WO2008055564A1 - Hydrodynamic coupling - Google Patents

Abstract

The invention relates to a hydrodynamic coupling - having a bladed primary wheel and a bladed secondary wheel, which are positioned axially opposite of each other, and together form a toroidal working space, which can be filled, or is filled with a working medium; - wherein at least one of the two bladed wheels is supported on a thread, helical toothing or the like so that, by means of a relative rotational movement in relation to the thread, helical toothing or the like, it can be displaced in a first direction by the other bladed wheel in the axial direction of the hydrodynamic coupling and, by means of a relative rotational movement in a second direction that is opposite to the first direction, it can be displaced in the direction of the other bladed wheel. The invention is characterized in that - the hydrodynamic coupling has no return device for the wheel that is displaceable in the axial direction, which applies a direct or indirect spring force or an axial pressure force to the displaceable wheel for displacing the same.

Description

 Hydrodynamic coupling

The invention relates to a hydrodynamic coupling, that is a turbomachine, which operates on the Föttinger principle.

Hydrodynamic couplings are known to have a bladed primary wheel, also called pump impeller, and a bladed secondary wheel, also called a turbine wheel. Both impellers face each other axially to form a separating gap and together form a generally toroidal working space. The working space can be filled with a working medium, for example oil, water or a mixture thereof, in order to transfer torque from the impeller to the turbine wheel via a working medium circuit in the working space which is established during operation of the hydrodynamic coupling.

A particular application for a hydrodynamic coupling, as it relates to the present invention according to an advantageous embodiment, is a so-called turbocompound system. In a turbocompound system which is generally used in a motor vehicle, for example a truck, a useful turbine is arranged in the exhaust gas stream of an internal combustion engine, which is acted upon by the exhaust gas. The power turbine converts the energy contained in the exhaust gas into a rotational movement. The rotational movement is transmitted to the crankshaft of the internal combustion engine to drive the crankshaft. In the drive connection between the exhaust gas turbine and the crankshaft, a hydrodynamic coupling is introduced to the

Drive power from the power turbine to the crankshaft without wear.

When the hydrodynamic coupling in such a turbocompound system is designed as a constant filling coupling, that is, as a hydrodynamic coupling whose working space is always at least one predetermined Working fluid quantity is filled, the power turbine is protected from overspeeding due to lack of torque support.

In order to switch on or off the torque transmission of a constant filling coupling, it is proposed in US Pat. No. 2,359,930, which relates generally to a hydrodynamic coupling but not to a turbocompound system, to mount the impeller on a shaft with an external thread. The impeller itself has a sleeve with an internal thread which engages with said external thread. When applying a drive power to the shaft, the impeller moves on the external thread against the force of compression springs in the direction of the turbine wheel and thus "closes" the working fluid circuit in the working space, so that drive power from the impeller to the turbine wheel and thereby from the impeller bearing input shaft to a When the torque acting on the pump impeller or its shaft is reduced, the force of the compression springs outweighs the force driving the pump impeller towards the turbine wheel from the input torque and drives the impeller away from the turbine wheel an interruption of the torque transmission from the impeller to the turbine reaches.

In order to provide the compression springs in the hydrodynamic coupling, a corresponding space is necessary, which leads to relatively large dimensions of the hydrodynamic coupling in the axial direction. Further, a plurality of bearings is required to support the input shaft and the output shaft in alignment with each other. Finally, the proposed construction of the hydrodynamic coupling is complex and susceptible to disturbances.

Furthermore, hydrodynamic retarder are known in which the rotor with a return device, which a pressure surge on a rotor formed by the Piston surface selectively exerts, is axially displaceable from a working position to an idle position. Such a hydrodynamic retarder is described in German Utility Model DE 299 03 829 U1.

Finally, patent specification DE 518 828 also describes a return device for the primary wheel or the secondary wheel of a hydrodynamic coupling, by means of which pressure oil can be selectively applied to a piston ring surface of the rotor of the displaceable wheel in order to effect an axial displacement.

As can easily be seen, even those restoring devices, which operate with optionally applicable axial compressive forces, lead to a complexity of the structure of a hydrodynamic machine and thus to a larger space, higher manufacturing and maintenance costs. Furthermore, such devices that operate with a pressure surge or a pressure pulse, prone to failure.

The present invention has for its object to provide a hydrodynamic coupling, in particular constant filling, in which the torque or rotational power transmission between the two paddle wheels is automatically high in a first direction and is interrupted or reduced in a second, opposite direction. The hydrodynamic coupling should have the simplest possible and compact construction and, in particular when used in a turbocompound system, improve this compared to the prior art.

The object of the invention is achieved by a hydrodynamic coupling with the features of claim 1 and a method having the features of claim 10. The dependent claims describe advantageous and particularly expedient embodiments of the invention.

The hydrodynamic coupling according to the invention is particularly suitable for systems, for example turbocompound systems, in which certain Operating conditions, a torque transmission from the primary to the secondary takes place, and in other operating conditions, an undesirable torque transmission from the secondary to the primary wheel should be prevented or reduced, thus a kind of free-wheeling function should be achieved. This is inventively achieved in that at least one of the two wheels is mounted on a thread, in particular normal thread, coarse thread, swirl, helical or the like, that it by a rotational movement or a relative rotational movement relative to the thread / teeth in the axial direction of the hydrodynamic Clutch can be moved or moved so as to be approached in certain operating conditions in the direction of the other paddle or held with a predetermined minimum separation gap with respect to this, and can be traversed in other operating conditions of the other paddle wheel to the torque transmission through the working medium circuit largely or completely prevent or at least mitigate it.

Instead of the thread, a helical toothing or the like may be provided, by means of which the movable bladed wheel is supported, usually on a shaft.

In contrast to the prior art described in the hydrodynamic coupling according to the invention, however, the previously required compression springs as restoring device and also any, a spring force on the movable wheel applying restoring device omitted. Rather, the startup and shutdown of the movable in the axial direction bladed wheel, the primary and / or the secondary, exclusively by the speed ratio between the two paddle wheels. If the primary wheel rotates at a higher speed than the secondary wheel, a force is applied in a first axial direction to the movable wheel by the thread or the helical toothing. If the secondary wheel rotates at a higher speed than the primary wheel, the movable wheel will move a force applied in a second axial direction, wherein the second axial direction is directed opposite to the first axial direction. Solely by this application of force, that is, the conversion of torque in a thrust by means of the thread, the process, that is, the startup and shutdown of the movable wheel with respect to the other bladed wheel.

The two bladed wheels can advantageously be mounted on a common shaft. For example, one of the two bladed wheels, for example the secondary wheel, can be mounted directly on the shaft, in particular by means of the toothing, and the second bladed wheel, in particular the primary wheel, can be relatively supported on this shaft, that is to say via an interposed bearing, in particular Rolling bearings, be mounted on the shaft. The first bladed wheel thus rotates with the speed of the shaft, whereas the speed of the second bladed wheel rotates in accordance with the torque or rotational power transmission in the working space at a different speed.

The hydrodynamic coupling advantageously has an oblique blading, that is to say the blades of the primary wheel and of the secondary wheel do not run in axial sectional planes through the axis of rotation, but are arranged at an angle thereto. In other words, the blades are not perpendicular to an axially perpendicular plane through the separation gap. The inclination or the angle of attack with respect to an axial section plane is such that the blades, which are advantageously aligned with each other, move in a first direction to each other in a first direction in a power transmission between the two paddles and in a second, opposite direction, moving spit each other.

The terms fleeing and Spießend are known in the art. Fled means that the inclination of the faster-rotating impeller, starting in the separating gap in the direction of the Schaufelradbodens is designed in the direction of rotation, whereas spit means that the inclination of the Blades of the faster rotating paddle wheel, starting in the separating gap in the direction of the Schaufelradbodens counter to the direction of rotation is executed. In spießenden operation hydrodynamically relatively more power at the same amount of working fluid in the working space is transferred as in the fleeing operation.

When using a turbo coupling according to the invention in a turbocompound system, the following method can be implemented: In Bethebszuständen in which sufficient exhaust gas is present with sufficient exhaust energy, which is applied to the exhaust gas turbine, finds a drive power transmission from the exhaust gas turbine via the hydrodynamic coupling to the crankshaft of the engine instead of. In Bethebszuständen in which only little exhaust gas and / or too low exhaust gas energy is available, and so a power transfer from the crankshaft via the hydrodynamic coupling would take place on the exhaust gas turbine, which is undesirable in traction, travels the movable paddle wheel, for example, the secondary , automatically from the other paddle wheel, that the connected to the crankshaft in a drive connection secondary bucket wheel rotates faster than the standing in a drive connection with the exhaust gas turbine primary wheel. The axial shutdown causes a reduction or interruption of the drive power transmission via the hydrodynamic coupling, so that no undesirable drag torque is transmitted to the crankshaft of the exhaust gas turbine.

In the former case, however, in traction with

Exhaust gas energy utilization, that is, with transmission of drive power from the exhaust gas turbine to the crankshaft, moves the movable paddle wheel automatically to the other paddle wheel or remains approached, because the primary wheel connected to the exhaust gas turbine rotates faster than the secondary wheel connected to the crankshaft. The startup and shutdown is thus exclusively due to the speed ratio between Primary and secondary determines or depending on which of the two wheels rotates faster compared to the other.

The coupling according to the invention can be designed as a constant filling coupling. Under Konstantfüllungskupplung be understood according to one embodiment, such clutches that have the same or substantially the same amount of working fluid in the working space and / or within the clutch in all operating conditions. According to another embodiment, constant fill coupling in the present case is understood to mean a coupling in which the quantity of working medium in the working space and / or within the coupling varies, but there is always a minimum amount of working medium in the working space and / or the coupling. In both embodiments, an external working medium circuit may or may not be provided.

The invention will be described below by way of example with reference to an embodiment.

Show it:

Figure 1 is a schematic diagram of a hydrodynamic coupling in one

Turbocompound system;

FIG. 2 shows a section through a hydrodynamic coupling designed according to the invention in a first operating state with a secondary wheel approached;

Figure 3 shows the hydrodynamic coupling of Figure 2 in a second

Operating condition with worn secondary wheel;

FIG. 4 shows a representation corresponding to FIG. 2 in a hydrodynamic coupling with inlet control; Figure 5 shows the hydrodynamic coupling of Figure 4 in a worn state of the secondary wheel, in addition, a bypass is opened by the shutdown.

1 shows a turbocompound system with an internal combustion engine 10, which has a crankshaft 11, and an exhaust gas turbine 12 in the exhaust stream 13 of the internal combustion engine 10. The exhaust gas turbine 12 is in a drive connection with the crankshaft 11, in the present case via the gear train 15th , the hydrodynamic coupling 14 and the gear train 16. About this drive connection, if sufficient exhaust gas or exhaust gas energy is present in the exhaust stream 13, transmitted drive power from the exhaust gas turbine 12 to the crankshaft 11.

In operating states in which not enough exhaust gas or exhaust gas energy is present, a drag torque is previously transmitted from the exhaust gas turbine 12 to the crankshaft 11 via the hydrodynamic clutch 14, which is undesirable. The hydrodynamic coupling 14 is therefore provided to reduce or prevent this drag torque according to the invention with an axially displaceable paddle wheel, which automatically when the Abgasnutzturbine 12 generates a drag torque is traversed by the other paddle wheel.

A section through such a hydrodynamic coupling is shown in FIGS. 2 to 5. One recognizes the primary wheel 1 and the secondary wheel 2, which together form a working space 3. The working space 3, of which in the present case only one side is shown with respect to the axis of rotation 17 of the hydrodynamic coupling, has a toroidal shape. The primary wheel 1 is the secondary wheel 2, while maintaining a more or less large separation gap axially opposite. The size of the separating gap is determined by the axial position of the secondary wheel 2, which is directly supported on a thread 4 of a shaft 5. Both the primary wheel 1 and the secondary wheel 2 each have a blading 7, which is advantageously designed as an inclined blading.

The shaft 5 carries a rolling bearing 6, here in the form of a double ball bearing, and the primary wheel. 1

Due to the fact that the coupling shell 18, which is presently connected to the primary wheel 1 and completely encloses the secondary wheel 2 in the axial direction on both sides and in the circumferential direction together with the primary wheel 1, no outlets or nozzles for discharging on its outer circumference

Having working medium, the working space 3 is always filled with a minimum amount of working fluid.

The primary wheel 1 is connected via the flange 19 indirectly to the exhaust gas turbine (not shown). The secondary wheel 2 is (not shown) via the shaft 5 and a provided on this gear 20 or flange indirectly with the crankshaft (not shown).

Now, if drive power is transmitted from the exhaust gas turbine to the crankshaft, as shown in the figure 2 by the arrows, the primary wheel 1 runs at a greater speed than the secondary 2. The selected direction of rotation of the thread 4 causes the secondary 2 is moved up to a minimum possible distance or minimum separation gap to the primary wheel 1, as shown in Figure 2. This approach or holding in the approached position results solely on the basis of the power flow direction or the speed ratio between the primary wheel 1 and the secondary wheel 2. Springs or a hydraulic actuator to bring the secondary 2 to the primary wheel 1, are not provided. The hydrodynamic coupling is therefore free of a restoring device. FIG. 3 shows the conditions which result when the power flow from the crankshaft (not shown) via the secondary wheel 2 to the primary wheel 1 and then the exhaust gas utilization turbine (not shown) takes place, see the arrows. In this case, the secondary wheel 2 runs at a higher speed than the primary wheel 1. The secondary wheel 2 is thereby automatically driven off the primary wheel 1. The shutdown is again without the force of springs or a hydrodynamic actuator. The power transmission is prevented or at least reduced by the larger axial distance between the secondary 2 and the primary wheel 1.

When driving down, the following further advantage results: Working medium, which was previously present in the space between the back of the secondary wheel 2 and the inside of the shell 18, is displaced by the returning secondary wheel 2 and ejected via the radially inner gap between the shell 18 and shaft 5. Due to the fact that the gap between the shell 18 and shaft 5 for the discharge of the working medium in particular is greater than that at the outer periphery of the primary wheel 2 between the primary wheel 2 and the shell 18, prevents the working fluid from the space between the shell 18th and the back of the primary wheel 2 flows into the working space 3. Thus, the remaining amount in the working space 3 is comparatively reduced.

Another fact, which counteracts the overflow of working fluid into the working space 3 when the secondary wheel 2 travels, is the comparatively higher flow pressure in the separating gap between the primary wheel 1 and the secondary wheel 2 in comparison to the flow pressure on the rear side of the secondary wheel 2. These favorable properties For example, they can be reinforced by providing corresponding blades or guides on the rear side or on the radially outer circumference of the secondary wheel 2 in order to convey working medium in the direction of the rear side of the secondary wheel 2 and thus away from the working space 3. In Figures 4 and 5 further measures are shown, which can be provided, for example, to prevent the working space 3 after the shutdown of the secondary 2 of the primary wheel 1 again filled more or automatically automatically emptied after the departure or further emptied , So an inlet 8 is provided to

Insert working medium in the working space 3. In the approached state of the secondary wheel 2 (Figure 4), the inlet 8 is not closed, whereas it is closed in the extended state of the secondary wheel 2 (Figure 5). This closing takes place automatically by the shutdown of the secondary wheel 2. In the embodiment shown, the outlet opening of the inlet 8 is an inlet opening of a bore 9 in the secondary wheel 2 opposite. The bore 9 opens into the working space 3. During axial displacement (retraction) of the secondary wheel 2, the bore 9 is moved along, so that the inlet 8 in the extended state of the secondary wheel 2 of the bore 9 no longer faces. Rather, the inlet 8 is then closed by a radially inner surface of the secondary wheel 2.

Additionally or alternatively, as shown in Figure 5, a bypass 21 may be provided, by means of which working medium in the worn state of the secondary wheel 2 is guided past the working space 3. In the present case, this is achieved in that the bypass 21 facing the inlet 8 in the worn state of the secondary wheel 2 such that the working fluid is passed from the inlet 8 through the bypass 21 and outside the working chamber 3 and the coupling shell 18 is output.

The bypass 21 is also executed in the case shown in the form of a bore through the secondary wheel 2. When approached, the secondary wheel 2, the mouth of the bypass 21 is axially offset from the inlet 8 and is covered by a radially outer surface of the shaft 5. Although in this case the secondary wheel is shown as axially displaceable, additionally or alternatively, the primary wheel may be axially displaceable in order to achieve the effect according to the invention.

Claims

claims 1. Hydrodynamic coupling 1.1 with a bladed primary wheel (1) and a bladed secondary wheel (2) axially facing each other and form a toroidal working space (3) which can be filled or filled with a working medium; 1.2 at least one of the two bladed wheels (2) is mounted on a thread (4), a helical gear or the like, so that it by a relative rotational movement relative to the thread (4), the Helical gearing or the like in a first direction from the other bladed wheel (1) in the axial direction of the hydrodynamic coupling is retractable, and by a relative rotational movement in a second, opposite to the first direction direction in the direction of the other bladed wheel (1) is approachable; characterized in that 1.3 the hydrodynamic coupling is free from a restoring device for the axially movable wheel (2), which acts on the movable wheel (2) directly or indirectly with a spring force or with an axial compressive force for the same procedure. 2. Hydrodynamic coupling according to claim 1, characterized in that the approach and retraction of the wheel movable in the axial direction (2) exclusively by selectively driving the primary wheel (1) or the secondary wheel (2) with a comparatively greater speed with respect to the other bladed wheel ( 1, 2) is feasible. 3. Hydrodynamic coupling according to one of claims 1 or 2, characterized in that the two bladed wheels (1, 2) are mounted on a common shaft (5). 4. Hydrodynamic coupling according to claim 3, characterized in that the shaft (5) has the thread (4) or the helical toothing on which / which the axially movable wheel (2) is directly mounted, and at least one bearing, in particular Rolling bearing (6), the other wheel (1) carries relatively stored. 5. Hydrodynamic coupling according to one of claims 1 to 4, characterized in that the hydrodynamic coupling is designed as a constant filling coupling with an always filled with working fluid, in particular substantially constantly filled, working space (3), wherein an external circuit for supplying and discharging Working fluid is provided in and out of the hydrodynamic coupling, or all working fluid is always kept within the hydrodynamic coupling. 6. Hydrodynamic coupling according to one of claims 1 to 5, characterized in that the bladed wheels (1, 2) are provided with an opposite to an axial section through the coupling angularly arranged blading (7), wherein the angle of attack is designed such that the Blades (7) of the two wheels (1, 2) are arranged to be mutually fleeing, when the movable wheel in the axial direction (2) is traveled by the other wheel (1), and are arranged spießend each other when the movable wheel (2) approached is arranged. 7. Hydrodynamic coupling according to one of claims 1 to 6, characterized in that an inlet (8) for supplying working fluid in the working space (3) is provided, and the inlet (8) by closing the wheel (2) is automatically closed , 8. Hydrodynamic coupling according to claim 7, characterized in that the inlet (8) in the form of a bore in a the retractable wheel (2) carrying shaft (5) is executed, which in particular in the axially to the another wheel (1) struck state of the retractable wheel (2) in the working space (3) opening bore (9) in the retractable wheel (2) facing, and the retractable wheel (2) closing the bore of the inlet (8) in the worn state or substantially occlusive. 9. hydrodynamic coupling according to one of claims 1 to 8, characterized in that a bypass (21) is provided for working fluid, by means of which working fluid within the clutch on the working space (3) can be vorbeileitbar, and this bypass (21) by the position of the abfahrbaren Rads (2) in the started state of the retractable wheel (2) is closed and opened in the worn state. 10. Hydrodynamic coupling according to one of claims 1 to 9, characterized in that on the working space (3) facing away from the axial Rear side of the movable wheel (2) a conveying device, in particular in the form of blades, projections and / or recesses, is provided to promote when moving the wheel (2) working fluid in the direction of the working space (3) away. 11. Turbocompound system comprising 11.1 an internal combustion engine (10) with a crankshaft (11); 11.2 an exhaust gas turbine (12), which is arranged in an exhaust gas flow (13) of the internal combustion engine (10), in particular in the flow direction behind an exhaust gas turbocharger; characterized in that 11.3 a hydrodynamic coupling (14) according to one of claims 1 to 10 is arranged in a drive connection between the crankshaft (11) and the exhaust gas turbine (12) whose primary wheel (1) in a drive connection to the exhaust gas turbine (12) and the secondary wheel ( 2) is connected in a drive connection to the crankshaft (11). 12. A method for operating a turbocompound system according to claim 11, comprising the following steps: in operating states in which the from the exhaust gas turbine (12) from the exhaust stream (13) recorded energy sufficient to drive the crankshaft (11) of the internal combustion engine (10) , becomes Drive power from the exhaust gas turbine (12) on the primary wheel (1) transferred so that this rotates faster than the secondary wheel (2), the secondary (2) is axially approached to the primary wheel (1) or stopped, and the primary wheel (1 ) drives the secondary wheel (2) via the working medium circuit in the working space (3); In operating states in which the energy taken up by the exhaust gas turbine (12) from the exhaust gas flow (13) is insufficient to drive the crankshaft (11) of the internal combustion engine (10), drive power is transmitted from the crankshaft (11) to the secondary wheel (2) so that it rotates faster than the primary wheel (1), the secondary wheel (2) is axially moved away from the primary wheel (1) or held off, and the power transmission from the secondary wheel (2) on the primary wheel (1) over the working medium circuit in the working space (3) is prevented or reduced. 13. The method according to claim 12, characterized in that the startup and shutdown of the secondary wheel (2) solely by setting said speed ratios between the primary wheel (1) and secondary wheel (2) and free of any additional mechanical or axial pressurization.