AT521501B1 - Length-adjustable connecting rod with press connection - Google Patents

Abstract

The invention relates to a length-adjustable connecting rod (100) for a reciprocating piston machine, a method for producing such a connecting rod (100), a reciprocating piston machine and a vehicle, an effective connecting rod length (L) of the connecting rod (100) being variable and the connecting rod (100) has a first connecting rod part (102) and a second connecting rod part (103), the first connecting rod part (102) having a shaft (106) and a first connecting section (107) for at least partially supporting the connecting rod (100) in a reciprocating piston machine, the first connecting section (107) has a first thread (108) and the shaft (106) has a second thread (109) designed to cooperate with the first thread (108), the shaft (106) being fixed to the first connecting section (17) by means of a screw connection 107) is connected, and wherein the shaft (106) and the first connecting section (107) in at least one operating state of the connecting rod (100) in addition to the screw Connection (108, 109) are firmly connected to one another by a press connection (130).

Description

LENGTH-ADJUSTABLE CONNECTING ROD WITH PRESS CONNECTION The present invention relates to a length-adjustable connecting rod for a reciprocating piston engine, in particular for a reciprocating piston internal combustion engine, an effective connecting rod length of the connecting rod being variable and the connecting rod having a first connecting rod part and a second connecting rod part. In order to change the effective connecting rod length, the first connecting rod part and the second connecting rod part can be moved relative to one another along a longitudinal axis of the connecting rod, the first connecting rod part having a shaft and a first connecting section for at least partially supporting the connecting rod in a reciprocating piston machine, and the second connecting rod part having a second connecting section , which is also designed to at least partially support the connecting rod in a reciprocating piston machine. The first connecting section has a first thread and the shaft has a second thread designed to interact with the first thread, the shaft being firmly connected to the first connecting section by means of a screw connection.

The present invention further relates to a method for producing such a length-adjustable connecting rod and a reciprocating machine with a length-adjustable connecting rod and a vehicle with a reciprocating machine with such a connecting rod.

In order to make vehicles, in particular motor vehicles, more powerful and / or more efficient, reciprocating internal combustion engines with a variable compression ratio are known from the prior art. Various measures are generally known from the prior art for changing the compression ratio in a reciprocating piston machine. One of these measures is, for example, to vary the absolute positions of the top and bottom dead centers of a reciprocating piston that can be moved up and down in a cylinder of the reciprocating piston internal combustion engine by changing an effective length of a connecting rod accordingly, the effective length of the connecting rod being particularly defined by a distance between a first axis of rotation, about which the connecting rod, preferably with its large connecting rod eye in a functional state of use in a reciprocating piston machine, can be rotated about a crankshaft, and a second axis of rotation about which the connecting rod can preferably be rotated with its small connecting rod about a piston pin.

To change the effective connecting rod length, it is known to provide an appropriately trained length adjustment device, various concepts for length adjustment being known.

From DE 10 2012 020 999 A1, for example, a length-adjustable connecting rod with a hydraulically adjustable eccentric in the small connecting rod eye is known, the effective connecting rod length being able to be changed by adjusting the eccentric.

Known from WO 2016/203047 A1 is a hydraulic length adjustment device with connecting rod parts that can be displaced relative to one another, in particular telescopically pushed into one another or pulled apart, one of the connecting rod parts having a guide cylinder and the other connecting rod part having a shaft with a correspondingly designed piston element at one end , in particular a piston element designed as a double-acting stepped piston, which projects into the guide cylinder and can be displaced along the longitudinal axis of the connecting rod in order to change the effective connecting rod length in the guide cylinder. The length adjustment device has a plurality of hydraulic chambers, which are partly delimited by the guide cylinder and the piston element and which, depending on the desired connecting rod length, can be filled or drained with a hydraulic medium. With the help of several control valves and several non-return valves, the hydraulic flow to and from the hydraulic chambers can be controlled and thus the length adjustment.

On the one hand, it is known from the prior art to form the shaft in one piece with a first connecting section of the connecting rod, in particular a small connecting rod eye.

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AT 521 501 B1 2020-02-15 Austrian Patent Office [0008] It is also known to manufacture the shaft and the first connecting section, which in particular can have a small connecting rod eye for connecting the connecting rod to a reciprocating piston, as separate components and then to connect them to one another , DE 10 2017 217 492 A1 teaches, for example, to screw the shaft into the first connecting section with one end facing away from the piston element, ie to connect the parts to each other using a screw connection.

From WO 2017/075646 A1 it is known to firmly connect the shaft and the first connecting section to one another by means of a press connection, i.e. purely non-positive.

It is an object of the invention to provide an alternative, in particular an improved, hydraulically adjustable connecting rod, preferably an improved, adjustable connecting rod, which enables a more reliable connection of a shaft to a connecting section of a connecting rod.

This object is achieved by a length-adjustable connecting rod, by a method for producing a length-adjustable connecting rod, by a reciprocating machine with such a connecting rod and by a vehicle with such a reciprocating machine according to the independent claims.

A first aspect of the invention relates to a length-adjustable connecting rod for a reciprocating piston engine, in particular for a reciprocating piston internal combustion engine, wherein an effective connecting rod length of the connecting rod can be changed and the connecting rod has a first connecting rod part and a second connecting rod part, the first connecting rod part and the second connecting rod part Changing the effective connecting rod length along a longitudinal axis of the connecting rod can be moved relative to one another, the first connecting rod part having a shaft and a first connecting section for at least partially supporting the connecting rod in a reciprocating piston machine, the second connecting rod part having a second connecting section which also for at least partially supporting the connecting rod is formed in a reciprocating piston machine, the first connecting section having a first thread and the shaft a second thread designed to cooperate with the first thread, and the shaft by means of a screw b connection is firmly connected to the first connecting section.

According to the invention, the shaft and the first connecting section are firmly connected to one another in at least one operating state of the connecting rod in addition to the screw connection by means of a press connection, i.e. a force fit.

The existing in addition to the screw connection press connection between the shaft and the first connection section, a firmer, in particular more reliable, connection between the shaft and the first connection section can be ensured. In particular, the risk of loosening and / or loosening of the screw connection can be reduced by the additional press connection.

In the context of the invention, a “shaft” is understood here to mean an elongated, in particular rod-shaped component which can be cylindrical at least in sections, but also, at least in sections, can have a different cross-sectional geometry, for example a square cross-section or the like, in particular in order to avoid twisting in relation to a component interacting with the shaft, for example the second connecting rod part, in particular around the longitudinal axis of the connecting rod.

In the context of the invention, an “operating state” is understood to mean at least one defined state of a reciprocating piston engine, in particular a reciprocating piston internal combustion engine, during an operation for which the connecting rod according to the invention is designed.

Preferably, the press connection between the shaft and the first connecting section is designed such that the shaft and the first connecting section over a defined operating range, i.e. in more than one operating state, in particular in

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AT 521 501 B1 2020-02-15 Austrian patent office at least one defined operating temperature range, are firmly connected by means of the press connection, in particular at least in a temperature range between -20 ° C and + 300 ° C, in particular in a temperature range from -40 ° C to + 500 ° C.

In an advantageous embodiment of a connecting rod according to the invention, the first connecting rod part and the second connecting rod part are in particular along the longitudinal axis of the connecting rod, i.e. slidable relative to one another in the axial direction with respect to the longitudinal axis of the connecting rod, the first connecting rod part and the second connecting rod part being in particular telescopically pushed and pulled apart. This allows a particularly simple and space-saving, in particular space-saving, length adjustment to be implemented.

The first connecting rod part is for changing the effective connecting rod length in particular at least partially, in particular with at least one section, preferably with its shaft, insertable into and withdrawable from the second connecting rod part.

The first connecting section of the connecting rod, in particular the first connecting rod part, is, in an advantageous embodiment, in particular a piston-side connecting section, the first connecting section in particular having a piston pin or a small connecting rod eye for at least partially, in particular piston-side, mounting the connecting rod in a reciprocating piston machine, in particular for connection to a reciprocating piston of a reciprocating piston machine, preferably in a manner which is generally known and customary from the prior art.

The second connecting section of the connecting rod, in particular the second connecting rod part, is, in an advantageous embodiment, in particular a crankshaft-side connecting section, the second connecting section in particular having a large connecting rod eye for at least partially, in particular crankshaft-side, mounting of the connecting rod in a reciprocating piston engine, preferably for connection of the second connecting section with a crankshaft of a reciprocating piston machine, in particular in a manner which is generally known and customary from the prior art.

In a possible and particularly advantageous embodiment of a connecting rod according to the invention, in particular the second connecting rod part has a guide cylinder, the guide cylinder preferably being firmly connected to the second connecting rod part or directly into the second connecting rod part, in particular the second, in particular the crankshaft-side, connecting section, can be introduced.

Is also conceivable according to the present invention, however, an alternative, reverse embodiment of a length-adjustable connecting rod, in which the shaft is fixedly connected to the connecting portion on the crankshaft side. That in an alternative embodiment of a connecting rod according to the invention, the first connecting section can be a connecting section on the crankshaft side and the second connecting section can in particular be a connecting section on the piston side.

In an advantageous embodiment of a length-adjustable connecting rod according to the invention, the shaft of the first connecting rod part is fixedly connected to the first connecting section in the region of a first end and, in particular, preferably projects into the guide cylinder with a second end and can particularly preferably be used to change the effective connecting rod length be pushed axially back and forth in the guide cylinder like a piston along the longitudinal rod axis.

In a possible and particularly advantageous embodiment of a length-adjustable connecting rod according to the present invention, the shaft of the first connecting rod part has a piston element, in particular the second end of the shaft can be designed as a piston element, in particular as a double-acting step piston, such as in the aforementioned DE 10 2017 2017 492 A1, the shaft, in particular the piston element, particularly preferably spanning a first lower and a second upper hydraulic working space with the guide cylinder of the second connecting rod part, and preferably together with the guide cylinder in particular a first lower and one

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AT 521 501 B1 2020-02-15 Austrian patent office second upper hydraulic work area at least partially limited.

In a further development of a length-adjustable connecting rod according to the invention, an adjustment of the effective connecting rod length can be effected in particular by alternately filling and draining (releasing a hydraulic medium drain) of the two hydraulic working spaces, for example as described in WO 2015/055582 A2 principle of operation or how described in WO 2016/203047 A1.

Instead of as a piston element, the shaft, in particular its second end, could also be designed as a spindle in an alternative embodiment of a length-adjustable connecting rod according to the invention and, for example, have a spindle section with an external thread and the second connecting rod part instead of a guide cylinder has a spindle nut which is in the axial direction Direction is firmly connected to the connecting portion of the second connecting rod part, but is rotatably mounted about the longitudinal axis of the connecting rod, the spindle drive is preferably not designed to be self-locking, and rotation of the spindle nut can preferably be blocked or released, in particular by means of a control device, the length adjustment in particular can be controlled by specifically releasing and locking a rotation of the spindle nut.

In a further advantageous embodiment of a length-adjustable connecting rod according to the present invention, in particular in a further development, the first thread of the connecting section is an internal thread and the second thread of the shaft is a correspondingly designed external thread, the shaft with the external thread preferably being in the first Connection section of the first connecting rod part is screwed, in particular with a first end.

This makes it possible to provide a connecting rod which is particularly easy to manufacture and which is advantageous for a hydraulic length adjustment.

The internal thread of the first connecting section is in particular introduced into an inner circumferential surface of a blind hole which is introduced into the first connecting section of the first connecting rod part. The thread of the shaft is particularly preferably located on a first, facing the first connecting section End of the shaft, the thread of the shaft preferably being part of a threaded section at the outer end of the shaft, in particular a threaded section adjoining an end face, which for easier insertion into the first connecting section in particular additionally has a chamfer which extends in particular to the thread. At the other end of the thread, i.e. on the side of the thread facing away from the first connecting section, the threaded section preferably also has an undercut.

[0032] Alternatively, the first connecting section could also be screwed into the shaft and have the external thread and the shaft the internal thread.

In an advantageous embodiment of a length-adjustable connecting rod according to the present invention, the shaft has a shaft-press connection contact surface which forms an interference fit with a connection section press connection contact surface of the first connection section which corresponds to the shaft press connection contact surface of the shaft, wherein the interference fit is dimensioned such that in at least one operating state, the first connecting section and the connecting rod shaft are connected to one another in a force-fitting manner, the interference fit particularly causing the press connection between the shaft and the piston-side connecting section of the first connecting rod part.

In an advantageous embodiment of a length-adjustable connecting rod according to the present invention, the shaft press connection contact surface is formed in particular by a region of an outer circumferential surface of the shaft, in particular by a circumferential circumferential surface region.

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AT 521 501 B1 2020-02-15 Austrian Patent Office [0035] The connecting section press connection contact surface is preferably formed by a region of an inner lateral surface of the first connecting section, in particular by a circumferential lateral surface region, in particular by an inner lateral surface region of a bore, in particular one together with the blind hole for the internal thread.

Preferably, the shaft press connection contact surface extends in the direction of the first connection section up to the undercut of the threaded section of the shaft. This means that the shaft press connection contact surface is preferably located in a shaft section adjoining the threaded section of the shaft, the shaft press connection contact surface particularly bordering on the threaded section of the shaft, in particular on an associated thread undercut.

The shaft press connection contact surface can alternatively, however, also with a distance in the axial direction, i.e. be arranged offset in the longitudinal direction of the connecting rod to the threaded portion of the shaft and thus do not directly adjoin the threaded portion.

However, it is particularly advantageous if the shaft-press-connection contact surface directly adjoins the threaded section of the shaft, since in this way a risk of loosening or loosening of the screw connection between the shaft and the first connecting section can be countered particularly advantageously.

In an advantageous embodiment of a length-adjustable connecting rod according to the present invention, the shaft-press connection contact surface of the shaft and / or the connection section-press connection contact surface of the first connection section in an initial state before the press connection is established has an at least partially convexly curved contour which is in particular at least partially spherical or cambered, in particular in the axial direction with respect to the connecting rod longitudinal axis.

This enables a particularly firm press connection to be achieved, in particular if the spherical or cambered contour extends over the entire circumference of the shaft-press-connection contact surface of the shaft and / or the connecting section-press-connection contact surface of the first connecting section.

In an advantageous embodiment of a length-adjustable connecting rod according to the present invention, the shaft has a coating at least in at least one area, preferably a carbon coating, in particular an amorphous carbon coating, i.e. a so-called DLC coating (DLC = "diamond-like carbon"), in particular at least one outer surface, in particular at least a region of an outer lateral surface, of the shaft being at least partially coated.

Carbon coatings are fundamentally known from the prior art and enable a variety of surface functions, wear and friction being reduced by means of a carbon coating with a corresponding configuration of the coating of the components to be coated.

As particularly advantageous for the use described above, i.e. for coating parts of the connecting rod, in particular for coating the shaft, in particular metal-containing, hydrogen-containing amorphous carbon layers appear which are known in the art, e.g. according to VDI guideline 2840, with "a-C: H: Me:". With such coatings, high wear resistance and low coefficients of friction are possible with good adhesion of the coating to the substrate.

In a particularly advantageous embodiment of a length-adjustable connecting rod according to the present invention, the shaft is at least partially coated, at least in the area of the shaft press connection contact surface, in particular the entire shaft press connection contact surface, preferably with a carbon coating, in particular with an amorphous carbon coating (DLC coating) ).

In some cases, it may be advantageous if the first connecting section of the

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AT 521 501 B1 2020-02-15 Austrian patent office

Connecting rods, in particular the connecting section press connection contact surface, alternatively or additionally have a coating, preferably also a carbon coating, in particular a DLC coating.

In an advantageous embodiment of a length-adjustable connecting rod according to the present invention, in particular in a further development, the shaft, in particular additionally, has at least one further functional surface, in particular at least one sealing surface and / or at least one sliding surface, the shaft in particular at least in the Area of the at least one further functional surface is at least partially coated, in particular over the entire at least one further functional surface, preferably with a carbon coating, in particular with a DLC coating, the coating in an advantageous embodiment of a length-adjustable connecting rod according to the invention, in particular by means of a CVD or PVD (CVD = "chemical vapor deposition"; PVD = "physical vapor deposition") has been applied.

In a particularly advantageous embodiment of a length-adjustable connecting rod according to the present invention, the shaft-press connection contact surface and at least one further functional surface of the shaft, in particular at least one sealing surface, are preferably formed by a coherent surface of the shaft, in particular by a coherent outer surface, in particular through a coherent outer surface. That the shaft press connection contact surface and at least one further functional surface of the shaft, in particular at least one sealing surface, preferably adjoin one another directly, in particular without shoulders, grooves or the like in between.

As a result, several functional surfaces can be produced in particular in one operation, which means that in some cases, complex clamping and retrofitting processes can be omitted and the manufacture of the shaft can be simplified.

Alternatively, the shaft-press-connection contact surface and one or more further functional surfaces of the shaft can also be designed as separate and in particular not directly adjacent surfaces.

In an advantageous embodiment of a length-adjustable connecting rod according to the present invention, the shaft, in particular also, has a coherently formed coating which extends over the shaft press connection contact surface and over at least one further functional surface, in particular a sealing surface.

In a particularly advantageous embodiment of a length-adjustable connecting rod according to the present invention, the connecting rod, in particular the length adjustment device, has a hydraulic cylinder, which can be formed, for example, by a guide cylinder in the second connecting rod part, with a first hydraulic working space and a second hydraulic working space. which in particular by a double-acting hydraulic piston, which in particular as a stepped piston, ie with two differently sized active surfaces can be formed, wherein the hydraulic piston can be formed, for example, by a piston element connected to a shaft.

In a further development, the connecting rod also has a hydraulic medium supply line and / or a drainage line, which can each be connected in a fluid-communicating manner to the first hydraulic work space and / or the second hydraulic work space. In this advantageous embodiment, the length of the connecting rod can be set directly via the position of the hydraulic piston in the hydraulic cylinder. In particular, an inflow and outflow of a hydraulic medium into and out of the two hydraulic working spaces of the hydraulic cylinder can be controlled by means of the length adjustment device.

The forces acting during the movement of the connecting rod can be absorbed by the hydraulic cylinder and passed on to the hydraulic medium. If the hydraulic medium supply line and, if necessary, the drainage are closed, a change in the length of the connecting rods can be prevented. If, on the other hand, the hydraulic medium supply line or the drainage is open, particularly due to the corresponding switching position of the switching valve,

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AT 521 501 B1 2020-02-15 Austrian patent office, depending on the applied forces or pressures, a change in the length of the connecting rods can be effected.

For the basic functioning of such a connecting rod adjustable in length, reference is made to the already mentioned WO 2016/203047 A1.

In an advantageous, possible embodiment of a connecting rod according to the invention, the length adjustment device can have, in particular, a control valve device for each hydraulic work space, preferably a previously described control valve device, for opening and / or blocking a hydraulic medium outflow from the associated hydraulic work space, as well as a check valve device which can be sucked into the associated hydraulic workspace during a lifting movement, but cannot drain off.

In an advantageous, possible embodiment of a connecting rod according to the invention, both control valve devices can be actuated by means of a common, rod-shaped, axially displaceable actuating element, the actuating element in particular by means of a double-acting actuating piston as a function of an applied hydraulic pressure, in particular as a function of one in one Reciprocating engine, in particular a reciprocating internal combustion engine, applied oil pressure.

In an advantageous embodiment of a length-adjustable connecting rod according to the present invention, the connecting rod has at least one sealing device, in particular for sealing an adjacent hydraulic working space, at least one sealing device preferably being arranged on the shaft, in particular in the region of at least one sealing surface, at least a sealing device has been arranged on the shaft, in particular before it has been connected to the first connecting section, in particular has been pushed onto the shaft.

This enables a simple and therefore advantageous assembly of a length-adjustable connecting rod, in particular a previously described connecting rod, with a hydraulic length adjustment device.

A second aspect of the invention relates to a method for producing a length-adjustable connecting rod for a reciprocating piston engine, which is designed according to a first aspect of the invention, the method being characterized by the steps:

Providing a first connecting section with a first thread,

Providing a shank having a second thread configured to cooperate with the first thread, and

Connecting the shaft to the first connecting section to form a first connecting rod part by screwing the first thread onto the second thread and establishing a press connection between the first connecting section and the shaft,

Providing a second connecting rod part, and

Assembling the first connecting rod part with the second connecting rod part to form a length-adjustable connecting rod.

The individual method steps do not necessarily have to be carried out one after the other and in the above order: a parallel or combined execution is also possible, provided that this is technically feasible.

In an advantageous embodiment of a method according to the invention for establishing the press connection between the first connecting section of the first connecting rod part and the shank, the first connecting section and the shank are first brought to a defined joining temperature, in particular to different component temperatures, in particular the different, before screwing first connection section is heated. The shaft preferably remains at ambient temperature, the joining temperature of the shaft preferably being between 10 ° C. and 40 ° C., in particular between 15 ° C. and

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AT 521 501 B1 2020-02-15 Austrian patent office

35 ° C. The first connecting section is preferably heated to at least more than 100 ° C., in particular to more than 200 ° C. Temperatures of more than 250 ° C are also possible in order to achieve good connection results.

[0062] As a result, the shaft and the first connecting section can be press-connected particularly easily and advantageously in addition to the screw connection, in particular by means of an interference fit.

The joining temperatures are preferably chosen such that, in particular, the first connecting section shrinks onto the shaft after it has been screwed to the shaft, in particular after the shaft has been screwed in.

After connecting, in particular screwing, the shaft to the first connection section, a temperature difference between the shaft and the first connection section is preferably compensated, in particular by cooling (active or passive) the connection section. The press connection is particularly preferably produced when both parts (shaft and first connecting section), in particular again, have ambient temperature.

Heating only the first connecting section enables one or more, in particular temperature-sensitive, sealing devices to be mounted on the shaft before being connected to the first connecting section, in particular without damaging the sealing devices by heating.

In an advantageous embodiment of a method according to the invention, the shaft is at least partially coated with the first connecting section before screwing, preferably with a carbon layer, in particular with a DLC coating.

In an advantageous embodiment of a method according to the invention for producing a connecting rod according to the first aspect of the invention, wherein the shaft has a shaft press connection contact surface and / or at least one further functional surface, at least the shaft press connection contact surface and / or the at least one additional functional surface of the shaft is at least partially coated, preferably with a carbon layer, in particular with a DLC coating. This enables a particularly wear-resistant and low-friction shaft to be provided.

If the shaft has a piston element which slides longitudinally on an inner wall of a guide cylinder, in particular an outer surface, in particular an outer lateral surface of the piston element of the shaft, is designed as a functional surface, this functional surface being in particular provided with a coating, in particular a carbon coating, in particular a DLC coating.

In an advantageous embodiment of a method according to the invention, at least one sealing device is further arranged on the shaft before screwing the shaft to the first connecting section, in particular in the region of at least one sealing surface, preferably after coating the sealing surface and / or after coating the shaft -Pressverbindungs-contact surface. This enables a particularly advantageous assembly of the connecting rod and thus a particularly advantageous manufacture.

A third aspect of the invention relates to a reciprocating piston engine, in particular a reciprocating piston internal combustion engine, with a length-adjustable connecting rod, the connecting rod being designed according to the first aspect of the invention and / or the connecting rod being produced by a method according to a second aspect of the invention.

A fourth aspect of the invention relates to a vehicle, in particular a motor vehicle, with a reciprocating piston engine which is designed according to the third aspect of the invention.

These and other features and advantages emerge from the claims and from the description and from the drawings, the individual features can be realized individually or in groups, in the form of sub-combinations in one embodiment of the invention and one advantageous as well as protective design

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AT 521 501 B1 2020-02-15 Austrian patent office, if these are technically reasonable.

Some of the features or properties mentioned relate both to a connecting rod according to the invention which is adjustable in length and also to a method according to the invention and a reciprocating piston machine according to the invention and / or a vehicle according to the invention. Some of these features and properties are described only once, but apply independently of one another within the scope of technically possible configurations both for a length-adjustable connecting rod according to the invention and for a method according to the invention and for a reciprocating piston machine according to the invention and for a vehicle according to the invention.

The invention is explained in more detail below on the basis of non-restrictive exemplary embodiments which are shown in the figures, wherein functionally identical components and / or devices can have the same reference numerals, even across several exemplary embodiments. Some of them show schematically:

Fig. 1 1 shows an exemplary embodiment of a length-adjustable connecting rod according to the invention in a perspective view with a first connecting rod part and a second connecting rod part, Fig. 2 Fig. 3 Fig. 4 1 in front view, a section through the first connecting rod part along a sectional plane B-B ', a shaft of the first connecting rod part from FIGS. 2 and 3 in individual parts in front view and Fig. 5 the first connecting rod part of FIGS. 1 to 3 in an exploded view.

1 shows a perspective view of a first exemplary embodiment of a length-adjustable connecting rod 100, the connecting rod 100 having a first connecting rod part 102 with a connecting portion 107 on the piston side with a small connecting rod eye 104 for connecting the connecting rod 100 to a piston of a reciprocating machine, not shown here , as well as a second connecting rod part 103 with a connecting portion 120 on the crankshaft side with a large connecting rod eye 105 for connecting the connecting rod 100 to a crankshaft of a reciprocating machine, also not shown here, the small connecting rod eye 104 and the large connecting rod eye 105 each being designed as a connecting rod bearing, the connecting rod bearing 100 comprises a bearing shell 101 pressed into the small connecting rod eye 104.

To adjust an effective connecting rod length L of the connecting rod, which is defined by a distance between the axes of rotation of the small connecting rod eye 104 and the large connecting rod eye 105, the first connecting rod part 102 and the second connecting rod part 103 can be telescopically pulled apart and pushed into one another along the longitudinal axis A of the connecting rod, in particular, the first connecting rod part 102 can be at least partially inserted into or pulled out of the second connecting rod part 103.

For this purpose, the second connecting rod part 103, based on the illustration in FIG. 1 above the large connecting rod eye 105, has a guide cylinder 111, indicated only by the reference number 111 and the associated reference arrow, in which a rod-like shaft 106 (see, for example, FIG. 2 ) of the first connecting rod part 102, which at its end facing the small connecting rod eye 104 is firmly connected to the connecting portion 107 on the piston side, protrudes at least partially and is axially displaceable along the longitudinal axis A in the guide cylinder 111, which is symbolized by the double arrow in FIG. 1. 1 shows the connecting rod 100 in a state with a minimum effective connecting rod length L.

Via a hydraulic supply, not shown here, which can be supplied with hydraulic medium from the large connecting rod eye 105 in particular via a hydraulic medium channel, and a control device 122 which is arranged below the guide cylinder 111 and above the large connecting rod eye 105 in the second connecting rod part 103, and The length change can be controlled in FIG. 1 only by reference number 122 and an associated reference arrow.

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AT 521 501 B1 2020-02-15 Austrian Patent Office [0084] FIGS. 2 and 3 show the first connecting rod part 102 of the connecting rod 100 according to the invention from FIG. 1 in different views, with FIGS. 2 and 3 particularly showing how the rod-like shaft 106 is connected according to the invention to the connecting portion 107 on the piston side, in which the small connecting rod eye 104 is integrated.

The shaft 106 is screwed on the one hand into the piston-side connection section 107 and, on the other hand, according to the invention additionally connected to the piston-side connection section 107 by means of a press connection 130.

For this purpose, the shaft 106 has in the region of its end 124 facing the small connecting rod eye 104 a threaded section 129 with an external thread 109 and the piston-side connecting section 107 has a blind hole with a correspondingly configured internal thread 108. For easier insertion of the shaft 106 into the connecting portion 107 on the piston side when screwing into the connecting portion 107, the shaft 106 has a chamfer 126 at its end 124, in particular in the region of the threaded portion 129 on the side of the thread 109 facing the small connecting rod eye 104. In this connecting rod 100, the threaded section 129 further comprises a thread undercut 121 for a simpler tool runout during the production of the external thread 109.

The press connection 130 present in addition to the screw connection according to the invention is brought about by an interference fit between a shaft press connection surface 130A of the shaft 106 and a correspondingly configured connection section press connection contact surface 130B of the piston-side connection section 107, the diameters of the press connection contact surfaces 130A and 130B being such in relation to one another are coordinated so that, based on a functional state of use, in particular in the operating state in which the press connection 130 is to be fixed, they form an interference fit and thus a non-positive connection. The press connection 130 is preferably designed such that it is fixed over the widest possible operating range.

The term “interference fit” is to be understood in the usual mechanical engineering sense, in particular in such a way that the size of the bore, in particular a bore diameter, is in any case, i.e. in any tolerance position, is smaller than the smallest outer diameter of an associated "shaft". That is, in this case, the inner diameter of the connection portion 107 in the area of the connection portion press-connection contact surface 130B is dimensioned such that in any case, i.e. in any tolerance position, is smaller than a smallest outer diameter of the shaft 106 in the region of the shaft press connection contact surface 130B.

For a press connection 130 that is as firm as possible, the shaft press connection contact surface 130A of the shaft 106 and the connection section press connection contact surface 130B of the first, piston-side connection section 107 are designed and dimensioned such that they are in an initial state, not shown here, prior to manufacture of the press connection 130 each have an at least partially convexly curved contour and are each cambered outward, in particular in the axial direction with respect to the connecting rod longitudinal axis A, the cambering in each case extending over an entire circumference.

As can further be seen from FIG. 3, in the exemplary embodiment of a connecting rod 100 according to the invention shown in FIG. 3, the area in which the shaft 106 by means of a press connection 130 with the piston-side connecting section 107 is additionally limited by means of a press connection 130 is connected, in particular the shaft press connection contact surface 130A, directly to the threaded section 129, in particular the thread undercut 121, of the shaft 106. However, the thread undercut 121 does not pass into the shaft-press connection contact surface 130A with a (straight) chamfer, as is usually the case with a conventional undercut (e.g. according to DIN 509), but with a radius, i.e. with a curved surface contour instead of a straight, frustoconical surface. This has proven to be particularly advantageous for reasons of strength.

The fact that the shaft press connection contact surface 130A extends to the thread

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AT 521 501 B1 2020-02-15 Austrian patent office section 129 of the shaft 106, and thus the press connection 130 can be located in the immediate vicinity of the screw connection from the internal thread 108 introduced into the piston-side connecting section 107 and the external thread 109 inserted into the shaft 106 loosening and / or loosening of the screw connection can be counteracted particularly effectively. Furthermore, this configuration of a connecting rod 100 according to the invention enables a configuration of the connection of the shaft 106 with the associated connecting section 107 on the piston side that is compact in the axial direction.

Contrary to the representations in FIG. 3, in a variant in a connecting rod 100 according to the invention, the end 124 of the shaft 106 does not rest with its end face on the connecting portion 107 on the piston side. That is, the shaft 106 can preferably only be screwed into the connecting portion 107 on the piston side so that the end of the shaft 106 does not go “on block”. In this way, it can be avoided that an over-determination occurs and the shaft 106 may not be able to be inserted sufficiently far into the connecting section 107 on the piston side.

In order to prevent the first connecting rod part 102, in particular the shaft 106, from being pulled out of the guide cylinder 111, a stop sleeve 113 is provided which has an external thread 127 and can be screwed into the second connecting rod part 103 at an upper end of the guide cylinder 111 ,

In order to avoid twisting of the two connecting rod parts 102 and 103, the connecting rod 100 according to the invention also has a securing recess 150 (see FIG. 2), by means of which a twisting is achieved by means of a centering pin placed in the securing recess 150 but not shown here of the first connecting rod part 102 relative to the second connecting rod part 103, in particular about the connecting rod longitudinal axis A, can be avoided.

In the area of its other end, i.e. In the region of an end facing the large connecting rod eye 105, the shaft 106 is designed as a piston element 118, the shaft 106, in the exemplary embodiment of a connecting rod 100 according to the invention described in FIG. 1, engaging in particular with the piston element 118 in the guide cylinder 111 in the second connecting rod part 103 can and is axially displaceable in the guide cylinder 111 along the connecting rod longitudinal axis A, the piston element 118 with an outer lateral surface designed as a sliding surface 143 being able to slide along an inner lateral surface of the guide cylinder 111, also designed as a sliding surface, preferably with a defined gap in between.

The piston element 118 is designed as a double-acting step piston 118 and can span a first hydraulic working space with the guide cylinder 111, in particular with a bottom surface of the guide cylinder 111 and an inner lateral surface of the guide cylinder 111, and in particular an underside of the piston element 118, and with an upper side of the piston element 118, an inner lateral surface of the guide cylinder 111 and a lower end face of the stop sleeve 113, a second hydraulic working space, similar to the connecting rods described in DE 10 2017 217 492 A1.

In order to achieve a sufficient pressure build-up in the hydraulic working spaces of the connecting rod 100, corresponding sealing devices 110, 114 and 115 are provided, which can each be secured and held with the aid of a corresponding support element 112, 116 and 117.

A first sealing device 110 is in particular arranged immediately below the stop sleeve 113 and can be held in position in the functional use state of the connecting rod 100 within the guide cylinder 111 by means of a first support ring 112.

For sealing a gap between the piston element 118 and the guide cylinder 111, a second sealing device 114 and a third sealing device 115 are provided, each of which is provided by a second support ring 116 and a third support ring 117/21

AT 521 501 B1 2020-02-15 Austrian patent office can be held on the shaft 106, in particular adjacent to the piston element 118, in particular on corresponding further functional surfaces 141 and 142 designed as second and third sealing surfaces 141 and 142.

The connecting rod 100 according to the invention, in particular the shaft 106, furthermore has a carbon coating 125, the coating 125 being in particular a so-called DLC coating 125 (“diamond-like carbon” coating), and which is the case here Embodiment of a connecting rod 100 according to the invention, on the one hand, extends from the area of the press connection 130 in the direction of the large connecting rod eye 105 to a functional surface 140 designed as a sealing surface 140 in the region of the first sealing device 110, in particular up to an adjacent shaft shoulder, on which in a functional manner State of use of the connecting rod 100, the second sealing device 114 and the associated support ring 116 are arranged.

For an optimal application of the DLC coating 125 on the shaft 106, in particular on the sealing surface 140 and the area in which the shaft forms the press connection 130 with the piston-side connecting section 107, i.e. the shaft press connection contact surface 130A, these surfaces in this exemplary embodiment of a connecting rod 100 according to the invention are advantageously designed as a common, contiguous outer surface of the shaft 106, so that a coherent DLC coating 125 can also be provided, in particular in one operation ,

On the other hand, an outer surface 143, which is designed in particular as a further functional surface 143, in particular as a sliding surface 143, is provided with a DLC coating 143.

Fig. 4 shows the shaft 106 of the first connecting rod part 102 from Figs. 2 and 3 in an individual part representation in a view from the front, with the thread section 129 with the chamfer 126, the external thread 109 and the thread section 121 being particularly good in this representation can be recognized, as well as the DLC coating 125, which extends from the edge of the threaded section 129, in particular the thread undercut 121, via the shaft press-connection contact surface 130A and the first sealing surface 140 to the adjacent shaft shoulder with the second sealing surface 141. The DLC coating 125 of the sliding surface 143 can also be clearly seen in the region of the piston element 118 designed as a double-acting step piston.

FIG. 5 shows an exploded view of the first connecting rod part 102 from FIGS. 1 to 3, the manufacture of the connecting rod 100 according to a variant of a method according to the invention being explained on the basis of this illustration below.

To produce the above-described connecting rod 100 according to the invention, the shaft 106 has first been provided, specifically with the threaded section 129 with the thread undercut 121, the external thread 109 and the chamfer 126, and with a shaft-press connection contact surface 130A made to measure and made-to-measure sealing surfaces 140, 141 and 142, the shaft-press-connection contact surface 130A, in particular, having a domed shape.

In a subsequent step, an outer lateral surface of the shaft 106 above the piston element 118 has been coherently coated with the DLC coating 125 in the PVD process, the DLC coating 125 extending over the sealing surface 140 and the shaft press-connection surface 130A and on one side as far as the threaded portion, in particular up to the thread undercut 121, and on the other side up to the adjacent shaft shoulder with the second sealing surface 141. Furthermore, the sliding surface 143 of the piston element 118 of the shaft 118 was coated with a DLC coating 125 provided, the layer thickness is only 3 to 5 microns.

In a further subsequent step, the second sealing device 114, the associated support ring 116 and the first sealing device 110 and the support ring 112 and the stop sleeve 113 are pushed onto the shaft 106 in the axial direction from the end 124

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AT 521 501 B1 2020-02-15 Austrian patent office and the third sealing device 115 and the associated support ring 117 from the other end, wherein the sealing devices 110, 114 and 115 and the support rings are each formed as circumferentially closed rings.

In a further step, the connecting portion 107 on the piston side has been provided with the internal thread 108 correspondingly designed for the external thread 109 and with the dimensioned and also cambered connecting portion press-connecting contact surface 130B and has been heated to a joining temperature of greater than 200.degree.

The inside diameter of the connection section 107 in the region of the connection section press-connection contact surface 130B was dimensioned in such a way that in each case, i.e. in any tolerance position, is smaller than a smallest outer diameter of the shaft 106 in the region of the shaft press connection contact surface 130B.

In a further step, the shaft 106, which was neither heated nor cooled but had ambient temperature (in this case 20 ° C.), was screwed into the connecting section 107 on the piston side.

Heating only the piston-side connecting section 107 without heating or cooling the shaft 106 has the advantage that one or more of the sealing devices 110, 114 and 115, in particular the sealing devices 110 and 114 and 115, already before the connection of the shaft 106 with the connecting portion 107 on the piston side, onto which the shaft can be pushed without being damaged, which enables the use of sealing devices 110, 114, and 115 which are closed in the circumferential direction, in particular the use of sealing rings 110, 114, 115. The same applies to the associated support rings 112, 116 and 117.

Subsequently, a temperature difference between the shaft 106 and the piston-side connection section 107 was compensated for by cooling, in particular by allowing the piston-side connection section 107 to cool, the piston-side connection section 107 being shrunk onto the shaft 106, so that the shaft 106 and the piston-side connection section 107 are connected to each other in addition to the screw connection by means of a press connection 130. To accelerate the cooling process, active cooling of the connecting section 107 on the piston side is also conceivable.

Subsequently, the first connecting rod part 102 manufactured and assembled in the manner described above was assembled with the second connecting rod part 103 to form a length-adjustable connecting rod 100 according to the invention, in particular the shaft 106 of the first connecting rod part 102 with the sealing devices 110, 114 and 115 arranged thereon and the associated support rings 112, 116 and 117 has been at least partially inserted into the second connecting rod part 103, in particular the guide cylinder 111 and the stop sleeve has been screwed into the second connecting rod part 103.

A centering pin was also inserted into the securing recess 150 in order to prevent the two connecting rod parts 102 and 103 from rotating against one another.

In addition to the above-described, exemplary embodiment of a connecting rod according to the invention, further designs, in particular a large number of structural modifications, are possible which fall within the scope of protection defined by the associated patent claims.

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LIST OF REFERENCE NUMBERS

100 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 120 122 121 124 125 126 127 129 130 130A 130B 140 141 142 143 150 length-adjustable connecting rod according to the invention, first connecting rod part second connecting rod part small connecting rod eye large connecting rod eye shaft first, piston-side connecting section internal thread of the first connecting section external thread of the shaft first sealing device Guide cylinder first support ring stop sleeve second sealing device third sealing device second support ring third support ring piston element second, crankshaft-side connecting section control device for length adjustment thread undercut End of shaft Coating, especially DLC coating chamfer external thread threaded portion press connection Shank press connection contact surface Connection section press connection contact surface first sealing surface second sealing surface third sealing surface additional functional surface (sliding surface) securing recess A L Connecting rod longitudinal axis effective connecting rod length

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Claims (15)

claims 1. Length-adjustable connecting rod (100) for a reciprocating piston machine, in particular for a reciprocating piston internal combustion engine, wherein an effective connecting rod length (L) of the connecting rod (100) can be changed and the connecting rod (100) has a first connecting rod part (102) and a second connecting rod part (103) , wherein the first connecting rod part (102) and the second connecting rod part (103) for changing the effective connecting rod length (L) along a connecting rod longitudinal axis (A) are movable relative to each other, the first connecting rod part (102) having a shaft (106) and a first connecting section (107) for at least partially supporting the connecting rod (100) in a reciprocating piston machine, the second connecting rod part (103) having a second connecting section, which is also designed for at least partially supporting the connecting rod in a reciprocating piston machine, the first connecting section (107) has a first thread (108) and the shaft (106) is designed to cooperate with the first thread (108) es second thread (109), and wherein the shaft (106) is fixedly connected to the first connecting section (107) by means of a screw connection, characterized in that the shaft (106) and the first connecting section (107) in at least one operating state of the connecting rod (100) in addition to the screw connection (108, 109) are firmly connected to one another by a press connection (130). 2. Length-adjustable connecting rod (100) according to claim 1, characterized in that the first thread (108) of the first connecting section (107) is an internal thread (108) and the second thread (109) of the shaft (106) is a correspondingly designed external thread ( 109), the shaft (106) with the external thread (109) preferably being screwed into the first connecting section (107) of the first connecting rod part (102). 3. Length-adjustable connecting rod (100) according to claim 1, characterized in that the shaft (106) has a shaft-press connection contact surface (130A) which is formed with a corresponding to the shaft-press connection contact surface (130A) of the shaft (106) Connection section press connection contact surface (130B) of the first connection section (107) forms an interference fit, the interference fit being dimensioned such that in at least one operating state the first connection section (107) and the shaft (106) of the connecting rod (106) are non-positively connected to one another are. 4. Length-adjustable connecting rod (100) according to claim 3, characterized in that the shaft press connection contact surface (130A) of the shaft (106) and / or the connection section press connection contact surface (130B) of the first connection section (107) in an initial state prior to establishing the press connection (130) has an at least partially convexly curved contour, in particular at least partially spherical or cambered, in particular in the axial direction with respect to the connecting rod longitudinal axis (A). 5. Length-adjustable connecting rod (100) according to one of claims 1 to 4, characterized in that the shaft (106) has at least in one area a coating (125), preferably a carbon coating (125), in particular a DLC coating (125). 6. Length-adjustable connecting rod (100) according to claim 5, characterized in that the shaft (106) is at least partially coated at least in the region of the shaft press connection contact surface (130A). 7. Length-adjustable connecting rod (100) according to one of claims 1 to 6, characterized in that the shaft (106) has at least one further functional surface (140, 141, 142, 143), the shaft (106) in particular at least in the area of at least one further functional surface (140, 143) is at least partially coated. 15/21 AT 521 501 B1 2020-02-15 Austrian patent office 8. Length-adjustable connecting rod (100) according to one of claims 1 to 7, characterized in that the connecting rod (100) has at least one sealing device (110, 114, 115), preferably at least one sealing device (110, 114, 115) on the Shaft (106) is arranged, in particular at least one sealing device (110, 114, 115) being arranged on the shaft (106) before the shaft (106) is connected to the first connecting section (107). 9. A method for producing a length-adjustable connecting rod (100) for a reciprocating piston engine, which is designed according to one of claims 1 to 8, characterized by the steps: Providing a first connecting section (107) with a first thread (108), providing a shaft (106) with a second thread (109) designed to cooperate with the first thread (108), and Connecting the shaft (106) with the first connecting section (107) to a first connecting rod part (102) by screwing the first thread (108) with the second thread (109) and establishing a press connection (130) between the first connecting section (107) and the shaft (106), providing a second connecting rod part (103), assembling the first connecting rod part (102) with the second connecting rod part (103) to form a length-adjustable connecting rod (100). 10. The method according to claim 9, characterized in that for establishing the press connection (130) between the first connecting section (107) of the first connecting rod part (102) and the shaft (106), the first connecting section (107) and the shaft (106) the screwing is first brought to a defined joining temperature, the first connecting section (107) in particular being heated. 11. The method according to claim 9 or 10, characterized in that the shaft (106) is at least partially coated before screwing with the first connecting section (107), preferably with a carbon layer (125), in particular with a DLC coating (125) , 12. The method according to claim 11, wherein the shaft has a shaft press connection contact surface (130A) and / or at least one further functional surface (140, 141, 142, 143), characterized in that at least the shaft press connection contact surface (130A ) and / or the at least one further functional surface (140, 143) of the shaft (106) is at least partially coated, preferably with a carbon layer (125), in particular with a DLC coating (125). 13. The method according to any one of claims 9 to 12, characterized in that at least one sealing device (110, 114, 115) is arranged on the shaft (106) before the shaft (106) is screwed to the first connecting section (107). 14. Reciprocating piston engine, in particular reciprocating piston internal combustion engine, which has a length-adjustable connecting rod (100) which is designed according to one of claims 1 to 8 and / or which is produced by a method according to one of claims 9 to 13. 15. Vehicle, in particular motor vehicle, which has a reciprocating piston machine according to claim 14.