Compound transmission

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.

The invention relates to a compound drive in combination with a combustion engine.

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.

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.

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.

The object of the invention is therefore to provide a composite drive which both minimizes torsion vibrations and is economical.

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.

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).

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.

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.

The invention will now be explained in greater detail on the basis of the figures.

The figures show the following:

FIG. 1 : A schematic depiction of the existing art;

FIG. 2 : a schematic depiction according to the invention;

FIG. 3 : a cross sectional depiction of a torsion vibration damper;

FIG. 4 : a cross section through another design of a torsion vibration damper;

FIG. 5 : a cross section through a torsion vibration damper with freewheeling;

FIG. 6 : a schematic view of the energy storage devices at the outermost diameter of the torsion vibration damper; and,

FIG. 7 : a partial schematic view of the oil lubricant system of the compound drive of the present invention connected to the oil lubrication system of the internal combustion engine.

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 .

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.

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.

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. FIG. 6 depicts another design of the invention the springs 40 situated at the outermost diameter 12 a in which they are guided by means of sliding blocks 42 ; that is, the springs 40 are provided on their radial outer side with sliding blocks 42 , which mesh between at least two turns of the springs 40 by means of a stop tab 42 a . In another design of this idea, also seen in FIG. 6 , there also rollers 44 situated between a slideway 46 located radially on the outside and the sliding blocks 42 , so that the friction is reduced.

The damping behavior of a torsion vibration damper 12 can be determined, that is adjusted or tuned, 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 . FIG. 7 shows engine 1 connected to oil channel 32 of shaft 16 by oil line 33 extending from engine 1 and return line 33 a extending from channel 32 to engine 1 .

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.

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 or tunable, and can also be designed to fall clearly outside of the operating spectrum.

In another design of the invention there is an absorber 50 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.

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.

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.

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 .

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.

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 .

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.

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