Patent Publication Number: US-2006019796-A1

Title: Toroidal continuously variable transmission with offset rollers

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This is a continuation-in-part application that claims the benefit of U.S. Non-provisional patent application Ser. No. 10/814,542, filed Mar. 31, 2004. 
    
    
     FIELD OF THE INVENTION  
      The present invention relates to improvements of a toroidal continuously variable transmission (toroidal CVT), and specifically to the improved angular off-set roller control for a toroidal CVT that permits the design of a very compact toroidal CVT control mechanism housed within the area between two parallel toroidal disks. More specifically, the present invention uses a translating motion along the primary axis of the rotating toroids to control the rotational tilt of the off-set rollers.  
     DESCRIPTION OF THE RELATED ART  
      Continuously variable toroidal transmissions known in the art fall into two groups: those using essentially disk-like rollers to transmit torque from the driving disk to the driven disk and those using spherical rollers to transmit torque from the driving to the driven disk. The cylindrical face of the essentially disk shaped roller is generally curved outwardly from the axis of rotation of the cylinder producing what would be single point contact with the driving and driven disks absent surface deformation produced by the pressure of said contact.  
      The continuously variable toroidal transmission with offset rollers falls within the class using essentially disk shaped rollers to transfer torque from the driving disk to the driven disk. In both these classes of transmission, an essential problem involves controlling the angle formed between the roller&#39;s plane of rotation and the common axis of rotation shared by the driving and driven disks, herein referred to as the tilt angle. The known transmissions of this type include a mechanism which controls the tilt angle by rotating the roller&#39;s plane of rotation about the roller&#39;s center point. The roller&#39;s plane of rotation rotates about a pivot point placed outside the roller&#39;s plane of rotation in the continuously variable toroidal transmission with offset rollers. This change enables control of the tilt angle by varying the position of the roller support mechanism along the common axis of rotation of the driving and driven disks.  
      However, the control mechanisms for controlling the roller&#39;s plane of rotation are usually cumbersome due to control related mechanical linkages and usually consume much of the design space around the toroidal CVT making it large, heavy, and awkward to configure for applications needing a small lightweight toroidal CVT.  
      Accordingly, there is a need for a toroidal CVT of a compact, lightweight design that can be readily adapted for use in a variety of applications that prior art toroidal CVTs could not functionally address due to issues of size, weight and complexity.  
     SUMMARY OF THE INVENTION  
      The toroidal continuously variable transmission with offset rollers of the present invention includes a first toroidal disk having an inwardly facing toroidal portion, a second toroidal disk having an inwardly facing toroidal portion, wherein each of the first and second inwardly facing toroidal portions face opposite each other. A shaft having a longitudinal axis mounts the first toroidal disk on a first end and mounts the second toroidal disk on a second end. A sliding collar is mounted on the shaft between the first and the second toroidal disks and has at least two off-set rollers attached thereto in communication with the first and the second inwardly facing toroidal portions of the toroidal disks. Translation of the sliding collar on the shaft causes the at least two off-set rollers to rotate about a first axis, wherein the first axis is orthogonally disposed with respect to the longitudinal axis of the shaft.  
      A further embodiment of the toroidal continuously variable transmission with offset rollers of the present invention includes a hollow shaft having a longitudinal axis with a first end for affixing a first toroidal disk to freely rotate thereupon, and a second end for affixing a second toroidal disk to freely rotate thereupon. Each first and second toroidal disks have toroidal portions facing each other. The hollow shaft further includes a either a circular or non-circular center shaft portion between the first and second ends wherein is found at least one longitudinal slot disposed parallel to the longitudinal axis of the hollow shaft.  
      A sliding collar having a longitudinal axis is shaped to be slidingly received on the center shaft portion of the hollow shaft. The sliding collar has at least two projections thereon for receiving at least two off-set roller assemblies. Each off-set roller assembly includes an off-set roller having a rim on the outer circumference, a roller support shaft to support rotation of the off-set roller about a longitudinal axis of the roller support shaft, and a roller support coupling affixed to an end of the roller support shaft to allow rotation of the off-set roller about a first axis orthogonal to the longitudinal axis of the roller support shaft. The roller support coupling of each off-set roller assembly is rotatably attached to the projection on the sliding collar to allow rotation of the off-set roller assembly about the first axis.  
      A sliding shaft having a longitudinal axis and connector receiving means is received within the hollow shaft. Finally, a connector attaches to the receiving means of the sliding shaft and projects through the longitudinal slot of the hollow shaft to affix to the sliding collar. Translation of the a sliding shaft causes the sliding collar to translate on the hollow shaft thereby causing the off-set roller assemblies to rotate about the first axis of the roller support coupling while the off-set roller assemblies contact both the first and second toroidal disks.  
      These and other features of the present invention will become readily apparent upon further review of the following specification and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1A  shows a schematic side view of a traditional toroidal continuously variable transmission with offset rollers in the configuration where the upper toroidal disk D 1  is rotating at a slower speed than the lower toroidal disk D 2 .  
       FIG. 1B  shows a schematic side view of a traditional toroidal continuously variable transmission with offset rollers in the configuration where the upper toroidal disk D 1  is rotating at the same speed than the lower toroidal disk D 2 .  
       FIG. 1C  shows a schematic side view of a traditional toroidal continuously variable transmission with offset rollers in the configuration where the upper toroidal disk D 1  is rotating at a faster speed than the lower toroidal disk D 2 .  
       FIG. 2  shows a schematic side sectional view of a pair of toroidal disk and off-set rollers of the present invention.  
       FIG. 3  shows a perspective assembly view of the present invention.  
       FIG. 4  shows a perspective view of the slide shaft, hollow slotted axle and the sliding off-set roller collar in an assembled configuration.  
       FIG. 5  shows a perspective view of  FIG. 4  additionally including the offset rollers mounted on the sliding roller-carrying collar in an assembled configuration.  
       FIG. 6  shows a perspective view of  FIG. 5  additionally including the mating toroidal disks and the fastening hardware in an assembled configuration.  
       FIG. 7  shows a side view of the present invention with the slide shaft in a retracted position with respect to the hollow shaft causing the off-set rollers to pivot about a rotational connection in a direction opposite to the motion of the slide shaft.  
       FIG. 8  shows a side view of the present invention with the slide shaft in a neutral position with respect to the hollow shaft causing the off-set rollers maintain their positions relative to their titling rotational connection.  
       FIG. 9  shows a side view of the present invention with the slide shaft in an extended position with respect to the hollow shaft causing the off-set rollers to pivot about their rotational connections in a direction opposite to the motion of the slide shaft.  
       FIG. 10  shows a perspective cut-away view of an alternative embodiment of the present invention having a toroidal disk with a cover extending over the off-set roller section of the transmission and in contact with a roller bearing mounted on an outer annual surface of the opposing toroidal disk. 
    
    
      Similar reference characters denote corresponding features consistently throughout the attached drawings.  
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      A toroidal CVT system replaces the belts and pulleys of a conventional CVT system with disks and power rollers. Although such a system seems drastically different, all of the components are analogous to a belt-and-pulley system and lead to the same results—a continuously variable transmission with offset rollers. (A toroid is a surface generated by a closed curve rotating about, but not intersecting or containing, an axis in its own plane.)  
       FIGS. 1A-1C  demonstrate a prior art configuration of a toroidal CVT. One disc, e.g., D 1 , connects to the engine. This is equivalent to the driving pulley. Another disk D 2  connects to the drive shaft. This is equivalent to the driven pulley. Rollers R located between the discs D 1  and D 2  act like the belt, transmitting power from one disk to the other.  
      The rollers R can rotate along two axes, a first vertical axis, shown as “a,” and a second horizontal second axis orthogonal to the vertical axis “a”. The rollers R spin around the horizontal second axis and tilt in or out around the vertical axis “a”, which allows the rollers R to contact the discs D 1  and D 2  in different areas. When the rollers R touch the driving disk D 1  near the rim, as in  FIG. 1A , they must contact the driven disk D 2  near the center, resulting in an increase in speed and a decrease in torque (i.e., overdrive gear). When the rollers R are in contact with the driving disk D 1  near the center, as in  FIG. 1C , they must contact the driven disk D 2  near the rim, resulting in a reduction in speed and an increase in torque (i.e., low gear). When the horizontal rotational axes of the rollers R are orthogonal to the rotational axes of the discs D, as in  FIG. 1B , touching the discs D 1  and D 2  at the same location, respectively, the driving disk D 1  and driven disk D 2  are in a direct drive configuration—the gear ratio of D 1 :D 2  being 1:1. A simple tilt of the rollers R incrementally changes the gear ratio, providing for smooth, nearly instantaneous ratio changes.  
       FIG. 2  is a representative schematic diagram of the present invention demonstrating the tilting of the off-set rollers R with respect to the toroidal disks D 1  and D 2  as the rollers R are rotated around their center point C. Toroidal disks D 1  and D 2  rotate about a horizontal axis of rotation AR. The rollers R have a roller center point C around which rollers R rotate.  
      A roller tilting link A-C is positioned between points A and roller center point C of the roller R and is illustrated by a bold line. This roller tilting link A-C is fixed at one end at roller center point C, but translates at an opposite end along a path defined by the points A-B, parallel to the rotational axis AR of disks D 1  and D 2 . As point A of the roller tilting link A-C moves along the path A-B towards point B, the roller R tilts and creates a larger radius R 1  on disk D 1 , and consequently, a smaller radius R 2  on disk D 2 . The opposite will happen when point A of the roller tilting link A-C moves in an opposite direction along the path A-C′ toward point B′. Here the roller R will tilt in an opposite direction to create a smaller radius on disk D 1 , and consequently, a larger radius on disk D 2 .  
      The limits of travel of the roller tilting link A-C are illustrated by distances d and d′. These distances d and d′ away from a center point A cause the roller disks to stop tilting when point A of the roller tilting link A-C moves toward B or B′.  
       FIG. 3  represents the general preferred embodiment of the invention and correlates to  FIGS. 4-6  demonstrating assembly build-up views of the present invention.  
      The toroidal CVT  10  of the present invention includes hollow shaft  16  having a longitudinal axis with a first end  22  for affixing a first toroidal disk  60  to freely rotate thereupon, and a second end  20  for affixing a second toroidal disk  70  to freely rotate thereupon. The first  60  and second  70  toroidal disks have toroidal portions  62  and  72  that face opposite to each other.  
      A center shaft portion is formed on the hollow shaft  16  between the first  22  and second  20  ends and may consist of a circular, triangular, square, hexagonal, octagonal, or any other non-circular shape.  
      At least one longitudinal slot  18  is disposed parallel to the longitudinal axis of the hollow shaft  16 . In the preferred embodiment, two longitudinal slots project through the center shaft portion and create longitudinal openings on two opposite sides.  
      A sliding collar  24  having a longitudinal axis coincident with the longitudinal axis of the hollow shaft  16  is shaped to be slidingly received upon the center shaft portion. The sliding collar may consist of a circular, triangular, square, hexagonal, octagonal or any other non-circular shape to prevent independent rotation of the sliding collar  24  about the hollow shaft  16 . When the center shaft portion and sliding collar  24  is circular in shape, a connecting means, e.g., pin  34 , may prevent the sliding collar  24  from rotating about hollow shaft  16 . Under operation of increased torque loading, a non-circular configuration is preferred to minimize stress upon any connecting member, like pin  34 , wherein the torque loading is transferred between the non-circular geometry of the sliding collar  24  and the similarly shaped non-circular center shaft portion of hollow shaft  16 .  
      The sliding collar  24  has at least two projections  28  thereon for rotatably receiving an off-set roller assembly  40 . The configuration of the projections  28  on the sliding collar  24  may be in multiple configurations depending on the application and geometry of the toroidal CVT. A first configuration contemplates two projections where the sliding collar is square shaped to be received on a square shaped non-circular center shaft portion of the hollow shaft. These two projections would be disposed on opposite faces of the square shaped sliding collar.  
      A second configuration, for example, may have three projections  28  where the sliding collar  24  is either triangular or hexagonal shaped (as shown in  FIGS. 3-6 ) to be received on a triangular or hexagonal shaped non-circular center shaft portion (at  18 ) of the hollow shaft  16 . These three projections  28  would be disposed 120 degrees from each other on the triangular or hexagonal shaped sliding collar  24 .  
      A third configuration, for example, may include four projections where the sliding collar is square or octagonal shaped to be received on a square or octagonal shaped non-circular center shaft portion of the hollow shaft. The four projections are disposed at right angles to each other on the square or octagonal shaped sliding collar.  
      Received upon each projection  28  of the sliding collar  24 , are off-set roller assemblies  40 . Each off-set roller assembly  40  includes an off-set roller  42  having a rim  44  on the outer circumference thereof. The rim material may of be metal, or a highly compression resistant resilient material to efficiently transmit rotational energy between the first toroidal disk  60  and the second toroidal disk  70 . A roller support shaft  46  supports rotation of the off-set roller  42  about a longitudinal axis of the roller support shaft  46 . A roller bearing (not shown) mounted on the shaft portion and connected to the off-set roller  42  allows for free rotation of the off-set roller  42 . Additionally, the roller support shaft  46  allows for the off-set roller  42  to translate in an axial direction along the roller support shaft  46  as shown by the longer distance between points B-C in  FIG. 2 , as opposed to the shorter distance between points A-C. Though the axial translation distance is small, this feature ensures for efficient and non-binding motion of the rollers during a change in gear ratio that moves toward either limit of the roller tilting range.  
      A roller support coupling  48  rotatably attaches to the projection  28  on the sliding collar  24  via hole  30  with roller fastener hardware  50  to allow rotation of the off-set roller assembly  40 . See  FIG. 5 . Roller support coupling  48  allows rotation of the off-set roller  42  about an axis defined by projection  28  and orthogonal to the longitudinal axis of the roller support shaft  46 . Additionally, the axis of the roller support coupling  48  is orthogonally disposed with respect to the longitudinal axis of the sliding collar  24  and the hollow support shaft  16 .  
      A sliding shaft  12  having a longitudinal axis and connector receiving means comprising a hole  14  is received within the hollow shaft  24 , such that the longitudinal axes of the sliding shaft  12 , the sliding collar  24  and the hollow shaft  16  are coincident with one another.  
      A connector, in the preferred embodiment comprising a pin  34 , attaches to the receiving means  14  of the sliding shaft  12 , projects through the longitudinal slot  18  of the hollow shaft  16  and is received by the sliding collar  16  by means of at least one receiving hole.  FIG. 3  shows a set of holes  32  projecting through the sliding collar  24  for receiving pin  34 . A clip  36  may attach pin  34  in place once assembled as shown in  FIG. 4 .  
      A fastening assembly  80  for fastening at least one of the toroidal disks (e.g.,  70 ) to the hollow shaft  16 , includes a bearing washer  82  proximate the toroidal disk  70 , a disk spring  82  for biasing the toroidal disk  70  toward the other oppositely disposed toroidal disk, spacing element  86 , and at least one nut  88  disposed on the second end  20  of the hollow shaft  16 .  
      The translation motion of the a sliding shaft  12  causes the sliding collar  24  to translate on the hollow shaft  16  thereby causing the off-set roller assemblies  40  to rotate about the first axis of the roller support coupling  48  while the off-set roller assemblies  40  contact both the first  60  and second  70  toroidal disks,  FIG. 6 .  
       FIGS. 7-9  represent the three states of tilting the off-set rollers  40  in the present invention as a result of the linear translation of the roller collar  24 .  
      It is important to understand the longitudinal slot  18  of the hollow shaft  16  limits the rotation of the off-set roller assemblies about the first axis of the roller support coupling  48  by limiting the translating movement of the sliding collar  24 . Secondly, the longitudinal slot  18  of the hollow shaft  16  also confines the travel of the roller rims  44  within the boundaries the toroidal face portions  62  and  72  by limiting the translating movement of the sliding collar  24 .  
       FIG. 7  shows the configuration of toroidal CVT  10  when the sliding shaft  12  is moved in an inward direction or a retracted position causing the off-set rollers  40  to rotate in a direction opposite that of the inward direction of the sliding shaft. In this configuration, the longitudinal axis of the roller support shaft  46  is at an angle other than orthogonal to the longitudinal axis of the hollow shaft  16  when the driving input configuration speed will not be equal to the output configuration speed.  
      Alternatively stated, when the sliding shaft  12  connected to the sliding collar  24  moves in a first direction (as indicated by the rightward arrow at  12 ), the rotational axes of the off-set rollers  40  around support shaft  46  move in a first direction and are no longer orthogonal to the longitudinal axis of the hollow shaft  16 . The speed ratio between the driving input configuration speed through one toroidal disk and the output configuration speed of the other toroidal disk is other than 1:1, and as the sliding collar  24  continues to move in the same direction, the rate of change of the ratio is in a positive direction.  
       FIG. 8  shows the configuration of toroidal CVT  10  when the sliding shaft  12  is in a neutral position causing the rotational axes of the off-set rollers  40  about roller support shaft  46  to not rotate, the axis of rotation of the off-set rollers  42  being orthogonal to the longitudinal axis of the hollow shaft  16 . The ratio of the driving input configuration speed through one toroidal disk is equal to the output configuration speed of the other toroidal disk.  
      Alternatively stated, when the longitudinal axis of the roller support shaft  46 , the first axis of the roller support coupling  48 , and the longitudinal axis of the hollow shaft  16  are each disposed orthogonally to each other, the driving input configuration speed through one toroidal disk is equal to the output configuration speed of the other toroidal disk.  
       FIG. 9  shows the configuration of toroidal CVT  10  when the sliding shaft  12  is moved in an outward direction or extended position causing the off-set rollers  40  to rotate in a direction opposite that of the outward direction of the sliding shaft. In this configuration, as in  FIG. 7 , the longitudinal axis of the roller support shaft  46  is at an angle other than orthogonal to the longitudinal axis of the hollow shaft  16  when the driving input configuration speed will not be equal to the output configuration speed.  
      Alternatively stated, when the sliding shaft  12  connected to the sliding collar  24  moves in the opposite direction of  FIG. 7 , (as indicated by the leftward arrow at  12 ), the rotational axes of the off-set rollers  40  around support shaft  46  move in an opposite direction and are no longer orthogonal to the longitudinal axis of the hollow shaft  16 . As before, the speed ratio between the driving input configuration speed through one toroidal disk and the output configuration speed of the other toroidal disk is other than 1:1. However, as the sliding collar  24  moves in the opposite direction, the rate of change of the ratio is in a negative direction with respect to the direction of the sliding shaft  12  of  FIG. 7 .  
      In each of the configurations of  FIGS. 7-9 ,  1 ) the first toroidal disk  60 ,  2 ) the second toroidal disk  70 , and  3 ) the assembly of the roller collar  24  slidingly attached to hollow shaft  16 , each are able to rotate independently of each other. Each may be configured in one of a fixed position, a driving input configuration, or an output configuration with respect to each other. Altogether there are six configurations as described hereinafter.  
      For example, when the hollow shaft  16  is in a fixed position, and the first toroidal disk  60  is in a driven configuration, the second toroidal disk  70  is in an output configuration. And when the second toroidal disk  70  is in a driven configuration, the first toroidal disk  60  is in an output configuration.  
      Another example is when the first toroidal disk  60  is in a fixed position, and the second toroidal disk  70  is in a driven configuration, the hollow shaft  16  is in an output configuration. And when the hollow shaft  16  is in a driven configuration, the second toroidal disk  70  is in an output configuration.  
      A final example is when the second toroidal disk  70  is in a fixed position, and the first toroidal disk  60  is in a driven configuration, the hollow shaft  16  is in an output configuration. And when the hollow shaft  16  is in a driven configuration, the first toroidal disk  60  is in an output configuration.  
       FIG. 10  demonstrates an alternative embodiment of the invention showing an enclosure over the area between the two toroidal disks containing the tilt adjustment mechanism and the off-set rollers. An alternatively designed toroidal disk  90  may replace either the first  60  or second  70  toroidal disk of  FIGS. 3-9 . However, this toroidal disk  90  includes an integral axially projecting cover portion  94  extending between the outer circumferential edges of the toroidal disks  70  and  90 . A roller bearing  98  is mounted on the circumferential outer edge of the other toroidal disk  70  for receiving the cover portion to rotate freely thereon and totally enclose the roller assemblies  40  therein. The advantages to this design prevent dirt and foreign particles from entering into the toroidal chamber and allow for the integral cover portion  94  and toroidal disk  90  to be used to receive a belt-drive or be connected to spokes of a wheel, e.g., a motorcycle or bicycle wheel. In this latter configuration, the hollow shaft  16  would act as a fixed axle attached to the fork of a bike, toroidal disk  70  would be configured to be driven from a chain drive, and cover portion  94  and toroidal disk  90  would connect to and drive the spokes of the bike wheel.  
      It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.