Abstract:
An infinitely variable transmission that utilizes a wobbler in driving engagement with a planetary gear arrangement. The planetary gear arrangement drives a sun gear that provides an output from the transmission. As the tilt angle of the wobbler is adjusted, the overall speed reduction (or increase) ratio of the transmission is adjusted. It is possible to adjust the output speed all the way to zero depending on the tilt angle of the wobbler. In the present invention, two or more drives with two or more wobblers and two or more planetary and sun gears are utilized so that torque can be divided between multiple drives and so that cyclical variations in the output speed of the transmission are smoothed

Description:
RELATED PATENTS 
       [0001]    This application is a Continuation In Part of co-pending U.S. patent application Ser. No. 12/450,831 which was filed on Mar. 8, 2010. U.S. patent application Ser. No. 12/450,831 and is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Power sources such as electric motors, internal combustion engines, and humans typically generate power most efficiently when operating within a narrow range of speeds, while a specific application for the power, a wheeled vehicle for example, might require a broad range of speeds. A transmission is often used to adapt the speed characteristics of the power generator to the speed characteristics of the power application. Many transmissions function, for example, as rotary speed changers. Transmissions are also used to convert one kind of motion to another kind of motion, converting a rotary motion input to a linear motion output for example. 
         [0003]    Transmissions may provide a torque-speed conversion from a higher speed motor to a slower but more forceful output, reducing the speed from the input to the output, or from a slower speed motor to a faster but less forceful output, increasing the speed from the input to the output. An infinitely variable transmission (IVT) is a transmission in which the ratio of the torque and speeds of the input and the output can be varied continuously within a given range, providing an infinite number of possible output torque-speed ratios within that range including zero speed. 
         [0004]    A novel IVT was described in U.S. patent application Ser. No. 12/450,831. The transmission presented in that application is successful at providing an infinite number of speed ratios within a limited range. However, it is limited in the amount of torque that can be transmitted through the transmission. As the output speeds approach zero the following loads on the wobbler and the freewheeling gear can be significant and limit the applications for this transmission. It would be desirable to provide an infinitely variable transmission such as that described in U.S. patent application Ser. No. 12/450,831 that is capable of carrying a higher torque load. Furthermore, the output speed of the transmission described in U.S. patent application Ser. No. 12/450,831 experiences cyclic variations with a frequency of six pulses per rotation of the input shaft. It would be desirable to provide a transmission that has reduced amplitude of cyclic speed variations in the output shaft for applications that require a smoother output. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention is a modification of the infinitely variable transmission described in U.S. patent application Ser. No. 12/450,831 by adding additional transmission units in parallel to allow a higher torque load to be carried by the transmission. Two transmissions are mounted on a common input shaft, with torque being split between the two transmissions. Output of the two transmissions is consolidated into a single output shaft. By utilizing two transmissions in parallel, the torque load capability of the combined transmission is effectively doubled. 
         [0006]    While one embodiment of the present invention includes two transmissions in parallel, it would be possible to construct other embodiments of the transmission utilizing three or more transmissions in parallel in a similar manner to triple or more than triple the torque carrying capability of the transmission. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a perspective view of the transmissions, according to the embodiment of the invention 
           [0008]      FIG. 2  is an exploded perspective view of the transmission assembly shown in  FIG. 1 . 
           [0009]      FIG. 3  is a perspective view of the stacked planetary gear set shown in  FIG. 2 . 
           [0010]      FIG. 4  is an exploded view of the stacked planetary gear set shown in  FIGS. 2 and 3 . 
           [0011]      FIG. 5  is a perspective view of the input drive and shifting linage system in the transmission shown in  FIG. 2 . 
           [0012]      FIG. 6  is an exploded view of the shifting linkage system in the transmission shown in  FIGS. 2 and 5 . 
           [0013]      FIG. 7  is a perspective view of the input shafts and wobbler assemblies. 
           [0014]      FIG. 8  is an exploded view of a second input drive shaft including a support ball assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    The present invention will be described with reference to  FIGS. 1-8 . Many aspects of the present invention are the same as previously described in U.S. patent application Ser. No. 12/450,831, which is incorporated herein by reference in its entirety. Some details of the transmission can be found in that document and are omitted here. 
         [0016]      FIG. 1  shows a transmission that includes a hub  11  which encloses many of the parts of the transmission. The hub  11  rotates as the transmission is driven and is connected to output sprocket  12 . Output sprocket  12  rotates together with hub  11 . The entire transmission is supported on axle  15 . Axle  15  is mounted to be stationary, where stationary means fixed relative to the device on which the transmission is used. For example, axle  15  could be mounted on a bicycle, vehicle, wind turbine, or other piece of machinery. Axle  15 , however, is not contemplated to rotate during operation of the transmission. It should be noted that U.S. patent application Ser. No. 12/450,831 described two embodiments of the invention, one in which a wobbler rotates and a cage is stationary, and one in which the wobbler is stationary and the cage rotates. Either embodiment could be utilized with the present invention, but the description given here is in reference to the first embodiment in which the wobbler rotates and the cage is stationary and fixed to the axle. In fact, it would be possible to drive the wobbler one direction and the cage in the opposite direction. The requirement is that at least one of the axle, the cage, or the follower portion of the wobbler must be held stationary. It is possible to hold two of these items stationary, for example in the description given here where the axle and the cage are both held stationary. However, at least one of these three items must be held stationary against rotation in order for the transmission to function. An input sprocket  13  is mounted concentrically around the axle  15  for rotation thereupon. A shifting assembly  14  is attached to the input sprocket  13 . The shifting assembly is substantially similar to that described in U.S. patent application Ser. No. 12/450,831. An output sprocket  12  is attached to hub  11  for rotation therewith. While the present invention is shown with sprockets  12 ,  13  for input and output of power and torque, any other suitable connection to the input and output of the transmission could be used, as would be appreciated by one of ordinary skill in the art. For example, the sprockets  12 ,  13  could be replaced with sheaves that work with v-belts. They could also be replaced with splined connections to other drive shafts. Many other suitable connections for input and output of power and torque can be contemplated and are known to those of ordinary skill in the art. 
         [0017]      FIG. 2  shows an exploded view of the transmission of the present invention. It can be seen in  FIG. 2  that input sprocket  13  is drivingly connected to a first drive shaft  22  which drives a first wobbler assembly  23 . A second drive shaft  24  is drivingly connected to the first wobbler assembly  23  for rotation therewith. The second drive shaft  24  rotates along with the first wobbler assembly  23  during operation of the transmission. The second drive shaft  24  is drivingly connected to a second wobbler assembly  25 . Both drive shafts  22 ,  24  and both wobbler assemblies  23 ,  25  are supported for rotation on axle  15 . Wobbler assemblies  23 ,  25  operate together with first and second planetary gear assemblies  32 ,  33 , respectively. Each of the planetary gear assemblies  32 ,  33  includes three planetary gear sets  26 ,  27 ,  28 . The planetary gear sets  26 ,  27 ,  28  are supported by a cage  29  which is fixedly secured to the axle  15 . The planetary gear sets  26 ,  27 ,  28  are all substantially similar to the planetary gear sets described in U.S. patent application Ser. No. 12/450,831. The planetary gear sets  26 ,  27 ,  28  in each of the two planetary gear assemblies  32 ,  33  mate with a respective sun gear that is fixedly attached to an output speed disk  34 . Output speed disk is attached to hub  11  for rotation therewith such that hub  11  is driven when planetary gear sets  26 ,  27 ,  28  drive the sun gears and the output speed disk  34 . 
         [0018]    The arrangement shown results in input torque being split between wobbler assembly  1  and wobbler assembly  2 . Therefore, operational loads are shared by the two planetary gear assemblies and the loads in each assembly are cut in half compared to using a single drive. Drive torque from each of the planetary gear assemblies is transmitted to a respective sun gear and recombined in the output speed disk  34  such that all of the drive torque is transmitted through hub  11  and to output sprocket  12  via a hub side cover  20 . 
         [0019]      FIG. 3  shows details of the first and second planetary gear assemblies  32 ,  33  of the transmission  10 . It can be seen that each planetary gear assembly  32 ,  33  includes three planetary gear sets  26 ,  27 ,  28 . The planetary gear sets  26 ,  27 ,  28  are contemplated as including a freewheeling clutch as described in U.S. patent application Ser. No. 12/450,831. Details of the planetary gear sets and freewheeling clutches are not repeated here. The planetary gear sets are supported by cage  29  which is fixedly attached to axle  15 . Output power and torque are transmitted through output speed disk  34 . 
         [0020]      FIG. 4  shows an exploded view of the internal components of the transmission of the present invention. The entire transmission is supported on axle  15 . First and second wobbler assemblies  23 ,  25  are supported for rotation on the axle  15 . The mechanisms for supporting the wobbler assemblies  23 ,  25  are substantially similar to that described in U.S. patent application Ser. No. 12/450,831 with a round bearing with arcuate ridges and mating arcuate slots in the wobblers. Details of the wobbler support mechanism are incorporated by reference from U.S. patent application Ser. No. 12/450,831 and are not provided herein. The wobbler assemblies  23 ,  25  mate with planetary gear assemblies  32 ,  33 . Planetary gear assemblies  32 ,  33  include planetary gear sets  26 ,  27 ,  28  that mate with first and second sun gears  42 . The sun gears are fixedly mounted to output speed disk for rotation therewith. The wobbler assemblies drive planetary gear sets  26 ,  27 ,  28  through drive posts on the wobblers that engage an arcuate drive track on a planetary gear. Details of the interaction between the wobbler and the planetary gear are substantially similar to that described in U.S. patent application Ser. No. 12/450,831 and are incorporated herein by reference without detailed description being provided in the present application. 
         [0021]      FIG. 5  shows detail of the input shaft and connections with the wobbler assemblies  23 ,  25 . The arrangement shown in  FIG. 5  allows the two wobblers to be tilted together so that the two drives have the same speed reduction (or increase) ratio. An input sprocket  13  is attached to a first drive shaft  22 . The first drive shaft  22  is pinned or gimbaled to the input sprocket via a hinge that allows the first input shaft  22  to be tilted relative to sprocket  13 . A shifter assembly  14  is attached to input sprocket  13 . When the shifter assembly  14  is rotated relative to input sprocket  13  it translates in or out and thereby tilts the first drive shaft  22 . First drive shaft  22  is pinned or gimbaled to the first wobbler assembly  23  via a hinge. When the first drive shaft  22  is tilted by the shifter assembly, the first wobbler assembly  23  is also tilted. Details of this shifting mechanism are substantially similar to that described in U.S. patent application Ser. No. 12/450,831 and are incorporated by reference and not described in detail here. The first wobbler assembly  23  is pinned or gimbaled to a second drive shaft  24  and the second drive shaft  24  is pinned or gimbaled to the second wobbler assembly  25 . When the first wobbler assembly  23  is tilted by the shifting mechanism, the second drive shaft  24  causes the second wobbler assembly  25  to tilt by the same amount. The second drive shaft  24  is supported on the axle  15  by a support ball  41 . Also, the support ball  41  allows the length of the second drive shaft  24  to increase or decrease. Details of the second drive shaft  24  and the support ball  41  are given later in reference to  FIGS. 7 and 8 . 
         [0022]      FIG. 6  shows an exploded view of the input sprocket  13 , input shafts  22 ,  24 , and wobbler assemblies  23 ,  25 . It can be seen that the first drive shaft  22  includes a shaft segment  62  that is attached to input sprocket segment  61  and to the first wobbler assembly  23  via pins  59 . The second drive shaft  24  is attached to the first wobbler assembly  23  and the second wobbler assembly  25  via pins. The second drive shaft  24  is fabricated with first and second drive shafts  63 ,  64  connected with support ball  41 . The support ball  41  is supported on axle  15  to allow rotation and rocking. The support ball  41  forms a pivot point in the center of drive shaft  24 . 
         [0023]      FIGS. 7 and 8  show details of the input shafts and wobbler assemblies with special attention to second input shaft  24 . The second input shaft  24  includes a first shaft segment  63  and a second shaft segment  64 . Each of the shaft segments  63 ,  64  are held captive by the support ball  41 . Support ball  41  is supported on axle  15  for rotation thereabout. The support ball  41  is allowed to tilt relative to axle  15  but it cannot translate radially relative to axle  15 . Ridges  65 ,  66  on the exterior portions of shaft segments  65 ,  66  fit into mating slots  67  in the support ball. The ridges  65 ,  66  and slots  67  allow the shaft segments  63 ,  64  to slide within the support ball  41  to increase or decrease the overall length of the second input shaft  24 . If the second input shaft were not held at its midpoint by support ball  41  then the second wobbler assembly would not be tilted when the shifter mechanism is moved. Also, if the second input drive shaft  24  could not be adjusted in length then the entire mechanism would become jammed. 
         [0024]    The description provided herein discusses a linkage that tilts the two wobblers in unison. However, it is contemplated that separate shifting mechanisms could be provided for the two wobblers such that they can be tilted independently. This would allow the two infinitely variable speed adjusters to have different speed reduction (or increase) ratios. In this case, all of the input torque and power would be transmitted through one of the two infinitely variable speed adjusters and the freewheeling clutches in the other speed adjuster would allow that mechanism to spin freely and not carry torque or power. This mode of operation could be desirable to force all of the power and torque through a single infinitely variable speed adjuster, for example to increase efficiency at low levels of power and torque. 
         [0025]    One of the advantages of the present invention include increased torque carrying capacity. While the invention has been described with two sets of wobblers and output drives, it would be possible to utilize three or more sets of wobblers and output drives. Each subsequent wobbler would need to be connected by an additional input drive shaft similar to the second input drive shaft  24  with a support ball mechanism that supports the midpoint of the shaft and allows the length of the shaft to be adjusted. 
         [0026]    Another advantage of the present invention is that it smooths the output of the transmission compared to that of the transmission described in U.S. patent application Ser. No. 12/450,831. The previous transmission with a single wobbler and a single output drive pulses six times for every revolution of the input shaft. The pulsing is not especially problematic, but there could be applications where a smoother output is desired. By including a second wobbler and a second output drive assembly there are 12 pulses in the output for every revolution of the input shaft. However, the pulses are reduced in magnitude by half. Inclusion of a third or even more than three wobblers and drive assemblies would further smooth the output. 
         [0027]    While preferred embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that various modifications may be made in these embodiments without departing from the scope of the invention. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed but that the scope of the invention be defined by the following claims.