Abstract:
A connecting rod ( 10 ) has a pin bearing eye connected to a crankshaft and a connecting rod bearing eye ( 12 ) connected to a piston. An eccentric adjusting device ( 13 ) adjusts an effective connecting rod length and has eccentric rods ( 15, 16 ) that act on an eccentric lever ( 14 ) of the adjusting device ( 13 ). The eccentric adjusting device ( 13 ) has an eccentric ( 36 ) guided in a recess of the lever ( 14 ) and a recess for receiving a gudgeon pin ( 37 ). Lubricating oil bores extend radially of the eccentric in the connecting rod bearing eye ( 12 ) and in the eccentric ( 36 ). Lubricating oil builds up via the lubricating oil bores between the connecting rod bearing eye ( 12 ) and the eccentric ( 36 ) and between the eccentric ( 36 ) and the gudgeon pin ( 37 ). Lubricating oil bores of the eccentric ( 36 ) are diametrically larger than lubricating oil bores of the connecting rod bearing eye ( 12 ).

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority under 35 USC 119 to German Patent Appl. No. 10 2015 103 201.5 filed on Mar. 5, 2015, the entire disclosure of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a connecting rod for an internal combustion engine and to an internal combustion engine. 
         [0004]    2. Description of the Related Art 
         [0005]    DE 10 2010 016 037 A1 and  FIG. 1  herein show a connecting rod of an internal combustion engine having an adjustable compression ratio. The connecting rod  10  has a pin bearing eye  11  and a connecting rod bearing eye  12 . The pin bearing eye  11  connects the connecting rod  10  to a crankshaft (not shown in  FIG. 1 ) and the connecting rod bearing eye  12  connects the connecting rod  10  to a cylinder piston (not shown in  FIG. 1 ) of the internal combustion engine. The connecting rod  10  is assigned an eccentric adjusting device  13  that has an eccentric (not shown in  FIG. 1 ), an eccentric lever  14  and eccentric rods  15 ,  16 . The eccentric lever  14  has a recess that is arranged eccentrically with respect to a center point  17  of the connecting rod bearing eye  12  and has a center point  18 . The recess in the eccentric lever  14  receives the eccentric and a recess in the eccentric receives a gudgeon pin. The eccentric adjusting device  13  functions to adjust an effective connecting rod length l eff . The spacing of the center point  18  of the recess in the eccentric lever  14  from a center point  19  of the pin bearing eye  11  is understood to be the connecting rod length. The eccentric rods  15 ,  16  can be moved to rotate the eccentric body  14  and therefore to change the effective connecting rod length l eff . Each eccentric rod  15 ,  16  is assigned a piston  20 ,  21  that is guided displaceably in a hydraulic chamber  22 ,  23 . A hydraulic pressure that acts on the pistons  20 ,  21  that are assigned to the eccentric rods  15 ,  16  prevails in the hydraulic chambers  22 ,  23 . The movement of the eccentric rods  15 ,  16  is possible or not possible depending on the oil quantity in the hydraulic chambers. 
         [0006]    The adjustment of the eccentric adjusting device  13  is initiated by the action of mass and load forces of the internal combustion engine that act on the eccentric adjusting device  13  during a work stroke of the internal combustion engine. The directions of action of the forces that act on the eccentric adjusting device  13  change continuously during a work stroke. The adjusting movement is assisted by the pistons  20 ,  21  that are loaded with hydraulic oil and act on the eccentric rods  15 ,  16 . The pistons  20 ,  21  prevent restoring the eccentric adjusting device  13  on account of varying directions of force action of the forces that act on the eccentric adjusting device  13 . The eccentric rods  15 ,  16  are connected on both sides to the eccentric body  14  and interact with the pistons  20 ,  21 . The pistons  20 ,  21  are guided in the hydraulic chambers  22  and  23 , and the hydraulic chambers  22  and  23  can be loaded with hydraulic oil from the pin bearing eye  11  via hydraulic oil lines  24  and  25 . Check valves  26  and  27  prevent a return flow of the hydraulic oil from the hydraulic chambers  23  and  24  back into the hydraulic lines  24  and  25 . A switchover valve  29  is received in a bore  28  of the connecting rod  10 . The switching position of the switchover valve  29  determines which of the hydraulic chambers  22  and  23  is filled with hydraulic oil and which is emptied, with the adjusting or rotational direction of the eccentric adjusting device  13  depending on this. Fluid lines  30  and  31  contact with the hydraulic chambers  22  and  23 , which, in turn, are in contact via with the bore  28  that receives the switchover valve  29 . In  FIG. 1 , an actuating means  32 , a spring device  33  and a control piston  34  of the switchover valve  29  are shown diagrammatically, and function substantially as described in DE 10 2010 016 037 A1. 
         [0007]    As described above, the hydraulic oil acts on the pistons  20 ,  21  that are guided in the hydraulic chambers  22 ,  23  and is fed to the hydraulic chambers  22 ,  23  via hydraulic lines  24  and  25 , starting from the pin bearing eye  11 . The connecting rod  10  acts by way of the pin bearing eye  11  on the crankshaft (not shown in  FIG. 1 ) so that a connecting rod bearing shell  35  is arranged between a crankshaft bearing journal of the crankshaft, and the pin bearing eye. 
         [0008]    DE 101 08 461 B4 discloses a crankshaft bearing for an internal combustion engine having an adjustable compression ratio. The crankshaft is mounted in eccentric rings in the crankshaft bearing. The eccentric ring in the crankshaft bearing has a circumferential oil distribution groove on its outer circumferential face. Oil can pass in the direction of the oil distribution groove via an oil feed channel in the engine housing. 
         [0009]    It is an object of the invention to provide a novel internal combustion engine and a novel connecting rod. 
       SUMMARY 
       [0010]    Lubricating oil bores are made in the connecting rod bearing eye and in the eccentric and extend in the radial direction of the eccentric and the connecting rod bearing eye. The lubricating oil bores enable a lubricating oil film to be built up first between the connecting rod bearing eye and the eccentric, and second between the eccentric and the gudgeon pin. Each lubricating oil bore of the eccentric has a greater diameter than each lubricating oil bore of the connecting rod bearing eye. 
         [0011]    The invention permits advantageous lubrication of the contact points between the connecting rod and the eccentric and between the eccentric and the gudgeon pin. A lubricating oil reservoir for the lubrication between the eccentric and the gudgeon pin is provided by the greater diameter of each lubricating oil bore of the eccentric. 
         [0012]    In the first end position of the eccentric, a first lubricating oil bore extends in the radial direction of the eccentric, and a first lubricating oil bore extends in the radial direction of the connecting rod bearing eye and has a smaller diameter than the first lubricating oil bore of the eccentric. The first lubricating oil bores of the eccentric and the connecting rod bearing eye lie behind one another in the radial direction, so that a lubricating oil film can build up between the eccentric and the gudgeon pin via the lubricating oil bores in the first end position. In a second end position of the eccentric, a second lubricating oil bore extends in the radial direction of the eccentric and a second lubricating oil bore extends in the radial direction of the connecting rod bearing eye and has a smaller diameter than the second lubricating oil bore of the eccentric. The second lubricating oil bores of the eccentric and the connecting rod bearing eye lie behind one another in the radial direction, so that a lubricating oil film can be built up between the eccentric and the gudgeon pin via the lubricating oil bores in the second end position. The second lubricating oil bore of the eccentric and the second lubricating oil bore of the connecting rod bearing eye preferably do not lie radially behind one another in the first end position. As a result, a lubricating oil film can build up between the connecting rod bearing eye and the eccentric via the second lubricating oil bore of the connecting rod bearing eye in the first end position. Similarly, the first lubricating oil bore of the eccentric and the first lubricating oil bore of the connecting rod bearing eye do not lie radially behind one another in the second end position of the eccentric. As a result, a lubricating oil film can be built up between the connecting rod bearing eye and the eccentric via the first lubricating oil bore of the connecting rod bearing eye in the second end position. This configuration of the lubricating oil bores allows satisfactory lubrication of the relevant contact points in the end positions of the eccentric adjusting device and during the adjustment thereof. 
         [0013]    The lubricating oil bores of the eccentric may be offset axially or displaced with respect to the lubricating oil bores of the connecting rod bearing eye in such a way that, in the first end position of the eccentric, axes of the first lubricating oil bore of the eccentric and of the first lubricating oil bore of the connecting rod bearing eye do not coincide. In the second end position of the eccentric, axes of the second lubricating oil bore of the eccentric and of the second lubricating oil bore of the connecting rod bearing eye do not coincide but rather are offset in the circumferential direction of the eccentric and the connecting rod bearing eye. As a result of said axial offset, a reliable oil supply of the respective lubricating oil reservoir can be ensured in the case of micromovements of the eccentric in its respective end position. 
         [0014]    Exemplary embodiments of the invention will be explained in greater detail using the drawing, without being restricted thereto. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  shows a connecting rod of an internal combustion engine known from the prior art with an adjustable compression ratio. 
           [0016]      FIG. 2  shows a detail of a connecting rod according to the invention with an adjustable compression ratio in a first state. 
           [0017]      FIG. 3  shows the detail from  FIG. 2  in a second state. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    An internal combustion engine having an adjustable compression ratio has at least one, preferably a plurality of cylinders. Each cylinder has a piston that is coupled via a connecting rod  10  to a crankshaft of the internal combustion engine. Each connecting rod  10  has a connecting rod bearing eye  12  at one end and a pin bearing eye  11  at an opposite end. The respective connecting rod  10  acts with its pin bearing eye  11  on a crankshaft bearing journal of the crankshaft with a connecting rod bearing shell positioned between the crankshaft bearing journal and the pin bearing eye. A lubricating oil film can be built up between the connecting rod bearing shell and the crankshaft bearing journal. 
         [0019]    An internal combustion engine having an adjustable compression ratio has an eccentric adjusting device  13  in the region of each connecting rod  10  for adjusting the effective length of the respective connecting rod  10 . The eccentric adjusting device  13  has an eccentric  36 , an eccentric lever  14  and eccentric rods  15 ,  16  that can be moved to set the compression ratio depending on a hydraulic pressure that prevails in hydraulic chambers that interact with the eccentric rods. The hydraulic chambers that interact with the eccentric rods  15 ,  16  can be supplied with hydraulic oil starting from the pin bearing eye  11  of the respective connecting rod. The adjustment of the eccentric adjusting device is initiated by the action of mass and load forces of the internal combustion engine. 
         [0020]    The eccentric lever  14  has a bore or recess for receiving the eccentric  36 , and the eccentric  36  has a bore or recess that can receive a gudgeon pin  37 . Lubricating oil bores  38 ,  39  and  40 ,  41  are made in the connecting rod bearing eye  12  and in the eccentric  36  and enable a lubricating oil film to be built up first between the connecting rod bearing eye  12  and the eccentric  36  and second between the eccentric  36  and the gudgeon pin  37 . The lubricating oil bores  38 ,  39 ,  40 ,  41  allow satisfactory lubrication of the contact points between the connecting rod bearing eye  12  and the eccentric  36  and between the eccentric  36  and the gudgeon pin  37  in the end positions of the eccentric adjusting device  13  and during the adjustment of the eccentric adjusting device  13 . 
         [0021]    In the embodiment shown in  FIGS. 2 and 3 , two lubricating oil bores  38 ,  39  are made in the connecting rod bearing eye  12  and two lubricating oil bores  40 ,  41  are made in the eccentric  36 . The lubricating oil bores  38 ,  39 ,  40 ,  41  are made in the connecting rod bearing eye  12  and in the eccentric  36  in such a way that, in a first end position of the eccentric  36  or the eccentric adjusting device  13 , a first lubricating oil bore  40  of the eccentric  36  and a first lubricating oil bore  38  of the connecting rod bearing eye  12  lie behind one another in the radial direction of the eccentric or connecting rod bearing eye. As a result, a lubricating oil film can be built up between the eccentric  36  and the gudgeon pin  37  via said lubricating oil bores  40 ,  38  in the first end position (see  FIG. 2 ). The lubricating oil bores  38 ,  39 ,  40 ,  41  are made in the connecting rod bearing eye  12  and in the eccentric  36  so that in a second end position of the eccentric  36 , a second lubricating oil bore  41  of the eccentric  36  and a second lubricating oil bore  39  of the connecting rod bearing eye  12  lie behind one another in the radial direction (see  FIG. 3 ). As a result, a lubricating oil film can be built up between the eccentric  36  and the gudgeon pin  37  via said lubricating oil bores  41 ,  39  in the second end position. 
         [0022]    In the first end position of the eccentric  36  or the eccentric adjusting device  13  (see  FIG. 2 ), the second lubricating oil bore  41  of the eccentric  36  and the second lubricating oil bore  39  of the connecting rod bearing eye  12  do not lie behind one another in the radial direction of the eccentric and connecting rod bearing eye. As a result, a lubricating oil film can be built up between the connecting rod bearing eye  12  and the eccentric  36  via the second lubricating oil bore  39  of the connecting rod bearing eye  12  in the first end position. In the second end position of the eccentric  36  or the eccentric adjusting device  13  (see  FIG. 3 ), the first lubricating oil bore  40  of the eccentric  36  and the first lubricating oil bore  38  of the connecting rod bearing eye  12  do not lie behind one another in the radial direction of the eccentric and the connecting rod bearing eye. As a result, a lubricating oil film can then be built up between the connecting rod bearing eye  12  and the eccentric  36  via the first lubricating oil bore  38  of the connecting rod bearing eye  12  in the second end position. 
         [0023]    The lubricating oil bores  38 ,  39  in the connecting rod bearing eye  12  and the lubricating oil bores  40 ,  41  in the eccentric  36  extend in each case in the radial direction of the eccentric  36  and in the radial direction of the connecting rod bearing eye  12 . 
         [0024]    The lubricating oil bores  40 ,  41  of the eccentric  36  have a greater diameter than the lubricating oil bores  38 ,  39  of the connecting rod bearing eye  12 . The first lubricating oil bore  40  of the eccentric  36  thus has a greater diameter than the first lubricating oil bore  38  of the connecting rod bearing eye  12 , and the second lubricating oil bore  41  of the eccentric  36  has a greater diameter than the second lubricating oil bore  39  of the connecting rod bearing eye  12 . 
         [0025]    A lubricating oil reservoir for the lubrication between the eccentric  36  and the gudgeon pin  37  is provided by way of the greater diameter of the lubricating oil bores  40 ,  41  of the eccentric  36 . Weakening of the connecting rod bearing eye  12  is avoided and sufficient lubricating oil is provided for the lubrication of the gudgeon pin  37 . 
         [0026]    Furthermore, the lubricating oil bores  40 ,  41  of the eccentric  36  are axially offset or displaced with respect to the lubricating oil bores  38 ,  39  of the connecting rod bearing eye  12  so that, in the first end position of the eccentric  36  (see  FIG. 2 ), axes  40   a ,  38   a  of the first lubricating oil bore  40  of the eccentric  36  and of the first lubricating oil bore  38  of the connecting rod bearing eye  12  and, in the second end position of the eccentric  36  (see  FIG. 3 ), axes  41   a ,  39   a  of the second lubricating oil bore  41  of the eccentric  36  and of the second lubricating oil bore  39  of the connecting rod bearing eye  12  do not coincide, but rather are offset in the circumferential direction of the eccentric  36  and the connecting rod bearing eye  12 . As a result of said axial offset of the lubricating oil bores  38 ,  40  and  39 ,  41  in the respective end position of the eccentric  36 , a reliable oil supply from the respective lubricating oil reservoir can be ensured in the case of micromovements of the eccentric  36  in its respective end position. The axial offset or displacement of the respective lubricating oil bore  40 ,  41  of the eccentric  36  with respect to the respective lubricating oil bore  38 ,  39  of the connecting rod bearing eye  12  in an end position of the eccentric  36  is in an opposite direction to the displacement direction of the eccentric  36  out of the end position in the direction of the other end position. This can be gathered from the relative position of the axes  38   a ,  40   a  in  FIG. 2  and the relative position of the axes  39   a ,  41   a  in  FIG. 3 . 
         [0027]    According to  FIG. 2 , the axis  40   a  of the first lubricating oil bore  40  of the eccentric  36  is behind the axis  38   a  of the first lubricating oil bore  38  of the connecting rod bearing eye  12  in the first end position of the eccentric  36  or the eccentric adjusting device  13 , in relation to the displacement direction (arrow  42 ) of the eccentric  36  toward the second end position thereof. As viewed in the displacement direction of the eccentric  36  shown by the arrow  42 , front edges of the first lubricating oil bores  38 ,  40  of the eccentric  36  and the connecting rod bearing eye  12  lie on a circumferential position in the first end position of the eccentric  36 , whereas a rear edge of the lubricating oil bore  40  of the eccentric  36  is recessed with respect to a rear edge of the lubricating oil bore  38  of the connecting rod bearing eye  12  in the displacement direction of the eccentric  36  (arrow  42 ). 
         [0028]    According to  FIG. 3 , the axis  41   a  of the second lubricating oil bore  41  of the eccentric  36  is behind the axis  39   a  of the second lubricating oil bore  39  of the connecting rod bearing eye  12  in the second end position of the eccentric  36  or the eccentric adjusting device  13 , in relation to the displacement direction of the eccentric  36  shown by the arrow  43  in the direction of the first end position. As viewed in the displacement direction of the eccentric  36  shown by the arrow  43 , front edges of the second lubricating oil bores  39 ,  41  of the eccentric  36  and the connecting rod bearing eye  12  lie on a circumferential position in the second end position of the eccentric  36 , whereas a rear edge of the lubricating oil bore  41  of the eccentric  36  is recessed with respect to a rear edge of the lubricating oil bore  39  of the connecting rod bearing eye  12  in the displacement direction of the eccentric  36  shown by the arrow  43 . 
         [0029]    An internal combustion engine according to the invention has an adjustable compression ratio, a plurality of cylinders, and a crankshaft, on which each cylinder acts via a connecting rod  10  as described above.