Connecting rod and internal combustion engine

A connecting rod (10) has a crankpin bearing eye (11) attached to a crankshaft (38) and a connecting-rod bearing eye (12) attached to a piston. An eccentric adjustment device (13) adjusts an effective connecting rod length and has eccentric rods (15, 16) that engage a lever (14) of the eccentric adjustment device (13). Each eccentric rod (15, 16) has a piston (20, 21) guided in a hydraulic chamber (22, 23). The hydraulic chambers (22, 23) can be charged with hydraulic oil from first hydraulic lines (41) that lead to the crankpin bearing eye (11) and second hydraulic oil lines (24, 25) that lead from the crankpin bearing eye (11). Check valves (26, 27) prevent a backflow of hydraulic oil back into the second hydraulic lines (24, 25). At least one filter prevents an ingress of contaminants from the crankshaft into the hydraulic chambers (22, 23) via the hydraulic oil.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority under 35 USC 119 to German Patent Appl. No. 10 2015 103 205.8 filed on Mar. 5, 2015, the entire disclosure of which is incorporated herein by reference.

BACKGROUND

1. Field of the Invention

The invention relates to a connecting rod for an internal combustion engine, and to an internal combustion engine.

2. Description of the Related Art

DE 10 2010 016 037 A1 andFIG. 1and show a connecting rod10of an internal combustion engine having an adjustable compression ratio. The connecting rod10has a crankpin bearing eye11and a connecting-rod bearing eye12. The crankpin bearing eye11attaches the connecting rod10to a crankshaft (not shown inFIG. 1) and the connecting-rod bearing eye12attaches the connecting rod10to a cylinder piston (not shown inFIG. 1) of the internal combustion engine. The connecting rod10has an eccentric adjustment device13with an eccentric (not shown inFIG. 1), an eccentric lever14and eccentric rods15,16. The eccentric lever14has a bore that is arranged eccentrically with respect to a center point17of the connecting-rod bearing eye12and that has a center point18. The bore in the eccentric lever14receives the eccentric and a bore in the eccentric receives a piston pin. The eccentric adjustment device13enables adjustment of an effective connecting rod length leff, where the connecting rod length is to be understood to mean the spacing of the center point18of the bore in the eccentric lever14from a center point19of the crankpin bearing eye11. The eccentric rods15,16can be moved to rotate the eccentric body14and thus change the effective connecting rod length leff. Each eccentric rod15,16has a piston20,21that is guided displaceably in a hydraulic chamber22,23. A hydraulic pressure acts exists in the hydraulic chambers22,23and on the pistons20,21assigned to the eccentric rods15,16so that movement of the eccentric rods15,16is possible or not possible depending on the amount of oil in the hydraulic chambers.

The adjustment of the eccentric adjustment device13is initiated by the action of inertia and load forces of the internal combustion engine that act on the eccentric adjustment device13during a work stroke of the internal combustion engine. The directions of action of the forces that act on the eccentric adjustment device13change continuously during a work stroke. The adjustment movement is assisted by the pistons20,21that are loaded with hydraulic oil and act on the eccentric rods15,16. The pistons20,21prevent a restoring movement of the eccentric adjusting device13on account of varying directions of the forces that act on the eccentric adjustment device13. The eccentric rods15,16that interact with the pistons20,21are attached to the eccentric body14on both sides. The hydraulic chambers22and23, in which the pistons20,21are guided, can be charged with hydraulic oil from the crankpin bearing eye11via hydraulic oil lines24and25. Check valves26and27prevent a return flow of the hydraulic oil from the hydraulic chambers23and24back into the hydraulic lines24and25. A switchover valve29is received in a bore28of the connecting rod10. The switching position of the switchover valve29determines which of the hydraulic chambers22and23is filled with hydraulic oil and which of the hydraulic chambers22and23is evacuated, and the adjustment direction or direction of rotation of the eccentric adjustment device13is dependent on this switching. The hydraulic chambers22and23are in contact via fluid lines30and31with the bore28that receives the switchover valve29. An actuation means32, a spring device33and a control piston34of the switchover valve29are shown schematically inFIG. 1, and the function of these components of the switchover valve29is known from DE 10 2010 016 037 A1.

As described above, the hydraulic oil that acts on the pistons20,21that are guided in the hydraulic chambers22,23is fed to the hydraulic chambers22,23from the crankpin bearing eye11via hydraulic lines24and25. The connecting rod10is engaged by the crankpin bearing eye11on the crankshaft (not shown inFIG. 1) so that a crankshaft bearing journal of a connecting rod bearing shell35is arranged between the crankshaft and the crankpin bearing eye11.

Hydraulic oil can be fed from the crankpin bearing eye11of the connecting rod10to the hydraulic chambers22and23via the hydraulic lines24and25that are integrated into the connecting rod10and is conducted in the direction of the crankpin bearing eye via first hydraulic lines integrated into the crankshaft. There is the risk of contaminants passing from the crankshaft into the hydraulic chambers, and thus into the connecting rod, via the hydraulic oil. These contaminants could impair the functioning of the check valves of the eccentric adjustment device and the switchover valve. In the extreme case, the eccentric adjustment device and the connecting rod may fail.

DE 101 08 461 B4 discloses a crankshaft bearing arrangement for an internal combustion engine having an adjustable compression ratio. The crankshaft bearing arrangement has the crankshaft mounted in eccentric rings, and an oil distribution groove is provided on the outer circumferential face of the eccentric ring. Oil can pass in the direction of the oil distribution groove via an oil feed channel in the engine housing.

It is an object of the invention to provide an improved internal combustion engine and an improved connecting rod.

SUMMARY

The invention relates to a connecting rod and an engine that has at least one filter element that prevents a flow of contaminants from the crankshaft into the hydraulic chambers via the hydraulic oil. Thus, contaminants cannot pass from the crankshaft into the hydraulic chambers and into the connecting rod via the hydraulic oil. In this way, the functional reliability of the connecting rod, or of an internal combustion engine that comprises the connecting rod, can be increased.

The filter element may be integrated into a first hydraulic line of the crankshaft. More particularly, a filter element may be integrated into a hydraulic line of the crankshaft for each connecting rod and protects the connecting rod against contaminants from an engine oil circuit in an effective manner. Hydraulic lines in the region of the crankshaft have a relatively large diameter, and filter elements integrated into said hydraulic lines can have large filter surfaces. Corresponding filters accordingly have a large storage volume for the contaminants to be filtered out of the hydraulic oil. Furthermore, filter elements integrated into the crankshaft can exhibit low pressure losses.

Each check valve may have a filter element, so that a filter element may be incorporated into each of the hydraulic chambers of the connecting rod or into each of the second hydraulic lines of the connecting rod to prevent an ingress of contaminants into the hydraulic chambers of the connecting rod. Positioning the filter elements immediately upstream of the hydraulic chambers or of the check valves provides protection in an effective manner against contaminants from the hydraulic oil.

Exemplary embodiments of the invention will be discussed in more detail on the basis of the drawing, without being restricted thereto.

DETAILED DESCRIPTION

An internal combustion engine with an adjustable compression ratio has at least one, preferably several, cylinders. Each cylinder has a piston that is coupled via a connecting rod10to a crankshaft of the internal combustion engine. Each connecting rod10has a connecting-rod bearing eye12at one end and a crankpin bearing eye11at an opposite end. The crankpin bearing eye11engages on a crankshaft bearing journal of the crankshaft in such a way that a connecting rod bearing shell is positioned between the crankshaft bearing journal and the crankpin bearing eye11and so a lubricating oil film can be built up between the connecting rod bearing shell and the crankshaft bearing journal.

An internal combustion engine having an adjustable compression ratio has an eccentric adjustment device13in the region of each connecting rod10for adjusting the effective length of the respective connecting rod10. The eccentric adjustment device13has an eccentric, an eccentric lever14and eccentric rods15,16that can be moved in a manner dependent on a hydraulic pressure prevailing in hydraulic chambers22,23that interact with the eccentric rods15,16for adjusting the compression ratio. The hydraulic chambers22,23that interact with the eccentric rods15,16can be supplied with hydraulic oil from the crankshaft and from the crankpin bearing eye11of the respective connecting rod10. The adjustment of the eccentric adjustment device is initiated by the action of inertia and load forces of the internal combustion engine.

A filter element interacts with each connecting rod10to prevent an ingress of contaminants from the crankshaft into the hydraulic chambers22,23via the hydraulic oil.

FIG. 2shows a detail of a connecting rod10in the region of a check valve27and in the region of a piston21that is guided in a hydraulic chamber23of an eccentric rod15. In the exemplary embodiment ofFIG. 2, each check valve27has a filter element36that is integrated with the check valve27into the hydraulic chamber23upstream of the check valve27as viewed in the flow direction37of the hydraulic oil.

InFIG. 2, the filter element36is a plate-like filter element in the form of a separate assembly and is pressed into the hydraulic chamber23before the arrangement of the check valve27in the hydraulic chamber23. In contrast to the embodiment ofFIG. 2, the filter element36may be an integral constituent part of the check valve27.

It is likewise possible for a filter element to be integrated into the respective hydraulic line24and25that conducts the hydraulic oil in the direction of the respective hydraulic chambers22,23from the crankpin bearing eye11.

FIG. 3shows a highly schematized detail of an internal combustion engine in the region of a crankshaft38and of a connecting rod10, and shows the crankpin bearing eye11of the connecting rod10and oil-guiding grooves39in the region of the crankpin bearing eye11or in the region of the connecting rod bearing shell35.

FIG. 3shows a main bearing journal40and hydraulic lines41integrated into the crankshaft38. The hydraulic lines41conduct hydraulic oil from the crankshaft38in the direction of the oil-guiding grooves39in the region of the crankpin bearing eye11. A filter element42is integrated into one of the hydraulic lines41of the crankshaft38so that no contaminants can pass in the direction of the connecting rod10via the hydraulic oil.

In accordance with the invention, contaminants such as dirt or chips that may be contained in the hydraulic oil of an engine oil circuit, can be filtered out by filter elements assigned to connecting rods10to prevent such contaminants from passing into the region of hydraulic chambers22,23or check valves26,27of an eccentric adjustment device13of the connecting rods10and thereby being able to impair the functionality of the respective connecting rod10. InFIG. 2, each hydraulic chamber22,23, or each check valve26,27has a separate filter element36integrated into the respective connecting rod10. In the variant ofFIG. 3, a filter element42is integrated into a hydraulic line41of the crankshaft38and interacts with each connecting rod10. The filter elements36,42ofFIGS. 2 and 3may also be used in combination with one another. Thus, it is possible to prevent contaminants from passing in the direction of the connecting rod10via the hydraulic oil. In this way, internal combustion engines that have low cleanliness requirements with regard to the engine oil circuit can be equipped with connecting rods10that have an eccentric adjustment device13for varying the effective connecting rod length.