EP3351764B1 - Hydraulic module for controlling a hydraulic fluid stream of a connecting rod for a combustion engine with variable compression and connecting rod - Google Patents

Description

Technical area

The invention relates to a hydraulic module for controlling a hydraulic fluid flow of a connecting rod for an internal combustion engine with variable compression with an eccentric adjusting device for adjusting an effective connecting rod length and a connecting rod with such a hydraulic module.

State of the art

In internal combustion engines, a high compression ratio has a positive effect on the efficiency of the internal combustion engine. Under compression ratio is generally understood the ratio of the entire cylinder space before compression to the remaining cylinder space after compression. In internal combustion engines with spark ignition, in particular gasoline engines, which have a fixed compression ratio, the compression ratio, however, may only be selected so high that a so-called "knocking" of the internal combustion engine is avoided during full load operation. However, for the much more frequently occurring partial load range of the internal combustion engine, that is to say with low cylinder filling, the compression ratio could be selected with higher values without "knocking" occurring. The important part load range of a Internal combustion engine can be improved if the compression ratio is variably adjustable. To adjust the compression ratio, for example, systems with variable connecting rod length are known.

A hydraulic module for a connecting rod for an internal combustion engine with variable compression with an eccentric adjustment device for adjusting an effective connecting rod length is for example from DE 10 2012 020 999 A1 as well as from the DE 10 2015 100 662 A1 known.

Disclosure of the invention

An object of the invention is to provide a hydraulic module for a connecting rod for a variable compression internal combustion engine with an eccentric adjusting device for adjusting an effective connecting rod length, which has a stable operating behavior.

Another object is to provide an improved connecting rod with such a hydraulic module.

The aforementioned objects are achieved with the features of the independent claims.

Favorable embodiments and advantages of the invention will become apparent from the other claims, the description and the drawings.

It is proposed according to one aspect of the invention, a hydraulic module for controlling a hydraulic fluid flow of a connecting rod for a variable compression internal combustion engine with an eccentric adjusting device for adjusting an effective connecting rod length, wherein the eccentric adjusting device has at least a first cylinder and a second cylinder as hydraulic chambers and wherein both each have an inlet for supplying hydraulic fluid into the cylinder via a supply line and in each case a drain for discharging Hydraulic fluid are provided by the cylinders. On the module side, at least one movable piston in a housing is present, which is selectively displaceable in a first switching position or a second switching position, wherein in the first switching position, the flow of the second cylinder and in the second switching position, the outlet of the first cylinder is connected to the supply line. The cylinders are each associated with a check valve, which allows a supply of hydraulic fluid into the cylinder and prevents discharge of hydraulic fluid from the cylinders. In this case, the cylinders are connected such that in the second switching position hydraulic fluid can be conducted from the first cylinder into the second cylinder via a channel in the hydraulic module.

At a first working connection of the hydraulic module according to the invention, the first cylinder may be connected as a hydraulic chamber of the adjustable connecting rod, for example the cylinder on a gas side (GKS) of the connecting rod, and at the second working connection, the second cylinder as a hydraulic chamber, for example the cylinder on the mass side ( MKS) of the connecting rod. The corresponding chambers are commonly referred to as GKS chamber or MBS chamber.

The speed-dependent acceleration of the relatively long hydraulic fluid columns in the connecting rod of the engine oil used as hydraulic fluid can produce pressure differences. These can be both positive and negative, ie the hydraulic fluid columns can be accelerated to assist in draining and filling the hydraulic chambers of the cylinder of the connecting rod, but also to hinder this. Especially with a cylinder on the mass force side (MBS) of the connecting rod, this effect can have a negative effect. The acceleration of the hydraulic fluid columns can cause that in front of and behind the MKS-side check valve no positive pressure difference longer forms, which causes hydraulic fluid can be nachgefördert in the MKS chamber. Since the chambers always lose hydraulic fluid due to leakage and other effects, this causes a gradual, slow adjustment of the eccentric over several revolutions and thus the effective one Length of the connecting rod from a low compression position (ε _low ), which corresponds to the first switching position of the hydraulic module, in a position of high compression (ε _high ), which corresponds to the second switching position of the hydraulic module. This is called drifting off. This occurs especially in engine load cases with high mass forces (tensile force and compressive force on the connecting rod) and low gas forces (pressure force on the connecting rod). A possible adjustment of the connecting rod in the direction of high compression ε _high by the inertial forces in the pulling direction can not be completely reset by the mass forces in the pressure direction and the gas forces.

This effect can be advantageously avoided with the hydraulic module according to the invention in that the GKS chamber can direct the nachgeförderte in the position of low compression (ε _low ) hydraulic fluid directly and unthrottled in the MKS chamber. This can be effected because the hydraulic fluid which presses the GKS chamber in the direction of pressure in the MKS chamber by the connecting rod acting on the gas and mass forces, has a substantially higher pressure than the hydraulic fluid pressure of the hydraulic supply in the bearing shell of the connecting rod. As a result, the hydraulic fluid can be pressed from the GKS chamber into the MKS chamber.

In addition to the positional stability of the eccentric adjusting device of the connecting rod in the position ε _low , ie that after one revolution of the connecting rod is again in its final position ε _low , the position stability on the rotation, or the stiffness of the connecting rod can increase. During one revolution, there is always a movement of the eccentric lever, since the hydraulic fluid columns also have a certain flexibility and there is always a certain sinking of the support piston in the filled chamber. If the connecting rod completely returns to the end of the turn, it is called "stable in position". Nevertheless, with a change in the angle of the eccentric, or the lever assembly when resetting the respective support piston could hit the bottom of the chamber, which can affect the life of negative. For this reason, the adjustment speed of the eccentric adjusting can be limited by Throttling points in the hydraulic lines. A pressure-loaded prestressed MBS hydraulic fluid column advantageously sinks less than a non-prestressed hydraulic fluid column. Less sinking means less lever movement, whereby the positional stability can be improved in the position ε _low .

The hydraulic module according to the invention represents an advantageous design solution for biasing the MBS chamber combined with a hydraulic switching valve and integrated check valves. An advantageous feature is that the hydraulic fluid supply of the MBS chamber is deactivated or activated via a circumferential groove in a step piston of the hydraulic module can be. For this purpose, frontal bores introduced into the housing of the hydraulic module are interconnected.

The hydraulic module according to the invention advantageously makes possible a hydraulic adjustment of a connecting rod via a quasi-static change of the hydraulic bearing shell pressure. Due to the change in the hydraulic pressure at the supply connection, the stepped piston is displaced in the axial direction counter to or in the direction of the spring force and thus opens or closes the GKS or MKS drain holes in order to initiate the eccentric adjustment.

The stepped piston is also provided with a circumferential groove, the already introduced in the housing holes in a defined switching position ε _low together and thus allows a bias of the MKS chamber.

Furthermore, band check valves are incorporated over the outer periphery of the hydraulic module, which simplify the overall system connecting rod. The band elements can advantageously be provided with slots or holes to allow for a compact space, consistent functionality, and similar band rigidities sufficiently large flow cross-sections and to ensure high functionality in a small space. Conveniently, only 3 holes in Pleuelgrundkörper are necessary.

To seal the additionally introduced holes against each other and to the outside, a locking ring can be introduced in combination with a sealing washer in the housing and the front side welded to the housing.

Another alternative hydraulic module could push two inclined planes in one of the two end positions of the stepped piston, which in turn deactivate or activate a hydraulic fluid connection.

According to an advantageous embodiment, a switching element may be provided in the piston for controlling the hydraulic fluid flow in the channel. The hydraulic fluid supply of the MBS chamber can advantageously be deactivated or activated via the switching element in the piston. The switching element connects the holes introduced in the housing in one of the two switching positions, preferably in the first switching position for low compression ε _low and thus allows a bias of the MKS chamber.

According to an advantageous embodiment, the switching element may be provided as a contour shape on the piston. Alternatively, for example, to a circumferential groove in the stepped piston can also be a shape contour on the stepped piston be present, which opens a certain spring stroke slider or slider system opens when a certain stroke, which in turn allows a connection between the MKS chamber and GKS chamber.

According to an advantageous embodiment may be provided as a switching element, a circumferential groove of the piston, which forms part of the channel. The circumferential groove can connect holes introduced in the housing in one of the two switch positions, preferably in the second switch position for low compression ε _low , and thus advantageously enable a pretensioning of the MBS chamber.

According to an advantageous embodiment of the hydraulic fluid flow in the channel via the circumferential groove by an axial displacement of the piston in the first or switchable second switching position. As a result, the drain holes of the GKS chamber and the MBS chamber can be opened or closed in an advantageous manner, so as to initiate an eccentric adjustment.

According to an advantageous embodiment, in the second switching position, the outlet of the first cylinder can be connectable via the peripheral groove to the inlet of the second cylinder. As a result, the connecting rod can advantageously be switched to a low compression position ε _low , in that the hydraulic fluid can be conducted unthrottled from the GKS chamber into the MBS chamber.

According to an advantageous embodiment, in the second switching position, the outlet of the first cylinder can be connectable to the circumferential groove via an end-side transverse bore and / or via an oblique bore. Conveniently, the interconnection of the hydraulic lines in the housing of the hydraulic module via the circumferential groove by transverse bores and / or oblique holes. In this way, a very compact design of the hydraulic module is possible.

According to an advantageous embodiment, end-side bores of the housing can be sealed by means of an annular sealing washer and / or a locking ring. As a result, a permanent sealing of the holes can be achieved, so that reliable operation of the eccentric adjusting mechanism can be ensured over the long term.

According to an advantageous embodiment, the check valves may be integrated into the hydraulic module. The integration of the check valves in the hydraulic module results in a particularly compact design of the entire hydraulic system of the connecting rod, since only the combined supply and discharge of the hydraulic chambers and a supply line in Pleuelgrundkörper and / or connecting rod cover are provided.

According to an advantageous embodiment, at least one of the check valves as a closing element is a substantially annular Have band member which surrounds the housing at least partially on its circumference and is at least partially supported on the housing and by means of which in a closed position working ports are closed. Such a so-called band check valve represents a particularly compact design of a check valve and also allows a particularly compact design of the hydraulic module including integration in the Pleuelgrundkörper and / or connecting rod cover.

According to an advantageous embodiment, the at least one check valve can open radially outward. Such a band-check valve can be arranged particularly favorable on the outer circumference of the housing of the hydraulic module. The check valve is very easy to install in this way and results in a compact design of the hydraulic module.

According to an advantageous embodiment, the band member may have at least one arranged in its peripheral surface radial opening. In this way, a compact space, consistent functionality and similar tape stiffness can be achieved and it can be particularly favorable parallel throttle points to the check valves.

According to an advantageous embodiment, the opening may be formed in the circumferential direction as a slot. A favorable throttle point in a band element of a check valve is a slot, which defines the flow resistance by forming its length, which can be suitably varied by the geometric design.

According to an advantageous embodiment, the band element may have at least one radially inwardly disposed on its circumference groove. Such arranged on the inside of the band member groove is a favorable alternative to an opening such as a hole or a slot in the circumferential direction of the band member.

According to a further aspect of the invention, a connecting rod is proposed for an internal combustion engine with variable compression with an eccentric adjusting device for adjusting an effective connecting rod length with a hydraulic module. The eccentric adjusting device has at least a first cylinder and a second cylinder. In this case, both an inlet for supplying hydraulic fluid into the cylinder via a supply line and in each case a drain for discharging hydraulic fluid from the cylinders are provided in each case.

The connecting rod according to the invention advantageously requires only three hydraulic fluid lines in the connecting rod main body, whereby a favorable production can be achieved. Further, only a 3/2-way valve is required as a changeover valve in the hydraulic module, which advantageously simplifies the construction of the connecting rod. The MBS hydraulic chamber can be biased by the GKS hydraulic chamber in the first low compression position ε _low . Conveniently, only differential volumes of hydraulic fluid between GKS and MBS hydraulic chamber are thus exchanged with the bearing shell of the connecting rod, ie no additional hydraulic fluid flows via the hydraulic fluid lines in the bearing shells. Check valves and chokes can conveniently be structurally integrated in a hydraulic module. Thus, the hydraulic circuit diagram for both variants without or with additional check valve can be accommodated in a hydraulic module.

Brief description of the drawings

Further advantages emerge from the following description of the drawing. In the drawings, an embodiment of the invention is shown schematically. The drawings, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into meaningful further combinations.

They show by way of example:

Fig. 1

a side view of a hydraulic module according to the invention with marked sectional planes of the in the FIGS. 3 to 17 illustrated longitudinal sections;

Fig. 2

the hydraulic module off Fig. 1 in perspective view;

Fig. 3

a longitudinal section in section plane AA of the hydraulic module according to Fig. 2 in a first switching position;

Fig. 4

a longitudinal section in section plane BB of the hydraulic module according to Fig. 2 in a first switching position;

Fig. 5

a longitudinal section in the sectional plane CC of the hydraulic module according to Fig. 2 in a first switching position;

Fig. 6

a longitudinal section in the sectional plane DD of the hydraulic module according to Fig. 2 in a first switching position;

Fig. 7

a longitudinal section in the sectional plane EE of the hydraulic module according to Fig. 2 in a first switching position;

Fig. 8

a longitudinal section in section plane AA of the hydraulic module according to Fig. 2 during a switching operation;

Fig. 9

a longitudinal section in section plane BB of the hydraulic module according to Fig. 2 during a switching operation;

Fig. 10

a longitudinal section in the sectional plane CC of the hydraulic module according to Fig. 2 during a switching operation;

Fig. 11

a longitudinal section in the sectional plane DD of the hydraulic module according to Fig. 2 during a switching operation;

Fig. 12

a longitudinal section in the sectional plane EE of the hydraulic module according to Fig. 2 during a switching operation;

Fig. 13

a longitudinal section in section plane AA of the hydraulic module according to Fig. 2 in a second switching position;

Fig. 14

a longitudinal section in section plane BB of the hydraulic module according to Fig. 2 in a second switching position;

Fig. 15

a longitudinal section in the sectional plane CC of the hydraulic module according to Fig. 2 in a second switching position;

Fig. 16

a longitudinal section in the sectional plane DD of the hydraulic module according to Fig. 2 in a second switching position;

Fig. 17

a longitudinal section in the sectional plane EE of the hydraulic module according to Fig. 2 in a second switching position;

Fig. 18

a hydraulic circuit diagram of a connecting rod according to the invention with the hydraulic module according to Fig. 2 in the first switching position;

Fig. 19

a hydraulic circuit diagram of the connecting rod according to the invention with the hydraulic module according to Fig. 2 in the second switching position and

Fig. 20

a pressure-stroke diagram of the hydraulic module according to the invention with a hysteresis loop.

Embodiments of the invention

In the figures, the same or similar components are numbered with the same reference numerals. The figures are merely examples and are not intended to be limiting.

The FIGS. 1 to 17 is an inventive hydraulic module 10 can be seen in various representations and sections. It shows FIG. 1 a side view of the hydraulic module 10 with various marked sectional planes, which for the representations in the FIGS. 3 to 17 were used while FIG. 2 the hydraulic module off FIG. 1 in a perspective view. In the FIGS. 3 to 7 is the hydraulic module 10 in a first switching position S1 for high compression ε _high and in the FIGS. 13 to 17 shown in a second switching position S2 for low compression ε _low . The FIGS. 8 to 12 show the hydraulic module 10 and the corresponding sections during a switching operation, ie in a position between the two switching positions S1 and S2. Corresponding hydraulic circuit diagrams of a connecting rod 1 according to the invention are the FIGS. 18 and 19 refer to.

The connecting rod 1 according to the invention is in the hydraulic circuit diagrams according to the FIGS. 18 and 19 shown only schematically, but for example from the DE 10 2013 107 127 A1 known, to which express reference is made.

As in the FIGS. 18, 19 illustrated, the connecting rod 1 for an internal combustion engine with variable compression, for example, a not entirely and in detail illustrated eccentric adjusting device 40 for adjusting an effective connecting rod length. This eccentric adjusting device 40 comprises a first cylinder 4 and a second cylinder 5 as hydraulic chambers, wherein both an inlet 6, 7 for supplying hydraulic fluid into the cylinders 4, 5 and in each case a drain 11, 12 for discharging hydraulic fluid from the Cylinders 4, 5 are provided. The trained as a switching valve 41 and functioning hydraulic module 10 has a movable in a housing 3 stage piston 17th which is selectively displaceable in a first switching position S1 or a second switching position S2, wherein in the first switching position S1, the outlet 12 of the second cylinder 5 and in the second switching position S2, the outlet 11 of the first cylinder 4 is connected to a supply line 8.

The basic function of the switching valve 41 is also from the DE 10 2013 107 127 A1 known.

The cylinders 4, 5 are connected in the hydraulic module 10 according to the invention such that in the second switching position S2 hydraulic fluid from the first cylinder 4 into the second cylinder 5 via a channel 32 in the hydraulic module 10 can be conducted.

In the piston 17 of the hydraulic module 10, a switching element 36 is provided for controlling the hydraulic fluid flow in the channel 32, which is provided for example as a circumferential groove 27 of the piston 17, which forms part of the channel 32. The hydraulic fluid flow is in the channel 32 via the circumferential groove 27 by an axial displacement of the piston 17 in the first or second switching position S1, S2 switchable. In the second switching position S2, the outlet 11 of the first cylinder 4 can be connected via the peripheral groove 27 to the inlet 7 of the second cylinder 5.

In this case, the cylinder 4 represents a hydraulic chamber on the gas-force side (GKS) of the connecting rod 1, while the cylinder 5 represents a hydraulic chamber on the mass-force side (MCS) of the connecting rod 2.

The cylinders 4, 5 each have a check valve 18, 19 assigned in the inlet 6, 7, which allows a supply of hydraulic fluid into the cylinders 4, 5 and prevents the discharge of hydraulic fluid from the cylinders 4, 5. Advantageously, only two check valves 18, 19 are necessary in the context of the invention. Further check valves need not be provided. Inlet 6, 7 and outlet 11, 12 of a cylinder 4, 5 each open into a common line 13, 14 in the cylinder 4, fifth

The check valves 18, 19 are integrated in the hydraulic module 10 and have as closing element a substantially annular band member 33, 34 which surrounds the housing 3 at least partially on its circumference and is at least partially supported on the housing 3 and by means of which in a closed position Working connections 21, 22 are closable. The two check valves 18, 19 open radially outward. The band element 33, 34 has in each case at least one radial opening 35 arranged in its peripheral surface, wherein the opening 35 is designed as a slot in the circumferential direction. Alternatively, the band element 33, 34 have at least one radially inwardly disposed on its circumference groove.

The outlet 11 of the first cylinder 4 can be connected to the peripheral groove 27 in the second switch position S2 via an end-side transverse bore 28 and / or via an oblique bore 29.

In the starting position, the connecting rod 1 is in the switching position S1 for high compression ε _high . In this operating state, the GKS hydraulic chamber 4 is filled with hydraulic fluid, for example engine oil, and the MKS hydraulic chamber 5 is preferably throttled via the outlet 12 to the supply line 8, which is connected to a supply source P. The step piston 17 of the hydraulic module 10 takes in the FIGS. 3 to 7 shown position.

In this first shift position S1, at least one first working port 21 of the housing 3 of the hydraulic module 10 assigned to the GKS hydraulic chamber 4 is connected to a supply port 20 in communication with the supply line 8, in particular in FIG FIG. 5 is apparent. The working port 21, which can be opened in the direction of the cylinder 4 by means of the non-return valve 18 designed as a band check valve, is connected to the inlet 6 designed as a transverse bore or several transverse bores, which is connected to the supply port 20 via one or more radial bores 15 ,

The connected to the first working port 21, preferably throttled drain 11 is closed by the piston 17, as in particular from FIG. 4 in the longitudinal section according to the sectional plane BB FIG. 2 is apparent. A second, the MKS hydraulic chamber associated working port 22 is connected via the outlet 12 and the radial bore 15 to the supply port 20, so that the MKS hydraulic chamber 5 can empty. As in FIG. 4 can be seen, this is realized over a section of the stepped piston 17.

The supply port 20 and the working ports 21, 22 are formed as circumferential annular grooves, in which the inlets 6, 7, runs 11, 12 and other holes open. All holes (inlet 6, 7, drain 11, 12, etc.) in the housing 3 may be provided as a single bore, but are preferably distributed evenly over the circumference of the housing 3 several times.

If the pressure of the supply source P, for example, the gallery pressure of the internal combustion engine, increases, the force acting on an end face 23 of the stepped piston 17 compressive force exceeds the spring force of the piston 17 acting on the spring 24 and the piston 17 moves against the spring force and obtains a in the FIGS. 8 to 12 shown position between the two switching positions S1 and S2.

The stepped piston 17 passes over at a defined switching stroke an edge 25 of an overflow channel 26, which from FIG. 8 is apparent. From this point, the pressure-acting surface of the piston 17 increases abruptly, so that the step piston 17 snaps into the other end position or in the switching position S2, which in the FIGS. 13 to 17 is shown.

The hydraulic fluid from the GKS hydraulic chamber 4 can flow via the outlet 11 and the supply port 20 throttled to P, while the drain 12 of the MKS hydraulic chamber 5 is closed via the step piston 17.

In the second shift position S2, according to the invention, hydraulic fluid can be conducted from the first cylinder 4 into the second cylinder 5 via a channel in the hydraulic module 10. For this purpose, the piston 17 has a circumferential groove 27, which can be activated and deactivated by the switching positions S1, S2.

As in particular the FIGS. 16 and 17 can be removed, the outlet 11 of the first cylinder 4 via one or more end-side transverse bores 28, one or more oblique bores 29 and the circumferential groove 27 with the inlet 7 of the second cylinder 5 unthrottled connectable.

Thus, the MKS hydraulic chamber 5 sucks in hydraulic fluid (oil) from the circumferential groove 27 of the stepped piston 17 now connected to the GKS hydraulic chamber 4 via the check valve 19. This ensures that hydraulic fluid with GKS chamber pressure is available to the MKS hydraulic chamber 5. As a result, a more reliable filling of the MKS hydraulic chamber 5 is achieved in comparison to a direct suction from the supply source P at gallery pressure.

If the pressure in the hydraulic gallery of the internal combustion engine or the supply source P drops again, the stepped piston 17 moves in the spring force direction back to the starting position, ie into the switching position S1. However, since the pressure-acting surface is still increased, the switching position of the stepped piston 17 in the other direction is reached only at a lower pressure. A hysteresis behavior sets in, as in FIG. 20 shown.

The band check valves 18, 19 are disposed over the outer periphery of the hydraulic module 10, whereby the overall system connecting rod can be simplified. The band members 33, 34 are provided with openings 35 such as slots or holes to allow for a compact space, consistent functionality, and similar band rigidities sufficiently large flow cross-sections. As is apparent from the schematic circuit diagrams according to the FIGS. 18 and 19 shows that there are only three holes in the Basic body of the connecting rod 1 necessary to operate the hydraulic module for advantageous operation of the eccentric adjusting device 40.

In order to seal the additionally introduced holes against each other and to the outside, a closure ring 30 is introduced into the housing 3 in combination with a sealing washer 31 and welded to the front side of the housing 3.

FIG. 20 represents a pressure-stroke diagram of the hydraulic module according to the invention with a hysteresis loop. In the diagram are a stroke of the stepped piston 17 with increasing pressure for a switching from ε _high to ε _low (solid line) and a stroke curve at falling pressure for a Switching operation from ε _low to ε _high (wide dashed line). Next, the stroke is shown when switching (narrow dashed line).

The illustrated hysteresis loop of the hydraulic module 10 is reflected in a bistable behavior of the connecting rod 1 again. If the pressure in the gallery or the supply source P never increases above a certain switching pressure addition, the connecting rod 1 is always in the operating state ε _high . When the switching pressure is exceeded, the connecting rod 1 changes the operating state to ε _low . This state is maintained until the gallery pressure again falls below a certain switching pressure, which is lower than in the previous switching operation.

The hydraulic module according to the invention is thus a possible design solution for biasing the MKS hydraulic chamber 5 combined with a hydraulic changeover valve and integrated non-return valves 18, 19th

The hydraulic fluid supply of the MKS hydraulic chamber 5 via the gallery pressure can advantageously be deactivated and activated via a circumferential groove 27 in the stepped piston 17. For this purpose, in the housing 3 of the hydraulic module 10 introduced frontal bores 15, 28, 29 interconnected.

As an alternative to a circumferential groove 27 in the piston 17, a shape contour on the stepped piston 17 is also conceivable which, when a certain stroke is exceeded, opens a spring-loaded slide or slide system, which in turn enables a connection between the MBS chamber 5 and the GKS hydraulic chamber 4.

A similar system could push two inclined planes in one of the two end positions, which in turn deactivate or activate an oil connection.

Claims (15)

1. Hydraulic module (10) for the control of a hydraulic fluid flow of a connecting rod (1) for an internal combustion engine with variable compression having an eccentric adjusting device (40) for the adjustment of an effective connecting rod length, there being at least one piston (17) on the module side, which piston (17) can be moved in a housing (3) and can be displaced selectively into a first switching position (S1) or a second switching position (S2), the hydraulic module (10) having at least a first and a second working connector (21, 22) and a supply connector (20), and the working connectors (21, 22) being assigned in each case one check valve (18, 19), and the working connectors (21, 22) in the hydraulic module (10) being connected in such a way that, in the first switching position (S1), the first working connector (21) is connected via an inlet (6) to the supply connector (20) and the second working connector (22) is connected via an outlet (12) to the supply connector (20), an outlet (11) of the first working connector (21) and an inlet (7) of the second working connector (22) being closed, and, in the second switching position (S2), the outlet (12) of the second working connector (22) being closed and the outlet (11) of the first working connector (21) being connected via a duct (32) in the hydraulic module (10) directly to the inlet (7) of the second working connector (22), with the result that hydraulic fluid can be conducted from the first working connector (21) directly to the second working connector (22).
2. Hydraulic module according to Claim 1, characterized in that a switching element (36) is provided in the piston (17) for the control of the hydraulic fluid flow in the duct (32).
3. Hydraulic module according to Claim 2, characterized in that the switching element (36) is provided as a shaped contour on the piston (17).
4. Hydraulic module according to Claim 2, characterized in that a circumferential groove (27) of the piston (17) is provided as switching element (36), which circumferential groove (27) forms a part of the duct (32).
5. Hydraulic module according to Claim 4, characterized in that the hydraulic fluid flow in the channel (32) via the circumferential groove (27) can be switched into the first or second switching position (S1, S2) by way of an axial displacement of the piston (17).
6. Hydraulic module according to Claim 4 or 5, characterized in that, in the second switching position (S2), the outlet (11) of the first working connector (21) can be connected via the circumferential groove (27) to the inlet (7) of the second working connector (22).
7. Hydraulic module according to one of Claims 4 to 6, characterized in that, in the second switching position (S2), the outlet (11) of the first working connector (22) can be connected via an end-side transverse bore (28) and/or via an oblique bore (29) to the circumferential groove (27).
8. Hydraulic module according to one of the preceding claims, characterized in that end-side bores (6, 28) of the housing (3) are provided in a manner which is sealed by means of an annular sealing washer (31) and/or a closure ring (30).
9. Hydraulic module according to one of the preceding claims, characterized in that the check valves (18, 19) are integrated into the hydraulic module (10).
10. Hydraulic module according to Claim 9, characterized in that at least one of the check valves (18, 19) has, as closing element, a substantially annular strip element (33, 34) which encloses the housing (3) at least partially on its circumference, is supported at least partially on the housing (3), and by means of which working connectors (21, 22) can be closed in a closed position.
11. Hydraulic module according to Claim 10, characterized in that the at least one check valve (18, 19) opens radially to the outside.
12. Hydraulic module according to Claim 10 or 11, the strip element (33, 34) having at least one radial opening (35) which is arranged in its circumferential face.
13. Hydraulic module according to Claim 12, characterized in that the opening (35) is configured in the circumferential direction as a slot.
14. Hydraulic module according to Claim 10 or 11, characterized in that the strip element (33, 34) has at least one groove which is arranged so as to lie radially on the inside on its circumference.
15. Connecting rod (1) for an internal combustion engine with variable compression having an eccentric adjusting device (40) for the adjustment of an effective connecting rod length, having a hydraulic module (10) according to one of Claims 1 to 14, the eccentric adjusting device (40) having at least a first cylinder (4) which is connected to the first working connector (21) of the hydraulic module (10) and a second cylinder (5) which is connected to the second working connector (22) of the hydraulic module (10), and both in each case one inlet (6, 7) for feeding hydraulic fluid into the cylinders (4, 5) via a supply line (8) and in each case one outlet (11, 12) for discharging hydraulic fluid from the cylinders (4, 5) being provided.

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