Abstract:
A transmission includes a variator including a cone secured to an input, and a second cone driveably connected to the cone, producing a variable speed ratio between the cones, a gearset including a member secured to the second cone, and second and third members, a first clutch opening and closing a connection between the input and the second member, and a second clutch opening and closing a connection between an output and the third member.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates generally to the power train of a motor vehicle, and more particularly to a transmission having a variator that produces a stepless, continuously variable range of speed ratios. 
         [0003]    2. Description of the Prior Art 
         [0004]    An efficient transmission that requires minimum space and is able to produce a continuously variable range of speed ratios is required to optimize fuel economy and performance of motor vehicles equipped with a relatively small engine, particularly in a transverse, front-wheel-drive arrangement of the engine and transmission. 
       SUMMARY OF THE INVENTION 
       [0005]    A transmission includes a variator including a cone secured to an input, and a second cone driveably connected to the cone, producing a variable speed ratio between the cones, a gearset including a member secured to the second cone, and second and third members, a first clutch opening and closing a connection between the input and the second member, and a second clutch opening and closing a connection between an output and the third member. 
         [0006]    The transmission is more efficient than a transmission that incorporates other types of variator, as there are fewer gears in the power path, which improves overall mechanical efficiency. 
         [0007]    During operation in the third mode, the powerflow is split, such that the variator receives only a portion of the power produced by the engine, thereby reducing variator efficiency losses. 
         [0008]    The scope of applicability of the preferred embodiment will become apparent from the following detailed description, claims and drawings. It should be understood, that the description and specific examples, although indicating preferred embodiments of the invention, are given by way of illustration only. Various changes and modifications to the described embodiments and examples will become apparent to those skilled in the art. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0009]    The invention will be more readily understood by reference to the following description, taken with the accompanying drawings, in which: 
           [0010]      FIG. 1  is a schematic diagram of a dual-mode continuously variable transmission; 
           [0011]      FIG. 2  shows a preferred number of gear teeth of the first mode gearset and the final drive of the transmission of  FIG. 1 ; 
           [0012]      FIG. 3  shows the beta ratio and a preferred number of gear teeth of the sun gear, ring gear and planet pinions of the mixing planetary gearset of the transmission of  FIG. 1 ; 
           [0013]      FIG. 4  is a chart showing the variation of the speed ratios of system components as the variator speed ratio changes in the transmission of  FIG. 1 ; 
           [0014]      FIG. 5  is a schematic diagram of a triple-mode continuously variable transmission; 
           [0015]      FIG. 6  shows a preferred number of gear teeth of the first mode gearset, third mode gearset, and the final drive of the transmission of  FIG. 5 ; 
           [0016]      FIG. 7  shows the beta ratio, and a preferred number of gear teeth of the sun gear, ring gear and planet pinions of the mixing gearset of the transmission of  FIG. 5 ; 
           [0017]      FIG. 8  shows the states of the clutches during operation in the three modes of the transmission of  FIG. 5 ; and 
           [0018]      FIG. 9  is a chart showing the variation of the speed ratios of system components as the variator speed ratio changes in the transmission of  FIG. 5 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0019]    Referring now to the drawings,  FIG. 1  illustrates a dual mode transmission  10  for transmitting power between an engine  12  and a final drive pinion  14 . The transmission  10  includes a torsional damper  16 ; a cone ring variator  18 ; a first mode gearset comprising pinion  20  and gear  22 ; a first mode clutch  28 ; a second mode clutch  30 ; and a mixing planetary gearset  32 . Pinion  20  is secured to input shaft  34  and meshes with gear  22 . Variator  18  in combination with mixing planetary gearset  32 , gearset  20 - 22 , and clutches  28 ,  30  produce the multi-mode continuously variable transmission  10 . 
         [0020]    Cone ring variator  18  produces a continuously variable ratio of the speed of cone  36  to the speed of cone  38  depending on the position of a ring  40 , which is controlled to move along the cones changing the speed ratio produced by the variator. The cone  38  is secured to input shaft  34 ; second cone  36  is secured to layshaft  44 , whose axis  46  is substantially parallel to the axis  42  of input shaft  34 . Ring  40  transmits rotary power between the cones, and the cones rotate in opposite directions about axes  42  and  46 . 
         [0021]    Mixing planetary gearset  32  includes a sun gear  50  secured to layshaft  44 ; a ring gear  52  secured to an output shaft  54 ; a carrier  56  connected to first mode clutch  28 ; and planet pinions  58 , supported on the carrier and meshing with the ring gear and sun gear. 
         [0022]    For the dual mode transmission  10 , the cone ring variator is combined with mixing planetary  32 , the first mode gearset  20 - 22 , and two control clutches  28 ,  30 . The first mode produces reverse drive and the low forward drive range, in which the output cone  36  of the variator is connected to one member of the mixing planetary gearset  32 . A second member of planetary gearset  32  is connected to the output of the first mode gearset  20 - 22 , and the third member of planetary gearset  32  is connected to the output  54  of the transmission  10 . The second mode is the high mode, in which the output cone  36  of variator  18  is directly connected to the output  54  and bypasses the mixing planetary gearset  32 . 
         [0023]    For operation of transmission  10  in the first mode, the first mode clutch  28  is engaged, and the second mode clutch  30  is disengaged. A component on the mixing planetary gearset  32 , e. g. carrier  56 , is connected to input shaft  34  through gearset  20 - 22  and first mode clutch  28 . A second component on the mixing planetary gearset  32 , e. g. sun gear  50 , is connected to input shaft  34  through variator  18 . A third element of the mixing planetary gearset  32 , e.g., ring gear  52 , is connected to the output shaft  54  of the transmission  10 . 
         [0024]    For operation in the second mode, first mode clutch  28  is disengaged, and second mode clutch  30  is engaged. The second mode is the high forward drive mode, in which power is transmitted from engine  12  to output shaft  54  in a power path that includes in successive order input shaft  34 , cone  38 , ring  40 , cone  36 , layshaft  44 , and second mode clutch  30 , thereby bypassing the mixing planetary gearset  32 . 
         [0025]    With proper selection of the planetary gearset beta ratio, i.e., the ratio of the pitch diameter of ring gear  52  and the pitch diameter of sun gear  50 , and the speed ratio of gearset  20 - 22 , operation in the first mode will produce reverse drive, neutral, and low speed forward drive ranges. In addition, a node point is produced, at which the overall speed ratios in first mode and second mode overlap to allow smooth switching between modes. 
         [0026]      FIG. 2  the shows preferred number of gear teeth of gearset  20 - 22  and the final drive. 
         [0027]      FIG. 3  shows the beta ratio and a preferred number of gear teeth of the sun gear  50 , ring gear  52  and planet pinions  58  of the mixing gearset  32 . 
         [0028]    As  FIG. 4  shows, during a positive torque condition with transmission operating in the first mode, the speed ratio of variator  18  at its maximum −1.6923 and engine speed at reference speed 1.000, the speed of the variator output cone  36  and sun gear  50  is −1.6923, gear  22  and carrier  56  is −0.2959, ring gear  52  and final drive pinion  14  is 0.3383, and the final drive output is −0.0908, reverse drive. 
         [0029]    The final drive output speed is zero when the speed ratio of variator  18  decreases to −0.9474 during first mode operation. The final drive output speed is 0.0795 when the speed ratio of variator 18 decreases further to its minimum −0.2959 during first mode operation. 
         [0030]    During a positive torque condition with transmission  10  operating in the second mode, with speed ratio of variator  18  at its minimum −0.2959 and engine speed at 1.000, the speed of the variator output cone  36  and sun gear  50  is −0.2959, gear  22  is −0.2959, carrier  56  is −0.2959, ring gear  52  and final drive pinion  14  is −0.2959, and the final drive output is 0.0795, forward drive. 
         [0031]    The final drive output speed is 0.1596 when the speed ratio of variator  18  increases to −0.5944 during second mode operation. The final drive output speed is 0.4544 when the speed ratio of variator 18 increases further to −1.6923 during second mode operation. 
         [0032]    For the triple mode transmission  60 , in addition to the components of the dual-mode transmission  10  of  FIG. 1 , the triple-mode transmission  60  of  FIG. 5  includes a third mode transfer gearset, comprising a pinion  62  journalled on shaft  34  and a gear  64  secured to carrier  56 ; and a third mode clutch  66 , which alternately connects and disconnects pinion  62  and input shaft  34 . Alternatively, pinion  62  is secured to shaft  34 , gear  64  is journalled on carrier  56 , and the third mode clutch  66  connects input shaft  34  to the carrier  56  through pinion  62  and gear  64  when clutch  66  is engaged. 
         [0033]    In the third mode of triple mode transmission  60 , the output cone  36  of the variator  18  is connected to one member of the mixing planetary gearset  32 , a second member of planetary gearset  32  is connected to the output gear of the third mode gearset  62 - 64 , and the third member is connected to the output  54  of transmission  60 . 
         [0034]    During operation in the first mode, clutches  30  and  66  are disengaged and clutch  28  is engaged. Operation in the first mode is substantially identical to that of transmission  10 . During operation in the second mode, clutches  28  and  66  are disengaged and clutch  30  is engaged. Operation in the second mode is substantially identical to that of transmission  10 . During operation in the third mode, clutches  28  and  30  are disengaged and clutch  66  is engaged. 
         [0035]    In the third mode, the output cone  36  of variator  18  is connected to one component of the mixing planetary gearset  32 , e.g. sun gear  50 ; a second component of planetary gearset  32 , e.g., carrier  56  is connected to the output of the third mode gearset  62 - 64  due to the engagement of clutch  66 , and a third component of planetary gearset  32 , e.g., ring gear  52 , is connected to the final drive output pinion  14 . 
         [0036]    With proper selection of beta, the speed ratios, and the ratio range of variator  18 , there is a node point at which the overall ratios of second mode and third mode overlap to allow smooth switching between the second and third modes. 
         [0037]      FIG. 6  shows preferred number of gear teeth of the first mode gearset  20 - 22 , third mode gearset  62 - 64 , and the final drive. 
         [0038]      FIG. 7  shows the beta ratio, and a preferred number of gear teeth of the sun gear  50 , ring gear  52  and planet pinions  58  of the mixing gearset  32 . 
         [0039]      FIG. 8  shows the states of clutches  28 ,  30  and  66  during operation in the first, second and third modes. 
         [0040]    As  FIG. 9  shows, during a positive torque condition with transmission  60  operating in the first mode, the speed ratio of variator  18  is its maximum −1.6923 at reference speed 1.000, the speed of the variator output cone  36  and sun gear  50  is −1.6923, gear  22  and carrier  56  is −0.2959, ring gear  52  and final drive pinion  14  is 0.4969, and the final drive output is −0.0909, reverse drive. 
         [0041]    The final drive output speed is zero when the speed ratio of variator  18  decreases to − 0 .8171 during first mode operation. The final drive output speed is 0.0541 when the speed ratio of variator  18  decreases further to its minimum −0.2959 during first mode operation. 
         [0042]    During a positive torque condition with transmission  10  operating in the second mode, with speed ratio of variator  18  at its minimum −0.2959 and engine speed at 1.000, the speed of the variator output cone  36  and sun gear  50  is −0.2959, gear  22  is −0.2959, carrier  56  is −0.2959, ring gear  52  and final drive pinion  14  is −0.2959, and the final drive output is 0.0541, i.e., forward drive. 
         [0043]    The final drive output speed is 0.1087 when the speed ratio of variator 18 increases to −0.5944 during second mode operation. The final drive output speed is 0.3096 when the speed ratio of variator  18  increases further to −1.6923 during second mode operation. 
         [0044]    During a positive torque condition with transmission  10  operating in the third mode, with speed ratio of variator  18  at −1.6923 and engine speed at 1.000, the speed of the variator output cone  36  and sun gear  50  is −1.6923, gear 64 is −0.2959, carrier 56 is −1.6923, ring gear  52  and final drive pinion  14  is −1.6923, and the final drive output is 0.3096. 
         [0045]    The final drive output speed is 0.3978 when the speed ratio of variator  18  decreases to −0.8425 during third mode operation. The final drive output speed is 0.4546 when the speed ratio of variator  18  decreases further to −0.2959 during third mode operation. 
         [0046]    In accordance with the provisions of the patent statutes, the preferred embodiment has been described. However, it should be noted that the alternate embodiments can be practiced otherwise than as specifically illustrated and described.