Arrangement for driving an adjusting shaft for adjusting the expansion stroke and / or the compression ratio of an internal combustion engine

Abstract

Arrangement for driving an adjusting shaft (2) for adjusting the expansion stroke and / or the compression ratio of an internal combustion engine (1), wherein the arrangement has a drive motor (11) which is or can be connected to the adjusting shaft (2) via a gear mechanism, characterized in that the gear mechanism is designed as a tension wave gear mechanism (13) with a wave generator (14), an externally toothed flexspline (16) and an internally toothed ring gear meshing with the flexspline (16), and is arranged in a gear housing (22) which is or can be fastened to the crankcase (25) of the internal combustion engine (1) in such a way that the flexspline (16) always remains in the same rotational position relative to the gear housing (22), wherein the tension wave gear mechanism (13) is designed to transmit a torque to the adjusting shaft (2), the coupling end of which executes an axial and / or radial movement in an externally driven manner,an output element (35) comprising the ring gear, which is torsionally rigid and at the same time flexible and at least partially, in particular completely, decouples the flexspline (16) from the externally driven axial and / or radial movement.

Description

The invention relates to an arrangement for driving an adjustment shaft for adjusting the expansion stroke and / or the compression ratio of an internal combustion engine, wherein the arrangement has a drive motor which is operatively connected or can be connected to the adjustment shaft in terms of drive technology via a transmission.The invention also relates to an internal combustion engine having such an arrangement.DE 10 2011 116 952 A1 discloses a multi-joint crank drive of an internal combustion engine, having a plurality of coupling members rotatably mounted on crankpins of a crankshaft and a plurality of articulation sliders rotatably mounted on crankpins of an adjustment shaft, wherein each of the coupling members is pivotably connected to a piston slider of a piston of the internal combustion engine and one of the articulation sliders and the rotational angle position of the adjustment shaft is adjustable within a specific rotational angle range by means of an adjustment device. It is provided here that the adjusting shaft can be fixed in at least one rotational angle locking position by means of a locking device. Specifically, it is proposed that the adjusting device has a gear with a drive wheel arranged on the adjusting shaft in a rotationally fixed manner. In particular, the gear is a worm gear, wherein the output wheel is designed as a worm wheel. This device is disadvantageously not very long-lived and is not very precise over the long term.EP 2 022 959 A2 discloses a device for variable adjustment of the compression, which device has a multi-joint crank drive and in which an adjusting device for adjusting the angle of rotation of an adjusting shaft comprises a lever arrangement. The adjusting shaft can be rotated via the lever arrangement and thus a desired rotational angle position can be set. This device, too, is disadvantageously not very long-lived and does not permit precise setting over the long term.DE 10 2011 120 162 A1 discloses an internal combustion engine with a variable compression. The internal combustion engine has a cylinder crankcase with a plurality of connecting rods mounted on a crankshaft and carrying a reciprocating piston, with an eccentric crankshaft mounting. The crankshaft bearings are connected to torsionally rigid connections. At least one gear segment and a gear comprising a gear wheel is arranged on one of the axially outer crankshaft bearings. Here, the gearwheel segment is fastened to this crankshaft bearing, wherein the gearwheel acts on the gearwheel segment for introducing a torque in order to adjust the eccentric crankshaft bearing. In this case, the gearwheel engages in the gearwheel segment perpendicularly to an axis of rotation of a crankshaft and perpendicularly to a cylinder axis of the cylinder crankcase.DE 41 27 487 A1 discloses a device for converting a rotational movement into a translational movement for papermaking machines or for plastic extrusion machines having a reduction gear driven by a drive unit which acts on a mechanical transmission element with a linearly movable actuator. In order to achieve, among other things, optimum positionability of the actuator with the drive that is as free from play as possible, with exact maintenance of the respectively approached position, a coaxial reduction gear designed to be self-locking with respect to a restoring torque exerted by the transmission element is provided, wherein the transmission element is not designed to be self-locking. The device known from DE 41 27 487 A1 does not disclose an internal combustion engine, in particular an internal combustion engine with an adjustable expansion stroke.DE 10 2009 006 633 A1 discloses an internal combustion engine having a crankshaft and an eccentric shaft driven by the crankshaft, which is connected to the crankshaft by connecting rods and coupling elements in order to extend an expansion stroke of pistons of the internal combustion engine. In order to make it possible in a simple manner to change the compression ratio ε during operation of the internal combustion engine, a phase adjustment device is provided with which the mutual phase relationship of the crankshaft and the eccentric shaft can be adjusted.From the German laid-open specification DE 10 2008 053 913 A1, a bearing arrangement for supporting the shaft generator of a tension shaft transmission with at least one bearing for supporting the shaft generator is known. The bearing is formed by at least one component of the tension wave gearing that performs a gearing function. The laid-open specification further discloses a tension wave transmission with such a bearing arrangement and a device for superimposing movements, in particular a camshaft adjusting device or a vehicle steering system.It is therefore the object of the present invention to specify an arrangement of the type mentioned at the beginning which allows precise and reliable setting of a desired rotational position of an adjustment shaft, in particular of an eccentric shaft, for adjusting the expansion stroke and / or the compression ratio of an internal combustion engine in a long-term manner.The object is achieved by an arrangement of the type mentioned at the beginning, which is characterized in that the transmission is designed as a tension wave transmission with a wave generator, an externally toothed flexspline and an internally toothed ring gear which is in toothed engagement with the flexspline and is arranged in a transmission housing which is fastened or can be fastened to the crankcase of the internal combustion engine in such a way that the flexspline always remains in the same rotational position relative to the transmission housing, wherein the tension wave transmission, for transmitting a torque to the adjustment shaft, the coupling end of which carries out an axial and / or radial movement, contains an output element which has the ring gear and is designed to be torsionally rigid and at the same time flexurally soft and at least partially, in particular completely, decouples the flexspline from the externally driven axial and / or radial movement.A strain wave gear is mostly constructed in such a way that it comprises a rigid, circular and internally toothed ring gear, which is referred to as a circular spline, and a radially flexible externally toothed gear, which is arranged in the interior of the rigid internally toothed ring gear and is referred to as a flex spline. In the externally toothed gear, a mostly elliptical wave generator is rotatably arranged by means of a rolling bearing which bends the radially flexible externally toothed gear into an elliptical shape in order to bring the toothings of the internally toothed gear and the radially flexible externally toothed gear into engagement with one another at each end of the ellipse main axis.In a manner according to the invention, it has been recognized that when such strain wave gearings are coupled to a shaft of a system, the coupling end of which, for example on account of system-induced bending movements, carries out movements, in particular periodic oscillation movements, in the radial and / or axial direction, in particular wobbling movements, the system and / or the strain wave gearing and / or the mechanical coupling can be damaged in particular by permanent loading.In a manner according to the invention, it has been further recognized that the forces and torques occurring when a transmission is coupled to a coupling end of a shaft, which executes oscillatory movements, such as wobble movements, in the radial and / or axial direction, have a particularly disadvantageous effect the greater the play of the transmission. It has therefore been further recognized that the fundamental use of a strain wave gearing for such applications, which is naturally free of play, is particularly advantageous.The use according to the invention of a tension shaft transmission for coupling to an adjusting shaft for adjusting the expansion stroke and / or the compression ratio of an internal combustion engine is therefore particularly advantageous.In a manner according to the invention, it was namely additionally recognized that an arrangement for adjusting the rotational position of an adjustment shaft of a system for adjusting the expansion stroke and / or the compression ratio, as is known from the prior art, does not only have to apply the torque for adjusting the adjustment shaft, but forces and torques act from the adjustment shaft on the arrangement, which loads the arrangement. These forces result from the fact that the internal combustion engine continuously and repeatedly transmits forces and torques to the adjusting shaft via the coupling mechanism via which it is coupled to the adjusting shaft. These forces cause, in particular, a bending of the adjustment shaft. In the region in which the arrangement for adjusting the adjusting shaft is coupled, forced radial oscillations of the adjusting shaft occur in particular, which loads the drive motor and or the transmission permanently. A play of the transmission which is already present would namely be increased after a relatively short time by the described permanent and high-frequency load such that a precise setting of a desired rotational position is no longer possible reliably.In addition to the freedom from play, which substantially protects the strain wave transmission itself from damage, the preferably flexurally soft and torsionally stiff, cup-shaped output bell of the output element, in particular the coupled system and the coupled mechanism, sustainably protect against damage due to radial and / or axial oscillatory movements, in particular wobbling movements, of the coupling end of the shaft to which the strain wave transmission is coupled.Preferably, the ring gear is rotatable, but supported in a fixed position, relative to a housing and / or the axis of symmetry of the tension shaft transmission by means of a ring gear bearing arrangement.In the sense of the present invention, the term output bell is understood to mean a component which is suitable and arranged for transmitting a torque from the ring gear to an output shaft, wherein the output bell does not necessarily have to have the shape of a classic bell, such as a Kirch bell. For example, it can also be cup-shaped and / or asymmetrical. The output bell does not necessarily have to be designed to be rotationally symmetrical. For example, the output bell can also have a plurality of spokes arranged at least partially radially. In particular, the output bell does not necessarily have to have a closed wall. However, a rotationally symmetrical embodiment of the output bell, in particular in the form of a pot or in a classic bell shape, is particularly advantageous since, in the case of such an embodiment, imbalance is avoided and the radial and / or axial forces to be absorbed always cause the same deformation, independently of the rotational position.By means of the flexurally soft and torsionally rigid output element, which can include, for example, a preferably flexurally soft and torsionally rigid, cup-shaped output bell, in combination with the stationary mounting of the ring gear, the flexspline, as well as the shaft generator and / or a dynamicspline and / or a ring gear mounting, are effectively at least largely decoupled from the radial and / or axial movements, in particular wobbling movements, which the shaft of the coupled system, in particular an adjusting shaft for adjusting the expansion stroke and / or the compression ratio, without the play-free transferability of a torque from the tension shaft transmission to the shaft or from the shaft to the tension shaft transmission being adversely affected. The ring gear bearing therefore has to accommodate at most a small residual portion of the radial and / or axial movements, in particular wobble movements.In particular, it can be advantageously provided that the ring gear bearing arrangement has at least one ring gear bearing which is designed as a plain bearing or as a rolling bearing, and / or that the ring gear bearing arrangement has at least one ring gear bearing which supports the ring gear in the radial and / or axial direction relative to a housing of the tension wave transmission. Alternatively or additionally, it is also possible for the ring gear bearing arrangement to have at least one ring gear bearing which radially surrounds the ring gear, and / or for the ring gear bearing arrangement to have at least one ring gear bearing which has a plain bearing or rolling bearing which coaxially surrounds the ring gear on its outer circumference. In a particular embodiment, the ring gear bearing arrangement has a plurality of support points surrounding the ring gear on its outer circumference. In order to prevent axial movements of the ring gear, it can advantageously be provided that the ring gear bearing arrangement has at least one ring gear bearing which bears axially against the ring gear.In a special embodiment, the stationary mounting of the ring gear takes place via the mounting of the wave generator and via the flexspline, so that the bearings of these components simultaneously form the ring gear bearing arrangement. In such an embodiment, the output element is preferably designed to be particularly flexurally soft in order to avoid overloading of the other components of the transmission.The output element is preferably designed to be elastic in such a way and the hollow shaft bearing is dimensioned in such a way that radial movements of a coupled adjusting shaft can occur in the range from 0 to 1 / 4000 of the diameter of the ring gear, in particular in the range from 0 to 1 / 2000 of the diameter of the ring gear, in particular in the range from 0 to 1 / 1000 of the diameter of the ring gear, in particular in the range from 0 to 1 / 100 of the diameter of the ring gear, without these movements of the coupled shaft leading to a movement of the ring gear and without the output element being damaged.Alternatively or additionally, the output element is preferably designed to be elastic in such a way and the hollow shaft bearing is dimensioned in such a way that axial movements of a coupled adjusting shaft can occur in the range from 0 to 1 / 4000 of the diameter of the ring gear, in particular in the range from 0 to 1 / 2000 of the diameter of the ring gear, in particular in the range from 0 to 1 / 1000 of the diameter of the ring gear, in particular in the range from 0 to 1 / 100 of the diameter of the ring gear, without these movements of the coupled shaft leading to a movement of the ring gear and without the output element being damaged.Preferably, the output element is rigid with respect to forces acting in the tangential direction in order to achieve a torsional rigidity for the delay-free transmission of torques to the coupled shaft. The output element preferably has a torsional rigidity which is so great that the output element is twisted by less than one radians over its axial length when a torque of 10,000 Nm, in particular of 20,000 Nm, in particular of 50,000 Nm, in particular of 100,000 Nm, is applied to it.In a special embodiment, the radial distance from the root circle of the internal toothing of the ring gear to the outer circumference of the ring gear is more than four times greater, in particular more than ten times greater, in particular more than 25 times greater, than the wall thickness of the output bell and / or the wall thickness of the output bell in a bending region of reduced wall thickness. Such an embodiment offers a particularly good ratio of stability, flexibility and torsional rigidity. Alternatively or additionally, the wall thickness of the driven bell can be in particular 0.2 mm to 1.5 mm, in particular 0.3 mm to 0.7 mm, in particular 0.4 to 0.5 mm. Such a wall thickness is advantageous largely independently of the diameter of the ring gear.In a special embodiment, the quotient of the axial length of the ring gear and the axial length of the output bell is in the range from 0.25 to 1.2, in particular in the range from 0.5 to 1.1. Such embodiments have the advantage that the ring gear is sufficiently wide for the torques to be transmitted and that a sufficient torsional rigidity is present for these torques. This is especially true when the output bell has the wall thickness described above.In a special embodiment, the tension shaft transmission is designed as an annular transmission. In such an embodiment, the elastic flexspline is not embodied in pot shape, but in ring shape (flexring). Such a construction is advantageously particularly compact in particular axially, which substantially facilitates the connection to an internal combustion engine, for example. In addition, such an embodiment of the tension wave transmission is particularly insensitive to radial and / or axial oscillations, in particular wobbling movements, of a coupled adjusting shaft. This is in contrast to a top-shape design because a flex pot, which is sensitive to radial loads, in particular permanent radial loads, due to its flexibility and the oval deformation, is not present. However, a design of the strain wave transmission with a flexspun is basically possible.As already mentioned, the output element, in particular the output bell, is designed to be torsionally rigid with respect to torques whose torque vector is aligned axially. Such a configuration can be realized in particular in that an essentially circular cylindrical section of the output bell has the largest possible diameter, in particular a diameter in the region of the diameter of the ring gear. Furthermore, it can advantageously be provided that the circular cylindrical section is adjoined by a base section, in particular in the form of a circular disk, which is arranged in a radial plane.As likewise already mentioned, the output element, in particular an output bell of the output element, is designed to be flexurally flexible in order to be able to compensate for the radial movements and / or axial movements, in particular wobble movements, carried out by a coupling end of a coupled shaft. In particular, the output element can be designed to be elastic with respect to forces which act in the axial direction and / or in the radial direction. In order to achieve this, the base portion and / or the circular cylindrical portion can be designed to be corrugated. In particular, the output element, in particular the output bell, can have a bellows-like region. The shafts are preferably arranged concentrically with respect to the ring gear and / or an output shaft.In a special embodiment, the output element, in particular the output bell, is designed as a coupling that is radially flexible and / or bendable transversely to the axial direction and torsion-resistant. The coupling can advantageously be designed, for example, as a claw coupling or as a multiplate coupling or as a flexible shaft coupling or as an Oldham coupling or as a bellows coupling. The use of a multiplate clutch is particularly advantageous because, due to its construction, it requires few components. In particular, in a multiplate clutch, unlike, for example, in an Oldham clutch, no movable components need to be mounted so as to slide relative to one another. The coupling does not necessarily have to be designed as a releasable coupling.In a very particularly advantageous embodiment, in particular in an embodiment which has an output element produced in one piece from a raw material, no further device for decoupling radial and / or axial, in particular wobble movements, of the adjustment shaft is connected between the adjustment shaft and the output element of the tension shaft transmission.An embodiment in which the output element, in particular the output bell, has no movable components and / or is formed in one piece is very particularly advantageous. The output element, in particular the output bell, can be produced, in particular also together with the ring gear and / or an output shaft, from a single piece of raw material, in particular in a machining process, such as, for example, a turning process with a subsequent milling or impact process. In the case of a driven element produced in one piece, for example, flexibility with simultaneous torsional rigidity can be realized by a bending section which has a smaller wall thickness than the other sections of the driven bell or by a bellows-like corrugated region.Also, regardless of whether or not the output element, in particular the output bell, has movable components, at least one bending section with a reduced wall thickness can be present in order to achieve flexibility while at the same time providing torsional rigidity. In particular, the bending section can advantageously be arranged in a transition region from a circular cylindrical section to a base section.In a special embodiment, the output element has an output shaft which is connected to the output bell in a rotationally fixed manner and is preferably arranged on the axis of symmetry of the tension shaft transmission. A drive shaft of a system to be driven, for example a system for adjusting the expansion stroke and / or the compression ratio of an internal combustion engine, can be coupled to the output shaft. It is also possible for the output shaft to transition integrally into the drive shaft of a system to be driven or at the same time to be the drive shaft of a system to be driven.In an embodiment of the tension wave gearing that is space-saving and particularly robust, the ring gear and the output shaft are arranged at mutually opposite ends of the output bell.An embodiment is particularly robust in which the output element, in particular the output bell, is produced integrally together with the ring gear and / or in which the output element, in particular the output bell, is produced integrally together with the output shaft. For example, the output bell and in particular the entire output element can be produced from a single piece of raw material in a machining process, such as a turning process.In a particularly advantageous embodiment, the ring gear is mounted in a sliding manner, in particular exclusively. Such an embodiment is particularly robust and solid. In particular, such an embodiment can be designed in such a way that, despite the flexibility, radial and / or axial movements coupled in via the transmission output drive are derived via the plain bearing and further components of the arrangement, for example a transmission or actuator housing, to a housing, in particular a crankshaft housing, of the internal combustion engine and / or to a vehicle body. A plain bearing also has the very particular advantage that it can be made very robust and, in addition, can be produced cost-effectively. Such an embodiment also has the advantage that it is particularly long-lived and the effects of cumulative forces and / or torques, which ultimately lead to early wear, can be effectively avoided.As already mentioned, the ring gear can be designed as a circular spline or as a dynamic spline.According to the invention, the flexspline always remains in the same rotational position relative to a transmission housing. In particular, it can be advantageously provided that the flexspline is held in its housing-fixed rotational position by means of a housing-fixed, internally toothed dynamicspline, which has the same number of teeth as the flexspline. Alternatively, it can also be provided that the flexspline is fastened directly to the housing.An arrangement for driving an adjustment shaft for adjusting the expansion stroke and / or the compression ratio of an internal combustion engine is particularly advantageous, wherein the arrangement has a drive motor which is operatively connected to the adjustment shaft by a tension shaft transmission according to the invention in a driving manner.In this case, it can advantageously be provided that the drive motor and the strain wave gearing are arranged in a common housing. The housing may also include additional components, such as a clutch for coupling to an internal combustion engine. In particular, it can advantageously be provided that the arrangement for driving an adjustment shaft is designed as an actuator module, which can be coupled to an internal combustion engine as a prefabricated system part.The drive motor and the tension shaft gear can advantageously be arranged coaxially with respect to one another or arranged axially parallel to one another. However, other arrangements are also possible.A particularly advantageous embodiment includes a blocking device for blocking a rotational movement of a rotational component of the drive motor or of the transmission. Such an embodiment has the particular advantage that the arrangement for driving an adjustment shaft for adjusting the expansion stroke and / or the compression ratio-and thus indirectly also the adjustment shaft itself-can be held in a predefined position, in particular an emergency position, for example in the event of a fault. In this way, it is advantageously prevented that the system is left over in an uncontrolled manner in the event of a fault and settings are reached which are disadvantageous for emergency operation or even lead to damage to the arrangement for driving and / or the internal combustion engine.It can also be advantageously avoided by means of a locking device that when the system is switched off-for example when the vehicle is switched off-the crankshaft is unintentionally rotated relative to the adjustment shaft, which would result in the actual rotational angle of the adjustment shaft not matching the original rotational angle which a controller has stored as the last one after the switching on again.In particular, the blocking device can have a movable blocking bolt which can be moved from a release position into a blocking position in which the blocking bolt engages into a locking receptacle of the rotation component in order to block a rotational movement of the rotation component.For example, it can be advantageously provided that a movable locking bolt is pressed into the blocking position by means of a spring device and that an adjusting device, for example an electromagnet, is provided in order to pull the locking bolt into the release position against the force of the spring device. However, this embodiment has the disadvantage that the locking bolt is automatically transferred into the blocking position in the event of a fault, for example in the event of a power failure, and the blocking can only be released again with difficulty.In a very particularly advantageous embodiment, it is provided that the locking bolt can be moved by an adjusting means from the release position counter to the force of a restoring element into the blocking position and that the locking bolt can be fixed in the blocking position by means of the rotational component, for example by frictional engagement and / or by positive engagement. Such a system solves the conflict of goals that, on the one hand, blocking, in particular automatic blocking, can take place in the presence of a fault, such as in particular in the event of a power failure, and that the blocking can be released again despite the fault.Because the locking bolt can be held in the blocking position by means of the rotational component against the force of the restoring element, a bistable system is created de facto-also in the fault situation. On the one hand, the blocking position can be maintained by means of the rotation component itself; on the other hand, the rotation component can release the locking bolt, so that the restoring element, which can be designed, for example, as a spring tensioned in the blocking position, can move the latter into the release position.The drive motor can advantageously be designed, for example, as a brushless motor and / or as a direct current motor. In a special embodiment, which can be designed to be very compact in particular, the drive motor is designed as a hollow shaft motor. In particular, the drive motor can advantageously be designed as an electronically commutated three-phase motor.In a particularly advantageous embodiment, the tension shaft transmission and / or the arrangement for driving an adjustment shaft for adjusting the expansion stroke and / or the compression ratio have a rotational position sensor in order to be able to measure the rotational angle position of at least one rotational component of the drive motor and / or of the transmission and / or of the adjustment shaft directly or indirectly.In a particularly advantageous manner, the arrangement for driving an adjustment shaft for adjusting the expansion stroke and / or the compression ratio can contain a control and sensor module. In particular, it can be advantageously provided that different control and sensor modules are available for use with different internal combustion engines, so that an arrangement according to the invention for driving an adjustment shaft can be easily adapted to changed requirements by replacing the control and sensor module. Advantageously, it can be provided in particular that the control electronics of such a control and sensor module contain both the functional electronics which are basically necessary-for example for controlling and / or regulating commutation-at all in order to be able to operate a drive motor of an actuator, and the actual command electronics which control or regulate the desired parameters, such as the direction of rotation and / or rotational speed and / or torque and / or rotational position, etc. In an advantageous manner, it can also be provided in particular that the rotational position sensor already mentioned above is a component of the control and sensor module.An internal combustion engine with an adjustment shaft for adjusting the expansion stroke and / or the compression ratio is particularly advantageous, which has an arrangement according to the invention for adjusting the adjustment shaft. Such an internal combustion engine is distinguished in particular in that the expansion stroke and / or the compression ratio can be adjusted exactly and reliably even over longer periods of use.In a particularly advantageous embodiment of the internal combustion engine, an adjustment of the expansion stroke and / or the compression ratio is possible exclusively at a predefined or predefinable phase position of the crankshaft of the internal combustion engine. In particular, it can be provided that the arrangement, in particular the drive motor of the arrangement, can be activated exclusively at a predetermined or predeterminable phase position of the crankshaft of the internal combustion engine. In this way, it can be achieved that an adjustment is carried out exclusively in periods of the working stroke of the internal combustion engine that are favorable for this purpose.Alternatively or additionally, it can also be provided that the tension wave transmission is designed as a non-re drivable transmission. In this way, it is ensured that a setting made is maintained even when the drive motor is temporarily switched off, for example for energy saving.The coupling of the adjusting shaft to a crankshaft of the internal combustion engine can be realized, for example, via a multi-joint crank drive.The subject matter of the invention is schematically illustrated in the drawing, in particular on the basis of examples of applications for setting the expansion stroke and / or the compression ratio of an internal combustion engine, and is described below with reference to the figures, wherein elements which are the same or act in the same way are usually provided with the same reference symbols. The following are shown: FIGS. 1 and 2 are each an overview illustrating the phenomenon of transmission of forces and torques via an adjustment shaft to an arrangement for adjusting the rotational position of the adjustment shaft, FIG. 3 shows an exemplary embodiment of an arrangement according to the invention for adjusting the rotational position of an adjusting shaft, FIG. 4 shows a second exemplary embodiment of an arrangement according to the invention for adjusting the rotational position of an adjusting shaft, FIG. 5 shows an exemplary embodiment of a voltage wave transmission for an arrangement according to the invention, and FIG. 6 shows a further exemplary embodiment of a strain wave transmission for an arrangement according to the invention.FIG. 1 shows schematically in cross section an internal combustion engine 1 with a multi-joint crank drive, with which the expansion stroke and the compression ratio can be adjusted. For adjustment, an adjustment shaft 2, which can be designed as an eccentric shaft, is rotated and the adjustment movement is transmitted via an adjustment rod 3 and an adjustment lever 4 connected in an articulated manner to the adjustment rod 3. The piston 5 of the internal combustion engine 1 shown in this figure is coupled to the adjusting lever in an articulated manner via a connecting rod 6. The adjusting lever 4 is in turn coupled to a crankshaft 8 via a lifting arm 7.Mass and gas forces F of the piston 5 act on the connecting rod 4 in an oscillating manner and with alternating signs, which are transmitted to the adjusting shaft 2 via the adjusting lever 4 and the adjusting connecting rod 3.FIGS. 2 aand 2 bschematically show this situation in a longitudinal cross-sectional view. The adjusting shaft 2 is mounted several times, for example in the crankcase, and is continuously and repeatedly loaded at different points by the described forces F. Due to the described forces, the adjustment shaft bends and tilts in the bearings, which is illustrated in FIG. 2 b. In the end region 9 shown in FIG. 2 b, in which an arrangement for adjusting the adjusting shaft 2 is to be coupled, forced radial oscillations of the adjusting shaft 2 occur in particular, which can load the drive motor and or the transmission of an arrangement for adjusting in a sustained manner.FIG. 3 shows an exemplary embodiment of an arrangement 10 according to the invention for adjusting the rotational position of an adjustment shaft 2, in particular an eccentric shaft. The arrangement 10 has a drive motor 11 and a backlash-free gear 12 connected downstream of the drive motor 11, which is designed as a strain wave gear 13 in the form of an annular gear.The tension wave transmission 13 has a wave generator 14 which is driven by the drive motor 11 and is elliptical in cross section. The wave generator 14 is rotatably mounted in an annular flexspline 16 by means of a rolling bearing 15 and deforms it. The flexspline 16 engages with its external toothing both in the internal toothing of a dynamicspline 17 firmly connected to a transmission housing 22 and in the internal toothing of a circularspline 18.The circular spline 18 forms the transmission output and is coupled to the adjusting shaft 2 in a rotationally fixed manner via a coupling 19 which is radially flexible and / or bendable transversely to the axial direction and which is torsionally rigid, for example, can be designed as a steel plate coupling 20.The circular spline 18 is mounted rotatably radially relative to the transmission housing 22 via a first slide bearing 21. In addition, a coupling plate 23 connected in a rotationally fixed manner to the circular spline 18 for connecting the circular spline 18 to the clutch 19-and thus indirectly also the circular spline 18 itself-is rotatably mounted axially by means of a second slide bearing 24.The transmission housing 22 is directly fixed to the crankcase 25 of an internal combustion engine.FIG. 4 shows a second exemplary embodiment of an arrangement 10 according to the invention for adjusting the rotational position of an adjusting shaft 2. in this embodiment, the drive motor 11, unlike in the embodiment shown in FIG. 3, is coupled axially parallel to the transmission 12 and the adjusting shaft 2. In this embodiment, the torque is transmitted from the drive motor 11 to the shaft generator 14 of the tension shaft transmission 13 via a traction drive, namely a belt drive 26. The belt drive 26 has a first belt pulley 27 coupled to the drive motor 11 and a second belt pulley 28 coupled to the wave generator 14, as well as a belt 29. In this embodiment, the wave generator 14 is rotatably mounted relative to the transmission housing 22 by means of further rolling bearings 30.In the second exemplary embodiment, too, the circular spline 18 forms the transmission output which is coupled to the adjusting shaft 2 in a rotationally fixed manner via a coupling 19 which is radially flexible on the one hand and / or bendable transversely with respect to the axial direction and on the other hand torsionally rigid, which coupling can be designed, for example, as a steel plate coupling 20.In the second exemplary embodiment, too, the circular spline 18 is mounted rotatably radially relative to the transmission housing 22 via a first slide bearing 21. In addition, a coupling plate 23 connected in a rotationally fixed manner to the circular spline 18 for connecting the circular spline 18 to the clutch 19-and thus indirectly also the circular spline 18 itself-is rotatably mounted axially by means of a second slide bearing 24.FIG. 5 shows an exemplary embodiment of a strain wave transmission 13 with a wave generator 14, an externally toothed flexspline 16 for an arrangement according to the invention. The wave generator 14 is rotatably mounted in an annular flexspline 16 by means of two rolling bearings 33, 34 and deforms the latter. The flexspline 16 engages with its external toothing both in the internal toothing of a first ring gear, namely a dynamicspline 17, and in the internal toothing of a second ring gear, namely a circularspline 18. The dynamic spline 17 has a bore 32 in order to be able to fix it in a rotationally fixed manner, for example in a transmission housing 22, by means of a screw connection.The tension shaft transmission 13 has an output element 35 which has the circular spline 18 and a pot-shaped output bell 36 connected to it in a rotationally fixed manner, and an output shaft 37. The output bell 36 is manufactured in one piece together with the circular spline 18 and the output shaft 37. The driven bell 36 is flexible and at the same time torsion-resistant.FIG. 6 shows a further exemplary embodiment of a strain wave transmission 13 for an arrangement according to the invention, which corresponds in its basic structure to the strain wave transmission 13 shown in FIG. 5 and which is arranged in a transmission housing 22. The dynamic spline 17 is fixed in the transmission housing 22 in a rotationally fixed manner, while the circular spline 18 is rotatably mounted relative to the transmission housing 22 via a slide bearing, not shown in this figure.The tension shaft transmission 13 has an output element 35 which has the circular spline 18 and a pot-shaped output bell 36 connected to it in a rotationally fixed manner, and an output shaft 37. The output bell 36 is manufactured in one piece together with the circular spline 18 and the output shaft 37. The output shaft 37 is designed as a hollow shaft, for example for coupling to an adjusting shaft of a system for adjusting the expansion stroke and / or the compression ratio of an internal combustion engine. The driven bell 36 is flexible and at the same time torsion-resistant.List of reference numbers:1 Internal combustion engine 2 Adjusting shaft 3 Adjusting connecting rod 4 Adjusting lever 5 Piston 6 Connecting rod 7 Lifting arm 8 Crankshaft 9 End region of the adjusting shaft 2 10 Arrangement for adjusting the rotational position of the adjusting shaft 2 11 Drive motor 12 Play-free transmission 13 Tension shaft transmission 14 Shaft generator 15 Rolling bearing 16 Flexspline 17 Dynamicspline 18 Circularspline 19 Clutch 20 Steel plate clutch 21 First sliding bearing 22 Transmission housing 23 Coupling plate 24 Second sliding bearing 25 Crankcase 26 Belt drive 27 First belt pulley 28 Second belt pulley 29 Belt 30 Further rolling bearing 31 Holding device 32 Bore 33 Rolling bearing 34 Rolling bearing 35 Output element 36 Output bell 37 Output shaft

Claims

Arrangement for driving an adjusting shaft (2) for adjusting the expansion stroke and / or the compression ratio of an internal combustion engine (1), wherein the arrangement has a drive motor (11) which is operatively connected or can be connected to the adjusting shaft (2) by means of a transmission in terms of drive engineering, characterized in that the transmission is designed as a tension shaft transmission (13) having a shaft generator (14), an externally toothed flexspline (16) and an internally toothed ring gear which is in toothed engagement with the flexspline (16), and is arranged in a transmission housing (22) which is fastened or can be fastened to the crankcase (25) of the internal combustion engine (1) in such a way that the flexspline (16) always remains in the same rotational position relative to the transmission housing (22), wherein the tension shaft transmission (13) for transmitting a torque to the adjusting shaft (2), their coupling external gears execute an axial and / or radial movement, including an output element (35) having the ring gear, which is designed to be torsionally stiff and at the same time flexurally soft and at least partially, in particular completely, decouples the flexspline (16) from the external-gear axial and / or radial movement.Arrangement according to Claim 1, characterized in that the ring gear is mounted rotatably, but in a fixed manner, by means of a ring gear bearing arrangement relative to a housing of the arrangement or of the tension shaft transmission (13) and / or relative to the axis of symmetry of the tension shaft transmission (13).Arrangement according to Claim 2, characterized in that a. the ring gear bearing arrangement has at least one ring gear bearing which is designed as a plain bearing (21) or as a rolling bearing (15), and / or in that b. the ring gear bearing arrangement has at least one ring gear bearing which supports the ring gear in the radial and / or axial direction relative to a housing of the tension shaft transmission (13), and / or in that c. the ring gear bearing arrangement has at least one ring gear bearing which radially surrounds the ring gear, and / or in that d. the ring gear bearing arrangement has at least one ring gear bearing which has a plain bearing (21) or rolling bearing (15) which surrounds the ring gear coaxially on its outer circumference, and / or in that e. the ring gear bearing arrangement has a plurality of supporting points which surround the ring gear on its outer circumference, and / or in that f. the ring gear bearing arrangement has at least one ring gear bearing which bears axially on the ring gear.Arrangement according to one of Claims 1 to 3, characterized in that the output element (35) has an output bell (36) and / or in that the output element (35) has an output bell (36) which is torsionally rigid and at the same time flexurally soft.Arrangement according to one of Claims 1 to 4, characterized in that a. the output element (35)) is designed to be torsionally rigid with respect to torques whose torque vector is aligned axially, and / or in that b. the output element (35) is designed to be elastically resilient with respect to forces which act in the axial direction and / or in the radial directionArrangement according to one of Claims 1 to 5, characterized in that the output element (35) is designed as a coupling (19) which is radially flexible on the one hand and / or bendable transversely with respect to the axial direction and is torsionally rigid on the other hand.Arrangement according to one of Claims 1 to 6, characterized in that a. the output element (35) has at least one bending section with a reduced wall thickness, and / or in that b. the output element (35) has a region which is designed in the manner of a bellows.Arrangement according to one of Claims 1 to 7, characterized in that the output element (35) has a circular-cylindrical section and / or in that it has a base section which extends in the radial direction.Arrangement according to claim 8, characterised in that a. the base section is formed elastically and / or that b. the base section and / or the circular cylindrical section is wavy and / or that c. the circular cylindrical section and the base section merge into one another in a region with reduced wall thickness.Arrangement according to one of Claims 1 to 9, characterized in that a. the output element (35) has an output shaft (37) which is connected to the ring gear in a rotationally fixed manner, and / or in that b. the output element (35) has an output shaft (37) which is arranged on the axis of symmetry of the tension shaft transmission (13) and is connected to the ring gear in a rotationally fixed manner.Arrangement according to Claim 10, characterized in that the ring gear and the output shaft (37) are arranged at mutually opposite ends of the output bell (36).Arrangement according to Claim 4 or according to one of Claims 5 to 11 insofar as it relates back to Claim 4, characterized in that a. the output bell (36) is produced integrally together with the ring gear, and / or in that b. the output bell (36) is produced integrally together with the output shaft (37), and / or in that c. the output element (35) has a coupling element for coupling the shaft, and / or in that d. the output element (35) has a coupling element for coupling the shaft, which coupling element has a smaller diameter than the ring gear.Arrangement according to one of Claims 1 to 12, characterized in that the ring gear is a circular spline (18) or a dynamic spline (17).Arrangement according to one of Claims 1 to 13, characterized in that a. the drive motor (11) and the tension shaft transmission (13) are arranged in a common housing, and / or in that b. the output element (35) and the adjusting shaft (2) are produced jointly in one piece.Arrangement according to Claim 13 or 14, characterized in that the drive motor (11) and the strain wave gear (13) are arranged coaxially with respect to one another, or in that the drive motor (11) and the strain wave gear (13) are arranged axially parallel with respect to one another.Arrangement according to one of Claims 13 to 15, characterized bya blocking device for blocking a rotational movement of a rotational component of the drive motor (11) or of the tension shaft transmission (13).Arrangement according to claim 16, characterised in that the blocking device has a movable blocking bolt which is movable from a release position into a blocking position in which the blocking bolt engages into a locking receptacle of the rotary component in order to block a rotational movement of the rotary component.Internal combustion engine having an arrangement according to one of Claims 1 to 17.Power shaft transmission (13) for producing an arrangement according to one of Claims 1 to 17 and / or for producing an internal combustion engine (1) according to Claim 18.

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