Abstract:
A transmission includes an input, a variator including an output and a race connected to the input for producing a variable speed ratio between the output and the race, a gearset including a component connected to the output, and second and third components, a first clutch opening and closing a connection between the input and the second component, and a second clutch opening and closing a connection between the output and the third component.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates generally to the powertrain 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 an input, a variator including an output and a race connected to the input for producing a variable speed ratio between the output and the race, a gearset including a component connected to the output, and second and third components, a first clutch opening and closing a connection between the input and the second component, and a second clutch opening and closing a connection between the output and the third component. 
         [0006]    The transmission includes a ball variator and requires a smaller package space than transmissions that incorporate other variators. 
         [0007]    Because fewer gears are in the power path as compared to transmissions having other variators, particularly half or full toroidal variator, the overall mechanical efficiency of the transmission is improved. 
         [0008]    While operating in third mode of the triple mode embodiments, the powerflow is split, such that the variator only sees part of the input power, thereby reducing variator efficiency losses. 
         [0009]    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 
         [0010]    The invention will be more readily understood by reference to the following description, taken with the accompanying drawings, in which: 
           [0011]      FIG. 1  is a schematic diagram of a dual-mode continuously variable transmission; 
           [0012]      FIG. 2  shows preferred number of gear teeth of the transfer gearset, first mode gearset and the final drive of the transmission of  FIG. 1 ; 
           [0013]      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 ; 
           [0014]      FIG. 4  is a chart showing the variation of the speed ratios of system components as the variator speed ratio changes of in the transmission of  FIG. 1 ; 
           [0015]      FIG. 5  is a schematic diagram of a triple-mode continuously variable transmission; 
           [0016]      FIG. 6  shows preferred number of gear teeth of the transfer gearset, first mode gearset, third mode gearset, and the final drive of the transmissions of  FIGS. 5 and 10 ; 
           [0017]      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 transmissions of  FIGS. 5 and 10 ; 
           [0018]      FIG. 8  shows the states of the clutches during operation in the three modes of the transmission of  FIG. 5 ; 
           [0019]      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 ; 
           [0020]      FIG. 10  is a schematic diagram of a triple-mode continuously variable transmission; 
           [0021]      FIG. 11  shows the states of the clutches during operation in the three modes of the transmission of  FIG. 10 ; 
           [0022]      FIG. 12  is a chart showing the variation of the speed ratios of system components as the variator speed ratio changes in the transmission of  FIG. 10 ; and 
           [0023]      FIG. 13  is a schematic diagram of another triple-mode continuously variable transmission. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0024]    Referring now to the drawings,  FIG. 1  illustrates a transmission  10  for transmitting power between an engine  12  and a final drive pinion  14 . The transmission  10  includes a torsional damper  16 ; a Milner ball variator  18 ; a transfer gearset comprising pinion  20  and gear  22 ; a first mode gearset comprising pinion  24  and gear  26 ; a first mode clutch  28 ; a second mode clutch  30 ; and a mixing planetary gearset  32 . Pinion  20  is secured to variator output  42 . Pinion  24  is secured to shaft  46 . Gear  26  is journalled on shaft  50 . 
         [0025]    The Milner ball variator  18  includes spherical balls  34  and is a type of variable geometry, 4-point contact ball bearing. The inner race is divided in two parts  36 ,  37 , and the outer race is divided in two parts  38 ,  39 . By varying the axial distance between the parts of the outer race  38 ,  39  the distance between the parts of the inner race  36 ,  37  changes and the balls  34  are displaced radially between the inner and outer races. As the position of the balls changes relative to the races, the location of the contact between the balls  34  and the races varies, thereby changing the speed ratio of the variator. 
         [0026]    As used here, the inner races  36 ,  37 , which are driveably connected to shaft  46 , are the input to variator  18 . The outer races  38 ,  39  are grounded, i.e., held against rotation on the case  40 . The ball carrier  42  is the variator output. The output speed of variator  18  is always less than the speed of its input  36 ,  37 . 
         [0027]    The variator  18  is combined with the mixing planetary gearset  32 , the transfer gearset, first mode gearset, and clutches  28 ,  30  to produce a multi-mode transmission. The damper  16 , supported on the input shaft  46 , is connected to the engine shaft  48 . Power is transmitted toward layshaft  50  from input shaft  46 . In forward drive, shaft  52 , the output on the layshaft centerline  54 , rotates in the opposite direction as the engine shaft  48 . The final drive pinion  14  is in mesh with a final drive gear located on the differential/wheel centerline. The ball variator  18  can be located on either the shaft  46  or shaft  50 . 
         [0028]    For operation in the first mode, first mode clutch  28  is engaged, second mode clutch  30  is disengaged, and the variator  18  is combined with mixing planetary  32 , the variator transfer gearset  20 - 22 , the first mode gearset  24 - 26 . The first mode produces reverse drive and low range forward drive, in which the variator output  42  is connected to the sun gear  60  of the mixing planetary gearset  32  through the variator transfer gearset  20 - 22 . A second element of the mixing planetary gearset  32 , carrier  62 , is connected to the output of the first mode gearset  24 - 26  due to engagement of the first mode clutch  28 . A third element of the mixing planetary gearset  32 , ring gear  64 , is connected to the output  52  of the transmission  10 . Planet pinions  66  are supported on carrier  62  and mesh with sun gear  60  and ring gear  64 . 
         [0029]    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-mode, in which the variator output  42  is connected through the variator transfer gearset  20 ,  22  due to engagement of the second mode clutch  30  to the output  52  bypassing the mixing planetary gearset  32 . 
         [0030]    With proper selection of the planetary gearset beta ratio, i.e., the ratio of the pitch diameter of ring gear  64  and the pitch diameter of sun gear  60 , and the speed ratios of the transfer gearsets  20 - 22 ,  24 - 26 , operation in low-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. 
         [0031]      FIG. 2  shows preferred number of gear teeth of the transfer gearset  20 - 22 , first mode gearset  24 - 26  and the final drive. 
         [0032]      FIG. 3  shows beta ratio, and a preferred number of gear teeth of the sun gear  60 , ring gear  64  and planet pinions  66  of the mixing gearset  32 . 
         [0033]    As  FIG. 4  shows, during a positive torque condition with transmission  10  operating in the first mode, the speed ratio of variator  18  at its maximum 0.6250 and engine speed at reference speed 1.000, the speed of the variator output  42  is 0.6250, gear  22  and sun gear  60  is −1.8421, gear  26  and carrier  62  is −0.4608, ring gear  64  and final drive pinion  14  is 0.2209, and the final drive output is −0.0545. 
         [0034]    The final drive output speed is zero when the speed ratio of variator  18  decreases to 0.4731 during first mode operation. The final drive output speed is 0.1137 when the speed ratio of variator  18  decreases further to 0.1563 during first mode operation. 
         [0035]    During a positive torque condition with transmission  10  operating in the second mode, with speed ratio of variator  18  at its minimum 0.1563 and engine speed is 1.000, the speed of the variator output  42  is 0.1563, gear  22  and sun gear  60  is −0.4608, gear  26  is −0.4608, carrier  62  is −0.4608, ring gear  64  and final drive pinion  14  is −0.4608, and the final drive output is 0.1137. 
         [0036]    The final drive output speed is 0.1979 when the speed ratio of variator  18  increases to 0.2721 during second mode operation. The final drive output speed is 0.4545 when the speed ratio of variator  18  increases further to 0.6250 during second mode operation. 
         [0037]    In addition to the components of the dual-mode transmission  10  of  FIG. 1 , the triple-mode transmission  70  of  FIG. 5  includes a third mode transfer gearset, comprising a pinion  72  journalled on shaft  46  and a gear  74  secured to shaft  50 ; and a third mode clutch  76 , which alternately connects and disconnects pinion  72  and shaft  46 . 
         [0038]    During operation in the third mode, the output  42  of variator  18  is connected to one component of the mixing planetary gearset  32 , e.g. sun gear  60 , through the transfer gearset  20 - 22 , a second component of planetary gearset  32 , e.g., carrier  62  is connected to the output of the third mode gearset  72 - 74  due to the engagement of clutch  76 , and a third component of planetary gearset  32 , e.g., ring gear  64 , is connected to the final drive output pinion  14 . 
         [0039]    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. 
         [0040]      FIG. 6  shows preferred number of gear teeth of the transfer gearset  20 - 22 , first mode gearset  24 - 26 , third mode gearset  72 - 74 , and the final drive. 
         [0041]      FIG. 7  shows the beta ratio, and a preferred number of gear teeth of the sun gear  60 , ring gear  64  and planet pinions  66  of the mixing gearset  32 . 
         [0042]      FIG. 8  shows the states of clutches  28 ,  30  and  76  during operation in the three modes. 
         [0043]    As  FIG. 9  shows, during a positive torque condition with transmission  70  operating in the first mode, the speed ratio of variator  18  is its maximum 0.6250 and engine speed is at reference speed 1.000, the speed of the variator output  42  is 0.6250, gear  22  and sun gear  60  is −1.5833, gear  26  and carrier  62  is −0.3953, ring gear  64  and final drive pinion  14  is 0.2706, and the final drive output is −0.0547. 
         [0044]    The final drive output speed is zero when the speed ratio of variator  18  decreases to 0.4344 during first mode operation. The final drive output speed is 0.0799 when the speed ratio of variator  18  decreases further to 0.1561 during first mode operation. 
         [0045]    During a positive torque condition with transmission  70  operating in the second mode, the speed ratio of variator  18  at its minimum 0.1561 and engine speed at 1.000, the speed of the variator output  42  is 0.1561, gear  22  and sun gear  60  is −0.3953, gear  26  is −0.3953, carrier  62  is −0.3953, ring gear  64  and final drive pinion  14  is −0.3953, and the final drive output is 0.0799. 
         [0046]    The final drive output speed is 0.1392 when the speed ratio of variator  18  increases to 0.2718 during second mode operation. The final drive output speed is 0.3200 when the speed ratio of variator  18  increases further to 0.6250 during second mode operation. 
         [0047]    During a positive torque condition with transmission  70  operating in the third mode, the speed ratio of variator  18  at its maximum 0.6250 and engine speed at 1.000, the speed of the variator output  42  is 0.6250, gear  22  and sun gear  60  is −1.5833, gear  26  is −0.3953, carrier  62  is −1.5833, ring gear  64  and final drive pinion  14  is −1.5833, and the final drive output is 0.3200. 
         [0048]    The final drive output speed is 0.3965 when the speed ratio of variator  18  decreases to 0.3588 during third mode operation. The final drive output speed is 0.4547 when the speed ratio of variator  18  decreases further to 0.1561 during third mode operation. 
         [0049]    Referring now to  FIG. 10 , the transmission  80  transmits power between an engine  12  and a final drive pinion  14 . Transmission  80  further includes a torsional damper  16 ; a Milner ball variator  82 ; a transfer gearset comprising pinion  84  and gear  86 ; a first mode gearset comprising pinion  88  and gear  90 ; a first mode clutch  92 ; a second mode clutch  94 ; a third mode clutch  96 ; a third mode gearset comprising pinion  98  and gear  100 , and a mixing planetary gearset  102 . Pinion  84  is secured to input shaft  46 . Pinion  88  is secured to shaft  46 . Pinion  98  is journalled on shaft  46 . Gear  90  is journalled on shaft  104 . Gear  100  is secured to a carrier  106 . 
         [0050]    The Milner ball variator  82  includes spherical balls  34 ; split inner races  36 ,  37 ; split outer races  38 ,  39 ; and a carrier  42 , secured to shaft  104 . The races are each split, which allows the contact point between the balls and the races to be varied, thereby changing the speed ratio of the variator. As used here, the inner races  36 ,  37  are the input to the variator  18 , the outer races  38 ,  39  are grounded, i.e., held against rotation on the case  40 , and the ball carrier  42  is the output, whose speed is always less than the input speed. The balls  34  revolve about axis  44  in the torus between the inner and outer races. 
         [0051]    The variator  18  is combined with the mixing planetary gearset  102 , the transfer gearset, first and third mode gearsets, and clutches  92 ,  94  and  96  to produce a multi-mode transmission  80 . The damper  16 , supported on the input shaft  46 , is connected to the engine shaft  48 . In forward drive, shaft  52 , the output on the layshaft centerline  44 , rotates in the opposite direction as the engine shaft  48 . The final drive pinion  14  is in mesh with a final drive gear located on the differential/wheel centerline. 
         [0052]    For operation in the first mode, first mode clutch  92  is engaged, and clutches  94 ,  96  are disengaged. Power from engine  12  is transmitted from input shaft  46  through gearset  88 - 90  and clutch  92  to the carrier  106  of the mixing planetary gearset  102 . Power from engine  12  is also transmitted from input shaft  46  through gearset  84 - 86  to the inner races  36 ,  37  of variator  82 . The variator output  42  is connected to the sun gear  108  of the mixing planetary gearset  102 . A third component of the mixing planetary gearset  102 , ring gear  110 , is connected to the output  52  of the transmission  80 . Planet pinions  112  are supported on carrier  106  and mesh with sun gear  108  and ring gear  110 . 
         [0053]    For operation in the second mode, clutches  92 ,  96  are disengaged, and second mode clutch  94  is engaged. In the second mode, power from engine  12  is transmitted from input shaft  46  through gearset  84 - 86  to the inner races  36 ,  37  of variator  82 . The variator output  42  is connected to the sun gear  108  of the mixing planetary gearset  102 . A third component of the mixing planetary gearset  102 , ring gear  110 , is also connected to variator output  42  and sun gear  108  due to the engagement of clutch  94 , thereby bypassing the mixing planetary gearset  102 . Output  52  is continually driven at the speed of variator output  42  and sun gear  108  due to the engagement of clutch  94 . 
         [0054]    For operation in the third mode, clutches  92 ,  94  are disengaged, and third mode clutch  96  is engaged. During operation in the third mode, power from engine  12  is transmitted from input shaft  46  through gearset  84 - 86  to the inner races  36 ,  37  of variator  82 . Power from engine  12  is also transmitted from input shaft  46  through gearset  98 - 100  to the carrier  106  of the mixing planetary gearset  102  due to the engagement of third mode clutch  96 . The output  42  of variator  82  is connected to one component of the mixing planetary gearset  102 , e.g. sun gear  108 . A third component of planetary gearset  102 , e.g., ring gear  110 , is connected to the final drive output pinion  14 . 
         [0055]    With proper selection of the planetary gearset&#39;s beta ratio and the speed ratios of the transfer gearsets  84 - 86 ,  88 - 90 ,  98 - 100 , 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 the adjacent modes overlap to allow smooth switching between modes. 
         [0056]      FIG. 6  shows preferred number of gear teeth of the transfer gearset  84 - 86 , first mode gearset  88 - 90 , third mode gearset  98 - 100 , and the final drive. 
         [0057]      FIG. 7  shows the beta ratio, and a preferred number of gear teeth of the sun gear  108 , ring gear  110  and planet pinions  108  of the mixing gearset  102 . 
         [0058]      FIG. 11  shows the states of clutches  92 ,  94 ,  96  during operation in the three modes. 
         [0059]    As  FIG. 12  shows, during a positive torque condition with transmission  80  operating in the first mode, the speed ratio of variator  82  is its maximum 0.6250 and engine speed is at reference speed 1.000, the speed of the variator output  42  and sun gear  108  is −1.5833, gear  90  and carrier  106  is −0.3953, and ring gear  110  and final drive pinion  14  is 0.2706, and the final drive output is −0.0547. 
         [0060]    The final drive output speed is zero when the speed ratio of variator  82  decreases to 0.4344 during first mode operation. The final drive output speed is 0.0799 when the speed ratio of variator  82  decreases further to 0.1561 during first mode operation. 
         [0061]    During a positive torque condition with transmission  80  operating in the second mode, the speed ratio of variator  82  at its minimum 0.1561 and engine speed at 1.000, the speed of the variator output  42  and sun gear  108  is −0.3953, gear  90  is −0.3953, carrier  106  is −0.3953, ring gear  110  and final drive pinion  14  is −0.3953, and the final drive output is 0.0799. 
         [0062]    The final drive output speed is 0.1392 when the speed ratio of variator  82  increases to 0.2718 during second mode operation. The final drive output speed is 0.3200 when the speed ratio of variator  82  increases further to 0.6250 during second mode operation. 
         [0063]    During a positive torque condition with transmission  80  operating in the third mode, the speed ratio of variator  82  at its maximum 0.6250 and engine speed at 1.000, the speed of the variator output  42  and sun gear  108  is −1.5833, gear  90  is −0.3953, carrier  106  is −1.5833, ring gear  110  and final drive pinion  14  is −1.5833, and the final drive output is 0.3200. 
         [0064]    The final drive output speed is 0.3965 when the speed ratio of variator  82  decreases to 0.3588 during third mode operation. The final drive output speed is 0.4547 when the speed ratio of variator  82  decreases further to 0.1561 during third mode operation. 
         [0065]    In second mode of both the dual mode transmission  10  and triple mode transmissions  70 ,  80 , the powerpath is entirely through the ball variator  18 ,  82 . 
         [0066]    In the third mode of the triple mode transmissions  70 ,  80 , the powerflow is split, so that the variator  18 ,  82  only sees part of the power, thereby reducing variator efficiency losses. 
         [0067]    In addition to the components of the dual-mode transmission  10  of  FIG. 1 , the triple-mode transmission  120  of  FIG. 13  includes a third mode transfer gearset, comprising a pinion  72  secured to shaft  46 , and a gear  74  journalled on shaft  50 ; and a third mode clutch  76 , which alternately connects and disconnects gear  74  and shaft  50 . 
         [0068]    During operation in the third mode, the output  42  of variator  18  is connected to one component of the mixing planetary gearset  32 , e.g. sun gear  60 , through the transfer gearset  20 - 22 , a second component of planetary gearset  32 , e.g., carrier  62  is connected to the output of the third mode gearset  72 - 74  due to the engagement of clutch  76 , and a third component of planetary gearset  32 , e.g., ring gear  64 , is connected to the final drive output pinion  14 . 
         [0069]    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. 
         [0070]    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.