Abstract:
The invention relates to an infinitely variable transmission comprising a support body, peripheral gears mounted on the support body or on elements that are coupled thereto such that the rotating shafts thereof are oriented parallel to each other. The distances between the rotational shafts of the peripheral gears can be adjusted to always be located on the outer surface of an (imaginary) cylinder; at least one row of elements which surround the peripheral gears and with which at least one of the peripheral gears engages; a rotational body, preferably coaxial to the axis of rotation of the (imaginary) cylinder, whose rotary movement is coupled to the rotary movement of the peripheral gears. The rotational coupling between the peripheral gears and the (central) rotational body is effected by means of one or more differentials, so that an asynchronous rotation of the peripheral gears is possible.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an infinitely variable transmission comprising a support body, at least two peripheral gears which are mounted on the support body or on elements that are mechanically coupled thereto in such a way that the rotating shafts thereof are oriented parallel to each other. The distances between the rotational shafts of the peripheral gears can be adjusted so as to always be located on the outer surface of an (imaginary) cylinder. Said transmission further comprises at least one row of elements which surround the peripheral gears on the outside and with which at least one of the gears engages, and a rotational body, preferably coaxial to the axis of rotation of the (imaginary) cylinder, whose rotary movement is coupled to the rotary movement of the peripheral gears; furthermore to a preferred application of such a transmission and an operating method for the same. 
     2. Description of the Prior Art 
     Mechanical infinitely variable transmissions are known, in particular with a level friction ring which surrounds two pairs of bevel gears whose tips are inclined towards each other and which are adjustable in an axial direction with respect to each other. The distances between the two pairs of bevel gears are adjusted in opposite directions for the two pairs, so that the friction ring is always frictionally coupled to the two pairs of bevel gears, but finds different circumferences there. Such a transmission is principally infinitely variable, but it is not possible to transmit forces of all magnitudes with them, because the frictional connection tends to slip. 
     For this reason, attempts have already been made to work with a positive connection-type coupling. For example WO 98/11364 proposes an open chain, the two ends of which are fixed. On a disk-shaped support there are at least two radially adjustable gears which engage with the fixed chain when the disk-shaped support rotates. The peripheral gears then begin to rotate, and this rotation is transmitted to a central shaft by means of drive shafts. The chain surrounds the axle of the disk-shaped support, approximately along a semicircle. Of at least two gears, at least one therefore engages with the chain, in the transitional range both engage to ensure that no slip is possible. Since the at least two gears, via the drive shafts, and the central axle are coupled to each other, they always rotate at the same speed. However, this causes problems with the chain when several gears engage simultaneously, namely during the adjustment of the radial distance of these gears from the rotating shaft. Since they are not capable of rotating relatively to each other, the distance between their teeth is reduced or increased, and the chain engaged there must break. 
     With respect to this disadvantage, the lesson drawn from DE 35 01 663 does not lead to any improvement. In this attempt to create an infinitely variable transmission with a positive engagement, a gear wheel with a variably effective radius is used; this can be engaged with a chain. The gear wheel is embodied as a disk-shaped support with several eccentric gears which are radially adjustable in relation to its rotating shaft, in particular by means of levers that can be swivelled in and out. Each of the eccentric gears is freely rotatably mounted in one direction of rotation, but is not freely rotatable in the opposite direction of rotation. This gear wheel is coupled in a rotationally fixed manner to another gear wheel by the chain, whereby the chain can be tensioned by a mechanical system regardless of the effective radius of the gear wheel. A reciprocal relative rotation is possible with the gear wheels known from this example, but only in one direction of rotation. This is why all gears except one must be swivelled against the direction of power transmission if the effective radius is to be adjusted, and so they cannot transmit any power. This means that the entire power has to be transmitted via one single gear. Each individual gear must therefore be designed to transmit the maximum power. Moreover, no braking effect is possible with the above-mentioned transmission, and thus no reversal of the direction of rotation. 
     SUMMARY OF THE INVENTION 
     This leads to the problem initiating the invention of designing a mechanical, infinitely variable transmission with positive engagement in such a way that several gears mounted eccentrically to a symmetrical axis should engage simultaneously with a chain or the like and should be in a position to transmit power, the distance between said gears and the symmetrical axis being adjustable without their frictional connection to a support for the peripheral gears or a common (output) shaft of the transmission coupled with these having to be interrupted. 
     The solution to this problem is that the peripheral gears are coupled to each other and/or to the (central) rotational body without a freewheel by means of a compensating or differential gear unit, so that asynchronous rotation of the peripheral gears is possible without the frictional connection being interrupted. 
     This allows several or even all peripheral gears to remain engaged with the chain, on the one hand, and with each other or with a (central) rotational body on the other hand, that is, to contribute to the power transmission, while an adjustment of the gear transmission ratio is carried out. This means that the chain can surround the support body by more than 180°, and that all gears can constantly transmit an approximately equal share of the total power, so that the individual gears and their bearings or adjustment mechanisms only have to be designed for a reduced torque. This is effected by the compensating or distribution transmission in accordance with the invention, said transmission simultaneously guaranteeing approximately constant power transmission, but allowing relative rotations of the individual gears with respect to each other. This follows from the fact that all peripheral gears are adjusted uniformly, so that the differential speeds between neighbouring gears must also be equal. 
     It has proved to be favourable that the body supporting the peripheral gears has a point-symmetric structure. This means that for example and arm or an adjusting mechanism is assigned to each of the n peripheral gears, and a rotation of 360°/n leads to an identical arrangement. 
     It is within the framework of the invention that devices are provided for on the support body to adjust the distance between the peripheral gears themselves or between the peripheral gears and the central axis of an (imaginary) cylinder. This allows the transmission ratio of the gear unit to be adjusted. 
     Guides running preferably radially with respect to a central axis of an (imaginary) cylinder represent a first option for realising radial adjustment, whereby each of the bodies guided on such a guide contains the bearing for one peripheral gear each. In this case, radial adjustment can be effected by means of radial spindles, for example. 
     On the other hand, the distance adjustment devices can have levers which can be swivelled around decentral shafts, the bearing for one peripheral gear each being located on said levers. In the event of adjustment, the radial movement is always overlaid by a tangential movement in such a case; however, if the levers are all adjusted synchronously, they effect tangential movements symmetrical to the common shaft, and the purely radial component remains as the relative movement. 
     For the above-mentioned reason, among other things, the adjustment mechanisms must be coupled to each other, so that the distance adjustment of all peripheral gears is effected uniformly. Then the forces to be transmitted are also always approximately equally great, and this standard load case can accordingly be expected when designing the transmission, whereby each gear must only transmit a fraction of approximately 1/n of the total force. 
     Synchronous or uniform adjustment of the intercoupled gears is effected by means of a common control element, which acts equally on all adjustment mechanisms. This can be a (toothed) wheel, which is coupled to all adjusting spindles or adjusting levers and which can be influenced preferably by an actuation device which is accessible from the outside. 
     If at least one row of tooth-engaging elements surrounding the peripheral gears on the outside is flexible and/or adjustable, it is possible to engage with at least one peripheral gear, regardless of its current distance setting. This engagement is ensured if one row of tooth-engaging elements surrounding the peripheral gears on the outside is also pretensioned in the direction of the peripheral gears. 
     The above design requirements can be met at little expense if at least one row of tooth-engaging elements surrounding the peripheral gears on the outside is formed by a chain whose links engage with the teeth of at least one of the peripheral gears, and which is flexible and is consequently in a position to adapt to the different radial distances between the peripheral gears. 
     Depending on the structure of the transmission with a fixed or revolving chain, the latter may have a tensioning element or may be coupled to such an element which generates tensile stress between the links of the chain and accordingly pulls these towards the peripheral gears. A closed chain could surround the driven shaft; in such a case the distance to a driven gear could be altered with the purpose of tensioning the chain, and/or a coupling element influencing the synchronous adjustment of the peripheral gears could be pretensioned by a spring element in such a way that the gears are pushed outwards. It is also conceivable to couple two transmission units in accordance with the invention to each other using the same surrounding chain and then to adjust these transmission units in opposite directions to each other so that the distance between the shafts of the peripheral gears is increased in one transmission unit and simultaneously reduced to the same extent in the other, so that the chain always remains tensioned. 
     This invention-related thought can be further developed to the extent that the link section of the chain is not closed or is only closed by means of a tensioning element. This case preferably refers to a fixed chain, the ends of which are located outside the engaging range of the peripheral gears, so that one or more tensioning elements, for example tensioning springs, can be mounted there. 
     A pivot bearing located between the support body and the (central) rotational body allows a relative rotation between these bodies, whereby the coupling can be influenced by the adjustable gears. These bodies can then serve as input and output shafts of the transmission according to the invention. 
     Furthermore, the invention provides for one or more differentials being located on the (central) rotational body, in particular on a central rotating shaft. All rotary movements of the peripheral gears are brought together here in a star shape, so that the differential gear can be implemented in a very small space. 
     In order to couple two or more gears with each other, several differentials or differential units are arranged one after the other in the direction of the axis of rotation of the (central) rotational body and coupled to each other. Each gear is preferably coupled to one or two other and/or to a central rotating shaft in such a way that its rotary movement influences the others or is influenced by the others. This ensures that no idle running, which could lead to undefined rotary speeds of a gear wheel which is not engaged with the chain, can occur. This ensures that the transmission is really infinitely variable, that is, fully independent of a random intermediate position of the gear, a synchronous re-engagement of a peripheral gear with the chain can be effected. 
     It is within the framework of the invention that the (central) rotational body, in particular a central rotating shaft, is rotatably coupled to an input or output shaft or the housing of the infinitely variable transmission. The uniform rotary movement originating from the combined effect of the individual rotary movements of the gears can be assigned to each of the above three connecting elements of the transmission in accordance with the invention. 
     A planetary gear is highly advantageously located between the support body and/or the (central) rotational body, on the one hand, and the input or output shaft or the housing of the infinitely variable transmission on the other hand. An upstream or downstream planetary gear allows an adjustment of gear speed conditions to certain applications; for example synchronous operation, in the course of which internal gear movements and thus internal friction are minimised, can be implemented at maximum speed. 
     A preferred version of the transmission consists in equipping the support body with a rotating shaft or a ring gear which is rotatably coupled to an input or output shaft or the housing of the infinitely variable transmission. 
     Furthermore it is also possible to couple or to integrate the ring gear of a planetary gear rotatably with the support body or the (central) rotational shaft, while the sun wheel of the planetary gear is preferably rotatably coupled or integrated with the other respective element (support body or (central) rotational shaft). A differential speed is then at the disposal of the planetary gear support. This can be picked up at the transmission if the planetary gear support of the planetary gear is rotatably coupled to the input or output shaft or the housing of the infinitely variable transmission. 
     Preferred applications of the infinitely variable transmission according to the invention can be found in passenger cars and/or trucks, agricultural implements and/or vehicles, construction engines and/or vehicles, conveying machines or vehicles, elevators, motorbikes and bicycles etc. In these applications it is a great advantage that far greater forces can be transmitted with the transmission according to the invention than has been the case so far, because several gears are always involved approximately uniformly in the transmission of the power, preferably always at least (n-1), where n is the number of all peripheral gears. 
     A process according to the invention for operating the infinitely variable transmission described above is characterised in that at least one end of a row of tooth-engaging elements engaging with the peripheral gears is coupled to the chassis of a vehicle or the base of a machine, the input shaft of the infinitely variable transmission is coupled to the support body or the (central) rotational shaft, the output shaft of the infinitely variable transmission is coupled to the other respective element (support body or (central) rotational shaft), and a control element coupled with the distance-adjusting mechanism of one or several peripheral gears is influenced manually or with the aid of an electronic controller in order to adjust the desired transmission ratio. This permits the implementation of an infinitely variable transmission ratio for transmitting very large torques in a very small space, without slip, with it being possible to adjust the transmission ratio under full load, and, even when the direction of rotation of the output shaft is reversed, using suitable gears, for example by means of a downstream planetary gear. This allows, among other things, the implementation of a traction machine whose engine speed can always be kept constant, while travelling speed and direction are defined solely by means of the transmission according to the invention. A clutch is not required. 
     Further features, details, advantages and effects on the basis of the invention can be seen from the following description of a preferred embodiment of the invention and with the help of the drawing. Here, 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a front view of the transmission according to the invention; 
         FIG. 2  shows a longitudinal section through the transmission from  FIG. 1  coaxial to a central rotating shaft; and 
         FIG. 3  shows an illustration of a modified embodiment of the invention corresponding to  FIG. 2 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The core of the transmission  1  according to the invention is a support body  2 , which in the example described above has approximately the form of a hollow cylinder. This cylinder-shaped support body  2  is rotatably mounted on an axle  3  which passes through its inner cavity  4  coaxially to its outer surface  5 . 
     Several equidistant rotating shafts  6  whose axes are aligned parallel to each other pass through the periphery of the cavity  4 . These rotating shafts  6  are mounted in the two end sides  7 ,  8  of the support body  2  and emerge on an end side  8 . There they each pass through the inner end  21  of a corresponding swivelling lever  9  and each end in the hub of a gear wheel  10  with which they are connected in a rotationally fixed manner. At the peripheral end  11  of each lever  9  a shaft  12  is mounted for a further gear wheel  13 , which is coupled in a rotationally fixed manner to the gear wheel  10  at the inner end of the lever in question  9  by means of a closed chain  14 . A further gear wheel  15 , which in the following is to be designated as “peripheral gear wheel”, is also fixed to each shaft  12 . 
     By the uniform, synchronous swivelling of all levers  9 , the rotating shafts  12  can be adjusted from a minimum radial distance to the central axle  3  to a maximum radial distance. At the minimum distance, the levers  9  are adjusted approximately tangentially  16  to the rotating shaft  3 , the shafts  12  of the peripheral gears turn in a circle  17  with a small radius r; at the maximum distance, on the other hand, the levers  9  turn approximately radially outwards  18 , the shafts  12  move in a large circle  19  with radius R. The adjustment  20  can, for example, be effected by a further gear wheel—not shown—which is also mounted on the rotating shaft  3  and which engages with a toothed area at the rear or radially internal ends  21  of the levers  9 , being (slightly) rotatably adjusted vis-á-vis the support body  2 . Other mechanisms are conceivable. 
     The peripheral gears  15  are surrounded on the outside by an open chain  22 , which—like the gear wheels  15 —may be formed by several identical elements on levels parallel to each other in order to multiply the transmittable forces. 
     One end  23  of the chain  22  is fixed to the housing or chassis  24  of the transmission  1  according to the invention, the other end  25  of the chain  22  is also connected to the housing or chassis  24 , but here a tensioning or spring element  26  is interposed. Depending on the position of the levers  9  between the small and the large circle  17 ,  19 , the tensioning element  26  is in a position to compensate for a change in the required chain length of approximately I=2p (R-r), without the chain tension falling below a lower limit value, so that the engagement between the chain  22  and the peripheral gears  15  is always guaranteed, irrespective of the gear setting  20 . 
     If the support body  2  is rotated around its rotating shaft  3  at a speed of w 1 , the peripheral gears  15  roll along the chain  22  at a speed of w 2 , with the speed ratio w 2 /w 1  depending on the radius set between r and R. This rotary movement is transmitted via the gear wheels  13 , the chains  14  and the internal gear wheels  10  to the rotating shafts  6  passing through the cavity  4 . Fixed to each rotating shaft  6  within the cavity  4  is a further gear wheel  27 , which by means of another chain each  28  is connected to each connection of a differential assembly  29 , which is located concentrically on the shaft  3 . In the differential assembly  29 , the torques of the various rotating shafts are added up and transmitted to the shaft  3 . 
     In the differential assembly  29  the gear wheels in question, as in the illustrated embodiment, may be axially arranged gear wheels coupled to each other by means of gear wheels with radial axes (axial differential), or this may be a radial differential with radially arranged gear wheels, particularly in the form of a modified planetary gear, with the three intercoupled units corresponding to the sun wheel, the planetary gear support and the ring gear of such a planetary gear. The common criterion for this embodiment is the presence of synchronous operation, on the one hand, with 3 intercoupled gear wheels or units rotating at the same speed (provided that no transmission adjustment is taking place), and, on the other hand, the specification of defined conditions with respect to the relative speeds when the transmission according to the invention is being adjusted. 
     The rotating shaft  3  preferably forms the output shaft of the transmission  1 , and for this purpose has been extended outwards through the level of the chain  22 . At the other end it may also pass through the opposite end side  7  of the support body  2  and there be fitted with a sun wheel  30  which rotates concentrically within a ring gear  31  which is formed on the outer surface of the end side  7  of the support body  2 . Several planetary gear wheels  32 , which are mounted on a common planetary gear wheel support  33 , rotate within the ring-shaped space between the ring gear  31  and the sun wheel  30 . This planetary gear wheel support is in turn connected to a further rotating shaft  34 , which can serve as an input or output shaft. 
     The planetary gear  30 - 33  is optional, but can preferably supplement the transmission according to the invention  1  to the extent that this would allow synchronous operation to be specified at a desired speed. 
     Depending on the design of the differential assembly  29 , the number of peripheral gears  15  may be even or odd. Both configurations may be advantageous. 
     All peripheral gears  15  are connected to the differential, from which a connection to rotating shaft  3  is coupled. Then a pair of peripheral gears  15 , both of which engage with the chain  22 , define the speed of the output shaft  3  and the speed of the gear  15 , which does not engage with the chain  22 , through the differential, so that there are no undefined speeds and, on the contrary, the remaining gear  15  is rotated exactly so that its teeth engage exactly with the future ends  23 ,  24  of chain  22 . 
     If transmission  1  is adjusted  20 , all peripheral gears  15  rotate at different speeds because the distances between these gears  15  change. This is compensated for by the differentials in the differential assembly  29 , while the force distribution remains approximately uniform among all peripheral gears  15  that engage with the chain  22 . This means that an adjustment  20  can take place under full load. The chain  22  is guided by means of a roller  35 , so that the “aperture” in which at least one gear wheel  15  is not engaged with the chain  22  remains approximately constant, preferably at approx. 360°/n, where n is the number of peripheral gears  15 . 
     Transmission  1  could also be used in a modified form for special applications. For example, if used as an infinitely variable transmission, it would be conceivable in a bicycle to design axle  3  and shaft  34  as one unit and, for example, to couple these with the pedals. This means that the circumferential speed of the peripheral gears  15  around their own axes  12  is blocked, or zero. It changes only during a transmission adjustment operation. It is therefore possible to change the transmission ratio by means of a radial adjustment of the peripheral gears  15 , as with a (large) gear whose diameter is varied. The chain, which in this case closes over an output gear wheel on the rear axle of the bicycle, accordingly transmits the circumferential speed, which varies according to the transmission setting, to the rear wheel. 
     In transmission  1 ′ in accordance with  FIG. 3 , the functions of the driving and driven shafts are reversed for standard applications: the shaft  34 ′ is the driving shaft or input shaft, the shaft  3 ′ is the driven shaft or output shaft. With motor vehicle applications, for example, the shaft  34 ′ could correspond to the engine shaft, the chain  22  could be coupled to a wheel axle. If required, a gearbox, for example, could be installed upstream or downstream of the transmission in such an application, in order to extend the speed adjustment range further. 
     In other respects, this transmission  1 ′ differs from that described above among other things by the fact that the internal gears  10 ′ and the gears  13 ′ rotatably mounted on the periphery  11  of the swivelling levers  9  are dimensioned in such a way that the relevant gears  10 ′,  13 ′ of a lever  9  engage directly with each other and the chain  14  thus becomes dispensable. Furthermore, the diameter of the inner gear  10 ′ or of the outer gear  13 ′, or both, may be enlarged; the important thing is that one gear  13 ′ and one gear  10 ′ should be constantly meshed. Besides increasing the gear ratio, a reversal of the direction of rotation is also a consequence. 
     Furthermore, the gears of the differential  29 ′ are so large that they each engage directly with one gear  27  on a rotating shaft  6 , so that the chains  28  also become superfluous here. Once more, a change in the gear ratio and a reversal of the direction of rotation are the consequences. Thanks to the double reversal of the direction of rotation, the function of this transmission  1 ′ is exactly like that of transmission  1 . 
     In this embodiment, the planetary gear  30 - 33  is dispensed with. Instead, the input shaft  34 ′ is directly connected in a rotationally fixed manner and rigidly to the support body  2 ′, on the end side  7 ′ and coaxially to the output shaft  3 ′. In this case the latter is only coupled in a rotationally fixed manner to the differential  29 ′, in other respects it is rotatably mounted  36  in the support body  2 ′. The design of this transmission  1 ′ is simpler than that described before, but generates the same effect of an infinitely variable speed adjustment under load and without slip, with a reversal of the direction of rotation between the input and output shafts  34 ′,  3 ′ being implemented if suitable transmission ratio is selected. 
     In an intermediate position (zero position) the output shaft  3 ′ is at a standstill, while the input shaft  34 ′ is driven. However, the output shaft  3 ′ is not free, but blocked; this makes it possible to start up on a hill without actuating the brake.