Abstract:
A continuously variable transmission (CVT) with a roller variator as an actuator for adjusting the speed ratio of the CVT. The CVT is of the variable-diameter pulley type and has first and second variable-diameter pulleys mechanically linked by a drive belt or other flexible drive member, the pulleys each having first and second relatively axially movable pulley portions. A roller variator is operatively connected to the first pulley, preferably the drive pulley, for control of its effective diameter. The roller variator has first and second disks mounted on the axis of the first pulley, a roller interconnecting the disks, and a roller support adapted to tilt the spin axis of the roller so as to change its points of contact with the disks and thereby change the speed ratio of the variator. The first disk is rotatably fixed with respect to the first pulley portion of the first pulley, for example, the pulley portion fixed to an engine shaft. In certain embodiments, the second disk directly drives the second pulley portion relative to the first, and, in other embodiments, the second disk drives the second pulley portion through a threaded connection, for example, one having directly engaging male and female threaded parts, or a ball screw.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of patent application Ser. No. 11/415,391, filed May 1, 2006, now U.S. Pat. No. 7,771,300, issued Aug. 10, 2010, which is hereby incorporated by reference. This application also claims the benefit of U.S. Provisional Patent Application Ser. No. 60/873,446, filed Dec. 7, 2006, which application is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to transmissions, and more particularly to methods and apparatus for actuation of continuously variable transmissions. 
     Transmissions are devices that transform the speed and torque in vehicles using gears, belts, or other drive components. Most transmission designs use discrete speed ratios: low ratios for acceleration, hill climbing, and heavy hauling, and high ratios for higher-speed travel. They use multiple parallel gear sets between input and output shafts. By changing which gear set carries the loads between the shafts, the speed ratio between the input and output shafts is altered. 
     Transmissions have also been designed that are continuously variable (CVTs). These generally use friction to transfer load from an input shaft to an output shaft. By altering the radial position of friction rollers, belts, or other components, the speed ratio is changed. 
     Most current CVTs rely upon fixed-design mechanical or hydraulic actuation that cannot be easily changed to respond to differing demands, such as varying vehicle cargo loads and operator performance demands. Accordingly, there is need for a CVT actuation system that is more flexible and adaptable than the current state of technology. 
     SUMMARY OF THE INVENTION 
     The present invention provides a continuously variable transmission (CVT) with a roller variator as an actuator for adjusting the speed ratio of the CVT. According to one aspect of the invention, the CVT is of the variable-diameter pulley type and has first and second variable-diameter pulleys mechanically linked by a drive belt or other flexible drive member, the pulleys each having first and second relatively axially movable pulley portions as shown in  FIGS. 6A and 6B . A roller variator is operatively connected to the first pulley, preferably the drive pulley, for control of its effective diameter. The roller variator has first and second disks mounted on the axis of the first pulley, a roller interconnecting the disks, and a roller support adapted to tilt the spin axis of the roller so as to change its points of contact with the disks and thereby change the speed ratio of the variator. The first and second disks are connected respectively to the first and second relatively axially movable pulley portions of the first pulley. 
     In certain embodiments, the first and second disks are rotatably fixed with respect to the first and second pulley portions, respectively, and one disk directly drives one axially movable pulley portion relative to the other pulley portion. 
     In other embodiments, a first disk is rotatably fixed with respect to a first pulley portion, and the other disk drives the other pulley portion through a threaded connection, including but not limited to directly engaging male and female threaded parts, and ball screws. 
     The objects and advantages of the present invention will be more apparent upon reading the following detailed description in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a cross-sectional view of an embodiment of a variable actuator in accordance with the present invention, in a lower speed ratio configuration. 
         FIG. 1B  is a cross-sectional view of the variable actuator of  FIG. 1A , shown in a higher speed ratio configuration. 
         FIG. 2A  is a side view of an embodiment of an actuator to control the actuation angle of the roller in accordance with the present invention. 
         FIG. 2B  is an end view of the roller shown in  FIG. 2A . 
         FIG. 3A  is a cross-sectional view of another embodiment of a variable actuator in accordance with the present invention, in a lower speed ratio configuration. 
         FIG. 3B  is a cross-sectional view of the variable actuator of  FIG. 3A , shown in a higher speed ratio configuration. 
         FIG. 4A  is a cross-sectional view of yet another embodiment of a variable actuator in accordance with the present invention, in a lower speed ratio configuration. 
         FIG. 4B  is a cross-sectional view of the variable actuator of  FIG. 4A , shown in a higher speed ratio configuration. 
         FIG. 5A  is a side view of the base plate of the variable actuator of  FIGS. 4A and 4B . 
         FIG. 5B  is a side view of the linear bearing plate of the variable actuator of  FIGS. 4A and 4B . 
         FIG. 5C  is a side view of the push pin plate of the variable actuator of  FIGS. 4A and 4B . 
         FIG. 6A  is a perspective view of first and second variable-diameter pulleys mechanically linked by a flexible drive member, the pulleys each having first and second relatively axially movable pulley portions, with the pulleys set for a first speed ratio. 
         FIG. 6B  shows the variable-diameter pulleys of  FIG. 6A  with the pulleys set for a second speed ratio. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. 
       FIGS. 1A and 1B  show an embodiment of a variable actuator  10  according to the present invention. Actuator  10  is a roller variator, also known as a roller-based or toroidal CVT, and it is used to control a variable-diameter pulley CVT. One aspect of the present invention is therefore a CVT controlled by another CVT. In the embodiment of  FIGS. 1A and 1B , the roller variator is connected to the drive pulley of the variable-diameter pulley CVT. The drive pulley is adapted for mounting on an output shaft of an engine (not shown) or other source of power, and it includes a fixed pulley half  12  next to the engine (or other source of power), and a movable pulley half  14  outboard from the engine. The movable pulley half is concentric with the fixed pulley half and can move axially relative to it. The movable pulley half is also constrained by a cup  16 , such that it can move axially, but not rotate, as by spline  18  relative to the fixed pulley half  12 . The cup is fixed to the engine shaft  20 . The movable pulley half is also coupled to one of two variator disks  22  and  24  by a threaded connection  26  which constrains the relative motion between the movable pulley half and variator disk  22  to be helical, as by the threaded connection shown. This same variator disk, disk  22 , is also constrained by a bearing  28  so that its only relative motion with respect to the engine shaft is rotation about the axis of the engine shaft. The second variator disk  24  is fixed to the engine shaft. 
     A roller  30 , with a substantially barrel-shaped surface, is in friction contact with the two variator disks  22  and  24 . The roller is mounted on a shaft as shown in  FIGS. 2A and 2B  and constrained to spin by bearings  32 , mounted in a cradle or yoke  34 . The yoke  34  is fitted into bearing  100  which is preferably a rolling element bearing of the type that allows angular misalignment. Bearing  100  is preferably pressed into the actuator bearing ring  102 , which is threaded onto a shaft or pin  104 . Pin  104  is free to translate within guide bushing  106 , which is fixed to the frame of the machine to which the engine shaft of the CVT is constrained by the plate  108 . A spring  110  provides preload force between the plate  108  and the shaft  104  by pushing on the washer  112  and jam nut  114 . This preloads the roller into contact with the variator disks of the CVT to maintain normal forces between the roller and the disks, to allow friction forces to be transmitted through the roller-disk contact regions for actuation of the CVT. The surface of the roller is preferably shaped so that the axis of shaft  116  intersects the center of curvature at point  122  shown in  FIG. 2B , such that the roller&#39;s contact surface (the lower surface as viewed in  FIG. 2B ) remains in frictional engagement with both disks as the roller axis is tilted. One end of actuator shaft  116  is preferably pressed or threaded into the yoke  34  and the other end of the actuator shaft  116  is connected to a gear-motor  118 , preferably with a speed-reducing gear train, through a universal joint  120 . 
     Operation of the variable actuator  10  is as follows. When the roller  30  is substantially centered, as shown in  FIGS. 1A and 1B , the two variator disks  22  and  24  are urged to spin at the same speed, causing no relative rotation across the threads  26 , and therefore no axial motion of the movable pulley half  14 . Angular actuation of the roller  30  is accomplished by energizing the coils of the electric gear-motor  118  of  FIGS. 2A and 2B . Energization which results in rotation in one direction will cause the roller  30  to rotate one way about the axis of the shaft  116 , causing it to contact the variator disks  22  and  24  at differing radial position on roller  30 . Rotation of the gear-motor  118  in the opposite direction will rotate the roller  30  in the opposite direction, imparting an opposite sense speed difference to the variator disks. When the roller is inclined or rotated about the roller actuation axis  36  of  FIGS. 1A and 1B , which is oriented into the page of the drawing, it urges the two variator disks to spin at different speeds, which causes relative rotation across the threaded connection. This imparts axial motion to the movable pulley half relative to the fixed pulley half  12 , which actuates the CVT to change ratio. Because the roller can be actuated in either direction from the centered position shown, the movable pulley half can be moved toward or away from the fixed pulley half. Regulation of the roller actuation angle, as by a suitable electric motor and control system, can control the relative axial position of the pulley halves, and thereby control the CVT ratio. One example of a suitable electric motor and control system is disclosed in U.S. Pat. No. 7,771,300, issued Aug. 10, 2010, which is hereby incorporated by reference along with all references cited therein. 
     In the embodiment as shown in  FIGS. 1A and 1B , pulley half  12  is rotatably fixed or nonrotatable, i.e., not capable of rotating, with respect to the engine shaft, and it is also axially fixed. It will be understood, however, that this is but one example of a pulley with relatively axially movable pulley portions, and that both pulley halves may be axially movable or floating to some degree while still having their relative axial spacing controlled by an actuator in accordance with the present invention. It should also be understood that, in some applications, it may be suitable to have an actuator according to the present invention alternatively mounted on the CVT&#39;s driven pulley, i.e., the pulley driven by the illustrated pulley via a drive belt or other flexible drive member. It should also be understood that, in accordance with the present invention, the movable pulley half could be on the inboard or engine side of the CVT driver pulley and the fixed pulley half could be on the outboard side. 
     Advantages of this embodiment include:
         (1) The power requirements for moving the pulley halves  12  and  14  apart and together come primarily from the engine shaft, through the second variator disk  24 . This greatly reduces the actuator power requirements for the system.   (2) The spline coupling  18  between the pulley halves decouples the belt forces from the actuation of the pulley halves.       

       FIGS. 3A and 3B  show another embodiment of a variable actuator  38  according to the present invention. This embodiment also shows a fixed pulley half  40  next to an engine (or other source of power), and the movable pulley half  42  outboard from the engine (not shown). In this embodiment, the movable pulley half is constrained to the fixed pulley half by a helical connection  44 , as by threads, or the ball screw shown in  FIGS. 2A and 2B . Two variator disks  46  and  48  are also used, one,  46 , fixed to the engine shaft  50  as shown, and the second,  48 , constrained to rotate about the engine shaft by the bearing  52  as shown. The second variator disk is fixed to at least two linear bearings  54 , which allow axial relative motion of pins  56  which are connected to the movable pulley half by the base plate  58 . A roller  60  is in friction contact with the two variator disks, and can actuate them as previously disclosed above. 
     Operation of this variable actuator embodiment is as follows. When the roller  60  is substantially centered, as shown, the two variator disks  46  and  48  are urged to spin at the same speed, causing no relative rotation across the ball screw  44 , and therefore no axial motion of the movable pulley half  42 . When the roller is inclined or rotated about the roller actuation axis  62  (into the page of the drawing), it urges the two variator disks to spin at different speeds, which causes the linear bearings  54  to push the pins  56  rotationally, i.e., to transfer a rotational force from disk  48  to pins  56 , thereby rotating the movable pulley half on the ball screw relative to the fixed pulley half  40 . That is, the linear bearing and the pins within them rotate with disk  48 , as does the movable pulley half. Because of the constraint of the ball screw, relative rotation of the pulley halves also causes relative axial motion, which actuates the CVT. Because the roller can be actuated in either direction from the centered position shown, the movable pulley half can be moved toward or away from the fixed pulley half. Regulation of the roller actuation angle, as by the above-referenced electric motor and control system, can control the relative axial position of the pulley halves, and thereby control the CVT ratio. 
     Advantages of this embodiment include:
         (1) The power requirements for moving the pulley halves  40  and  42  apart and together come primarily from the engine shaft  50 , through the first variator disk  46 . This greatly reduces the actuator power requirements for the system.   (2) Belt tension (resulting from engine drive torque) tends to actuate the pulley halves because of the helical motion constraint of the ball screw  44 . The lead of the screw (angle and hand) can be tuned to optimize this effect.   (3) Rolling elements are used to reduce friction at three key places in the CVT: in the ball screw, in the linear bearings  54 , and in the bearing  52  connecting the second variator disk  48  to the engine shaft.       

     It should be understood by one of ordinary skill in the art that the linear bearings  54 , which contain rolling elements, could be replaced with bushings, and the ball screw  44  could be replaced with a threaded joint containing no rolling elements. It should also be understood that an actuator of the type shown in  FIGS. 2A and 2B  could also be used to control the angular orientation of the roller in the embodiment shown in  FIGS. 3A and 3B . 
       FIGS. 4A ,  4 B, and  FIG. 5  show a further embodiment of a variable actuator  64  according to the present invention. This embodiment also shows a fixed pulley half  66  next to an engine, and the movable pulley half  68  outboard from the engine. In this embodiment, the movable pulley half is constrained to the fixed pulley half such that their relative motion is only along the axis  70  of the pulley halves. The linear bearing plate  72  is fixed, preferably by a press fit or threaded connection, to the fixed pulley half. Two or more linear bearings  74  are fixed to the linear bearing plate, and linear bearing pins  76  are constrained to move axially through each linear bearing. The linear bearing pins are fixed to the base plate  78 , which is fixed to the movable pulley half. The base plate may have alternating bearing pins  76  and push pins  80  as shown in  FIG. 4A . Two variator disks  82  and  84  are also used, one,  82 , fixed to the engine shaft  86  as shown, and the second,  84 , fixed to a ball screw thread  88  which is rotatably mounted on the engine shaft. The ball screw thread  88  is free to rotate relative to the fixed pulley half  66 , but is constrained axially by contact at its ends with disk  82  and linear bearing  72 . It should be understood that thrust bearings could be placed in these locations as part of this invention. The ball screw nut  90  is fixed to the three push pins  80 , which are fixed to the movable pulley half by means of the base plate. A roller  92  is in friction contact with the two variator disks, and can actuate them as disclosed above in the first embodiment. The combined effect of these constraints is that the movable pulley half and the ball screw nut can only translate relative to the fixed pulley half. There can be no relative rotation between the movable pulley half and the ball screw nut. There can also be no relative rotation between the movable pulley half and the fixed pulley half because of the constraints discussed above. 
     The operation of this embodiment is as follows. When the roller  92  is substantially centered, as shown, the two variator disks  82  and  84  are urged to spin at the same speed, causing no relative rotation between the ball screw thread  88  and the ball screw nut  90 . Because of the helix angle of the ball screw, there is therefore also no axial relative motion between the ball screw nut and the ball screw thread. Because of the constraints detailed above, this prevents relative axial movement between the pulley halves  66  and  68 . Thus, when the roller is substantially centered, there is no relative rotation between the ball screw nut and ball screw thread, so there is no actuation of the CVT, and the pulley halves are not urged to separate or move together axially. 
     When the roller  92  is inclined or rotated about the roller actuation axis  94 , it urges the two variator disks  82  and  84  to spin at different speeds, which causes the ball screw thread  88  to spin at a different speed from the ball screw nut  90  (which rotates at the same speed as the engine and the movable pulley half  68 ). Relative rotation of the ball screw nut and threads causes relative axial motion between the pulley halves  66  and  68 , which actuates the CVT. Because the roller can be actuated in either direction from the centered position shown, the movable pulley half can be moved toward or away from the fixed pulley half. Regulation of the roller actuation angle, as by the above-referenced electric motor and control system, can control the relative axial position of the pulley halves, and thereby control the CVT ratio. 
     Advantages of this embodiment include:
         (1) The power requirements for moving the pulley halves  66  and  68  apart and together come primarily from the engine shaft  86 , through the variator disk  82 . This greatly reduces the actuator power requirements for the system.   (2) The linear bearing coupling  74  between the pulley halves decouples the belt forces from the actuation of the pulley halves. Belt tension forces are transferred directly between the movable pulley half and the engine shaft through the base plate  78 , the push pins  80 , the linear bearings, and the linear bearing plate  72 .   (3) Rolling elements are used to reduce friction at the key places in the CVT: in the ball screw,  88  and  90 , and in the linear bearings.       

     It should be understood by one of ordinary skill in the art that the linear bearings  74 , which contain rolling elements, could be replaced with bushings, and the ball screw,  88  and  90 , could be replaced with a threaded joint containing no rolling elements. It should also be understood that an actuator of the type shown in  FIGS. 2A and 2B  could also be used to control the angular orientation of the roller in the embodiment shown in  FIGS. 4A and 4B , and  FIG. 5 . 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.