Abstract:
An internal combustion engine comprises a turbo-compound and the known Föttinger-coupling is replaced by a torsion vibration damper. The Föttinger-coupling, which is used to transmit power, has high losses in power when it is necessary to have a differential rotational speed between the input side and the output side, i.e., the appearance of a slip. The losses are not used in a torsion vibration damper which has at least the same quality as a Föttinger-coupling.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of International Application PCT/DE2006/000519, filed 24 Mar. 2006, which claims priority from German Application DE 10 2005 014 000.9, filed 26 Mar. 2005, said applications are incorporated-by-reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a compound drive in combination with a combustion engine. 
       BACKGROUND OF THE INVENTION 
       [0003]    Compound drives are also called turbo-compounds. In such compound drives, the stream of exhaust gas from a combustion engine—in many cases a diesel engine—is routed through the exhaust gas turbine of a turbocharger. The charge air is fed to the combustion engine through a blower that is connected to the exhaust gas turbine with a rotationally fixed connection. As the exhaust gases continue on their way, in the existing art—in combination with a compound drive—they pass through a second turbine. This second turbine may transmit its rotational energy to a reduction gear, which is then connected in turn to a Föttinger coupling. After the Föttinger coupling there can again be a reduction gear, in order to further reduce the speed of rotation. Finally, the rotational energy is led into the crankshaft or into the centrifugal mass of the combustion engine. Through such a design, the energy content of the exhaust gases is used to increase the drive energy of the combustion engine. 
         [0004]    Non-uniformities of rotation between the crankshaft and the turbocharger are evened out through the use of the Föttinger coupling. Otherwise a rigid power train of the composite drive would convey non-uniformities of rotation of the crankshaft all the way to the power turbine, which would lead to significant torsion vibration problems. 
         [0005]    The design of a Föttinger coupling is very complex, which also makes this solution very costly. Furthermore, the efficiency is not optimal, due to the slippage inherent in the system. 
       SUMMARY OF THE INVENTION 
       [0006]    The object of the invention is therefore to provide a composite drive which both minimizes torsion vibrations and is economical. 
         [0007]    The problem is solved by employing a torsion vibration damper instead of a Föttinger coupling in a compound drive. A torsion vibration damper may have various designs here. In a first design, the torsion vibration damper comprises an input part and an output part, there being extensively acting energy storage devices (for example in the form of springs) situated between the input and output parts. 
         [0008]    In a second design of the torsion vibration damper there are also an input part and an output part present, but rolling elements move on imagined ramps in both directions between the input and output parts. The input and output parts here are braced axially against each other (for example by means of a diaphragm spring). 
         [0009]    In a Föttinger coupling, the rotational coupling from the pump side to the turbine side takes place by means of the hydrodynamic principle. That also makes it possible to eliminate torsional vibrations—at least partially. Since because of the hydrodynamic principle no rotationally fixed connection exists within the Föttinger coupling, the rotational speeds can fluctuate between the pump side and the turbine side without the transmission of torque being disrupted. 
         [0010]    In contrast to this, in a compound drive without Föttinger coupling but having a torsion vibration damper there is always a rotationally fixed connection. However, a torsion vibration damper permits only a relatively small relative angle of rotation between the input and output parts. These angle dimensions can be a maximum of +/−90°. In other words: With a torsion vibration damper, the rotary motions of the input and output parts—aside from the superimposed vibrations—are always rotationally synchronous. With a torsion vibration damper, “overtaking” of the output part by the input part is not possible. Given these facts, it is therefore all the more surprising that a compound drive with a torsion vibration damper instead of a Föttinger coupling can be realized. 
         [0011]    The invention will now be explained in greater detail on the basis of the figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0012]    The figures show the following: 
           [0013]      FIG. 1 : A schematic depiction of the existing art; 
           [0014]      FIG. 2 : a schematic depiction according to the invention; 
           [0015]      FIG. 3 : a cross sectional depiction of a torsion vibration damper; 
           [0016]      FIG. 4 : a cross section through another design of a torsion vibration damper; 
           [0017]      FIG. 5 : a cross section through a torsion vibration damper with freewheeling. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    In  FIG. 1 , a combustion engine  1  is connected to a turbocharger  4  through an exhaust gasoline  5   a . Turbocharger  4  is subdivided into the exhaust gas turbine  4   a  and the charge air turbine  4   b . During operation of turbocharger  4 , a charge air stream  6   b  passes through charge air turbine  4   b  and becomes charge air stream  6   a , which is blown into combustion engine  1 . 
         [0019]    Farther along in exhaust gas line  5  is exhaust gas line  5   b , which is flow-connected to a compound drive turbine  7 . A second yield is obtained here from the exhaust air, the intent here being to obtain rotational energy for the compound drive. Compound drive turbine  7  is connected to a reduction gear by a rotationally fixed connection. The intent of this reduction gear  8  is to reduce the high speed of the compound drive turbine  7  to the nominal speed of the down-line Föttinger coupling  9 . The right side of Föttinger coupling  9  here is the pump, while the left half shell of the Föttinger coupling embodies the turbine. Another reduction gear  10  is connected by a rotationally fixed connection to the left side of the Föttinger coupling—i.e. the turbine. This is followed by a mechanical connection  11  of reduction gear  10  to the crankshaft or the flywheel. The crankshaft or flywheel here would represent an input point for the flow of power. The only thing that is critical here is that the input point must be on the engine side of the clutch  2 . Input into a transmission input shaft  3  would make no sense, since with combustion engine  1  running it would then never be possible to bring about a non-driven condition. 
         [0020]    The compound drive according to the invention can be described well by comparing  FIG. 2  directly to  FIG. 1 , which was just described. As may be seen from  FIG. 2 , according to the invention the presence of a turbocharger  4  is not absolutely necessary. The only thing that is essential to the invention is that an exhaust line  5  be routed through compound drive turbine  7 . An interposed turbocharger  4  would be entirely optional. The presence of two reduction gears  8  and  10  is also not absolutely necessary. Only one reduction gear  8  or  10  is important, because it is necessary to match the high speed of compound drive turbine  7  to the speed of the crankshaft. This can be done either with reduction gear  8  between compound drive turbine  7  and torsion vibration damper  12 , or can also be realized between torsion vibration damper  12  and the mechanical connection  11  to the crankshaft or to the flywheel. But in another design of the invention it is also possible to employ both reduction gears  8  and  10 , as is known from the existing art. 
         [0021]    Torsion vibration damper  12  shown schematically in  FIG. 2  comprises a right-hand, disk-shaped input part and a left-hand output part, also disk-shaped. Located between the input and output parts is at least one extensively acting energy storage device, which may be in the form of a spring. In another design of the invention there is a plurality of extensively active energy storage devices present; these may be connected in parallel or in series. By designing torsion vibration damper  12  appropriately, it is possible here to influence the damping behavior and thus the frequency response curve. By designing energy storage devices having different spring characteristics, it is possible to generate overall spring characteristics that are either progressive or regressive in shape. In another design of the invention, the energy storage devices are situated at the outermost diameter of torsion vibration damper  12 . Here the energy storage devices (springs) may be guided in a sliding form. In another design of the invention the springs are guided by means of sliding blocks; that is, the springs are provided on their radial outer side with sliding blocks, which mesh between at least two turns of the springs by means of a stop tab. In another design of this idea there also rollers situated between a slideway located radially on the outside and the sliding blocks, so that the friction is reduced. 
         [0022]    The damping behavior of a torsion vibration damper  12  can be determined in a substantial way through dimensioning of frictions within the torsion vibration damper  12 . For that reason, in a first design of this invention the torsion vibration damper  12  can be provided with a lubrication of grease. In a second design the torsion vibration damper  12  is provided with a lubrication of oil; care must be taken to ensure that the oil is not thrown off. In another advantageous design of the invention, the oil lubrication can be designed as a component of the oil lubrication of combustion engine  1 . 
         [0023]      FIG. 3  reveals a torsion vibration damper  12  that is equipped with extensively active energy storage devices. In this case these energy storage devices are springs  21 . Torque is introduced from compound drive turbine  7  through a gear wheel  14 . Gear wheel  14  is connected by a rotationally fixed connection to an additional mass  15 , which is situated on a shaft  16  by means of a bearing  17 . According to the invention, gear wheel  14  and additional mass  15  may also be executed in one piece. By means of a mounting designed for example as a riveted connection  18 , the flow of force into input part  19  takes place, where input part  19  comprises two disks that are riveted together. The flow of force then takes place from input part  19  to an output part  20  through the springs  21 . As can be seen from  FIG. 3 , output part  20  touches left-hand input part  19 . This is achieved by positioning a diaphragm spring between output part  20  and the right-hand input part  19 . Depending on the dimensioning of this diaphragm spring, a defined friction then occurs between input part  19  and output part  20 , which can dissipate part of the vibrational energy. This metered friction can also be disadvantageous, however, because with the relative rotational motions between input part  19  and output part  20  there may thus be drag torque. 
         [0024]    In another design of the invention, the attempt is made to keep the friction between input part  19  and output part  20  as low as possible. In that case one then also speaks of so-called vibration insulation. With vibration isolation the frequency response curve appears in a very narrow band, which has the advantage that the natural frequency of torsion vibration damper  12  can be defined more clearly, and can also be designed to fall clearly outside of the operating spectrum. 
         [0025]    In another design of the invention there is an absorber located between exhaust turbine  7  and the input point on the crankshaft or flywheel. This absorber can be designed so that it vibrates in the opposite phase. 
         [0026]      FIG. 4  depicts a compound drive which is situated in a housing comprising housing parts  25 ,  26 . Shaft  16  is guided by means of roller bearings  22 . The introduction of torque  13  takes place here at the larger gear wheel. A power take-off gear  23  has a smaller diameter. The explanation for this is that the speeds of rotation must be reduced from the high-speed compound drive turbine  7  to the mechanical connection  11  to the crankshaft. 
         [0027]    As explained earlier, the flow of torque enters the compound drive through the torque input  13 . Torque input  13  is connected by means of a severable connection to a sleeve which is mounted on shaft  16  by means of two roller bearings  17 . Input part  19  of torsion vibration damper  12  is connected to the sleeve with a rotationally fixed connection. In the exemplary embodiment in  FIG. 4 , the springs  21  of torsion vibration damper  12  are guided radially on the outside by means of a sliding form  24 . The output part  20  of torsion vibration damper  12  is connected in turn to shaft  16  by a rotationally fixed connection. Due to the precise positioning of both input part  19  and output part  20 —both axially and radially—it is possible for torsion vibration damper  12  to work precisely. 
         [0028]    Shaft  16  has an oil channel  32  at its right end, which is depicted with dashed lines because of its hidden position. This oil channel  32  also has two transverse channels, through which oil can be directed both to torsion vibration damper  12  and to torque input  13 . The inlet for oil channel  32 —not shown here—can advantageously be situated in the area of right-hand bearing  22  in right-hand housing part  26 . It must also be mentioned that the angular ball bearings  17  are fixed in the sleeve or on shaft  16  by means of a lock nut  30  or retaining ring  29 . 
         [0029]      FIG. 5  differs from  FIG. 4  in that it is provided with a free wheeling mechanism  31 . This free wheeling mechanism  31  is designed so that it locks when there is a flow of torque from torque input  13  to take-off gear wheel  23 . In other words: When shaft  16  rotates faster than output part  20 , shaft  16  can turn freely. The free-wheeling is especially effective from the perspective of energy when the engine is being started or during acceleration. In these cases the combustion engine is faster than exhaust turbine  7 , because the exhaust turbine  7  needs some time before it reaches its optimal operating speed. 
         [0030]    Since a torsion vibration damper  12  is usually operated with pulsation—that is, a basic load with undulation overlaid—in this case free wheeling mechanism  31  is not used. But if the basic load is small and the vibration amplitudes are correspondingly large, the vibrations can go beyond the zero position. In these cases the free wheeling mechanism  31  is also advantageous for the damping behavior of torsion vibration damper  12 . 
         [0031]    In the exemplary embodiment in  FIG. 5 , free wheeling mechanism  31  is situated between an outer sleeve and shaft  16 . In this exemplary embodiment the rolling elements of free wheeling mechanism  31  do not run directly on shaft  16 , however, but rather they run on an inner sleeve  27 , which preferably has a hardened surface. This inner sleeve  27  is then fixed on the shaft  16  for example by means of a shrink joint. 
       REFERENCE LABELS 
       [0000]    
       
           1  combustion engine (motor) 
           2  clutch 
           3  transmission input shaft 
           4  turbocharger 
           4   a  exhaust gas turbine 
           4   b  charge air turbine 
           5  exhaust line 
           5   a  exhaust line between engine and turbocharger 
           5   b  exhaust line between turbocharger and additional exhaust gas turbine (compound drive turbine) 
           6   a  charge air stream (between turbocharger and engine) 
           6   b  charge air stream (on the intake side of the turbocharger) 
           7  compound drive turbine 
           8  reduction bear (between compound drive turbine and Föttinger coupling 
           9  Föttinger coupling 
           10  reduction gear 
           11  mechanical connection to the crankshaft or to the flywheel 
           12  torsion vibration damper/vibration insulator 
           13  torque input of compound drive turbine 
           14  gear wheel 
           15  additional mass 
           16  shaft 
           17  roller bearing 
           18  riveted connection 
           19  input part 
           20  output part 
           21  spring 
           22  roller bearing of shaft  16   
           23  power take-off gear 
           24  sliding form 
           25  housing part 
           26  housing part 
           27  inner sleeve 
           28  riveted connection 
           29  retaining ring 
           30  lock nut 
           31  free wheeling mechanism 
           32  oil channel