Abstract:
A coaxial transmission, especially a hollow shaft transmission for industrial drive engineering, having a high power density. The transmission comprises an input element ( 7 ), an element ( 3 ) and an output element, a drive torque being multiplied and transmitted between the input element ( 7 ) and the output element via a plurality of radially mobile toothed sections ( 5 ). At least one toothed section ( 5 ) has a bearing element ( 11 ) which is enlarged in its effective zone with respect to an input element ( 7 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a coaxial transmission, especially hollow shaft transmission for industrial drive engineering, having high power density, with a drive element, with an element and with an output element, a step-up and a transfer of a drive torque between the drive element and output element taking place via a plurality of radially movable toothed segments, the at least one toothed segment having a supporting element in the range of action with respect to the drive element. 
         [0002]    Conventional transmissions are known and obtainable commercially in any form and version. 
         [0003]    Essentially three different technologies of transmissions are employed commercially. On the one hand, epicyclic transmissions are known commercially, in which, for example within a ring wheel, one or more planet wheels are provided coaxially, by means of a mostly centrally arranged sunwheel, with the transfer of a torque to a planet wheel carrier or an output element. 
         [0004]    In planetary or epicyclic transmissions of this type, they cannot run at high transfer speeds and, because generally there are only very small possible hollow shaft diameters, they cannot transfer high torques. Moreover, transmissions of this type suffer from low rigidity and low robustness and have a low overload capacity. 
         [0005]    Furthermore, there is the disadvantage that, especially in case of high drive-side rotational speeds, a step-up or a step-up ratio is restricted. 
         [0006]    Furthermore, eccentric transmissions are known in which, mostly, a planet wheel is provided within an internally toothed ring wheel for transferring the torques and for effecting step-ups. 
         [0007]    The disadvantage of eccentric transmissions is that these require high separating forces in very large bearing elements, especially in hollow shaft versions, and are suitable only for hollow shaft versions having a smaller diameter. Even here, these eccentric transmissions have low overload capacities and low robustnesses. 
         [0008]    Moreover, the step-up ranges are restricted to about i=30 to i=100, and only at low drive rotational speeds. At higher drive rotational speeds, eccentric transmissions of this type are subject to high wear and therefore have a short service life, which is undesirable. 
         [0009]    Moreover, eccentric transmissions of this type have high frictional losses and therefore low efficiencies when clutches or the like follow eccentric transmissions in order to shift eccentric output movement to a centric movement. Efficiency of the eccentric transmission is therefore very low. 
         [0010]    Especially at high rotational speeds, serious vibration problems arise which are likewise undesirable. 
         [0011]    Furthermore, harmonic drive transmissions are known, which, indeed, can also be implemented as hollow shaft transmissions, there being arranged between the drive element of mostly oval design and an internally toothed ring wheel a flexible spline, as it is known, which is designed to be soft and resilient and which transfers the corresponding torque between the drive and ring wheel and allows a step-up. 
         [0012]    The flexible spline, as it is known, is subject to permanent loads and often fails under high torques. Moreover, the flexible spline does not have overload capacity and often quickly breaks off when torques are too high. Furthermore, the harmonic drive transmission has poor efficiency and low torsional rigidity. 
         [0013]    DE 31 21 64 represents the prior art closest to the present invention. Said document relates to a self-locking shift transmission in which a plurality of arms, which are arranged in a stellate fashion around a shaft, are mounted with their inner ends eccentrically on the shaft. The arms are designed as two-armed levers, their centers of rotation are guided in a crossed fashion and their inner ends rest independently of one another on the driving eccentric, such that the outer ends perform a connecting rod movement. Here, said ends engage in succession into the gearwheel and drive the latter in the opposite direction to the rotation of the driveshaft. The contact surfaces are widened in relation to the tooth roots. However, said contact surfaces are fixedly connected, not connected loosely or in a joint-like manner, to the tooth or toothed wheel. 
         [0014]    The object on which the present invention is based, therefore, is to provide a coaxial transmission of the type initially mentioned, which eliminates said disadvantages of the hitherto known coaxial transmissions, epicyclic transmissions, eccentric transmissions and harmonic drive transmissions, while force transfer between the drive element and toothed segment is to be improved markedly with the transfer of very high forces. 
         [0015]    Moreover, the coaxial transmission is to have very high compactness and complexity, with the smallest possible installation space and lowest possible weight at a certain power rating. 
         [0016]    The fact that the supporting element is movable, in particular in an articulated manner, in a joint-like manner, pivotably connecting or supported slidably, with respect to a basic body of the respective toothed segment and that the supporting segments together result in a segmented mounting leads to the achievement of this object. 
       SUMMARY OF THE INVENTION 
       [0017]    In the present invention, it has proved advantageous to provide a coaxial transmission in which a plurality of toothed segments are linearly guided radially outward within an element. 
         [0018]    The individual toothed segments have at one end corresponding tooth flanks which engage into corresponding tooth spaces of an outer ring wheel. 
         [0019]    The toothed segments are moved into the toothing of the ring wheel by means of a drive element which possesses an outer profiling and an outer contour, in order to effect a stepped-up rotational movement by means of a corresponding rotational drive movement. 
         [0020]    In this case, it has proved especially advantageous, in the present invention, to form enlarged supporting elements in the root region of the toothed segments, in order to transfer very high radially acting forces of the drive element, especially of its profiling, to the toothed segment. 
         [0021]    In this case, the supporting elements may be connected to the toothed segment in a joint-like manner directly or indirectly, via intermediate elements, intermediate bearings or joints, or directly in one piece via corresponding contractions, narrowings or the like. 
         [0022]    As a result of a greater length of the supporting elements in relation to the thickness of the toothed segment, the contact area of the supporting elements is markedly enlarged, so that there, in this region, a plurality of bearing elements transfer the forces of the drive element to the toothed segment. High load distribution occurs, and therefore even very high rotational speeds of the coaxial transmission, along with high torque transfer, can be ensured. 
         [0023]    Furthermore, it has proved especially advantageous that the individual supporting elements adjacent to one another engage one in the other on the end faces and allow a certain play in the circumferential direction and in the radial direction. 
         [0024]    However, an axial play is ensured by a corresponding engagement of end-face projections into corresponding adjacent recesses of the adjacent supporting elements. 
         [0025]    The bearing elements are preferably needle rollers or balls which can be inserted, fully fitted or spaced apart individually, in cages or spacers with positive guidance. 
         [0026]    In this case, it is also to come within the scope of the present invention that an additional distribution of the forces becomes possible, for example via an additional elastic bearing outer ring, between an underside of the supporting element and the bearing elements. 
         [0027]    Overall, the present invention provides a coaxial transmission, in which extremely high forces can be transferred at very high speeds from the drive element to the radial movement of the toothed segments and therefore to the toothing of the ring wheel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    Further advantages, features and details of the invention may be gathered from the following description of preferred exemplary embodiments and with reference to the drawing, in which: 
           [0029]      FIG. 1   a  shows a diagrammatically illustrated cross section through a coaxial transmission; 
           [0030]      FIG. 1   b  shows a perspective top view of part of the coaxial transmission in the region of the drive element and toothed segments; 
           [0031]      FIG. 1   c  shows a part cross section, illustrated enlarged, of the coaxial transmission according to  FIG. 1   a;    
           [0032]      FIG. 2  shows a diagrammatically illustrated perspective illustration of a further exemplary embodiment of a coaxial transmission in the region of toothed segments and the drive element; 
           [0033]      FIGS. 3   a  to  3   c  show cross-sectionally enlarged illustrations of individual toothed segments with different directly or indirectly connected and adjoining supporting elements for support on bearing outer rings or needle bearings; 
           [0034]      FIG. 4  shows a diagrammatically illustrated perspective illustration of part of a further exemplary embodiment of a coaxial transmission with toothed segments and supporting elements; 
           [0035]      FIG. 5  shows a perspective bottom view of an exemplary embodiment of a supporting element for transferring the thrust movement of the toothed segments. 
       
    
    
     DETAILED DESCRIPTION 
       [0036]    According to  FIG. 1   a , a coaxial transmission R 1  has a ring wheel  1  which possesses an internal toothing  2  with a plurality of tooth spaces  2 ′. An element  3  is inserted in an annulus-like manner within the ring wheel  1 , a plurality of toothed segments  5  being inserted radially next to one another and into corresponding guides  4  in the annulus-like element  3 . The toothed segments  5  are mounted so as to be displaceable radially to and fro within the guide  4  and have a tooth flank  6 . 
         [0037]    Within the element  3  having received toothed segments  5  is provided a drive element  7  designed as a shaft or as a hollow shaft and having an outer profiling  8  which, for example with a contour  9 , may be designed as an elevation in the polygonal or cam-like manner. 
         [0038]    Bearing elements  10  are likewise provided between the outer contour  9  of the profiling  8  of the drive element  7  and the toothed segments  5 , as is indicated especially in  FIGS. 1   b  and  1   c.    
         [0039]    In the present invention, it has proved especially advantageous, particularly with regard to the coaxial transmission R 1 , that a supporting element  11  of enlarged design adjoins the toothed segment  5 . 
         [0040]    As is evident especially from  FIGS. 1   a ,  1   b  and  1   c , a joint  12  connects the toothed segment  5  to the supporting element  11  in a joint-like manner. 
         [0041]    Furthermore, in the present invention, it has proved to be advantageous that adjacent supporting elements  11  can be connected in a chain-like or link-like manner in each case in the end-face region of the supporting elements  11 , while at the same time a play is possible in the direction of the double arrow x illustrated, that is to say with respect to the movement of the circumferential surface, and a play is possible in the y-direction, that is to say in the radial direction, as illustrated in  FIG. 1   c.    
         [0042]    In this case, it has proved especially advantageous that the supporting element  11  can be adapted to the contour  9  of the profiling  8  by means of the joint  12  and is thereby at the same time tied to the positively guided position of the toothed segment  5  inserted in the guide  4 . 
         [0043]    The supporting element  11  can therefore easily be adapted in a joint-like manner, during the rotation or rotational movement of the drive element  7  with respect to the ring wheel  1  and/or to the element  3 , to the contour  9  of the drive element  7 , said contour changing as a result of rotation. 
         [0044]    In the present exemplary embodiment, according to  FIGS. 1   a ,  1   b  and  1   c , the supporting elements  11  lie directly on the bearing elements  10  which, in turn, are supported on the outside on the contour  9  of the drive element  7 . 
         [0045]    A plurality of rolling bodies, in particular needle rollers or balls, are preferably used as bearing elements  10 . 
         [0046]    With regard to the functioning of the coaxial transmission, reference is made to German patent application DE 10 2006 042 786. The functioning is described exactly there. 
         [0047]    The present application relates to a further development and an improvement in the kinematics between the drive element  7  and element  3 , especially in the region of the mounting of the toothed segments  5 . 
         [0048]      FIG. 1   b  illustrates part of the coaxial transmission R 1  in perspective. It can be gathered there, how the individual supporting elements  11  engage one in the other by corresponding projections  13  and recesses  14  next to one another on the end faces and, as illustrated in  FIG. 1   c , allow play in the x- and y-direction. By the projection  13  of one supporting element  11  engaging into the recess  14  of the adjacent supporting element  11 , good guidance and, at the same time, mounting and hold in the axial direction are ensured. 
         [0049]    It is also important in the present invention, however, that, because the supporting elements  11  are enlarged, they are supported and cushioned via a plurality of individual bearing elements  10 , in particular needle bearings, so that very high radial forces can be absorbed by the toothing  2  for operating the coaxial transmission R 1 . 
         [0050]    In the present invention, furthermore, it has proved advantageous that, as is not illustrated in any more detail here and is indicated merely in  FIG. 3   a , a bearing outer ring  15  ( FIG. 3   a ) can be inserted between the supporting element  11  and the bearing element  10  or directly between the supporting element  11  and a contour  9  of the drive element  7 . The bearing outer ring  15  is of the elastic type and assists force distribution between the supporting element  11  and bearing element  10  or force distribution between the supporting elements  11  and the outer contour  9  of the drive element  7 . 
         [0051]    In the exemplary embodiment of the present invention according to  FIG. 2 , a coaxial transmission R 2  is shown, in which spacers  16  are provided between the supporting elements  11  and the drive elements  7 , especially its contours  9 , and between individual adjacent bearing elements  10 , especially needle rollers. The spacers  16  in each case engage radially and on the end faces onto the bearing elements  10 , preferably on both sides, and space these apart from one another in a chain-like or link-like manner. 
         [0052]    Thus, the individual needle rollers can be spaced radially apart from one another around the contour  9  of the drive element  7 , a guidance of the individual supporting elements  11  in each case being ensured laterally. 
         [0053]      FIG. 3   a  illustrates, enlarged, a toothed segment  5  with a supporting element  11 , a corresponding profiling  18  of the supporting element  11  being provided in a recess  17  in the root region of the toothed segment  5 , so that a joint-like movement of the supporting elements  11  with respect to the toothed segment  5  is also ensured. 
         [0054]    As illustrated in  FIG. 3   c , it may also be conceivable to form the corresponding profiling  18  from the root region of the toothed segment  5 , said profiling then cooperating in a joint-like manner with a corresponding recess  17  of the supporting element  11 . 
         [0055]    If, for example, the use of a bearing outer ring  15 , as illustrated in  FIG. 3   a , is dispensed with, it has proved advantageous if the supporting elements  11  have introduction chamfers  20  on their underside  19  directed toward the bearing element  10 , particularly in the end-face regions. 
         [0056]    Thus, for example without an interposed bearing outer ring  15 , the load can be transferred via the bearing elements  10  directly to the supporting element  11  and therefore directly to the toothed segment  5 . 
         [0057]    Furthermore, in the present invention, it is advantageous that the supporting elements  11  have on the end faces corresponding overlaps  13 ,  14 , for example as a projection  13  or recess  14  or as a setback, in order in the circumferential direction to ensure, as a segmented bearing outer ring, a guidance of the bearings  10  in the circumferential direction. 
         [0058]    Moreover, a defined gap  26  is established between two supporting elements  11 , spaced apart on the end faces, as a function of the contour  9  or profiling  8  of the drive element  7 , in order to compensate different radii of the drive element  7  during a rotational movement in cooperation with the supporting elements  11 . 
         [0059]    In the exemplary embodiment according to  FIG. 3   b , it is illustrated that the supporting element  11  and toothed segment  5  are formed in one piece, the contraction  21 , as a taper, being formed in the root region of the toothed segment  5 , in order to allow an articulated or joint-like pivoting of the supporting elements  11  with respect to the toothed segment  5 , as indicated in the direction of the double arrow. 
         [0060]    In the present invention, however, it is important, as is also illustrated clearly in  FIGS. 3   a  to  3   c , that a length L of the supporting elements  11  is greater than a thickness D of the toothed segment  5 . 
         [0061]    The length L of the supporting elements  11  may amount to 1.5 to 4 times the thickness D of the toothed segment  5 . This is likewise to come within the scope of the present invention. 
         [0062]    Furthermore, it has proved to be especially advantageous in the present invention, as is clear particularly from the exemplary embodiment according to  FIG. 4 , that a plurality of supporting elements  11  are arranged, spaced apart radially next to one another, on an outer contour  9  of the drive element  7 . In this case, the bearing elements  10  are embedded in a bearing groove  23  on the outside in the contour  9  or profiling  8 , so that said bearing elements cannot emerge axially either in one direction or the other. 
         [0063]    A plurality of supporting elements  11  arranged next to one another are laid onto the bearing elements  10  and likewise possess corresponding bearing grooves  24  on their underside, so that, as illustrated in  FIG. 5 , corresponding flanges  25  engage over the bearing elements  10  on the end faces, with the result that the bearing element  11  is held, secured axially, on the bearing elements  10 , particularly the needle rollers, and allows optimal mounting radially. 
         [0064]    The supporting element  11  possesses laterally a projection  13  which is preferably triangle-like and is shaped as an obtuse triangle, and engages into a corresponding matching recess  14  of an adjacent supporting element  11 . The supporting element possesses, on the one hand, a corresponding projection  13  and, on the other hand, a corresponding recess  14  which serves for the engagement of the projection  13  of the adjacent supporting element  11 . 
         [0065]    Furthermore, the corresponding recess  17  is preferably designed to be continuous, so that at least one toothed segment  5  can engage there in its root region  22 . 
         [0066]    In the present invention, it has proved to be particularly advantageous for a plurality of individual supporting elements  11  with bearing elements  10  to have a segment-like design and, as segment-like bearing outer rings, to surround the actual drive element  7 , in particular its profiling  8 . At the same time, the supporting element  11  serves for distributing the forces to the toothed segments  5 , the toothed segments  5  being separately mounted or supported within the supporting elements  11 . A bearing outer ring segmented in this way and formed from a plurality of segment-like supporting elements  11  is highly rigid and can transfer very high forces at high circumferential speeds to the individual toothed segments. 
         [0067]    It has proved advantageous in the present invention to insert a plurality of, preferably two, cylindrically designed toothed segments  5  arranged next to one another in the axial direction into the element  3 , in particular into the output element, into a corresponding, matching, cylindrical guide  4 , said toothed segments then being supported together in one supporting element  11 .