along this recess axis 21 ′, in particular in the form of the aforementioned bolt 26. The bolt 26 has an essentially cylindrical shape and its length is dimensioned such that it does not over the outer circumference of the piston element 12 protrudes.

A form-fitting connection between the piston element 12 and the first connecting rod part 2 is produced by means of the securing element 22 . The combination of first recess 21 in the form of a bore and bolt 26 is particularly advantageous since it is simple and inexpensive to manufacture. At the same time, this combination represents a particularly safe solution, since a bolt can transfer large forces and is held securely by the bore.

In addition, an anti-twist element 27 is shown in FIG. 7a. The anti-rotation element 27 stabilizes the piston element 12 in relation to the second connecting rod part 3. In particular, the anti-rotation element 27 is set up in such a way that it prevents rotation between the piston element 12 and the second connecting rod part 3, but at least partially enables a translation between the piston element 12 and the second connecting rod part 3. In particular, the anti-rotation element 27 is fastened as a bolt or screw element in the part of the second connecting rod eye 3 surrounding the guide cylinder 10 and protrudes into the guide cylinder 10 where it interacts with a guide groove 28 on the outside of the second piston element 12 . The guide groove 28 runs essentially parallel to the longitudinal axis 1a of the connecting rod 1. By dimensioning the length of the guide groove 28 in a direction parallel to the longitudinal axis 1a of the connecting rod 1, the movement of the piston element 12 and the first connecting rod part 2 relative to the second connecting rod part 3 can be limited .

In other words, an anti-rotation device is provided, which has an anti-rotation device 27 and a guide groove 28 that corresponds thereto in the assembled state. The anti-twist device protects the piston element 12 and the first connecting rod part 2 connected to it against twisting with respect to the second connecting rod part 3 . The risk of damage to the components caused by undesired twisting is thus further reduced.

7b shows a sectional view of the length-adjustable connecting rod 1 of the third exemplary embodiment, cut in a plane that is orthogonal to the longitudinal axis 1a of the connecting rod and runs centrally along the recess axis 21' through the securing element 22 in the form of the bolt 26. It can be seen here that the bolt 26 both touches the first connecting rod part 2 and penetrates through the piston element 12 and thus produces a form-fitting connection.

In Fig. 7c, the second connecting rod part 2 of the third embodiment is shown alone in a perspective view, so that the transverse second recess 23 can be seen clearly in the form of a cutout.

8a and 8b show a fourth exemplary embodiment of a length-adjustable connecting rod 1 for a reciprocating engine in sectional views along the longitudinal axis 1a of the connecting rod (FIG. 8a, section along line VIIIa-Villa in FIG. 8b) and normal to the longitudinal axis 1a (Fig. 8b, section along line VIllb-VIllb in Fig. 8a). The structure is essentially analogous to the third exemplary embodiment. The difference is the position of the si-

Securing element 22. According to the fourth exemplary embodiment, this is arranged on the side of a threaded end of a screw connection 5 on the first connecting rod part 2. The beginning of the thread on the first connecting rod part 2 is preferably the side from which the first connecting rod part 2 or its piston rod 11 is screwed into the piston element 12 . A thread end is preferably the opposite side of the same thread. Depending on the structure of the length-adjustable connecting rod 1, the arrangement of the securing element 22 at the start of the thread or at the end of the thread of the screw connection 5 can be advantageous, in particular for reasons of space.

9a shows a fifth exemplary embodiment of a length-adjustable connecting rod 1 for a reciprocating piston engine, a ball element 29 being provided as a securing element 22 here. The first recess 21 is at least partially cylindrical, in particular as a through bore, which is formed to run essentially normal to the longitudinal axis 1a of the connecting rod 1 and leads from the outside of the piston element 12 into the cylinder bore 19; the second recess 23 is provided in the outside of the piston rod 11 and is at least partially spherical in shape, in particular hemispherical or as a spherical segment or spherical cap. The second recess 23 is designed to correspond to the ball element 29 so that it can be accommodated at least partially in the second recess 23 in the assembled state.

In this embodiment, a retaining ring 30 is additionally provided, in particular in the form of a ring, which is arranged to hold the ball element 29 in a position in which it is fully received in the first recess 21 and so far into the cylinder bore 19 of the piston element 12 protrudes so that it is positively received in the second recess 23 - this results in a positive connection between the piston element 12 and the first connecting rod part 2. A substantially spherical securing element 22 offers the particular advantage that there are forces in all directions can take in and give away in equal measure. In interaction with a second recess 23, which is in particular designed in the form of a hemisphere, the securing element 22, which is in particular designed in the form of a sphere, can thus optimally transmit the forces.

In order to mount the ball element 29, it is inserted through the first recess 21, which is in particular cylindrical in shape, until it is in contact with the second recess 23. In order to prevent the at least partially spherical securing element 22 from slipping out of the first recess 21 and to keep the ball element 29 in contact with the piston rod 11, the retaining ring 30 is attached. For this purpose, the retaining ring 30 is pushed onto the piston element 12 from below, ie from the side facing away from the smaller connecting rod eye 2a, along the longitudinal axis 1a of the connecting rod 1 in the direction of the smaller connecting rod eye 2a. The retaining ring 30 is preferably held on the piston element 12 with a press fit; it is also fixed by attaching the piston seal 15 and the associated retaining element 16 .

9b shows the length-adjustable connecting rod 1 of the fifth exemplary embodiment with an alternative configuration in which a retaining sleeve 31 is provided instead of the retaining ring 30 (FIG. 9a). Retaining ring 30 and retaining sleeve 31 differ in the different longitudinal extent in a direction along longitudinal axis 1a of connecting rod 1. In addition, the arrangement of piston seal 15 described in the fifth exemplary embodiment is different. According to FIG. 9b, the holding sleeve 31 acts as a holding element for the piston seal 15 and at the same time holds the securing element 22 in position. For this purpose, the piston seal 15 is arranged in particular on a recess of a lateral surface of the piston element 12 which faces the second connecting rod part 3 and accommodates the piston seal 15 with a precise fit. This lateral surface extends beyond the first recess 21 of the piston element 12 . In other words, the piston seal 15 is located after the recess 21, viewed from the direction of attachment of the retaining sleeve 31. During assembly, after the ball element 29 has been inserted into the first recess 21, the piston seal 15 is pushed onto the piston element 12 and then the retaining sleeve 31 is mounted .

In contrast to this, in Fig. 9a the piston seal 15 is located in front of the first recess 21, seen from the direction of attachment of the support ring 30.

By arranging the piston seal 15 after the first recess 21 as in FIG. The piston seal 15 is thus prevented from slipping off the piston element 12 , in particular from slipping out of the recesses of the piston element 12 . The securing element 22 in the form of the ball element 29 is held in position and thus creates a positive connection between the piston element 12 and the first connecting rod part 2 , thereby preventing a screw connection 5 between the piston element 12 and the first connecting rod part 2 from loosening. Damage to the length-adjustable connecting rod 1 can thus be prevented. By combining the functions of the holding sleeve 31 and the support element in one component, the manufacturing costs of the length-adjustable connecting rod 1 are reduced.

In a sixth embodiment shown in Figs. 10a and 10b with details of sectional views, a locking screw 32 is provided as the securing element 22, which is screwed from the outside into the first recess 21 provided in the outer wall of the piston element 12. For this purpose, the locking screw 32 has a tool profile 33 in order to enable simple assembly. In the assembled state, the screw plug 32 is located completely within the outer circumference of the piston element 12.

The first recess 21 has a first section with a first diameter and a second section with a second diameter different from the first diameter. Preferably, the first diameter is larger and the first section is located in the outer area of the first recess 21 with respect to a central axis of the piston element 12 in the radial direction, while the second section is located in the inwardly oriented area of the first recess 21 . A conical sealing seat 34 is formed at the transition between the first and the second section, so that the outside and the inside of the piston element 12 are sealed against one another when the screw plug 32 is screwed in. The locking screw 32 protrudes into the cylinder bore 19 inside the piston element 12 and is accommodated in a second recess 23 formed in the piston rod 11 .

The securing element 22 is preferably attached when the piston rod 11 and the piston element 12 are screwed together. In this configuration, the first recess 21 in the piston element 12 is made from the outside with two sections of different diameters—usually by drilling—and then the thread for screwing in the screw plug 32 is provided in the first and/or second section. The second recess 23 in the piston rod 11 can either be produced together with the first recess 21 or introduced into the piston rod 11 in advance.

The seventh embodiment in Figs. 11a and 11b is comparable to the sixth exemplary embodiment, but instead of the locking screw 32, a pin element 35 is provided as the securing element 22, which is essentially cylindrical and is pressed into the first recess 21. The pin element 35 is pressed from the outside along the axis 21' of the recess so far in the radial direction into the first recess 21 that on the one hand it protrudes into the second recess 23 in the piston rod 11 of the first connecting rod part 2 and a form fit results and on the other hand Pin element 35 does not protrude beyond the outer circumference of the piston element 12. The sealing between the interior and the exterior of the piston element 12 results from the press fit of the pin element 35 in the first recess 21.

The eighth embodiment in Figs. 12a and 12b shows a slight variation of the concept of the seventh embodiment in that a pin element 35' made of a readily deformable material, for example copper, is used as the securing element 22: If this pin element 35' is pressed into the first recess 21, it can With a corresponding design of the second recess 23, the inside opening of the first recess 21 can be reached and ensure an even better form fit between the piston rod 11 and the piston element 12.

In the ninth embodiment according to FIGS. 13a and 13b, the concept of the seventh and eighth example is changed in that a medium plug 36 of a hardening medium acts as the securing element 22, which plug is poured into the first recess 21 in the piston element 12 in a liquid state and solidifies there. In this case, for example, a liquid metal can be used. The advantage of this variant is that the medium plug 36 not only fills the first recess 21 and parts of the second recess 23, but also the hardening medium in the liquid state, starting from the recesses 21, 23, into other gaps and slots between the piston rod 11 and Piston element 12 creeps, resulting in even better protection against twisting.

The positioning of the securing element 22 can be done very easily in that at least the first recess 21 - optionally also the second recess 23 - is made after the piston rod 11 has been screwed to the piston element 12 and then the liquid medium is poured into the first recess 21 will. The first recess 21 can only partially - see Figs. 13a and 13b - or completely filled.

An advantage of the ninth embodiment is that with little effort, a particularly simplified attachment of the securing element 22 is possible without post-processing after the piston rod 11 and piston element 12 have been screwed together. For this purpose, one of the recesses 21, 23 is provided four times at a distance of 90° over the circumference of the piston element 12 or rod 11 and the other of the recesses 21, 23 three times at a distance of 120° from one another.

14 shows, in a sectional view normal to the longitudinal axis 1a of the connecting rod 1, a variant in which four first recesses 21 are provided, the recess axes 21' of which are oriented normal to the respectively adjacent recess axis 21', while three second recesses 23 are provided , which are spaced 120° apart. Regardless of which end position results when the piston rod 11 is screwed to the piston element 12, there will always be an at least partial overlap of the first 21 and second recess 23, so that the liquid medium is filled in and a form fit is achieved between the piston rod 11 and the piston element 12 can be. This effect is shown in FIG. 14 by recesses on the one hand in solid lines and on the other hand in dashed lines. In the illustration in FIG. 14, no liquid medium is filled.

In the tenth embodiment according to FIGS. 15a and 15b, the securing element 22 is designed as a weld seam 37. Only a first recess 21 is necessary, a second recess 23 in the first connecting rod part or the piston rod 11 can be omitted. At the transition between the first recess 21 and the piston rod 11 , a preferably all-round weld seam is created by laser welding, which results in a form fit between the piston element 12 and the piston rod 11 .

In an eleventh embodiment shown in Figs. 16a and 16b, a blocking pin 38 is arranged as a securing element 22 in a first recess 21 in the bottom surface of the cylinder bore 19 within the piston element 12, the blocking pin 38 being oriented in a direction parallel to the longitudinal axis 1a of the connecting rod 1. The side of the piston rod 11 facing this bottom surface of the cylinder bore 19, which in the installed state is oriented in the direction of the larger connecting rod eye 3a, is provided with wedge surfaces 39 adjoining one another in the circumferential direction. For this purpose, the wedge surfaces 39 can either be worked directly into the underside of the piston rod 11 or the wedge surfaces 39 are designed in a disk that can be arranged on the piston rod 11 subsequently.

The angle of inclination of the wedge surfaces 39 is selected to be larger than the angle of the thread pitch of the screw connection 5 between the piston rod 11 and the piston element 12. If the internal thread 5a and the external thread 5b are designed with different thread pitches, the angle of inclination is selected to be larger than the largest angle of the selected thread pitches. The anti-twist protection of the piston element 12 relative to the first connecting rod part 2 or to the piston rod 11 results from the form fit between the wedge surfaces 39 and the blocking pin 38. The blocking pin 38 together with the wedge surfaces 39 acts as a securing element

22

Fig. 17 shows a twelfth embodiment, in which a spring-loaded blocking screw 40 is arranged as a securing element 22 in a running in the piston element 12 without a thread first recess 21 and is supported on a spring element in the form of a spring pact 41. The blocking screw 40 is oriented in a direction normal to the longitudinal axis 1a of the connecting rod 1 and arranged in such a way that it engages tangentially along the recess axis 21' in a threaded section 42 which is machined in a circumferential groove in the piston rod 11. The preload of this blocking screw 40 acts in the direction of rotation of the tightening of the piston element 12. The spring assembly 41, which prevents the blocking screw 40 from loosening, acts against the micro-movements caused by the dynamic loads when the connecting rod 1 is used as intended. Sealing between the interior and exterior of the piston member 12 is achieved by pressing a cup-shaped plug 43 of a malleable material such as copper over the top of the locking screw 40. This closure part 43 is connected to the blocking screw 40 in a form-fitting manner. In this embodiment, no machining is required in assembly.

In all exemplary embodiments apart from the eleventh exemplary embodiment, the first connecting rod part 2 has in particular a first stop 24 and the piston element 12 has a second stop 25, the first 24, the second stop 25 and the screw connection 5 being set up and coordinated with one another in such a way that that a compressive force between the piston element 12 and the first connecting rod part 2 or vice versa is transmitted by means of the stops 24, 25. This is advantageous because the load on the screw connection 5 is reduced, which also reduces the risk of the screw connection 5 becoming loose on its own.

The exemplary embodiments explained are merely examples that are not intended to limit the scope, applications and structure of the invention in any way. Rather, the preceding description gives the person skilled in the art a guideline for the implementation of at least one exemplary embodiment, with changes, in particular combinations of individual features of different embodiments, being able to be made with regard to the function and arrangement of the components described, without affecting the disclosed scope of protection leaving.

REFERENCE LIST

1 connecting rod

1a longitudinal axis

2 first connecting rod part

2a smaller connecting rod eye 3 second connecting rod eye 3a larger connecting rod eye 3b bearing shell

4 connecting rod bolt

5 screw connection 5a internal thread

5b external thread

6 length adjustment device

7, 7°' hydraulic channel

8 hydraulic medium supply channel 9 control device

10 guide cylinders

11 piston rod

12 piston element

13 upper pressure chamber 14 lower pressure chamber 15 piston seal

16 holding element

17 sleeve member

18 Piston rod seal 19 Cylinder bore

21 first recess 21' recess axis 21a bottom

21b bottom holding element 20 cylinder bottom

22 securing element 23 second recess

24 first stop

25 second stop

26 bolts

27 Anti-rotation element 28 Guide groove

29 spherical element

30 retaining ring

31 retaining sleeve

32 locking screw 33 tool profile

34 sealing seat

35, 35' pin element

36 medium plugs

37 weld

38 locking pin

39 wedge surface

40 locking screw

41 spring package

42 threaded section 43 locking part

PL connecting rod length

Claims (10)

Expectations 1. Length-adjustable connecting rod (1) for a reciprocating engine, in particular for an internal combustion engine, the connecting rod (1) having a first connecting rod part (2) and a second connecting rod part (3) and the two connecting rod parts (2, 3) in the direction of a longitudinal axis ( 1a) of the connecting rod (1), in particular telescopically, are designed to be movable towards and/or into one another and the second connecting rod part (3) has a guide cylinder (10) at its end facing the first connecting rod part (2) and the first connecting rod part (2) has a piston element (12) that can be displaced in the guide cylinder (10), characterized in that the piston element (12) is connected to the first connecting rod part (2) by means of a screw connection (5) and the length-adjustable connecting rod (1) has at least one preferably mechanical securing element ( 22), wherein the piston element (12) and the first connecting rod part (2) are set up to interact with the securing element (22) in order to automatically release d he screw connection (5) to prevent. 2. Length-adjustable connecting rod (1) according to claim 1, wherein the piston element (12) has a first recess (21) and the first connecting rod part (2) has a second recess (23), the recesses (21, 23) being set up to interact with the securing element (22) as a positive connection. 3. Length-adjustable connecting rod (1) according to claim 2, wherein the first recess (21), which is in particular designed as a blind hole, has a base (21a) which serves at least partially as a securing element (22) by being deformed and/or is deformable in that it interacts with the second recess (23), which is designed in particular as a milled out area, as a form-fitting connection. 4. Length-adjustable connecting rod (1) according to claim 3, wherein the bottom (21a) of the first recess (21) is deformed and/or deformable substantially symmetrically. 5. Length-adjustable connecting rod (1) according to claim 3, wherein the bottom (21a) of the first recess (21) is deformed and/or deformable substantially asymmetrically and is therefore in particular in the shape of a nose, with the bottom (21a) preferably being deformed State is at least partially broken. 6. Length-adjustable connecting rod (1) according to claim 2, wherein the first recess (21) and the second recess (23) are formed in such a way that they extend essentially along a common recess axis (21°), and the securing element (22) is designed in such a way that it also extends along this recess axis (21°), and as a result a form-fitting connection is produced between the piston element (12) and the first connecting rod part (2). 7. Length-adjustable connecting rod (1) according to claim 6, wherein the first recess (21) is at least partially cylindrical, in particular as a through hole through the piston element (12), and the second recess (23) is at least partially spherical, in particular hemispherical, and the securing element (22) is designed as a ball element (29), with at least one retaining ring (30) or a retaining sleeve (31) being provided which are designed to hold the securing element (22) in position, so that a form-fitting connection between the Piston element (12) and the first connecting rod part (2) is made. 8. Length-adjustable connecting rod (1) according to one of claims 1 to 7, wherein the first connecting rod part (2) has a first stop (24) and the piston element (12) has a second stop (25), the first stop (24) , the second stop (25) and the screw connection (5) are set up and coordinated with one another in such a way that a compressive force between the piston element (12) and the first connecting rod part (2) is applied by means of the stops (24, 25), in particular predominantly via the stops (24 , 25) is transmitted. 9. Length-adjustable connecting rod (1) according to any one of claims 1 to 8, wherein a torsional securing element (27) is provided, which is connected to the second connecting rod part (3) and set up to interact with the piston element (12) in such a way that a rotary movement of the piston element (12) about a longitudinal axis (1a) of the connecting rod (1st ) is prevented and movement of the piston element (12) along the longitudinal axis (1a) of the connecting rod (1) and relative to the second connecting rod part (3) is made possible. 10. Internal combustion engine (100) with at least one connecting rod (1) according to one of claims 1 to 9. 15 sheets of drawings