Patent Document

TECHNICAL FIELD  
       [0001]     The present invention relates to a family of power transmissions having three planetary gear sets that are controlled by seven torque-transmitting devices to provide at least eight forward speed ratios and at least one reverse speed ratio.  
       BACKGROUND OF THE INVENTION  
       [0002]     Passenger vehicles include a powertrain that is comprised of an engine, multi-speed transmission, and a differential or final drive. The multi-speed transmission increases the overall operating range of the vehicle by permitting the engine to operate through its torque range a number of times. The number of forward speed ratios that are available in the transmission determines the number of times the engine torque range is repeated. Early automatic transmissions had two speed ranges. This severely limited the overall speed range of the vehicle and therefore required a relatively large engine that could produce a wide speed and torque range. This resulted in the engine operating at a specific fuel consumption point during cruising, other than the most efficient point. Therefore, manually-shifted (countershaft transmissions) were the most popular.  
         [0003]     With the advent of three- and four-speed automatic transmissions, the automatic shifting (planetary gear) transmission increased in popularity with the motoring public. These transmissions improved the operating performance and fuel economy of the vehicle. The increased number of speed ratios reduces the step size between ratios and therefore improves the shift quality of the transmission by making the ratio interchanges substantially imperceptible to the operator under normal vehicle acceleration.  
         [0004]     It has been suggested that the number of forward speed ratios be increased to six or more. Six-speed transmissions are disclosed in U.S. Pat. No. 4,070,927 issued to Polak on Jan. 31, 1978; and U.S. Pat. No. 6,422,969 issued to Raghavan and Usoro on Jul. 23, 2002.  
         [0005]     Six-speed transmissions offer several advantages over four- and five-speed transmissions, including improved vehicle acceleration and improved fuel economy. While many trucks employ power transmissions having six or more forward speed ratios, passenger cars are still manufactured with three- and four-speed automatic transmissions and relatively few five or six-speed devices due to the size and complexity of these transmissions.  
         [0006]     Seven-speed transmissions are disclosed in U.S. Pat. No. 6,623,397 issued to Raghavan, Bucknor and Usoro. Eight speed transmissions are disclosed in U.S. Pat. No. 6,425,841 issued to Haka. The Haka transmission utilizes three planetary gear sets and six torque transmitting devices, including two brakes and two clutches, to provide eight forward speed ratios and a reverse speed ratio. One of the planetary gear sets is positioned and operated to establish two fixed speed input members for the remaining two planetary gear sets. Seven-, eight- and nine-speed transmissions provide further improvements in acceleration and fuel economy over six-speed transmissions. However, like the six-speed transmissions discussed above, the development of seven-, eight- and nine-speed transmissions has been precluded because of complexity, size and cost.  
       SUMMARY OF THE INVENTION  
       [0007]     It is an object of the present invention to provide an improved family of transmissions having three planetary gear sets controlled to provide at least eight forward speed ratios and at least one reverse speed ratio.  
         [0008]     In one aspect of the present invention, the family of transmissions has three planetary gear sets, each of which includes a first, second and third member, which members may comprise a sun gear, a ring gear, or a planet carrier assembly member.  
         [0009]     In referring to the first, second and third gear sets in this description and in the claims, these sets may be counted “first” to “third” in any order in the drawings (i.e., left to right, right to left, etc.).  
         [0010]     In another aspect of the present invention, each of the planetary gear sets may be of the single pinion-type or of the double pinion-type.  
         [0011]     In yet another aspect of the present invention, members of each of the planetary gear sets are not continuously interconnected with members of other planetary gear sets.  
         [0012]     In yet a further aspect of the invention, each family member incorporates an input shaft which is continuously connected with a member of the planetary gear sets, and an output shaft which is continuously connected with another member of the planetary gear sets.  
         [0013]     In still a further aspect of the invention, a first torque-transmitting mechanism, such as a clutch, selectively interconnects a member of the first planetary gear set with a member of the second planetary gear set.  
         [0014]     In another aspect of the invention, a second torque-transmitting mechanism, such as a clutch, selectively interconnects a member of the second planetary gear set with a member of the third planetary gear set.  
         [0015]     In a still further aspect of the invention, a third torque-transmitting mechanism, such as a clutch, selectively interconnects a member of the third planetary gear set with a member of the first planetary gear set.  
         [0016]     In a still further aspect of the invention, a fourth torque-transmitting mechanism, such as a clutch, selectively interconnects a member of the first planetary gear set with a member of the second or third planetary gear set.  
         [0017]     In a still further aspect of the invention, a fifth torque-transmitting mechanism, such as a clutch, selectively interconnects a member of the first, second or third planetary gear set with another member of the first, second or third planetary gear set.  
         [0018]     In still another aspect of the invention, a sixth torque-transmitting mechanism, such as a brake, selectively connects a member of the first, second or third planetary gear set with the stationary member (transmission case).  
         [0019]     In still another aspect of the invention, a seventh torque-transmitting mechanism, such as a clutch, selectively interconnects a member of the first, second or third planetary gear set with another member of the first, second or third planetary gear set. Alternatively, the seventh torque-transmitting mechanism, such as a brake, selectively connects a member of the first, second or third planetary gear set with the stationary member (transmission case).  
         [0020]     In still another aspect of the invention, the seven torque-transmitting mechanisms are selectively engageable in combinations of five to yield at least eight forward speed ratios and at least one reverse speed ratio.  
         [0021]     The above objects and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]      FIG. 1   a  is a schematic representation of a powertrain including a planetary transmission incorporating a family member of the present invention;  
         [0023]      FIG. 1   b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in  FIG. 1   a;    
         [0024]      FIG. 2   a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention;  
         [0025]      FIG. 2   b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in  FIG. 2   a;    
         [0026]      FIG. 3   a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention;  
         [0027]      FIG. 3   b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in  FIG. 3   a;    
         [0028]      FIG. 4   a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention;  
         [0029]      FIG. 4   b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in  FIG. 4   a;    
         [0030]      FIG. 5   a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention;  
         [0031]      FIG. 5   b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in  FIG. 5   a;    
         [0032]      FIG. 6   a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention;  
         [0033]      FIG. 6   b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in  FIG. 6   a;    
         [0034]      FIG. 7   a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention;  
         [0035]      FIG. 7   b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in  FIG. 7   a;    
         [0036]      FIG. 8   a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention;  
         [0037]      FIG. 8   b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in  FIG. 8   a;    
         [0038]      FIG. 9   a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention;  
         [0039]      FIG. 9   b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in  FIG. 9   a;    
         [0040]      FIG. 10   a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention; and  
         [0041]      FIG. 10   b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in  FIG. 10   a.   
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0042]     Referring to the drawings, wherein like characters represent the same or corresponding parts throughout the several views, there is shown in  FIG. 1   a  a powertrain  10  having a conventional engine and torque converter  12 , a planetary transmission  14 , and a conventional final drive mechanism  16 .  
         [0043]     The planetary transmission  14  includes an input shaft  17  continuously connected with the engine and torque converter  12 , a planetary gear arrangement  18 , and an output shaft  19  continuously connected with the final drive mechanism  16 . The planetary gear arrangement  18  includes three planetary gear sets  20 ,  30  and  40 .  
         [0044]     The planetary gear set  20  includes a sun gear member  22 , a ring gear member  24 , and a planet carrier assembly  26 . The planet carrier assembly  26  includes a plurality of pinion gears  27  rotatably mounted on a carrier member  29  and disposed in meshing relationship with both the sun gear member  22  and the ring gear member  24 .  
         [0045]     The planetary gear set  30  includes a sun gear member  32 , a ring gear member  34 , and a planet carrier assembly member  36 . The planet carrier assembly member  36  includes a plurality of pinion gears  37  rotatably mounted on a carrier member  39  and disposed in meshing relationship with both the sun gear member  32  and the ring gear member  34 .  
         [0046]     The planetary gear set  40  includes a sun gear member  42 , a ring gear member  44 , and a planet carrier assembly member  46 . The planet carrier assembly member  46  includes a plurality of pinion gears  47  rotatably mounted on a carrier member  49  and disposed in meshing relationship with both the sun gear member  42  and the ring gear member  44 .  
         [0047]     The planetary gear arrangement also includes seven torque-transmitting mechanisms  50 ,  52 ,  54 ,  56 ,  57 ,  58  and  59 . The torque-transmitting mechanisms  50 ,  52 ,  54 ,  56 ,  57  and  58  are rotating-type torque-transmitting mechanisms, commonly termed clutches. The torque-transmitting mechanisms  59  is a stationary-type torque transmitting mechanism, commonly termed brake or reaction clutch.  
         [0048]     The input shaft  17  is continuously connected with ring gear member  24 . The output shaft  19  is continuously connected with the ring gear member  44 .  
         [0049]     The clutch  50  selectively connects the planet carrier assembly member  26  with the sun gear member  32 . The clutch  52  selectively connects the sun gear member  22  with the sun gear member  32 . The clutch  54  selectively connects the sun gear member  22  with the sun gear member  42 . The clutch  56  selectively connects the ring gear member  24  with the planet carrier assembly member  46 . The clutch  57  selectively connects the planet carrier assembly member  36  with the sun gear member  42 . The clutch  58  selectively connects the planet carrier assembly member  36  with the planet carrier assembly member  46 . The brake  59  selectively connects the ring gear member  34  with the transmission housing  60 .  
         [0050]     As shown in  FIG. 1   b , and in particular the truth table disclosed therein, the torque-transmitting mechanisms are selectively engaged in combinations of five to provide eight forward speed ratios and one reverse speed ratio.  
         [0051]     The reverse speed ratio is established with the engagement of the clutches  50 ,  54 ,  56 ,  58  and brake  59 . The clutch  50  connects the planet carrier assembly member  26  with the sun gear member  32 . The clutch  54  connects the sun gear member  22  with the sun gear member  42 . The clutch  56  connects the ring gear member  24  with the planet carrier assembly member  46 . The clutch  58  connects the planet carrier assembly member  36  with the planet carrier assembly member  46 . The brake  59  connects the ring gear member  34  with the transmission housing  60 . The ring gear member  24  and planet carrier assembly members  36 ,  46  rotate at the same speed as the input shaft  17 . The planet carrier assembly member  26  rotates at the same speed as the sun gear member  32 . The sun gear member  22  rotates at the same speed as the sun gear member  42 . The speed of the planet carrier assembly member  26  is determined from the speed of the ring gear member  24 , the speed of the sun gear member  22 , and the ring gear/sun gear tooth ratio of the planetary gear set  20 . The ring gear member  34  does not rotate. The speed of the sun gear member  32  is determined from the speed of the planet carrier assembly member  36  and the ring gear/sun gear tooth ratio of the planetary gear set  30 . The ring gear member  44  rotates at the same speed as the output shaft  19 . The speed of the ring gear member  44 , and therefore the output shaft  19 , is determined from the speed of the planet carrier assembly member  46 , the speed of the sun gear member  42 , and the ring gear/sun gear tooth ratio of the planetary gear set  40 . The numerical value of the reverse speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  20 ,  30 , and  40 .  
         [0052]     The first forward speed ratio is established with the engagement of the clutches  50 ,  52 ,  54 ,  58  and the brake  59 . The clutch  50  connects the planet carrier assembly member  26  with the sun gear member  32 . The clutch  52  connects the sun gear member  22  with the sun gear member  32 . The clutch  54  connects the sun gear member  22  with the sun gear member  42 . The clutch  56  connects the planet carrier assembly member  36  with the planet carrier assembly member  46 . The brake  59  connects the ring gear member  34  with the transmission housing  60 . The planetary gear set  20  and sun gear members  32 ,  42  rotate at the same speed as the input shaft  17 . The planet carrier assembly member  36  rotates at the same speed as the planet carrier assembly member  46 . The ring gear member  34  does not rotate. The planet carrier assembly member  36  rotates at a speed determined from the speed of the sun gear member  32  and the ring gear/sun gear tooth ratio of the planetary gear set  30 . The ring gear member  44  rotates at the same speed as the output shaft  19 . The ring gear member  44 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the planet carrier assembly member  46 , the speed of the sun gear member  42 , and the ring gear/sun gear tooth ratio of the planetary gear set  40 . The numerical value of the first forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  30  and  40 .  
         [0053]     The second forward speed ratio is established with the engagement of the clutches  52 ,  54 ,  56 ,  58  and the brake  59 . The clutch  52  connects the sun gear member  22  with the sun gear member  32 . The clutch  54  connects the sun gear member  22  with the sun gear member  42 . The clutch  56  connects the ring gear member  24  with the planet carrier assembly member  46 . The clutch  58  connects the planet carrier assembly member  36  with the planet carrier assembly member  46 . The brake  59  connects the ring gear member  34  with the transmission housing  60 . The ring gear member  24  and planet carrier assembly members  36 ,  46  rotate at the same speed as the input shaft  17 . The sun gear members  22 ,  32  and  42  rotate at the same speed. The ring gear member  34  does not rotate. The speed of the sun gear member  32  is determined from the speed of the planet carrier assembly member  36  and the ring gear/sun gear tooth ratio of the planetary gear set  30 . The ring gear member  44  rotates at the same speed as the output shaft  19 . The ring gear member  44 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the planet carrier assembly member  46 , the speed of the sun gear member  42 , and the ring gear/sun gear tooth ratio of the planetary gear set  40 . The numerical value of the second forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  30  and  40 .  
         [0054]     The third forward speed ratio is established with the engagement of the clutches  50 ,  52 ,  57 ,  58  and the brake  59 . The clutch  50  connects the planet carrier assembly member  26  with the sun gear member  32 . The clutch  52  connects the sun gear member  22  with the sun gear member  32 . The clutch  57  connects the planet carrier assembly member  36  with the sun gear member  42 . The clutch  58  connects the planet carrier assembly member  36  with the planet carrier assembly member  46 . The brake  59  connects the ring gear member  34  with the transmission housing  60 . The planetary gear set  20  and sun gear member  32  rotate at the same speed as the input shaft  17 . The ring gear member  34  does not rotate. The planet carrier assembly member  36  and planetary gear set  40  rotate at the same speed as the output shaft  19 . The speed of the planet carrier assembly member  36 , and therefore the output shaft  19 , is determined from speed of the sun gear member  32  and the ring gear/sun gear tooth ratio of the planetary gear set  30 . The numerical value of the third forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  30 .  
         [0055]     The fourth forward speed ratio is established with the engagement of the clutches  52 ,  56 ,  57 ,  58  and the brake  59 . The clutch  52  connects the sun gear member  22  with the sun gear member  32 . The clutch  56  connects the ring gear member  24  with the planet carrier assembly member  46 . The clutch  57  connects the planet carrier assembly member  36  with the sun gear member  42 . The clutch  58  connects the planet carrier assembly member  36  with the planet carrier assembly member  46 . The brake  59  connects the ring gear member  34  with the transmission housing  60 . The ring gear member  24 , planet carrier assembly member  36  and planetary gear set  40  rotate at the same speed as the output shaft  19 . The sun gear member  22  rotates at the same speed as the sun gear member  32 . The ring gear member  34  does not rotate. The speed of the planet carrier assembly member  36 , and therefore the output shaft  19 , is determined from the speed of the sun gear member  32  and the ring gear/sun gear tooth ratio of the planetary gear set  30 . The numerical value of the fourth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  30 .  
         [0056]     The fifth forward speed ratio is established with the engagement of the clutch  50 ,  52 ,  56 ,  57  and  58 . In this configuration, the input shaft  17  is directly connected to the output shaft  19 . The numerical value of the fifth forward speed ratio is 1.  
         [0057]     The sixth forward speed ratio is established with the engagement of the clutches  50 ,  52 ,  56 ,  57  and the brake  59 . The clutch  50  connects the planet carrier assembly member  26  with the sun gear member  32 . The clutch  52  connects the sun gear member  22  with the sun gear member  32 . The clutch  56  connects the ring gear member  24  with the planet carrier assembly member  46 . The clutch  57  connects the planet carrier assembly member  36  with the sun gear member  42 . The brake  59  connects the ring gear member  34  with the transmission housing  60 . The planetary gear set  20 , sun gear member  32 , and planet carrier assembly member  46  rotate at the same speed as the input shaft  17 . The ring gear member  34  does not rotate. The planet carrier assembly member  36  rotates at the same speed as the sun gear member  42 . The speed of the planet carrier assembly member  36  is determined from the speed of the sun gear member  32  and the ring gear/sun gear tooth ratio of the planetary gear set  30 . The ring gear member  44  rotates at the same speed as the output shaft  19 . The ring gear member  44 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the planet carrier assembly member  46 , the speed of the sun gear member  42 , and the ring gear/sun gear tooth ratio of the planetary gear set  40 . The numerical value of the sixth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  30  and  40 .  
         [0058]     The seventh forward speed ratio is established with the engagement of the clutches  50 ,  54 ,  56 ,  57  and the brake  59 . The clutch  50  connects the planet carrier assembly member  26  with the sun gear member  32 . The clutch  54  connects the sun gear member  22  with the sun gear member  42 . The clutch  56  connects the ring gear member  24  with the planet carrier assembly member  46 . The clutch  57  connects the planet carrier assembly member  36  with the sun gear member  42 . The brake  59  connects the ring gear member  34  with the transmission housing  60 . The ring gear member  24  and planet carrier assembly member  46  rotate at the same speed as the input shaft  17 . The planet carrier assembly member  26  rotates at the same speed as the sun gear member  32 . The sun gear member  22  rotates at the same speed as the sun gear member  42  and the planet carrier assembly member  36 . The speed of the planet carrier assembly member  26  is determined from the speed of the ring gear member  24 , the speed of the sun gear member  22 , and the ring gear/sun gear tooth ratio of the planetary gear set  20 . The ring gear member  34  does not rotate. The speed of the planet carrier assembly member  36  is determined from the speed of the sun gear member  32  and the ring gear/sun gear tooth ratio of the planetary gear set  30 . The ring gear member  44  rotates at the same speed as the output shaft  19 . The ring gear member  44 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the planet carrier assembly member  46 , the speed of the sun gear member  42 , and the ring gear/sun gear tooth ratio of the planetary gear set  40 . The numerical value of the of the seventh forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  20 ,  30  and  40 .  
         [0059]     The eighth forward speed ratio is established with the engagement of the clutches  52 ,  54 ,  56 ,  57  and the brake  59 . The clutch  52  connects the sun gear member  22  with the sun gear member  32 . The clutch  54  connects the sun gear member  22  with the sun gear member  42 . The clutch  56  connects the ring gear member  24  with the planet carrier assembly member  46 . The clutch  57  connects the planet carrier assembly member  36  with the sun gear member  42 . The brake  59  connects the ring gear member  34  with the transmission housing  60 . The ring gear member  24  and planet carrier assembly member  46  rotate at the same speed as the input shaft  17 . The sun gear members  22 ,  42  and planetary gear set  30  do not rotate. The ring gear member  44  rotates at the same speed as the output shaft  19 . The ring gear member  44 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the planet carrier assembly member  46  and the ring gear/sun gear tooth ratio of the planetary gear set  40 . The numerical value of the eighth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  40 .  
         [0060]     As set forth above, the engagement schedule for the torque-transmitting mechanisms is shown in the truth table of  FIG. 1   b . This truth table also provides an example of speed ratios that are available utilizing the ring gear/sun gear tooth ratios given by way of example in  FIG. 1   b . The N R1 /N S1  value is the tooth ratio of the planetary gear set  20 ; the N R2 /N S2  value is the tooth ratio of the planetary gear set  30 ; and the N R3 /N S3  value is the tooth ratio of the planetary gear set  40 . Also, the chart of  FIG. 1   b  describes the ratio steps that are attained utilizing the sample of tooth ratios given. For example, the step ratio between the first and second forward speed ratios is 1.66, while the step ratio between the reverse and first forward ratio is −0.40.  
         [0061]      FIG. 2   a  shows a powertrain  110  having a conventional engine and torque converter  12 , a planetary transmission  114 , and a conventional final drive mechanism  16 .  
         [0062]     The planetary transmission  114  includes an input shaft  17  continuously connected with the engine and torque converter  12 , a planetary gear arrangement  118 , and an output shaft  19  continuously connected with the final drive mechanism  16 . The planetary gear arrangement  118  includes three planetary gear sets  120 ,  130  and  140 .  
         [0063]     The planetary gear set  120  includes a sun gear member  122 , a ring gear member  124 , and a planet carrier assembly  126 . The planet carrier assembly  126  includes a plurality of pinion gears  127  rotatably mounted on a carrier member  129  and disposed in meshing relationship with both the sun gear member  122  and the ring gear member  124 .  
         [0064]     The planetary gear set  130  includes a sun gear member  132 , a ring gear member  134 , and a planet carrier assembly member  136 . The planet carrier assembly member  136  includes a plurality of pinion gears  137  rotatably mounted on a carrier member  139  and disposed in meshing relationship with both the sun gear member  132  and the ring gear member  134 .  
         [0065]     The planetary gear set  140  includes a sun gear member  142 , a ring gear member  144 , and a planet carrier assembly member  146 . The planet carrier assembly member  146  includes a plurality of pinion gears  147  rotatably mounted on a carrier member  149  and disposed in meshing relationship with both the sun gear member  142  and the ring gear member  144 .  
         [0066]     The planetary gear arrangement  118  also includes seven torque-transmitting mechanisms  150 ,  152 ,  154 ,  156 ,  157 ,  158  and  159 . The torque-transmitting mechanisms  150 ,  152 ,  154 ,  156  and  157  are rotating-type torque-transmitting mechanisms, commonly termed clutches. The torque-transmitting mechanisms  158  and  159  are stationary-type torque transmitting mechanisms, commonly termed brakes or reaction clutches.  
         [0067]     The input shaft  17  is continuously connected with the ring gear member  124 . The output shaft  19  is continuously connected with the planet carrier assembly member  136 .  
         [0068]     The planet carrier assembly member  126  is selectively connectable with the sun gear member  132  through the clutch  150 . The planet carrier assembly member  126  is selectively connectable with the planet carrier assembly member  146  through the clutch  152 . The sun gear member  122  is selectively connectable with the sun gear member  132  through the clutch  154 . The sun gear member  122  is selectively connectable with the ring gear member  144  through the clutch  156 . The ring gear member  134  is selectively connectable with the ring gear member  144  through the clutch  157 . The ring gear member  134  is selectively connectable with the transmission housing  160  through the brake  158 . The sun gear member  142  is selectively connectable with the transmission housing  160  through the brake  159 .  
         [0069]     The truth table of  FIG. 2   b  describes the engagement sequence utilized to provide eight forward speed ratios and one reverse speed ratio in the planetary gear arrangement  118  shown in  FIG. 2   a.    
         [0070]     The truth tables given in  FIGS. 2   b ,  3   b ,  4   b ,  5   b ,  6   b ,  7   b ,  8   b ,  9   b  and  10   b  show the engagement sequences for the torque-transmitting mechanisms to provide at least eight forward speed ratios and one reverse ratio. As shown and described above for the configuration in  FIG. 1   a , those skilled in the art will understand from the respective truth tables how the speed ratios are established through the planetary gear sets identified in the written description.  
         [0071]     As set forth above, the truth table of  FIG. 2   b  describes the engagement sequence of the torque-transmitting mechanisms utilized to provide one reverse drive ratio and eight forward speed ratios. The truth table also provides an example of the ratios that can be attained with the family members shown in  FIG. 2   a  utilizing the sample tooth ratios given in  FIG. 2   b . The N R1 /N S1  value is the tooth ratio of the planetary gear set  120 ; the N R2 /N S2  value is the tooth ratio of the planetary gear set  130 ; and the N R3 /N S3  value is the tooth ratio of the planetary gear set  140 . Also shown in  FIG. 2   b  are the ratio steps between single step ratios in the forward direction as well as the reverse to first ratio step ratio. For example, the first to second step ratio is 1.67.  
         [0072]     Turning to  FIG. 3   a , a powertrain  210  includes the engine and torque converter  12 , a planetary transmission  214 , and a final drive mechanism  16 . The planetary transmission  214  includes an input shaft  17  continuously connected with the engine and torque converter  12 , a planetary gear arrangement  218 , and an output shaft  19  continuously connected with the final drive mechanism  16 . The planetary gear arrangement  218  includes three planetary gear sets  220 ,  230  and  240 .  
         [0073]     The planetary gear set  220  includes a sun gear member  222 , a ring gear member  224 , and a planet carrier assembly  226 . The planet carrier assembly  226  includes a plurality of pinion gears  227  rotatably mounted on a carrier member  229  and disposed in meshing relationship with both the sun gear member  222  and the ring gear member  224 .  
         [0074]     The planetary gear set  230  includes a sun gear member  232 , a ring gear member  234 , and a planet carrier assembly member  236 . The planet carrier assembly member  236  includes a plurality of pinion gears  237  rotatably mounted on a carrier member  239  and disposed in meshing relationship with both the sun gear member  232  and the ring gear member  234 .  
         [0075]     The planetary gear set  240  includes a sun gear member  242 , a ring gear member  244 , and a planet carrier assembly member  246 . The planet carrier assembly member  246  includes a plurality of pinion gears  247  rotatably mounted on a carrier member  249  and disposed in meshing relationship with both the sun gear member  242  and the ring gear member  244 .  
         [0076]     The planetary gear arrangement  218  also includes seven torque-transmitting mechanisms  250 ,  252 ,  254 ,  256 ,  257 ,  258  and  259 . The torque-transmitting mechanisms  250 ,  252 ,  254 ,  256  and  257  are rotating type torque-transmitting mechanisms, commonly termed clutches. The torque-transmitting mechanisms  258  and  259  are stationary-type torque transmitting mechanisms, commonly termed brakes or reaction clutches.  
         [0077]     The input shaft  17  is continuously connected with the ring gear member  224 . The output shaft  19  is continuously connected with the planet carrier assembly member  236 .  
         [0078]     The planet carrier assembly member  226  is selectively connectable with the sun gear member  232  through the clutch  250 . The planet carrier assembly member  226  is selectively connectable with the planet carrier assembly member  246  through the clutch  252 . The sun gear member  222  is selectively connectable with the sun gear member  232  through the clutch  254 . The sun gear member  222  is selectively connectable with the ring gear member  244  through the clutch  256 . The ring gear member  234  is selectively connectable with the planet carrier assembly member  246  through the clutch  257 . The ring gear member  234  is selectively connectable with the transmission housing  260  through the brake  258 . The sun gear member  242  is selectively connectable with the transmission housing  260  through the brake  259 .  
         [0079]     As shown in the truth table in  FIG. 3   b , the torque-transmitting mechanisms are engaged in combinations of five to establish eight forward speed ratios and one reverse speed ratio.  
         [0080]     As previously set forth, the truth table of  FIG. 3   b  describes the combinations of engagements utilized for the forward and reverse speed ratios. The truth table also provides an example of speed ratios that are available with the family member described above. These examples of speed ratios are determined utilizing the tooth ratios given in  FIG. 3   b . The N R1 /N S1  value is the tooth ratio of the planetary gear set  220 ; the N R2 /N S2  value is the tooth ratio of the planetary gear set  230 ; and the N R3 /N S3  value is the tooth ratio of the planetary gear set  240 . Also depicted in FIG.  3   b  is a chart representing the ratio steps between adjacent forward speed ratios and between the first and reverse speed ratio. For example, the first to second ratio interchange has a step of 1.67.  
         [0081]     A powertrain  310 , shown in  FIG. 4   a , includes the engine and torque converter  12 , a planetary transmission  314 , and the final drive mechanism  16 . The planetary transmission  314  includes an input shaft  17  continuously connected with the engine and torque converter  12 , a planetary gear arrangement  318 , and output shaft  19  continuously connected with the final drive mechanism  16 . The planetary gear arrangement  318  includes three planetary gear sets  320 ,  330  and  340 .  
         [0082]     The planetary gear set  320  includes a sun gear member  322 , a ring gear member  324 , and a planet carrier assembly member  326 . The planet carrier assembly member  326  includes a plurality of pinion gears  327  rotatably mounted on a carrier member  329  and disposed in meshing relationship with both the sun gear member  322  and the ring gear member  324 .  
         [0083]     The planetary gear set  330  includes a sun gear member  332 , a ring gear member  334 , and a planet carrier assembly member  336 . The planet carrier assembly member  336  includes a plurality of pinion gears  337  rotatably mounted on a carrier member  339  and disposed in meshing relationship with both the sun gear member  332  and the ring gear member  334 .  
         [0084]     The planetary gear set  340  includes a sun gear member  342 , a ring gear member  344 , and a planet carrier assembly member  346 . The planet carrier assembly member  346  includes a plurality of pinion gears  347  rotatably mounted on a carrier member  349  and disposed in meshing relationship with both the sun gear member  342  and the ring gear member  344 .  
         [0085]     The planetary gear arrangement  318  also includes seven torque-transmitting mechanisms  350 ,  352 ,  354 ,  356 ,  357 ,  358  and  359 . The torque-transmitting mechanisms  350 ,  352 ,  354 ,  356  and  357  are rotating type torque-transmitting mechanisms, commonly termed clutches. The torque-transmitting mechanisms  358  and  359  are stationary-type torque transmitting mechanisms, commonly termed brakes or reaction clutches.  
         [0086]     The input shaft  17  is continuously connected with the sun gear member  322 . The output shaft  19  is continuously connected with the planet carrier assembly member  336 .  
         [0087]     The ring gear member  324  is selectively connectable with the ring gear member  344  through the clutch  350 . The planet carrier assembly member  326  is selectively connectable with the sun gear member  332  through the clutch  352 . The planet carrier assembly member  326  is selectively connectable with the planet carrier assembly member  346  through the clutch  354 . The ring gear member  334  is selectively connectable with the ring gear member  344  through the clutch  356 . The ring gear member  334  is selectively connectable with the sun gear member  342  through the clutch  357 . The ring gear member  324  is selectively connectable with the transmission housing  360  through the brake  358 . The sun gear member  332  is selectively connectable with the transmission housing  360  through the brake  359 .  
         [0088]     The truth table shown in  FIG. 4   b  describes the engagement combination and the engagement sequence necessary to provide one reverse drive ratio and eight forward speed ratios. A sample of the numerical values for the ratios is also provided in the truth table of  FIG. 4   b . These values are determined utilizing the ring gear/sun gear tooth ratios also given in  FIG. 4   b . The N R1 /N S1  value is the tooth ratio for the planetary gear set  320 ; the N R2 /N S2  value is the tooth ratio for the planetary gear set  330 ; and the N R3 /N S3  value is the tooth ratio for the planetary gear set  340 . Also given in  FIG. 4   b  is a chart describing the step ratios between the adjacent forward speed ratios and the reverse to first forward speed ratio. For example, the first to second forward speed ratio step is 1.51.  
         [0089]     A powertrain  410 , shown in  FIG. 5   a , includes the engine and torque converter  12 , a planetary transmission  414  and the final drive mechanism  16 . The planetary transmission  414  includes a planetary gear arrangement  418 , input shaft  17  and output shaft  19 . The planetary gear arrangement  418  includes three simple planetary gear sets  420 ,  430  and  440 .  
         [0090]     The planetary gear set  420  includes a sun gear member  422 , a ring gear member  424 , and a planet carrier assembly  426 . The planet carrier assembly  426  includes a plurality of pinion gears  427 ,  428  rotatably mounted on a carrier member  429  and disposed in meshing relationship with the sun gear member  422  and the ring gear member  424 , respectively.  
         [0091]     The planetary gear set  430  includes a sun gear member  432 , a ring gear member  434 , and a planet carrier assembly member  436 . The planet carrier assembly member  436  includes a plurality of pinion gears  437  rotatably mounted on a carrier member  439  and disposed in meshing relationship with both the ring gear member  434  and the sun gear member  432 .  
         [0092]     The planetary gear set  440  includes a sun gear member  442 , a ring gear member  444 , and a planet carrier assembly member  446 . The planet carrier assembly member  446  includes a plurality of pinion gears  447  rotatably mounted on a carrier member  449  and disposed in meshing relationship with both the sun gear member  442  and the ring gear member  444 .  
         [0093]     The planetary gear arrangement  418  also includes seven torque-transmitting mechanisms  450 ,  452 ,  454 ,  456 ,  457 ,  458  and  459 . The torque-transmitting mechanisms  450 ,  452 ,  454 ,  456  and  457  are rotating type torque-transmitting mechanisms, commonly termed clutches. The torque-transmitting mechanisms  458  and  459  are stationary-type torque transmitting mechanisms, commonly termed brakes or reaction clutches.  
         [0094]     The input shaft  17  is continuously connected with the sun gear member  422 . The output shaft  19  is continuously connected with the planet carrier assembly member  436 .  
         [0095]     The planet carrier assembly member  426  is selectively connectable with the ring gear member  444  through the clutch  450 . The ring gear member  424  is selectively connectable with the sun gear member  432  through the clutch  452 . The ring gear member  424  is selectively connectable with the planet carrier assembly member  446  through the clutch  454 . The ring gear member  434  is selectively connectable with the ring gear member  444  through the clutch  456 . The ring gear member  434  is selectively connectable with the sun gear member  442  through the clutch  457 . The planet carrier assembly member  426  is selectively connectable with the transmission housing through the brake  458 . The sun gear member  432  is selectively connectable with the transmission housing  460  through the brake  459 .  
         [0096]     The truth table shown in  FIG. 5   b  describes the engagement combination and sequence of the torque-transmitting mechanisms  450 ,  452 ,  454 ,  456 ,  457 ,  458  and  459  that are employed to provide the forward and reverse drive ratios.  
         [0097]     Also given in the truth table of  FIG. 5   b  is a set of numerical values that are attainable with the present invention utilizing the ring gear/sun gear tooth ratios shown. The N R1 /N S1  value is the tooth ratio of the planetary gear set  420 ; the N R2 /N S2  value is the tooth ratio of the planetary gear set  430 ; and the N R3 /N S3  value is the tooth ratio of the planetary gear set  440 .  
         [0098]      FIG. 5   b  also provides a chart of the ratio steps between adjacent forward ratios and between the reverse and first forward ratio. For example, the ratio step between the first and second forward ratios is 1.51.  
         [0099]     A powertrain  510 , shown in  FIG. 6   a , includes an engine and torque converter  12 , a planetary gear transmission  514  and the final drive mechanism  16 . The planetary transmission  514  includes the input shaft  17 , a planetary gear arrangement  518  and the output shaft  19 . The planetary gear arrangement  518  includes three planetary gear sets  520 ,  530  and  540 .  
         [0100]     The planetary gear set  520  includes a sun gear member  522 , a ring gear member  524 , and a planet carrier assembly  526 . The planet carrier assembly  526  includes a plurality of pinion gears  527  rotatably mounted on a carrier member  529  and disposed in meshing relationship with both the sun gear member  522  and the ring gear member  524 .  
         [0101]     The planetary gear set  530  includes a sun gear member  532 , a ring gear member  534 , and a planet carrier assembly member  536 . The planet carrier assembly member  536  includes a plurality of pinion gears  537  rotatably mounted on a carrier member  539  and disposed in meshing relationship with both the sun gear member  532  and the ring gear member  534 .  
         [0102]     The planetary gear set  540  includes a sun gear member  542 , a ring gear member  544 , and a planet carrier assembly member  546 . The planet carrier assembly member  546  includes a plurality of pinion gears  547  rotatably mounted on a carrier member  549  and disposed in meshing relationship with both the sun gear member  542  and the ring gear member  544 .  
         [0103]     The planetary gear arrangement  518  also includes seven torque-transmitting mechanisms  550 ,  552 ,  554 ,  556 ,  557 ,  558  and  559 . The torque-transmitting mechanisms  550 ,  552 ,  554 ,  556  and  557  are rotating type torque-transmitting mechanisms, commonly termed clutches. The torque-transmitting mechanisms  558  and  559  are stationary-type torque transmitting mechanisms, commonly termed brakes or reaction clutches.  
         [0104]     The input shaft  17  is continuously connected with the planet carrier assembly member  526 . The output shaft  19  is continuously connected with the planet carrier assembly member  536 .  
         [0105]     The sun gear member  522  is selectively connectable with the sun gear member  542  through the clutch  550 . The ring gear member  524  is selectively connectable with the ring gear member  534  through the clutch  552 . The ring gear member  524  is selectively connectable with the planet carrier assembly member  546  through the clutch  554 . The sun gear member  532  is selectively connectable with the sun gear member  542  through the clutch  556 . The sun gear member  532  is selectively connectable with the ring gear member  544  through the clutch  557 . The sun gear member  522  is selectively connectable with the transmission housing  560  through the brake  558 . The ring gear member  534  is selectively connectable with the transmission housing  560  through the brake  559 .  
         [0106]     The truth table shown in  FIG. 6   b  describes the engagement sequence and combination of the torque-transmitting mechanisms to provide the reverse speed ratio and eight forward speed ratios. The chart of  FIG. 6   b  describes the ratio steps between adjacent forward speed ratios and the ratio step between the reverse and first forward speed ratio.  
         [0107]     The sample speed ratios given in the truth table are determined utilizing the tooth ratio values also given in  FIG. 6   b . The N R1 /N S1  value is the tooth ratio of the planetary gear set  520 ; the N R2 /N S2  value is the tooth ratio of the planetary gear set  530 ; and the N R3 /N S3  value is the tooth ratio of the planetary gear set  540 .  
         [0108]     A powertrain  610 , shown in  FIG. 7   a , has the engine and torque converter  12 , a planetary transmission  614  and the final drive mechanism  16 . The planetary transmission  614  includes the input shaft  17 , a planetary gear arrangement  618  and the output shaft  19 . The planetary gear arrangement  618  includes three planetary gear sets  620 ,  630  and  640 .  
         [0109]     The planetary gear set  620  includes a sun gear member  622 , a ring gear member  624 , and a planet carrier assembly  626 . The planet carrier assembly  626  includes a plurality of pinion gears  627  rotatably mounted on a carrier member  629  and disposed in meshing relationship with both the sun gear member  622  and the ring gear member  624 .  
         [0110]     The planetary gear set  630  includes a sun gear member  632 , a ring gear member  634 , and a planet carrier assembly member  636 . The planet carrier assembly member  636  includes a plurality of pinion gears  637  rotatably mounted on a carrier member  639  and disposed in meshing relationship with both the sun gear member  632  and the ring gear member  634 .  
         [0111]     The planetary gear set  640  includes a sun gear member  642 , a ring gear member  644 , and a planet carrier assembly member  646 . The planet carrier assembly member  646  includes a plurality of pinion gears  647  rotatably mounted on a carrier member  649  and disposed in meshing relationship with both the sun gear member  642  and the ring gear member  644 .  
         [0112]     The planetary gear arrangement  618  also includes seven torque-transmitting mechanisms  650 ,  652 ,  654 ,  656 ,  657 ,  658  and  659 . The torque-transmitting mechanisms  650 ,  652 ,  654 ,  656  and  657  are rotating type torque-transmitting mechanisms, commonly termed clutches. The torque-transmitting mechanisms  658  and  659  are stationary-type torque transmitting mechanisms, commonly termed brakes or reaction clutches.  
         [0113]     The input shaft  17  is continuously connected with the planet carrier assembly member  626 . The output shaft  19  is continuously connected with the planet carrier assembly member  636 .  
         [0114]     The sun gear member  622  is selectively connectable with the sun gear member  642  through the clutch  650 . The ring gear member  624  is selectively connectable with the ring gear member  634  through the clutch  652 . The ring gear member  624  is selectively connectable with the planet carrier assembly member  646  through the clutch  654 . The sun gear member  632  is selectively connectable with the ring gear member  644  through the clutch  656 . The sun gear member  632  is selectively connectable with the planet carrier assembly member  646  through the clutch  657 . The sun gear member  622  is selectively connectable with the transmission housing  660  through the brake  658 . The ring gear member  634  is selectively connectable with the transmission housing  660  through the brake  659 .  
         [0115]     The truth table shown in  FIG. 7   b  describes the combination of torque-transmitting mechanism engagements that will provide the reverse drive ratio and eight forward speed ratios, as well as the sequence of these engagements and interchanges. The torque-transmitting mechanisms  650 ,  654 ,  657  and  659  can be engaged through the neutral condition, thereby simplifying the forward/reverse interchange.  
         [0116]     The ratio values given are by way of example and are established utilizing the ring gear/sun gear tooth ratios given in  FIG. 7   b . For example, the N R1 /N S1  value is the tooth ratio of the planetary gear set  620 ; the N R2 /N S2  value is the tooth ratio of the planetary gear set  630 ; and the N R3 /N S3  value is the tooth ratio of the planetary gear set  640 . The ratio steps between adjacent forward ratios and the reverse to first ratio are also given in  FIG. 7   b.    
         [0117]     A powertrain  710 , shown in  FIG. 8   a , has the conventional engine and torque converter  12 , a planetary transmission  714 , and the conventional final drive mechanism  16 . The engine and torque converter  12  are drivingly connected with the planetary transmission  714  through the input shaft  17 . The planetary transmission  714  is drivingly connected with the final drive mechanism  16  through the output shaft  19 . The planetary transmission  714  includes a planetary gear arrangement  718  that has a first planetary gear set  720 , a second planetary gear set  730 , and a third planetary gear set  740 .  
         [0118]     The planetary gear set  720  includes a sun gear member  722 , a ring gear member  724 , and a planet carrier assembly  726 . The planet carrier assembly  726  includes a plurality of pinion gears  727  rotatably mounted on a carrier member  729 . The pinion gears  727  are disposed in meshing relationship with the sun gear member  722  and the ring gear member  724 .  
         [0119]     The planetary gear set  730  includes a sun gear member  732 , a ring gear member  734 , and a planet carrier assembly member  736 . The planet carrier assembly member  736  includes a plurality of pinion gears  737  rotatably mounted on a carrier member  739  and disposed in meshing relationship with both the sun gear member  732  and the ring gear member  734 .  
         [0120]     The planetary gear set  740  includes a sun gear member  742 , a ring gear member  744 , and a planet carrier assembly member  746 . The planet carrier assembly member  746  includes a plurality of pinion gears  747  rotatably mounted on a carrier member  749  and disposed in meshing relationship with both the sun gear member  742  and the ring gear member  744 .  
         [0121]     The planetary gear arrangement  718  also includes seven torque-transmitting mechanisms  750 ,  752 ,  754 ,  756 ,  757 ,  758  and  759 . The torque-transmitting mechanisms  750 ,  752 ,  754 ,  756  and  757  are rotating type torque-transmitting mechanisms, commonly termed clutches. The torque-transmitting mechanisms  758  and  759  are stationary-type torque transmitting mechanisms, commonly termed brakes or reaction clutches.  
         [0122]     The input shaft  17  is continuously connected with the planet carrier assembly member  726 . The output shaft  19  is continuously connected with the planet carrier assembly member  746 .  
         [0123]     The sun gear member  722  is selectively connectable with the sun gear member  742  through the clutch  750 . The ring gear member  724  is selectively connectable with the sun gear member  732  through the clutch  752 . The ring gear member  724  is selectively connectable with the sun gear member  742  through the clutch  754 . The sun gear member  732  is selectively connectable with the ring gear member  744  through the clutch  756 . The ring gear member  734  is selectively connectable with the ring gear member  744  through the clutch  757 . The sun gear member  722  is selectively connectable with the transmission housing  760  through the brake  758 . The planet carrier assembly member  736  is selectively connectable with the transmission housing  760  through the brake  759 .  
         [0124]     The truth table of  FIG. 8   b  defines the torque-transmitting mechanism engagement sequence utilized for each of the forward and reverse speed ratios. Also given in the truth table is a set of numerical values that are attainable with the present invention utilizing the ring gear/sun gear tooth ratios given in  FIG. 8   b . The N R1 /N S1  value is the tooth ratio of the planetary gear set  720 ; the N R2 /N S2  value is the tooth ratio of the planetary gear set  730 ; and the N R3 /N S3  value is the tooth ratio of the planetary gear set  740 .  
         [0125]      FIG. 8   b  also provides a chart of the ratio steps between adjacent forward ratios and between the reverse and first forward ratio. For example, the ratio step between the first and second forward ratios is 1.44.  
         [0126]     A powertrain  810 , shown in  FIG. 9   a , has the conventional engine and torque converter  12 , a planetary transmission  814 , and the final drive mechanism  16 . The engine and torque converter  12  are drivingly connected with the planetary transmission  814  through the input shaft  17 . The planetary transmission  814  is drivingly connected with the final drive mechanism  16  through the output shaft  19 . The planetary transmission  814  includes a planetary gear arrangement  818  that has a first planetary gear set  820 , a second planetary gear set  830 , and a third planetary gear set  840 .  
         [0127]     The planetary gear set  820  includes a sun gear member  822 , a ring gear member  824 , and a planet carrier assembly  826 . The planet carrier assembly  826  includes a plurality of pinion gears  827  rotatably mounted on a carrier member  829  and disposed in meshing relationship with the sun gear member  822  and the ring gear member  824 .  
         [0128]     The planetary gear set  830  includes a sun gear member  832 , a ring gear member  834 , and a planet carrier assembly member  836 . The planet carrier assembly member  836  includes a plurality of pinion gears  837  rotatably mounted on a carrier member  839  and disposed in meshing relationship with both the sun gear member  832  and the ring gear member  834 .  
         [0129]     The planetary gear set  840  includes a sun gear member  842 , a ring gear member  844 , and a planet carrier assembly member  846 . The planet carrier assembly member  846  includes a plurality of pinion gears  847  rotatably mounted on a carrier member  849  and disposed in meshing relationship with both the ring gear member  844  and the sun gear member  842 .  
         [0130]     The planetary gear arrangement  818  also includes seven torque-transmitting mechanisms  850 ,  852 ,  854 ,  856 ,  857 ,  858  and  859 . The torque-transmitting mechanisms  850 ,  852 ,  854 ,  856  and  857  are rotating type torque-transmitting mechanisms, commonly termed clutches. The torque-transmitting mechanisms  858  and  859  are stationary-type torque transmitting mechanisms, commonly termed brakes or reaction clutches.  
         [0131]     The input shaft  17  is continuously connected with the sun gear member  822 . The output shaft  19  is continuously connected with the ring gear member  844 .  
         [0132]     The sun gear member  822  is selectively connectable with the planet carrier assembly member  846  through the clutch  850 . The planet carrier assembly member  826  is selectively connectable with the planet carrier assembly member  836  through the clutch  852 . The planet carrier assembly member  826  is selectively connectable with the planet carrier assembly member  846  through the clutch  854 . The ring gear member  824  is selectively connectable with the sun gear member  832  through the clutch  856 . The ring gear member  834  is selectively connectable with the sun gear member  842  through the clutch  857 . The planet carrier assembly member  836  is selectively connectable with the transmission housing  860  through the brake  858 . The sun gear member  832  is selectively connectable with the transmission housing  860  through the brake  859 .  
         [0133]     The truth table shown in  FIG. 9   b  defines the torque-transmitting mechanism engagement sequence that provides the reverse speed ratio and eight forward speed ratios shown in the truth table and available with the planetary gear arrangement  818 . A sample of numerical values for the individual ratios is also given in the truth table of  FIG. 9   b . These numerical values have been calculated using the ring gear/sun gear tooth ratios also given by way of example in  FIG. 9   b . The N R1 /N S1  value is the tooth ratio of the planetary gear set  820 ; the N R2 /N S2  value is the tooth ratio of the planetary gear set  830 ; and the N R3 /N S3  value is the tooth ratio of the planetary gear set  840 .  FIG. 9   b  also describes the ratio steps between adjacent forward ratios and between the reverse and first forward ratio.  
         [0134]     The powertrain  910 , shown in  FIG. 10   a , includes the conventional engine and torque converter  12 , a planetary transmission  914 , and the conventional final drive mechanism  16 . The engine and torque converter  12  are drivingly connected with the planetary transmission  914  through the input shaft  17 . The planetary transmission  914  is drivingly connected with the final drive mechanism  16  through the output shaft  19 . The planetary transmission  914  includes a planetary gear arrangement  918  that has a first planetary gear set  920 , a second planetary gear set  930 , and a third planetary gear set  940 .  
         [0135]     The planetary gear set  920  includes a sun gear member  922 , a ring gear member  924 , and a planet carrier assembly  926 . The planet carrier assembly  926  includes a plurality of pinion gears  927  that are rotatably mounted on a carrier member  929  and disposed in meshing relationship with the sun gear member  922  and the ring gear member  924 , respectively.  
         [0136]     The planetary gear set  930  includes a sun gear member  932 , a ring gear member  934 , and a planet carrier assembly member  936 . The planet carrier assembly member  936  includes a plurality of pinion gears  937  rotatably mounted on a carrier member  939  and disposed in meshing relationship with both the sun gear member  932  and the ring gear member  934 .  
         [0137]     The planetary gear set  940  includes a sun gear member  942 , a ring gear member  944 , and a planet carrier assembly member  946 . The planet carrier assembly member  946  includes a plurality of pinion gears  947  rotatably mounted on a carrier member  949  and disposed in meshing relationship with both the sun gear member  942  and the ring gear member  944 .  
         [0138]     The planetary gear arrangement  918  also includes seven torque-transmitting mechanisms  950 ,  952 ,  954 ,  956 ,  957 ,  958  and  959 . The torque-transmitting mechanisms  950 ,  952 ,  954 ,  956  and  957  are rotating-type torque-transmitting mechanisms, commonly termed clutches. The torque-transmitting mechanisms  958  and  959  are stationary-type torque-transmitting mechanisms, commonly termed brakes or reaction clutches.  
         [0139]     The input shaft  17  is continuously connected with the sun gear member  922 . The output shaft  19  is continuously connected with the planet carrier assembly member  946 .  
         [0140]     The sun gear member  922  is selectively connectable with the ring gear member  944  through the clutch  950 . The ring gear member  924  is selectively connectable with the planet carrier assembly member  936  through the clutch  952 . The planet carrier assembly member  926  is selectively connectable with the ring gear member  934  through the clutch  954 . The planet carrier assembly member  926  is selectively connectable with the ring gear member  944  through the clutch  956 . The sun gear member  932  is selectively connectable with the sun gear member  942  through the clutch  957 . The planet carrier assembly member  936  is selectively connectable with the transmission housing  960  through the brake  958 . The ring gear member  934  is selectively connectable with the transmission housing  960  through the brake  959 .  
         [0141]     The truth table of  FIG. 10   b  describes the torque-transmitting mechanism engagement sequence utilized to provide the reverse speed ratio and eight forward speed ratios. The truth table also provides a set of examples for the ratios for each of the reverse and forward speed ratios. These numerical values have been determined utilizing the ring gear/sun gear tooth ratios given in  FIG. 10   b . The N R1 /N S1  value is the tooth ratio of the planetary gear set  920 ; the N R2 /N S2  value is the tooth ratio of the planetary gear set  930 ; and the N R3 /N S3  value is the tooth ratio of the planetary gear set  940 .  
         [0142]     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.

Technology Category: 2